TW201609892A - Superabsorbent polymer having fast absorption - Google Patents

Abstract

The present invention relates to a particulate superabsorbent polymer composition having fast absorption and a method of making the particulate superabsorbent polymer comprising a monomer solution comprising a foaming agent and a mixture of a lipophile surfactant and a polyethoxylated hydrophilic surfactant wherein the particulate superabsorbent polymer composition has a mean particle size distribution of from 300 to 500 [mu]m and a vortex time of 30 to 60 seconds. The present invention further includes particulate superabsorbent polymer compositions surface treated with other components. The present invention further includes absorbent cores and articles including the particulate superabsorbent polymer compositions.

Description

Superabsorbent polymer with fast absorption

The present invention relates to superabsorbent polymers that absorb water, aqueous liquids, and blood, wherein the superabsorbent polymers of the present invention have rapid absorption. The invention also relates to the preparation of such fast-absorbing superabsorbent polymers and their use as absorbents in sanitary articles.

Superabsorbent polymer generally refers to a water-swellable, water-insoluble polymer or material capable of absorbing at least about 10 times its weight and up to about 30 times its weight in an aqueous solution containing 0.9% by weight of sodium chloride in water or More than 30 times. Examples of superabsorbent polymers may include a partially neutralized crosslinked acrylate polymer capable of retaining an aqueous liquid under pressure, and a superabsorbent polymer hydrogel formed by polymerization, according to the general definition of superabsorbent polymer, and A particulate superabsorbent polymer composition is formed.

The superabsorbent polymer hydrogel can be formed into particles, generally referred to as microparticle superabsorbent polymers, wherein the particulate superabsorbent polymer can be surface treated by surface crosslinking and other surface treatments, and crosslinked at the surface to form microparticle superabsorbent polymerization. The composition is then post-treated. The abbreviation SAP can be used in place of the superabsorbent polymer, superabsorbent polymer composition, particulate superabsorbent polymer composition, or variations thereof. In general, the particulate retention capacity (CRC) of such particulate superabsorbent polymer compositions is at least 25 grams of 0.9 weight percent aqueous sodium chloride solution per gram of the polymer. The particulate superabsorbent polymer composition is also designed to rapidly absorb body fluids, which require high gelation Bed permeability (GBP).

Commercially available particulate superabsorbent polymer compositions are widely used in a variety of personal care products such as baby diapers, child training pants, adult incontinence products, feminine care products, and the like.

The rate of absorption and speed increase to one aspect of the superabsorbent polymer. The addition of a blowing agent such as sodium carbonate or sodium bicarbonate to the superabsorbent polymer prior to polymerization has been disclosed as a means of increasing the rate of absorption of the superabsorbent polymer. The use of a blowing agent produces a method of pyrolysis to form bubbles in a superabsorbent polymer and relies on the heat generated by the polymerization to initiate foaming. This foaming method has problems such as a large change in volume caused by the polymerization process, making it difficult to control and produce a polymer which lacks a homogeneous quality and a particularly high content of water-insoluble components, and the resulting foam lacks pore diameter and distribution. The stability of the absorption is now fully controlled.

When the method is carried out by using an azo-based polymerization initiator, the amount of the initiator is generally increased to form bubbles in an amount sufficient to improve the absorption rate, and thus the content of the water-soluble component in the produced polymer tends to increase. . In addition, similar to the method using a blowing agent, the method using an azo-based polymerization initiator has a problem that the polymerization process will cause a large change in volume and thus will make the distribution of pore particles and bubbles not easily controlled.

When this method is carried out in the presence of a dispersion of a water-insoluble blowing agent such as a volatile organic compound, although the polymerization can achieve relative stability, since the polymerization is due to the use of volatile organic compounds and the volatile organic compounds used are discharged from the system. And because of the need for special equipment for safety reasons, this method causes severe energy waste, proves to be expensive, and lacks practical availability.

However, the inadequacy of these particulate superabsorbent polymers is always at no load. Under- and under-loading exhibits insufficient absorption speeds, making it difficult to dry, being burdened by large loads during pulverization, lacking pore diameter uniformity, and having a large content of water-soluble components.

Accordingly, it is an object of the present invention to provide a particulate superabsorbent polymer capable of rapidly absorbing water and a method of producing the same. Accordingly, it is an object of the present invention to provide a superabsorbent polymer that exhibits an increase in water absorption rate and maintains excellent characteristics. The present invention has achieved a foam which allows uniform bubble distribution, a water absorbing resin which permits rapid absorption of water, and a method for producing the same.

The present invention relates to a superabsorbent polymer comprising a blowing agent, a lipophilic nonionic surfactant, and a polyethoxylated hydrophilic nonionic surfactant, wherein the particulate superabsorbent polymer has from 30 seconds to 60 seconds The vortex time.

The invention also relates to a particulate superabsorbent polymer comprising from about 0.05 wt.% to about 2.0 wt.% of a blowing agent and from about 0.001 wt.% to about 1.0 wt.% of a lipophilic surfactant and polyethylene An internal crosslinked structure of an oxygenated hydrophilic surfactant mixture having a surface which has been subjected to a crosslinking treatment to crosslink the surface, the particulate superabsorbent polymer having a vortex time of 30 seconds to 60 seconds.

The present invention also relates to a process for producing a superabsorbent polymer having a rapid water absorption comprising the following steps a) preparing a monomer aqueous solution containing a mixture of a monomer of a polymerizable unsaturated acid group and an internal crosslinking agent monomer, wherein The aqueous monomer solution comprises dissolved oxygen; b) bubbling the aqueous monomer solution of step a), comprising adding an inert gas to the aqueous monomer solution of step a) to displace the dissolved oxygen of the aqueous monomer solution; c) making step b) Polymerization of monomer aqueous solution, including the following steps C1) adding to the aqueous monomer solution of step a): i) an aqueous solution containing from about 0.05 wt.% to about 2.0 wt.% of the blowing agent based on the total amount of the monomer solution containing the polymerizable unsaturated acid group. And ii) comprising from about 0.001 wt.% to about 1.0 wt.% of the lipophilic surfactant and the polyethoxylated hydrophilic surfactant, based on the total amount of the monomer solution containing the polymerizable unsaturated acid group. An aqueous solution of the mixture; c2) treating the monomer solution of step c1) with high-speed shear mixing to form a treated monomer solution, wherein component i) comprises from about 0.05 wt.% to about 2.0 wt.% of the foam. And an aqueous solution comprising ii. And then adding to the aqueous monomer solution before the high-speed shear mixing of the aqueous monomer solution in step c2); c3) forming a hydrogel by adding a polymerization initiator to the treated monomer solution of step c2), wherein the initiation The agent is added to the treated monomer solution after the blowing agent and the surfactant mixture, wherein the polymer is formed To include the bubbles of the blowing agent in the polymer structure; and d) to dry and grind the hydrogel of step c) to form a particulate superabsorbent polymer; and e) to superimpose the particles of step d) with a surface crosslinking agent The surface of the absorbent polymer is crosslinked wherein the surface crosslinked superabsorbent polymer has a vortex time of from about 30 seconds to about 60 seconds.

In view of the foregoing, it is a feature and advantage of the present invention to provide a particulate superabsorbent polymer composition and a method of increasing the rate of particulate superabsorbent polymer composition. Many other features and advantages of the present invention will be apparent from the description.

10‧‧‧Products

20‧‧‧ Cover

22‧‧‧ body side liner

23‧‧‧ outer surface

24‧‧‧Absorbent core

25‧‧‧Back waist area

26‧‧‧Flexible components

27‧‧‧Back waist area

28‧‧‧Flexible components

29‧‧‧裆区

30‧‧‧ fastening members

34‧‧‧ Surge management

36‧‧‧ longitudinal direction

38‧‧‧ transverse direction

400‧‧‧AUL assembly

410‧‧‧Particle superabsorbent polymer composition

412‧‧‧Cylinder

414‧‧400 mesh stainless steel wire cloth

416‧‧‧Piston

418‧‧ ‧ weight

420‧‧‧Plastic tray

422‧‧‧Saline

424‧‧‧Frit

426‧‧‧ filter paper

500‧‧‧ equipment

528‧‧‧Test equipment assembly

530‧‧‧ sample container

534‧‧‧Cylinder

534a‧‧‧Area

536‧‧‧Plunger

538‧‧‧ shaft

540‧‧‧o ring

544‧‧‧ hole

548‧‧‧ ring weight

548a‧‧‧through hole

550‧‧‧ end

554‧‧‧ hole

560‧‧‧ hole

562‧‧‧ shaft hole

564‧‧100 mesh stainless steel screen

566‧‧400 mesh stainless steel screen

568‧‧‧ gel particle sample

600‧‧‧堰

601‧‧‧Separation collection device

602‧‧ ‧ balance

603‧‧‧ beaker

604‧‧ metering pump

Figure 1 is a side view of a test apparatus for free swelling gel bed permeability test; Figure 2 is a cross-sectional side view of the cylinder/cup assembly used in the free swell gel bed permeability test apparatus shown in Figure 1; Figure 3 is a free swell gel bed permeability test shown in Figure 1. A top view of the plunger used in the apparatus; FIG. 4 is a side view of the test apparatus for the absorption test under load; and FIG. 5 representatively shows a top plan view of a partially cutaway view of the absorbent article in a stretched and laid-back state, Where the surface of the article contacting the wearer's skin faces the viewer;

definition

Within the context of this specification, each of the following terms or phrases shall include the following meanings.

It should be noted that the terms "comprises,comprising" and other derivatives derived from the root term "comprise" are intended to be open-ended terms when used in the present invention, which recite any of the described features, elements, The integers, steps or components are not intended to exclude the presence or addition of one or more other features, elements, integers, steps, components or groups thereof.

As used herein, the term "about" as used to modify the amount of the ingredients used in the compositions of the invention or in the method of the invention is a numerical deviation of the index value, which may occur, for example, via the following: in the real world for the manufacture of concentrated Typical measurements and liquid handling procedures for the use or use of the solution; unintentional errors in such procedures; manufacturing, source or purity differences through the ingredients used to make the composition or performing the method; and the like. The term also encompasses amounts that differ by the different equilibrium states of the compositions produced by the particular initial mixture. Whether or not modified by the term "about", the scope of the patent application includes the equivalent of the quantity.

The term "Centrifuge Retention Capacity (CRC)" as used herein refers to the ability of a particulate superabsorbent polymer to retain its liquid after saturation and centrifugation under controlled conditions, and is stated as being centrifuged as described herein. The grams of liquid (g/g) retained per gram of sample weight measured by the retention capacity test.

The term "crosslinked, cross-linking" or "crosslinker" as used herein refers to any means effective to render a generally water-soluble substance substantially insoluble in water but swellable in water. . Such cross-linking means may include, for example, physical entanglement, crystalline domains, covalent bonds, ion mismatches and associations, hydrophilic associations such as hydrogen bonding, hydrophobic associations or Van der Waals force. ).

The term "internal crosslinker" or "monomer crosslinker" as used herein refers to the use of a crosslinking agent in a monomer solution to form a polymer.

The term "dry particulate superabsorbent polymer composition" as used herein generally refers to a superabsorbent polymer composition having less than about 20% moisture.

The term "gel permeability" is a property of a cluster of particles as a whole and is related to the particle size distribution, the shape of the particles and the connectivity of the pores between the particles, the shear modulus, and the surface modification of the swollen gel. In fact, the gel permeability of the superabsorbent polymer composition is a measure of how fast the liquid flows through the swollen particle mass. Low gel permeability indicates that the liquid cannot easily flow through the superabsorbent polymer composition, which is commonly referred to as gel plugging, and any forced flow of the liquid (such as the second application of urine during use of the diaper) must be replaced Path (eg diaper leak).

The abbreviation "HLB" means a measure of the hydrophilic-lipophilic balance of a surfactant and is hydrophilic or lipophilic, as determined by calculations for different regions of the molecule. The HLB value can be used to predict the surfactant properties of the molecule, with HLB values < 10 being lipid soluble (insoluble in water) and HLB values > 10 being water soluble (insoluble in lipids).

The term "mass median particle size" of a given sample of superabsorbent polymer composition particles is defined as the particle size that divides the sample into two halves based on mass, ie one half of the sample by weight has a mass median greater than the mass median. The particle size, and one-and-a-half of the sample by mass has a particle size smaller than the mass median particle size. Thus, for example, if one-half of the sample by weight is greater than 2 microns, the superabsorbent polymer composition particle sample has a mass median particle size of 2 microns.

The term "moisture content" as used herein means the amount of water contained in the particulate superabsorbent polymer composition, as measured by the moisture content test.

The term "non-ionic surfactants" are surfactants that have no charge and that can greatly reduce the surface tension of water when used at very low concentrations. It is not ionized in aqueous solution because its hydrophilic group is non-dissociable.

When used in connection with the term "superabsorbent polymer", the terms "particle", "particulate" and the like mean the form of discrete units. The units may comprise flakes, fibers, agglomerates, granules, powders, spheres, powdered materials or the like, and combinations thereof. The particles may have any desired shape: for example, a cubic shape, a rod shape such as a polyhedron, a sphere or a hemisphere, a circle or a semicircle, an angle, an irregular shape, or the like.

The terms "particulate superabsorbent polymer" and "particulate superabsorbent polymer composition" By means of a superabsorbent polymer and a superabsorbent polymer composition in discrete form, wherein the "microparticle superabsorbent polymer" and "microparticle superabsorbent polymer composition" may have a particle size of less than 1000 μm or from about 150 μm to about 850 μm. .

The term "permeability" as used herein shall mean a measure of the effective connectivity of a porous structure (in this case, a crosslinked polymer), and may utilize the void fraction of the particulate superabsorbent polymer composition. Rate and connectivity are detailed.

The term "polymer" includes, but is not limited to, homopolymers, copolymers (e.g., block, graft, random, and alternating copolymers), terpolymers, and the like, and blends and variants thereof. Further, unless otherwise specifically limited, the term "polymer" shall include all possible configurational isomers of the substance. Such configurations include, but are not limited to, isotactic, syndiotactic, and non-linear symmetric structures.

The term "polyolefin" as used herein generally includes, but is not limited to, the following: such as polyethylene, polypropylene, polyisobutylene, polystyrene, ethylene-vinyl acetate copolymers, and the like, all of which are Polymers, copolymers, terpolymers, and the like, and blends and variants thereof. The term "polyolefin" shall include all possible structures including, but not limited to, isotactic, syndiotactic, and random symmetrical structures. Copolymers include both random and block copolymers.

The term "superabsorbent polymer" as used herein refers to a water-swellable, water-insoluble organic or inorganic material, including superabsorbent polymers and superabsorbent polymer compositions, which are contained in the most advantageous state. An aqueous solution of 0.9 weight percent sodium chloride can absorb at least about 10 times its weight or at least about 15 times its weight or at least about 25 times its weight.

The term "superabsorbent polymer composition" as used herein refers to a superabsorbent polymer comprising a surface additive according to the present invention.

The term "surface crosslinking" as used herein refers to the degree of functional crosslinking near the surface of the superabsorbent polymer particles, which is generally higher than the degree of functional crosslinking within the superabsorbent polymer particles. As used herein, "surface" describes the outward boundary of a particle.

The term "thermoplastic" as used herein describes a material that softens upon exposure to heat and substantially returns to a non-softened state upon cooling to room temperature.

The term "vortex time" measures 2 grams of SAP close to the amount of time (in seconds) required to vortex a 50 ml saline solution by stirring at 600 rpm on a magnetic stir plate. The time taken to approach the vortex is an indication of the free swelling rate of SAP.

The term "% by weight or % wt" as used herein and referring to components of the dried particulate superabsorbent polymer composition, unless otherwise specified herein, is to be construed as being based on the weight of the dry superabsorbent polymer composition.

These terms may be defined by other terms in the remainder of the specification, including the following embodiments.

Although a typical example of a specific example has been set forth for the purpose of illustration, it should not be construed as a limitation of the scope of the invention. Thus, various modifications, improvements and substitutions may be made by those skilled in the art without departing from the spirit and scope of the invention. By way of a hypothetical illustrative example, the scope of disclosures 1 through 5 in this specification will be considered to support any of the following ranges: 1-5; 1-4; 1-3; 1-2; 2-5; -4; 2-3; 3-5; 3-4; and 4-5.

In accordance with the present invention, a particulate superabsorbent polymer composition with rapid absorption can be achieved using the methods described herein. The invention further includes an absorbent article comprising a topsheet; a backsheet; and an absorbent core disposed between the topsheet and the backsheet, the absorbent core comprising the particulate superabsorbent polymer of the present invention Various specific examples of the composition of the composition.

The invention also relates to a particulate superabsorbent polymer comprising from about 0.05 wt.% to about 2.0 wt.% of a blowing agent and from about 0.001 wt.% to about 1.0 wt.% of a lipophilic surfactant within the particle. An internal crosslinked structure of a mixture with a polyethoxylated hydrophilic surfactant having a surface which has been subjected to a crosslinking treatment to crosslink the surface, the particulate superabsorbent polymer having a vortex time of 30 seconds to 60 seconds .

The invention also relates to a particulate superabsorbent polymer wherein the lipophilic surfactant has an HLB of 4 to 9 and the polyethoxylated hydrophilic surfactant has an HLB of 12 to 18; or wherein the lipophilic surfactant is combined with a mixture of ethoxylated hydrophilic surfactants having an HLB of 8 to 14; or wherein the lipophilic surfactant is a sorbitan ester and the polyethoxylated hydrophilic surfactant is a polyethoxylated dehydrated sorbent a sugar alcohol ester; or wherein the lipophilic surfactant is nonionic and the polyethoxylated hydrophilic surfactant is nonionic; or wherein the blowing agent is selected from the group consisting of alkali metal carbonates or alkali metal hydrogencarbonates, Wherein the alkali metal may be sodium or potassium; or wherein the superabsorbent polymer has a pressure absorption index of from about 120 to about 150; or wherein the internal crosslinking agent comprises at least one vinyl or allyl group and at least one Si-O bond A decane compound in which a vinyl group or an allyl group is directly bonded to a ruthenium atom.

The present invention also relates to a particulate superabsorbent polymer comprising from about 0.05 wt.% to about 2.0 wt.% of a blowing agent and from about 0.001 wt.% to about 1.0 wt.% of a lipophilic nonionic interface inside the particle. An internal crosslinked structure of a mixture of an active agent and a polyethoxylated hydrophilic nonionic surfactant having particles having a crosslinked surface to crosslink the surface, and the particulate superabsorbent polymer having a vortex of 30 seconds to 60 seconds Spinning time and, as specified by the standard sieve classification, the particulate superabsorbent polymer in an amount of from about 6 wt% to about 15 wt% of the particulate superabsorbent polymer has a particle size greater than 600 μm; Or having a weight average particle size (D50) of from 350 μm to about 500 μm as specified by the standard sieve classification; or a particulate superabsorbent polymer not less than about 85 wt% of the particulate superabsorbent polymer composition as specified by the standard sieve classification Having a particle size of less than 600 μm and greater than 150 μm; or as specified by the standard sieve classification, particles of not less than about 90% by weight of the particulate superabsorbent polymer composition have a particle size of less than 600 μm and greater than 150 μm and the particles have a standard sieve classification The weight average particle diameter (D50) of 300 μm to 400 μm is specified.

The present invention also relates to a particulate superabsorbent polymer comprising from about 0.05 wt.% to about 5.0 wt.% of a blowing agent and from about 0.001 wt.% to about 1.0 wt.% of a lipophilic nonionic interface inside the particle. An internal crosslinked structure of a mixture of an active agent and a polyethoxylated hydrophilic nonionic surfactant having particles having a crosslinked surface to crosslink the surface, and the particulate superabsorbent polymer having a vortex of 30 seconds to 60 seconds The spin time and particulate superabsorbent polymer additionally comprises clay to form a superabsorbent polymer comprising from about 90 wt.% to about 98 wt.% superabsorbent polymer and from about 0.5 wt.% to about 10 wt.% clay. a gum; or comprising from about 0.001 to about 10 parts by weight per 100 parts by weight of the particulate superabsorbent polymer; or additionally comprising from about 0.05 wt.% to about 5.0 wt.% of the blowing agent added to the aqueous hydrogel.

The present invention relates to a particulate superabsorbent polymer comprising from about 0.05 wt.% to about 2.0 wt.% of a blowing agent and from about 0.001 wt.% to about 1.0 wt.% of a lipophilic nonionic interface inside the particle. An internal crosslinked structure of a mixture of an active agent and a polyethoxylated hydrophilic nonionic surfactant having particles having a crosslinked surface to crosslink the surface, and the particulate superabsorbent polymer having a vortex of 30 seconds to 60 seconds The spin time and particulate superabsorbent polymer additionally comprises a chelating agent, wherein the chelating agent is selected from the group consisting of amino carboxylic acids having at least three carboxyl groups and salts thereof.

The invention also relates to a particulate superabsorbent polymer comprising From about 0.05 wt.% to about 2.0 wt.% of the blowing agent and from about 0.001 wt.% to about 1.0 wt.% of the lipophilic nonionic surfactant and the polyethoxylated hydrophilic nonionic surfactant mixture Internal cross-linking structure, the particles have a surface that has been cross-linked to cross-link the surface, the particulate superabsorbent polymer has a vortex time of 30 seconds to 60 seconds, and the particulate superabsorbent polymer additionally contains dry polymer powder weight a thermoplastic polymer of from about 0.01 wt.% to 0.5 wt.%; or wherein the thermoplastic polymer is selected from the group consisting of polyethylene, polyester, polyurethane, linear low density polyethylene (LLDPE), ethylene acrylic acid copolymerization (EAA), styrene copolymer, ethylene alkyl methacrylate copolymer (EMA), polypropylene (PP), ethylene vinyl acetate copolymer (EVA) or blends thereof or copolymers thereof; or The thermoplastic polymer is added to the particulate superabsorbent polymer along with the surface crosslinking agent.

The present invention relates to a particulate superabsorbent polymer comprising from about 0.05 wt.% to about 2.0 wt.% of a blowing agent and from about 0.001 wt.% to about 1.0 wt.% of a lipophilic nonionic interface inside the particle. An internal crosslinked structure of a mixture of an active agent and a polyethoxylated hydrophilic nonionic surfactant having particles having a crosslinked surface to crosslink the surface, and the particulate superabsorbent polymer having a vortex of 30 seconds to 60 seconds Rotating time and additionally comprising neutralizing the aluminum salt in an amount of from 0.01% by weight to about 5% by weight based on the weight of the particulate superabsorbent polymer composition, the neutralized aluminum salt being in the form of an aqueous solution of a neutralized aluminum salt having a pH of from about 5.5 to about 8. Applied to the surface of the particulate superabsorbent polymer.

The present invention also relates to a particulate superabsorbent polymer comprising from about 0.05 wt.% to about 2.0 wt.% of a blowing agent and from about 0.001 wt.% to about 1.0 wt.% of a lipophilic nonionic interface inside the particle. An internal crosslinked structure of a mixture of an active agent and a polyethoxylated hydrophilic nonionic surfactant having particles having a crosslinked surface to crosslink the surface, and the particulate superabsorbent polymer having a vortex of 30 seconds to 60 seconds a centrifuge retention capacity (CRC) having a spin time and having a 0.9 weight percent aqueous sodium chloride solution of from about 25 grams to about 40 grams per gram of particulate superabsorbent polymer composition; or a particulate superabsorbent polymerization having from about 2 wt% to about 10 wt% the water content thereof; or of about 20 × 10 ^-8 cm ² to about 200 × 10 ^-8 cm free swell gel bed permeability (FSGBP) ² of the;. or to 0.9wt% in terms of load of 4.83kPa It has a 60 minute absorption capacity of from about 15 g/g to about 26 g/g.

The present invention also relates to a process for producing a superabsorbent polymer having a rapid water absorption comprising the following steps a) preparing a monomer aqueous solution containing a mixture of a monomer of a polymerizable unsaturated acid group and an internal crosslinking agent monomer, wherein The aqueous monomer solution comprises dissolved oxygen; b) bubbling the aqueous monomer solution of step a), comprising adding an inert gas to the aqueous monomer solution of step a) to displace the dissolved oxygen of the aqueous monomer solution; c) making step b) Polymerization of the aqueous monomer solution, comprising the following step c1) adding to the aqueous monomer solution of step a): i) comprising from about 0.05 wt.% to about 2.0 wt% based on the total amount of the monomer solution containing the polymerizable unsaturated acid group. a water-soluble nonionic surfactant of from 0.001% by weight to about 1.0% by weight, based on the total amount of the monomer solution containing the polymerizable unsaturated acid group; An aqueous solution of a polyethoxylated hydrophilic nonionic surfactant mixture; c2) a high speed shear mixing of at least 2500 rpm to treat the monomer solution of step c1) to form a treated monomer solution, wherein in step b) After the aqueous solution is bubbled and at step c2) high speed shear mixing Prior to the aqueous monomer solution, component i) (containing from about 0.05 wt.% to about 2.0 wt.% of the aqueous solution of the blowing agent); and component ii) (containing from about 0.001 wt.% to about 1.0 wt.%) Adding an aqueous solution of a mixture of a lipophilic nonionic surfactant and a polyethoxylated hydrophilic nonionic surfactant) to the aqueous monomer solution; c3) by adding a polymerization initiator to the treated monomer solution of step c2) Forming water a gel, wherein the initiator is added to the treated monomer solution after the blowing agent and the surfactant, wherein the polymer is formed to include bubbles of the blowing agent in the polymer structure; and d) drying and Grinding the hydrogel of step c) to form a particulate superabsorbent polymer; and e) crosslinking the surface of the particulate superabsorbent polymer of step d) with a surface crosslinking agent, wherein the surface crosslinked superabsorbent polymer has about 30 A vortex of seconds to about 60 seconds.

The invention further includes an absorbent article comprising a topsheet; a backsheet; and an absorbent core disposed between the topsheet and the backsheet, the absorbent core comprising the particulate superabsorbent polymer of the present invention described above.

Suitable superabsorbent polymers can be selected from synthetic, natural, biodegradable, and modified natural polymers. The term crosslinked as used in relation to superabsorbent polymers refers to any means effective to render a generally water soluble material substantially insoluble in water but swellable in water. Such cross-linking means may include, for example, physical entanglement, crystalline domains, covalent bonds, ion mismatches and associations, hydrophilic associations such as hydrogen bonding, hydrophobic associations or van der Waals forces. The superabsorbent polymer as set forth in the specific examples of the present invention can be obtained by initial polymerization of from about 55% to about 99.9% by weight of a monomer containing a polymerizable unsaturated acid group of the superabsorbent polymer. Suitable monomers include any monomer containing a carboxyl group such as acrylic acid or methacrylic acid; or 2-acrylamido-2-methylpropanesulfonic acid, or a mixture thereof. It is desirable that at least about 50% by weight and more desirably at least about 75% by weight of the acid group be a carboxyl group.

The process for producing the superabsorbent polymer of the present invention can be obtained by initial polymerization of from about 55% to about 99.9% by weight of a monomer containing a polymerizable unsaturated acid group of the superabsorbent polymer. Suitable monomers include any monomer having a carboxyl group such as acrylic acid, methacrylic acid or 2-acrylamido-2-methylpropanesulfonic acid, or a mixture thereof. Requiring at least about 50% by weight and more desirably at least about 75% by weight The acid group is a carboxyl group.

The impurities contained in the acrylic acid can be defined as follows. Acrylic acid may include protoanemonin and/or furfural, which may be controlled to a predetermined amount or less than a predetermined amount in view of tone stability or residual monomers. The content of the original pulsatilla and/or furfural may range from 0 to about 10 ppm, or from 0 to about 5 ppm, or from 0 to about 3 ppm, or from 0 to about 1 ppm. For the same reason, acrylic acid may include a minor amount of aldehyde and/or maleic acid other than furfural. The amount of aldehyde relative to acrylic acid is from 0 to about 5 ppm, or from 0 to about 3 ppm, or from 0 to about 1 ppm. Examples of the aldehyde other than furfural include benzaldehyde, acrolein, acetaldehyde, and the like. The acrylic acid includes a dimer acrylate in an amount of from 0 to about 500 ppm, or from 0 to about 200 ppm, or from 0 to about 100 ppm from the viewpoint of reducing residual monomers.

The acid group is neutralized with an alkali metal base to a range of at least about 25 mol% or from about 50 mol% to about 80 mol%, i.e., the acid group is desirably present in the form of a sodium salt, a potassium salt or an ammonium salt. The amount of alkali metal base can range from about 14% to about 45% by weight of the particulate superabsorbent polymer composition. The alkali metal base may include sodium hydroxide or potassium hydroxide. In some aspects, it is desirable to utilize a polymer obtained by polymerization of acrylic acid or methacrylic acid, the carboxyl group of which is neutralized in the presence of an internal crosslinking agent. It should be noted that neutralization can be achieved by adding an alkali metal base to the monomer solution or adding a monomer such as acrylic acid to the alkali metal base. The temperature or neutralization (neutralization temperature) is not particularly limited, but may be from 10 ° C to 100 ° C or from 30 ° C to 90 ° C.

In some aspects, the second suitable monomer copolymerizable with the ethylenically unsaturated monomer can include, but is not limited to, acrylamide, methacrylamide, hydroxyethyl acrylate, (meth)acrylic acid Methyl aminoalkyl ester, ethoxylated (meth) acrylate, dimethylaminopropyl acrylamide or acrylamidopropyltrimethylammonium chloride. Such monomers may range from 0 wt% to about 40 wt% Copolymerized monomers are present.

In the case where the monomer is acrylic acid, the partially neutralized acrylate becomes a polymer in the particulate water absorbing agent after polymerization, and the conversion value in terms of acrylic acid can be completely converted into the equimolar via the hypothetical partially neutralized polyacrylate. The concentration was not neutralized with polyacrylic acid to determine.

The superabsorbent polymer of the present invention also includes from about 0.001% by weight to about 5% by weight (by weight) or from about 0.2% by weight to about 3% by weight, based on the total of the monomers containing the polymerizable unsaturated acid group. Crosslinker. The internal crosslinking agent generally has at least two ethylenically unsaturated double bonds, or one ethylenically unsaturated double bond and one functional group or p-acid group reactive with an acid group of a monomer having a polymerizable unsaturated acid group. A number of functional groups that are reactive, which can be used as internal crosslinking components and are present during polymerization of monomers containing polymerizable unsaturated acid groups. The internal crosslinking agent may contain a decane compound comprising at least one vinyl or allyl group directly bonded to a ruthenium atom and at least one Si-O bond.

Examples of internal crosslinking agents for superabsorbent polymers include aliphatically unsaturated decylamines such as methylenebis acrylamide or methylene bis methacrylamide or ethyl bis acrylamide; An aliphatic ester of a polyhydric alcohol or alkoxylated polyol with an ethylenically unsaturated acid, such as butanediol or ethylene glycol, polyethylene glycol or trimethylolpropane di(meth)acrylate or tri Methyl) acrylate, preferably alkoxylated (preferably ethoxylated) trimethylolpropane diacrylate and triacrylate, glycerol and pentaerythritol acrylate and 1 mol to 30 mol of alkylene oxide a methacrylate and an acrylate and a methacrylate of glycerol and pentaerythritol ethoxylated with from 1 mol to 30 mol of propylene oxide; and further, an allyl compound such as allyl (meth)acrylate, and 1 mol Alkylation of allyl (meth) acrylate, triallyl cyanurate, triallyl isocyanate, diallyl maleate, poly to 30 mol of propylene oxide reaction Allyl ester Vinyl trimethoxy decane, vinyl decane, such as Dynasylan® 6490, Dynasylan® 6498; vinyl alkoxy decane, such as vinyl trimethoxy decane, methyl vinyl trimethoxy decane, vinyl triisopropoxy Base decane, vinyl triethoxy decane, methyl vinyl triethoxy decane, vinyl methyl dimethoxy decane, vinyl ethyl diethoxy decane, diethoxy methyl vinyl decane And vinyl ginseng (2-methoxyethoxy) decane; vinyl ethoxy decane, such as vinylmethyldiethoxydecane, vinylethyldiethoxydecane, and vinyl III Ethoxy decane; allyl alkoxy decane, such as allyl trimethoxy decane, allyl methyl dimethoxy decane, and allyl triethoxy decane; divinyl alkoxy decane And divinyl ethoxy decane, such as divinyl dimethoxy decane, divinyl diethoxy decane, and divinyl decyl decane; diallyl alkoxy decane and diene Propyl ethoxy decane, such as diallyl dimethoxy decane, diallyl Diethoxydecane and diallyldimethyl methoxy decane, vinyl triethoxy decane; polyoxy siloxane, tetraallyloxyethane, tetraallyloxy containing at least two vinyl groups Ethane, triallylamine, tetraallylethylenediamine, diol, polyol, hydroxyallyl or acrylate compound and allyl phosphate or phosphoric acid, and, in addition, crosslinkable An N-methylol compound such as an unsaturated decylamine such as methacrylamide or acrylamide and an ether derived therefrom. An ionic crosslinking agent such as an aluminum metal salt may also be used, or other compounds containing a polyvalent cation may also be used. The post-polymerization reactive crosslinker forms additional crosslinks after polymerization, or after polymerization, for example, by temperature (for example during drying or heat treatment) or by adding water or other chemicals, or by pH changes or some other change Upon triggering (e.g., when in contact with body fluids), hydrolysis or reaction forms less crosslinks. Mixtures of the mentioned crosslinkers can also be employed.

The superabsorbent polymer may comprise a total of monomers containing a polymerizable unsaturated acid group Measuring from about 0.001% by weight to about 0.1% by weight of the second internal crosslinking agent, which may comprise a composition having at least two ethylenically unsaturated double bonds, such as methylene bis acrylamide or methylene bismethyl a acrylamide or an ethyl bis acrylamide; in addition, an unsaturated monocarboxylic acid or a polycarboxylic acid ester of a polyol such as a diacrylate or a triacrylate such as butanediol or ethylene glycol diacrylate Or methacrylate; trimethylolpropane triacrylate and alkoxylated derivatives thereof; in addition, allyl compounds such as allyl (meth)acrylate, triallyl cyanurate, cis Diallyl methacrylate, polyallyl ester, tetraallyloxyethane, diallylamine and triallylamine, tetraallylethylenediamine, phosphoric acid or phosphite Propyl ester. Further, a compound having at least one functional group reactive with an acid group can also be used. Examples thereof include an N-methylol compound of decylamine such as methacrylamide or acrylamide, and an ether derived therefrom, and a diglycidyl group and a polyglycidyl compound. The second internal crosslinking agent may comprise polyethylene glycol monoallyl ether acrylate, ethoxylated trimethylolpropane triacrylate, and/or polyethylene glycol diacrylate.

Common initiators, such as azo or peroxy compounds, redox systems or UV initiators, (sensitizers) and/or radiation, are used to initiate free radical polymerization. In some aspects, an initiator can be used to initiate free radical polymerization. Suitable initiators include, but are not limited to, azo or peroxy compounds, redox systems or ultraviolet initiators, sensitizers, and/or radiation.

The polymerization initiator used in the present invention is selected as needed depending on the type of polymerization, and is not particularly limited. Examples of the polymerization initiator include a thermally degradable polymerization initiator, a photodegradable polymerization initiator, and a redox type polymerization initiator or the like. Specific examples of thermally degradable polymerization initiators include persulphates such as sodium persulfate, potassium persulfate or ammonium persulfate; and peroxides such as hydrogen peroxide, tributyl peroxide or methyl ethyl peroxide Ketones; and azo compounds such as 2,2'-azobis(2-methylindenyl-propane) dihydrochloride, 2.2'-azobis[2-(2-imidazolin-2-yl)propane ]two Hydrochloride or an analogue thereof. Specific examples of the photodegradable polymerization initiator include benzoin derivatives, benzyl derivatives, acetophenone derivatives, benzophenone derivatives, and azo compounds or the like. Examples of the redox type polymerization initiator include a combination of a reducing compound such as L-ascorbic acid or sodium hydrogen sulfite with a persulfate or a peroxide as described above. Preferred examples encompass the use of a combination of a photodegradable polymerization initiator and a thermally degradable polymerization initiator as described above. The polymerization initiator may be used in an amount of from about 0.001 mol% to about 1 mol% or about 0.05 mol% or to 1.0 mol% relative to the monomer. When the amount of the polymerization initiator used is more than 1 mol%, coloring of the water absorbing resin may occur. When the amount of the polymerization initiator used is less than 0.0001 mol%, it may cause an increase in residual monomers.

Meanwhile, it should be noted that the monomer can be polymerized by irradiating an activation energy ray such as a radiation, an electron beam, and a UV line instead of using the above polymerization initiator. Further, the polymerization can be carried out by using a combination of a polymerization initiator and an activation energy ray.

The present invention additionally includes from about 0.05 wt.% to about 2.0 wt.% or from about 0.1 wt% to about 1.0 wt% of the blowing agent, based on the total of the monomer solution containing the polymerizable unsaturated acid group. The blowing agent may include a salt or mixed salt containing any alkali metal carbonate or alkali metal hydrogencarbonate, sodium carbonate, potassium carbonate, ammonium carbonate, magnesium carbonate or (basic) magnesium carbonate, calcium carbonate, barium carbonate, hydrogen carbonate. Salts and hydrates thereof, azo compounds or other cations as well as naturally occurring carbonates such as dolomite, or mixtures thereof. The blowing agent may include a carbonate of a multivalent cation such as Mg, Ca, Zn, and the like. While certain polyvalent transition metal cations may be used, some of them, such as ferric cations, can cause dyeing and can undergo a reduction-oxidation reaction or a hydrolysis equilibrium in water. This can lead to difficulties in quality control of the final polymerization product. In addition, other multivalent cations such as Ni, Ba, Cd, Hg are unacceptable due to possible toxicity or skin sensitizing effects. Blowing agents can include Sodium carbonate and sodium bicarbonate.

The invention further comprises from about 0.001 wt.% to about 1.0 wt.% or from about 0.002 wt% to about 0.5 wt% or about 0.003 wt.%, based on the total of the monomer solution containing the polymerizable unsaturated acid group. An aqueous solution of a mixture of a lipophilic surfactant and a polyethoxylated hydrophilic surfactant of about 0.1% by weight, wherein the lipophilic surfactant may have an HLB of 4 to 9 and the polyethoxylated hydrophilic surfactant has The HLB of 12 to 18; or the lipophilic surfactant may be a nonionic or polyethoxylated hydrophilic surfactant which may be nonionic.

Typical examples of the surfactant include polyoxyethylene alkyl aryl ethers such as polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxygen Vinyl alkyl ethers such as polyoxyethylene higher alcohol ethers and polyoxyethylene nonylphenyl ethers; sorbitan fatty esters such as sorbitan monolaurate, sorbitan monopalmitate, dehydrated Sorbitol monostearate, sorbitan tristearate, sorbitan monooleate, sorbitan trioleate, sorbitan sesquioleate and sorbitan Alcohol distearate; polyoxyethylene sorbitan fatty ester, such as polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan Palmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan monooleate and polyoxyethylene sorbitan III Oleate; polyoxyethylene sorbitan fatty ester, such as Oleic acid polyoxyethylene sorbitol; glycerol fatty esters such as glyceryl monostearate, glycerol monooleate and self-emulsifying glyceryl monostearate; polyoxyethylene fatty esters such as polyethylene glycol monolaurate , polyethylene glycol monostearate, polyethylene glycol distearate and polyethylene glycol monooleate; polyoxyethylene alkylamine; polyoxyethylene hardened castor oil; and alkyl alcohol amine. Mixture of nonionic surfactants may include lipophilic surfactants It is a sorbitan ester and the polyethoxylated hydrophilic surfactant is a mixture of polyethoxylated sorbitan esters.

Preferably, the process of the invention is carried out by polymerization or copolymerization in the presence of a mixture of a lipophilic surfactant and a polyethoxylated hydrophilic surfactant. The use of a mixture of two surfactants allows the bubbles to be stably dispersed. Further, by appropriately controlling the kind and amount of the mixture of the two surfactants, the pore diameter and the water absorption speed of the produced hydrophilic polymer can be controlled. The method for producing the superabsorbent polymer superabsorbent polymer of the present invention comprises the steps of: a) preparing a monomer containing the polymerizable unsaturated acid group of from about 55 wt.% to about 99.9 wt.% of the monomer solution a1) A2) from about 0.001 wt.% to about 5.0 wt.% of the internal crosslinker; a3) from about 14 wt% to about 45 wt% of the alkali metal, wherein the composition has a degree of neutralization of from about 50 mol% to about 70 mol%; A4) bubbling the monomer solution of step c) by bubbling an inert gas into the monomer solution such that the monomer solution has less than 1 wt% oxygen; b) polymerizing the monomer solution of step a), Including the following step b1) adding the following to the monomer solution of step a): i) comprising from about 0.05 wt.% to about 2.0 wt.%, based on the total amount of the monomer solution containing the polymerizable unsaturated acid group. An aqueous solution of a foaming agent; and ii) comprising from about 0.001 wt.% to about 1.0 wt.% of a lipophilic surfactant and a polyethoxylated hydrophilicity, based on the total amount of the monomer solution containing the polymerizable unsaturated acid group. An aqueous solution of the surfactant mixture; b2) treating step a) and step b1 with a high speed shear mixing of at least about 2500 rpm a monomer solution to form a treated monomer solution; b3) forming a hydrogel by adding a polymerization initiator to the treated monomer solution of step b2), wherein the initiator is at a blowing agent and interface The active agent is then added to the treated monomer solution, wherein the bubbles comprising the blowing agent are included in the polymer structure and the bubbles therein; and c) the hydrogel of step b) is dried and ground to form particles Superabsorbent polymer; and d) crosslinking the surface of the particulate superabsorbent polymer of step c) with a surface crosslinking agent, wherein the surface crosslinked superabsorbent polymer has a vortex of from about 30 seconds to about 60 seconds.

The temperature at the start of the polymerization, although varying depending on the kind of the radical polymerization initiator to be used, may be in the range of 0 to 50 ° C or in the range of 10 ° C to 40 ° C. The polymerization temperature during the reaction may range from 20 ° C to 110 ° C or from 30 ° C to 90 ° C, although it varies depending on the kind of the radical polymerization initiator to be used. If the temperature at the start of the polymerization or the polymerization temperature during the reaction deviates from the range mentioned above, there may be disadvantages such as: (1) an undue increase in the amount of residual monomers in the water absorbing resin produced, ( b) It is difficult to control the foaming of the blowing agent, which will be specifically described below, and (c) the excessive self-crosslinking reaction accompanying the undue decrease in the amount of water absorbed by the water absorbing resin.

The reaction time is not particularly limited, but is only required to be set depending on a combination of an unsaturated monomer, a crosslinking agent, and a radical polymerization initiator or a reaction condition such as a reaction temperature.

The water absorbing resin or hydrophilic polymer having an almost closed cell structure has an average pore diameter in the range of 10 to 500 μm , or in the range of 20 to 400 μm , or in the range of 30 to 300 μm , or in the 40- Within the range of 200 μm, or in the range of 70 μm to about 110 μm. The pore diameter mentioned above was found by image analysis of a cross section of a water absorbing resin or a hydrophilic polymer in a dry state by means of an electron microscope. Specifically, the average pore diameter is obtained by forming a histogram of the pore diameter distribution of the water absorbing resin indicating the image analysis result and calculating the average number of the pore diameters based on the histogram.

To further enhance the properties of the particulate superabsorbent polymer, an additional amount of a blowing agent as described herein can also be added to the aqueous superabsorbent polymer prior to the drying step.

The drying temperature is not particularly limited, but needs to fall within the range of, for example, 100 ° C to 250 ° C or in the range of 120 ° C to 200 ° C. Although the drying time is not particularly limited, it is preferably in the approximate range of 10 seconds to 5 hours. The hydrogel resin can be neutralized or further disintegrated prior to drying for subdivision.

The drying method to be employed is not particularly limited, but may be selected from various methods such as drying by heating, drying with hot air, drying under reduced pressure, drying with infrared rays, drying with microwave, drying in a cylinder drier. It is dehydrated by azeotropy with a hydrophobic organic solvent and dried by high humidity by using hot steam. In the drying method mentioned above, the use of hot air drying and the use of microwave drying prove to be particularly advantageous. When the hydrogel containing bubbles is irradiated with microwaves, the resulting water-absorbent resin enjoys a further increased water absorption speed due to the expansion of the bubbles to several times to several tens of times the original volume.

Microparticle superabsorbent polymer (SAP)-clay blend

As indicated previously, the polymerization proceeds rapidly to produce a very viscous hydrogel which is for example extruded onto a flat surface such as a continuously moving conveyor belt. The neutralized superabsorbent polymer hydrogel is then comminuted, and the clay can typically be added to the comminuted superabsorbent polymer hydrogel particles in the form of an aqueous clay slurry and intimately mixed therewith. Clay can also be added in the form of solid particles or powder. The SAP hydrogel and clay components can then be intimately mixed, for example by extrusion, to disperse the clay in and on the hydrogel particles. The resulting neutralized SAP-clay mixture is then dried Dry and size, and surface cross-linking as appropriate to obtain neutralized SAP-clay particles. The pulverization of the SAP-clay hydrogel particles can be carried out simultaneously or sequentially.

After comminution, the viscous SAP-clay hydrogel particles are dehydrated (i.e., dried) to obtain SAP-clay particles in solid or powder form. The dehydrating step can be performed, for example, by heating the viscous SAP-clay hydrogel particles in a forced air oven at a temperature of from about 190 ° C to about 210 ° C for from about 15 minutes to about 120 minutes, or from about 15 minutes to about 110 minutes, or about 15 minutes. The period of time is from about 100 minutes, or from about 20 minutes to about 100 minutes. The dried SAP-clay hydrogel can then be subjected to other mechanical means for particle size reduction and classification, including chopping, grinding and sieving.

Such SAP-clay compositions can include superabsorbent polymers present in an amount from about 90 wt.% to about 99.5 wt.% or from about 91 wt.% to about 99 wt.%, or from about 92 wt.% to about 98 wt.%, And the clay is present in an amount from about 0.5 wt.% to about 10 wt.%, or from about 1 wt.% to about 9 wt.%, or from about 2 wt.% to about 8 wt.%.

The clay suitable for the SAP-clay particles of the present invention may be a swollen or non-swellable clay. The swollen clay has a water absorbing ability and is a swellable layered organic material. Suitable swelling clays include, but are not limited to, montmorillonite, saponite, nontronite, laponite, beidelite, hectorite ), sauconite, stevensite, vermiculite, volkonskoite, magadite, montmontite, sulphate Stone (kenyaite) and its mixture.

Suitable non-swelling clays include, but are not limited to, kaolinites (including kaolinite, dickite, and nacrite), serpentine minerals, and mica (including illite). Illite)), chlorite minerals, sea Sepolite, palygorskite, bauxite, and mixtures thereof.

Clay can also be an organophilic clay. As used herein and hereinafter, the term "organophilic" is defined as the property of a compound that absorbs at least its own weight and preferably many times its own weight of water-immiscible organic compound. The organophilic compound can absorb water or water miscible compounds as appropriate.

Commercially available clays include those available from BASF Corporation, Florham Park, NJ The ULTRAGLOSS ^® clay (hydrous kaolin); available from Nanocor Technologies, Arlington Heights, Ill of the purified clay;. And available from Huber, Atlanta, Ga of HYDROGLOSS ^®.

granularity

The polymerization forms a superabsorbent polymer gel which is granulated into superabsorbent polymer particles or particulate superabsorbent polymers. The superabsorbent polymer gel typically has a moisture content of from about 40% to 80% by weight of the superabsorbent polymer gel. The particulate superabsorbent polymer generally comprises a particle size ranging from about 50 [mu]m to about 1000 [mu]m, or from about 150 [mu]m to about 850 [mu]m. The present invention may comprise at least about 40% by weight of the superabsorbent polymer particles having a particle size of from about 300 μm to about 600 μm, at least about 50% by weight of the particles having a particle size of from about 300 μm to about 600 μm, or at least about 60% by weight of the particles having from about 300 μm to about Particle size of 600 μm, as measured by US Standard 30 mesh screen screening and retained on a US standard 50 mesh screen. In addition, the mass average particle diameter D50 may be 200 μm to 450 μm or 300 μm to 430 μm.

Further, the percentage of particles smaller than 150 μm is generally 0 to 8% by mass, or 0 to 5% by mass, or 0 to 3% by mass, or 0-1% by mass. In addition, the percentage of particles larger than 600 μm may be 0 to 25% by mass, or 3 to 15% by mass, or 5 to 12% by mass, or 5 to 8% by mass, as used, for example, from WSTyler, Inc., Mentor Ohio. RO-TAP ^® mechanical sieve shaker model B is measured.

The particle size can be adjusted by dispersion polymerization and dispersion drying of the particles. However, in general, particularly in the case of carrying out aqueous solution polymerization, the particles are pulverized and classified after drying, and then the mass average diameter of D50 and the amount of particles smaller than 150 μm and larger than 600 μm are adjusted to obtain a specific particle size distribution. For example, if a specific particle size distribution is achieved by reducing the diameter of particles having a mass average diameter of D50 to 400 μm or less and reducing the amount of fine particles having a diameter of less than 150 μm and more than 600 μm, the particles may be After drying, it is first classified into coarse particles and fine particles by using a general sorting device such as a sieve. This method preferably removes coarse particles having a diameter of from 5000 μm to 600 μm or from 2000 μm to 600 μm or from 1000 μm to 600 μm. Next, fine particles having a diameter of less than 150 μm are removed during the main conditioning process. The removed coarse particles can be discarded, but they are more likely to be pulverized again by the above pulverization method. Therefore, the resulting particulate superabsorbent polymer having a specific particle size distribution thus produced by the pulverization method is composed of irregularly pulverized particles.

The particulate superabsorbent polymer is surface treated with other chemicals and treating agents as described herein. In particular, the surface of the particulate superabsorbent polymer can be crosslinked by the addition of a surface crosslinking agent and heat treatment, commonly referred to as surface crosslinking. In general, surface crosslinking is a method of increasing the crosslink density of a polymer matrix near the surface of the particulate superabsorbent polymer relative to the crosslink density within the particle. The amount of surface crosslinking agent may be present in an amount from about 0.01% to about 5% by weight of the dry particulate superabsorbent polymer composition, such as from about 0.1% to about 3% by weight based on the weight of the dry particulate superabsorbent polymer composition. , such as from about 0.1% by weight to about 1% by weight.

Desirable surface crosslinking agents include those having one or more functional groups reactive toward the pendant groups (typically, acid groups) of the polymer chain. Surface crosslinking agent is included in A functional group that reacts with a functional group of a polymer structure in a condensation reaction (condensation crosslinking agent), in an addition reaction, or in a ring opening reaction. Such compounds may include, for example, diethylene glycol, triethylene glycol, polyethylene glycol, glycerol, polyglycerol, propylene glycol, diethanolamine, triethanolamine, polyoxypropylene, oxyethylene-oxypropylene block copolymers. , sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, trimethylolpropane, pentaerythritol, polyvinyl alcohol, sorbitol, 1,3-dioxolan-2-one (carbonic acid Diester), 4-methyl-1,3-dioxolan-2-one (propylene carbonate) or 4,5-dimethyl-1,3-dioxolan-2-one.

After the particulate superabsorbent polymer has been contacted with a surface crosslinking agent or with a fluid comprising a surface crosslinking agent, the treated particulate superabsorbent polymer is heat treated to a temperature of from about 50 ° C to about 300 ° C, or from about 75 ° C to about 275. °C, or a temperature of from about 150 ° C to about 250 ° C, maintained for a period of from about 5 minutes to about 90 minutes (depending on temperature) such that cross-linking (ie, surface cross-linking) of the outer region of the polymer structure is greater than the internal region Stronger. The duration of the heat treatment is limited by the risk that the desired property characteristics of the polymer structure will be destroyed by thermal effects.

In a specific aspect of surface crosslinking, the particulate superabsorbent polymer is surface treated with ethylene carbonate, followed by surface crosslinking of the superabsorbent polymer particles by heating, which improves the surface cross-linking of the particulate superabsorbent polymer. Joint density and gel strength characteristics. More specifically, the surface crosslinking agent is applied to the particulate superabsorbent polymer by mixing the particulate superabsorbent polymer with an aqueous alcohol solution of the ethylene carbonate surface crosslinking agent. The amount of alcohol in the aqueous alcohol solution can be determined by the solubility of the alkylene carbonate and is kept as low as possible for various reasons, such as to prevent explosion. Suitable alcohols are methanol, isopropanol, ethanol, butanol or butyl glycol and mixtures of such alcohols. In some aspects, the solvent is desirably water, which is typically used in an amount of from about 0.3% to about 5.0% by weight, based on the weight of the dry particulate superabsorbent polymer composition. In other aspects, the ethylene carbonate surface crosslinking agent can be applied in a vapor state, for example, by a powder mixture with an inorganic carrier material such as cerium oxide (SiO ₂ ), or by sublimation of ethylene carbonate.

To achieve the desired surface crosslinking characteristics, surface crosslinking agents such as ethylene carbonate should be evenly distributed over the particulate superabsorbent polymer. For this purpose, the mixing is effected in a suitable mixer known in the art, such as a fluidized bed mixer, a slurry mixer, a tumbler mixer or a twin screw mixer. Coating of the particulate superabsorbent polymer can also be carried out during one of the processing steps of making the particulate superabsorbent polymer. In one particular aspect, the method suitable for this purpose is reversed phase suspension polymerization.

The solution of the surface crosslinking agent may also include from 0 wt% to about 1 wt%, or from about 0.01 wt% to about 0.5 wt% of the thermoplastic polymer based on the dry particulate superabsorbent polymer composition. Examples of thermoplastic polymers include polyolefins, polyethylene, polyester, linear low density polyethylene (LLDPE), ethylene acrylic acid copolymer (EAA), ethylene alkyl methacrylate copolymer (EMA), polypropylene (PP), Maleic acid polypropylene, ethylene vinyl acetate copolymer (EVA), polyester, and may also be suitable to use blends of all polyolefin families, such as PP, EVA, EMA, EEA, EBA, HDPE, MDPE, LDPE a blend of LLDPE and/or VLDPE. In a particular aspect, the maleated polypropylene is a preferred thermoplastic polymer suitable for use in the present invention. Thermoplastic polymers can be functionalized to have additional benefits such as water solubility or water dispersibility.

The heat treatment after the treatment of the particulate superabsorbent polymer can be carried out as follows. Generally, the heat treatment is carried out at a temperature of from about 100 ° C to about 300 ° C. Low temperature is possible if a highly reactive epoxide crosslinker is used. However, if ethylene carbonate is used, the heat treatment is suitably carried out at a temperature of from about 150 ° C to about 250 ° C. In this particular aspect, the processing temperature depends on the residence time and type of ethylene carbonate. For example, at a temperature of about 150 ° C, heat treatment is carried out 1 hour or more. In contrast, at a temperature of about 250 ° C, a few minutes (eg, about 0.5 minutes to about 5 minutes) is sufficient to achieve the desired surface crosslinking characteristics. The heat treatment can be carried out in a conventional dryer or oven known in the art.

The particulate superabsorbent polymer composition can be further surface treated before, during or after crosslinking with other chemical compositions. Insert aluminum sulfate slices.

The particulate superabsorbent polymer composition according to the present invention may comprise from about 0.01% to about 5% by weight, based on the weight of the particulate superabsorbent composition, of an aluminum salt having from about 5.5 to about 8 or from about 6 to about 7 An aqueous solution of the pH is applied to the surface of the particulate superabsorbent polymer. Alternatively, the particulate superabsorbent polymer composition comprises from about 6 wt% to about 15 wt% of an aqueous aluminum salt solution applied to the surface of the surface crosslinked microparticle superabsorbent polymer, by weight of the particulate superabsorbent composition, wherein the aqueous aluminum salt solution has A pH of from about 5.5 to about 8 or from about 6 to about 7. The aqueous solution of the aluminum salt may comprise an aluminum cation and an anion of a hydroxyl ion or a deprotonated hydroxy organic acid. Examples of preferred organic acids are hydroxymonocarboxylic acids such as lactic acid, glycolic acid, gluconic acid or 3-hydroxypropionic acid.

The aluminum salt aqueous solution includes the reaction product of an alkali metal hydroxide with aluminum sulfate or aluminum sulfate hydrate. In another embodiment, the aqueous aluminum salt solution comprises the reaction product of sodium hydroxide with aluminum sulfate or aluminum sulfate hydrate. In another embodiment, the aqueous aluminum salt solution comprises an aluminum compound and an organic acid. The mixture of the aluminum compound and the organic acid (salt) may be acidic or basic. And the pH can be adjusted to the desired range with an alkaline or acidic substance. Examples of alkaline materials for pH adjustment include, but are not limited to, sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium carbonate or sodium hydrogencarbonate. Examples of acidic materials for pH adjustment include, but are not limited to, hydrochloric acid, sulfuric acid, methanesulfonic acid or water containing carbon dioxide. Acidic aluminum salts such as aluminum chloride, aluminum sulfate, aluminum nitrate and polyaluminum chloride or basic aluminum salts such as sodium aluminate, potassium aluminate and ammonium aluminate can also be used for pH adjustment.

The aqueous aluminum salt solution can be added at various stages of the surface treatment of the particulate superabsorbent polymer. In one embodiment, an aqueous aluminum salt solution can be applied to the particulate superabsorbent polymer along with the surface crosslinking solution.

The aluminum salt aqueous solution may be added after the surface crosslinking step, which may be referred to as post treatment. In one embodiment, the surface crosslinked particulate superabsorbent polymer and aluminum salt are mixed using methods well known to those skilled in the art. In particular, from about 6 wt% to about 15 wt% of an aqueous aluminum salt solution is applied to the surface crosslinked particulate superabsorbent polymer composition.

The particulate superabsorbent polymer composition according to the present invention may be applied to the surface of the particulate superabsorbent polymer from 0.01% by weight to about 5% by weight based on the weight of the particulate superabsorbent composition before, during or after surface crosslinking. A variety of compounds of polyvalent metal cations are surface treated. Examples include cations of aluminum, calcium, iron, zinc, magnesium and zirconium. Among them, aluminum can be used. Examples of the anion in the polyvalent metal salt may include a halide ion, a hydrochloric acid chloride, a sulfate, a nitrate, and an acetate. Aluminum sulfate can be used and it can be readily obtained commercially. The aluminum sulfate may be hydrated aluminum sulfate, wherein the aluminum sulfate may have a hydration of 12 to 14 waters. Mixtures of polyvalent metal salts can be employed. In one embodiment, the invention can comprise from about 0.01% to about 5% by weight, based on the weight of the particulate superabsorbent composition, of an aluminum salt having a pH of from about 5.5 to about 8, or from about 6 to about 7. The aqueous solution form is applied to the surface of the particulate superabsorbent polymer.

The aluminum salt aqueous solution may include a reaction product of an alkali metal hydroxide with aluminum sulfate or aluminum sulfate hydrate. In another embodiment, the aqueous aluminum salt solution comprises a single aluminum salt such as aluminum sulfate or aluminum chloride, or a mixture of compounds with other polyvalent cations that may be applied with or without pH adjustment. In another embodiment, the aqueous aluminum salt solution may comprise an aluminum compound and an organic acid. a mixture of an aluminum compound and an organic acid (salt) may be acidic or basic and may have Or apply without pH adjustment. If pH adjustment is desired, the pH can be adjusted to the desired range with an alkaline or acidic material.

The particulate superabsorbent polymer composition according to the present invention may be surface-treated with from about 0.01% by weight to about 2% by weight, or from about 0.01% by weight to about 1% by weight, of the water-insoluble inorganic metal compound, based on the anhydrous superabsorbent polymer composition. The water-insoluble inorganic metal compound may include an anion selected from aluminum, titanium, calcium or iron and an anion selected from the group consisting of phosphate, borate or chromate. Examples of the water-insoluble inorganic metal compound include aluminum phosphate. The inorganic metal compound can have a mass median particle size of less than about 2 [mu]m and can have a mass median particle size of less than about 1 [mu]m.

The particulate superabsorbent polymer composition can comprise from about 0 wt% to about 5 wt%, or from about 0.001 wt% to about 3 wt%, or from about 0.01 wt% to about 2 wt% cation by weight of the dry particulate superabsorbent polymer composition. polymer. As used herein, a cationic polymer refers to a polymer or mixture of polymers comprising functional groups that may become positively charged ions upon ionization in an aqueous solution. Suitable functional groups for the cationic polymer include, but are not limited to, primary, secondary, or tertiary amine groups, imine groups, quinone imine groups, guanidinium groups, and quaternary ammonium groups. Examples of synthetic cationic polymers include salts of poly(vinylamine), poly(allylamine), or poly(ethyleneimine) or partial salts. Examples of natural cationic polymers include partially deacetylated chitin, polyglucosamine, and polyglucosamine.

The particulate superabsorbent polymer composition can comprise from about 0 wt% to about 5 wt%, or from about 0.001 wt% to about 3 wt%, or from about 0.01 wt% to about 2 wt% water, by weight of the dry particulate superabsorbent polymer composition. Insoluble inorganic powder. Examples of the insoluble inorganic powder include cerium oxide, vermiculite, titanium oxide, aluminum oxide, magnesium oxide, zinc oxide, talc, calcium phosphate, clay, diatomaceous earth, zeolite, bentonite, kaolin, hydrotalcite, activated clay, and the like. The insoluble inorganic powder additive may be a single compound or a mixture of compounds selected from the list above. Examples of vermiculite include smoky vermiculite, precipitated vermiculite, cerium oxide, citric acid, and ceric acid. In some specific aspects, microscopic amorphous ceria is desirable. Products include SIPERNAT ^® 22S and AEROSIL ^® 200, available from Evonik, Parsippany, New Jersey. In some aspects, the inorganic powder may have a particle diameter of 1,000 μm or less, such as 100 μm or less.

The particulate superabsorbent polymer composition may also comprise from 0 wt% to about 30 wt%, or from about 0.001 wt% to about 25 wt%, or from about 0.01 wt% to about 20 wt%, water soluble, by weight of the dry particulate superabsorbent polymer composition. The polymer, such as partially or fully hydrolyzed polyvinyl acetate, polyvinylpyrrolidone, starch or starch derivatives, polyethylene glycol or polyacrylic acid, is preferably in polymerized form. The molecular weight of such polymers is not critical as long as it is water soluble. Preferred water soluble polymers are starch and polyvinyl alcohol. In the absorbent polymer according to the present invention, the content of such a water-soluble polymer is from 0 to 30% by weight or from 0 to 5% by weight based on the total of the dry particulate superabsorbent polymer composition. A water-soluble polymer, preferably a synthetic polymer such as polyvinyl alcohol, can also serve as a graft base for the monomer to be polymerized.

The particulate superabsorbent polymer composition may also comprise from 0 wt% to about 5 wt%, or from about 0.001 wt% to about 3 wt%, or from about 0.01 wt% to about 2 wt%, by weight of the dry particulate superabsorbent polymer composition. Agents, such as hydrophilic and hydrophobic dedusting agents, such as those described in U.S. Patent Nos. 6,090,875 and 5,994,440.

In some aspects, other surface additives may optionally be used with particulate superabsorbent polymer compositions, such as odor-binding materials such as cyclodextrins, zeolites, inorganic or organic salts, and the like; anti-caking additives, flow modifying Agents, surfactants, viscosity modifiers and the like.

The particulate superabsorbent polymer composition of the present invention can be used after the heat treatment step Aqueous solution treatment, such as deprotonated organic acid salts, aluminum salts or aqueous solutions of water soluble polymers such as polyethylene glycol.

The treated particulate superabsorbent polymer composition has a moisture content of from about 3 wt% to about 15 wt%, or from about 4 wt% to about 12 wt%, or from 5 wt% to about 11 wt%, based on the particulate superabsorbent polymer composition, such as Measured by the moisture content test contained herein.

In another embodiment, a chelating agent can be added to the particulate superabsorbent polymer composition of the present invention and become part of the particulate superabsorbent polymer composition. The chelating agent may be selected from a specific aminocarboxylic acid which may be immobilized on the surface of the water absorbing resin by mixing an amine-based polycarboxylic acid and a surface crosslinking agent with a water absorbing resin before crosslinking the surface of the water absorbing resin, thereby allowing water absorption The resin surface is crosslinked, or an amine-based polycarboxylic acid and water are added to a water-absorbent resin crosslinked by a specific surface, thereby granulating the resin. Since the water absorbing resin is deteriorated from the surface thereof, the chelating agent is preferably placed in the vicinity of the surface of the particulate superabsorbent polymer composition. For example, in one of the production methods of the present invention, a chelating agent and a surface crosslinking agent reactive with a carboxyl group are mixed with the superabsorbent polymer having a carboxyl group obtained above.

Examples of the chelating agent used in the present invention include the following compounds: (1) an aminocarboxylic acid and a salt thereof; (2) a monoalkyl lemon decylamine, a monoalkenyl lemon decylamine and a salt thereof; (3) a monoalkane Dipropylamine, monoalkenyl propylene glycol and its salts; (4) monoalkyl phosphates, monoalkenyl phosphates and salts thereof; (5) N-thiolated glutamic acid, N-oxime Aspartic acid and its salt; (6) β-diketone derivative; (7) a phenol ketone derivative; and (8) an organic phosphoric acid compound.

The amount of the chelating agent is generally from about 0.0001 part by weight to about 10 parts by weight, or from about 0.0002 part by weight to about 5 parts by weight per 100 parts by weight of the particulate superabsorbent polymer composition. In the present invention, the chelating agent may be added to the particulate superabsorbent polymer during surface crosslinking or Add to the surface crosslinked particulate superabsorbent polymer.

The particulate superabsorbent polymer composition of the present invention exhibits certain characteristics or characteristics such as free swell gel bed permeability (FSGBP), centrifuge retention capacity (CRC), and absorption at a load of about 0.9 psi (0.9 psi AUL). Measured. The FSGBP test measures the permeability (using 10 ^-8 cm ² ) of a swollen bed (e.g., self-absorbent structure separation) of a particulate superabsorbent polymer composition under a limiting pressure commonly referred to as "free swell" conditions. In this case, the term "free swell" means allowing the particulate superabsorbent polymer composition to swell while absorbing the test solution as will be described without a swelling limiting load.

Permeability is a measure of the effective connectivity of the porous structure, which is a fibrous mat or foam sheet, or in the case of the present application, a particulate superabsorbent polymer and a particulate superabsorbent polymer composition, This is generally referred to herein as a particulate superabsorbent polymer composition or SAP, and can be illustrated by the void fraction and connectivity of the particulate superabsorbent polymer composition. Gel permeability is a property of the particulate superabsorbent polymer composition as a bulk of the mass and is related to particle size distribution, particle shape, open cell connectivity, shear modulus, and surface modification of the swollen gel. In fact, the permeability of the particulate superabsorbent polymer composition is a measure of how fast the liquid flows through the swollen particle mass. Low permeability indicates that the liquid cannot easily flow through the particulate superabsorbent polymer composition, which is generally referred to as gel plugging, and any forced flow of the liquid, such as the second application of urine during use of the diaper, must take an alternate path (eg, Diaper leaks).

Vortex test measured 2 grams of SAP close to the amount of time (in seconds) required to vortex by stirring 50 ml of saline solution at 600 rpm on a magnetic stir plate. The time taken to approach the vortex is an indication of the free swelling rate of SAP.

Centrifuge Retention Capacity (CRC) test measures the particulate superabsorbent polymer composition at The ability to saturate and retain liquids after centrifugation under controlled conditions. The resulting retained capacity is expressed in grams of liquid (g/g) retained per gram of sample weight.

The Under Load Absorption (AUL) test measures the ability of the particulate superabsorbent polymer composition particles to absorb a 0.9 weight percent solution (test solution) of sodium chloride in distilled water at room temperature while the material is under a load of 0.9 psi. .

The pressure absorption index (PAI) is the sum of the absorption values (described below) of the load measured by SAP under the following load: 0.01 pounds per square inch (dynes per square centimeter); 0.29 pounds per Square 吋 (19995 Dyne per square centimeter); 0.57 pounds per square foot (39,300 dynes per square centimeter); and 0.90 pounds per square foot (62053 dynes per square centimeter). That is, the absorbance under load for a given SAP is determined under the limiting forces set forth above in accordance with the methods set forth below in connection with the examples. The absorption values under load measured under the limiting load set forth above are then summed to produce a pressure absorption index.

All values for centrifugation retention capacity, absorption under load, and gel bed permeability as set forth herein are understood to be determined by a centrifuge retention capacity test, a load under load test, and a free swell gel bed permeability test as provided herein.

The fast-absorbing particulate superabsorbent polymer composition produced by the process of the present invention may have a vortex time of from about 30 seconds to 60 seconds or from 40 seconds to about 60 seconds, from about 25 g/g to about 40 g/g or about 27 g. a centrifuge retention capacity of from /g to about 35 g/g; and a absorption of from about 15 g/g to about 24 g/g or from about 16 g/g to about 22 g/g at a load of 0.9 psi, a PAI of from about 120 to about 140, and about 20 Original free swell gel bed permeability (FSGBP) of from 10 ^-8 cm ² to about 200 x 10 ^-8 cm ² .

The particulate superabsorbent polymer composition according to the present invention can be used in many absorbent articles, including sanitary napkins, diapers or wound covers, and it has a rapid absorption of a large amount of menstrual blood, Characteristics of urine or other body fluids. Since the agent according to the present invention retains the absorbed liquid even under pressure and is capable of distributing more liquid in the structure of the swollen state, it is preferably higher than the conventional superabsorbent composition. The concentration of the hydrophilic fibrous material such as fluff is used. It is also suitable for use as a homogenous superabsorbent layer free of fluff within the diaper construction, with the result that particularly thin articles are possible. The polymer is additionally suitable for use in hygiene products for adults (eg incontinence products).

The particulate superabsorbent polymer composition according to the present invention is also useful in absorbent articles suitable for other uses. In particular, the particulate superabsorbent polymer composition of the present invention can be used for absorbing absorbent compositions of water or aqueous liquids, or for absorbing body fluids, for foaming and unfoamed sheet structures, for packaging Materials, structures for plant growth, used as soil amendments or as active compound carriers. To this end, it is processed into a mesh fabric by mixing with paper or fluff or synthetic fibers or by distributing the superabsorbent polymer between a substrate of paper, fluff or non-woven fabric or by processing into a carrier material.

The particulate superabsorbent polymer composition according to the present invention can be used in many absorbent articles, including sanitary napkins, diapers or wound covers, and has the property of rapidly absorbing large amounts of menstrual blood, urine or other body fluids. Since the agent according to the present invention retains the absorbed liquid even under pressure and is capable of distributing more liquid in the structure of the swollen state, it is preferably higher than the conventional superabsorbent composition. The concentration of the hydrophilic fibrous material such as fluff is used. It is also suitable for use as a homogenous superabsorbent layer free of fluff within the diaper construction, with the result that particularly thin articles are possible. The polymer is additionally suitable for use in hygiene products for adults (eg incontinence products).

For example, referring now to Figure 5, in one aspect, the micro described herein is employed. The absorbent article of the particulate superabsorbent polymer composition is a disposable article 10 comprising a backsheet or outer cover 20, a liquid permeable topsheet or bodyside liner 22 disposed in facing relationship with the outer cover 20, and a body side An absorbent core 24, such as an absorbent pad, between the liner 22 and the outer cover 20. The article 10 has an outer surface 23, a front waist region 25, a back waist region 27, and a crotch region 29 connecting the front waist region 25 and the back waist region 27. The outer cover 20 defines a length and a width which, in the illustrated embodiment, coincide with the length and width of the article 10. The absorbent core 24 is generally defined as having a length and width that are less than the length and width of the outer cover 20, respectively. Thus, the edge portion of the article 10, such as the edge section of the outer cover 20, can extend beyond the end edge of the absorbent core 24. For example, in the illustrated aspect, the outer cover 20 extends outward beyond the end edges of the absorbent core 24 to form the side edges and end edges of the article 10. The bodyside liner 22 is generally coextensive with the outer cover 20, but may optionally cover an area that is larger or smaller than the area of the outer cover 20 as desired. In other words, the body side liner 22 is attached to the outer cover 20 in a superposed relationship. The outer cover 20 and the body side liner 22 are intended to face the wearer's garment and body, respectively, when in use.

To provide improved fit and to help reduce body exudate leakage from the article 10, the side edges and end edges of the article can be elasticized using suitable elastic members, such as single or multiple elastic strands. The elastic strands may be composed of natural or synthetic rubber and may optionally be heat shrinkable or thermally elasticizable. For example, as representatively illustrated in Figure 5, the article 10 can include a leg elastic 26 that is configured to operatively gather and elasticize the side edges of the article 10 to provide a resilient fit around the wearer's legs. The leg straps reduce leakage and provide improved comfort and appearance. Similarly, the waist elastics 28 can be used to impart elasticity to the end edges of the article 10 to provide an elasticized waist. The waist elastic 28 is configured to operatively gather and tighten the waist section to provide a resilient fit that fits snugly around the wearer's waist. In the illustrated aspect, the elastic member is illustrated in its non-contracted stretched state for clarity purposes.

Fastening members, such as hook and loop fasteners 30, can be used to secure the article 10 to the wearer. Alternatively, other fastening members may be employed, such as buttons, pins, snaps, adhesive tape fasteners, adhesives, mushroom head and loop fasteners, belts, and the like, as well as combinations comprising at least one of the fasteners described above. In addition, more than two fasteners may be provided, especially if the article 10 is intended to be provided in a pre-fastened configuration.

The article 10 can additionally include other layers between the absorbent core 24 and the bodyside liner 22 or the outer cover 20. For example, the article 10 can also include a surge management layer 34 between the bodyside liner 22 and the absorbent core 24 to prevent pooling of liquid exudates and further improve air exchange and distribution of fluid exudates within the article 10.

Article 10 can have a plurality of suitable shapes. For example, article 10 can have an overall rectangular shape, a T-shape, or a generally hourglass shape. In the illustrated form, the article 10 has a generally I-shape. The article 10 further defines a longitudinal direction 36 and a transverse direction 38. Other suitable article components that can be incorporated into an absorbent article include receiving flaps, waist flaps, elastic side panels, and the like.

The various components of article 10 are integrally assembled using a plurality of types of joining mechanisms, such as adhesives, sonic bonding, thermal bonding, and the like, and combinations comprising at least one of the above mechanisms. For example, in the illustrated aspect, the bodyside liner 22 and the outer cover 20 are assembled to the absorbent core 24 along an adhesive (such as a hot melt pressure sensitive adhesive) wire. Similarly, other article components, such as elastic members 26 and 28, fastening members 30, and surge layer 34, can be assembled into article 10 by employing the attachment mechanisms identified above.

The outer cover 20 of the article 10 can comprise any material for such applications, such as a material that is substantially permeable to vapor. The permeability of the outer cover 20 can be configured to enhance the breathability of the article 10 and reduce the hydration of the wearer's skin during use, and does not allow excessive condensation of vapors, such as urine, on the garment facing the surface of the outer cover 20, which can Improperly wet the wearer's clothes. The housing 20 may be constructed to at least water vapor permeable and may have a water vapor transmission rate of greater than or equal to about 000 grams per square meter per 24 hours (g / m ² / 24hr) of. For example, the outer cover 20 can define a water vapor transmission rate of from about 1,000 to about 6,000 g/m ² /24 hr.

The outer cover 20 is also desirably substantially liquid impermeable. For example, the outer cover 20 can be configured to provide a static head value greater than or equal to about 60 centimeters (cm) or more specifically greater than or equal to about 80 cm and, even more specifically, greater than or equal to about 100 cm. A technique suitable for determining the resistance of a material to liquid permeability is the Federal Test Method Standard (FTMS) 191 Method 5514, which began on December 31, 1968.

As noted above, the outer cover 20 can comprise any material for such applications, and desirably includes materials that directly provide the above-described desired levels of liquid impermeability and gas permeability and/or can be modified or otherwise treated to provide This level of material. The outer cover 20 can be a nonwoven web that is configured to provide a desired level of liquid impermeability. For example, a nonwoven web comprising spunbond and/or meltblown polymeric fibers can be selectively treated with a water repellent coating and/or laminated with a liquid impermeable, vapor permeable polymeric film to provide outer cover 20. In another aspect, the outer cover 20 can comprise a nonwoven web comprising a plurality of randomly deposited hydrophobic thermoplastic meltblown fibers that are sufficiently bonded or otherwise joined to each other to provide substantially vapor permeable and substantially Liquid impermeable mesh. The outer cover 20 can also include a vapor permeable, non-woven layer that has been partially coated or otherwise configured to provide liquid impermeability in selected areas. In another example, the outer cover 20 is provided from an extendable material. Additionally, the outer cover 20 material can be stretched in the longitudinal direction 36 and/or the transverse direction 38. When the outer cover 20 is made of an extensible or stretchable material, the article 10 provides additional benefits to the wearer, including improved fit.

The bodyside liner 22 for helping to isolate the wearer's skin from the liquid contained in the absorbent core 24 can determine an adaptive, soft, non-irritating sensation of the wearer's skin. Additionally, the bodyside liner 22 may be less hydrophilic than the absorbent core 24 to present a relatively dry surface to the wearer and may be sufficiently porous for liquid permeable to allow liquid to readily penetrate through its thickness. Suitable body side liners 22 can be made from a wide selection of web materials, such as porous foams, reticulated foams, perforated plastic films, natural fibers (such as wood or cotton fibers), synthetic fibers (such as polyester or poly). A combination of propylene fibers and the like, and materials comprising at least one of the foregoing materials.

A variety of woven and non-woven fabrics can be used for the bodyside liner 22. For example, the bodyside liner 22 can comprise a meltblown or spunbond web (eg, of polyolefin fibers), a bonded-carded web (eg, natural and/or synthetic fibers), a substantially hydrophobic material (eg, an interface) The active agent is treated or otherwise processed to impart the desired level of wettability and hydrophilicity, and analogs thereof, and combinations comprising at least one of the foregoing. For example, the bodyside liner 22 can comprise a non-woven, spunbond, polypropylene fabric, optionally comprising from about 2.8 to about 3.2 denier fibers, formed to have about 22 grams per square meter (g/m ^{2 ).} The basis weight and a mesh fabric having a density of about 0.06 grams per cubic centimeter (g/cc).

The absorbent core 24 of the article 10 can comprise a hydrophilic fibrous matrix, such as a fibrous web of cellulosic fibers, mixed with particles of the particulate superabsorbent polymer composition. Wood pulp fluff may be replaced with synthetic, polymeric, meltblown fibers and the like, and combinations comprising at least one of the foregoing. The particulate superabsorbent polymer composition may be substantially uniformly mixed with the hydrophilic fibers or may be unevenly mixed. Alternatively, the absorbent core 24 can comprise a laminate of fibrous web and particulate superabsorbent polymer composition and/or a matrix suitable for maintaining the particulate superabsorbent polymer composition in a localized region. When the absorbent core 24 comprises a combination of hydrophilic fibers and particulate superabsorbent polymers, the hydrophilic fibers and particulate superabsorbent polymer composition can form an average basis weight of from about 400 grams per square meter (g/m ² ) to About 900 g/m ² or more specifically, from about 500 g/m ² to about 800 g/m ² and even more specifically, from about 550 g/m ² to about 750 g/m ² of absorbent core 24.

Generally, the particulate superabsorbent polymer composition is present in the absorbent core 24 in an amount greater than or equal to about 50 weight percent (wt%) or more desirably greater than or equal to about 70 wt%, based on the total weight of the absorbent core 24. . For example, in a particular aspect, the absorbent core 24 can comprise a web or other suitable for maintaining the superabsorbent material in a localized region having greater than or equal to about 50 wt% or more desirably greater than or equal to about 70 wt%. A laminate of material-outsourced particulate superabsorbent polymer.

Optionally, the absorbent core 24 can additionally include a support (e.g., a substantially hydrophilic tissue or non-woven wrap (not shown)) that helps maintain the structural integrity of the absorbent core 24. The tissue wrap layer can be placed around the web/fabric of the high absorbency material and/or the fiber, optionally over at least one or both of its facing major surfaces. The tissue wrap layer may comprise an absorbent cellulosic material such as a wrinkle wrap or a high wet strength tissue. The tissue wrap layer can optionally be configured to provide a wicking layer that facilitates rapid distribution of liquid over the absorbent fiber mass that constitutes the absorbent core 24. If such a support is used, the colorant 40 can optionally be placed in the support on the side of the absorbent core 24 opposite the outer cover 20.

Since the absorbent core 24 is thin and the absorbent material is within the absorbent core 24, the rate of liquid absorption of the absorbent core 24 itself may be too low or sufficient to survive the multiple liquid attack of the absorbent core 24. To improve overall liquid absorption and air exchange, the article 10 can additionally include a porous liquid permeable layer of the surge management layer 34, as illustrated in Figure 5. The surge management layer 34 is typically less hydrophilic than the absorbent core 24 and can have an operational level of density and basis weight for rapid collection and The liquid surge is temporarily contained, the liquid is delivered from its initial entry point and the liquid is substantially completely released to other portions of the absorbent core 24. This configuration can help prevent liquid from collecting and collecting portions of the article 10 placed against the wearer's skin, thereby reducing the wearer's moist feel. The structure of the surge management layer 34 also enhances the air exchange within the article 10.

A variety of woven and non-woven fabrics can be used to construct the surge management layer 34. For example, surge management layer 34 can be a meltblown or spunbond web comprising the following layers: synthetic fibers (such as polyolefin fibers); including, for example, natural and/or synthetic fibers bonded-carded webs; Surfactant treated or otherwise processed to impart a desired level of wettability and hydrophilicity to hydrophobic materials; and the like, and combinations comprising at least one of the foregoing. The bonded carded web can be, for example, a thermally bonded web bonded using low melt binder fibers, powders and/or adhesives. This layer may optionally comprise a mixture of different fibers. For example, surge management layer 34 can include a hydrophobic nonwoven material having a basis weight of from about 30 g/m ² to about 120 g/m ² .

test program

Vortex test

Vortex test measured 2 grams of SAP close to the amount of time (in seconds) required to vortex by stirring 50 ml of saline solution at 600 rpm on a magnetic stir plate. The time taken to approach the vortex is an indication of the free swelling rate of SAP.

Equipment and materials

1. Schott Duran 100mL beaker and 50ml graduated cylinder.

2. capable of providing 600 revolutions / minute Programmable magnetic stir plate (such as available under the trade Dataplate ^® Model 721 commercially available from PMC Industries).

3. Acyclic a magnetic stir bar, 7.9 mm × 32 mm, Teflon ^® cover (such as available under the trade name S / PRIM brand available from Baxter Diagnostics, having a single round package Removable pivot rings stir bar).

4. Horse watch

5. Balance, accurate to +/- 0.01g

6. Aqueous saline solution, available from Baxter Diagnostics, 0.87 w/w% blood pool brine (for the purposes of this application, deemed equivalent of 0.9 wt.% brine)

7. Weighing paper

8. Indoors with standard conditions: temperature = 23 ° C +/- 1 ° C and relative humidity = 50% +/- 2%.

test program

1. Measure 50 ml +/- 0.01 ml saline solution in a 100 ml beaker.

2. Place the magnetic stir bar in the beaker.

3. Stylize the magnetic stir plate to 600 rpm.

4. Place the beaker on the center of the magnetic stir plate to activate the magnetic stir bar. The bottom of the vortex should be close to the top of the stir bar.

5. Weigh 2g +/- 0.01g of the SAP to be tested on the weighing paper.

Note: SAP is tested as is (ie, it will become an absorbing complex, such as those described herein). Even if a particular granularity is known to have an impact on this test, the granularity is not filtered.

6. While stirring the saline solution, quickly pour the SAP to be tested into the saline solution and turn on the horse. The SAP to be tested should be added to the brine solution between the center of the vortex and the side of the beaker.

7. Stop the watch when the surface of the saline solution is flat and record the time.

8. The time recorded in seconds is reported as the vortex time.

Centrifuge Retention Capacity Test (CRC)

The CRC test measures the ability of the particulate SAP composition to retain its liquid after saturation and centrifugation under controlled conditions. The resulting retained capacity is expressed in grams of liquid (g/g) retained per gram of sample weight. The SAP samples to be tested were prepared using particles pre-screened through a US standard 30 mesh screen and retained on a US standard 50 mesh screen. Thus, the particulate SAP sample comprises particles having a size ranging from about 300 microns to about 600 microns. These particles can be pre-screened manually or automatically.

Retention capacity was measured by placing approximately 0.20 grams of pre-screened particulate SAP sample in a water permeable bag containing the sample while allowing the sample to freely absorb the test solution (distilled water containing 0.9 weight percent sodium chloride). The heat sealable tea bag material (such as the model name 1234T heat sealable filter paper available from Dexter (in Windsor Locks, Connecticut, U.S.A.)) works well for most applications. The bag was formed as follows: a 5 inch by 3 inch bag material sample was folded in half and the two open sides were heat sealed to form a 2.5 inch by 3 inch rectangular pouch. The heat seal is about 0.25 inch inside the edge of the material. After the sample is placed in the pouch, the remaining open sides of the pouch are also heat sealed. Empty bags were also made for use as controls. Three samples were prepared for each particle SAP to be tested.

The sealed bag was immersed in a flat plate containing a test solution of about 23 ° C to ensure that the bag was pressed until it was completely wetted. After wetting, the particulate SAP sample was held in solution for about 30 minutes, at which point it was removed from the solution and temporarily laid on a non-absorbent flat surface.

The wet bag is then placed in a drum where the wet bags are separated from one another and placed at the outer circumferential edge of the drum, where the drum is a suitable centrifuge capable of subjecting the sample to a force of about 350 g. One suitable centrifuge is the CLAY ADAMS DYNAC II Model 0103, which has a water collection drum, a digital rpm gauge, and a machined drain drum that is adapted to hold and drain a flat bag sample. When centrifuging multiple samples, the sample is placed in an opposite position within the centrifuge to balance the drum as it rotates. The bags (including wet empty bags) are centrifuged at about 1,600 rpm (e.g., to achieve a target g force of about 350 g force, offset from about 240 to about 360 g force) for 3 minutes. The G force is defined as the unit of inertial force on an object subjected to rapid acceleration or gravity, equal to 32 ft/sec ² at sea level. The bags were removed and weighed, first empty bags (control) were weighed, and the bags containing the particulate SAP samples were weighed. The amount of solution retained by the particulate SAP sample is the centrifuge retention capacity (CRC) of the SAP, expressed as the fluid grams per gram of SAP, taking into account the solution retained by the bag itself. More specifically, the retention capacity is determined by the following equation: CRC = [sample bag after centrifugation - empty bag after centrifugation - dry sample weight] / dry sample weight

Three samples were tested and the results were averaged to determine the CRC of the particulate SAP.

Free Swelling Gel Bed Permeability Test (FSGBP)

As used herein, the free swell gel bed permeability test is also referred to as the Gel Bed Permeability Test (FSGBP) at 0 psi swell pressure, which measures gel particles (eg, particulate SAP or particulate SAP prior to surface treatment) The permeability of a swollen bed under conditions commonly referred to as "free swelling." The term "free swell" means that the gel particles are allowed to swell without a limiting load when absorbing the test solution, as will be described below. Apparatus suitable for performing gel bed permeability testing is shown in Figures 1, 2 and 3 and is generally indicated at 500. Test equipment assembly 528 includes a sample container, generally indicated at 530, and a plunger, generally indicated at 536. The plunger includes a shaft 538 having a cylindrical bore drilled down the longitudinal axis and a tip 550 positioned at the bottom of the shaft. The shaft hole 562 has a diameter of about 16 mm. The plunger tip is attached to the shaft, such as by adhesive bonding. Twelve holes 544 are drilled into the radial axis of the shaft, and three holes positioned every 90 degrees have a diameter of about 6.4 mm. axis Rod 538 is machined from LEXAN or equivalent material and has an outer diameter of about 2.2 cm and an inner diameter of about 16 mm.

The plunger tip 550 has seven concentric inner ring holes 560 and four outer ring holes 554, all having a diameter of about 8.8 millimeters and about 16 mm holes aligned with the shaft. The plunger tip 550 is machined from a LEXAN rod or equivalent material and has a height of about 16 mm and is sized to fit within the cylinder 534 with a minimum wall clearance but still free to slide. The total length of the plunger tip 550 and shaft 538 is about 8.25 cm, but can be machined on top of the shaft to obtain the plunger 536 of the desired mass. The plunger 536 includes a 100 mesh stainless steel screen 564 that is biaxially tensioned and attached to the lower end of the plunger 536. The screen is attached to the plunger tip 550 using a suitable solvent such that the screen is firmly adhered to the plunger tip 550. Care must be taken to avoid excessive solvent migration into the open portion of the screen and to reduce the open area for liquid flow. The acrylic adhesive Weld-On #4 from IPS (which has a business office in Gardena, California, USA) is a suitable adhesive.

The sample container 530 includes a barrel 534 and a 400 mesh stainless steel screen 566 that is biaxially tensioned and attached to the lower end of the barrel 534. The screen is attached to the cylinder using a suitable solvent so that the screen adheres firmly to the cylinder. Care must be taken to avoid excessive solvent migration into the open portion of the screen and to reduce the open area for liquid flow. The acrylic adhesive Weld-On #4 from IPS is a suitable adhesive. During the test, a sample of gel particles indicated as 568 in Figure 2 was loaded onto screen 566 in cylinder 534.

The barrel 534 can be drilled from a transparent LEXAN rod or equivalent material, or it can be cut from a LEXAN tube or equivalent material and has an inner diameter of about 6 cm (eg, a cross-sectional area of about 28.27 cm ² ), about The wall thickness of 0.5 cm and the height of about 7.95 cm. The step is machined into the outer diameter of the cylinder 534 such that the bottom 31 mm of the cylinder 534 has a region 534a having an outer diameter of 66 mm. The o-ring 540 of the diameter of the mating region 534a can be placed on top of the step.

The annular weight 548 has a countersunk bore of approximately 2.2 cm diameter and 1.3 cm depth that allows it to slide freely on the shaft 538. The annular weight also has a through hole 548a of about 16 mm. The annular weight 548 can be made of stainless steel or other suitable material that is resistant to corrosion in the presence of a test solution which is distilled water containing 0.9 weight percent sodium chloride solution. The total weight of plunger 536 and annular weight 548 is equal to about 596 grams (g), which is equivalent to applying a pressure of about 0.3 pounds per square inch (psi) on sample 568, or applying a sample area of about 28.27 cm ² . A pressure of about 20.7 dynes/cm 2 (2.07 kPa).

The sample container 530 is typically placed on the crucible 600 when the test solution flows through the test apparatus during the test as described below. The purpose of the crucible is to split the liquid overflowing the top of the sample container 530 and to divert the overflow liquid into the separation collection device 601. The crucible can be positioned above the balance 602 with the beaker 603 resting thereon to collect the brine solution that passes through the swollen sample 568.

To perform a gel bed permeability test under "free swell" conditions, a plunger 536 having a weight 548 placed thereon was placed in an empty sample container 530 and a suitable gauge weight 548 accurate to 0.01 mm was used. The height from the top to the bottom of the sample container 530. The force exerted by the gauge during the measurement should be as low as possible, preferably less than about 0.74 Newtons. It is important to measure the height of each empty sample container 530, plunger 536, and weight 548 combination and remember which plunger 536 and weight 548 were used when using multiple test equipment. The same plunger 536 and weight 548 should be used when sample 568 swells later after saturation. The base on which the sample cup 530 rests is also preferably horizontal, and the top surface of the weight 548 is parallel to the bottom surface of the sample cup 530.

The sample to be tested was prepared from microparticulate SAP which was pre-screened through a US standard 30 mesh screen and retained on a US standard 50 mesh screen. Therefore, the test sample contains dimensions of about 300 Particles up to about 600 microns. SAP particles can be pre-screened using, for example, RO-TAP Mechanical Screening Oscillator Model B, available from W.S. Tyler, Inc., Mentor Ohio. Screen for 10 minutes. Approximately 2.0 grams of sample was placed in sample container 530 and spread evenly over the bottom of the sample container. A container containing 2.0 grams of sample without the plunger 536 and weight 548 was then immersed in a 0.9% saline solution for a period of about 60 minutes to saturate the sample and allow the sample to swell without any limiting load. During saturation, the sample cup 530 is placed on a screen located in the reservoir to raise the sample cup 530 slightly above the bottom of the reservoir. The screen does not inhibit the flow of saline solution into the sample cup 530. A suitable screen is available as Part No. 7308 from Eagle Supply and Plastic, which has a place of business in Appleton, Wisconsin, U.S.A. The brine did not adequately cover the SAP particles as evidenced by the completely flat saline surface in the test unit. In addition, the depth of the brine is not allowed to be too low such that the surface within the unit is only defined by the swollen SAP rather than the brine.

At the end of this period, plunger 536 and weight 548 assembly are placed on saturated sample 568 in sample container 530, and sample container 530, plunger 536, weight 548, and sample 568 are then removed from the solution. After removal and prior to measurement, sample container 530, plunger 536, weight 548, and sample 568 were allowed to rest on a flat, large grid, non-deformed plate of uniform thickness for about 30 seconds. The thickness of the saturated sample 568 is determined by again measuring the height of the top of the weight 548 to the bottom of the sample container 530 using the same thickness gauge as previously used (the constraint is zero and the initial height measurement). Sample container 530, plunger 536, weight 548, and sample 568 can be placed on a flat, large grid, non-deformed plate of uniform thickness that will be provided for drainage. The panel has a total size of 7.6 cm by 7.6 cm, and each grid has a cell size of 1.59 cm long by 1.59 cm wide by 1.12 cm deep. A suitable flat large grid non-deformable sheet material is a parabolic diffuser plate purchased from McMaster Carr Supply, Inc., which has a business office in Chicago, Illinois, U.S.A., catalog number

1624K27, which can then be cut to size. This flat large screen non-deformable plate must also exist when the height of the initial empty assembly is measured. Once the thickness gauge is engaged, the height measurement should be performed immediately. The height measurements obtained after saturation of sample 568 are subtracted from the height measurements obtained from the volumetric empty sample container 530, plunger 536, and weight 548. The value obtained is the thickness or height "H" of the swollen sample.

Permeability measurements were initiated by delivering a 0.9% saline solution stream to a sample container 530 containing a saturated sample 568, a plunger 536, and a weight 548. The flow rate of the test solution into the vessel is adjusted such that the brine solution overflows the top of the cylinder 534, resulting in a constant discharge pressure equal to the height of the sample vessel 530. The test solution can be added by any suitable means sufficient to ensure a small but constant amount of overflow from the top of the cylinder, such as by metering pump 604. The overflow liquid is split into another collection device 601. The amount of solution passing through sample 568 relative to time was measured gravimetrically using balance 602 and beaker 603. Once the overflow has begun, the data points of the balance 602 are collected every second for at least sixty seconds. Data collection can be done manually or with data collection software. The flow rate Q through the swollen sample 568 was measured in grams per second (g/s) by a linear least squares fit through time (seconds) of fluid passing through sample 568 (grams).

The permeability (cm ² ) is obtained by the following equation: K = [Q * H * μ] / [A * ρ * P]

Where K = permeability (cm ² ), Q = flow rate (g / s), H = height of the swollen sample (cm), μ = liquid viscosity (poise) (about 1 centipoise used in this test) Test solution), A = cross-sectional area of liquid flow (sample container used in this test is 28.27 cm ² ), ρ = liquid density (g/cm ³ ) (test solution used in this test is about 1 g/cm ³ And P = hydrostatic pressure (dynes / square centimeters) (usually about 7,797 dyne / cm ^ 2). For the gel bed permeability test described herein, the hydrostatic pressure is calculated from P = ρ * g * h , where ρ = liquid density (g / cm ³ ), g = gravity acceleration, nominally 981 cm / sec ² and h = fluid height, for example 7.95 cm.

A minimum of two samples were tested and the results were averaged to determine the gel bed permeability of the particulate SAP sample.

The FSGBP can be measured as described herein prior to performing the processing test on the particulate SAP as described herein. Such FSGBP values can be referred to as the "raw" FSGBP of the particulate SAP. FSGBP can also be measured after processing the particulate SAP. Such FSGBP values can be referred to as "processed" FSGBP. The processed FSGBP of the original FSGBP and particulate SAP comparing the particulate SAP can be used as a measure of the stability of the composition. It should be noted that all "raw" and "post-processed" FSGBP values reported herein are measured using pre-screened 300 to 600 μm particle samples.

Absorption test under load (AUL (0.9psi))

The Under Load (AUL) test measures the ability of the particulate SAP to absorb a 0.9 weight percent solution (test solution) of sodium chloride in distilled water at room temperature while the material is under a load of 0.9 psi. The equipment for testing AUL consists of the following:

• AUL assembly, including cylinder, 4.4g piston and standard 317g weight. The components of this assembly are described in additional detail below.

A flat-bottom square plastic tray that is wide enough to allow the frit to be on the bottom without coming into contact with the tray wall. A plastic tray of 9" by 9" (22.9 cm x 22.9 cm) and a depth of 0.5 to 1" (1.3 cm to 2.5 cm) is usually used in this test.

• 9 cm diameter sintered frit with "C" porosity (25 microns to 50 microns). This glass frit was prepared in advance by equilibration in brine (0.9 wt% aqueous sodium chloride solution). In addition to washing with at least two portions of fresh brine, the frit must be immersed in the brine for at least 12 hours prior to AUL measurement.

● Whatman 1 grade 9cm diameter filter paper ring.

• Brine supply (0.9 wt% sodium chloride in distilled water).

Referring to Figure 4, a cylinder 412 for an AUL assembly 400 containing particulate superabsorbent polymer composition 410 is fabricated from a one-inch (2.54 cm) inner diameter thermoplastic pipe machined to provide a slight outward concentricity. After machining, the 400 mesh stainless steel wire cloth 414 is attached to the bottom of the cylinder 412 by heating the wire cloth 414 in a flame until red heat, after which the cylinder 412 is held on the wire cloth until cooling. If it is unsuccessful or if it breaks, a soldering iron can be used to complete the seal. Care must be taken to maintain the bottom of the cylinder 412 flat and smooth without distortion inside.

4.4g piston (416) by a 1 inch diameter solid material (e.g., PLEXIGLAS ^®) is made and machined to mate with the cylinder 412 without bonding.

A standard 317 g weight 418 was used to provide a limiting load of 62,053 dynes/cm 2 (about 0.9 psi). The weight is a 1 inch (2.5 cm) diameter cylindrical stainless steel weight that is machined to fit tightly into the cylinder without sticking.

Sample 410 corresponds to a layer of at least about 300 gsm unless otherwise specified. AUL was tested using (0.16 g) SAP particles. Sample 410 was taken from SAP particles pre-screened through a U.S. Standard #30 screen and retained on a U.S. Standard #50 screen. SAP particles can be used, for example, commercially available from WSTyler, Corporation, Mentor Ohio the RO-TAP ^® mechanical sieving shaker type B pre-screening. Screen for about 10 minutes.

Prior to placing the SAP particles 410 in the cylinder 412, the interior of the cylinder 412 was wiped with an antistatic cloth.

A sample of the desired amount of sieved particulate SAP 410 (about 0.16 g) was weighed out on the weighing paper and evenly distributed over the wire cloth 414 at the bottom of the cylinder 412. Particle SAP in the bottom of the cylinder The weight is recorded as "SA" for the AUL calculation described below. Care is taken to ensure that no particulate SAP adheres to the cylinder wall. After the 4.4 g piston 412 and 317 g weight 418 were carefully placed on the SAP particles 410 in the cylinder 412, the AUL assembly 400 including the cylinder, piston, weight and SAP particles was weighed and the weight recorded as Weight "A".

Sintered frit 424 (described above) is placed in plastic tray 420 and brine 422 is added to the height of the upper surface of frit 424. A single circular filter paper 426 is gently placed over the frit 424, and then the AUL assembly 400 with particulate SAP 410 is placed on top of the filter paper 426. The AUL assembly 400 is then held on top of the filter paper 426 for a one hour test period while taking care to keep the brine content in the tray constant. At the end of the 1 hour test period, the AUL equipment was then weighed and this value was recorded as weight "B".

AUL (0.9 psi) is calculated as follows: AUL (0.9 psi) = (B-A) / SA

among them

A = weight of AUL unit with dry SAP

B = weight of the AUL unit of SAP after 60 minutes of absorption

SA=actual SAP weight

A minimum of two tests were performed and the average of the results was taken to determine the AUL value at 0.9 psi load. The particulate SAP sample was tested at about 23 ° C and about 50% relative humidity.

PAI test

The pressure absorption index is the sum of the absorption values of SAP under load (described below) measured under the following load: 0.01 pounds per square foot (690 dyne per square centimeter); 0.29 pounds per square foot (19995 dyne per square foot) Cm); 0.57 pounds per square foot (39,300 dyne per square foot) (cm); and 0.90 pounds per square foot (62053 dyne per square centimeter). That is, the absorption value of a given SAP under load is determined under the limiting forces set forth above in accordance with the methods set forth below in connection with the examples. The pressure absorption index is then generated by summing the absorption values under load measured under the limiting load as set forth above.

Moisture content test

The amount of water content measured in the form of "% Moisture" can be measured as follows: 1) Accurately weigh 5.0 gram of superabsorbent polymer composition (SAP) in a pre-weighed aluminum weighing pan; 2) SAP and Place the flat plate in a standard laboratory oven preheated to 105 ° C for 3 hours; 3) remove and reweigh the flat plate and contents; and 4) calculate the percentage humidity using the following formula: moisture % = { (( flat Disc weight + initial SAP weight) - (dry SAP and flat weight) * 100} / initial SAP weight

Example

The following Comparative Examples 1 to 4 and Examples 1 to 12 and Tables 1 and 2 are provided to illustrate the product comprising the particulate superabsorbent polymer of the present invention as set forth in the scope of the patent application and to manufacture microparticle superabsorbent. The method of the polymer does not limit the scope of the patent application. All parts and percentages are based on dry particulate superabsorbent polymer unless otherwise stated.

Example 1 To a polyethylene vessel equipped with a stirrer and a cooling coil, 2.0 kg of 50% NaOH and 3.32 kg of deionized water were added and cooled to 20 °C. 0.8 kg of glacial acrylic acid was then added to the caustic solution and the solution was again cooled to 20 °C. Add 0.6 g of polyethylene glycol monoallyl ether acrylate, 1.2 g of ethoxylated trimethylolpropane triacrylate SARTOMER ^® 9035 product and 1.6 kg of glacial acrylic acid to the first solution, followed by cooling to 4-6 °C. Nitrogen gas was bubbled through the monomer solution for about 5 minutes. 4.38 g of sodium hydrogencarbonate, 0.0364 g of Tween 80 and 0.0364 g of Span 20 were dissolved in 95.55 g of water. The mixture was added to the monomer solution and mixed using a Silverson high shear mixer at 6500 RPM for 30 seconds. The monomer solution is then discharged into a rectangular tray. 80 g of a 1 wt% aqueous solution of H ₂ O ₂ , 120 g of a 2 wt% aqueous sodium persulfate solution, and 72 g of 0.5 wt% sodium erythorbate were added to the monomer solution to initiate polymerization. The stirrer was stopped and the initiated monomer was polymerized for 20 minutes.

The resulting hydrogel was cut short and extruded using a Hobart 4M6 commercial extruder, followed by a flow of air at 175 ° C on a 20 吋 x 40 吋 perforated metal tray in a Procter & Schwartz Model 062 forced air oven. It was dried for 12 minutes and dried with downward flowing air for 6 minutes until the final product moisture content was less than 5% by weight. The dried material was coarsely ground in a Prodeva Model 315-S crusher, ground in an MPI 666-F three-stage roll mill and sieved with a Minox MTS 600DS3V to remove particles larger than 850 μm and smaller than 150 μm.

8 g of ethylene carbonate solution (50% wt/wt in water) was applied to 400 g of the surface of the above particles. When the superabsorbent polymer particles are fluidized in air, a fine atomized spray of a Paasche VL sprayer is used and mixing is continued. The coated material was then heated in a convection oven at 185 ° C for 55 minutes for surface crosslinking. The surface crosslinked particulate material is then sieved through a 20/100 mesh U.S. standard sieve to remove particles greater than 850 [mu]m and less than 150 [mu]m. The surface crosslinked particulate material was cooled to below 60 ° C and coated with a solution containing 0.4 g of polyethylene glycol (molecular weight 8000) and 40 g of deionized water. The coated material was allowed to relax at room temperature for one day and then sieved with a 20/100 mesh U.S. standard sieve to remove particles greater than 850 [mu]m and less than 150 [mu]m.

The following is a representative PSD and average particle size (D50) of Example 1:

Example 2 The same as Example 1 except that 0.0364 g of Tween 80 and 0.0364 g of Span40 were used to replace 0.0364 g of Tween 80 and 0.0364 g of Span20.

Example 3 The same as Example 1 except that 0.0364 g of Tween 80 and 0.0364 g of Span60 were used in place of 0.0364 g of Tween 80 and 0.0364 g of Span20.

Example 4 The same as Example 1 except that 0.0364 g of Tween 20 and 0.0364 g of Span20 were used to replace 0.0364 g of Tween 80 and 0.0364 g of Span20.

Example 5 - The same as Example 1 except that 0.0364 g of Tween 40 and 0.0364 g of Span20 were substituted for 0.0364 g of Tween 80 and 0.0364 g of Span20.

Example 6 - The same as Example 1 except that 0.0364 g of Tween 60 and 0.0364 g of Span20 were substituted for 0.0364 g of Tween 80 and 0.0364 g of Span20.

Comparative Example 1 Control - a superabsorbent polymer that is regularly surface crosslinked in the absence of a surfactant or blowing agent.

Comparative Example 2 - a surfactant mixture comprising 0.0364 g Tween 80 and 0.0364 g Span 20, but no blowing agent.

Comparative Example 3 - Example 1 comprising only 0.025% Span 20 but no Tween 80.

Comparative Example 4 - Example comprising only 0.025% Tween 80 but no Span 20 1.

Neutralized aluminum salt A

A 200 g aluminum sulfate solution (20% aqueous solution) was stirred in a beaker using a magnetic stir bar. To this solution was added a sodium hydroxide solution (50% aqueous solution) until the pH of the mixture reached 7. A total of 130 g of sodium hydroxide solution was consumed. The white colloidal suspension was stirred for 15 minutes and further sheared with a Turnax mixer for about 1 minute to break up the clot. The neutralized aluminum solution was used for superabsorbent polymer modification without further purification.

Example 7 - Example 1 wherein the surface crosslinked particulate material was cooled to below 60 ° C and a solution containing 16 g of neutralized aluminum salt A and 0.4 g of polyethylene glycol (molecular weight 8000) and 40 g of deionized water was used. Coating. The coated material was allowed to relax at room temperature for one day and then sieved with a 20/100 mesh U.S. standard sieve to remove particles greater than 850 [mu]m and less than 150 [mu]m.

Example 8 - When the SAP particles were fluidized in air, 16 g of neutralized aluminum salt A and 8 g of ethylene carbonate solution (50% wt/wt in water) were applied to 400 g using a fine atomized spray of a Paasche VL sprayer. The surface of the SAP of Example 1 was continuously mixed. The coated material was then heated in a convection oven at 185 ° C for 55 minutes for surface crosslinking. The surface crosslinked particulate material is then sieved through a 20/100 mesh U.S. standard sieve to remove particles greater than 850 [mu]m and less than 150 [mu]m. The surface crosslinked particulate material was cooled to below 60 ° C and coated with a solution containing 16 g of neutralized aluminum salt A and 0.4 g of polyethylene glycol (molecular weight 8000) and 40 g of deionized water. The coated material was allowed to relax at room temperature for one day and then sieved with a 20/100 mesh U.S. standard sieve to remove particles greater than 850 [mu]m and less than 150 [mu]m.

Example 9 - When the SAP particles were fluidized in air, a 0.02 wt% ethylene acrylic acid thermoplastic polymer and 8 g of ethylene carbonate were dissolved using a fine atomized spray of a Paasche VL sprayer. Liquid (50% wt/wt in water) was applied to 400 g of the surface of the SAP of Example 1 and mixing was continued.

Example 10 - The surface crosslinked particulate material of Example 1 was cooled to below 60 ° C and contained 0.2 wt% of (penta-sodium salt of diethylenetriamine pentaacetic acid, Na5DTPA) and 0.4 g of polyethylene glycol (molecular weight 8000) and 40 g of deionized water solution coating. The coated material was allowed to relax at room temperature for one day and then sieved with a 20/100 mesh U.S. standard sieve to remove particles greater than 850 [mu]m and less than 150 [mu]m.

Example 11 - Example 1 was changed to add 0.5% by weight of kaolin to the hydrogel of Example 1.

Example 12 - In addition to 1.2 g of ethoxylated trimethylolpropane triacrylate SARTOMER ^® 9035 internal crosslinker via 1.705 g of Dynasylan® 6490 polyoxane (0.275% boaa), 0.744 g of polyethylene glycol 300 The same procedure as in Example 1 except that acrylate (Peg300DA) (0.120% boaa) and 0.12 g of polyethylene glycol monoallyl ether acrylate (PEGMAE) (0.120% boaa) were substituted. The product of Example 12 had a CRC increment of 2.7 g/g.

Notwithstanding that the numerical ranges and parameters set forth in the broad scope of the invention are approximations, the values set forth in the particular embodiments are as accurate as possible. Except in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and the like, which are used in the specification and claims, are understood to be modified in all instances by the term "about." However, any numerical value inherently contains certain errors necessarily resulting from the standard deviation found in its respective test.

500‧‧‧ equipment

528‧‧‧Test equipment assembly

530‧‧‧ sample container

600‧‧‧堰

601‧‧‧Separation collection device

602‧‧ ‧ balance

603‧‧‧ beaker

604‧‧ metering pump

Claims (20)

A method for producing a particulate superabsorbent polymer having rapid water absorption, comprising the steps of a) preparing an aqueous monomer solution containing a mixture of a monomer of a polymerizable unsaturated acid group and an internal crosslinking agent monomer, wherein the single The bulk aqueous solution comprises dissolved oxygen; b) bubbling the aqueous monomer solution of step a), comprising adding an inert gas to the aqueous monomer solution of step a) to displace dissolved oxygen in the aqueous monomer solution; c) causing step b The aqueous solution of the monomer is polymerized, comprising the following step c1) adding to the aqueous monomer solution of step a): i) comprising about 0.05 wt. based on the total amount of the monomer solution containing the polymerizable unsaturated acid group. From about 0.001 wt.% to about 1.0 wt.% of the aqueous solution of the foaming agent; An aqueous solution of a mixture of a surfactant and a polyethoxylated hydrophilic surfactant; c2) treating the monomer solution of step c1) with high shear mixing to form a treated monomer solution, wherein the components i) an aqueous solution comprising from about 0.1 wt.% to about 1.0 wt.% of a blowing agent; and ii) comprising about 0 001 wt.% to about 1.0 wt.% of an aqueous solution of a lipophilic surfactant and a mixture of polyethoxylated hydrophilic surfactants after bubbling the aqueous monomer solution in step b) and shearing at high speed in step c2) Adding to the aqueous monomer solution before mixing the aqueous solution of the monomer; c3) forming a hydrogel by adding a polymerization initiator to the treated monomer solution of the step c2), wherein the initiator is in the blowing agent And a mixture of the surfactant is added to the treated monomer solution, wherein the polymer is formed to include bubbles of the blowing agent And d) drying and grinding the hydrogel of step c) to form a particulate superabsorbent polymer; and e) crosslinking the surface of the particulate superabsorbent polymer of step d) with a surface crosslinking agent Wherein the surface crosslinked superabsorbent polymer has a vortex of from about 30 seconds to about 60 seconds. A method for producing a particulate superabsorbent polymer according to claim 1, wherein the lipophilic surfactant is nonionic and has an HLB of 4 to 9 and the polyethoxylated hydrophilic surfactant is Non-ionic and has an HLB of 12 to 18. A method for producing a particulate superabsorbent polymer according to claim 1, wherein the mixture of the lipophilic surfactant and the polyethoxylated hydrophilic surfactant has an HLB of 8 to 14. A method for producing a particulate superabsorbent polymer according to claim 1, wherein the lipophilic surfactant is sorbitan ester and the polyethoxylated hydrophilic surfactant is polyethoxylated. Sorbitan ester. A method for producing a particulate superabsorbent polymer according to claim 1, wherein the foaming agent is selected from the group consisting of alkali metal carbonates or alkali metal hydrogencarbonates. A method for producing a particulate superabsorbent polymer according to claim 1, wherein the superabsorbent polymer has a pressure absorption index of from about 120 to about 150. The method for producing a particulate superabsorbent polymer according to claim 1, wherein the particulate superabsorbent polymer comprises about 0.05 wt.% to the total of the monomer solution containing the polymerizable unsaturated acid group. About 1.0 wt.% of the polymerization initiator. A method for producing a particulate superabsorbent polymer according to claim 1, wherein the particulate superabsorbent polymer composition has a particulate superabsorbent polymer composition having a content of not less than about 85 wt% and a particle diameter of less than 600 μ. Particles of m and greater than 150 μm , as specified by the standard sieve classification, and having a weight average particle size (D50) of from 300 μm to 400 μm as specified by the standard sieve classification. The method for producing a particulate superabsorbent polymer according to claim 1, further comprising the step of: e) mixing the surface crosslinked superabsorbent polymer with a chelating agent, wherein the amount of the chelating agent is 100 per 100 Å. The particulate superabsorbent polymer is used in an amount of from about 0.001 part by weight to about 10 parts by weight. A method for producing a particulate superabsorbent polymer according to claim 9 wherein the chelating agent is selected from the group consisting of aminocarboxylic acids having at least three carboxyl groups and salts thereof. A method for producing a particulate superabsorbent polymer according to claim 1, which comprises the steps of: adding a thermoplastic polymer of from about 0.01 wt.% to 0.5 wt.%, based on the weight of the dry polymer powder, to the surface of the particle. Wherein the thermoplastic polymer is added to the particulate superabsorbent polymer together with the surface crosslinking agent or to the particulate superabsorbent polymer before the surface crosslinking agent is added to the particulate superabsorbent polymer, and The coated superabsorbent polymer particles are heat treated at a temperature between 150 ° C and 250 ° C for about 0.5 minutes to about 60 minutes to effect surface crosslinking of the superabsorbent polymer particles. A method for producing a particulate superabsorbent polymer according to claim 11, wherein the thermoplastic polymer is selected from the group consisting of polyethylene, polyester, polyurethane, linear low density polyethylene (LLDPE), ethylene Acrylic copolymer (EAA), styrene copolymer, ethylene alkyl methacrylate copolymer (EMA), polypropylene (PP), ethylene vinyl acetate copolymer (EVA) or blends thereof, or copolymers thereof. A method for producing a particulate superabsorbent polymer according to claim 11 wherein the thermoplastic polymer is added to the particulate superabsorbent polymer together with the surface crosslinking agent. A method for producing a particulate superabsorbent polymer according to claim 11, wherein the thermoplastic polymer is added to the particulate superabsorbent polymer before the surface crosslinker c) is added to the particulate superabsorbent polymer. in. A particulate superabsorbent polymer comprising, within the particle, an internal crosslinked structure produced by using from about 0.1 wt.% to about 1.0 wt.%, based on the total of the monomer solution containing the polymerizable unsaturated acid group. a foaming agent, and a lipophilic nonionic surfactant and polyethoxylated hydrophilicity of from about 0.001 wt.% to about 1.0 wt.%, based on the total of the monomer solution containing the polymerizable unsaturated acid group A nonionic surfactant mixture is produced which has a surface which has been subjected to a crosslinking treatment to crosslink the surface, the particulate superabsorbent polymer having a vortex time of 30 seconds to 60 seconds. The particulate superabsorbent polymer of claim 15 wherein the lipophilic nonionic surfactant has an HLB of from 4 to 9 and the polyethoxylated hydrophilic nonionic surfactant has an HLB of from 12 to 18. The particulate superabsorbent polymer of claim 15 wherein the mixture of the lipophilic nonionic surfactant and the polyethoxylated hydrophilic nonionic surfactant has an HLB of from 8 to 14. The particulate superabsorbent polymer of claim 17, wherein the lipophilic nonionic surfactant is sorbitan ester and the polyethoxylated hydrophilic nonionic surfactant is polyethoxylated dehydrated Sorbitol ester. The particulate superabsorbent polymer of claim 15 wherein the particulate superabsorbent polymer composition has a particulate superabsorbent polymer composition of not less than about 85 wt% and a particle size of less than 600 μm and greater than 150 μ. Particles of m, as specified by the standard sieve classification, and having a weight average particle size (D50) of from 300 μm to 400 μm as specified by the standard sieve classification. An absorbent article comprising: a topsheet; a backsheet; an absorbent core disposed between the topsheet and the backsheet, the absorbent core comprising a particulate superabsorbent polymer composition, the particulate superabsorbent polymer composition being internal to the particle Including an internal crosslinking structure having a foaming agent of from about 0.1 wt.% to about 1.0 wt.%, based on the total amount of the monomer solution containing the polymerizable unsaturated acid group, and the polymerizable unsaturated acid The total amount of the monomer solution is from about 0.001 wt.% to about 1.0 wt.% of a mixture of a lipophilic nonionic surfactant and a polyethoxylated hydrophilic nonionic surfactant having crosslinks The surface is treated to crosslink the surface, and the particulate superabsorbent polymer has a vortex time of 30 seconds to 60 seconds.