KR20000029883A - Absorbent macrostructure made from mixtures of different hydrogel-forming absorbent polymers for improved fluid handling capability - Google Patents

Abstract

PURPOSE: Porous, absorbent macrostructure including inter-particle bonded aggregates are provided which have improved fluid handling capability including inter-particle bonded aggregates, and are useful in absorbent articles such as diapers, adult incontinence pads and sanitary napkins, are provided. CONSTITUTION: The inter-particle bonded aggregates of these macrostructure (52) are made from mixtures of particulate absorbent polymers having different fluid handling properties, different shapes, or both. These macrostructure (52) can be made from a wider variety of hydrogel-forming absorbent polymers without sacrificing desired fluid handling properties, and without being prone 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. It is also packed tightly, making it easy 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 required 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, also referred to as "hydrogel", "super absorbent" or "hydrocolloid" materials. For example, US Pat. No. 3,699,103, issued to Harper et al. On June 13, 1972, and US Pat. No. 3,770,731, issued to Harmon on June 20, 1972, describe such absorbent polymers , "Hydrogel-forming absorbent polymers") for use in absorbent articles. Indeed, the development of thin diapers has been a direct result of thin 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 using such hydrogel-forming absorbent polymers, it was common to form absorbent structures, etc., suitable for use in baby diapers as a whole from wood pulp fluff. 1 g of wood pulp fluff absorbed by 1 g of wood pulp fluff The amount of fluid absorbed by the wood pulp fluff is relatively small, so 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) or ammonium salts of acrylic acid, 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 is an important factor in determining the water insolubility of the hydrogel-forming absorbent polymer as well as in two other properties: absorbency and gel strength. Absorptive power 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 absorbents 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 the capillary voids in the absorbent structure or product cannot be accommodated so as not to impair the 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 such hydrogel-forming absorbent polymers in relatively small amounts (eg, less than about 50% by weight). For example, see US Pat. No. 4,834,735, issued May 30, 1989 to Alemanny et al., Which preferably contains about 9 to about 50% hydrogel-forming absorbent polymer in a fibrous matrix. Can be. 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 the “spray” form. Thus, there is a need to act as a temporary reservoir holding secretions until they are absorbed by the hydrogel-forming absorbent polymer, including fibers, typically wood pulp fibers.

More importantly, many known hydrogel-forming absorbent polymers exhibit gel blocking properties, 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 member 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, eg, 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 large 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 a reverse emulsion polymerization or reverse suspension polymerization process. Examples include U.S. Pat. See US Pat. No. 4,735,987, issued to Morita et al. On 5 May. Since these spherical particles are prone to gel blocking, it was believed that the multiphase polymerization process was not very desirable for hydrogel-forming absorbent polymer synthesis. See US Patent No. 5,124, 188 to Roe et al. On June 23, 1992.

In order to improve capillary functionality to minimize gel blocking, hydrogel-forming absorbent polymer particles are typically formed into crosslinked aggregated macrostructures in the form of sheets or strips. These agglomerate macrostructures were prepared by initial mixing the hydrogel-forming absorbent polymer particles with a solution of nonionic crosslinkers such as glycerol, water and a hydrophilic organic solvent such as isopropanol. Examples include U.S. Patent No. 5,102,597 to Loh et al. On April 7, 1992, U.S. Patent No. 5,124,188 to Loh et al. On June 23, 1992, and Rahrman on Sep. 22, 1992. See US Pat. No. 5,149,344, which is incorporated herein by reference. In addition, Rezai (June 23, 1994) discloses an improved porous aggregate 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 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 speed, 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, absorbent agglomerate macrostructures of bound absorbent particles can be used (1) using hydrogel-forming absorbent polymers prepared by several methods, (2) less prone to gel blocking, and (3) have optimal permeability (4). ) To provide an improved combination of fluid handling capabilities.

Summary of the Invention

The present invention relates 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. The hydrogel-forming polymeric material has (a) a saline flow conductivity (SFC) of at least about 5 × 10 ⁻⁷ cm ³ sec / g and a performance under pressure (PUP) 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 a second hydrogel-forming polymer having an absorption capacity of at least about 25 g / g under 5 kPa), (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. Such porous absorbent macrostructures provide a particularly preferred combination of fluid permeability and fluid handling with relatively high fluid capacity. The macrostructures of the present invention may also be made from a wider variety of hydrogel-forming absorbent polymers without the tendency of gel blocking without sacrificing desirable fluid treatability. 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 comprising flexible aggregates bound between particles. In particular, the present invention relates to porous absorbent macrostructures in which interparticle-bound aggregates are prepared from a mixture of different particulate absorbent polymers, both in fluid treatability or in form, or both.

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

2 is a scanning electron micrograph of the macrostructure of the present invention. The structure is made by attaching an irregularly shaped superabsorbent polymer to one side of the fibrous web and a spherical polymer on the other side.

3 is a perspective view of a disposable diaper embodiment according to the present invention wherein the topsheet portion is cut apart to further illustrate the absorbent core of the diaper (an aspect of the absorbent member according to the present invention), and the absorbent member is the present invention. It includes a porous absorbent macrostructure according to.

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 in which the topsheet portion is cut apart to further illustrate the bilayer absorbent core embodiment.

Figure 6 shows the components of a diaper structure, in which the absorbent macrostructure is a component of a double layer absorbent core in the form of a plurality of strips.

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

Justice

"Human body fluid" includes urine, menstrual blood and vaginal discharge.

"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 as more restrictive terms in the art.

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 individual nature of the precursor particles, the macrostructures have voids between adjacent precursor particles. These voids are connected by communication conduits so that the macrostructures are liquid permeable (ie have capillary transport conduits).

Because of the bonds formed between the precursor particles, the resulting aggregate macrostructures have improved structural integrity, increased liquid trapping and partitioning rate, and minimal gel blocking properties. It has been found that when a macrostructure is in contact with a liquid, the macrostructure is generally isotropically swelled uniformly under suitable limiting pressure, and this liquid is absorbed into the pores between the precursor particles and then absorbs this liquid into the particles. Isotropic swelling of the macrostructure allows to maintain relative bonding structure and spatial correlation upon swelling 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 conduits upon swelling, thereby allowing the macrostructures to absorb liquid, even excess liquid loads. 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 or more, more preferably substantially only upon drying of about 500mm ³ or more volume (that is, dry volume defined) . Typically, the macrostructures of the present invention will have a defined dry volume of at least about 500 mm ³ . In a preferred embodiment of the invention, large structure has a limited drying volume of about 1,000mm ³ to about 100,000mm ^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 forming elements. The macrostructures will generally have a thickness or diameter of about 0.2 mm to about 10.0 mm. Preferably the macrostructures for use in the absorbent article are in the form of sheets. The term "sheet" means a macrostructure having a thickness of about 0.2 mm or more. The sheet will preferably have a thickness of about 0.5 mm to about 10 mm, typically about 1 mm 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 defined dry volume and size of the individual precursor particles as used herein, the aggregated aggregates between these particles are typically formed of at least about 100,000 individual precursor particles. These individual precursor particles may comprise granules, powders, spheres, flakes, fibers, aggregates or aggregates. Individual precursor particles may be in various forms such as cuboid, rod, polyhedron, spherical, circular, angular, irregular, irregularly sized irregularities (e.g., grinding products of the grinding or grinding stage) or needle, flake or It may have a shape with the largest dimension / smallest dimension to be fibrous.

Intergranular bound aggregates comprising the macrostructures of the present invention are essentially formed by bonding or adhering 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 crosslinking agent 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 join together as discrete bonding sites between the particles. Attached. The crosslinking reaction between the particles fixes this 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 that do not have the largest dimension / smallest dimension ratio, such as fibers (eg granules, flakes or powders) as the dimension of the precursor particles measured by sieve size analysis. For the purposes of the present invention, the mass mean particle diameter of the precursor particles is important for determining the properties and properties of the resulting macrostructures. The mass mean particle diameter of a given reagent of precursor particles is defined as the mean particle diameter of the reagent on the mass. Methods for determining the mass mean particle size of reagents are described in the field of test methods 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 from about 20 microns to about 1,500 microns, more preferably from about 50 microns to about 1,000 microns. In a preferred embodiment of the invention, the precursor particles have a mass mean particle size of less than about 1,000 microns, more preferably less than about 600 microns, more preferably less than about 500 microns.

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 (i.e. superabsorbent fibers) are used in the macrostructures of the present invention, the length of the fibers is used to define the "particle diameter" (denier and / or diameter of the fibers 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 mm to about 100 mm, more preferably from about 10 mm to about 50 mm.

Hydrogel-forming absorbent polymeric materials comprising these precursor particles have a number of anionic functional groups, such as sulfonic acids, more typically carboxy groups. Examples of suitable polymeric materials for use as precursor particles herein include those prepared from polymerizable unsaturated acid containing monomers. Accordingly, such monomers include olefinic 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. U.S. Patent 5,324,561 (Rezai et al.), Issued 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 acid ester copolymers, hydrolyzed acrylonitrile or acrylamide copolymers, slightly networked crosslinked polymers of any preceding 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 issued to June 6, 1978 (Aoki et al.), U.S. Patent No. 4,666,983 issued to May 19, 1987 (Tsubakimoto et al.) And 1988 U.S. Patent No. 4,734,478 (Tsubakimoto et al.), Issued March 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.

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 Re-issued 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 reversible emulsion polymerization or reversible suspension polymerization procedures. For methods involving reversible suspension polymerization, for example, U.S. Patent No. 4,340,706 issued July 20, 1982 (Obaisashi et al.), U.S. Patent No. 4,506,052 issued March 19,1985 (Fresher et al.) And US Pat. No. 4,735,987 (Morita et al.), Issued April 5, 1988. As discussed below, the particular method used to prepare these precursor particles may be important for the determination of their fluid permeability and capacity properties as well as for the measurement of the resulting particles' form.

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, precursor particles may vary in size, shape, absorption capacity or any other property or property. 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. By "substantially dry" is meant that the precursor particles have a liquid content of typically less than about 50%, preferably less than about 20%, more preferably less than about 10% by weight of water or other solution content. Generally, the liquid content of the precursor particles is in the range of about 0.01 to about 5% by weight of precursor particles. The individual precursor particles are dried by any conventional method such as by heating. On the one hand, when precursor particles are formed using an aqueous reaction mixture, water can 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 dewatering mass of the polymeric material may then be subdivided or comminuted to form substantially dry precursor particles of the substantially water insoluble absorbent hydrogel-forming polymeric material.

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) a mixture of precursor particles having both. It has been found that mixtures, forms or both of precursor particles having different fluid handling properties can impart improved overall fluid handling to the resulting macrostructures. This is typically evident as high fluid permeability / performance and high fluid capacity in the resulting macrostructures made from these mixtures. Macrostructures made from mixtures of precursor particles according to the present invention minimize the potential problem of "gel blocking" without losing the desired fluid capacity.

The mixture according to variant (1) of the present invention comprises: (a) a first hydrogel having a relatively high salt flow conductivity (SFC) value and a relatively high pressurization (PUP) capability (high gel permeability / performance); Forming polymers; 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% high gel permeable / performing hydrogel-forming polymer and about 5 to about 50% high fluidity hydrogel-forming polymer. Preferably, these mixtures contain from about 60 to about 95% high gel permeable / performing hydrogel-forming polymer and from about 5 to about 40% high fluidity hydrogel-forming polymer and more preferably from about 60 to about 80% High gel permeability / performing hydrogel-forming polymers and about 20 to about 40% high fluidity hydrogel-forming polymers.

Precursor particles useful in the present invention having relatively high salt flow conductivity (SFC) values and relatively high performance under pressure (PUP) capability are described in pending US patent application Ser. No. 219,574, filed March 29, 1994 (Goldman et al.). Is disclosed. 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 performance 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 capacity 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 polyfunctional reagent is added, but the addition reaction is present in the hydrogel-forming absorbent polymer during or after the first polymerization reaction to produce a higher level of crosslinking at or near the surface. To induce suspension polymerization processes (eg, anhydride and / or ester crosslink formation between 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 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 the crosslinker, other components may also be added to the surface to aid or control the distribution of the crosslink (ie, dispersion and permeation of the surface crosslinker). 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 invention is U.S. Patent No. 4,541,871 to Obayashi on September 17, 1985, October 1, 1992 PCT application WO92 / 16565 to Stanley, published as 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 US Pat. No. 219,574 to Goldman et al., Filed March 29, 1994, in particular Examples 1-4. Suitable hydrogel-forming absorbent polymers with relatively high SFC and PUP dose values are L76lf, manufactured by Nippon Shokubai, SXP, Dow Chemical manufactured by Chemische Fabrik Stockhausen. XZ manufactured by Dow Chemical 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 1988 19 U.S. Patent No. 32,649, reissued to Brandt et al., U.S. Patent No. 4,625,001, issued to Tsubakimoto et al. On November 25, 1986, and U.S. Pat. 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 is. The "absorption capacity" refers to the capacity to absorb a fluid to which a given polymeric material comes in contact 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 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 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 dose 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 above-mentioned U.S. Pat. The aqueous reaction mixture is then given sufficient polymerization reaction conditions to produce a substantially water insoluble, slightly networked crosslinked polymeric material. Suitable hydrogel-forming absorbent polymers having relatively high absorption capacity and AAP values are obtained by IM 1000, manufactured by Hoechst Celanese, L74, manufactured by Nippon Shokubai, and Nippon Gohsei. Including but not limited to F201 prepared.

The mixture according to variant process (2) of the present invention comprises: (a) a first hydrogel in the form of a spherical particle which may comprise a spherical mass of a first hydrogel-forming polymer (typically produced by a suspension polymerization process). Forming polymers; And (b) precursor particles made of a second hydrogel-forming polymer, typically in an aspheric or irregular form, prepared by a bulk polymerization process. It is believed that the macrostructures produced predominantly from spherical particles of the hydrogel-forming absorbent polymer readily form gel blocks due to the formation of tight and dense structures with low fluid flowability. Inclusion of non-spherical (irregular) particles has been known to interfere with the self-assembly properties of spherical particles during the production of macrostructures, in particular sheet-like macrostructures. As a result, it is not easy to shield fluid with macrostructures.

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% of non-spherical particles.

Spherical particles and spherical agglomerates can be obtained by multiphase polymerization process techniques such as reverse phase emulsion polymerization or reverse phase suspension polymerization. In the course of a reverse phase emulsion polymerization reaction or a reverse phase suspension polymerization reaction, the aqueous reaction mixture is suspended in the form of droplets in a matrix of an inert organic solvent which is not mixed with water such as cyclohexane. The resulting precursor particles are generally spherical. US Patent 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 Obayashi et al. On September 17, 1985, US Patent No. 4,541,871, October 6, 1987 US Pat. No. 4,698,414 to Cramm et al., US Pat. No. 4,735,987 to Morita et al. April 5, 1988; US patent to Young on May 23, 1989. 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 procedures including aqueous solutions or other solution polymerization methods. As described in the above-referenced U.S. Pat. The aqueous reaction mixture is then subjected to polymerization reaction conditions sufficient to produce a substantially water insoluble and slightly networked crosslinked polymeric material. The polymer material mass thus formed is then comminuted or cut to form individual precursor particles. Suitable non-spherical hydrogel-forming absorbent polymer particles include L76f, manufactured by Nippon Shokubai, SXP or SXM, manufactured by Chemish Fabric Stockhausen, and 1180 or XP30, 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 the 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 expands less in the presence of an aqueous (sieve) liquid compared to the other non-crosslinked portions of the particles.

Crosslinkers suitable for this purpose are nonionic and contain at least two functional groups per molecule that can react with the carboxy group. 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; Polyaldehydes such as glutaraldehyde and glyoxazole; Polyamine compounds such as ethylene diamine, diethylene triamine, triethylene tetraamine, tetraethylene pentaamine, pentaethylene hexaamine and polyethylene imine; And various nonionic crosslinkers including polythiocyanate 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 polymerizable amine forms. See US Pat. No. 5,324,561 to Rezai et al., June 23, 1994, which discloses suitable cationic amino-epichlorohydrin adduct crosslinkers. Such amino-epichlorohydrin adducts, especially polymerizable resin modifications of such adducts, are preferred crosslinkers because they react only with the polymerizable material in the surface precursor particles. In addition, cationic functional groups of such adducts (e.g. azetedinium groups), in particular polymerizable resin modifications, are also suitable for anionic functional groups of polymer materials of absorbent particles, typically at carboxy groups and at room temperature (e.g., about 18 to about 25 ° C). It seems to react very quickly. As a result, a very moderate amount of such amino-epichlorohydrin adducts (eg as little as about 1% by weight of the particles) is needed to provide effective surface crosslinking of the polymeric material present in the absorbent precursor particles.

Suitable cationic amino-epichlorohydrin adducts useful as crosslinkers include higher amines having monomeric di-, tri-, and primary or secondary amine 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; Polymerizable amines such as polyethylenimine and certain polyamide-polyamines derived from saturated C ₃ -C ₁₀ divalent carboxylic acids with polyalkylene polyamines. These epichlorohydrin / polyamide-polyamine adducts are well known in the art as wet strength 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 1-3 secondary amine groups, and saturated aliphatic C ₃ -C ₁₀ di Those derived from carboxylic acids, more preferably those containing from 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 commercially available from Hercules Inc. under the trade name Chimen. 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% by weight active resin.

E. Process for producing aggregates and macrostructures bonded between particles

In preparing the intergranular aggregated aggregates constituting 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 crosslinking agent that reacts with the polymeric material at the surface of the particles so as to swell less under. The construction of an "enough amount" of crosslinker depends on a number of factors, including the particular absorbent precursor particle treated, the crosslinker used and the particular effect desired in forming the aggregated particles between the particles and the like. US Patent Nos. 5,102,597 entitled "nonionic crosslinking agents such as glycerol," issued to Lo et al. On April 7, 1992, and 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 chemicals can be used as an adjuvant when preparing the aggregated particles. 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 causes penetration of the crosslinker into the surface area of these particles. In addition, water promotes stronger physical bonding between the treated precursor particles and provides greater integrity to the resulting interparticle bonded crosslinked aggregates. The actual amount of water used will vary depending 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 such as glycerol. can do. US Patent Nos. 5,102,597 entitled "nonionic crosslinking agents such as glycerol," issued to Lo et al. On April 7, 1992, and Rezai et al. On June 23, 1994. See US Pat. No. 5,324,561 entitled "cationic amino-epichlorohydrin adduct crosslinking agents."

Although not absolutely necessary, organic solvents can be used, which generally promotes uniform dispersion of the crosslinker on the surface of the precursor particles. Such 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 adducts used, the polymeric materials used to form the precursor particles, the particle size of these precursor particles, and the like. US Patent Nos. 5,102,597 entitled "nonionic crosslinking agents such as glycerol," issued to Lo et al. On April 7, 1992, and Rezai et al. On June 23, 1994. See US Pat. No. 5,324,561 entitled "cationic amino-epichlorohydrin adduct crosslinking agents."

Other optional components can also be used with the crosslinking agent, in particular with the aqueous treatment solution thereof. 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 are glycerol, propylene glycol (ie 1,2-propanediol), 1,3-propanediol, ethylene glycol, sorbitol, sucrose, polymerizable solutions (e.g. ester precursors of polyvinyl alcohol, 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 moisturizers, co-plasticizers, or both, with water being the main plasticizer. Particularly when the aqueous solution of the cationic amino-epichlorohydrin adduct is included as part of the aqueous solution of glycerol to water in a ratio of about 0.5: 1 to about 2: 1, preferably about 0.8: 1 to about 1.7: 1, Preferred plasticizers for use 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 used in an amount of about 5 to about 60 parts by weight, more preferably about 10 to about 30 parts by weight, most preferably about 15 to about 20 parts by weight per 100 parts by weight of the precursor particles. 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 bonded to cause surface crosslinking has an effective amount of adduct thereon. 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 is coated over the entire surface of most (preferably total) absorbent precursor particles in order to increase the desired surface crosslinking of the polymeric material at the surface of such precursor particles as well as the efficiency, strength and density of the interparticle precursors. do.

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. US Patent Nos. 5,102,597 entitled "nonionic crosslinking agents such as glycerol," issued to Lo et al. On April 7, 1992, and Rezai et al. On June 23, 1994. See US Pat. No. 5,324,561 entitled "cationic amino-epichlorohydrin adduct crosslinking agents." 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 bonded together by applying a binder over the precursor particles and physically contacting the precursor particles to at least a portion of the surface of the precursor particles to which the binder is applied. Binders useful in the present invention include hydrophilic organic solvents, typically low molecular weight alcohols such as methanol and ethanol; water; Mixtures of hydrophilic organic solvents and water; Crosslinking agents or mixtures thereof. Preferred binders are water, methanol, ethanol, cationic polymerizable amino-epichlorohydrin resins (e.g., chimen 557H, 557LX or plus) or mixtures thereof. Typically the binder contains a mixture comprising a crosslinker such that the step of applying the crosslinker is carried out simultaneously with the step of applying the binder.

The binder is applied to the precursor particles by any of a variety of methods and apparatus used to apply a solution to a material, including coating, dumping, pouring, spraying, spraying, condensing, or dipping the binder onto the precursor particles. Can be. US Patent Nos. 5,102,597 entitled "nonionic crosslinking agents such as glycerol," issued to Lo et al. On April 7, 1992, and Rezai et al. On June 23, 1994. See US Pat. No. 5,324,561 entitled "cationic amino-epichlorohydrin adduct crosslinking agents." When a binder is applied to the precursor particles, the precursor particles may be physically contacted in a number of different ways. For example, the binder alone can fix the contacted particles. Alternatively, gravity may be used to, for example, stack the precursor particles to ensure contact between 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) can 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 macrostructures 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 can be shaped by any conventional shaping method known in the art. Preferred methods for shaping the aggregates include casting, molding or shaping operations. Casting and molding methods generally introduce the precursor particles into the molds produced to apply pressure to the (pressing) agglomerates so that the agglomerates conform to the shape of the molds. Examples of specific molding methods for use herein include compression molding, injection molding, extrusion molding or lamination. For example, various precursor particles can be added to a container having a fixed volume molding mold, and the aggregates are compressed to conform to the shape of the molding mold 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 the 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 can 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 aggregate macrostructure of the present invention as a sheet is described in Rezai et al. On June 23, 1994, "cationic amino-epichlorohydrin adduct. crosslinking agents. "US Pat. No. 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 the application of the treatment solution and the precursor particles are physically bound to form an aggregate and the aggregate is shaped, the crosslinker reacts with the polymeric material of the precursor particles while maintaining the physical bond of the precursor particles to form an aggregate macrostructure. It provides effective surface crosslinking in the precursor particles of. US Patent Nos. 5,102,597 entitled "nonionic crosslinking agents such as glycerol," issued to Lo et al. On April 7, 1992, and Rezai et al. On June 23, 1994. See US Pat. No. 5,324,561 entitled "cationic amino-epichlorohydrin adduct crosslinking agents." 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 carried out 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 particular temperature and time used for thermosetting will depend on the specific crosslinker and polymeric material present in the precursor particles used. [US Pat. No. 5,102,597 to Roh et al. Same nonionic crosslinker) and US Patent No. 5,324,561 to Cathay et al., Filed June 23, 1994 (cationic amino-epichlorohydrin addition salt crosslinker). In the case of preferred cationic amino-epichlorohydrin addition salts, 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 during the curing step is maintained such that adjacent precursor particles bond closely to each other as the crosslinking proceeds. If sufficient 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 that lack structural integrity. Physical association of precursor particles is typically maintained by minimizing 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 form into the desired shape and typically the desired density, after which the step is terminated or the aggregates are allowed to settle for a period of time before the crosslinking agent in the precursor particles. In reaction with the polymeric material, the precursor particles were simultaneously surface crosslinked to form an aggregate macrostructure. Typically, the 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 extruded and rolled as described above is then formed to form the bound aggregates (ie associated precursor particles and aqueous mixture) into a compacted sheet. The plasticizer is then reacted with the polymeric material such that ambient temperature or heat cure occur simultaneously on the surface of the precursor particles to form a tightly coupled aggregate macrostructure.

Even after curing, the macrostructures can be treated with a plasticizer to perform surface plasticization. Suitable plasticizers include water alone or mixtures with the aforementioned wetting / adjuvant plasticizers, preferably glycols. The plasticizer can be applied to the macrostructure by a number of different methods, for example spraying, coating, spraying, dipping or dumping the plasticizer into the macrostructure. Optionally, when water is used alone, the macrostructure can be left in an environment of high relative humidity (eg, when relative humidity is at least 70%). The amount of plasticizer applied to the macrostructure can be selected 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 include 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 fibrous materials can be used as reinforcing members in the macrostructures of the present invention. Fiber materials in a form suitable for use in conventional absorbent articles are 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. Examples of other fibrous materials for use in the present invention besides some of the materials mentioned above are derived from hydrophilized hydrophobic fibers such as polyolefins (such as polyethylene or polypropylene), polyacryl, polyamides, polystyrenes, polyurethanes, etc. Surfactant-treated or silica-treated thermoplastic fibers. Indeed, hydrophilized hydrophobic fibers that are not good absorbent by themselves and do not provide sufficient absorbent webs useful in conventional absorbent structures are suitable for use in the macrostructures of the present invention because of their good wicking ability. This is because, in the macrostructures of the present application, the macrostructures of the present invention have a high speed of raising the fluid and lack gel blocking properties, so that the wicking properties of the fibers are not so important as those of the fiber materials themselves. Because it is important. In general, synthetic fibers are preferred for use herein as the fiber component of the macrostructure. Polyolefin fibers, preferably polyethylene fibers are more preferred.

Other cellulosic fibrous materials that may be useful in certain macrostructures herein are chemically reinforced cellulosic fibers. Preferred chemically reinforced cellulosic fibers are reinforced, twisted and curled cellulosic fibers that can be prepared by internally crosslinking the crosslinker and the cellulosic fibers. Suitable reinforced, twisted and curled fibers useful as the hydrophilic fibrous materials herein include Heron, filed December 19, 1989, US Pat. No. 4,888,093, filed December 26, 1989. US Pat. No. 4,889,595, issued December 26, 1989, US Pat. No. 4,889,596, issued December 26, 1989, and US Pat. No. 4,889,597, issued December 26, 1989. , And US Pat. No. 4,898,647 to Moore et al., Filed February 6, 1990.

The term "hydrophilic" is used to describe the surface of a fiber or fiber that is wetted with a liquid adhering on the fiber (ie, the surface of the fiber regardless of whether the water or aqueous body fluid actually absorbs the fluid or forms a gel) Spreading in the phase). Descriptions in the art of wetting of materials define hydrophobicity (and wettability) for the use of contact angles and surface tensions of the associated liquids and solids. This is described in more detail in "Contact Angle, Wettability, and Adhesion", published by the American Chemical Society Publication, owned by Robert F. Gould and 1964. The fiber or the surface of the fiber, if the contact angle between the liquid and the fiber or the surface is 90 ° or the liquid tends to spread simultaneously with the surface of the fiber, or both generally meet the conditions, It is said to be wet by the liquid.

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

F. Selective Support Layer

If desired, porous absorbent macrostructures may be attached to the optional substrate (see co-pending US Pat. No. 142,253, filed on October 22, 1993, Hsueh et al.). The substrate has a number of functions, such as (1) improving the dispersion of the fluid to be absorbed by the macrostructure and (2) additional integrity, especially at the point when the absorbent particles begin to swell after absorbing the fluid. Provide support for large structures. The substrate may include 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. have. Most of these base materials can disperse fluids as well as support large structures. Preferably, the substrate consists of a cellulosic material or a material comprising cellulosic functional groups. Preferred substrates for dispersing 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, imparting these properties to the resulting absorbent combinations that include macrostructures. The substrate is substantially resilient and non-extensible 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 of the substrate material (weight per unit area of the substrate) may vary depending on the shape of the substrate and the desired properties. The substrate may comprise a plurality of individual sheets or plies or one or more substrate layers of a particular substrate material in the stack. Such suitable substrates have a thickness of about 0.02 mm to about 1.2 mm, more preferably about 0.3 mm to about 0.8 mm, and a basis weight of about 5 gm / m 2 to about 100 gm / m 2, more preferably about 10 gm / m 2. From about 60 gm / m 2, more preferably from about 15 gm / m 2 to about 40 gm / m 2 BOUNTY® sheet. Other suitable substrates include a dry compressive thickness of about 0.5 mm to about 3.0 mm, more preferably about 0.8 mm to about 2.0 mm, a wet expansion thickness of about 0.8 mm to about 6.0 mm, more preferably about 1.0 And cellulosic foams having a basis weight of about 50 gm / m 2 to about 2,000 gm / m 2, more preferably about 100 gm / m 2 to about 1,000 gm / m 2.

Suitable substrates for supporting macrostructures typically have a dry tensile strength of about 500 gm / inch to about 8,000 gm / inch, more preferably about 1,000 gm / inch to about 3,000 gm / inch, and wet tensile strength. Is about 200 gm / inch to about 5,000 gm / inch, even more preferably about 400 gm / inch to about 1,000 gm / inch, and the wet burst strength is about 100 gm to about 2,000 gm, even more preferably about 200 gm to about 1,000 The base material which is gm is mentioned. Preferred substrates of this type include U.S. Patent No. 3,953,638, filed April 27, 1976, U.S. Patent No. 4,469,735, filed September 4,1984, U.S. Patent No. Cellulosic fibrous webs, such as pairer towels and tissues, as described in US Pat. No. 4,986,882, filed Jan. 4,468,428 and Jan. 22, 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 dispersion properties. Suitable cellulosic foams can be made from recycled rayon fibers by known methods, which are described in European Patent Application No. 293,208, published November 30, 1988.

Porous absorber macrostructures can be attached to a substrate as a number of chemical and physical methods and adhesives. Adhesives for bonding the substrate to the macrostructure include glue and hot melt adhesives. It is preferable to bond the substrate and the macrostructure by adhering the precursor absorbent particles onto the substrate, treating the adhered particles with a solution comprising a crosslinking agent, and then curing the treated particles / substrate as described above. . In a preferred embodiment of the method, cellulosic substrates such as pairer towels are used. The precursor absorbent particles are then adhered to this cellulosic substrate. Applying a treatment solution comprising an amino-epichlorohydrin addition salt, preferably a polymerizable epichlorohydrin-polyamide / polyamine wet strength resin, for example chimen, onto the cellulosic substrate and the absorber (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. "Sintering" means a condensation mechanism that occurs upon drying of a suspended liquid emulsion or dispersion, such as latex; "Sinter" is synonymous with "film formation". Treatment of these macrostructures with these latexes has been found to greatly increase the flexibility of the macrostructures, especially the macrostructures in the form of sheets or even bonded to substrates such as pairer towels. In addition to the improved flexibility, the latex treatment according to the present invention improves the bonds 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 "rubbery" 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 avoid drying the macrostructures. 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 a substance or surface of a substance may be wetted by an aqueous fluid (eg, an aqueous body fluid) adhered to these substances. Hydrophilicity and wettability are typically defined in terms of the contact angle and surface tension of the fluids and solids involved. This is described in detail in Gold, edited by American Chemical Society publication, "Contact Angle, Wettability and Adhesion", 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 latex produced using 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 ethersulfates; Block copolymers of oxyethylated fatty alcohols or oxyethylated alkylphenols and ethylene oxide and propylene oxide; Cationic addition salts 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 may 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. Essentially suitable monomers for use in the present invention are emulsions of polymethyl methacrylate. More preferred latexes include those marketed as MONWINYL 963 (Ghost Celanese) and Roflex (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 the latex will be sufficient for the macrostructure to have significantly improved flexibility. However, the macrostructures can be effectively treated with from about 1% to about 10%, more preferably from about 2% to about 5% by weight of the 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 include spraying, printing (e.g. flexographic printing), coating (e.g. gravure coating), dipping, brushing, foaming or a combination of these application techniques. Include. 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 such method 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 ingredient (glycerol). 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 casted latex. 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 dry and especially wet integrity.

However, another method includes applying a pressure to 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. The blown or sprayed foam latex is highly porous and is to some extent in the form of porous fibers to further improve the absorbency of the macrostructures. 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 wrappers or water-retaining materials) and industrial uses ( For example, sludge or oil dehydrating agents, anti dewing substances, desiccants and humidity control substances).

Due to the unique absorbent nature of the porous absorbent macrostructures of the present invention, the macrostructures are suitable for use as absorbent cores in absorbent articles, essentially disposable absorbent articles. "Absorbent product" refers to a product that absorbs and retains body secretions, and more specifically, refers to a product that is located towards or close to the body to absorb and retain various secretions released by the wearer's body. In addition, "disposable" absorbent products are intended to be discarded after one use (ie, certain materials or all materials in the absorbent product may be recycled, reused or decayed, 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. "Diapers" generally refers to garments worn by infants and incontinents 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, pairer towels, and the like).

3 is a perspective view of the unfolded state of the diaper 20 of the present invention (ie, the state in which all elastically induced shrinkage has been removed). A portion of the cut out structure for viewing and a portion of the diaper 20 in contact with the wearer are shown toward the viewer. The diaper 20 shown in FIG. 3 is preferably a liquid permeable topsheet 38, a liquid impermeable backsheet 40, topsheet 38 and backsheet 40 bonded to the topsheet 38. An absorbent core 42, an elastic member 44, and a tape tab fastener 46 positioned therebetween. 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 engaged with the back sheet 40 and superimposed on the back sheet 40 to form the periphery of the diaper 20. The perimeter is defined by 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 immediately permeate through the thickness of the topsheet. Suitable topsheets 38 are from various materials, such as porous foams, reticulated foams, perforated plastic films, natural fibers (eg wood fibers or cotton fibers), synthetic fibers (eg polyester or polypropylene fibers). Or from a combination of natural and synthetic fibers. Preferably, the topsheet 38 is made of a hydrophobic material to isolate the wearer's skin and liquid at the absorbent core 42.

More preferred topsheet 38 is a denier of about 1.5, such as Hercules type 151 polypropylene commercially available from Hercules, Inc., Wilmington, Delaware. Polypropylene fibers of standard length with "Standard length fibers" refers to fibers 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, the 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 direction crossing the machine direction.

The backsheet 40 is impermeable to liquid and is preferably made from a thin plastic film, but other flexible fluid impermeable materials may also be used. The backsheet 40 prevents the products absorbed and retained by the absorbent core 42 from coming into contact with the diaper 20, such as a bedsheet and an undergarment, from getting wet. Preferably, the 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 fluid impermeable materials may be used. "Flexible material" refers to a material that is flexible and can immediately fit 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 beyond the absorbent core 42 at a minimum distance of at least about 1.3 cm to about 2.5 cm around the entire diaper perimeter.

Top sheet 38 and back sheet 40 are joined in any suitable manner. The term " bonded " refers to a structure in which the top sheet 38 is attached to the back sheet 40, thereby directly joining the top sheet 38 and the back sheet 40, and the top sheet 38 is attached to the intermediate member in turn. It is attached to the back sheet 40, and includes the arrangement structure which indirectly couples the top sheet 38 and the back sheet 40. In a preferred embodiment, the topsheet 38 and backsheet 40 are attached 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 can be used to attach 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's do it. Alternatively, the elastic member 44 is placed adjacent one or both distal edges 32 of the diaper 20 to provide a waist band with or rather than leg cuffs. 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 elastomeric members is described in US Pat. No. 4,081,301, issued March 28, 1978 to Buell.

The elastic member 44 adheres to the diaper 20 in an elastically shrinking condition and is in a generally unrestricted arrangement structure, which allows the elastic member 44 to effectively contract or collect the diaper 20. The elastic member 44 can adhere in elastically shrinking conditions 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 attached 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 should be compatible with the design that receives the fluid, 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 consisting of 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 fluid transfer layer between the topsheet 38 and the macrostructure 52 to capture fluid. 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, fairer 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 microstructures of the invention, or of the invention It can include any other absorbent core contour 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 point of contact by suction into other portions of the absorbent member 60 and the macrostructure sheet 62. Absorbent member 60 preferably comprises a bat 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 certain 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 may contain 0 to about 8 percent by weight 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 are described in US Pat. No. 4,673,402 issued to June 18, 1987 (Weisman et al.); And US Pat. No. 4,834,735 (Alemani et al.), Issued May 30, 1989. Particularly preferred for use herein is 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 so as to effectively and efficiently capture liquid secreted in the capture zone.

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 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 in the diaper. More specifically, the macrostructure sheet 62 is generally positioned 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 two to six macrostructure 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 structure 142. For example, an additional absorbent member may be positioned between the macrostructure sheet 62 and the backsheet 40 to allow fluid to pass through the macrostructure sheet 62 so as to absorb the absorbent core 142 or other portion of the macrostructure sheet 62. Retention capacity for the absorbent core 142 and / or layers to be dispensed with. The macrostructure sheet 62 may also be positioned on the absorbent member 60 to alternatively be positioned between the upper sheet 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 bat of web or 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 microstructured 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 obtain dispensed liquid.

In use, the diaper is applied to the wearer by placing the diaper in the back waistband area under the wearer's back and dragging the rest of the diaper 20 between the wearer's legs so that the front waistband area is positioned across the front of the wearer. . 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 liquid more quickly and effectively and remain dry due to the high absorbent capacity of the macrostructures. Disposable diapers incorporating the macrostructures of the present invention are also 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 elements capable of expanding in z-direction when in contact with the aqueous body fluid to form a fluid capture zone, wherein the upper fluid storage element is in direct fluid communication with the upper sheet and the upper fluid storage The element also includes an absorbent macrostructure of the present invention. The absorbent core also includes a fluid capture zone capable of receiving aqueous body fluid, the fluid capture zone being at least partially surrounded by an upper fluid storage element and located at least partially below the fluid secretion region of the absorbent core. The absorbent core also includes a fluid capture / distribution element capable of capturing and moving the aqueous body fluid and at least a portion of the fluid capture / distribution element is located under and in fluid communication with the upper fluid storage element, and the fluid capture / distribution element At least a portion of is located at the bottom of 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 fluid loading level (g or ml of fluid) and fluid capture rate (ml / sec) was generally accepted for the absorbent article. Found the ability to overcome. Thus, in one aspect, the invention relates to absorbent articles that exhibit the ability to maintain fluid capture rate for each of two consecutive fluid loadings in addition to being relatively thin. In another aspect, the present invention is directed to an absorbent article that exhibits the ability to increase the fluid capture rate for each of two consecutive fluid loads. Preferably, the article 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 absorbent products to meet this criterion is measured as described in more detail in the Test Methods section using the following capture test. Briefly, the fluid capture rate for a given absorbent product is determined for each of 4 consecutive loads of 50 ml per load, with each load moving the synthetic urine at a constant rate of about 10 ml / sec, with 5 between each load. 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 the topsheet, backsheet and absorbent core but excluding tape, leg cuffs or other optional elements) are about 0.5 inches or less in dry state, preferably Is required to have a thickness of 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 four or more continuous loads, it is preferred that these absorbent articles also meet the above thickness conditions.

In addition to exhibiting a sustained or increased capture rate for continuous fluid loading, preferred absorbent articles capture fluid at a rate of at least about 2 ml / sec, more preferably at least about 5 ml / sec, for the initial 50 ml load. 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 article is measured according to the absorbent capacity test described in columns 27-28 of US Pat. No. 5,124,188 (Rho et al.), Issued June 23, 1992. In this test, absorbent particles are placed in “tea bags” and impregnated with 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 saline flow conductivity (SFC) of the precursor absorbent particles is measured according to the test method disclosed in co-pending U. S. Patent 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 absorb and distribute body fluids when the particles are present at high concentrations and exposed to use mechanical pressure. Darcy's law and rectification 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. Function under Pressure (PUP)

The action under pressure (PUP) of the precursor absorbent particles is measured according to the test method disclosed in co-pending U. S. Patent No. 219,574 (Goldman et al.) Filed March 29, 1994. This test determines the 60 min g / g uptake of synthetic urine for the laterally defined absorbent material in the piston / cylinder combination under a defined pressure of 0.7 psi (about 5 kPa). This test evaluates the ability of an absorbent product layer to absorb body fluids for practical periods when particles are present at high basis weights and high concentrations and exposed to working pressure. These working pressures may be 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 fluids. Contains hydrostatic pressure. The test fluid for the PUP ability test is J. Synthetic urine. This fluid is absorbed by the absorbent particles under the required absorption conditions at an almost hydrostatic pressure.

D. Required Absorption Capacity

The required absorbent capacity of the absorbent macrostructure is 60 minutes g of synthetic urine for the absorbent structure 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, swollen state). / 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 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 fluids. Contains hydrostatic pressure. The test fluid for the required absorbent capacity test is Jj synthetic urine. This fluid is absorbed by the absorbent structure under the required absorption conditions.

The following describes the required absorption capacity measurements. The reagent cell is a square piston / cylinder combination and has a mesh bottom of 10 cm x 10 cm dimensions. The absorbent structure (with and without fibers) was sampled in dimensions of 3.7 cm x 3.7 cm and placed under a 1.4 psi piston. Upon contact of the reagents with Jacob synthetic urine it begins to absorb the Jacob synthetic urine. Changes in weight are monitored and recorded for the next 60 minutes. As a result, the reagent dimensions increased 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) Synthetic urine is applied to the diaper sample at a rate of 10 ml / sec at least twice in total with an interval of 5 minutes each (equilibration time).

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 "x 12" x 1 "foam covered with polyethylene backsheet material-Foam Type: Density 1.0 lb / 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: Jayco SynUrine

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 spray 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. The second crosslinked sodium polyacrylate is IM-1000, commercially available from Sanyo Chemical Industry, and has a low PUP and high gel volume. Cellulose web is a tissue towel commercially available under the trade name BOUNTY having a basis weight of 20 g / m ² . Kimmen is marketed by Hercules Company under the trade name KYMENE-PLUS and contains 30% of polymer resin. Blend two or more superabsorbent polymer microparticles with a food mixer. 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 of polyethylacrylate-based latex polymers increases the flexibility and flexibility of the macrostructures.

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 , including 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% to 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 , including 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% to 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 . Subsequently, the macrostructure is slitted and stretched to form a net 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 macrostructures of the present invention improves the demand absorption capacity of the macrostructures.

Figure 7 compares the three different samples with the required absorbent capacity of the absorbent macrostructures of the present invention. Specifically, the curve “… ○…” illustrates the surprising effect of the chimens that significantly increase 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 using chimen, in which the 0.7psi required absorption capacity is increased only when increasing the weight percentage of high PUP superabsorbent particulate (L-76) (curve "… ◇…") . The curve "... ◇ ..." is also the same as the curve "... Δ ..." which is the result of the test of the mixed superabsorbent particulate layer without the use of chimen or adhesive additives. 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 laminated structure (curve "... □ ...") does not exhibit an extraordinary relationship between the required absorption capacity under pressure and the mixing ratio of the superabsorbent polymer (as can be seen in the curve "...? ...").

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) of at least about 23 g / g under a Saline Flow Conductivity (SFC) value of at least about 5 × 10 ⁻⁷ cm ³ sec / g and a defined pressure of 0.7 psi (5 kPa). a mixture of about 50 to about 95% of a first hydrogel-forming polymer having a capacity) and about 5 to about 50% of a second hydrogel-forming polymer having an Absorptive Capacity value 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 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, which has a circumscribed dry volume of about 0.008 mm ³ Greater than, Porous, absorbent macrostructures with improved fluid handling capabilities. The method of claim 1, The hydrogel-forming polymer material comprises 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. Absorbent macrostructures. The method of claim 1, The hydrogel-forming polymer material has a saline flow conductivity (SFC) value of at least about 5 × 10 ⁻⁷ cm ³ sec / g and a PUP value of at least about 23 g / g under a defined pressure of 0.7 psi (5 kPa). A porous, absorbent macrostructure comprising a mixture of about 50 to about 95% of a first hydrogel-forming polymer and about 5 to about 50% of a second hydrogel-forming polymer having an absorption capacity value of at least about 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 bonded to the topsheet; And an absorbent core positioned between the topsheet and the backsheet and comprising at least one macrostructure of 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) a first hydrogel-forming polymer having a brine flow conductivity (SFC) value of at least about 5 × 10 ⁻⁷ cm ³ sec / g and a performance value under pressure at least about 23 g / g under a defined pressure of 0.7 psi (5 kPa) A mixture of about 50 to about 95% and about 5 to about 50% of a second hydrogel-forming polymer having an absorption capacity value 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 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, which pores are interconnected by intercommunication channels to form a liquid permeable macrostructure, wherein the boundary dry volume of the macrostructure is greater than about 0.008 mm ³ , Flexible, porous and absorbent sheet.