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WO1993019099A1 - Particules absorbantes plissees a grande aire de surface efficace et forte vitesse d'absorption - Google Patents

Particules absorbantes plissees a grande aire de surface efficace et forte vitesse d'absorption Download PDF

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Publication number
WO1993019099A1
WO1993019099A1 PCT/US1992/007336 US9207336W WO9319099A1 WO 1993019099 A1 WO1993019099 A1 WO 1993019099A1 US 9207336 W US9207336 W US 9207336W WO 9319099 A1 WO9319099 A1 WO 9319099A1
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WIPO (PCT)
Prior art keywords
polymer
monomer
mixture
ethylenically unsaturated
microns
Prior art date
Application number
PCT/US1992/007336
Other languages
English (en)
Inventor
Jack C. Lamphere
Larry R. Wilson
Frederick W. Stanley
Original Assignee
The Dow Chemical Company
Stanley, Caroline
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from EP92104434A external-priority patent/EP0516925B1/fr
Application filed by The Dow Chemical Company, Stanley, Caroline filed Critical The Dow Chemical Company
Priority to US08/140,182 priority Critical patent/US5744564A/en
Publication of WO1993019099A1 publication Critical patent/WO1993019099A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2/00—Processes of polymerisation
    • C08F2/32—Polymerisation in water-in-oil emulsions
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
    • A61L15/00—Chemical aspects of, or use of materials for, bandages, dressings or absorbent pads
    • A61L15/16—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons
    • A61L15/42—Use of materials characterised by their function or physical properties
    • A61L15/60—Liquid-swellable gel-forming materials, e.g. super-absorbents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
    • B01J20/26—Synthetic macromolecular compounds

Definitions

  • the present invention relates to absorbents formed of water insoluble, typically gel-forming, polymeric materials that are capable of, for example, absorbing many times their own weight upon contact with aqueous fluids. More particularly, the present invention focuses upon polymeric materials that absorb substantial volumes of such fluids at a high rate of absorption, processes for making them, uses thereof in absorbent articles, and absorbent articles incorporating such polymeric materials.
  • aqueous fluid absorbent polymer having large capacities for absorbing aqueous fluids have been developed and have found use in personal care productsfor absorbing aqueous biological fluids.
  • the aqueous fluid absorbent polymer is utilized in powder form, and is often mixed with cellulosic fibers that help initially absorb and distribute the fluid load.
  • polymeric materials of interest in such products are based upon a variety of polymers including those derived from water soluble ethylenically unsaturated monomers or graft polymers in which unsaturated monomers are graft polymerized onto a polysaccharide (such as starch or cellulose) or other polymeric backbone.
  • a polysaccharide such as starch or cellulose
  • a preferred absorbent material is derived from a water insoluble gel formed by copolymerizing an ethylenically unsaturated carboxylic acid with a multifunctional crosslinking monomer.
  • the acid monomer or polymer is substantially neutralized with an alkali metal hydroxide, dried and pulverized into a powder form before use in a personal care product.
  • a preferred polymer gel is a copolymer of acrylic acid/sodium acrylate and any of a variety of crossl inkers.
  • aqueous fluid absorbent polymer at least for diaper use, is that it have high fluid capacity, e.g., a centrifuge capacity greater than 10 grams/gram.
  • a most desired characteristic of the aqueous fluid absorbent polymer is that it has a fast rate of absorption, adequate to imbibe and hold the fluid during absorption without leakage of fluid from the device in which it is employed. It is adequate fast rate, while maintaining all of the other desired qualities of the aqueous absorbent, that has eluded prior researchers.
  • a number of workers have attempted to produce a non-dusting and/or fast absorbency rate product by making somewhat larger particles that still possess useful absorbency, changing polymer particle surface characteristics or adhering fines particles together.
  • the balancing of desirable product end-use qualities with manufacturing limitations has heretofore meant accepting one or more less desirable characteristics.
  • the present invention is a fluid absorbent polymer having a fast rate of absorption for aqueous fluids, comprising individual polymer particles each having a high surface area, each said particle surface substantially continuous but including a plurality of wrinkles comprising folds, ridges, crevices, and channels.
  • the polymer particles are swellable such that a fluid in contact with said particles is effectively exposed to a substantial portion of the surface area of said particles for absorption of said fluid.
  • the wrinkles of the invention including folds, ridges, crevices, and channels, are further characterized and depicted in Figures 1 through 4.
  • the resulting product has a rate of absorption of less than one minute, preferably less than 20 seconds, as measured by a "vortex test" described below.
  • the particle size of the fluid absorbent polymer particles is substantially greater than 75 micrometers in diameter, preferably greater than 100 micrometers.
  • the invention also includes a method for making the fast rate aqueous fluid absorbent of the invention, comprising: suspending a water soluble monomer mixture in a continuous, inert, organic liquid phase, containing suspending agents, with agitation such that droplets of said monomer mixture form in said continuous phase;
  • the invention also includes the use of the fluid absorbent polymer of the invention in an article for absorbing biological fluids.
  • the invention includes such use wherein the article is a disposable diaper.
  • the absorbent polymer of the invention are particularly useful in forming personal care articles for absorbing biological fluids, such as disposable diapers.
  • Figure 1(a) is a photomicrograph at a magnification of 50 of the polymer particles of the invention wherein the initial monomer mixture comprises 24 percent acrylic acid.
  • Figure 2(a) is a photomicrograph at 50 magnification of the polymer particles of the invention wherein the initial monomer mixture comprises 26 percent acrylic acid.
  • Figure 2(b) is a photomicrograph at 50 magnification showing the particles of Figure 2(a) in cross section.
  • Figure 3(a) is a photomicrograph at 50 magnification showing the polymer particles of the invention wherein the initial monomer concentration of the polymerization mixture is 29 percent acrylic acid.
  • Figure 4(a) is a photomicrograph at a magnification of 50 showing the polymer particles of the invention wherein the initial monomer concentration is 33 percent acrylic acid.
  • Figure 5 is a photomicrograph at a magnification of 50 showing the polymer particles of Comparative Example A, representative of the prior art.
  • a key element of the invention is a high surface area aqueous absorbent polymer particle that is characterized by a continuous but wrinkled surface and an exceptionally high rate of absorbency for aqueous fluids, in comparison with conventional spherical absorbent materials.
  • Figures 1-4 are photomicrographs of the polymer particles of the invention, at a magnification of 50, for a crosslinked polymer based upon acrylic acid, as further described in the examples below. Each polymer particle is also shown in cross section which further suggests its uniqueness and exceptionally high surface area of the resin available for absorbing aqueous fluids.
  • the phrase "particle surface substantially continuous but including a plurality of wrinkles comprising folds, ridges, crevices, and channels” is defined to mean the surface morphology depicted in Figures 1-4.
  • the polymer particles of the invention have a high surface area. Preferred areas are between 0.3 and 0.5 m 2 /g. An especially preferred surface area is 0.3 m 2 /g.
  • the monomer droplets must be of a certain minimum size for adequate wrinkling to occur. It is preferred that the monomer droplets be larger than 75 micrometers in diameter at initiation of the polymerization. More preferably, the monomer droplets will be between 75 and 1000 micrometers in diameter, most preferably between 150 and 1000 micrometers, and most preferably with an average diameter of 400 micrometers at the initiation of polymerization.
  • the water absorbent compositions of the invention may be made from a variety of polymers or copolymers. Basically, any water-soluble ethylenically unsaturated monomer or mixture thereof that crosslinks to form a substantially water insoluble gel or particle is suitable.
  • Crosslinked structures may be obtained by the copolymerization of a water-soluble monomer and a crosslinking monomer possessing at least two polymerizable double bonds in a molecular unit, as is well-known in the art.
  • Monomer mixtures that include graft, as well as addition polymerizing systems may be employed so long as the wrinkled surface can be imparted to the resulting polymer or copolymer particles.
  • Exemplary water-soluble monomers include ethylenically unsaturated amides such as acrylamide, methacrylamide, and fumaramide as well as their N-substituted derivatives.
  • hydroxyethylacrylate hydroxyethylmethacrylate, and esters of acrylic and methacryiic acids with polyethylene oxide.
  • Vinyl amines such as vinyl pyridine and vinyl morpholine, and diallyl amines are also useful.
  • Other suitable monomers are well known to those skilled in the art as discussed in U.S. Patent No.4,708,997.
  • the ethylenically unsaturated monomer may be partially neutralized as set forth below.
  • the monomer mixture will further comprise the salt of the ethylenically unsaturated monomer.
  • the monomer mixture may also include components that graft polymerize onto one or more other monomer additional monomers of the monomer mixture.
  • Polysaccharides, such as starch and cellulose are examples of graft-polymerizable components. Particularly suitable is a graft-polymerizable polyvinyl alcohol.
  • the concentration of monomer in the monomer mixture used to make the wrinkled particles of the invention is a key factor in determining the degree of wrinkling achieved.
  • concentration of monomer depends upon the particular system of interest.
  • varying the concentration of acrylic acid monomer in the initial monomer mixture has a profound effect upon the degree of wrinkling, as demonstrated by Figures 1-4, wherein the concentration of monomer varies between 24 and 33 weight percent.
  • the acrylic acid/sodium acrylate system at least about 10 percent acrylic acid in the initial monomer mixture (prior to neutralization) is required to achieve useful wrinkling, useful at least from an economic view.
  • the initial monomer mixture will containfrom 10to 50 percent acrylic acid, more preferably from 24 to 35 percent acrylic acid.
  • the suspension polymerization of the present invention when carboxylic acid monomers are employed, generally provides that the monomers be neutralized at least partially prior to the polymerization.
  • the acid monomers will be between 75 and 95 percent neutralized, more preferably between 80 and 90 percent neutralized.
  • the neutralization is generally carried out, as is well known in the art, by simply mixing the monomers, including any crosslinking agents, with any suitable base, e.g. an alkali hydroxide such as sodium hydroxide or potassium hydroxide or an alkali carbonate or bicarbonate such as sodium or potassium carbonate or bicarbonate, as the initial step of the process of preparation of the polymers of the invention.
  • the neutralization is advantageously carried out at temperatures below about 40°C, preferably below about 35°C.
  • crosslinkers include methylene-bis-acrylamide, trimethylol propanetriacrylate and diethylene glycol diacrylate and tetraethylene glycol diacrylate.
  • Crosslinking monomers are present in the dispersion of water-soluble monomer in an amount effective to crosslink the water-soluble polymer. Typically, the crosslinking monomer is used in amounts ranging from about 0.0001 to about 5 parts by weight, based on 100 parts by weight of the water-soluble monomer used.
  • the monomer mixture is suspended in an inert organic phase or oil phase comprising an organic material that is non-reactive with the monomers and resulting products.
  • the water-immiscible oil phase of the suspension generally comprises as least one inert hydrophobic liquid, such as a liquid hydrocarbon or substituted liquid hydrocarbon.
  • Preferred organic liquids are the halogenated hydrocarbons such as perchloroethylene, methylene chloride, and liquid hydrocarbons having 4 to 15 carbon atoms per molecule, including aromatic and aliphatic hydrocarbons and mixtures thereof such as benzene, xylene, toluene, mineral oils, liquid paraffins such as kerosene, and naphtha.
  • hydrocarbons are the more preferred, with the aliphatic hydrocarbons being most preferred.
  • a preferred commercially available aliphatic hydrocarbon is ISOPAR ® M deodorized kerosene, sold by Exxon.
  • the inert organic or oil phase includes dispersing agents to keep the aqueous soluble monomer droplets suspended in an oil phase for the suspension polymerization.
  • These dispersing agents include surface active materials such as sucrose fatty acid esters and/or polyglycerol fatty acid esters. Also included are nonionic surface active agents having HLB values of from 2 to 6.
  • Polymeric materials useful as dispersants include the various cellulose ethers, such as ethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxyethyl cellulose and combinations thereof.
  • such cellulose ethers will be provided at a concentration of from 0.1 to 2 weight percent, based on the weight of the monomer, more preferably 0.5 weight percent based on the weight of the monomer.
  • Other useful materials include the hydrophobic clays such as cationic surfactant treated bentonite clays.
  • the preferred dispersing agent is a mixture of a fumed hydrophobic silica (such as AEROSIL TM R-972 fumed silica manufactured by Degussa, Inc.) and a copolymer of lauryl methacrylate and acrylic acid. In a preferred copolymer, the mole ratio of lauryl methacrylate to acrylic acid in the copolymer is 99 to 1.
  • a key element of the invention is the wrinkling and the other surface and internal characteristics of the polymer particles as shown in Figures 1-4.
  • Such wrinkling is attributable to crosslinking of the monomer droplet in the vicinity of its surface.
  • Introducing the wrinkling and high surface characteristics to the particles of the invention is thought to be related to at least the process of the invention which requires the utilization of an initiator system that is at least partially oil phase soluble.
  • a redox system is employed which comprises, as a reducing component thereof, an at least partially oil phase soluble material.
  • Partially soluble in the organic liquid phase is defined to mean possessing sufficient solubility in the oil phase to yield polymer particles as depicted in any of Figures 1-4.
  • the reducing agent will partition such as to provide between 10 and 2500 ppm reducing agent in the oil phase, more preferable at least 100 ppm reducing agent in the oil phase.
  • Suitable oxidizing components include, for example, t-butyl hydroperoxide (t-BHP); 2,5-dihydroperoxy-2,5-dimethylhexane; and cumene hydroperoxide.
  • a preferred reducing component of the redox system is sulfur dioxide gas.
  • Thermal initiators that have sufficient oil phase solubility, such as VAZO TM 64 azobisisobutyronitrile available from DuPont and benzoyl peroxide are also suitable.
  • the monomer mixture is suspended in the inert oil phase, typically utilizing agitation, to form monomer mixture droplets.
  • the monomer droplets must be large enough such that the wrinkling characteristic imparted to the particles is useful, for example, in increasing absorbency rate when employed in a personal care product.
  • variation of agitation intensity and shear may be used to control monomer droplet size.
  • the reaction is carried out at any convenient temperature at which the initiator system operates efficiently.
  • the temperature of reaction may range from less than room temperature to 90°C.
  • the reaction is initiated at room temperature or lower, preferably about 20°C; proceeds adiabatically (to a temperature between 55°C to 65°C); and optionally includes a final temperature increase to 75°C.
  • the reaction is initiated by bubbling the reducing agent, such as sulfur dioxide, into the reaction mixture.
  • the polymer product is recovered by removing the inert oil phase and drying.
  • the dried, finished product may then be treated with a wetting agent, such as VORANOL ® 2070 polyol, manufactured by The Dow Chemical Company.
  • the wetting agent helps overcome the adverse effect of any remaining dispersing agent, such as hydrophobic inert inorganic silica material, remaining on the finished product.
  • the dry polymer beads will be provided with 0.25 to 2 weight percent wetting agent based on the weight of the dry beads, more preferably 0.5 to 1.5 weight percent. More preferably, 1 weight percent wetting agent based on the weight of dry polymer will be provided.
  • Swelling capacity under pressure is closely related to the modulus of a polymer.
  • SCUP measures the ability of a polymer to swell against a pressure of 0.29 psi (2 kPa) which pressure simulates the pressures that the polymer must swell against in a disposable infant diaper.
  • 0.160 gram of the polymer of interest is placed in a cylinder including a
  • Centrifuge capacity is calculated as [(W 3 - B 1 ) - (W 2 - W 1 )]/(W 2 - W 1 ), where W 1 is the weight of an empty dry tea bag, W 2 is the weight of an empty dry tea bag containing the sample, W 3 is the weight of the wet centrifuged sample and tea bag, and B 1 is the average weight of a wet centrifuged tea bag.
  • Preferred centrifuge capacities are greater than 10 grams saline solution/gram polymer, are more preferably greater than 15 grams saline solution/gram polymer, are even more preferably greater than 20 grams saline solution/gram polymer, and are most preferably greater than 25 grams saline solution/gram polymer.
  • the rate at which the polymers of interest will absorb aqueous fluid is a key advantage of the invention. It is characterized by a "vortex rate" test. This test measures and reports in seconds the time required for a vortex generated by a magnetic stir in a container to disappear when 2 grams of absorbent polymer are added to 50 milliliters of 0.9 percent saline solution. Preferred vortex rates are less than 65 seconds, are more preferably less than 40 seconds, and are even more preferably less than 20 seconds.
  • the swell rate of the polymer is determined using the following procedure.
  • a pulverized sample of the dry polymer is screened to pass through a 30-mesh (500 micrometers) screen, but to be retained on a 50-mesh (300 micrometers) screen.
  • a 1.0 gram portion of this material is placed into a weighing boat.
  • 30.0 grams of a 0.9 percent sodium chloride saline solution is rapidly added.
  • the swell time equals the time it takes for the sample to swell to form a continuous barrier atop the surface of the saline solution.
  • Preferred swell times are less than one minute, are more preferably less than 35 seconds, and are even more preferably less than 25 seconds, and are most preferably less than 10 seconds.
  • absorbent structures into which the polymers of the invention may be utilized include incontinence devices, sanitary napkins, paper towels, and facial tissues.
  • the monomer mix is cooled to 25°C and added to a mixture of 0.6 grams of AEROSIL TM R-972 fumed hydrophobic silica of Degussa, Inc., 0.32 grams of a copolymer of laurylmethacrylate and acrylic acid in a weight ratio of 99: 1 as a dispersing agent, and 800 grams of ISOPAR ® M deodorized kerosene of Exxon in a 2 liter reactor.
  • the reactor is equipped with a 4-bladed agitator rotating at 250 rpm.
  • 0.089 grams of 70 percent t-butyl hydroperoxide (t-BHP) is added.
  • the suspension is purged for 30 minutes with nitrogen and then heated to 50°C.
  • the polymerization is initiated by bubbling into the suspension of 0-1 weight percent a dilute stream of sulfur dioxide in nitrogen at a flow rate between 200 mL/min and 1000 mL/min.
  • the reaction temperature adiabatically rises to 55°C.
  • the reaction mixture is heated at 75°C for one hour.
  • the ISOPAR ® deodorized kerosene is removed by filtration and the polymer product of the invention dried in an oven.
  • the polymer is slurried in methanol and 0.58 grams of VORANOL ® 2070 polyol wetting agent of The Dow Chemical Company is added.
  • the methanol is removed by vacuum stripping at 50°C.
  • the wrinkled polymer particles of the invention are characterized in Table II and Figure 3.
  • Example 1 The polymerization of Example 1 is repeated with regard to process and reaction components, except the initiator system is of the prior art.
  • the t-BHP oil phase soluble reducing component of the redox initiator system of the invention is replaced with an aqueous soluble reducing component.
  • 0.86 gram of sodium persulfate is added to the aqueous reaction mixture before the mixture is added to the ISOPAR ® M deodorized kerosene oil phase.
  • the persulfate initiates the polymerization at 45°C and the reaction is allowed to proceed adiabatically at 55°C for 2 hours, followed by an additional one hour heating at 75°C.
  • the product produced by the process of Comparative Example A is substantially spherical in shape and round in cross section, as shown in Figure 5.
  • the vortex rate for the spherical beads is 145 seconds.
  • Example 1 The process of Example 1 is repeated except that 2,5-dihydroperoxy-2,5-dimethylhexane is substituted for t-BHP as the reducing component of the redox initiator system.
  • the wrinkled polymer particles of the invention are characterized in Table III.
  • Example 1 The process of Example 1 is repeated except that cumene hydroperoxide is substituted fort-BHP as the reducing component of the redox initiator system.
  • the wrinkled polymer particles of the invention are characterized in Table IV.
  • Example 10- Preparation of Polymer Particles of the Invention Including Graftable Monomers in the Monomer Mixture (29 Percent Acrylic Acid, in the Aqueous Phase, Neutralized to 85.3
  • the reactor is equipped with a 4-bladed agitator rotating at 250 rpm. Then 0.089 gram of 70 percent t-butyl hydroperoxide is added. The suspension is purged for 30 minutes with nitrogen and then heated to 50°C. At 25°C, the polymerization is initiated by bubbling in a dilute steam of sulfur dioxide in nitrogen. The reaction temperature proceeds adiabatically at 55°C. After the polymerization is complete, the reaction mixture is heated at 75°C for one hour. The ISOPAR ® deodorized kerosene is removed by filtration and the polymer product dried in an oven. When dry, the polymer is, as an optional treatment, slurried in methanol and 0.58 gram of VORANOL ® 2070 polyol wetting agent is added. The methanol is removed by vacuum stripping at 50°C.
  • the product is characterized by a vortex rate of 14 seconds.
  • Example 1 Preparation of Wrinkled Particles of the Invention (31.6 Percent Acrylic Acid in the Aqueous Phase, Neutralized to 80 Percent Sodium Salt)
  • the monomer mix is cooled to 25°C and added to a mixture of 0.6 grams of AEROSIL TM R-972 fumed hydrophobic silica of Degussa, Inc., 0.32 grams of a copolymer of laurylmethacrylate and acrylic acid in a weight ratio of 99:1 as a dispersing agent, and 800 grams of ISOPAR ® M deodorized kerosene of Exxon in a 2 liter reactor.
  • the reactor is equipped with a 4-bladed agitator rotating at 250 rpm.
  • 0.9 grams of 7 percent t-butyl hydroperoxide (t-BHP) is added.
  • the suspension is purged for 30 minutes with nitrogen and then heated to 50°C.
  • the polymerization is initiated by bubbling into the suspension a dilute stream of 0.1 weight percent sulfur dioxide in nitrogen at a flow rate of 750 mL/min.
  • the reaction temperature adiabatically rises to 55°C.
  • the reaction mixture is heated at 75°C for one hour.
  • the ISOPAR ® deodorized kerosene is removed by filtration and the polymer product of the invention is dried in an oven.
  • the polymer is slurried in methanol and 1 weight percent of VORANOL ® 2070 polyol wetting agent of The Dow Chemical Company based on the weight of the dry polymer is added.
  • the methanol is removed by vacuum stripping at 50°C.
  • the polymer produced exhibits a 30 second SCUP of 5.2, a 5 minute SCUP of 7.5, a 60 minute SCUP of 23.4, a centrifuge capacity of 32.3 grams/gram and a vortex rate of 13.5 seconds.
  • Example 12 Preparation of Wrinkled Particles of the Invention (35 Percent Acrylic Acid in the
  • Example 13 Preparation of Polymer Particles of the Invention Including Graftable Monomers in the Monomer Mixture (27 Percent Acrylic Acid, in the Aqueous Phase, Neutralized to 75 Percent Na Salt)
  • VERSENEX ® 80 chelating agent The monomer mix is cooled to 25°C and added to a mixture of 0.6 gram of AEROSIL TM R-972 fumed hydrophobic silica of Degussa, Inc., 0.32 gram of a copolymer of laurylmethacrylate and acrylicacid and 800 grams of ISOPAR ® M deodorized kerosene in a 2 liter reactor.
  • the reactor is equipped with a 4-bladed agitator rotating at 250 rpm. Then 0.39 gram of 7 percent t-butyl hydroperoxide is added. The suspension is purged for 30 minutes with nitrogen and then heated to 50°C.
  • the polymerization is initiated by bubbling in a dilute stream of sulfur dioxide in nitrogen at a rate of 750 mL/min.
  • the reaction temperature proceeds adiabatically to 55°C.
  • the reaction mixture is heated at 75°C for one hour.
  • the ISOPAR ® M deodorized kerosene is removed by filtration and the polymer product dried in an oven.
  • the polymer is, as an optional treatment, slurried in methanol and 1 weight percent VORANOL ® 2070 polyol wetting agent based on the weight of the dry polymer is added.
  • the methanol is removed by vacuum stripping at 50°C.

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Abstract

L'invention a trait à des polymères absorbant les fluides aqueux, à grande aire de surface continue mais plissée, résistants à l'usure et dotés de grosses particules, et de préférence à des polymères d'acide acrylique ou d'acrylate réticulé. Ces éléments absorbants présentent des taux d'absorption dépassant ceux des absorbants sphériques. L'invention porte aussi sur un procédé concernant la préparation de ces polymères qui comporte la polymérisation d'une suspension avec un initiateur au moins partiellement soluble en phase huileuse. L'invention concerne aussi des structures absorbantes contenant de tels polymères et l'utilisation desdits polymères dans de telles structures.
PCT/US1992/007336 1991-03-19 1992-08-28 Particules absorbantes plissees a grande aire de surface efficace et forte vitesse d'absorption WO1993019099A1 (fr)

Priority Applications (1)

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US08/140,182 US5744564A (en) 1991-03-19 1992-08-28 Wrinkled absorbent particles of high effective surface area having fast absorption rate

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US67161691A 1991-03-19 1991-03-19
DE92104434.3 1992-03-14
EP92104434A EP0516925B1 (fr) 1991-03-19 1992-03-14 Particules absorbantes plissées de grande surface effective rapide ayant une vitesse d'absorption

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0675142A1 (fr) * 1994-04-02 1995-10-04 Hoechst Aktiengesellschaft Polymères hydrophiles gonflables à l'eau
US6753051B1 (en) 2002-07-30 2004-06-22 Eastman Kodak Company Ink recording element utilizing wrinkled particles
US7128972B2 (en) 2002-07-30 2006-10-31 Leon Jeffrey W Wrinkled polyester particles
US8013049B2 (en) 2004-01-28 2011-09-06 Dainippon Ink And Chemicals, Inc. Method for producing core-shell type highly liquid absorbent resin particles

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US4340706A (en) * 1980-03-19 1982-07-20 Seitetsu Kagaku Co., Ltd. Alkali metal acrylate or ammonium acrylate polymer excellent in salt solution-absorbency and process for producing same
US4446261A (en) * 1981-03-25 1984-05-01 Kao Soap Co., Ltd. Process for preparation of high water-absorbent polymer beads
US4578068A (en) * 1983-12-20 1986-03-25 The Procter & Gamble Company Absorbent laminate structure
US4666983A (en) * 1982-04-19 1987-05-19 Nippon Shokubai Kagaku Kogyo Co., Ltd. Absorbent article
US4683274A (en) * 1984-10-05 1987-07-28 Seitetsu Kagaku Co., Ltd. Process for producing a water-absorbent resin

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4340706A (en) * 1980-03-19 1982-07-20 Seitetsu Kagaku Co., Ltd. Alkali metal acrylate or ammonium acrylate polymer excellent in salt solution-absorbency and process for producing same
US4446261A (en) * 1981-03-25 1984-05-01 Kao Soap Co., Ltd. Process for preparation of high water-absorbent polymer beads
US4666983A (en) * 1982-04-19 1987-05-19 Nippon Shokubai Kagaku Kogyo Co., Ltd. Absorbent article
US4578068A (en) * 1983-12-20 1986-03-25 The Procter & Gamble Company Absorbent laminate structure
US4683274A (en) * 1984-10-05 1987-07-28 Seitetsu Kagaku Co., Ltd. Process for producing a water-absorbent resin

Cited By (6)

* Cited by examiner, † Cited by third party
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EP0675142A1 (fr) * 1994-04-02 1995-10-04 Hoechst Aktiengesellschaft Polymères hydrophiles gonflables à l'eau
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US8013049B2 (en) 2004-01-28 2011-09-06 Dainippon Ink And Chemicals, Inc. Method for producing core-shell type highly liquid absorbent resin particles

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