High efficiency absorbent articles for incontinence management.

The present invention relates to absorbent articles which are intended for use by incontinent individuals in order to receive and store aqueous body fluids discharged by the user of the absorbent article. Absorbent articles of this type include disposable child diapers, diaper supplements, pads and bags to control relatively large amounts of body-discharged fluids. · '·

Incontinence control articles, such as non-woven disposable diapers, have traditionally used absorbent structures comprising tangled masses of fibers, i.e. nonwoven fibrous webs, to provide the necessary absorption yield. These structures can soak liquids such as body-discharged fluids, so much absorption where fluid is received by the fibrous material itself and by twisting where the fluid is distributed and stored in the capillary interstices between the fibers. An objective in the development of improved incontinence control articles over the years5 has been to increase both the ability of total absorbency of such articles as well as the toughness with which such articles maintain their absorbed load of body fluids. A means to achieve this goal and to improve. Absorbent characteristics of fibrous web structures have been incorporated into the same so-called superabsorbent polymers that soak the absorbed fluid to thereby form a swollen hydrogel material. The resulting hydrogel serves to retain fluid such as body discharged liquids within the structure. A structure

-110

Mod, 71 - 20,000. An absorbent of this type wherein the particle-shaped hydrogel-forming materials are incorporated into the fibrous webs is described in Weisman and Goldman; US Patent No. 2. 4,610,678; issued September 9, 1986.

Other means for making incontinence delivery articles having improved absorbency characteristics have been to utilize in the absorbent cores of such articles various types of spongy materials as a fluid absorbing element. For example, Lindquist, in US Patent No. 2.

563 243, issued February 16, 1971, discloses an absorbent diaper and similar pad wherein the primary absorbent therein is a hydrophilic foam sheet formed from hydrophilic polymers. also

Dabi, in US Patent No. 2. No. 4,554,297, issued November 19, 1985, discloses body fluid-absorbing cellular polymers that can be used in diapers or catamenial products.

While both fiber / superabsorbent and polymer foam based absorbent structures may provide improved absorbency characteristics, structures of both types may have problems in transporting or distributing the absorbed fluid from one region or zone. absorbent structure to another. This can be unpleasant in incontinence control articles wherein the body fluid to be absorbed is often discharged in discontinuous streams during the time period in which the. article is used. Each fluid stream discharged in this way will generally find the absorbent structure in the same place or area. Thus, the absorbance of the entire structure can be decreased unless a mechanism is provided to efficiently move fluid within the structure to other unused or reactively dried parts of the structure.

Mod. 71 · 20,000 · χ. - 90/06 absorbent structure.

A variety of absorbent structures have been developed to improve the distribution of absorbed fluid through the absorbent structure or absorbent material employed therein. For example, Weisman / Houghton / Gellert in U.S. No. 4,673,402, issued June 16, 1987, describes absorbent articles having a double layer absorbent core configuration. In such a configuration, a structure comprising a first upper absorbent layer is disposed on a lower interlayer absorbent layer which serves to drain the fluid absorbed by the upper layer absorbent structure. .

Another absorbent structure configuration for absorbent articles such as diapers designed to provide improved fluid handling performance is described in Alemany / Berg, U.S. No. 4,834,735, May 30, 1989. This patent discloses articles with an absorbent element having a relatively low density, relatively low weight base fluid acquisition zone surrounded by a fluid storage zone. These areas of the absorbent element are positioned towards the front of the absorbent article to efficiently and effectively absorb, distribute and store the fluid discharged by the body. Still other absorbent articles designed to receive and store fluid discharged rapidly by the body are those described by Reising. , in U.S. Pat. 4,988,345 and by Reising / Bergman / Clear / - Guinn / Gomez-Santiago, U.S. Pat. 4 No. 988,344, both issued January 29, 1991. These patents both describe absorbent articles such as diapers having multilayer absorbent cores. These absorbent cores contain storage layers of

<img file="PT101751B_D0001.tif" />

• fluid within which body-discharged fluids are directed by fluid-absorbing openings or fluid-absorbing zones to other core layers.

Notwithstanding the existence of the products described in the aforementioned patents, there is a continuing need to further identify additional preferred configurations for absorbent articles which allow for more effective and efficient use of the absorbent materials and structures used therein. Arti10

Mod. 71 · 20,000 · χ. · 08/2014 which permits a more complete use of its absorbent material through improved fluid transport and distribution characteristics will be articles which may employ only minimal amounts of such absorbent material. These articles are in turn more cost effective and may provide lower volume benefits, better attachment and greater comfort for the user of the articles. It is therefore an object of the present invention to provide such absorbent articles which have improved efficiency in treating discharged body fluids therein and more effective use of the absorbent materials from which they are manufactured.

SUMMARY OF THE INVENTION

The present invention relates to articles useful for absorbing aqueous body fluids discharged by incontinent individuals using the articles. Such relatively impermeable back absorbent articles, relatively impermeable back absorbent articles comprise a topsheet.

placed between the sheet to liquids, liquids and thereafter a core sheet absorbent core sheet comprises fluid absorbing / dispensing arranged to receive discharges of body fluids that pass their own component one through the topsheet of the article and a fluid component.

-435 Fluid storage / redistribution maintained in Fluid communication with the Fluid absorption / distribution component.

Mod. 71

-4.A60.1995 /

The absorbent core fluid absorption / distribution component comprises a porous hydrophilic absorbent structure having an initial Fluid Absorption Rate of at least about 2.0 ml synthetic urine per second. The porous hydrophilic absorbent structure of the absorption / distribution component will also preferably exhibit a 30 minute Vertical Absorption Height of at least about 2 cm. 0 The fluid storage / redistribution component of the absorbent core comprises a polymeric foam material in the form of an open, flexible and hydrophilic cell structure. Such a foam structure has an absorbent capacity at 37 ° C of at least 12 ml synthetic urine per gram of dry foam material. This foam also has a synthetic urine absorbent capacity, under a limited pressure of 5.1 kPa maintained for 15 minutes at 37 ° C, which is at least about 57% of the free foam absorbent capacity.

A preferred absorbent core configuration, the fluid absorption / distribution component comprises a layer greater than. fiber base or foam base covering a lower layer underlying the fluid storage / redistribution foam base. A preferred material for use in molding the upper fluid absorption / dispensing layer in such a preferred absorbent core configuration is a nonwoven fibrous web comprising from about 507 to 1007. by weight of chemically hardened, twisted, twisted cellulosic fibers and up to about 507% of a binder for these fibers. The fibrous web formed from such materials will preferably have certain characteristics of moisture density and dryness and basis weight.

<img file="PT101751B_D0002.tif" />

Preferred absorbent foam materials for use in or as the underfloor storage / redistribution layer of the preferred absorbent core configuration in this case comprise foams which may be prepared by polymerization of a specific type of oil-in-emulsion. —Water having a relatively smaller amount of an oil phase and a relatively larger amount of a water phase. This type of polymerizable emulsion is generally known in the art as a high internal phase emulsion (EFIE). Foams based on

EFIE's are preferred so that a specific volume of capillary suction is determined, and the compression shift deviation is determined.

in the present invention are pores, surface area characteristics of> resis15

SHORT

Mod. 71 20,000 · «. »0 / 0β

DESCRIPTION OF DRAWINGS

Figure 1 of the drawings is a photomicrograph. of the interstices of an absorbent EFIE foam material of the type preferably used in the article storage / redistribution component described herein.

Absorbent core fluid figures in the drawings is a depiction of a disposable diaper utilizing an absorbent foam material such as lane fluid storage / redistribution underlying a fibrous one component. A fluid-absorbing / dispensing ampoule-shaped component is removed in a double-layer absorbent diaper core.

Figures 3 and 4 of the drawings represent respectively a top view and a side view of an alternative absorbent core configuration in which a fluid absorption / distribution component is surrounded by a storage / redistribution component.

Foam based fluids.

-6Figures 5 and 6 of

<img file="PT101751B_D0003.tif" />

The drawings represent, respectively, a top view of another alternative embodiment and an absorbent core side view utilizing a fluid storage / redistribution component in the form of separate strips of foam material.

Figures 7 and B of the drawings respectively represent a top view and a side view of yet another alternative core configuration wherein the fluid storage / redistribution component overlaps an underlying fluid absorption / distribution component.

Mod. 71 · 20,000 · χ. Μ / Οβ

Figure 9 of the drawings represents an exploded view of the components of a double layer configuration diaper structure having an hourglass-shaped fluid absorption / dispensing layer overlapping a fluid storage / redistribution layer. absorbent foam with a modified hourglass shape.

PENDERED DESCRIPTION OF THE INVENTION

The absorbent articles of the present invention may be manufactured with the configuration of usable disposable products which are capable of absorbing significant amounts of residual aqueous body fluids (i.e. liquids) such as urine and feces. Articles such as these, for example, may be prepared in the form of disposable diapers, diaper inserts, adult incontinent bags, adult incontinent pads and the like, which are used by incontinent individuals.

F1 ABSORBENT ARTICLES

The absorbent articles considered herein

<img file="PT101751B_D0004.tif" />

Mod. 71 · 20,000 · «. - ΤΟ / Οβ generally comprise three basic structural components. One such component is a liquid impermeable backsheet. At the top of this backsheet is an absorbent core which itself comprises two or more separate components or layers. On top of this absorbent core is a water-impermeable topsheet. The topsheet is the element of the article that is placed closest to or following the user's skin.

Especially preferred absorbent articles of the present invention are disposable diapers. Disposable diaper articles are described in detail in Duncan and Baker, U.S. Pat. 26,151, issued January 31, 1967; Duncan, US Patent No. 3,592,194, issued July 13, 1971; Duncan and Gellert, U.S. Pat. 3,489,148, issued January 13, 1970; Buell U.S. Pat. 3 860,003, issued January 14, 1975; Weisman and Goldman, U.S. Pat. 4,610,678 issued September 9, 1986; Weisman, Houghton and Gellert, U.S. Pat. No. 4,673,402, issued June 16, 1987, and Alemany and Berg, U.S. Patent No. 4,672,408. No. 4,874,735 issued May 30, 19B9, which patents are incorporated herein by reference. A disposable diaper. Preferred for purposes of the present invention comprises an absorbent core; an overlapping or coextensive topsheet with a core face, and an overlapping or coextensive topsheet with the core face opposite the face covered by the topsheet^-. Both the backsheet^-· As the topsheet should preferably be wider than the core, thus providing lateral marginal potions of the backsheet and topsheet extending beyond the core. Often, the backsheet and the topsheet will be fused together in these marginal portions.

<img file="PT101751B_D0005.tif" />

Mod. 71 - 20,000 · χ. · $ Ό / 0β sides. The diaper is preferably in a modified hourglass or hourglass configuration.

The backsheet of the articles described herein may be constructed, for example, from a thin plastic film of polyethylene, polypropylene, or any other flexible material that imparts moisture ingress that is substantially impermeable to water. Polyethylene, having an embossing gauge of approximately 0.0381 mm (1.5 mils), is especially preferred.

The topsheet of the articles described herein may be made in part or completely of synthetic fibers or films comprising such materials, such as polyester, polyolefin, rione, or the like, or of natural fibers such as cotton. In the nonwoven topsheets, the fibers are typically bonded together by a thermal bonding process or by a polymeric binder such as polyacrylate. This sheet is substantially porous and allows fluid to easily pass through it into the underlying absorbent core. The topsheet material will preferably have no affinity for maintaining aqueous carpal fluids in the contact area between the topsheet and the user's skin.

Another suitable type of topsheet comprises the upper flaws formed from liquid impermeable polymeric material such as polyolefins. Such topsheets may have conical capillaries of a certain diameter to allow flow of fluid discharged through the topsheet into the underlying absorbent core of the article.

All topsheets used in the articles of the present invention are relatively hydrophobic compared to the absorbent core of said articles. The construction of the topsheet is generally described in Davidson, US Patent ηθ. 2,905,165, issued September 22, 1959; Del Guercio,

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<img file="PT101751B_D0006.tif" />

U.S. Patent No. 2. 3,063,452, Issued November 13, 1962; Holiday, U.S. Pat. No. 3,537,570, issued December 19, 1963, and Thompson, U.S. Patent No. 4,372,751. No. 3,929,135, issued December 30, 1975, which patents are incorporated herein by reference. Preferred topsheets are constructed from polyester, rione, rione / polyester, polyethylene or polypropylene blends.

ABSORBENT CORE EHENTOS

Mod. 71 - 20,000 · «. · 8/20

An absorbent core, which itself comprises two or more distinct components, zones or layers, and which is preferably flexible, is disposed between the backsheet and the topsheet to form the absorbent articles described herein. This core essentially comprises both a fluid absorption / distribution component and a fluid storage / distribution component. The fluid absorbing / dispensing component is disposed within the absorbent article in such a way as to receive or contact the aqueous body fluid that has been discharged into the absorbent article by the user of the article. The fluid storage / redistribution component in turn is placed within the article to be in fluid communication with the fluid absorption / distribution component. In the context of the present invention, it should be noted that the term fluid means liquid.

To the extent that the absorption / distribution and storage / redistribution components are in fluid communication with one another, they can be placed relative to one another in a wide variety of configurations. Most preferred absorbent cores wherein the absorption / distribution and storage / redistribution components are in a stratified configuration. However, other positional relationships between these components35

-1010 ths are also contemplated. Preferred layer combinations as well as other alternative absorbent core configurations are described in more detail below. The nature of the absorption / distribution and storage / distribution components are themselves described in detail as follows:

ABSORPTION COMPONENT / DISTRIBUTION OF CORE FLUIDS

Mod. 71 · 20,000 · χ. · 90/08

PAD

An essential element of the absorbent core is a fluid absorption / distribution component comprising a porous hydrophilic absorbent structure that has certain fluid treatment characteristics with respect to discharged aqueous body fluids, i.e. urine, which passes over and inwardly. this structure through the top sheet of the article. This fluid absorption / distribution component serves to quickly gather and temporarily maintain such discharged body fluids. Since fluid is often discharged in spurts, the absorption / dispensing component should be capable of receiving rapidly and should preferably also carry fluid, for example by twisting or other mechanisms, from the initial contact point of the fluid to other parts. absorption / distribution component for eventual absorption within the adjacent fluid storage / redistribution component.

As indicated, the main function of the absorption / distribution component is to receive fluids passing through the liquid impermeable topsheet and to transport such fluids to other areas of the absorption / distribution component and eventually to the fluid retaining component, based on storage foam / fluid redistribution from the absorbent core. Accordingly, the fluid absorption / distribution component

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<img file="PT101751B_D0007.tif" />

must be molded from material which has a

Mod. 71 - 20,000 · χ. - TO / Οβ

Fluid Absorption urine protection of at least about 2 ml synthetic per second. More preferably, the fluid absorption / diffusion component will comprise an absorbent material having a Fluid Absorption Ratio of at least about 6 ml of synthetic urine.

Process ratio, per second. For purposes of the present invention, Fluid Absorption may be described further to be determined in more detail thereafter in section surface liquid are made. TEST METHODS | It is considered for synthetic urine to test an internal structure whereby the aliquots of the measurements deposited on absorbent material to be absorbed on that of the absorbent material. THE

Initial Fluid Absorption is the time taken by half aliquot of such test liquid to

Ratio of pride to be absorbed into the absorbent material before the material already contains any of the synthetic urine test liquids.

As indicated hereinbefore, the material comprising the fluid absorption / distribution component of the articles described herein will also preferably be suitably effective in conveying absorbed liquid from one part or region of the absorption / distribution component to another. Such liquid transport will often result from the propensity of the absorbent material of the absorption / distribution component to drain liquid through its structure. Accordingly, a measure of the fluid distribution efficiency of the absorbent material used to form the absorption / distribution component relates to the ability of such an absorbent material to drain synthetic urine vertically.

The effectiveness of the vertical twist can be measured and quantified in a number of ways, but a typical indicator of vertical twist performance is the height at which an absorbent test strip is placed

<img file="PT101751B_D0008.tif" />

«0.1995'

<img file="PT101751B_D0009.tif" />

Mod. 71 - 20,000 · «. 90/08 vertically you will receive synthetic urine from a reservoir within a specified period of time. The fluid absorption / distribution component of the articles described herein will preferably be formed from absorbent material having a 30-minute Vertical Twist Height of at least about 2 cm. More preferably, the fluid absorption / dispensing component will comprise absorbent material having a 30-minute Vertical Twist Height of at least about 4.5 cm. For purposes of the present invention, the Vertical Twist Height is determined by the process described in more detail in the TEST METHODS section below.

Any porous hydrophilic absorbent material that soaks and carries aqueous body fluids to the extent indicated above in terms of Fluid Acquisition Ratio and preferably Vertical Twist Height may be used as, or as part of, the absorption / distribution component of absorbent articles described herein. Often such absorbent materials will be either foam based or fiber based in nature.

One type of absorbent material contemplated for use in or as a fluid absorption / dispensing component in the articles described herein comprises hydrophilic, flexible, open cell polymeric absorbent foam, which has certain structural characteristics. In particular, absorbent foams useful in or as an absorption / distribution component are those having a pore volume of about 2 to 100 ml / g, a specific area of ​​capillary suction surface area of ​​about. 0.2. at 1 m²/ g; a cell size of about 10 to 300 microns and a cavern density of 0.01 to 0.5 g / cm³provided that the values ​​for these parameters are chosen such that the absorbent foams exceed the minimum of the aforementioned Fluid Absorption Ratio. The concepts

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<img file="PT101751B_D0010.tif" />

of foam flexibility, hydrophilicity, pore volume, capillary suction, specific surface area, cell size, and density are described in more detail below in connection with the description of foam materials. foam which are to be used in or as a fluid storage / redistribution component of the absorbent articles described herein.

A more preferred type of absorMod structure. 71 · 20,000 · «. The invention for use in or as a fluid absorption / distribution component comprises non-woven fiber structures which will provide handling characteristics which will be described hereinafter. In particular, non-woven structures molded from hydrophilic or hydrophilic fibers may usefully be used as such or in the absorption / distribution component. The most common structures of this type are fibrous webs formed from cellulosic material, for example wood pulp fibers. Such webs, for example, are typically air storage structures having a drying density of about 0.04 to 0.3 g / cm2.³ and a basis weight of about 0.015 to 0.35 gem² . Non-woven wood pulp fiber air storage webs of this type are known in the art as airfelt. A common type of air felt material molded from southern softwood kraft pulp is marketed by The Procter. 8c Gamble Cellulose Company by the name of Foley Fluff.

□ Other types of nonwoven structures suitable for use as a fluid absorption / dispensing component include structures such as active surfactant treated bonded webs, fused or microfiber blown synthetic webs, shaped webs, shaped webs. in cotton fiber and the like. Structures of this type are described in detail in Latimer et al .; European Patent Application No. EP-A-397,110, issued November 14

-1410

Mod. 71 - 20,000 · «. 90 (08, 1990), incorporated herein by reference.

The most preferred web structures for use as a fluid absorption / distribution component described herein are those which are formed from treated cellulose fibers which impart certain density and drying characteristics to the structures and which are used on appropriate weight bases. More specifically, portions or regions of such a preferred fiber-based absorption / distribution component which encounters body fluids will preferably have an average drying density of at least about 0.30 g / cm3.³insofar as its use as an absorbent and an average density over moisture to synthetic urine saturation (Jayco as will be described below), on a dry weight basis, or less than about 0, 20 g / c³more preferably less than about 0.15 g / cm 2. Even more preferable, the average drying density and the density on wetting to saturation will both be about 0.02 g / cm³ and 0.20 g / cm³most preferably between about 0.02 g / cm³ and about 0.15 g / cm 2. The average drying weight of the portion or region of the preferred fiber-based absorption / dispensing components that meet the discharged fluid will typically range from about 0.001 to about 0.10 g / cm3, more preferably from about 0.001 to about 0.000 g. 0.01 to about 0.08 g / cm^Themore preferably from about 0.015 to about 0.04 g / cm¹ .

All of the above values ​​for density and basis weight are calculated on a dry basis (at moisture equilibrium levels of no more than about 6%). Density and basis weight will generally be substantially uniform across the absorption / distribution component although non-uniform density and / or basis weight and density and / or basis weight gradients are also intended to be circumvented herein. . Thus, the fluid absorption regions of the

<img file="PT101751B_D0011.tif" />

Mod. 71 20,000 · «. Absorption / distribution may contain regions of high or relatively low density and weight based values ​​within the following values.

□ Average drying density values ​​and average density after humidification to saturation with synthetic urine are determined from the dry weight base weight and the dry or wet structure gauge measurement. Both dry gauge and gauge after wetting to saturation are measured under a confirming pressure on the structure of 0.2 psi (1.43 kPa). The average density after wetting to saturation is calculated from the basis weight on drying and the gauge of the saturated layer. □ Saturated structure gauge> is measured after the structure is saturated (under non-confining pressure conditions) with the synthetic urine test fluid and allowed to equilibrate.

Non-woven fibrous absorbent structures which will provide fluid absorption / distribution components having the above density and basis weight characteristics are most preferably constructed essentially from chemically hardened hydrophilic cellulosic fibers. Such cellulosic fibers are typically wood pulp fibers that have been hardened with intrafiber chemical hardener and otherwise processed to be formed into a twisted, twisted configuration. Such highly preferred fluid absorption / distribution component forms thus comprise a nonwoven fibrous web formed from about 50% to 100%, more preferably from about 75% to 100% by weight of the fibers. chemically hardened, twisted, twisted cellulosics from 0% to about 50%, more preferably from 0% to about 25% by weight of a binder for such fibers.

For the purposes of the present invention, the term chemically hardened fibers means any

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AUG'1995

Mod. 71 - 20,000 · «. - 08/20

Fibers which have been chemically treated to increase the hardening of such fibers under both dry and aqueous conditions. Such chemical media include the addition of chemical hardening agents which, for example, coat or impregnate the fibers. Such chemical media also include fiber hardening by altering the chemical structure of the fibers themselves, i.e. by crosslinking the polymer chains with the fibers.

By way of example, polymeric hardening agents which may coat or impregnate cellulosic fibers include: modified cationic starch having nitrogen-containing groups (for example amino groups) such as those sold by the National Starch and Chemical Corp., Bridgewater, NJ, USA; latex; wet full resins such as polyamide-epichlorohydrin resin (e.g., Kymene ™ 557H, Hercules, Inc., Wilmington, Delaware. U.S.A.), polyacrylamide resins (described, for example, in Coscia et al., U.S. Patent No. 3,556,932, issued January 19, 1971 and also, for example, commercially available polyacrylamide marketed by American Cyanamid Co., Stanford, CT, USA under the brand name Parez®, NC, Urea formaldehyde and melamine formaldehyde resins and polyethylenimine resins. A general dissertation on wet strong resins used in the paper art, including those useful herein as fiber hardening agents, can be found in the TAPPI N2 series monograph. 29. Wet Strength in Paper and Paperboard, Pulp and Paper Industry Technical Association (New York_r 1965).

More preferably, the chemically hardened fibers that may be used in the absorption / distribution component will be hardened by chemical reaction. In particular, crosslinking agents may be applied to fibers which, after such application, are compelled to chemically form crosslinking bonds.

-17 intra-fibers. These crosslinked bonds serve to harden the fibers.

Hardened fibers

<img file="PT101751B_D0012.tif" />

to increase by crosslinked bonds in-Individualized form (ie -felpudo) are revealed,

Mod. 71 - 20,000 · «. · 8/20

2530 for example, in Bernardin, U.S. Pat.

224 926, issued December 21, 1965; Chung,

U.S. Patent No. 3,440,135, issued April 22, 1969; Chatterjee, U.S. Patent No. No. 3,932,209, issued January 13, 1976 and Sangenis et al., US Patent No. 2. No. 4,035,147, issued July 12, 1977. More preferred fibers are described in Dean et al., U.S. Pat. No. 4,822,453, Issued April 18, 1989, Dean et al. U.S. Patent ηθ. 4 No. 888,093, issued December 19, 1989, Moore et al., US Patent No. 2. No. 4,898,642, issued February 6, 1990, and Lash et al., U.S. Pat. 4,935,022, issued January 19,

June 1990. All of these patents are incorporated herein by reference. In addition to being hydrophilic, these hardened fibers remain hardened remain hard even after wetting. Thus, the preferred webs manufactured a. from these fibers do not compress, as do webs made from conventional unhardened fibers when wetted. This arrangement thus provides the absorption / distribution layer with the increased ability to receive and distribute fluids from the second and subsequent discharges that are received by the absorption / distribution component.

Suitable crosslinked fiber hardening agents comprise monomeric crosslinking agents which include, but are not limited to, C-dialdehydes.₂- (^ and monoaldehydes C ₂Which have an acid functionality. These compounds are capable of reacting with at least two hydroxyl groups on a single cellulose chain or on nearby cellulose chains on a single

-Ί8IC ('Ç

-4 # ®J995 /

-fiber. Specific cross-linking agents considered for use in the preparation of hardened cellulose fibers

Mod. 71 20,000 - W / β include, but are not limited to, glutaraldehyde, glyoxal, formaldehyde, and glyoxylic acid. Other suitable curing agents include polycarboxylates such as citric acid. Polycarboxylic hardening agents and a process for making hardened fibers using such agents are described in U.S. Pat. No. 596,606, filed October 17, 1990 (corresponds to Canadian Patent Specification No. 2028977-5, Available May 8, 1991), incorporated herein by reference.

For more preferred hardened cellulosic fibers, chemical processing will involve intrafiber crosslinking with crosslinking agents of the above type, while such fibers are in a relatively dehydrated, defibrated (i.e. individualized), twisted twisted condition. The crosslinking effect under these conditions tends to retain its twisted and coiled configuration during use in the absorption / dispensing component of the absorbent articles considered herein.

The extent to which preferred chemically hardened fibers are also twisted and rolled can be quantified by referring to both a twist count fiber and a curl factor fiber. As used herein, the term twist count refers to the number of twisted nodes present in a given fiber length. Twist counting is used as a means of measuring the degree to which a fiber is rotated about its longitudinal axis. The term twist node refers to a substantially axial rotation of 1802. about the longitudinal axis of the fiber, wherein a portion of the fiber (i.e. the knot) appears black relative to the rest of the fiber when viewed under a microscope. transmitted light. □ twisted knot appears black where transmitted light passes through

-19 '1995 an additional fiber wall due to the rotation mentioned above. The distance between nodes corresponds to an axial rotation of 1802. The number of twisted nodes in a fiber length (i.e. the count of a directly determined twisted nodes parameter) is indicative of the degree of twist of the fibers, which is physical to the fiber. Procedures for determining and total torsion counting are described in U.S. Pat. No. 4,898,642, previously reported.

At

Preferred hardened cellulose fibers will have a sum of about 2.7% of average dry fiber twist preferably at least about 4.5 twisted knots per millimeter. In addition, wet twisted fibers should be the average count of at least 1.8, preferably of at least about 3.0, and should also be

Mod. 71 - 20,000 ««. K / 08 prefers to have less millimeter »» by what

Even more preferable should be at least average fiber sum minus about 0.5 knots twisted by the average dry twisted fiber sound average average dry twisted fiber sum

5.5 twisted knots per millimeter, and the dry twisted must have at least 4.0 twisted knots per millimeter and must also have twisted fiber twisted fiber twisted fiber at least 1.0 per millimeter less than its dryness. With drought should millimeter, the most preferred average sum, the sum must have at least the average sum of about

6.5 average knot wet twisted fiber should have at least about 5.0 twisted knots per millimeter and should also have at least 1.0 twisted knots per millimeter less than the average sum of dry twisted fiber

In addition to being twisted, the preferred fibers in the absorbing / dispensing component of the absorbent articles described herein are also coiled. Fiber winding may be described as fractional shortening of the fiber due to kinks, twists and / or bends in the fiber. The length of the fiber winding can be quantified by reference to a winding factor35.

<img file="PT101751B_D0013.tif" />

Mod. 71 - 20,000 · «. 08/20 of the fiber. □ Fiber winding factor, a two-dimensional measurement of winding, is determined by looking at the fiber in a two-dimensional plane. To determine the curl factor, the projected length of the fiber as the longest dimension of a two-dimensional rectangle surrounding the fiber, L *, and the actual fiber length, L 2 are both measured. The fiber curl factor can then be calculated from the following equation:

Winding Factor = (L ^ / L ^) - 1

An image analysis method that can be used to measure L1 and L * is described in U.S. Pat. 4,898,642 referred to above. Preferably the fibers used in the absorbing / dispensing layer of the absorbent articles described herein will have a curl factor of at least 0.30, and more preferably have a curl factor of at least about 0.50.

The degree of hardening, depending on the type and amount of hardening agent (e.g., crosslinking agent) used, the degree of fiber dehydration during curing of the crosslinking agent and

Time and curing conditions affect the fiber's ability to receive fluid and the tendency of the fiber to swell.

Fiber hardening can be quantified by reference to the water retention value^- (VRA) of the hardened cellulosic fibers used in the absorption / distribution components of the absorbent articles described herein. VRA is a measure of the amount of water retained by a fiber mass after substantially all of the water within the fibers has been removed. Another parameter that can be used to characterize the nature of hardened fibers formed by cross-linking fibers in relatively dehydrated form is the alcohol retention value (VRA). □ VRA is a measure of the extent to which a fluid, for example isopropyl alcohol, which does not induce

-21A-.

®H995. ·

Substantial swelling of the fiber is taken by the hardened fibers. The alcohol retention value (VRA) of the hardened fibers is directly related to the extent to which the fibers were swelled with the crosslinking agent solution during the hardening process. Relatively high VRAs mean that the fibers have generally been swollen to a relatively greater extent during crosslinking. Methods for determining WRV and ARV are described in U.S. Pat.

898 642 mentioned above.

Mod. 71 - 20,000 · «. -? 0 / 0β □ WRV for the hardened, twisted and rolled fibers that may be used in the absorption / distribution layers described herein will generally range from about 28% to about 50%. In the above embodiments, the WRV of the fibers may range from about 30% to 45%. Fibers having a WRV within these ranges are considered to provide an optimal balance of non-twisting and induced swelling and fiber hardness.

Preferred hardened cellulose fibers for use in the absorption / distribution component described herein are also those having an ARV (isopropyl alcohol) of less than about 30%. The limitation such fibers have is an ARV (isopropyl alcohol) of less than about 30% is indicative of the relatively dehumidified, relatively dehydrated state of these fibers during the hardening process. More preferably, the ARV (isopropol alcohol) of the

Useful fibers in the absorption / distribution component will be less than less than 27%.

The described fiber fibers having the preferred twisting number, hardened cellulose characteristics herein, WRV factor and ARVs previously indicated may be prepared by internal crosslinking of: the fibers in relatively dehydrated form during or after such fibers are being or have already been dried and defibrated (i.e. fluffed as described in US Patent

-2215

<img file="PT101751B_D0014.tif" />

North American π °. No. 4 89B 642 previously referenced. Alternative processes for preparing hydrophilic chemically hardened fibers are those described in U.S. Pat. 3,224,926, 3,440,135, 3,932,209 and 4,035,147, previously referenced.

For conventional non-hardened cellulosic fibers, the hardened, twisted, crosslinked fibers as described above form sheets or

Mod. 71 10,000 · κ. 90/06 webs with relatively low tensile strength, especially in the non-dried condition. Therefore, in order to facilitate processing and increase the integrity of the absorbing / dispensing component embodiments which are molded from curled, twisted and hardened cellulosic fibers, a binder may be integrally in or on the structure. absorption / distribution layer web surface. This can be accomplished by adding the binder to the hardened fibers prior to the formation of the web (moisture or airborne web formation) by applying the binder (e.g. chemical additive binder) to a moisture web after deposition of the web. web over the forming wire and before drying by applying binder to a dry web (after wetting), By any combination of these binder application methods Binding agents suitable for addition to or combination with cellulosic fibers either by air-laying processes or prior to the formation of the wet web from a pulp paste include, but are not included with, binder limited, a variety of synthetic cellulosic fibrous materials. Such fibrous materials include unrefined, i.e., highly refined, non-hardened cellulosic pulp fibers (i.e. conventional cellulosic pulp fibers), cellulosic fibers that are refined to Canadian Standard Freeness (CSF) of less than about 200 CFS, more preferably from about 200 CFS. 100 CSF to about 200 CSF and

-23 / f. y

Mod. 71 - 20,000 · «. · Μ / Οβ high surface area cellulosic material such as expanded cellulose fibers. Fibrous binding agents of this type are described in more detail in U.S. Patent Application no. 07 / 625,776, filed December 17, 1990 and incorporated herein by reference.

Other types of binding agents that may be used in combination with the hardened cellulosic fibers in the absorption / distribution component include additive binding agents such as resins, latex materials, modified starches, and thermoplastic binding agents. These types of chemical additive binders are also described in more detail in U.S. Pat. Series 07 / 625,776 mentioned above. As indicated, the binder, if present, may comprise up to about 507% by weight of the absorption / distribution component. More preferably, the binder will comprise from about 17 to 257% by weight of the absorption / distribution component.

Preferred nonwoven fibrous absorption / distribution component structures comprising hardened, twisted and rolled cellulosic fibers, with or without binding agents, may be prepared by either air or wet laying to form webs of any given desired density and weight. of base. Hardened fiber-containing structures for use in the present invention may be air-laid according to techniques well known to those skilled in the art of air-laying cellulosic fibers. In general, air settling can be accomplished by measuring an air flow containing the hardened fibers, in the substantially dry condition, over a wire mesh and optionally compressing the resulting web to the desired density. Alternatively, the fibers may be air laid to the desired density without compression. Web based on buy 30

-24-4 itd 1995

Mod. 71 · 20,000 ««. · 20/06 address at least about 50 * /. hardened cellulosic fibers as described above and may comprise up to and including 1007% of such fibers. The web may optionally contain bonding media as described below or other optional components such as ingredients that modify the fluid handling properties of webs (e.g. hydrophilic surfactants), or improved absorbency (e.g. polymeric gelling agents) and the like.

Preferred structures of the nonwoven fibrous absorption / distribution component comprising hardened, twisted, twisted cellulosic fibers may be prepared by wet laying. The techniques for wet laying of cellulosic fibrous material to form sheets such as dry flap and paper are well known in the art. These techniques are generally applicable to the wet laying of the hardened fibers to form the wet laid sheets useful in the present invention. Suitable wet laying techniques include sheet handling and wet laying using papermaking machines as disclosed, for example, in Sanford et al., U.S. Patent ηθ. No. 3,301,746 issued January 31, 1967. Due to the behavior of hardened fibers, particularly their tendency to flocculate in aqueous pastes, certain processing modifications, described below, are preferably implemented upon wet laying with papermaking machines.

In general, wet laid webs can be fabricated by depositing an aqueous slurry of fibers on a foraminous forming net, which separates the wet laid slurry to form a wet web, and drying the wet web. Preferably, the aqueous wetting fiber pastes will have a fiber consistency of about 0.057. and about 2.07., preferably between about

<img file="PT101751B_D0015.tif" />

from 0.05 to about 0.2%, based on the total weight of the pulp. Slurry deposition is typically performed using a device known in the art as a headbox. The headbox has an opening, known as a notch, for releasing the aqueous fiber slurry over the foraminous deformation net. The foraminous deformation net is often referred to in the art as a Fourdrinier web. The Fourdrinier web can be of construction and mesh size used for dry flap or other papermaking process. Preferably, mesh sizes of 70 to about 100 (standard sieve scale) are used.

Tyler). (All mesh sizes referred to herein should be based on the standard Tyler sieve scale, as otherwise specifically indicated).

Do not be

Conventional Headbox Models Known in the Art

Mod. 7) - 20,000 · χ. - 08/20 for the used flap formation. Available boxes include, per dried boxes. The other dry fence increases and the fabric sheet may be commercially suitable head eg fixed ceiling, twin net, and drum forming head.

Once formed, the wet web is separated, and separation can be carried out with vacuum box devices.

fiber consistency

45% based on suction weight

Typically, the

X to between about 8% separation and total wet web of about 22%. The separation preferably between about 8% and

I up to consistencies above about 22% - may require wet pressure and is less preferred. After dehydration, the web may be, but not necessarily, transferred from the fortification net to the drying facility which transports the web to the drying apparatus. The drying fabric is preferably thicker than the forming net to increase drying efficiency. 0 The drying fabric is preferably about 30% to about 50% open area and about 15% to about 25% knotted area, such as a 31 X 25 3S (satin-like) fabric

<img file="PT101751B_D0016.tif" />

Mod. 71 · 20,000 · 90 / 0β which has been sanded to increase the knot area to within the preferred range. Wet microcontraction is preferably implemented during transfer from the forming network to the tissue. Wet microcontraction can be performed by running the forming net at a speed that is about 57 ° to about 207 ° faster than the speed at which tissue is to be slid.

Drying may be performed with a thermal fan drier or vacuum device such as a suction box, although thermal fan drier drying is preferred. The wet laid webs are preferably dried to completion (generally to fiber consistency between about 907 ° C and about 957 °) by the thermal fan dryers. Fan drying is regarded as a method of efficiently drying hardened fiber webs due to the high vacuum volume of the steels. Steam drum drying apparatus known in the art, such as Yankee drum dryers, may be used, but are less preferred. Drum dryers are believed to be less efficient at drying webs of hardened fibers and can also compact the webs! The dried webs are preferably unruffled.

Web structures containing curled, twisted, hardened, air or wet laid cellulosic fibers may be processed within absorbent cores of the absorbent articles described herein in a more fully described manner below. This process will preferably involve associating the nonwoven web of hardened cellulosic fibers as an absorbing / dispensing layer that overlaps with a foam-based absorbent structure forming the fluid storage / redistribution layer component of the absorbent articles described herein. .

-2735

0^

COMPONENTS OF

FLUID

OF

Mod. 71 - 20,000 x. 90/08

ABSORBENT CORE

In addition to the upper fluid absorption / distribution component, the absorbent cores of the absorbent articles described herein also essentially contain a fluid storage / redistribution component comprising an absorbent foam polymeric material. This fluid storage / redistribution component is maintained in fluid communication with the fluid absorption / distribution component such that urine or other aqueous body fluids present in the absorption / distribution component may be absorbed by the foam material. polymer in the fluid storage / redistribution component.

Polymeric foams that are used in the fluid storage / redistribution component can generally be characterized as structures that result when a relatively monomer-free gas or relatively monomer-free liquid is dispersed as bubbles in a monomer-containing polymerizable liquid, followed by polymerization. of the polymerizable monomers in the monomer-containing liquid surrounding the bubbles. The resulting polymerized dispersion may be in the form of a porous solidified structure which is an aggregate of cells whose boundaries or walls comprise polymerized solid material. The cells themselves contain the relatively monomer-free gas or relatively monomer-free liquid that, prior to polymerization, formed bubbles in the liquid dispersion.

As will be described in more detail below, the preferred polymeric foam materials useful as absorbents in the absorbent core fluid storage / redistribution component are those prepared by polymerizing a particular type of emulsion.

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<img file="PT101751B_D0017.tif" />

Mod. 71 · 20,000 · χ. 08/20 oil in water. Such an emulsion is formed from a relatively small amount of a polymerizable monomer-containing oil phase and a substantially larger amount of a relatively monomer-free water phase. The relatively monomer-free discontinuous internal water phase thus forms the dispersed bubbles surrounded by the monomer-containing polymerizable oil phase. Subsequent polymerization of the monomers in the continuous oil phase forms the cellular foam structure. Aqueous liquid remaining in the foam structure formed in the polymerization may be removed by pressing and / or drying the foam.

Polymeric foams, including preferred foams prepared from oil-in-water emulsions described herein, may be of relatively closed cell or relatively closed cell nature, depending on the time and / or extent to which cell walls or boundaries, that is, the cell windows are filled or loaded with polymeric material. The polymeric foam materials useful in the absorbent articles and structures of the present invention are those having relatively open cells where the individual foam cells are for the most part not completely isolated from each other by the polymeric material of the cell walls. Thus, cells in such substantially open cell foam structures have intercellular openings.

windows or windows that are large enough to allow rapid transfer of fluid from one cell to another within the foam structure.

In substantially open cell structures of the type useful in the present invention, the foam will generally have a cross-linked nature with the individual cells being defined by a plurality of mutually linked three-dimensional branched webs. The fibers of the polymeric material constituting the branched webs of the open cell foam structure can be referred to as

-2910 ι 7 /

/

Mod. 71 - 20,000 · «. · 90 / 0β as supports. For the purposes of the present invention, a foam material is open cell if at least ΘΟ7. cells in the foam structure are in fluid communication with at least one adjacent cell. Alternatively, a foam material can be considered to be substantially open cell if it has an available pore volume, as will be described below, which exceeds the minimum value for this parameter also given below.

In addition to being open cell, the polymeric foam absorbents essentially used in the Fluid storage / redistribution component of the articles described herein are hydrophilic in nature. The foams described herein should be sufficiently hydrophilic to allow the foam to absorb aqueous body fluids in the amounts specified below. As will be discussed below with respect to preferred foam types and foam preparation methods, the inner surfaces of the foams described herein may be rendered hydrophilic as a function of the particular monomers chosen for use in the preparation of polymeric foams as a function of residual hydrophilizing agents. left in the foam structure after polymerization or by virtue of the foam treatment processes chosen after polymerization, which may be used to alter the surface energy of the foam forming material.

The extent to which foam structures such as those used in the present invention are. Hydrophilic compounds can be quantified by reference to the adhesion force exhibited by such foams in contact with an absorbable test liquid. Adhesion strength is defined by the formula

AT = COS 0

-30 Friend:

Mod. 71 -20,000 · «.- 90/06 /

where AT is the bond strength in dynes / cm;

Y is the surface tension of a test liquid absorbed by the foam material in dynes / cm;

is the contact angle in degrees between the surface of the foam polymer material and the vector that is tangent to the test liquid at the point where the test liquid contacts the foam polymer surface.

For any hydrophilic foam material considered, the adhesion strength exhibited by the foam can be determined experimentally using a process wherein the load weight of a test liquid, for example synthetic urine, is measured from a size foam sample. known characteristics and specific surface area of ​​capillary suction. Such a process is described in more detail in the TEST METHODS section below. Foams that are useful as absorbents in the fluid storage / redistribution component of the present invention are generally those which have been rendered hydrophilic to the extent that they exhibit an adhesion force of about 15 to 65 dynes / cm, more preferably between about 20 to 65 dynes / cm as determined by the synthetic urine capillary suction load having a surface tension of 65-5 dynes / cm.

In addition to being open cell and hydrophilic, the polymeric foam materials useful in the fluid storage / redistribution compound of the absorbent articles of the present invention are those which have yield, for example fluid control, properties which make such foams especially suitable and useful as absorbents for aqueous body fluids that are introduced into the fluid storage / redistribution component. These fluid control characteristics are in turn related and determined by the structural and mechanical characteristics of the absorbent foam materials.

<img file="PT101751B_D0018.tif" />

used herein. Foams that have a specific set of structural and mechanical properties can in fact be used as absorbents in the fluid storage / redistribution component because they will provide the necessary fluid treatment characteristics.

Mod. 71 · 20,000 ex. - 08/20

I) Fluid Treatment and Absorption Characteristics

The characteristics of treatment and absorbance of fluids that have been observed to be very relevant for making absorbent foams suitable for the fluid storage / redistribution component are: A) the equilibrium of the foam absorbent capacity, especially under pressure, B) the vertical twisting ratio of fluid through the foam structure, C) the foam absorbent capacity at specific reference twisting heights, and D) the capacity of the absorbent foam structures for draining (partitioning) fluid from competing absorbent structures such as the absorption / distribution component with which the foam will be in fluid communication. Each of these features is described in more detail as follows:

A) Absorbent Capacity and Absorbent Capacity Under

Pressure

The absorbent capacity is the total amount of test fluid (synthetic urine) that a given foam sample absorbs within its cellular structure per unit mass of solid material in the sample. Pressure absorbing capacity refers to the amount of this fluid kept under unconfined pressure (free capacity) that the foam will retain within its cellular structure when the foam sample is subjected to compressive force. Such

-32-4 «501995 /

Mod. 71 * 20,000 · 90/08 Absorbent capacity measurements are calculated here for equilibrium, that is, after the foam sample has been allowed to acquire and / or maintain all fluid which it may maintain during any period of time. as long as necessary to form a foam sample completely saturated with the test liquid. Foam materials which are especially useful as absorbents in the fluid storage / redistribution component of the absorbent articles herein considered as diapers will exceed a minimum free absorbent capacity and also exceed a minimum absorbent pressure capacity.

Using the process described in more detail below in the TEST METHODS section, the free absorbing capacity and pressure absorbing capacity can both be determined for any foam sample by a gravimetric analysis technique. In such a technique, a foam sample of specified size and weight specified is placed in a test fluid (synthetic urine) and allowed to absorb the test fluid to equilibrium. After removal of the saturated fluid sample, the amount of fluid retained per gram of foam, i.e. the measured free capacity, is then calculated. This saturated foam sample is then subjected to the prudent molding phase to increase the compressive pressure in various increments with the squeezed fluid being drained out in each phase. The amount of fluid retained in the sample at each pressure load up to about 1.0 psi (6.9 kPa) is determined gravimetrically.

To be particularly useful for absorbing urine in the fluid storage / redistribution component, the foam absorbent material should have a free balance capacity of at least about 12, and preferably at least about 20 ml of synthetic urine per gram of Dry foam material. In addition, the capacity

<img file="PT101751B_D0019.tif" />

such foam materials under a limited pressure of about 0.74 psi (5.1 kPa) maintained for 15 minutes at

3720 it should be at least about 57%, more preferably at least about 207%, of the free balance capacity of such foams.

B) Vertical Twist Yield

Mod. 71 - 20,000 · χ. · TO / Οβ

Yet another fluid treatment attribute of absorbent foams useful in the fluid storage / redistribution component relates to their ability to move relatively rapidly or to transport acceptable amounts of carpal fluid through their foam structures. Vertical twisting, i.e. fluid twisting in the opposite direction from the gravitational force, is a measure of the especially desirable fluid transport performance attribute for the absorbent storage / redistribution foam materials described herein. this is due to the fact that such materials are often used in storage / redistribution components such that the absorbed fluid must be moved, i.e. redistributed, into the foam from a relatively lower position to a relatively higher position within. absorbent core storage / redistribution component. It is believed that the vertical twist contributes to this propensity for redistribution and fluid from the foams that are useful for the purposes of the present invention.

Vertical twisting performance is related to the magnitude of the driving force: the capillary suction that moves the liquid through the foam and keeps it in the foam structure. The foam characterizing parameters that refer to the vertical twisting propensity thus provide an indication as to how the foams preferred herein will behave as absorbents.

<img file="PT101751B_D0020.tif" />

storage / redistribution component in absorbent articles. For the foam components of the storage / redistribution component of the present invention, the propensity for fluid twisting can be quantified by reference to both a vertical twist ratio test and a vertical twist absorbent capacity test.

1) Vertical Twist Ratio

Mod. 71 - 20,000 · κ. · W / Οβ vertical ratio test measures the time it takes a colored test liquid (eg synthetic urine) from a reservoir to travel a vertical distance of 5 cm through a foam test strip of the specified size when The test is performed at 37 ° C. Such a vertical twist ratio test is described in more detail in the TEST METHODS section below. To be especially useful for absorbing urine in the storage / redistribution component, the foam absorbents of the storage / redistribution component will preferably have a vertical twisting ratio of 5 cm of no more than about 30 minutes when draining synthetic urine ( More preferably, the preferred foam absorbents of the present invention; they will have a vertical twist ratio of 5 cm of no more than 5 minutes when absorbing synthetic urine2) Vertical Twist Absorbing Capacity Vertical twisting absorber capacity test 30 is performed in conjunction with the vertical twisting ratio test. The absorbent capacity of the vertical twist measures the amount of test fluid per gram of absorbent foam that is drained to each inch of vertical section of the same standard size of 35.

<img file="PT101751B_D0021.tif" />

-4 &lt;$ 01995 Standard foam sample used in the vertical twist ratio test. Such determination is generally made after the sample has been allowed to vertically absorb the test fluid to equilibrium (for example, after about 18 hours). Like the vertical absorption rate test, the vertical drainage absorbency test is described in more detail below in the TEST METHODS section.

To be especially useful for absorbing

Mod. 71 · 20,000 <String>. · 90 / ϋβ urine in the storage / redistribution component, the preferred foam absorber storage / redistribution component of the present invention will generally have a vertical twisted absorptive capacity such that at 11.4 cm (4.5 inches) in height. Vertical absorption, the epsuma strip and test has an absorbent capacity of at least about 10 ml synthetic urine (65 + 5 dynes / cm) per gram of absorbent foam. More preferably, the preferred storage / redistribution component foam absorbers will have a vertical suction absorbent capacity at 11.4 cm (4.5 inches) of about 20 to 45 ml synthetic urine per gram of foam. .

C) Separation

It is, of course, desirable to foam them.

storage / redistribution components of this¹invention have a propensity to remove body fluid from the foam structure from other absorbent article components such as the fluid absorbing / distributing component which are also absorbing such fluids. Other components of absorbent articles are known in the art as separation. The concept of separation and some processes for determining the separation yield are described, for example, in Weisman / Golman. Patent nnr + i »-₃mori cana no. 4

<img file="PT101751B_D0022.tif" />

610 678, issued September 9, 1966. When tested for separation yield using procedures similar to those described in U.S. Pat. No. 4,610,678, the absorbent foam structures of the fluid storage / redistribution component must have particularly desirable fluid separation characteristics relative to the absorbent materials used in the fluid absorption / distribution component of the articles herein.

II) Structural Characteristics of Preferred Foams of

Storage / Redistribution Component

Mod. 71 - 20,000 · «. 90/08

<img file="PT101751B_D0023.tif" />

Some specific interrelated and interdependent properties of foam absorbers have been identified as being highly desirable in foams that are especially suitable for absorbing aqueous body fluids in the storage / re-distribution component of the absorbent articles herein. It should be understood that the storage / redistribution component foam materials may have structural properties that are different from those specified hereinafter. at some point prior to contact between the foam and aqueous body fluid to be absorbed into the storage / redistribution component. For example, during your. manufacture - shipment_T storage, etc., the foams described herein should have a pore volume , specific surface area, density values ​​and / or cell size outside the ranges given below for these parameters. such absorbent foam structures are, however, still within the scope of the present invention if they subsequently resist physical or rheological changes so that they then have the values ​​specified below for these structural properties at least at some point during the period. of contact

-3716

<img file="PT101751B_D0024.tif" />

between the foam and the aqueous body fluid in which it is in the storage / redistribution component. The various structural properties of the preferred foam absorbents for use in the storage / redistribution component of the articles described herein can be summarized as follows:

A) Pore Volume

Mod. 71 - 20,000 x. - 90/06

25.

Pore ​​volume is a measure of the volume of the openings or cells in a porous foam structure per unit mass of solid material (polymer structure plus any residual solids) that were the foam structure. Pore ​​volume may be important in influencing a number of yield and mechanical characteristics of the absorbent foams described herein. Such mechanical and performance characteristics include the absorbent capacity of the body's aqueous fluid foams, the extent and rate of fluid distribution within the structure by absorbing fluids absorbed from one part of the absorbent foam to another, and exhibited foam e. Compression characteristics foam deflection.

Pore ​​volume may be determined by any suitable experimental method which will give an accuracy indication of the actual pore volume of the structure. Such experimental methods will generally involve the measurement of. The volume and / or mass of a test liquid that can be introduced into the foam structure and is therefore representative of the volume occupied by the open foam cells. For this reason the foam pore volume parameter useful in the fluid storage / redistribution component considered herein may also be referred to as the available pore volume.

A conventional way to experimentally determine the available pore volume involves

-3815

<img file="PT101751B_D0025.tif" />

Mod. 71 20,000 · «. - 08/20 introducing a low surface tension liquid such as isopropanol into the foam structure from outside the foam structure. A process for determining available pore volume using isopropanol is shown as follows in the TEST METHODS section, however it should be understood that liquids and alternative test procedures may also be used to determine available pore volume.

The pore volume of the absorbent foams useful in the fluid storage / redistribution component can be influenced and controlled by adjusting a number of foam composition and processing characteristics. For example, with the preferred EFIE emulsion-based foam described herein, these pore volume influencing characteristics may include the water-in-oil ratio of the EFIE emulsion, type and amount of water phase electrolyte using, type and amount of oil phase emulsifier used, post-polymerization foam compression steps for effecting the washing and / or densification of the foam and the degree of recovery of the polymerized foam structure after the compression steps.

Foam materials used in the fluid storage / redistribution component of the articles described herein will generally have a pore volume of about 12 to about 100 ml / g; more. preferably from about 20 to 70 ml / g and more preferably from about 25 to 50 ml / g. Such pore volume ranges are intended to be an inclusive definition of the theoretical pore volume for the foams contemplated by the present invention. Thus, if any experimental method that can reasonably be expected to give theoretically approximate pore volume measurements provides values ​​within the following ranges, then the foam materials tested by either method will be within the scope of the present invention.

<img file="PT101751B_D0026.tif" />

B) Capillary Suction Specific Surface Area.

Mod. 71 - 20,000 · «. rO / ΰβ

Another structural feature of preferred foam materials suitable for use in the storage / redistribution and fluid component is a certain capillary suction specific surface area. The specific surface area of ​​capillary desiccation is generally a measure of the surface area accessible to the test net of the polymer network which forms a particular foam per unit mass of the foamed material by volume (polymer structural material plus residual material). solid). The specific surface area of ​​capillary suction is determined by both the dimensions (i.e. the diameter of the cell units in the foam, and the size (length, width and thickness) of the struts that form such cell units. Capillary suction specificity is thus a way of quantifying the total solid surface provided by the foam networks to the extent that such a surface participates in absorbance.

The specific surface area of ​​capillary suction of an open cell foam structure such as the absorbent foams of the storage / redistribution component in the foam characteristic that influences the capillarity (or capillary suction) exhibited by the foam has been found. that the capillarity of. The foam should be controlled and chosen so that the storage layer of the foam materials described herein has sufficient capillarity to provide acceptable fluid retention while still allowing some transport, for example by absorption, of the fluid to occur within the foam. warehouse component foam structure—

-40ObΛ50.1-995 '

<img file="PT101751B_D0027.tif" />

Mod. 71 · fluid design / redistribution. Adjustment of the capillary suction specific surface area, adjustment of the capillary suction specific surface area, as well as the control of the hydrophilicity of the polymer surfaces is thus the means to provide the required degree of capillarity for the absorbent foams. storage / redistribution component of the present invention. Relatively high capillary suction specific surface area foams provide the very desirable combination of high capacity (and low density) and high capillarity. The high specific surface area is a consequence of the fineness of the struts constituting the foam structure. . ,

The specific capillary suction surface area of ​​the storage / redistribution component foams is influenced and controlled by adjusting many of the same composition and processing parameters that affect the foam pore volume. For EFIE emulsion based foam, these parameters include the water-in-oil ratio of the EFIE emulsion, the type and amounts of monomers, emulsifiers and electrolytes used in the EFIE emulsion. Process parameters that affect the specific surface area of ​​capillary suction include mixing energy and temperature.

As noted, for purposes of the present invention, the specific surface area of ​​any foam material considered to be contemplated for use as or in the fluid storage / redistribution component of the absorbent articles described herein may and will normally be. determined by a process involving the principle of capillary suction. In such a process, the specific capillary suction surface area is determined by measuring the amount of capillary charge of a low surface tension liquid (e.g., ethanol) that occurs within a foam sample having

-4110

<img file="PT101751B_D0028.tif" />

Mod. 71 - 20,000 · «. · 90/08

<img file="PT101751B_D0029.tif" />

I mass and known dimensions. A detailed description of such a process for determining the specific surface area by the capillary suction method is shown in the TEST METHODS section below. Any reasonable alternative method for determining the specific surface area of ​​capillary suction may also be used.

Open cell absorbent porous foams that are useful in the fluid storage / redistribution component are generally those which are prepared to have certain capillary suction specific surface area characteristics. In particular, the storage / redistribution component foams described herein should have a specific capillary suction surface area ranging from about 0.5 to 5.0 m.²/ g, most preferably from about 0.75 to 4.5 m²/ g, most preferably between about 1.0 to 4.0 m / g. Hydrophilic foams having such specific capillary suction surface area values ​​have been found to generally have an especially desirable balance of absorbent capacity, fluid retention, and fluid absorption or distribution characteristics for aqueous body fluids such as urine. in order to make such foams particularly useful in the fluid storage / redistribution component.

Supplementary or Alternate Structural Characteristics

Two additional characteristics of the storage / redistribution component absorbent foams considered herein are related to the pore volume and capillary suction specific surface area and which may be used as an additional or alternative means of characterizing the preferred foams of the product.

The storage / redistribution component of the present invention is the density of the foam and the average size or diameter of the cells making up the foam. Each of these two additional / alternative structural features is described as follows:

1) Foam Density

Mod. 71 · 20,000 · &lt;. - Μ / 0β

The density of the foam materials of the storage / redistribution component considered herein, such as pore volume and capillary suction-specific surface area, may influence a number of performance and mechanical characteristics of these foams. These include the absorbent capacity for aqueous body fluids, extent and rate of fluid distribution within the foam and characteristics of foam compression flexibility and deflection. Also importantly, the density of the epsuma absorbent materials of the storage / redistribution component considered herein may determine the cost effectiveness of the absorbent articles considered herein.

The foam density in grams of foam material cubic centimeter of air foam volume is specified herein on a dry basis. Thus, the amount of aqueous liquid absorbed, for example the residual liquid that may be left in the foam, for example after EFIE emulsion polymerization^-washing and / or hydrophilizing is neglected in the calculation and expression of foam density. The foam density as specified herein does not, however, include residual solid material such as electrolyte, emulsifying, hydrophilizing, etc. agents in the polymerized foam. Such residual material can in fact contribute significant mass to the foam material.

Any suitable gravimetric process that

-43^/16411995

<img file="PT101751B_D0030.tif" />

Mod. 71 - 20,000 · «. · 90/06k

can provide a mass determination of solid foam material per unit volume of the foam structure may be used to measure foam density. For example, an ASTM gravimetric process described more fully in the TEST METHODS section below is a method that can be used for density determination. For these situations, where foam sample preparation processes (drying, aging, pre-bending, etc.) may inadvertently change density measurements, alternate density determination tests may also be used. Such alternative methods, for example, may include gravimetric density measurements using a test liquid absorbed within the foam material. This type of density determination method may be useful for characterizing very low density foams such as foams considered herein where the drying density approximates the inverse of the pore volume of the foam. CVer Chatterjee, Absorbency, Textile Science and Technology, Vol. 7, 1985, p-411. As with the pore volume and the specific surface area of ​​capillary suction, the following foam density ranges are to be considered exclusive, ie they are designed to take into account the density values ​​that can be determined by any rare experimental test method.

The foam absorbers of the storage / redistribution component of the present invention will preferably have varying dry base density values. from = about 0.01 to Ο g / cm³more preferably from about 0.014 to about 0.05 g / cm³and most preferably between about 0.02 to 0.04 g / cm³, at the time such epsuma absorbers find aqueous body fluids to be absorbed. The density of the foam materials of the storage / redistribution component may be

-44Mod. 71 · 20,000 · «. - w / οβ

<img file="PT101751B_D0031.tif" />

<img file="PT101751B_D0032.tif" />

is adjusted within the following limits by controlling many of the parameters of the same foam composition and processing hereinafter for pore volume adjustment. The density of the absorbent foam structures of the storage / redistribution component considered herein need not be uniform across the entire structure. Some portions or zones of the foam structure may have relatively higher or higher densities than other portions or zones thereof.

<img file="PT101751B_D0033.tif" />

Another alternative or additional structural feature of the storage / redistribution component absorbent foams considered herein, which is not an essentially established parameter but which may be useful in defining the preferred foam materials of the storage / redistribution component of the present invention, is the size. Cell Foam cells, and especially cells which are formed by polymerization of a monomer-containing oil phase surrounding the relatively monomer-free water phase bubbles, will often be: spherically deformed. The size or diameter of such substantially spherical cells is thus yet another parameter commonly used for characterization of foams in general. thus, as for, characterize certain preferred absorbent foams of the type used in the present invention as the cells in a given foam sample. polymeric no. they will necessarily be approximately the same size, an average cell size, ie the average cell diameter, will be specified several times.

As with foam density, capillary suction surface area and pore volume, cell size is a foam parameter that can

-4510

<img file="PT101751B_D0034.tif" />

also impact on a number of important mechanical and yield characteristics of the absorbent foam material of the storage / redistribution component of the present invention. Since cell size is a factor, along with the specific surface area of ​​foam capillary suction, pore volume and hydrophilicity, which determines foam capillarity, cell size is a parameter of the foam structure that can directly affect both the absorbent capacity and internal fluid transport properties of the storage / redistribution component foam absorbers considered herein. Cell size may also affect the mechanical properties of the foams of the

Mod. 71 - 20,000 οχ. · 90/08 storage / redistribution component considered herein including characteristics such as flexibility and strength and recovery from compression deviation.

A number of techniques are available to determine the average cell size in foams. These techniques include mercury porosimetry methods that are well known in the art. The most useful technique, however, for determining cell size in foams involves the simple photographic measurement of a foam sample. Figure 1 of the drawings, for example, is a photomicrograph of a fracture surface of an EFIE foam absorbent structure. useful in the present invention. Overlaid on the photomicrograph is a scale representing a dimension of 10 microns. Such a scale can be used to average cell size through an image analysis process. Photomicrograph image analysis of foam samples is, in fact, a commonly used analytical tool that can be used to determine the average cell size of the storage / distribution component foam structures considered herein. Such a technique is described in more detail in Edwards et al., US Pat.

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01995/

Mod. 21 · 20,000 · «. · 90/0 'cane no. No. 4,788,225, issued November 29, 1988. This patent is incorporated herein by reference.

As determined by direct photographic measurement, foams useful as absorbent for aqueous body fluids in the storage / redistribution component according to the present invention will preferably have an average cell size ranging from about 5 to 100 microns. More preferably, the cell size ranges from about 10 to 90 microns. More preferably, the cell size will be between about 15 to 80 microns.

The size or diameter of the cells in the storage / redistribution component foam absorbers can be influenced and controlled by the variation of the same type of foam composition and processing characteristics that influence the specific capillary suction surface area and volume. Available pore. For preferred RFIE-based foams, these primarily include those factors that determine the size of the water phase bubbles in the EFIE emulsion precursor of the polymeric foam structures considered herein. Thus, cell size may vary by adjusting the ratio of the EFIE emulsion, and the type and amount of emulsifier to form the EFIE emulsion. The cell size can also be changed by simply compressing the solid foam structures after they have been prepared.

As indicated above, cell sizes in the absorbent foams of the storage / redistribution component of the present invention will not be generally uniform and thus an average cell size for any foam sample or zone considered in a foam sample pruning should be calculated. It is, of course, possible to use absorbent foams in the fluid storage / redistribution component which have separate, identifiable zones of larger or larger average cell size.

<img file="PT101751B_D0035.tif" />

rslativaments smaller.

III) Mechanical Characteristics

Mod. 71 · 20,000 x. W / 08

Absorbent foams having suitable polymeric compositions and the structural characteristics described hereinabove will generally have mechanical properties, for example, compressive deviation resistance, flexibility, compression deviation recovery, integrity, softness, etc., which render such foam. suitable for use in the fluid storage / redistribution component of absorbent articles such as disposable diapers. Within the aforementioned structural limitations, however, it is possible to select some parameter combinations and / or some foaming techniques and conditions that provide storage / redistribution component foam absorbers which exhibit especially desirable mechanical properties. The specific, somewhat related mechanical properties that have been identified as contributing to the realization of absorbent foams especially suitable for use in incontinence control absorbent articles can be summarized as follows:

A) Resistance to Compression Deviation

The most important mechanical characteristic of polymeric foams used in or as a fluid storage / redistribution component is the strength of the foam absorber as determined by its resistance to compression drift. The compressive deflection resistance exhibited by the storage / redistribution component foam absorbers described herein is a function of the elastic modulus of the polymer and the dimensions of the strands forming the foam network. □ elastic modulus of the supports

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Mod. 71 · 20,000 ·>. W / Οβ is determined by: a) the polymeric composition of the supports and b) the extent to which the supports may be plasticized by residual material, eg emulsifiers, water-phase synthesis or agents. subsequently added hydrophilization compounds left in the foam structure after processing.

To be useful as absorbent structures in absorbent articles such as diapers, the absorbent foam materials of the storage / redistribution component must be suitably resistant to the deformation or compression by forces encountered when such absorbent materials are engaged in fluid absorption and retention. Foams that do not have sufficient foam strength in terms of compressive deviation resistance may be able to acquire and store acceptable amounts of body fluid under storage / redistribution behavior under no-load conditions but will too easily give such fluid under the condition. pressure caused by movement

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<td>dog - THE</td><td colspan="2">resistance to</td><td>to</td><td>compression deviation</td>

exhibited by the foam absorbents used in the fluid storage / redistribution component of the present invention can be quantified to determine the amount of stress produced in a saturated foam material sample maintained under a certain confining pressure over a specified period of time. For purposes of the present invention such measurements may be made on one. standard size foam (cylinders that are 0.8 'cm thick and a circular cross-sectional area of ​​6.5 cm²). Such samples are saturated with synthetic urine having a surface tension of 65 + dynes / cm and are then subjected to a limiting pressure of 5.1 kPa over a period of 15 minutes at a temperature of 37 ° C. The amount

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<img file="PT101751B_D0036.tif" />

Mod. 71 20,000 · «. · W / Οβ tensile strength produced in such a test is reported as a percentage of the original sample thickness that the compressed sample thickness represents. The method for performing this particular type of test to quantify compressive drift strength is shown in more detail below in the TEST METHODS section.

The absorbent storage / redistribution component foams useful herein are those which have a compressive deflection resistance such that a limited pressure of 5.1 kPa produces a tension of about 57 to 957. compression of the foam structure when it has saturated to its free absorbent capacity with synthetic urine having a surface tension of 65 ± 5 dynes / cm. Preferably the voltage produced under such conditions will range from about 57 ° C. 757, more preferably from about 57 to 507. For the preferred EFIE storage / redistribution component foams of the present invention, the compression bias resistance may be adjusted to stress values ​​within the following ranges by appropriate sealing monomer, comanomer and crosslinker types and concentrations in combination with the selection of appropriate emulsion formation and polymerization and emulsion conditions and techniques. Thus, such preferred foams may be formed from materials with large elastic moduli sufficient to provide adequate strength for compression deviation even though such foams have a density lower than very thin supports to provide a high specific surface area.

B)

F1ex i BIity

The absorbent foams of the storage / redistribution component of the present invention should be sufficiently flexible that they can be

<img file="PT101751B_D0037.tif" />

<img file="PT101751B_D0038.tif" />

absorbent products that will conform to the body shape of the wearer. The characterization of the storage / redistribution component absorbent foams herein considered to be flexible, therefore, means that these foams may be deformed or curved to the extent necessary for use in such absorbent articles without significant damage to their structural integrity or significant loss of their properties. absorbent properties.

Preferred storage / redistribution component absorbent foams should also be sufficiently flexible to withstand the deformation that is encountered in processing, packaging, compressive forces or during preparation, and storage of absorbent articles containing such foam materials. Disposable diapers are generally packaged and marketed in a folded condition where the diaper core is

Mod. 71 · 20,000 · &lt;. · 90/08 bent in two directions, ie salt. Disposable diapers are cialised in the form of piles which are contained and surrounding. According to longitudinal and transverse - also generally eaten - folded diapers, piles compressed by their packaging, the deformation and compression forces to which the storage / redistribution component foam pads described herein may be subjected during processing and marketing may even be larger than those applied to the foam materials in use.

Given the nature of the treatment to which the storage / redistribution component absorbent foams described herein are to be subjected, the preferred storage / redistribution component absorbent foam materials of the present invention will have flexibility characteristics which may be quantified by reference to their ability to withstand bending without supporting significant damage to their structural integrity. described in the TEST METHODS section below is a

-51process for determining whether the component of descriptions determined is foamed of a given size around

<img file="PT101751B_D0039.tif" />

Flexibility of absorbing / storing / redistributing foams here and how often a specified sample can be wound from a cylindrical mandrel at a specified rate without fracturing. Preferred tufting / redistribution foams of the stock component are those which are sufficiently flexible so that, at their point of use as a body fluid absorber, the saturated foam material at 37 ° C may be subjected to this bending test. no fracture (ie displays a curvature value of at least one cycle). More preferably, preferred foams may be curved at least 2 times, even more preferably at least 5 times without fracture when subjected to such a test procedure.

Mod. 71 -20,000 · &lt;. · «/ 08

C) Preferred or Supplemental Mechanical Properties

In addition to their compressive drift resistance and flexibility characteristics, the preferred foam pads 20 used in the fluid storage / dispensing component will also have several additional types of mechanical attributes. These preferred mechanical attributes include desirable recovery from deviation by^- compression (ie elasticity), foam integrity, - softness of touch. Each of these preferred mechanical properties is described in more detail as follows:

1) Recovery- From Compression bypass-

Recovery from compression drift refers to the tendency or propensity of a foam material fragment to return to its original dimensions after it has been deformed or compressed under

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Mod. 71 - 20,000. &lt;· · 90/08

-forces found in the manufacture, storage or use. For purposes of the present invention, the recovery from the compression bias of the preferred foam absorbents of the storage / redistribution component considered herein should be determined on foams that are at their appropriate point-of-use density, and often under such conditions, to foam will contain absorbed body fluid. Accordingly, recovery from compression drift can be measured on foams that are not either dried or saturated with synthetic urine.

A suitable procedure for determining recovery from compression drift is given in the TEST METHODS section below. Such a procedure generally involves the compression and release of a standard size foam sample that is dried or saturated to its free absorbent capacity with synthetic urine. The samples are kept under 50% compression for a certain period of time and then released from compression. The extent to which the sample recovers its thickness within one minute after release of the compressive force is taken as a recovery measure from the propensity of the compression deviation (elasticity) of the sample.

Preferred absorbent foams useful in the fluid storage / redistribution component will generally exhibit a recovery of at least 85% of the original gauge when dried and / or at least 75% of the original gauge when wet after a minute. More preferably, such preferred storage / redistribution component foam materials will have a compression recovery from at least 90% dry and / or 80% wet.

-5335

2)

Foam Integrity and Softness

<img file="PT101751B_D0040.tif" />

Mod. 71 20,000 · χ. · 20 / Οβ

While not absolutely essential for making operable or useful absorbent structures, the foam absorbents of the storage / redistribution component of the present invention will preferably have the additional mechanical attributes of structural integrity in use and softness (no irritation) to the touch. For example, the storage / redistribution component foam materials that will be used in such absorbent articles, such as baby diapers, will often be subjected to both dynamic and static forces that occur when the wearer walks, runs, crawls or jumps, such forces may not only tend to compress the foam absorbents of the storage / dispensing component and expel fluid therefrom, but such forces may also tend to tear or cut or otherwise fragment the foam structure. Obviously, it would be advantageous for foam structures which are to be used in this way to have sufficient structural integrity to minimize the incidence of cutting or fragmentation of the foam in use.

The foam elements of the storage / redistribution component of the present invention may also be used in absorbent articles in configurations wherein even the surface of the foam material of the storage / redistribution component may come very close to the wearer's skin. Accordingly, it would be very desirable for the surface of the foam absorbent, storage / redistribution component considered herein to be acceptably soft and non-irritating on contact.

-5435

<img file="PT101751B_D0041.tif" />

IV) Preferred EFIE Absorbent Foams for Storage / Redistribution Component Use

Mod. 7J · 20,000 · χ. · 90 | 0β

As noted above, absorbent storage / redistribution component foam materials which can be prepared to have the required fluid handling characteristics and preferred structural / mechanical properties as described above are the products that result from the polymerization of certain oil-emulsions. in-water having a relatively high rate of water phase to oil phase. Emulters of this type having these relatively high water rates for the oil phase are known in the art as¹high internal phase emulsions (EFIEs or EFIE emulsions). Preferred storage / redistribution component polymeric foam materials resulting from the polymerization of such emulsions are referred to herein as EFIE foams.

The relative amounts of the water and oil phases to form the EFIE emulsions of the polymeric foam precursor are, among many other parameters, important in determining the structural, mechanical, and yield properties of the resulting preferred polymeric foams for the storage / redistribution component. Foam may influence foam density, cell size, specific surface area of ​​the foam and the dimensions of the foam forming supports. Emulsions used to prepare preferred polymeric EFIE foam materials for the fluid storage / redistribution component will generally have water-to-oil ratios ranging from about 12: 1 to 100: 1; most preferably from about 20: 1 to 70: 1; more preferably from about 25: 1 to 50: 1.

The continuous oil layer of emulsions used to prepare the preferred EFIE foams of the storage / redistribution component considered herein comprises

-55/. &lt;

'0 / 04 · «» 000'05 · UP ° W monomers which are to be ρα1imerized to -Shape the solid foam structure. Such monomers include a major monomer component, a comonomer component and a cross-linking agent component. Selection of the types and amounts of the major monofunctional monomer (s) and monofunctional comonomers (s) and polyfunctional crosslinking agent (s) may be important for the realization of EFIE absorbent foam materials which have the combination of structure, mechanics and handling properties. desired materials which make such materials suitable for use in the storage / redistribution component.

The major monofunctional monomer component used in the preferred EFIE foam precursor emulsion oil phase comprises one or more monomers having to impart glass-like properties to the resulting foam structure. Such monomers are hereinafter referred to as vitreous monomers and are, for purposes of the present invention, defined as monomeric materials which could produce high molecular weight homopolymers (greater than 6000) having a glass transition temperature, T T, above about 402 ° C. The preferred monofunctional glassy monomer type is a styrene based monomer with styrene itself being the most preferred monomer of this type. Substituted styrene may also be used, for example monosubstituted, such as p-methylstyrene. The monofunctional glassy monomer component will normally comprise from about 3% to 41%, more preferably from about 77 to 407% by weight of the oil phase used to form the EFIE emulsion to be polymerized.

The monofunctional comonomer component, which will also be present in the oil phase of the EFIE emulsion together with the main vitreous monomer material, comprises one or more comonomers which tend to provide rubber-like properties to the structure.

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<img file="PT101751B_D0042.tif" />

Mod. 71 20,000 · κ. - 5Ό / ΟΒ of foam possibly resulting. Such comonomers are hereinafter referred to as rubber-like comonomers and are, for purposes of the present invention, defined as monomeric materials which would produce high molecular weight homopolymers (greater than 100,000) having a transition temperature to glass, T_gabout 40 ° C or below. Monofunctional rubber-like comonomers of this type include, for example, alkyl acrylates, alkyl methacrylates, allyl acrylate, butadiene, substituted butadienes, vinylidine halogenides and combinations of such comonomers and comonomer types. Preferred rubber-like comonomers include butyl acrylate, 2-ethylhexyl acrylate, butadiene, isoprene and combinations of these comonomers. Of all these species, butyl acrylate and 2-ethylhexyl acrylate are most preferred. The rubber-like monofunctional comonomer component will generally comprise from about 277 to 73%, more preferably from about 27% to 667, by weight of the oil phase.

In the EFIE emulsions used to form the preferred storage / redistribution component absorbent foams considered herein, both the monofunctional major glassy monomer (s) and the rubber-like monofunctional comonomer (s) must be present in the oil phase within the ranges. concentration described above. In addition, the molar ratio of the monofunctional glassy monomer component to the rubber-like monofunctional component will generally range from about 1:25 to 2.5: 1, more preferably from about 1: 9 to 1.5: 1.

Since the polymer chains formed from the glassy monomer (s) and rubber-like comonomer (s) are to be crosslinked, the oil phase of the emulsions used to form the EFIE component foams herein should also be crosslinked. contain an agent of

-57-47f) 1995

90/06 - '' · 000 ot · tz P ° W crosslinking. As with monofunctional monomers and comonomers, selection of a particular type and amount of crosslinking agent is very important for the eventual realization of preferred polymeric foams having the desired combination of mechanical and fluid absorption properties.

Depending on the type and amounts of monofunctional monomers and comonomers used, and depending on the desired foam characteristics of the preferred polymeric storage / redistribution component, the polyfunctional crosslinking agent component for use in the preferred EFIE emulsion foam precursor may be selected from. from a wide variety of polyfunctional, preferably dysfunctional monomers. Thus, the crosslinking agent may be an aromatic divinyl material such as divinylbenzene, divinyl toluene or diallylphthalate. Alternatively, aliphatic divinyl crosslinkers such as any of the diacrylic acid esters of polyols may be used. The crosslinking agent found to be suitable for the preparation of the most acceptable foam from preferred EFIE emulsions herein is diviniylbenzene.

□ crosslinking agent no matter what type it will generally be employed in. oil phase of the preferred foaming emulsions in this case in an amount from about 8% to 40%, more preferably from about 107 to 257 by weight. Amounts of cross-linking agent (s) within such ranges will generally provide a cross-linking molar concentration of about 5^- mole percent to about 60 mole percent, based on the total monomers present in the oil phase.

The major portion of the oil phase of the preferred EFIE emulsions herein will comprise the aforementioned monomers, comonomers and crosslinking agents which eventually form the foam absorbents of the component.

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<img file="PT101751B_D0043.tif" />

Mod. 71 - 20,000 · «. 90/08 polymeric storage / redistribution. It is therefore essential that these monomers, comonomers and cross-linking agents are substantially soluble in the oil phase and not in the water phase. The use of such substantially water-insoluble monomer materials ensures that preferred EFIE emulsions of appropriate characteristics and stability are achieved.

It is of course preferred that the monomers, comonomers and cross-linking agents used to form the preferred polymeric foam materials for the storage / redistribution component considered herein are of a type such that the eventually formed foam polymer is suitably and chemically stable in an appropriate manner. . Thus, such monomers, comonomers and cross-linking agents should preferably have a small or a toxicity at the very low residual concentrations that may be encountered during foam processing after polymerization and / or use.

Another essential oil phase component of the EFIE emulsions used to form the foams of the preferred polymer storage / redistribution component of the present invention comprises an emulsifier which allows the formation of stable EFIE emulsions. Such emulsifiers are those which are soluble in the phase of. oil used to form the emulsion. The emulsifiers used may be nonionic, cationic, anionic or amphoteric provided the emulsifier or combination of emulsifiers forms a stable emulsion. Preferred types of emulsifiers which may be used to provide an emulsifier component having suitable characteristics include sorbitan fatty acid esters, polyglycerol fatty acid esters, polyoxyethylene fatty acid (POE) esters. Especially preferred are sorbitan fatty acid esters such as sorbitan monolaurate (SPAN © 20>, sorbitan monooleate (SPAff 80) and blends.

-59ί * Ζ / '

Mod. 71 · 20,000 · «. · »0/08 ions of sorbitan monooleate (SPANtJ 80) and sorbitan trioleate (SPAN © 85). Such a particularly preferred emulsifier combination comprises the combination of sorbitan monooleate and sorbitan trioleate in a weight ratio greater than or equal to about 3: 1, more preferably about 4: 1. Other operational emulsifiers include TRI0DAN®20 which is a commercially available polyglycerol ester marketed by Grindssted and EMSORBB 2502 which is a sorbitan skiolate marketed by Henkel.

The emulsifying component will generally comprise from about 27 to 337 by weight of the oil phase used to form the EFIE emulsions which in turn are used to prepare the foam of the preferred polymeric storage / redistribution component described herein. More preferably, the emulsifying component will comprise from about 47 to 25% by weight of the phase. oil.

In addition to the monomeric components and emulsifiers described above, the step of forming polymerizable EFIE emulsions may also contain additional oil-optional components described herein. Such an optional oil phase component may be an oil-soluble polymerization initiator of the general type, described below. Another possible optional oil phase component may be a substantially water-insoluble solvent for the oil phase monomer and emulsifying components. Such a solvent should, of course, not be able to dissolve any polymerized monomers. The use of such a solvent is not preferred, but if such a solvent is used, it will generally comprise no more than about 107% by weight of the oil phase.

As indicated, the EFIE oil phase as described hereinabove is the continuous phase in the emulsions to be polymerized to make the preferred foams of the

-60- -UW-1995 /

Mod. 71 20,000 · &lt;. - Storage / redistribution component of the present invention. The discontinuous internal phase of polymerizable EFIE emulsions is the Water Phase which will generally be an aqueous solution containing one or more dissolved components. An essential dissolved component of the water phase is a water soluble electrolyte. 0 The electrolyte dissolved in the water phase of the EFIE emulsion serves to minimize the tendency of monomers and crosslinkers that are mainly oil soluble to dissolve in the water phase as well. This in turn can minimize the extent to which, during emulsion polymerization, the polymeric material fills the cell windows at the oil / water interfaces formed by the water phase bubbles. Thus, the presence of electrolyte and the resulting ionic strength of the water phase can determine whether and to what degree the preferred polymeric foams of the storage / redistribution component can be from open cells.

Any electrolyte providing ionic species to transmit ionic strength to the water phase may be used. Preferred electrolytes are mono-, bi-, or trivalent inorganic salts such as water-soluble halogenides, for example alkali metal chlorides, nitrates to sulfates and alkaline earth metals. Examples include sodium chloride, calcium chloride, sodium sulfate and magnesium sulfate. 0 Calcium chloride is most preferred for use in these preferred embodiments of the present invention.

Generally the electrolyte will be used in the water phase of the EFIE emulsions which are precursors of the preferred polymeric storage / redistribution component foams described herein at a concentration ranging from about 0.27. to about 407% by weight of the water phase. More preferably, the electrolyte will comprise from about 0.57. to 207% by weight of the water phase.

EFIE emulsts used to prepare the

-614 tqi

<img file="PT101751B_D0044.tif" />

Preferred polymeric foams of the storage / redistribution component considered herein will also typically contain a polymerization initiator. Such a initiator component is generally added to the water phase of the EFIE emulsions and can be any conventional water soluble free radical initiator. Materials of this type include peroxygen compounds such as sodium, potassium and ammonium persulphates, caprylyl peroxide, benzoyl peroxide, hydrogen peroxide, cumene hydroperoxides, tertiary butyl diperphthalate, tertiary butyl perbenzoate.

Mod. 71 20,000 · 20/06 rio, sodium peracetate, sodium percabonate and the like. Conventional redox initiator systems may also be used. Such systems are formed by combining the following peroxygen compounds with reducing agents such as sodium bisulfite, L-ascorbic acid or ferrous salts.

The initiator material may comprise up to about 5 mole percent based on the total moles of the polymerizable monomers present in the oil phase. More preferably, the initiator comprises from about 0.001 to 0.5 mole percent based on the total moles of polymerizable oil phase monomers. When used in the water phase, such initiator concentrations may be realized by adding initiator to the water phase to one. about 0.02% to 0.4%, more preferably about 0.1% to 0.2% by weight of the water phase.

By a process described more fully below, the oil and water phases as described above are combined under stirring to form an emulsion in the form of a stable foam. The EFIE foam is then subjected to polymerization conditions which are sufficient and suitable to bring near the polymerization of the monomers in the oil fae and thus form a solid cellular foam structure.

The chemical nature, composition and morphology,

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1995/’ ' ?/ /

/

Mod. 71 · 20,000 · ». 90/06 of the foamed polymer material of the preferred storage / redistribution component is herein determined by both types of monomer concentration. comonomers and crosslinkers used in the HIPE emulsion and the emulsion polishing conditions used. Such a polymeric material will generally be swellable in aqueous liquids so that the material itself plasticizes or significantly absorbs contacting aqueous liquids. However, no matter what the composition of the specific monomer, molecular weight or morphology of the polymer material may be, the resulting preferred polymeric material will generally be viscoelastic in character. Thus the polymer of the present preferred storage / redistribution component foam structures are both viscous, i.e. as fluid properties and elastic, i.e. as spring properties. It is important that the polymeric material forming the cellular foam structure has physical, rheological to morphological attributes that, under conditions of use, impart adequate flexibility, compressive deflection resistance, and dimensional stability to the absorbent foam material.

The cross-linked polymer material which forms the absorbent foam structures of the preferred storage / redistribution component herein will preferably be substantially free of polar groups, functional in their polymeric structure. Thus, immediately after the polymerization step, the polymer forming the foam structure surfaces of such preferred absorbent foam will normally be realistically hydrophobic in character. Thus, preferred freshly polymerized foams may need to be further treated to return the relatively more hydrophobic foam structure surfaces so that such foams can be used as absorbents for aqueous body fluids in the article storage / redistribution component.

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-—4 Μ1925 /

Mod. 71 · 20,000 · «. · 90/08 present. Hydrophilization of the foam surfaces, if necessary, may generally be accompanied by treating the HIPE foam structures as polymerized with the hydrophilizing agent in a more described manner below.

Hydrophilizing agents are any materials that will increase the water moisture value of the polymeric surfaces that are contacted and on which they are deposited. Hydrophilizing agents are well known in the art. Such known agents will generally include anionic, cationic and nonionic surfactant materials, hydrophilizing agents will generally be employed in liquid form, typically dissolved in water to form an aqueous hydrophilization solution that is applied to HIPE foam surfaces. Thus, the hydrophilizing agents may be adsorbed to the polymeric surfaces of the preferred HIPE foam structures in amounts suitable to develop such substantially hydrophilic surfaces but without altering the desired flexibility and compression deflection characteristics of which they have been treated with a hydrophilizing agent. hydrophilizing foam. In the hydrophilization preferred foams are incorporated into the foam, the foam structure such that the residual amounts of the agent remaining in the foam structure comprise at least about 0.05% by weight, more preferably from about about

0.1% to 10% by weight of foam.

A suitable type of hydrophilizing agent comprises mild, relatively non-irritating surfactants applied to the foam structure in amounts sufficient to provide residual surfactant in the foam for an increase from about 0.5% to 5.0% by weight, more preferably from about 5%. 1% to 3% by weight based on the weight of the foam. Such surfactants may include, for example, alkyl sulfates and ethoxy alkyl sulfates

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760 1995 / / eo / oó ·> · ooo oj · iz p ° w of a kind used in dishwashing liquids registered as JOY LIQUID DETERGENT. Aqueous solutions of such surfactants are typically used to wash the HIPE foam structure both after removal of the residual aqueous phase material left from the foam polymerization operation and, more preferably, as part of the wash treatment that serves to remove this material. of residual aqueous phase.

Still another preferred type of hydrophilizing agent comprises inorganic, water-soluble, preferably hygroscopic or deliquent salts. Such materials include, for example, toxicologically acceptable salts of calcium and magnesium. Materials of this type and their use in conjunction with water-insoluble sufactants as foam hydrophilizing agents are described in greater detail in US Patent Application in the name of Thomas A. _________________ (P&amp;G Case No. 4454) commonly filed herein and incorporated herein by reference. Preferred salts of this type include halides and calcium and magnesium such as calcium chloride which, as noted below, may also be employed as an electrolyte in the aqueous phase of HIPE emulsions used to prepare absorbent foams of the preferred storage / redistribution component.

Hydrophilizing agents in the form of hydratable inorganic salts may easily be incorporated into the absorbent foams of the storage / redistribution component referred to herein for treating the foams with aqueous solutions of such salts. As with surfactant hydrophilizing agents, hydratable inorganic salt solutions can generally be used to treat and hydrophilize hydrophobic foams after the completion of, or part of, the process of removing the residual aqueous phase from freshly formed foams. polymerized. Contact of foams with such solutions is used.

<img file="PT101751B_D0045.tif" />

Mod. 7) · 20,000 ««. Preferably, evenly deposit hydratable inorganic salts such as calcium chloride in residual amounts ranging from about 0.1% to 77% by weight of the foam.

Hydrophilizing treatment of such preferred storage / redistribution component foam structures which are actually hydrophobic as polymerization will typically be carried out to the extent that is necessary and sufficient to provide adequate hydrophilicity to the HIPE preferred storage component foams of the present invention. Some preferred HIPE emulsion type foams, however, may be suitably hydrophilic as prepared and thus may not require further treatment with hydrophilizing agents. In particular, such preferred HIPE foams may be those wherein sorbitan fatty acid esters are used as emulsifiers added to the oil and calcium chloride phase which is used with the electrolyte in the aqueous phase of HIPE emulsion precursors. The residual aqueous phase liquid remains in the foams after the polymerization may contain or deposit sufficient amounts of calcium chloride to return the inner foam surfaces containing suitably hydrophilic residual emulsifier even after the polymerized emulsion foams have been dehydrated.

V) Methods of Preparation of Absorbent Foam

The absorbent foam materials in the storage / redistribution component of the absorbent articles disclosed herein may be prepared using any suitable polymerization steps ε post-polymerization and using any suitable combination of monomeric materials, provided that hydrophilic foams result in □ which has included herein. described above, and if the desired

<img file="PT101751B_D0046.tif" />

Mod. 71 · 20,000 · κ. · Preferred TO / Οβ is the mechanical and structural characteristics of the direction of the fluid. As noted, a preferred method of polymeric foam realized having required fluid direction properties and desired mechanical and structural characteristics involves the polymerization of High Internal Phase Emulters (HIPEs). Preparation of absorbent storage / redistribution component foams using this preferred process will then be described to illustrate how foams using this preferred process will then be described to illustrate how foams of the type examined herein can be made.

This preferred foaming method involves the steps of A) forming a stable high internal phase emulsion (HIPE), B) further polymerizing this stable emulsion under conditions suitable for forming a solid polymeric foam structure, C) wash if necessary hydrophilizing the solid polymeric foam structure by treating the structure with water and / or liquid hydrophilizing agents to remove the original residual aqueous phase from the polymeric foam structure and to deposit any necessary hydrophilizing agents and D) dehydration back of this polymeric foam structure to the extent necessary to return the foam material useful as a body fluid storage component absorber watery. Each of these basic process steps is described in greater detail below:

A) HIPE Emulsion Formation The HIPE emulsion precursor to the preferred foam absorbent materials disclosed herein can be formed by combining an oil phase as described above with the aqueous phase also described above. The weight ratio of the aqueous phase to afc_and of oil and

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Mod. 71 - 20,000 x. ·? 0 / 0β such a combination will generally range from about 12: 1 to about

100: 1, more preferably from about 20: 1 to 70: 1.

The oil phase used to form the HIPE emulsions presented herein will contain the essential components specified above such as the required monomers, comonomers, crosslinkers and emulsifiers. The oil phase may also contain optional components such as solvents and polymerization initiators. The oil phase used to form the HIPE emulsions presented herein will contain electrolyte specified above as an essential component and may also contain optional components such as water soluble emulsifiers, and / or polymerization initiators.

The HIPE emulsion may be formed from a combined oil and water phase by subjecting this phase combination to shear agitation. Cutting agitation is generally applied to the extent and for a period of time necessary to form a stable emulsion of the combined oil and water phases. Such a process may be conducted in both portioned and continuous fashion and is generally carried out under conditions suitable to form an emulsion wherein the droplets of the oil phase are dispersed to such an extent that the polymerized foam which is eventually formed from the emulsion. The emulsion will have the desired pore volume and other structural characteristics. Emulsification of the oil and water phase combination will often involve the use of a stirring mixture or device such as a pin impeller.

A preferred method of HIPE emulsion formation which may be employed herein involves a continuous process for combining and emulsifying the desired oil and water phases. In such a process, a liquid stream comprising the oil phase as described above is formed and provided at a flow rate comprising the aqueous phase as described above is also formed.

-681995 z

/ formed at a Flow rate ranging from about 4 to 550 ml / sec. At the flow rate within the previous ranges, these two streams are then combined in a suitable mixing chamber or so that the water required for the oil phase weight ratios as mentioned is approximated, achieved.

In the mixing chamber or zone, the combined streams are generally subjected to shear agitation as provided, for example, by a pin impeller of suitable configuration and size. The cut will typically be applied to the range of about 1000 to 4000 sec.¹.

The resistance time in the mixing chamber will often vary from about 5 to 30 seconds. Once formMod. 71 20,000 · «. Thus, the stable HIPE emulsion in liquid form may be withdrawn into the mixing chamber or zone at a flow rate of from about 4 to 52 ml / sec.

This preferred method for forming useful HIPE emulsions by a continuous process is described in greater detail in US Patent Application in the name of Thomas A. DasMarais, Stephan T. Dick and Thomas M. Shiveley having 0 n2. ___________________ 8P &amp; G Case 4453).

This application, which is commonly filed herein, is incorporated herein by reference.

B) HIPE Emulsion Polymerization

The HIPE emulsion formed as described above will generally be placed in a reaction vessel, container or region to be polymerized. In one embodiment herein, the reaction vessel comprises a polyethylene tube from which the polymerized solid foam material may eventually be easily removed for further processing after polymerization has been carried out to the desired extent.

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<img file="PT101751B_D0047.tif" />

The polymerization conditions to which the HIPE emulsion will be subjected will vary depending upon the monomeric and other composition of the emulsion oil and water phases and the type of amounts of polymerization initiators used. Often, however, the polymerization conditions will comprise maintaining the HIPE emulsion at elevated temperatures from about 55 ° C to 90 ° C, more preferably from about 6020 to 662C, for a period of time ranging from about 4 to 24 ° C. hours, more preferably from about 4 to 12 hours.

C) Washing and Hydrophilization of HIPE Foam and / o · · · · οοο'οδ · iz p ° w

The HIPE solid foam which is formed upon completion of the above described polymerization step will generally be a flexible open cell porous structure having its cells filled with the residual aqueous phase material that was used to prepare the pre-polymerization HIPE emulsion. . 0 Residual aqueous phase material, which generally comprises an aqueous electrolyte solution, residual emulsifier, and polymerization initiator, may be removed from the foam structure at this point prior to further processing and use of the foam.

Removal of the aqueous phase material will usually be taken from the foam structure, to make residual and / or washing of the other washing solutions several washing steps and example 2 cycles will be used.

After the compression phase cable material exits the foam structure with water or aqueous liquid by compression

Often, because when the HIPE foam structure has been removed from the foam structure it may need to be desired, the foam to be originally extended treated, that is, by continuous aqueous washing with a suitable hydrophilizing agent solution. Hydrophilizing agents that may be employed are listed above.

<img file="PT101751B_D0048.tif" />

·/

Mod. 71 20,000 ««. - 90/06

As noted, treatment of the HIPE foam structure with the hydrophilizing agent solution is continued, if necessary until the desired amount of hydrophilizing agent has been incorporated and until the foam exhibits a desired adhesion stress value for any aqueous liquid absorbent. choice.

D) Foam Dehydration

After the HIPE foam has been treated to the desired extent to return the eventually dry hydrophilic suitable foam, the foam will generally be dehydrated before being cut or otherwise ready for use as an absorbent structure in the storage / redistribution component. an absorbent article. Dehydration may be effected by compressing the foam to impress waste water, subjecting the foam, or water therein, to elevated temperatures, for example at temperatures between about 60 ° C to 200 ° C or by microwave treatment, or by combining both compression and water heating techniques. The dehydration step of HIPE foam processing will generally be carried out until the HIPE foam is ready for use and dried as a practice. Often such dehydrated compression foams will have a water content (humidity) of from about 50% to 500%, more preferably from about 50% to 200% by weight on a dry weight basis.

Subsequently, the heated foams may be dried to a moisture content of from about 5% to 40%, more preferably from about 5% to 15% by weight.

ABSORBENT CORE PREPARATION COMPONENT - ABSORPTION / DISTRIBUTION AND STORAGE / REDISTRIBUTION RATIO

As noted, both the absorption component

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Mod. 71 · 20,000 · «. Higher distribution / distribution as a storage / redistribution component of fluids are arranged in an absorbent core between the topsheet and the backsheet to form the absorbent articles described herein. There is no particular requirement regarding the positional relationship of the absorption / distribution component and the fluid storage / redistribution component within the absorbent core, as these components are in effective fluid communication with one another and to the extent wherein each component is large enough to effectively maintain and / or carry the amount of aqueous body fluid expected to be discharged into the absorbent article.

As indicated above, the most preferred relationship between the fluid absorption / distribution component and the fluid storage / redistribution component within the absorbent core of the articles described herein is to layer these components in a layered configuration. In such a layered configuration, the fluid absorption / distribution component comprises an upper layer that overlaps an underlying fluid storage / redistribution component in the form of a lower layer. It will be understood that for the purposes of the present invention these two types of layers merely refer to the upper and lower regions of the absorbent core and are not necessarily limited to single or even physically separated layers, layers or sheets of material. Both the fluid absorption / distribution zone, i.e. the upper layer, and the fluid storage / redistribution zone, i.e. the lower layer, may simply comprise regions of different characteristics within the same material or may comprise laminates or combinations of various sheets or polymeric webs or foams of the required type of materials as described hereinbefore. Thus, as used herein, the

-7210 item 4 ·

BO / M ·· * »OOO OITZ * P ° W term“ layer includes the terms layers and stratified. For purposes of the present invention, it should also be understood that the upper term refers to the absorbent core layer that is relatively closest to the topsheet of the article; conversely, the term lower refers to the absorbent core layer that is actually closest to the backsheet of the article.

In stratified structures it is of course desirable for economic reasons to use as little absorbent material as possible in each component of the absorbent core consistent with the need to provide adequate absorption of body fluids with minimal loss of such fluid from the article. The interaction of the particular types of absorption / distribution and storage / redistribution layers used in the preferred stratified articles of the present invention results in especially efficient handling of the discharged fluids and this in turn allows the use of relatively small amounts of absorbent material in particular. each layer. In the preferred absorbent articles of the present invention, the upper fluid absorbing / dispensing layer will preferably comprise from about 1 to 25 grams, more preferably from about 2 to 20 grams of the fluid absorbing material. The lower fluid storage / redistribution layer of the preferred absorbent articles in this invention comprises from about 2 to 20 grams, more preferably from about 3 to IT grams of foam-based absorbent material. The weight ratio of the absorption / distribution layer to the storage / redistribution layer will generally range from about 1: 4 to 5: 1, more preferably from about 1: 3 to 4: 1, in absorbent articles. Preferred here.

In preferred embodiments, the absorbent core absorption / distribution layer will be placed in a specific positional relationship with respect to the

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80 / «« »000 000« «« «U

<img file="PT101751B_D0049.tif" />

upper sheet of the article and the storage / redistribution layer of the absorbent core. More particularly, the core absorption / delivery layer is preferably positioned such that it is effectively located to receive body discharged fluids and to transport such fluids to other regions of the core. Thus, the absorption / dispensing layer should preferably contour in proximity to the discharge point of body fluids. These areas should include the bifurcation area and preferably in articles for use by males, also the region where urine discharge occurs on the front of the diaper. For a diaper, the front of the absorbent articles here means the portion of the absorbent article that is intended to be placed in front of the wearer. Additionally, for male users, it is desirable for the absorption / distribution layer to extend close to the front area of ​​the user's waist to effectively receive the load.

Relatively high X fluid that occurs on the front of diapers for male users, and to compensate for directional variations in discharges. The corresponding regions of the absorbent article will vary depending on the design and fit of the absorbent article.

For diaper runs, the core absorption / distribution layer is preferably positioned relative to a topsheet and / or the storage / redistribution layer so that the absorption / distribution layer is of sufficient length to form. extend to areas corresponding to at least about 50%, preferably 75%, of the length of the topsheet and / or storage / redistribution layer. The absorption / distribution layer should be wide enough to receive body fluid spurts and to prevent direct discharge of fluid onto the storage / redistribution layer. Generally, for diapers, the width of the

-74υ_-4 AUG.-1995-7

-ρ ·

Mod. 71 - 20,000 · κ. »08/08 /

The absorption / distribution will be at least about 5 cm, preferably at least about 6 cm.

In order to determine such preferred absorption / distribution layer as described hereinbefore, the length of the absorbent article will be taken as the widest normal longitudinal dimension of the backsheet of the elongate article. This longer normal length of the elongated backsheet can be defined relative to the article as it is even applied to the user. When worn, the opposite ends of the backsheet are fixed to one another so that these connected ends form a circle around the wearer's waist. The normal length of the backsheet will thus be the length of the line running through the backsheet a) of the point on the edge of the backsheet at the middle of the back of the wearer's waist through the fork until

b) the point on the opposite edge of the backsheet in the middle of the front of the wearer's waist. The size and shape of the topsheet will generally correspond substantially to the backsheet.

In the usual example, it will be the storage / redistribution layer of the preferred absorbent cores which generally defines the shape of the absorbent article and the normal length of the elongate article topsheet will be approximated by the longer longitudinal dimension of the storage / redistribution layer. from the core. However, in certain applications (eg adult incontinent articles) where minimal volume reduction or costs are important, the storage / redistribution layer should not take the general shape of the diaper or incontinence structure. Instead the storage / redistribution layer would generally be located to cover only the user's genital region and a reasonable area close to the genital area. In this example, both the fluid absorption / distribution layer and the storage / redistribution layer must be

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<img file="PT101751B_D0050.tif" />

Mod. 71 · 20,000 · «. · 8/20

25.

be located towards the front of the article as defined by the topsheet such that the absorption / distribution and storage / redistribution layers must be at the front two thirds of the length of the article.

As noted, the relative size of the absorption / distribution layer and the fluid storage / redistribution layer in preferred articles may vary widely. Preferably, however, the absorption / distribution layer of the preferred absorbent core configuration will have a smaller surface area (in an unfolded planar configuration) than the storage / redistribution layer and, in fact, may have a surface area which is substantially smaller than that of the fluid storage / redistribution layer. Often, the surface area of ​​the absorption / distribution layer will range from about 157. to about 957 °, preferably from about 307 to about 857, more preferably from about 307 to about 757, of the surface area of ​​the storage / distribution layer.

The absorption / distribution layer may have any desired shape consistent with the comfortable attachment and acoma size limitations discussed. Such shapes include, for example, rectangular, trapezoidal or oblong shapes, that is, watch glass, dog bone, half dog bone, oval or irregular shape. The absorption / distribution layer may be similar or different from the storage / redistribution layer. The storage / redistribution layer of the preferred absorbent core configuration may also be in any desired shape in accordance with comfortable attachment including, for example, circular, rectangular, trapezoidal or oblong, for example the watch glass shape, shape. of dog bone, half dog bone shape, oval or irregular shape. The layer

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<img file="PT101751B_D0051.tif" />

Mod. 71 20,000 ·>. 90/00 storage / redistribution need not be physically separated from the absorption / distribution layer or completely disconnected from the storage / redistribution layer.

A preferred embodiment of a disposable diaper according to the present invention is shown in Figure 2 of the drawings. Such a diaper includes an absorbent core 50 comprising a top fluid receiving layer 51 and an underlying fluid storage / redistribution layer 52 comprising a foam absorbent structure. A topsheet 53 is overlapped and co-extensive with a core face, and a backsheet 54 is overlapped and co-extensive with the face of the opposite core covered by the topsheet. The backsheet is more preferably wider than the core thus providing lateral marginal portions of the backsheet extending beyond the core. The diaper is preferably as shown in a watch glass configuration.

As noted, the absorption / distribution component and the storage / redistribution component of the absorbent core need not be in a stratifying relationship in the articles described herein. An alternative non-stratified absorbent core configuration is shown in Figures 3 and 4. In Figures 3 and 4, the fluid absorption / distribution component comprises an intermediate member 60 of low density elastic composite material which is embedded in and surrounded by a foam-based fluid storage / redistribution component 61. Composite interstitial absorption / dispensing member 60 is disposed at the point within the absorbent core where it will receive body fluids discharged by the user from the absorbent article.

Figures 5 and 6 show another alternative embodiment of the absorbent core. In this embodiment, a cellulosic fibrous material in the form of a sheet

<img file="PT101751B_D0052.tif" />

In the form of a watch glass, it is placed on top of a foam-based fluid storage / distribution component comprising two parallel strips 63 of a generally rectangular shape.

Figures 7 and B show yet another alternative absorbent core configuration wherein the foam-based fluid storage / redistribution component comprises an upper layer of generally rectangular form 64 which is disposed over an underlying lower layer 65 of a foamed fluid. absorption / distribution and watch-glass-like fluids. The fluid storage / redistribution layer contains a fluid receiving aperture 66 through which body fluid is discharged to compress onto the underlying lower absorption / distribution layer 65.

Mod. 71 · 20,000 · «. · W / Οβ

Assay Methods

In describing the present invention, a number of fluid handling, structural and mechanical characteristics of materials or structures used in the two absorbent core components of the absorbent articles considered herein are highlighted. In some cases, processes for determining and measuring some of these characteristics are referenced from other patents or publications. In other cases, such characteristics may be determined and measured using the following test fluids and test methods.

I) Test Fluids and Structure Sample Preparation

A) Test Fluid - Synthetic Urine

Several of the measures described in the assays described herein involve the use of a test fluid such as synthetic urine and ethanol or isopropanol. The urine

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<img file="PT101751B_D0053.tif" />

The synthetic compound used in a number of the assays described below is manufactured from a commercially available synthetic urine manufactured by Jayco Pharmaceutics (Mechanicsburg, PA, 17055). This synthetic urine from

Jayco from the preparation comprises KCl, 0.27; Na, SQ ,, 0857 .; (ΝφΝφΡΟΡΟ, 0.0157 .; CaCl ^Hp, 0.0257 .;

0.057. (Percentages by weight)). The samples

0.27. NH „HfO₄ and MggCl / 6H, 0, of synthetic urine are prepared according to label instructions using distilled water. To Jayco salt is added filtered if necessary to remove dissolution, the mixture to water. The sample is

1ly any particles.

Any unused synthetic urine is discharged after one week. To increase the

Mod. 71 20,000 ««. · 90 (06 fluid visibility, 5 drops of blue food coloring per liter of synthetic urine solution may be added. The Jayco synthetic urine used has a surface tension of 65 + 5dines / cm.

B) Sample Preparation of Absorbent Structure

A number of the following tests involve the preparation and testing of the absorbent structure, i.e. foam samples, of a particular size specified. Unless otherwise specified, specimens of absorbent structure of the required size shall be cut from large blocks of the same material using a moving, reciprocating thin saw. The use of this type, or equivalent type¹ The thin cutting device serves to substantially eliminate defects in the sample edge and edge densification effects that may have an adverse impact on the accuracy of some measurements made when performing the various test procedures given below.

Specification of the sample size will also generally include a dimension for size or weight30.

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<img file="PT101751B_D0054.tif" />

Mod. 71 20,000 x. · ΊΟ / Οβ sample thickness. Measurements of gauge or thickness for the purposes of the present invention should be made when the absorbent structure sample is under confining pressure of 0.05 psi (350 Pa).

II) Determination of Absorption / Distribution Layer Fluid Manipulation Characteristics

A) Absorption Fluid Standard

The proportion at which a particular type of fiber-based or foam-based absorbent material will accept fluid within its internal structure may be determined for the purposes of the present invention by means of a Fluid Absorption Ratio Test. In such a test, a specified amount of the test liquid is introduced onto the upper surface of the structure being tested, and the time required for all this test liquid to be absorbed by the measured structure.

Assembly for the Fluid Absorption Ratio test involves preparing a 4 x 4 ”(10.16 cmm x 10.16 cm) piece of absorbent frame material of any suitable caliber. This test sample is weighed and is placed on top of a 5 x 5 ”Plexiglas plate (12.7 cm x 12.7 cm). Placed on top of the absorbent structure is an Intermediate Cutting Device comprising a 4 x 4 ”(10.16 cm x 10.16 cm) Plexiglas plate with a 1 x 2.54 cm diameter cylindrical bore 3/4 1.9 cm) depth that acts as a load cell. The load cell is equipped with electrical sensors that detect the presence of test liquid in the load cell. The sensors are connected to a disconnector such that the length of time the liquid remains in the load cell can be automatically determined. The device that places the sensor in the

-8010

Mod. 71 · 20,000 · χ. SO / Οβ \ · - \ W ί9 «5 · /

The load limits the cross-sectional area through which the test liquid flows to about 0.33 in.²). Weights are placed over the top of the Cutter Through which the sample of the absorbent structure to be tested is maintained at a set pressure of 0.2 psi (1.43 kPa).

An amount of Jayco synthetic urine test liquid equal to twice (2:) the weight of the absorbent structure test sample is placed in a dispensing funnel that is placed above the Intermediate Cutting Device load cell. At time zero, the timer is triggered, and the test liquid is dispensed from the in-cell dispensing funnel of the Intermediate Cutoff device. (When the valve over the dispensing funnel is fully open, □ fluid flows into the load cell at a rate of about 11 ml / sec.). The timer is stopped when the electric sensors detect that all test liquid has been drained from the load cell and absorbed by the test frame.

The period of time that elapses for the first aliquot portion of the test liquid to be absorbed by the test structure is taken as the Fluid Absorption Ratio. 2x subsequent aliquots of the. Test liquid can be fed into the load cell at intervals of 2 - 3 minutes. In this way, the Fluid Absorption Ratio as a function of the fluid load on the structure can also be determined.

B) Vertical Twisting Height

The vertical twisting characteristics of the material suitable for use as or in the fluid absorption / distribution component of the articles described herein may be determined by the Twisting Height test.

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Mod. 71 · 20,000 · «. - ΡΟ / Οβ

'. / ^11995' / /

Vertical. In this test, a 10 x 1 strip (25.4 cm: &lt;

2.54 cm) of an absorbent structure test sample of any suitable size (eg 0.15 in. (0.38 cm) for fiber-based structures; 0.25 in. (0.13 cm) for foam-based structures is used.This test strip is placed vertically over a reservoir of a Jayco synthetic urine test liquid. At time zero, the test strip is lowered into the reservoir to a point above the strip marked as zero point. After 30 minutes, the level at which the test liquid has twisted above the zero point on the test strip is measured. This distance is then taken as the Vertical Twist Height at 30 minutes. ._;

III) Determination of Fluid Handling Characteristics of Fluid Storage / Redistributive Component Absorbent Foam Structures

A) Foam Absorbing Capacity »

Both the free absorbent capacity and the pressure absorbent capacity of the foam structures can be determined by a gravimetric analytical technique using synthetic urine as the fluid for which the foam absorbent capacity is to be calculated.

1) Absorbent Capacity Test Principle

In this assay, a foam sample is saturated with synthetic urine test liquid to measure the unloaded or free absorbent capacity of the foam sample, pressure is then applied in various increments to determine the absorbent capacity under load. This pressure absorbing capacity is measured after the foam sample has been kept in a compressed state for a fixed time period.

·>

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<img file="PT101751B_D0055.tif" />

Mod. 71 · 20,000 · «. · Μ / Οβ

2) End of Test

This test measures the absorbent capacity of a foam sample under pressures of interest, namely 0 to 1.0 per square inch (psi) (0 to 6.9 kPa), and at the temperature of interest, ie 992F (3720 .

3) Equipment

Sieve, 25 meshes, 8 cm in diameter; crystallization addition, 15 cm in diameter: &lt;7.5 cm high; filtration vessel, 50 ml; analytical balance; dial-type measuring apparatus, fitted with a fur foot^; 1 in² (6.5 cm3 and covers measuring up to 0.001 inch (0.025 mm), for example the Ames 482 model (Ames Co., Waltham, MA) or the Ono-Sokki EB-225 model, Ono-Sokki Co., Ltd. , Japan); weights for dial-type measuring apparatus capable of producing pressures of 0,2, 0,7 and 1,0 psi (1,4, 5,1 and 6,9 kPa).

4) Materials

JAYCO synthetic urine; Foam samples.

/

5) Operative Mode

i) The equipment and materials described hereinabove are equilibrated at a constant ambient temperature of 992 ° F (3720 ° C. Memoranda are also performed at this temperature.

i.)) Uncut cylinder foam samples with a thickness of 1 in.² (6.5 crif) x 0.3-in. (0.8 cm) or equivalent. These samples are weighed to provide an average dry weight (DW).

iii) The Free Absorption (FAC) capacity of each

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Mod. 71 · 20,000 x. · August 20, 1795 /

Foam sample is determined as follows:

a) The foam sample is dipped into synthetic urine on a crystallization disc and allowed to saturate. The sample may be compressed a few times to expel air.

b) The foam is removed without compressing the fluid out of it. □ Excess fluid is allowed to drip out of the flattened sample for about 30 seconds, and then the wet sample is weighed.

c) Steps a) and b) are repeated twice more and an average wet weight (WW) is calculated. ·

d) Free Absorbent Capacity (FAC, g / g) is calculated as

FAC = weight of synthetic foam in saturated foam / dry weight foam = CWW (g) -DW (G) 3 / DW (g)

IV) Pressure Absorbing Capacity (Pressure Disorption) for each foam sample is determined as follows:

(a) The 50 ml filter vessel, with the sieve at its top, is placed under the center of the foot of the standard measuring device with the foot resting on the screen. _/

b) The saturated sample is placed on top of the screen, ensuring that the sample is over the center of the filtration vessel, and the measuring apparatus is placed to apply limited pressure on the foam sample.

c) Weights are placed on the measuring apparatus to apply 0.2 psi (1.4 kPa) of pressure to the sample.

d) After 15 minutes the foam sample is weighed (WW, 0.2).

GO 19?

e) The same sample is again saturated, and then steps a) - d) are repeated except that 0.74 and 1.0 psi are used to determine WW, 0.74 and WW, 1.0.

• F) Using new samples, steps a) - e) are repeated twice more to determine wet weight averages after samples are kept under different pressures.

(g) Absorbent capacities under pressure (load X, g / g are calculated as follows.

(Z load under a given pressure is the weight of synthetic wet urine in epsuma / dry foam weight).

Mod. 71 · 20,000 · «. - 20 / Οβ

Capacity under 0.2 psi

X, 0.2 (g / g) = CWW, 0.2 (g) - DW (g)] / DW (g>

Capacity under 0.74 psi

X, 0.74 (g / g) = CWW, 0.74 (g) - DW (g)] / DW (g)

Capacity under 1.0 psi

Χ, Ι, Ο (g / g) = CWW, 1.0 (g) - DW (g) J / DW (g).

Absorbent capacity values ​​in ml of synthetic urine per gram of dry foam can be obtained by dividing the FAC and loading values ​​X by the specific gravity of JAYCO synthetic urine which is approximately 1 g / ml.

B) Vertical Twist Ratio and Foam Vertical Twist Absorption Capacity

The vertical twisting ratio and absorbance capacity dc? Vertical twisting is a measure of the ability of a dry foam to drain fluid vertically from a reservoir. The time required for the front of the fluid to drain through a 954.

'Ogoj' 95 /

5 cm vertical length of a foam strip is measured to give a vertical twisting ratio. After the fluid has risen to its equilibrium height, the amount of fluid maintained by the foam strip at a particular drainage height (eg 4.5 inches or 11.4 cm) is determined to give an absorbent capacity. Vertical twisting.

Jayco synthetic urine colored with a blue food coloring is used in the following methods to determine the vertical twist ratio and the vertical twist absorbent capacity. In this test process, the materials are equilibrated at 37 ° C and the test is performed at the same temperature. . ·.

1)

Mod. 71 · 20,000 · «. - 90/09

<img file="PT101751B_D0056.tif" />

Sample Preparation

(i) A foam strip approximately 25 cm x 2.0 cm x is cut from a master sample.

(ii) A fluid reservoir is placed on top of a lab jack ”and the foam sample is fixed to one end so that it is vertically suspended over the fluid reservoir.

iii) A ruler is fixed close to the foam sample so that the bottom (0 cm) of the ruler is about 1 - 2 mm above the bottom of the foam sample.

iv) · □ Flow reservoir is filled to 3/4 of its capacity with colored synthetic urine solution.

2) Vertical Twist Ratio ·

(i) The reservoir is raised to the bottom of the foam sample with □ laboratory jack. A timer is started as soon as the fluid touches the bottom of the foam sample.

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3)

<img file="PT101751B_D0057.tif" />

ii) The reservoir is immediately raised until the liquid precisely touches the bottom of the ruler.

iii) The time taken for the front of the fluid to reach 5 cm is recorded iv) The foam is allowed to twist until it reaches equilibrium (eg about 18 hours). The laboratory jack may need to be adjusted to keep 1 - 2 mm of the sample immersed, and the sample should be protected to prevent evaporation.

Absorption Capacity (ml / g) by Vertical Foam Length

Mod. 71 - 20,000 · &lt;. · Μ / Οβ

(i) The foam sample is removed and placed on a non-absorbent surface.

ii) The sample is immediately cut into separate 1 inch (2.54 cm) pieces using a tool with sufficient cutting power not to compress the foam sample, each such piece is weighed.

iii) Excess fluid is expressed from each piece, and each piece is placed on an absorbent towel.

iv) Each piece is allowed to dry completely.

v) Each dry piece is then weighed and an absorbent capacity for each piece is calculated based on the difference between wet and dry weights. For the purposes of the present invention, the absorbent capacity of a one inch segment representing 4.5 inches (11.4 cm) of twisting weight is the most desirably determined parameter.

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<img file="PT101751B_D0058.tif" />

Foam Adhesion Strength Characteristics

The adhesion force of hydrophilic foam samples that inhibit test fluid by capillary suction is the product of the surface force, Z, of the test fluid times the contact angle consensus, O, shown by the test fluid in contact with the inner surfaces of the foam sample. Adhesion strength can be determined experimentally by measuring the load to α equilibrium weight by capillary suction presented by the two test samples of the same foam using two different test liquids. In the first phase of such a process, the surface area of ​​the foam sample is determined using ethanol as the test fluid as will be described later in the discussion of the foam area.

Mod. 71 · 20,000 x. · Κι &lt;»

Specific Surface Of This Section TEST METHODS.

The capillary suction absorption process is then repeated in the same manner as the axcept ethanol process in which JAYCO synthetic urine is used as the test fluid and the test is performed at 37 ° C. The contact angle of synthetic urine can then be calculated as follows from the known specific surface area and synthetic urine loading data:

MUGU

COS0_U = _______________ where 6_U = the contact angle in degrees of Jayco synthetic urine; = Jayco synthetic urine net loading mass in grams; G = the gravitational constant which is 980 cm / sec²; = the mass of the dry foam sample in g; il = JAYCO urine surface tension which is -65 di35

<img file="PT101751B_D0059.tif" />

nes / cm; s_ç = the specific surface area of ​​the foam sample in cm² / g as determined by the ethanol loading process; and L_no = the length of the foam sample in cm.

When a surfactant is present (on the foam sample surfaces and / or in the advanced test liquid), the front and forward liquid characterization is defined by applying the adhesion stress equation (TA).

TA = ____________

Mod. 71 · 20,000 * &lt;. Μ / 0β where M_T is the mass of the test liquid taken by the foam sample, and G, L_N , ΓΧ, and S_ç are as previously defined. CV Hodgson and Berg, J. Col. Int. Sci., 121 (1), 1988, pp 22-311.

In determining the adhesion stress for any test liquid considered, no numerical presumption of surface tension is made at any point in time, so that changes in surfactant concentration on the sample surfaces and / or the liquid that advances during the crowd are immaterial. □ experimental value of adhesion stress co50) is especially useful when viewed as a percentage of the maximum adhesion stress which is the surface tension of the test liquid (for example, the maximum adhesion stress using JAYCO synthetic urine) would be C65 + 51. Ccos Cf 3 =

I + 5 dynes / cm.

<img file="PT101751B_D0060.tif" />

IV) Determination of the Structural Characteristics of

Component Absorbent Foam Structures

Fluid Storage / Redistribution

<img file="PT101751B_D0061.tif" />

Available Foam Pore Volume

Mod. 71 20,000 · «. 90/06

One process for determining the available pore volume involves measuring the amount of isopropanol (firing point 12 ° C) that can be introduced into the structure of an absorbent foam sample. The equipment and materials used to make such a measurement are equilibrated at 22 + 2 ° C. Measurements are also performed at this temperature.

Dry foam samples are cut into 1 inch thick or equivalent cylinders² (6.5 crif) x 0.3 inch (0.8 cm). Such cylindrical samples may be prepared using a 1.13 inch (2.87 cm) diameter die cut on a 0.3 inch (0.8 cm) foam sheet. These dry foam samples are each weighed to determine dry weight (dw). Three of such samples are weighed to determine an average dry weight (DW).

The Measured Free Capacity (MFC) of these samples is then determined by the following phases:

1) Foam samples are immersed in isopropanol in one; crystallization disc and kept until saturation. At this point the sample may be expressed a few times to expel the ar-

2) Each sample is removed without compressing the isopropanol out of it. Excess fluid is allowed to drip out of the sample in the flat position for about 30 seconds. Each sample is then wet weighed to determine the wet weight (ww).

3) Phases 1) and 2) are repeated two more times and one

Ml 19 £ · 'average wet weight (WW) is calculated.

Measured Free Capacity (MFC, g / g) is the weight of isopropanol in saturated foam per unit mass of dry foam. CFR is calculated according to the formula

MFC = ri »JbJ (q> -DW (q) 1

DW (g) available pore volume is then calculated by dividing the foam MFC for isopropanol by the isopropanol density which is 0.785 g / ml. This gives an available pore volume for the foam in ml / g.

B)

Foam Capillary Suction Specific Surface Area

Mod. 71 -20,000 · W / Οβ

25:

/

The Capillary Suction Specific Surface area of ​​the absorbent useful in the fluid storage / redistribution component herein can be determined from the equilibrium weight load of a known low surface tension test liquid. in this case absolute ethanol is used (illumination point is 1020).

To conduct the test, a suitable sized strip-shaped foam sample (eg 25^- cm long x 2 cm wide: &lt;0.8 cm thick) is equilibrated at 22 ° C, is placed vertically and at one end is immersed by 1-2 mm in an ethanol reservoir using a laboratory jack. Ethanol is allowed to absorb the foam strip to its equilibrium height which should be less than the sample length. The ethanol-containing strip is then weighed while still in contact with the reservoir to determine the weight of the total ethanol filler. During this process the sample should be protected, for example with a covered glass cylinder, to avoid

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the evaporation of ethanol.

The specific surface area of ​​the foam sample may be calculated from the following formula:

Mod. 71 - 20,000 · &lt;. 90/08 in which S_and = the specific surface area of ​​capillary suction in cm²/ g; r = the net mass of EtOH in grams; G = the gravitational constant which 'is 980 cm / sec² ; L „= the total length of the sample in cm; M_no = the dry mass of the sample in grams, eV and the EtDH surface tension of 22,3 dynes / cm. The values ​​obtained can then be divided by 10000 cm^The/ rô to provide the specific surface area of ​​capillary suction in m²/ g.

Ç)

Foam Density

One process that can be used to determine foam density is that described in the ASTMNa method. D 3574-86, Test A, which is intended primarily for testing the foam? but may also be used to measure the absorbent foam density of the EIFE type storage / redistribution component of the present invention. In particular, density measurements made according to this ASTM process are performed on foam samples that have been pre-packed in a manner as specified in this test.

Density is determined by measuring both the dry mass of a given foam sample and volume at 22 + 22 ° C. The volume determination over May35

Foam samples are calculated from measurements of the sample size made under unrestricted pressure. At

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volume unit, for the purposes of the present invention, density is generally expressed in terms of g / cm³.