Durable, absorbent latex foam composition having high vertical wicking

<td>REPUBLIC POLAND</td><td>(12) PATENT DESCRIPTION ₀9&gt; PL (21) cgłoscenip number: 358550</td><td>(11) 201 224 (13) B1</td>

<td></td><td>(22) Dptp cgłoscenip: 04/09/2001</td><td>(51) Int.Cl. A61L 15/24 (2006.01)</td>

<td></td><td>(86) Dptp and myctinptoy cgloscenip number: 2001-04-09, PCT / US01 / 11515</td><td>A61L 15/42 (2006.01)</td>

<td>Pptent Office</td><td>(87) Dptp and publication number of the myocynptoy cgloscenip:</td><td></td>

<td>Rceycypolitej Pslskizj</td><td>2001-11-01, WO01 / 80916 PCT Gazette No. 44/01</td><td></td>

Durable, absorbent latex foam with high vertical suction force and the method of its production and products made of it

<td>(30) Piety: 2000-04-26, US, 60/200026 2000-09-06, US, 60/230268</td><td>(73) Qualified pptent: DOW GLOBAL TECHNOLOGIES, INC., Midland, US</td>

<td>(43) The notification was approved: 09.08.2004 BUP 16/04</td><td>(72) Creators ^) wyplpcku: Steven W. Mork, Midland, US Andrew T. Graham, Midland, US</td>

<td>(45) The development of the pptent was announced: March 31, 2009 WUP 03/09</td><td>(74) Representative: Kossowska Janina, PATPOL Sp. z o. o</td>

(57) The invention relates to a durable, conformable, absorbent, hydrophilic, latex polymer foam, which is capable of cpkykpyip in a vertical aqueous cola formation with a concentration of 0.9% by weight, yp, height of 5 cm, and γCp, representing the expression of the expression of pbpmcorismic expression. , 0.9% of a water solution of kola water, e.g. 1 grpm of a pipette. In a short time, after squeezing the kompoczyjp pipnki lptzkkkowzj pocoktpjz cienkp to the ccpku cwidyenip, after ccym rockcercp he can and exaggerate the exuberant absorbency and the ability to cpkzkpnip vertically, e.g. a large height. Wynplpcek dotyccy also kpokobu wztwprzpnip tpkiej pipnki orpc products cpwizrpjącycC tpką pipnkę wybrpnycC kpośród pielukcek, wkłpdów DLP Okoba dorokłycC c nietrcympniem moccu, mpetek DLP Okoba dorokłycC c nietrcympniem moccu, products CigieniccnycC DLP women ręccników, sponges wycierpnip, opptrunków e.g. rpny, sponges cCirurgiccnycC, ubrpnia elements, food opposition, kpbli and tp belts.

PL 201 224 B1

Description of the invention

The subject of the invention is a durable, absorbent latex foam with high vertical suction force and a method of its production and products made of it.

Absorbent, hydrophilic polymer foams find use in products that are used to absorb and distribute aqueous fluids, such as diapers, pads, and panty for elderly incontinence; feminine hygiene products such as sanitary napkins and tampons; cloths and sponges; wound dressings and surgical sponges; items of clothing such as sweatshirts, nursing pads; food packaging, e.g. as absorbent pads for juice and sauces (e.g. chicken juice and roasting sauces); cable wraps and waterproof tape.

Flexible, hydrophilic, nonionic, polymeric foams with absorptive properties, i.e. capable of absorbing and distributing liquids, are known, the foam being produced by polymerization in a water-in-oil (w / o) emulsion with a high internal phase content (HIPE). The disclosures in US Patent Nos. 5,550,167, 5,741,581, and 5,786,395 may be cited as examples of such embodiments. Unfortunately, the production of the polymerized HIPE foam requires the treatment of large volumes of water, which complicates the foam manufacturing process. Moreover, it is difficult to obtain a dry foam in the process of w / o HIPE polymerization. A further disadvantage is that HIPE foams typically require a post-synthesis functional grouping or rinsing treatment to render the foam hydrophilic and thus be able to absorb aqueous fluids. US Patent No. 5,741,581 further discloses that the polymer foam material may "collapse" but exhibit the ability to expand on contact with aqueous fluids. This property can only be achieved by extensive post-foaming treatment. The treatment steps include multiple washes with a hydratable salt solution, the foam being squeezed between rollers after each wash. Final wringing between the rollers is done under vacuum followed by drying in a circulating air dryer. A further disadvantage is that HIPE foams may have a user breaking stress, percentage elongation at user tear, and toughness, especially wet, toughness that is less than required for some absorbent applications.

Latex foams for use as absorbents are also known. For example, U.S. Patent Nos. 3,887,408, 3,901,240, 4,000,028, and 4,069,366 disclose absorbent pads in the form of a laminate comprising a crumpled polymer latex foam bonded directly to an absorbent layer or bonded to a nonwoven layer that is bonded to the absorbent layer. The liner is produced by molding the foam, drying it without cross-linking, assembling the foam and laminate layers, compressing the foam under pressure to a specified thickness, and then curing the crushed foam. It is expected that the crush cured foam will have a relatively small pore volume and therefore a low absorption capacity. Moreover, such foam is not expected to expand on contact with aqueous fluids or to exhibit a vertical suction effect at a great height.

U.S. Patent No. 4,990,541 discloses combining a latex foam with a starch or cellulose based polymer to produce an absorbent article. Latex foam is combined with another polymer to achieve the required high liquid absorption capacity. US Patent No. 5,763,067 discloses latex foams with a salt solution absorption capacity of 1.2-7.3 g salt solution / g latex foam too low for use as an absorbent layer.

Suction, that is, the ability to draw fluids beyond the point of contact, can be advantageous in that it allows the use of areas of absorbent material remote from the point of contact with the fluid. Vertical suction, i.e., vertical sucking of the liquid against gravity, should be highly desirable as it allows the absorbent article to be used more fully. Suction can also give the user of the absorbent article a feeling of drier skin by moving the fluid away from the point of contact. Traditional latex foams typically do not wick fluid from the point of contact. Without being bound by theory, it is believed that the poor wicking can be attributed to the relatively large (greater than 50 µm) pore size in latex foams.

In view of the foregoing, it would be convenient to develop a hydrophilic polymeric foam which is capable of absorbing and distributing aqueous fluids but which is simpler to manufacture than

HIPE foams. It would also be advantageous if the absorbent polymer foam were inherently hydrophilic, so that no functional groups or rinses were required after synthesis to achieve hydrophilicity. It would be even more advantageous if the hydrophilic polymer foam had a high free absorption capacity. It would be even more advantageous if the hydrophilic polymer foam was a durable material, for example having good stress at user break, percent elongation at user tear characteristics, and toughness, both before and after fluid absorption. Most preferably, the hydrophilic polymer foam should be capable of sucking up aqueous fluids vertically, high in height and quickly. A polymer foam composition showing all the above-mentioned properties would be highly desirable for use as an absorbent.

It has surprisingly been found that latex foams can be produced with a fluid absorption capacity of more than 10 g saline solution / g foam, which can also suck the saline solution vertically more than 15 cm without complicated post-foaming treatment.

The inventive foam is durable, conformable, hydrophilic, made of polymer latex and has the ability to absorb and distribute aqueous fluids, and is capable of vertically sucking 0.9 wt% sodium chloride solution in water. (hereinafter "0.9 wt.% aqueous saline"), to a height of more than 5 centimeters (cm). As used herein, the term "vertical aspiration" means drawing fluid from the point of contact vertically against the force of gravity. Throughout the description, vertical suction is expressed in units of height (e.g. cm) and is measured as described below in the Measuring Procedures section. In a preferred embodiment, the latex foam of the invention remains thin after compression and before wetting, without the need for complex operations; however, when wetted, the compressed foam expands as it absorbs fluid. This property of remaining compressed until wetted will be hereinafter referred to as "thin until wetted".

The novel polymeric foam of the invention can be used as an absorbent in articles used to absorb and distribute aqueous fluids such as, but not limited to, diapers, adult incontinence products, feminine hygiene products, cloths and sponges; wound dressings and surgical sponges, items of clothing, food packaging, cable wraps and waterproof tape. Conveniently, the absorbent polymer foam of the present invention is inherently hydrophilic, eliminating the need for post-synthesis functional groups or a wash treatment to render it hydrophilic. As a further advantage, the absorbent polymer foam of the invention has good absorption capacity and good consumer tear, good consumer elongation percentage and toughness, both before and after fluid absorption. The absorbent polymer foam according to the invention is capable of sucking up aqueous fluids vertically, to a great height and quickly.

The invention also relates to an article selected from diapers, feminine hygiene products, items of clothing, cloths, abrasive sponges, wound dressings, surgical sponges, food packaging, cable wraps, and waterproof tapes, which articles include a durable, absorbent, conformable the hydrophilic polymer latex foam according to the invention.

The novel foam according to the invention is a durable, conformable, hydrophilic polymer latex foam, capable of taking up and distributing aqueous fluids. The term "aqueous fluid" includes substantially pure water, aqueous saline solutions, as well as aqueous solutions containing one or more soluble components selected from inorganic and organic compounds and ions, including, but not limited to, body fluids (including, but not limited to, urine, blood or fluid, sweat, etc.), water, milk, juice, meat juice, etc.

The polymeric foam according to the invention is characterized by the vertical sucking of a 0.9 wt.% Aqueous saline solution over 5 cm, preferably over 10 cm, more preferably over 15 cm and most preferably over 20 cm. vertical for the purposes of the invention is measured as described below in the Measurement Procedures section.

As used herein, the term "durability" will refer to the desired level of stress at break by the user, percent elongation at break by the user, and toughness. These three physical properties are known to those skilled in the field of materials science, in particular polymer science. General definitions of the above-mentioned physical properties and how to measure them can be found in general textbooks, e.g. in Textbook of Polymer Science, 2nd ed., Fred W. Billmeyer, Jr., Wiley-Interscience, John Wiley &amp; Sons, Inc., New York, 1971. Stress at break by user, percentage elongation at break

User quality and toughness are further defined for the purposes of the invention below in the Measurement Procedures section. The desired levels of stress at break by the user, percent elongation at break by the user, and toughness, with respect to the foam of the invention, are also given below in the Measurement Procedures section.

As used herein, the term "conforming" means having the ability to bend and bend to the desired shape of a user, eg, a person wearing an absorbent article.

As used herein, the term "hydrophilic" will describe a material or surface of a material that is wettable by aqueous fluids, including aqueous body fluids, deposited on the materials. Hydrophilicity and wettability are usually defined by the value of the contact angle. Contact angles are determined by placing a drop of fluid on a material or surface, also referred to as a substrate. "Contact angle" is defined as the angle between the substrate and the line tangent to the liquid droplet at the point where the drop contacts the substrate.

A material or material surface is considered to be wetted by a fluid (i.e., hydrophilic) when the contact angle between the fluid and the material, or its surface, is less than 90 °, or when the fluid tends to spread spontaneously over the surface of the material, both of which conditions normally interact with each other. A contact angle of 0 ° corresponds to a droplet which completely wets the substrate. Conversely, a material or surface is considered to be hydrophobic when its contact angle is 90 ° or greater than 90 ° and the fluid does not spontaneously spread over the surface of the material. A contact angle of 180 ° corresponds to an essentially perfectly spherical droplet on the surface. The problem of wettability of contact angles is discussed in detail by Milton J. Rosen in Surfactants and Interfacial Phenomena, ed., John Wiley &amp; Sons, Inc., 1989.

In preferred embodiments of the invention, the stable, conformable, hydrophilic polymeric foam is further characterized in that its free absorption capacity of a 0.9 wt.% Aqueous salt solution is is greater than 5g, preferably 10g, more preferably greater than 15g and most preferably greater than 18g of saline per gram of foam (g / g). The term "dry foam" refers to a foam that has essentially not been wetted, with the exception of moisture that may be present in the foam after curing or as a result of being left in the ambient environment. A detailed description of the measurement of the free absorption capacity is given below in the Measurement Procedures section.

In another preferred embodiment of the invention, the durable, conformable, hydrophilic, polymeric latex foam is ionic. As used herein, the term "ionic" means a material containing ionic groups, the ion being an atom or radical that has lost or taken one or more electrons and thus has an electrical charge. This applies to both cations (positively charged) and anions (negatively charged). The ionicity of the inventive foam can be derived from ionic substituents present on the latex polymer chain, including residual unreacted ionic functional groups such as carboxylate groups, or from ionic substituents present on additives in the polymer composition, e.g. pH and thickeners. Typically, however, inorganic salts such as calcium chloride are not present in the bulk of the polymer and therefore are not a source of ionic charge.

The invention also relates to a method for producing a durable, conformable, hydrophilic, polymer latex foam capable of absorbing and distributing fluids, having high vertical suction and the above-mentioned preferred free absorption capacity. According to the invention, the method for producing such a foam comprises the following steps:

(a) ερίθηίθηίθΚοιτροζ ^^ ί reactive pollmer which is intended for the production of a durable, conformable, hydrophilic, polymer latex foam, capable of absorbing and distributing aqueous fluids and capable of vertically sucking up a 0.9 wt.% aqueous salt solution. for a height of more than 5 cm;

(b) stretching the foamed latex composition into a desired shape;

(c) setting the latex composition uk ^^ t ^^ ^ t ^ and ^^ n ^ j under conditions sufficient to produce a durable, conformable, hydrophilic, polymer latex foam; and (d) optionally compressing a foam ww ^ r ^^ un ^^ r ^ ih sufficient to produce a "thin-to-wet" foam.

The process of the present invention is a desirable method of producing durable, absorbent latex foams with a high vertical suction capacity of aqueous fluids as well as a high free absorption capacity. Another advantage is that the method according to the invention is

It is less complex than the known high internal phase emulsion polymerization processes. Yet another advantage of the invention is that the production of the new foam does not require vulcanization, which is often used with known latex foams.

As noted above, the term "thin until wet" means that the foam remains thin or compressed after being compressed and prior to wetting; but when wetting, the foam expands and becomes thicker. The degree of compression, and therefore the thickness of the foam prior to wetting, may vary depending on the application. Typically, the thickness of the wet-thin foam is less than 75%, more usually less than 50%, even more usually less than 25% of its thickness in a pre-compressed state prior to wetting. The thickness of the thin until wetting foam may be less than 10% of its thickness in the pre-compressed state prior to wetting. As a result of the fluid absorbing to its total or nearly total capacity, the foam typically achieves greater than 50%, more usually greater than 75%, and even more typically greater than 90% of its thickness in the pre-compressed state in the absence of any forcing forces.

The composition in step (a) of the process is a latex polymer containing certain reactive functional groups. Preferably, the composition additionally comprises a water-dispersible co-reactive material (crosslinker) containing two or more groups capable of reacting with the reactive functional groups of the latex polymer. A "water-dispersible material" is a material that is soluble or dispersible in water or a water-miscible liquid. The composition may also contain other ingredients such as foaming agents, foam stabilizers, pH regulators, thickeners, fillers, antioxidants, gelling agents, softening ingredients. Foaming or foaming of the composition can be achieved by any of a number of known methods, e.g., by the use of blowing agents, by tamping, or by the use of any suitable equipment including commercially available foaming heads.

The reactive latex polymers suitable for use in the invention are preferably polymers of one or more ethylenically unsaturated monomers selected from the styrene class and styrene copolymerizable monomers, e.g. a copolymer containing a monovinylidene aromatic monomer, an aliphatic conjugated diene monomer, and / or an α, β-ethylenically unsaturated acid carboxylic.

At least one of such ethylenically unsaturated monomers which polymerize to form a reactive latex includes those polymerizable ethylenically unsaturated monomers that contain at least one type of side reactive group such as carboxyl, sulfonate, primary amine, secondary amine, amide group, methylolamide group, sulfonamide group, primary hydroxyl group, secondary hydroxyl group, phenolic hydroxyl group, aldehyde group and epoxy group. Alternatively, the polymerizable ethylenically unsaturated monomer may contain substituents that can be polymerized into such reactive substituents, e.g., an ester, nitrile, amide, or salt group that can be hydrolyzed to a reactive acid, amino or hydroxyl group. The amphoteric monomers can also be used to prepare the amphoteric latex polymers as described in US Patent No. 6,025,404.

Ethylenically unsaturated monomers containing lateral reactive substituents include acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, ethyl acid maleate, 2-sulfoethyl acrylate, 2-sulfoethyl methacrylate, 2-aminoethyl methacrylate hydrochloride, 2- acrylate hydrochloride. aminoethyl, vinylbenzylamine, glycidyl methacrylate, hydroxystyrene, acrolein, methacrolein, allyl alcohol, vinylbenzyl alcohol, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, acrylamide, bis-N-methylolacrylamide, N-methylolmethacrylamide, N-methylolmethacrylamide, bis-N-methylolmethacrylamide, methacrylamide, Ne-hydroxyethylacrylamide, N-3-hydroxyethylmethacrylamide, β-hydroxypropyl acrylate, β-hydroxypropyl acrylate, γ-propyl methacrylate acrylate 6-hydroxyhexyl, 6-hydroxyhexyl methacrylate, sodium styrenesulfonate, sodium α-methylstyrenesulfonate, 2-methylaminoethyl acrylate hydrochloride, 2-methylaminoethyl methacrylate hydrochloride, 3-methylaminopropyl acrylate hydrochloride, 3-methylaminopropyl methacrylate hydrochloride, 3-methylaminobutyl acrylate hydrochloride, 3-methylaminobutyl methacrylate hydrochloride, 3-ethylaminopropyl acrylate hydrochloride and styrenesulfonamide.

Ethylenically unsaturated styrene grade monomers and styrene copolymerizable monomers include monomers containing one or more of the reactive substituents listed above; monovinylidene aromatic monomers (styrenic compounds); unsaturated acid derivatives such as acrylic esters, acrylic nitriles, maleic esters and fumaric esters;

Unsaturated alcohol esters; unsaturated ketones; conjugated olefins; and other compounds containing one or more addition polymerizable ethylene linkages.

Specific such ethylenically unsaturated compounds include styrene, α-methyl styrene, ar-methylstyrene, ar-ethylstyrene, α-ar-dimethylstyrene, ar, ar-dimethylstyrene, ar-t-butylstyrene, vinylnaphthalene, methoxystyrene, cyanostyrene, acetylstyrene, monochlorostyrene, , dichlorostyrene and other halostyrenes, methyl methacrylate, ethyl acrylate, butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, lauryl methacrylate, phenyl acrylate, acrylonitrile, methacrylonitrile, ethyl α-chloroacrylate, diethyl maleate, polyglycol maleate, vinyl chloride, vinyl bromide, vinylidene chloride, vinylidene bromide, methyl vinyl ketone, methyl isopropenyl ketone, vinyl ethyl ester, 1,3-butadiene, isoprene, etc.

The latexes of the above polymers are prepared by polymerizing one or more ethylenically unsaturated monomers of the styrene class and styrene copolymerizable monomers, at least one of which contains a side reactive substituent, by conventional emulsion polymerization methods.

In one preferred embodiment, the reactive latex is selected from epoxy modified styrene / butadiene latex polymers, preferably styrene / butadiene / glycidyl methacrylate latex.

In another preferred embodiment, the reactive latex polymer is an ionically functional latex polymer that yields an ionically functional foam; more preferably an ionically functional styrene / butadiene latex polymer, and even more preferably a carboxylated styrene / butadiene latex polymer. Most preferably, the reactive latex is a styrene / butadiene / acrylic acid, styrene / butadiene / itaconic acid, or styrene / butadiene / glycidyl methacrylate latex polymer.

Any reactive latex with any solids content can be used in the latex polymer composition, as long as the foam according to the invention is obtained. Preferably the reactive latex has a solids content of more than 20 wt%, preferably more than 30 wt%, more preferably more than 40 wt%, based on the total weight of the composition. Typically, the reactive latex solids content of the composition is less than 80 wt.%, Typically less than 70 wt.%, And more usually less than 60 wt.%, Based on the total weight of the composition.

The co-reactive materials or crosslinkers which are preferably mixed with the reactive latices used in the invention are those which are soluble or dispersible in water or in water miscible liquids and which contain at least one carbon atom and at least two substituents which are compatible with reactive groups in the copolymer of this latex. Other latexes can be selected as co-reactive material for use with the reactive latex component that contain polymers containing a number of substituents that are also co-reactive with the substituents in the copolymer of that reactive latex. Representative co-reactive substituents include (a) methylol groups attached to a nitrogen atom, (b) modified methylol groups, alkylated with an alcohol containing 1-4 carbon atoms, which groups are attached to the nitrogen atom, (c) methylol groups attached to an aromatic ring a phenolic compound, (d) carboxyl groups, (e) primary amino groups, (f) secondary amino groups, (g) epoxy groups, and (h) amphoteric functional groups. The nitrogen atom in (a) and (b) may form part of the backbone chain or ring of the compound or polymer. According to the invention, vulcanization, i.e., sulfur cross-linking, is preferably not used.

Non-limiting examples of suitable co-reactive materials include melamine, melamine formaldehyde condensates, urea, urea formaldehyde condensates, methylated melamine formaldehyde condensates, methylated urea formaldehyde condensates, butylated melamine formaldehyde condensates, butylated urea formaldehyde condensates, phenol amaldehyde condensates, phenol formaldehyde condensates. -formaldehyde-hydrochloric acid, liquid epoxy resins, ethylenediamine-formaldehyde condensate, hexamethylene diamine-formaldehyde condensate, polyethyleneimine, ethylenediamine, diethylene triamine, triethylene tetramine acetate, trimethylene diamine, tetramethylene diamine, hexamethylenediamine, decamethylenediamine, tetraethylene penta diamine, guananidinic acid, glucanidinic acid, sucanidinic acid, sucanidinic acid, pimelic acid, suberic acid, azaleic acid, sebacic acid, polyacylic acid, latex containing a copolymer of styrene, 1,3-butadiene and 2-aminoethyl methacrylate hydrochloride, and a latex containing vinyl chloride, vinylidene chloride, 2-sulfoethyl methacrylate, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycidyl glycidyl sorbitol ether polyglycerin polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerin polyglycidyl ether, ether

PL 201 224 B1 glycerin polyglycidyl, trimethylolpropane polyglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, resorcinol diglycidyl ether, glycidyl ester / glycidyl ether, p-hydroxybenzene diglycidyl ester / glycidyl ester diglycidyl ether, diglycol ether diglycidyl ether o-phthalic acid; and a high molecular weight dicarboxylic acid diglycidyl ester. Preferred coreactive materials include ethylene glycol diglycidyl ether, glycol diglycidyl ether, polyethylene glycol diglycidyl ether, diethylene ether, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol, diglycerol ether, glycerol polyglycidyl ether, polyglycidyl trimethylolpropane ether, propylene glycol diglycidyl ether, diglycidyl polypropylene glycol, resorcinol diglycidyl ether, p-hydroxybenzoic acid glycidyl ester / glycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, o-phthalic acid diglycidyl ester and high molecular weight dicarboxylic acid diglycidyl ester. The more preferred co-reactive materials include epoxy-substituted polyalkylene polyethers. The most preferred co-reactive materials are ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether and diethylene glycol diglycidyl ether.

When the co-reactive material is water-soluble, it can simply be mixed with the latex, or it can be added as an aqueous solution or as a solution in a water-miscible solvent. When the co-reactive material is not significantly water-soluble or a water-miscible liquid, it is added as an aqueous dispersion. However, any emulsifiers used to prepare such dispersions, as well as the emulsifiers used to make the latex, are preferably selected to be compatible with each other and with the reactive groups in the latex polymer and with the reactive groups in the co-reactive material.

When a co-reactive material is used, it may be present in the latex composition in any amount ranging from greater than 0 to 100 parts of the co-reactive material per 100 parts solids or more based on the weight of the reactive latex solids. When a co-reactive material is used, it is preferably present in an amount greater than 0, more preferably greater than 3 parts per 100 parts solids, based on the weight of the reactive latex solids. When a co-reactive material is used, it is preferably present in an amount of less than 20 parts, more preferably, less than 10 parts, and most preferably less than 8 parts per 100 parts solids, based on the weight of reactive latex solids.

Foaming aids, foam stabilizers, pH regulators, thickeners, fillers, antioxidants, gelling agents, softening ingredients and the like may be included as optional additional ingredients in the composition. A substance will often fulfill more than one of these roles, which may be obvious to those skilled in the art, even though the material may primarily be represented in a paragraph for one specific additive.

The composition may optionally contain foaming aids. Foaming aids facilitate the formation of foams and foams and include substances such as sodium lauryl sulfate, sodium dodecyl sulfate, and mixtures thereof. If used, foam aids will be present in an amount greater than 0 parts per 100 parts solids, based on the weight of the reactive latex solids. If used, foam boosters will be present in an amount of less than 50, preferably less than 10, more preferably less than 5 parts per 100 parts solids, based on the weight of the reactive latex solids.

As another optional ingredient, the composition may contain foam stabilizers. Foam stabilizers increase the integrity of the foam / foam in the shaping and setting process and can also act as foam aids. Foam stabilizers include, for example, potassium oleate, disodium N-octyl decylsulfosuccinimate, and mixtures thereof. A preferred foam stabilizer is disodium N-octyldecyl sulfosuccinimate. If used, the stabilizer will be present in an amount greater than 0 parts per 100 parts solids, based on the weight of the reactive latex solids. Typically, the stabilizer may be added in an amount of less than 50, preferably less than 20, more preferably less than 10, and most preferably less than 5 parts per 100 parts solids, based on the weight of reactive latex solids.

The composition may optionally contain pH regulators. The inclusion of pH regulators can serve to regulate the rate of reaction between the reactive latex and the co-reactive material as well as to modify the viscosity of the composition. The pH of the composition may be adjusted, if desired, by adding conventional acidifying or basifying agents such as acetic acid, citric acid, dilute mineral acids (e.g. HCl, H2SO4, HNO3), ammonium hydroxide, dilute aqueous solutions of alkali metal hydroxides, etc. When the composition does not show the desired

Due to the pH level, the pH is usually adjusted to a value greater than 7, preferably greater than 8, and less than 13, preferably less than 11, more preferably less than 10.

As yet another additional ingredient, a thickener may be used to modify the viscosity of the composition. Suitable non-limiting examples of thickeners are methyl cellulose, ethyl cellulose, alkaline swellable latexes and alkaline soluble latexes. Thickening agents can fulfill various functions, depending on the thickener used; for example, certain thickeners can render the polymer hydrophilic and / or sticky. The amount of thickener used will depend on the thickening properties of the particular thickener used as well as the final viscosity desired. Those skilled in the art should know how to determine the amount of a particular thickener needed to achieve the desired viscosity. Typically, the amount of thickener used is from greater than 0 to less than 20 parts per 100 parts solids, based on the weight of the reactive latex solids.

One or more fillers may optionally be included in the composition to modify the solids content or the physical and / or visual properties of the foam. Fillers that may be used include, for example, talc, calcium carbonate, titanium dioxide, carbon black, redispersible latex, pigments for plastics, colloidal silica, hollow ceramic microspheres and hollow glass microspheres. Rigid fillers can be used to increase the stiffness of the finished foam, while flexible fillers can be used to reduce the stiffness of the finished foam. Low density fillers, such as hollow ceramic microspheres and hollow glass microspheres, can be used to reduce the density of the finished foam and thus increase the g / g fluid absorbency of the foam without the need for foaming to achieve a larger pore volume. If a filler is used, the amount will typically be from greater than 1 to less than 100 parts per 100 parts solids, based on the weight of the reactive latex solids.

Optionally, antioxidants can also be used in the composition. Antioxidants inhibit foam / foam oxidation during solidification. Oxidation can discolor the foam and degrade its final physical properties. Antioxidants are well known. Examples of antioxidants include, but are not limited to, substituted phenolic compounds such as butylated dihydroxyanisole, di-t-butyl-p-cresol, and propyl gallate. Additional examples of antioxidants include aromatic amines such as di-α-naphthyl-p-phenylenediamine and phenyl-α-naphthylamine. The two commercially available antioxidant compositions are Aquamix ™ 494 (Harwick Chemical Corporation) and Lowinox® Emulsion L (Chemische Werke Lowi GmbH &amp; Company) antioxidants. Aquamix ™ 494 antioxidant is a composition containing 3- (dodecylthio) propionic acid diester, tetraethylene glycol and the reaction products of 4-methylphenol with dicyclopentadiene and isobutylene. When used, antioxidants may be present in the composition at a concentration greater than 0 parts per 100 parts solids, based on the weight of the reactive latex solids. When used, antioxidants may be present in the composition in a concentration of less than 10, preferably less than 5, more preferably less than 2 parts per 100 parts solids, based on the weight of the reactive latex solids.

Optionally, gelling agents may also be used in the composition to facilitate gelation of the semi-liquid viscous foam to form a solid cellular structure upon drying and curing.

The gelling mechanism must be carefully monitored and regulated. Gelation of the foam can occur by hydrolysis of relatively insoluble acid-forming chemicals, such as the ammonium, sodium or potassium salts of silicon fluorides. Gelation of the foam can also occur by decomposition of suitable thermally sensitive ammonium salts such as sulfates, nitrates, chlorides, thiocyanates, ammonium formates and acetates. Hydrolysable electrolytes or thermally sensitive ammonium salts can be introduced after the liquid foam has been mixed and frothed. Typically, gelling agents are carefully dosed into the foam after foaming but prior to forming the foam to the desired shape. Gelling agents, such as those disclosed in U.S. Patent 4,205,103, may also be incorporated into the foam latex or finished foam composition prior to frothing. The amount of gelling agent used will be selected based on the gelling effect of the selected gelling agent and depending on the target viscosity to be achieved.

Optionally, softening ingredients may also be used in the composition to lower the effective glass transition temperature (Tg) of the foam latex composition of the invention.

The effective Tg is the temperature at which the foam changes from rigid (non-conformable) to flexible (conformable). Softeners are any additives,

Which increase the flexibility of the polymer. Plasticizers include surfactants with long chain hydrophobic ends, oils, solvents, etc. The amount of plasticizer used will be selected taking into account the required flexibility of the foam.

The composition is intended to produce a conformable foam after shaping and solidification. The skilled person can design the recipe in many ways so as to obtain a conformable foam; however, in general, the conformability is governed by the effective Tg of the foam.

Accordingly, the effective Tg of the foam of the invention preferably lies below the temperature at which the material is to be used. Preferably, the effective Tg of the inventive foam is less than 40 ° C, more preferably, less than about ambient temperature (taken as 25 ° C), more preferably, less than 10 ° C. The effective Tg can e.g. be determined by known standardized rheological methods, including e.g. measuring the modulus of elasticity in compression. The effective Tg can be regulated e.g. selection of the reactive latex, optionally used co-reactive material (or crosslinker) and optionally used softening ingredients. Accordingly, the effective Tg of the finished foam may differ from the Tg of the latex polymer itself.

The reactive latex composition and any additional ingredients can be foamed or made into a foam using the blowing agents and methods used with known latex foams. One way is to release a gas, such as nitrogen or air, into the composition. Other suitable gases include, for example, carbon dioxide, helium, argon, and freons. Another approach is to chemically react a gas-releasing material with a component in the composition to generate gas as a reaction product. The mixture of reactive latex and additional ingredients may also be foamed by tamping or by using any suitable equipment including commercially available foaming heads. Typically, the volume of the frothed composition is increased by more than 5 times, preferably more than 10 times, more preferably more than 15 times, and most preferably more than 20 times the volume of the original composition before frothing. Typically, the volume of the foamed composition is less than 50 times the original volume.

Typically, the density of the foam is the target at which the free absorption capacity of the finished latex foam, without filler, of more than 5 g of 0.9 wt% is achieved. saline solution / g of latex foam. Preferably, the density of the foam is the target at which a free absorption capacity, without filler, of greater than 10 g / g, more preferably greater than 15 g / g, and most preferably greater than 18 g / g can be achieved.

For a given pore volume, the free absorption capacity in g / g can be increased by incorporating into the foam a low density filler material that reduces the density of the foam, e.g. hollow ceramic or glass microspheres. Suitable foam densities, before compression and without filler, are typically over 0.02 grams per cubic centimeter (g / cm³). Typically, before compression and without filler, the foam has a density of less than 0.20 g / cm3. Preferably, the density of the foam before compression and without filler is below 0.10 g / cm3, more preferably below 0.07 g / cm3, even more preferably below 0.05 g / cm3.³.

The foamed composition is then shaped by any known method, such as one or more of the following: (a) pouring or spreading in molds, (b) spreading on a flat tray or tape, (c) coating or laminating onto substrates, or (d) layering or mixing two or more froths. As used herein, the term "substrate" means any material such as a collection of fibers, woven fabric, textile material, synthetic non-woven material, polymer film, non-latex polymer foam, including polypropylene and urethane foams, leather, wood, glass, metal, or any other form of substrate. to which the foamed mixture will stick after application and curing. If desired, the backing and / or latex foam may be punctured to form a set of microholes to facilitate fluid aspiration. In a preferred example, the absorbent latex foam of the invention can be laminated onto a nonwoven fabric with micro-holes. This design is desirable for diapers and feminine hygiene products as the non-woven fabric provides a softer feel to the skin and the micro-holes improve suction for a dry feeling.

Another preferred shaping process is to foam-coat a substrate having a superabsorbent polymer incorporated into the substrate or applied as a layer, "substrate" having the above meaning. For example, the substrate may be superabsorbent fibers or a powder incorporated into the substrate; the substrate may include a superabsorbent film on the surface to be coated, uniformly coated or patterned; substrate can

The superabsorbent polymer in the form of fibers or granules distributed randomly or in a predetermined pattern on the surface of the substrate to be coated. The superabsorbent may conveniently be patterned in the substrate or on the substrate such that, in the case of a diaper, fluid is absorbed by the superabsorbent polymer at the desired target locations in the diaper. An advantage of such an embodiment of the invention is that the superabsorbent components do not substantially move freely in the article, unlike conventional diapers where the superabsorbent granules are distributed in the cellulose fluff. Other advantages of the superabsorbent polymer as a pattern in the substrate or on a coated substrate include that (1) the fluid can be stored at the target locations of the article, such as a diaper, and (2) patterns, logos, pictures, etc. can be applied as a pattern in and / or onto a substrate such that when the article is wet, the pattern, logo, image etc. will swell and become visible.

In another variant of the process, two or more foams may be combined in a shaping process to form layered or blended foams. For example, the first foam may be produced to obtain a foam with large diameter cells, and the second foam may be produced to obtain a foam with small diameter cells. The first foam may be shaped as previously described and the second foam may then be shaped on the surface of the first foam, either before or after solidification. Large and small diameter cells are defined below. In addition to layering, two or more foams may be swirled or mixed just prior to shaping, so as to obtain shaped foams with zones of different properties. For example, the first and second foams described in the example of a layered foam can be swirled together before or during shaping to obtain, after solidification of the foam, vortex zones with large and small cells. Likewise, if desired, a substrate and / or a separate superabsorbent layer may be applied between the foam layers.

Preferably, the shaping is performed on a continuously moving belt such that the shaped foam is directed directly to the solidification process. In a continuously moving belt process, for example, a scraper bar can be used that levels the top surface of the foam to achieve the desired thickness. Moreover, the sides of the strip may be shaped to define the shape of the foam in the final product. For example, the belt may be shaped to obtain a rolled foam stock having continuous "hourglass" -type sections that can be cut at unit intervals to obtain diaper inserts. By shaping the edges of the foam in this manner, it is possible to reduce the amount of foam waste that would arise if the hourglass shape was cut from the rectangular section.

The shaped foam is subjected to solidification and drying, typically for a time sufficient to form a substantially dry polymer foam structure. The setting and drying processes are well known for latex foam foams and depend on the type of reactive latex used, whether and what co-reactive material is used, and whether and what a gelling agent is used. Setting and drying are usually carried out at a temperature above 90 ° C and below 200 ° C for a period from less than 1 minute to 90 minutes. Thicker foams often take longer to set and dry at a given temperature than thinner foams. Higher density foams require longer setting and drying time at a given temperature than lower density foams.

The foams of the invention are also characterized by an open-cell structure and, prior to compression, a cell size ranging from greater than 50 µm to less than 2 mm with respect to the diameter (cross-sectional size) as determined by scanning electron microscopy (SEM).

The polymeric walls or struts of the foams of the invention are typically characterized by having prominent domains derived from the surface materials of the latex particles (typically a carboxylate-rich material). For example, it is known that carboxylated latex films produced at a higher pH (greater than about 7) contain trabecular meshes of carboxylated material in the latex film to outline the surface of the individual latex particles. It is also known that in carboxylated latex films produced at a lower pH (about 3) the carboxylated material is highly dispersed as discrete particles in the latex film. These two types of domains have been well documented, eg, by CS Kan and JH Blackson, in "Effect of lonomeric Behavior on the Viscoelastic Properties and Morphology of Carboxylated Latex Films", Macromolecules, 29 (1996), 6853-6864. Such cell wall domains are believed to contribute to the durability of the latex foam and are not to be expected in foams obtained directly from monomers, such as polymerized HIPE foams, as HIPE foams are not formed from particles.

PL 201 224 B1

Without being bound by theory, it is believed that the domains described above, arranged in the walls or struts of the latex, contribute to the durability of the latex foam by strengthening the polymer. The carboxylated latex compositions used to make the foams of the invention typically have a pH greater than 7, so it is expected that they will have a substantially carboxylate-rich honeycomb structure in their polymer walls. Indeed, analysis of the foam of Example 2 below by Transmission Electron Microscopy (TEM) confirmed the existence of the expected honeycomb structure. Crosslinking of the latex typically occurs through surface functional groups, usually carboxylate groups, on the latex particle. Therefore, it is expected that the resulting honeycomb structure corresponds largely to a continuous film with the interconnection of individual latex particles by cross-links, whereby a reinforcing structure is formed in the polymer wall or strut. Likewise, if highly dispersed domains are generated, it is expected that they will correspond to zones of higher cross-linking that may interfere with tear expansion or fracture in the polymer wall.

Blend compositions of higher Tg and lower Tg latexes can also provide foams with different types of advantageous structure in the polymer walls or struts. A lower Tg latex may be selected to ultimately form a continuous wall or spacer structure, while the higher Tg latex will remain primarily as particles in the wall or spacer cross-linked to the lower Tg latex film. In this situation, the higher Tg latex essentially acts as a cross-linker to reinforce the polymer wall or spacer.

One preferred embodiment of the invention involves shaping a relatively thick foam and then setting and drying slowly enough such that the cells in the center of the foam are relatively large and progressively smaller towards the surface of the foam. The gradient structure is a result of the relatively quick solidification of the foam surface as compared to the interior of the foam. As a result, there is a possibility of cell growth inside the foam after the bonding of the surface structure. The resulting foam can optionally be split, e.g. approximately in half, i.e. approximately in the middle between the surfaces perpendicular to the thickness axis, yielding two foams with a cell size gradient, large cells on one surface and small cells on the opposite surface. Another method of achieving a cell size gradient involves curing one side of the foam at a temperature lower than the opposite side of the foam. Foams with this gradient structure are particularly suitable for rapidly absorbing fluids and solid particles on a surface with large cells, with the fluid being quickly sucked up from the acquisition point by small cells adjacent to the opposite surface. In view of the invention, the size of the small cell is typically 50-150 µm and the size of the large cell is greater than 150 µm to 2 mm.

The foams of the invention are hydrophilic in nature and do not need to be modified after manufacture. The hydrophilicity may be provided by the latex polymer itself, e.g. in the case where hydrophilic functional groups, such as hydroxyl groups or carboxylic acid groups, are present in the polymer.

Additionally or alternatively, hydrophilicity may be achieved by hydrophilic components in the latex composition such as hydrophilic foaming aids, foam stabilizers, thickeners, etc.

As stated above, the inventive foam is capable of vertical wicking of 0.9 wt.% Aqueous saline solution. to a height typically greater than 5 cm, preferably greater than 10 cm, more preferably greater than 15 cm, and most preferably greater than 20 cm. Typically, the inventive foam sucks up aqueous fluids quickly; for example, vertical suction of 0.9 wt.% aqueous saline is usually achieved. to a height of typically greater than 5 cm, preferably greater than 7 cm, more preferably greater than 10 cm in 2 minutes.

Durability, as measured by user fracture stress, consumer elongation percentage, and toughness, are also useful in characterizing the latex foam of the invention.

Prior to wetting, the latex foams of the invention typically exhibit durability characterized by: (1) a user breaking stress of typically more than 345 kPa (50 psi).² (psi)), preferably, greater than 517 kPa (75 psi), more preferably, greater than 689 kPa (100 psi); (2) an elongation at user break of typically greater than 100%, preferably greater than 150%, more preferably greater than 200%, even more preferably greater than 250% and most preferably greater than 280%; and (3) a toughness of typically greater than 689 kPa (100 psi), preferably greater than 1034 kPa (150 psi), more preferably greater than 1374 kPa (200 psi).

Upon absorption of a 0.9 wt.% Aqueous saline solution in an amount corresponding to substantially full absorption capacity, the latex foams according to the invention exhibit characteristic durability

A stress at user break is typically greater than 34.5 kPa (5 psi), preferably greater than 68.9 kPa (10 psi), more preferably greater than 103.4 kPa (15 psi), and most preferably greater than 137.9 kPa (20 psi); (2) an elongation at user break of substantially greater than 25%, preferably greater than 50%, more preferably greater than 100%, even more preferably greater than 150%, even more preferably greater than 200% and most preferably greater than 250%; and (3) a toughness of typically greater than 6.9 kPa (1 psi), preferably greater than 68.9 kPa (10 psi), more preferably greater than 103.4 kPa (15 psi), even more preferably greater than 137.9 kPa ( 20 psi), and most preferably in excess of 172 kPa (25 psi).

The setting and drying step is optionally followed by a compression step to reduce the thickness of the foam. The compression of the foam can be achieved either continuously or batchwise. Preferably, the compression is carried out continuously by passing the foam through one or more pairs of nip rollers. Pressing can also be performed, for example, in a hydraulic press. Any pressure can be applied to achieve the desired thickness of the foam. Typically, the pressure is greater than 193 kPa (28 psig), preferably greater than 483 kPa (70 psig). Typically the pressure is less than 4826 kPa (700 psig), preferably less than 1448 kPa (210 psig). Typically, the compression is carried out at a temperature close to ambient temperature (which in this case is taken to be around 22 ° C), however, it is also possible to compress at a different temperature and may be a preferred way of achieving optimal adhesion of the foam as thin as possible. wetting.

In another embodiment of the invention, the foam may be micro-punctured during pressing or afterwards. Micro-punctures facilitate the faster passage of fluid through the foam and are particularly useful on the surface of the foam if a skin is formed during the curing step. Micro-punctures can be made in the foam by piercing one or both of its surfaces with one or more pairs of pinch rollers with needles disposed on the surface.

In another embodiment of the invention, the foam may be embossed with a pattern or logo in the pressing step to create a pattern or to create a more fabric-like feel or to aid in the distribution of fluid.

Preferably, the compressed foam remains compressed without the need for external restraining forces. More preferably, the foam will remain compressed until wetted (it will be "thin until wet") and the foam will expand as the fluid is absorbed. Compressed foam takes up less space than expanded foam, which can be an important feature for articles such as diapers as thinner articles are more comfortable to wear and take up less space during transport and storage. Surprisingly, compressing the foam dramatically increases the vertical wicking height of the fluid. It is believed, but not bound by the theory, that smaller sized cells provide higher suction than larger sized cells, e.g. in the same way that smaller diameter capillaries provide higher capillary suction for fluid suction than larger capillaries. An additional advantage of a "thin-to-wet" foam is that the viscous component of the hydrodynamic drag creating resistance to the rapid wicking of the fluid is reduced as the foam expands, and the small-sized cells at the fluid boundary continue to induce strong capillary suction pulling the fluid. up the foam.

Foams that remain thin after compression may require a tackifier component to counter the resilient force of the polymeric struts in the foam. The resilient force of the foam struts, which causes the compressed foam to expand again, must be overcome by the "sticking force" holding the cell walls together. The sticking effect can be achieved in any of a number of ways. Foam, which was e.g. when compressed at a temperature above the effective Tg of the foam, it may remain compressed due to entanglement of the polymer chains. In such a method, care should be taken to stick the foam in a compressed state, but not to permanently stick the walls together. In an alternative, or concurrent with, the polymer entanglement process, tackifying agents can be incorporated into the composition to cause the cell walls to stick together when the foam is pressed. A number of materials can act as tackifying agents, including, for example, the above-mentioned thickeners, the above-mentioned foam stabilizing ingredients, as well as sticky hydrophobic materials such as polyacrylic acid, partially or fully neutralized polyacrylic acid such as sodium polyacrylate; and glycol, polyglycols, glycerin, sugars, surfactants, etc. Preferably, the sticking force is sufficiently released upon wetting to allow at least partial re-expansion of the foam. The amount of tackifying agent will depend greatly on the other ingredients of the composition. Usually one or more already

The tackifier of the listed components sufficiently acts as a tackifier, so that an additional tackifier as such is not necessary. The skilled artisan can quickly determine the amount of tackifier if required.

Measurement procedures

Unless expressly stated otherwise, the following measurement procedures were used in this patent application. The vertical wicking height was determined using a foam strip-shaped sample approximately 1 inch (2.54 cm) wide and approximately 30 cm long. The strip-shaped sample was glued to a plastic plate with double-sided adhesive tape and positioned next to the ruler so that the lower end of the strip-shaped sample coincided with the lower end of the ruler. The plate was suspended over a bath of 0.9 wt. (%) aqueous salt solution with a minimum amount of blue food coloring (to facilitate visualization of the fluid front). At "time zero", the bath was raised to contact the bottom end of the foam. The height of the fluid level on the front surface of the foam was recorded at specified intervals (typically 2, 10, 30, and 60 minutes).

The free absorption capacity was determined using a strip-shaped sample from the vertical suction measurement. The strip-shaped sample was placed in a bath of 0.9 wt% saline solution. After the foam was fully saturated, it was removed from the bath with a spatula and placed on a coarse wire mesh to allow excess liquid to drain. The saturated foam was then weighed to obtain a wet weight. After weighing, the strip-shaped sample was dried in a forced air oven at 60 ° C and then reweighed to obtain a dry weight. The free absorption capacity was calculated by dividing the difference between the wet and dry weight by the dry weight of the foam.

Measurements of stress at break by the user, percent elongation (strain) at break by the user, and tensile strength (strain energy) were made on an Instron 55R4201, using 45.3 kg (100 lb) loading cell and a tensile rate of 50.8 cm / min (20 inches / minute). Measurements were made on foam specimens 10.16 cm (4 inches) long by 2.54 cm (1 inch) wide. The dry specimens were 0.6 mm (0.024 inch) thick; the wet thickness of the samples was about 5.8 mm (0.23 inch).

The invention will become clearer on considering the following examples which are intended to illustrate the application of the invention by way of example only. Other aspects of the invention will become apparent to those skilled in the art from considering the description or from practicing the disclosed invention.

Example 1

A latex composition was prepared having the composition given in Table 1. The latex grades used (The Dow Chemical Company latex grades DL532 and DL313) were based on carboxylate / styrene / butadiene monomers. The composition of DL532 grade latex monomers (Tg -37 ° C) was 60% butadiene, 37% styrene and 3% acrylic acid. The composition of the DL313 latex monomers (Tg 2 ° C) was as follows: 58% styrene, 39% butadiene, 3% itaconic acid. Latex compositions were prepared by adding the ingredients, in the order shown in Table 1, to a beaker while agitating with a Cowles spatula. Efforts were made to minimize the amount of trapped air.

Table 1.

The latex foam composition of Example 1

<td>Sktadnik³</td><td>Name</td><td>% solids</td><td>Dry parts by weight</td><td>Parts wet by weight</td>

<td>Latex</td><td>DL532</td><td> 51</td><td> 65</td><td> 126,95</td>

<td>Latex</td><td>DL313</td><td> 49</td><td> 35</td><td> 71,14</td>

<td>Antioxidant</td><td>Aquamix ™ 494</td><td> 58</td><td> 1,50</td><td> 2,59</td>

<td>Foam stabilizer</td><td>Stanfax ™ 318</td><td> 35</td><td> 3,50</td><td> 10,00</td>

<td>Thickener</td><td>Methocel ™ E4M</td><td> 2,5</td><td> 0,33</td><td> 13,20</td>

<td>Principle</td><td>NH4OH</td><td> 28</td><td>(up to pH 9)</td><td>(up to pH 9)</td>

<td>Co-reactive material: epoxy</td><td>Ethylene glycol diglycidyl ether</td><td> 100</td><td> 6,00</td><td> 6,00</td>

PL 201 224 B1

a. Latexes of grades DL532 and DL313 and thickener grade Methocel ™ E4M were obtained from The

Dow Chemical Company. Aquamix ™ 494 grade antioxidant was obtained from Harwick Chemical

Corporation. Stanfax ™ 318 grade foam stabilizer was obtained from Standard Adhesive &amp; Chemical

Company, Inc. Ethylene glycol diglycidyl ether (EGDGE) was obtained from Nagase Chemical Ltd.

as a grade of Denacol ™ EX-810.

The latex composition in Table 1 was foamed in a Kitchen-Aid Mixer (Professional Model) to give a cup weighing 8.6 g. The weight of the cup corresponded to the weight of the foam filling to the brim of the 88.7 cm cup.³. The foam was spread over 10 inch x 14 inch (25.4 cm x 35.56 cm) silicon release paper and leveled to a height of 1.27 cm (0.5 inch).

The assembly was passed through a radiant dryer (Holman Minimeyor ™ Model 214) on a chain conveyor belt. The assembly was passed through a radiant dryer by pressing pins through the separation paper that engage the chain conveyor. A scraper bar was secured over the mesh at a distance corresponding to the desired thickness of the foam after scraping. The top of the latex was pressed against the scraper bar.

The radiant dryer had heaters located above and below the conveyor. The heaters, top and bottom, were set to a temperature of about 100 ° C. The speed of the conveyor was adjusted to provide a residence time in the dryer of 30 seconds. After passing through the infrared dryer, the foam was placed in a forced air dryer at 150 ° C for 20 minutes to give an uncompressed foam. The foam was cooled to room temperature and then pressed under 965 kPa (140 psig) gauge in a hydraulic press. The compressed foam remained thin until wetted.

Within 24 hours of compressing the foam, the vertical wicking height and the free absorption capacity of the uncompressed and compressed foam were measured as described above in the Measurement Procedures section. The results are shown in Table 2 below.

Table 2.

Suction height (cm)

<td>Time (minutes)</td><td>Not ironed</td><td>Compressed</td>

<td> 2,0</td><td> 2,8</td><td> 7,0</td>

<td> 10</td><td> 4,0</td><td> 13,7</td>

<td> 30</td><td> 4,5</td><td> 17</td>

<td> 60</td><td> 4,9</td><td> 18</td>

<td>Free absorption capacity</td><td>17.1 g / g</td><td>17.8 g / g</td>

Surprisingly, in an alternative, preferred form of the invention, compression of such foams provides a significant improvement in wicking properties without loss of fluid absorption.

Example 2

A latex composition was prepared having the composition given in Table 1. The latex grades used (The Dow Chemical Company latex grades DL532 and DL313) were based on carboxylate / styrene / butadiene monomers as monomers. The composition of DL532 grade latex monomers (Tg -37 ° C) was 60% butadiene, 37% styrene and 3% acrylic acid. The composition of the DL313 latex monomers (Tg 2 ° C) was as follows: 58% styrene, 39% butadiene, 3% itaconic acid. Latex compositions were prepared by adding the ingredients, in the order shown in Table 3, to a beaker with a Cowles style spatula. Efforts were made to minimize the amount of trapped air.

Table 3.

The latex foam composition of Example 1

<td>Skł^anddiary^and</td><td>Name</td><td>% solids</td><td>Dry parts by weight</td><td>Parts wet by weight</td>

<td> 1</td><td> 2</td><td> 3</td><td> 4</td><td> 5</td>

<td>Latex</td><td>DL595</td><td> 51</td><td> 65</td><td> 126,95</td>

<td>Latex</td><td>DL313</td><td> 49</td><td> 35</td><td> 71,14</td>

<td>Antioxidant</td><td>Aquamix ™ 494</td><td> 58</td><td> 1,50</td><td> 2,59</td>

PL 201 224 B1 cont. table 3

<td> 1</td><td> 2</td><td> 3</td><td> 4</td><td> 5</td>

<td>Foam stabilizer</td><td>Stanfax ™ 318</td><td> 35</td><td> 3,50</td><td> 10,00</td>

<td>Thickener</td><td>Methocel ™ E4M</td><td> 2,5</td><td> 0,33</td><td> 13,20</td>

<td>Principle</td><td>NH4OH</td><td> 28</td><td>(up to pH 9)</td><td>(up to pH 9)</td>

<td>Co-reactive material: epoxy</td><td>Ethylene glycol diglycidyl ether</td><td> 100</td><td> 6,00</td><td> 6,00</td>

The latexes DL595 and DL313 grades and Methocel ™ grade E4M thickener were obtained from The Dow Chemical Company. Aquamix ™ 494 grade antioxidant was obtained from Harwick Chemical Corporation. Stanfax ™ 318 grade foam stabilizer was obtained from Standard Adhesive &amp; Chemical Company, Inc. Ethylene glycol diglycidyl ether (EGDGE) was obtained from Nagase Chemical Ltd. as a Denacol ™ EX-810 grade.

The latex composition was foamed using a Cowie-Riding (CR-twin) foaming machine using only the first of the two mixing heads. The pump speed of the composition was maintained at 10 rpm (RPM) and the speed of the mix head was kept at 650 RPM. The air pressure was adjusted to obtain a cup weight of 8.7-9.0 g. The cup weight corresponded to the weight of the foam filling to the brim of the cup with a capacity of 88.7 cm.³. The weight of the cup was measured before and after the foam was drawn to check the stability of the foam density. The foam was discharged from the mix head through a 134.6 cm (53 inch) long Tygon ™ tube (6.3 mm (1/4 inch) ID).

Foam was leveled to a thickness of 6.3 mm (0.25 inches) on a Teflon ™ coated 25.4 cm (10 inches) x 35.6 cm (14 inches) mesh of approximately 1 mm thick fibers with approximately 1 mm with fiber spacing. The web was loaded into a radiant dryer (Holman Minimeyor ™ Model 214) on a chain conveyor belt. The mesh was passed through the radiant dryer by pinning through the mesh with pins that engage the chain conveyor. A scraper bar was secured over the mesh at a distance corresponding to the desired thickness of the foam after scraping. The top of the latex was pressed against the scraper bar.

Within 24 hours of compressing the foam, the vertical wicking height and free absorption capacity of the uncompressed and compressed foam were measured as described above in the Measurement Procedures section. The results are given in Table 4 below.

Table 4.

Measurement results of the free absorption capacity and the suction height

<td>Time (minutes)</td><td>Not ironed / pressed 2^and</td><td>Not ironed / pressed 2^b</td>

<td> 2,0</td><td> 5,8/8,0</td><td> 6,4/7,1</td>

<td> 10</td><td> ...</td><td> 9,9/19</td>

<td> 30</td><td> 11,6/24,5</td><td> 11,1/&gt;25</td>

<td> 60</td><td> 14,1/26,6</td><td> 11,6/ &gt; 25</td>

<td>Free absorption capacity</td><td>18 g / g</td><td>15 g / g</td>

a. Thickness of aligned foam = 6.3 mm (0.25 inch).

b. Thickness of aligned foam = 12.5 mm (0.5 inch). The compression of these foams provides a significant improvement in wicking properties without losing the wicking properties of the fluids.

It has been found, as is evident from Examples 2 and 3 above, that the latex foam compositions of the present invention are capable of vertically sucking 0.9 wt% aqueous saline. to a height of more than 20 cm. The wicking height of the latex foam compositions has been observed to be greater than 5 cm after 2 minutes, and in a preferred embodiment is 10 cm after 2 minutes. In addition, it has been found that the latex foam compositions of the present invention have a free absorption capacity of more than 15 g of aqueous saline / g of foam.

Example 3

The foam was prepared and tested as in Example 2 except that the thickness of the foam strip for the Vertical Wipe and Free Absorption Capacity measurements was 12.5 mm (0.5 inch), not 6.3 mm.

PL 201 224 B1 (0.25 inch). After pressing, the foam remained thin until it was wet. Vertical wicking and free absorbent capacity measurements were taken within 24 hours after the foam was compressed as described in the measurement procedures above. The results are given in Table 4.

Additionally, a comparison of the data in Tables 2 and 4 illustrates the advantages of using an industrial foaming device. In particular, for example, the foams obtained using the industrial frothing machine exhibited a suction lift of 30 minutes twice as high as that achieved with the laboratory Kitchen Aid Mixer.

Example 4

A latex composition was prepared having the composition given in Table 5. The composition was prepared by adding the ingredients in the order indicated to a beaker while mixing with a Cowles type spatula. Efforts were made to minimize the amount of trapped air.

Table 5.

The latex foam composition of Example 4

<td>Component 3</td><td>Name</td><td>% solids</td><td>Dry parts by weight</td><td>Parts wet by weight</td>

<td>Latex</td><td>DL595</td><td> 51</td><td> 65</td><td> 126,95</td>

<td>Latex</td><td>DL313</td><td> 49</td><td> 35</td><td> 71,14</td>

<td>Anti / oxidant</td><td>Aquamix ™ 494</td><td> 58</td><td> 1,50</td><td> 2,59</td>

<td>Foam stabilizer</td><td>Stanfax ™ 318</td><td> 35</td><td> 3,50</td><td> 10,00</td>

<td>Thickener</td><td>Methocel ™ E4M</td><td> 2,5</td><td> 0,33</td><td> 13,20</td>

<td>Filler</td><td>Pigment dispersion for plastics (RAP380NA)</td><td> 51,2</td><td> 50</td><td> 97,66</td>

<td>PH modifier</td><td>Ammonium hydroxide</td><td> 28</td><td colspan="2">(up to pH 9)</td>

<td>Co-reactive material: epoxy</td><td>Ethylene glycol diglycidyl ether</td><td> 100</td><td> 6,00</td><td> 6,00</td>

a. DL595 and DL313 grades latexes, Methocel ™ E4M grade thickener and RAP380NA plastic pigment dispersion were obtained from The Dow Chemical Company. Aquamix ™ 494 grade antioxidant was obtained from Harwick Chemical Corporation. Stanfax ™ 318 grade foam stabilizer was obtained from Standard Adhesive &amp; Chemical Company, Inc. Ethylene glycol diglycidyl ether (EGDGE) was obtained from Aldrich Chemical Company.

The latex composition was foamed, formed into a 12 mm (0.5 inch) sheet, and bonded as described in Example 2, except that the foam was placed in a forced air oven at 150 ° C for 30 minutes, not 20 minutes. minutes. The resulting foam was split approximately halfway on the thickness axis to yield 6 mm (0.25 inch) thick sheets with large diameter cells (about 1.4 mm) on one face and smaller diameter cells (about 100 µm) on the opposite surface. The foam was pressed in a hydraulic press at an overpressure of about 1034 kPa (150 psig), which caused the thickness of the foam to be reduced to about 1 mm. The compressed foam remained thin until wetted.

The vertical wicking of the compressed foam was measured as described in the measurement procedures using stripe samples approximately 28 cm long and 1 cm wide cut from the compressed foam. The results are given in Table 6.

Table 6.

Vertical Suction Measurement Results for Example 4

<td>Time (minutes)</td><td> 2</td><td> 10</td><td> 30</td><td> 60</td>

<td>Height (cm)</td><td> 7,3</td><td> 13,5</td><td> 15</td><td> 15</td>

The non-wetted foam remained 1 mm thick, while at the end of the foam in contact with the water, the thickness increased to about 5 mm.

PL 201 224 B1

It was observed that the latex polymer foam according to the invention was able to vertically suck 0.9 wt% aqueous salt solution. to a height of 15 cm, reaching a height of more than 7 cm in 2 minutes.

Example 5

Latex foam was produced as in Example 4, except that the foam was foamed, shaped, and cured into a 6.3 mm (0.25 inch) thick sheet. Contrary to the foam of example 4, the foam was used as received and was not cut in half. The foam was pressed in a hydraulic press at a pressure of about 1034 kPa (150 psi), which caused the thickness of the foam to be reduced to about 0.6 mm (0.024 inch). The compressed foam remained thin until wetted.

Within 24 hours of compressing the foam, the vertical wicking was measured as described in the measuring procedures, and the results are given in Table 7 below.

Table 7.

Vertical suction of the foam from example 5

<td>Time (minutes)</td><td>Vertical suction height (cm)</td>

<td> 0,5</td><td> 0,8</td>

<td> 1</td><td> 1,3</td>

<td> 2</td><td> 2,0</td>

<td> 3</td><td> 3,2</td>

<td> 4</td><td> 4,5</td>

<td> 5</td><td> 5,0</td>

<td> 10</td><td> 7,3</td>

<td> 30</td><td> 11,5</td>

<td> 60</td><td> 13,5</td>

<td> 90</td><td> 14,0</td>

The physical properties of the foam composition, user breaking stress, percent elongation at user break, and toughness, were measured on a compressed foam sample before wetting (dry) and after wetting in 0.9% aqueous saline (wet) according to the measurement procedures. The results of physical properties measurements are given in Table 8.

Table 8.

Physical Properties (Durability)

<td>The state of the polymer</td><td>User fracture stress;</td><td>% elongation at user break</td><td>Resistance to dynamic loads</td>

<td>Dry</td><td>757 kPa</td><td> 314,77</td><td>1386 kPa</td>

<td>Wet</td><td>140 kPa</td><td> 285,11</td><td>196 kPa</td>

It was found that the inventive polymer latex foam composition sucked the salt solution vertically nearly 14 cm in 60 minutes. The composition, in both dry and wet conditions, was found to exhibit good stress at user break, percent elongation at user break, and toughness.

Example 6

A latex composition was prepared having the composition shown in Table 9. Latex compositions were prepared by adding the ingredients, in the order indicated, to a beaker with a Cowles spatula under agitation. Efforts were made to minimize the amount of trapped air.

PL 201 224 B1

Table 9.

Composition of the latex foam from Example 6

<td>Skł^anddⁿik^and</td><td>Name</td><td>% solids</td><td>Dry parts by weight</td><td>Parts wet by weight</td>

<td>Latex</td><td>DL595</td><td> 51</td><td> 100</td><td> 195,31</td>

<td>Antioxidant</td><td>Aquamix ™ 494</td><td> 58</td><td> 1,50</td><td> 2,59</td>

<td>Foam stabilizer</td><td>Stanfax ™ 318</td><td> 35</td><td> 3,50</td><td> 10,00</td>

<td>Thickener</td><td>Methocel ™ E4M</td><td> 2,5</td><td> 0,33</td><td> 13,20</td>

<td>Principle</td><td>NH4OH</td><td> 28</td><td colspan="2">--- (up to pH 9) ---</td>

<td>Co-reactive material: epoxy</td><td>Ethylene glycol diglycidyl ether</td><td> 100</td><td> 6,00</td><td> 6,00</td>

a. DL595 and Methocel ™ grade E4M thickener were obtained from The Dow Chemical Company. Aquamix ™ 494 grade antioxidant was obtained from Harwick Chemical Corporation. Stanfax ™ 318 grade foam stabilizer was obtained from Standard Adhesive &amp; Chemical Company, Inc. Ethylene glycol diglycidyl ether (EGDGE) was obtained from Aldrich Chemical Company.

The latex composition was foamed, formed into a 6 mm (0.25 inch) thick sheet and bonded as described in Example 1. The foam was only lightly compressed by hand to about 20% of the original thickness. The compressed foam remained thin until it was wet.

Vertical wicking measurements of the compressed foam were performed as described in the measurement procedures, using a 15 cm long sample instead of a typical 30 cm sample. The compressed foam sucked in a 0.9 wt.% Aqueous saline solution. to a height of 12 cm in 10 minutes. The saline solution reached the top of the 15 cm strip in 60 minutes. The foam also had a free absorption capacity of 18 g / g.

Example 7

Latex foams were prepared in the same manner as in Example 1, except that the ratio of DL532 to DL313 was systematically changed. Increasing the proportion of the polymer with a higher glass transition temperature increases the degree of compression after the compressive force is removed. The DL532 / DL313 ratios were 68/32, 50/50, 25/75 and 0/100 and all other components were kept constant. The height of the foams was measured. The foams were compressed as described in Example 1. The force was released and the foam was allowed to recover. The measured foam height is reported as a percentage of the original, unpressed foam height.

Table 10.

Compression ratio (% of the thickness of uncompressed foam)

<td>Ratio DL 532 / DL3 13</td><td> 68/32</td><td> 50/50</td><td> 25/75</td><td> 0/100</td>

<td>Foam height (after pressing &amp; recovery)</td><td> 29%</td><td> 27%</td><td> 22%</td><td> 13%</td>

These results indicate the possibility of adjusting the thickness of the finished compressed foam. The degree of compression is given as a percentage of the height of the original, uncompressed foam.