US20040236016A1 - Acidic superabsorbent polysaccharides - Google Patents
Acidic superabsorbent polysaccharides Download PDFInfo
- Publication number
- US20040236016A1 US20040236016A1 US10/878,459 US87845904A US2004236016A1 US 20040236016 A1 US20040236016 A1 US 20040236016A1 US 87845904 A US87845904 A US 87845904A US 2004236016 A1 US2004236016 A1 US 2004236016A1
- Authority
- US
- United States
- Prior art keywords
- polysaccharide
- superabsorbent
- gel
- containing acidic
- acidic groups
- 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
- 239000005017 polysaccharide Substances 0.000 title claims abstract description 88
- 229920001282 polysaccharide Polymers 0.000 title claims abstract description 83
- 150000004676 glycans Chemical class 0.000 title claims abstract description 41
- 230000002378 acidificating effect Effects 0.000 title claims abstract description 31
- 238000004132 cross linking Methods 0.000 claims abstract description 34
- 239000003431 cross linking reagent Substances 0.000 claims abstract description 12
- 238000000034 method Methods 0.000 claims abstract description 10
- 238000001035 drying Methods 0.000 claims abstract description 9
- 229920002134 Carboxymethyl cellulose Polymers 0.000 claims abstract description 8
- 239000001768 carboxy methyl cellulose Substances 0.000 claims abstract description 8
- 239000008112 carboxymethyl-cellulose Substances 0.000 claims abstract description 8
- 235000010948 carboxy methyl cellulose Nutrition 0.000 claims abstract description 7
- 229920002472 Starch Polymers 0.000 claims description 32
- 239000008107 starch Substances 0.000 claims description 32
- 235000019698 starch Nutrition 0.000 claims description 32
- 238000007254 oxidation reaction Methods 0.000 claims description 30
- 230000003647 oxidation Effects 0.000 claims description 29
- 239000002250 absorbent Substances 0.000 claims description 24
- 230000002745 absorbent Effects 0.000 claims description 24
- -1 carboxymethyl polysaccharide Chemical class 0.000 claims description 20
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 claims description 14
- 239000002253 acid Substances 0.000 claims description 12
- 229940105329 carboxymethylcellulose Drugs 0.000 claims description 7
- 239000007788 liquid Substances 0.000 claims description 6
- 150000007513 acids Chemical class 0.000 claims description 5
- 235000010233 benzoic acid Nutrition 0.000 claims description 3
- ABLZXFCXXLZCGV-UHFFFAOYSA-N Phosphorous acid Chemical compound OP(O)=O ABLZXFCXXLZCGV-UHFFFAOYSA-N 0.000 claims description 2
- 125000004029 hydroxymethyl group Chemical group [H]OC([H])([H])* 0.000 claims description 2
- 150000001559 benzoic acids Chemical class 0.000 claims 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-N carbonic acid Chemical class OC(O)=O BVKZGUZCCUSVTD-UHFFFAOYSA-N 0.000 claims 2
- 125000001483 monosaccharide substituent group Chemical group 0.000 claims 2
- BDHFUVZGWQCTTF-UHFFFAOYSA-N sulfonic acid Chemical group OS(=O)=O BDHFUVZGWQCTTF-UHFFFAOYSA-N 0.000 claims 1
- 239000012530 fluid Substances 0.000 abstract description 2
- 239000000499 gel Substances 0.000 description 62
- 150000004804 polysaccharides Chemical class 0.000 description 48
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 29
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical group OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 25
- 239000000463 material Substances 0.000 description 24
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 22
- 239000000203 mixture Substances 0.000 description 17
- 210000002700 urine Anatomy 0.000 description 17
- 238000006467 substitution reaction Methods 0.000 description 14
- 239000000243 solution Substances 0.000 description 13
- 238000010521 absorption reaction Methods 0.000 description 12
- SHKUUQIDMUMQQK-UHFFFAOYSA-N 2-[4-(oxiran-2-ylmethoxy)butoxymethyl]oxirane Chemical compound C1OC1COCCCCOCC1CO1 SHKUUQIDMUMQQK-UHFFFAOYSA-N 0.000 description 11
- 239000002245 particle Substances 0.000 description 11
- 150000003839 salts Chemical class 0.000 description 10
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 9
- 229920002678 cellulose Polymers 0.000 description 9
- 239000001913 cellulose Substances 0.000 description 9
- 239000004971 Cross linker Substances 0.000 description 8
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 7
- 238000006243 chemical reaction Methods 0.000 description 7
- 150000002772 monosaccharides Chemical group 0.000 description 7
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 6
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 5
- 150000008064 anhydrides Chemical class 0.000 description 5
- 125000002057 carboxymethyl group Chemical group [H]OC(=O)C([H])([H])[*] 0.000 description 5
- 239000007863 gel particle Substances 0.000 description 5
- 238000003756 stirring Methods 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- 239000007864 aqueous solution Substances 0.000 description 4
- 150000001875 compounds Chemical class 0.000 description 4
- AFOSIXZFDONLBT-UHFFFAOYSA-N divinyl sulfone Chemical compound C=CS(=O)(=O)C=C AFOSIXZFDONLBT-UHFFFAOYSA-N 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 4
- 230000020477 pH reduction Effects 0.000 description 4
- 239000002904 solvent Substances 0.000 description 4
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 3
- 229920000856 Amylose Polymers 0.000 description 3
- 239000004593 Epoxy Substances 0.000 description 3
- DNIAPMSPPWPWGF-UHFFFAOYSA-N Propylene glycol Chemical compound CC(O)CO DNIAPMSPPWPWGF-UHFFFAOYSA-N 0.000 description 3
- 150000004805 acidic polysaccharides Chemical class 0.000 description 3
- 230000001580 bacterial effect Effects 0.000 description 3
- 239000003153 chemical reaction reagent Substances 0.000 description 3
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 3
- GYZLOYUZLJXAJU-UHFFFAOYSA-N diglycidyl ether Chemical class C1OC1COCC1CO1 GYZLOYUZLJXAJU-UHFFFAOYSA-N 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 238000010907 mechanical stirring Methods 0.000 description 3
- 230000007935 neutral effect Effects 0.000 description 3
- 239000003960 organic solvent Substances 0.000 description 3
- 230000026731 phosphorylation Effects 0.000 description 3
- 238000006366 phosphorylation reaction Methods 0.000 description 3
- 239000004014 plasticizer Substances 0.000 description 3
- 229920005862 polyol Polymers 0.000 description 3
- 150000003077 polyols Chemical class 0.000 description 3
- HPILSDOMLLYBQF-UHFFFAOYSA-N 2-[1-(oxiran-2-ylmethoxy)butoxymethyl]oxirane Chemical compound C1OC1COC(CCC)OCC1CO1 HPILSDOMLLYBQF-UHFFFAOYSA-N 0.000 description 2
- CPELXLSAUQHCOX-UHFFFAOYSA-M Bromide Chemical compound [Br-] CPELXLSAUQHCOX-UHFFFAOYSA-M 0.000 description 2
- 229920002261 Corn starch Polymers 0.000 description 2
- ZFIVKAOQEXOYFY-UHFFFAOYSA-N Diepoxybutane Chemical compound C1OC1C1OC1 ZFIVKAOQEXOYFY-UHFFFAOYSA-N 0.000 description 2
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 2
- 229920002907 Guar gum Polymers 0.000 description 2
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 2
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 description 2
- 229920000881 Modified starch Polymers 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 2
- 229960000583 acetic acid Drugs 0.000 description 2
- 229920001284 acidic polysaccharide Polymers 0.000 description 2
- 239000002535 acidifier Substances 0.000 description 2
- 239000004411 aluminium Substances 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-O ammonium group Chemical group [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 2
- WPYMKLBDIGXBTP-UHFFFAOYSA-N benzoic acid Chemical compound OC(=O)C1=CC=CC=C1 WPYMKLBDIGXBTP-UHFFFAOYSA-N 0.000 description 2
- 210000001124 body fluid Anatomy 0.000 description 2
- 239000010839 body fluid Substances 0.000 description 2
- 125000004181 carboxyalkyl group Chemical group 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
- 239000008120 corn starch Substances 0.000 description 2
- 239000012153 distilled water Substances 0.000 description 2
- 238000011067 equilibration Methods 0.000 description 2
- 238000001125 extrusion Methods 0.000 description 2
- 235000010417 guar gum Nutrition 0.000 description 2
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 description 2
- WQYVRQLZKVEZGA-UHFFFAOYSA-N hypochlorite Chemical compound Cl[O-] WQYVRQLZKVEZGA-UHFFFAOYSA-N 0.000 description 2
- 150000007522 mineralic acids Chemical class 0.000 description 2
- 235000019426 modified starch Nutrition 0.000 description 2
- 239000001814 pectin Substances 0.000 description 2
- 229920001277 pectin Polymers 0.000 description 2
- 235000010987 pectin Nutrition 0.000 description 2
- XHXFXVLFKHQFAL-UHFFFAOYSA-N phosphoryl trichloride Chemical compound ClP(Cl)(Cl)=O XHXFXVLFKHQFAL-UHFFFAOYSA-N 0.000 description 2
- 229920000058 polyacrylate Polymers 0.000 description 2
- 229920000768 polyamine Polymers 0.000 description 2
- 229920001592 potato starch Polymers 0.000 description 2
- YGSDEFSMJLZEOE-UHFFFAOYSA-N salicylic acid Chemical compound OC(=O)C1=CC=CC=C1O YGSDEFSMJLZEOE-UHFFFAOYSA-N 0.000 description 2
- 229920000247 superabsorbent polymer Polymers 0.000 description 2
- 230000008961 swelling Effects 0.000 description 2
- 238000007669 thermal treatment Methods 0.000 description 2
- 229910052726 zirconium Inorganic materials 0.000 description 2
- ZFTFOHBYVDOAMH-XNOIKFDKSA-N (2r,3s,4s,5r)-5-[[(2r,3s,4s,5r)-5-[[(2r,3s,4s,5r)-3,4-dihydroxy-2,5-bis(hydroxymethyl)oxolan-2-yl]oxymethyl]-3,4-dihydroxy-2-(hydroxymethyl)oxolan-2-yl]oxymethyl]-2-(hydroxymethyl)oxolane-2,3,4-triol Chemical class O[C@H]1[C@H](O)[C@@H](CO)O[C@@]1(CO)OC[C@@H]1[C@@H](O)[C@H](O)[C@](CO)(OC[C@@H]2[C@H]([C@H](O)[C@@](O)(CO)O2)O)O1 ZFTFOHBYVDOAMH-XNOIKFDKSA-N 0.000 description 1
- RYHBNJHYFVUHQT-UHFFFAOYSA-N 1,4-Dioxane Chemical compound C1COCCO1 RYHBNJHYFVUHQT-UHFFFAOYSA-N 0.000 description 1
- FALRKNHUBBKYCC-UHFFFAOYSA-N 2-(chloromethyl)pyridine-3-carbonitrile Chemical compound ClCC1=NC=CC=C1C#N FALRKNHUBBKYCC-UHFFFAOYSA-N 0.000 description 1
- XNWFRZJHXBZDAG-UHFFFAOYSA-N 2-METHOXYETHANOL Chemical compound COCCO XNWFRZJHXBZDAG-UHFFFAOYSA-N 0.000 description 1
- FEBUJFMRSBAMES-UHFFFAOYSA-N 2-[(2-{[3,5-dihydroxy-2-(hydroxymethyl)-6-phosphanyloxan-4-yl]oxy}-3,5-dihydroxy-6-({[3,4,5-trihydroxy-6-(hydroxymethyl)oxan-2-yl]oxy}methyl)oxan-4-yl)oxy]-3,5-dihydroxy-6-(hydroxymethyl)oxan-4-yl phosphinite Chemical compound OC1C(O)C(O)C(CO)OC1OCC1C(O)C(OC2C(C(OP)C(O)C(CO)O2)O)C(O)C(OC2C(C(CO)OC(P)C2O)O)O1 FEBUJFMRSBAMES-UHFFFAOYSA-N 0.000 description 1
- UXBLSWOMIHTQPH-UHFFFAOYSA-N 4-acetamido-TEMPO Chemical compound CC(=O)NC1CC(C)(C)N([O])C(C)(C)C1 UXBLSWOMIHTQPH-UHFFFAOYSA-N 0.000 description 1
- UZFMOKQJFYMBGY-UHFFFAOYSA-N 4-hydroxy-TEMPO Chemical group CC1(C)CC(O)CC(C)(C)N1[O] UZFMOKQJFYMBGY-UHFFFAOYSA-N 0.000 description 1
- 229920000310 Alpha glucan Polymers 0.000 description 1
- 229920000945 Amylopectin Polymers 0.000 description 1
- 239000005711 Benzoic acid Substances 0.000 description 1
- 229920002498 Beta-glucan Polymers 0.000 description 1
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- 229920002101 Chitin Polymers 0.000 description 1
- FBPFZTCFMRRESA-FSIIMWSLSA-N D-Glucitol Natural products OC[C@H](O)[C@H](O)[C@@H](O)[C@H](O)CO FBPFZTCFMRRESA-FSIIMWSLSA-N 0.000 description 1
- FBPFZTCFMRRESA-KVTDHHQDSA-N D-Mannitol Chemical compound OC[C@@H](O)[C@@H](O)[C@H](O)[C@H](O)CO FBPFZTCFMRRESA-KVTDHHQDSA-N 0.000 description 1
- FBPFZTCFMRRESA-JGWLITMVSA-N D-glucitol Chemical compound OC[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO FBPFZTCFMRRESA-JGWLITMVSA-N 0.000 description 1
- PHOQVHQSTUBQQK-SQOUGZDYSA-N D-glucono-1,5-lactone Chemical compound OC[C@H]1OC(=O)[C@H](O)[C@@H](O)[C@@H]1O PHOQVHQSTUBQQK-SQOUGZDYSA-N 0.000 description 1
- 206010012444 Dermatitis diaper Diseases 0.000 description 1
- 208000003105 Diaper Rash Diseases 0.000 description 1
- XTHFKEDIFFGKHM-UHFFFAOYSA-N Dimethoxyethane Chemical compound COCCOC XTHFKEDIFFGKHM-UHFFFAOYSA-N 0.000 description 1
- BRLQWZUYTZBJKN-UHFFFAOYSA-N Epichlorohydrin Chemical compound ClCC1CO1 BRLQWZUYTZBJKN-UHFFFAOYSA-N 0.000 description 1
- 229920002670 Fructan Polymers 0.000 description 1
- 229920000926 Galactomannan Polymers 0.000 description 1
- 229920002581 Glucomannan Polymers 0.000 description 1
- 229920002488 Hemicellulose Polymers 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical group [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229920000161 Locust bean gum Polymers 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- 229930195725 Mannitol Natural products 0.000 description 1
- 240000007594 Oryza sativa Species 0.000 description 1
- 235000007164 Oryza sativa Nutrition 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 239000002202 Polyethylene glycol Substances 0.000 description 1
- 229910006069 SO3H Inorganic materials 0.000 description 1
- 229920002305 Schizophyllan Polymers 0.000 description 1
- 244000061456 Solanum tuberosum Species 0.000 description 1
- 235000002595 Solanum tuberosum Nutrition 0.000 description 1
- 235000021307 Triticum Nutrition 0.000 description 1
- 244000098338 Triticum aestivum Species 0.000 description 1
- 229920004890 Triton X-100 Polymers 0.000 description 1
- 239000013504 Triton X-100 Substances 0.000 description 1
- 240000008042 Zea mays Species 0.000 description 1
- 235000005824 Zea mays ssp. parviglumis Nutrition 0.000 description 1
- 235000002017 Zea mays subsp mays Nutrition 0.000 description 1
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 1
- VJHCJDRQFCCTHL-UHFFFAOYSA-N acetic acid 2,3,4,5,6-pentahydroxyhexanal Chemical compound CC(O)=O.OCC(O)C(O)C(O)C(O)C=O VJHCJDRQFCCTHL-UHFFFAOYSA-N 0.000 description 1
- 150000008065 acid anhydrides Chemical class 0.000 description 1
- 239000008186 active pharmaceutical agent Substances 0.000 description 1
- 125000003172 aldehyde group Chemical group 0.000 description 1
- 235000010443 alginic acid Nutrition 0.000 description 1
- 229920000615 alginic acid Polymers 0.000 description 1
- 125000000217 alkyl group Chemical group 0.000 description 1
- 125000003277 amino group Chemical group 0.000 description 1
- 230000001588 bifunctional effect Effects 0.000 description 1
- 229920001222 biopolymer Polymers 0.000 description 1
- 230000003139 buffering effect Effects 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- PASHVRUKOFIRIK-UHFFFAOYSA-L calcium sulfate dihydrate Chemical compound O.O.[Ca+2].[O-]S([O-])(=O)=O PASHVRUKOFIRIK-UHFFFAOYSA-L 0.000 description 1
- 239000004202 carbamide Substances 0.000 description 1
- 150000001735 carboxylic acids Chemical class 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 229910001919 chlorite Inorganic materials 0.000 description 1
- 229910052619 chlorite group Inorganic materials 0.000 description 1
- QBWCMBCROVPCKQ-UHFFFAOYSA-N chlorous acid Chemical compound OCl=O QBWCMBCROVPCKQ-UHFFFAOYSA-N 0.000 description 1
- 235000005822 corn Nutrition 0.000 description 1
- MGNCLNQXLYJVJD-UHFFFAOYSA-N cyanuric chloride Chemical compound ClC1=NC(Cl)=NC(Cl)=N1 MGNCLNQXLYJVJD-UHFFFAOYSA-N 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 150000004985 diamines Chemical class 0.000 description 1
- 125000005442 diisocyanate group Chemical group 0.000 description 1
- 230000032050 esterification Effects 0.000 description 1
- 238000005886 esterification reaction Methods 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 239000012362 glacial acetic acid Substances 0.000 description 1
- 229960003681 gluconolactone Drugs 0.000 description 1
- 239000000665 guar gum Substances 0.000 description 1
- 229960002154 guar gum Drugs 0.000 description 1
- 229940093915 gynecological organic acid Drugs 0.000 description 1
- 239000001257 hydrogen Chemical group 0.000 description 1
- 229910052739 hydrogen Chemical group 0.000 description 1
- 150000001261 hydroxy acids Chemical class 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 150000002576 ketones Chemical class 0.000 description 1
- 238000004898 kneading Methods 0.000 description 1
- 150000002596 lactones Chemical class 0.000 description 1
- 235000010420 locust bean gum Nutrition 0.000 description 1
- 239000000711 locust bean gum Substances 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 229910052943 magnesium sulfate Inorganic materials 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- FPYJFEHAWHCUMM-UHFFFAOYSA-N maleic anhydride Chemical class O=C1OC(=O)C=C1 FPYJFEHAWHCUMM-UHFFFAOYSA-N 0.000 description 1
- 239000000594 mannitol Substances 0.000 description 1
- 235000010355 mannitol Nutrition 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Chemical class 0.000 description 1
- 229910000402 monopotassium phosphate Inorganic materials 0.000 description 1
- 235000019796 monopotassium phosphate Nutrition 0.000 description 1
- HWPKGOGLCKPRLZ-UHFFFAOYSA-M monosodium citrate Chemical compound [Na+].OC(=O)CC(O)(C([O-])=O)CC(O)=O HWPKGOGLCKPRLZ-UHFFFAOYSA-M 0.000 description 1
- 239000002524 monosodium citrate Substances 0.000 description 1
- 235000018342 monosodium citrate Nutrition 0.000 description 1
- 239000004570 mortar (masonry) Substances 0.000 description 1
- 150000007524 organic acids Chemical class 0.000 description 1
- 235000005985 organic acids Nutrition 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- FJKROLUGYXJWQN-UHFFFAOYSA-N papa-hydroxy-benzoic acid Natural products OC(=O)C1=CC=C(O)C=C1 FJKROLUGYXJWQN-UHFFFAOYSA-N 0.000 description 1
- KHIWWQKSHDUIBK-UHFFFAOYSA-N periodic acid Chemical compound OI(=O)(=O)=O KHIWWQKSHDUIBK-UHFFFAOYSA-N 0.000 description 1
- 150000004965 peroxy acids Chemical class 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
- 125000002467 phosphate group Chemical group [H]OP(=O)(O[H])O[*] 0.000 description 1
- ACVYVLVWPXVTIT-UHFFFAOYSA-N phosphinic acid Chemical group O[PH2]=O ACVYVLVWPXVTIT-UHFFFAOYSA-N 0.000 description 1
- 230000000865 phosphorylative effect Effects 0.000 description 1
- 229920000728 polyester Polymers 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920001223 polyethylene glycol Polymers 0.000 description 1
- 229920001451 polypropylene glycol Polymers 0.000 description 1
- 230000008092 positive effect Effects 0.000 description 1
- GNSKLFRGEWLPPA-UHFFFAOYSA-M potassium dihydrogen phosphate Chemical compound [K+].OP(O)([O-])=O GNSKLFRGEWLPPA-UHFFFAOYSA-M 0.000 description 1
- LWIHDJKSTIGBAC-UHFFFAOYSA-K potassium phosphate Substances [K+].[K+].[K+].[O-]P([O-])([O-])=O LWIHDJKSTIGBAC-UHFFFAOYSA-K 0.000 description 1
- 102000004169 proteins and genes Human genes 0.000 description 1
- 108090000623 proteins and genes Proteins 0.000 description 1
- 230000005588 protonation Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000011541 reaction mixture Substances 0.000 description 1
- 238000009717 reactive processing Methods 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 235000009566 rice Nutrition 0.000 description 1
- 229960004889 salicylic acid Drugs 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 239000000600 sorbitol Substances 0.000 description 1
- 238000003892 spreading Methods 0.000 description 1
- 125000001424 substituent group Chemical group 0.000 description 1
- 229940014800 succinic anhydride Drugs 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L sulfate group Chemical group S(=O)(=O)([O-])[O-] QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- LSNNMFCWUKXFEE-UHFFFAOYSA-L sulfite Chemical compound [O-]S([O-])=O LSNNMFCWUKXFEE-UHFFFAOYSA-L 0.000 description 1
- 239000002982 water resistant material Substances 0.000 description 1
- 229920001285 xanthan gum Polymers 0.000 description 1
- 239000000230 xanthan gum Substances 0.000 description 1
- 235000010493 xanthan gum Nutrition 0.000 description 1
- 229940082509 xanthan gum Drugs 0.000 description 1
- 229920001221 xylan Polymers 0.000 description 1
- 150000004823 xylans Chemical class 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S526/00—Synthetic resins or natural rubbers -- part of the class 520 series
- Y10S526/903—Monomer polymerized in presence of transition metal containing catalyst and hydrocarbon additive affecting polymer properties of catalyst activity
Definitions
- the present invention relates to a superabsorbent material which has enhanced odour control and prevents bacterial growth, based on polysaccharides, and to a method of producing such material.
- Superabsorbent materials of various types are known in the art. Examples are crosslinked polyacrylates and polysaccharides grafted with polyacrylates.
- a problem related to the use of superabsorbent materials is the odour caused by urine components which cause superabsorbent materials to become objectionable long before their maximum absorbing capacity has been used.
- the known absorbent materials are normally based on non-renewable and/or non-biodegradable raw materials. Consequently, there is a need for superabsorbent materials, which have odour control and reduced bacterial growth when contacted with body fluids, and which are biodegradable.
- WO 98/27117 discloses a superabsorbent polysaccharide derivative obtained by oxidation and crosslinking of a polysaccharide such as starch, in which at least 0.1 carbinol group per monosaccharide unit of the polysaccharide derivative has been oxidised to a carboxyl group, the total number of carboxyl groups per monosaccharide unit being 0.2-3.0, and the derivative results from reaction with at least 0.001 equivalent of crosslinking agent per monosaccharide unit.
- the derivatives are not devised for odour control.
- EP-A-202127 discloses superabsorbent articles for reducing diaper rash, which contain acid in distinct zones to control the skin pH between 3.0 and 5.5.
- polysaccharide containing acidic groups is understood to comprise polysaccharides having a pK of less than 5, down to about 1.5.
- Such polysaccharides may contain carboxylic groups, sulphonic groups (—(O)—SO 2 —OH), phosphonic groups (—(O)—PO(OH) 2 ), ammonium groups (—NR 2 H + , wherein R is alkyl or hydrogen) and combinations thereof
- the carboxylic groups may be present as a result of carboxyalkylation, in particular carboxymethylation, or as a result of reaction with an anhydride such as maleic or succulic anhydride or as a result of oxidation, e.g.
- a hydroxymethyl group (—CH 2 OH, usually at C6 of a monosaccharide unit), or of a bis(hydroxymethylene) group (—CHOH—CHOH—, usually at C2-C3 of a monosaccharide unit).
- the phosphonic groups may be present as phosphate groups, resulting e.g. from reaction with phosphorylating agents (see e.g. WO 97/28298), or as phosphonic or phosphinic acid groups, resulting e.g. from reaction with halomethyl phosphonic acids.
- the sulphonic acids may be present e.g as sulphate groups or as a result of sulphite addition to polysaccharide aldehydes (see e.g. WO 99/29354) or to maleic anhydride adducts (products with —O—CO—CH—CH(COOH)—SO 3 H groups).
- the ammonium groups are also acidic groups, and can result from protonation of amine groups, such as in chitosan-type polysaccharides or in aminoalkylated polysaccharides.
- the polysaccharides may be ⁇ -glucans like starch, amylose and amylopectin, ⁇ -glucans like cellulose and chitin and scleroglucan, galactomannans like guar gum (guaran) and locust bean gum, glucomannans including e.g. xanthan gum, fructans, (arabino)xylans, galactans including alginates and pectin and other mixed polysaccharides.
- Starch and cellulose are particularly preferred.
- Starch may be derived from any suitable source, such as corn, wheat, potato, rice and the like; it may also be a residual, crude or lower-grade starch product containing minor amounts of other biopolymers such as cellulose, pectin or protein. Cellulose may also contain minor amounts of other materials such as hemicellulose.
- the polysaccharides may comprise non-ionic, non-carboxylated derivatives such as hydroxyalkyl polysaccharides, but the presence of such non-ionic derivatives does not have a particular advantage.
- the chain length of the polysaccharides is important although there is no critical minimum for the molecular weight. In general, polysaccharides having a molecular weight of more than 1,000 are preferred. A molecular weight above about 25,000 may have a positive effect on the properties of the oxidised product.
- the acidic polysaccharide can be a carboxymethyl polysaccharide without further substitution, such as carboxyrnethyl cellulose, preferably having a degree of substitution of 0.3-3.0, more preferably 0.5-1.5.
- the process advantageously comprises the further step of contacting the crosslinked polysaccharide with an organic solvent which is at least partly miscible with water, between step (b) and step (c).
- the organic solvent is preferably a water-rmiscible alcohol such as methanol, ethanol, methoxyethanol or isopropanol, a water-miscible ether such as dioxane, tetrahydrofiran or dimethoxyethane, or a water-miscible ketone, such as acetone. Most preferred are methanol and ethanol.
- the amount of solvent can be e.g. 2-30 times the amount of the gelled poly-saccharide.
- the water-miscible solvent is evaporated before or during step (d).
- the carboxymethylated polysaccharide can also be a carboxyrnethyl polysaccharide containing further carboxyl groups produced by oxidation of saccharide carbinol groups.
- Such carboxyl groups may be 2- and/or 3-carboxyl groups obtained by oxidation of anhydroglycose rings of the polysaccharide using hypochliorite or periodate/chlorite, but preferably they are 6-carboxyl groups obtained by oxidation of the 6-hydroxymethyl group, e.g.
- TEMPO nitroxyl compound
- carboxy-carboxymethyl poly-saccharide such as 6-carboxycarboxymethyl starch or 6-carboxy-carboxymethyl-cellulose
- the degree of substitution for carboxymethyl is preferably 0.2-0.8, especially 0.3-0.6
- the degree of subtitution for (6-carboxyl groups is preferably 0.1-0.5, more preferably 0.15-0.4.
- Suitable oxidation methods are described in WO 98/27117 and references cited therein.
- TEMPO oxidation may be performed with hypochlorite with or without bromide as a catalyst, or with peracid/bromide or another oxidant.
- Unsubstituted TEMPO or 4-hydroxy or 4-acetamido-TEMPO or mixtures thereof may be used.
- the salts may advantageously be removed after the oxidation reaction.
- the acidic polysaccharide may contain both other acidic groups obtained by substitution, and carboxyl groups obtained by oxidation.
- Such other acidic groups obtained by oxidation include e.g. phosphonic groups obtained by phosphorylation of the polysaccharide, sulphonyl groups and carboxyalkylcarbonyl groups obtained by reaction with a dicarboxylic anhydride.
- Substitution and oxidation may be performed in either order, e.g. first phosphorylation and then oxidation, or first oxidation and then phosphorylation. Combinations of different acidic substituents e.g. carboxylalkyl groups and phosphonic groups are also suitable.
- the polysaccharide containing acidic groups can also be a carboxylated poly-saccharide wherein the carboxyl groups have been introduced by oxidation of saccharide carbinol groups in a manner as described above, without carboxyalkylation.
- oxidised polysaccharides include dicarboxy polysaccharides (obtained by C2-C3 oxidation) and, especially 6-carboxy polysaccharides, e.g. obtained by TEMPO oxidation, especially 6-carboxy starch. These polysaccharides do not require the use of a water-miscible solvent after crosslinking.
- the polysaccharide containing acidic groups may also be a mixture of acidic poly-saccharides as described above.
- a particularly useful mixture is a mixture of carboxymethyl cellulose and 6-carboxy starch, e.g. in a ratio of between 1:1 and 1:20.
- Other mixtures are also quite useful, e.g. carboxymethyl cellulose and carboxymethyl starch, or carboxymethyl starch and cellulose phosphate having a degree of substitution of about 0.3 to about 0.5.
- a gel is defined herein as a polymeric network based on polysaccharides, which swells in water and does not dissolve in water.
- Crosslinking agents are reagents containing two or more functions capable of reacting with a hydroxyl group, resulting in intra- and inter-molecular bonds between different mono-saccharide units.
- Suitable cross-linking agents may act on the hydroxyl groups of different polysaccharide chains and include divinyl sulphone, epichlorohydrin, diepoxybutane, diglycidyl ethers, diisocyanates, cyanuric chloride, trimetaphosphates, phosphoryl chloride, and mixed anhydrides, and also inorganic crosslinkers such as aluminium and zirconium ions, but are not restricted to these examples. Mixtures of crosslinkers may also be used.
- crosslinkers in particular for crosslinking at elevated temperature and/or concentration, are crosslinkers that are active under neutral or acidic conditions, such as bis-epoxy crosslinkers, for example diepoxybutane, 1,5-diepoxyhexane, 1,7-diepoxyoctane, bis-glycidyl ether, glycol bis-glycidyl ether, butanediol bis-glycidyl ether and the like, as well as mixtures of different crosslinkers.
- Crosslinking can also be performed using carboxyl or aldehyde groups formed by oxidation or carboxyl groups introduced by carboxyalkylation, e.g.
- crosslinking is performed under conditions of increased temperatures and high concentrations.
- the temperatures are typically at least 100° C., more preferably between 120 and 180° C.
- the concentration of the polysaccharide to be crosslinked is at least 20% by weight, more particularly between 25 and 65% by weight with respect to the total aqueous crosslinking mixture.
- the crosslinking mixture may further contain a plasticiser such as a polyol. Suitable polyol plasticisers include glycerol, ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, glycol and glycerol monoesters, sorbitol, mannitol, monosaccharides, citric acid monoesters and the like.
- the amount of plasticiser may vary from 1 to 25% weight of the crosslinking mixture.
- the crosslinking can be conveniently performed in a kneading apparatus or an extruder under conditions of reactive processing.
- the various components of the crosslinking mixture can be mixed before entering the extruder, or one or more of them, e.g. the crosslinking agent, may be added at a later stage in the extruder.
- the crosslinked polysaccharide is treated with an acid so as to reduce the pH to 3.5 to 5.5.
- the acidification takes place before cross-linking, and an adjustment of a pH to between 3.5 and 5.5 may or may not be needed after the crosslinking step.
- Suitable acidifying reagents include inorganic and organic acids such as hydrochloric, phosphoric, acetic acid etc. If crosslinking is performed under normal conditions (ambient temperature or up to about 100° C., atmospheric pressure, lower concentration) or before acidification, it is preferred that the polysaccharide is acidified to pH 4.9 or lower. After acidification, the cross-linked, gel-like material is comminuted to smaller particles, e.g. in the range of 0.5-5 mm.
- an additional post-crosslinking step may be applied to strengthen the gel.
- This post-crosslinking may be performed after the comminuting step c or even after the drying step d, resulting in different swelling degrees of the gel particles obtained.
- the crosslinking agent to be used in this post-crosslinking step can be the same as those referred to above for the first crosslinking step. In this procedure, the gel particles are slightly swollen, and treated and mixed with a crosslinking agent, and subsequently the particles are dried at a temperature which depends on the liquid used to swell the gel particles and on the crosslinking agent.
- the post-crosslinking may be performed in the presence of compounds providing further crosslinks at the outside of the gel particle.
- Such compounds may include bifunctional or multifunctional capable of reacting with hydroxyl and (if still present) carboxyl functions, for example diamines, polyamines, polyamide-amine-epichlorohydrin (PAE resin), bis-epoxy compounds, chitosan-like compounds, metal salts (zirconium, aluminium), dialdehydes, or polyaldehyde-polycarboxy starch derivatives.
- the comminuted material is dried, preferably in a fluidised bed drier. Drying can be performed at ambient temperatures, but preferably increased temperatures are used, in particular above 50° C., more in particular above 70° C. Drying times from 15 minutes up to 8 hours or more can be applied. Preferably an additional heat treatment is performed after the initial (fluidised bed) drying; this additional drying step can be performed at 80-150° C. e.g. for 2 minutes to 2 hours, and results in a further enhanced gel strength of the product.
- the invention also pertains to a bacteriologically stable superabsorbent poly-saccharide derivative having odour control of absorbed liquid, as well as to a superabsorbent article in which this derivative is incorporated.
- the derivative and the article preferably have a pH below 5 (down to 3.5) when contacted with neutral or near-neutral water; if necessary, an acidifying agent can be incorporated in a sufficient amount to maintain the required low pH.
- Suitable acidifying agents include organic di- or poly-carboxylic acids such as citric, maleic, fulmaric, oxalic, malonic, succinic, tataric and similar acids, hydroxyacids such as gluconic, ascorbic, glycolic, glyceric, lactic, malic, salicylic acid and the like, as well as benzoic acid and phosphoric and other inorganic acids. These acids may be used in combination with their partially neutralised salts (e.g. monosodium citrate or monopotassium phosphate) to provide buffering capacity. Also, neutral materials such as acid anhydrides and lactones, e.g. maleid anhydride, succinic anhydride, ⁇ -gluconolactone, can be incorporated for lowering the pH.
- organic di- or poly-carboxylic acids such as citric, maleic, fulmaric, oxalic, malonic, succinic, tataric and similar acids, hydroxyacids such as
- the superabsorbent polysaccharides combine high absorption capacity with control of bacterial growth and control of odour, as well as with biodegradability.
- the absorption capacity can be expressed as free swelling capacity (FSC) and the centrifugal retention capacity (CRC), and with the absorption under load (AUL), using synthetic urine (SU) as test liquid.
- the composition of the synthetic urine is as follows: 300 mM urea, 60 mM KCl, 130 mM. NaCl, 2.0 mM CaSO 4 .2H 2 O, 3.5 mM MgSO 4 , and 1 mg/l Triton X-100 in deionised water.
- the superabsorbent polysaccharide derivatives of the invention can be used for absorbing liquids, especially of body fluids which contain various salts and non-ionic substances.
- the product is particularly suitable for the production of absorbent hygiene articles, such as diapers, sanitary napkins and the like. Such articles can be produced entirely on the basis of the polysaccharides according to the invention, but they can also contain conventional absorbent materials, such as cellulose pulp in addition to the absorbents according to the invention.
- the absorbent article is preferably part of a layered product, in which the superabsorbent polymer constitutes at least one layer.
- the absorbent layer can be located between a liquid-pervious top layer and a liquid-impervious bottom layer. In particular the product may have four layers.
- the first one can be a thin, non-woven layer of polyester fibres or other fibres.
- the second layer can be a wadding which is used for acquiring and spreading the absorbed fluid such as urine.
- the third layer can consist of fluff pulp wherein the SAP is spread as fine particles, especially 50-800 ⁇ m.
- the last layer can be a back sheet of a water-resistant material such as polyethylene, which prevents leakage from the layered absorption product.
- Carboxymethyl starch (degree of substitution 0.5) derived from potato starch was converted to 6-carboxy carboxymethyl starch by TEMPO-catalysed oxidation (degree of oxidation 0.25).
- a 20% aqueous solution of the product was cross-linked with different amounts of divinyl sulphone (0.5, 0.6, 0.7 mol % DVS). After 15 hours, an insoluble network was formed.
- the gel was brought into distilled water and allowed to swell. The pH of the material was lowered to pH 4.1 by controlled addition of 1M HCl. After equilibration, the gel was filtrated and dried in a fluidised bed drier at 70° C.
- Carboxymethyl starch (degree of substitution 0.53) derived from high amylose corn starch was converted to 6-carboxy carboxymethyl starch by TEMPO-catalysed oxidation (degree of oxidation 0.09).
- a 20% aqueous solution of the product was cross-linked with different amounts of divinyl sulphone (1.0, 1.5, 2.0, 2.5 mol % DVS). After 16 hours, an insoluble network was formed.
- the gel was brought into distilled water and allowed to swell. The pH of the material was lowered to about pH 4.1 by controlled addition of 1M HCl. After equilibration, the gel was filtrated and dried in a fluidised bed drier at 80° C.
- a 2 wt. % aqueous solution of CMC (Cekol 50,000 from Metsa Specialty Chemicals, degree of substitution 0.8) was prepared and the pH was adjusted to 4.0 by slow addition of HCl under stirring (alternatively, glacial acetic acid can be used according to WO 86/00912, example 2b).
- the required amount of a 10 or 20 vol. % aqueous solution of 1,4-butanediol diglycidyl ether (BDDE) was added and the reaction mixture was thoroughly mixed. The gel obtained was cut into pieces and suspended overnight in a fivefold excess of methanol.
- the dried gel was ground and washed with excess demi water on a 80 ⁇ m sieve to remove any salts present. Then the gel was dried in the fluidised bed drier at 80° C. for 1 hour.
- the material was characterised in synthetic urine with the following results: 93% TOS/7% CMC: FSC: 26 g/g, CRC: 15.5 g/g, AUL: 19 g/g, pH gel 4.9.
- TEMPO-oxidised starch (TOS, degree of oxidation 0.70) was dissolved in 20 ml of demi water under mechanical stirring for 1 h. The pH was adjusted to 4.5 using 25% HCl. The mixture was crosslinked with 2.0 mol % of BDDE (113 ⁇ l) at 50° C. for 18 hours. The gel was chopped and the pieces were dried in a fluidised bed drier for 30 minutes at 100° C. The dried gel was ground and washed with excess demi water on a 80 ⁇ m sieve to remove any salts present Then the gel was dried in the fluidised bed drier at 80° C. for 1 hour. The material was characterised in synthetic urine with the following results: 100% TOS: FSC: 27 g/g, CRC: 16 g/g, AUL: 19 g/g, pH gel 4.8.
- the dried gels were ground and re-swollen in an excess of demi water. By addition of 2 M HCl, pH of the gel was adjusted to pH of 4.7-4.8 in demi water. Subsequently, the re-swollen gels were washed with excess demi water on a 80 ⁇ m sieve to remove salts present. Then the gels were dried in the fluidised bed drier at 100° C. for 1 hour.
- TOS desalted TEMPO-oxidised starch
- the pH of solutions was about 4.6.
- CMC Cekol 50,000, degree of substitution 0.8
- Mixtures were cross-linked with 0.7 mol % of BDDE at 50° C. for 18 hours, 70° C. for 2.5 hours, and 100° C. for 1 hour, respectively.
- Gels obtained were sized and, subsequently, dried in a fluidised bed drier for 1 hour at 100° C. The dried gels were ground and re-swollen in an excess of demi water.
- Dried gel particles were re-swollen in 10 liters of demi water, and subsequently dried in the fluidised bed drier for 1.5 hours at 80 ° C.
- the material was characterised in synthetic urine with the following results: FSC: 27 g/g, CRC: 14.5 g/g, AUL: 17.5 g/g, pH gel 4.9.
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Abstract
A process is disclosed for producing an acidic superabsorbent polysaccharide derivative, comprising the steps of. (a) crosslinking at least one polysaceharide containing acidic groups, such as carboxymethyl cellulose and/or 6-carboxy stanch, with a crosslinking agent to produce a gel; (b) if necessary, adjusting the pH of the polysaccharide to a value between 3.5 and 5.5; (c) comminuting the acidified polysaccharide gel; and (d) drying the comminuted polysaccharide at elevated temperature. The superabsorbent polysaccharide obtainable by this process has a pH below 5 and provides odour control when contacted with malodorous fluids.
Description
- The present invention relates to a superabsorbent material which has enhanced odour control and prevents bacterial growth, based on polysaccharides, and to a method of producing such material.
- Superabsorbent materials of various types are known in the art. Examples are crosslinked polyacrylates and polysaccharides grafted with polyacrylates. A problem related to the use of superabsorbent materials is the odour caused by urine components which cause superabsorbent materials to become objectionable long before their maximum absorbing capacity has been used. Furthermore, the known absorbent materials are normally based on non-renewable and/or non-biodegradable raw materials. Consequently, there is a need for superabsorbent materials, which have odour control and reduced bacterial growth when contacted with body fluids, and which are biodegradable.
- WO 98/27117 discloses a superabsorbent polysaccharide derivative obtained by oxidation and crosslinking of a polysaccharide such as starch, in which at least 0.1 carbinol group per monosaccharide unit of the polysaccharide derivative has been oxidised to a carboxyl group, the total number of carboxyl groups per monosaccharide unit being 0.2-3.0, and the derivative results from reaction with at least 0.001 equivalent of crosslinking agent per monosaccharide unit. The derivatives are not devised for odour control. U.S. Pat. No. 5,247,072 describes superabsorbent carboxyalkyl polysaccharides, especially carboxymethyl cellulose, without odour control, obtained by crosslinking as a result of heat treatment. EP-A-202127 discloses superabsorbent articles for reducing diaper rash, which contain acid in distinct zones to control the skin pH between 3.0 and 5.5.
- It has been found that a superabsorbent polymer with improved odour control can be produced by a process comprising the steps of:
- (a) crosslinking at least one polysaccharide containing acidic groups with a crosslinking agent to produce a gel;
- (b) ensuring that pH of the polysaccharide is between 3.5 and 5.5 and, if necessary, adjusting the pH to between 3.5 and 5.5, especially to between 3.9 and 4.9;
- (c) comminuting the acidified polysaccharide gel; and
- (d) drying the comminuted polysaccharide at elevated temperature.
- The term “polysaccharide containing acidic groups” is understood to comprise polysaccharides having a pK of less than 5, down to about 1.5. Such polysaccharides may contain carboxylic groups, sulphonic groups (—(O)—SO2—OH), phosphonic groups (—(O)—PO(OH)2), ammonium groups (—NR2H+, wherein R is alkyl or hydrogen) and combinations thereof The carboxylic groups may be present as a result of carboxyalkylation, in particular carboxymethylation, or as a result of reaction with an anhydride such as maleic or succulic anhydride or as a result of oxidation, e.g. of a hydroxymethyl group (—CH2OH, usually at C6 of a monosaccharide unit), or of a bis(hydroxymethylene) group (—CHOH—CHOH—, usually at C2-C3 of a monosaccharide unit).
- The phosphonic groups may be present as phosphate groups, resulting e.g. from reaction with phosphorylating agents (see e.g. WO 97/28298), or as phosphonic or phosphinic acid groups, resulting e.g. from reaction with halomethyl phosphonic acids. The sulphonic acids may be present e.g as sulphate groups or as a result of sulphite addition to polysaccharide aldehydes (see e.g. WO 99/29354) or to maleic anhydride adducts (products with —O—CO—CH—CH(COOH)—SO3H groups). The ammonium groups are also acidic groups, and can result from protonation of amine groups, such as in chitosan-type polysaccharides or in aminoalkylated polysaccharides.
- The polysaccharides may be α-glucans like starch, amylose and amylopectin, β-glucans like cellulose and chitin and scleroglucan, galactomannans like guar gum (guaran) and locust bean gum, glucomannans including e.g. xanthan gum, fructans, (arabino)xylans, galactans including alginates and pectin and other mixed polysaccharides. Starch and cellulose are particularly preferred. Starch may be derived from any suitable source, such as corn, wheat, potato, rice and the like; it may also be a residual, crude or lower-grade starch product containing minor amounts of other biopolymers such as cellulose, pectin or protein. Cellulose may also contain minor amounts of other materials such as hemicellulose.
- The polysaccharides may comprise non-ionic, non-carboxylated derivatives such as hydroxyalkyl polysaccharides, but the presence of such non-ionic derivatives does not have a particular advantage. The chain length of the polysaccharides is important although there is no critical minimum for the molecular weight. In general, polysaccharides having a molecular weight of more than 1,000 are preferred. A molecular weight above about 25,000 may have a positive effect on the properties of the oxidised product.
- The acidic polysaccharide can be a carboxymethyl polysaccharide without further substitution, such as carboxyrnethyl cellulose, preferably having a degree of substitution of 0.3-3.0, more preferably 0.5-1.5. For such carboxymethylated polysaccharides, the process advantageously comprises the further step of contacting the crosslinked polysaccharide with an organic solvent which is at least partly miscible with water, between step (b) and step (c). The organic solvent is preferably a water-rmiscible alcohol such as methanol, ethanol, methoxyethanol or isopropanol, a water-miscible ether such as dioxane, tetrahydrofiran or dimethoxyethane, or a water-miscible ketone, such as acetone. Most preferred are methanol and ethanol. The amount of solvent can be e.g. 2-30 times the amount of the gelled poly-saccharide. The water-miscible solvent is evaporated before or during step (d).
- The carboxymethylated polysaccharide can also be a carboxyrnethyl polysaccharide containing further carboxyl groups produced by oxidation of saccharide carbinol groups. Such carboxyl groups may be 2- and/or 3-carboxyl groups obtained by oxidation of anhydroglycose rings of the polysaccharide using hypochliorite or periodate/chlorite, but preferably they are 6-carboxyl groups obtained by oxidation of the 6-hydroxymethyl group, e.g. with a nitroxyl compound (TEMPO) as a catalyst In such carboxy-carboxymethyl poly-saccharide, such as 6-carboxycarboxymethyl starch or 6-carboxy-carboxymethyl-cellulose, the degree of substitution for carboxymethyl is preferably 0.2-0.8, especially 0.3-0.6, and the degree of subtitution for (6-carboxyl groups is preferably 0.1-0.5, more preferably 0.15-0.4.
- Suitable oxidation methods are described in WO 98/27117 and references cited therein. TEMPO oxidation may be performed with hypochlorite with or without bromide as a catalyst, or with peracid/bromide or another oxidant. Unsubstituted TEMPO or 4-hydroxy or 4-acetamido-TEMPO or mixtures thereof may be used. When oxidations resulting in salt production are used, the salts may advantageously be removed after the oxidation reaction.
- Similarly, the acidic polysaccharide may contain both other acidic groups obtained by substitution, and carboxyl groups obtained by oxidation. Such other acidic groups obtained by oxidation include e.g. phosphonic groups obtained by phosphorylation of the polysaccharide, sulphonyl groups and carboxyalkylcarbonyl groups obtained by reaction with a dicarboxylic anhydride. Substitution and oxidation may be performed in either order, e.g. first phosphorylation and then oxidation, or first oxidation and then phosphorylation. Combinations of different acidic substituents e.g. carboxylalkyl groups and phosphonic groups are also suitable.
- In such oxidised and subsituted (carboxyalkyl or other) polysaccharides the addition of an organic water-miscible solvent can be dispensed with, as a gel with the required structure already results from direct cross-linking.
- The polysaccharide containing acidic groups can also be a carboxylated poly-saccharide wherein the carboxyl groups have been introduced by oxidation of saccharide carbinol groups in a manner as described above, without carboxyalkylation. Such oxidised polysaccharides include dicarboxy polysaccharides (obtained by C2-C3 oxidation) and, especially 6-carboxy polysaccharides, e.g. obtained by TEMPO oxidation, especially 6-carboxy starch. These polysaccharides do not require the use of a water-miscible solvent after crosslinking.
- The polysaccharide containing acidic groups may also be a mixture of acidic poly-saccharides as described above. A particularly useful mixture is a mixture of carboxymethyl cellulose and 6-carboxy starch, e.g. in a ratio of between 1:1 and 1:20. Other mixtures are also quite useful, e.g. carboxymethyl cellulose and carboxymethyl starch, or carboxymethyl starch and cellulose phosphate having a degree of substitution of about 0.3 to about 0.5.
- The polysaccharide containing acidic groups is reacted with a crosslinking agent to produce a gel. A gel is defined herein as a polymeric network based on polysaccharides, which swells in water and does not dissolve in water. Crosslinking agents are reagents containing two or more functions capable of reacting with a hydroxyl group, resulting in intra- and inter-molecular bonds between different mono-saccharide units. Suitable cross-linking agents may act on the hydroxyl groups of different polysaccharide chains and include divinyl sulphone, epichlorohydrin, diepoxybutane, diglycidyl ethers, diisocyanates, cyanuric chloride, trimetaphosphates, phosphoryl chloride, and mixed anhydrides, and also inorganic crosslinkers such as aluminium and zirconium ions, but are not restricted to these examples. Mixtures of crosslinkers may also be used.
- Especially preferred crosslinkers, in particular for crosslinking at elevated temperature and/or concentration, are crosslinkers that are active under neutral or acidic conditions, such as bis-epoxy crosslinkers, for example diepoxybutane, 1,5-diepoxyhexane, 1,7-diepoxyoctane, bis-glycidyl ether, glycol bis-glycidyl ether, butanediol bis-glycidyl ether and the like, as well as mixtures of different crosslinkers. Crosslinking can also be performed using carboxyl or aldehyde groups formed by oxidation or carboxyl groups introduced by carboxyalkylation, e.g. using polyols, polyamines or other polyfunctional reagents. Esterification and other crosslinking methods described herein can also be effected intramolecularly at the surface between the carboxyl group of one polysaccharide chain and a hydroxyl group of another chain as known in the art. This interhain crosslinking can be catalysed by an acid or a multivalent ion such as magnesium or calcium, or by heating. Divinyl sulphone is another preferred crosslinker. Crosslinking of starch and other poly-saccharides is well-known in the art. A description of crosslinking agents and reaction conditions can be found e.g. in “Starch Derivatives: Production and Uses” by M. W. Rutenberg and D. Solarek, Acad. Press Inc., 1984, pages 324-332.
- According to a preferred embodiment of the invention, crosslinking is performed under conditions of increased temperatures and high concentrations. The temperatures are typically at least 100° C., more preferably between 120 and 180° C. The concentration of the polysaccharide to be crosslinked is at least 20% by weight, more particularly between 25 and 65% by weight with respect to the total aqueous crosslinking mixture. The crosslinking mixture may further contain a plasticiser such as a polyol. Suitable polyol plasticisers include glycerol, ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, glycol and glycerol monoesters, sorbitol, mannitol, monosaccharides, citric acid monoesters and the like. The amount of plasticiser may vary from 1 to 25% weight of the crosslinking mixture. The crosslinking can be conveniently performed in a kneading apparatus or an extruder under conditions of reactive processing. The various components of the crosslinking mixture can be mixed before entering the extruder, or one or more of them, e.g. the crosslinking agent, may be added at a later stage in the extruder.
- After crosslinking, the crosslinked polysaccharide is treated with an acid so as to reduce the pH to 3.5 to 5.5. However, if the crosslinking is performed under acidic conditions, such as with bis-epoxy crosslinkers, the acidification takes place before cross-linking, and an adjustment of a pH to between 3.5 and 5.5 may or may not be needed after the crosslinking step. Suitable acidifying reagents include inorganic and organic acids such as hydrochloric, phosphoric, acetic acid etc. If crosslinking is performed under normal conditions (ambient temperature or up to about 100° C., atmospheric pressure, lower concentration) or before acidification, it is preferred that the polysaccharide is acidified to pH 4.9 or lower. After acidification, the cross-linked, gel-like material is comminuted to smaller particles, e.g. in the range of 0.5-5 mm.
- Instead of or in addition to the treatment with the water-miscible organic solvent described above, an additional post-crosslinking step (surface crosslinking) may be applied to strengthen the gel. This post-crosslinking may be performed after the comminuting step c or even after the drying step d, resulting in different swelling degrees of the gel particles obtained. The crosslinking agent to be used in this post-crosslinking step can be the same as those referred to above for the first crosslinking step. In this procedure, the gel particles are slightly swollen, and treated and mixed with a crosslinking agent, and subsequently the particles are dried at a temperature which depends on the liquid used to swell the gel particles and on the crosslinking agent. The post-crosslinking may be performed in the presence of compounds providing further crosslinks at the outside of the gel particle. Such compounds may include bifunctional or multifunctional capable of reacting with hydroxyl and (if still present) carboxyl functions, for example diamines, polyamines, polyamide-amine-epichlorohydrin (PAE resin), bis-epoxy compounds, chitosan-like compounds, metal salts (zirconium, aluminium), dialdehydes, or polyaldehyde-polycarboxy starch derivatives.
- The comminuted material is dried, preferably in a fluidised bed drier. Drying can be performed at ambient temperatures, but preferably increased temperatures are used, in particular above 50° C., more in particular above 70° C. Drying times from 15 minutes up to 8 hours or more can be applied. Preferably an additional heat treatment is performed after the initial (fluidised bed) drying; this additional drying step can be performed at 80-150° C. e.g. for 2 minutes to 2 hours, and results in a further enhanced gel strength of the product.
- The invention also pertains to a bacteriologically stable superabsorbent poly-saccharide derivative having odour control of absorbed liquid, as well as to a superabsorbent article in which this derivative is incorporated. The derivative and the article preferably have a pH below 5 (down to 3.5) when contacted with neutral or near-neutral water; if necessary, an acidifying agent can be incorporated in a sufficient amount to maintain the required low pH. Suitable acidifying agents include organic di- or poly-carboxylic acids such as citric, maleic, fulmaric, oxalic, malonic, succinic, tataric and similar acids, hydroxyacids such as gluconic, ascorbic, glycolic, glyceric, lactic, malic, salicylic acid and the like, as well as benzoic acid and phosphoric and other inorganic acids. These acids may be used in combination with their partially neutralised salts (e.g. monosodium citrate or monopotassium phosphate) to provide buffering capacity. Also, neutral materials such as acid anhydrides and lactones, e.g. maleid anhydride, succinic anhydride, δ-gluconolactone, can be incorporated for lowering the pH.
- The superabsorbent polysaccharides combine high absorption capacity with control of bacterial growth and control of odour, as well as with biodegradability. The absorption capacity can be expressed as free swelling capacity (FSC) and the centrifugal retention capacity (CRC), and with the absorption under load (AUL), using synthetic urine (SU) as test liquid. The composition of the synthetic urine is as follows: 300 mM urea, 60 mM KCl, 130 mM. NaCl, 2.0 mM CaSO4.2H2O, 3.5 mM MgSO4, and 1 mg/l Triton X-100 in deionised water.
- The superabsorbent polysaccharide derivatives of the invention can be used for absorbing liquids, especially of body fluids which contain various salts and non-ionic substances. The product is particularly suitable for the production of absorbent hygiene articles, such as diapers, sanitary napkins and the like. Such articles can be produced entirely on the basis of the polysaccharides according to the invention, but they can also contain conventional absorbent materials, such as cellulose pulp in addition to the absorbents according to the invention. The absorbent article is preferably part of a layered product, in which the superabsorbent polymer constitutes at least one layer. The absorbent layer can be located between a liquid-pervious top layer and a liquid-impervious bottom layer. In particular the product may have four layers. The first one can be a thin, non-woven layer of polyester fibres or other fibres. The second layer can be a wadding which is used for acquiring and spreading the absorbed fluid such as urine. The third layer can consist of fluff pulp wherein the SAP is spread as fine particles, especially 50-800 μm. The last layer can be a back sheet of a water-resistant material such as polyethylene, which prevents leakage from the layered absorption product.
- Carboxymethyl starch (degree of substitution 0.5) derived from potato starch was converted to 6-carboxy carboxymethyl starch by TEMPO-catalysed oxidation (degree of oxidation 0.25). A 20% aqueous solution of the product was cross-linked with different amounts of divinyl sulphone (0.5, 0.6, 0.7 mol % DVS). After 15 hours, an insoluble network was formed. The gel was brought into distilled water and allowed to swell. The pH of the material was lowered to pH 4.1 by controlled addition of 1M HCl. After equilibration, the gel was filtrated and dried in a fluidised bed drier at 70° C. The following absorption characteristics (FSC, CRC, AUL at 2.0 kPa) measured in synthetic urine (SU) were obtained:
Cross-linking degree AUL (g/g) (mol % DVS) FSC (g/g) CRC (g/g) 2 kPa pH gel 0.5 31 19 12 4.1 0.6 30 18 14 4.1 0.7 27.5 17 18.5 4.1 - Carboxymethyl starch (degree of substitution 0.53) derived from high amylose corn starch was converted to 6-carboxy carboxymethyl starch by TEMPO-catalysed oxidation (degree of oxidation 0.09). A 20% aqueous solution of the product was cross-linked with different amounts of divinyl sulphone (1.0, 1.5, 2.0, 2.5 mol % DVS). After 16 hours, an insoluble network was formed. The gel was brought into distilled water and allowed to swell. The pH of the material was lowered to about pH 4.1 by controlled addition of 1M HCl. After equilibration, the gel was filtrated and dried in a fluidised bed drier at 80° C. The above table summarises the absorption characteristics (FSC, CRC, AUL) measured in synthetic urine (SU) as obtained.
Cross-linking degree AUL (g/g) (mol % DVS) FSC (g/g) CRC (g/g) 2 kPa pH gel 1.0 29.5 20 17 4.0 1.5 34.5 20.5 13 4.1 2.0 33.0 18 16 4.3 2.5 28.5 16 17 4.0 -
XL reaction2 FBD FSC CRC AUL DXL1 cond. (° C./h) (° C./min) (g/g) (g/g) (g/g) 10 20°/20 h3 100°/10 m 29 11 17 10 20°/20 h 100°/10 m 34 16 22 10 80°/3 h 100°/10 m 38 18 20 20 50°/8 h 100°/10 m 19.5 6.5 14 10 50°/8 h 100°/10 m 28.5 12 19.5 5 50°/8 h 100°/10 m 31.5 15 20.5 5 50°/15 h 100°/15 m 34.5 18 23 5 50°/15 h 80°/15 m 40 19.5 21 5 50°/15 h 60°/15 m 34 15.5 20 5 50°/15 h 40°/30 m 33 15 18.5 - A 2 wt. % aqueous solution of CMC (Cekol 50,000 from Metsa Specialty Chemicals, degree of substitution 0.8) was prepared and the pH was adjusted to 4.0 by slow addition of HCl under stirring (alternatively, glacial acetic acid can be used according to WO 86/00912, example 2b). The required amount of a 10 or 20 vol. % aqueous solution of 1,4-butanediol diglycidyl ether (BDDE) was added and the reaction mixture was thoroughly mixed. The gel obtained was cut into pieces and suspended overnight in a fivefold excess of methanol. The methanol was filtered out and the gel was milled in a blender, and the particles were dried in a fluidised bed drier (FBD). The dried product was ground in a mortar. The absorption characteristics for synthetic urine (SU) are summarised in the table above, with details on crosslinking and drying.
- A 2 wt. % solution of CMC (Cekol 50,000 from Metsa Specialty Chemicals, degree of substitution 0.8) in 0.05 M aqueous NaOH was reacted with 14 mol % of DVS for 18 hours at room temperature. The gel obtained was chopped in pieces of roughly 3-4 cm and the pieces were brought in a fivefold excess of methanol. The gel was then acidified using 1M HCl to a pH varying from 4.4 to 4.0. After about 24 h the swollen gel was milled in a blender to obtain smaller particles, and then put back in the methanol for another 24 h to achieve homogeneous acidification of the gel material. Thereafter ground particles were dried in a fluidised bed drier at 100° C. for 30 min, and then further heat-treated at 120° C. in an oven for about 30 min. The absorption characteristics for SU are summarised in the following table.
before After thermal treatment thermal treatment amount of acid FSC CRC AUL FSC CRC AUL added (ml) pH gel (g/g) (g/g) (g/g) (g/g) (g/g) (g/g) 28 4.4 83 64 10 40 26 17 30 4.2 57 42 12 29 17 16.5 33 4.0 55 41 13 28 15 16 35 4.0 39 26 13 21 11 15 - Ten grams of CMC (Cekol 50,000) were dissolved in 500 ml NaOH (0.05 mol/l). At room temperature 0.62 ml DVS (14 mol %) was added under stirring. After 18 hours the crosslinked gel (450 g) was chopped into pieces and 28 ml of 1 mol/l HCl was added and thoroughly mixed to decrease the pH of the gel to 4.4. After 1 h 1400 ml of ethanol was added. After one week, the precipitated gel was ground with a blender and dried in an FBD for 30 minutes at 100° C. The dry particles were milled and sieved to obtain a final particle size of 100-800 μm. The following absorption characteristics (FSC, CRC, AUL) measured in synthetic urine were obtained: FSC: 132 g/g; CRC: 111 g/g; AUL: 11 g/g; pH gel 4.4.
- In addition to the sample of example 5, a heat treatment was applied for 30 minutes at 120° C. in an oven to improve the gel strength (AUL). The following absorption characteristics measured in synthetic urine were obtained: FSC: 52 g/g; CRC: 37 g/g; AUL: 17 g/g; pH gel 4.5.
- Ten grams of CMC (Cekol 50,000, DS 0.8) were dissolved in 500 ml water and 8.5 ml 1 mol/l HCl (pH 4.4). Then 1.27 ml of 20% (v/v) BDDE in water (3 mol %) was added with stirring. After 8 hours at 50° C., the crosslinked gel was suspended in a threefold volume of ethanol with stirring. After one week, the precipitated gel was ground into small pieces with a blender and dried in a FBD for 15 minutes at 100° C. The dry particles were milled and sieved to obtain a final particle size of 100-800 μm. The following absorption characteristics measured in synthetic urine were obtained: FSX: 21 g/g; CRC: 13 g/g; AUL: 18 g/g; pH gel 4.3.
- Five g of TEMPO-oxidised starch (TOS, degree of oxidation 0.70) and 0.4 g of CMC (Cekol 50,000 from Metsa Specialty Chemicals, degree of substitution 0.8) were dissolved in 20 ml of 0.05 M aqueous NaOH (pH 12) under mechanical stirring for 4 h. The mixture was crosslinked with 0.8 mol % of DVS (23 μl) at 5° C. for 18 hours. Three g of the gel obtained was chopped in pieces and the pieces were brought in 600 ml of demi water and acidified with 1.8 ml of 1M HCl with mild stirring (stepwise addition of acid). The next day, the swollen gel was filtered over a 80 μm sieve, and brought in another 600 ml of demi water for half an hour. Subsequently the gel was dried in a fluidised bed drier at 80° C. for 1 hour. The material was characterised in synthetic urine with the following results: 93% TOS/7% CMC: FSX: 30 g/g, CRC: 17 g/g. AUL: 16.5 g/g, pH gel 4.6.
- Five g of TEMPO-oxidised starch (TOS, degree of oxidation 0.70) and 0.4 g of CMC (Cekol 50,000 from Metsa Specialty Chemicals, degree of substitution 0.8) were dissolved in 20 ml of demi water under mechanical stirring for 1 h. The pH was adjusted to 4.5 using 25% HCl. The mixture was crosslinked with 1.4 mol % of BDDE (1,4-butanediol diglycidyl ether) (78 μl) at 50° C. for 18 hours. The gel was chopped and the pieces were dried in a fluidised bed drier for 30 minutes at 100° C. The dried gel was ground and washed with excess demi water on a 80 μm sieve to remove any salts present. Then the gel was dried in the fluidised bed drier at 80° C. for 1 hour. The material was characterised in synthetic urine with the following results: 93% TOS/7% CMC: FSC: 26 g/g, CRC: 15.5 g/g, AUL: 19 g/g, pH gel 4.9.
- Five g of TEMPO-oxidised starch (TOS, degree of oxidation 0.70) was dissolved in 20 ml of demi water under mechanical stirring for 1 h. The pH was adjusted to 4.5 using 25% HCl. The mixture was crosslinked with 2.0 mol % of BDDE (113 μl) at 50° C. for 18 hours. The gel was chopped and the pieces were dried in a fluidised bed drier for 30 minutes at 100° C. The dried gel was ground and washed with excess demi water on a 80 μm sieve to remove any salts present Then the gel was dried in the fluidised bed drier at 80° C. for 1 hour. The material was characterised in synthetic urine with the following results: 100% TOS: FSC: 27 g/g, CRC: 16 g/g, AUL: 19 g/g, pH gel 4.8.
- In an extruder, 50 grams of 6-carboxy starch (0.25 mol) is mixed with 50 ml of a 0.3 M HCI solution containing 30 μl butanediol diglycidyl ether (0.15 mmol). The paste is then extruded at 150° C. with an average residence time of 1 minute in the extruder. At the extrusion die the crosslinked polysaccharide is chopped into small pieces. The small pieces of gel are then dried in a fluidised bed drier for 30 minutes at 100° C. The dried particles are ground and sieved to obtain a final particle size of 100-800 μm. The absorption properties are comparable to those of the superabsorbent polysaccharide crosslinked in a conventional way.
- Three batches of 4 g of desalted TEMPO-oxidised starch (TOS, degree of oxidation 0.70) were dissolved in demi water to obtain 20 wt %, 40 wt % and 50 wt % TOS solutions, respectively. The pH of the solutions was about 4.6. To the solutions 0.124 g of CMC (Cekol 50,000, degree of substitution 0.8) was added, followed by thoroughmixing. The mixtures were crosslinked at 50° C. for 18 hours, with 1.4, 0.7, and 0.5 mol % of BDDE, respectively. Gels obtained were sized and, subsequently, dried in a fluidised bed drier for 1 hour at 100° C. The dried gels were ground and re-swollen in an excess of demi water. By addition of 2 M HCl, pH of the gel was adjusted to pH of 4.7-4.8 in demi water. Subsequently, the re-swollen gels were washed with excess demi water on a 80 μm sieve to remove salts present. Then the gels were dried in the fluidised bed drier at 100° C. for 1 hour. The materials were characterised in synthetic urine with the following results for the 40% TOS material: DXL (=degree of crosslinking in mol % BDDE): 0.7; FSC: 26.5 g/g; CRC: 15.5 g/g; AUL 14 g/g; pH gel:4.2. Comparable results were obtained when using 20% or 50% TOS solutions, instead of 40%.
- Three batches of 4 g of desalted TEMPO-oxidised starch (TOS, degree of oxidation 0.70) were dissolved in demi water to obtain 20 wt %, 40 wt % and 50 wt % TOS solutions, respectively. The pH of the solutions was about 4.6. The solutions were cross-linked at 50° C. for 18 hours, with 2.0, 0.75, and. 0.6 mol % of BDDE, respectively. Gels obtained were sized and, subsequently, dried in a fluidised bed drier for 1 hour at 100° C. The dried gels were ground and re-swollen in an excess of demi water. By addition of 2 M HCl, pH of the gel was adjusted to pH of 4.7-4.8 in demi water. Subsequently, the re-swollen gels were washed with excess demi water on a 80 μm sieve to remove salts present Then the gels were dried in the fluidised bed drier at 100° C. for 1 hour. The materials were characterised in synthetic urine with the following results for the 40% TOS material: DXL 0.75; FSC: 28 g/g; CRC: 15 g/g; AUL 14 g/g; pH gel: 4.1. Comparable results were obtained when using 20% or 50% TOS solutions instead of 40%.
- Three batches of 4 g of desalted TEMPO-oxidised starch (TOS, degree of oxidation 0.70) were dissolved in demi water to obtain 40wt% TOS-solutions. The pH of solutions was about 4.6. To each solution 0.124 g of CMC (Cekol 50,000, degree of substitution 0.8) was added, and the whole was mixed thoroughly. Mixtures were cross-linked with 0.7 mol % of BDDE at 50° C. for 18 hours, 70° C. for 2.5 hours, and 100° C. for 1 hour, respectively. Gels obtained were sized and, subsequently, dried in a fluidised bed drier for 1 hour at 100° C. The dried gels were ground and re-swollen in an excess of demi water. By addition of 2 M HCl, pH of the gel was adjusted to pH of 4.7-4.8 in demi water. Subsequently, the re-swollen gels were washed with excess demi water on a 80 μm sieve to remove any salts present. Then the gels were dried in the fluidised bed drier at 100° C. for 1 hour. The materials were characterised in synthetic urine with the following results:
XL temp. XL time FSC CRC AUL (° C.) (h) (g/g) (g/g) (g/g) pH gel 50 18 26.5 15.5 14 4.2 70 2.5 27 14 13 3.8 100 1 27 15.5 11.5 3.9 - Fifty g of desalted freeze-dried TEMPO-oxidised starch (TOS, degree of oxidation 0.70) was kneaded till a fibrous structure was obtained, and subsequently demi water (21.4 ml of demi water) was added. The whole was kneaded for 3 minutes at 17° C. to obtain 70 wt % TOS paste (pH of paste was ca. 4.6). To this paste 0.4 mol % BDDE was added and the whole was again kneaded for 3.5 minutes at 17° C. Then the paste was crosslinked for 16 hours at 50° C. The gel obtained was sized and dried in a fluidised bed drier for 1 hour at 80° C. Dried gel particles were re-swollen in 10 liters of demi water, and subsequently dried in the fluidised bed drier for 1.5 hours at 80 ° C. The material was characterised in synthetic urine with the following results: FSC: 27 g/g, CRC: 14.5 g/g, AUL: 17.5 g/g, pH gel 4.9.
Claims (15)
1-15. (Cancelled)
16. A superabsorbent polysaccharide derivative obtained by the process of:
(a) crosslinking at least one polysaccharide containing acidic groups with a crosslinking agent to produce a gel;
(b) ensuring that the pH of the polysaccharide is between 3.5 and 5.5;
(c) comminuting the acidified polysaccharide gel; and
(d) drying the comminuted polysaccharide at elevated temperature;
the superabsorbent polysaccharide derivative, when wetted, having a pH below 5.
17. A superabsorbent polysaccharide derivative according claim 16 , also comprising an acid selected from organic di- and polycarboxylic acids, hydroxycarboxylic acids and benzoic acids.
18. An absorbent article comprising a superabsorbent polysaccharide derivative according to claim 16 .
19. A superabsorbent polysaccharide derivative, the polysaccharide derivative containing acidic groups and being crosslinked, comminuted and dried, and, when wetted, having a pH below 5.
20. A superabsorbent polysaccharide derivative according to claim 19 , also comprising an acid selected from organic di- and polycarboxylic acids, hydroxycarboxylic acids and benzoic acids.
21. A superabsorbent polysaccharide derivative according to claim 19 , in which the polysaccharide containing acidic groups comprises carboxymethyl-cellulose.
22. A superabsorbent polysaccharide derivative according to claim 19 , in which the polysaccharide containing acidic groups is a carboxymethyl polysaccharide further containing carboxyl groups resulting from oxidation of saccharidic hydroxymethyl or hydroxymethylene groups, or phosphonic or sulphonic acid groups.
23. A superabsorbent polysaccharide derivative according to claim 19 , in which the polysaccharide containing acidic groups comprises a 6-carboxy polysaccharide.
24. A superabsorbent polysaccharide derivative according to claim 23 , in which the polysaccharide containing acidic groups comprises a 6-carboxy polysaccharide mixed with a carboxyalkylated polysaccharide.
25. A superabsorbent polysaccharide derivative according to claim 19 , in which the polysaccharide containing acidic groups contains 0.3-3.0 carboxyl groups per monosaccharide unit.
26. An absorbent hygiene article comprising a superabsorbent polysaccharide, the polysaccharide containing acidic groups and being crosslinked, comminuted and dried, and, when wetted, having a pH below 5.
27. An absorbent hygiene article according to claim 26 , in which the polysaccharide containing acidic groups contains 0.3-3.0 carboxyl groups per monosaccharide unit.
28. An absorbent hygiene article according to claim 26 , in which the polysaccharide containing acidic groups comprises 6-carboxy starch.
29. A method of absorbing liquids, comprising contacting the liquid with a superabsorbent polysaccharide derivative, the polysaccharide derivative containing acidic groups and being crosslinked, comminuted and dried, and, when wetted, having a pH below 5.
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Also Published As
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BR9916235A (en) | 2001-09-04 |
AU1897500A (en) | 2000-07-03 |
KR20010105311A (en) | 2001-11-28 |
CA2356849A1 (en) | 2000-06-22 |
US6765042B1 (en) | 2004-07-20 |
MXPA01006098A (en) | 2002-03-27 |
WO2000035504A1 (en) | 2000-06-22 |
CA2356849C (en) | 2008-06-03 |
EP1140229A1 (en) | 2001-10-10 |
DE69942840D1 (en) | 2010-11-18 |
SK7982001A3 (en) | 2002-02-05 |
AU767859B2 (en) | 2003-11-27 |
RU2227753C2 (en) | 2004-04-27 |
PL348821A1 (en) | 2002-06-17 |
ATE483480T1 (en) | 2010-10-15 |
JP2002532573A (en) | 2002-10-02 |
EP1140229B1 (en) | 2010-10-06 |
TNSN99243A1 (en) | 2001-12-31 |
NZ512254A (en) | 2003-11-28 |
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