JP4198266B2 - Method for producing water absorbent resin - Google Patents
Method for producing water absorbent resin Download PDFInfo
- Publication number
- JP4198266B2 JP4198266B2 JP11439499A JP11439499A JP4198266B2 JP 4198266 B2 JP4198266 B2 JP 4198266B2 JP 11439499 A JP11439499 A JP 11439499A JP 11439499 A JP11439499 A JP 11439499A JP 4198266 B2 JP4198266 B2 JP 4198266B2
- Authority
- JP
- Japan
- Prior art keywords
- water
- polymerization
- unsaturated monomer
- hydrogel polymer
- aqueous solution
- 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.)
- Expired - Lifetime
Links
- 239000011347 resin Substances 0.000 title claims description 80
- 229920005989 resin Polymers 0.000 title claims description 80
- 239000002250 absorbent Substances 0.000 title claims description 56
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims description 49
- 238000004519 manufacturing process Methods 0.000 title claims description 17
- 230000002745 absorbent Effects 0.000 title description 21
- 239000000178 monomer Substances 0.000 claims description 87
- 238000006116 polymerization reaction Methods 0.000 claims description 87
- 229920000642 polymer Polymers 0.000 claims description 81
- 239000007864 aqueous solution Substances 0.000 claims description 78
- 239000000017 hydrogel Substances 0.000 claims description 70
- 230000032683 aging Effects 0.000 claims description 34
- 150000003839 salts Chemical class 0.000 claims description 28
- 239000003505 polymerization initiator Substances 0.000 claims description 26
- 239000003431 cross linking reagent Substances 0.000 claims description 19
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 claims description 16
- NIXOWILDQLNWCW-UHFFFAOYSA-N 2-Propenoic acid Natural products OC(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 claims description 16
- 238000000034 method Methods 0.000 claims description 12
- 238000010528 free radical solution polymerization reaction Methods 0.000 claims description 10
- 125000000129 anionic group Chemical group 0.000 claims description 9
- 239000003638 chemical reducing agent Substances 0.000 claims description 7
- 125000002091 cationic group Chemical group 0.000 claims description 4
- 230000000717 retained effect Effects 0.000 claims description 3
- 239000000499 gel Substances 0.000 description 32
- -1 2-hydroxypropyl Chemical group 0.000 description 27
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 25
- 238000010521 absorption reaction Methods 0.000 description 25
- CIWBSHSKHKDKBQ-JLAZNSOCSA-N Ascorbic acid Chemical compound OC[C@H](O)[C@H]1OC(=O)C(O)=C1O CIWBSHSKHKDKBQ-JLAZNSOCSA-N 0.000 description 24
- 235000002639 sodium chloride Nutrition 0.000 description 23
- 229910001873 dinitrogen Inorganic materials 0.000 description 21
- LXEKPEMOWBOYRF-UHFFFAOYSA-N [2-[(1-azaniumyl-1-imino-2-methylpropan-2-yl)diazenyl]-2-methylpropanimidoyl]azanium;dichloride Chemical compound Cl.Cl.NC(=N)C(C)(C)N=NC(C)(C)C(N)=N LXEKPEMOWBOYRF-UHFFFAOYSA-N 0.000 description 16
- 238000003756 stirring Methods 0.000 description 16
- NIXOWILDQLNWCW-UHFFFAOYSA-M Acrylate Chemical compound [O-]C(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-M 0.000 description 14
- 229940048053 acrylate Drugs 0.000 description 14
- 230000000052 comparative effect Effects 0.000 description 14
- 238000002156 mixing Methods 0.000 description 14
- LCPVQAHEFVXVKT-UHFFFAOYSA-N 2-(2,4-difluorophenoxy)pyridin-3-amine Chemical compound NC1=CC=CN=C1OC1=CC=C(F)C=C1F LCPVQAHEFVXVKT-UHFFFAOYSA-N 0.000 description 13
- JRKICGRDRMAZLK-UHFFFAOYSA-L peroxydisulfate Chemical compound [O-]S(=O)(=O)OOS([O-])(=O)=O JRKICGRDRMAZLK-UHFFFAOYSA-L 0.000 description 13
- 229920001223 polyethylene glycol Polymers 0.000 description 13
- 239000000047 product Substances 0.000 description 13
- CHQMHPLRPQMAMX-UHFFFAOYSA-L sodium persulfate Substances [Na+].[Na+].[O-]S(=O)(=O)OOS([O-])(=O)=O CHQMHPLRPQMAMX-UHFFFAOYSA-L 0.000 description 13
- 239000008367 deionised water Substances 0.000 description 12
- 229910021641 deionized water Inorganic materials 0.000 description 12
- 239000002202 Polyethylene glycol Substances 0.000 description 11
- 229960005070 ascorbic acid Drugs 0.000 description 11
- 235000013372 meat Nutrition 0.000 description 11
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 10
- 238000010438 heat treatment Methods 0.000 description 10
- 239000000243 solution Substances 0.000 description 10
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 9
- 239000002211 L-ascorbic acid Substances 0.000 description 9
- 235000000069 L-ascorbic acid Nutrition 0.000 description 9
- DNIAPMSPPWPWGF-UHFFFAOYSA-N Propylene glycol Chemical compound CC(O)CO DNIAPMSPPWPWGF-UHFFFAOYSA-N 0.000 description 9
- 238000001816 cooling Methods 0.000 description 9
- 229910052757 nitrogen Inorganic materials 0.000 description 9
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 8
- 238000006243 chemical reaction Methods 0.000 description 8
- 239000003999 initiator Substances 0.000 description 8
- 210000002700 urine Anatomy 0.000 description 8
- PQUXFUBNSYCQAL-UHFFFAOYSA-N 1-(2,3-difluorophenyl)ethanone Chemical compound CC(=O)C1=CC=CC(F)=C1F PQUXFUBNSYCQAL-UHFFFAOYSA-N 0.000 description 7
- HRPVXLWXLXDGHG-UHFFFAOYSA-N Acrylamide Chemical compound NC(=O)C=C HRPVXLWXLXDGHG-UHFFFAOYSA-N 0.000 description 7
- 125000004386 diacrylate group Chemical group 0.000 description 7
- 239000000706 filtrate Substances 0.000 description 7
- 239000000463 material Substances 0.000 description 7
- 229920003023 plastic Polymers 0.000 description 7
- 239000004033 plastic Substances 0.000 description 7
- 230000005070 ripening Effects 0.000 description 7
- 229940047670 sodium acrylate Drugs 0.000 description 7
- 239000000126 substance Substances 0.000 description 7
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 6
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
- 150000002978 peroxides Chemical class 0.000 description 6
- 238000004448 titration Methods 0.000 description 6
- 150000001875 compounds Chemical class 0.000 description 5
- 238000005520 cutting process Methods 0.000 description 5
- 238000001035 drying Methods 0.000 description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical class [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 description 4
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 4
- 229910052783 alkali metal Inorganic materials 0.000 description 4
- WERYXYBDKMZEQL-UHFFFAOYSA-N butane-1,4-diol Chemical compound OCCCCO WERYXYBDKMZEQL-UHFFFAOYSA-N 0.000 description 4
- 238000004132 cross linking Methods 0.000 description 4
- 230000007423 decrease Effects 0.000 description 4
- 238000001125 extrusion Methods 0.000 description 4
- 239000000835 fiber Substances 0.000 description 4
- 235000011187 glycerol Nutrition 0.000 description 4
- QYZFTMMPKCOTAN-UHFFFAOYSA-N n-[2-(2-hydroxyethylamino)ethyl]-2-[[1-[2-(2-hydroxyethylamino)ethylamino]-2-methyl-1-oxopropan-2-yl]diazenyl]-2-methylpropanamide Chemical compound OCCNCCNC(=O)C(C)(C)N=NC(C)(C)C(=O)NCCNCCO QYZFTMMPKCOTAN-UHFFFAOYSA-N 0.000 description 4
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 3
- 229920002125 Sokalan® Polymers 0.000 description 3
- ZJCCRDAZUWHFQH-UHFFFAOYSA-N Trimethylolpropane Chemical compound CCC(CO)(CO)CO ZJCCRDAZUWHFQH-UHFFFAOYSA-N 0.000 description 3
- 230000015556 catabolic process Effects 0.000 description 3
- 238000006731 degradation reaction Methods 0.000 description 3
- MTHSVFCYNBDYFN-UHFFFAOYSA-N diethylene glycol Chemical compound OCCOCCO MTHSVFCYNBDYFN-UHFFFAOYSA-N 0.000 description 3
- 238000006386 neutralization reaction Methods 0.000 description 3
- WXZMFSXDPGVJKK-UHFFFAOYSA-N pentaerythritol Chemical compound OCC(CO)(CO)CO WXZMFSXDPGVJKK-UHFFFAOYSA-N 0.000 description 3
- 239000004584 polyacrylic acid Substances 0.000 description 3
- 238000010298 pulverizing process Methods 0.000 description 3
- 229910052708 sodium Inorganic materials 0.000 description 3
- 239000011734 sodium Substances 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- 230000003068 static effect Effects 0.000 description 3
- AOSFMYBATFLTAQ-UHFFFAOYSA-N 1-amino-3-(benzimidazol-1-yl)propan-2-ol Chemical compound C1=CC=C2N(CC(O)CN)C=NC2=C1 AOSFMYBATFLTAQ-UHFFFAOYSA-N 0.000 description 2
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 229920001661 Chitosan Polymers 0.000 description 2
- XQVSSOCMDXLKJN-UHFFFAOYSA-N Cl.Cl.C1N2C(C(C1)(C)C2)=O Chemical compound Cl.Cl.C1N2C(C(C1)(C)C2)=O XQVSSOCMDXLKJN-UHFFFAOYSA-N 0.000 description 2
- CIWBSHSKHKDKBQ-DUZGATOHSA-N D-araboascorbic acid Natural products OC[C@@H](O)[C@H]1OC(=O)C(O)=C1O CIWBSHSKHKDKBQ-DUZGATOHSA-N 0.000 description 2
- PQUCIEFHOVEZAU-UHFFFAOYSA-N Diammonium sulfite Chemical compound [NH4+].[NH4+].[O-]S([O-])=O PQUCIEFHOVEZAU-UHFFFAOYSA-N 0.000 description 2
- 239000004593 Epoxy Substances 0.000 description 2
- PIICEJLVQHRZGT-UHFFFAOYSA-N Ethylenediamine Chemical compound NCCN PIICEJLVQHRZGT-UHFFFAOYSA-N 0.000 description 2
- 206010021639 Incontinence Diseases 0.000 description 2
- 229920002873 Polyethylenimine Polymers 0.000 description 2
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 description 2
- 229920002472 Starch Polymers 0.000 description 2
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 150000001299 aldehydes Chemical class 0.000 description 2
- 150000001412 amines Chemical class 0.000 description 2
- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium peroxydisulfate Substances [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 description 2
- VAZSKTXWXKYQJF-UHFFFAOYSA-N ammonium persulfate Chemical compound [NH4+].[NH4+].[O-]S(=O)OOS([O-])=O VAZSKTXWXKYQJF-UHFFFAOYSA-N 0.000 description 2
- 229910001870 ammonium persulfate Inorganic materials 0.000 description 2
- 235000010323 ascorbic acid Nutrition 0.000 description 2
- 239000011668 ascorbic acid Substances 0.000 description 2
- 239000001110 calcium chloride Substances 0.000 description 2
- 229960002713 calcium chloride Drugs 0.000 description 2
- 229910001628 calcium chloride Inorganic materials 0.000 description 2
- 235000011148 calcium chloride Nutrition 0.000 description 2
- 239000004202 carbamide Substances 0.000 description 2
- 239000001913 cellulose Substances 0.000 description 2
- 229920002678 cellulose Polymers 0.000 description 2
- 229920001577 copolymer Polymers 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000004318 erythorbic acid Substances 0.000 description 2
- 235000010350 erythorbic acid Nutrition 0.000 description 2
- 239000010419 fine particle Substances 0.000 description 2
- 229920000578 graft copolymer Polymers 0.000 description 2
- 229910000358 iron sulfate Inorganic materials 0.000 description 2
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 2
- 230000001678 irradiating effect Effects 0.000 description 2
- 229940026239 isoascorbic acid Drugs 0.000 description 2
- 239000012948 isocyanate Substances 0.000 description 2
- 229910052943 magnesium sulfate Inorganic materials 0.000 description 2
- 229960003390 magnesium sulfate Drugs 0.000 description 2
- 235000019341 magnesium sulphate Nutrition 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 150000002825 nitriles Chemical class 0.000 description 2
- 150000002976 peresters Chemical class 0.000 description 2
- 230000000704 physical effect Effects 0.000 description 2
- USHAGKDGDHPEEY-UHFFFAOYSA-L potassium persulfate Chemical compound [K+].[K+].[O-]S(=O)(=O)OOS([O-])(=O)=O USHAGKDGDHPEEY-UHFFFAOYSA-L 0.000 description 2
- OTYBMLCTZGSZBG-UHFFFAOYSA-L potassium sulfate Chemical compound [K+].[K+].[O-]S([O-])(=O)=O OTYBMLCTZGSZBG-UHFFFAOYSA-L 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000010008 shearing Methods 0.000 description 2
- 239000011780 sodium chloride Substances 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 239000008107 starch Substances 0.000 description 2
- 235000019698 starch Nutrition 0.000 description 2
- 239000010409 thin film Substances 0.000 description 2
- 229950003937 tolonium Drugs 0.000 description 2
- HNONEKILPDHFOL-UHFFFAOYSA-M tolonium chloride Chemical compound [Cl-].C1=C(C)C(N)=CC2=[S+]C3=CC(N(C)C)=CC=C3N=C21 HNONEKILPDHFOL-UHFFFAOYSA-M 0.000 description 2
- DNIAPMSPPWPWGF-VKHMYHEASA-N (+)-propylene glycol Chemical compound C[C@H](O)CO DNIAPMSPPWPWGF-VKHMYHEASA-N 0.000 description 1
- ORTVZLZNOYNASJ-UPHRSURJSA-N (z)-but-2-ene-1,4-diol Chemical compound OC\C=C/CO ORTVZLZNOYNASJ-UPHRSURJSA-N 0.000 description 1
- ZZXUZKXVROWEIF-UHFFFAOYSA-N 1,2-butylene carbonate Chemical compound CCC1COC(=O)O1 ZZXUZKXVROWEIF-UHFFFAOYSA-N 0.000 description 1
- KOMNUTZXSVSERR-UHFFFAOYSA-N 1,3,5-tris(prop-2-enyl)-1,3,5-triazinane-2,4,6-trione Chemical compound C=CCN1C(=O)N(CC=C)C(=O)N(CC=C)C1=O KOMNUTZXSVSERR-UHFFFAOYSA-N 0.000 description 1
- YPFDHNVEDLHUCE-UHFFFAOYSA-N 1,3-propanediol Substances OCCCO YPFDHNVEDLHUCE-UHFFFAOYSA-N 0.000 description 1
- UWFRVQVNYNPBEF-UHFFFAOYSA-N 1-(2,4-dimethylphenyl)propan-1-one Chemical compound CCC(=O)C1=CC=C(C)C=C1C UWFRVQVNYNPBEF-UHFFFAOYSA-N 0.000 description 1
- RESPXSHDJQUNTN-UHFFFAOYSA-N 1-piperidin-1-ylprop-2-en-1-one Chemical compound C=CC(=O)N1CCCCC1 RESPXSHDJQUNTN-UHFFFAOYSA-N 0.000 description 1
- WLPAQAXAZQUXBG-UHFFFAOYSA-N 1-pyrrolidin-1-ylprop-2-en-1-one Chemical compound C=CC(=O)N1CCCC1 WLPAQAXAZQUXBG-UHFFFAOYSA-N 0.000 description 1
- VILCJCGEZXAXTO-UHFFFAOYSA-N 2,2,2-tetramine Chemical compound NCCNCCNCCN VILCJCGEZXAXTO-UHFFFAOYSA-N 0.000 description 1
- IVIDDMGBRCPGLJ-UHFFFAOYSA-N 2,3-bis(oxiran-2-ylmethoxy)propan-1-ol Chemical compound C1OC1COC(CO)COCC1CO1 IVIDDMGBRCPGLJ-UHFFFAOYSA-N 0.000 description 1
- BJELTSYBAHKXRW-UHFFFAOYSA-N 2,4,6-triallyloxy-1,3,5-triazine Chemical compound C=CCOC1=NC(OCC=C)=NC(OCC=C)=N1 BJELTSYBAHKXRW-UHFFFAOYSA-N 0.000 description 1
- HDPLHDGYGLENEI-UHFFFAOYSA-N 2-[1-(oxiran-2-ylmethoxy)propan-2-yloxymethyl]oxirane Chemical compound C1OC1COC(C)COCC1CO1 HDPLHDGYGLENEI-UHFFFAOYSA-N 0.000 description 1
- KFNAHVKJFHDCSK-UHFFFAOYSA-N 2-[2-(4,5-dihydro-1,3-oxazol-2-yl)ethyl]-4,5-dihydro-1,3-oxazole Chemical compound N=1CCOC=1CCC1=NCCO1 KFNAHVKJFHDCSK-UHFFFAOYSA-N 0.000 description 1
- TXBCBTDQIULDIA-UHFFFAOYSA-N 2-[[3-hydroxy-2,2-bis(hydroxymethyl)propoxy]methyl]-2-(hydroxymethyl)propane-1,3-diol Chemical compound OCC(CO)(CO)COCC(CO)(CO)CO TXBCBTDQIULDIA-UHFFFAOYSA-N 0.000 description 1
- 125000000954 2-hydroxyethyl group Chemical group [H]C([*])([H])C([H])([H])O[H] 0.000 description 1
- QENRKQYUEGJNNZ-UHFFFAOYSA-N 2-methyl-1-(prop-2-enoylamino)propane-1-sulfonic acid Chemical compound CC(C)C(S(O)(=O)=O)NC(=O)C=C QENRKQYUEGJNNZ-UHFFFAOYSA-N 0.000 description 1
- NWIIFBPIDORBCY-UHFFFAOYSA-N 2-methylprop-2-enoic acid;propane-1,2,3-triol;prop-2-enoic acid Chemical compound OC(=O)C=C.CC(=C)C(O)=O.OCC(O)CO NWIIFBPIDORBCY-UHFFFAOYSA-N 0.000 description 1
- AGBXYHCHUYARJY-UHFFFAOYSA-N 2-phenylethenesulfonic acid Chemical compound OS(=O)(=O)C=CC1=CC=CC=C1 AGBXYHCHUYARJY-UHFFFAOYSA-N 0.000 description 1
- KGIGUEBEKRSTEW-UHFFFAOYSA-N 2-vinylpyridine Chemical compound C=CC1=CC=CC=N1 KGIGUEBEKRSTEW-UHFFFAOYSA-N 0.000 description 1
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- PUEFXLJYTSRTGI-UHFFFAOYSA-N 4,4-dimethyl-1,3-dioxolan-2-one Chemical compound CC1(C)COC(=O)O1 PUEFXLJYTSRTGI-UHFFFAOYSA-N 0.000 description 1
- LWLOKSXSAUHTJO-UHFFFAOYSA-N 4,5-dimethyl-1,3-dioxolan-2-one Chemical compound CC1OC(=O)OC1C LWLOKSXSAUHTJO-UHFFFAOYSA-N 0.000 description 1
- UHIIHYFGCONAHB-UHFFFAOYSA-N 4,6-dimethyl-1,3-dioxan-2-one Chemical compound CC1CC(C)OC(=O)O1 UHIIHYFGCONAHB-UHFFFAOYSA-N 0.000 description 1
- JFMGYULNQJPJCY-UHFFFAOYSA-N 4-(hydroxymethyl)-1,3-dioxolan-2-one Chemical compound OCC1COC(=O)O1 JFMGYULNQJPJCY-UHFFFAOYSA-N 0.000 description 1
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- AEYSASDBPHWTGR-UHFFFAOYSA-N 4-oxohex-5-ene-3-sulfonic acid Chemical compound CCC(S(O)(=O)=O)C(=O)C=C AEYSASDBPHWTGR-UHFFFAOYSA-N 0.000 description 1
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 1
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- RPNUMPOLZDHAAY-UHFFFAOYSA-N Diethylenetriamine Chemical compound NCCNCCN RPNUMPOLZDHAAY-UHFFFAOYSA-N 0.000 description 1
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
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- WHNWPMSKXPGLAX-UHFFFAOYSA-N N-Vinyl-2-pyrrolidone Chemical compound C=CN1CCCC1=O WHNWPMSKXPGLAX-UHFFFAOYSA-N 0.000 description 1
- ALQSHHUCVQOPAS-UHFFFAOYSA-N Pentane-1,5-diol Chemical compound OCCCCCO ALQSHHUCVQOPAS-UHFFFAOYSA-N 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 239000004372 Polyvinyl alcohol Substances 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- OFOBLEOULBTSOW-UHFFFAOYSA-N Propanedioic acid Natural products OC(=O)CC(O)=O OFOBLEOULBTSOW-UHFFFAOYSA-N 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 1
- UWHCKJMYHZGTIT-UHFFFAOYSA-N Tetraethylene glycol, Natural products OCCOCCOCCOCCO UWHCKJMYHZGTIT-UHFFFAOYSA-N 0.000 description 1
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 1
- GSEJCLTVZPLZKY-UHFFFAOYSA-N Triethanolamine Chemical compound OCCN(CCO)CCO GSEJCLTVZPLZKY-UHFFFAOYSA-N 0.000 description 1
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- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 1
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- 229910000387 ammonium dihydrogen phosphate Inorganic materials 0.000 description 1
- 239000012298 atmosphere Substances 0.000 description 1
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- LLSDKQJKOVVTOJ-UHFFFAOYSA-L calcium chloride dihydrate Chemical compound O.O.[Cl-].[Cl-].[Ca+2] LLSDKQJKOVVTOJ-UHFFFAOYSA-L 0.000 description 1
- 229940052299 calcium chloride dihydrate Drugs 0.000 description 1
- 238000011088 calibration curve Methods 0.000 description 1
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- 229910000388 diammonium phosphate Inorganic materials 0.000 description 1
- 235000019838 diammonium phosphate Nutrition 0.000 description 1
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- 229910052700 potassium Inorganic materials 0.000 description 1
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- FAGUFWYHJQFNRV-UHFFFAOYSA-N tetraethylenepentamine Chemical compound NCCNCCNCCNCCN FAGUFWYHJQFNRV-UHFFFAOYSA-N 0.000 description 1
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 1
- DVKJHBMWWAPEIU-UHFFFAOYSA-N toluene 2,4-diisocyanate Chemical compound CC1=CC=C(N=C=O)C=C1N=C=O DVKJHBMWWAPEIU-UHFFFAOYSA-N 0.000 description 1
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F2/00—Processes of polymerisation
- C08F2/04—Polymerisation in solution
- C08F2/10—Aqueous solvent
Landscapes
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Absorbent Articles And Supports Therefor (AREA)
- Solid-Sorbent Or Filter-Aiding Compositions (AREA)
- Polymerisation Methods In General (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は、重合して吸水性樹脂となる単量体成分を静置水溶液重合して吸水性樹脂を製造する方法に関する。さらに詳しくは、紙オムツや生理用ナプキン等の衛生材料に好適に用いられる吸水性樹脂の製造方法に関するものである。
【０００２】
【従来技術】
近年、紙オムツや生理用ナプキン、いわゆる失禁パッド等の衛生材料等の分野では、体液を吸収させることを目的として吸水性樹脂が幅広く利用されている。
【０００３】
上記の吸水性樹脂としては、例えば、ポリアクリル酸部分中和物架橋体、澱粉−アクリロニトリルグラフト共重合体の加水分解物、澱粉−アクリル酸グラフト共重合体の中和物、酢酸ビニル−アクリル酸エステル共重合体のケン化物、アクリロニトリル共重合体もしくはアクリルアミド共重合体の加水分解物またはこれらの架橋体、カチオン性モノマーの架橋体などが知られている。
【０００４】
これら吸水性樹脂を製造する方法として、アクリル酸またはその塩等を主成分とする親水性単量体を含む水溶液を攪拌しながら水溶液重合を行う方法が一般的に採用されている。
【０００５】
攪拌重合は、重合の進行とともに生成する含水ゲル状重合体を小塊に切断しながら重合できるため、比較的コンパクトな装置で重合熱を除去して重合ピーク温度をある程度コントロールした重合ができるという点で優れているものの、攪拌によるせん断力によって分子鎖が切断されるため、分子量が上がりにくい、架橋構造のネットワークが乱れやすい等の問題がある。これに対し、特開平３−１７４４１４号公報、特開平４−１７５３１９号公報等で提案されている、単量体水溶液を無攪拌で静置重合する方法によると、上記問題なく、吸水性樹脂を得ることができる。
【０００６】
具体的には、特開平３−１７４４１４号公報では、比較的低濃度の親水性単量体を含む水溶液を、特定の重合開始剤を用いて断熱重合し、得られた含水ゲル状重合体を細断し、塩基水溶液により中和する方法が開示されている。このような断熱重合を行うためには、その実施例に示されているように単量体水溶液の濃度を２０重量％程度とし、かつ１〜５時間の重合を行う必要があり、さらに後中和工程を必要とし、これにも相当な時間を要し、生産性が低い。また、粉体で製品を得ようとする場合、乾燥工程が必要となり、単量体水溶液の濃度が低いため、必然的に乾燥に多大なエネルギーが必要となり、生産性が低いばかりでなく、経済的な面からも工業的規模では採用し難い。また、物性的にも、単量体水溶液の濃度が低いため残存モノマーが多く残るという問題点もある。
【０００７】
特開平４−１７５３１９号公報では、比較的高濃度の親水性単量体を含む水溶液を、無攪拌（静置状態）で、かつ重合温度を２０〜７０℃に制御して定温重合する方法が開示されている。このような比較的低温で定温重合を行うためには、その実施例に示されるように単量体水溶液の厚みを８ｍｍ以下程度と薄くし、かつ４５分以上の重合時間として重合系の温度を制御する必要があり、生産性が低く工業的規模では採用し難い。
【０００８】
【発明が解決しようとする課題】
本発明の課題は、上記従来の問題点を解決し、水溶液重合において、高い生産性で、吸収倍率が高く、水可溶成分量および残存モノマー量が従来よりも低減されている優れた品質の吸水性樹脂を得ることができるような製造方法を提供することにある。
【０００９】
【課題を解決するための手段】
本願発明者等は、上記目的を達成すべく鋭意検討した結果、重合装置中で静置水溶液重合を行い、内部架橋剤と、重合により吸水性樹脂となる不飽和単量体成分または不飽和単量体成分の塩とから、架橋構造を有する含水ゲル状重合体を得る過程において、前記重合装置中の含水ゲル状重合体がピーク温度を示した後、前記含水ゲル状重合体を前記ピーク温度より少なくとも１０℃低い温度で少なくとも３０分保持し、乾燥すること、前記内部架橋剤は、２個以上の重合性不飽和基あるいは２個以上の反応性基を有すること、ならびに、前記不飽和単量体成分は、アニオン性不飽和単量体、ノニオン性の親水基含有不飽和単量体、およびカチオン性不飽和単量体からなる群より選択される少なくとも１種であり、前記不飽和単量体成分の塩はアニオン性不飽和単量体の塩であること、により、吸収倍率が高く、水可溶成分量および残存モノマー量が従来よりも低減されている吸水性樹脂を安定して得ることができることを見出した。
【００１０】
さらに、該含水ゲル状重合体に重合開始剤を添加することが好ましい。
【００１１】
また、前記静置水溶液重合は重合開始剤と還元剤とを併用したレドックス系により、行われることが好ましい、
また、前記含水ゲル重合体は、前記ピーク温度を示した後に、前記重合装置から熟成用の装置に移されて前記保持されるか、または前記重合装置から移されずに前記保持されることが好ましい。
【００１２】
また、前記保持の後、含水ゲル状重合体を粉砕および乾燥することが好ましい。
【００１３】
また、前記ピーク温度は８０℃以上であることが好ましい。
【００１４】
また、前記保持の際の相対湿度は、５０％ＲＨ以上であることが好ましい。
【００１５】
また、前記アニオン性不飽和単量体としてアクリル酸を含むか、または前記アニオン性不飽和単量体の塩としてアクリル酸の塩を含むことが好ましく、
また、前記不飽和単量体成分または前記不飽和単量体成分の塩の含有量は１５〜４５重量％であることが好ましく、
また、前記内部架橋剤の含有量は、前記不飽和単量体成分または前記不飽和単量体成分の塩に対して０．００５〜３モル％であることが好ましい。
【００１６】
また、前記静置水溶液重合を開始する際の温度は０〜３０℃であることが好ましく、
前記保持されている含水ゲル状重合体の比表面積は１０ｃｍ ２ ／ｇ以下であることが好ましい。
【００１７】
また、前記において、単量体成分の中和率が、４０〜１００mol%であることを特徴とする方法を採用する。
【００１８】
また、前記において、重合開始剤に過硫酸塩、アゾ系反応開始剤、酸化剤および還元剤、を用いることを特徴とする方法を採用する。
【００１９】
上記の構成によれば、吸収倍率が高く、しかも水可溶成分量および残存モノマー量が従来よりも低減されている吸水性樹脂の製造方法を提供することができる。
【００２０】
【発明の実施の形態】
以下に本発明の実施の一形態について詳しく説明する。
【００２１】
本発明で用いられる重合して吸水性樹脂となる単量体成分としては、文字どおり重合により吸水性樹脂となり得るものであれば特に限定されないが、例えば、アクリル酸、メタクリル酸、マレイン酸、ビニルスルホン酸、スチレンスルホン酸、２−（メタ）アクリルアミド−２−メチルプロパンスルホン酸、２−（メタ）アクリロイルエタンスルホン酸、２−（メタ）アクリロイルプロパンスルホン酸などのアニオン性不飽和単量体およびその塩；アクリルアミド、メタクリルアミド、Ｎ−エチル（メタ）アクリルアミド、Ｎ−ｎ−プロピル（メタ）アクリルアミド、Ｎ−イソプロピル（メタ）アクリルアミド、Ｎ，Ｎ−ジメチル（メタ）アクリルアミド、２−ヒドロキシエチル（メタ）アクリレート、２−ヒドロキシプロピル（メタ）アクリレート、メトキシポリエチレングリコール（メタ）アクリレート、ポリエチレングリコールモノ（メタ）アクリレート、ビニルピリジン、Ｎ−ビニルピロリドン、Ｎ−ビニルアセトアミド、Ｎ−アクリロイルピペリジン、Ｎ−アクリロイルピロリジンなどのノニオン性の親水基含有不飽和単量体；Ｎ，Ｎ−ジメチルアミノエチル（メタ）アクリレート、Ｎ，Ｎ−ジメチルアミノエチル（メタ）アクリレート、Ｎ，Ｎ−ジメチルアミノプロピル（メタ）アクリレート、Ｎ，Ｎ−ジメチルアミノプロピル（メタ）アクリルアミドおよびそれらの四級塩等のカチオン性不飽和単量体などを挙げることができる。これらは１種または２種以上を使用することができる。
【００２２】
これらの中でアクリル酸またはその塩（例えば、ナトリウム、リチウム、カリウム、アンモニウム、アミン類等の塩）を主成分として用いることが好ましく、より好ましくはアクリル酸またはそのナトリウム塩である。アクリル酸またはその塩以外の他の単量体の使用量は通常全単量体中の０〜５０モル％未満とすることが好ましく、より好ましくは０〜３０モル％である。
【００２３】
アニオン性不飽和単量体の中和率としては、酸基の４０〜１００モル％が中和されていることが好ましい。中和率が１００モル％を超える場合にはアルカリ性が強く人体に害を及ぼすおそれがある。４０モル％未満では得られる吸水性樹脂の吸収倍率が低下する。
【００２４】
重合して吸水性樹脂となるモノマー成分の濃度は１５〜４５重量％とすることが好ましく、より好ましくは２５〜４５重量％であり、さらにより好ましくは３０〜４０重量％である。１５重量％未満の場合には、生産性が低くなることがあり、４５重量％を超えると、高分子鎖の自己架橋成分の割合が高くなり、得られる吸水性樹脂の吸収倍率が低下することがある。
【００２５】
重合に際しては、澱粉・セルロース、澱粉・セルロースの誘導体、ポリビニルアルコール、ポリアクリル酸（塩）、ポリアクリル酸（塩）架橋体等の親水性高分子や、次亜リン酸（塩）等の連鎖移動剤を添加してもよい。
【００２６】
本発明において吸水性樹脂は架橋構造を有することが好ましく、架橋剤を使用しない自己架橋型のものや、２個以上の重合性不飽和基あるいは２個以上の反応性基を有する内部架橋剤を共重合または反応させた型のものが例示できる。好ましくは親水性不飽和単量体に内部架橋剤を共重合または反応させた架橋構造を有する吸水性樹脂である。
【００２７】
これらの内部架橋剤の具体例としては、例えば、Ｎ，Ｎ‘−メチレンビス（メタ）アクリルアミド、（ポリ）エチレングリコールジ（メタ）アクリレート、（ポリ）プロピレングリコールジ（メタ）アクリレート、トリメチロールプロパントリ（メタ）アクリレート、トリメチロールプロパンジ（メタ）アクリレート、グリセリントリ（メタ）アクリレート、グリセリンアクリレートメタクリレート、エチレンオキサイド変性トリメチロールプロパントリアクリレート、ペンタエリスリトールテトラ（メタ）アクリレート、ジペンタエリスリトールヘキサ（メタ）アクリレート、トリアリルシアヌレート、トリアリルイソシアヌレート、トリアリルホスフェート、トリアリルアミン、ポリ（メタ）アリロキシアルカン、（ポリ）エチレングリコールジグリシジルエーテル、グリセロールジグリシジルエーテル、エチレングリコール、ポリエチレングリコール、プロピレングリコール、グリセリン、１，４−ブタンジオール、ペンタエリスリトール、エチレンジアミン、ポリエチレンイミン、グリシジル（メタ）アクリレートなどを挙げることができる。またはこれらの内部架橋剤は２種以上使用してもよい。
【００２８】
内部架橋剤の使用量としては前記単量体成分に対して０．００５〜３モル％が好ましく、より好ましくは０．０１〜１．５モル％である。内部架橋剤が少なすぎると、水可溶成分が多くなる傾向があり、逆に内部架橋剤量が多すぎると、吸収倍率が低下する傾向がある。
【００２９】
上記単量体成分の重合方法としては、静置水溶液重合であれば、特に限定されるものではなく、ベルト上で無攪拌で行う連続静置重合を行ってもよいし、バッチで静置重合を行ってもよいが、生産性や得られる吸水性樹脂の物性の均一さからベルト上で無攪拌で行う連続静置重合が好ましい。
【００３０】
本発明において、重合開始剤としては、過硫酸塩を用いることが好ましい。過硫酸塩以外の重合開始剤のみで重合を行った場合、残存モノマーの高いものになることがある。
【００３１】
過硫酸塩を単独で使用してもよいが、過硫酸塩以外のアゾ化合物や過酸化物、のような重合開始剤を併用してもよい。また、還元剤とともにレドックス系で行ってもよい。
【００３２】
過硫酸塩としては、過硫酸ナトリウム、過硫酸カリウム、過硫酸アンモニウム等が例示され、アゾ化合物としては、２，２'−アゾビス（Ｎ，Ｎ'−ジメチレンイソブチルアミド）ジハイドロクロライド、２，２'−アゾビス（２−アミジノプロパン）ジハイドロクロライド、２，２'−アゾビス（Ｎ，Ｎ'−ジメチレンイソブチルアミド）、４，４'−アゾビス４−シアノペンタノイックアシッド、アゾビスイソブチロニトリル等が例示され、過酸化物としては、過酸化水素、アルキルハイドロパーオキサイド類、過エステル類、ジアクリル過酸化物が例示され、還元剤としては、アルカリ金属の亜硫酸塩、アルカリ金属の重亜硫酸塩、亜硫酸アンモニウム、重亜硫酸アンモニウム、アスコルビン酸、エリトルビン酸、硫酸鉄のような鉄金属塩、糖類、アルデヒド類等が例示される。
【００３３】
これらの重合開始剤の使用量としては、前記単量体成分に対して、０．００１モル％〜２モル％の範囲が好ましく、０．０１〜０．５モル％の範囲内がより好ましい。尚、重合開始剤は、水等の溶媒に溶解または分散させればよい。
【００３４】
重合開始温度は適宜選択できるが、０〜３０℃の範囲が好ましく、より好ましくは１５〜２５℃である。重合開始温度が０℃未満では誘導期間、重合時間が長くなり、生産性が低下することがある。一方、開始温度が３０℃を超えると、モノマー濃度にもよるが、重合系の最高到達温度の制御が困難となり、最高到達温度が１００℃を超える場合があり、その結果、得られる吸水性樹脂の水可溶成分が増加する場合がある。
【００３５】
重合系の最高到達温度（以後ピーク温度）は８０℃以上にすることが好ましく、より好ましくは８０℃以上１００℃未満、さらにより好ましくは８５〜９５℃である。ピーク温度が８０℃未満では得られる吸水性樹脂の吸収倍率が小さくなることがあり、残存モノマーが多くなる場合がある。一方、ピーク重合温度が１００℃以上になると得られる吸水性樹脂の水可溶成分が増加する場合がある。
【００３６】
重合にともない重合熱が発生するため、本発明では冷却しながら重合を行う。冷却を行わない場合には重合系の温度が１００℃以上に上昇することがある。冷却しながら重合を行うとは、重合が開始してから重合系が重合熱によりピーク温度に達するまでの間、実質的に重合系よりも低い温度のもの、例えば接触面や窒素気流で重合系を冷却することである。接触面で冷却を行う場合には、接触面の温度を０〜３０℃とすることが好ましい。
【００３７】
該温度が０℃よりも低い場合にはその温度を達成するための特別な手段が必要となるため実用的でない。該温度が３０℃よりも高い場合には重合熱の除去が十分に行えない。
【００３８】
重合系の厚み（単量体成分水溶液の液高）は、特に制限はないが、１５〜５０ｍｍの範囲が好ましく、２０〜３０ｍｍの範囲がより好ましい。重合系の厚みが１５ｍｍ未満の場合には生産性が低くなることがあり、一方重合系の厚みが５０ｍｍを超えると重合系の温度の制御が困難となり、ピーク温度が高くなり、得られる吸水性樹脂の水可溶成分が増加することがある。
【００３９】
本発明は、ピーク温度を示した後、得られた含水ゲル状重合体をピーク温度より少なくとも１０℃低い温度で少なくとも３０分保持する。
【００４０】
ピーク温度を示した後、得られた含水ゲル状重合体の保持するとき（本発明では以後“熟成”という）の含水ゲル状重合体の温度（本発明では以後、“熟成ゲル温度”という）が、ピーク温度と同じまたはピーク温度以上であると水可溶成分が増加する。熟成ゲル温度は、好ましくは５０〜８０℃、より好ましくは５０〜７０℃である。
【００４１】
この時の温度は、含水ゲル状重合体の中心温度である。
【００４２】
この熟成の方法は特に制限されないが、得られた含水ゲル状重合体が上記温度範囲内になるように、加熱または冷却してもよいし、断熱・保温してもよい。また、そのときの熟成工程内の相対湿度は５０％RH以上であることが好ましく、７０％RH以上であることがより好ましい。
【００４３】
熟成時の相対湿度が５０％RH未満であると、得られる吸水性樹脂の劣化可溶分が増加する場合がある。
【００４４】
ここで、本発明における劣化可溶分とは、所定量の人工尿を吸水性樹脂に吸収させて所定倍率に膨潤させた含水ゲルを、所定条件下で、所定時間放置した後の水可溶分量である。人工尿吸液後の吸水性樹脂は、経時的に劣化し、同時に可溶分が増大するが、この増加した可溶分量が多いと吸水性樹脂の常圧下および荷重下の吸収倍率を低下したり、そのヌルつきのために著しく不快感を与える等、特に衛生材用吸水剤として好ましくない。よって、この劣化可溶分が少ないほど、尿に対するゲル安定性が高く、かつ長時間優れた性能を維持し、紙おむつ等に使用される吸水性樹脂としては最適である。尚、人工尿とは、尿素、塩化ナトリウム、硫酸マグネシウム、塩化カルシウム、およびL−アスコルビン酸を実際の尿と含有率がほぼ等しくなるように溶解させた水溶液である。また、劣化可溶分量の測定方法については、後段の実施例にて詳述する。
【００４５】
熟成時間は、好ましくは３０〜３００分、より好ましくは９０〜１８０分である。熟成時間が３０分未満では得られる吸水性樹脂の吸収倍率が低く、残存モノマーが多いものになる。熟成時間が３００分を超えるのは、生産性の面から実用的ではない。
【００４６】
熟成するときの含水ゲル状重合体の比表面積は１０cm2/g以下が好ましく、５cm2/g以下がより好ましく、１cm2/g以下がさらにより好ましい。熟成時の含水ゲル状重合体の比表面積が１０cm2/gより大きい場合は得られる吸水性樹脂の吸水倍率が低く、残存モノマーが多いものになることがある。
【００４７】
本発明で使用される重合装置としては、熟成時のゲルサイズを大きくすることが好ましい為、ベルトコンベアの下部片面から加熱および／または冷却が行えるベルトコンベアー型重合装置；プレート面からの片面から加熱および／または冷却が行える熱交換プレート式重合装置；周囲の壁から加熱および／または冷却が行える遠心薄膜型装置または円筒装置のような静置重合装置が好ましい。
【００４８】
本発明で使用される熟成装置としては、上記重合装置をそのまま使用してもよいし、新たに熟成用の装置を設けてもよい。熟成装置の例としては、装置内を密閉にしたベルトコンベア型熟成装置；装置内を温度コントロールできるベルト型熟成装置；プレート面から温度コントロールできる熱交換プレート式熟成装置；周囲の壁から加熱および／または冷却が行える遠心薄膜型熟成装置；紫外線を照射できる紫外線照射熟成装置；赤外線を照射できる赤外線照射熟成装置等を挙げることができる。
【００４９】
上記重合および熟成により得られた含水ゲル状重合体は、まず粗砕され、これをさらに粉砕し、乾燥される。その際の粗砕機としては、板状の含水ゲル状重合体を１０〜１００ｍｍ程度の大きさに砕けるものであれば特に限定されないが、例えば、回転刃と固定刃とを備える竪型切断機（ロートプレックスまたはカティングミルともいう）；互いに対向して設けられた送り速度の異なる対の螺旋状の回転刃で挟んでせん断する粉砕機等を例示できる。また、二次粉砕機としては、乾燥するため平均粒子径が１〜１０ｍｍ程度に粉砕できるものであれば特に限定されないが、例えばカッター刃を備えた縦切り型スリッター、カッター刃を備えた横切り型スリッター、回転刃を備えたカッター式の破断機、所定の口径の目皿と回転刃を備えたミートチョッパー、スクリュー型前押し出し式造粒機、スクリュー型横押し出し式造粒機等が例示できる。
【００５０】
本発明では、得られた含水ゲル状重合体に、重合開始剤を添加してもよい。
【００５１】
得られた含水ゲル状重合体に、重合開始剤を添加する時の含水ゲル状重合体は、重合後熟成前の板ゲル状の含水ゲル状重合体でも、熟成後の板ゲル状の含水ゲル状重合体でも、熟成後粗砕した後の１０〜１００ｍｍ程度の大きさの含水ゲル状重合体でも、さらに、二次粉砕した後の１〜１０ｍｍ程度に粉砕した含水ゲル状重合体でもよいが、重合開始剤の添加の容易さと得られる吸水性樹脂の物性を考えて、熟成後粗砕した後の１０〜１００ｍｍ程度の大きさの含水ゲル状重合体又は二次粉砕した後の１〜１０ｍｍ程度に粉砕した含水ゲル状重合体に重合開始剤を添加するのが好ましく、熟成後粗砕した後の１０〜１００ｍｍ程度の大きさの含水ゲル状重合体に重合開始剤を添加し、二次粉砕時に同時に重合開始剤を混合することがより好ましい。
【００５２】
含水ゲル状重合体に重合開始剤を添加する時の含水ゲル状重合体の比表面積は特に限定されないが、１０cm2/g以下が好ましく、5cm2/g以下がより好ましく、1cm2/g以下がさらにより好ましい。
【００５３】
含水ゲル状重合体に重合開始剤を添加する時の重合開始剤は、特に限定されないが、過硫酸塩を用いることが好ましい。過硫酸塩以外の重合開始剤のみ場合、残存モノマーの残存モノマーの低減効果が少なくなることがある。
【００５４】
過硫酸塩を単独で使用してもよいが、過硫酸塩以外のアゾ化合物や過酸化物のような重合開始剤を併用してもよい。また、還元剤とともにレドックス系で行ってもよい。
【００５５】
過硫酸塩としては、過硫酸ナトリウム、過硫酸カリウム、過硫酸アンモニウム等が例示され、アゾ化合物としては、２，２’−アゾビス（Ｎ，Ｎ’−ジメチレンイソブチルアミド）ジハイドロクロライド、２，２'−アゾビス（２−アミジノプロパン）ジハイドロクロライド、２，２'−アゾビス（Ｎ，Ｎ'−ジメチレンイソブチルアミド）、４，４'−アゾビス４−シアノペンタノイックアシッド、アゾビスイソブチロニトリル等が例示され、過酸化物としては、過酸化水素、アルキルハイドロパーオキサイド類、過エステル類、ジアクリル過酸化物が例示され、還元剤としては、アルカリ金属の亜硫酸塩、アルカリ金属の重亜硫酸塩、亜硫酸アンモニウム、重亜硫酸アンモニウム、アスコルビン酸、エリトルビン酸、硫酸鉄のような鉄金属塩、糖類、アルデヒド類等が例示される。
【００５６】
これらの重合開始剤の使用量としては、前記単量体成分に対して、０．００１モル％〜２モル％の範囲が好ましく、０．０１〜０．５モル％の範囲内がより好ましい。尚、重合開始剤は、水等の溶媒に溶解または分散させればよい。
【００５７】
含水ゲル状重合体に重合開始剤を添加する時の混合機は、重合開始剤を含水ゲル状重合体に均一に混合できるものであれば特に限定されないが、上記した粗砕機や二次粉砕機を用いれば、含水ゲル状重合体の粉砕と重合開始剤の添加混合が同時に行えるため好ましい。
【００５８】
粗砕機としては、例えば、回転刃と固定刃とを備える竪型切断機（ロートプレックスまたはカッティングミルともいう）；互いに対向して設けられた送り速度の異なる対の螺旋状の回転刃で挟んでせん断する粉砕機等を例示できる。また、二次粉砕機としては、例えば、カッター刃を備えた縦切り型スリッター、カッター刃を備えた横切り型スリッター、回転刃を備えたカッター式の破断機、所定の口径の目皿と回転刃を備えたミートチョッパー、スクリュー型前押し出し式造粒機、スクリュー型横押し出し式造粒機等が例示できる。
【００５９】
上記粗砕機、二次粉砕機を通した含水ゲル状重合体の乾燥には、通常の乾燥機や加熱炉を用いることができる。例えば、薄型攪拌乾燥機、回転乾燥機、円盤乾燥機、流動層乾燥機、気流乾燥機、赤外線乾燥機等が例示できる。
【００６０】
上記乾燥により得られた吸水性樹脂はそのまま粗粒状として、あるいは粉砕して粉末状として、用いられる。
【００６１】
本発明ではさらに粒子状の吸水性樹脂の表面近傍を架橋処理してもよく、これにより荷重下の吸収倍率の大きい吸水性樹脂を得ることができる。表面架橋処理には、吸水性樹脂の有する官能基、例えば酸性基と反応し得る架橋剤を用いればよく、通常該用途に用いられている公知の架橋剤が例示される。
【００６２】
表面架橋剤としては、例えば、エチレングリコール、ジエチレングリコール、プロピレングリコール、トリエチレングリコール、テトラエチレングリコール、ポリエチレングリコール、１，３−プロパンジオール、ジプロピレングリコール、２，２，４−トリメチル−１．３−ペンタジオール、ポリプロピレングリコール、グリセリン、ポリグリセリン、２−ブテン−１，４−ジオール、１，４−ブタンジオール、１．５−ペンタンジオール、１，６−ヘキサンジオール、１，２−シクロヘキサンジメタノール、１，２−シクロヘキサノール、トリメチロールプロパン、ジエタノールアミン、トリエタノールアミン、ポリオキシプロピレン、オキシエチレン−オキシプロピレンブロック共重合体、ペンタエリスリトール、ソルビトール等の多価アルコール化合物；エチレングリコールジグリシジルエーテル、ポリエチレンジグリシジルエーテル、グリセロールポリグリシジルエーテル、ジグリセロールポリグリシジルエーテル、ポリグリセロールポリグリシジルエーテル、プロピレングリコールジグリシジルエーテル、ポリプロピレングリシジルエーテル、グリシドール等の多価エポキシ化合物；エチレンジアミン、ジエチレントリアミン、トリエチレンテトラミン、テトラエチレンペンタミン、ペンタエチレンヘキサミン、ポリエチレンイミン等の多価アミン化合物や、それらの無機塩ないし有機塩（例えば、アジチニウム塩）；２，４−トリレンジイソシアネート、ヘキサメチレンジイソシアネート等の多価イソシアネート化合物；１，２−エチレンビスオキサゾリン等の多価オキサゾリン化合物；１，３−ジオキソラン−２−オン、４−メチル−１，３−ジオキソラン−２−オン、４，５−ジメチル−１，３−ジオキソラン−２−オン、４，４−ジメチル−１，３−ジオキソラン−２−オン、４−エチル−１，３−ジオキソラン−２−オン、４−ヒドロキシメチル−１，３−ジオキソラン−２−オン、１，３−ジオキサン−２−オン、４−メチル−１，３−ジオキサン−２−オン、４，６−ジメチル−１，３−ジオキサン−２−オン、１，３−ジオキソパン−２−オン等のアルキレンカーボネート化合物；エピクロロヒドリン、エピブロムヒドリン、α−メチルエピクロロヒドリン等のハロエポキシ化合物、および、その多価アミン付加物（例えばハーキュレス製カイメン：登録商標）；亜鉛、カルシウム、マグネシウム、アルミニウム、鉄、ジルコニウム等の水酸化物及び塩化物等の多可金属化合物等が挙げられる。これらの中でも多価アルコール化合物、多価エポキシ化合物、多価アミン化合物やそれらの塩、アルキレンカーボネート化合物が好ましい。これらの表面架橋剤は単独で用いてもよいし、二種以上併用してもよい。
【００６３】
表面架橋剤の量としては、吸水性樹脂１００重量部に対して０．００１〜１０重量部用いるのが好ましく、０．０１〜５重量部用いるのが好ましい。
【００６４】
加熱処理には通常の乾燥機や加熱炉を用いることができる。例えば、薄型攪拌乾燥機、回転乾燥機、円盤乾燥機、流動層乾燥機、気流乾燥機、赤外線乾燥機等がある。その場合、加熱処理温度は好ましくは４０〜２５０℃、より好ましくは９０〜２３０℃、さらに好ましくは１２０〜２２０℃である。加熱処理時間としては、通常１〜１２０分が好ましく、１０〜６０分がより好ましい。
【００６５】
本発明の製造方法で得られた吸水性樹脂は酸化チタン、酸化ケイ素、活性炭、等の無機微粒子；ポリメタクリル酸メチル等の有機微粒子；パルプなどの親水性繊維；ポリエチレン繊維、ポリプロピレン繊維等の合成繊維；ポリエチレングリコール、ポリオキシエチレンシルビタンモノステアレート等の界面活性剤等をその製造工程の途中であるいは製造後に添加してもよい。
【００６６】
【実施例】
以下に実施例によりさらに詳細に本発明を説明するが、本発明はこれに限定されるものではない。
【００６７】
実施例中で「部」および「％」とは特にことわりがない限り「重量部」および「重量％」を表すものとする。
【００６８】
［吸収倍率］
吸水性樹脂Ａ(g)（約０．２ｇ）を不織布製の袋（６０ｍｍ×６０ｍｍ）に均一に入れ、人工尿（硫酸ナトリウム０．２００％、塩化カリウム０．２００％、塩化マグネシウム６水和物０．０５０％、塩化カルシウム２水和物０．０２５％、リン酸２水素アンモニウム０．０８５％、リン酸水素２アンモニウム０．０１５％、脱イオン水９９．４２５％）中に浸漬した。６０分後に袋を引き上げ、遠心分離機を用いて２５０Gにて３分間水切りを行った後、袋の重量W（ｇ）を測定した。同様の操作を吸水性樹脂を用いずに行い、そのときの袋の重量B（ｇ）を測定した。そして、得られた重量から次式にしたがって、吸水性樹脂の吸収倍率を算出した。
【００６９】
吸収倍率（ｇ／ｇ）＝（Ｗ（ｇ）−Ｂ（ｇ）−Ａ（ｇ））／Ａ（ｇ）
［水可溶成分］
吸水性樹脂Ｃ（ｇ）（約０．５ｇ）を１０００ｇの脱イオン交換水中に分散し、１６時間攪拌した後、濾紙で濾過した。次に、得られた濾液５０ｇを１００ｍｌビーカーにとり、該濾液に０．１Ｎ−水酸化ナトリウム水溶液１ｍｌ、Ｎ／２００−メチルグリコールキトサン水溶液１０ｍｌ、および０．１％トルイジンブルー水溶液４滴を加えた。次いで、上記ビーカーの溶液を、Ｎ／４００ポリビニル硫酸カリウム水溶液を用いてコロイド滴定し、溶液の色が青色から赤紫色に変化した時点を滴定の終点として滴定量Ｄ（ｍｌ）を求めた。
【００７０】
また、濾液５０ｇに代えて脱イオン水５０ｇを用いて同様の操作を行い、ブランクとして滴定量Ｅ（ｍｌ）を求めた。そして、これら滴定量と吸水性樹脂を構成するモノマーの平均分子量Ｆとから、次式にしたがって水可溶成分（重量％）量を算出した。
【００７１】
水可溶成分（重量％）＝（Ｅ（ｍｌ）−Ｄ（ｍｌ））×０．００５／Ｃ（ｇ）×Ｆ
［劣化可溶分］
人工尿（人工尿組成：尿素９５ｇ、塩化ナトリウム４０ｇ、硫酸マグネシウム５ｇ、塩化カルシウム５ｇ、L−アスコルビン酸０．２５ｇ、脱イオン水４８５５ｇ）を用いて、１００ｍｌの蓋付プラスチック容器中で、吸水性樹脂１ｇを２５倍に膨潤させ、温度３７℃で１６時間放置した。１６時間後、上記膨潤ゲルを９７５ｇの脱イオン水中に分散し、１時間攪拌した後、濾紙で１分間濾過した。次に、得られた濾液５０ｇを１００ｍｌビーカーにとり、該濾液に０．１Ｎ−水酸化ナトリウム水溶液１ｍｌ、Ｎ／２００−メチルグリコールキトサン水溶液１０ｍｌ、および、０．１％トルイジンブルー水溶液４滴を加えた。
【００７２】
次いで、上記ビーカーの溶液を、Ｎ／４００−ポリビニル硫酸カリウム水溶液を用いてコロイド滴定し、溶液の色が青色から赤紫色に変化した時点を終点として滴定量G（ｍｌ）を求めた。また、吸水性樹脂を用いないで同様の操作を行い、ブランクとして滴定量H（ｍｌ）を求めた。そして、これら滴定量GおよびHと吸水性樹脂の構成単量体の平均分子量Iとから、次式に従って劣化可溶分（重量％）を算出した。
【００７３】
劣化可溶分（重量％）＝（H−G）×０．００５×I
［残存モノマー］
脱イオン水１０００ｇに吸水性樹脂０．５ｇを加え、攪拌下で２時間抽出した後、膨潤ゲル化した吸水性樹脂を濾紙を用いて濾別し、濾液中の残存モノマー量を液体クロマトグラフィーで分析した。一方、既知濃度のモノマー標準溶液を同様に分析して得た検量線を外部標準とし、濾液の希釈倍率を考慮して、吸水性樹脂中の残存モノマー量を求めた。
【００７４】
［ゲルの比表面積］
代表ゲルを選び、これらの３軸径を測定し、それから表面積を求め、その時のゲルの重量から次式に従って、ゲルの比表面積を算出した。ゲルサイズにバラツキがある場合には１５〜２０個のゲルを測定し、平均値を出した。
【００７５】
ゲルの比表面積（cm2/g）＝ゲルの表面積（cm2）／ゲルの重量（ｇ）
実施例１
アクリル酸１０．７０部、３７重量％アクリル酸ナトリウム水溶液７０．０７部、ポリエチレングリコールジアクリレート（平均分子量４７８）０．０８部、および脱イオン水１９．１５部からなる水溶液を調整し、窒素ガスを導入し脱気した。上記水溶液１１５６ｇ／分と窒素ガスを導入し脱気した０．９８２％Ｖ−５０（和光純薬工業製アゾ系開始剤）水溶液１０ｇ／分、０．９８２％過硫酸ナトリウム水溶液１０ｇ／分、および０．０８８％Ｌ−アスコルビン酸水溶液１０ｇ／分をラインミキシングした後、更に窒素ガスを導入し脱気した０．０７０７％過酸化水素水を１０ｇ／分でラインミキシングし、窒素気流雰囲気下の可動式ベルト重合機に供給した。単量体濃度は３５重量％、水溶液の厚みは２５ｍｍであった。可動式ベルトは１４０ｍｍ／分で駆動させた。ベルトに供給後１分後に重合が開始し、反応系温度は２１℃であった。重合系は攪拌されることなく、ベルト面の温度を１０℃にして冷却された。９分後に重合系は最高到達温度の８５℃を示した。この後、３分後にベルト面の温度を７０℃にして１２分間、含水ゲル状重合体をベルト上で保持した。この含水ゲル状重合体の幅は３００ｍｍ、厚さは２３ｍｍ、温度は７３℃であった。この含水ゲル状重合体を４００ｍｍで切断し（ゲル重量２７４４ｇ、比表面積０．９９cm2/g）、その板状の含水ゲル状重合体をビニール袋に入れ、７５℃に調温した加熱装置に６０分間保持した。保持後のゲル温度は７４℃であった。（ピーク後の合計熟成時間は７５分、ピーク温度よりも１０℃低くなってからの熟成時間６０分以上）
この含水ゲル状重合体をミートチョッパーで粉砕し、１６０℃、６５分間熱風乾燥機で乾燥した。得られた乾燥物を粉砕し、吸水性樹脂（１）を得た。
【００７６】
吸水性樹脂（１）は、吸収倍率６３ｇ／ｇ、可溶成分１０％、劣化可溶分１９％および残存モノマー２３０ｐｐｍであった。
【００７７】
比較例１
アクリル酸１０．７０部、３７重量％アクリル酸ナトリウム水溶液７０．０７部、ポリエチレングリコールジアクリレート（平均分子量４７８）０．０８部、および脱イオン水１９．１５部からなる水溶液を調整し、窒素ガスを導入し脱気した。上記水溶液６６０ｇ／分と窒素ガスを導入し脱気した０．９８２％Ｖ−５０（和光純薬工業製アゾ系開始剤）水溶液５．７ｇ／分、０．９８２％過硫酸ナトリウム水溶液５．７ｇ／分、および０．０８８％Ｌ−アスコルビン酸水溶液５．７ｇ／分をラインミキシングした後、更に窒素ガスを導入し脱気した０．０７０７％過酸化水素水を５．７ｇ／分でラインミキシングし、窒素気流雰囲気下の可動式ベルト重合機に供給した。単量体濃度は３５重量％、水溶液の厚みは２５ｍｍであった。可動式ベルトは８０ｍｍ／分で駆動させた。ベルトに供給後１分後に重合が開始し、反応系温度は２１℃であった。重合系は攪拌されることなく、ベルト面の温度を１０℃にして冷却された。９分後に重合系は最高到達温度の８５℃を示した。この後、３分後にベルト面の温度を７０℃にして１２分間、含水ゲル状重合体をベルト上で保持した。この含水ゲル状重合体の幅は３００ｍｍ、厚さは２３ｍｍ、温度は７２℃であった。（ピーク後の合計熟成時間は１５分、ピーク温度よりも１０℃低くなってからの熟成時間１５分以下）この含水ゲル状重合体をミートチョッパーで粉砕し、１６０℃、６５分間熱風乾燥機で乾燥した。得られた乾燥物を粉砕し、比較用吸水性樹脂（１）を得た。
【００７８】
比較用吸水性樹脂（１）は、吸収倍率６０ｇ／ｇ、可溶成分１１％、劣化可溶分２２％および残存モノマー９５０ｐｐｍであった。
【００７９】
実施例２
アクリル酸１０．７０部、３７重量％アクリル酸ナトリウム水溶液７０．０７部、ポリエチレングリコールジアクリレート（平均分子量４７８）０．０８部、および脱イオン水１９．１５部からなる水溶液を調整し、窒素ガスを導入し脱気した。上記水溶液１１５６ｇ／分と窒素ガスを導入し脱気した０．９８２％Ｖ−５０（和光純薬工業製アゾ系開始剤）水溶液１０ｇ／分、０．９８２％過硫酸ナトリウム水溶液１０ｇ／分、および０．０８８％Ｌ−アスコルビン酸水溶液１０ｇ／分をラインミキシングした後、更に窒素ガスを導入し脱気した０．０７０７％過酸化水素水を１０ｇ／分でラインミキシングし、窒素気流雰囲気下の可動式ベルト重合機に供給した。単量体濃度は３５重量％、水溶液の厚みは２５ｍｍであった。可動式ベルトは１４０ｍｍ／分で駆動させた。ベルトに供給後１分後に重合が開始し、反応系温度は２０℃であった。重合系は攪拌されることなく、ベルト面の温度を７℃にして冷却された。１０分後に重合系は最高到達温度の８０℃を示した。この後、２分後にベルト面の温度を６０℃にして１２分間、含水ゲル状重合体をベルト上で保持した。この含水ゲル状重合体の幅は３００ｍｍ、厚さは２３ｍｍ、温度は６２℃であった。この含水ゲル状重合体を４００ｍｍで切断し（ゲル重量２７４５ｇ、比表面積０．９９cm2/g）、その板状の含水ゲル状重合体をビニール袋に入れ、６０℃に調温した加熱装置に９０分間保持した。保持後のゲル温度は６１℃であった。（ピーク後の合計熟成時間は１０４分、ピーク温度よりも１０℃低くなってからの熟成時間９０分以上）
この含水ゲル状重合体をミートチョッパーで粉砕し、１６０℃、６５分間熱風乾燥機で乾燥した。得られた乾燥物を粉砕し、吸水性樹脂（２）を得た。
【００８０】
吸水性樹脂（２）は、吸収倍率６０ｇ／ｇ、可溶成分８％、劣化可溶分１８％および残存モノマー３４０ｐｐｍであった。
【００８１】
比較例２
アクリル酸１０．７０部、３７重量％アクリル酸ナトリウム水溶液７０．０７部、ポリエチレングリコールジアクリレート（平均分子量４７８）０．０８部、および脱イオン水１９．１５部からなる水溶液を調整し、窒素ガスを導入し脱気した。上記水溶液１１５６ｇ／分と窒素ガスを導入し脱気した０．９８２％Ｖ−５０（和光純薬工業製アゾ系開始剤）水溶液１０ｇ／分、０．９８２％過硫酸ナトリウム水溶液１０ｇ／分、および０．０８８％Ｌ−アスコルビン酸水溶液１０ｇ／分をラインミキシングした後、更に窒素ガスを導入し脱気した０．０７０７％過酸化水素水を１０ｇ／分でラインミキシングし、窒素気流雰囲気下の可動式ベルト重合機に供給した。単量体濃度は３５重量％、水溶液の厚みは２５ｍｍであった。可動式ベルトは１４０ｍｍ／分で駆動させた。ベルトに供給後１分後に重合が開始し、反応系温度は２１℃であった。重合系は攪拌されることなく、ベルト面の温度を１０℃にして冷却された。９分後に重合系は最高到達温度の８５℃を示した。この後、３分後にベルト面の温度を９５℃にして１２分間、含水ゲル状重合体をベルト上で保持した。この含水ゲル状重合体の幅は３００ｍｍ、厚さは２３ｍｍ、温度は９３℃であった。この含水ゲル状重合体を４００ｍｍで切断し（ゲル重量２７４３ｇ、比表面積０．９９cm2/g）、その板状の含水ゲル状重合体をビニール袋に入れ、９５℃に調温した加熱装置に６０分間保持した。保持後のゲル温度は９３℃であった。（ピーク後の合計熟成時間７５分、ピーク温度よりも８℃以上になってからの熟成時間６０分、よってピーク温度よりも１０℃低くなってからの熟成時間１５分以下、実際上ほとんどなし）
この含水ゲル状重合体をミートチョッパーで粉砕し、１６０℃、６５分間熱風乾燥機で乾燥した。得られた乾燥物を粉砕し、比較用吸水性樹脂（２）を得た。
【００８２】
比較用吸水性樹脂（２）は、吸収倍率６０ｇ／ｇ、可溶成分１６％、劣化可溶分３７％および残存モノマー２４０ｐｐｍであった。
【００８３】
実施例３
アクリル酸１０．７０部、３７重量％アクリル酸ナトリウム水溶液７０．０７部、ポリエチレングリコールジアクリレート（平均分子量４７８）０．１０部、および脱イオン水１９．１３部からなる水溶液を調整し、窒素ガスを導入し脱気した。上記水溶液１１５６ｇ／分と窒素ガスを導入し脱気した０．９８２％Ｖ−５０（和光純薬工業製アゾ系開始剤）水溶液１０ｇ／分、０．９８２％過硫酸ナトリウム水溶液１０ｇ／分、および０．０８８％Ｌ−アスコルビン酸水溶液１０ｇ／分をラインミキシングした後、更に窒素ガスを導入し脱気した０．０７０７％過酸化水素水を１０ｇ／分でラインミキシングし、窒素気流雰囲気下の可動式ベルト重合機に供給した。単量体濃度は３５重量％、水溶液の厚みは２５ｍｍであった。可動式ベルトは１４０ｍｍ／分で駆動させた。ベルトに供給後１分後に重合が開始し、反応系温度は２２℃であった。重合系は攪拌されることなく、ベルト面の温度を１５℃にして冷却された。６分後に重合系は最高到達温度の９３℃を示した。この後、６分後にベルト面の温度を５０℃にして１２分間、含水ゲル状重合体をベルト上で保持した。この含水ゲル状重合体の幅は３００ｍｍ、厚さは２３ｍｍ、温度は６５℃であった。この含水ゲル状重合体を４００ｍｍで切断し（ゲル重量２７４４ｇ、比表面積０．９９cm2/g）、その板状の含水ゲル状重合体をビニール袋に入れ、６５℃に調温した加熱装置に１２０分間保持した。保持後のゲル温度は６５℃であった。（ピーク後の合計熟成時間は１３８分、ピーク温度よりも１０℃低くなってからの時間１２０分以上）
この含水ゲル状重合体をミートチョッパーで粉砕し、１６０℃、６５分間熱風乾燥機で乾燥した。得られた乾燥物を粉砕し、吸水性樹脂（３）を得た。
【００８４】
吸水性樹脂（３）は、吸収倍率６８ｇ／ｇ、可溶成分１４％、劣化可溶分２０％および残存モノマー２２０ｐｐｍであった。
【００８５】
比較例３
アクリル酸１０．７０部、３７重量％アクリル酸ナトリウム水溶液７０．０７部、ポリエチレングリコールジアクリレート（平均分子量４７８）０．１０部、および脱イオン水１９．１３部からなる水溶液を調整し、窒素ガスを導入し脱気した。上記水溶液１１５６ｇ／分と窒素ガスを導入し脱気した０．９８２％Ｖ−５０（和光純薬工業製アゾ系開始剤）水溶液１０ｇ／分、０．９８２％過硫酸ナトリウム水溶液１０ｇ／分、および０．０８８％Ｌ−アスコルビン酸水溶液１０ｇ／分をラインミキシングした後、更に窒素ガスを導入し脱気した０．０７０７％過酸化水素水を１０ｇ／分でラインミキシングし、窒素気流雰囲気下の可動式ベルト重合機に供給した。単量体濃度は３５重量％、水溶液の厚みは２５ｍｍであった。可動式ベルトは１４０ｍｍ／分で駆動させた。ベルトに供給後１分後に重合が開始し、反応系温度は２２℃であった。重合系は攪拌されることなく、ベルト面の温度を１５℃にして冷却された。６分後に重合系は最高到達温度の９３℃を示した。この後、６分後にベルト面の温度を８５℃にして１２分間、含水ゲル状重合体をベルト上で保持した。この含水ゲル状重合体の幅は３００ｍｍ、厚さは２３ｍｍ、温度９０℃であった。この含水ゲル状重合体を４００ｍｍで切断し（ゲル重量２７４３ｇ、比表面積０．９９cm2/g）、その板状の含水ゲル状重合体をビニール袋に入れ、９０℃に温調した加熱装置に６０分保持した。保持後のゲル温度は９０℃であった。（ピーク後の合計熟成時間は７８分、ピーク温度よりも３℃低くなってからの時間６０分以上、よってピーク温度より１０℃低くなってからの時間１８分以下、実際上ほとんどなし）この含水ゲル状重合体をミートチョッパーで粉砕し、１６０℃、６５分間熱風乾燥機で乾燥した。得られた乾燥物を粉砕し、比較用吸水性樹脂（３）を得た。
【００８６】
比較用吸水性樹脂（３）は、吸収倍率６３ｇ／ｇ、可溶成分１７％、劣化可溶分４０％および残存モノマー２２０ｐｐｍであった。
【００８７】
実施例４
実施例１において、含水ゲル状重合体をミートチョッパーで粉砕する時に過硫酸ナトリウム０．６％水溶液を０．０２g/mol（含水ゲル状重合体の固形分１ｍｏｌに対して０．０２ｇの過硫酸ナトリウムを０．６％濃度の水溶液で添加した。）均一に添加混合した以外は、実施例１と同様に行い、吸水性樹脂（４）を得た。
【００８８】
吸水性樹脂（４）は、吸収倍率６４ｇ／ｇ、可溶成分１０％、劣化可溶分１９％および残存モノマー１４０ｐｐｍであった。
【００８９】
比較例４
比較例１において、含水ゲル状重合体をミートチョッパーで粉砕する時に過硫酸ナトリウム０．６％水溶液を０．０２g/mol（含水ゲル状重合体の固形分１ｍｏｌに対して０．０２ｇの過硫酸ナトリウムを０．６％濃度の水溶液で添加した。）均一に添加混合した以外は、比較例１と同様に行い、比較用吸水性樹脂（４）を得た。
【００９０】
比較用吸水性樹脂（４）は、吸収倍率６１ｇ／ｇ、可溶成分１２％、劣化可溶分２３％および残存モノマー７４０ｐｐｍであった。
【００９１】
実施例５
アクリル酸１０．７０部、３７重量％アクリル酸ナトリウム水溶液７０．０７部、ポリエチレングリコールジアクリレート（平均分子量４７８）０．０８部、および脱イオン水１９．１５部からなる水溶液を調整し、窒素ガスを導入し脱気した。上記水溶液１１５６ｇ／分と窒素ガスを導入し脱気した０．９８２％Ｖ−５０（和光純薬工業製アゾ系開始剤）水溶液１０ｇ／分、０．９８２％過硫酸ナトリウム水溶液１０ｇ／分、および０．０８８％Ｌ−アスコルビン酸水溶液１０ｇ／分をラインミキシングした後、更に窒素ガスを導入し脱気した０．０７０７％過酸化水素水を１０ｇ／分でラインミキシングし、窒素気流雰囲気下の可動式ベルト重合機に供給した。単量体濃度は３５重量％、水溶液の厚みは２５ｍｍであった。可動式ベルトは１４０ｍｍ／分で駆動させた。ベルトに供給後１分後に重合が開始し、反応系温度は２２℃であった。重合系は攪拌されることなく、ベルト面の温度を１０℃にして冷却された。９分後に重合系は最高到達温度の８６℃を示した。この後、３分後にベルト面の温度を７０℃にして１２分間、含水ゲル状重合体をベルト上で保持した。この含水ゲル状重合体の幅は３００ｍｍ、厚さは２３ｍｍ、温度は７３℃であった。この含水ゲル状重合体を１００ｍｍ×１００ｍｍ×２３ｍｍで切断し（ゲル重量２２９ｇ、比表面積１．２８cm2/g）、その含水ゲル状重合体をビニール袋に入れ、７５℃に調温した加熱装置に６０分間保持した。保持後のゲル温度は７４℃であった。（ピーク後の合計熟成時間は７５分、ピーク温度よりも１０℃低くなってからの熟成時間６０分以上）
含水ゲル状重合体をミートチョッパーで粉砕する時に過硫酸ナトリウム０．６％水溶液を０．０２g/mol（含水ゲル状重合体の固形分１ｍｏｌに対して０．０２ｇの過硫酸ナトリウムを０．６％濃度の水溶液で添加した。）均一に添加混合しながらミートチョッパーで粉砕し、１６０℃、６５分間熱風乾燥機で乾燥した。得られた乾燥物を粉砕し、吸水性樹脂（５）を得た。
【００９２】
吸水性樹脂（５）は、吸収倍率６３ｇ／ｇ、可溶成分１０％、劣化可溶分１９％および残存モノマー１７０ｐｐｍであった。
【００９３】
【発明の効果】
本発明によると、吸収倍率が高く、水可溶成分および残存モノマーの少ない吸水性樹脂を高い生産性で得ることができる。
【００９４】
上記効果を奏することから、本発明により得られた吸水性樹脂は、衛生材料（子供用および大人用オムツ、生理用ナプキン、失禁用パッドなど）などの人体に接する用途；油中の水の分離材；その他の脱水または乾燥剤；植物や土壌などの保水材；ヘドロなどの凝固剤；電線あるいは光ファイバー用止水材；土木建築用止水材など、吸水、保水、湿潤、ゲル化を必要とする各種産業用途に有用である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a water-absorbent resin by polymerizing a monomer component that becomes a water-absorbent resin by polymerization by standing aqueous solution polymerization. More specifically, the present invention relates to a method for producing a water-absorbent resin suitably used for sanitary materials such as paper diapers and sanitary napkins.
[0002]
[Prior art]
In recent years, in the field of sanitary materials such as paper diapers and sanitary napkins, so-called incontinence pads, water-absorbing resins have been widely used for the purpose of absorbing body fluids.
[0003]
Examples of the water-absorbing resin include a polyacrylic acid partially neutralized crosslinked product, a starch-acrylonitrile graft copolymer hydrolyzate, a starch-acrylic acid graft copolymer neutralized product, and vinyl acetate-acrylic acid. A saponified ester copolymer, a hydrolyzate of acrylonitrile copolymer or acrylamide copolymer, a crosslinked product thereof, a crosslinked product of a cationic monomer, and the like are known.
[0004]
As a method for producing these water-absorbent resins, a method is generally employed in which aqueous solution polymerization is performed while stirring an aqueous solution containing a hydrophilic monomer mainly composed of acrylic acid or a salt thereof.
[0005]
Stir polymerization can be performed while cutting the hydrogel polymer that is produced as the polymerization proceeds into small lumps, so that the polymerization peak temperature can be controlled to some extent by removing the heat of polymerization with a relatively compact device. However, since the molecular chain is broken by the shearing force by stirring, the molecular weight is difficult to increase, and the network of the crosslinked structure tends to be disturbed. On the other hand, according to the method proposed in JP-A-3-174414, JP-A-4-175319, and the like, in which the monomer aqueous solution is allowed to stand and polymerize without stirring, the water-absorbing resin is obtained without the above-mentioned problems. Obtainable.
[0006]
Specifically, in JP-A-3-174414, an aqueous solution containing a relatively low concentration of hydrophilic monomer is subjected to adiabatic polymerization using a specific polymerization initiator, and the resulting hydrogel polymer is obtained. A method of chopping and neutralizing with an aqueous base solution is disclosed. In order to perform such adiabatic polymerization, it is necessary to set the concentration of the aqueous monomer solution to about 20% by weight as shown in the examples, and to perform polymerization for 1 to 5 hours. A summing process is required, which requires a considerable amount of time, and the productivity is low. Also, when trying to obtain a product with powder, a drying process is required, and since the concentration of the monomer aqueous solution is low, a large amount of energy is inevitably required for drying, not only low productivity but also economic From an industrial point of view, it is difficult to adopt on an industrial scale. In addition, the physical properties also have a problem that a large amount of residual monomer remains because the concentration of the aqueous monomer solution is low.
[0007]
In JP-A-4-175319, there is a method in which an aqueous solution containing a relatively high concentration hydrophilic monomer is subjected to constant temperature polymerization without stirring (stationary state) and controlling the polymerization temperature to 20 to 70 ° C. It is disclosed. In order to perform constant temperature polymerization at such a relatively low temperature, as shown in the examples, the thickness of the aqueous monomer solution is reduced to about 8 mm or less, and the polymerization system temperature is set to 45 minutes or more. It is necessary to control, and productivity is low and it is difficult to adopt it on an industrial scale.
[0008]
[Problems to be solved by the invention]
An object of the present invention is to solve the above-mentioned conventional problems, and in aqueous solution polymerization, with high productivity, high absorption capacity, and the amount of water-soluble components and the amount of residual monomers are reduced compared to the conventional quality. It is providing the manufacturing method which can obtain a water absorbing resin.
[0009]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above object, the inventors of the present application,A hydrogel polymer having a cross-linked structure from an internal cross-linking agent and an unsaturated monomer component or salt of an unsaturated monomer component that becomes a water-absorbing resin upon polymerization by performing aqueous solution polymerization in a polymerization apparatus In the process of obtaining, after the hydrogel polymer in the polymerization apparatus exhibits a peak temperature, the hydrogel polymer is held at a temperature at least 10 ° C. lower than the peak temperature for at least 30 minutes and dried. The internal cross-linking agent has two or more polymerizable unsaturated groups or two or more reactive groups, and the unsaturated monomer component includes an anionic unsaturated monomer and a nonionic hydrophilic group. It is at least one selected from the group consisting of a group-containing unsaturated monomer and a cationic unsaturated monomer, and the salt of the unsaturated monomer component is a salt of an anionic unsaturated monomer thing,Thus, it has been found that a water-absorbing resin having a high absorption capacity and a reduced amount of water-soluble components and residual monomers can be obtained stably.
[0010]
Furthermore, it is preferable to add a polymerization initiator to the hydrogel polymer.
[0011]
The standing aqueous solution polymerization is preferably performed by a redox system in which a polymerization initiator and a reducing agent are used in combination.
In addition, the hydrogel polymer may be held by being transferred from the polymerization apparatus to an aging apparatus after the peak temperature, or may be held without being transferred from the polymerization apparatus. preferable.
[0012]
Moreover, it is preferable to grind | pulverize and dry a hydrogel polymer after the said holding | maintenance.
[0013]
The peak temperature is preferably 80 ° C. or higher.
[0014]
The relative humidity during the holding is preferably 50% RH or more.
[0015]
Further, it is preferable that acrylic acid is included as the anionic unsaturated monomer, or a salt of acrylic acid is included as a salt of the anionic unsaturated monomer,
The content of the unsaturated monomer component or the salt of the unsaturated monomer component is preferably 15 to 45% by weight,
Moreover, it is preferable that content of the said internal crosslinking agent is 0.005-3 mol% with respect to the salt of the said unsaturated monomer component or the said unsaturated monomer component.
[0016]
Further, the temperature at the start of the standing aqueous solution polymerization is preferably 0 to 30 ° C,
The specific surface area of the retained hydrogel polymer is 10 cm. 2 / G or less is preferable.
[0017]
Moreover, in the above, the method characterized by the neutralization rate of a monomer component being 40-100 mol% is employ | adopted.
[0018]
Moreover, in the above, the method characterized by using a persulfate, an azo reaction initiator, an oxidizing agent, and a reducing agent as the polymerization initiator is adopted.
[0019]
According to the above configuration, it is possible to provide a method for producing a water-absorbent resin that has a high absorption capacity, and further has a water-soluble component amount and a residual monomer amount that are reduced as compared with the prior art.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail.
[0021]
The monomer component used in the present invention to become a water-absorbent resin by polymerization is not particularly limited as long as it can literally become a water-absorbent resin by polymerization. For example, acrylic acid, methacrylic acid, maleic acid, vinyl sulfone Anionic unsaturated monomers such as acid, styrenesulfonic acid, 2- (meth) acrylamido-2-methylpropanesulfonic acid, 2- (meth) acryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid and the like Salt: acrylamide, methacrylamide, N-ethyl (meth) acrylamide, Nn-propyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, 2-hydroxyethyl (meth) Acrylate, 2-hydroxypropyl (meth) ac Nonionic hydrophilic group-containing unsaturation such as rate, methoxypolyethylene glycol (meth) acrylate, polyethylene glycol mono (meth) acrylate, vinylpyridine, N-vinylpyrrolidone, N-vinylacetamide, N-acryloylpiperidine, N-acryloylpyrrolidine Monomer; N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminopropyl (meth) Examples include cationic unsaturated monomers such as acrylamide and quaternary salts thereof. These can use 1 type (s) or 2 or more types.
[0022]
Among these, acrylic acid or a salt thereof (for example, a salt of sodium, lithium, potassium, ammonium, amines, etc.) is preferably used as a main component, more preferably acrylic acid or a sodium salt thereof. It is preferable that the usage-amount of other monomers other than acrylic acid or its salt normally makes it less than 0-50 mol% in all the monomers, More preferably, it is 0-30 mol%.
[0023]
As a neutralization rate of an anionic unsaturated monomer, it is preferable that 40-100 mol% of acid groups are neutralized. When the neutralization rate exceeds 100 mol%, the alkalinity is strong and there is a risk of harming the human body. If it is less than 40 mol%, the absorption capacity of the resulting water-absorbent resin is lowered.
[0024]
The concentration of the monomer component that becomes a water-absorbing resin by polymerization is preferably 15 to 45% by weight, more preferably 25 to 45% by weight, and still more preferably 30 to 40% by weight. If it is less than 15% by weight, the productivity may be low, and if it exceeds 45% by weight, the ratio of the self-crosslinking component of the polymer chain increases and the absorption capacity of the resulting water-absorbent resin decreases. There is.
[0025]
Upon polymerization, starch / cellulose, starch / cellulose derivatives, polyvinyl alcohol, polyacrylic acid (salt), hydrophilic polymers such as cross-linked polyacrylic acid (salt), and chains such as hypophosphorous acid (salt) A transfer agent may be added.
[0026]
In the present invention, the water-absorbing resin preferably has a cross-linked structure, and includes a self-cross-linking type that does not use a cross-linking agent, an internal cross-linking agent having two or more polymerizable unsaturated groups, or two or more reactive groups. Examples of the copolymerized or reacted type can be given. A water-absorbing resin having a crosslinked structure obtained by copolymerizing or reacting an internal crosslinking agent with a hydrophilic unsaturated monomer is preferable.
[0027]
Specific examples of these internal crosslinking agents include, for example, N, N′-methylenebis (meth) acrylamide, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, trimethylolpropane tri (Meth) acrylate, trimethylolpropane di (meth) acrylate, glycerin tri (meth) acrylate, glycerin acrylate methacrylate, ethylene oxide modified trimethylolpropane triacrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate , Triallyl cyanurate, triallyl isocyanurate, triallyl phosphate, triallylamine, poly (meth) allyloxyalkane, (poly) ethylene glycol Lumpur diglycidyl ether, glycerol diglycidyl ether, ethylene glycol, polyethylene glycol, propylene glycol, glycerin, 1,4-butanediol, pentaerythritol, ethylenediamine, polyethyleneimine, and the like glycidyl (meth) acrylate. Alternatively, two or more of these internal crosslinking agents may be used.
[0028]
The amount of the internal crosslinking agent used is preferably 0.005 to 3 mol%, more preferably 0.01 to 1.5 mol%, based on the monomer component. If the amount of the internal cross-linking agent is too small, the amount of water-soluble components tends to increase. Conversely, if the amount of the internal cross-linking agent is too large, the absorption capacity tends to decrease.
[0029]
The polymerization method of the monomer component is not particularly limited as long as it is a static aqueous solution polymerization, and continuous static polymerization performed without stirring on a belt may be performed, or static polymerization in batches. However, continuous stationary polymerization performed without stirring on the belt is preferable from the viewpoint of productivity and uniformity of physical properties of the obtained water-absorbent resin.
[0030]
In the present invention, it is preferable to use a persulfate as the polymerization initiator. When polymerization is carried out only with a polymerization initiator other than persulfate, the residual monomer may be high.
[0031]
A persulfate may be used alone, or a polymerization initiator such as an azo compound or a peroxide other than the persulfate may be used in combination. Moreover, you may carry out by a redox system with a reducing agent.
[0032]
Examples of the persulfate include sodium persulfate, potassium persulfate, and ammonium persulfate. Examples of the azo compound include 2,2′-azobis (N, N′-dimethyleneisobutyramide) dihydrochloride, 2,2 '-Azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis (N, N'-dimethyleneisobutyramide), 4,4'-azobis-4-cyanopentanoic acid, azobisisobutyro Nitriles and the like are exemplified, and peroxides are exemplified by hydrogen peroxide, alkyl hydroperoxides, peresters, and diacryl peroxides, and the reducing agents are alkali metal sulfites and alkali metal bisulfites. Salt, iron metal salt such as ammonium sulfite, ammonium bisulfite, ascorbic acid, erythorbic acid, iron sulfate, sugar , Aldehydes and the like.
[0033]
The amount of these polymerization initiators used is preferably in the range of 0.001 mol% to 2 mol%, more preferably in the range of 0.01 to 0.5 mol%, based on the monomer component. The polymerization initiator may be dissolved or dispersed in a solvent such as water.
[0034]
The polymerization initiation temperature can be appropriately selected, but is preferably in the range of 0 to 30 ° C, more preferably 15 to 25 ° C. When the polymerization start temperature is less than 0 ° C., the induction period and the polymerization time become long, and the productivity may decrease. On the other hand, if the starting temperature exceeds 30 ° C., depending on the monomer concentration, it becomes difficult to control the maximum temperature of the polymerization system, and the maximum temperature may exceed 100 ° C. As a result, the resulting water absorbent resin May increase the water-soluble component.
[0035]
The maximum temperature reached (hereinafter peak temperature) of the polymerization system is preferably 80 ° C. or higher, more preferably 80 ° C. or higher and lower than 100 ° C., still more preferably 85 to 95 ° C. When the peak temperature is less than 80 ° C., the absorption capacity of the resulting water-absorbent resin may be small, and the residual monomer may be increased. On the other hand, when the peak polymerization temperature is 100 ° C. or higher, the water-soluble component of the resulting water-absorbent resin may increase.
[0036]
Since polymerization heat is generated along with the polymerization, the polymerization is carried out while cooling in the present invention. When cooling is not performed, the temperature of the polymerization system may rise to 100 ° C or higher. Polymerization with cooling means that the polymerization system is substantially lower in temperature than the polymerization system from the start of polymerization until the polymerization system reaches the peak temperature due to the heat of polymerization, such as a contact surface or a nitrogen stream. Is to cool. When cooling on the contact surface, the temperature of the contact surface is preferably 0 to 30 ° C.
[0037]
When the temperature is lower than 0 ° C., a special means for achieving the temperature is required, which is not practical. When the temperature is higher than 30 ° C., the polymerization heat cannot be removed sufficiently.
[0038]
Although there is no restriction | limiting in particular in the thickness (liquid height of monomer component aqueous solution) of a polymerization system, the range of 15-50 mm is preferable and the range of 20-30 mm is more preferable. If the thickness of the polymerization system is less than 15 mm, the productivity may be low. On the other hand, if the thickness of the polymerization system exceeds 50 mm, it becomes difficult to control the temperature of the polymerization system, the peak temperature becomes high, and the water absorption obtained The water soluble component of the resin may increase.
[0039]
In the present invention, after the peak temperature is exhibited, the obtained hydrogel polymer is held at a temperature at least 10 ° C. lower than the peak temperature for at least 30 minutes.
[0040]
After showing the peak temperature, the temperature of the hydrogel polymer when the obtained hydrogel polymer is retained (hereinafter referred to as “aged” in the present invention) (hereinafter referred to as “aged gel temperature” in the present invention) However, if it is the same as or higher than the peak temperature, the water-soluble component increases. The aging gel temperature is preferably 50 to 80 ° C, more preferably 50 to 70 ° C.
[0041]
The temperature at this time is the center temperature of the hydrogel polymer.
[0042]
The aging method is not particularly limited, but the hydrated gel polymer obtained may be heated or cooled so as to be within the above temperature range, or may be insulated and kept warm. Further, the relative humidity in the aging step at that time is preferably 50% RH or more, and more preferably 70% RH or more.
[0043]
When the relative humidity at the time of aging is less than 50% RH, the deteriorated soluble content of the obtained water absorbent resin may increase.
[0044]
Here, the degradation soluble component in the present invention means a water-soluble gel after a predetermined amount of artificial urine is absorbed in a water-absorbing resin and swollen at a predetermined magnification under a predetermined condition for a predetermined time. The amount. The water-absorbent resin after artificial urine absorption deteriorates with time, and the soluble content increases at the same time, but if this increased amount of soluble content is large, the absorption capacity of the water-absorbent resin under normal pressure and load will decrease. In particular, it is unpreferable as a water-absorbing agent for sanitary materials, for example, due to the presence of nulls, which makes it extremely uncomfortable. Therefore, the smaller the degradation soluble content is, the higher the gel stability against urine is, and the excellent performance is maintained for a long time, and it is most suitable as a water-absorbing resin used for disposable diapers and the like. Artificial urine is an aqueous solution in which urea, sodium chloride, magnesium sulfate, calcium chloride, and L-ascorbic acid are dissolved so that the content is substantially equal to that of actual urine. Further, the method for measuring the deteriorated soluble content will be described in detail in the Examples below.
[0045]
The aging time is preferably 30 to 300 minutes, more preferably 90 to 180 minutes. When the aging time is less than 30 minutes, the water-absorbing resin obtained has a low absorption rate and a large amount of residual monomer. The aging time exceeding 300 minutes is not practical from the viewpoint of productivity.
[0046]
The specific surface area of the hydrogel polymer during aging is preferably 10 cm2 / g or less, more preferably 5 cm2 / g or less, and even more preferably 1 cm2 / g or less. When the specific surface area of the hydrogel polymer at the time of aging is larger than 10 cm2 / g, the water-absorbing capacity of the obtained water-absorbent resin may be low and the residual monomer may be large.
[0047]
The polymerization apparatus used in the present invention is preferably a belt conveyor type polymerization apparatus capable of heating and / or cooling from the lower surface of the belt conveyor; A heat exchange plate type polymerization apparatus capable of cooling and / or cooling; a stationary polymerization apparatus such as a centrifugal thin film type apparatus or a cylindrical apparatus capable of heating and / or cooling from a surrounding wall is preferable.
[0048]
As the aging apparatus used in the present invention, the polymerization apparatus may be used as it is, or a new aging apparatus may be provided. Examples of the aging apparatus include a belt conveyor type aging apparatus in which the inside of the apparatus is sealed; a belt type aging apparatus capable of controlling the temperature inside the apparatus; a heat exchange plate type aging apparatus capable of controlling the temperature from the plate surface; Alternatively, a centrifugal thin film type ripening apparatus capable of cooling; an ultraviolet irradiation ripening apparatus capable of irradiating ultraviolet rays; an infrared irradiation ripening apparatus capable of irradiating infrared rays, and the like can be given.
[0049]
The hydrogel polymer obtained by the above polymerization and aging is first roughly crushed, further pulverized and dried. The crushing machine in that case is not particularly limited as long as it can crush the plate-like hydrogel polymer into a size of about 10 to 100 mm. For example, a vertical cutting machine including a rotary blade and a fixed blade ( (Also referred to as a rotoplex or cutting mill); a crusher or the like that is sandwiched between a pair of spiral rotating blades that are provided opposite to each other and that have different feeding speeds and shears. The secondary pulverizer is not particularly limited as long as it can be pulverized to an average particle size of about 1 to 10 mm for drying. For example, a vertical slitting slitter equipped with a cutter blade, and a transverse cutter equipped with a cutter blade. Examples thereof include a slitter, a cutter-type breaker equipped with a rotary blade, a meat chopper equipped with a predetermined caliber and a rotary blade, a screw-type pre-extrusion type granulator, a screw-type side-extrusion type granulator, and the like.
[0050]
In the present invention, a polymerization initiator may be added to the obtained hydrogel polymer.
[0051]
When the polymerization initiator is added to the obtained water-containing gel polymer, the water-containing gel polymer may be a plate-gel water-containing polymer before polymerization and aging, or a plate-gel water-containing gel after aging. The polymer may be a hydrated gel-like polymer having a size of about 10 to 100 mm after ripening after aging, or a hydrated gel-like polymer crushed to about 1 to 10 mm after secondary pulverization. Considering the ease of addition of the polymerization initiator and the properties of the resulting water-absorbent resin, the hydrogel polymer having a size of about 10 to 100 mm after ripening after aging or 1 to 10 mm after secondary pulverization It is preferable to add a polymerization initiator to the hydrogel polymer that has been pulverized to the extent that the secondary polymer is added to the hydrogel polymer having a size of about 10 to 100 mm after aging and coarse crushing. It is more preferable to mix the polymerization initiator at the same time when grinding. There.
[0052]
The specific surface area of the hydrogel polymer when adding a polymerization initiator to the hydrogel polymer is not particularly limited, but is preferably 10 cm2 / g or less, more preferably 5 cm2 / g or less, and even more preferably 1 cm2 / g or less. preferable.
[0053]
The polymerization initiator for adding the polymerization initiator to the hydrogel polymer is not particularly limited, but it is preferable to use a persulfate. When only a polymerization initiator other than persulfate is used, the residual monomer reducing effect of the residual monomer may be reduced.
[0054]
A persulfate may be used alone, but a polymerization initiator such as an azo compound or a peroxide other than the persulfate may be used in combination. Moreover, you may carry out by a redox system with a reducing agent.
[0055]
Examples of the persulfate include sodium persulfate, potassium persulfate, and ammonium persulfate. Examples of the azo compound include 2,2′-azobis (N, N′-dimethyleneisobutyramide) dihydrochloride, 2,2 '-Azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis (N, N'-dimethyleneisobutyramide), 4,4'-azobis-4-cyanopentanoic acid, azobisisobutyro Nitriles and the like are exemplified, and peroxides are exemplified by hydrogen peroxide, alkyl hydroperoxides, peresters, and diacryl peroxides, and the reducing agents are alkali metal sulfites and alkali metal bisulfites. Salts, iron metal salts such as ammonium sulfite, ammonium bisulfite, ascorbic acid, erythorbic acid, iron sulfate, Examples include saccharides and aldehydes.
[0056]
The amount of these polymerization initiators used is preferably in the range of 0.001 mol% to 2 mol%, more preferably in the range of 0.01 to 0.5 mol%, based on the monomer component. The polymerization initiator may be dissolved or dispersed in a solvent such as water.
[0057]
The mixer for adding the polymerization initiator to the hydrogel polymer is not particularly limited as long as the polymerization initiator can be uniformly mixed with the hydrogel polymer. Is preferable because pulverization of the hydrogel polymer and addition and mixing of the polymerization initiator can be performed simultaneously.
[0058]
As a crusher, for example, a vertical cutting machine (also referred to as a rotoplex or cutting mill) provided with a rotary blade and a fixed blade; sandwiched by a pair of spiral rotary blades provided opposite to each other and having different feed speeds A shearing pulverizer can be exemplified. Further, as the secondary pulverizer, for example, a longitudinal slitting slitter equipped with a cutter blade, a transverse slitting slitter equipped with a cutter blade, a cutter-type breaking machine equipped with a rotating blade, a pan with a predetermined diameter and a rotating blade Meat chopper, a screw type pre-extrusion type granulator, a screw type horizontal extrusion type granulator, and the like.
[0059]
A normal dryer or a heating furnace can be used for drying the hydrogel polymer through the crusher and the secondary pulverizer. For example, a thin agitation dryer, a rotary dryer, a disk dryer, a fluidized bed dryer, a flash dryer, an infrared dryer, and the like can be exemplified.
[0060]
The water-absorbent resin obtained by the above drying can be used as it is in the form of coarse particles or as a powder after being pulverized.
[0061]
In the present invention, the vicinity of the surface of the particulate water-absorbent resin may be subjected to a crosslinking treatment, whereby a water-absorbent resin having a large absorption capacity under load can be obtained. For the surface cross-linking treatment, a cross-linking agent capable of reacting with a functional group of the water-absorbent resin, such as an acidic group, may be used, and known cross-linking agents usually used for the application are exemplified.
[0062]
Examples of the surface crosslinking agent include ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, 1,3-propanediol, dipropylene glycol, 2,2,4-trimethyl-1.3-. Pentadiol, polypropylene glycol, glycerin, polyglycerin, 2-butene-1,4-diol, 1,4-butanediol, 1.5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,2-cyclohexanol, trimethylolpropane, diethanolamine, triethanolamine, polyoxypropylene, oxyethylene-oxypropylene block copolymer, pentaerythritol, sorbitol, etc. Alcohol compounds; polyhydric epoxy compounds such as ethylene glycol diglycidyl ether, polyethylene diglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycidyl ether, glycidol; ethylenediamine , Diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyethyleneimine, and other polyvalent amine compounds and their inorganic or organic salts (eg, aditinium salts); 2,4-tolylene diisocyanate, hexamethylene Polyvalent isocyanate compounds such as diisocyanate; polyvalent isocyanates such as 1,2-ethylenebisoxazoline Xazoline compound; 1,3-dioxolan-2-one, 4-methyl-1,3-dioxolan-2-one, 4,5-dimethyl-1,3-dioxolan-2-one, 4,4-dimethyl-1 , 3-dioxolan-2-one, 4-ethyl-1,3-dioxolan-2-one, 4-hydroxymethyl-1,3-dioxolan-2-one, 1,3-dioxan-2-one, 4- Alkylene carbonate compounds such as methyl-1,3-dioxan-2-one, 4,6-dimethyl-1,3-dioxan-2-one, 1,3-dioxopan-2-one; epichlorohydrin, epibrom Haloepoxy compounds such as hydrin and α-methylepichlorohydrin, and polyvalent amine adducts thereof (for example, Hercules Kaimen: registered trademark); zinc, calcium, magnesi Beam, aluminum, iron, Taka metal compound hydroxides and chlorides of zirconium, and the like. Among these, polyhydric alcohol compounds, polyhydric epoxy compounds, polyhydric amine compounds and salts thereof, and alkylene carbonate compounds are preferable. These surface crosslinking agents may be used alone or in combination of two or more.
[0063]
The amount of the surface cross-linking agent is preferably 0.001 to 10 parts by weight, and preferably 0.01 to 5 parts by weight with respect to 100 parts by weight of the water absorbent resin.
[0064]
A normal dryer or a heating furnace can be used for the heat treatment. For example, there are a thin stirring dryer, a rotary dryer, a disk dryer, a fluidized bed dryer, a flash dryer, an infrared dryer, and the like. In that case, heat processing temperature becomes like this. Preferably it is 40-250 degreeC, More preferably, it is 90-230 degreeC, More preferably, it is 120-220 degreeC. As heat processing time, 1-120 minutes are preferable normally and 10-60 minutes are more preferable.
[0065]
The water-absorbent resin obtained by the production method of the present invention is composed of inorganic fine particles such as titanium oxide, silicon oxide, activated carbon, etc .; organic fine particles such as polymethyl methacrylate; hydrophilic fibers such as pulp; synthesis of polyethylene fibers, polypropylene fibers, etc. Fibers: Surfactants such as polyethylene glycol and polyoxyethylenesilbitan monostearate may be added during or after the production process.
[0066]
【Example】
The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.
[0067]
In the examples, “parts” and “%” represent “parts by weight” and “% by weight” unless otherwise specified.
[0068]
[Absorption magnification]
Water-absorbing resin A (g) (approximately 0.2 g) is uniformly placed in a non-woven bag (60 mm × 60 mm) and artificial urine (sodium sulfate 0.200%, potassium chloride 0.200%, magnesium chloride hexahydrate) Product 0.050%, calcium chloride dihydrate 0.025%, ammonium dihydrogen phosphate 0.085%, diammonium hydrogen phosphate 0.015%, deionized water 99.425%). After 60 minutes, the bag was pulled up, drained at 250 G for 3 minutes using a centrifuge, and the weight W (g) of the bag was measured. The same operation was performed without using the water absorbent resin, and the weight B (g) of the bag at that time was measured. Then, the absorption capacity of the water absorbent resin was calculated from the obtained weight according to the following formula.
[0069]
Absorption capacity (g / g) = (W (g) -B (g) -A (g)) / A (g)
[Water-soluble component]
Water-absorbent resin C (g) (about 0.5 g) was dispersed in 1000 g of deionized exchange water, stirred for 16 hours, and then filtered through filter paper. Next, 50 g of the obtained filtrate was placed in a 100 ml beaker, and 1 ml of 0.1N sodium hydroxide aqueous solution, 10 ml of N / 200-methylglycol chitosan aqueous solution, and 4 drops of 0.1% toluidine blue aqueous solution were added to the filtrate. Next, the solution of the beaker was colloidally titrated with an aqueous N / 400 potassium potassium sulfate solution, and the titration point D (ml) was determined with the time when the color of the solution changed from blue to reddish purple as the end point of titration.
[0070]
Moreover, it replaced with 50 g of filtrates, performed the same operation using 50 g of deionized water, and calculated | required titer E (ml) as a blank. Then, from these titration amounts and the average molecular weight F of the monomer constituting the water-absorbent resin, the amount of water-soluble component (% by weight) was calculated according to the following formula.
[0071]
Water-soluble component (% by weight) = (E (ml) −D (ml)) × 0.005 / C (g) × F
[Degraded soluble content]
Using artificial urine (artificial urine composition: urea 95 g, sodium chloride 40 g, magnesium sulfate 5 g, calcium chloride 5 g, L-ascorbic acid 0.25 g, deionized water 4855 g) in a 100 ml plastic container with a lid. 1 g of resin was swollen 25 times and allowed to stand at a temperature of 37 ° C. for 16 hours. After 16 hours, the swollen gel was dispersed in 975 g of deionized water, stirred for 1 hour, and then filtered through filter paper for 1 minute. Next, 50 g of the obtained filtrate was placed in a 100 ml beaker, and 1 ml of 0.1N sodium hydroxide aqueous solution, 10 ml of N / 200-methylglycol chitosan aqueous solution, and 4 drops of 0.1% toluidine blue aqueous solution were added to the filtrate. .
[0072]
Next, the solution of the beaker was colloidally titrated using an N / 400-polyvinyl potassium sulfate aqueous solution, and the titration amount G (ml) was determined with the time point when the color of the solution changed from blue to reddish purple. Moreover, the same operation was performed without using a water-absorbent resin, and a titration amount H (ml) was determined as a blank. Then, from these titration amounts G and H and the average molecular weight I of the constituent monomers of the water-absorbent resin, the degradation soluble content (% by weight) was calculated according to the following formula.
[0073]
Degradable soluble content (% by weight) = (H−G) × 0.005 × I
[Residual monomer]
After adding 0.5 g of water-absorbing resin to 1000 g of deionized water and extracting with stirring for 2 hours, the swollen gelled water-absorbing resin was filtered off using filter paper, and the amount of residual monomer in the filtrate was determined by liquid chromatography. analyzed. On the other hand, a calibration curve obtained by analyzing a monomer standard solution having a known concentration in the same manner was used as an external standard, and the amount of residual monomer in the water-absorbent resin was determined in consideration of the dilution rate of the filtrate.
[0074]
[Specific surface area of gel]
Representative gels were selected, their triaxial diameters were measured, the surface area was determined therefrom, and the specific surface area of the gel was calculated from the weight of the gel at that time according to the following formula. When there was a variation in gel size, 15 to 20 gels were measured and averaged.
[0075]
Specific surface area of the gel (cm2 / g) = Surface area of the gel (cm2) / Gel weight (g)
Example 1
An aqueous solution comprising 10.70 parts of acrylic acid, 70.07 parts of a 37 wt% sodium acrylate aqueous solution, 0.08 part of polyethylene glycol diacrylate (average molecular weight 478), and 19.15 parts of deionized water was prepared, and nitrogen gas was prepared. Was degassed. 0.956% V-50 (azo initiator manufactured by Wako Pure Chemical Industries, Ltd.) aqueous solution 10 g / min, 0.982% sodium persulfate aqueous solution 10 g / min, degassed by introducing 1156 g / min of the above aqueous solution and nitrogen gas, and Line mixing of 10 g / min of 0.088% L-ascorbic acid aqueous solution, followed by line mixing of 0.0707% hydrogen peroxide solution degassed by introducing nitrogen gas at 10 g / min. Was fed to a belt polymerization machine. The monomer concentration was 35% by weight, and the thickness of the aqueous solution was 25 mm. The movable belt was driven at 140 mm / min. Polymerization started 1 minute after feeding to the belt, and the reaction system temperature was 21 ° C. The polymerization system was cooled to a temperature of 10 ° C. without stirring. After 9 minutes, the polymerization system showed a maximum temperature of 85 ° C. Thereafter, after 3 minutes, the temperature of the belt surface was raised to 70 ° C. and the hydrogel polymer was held on the belt for 12 minutes. This hydrogel polymer had a width of 300 mm, a thickness of 23 mm, and a temperature of 73 ° C. This hydrogel polymer was cut at 400 mm (gel weight 2744 g, specific surface area 0.99 cm 2 / g), the plate-like hydrogel polymer was put in a plastic bag, and heated to 75 ° C. in a heating device 60 Hold for a minute. The gel temperature after holding was 74 ° C. (Total aging time after peak is 75 minutes, aging time is 60 minutes or more after 10 ° C lower than peak temperature)
This hydrogel polymer was pulverized with a meat chopper and dried with a hot air dryer at 160 ° C. for 65 minutes. The obtained dried product was pulverized to obtain a water absorbent resin (1).
[0076]
The water-absorbent resin (1) had an absorption rate of 63 g / g, a soluble component of 10%, a deteriorated soluble component of 19% and a residual monomer of 230 ppm.
[0077]
Comparative Example 1
An aqueous solution comprising 10.70 parts of acrylic acid, 70.07 parts of a 37 wt% sodium acrylate aqueous solution, 0.08 part of polyethylene glycol diacrylate (average molecular weight 478), and 19.15 parts of deionized water was prepared, and nitrogen gas was prepared. Was degassed. The above aqueous solution 660 g / min and nitrogen gas were introduced and degassed 0.982% V-50 (azo initiator manufactured by Wako Pure Chemical Industries) 5.7 g / min, 0.982% sodium persulfate aqueous solution 5.7 g Line mixing of 5.7 g / min of 0.088% L-ascorbic acid aqueous solution, and then demixing 0.0707% hydrogen peroxide water degassed by introducing nitrogen gas at 5.7 g / min. Then, it was supplied to a movable belt polymerization machine in a nitrogen stream atmosphere. The monomer concentration was 35% by weight, and the thickness of the aqueous solution was 25 mm. The movable belt was driven at 80 mm / min. Polymerization started 1 minute after feeding to the belt, and the reaction system temperature was 21 ° C. The polymerization system was cooled to a temperature of 10 ° C. without stirring. After 9 minutes, the polymerization system showed a maximum temperature of 85 ° C. Thereafter, after 3 minutes, the temperature of the belt surface was raised to 70 ° C. and the hydrogel polymer was held on the belt for 12 minutes. This hydrogel polymer had a width of 300 mm, a thickness of 23 mm, and a temperature of 72 ° C. (The total aging time after the peak is 15 minutes, and the aging time is 15 minutes or less after 10 ° C. lower than the peak temperature.) This hydrogel polymer is crushed with a meat chopper and heated at 160 ° C. for 65 minutes with a hot air dryer Dried. The obtained dried product was pulverized to obtain a comparative water absorbent resin (1).
[0078]
The comparative water absorbent resin (1) had an absorption capacity of 60 g / g, a soluble component of 11%, a deteriorated soluble content of 22% and a residual monomer of 950 ppm.
[0079]
Example 2
An aqueous solution comprising 10.70 parts of acrylic acid, 70.07 parts of a 37 wt% sodium acrylate aqueous solution, 0.08 part of polyethylene glycol diacrylate (average molecular weight 478), and 19.15 parts of deionized water was prepared, and nitrogen gas was prepared. Was degassed. 0.956% V-50 (azo initiator manufactured by Wako Pure Chemical Industries, Ltd.) aqueous solution 10 g / min, 0.982% sodium persulfate aqueous solution 10 g / min, degassed by introducing 1156 g / min of the above aqueous solution and nitrogen gas, and Line mixing of 10 g / min of 0.088% L-ascorbic acid aqueous solution, followed by line mixing of 0.0707% hydrogen peroxide solution degassed by introducing nitrogen gas at 10 g / min. Was fed to a belt polymerization machine. The monomer concentration was 35% by weight, and the thickness of the aqueous solution was 25 mm. The movable belt was driven at 140 mm / min. Polymerization started 1 minute after feeding to the belt, and the reaction system temperature was 20 ° C. The polymerization system was cooled to a belt surface temperature of 7 ° C. without stirring. After 10 minutes, the polymerization system showed a maximum temperature of 80 ° C. Thereafter, the temperature of the belt surface was changed to 60 ° C. after 2 minutes, and the hydrogel polymer was held on the belt for 12 minutes. This hydrogel polymer had a width of 300 mm, a thickness of 23 mm, and a temperature of 62 ° C. This hydrogel polymer was cut at 400 mm (gel weight 2745 g, specific surface area 0.99 cm 2 / g), the plate-like hydrogel polymer was placed in a plastic bag, and heated to 60 ° C. in a heating device 90 Hold for a minute. The gel temperature after the holding was 61 ° C. (The total aging time after the peak is 104 minutes, and the aging time is 90 minutes or more after 10 ° C. lower than the peak temperature)
This hydrogel polymer was pulverized with a meat chopper and dried with a hot air dryer at 160 ° C. for 65 minutes. The obtained dried product was pulverized to obtain a water absorbent resin (2).
[0080]
The water absorbent resin (2) had an absorption capacity of 60 g / g, a soluble component of 8%, a deteriorated soluble content of 18% and a residual monomer of 340 ppm.
[0081]
Comparative Example 2
An aqueous solution comprising 10.70 parts of acrylic acid, 70.07 parts of a 37 wt% sodium acrylate aqueous solution, 0.08 part of polyethylene glycol diacrylate (average molecular weight 478), and 19.15 parts of deionized water was prepared, and nitrogen gas was prepared. Was degassed. 0.956% V-50 (azo initiator manufactured by Wako Pure Chemical Industries, Ltd.) aqueous solution 10 g / min, 0.982% sodium persulfate aqueous solution 10 g / min, degassed by introducing 1156 g / min of the above aqueous solution and nitrogen gas, and Line mixing of 10 g / min of 0.088% L-ascorbic acid aqueous solution, followed by line mixing of 0.0707% hydrogen peroxide solution degassed by introducing nitrogen gas at 10 g / min. Was fed to a belt polymerization machine. The monomer concentration was 35% by weight, and the thickness of the aqueous solution was 25 mm. The movable belt was driven at 140 mm / min. Polymerization started 1 minute after feeding to the belt, and the reaction system temperature was 21 ° C. The polymerization system was cooled to a temperature of 10 ° C. without stirring. After 9 minutes, the polymerization system showed a maximum temperature of 85 ° C. Thereafter, after 3 minutes, the temperature of the belt surface was set to 95 ° C. and the hydrogel polymer was held on the belt for 12 minutes. The hydrogel polymer had a width of 300 mm, a thickness of 23 mm, and a temperature of 93 ° C. This hydrogel polymer was cut at 400 mm (gel weight 2743 g, specific surface area 0.99 cm 2 / g), the plate-like hydrogel polymer was put in a plastic bag, and heated to 95 ° C. in a heating device 60 Hold for a minute. The gel temperature after holding was 93 ° C. (Total aging time after peak is 75 minutes, aging time is 60 minutes after peak temperature is 8 ° C. or higher, therefore aging time is 15 minutes or less after 10 ° C. lower than peak temperature, practically almost none)
This hydrogel polymer was pulverized with a meat chopper and dried with a hot air dryer at 160 ° C. for 65 minutes. The obtained dried product was pulverized to obtain a comparative water absorbent resin (2).
[0082]
The comparative water absorbent resin (2) had an absorption ratio of 60 g / g, a soluble component of 16%, a deteriorated soluble content of 37% and a residual monomer of 240 ppm.
[0083]
Example 3
An aqueous solution comprising 10.70 parts of acrylic acid, 70.07 parts of a 37 wt% sodium acrylate aqueous solution, 0.10 parts of polyethylene glycol diacrylate (average molecular weight 478), and 19.13 parts of deionized water was prepared, and nitrogen gas was prepared. Was degassed. 0.956% V-50 (azo initiator manufactured by Wako Pure Chemical Industries, Ltd.) aqueous solution 10 g / min, 0.982% sodium persulfate aqueous solution 10 g / min, degassed by introducing 1156 g / min of the above aqueous solution and nitrogen gas, and Line mixing of 10 g / min of 0.088% L-ascorbic acid aqueous solution, followed by line mixing of 0.0707% hydrogen peroxide solution degassed by introducing nitrogen gas at 10 g / min. Was fed to a belt polymerization machine. The monomer concentration was 35% by weight, and the thickness of the aqueous solution was 25 mm. The movable belt was driven at 140 mm / min. Polymerization started 1 minute after feeding to the belt, and the reaction system temperature was 22 ° C. The polymerization system was cooled to a belt surface temperature of 15 ° C. without stirring. After 6 minutes, the polymerization system showed a maximum temperature of 93 ° C. Then, after 6 minutes, the temperature of the belt surface was set to 50 ° C., and the hydrogel polymer was held on the belt for 12 minutes. This hydrogel polymer had a width of 300 mm, a thickness of 23 mm, and a temperature of 65 ° C. This hydrogel polymer was cut at 400 mm (gel weight 2744 g, specific surface area 0.99 cm 2 / g), the plate-like hydrogel polymer was put in a plastic bag, and heated to 65 ° C. in a heating device 120. Hold for a minute. The gel temperature after holding was 65 ° C. (Total ripening time after peak is 138 minutes, 120 minutes or more after 10 ° C lower than peak temperature)
This hydrogel polymer was pulverized with a meat chopper and dried with a hot air dryer at 160 ° C. for 65 minutes. The obtained dried product was pulverized to obtain a water absorbent resin (3).
[0084]
The water-absorbent resin (3) had an absorption rate of 68 g / g, a soluble component of 14%, a deteriorated soluble content of 20%, and a residual monomer of 220 ppm.
[0085]
Comparative Example 3
An aqueous solution comprising 10.70 parts of acrylic acid, 70.07 parts of a 37 wt% sodium acrylate aqueous solution, 0.10 parts of polyethylene glycol diacrylate (average molecular weight 478), and 19.13 parts of deionized water was prepared, and nitrogen gas was prepared. Was degassed. 0.956% V-50 (azo initiator manufactured by Wako Pure Chemical Industries, Ltd.) aqueous solution 10 g / min, 0.982% sodium persulfate aqueous solution 10 g / min, degassed by introducing 1156 g / min of the above aqueous solution and nitrogen gas, and Line mixing of 10 g / min of 0.088% L-ascorbic acid aqueous solution, followed by line mixing of 0.0707% hydrogen peroxide solution degassed by introducing nitrogen gas at 10 g / min. Was fed to a belt polymerization machine. The monomer concentration was 35% by weight, and the thickness of the aqueous solution was 25 mm. The movable belt was driven at 140 mm / min. Polymerization started 1 minute after feeding to the belt, and the reaction system temperature was 22 ° C. The polymerization system was cooled to a belt surface temperature of 15 ° C. without stirring. After 6 minutes, the polymerization system showed a maximum temperature of 93 ° C. Thereafter, after 6 minutes, the temperature of the belt surface was raised to 85 ° C. and the hydrogel polymer was held on the belt for 12 minutes. This hydrogel polymer had a width of 300 mm, a thickness of 23 mm, and a temperature of 90 ° C. This hydrogel polymer was cut at 400 mm (gel weight 2743 g, specific surface area 0.99 cm 2 / g), the plate-like hydrogel polymer was put in a plastic bag, and the temperature was adjusted to 90 ° C. in a heating device 60 Held for a minute. The gel temperature after holding was 90 ° C. (Total ripening time after peak is 78 minutes, 60 minutes or more after 3 ° C. lower than peak temperature, and therefore less than 18 minutes after 10 ° C. lower than peak temperature, practically almost none) The gel polymer was pulverized with a meat chopper and dried with a hot air dryer at 160 ° C. for 65 minutes. The obtained dried product was pulverized to obtain a comparative water absorbent resin (3).
[0086]
The comparative water absorbent resin (3) had an absorption capacity of 63 g / g, a soluble component of 17%, a deteriorated soluble component of 40% and a residual monomer of 220 ppm.
[0087]
Example 4
In Example 1, when the hydrogel polymer was pulverized with a meat chopper, a sodium persulfate 0.6% aqueous solution was 0.02 g / mol (0.02 g persulfate per 1 mol of the solid content of the hydrogel polymer). Sodium was added as an aqueous solution having a concentration of 0.6%.) A water absorbent resin (4) was obtained in the same manner as in Example 1 except that the mixture was uniformly added and mixed.
[0088]
The water absorbent resin (4) had an absorption capacity of 64 g / g, a soluble component of 10%, a deteriorated soluble component of 19% and a residual monomer of 140 ppm.
[0089]
Comparative Example 4
In Comparative Example 1, 0.02 g / mol of a sodium persulfate 0.6% aqueous solution (0.02 g persulfate per 1 mol of the solid content of the hydrogel polymer) was pulverized with a meat chopper. Sodium was added in an aqueous solution having a concentration of 0.6%.) A comparative water-absorbing resin (4) was obtained in the same manner as in Comparative Example 1 except that it was uniformly added and mixed.
[0090]
The comparative water absorbent resin (4) had an absorption ratio of 61 g / g, a soluble component of 12%, a deteriorated soluble content of 23% and a residual monomer of 740 ppm.
[0091]
Example 5
An aqueous solution comprising 10.70 parts of acrylic acid, 70.07 parts of a 37 wt% sodium acrylate aqueous solution, 0.08 part of polyethylene glycol diacrylate (average molecular weight 478), and 19.15 parts of deionized water was prepared, and nitrogen gas was prepared. Was degassed. 0.956% V-50 (azo initiator manufactured by Wako Pure Chemical Industries, Ltd.) aqueous solution 10 g / min, 0.982% sodium persulfate aqueous solution 10 g / min, degassed by introducing 1156 g / min of the above aqueous solution and nitrogen gas, and Line mixing of 10 g / min of 0.088% L-ascorbic acid aqueous solution, followed by line mixing of 0.0707% hydrogen peroxide solution degassed by introducing nitrogen gas at 10 g / min. Was fed to a belt polymerization machine. The monomer concentration was 35% by weight, and the thickness of the aqueous solution was 25 mm. The movable belt was driven at 140 mm / min. Polymerization started 1 minute after feeding to the belt, and the reaction system temperature was 22 ° C. The polymerization system was cooled to a temperature of 10 ° C. without stirring. After 9 minutes, the polymerization system showed a maximum temperature of 86 ° C. Thereafter, after 3 minutes, the temperature of the belt surface was raised to 70 ° C. and the hydrogel polymer was held on the belt for 12 minutes. This hydrogel polymer had a width of 300 mm, a thickness of 23 mm, and a temperature of 73 ° C. This hydrogel polymer was cut at 100 mm × 100 mm × 23 mm (gel weight 229 g, specific surface area 1.28 cm 2 / g), and the hydrogel polymer was put in a plastic bag and heated to 75 ° C. Hold for 60 minutes. The gel temperature after holding was 74 ° C. (Total aging time after peak is 75 minutes, aging time is 60 minutes or more after 10 ° C lower than peak temperature)
When the hydrogel polymer is pulverized with a meat chopper, the sodium persulfate 0.6% aqueous solution is 0.02 g / mol (0.02 g of sodium persulfate is 0.6 mol per 1 mol of the solid content of the hydrogel polymer). The solution was added with an aqueous solution having a concentration of%). The obtained dried product was pulverized to obtain a water absorbent resin (5).
[0092]
The water absorbent resin (5) had an absorption capacity of 63 g / g, a soluble component of 10%, a deteriorated soluble component of 19% and a residual monomer of 170 ppm.
[0093]
【The invention's effect】
According to the present invention, it is possible to obtain a water-absorbing resin having a high absorption capacity and a small amount of water-soluble components and residual monomers with high productivity.
[0094]
Because of the above effects, the water-absorbent resin obtained by the present invention is used for contact with the human body such as sanitary materials (diapers for children and adults, sanitary napkins, incontinence pads, etc.); separation of water in oil Materials; Other dehydration or desiccants; Water retention materials such as plants and soils; Coagulants such as sludge; Electric water or optical fiber waterproofing materials; It is useful for various industrial applications.
Claims (9)
前記重合装置中の含水ゲル状重合体がピーク温度を示した後、前記含水ゲル状重合体を前記ピーク温度より少なくとも１０℃低い温度で少なくとも３０分保持し、乾燥すること、 After the hydrogel polymer in the polymerization apparatus exhibits a peak temperature, the hydrogel polymer is held at a temperature at least 10 ° C. lower than the peak temperature for at least 30 minutes and dried.
前記内部架橋剤は、２個以上の重合性不飽和基あるいは２個以上の反応性基を有すること、ならびに、 The internal crosslinking agent has two or more polymerizable unsaturated groups or two or more reactive groups; and
前記不飽和単量体成分は、アニオン性不飽和単量体、ノニオン性の親水基含有不飽和単量体、およびカチオン性不飽和単量体からなる群より選択される少なくとも１種であり、前記不飽和単量体成分の塩はアニオン性不飽和単量体の塩であること、 The unsaturated monomer component is at least one selected from the group consisting of an anionic unsaturated monomer, a nonionic hydrophilic group-containing unsaturated monomer, and a cationic unsaturated monomer, The salt of the unsaturated monomer component is a salt of an anionic unsaturated monomer;
を特徴とする吸水性樹脂の製造方法。 A method for producing a water-absorbent resin characterized by
前記重合装置から熟成用の装置に移されて前記保持されるか、または Transferred from the polymerization apparatus to the aging apparatus and held, or
前記重合装置から移されずに前記保持されることを特徴とする請求項１〜３のいずれかに記載の吸水性樹脂の製造方法。 The method for producing a water-absorbent resin according to claim 1, wherein the water-absorbing resin is held without being transferred from the polymerization apparatus.
前記アニオン性不飽和単量体の塩としてアクリル酸の塩を含み、 A salt of acrylic acid as the salt of the anionic unsaturated monomer,
前記不飽和単量体成分または前記不飽和単量体成分の塩の含有量は１５〜４５重量％であり、 The content of the unsaturated monomer component or the salt of the unsaturated monomer component is 15 to 45% by weight,
前記内部架橋剤の含有量は、前記不飽和単量体成分または前記不飽和単量体成分の塩に対して０．００５〜３モル％であることを特徴とする請求項１〜７のいずれかに記載の吸水性樹脂の製造方法。 The content of the internal cross-linking agent is 0.005 to 3 mol% with respect to the unsaturated monomer component or the salt of the unsaturated monomer component. A method for producing the water-absorbent resin according to claim 1.
前記保持されている含水ゲル状重合体の比表面積は１０ｃｍ The specific surface area of the retained hydrogel polymer is 10 cm. ２2 ／ｇ以下であることを特徴とする請求項１〜８のいずれかに記載の吸水性樹脂の製造方法。/ G or less, The manufacturing method of the water absorbing resin in any one of Claims 1-8 characterized by the above-mentioned.
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| JP11439499A JP4198266B2 (en) | 1998-05-14 | 1999-04-22 | Method for producing water absorbent resin |
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| JP11439499A JP4198266B2 (en) | 1998-05-14 | 1999-04-22 | Method for producing water absorbent resin |
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| BR0116761A (en) * | 2000-12-29 | 2004-02-25 | Dow Global Technologies Inc | Process for the preparation of water-absorbing resin particles of low monomer cross-linked carboxyl-containing polymers, obtained particles and their use |
| US7214753B2 (en) | 2004-03-24 | 2007-05-08 | Nippon Shokubai Co., Ltd. | N-vinyl amide polymer and production method thereof |
| JP4878116B2 (en) * | 2004-11-18 | 2012-02-15 | 旭化成ケミカルズ株式会社 | Water absorbent resin production method |
| JP5042674B2 (en) * | 2006-03-29 | 2012-10-03 | 株式会社日本触媒 | Method for producing polyacrylic acid (salt) water-absorbing resin |
| DE102010043113A1 (en) * | 2010-10-29 | 2012-05-03 | Evonik Stockhausen Gmbh | Process for the preparation of improved absorbent polymers by cryogenic milling |
| JP7105586B2 (en) * | 2017-03-24 | 2022-07-25 | 住友精化株式会社 | Method for manufacturing water absorbent resin |
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