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
  • A61L15/28—Polysaccharides or their derivatives
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
  • C08B11/00—Preparation of cellulose ethers
  • C08B11/02—Alkyl or cycloalkyl ethers
  • C08B11/04—Alkyl or cycloalkyl ethers with substituted hydrocarbon radicals
  • C08B11/08—Alkyl or cycloalkyl ethers with substituted hydrocarbon radicals with hydroxylated hydrocarbon radicals; Esters, ethers, or acetals thereof
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
  • C08B11/00—Preparation of cellulose ethers
  • C08B11/02—Alkyl or cycloalkyl ethers
  • C08B11/04—Alkyl or cycloalkyl ethers with substituted hydrocarbon radicals
  • C08B11/10—Alkyl or cycloalkyl ethers with substituted hydrocarbon radicals substituted with acid radicals
  • C08B11/12—Alkyl or cycloalkyl ethers with substituted hydrocarbon radicals substituted with acid radicals substituted with carboxylic radicals, e.g. carboxymethylcellulose [CMC]
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
  • C08B11/00—Preparation of cellulose ethers
  • C08B11/20—Post-etherification treatments of chemical or physical type, e.g. mixed etherification in two steps, including purification
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
  • C08B15/00—Preparation of other cellulose derivatives or modified cellulose, e.g. complexes
  • C08B15/005—Crosslinking of cellulose derivatives
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
  • C08B37/00—Preparation of polysaccharides not provided for in groups C08B1/00 - C08B35/00; Derivatives thereof
  • C08B37/006—Heteroglycans, i.e. polysaccharides having more than one sugar residue in the main chain in either alternating or less regular sequence; Gellans; Succinoglycans; Arabinogalactans; Tragacanth or gum tragacanth or traganth from Astragalus; Gum Karaya from Sterculia urens; Gum Ghatti from Anogeissus latifolia; Derivatives thereof
  • C08B37/0087—Glucomannans or galactomannans; Tara or tara gum, i.e. D-mannose and D-galactose units, e.g. from Cesalpinia spinosa; Tamarind gum, i.e. D-galactose, D-glucose and D-xylose units, e.g. from Tamarindus indica; Gum Arabic, i.e. L-arabinose, L-rhamnose, D-galactose and D-glucuronic acid units, e.g. from Acacia Senegal or Acacia Seyal; Derivatives thereof
  • C08B37/0096—Guar, guar gum, guar flour, guaran, i.e. (beta-1,4) linked D-mannose units in the main chain branched with D-galactose units in (alpha-1,6), e.g. from Cyamopsis Tetragonolobus; Derivatives thereof
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J3/00—Processes of treating or compounding macromolecular substances
  • C08J3/02—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques
  • C08J3/03—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques in aqueous media
  • C08J3/075—Macromolecular gels
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J3/00—Processes of treating or compounding macromolecular substances
  • C08J3/24—Crosslinking, e.g. vulcanising, of macromolecules
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L1/00—Compositions of cellulose, modified cellulose or cellulose derivatives
  • C08L1/08—Cellulose derivatives
  • C08L1/26—Cellulose ethers
  • C08L1/28—Alkyl ethers
  • C08L1/284—Alkyl ethers with hydroxylated hydrocarbon radicals
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L1/00—Compositions of cellulose, modified cellulose or cellulose derivatives
  • C08L1/08—Cellulose derivatives
  • C08L1/26—Cellulose ethers
  • C08L1/28—Alkyl ethers
  • C08L1/286—Alkyl ethers substituted with acid radicals, e.g. carboxymethyl cellulose [CMC]
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2301/00—Characterised by the use of cellulose, modified cellulose or cellulose derivatives
  • C08J2301/08—Cellulose derivatives
  • C08J2301/32—Cellulose ether-esters
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2401/00—Characterised by the use of cellulose, modified cellulose or cellulose derivatives
  • C08J2401/08—Cellulose derivatives
  • C08J2401/26—Cellulose ethers
  • C08J2401/28—Alkyl ethers

Definitions

• the invention relates to a method for manufacturing of a highly absorbent, polysaccharide-based absorption material, wherein a water containing solution comprising a starting material in the form of a crosslinkable polysaccharide- based polymer is subjected to crosslinking in order to produce a water-swelled gel.
• Superabsorbent materials are polymers which are capable of absorbing liquid in amounts corresponding to several times the weight of the polymer and which upon absorption form an aqueous gel.
• the main advantage of using superabsorbent materials in absorbent articles is that the volume of the absorbent articles can be considerably reduced in comparison to the volume of absorbent articles mainly formed from absorbent fibrous materials such as fluffed cellulose pulp, or the like.
• Another advantage is that superabsorbents, when compared to fibrous absorbents such as, for instance, fluffed cellulose pulp, have a higher capability of retaining liquid under pressure.
• Such a property is, for instance, advantageous when the absorption material is used in diapers, incontinence guards or sanitary napkins, since absorbed body fluid is retained in the absorbent article and is not squeezed out of the article, for instance when the user is sitting down.
• WO 95/31500 a method for producing absorbent, preferably superabsorbent, foam materials by phase separation and crosslinking of a polymer solution is described.
• the absorbent materials obtained exist in the form of a crosslinked open-celled polymer foam, which implies that fluid may pass between cells.
• Preferred polymers for producing the absorbent materials which are disclosed in WO 95/31500 are hydroxyethyl cellulose (HEC) and hydroxypropyl cellulose (HPC), which are preferably crosslinked with divinyl sulphone (DVS).
• the known absorbent foam materials are relatively expensive to produce and are primarily intended for medical applications, such as controlled release systems or as artificial skin and blood vessels. However, a further possible use for the described foam materials is said to be in reusable diapers or the like. The high production cost does, however, mean that the known foam materials would, in practice, not be contemplated as absorption material for absorbent articles intended for single use only.
• the present invention provides a process for the production of superabsorbent materials of the kind mentioned in the introduction and which exhibit improved absorbency as compared to previously known superabsorbent materials of the same type.
• the process according to the invention is primarily distinguished in that the at least partially crosslinked, liquid-swollen gel is soaked in a water-miscible organic solvent so that water is partially removed from the gel prior to desiccation of the gel.
• the liquid- swollen gel is soaked in excess methanol.
• the invention further provides a highly absorbent polysaccharide-based absorption material which has been produced by soaking an at least partially cross-linked liquid-swollen gel in a water-miscible organic solvent, preferably methanol, prior to desiccation of the gel.
• a water-miscible organic solvent preferably methanol
• the solution containing the starting material is preferably an aqueous solution.
• a superabsorbent material can be obtained exhibiting superior absorbency when compared to a material of the same composition but which has been produced by conventional methods.
• the improved absorbency is evident both in a higher absorption capacity and in a greater ability to retain absorbed liquid even when the absorption material is placed under load.
• the absorbency of a superabsorbent material which has been soaked in methanol prior to drying of the gel is considerably higher than that of a corresponding superabsorbent material where no methanol soaking step has been performed, regardless of whether the absorbed liquid is water or a salt-containing solution such as urine.
• the starting material may comprise a polymer blend comprising an electrically charged polysaccharide-based polymer and an electrically uncharged polysaccharide-based polymer.
• the ratio between the charged polymer and the uncharged polymer is preferably between about 2:1 and about 4:1 and most preferably about 3:1.
• CMC carboxymethyl cellulose
• CMC hydroxyethyl cellulose
• Suitable charged polysaccharides are carboxymethyl starch, oxidized starch and oxidized cellulose.
• Suitable uncharged polysaccharides include, but are not limited to: ethylhydroxyethyl cellulose (EHEC), hydroxypropyl cellulose (HPC), guar gum and hydroxypropyl starch (HPS).
• the polymer solution is preferably crosslinked with a crosslinking agent producing covalent crosslinks.
• crosslinking agents of this kind are divinylsulphone (DVS), acetaldehyde, formaldehyde, glutaraldehyde, diglycidyl ether, diisocyanates, dimethyl urea, epichlorohydrin, oxalic acid, phosphoryl chloride, trimetaphosphate, trimethylomelamine and polyacrolein.
• VPS divinylsulphone
• acetaldehyde formaldehyde
• glutaraldehyde diglycidyl ether
• diisocyanates dimethyl urea
• epichlorohydrin oxalic acid
• phosphoryl chloride trimetaphosphate
• trimethylomelamine trimethylomelamine
• polyacrolein polyacrolein.
• ionic crosslinking or physical crosslinking such as hydrophobic/hydrophilic interactions, or the
• a superabsorbent material of the above-described kind may be readily combined with fibres and can accordingly be mixed with absorbent fibres such as fluffed cellulose pulp, rayon, peat moss, cotton, hemp, flax, nylon, or the like, using any conventional method.
• the highly absorbent material may be mixed with non-absorbent fibres such as polyethylene, polypropylene, polyester, bicomponent fibres, or the like.
• non-absorbent fibres such as polyethylene, polypropylene, polyester, bicomponent fibres, or the like.
• the fibrous structure may be bonded, for instance by fusing of thermoplastic fibres comprised in the fibrous structure, or by adding a special binding agent.
• the fibrous structure may have been subjected to further processing, such as compression, needling, softening, or the like.
• the highly absorbent material may, of course, alternatively be placed in a layer in an absorbent body comprising further layers of fibres, nonwoven sheets, tissue paper, or the like.
• the highly absorbent material may be a self- sustaining layer, or may be applied onto or within a substrate.
• Some examples of materials which may serve as substrates are tissue sheets, foam materials, nonwoven sheets, fibrous webs, structures having pockets or recesses in which the highly absorbent material is arranged, or the like.
• the gel was dried to produce a highly absorbent material for use in absorbent structures.
• desiccation methods exist. The simplest method is air drying at atmospheric pressure which simply means that the swollen hydrogel is left at room conditions (25°C and 50% relative humidity) until completely dry.
• the gel may be dried using vacuum or by extraction with a solvent, for example acetone.
• Fig. 1 shows the free swelling capacity and liquid retention for gels which have been treated with different solvents
• Fig. 2 shows free swelling capacity and liquid retention for air-dried gels produced from mixtures having different CMC: HEC ratios;
• Fig. 3 shows free swelling capacity and liquid retention for air-dried gels produced from guar gum and which have been treated with different solvents
• DVS crosslinking agent
• DVS is well suited for the production of crosslinked materials for use in comparative work.
• the invention shall not in any way be regarded as being restricted to the use of DVS as crosslinking agent. Accordingly, and as mentioned above, any suitable crosslinking agent or crosslinking method may be used.
• the crosslinking reaction was performed in an alkaline aqueous solution with 1.0 M potassium hydroxide (KOH) at 20°C.
• CMCNa and HEC were dissolved in distilled water containing the desired amount of DVS. After mixing, the sample was left for 12-24 hours in order to obtain proper dissolution of the polymers. Potassium hydroxide was added, thereby starting the crosslinking reaction. All reactions were performed with a reaction solution having an overall polymer concentration equal to 2% by weight.
• the crosslinked hydrogel was broken into smaller pieces, by manually cutting the gel or by using an electric whisk, and was subsequently soaked in excess alcohol in order to reach an equilibrium.
• the solution surrounding the hydrogel was exchanged at least three times. Each time, an amount of alcohol corresponding to at least 5 times the weight of the hydrogel measured immediately after the crosslinking reaction was used. The soaking procedure was terminated after 36-48 hours. Subsequently, the swelled hydrogel was removed from the solution and desiccated. After desiccation, the dried gels were ground using a laboratory mill. All subsequent measurements were performed on desiccated gel which had been treated in this manner.
• the test liquid which was used in the following test methods was synthetic urine, SUR.
• the composition of the SUR was 60 mmol/1 KC1, 130 mmol/1 NaCl, 3.5 mmol/1 MgS0 4 , 2.0 mmol/1 CaS0 4 »2H 2 0, 300 mmol/1 urea, 1 g/1 of a 0.1% solution of Triton X-100 which is a surfactant sold by Aldrich.
• Free swelling was determined by immersing a piece of dried gel in test liquid and allowing the gel to absorb liquid until saturated. The gel was subsequently removed from the liquid and weighed.
• the liquid retention after centrifugation for 10 minutes at 1500 rpm was determined by weighing the gel before and after centrifugation.
• the liquid uptake capacity for fibrous structures containing superabsorbent material was determined by letting test bodies made from fluffed cellulose pulp having 20% by weight of a crosslinked, dried, and ground gel absorb liquid according to a principle commonly known as "demand wettability" . The measurements were made with a GATS-like apparatus. The test bodies were allowed to absorb liquid from a communicating vessel. The amount of liquid in the vessel was continuously measured using scales. The test continued for 2 hours, whereafter the amount of liquid which had been absorbed by the test body was recorded. By knowing the water uptake capacity of the fluffed cellulose pulp, the amount of liquid absorbed by the crosslinked gel could subsequently be calculated.
• Liquid uptake was measured after free swelling for 60 minutes and 120 minutes. Liquid retention after centrifugation was also determined. As can be seen in Fig. 1, soaking in methanol produced a gel having excellent absorption characteristics.
• the free swelling capacity was determined for desiccated gels comprising a mixture of HEC and CMC.
• the crosslinked gels were soaked in excess methanol, broken up into smaller pieces and air dried.
• the free swelling capacity was determined after 60 minutes and after 120 minutes soaking in synthetic urine. Liquid retention after centrifugation was also measured.
• the samples were air dried after the solvent soaking step.
• Liquid uptake was measured after free swelling for 60 minutes and 120 minutes. Liquid retention after centrifugation was also determined. The results are shown in Fig. 3. As for the CMC/HEC samples in Example 2, soaking in methanol produced a gel having considerably improved absorption characteristics.
• the absorption capacity under compressive load was determined according to the liquid uptake capacity method for samples of a highly absorbent material produced in accordance with the invention.
• the absorption capacity was also measured for Sanwet IM7100 which is a commercially available polyacrylate-based absorption material produced by Clariant AG in Frankfurt, Germany and, further, for one type of CMC.
• Samples A and B methanol treated CMC/HEC (3:1) samples * the preparation of superabsorbent based on crosslinked CMC is described, for instance, in EP-A-0 201 895

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Organic Chemistry (AREA)
• Polymers & Plastics (AREA)
• Medicinal Chemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Biochemistry (AREA)
• Dispersion Chemistry (AREA)
• General Health & Medical Sciences (AREA)
• Veterinary Medicine (AREA)
• Hematology (AREA)
• Epidemiology (AREA)
• Animal Behavior & Ethology (AREA)
• Public Health (AREA)
• Emergency Medicine (AREA)
• Molecular Biology (AREA)
• Solid-Sorbent Or Filter-Aiding Compositions (AREA)
• Absorbent Articles And Supports Therefor (AREA)
• Processes Of Treating Macromolecular Substances (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Orthopedics, Nursing, And Contraception (AREA)
• Materials For Medical Uses (AREA)

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• 1998
  • 1998-10-09 SE SE9803448A patent/SE517075C2/sv not_active IP Right Cessation
• 1999
  • 1999-10-07 JP JP2000575553A patent/JP4558939B2/ja not_active Expired - Lifetime
  • 1999-10-07 WO PCT/SE1999/001793 patent/WO2000021581A1/en not_active Ceased
  • 1999-10-07 DE DE69908391T patent/DE69908391T2/de not_active Expired - Lifetime
  • 1999-10-07 PL PL364940A patent/PL194949B1/pl unknown
  • 1999-10-07 SK SK461-2001A patent/SK4612001A3/sk unknown
  • 1999-10-07 AT AT99956437T patent/ATE241393T1/de not_active IP Right Cessation
  • 1999-10-07 TN TNTNSN99187A patent/TNSN99187A1/fr unknown
  • 1999-10-07 AU AU13049/00A patent/AU1304900A/en not_active Abandoned
  • 1999-10-07 EP EP99956437A patent/EP1119378B1/en not_active Expired - Lifetime
  • 1999-10-07 DK DK99956437T patent/DK1119378T3/da active

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