Absorbent core for an absorbent article

USEFUL ABSORBENT CORE FOR AN ABSORBENT ITEM, PROCESS TO PROVIDE A STORAGE COAT FOR AN ABSORBENT CORE AND STORAGE COAT FOR AN ABSORBENT CORE

FIELD OF THE INVENTION

This invention relates to an absorbent article, preferably a disposable absorbent article, such as a diaper. The present invention specifically relates to an absorbent core for such an absorbent article, which provides improved immobilization of absorbent polymer material when the article is fully or partially loaded with urine. This absorbent core is useful for providing an absorbent article with greater comfort of use, which is thin and dry.

BACKGROUND OF THE INVENTION

Absorbent articles, such as diapers and adult incontinence products are well known articles of basic production. Multiple attempts have been made to provide them with a good general fit and with a high absorption capacity. Modern diapers use absorbent polymer materials or so-called super absorbent materials, which allow you to store up to 300 ml of liquid in a typical baby diaper.

While such a diaper is generally a disposable product, in some cases it is used for many hours, and is used both in a dry state and in a state loaded with urine.

5074 / Jun-ll

-2Therefore, in order to provide good wearing comfort, it is very important to keep the absorbent materials comprised of a diaper or other absorbent article in position, both when the article is dry and when the article is fully or partially loaded with urine (or other body fluids).

US Patent No. 4,381,783 (Elias) discloses an absorbent article with a core, which comprises pockets of absorbent hydrocolloidal material. These pockets are provided to confine the movement of the hydrocolloidal material, particularly when the article is fully or partially loaded or urinated . The pockets are part of an absorbent layer and are typically provided with cellulose material. So, to achieve a good immobilization of the hydrocolloidal material according to what this patent teaches, a relatively high amount of cellulose material is required. Moreover, the provision of such pockets can hinder the free distribution of liquid to the most absorbent areas of the core, for example the areas of hydrocolloidal materials.

WO 951 / 17.868 (Palumbo) discloses an absorbent structure comprising two layers of fiber and an intermediate layer. This intermediate layer comprises an absorbent hydrogel material in an amount exceeding 120 g / m² and particles of a thermoplastic material. While this construction certainly provides good immobilization of the absorbent hydrogel particles in the dry state, it seems that only less immobilization can be achieved in the urine-laden state. The thermoplastic materials revealed appear to swell much less than the hydrogel materials disclosed. So, in particular when the absorbent structure will be used in a product for

-3absorb high amounts of liquids, for example a diaper, wet immobilization may not be entirely satisfactory.

EP 724,418 (Tanzer) discloses an absorbent article, which includes super absorbent material located in discrete pockets. The absorbent article comprises a first and a second carrier layer and a water-sensitive bonding means to secure the carrier layers together and to provide a plurality of pocket regions. The article comprises highly absorbent material located within said pocket regions. The water-sensitive bonding means provides a wet force, which is less than a separation force imparted by a swelling of such highly absorbent material when such highly absorbent material is exposed to an aqueous liquid. The absorbent material is said to provide an absorbent structure, which more securely locates and contains the highly absorbent material in a form of selected pockets when the article is dry. However, due to the construction of the pockets, and specifically due to the selection of the water-sensitive bonding medium, these pockets are not maintained when the article is fully or partially filled with liquids. Thus, it is believed that this absorbent article does not provide a very satisfactory immobilization of the absorbent material in the fully or partially charged state of urine.

SHORT DESCRIPTION

The present invention relates to an absorbent article, preferably a disposable absorbent article, such as a diaper. It involves an absorbent core useful for the absorbent article, which imparts greater comfort of use to the article and makes it thin and dry, as well as a process for obtaining such a core. Specifically, the absorbent core useful for the article

The absorbent comprises a substrate layer, a discontinuous layer of absorbent material which comprises an absorbent polymer material and, optionally, an absorbent fibrous material that does not represent more than 20 percent by weight of the total weight of the absorbent polymer material and a layer of thermoplastic material, where: a surface of the discontinuous layer of absorbent material is at least partially in contact with a first surface of the substrate layer, portions of a surface of the layer of thermoplastic material are in direct contact with the first surface of the substrate layer and portions of that surface of the layer of thermoplastic material are in direct contact with the other surface of the discontinuous layer of absorbent material. ¡¡

It also involves a process to provide a storage layer for an absorbent core useful in an absorbent article, the process comprising the steps of:

- provide a substrate material comprising a first surface and a _tsecond surface.

- depositing absorbent material on the first surface of the substrate material in a configuration comprising at least one area, which is substantially free of absorbent material, the configuration comprising at least one area comprising absorbent material.

- depositing a thermoplastic material on the first surface of the substrate material and the absorbent material, such that portions of the thermoplastic material are in direct contact with the first surface of the substrate and portions of the thermoplastic material are in direct contact with it; Absorbent material.

-5 To maintain the stability of the shape of the thermoplastic material at B high ambient temperatures and so that the thermoplastic composition B does not lose its integrity if the absorbing product is used in hot climates, the B storage module G ', measured at 60 ° C, must be bounded between kPa and 300 kPa, preferably being greater than 24 kPa and, more preferably, greater than 30 kPa. B

STATEMENTS OF THE DRAWINGS 1

Figure 1 is a plan view of a diaper, in its stretched state, not K contracted, as a preferred embodiment of an absorbent article according to the present invention. K

Figure 2 shows a section of Figure 1 taken on the transverse axis. B

Figure 3 shows a core structure in a preferred embodiment K of the present invention. B

Figure 4 shows the absorbent core with a cover layer according to B another embodiment of the present invention. B

Figure 5 shows splice zones arranged in a B configuration along rows. B

Figure 6 shows a further aspect of the present invention, according to B which forms an absorbent core by combining two layers as shown in figure 3 to provide good wet immobilization. Ϊ

Figure 7 provides a schematic representation of a rheometer B for the bleed test. Ϊ

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-6 DETAILED DESCRIPTION

The present invention relates to an absorbent article, preferably a disposable absorbent article, such as a diaper.

As used herein, the following terms have the following meanings:

"Absorbent article" refers to devices that absorb and contain liquid, and more specifically, it refers to devices that are placed against or in the vicinity of the user's body to absorb and contain the various exudates discharged from the body. Absorbent items include, but are not limited to diapers, adult incontinence diapers, training pumps, diaper liners and bras, sanitary napkins, and the like.

"Disposable" is used herein to describe items whose general purpose is not to be washed or otherwise restored or used again (for example, the purpose is to be discarded after a single use, preferably recycled, be converted into fertilizer, or otherwise disposed of in a manner compatible with the environment).

"Diaper" refers to an absorbent article generally used by infants and incontinent persons around the lower torso.

"Understand", "understanding" and "understand" is a broad term that specifies the presence of the following, for example, a component but does not exclude those present from other features, elements, steps or components known in the art, or disclosed at the moment.

Figure 1 is a plan view of a diaper 20 as a preferred embodiment of an absorbent article according to the present invention. The diaper is shown in its stretched, not contracted state (for example, without contraction

-Ί induced by an elastic). Portions of the structure are cut out B to show more clearly the inner structure of the diaper 20. The portion of the diaper B 20 that comes into contact with the user faces the observer B dor. The frame 22 of the diaper 20 in Figure 1 comprises the main body of the diaper B 20. The frame 22 comprises an outer covering including a liquid permeable top sheet 24 and / or a liquid permeable backsheet 26. The frame may include a portion of an absorbent core B 28 fitted between the topsheet 24 and the backsheet 26. The frame B can also include most or all of the absorbent core 28 B fitted between the topsheet 24 and the backsheet 26 . The frame B further preferably includes side panels 30, elasticized cuffs for B legs 32, and characteristic of elastic waist 34, leg cuffs 32, and characteristic B of elastic waist each typically comprises elastic B members 33. A portion of the diaper tip 20 is configured B as a first waist area 36 of diaper 20. The opposite tip portion B is configured as a second waist zone 38 of diaper B 20. An intermediate portion of the diaper 20 is configured as B a crotch area 37, which extends longitudinally between the first E and the second waist zones 36 and 38. The waist zones 36 and 38 B may include elastic elements such that they are collected around the user's waist B to provide improved fit and containment (characteristic of elastic waist B 34). The crotch area 37 is the portion of the diaper 20 the B which, when the diaper 20 is used, is generally located between the B legs of the user. The diaper 20 is shown with its longitudinal axis 10 and its transverse axis B 12. The periphery of the diaper 20 is defined by the outer edges B

-8 of the diaper 20 in which the longitudinal edges 44 generally run parallel to the longitudinal axis 10 of the diaper 20 and the pointed edges 46 run between the longitudinal edges 44 generally parallel to the transverse axis 12 of the diaper 20. The framework also it comprises a fastening system, which can include at least one fastening member 42 and at least one stored landing zone 45.

For unit absorbent articles, the frame 22 comprises the main structure of the diaper with other features added to form the composite structure of the diaper. While the topsheet 24, the backsheet 26 and the absorbent core 28 can be assembled in a number of well-known configurations, preferred diaper configurations are generally described in US Patent No. 5,554,145, entitled “Absorbent Article with Extensible Waist Feature of Structurally Similar Elastic Film with Multiple Zones” (“Absorbent Article ITU Multiple Zone Structural Elastic-Like Film Web Extensible Waist Feature”) issued to Roe et al. on September 10, 1996; United States Patent No. 5,569,234, entitled "Disposable Pull-On Pant" issued to Buell et al. on October 29, 1996; and U.S. Patent No. 6,004,306, entitled "Absorbent Article With Multi-Directional Extensible Side Panels" ("Absorbent Article With MultiDirectional Extensible Side Panels") issued to Robles et al. on December 21, 1999.

The topsheet 24 in Figure 1 can be fully or partially elasticized or can be trimmed to provide an empty space between the topsheet 24 and the absorbent core 28. Exemplary structures including

-9 elastised or trimmed upper sheets are described in more detail in US Patent No. 5,037,416 entitled "Absorbent Article Presenting Elastic Extensible Upper Sheets" ("Absorbent Article Having Elastically Extensible Topsheet 'j issued to Alien et al. August 6, 1991; and US Patent No. 5,269,775 entitled "Trisection Upper Sheets For Disposable Absorbent Articles and Disposable Absorbent Articles Presenting Such Trisection Upper Sheets" issued to Freeland and others on December 14, 1993.

The absorbent core 28 in Figure 1 is generally disposed between the topsheet 24 and the backsheet 26. The absorbent core 28 may comprise any absorbent material that is generally compressible, comfortable, not irritable to the user's skin, and capable of absorbing and retain fluids such as urine and certain other exudates from the body. The absorbent core 28 may comprise a wide variety of liquid absorbent materials commonly used in disposable diapers and other absorbent articles such as crushed wood pulp, which is generally referred to as air felt ("air felt'j. Examples of other suitable absorbent materials include curly cellulose filler; molten blown polymers, including coform; hardened, modified or chemically intertwined cellulosic fibers; tissue, including tissue wrappings and tissue laminates; absorbent foams; absorbent sponges; super absorbent polymers; absorbent gelling materials; or any other known absorbent material or combination of materials. The absorbent core 28 may further comprise amounts

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-10-10 less (typically less than 10%) of non-liquid absorbent materials, such as adhesives, waxes, oils and the like.

Exemplary absorbent structures for use as absorbent mounts are described in US Patent No. 4,610,678 (Weisman et al.); U.S. Patent No. 4,834,735 (Alemany et al.); United States Patent No. 4,888,231 (Angstadt); U.S. Patent No. 5,260,345 (DesMarais et al.); United States Patent No. 5,387,207 (Dyer et al.); U.S. Patent No. 5,397,316 LaVon et al.); and U.S. Patent No. 5,625,222 (DesMarais et al.).

The backsheet 26 may be attached to the topsheet 24. The backsheet 26 prevents exudates absorbed by the absorbent core 28 and contained within article 20 from staining other external articles that may be in contact with the diaper 20, such as sheets of bed and underwear. In preferred embodiments, the backsheet 26 is substantially impervious to liquids (eg, urine) and comprises a laminate of a notch and a thin plastic film such as a thermoplastic film having a thickness of about 0.012 mm (0.5 mil ) to approximately 0.051 mm (2.0 mils). Suitable back sheets include those manufactured by Tredgar Industries Inc. of Terre Haute, IN, USA. and marketed under the trademark XI5306, XI0694. Other materials suitable for backsheets may include breathing materials, which allow vapors to escape from diaper 20 while still preventing exudates from passing through the backsheet 26. Exemplary breathing materials may include materials such as continuous materials. tissues,

-11 nonwoven fabrics, composite materials such as nonwoven fabrics coated by a film, and micro porous films such as those manufactured by Mitsui Toatsu Co. of Japan under the designation ESPOIR NO and by EXXON Chemical Co. of Bay City, TX, USA, under the designation EXXAIRE. Suitable breathing materials comprising polymer blends are available from Clopay Corporation, Cincinnati, OH, USA, under the name HYTREL blend P18-3097. Such breathing composite materials are described in greater detail in PCT application No. WO 95/1646, published June 22, 1995 in the name of EI Du Pont. Other posterior sheets that breathe including nonwoven fabrics and films formed with openings are described in U.S. Patent No. 5,571,096 issued to Dobrin et al. On November 5, 1996.

The diaper 20 may also include such other features as are known in the art, including front and rear panels, waist, elastic and the like features to provide better fit, containment and aesthetic features. Such additional features are well known in the art and are for example described in U.S. Patent No. 3,860,003 and in U.S. Patent No. 5,151,092.

In order to keep the diaper 20 in place around the user, preferably at least a portion of the first waist area 36 is adhered by means of the clamping member 42 to at least a portion of the second waist area 38, preferably to form opening (s) for the leg (s) and a waist for the article. When fastened, the restraint system carries a tension load around the waist of the article. The fastening system is designed to allow the user of an item to be able to

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12 hold an element of the restraint system such as the restraint member 42, and connect the first waist zone 36 to the second waist zone 38 in at least two places. This is achieved through the manipulation of link forces between the clamping devices.

Diapers 20, according to the present invention, can be provided with a fastening system such that it can be closed again, or it can alternatively be provided in the form of pants-like diapers.

The fastening system and any component thereof may include any material suitable for such use, including, but not limited to plastics, films, foams, nonwoven fabrics, continuous materials, paper, laminates, fiber reinforced plastics and the like, or combinations thereof. It may be preferable that the materials that make up the fastening system are flexible. Flexibility is designed to allow the restraint system to conform to the shape of the body and thereby reduce the likelihood of the restraint system irritating or injuring the user's skin.

Figure 2 shows a section of Figure 1 taken on the transverse axis 12. Starting from the user side, the diaper 20 comprises the top sheet 24, the components of the absorbent core 28 and the backsheet 26. The absorbent core preferably comprises the acquisition system 50, which comprises an upper acquisition layer 52, which faces the user's skin and a lower acquisition layer 54, which faces the user's garment. In a preferred embodiment, the upper acquisition layer 52 comprises a non-woven, while the lower acquisition layer preferably comprises a mixture of twisted, curled and chemically hardened fibers, high surface area fibers and thermo-bonded fibers.

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-13plastics. In another preferred embodiment, both acquisition layers are provided with a non-woven material, which is preferably hydrophilic. The acquisition layer is preferably in direct contact with the storage layer 60.

The storage layer 60 can be found wrapped by a core wrapping material. In a preferred embodiment, the core wrapping material comprises an upper layer 56 and a lower layer 58. The core wrapping material, the upper layer 56 or the lower layer 58 may be provided with a non-woven material. A preferred material is the so-called SMS material, which comprises a layer of thermo-bonded yarn, a meltblown layer and an additional layer of thermo-bonded yarn. Highly preferred are permanently hydrophilic and, in particular, nonwovens with durably hydrophilic coatings. A preferred material alternatively comprises an SMMS structure.

The upper layer 56 and the lower layer 58 may be provided with two or more sheets of materials or may alternatively be provided with a sheet of unitary material. Such a unit sheet of material can be found wrapped around the storage layer 60, for example in a fold C.

Preferred non-woven materials are provided with synthetic fibers, such as PE, PET and more preferably PP. Since the polymers used for the production of nonwovens are inherently hydrophobic, they are preferably coated with hydrophilic layers.

A preferred way of producing nonwovens with durably hydrophilic coatings is by applying a hydrophilic monomer and a radical polymerization initiator on the nonwoven and conducting a UV-activated polymerization resulting in a monomer chemically linked to the Non-woven surface as described in European Patent (EP) 1,403,419.

An alternative way of producing nonwovens with durably hydrophilic coatings is to coat the nonwoven with nanoparticles as described in published application WO 02 / 64,877.

Typically, nanoparticles have a larger dimension below 750 nm. Nanoparticles with sizes ranging from 2 to 750 nm can be produced economically. The advantage of the nanoparticles is that many of them can be easily dispersed in water solution to allow an application of a coating on the nonwoven; typically they form transparent coatings, and the applied coatings of water solutions, are typically sufficiently durable upon exposure to water.

The nanoparticles can be organic or inorganic, synthetic or natural. Inorganic nanoparticles generally exist as oxides, silicates and carbonates. Typical examples of suitable nanoparticles are layered minerals (for example, LAPONITA ™ from Southern Clay Products, Inc. (USA) and Bohemite alumina (for example, Disperal P2 ™ from North American Sasol, Inc.).

A highly preferred non-woven nanoparticle coated is disclosed in Mexican Patent Publication MX PA 05007935 originally entitled "Disposable absorbent article comprising a durable hydrophilic core wrap" ("Disposable absorbent article comprising a durable hydro

-15philic core wrap ”), whose inventors are Ekaterina Anatolyevna Ponomarenko and Mattias Schmidt.

Additional useful nonwovens are described in patent publications WO 2002 / 192.366, WO 2002 / 150.678, EP-A-1,356,152 and EP-A-1,470,282.

In some cases, the non-woven surface can be pre-treated with high energy treatment (corona, plasma) before the application of nanoparticle coatings. High energy pretreatment typically temporarily increases the surface energy of a low energy surface (such as PP) and thereby allows better wetting of a nonwoven by dispersing nanoparticles in water.

Notably, permanently hydrophilic nonwovens are also useful in other parts of an absorbent article. For example, upper sheets and acquisition layers comprising permanently hydrophilic nonwovens as described above have been found to be suitable.

In summary, in one aspect of the present invention, absorbent articles are preferred, comprising a nonwoven fabric, the nonwoven fabric comprising a plurality of fibers and having a surface tension of at least 55, preferably at least 60 and more preferably at minus 65 mN / m or higher when wetted with a saline solution and has an impact time of liquid penetration of less than 5 s for a fifth jet of liquid.

Surface tension is a measure of how permanently a certain level of hydrophilicity is achieved. The value should be measured using the test method described herein below.

-16E1 liquid penetration time per impact is a measure of a certain level of hydrophilicity. The value should be measured using the test method described herein below.

In the present invention, the absorbent core 28 comprises a substrate layer 100, absorbent polymer material 110 and, a preferred embodiment, a fibrous layer of adhesive 120. The substrate layer 100 is preferably provided with a non-woven material; nonwovens are preferably those exemplified above for upper sheet 56 or lower sheet 58.

The substrate layer 100 comprises a first surface and a second surface. At least portions of the first surface of the substrate layer 100 are in direct contact with a layer of absorbent polymer material 110. This layer of absorbent polymer material 110 is preferably a discontinuous layer, and comprises a first surface and a second surface. As used herein, a discontinuous layer is a layer comprising openings. Typically, these openings have a diameter or light of less than 10 mm, preferably less than 5 mm, 3 mm, 2 mm and less than 0.5 mm, 1 mm or 1.5 mm. At least portions of the second surface of the absorbent polymer material 110 are in contact with at least portions of the first surface of the material of the substrate layer 100. The first surface of the absorbent polymer material 110 defines a certain height of the absorbent polymer layer above the first surface of the material of the substrate layer 100. When the layer of the absorbent polymer material 110 is provided as a discontinuous layer, portions of the first surface of the substrate layer 100 are not covered by the material

-17 of absorbent polymer 110. The absorbent core 28 further comprises a thermoplastic composition 120. This thermoplastic composition 120 serves to at least partially immobilize the absorbent polymer material 110.

However, in an even more preferred embodiment, the thermoplastic material 120 is provided as a fibrous layer, which is partially in contact with the absorbent polymer material 110 and partially in contact with the substrate layer 100. Figure 3 shows Such preferred structure. In this preferred structure, the layer of absorbent polymer material 110 is provided as a discontinuous layer and a layer of thermoplastic fibrous material 120 is placed over the layer of absorbent polymer material 110, such that the thermoplastic layer 120 is in direct contact with the first surface of the absorbent polymer material layer 110, but also in direct contact with the first surface of the substrate layer 100, wherein the substrate layer is not covered by the absorbent polymer material 110. This imparts an essentially three-dimensional structure to the fibrous layer of thermoplastic material 120, which is itself a two-dimensional structure of a relatively thickness small (in the z direction), as compared to the extension in the xy direction of y. In other words, the thermoplastic fibrous material layer 120 undulates between the first surface of the absorbent polymer material 110 and the first surface of the substrate layer 100.

So, the thermoplastic material 120 provides cavities to contain the absorbent polymer material 110, so that it immobilizes such material. In another aspect, the thermoplastic material 120 is bonded to the substrate 100, so that it fixes the absorbent polymer material 110 to the substrate 100.

I

-18 Highly preferred thermoplastic materials will also penetrate both the absorbent polymer material 110 and the substrate layer 100, thereby providing even more immobilization and fixation.

Obviously, although the thermoplastic materials disclosed herein provide a much better wet immobilization, for example, immobilization of the absorption material when the article is wet or at least partially loaded, these thermoplastic materials also provide a very good immobilization of the absorbent material. When the items are dry.

The absorbent polymer material 110 can also be mixed with fibrous material, such as air felt material ("airfelt'j, which can provide a matrix for further immobilization of the super absorbent polymer material. However, it is preferably used a relatively small amount of cellulose fibrous material, preferably less than 20 or 10% by weight of cellulose fibrous material compared to the weight of absorbent polymer material 110.

An alternative preferred embodiment of the present invention is shown in Figure 4. The absorbent core shown in Figure 4 further comprises a cover layer 130. This cover layer may be provided with the same material as the substrate layer 100 or A different material. Preferred materials for the cover layer are nonwoven materials, typically the materials described above as useful for upper layer 56 and lower layer 58. In this embodiment, portions of the covering layer 130 are linked to portions of the substrate layer 100 by the thermoplastic material 120. So that the substrate layer 100 together with the

-19 cover layer 130 provides cavities for immobilizing absorbent polymer material 110.

With reference to Figures 3 and 4, the areas of direct contact between the thermoplastic material 120 and the substrate material 100 are referred to as splice zones 140. The shape, quantity and configuration of the splice zones 140 will have an influence on immobilization of the absorbent polymer material 110. The splice areas may have a square, rectangular or circular shape. Preferred splice areas have a circular shape. Preferably, they have a diameter of more than 0.5 mm, 1 mm or 1.5 mm and less than 10 mm, 5 mm, 3 mm or 2 mm. If the splice zones 140 i do not have a circular shape, they preferably have a size such that they can fit within a circle with any of the parameters given above. ·

Junction zones 140 may be arranged in a regular or irregular configuration. For example, the splice zones 140 may be arranged along rows as shown in Figure 5. These rows may be aligned with the longitudinal axis of the absorbent core or, alternatively, they may have a certain angle with respect to the edges length

core channels. It has been determined that a configuration along parallel rows with the longitudinal edges of the absorbent core 28 creates channels in the longitudinal direction, which lead to less wet immobilization.

So, preferably, the splice zones 140 should be arranged along rows that form an angle of 20 degrees, 30 degrees, 40 degrees or 45 degrees with the longitudinal edges of the absorbent core 28. Another preferred configuration for the zones splice 140 is a configuration that includes .......................................... .....................

-20 Learn polygons, for example pentagons, hexagons or combinations of pentagons and hexagons. Also preferred are irregular arrangements of splice zones 140, which have also been found to have good wet immobilization.

Two arrangements of fundamentally different splice zones 140 may be chosen according to the present invention. In one embodiment, the splice zones are discrete. They are positioned within areas of absorbent material, such as islands in the sea. The areas of absorbent materials are then referred to as connected zones. In an alternative embodiment, the splice zones may be connected. Then, the absorbent material can be deposited in a discrete configuration, or in other words, the absorbent material represents islands in a sea of ​​thermoplastic material (120). Thus, a discontinuous layer of absorbent polymer material 110 may comprise connected areas of absorbent polymer material 110 or may comprise discrete areas of absorbent polymer material 110.

In a further aspect, it has been discovered that absorbent cores that provide good wet immobilization can be formed by combining two layers as shown in Figure 3 and as described in the context herein. Such an embodiment is shown in Figure 6. The absorbent core material shown in Figure 6 comprises two layers of substrate 100, two layers of absorbent polymer material 110 and two layers of fibrous thermoplastic materials 120. When two discontinuous layers of an absorbent polymer material 110 are used, they would typically have a configuration such that the absorbent polymer material of one of the layers is

-21 find facing the splice zones 140 of the other layer. In a preferred alternative embodiment, however, the splice zones 140 have been compensated and are not facing each other. So, preferably when two storage layers are joined together, this is done such that the first surface of the substrate layer (100) of the first storage layer (60) faces the first surface of the substrate layer ( 100) of the second storage layer (60).

The present invention, and specifically the preferred embodiment described with reference to Figures 3; 4 and 6, can be used to provide the storage layer 60 of an absorbent core. However, they can also be used to provide the entire absorbent core 28. In that case, no additional materials are used to wrap the core, such as the top layer 56 and the bottom layer 58. With reference to the embodiment of Figure 3, the substrate layer 100 can provide the function of the lower layer 58 and the layer of fibrous thermoplastic material 120 can provide the function of the upper layer 56. With reference to Figure 4, the cover layer 130 may provide the function of the upper layer 56 and the substrate layer 100 may provide the function of the lower layer 58. With reference to Figure 6, the two substrate layers used can provide the function of the upper layer 56 and that of the lower layer 58, respectively.

According to the present invention, the thermoplastic layer 120 comprises any thermoplastic composition, with thermoplastic adhesive compositions being preferred, also referred to as hot melt adhesives. A variety of thermoplastic compositions are suitable for immobilizing absorbent material.

-22 Some initially thermoplastic materials may then lose their plasticity due to a curing step, for example, initiated by heat, UV radiation, electron beam exposure, or other means to cure, leading to the irreversible formation of a network of bonds cross-links i £

covalent At present, those materials that lost their initial plasticity behavior are also thermoplastic materials 120.

Without wishing to be limited to one theory, it was discovered that those thermoplastic compositions are more useful for immobilizing absorbent polymer material 110, which combine good cohesion and good adhesion behavior. Good adhesion is critical to ensure that the thermoplastic layer 120 maintains good contact with the absorbent polymer material 110 and in particular with the substrate. Good adhesion is a challenge, especially if a non-woven substrate is used. Good adhesion ensures that the adhesive does not break, particularly in response to external forces and, over ^:Everything, in response to tension. The adhesive is subject to external forces when the absorbent product has acquired liquid, which is then stored in the absorbent polymer material 110, which in response swells. A preferred adhesive will allow such swelling, without breaking and without imparting too many compression forces, which would limit the absorbent polymer material 110 to swell. It is important, according to the present invention, that the adhesive does not break, which would deteriorate the wet immobilization. Preferred thermoplastic compositions that meet these requirements have the following characteristics.

The thermoplastic composition may comprise, in its entirety, a single thermoplastic polymer or a mixture of thermoplastic polymers,

-23 presenting a softening point, as determined by the ASTM D-36-95 "Ring and Ball" method, in a range between 50 ° C and 300 ° C, or alternatively the composition Thermoplastic may be a hot melt adhesive comprising a thermoplastic polymer in combination with other thermoplastic diluents such as resins to increase "tackiness" ("tackifying resins'j, plasticizers and additives such as antioxidants.

The thermoplastic polymer typically has a molecular weight (Mw) of more than 10,000 and a glass transition temperature (Tg) usually below room temperature. Typical concentrations of the polymer in a hot melt are in the range of 20-40% by weight. A wide variety of thermoplastic polymers are suitable for use in the present invention. Such thermoplastic polymers are preferably not sensitive to water. Exemplary polymers are block copolymers (styrenic) including ABA triblock structures, AB block structures and (AB) in radial block copolymer structures where blocks A are non-elastomeric polymer blocks, typically comprising polystyrene, and blocks B are versions unsaturated, conjugated diene or (partially) hydrogenated thereof. Block B is typically isoprene, butadiene, ethylene / butadiene (hydrogenated butadiene), ethylene / propylene (hydrogenated isoprene), and mixtures thereof.

Other suitable thermoplastic polymers that can be used are metallocene polyolefins, which are ethylene polymers prepared using single site catalysts or metallocenes. In that regard, at least one comonomer can be polymerized with ethylene to make a copolymer,

-24terpolymer or higher order polymer. Also applicable are amorphous polyolefins or amorphous polyalphaolefins (APAO), which are homopolymers, copolymers or terpolymers of C2 to C8 alphaolefins.

The resin typically has a molecular weight (Mw) below 5,000 and a Tg usually above room temperature, typical concentrations of the resin in a hot melt are in the range of 30-60%. The plasticizer has a low Mw of typically less than 1,000 and a Tg below room temperature, a typical concentration is 0-15%.

Preferably the adhesive is present in the forms of the fibers along the core, for example, the adhesive is fibrized. Preferably, the fibers will have an average thickness of 1-50 micrometers and an average length of 5 mm to 50 cm.

To improve the adhesive of the thermoplastic material 120 to the substrate layer 100 or any other layer, in particular any other nonwoven layer, such layers can be pretreated with an auxiliary adhesive.

In accordance with the present invention, the storage module G 'measured at 60 ° C must be less than 300,000 Pa, and greater than 18,000 Pa, preferably greater than 24,000 Pa, more preferably greater than 30,000 Pa. The storage module G' measured at 60 ° C is a measure for the stability of the shape of the thermoplastic material at elevated ambient temperatures. The value is particularly important if the absorbent product is used in a warm climate in which the thermoplastic composition could lose its integrity if the storage module G 'at 60 ° C is not sufficiently high.

-25 Preferably, the adhesive will meet some, several or all of the following parameters:

A preferred adhesive will have a storage module G 'measured at 20 ° C of at least 30,000 Pa and less than 300,000 Pa, preferably less than 200,000 Pa, more preferably less than 100,000 Pa. The storage module G' at 20 ° C is a measure for permanent “tackiness” or permanent adhesion of the thermoplastic material used. Good adhesion will ensure a good and permanent contact between the thermoplastic material and for example the substrate layer 100.

In a further aspect, the loss angle tg δ (delta tangent) of the adhesive at 60 ° C should be below the value 1, preferably below the value 0.5. The loss angle tg δ at 60 ° C is correlated with the liquid character of an adhesive at high ambient temperature. The lower the tg δ, the more the adhesive resembles a solid instead of a liquid, for example, the lower its tendency to flow or migrate and the lower the tendency of a super adhesive structure as it is described herein to deteriorate or even collapse over time. Value is particularly important if the absorbent article is used in a warm climate.

In a further aspect, the preferred adhesive should have a glass transition temperature Tg of less than 25 ° C, preferably less than 22 ° C, more preferably less than 18 ° C, and even more preferably less than 15 ° C A temperature Low Tg glass transition is beneficial for good adhesion. In a further aspect a low glass transition temperature Tg ensures that the adhesive thermoplastic material does not become too brittle.

-26 In yet another additional aspect, a preferred adhesive will have a cross-over temperature_x high enough A sufficiently high crossing temperature T_x it has been found that it is beneficial for the high temperature stability of the thermoplastic layer so as to ensure good performance of the absorbent product and in particular good wetting even under conditions of hot climates and high temperatures. So that T_x it should be above 80 ° C, more preferably above 85 ° C, and even more preferably above 90 ° C.

In a further important aspect, preferred adhesives will have a sufficient parameter of γ cohesion strength. The parameter of cohesion force γ is measured using the rheological creep test, as described herein. A sufficiently low γ cohesion force parameter is representative of elastic adhesive, which, for example, can be stretched without tearing. If a voltage of τ = 10,000 Pa is applied, the cohesion force parameter γ is preferably less than 100%, more preferably less than 90%, and even more preferably less than 75%. For a tension of τ = 125,000 Pa, the cohesion nut parameter γ is preferably less than 1,200%, more preferably less than 1,000%, and even more preferably less than 800%.

A highly preferred adhesive useful as a thermoplastic material (120) as described herein will meet most or all of the preceding parameters. Specific care must be taken to ensure that the adhesive provides good cohesion and good adhesion at the same time.

The process for producing preferred absorbent cores 28 according to the present invention comprises the following steps:

-27E1 absorbent core 28 is placed on a down drum, which has an uneven surface. In a first step of the process, the substrate layer 100 is placed on the uneven surface. Due to the gravity, or preferably by the use of vacuum means, the material of the substrate layer will follow the contours of the uneven surface, so that the material of the substrate layer will assume a mountain and valley shape. On this substrate layer (100) absorbent polymer material is arranged by means known in the art. The absorbent polymer material will accumulate in the valleys presented by the substrate layer 100. In a further process step a hot melt adhesive is placed on the absorbent polymer material.

While any adhesive application means known in the art can be used to place the hot melt adhesive on the absorbent polymer material, the hot melt adhesive is preferably applied by a nozzle system. Preferably, a nozzle system is used, which can provide a relatively thin but wide adhesive curtain. This adhesive curtain is then placed on the substrate layer 100 and the absorbent polymer material. Since the mountain peaks of the substrate layer 100 are less covered by absorbent polymer material, the adhesive will make contact with these areas of the substrate layer.

In an optional additional process step a cover layer 130 is placed on the substrate layer 100, the absorbent polymer material, and the hot adhesive melt adhesive. The cover layer 130 will be in adhesive contact with the substrate layer 100 in the areas of

-28 junction 140. In these splice zones 140 it is in direct contact with the substrate layer 100. The cover layer 130 will typically not be in adhesive contact with the substrate layer 100 where the valleys of the substrate layer 100 They are filled with absorbent polymer material.

Alternatively, the cover layer 130 can be placed on a drum with an uneven surface and the substrate layer 100 can be added in a consecutive process step. The embodiment shown in Figure 4 can be produced by such a process.

In an alternative embodiment, the cover layer 130 and the substrate layer 100 are provided with a unit sheet of material. Placing the cover layer 130 on the substrate layer 100 will then involve folding the unit sheet of material.

So that the uneven surface of the placement system, which is preferably a "lay-down drum", typically determines the distribution of absorbent polymer material along the storage layer 60 and also determines the configuration of splice zones 140. Alternatively, the distribution of absorbent polymer material can be influenced by vacuum means.

Preferably, the distribution of absorbent polymer material is profiled and more preferably profiled in the longitudinal direction. So, along the longitudinal axis of the absorbent core, which is normally coincident with the longitudinal axis of the absorbent article, for example, the diaper, the average base weight of the absorbent polymer material will change. Preferably the average base weight of the ab-29 absorbent polymer material in at least one first square measuring 1 cm x 1 cm, freely chosen, is at least 10%, 20%, 30%, 40% or 50% greater than the weight Average base of the absorbent polymer material in at least one second square measuring 1 cm x 1 cm, freely chosen. Preferably the criterion is met if the first and second squares are centered around the longitudinal axis.

Optionally, the absorbent core may also comprise a material of absorbent fibers, for example cellulose fibers. This fibrous material can be pre-mixed with the absorbent polymer material and placed in a process step or alternatively it can be placed in separate process steps.

It has been found that it is beneficial to use a particular absorbent polymer material for absorbent cores made in the present invention. Without wishing to be bound by a theory, it is understood that such material, even in the swollen state, for example when the liquid has been absorbed, does not substantially obstruct the flow of the liquid through the material, especially when the permeability as expressed by The salt flow conductivity of the absorbent polymer material is greater than 10; twenty; 30 or 40 SFC units, where 1 SFC unit is 1 x 10 '⁷ (cm³ xs) / g. The conductivity of the saline flow is a parameter well recognized in the art and should be measured according to the test revealed in EP 752,892 B.

To achieve a sufficient absorption capacity in an absorbent article according to the present invention and especially if the absorbent article is a diaper or an adult incontinence product, material

-30 super absorbent polymer will be present, with a base weight greater than 50,100,200,300,400,500,600,700, 800 or 900 g / m³.

Preferred articles according to the present invention reach a relatively narrow crotch width, which improves comfort of use. A

The preferred article according to the present invention reaches a crotch width of less than 100 mm, 90 mm, 80 mm, 70 mm, 60 mm or even less than 50 mm. So that an absorbent core according to the present invention has a crotch width as measured along a transverse line, which is positioned at an equal distance from the leading edge and the trailing edge of the core, which it is less than 100 mm, 90 mm, 80 mm, 70 mm, 60 mm or even less than 50 mm. It has been found that for most absorbent articles, liquid discharge occurs predominantly in the front half. The front half of the absorbent core should therefore comprise most of the core's absorbent capacity. Preferably the front half of such absorbent core comprises more than 60% of the absorbent capacity, more, preferably more than 65%, 70%, 80%, 85% or 90%.

All patents and patent applications (including any patent issued from them) belonging to the Procter &amp; Gamble company referred to herein are hereby incorporated by reference to such a degree that they are consistent with this.

Theological shift test £

<img file="AR102902A2_D0003.tif" />

Equipment:

• AR 200 Rheometer by TA Instruments as described below.

• Balance

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-31 Rheometer:

A test prepared to carry out the rheological run test uses the AR 200 Rheometer by TA Instruments. There are other commercially available rheometers, which produce substantially the same test results. Figure 7 provides a schematic representation of the rheometer (400). The rheometer is able to apply a shear stress to the adhesive and measure the resulting tension (shear deformation) of constant temperature response. The adhesive is placed between a Peltier element which acts as a lower, fixed plate (410) and an upper plate (420) with a radius of 10 mm, which is connected to the drive shaft of a motor to generate the voltage of shearing. The separation between the two plates has a height H of 1500 microns. The Peltier element allows to control the temperature of the material (± 0.5 ° C).

Preparation of sample:

• Homogenize the adhesive at 150 ° C-175 ° C (depending on the type of adhesive) for 1 hour in a laboratory oven • Mix occasionally to ensure proper mixing of wrap and adhesive, but avoid the formation of bubbles • After homogenization in the homo, pour the sample on siliconized paper to cool • Once the material has cooled to RT, Approximately 0.6 g of adhesive is passed for the creep test and the material is placed on the Peltier plate.

Performing Test:

• Melt the adhesive at 120 ° C (or more if necessary) on the Peltier plate

-32 • As soon as the adhesive is completely molten, lower the top plate to a gap of 1500 micrometers to place it on a

Correct contact with adhesive melt I • Remove excess material • Calibrate the temperature to the measuring temperature of 3 5 ° C:

• Calibrate the conditioning time at 20 min to ensure thermal equilibrium between the Peltier, the adhesive and the top plate • Calibrate the constant measurement effort τ (for example 10,000 Pa resp.

125,000 Pa) to be applied immediately to the adhesive at the beginning of the delay step • Calibrate the delay time to 5 min • Calibrate the effort to zero to immediately remove the effort at the beginning of the recovery step • Calibrate the 5 min recovery • Once the test is complete, melt the adhesive, lift the upper plate and remove the adhesive from both the Peltier and the upper plate • Calibrate the temperature again to the measuring temperature or temperature (standby temperature (j) (stand-by temperature 'j (RT) i

Result Report:

• Report the tension in% (value of γ, hereinafter referred to as a parameter of cohesion force) as a function of temperature and effort after 5 min of application of effort (at the end of the delay step), by example at 35 ° C and 10,000 Pa resp. 35 ° C and 1125,000 Pa as described herein.

I '

-33 Dynamic Mechanical Analysis (DMA) - Temperature Sweep Equipment:

• AR 200 Rheometer by TA Instruments as described below.

• Balance

Rheometer:

A test prepared to carry out the rheological run test uses the AR 200 Rheometer by TA Instruments. There are other commercially available rheometers, which produce substantially the same test results. Figure 8 provides a schematic representation of the rheometer (400). The rheometer is able to apply a shear stress to the adhesive and measure the resulting tension (shear deformation) of constant temperature response.

The rheometer is capable of applying a small oscillatory tension to achieve a constant oscillatory tension within the linear viscoelastic region of the adhesive (for example 0.05%). The instrument allows the measurement of the resulting Storage Module, Loss Module and the phase shift between stress and stress (Loss Factor) depending on the temperature. The oscillation frequency is 1 Hz. The adhesive is placed between a Peltier element which acts as a lower, fixed plate (410) and an upper plate (420) with a radius of 10 mm, which is connected to the drive shaft of a motor to generate the voltage of shearing. The separation between the two plates has a height H of 1500 microns. The Peltier element allows to control the temperature of the material (± 0.5 ° C).

ί

-34 Sample Preparation:

• Homogenize the adhesive at 150 ° C-175 ° C (depending on the type of adhesive) for 1 hour in a laboratory oven • Mix occasionally to ensure proper mixing of wrap and adhesive, but avoid the formation of bubbles • After homogenization in the homo, pour the sample on siliconized paper to cool • Once the material has cooled to RT, Approximately 0.6 g of adhesive is passed for the temperature sweep (“temperature sweep 'j and the material is placed on the Peltier plate.

Performing Test:

• Melt the adhesive at 120 ° C (or more if necessary) on the Peltier plate • As soon as the adhesive is completely melted, lower the top plate to a 1500 micrometer gap to put it in a correct contact with the adhesive melt • Remove excess material and calibrate the temperature to the start measurement temperature (for example 150 ° C, depending on the temperature range of interest -&gt; see below) • Calibrate the temperature at the start measurement temperature depending on the temperature range at which the rheological properties of the adhesive must be determined (for example 150 ° C, in any case , start with the highest temperature) • Calibrate the conditioning time to 20 min to ensure thermal equilibrium between the Peltier, the adhesive and the top plate • Calibrate the starting temperature (see above)

<img file="AR102902A2_D0005.tif" />

-35 • Calibrate the constant measuring effort (for example 0.05%) • Calibrate the constant frequency (for example 1 Hz) • Calibrate the cooling rate (for example 2 ° C / min) • Calibrate the final temperature ( for example -5 ° C) depending on the temperature range at which the rheological properties of the adhesive must be determined and depending on the cooling capacity of the Peltier • Calibrate the temperature to RT • Once the test has been completed, melt the adhesive, lift the top plate and remove the adhesive from both the Peltier and the top plate • Calibrate the temperature back to RT

Result Report:

• Report the Storage Module G 'in Pa and the Loss Factor tg δ (dimensionless) at 20 ° C and 60 ° C • Report the glass transition temperature Tg in ° C (inflection point of G') • Report the T crossing temperature_x in ° C in which G 'equals G "at the end of the rubber plate towards a higher temperature (beginning of the end zone)

Surface Tension Determination

The surface tension (unit: mN / m) is determined according to the following test.

Apparatus:

Equipment: K10 tensiometer provided by Krüss GmbH, Germany or similar. The lifting speed of the container must be 4 mm / min. The height of the

-36 The surface of the liquid should be sensed automatically when a plate or a ring is used. The equipment must be able to adjust the position of the sample automatically to the correct height. The accuracy of the test must be ± 0.1 mN / m.

Process:

1. Pouring 40 ml of saline solution (0.9% by weight of NaCl in deionized water) into a clean laboratory glass.

two. Test the surface tension with a platinum ring or a platinum plate.

The surface tension should be 71-72 mN / m at 20 ° C.

3. Clean the laboratory vessel with deionized water and isopropanol and burn it with a gas burner for several seconds. Waiting until equilibrium is reached at room temperature.

Four. Placing 10 pieces of 60x60 mm of non-woven test in a clean laboratory glass. The nonwoven must have a basis weight of at least 10 gsm.

5. Adding 40 ml of saline solution (0.9% by weight NaCl in deionized water)

6. Mixing with a clean plastic stick free of surfactants for 10 seconds.

7. Letting the solution stand with non-tissues for 5 minutes.

8. Mixing again for 10 seconds.

9. Removing the non-woven from the solvent with a clean plastic stick free of surfactants.

10. Letting the solution stand for 10 minutes.

eleven. Test the surface tension with a platinum plate or a platinum ring.

-37 Determination of Impact Penetration

The test is carried out based on the Edana Method 150.3-96 (February 1996) Time of Liquid Penetration by Impact. ("Liquid Strike Through Time"). A major modification compared to the Edana Method is that the test described below not only measures the first jet, but also several subsequent jets.

Apparatus:

Lister Impact Penetration Team

Funnel equipped with magnetic valve: Discharge speed of 25 ml in 3.5 (± 0.25) seconds

Contact plate: Constructed of 25 mm thick acrylic glass. The total weight of the plate must be 500 g. The electrodes must be of a non-corrosive material. The electrodes are mounted in cross-section slots (4.0 x 7.0 mm), trimmed at the base of the plate and fixed with quick-setting epoxy resin.

Base plate: A square of acrylic glass of approximately 125 mm x 125 mm.

Ring base to support the funnel.

Electronic stopwatch measuring 0.01 seconds.

50 ml test tube.

Ahlstrom Grade 989 Core Filter Paper or equivalent (average Impact Penetration time 1.7 s ± 0.3 s, dimensions: 10x10 cm) Procedure

1. Carefully cutting the required amount of samples, 12.5 cm x 12.5 cm by touching the sample only at the edge of the sample.

-382. Taking 10 sheets of core filter paper.

3. Placing a sample on the set of 10 sheets of filter paper on the motherboard. The sample should be positioned on the filter paper in such a way that the edge of the nonwoven, which is designed to face the user's skin (when applied on an absorbent article) is facing up.

Four. Place the contact plate on top of everything, with the center of the plate on the center of the test piece.

5. Centering the specimen and funnel on the plate.

6. Ensuring that the electrodes are connected to the stopwatch.

Connecting the stopwatch and calibrate the clock to zero.

7. Filling the test tube with saline solution (0.9% by weight of NaCl in deionized water).

8. Keeping the funnel discharge valve closed, run 5.0 ml of liquid (= one jet) from the specimen to the funnel.

9. Opening the magnetic funnel valve to discharge 5.0 ml of liquid.

The initial flow of the liquid will complete the electrical circuit and connect the stopwatch. It will stop when the liquid has penetrated the buffer and has fallen below the level of the electrodes in the contact plate.

9. Recording the time indicated on the electronic stopwatch.

10. Waiting for 60 seconds and returning to point 6 for the second, the third jet and any other subsequent jet, each jet comprising 5 ml of liquid.

eleven. Report: Time for the 1st, 2nd and any subsequent jet in seconds.