Classifications

• • 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
• • 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
  • B01D—SEPARATION
  • B01D15/00—Separating processes involving the treatment of liquids with solid sorbents; Apparatus therefor

Definitions

• the present invention relates to the absorption of water containing ions having a multiple valency. More particularly, the present invention relates to the use of a water-absorbent polymeric composition of the kind known as superabsorbent material to absorb water containing multiple valent ions, particularly divalent ions.
• water when used alone or in phrases such as “water- absorbing”, “water-absorbent” and “water-swellable” is understood to mean not only water but also aqueous media such as, in particular, electrolyte solutions such as body fluids.
• compositions which exhibit the capacity to be water- absorbing.
• Known compositions may be in any suitable form including powders, particles and fibers. Examples of two such water-absorbent compositions are described in US 3,954,721 and 3,983,095, inco ⁇ orated herein by reference, which disclose preparations for derivatives of copolymers of maleic anhydride with at least one vinyl monomer in fibrous form.
• the fibrous copolymers are rendered hydrophillic and water-swellable by reaction with ammonia or an alkali metal hydroxide.
• 3 810 468 which is incorporated herein by reference, discloses lightly cross-linked olefin-maleic anhydride copolymers prepared as substantially linear copolymers and then reacted with a diol or a diamine to introduce cross-linking.
• the resultant lightly cross-linked copolymers are treated with ammonia or an aqueous or alcohol solution of an alkali metal hydroxide.
• US Patent No. 3 980 663 which is inco ⁇ orated herein by reference, describes water-swellable absorbent articles made from carboxylic polyelectrolytes via cross-linking with glycerine diglcidyl ether.
• European Published Application No. 0 268 498 (inco ⁇ orated herein by reference) describes a water-absorbent composition formed by causing a substantially linear polymer of water- soluble ethylenically unsaturated monomer blends comprising carboxylic and hydroxylic monomers to cross-link internally.
• water-absorbent compositions are those produced from copolymers of an ⁇ , ⁇ unsaturated monomer having at least one pendant unit selected from a carboxylic acid group and derivatives thereof and a copolymerisable monomer.
• a proportion of the pendant units are present in the final copolymer as the free acid and a proportion as the salt of the acid.
• These copolymers are capable of being cross-linked, either internally or with a variety of cross-linking agents, to form the water-swellable composition. Examples of water-swellable compositions of this type can be found in US 4,616,063, 4,705,773, 4,731,067, 4,743,244, 4,788,237, 4,813,945, 4,880,868 and 4,892,533 and EP 0272 074, 0 264 208 and 0 436 514. These patents and applications are inco ⁇ orated herein by reference.
• carboxylic acid groups include carboxylic acid salt groups, carboxylic acid amide groups, carboxylic acid imide groups, carboxylic acid anhydride groups, carboxylic acid ester groups and the like.
• water-absorbent compositions can be found in US 4,798,861, W0 93/17066, W0 93/255735, W0 93/24684, W0 93/12275, EP 0 401 044, 0 269 393, 0 326 382, 0 227 305, 0 101 253, 0 213 799, 0 232 121, 0 342 919, 0 233 014, 0 268 498 and 0 397 410, GB 2082614, 2022505, 2270030, 2269602 and 2126591, US 4418163, 3989586, 4332917, 4338417, 4420588 and 4155957 and FR 2525121 which are all inco ⁇ orated herein by reference.
• the water to be absorbed contains a large proportion of multivalent ions.
• multivalent ions include divalent ionic salts such as MgCl 2 , CaCl 2 and SrCl 2 .
• the ability to absorb sea water is particularly important.
• Multivalent ions can also be found in other "waters" which are generally absorbed by these water-absorbent materials. Examples of the waters include, general spillages, bodily fluids and the like.
• a water-absorbent composition to absorb water containing multivalent ions wherein the water-absorbent composition has pendant carboxylic acid groups and wherein two or more such groups react with the ions and the composition does not precipitate.
• the two or more such pendant carboxylic acid groups are preferably located in close proximity.
• the pendant carboxylic acid groups are preferably located on the polymeric backbone in close proximity, most preferably, the carboxylic acid groups are located on adjacent carbons on the backbone of the polymer.
• each of the carboxylic acid groups in the two or more pendant groups react with, and complex, the multivalent ion.
• the resultant composition does not precipitate thereby overcoming the aforementioned problem.
• Particularly suitable copolymers for use in the production of the water-absorbing compositions used in the present invention will contain from about 25 to about 75 mole percent recurring units of at least one ⁇ , ⁇ -unsaturated monomer and from about 75 to about 25 mole percent recurring units of at least one copolymerizable monomer.
• the copolymer preferably contains from about 35 to about 65 mole percent of recurring units of at least one ⁇ , ⁇ -unsaturated monomer and from about 65 to about 35 mole percent of at least one copolymerizable co-monomer.
• the copolymer will be an equimolar copolymer.
• Suitable ⁇ , ⁇ -unsaturated monomers are those bearing at least one pendant carboxylic acid unit or derivative of a carboxylic acid unit.
• Derivatives of carboxylic acid units include carboxylic acid salt groups, carboxylic acid amide groups, carboxylic acid imide groups, carboxylic acid anhydride groups and carboxylic acid ester groups.
• Suitable ⁇ , ⁇ -unsaturated monomers include maleic acid, crotonic acid, fumaric acid, mesaconic acid, the sodium salt of maleic acid, the sodium salt of 2-methyl, 2-butene dicarboxylic acid, the sodium salt of itatonic acid, maleamic acid, maleamide, N-phenyl maleimide, maleimide, maleic anhydride, fumaric anhydride; itaconic anhydride, citraconic anhydride; mesaconic anhydride, methyl itaconic anhydride, ethyl maleic anhydride, diethylmaleate, methylmaleate; and the like, and their mixtures.
• Monomers having two carboxylic acid groups attached to adjacent carbon atoms are particularly preferred.
• Any suitable copolymerizable co-monomer can be employed.
• suitable copolymerizable co-monomers include ethylene, propylene, isobutylene, to C 4 alkyl methacrylates, vinyl acetate, methyl vinyl ether, isobutyl vinyl ether, and styrenic compounds having the formula:
• R represents hydrogen or an alkyl group having from 1 to 6 carbon atoms, and wherein the benzene ring may be substituted with low molecular weight alkyl or hydroxyl groups.
• Suitable C, to C 4 alkyl acrylates include, for example, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-propyl acrylate, n-butyl acrylate, and the like, and their mixtures.
• Suitable C- to C 4 alkyl methacrylates include, for example, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-propylmethacrylate, n-butyl methacrylate, and the like, and their mixtures.
• Suitable styrenic compounds include, for example, styrene, ⁇ -methylstyrene, p-methylstyrene, t-butystyrene, and the like, and their mixtures.
• the pendant units on the ⁇ , ⁇ -unsaturated monomer will determine what, if any, additional reactions must be carried out to obtain a copolymer having the requisite pendant units necessary to produce the water-absorbing compositions of this invention.
• these water-absorbing compositions will contain from about 20 to about 80 percent pendant carboxylic acid units and from about 80 to about 20 percent pendant carboxylate salt units.
• both units are present in an amount of from about 30 to about 70 percent.
• the ⁇ , ⁇ -unsaturated monomer bears only carboxylic acid amide, carboxylic acid imide, carboxylic acid anhydride, carboxylic acid ester groups or mixtures thereof, it will be necessary to convert at least a portion of such carboxylic acid derivative groups to carboxylic acid groups by, for example, a hydrolysis reaction. If the ⁇ , ⁇ -unsaturated monomer bears only carboxylic acid salt groups, acidification to form carboxylic acid groups will be necessary using methods and materials well known in the art.
• the final copolymer should contain from about 80 to 20 percent pendant carboxylate salt units. Accordingly, it may be necessary to carry out a neutralization reaction. Neutralization of carboxylic acid groups with a strong organic or inorganic base such as NaOH, KOH, ammonia, ammonia-i ⁇ -water solution, or organic amines will result in the formation of carboxylate salt units, preferably carboxylate metal salt units.
• a strong organic or inorganic base such as NaOH, KOH, ammonia, ammonia-i ⁇ -water solution, or organic amines
• One copolymer particularly suitable for use in the present invention is a copolymer of maleic anhydride and isobutylene. Another is maleic anhydride and styrene. Suitable copolymers will have peak average molecular weights of from about 6,000 to about 500,000 or more.
• Suitable copolymers of maleic anhydride and isobutylene can be prepared using any suitable conventional method. Such copolymers are also commercially available from Kurary Isoprene Chemical Company, Ltd., Tokyo, Japan under the trademark ISOBAM. ISOBAM copolymers are available in several grades which are differentiated by average viscosity molecular weight: ISOBAM-10, 160,000 to 170,000; ISOBAM-06, 80,000 to 90,000; ISOBAM-04, 55,000 to 65,000 and ISOBAM-600, 6,000 to 10,000.
• the copolymer is then preferably cross-linked either internally via covalent or hydrogen bonding or using an external cross-linking agent.
• Suitable cross-linking agents include: monomers containing at least two hydroxyl groups such as alkylene glycols containing 2-10 carbon atoms and their ethers, cycloalkylene glycols, Bisphenol A, hydroxy alkylene derivatives of Bisphenol A, hydroquinone, phloroglucinol, hydroxy alkylene derivatives of diphenols, glycerols, erythritol, pentaerythritol, and mono-, di- or oligosaccharides; heterocyclic carbonates; and monomers containing at least one amine group and at least one hydroxyl group such as ethanolamine, tris (hydroxymethyl) aminomethane, 3-amino-l- propanol, DL-l-amino-2-propanol, 2-amino-l-butanol, N,N-di
• cross-linking will not occur and the product will not become absorbent until the partially neutralized polymer reaction product is heated to a temperature sufficient to effect reaction between the cross-linking agent and the copolymer.
• the cure conditions required to achieve optimal cross-linking depends upon several factors, including the particular polymer employed.
• the cure temperature will depend on the polymer. If the polymer is a partially neutralized ethylene/maleic anhydride copolymer, a cure temperature of at least 140°C will be required to achieve cross-linking. If the polymer is partially neutralized styrene/maleic anhydride copolymer, a temperature of at least about 150°C is required to cross-link; and if a partially neutralized isobutylene/maleic anhydride copolymer is employed, a temperature of at least about 170°C will be required to achieve cross-linking. Cure times can vary depending on cure temperatures and on the amount of reactive compound used.
• Cure times will typically be within the range of from about 0.5 to about 20 minutes, preferably 0.5 to 15 minutes, and most preferably 0.5 to 12 minutes.
• optimal cure of the composition ie. minimal amount of cross-linking needed to form a cross-linked network
• Optimal cure is achieved by adjusting a number of variables within wide ranges depending upon the specific syrup composition.
• Optimal cure conditions require, among other things, a balance between cure time and cure temperature.
• the aqueous reaction product of the partially neutralized polymer and the reactive compound ie. the grafted polymer syrup
• the aqueous reaction product of the partially neutralized polymer and the reactive compound ie. the grafted polymer syrup
• the syrup can be further processed by casting, spray drying, air-assisted spray drying, air attenuation, wet spinning, dry spinning, flash spinning, and the like.
• minor amounts of other polar solvents such as alcohol can be added to the aqueous syrups.
• the resultant fibers can be further processed into milled fibers, chopped fibers, fluff or bulk fibers, strands, yarns, webs, composites, woven fabrics, non-woven fabrics, non-woven mats, tapes, scrim, and the like, using a variety of methods including twisting, beaming, slashing, wa ⁇ ing, quilling, severing, crimping, texturizing, weaving, knitting, braiding, etc., and the like.
• the water-absorbent compositions may be formed into a composite web comprising non- water absorbent fibers and water-absorbent fibers.
• the fibers of these webs may be bonded using any suitable technique.
• Suitable non-water-absorbent fibers include rayon fiber, cellulose ester fiber, protein fiber, polyamide fiber, polyester fiber, polyvinyl fiber, polyolefin fiber, polyurethane fiber, aramid fiber, glass fibers and mixtures thereof.
• the composite webs may be used in articles of manufacture such as disposable diapers, sanitary napkins, tampons, pant liners, adult incontinence pads, coverstock for feminine hygiene products, surgical and dental sponges, bandages, patient unde ⁇ ads (for example pairs of the type described in US5814101, US4342314 and EP0052403 when are inco ⁇ orated herein by reference), wipes, domestic wipes, industrial wipes, packaging, filters, medical tray pads, fenestration drapes, operating gowns; mortuary pads, other medical related devices, casket liners, forensic examination pads, cable wrap, food tray pads, food preservation articles, seed germination pads, capillary mats, baby bibs, desiccant strips for anti-rust use, bath mats, sorbents, breast pads, underarm pads, wound covers, pet litter, roofing materials, automotive trim, furniture, bedding, clothing, soil modifiers, spill control materials; waste management materials and protective articles.
• articles of manufacture such as disposable diapers, sanitary napkins,
• Water containing divalent ions include sea water, menses and urine.
• the composition of synthetic sea water - which is believed to correspond to a typical sea water - is set out in Table 1.
• sea water contains a substantial amount of divalent ions. Therefore using the compositions of the present invention as cable wrap for undersea applications is particularly suitable to protect the cable from the effect of the sea water.
• composition of synthetic adult urine - which is believed to correspond to typical adult urine - is set out in Table 2.
• compositions of the present invention are particularly useful in, for example, adult incontinence pads.
• the triplicate sample containing tea bags are then placed in a test solution, with stirring, for 10 minutes. Each tea bag is then removed from the test solution, allowed to drain for 10 seconds and then dabbed lightly with filter paper to remove excess test solution. Each sample containing tea bag is then weighed and recorded as "W-”. Each sample containing tea bag is then placed in a Buchner porcelain funnel, a small amount of test solution is poured over the same to re-saturate it, and then the sample containing tea bag is exposed to a vacuum of 0.5 psi for 5 minutes. The sample is removed and weighed and the weight is recorded as "W 4 ".
• the Free Swell Liquid Retention (FS) is determined using the formula:
• RT 0.5 psi Liquid Retention
• W- final free swell weight in grams of gel plus wet tea bag
• W 2 average weight in grams of 10 empty, wet tea bags
• W 3 original weight in grams dry staple fiber
• W 4 final 0.5 psi weight in grams of gel plus wet tea bag.

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Analytical Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Materials Engineering (AREA)
• Dispersion Chemistry (AREA)
• Hematology (AREA)
• Engineering & Computer Science (AREA)
• Organic Chemistry (AREA)
• Epidemiology (AREA)
• Life Sciences & Earth Sciences (AREA)
• Animal Behavior & Ethology (AREA)
• General Health & Medical Sciences (AREA)
• Public Health (AREA)
• Veterinary Medicine (AREA)
• Absorbent Articles And Supports Therefor (AREA)
• Solid-Sorbent Or Filter-Aiding Compositions (AREA)

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Cited By (19)

Citations (4)

• 1996
  • 1996-10-21 EP EP96934765A patent/EP0862488A1/de not_active Withdrawn
  • 1996-10-21 WO PCT/EP1996/004557 patent/WO1997015367A1/en not_active Application Discontinuation
  • 1996-10-21 AU AU72963/96A patent/AU7296396A/en not_active Abandoned
  • 1996-10-21 CA CA 2242642 patent/CA2242642A1/en not_active Abandoned

Patent Citations (4)

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