CZ20002400A3 - Absorption polymeric mixtures exhibiting high sorptive capacity and high permeability to liquids when applying pressure - Google Patents

Abstract

This solution provides absorbent materials suitable for retaining body fluids, such as synthetic urine. In particular, the present invention relates to mixtures of an absorbent polymer s excellent absorption properties in terms of absorption capacity at applied pressure of 4.8 kPa and 9.6 kPa, as well in terms of excellent fluid permeability. Solution up it further relates to an absorbent element which comprises said mixtures absorbent polymer, and absorbent articles therewith absorbent element.

Description

Technical field

The invention relates to absorbent polymer compositions having a high sorption capacity and a high liquid permeability at the applied pressure. These compositions are particularly useful for absorbing body fluids such as urine and menstrual fluid. The invention also relates to absorbent articles comprising said absorbent polymers as well as absorbent articles comprising said absorbent articles.

BACKGROUND OF THE INVENTION

It is of constant commercial interest to develop highly absorbent articles which are used as disposable diapers, such as incontinence pads, sanitary napkins, sanitary napkins, and the like. A very desirable property of such products is their thinness. Thin diapers do not fume when worn, are more adaptable to underwear and are not perceived by the wearer. They are very compact when packed, giving the user the convenience of carrying and storing. Compactness means reduced storage and transport costs for the manufacturer and distributor, and much less storage space.

The ability to provide thinner absorbent articles, such as diapers, means the need to develop relatively thin absorbent cores or elements that are able to recruit and retain large amounts of body exudates, particularly urine. In this sense, the use of certain absorbent polymers, often referred to as "hydrogels", "superabsorbents", "xerogels" or "hydrocolloids", is very important. For example, U.S. Pat. U.S. Patent 3,699,103 (Harper et al.) issued June 13, 1972; No. 3,770,731 (Harmon), issued June 20, 1972, discloses the use of such a material (referred to herein as an absorbent polymer) in absorbent articles. The development of thinner diapers is directly dependent on the development of thinner absorbent cores, which can utilize the ability of absorbent polymers to absorb large amounts of body exudates, particularly in combination with a fiber matrix. U.S. Pat. No. 4,673,402 to Weisman et al., issued Jun. 6, 1987; U.S. Patent 4,93 5,022 (Lash et al.), issued June 19, 1990, discloses a two-layer core structure that includes a fibrous matrix and an absorbent polymer to provide a thin, compact, and bulky diaper.

Absorbent polymers are often produced by initial polymerization of unsaturated carboxylic acids or derivatives thereof, for example acrylic acid, an alkali metal (for example sodium and / or potassium), or an ammonium salt of acrylic acid, and the like, in the presence of relatively small amounts of di- or poly-functional. monomers such as N, N 'methylenebisacrylamides, trimethylpropane triacrylate, ethylene glycol di (meth) acrylate, or triallylamine. The di- or poly-functional monomers serve to slightly crosslink the polymer chains, thereby providing them with insolubility in water with the possibility of swelling in water. Such light crosslinking polymers contain multiple carboxyl groups attached to the polymeric base. Carboxyl groups generate an osmotic driving force which acts to absorb body fluids through a cross-linked polymer network. Absorbent polymers can also be prepared by polymerizing unsaturated amines or derivatives thereof in the presence of relatively small amounts of di- or poly-functional monomers (in an analogous manner).

The degree of crosslinking of these absorbent polymers is an important factor in determining their absorption capacity and gel strength. Absorbent polymers useful as absorbents in absorbent articles and articles, such as disposable diapers, must have high sorption capacity as well as high gel strength. The sorption capacity must be large enough to allow the absorbent polymer to absorb a significant amount of aqueous body exudate at the time of use. Gel strength refers to the tendency of swollen polymer particles to deform upon application of some pressure, said gel strength being such that the polymer particles do not deform under pressure, thereby unacceptably filling the free capillary spaces in the absorbent element or article, prevent liquid wicking and distribution in said element or article. In general, increasing the permeability of a region or layer that contains swollen absorbent polymers can be realized by increasing the crosslinking density of the polymer gel and thereby increasing the gel strength. While this inadvertently reduces the gel absorption capacity, see U.S. Pat. U.S. Patent 4,654,039 (Brandt et al.) issued March 31, 1987 (reissued April 19, 1988 as U.S. Patent 32,649); No. 4,834,735 (Alemany et al.), issued May 30, 1989.

Under certain conditions, many absorbent polymers may exhibit gel blocking. A "gel block" occurs when the absorbent polymer particles deform to unacceptably fill free capillary spaces in the absorbent element or article, thereby preventing the rate of capillary action or fluid distribution within the element or article. If gel blocking occurs, further capillary action and distribution is accomplished through a slow diffusion process. Practically, this means that gel blocking can substantially affect the distribution of fluids

to relative dry areas or zones in the sorbent and product. The leakage from the absorbent article may take place before the absorbent polymer particles are fully saturated in the absorbent article, or before the fluid can diffuse or wick behind the "blocking" particles into the rest of the absorbent article, see U.S. Pat. No. 4,834,735 (Alemany et al.), issued May 30, 1989.

Gel blocking necessarily requires the use of a fiber matrix in which the absorbent polymer particles are dispersed. The fibrous matrix separates the absorbent polymer particles from each other and forms a capillary structure that allows the fluid to reach the absorbent polymer located in areas distant from the initial fluid loading point, see U.S. Pat. U.S. Pat. No. 4,834,735 (Alemany et al.), May 30, 1989. Dispersing the absorbent polymer in a fiber matrix at relatively low concentrations to minimize or eliminate gel blocking can significantly increase the absorbent article volume, as well as the overall retention capacity of the thinner absorbent article. structure.

The use of a low concentration of absorbent polymers limits the true benefit of such materials, such as their ability to absorb and retain more body fluids based on volume.

At relatively high concentrations, an important property of these polymers is their conductivity, i.e. throughput / flow. This conductivity of a material can be defined by its "Saline Flow Conductivity (SFC)" conductivity. SFC is a measure of the ability of a material to convey saline fluids, for example, the ability of a layer containing a swollen absorbent polymer to conduct (convey body fluids). A fabric made by laying a fibrous slurry in an air stream (e.g., at a density of 0.15 cm ³ ) will have an SFC of about 200 x 10 ⁷ cm ³ sec / g.

Optimization of either PUP capacity (Performance Under Pressure) or conductivity (permeability / flow) of the absorbent polymer results in reduced liquid permeability when the polymer is in the swollen state. It would therefore be desirable to provide an absorbent polymer composition capable of absorbing large amounts of synthetic urine solution under pressure (4.8 kPa or greater). It would also be desirable to provide a high liquid permeability absorbent polymer blend when the polymer is in the swollen state. It would also be desirable that a relatively high capacity (PUP) be obtained after a period of time that is less than the time of use (at night) of the article containing said absorbent polymer blend. The absorbent polymer should reach a high capacity after, for example, 2, 4, 8 or 16 hours.

SUMMARY OF THE INVENTION

The invention relates to absorbent materials useful as body fluid retention means, such as urine. In particular, the invention relates to absorbent polymers having a high absorbent capacity under a pressure of 4.8 kPa and / or 9.6 kPa, and further having a high liquid permeability when the polymer is in the swollen state.

In one aspect, the invention relates to an absorbent polymer composition having a PUP capacity of at least 39 g / g under a pressure of 4.8 kPa after 4 hours and an SFC of at least 50 x 10 ⁷ cm ³ sec / g. (Methods for measuring PUP capacity and SFC are described below). In another aspect, the invention relates to an absorbent polymer composition having a PUP capacity of at least 40 g / g under a pressure of 4.8 kPa after 8 hours and having an SFC value of at least 50 x 10 ⁷ cm ³ sec / g. In another aspect, the invention relates to an absorbent polymer composition having a PUP capacity of at least 42 g / g under a pressure of 4.8 kPa after 16 hours and having an SFC of at least 50 x 10 ⁷ cm ³ sec / g. The term "po" used means immediately after.

In another aspect, the invention relates to an absorbent polymer composition having a PUP capacity of at least 35 g / g under a pressure of 9.6 kPa after 4 hours and an SFC of at least 50 x 10 ^-7 cm ³ sec / g. In yet another aspect, the invention relates to an absorbent polymer composition having a PUP capacity of at least 36 g / g under a pressure of 9.6 kPa after 8 hours and an SFC of at least 50 x 10 ^-7 cm ³ sec / g. In another aspect, the invention relates to an absorbent polymer composition having a PUP capacity of at least 37 g / g under a pressure of 9.6 kPa after 16 hours and an SFC of at least 50 x 10 ^-7 cm ³ sec / g.

In another aspect, the invention relates to an absorbent polymer composition having a PUP capacity of at least 30 g / g under a pressure of 4.8 kPa after 4 and 8 hours and having an SFC of at least 50 x 10 ⁷ cm ³ sec / g. In yet another aspect, the invention relates to an absorbent polymer composition having a PUP capacity of at least 27 g / g under a pressure of 9.6 kPa after 4, 8 and 16 hours and an SFC of at least 50 x 10 ⁷ cm ³ sec / g. In another aspect, the invention relates to an absorbent polymer composition having a PUP capacity of at least 27 g / g under a pressure of 9.6 kPa after 4, 8 and 16 hours and an SFC of at least 50 x 10 ⁷ cm ³ sec / g.

In a preferred embodiment, the invention relates to a composition comprising cation exchange absorbent polymers containing weak acid groups in non-neutralized form, further anion exchange absorbent polymers containing weak basic groups in non-neutralized form, wherein the compositions exhibit high absorbency of a synthetic urine solution under PUP absorption conditions and at relatively high liquid conductivity values. Such a composition relates to an absorbent polymer with a mixed ion exchange

bed-ion-exchange polymer composition) This mixture exhibits at least one of the PUP capacities already described.

Overview of the drawings

Giant. 1 is a schematic view of a device for measuring the PUP capacity of an absorbent polymer; FIG. 2 is an enlarged cross-sectional view of the piston / cylinder assembly of FIG. 1; FIG. 3 graphically depicts PUP capacity data of absorbent polymer blends of the present invention and prior art; where PUP capacity is measured under a pressure of 4.8 kPa, FIG. 4 graphically depicts PUP capacity data of the absorbent polymer blends of the present invention and prior art, where PUP capacity is measured under a pressure of 9.6 kPa, FIG. an apparatus for the preparation of samples of blends of absorbent polymers which are used to measure the strength by the BBS (Baling Burst Strength) method.

Fig. 6 schematically illustrates a device used for BBS measurement of absorbent polymer blends.

DETAILED DESCRIPTION OF THE INVENTION

A. Definitions

The term "body fluids" as used herein includes urine, menstrual blood, and vaginal secretions.

The term "synthetic urine solution" as used herein refers to an aqueous solution prepared by dissolving 2.0 g KCL, 2.0 g Na ₂ SO 4, 0 85 g NH 4 H ₂ PO 4.05,15 g (NH 4) 2 HPO4,0,25 g CaCl ₂ 2H ₂ O, and 0.50 g MgCl ₂ .6H ₂ O in distilled water to give 1 liter of solution.

The term "ion exchange capacity" as used herein refers to the theoretical or calculated ion exchange capacity of the polymer or polymers in milliequivalents / g, provided that each non-neutralized acid or base group is neutralized during ion exchange.

As used herein, the term "absorbent polymer" refers to a polymer capable of absorbing at least ten times its mass in deionized water and allowing the pH of the system to be adjusted.

As used herein, the term " absorbent core " refers to a component of an absorbent article that is responsible for handling the fluid in the article, i.e., receiving the fluid, distributing the fluid and retaining it. The absorbent core will not include an upper or a lower layer of the absorbent article.

As used herein, the term "absorbent member" refers to absorbent core components that provide one or more handling capabilities, for example, fluid acquisition, fluid distribution, fluid transport and containment. The absorbent element may comprise all or part of the absorbent core, meaning that the absorbent core may comprise one or more absorbent elements. The improved absorbent polymer compositions described herein are particularly useful in absorbent articles, the primary function of which is to retain aqueous body fluids. These compositions may also be used in other absorbent articles.

As used herein, the term "region" or "zone" refers to parts or sections, on a macroscopic scale, of an absorbent element.

As used herein, the term "layer" refers to a portion of an absorbent article whose main dimensions are length and width. Obviously, the term layer is not limited to a single layer or thin material of the material. The layer may consist of a laminate or a combination of several layers of the desired material. Accordingly, the term "layer" includes both layer and layering.

As used herein, the term "includes" means the possibility of using various components, elements, steps and the like, according to the present invention. Accordingly, the term "comprises" represents a much more restrictive term "consisting essentially of" and "consisting of", these restrictive terms having their standard meaning known in the art.

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

All publications and references mentioned in this application are given for comparison, at least to the extent that they correspond to the terms and definitions of this application.

B. Mixtures of Absorbent Polymers

The present invention relates, at least in part, to blends of absorbent polymers that exhibit a high ability to absorb a synthetic urine solution under an applied load as well as a high liquid permeability when in a swollen state. The absorbent polymer blends of the present invention are present in a mixed ion exchange base form, including an anion exchange absorbent polymer and an absorbent polymer.

-ΊPolymer with cation exchange. These preferred mixed ion exchange bases are described in more detail below.

1. Absorbent polymers with a mixed ion exchange base

(a) Chemical composition

(i) Anion exchange absorbent polymers

Anion exchange absorbent polymers containing weak basic groups include various, water-insoluble polymers capable of swelling. They are primarily lightly crosslinked polymers containing many basic functional groups, for example primary, secondary and / or tertiary amines or phosphines. Examples of suitable polymers include those made from polymerizable monomers that contain basic groups or groups that can be converted to basic groups after polymerization. Such monomers include primary, secondary or tertiary amines or phosphines. Representative monomers include, but are not limited to, ethyleneimine (aziridine), allylamine, diallylamine, 4asminobutene, alkyl oxazoline, vinylformamide, 5-aminopentene, carbodimide, formaldazine, mealmin and the like, and secondary or tertiary amine derivatives thereof. Representative functional groups that may be included after polymerization include alkylamine, guanidine, triazole, triazine, triamino-triazine and the like.

In order to prepare anion exchange absorbent polymers, some monomers which do not contain basic groups may also be included in small amounts. The absorbent polymers described may be homopolymers, copolymers (including terpolymers and higher copolymers), or mixtures of various homopolymers or copolymers. The polymers may be random, grafted or block polymers, which may have a linear or branched structure. Polymers are considered to be water-insoluble but swellable, with a relatively low degree of cross-linking. This can be accomplished by adding an appropriate amount of a suitable monomer that becomes crosslinked monomer during polymerization. Examples of such crosslinking polymers include Ν, Ν'-methylenebisacrylamide, ethylene glycol di (meth) acrylate, trimethylpropane tri (meth) acrylate, triallylamine, diaziridine compounds and the like. Alternatively, the polymers may be cross-linked after polymerization by reaction with a suitable crosslinker, e.g. - or poly-halogenated compounds and / or di- or polyepoxy compounds. Examples include diiodopropane, dichloropropane, ethylene glycol diglycidyl ether, and the like. The crosslinking may be distributed homogeneously throughout the gel particles, or may be concentrated in or near the surface of the particles.

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It is preferred that the absorbent polymers be of the same type (homogeneous), but mixtures of polymers with anion exchange can also be used in the present invention. For example, mixtures of cross-linked polyethyleneimine and cross-linked polyallylamine can be used. If an anionic-absorbent absorption polymer is used as part of the mixed ion exchange base, it starts in the form of a non-neutralized base of from 50% to 100%, preferably from 80% to 100%. even more preferably from 90% to 100%.

In order to minimize the ion exchange capacity of the absorbent polymer blend with the mixed ion exchange base, it is desirable that the absorbent polymer have a high ion exchange capacity per gram of dry polymer. It is preferred that the ion exchange capacity of the anion exchange absorbent polymer be at least 10 meq / g, more preferably at least 15 meq / g, most preferably at least 20 meq / g.

ii) Cation-exchange absorbent polymers

Absorbent polymers suitable for cation exchange include a number of acidic action groups, such as carboxylic acid groups. Examples of cation exchange polymers include polymers prepared from polymerizable, acid-containing monomers, or monomers containing cationic groups, which can be converted to acid groups after polymerization. Such monomers include olefinically unsaturated carboxylic acids, anhydrides and compounds thereof. Cation exchange polymers may also include polymers that are not prepared from olefinically unsaturated monomers. Examples of such polymers include polymers based on polysaccharides such as carboxymethyl starch, and carboxymethyl pulp, and further polymers based on poly (amino acid) such as poly (aspartic acid). A description of poly (amino acid) is disclosed in U.S. Pat. No. 5,247,068 issued to Donachy et al. on Jan. 21, 1993. The patent is cited for comparison.

Non-acidic monomers may also be used to prepare absorbent polymers, but usually in small amounts. Non-acidic monomers may include, for example, monomers containing the following types of functional groups: carboxylate or sulfonate esters, hydroxy groups, amide groups, amino groups, nitrile groups, quaternary ammonium salt groups, and aryl groups (e.g. phenyl groups, for example those derived) from styrene monomer). Other optional non-acidic monomers include unsaturated hydrocarbons such as ethylene, propylene, 1-butene, butadiene and isoprene. Non-acidic monomers are known materials described in great detail in U.S. Pat. No. 4,062,817 (Westerman), issued on

December 9, 1977 and U.S. Pat. No. 4,076,663 (Masuda et al.), issued Feb. 28, 1978. Both patents are incorporated herein by reference.

Olefinically unsaturated carboxylic acid and anhydride monomers include acrylic acids representing acrylic acid alone, methacrylic acid, chloroacrylic acid, β-methyl acrylic acid (crotonic acid), α-phenylacrylic acid, β-acryloxypropionic acid, sorbic acid, and-sorbic acid, and -sorbic acid. , cinnamic acid, β-cinnamic acid, β-stearyl acrylic acid, itaconic acid, citric acid, masaconic acid, glutaconic acid, acid, aconitic acid, maleic acid, furmaric acid, tricarboxyethylene, maleic anhydride.

Preferred cation exchange absorbent polymers contain carboxyl groups. These polymers include hydrolyzed graft starch acrylonitrile copolymers, partially neutralized hydrolyzed graft starch acrylic nitrile copolymers, hydrolyzed vinyl acetate-acrylic ester copolymers, hydrolyzed acrylonitrile or acrylamide copolymers, light cross-linking polymers with all of the aforementioned copolymers, all of the aforementioned copolymers, bonding polyacrylic acid. These polymers can be used either alone or in the form of mixtures of two or more different polymers. Examples of such polymers are disclosed in U.S. Pat. No. 3,661,875, U.S. Pat. No. 4,076,663, U.S. Pat. No. 4,093,776, U.S. Pat. No. 4,666,983 and U.S. Pat. No. 4,734,478.

The most preferred polymers for the production of cation exchange absorbent polymers are polyacrylic acid crosslinking polymers and their starch derivatives. The crosslinking provides a substantially water-insoluble polymer and partially determines the absorbent capacity and content characteristics of the extractable polymer of the absorbent polymers. The process for crosslinking these polymers as well as the crosslinkers are described in U.S. Pat. No. 4,076,663.

While cation exchange absorbent polymers are usually of one type (homogeneous), mixtures of these polymers can also be used in the present invention. For example, mixtures of graft copolymers of starch-acrylic acid and polymers of slightly cross-linked polyacrylic acid can be used.

When used as part of a mixed ion exchange base composition, the cation exchange absorbent polymer begins with a value of from 50% to 100%, preferably from 80% to 100%, more preferably from 90% to 100%, in the form of a neutralized acid. .

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In order to minimize the ion exchange capacity of the blend of absorbent polymer with a mixed ion exchange base, it is desirable that the cation exchange polymer have a large ion exchange capacity, based on a gram of dry polymer. Preferably, the ion exchange capacity of the cation exchange absorbent polymer is at least 4 meq / g, more preferably about 8 meq / g, more preferably about 10 meq / g, and most preferably about 13 meq / g.

iii) Mixture and common properties of the material

The anionic and cation exchange capacity equivalents should be equal or different in the blend of absorbent polymers with a mixed ion exchange base. For example, it may be desirable to have multiple equivalents of anionic or cationic bonded absorbent polymers, that is, to compensate for differences in pK, to compensate for differences in neutralization, to change the pH (e.g., to acidity) of urine with ion exchange, and the like.

With a mixed ion exchange polymer composition in a high concentration absorbent core, it is not possible to rely on solution flow, agitation, etc. to facilitate ion exchange between particles and hence ion exchange rate. It is desirable to have morphologies suitable to increase the ion exchange kinetics. Suitable morphologies include i) mixed-base aggregates with a high surface area (i.e. small and / or porous) and a wide or narrow particle size distribution, ii) particles, for example anion exchange absorbent polymer, which contain, for example, less discontinuous (non-gaseous) domains, cation-exchange absorbent polymer, (iii) particles containing the bicontinuous domains of both anionic and cation-exchange absorbent polymers, (iv) mixtures in which the anionic or cation-exchange absorbent polymers are in the form of fibers, v) fibers that contain the discontinuous and / or bi-continuous domains of anionic and / or cation exchange absorbent polymers; vi) mixtures of said particles and / or fibers. Other forms include balls, cubes, rods, films or thin materials, foams, flakes, etc.

Absorbent polymers may also include low level compositions of one or more additives, which may be, for example, silicon powder, adhesives, binders, and the like. The components in these compositions may be physically and / or chemically combined such that the absorbent polymer components and the non-absorbent polymer in the form of an additive cannot readily be physically separated from one another. Absorbent polymers may be substantially non-porous (without intrinsic porosity) or may have intrinsic porosity. In compositions with a mixed ion exchange base, the absorbent polymer of one type may have a higher crosslink density than the absorbent polymer of another type.

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The absorbent polymer particles useful in the present invention may have a size in the range of from 1 to 2000 µ, preferably from 20 to 1000 µ. The mean particle size of the mass should be from 20 to 1500 μ, preferably from 50 to 1000 μ, and more preferably from 100 to 800 μ.

An important property of the absorbent polymer useful in the present invention is the level of extracts present in the polymer itself; U.S. Patent 4,654,039 (Brandt et al.), issued March 31, 1987 (reissued April 19, 1988 as patent 32,649), both of which are incorporated by reference. Many absorbent polymers contain a significant amount of extractable polymeric materials that can be leached from swollen polymer matrices by body fluids (urine) while body fluids remain in contact with the absorbent polymer. Such polymeric material, extracted by body fluids in the manner described, may alter both the chemical and physical properties of the body fluid to the extent that the fluid is absorbed more slowly by the absorbent polymer in the absorbent article and is more difficult to retain. Extractable polymers are believed to be detrimental in the mixed ion exchange absorbent polymer system since the soluble polymer tends to migrate to the gel particles contained in the oppositely charged polymer. Both polymers will be neutralized, thereby reducing the ion exchange capacity of the system. Since the extractable polymer comprises a polyvalent ion with a counter-charge to the counter-charged polymer, it can also form ionic network bonds, which suppresses the gel's ability to swell.

Accordingly, it is preferred for the absorbent polymer to have an extractable polymer level of about 15% or less, more preferably 10% or less, even more preferably 7% or less by weight of the total polymer.

b. Physical properties

(i) Pressure behavior / performance

Measuring the desired wettability, or gravimetric absorption, may provide information about the ability of highly concentrated zones or layers of the absorbent polymer and the ability to absorb body fluids under the applied pressure. See, for example, U.S. Pat. U.S. Patent 5,562,646 (Goldman et al.), issued Oct. 8, 1996; No. 5,599,335 (Goldman et al.), issued Feb. 4, 1997, where wettability or gravimetric absorption is referred to as PUP. When measuring PUP, the initial 100% dry absorbent polymer blend is placed in a cylinder-piston device (the cylinder bottom is permeable to the solution but impervious to the absorbent polymer) and is loaded with mechanical pressure and allowed to absorb synthetic urine while maintaining the desired conditions

-12 • ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti titi titi at zero hydrostatic suction and high mechanical pressure. PUP capacity is defined as the g / g absorption of a synthetic urine solution at a 0.032 g / cm ² layer of absorbent polymer under a specific pressure load for a specific period of time. High PUP capacity is an important critical property of the absorbent polymer when used with a high concentration in the absorbent element.

The pressure applied to the absorbent polymers relates both to the mechanical pressure (induced by the weight and movements of the user, the contact forces, etc.) and to the capillary pressure (the capillary desorption pressure of the components obtained in the absorbent core that temporarily retains liquids until absorbed by the absorbent polymer). The total pressure of about 4.8 kPa reflects the sum of the two pressures on the absorbent polymer blend under body fluid absorption and operating conditions. Both low and high pressure can be used under normal conditions. It is preferred that the absorbent polymer of the present invention exhibit a high PUP capacity at pressures in excess of 9.6 kPa and a high SFC value. It is preferred that the relatively high PUP capacity be achieved within a period of time that is less than the period of use of the articles comprising absorbent compositions. Absorbent articles show improved capacity when PUP capacity is measured after 2, 4, 8, and / or 16 hours.

The method of determining the PUP capacities of these absorbent polymers is described in the "Testing of polymers" section. The method is based on the process described in U.S. Pat. No. 5,562,646 (Goldman et al.), issued Oct. 8, 1996, and modified for extended periods of time at various pressures to further simulate operating conditions.

ii) Permeability of zones or layers that include the absorbent polymer

A desirable property of the absorbent polymers of the present invention is their high liquid permeability. In the absorbent member or article, the permeability is directly affected by the ability of the material, such as the layer comprising the swollen absorbent polymer, to transport body fluids from the receiving regions at an acceptable rate. Permeability / flow conductivity can be defined as SFC (salt fluid conductivity) which is a measure of the material's ability to transport salt fluid. A method for measuring SFC is described in U.S. Pat. No. 5,562,646 (Goldman et al), issued Oct. 8, 1996. This method is modified to calculate gel base runoff during measurement of mixed ion exchange absorbent polymers as described in the "Test Methods" section. Without wishing to be bound by theory, we believe that during the measurement of absorbent polymers with a mixed ion exchange base, the polymer sample will continue to exchange ions from the saline solution. The ion exchange capacity of the absorbent polymer is eventually exceeded and

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the ionic strength of the solution surrounding the swollen polymer increases, resulting in a runoff of the gel base (bed). The amount of fluid leaving the gel base due to effluent is substantially less than the amount of fluid passing through the gel base during the SFC measurement. Since the final thickness of the gel base is significantly smaller than the initial thickness, the final thickness value is used to calculate the SFC values. Using the final gel basis thickness value for the calculation, it provides the minimum SFC value obtained during the measurement. By using the initial value or the intermediate value of the gel base thickness, we obtain higher SFC values.

iii) The porosity of the zone / layer comprising the absorbent polymer

Another important characteristic of the absorbent polymers of the present invention is their openness / porosity of the zone or layer comprising the absorbent polymers when the polymers are swollen with body fluids and are exposed to a certain pressure. It is believed that when the absorbent polymers used are present in absorbent articles or absorbent articles at high concentrations, they will swell at a certain pressure, with the boundary portions of the particles coming into contact and voids in these high concentration areas bounded by the swollen polymer. thus, the openness / porosity properties of this region will reflect the porosity of the zone or layer formed from the swollen polymer itself. As used herein, the term "porosity" refers to a negligible volume not occupied by solid material. See J., M. Coulson et al., Chemical Engeneering, Volume 2, Third Edition, Pergamon Press, 1978, p. 126.

Porosity is an effective measure of the ability of a zone or layer, including a swollen polymer, to remain open and thus be able to receive and distribute body fluids that are exposed to a certain pressure. It is believed that by increasing the porosity of the swollen and highly concentrated areas, excellent absorption and fluid handling capability of the absorbent core can be provided, thereby reducing the possibility of leakage, particularly at high fluid loading. The porosity of the zone or layer comprising the swollen absorbent polymer approaches, but exceeds, the porosity of conventional materials capable of receiving and distributing liquids, such as wood pulp fluff. See U.Š. No. 5,562,646 issued to Goldman on Oct. 8, 1996.

iv) Integrity of the zone or layer of hydrogel

Another important factor that affects the transport of fluid in the absorbent element is the integrity of the region or regions containing said polymer. Such an area or areas

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9999 999 99 99 99 99 having a high concentration of absorbent polymer should have sufficient integrity in a state of partial or total wetting so that the physical continuity (and hence the ability to acquire and transport fluid into and through the void / capillary) of the absorbent element is not seriously impaired or changed when operating under normal conditions. During normal use, absorbent cores in absorbent articles are subjected to tensile stresses as well as torsional forces of varying intensity and direction. These tensions and torsional forces cause the crotch layer to build up and shake, tensions and the occurrence of torsional forces at the time of wear, as well as walking and bending. If wet integrity is inadequate, these tension and torsion forces can cause a substantial change and / or break in the physical continuity of the absorbent element, so that the ability to acquire and transport fluids to and through adjacent voids and capillaries is reduced. The absorbent polymer layer may be partially detached, completely detached, may include gaps and areas that are substantially tapered and / or disintegrated into a number of substantially smaller segments. Such a change may minimize or completely negate any porosity and permeability / flow conductivity properties of the absorbent polymer.

The good integrity of the zone or layer comprising the absorbent polymer can be achieved, according to the present invention, by various design, arrangement, composition and the like, in an absorbent element with a high concentration of absorbent polymer, other components in the absorbent core (i.e. ), other components in the absorbent article (i.e., another topsheet and / or backsheet and a combination of these). See U.S. Pat. U.S. Patent 5,562,646 issued to Goldman et al. on October 5, 1996.

In a preferred mixed ion exchange system, the cation exchange and anion exchange components tend to adhere to each other. Without wishing to be bound by theory, it is believed that this is due to the reverse charge of polyions and acidic / alkaline species on the surfaces of the gelled polymer particles that are inherently attracted to the oppositely charged species in adjacent particles. This results in the formation of a three-dimensional network of adjacent polymer particles in the zone / layer containing the absorbent polymer, whereby the integrity of the zone / layer is greatly increased.

The integrity of the regions (s) that comprise the polymer blends of the present invention can be measured using the Bal! Burst Strength Test (BBS), which will be described later. The BBS test is the force (in grams force) required to tear a layer of an absorbent polymer blend that is swollen in synthetic urine. The absorbent polymer composition of the present invention is likely to have a value, although not necessarily

At least 50 gf, preferably at least 100 gf, more preferably at least 150 gf, and most preferably at least 200 gf. Typically, the BBS will have a value of from 150 to 400 gf, typically about 200 to 300 gf. c) Embodiment of the absorbent polymer

As already mentioned, a desirable property of the absorbent polymers of the present invention is their ability to absorb relatively large amounts of body fluid under pressure (defined as PUP capacity) and their ability to allow fluid transport from the receiving area at an acceptable rate (i.e., permeability defined as SFC). Various embodiments of the invention will be discussed later in terms of SFC and PUP values. PUP values at 4.8 kPa and 9.6 kPa will be described separately. It will be appreciated that certain absorbent materials exhibit the absorbent properties described at both a pressure of 4.8 kPa and a pressure of 9.6 kPa.

(i) an SFC of at least 50 x 10 'cm sec / g

The present invention includes blends of absorbent polymers with SFCs of at least 50x

10 ' ⁷ cm ³ sec / g. In these embodiments, the absorbent polymers will have an SFC value of at least 70 x 10 ⁷ cm ³ sec / g, more preferably at least 70 x 10 ⁷ cm ³ sec / g. Typical absorbent polymers will have an SFC value of from 50 to 100 x 10 ⁷ cm ³ sec / g, preferably from 60 to 90 x 10 ⁷ cm ³ sec / g, more preferably from 70 to 80 x 10 ⁷ cm ³ sec /G

Absorbent polymer blends are described, in one aspect, with respect to their ability to absorb synthetic urine at a pressure of 4.8 kPa. Accordingly, the present invention relates to blends of absorbent polymers having a PUP capacity in a synthetic urine solution of at least 39 g / g, at a pressure of 4.8 kPa after 4 hours. It is preferred that the polymer blend have a PUP capacity in the synthetic solution of at least 41 g / g, more preferably at least 43 g / g, more preferably 44 g / g, after 4 hours of application of said pressure of 4.8 kPa. Typically, the polymer blend will have a PUP capacity of from 39 g / g to 58 g / g, preferably from 41 g / g to 55 g / g, and more preferably from 43 g / g to 50 g / g after 4 hours of exposure pressure 4.8 kPa. In the same aspect, the absorbent polymer blend will have a PUP capacity in the synthetic urine solution of at least 40 g / g after 8 hours of pressure. It is preferred that the absorbent polymer composition have a PUP capacity of at least 42 g / g, more preferably at least 44 g / g, and most preferably at least 46 g / g after 8 hours of pressure of 4.8 kPa. Typically, the polymer blend will have a PUP capacity in the range of from 40 g / g to 55 g / g, preferably from 42 g / g to 57 g / g and even more preferably from 44 g / g to 55 g / g, and most preferably from 46 g. / g to 52 g / g, after 8 hours under a pressure of 4.8 kPa. In another similar aspect, the absorbent polymer blend will have a PUP capacity of at least 42 g / g after 16 hours of pressure. Priority

It provides that the absorbent polymer mixture has a PUP value of at least 44 g / g, preferably at least 46 g / g, more preferably at least 48 g / g after 16 hours of pressure of 4.8 kPa. Typically, the absorbent polymer blend has a PUP capacity of from 42 g / g to 61 g / g, preferably from 44 g / g to 59 g / g, more preferably from 46 g / g to 57 g / g, and most preferably from 48 g / g. to 54 g / g, after 16 hours under a pressure of 4.8 kPa.

These embodiments relate to an absorbent polymer blend having a PUP capacity of at least 35 g / g after 4 hours under a pressure of 9.6 kPa. It is preferred that the absorbent polymer composition have a PUP value of at least 36 g / g after 4 hours of pressure at 9.6 kPa, more preferably at least 37 g / g at 9.6 kPa. Typically, the PUP absorbent polymer blend will have a capacity in the range of from 35 g / g to 50 g / g, preferably from 36 g / g to 45 g / g, more preferably from 37 g / g to 42 g / g after 4 hours of pressure. 6 kPa.

In the same aspect, the absorbent polymer blend will have a PUP capacity of at least 36 g / g after 8 hours of pressure at 100 psi. 8 g / g, preferably 40 g / g after 8 hours under a pressure of 9.6 kPa. Typically, the absorbent polymer composition will have a PUP capacity in the range of from 36 g / g to 54 g / g, preferably from 38 g / g to 50 g / g, more preferably from 40 g / g to 46 g / g. 8 hours pressure of 9.6 kPa. In another similar aspect, the absorbent polymer blend will have a PUP capacity of at least 37 g / g after 16 hours of application of 9.6 kPa. It is preferred that the absorbent polymer composition have a PUP capacity of at least 39 g / g, more preferably at least 41 g / g, after a 16 hour pressure of 9.6 kPa. Typically, the absorbent polymer blend will have a PUP capacity in the range of from 37 g / g to 56 g / g, preferably from 39 g / g to 52 g / g, more preferably from 41 g / g to 48 g / g. 16 hour pressure of 9.6 kPa.

(ii) an SFC of at least 500 x lff ⁷ cm ³ sec / g

The present invention also provides an absorbent polymer blend having an SFC value of about

500 x 10 ⁷ cm ³ sec / g. In these embodiments, it would be preferred that the absorbent polymers have an SFC of at least 700 x 10 ⁷ cm ³ sec / g, more preferably about 800 x 10 ⁷ cm ³ sec / g. Typically, absorbent polymers have an SFC value of about 500 x 1100 ^-7 cm ³ sec / g, more preferably about 600 x 1100 ^-7 cm ³ sec / g, more preferably about 700 x 1100 ^-7 cm ³ sec / g.

These absorbent polymer compositions are described, in one aspect, in relation to their ability to absorb synthetic urine under a pressure of 4.8 kPa.

Accordingly, the invention relates to a blend of absorbent polymer having a PUP capacity in a synthetic urine solution of at least 30 g / g after 4 hours under a pressure of 4.8 kPa. Typically, the composition will have a PUP capacity ranging from 30 g / g to 50 g / g, more typically from 35 to 50 g / g.

G / g to 45 g / g after 4 hours of pressure of 4.8 kPa. According to the same aspect, the absorbent polymer composition may have a PUP capacity in the synthetic urine solution of at least 30 g / g, after 8 hours of application of 4.8 kPa. It is preferred that the polymer blend have a PUP capacity of at least 36 g / g, more preferably at least 42 g / g, after 8 hours of pressure of 4.8 kPa. Typically, the polymer blend will have a PUP capacity ranging from 30 g / g to 55 g / g, more typically from 35 g / g to 50 g / g, after an 8 hour pressure of 4.8 kPa. In another similar aspect, the absorbent polymer blend will have a PUP capacity of at least 30 g / g after a 16 hour pressure of 4.8 kPa. It is preferred that the polymer blend have a PUP capacity of at least 37 g / g, more preferably at least 45 g / g, after a 16 hour pressure of 4.8 kPa. Typically, the polymer blend will have a PUP capacity in the range of from 30 g / g to 58 g / g, more usually from 38 g / g to 53 g / g, after a 16 hour pressure of 4.8 kPa.

These embodiments also relate to a polymer blend having a PUP capacity of at least 25 g / g after a 2 hour pressure of 9.6 kPa. The absorbent polymer blend will further have a PUP capacity of at least 27 g / g after 4 hours of application of 9.6 kPa. It is preferred that the polymer blend have a PUP capacity of 33 g / g, more preferably 37 g / g, after a 4 hour pressure of 9.6 kPa. Typically, the polymer blend will have a PUP capacity in the range of from 27 g / g to 47 g / g, more usually from 33 g / g to 42 g / g, after 4 hours of application of 9.6 kPa. In the same aspect, the absorbent polymer blend will have a PUP capacity of at least 27 g / g after an 8 hour pressure of 9.6 kPa. It is preferred that the polymer blend have a PUP capacity of at least 33 g / g, more preferably 39 g / g, after an 8 hour pressure of 9.6 kPa. Typically, the polymer blend will have a PUP capacity ranging from 27 g / g to 52 g / g, more usually from 33 g / g to 47 g / g, after an 8 hour pressure of 9.6 kPa. In another similar aspect, the absorbent polymer blend will have a PUP capacity of at least 27 g / g after a 16 hour pressure of 9.6 kPa. It is preferred that the polymer mixture have a PUP capacity of at least 34 g / g, more preferably at least 42 g / g, after a 16 hour pressure of 9.6 kPa. Typically, the polymer blend will have a PUP capacity in the range of from 27 g / g to 55 g / g, more typically from 35 g / g to 50 g / g, after a 16 hour pressure of 9.6 kPa.

d. Methods of producing an absorbent polymer

The absorbent polymer useful in the present invention may be formed by polymerization and / or crosslinking techniques. A typical process for producing these polymers is described in U.S. Pat. Reissue Patent 32649 (Brandt et al.), issued April 19, 1988, U.S. Pat. No. 4,666,983 (Tsubakimoto et al.), issued May 19, 1987; and U.S. Pat.

18 (Tsubakimoto et al.), Issued Nov. 25, 1986, all of which are incorporated herein by reference.

Polymerization methods for preparing ion exchange polymers suitable for the present invention include free radical, closed chain opening, condensation, anions, cations, or radiation techniques. The polymers can be prepared in neutralized, not neutralized or partially neutralized form, although the desired product has a non-neutralized form. The absorbent polymer can be prepared by a homogeneous solution polymerization process, or by multiphase polymerization techniques, for example, inverse emulsion or suspension polymerization procedures.

During polymerization, crosslinking of the polymer can be achieved by including suitable crosslinking monomers. Alternatively, the polymers may be crosslinked after polymerization by reaction with a suitable crosslinking reactive agent. Surface crosslinking of the initially formed polymers is a preferred process and provides an absorbent polymer with relatively high PUP capacity, porosity and permeability. Without wishing to be bound by theory, it is believed that surface crosslinking of the polymer increases resistance to surface deformation of the swollen absorbent polymer particles, thereby reducing the degree of contact between adjacent polymer particles when the swollen particles are deformed by external pressure. Surface-crosslinked absorbent polymers have a higher level of cross-linking near the surface than inside. As used herein, the term " surface " For porous absorbent polymers (porous particles, etc.), internal exposed limits / ranges may also be included. By a high level of crosslinking near the surface is meant that the level of functional crosslinking of the absorbent polymer near the surface is generally higher than the level of functional crosslinking within the polymer. The gradation of crosslinking from surface to interior by polymers varies, both in depth and in profile.

A number of methods for carrying out crosslinking are disclosed in the prior art.

Suitable methods of crosslinking the surface include those wherein: i) di or polyfunctional agents capable of reacting with existing functional groups in the absorbent polymers are applied to the surface of the absorbent polymer; ii) di or polyfunctional agents that are capable of reacting with other added agents and possible functional groups in the absorbent polymer, for example to increase the crosslinking level at the surface, are applied to the surface (i.e., adding monomer plus crosslinking agent and initiating the second polymerization reaction); ) no additional polyfunctional reagents are added, but an additional reaction is induced between the existing components of the absorbent polymer during or after the primary polymerization process to generate a higher level of crosslinking at or near the surface (process)

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9999 999 99 99 · · «9 intermittent polymerisation in which a crosslinking agent is present at a high level near the surface); iv) other materials are added to the surface to induce a higher level of crosslinking, or otherwise the surface deformability of the resulting hydrogel is reduced. Suitable general methods for carrying out the crosslinking of the absorbent polymer of the present invention are disclosed in U.S. Pat. No. 4,541,871 (Obayashi), issued Sep. 17, 1985, in PCT application WO92 / 16565 (Stanley) published October 1, 1992, in patent application WO90 / 08789 (Tai) published August 9, 1990, in patent application WO93 / 05080 ( Stanley), published Mar. 18, 1993, in the US No. 4,824,901 to Alexander, issued April 25, 1989; No. 4,789,861 (Johnson), issued Jan. 17, 1989; No. 4,587,308 (Makita), issued May 6, 1986; No. 4,734,478 (Tsubakimoto), issued Mar. 29, 1988; No. 5,164,459 (Kimura et al.), issued Nov. 17, 1992, in German Patent Application 4,020,780 (Dahmen) published August 29, 1991, in European Patent Application 509,708 (Gartner, published October 21, 1992), all of said documents being cited for comparison. For cationic absorbent polymers, suitable di- or polyfunctional crosslinkers include di / polyhaloalkanes, di / poly epoxides, di / poly acid chlorides, di / polyosyl alkanes, di / polyaldehydes, di / poly acids and the like.

C. Methods of testing

1. PUP capacity

This assay is based on the method described in U.S. Pat. No. 5,599,335 issued to Goldman et al. on Feb. 4, 1997. The assay determines the amount of synthetic urine solution absorbed by absorbent polymers (including mixed ion exchange absorbent polymers) that are transversely mounted in a piston / cylinder assembly under a pressure of 4.8 or under a pressure of 9.6 kPa. The aim of this test is to determine the ability of an absorbent polymer to absorb body fluids after a period of time comparable to the use (overnight) of articles comprising a blend of absorbent polymer (ie, 1,21,4, 8,16 hours), with the polymers present in the absorbent element. in high concentration and are exposed to operating pressure. The operating pressure against which the absorbent polymers are forced to absorb fluids includes mechanical pressures generated by the weight and / or movement of the user, mechanical pressures from the resilient and fastening system, and hydrostatic desorption pressures of adjacent layers and / or elements.

The test fluid for the PUP capacity test is a synthetic urine solution. The fluid is absorbed by the absorbent polymer under the desired absorption conditions and under near-zero hydrostatic pressure.

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A suitable apparatus for this test is shown in Figure 1. At one end of the apparatus is a tank 712 (as a petri dish) with a lid 714. The tank 712 rests on an analytical balance 716. At the other end of the apparatus 710 is a fry funnel 718. a piston / cylinder assembly 720 that fits into the funnel; and a cylindrical fried funnel lid 722 that closely covers the funnel 718, which is open at the bottom and closed at the bottom, where a small hole is formed at the top. The device 710 includes a system for guiding the fluid in all directions, consisting of a section of glass tubes 724 and 731a of a flexible plastic pipe 731b (1/4 inch and 3/8 inch trademark Tygon pipe), a cock assembly 726 and 738, and Teflon connectors ® 748, 750 and 752, which connect glass tubes 724, 731 and tap assembly 726, 738. The tap assembly 726 consists of a three-way valve 728, glass capillary tube 730, 734 located in the main fluid system, and a glass capillary tube section 732 Similarly, the cock assembly 738 includes a three-way valve 740, glass capillary tubes 742 and 746 in the main fluid conduit, and a section of glass capillary tubes 744 that serve to drain fluids from the system. .

The assembly 720 shown in FIG. 1 consists of a cylinder 754, a cup-shaped piston 756, and a weight 758 disposed within the piston 756. A cylinder 759 of stainless steel 400, which is expanded in collection, is secured to the bottom of cylinder 754. two axes before mounting.

A blend of absorbent polymer 760 is placed on the mesh 759. The cylinder 754 is formed by drilling a transparent Lexan ® rod (or equivalent) to an inside diameter of 6.0 cm (28.27 cm ² ) with a cylinder wall thickness of approximately 5 mm and the cylinder height is approximately 5 cm. The piston 756 has the shape of a Teflon® or Kel-F® cup and is machined to fit precisely into the cylinder 754, with a gap between the cylinder and the piston ranging from 0.114 to 0.191 mm. The stainless steel cylindrical weight 758 is designed to fit snugly into the piston 756 and is provided with a handle at the top for easy removal from the piston. To achieve a pressure of 4.8 kPa, the combined weight of the piston 756 and the weight 758 is 1390 g, which corresponds to a pressure of 9.6 kPa over an area of 28.27 cm ² . To achieve a pressure of 9.6 kPa, the combined weight is 2780 g.

The components of the device 710 have a dimension such that the synthetic urine flow rate of the fryer disc of the fryer funnel 718, at a hydrostatic height of 10 cm, is 36 g / hr / cm ² . Factors that significantly affect flow include the throughput of the fryer in the fryer funnel 718, as well as the inner diameters of the glass tubes 724,730, 734, 742 and 731a, and the tap valves 728 and 740.

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The tank 712 is placed on an analytical balance 716 (with an accuracy of 0.01 g and a displacement of less than 0.1 g / h). The balance is connected to a computer that has software that can: i) monitor weight changes at predetermined intervals from the start of the PUP test; ii) set automatic data collection initialization at 0.01 - 0.05 g changes, depending on the sensitivity of the balance. The tube 724 entering the tank 712 should not touch the bottom of the tank or the lid 714. The volume of fluid in the tank 712 should be large enough to prevent air from entering into the tube 724. The fluid level in reservoir 712 should be 2 mm below the top surface of the fryer funnel 718 at the start of the measurement. This can be done by placing a small amount of drops on the fritted disk while gravitationally monitoring the flow of that fluid back into reservoir 712. it should not change substantially when the piston / cylinder assembly 720 is located inside the funnel 718. The reservoir 712 should have a sufficiently large diameter (about 14 cm), removing about 40 mL of fluid would result in a level change of less than 3 mm.

Prior to measurement, the assembly is filled with a synthetic urine solution and the fried funnel disk is rinsed so that it is filled with fresh synthetic urine solution. As far as possible, bubbles are removed from the bottom surface of the fryer and the funnel-to-tank system. The following procedures are performed using three-way tap sequencing operations:

1. Remove excess fluid on the upper surface of the fryer from fryer funnel 718.

2. Adjust the height / weight of solution in tank 712 to the correct level / value.

3. Fry funnel 718 is positioned at the correct height relative to the tank.

4. Cover fryed funnel 718 with cover of fryed funnel 722.

5. The tank 712 and the deep-fried funnel 718 are balanced by the valves 728 and 740 of the faucet assembly 726 and 738 in the open state.

6. Valves 728 and 740 close.

7. The valve 740 is rotated so that the funnel opens toward the drain pipe 744.

8. The system is allowed to balance in this position after 5 min.

9. Valve 740 returns to the closed position.

Steps 7-9 temporarily dry the surface of the fryer funnel 718 by allowing a small hydrostatic suction of -5 cm. This suction takes place when the open end of the tube 744 is 5 cm below the level of the fryer in the fryer funnel 718 and is filled with synthetic urine. Typically, 0.2 g of fluid is drained from the system during this procedure. This procedure prevents premature absorption of synthetic urine when the assembly is in place

9

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99 the piston / cylinder 720 located inside the fryer funnel 718. The amount of fluid that flows from the fryer during the procedure (called the fryer funnel correction weight) is measured in the PUP test (see below) for 15 minutes without the piston / cylinder 720 assembly. the liquid drained from the fry funnel during the procedure is reabsorbed very quickly, at the start of the test. It is therefore necessary to subtract this correction weight from the weight of liquid removed from the tank during the PUP test (see below).

The absorbent polymer blend 760 is dried by suitable techniques, for example by drying under high vacuum, corresponding to temperature and sufficiently long to reduce the amount of moisture as determined by appropriate techniques, such as Karl Fischer titration, or thermogravimetric analysis where the moisture content should be less than 5%, preferably less than 3%. Approximately 0.9 g (W _ap ) of the dried absorbent polymer compound 760 (corresponding to a basis weight of 0.032 g / cm ² ) is added to the cylinder 754 and evenly distributed over said netting 759. Care is taken to prevent the absorbent polymer 760 from adhering to the inner walls of the cylinder 754. The piston 756 is inserted into the cylinder 754 and placed on the surface of the absorbent polymer 760, taking care to allow the piston to slide freely within the cylinder. The plunger can be rotated gently to help distribute the absorbent polymer. The piston / cylinder assembly 720 is placed on the top of the fritted portion of the funnel 718, the weight 758 is inserted into the piston 756, and the top of the funnel 718 is covered with the lid 722 of the fried funnel. Upon detection of a balanced condition, the test is started by opening valves 728 and 740, thereby connecting the funnel 718 to the tank 712. At automatic initiation, the data appears immediately when the funnel begins to absorb liquid again.

The weight of fluid remaining in tank 712 is recorded at certain time intervals throughout the duration of the test. The PUP capacity is calculated at any time t according to the following equation:

PUP capacity (g / g, t) = [W _r (t = 0) - Wf _c ] / W _ap , where W _r (t = 0) is the weight in grams of tank 712 before installation, W _r (t) is tank weight in grams after time t (1,2, 4, 8,16 hours), Wf _c is the frying funnel correction weight in grams (measured separately) and W _{and p} is the initial dry weight in grams of the absorbent polymer.

2. BBS test

This test determines the tear strength of the absorbent polymer blend. BBS represents the force (peak load in grams of force) required to rupture a layer of an absorbent polymer blend that swelled in synthetic urine solution according to procedures

-23 9 9 9 99 9 9 9 9 Specified in the Test Method chapter. BBS is a measure of the integrity of the layer of absorbent polymer blend in the swollen state.

A suitable apparatus for performing BBS measurements is shown in Figure 5. This apparatus includes an inner cylinder 270 that is used to deposit a layer of absorbent polymer 260, further comprising an outer cylinder 230. a Teflon flat bottom tray 240, a cover plate of the inner cylinder 220 and stainless steel 210. The inner cylinder is made by drilling a Lexan® transparent rod and has an inside diameter of 6.0 cm (28.27 cm ² ) and a wall thickness of about 0.5 cm and a height of about 1.5 cm. The outer cylinder 230 is also made by drilling a Lexan rod and has an inner diameter that is slightly larger than the outer diameter of the inner cylinder 270 so that the inner cylinder fits into the outer cylinder 230 where it can slide freely. The outer cylinder 230 has a wall thickness of about 0.5 cm and a height of about 1.0 cm. The bottom of the outer cylinder 230 is covered with a stainless steel mesh 400 that extends in the direction of the two axes prior to attachment to the bottom. war. The cover plate of the inner cylinder 220 is made of 0.8 cm thick glass plate having a weight of 500 g. The stainless steel weight is 1700 g.

This type of test uses a tensile tester with a test cell (available from Intelect-II-Std Tensile Tester manufactured by Thwing-Albert Instrument Co., Pennsylvania). According to FIG. 6, the apparatus comprises a load cell sensitive to the applied force 330, which is equipped with a polished ball-shaped probe 290, a movable crosshead 320, a stationary crosshead 310, a circular lower pressure plate 280 and an upper clamping pressure plate 300. The lower clamping pressure plate 280 is mounted on a stationary crosshead 310. Both pressure plates 280, 300 have a diameter of 115 mm. 2.9 mm thick and a circular hole 18.65 mm in diameter. The stainless steel ball-shaped probe 290 has a diameter of 15.84 mm. During the BBS test procedure, the movable crosshead 320 moves upward, resulting in the probe 290 touching the sample 260 and then penetrating the sample. If the probe penetrates the specimen, the test is considered complete and the relevant data recorded.

The sampling device shown in FIG. 5 shows that the inner cylinder 270 is inserted into the outer cylinder 230. A sample of the 1.0 g absorbent polymer blend is loaded into the inner cylinder 270 where it is uniformly dispersed on 400 stainless steel mesh 250. Assembled the absorbent polymer rolls are transferred to a lower Teflon flat tray 240, and the inner cylindrical neck plate is placed on the inner cylinder 270. 30.0 ml of synthetic urine solution is poured into the flat Teflon tray 240. The synthetic urine solution passes through a stainless steel screen and is absorbed by the absorbent polymer mixture 260. A stainless steel weight 210 is placed on the cover plate of the inner cylinder 220, five minutes after the addition of the fluid. After

For the next 25 minutes the weight 210 is removed and the cover plate of the inner cylinder 220 is removed. For the entire procedure to be valid, the entire amount of the synthetic urine solution, after this time, must be absorbed by the absorbent polymer mixture. The inner cylinder 270 with the swollen absorbent polymer layer 260 is immediately transferred to a BBS measurement tester.

In the test apparatus shown in FIG. 6, the inner cylinder 270 with the swollen absorbent polymer layer 260 is centrally located on the lower clamping pressure plate 280 and is pneumatically coupled to the upper clamping pressure plate 300. The measurement is performed at a burst sensitivity of 10.00 g and test speed. 12.7 cm / min. The measurement is started with the crosshead 320 moving upwards until the polished stainless steel spherical probe 290 has penetrated the gel layer of absorbent material 260. Once the tear is registered, the moving crosshead 320 returns to its starting position. The bulletin board is expressed as peak load per grammile. The average of the three measurements is given as the BBS for the absorbent polymer blend.

3. Conductivity of salt solution (SFC)

The permeability and porosity indication is measured by conductivity of the saline gel base solution as described in U.S. Pat. No. 5,562,646 (Goldman et al.), issued Oct. 8, 1996. This method is modified for absorbent polymer systems having a mixed ion exchange base, as will be described later.

It is believed that the absorbent polymer sample, with a mixed ion exchange base, continues to ion exchange from the saline solution during the SFC measurement. Finally, the ion exchange capacity of the absorbent polymer is exceeded and the ionic strength of the solution surrounding the swollen polymer increases, resulting in some reduction in the swelling of the gel base. The amount of fluid ejected from the gel due to the reduction in swelling is small compared to the amount of fluid flowing through the gel base during the SFC measurement. Since the final thickness of the gel base is substantially smaller than the initial thickness, the final thickness of the gel base is used to calculate the SFC values. Using the final gel base thickness values in the calculation, it provides the minimum SFC values achieved in the measurement.

Although SFC is not a direct porosity measurement, the high liquid permeability of a particulate absorbent polymer system also requires a high degree of porosity. Thus, the relatively high SFC value of the blend of absorbent polymers with a mixed ion exchange base also indicates a relatively high level of porosity.

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D. Absorption elements

The absorbent elements of the present invention include the previously described blends of absorbent polymers, with or without other optional components, such as fibers, thermoplastic materials, and the like. Preferred materials are described in detail in paragraph 23, line 13 to paragraph 29, line 16 of U.S. Pat. No. 5,562,646 (Goldman et al.). These absorbent elements including these absorbent polymers can function as fluid storage elements in the absorbent core. The basic function of such fluid storage elements is to absorb liquid body exudates, either directly or from other absorbent elements (from elements that receive and distribute the fluid), and to retain them even when pressures are induced by the user's movements. It will be appreciated that absorbent elements comprising such absorbent polymer may have functions other than fluid retention.

In a preferred embodiment, the absorbent elements of the present invention comprise one or more regions with a relatively high concentration of these absorbent polymers. In order to provide relatively thin absorbent articles capable of absorbing and retaining large amounts of body fluids, it is desirable to maximize the level of these absorbent polymers and to minimize the level of other components, particularly fibrous components.

In order to maintain these absorbent polymers at a high concentration, it is important that the polymers have a relatively high absorbent capacity under relatively high pressure (PUP) and a high pressure permeability (SFC). This is because the polymer, when swollen in the presence of a fluid, provides adequate ability to receive body fluids, transport them through zones or layers, with relatively high gel concentration, to and / or retain other areas of the absorbent element and / or absorbent core. .

When measuring the concentration of the absorbent polymer mixture in a given region of the absorbent element, the weight percent of the absorbent polymer relative to the combined weight of the absorbent polymer and other components (fibers, thermoplastic material, etc.) present in the absorbent region. The concentration of the absorbent polymer composition in the region of the absorbent element of the present invention has a value in the range of from 40 to 100%, or from 90 to 100%. In general, the higher the concentration of the absorbent polymer, the thinner the absorbent element and the less bulky it is.

E. Absorbent cores and absorbent articles

The absorbent polymer compositions of the present invention can be used as a conventional absorbent polymer in any absorbent core and / or absorbent article which is

Or · · · · ♦ * "and ZO ^w ·« ··· «* • ** ♦ ·····" ···· ·· ·· ·· · ♦ * used for the absorption of body fluids, such as this is described in US Patent 5,562,646 (Goldman et al). This patent details the absorbent cores in paragraph 52. line 24, as well as absorbent articles in paragraph 52, line 25 to paragraph 54, line 9. Such articles include diapers, articles used in menstruation and / or incontinence articles for adults. By replacing conventional absorbent polymers with absorbent polymers having a mixed ion exchange basis of equal weight, products with increased absorbent capacity can be obtained. Alternatively, the low weight absorbent polymer may be replaced without increasing the absorbent capacity of the article, but a lighter, thinner and less bulky article may be obtained.

The inclusion of the absorbent polymer of the present invention in any of the products described herein will be apparent to those skilled in the art. Such products are characterized by features such as breathability of the backsheet, hook / loop fasteners, two-component fiber matrix, and the like.

Absorbent articles may include absorbent polymer blends described and disclosed, for example, in U.S. Pat. No. 3,224,926 (Bemardin), issued Dec. 21, 1965; No. 3,440,135 to Chung, issued Apr. 22, 1969; No. 3,932,209 (Chatteijee), issued Jan. 13, 1976; No. 4,035,147, Sangenis et al., issued Jul. 12, 1977. Preferred reinforced fibers are disclosed in U.S. Pat. No. 4,822,453 (Dean et al.), issued Apr. 18, 1989; No. 4,888,093 (Dean et al.), issued December 19, 1989; U.S. Patent 5,137,537 (Herrow et al.), issued April 11, 1992; U.S. Patent 4,818,598 (Wong), issued April 4, 1989; (Goldman et al.), Issued Oct. 8, 1996, U.S. Pat. No. 5,217,445 (Young et al.), Issued June 8, 1993, U.S. Pat. No. 5,360,420 (Lash et al.), U.S. Patent Application Serial No. 08 / 153,739 (Dragoo). et al., filed Nov. 16, 1993, in the US No. 08 / 164,049 (Dragoo et al.), filed Dec. 8, 1993, U.S. Pat. No. 4,260,443 (Lindsay et al.), U.S. Pat. No. 4,467,012 (Pedersen et al.), issued August 21, 1984, U.S. Pat. No. 4,715,918 (Lang), issued December 29, 1987; U.S. Pat. No. 4,851,069 (Packard et al.), Issued July 25, 1989; U.S. Pat. No. 4,950,264 (Osborn), issued August 21, 1990; U.S. Pat. February 19, 1991, US Pat. No. 5,009,650 (Bernardin), issued April 23, 1991, US Patent (Osborn), issued April 23, 1991, US Pat. No. 5,128,082 (Makoui), issued July 7, 1992, US Patent 5,149,335 (Kellenberger et al.), Issued Sep. 22, 1992, U.S. Pat. No. 5,176,668 (Bemardin), issued Jan. 5, 1993, U.S. Patent Application 141,156 (Richards et al.), Filed Oct. 21, 1993, U.S. Pat. No. 4,429,001 ( Kolpin et al., Issued Jan. 31, 1984, in US Patent Application 07 / 794,745

99

9

-279 «·«

9 9 • 9 9

9 9

9 Φ

9

99 (Aziz et al), filed Nov. 19, 1991, all of which are incorporated herein by reference.

F. Specific examples

A slightly crosslinked, partially neutralized absorbent polymer of poly (acrylic acid) with a relatively high PUP capacity (33 g / g at 4.8 kPa, 60 minutes) can be obtained from Chemdal Corporation of Palantine, Illinois (ASAP-2300 Group No. 426.152). (Similar samples to AS / PA-2300 are available from The Procter & Gamble CO., Paper Technology Division, Cincinnati, OH.) This material serves as a control and is referred to herein as a " control ".

A sample of the absorbent polymer that provides increased integrity to conventional polyacrylate absorbent polymers can be obtained from Nippon Shokubai (Group # TN37408). It is a polyacrylate with a polyethyleneimine treated surface. The polymer is described in detail in U.S. Pat. No. 5,382,610, filed Jan. 17, 1995. This material is herein referred to as " Sample ST ".

Example 1

Preparation of ion exchange absorption polymers

(i) Cation exchange absorbent polymer

When preparing a cation exchange absorbent polymer, a portion of the control sample is passed through a U.S.A standard 50 sieve to remove particles having a diameter greater than 300 µ. About 50 g of a sieved absorbent polymer with particles smaller than 300 μm is converted to an acid form by dissolving the polymer in a dilute hydrochloric acid solution prepared by adding about 46.5 g of concentrated HCl (Baker, 36.5-38% HCl). The suspension is gently stirred for about 1.5 hours, after which time the absorbent polymer is allowed to settle and the liquid is removed by centrifugation. The removed liquid is replaced with an equal portion of distilled deionized water, the suspension is stirred gently for about an hour, the absorbent polymer is allowed to settle and the liquid is removed again. The exchange process is repeated (about eight times) with equal volumes of distilled and deionized water until the pH of the water removed reaches 5-6. The exchange process is then repeated three times with isopropanol (VWR reagent class, West Chester, PA), three times with acetone (VWR reagent class), and once with anhydrous ether (reagent class EM Science, Gibbstown, NJ). layer of polytetrafluoroethylene and allowed to dry overnight. After gently agitating with a spatula, the product is dried under high vacuum for 96 hours at room temperature to remove any residual solvents. The sample is sieved

-28 through a U S20 mesh screen to remove any larger particles or agglomerates. Approximately 30 g of crosslinked absorbent polymer with ion exchange (acrylic acid) is obtained and stored in a dry atmosphere (PAA sample).

ii) Anion exchange absorbent polymer

A small polyethyleneimine having an average molecular weight of 750,000 g / mol was obtained with a 50% aqueous solution from Aldrich Chemical Co., Milwaukee, Wisconsin (Catalog No. 18,917-8, Part No. 12922PQ). 20 grams of this solution is further diluted with 37 grams of distilled water and stirred for 30 minutes in a 250 ml beaker to achieve complete dissolution. Ethylene glycol diglycidyl ether (50% solution) in an amount of 2.14 g is added to the polyethyleneimine solution, the resulting mixture is stirred at room temperature for about two minutes at oak and then placed in a ventilated oven at 65 ° C and left therein. about three hours. The result is a gel which is allowed to cool and then crushed into smaller pieces of about 1 to 5 mm in diameter. The mixture was transferred to a 4000 ml beaker containing two liters of distilled water and stirred overnight. Excess water is removed and the remaining sample is dried under high vacuum for about 96 hours to give a slightly cross-linked polyethyleneimine absorbent polymer with a mixed ion exchange base stored in a dry atmosphere (sample ΒΡΕΙ).

iii) An absorbent polymer with a mixed ion exchange base

The cross-linked anion exchange absorbent polymer (sample ΒΡΕΙ) is cooled to a low temperature and sieved in dry nitrogen. The individual particles of the size fraction are collected and sieved through a U.S. sieve. And standard 25, but not a U.S.A standard 70 (i.e., fractions with particle diameters ranging from 200 to 700 μ).

Mix approximately the same weight of the sieved crosslinked absorbent polymer by cation exchange poles (acrylic acid) (sample PAA) with the sieved crosslinked absorbent polymer anion exchange polyethyleneimine (sample aΕΙ) because of the uniform distribution of particles of both types of polymers in the blend. The resulting mixture comprises an absorbent polymer blend with a mixed ion exchange base (MB-1 sample) of the present invention.

iv) Measurement of PUP capacity

Approximately 0.9 g of the mixed ion exchange absorbent polymer (MB-1 sample) is transferred to a PUP cylinder (described in the "Test Method" section) and gently blended.

-299 · ♦ 9 4 9 · * 9 99 9 9 9 9

9

9 9 9 9 9 9 • 9 9 9 9

9 * 99 999 9 »99 extends over the entire screen area including the cylinder base. PUP capacities are determined on individual samples at 4.8 and 9.6 kPa pressure, with the amount of absorbed liquid measured at regular intervals for 16 hours. Measured PUP capacities at 4.8 and 9.6 kPa are shown as a function of time in Figures 3 and 4. Selected data values after 2.4, 8, and 16 hours are shown in Table 1.

Tab.l

PUP capacity of absorbent polymer blends

4,8 kPa 4 hours 4,8 kPa 4 hours 4,8 kPa 4 hours 9,6 kPa 2 hrs 9,6 kPa 8 hours 9,6 kPa 16 hrs Sample MB-1 44 / g 48 g / g 50 g / g 32 g / g 40 g / g 42 g / g Control pattern 33 g / g 33 g / g 33 g / g 20 g / g 20 g / g 20 g / g

Comparison of PUP capacities suggests that the mixed ion exchange absorbent polymer blends (sample MB-1) show an approximately 100% increase in PUP capacity at 9.6 kPa and an approximately 40% increase in PUP capacity at 4.8 kPa after 8 hours, due to the capacities of the partially neutralized absorbent polyacrylate polymers under analogous test conditions (control sample).

(v) Throughput measurement

Measurement of permeability and porosity indication provides the SFC gel base as described in U.S. Pat. No. 5,562,646 (Goldman et al.), issued Oct. 8, 1996. This method is modified for absorbent polymer systems having a mixed ion exchange base as described in (Methods of Testing), about 0.9 g of an absorbent polymer blend. with a mixed ion exchange base (MB-1 sample) is transferred to a salt conductivity (SFC) conducting cylinder, where it gently spreads over the entire surface area of the sieve including the cylinder base. titi

-30 • tititi

Tab.2

SFC values of absorbent polymer blends

SFC values Sample MB-1 ~ 68 x 10 cm ^{of 3} sec / g Control pattern ~ 10 x 10 ⁷ cm ³ sec / g

Comparison of SFCs indicates that the porosity and permeability of the mixed ion exchange absorbent polymer blend (MB-1 sample) is substantially greater than that of partially neutralized polyacrylate absorbent polymers (control sample) under analogous test conditions vi. ) Gel base integrity

The measurement of the integrity of the layer of the absorbent polymer blend in the swollen state is carried out by means of the BBS test as described above. The values of this BBS for the MB-1 sample, the ST sample, and the control sample are shown in Table 3

Tab.3

BBS values of an absorbent polymer blend with a mixed ion exchange base

BBS Sample MB-1 225 gf Sample Of ST 133 gf Control pattern 17 gf

Comparison of the BBS test values in Table 3 shows that the mixed ion-exchange absorbent polymer blend (MB-1 sample) exhibits a substantially increased gel layer integrity value compared to the partially neutralized acrylic absorbent polymer (control) and ST sample values. , under analogous test conditions.

φφφ

-31 ΦΦΦ ΦΦΦ · · · · φ • φ φ φ φ φ φ φ φ φ · ·

EXAMPLE 2 i) Cation Exchange Absorption Polymers

The cation exchange absorbent polymer is prepared as described in Example 1, section i), (sample PAA).

ii) Anion exchange absorbent polymer

a) Preparation of cross-linked polyallylamine

Polyallylamine hydrochloride with a nominal average molecular weight of 60,000 g / mol can be obtained from Polysciences, Inc. Warrington, Pennsylvania (catalog number 18378, part number 455913). A polyallylamine hydrochloride solution is prepared by dissolving 16.4 g of polymer in 165 ml of distilled water. 15.6 g of a 50% aqueous solution of sodium hydroxide are added dropwise with stirring. Ethylene glycol diglycidyl ether (50% solution), 2.0 g (Aldrich Chemical Co., Catalog No. E2,720-3, ref. No. E2,720-3) was added to the polyallylamine solution, with stirring for two minutes at room temperature. part, 07405DN), the resulting solution is placed in a ventilating oven at about 65 ° C and left there for about three hours. The resulting gel is crushed into smaller pieces of 5 mm diameter and transferred to a 4000 ml beaker containing a liter of distilled water. Mix gently and discard excess liquid. The remaining sample is dried under high vacuum at room temperature for about 96 hours to give a slightly cross-linked anion exchange polyallylamine absorbent polymer that is stored in a dry atmosphere.

(b) methylation of the ΡΑΑΜ sample

Formic acid (96% solution), 21.02 g (Aldrich Chemical Co., catalog no. 25.136-4), formaldehyde (37% solution), 36.56 g (Aldrich Chermical Co., catalog) were added to 800g of distilled water. Part No. 25,254-9, Part No. 04717TZ). 10 grams of cross-linked polyallylamine (PAAM sample) is added to said solution and the new mixture is placed in an oven at 70 ° C for 24 hours. The gel was drained and stirred overnight in 1000 ml of water to remove the extracts. The sludge solution is devoid of liquid, which is replaced with one liter of 1.7% aqueous sodium hydroxide solution to remove excess formic acid from the gel. The mixture is left to stand for about 24 hours and the polymer is freed of sludge liquid. The process is repeated (usually three times) with one liter of 1.7% aqueous sodium hydroxide solution until a pH of 13 is reached. The gel is treated by vacuum filtration and

-32 «φ φ 9 9 9 9 32 * 32 32 32 32 32 32 32 32 32 32 32 Soak 3000 ml of water overnight. Excess water is removed and the sample is dried under high vacuum at room temperature for about 96 hours to give a slightly cross-linked anion exchange tertiary polyallylamine absorption polymer that is stored in a dry atmosphere. NMR spectroscopic analysis indicated that approximately 90% of the amine groups in the polymer are methylated groups that form tertiary amine moieties (tPAAM sample).

iii) An absorbent polymer with a mixed ion exchange base

The cross-linked anion exchange tertiary-polyallylamine absorption polymer (t-PAAM sample) is frozen and sieved in a dry nitrogen atmosphere. A fraction of a certain particle size that passed the U.S.A Series Standard 25 but not the U.S.A. Series Standard 70 (that is, fractions with particles with a diameter in the range of 200 to 700 μ).

About 0.29 grams of a sieved crosslinked cation exchange poly (acrylic acid) absorbent polymer (sample of PAA) and 0.71 grams of a sieved crosslinked tertiary-polyallylamine absorbent polymer with anion exchange (t-PAAM sample) are blended and spread. The composition comprises an absorbent polymer with a mixed ion exchange base (MB-2 sample according to the present invention).

iv) Measurement of PUP capacity

Approximately 0.9 grams of the mixed ion exchange absorbent polymer blend (sample MB-2) is transferred to a PUP cylinder (as described in the "Test Methods" section) and gently spread over the entire area of the screen including the cylinder base. PUP capacities are determined for individual samples under a pressure of 4.8 and 9.6 kPa, measuring the amount of absorbed liquid at regular intervals and for 16 hours. The measured PUP capacitance values at 4.8 and 9.6 kPa are shown as a function of time in Figures 3 and 4.

Selected capacity values at 2.4, 8.16 hours are shown in Table 4

-33 · • f 33 33 33 33 33 33 33 33 33 ** 33 33 ** ** ** ** ** ** ** ** ** ** ** ** ** ** · ♦ »

Tab.4

PUP capacities for absorbent polymer blends

4,8 kPa 4 hours 4,8 kPa 8 hours 4,8 kPa 16 hrs 9,6 kPa 2 hrs 9,6 kPa 8 hours 9,6 kPa 16 hrs Sample MB-2 41 g / g 43 g / g 44 g / g 33 g / g 40 g / g 42 g / g Checklist sample 33 g / g 33 g / g 33 g / g 20 g / g 20 g / g 20 g / g

Comparison of PUP capacities shows that the mixed ion-exchange absorbent polymer blends (MB-2 sample) absorb significantly more synthetic urine solution than the partially neutralized polyacrylate absorbent polymer (control sample) under the test conditions already described.

Example 3

(i) Cation exchange absorbent polymer

The cation-exchange absorbent polymer is prepared as described in Example 1, section i), (sample PAA) ii) Anion-exchange absorbent polymer a) Preparation of a linear polyethyleneimine

Poly (2-ethyl-2-oxazoline) having a nominal average molecular weight of 500,000 g / mol can be obtained from Aldrich Chemical Co., Milwaukee, Wisconsin (Cat. No. 37,397-4, part no.

17223HB). 100 grams of the sample (2-ethyl-2-oxazoline) was dissolved in hydrochloric acid solution, which was prepared by mixing 1000 ml of water and 200 ml of concentrated hydrochloric acid. The solution was drained at 100 ° C for 72 hours and then cooled to room temperature. The product is obtained by settling the solution by adding 256 ml of a 50% sodium hydroxide solution dropwise with stirring. The white solid is vacuum filtered and washed with 5000 mL of water. The product is frozen and dried for 48 hours to give linear polyethyleneimine.

-34 «· • φ

9999

• 99 99 ΦΦ 99 ♦ · Φ Φ * 9 9 9 9 9 • 9 Φ 99 • · 9 Φ 9 999 Φ • · • Φ * »· 9 » 99 9 Φ • Φ

b) Preparation of cross-linked linear polyethyleneimine

5.0 grams of linear polyethyleneimine prepared as described above was dissolved in 50 ml of methanol. Ethylene glycol diglycidyl ether (50 solution), 0.5 g (Aldrich Chemical Co., Cat. No. E2,720-3, Part No. 07405DN) is added to the linear polyethyleneimine solution, stirred at room temperature for approximately two minutes, and then placed in a ventilated oven at about 65 ° C for three hours. The resulting gel was crushed to about 5 mm diameter and stirred gently in 500 ml of methanol overnight. The sample was drained, dried under high vacuum for about 48 hours to give a slightly cross-linked anion exchange polyethyleneimine absorbent polymer stored in a dry atmosphere (sample LPRI-1).

c) Partial methylation of the cross-linked polyethyleneimine

5.37 grams of linear polyethyleneimine are dissolved in 45 g of methanol. Ethylene glycol diglycidyl ether (50% solution), 1.07 grams (Aldrich Chemical Co., Cat. No. E2.7820-3, Part No. 07405 DN) is added to a linear polyethyleneimine solution while stirring at room temperature. at room temperature for about two minutes, then placed in a ventilated oven at about 65 ° C for three hours. The resulting gel was crushed to about 5 mm diameter and stirred overnight in 500 mL of methanol. The sample was drained and dried under high vacuum for 48 hours to give a slightly cross-linked anion exchange polyethyleneimine absorbent polymer stored in a dry atmosphere (sample LPEI-2).

Formic acid (96% solution), 48.44 grams ((Aldrich Chemical Co., cat. No. 25,136-4), formaldehyde (37% solution), 81.17 grams (Aldrich Chemical Co., cat. No. 25,254- 9) is added to 370.39 g of distilled water to give 500 grams of complete solution, 46.98 grams of this solution is added to 5.37 grams of cross-linked linear polyethyleneimine (sample LPEI-2). The gel was drained and stirred overnight in 2500 ml of water to remove the extracts. The supernatant was removed and replaced with 20 ml of 50% aqueous sodium hydroxide solution to remove the supernatant. The mixture is allowed to settle for about three hours, the polymer is freed from the supernate, and the process is repeated (approximately three times) with 20 ml of 50% aqueous sodium hydroxide until pH 13 is reached. vacuum filtration and soaked overnight at 1000 The supernatant liquid was removed and replaced with 500 mL of tetrahydrofuran. After 24 hours, tetrahydrofuran was removed and replaced with 500 mL of anhydrous ether. After 24 hours, ether was added

99 9 • 9 99 99 99 • 9 ·· • 9 9 O 9 9 9 «1 • • • • 99 « 9 9 9 9 9 • • 9 • 9 9 9 9 9 9 ···· ··· 9 « 99 49 99

discarded and the gel was dried under high vacuum at room temperature for 48 hours.

NMR product spectroscopic analysis of the product indicated that approximately 65% of the amine groups in the polymer were methylated to form tertiary amine moieties (sample NMEI-65).

iii) Absorbent polymers with a mixed ion exchange base

The crosslinked linear anion exchange polyethyleneimine and poly (N-methylethyleneimine) absorption polymers (LPEI-1 and NMEI-65 samples) are separately frozen and sieved in a dry nitrogen atmosphere. Fractions of individual size-sized materials are collected and passed through a U S A Senes Standard 25 sieve, but do not pass through a U.S.A Series Standard 70 sieve (i.e., fractions with a particle diameter in the range of 200 to 700 μ).

Approximately one gram of each sieved crosslinked absorbent polymer (samples LPEI-1 and NMEI-65) are separately mixed with one gram sieved crosslinked absorbent polymer of poly (acrylic acid) with cation exchange (PAA sample) to distribute the particles of each type of polymer uniformly. the whole mixture. Each blend comprises an absorbent polymer blend with a mixed ion exchange base (MB-3a and MB-3b samples), according to the present invention.

iv) Measurement of PUP capacity

Approximately 0.9 grams of mixed ion exchange absorbent polymer blend (sample MB-3a and MB-3b) is transferred to separate PUP cylinders (as described in the "Test Methods" section) and finely distributed over the entire screen area including a cylinder base. PUP capacities are determined for individual samples at 4.8 kPa and 9.6 kPa pressures and absorbed fluid measurements at given intervals for 16 hours. Measured PUP capacities at 4.8 and 9.6 kPa are shown as a function of time in Figures 3 and 4. Selected values of PUP capacities at 4, 8 and 16 hours are shown in Table 5.

Tab.5

PUP capacity of ion exchange absorbent polymer

4,8 kPa 4,8 kPa 4,8 kPa 9,6 kPa 9,6 kPa Sample MB-3a - - - 32 37 Sample MB-3b 39 g / g 42 g / g 43 g / g - - Check pattern. 33 g / g 33 g / g 33 g / g 20 g / g 20 g / g

Comparison of PUP capacitance values suggests that mixed ion exchange absorbent polymer blends (sample MB-3a and MB-3b) absorb significantly more synthetic urine solution than partially neutralized polyacrylate absorbent polymer (control sample) under the test conditions described previously .

Example 4

Preparation of ion exchange absorption polymers

(i) Cation exchange absorbent polymers

Homogeneously crosslinked poly (acrylic acid) is synthesized by placing 24.03 grams of acrylic acid monomer (Aldrich Chemical Co., Cat. No. 14,723-0, Part No. 10115JC) in a clean 250 ml resin kettle. Ν, Ν'-methylenebisacrylamide (Aldrich Chemical CO., Cat. No. 14,607-2, part number 0762EQ), 077 g and 2,2'-Azobis (2-amidinopropane) dihydrochloride (Wako, part number P2197) 0.093 grams is dissolved in 96 grams of water and added to the acrylic monomer in a resin kettle. The kettle was sealed and flushed with nitrogen for 15 minutes and then placed in an oven at 65 ° C for 16 hours.

The resulting gel was cooled and crushed into 1 to 5 mm pieces and dried under vacuum at 70 ° C for 16 hours. The sample is ground in a Wiley mill and passed through a U.S. sieve. A. 20 to obtain homogeneously crosslinked poly (acrylic acid) particles. The sample is further screened through a U.S.A Series Standard 25 screen but not through a U.S. screen. A Series Standard 70 (particle fraction with diameters ranging from approximately 212 to 710 μ) (PAA-2 sample).

ii) Anion exchange absorbent polymer

0.15 grams Span 40 (Ruger Chemical Co., Part No. W4250C12) is added to 200 mL of cyclohexane (Aldrich, Part No. LR00246KR) in a 500 mL resin kettle. The mixture was stirred for 30 minutes at 60 ° C to completely dissolve the mixture. Branched polyethyleneimine with a nominal average molecular weight of 750,000 g / mol is available as a 50% aqueous solution from Aldrich Chemical Co., Milwaukee, Wisonsin (Cat. No. 18,917-8, Part No. 12922PQ). 20 grams of this sample is further diluted with 30 grams of distilled water and further stirred for 30 minutes in a 250 ml beaker to dissolve the mixture completely. To the polyethyleneimine solution was added ethylene glycol diglycidyl ether (50% solution), 2.4 g (Aldrich Chemical Co., Cat. No. E2,720-3, Part No. 07405DN), and the mixture was stirred at room temperature for approximately one and then slowly add the cyclohexane solution while stirring. The mixture was stirred at 60 ° C for two hours. Excess cyclohexane is filtered off and the remaining beads are rinsed with 200 ml hot fresh cyclohexane. The beads are allowed to soak overnight •

300 ml distilled water. Excess water is then filtered off and the remaining beads are washed in 1000 ml of distilled water. The crosslinked polyethyleneimine beads are transferred to a 100 ml wide-necked flask, 0.005 grams of hydrophobic quartz (Sipemat D17, CAS No. 68611-44-9) is added and the mixture is shaken gently to distribute the silicon evenly throughout the mixture. The material is dried under high vacuum for about 96 hours to give slightly crosslinked polyethyleneimine beads of the absorbent polymer which are stored in a dry atmosphere. The material is sieved to obtain particles that pass through the US Series Standard 25 sieve but which do not pass through the US Series Standard 50 sieve (fractions with particle diameters ranging from approximately 300 to 700 μ in diameter) (BPEI-2 Sample) .

iii) An absorbent polymer with a mixed ion exchange base

Approximately equal weight amounts of screened and crosslinked cation exchange poly (acrylic acid) absorbent polymer particles (PAA-2 sample) and screened crosslinked anion exchange polyethyleneimine absorbent polymer particles (BPEI-2 sample) are mixed together to mix particles of both types of the polymer evenly dispersed throughout the mixture. The resulting mixture is a blend of an absorbent polymer with a mixed ion exchange base (MB-4 sample) of the present invention.

iv) Measurement of PUP capacity

Approximately 0.9 grams of mixed ion exchange absorbent polymer blend (MB-4 sample) is transferred to a PUP cylinder (described in the Test Methods section and gently spreads over the entire screen area including the cylinder base. PUP capacities are determined for each sample at a pressure of 4.8 kPa and 9.6 kPa by measuring the absorbed fluid at regular intervals for 16 hours.The measured PUP values at these pressures are given as a function of time in Figs. The PUP capacities at 2.4, 8 and 16 are shown in Table 6

Tab.6

PUP capacity of absorbent polymer blends

4,8 kPa 4 hours 4,8 kPa 8 hours 4,8 kPa 16 hrs 9,6 kPa 2 hrs 9,6 kPa 8 hours 9,6 kPa 16 hrs Sample MB-4 30 g / g 33 g / g 36 g / g 25 g / g 30 g / g 32 g / g Checklist sample 33 g / g 33 g / g 33 g / g 20 g / g 20 g / g 20 g / g

Comparison of PUP capacities shows that the mixed ion exchange absorbent polymer blend (MB-4 sample) shows an approximately 60% increase in PUP capacities at 9.6 kPa and approximately 9% at 4.8 kPa after 16 hours, against a partially neutralized polyacrylate absorbent polymer (control) under analogous testing conditions

(v) Throughput measurement

The permeability measurement and the porosity indication are performed using an SFC gel base as disclosed in U.S. Pat. No. 5,562,646 (Goldman et al.), issued Oct. 8, 1996. This method is modified for absorbent polymer systems having a mixed ion exchange base as described in the Test Methods section. Approximately 0.9 grams of the mixed ion exchange absorbent polymer blend (sample MB-4) is transferred to a SFC measuring cylinder where it gently spreads over the entire area of the sieve including the cylinder base. The SFC values are given in Tab. 7

Tab.7

SFC values of the absorbent polymer blend

SFC values Sample MB4 ~ 800 x 10 ⁷ cm ³ sec / g Checklist sample ~ 10 x 10 ⁷ cm ³ sec / g

Comparison of the SFC values indicates that the porosity and permeability values of the mixed ion exchange absorbent polymer blend (sample MB-4) are substantially higher than the partially neutralized polyacrylate absorbent polymer (control) values under analogous test conditions.

Claims (56)

PATENT CLAIMS An absorbent polymer composition having a PUP capacity (pressure behavior), a synthetic urine solution at a pressure of 4.8 kPa, at least 39 g / g after 4 hours and an SFC (saline conductivity) of at least 50 x 10 ⁷ cm ³ sec / g. The absorbent polymer composition of claim 1, wherein the composition has an SFC of at least 50 to 100 x 10 ^-7 cm ³ sec / g. An absorbent polymer composition according to claims 1 to 2 having a PUP capacity in the synthetic urine solution, at an applied pressure of 4.8 kPa and after 4 hours, of at least 41 g / g. An absorbent polymer composition according to any one of claims 1 to 3 having a PUP value in a synthetic urine solution at an applied pressure. 4.8 kPa and after 4 hours, at least 43 g / g. An absorbent polymer composition according to any one of claims 1 to 4 having a PUP value in the synthetic urine solution at the applied pressure. 4.8 kPa and after 4 hours in the range of 39 to 58 g / g. An absorbent polymer composition according to any one of claims 1 to 5 having a PUP value in the synthetic urine solution at the applied pressure. 4.8 kPa and after 4 hours in the range of 41 to 55 g / g. An absorbent polymer composition according to any one of claims 1 to 6 having a PUP capacity in the synthetic urine solution at a pressure of 4.8 kPa and after 4 hours in the range of 43 to 50 g / g. 8. The absorbent polymer composition has (i) a PUP value in the synthetic urine solution at an applied pressure of 4.8 kPa and at least 30 g / g after 4 hours; and (ii) a value of SFC of at least 500 x 10 ⁷ cm ³ sec / g. -41 · ···································· The absorbent polymer composition of claim 8, wherein the composition has an SFC of at least 500 x 10 ⁷ cm ³ sec / g. The absorbent polymer composition of claims 8 to 9, wherein the PUP capacity in the synthetic urine solution, at an applied pressure of 4.8 kPa, has a value of at least 35 g / g after 4 hours. The absorbent polymer composition of claims 8 to 10, wherein the PUP capacity in the synthetic urine solution, at an applied pressure of 4.8 kPa, has a value of at least 40 g / g after 4 hours. The absorbent polymer composition of claims 8 to 11, wherein the PUP capacity in the synthetic urine solution, at an applied pressure of 4.8 kPa, has a value in the range of 30 to 50 g / g after 4 hours. The absorbent polymer composition of claims 8 to 12, wherein the PUP capacity in the synthetic urine solution, at an applied pressure of 4.8 kPa, has a value in the range of 30 to 50 g / g after 4 hours. 14. The absorbent polymer composition has i) a PUP capacity in a synthetic urine solution, at an applied pressure of 4.8 kPa, has a value of at least 40 g / g and an SFC value of at least 50 x 10 ^-7 cm ³ sec / g after 8 hours. 15. The absorbent polymer composition of claim 14 wherein the composition has an SFC of at least about 50 to about 100 * 10 < ⁷ & gt ^; cm < ³ > sec / g. The absorbent polymer composition of claims 14 to 15, wherein the PUP capacity in the synthetic urine solution has a value of at least 42 g / g after 8 hours and at a pressure of 4.8 kPa. The absorbent polymer composition of claims 14 to 16, wherein the PUP capacity in the synthetic urine solution has a value of at least 44 g / g after 8 hours and at a pressure of 4.8 kPa. • • • -4218. Absorbent polymer composition according to claims 14 to 17, characterized in that the PUP capacity in the synthetic urine solution has a value in the range from 40 to 59 g / g after 8 hours and at a pressure of 4.8 kPa. 19. An absorbent polymer composition according to claim 14, wherein the PUP capacity in the synthetic urine solution has a value in the range of 42 to 57 g / g after 8 hours and at a pressure of 4.8 kPa. The absorbent polymer composition of claims 14 to 19, wherein the PUP capacity in the synthetic urine solution has a value in the range of 44 to 55 g / g after 8 hours and at a pressure of 4.8 kPa. 21. The absorbent polymer composition has i) a PUP capacity in a synthetic urine solution, at a pressure of 4.8 kPa, at least 42 g / g after 16 hours, and ii) an SFC value of at least 50 x 10 ^-7 cm ³ sec / g . 22. An absorbent polymer composition according to claim 21 wherein the composition has an SFC in the range of from about 50 to about 100 * 10 < ⁷ & gt ^; cm < ³ > sec / g. 23. The absorbent polymer composition of claims 21 to 22 having a PUP capacity of at least 44 g / g in a synthetic urine solution at a pressure of 4.8 kPa after 16 hours. 24. The absorbent polymer composition of claims 21 to 23 having a PUP capacity in the synthetic urine solution at a pressure of 4.8 kPa (16 psi) of at least 46 g / g after 16 hours. 25. An absorbent polymer composition according to claim 21 to 24 having a PUP capacity in a synthetic urine solution at a pressure of 4.8 kPa (16 to 50 psi) in the range of 42 to 61 g / g after 16 hours. 26. The absorbent polymer composition of claims 21 to 25 having a PUP capacity in a synthetic urine solution at an applied pressure of 4.8 kPa (16 psi) in the range of 44 to 59 g / g after 16 hours. 27. An absorbent polymer composition according to claim 21 to 26 having a PUP capacity in a synthetic urine solution at a pressure of 4.8 kPa at 16 to 57 g / g after 16 hours. An absorbent polymer composition according to claims 21 to 27 having a PUP capacity in a synthetic urine solution at a pressure of 4.8 kPa at a pressure of 48 to 54 g / g after 16 hours. 29. The absorbent polymer blend has a PUP value in the synthetic urine solution at a pressure of 9.6 kPa, at least 35 g / g after 4 hours, and ii) an SFC value of at least 50 x 10 ^-7 cm ³ sec / g. The absorbent polymer composition of claim 29, wherein the composition has an SFC of at least 50 x 10 ^-7 cm ³ sec / g. An absorbent polymer composition according to claims 29 to 30 having a PUP value after 4 hours in a synthetic urine solution at an applied pressure. 9.6 kPa, at least 36 g / g. An absorbent polymer composition according to claims 29 to 31 having a PUP capacity after 4 hours in a synthetic urine solution at an applied pressure. 9.6 kPa, at least 37 g / g. An absorbent polymer composition according to claims 29 to 32 having a PUP value after 4 hours in a synthetic urine solution at an applied pressure. 9.6 kPa, ranging from 35 to 50 g / g. 34. An absorbent polymer composition according to claim 29 to 33 having a PUP value after 4 hours in a synthetic urine solution at an applied pressure. 9.6 kPa, ranging from 36 to 45 g / g. -44 • 4 9 9 ·· ··· · 4 · * 4 · 4 44 4 4 4 4 4 · 4 4 4 4 4 9 9 4 4 4 9 9 4 9 9 4 4444 494 ·· ·· · «·· 35. An absorbent polymer composition according to any one of claims 29 to 34 having a PUP capacity in a synthetic urine solution after 4 hours at the applied pressure. 9.6 kPa, in the range of 37 to 42 g / g. 36. The absorbent polymer composition has (i) at 4 hours a PUP value in the synthetic urine solution at an applied pressure of 9.6 kPa of at least 27 g / g and (ii) an SFC value of at least 500 χ 10 ' ⁷ cm ³ sec / g. 37. The mixture of absorbent polymer according to claim 36, wherein the composition has an SFC value of at least between 500-1100 χ 10 ^"7 cm ³ sec / g. 38. An absorbent polymer composition according to claim 36 to 37 having a PUP capacity in a synthetic urine solution after 4 hours at the applied pressure. 9.6 kPa, at least 33 g / g. 39. An absorbent polymer composition according to claim 36 to 38 having a PUP value after 4 hours in a synthetic urine solution at an applied pressure. 9.6 kPa, at least 47 g / g. 40. An absorbent polymer composition according to claim 36 to 39 having a PUP capacity after 4 hours in a synthetic urine solution at an applied pressure. 9.6 kPa, ranging from 27 to 47 g / g. 41. An absorbent polymer composition according to claim 36 to 40 having a PUP capacity in a synthetic urine solution after 4 hours at the applied pressure. 9.6 kPa, ranging from 33 to 42 g / g. 42. The absorbent polymer blend has (i) a PUP capacity in a synthetic urine solution of at least 36 g / g at an applied pressure of 9.6 kPa after 8 hours; and (ii) an SFC of at least 50 χ 10 ' ⁷ cm ³ sec / g. 43. The absorbent polymer composition of claim 42, wherein the composition has an SFC in the range of from about 50 to about 100 cm < ⁷ & gt ^; cm ³ sec / g. -459 * 999 · 99999 9 · 9 9 9 9 9 9999 9 9 9999 99 * 9 9 9 9 9999 9999 999 99 99 99 99 44. An absorbent polymer composition as claimed in claim 42 to 43 having a PUP value after 8 hours in a synthetic urine solution at an applied pressure. 9.6 kPa, at least 38 g / g. 45. An absorbent polymer composition according to claim 42 to 44 having a PUP value after 8 hours in a synthetic urine solution at an applied pressure. 9.6 kPa, at least 40 g / g. 46. An absorbent polymer composition according to any one of claims 42 to 45 having a PUP value after 8 hours in a synthetic urine solution at an applied pressure. 9.6 kPa, ranging from 36 to 54 g / g. 47. An absorbent polymer composition according to claim 42 to 46 having a PUP value after 4 hours in a synthetic urine solution at an applied pressure. 9.6 kPa, in the range of 38 to 50 g / g. 48. An absorbent polymer composition according to any one of claims 42 to 47 having a PUP capacity in a synthetic urine solution after 4 hours at the applied pressure. 9.6 kPa, in the range of 40 to 46 g / g. 49. The absorbent polymer composition has (i) at least 37 g / g after 16 hours of PUP capacity in the synthetic urine solution at an applied pressure of 9.6 kPa and (ii) an SFC of at least 50 x 10 < ⁷ & gt ^; cm ³ sec / g. 50. The absorbent polymer composition of claim 49, wherein the composition has an SFC in the range of 50 to 100 * 10 < ⁷ & gt ^; cm < ³ > sec / g. 51. The absorbent polymer composition of claims 49 to 50 having a PUP capacity in the synthetic urine solution at a pressure of 9.6 kPa (16 psi) of at least 39 g / g after 16 hours. 52. The absorbent polymer composition of claim 49-51 having a PUP capacity in the synthetic urine solution at a pressure of 9.6 kPa (16 psi) of at least 41 g / g after 16 hours. -46 ♦ · 0 00 00 00 00 0 000 0 00 0 0 0 0 0 0 0 00 00 0000 0 0 00 00 000 000 0 0 0 0000 0000 000 000 00 00 00 00 00 53. The absorbent polymer blend of claims 49-52, having a PUP capacity in a synthetic urine solution at a pressure of 9.6 kPa (16 psi) in the range of from about 37 to about 16 hours. 56 g / g. 54. The absorbent polymer composition of claims 49-53 having a PUP capacity in a synthetic urine solution at a pressure of 9.6 kPa at 16-5 g / g after 16 hours. 55. An absorbent polymer composition according to claim 49-54 having a PUP capacity in a synthetic urine solution at a pressure of 9.6 kPa (16 psi) in the range of 41 to 48 g / g after 16 hours. The absorbent element for retaining aqueous body exudates comprises at least one absorbent polymer region according to any one of claims 1-55. An absorbent article comprising a liquid pervious topsheet, a backsheet, and an absorbent core positioned between the topsheet and the backsheet is characterized in that the absorbent core comprises an absorbent element according to any one of claims 1-56.