Classifications

• • 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
• • 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
  • A61L15/22—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons containing macromolecular materials
  • A61L15/32—Proteins, polypeptides; Degradation products or derivatives thereof, e.g. albumin, collagen, fibrin, gelatin
• • 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
  • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
  • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
  • C08F220/04—Acids; Metal salts or ammonium salts thereof
  • C08F220/06—Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
• • 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
  • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
  • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
  • C08F220/52—Amides or imides
  • C08F220/54—Amides, e.g. N,N-dimethylacrylamide or N-isopropylacrylamide
  • C08F220/56—Acrylamide; Methacrylamide
• • 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
  • C08F222/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a carboxyl radical and containing at least one other carboxyl radical in the molecule; Salts, anhydrides, esters, amides, imides, or nitriles thereof
  • C08F222/10—Esters
  • C08F222/1006—Esters of polyhydric alcohols or polyhydric phenols
  • C08F222/102—Esters of polyhydric alcohols or polyhydric phenols of dialcohols, e.g. ethylene glycol di(meth)acrylate or 1,4-butanediol dimethacrylate
• • 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
  • C08F222/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a carboxyl radical and containing at least one other carboxyl radical in the molecule; Salts, anhydrides, esters, amides, imides, or nitriles thereof
  • C08F222/10—Esters
  • C08F222/1006—Esters of polyhydric alcohols or polyhydric phenols
  • C08F222/103—Esters of polyhydric alcohols or polyhydric phenols of trialcohols, e.g. trimethylolpropane tri(meth)acrylate

Definitions

• the present invention pertains to the field of absorbent and superabsorbent hydrogels and, more specifically, to hydrogels derived from soy protein isolate.
• Absorbent and superabsorbent hydrogels are typically obtained from vegetable or animal proteins, mixtures of vegetable and animal proteins, cellulose, hemicellulose, saccharides (typically C5 and C6 sugars present in plant derived proteins), and polysaccharides.
• hydrogels are utilized in industrial dewatering applications; maintaining moisture retention in soils, especially in regions experiencing low rainfall; remediation of heavy metal contaminated soil, based on complexation of heavy metal cations with polycarboxylic acids; in control of wildfires, based on application of water-saturated hydrogels; and in diaper and other water/urine absorbing applications.
• hydrogels The combined market for hydrogels is over one billion pounds per year in the U.S. and about 2.5 times that globally, with a growth rate in both markets of approximately 3% per year.
• Petroleum-based feedstocks for hydrogels include polyvinyl alcohol, polyacrylic acid, polyacrylamide and maleic anhydride/butylene copolymers.
• Existing hydrogels are characterized by incorporation of a relatively high percentage of water solubilizing groups such as carboxylic acid, amide and alcohol groups.
• High performance hydrogels are further characterized by appropriate levels of cross-linking as illustrated in polysuccinimide cross-linked with polyaspartic acid and cross-linked copolymers of maleic anhydride and maleimide.
• soluble soy protein from soy protein isolate has been converted to high performance hydrogels by using ethylenediaminetetraacetic dianhydride (EDTAD) as the key reagent to provide protein cross-linking and introduce pendant carboxylic acid groups by reaction with lysine amine groups.
• EDTAD ethylenediaminetetraacetic dianhydride
• this work has economic disadvantages in that EDTAD is priced at $1139/50 g (equivalent to $1262/pound) in the 2007-2008 Aldrich catalog.
• EDTAD is not available at bulk scale.
• the present invention is directed to forming absorbent hydrogels from soy protein isolate. More specifically, in accordance with the invention, an absorbing hydrogel is formed by initially contacting soy protein isolate with urea at elevated temperature for about 0.5 hours to produce solubilized soy protein isolate. The solubilized soy protein isolate is then mixed with 2-mercaptoethanol, wherein the 2-mercaptoethanol is preferably in an amount of about 25% by weight of the soy protein isolate. The first mixture is then heated at a temperature of about 80° C. for approximately 1 hour.
• a polymerizable monomer in an amount of about 200% by weight of soy protein isolate and a radical initiator, preferably, ammonium persulfate, in an amount of about 20% by weight of soy protein isolate are combined with the first mixture to form a second mixture.
• the hydrogel is removed from the second mixture.
• the as-formed hydrogel may be subjected to a washing process utilizing either water or an organic solvent, an initial water wash followed by washing with organic solvent, or using a mixture of water and organic solvent in order to extract non-reactant components from the gel, before subjecting the gel to a final drying process.
• the resultant dried absorbent and superabsorbent hydrogels have high water uptake ratios, and can be utilized for a variety of applications.
• the present invention is generally directed to the formation of absorbent and superabsorbent hydrogels utilizing a soy protein isolate base.
• absorbent hydrogel is meant be inclusive of all hydrogels herein, while the term superabsorbent hydrogel is an absorbent hydrogel (typically a polymer) that can absorb about 100 times or more its weight in water and does not easily release this liquid under pressure.
• a solubilized protein isolate is combined at elevated temperatures with a disulfide cleavage reagent, a polymerizable monomer and a radical initiator, preferably ammonium persulfate (APS), to produce an absorbent hydrogel. More specifically, soy protein isolate and urea are heated at a temperature of approximately 80° C. for approximately 0.5 hours to produce a solubilized soy protein isolate. The solubilized soy protein isolate is then combined with a disulfide cleavage reagent of 2-mercaptoethanol in an amount of about 25% by weight of the soy protein isolate and heated at a temperature of about 80° C. for approximately 1 hour to produce a first mixture.
• APS ammonium persulfate
• the first mixture is combined with a polymerizable monomer of methacrylic acid in an amount of about 200% by weight of the soy protein isolate, and APS in an amount of about 20% by weight of the soy protein isolate to form a second mixture.
• an acrylate cross-linking agent is also utilized in an amount of about 20% by weight of soy protein isolate.
• Acceptable acrylate cross-linking agents include difunctional polyethylene glycol diacrylate (PEGDA) and trimethylolpropane triacrylate.
• PEGDA polyethylene glycol diacrylate
• This second mixture is degassed and then heated at a temperature of about 80° C. for approximately 1.0 hour, and a hydrogel is extracted from the mixture.
• additives may be included in the formation of the hydrogel.
• clays such as sepiolite, bentonite and/or hydrotalcite, may be utilized to vary the quantity and rate of water uptake.
• mold inhibitors may be incorporated into the hydrogel compositions.
• the hydrogel is extracted by pouring the second mixture into a liquid in which the hydrogel is not readily soluble, such as acetone.
• the hydrogel is extracted by adjusting the pH to precipitate the hydrogel, and the hydrogel is filtered out of the mixture and extracted with methanol using a Soxhlet extractor.
• the as-formed hydrogel may be subjected to a washing process utilizing either water or an organic solvent, an initial water wash followed by washing with organic solvent, or using a mixture of water and organic solvent in order to extract non-reactant components from the gel, before subjecting the gel to a final drying process.
• the resultant dried absorbent and superabsorbent hydrogels have high water uptake ratios, and can be utilized for a variety of applications.
• the above-described methods of the present invention can be utilized to produce a superabsorbent hydrogel. While not intending to limit the present invention, the invention can be readily understood by the example set forth below.
• the soy protein isolate utilized in the examples discussed below was Pro-Cote 200 obtained from DuPont Soy Polymers, St. Louis, Mo. All acrylic monomers and cross-linking agents were supplied with phenolic radical inhibitors so all were pre-treated by passing through columns of Aldrich Inhibitor Remover (No. 311332) and then stored at freezer temperatures until use. However, it was found that removal of inhibitor was not necessary if the reactive solution was degassed to remove oxygen which is a strong free radical inhibitor. The oxygen can also be removed at the beginning of the process or at initial steps by bringing the liquids to a boil, or degassing by bubbling an inert gas through the liquid typically with heating.
• the inert gas can be nitrogen, argon or the like.
• Soy protein isolate was prepared by solubilization of soy protein from soy meal at high pH, removing insoluble material, and then precipitating dissolved soy protein at its isoelectric point (pH ⁇ 4.5) or by precipitation from solvents such as acetone in connection with grafting of methacrylic acid to the soy protein isolate.
• FTIR Fourier Transform Infrared.
• This method involved construction of a calibration curve by preparing a series of analytical standards of soy protein isolate containing variable amounts of polyacrylic acid, finely grinding these mixtures, and measuring the ratio of infra-red (IR) absorbencies of carboxylic acid plus carboxylate ion (formed by zwitterion formation with basic amino acids such as lysine) to the soy protein isolate Amide 1 band in these mixtures.
• IR infra-red
• Soy protein isolate was typically immersed in 8M urea at 80° C. for 0.5 hours to help solubilize protein components and this mixture was then mixed with 2-mercaptoethanol (25% of soy protein isolate) and held at 80° C. for 1.0 hour to cause cleavage of protein disulfide bridges to thiol groups.
• methacrylic acid (MAA) (200% of soy protein isolate
• optionally an acrylate cross-linker (20% of soy protein isolate)
• APS 20% of soy protein isolate
• the cross-linkers employed were PEGDA or trimethylolpropane triacrylate. These mixtures were then either poured into acetone or adjusted to pH 4.5 to cause appreciable precipitation before being filtered and dried under vacuum. These materials were then extracted with methanol with a Soxhlet extractor to remove methacrylic acid homopolymer.
• Typical Grafting Percentages (GP) obtained were in the 60%-70% range and were calculated using the relationship:
• GP 100 ⁇ (weight product ⁇ weight soy protein isolate)/weight soy protein isolate ⁇ .
• the as-prepared hydrogel is preferably washed or subjected to an extraction process in order to improve the performance of the gel. More specifically, the as-prepared hydrogel may be washed multiple times with water, or may be washed with an organic solvent, such alcohols, ketones and ethers, although methanol is preferred. Organic solvent washing/extraction can be efficiently performed in a Soxhlet extractor. This additional washing/extraction process removes unreacted monomers and low molecular weight products, resulting in a final hydrogel or superabsorbent hydrogel product having faster and more efficient water uptake values compared to as-prepared hydrogels or once-swelled gels.
• an organic solvent such alcohols, ketones and ethers, although methanol is preferred.
• Organic solvent washing/extraction can be efficiently performed in a Soxhlet extractor. This additional washing/extraction process removes unreacted monomers and low molecular weight products, resulting in a final hydrogel or superabsorbent hydrogel product having faster and more efficient

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• Dispersion Chemistry (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
• Materials For Medical Uses (AREA)
• Solid-Sorbent Or Filter-Aiding Compositions (AREA)
• Medicinal Preparation (AREA)

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• 2009
  • 2009-02-23 EP EP09713454A patent/EP2249877B1/de not_active Not-in-force
  • 2009-02-23 US US12/918,929 patent/US8148501B2/en not_active Expired - Fee Related
  • 2009-02-23 WO PCT/US2009/034873 patent/WO2009105753A1/en active Application Filing
  • 2009-02-23 BR BRPI0905986-5A patent/BRPI0905986A2/pt not_active Application Discontinuation
  • 2009-02-23 US US12/390,923 patent/US20090215619A1/en not_active Abandoned

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