CA2204889A1 - Anionic polymer - Google Patents
Anionic polymerInfo
- Publication number
- CA2204889A1 CA2204889A1 CA002204889A CA2204889A CA2204889A1 CA 2204889 A1 CA2204889 A1 CA 2204889A1 CA 002204889 A CA002204889 A CA 002204889A CA 2204889 A CA2204889 A CA 2204889A CA 2204889 A1 CA2204889 A1 CA 2204889A1
- Authority
- CA
- Canada
- Prior art keywords
- polysaccharide
- cross
- cellulose
- process according
- pyridine
- Prior art date
- Legal status (The legal status 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 status listed.)
- Abandoned
Links
- 229920006318 anionic polymer Polymers 0.000 title description 3
- 229920002678 cellulose Polymers 0.000 claims abstract description 48
- 239000001913 cellulose Substances 0.000 claims abstract description 48
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 26
- 229920001282 polysaccharide Polymers 0.000 claims abstract description 24
- 239000005017 polysaccharide Substances 0.000 claims abstract description 24
- 150000004804 polysaccharides Chemical class 0.000 claims abstract description 22
- 238000000034 method Methods 0.000 claims abstract description 19
- 239000003431 cross linking reagent Substances 0.000 claims abstract description 14
- QAOWNCQODCNURD-UHFFFAOYSA-L sulfate group Chemical group S(=O)(=O)([O-])[O-] QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims abstract description 11
- 229920001586 anionic polysaccharide Polymers 0.000 claims abstract description 10
- 150000004836 anionic polysaccharides Chemical class 0.000 claims abstract description 10
- 238000004132 cross linking Methods 0.000 claims abstract description 10
- 239000002904 solvent Substances 0.000 claims abstract description 9
- 238000006243 chemical reaction Methods 0.000 claims description 16
- WFPZPJSADLPSON-UHFFFAOYSA-N dinitrogen tetraoxide Chemical compound [O-][N+](=O)[N+]([O-])=O WFPZPJSADLPSON-UHFFFAOYSA-N 0.000 claims description 11
- TWNIBLMWSKIRAT-VFUOTHLCSA-N levoglucosan Chemical group O[C@@H]1[C@@H](O)[C@H](O)[C@H]2CO[C@@H]1O2 TWNIBLMWSKIRAT-VFUOTHLCSA-N 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 claims description 5
- 150000001450 anions Chemical class 0.000 claims description 4
- TWJYXMZUQAMMKA-UHFFFAOYSA-N n,n-dimethyl-1-(oxiran-2-yl)methanamine Chemical compound CN(C)CC1CO1 TWJYXMZUQAMMKA-UHFFFAOYSA-N 0.000 claims description 3
- 150000001408 amides Chemical class 0.000 claims description 2
- 150000002391 heterocyclic compounds Chemical class 0.000 claims description 2
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 claims 4
- 150000001875 compounds Chemical class 0.000 claims 2
- 239000001294 propane Substances 0.000 claims 2
- BRKUEPJSZFSMPC-UHFFFAOYSA-N 2-(oxiran-2-yl)ethanamine Chemical compound NCCC1CO1 BRKUEPJSZFSMPC-UHFFFAOYSA-N 0.000 claims 1
- ATTZFSUZZUNHBP-UHFFFAOYSA-N Piperonyl sulfoxide Chemical compound CCCCCCCCS(=O)C(C)CC1=CC=C2OCOC2=C1 ATTZFSUZZUNHBP-UHFFFAOYSA-N 0.000 claims 1
- -1 anion polysaccharide Chemical class 0.000 claims 1
- JUJWROOIHBZHMG-UHFFFAOYSA-N Pyridine Chemical compound C1=CC=NC=C1 JUJWROOIHBZHMG-UHFFFAOYSA-N 0.000 abstract description 10
- 150000003839 salts Chemical class 0.000 abstract description 7
- 239000007788 liquid Substances 0.000 abstract description 5
- UMJSCPRVCHMLSP-UHFFFAOYSA-N pyridine Natural products COC1=CC=CN=C1 UMJSCPRVCHMLSP-UHFFFAOYSA-N 0.000 abstract description 5
- 239000000047 product Substances 0.000 description 20
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-dimethylformamide Substances CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 description 19
- AKEJUJNQAAGONA-UHFFFAOYSA-N sulfur trioxide Inorganic materials O=S(=O)=O AKEJUJNQAAGONA-UHFFFAOYSA-N 0.000 description 15
- 229920000642 polymer Polymers 0.000 description 13
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 12
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 10
- 239000002250 absorbent Substances 0.000 description 10
- 230000002745 absorbent Effects 0.000 description 10
- 239000012153 distilled water Substances 0.000 description 8
- 238000003756 stirring Methods 0.000 description 7
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 6
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 5
- 239000002253 acid Substances 0.000 description 5
- 125000000129 anionic group Chemical group 0.000 description 5
- 239000011780 sodium chloride Substances 0.000 description 5
- 239000001117 sulphuric acid Substances 0.000 description 5
- 235000011149 sulphuric acid Nutrition 0.000 description 5
- 229920003043 Cellulose fiber Polymers 0.000 description 4
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 4
- 229920001131 Pulp (paper) Polymers 0.000 description 4
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 4
- 238000005119 centrifugation Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- YLQBMQCUIZJEEH-UHFFFAOYSA-N Furan Chemical compound C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 3
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
- 210000001124 body fluid Anatomy 0.000 description 3
- 239000010839 body fluid Substances 0.000 description 3
- 239000003153 chemical reaction reagent Substances 0.000 description 3
- 238000000502 dialysis Methods 0.000 description 3
- 125000000524 functional group Chemical group 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 210000002700 urine Anatomy 0.000 description 3
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 description 2
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 239000003513 alkali Substances 0.000 description 2
- 125000000217 alkyl group Chemical group 0.000 description 2
- 125000002947 alkylene group Chemical group 0.000 description 2
- 239000002585 base Substances 0.000 description 2
- 229960001760 dimethyl sulfoxide Drugs 0.000 description 2
- 238000010494 dissociation reaction Methods 0.000 description 2
- 230000005593 dissociations Effects 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 230000007062 hydrolysis Effects 0.000 description 2
- 238000006460 hydrolysis reaction Methods 0.000 description 2
- 239000002655 kraft paper Substances 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 210000004914 menses Anatomy 0.000 description 2
- 238000006386 neutralization reaction Methods 0.000 description 2
- 231100000572 poisoning Toxicity 0.000 description 2
- 230000000607 poisoning effect Effects 0.000 description 2
- 230000035484 reaction time Effects 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 229910021653 sulphate ion Inorganic materials 0.000 description 2
- VZGDMQKNWNREIO-UHFFFAOYSA-N tetrachloromethane Chemical compound ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 description 2
- RYHBNJHYFVUHQT-UHFFFAOYSA-N 1,4-Dioxane Chemical compound C1COCCO1 RYHBNJHYFVUHQT-UHFFFAOYSA-N 0.000 description 1
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 1
- 235000016068 Berberis vulgaris Nutrition 0.000 description 1
- 241000335053 Beta vulgaris Species 0.000 description 1
- LSNNMFCWUKXFEE-UHFFFAOYSA-M Bisulfite Chemical compound OS([O-])=O LSNNMFCWUKXFEE-UHFFFAOYSA-M 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- 229920000742 Cotton Polymers 0.000 description 1
- ZNZYKNKBJPZETN-WELNAUFTSA-N Dialdehyde 11678 Chemical compound N1C2=CC=CC=C2C2=C1[C@H](C[C@H](/C(=C/O)C(=O)OC)[C@@H](C=C)C=O)NCC2 ZNZYKNKBJPZETN-WELNAUFTSA-N 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- 206010021639 Incontinence Diseases 0.000 description 1
- 229910002651 NO3 Inorganic materials 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- IOVCWXUNBOPUCH-UHFFFAOYSA-M Nitrite anion Chemical compound [O-]N=O IOVCWXUNBOPUCH-UHFFFAOYSA-M 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- XBDQKXXYIPTUBI-UHFFFAOYSA-M Propionate Chemical compound CCC([O-])=O XBDQKXXYIPTUBI-UHFFFAOYSA-M 0.000 description 1
- 229910006069 SO3H Inorganic materials 0.000 description 1
- VMHLLURERBWHNL-UHFFFAOYSA-M Sodium acetate Chemical compound [Na+].CC([O-])=O VMHLLURERBWHNL-UHFFFAOYSA-M 0.000 description 1
- 125000001931 aliphatic group Chemical group 0.000 description 1
- 150000001449 anionic compounds Chemical class 0.000 description 1
- 239000012296 anti-solvent Substances 0.000 description 1
- JXLHNMVSKXFWAO-UHFFFAOYSA-N azane;7-fluoro-2,1,3-benzoxadiazole-4-sulfonic acid Chemical compound N.OS(=O)(=O)C1=CC=C(F)C2=NON=C12 JXLHNMVSKXFWAO-UHFFFAOYSA-N 0.000 description 1
- 150000001720 carbohydrates Chemical class 0.000 description 1
- 125000004432 carbon atom Chemical group C* 0.000 description 1
- 125000002091 cationic group Chemical group 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 125000000753 cycloalkyl group Chemical group 0.000 description 1
- 125000002993 cycloalkylene group Chemical group 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 150000001991 dicarboxylic acids Chemical class 0.000 description 1
- 125000005442 diisocyanate group Chemical group 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 150000004820 halides Chemical class 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- ILVUABTVETXVMV-UHFFFAOYSA-N hydron;bromide;iodide Chemical compound Br.I ILVUABTVETXVMV-UHFFFAOYSA-N 0.000 description 1
- 229920001477 hydrophilic polymer Polymers 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000010907 mechanical stirring Methods 0.000 description 1
- WSFSSNUMVMOOMR-NJFSPNSNSA-N methanone Chemical compound O=[14CH2] WSFSSNUMVMOOMR-NJFSPNSNSA-N 0.000 description 1
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 229920005615 natural polymer Polymers 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 150000002891 organic anions Chemical class 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 239000003495 polar organic solvent Substances 0.000 description 1
- 229920000058 polyacrylate Polymers 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- KGMXPXPXPAAUMD-UHFFFAOYSA-N propane;dihydrochloride Chemical compound Cl.Cl.CCC KGMXPXPXPAAUMD-UHFFFAOYSA-N 0.000 description 1
- QQONPFPTGQHPMA-UHFFFAOYSA-N propylene Natural products CC=C QQONPFPTGQHPMA-UHFFFAOYSA-N 0.000 description 1
- 125000004805 propylene group Chemical group [H]C([H])([H])C([H])([*:1])C([H])([H])[*:2] 0.000 description 1
- 239000011541 reaction mixture Substances 0.000 description 1
- 239000004627 regenerated cellulose Substances 0.000 description 1
- 239000001632 sodium acetate Substances 0.000 description 1
- 235000017281 sodium acetate Nutrition 0.000 description 1
- 238000007614 solvation Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 125000000020 sulfo group Chemical group O=S(=O)([*])O[H] 0.000 description 1
- UDYFLDICVHJSOY-UHFFFAOYSA-N sulfur trioxide pyridine complex Chemical compound O=S(=O)=O.C1=CC=NC=C1 UDYFLDICVHJSOY-UHFFFAOYSA-N 0.000 description 1
- 230000000930 thermomechanical effect Effects 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
Classifications
-
- 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
-
- 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
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07H—SUGARS; DERIVATIVES THEREOF; NUCLEOSIDES; NUCLEOTIDES; NUCLEIC ACIDS
- C07H5/00—Compounds containing saccharide radicals in which the hetero bonds to oxygen have been replaced by the same number of hetero bonds to halogen, nitrogen, sulfur, selenium, or tellurium
- C07H5/04—Compounds containing saccharide radicals in which the hetero bonds to oxygen have been replaced by the same number of hetero bonds to halogen, nitrogen, sulfur, selenium, or tellurium to nitrogen
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07H—SUGARS; DERIVATIVES THEREOF; NUCLEOSIDES; NUCLEOTIDES; NUCLEIC ACIDS
- C07H5/00—Compounds containing saccharide radicals in which the hetero bonds to oxygen have been replaced by the same number of hetero bonds to halogen, nitrogen, sulfur, selenium, or tellurium
- C07H5/08—Compounds containing saccharide radicals in which the hetero bonds to oxygen have been replaced by the same number of hetero bonds to halogen, nitrogen, sulfur, selenium, or tellurium to sulfur, selenium or tellurium
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
- C08B5/00—Preparation of cellulose esters of inorganic acids, e.g. phosphates
- C08B5/14—Cellulose sulfate
Abstract
The invention relates to an anionic polysaccharide having superabsorbent characteristics, its polysaccharide being substituted by sulphate groups and the polysaccharide being cross-linked to a sufficient extent that it remains insoluble in water. The polysaccharide is preferably cellulose. The anionic polysaccharide can be made by a process which comprises (i) reacting a polysaccharide with a pyridine -SO3 complex in a solvent; followed by (ii) reacting with a cross-linking agent to provide a degree of cross-linking sufficient that the product remains insoluble in water. The sulphated polysaccharides show superabsorbent properties largely independent of pH over a wide range and can be used in applications where it is desired to absorb salt containing aqueous liquids, for example in diapers and catamenials.
Description
CA 02204889 1997-0~-08 ANIONIC POLYMER
The present invention relates to an anionic polymer, more particularly a water absorbent polymer of the type commonly referred to as a "superabsorbent".
The substances currently termed "superabsorbents~' are typically slightly cross-linked hydrophilic polymers. The polymers may differ in their chemical nature but they have the property of being capable of absorbing and retaining even under moderate pressure amounts of aqueous fluids equivalent to many times their own weight. For example superabsorbents can typically absorb up to 100 times their own weight or even more of distilled water.
Superabsorbents have been suggested for use in many different industrial applications where advantage can be taken of their water absorbing and/or retaining properties and examples include agriculture, the building industry, the production of alkaline batteries and filters. However, the primary field of application for superabsorbents is in the production of hygienic and/or sanitary products such as disposable sanitary napkins and disposable diapers either for children or for incontinent adults. In such hygienic and/or sanitary products, superabsorbents are used, generally in combination with cellulose fibres, to absorb body fluids such as menses or urine. However, the absorbent capacity of superabsorbents for body fluids is dramatically lower than for deionised water. It is generally believed that this effect results from the electrolyte content of body fluids and the effect is often referred to as "salt poisoning~.
The water absorption and water retention characteristics of superabsorbents are due to the presence in the polymer structure of ionisable functional groups. These groups are CA 02204889 1997-0~-08 WO96/15137 PCT~S95/14729 usually anionic and may be carboxyl groups, a high proportion of which are in the salt form when the polymer is dry but which undergo dissociation and solvation upon contact with water. In the dissociated state, the polymer chain will have a series of functional groups attached to it which groups have the same electric charge and thus repel one another.
This leads to expansion of the polymer structure which, in turn, permits further absorption of water molecules although this expansion is subject to the constraints provided by the cross-links in the polymer structure which must be sufficient to prevent dissolution of the polymer. It is assumed that the presence of a significant concentration of electrolytes in the water interferes with dissociation of the functional groups and leads to the "salt poisoning" effect. The backbone polymer can be synthetic, for example as polyacrylate, or can be a natural polymer such as a polysaccharide, more particularly cellulose, which has been modified so that anionic groups are attached to the polymer backbone.
Although the anionic groups are usually carboxyl a similar effect is theoretically possible with other anionic groups such as sulphate groups. Cellulose which has been modified to introduce sulphate groups has been reported in the literature. Concentrated sulphuric acid cannot be used to prepare sulphated cellulose since the result of treating cellulose with concentrated sulphuric acid is a soluble product, presumably resulting from hydrolysis of the cellulose backbone by the sulphuric acid. "Cellulose Chemistry and its Applications", Ed. T.P. Nevell and S.H.
Zeronian, Halsted Press (Division of John Wiley ~ Sons), 1985, page 350 reports sulphation of cellulose by direct action of aqueous sulphuric acid or sulphuric acid dissolved in a volatile organic solvent such as toluene, carbon tetrachloride or a lower alkanol. However, this reaction may also lead to hydrolysis of the cellulose chain and no use was suggested by Nevell and Zeronian for the products in question.
CA 02204889 1997-0~-08 WO96/15137 PCT~S95/14729 Philipp & Wagenknecht in Carbohydrate Research, 164, 107-116, (1987) report the homogenous sulphation of cellulose using a pyridine-SO3 complex in an N2O4-DMF system, the result being a product which is completely soluble in water.
An object of the present invention is to provide a sulphated polysaccharide having superabsorbent properties.
Another object of the invention is to provide a method for the production of such a sulphated polysaccharide.
According to one aspect the present invention provides an anionic polysaccharide having superabsorbent characteristics, the polysaccharide being substituted by sulphate groups and the polysaccharide being cross-linked to a sufficient extent that it remains insoluble in water.
Preferably the polysaccharide is cellulose.
The present invention also provides a process for the production of an anionic polysaccharide having superabsorbent characteristics which comprises:
(i) reacting a polysaccharide with a pyridine-S03 complex in a suitable solvent to provide a sulphated polysaccharide; and subsequently (ii) reacting the sulphated polysaccharide with a suitable cross-linking agent to provide a degree of cross-linking sufficient that the product remains insoluble in water.
The process according to the invention has the advantage that sulphation takes place readily in ? homogeneous phase reaction and the cross-linking step provides a product with superabsorbent properties and with the advantage that these properties are largely independent of pH over a range of about pH 3 to 10.
The polysaccharide according to the invention is CA 02204889 1997-0~-08 WO96/15137 PCT~S95/14729 preferably based on cellulose, for example fibrous cellulose.
The invention can be applied to fibrous cellulose derived by any chemical and/or mechanical treatment, for example cellulose fibres obtained from wood pulp purified by the sulphate process or the bisulphite process, cellulose fibres obtained from wood pulp by thermomechanical or mechanical treatment, beet cellulose, regenerated cellulose or cotton linters. Preferably the cellulose fibres are obtained from wood pulp purified by the sulphate process or as cellulose "fluff" derived from mechanical treatment or wood pulp and are of the type generally used for the preparation of absorbent pads in disposable products, for example sanitary napkins and towels and diapers. The invention may also be applied to non-fibrous cellulose, for example powdered or crystalline cellulose.
The pyridine-SO3 complex used in the first stage of the process is commercially available from manufacturers such as Aldrich & Merck and is also known as "sulphur trioxide pyridine complex".
Reaction is carried out in the presence of a solvent under anhydrous conditions for example at a temperature of 20-80~C for a period of 1 to 32 hours, for example, 6 to 24 hours. According to one embodiment the reaction is carried out at room temperature for about 12 hours. Suitable solvents include polar organic solvents, for example amides such as dimethylformamide (DMF), sulphoxides such as dimethylsulphoxide (DMSO), and heterocyclic compounds which may be saturated or unsaturated such as furan, tetrahydrofuran, dioxan and pyridine. The pyridine - SO3 complex should generally be used in excess and the pyridine forming part of the pyridine-SO3 complex may itself serve-as the solvent. DMF is particularly preferred as the solvent.
Water reacts with the pyridine -SO3 complex so that in all cases care must be taken to maintain anhydrous conditions, for example, by drying the reagents and the solvents used and the reaction vessels.
CA 02204889 1997-0~-08 WO96/15137 PCT~S95/14729 In general, the pyridine-S03 should be used in excess relative to the cellulose and, for example the ratio of cellulose anhydroglucose units to pyridine-SO3 complex may be in the range l:2 to l:5. The degree of substitution ("ds") of the sulphonate cellulose product can be adjusted by varying the amount of pyridine-SO3 complex and the ds will generally be in the range O.l to l.5. The ds is a measure of the ratio of sulphate groups to cellulose anhydroglucose units and can be determined as described in WO 92/19652.
According to a modification, the reaction with pyridine-S03 complex is carried out in the presence of dinitrogen tetroxide (N204). N204 can be added to the reaction mixture, preferably before addition of the pyridine-S03 complex.
Addition of dinitrogen tetroxide increases the solubility of the cellulose in the reaction system and can increase the yield of sulphated cellulose in the sense that a product of higher ds is obtained.
The reaction with pyridine-S03 complex generally produces a soluble sulphated cellulose which can be purified for example by the following steps:
neutralisation with alkali;
precipitation from solution using an anti-solvent such as an excess of methanol;
washing with distilled water;
re-dissolving in distilled water and dialysis to remove low molecular weight fractions.
The purified sulphated cellulose is then subjected to cross-linking to provide a product which is insoluble in water and shows superabsorbent properties.
In principle any reagent capable of cross-linking cellulose can be used and a wide range of such reagents are known from the literature (see for example US-A-3589364, US-CA 02204889 1997-0~-08 A-3658613, US-A-4066828, US-A-4068068). However, the cross-linking agent should be capable of reacting with the sulphated cellulose under conditions which do not affect the sulphate groups. Some cross-linking agents require the use of severe alkaline conditions and sulphate groups may also react under these conditions.
Preferred cross-linking agents, which will cross-link sulphated cellulose under conditions which do not destroy the sulphate groups, can be represented by the formula Rl ~4 15 . CH2-- CH_ CH2_ N_ CH2_ R _ CH2 _ ~_ CH2_ C\ ~2 2xe _ where R1, R2, R4 and R5, which may be the same or different, are each monovalent organic radicals and R3 is a divalent organic radical; and xe is a suitable anion.
Preferably R1, R2, R3, R4 and R5 are all saturated aliphatic or cycloaliphatic hydrocarbon radicals, i.e. alkyl in the case of Rl, R2, R4 and R5 and alkylene in the case of R3. The terms alkyl and alkylene include radicals which may be or which may include cycloalkyl or cycloalkylene moieties.
Each of Rl, R2, R3, R4 and Rs is preferably a group containing to 20 carbon atoms. Most preferably Rl, R2, R4 and Rs are each methyl. Most preferably R3 is propylene.
xe may be an inorganic or organic anion, for example halide (fluoride, chloride, bromide iodide), nitrate, nitrite, phosphate, acetate, propionate, hydroxide.
A particularly preferred cross-linking agent is 1,3-bis (glycidyldimethylammonium~propanedichloride. Other suitable cross-linking agents include epicholohydrin, formaldehyde, diepoxide, dicarboxylic acids, dialdehyde and diisocyanates.
CA 02204889 1997-0~-08 W096/15137 PCT~S95/14729 The conditions of the cross-linking reaction should be such as to ensure that the cross-linked sulphated - polysaccharide (preferably cellulose) is insoluble in water.
In the case of cellulose, the cellulose anhydroglucose units in the ratio of sulphated cellulose to cross-linking agent can be in the range of about l:l to 15:l. The reaction temperature can be, for example, in the range of about 4~C to 80~C and the reaction time for the cross-linking can be about l hour to 16 hours. Overall reaction time will usually be in the range of 4 to 34 hours.
Cross-linking conditions will depend on the nature of the cross-l-inking agent but the reaction will generally be carried out in the presence of base. This leads to neutralisation of -S03H groups in the sulphated cellulose and the groups are more stable in salt form.
The sulphated polysaccharide according to the invention is useful as a superabsorbent and as an ion-exchanger. The product contains SO3H groups which are stronger acid groups than the CO2H groups found in most convention anionic superabsorbents so that equivalent absorbent capacity can be obtained at lower ds than with polymers containing CO2H
groups.
The absorbent according to the invention is particularly suitable for use in applications where it is desired to absorb salt containing aqueous liquids. Examples of such liquids include in particular menses and urine and the absorbent material can be used as the filling in catamenials and diapers, generally in admixture with a fibrous absorbent such as cellulose fluff. The absorbent according to the invention in acid form can also be used as an ion exchanger and superabsorbent in conjunction with a cationic superabsorbent in basic form as described in our copending Italian patent application No. T094A00099l filed on 94/12/06 or in conjunction with an anion exchanger in basic form as CA 02204889 1997-0~-08 W O 96/15137 PC~rrUS95/14729 described in our copending Italian patent application No.
TO94A000889 filed on 94/11/10.
As already indicated, the superabsorbent properties of the superabsorbent according to the present invention are largely independent of pH over quite a wide pH range (about 3 to 10). This can have advantages in the use of the absorbent in diapers for example since although the mean pH
of urine is around 6.5 the pH can vary within the range of about 5 to 7.3. However the absorbents according to the present invention show particular advantage in absorbing solutions at low pH (3 to 5) and can be particularly in the control of environmental pollution where acid solutions are involved, e.g. the absorbtion of acid leakage or spillage.
The invention is illustrated by the following example.
Example a. Sul~hation of Cellulose 1. 2 g of bleached cellulose kraft pulp was added to 20 ml of anhydrous dimethylformamide (DMF) with stirring and stirring was continued at room temperature for 12 hours.
7.8 g of pyridine-SO3 complex (Aldrich Chimica, Milan, Italy) was then added and after 4 hours at room temperature with continued stirring the temperature is raised to 70~C and maintained for 30 minutes.
200 ml distilled water were then added and the solution neutralized with lN NaOH. The soluble sulphated cellulose derivative thus obtained was precipitated by addition of a large excess of methanol, the precipitate was washed with distilled water and dialysed against distilled water for 1 to 3 days using a dialysis membrane with a molecular weight cut off point of 14,000 Da. The dialysed product was then lyophilised.
CA 02204889 1997-0~-08 WO96/15137 PCT~S95/14729 2. 4 g of bleached cellulose kraft pulp were placed in a 2 neck flask and 150 ml of anhydrous DMF were added. N204 was bubbled in under mechanical stirring until a brown-green colour was obtained in the solution. 12 g pyridine-SO3 complex were added (ratio of cellulose anhydroglucose units to pyridine-SO3 complex 1:3) and the mixture maintained at 4~C for 16 hours with stirring. N2 was then bubbled into the reaction vessel to eliminate residual N2O4 from the reaction vessel.
The polymer was precipitated by addition of a large excess of ethanol saturated with sodium acetate and the product separated by filtration using a G3 glass filter. The product was washed with ethanol, the polymer dissolved in water and the pH maintained at 7.5 by addition of acid (HCl) or alkali (NaOH) as required. The product was then reprecipitated using the procedure described above, re-dissolved in water and dialysed against distilled water for 3 days using a dialysis membrane with a molecular weight cut off point of 14,000 Da. The dialysed product was then lyophilised.
b. Cross-linkinq 0.5 g (2.5 mmol) of the purified sulphated cellulose prepared in (1) above was mixed with 2.5 ml of 19~ aqueous sodium hydroxide with stirring. 0.063 ml of 65% aqueous 1,3-bis(glycidyldimethyl-ammonium) propane dichloride and 2 ml of 1~ aqueous NaCl was added at room temperature with stirring and stirring was continued at this temperature for 16 hours.
The addition of NaCl and base leads to a product with anlonic groups in the salt (Na+) form. The product is then washed with distilled was to neutral pH, filtered and lyophilised.
c. Test Results When tested with 1~ NaCl solution, the sample had an CA 02204889 1997-0~-08 WO96/15137 PCT~S95/14729 absorbency (tea-bag test) of 54 (after draining) and 45 (after centrifugation at 60 g).
To illustrate the fact that absorbency is relatively unaffected by pH, the following figures were obtained for absorbency using the tea-bag test in 1~ aqueous NaCl adjusted to different pH values using lN hydrochloric acid or lN
sodium hydroxide.
pH AFTER DRAINING AFTER
CENTRIFUGATION
3 34.0 18.9 7 32.6 19.5 9.5 32.1 20.4 In each case the tea-bag test was performed by weighing about 0.3 g of the product into a tea-bag envelope which was itself then weighed and immersed in 150 ml of liquid (1~ NaCl solution or distilled water) in a 250 ml beaker for 1 hour.
The envelope was then Le"-oved from the liquid and allowed to drain for 10 minutes, weighed, and then centrifuged at 60 g for 10 minutes and weighed again. Absorbency is calculated as follows:
A = (Wwet - Wd~)/G
25 where:
A = absorbency (after draining or centrifugation);
Wwet = weight of envelope containing sample after draining or centrifugation (grams);
Wd~ = weight of envelope containing sample before immersion (grams);
G = weight of sample used for the test (grams).
The present invention relates to an anionic polymer, more particularly a water absorbent polymer of the type commonly referred to as a "superabsorbent".
The substances currently termed "superabsorbents~' are typically slightly cross-linked hydrophilic polymers. The polymers may differ in their chemical nature but they have the property of being capable of absorbing and retaining even under moderate pressure amounts of aqueous fluids equivalent to many times their own weight. For example superabsorbents can typically absorb up to 100 times their own weight or even more of distilled water.
Superabsorbents have been suggested for use in many different industrial applications where advantage can be taken of their water absorbing and/or retaining properties and examples include agriculture, the building industry, the production of alkaline batteries and filters. However, the primary field of application for superabsorbents is in the production of hygienic and/or sanitary products such as disposable sanitary napkins and disposable diapers either for children or for incontinent adults. In such hygienic and/or sanitary products, superabsorbents are used, generally in combination with cellulose fibres, to absorb body fluids such as menses or urine. However, the absorbent capacity of superabsorbents for body fluids is dramatically lower than for deionised water. It is generally believed that this effect results from the electrolyte content of body fluids and the effect is often referred to as "salt poisoning~.
The water absorption and water retention characteristics of superabsorbents are due to the presence in the polymer structure of ionisable functional groups. These groups are CA 02204889 1997-0~-08 WO96/15137 PCT~S95/14729 usually anionic and may be carboxyl groups, a high proportion of which are in the salt form when the polymer is dry but which undergo dissociation and solvation upon contact with water. In the dissociated state, the polymer chain will have a series of functional groups attached to it which groups have the same electric charge and thus repel one another.
This leads to expansion of the polymer structure which, in turn, permits further absorption of water molecules although this expansion is subject to the constraints provided by the cross-links in the polymer structure which must be sufficient to prevent dissolution of the polymer. It is assumed that the presence of a significant concentration of electrolytes in the water interferes with dissociation of the functional groups and leads to the "salt poisoning" effect. The backbone polymer can be synthetic, for example as polyacrylate, or can be a natural polymer such as a polysaccharide, more particularly cellulose, which has been modified so that anionic groups are attached to the polymer backbone.
Although the anionic groups are usually carboxyl a similar effect is theoretically possible with other anionic groups such as sulphate groups. Cellulose which has been modified to introduce sulphate groups has been reported in the literature. Concentrated sulphuric acid cannot be used to prepare sulphated cellulose since the result of treating cellulose with concentrated sulphuric acid is a soluble product, presumably resulting from hydrolysis of the cellulose backbone by the sulphuric acid. "Cellulose Chemistry and its Applications", Ed. T.P. Nevell and S.H.
Zeronian, Halsted Press (Division of John Wiley ~ Sons), 1985, page 350 reports sulphation of cellulose by direct action of aqueous sulphuric acid or sulphuric acid dissolved in a volatile organic solvent such as toluene, carbon tetrachloride or a lower alkanol. However, this reaction may also lead to hydrolysis of the cellulose chain and no use was suggested by Nevell and Zeronian for the products in question.
CA 02204889 1997-0~-08 WO96/15137 PCT~S95/14729 Philipp & Wagenknecht in Carbohydrate Research, 164, 107-116, (1987) report the homogenous sulphation of cellulose using a pyridine-SO3 complex in an N2O4-DMF system, the result being a product which is completely soluble in water.
An object of the present invention is to provide a sulphated polysaccharide having superabsorbent properties.
Another object of the invention is to provide a method for the production of such a sulphated polysaccharide.
According to one aspect the present invention provides an anionic polysaccharide having superabsorbent characteristics, the polysaccharide being substituted by sulphate groups and the polysaccharide being cross-linked to a sufficient extent that it remains insoluble in water.
Preferably the polysaccharide is cellulose.
The present invention also provides a process for the production of an anionic polysaccharide having superabsorbent characteristics which comprises:
(i) reacting a polysaccharide with a pyridine-S03 complex in a suitable solvent to provide a sulphated polysaccharide; and subsequently (ii) reacting the sulphated polysaccharide with a suitable cross-linking agent to provide a degree of cross-linking sufficient that the product remains insoluble in water.
The process according to the invention has the advantage that sulphation takes place readily in ? homogeneous phase reaction and the cross-linking step provides a product with superabsorbent properties and with the advantage that these properties are largely independent of pH over a range of about pH 3 to 10.
The polysaccharide according to the invention is CA 02204889 1997-0~-08 WO96/15137 PCT~S95/14729 preferably based on cellulose, for example fibrous cellulose.
The invention can be applied to fibrous cellulose derived by any chemical and/or mechanical treatment, for example cellulose fibres obtained from wood pulp purified by the sulphate process or the bisulphite process, cellulose fibres obtained from wood pulp by thermomechanical or mechanical treatment, beet cellulose, regenerated cellulose or cotton linters. Preferably the cellulose fibres are obtained from wood pulp purified by the sulphate process or as cellulose "fluff" derived from mechanical treatment or wood pulp and are of the type generally used for the preparation of absorbent pads in disposable products, for example sanitary napkins and towels and diapers. The invention may also be applied to non-fibrous cellulose, for example powdered or crystalline cellulose.
The pyridine-SO3 complex used in the first stage of the process is commercially available from manufacturers such as Aldrich & Merck and is also known as "sulphur trioxide pyridine complex".
Reaction is carried out in the presence of a solvent under anhydrous conditions for example at a temperature of 20-80~C for a period of 1 to 32 hours, for example, 6 to 24 hours. According to one embodiment the reaction is carried out at room temperature for about 12 hours. Suitable solvents include polar organic solvents, for example amides such as dimethylformamide (DMF), sulphoxides such as dimethylsulphoxide (DMSO), and heterocyclic compounds which may be saturated or unsaturated such as furan, tetrahydrofuran, dioxan and pyridine. The pyridine - SO3 complex should generally be used in excess and the pyridine forming part of the pyridine-SO3 complex may itself serve-as the solvent. DMF is particularly preferred as the solvent.
Water reacts with the pyridine -SO3 complex so that in all cases care must be taken to maintain anhydrous conditions, for example, by drying the reagents and the solvents used and the reaction vessels.
CA 02204889 1997-0~-08 WO96/15137 PCT~S95/14729 In general, the pyridine-S03 should be used in excess relative to the cellulose and, for example the ratio of cellulose anhydroglucose units to pyridine-SO3 complex may be in the range l:2 to l:5. The degree of substitution ("ds") of the sulphonate cellulose product can be adjusted by varying the amount of pyridine-SO3 complex and the ds will generally be in the range O.l to l.5. The ds is a measure of the ratio of sulphate groups to cellulose anhydroglucose units and can be determined as described in WO 92/19652.
According to a modification, the reaction with pyridine-S03 complex is carried out in the presence of dinitrogen tetroxide (N204). N204 can be added to the reaction mixture, preferably before addition of the pyridine-S03 complex.
Addition of dinitrogen tetroxide increases the solubility of the cellulose in the reaction system and can increase the yield of sulphated cellulose in the sense that a product of higher ds is obtained.
The reaction with pyridine-S03 complex generally produces a soluble sulphated cellulose which can be purified for example by the following steps:
neutralisation with alkali;
precipitation from solution using an anti-solvent such as an excess of methanol;
washing with distilled water;
re-dissolving in distilled water and dialysis to remove low molecular weight fractions.
The purified sulphated cellulose is then subjected to cross-linking to provide a product which is insoluble in water and shows superabsorbent properties.
In principle any reagent capable of cross-linking cellulose can be used and a wide range of such reagents are known from the literature (see for example US-A-3589364, US-CA 02204889 1997-0~-08 A-3658613, US-A-4066828, US-A-4068068). However, the cross-linking agent should be capable of reacting with the sulphated cellulose under conditions which do not affect the sulphate groups. Some cross-linking agents require the use of severe alkaline conditions and sulphate groups may also react under these conditions.
Preferred cross-linking agents, which will cross-link sulphated cellulose under conditions which do not destroy the sulphate groups, can be represented by the formula Rl ~4 15 . CH2-- CH_ CH2_ N_ CH2_ R _ CH2 _ ~_ CH2_ C\ ~2 2xe _ where R1, R2, R4 and R5, which may be the same or different, are each monovalent organic radicals and R3 is a divalent organic radical; and xe is a suitable anion.
Preferably R1, R2, R3, R4 and R5 are all saturated aliphatic or cycloaliphatic hydrocarbon radicals, i.e. alkyl in the case of Rl, R2, R4 and R5 and alkylene in the case of R3. The terms alkyl and alkylene include radicals which may be or which may include cycloalkyl or cycloalkylene moieties.
Each of Rl, R2, R3, R4 and Rs is preferably a group containing to 20 carbon atoms. Most preferably Rl, R2, R4 and Rs are each methyl. Most preferably R3 is propylene.
xe may be an inorganic or organic anion, for example halide (fluoride, chloride, bromide iodide), nitrate, nitrite, phosphate, acetate, propionate, hydroxide.
A particularly preferred cross-linking agent is 1,3-bis (glycidyldimethylammonium~propanedichloride. Other suitable cross-linking agents include epicholohydrin, formaldehyde, diepoxide, dicarboxylic acids, dialdehyde and diisocyanates.
CA 02204889 1997-0~-08 W096/15137 PCT~S95/14729 The conditions of the cross-linking reaction should be such as to ensure that the cross-linked sulphated - polysaccharide (preferably cellulose) is insoluble in water.
In the case of cellulose, the cellulose anhydroglucose units in the ratio of sulphated cellulose to cross-linking agent can be in the range of about l:l to 15:l. The reaction temperature can be, for example, in the range of about 4~C to 80~C and the reaction time for the cross-linking can be about l hour to 16 hours. Overall reaction time will usually be in the range of 4 to 34 hours.
Cross-linking conditions will depend on the nature of the cross-l-inking agent but the reaction will generally be carried out in the presence of base. This leads to neutralisation of -S03H groups in the sulphated cellulose and the groups are more stable in salt form.
The sulphated polysaccharide according to the invention is useful as a superabsorbent and as an ion-exchanger. The product contains SO3H groups which are stronger acid groups than the CO2H groups found in most convention anionic superabsorbents so that equivalent absorbent capacity can be obtained at lower ds than with polymers containing CO2H
groups.
The absorbent according to the invention is particularly suitable for use in applications where it is desired to absorb salt containing aqueous liquids. Examples of such liquids include in particular menses and urine and the absorbent material can be used as the filling in catamenials and diapers, generally in admixture with a fibrous absorbent such as cellulose fluff. The absorbent according to the invention in acid form can also be used as an ion exchanger and superabsorbent in conjunction with a cationic superabsorbent in basic form as described in our copending Italian patent application No. T094A00099l filed on 94/12/06 or in conjunction with an anion exchanger in basic form as CA 02204889 1997-0~-08 W O 96/15137 PC~rrUS95/14729 described in our copending Italian patent application No.
TO94A000889 filed on 94/11/10.
As already indicated, the superabsorbent properties of the superabsorbent according to the present invention are largely independent of pH over quite a wide pH range (about 3 to 10). This can have advantages in the use of the absorbent in diapers for example since although the mean pH
of urine is around 6.5 the pH can vary within the range of about 5 to 7.3. However the absorbents according to the present invention show particular advantage in absorbing solutions at low pH (3 to 5) and can be particularly in the control of environmental pollution where acid solutions are involved, e.g. the absorbtion of acid leakage or spillage.
The invention is illustrated by the following example.
Example a. Sul~hation of Cellulose 1. 2 g of bleached cellulose kraft pulp was added to 20 ml of anhydrous dimethylformamide (DMF) with stirring and stirring was continued at room temperature for 12 hours.
7.8 g of pyridine-SO3 complex (Aldrich Chimica, Milan, Italy) was then added and after 4 hours at room temperature with continued stirring the temperature is raised to 70~C and maintained for 30 minutes.
200 ml distilled water were then added and the solution neutralized with lN NaOH. The soluble sulphated cellulose derivative thus obtained was precipitated by addition of a large excess of methanol, the precipitate was washed with distilled water and dialysed against distilled water for 1 to 3 days using a dialysis membrane with a molecular weight cut off point of 14,000 Da. The dialysed product was then lyophilised.
CA 02204889 1997-0~-08 WO96/15137 PCT~S95/14729 2. 4 g of bleached cellulose kraft pulp were placed in a 2 neck flask and 150 ml of anhydrous DMF were added. N204 was bubbled in under mechanical stirring until a brown-green colour was obtained in the solution. 12 g pyridine-SO3 complex were added (ratio of cellulose anhydroglucose units to pyridine-SO3 complex 1:3) and the mixture maintained at 4~C for 16 hours with stirring. N2 was then bubbled into the reaction vessel to eliminate residual N2O4 from the reaction vessel.
The polymer was precipitated by addition of a large excess of ethanol saturated with sodium acetate and the product separated by filtration using a G3 glass filter. The product was washed with ethanol, the polymer dissolved in water and the pH maintained at 7.5 by addition of acid (HCl) or alkali (NaOH) as required. The product was then reprecipitated using the procedure described above, re-dissolved in water and dialysed against distilled water for 3 days using a dialysis membrane with a molecular weight cut off point of 14,000 Da. The dialysed product was then lyophilised.
b. Cross-linkinq 0.5 g (2.5 mmol) of the purified sulphated cellulose prepared in (1) above was mixed with 2.5 ml of 19~ aqueous sodium hydroxide with stirring. 0.063 ml of 65% aqueous 1,3-bis(glycidyldimethyl-ammonium) propane dichloride and 2 ml of 1~ aqueous NaCl was added at room temperature with stirring and stirring was continued at this temperature for 16 hours.
The addition of NaCl and base leads to a product with anlonic groups in the salt (Na+) form. The product is then washed with distilled was to neutral pH, filtered and lyophilised.
c. Test Results When tested with 1~ NaCl solution, the sample had an CA 02204889 1997-0~-08 WO96/15137 PCT~S95/14729 absorbency (tea-bag test) of 54 (after draining) and 45 (after centrifugation at 60 g).
To illustrate the fact that absorbency is relatively unaffected by pH, the following figures were obtained for absorbency using the tea-bag test in 1~ aqueous NaCl adjusted to different pH values using lN hydrochloric acid or lN
sodium hydroxide.
pH AFTER DRAINING AFTER
CENTRIFUGATION
3 34.0 18.9 7 32.6 19.5 9.5 32.1 20.4 In each case the tea-bag test was performed by weighing about 0.3 g of the product into a tea-bag envelope which was itself then weighed and immersed in 150 ml of liquid (1~ NaCl solution or distilled water) in a 250 ml beaker for 1 hour.
The envelope was then Le"-oved from the liquid and allowed to drain for 10 minutes, weighed, and then centrifuged at 60 g for 10 minutes and weighed again. Absorbency is calculated as follows:
A = (Wwet - Wd~)/G
25 where:
A = absorbency (after draining or centrifugation);
Wwet = weight of envelope containing sample after draining or centrifugation (grams);
Wd~ = weight of envelope containing sample before immersion (grams);
G = weight of sample used for the test (grams).
Claims (16)
1. An anionic polysaccharide having superabsorbent characteristics, the polysaccharide being substituted by sulphate groups and the polysaccharide being cross-linked to a sufficient extent that it remains insoluble in water.
2. An anionic polysaccharide according to claim 1 which is cellulose.
3. An anionic polysaccharide according to claim 2 wherein the cellulose is fibrous cellulose.
4. An anionic polysaccharide according to any of claims 1 to 3 having a ds of 0.1 to 1.5.
5. An anionic polysaccharide according to any of claims 1 to 4 wherein the cross-linking agent is a compound of formula where R1, R2, R4 and R5, which may be the same or different, are each monovalent organic radicals and R3 is a divalent organic radical; and X- is a suitable anion.
6. An anion polysaccharide according to claim 5 wherein the cross-linking agent is 1,3-bis(glycidylmethylammonium)propane dichloride.
7. A process for the production of an anionic polysaccharide having superabsorbent characteristics which comprises:
(i) reacting a polysaccharide with a pyridine-SO3 complex in a suitable solvent to provide a sulphated polysaccharide; and subsequently (ii) reacting the sulphated polysaccharide with a suitable cross-linking agent to provide a degree of cross-linking sufficient that the product remains insoluble in water.
(i) reacting a polysaccharide with a pyridine-SO3 complex in a suitable solvent to provide a sulphated polysaccharide; and subsequently (ii) reacting the sulphated polysaccharide with a suitable cross-linking agent to provide a degree of cross-linking sufficient that the product remains insoluble in water.
8. A process according to claim 7 wherein the polysaccharide is cellulose.
9. A process according to claim 8 wherein the cellulose is fibrous cellulose.
10. A process according to any of claims 7 to 9 wherein the reaction with pyridine-SO3 complex is carried under anhydrous conditions in a solvent which is an amide, sulphoxide or heterocyclic compound.
11. A process according to any of claims 7 to 10 wherein the reaction with pyridine-SO3 complex is carried out to provide a ds of 0.1 to 1.5.
12. A process according to any of claims 7 to 11 wherein the reaction with pyridine-SO3 complex is carried out in the presence of dinitrogen tetroxide.
13. A process according to any of claims 7 to 12 wherein the cross-linking agent is a compound of formula where R1, R2, R4 and R5, which may be the same or different, are each monovalent organic radicals and R3 is a divalent organic radical; and X- is a suitable anion.
14. A process according to claim 13 wherein the cross-linking agent is 1,3-bis(glycidyldimethylammonium)propane dichloride.
15. A process according to any of claims 7 to 14 wherein cross-linking is carried out in the presence of base.
16. A process according to any of claims 7 to 15 wherein the ratio of cellulose anhydroglucose units to cross-linking agent is 1:1 to 15:1.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
ITTO94A000892 | 1994-11-10 | ||
IT94TO000892A IT1267497B1 (en) | 1994-11-10 | 1994-11-10 | ANIONIC POLYMER, FOR EXAMPLE OF SUPER ABSORBENT TYPE AND RELATED PRODUCTION PROCESS. |
PCT/US1995/014729 WO1996015137A1 (en) | 1994-11-10 | 1995-11-13 | Anionic polymer |
Publications (1)
Publication Number | Publication Date |
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CA2204889A1 true CA2204889A1 (en) | 1996-05-23 |
Family
ID=11412882
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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CA002204889A Abandoned CA2204889A1 (en) | 1994-11-10 | 1995-11-13 | Anionic polymer |
Country Status (7)
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EP (1) | EP0791002A4 (en) |
JP (1) | JPH10509754A (en) |
KR (1) | KR970707137A (en) |
AU (1) | AU4156496A (en) |
CA (1) | CA2204889A1 (en) |
IT (1) | IT1267497B1 (en) |
WO (1) | WO1996015137A1 (en) |
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KR20020064990A (en) * | 2000-01-19 | 2002-08-10 | 웨이어해유저 컴파니 | Superabsorbent cellulosic fiber |
US6500947B1 (en) | 2001-08-24 | 2002-12-31 | Weyerhaeuser Company | Superabsorbent polymer |
US7393905B2 (en) | 2004-12-29 | 2008-07-01 | Weyerhaeuser Company | Crosslinked mixed carboxylated polymer network |
US7230049B2 (en) | 2004-12-29 | 2007-06-12 | Weyerhaeuser Co. | Method of crosslinking a carboxylated polymer using a triazine crosslinking activator |
US7300965B2 (en) | 2004-12-29 | 2007-11-27 | Weyerhaeuser Company | Mixed polymer network |
US7541396B2 (en) | 2004-12-29 | 2009-06-02 | Weyerhaeuser Nr Company | Method for making carboxyalkyl cellulose |
US7241836B2 (en) | 2004-12-29 | 2007-07-10 | Weyerhaeuser Co. | Method of crosslinking a mixture of carboxylated polymers using a triazine crosslinking activator |
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US3589364A (en) * | 1968-03-14 | 1971-06-29 | Buckeye Cellulose Corp | Bibulous cellulosic fibers |
US3737406A (en) * | 1971-03-22 | 1973-06-05 | Alelio G D | Reactive epoxy-onium catalysts for synthesis of polyoxazolidones |
DE2519927C2 (en) * | 1975-05-05 | 1986-10-23 | Hoechst Ag, 6230 Frankfurt | Process for the production of cellulose ethers which absorb water but are more than 50% by weight insoluble therein |
DE2520337A1 (en) * | 1975-05-07 | 1976-11-18 | Hoechst Ag | PROCESS FOR PRODUCING WATER-ABSORBING BUT INSOLUBLE CELLULOSE ETHERS |
JPS5684701A (en) * | 1979-12-14 | 1981-07-10 | Kohjin Co Ltd | Production of absorbing material |
-
1994
- 1994-11-10 IT IT94TO000892A patent/IT1267497B1/en active IP Right Grant
-
1995
- 1995-11-13 AU AU41564/96A patent/AU4156496A/en not_active Abandoned
- 1995-11-13 EP EP95939920A patent/EP0791002A4/en not_active Withdrawn
- 1995-11-13 WO PCT/US1995/014729 patent/WO1996015137A1/en not_active Application Discontinuation
- 1995-11-13 CA CA002204889A patent/CA2204889A1/en not_active Abandoned
- 1995-11-13 KR KR1019970703147A patent/KR970707137A/en not_active Application Discontinuation
- 1995-11-13 JP JP8516257A patent/JPH10509754A/en active Pending
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KR970707137A (en) | 1997-12-01 |
AU4156496A (en) | 1996-06-06 |
EP0791002A4 (en) | 1998-10-07 |
MX9703448A (en) | 1998-07-31 |
WO1996015137A1 (en) | 1996-05-23 |
EP0791002A1 (en) | 1997-08-27 |
JPH10509754A (en) | 1998-09-22 |
ITTO940892A0 (en) | 1994-11-10 |
ITTO940892A1 (en) | 1996-05-10 |
IT1267497B1 (en) | 1997-02-05 |
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