KR100323818B1 - Absorbent macrostructure made from mixtures of different hydrogel-forming absorbent polymers for improved fluid handling capability - Google Patents

Abstract

A porous, absorbent macrostructure 52 is disclosed that has improved fluid handling capabilities, including intergranular aggregated aggregates, and useful for absorbent articles 48 such as diapers, adult incontinence pads, and sanitary napkins. The interparticle bound aggregates of these macrostructures 52 are made from a mixture of particulate absorbent polymers having different fluid treatment properties, different morphologies or different fluid treatment properties and morphologies. These macrostructures 52 can be made from a wider variety of hydrogel-forming absorbent polymers without reducing the desired fluid treatment properties and without exhibiting a tendency to gel blocking.

Description

Absorbent macrostructure made from mixtures of different hydrogel-forming absorbent polymers for improved fluid handling capability

The development of superabsorbent members for use as sanitary articles such as disposable diapers, adult incontinence pads and briefs, and sanitary napkins is of substantial commercial interest. The most demanding characteristic of these products is their thin thickness. For example, thinner diapers are less bulky when worn, fit well in clothing and are less noticeable. In addition, more compact packaging makes it easier for consumers to carry and store diapers. In addition, the compact packaging reduces the cost for manufacturers and distributors to distribute, such as less space for storage per diaper unit.

The ability to thin an absorbent product, such as a diaper, depends on the ability to develop relatively thin absorbent cores or structures that can capture and store large quantities of secreted fluid, especially urine. In this regard, it was particularly important to use certain absorbent polymers, sometimes referred to as 'hydrogel', 'superabsorbent' or 'hydrocolloid' materials. For example, US Pat. No. 3,699,103 to Harper et al., June 13, 1972, and US Pat. No. 3,770,731 to Harmon, dated June 20, 1972, describe such products in absorbent products. The use of absorbent polymers (hereinafter referred to as 'hydrogel-forming absorbent polymers') is disclosed. Indeed, the development of thin diapers has been a direct result of thinner absorbent cores, typically using the ability of hydrogel-forming absorbent polymers to absorb large amounts of secreted body fluids when used in combination with fibrous matrices. For example, US Pat. No. 4,673,402 to Weisman et al. On June 16, 1987 and US Pat. No. 4,935,022 to Lash et al. On June 19, 1990 are thin and bulky. Bilayer core structures are disclosed that include hydrogel-forming absorbent polymers and fibrous matrices useful for forming non-dense diapers.

Prior to the use of such hydrogel-forming absorbent polymers, it was common to form absorbent structures and the like suitable for use in infant diapers as a whole from wood pulp fluff. Since the fluid absorbed by the wood pulp fluff is relatively small, 1 g of fluid absorbed per gram of wood pulp fluff, a relatively large amount of wood pulp fluff has to be used and therefore a relatively bulky and thick absorbent structure has to be used. . Incorporating these hydrogel-forming absorbent polymers into these structures may use less wood pulp fluff. These hydrogel-forming absorbent polymers have a superior ability to absorb large amounts of aqueous body fluids, such as urine (ie, greater than about 15 g / g), resulting in smaller and thinner absorbent structures.

These hydrogel-forming absorbent polymers may also be prepared by initial polymerizable unsaturated carboxylic acids or derivatives thereof such as acrylic acid, alkali metals (such as sodium and / or potassium) of acrylic acid or ammonium salts, alkyl acrylates and the like. These polymers are insoluble but not water-soluble by slightly crosslinking the carboxyl group-containing polymer chains with conventional di- or polyfunctional monomer materials such as N, N'-methylenebisacrylamide, trimethylol propane triacrylate or triallyl amine. It becomes a swellable polymer. The slightly crosslinked absorbent polymer still contains a large number of anionic (charged) carboxyl groups attached to the polymer backbone. These charged carboxyl groups allow the polymer to absorb body fluids as a result of osmotic pressure to form hydrogels.

The degree of crosslinking not only determines the degree of water insolubility of the hydrogel-forming absorbent polymer, but is also an important factor in indicating two other properties: absorbency and gel strength. Absorbency or 'gel volume' is a measure of the amount of water or body fluid absorbed by a given amount of hydrogel-forming polymer. Gel strength relates to the tendency of hydrogels formed from these polymers to deform or 'flow' under applied stress. Hydrogel-forming polymers useful as absorbers in absorbent structures and articles (such as disposable diapers) need not only to have a sufficiently high gel strength but also a sufficiently large gel volume. The gel volume needs to be large enough to allow the hydrogel-forming polymer to absorb significant amounts of aqueous body fluid during use of the absorbent article. The gel strength should be such that the formed hydrogel deforms and fills such that it does not accept capillary voids in the absorbent structure or product, so as not to impair their absorbency as well as the fluid distribution of the absorbent structure or product. Examples include US Pat. No. 4,654,039, issued March 31, 1987 to Brandt et al., US Pat. No. 32,649, issued April 19, 1988, and May 30, 1989. See US Pat. No. 4,834,735 to Alemany et al.

Conventional absorbent structures generally comprise these hydrogel-forming absorbent polymers in relatively small amounts (eg, less than about 50% by weight). See, for example, US Pat. No. 4,834,735, issued May 30, 1989 to Alemanny et al., Which preferably contains about 9 to about 50% of a hydrogel-forming absorbent polymer in a fibrous matrix. do. There are several reasons for this. Hydrogel-forming absorbent polymers used in conventional absorbent structures generally do not have an absorption rate that allows for the rapid absorption of bodily fluids, particularly in 'spray' form. Thus, it is necessary to include fibers, typically wood pulp fibers, which serve as a temporary reservoir to retain secreted fluid until absorbed by the hydrogel-forming absorbent polymer.

More importantly, many known hydrogel-forming absorbent polymers exhibit gel blocking, especially when included in large amounts in absorbent structures. 'Gel blocking' occurs to prevent fluid transfer to other areas of the absorbent structure when the hydrogel-forming absorbent polymer particles are wet swelled. Thus, other areas of the absorbent member are wetted through a very slow diffusion process. In practice, this means that fluid capture by the absorbent structure occurs much slower than the rate at which the fluid is secreted, especially in the form of a jet. Leakage may occur from the absorbent article before the hydrogel-forming absorbent polymer particles in the absorbent member are fully saturated or before the fluid can diffuse or wick through the 'blocking' particles to the rest of the absorbent member.

Gel blocking can be a particularly urgent problem once the hydrogel-forming absorbent polymer particles do not have sufficient gel strength and are deformed or diffused under stress once the particles are swollen by the absorbed fluid. See, for example, US Pat. No. 4,834,735, issued May 30, 1989 to Alemani et al. Low gel strength hydrogel-forming absorbent polymers also tend to have higher fluid capacities. Gel strength can be increased by surface crosslinking of such hydrogel-forming absorbent polymers with high fluid capacity. Unfortunately, surface crosslinking tends to increase gel strength while lowering the fluid capacity of the hydrogel-forming absorbent polymer.

Gel blocking can also occur when the hydrogel-forming absorbent polymer is a particle of regular shape, such as spherical particles. Spherical particles are typically produced when the hydrogel-forming absorbent polymer is formed by a multiphase polymerization method such as reverse emulsion polymerization or reverse suspension polymerization process. For example, U.S. Pat. See US Pat. No. 4,735,987, issued April 5 to Morita et al. Since these spherical particles are likely to gel-block, the polyphase polymerization method was thought to be less desirable for hydrogel-forming absorbent polymer synthesis. See US Pat. No. 5,124,188, issued June 23, 1992 to Roe et al.

In order to improve capillary functionality and minimize gel blocking, hydrogel-forming absorbent polymer particles are typically formed into crosslinked cohesive macrostructures in the form of sheets or strips. These cohesive macrostructures were prepared by initial mixing the hydrogel-forming absorbent polymer particles with a solution of nonionic crosslinkers such as glycerol, water and hydrophilic organic solvents such as isopropanol. For example, US Pat. No. 5,102,597 to Loe et al. On April 7, 1992, US Pat. No. 5,124,188 to Loe et al. On June 23, 1992, and Larman on September 22, 1992. See US Pat. No. 5,149,344 to Lahrman et al. In addition, Rezai (June 23, 1994) discloses an improved porous cohesive macrostructure crosslinked with cationic amino-epichlorohydrin adducts such as KYMENE. See US Patent No. 5,324,561 to Rezai et al.

Since the particulate properties of the absorbent polymer are retained, these macrostructures provide voids (ie, capillary transport channels) between adjacent particles that are interconnected to be fluid permeable. Due to the interparticle crosslinks formed between the particles, the resulting macrostructures also have improved structural integrity, increased fluid trapping and distribution rates, and minimal gel blocking properties. Nevertheless, the fluid handling capacity of these macrostructures depends somewhat on the fluid handling capacity of the hydrogel-forming absorbent polymer particles produced therefrom. For example, macrostructures made from low gel strength hydrogel-forming absorbent polymers or spherical particles of hydrogel-forming absorbent polymers are still prone to gel blocking. In addition, macrostructures made from surface crosslinked hydrogel-forming absorbent polymers still have permeability below optimal permeability.

Thus, the absorbent cohesive macrostructures of the bound absorbent particles can (1) use hydrogel-forming absorbent polymers prepared by several methods, (2) have a low tendency to gel-block and (3) have optimal permeability Or (4) to be able to provide a combination of improved fluid handling capabilities.

Summary of the Invention

The present invention is directed to porous, absorbent macrostructures with improved fluid handling capabilities, including aggregates bound between particles. These aggregates comprise a plurality of interconnected crosslinked particles comprising a substantially water insoluble absorbent hydrogel-forming polymeric material. Hydrogel-forming polymeric materials have (a) a saline flow conductivity (SFC) of at least about 5 × 10 ⁻⁷ cm ³ sec / g and a performance under pressure (PUP) value of 0.7 psi. A mixture of about 50 to about 95% of a first hydrogel-forming polymer having at least about 23 g / g and (5 kPa) and about 5 to about 50% of a second hydrogel-forming polymer having an absorption capacity of at least about 25 g / g, (b) A mixture of about 20 to about 40% of the first hydrogel-forming polymer in the form of spherical particles and about 60 to about 80% of the second hydrogel-forming polymer in the form of non-spherical particles, and (c) (a) and (b Mixtures selected from The interparticle bound agglomerates include pores between adjacent particles. The voids are interconnected by channels communicated to form a liquid permeable macrostructure. The circumscribed dry volume of the macrostructure is greater than about 0.008 mm ³ .

Porous absorbent macrostructures according to the invention are used alone or in combination with other absorbent materials in absorbent structures used in various absorbent articles, including diapers, adult incontinence pads, sanitary napkins and the like. These porous absorbent macrostructures provide particularly preferred combinations of fluid permeability and fluid handling with relatively high fluid capacities. The macrostructures of the present invention may also be prepared from a wider variety of hydrogel-forming absorbent polymers without reducing the desired fluid treatability and without exhibiting a tendency to gel blocking. Indeed, the ability to use higher amounts of hydrogel-forming absorbent polymers in the form of spherical particles provides processing advantages such as more constant flow rates during the manufacture of these macrostructures.

The present invention relates to a porous, absorbent macrostructure consisting of flexible aggregates bound between particles. In particular, the present invention relates to porous, absorbent macrostructures in which the interparticle bound aggregates are prepared from mixtures of different particulate type absorbent polymers, or both of which are different in fluid treatability or form.

1 is a scanning electron micrograph of a typical macrostructure of the invention. The depicted macrostructures are fabricated using irregular shaped and spherical superabsorbent polymers.

2 is a scanning electron micrograph of the macrostructure of the present invention. This structure is fabricated by attaching irregularly shaped superabsorbent polymers to one side of the fibrous web and spherical polymers to the other side.

3 is a perspective view of a disposable diaper embodiment in accordance with the present invention, the topsheet portion being cut away to more clearly show the absorbent core (an aspect of the absorbent member according to the present invention) of the diaper below, the absorbent member being It includes a porous absorbent macrostructure according to the present invention.

4 is a cross-sectional view of the absorbent core of the diaper shown in FIG. 3, obtained by dividing along the dividing line 6-6 of FIG. 3.

Fig. 5 is a perspective view of a disposable diaper embodiment in accordance with the present invention, with the topsheet portion cut away to more clearly show another double layer absorbent core embodiment.

FIG. 6 shows the components of the diaper structure separately, with another bilayer absorbent core having the absorbent macrostructure in the form of a plurality of strips as one component.

FIG. 7 is a profile of the weight percent of the high PUP L-76 superabsorbent polymer versus the demand absorbent capacity of the various macrostructures for the different macrostructures.

Justice

Body fluids include urine, menstrual blood and vaginal secretions.

"Including" means that various components, members, steps, and the like may be used together in accordance with the present invention. Thus, the term 'comprising' encompasses the more restrictive term 'consisting essentially of' and 'consisting of' known in the art as more restrictive term having standard meaning.

All percentages, ratios, and ratios used herein are by weight unless otherwise specified.

I. Porous, Absorbent Macrostructures

A. General Characteristics

Porous, absorbent macrostructures according to the present invention are structures that can retain large amounts of liquid, such as water and / or body waste (eg, urine or menstrual blood) and then retain such liquid under appropriate pressure. Because of the particulate nature of the precursor particles, the macrostructures have voids between adjacent precursor particles. These pores are connected by communication channels such that the macrostructures are liquid permeable (ie have capillary transport channels).

Because of the bonds formed between the precursor particles, the resulting coherent macrostructures have improved structural integrity, increased liquid trapping and partitioning rate, and minimal gel blocking properties. It has been found that when the macrostructure is in contact with a liquid, the macrostructure is generally isotropically swelled even under suitable limiting pressure, and the liquid is absorbed into the pores between the precursor particles and then absorbs this liquid between the particles. Isotropic swelling of the macrostructures allows to maintain relative bonding structure and spatial correlation even upon swelling of the precursor particles and voids. Thus, the macrostructures are relatively 'fluidically stable' in that the precursor particles do not separate from each other, thus minimizing the influx of gel blocking and maintaining and expanding the capillary channels upon swelling, thereby allowing the macrostructures to absorb liquid, even excess liquid loading. Can be captured and transported continuously.

"Giant structure" is a structure having from about 0.008mm ³ or more, preferably about 10.0mm ^3, and more preferably about 100mm ^3, and more preferably about 500mm ³ or more when substantially dry volume boundary (i.e., boundary dry volume) . Typically, the macrostructures of the present invention will have a boundary drying volume much greater than about 500 mm ³ . In a preferred embodiment of the present invention, the macrostructure has a boundary drying volume of about 1,000 to about 100,000 mm ³ .

Although the macrostructures of the present invention may have a number of shapes and sizes, they are typically in the form of sheets, films, cylinders, blocks, spheres, fibers, filaments or other shaped elements. The macrostructures will generally have a thickness or diameter of about 0.2 to about 10.0 mm. Preferably the macrostructures for use in the absorbent article are in the form of sheets. The term 'sheet' refers to a macrostructure having a thickness of about 0.2 mm or more. The sheet will preferably have a thickness of about 0.5 to about 10 mm, typically about 1 to about 3 mm.

Porous absorbent macrostructures of the invention include aggregates bound between particles. These interparticle bound aggregates usually comprise at least about 8 previously independent precursor particles. For the preferred boundary dry volume and size of the individual precursor particles as used herein, these aggregated aggregates are typically formed from about 100,000 or more individual precursor particles. These individual precursor particles may include granules, powders, spheres, flakes, fibers, aggregates or aggregates. Individual precursor particles can be in various forms such as cuboid, rod, polyhedron, spherical, circular, angular, irregular, randomly sized irregularities (e.g. grinding products of the grinding or grinding step) or needles, flakes or It may have a shape with the largest dimension / smallest dimension ratio to be fibrous.

The interparticle bonded aggregates comprising the macrostructures of the present invention are formed by being linked or attached together with adjacent particles. The adhesive is essentially a polymeric material present on the surface of these particles. When these precursor particles are treated with a crosslinker and physically bound, the polymeric material present on the surface of these particles is sufficiently plastic and adhesive (eg, sticky) so that adjacent particles typically adhere together as separate bonding sites between the particles. do. The crosslinking reaction between the particles anchors the attached structure so that the particles of the aggregate are adhesively bonded together.

B. Precursor Absorbent Particles

The macrostructures of the present invention are formed from precursor particles comprising a substantially water-insoluble polymeric material capable of absorbing large amounts of liquid. Such polymeric materials are hereinafter referred to as 'hydrogel-forming absorbent polymers'. Since the macrostructures of the invention include aggregates bound between particles, these hydrogel-forming absorbent polymer materials will be discussed herein in connection with the formation of precursor particles.

Although precursor particles may have a wide range of sizes, certain particle size distributions and sizes are preferred. For the purposes of the present invention, particle diameter is defined as precursor particles (eg granules, flakes or powders) that do not have the largest dimension / smallest dimension ratio such as fibers as the dimension of the precursor particles measured by sieve size analysis. For the purposes of the present invention, the mass average particle diameter of the precursor particles is important for determining the properties and properties of the resulting macrostructures. The mass average particle diameter of a given sample of precursor particles is defined as the average particle diameter of the sample based on mass. The measurement of the mass mean particle size of the sample is described in the test method section of US Pat. No. 5,324,561 to Rezai et al. On June 23, 1994. The mass average particle diameter of the precursor particles will generally be about 20 to about 1,500 μm, more preferably about 50 to about 1,000 μm. In a preferred embodiment of the present invention, the precursor particles have a mass average particle diameter of less than about 1,000 μm, more preferably less than about 600 μm, more preferably less than about 500 μm.

The particle diameter of a material with the largest dimension / smallest dimension, such as a fiber, is typically defined by its largest dimension. For example, when absorbent polymer fibers (ie, superabsorbent fibers) are used in the macrostructures of the present invention, the length of the fibers is used to define the 'particle size'. (The denier and / or diameter of the fiber may also be defined). In an exemplary embodiment of the invention, the fibers have a length of at least about 5 mm, preferably from about 10 to about 100 mm, more preferably from about 10 to about 50 mm.

Hydrogel-forming absorbent polymer materials comprising these precursor particles have a number of anionic functional groups, more typically carboxy groups, such as sulfonic acids. Examples of suitable polymeric materials for use as precursor particles herein include those prepared from polymerizable unsaturated acid containing monomers. Accordingly, such monomers include olefinically unsaturated acids and anhydrides containing one or more carbon-carbon olefin double bonds. More specifically, these monomers may be selected from olefinically unsaturated carboxylic acids and acid anhydrides, olefinically unsaturated sulfonic acids and mixtures thereof. US Patent No. 5,324,561, issued to Rezai et al. On June 23, 1994, generally describes suitable monomers for the preparation of hydrogel-forming absorbent polymers.

Preferred polymeric materials for use in the present invention contain a carboxy group. These polymers include hydrolyzed starch-acrylonitrile graft copolymers, partially neutralized starch-acrylonitrile graft copolymers, starch-acrylic acid graft copolymers, partially neutralized starch-acrylic acid graft copolymers, saponified vinyl acetate Slightly networked crosslinking of acrylic ester copolymers, hydrolyzed acrylonitrile or acrylamide copolymers, slightly networked crosslinked polymers of any of said copolymers, partially neutralized polyacrylic acid and partially neutralized polyacrylic acid Bound polymers. These polymers may be used alone or in the form of a mixture of two or more other polymers. For example, U.S. Patent No. 4,093,776 to Aoki et al., June 6, 1978, U.S. Patent No. 4,666,983 to Tsubakimoto et al., May 19, 1987, and March 1988. U.S. Patent No. 4,734,478 to Tsubakimoto et al., Dated 29, discloses a representative example of this type of hydrogel-forming absorbent polymer.

More preferred polymeric materials for use in the preparation of precursor particles are slightly networked crosslinked polymers of partially neutralized polyacrylic acid and starch derivatives thereof. Preferably, the precursor particles comprise about 50 to about 95%, preferably about 75%, neutralized slightly reticulated crosslinked polyacrylic acid (ie, poly (sodium acrylate / acrylic acid)). Network crosslinking methods of polymers and typical network crosslinkers are described in more detail in US Pat. No. 4,076,663, supra.

Individual precursor particles may be formed by any conventional method. For example, precursor particles can be prepared by methods comprising aqueous solutions or by other solution polymerization methods. See, for example, US Reissued Patent No. 32,649 (Brand et al.), Issued April 19, 1988. Precursor particles useful in the present invention can also be prepared using polyphase polymerization process techniques such as reverse emulsion polymerization or reverse suspension polymerization processes. For methods involving reverse suspension polymerization, for example, U.S. Pat. No. 4,340,706 to Obisashi et al. On July 20, 1982, US Pat. Nos. 4,506,052 to Fletcher et al. On March 19, 1985, and 1988 See US Pat. No. 4,735,987, issued April 5, 2005 to Morita et al. As discussed below, the particular method used to prepare these precursor particles can be important for the measurement of the shape of the resulting particles as well as for their measurement of fluid permeability and capacity properties.

All precursor particles are preferably formed from the same polymeric material having the same properties, but this is not necessary in this case. For example, some precursor particles may comprise starch-acrylic acid graft copolymers while other precursor particles may comprise a slightly networked crosslinked polymer of partially neutralized polyacrylic acid. Moreover, the size, shape, absorption capacity or any other property or characteristic of the precursor particles may vary. In a preferred embodiment of the invention, the precursor particles consist essentially of a slightly networked crosslinked polymer of partially neutralized polyacrylic acid, each precursor particle having similar properties.

In a preferred embodiment of the invention, the precursor particles used to form the bound particle aggregates are substantially dry. "Substantially dry" means that the precursor particles have a liquid content, typically water or other solution content, of less than about 50%, preferably less than about 20%, more preferably less than about 10% by weight. Generally, the liquid content of the precursor particles is in the range of about 0.01 to about 5% by weight of precursor particles. Individual precursor particles may be dried by any conventional method, such as by heating. Alternatively, when precursor particles are formed using an aqueous reaction mixture, water may be removed from the reaction mixture by azeotropic distillation. The polymer-containing aqueous reaction mixture may also be treated with a dehydration solvent such as methanol. Combinations of these drying procedures can also be used. The dehydrated mass of the polymeric material may then be broken down or comminuted to form substantially dry precursor particles of the absorbent hydrogel-forming polymeric material that are substantially water insoluble.

C. Mixtures of Precursor Particles Providing Improved Fluid Handling Properties

The main features of the invention are (1) different fluid handling properties; (2) different forms; Or (3) using a mixture of precursor particles having both. It has been found that mixtures of precursor particles having different fluid treatment properties, shapes, or both can impart improved overall fluid handling capabilities to the resulting macrostructures. This is typically demonstrated by the combination of high fluid permeability / performance and high fluid capacity in the resulting macrostructures made from these mixtures. In fact, macrostructures made from mixtures of precursor particles according to the present invention minimize the potential problem of 'gel blocking' without loss of the desired fluid capacity.

The mixture according to variant (1) of the present invention comprises: (a) a first hydrogel-forming polymer having a relatively high salt flow conductivity (SFC) value and a relatively high pressure under pressure (PUP) (high gel permeability / performance). ; And (b) precursor particles made from a second hydrogel-forming polymer having a relatively high absorption capacity. Generally, these mixtures comprise about 50 to about 95% higher gel permeable / performing hydrogel-forming polymers and about 5 to about 50% high fluid dose hydrogel-forming polymers. Preferably, these mixtures contain about 60 to about 95% higher gel permeable / performing hydrogel-forming polymer and about 5 to about 40% higher fluid dose hydrogel-forming polymer and more preferably about 60 to about 80% high gel permeable / performing hydrogel-forming polymer and about 20 to about 40% high fluid dose hydrogel-forming polymer.

Precursor particles useful in the present invention having a relatively high salt flow conductivity (SFC) value and a relatively high pressure under performance (PUP) are disclosed in co-pending US patent application No. 219,574 filed March 29, 1994 (Goldman). And the like). These high gel permeable / performing precursor particles are at least about 5 × 10 ⁻⁷ cm ³ sec / g, preferably at least about 10 × 10 ⁻⁷ cm ³ sec / g and more preferably at least about 100 × 10 ⁻⁷ cm ³ sec. It has an SFC value of / g or more. Typically, these SFC values are about 30 to about 1,000 × 10 ⁻⁷ cm ³ sec / g, more typically about 50 to about 500 × 10 ⁻⁷ cm ³ sec / g, more typically about 100 to about 350 × 10 ^-7 cm ³ sec / g. These high gel permeable / performing precursor particles also generally have a PUP performance of at least about 23 g / g, preferably at least about 25 g / g and more preferably at least about 29 g / g. Typically these PUP values range from about 23 to about 35 g / g, more typically from about 25 to about 33 g / g, more typically from about 29 to about 33 g / g.

Preferred methods for obtaining precursor particles having relatively high SFC and PUP values include surface crosslinking of the initially formed polymer. Various methods for inducing surface crosslinking are known in the art. These are (i) bifunctional or multifunctional reagent (s) capable of reacting with the functional groups present in the hydrogel-forming absorbent polymer (ie glycerol, 1,3-dioxolan-2-one, polyvalent metal ions, poly- Quaternary amines) are applied to the surface of the hydrogel-forming absorbent polymer; (ii) bifunctional or multifunctional reagents are applied to the surface (i.e. monomer and Addition of crosslinker and initiation of second polymerization reaction); (iii) no additional multifunctional reagent is added, but the addition reaction is present in the hydrogel-forming absorbent polymer during or after the first polymerization process to produce a higher level of crosslinking at or around the surface. To induce suspension processes (e.g., anhydrides and / or ester crosslinks between the polymer carboxylic acids and / or hydroxyl groups present and crosslinking agents present at high levels near the original surface). Heating); (iv) adding other materials to the surface to induce higher levels of crosslinking or otherwise reduce the likelihood of surface modification of the resulting hydrogel. Combinations of these surface crosslinking processes can also be used simultaneously or sequentially. In addition to crosslinkable reagents, other ingredients may also be added to the surface to assist or control the distribution of crosslinks (eg, dispersion and permeation of surface crosslinkable reagents). See US Patent Application No. 219,574 to Goldman et al., Filed March 29, 1994, co-pending.

A suitable general method for carrying out the surface crosslinking of the hydrogel-forming absorbent polymer according to the present invention is disclosed in U.S. Pat. Stanley's PCT Application WO92 / 16565, PCT Application WO90 / 08789 to Tai, published August 9, 1990; PCT Application WO93 / 05080 to Stanley, published March 18, 1993; US Patent No. 4,824,901, issued April 25, 1989 to Alexander; U.S. Patent No. 4,789,861 to Johnson, January 17, 1989; U.S. Patent No. 4,587,308 to Makita, dated May 6, 1986; U.S. Patent No. 4,734,478, issued to Tsubakimoto on March 29, 1988; US Patent No. 5,164,459, issued to Kimura et al. On November 17, 1992; German Patent Application No. 4,020,780 to Dahmen, published August 29, 1991; And European Patent Application No. 509,708 to Gartner, published October 21, 1992. See also, in particular, Examples 1-4 of co-pending US patent application Ser. No. 219,574, filed March 29, 1994. Suitable hydrogel-forming absorbent polymers with relatively high SFC and PUP values are L76lf, manufactured by Nippon Shokubai, SXP, Dow Chemical manufactured by Chemische Fabrik Stockhausen. XZ manufactured by and XP-30 manufactured by Nalco Chemical.

Precursor particles useful in the present invention having a relatively high absorption capacity and a relatively high absorption value (AAP) are described in US Pat. No. 4,076,663, issued April 28, 1978 to Matsuda et al., April 19, 1988. U.S. Re-licensed Patent No. 32,649 to Brandt et al., U.S. Patent No. 4,625,001 to Tsubakimoto et al. On November 25, 1986, US Patent to Tsubakimoto et al. On May 19, 1987 No. 4,666,983, U.S. Patent No. 4,734,478 to Tsubakimoto et al. On March 29, 1988, U.S. Patent No. 4,735,987 to Morita et al. On April 5, 1988, issued November 27, 1990. U.S. Patent No. 4,973,632 to Nagasuna et al., U.S. Patent No. 5,264,471 to Chmelir et al. On November 23, 1993 and Chambers, published March 10, 1993. Disclosed in European Patent Application No. 530,438, et al. It can control. 'Absorptive Capacity' refers to the capacity of a given polymer material to absorb the fluid it comes into contact with, and can vary widely depending on the nature of the absorbed fluid and the manner in which the liquid contacts the polymeric material. For the purposes of the present invention, absorption capacity is defined as the amount of synthetic urine absorbed by any given polymeric material, ie the number of g of synthetic urine per gram of polymeric material. See also the Test Methods section of this application. The AAP value represents the absorbency required for the hydrogel-forming polymer, ie the absorbent capacity of the polymer when an external pressure of 0.3 psi is applied. See also the Test Methods section of this application.

These high fluid volume precursor particles have an absorption capacity value of at least about 25 g of synthetic urine per gram of polymer, more preferably at least about 35 g, more preferably at least about 45 g. Typically, these high fluid volume precursor particles have an absorption capacity value of about 25 to about 70 g, more typically about 40 to about 60 g, of synthetic urine per gram of polymeric material.

Preferred methods for obtaining such precursor materials with relatively high absorption capacity values include aqueous solutions or other solution polymerization methods. As described in the aforementioned U.S. Pat.No. 32,649, the aqueous solution polymerization process involves the use of an aqueous reaction mixture to carry out the polymerization reaction to form precursor particles. The aqueous reaction mixture is then under polymerization conditions sufficient to produce a polymeric material that is substantially water-insoluble and slightly networked in the mixture. Suitable hydrogel-forming absorbent polymers having relatively high absorption capacity and AAP values are IM 1000 manufactured by Hoechst Celanese, L74 manufactured by Nippon Shokubai and Nippon Gohsei. Including, but not limited to, F201.

The mixture according to variant method (2) of the present invention comprises: (a) a first hydrogel in the form of a spherical particle which may comprise a spherical agglomerate of a first hydrogel-forming polymer (typically produced by a suspension polymerization process). Forming polymers; And (b) precursor particles prepared from non-spherical or irregularly shaped second hydrogel-forming polymers typically prepared by bulk polymerization processes. The reason why macrostructures made primarily from spherical particles of hydrogel-forming absorbent polymers are easily gel blocked is believed to be due to the formation of tight and dense structures with adverse fluid permeability. Inclusion of non-spherical (irregular) particles has been known to interfere with the self-assembly properties of the spherical particles during the production of the macrostructures, in particular sheet-like macrostructures. As a result, the macrostructure no longer blocks the fluid.

In general, these mixtures according to the modification method (2) comprise from about 5 to about 50% spherical particles and from about 50 to about 95% non-spherical particles. Preferably, these mixtures contain about 10 to about 50% spherical particles and about 50 to about 90% non-spherical particles, more preferably about 20 to about 40% spherical particles and about 60 to about 80% Non-spherical particles.

Spherical particles and spherical agglomerates can be obtained by polyphase polymerization process techniques such as reverse emulsion polymerization or reverse suspension polymerization. In the course of reverse emulsion polymerization or reverse suspension polymerization, the aqueous reaction mixture is suspended in the form of droplets in a matrix of inert organic solvent, which is not mixed with water such as cyclohexane. The resulting precursor particles are generally spherical. US Pat. No. 4,093,776, issued to Aoki et al. On June 6, 1978, and US Pat. No. 4,340,706, Yamasaki, et al., Issued to Obisashi on July 20, 1982. U.S. Patent No. 4,446,261, issued to Fletcher et al. On March 19, 1985, U.S. Patent No. 4,506,052, issued to September 17,1985, to Obisa, et al., U.S. Patent No. 4,541,871, October 1987 US Pat. No. 4,698,414, issued to Cramm et al., Dated 6, US Pat. No. 4,735,987, issued May 5, 1988 to Morita et al., Issued May 23, 1989 to Young et al. US Patent No. 4,833,179 and European Patent Application No. 522,570, published January 13, 1993. Suitable spherical hydrogel-forming absorbent polymer particles include F201 manufactured by Nippon Kose and Base 60 manufactured by Mitsubishi Chemical.

Non-spherical or irregularly shaped particles can be obtained by bulk polymerization reaction processes including aqueous solutions or other solution polymerization methods. As described in the above-referenced U.S. Pat. The aqueous reaction mixture is then under sufficient polymerization to produce a substantially water insoluble and slightly networked crosslinked polymeric material in the mixture. The formed polymeric material aggregates are then comminuted or broken down to form individual precursor particles. Suitable non-spherical hydrogel-forming absorbent polymer particles include L76lf, manufactured by Nippon Shokubai, SXP or SXM, manufactured by Chemish Fabric Stockhausen, and 1180 or XP 30, manufactured by Nalco Chemical.

D. Crosslinking Agent

In preparing the macrostructures according to the invention, crosslinkers are used to provide crosslinking at the surface of the mixture of absorbent precursor particles. This typically occurs as a result of the reaction of the crosslinker with the polymeric material in these particles. Typically, the polymeric material of the absorbent precursor particles is anionic and is preferably a carboxy functional group that forms ester type covalent bonds with crosslinkers. This portion of the effectively crosslinked absorbent particles will swell less in the presence of an aqueous (sieve) liquid as compared to the other non-crosslinked portions of the particles.

Crosslinkers suitable for this purpose are nonionic and contain two or more functional groups which can react with a carboxy group per molecule. See, for example, US Pat. No. 5,102,597 to Roh et al. On April 7, 1992, which discloses polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, glycerol ( 1,2,3-propanetriol), polyglycerol, propylene glycol, 1,2-propanediol, 1,3-propanediol, trimethylol propane, diethanolamine, triethanolamine, polyoxypropylene oxyethylene-oxypropylene Block copolymers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, pentaerythritol and sorbitol; Polyglycidyl ether compounds such as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitol polyglycol Cydyl ether, pentaerythritol polyglycidyl ether, propylene glycol diglycidyl ether and propylene glycol diglycidyl ether; Polyaziridine compounds such as 2,2, -bishydroxymethyl butanol-tris [3- (i-aziridine) propionate], 1,6-hexamethyl toluene diethylene urea and diphenyl methane-bis-4 , 4'-N, N'-diethylene urea; Haloepoxy compounds such as epichlorohydrin and α-methylfluorohydrin; Polyaldehyde compounds such as glutaraldehyde and glyoxazole; Polyamine compounds such as ethylene diamine, diethylene triamine, triethylene tetramine, tetraethylene pentamine, pentaethylene hexamine and polyethylene imine; And various nonionic crosslinkers including polyisocyanate compounds such as 2,4-toluene diisocyanate and hexamethylene diisocyanate. Particularly preferred nonionic crosslinkers are glycerol.

Preferred crosslinkers for use in the present invention are epichlorohydrin adducts having certain monomeric or polymeric amine forms. See US Pat. No. 5,324,561 to Rezai et al., June 23, 1994, which discloses suitable cationic amino-epichlorohydrin adduct crosslinkers. These amino-epichlorohydrin adducts, especially polymerizable resin modifications of these adducts, are preferred crosslinkers because they react only with the polymerizable material in the surface precursor particles. In addition, cationic functional groups of these adducts (e.g. azetedinium groups), in particular polymerizable resin modifications, are also suitable for the anionic functional groups of the polymeric material of the absorbent particles, typically at carboxy groups and at room temperature (e.g. from about 18 to about 25 ° C). It seems to react very quickly. As a result, very moderate amounts of these amino-epichlorohydrin adducts (eg, as low as about 1% by weight of the particles) are needed to provide effective surface crosslinking of the polymeric material present in the absorbent precursor particles.

Suitable cationic amino-epichlorohydrin adducts useful as crosslinking agents are monomeric di-, tri- and higher amines having primary or secondary amino groups in the structure, such as bis-2-aminoethyl ether, N, N- Dimethylethylenediamine, piperazine, ethylenediamine, N-aminoethyl piperazine and dialkylene triamines such as diethylenetriamine and dipropylenetriamine; Polymeric amines such as polyethylenimine and certain polyamide-polyamines derived from saturated C ₃ -C ₁₀ dibasic carboxylic acids with polyalkylene polyamines. These epichlorohydrin / polyamide-polyamine adducts are well known in the art as wet stiff resins used in paper products. More preferred epichlorohydrin / polyamide-polyamine adducts are polyethylene polyamines containing 2 to 4 ethylene groups, two primary amine groups and 1 to 3 secondary amine groups, and saturated aliphatic C ₃ -C ₁₀ di Adducts derived from carboxylic acids, more preferably adducts containing 3 to 8 carbon atoms such as malonic acid, succinic acid, glutaric acid, adipic acid and diglycolic acid. Particularly preferred cationic polyamide-polyamine epichlorohydrin resins for use herein as crosslinkers are available under the trade name Chimen from Hercules Inc. Kymene 557H, Kymene 557LX and Kymene 557 Plus are particularly useful, which are epichlorohydrin adducts of polyamide-polyamines, the reaction product of diethylenetriamine and adipic acid. They are typically commercially available in the form of an aqueous solution of cationic resin material containing from about 10 to about 33 weight percent active resin.

E. Process for producing aggregates and macrostructures bonded between particles

When preparing the intergranular bound aggregates that make up the porous absorbent macrostructure, the mixture of absorbent precursor particles generates effective crosslinking, i.e. the presence of aqueous body fluid relative to the portion where the crosslinked surface of the particles is uncrosslinked. It is treated with a sufficient amount of crosslinker that reacts with the polymeric material at the surface of the particles so that they swell less under. The construction of an 'a sufficient amount' of crosslinker depends on a number of factors, including the particular absorbent precursor particle treated, the crosslinker used and the particular effect desired to form the aggregated aggregates between the particles. To U.S. Patent No. 5,102,597 entitled `` nonionic crosslinking agents such as glycerol '' issued to Loe et al. On April 7, 1992 and to Rezai et al. On June 23, 1994. See US Pat. No. 5,324,561, entitled 'cationic amino-epichlorohydrin adduct crosslinking agents.'

In addition to the absorbent precursor particles and the crosslinking agent, other components or agents can be used as an adjuvant when preparing the aggregates in which the particles are bound. For example, water is typically used with crosslinkers to form aqueous treatment solutions thereof. Water encourages uniform dispersion of the crosslinker at the surface of the precursor particles and permeates the crosslinker into the surface area of these particles. In addition, water encourages stronger physical bonding between the treated precursor particles and provides greater integrity to the resulting cross-linked crosslinked aggregates. The actual amount of water used may depend on factors such as the type of crosslinker used, the type of polymeric material used to form the precursor particles, the particle size of the precursor particles, and the incorporation of other optional components (eg glycerol). have. U.S. Pat.No. 5,102,597, entitled `` Nonionic Crosslinking Agents Such As Glycerol, '' issued to Lo et al. On April 7, 1992, and cationic amino-epichlorohigh, issued to Rezai et al. On June 23, 1994. See US Pat. No. 5,324,561 entitled Adduct Crosslinker.

Although not absolutely necessary, organic solvents can be used, which typically promotes uniform dispersion of the crosslinker on the surface of the precursor particles. These organic solvents are typically hydrophilic and include lower alcohols such as methanol and ethanol; Amides such as N, N-dimethylformamide and N, N-diethylformamide; And sulfoxides such as dimethyl sulfoxide. The actual amount of hydrophilic solvent used may vary depending on factors such as the adduct used, the polymeric material used to form the precursor particles, the particle size of these precursor particles, and the like. U.S. Pat.No. 5,102,597, entitled `` Nonionic Crosslinking Agents Such As Glycerol, '' issued to Lo et al. On April 7, 1992, and cationic amino-epichlorohigh, issued to Rezai et al. On June 23, 1994. See US Pat. No. 5,324,561 entitled Adduct Crosslinker.

Other optional components can also be used with crosslinkers, in particular their aqueous solutions. It is particularly preferred that the treatment solution comprises a plasticizer, especially when cationic amino-epichlorohydrin adducts are used as crosslinkers. See US Pat. No. 5,324,561 to Rezai et al. On June 23, 1994. Suitable plasticizers include glycerol, propylene glycol (ie 1,2-propanediol), 1,3-propanediol, ethylene glycol, sorbitol, sucrose, polymeric solutions (e.g., polyvinyl alcohol, ester precursors of polyvinyl alcohol, Water in combination alone or in combination with other ingredients such as polyethylene glycol or mixtures thereof). These other components in plasticizers, such as glycerol, appear to act as wetting agents, co-plasticizers, or both, with water being the main plasticizer. Particularly when the glycerol and water are included in a weight ratio of about 0.5: 1 to about 2: 1, preferably about 0.8: 1 to about 1.7: 1 by weight as part of the treated aqueous solution of the cationic amino-epichlorohydrin adduct Preferred plasticizers for use in are mixtures of glycerol and water.

The actual amount of plasticizer used may vary depending on the particular plasticizer used, the type of polymeric material used when forming the precursor particles, and the particular flexible effect desired from the plasticizer. Typically, the plasticizer is about 5 to about 100 parts by weight, preferably about 5 to about 60 parts by weight, more preferably about 10 to about 30 parts by weight, even more preferably about 15 to about 20 parts by weight of the precursor particles. Used in parts by weight. See US Pat. No. 5,324,561 to Rezai et al. On June 23, 1994.

In the process of the invention, the absorbent precursor particles can be treated in any of a variety of ways using cationic amino-epichlorohydrin adducts, typically aqueous solutions thereof. They coat, dump, pour, drop, spray, spray, condense, or soak the absorbent precursor particles with a cationic amino-epichlorohydrin adduct or a solution thereof. And any method of applying a solution to a material, including those. 'Apply' means that at least a portion of the surface area of at least a portion of the precursor particles to be bound has an effective amount of adduct to cause surface crosslinking. That is, the cationic adduct may be applied over some of the precursor particles, all of the precursor particles, some of the surface of some or all of the precursor particles, or all of the surface of some or all of the precursor particles. Preferably, the adduct adds to the entirety of the majority (preferably all) of the absorbent precursor particles in order to enhance the desired surface crosslinking of the polymeric material at the surface of such precursor particles as well as the efficiency, strength and density of interparticle bonding between the precursor particles. Coated on the surface.

After the treatment solution is applied onto the precursor particles, the treated precursor particles may be mixed or laminated in any of a number of mixing or lamination methods such that the precursor particles are completely coated with the treatment solution. U.S. Pat. See US Pat. No. 5,324,561 entitled Adduct Crosslinker. Before, during or after application of the treatment solution, the precursor particles are physically bound together to form an aggregate macrostructure. The precursor particles are preferably physically bonded together by applying an associating agent onto the precursor particles and physically contacting the precursor particles to at least a portion of the surface of the precursor particles to which the association agent is applied. Associations useful in the present invention include hydrophilic organic solvents, typically low molecular weight alcohols such as methanol or ethanol; water; Mixtures of hydrophilic organic solvents and water; Crosslinking agents or mixtures thereof. Preferred associating agents are water, methanol, ethanol, cationic polymeric amino-epichlorohydrin resins (e.g., chimen 557H, 557LX or plus) or mixtures thereof. Typically the associating agent contains a mixture comprising a crosslinking agent so that the step of applying the crosslinking is carried out simultaneously with the step of applying the associating agent.

The associating agent may be used to apply the precursor particles by any of the various methods and apparatus used to apply a solution to a material, including coating, dumping, pouring, spraying, spraying, condensing, or immersing the association agent onto the precursor particles. Can be applied to U.S. Pat. See US Pat. No. 5,324,561 entitled Adduct Crosslinker. When the association agent is applied to the precursor particles, the precursor particles may be physically contacted in a number of different ways. For example, the contacting particles can be fixed only with the association agent. Alternatively, gravity may be used to ensure contact between the precursor particles, for example, by stacking the precursor particles. The particles may also be placed in a container having a fixed volume to ensure contact between the precursor particles.

Alternatively, the precursor particles can be physically bound by being physically constrained so that they contact each other. For example, precursor particles are densely packed in a container having a fixed volume such that the precursor particles are in physical contact with each other. Alternatively or in combination with the above procedure, gravity (eg, lamination) may be used to physically bind the precursor particles. The precursor particles can also be physically bonded to one another by means of electrostatic attraction or the introduction of an adhesive (eg, an adhesive material such as a water soluble adhesive) to adhere them together. The precursor particles may also be attached to the third member (substrate) such that they contact each other by the substrate.

In another method of forming the macrostructure of the invention, the aggregates of precursor particles are shaped into various shapes, spatial relationships and densities to form aggregates having defined shapes, sizes and / or densities. Aggregates may be shaped by any conventional shaping techniques known in the art. Preferred methods for shaping the aggregates include casting, molding or shaping operations. Casting and molding techniques generally introduce precursor particles into the prepared molding holes and apply pressure to the (compression) aggregates so that the aggregates conform to the shape of the molding holes. Examples of specific molding techniques for use herein include press molding, injection molding, extrusion or lamination. For example, a plurality of precursor particles may be added to a container having a fixed volume of molding holes, and the aggregates may be compressed to conform to the shape of the molding holes so that the resulting macrostructures have the same shape. Molding methods include performing various manipulations on the aggregates to alter the shape and / or size and / or density of the aggregates. Examples of specific molding methods for use herein include rolling, forging, extrusion, spinning, coating or stretching operations. For example, the aggregate mixture of precursor particles and at least the cationic amino-epichlorohydrin adduct may pass between a pair of compression rolls to form the aggregate sheet. Alternatively, the aggregate mixture may be extruded through an orifice to form an aggregate having a shape corresponding to the shape of the orifice. In addition, the aggregate mixture may be cast on the surface to form aggregates having the desired shape or surface morphology. In addition, any or all of these techniques may be used in combination to form shaped aggregates. The manipulation can be carried out using any suitable technique known in the art, which can be carried out using some of the hot and / or low temperature materials or devices. A preferred method and apparatus for continuously forming the coherent macrostructures of the present invention as sheets is a U.S. patent entitled 'cationic amino-epichlorohydrin adduct crosslinker' issued to Rezai et al. On June 23, 1994. 5,324,561. See, in particular, Figure 9 of US Pat. No. 5,324,561 and the detailed description associated with it.

At the same time or after applying the treatment solution and the precursor particles are physically bonded to form an aggregate and the aggregate is shaped, the crosslinker reacts with the polymer material of the precursor particles while maintaining the physical bond of the precursor particles in the form of an aggregate macrostructure. Provide effective surface crosslinking in the precursor particles. U.S. Pat. See US Pat. No. 5,324,561 entitled Adduct Crosslinker. Because of the relatively reactive cationic functionalities of the amino-epichlorohydrin adducts that can be used as crosslinkers in the present invention, this crosslinking reaction can be reacted at relatively low temperatures, including ambient temperature. Such ambient temperature curing is particularly preferred when the treatment solution additionally contains a plasticizer such as a mixture of water and glycerol. Curing at temperatures significantly above ambient temperature can eliminate the plasticizer due to the volatility of the plasticizer, thus requiring an additional step to plasticize the intergranular aggregates. Curing at this ambient temperature typically takes place at a temperature of about 18 to about 35 ° C. for about 12 to about 48 hours. Preferably, curing at this ambient temperature is performed at about 18 to about 25 ° C. for about 24 to about 48 hours.

Although crosslinking reactions may occur at ambient temperatures, such curing may also be carried out at higher temperatures to accelerate the reaction. Curing at higher temperatures involves heating the treated and bound precursor particles such that the crosslinking reaction occurs in a shorter time, typically in minutes. This heating step can be performed using a number of conventional heating devices, including various ovens or dryers well known in the art.

In general, the thermosetting may be carried out at temperatures higher than about 50 ° C. for a time sufficient to complete the crosslinking reaction. The specific temperature and time used for thermosetting will depend on the specific crosslinker and polymer material present in the precursor particles used. US Pat. No. 5,102,597 to Roh et al., Filed Apr. 7, 1992 (nonionic crosslinker such as glycerol) and US Pat. No. 5,324,561 to Rezai et al., Filed June 23, 1994 (cationic amino-epi) Chlorohydrin adduct crosslinker). In the case of preferred cationic amino-epichlorohydrin adducts, thermosetting is generally carried out at about 50 ° C. to about 205 ° C. for about 1 to about 20 minutes. Preferably, the thermosetting is carried out at about 180 ° C. to about 200 ° C. for about 5 to about 15 minutes.

Physical association of the treated precursor particles is maintained during the curing step such that adjacent precursor particles adhesively bond to each other as the crosslinking proceeds. If the force or stress is sufficient to separate the precursor particles present during the crosslinking reaction, insufficient binding of the precursor particles will occur. This creates aggregates with poor structural integrity. Physical association of precursor particles is typically maintained by minimizing the separation force or stress during the curing step.

The preparation of the macrostructures need not be performed in any particular order, but may be performed simultaneously. For example, the treatment solution may be applied simultaneously with the physical association of the precursor particles to be shaped to the desired form and typically the desired density, and then the step may be terminated or the aggregates may be allowed to settle for a period of time before In reaction with the polymeric material, the precursor particles were simultaneously surface crosslinked to form a coherent macrostructure. Typically, precursor particles are mixed or sprayed with a solution of crosslinker, water, wetting agent and / or coplasticizer (eg glycerol), and hydrophilic organic solvent (eg methanol) to form aggregates that are bound to each other. The bound aggregates (ie, associated precursor particles and aqueous mixture) are then extruded and rolled to form densified sheets as described above. Subsequently, the crosslinker is thermally cured to react with the polymeric material at ambient temperature or at the same time to crosslink at the surface of the precursor particles to form an adhesive intergranular coherent macrostructure.

Even after curing, the macrostructure can be treated with a plasticizer to achieve surface crosslinking. Suitable plasticizers include water alone or mixtures with the aforementioned wetting / adjuvant plasticizers, preferably glycerol. The plasticizer can be applied to the macrostructure by a number of different methods, such as spraying, coating, spraying, dipping or dumping. Alternatively, when water is used alone, the macrostructure may be placed in an environment of high humidity (eg, relative humidity greater than 70%). The amount of plasticizer applied to the macrostructure can be chosen differently depending on the specific plasticizer used and the desired effect. Typically, the amount of plasticizer applied is about 5 to about 100 parts by weight, preferably about 5 to about 60 parts by weight per 100 parts by weight of the macrostructure. Particularly preferred plasticizers comprise a mixture of glycerol and water (weight ratio of about 0.5: 1 to about 2: 1, preferably about 0.8: 1 to about 1.7: 1).

Various types of fiber materials can be used as reinforcing members in the macrostructures of the present invention. Any form of fibrous material suitable for use in conventional absorbent articles is also suitable for use in the macrostructures herein. Specific examples of such fibrous materials include cellulosic fibers, modified cellulosic fibers, rayon, polypropylene and polyester fibers such as polyethylene terephthalate (DACRON), hydrophilic nylon (HYDROFIL), and the like. Other fibrous materials for use in the present invention besides some of the materials mentioned above include, but are not limited to, hydrophilized hydrophobic fibers, such as polyolefins (such as polyethylene or polypropylene), polyacrylics, polyamides, polystyrenes. Surfactant-treated or silica-treated thermoplastic fibers derived from polyurethane, etc. Indeed, hydrophilicity is not good on its own and thus does not provide sufficient absorbent capacity webs useful in conventional absorbent structures. The hydrophobic fibers that have been oxidized, due to their excellent wicking ability, This is because, in the macrostructures of the present invention, the macrostructures of the present invention are fast to pull fluid up and lack gel blocking properties, even if they are less important than the absorbent capacity of the fiber material itself. In general, synthetic fibers are preferred for use herein as the fiber component of macrostructures, more preferably polyolefin fibers, preferably polyethylene fibers.

Other cellulosic fiber materials that can be used in certain macrostructures herein are chemically reinforced cellulosic fibers. Preferred chemically strengthened cellulosic fibers are reinforced, twisted and curled cellulosic fibers that can be prepared by internally crosslinking the cellulosic fibers using a crosslinking agent. Suitable reinforced, twisted and curled fibers useful as the hydrophilic fibrous material herein are described in US Pat. No. 4,888,093 to Dean et al. On December 19, 1989, Herron et al. On December 26, 1989. US Patent No. 4,889,595, issued to Schögen et al. On December 26, 1989, US Patent No. 4,889,596 to Bourbon et al., Issued on December 26, 1989, and US Pat. , And US Patent No. 4,898,647 to Moore et al. On February 6, 1990.

The term 'hydrophilic' is used to describe the surface of a fiber or fiber that has been wetted with a liquid deposited on the fiber (i.e., whether water or aqueous body fluid readily absorbs fluid or forms a gel, regardless of whether the fiber actually absorbs fluid or forms a gel). Spreading on the surface of the fiber). Descriptions in the art of wetting of materials define hydrophobicity (and wettability) in terms of the contact angle and surface tension of the liquids and solids involved. This is described in the American Chemical Society Publication, Robert F., entitled 'Contact Angle, Wettability, and Adhesion'. Edited by Robert F. Gould and all rights reserved in 1964]. The fiber or surface of the fiber is controlled by the liquid if the contact angle between the liquid and the fiber or surface is less than 90 °, or if the liquid tends to spread at the same time as it penetrates the surface of the fiber, or if both conditions are generally met. It is said to be wet.

The fiber material can be added to the macrostructure by introducing the fiber with the crosslinker into the treatment solution, mixing with the precursor particles prior to application to the treatment solution, or adding the fiber material to the treatment solution / precursor particle mixture. For example, the fiber material can be mixed with the treatment solution / precursor particle mixture. The fibrous material is preferably mixed throughout the solution so that the fibrous material is uniformly dispersed throughout the macrostructure. In addition, the fibers are preferably added prior to reacting the adduct with the polymeric material of the precursor particles.

F. Optional Substrate Layer

If desired, a porous absorbent macrostructure may be attached to the optional substrate (see co-pending US patent application Ser. No. 142,253, filed Oct. 22, 1993). The substrate includes (1) improving the dispersion of the fluid absorbed by the macrostructure and (2) providing additional integrity, particularly at the point where the absorbent particles begin to swell after absorbing the fluid, thereby supporting the macrostructure. It can provide a number of functions. The substrate can be a number of materials known in the art, such as cellulosic fibers, nonwoven webs, tissue webs, foams, polyacrylate fibers, perforated polymeric webs, synthetic fibers, metallic foils, elastomers, and the like. It can be prepared from. Most of these base materials can distribute fluids as well as support large structures. Preferably, the substrate is composed of a cellulosic material or a material having cellulosic functional groups. Preferred substrates for dispensing fluids include cellulosic materials, fibrous webs, cellulosic fibrous webs, solid foams, cellulosic foams and polyvinyl alcohol foams. Preferred substrates for supporting the macrostructures include cellulosic materials, fibrous webs, nonwoven webs, textiles, cellulosic fibrous webs, solid foams, cellulosic foams and polyvinyl alcohol foams.

The substrate is preferably flexible and flexible, thus imparting these properties to the composite with the resulting absorbent macrostructure. The substrate is substantially elastic and non-stretchable or stretchable or deformable to varying degrees with respect to forces applied vertically or horizontally to the surface of the substrate. The thickness and basis weight (weight per unit area of the substrate) of the substrate material may vary depending on the shape of the substrate and the desired properties. The substrate may comprise multiple individual sheets or plies of the particular substrate material or one or more substrate layers in the stack. Such suitable substrates include a thickness of about 0.02 to about 1.2 mm, more preferably about 0.3 to about 0.8 mm, a basis weight of about 5 to about 100 gm / m 2, more preferably about 10 to about 60 gm / m 2, More preferably, it is a BOUNTY® sheet that is about 15 to about 40 gm / m 2. Other suitable substrates include a dry compressive thickness of about 0.5 to about 3.0 mm, more preferably about 0.8 to about 2.0 mm, a wet expansion thickness of about 0.8 to about 6.0 mm, more preferably about 1.0 to about 5.0 Mm and a cellulosic foam having a basis weight of about 50 to about 2,000 gm / m 2, more preferably about 100 to about 1,000 gm / m 2.

Substrates suitable for supporting macrostructures typically have a dry tensile strength of about 500 to about 8,000 gm / inch, more preferably about 1,000 to about 3,000 gm / inch, and a wet tensile strength of about 200 to about 5,000 and gm / inch, even more preferably about 400 to about 1,000 gm / inch, and the wet burst strength is about 100 to about 2,000 gm, even more preferably about 200 to about 1,000 gm. Preferred substrates of this type include U.S. Patent No. 3,953,638, issued April 27, 1976, U.S. Patent No. 4,469,735, issued September 4,1984, U.S. Patent No. Cellulosic fibrous webs, such as paper towels and tissues, as disclosed in US Pat. No. 4,986,882, issued 4,468,428 and 22 January 1991. Other preferred substrate layers of this type include cellulosic foams, as they provide higher wicking rates at longer wicking distances than cellulosic fibrous webs. Preferably, the cellulosic foam is extruded to be sufficient to further improve its fluid uptake and dispensing properties. Suitable cellulosic foams can be made from recycled rayon fibers by known methods, which are described in European Patent Application No. 293,208 to Uchida et al. Published November 30, 1988.

Porous absorbent macrostructures can be attached to the substrate by a number of chemical and physical methods and adhesives. Adhesives for attaching the substrate to the macrostructure include glue and hot melt adhesives. It is desirable to bond the substrate and the macrostructure by depositing the precursor absorbent particles on the substrate, treating the deposited particles with a solution comprising a crosslinker, and then curing the treated particles / substrate as described above. In a preferred embodiment of the method, cellulosic substrates such as paper towels are used. The precursor absorbent particles are then deposited on this cellulosic substrate. A treatment solution comprising an amino-epichlorohydrin adduct, preferably a polymerizable epichlorohydrin-polyamide / polyamine wet stiff resin, for example chimene, is applied on the cellulosic substrate and the absorbent (eg spraying ). The treated substrate / particles were then cured at ambient temperature such that the porous macrostructures were formed by bonding to the cellulosic substrate.

G. Method of treating large structures using latex to improve flexibility

Optionally, the absorbent macrostructure (with or without optional substrate) can be treated with a specific latex. 'Latex' refers to an aqueous dispersion or emulsion of polymer particles in an aqueous phase and may also be referred to as an emulsion polymer. 'Sinter' refers to a fusion mechanism that occurs upon drying of a suspended liquid emulsion or dispersion, such as latex; 'Sinter' is synonymous with 'film forming'. The treatment of macrostructures with these latexes has been found to significantly increase the flexibility of macrostructures, especially macrostructures in the form of sheets or even attached to substrates such as paper towels. In addition to improved flexibility, the latex treatment according to the present invention improves the binding between the particles of aggregates comprising these macrostructures. This improves the drying and wetting integrity of the macrostructures. The presence of the latex also allows these macrostructures to thermally bond to the backsheet of nonwovens, such as absorbent articles (eg diapers).

It has been found that suitable latexes for use in the present invention need to have certain properties. One major property of these latexes is that they are 'rubber' below ambient temperature after they are sintered. In other words, latex useful in the present invention has a glass transition temperature (Tg) of about 25 ° C. or less. Preferably these latexes have a Tg of about 10 ° C. or less, more preferably about −10 ° C. or less. Another important property of these latexes is the temperature at which they can be sintered. Latex useful in the present invention needs to be sintered below ambient temperature. In other words, it is desirable that these latexes be sintered at a temperature of about 25 ° C. or less. The ability of the latex to sinter at ambient temperature is important to prevent the macrostructures from drying out. Another important property of these latexes is their hydrophilicity. For use in the present invention, the latex should be at least slightly hydrophilic when sintered. 'Hydrophilic' means that the substance or surface of the substance may be wetted by an aqueous fluid (e.g. aqueous body fluid) deposited on these substances. Hydrophilicity and wettability are typically defined in terms of the contact angle and surface tension of the fluids and solids that are typically included. This is described in the American Chemical Society publication, Robert F., entitled 'Contact angle, wettability and adhesion'. Edited by Gold, 1964.

Latexes useful in the present invention are typically prepared by emulsion polymerization of certain olefin (ethylenically unsaturated) monomers. This emulsion polymerization can be carried out by conventional methods of stabilizing the resulting latex with any of various anions, nonions, cations, zwitterions and / or amphoteric emulsifiers, wherein the emulsifiers are alkyl sulfates, alkylaryls Alkali metal and / or ammonium salts of alkoxy sulfates, alkylarylsulfonates, and alkyl- and alkaliaryl-polyglycol ether sulfates; Block copolymers of oxyethylated fatty alcohols or oxyethylated alkylphenols and ethylene oxide and propylene oxide; Cationic adducts of primary, secondary or tertiary fatty acid amines or fatty acid amine oxyethylates with organic or inorganic acids and quaternary alkyl ammonium surfactants; And alkylamidopropylbetaines. The olefin monomer may be a single type of monomer or a mixture of different olefin monomers, ie form copolymer particles dispersed or emulsified in the aqueous phase. Latexes suitable for use herein are preferably neutral or free of ionic charge, ie latexes are not cationic or anionic in nature.

Suitable latexes are C ₂ to C, selected from the group consisting of propyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, ethyl acrylate and mixtures thereof. It can be prepared through an emulsion polymerization reaction from an olefinic monomer including C ₄ alkyl and hydroxy alkyl acrylate. Suitable monomers also include propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, ethyl methacrylate, methyl methacrylate, C ₁ to C ₄ alkyl or hydroxy alkyl methacrylates selected from the group consisting of vinyl acetate and mixtures thereof. Suitable monomers also include C ₂ to C ₄ alkyl and hydroxy alkyl acrylates described above; And mixtures of C ₁ to C ₄ alkyl or hydroxy alkyl methacrylates. Particularly suitable monomers for use in the present invention are emulsions of polymethyl methacrylate. More preferred latexes include those commercially available as MONWINYL 963 (Hust Celanese) and RHOPLEX E 1845 (Rohm & Haas).

When producing the porous absorbent macrostructures of the present invention with improved flexibility, the macrostructures are treated with an effective amount of these latexes to coat at least a portion of the absorbent particles. The 'effective amount' will depend on various factors (the specific porous absorbent macrostructure included, the specific latex used, the desired flexibility benefits, and other factors). More preferably, treating the macrostructure with about 2% by weight of latex will be sufficient for the macrostructure to have significantly improved flexibility. However, the macrostructures can be effectively treated with about 1 to about 10 weight percent, more preferably about 2 to about 5 weight percent latex.

Porous absorbent macrostructures can be treated with latex by any of a variety of methods suitable for applying additives to conventional substrates. Suitable methods are spraying, printing (e.g., flexographic printing), coating (e.g., gravure coating), dipping, brushing, foaming or these application techniques. It includes a combination of. Typically, the latex is sprayed onto a preformed porous absorbent macrostructure and then sintered at ambient temperature (eg, about 25 ° C. or less). In addition, latex treatment may be required to provide improved particle immobilization to form more stable macrostructures.

In addition to spraying latex on preformed macrostructures, other methods may also be used when treating porous absorbent macrostructures with latex. One of these methods involves mixing the latex with the untreated precursor absorbent particles and then treating the latex / particle mixture with a solution containing a crosslinker and any other optional ingredients (eg glycerol). do. The treated latex / particle mixture is then cured at ambient temperature (eg, up to about 25 ° C.) to produce a porous absorbent macrostructure with improved flexibility.

Another method involves casting latex as a thin film. Precursor absorbent particles may then be deposited on the cast film. The cast film with deposited particles is then treated (by spraying) with a solution comprising a crosslinker and any other optional components. The treated particles / latex films are cured at ambient temperature (up to about 25 ° C.) to produce porous absorbent macrostructures with improved flexibility. In addition, the sintered latex film can serve as a support substrate for the macrostructures to provide dryness and especially wet integrity.

However, another method includes pressurizing the latex in the container to blow or spray the precursor particles in the form of foam, and then uniformly spread the latex with a compression roll or the like. Blown or sprayed foam latexes are, to some extent, in the form of porous fibers that are highly porous to further improve the absorbency of the macrostructure. Latex treated macrostructures of this type (the precursor particles in the macrostructures swell into porous latex fibers) have improved structural integrity.

III. Use of large structures

Porous absorbent macrostructures of the present invention can be used for a variety of purposes in many applications. For example, macrostructures can be used in packaging containers, drug delivery equipment, wound disinfection equipment, image processing equipment, ion exchange column materials, building materials, agricultural or floral materials (such as seed sheets or water-retaining materials) and industrial uses ( For example, sludge or oil dehydrating agents, anti- dew forming substances, desiccants and humidity control substances).

Due to the unique absorbency of the porous absorbent macrostructures of the present invention, the macrostructures are suitable for use as absorbent cores in absorbent articles, in particular disposable absorbent articles. 'Absorbent product' refers to a product that absorbs and retains body secretions, and more particularly, refers to a product that is located towards or close to the wearer's body to absorb and retain various secretions released by the wearer's body. In addition, a 'disposable' absorbent product is intended to be discarded after one use (ie, certain substances or all substances in the absorbent product may be recycled, reused or composted, but the original absorbent product is generally washed or otherwise absorbed). Product is not recovered or reused). A preferred embodiment of the diaper 20, which is a disposable absorbent product, is shown in FIG. A 'diaper' generally refers to a garment worn by the infant and incontinence around the lower body. However, it should be noted that the present invention is also applicable to other absorbent articles (incontinence briefs, incontinence pads, training panties, diaper inserts, sanitary napkins, cosmetic tissues, paper towels, etc.).

3 is a perspective view of the unfolded state (ie, all elastically induced shrinkage of the diaper 20) of the present invention, a portion of the cut out structure to more clearly show the structure of the diaper 20; A portion of the diaper 20 in contact with the wearer is shown towards the viewer. The diaper 20 shown in FIG. 3 is preferably a liquid permeable top sheet 38, a liquid impermeable backsheet 40 connected to the top sheet 38, between the top sheet 38 and the backsheet 40. And an absorbent core 42, an elastic member 44, and a tape tab fastener 46. The top sheet 38, the back sheet 40, the absorbent core 42 and the elastic member 44 can be assembled in a variety of well known arrangements, but the preferred diaper placement structure is generally Buell dated January 14, 1975. US Pat. No. 3,860,003 to Buell. Alternatively, the preferred construction of disposable diapers herein is also described in U.S. Patent No. 4,808,178 to Aziz et al. On Feb. 28, 1989, and US Pat. 4,695,278 and US Pat. No. 4,816,025 to Foreman on March 28, 1989.

3 shows a preferred embodiment of a diaper 20 in which the top sheet 38 and the back sheet 40 extend together and generally have a length and width size that is larger than the absorbent core 42. The top sheet 38 is connected to the back sheet 40 and is superimposed on the back sheet 40 to form the periphery of the diaper 20. The perimeter defines the outer perimeter or edge of the diaper 20. The perimeter includes a distal edge 32 and a longitudinal edge 30.

The top sheet 38 is flexible, soft to the touch, and non-irritating to the wearer's skin. In addition, the topsheet 38 is liquid permeable such that fluid can easily permeate through the thickness of the topsheet. Suitable topsheets 38 are synthetic with porous foams, reticulated foams, perforated plastic films, natural fibers (eg wood fibers or cotton fibers), synthetic fibers (eg polyester or polypropylene fibers) or natural fibers. It can be made from a variety of materials such as combinations of fibers. Preferably, the topsheet 38 is made of a hydrophobic material to isolate the wearer's skin and liquid at the absorbent core 42.

Particularly preferred topsheet 38 is approximately 1.5 denier, such as Hercules type 151 polypropylene available from Hercules, Inc., Wilmington, Delaware. Polypropylene fibers having standard length. 'Standard length fiber' refers to a fiber having a length of at least about 15.9 mm (0.62 inches).

There are many fabrication techniques that can be used to make the topsheet 38. For example, topsheet 38 may be woven, nonwoven, spun bond, carded or otherwise. Preferred topsheets are carded and thermally bonded by means well known to those skilled in the art. Preferably, topsheet 38 has a weight of about 18 to about 25 g per m ² , a minimum dry tensile strength of at least about 400 g per cm in the machine direction and a wet tensile strength of at least about 55 g per cm in the transverse machine direction.

The backsheet 40 is impermeable to liquid and is preferably made from a thin plastic film, although other flexible liquid impermeable materials may also be used. The backsheet 40 prevents the secretions absorbed and retained by the absorbent core 42 from coming into contact with the diaper 20 such as bed sheets and undergarments. Preferably, backsheet 40 is a polyethylene film having a thickness of about 0.012 mm (0.5 mil) to about 0.051 cm (2.0 mils), although other flexible liquid impermeable materials may be used. 'Flexible material' refers to a material that is flexible and can easily fit into the general shape and contour of the wearer's body.

Suitable polyethylene films are manufactured by Monsanto Chemical Corporation and are under the trade name Film No. It is marketed as 8020. The backsheet 40 is preferably embossed and / or matte finished to provide a more cloth-like appearance. In addition, vapor in the backsheet 40 can escape from the absorbent core 42, but secretions cannot flow out through the backsheet 40.

The size of the backsheet 40 is determined by the size of the selected absorbent core 42 and the exact diaper design. In a preferred embodiment, the backsheet 40 has a modified hourglass shape that extends larger than the absorbent core 42, with a minimum distance of at least about 1.3 cm to about 2.5 cm around the entire diaper perimeter.

The top sheet 38 and the back sheet 40 are connected in any suitable manner. The term " connected " refers to a structure that directly connects the top sheet 38 and the back sheet 40 by attaching the top sheet 38 to the back sheet 40, and the top sheet 38 to the intermediate member. It is fixed to the rear sheet 40 in turn and includes an arrangement structure indirectly connecting the upper sheet 38 and the rear sheet 40. In a preferred embodiment, the topsheet 38 and backsheet 40 are secured directly to each other at the periphery of the diaper by attachment means such as adhesive (not shown) or any other attachment means known in the art. For example, a uniform continuous layer of adhesive, a patterned layer of adhesive, or an arrangement of discrete lines or dots of adhesive may be used to secure the top sheet 38 to the backsheet 40.

Tape tab fasteners 46 are typically applied to the back waistband portion of the diaper 20 to provide fastening means for securing the diaper to the wearer. Tape tab fastener 46 may be any of those well known in the art, such as the fastening tape disclosed in US Pat. No. 3,848,594, issued November 19, 1974 to Buell. Such tape tab fasteners 46 or other diaper fastening means typically apply near the corner of the diaper 20.

The elastic member 44 is placed adjacent to the periphery of the diaper 20, preferably along each longitudinal edge 30, such that the elastic member 44 pulls and fastens the diaper 20 around the wearer's leg. Let it be Alternatively, the elastic member 44 may be placed adjacent to one or both distal edges 32 of the diaper 20 to provide a waist band with or rather than a leg cuff. For example, suitable waist bands are disclosed in US Pat. No. 4,515,595, issued to Kievit et al. On May 7, 1985. Also, a method and apparatus suitable for making disposable diapers having elastically shrinkable elastic members is described in US Pat. No. 4,081,301, issued March 28, 1978 to Buell.

The elastic member 44 is secured to the diaper 20 in an elastically retractable state, thereby effectively contracting or gathering the diaper 20 in a generally unrestricted arrangement. The elastic member 44 can be secured in an elastically retractable state in at least two ways. For example, while the diaper 20 is in the unfolded state, the elastic member 44 can be stretched and fixed. Alternatively, while the diaper 20 is in a contracted state, for example, by forming a pleat, the elastic member 44 is present in the unrolled or unstretched state to be fixed and connected.

In the embodiment shown in FIG. 3, the elastic member 44 extends along a portion of the diaper 20 length. Alternatively, the elastic member 44 may extend to the full length of the diaper 20 or any other length suitable for providing an elastically shrinking line. The length of the elastic member 44 is determined by the diaper design.

The elastic member 44 may be of various arrangement structures. For example, the width of the elastic member 44 can vary from about 0.25 mm (0.01 inch) to about 25 mm (1.0 inch) or more. Elastic member 44 may comprise a single strand of elastic material and may also include several parallel or non-parallel strands of elastic material. Alternatively, the elastic member 44 may be rectangular or curved. In addition, the elastic member 44 may be secured to the diaper in any of several ways known in the art. For example, the elastic member 44 may be ultrasonically coupled to the diaper 20 using various bonding patterns, sealed with heat and pressure, or the elastic member 44 may simply be attached to the diaper 20.

The absorbent core 42 of the diaper 20 is located between the top sheet 38 and the back sheet 40. Absorbent core 42 can be made from a variety of materials in a variety of sizes and shapes (eg, rectangular, hourglass, asymmetric, etc.). However, the total absorbent capacity of the absorbent core 42 must be compatible with designs that accept liquid loading, depending on the intended use of the absorbent article or diaper. In addition, the size and absorbent capacity of the absorbent core 42 may vary to suit the wearer, from infant to adult. The absorbent core 42 comprises the porous absorbent macrostructure of the present invention.

A preferred embodiment of the diaper 20 has a rectangular absorbent core 42. As shown in FIG. 4, the absorbent core 42 preferably consists of an absorbent member 48 comprising a wrapping web 50 and a porous absorbent macrostructure 52 contained within the wrapping web 50. The macrostructure 52 is wrapped in the packaging web 50 to minimize the likelihood of precursor particles traveling through the topsheet and provide an additional liquid moving layer between the topsheet 38 and the macrostructure 52 to capture liquid. Improve and minimize wet again. As shown in FIG. 4, a single wrapping web 50 is folded to surround the macrostructure 52 to form the first layer 54 and the second layer 56. The edge 58 of the packaging web 50 is sealed around the periphery of the edge by any conventional means such as adhesive 59 (shown), ultrasonic bonding or heat / pressure bonding to form a pouch. The packaging web 50 may include many materials, including nonwoven webs, paper webs, or webs of absorbent material (eg, tissue paper). The wrapping web 50 preferably comprises a nonwoven web similar to the web used to form the topsheet 38. The nonwoven web is preferably hydrophilic to allow fluid to pass quickly through the packaging web 50. A similar layered absorbent member (laminate) is described in more detail in US Pat. No. 4,578,068 to Kramer et al. On March 25, 1986.

Alternatively, the absorbent core 42 of the present invention may consist solely of one or more (multiple) of the porous absorbent macrostructures of the invention, or may comprise a combination of layers comprising the macrostructures of the invention, or of the invention It can include any other absorbent core placement structure that includes one or more macrostructures.

5 includes a modified hourglass-like absorbing member 60 and a sheet 62 of porous absorbent macrostructure adjacent to absorbent member 60 (ie, between absorbent member 60 and backsheet 40). Another aspect of a diaper including a bilayer absorbent core 142 is shown.

The absorbent member 60 quickly collects and temporarily retains the secreted liquid and moves this liquid from the initial contact point to the other portion of the absorbent member 60 and the macrostructure sheet 62 by suction. Absorbent member 60 preferably comprises a batt of web or fibrous material. Various types of fibrous materials as disclosed herein can be used for the absorbent member 60. Cellulose fibers are generally preferred for use herein and wood pulp fibers are particularly preferred. Absorbent member 60 may also contain a specific amount of particulate absorbent polymeric composition. Absorbent member 60 may contain, for example, less than about 50% by weight polymeric composition. In a more preferred embodiment, the absorbent member 60 contains 0 to about 8 weight percent of the particulate, absorbent polymeric composition. In another preferred embodiment, the absorbent member 60 comprises chemically reinforced cellulosic fibers as previously disclosed herein. Exemplary embodiments of the absorbent member 60 used in the present invention include US Pat. No. 4,673,402, issued to Weisman et al. On June 16, 1987; And US Pat. No. 4,834,735, issued May 30, 1989 to Alemani et al. For use herein, an absorbent member having a storage zone and a capture zone having a lower average density per unit area and a lower average basis weight than the storage zone to capture the secreted liquid effectively and efficiently quickly. Particularly preferred.

Absorbent member 60 may be of any desired shape, for example rectangular, oval, rectangular, asymmetrical or hourglass shaped. The shape of the absorbent member 60 may define the general shape of the resulting diaper 120. In a preferred embodiment as shown in FIG. 5, the absorbent member 60 is an hourglass.

The macrostructure sheet 62 of the present invention need not be the same size as the absorbent member 60 and may actually have an upper surface that is substantially larger or smaller than the upper surface area of the absorbent member 60. As shown in FIG. 5, the macrostructure sheet 62 is smaller than the absorbent member 60 and has an upper surface area of about 0.10 to about 1.0 times that of the absorbent member 60. More preferably, the upper surface area of the macrostructure sheet 62 will be about 0.10 to about 0.75 times, more preferably about 0.10 to about 0.5 times the absorbent member 60. In other embodiments, the absorbent member 60 is smaller than the macrostructure sheet 62 and has an upper surface area of about 0.25 to about 1.0 times, more preferably about 0.3 to about 0.95 times the macrostructure sheet 62. In another embodiment, the absorbent member 60 preferably comprises chemically reinforced cellulosic fibers as previously disclosed.

The macrostructure sheet 62 is preferably located in a specific position relative to the backsheet 40 and / or absorbent member 60 in the diaper. More specifically, the macrostructure sheet 62 is generally located in front of the diaper so that the macrostructure sheet 62 is more effective in capturing and retaining the dispensed liquid.

In another preferred embodiment, a plurality of macrostructures, preferably 2-6 macroscopic strips or sheets, may be replaced with a single macrostructure sheet 62 shown in FIG. In addition, additional absorbent layers, members or structures may be located in the absorbent core 142. For example, an additional absorbent member may be positioned between the macrostructure sheet 62 and the backsheet 40 to allow liquid to pass through the macrostructure sheet 62 to form another portion of the absorbent core 142 or the macrostructure sheet 62. Retention capacity may be provided for the absorbent core 142 and / or layers that dispense in portions. The macrostructure sheet 62 may alternatively be located on the absorbent member 60 to be positioned between the topsheet 38 and the absorbent member 60.

6 includes another bilayer absorbent core 242 that includes a rectangular absorbent member 260 and three long parallel spaced macroscopic strips 262 positioned between the absorbent member 260 and the backsheet 40. Another embodiment of the diaper 220 is shown.

The absorbent member 260 acts to quickly collect and temporarily retain the secreted liquid and to move such liquid to the other parts of the absorbent member 260 and to the macrostructure strip 262 at the initial contact point. This absorbent member 260 preferably comprises a web or batt of fibrous material, and more preferably comprises chemically reinforced cellulosic fibers as previously disclosed herein. The macrostructure strip 262 serves to capture and retain the liquid secreted together. By spacing the macroscopic strips 262 relative to each other, a more effective surface area is provided to capture and retain the secreted liquid. This is especially true because the spaced macrostructure strips 262 can swell and expand in the width direction without disturbing the ability of adjacent strips to capture the dispensed liquid.

In use, the diaper is applied to the wearer by positioning the rear waistband area under the wearer's back and pulling the rest of the diaper 20 between the wearer's legs to position the front waistband area across the wearer's front. The tape-tab fasteners 46 are then secured preferably to the outward area of the diaper 20. In use, disposable diapers or other absorbent articles incorporating the porous absorbent macrostructures of the present invention distribute and store liquids more quickly and effectively, and remain dry due to the high absorbent capacity of the macrostructures. Disposable diapers incorporating the macrostructures of the invention may also be thinner and more flexible.

Absorbent macrostructures of the present invention may also be used in absorbent articles as disclosed in US Pat. No. 08 / 621,030, filed March 22, 1996. Specifically, the absorbent article includes a fluid permeable topsheet, a backsheet and an absorbent core positioned between the topsheet and the backsheet. The absorbent core includes one or more upper fluid storage components that can expand in the z-direction to form a fluid capture zone when in contact with the aqueous body fluid, wherein the upper fluid storage component is in direct fluid communication with the topsheet and the upper fluid The storage component also includes the absorbent macrostructures of the present invention. The absorbent core also includes a fluid capture zone capable of receiving aqueous body fluid, wherein the fluid capture zone is at least partially surrounded by an upper fluid storage component and at least partially located below the fluid secretion region of the absorbent core. The absorbent core also includes a fluid capture / distribution component capable of capturing and moving aqueous body fluid, at least a portion of which is located in fluid communication with and in fluid communication with the lower fluid storage element, At least a portion of the dispensing component is located below the fluid capture zone.

IV. Absorbent product performance

For absorbent articles comprising the absorbent macrostructures of the present invention, the inventors note that the inverse relationship between the fluid loading level (g or ml of fluid) and the fluid capture rate (ml / sec) was generally accepted as reference for the absorbent article. Found the ability to overcome. Thus, in one aspect the present invention is directed to absorbent articles that are relatively thin and exhibit the ability to maintain fluid capture rates for each of two successive fluid loads. In another aspect, the present invention is directed to an absorbent article that exhibits the ability to increase fluid capture rate for each of two consecutive fluid loadings. Preferably, the product will exhibit a maintained or increased fluid capture rate for each of three consecutive fluid loads, more preferably each of four consecutive fluid loads.

The ability of an absorbent product to meet this criterion is measured as described in more detail in the Test Methods section, which uses the following capture test. Briefly, the fluid capture rate for a given absorbent product is determined for each of four consecutive loadings of 50 ml per load, each loading moving the synthetic urine at a constant rate of about 10 ml / sec, with 5 between each loading. The equilibrium period of minutes is given. Products of the invention exhibit fluid retention rates that are maintained or increased as the number of loads increases.

For those products exhibiting fluid capture rates maintained, these products (including topsheet, backsheet and absorbent core but excluding tape, leg cuff or other optional components) should be about 0.5 inches or less in dry state, preferably Preferably about 0.25 inches or less, more preferably about 0.2 inches or less. The thickness of the product is measured without applying pressure. In the case of absorbent articles of the present invention, which are not required, but exhibit increased fluid capture rates for two, three or more than four consecutive loads, it is preferred that these absorbent articles also meet the above thickness conditions.

Preferred absorbent articles, including those maintained or increased capture rates for continuous fluid loading, capture fluid at a rate of at least about 2 ml / sec and more preferably at least about 5 ml / sec for the first 50 ml loading. While this is not a criterion that these products must meet, meeting these criteria can produce products that are more useful for the intended purpose.

V. Test Method

A. Absorption Capacity

The absorbent capacity of the absorbent product is measured according to the absorbent capacity test described in columns 27-28 of US Pat. No. 5,124,188 to June et al., June 23, 1992. In this test, the absorbent particles are placed in 'tea bags' and immersed in excess synthetic urine for a certain period of time and then centrifuged for a certain time. The final weight of absorbent particles after centrifugation—initial weight (net fluid gain) to initial weight determines the absorbent capacity.

B. Brine Flow Conductivity (SFC)

The brine flow conductivity (SFC) of the precursor absorbent particles is measured according to the test method described in co-pending US patent application No. 219,574 (Goldman et al.) Filed March 29, 1994. In this test, a gel layer is formed from absorbent particles that swell in Jayco synthetic urine under defined pressure. This test evaluates the ability of a hydrogel layer formed from these absorbent particles to capture and distribute body fluids when particles are present at high concentrations and exposed to the use mechanical pressure. Darcy's law and steady flow method are used to determine the brine flow conductivity. (See, eg, PK Chatterjee, 'Absorbency', Elsevier, 1985, page 42-43) and 'Chemical Engineering vol. II, 3rd edition, JM Coulson and JF Richardson, Pergamon Press, 1978, pages 125-127.) The test fluid for the SFC test is JJ synthetic urine.

C. Pressurized Performance (PUP)

The performance under pressure (PUP) of the precursor absorbent particles is measured according to the test method described in co-pending US patent application Ser. No. 219,574 (Goldman et al.) Filed March 29, 1994. This test determines 60 minutes g / g absorption of synthetic urine for the laterally defined absorbent material in the piston / cylinder assembly under a defined pressure of 0.7 psi (about 5 kPa). This test evaluates the ability of the absorbent particle layer to absorb body fluids over a practical period of time when the particles are present at high basis weights and high concentrations and exposed to working pressure. These working pressures are generated from the mechanical pressure generated from the wearer's weight and / or movement, the mechanical pressure generated by the elastic and anchoring system, and from adjacent capillary (eg fiber) layers and / or structures when draining the fluid. Hydrostatic suction. The test fluid for the PUP capability test is JEI Synthetic urine. This fluid is absorbed by the absorbent particles under the required absorption conditions at almost zero hydrostatic suction.

D. Required Absorption Capacity

The required absorbent capacity of the absorbent macrostructure is 60 minutes g of synthetic urine for absorbent structures under pressure of 1.4 psi (about 10 kPa) at the beginning of the test (dry state) and 0.7 psi (about 5 kPa) at the end of the test (wet, swelling) / g is designed to measure absorption. This test measures the ability of an absorbent structure to absorb body fluids for a substantial period of time when the absorbent structure is present at high basis weights and high concentrations and exposed to operating pressure. These working pressures are generated from the mechanical pressure generated from the wearer's weight and / or movement, the mechanical pressure generated by the elastic and fastening system, and from adjacent capillary (eg fiber) layers and / or structures when draining the fluid. Fluid hydrodynamic suction. The test fluid for the required absorption capacity test is J. ikouriña. This fluid is absorbed by the absorbent structure under the required absorption conditions.

The following describes the required absorption capacity measurements. The sample cell is a square piston / cylinder assembly and has a mesh bottom of 10 cm x 10 cm dimensions. Absorbent structures (with and without fibers) were sampled in dimensions of 3.7 cm x 3.7 cm and placed under a 1.4 psi piston. Upon contact with the sample of synthetic urine, the sample begins to absorb the synthetic urine. Changes in weight are continuously monitored and recorded for the next 60 minutes. As a result, the dimensions of the sample increase about 100% when placed under constant 1.4 psi external pressure.

E. Take Test

This test is for absorbing urine in diapers under the following conditions:

1) A pressure of 0.4 psi (about 28 g / cm ² ) is applied to the diaper sample.

2) A total of two or more batches of synthetic urine are applied to the diaper sample at a rate of 10 ml / sec with 5 minutes (equilibration time) at each load.

Use the following device:

Conditioning Room: Temperature and relative humidity adjusted to 73 ± 2 ° F and 50 ± 2%.

Capture Tester: Concord-Renn Co., 6315 Cincinnati Warwick Street, Ohio, USA.

part

Test bed (PLEXIGLAS)

Foam Base-6 '' × 20 '' × 1 '' foam covered with polyethylene backsheet material-Foam Type: Density 1.0lb / ft ³

IDL 24psi

Nozzle

Cover plate

Graduated cylinder (100ml) (1,000ml): VWR Scientific, (100ml) Catalog number: 24711-310 (1,000ml) Catalog number: 24711-364 or equivalent.

Erlenmeyer flasks: VWR Scientific Catalog No .: 29135-307 or (6,000 ml) equivalent.

Digital pumps: Cole-Parmer Instrument Co .; Phone number (800) 323-4340, USA, catalog number: G-075323-20.

Easy Load Pump Head: Call-Parmer Instrument Company Catalog Number: G-07518-02

Distilled Water: A Convenient Source

Anhydrous Synthetic Urine: Jacob's Synthetic Urine

V. Specific examples of the preparation of macrostructures according to the invention

The following examples further illustrate and demonstrate preferred embodiments within the scope of the present invention. The following examples are intended to be illustrative only and should not be construed as limiting the invention as they may be varied without departing from the spirit and scope of the invention.

Example 1

This example shows a method for producing an absorbent macrostructure according to the present invention.

The absorbent macrostructure is prepared on a shuttle table by first spreading superabsorbent polymer fine particles on a cellulose web and then spraying an aqueous solution containing chimen. The shuttle table is designed to move back and forth to continuously lay superabsorbent polymer particulates and has a speed of 3 m / min to 30 m / min. The shuttle table is equipped with a fixed automatic powder supply system for supplying superabsorbent polymer particulates at a rate of 100 to 1000 g / min, and a fixed automatic solution dispensing system with a spray rate of 40 to 200 g / min. Typical operating conditions include a shuttle speed of 10 m / min, a superabsorbent polymer particulate feed rate of 212 g / min, and a solution spray rate of 76 g / min.

Two different superabsorbent polymer particulates are used in this example. These are both crosslinked sodium polyacrylates. The first superabsorbent polymer is available from Nippon Shokubai under the trade name AQUALIC CA-L76 and has a high PUP and medium gel volume. Secondary crosslinked sodium polyacrylate is IM-1000, commercially available from Sanyo Chemical Industry, and has a low PUP and high gel volume. Cellulosic webs are tissue towels available under the trade name Bounty, with a basis weight of 20 g / m ² . Kimmen is marketed by Hercules Company under the trade name KYMENE-PLUS and contains 30% polymer resin. Blend two or more superabsorbent polymer particulates with a food blender. The spray solution contains 10% by weight of the chimen polymer resin, 45% glycerol and 45% water. A polyethylacrylate-based latex polymer commercially available from Hoechst Gosei Co. under the trade name MOWINYL-963 is further added to the solution in an amount of 10%. The addition increases the flexibility and flexibility of the macrostructures due to the presence of polyethylacrylate-based latex polymers.

The resulting macrostructure contains 77% superabsorbent polymer, 19% solution and 4% cellulosic tissue towels. The total basis weight of the macrostructure is 480 g / m ² , comprising 370 g of superabsorbent polymer, 90 g of sprayed solution and 20 g of bounty towel. The weight ratio of the two superabsorbent polymers is 0-100%.

Example 2

This example shows a method for producing the absorbent macrostructure of the present invention.

Absorbent macrostructures were prepared according to the procedure described in Example 1, except that the structure was prepared by attaching an aqualic CA-L76 superabsorbent polymer to one side of the tissue web and an IM-1000 superabsorbent polymer to the other side. Manufacture.

The resulting macrostructure contains 77% superabsorbent polymer, 19% solution and 4% cellulosic tissue towels. The total basis weight of the macrostructure is 480 g / m ² , comprising 370 g of superabsorbent polymer, 90 g of sprayed solution and 20 g of bounty towel. The weight ratio of the two superabsorbent polymers is 0-100%.

Example 3

This example shows a method of making a baby diaper containing the absorbent macrostructure of the present invention.

The absorbent macrostructure of Example 1 was sampled to the diaper core size and a fluid impermeable backsheet film, a wood fiber capture layer, and a nonwoven topsheet were applied to form a baby diaper.

The resulting diaper has a very low caliper because the concentration of superabsorbent polymer is as high as 70% by weight compared to a typical baby diaper core containing about 40% superabsorbent polymer.

Example 5

This embodiment shows a method of manufacturing a diaper comprising the superabsorbent macrostructure of the present invention.

A superabsorbent macrostructure is prepared according to the method of Example 1 except that the concentration of the superabsorbent polymer is increased to 90% by increasing the basis weight of the superabsorbent polymer to at least 1550 g / m ² . The macrostructure is then slit and stretched to form a net-shaped core. The baby diaper is then made by applying a fluid impermeable backsheet film, a wood fiber capture layer, and a nonwoven topsheet to the core. Diapers have very low calipers compared to conventional baby diapers due to the high concentration of superabsorbent polymer in the core.

Example 6

This example shows that the use of cationic amino-epichlorohydrin adducts such as chimen in the absorbent macrostructure of the present invention improves the required absorbent capacity of the macrostructure.

Figure 7 compares the three different samples with the required absorbent capacity of the absorbent macrostructures of the present invention. Specifically, the curve '…' ○… 'Exemplifies the surprising effect of Kymen's significantly increasing the required absorption capacity under pressure over the full range of mixing ratios of the two different superabsorbent polymers. Compare this to a similar structure made without chimen (curve '… ◇…'), in which the 0.7 psi required absorption capacity is increased only when increasing the weight percent of high PUP superabsorbent particulate (L-76). . curve '… ◇… 'Is also the curve' ... results of the test of mixed superabsorbent particulate layers without the use of chimen or adhesive additives. Δ. Same as' Another example of making an absorbent structure without using chimen is to first sandwich a superabsorbent polymer particulate layer between two layers of tissue and stick the tissue to form a laminate composite. This laminate structure (curves '… □…') does not exhibit an exceptional relationship (as seen in curve '… ○…') between the required absorption capacity under pressure and the mixing ratio of the superabsorbent polymer.

All publications, patent applications, and issued patents mentioned above are incorporated herein by reference.

The examples and embodiments described herein are for illustrative purposes only, and one of ordinary skill in the art will be able to suggest various changes or modifications based on the present disclosure, and such changes and modifications may be applied to the principles and scope of the present application and the appended patents. It should be understood that it is included in the scope of the claims.

Claims (10)

(a) Performance under Pressure (PUP) capacity of at least 23 g / g under a Saline Flow Conductivity (SFC) value of at least 5 × 10 ⁻⁷ cm ³ sec / g and a defined pressure of 0.7 psi (5 kPa). A mixture of 50-95% of a first hydrogel-forming polymer having a value of) and 5-50% of a second hydrogel-forming polymer having an Absorptive Capacity value of at least 25 g / g, (b) a mixture of 20-40% of the first hydrogel-forming polymer in the form of spherical particles and 60-80% of the second hydrogel-forming polymer in the form of non-spherical particles, and (c) a mixture of (a) and (b) Inter-particle bound aggregates comprising a plurality of interconnected crosslinked particles comprising a substantially water-insoluble and absorbent hydrogel-forming polymeric material comprising a mixture selected from the group consisting of: Agglomerated aggregates between particles have pores between adjacent particles, which are interconnected by interconnecting channels to form a liquid permeable macrostructure, whose circumscribed dry volume is greater than 0.008 mm ³ . large, Porous, absorbent macrostructures with improved fluid handling capabilities. The method of claim 1, A porous, absorbent macrostructure, wherein the hydrogel-forming polymeric material comprises a mixture of 20-40% of a first hydrogel-forming polymer in the form of spherical particles and 60-80% of a second hydrogel-forming polymer in the form of non-spherical particles. The method of claim 1, A hydrogel-forming polymer material has a saline flow conductivity (SFC) value of at least 5 × 10 ⁻⁷ cm ³ sec / g and a PUP value of at least 23 g / g under a defined pressure of 0.7 psi (5 kPa). A porous, absorbent macrostructure comprising a mixture of 50-95% of a hydrogel-forming polymer and 5-50% of a second hydrogel-forming polymer having an absorbent capacity value of at least 25 g / g. The method of claim 1, An absorbent macrostructure in which particles are crosslinked at their surface with a cationic amino-epichlorohydrin adduct. The method of claim 1, Absorbent macrostructure further comprising a plasticizer. The method of claim 1, An absorbent macrostructure further comprising a latex material. Liquid permeable topsheets; A liquid impermeable backsheet connected to the topsheet; And an absorbent core positioned between the topsheet and the backsheet and comprising at least one macrostructure according to claim 1. The method of claim 7, wherein An absorbent article further comprising an absorbent member, wherein the absorbent core is positioned between the topsheet and the macrostructure, wherein the absorbent core comprises chemically strengthened cellulose fibers. The method of claim 7, wherein Absorbent product that is a diaper. (a) First hydrogel-forming having a brine flow conductivity (SFC) value of at least 5 × 10 ⁻⁷ cm ³ sec / g and a performance under pressure (PUP) of at least 23 g / g under a defined pressure of 0.7 psi (5 kPa) A mixture of 50-95% of the polymer and 5-50% of the second hydrogel-forming polymer having an absorption capacity value of at least 25 g / g, (b) a mixture of 20-40% of the first hydrogel-forming polymer in the form of spherical particles and 60-80% of the second hydrogel-forming polymer in the form of non-spherical particles, and (c) a mixture of (a) and (b) Inter-particle bound aggregates comprising a plurality of interconnected crosslinked particles comprising a substantially water-insoluble and absorbent hydrogel-forming polymeric material comprising a mixture selected from the group consisting of: The intergranular aggregated aggregates have pores between adjacent particles, the pores being interconnected by intercommunication channels to form a liquid permeable macrostructure, wherein the boundary dry volume of the macrostructure is greater than 0.008 mm ³ , Flexible, porous and absorbent sheet.