MXPA98002684A - Absorbent material that has improved absorbent permeability and method to make my - Google Patents

Abstract

The present invention relates to an absorbent material having substantially improved liquid permeability such that it does not undergo gel blocking while maintaining the preferred absorbent capacity. The absorbent material comprises (a) a plurality of gelling absorbent particles comprising an absorbent, water insoluble hydrogel-forming polymer, and (b) a polycationic polymer covalently bonded to the gelling absorbent particles, wherein the absorbent material has a Saline Flow Conductivity, greater than (500-11.5 VG) (10-7) cmüseg / g, where VG is the gel volume of the material absorbed

Description

ABSORBENT MATERIAL THAT HAS IMPROVED ABSORBENT PERMEABILITY AND METHOD TO DO THE SAME FIELD OF THE INVENTION The present invention relates to an absorbent material which, after contact with liquids such as water, body exudates and the like, swells and imbibes said liquids; a method for making said absorbent materials; and absorbent articles such as diapers, incontinence pads for adults, sanitary napkins, and the like, incorporating said absorbent materials.

BACKGROUND OF THE INVENTION Water-swellable, water-swellable absorbent polymers, hydrogel formers, are capable of absorbing large amounts of liquids, such as water, body exudates or fluids (eg, urine, blood, menstrual fluid), industrial and household fluids; fluids and are also capable of retaining said liquids absorbed under moderate pressures. The absorption characteristics of said polymer materials make them especially useful for incorporation in absorbent articles, such as disposable diapers, incontinence pads for adults and underpants, catamenial products such as sanitary napkins, and the like. The development of highly absorbent members used in such absorbent articles is the subject of substantial commercial interest. A highly desired feature for such products is thinness. For example, thinner diapers are less bulky when worn, fit better under clothing, and are less noticeable. They are also more compact in the package, making diapers easier to carry and store for the consumer. The compact feature when packing also results in reduced distribution costs for the manufacturer and the distributor, including less space required in the storage per diaper unit. The ability to provide thinner absorbent articles, such as diapers, has been contingent on the ability to develop thinner absorbent cores or structures, which can acquire and store large quantities of discarded body fluids; in particular, urine. In this regard, the use of certain absorbent polymers usually referred to as "hydrogels", "superabsorbents" or "hydrocolloid" material has been particularly important. See, for example, US patent. 3,699,103 (Harper et al.), Issued June 13, 1972, and patent of E.U.A. 3,770,731 (Harmon), issued June 20, 1972, which describe the use of such absorbent polymers (hereinafter referred to as "water-insoluble polymers, absorbers, hydrogel formers") in absorbent articles. In fact, the development of thinner diapers has been the direct consequence of thinner absorbent cores and take advantage of the ability of these hydrogel-forming absorbent polymers to absorb large amounts of discarded body fluids, typically used in combination with a fibrous matrix. . See, for example, US patent. 4,673,402 (Weisman et al.), Issued June 16, 1987 and patent of E.U.A. 4,935,022 (Lash et al.), Issued June 19, 1990, which disclose double-layer core structure comprising a fibrous matrix and hydrogel-forming absorbent polymers useful in the design of thin, compact, non-bulky diapers. The above absorbent structures have generally comprised relatively low amounts (eg, less than about 50% by weight) of water insoluble polymers, absorbers, hydrogel formers. There are several reasons for this. The hydrogel-forming absorbent polymers used in absorbent structures of the prior art generally have not had an absorption regime that would allow them to rapidly absorb body fluids, especially in "spill" situations. This has required the inclusion of fibers, typically wood pulp fibers to serve as temporary deposits to hold the waste fluids until they are absorbed by the absorbent hydrogel-forming polymer. More importantly, many of the known hydrogel-forming absorbent polymers exhibited a gel block when used in absorbent articles at a high concentration. "Gel blocking" occurs when the hydrogel-forming absorbent polymer particles become wet and the particles swell, so as to inhibit the transmission of fluid to other res of the absorbent structure. The wetting of these other res of the absorbent member, therefore, can occur through a very slow diffusion process. In practical terms, this means that the acquisition of fluids by the absorbent structure is much slower than the speed at which fluids are discarded, especially in spill situations. The leakage of the absorbent article can very well occur before the particles of the absorbent, hydrogel-forming polymer in the absorbent member are completely saturated or before the fluid can diffuse or penetrate beyond the "blocking" particles towards the rest of the absorbing member. Gel blocking can be a particularly acute problem, if the particles of the absorbent, hydrogel-forming polymer do not have adequate gel strength and deform or spread under pressure, once the particles swell with the absorbed fluid. See, patent of E.U.A. 4,834,735 (Alemany et al.), Issued May 30, 1989. This phenomenon of gel blocking has typically necessitated the use of a fibrous matrix, in which the particles of the hydrogel-forming, absorbent polymer are dispersed. This fibrous matrix keeps the particles of the absorbent, hydrogel-forming polymer separated from one another. This fibrous matrix also provides a capillary structure that allows the fluid to reach the absorbent, hydrogel-forming polymer, located in res far from the initial fluid discharge point. See, patent of E.U.A. 4,834,735 (Alemany et al.), Issued May 30, 1989. However, the dispersion of the absorbent, hydrogel-forming polymer in a fibrous matrix at relatively low concentrations in order to minimize or prevent gel blockage, can reduce all fluid storage capacity of thinner absorbent structures. The use of lower concentrations of these absorbent, hydrogel-forming polymers somewhat limits the real advantage of these materials, mainly their ability to absorb and retain large amounts of body fluids per given volume. In general, the increase in gel strength of absorbent, hydrogel-forming polymers can contribute to a reduced gel block. Gel resistance refers to the tendency of the hydrogel formed from these polymers to deform or "flow" under tensions of use. The resistance to the gel needs to be such that the hydrogel formed does not deform and fill to an acceptable degree the capillarity of hollow spaces in the absorbent structure or article, thus inhibiting the absorbent capacity of the structure / article, as well as the distribution of the fluid to through the structure / article. Generally, high gel strength is obtained through crosslinking. It is believed that the crosslinking increases the resistance to deformation of the hydrogel-forming absorbent polymer surfaces. However, normal crosslinking has a profound impact on the absorbent capacity of the hydrogel-forming absorbent polymer. In general, the absorbent capacity or "gel volume" depends on the law of inverse energy on the level of crosslinking. That is, a high level of crosslinking results in high gel strength but low volume. The gel volume is a measure of the amount of water or fluids in the body that a given amount of hydrogel-forming polymer can absorb. The gel volume is required to be sufficiently high so that the hydrogel-forming polymer can absorb significant amounts of the aqueous body fluids found during the use of the absorbent article. Another important factor that has to be considered is the liquid permeability of absorbent polymers, hydrogel formers. It has been found that the permeability or flow conductivity of the gel layer formed by swelling in the presence of body fluids is extremely important when these absorbent polymers are used in cores or absorbent members at a high concentration in their localized regions or through the same. It should be noted that the lack of liquid permeability or flow conductivity of absorbent polymers can directly impact the ability of the resulting gel layers to acquire and distribute body fluids. Based on the foregoing, there is a need for an absorbent material, which has improved fluid absorbency and fluid permeability.

BRIEF DESCRIPTION OF THE INVENTION The present invention is directed to an absorbent material having improved fluid absorbency and fluid permeability. In one aspect of the present invention, the absorbent material comprises: (a) a plurality of absorbent gelling particles comprising a water-insoluble, absorbent, hydrogel-forming polymer, and (b) a polycationic polymer covalently bound to the particles of absorbent gelling; wherein the absorbent material has a Saline Flow Conductivity greater than (500 - 11.5 • GV) • (10"7) cm3 sec / g, where GV is the gel volume of the absorbent material In another aspect of the present invention , the absorbent article comprises: (a) a liquid-permeable top sheet, (b) a liquid-impermeable backsheet, and (c) an absorbent core positioned between the top sheet and the backsheet, wherein the absorbent core it comprises the absorbent material described above The present invention also relates to a method for making an absorbent material, comprising, (a) preparing a solution containing a polycationic polymer and a solvent; (b) applying the solution on a plurality of absorbent gelling particles comprising a water-insoluble, absorbent, hydrogel-forming polymer; and (c) reacting the polycationic polymer with the absorbent gelling particles, so that the resulting absorbent material has a Saline Flow Conductivity greater than (500 - 11.5 • GV) • (10"7) cm3 sec / g, in where GV is the gel volume of the absorbent material The present invention further relates to a method for making an absorbent material, comprising: (a) preparing a solution containing a polycationic polymer and a solvent; a plurality of absorbent gelling particles comprising a water-insoluble, absorbent, hydrogel-forming polymer, (c) reacting the polycationic polymer with the absorbent gelling particles, (d) removing the solvent from the resulting material, and (e) heating the material resulting from step (d) at a temperature from about 100 ° C to about 35 ° C, sufficient to obtain at least 80% by weight of the polycatalyst polymer uniquely covalently bound to the absorbent gelling particles. These and other aspects, features and advantages of the present invention will be better understood with respect to the following description, appended claims and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a diagram showing the relationship between gel volume ("GV") and Saline Flow Conductivity ("SFC"). Figure 2 is a schematic view of an apparatus for measuring the SFC value of the absorbent materials. Figure 3 depicts an enlarged sectional view of the piston cylinder assembly shown in Figure 2. Figure 4 depicts a plan view of the bottom of the piston head of the piston / cylinder assembly shown in Figure 3.

DETAILED DESCRIPTION The following is a list of definitions of certain terms used in this: "Understanding" means other steps and other ingredients that can be added, which do not affect the final result. The term encompasses the terms "consisting of" and "consisting essentially of". "GV stands for gel volume." SCF "stands for Saline Flow Conductivity." "WAHP" means polymer insoluble in water, absorbent, hydrogel former.

A. Absorbent Material The absorbent material of the present invention is capable of absorbing large quantities of liquids such as water, body fluids, industrial fluids and household fluids at a rapid rate. In particular, the absorbent material of the present invention has a high degree of permeability, while also having a high degree of absorbent capacity, and structural integrity or strength. It is the combination of high permeability and high absorbent capacity, which forms the basis for the present invention on the absorbent materials, which have not provided said combination to the now achieved tier. The absorbent material of the present invention comprises: (a) a plurality of absorbent gelling particles comprising a WAHP; (b) a polycationic polymer covalently bonded to the absorbent gelling particles, wherein the absorbent material has a Saline Flow Conductivity, greater than (500 - 11.5 • GV) • (10"7) cm3 sec / g, where GV is the gel volume of the absorbent material The polycationic polymer used herein is a polymer, which has multiple functional groups that are capable of covalently bonding to the surface of the absorbent gelling particles. involves sharing the electron pairs between two chemical substances, ie between the polycationic polymer and the WAHP of the absorbent gelling particles, preferably at least about 80%, most preferably at least about 90%, by weight of the Polycationic polymer in the absorbent material is covalently bound to the WAHP of the absorbent gelling particles. Polycationic numbers that are attached to the absorbent material are evaluated by measuring the Percentage of Covalently United Polycationic Polymers (PCBPP). The "Percentage of Covalently Polycationic Polymer (PCBPP)" is defined as the percentage of polycationic polymer that is not extractable, extracting the absorbent material with an acid solution. Methods to determine the PCBPP of the absorbent material are provided below in the Test Method Section. Although not intended to be bound by theory, it is believed that the superior liquid permeability achieved by the absorbent material of the invention occurs as a result of the chemical reaction between the polycationic polymer and the WAHP on the surface of the absorbent gelling particles. In preferred embodiments, the WAHP of the absorbent gelling particles preferably includes a carboxy functional group (e.g., -COOH), especially on the surface of the particles, which is reactive with an amino functional group (e.g., NH2) typically included in the polycationic polymer. In this way, a covalent bond between the WAHP and the polycationic polymer (-COOH + -NH2 - -CONH-) is mainly made on the surface of the absorbent gelling particles, in order to form relatively rigid or hard particles. Said rigid or hard particles consequently have the ability to maintain their relative shape still subjected to large quantities ("spills") of fluids under pressure. Preferably, said reaction mainly occurs on the surface, thus forming a crosslinked shell on the surface through the polymer crosslinker. Consequently, the absorbent capacity can be maintained or only minimally affected. In other words, since the absorbent gelling particles will not be subjected to a large deformation after being swollen are the fluid, any remaining fluid will be able to penetrate through the interstitial voids between the particles at a rapid rate, to look for any particle of remaining absorbent gelling, which is not completely full. In a preferred embodiment, a polymer containing an amino group or an imine group is used as the polycationic polymer. Such polycationic polymers include polyamines, polyimins and mixtures thereof. Most preferably, the polyamine is selected from the group consisting of polymers having primary amine groups (e.g., polyvinylamine, polyallylamine) and polymers having secondary amine groups (e.g., polyethylene imines). Preferred poly-imines include polyethylene imines, modified polyethylene imines cross-linked with epihalohydrin, and mixtures thereof. Other suitable polycationic polymers include modified polyamidoamine grafted with ethyleneimine, polyetheramine, polyvinylamine, polyallylamine, polyamidopolyamine and mixtures thereof. In a preferred embodiment, the polycationic polymer is a polymer having an average molecular weight of at least 200, preferably at least about 5,000 and most preferably more than about 10,000. Polycationic polymers useful in the invention include those polymers having a maximum value (peak) in molecular weight distribution, as well as those polycationic polymers having one or more maximum values. The molecular weight distribution can be analyzed by, for example, gel permeation chromatography. Preferably, the amount of polycationic polymer used in the absorbent material is from about 0.05 to 10% by weight of the absorbent gelling particles, preferably from about 0.1 to about 5%, and most preferably from about 0.3 to 3% by weight of the gelling particles. The liquid permeability of the absorbent material of the present invention is measured and defined as the SCF Test. The SCF is a physical property of the absorbent material, which indicates the liquid permeability or the flow conductivity, when the absorbent material is exposed to fluids containing saline and then swells, which are typically associated with the human body. The SCF provides a measure of the ability of a swollen absorbent material to transport fluids with saline through its structure. The absorbent capacity of the absorbent material of the present invention is measured and defined by the GV test. The GV of an absorbent material is a physical property of the absorbent material, which indicates the absorbent capacity when the absorbent material is exposed to fluids containing saline and then swells. It provides a measurement of the maximum absorbent capacity of the material under the condition of use. In a preferred embodiment, the GV of the absorbent material is at least about 30 g / g, and most preferably at least about 40 g / g. The methods for measuring SFC and GV of absorbent materials are described later in the Test Method Section. Referring to Figure 1, the line R1 shows the relation SFC = (500 - 11.5 • GV) • (10"7) cm3 sec / g, where the horizontal axis indicates the GV value (g / g), while the vertical axis indicates the SFC value (cm3sec / g). Therefore, the absorbent material of the invention has the value of SFC and the value of GV in the upper area of the line R1. In a preferred embodiment, the absorbent material has an SFC of at least about 20 • (10"7) cm3 sec / g In a highly preferred embodiment, the absorbent material has a SFC greater than (500 - 11.0 • GV) • / 10"7) cm3 sec / g. Therefore, said absorbent material has a value of SFC and a value of GV in the upper area of line R2, which shows the relation SFC = (500 - 11.0 • GV) • (10"7) cm3 sec / g.

B. Aqua Insoluble Polymer, Absorbent, Hydrogel Former 1. Chemical Composition The WAHPs useful in the present invention are commonly referred to as "hydrogel formers", "hydrocolloids", or "superabsorbent" polymers, and may include polysaccharides such as starch. of carboxymethyl, carboxymethyl cellulose and hydroxypropyl cellulose; nonionic types such as polyvinyl alcohol and polyvinyl ethers; cationic types such as polyvinyl pyridine, polyvinyl morpholinione and N, N-dimethylaminoetyl or N, N-diethylaminopropyl; acrylates and methacrylates, and the respective quaternary salts thereof. Typically, the WAHPs useful in the present invention have a plurality of functional groups, anionic, such as sulfonic acid, and more typically carboxy groups. Examples of suitable polymers for use herein include those which are prepared from acid-containing, polymerizable, unsaturated monomers. In this way, said monomers include olefinically unsaturated acids and anhydrides containing at least one olefinic carbon-to-carbon double bond. More specifically, these monomers can be selected from olefinically unsaturated carboxylic acids and acid anhydrides, olefinically unsaturated sulfonic acids and mixtures thereof. Some monomers without acid may also be included, preferably in minor amounts, to prepare the WAHPs herein. Such monomers without acid can include, for example, water-soluble or water-dispersible esters of the acid-containing monomers, as well as monomers that do not contain any of the carboxylic or sulfonic acid groups. Optional monomers without acid which may thus include monomers containing the following types of functional groups: esters of carboxylic acid or sulfonic acid, hydroxyl groups, amide groups, amino groups, nitrile groups, quaternary ammonium salt groups, aryl groups (for example, phenyl groups, such as those derived from styrene monomer). These acid-free monomers are well known materials and are described in greater detail in, for example, the patent of E.U.A. 4,076,663 (Masuda et al.), Issued February 28, 1978, and in the 4,062,817 (Westman) patent, issued December 13, 1977. The olefinically unsaturated carboxylic acid and carboxylic acid anhydride monomers include the acids acrylics typified by the same acrylic acid, methacrylic acid, ethacrylic acid, chloroacrylic acid, α-cyanoacrylic acid, methacrylic acid (crotonic acid), phenylacrylic acid, acryloxypyrionic acid, sorbic acid, chlorosorbic acid, angelic acid, cinnamic acid , p-chlorocinamic acid, stearyl acid, itaconic acid, citroconic acid, mesaconic acid, glutaconic acid, aconitic acid, maleic acid, fumaric acid, tricarboxyethylene and maleic acid anhydride. Olefinically unsaturated sulfonic acid monomers include aliphatic or aromatic vinyl sulphonic acids, such as vinyl sulfonic acid, allyl sulfonic acid, toluene sulphonic acid and styrene sulfonic acid; acrylic and methacrylic sulfonic acid such as sulfoethyl acrylate, sulphoethyl methacrylate, sulfopropyl acrylate, sulfopropyl methacrylate, 2-hydroxy-3-methacryloxypropyl sulfonic acid and 2-acrylamide-2-methylpropanesulfonic acid. Preferred WAHPs for use in the present invention contain carboxy groups. These polymers include hydrolyzed starch-acrylonitrile graft copolymers, partially hydrolyzed starch-acrylonitrile graft copolymers, starch-acrylic acid graft copolymers, partially neutralized starch-acrylic acid graft copolymers, vinyl acetate-copolymers saponified acrylic ester, hydrolyzed acrylonitrile or acrylonitrile copolymers, lightly crosslinked polymers in the network of any of the above copolymers, partially neutralized polyacrylic acid and polymers slightly crosslinked in the network of a partially neutralized polyacrylic acid. These polymers can be used either alone or in the form of a mixture of two or more different polymers. Examples of these polymer materials are described in the U.S.A. 4,076,663 (Masuda et al.), Issued February 28, 1978, patent of E.U.A. 4,093,776 (Aoki et al.), Issued June 6, 1978, patent of E.U.A. 4,666,983 (Tsubakimoto et al.), Issued May 19, 1987, and the patent of E.U.A. 4,734,478 (Tsubakimoto et al.), Issued March 29, 1988. Most preferably, the polymer materials used to make hydrogel-forming polymers are lightly cross-linked polymers in the network of partially neutralized polyacrylic acids and their derivatives. Still most preferably, the hydrogel-forming polymers comprise from about 50 to about 95%, most preferably about 75% polyacrylic acid, lightly cross-linked in the network (ie, poly (sodium acrylate / acrylic acid)). Cross-linking in the network makes the polymer substantially insoluble in water and, in part, determines the absorption capacity and the extractable polymer content characteristics of the WAHPs. The procedures for network cross-linking of these typical network cross-linking agents and polymers are described in greater detail in the U.S.A. 4,076,663 (Masuda et al.), Issued on February 28. Hydrogel-forming polymers crosslinked on the surface are preferably used in a preferred embodiment of the present invention. They have a higher level of crosslinking near the surface than in the interior. As used herein, "surface" describes the boundaries that look outward from, for example, the particle, fiber. For absorbent polymers, hydrogel formers (for example, internal limits exposed to porous particles may also be included). A higher level of surface cross-linking means that the level of functional cross-links for the WAHP near the surface is generally higher than the level of functional cross-links for the WAHP in the interior. The gradation in the cross-linking from the surface to the interior can vary, both in depth and in profile. In this way, for example, the depth of the surface crosslinking may be shallow, with a relatively sharp transition to a lower level of crosslinking. Alternatively, for example, the depth of surface crosslinking may be a significant fraction of the dimensions of the absorbent, hydrogel-forming polymer with a wider transition.

Depending on size, shape, porosity, as well as functional considerations, the degree and gradient of surface crosslinking may vary within a given WAHP. For hydrogel-forming polymers, in particles, surface cross-linking may vary with particle size, porosity, etc. Depending on the variations in the surface / volume ratio within the WAHP (eg, between small and large particles), it is not common for the total level of crosslinking to vary within the material (eg, be greater for smaller particles). Surface cross-linking is generally achieved after the limits of the WAHP are essentially established (for example, by grinding, extrusion, foaming, etc.). However, it is also possible to carry out the cross-linking of the concurrent surface with the creation of final limits. In addition, some additional changes in the limits may occur, even after introducing the surface crosslinkers. Surface cross-linking can be achieved before or simultaneously with the covalent attachment of the polycationic polymer to the surface of the absorbent gelling particles. Since the WAHP is preferably of one type (ie, homogeneous), mixtures of polymers can also be used in the present invention. For example, blends of starch-acrylic acid graft copolymers and slightly cross-linked polymers in the partially neutralized polyacrylic acid network can be used in the present invention. 2. Physical Forms The absorbent gelling particles used in the present invention may have a size, shape and / or morphology that vary over a wide range. The absorbent gelling particles can have a large ratio of larger dimension to smaller dimension (eg, granules, flakes, powders, aggregates between particles, crosslinked aggregates between particles, and the like) and can be in the form of fibers, foams and the like . For WAHPs particles useful in the present invention, the average particle size is in the range of about 100 to about 800, preferably about 200 to about 600 microns, and most preferably in the range of about 250 to about 500 microns. The WAHPs may also comprise mixtures with low levels of one or more additives, such as, for example, silica powder, surfactants, gum, binders and the like. The components in this mixture can be physically and / or chemically associated in one form, so that the WAHP component and the non-hydrogel-forming polymer additive are not easily separable. The WAHPs can be essentially non-porous or have a substantial internal porosity. For particles, as described above, the particle size was defined as the dimension determined through sieve size analysis. In this way, for example, a particle that is retained in the Normal Test Sieve of E.U.A. with apertures of 710 microns (for example, Alternating Screen Designation Series U.S. No. 25) is considered to be larger than 710 microns; a particle that stops through a sieve with apertures of 710 microns and is retained on a sieve with apertures of 500 microns (eg, Alternate Sieve Designation Series US No. 35) is considered to have a particle size of between 500 and 710 microns; and a particle passing through a sieve with openings of 500 microns is considered to have a particle size of less than 500 microns. The mass average particle size of a given sample of WAHP particles is defined as the particle size that divides the sample in half with a mass basis, ie one half of the sample by weight will have a particle size less than the average mass size and one half of the sample will have a particle size greater than the average mass size. A normal particle size plotting method (wherein the cumulative weight percentage of the particle sample retained or passing through an aperture of sieve size given against the sieve size aperture in a probability paper) is typically used to determine the average particle size, when 50% of the mass value does not correspond to the size opening of a Normal Test Sieve of E.U.A. These methods for determining the particle sizes of the WAHP particles are further described in the U.S.A. 5,061, 259 (Goldman et al.), Issued October 29, 1991.

C. Method for Making Absorbent Material The present invention also provides a method for making absorbent material. The method comprises, (a) preparing a solution containing a polycationic polymer and a solvent; (b) applying the solution to a plurality of absorbent gelling particles comprising WAHP; and (c) reacting the polycationic polymer with the absorbent gelling particles, so that the resulting absorbent material has a SFC greater than (500-11.5 • GV) • (10 ~ 7) cm3 sec / g, where GV is the gel volume of the absorbent material. In a preferred embodiment, the solution is prepared by mixing the polycationic polymer with the solvent, said mixing can be accomplished through a variety of ways well known in the art, including, for example, agitation and / or mechanical vibration. In a preferred embodiment, a polar solvent, most preferably a polar organic solvent, is used as the solvent in step (a). The polycationic polymer preferably comprises from about 0.05% to 60%, most preferably from about 0.5% to about 30% by weight of the solution. In a highly preferred embodiment, the water and optionally a polar organic solvent constitute the remainder of the solution. Preferably, the organic solvent and water are contained in a weight ratio of about 2:98 to about 98: 2. In a highly preferred embodiment, the weight ratio of the polycationic polymer to the absorbent gelling particles is about 0.05: 100 to 10: 100, most preferably 0.1: 100 to 3: 100, approximately. Preferred polar organic solvents useful in the present invention include, but are not limited to, methanol, ethanol or propanol; acetone; dimethylformamide (DMF); dimethyl sulfoxide (DMSO); hexylmethylphosphoric triamide (HMPT); and mixtures thereof. Alternatively, a mixture of a polar organic solvent and a non-polar solvent may be used. Such non-polar solvents are well known and include hexane, toluene, xylene and benzene. In a preferred embodiment, the polycationic polymer comprises from about 0.05% to about 60%, most preferably from 0.5% to 30% by weight of the solution, approximately. In an even more preferred embodiment, the weight ratio of the polycationic polymer to the absorbent gelling particles is from about 0.05: 100 to about 10: 100, and most preferably about 0.1 100 to 3: 100. The solution containing the polycationic polymer is then applied to a plurality of the absorbent gelling particles. In particular, at least two, preferably all absorbent gelling particles have at least some portions covered with the solution. In a preferred embodiment, at least 70% of the surface area of the gelling particles is covered with the solution applied thereon. The solution can be applied using any of the various techniques and apparatuses well known in the art, which are suitable for applying a solution to a material including coating, unloading, pouring, dripping, spraying, atomizing, condensing or immersing the solution onto. the absorbent gelling particles. In a preferred embodiment, the polycationic polymer is mixed with the absorbent gelling particles, so that more than about 90% of the surface area of the gelation particles is covered with the solution. Mixing can be achieved using various forms known in the art, including agitation, mechanical vibration. In a preferred embodiment, the polycationic polymer is reacted with the absorbent gelling particles, so that the polycationic polymer is covalently bound to the absorbent gelling particles in the surface area of the absorbent gelling particles. Very preferably, the covalent bonds are made between the carboxy groups located on the surface of the absorbent gelling particles and the amino groups of the polycationic polymer. Optionally, catalysts, such as a Lewis or Lewis acid catalyst, plasma irradiation, or photoradiation can be used to aid in the formation of covalent bonds between the polycationic polymer and the gelation particles. In a preferred embodiment, at least about 80%, and most preferably more than about 90% by weight of the polycationic polymer is covalently bound to the absorbent gelling particles. In a most preferred embodiment, the reaction step (c) further comprises heating the material resulting from step (b). More specifically, the absorbent gelling particles and the applied solution are heated thereby facilitating the reaction between the polycationic polymer and the WAHP. In a most preferred embodiment, the reaction step (c) further comprises removing the solvent from the resulting material before the heating step. Said removal of the solvent may include, but is not limited to, evaporation. Preferably, the heating of the material resulting from step (b) is carried out at a temperature of from about 100 ° C to about 350 ° C, most preferably from 150 ° C to 250 ° C, approximately, so that at least about of 80% by weight of the polycationic polymer is covalently bound to the absorbent gelling particles. The time required for heating depends on a variety of factors, including the temperature of the heating source, the presence and / or type and / or amount of catalyst (s), the polycationic polymer (s) and the total amount of material that will be heated. Preferably, an absorbent material, according to the invention, can be obtained by heating for a period, preferably from about 10 minutes to about 2 weeks, most preferably from about 30 minutes to 600 minutes at a temperature of 100 ° C to 350 °. C, approximately. For example, when heating is conducted at 200 ° C without any catalyst, the period from about 30 minutes to about 150 minutes is preferred. In another example, when heating is conducted at 150 ° C without any catalyst, the period of about 360 minutes is preferred.

D. Absorbent Article Comprising Absorbent Materials Absorbent materials according to the present invention can be used for many purposes in many fields of use. For example, the absorbent material can be used to pack containers; drug delivery devices; wound cleaning devices; burn treatment devices; ion exchange column materials; Construction materials; agricultural or horticultural materials, such as seed covers or water retention materials; and industrial uses such as mud or oil dewatering agents, materials for the prevention of dew formation, desiccants and moisture control materials. In these environments, the absorbent material of the invention can have a number of shapes and sizes. For example, the absorbent material may be in the form of particles, sheets, films, cylinders, blocks, fibers, filaments, or other shaped elements. The absorbent material may comprise a cellulosic material to improve absorbency and / or be in a docile form for these and other applications, as described below. Due to the unique absorbent properties of the absorbent material of the present invention, it is especially suitable for use as an absorbent core in absorbent articles, especially disposable absorbent articles. As used herein, the term "absorbent article" refers to articles, which absorb and contain body fluids, and more specifically refers to articles that are placed against or close to the user's body to absorb and contain the various fluids discharged from the body. In addition, "disposable" absorbent articles are those that are intended to be discarded after a single use (i.e., the original absorbent article in its entirety does not intend to be washed or otherwise restored or reused as an absorbent article, although certain materials or the entire absorbent article can be recirculated, reused or formed into a compost). In general, an absorbent article comprises, (a) a liquid-permeable topsheet, (b) a liquid-impermeable backsheet, and (c) an absorbent core positioned between the topsheet and the backsheet. As used herein, the term "absorbent core" refers to the component of the absorbent article that is primarily responsible for the fluid handling properties of the article, including the acquisition, transportation, distribution and storage of body fluids. As such, the absorbent core preferably does not include the topsheet or backsheet of the absorbent article.

The absorbent core used in the present invention is an absorbent material of the present invention. The absorbent core further comprises two layered gauzes, wherein the absorbent material is distributed between the two layered gauzes. In a highly preferred embodiment, the absorbent material is the absorbent core having a basis weight of about 40 g / m2 to about 1500 g / rrf, preferably from about 100 g / m2 to about 1000 g / m2, most preferably 150 g / m2 to approximately 500 g / m 2 of the absorbent material. In a certain embodiment, the absorbent core or the absorbent member may further comprise fibers or lint pulp (fibrous or fiber material); more specifically, non-absorbent gelling fibers. Said fiber material can be used as a reinforcing or absorbent member in the absorbent core, improving the handling of core fluid, as well as serving as a co-absorbent with the absorbent polymers. As used herein, the term "absorbent member" refers to the components of the absorbent core that typically provide one or more fluid handling properties, eg, fluid acquisition, fluid distribution, fluid transportation, fluid storage, etc. The absorbent member may comprise the entire absorbent core or only a portion of the absorbent core, i.e., the absorbent core may comprise one or more absorbent members. Preferably, the absorbent core or absorbent member includes from about 40% to about 100% by weight absorbent material and from about 60% to about 0% by weight of said non-absorbent gelling fiber material distributed within the absorbent material. In a preferred embodiment, the absorbent material is in a concentration of at least about 40%, most preferably from about 45 to 100% by weight in at least one region of the absorbent core. In a highly preferred embodiment, the absorbent member comprises a fibrous matrix, wherein the absorbent material is distributed in the fibrous matrix. Any type of fiber material, which is suitable for use in conventional absorbent products, may be used in the absorbent core or absorbent member herein. Specific examples of such fiber material include cellulose fibers, improved cellulose fibers, rayon, polypropylene and polyester fibers such as polyethylene terephthalate (Dacron), nylon hydrophilic (HYDROFIL), and the like. Examples of other fiber materials for use in the present invention, in addition to some already discussed are hydrophobic hydrophobic fibers such as thermoplastic fibers treated with surfactant-treated or silica agent, derived from, for example, polyolefins such as polyethylene or polypropylene, polyacrylics, polyamides, polystyrenes, polyurethanes and the like. Indeed, the hydrophobic hydrophobic fibers, which are in and of themselves are not very absorbent and which, therefore, do not provide frames of sufficient absorbent capacity to be useful in conventional absorbent structures, they are suitable for use in the core Absorbent by virtue of its good penetration properties. This is why, in the absorbent core of the present, fiber penetration preference is as important, if not more important, than the absorbent capacity of the same fiber material due to the high speed of fluid consumption and the lack of gel blocking properties of the absorbent core. Synthetic fibers are generally preferred for use herein as the fiber component of the absorbent core. Most preferred are polyolefin fibers, preferably polyethylene fibers.

The other cellulosic fiber materials, which may be useful in certain absorbent cores or absorbent members thereof, are chemically hardened cellulosic fibers. Preferred chemically hardened cellulosic fibers are cured, twisted, curled cellulosic fibers, which can be produced by internally crosslinking the cellulosic fibers with a crosslinking agent. The hardened, twisted, crimped cellulose fibers useful as the hydrophilic fiber material herein are described in greater detail in the U.S.A. 4,888,093 (Dean et al.), Issued December 19, 1989; patent of E.U.A. 4,889,595 (Herrón et al.), Issued December 26, 1989; patent of E.U.A. 4,889,596 (Schoggen et al), issued December 26, 1989; patent of E.U.A. 4, 889,597 (Bourbon et al.), Issued December 26, 1989; and patent of E.U.A. 4,898,647 (Moore et al.), Issued February 6, 1990. A preferred embodiment of the absorbent article is a diaper. As used herein, the term "diaper" refers to a garment, generally worn by infants and incontinent persons, that is worn around the wearer's lower torso. A preferred diaper configuration for a diaper comprising an absorbent core is generally described in US Patent 3,860,003 (Buell), issued January 14, 1975. Alternatively, the preferred configurations for disposable diapers of the present are also described in US Pat. US patent 4,808,178 (Aziz et al.), Issued on February 28, 1989; patent of E.U.A. 4,695,278 (Lawson), issued September 22, 1987; patent of E.U.A. 4,816,025 (Foreman), issued March 28, 1989; and patent of E.U.A. 5,151,092 (Buell et al), issued September 29, 1992. Another preferred embodiment of the disposable absorbent article is a catamenial product. Preferred catamenial products comprise an apertured top sheet of formed film, as described in U.S. Pat. 4,285,343 (McNair), issued August 25, 1981; patent of E.U.A. 4,608,047 (Mattingly), issued August 26, 1986; and patent of E.U.A. No. 4,687,478 (Van Tilburg), issued August 18, 1987. Preferred catamenial products may comprise wings, side wings, and other structures and elements, as described in the application of E.U.A. commonly assigned, co-pending, series No. 984.071, issued to Yasuko Morita, entitled "Absorbent Article Having Elasticized Side Flaps", filed on November 30, 1992. However, it must be understand that the present invention is also applicable to other absorbent articles commercially known under other names, such as incontinence briefs, adult incontinence products, trainers, diaper inserts, facial gauzes, paper towels, and the like.

E. Test Methods 1. Synthetic Urine The specific synthetic urine used in the test methods set forth herein is referred to as "Synthetic Urine". Synthetic urine is commonly known as Jayco SynUrine or Jayco Synthetic Uriñe and is available from Jayco Pharmaceuticals Company of Camp Hill, Pennsylvania. The formula for Synthetic urine is: 2.0 g / l KCl; 2. 0 g / l of Na2SO4; 0.85 g / l of (NH4) H2P04; 0.15 g / l of (NH4) H2P04; 0.19 g / l of CaCj, and 0.23 g / l of MgCl2. All chemical products are reactive grade. The pH of Synthetic Urine is in the range of 6.0 to 6.4. 2. Saline Flow Conductivity Test (SFC) This test determines the Saline Flow Conductivity (SFC) of the gel layer formed from WAHP that swells in Jayco Synthetic Uriñe under a confining pressure. The objective of this test is to analyze the ability of the hydrogel layer formed from a WAHP to acquire and distribute body fluids when the polymer is present at high concentrations in an absorbent member and is exposed to mechanical pressures of use. Darcy's Law and steady-state flow methods are used to determine the conductivity of saline flow. (See, for example, "Absorbency", ed. by PK Chatterjee, Elsevier, 1985. Pages 42-43 and "Chemical Engineering Vol. II, third edition, JM Coulson and JF Richardson, Pergamon Press, 1978, pages 125-127.) A predetermined layer of the swollen absorbent material used for SFC measurements are formed by swelling the absorbent material in Jayco synthetic urine over a period of 60 minutes.The hydrogel layer is formed and its flow conductivity is measured under a mechanical confinement pressure of approximately 2 kPa. measured using a solution of 0.118 M NaCl For a hydrogel-forming absorbent polymer, whose contion of Jayco synthetic urine against time has been substantially leveled, it has been found that this concentration of NaCl keeps the thickness of the hydrogel layer substantially constant During the measurement For some hydrogel-forming absorbent polymers, small changes in hydrogel-layer thickness may occur as result of swelling of the polymer, deflation and / or changes in the porosity of the hydrogel-layer. A constant hydrostatic pressure of 4920 dynes / cm2 (5 cm of 0.118 M NaCl) is used for the measurement. The flow rate is determined by measuring the amount of solution flowing through the hydrogel layer as a function of time. The flow velocity may vary over the duration of the measurement. The reasons for the variation of the flow velocity include changes in the thickness of the hydrogel layer and changes in the viscosity of the interstitial fluid, since the fluid initially present in interstitial voids (which, for example, may contain the extractable polymer dissolved) is replaced with a NaCl solution. If the flow velocity depends on time, then the initial flow velocity, typically obtained by extrapolating the measured flow velocities to a zero time, is used to calculate the conductivity of the flow. The saline flow conductivity is calculated from the initial flow velocity, the dimensions of the hydrogel layer and the hydrostatic pressure. A suitable apparatus 610 for this test is shown in Figure 2. The apparatus comprises a constant hydrostatic head reservoir generally indicated with 612, which sits on a laboratory jacket 614. The reservoir 612 has a cap 616 with a plugged vent 618. , so that additional fluid can be added to the tank 612. An open end tube 620 is inserted through the cap 616 to allow air to enter the reservoir 612 for the purpose of supplying the fluid at a constant hydrostatic pressure. The bottom end of the tube 620 is positioned so as to maintain the fluid in a cylinder 634 at a height of 5.0 cm above the bottom of a layer of WAHP 668 (see Figure 3). The reservoir 612 is provided with a supply tube 622, generally L-shaped, having an inlet 622a which is below the surface of the fluid in the reservoir. The supply of fluid through the tube 622 is controlled through a faucet 626. The tube 622 supplies fluid from the reservoir 612 to a piston / cylinder assembly, generally indicated as 628. Below the assembly 628 is a strainer. support (not shown) and a collection tank 630 that sits on a laboratory scale 632. Referring to Figure 2, the assembly 628 basically consists of a cylinder 634, a piston generally indicated as 636 and a cover 637 provided with holes for the piston 636 and the supply tube 622. As shown in Figure 2, the outlet 622b of the tube 622 is positioned below the bottom end of the tube 620 and thus will also be below the surface of the fluid (not shown) in the cylinder 634. As shown in Figure 3, the piston 636 consists of a generally cylindrical LEXAN® arrow 638 having a concentric cylindrical hole 640 drilled to the longit axis. udinal of the arrow. Both ends of the arrow 638 are machined to provide a first end 642 and a second end 646. A load 648 rests on the first end 642 and has a cylindrical hole 648b punched through its center. Inserted at the second end 646 is a Teflon piston head, generally circular, 650, having an annular depression 652 at its bottom. The piston head 650 is dimensioned so as to move slidably within the cylinder 634.

As particularly shown in Figure 4, the piston head 650 is provided with four rings of 24 cylindrical holes, each generally indicated as a first ring 654, a second ring 656, a third ring 658 and a fourth ring 660. As can be seen in Figure 4, the concentric rings 654 to 660 fit within the area defined by a depression 652. The holes in each of these concentric rings are drilled from the top to the bottom of the piston head 650 The holes in each ring are approximately 15 degrees apart and deviated approximately 7.5 degrees from the holes in the adjacent rings. The holes in each ring have a progressively smaller diameter going inward from the first ring 654 (diameter 0.51816 cm) to the fourth ring (diameter 0.28194 cm). The piston head 650 also has a cylindrical hole 662 punched at its center to receive the second end 646 of the arrow 638. As shown in Figure 3, a worn circular glass disk 664 is fixed within the depression 652. Attached to the bottom end of the cylinder 634 is a No. 400, 666 mesh stainless steel cloth screen that is biaxially tension stretched prior to joining. The WAHP sample 668 is supported on the sieve 666. The cylinder 634 is drilled from a transparent LEXAN® bar or equivalent and has an internal diameter of 6.00 cm (area = 28.27 cm2), a wall thickness of approximately 0.5. cm, and a height of approximately 6.0 cm. The piston head 650 is machined from a solid Teflon rod. It has a height of 1.5875 cm and a diameter that is slightly smaller than the internal diameter of cylinder 634, so that it is fixed inside the cylinder with a minimum clearance of wall, but it continues to slide freely. The depression 652 has a diameter of approximately 56 mm by a depth of 4 mm. The hole 662 in the center of the piston head 650 has an opening of 1.5875 (18 threads / cm) for the second end 646 of the arrow 638. The worn disc 664 is chosen for a high permeability (e.g., Chemglass Cat. No. CG-201-40, diameter 60 mm, Porosity X-thick) and ground, so that it is tightly fixed within the depression 652 of the piston head 650, with the bottom of the disk being inside the bottom of the piston head. The arrow 638 is machined from a LEXANO bar and has an external diameter of 2.2225 cm and an external diameter of 0.635 cm. The end 646 has a length of approximately 1.27 cm and is threaded to match the first hole 662 in the piston head 650. The end 642 has a length of approximately 2.54 cm and a diameter of approximately 1.58242 cm, forming an annular shoulder for support the load of 648 stainless steel. The fluid that passes through the hole 640 in the arrow 638 can enter directly to the worn disc 664. The annular stainless steel load 648 has an internal diameter of 1.5875 cm, so that it slides on the first end 642 of the arrow 638 and rests on the annular shoulder formed therein. The combined load of the worn glass disk 664, the piston 636 and the load 648 equal to 596 g, which corresponds to a pressure of 0.02109 kg / cm2 for an area of 28.27 crrf. The cover 637 is machined from LEXAN® or its equivalent and is sized to cover the upper part of the cylinder 634. It has an opening of 2.22758 cm at its center for the arrow 638 of the piston 636 and a second opening near its edge for supply tube 622. Cylinder 634 is supported on a rigid 16 mesh stainless steel support screen (not shown) or equivalent. This support screen is sufficiently permeable so as not to impede the flow of fluid to the collection tank 630. The support screen is generally used to support the cylinder 634, when the flow velocity of the saline solution through the assembly 628 is greater than about 0.02 g / sec. For flow rates less than about 0.02 g / sec, it is preferred that there is a continuous fluid path between the cylinder 634 and the collection tank. The 0.118 M solution of NaCl is prepared by dissolving 6,896 g of NaCl (Baker Analized Reagent or equivalent) to 1.0 liters with distilled water. An analytical equilibrium 632 to 0.01 g (for example, Mettier PM4000 or equivalent) is typically used to measure the amount of fluid flowing through the WAHP 668 layer when the flow velocity is approximately 0.02 g / sec, or higher . The rest is preferably limited to a computer to check the amount of fluid against time. The thickness of the WAHP layer 668 in cylinder 634 is measured to an accuracy of approximately 0.1 mm. Any method that has the requisite accuracy can be used, as long as the charges are not removed and the hydrogel layer is not further compressed or deformed during the measurement. Using a calibrator (eg Manostat 15-100-500 or equivalent) to measure the vertical distance between the bottom of the 648 stainless steel load and the top of the 637 cover, relative to this distance without the WAHP 668 layer in cylinder 634, it is acceptable. The measurement of SFC is carried out at room temperature (ie, 20 ° -25 ° C) and is carried out as follows: 0.9 g of the WAHP aliquot (corresponding to a basis weight of 0. 032 g / cm2) to cylinder 634 and evenly distributed over sieve 666. For most WAHPs, the moisture content is typically less than 5%. For this, the amount of WAHP that will be added can be determined on a wet weight basis (as such). For WAHPs that have a moisture content greater than about 5%, the added polymer charge must be corrected for moisture (ie, the added polymer should be 0.9 g on a dry weight basis). Care must be taken to prevent the WAHP from adhering to the cylinder walls. The piston 636 (minus the load 648) with the disc 664 placed in the depression 652 of the piston head 650 is inserted in the cylinder 634 and placed in the upper part of the dry WAHP 668. If necessary, the piston 636 can be moderately turned to more evenly distribute the WAHP over the sieve 666. The cylinder 634 is covered with the cover 637 and the load 648 is then placed on the first end 642 of the arrow 638. A worn disc (thick or extra thick) having a Larger diameter than that of the cylinder 634 is placed in a wide / shallow flat bottom container that fills up to the top of the disc worn with Jayco synthetic urine. The piston / cylinder 628 assembly is then placed on top of this worn glass disc. The fluid in the container passes through the worn disc and is absorbed by the WAHP 668. As the WAHP absorbs the fluid, a layer of WAHP is formed in cylinder 634. After a period of 60 minutes, the thicknof the WAHP layer is determined. Care must be taken that the WAHP layer does not lose fluid or take in air during this procedure. The piston / cylinder assembly 628 is then transferred to the apparatus 610. The support screen (not shown) and any gap between it and the piston / cylinder assembly 628 is presaturated with saline. The measurement of SFC is initiated by adding the NaCl solution through the hole 640 in the arrow 638 in order to expel the air from the piston head 650 and then return the tap 626 to an open position, so that the tube Supply 622 supplies fluid to cylinder 634 at a height of 5.0 cm above the bottom of the WAHP 668 layer. Although the measurement is considered to have been initiated (t0) at the time the NaCl solution was first added , the moment in which a stable hydrostatic prre, corresponding to 5.0 cm of the saline solution, and a stable flow velocity is obtained (ts), is observed. (Time t / should typically be around one minute or l. The amount of fluid that passes through the WAHP 668 layer against time is determined gravimetrically over a period of 10 minutes. After the elapsed time, the piston / cylinder assembly 628 is removed and the thicknof the WAHP 668 layer is measured. Generally, the change in thicknof the hydrogel layer is lthan about 10%. In general, the flow velocity does not need to be constant. The time-dependent flow velocity through the system, Fs (t) is determined, in units of g / sec, by dividing the incremental weight of the fluid passing through the system (in grams) by incremental time (in seconds). Only the data collected for the times between ts and 10 minutes are used for flow rate calculations. The flow velocity that results between ts and 10 minutes is used to calculate a value for Fs (t = 0), the initial flow velocity through the WAHP layer. Fs (t = 0) is calculated by extrapolating the results of a least squares fit of Fs (t) against the time for t = 0. For each layer having a very high permeability (e.g., a flow rate greater than about 2 g / sec), it may not be practical to collect the fluid for the total period of 10 minutes. For flow rates greater than about 2 g / sec, the collection time can be reduced in proportion to the flow rate. For some WAHPs having an extremely low permeability, fluid uptake by the hydrogel competes with the transport of fluid through the WAHP layer and either without fluid flow through the WAHP layer and into the reservoir or possibly , there is a net absorption of fluid out of the tank. For these hydrogel layers with extremely low permeability, it is optional to extend the time for the absorption of Jayco SynUrine to longer periods (eg, 16 hours). In a separate measurement, the flow rate through the apparatus 610 and the piston / cylinder assembly 628 (Fa) is measured as described above, except that no WAHP layer is present. If Fa is much greater than the flow velocity through the system when the WAHP layer is present, Fs, then no correction is necry for the flow resistance of the SFC apparatus and the python / cylinder assembly. In this limit, Fg = Fs, where Fg is the contribution of the WAHP layer to the flow velocity of the system. However, if this requirement is not satisfied, then the following correction is used to calculate the value of Fg from the values of Fs and Fa: Fg = (Fa.Fs) / (Fa-Fs) The Saline Flow Conductivity (K) of the hydrogel layer is calculated using the following equation: K =. { Fg (t = 0) .L0} /. { q.A.P} , where Fg (t = 0) is the flow velocity in g / sec determined from the regron analysis of the results of the flow velocity and any correction due to the flow resistance of the apparatus / assembly, L0 is the initial thickness of the WAHP layer in cm, q is the density of the NaCl solution in g / cm3. A is the area of the hydrogel layer in cm2. P is the hydrostatic pressure in dynes / crí, and the conductivity of saline flow, K, is in units of cm3 sec / g. The average of the three determinations must be reported. 3. Gel Volume The gel volume of a WAHP is defined as its absorbent retention capacity after swelling in an excess of Jaco Synthetic Uriñe. It provides a measure of the maximum absorbent capacity of the polymer under conditions of use, where pressures on the polymer are relatively low. The gel volume is determined by the centrifuge capacity method, described below, using the Jayco Synthetic Uriñe. The gel volume is calculated on a dry weight basis. The dry weight used in the calculation of the gel volume is determined by drying the WAHP at 105 ° C in a furnace for three hours.

All chemical products are reactive grade. The pH of Jayco Synthetic Uriñe is on the scale of 6.0 to 6.4. A heat-sealable tea bag paper is cut into 6 cm x 12 cm, folded to half its length and sealed sealed to the edge along the two-sided length with a T-shaped bar sealer to produce box pouches of tea of 6 cm x 6 cm. They were transferred 0. 200 (+ 0.005) grams to a tea bag, and the top of the bag was sealed at its edge. The top of an empty tea bag was sealed and used as a template. Approximately 300 ml of Jayco Synthetic Uriñe was poured into a 1000 ml beaker, and the tea bag containing the WAHP and the template were immersed in the beaker. After being soaked for 30 minutes, the template and bag filled with WAHP were removed from the solution using tongues. A centrifuge (type H-122, Kokusan Enshimki Co. Ltd. Tokyo, Japan) with a direct reading tachometer, electric time controller, was used for this measurement. The sample of tea bags and the template tea bags were placed in the basket of the centrifuge and centrifuged at 1100 rpm for three minutes. The gel volume was calculated as follows: Gel Volume (g / g) = (Ws - Wb-Wo) / Wo where Ws is the sample tea bag after the centrifuge. Wb is the weight of the template tea bag after the centrifuge, Wo is the weight of the WAHP (0.200 g).

The average of at least two determinations must be reported. 4. Removable Component The percentage of the extractable polymer in carboxylic acid-based hydrogel-forming polymers was determined by the method of Determination of Removable Polymer Content-Hydrogel Forming Polymers based on Carboxylic Acid, described in the reissue patent of E.U.A. 32,649 (Brandt et al.), Reissued on April 19, 1988, but using 0.9% of a saline solution, filtering the supernatant through a 0.7 Micron GF / F microfiber filter of Whatman (for example, # Catalog 1825-125) or equivalent, and calculating the extractable polymer on a dry weight basis. It was also noted that in the Reexpedición patent of E.U.A. 32.649, Va must refer to the base volume and Vb must refer to the volume of acid.

. Percentage of the Covalently United Polycationic Polymer (PCBPP) This test determines the percentage of the covalently bound polycationic polymer (PCBBP) on the surface of the gelling particles in the absorbent material. The PCBPP is determined through a colloid titration procedure, where the samples of the absorbent material are stirred in an acid water solution, and the amount of the polymer extracted in the filtrate (supernatant) is titrated with 1/400 N a normal solution of Potassium-Polyvinyl Sulfate (PVSK) using the Toluidine Blue Indicator solution as the indicator. The particular procedure of the determination of colloid titration analysis to determine PCBBP is stable as follows: 1.0 gram of an aliquot of absorbent material was loaded into a 1000 ml beaker and recorded as Ws. 500 milliliters of a 0.1 HCl solution was added to the beaker and the mixture was stirred for 1 hour. The supernatant is separated through filtration using a filter paper. Twenty milliliters of the obtained supernatant were drained into a 50 ml beaker and a few drops of the Toluidine Blue Indicator solution (Wako Puré Chem. Ind., Ltd., Osaka, Japan). The supernatant solution with the Indicator (blue solution) was titrated with 1/400 N of a normal solution of Potassium Sulphate-Polyvinyl (PVSK) (Wako Puré Chem. Ind., Ltd., Osaka, Japan). The end point was reached when the solution was made from blue to violet. The amount of polycationic polymer extracted, We (g), from the gram of Ws of the sample of absorbent material was calculated through the following equation: W = MW • (Np • Vp) • 500 / (20 • 1000) where MW is the molecular weight of the polycationic polymer repeat unit, Np is the equivalent concentration of PVSK (eqVI), Vp (ml) is the volume of PVSK necessary to titrate the supernatant of 20 ml of blue to violet. The percentage of union was calculated through the following equation: PCBPP = (Wt - We) / Wt • 100% where Wt is the total amount of polycationic polymer in grams of Ws of the absorbent material and is calculated by the following equation: Wt = Ws • Cp in which Cp is the concentration of the polycationic polymer in the absorbent material.

F. Example of Precursor Part A solution of aqueous monomer was prepared, consisting of 4000 grams of partially neutralized acrylic acid having a portion thereof 75% molar neutralized with caustic soda, 3.7 grams of N, N'-methylene-bis-acrylamide , and 6000 grams of water. The aqueous monomer solution was fed into the reaction vessel, which was subsequently purged with nitrogen gas to remove trapped air remaining from the reaction system. Then, the mixture was stirred and heated to about 45 ° C and a solution of 20 grams of 2,2'-azo-bis- (2-amidinopropane) dihydrochloride in 100 grams of water was added thereto, as a polymerization initiator. Polymerization started approximately 15 minutes after the addition of the polymerization initiator. With the progress of the polymerization, the aqueous monomer solution gave rise to a mild gel containing water. The internal temperature of the reaction system was maintained at 80-90 ° C for several hours to further complete the polymerization. A swollen absorbent gelling polymer was formed. The resulting swollen absorbent gelling polymer was spread on a metal gauge with a normal # 50 size and dried with hot air at 150 ° C. The dry particles were pulverized with a hammer-type grinder and moved with a # 20 sieve (850 microns) to obtain particles that pass through the normal # 20 sieve. 0.5 parts of glycerin, 2 parts of water and 2 parts of a mixture of ethyl alcohol were sprayed on 100 parts of the resulting particles. The mixture was heated at 210 ° C for 10 minutes. As a result, white, dry precursor absorbent gelling particles were obtained.

G. EXAMPLES The following examples are presented for the purpose of illustrating various aspects of the absorbent material of the invention and are not intended to limit the scope of the appended claims in any way.

EXAMPLE 1 A solution consisting of 250 grams of a solution of polyallylamine at a concentration of 10% by weight (PAA-C, obtained from Nitto Boseki Co. Ltd., Tokyo), 1600 grams of ethanol and the balance water was prepared. The solution was applied to 2500 grams of precursor particles made according to the Precursor Particle Example discussed above in a 20 liter evaporator flask. The precursor particles have a particle size, so that the precursor particles pass through a normal # 20 sieve (850 microns) and are retained in a normal # 100 sieve (150 micras). The mixture was thoroughly mixed with a spatula until all the precursor particles were wetted with the previous solution. The solvent included in the resulting mixture was evaporated with a rotary evaporator (EYELA type N-11, available from TOKYO RIKAKIKAI CO. LTD., Tokyo) at 60 ° C. The resulting product was divided into 5 parts and placed in 5 trays (20 cm • 25 cm). These trays were placed in an oven and heated at 200 ° C for 2.5 hours. The dry absorbent material was pulverized with a hammer type crusher with a normal # 20 sieve (850 microns) to obtain particles that pass through the normal # 20 sieve. As a result, a particulate absorbent material with a light yellow color was obtained. The properties of the precursor particles made according to the Precursor Particle Example and the absorbent material made according to this Example, They were evaluated. The gel volume (GV) and CFS values of the precursor particles are 42 g / g and 0.8 • 10"7 cm3 sec / g.The gel volume (GV) and CFS values of the absorbent material are 35 g / kg. gy 108 • 10"7 cm3 sec / g. The percentage of covalently linked polyallylamine is 90%. The results surprisingly illustrate the superior liquid permeability (SFC), while maintaining a high absorptive capacity (GV).

EXAMPLE 2 In this example, absorbent gelling particles obtained from commercial sources were used. Specifically, 2500 grams of Aqualic CA L76lf (batch # 4N31-021), which was obtained from Nippon Shokubai Co. Ltd., Osaka, Japan) was placed in a 20 liter rotary evaporator flask. The particles of L76lf are absorbent gelling particles crosslinked on the surface. A solution consisting of 250 grams of polyallylamine (10,000 molecular weight) in a concentration of 10% by weight (PAA-C, obtained from Nitto Boseki Co. Ltd., Tokyo), 1600 grams of ethanol and the remainder water, was emptied at flask. The mixture was thoroughly mixed with a spatula until all the precursor particles were wetted with the previous solution. The solvent in the resulting mixture was evaporated with a rotary evaporator (EYELA type N-11, available from TOKYO RIKAKIKAI CO., LTD., Tokyo) at 60 ° C. The resulting product was divided into 5 parts and placed in 5 trays (20 cm • 25 cm). These trays were placed in an oven and heated to 150 ° C for approximately 16 hours. The hot absorbent material was pulverized with a hammer-type crusher and moved with a normal # 20 sieve (850 microns) to obtain particles that pass through the normal # 20 sieve. As a result, a particulate absorbent material with a light yellow color was obtained. The properties of the commercially purchased precursor particles ("L76lf) and the resulting absorbent material were evaluated and are presented in Table 1 below.

The results surprisingly illustrate the superior liquid permeability (SFC) obtained through the absorbent material, according to the invention, and its maintained high absorbent capacity (GV), as compared to the commercially purchased precursor particles L76lf, which were not made according to the invention.

EXAMPLE 3 In this example, absorbent gelling particles obtained from commercial sources were used. 2500 grams of Aqualic CA L76lf (batch # 4N31 obtained from Nippon Shokubai Co. Ltd., Osaka, Japan) were placed in a 20 liter rotary evaporator flask. A solution consisting of 83.3 grams of polyethylene imine (molecular weight 70,000, Epomin P1000, obtained from Nippon Shokubai Co. Ltd., Osaka, Japan) in a concentration of 30% by weight, 1600 grams of ethanol and the remainder water, emptied the flask. The mixture was thoroughly mixed with a spatula until all the precursor particles were wetted with the previous solution. The solvent included in the resulting mixture was evaporated with a rotary evaporator (EYELA type N-11, available from TOKYO RIKAKIKAI CO., LTD., Tokyo) at 60 ° C. The resulting product was divided into 5 parts and placed in 5 trays (20 cm • 25 cm). These trays were placed in an oven and heated at 200 ° C for 2.5 hours. The hot absorbent material was pulverized with a hammer-type crusher and moved with a normal # 20 sieve (850 microns) to obtain particles that pass through the normal # 20 sieve. As a result, a particulate absorbent material with a light yellow color was obtained. The properties of the absorbent material were evaluated and are presented in Table 2 below.

TABLE 2 Again, the absorbent material according to the invention possesses high liquid permeability (SFC) and maintains high absorbent capacity (GV).

EXAMPLE 4 In this example, absorbent gelling particles obtained from commercial sources were used. 2500 grams of Aqualic CA L76lf (batch # 4N31 obtained from Nippon Shokubai Co. Ltd., Osaka, Japan) were placed in a 20 liter rotary evaporator flask. A solution consisting of 83.3 grams of polyethylene imine (molecular weight 70,000, Epomin P1000, obtained from Nippon Shokubai Co. Ltd., Osaka, Japan) in a concentration of 30% by weight, 1600 grams of ethanol and the remainder water, emptied the flask. The mixture was thoroughly mixed with a spatula until all the precursor particles were wetted with the previous solution. The solvent included in the resulting mixture was evaporated with a rotary evaporator (EYELA type N-11, available from TOKYO RIKAKIKAI CO., LTD., Tokyo) at 60 ° C. The resulting product was divided into 5 parts and placed in 5 trays (20 cm • 25 cm). These trays were placed in an oven and heated at 150 ° C for 6 hours. The hot absorbent material was pulverized with a hammer-type crusher and moved with a normal # 20 sieve (850 microns) to obtain particles that pass through the normal # 20 sieve. As a result, a particulate absorbent material with a light yellow color was obtained. The properties of the absorbent material were evaluated and are presented in Table 3 below.

EXAMPLE 5 In this example, absorbent gelling particles obtained from commercial sources were used. 2500 grams of Aqualic CA L76lf (batch # 4N31 obtained from Nippon Shokubai Co. Ltd., Osaka, Japan) were placed in a 20 liter rotary evaporator flask. A solution consisting of 250 grams of polyallylamine (10,000 molecular weight) in a concentration of 10% by weight, 1600 grams of ethanol and the remainder water, was emptied into the flask. The mixture was thoroughly mixed with a spatula until all the precursor particles were wetted with the previous solution. The solvent included in the resulting mixture was evaporated with a rotary evaporator (EYELA type N-11, available from TOKYO RIKAKIKAI CO., LTD., Tokyo) at 60 ° C. The resulting product was divided into 5 parts and placed in 5 trays (20 cm • 25 cm). These trays were placed in an oven and heated at 180 ° C for 2 hours. The hot absorbent material was pulverized with a hammer-type crusher and moved with a normal # 20 sieve (850 microns) to obtain particles that pass through the normal # 20 sieve. As a result, a particulate absorbent material with a light yellow color was obtained. The properties of the absorbent material were evaluated and are presented in Table 3 below.

EXAMPLE 6 In this example, absorbent gelling particles obtained from commercial sources were used. 250 grams of Aqualic CA L76lf (batch # 4N31 obtained from Nippon Shokubai Co. Ltd., Osaka, Japan) were placed in a 20 liter rotary evaporator flask. A solution consisting of 25 grams of polyallylamine (molecular weight 10,000) in a concentration of 10% by weight, 160 grams of ethanol and the remainder water, was emptied into the flask. The mixture was thoroughly mixed with a spatula until all the precursor particles were wetted with the previous solution. The solvent included in the resulting mixture was evaporated with a rotary evaporator (EYELA type N-11, available from TOKYO RIKAKIKA! CO., LTD., Tokyo) at 60 ° C. The resulting product was divided into 10 parts and placed in 10 trays (10 cm x 13 cm). These trays were placed in an oven and heated at 200 ° C for 0.5 hours. The hot absorbent material was pulverized with a hammer-type crusher and moved with a normal # 20 sieve (850 microns) to obtain particles that pass through the normal # 20 sieve. As a result, a particulate absorbent material with a light yellow color was obtained. The properties of the absorbent material were evaluated and are presented in Table 3 below.

EXAMPLE 7 In this example, absorbent gelling particles obtained from commercial sources were used. 250 grams of Aqualic CA L76lf (lot # 4N31 obtained from Nippon Shokubai Co. Ltd., Osaka, Japan) were placed in a 20 liter rotary evaporator flask. A solution consisting of 83.3 grams of polyethylene imine (molecular weight 70,000, Epomin P1000, obtained from Nippon Shokubai Co. Ltd., Osaka, Japan) in a concentration of 30% by weight, 160 grams of ethanol and the remainder water, emptied the flask. The mixture was thoroughly mixed with a spatula until all the precursor particles were wetted with the previous solution. The solvent included in the resulting mixture was evaporated with a rotary evaporator (EYELA type N-11, available from TOKYO RIKAKIKAI CO., LTD., Tokyo) at 60 ° C. The resulting product was divided into 10 parts and placed in 10 trays (10 cm • 13 cm). These trays were placed in an oven and heated at 200 ° C for 0.5 hours. The hot absorbent material was pulverized with a hammer-type crusher and moved with a normal # 20 sieve (850 microns) to obtain particles that pass through the normal # 20 sieve. As a result, a particulate absorbent material with a light yellow color was obtained. The properties of the absorbent material were evaluated and are presented in Table 3 below.

TABLE 3 The absorbent material of Example 4 to 7, according to the present invention, possesses a high liquid permeability (SFC) and maintains a high absorbent capacity (GV).

COMPARATIVE EXAMPLES The properties of commercially available absorbent gelling particles were evaluated and are presented in Table 4 below.

TABLE 4 Sample Manufacturer SFC Gel Volume (g / g) (10"7 cm3 sec / g) SXM100 Stockhausen 43.0 3 XP30 Nalco 35.0 57 XP20 Nalco 35.0 43 L76lf NSKK 38.0 18 L74 NSKK 42.0 0.2 Stockhausen: Stockhausen GmbH, Germany Nalco: Nalco Chemical Co., Illinois, US NSKK: Nippon Shokubai Co., Osaka, Japan All publications, patent applications and patents issued mentioned hereinabove are incorporated herein by reference in their entirety. It is understood that the examples and embodiments described herein are for illustrative purposes only and that various changes, modifications in light thereof will be suggested by one skilled in the art and will be included in the spirit and vision of this application and the scope thereof. of the appended claims.

Claims (19)

1. CLAIMS 1. An absorbent material comprising: (a) a plurality of absorbent gelling particles comprising a water-insoluble, absorbent, hydrogel-forming polymer; and (b) a polycationic polymer covalently bonded to the absorbent gelling particles; where the absorbent material has a Saline Flow Conductivity greater than (500 - 11.5 • GV) • (10"7) cm3 sec / g, where GV is the gel volume of the absorbent material. according to claim 1, wherein the absorbent material has a Saline Flow Conductivity of at least about 20 • (10"7) cm3 sec / g. 3. The absorbent material according to claim 2, wherein the absorbent material has a Saline Flow Conductivity greater than (500 - 11.0 • GV) • (10"7) cm3 sec / g 4.- The absorbent material according to claim 1, wherein at least 80% by weight of the polycationic polymer is covalently bound to the absorbent gelling particles 5. The absorbent material according to claim 4, wherein at least 90 % by weight of the polycationic polymer is covalently bound to the absorbent gelling particles 6. The absorbent material according to claim 1, wherein the absorbent gelling particles have an average particle size in the range from about 100 to about 800 7. The absorbent material according to claim 1, wherein the polycationic polymer is selected from the group consisting of polyamines, polyimins and mixtures thereof. 8. The absorbent material according to claim 7, wherein the polyamines are selected from the group consisting of a polyvinylamine, a polyallylamine and mixtures thereof. 9. The absorbent material according to claim 7, wherein the poly-imines are selected from the group consisting of polyethylene imine, modified polyethylene imines, crosslinked with epihalohydrin and mixtures thereof. 10. A method for making an absorbent material comprising: (a) preparing a solution containing a polycationic polymer and a solvent; (b) applying the solution to a plurality of absorbent gelling particles comprising a water-insoluble, absorbent, hydrogel-forming polymer; (c) reacting the polycationic polymer with the absorbent gelling particles, so that the absorbent material has a Saline Flow Conductivity greater than (500 - 11.5 • GV) • (10_7) cm3 sec / g. 11. The method according to claim 10, wherein step (c) further comprises heating the material resulting from step (b) to a temperature from about 100 ° C to about 350 ° C. 12. The method according to claim 10, wherein the heating temperature is from about 150 ° C to about 250 ° C. 13. The method according to claim 10, further comprising removing the solvent from the material resulting from step (c). 14. The method according to claim 13, wherein the step of removing the solvent comprises evaporating the solvent of the material resulting from step (c). 15. - The method according to claim 10, wherein the solution contains from about 0.05% to about 60% by weight of the polycationic polymer. 16. The method according to claim 10, wherein the polycationic polymer is selected from the group consisting of polyamines, polyimins, and mixtures thereof. 17. The method according to claim 16, wherein the polyamines are selected from the group consisting of a polyvinylamine, a polyallylamine and mixtures thereof. 18. The method according to claim 16, wherein the poly-imines are selected from the group consisting of polyethylene imine, modified polyethylene imines, cross-linked with epihalohydrin and mixtures thereof. 19. An absorbent material made according to the method according to claim 10.