BR102018070271B1 - ABSORBENT PARTICLE PREPARED FROM ABSORBENT POLYMER FOAM - Google Patents

Abstract

ABSORBENT PARTICLE PREPARED FROM ABSORBENT POLYMER FOAM. The present invention relates to a polymeric foam and a process for producing the polymeric foam comprising the steps of (a) providing a monomeric solution consisting of a polymerizable, ethylenically unsaturated monomer containing one or more acid groups, water and one or more crosslinkers having more than one polymerizable group per molecule; (b) introducing a blowing agent to the monomer solution; (c) treating the monomer solution with an ultrasonic treatment; (d) introducing one or more initiating agents to the monomer solution; and (e) polymerizing the monomer solution.

Description

FIELD OF INVENTION

[001] The present invention relates to a process for producing absorbent polymeric foam and the resulting polymeric foam products produced therefrom. This polymerization process involves the use of ultrasonic radiation to control the pore size and compressibility of an absorbent foam, which is suitable for shoe insoles and other end products.

BACKGROUND OF THE INVENTION

[002] Polymeric foam insoles or shoe inserts are known for absorbing impact in shoes. For example, US 4,808,469 for Energy Absorbing Polyurethane Composite Article describes an energy absorbing and dampening device of a predetermined configuration, in which the composite is a foam element, and at least one visco-element through which energy is absorbed. . A "viscoelement" is an elastomeric polymer, such as polyurethane compositions, for shock absorption. The polyurethane layer provides energy absorption for the insole or insert. A disadvantage of this composite is that the composite article is hydrophobic. There is no mechanism in this '469 patent for moisture absorption.

[003] A variety of insoles or inserts in the art are specifically configured or designed for fit and comfort. Another example of a typical shock-absorbing insole is US 2016/0073730 for Contoured Support Insole, which discloses a specially molded insole with indentations formed in areas where cushions are attached. This invention is preferably made of polyurethane. The insole of this invention is not based on a layer of foam to absorb impact, but rather on the contour of the insole itself. A similar disadvantage is that the article in this publication is hydrophobic, which leads to difficulties in removing moisture, causing discomfort and smelly effects. There is no description about rapid moisture removal.

[004] The technique also provides a variety of insoles that have absorbent qualities. For example, US 2011/0078920 for Sweat-absorbing Shoe Insole Inserts Having Improved Sweat Absorption discloses a method for improving perspiration absorption in a shoe or boot using particulate amorphous silica as an absorbent in insoles for shoes and/or boots, as well as the shoe insole produced by such a method. The shoe insole of this invention contains an absorbent containing particulate silica. The amorphous silica particulate of this invention is not incorporated into the insole, but rather adhered to the lower surface of the article itself. This post has the disadvantage that the insole itself is not absorbent and the silica must attract and absorb moisture. There is no means of absorbing impact. The insole is not polymeric foam. There is also no means of controlling compressibility or pore size. The absorption of aqueous liquids by silica is also quite limited.

[005] Another example of an insole with absorbent means is US 2016/0015128 for Disposable Insert for Footwear. This publication discloses a thin shoe insert with an upper and lower surface made of non-woven spun polypropylene materials capable of keeping the wearer's foot clean by absorbing sweat, odor and dirt. The shoe insert in this publication has a significant disadvantage in that even though the insert attracts moisture into the non-woven material, the moisture is retained in open spaces. There is no mechanism to prevent moisture from being released as a result of compression. Thus, the shoe insert of this invention is intended to be disposable and changed from time to time. There is no description in this reference to address rapid moisture removal or impact absorption. Polypropylene is also hydrophobic and is not a good absorbent of hydrophilic liquids, such as sweat or other bodily fluids.

[006] In light of the deficiencies of the prior art, there is a need for an insole or shoe insert that is a polymeric foam capable of rapidly absorbing and retaining moisture, despite being compressible to a reasonable walking and running pressure. , and a manufacturing process for such a product, in which the pore size and compressibility of the polymeric foam can be adjusted easily and efficiently.

[007] The use of ultrasonic treatment to activate a polymerization process is known. For example, CN 104558322A discloses a polymer synthesis and particularly relates to a preparation method for activating a polymerization monomer and an initiator by an ultrasonic treatment technology to prepare instant dry anionic polyacrylamide powder of viscosity ultra-high intrinsic.

[008] However, the use of ultrasound to activate polymerization is impractical and requires high energy consumption. The disadvantages of the process disclosed in CN 104558322A become readily evident, in which the ultrasonic activation treatment is carried out at high intensities and with a duration of 5 to 30 minutes. Such use of ultrasound for activation is impractical in the commercial setting. There is no description in CN 104558322A regarding the use of less energy and shorter duration of ultrasonic treatment to control the pore size and compressibility of a polymeric foam. The process produces a product with no moisture absorption or impact absorption properties.

[009] US 5,859,077 describes a method and apparatus for producing an absorbent foam. The method includes forming a reaction solution comprising at least one compound capable of molding an absorbent foam, adding blowing agents under alternating pressures, continuously stirring the reaction solution, applying mechanical waves to the reaction solution, and repeating the stirring and alternating pressure applications a selected number of times continuously throughout the entire reaction, thereby shaping the absorbent foam. This method is based on a particularly complicated apparatus for implementation with repeated steps of alternating pressures, and scaling up in a commercial environment using the ultrasonic treatment disclosed in the '077 patent is impractical. Liquid absorption rates and the capacity of the foam produced were also still very low.

[0010] There is a need for a simplified process for the production of absorbent polymeric foam, in which it is possible to control the pore size and compressibility of the polymeric foam, in which the resulting product presents excellent impact absorption, in addition to having the ability to absorb moisture. There is also a need for an improved absorbent polymeric foam suitable for use in insoles or shoe inserts with improved comfort, and other applications that could benefit from an improved absorbent foam polymer. There is also a need for absorbent particles with a higher absorption speed, where the pore size can be easily controlled. There is also a need for a simpler and more economical process for the production of foamed polymeric absorbent materials.

SUMMARY OF THE INVENTION

[0011] The present invention relates to a polymeric foam and a process for producing a polymeric foam capable of absorbing aqueous fluids, comprising the steps of (a) providing a monomeric solution consisting of a polymerizable, ethylenically unsaturated monomer containing a or more acid groups, water and one or more crosslinkers having more than one polymerizable group per molecule; (b) introducing a blowing agent to the monomeric solution; (c) treating the monomer solution with an ultrasonic treatment; (d) introducing one or more initiating agents to the monomer solution; and (e) polymerizing the monomer solution.

[0012] In one embodiment, the absorbent polymeric foam can be formed into the shape of a foam sheet depending on the shape of the reaction vessel, and the foam sheet can be cut into a shoe insole shape.

[0013] In another embodiment, the polymeric foam can be fragmented into particles by cutting and extrusion processes.

[0014] In one embodiment, the blowing agent is a carbonate or bicarbonate or carbon dioxide-based compound.

[0015] In one embodiment, the treatment of the monomeric solution by ultrasonic treatment is by introducing energy through an ultrasonic probe or a surface driven by an ultrasonic transducer.

[0016] In one embodiment, the monomeric solution contains a monomer, a crosslinker and an initiator.

[0017] The present invention also relates to a process for producing an absorbent particle comprising the steps of (a) providing a monomeric solution consisting of a polymerizable, ethylenically unsaturated monomer containing one or more acid groups, water and one or more crosslinkers having more than one polymerizable group per molecule; (b) introducing a blowing agent to the monomer solution; (c) treating the monomer solution with an ultrasonic treatment; (d) introducing one or more initiating agents to the monomer solution; (e) polymerize the monomer solution; and f) fragmenting the polymeric foam (sheet) into particles.

[0018] Furthermore, the present invention relates to a polymeric foam capable of absorbing aqueous fluids prepared by a process comprising the steps of (a) providing a monomeric solution consisting of a polymerizable, ethylenically unsaturated monomer containing one or more groups acids, water and one or more crosslinkers having more than one polymerizable group per molecule; (b) introducing a blowing agent to the monomer solution; (c) treating the monomer solution with an ultrasonic treatment; (d) introducing one or more initiating agents to the monomer solution; and (e) polymerizing the monomer solution into an absorbent polymeric foam.

[0019] In addition, ultrasonic treatment produces one or more of the following changes in the polymeric foam when compared to the process without ultrasonic treatment (a) a 10% reduction in average pore diameter; (b) a 10% reduction in Young's modulus; (c) a 10% reduction in vortex time; and (d) a 10% increase in the Free Swelling Index (FSR).

[0020] It has been found that the polymeric foam of the present invention is applicable for the production of absorbent polymers and a process for producing absorbent polymers, sheets, pads or particles.

[0021] With the above in mind, it is a feature and advantage of the invention to provide a process of producing a foamed polymer by incorporating a blowing agent and using an ultrasonic treatment to control the pore size and compressibility of the foam. resulting polymer. In the present invention, the polymeric foam is hydrophilic and capable of rapidly absorbing and retaining aqueous fluids. Other features and advantages of the present invention will become apparent in the following description.

DEFINITIONS

[0022] Within the context of this specification, each term or phrase below will include the following meaning or meanings.

[0023] It should be noted that, when used in the present description, the terms "comprises", "comprising" and other derivatives of the source term "comprise" are intended to be open terms that specify the presence of any characteristics, elements, declared integers, steps, or components, and are not intended to preclude the presence or addition of other features, elements, integers, steps, components, or groups thereof.

[0024] As used herein, the term "about" modifying the amount of an ingredient in the compositions of the invention or employed in the methods of the invention refers to variation in the numerical amount that may occur, for example, through typical management procedures of liquid and measurement used for the production of concentrates or solutions in the real world; through inadvertent error in these procedures; through differences in the manufacture, source or purity of the ingredients used to produce the compositions or perform the methods; and the like. The term "about" also encompasses values that differ due to different equilibrium conditions for a composition resulting from a specific initial solution. The term "about" includes the given amount of the ingredient or property as stated. Whether or not modified by the term "about", the claims include equivalent amounts.

[0025] The terms "polymeric foam", "polymer foam" and "foam polymer" or their variants are used synonymously in the present description.

[0026] The term "Centrifugation Retention Capacity" or "CRC", as used herein, refers to the ability of the absorbent polymer or absorbent polymer composition to retain liquid after it has been saturated and subjected to centrifugation as set forth in the Procedures for Test published here.

[0027] The term "Absorption Under Load" or "AUL" refers to a test that measures the ability of an absorbent polymer, or absorbent polymeric composition, to absorb a 0.9 weight percent solution of sodium chloride in distilled water (test(e) solution) while the material is under a defined pressure as set forth in the Test Procedures disclosed herein.

[0028] The term "Vortex Test" refers to a measurement of absorption rate recorded as the time in seconds required for 2 g of an absorbent polymer to close a vortex created by stirring 50 mL of sodium chloride at 0. 9% in water at 600 rpm on a magnetic stir plate as set forth in the Test Procedures disclosed herein.

[0029] The term "Free Swelling Index" or "FSR" refers to a measurement to determine the swelling rate in g/g/s of materials that swell with water in an aqueous solution of sodium chloride in water at 0.9%, without agitation or confining pressure, as established in the Test Procedures published here.

[0030] The term "Young's modulus" refers to a measurement of the stiffness of a solid material, used here to describe the compressibility of a material, as established in the Test Procedures disclosed herein.

[0031] The term "monomeric solids" refers to the % by weight of the monomer solution that is composed of polymerizable monomers based on the weight of the total monomer solution.

[0032] The terms "crosslinked", "crosslinking", "crosslinking" or "crosslinking", as used herein, refer to any means of linking polymer chains. Such cross-linking means may include, for example, physical entanglement, crystalline domains, covalent bonds, ionic associations and complexes, hydrophilic associations such as hydrogen bonds, hydrophobic associations or Van der Waals forces. Cross-linking, when applied to water-soluble polymers, generally makes them insoluble in water but expandable in water.

[0033] The term internal crosslinker or monomeric crosslinker, as used herein, refers to the use of a crosslinker in the monomeric solution to form the polymer gel structure.

[0034] The term "shoe insole" or "shoe insert" refers to a composite or sheet that can be placed inside a shoe to absorb shock, provide compressibility, absorb moisture, increase wearer comfort, or some other combination thereof.

[0035] The term "dry particulate absorbent polymer", as used herein, generally refers to particulate absorbent polymer with less than about 20% by weight of water, as defined by the EDANA WSP 230.3 test method (10).

[0036] The terms "particle", "particulate" and the like, when used with the term "absorbent polymer", refer to the form of discrete units.

[0037] The terms "particulate absorbent polymer" and "particulate absorbent polymer composition" refer to the form of absorbent polymeric compositions and absorbent polymers in discrete form, wherein the "particulate absorbent polymer" and "particulate absorbent polymer compositions" can have a particle size of less than 1000 μm, typically from about 150 μm to about 850 μm, with more than 85% of particles between 150 μm and 600 μm.

[0038] The term "polyacrylic acid-based absorbent polymer (salt)", as used herein, refers to a cross-linked absorbent polymer that arbitrarily may contain a graft component and also contains, as a main component, acrylic acid and/or salt thereof (hereinafter referred to as "acrylic acid (salt)") as a repeating unit. Specifically, "polyacrylic acid (salt)-based water absorbent resin" indicates a polymer that preferably contains 30 mol% to 100 mol% acrylic acid (salt), based on the total moles of monomer used.

[0039] The term "polymer" includes, but is not limited to, homopolymers, copolymers, for example, block, graft, random, alternating copolymers, terpolymers, etc., and mixtures and modifications thereof. Furthermore, unless otherwise specifically limited, the term "polymer" shall include all possible configurational isomers of the material. These configurations include, but are not limited to, isotactic, syndiotactic, and atactic symmetries.

[0040] The acronym "PSD", as used herein, is an abbreviation for "Particle Size Distribution" and refers to the mass distribution of particles remaining on the specified sieves, measured through the sieves classification, according to the EDANA NWSP 220.0.R2 (15) standard test method. Furthermore, a mass average particle diameter (D50) and a particle diameter distribution width of the water absorbent resin are measured according to a method similar to a method disclosed herein.

[0041] The term "absorbent polymer", as used herein, refers to water-insoluble, water-swellable organic or inorganic materials, including absorbent polymers and absorbent polymeric compositions capable, under the most favorable conditions, of absorbing by the at least about 10 times its weight, or at least about 15 times its weight, or at least about 25 times its weight in an aqueous solution containing 0.9% by weight sodium chloride.

[0042] The term "surface crosslinking", as used herein, refers to the level of functional crosslinking around the surface of the absorbent polymer particle, which is generally higher than the level of functional crosslinking within the absorbent polymer particle. As used here, "surface" describes the outer boundaries of the particle.

[0043] As used herein, a range of "X to Y" means "X or more (upper) and Y or less (lower)". Additionally, "weight" is synonymous with "mass", "% by weight" is synonymous with "% by mass", and "parts by weight" is synonymous with "parts by mass". Additionally, unless otherwise noted, "ppm" means "ppm by weight" or "ppm by mass".

DESCRIPTION OF FIGURES

[0044] The above and other characteristics, aspects and advantages of the present invention will be better understood with reference to the following description, attached figure claims, in which

[0045] Figure 1 shows a comparison of the polymeric structures (foam) of Figures 1A, 1B and 1C.

[0046] Figure 1A shows a microscopic image of a polymer produced from monomer without blowing agent and without ultrasonic treatment.

[0047] Figure 1B shows a microscopic image of a polymer produced from monomer with a blowing agent, but without ultrasonic treatment.

[0048] Figure 1C shows a microscopic image of a polymer produced from monomer with a blowing agent and ultrasonic treatment according to the invention.

[0049] Figure 2 shows shoe inserts cut from polymer sheets (foam) as represented by Figures 2A and 2B.

[0050] Figure 2A shows a microscopic image of a polymeric foam shoe insole produced from monomer with carbon dioxide as the blowing agent, but without ultrasonic treatment.

[0051] Figure 2B shows a microscopic image of a polymeric foam shoe insole produced from monomer with carbon dioxide as the blowing agent and an ultrasonic treatment in accordance with the invention.

[0052] Figure 3 shows an accompanying polymer foam structure of Figures 3A and 3B.

[0053] Figure 3A shows a microscopic image of a polymeric foam structure produced from monomers with carbon dioxide as the blowing agent, but without ultrasonic treatment.

[0054] Figure 3B shows a microscopic image of a polymeric foam structure produced from monomers with carbon dioxide as the blowing agent and with ultrasonic treatment according to the invention.

[0055] Figure 4 shows a comparison of the shoe inserts that were cut from the polymeric sheets (foam) of Figures 4A, 4B and 4C.

[0056] Figure 4A shows a photographic image of a polymeric foam shoe insole produced from monomers without a blowing agent and without ultrasonic treatment.

[0057] Figure 4B shows a photographic image of a polymeric foam shoe insole produced from monomers with sodium carbonate, but without ultrasonic treatment.

[0058] Figure 4C shows a photographic image of a polymeric foam shoe insole produced from sodium carbonate monomers and ultrasonic treated according to the invention.

[0059] Figure 5 shows a comparison of the polymeric structure (foam) of Figures 5A and 5B.

[0060] Figure 5A shows a microscopic image of a polymeric foam structure produced with monomers containing a blowing agent, but without ultrasonic treatment.

[0061] Figure 5B shows a microscopic image of a polymeric foam structure produced with monomers containing a blowing agent and with ultrasonic treatment according to the invention.

[0062] Figure 6 shows a comparison of the polymeric structure (foam) of Figures 6A and 6B.

[0063] Figure 6A shows a microscopic image of a polymeric foam structure produced with monomers containing a blowing agent, but without ultrasonic treatment.

[0064] Figure 6B shows a microscopic image of a polymeric foam structure produced with monomers containing a blowing agent and with ultrasonic treatment according to the invention.

[0065] Figure 7 shows a comparison of the polymeric foam structure of Figures 7A, 7B and 7C.

[0066] Figure 7A shows a microscopic image of a polymeric foam structure produced with monomers containing sodium bicarbonate as a blowing agent and with ultrasonic treatment according to the invention.

[0067] Figure 7B shows another microscopic image of a polymeric foam structure produced with monomers containing sodium bicarbonate as a blowing agent and with ultrasonic treatment according to the invention.

[0068] Figure 7C shows another microscopic image of a polymeric foam structure produced with monomers containing sodium bicarbonate as a blowing agent and with ultrasonic treatment according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0069] Although typical aspects of embodiment and/or embodiments have been established for the purpose of illustration, this Detailed Description of the Invention should not be considered a limitation on the scope of the invention. Accordingly, various modifications, adaptations and alternatives may occur to a person skilled in the art without departing from the spirit and scope of the present invention. By way of hypothetical illustrative Example, the description in this specification of a range of 1 to 5 should be considered to support claims for any of the following ranges: 1-5; 1-4; 1-3; 1-2; 2-5; 2-4; 2-3; 3-5; 3-4; and 4-5.

[0070] According to the invention, processes for producing polymeric foam sheets, polymers and absorbent polymers and absorbent particles, as set out in the claims, can be achieved using the methods described herein.

[0071] An absorbent polymer, which is used as the main component in the particulate water absorbing agent that is obtained by the production method of the present invention, is generally a polyacrylic acid (salt)-based absorbent polymer and is an insoluble cross-linked polymer in water and swellable in water. This water-insoluble, water-swellable cross-linked polymer contains an acrylic acid (salt) as a polymerized unsaturated acid group containing monomer in a repeating unit (except the cross-linking agent described later), in an amount of 30 mol% to 100 mol%, or from 50 mol% to 100 mol%, or from 70 mol% to 100 mol%, or from 90 mol% to 100 mol%, or substantially 100 mol%.

[0072] An acidic group of a monomer before or after polymerization is generally neutralized. A neutralized salt may be an alkali metal salt or an ammonium salt, potentially with some di-, tri- or polyvalent cations, added to impart specific properties, such as, for example, absorption rate. Sodium is the most common neutralizing cation, and preferred degrees of neutralization are 20 mol% to 100 mol%, or 40 mol% to 99 mol%, or 50 mol% to 90 mol% of the groups acids to be neutralized. Neutralization can be performed before polymerization, or it can be performed in a hydrogel after polymerization, or both neutralizations can be performed. Generally, neutralization is performed prior to polymerization by adding a neutralizing agent to the monomer solution or the monomer to a solution of the neutralizing agent. Monomeric Solution

[0073] The polymeric foam production process of the present invention includes an initial step of providing a monomeric solution comprising a monomer, a crosslinker and an initiator. A suitable monomer, or combination of monomers, may include ethylenically unsaturated compounds, where free radical initiation and propagation will produce a polymer suitable for processing and application as a polymeric foam. Monomers with anionic functionalities such as sulfonic or carboxylic acid groups are suitable, and such monomers may also have alkyl, amido or other side groups. Monomers without acid functionality may also be included, although it is desirable that at least 50-99.9 mol% of the monomers in the polymer backbone have acid/acid-salt group characteristics, and it is particularly desirable that such acid/acid groups -salt are carboxylate/carboxylic acid groups.

[0074] A suitable polymerizable unsaturated acid group containing the monomer includes any of the acid-containing groups, such as acrylic acid or methacrylic acid; 2-acrylamido-2-methylpropanesulfonic acid, its salts or solutions thereof. It is desirable that at least about 50%, and more desirable that at least about 75% of the acid groups are carboxylate/carboxylic acid groups.

[0075] In some aspects, the monomeric solution may further include a second suitable polymerizable unsaturated acid group containing monomer that may be copolymerized with the ethylenically unsaturated monomer and may include, but is not limited to, acrylamide, methacrylamide, hydroxyethyl acrylate, dimethylaminoalkyl ( meth)-acrylate, ethoxylated (meth)-acrylates, dimethylaminopropylacrylamide or acrylamidopropyltrimethylammonium chloride. Such monomer may be present in a range of 0% by weight to about 40% by weight of the copolymerized monomer.

[0076] The monomeric solution may also include a neutralizing agent in order to neutralize the acid groups of the polymerizable unsaturated acid group containing monomer. Preferably, 20 mol% to 100 mol%, or 40 mol% to 99 mol%, or 50 mol% to 90 mol% of the acid groups are neutralized. The neutralizing agent may include an alkaline base material including sodium, potassium or ammonium salts, resulting in the presence of the acid groups as corresponding salts. The alkaline base can be the hydroxide salt, carbonate or bicarbonate of sodium, potassium, ammonia or similar. It is noted that neutralization can be obtained by adding the alkaline base to the monomer solution or by adding the monomer, such as acrylic acid, to the alkaline base.

[0077] According to one method, the polymerizable acid monomer is partially neutralized by adding the neutralizing agent, such as sodium hydroxide, to the monomer or by adding the polymerizable acid monomer to a neutralizing agent. Then, the partially neutralized monomer, such as acrylic acid, is converted into a gel by polymerization in the presence of crosslinking agents and any other components. The gel is optionally fragmented into particulate absorbent polymer.

[0078] A blowing agent or foaming agent is added to the monomer solution before polymerization. The amount of blowing agent added must be adapted to the individual application, but is generally in the range of 0.01 wt% to 5 wt%, more preferably, 0.05 wt% to 2 wt%, based on the total weight of the monomer solution. The blowing agent can be a compound that decomposes by chemical reaction to produce a gas. The blowing agents used can be carbonates from the group of lithium carbonate, sodium carbonate, potassium carbonate, or higher valence metal ions, such as calcium carbonate, magnesium carbonate or their solutions. Other compounds used can also be granulated carbonates, which are also produced as mixed salts of a carbonate and/or percarbonate with another salt that functions as an outer layer, for example a sulfate compound.

[0079] The blowing agents used can also be bicarbonates from the group of lithium bicarbonate, sodium bicarbonate and potassium bicarbonate; or higher valence metal ions, such as calcium bicarbonate, magnesium carbonate, or their solutions. Granulated bicarbonates can also be used.

[0080] An advantage of the invention is that the blowing agent can be added in a single step before polymerization or, in the case of a gas, in a single pressure before polymerization. No pressure cycles or repeated applications at alternating pressures are necessary. It is also not necessary to continue adding blowing agent throughout the entire polymerization, not even after the polymer has gelled during polymerization.

[0081] To achieve the desired foam porosity, the amount of gas or blowing agent needs to be adjusted to the treatment conditions, formulation and type of blowing agent.

[0082] Preferably, the amount of carbonate or bicarbonate blowing agent is between 0.01% by weight to 5% by weight, more preferably, 0.05% by weight to 2% by weight, and most preferably 0. 1% by weight to 1% by weight based on the weight of the total monomer solution.

[0083] It is also anticipated that the blowing agent may be carbon dioxide.

[0084] The blowing agent can also be a compound that thermally decomposes to release a gas. Examples of such blowing agents include azo compounds, carbamates, urea and the like.

[0085] Therefore, in one embodiment, the expanding agent used may be a carbonate or bicarbonate or carbon dioxide-based compound.

[0086] In another embodiment, the blowing agent may be a dissolved gas that forms bubbles as a reaction to the change in pressure or temperature of the monomeric solution, creating a change in the solubility of the gas.

[0087] The monomer solution of the invention also includes from about 0.001% by weight to about 5% by weight and, preferably, from about 0.05% by weight to about 3% by weight based on the total amount of the polymerizable unsaturated acid group containing monomer of at least one internal cross-linking agent. The internal cross-linking agent generally has at least two ethylenically unsaturated double bonds or one ethylenically unsaturated double bond and a functional group that is reactive to acid groups of the polymerizable unsaturated acid group containing monomers or several functional groups that are reactive acid groups can be used as the internal cross-linking component that is present during the polymerization of the polymerizable unsaturated acid group containing monomers.

[0088] Examples of internal crosslinking agents used in absorbent polymers include aliphatic unsaturated amides, such as methylenebisacryl- or -methacrylamide or ethylenebisacrylamide, and also aliphatic esters of polyols or polyols alkoxylated with ethylenically unsaturated acids, such as di(meth) acrylates or tri(meth)acrylates of butanediol or ethylene glycol, polyglycols or trimethylolpropane, di- and triacrylate esters of trimethylolpropane, which are preferably oxyalkylated, preferably ethoxylated, with 1 to 30 moles of alkylene oxide, acrylate and methacrylate esters of glycerol and pentaerythritol and of glycerol and pentaerythritol oxyethylated with, preferably, 1 to 30 moles of ethylene oxide and, additionally, allyl compounds, such as allyl (meth) acrylate, alkoxylated allyl (meth) acrylate reacted preferably with 1 to 30 moles of ethylene oxide, triallyl cyanurate, triallyl isocyanurate, maleic acid diallyl ester, polyallyl esters, vinyl trimethoxysilane, vinyl triethoxysilane, polysiloxane comprising at least two vinyl groups, tetraallyloxyethane, tetraallyloxyethane, triallylamine, tetra-allylethylenediamine, diols, polyols, allyl hydroxy or acrylate compounds and allyl esters of phosphoric acid or phosphorous acid, and even monomers that are capable of cross-linking, such as N-methylol compounds of unsaturated amides, such as methacrylamide or acrylamide, and the ethers derived from these. Ionic crosslinkers, such as aluminum metal salts, can also be used. Solutions of the mentioned crosslinking agents can also be employed.

[0089] The absorbent polymer may include from about 0.001% by weight to about 5% by weight based on the total amount of the monomer-containing polymerizable unsaturated acid group of additional internal crosslinkers which may comprise compositions containing at least two ethylenically unsaturated double bonds , for example, methylenebisacrylamide or -methacrylamide or ethylenebisacrylamide; additionally, unsaturated mono- or polycarboxylic acid esters of polyols, such as diacrylates or triacrylates, for example, butanediol- or ethylene glycol diacrylate or methacrylate; trimethylolpropane triacrylate, as well as its alkoxylated derivatives; additionally, allyl compounds such as allyl (meth) acrylate, triallyl cyanurate, diallyl ester of maleic acid, polyallyl ester, tetra-allyloxyethane, di- and triallylamine, tetra-allylethylenediamine, allyl esters of phosphoric acid or phosphorous acid. Furthermore, compounds with at least one functional group reactive to acidic groups can also be used. Examples of these compounds include N-methylol compounds of amides, such as methacrylamide or acrylamide, and the ethers derived therefrom, as well as di- and polyglycidyl compounds.

[0090] The monomeric solution also includes an initiator. Suitable initiators include, but are not limited to, azo or peroxo compounds, thermal or pyrolytic initiators, redox systems, photolytic or UV initiators (sensitizers or compounds that fragment to generate radicals on UV exposure), and/or radiation are used for initiation. free radical polymerization.

[0091] The monomeric solution may include a polymerization initiator that is selected as appropriate according to a form of polymerization, and is not limited to one in particular. The amount of polymerization initiator used is preferably 0.0001 mol% to 1 mol% and, more preferably, 0.001 mol% to 0.5 mol%, relative to the total moles of monomer in the monomer solution. .

[0092] Examples of the photolytic polymerization initiator include a benzoin derivative, a benzyl derivative, an acetophenone derivative, a benzophenone derivative, an azo compound and the like.

[0093] Examples of pyrolytic polymerization initiators include persulfates, such as sodium persulfate, potassium persulfate and ammonium persulfate; peroxides, such as hydrogen peroxide, t-butyl peroxide, and methyl ethyl ketone peroxide; azo compounds, such as an azonitrile compound, an azoamidine compound, a cyclic azoamidine compound, an azoamide compound, an alkylazo compound, 2,2'-azobis(2-amidinopropane)dihydrochloride, and 2,2'- azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride; and the like.

[0094] Examples of redox polymerization initiators cover a system that uses a combination of (i) an oxidizing compound, such as persulfate, peroxide or the like and (ii) a reducing compound, such as L-ascorbic acid, hydrogen sulfite sodium, or similar.

[0095] It is often desirable to use a combination of different types of initiators. For example, photolytic polymerization initiators can be used in combination with pyrolytic or redox polymerization initiators.

[0096] According to the present invention, the monomeric solution may further include, if necessary, preferably 5% by mass or less and, more preferably, 1% by mass or less of a water-soluble polymer, a surfactant, a deodorant agent, an antibacterial agent, a plasticizer, a perfume, a pigment, a dye, a hydrophilic short fiber, inorganic powder such as silicon dioxide or titanium oxide, a thermoplastic resin such as polyethylene or polypropylene, a chain transfer agent, such as hypophosphorous acid (salt), or the like. Furthermore, the monomeric solution may contain up to about 20% by weight of absorbent polymer fines with a particle size of about 150 μm or less.

[0097] After preparation, the monomer solution can be cooled to a temperature of about 0°C to 20°C or 3°C to 10°C. Nitrogen or other inert gas may be bubbled through the monomer solution to remove oxygen. In one embodiment, carbon dioxide is used to purify the oxygen monomer and to act as a blowing agent to create bubbles. The monomer solution can also be polymerized at room temperature or optionally elevated without nitrogen spraying before polymerization. In one embodiment, the monomer solution is heated to 50°C to 100°C prior to polymerization.

[0098] The monomeric solution can be characterized by several parameters, such as solids and viscosity. The monomer solution may have a solids content of from about 25% to about 60%, or from about 30% to about 40% solids. The monomer solution may have a viscosity of about 5 centipoise to about 200,000 centipoise, preferably, from about 7 centipoise to about 50,000 centipoise, more preferably, from about 10 centipoise to about 10,000 centipoise.

Ultrasonic Treatment

[0099] The monomer solution is subjected to ultrasonic waves. The monomer solution can be treated with ultrasound during the addition of the blowing agent or gas. More preferably, the monomer is subjected to ultrasonic waves after the addition of blowing agent or gas. The blowing agent can be added as a solid, as an aqueous solution or as a gas can be used. Such solid blowing agents, such as sodium bicarbonate and sodium carbonate, are preferably dissolved in water before addition to the monomer solution.

[00100] Ultrasonic treatment of the monomer solution is carried out before gelation of the monomer during polymerization, preferably before the start of polymerization.

[00101] Ultrasonic treatment is defined as using an ultrasonic power generator in combination with a probe, surface or sonotrode and ultrasonic transducer to transmit ultrasonic waves and energy to a medium of interest. The ultrasonic treatment, according to the present invention, can be carried out with a sonotrode, surface or probe, more preferably, with a sonotrode or probe, and, more preferably, with a sonotrode.

[00102] For the purposes of the present invention, the frequency of a vibrating probe or surface for ultrasonic treatment can be between 10kHz and 3000kHz, more preferably, between 15kHz and 180kHz and, most preferably, between 18kHz and 45kHz.

[00103] Ultrasonic waves can be introduced into the monomer solution, for example, by a vibrating surface as present in ultrasonic baths or submersible transducers, or by exposing the monomer directly to an ultrasonic probe. A vibrating surface is created by attaching one or more transducers to the surface.

[00104] Ultrasonic probes can have different shapes and can be, for example, a cylindrical probe or form a probe with several bumps, or a bar. Ultrasonic probes can be inserted into a flow cell and sealed in a location with little vibration. The monomer may be exposed to direct contact with the vibrating surface of the probe. Examples for a transducer driving a probe directly is the UIP500hdt with, for example, a 34 mm block sonotrode as a probe and is manufactured by Hielscher USA Inc., New Jersey.

[00105] An example for a treatment with vibrating surfaces is a flow through the UPR 1000s reactor of Ultrasonic Power Corporation, Illinois.

[00106] Depending on the equipment manufacturer, the amplitude can be adjusted within a certain range. Adjusting the amplitude of the ultrasonic vibration changes the amount of energy input into the material being treated with ultrasonic waves. Ultrasonic Power Corporation's Model 5400 generators allow intensity to be varied by adjusting the generator from minimum to maximum. This intensity setting affects the amplitude. For Hielscher devices, such as the UIP500hdt, the amplitude can be adjusted from 20 to 100%. The preferred range for ultrasonic processing is minimum to maximum intensity, as well as an amplitude setting of 1% to 100%. More preferably, it is an amplitude setting between 20% and 100%.

[00107] The energy transmitted to the monomer through ultrasonic processing is, preferably, in the range of 0.005kJ/kg of monomeric solution to 5kJ/kg of monomeric solution and is, more preferably, between 0.01kJ/kg of monomeric solutions to 3kJ/kg of monomer and, more preferably, between 0.1kJ/kg of monomeric solutions to 2kJ/kg of monomer.

[00108] In general, direct contact between the monomer solution and the vibrating surface is desired for simplicity. Ultrasonic treatment can be carried out in a batch or continuous process, for example with a flow reactor or flow cell.

[00109] Ultrasonic treatment times depend on conditions and can vary widely. The required treatment time depends, for example, on probe size, amplitude, mass to be treated and blowing agent or quantity of gas. In one embodiment, when carried out in batches, ultrasonic treatment times of less than 10 min, more preferably less than 1 min, are preferred. In another embodiment, when carried out continuously in a continuous flow cell, ultrasonic treatment times of less than 1 min, more preferably less than 30s, are preferred. Shorter treatment times are preferred due to better equipment utilization. One skilled in the art can easily match treatment time, amplitude and other parameters with the amount of monomer to achieve the desired properties of the final product.

[00110] The time between ultrasonic treatment of the monomer solution and initiation of polymerization is preferably less than 1 hour, more preferably less than 2 minutes and, most preferably, less than 30 seconds.

[00111] An advantage of the invention is that the application of ultrasonic treatment is carried out for a short period of time to the monomer solution. Ultrasonic radiation is used to influence the bubble size in the monomer solution before polymerization. Ultrasonic treatment is not necessary for the entire duration of the polymerization reaction as in the prior art, such as US5859077. It is also not necessary after the polymer gels during polymerization.

[00112] Ultrasonic treatment, combined with a blowing agent according to the present invention, allows precise control of bubble quantity and size and is therefore capable of controlling the foam structure after gelation. For example, for many applications, generating a large number of small diameter bubbles is preferable over generating fewer larger diameter bubbles by the same amount of blowing agent. The largest number of smaller diameter bubbles in the monomer are immobilized during gelation and remain as pores in the final product. Polymeric foam that is created with ultrasonically treated monomer has greater compressibility compared to a polymeric foam without an ultrasonic treatment. For many applications, such as shoe insoles, among others, increasing compressibility is a highly desirable attribute. The invention, therefore, can provide a process for producing polymeric foam with a specific compressibility by an economical, simple and efficient process.

[00113] The compressibility of a polymeric foam can be measured by a variety of standard methods well known in materials science. An especially useful measurement is Young's modulus, sometimes called modulus of elasticity, which can be determined using a Zwick tester or an Anton Paar rheometer in the methods in this document. For the purposes of the present invention, a lower Young's modulus indicates better compressibility and more desirable properties regarding shock absorption in products such as shoe insoles and many other applications.

[00114] Polymeric foam is also more robust and resistant to damage when the foam is composed of a greater number of smaller diameter pores than with a smaller number of much larger diameter pores that can serve as weak points in the foam structure . The greater number of homogeneously distributed smaller diameter pores also results in a foam that is more uniform in properties throughout the foam. Furthermore, foam sheets and foam particles generated from a polymeric foam show better absorption speed and better moisture absorption.

Polymerization

[00115] The foamed monomeric aqueous solution is polymerized to form a foamed microcellular polymer. The polymerization may be conducted by any of the methods well known in the art and may be conducted in a batch or continuous manner. The shape of the polymerization reactor is not particularly limited and may be a continuously moving conveyor, a tube, a kneader, a stirred reactor, a flat thin film, a droplet, a thread, or a depression in the final shape of the desired polymer. . The monomer can also be polymerized in suspension or the like.

[00116] In gel polymerization, a preferred embodiment, a monomeric solution of primarily acrylic acid, neutralizing agent, water, cross-linking agents and initiating chemicals are mixed and placed in a "reactor", which can be a continuous conveyor belt , trays, a kneader or similar. Shortly after polymerization begins, the liquid monomer polymerizes to a solid gel. For example, with a continuous belt, the monomer solution is contained in the continuous belt by dams or inclined sides, where polymerization is initiated. The process results in a continuous "sheet" of absorbent polymer, generally referred to as a polymer hydrogel, on the mat, where the sheet has overall thickness dimensions of about 3mm to about 300mm and a width of about 800mm to about 1500mm. for production purposes. Polymerization of the polymer for laboratory purposes is generally, for example, done in a plastic tray or bucket, and a gel thickness of about 3mm to about 100mm. In another preferred embodiment, the monomer is polymerized into shapes or depressions that approximate the desired final shape of the polymeric foam, such as that of shoe inserts.

[00117] Droplets or strings can also be considered as reactors where the liquid monomer polymerizes to form a solid gel in the initial stages of polymerization.

[00118] An advantage of the invention is that the blowing agent and ultrasonic treatment are added for a short duration to the monomer solution before polymerization. This is possible external to the polymerization reactor itself. After treatment, the monomer solution can be polymerized in any number of different types or shapes of reactors. It is not limited to the use of a single, special and complicated type of reactor to attempt to force bubbles in the gel during and after gelatinization polymerization using constant stirring or additions of blowing agent under alternating pressures, as attempted in the prior art.

Cut

[00119] In one embodiment, the polymeric foam absorbent polymer hydrogel obtained by polymerization (hereinafter, sometimes referred to as "hydrogel") can be left as a sheet or can be cut into smaller sizes, for example, into sole shapes shoes that are suitable for insertion into shoes. The hydrogel can also be cut into regular or irregular granules (for example, with an average mass particle length of preferably 0.1 mm to 10 mm or, more preferably, 0.5 mm to 3 mm) with known cutting apparatus. of those skilled in the art, such as extruders, knives, rotary cutters and the like.

[00120] In one embodiment, a resulting continuous plate or sheet of absorbent polymer hydrogel can be cut into a desired shape, or cut and extruded with a commercial extruder, followed by drying in a forced air oven to produce a level of moisture of the final product less than 20% by weight of water. The dried absorbent polymer can then be crushed or crushed and sieved. In a preferred embodiment, it is desirable to remove particles larger than 1000 μm or larger than 850 μm and smaller than 150 μm, to form what is generally referred to as a particulate absorbent polymer.

[00121] In another embodiment, the polymerized gel is not dried to a moisture level of less than 20% by weight water, but maintained at a level of about 20% by weight to 80% by weight water, so that additional water in the polymer may provide flexibility or other desirable properties.

Surface Treatment and Crosslinking

[00122] Absorbent polymers or particulate absorbent polymers may be surface treated with additional chemicals and treatments as set forth in this document. In particular, the surface of the particulate absorbent polymer can be further crosslinked, generally referred to as surface crosslinking, by adding a surface crosslinking agent and heat treatment. In general, surface crosslinking is a process to increase the crosslinking density of the polymer matrix surrounding the absorbent polymer (particulate) surface relative to the crosslinking density of the interior (particle). surface may be present in an amount of from about 0.01% by weight to about 5% by weight, or such as from about 0.1% by weight to about 3% by weight, or such as from about 0.1% by weight to about 1% by weight, based on the weight of the dry absorbent polymer (particulate).

[00123] Desirable surface crosslinking agents include chemicals with one or more functional groups that are reactive to pendant groups of the polymer chains, typically acidic groups. Surface crosslinking agents comprise functional groups that react with polymer backbone functional groups in a condensation reaction (condensation crosslinker), in an addition reaction or in a ring opening reaction.

[00124] Such compounds may include, for example, polyols including di- or polyfunctional alcohols, carbonates, polyfunctional amines and amines, β-hydroxyalkylamides, polyfunctional starch amines, oxazolidinones, polyfunctional epoxides and epoxides, diglycidyl ethers, and the like, and alkoxylated derivatives thereof, including propane diol, butane diol, ethylene glycol diglycidyl ether, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, polyglycerin, propylene glycol, diethanolamine, triethanolamine, polyoxypropylene, block copolymers of oxyethylene-oxypropylene, fatty acid esters of sorbitan, fatty acid esters of polyoxyethylene sorbitan, trimethylolpropane, pentaerythritol, polyvinyl alcohol, sorbitol, 2-hydroxyethyloxazolidin-2-one, oxazolidin-2-one, 1,3 -propanediol. 1,3-dioxolan-2-one (ethylene carbonate), 4-methyl-1,3-dioxolan-2-one (propylene carbonate), or 4,5-dimethyl-1,3-dioxolan-2-one and its alkoxylated derivatives.

[00125] After the absorbent polymer (particulate) has come into contact with the surface crosslinking agent, or with the fluid comprising the surface crosslinking agent, the treated absorbent polymer (particulate) is heat treated to a temperature of about 50°C to about 300°C, from about 75°C to about 275°C, or from about 150°C to about 250°C, and for a period of about 5 minutes at about 90°C. minutes, depending on the temperature, so that the outer region of the absorbent polymer (particulate) is more strongly cross-linked relative to the inner region (i.e., surface cross-linking). The duration of heat treatment is limited by the risk of that the desired property profile of the polymer structures is destroyed as a result of the heat effect.

[00126] In a particular aspect of surface crosslinking, the absorbent polymer (particulate) is surface treated with ethylene carbonate followed by heating to effect surface crosslinking of the absorbent polymer particle, which increases the surface crosslinking density and the gel strength characteristics of the absorbent polymer (particulate). More specifically, the surface crosslinking agent is coated onto the absorbent (particulate) polymer by mixing the particulate absorbent polymer with an aqueous alcohol solution of the ethylene carbonate surface crosslinking agent. The amount of alcohol in the aqueous alcoholic solution can be determined by the solubility of the alkylene carbonate and is kept as low as possible for various reasons, for example for protection against explosions. Suitable alcohols are methanol, isopropanol, ethanol, butanol, butyl glycol, as well as solutions of these alcohols. In some aspects, the solvent desirably is water, which is typically used in an amount of about 0.3% by weight to about 5.0% by weight, based on the weight of the dry (particulate) absorbent polymer composition. In still other aspects, the ethylene carbonate surface crosslinking agent can be applied with an inorganic carrier material, such as silicon dioxide (SiO2), or in a vapor state by sublimation of ethylene carbonate.

[00127] To obtain the desired surface crosslinking properties, surface crosslinking agents, such as ethylene carbonate, must be evenly distributed over the particulate absorbent polymer. For this purpose, mixing is carried out in suitable mixers known in the art, such as fluidized bed mixers, paddle mixers, rotary drum mixers or twin screw mixers. It is also possible to coat the absorbent polymer (particulate) during one of the process steps of absorbent polymer (particulate) production. The heat treatment, which follows the coating treatment of the absorbent polymer (particulate), can be carried out in the following manner. In general, heat treatment is at a temperature of about 100°C to about 300°C. Lower temperatures are possible if highly reactive epoxide crosslinking agents are used. However, if an ethylene carbonate is used, then heat treatment is suitably at a temperature of about 150°C and about 250°C. In this particular aspect, the treatment temperature depends on the residence time and the type of ethylene carbonate. For example, at a temperature of about 150°C, heat treatment is carried out for an hour or more. In contrast, at a temperature of about 250°C, a few minutes (e.g., from about 0.5 minutes to about 5 minutes) are sufficient to achieve the desired surface crosslinking properties. The heat treatment can be carried out in conventional dryers or ovens known in the art. Surface cross-linking can also be performed on the polymeric foam sheet if desired.

[00128] In addition to surface crosslinking, the absorbent polymer can also be treated on the surface with other chemical compositions, during or after the surface crosslinking step. The absorbent polymeric foam and the particulate absorbent polymer cut from the polymeric foam according to the invention can be treated with from about 0.001% to about 10% by weight, or from 0.01% to about 7.5% by weight. weight, or from 0.1% to about 5% by weight, of a salt or salts, in each case based on the absorbent weight of a salt or salts, in each case wherein the salt includes a divalent cation or of higher valence of a metal and at least one organic base such as an anion.

[00129] The divalent or higher valence metal of a metal can be selected from the group consisting of Mg2+, Ca2+, Ba2+, Al3+, Fe2+, Fe3+, Ga3+, Ti4+, Zr4+, Cu2+ and Zn2+. The organic base may be an at least partially deprotonated mono-, di- or tricarboxylic acid or deprotonated monocarboxylic acids. Also included may be hydroxycarboxylic acids, such as at least partially deprotonated mono-, di- or tricarboxylic acids and monohydroxycarboxylic acids.

[00130] Anions may include the corresponding bases of the following acids: anisic acid, benzoic acid, formic acid, valeric acid, citric acid, glyoxylic acid, glycolic acid, glycerolphosphoric acid, glutaric acid, chloracetic acid, chloropropionic acid, cinnamic acid, succinic acid, acetic acid, tartaric acid, lactic acid, pyruvic acid, fumaric acid, propionic acid, 3-hydroxypropionic acid, malonic acid, maleic acid, butyric acid, isobutyric acid, imidinoacetic acid, malic acid , isothionic acid, methylmaleic acid, itaconic acid, crotonic acid, oxalic acid, salicylic acid, gluconic acid, gallic acid, sorbic acid, fatty acids such as stearic acid and adipic acid, and p-hydroxybenzoic acid, including tartrate and lactate.

[00131] In another embodiment of the process of the invention, the salt used may be a salt comprising aluminum lactate. At least about 50% by weight, or at least about 75% by weight, or 100% by weight of that salt is based on aluminum lactate. In addition to aluminum lactate, it may be possible that one or two or more additional cations are present. This cation may be selected from monovalent, divalent or higher valence cations of a metal selected from the group consisting of Mg2+, Ca2+, Ba2+, Al3+, Fe2+, Fe3+, Ga3+, Ti4+, Zr4+, Cu2+ and Zn2+. Additionally, in addition to aluminum lactate, it is also possible that additional anions are present in the salt. Furthermore, in addition to aluminum lactate, it is also possible that oxides or mixed oxides of other metals are present, such as the oxides of the metal ions mentioned in this section. For example, in connection with the salt-containing solution, the solution may contain a secondary salt, an alkali metal or alkaline earth metal salt, an alkali metal salt of one of the above-mentioned anions, or the majority salt anion of the main salt. in the solution. These include lithium lactate and sodium lactate. The amount of the secondary salt can be from 0.001% to about 25% by weight, or from 0.01% to about 17% by weight, or from about 0.1% to about 12% by weight, in each case based on the main salt.

[00132] In another embodiment of the present invention, an anion other than the organic base can be used. The anion may be an inorganic base. This inorganic base may be a deprotonated inorganic acid. Such acids are capable of releasing two or more protons. They include acids containing sulfur, nitrogen or phosphorus. Sulfur-containing acids, especially sulfuric acid and hence sulfate as its salt, can be used for the base. According to another embodiment of the process of the invention, another salt comprising aluminum sulfate can be used. At least about 50% by weight, or at least about 75% by weight, or 100% by weight, of that salt may be based on aluminum sulfate. The two different anions can be used in a ratio of about 1:100 to about 100:1, or in a ratio of about 1:10 to about 10:1, or from about 1:5 to about 5:1.

[00133] The salt can be brought into contact with the untreated absorbent polymer by mixing the two components, the mixing apparatus being suitable for the purpose being a Patterson Kelley mixer, DRAIS turbulent mixer, Lodige mixer, Ruberg mixer, spindle mixer, mixer plate mixer, and fluidized bed mixer or continuously operating vertical or horizontal mixers in which the polymer structure is mixed at high frequency by means of rotating blades (Schugi mixer).

[00134] Furthermore, the salt can be brought into contact with the untreated absorbent polymer in the form of a fluid, comprising a solvent and the salt dissolved or dispersed in that solvent, or in dry form as a salt powder. Suitable solvents, in addition to water, may be water-miscible organic solvents, such as, for example, methanol, ethanol, 1-propanol, 2-propanol, 1,2-propanediol, 1,3-propanediol, 1-butanol , 2-butanol, tert-butanol, isobutanol, or organic solvent solutions or water solutions with one or more such organic solvents, such as water as the solvent. If the untreated absorbent polymer is contacted with the fluid comprising the solvent and the salt, the fluid may contain the salt in an amount of about 0.1% and about 50% by weight, or about 1%. to about 40% by weight, or from about 5% to about 25% by weight, in each case based on the total weight of the fluid.

[00135] The absorbent polymer composition may include from about 0% by weight to about 5% by weight, from about 0.001% by weight to about 3% by weight, from about 0.01% by weight to about 2% by weight based on the weight of the water-insoluble inorganic powder dry absorbent polymer composition. Examples of insoluble inorganic powders include silicon dioxide, silica, titanium dioxide, aluminum oxide, magnesium oxide, zinc oxide, talc, calcium phosphate, clays, diatomaceous earth, zeolites, bentonite, kaolin, hydrotalcite, activated clays etc. . The insoluble inorganic powder additive can be a single compound or a solution of compounds selected from the above list. Examples of silica include fumed silica, precipitated silica, silicon dioxide, silicic acid, and silicates. In some particular aspects, microscopic non-crystalline silicon dioxide is desirable. Products include SIPERNAT® 22S and AEROSIL® 200, available from Evonik Corporation, Parsippany, New Jersey. In some aspects, the particle diameter of the inorganic powder may be 1000 μm or smaller, such as 100 μm or smaller.

[00136] The absorbent polymer can also be further treated by adding from 0% by weight to about 30% by weight, or from about 0.001% by weight to about 25% by weight, or from about 0.01% by weight to about 20% by weight based on the weight of the dry particulate absorbent polymer composition, of water-soluble polymers such as partially or fully hydrolyzed polyvinyl acetate, polyvinylpyrrolidone, starch or starch derivatives, polyglycols or polyacrylic acids - cos. Preferred water-soluble polymers are starch and polyvinyl alcohol.

[00137] The absorbent polymer may also include from 0% by weight to 5% by weight, or from about 0.001% by weight to about 3% by weight, or from about 0.01% by weight and 2% by weight. weight based on the weight of the dry absorbent polymer composition, of dust removal agents, such as hydrophilic and hydrophobic dust removal agents, such as those described in US Patents 6,090,875 and 5,994,440.

[00138] In some aspects, additional surface additives may optionally be employed with the absorbent polymer composition, such as odor-binding substances, such as cyclodextrins, zeolites, inorganic or organic salts, and similar materials; antimicrobials, anti-odor compounds, anti-stick agents, anti-foam additives, flow modifying agents, surfactants, viscosity modifiers, urine stability promoters and the like. Antibacterial and anti-odor agents can be especially advantageous for shoe insoles and other applications with direct or indirect contact with the body.

[00139] In other embodiments, the absorbent polymer may include 0.0001% by weight to 5% by weight of additives that increase the polymer's whiteness or long-term color stability, such as against darkening, yellowing or browning. Such additives are well known in the art and include antioxidants, phosphorus- and sulfur-containing compounds, chelating agents, optical brighteners and the like. Preferred additives for color stability are 2-hydroxy-2-sulfonate-acetic acid, bisulfites, phosphonates, ethylene diaminetetraacetic acid, ethylenediamine-N,N'-disuccinic acid, diethylenediaminepentaacetic acid, their salts and derivatives, and their solutions.

[00140] The absorbent polymer of the present invention can be, after the heat treatment step, treated with an aqueous solution to adjust the water content of the absorbent polymer.

[00141] In some embodiments, it may be advantageous for the final absorbent polymer to have a water content as high as 80% by weight. In this embodiment, the treated absorbent polymer composition has a water content of about 20% by weight to about 80% by weight based on the total weight of the absorbent polymer. In some embodiments, the treated absorbent polymer has a water content of about 40% by weight to about 60% by weight based on the total weight of the absorbent polymer. The water or moisture content is measured according to the previously cited test method WSP 230.3 (10).

[00142] The absorbent polymer of the present invention has certain characteristics, or properties, measured by the Centrifuge Retention Capacity (CR(C), which measures the ability of the absorbent polymer (particulate) to retain liquid after being saturated and subjected to centrifugation under controlled conditions. The resulting retention capacity is indicated as grams of liquid retained per gram of sample weight (g/g). All CRC values set forth herein should be understood as being determined by the CRC Test as provided herein.

[00143] The absorbent polymer (particulate) produced by a process of the present invention can have a CRC of about 20g/g to about 50g/g, or of about 25g/g to about 45g/g.

[00144] When the state of the polymer is a particulate absorbent polymer, the particulate absorbent polymer generally has a particle size of less than 1000 μm, typically from about 150 μm to about 850 μm, with more than 85% of the particles between 150 μm and 600 μm. Additionally, it has a particle size with the majority of the particles by weight having a particle size between about 300 μm and about 600 μm, preferably at least about 60% by weight percent of the particles having a particle size of particle of about 300 μm to about 600 μm, or at least about 70% by weight of the particles having a particle size of about 300 μm to about 600 μm, or at least about 80% by weight of the particles having a particle size of about 300 μm to about 600 μm, as measured by sieving through a US standard 30 mesh sieve and holding on a US standard 50 mesh sieve.

[00145] The particulate absorbent polymer produced by a process of the present invention can have an Absorption Under Load at 0.9 psi (AUL(0.9)) of about 5g/g to about 26g/g, or about 10g /g to about 22 g/g. The FSR of the particulate absorbent polymer produced by the process of the present invention ranges from 0.2g/g/s to about 0.7g/g/s.

[00146] The absorbent polymer (particulate) according to the present invention can be used in many absorbent articles, including shoe insoles, absorbent pads, sanitary napkins, diapers, or bandages, and they have the property of quickly absorbing large amounts of sweat, menstrual blood, urine, or other bodily fluids. Since the agents according to the invention retain absorbed liquids even under pressure and are also capable of distributing more liquid within the construction in the swollen state, they can be employed in higher concentrations, in relation to hydrophilic fiber material, such as cellulose. They are also suitable for use as a homogeneous absorbent layer without cellulose fibers in an absorbent construction, as a result of which particularly thin articles are possible. The polymers are further suitable for use in hygiene articles (e.g. adult incontinence products).

[00147] The polymers according to the invention are also used in absorbent articles suitable for other uses. In particular, the polymers of the present invention can be used in absorbent compositions for absorbents for water or aqueous liquids, preferably, in constructions for absorbing bodily fluids, in structures similar to foam sheets, in packaging materials, in constructions for growing plants, as soil improvement agents or as carriers of active compounds. To do this, they are processed into a web by mixing paper or cellulosic fibers (fluff) or synthetic fibers, or by distributing the absorbent polymers between substrates of paper, cellulosic fibers or non-woven fabrics or by processing on carrier materials.

Test Procedures

[00148] For the purposes of the present invention, Young's modulus can be determined by the Zwick or Anton Paar methods as follows.

Zwick Compression Test Method for Determination of Young's Modulus

[00149] A Zwick Zwicki 1120 tester with a 4.8 cm diameter flat piston is used to compress the absorbent polymer sample using an A.S.T. load cell. GmbH of the KAP-S type. A sample of the polymer sheet after polymerization with a minimum diameter of 6cm is placed on a flat, horizontal sample holder, centered below the piston. A preload of 0.5N and a preload speed of 200mm/min are used to identify the sample interface. After the piston comes into contact with the sample surface, pressure displacement data is recorded by the connected software testXpert V3.31. The force is increased to about 79N and a travel speed of 8mm/min is selected. The thickness of the sample is determined with a gauge and must be between 1 mm and 20 mm.

[00150] Young's modulus is determined by the following equation: E = F*L0/(A0*ΔL) E is Young's modulus (modulus of elasticity(e); F is the force exerted on the polymer sheet; A0 is the actual cross-sectional area through which the force is applied; ΔL is the amount by which the thickness of the object changes; and L0 is the original thickness of the polymer sheet Anton Paar Compression Test Method for Determining Young's Modulus

[00151] An Anton Paar MCR 302 rheometer controlled with Rheoplus V3.62 software is used to determine Young's modulus. A PP50 plate geometry with a diameter of 5cm is used. A sample of the polymer sheet after polymerization with a minimum diameter of 6cm is placed on a flat, horizontal sample holder, centered below the plate. The plate is lowered at a speed of 4mm/min and normal force, distance and time are recorded with Rheoplus software. A value of 0.01/s is entered for d/d lift_speed/gap in the Rheoplus software and the test begins with a gap of 3 mm above the sample. 500 is entered for the measurement points and 0.25s is selected as the measurement duration per point. Young's modulus is calculated by the displacement between an applied normal force of 0.3N to 50N. The thickness of the sample is determined with a gauge and must be between 1 mm and 20 mm.

[00152] Young's modulus is determined by the following equation: E is Young's modulus (modulus of elasticity(e); F is the force exerted on the polymer sheet; A0 is the actual cross-sectional area through which the force is applied; ΔL is the amount by which the thickness of the object changes ; and L0 is the original thickness of the polymer sheet

Microscopic Imaging

[00153] Microscopic imaging is used to determine pore size and distribution in a polymer.

[00154] Gel samples are taken from the polymer sheet for microscopy. A piece measuring approximately 8cm x 8cm x 2cm is dehydrated in ethanol for two days. The sample is then removed from the ethanol and cut into thin strips of about 25 μm with a Leica RM 3335 microtome. If the samples are very brittle or soft, their moisture content should be adjusted slightly by adding moisture or dehydrating. additional ethanol until a smooth cut is obtained. A camera equipped with the Leica DM 2500 M microscope is used to image the thin cross sections using a 5x objective lens.

Average Pore Diameter

[00155] The average pore diameters were determined from cross-sectional images of the dehydrated polymeric foam obtained according to the Microscopic Imaging method using Image-Pro Insight ver. 8.0.3 by Media Cybernetics. The pores that were interconnected were not analyzed. The average pore diameter was used to characterize the polymeric foams.

Vortex Test

[00156] The Vortex Test measures the amount of time in seconds required for 2 grams of an absorbent polymer (particulate) to close a vortex created by stirring 50 milliliters of 0.9% by weight saline at 600 rotations per minute on a magnetic stir plate. The time it takes for the vortex to close is an indication of the free swelling absorption index of the absorbent polymer (particulate). Equipment and materials 1. 100 mL Schott Duran cup and 50 mL graduated cylinder. 2. Programmable magnetic stir plate capable of delivering 600 rotations per minute (such as that commercially available from PMC Industries under the trade name Dataplate® Model #721). 3. Ringless Magnetic Stir Bars, 7.9mm x 32mm, Teflon® Coated removable pivot). 4. Stopwatch 5. Balance, accurate to +/- 0.01g 6. Saline solution (0.9% by weight of NaCl in distilled water at 23°C (degrees Celsius) 7. Weighing paper 8. Room with atmosphere in standard condition: Temp = 23°C +/- 1°C and relative humidity = 50% +/- 2% Test Procedure 1. Measure 50 mL +/- 0.01 mL of saline solution in the 100 mL beaker. 2. Place the magnetic stir bar in the beaker. 3. Set the magnetic stir plate to 600 rotations per minute. 4. Place the beaker in the center of the magnetic stir plate so that the stir bar magnetic is activated. The bottom of the vortex should be near the top of the stir bar. 5. Weigh 2g +/- 0.01g of the absorbent polymer (particulate) to be tested onto weighing paper. NOTE: The absorbent polymer is tested on particulate form. No screening for a specific particle size is performed. 6. While the saline solution is being stirred, quickly pour the absorbent polymer (particulate) to be tested into the saline solution and start the timer. The absorbent polymer (particulate) to be tested must be added to the saline solution between the center of the vortex and the side of the cup. 7. Stop the stopwatch when the vortex disappears and the surface of the saline solution becomes flat, and record the time. 8. The time, recorded in seconds, is reported as Vortex Time.

Free Swelling Index (FSR)

[00157] This method serves to determine the swelling index of the water-swellable materials in this document in a 0.9% aqueous saline solution, without agitation or confining pressure. The amount of time required to absorb a certain amount of liquid is recorded and this is reported in grams of liquid (0.9% saline solution absorbed per gram of water-swellable material per second, e.g. g/g /s.

[00158] The sample material (1.0 g +/- 0.001g) is weighed and placed evenly over the bottom of a 25mL beaker. A 20.0 g aliquot of the saline solution (also at 23°C) is immediately poured into the cup. A timer is started immediately after the saline solution is poured and stopped when the final portion of the saline solution is absorbed by the swellable material in water. This is readily indicated by the loss of light reflection from the bulk salt surface, particularly at the interface with the walls of the cup. The elapsed time, ts, in seconds is recorded. The free swelling index, in g of liquid /g of sample material/s, is calculated as: FSR = 20g/g/ts. The test is performed in triplicate, and the average is used for the free swelling index of the sample material. Water Retention Capacity Test Centrifuge (CR(C)

[00159] The CRC test measures the ability of the particulate absorbent polymer composition to retain liquid after being saturated and subjected to centrifugation under controlled conditions. The resulting retention capacity is indicated as grams of liquid retained per gram of sample weight, (g/g). For particulate absorbent polymer, the sample to be tested is prepared from particles that are pre-screened through a US standard 30 mesh sieve and retained on a US standard 50 mesh sieve. As a result, the particulate absorbent polymer composition sample comprises particles with sizes ranging from about 300 microns to about 600 microns. Particles can be pre-selected manually or automatically. If particles are not used, then a rectangle is cut from a ~2mm thick sheet of the foamed polymer that achieves the initial target weight.

[00160] Retention capacity is measured by placing about 0.16 grams to 0.20 grams of pre-selected particulate absorbent polymer sample or rectangle of 2mm thick polymer sheet into a water permeable tea bag which will contain the sample while allowing a test solution (0.9 weight percent sodium chloride in distilled water) to be freely absorbed by the sample. A heat-sealable tea bag material, such as is available from Dexter Corporation (having a business base in Windsor Locks, Connecticut, U.S.A.) as model 1234T heat seal filter paper. The bag is formed by folding a 5 inch x 3 inch sample of the bag material in half and heat sealing two of the open edges to form a 2.5 inch x 3 inch rectangular pouch. Heat seals are about 0.25 inch inside the edge of the material. After the sample is placed in the pouch, the open edge remainder of the pouch is also heat sealed. Empty bags are also made to serve as controls. Three samples are prepared for each absorbent polymer to be tested.

[00161] The sealed bags are submerged in a pan containing the test solution at about 23°C, ensuring that the bags are kept submerged until completely wet. After wetting, the absorbent polymer samples remain in the solution for 30 minutes, at which point they are removed from the solution and temporarily placed on a flat, non-absorbent surface.

[00162] The wet bags are then placed in a centrifuge basket where the wet bags are separated from each other and are placed on the outer circumferential edge of the basket, wherein the basket is a centrifuge capable of subjecting the samples to a g-force of around 295g. A suitable centrifuge is a CLAY ADAMS DYNAC II, model #0103, having a water collection chute, a digital rpm pressure gauge, and a machined drain basket adapted to accommodate and drain the flat bag samples. When multiple samples are centrifuged, the samples are placed in opposite positions within the centrifuge to balance the basket as it spins. The bags (including wet and empty bags) are centrifuged at about 1,600 rpm (e.g., to achieve a target g-force of about 295 g of force over 3 minutes. G-force is defined as a unit of inertial force in a body that is subjected to rapid acceleration or gravity, equal to 32ft/s2 at sea level.The bags are removed and weighed, with the empty bags (controls) being weighed first, followed by the bags containing the absorbent polymer samples. The amount of solution retained by the absorbent polymer sample, taking into account the solution retained by the bag itself, is the centrifugal retention capacity (CR(C) of the absorbent polymer, expressed in grams of fluid per gram of absorbent polymer. More particularly , the retention capacity is determined by the following equation: CRC = [sample bag after centrifuge - empty bag after centrifuge - dry sample weight]/dry sample weight

[00163] The three samples are tested and the results are calculated to determine the CRC of the absorbent polymer.

Absorption Test Under Load (AUL (0.9psi))

[00164] The Absorption Under Load Test (AUL) measures the ability of the absorbent polymer to absorb a 0.9% by weight solution of sodium chloride in distilled water at 23°C (test solution) while the material is under a load of 0.9 psi.The apparatus for testing the AUL consists of: 1. An AUL assembly including a 1-inch bore cylinder, a 4.4g piston, and a 317g standard weight. The components of this set are described in further detail below. 2. A series of plastic Petri dishes measuring 14cm in diameter by 2.2cm deep 3. A 9cm diameter sintered glass frit with porosity 'C' (25- 50 micron(a). This frit is previously prepared by balancing in a saline solution (0.9% sodium chloride in distilled water, by weight). In addition to being washed with at least two portions of fresh saline solution, the frit should be immersed in saline solution for at least 12 hours before AUL measurements 4. Circles of Whatman Grade 1 filter paper, 9 cm in diameter. 5. Supply of saline solution (0.9% sodium chloride in distilled water, by weight).

[00165] The cylinder of the AUL assembly used to contain the absorbent polymer is made of thermoplastic tubing with an internal diameter of one inch (2.54cm) machined slightly to ensure concentricity. After machining, the 400 mesh stainless steel screen is attached to the bottom of the cylinder by heating the steel screen in a flame until it is hot, after which the cylinder is held on the steel screen until it cools. A soldering iron can be used to touch up the seal if it is unsuccessful or if it breaks. Care must be taken to maintain a flat, smooth bottom and not distort the inside of the cylinder.

[00166] The 4.4g piston is made of 1 inch diameter solid material (e.g., PLEXIGLAS®) and is machined to fit tightly without bonding in the cylinder.

[00167] A standard weight of 317 g is used to provide a restrictive load of 62,053 dyne/cm2 (about 0.9 psi). The weight is a cylindrical stainless steel weight, ~1 inch (2.5 cm) in diameter, that is machined to fit tightly without binding to the cylinder.

[00168] Unless otherwise specified, a sample corresponding to a layer of at least about 300 gsm (0.16g ± 0.005g) of absorbent polymer is used to test the AUL. The sample is taken from absorbent polymers that are pre-screened through 30 US standard mesh and retained in 50 US standard mesh. The absorbent polymer can be preselected with, for example, a RO-TAP® Model B Mechanical Sieve Shaker available from W. S. Tyler, Inc., Mentor Ohio. Sieving is carried out for about 10 minutes. If the AUL of a polymer form is to be determined, a 1 inch diameter plug is cut from the sheet and trimmed in thickness to arrive at a weight of 0.16g ± 0.005g.

[00169] The inside of the cylinder is cleaned with an anti-static cloth before placing the absorbent polymer in the cylinder.

[00170] The desired amount of absorbent polymer (about 0.16 g) is weighed and evenly distributed on the screen at the bottom of the cylinder. The weight of the absorbent polymer at the bottom of the cylinder is recorded as ‘SA’ for use in the AUL calculation described below. After carefully placing the 4.4g piston and 317g weight on top of the absorbent polymer in the cylinder, the AUL assembly including the cylinder, piston, weight and absorbent polymer is weighed, and the weight is recorded as "A" weight .

[00171] A sintered glass frit (described above) is placed in the plastic petri dish, with a salt solution added to a level equal to the top surface of the glass frit. A single circle filter paper is placed gently over the glass frit, and the AUL assembly containing the absorbent polymer is then placed on top of the filter paper. The AUL assembly then remains on top of the filter paper for a test period of one hour , taking care to maintain a constant salt level in the tray. At the end of the one-hour test period, the AUL device is then removed from the frit and weighed, with this value recorded as weight "B".

[00172] AUL (0.9psi) is calculated as follows: AUL (0.9 psi) = (B-(A) / SA where A = Unit Weight of AUL with initial absorbent polymer B = Unit Weight of AUL with absorbent polymer after 60 minutes of absorption SA = initial weight of absorbent polymer

[00173] A minimum of two tests are performed and the results are averaged to determine the AUL value under the 0.9 psi load. Absorbent polymer samples are tested at about 23°C and about 50% relative humidity.

EXAMPLES

[00174] The following examples and comparative examples are provided to illustrate the inventions of processes for producing polymeric sheets (foam), polymers and absorbent polymers and particulate absorbent polymers, as set out in the claims, and not to limit the scope of the claims. Example 1 Preparation of a monomeric stock solution A

[00175] In a polyethylene vessel equipped with a stirrer and a cooling coil, 1.21kg of 50% by weight aqueous NaOH solution and 1.81kg of distilled water were added and cooled to 20°C. 0.516kg of glacial acrylic acid was then added to the caustic solution and the solution was cooled again to 20°C. 4.11g of polyethylene glycol monoalkylether acrylate, 4.11g of ethoxylated trimethylol propane triacrylate (TMPTA 15EO), and 1.03kg of glacial acrylic acid were mixed and added to the first solution, followed by cooling to 4-6° W. Comparative Example 1-1

[00176] Nitrogen was bubbled through 119g of monomeric stock solution A for 5 minutes to remove dissolved oxygen. 6.25g of water was added. Under stirring, 1.25g of an aqueous solution of H2O2 at 1% by weight, 1.88g of an aqueous solution of sodium persulfate at 2% by weight, and 1.13g of an aqueous solution of sodium erythorbate at 0.5% by weight was added to the monomeric solution to initiate the polymerization reaction. The stirrer was stopped after 5s and the started monomer was poured into a round container with a diameter of about 15.5cm and polymerized for 25 minutes. The thickness of the resulting polymer gel sheet was 4mm to 5mm. Comparative Example 1-2

[00177] Nitrogen was bubbled through 119g of monomeric stock solution A for 5 minutes. Under stirring, 6.25g of a 2.95% by weight aqueous sodium bicarbonate solution was added to the monomer. Under stirring, 1.25g of an aqueous solution of H2O2 at 1% by weight, 1.88g of an aqueous solution of sodium persulfate at 2% by weight, and 1.13g of an aqueous solution of sodium erythorbate at 0. 5 wt% was added to the monomer solution to initiate the polymerization reaction. The stirrer was stopped after 5s and the started monomer was poured into a round container with a diameter of about 15.5cm and polymerized for 25 minutes. The thickness of the resulting polymer gel sheet was 4mm to 5mm. Example 1-3

[00178] Nitrogen was bubbled through 119g of monomeric stock solution A for 5 minutes. Under stirring, 6.25g of a 2.95% by weight aqueous sodium bicarbonate solution was added to the monomer. Then, the monomer solution was treated with a Hielscher UIP500 ultrasonic processor at an amplitude of 33% with simultaneous stirring on a magnetic stir plate. A 34mm diameter ultrasonic probe was used and the tip was submerged in the solution for about 1cm to 2cm. The treatment was carried out for 4s.

[00179] After interrupting the ultrasonic treatment and under stirring, 1.25g of an aqueous solution of H2O2 at 1% by weight, 1.88g of an aqueous solution of sodium persulfate at 2% by weight and 1.13g of a solution 0.5 wt% aqueous sodium erythorbate were added to the monomer solution to initiate the polymerization reaction. The stirrer was stopped after 5s and the started monomer was poured into a round container with a diameter of about 15.5cm and polymerized for 25 minutes. The thickness of the resulting polymer gel sheet was 4mm to 5mm.

[00180] Figure 1 is a comparison of the polymeric structures (in foam) of Comparative Example 1-1, Comparative Example 1-2 and Example 1-3 using microscopic imaging in accordance with the method described herein. The spherical objects are pores in the polymer structure. Figure 1A (Comparative Example 1-1) shows the polymer produced from monomer without blowing agent and without ultrasonic treatment. A porous structure is not evident. Figure 1B (Comparative Example 1-2 ) shows the polymer produced from monomer with blowing agent but without ultrasonic treatment. A porous structure with fewer larger diameter pores is produced. Figure 1C (Example 1-3) shows the polymer produced from monomer with a blowing agent and ultrasonic treatment. It can be clearly seen that the ultrasonic treatment produced a foam with many more smaller diameter, more uniformly sized pores, homogeneously distributed throughout the polymer. Comparative Example 1-4

[00181] 110g of monomeric stock solution A combined with 8.62g of polyethylene glycol 200 (PEG) and mixed. Nitrogen was bubbled through the monomer solution for 5 minutes. 6.25g of water was added. Under stirring, 1.25g of an aqueous solution of H2O2 at 1% by weight, 1.88g of an aqueous solution of sodium persulfate at 2% by weight and 1.13g of an aqueous solution of sodium erythorbate at 0.5 % by weight were added to the monomer solution to initiate the polymerization reaction. The stirrer was stopped after 5 s, and the initiated monomer was poured into a round container with a diameter of about 15.5 cm and polymerized for 25 minutes. The thickness of the resulting polymer gel sheet was 4mm to 5mm. Comparative Example 1-5

[00182] 110g of monomeric stock solution A was added to 8.62g of polyethylene glycol 200 (PEG) and mixed. Nitrogen was bubbled through the monomer solution for 5 minutes. Then, under stirring, 6.25g of an aqueous solution of sodium bicarbonate at 2.95% by weight was added to the monomer.

[00183] Under stirring, 1.25g of an aqueous solution of H2O2 at 1% by weight, 1.88g of an aqueous solution of sodium persulfate at 2% by weight and 1.13g of an aqueous solution of sodium erythorbate at 0.5 wt% was added to the monomer solution to initiate the polymerization reaction. The stirrer was stopped after 5s, and the initiated monomer was poured into a round container with a diameter of about 15.5cm and polymerized for 25 minutes. The thickness of the resulting polymer gel sheet was 4mm to 5mm. Example 1-6

[00184] 110g of monomeric stock solution A was combined with 8.62g of polyethylene glycol 200 (PEG) and mixed. Nitrogen was bubbled through the monomer solution for 5 minutes. Under stirring, 6.25g of a 2.95% by weight aqueous sodium bicarbonate solution was added to the monomer.

[00185] The monomer solution was treated with a Hielscher UIP500 ultrasonic processor at an amplitude of 33% with simultaneous stirring on a magnetic stir plate. A 34 mm diameter probe was used, and the tip was submerged in the solution for about 1 cm to 2 cm. The treatment was carried out for 4s.

[00186] After interrupting the ultrasonic treatment and under stirring, 1.25g of an aqueous solution of H2O2 at 1% by weight, 1.88g of an aqueous solution of sodium persulfate at 2% by weight and 1.13g of a solution 0.5% by weight aqueous sodium erythorbate were added to the monomer solution to initiate the polymerization reaction. The stirrer was stopped after 5 s, and the started monomer was poured into a round container with a diameter of 15.5 cm and polymerized for 25 minutes. The thickness of the resulting polymer gel sheet was 4mm to 5mm.

[00187] The Zwick compression test was used to determine the Young's modulus for the polymer sheets after polymerization for Examples 1-1 to 1-6.

[00188] Samples for CRC measurements were prepared for Examples 1-1 to 1-6 as follows: about 50 g of gel was dried in a laboratory oven for 4 days at 40°C plus one day at 60°C. °C. Then, the materials were crushed into small particles by a pestle and mortar. Samples were prescreened through a US standard 30 mesh sieve and retained on a US standard 50 mesh sieve. As a result, the particulate absorbent polymer samples contained particles sized in the range of about 300 microns to about 600 microns.

[00189] Table 1 shows the description, gel sheet thickness after polymerization, CRC and Young's modulus for Comparative Examples 1-1, 1-2, 1-4 and 1-5, as well as the Examples of the invention 1-3 and 1-6. The effect of ultrasonic treatment on Young's modulus can be seen. A foamed polymer produced by adding a blowing agent has greater compressibility (lower Young's modulus) than one without foam (without blowing agent). But the addition of ultrasonic treatment (and blowing agent) significantly increases compressibility further, resulting in a better impact-absorbing polymer while maintaining excellent absorbency. This is true with and without the presence of the PEG plasticizer. Example 2 Preparation of a monomeric stock solution B.

[00190] In a polyethylene vessel equipped with a stirrer and a cooling coil, 1.21kg of 50% by weight aqueous NaOH solution and 1.81kg of distilled water were added and cooled to 20°C. 0.516kg of glacial acrylic acid was then added to the caustic solution and the solution was cooled again to 20°C. 4.11g of polyethylene glycol monoalkylether acrylate, 4.11g of ethoxylated trimethylol propane triacrylate (TMPTA15EO), and 1.03kg of glacial acrylic acid were mixed and added to the first solution, followed by cooling to 4-6°C . Comparative Example 2-1

[00191] Nitrogen was bubbled through the monomeric stock solution B for 5 minutes. Then, 1.05 kg of monomer solution was poured into a 1 liter SodaStream bottle. Nitrogen was sprayed through the monomer in the flask for 10s. The bottle was attached to a SodaStream Fountain Jet from SodaStream USA with a 60 liter compressed CO2 cylinder. The CO2 release button was pressed twice for one second each to release CO2 into the attached SodaStream bottle. The pressure was slowly released by tilting the vial slightly away from the holder and the vial was then uncoupled. Then, 70g of carbonated monomeric solution from the SodaStream bottle was combined with 55g of monomeric solution from monomeric stock solution B in a 300mL beaker.

[00192] Under stirring, 1.25g of an aqueous solution of H2O2 at 1% by weight, 1.88g of an aqueous solution of sodium persulfate at 2% by weight, and 1.13g of an aqueous solution of sodium erythorbate at 0.5 wt% were added to the monomer solution to initiate the polymerization reaction. The stirrer was stopped after 5s and the started monomer was poured into a round container with a diameter of about 15.5cm and polymerized for 25 minutes. The thickness of the resulting polymer gel sheet was 4mm to 5mm. Example 2-2

[00193] Nitrogen was bubbled into the monomeric stock solution B for 5 minutes. Then, 1.05 kg of monomer solution was poured into a 1 liter SodaStream bottle. Nitrogen was sprayed through the monomer in the flask for 10s. The bottle was attached to a SodaStream Fountain Jet available from SodaStream USA with a 60 liter compressed CO2 cylinder. The CO2 release button was pressed twice for one second each to release the CO2 into the attached SodaStream bottle. The pressure was slowly released by tilting the vial slightly away from the holder and the vial was then uncoupled. 70g of carbonated monomeric solution from the SodaStream bottle was combined with 55g of monomeric solution from monomeric stock solution B in a 300mL beaker.

[00194] The monomer solution in the beaker was treated with a Hielscher UIP500 ultrasonic processor at an amplitude of 33% with simultaneous stirring on a magnetic stir plate. A 34 mm diameter probe was used and the tip was submerged in the solution for about 1 cm to 2 cm. The treatment was carried out for 4s.

[00195] After stopping the ultrasonic treatment and under stirring, 1.25g of an aqueous solution of H2O2 at 1% by weight, 1.88g of an aqueous solution of sodium persulfate at 2% by weight, and 1.13g of a 0.5 wt% sodium erythorbate aqueous solution were added to the monomer solution to initiate the polymerization reaction. The stirrer was stopped after 5s, and the started monomer was poured into a round container with a diameter of about 15.5cm and polymerized for 25 minutes. The thickness of the resulting polymer gel sheet was 4mm to 5mm.

[00196] Figure 2 shows shoe insoles cut from polymeric sheets (foam). Figure 2A (Comparative Example 2-1) is the polymeric foam shoe insole produced with CO2 as a blowing agent, but without a ultrasonic treatment. The final polymeric foam is produced from a clear gel containing relatively large, inhomogeneously distributed, widely spaced pores that are individually visible to the naked eye. Figure 2B (Example 2-2) shows a polymeric foam shoe insole produced with the same amount of CO2 as a blowing agent and an ultrasonic treatment. The addition of the ultrasonic treatment produced a polymeric foam with such a high density of homogeneously distributed microscopic pores that the polymer appears opaque white. The individual pores are too small to be seen at naked eye.

[00197] The polymer foam structure of Comparative Example 2-1 was compared with Example 2-2 using microscopic imaging and the images are shown in Figure 3. The spherical objects are from pores in the polymer structure. Figure 3A (Comparative Example 2-1) shows that polymeric foam produced using CO2 as the blowing agent in the monomer, but without ultrasonic treatment, contains large pores of non-uniform size that are not homogeneously distributed. Figure 3B (Example 2-2) shows that the polymeric foam made of monomer containing the same amount of CO2 as the blowing agent, but treated with ultrasound, contained a much larger number of homogeneously distributed smaller diameter pores.

[00198] Compression testing with the Zwick analyzer was used to determine the Young's modulus for the polymer sheets of Comparative Example 2-1 and Example 2-2.

[00199] Samples for CRC measurements were prepared for Comparative Example 2-1 and Example 2-2 as follows: 15g gel from each sample was cut into small pieces and the cut gel was placed in a Petri dish with a diameter of 10cm and dried in a laboratory oven at 100°C for 2 days. Then the sample was crushed into small particles by a pestle and mortar. Samples were prescreened through a US standard 30 mesh sieve and retained on a US standard 50 mesh sieve. As a result, the particulate polymer composition samples comprise particles sized in the range of about 300 microns to about 600 microns. Table 2: Properties of Comparative Example 2-1 and Example 2-2.

[00200] Table 2 again clearly shows that the use of ultrasound with a blowing agent produces foamed polymer with an advantageous lower Young's modulus and greater compressibility, while maintaining excellent absorption properties. Example 3 Preparation of a Monomeric Stock Solution C.

[00201] In a polyethylene vessel equipped with a stirrer and a cooling coil, 1.21kg of 50% by weight NaOH aqueous solution and 1.784kg of distilled water were added and cooled to 20°C. 0.516kg of glacial acrylic acid was then added to the caustic solution and the solution was cooled again to 20°C. 13.0g of methylene bisacrylamide and 1.03kg of glacial acrylic acid were mixed and added to the first solution, followed by cooling to 4-6°C. Comparative Example 3-1

[00202] Nitrogen was bubbled through 413g of monomeric C stock solution plus 11.7g of distilled water for 5 minutes. Under stirring, 1.74g of an aqueous solution of sodium anthraquinone-2-sulfonate at 0.5% by weight were added, 4.13g of aqueous solution of H2O2 at 1% by weight, 6.20g of aqueous solution of 2% by weight sodium persulfate and 3.72g of 0.5% by weight aqueous sodium erythorbate solution were added to the monomer solution. Then, the monomer solution was poured into a small tray, which had dimensions of 23cm x 23cm x 2cm deep. UV exposure was applied for 35 seconds with a FireFly 75 x 20AC365 at full power from an approximate distance of 10cm to evenly expose the monomer and initiate polymerization. 25 minutes were available for polymerization. After polymerization, the polymer gel sheet had a thickness of 5mm to 6mm. Comparative Example 3-2

[00203] Nitrogen was bubbled through 413g of monomeric stock solution C for 5 minutes. Under stirring, 11.7g of a 2.60% by weight aqueous sodium bicarbonate solution was added to the monomer. Under stirring, 1.74g of an aqueous solution of sodium anthraquinone-2-sulfonate at 0.5% by weight, 4.13g of aqueous solution of H2O2 at 1% by weight, 6.20g of aqueous solution of persulfate of 2% by weight sodium and 3.72g of 0.5% by weight sodium erythorbate aqueous solution were added to the monomer solution. Then, the monomer solution was poured into a small tray, measuring 23cm x 23cm x 2cm deep. UV exposure was applied for 35 seconds with a FireFly 75 x 20AC365 at full power from an approximate distance of 10cm to evenly expose the monomer and initiate polymerization. 25 minutes were available for polymerization. After polymerization, the polymer gel sheet had a thickness of 5mm to 6mm. Example 3-3

[00204] Nitrogen was bubbled through 375g of monomeric stock solution C for 5 minutes. 10.6g of an aqueous solution of sodium bicarbonate at 2.60% by weight was added to the monomer. Then, the monomer solution was treated with a Hielscher UIP500 ultrasonic processor at an amplitude of 33% while stirring with a magnetic stir plate. A 34 mm diameter probe was used and the tip was submerged in the solution for about 1 cm to 2 cm. The treatment was carried out for 4s.

[00205] Under stirring, 1.58g of an aqueous solution of sodium anthraquinone-2-sulfonate at 0.5% by weight, 3.75g of aqueous solution of H2O2 at 1% by weight, 5.63g of solution 2% by weight aqueous sodium persulfate solution and 3.38g of 0.5% by weight aqueous sodium erythorbate solution were added to the monomer solution. Then, the monomer solution was poured into a small tray, which has dimensions of 23cm x 23cm x 2cm. UV exposure was applied for 35 seconds with a FireFly 75x20AC365 at full power from an approximate distance of 10cm to evenly expose the monomer and initiate polymerization. 25 minutes were available for polymerization. After polymerization, the polymer gel sheet had a thickness of 5mm to 6mm.

[00206] Figure 4 shows shoe insoles that were cut from the polymeric sheets (foam) produced in Comparative Examples 3-1 and 3-2 and Invention Example 3-3. Figure 4A (Comparative Example 3-1 ) shows the polymeric foam insole produced without sodium bicarbonate blowing agent and without ultrasonic treatment. No porous structure is seen. Figure 4B (Comparative Example 3-2) shows the polymeric foam insole produced using sodium bicarbonate as the agent of expansion, but without ultrasonic treatment. The polymer is clear with relatively large pores distributed throughout it. Figure 4C (Example 3-3) shows the polymeric foam insole produced using sodium bicarbonate as a blowing agent with a treatment ultrasonic.The polymeric foam contains many more finer pores homogeneously distributed throughout it so that the shoe insert is completely opaque white.

[00207] The compression test with the Anton Paar rheometer was used to determine the Young's modulus for the polymer sheets of Comparative Examples 3-1 and 3-2, as well as Example 3-3.

[00208] Samples for CRC measurements were prepared for Examples 3-1 to 3-3 in the same way as for Comparative Example 2-1 and Example 2-2.

[00209] Table 3 shows the properties of Comparative Examples 3-1 and 3-2 and Example 3-3. Again, the addition of ultrasonic treatment dramatically improved the compressibility of the foamed polymer while maintaining excellent absorbency. Comparative Example 4 In a polyethylene container equipped with a stirrer and a cooling coil, 723g of 50% by weight NaOH aqueous solution and 1090g of distilled water were added and cooled to 20°C. 310g of glacial acrylic acid was then added to the caustic solution and the solution was cooled again to 20°C. 1.67g of polyethylene glycol monoalkylether acrylate and 1.67g of ethoxylated trimethylol propane triacrylate (TMPTA3EO), and 620g of glacial acrylic acid were mixed and then added to the first solution followed by cooling to 4-6° W.

[00210] Nitrogen was bubbled through the monomer solution for 5 minutes. The cooling coil has been removed from the container. Under stirring, 4.55g of NaHCO3 dissolved in 150g of distilled water were added to the monomeric solution followed by an addition of 30g of 1% by weight H2O2 aqueous solution, 45g of 2% by weight aqueous sodium persulfate solution , and 27g of a 0.5% by weight aqueous solution of sodium erythorbate to initiate the polymerization reaction. The stirrer was stopped after 30s and the started monomer was polymerized for 25 minutes. Example 5

[00211] In a polyethylene container equipped with a stirrer and a cooling coil, 723g of 50% by weight NaOH aqueous solution and 1090g of distilled water were added and cooled to 20°C. 310g of glacial acrylic acid was then added to the caustic solution and the solution was cooled again to 20°C. 1.67g of polyethylene glycol monoalkylether acrylate and 1.67g of ethoxylated trimethylol propane triacrylate (TMPTA3EO), and 620g of glacial acrylic acid were mixed and then added to the first solution followed by cooling to 4-6° W.

[00212] Nitrogen was bubbled through the monomer solution for 5 minutes. The cooling coil has been removed from the container. Under stirring, 3.41g of NaHCO3 dissolved in 150g distilled water were added to the monomeric solution. The monomer solution was treated with a Hielscher UIP500 at an amplitude of 100% while stirring with a magnetic stir plate. A 34mm diameter ultrasonic probe was used and the tip was submerged in the solution for 1cm to 2cm. Ultrasonic treatment was carried out for 10s followed by the addition of 30g of an aqueous solution of H2O2 at 1% by weight, 45g of an aqueous solution of sodium persulfate at 2% by weight, and 27g of an aqueous solution of sodium erythorbate. to 0.5% by weight to initiate the polymerization reaction. The stirrer was stopped after 30s and the started monomer was polymerized for 25 minutes.

[00213] In Figure 5, the polymeric structure (in foam) of Comparative Example 4 is compared to Example 5 using microscopic imaging. Figure 5A (Comparative Example 4) shows the foam polymer produced with monomer containing dehydrating agent. expansion without ultrasonic treatment. Figure 5B (Example 5) shows the foamed polymer produced with monomer containing blowing agent and treated with ultrasound. The monomer solution of both samples contained the same amount of sodium bicarbonate blowing agent. Use of an ultrasonic treatment produced finer and more homogeneously distributed pores Comparative Examples 4-1 to 4-3 and Examples 5-1 to 5-3

[00214] The polymer obtained in Comparative Example 4 and Example 5 was additionally processed as described below.

[00215] The foamed hydrogel polymer after polymerization was torn by hand and extruded with a commercial Hobart 4M6 extruder, followed by drying in a Procter & Schwartz Model 062 forced air oven at 175°C for 12 minutes with upward flow and 6 minutes with downward airflow in a 20 in. x 40 in. perforated metal tray for a final product moisture level of less than 5% by weight. The dried particulate absorbent polymer was placed in a basket and crushed with a hammer, ground in a Modern Process Equipment 666-F three-stage roller mill, and sieved with a Brinkmann Retsch Shaker to remove absorbent polymer particles larger than 850 μm and smaller than 150 μm.

[00216] The product was further sieved to arrive at the following particle size distribution based on US standard test sieves: 15% by weight at 100 mesh (150 μm), 50% by weight at 50 mesh (300 μm), 30% in mesh 35 (500 μm) and 5% in mesh 30 (600 μm).

[00217] A CRC and vortex were determined from the particulate absorbent polymers.

[00218] 200g of samples of the particulate absorbent polymers were each coated with 8g of a 25% by weight aqueous ethylene carbonate solution using a finely atomized spray while the absorbent polymer particles are fluidized in air . Each coated particulate absorbent polymer sample was placed in a Petri dish of a diameter of 10cm and then placed in a convection oven at a temperature of 185°C for 40 and 50 minutes. After the oven time had elapsed, the particulate absorbent polymer was cooled and sieved to remove particles larger than 850 μm and smaller than 150 μm.

[00219] Table 4 shows how the addition of an ultrasonic treatment reduced vortexing time (increasing the absorption rate), especially after surface cross-linking, while maintaining excellent CRC and AUL. Example Description Oven time at 185°C (min) Vortex (s) CRC (g/g) 0.9 AUL (g/g) Percentage reduction in Vortex by addition of ultrasound Comparative Example 6 In a polyethylene container equipped with a stirrer and a cooling coil, 723g of 50% by weight NaOH aqueous solution and 1090g of distilled water were added and cooled to 20°C. 310g of glacial acrylic acid was then added to the caustic solution and the solution was cooled again to 20°C. 3.83g of polyethylene glycol monoalkylether acrylate, 2.23g of polyethylene glycol 300 diacrylate, and 620g of glacial acrylic acid were mixed and then added to the first solution followed by cooling to 4-6°C.

[00220] Nitrogen was bubbled through the monomer solution for 5 minutes. The cooling coil has been removed from the container. Under stirring, 3.42g of NaHCO3 dissolved in 50g of distilled water were added followed by an addition of 30g of an aqueous solution of H2O2 at 1% by weight, 45g of an aqueous solution of sodium persulfate at 2% by weight, and 27g of an aqueous solution of sodium erythorbate at 0.5% by weight to initiate the polymerization reaction. The stirrer was stopped after 30s and the started monomer was polymerized for 25 minutes. Example 7

[00221] In a polyethylene container equipped with a stirrer and a cooling coil, 723g of 50% by weight NaOH aqueous solution and 1090g of distilled water were added and cooled to 20°C. 310g of glacial acrylic acid was then added to the caustic solution, and the solution was cooled again to 20°C. 3.83g of polyethylene glycol monoalkylether acrylate, 2.23g of polyethylene glycol 300 diacrylate, and 620g of glacial acrylic acid were mixed and then added to the first solution followed by cooling to 4-6°C.

[00222] Nitrogen was bubbled through the monomer solution for 5 minutes. The cooling coil has been removed from the container. Under stirring, 3.42g of NaHCO3 dissolved in 50g distilled water were added. Then, the monomer solution was treated with a Hielscher UIP500 at an amplitude of 100% while stirring with a magnetic stir plate. A 34 mm diameter probe was used and the tip was submerged in the solution for 1 cm to 2 cm. The treatment was carried out for 10s followed by the addition of 30g of an aqueous solution of H2O2 at 1% by weight, 45g of an aqueous solution of sodium persulfate at 2% by weight, and 27g of an aqueous solution of sodium erythorbate at 0.5% by weight to start the polymerization reaction. The stirrer was stopped after 30s and the started monomer was polymerized for 25 minutes.

[00223] The polymer foam structures of Comparative Example 6 were compared to Example 7 using microscopic imaging and the images are displayed in Figure 6.

[00224] Figure 6A (Example 6) shows the polymer structure (in foam) produced with monomer containing blowing agent and no ultrasonic treatment. Figure 6B (Example 7) shows the polymer structure in foam produced by monomer with blowing agent and with ultrasonic treatment.The monomer solution of both samples contained the same amount of blowing agent.The addition of ultrasonic treatment produced many more homogeneously distributed pores of much smaller diameter in the absorbent foam polymer.

[00225] The absorbent polymer gel obtained in Comparative Example 6 and Example 7 was further processed as described below.

[00226] A particulate absorbent polymer was prepared as follows. The resulting foamed polymer hydrogel after polymerization was torn by hand and extruded with a commercial Hobart 4M6 extruder, followed by drying in a Procter & Schwartz Model 062 forced air oven at 175°C for 12 minutes with upward flow and 6 minutes with downward airflow in a 20 in. x 40 in. perforated metal tray for a final product moisture level of less than 5% by weight. The dried particulate absorbent polymer was placed in a basket and crushed with a hammer, ground in a Modern Process Equipment 666-F three-stage roller mill, and sieved with a Brinkmann Retsch Shaker to remove absorbent polymer particles larger than 850 μm and smaller than 150 μm.

[00227] The product was sieved to arrive at the following particle size distribution based on US standard test sieves: 15% by weight at 100 mesh (150 μm), 50% by weight at 50 mesh (300 μm ), 30% in mesh 35 (500 μm) and 5% in mesh 30 (600 μm).

[00228] A CRC and vortex were determined from the uncoated particulate absorbent polymers.

[00229] Next, 200g of each sample of the absorbent particulate polymers was coated with 8g of a 25% by weight aqueous ethylene carbonate solution using a finely atomized spray while the SAP particles are fluidized in air. Each coated particulate absorbent polymer was included in a Petri dish of a diameter of 10 cm and then placed in a convection oven of a temperature of 185 ° C for 40 minutes. After the oven time had elapsed, the particulate absorbent polymer was cooled and sieved to remove particles larger than 850 μm and smaller than 150 μm. Examples 8 to 10

[00230] The absorbent polymer of the present invention can be produced as follows. Example 8

[00231] In a polyethylene container equipped with a stirrer and a cooling coil, 723g of 50% by weight NaOH aqueous solution and 1090g of distilled water were added and cooled to 20°C. 310g of glacial acrylic acid was then added to the caustic solution and the solution was cooled again to 20°C. 2.46g of polyethylene glycol monoalkylether acrylate, 2.46g of ethoxylated trimethylol propane triacrylate (TMPTA15EO), and 620g of glacial acrylic acid were mixed and then added to the first solution followed by cooling to 4-6° W.

[00232] Nitrogen was bubbled through the monomer solution for 5 minutes. The cooling coil has been removed from the container. Under stirring, 3.98g of NaHCO3 dissolved in 150g distilled water were added to the monomeric solution. Then, the monomer solution was treated with a Hielscher UIP500 at an amplitude of 67% while stirring with a magnetic stir plate. A 34mm diameter ultrasonic probe was used and the tip was submerged in the solution for 1cm to 2cm. The treatment was carried out for 5s followed by the addition of 30g of an aqueous solution of H2O2 at 1% by weight, 45g of an aqueous solution of sodium persulfate at 2% by weight, and 27g of an aqueous solution of sodium erythorbate at 0.5% by weight to start the polymerization reaction. The stirrer was stopped after 30s and the started monomer was polymerized for 25 minutes. Example 9

[00233] Same as Example 8, except that 5.01g of sodium carbonate was dissolved in 150g of distilled water and added to the monomer solution as a blowing agent instead of sodium bicarbonate. Example 10

[00234] Same as Example 9, except that 4.06g of polyethylene glycol monoalkylether acrylate and 2.37g of polyethylene glycol 300 diacrylate were used as crosslinkers in the monomer.

[00235] Figures 7A, B and C illustrate the microscopic imaging of Examples 8, 9 and 10 respectively. All samples show many more homogeneously distributed pores of a much smaller diameter compared to Comparative Examples 4 and 6.

[00236] The absorbent polymer gel obtained in Examples 8 to 10 after polymerization was further processed as described below.

[00237] A particulate polymer was prepared according to the method previously described in Comparative Example 6 and Example 7.

[00238] The product was sieved to arrive at the following particle size distribution based on US standard test sieves: 15% by weight at 100 mesh (150 μm), 50% by weight at 50 mesh (300 μm ), 30% in mesh 35 (500 μm) and 5% in mesh 30 (600 μm). A CRC and vortex were determined from the uncoated particulate absorbent polymers.

[00239] 200g of each exemplary sample was coated with 8g of a 25% by weight aqueous ethylene carbonate solution using a finely atomized spray while the particles are fluidized in air. The coated particulate polymer was included in Petri dishes of a diameter of 10 cm and then placed in a convection oven of a temperature of 185°C for 50 minutes. After the oven time had elapsed, the particulate polymer was cooled and sieved to remove particles larger than 850 μm and smaller than 150 μm.

[00240] CRC, AUL and vortex were determined from the coated and heat treated particulate absorbent polymers. Comparative Example 11

[00241] In a polyethylene container equipped with a stirrer and a cooling coil, 723g of 50% by weight NaOH aqueous solution and 1167g of distilled water were added and cooled to 20°C. 310g of glacial acrylic acid was then added to the caustic solution and the solution was cooled again to 20°C. 3.83g of polyethylene glycol monoalkylether acrylate, 2.23g of polyethylene glycol 300 diacrylate, and 620g of glacial acrylic acid were mixed and then added to the first solution followed by cooling to 4-6°C.

[00242] Nitrogen was bubbled through the monomer solution for 5 minutes. The cooling coil has been removed from the container. Under stirring, 4.56g of NaHCO3 dissolved in 67g of distilled water were added followed by an addition of 30g of an aqueous solution of H2O2 at 1% by weight, 45g of an aqueous solution of sodium persulfate at 2% by weight, and 27g of an aqueous solution of sodium erythorbate at 0.5% by weight to initiate the polymerization reaction. The stirrer was stopped after 30s and the started monomer was polymerized for 25 minutes. Example 12

[00243] Same as Comparative Example 11, except that, after adding the blowing agent, the monomer solution was ultrasonically treated with a Hielscher UIP500 at an amplitude of 100% while stirring with a magnetic stir plate. A 34mm diameter ultrasonic probe was used and the tip was submerged in the solution for 1cm to 2cm. The treatment was carried out for 10s.

[00244] The absorbent polymer gel obtained in Examples 11 and 12 was further processed as described below.

[00245] A particulate absorbent polymer was prepared as previously described in Comparative Example 6 and Example 7.

[00246] The product was sieved to arrive at the following particle size distribution based on US standard test sieves: 15% by weight at 100 mesh (150 μm), 50% by weight at 50 mesh (300 μm), 30% in mesh 35 (500 μm) and 5% in mesh 30 (600 μm). CRC and vortex were determined from the uncoated particulate absorbent polymers.

[00247] 200g of each exemplary sample were coated with aqueous ethylene carbonate solution, heated and sieved according to the process described in Examples 8, 9 and 10.

[00248] CRC, AUL, vortex and FSR were determined from the coated and heat treated particulate absorbent polymers. These values are summarized in Table 5. It can be clearly seen that the addition of an ultrasonic treatment increases the absorption rate (reduces the vortexing time and increases the FSR value) while maintaining excellent absorption properties.

[00249] Table 6 summarizes the average pore diameter for different Comparative Examples and examples listed above. This table also illustrates the reduction in average pore diameter, as described here, for monomeric solutions with blowing agent that were treated with ultrasound versus those that were not. As can be seen, all monomeric solutions with blowing agent that were also treated with ultrasound showed a drastic reduction in average pore diameter.

[00250] Although the numerical ranges and parameters that establish the broad scope of the invention are approximations, the numerical values established in the specific examples are reported as accurately as possible. Except in operational examples, or when otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, etc. used in the specification and claims are to be understood as being modified in all cases by the term "about". Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective test measurements.

Claims (8)

1. Absorbent particle, characterized by the fact that it is prepared by providing a polymeric foam and comminuting said polymeric foam into particles, said polymeric foam being prepared by a process comprising the steps of: (a) providing a solution monomeric, which consists of a polymerizable, ethylenically unsaturated monomer, containing one or more acid groups, water and one or more crosslinkers presenting more than one polymerizable group per molecule; (b) introducing a blowing agent into the monomeric solution; (c) treating the monomer solution with an ultrasonic treatment; (d) introducing one or more initiating agents to the monomer solution; and (e) polymerizing the monomer solution; and the energy transmitted to the monomer through ultrasonic processing is in the range of 0.005 kJ/kg to 5 kJ/kg of monomer solution. 2. Absorbent particle according to claim 1, characterized by the fact that the blowing agent is a compound based on carbonate or bicarbonate or carbon dioxide. 3. Absorbent particle, according to claim 1 or 2, characterized by the fact that the treatment of the monomeric solution by ultrasonic treatment comprises the introduction of energy through an ultrasonic probe or a surface activated by an ultrasonic transducer. 4. Absorbent particle according to any one of claims 1 to 3, characterized by the fact that the blowing agent is applied subsequently before the gelation of the monomeric solution during polymerization. 5. Absorbent particle according to any one of claims 1 to 4, characterized by the fact that ultrasonic radiation is applied subsequently before the gelation of the monomeric solution during polymerization. 6. Absorbent particle according to any one of claims 1 to 5, characterized by the fact that the energy transmitted to the monomer through ultrasonic processing is in the range between 0.01 kJ/kg of monomer solutions to 3 kJ/kg of monomer , or between 0.1 kJ/kg of monomer solutions to 2 kJ/kg of monomer. 7. Absorbent particle according to any one of claims 1 to 6, characterized by the fact that: when the process is carried out in batch, an ultrasonic treatment time of less than 10 min or less than 1 min is chosen; or when the process is carried out continuously through a flow cell, ultrasonic treatment times of less than 1 min or less than 30 s are chosen. 8. Absorbent particle according to any one of claims 1 to 7, characterized by the fact that the time between ultrasonic treatment of the monomer solution and the start of polymerization is less than 1 h, less than 2 min, or less of 30 s.