CN113748156B - Process for the preparation of superabsorbent polymers - Google Patents
Process for the preparation of superabsorbent polymers Download PDFInfo
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- CN113748156B CN113748156B CN202180003060.7A CN202180003060A CN113748156B CN 113748156 B CN113748156 B CN 113748156B CN 202180003060 A CN202180003060 A CN 202180003060A CN 113748156 B CN113748156 B CN 113748156B
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- superabsorbent polymer
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- polymer according
- polymer
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- 229920000247 superabsorbent polymer Polymers 0.000 title claims abstract description 209
- 238000000034 method Methods 0.000 title abstract description 59
- 239000004583 superabsorbent polymers (SAPs) Substances 0.000 title abstract description 28
- 230000008569 process Effects 0.000 title abstract description 21
- 238000002360 preparation method Methods 0.000 title description 11
- 229920000642 polymer Polymers 0.000 claims abstract description 144
- 239000000017 hydrogel Substances 0.000 claims abstract description 113
- 239000000654 additive Substances 0.000 claims abstract description 97
- 230000000996 additive effect Effects 0.000 claims abstract description 88
- 238000001035 drying Methods 0.000 claims abstract description 88
- 238000010298 pulverizing process Methods 0.000 claims abstract description 62
- 238000004519 manufacturing process Methods 0.000 claims abstract description 31
- 238000002156 mixing Methods 0.000 claims abstract description 18
- 239000002245 particle Substances 0.000 claims description 205
- 150000001732 carboxylic acid derivatives Chemical class 0.000 claims description 61
- 239000000126 substance Substances 0.000 claims description 55
- 239000000178 monomer Substances 0.000 claims description 51
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 39
- -1 alkali metal salts Chemical class 0.000 claims description 38
- 239000003431 cross linking reagent Substances 0.000 claims description 37
- 238000004132 cross linking Methods 0.000 claims description 21
- 239000003505 polymerization initiator Substances 0.000 claims description 19
- 150000001875 compounds Chemical class 0.000 claims description 17
- 125000000217 alkyl group Chemical group 0.000 claims description 14
- 125000004432 carbon atom Chemical group C* 0.000 claims description 14
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 claims description 11
- 229910052783 alkali metal Inorganic materials 0.000 claims description 9
- 229910052784 alkaline earth metal Inorganic materials 0.000 claims description 9
- 150000003839 salts Chemical class 0.000 claims description 9
- 239000002904 solvent Substances 0.000 claims description 9
- 150000001735 carboxylic acids Chemical class 0.000 claims description 7
- 230000000379 polymerizing effect Effects 0.000 claims description 7
- 239000002253 acid Substances 0.000 claims description 4
- 125000004429 atom Chemical group 0.000 claims description 4
- 239000000843 powder Substances 0.000 abstract description 23
- 239000000047 product Substances 0.000 description 51
- 238000006116 polymerization reaction Methods 0.000 description 27
- 239000000203 mixture Substances 0.000 description 21
- NIXOWILDQLNWCW-UHFFFAOYSA-M Acrylate Chemical compound [O-]C(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-M 0.000 description 19
- 230000002776 aggregation Effects 0.000 description 19
- 239000000463 material Substances 0.000 description 19
- 238000005054 agglomeration Methods 0.000 description 18
- 230000000052 comparative effect Effects 0.000 description 16
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- 239000011148 porous material Substances 0.000 description 15
- 230000002829 reductive effect Effects 0.000 description 14
- 235000013372 meat Nutrition 0.000 description 13
- DNIAPMSPPWPWGF-UHFFFAOYSA-N Propylene glycol Chemical compound CC(O)CO DNIAPMSPPWPWGF-UHFFFAOYSA-N 0.000 description 12
- 238000010438 heat treatment Methods 0.000 description 12
- 239000000243 solution Substances 0.000 description 12
- 238000012719 thermal polymerization Methods 0.000 description 12
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 11
- 239000003999 initiator Substances 0.000 description 11
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 9
- 125000000524 functional group Chemical group 0.000 description 9
- 230000002209 hydrophobic effect Effects 0.000 description 9
- 230000000704 physical effect Effects 0.000 description 9
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 8
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 8
- 238000010521 absorption reaction Methods 0.000 description 8
- 238000003756 stirring Methods 0.000 description 8
- 238000006386 neutralization reaction Methods 0.000 description 7
- 238000001179 sorption measurement Methods 0.000 description 7
- 229920006037 cross link polymer Polymers 0.000 description 6
- MTHSVFCYNBDYFN-UHFFFAOYSA-N diethylene glycol Chemical compound OCCOCCO MTHSVFCYNBDYFN-UHFFFAOYSA-N 0.000 description 6
- 230000001965 increasing effect Effects 0.000 description 5
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- WERYXYBDKMZEQL-UHFFFAOYSA-N butane-1,4-diol Chemical compound OCCCCO WERYXYBDKMZEQL-UHFFFAOYSA-N 0.000 description 4
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- 239000011734 sodium Substances 0.000 description 4
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- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 description 3
- IZXIZTKNFFYFOF-UHFFFAOYSA-N 2-Oxazolidone Chemical class O=C1NCCO1 IZXIZTKNFFYFOF-UHFFFAOYSA-N 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 3
- 229920002430 Fibre-reinforced plastic Polymers 0.000 description 3
- 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
- CERQOIWHTDAKMF-UHFFFAOYSA-N Methacrylic acid Chemical compound CC(=C)C(O)=O CERQOIWHTDAKMF-UHFFFAOYSA-N 0.000 description 3
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- 238000012360 testing method Methods 0.000 description 3
- 238000012546 transfer Methods 0.000 description 3
- 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 2
- 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 2
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 description 2
- NIXOWILDQLNWCW-UHFFFAOYSA-N 2-Propenoic acid Natural products OC(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 2
- LCZVSXRMYJUNFX-UHFFFAOYSA-N 2-[2-(2-hydroxypropoxy)propoxy]propan-1-ol Chemical compound CC(O)COC(C)COC(C)CO LCZVSXRMYJUNFX-UHFFFAOYSA-N 0.000 description 2
- XLLIQLLCWZCATF-UHFFFAOYSA-N 2-methoxyethyl acetate Chemical compound COCCOC(C)=O XLLIQLLCWZCATF-UHFFFAOYSA-N 0.000 description 2
- SVTBMSDMJJWYQN-UHFFFAOYSA-N 2-methylpentane-2,4-diol Chemical compound CC(O)CC(C)(C)O SVTBMSDMJJWYQN-UHFFFAOYSA-N 0.000 description 2
- YEJRWHAVMIAJKC-UHFFFAOYSA-N 4-Butyrolactone Chemical compound O=C1CCCO1 YEJRWHAVMIAJKC-UHFFFAOYSA-N 0.000 description 2
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- HRPVXLWXLXDGHG-UHFFFAOYSA-N Acrylamide Chemical compound NC(=O)C=C HRPVXLWXLXDGHG-UHFFFAOYSA-N 0.000 description 2
- CIWBSHSKHKDKBQ-JLAZNSOCSA-N Ascorbic acid Chemical compound OC[C@H](O)[C@H]1OC(=O)C(O)=C1O CIWBSHSKHKDKBQ-JLAZNSOCSA-N 0.000 description 2
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 2
- VZCYOOQTPOCHFL-OWOJBTEDSA-N Fumaric acid Chemical compound OC(=O)\C=C\C(O)=O VZCYOOQTPOCHFL-OWOJBTEDSA-N 0.000 description 2
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 239000002250 absorbent Substances 0.000 description 2
- 238000004220 aggregation Methods 0.000 description 2
- 238000013019 agitation Methods 0.000 description 2
- 150000001298 alcohols Chemical class 0.000 description 2
- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium persulfate Chemical compound [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 description 2
- 239000003963 antioxidant agent Substances 0.000 description 2
- 230000003078 antioxidant effect Effects 0.000 description 2
- 235000006708 antioxidants Nutrition 0.000 description 2
- 239000012267 brine Substances 0.000 description 2
- CDQSJQSWAWPGKG-UHFFFAOYSA-N butane-1,1-diol Chemical compound CCCC(O)O CDQSJQSWAWPGKG-UHFFFAOYSA-N 0.000 description 2
- 150000007942 carboxylates Chemical group 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- JHIVVAPYMSGYDF-UHFFFAOYSA-N cyclohexanone Chemical compound O=C1CCCCC1 JHIVVAPYMSGYDF-UHFFFAOYSA-N 0.000 description 2
- BGTOWKSIORTVQH-UHFFFAOYSA-N cyclopentanone Chemical compound O=C1CCCC1 BGTOWKSIORTVQH-UHFFFAOYSA-N 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 230000018109 developmental process Effects 0.000 description 2
- VFHVQBAGLAREND-UHFFFAOYSA-N diphenylphosphoryl-(2,4,6-trimethylphenyl)methanone Chemical compound CC1=CC(C)=CC(C)=C1C(=O)P(=O)(C=1C=CC=CC=1)C1=CC=CC=C1 VFHVQBAGLAREND-UHFFFAOYSA-N 0.000 description 2
- 238000001599 direct drying Methods 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 230000001747 exhibiting effect Effects 0.000 description 2
- 239000012467 final product Substances 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 2
- JRKICGRDRMAZLK-UHFFFAOYSA-L peroxydisulfate Chemical compound [O-]S(=O)(=O)OOS([O-])(=O)=O JRKICGRDRMAZLK-UHFFFAOYSA-L 0.000 description 2
- 239000004014 plasticizer Substances 0.000 description 2
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- 150000003254 radicals Chemical class 0.000 description 2
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- CHQMHPLRPQMAMX-UHFFFAOYSA-L sodium persulfate Substances [Na+].[Na+].[O-]S(=O)(=O)OOS([O-])(=O)=O CHQMHPLRPQMAMX-UHFFFAOYSA-L 0.000 description 2
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 description 2
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- 230000004580 weight loss Effects 0.000 description 2
- DNIAPMSPPWPWGF-VKHMYHEASA-N (+)-propylene glycol Chemical compound C[C@H](O)CO DNIAPMSPPWPWGF-VKHMYHEASA-N 0.000 description 1
- MYWOJODOMFBVCB-UHFFFAOYSA-N 1,2,6-trimethylphenanthrene Chemical compound CC1=CC=C2C3=CC(C)=CC=C3C=CC2=C1C MYWOJODOMFBVCB-UHFFFAOYSA-N 0.000 description 1
- 229940015975 1,2-hexanediol Drugs 0.000 description 1
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- RRQYJINTUHWNHW-UHFFFAOYSA-N 1-ethoxy-2-(2-ethoxyethoxy)ethane Chemical compound CCOCCOCCOCC RRQYJINTUHWNHW-UHFFFAOYSA-N 0.000 description 1
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- JAHNSTQSQJOJLO-UHFFFAOYSA-N 2-(3-fluorophenyl)-1h-imidazole Chemical compound FC1=CC=CC(C=2NC=CN=2)=C1 JAHNSTQSQJOJLO-UHFFFAOYSA-N 0.000 description 1
- FDSUVTROAWLVJA-UHFFFAOYSA-N 2-[[3-hydroxy-2,2-bis(hydroxymethyl)propoxy]methyl]-2-(hydroxymethyl)propane-1,3-diol;prop-2-enoic acid Chemical compound OC(=O)C=C.OC(=O)C=C.OC(=O)C=C.OC(=O)C=C.OC(=O)C=C.OCC(CO)(CO)COCC(CO)(CO)CO FDSUVTROAWLVJA-UHFFFAOYSA-N 0.000 description 1
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- CKSAKVMRQYOFBC-UHFFFAOYSA-N 2-cyanopropan-2-yliminourea Chemical compound N#CC(C)(C)N=NC(N)=O CKSAKVMRQYOFBC-UHFFFAOYSA-N 0.000 description 1
- 125000000954 2-hydroxyethyl group Chemical class [H]C([*])([H])C([H])([H])O[H] 0.000 description 1
- SPXWGAHNKXLXAP-UHFFFAOYSA-N 2-methylpentane-1,3-diol Chemical compound CCC(O)C(C)CO SPXWGAHNKXLXAP-UHFFFAOYSA-N 0.000 description 1
- QWGRWMMWNDWRQN-UHFFFAOYSA-N 2-methylpropane-1,3-diol Chemical compound OCC(C)CO QWGRWMMWNDWRQN-UHFFFAOYSA-N 0.000 description 1
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- BTYIFQSAIPDZQW-UHFFFAOYSA-N 2-propan-2-yl-4,5-dihydro-1h-imidazole Chemical compound CC(C)C1=NCCN1 BTYIFQSAIPDZQW-UHFFFAOYSA-N 0.000 description 1
- MJIFFWRTVONWNO-UHFFFAOYSA-N 3-oxopent-4-ene-1-sulfonic acid Chemical compound OS(=O)(=O)CCC(=O)C=C MJIFFWRTVONWNO-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
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- 239000013529 heat transfer fluid Substances 0.000 description 1
- CATSNJVOTSVZJV-UHFFFAOYSA-N heptan-2-one Chemical compound CCCCCC(C)=O CATSNJVOTSVZJV-UHFFFAOYSA-N 0.000 description 1
- ACCCMOQWYVYDOT-UHFFFAOYSA-N hexane-1,1-diol Chemical compound CCCCCC(O)O ACCCMOQWYVYDOT-UHFFFAOYSA-N 0.000 description 1
- FHKSXSQHXQEMOK-UHFFFAOYSA-N hexane-1,2-diol Chemical compound CCCCC(O)CO FHKSXSQHXQEMOK-UHFFFAOYSA-N 0.000 description 1
- AVIYEYCFMVPYST-UHFFFAOYSA-N hexane-1,3-diol Chemical compound CCCC(O)CCO AVIYEYCFMVPYST-UHFFFAOYSA-N 0.000 description 1
- XXMIOPMDWAUFGU-UHFFFAOYSA-N hexane-1,6-diol Chemical compound OCCCCCCO XXMIOPMDWAUFGU-UHFFFAOYSA-N 0.000 description 1
- OHMBHFSEKCCCBW-UHFFFAOYSA-N hexane-2,5-diol Chemical compound CC(O)CCC(C)O OHMBHFSEKCCCBW-UHFFFAOYSA-N 0.000 description 1
- 125000001183 hydrocarbyl group Chemical group 0.000 description 1
- 125000004435 hydrogen atom Chemical group [H]* 0.000 description 1
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 description 1
- 229910000041 hydrogen chloride Inorganic materials 0.000 description 1
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 229910001867 inorganic solvent Inorganic materials 0.000 description 1
- 239000003049 inorganic solvent Substances 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 125000000959 isobutyl group Chemical group [H]C([H])([H])C([H])(C([H])([H])[H])C([H])([H])* 0.000 description 1
- 125000001449 isopropyl group Chemical group [H]C([H])([H])C([H])(*)C([H])([H])[H] 0.000 description 1
- FPYJFEHAWHCUMM-UHFFFAOYSA-N maleic anhydride Chemical compound O=C1OC(=O)C=C1 FPYJFEHAWHCUMM-UHFFFAOYSA-N 0.000 description 1
- LVHBHZANLOWSRM-UHFFFAOYSA-N methylenebutanedioic acid Natural products OC(=O)CC(=C)C(O)=O LVHBHZANLOWSRM-UHFFFAOYSA-N 0.000 description 1
- 239000000693 micelle Substances 0.000 description 1
- ZIUHHBKFKCYYJD-UHFFFAOYSA-N n,n'-methylenebisacrylamide Chemical compound C=CC(=O)NCNC(=O)C=C ZIUHHBKFKCYYJD-UHFFFAOYSA-N 0.000 description 1
- 125000003136 n-heptyl group Chemical group [H]C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])* 0.000 description 1
- 125000001280 n-hexyl group Chemical group C(CCCCC)* 0.000 description 1
- 125000000740 n-pentyl group Chemical group [H]C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])* 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 150000002918 oxazolines Chemical class 0.000 description 1
- 239000011236 particulate material Substances 0.000 description 1
- PZXHOJFANUNWGC-UHFFFAOYSA-N phenyl 2-oxoacetate Chemical class O=CC(=O)OC1=CC=CC=C1 PZXHOJFANUNWGC-UHFFFAOYSA-N 0.000 description 1
- 239000002504 physiological saline solution Substances 0.000 description 1
- 229920000768 polyamine Polymers 0.000 description 1
- 239000002861 polymer material Substances 0.000 description 1
- 229920001451 polypropylene glycol Polymers 0.000 description 1
- 229920000166 polytrimethylene carbonate Polymers 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- USHAGKDGDHPEEY-UHFFFAOYSA-L potassium persulfate Chemical compound [K+].[K+].[O-]S(=O)(=O)OOS([O-])(=O)=O USHAGKDGDHPEEY-UHFFFAOYSA-L 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 125000001436 propyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])[H] 0.000 description 1
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 description 1
- LLHKCFNBLRBOGN-UHFFFAOYSA-N propylene glycol methyl ether acetate Chemical compound COCC(C)OC(C)=O LLHKCFNBLRBOGN-UHFFFAOYSA-N 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 125000002914 sec-butyl group Chemical group [H]C([H])([H])C([H])([H])C([H])(*)C([H])([H])[H] 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000002689 soil Substances 0.000 description 1
- 150000005846 sugar alcohols Polymers 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- 125000000999 tert-butyl group Chemical group [H]C([H])([H])C(*)(C([H])([H])[H])C([H])([H])[H] 0.000 description 1
- UWHCKJMYHZGTIT-UHFFFAOYSA-N tetraethylene glycol Chemical compound OCCOCCOCCOCCO UWHCKJMYHZGTIT-UHFFFAOYSA-N 0.000 description 1
- VZCYOOQTPOCHFL-UHFFFAOYSA-N trans-butenedioic acid Natural products OC(=O)C=CC(O)=O VZCYOOQTPOCHFL-UHFFFAOYSA-N 0.000 description 1
- LDHQCZJRKDOVOX-UHFFFAOYSA-N trans-crotonic acid Natural products CC=CC(O)=O LDHQCZJRKDOVOX-UHFFFAOYSA-N 0.000 description 1
- 125000005259 triarylamine group Chemical group 0.000 description 1
- 210000002700 urine Anatomy 0.000 description 1
- 239000008096 xylene Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/04—Oxygen-containing compounds
- C08K5/10—Esters; Ether-esters
- C08K5/11—Esters; Ether-esters of acyclic polycarboxylic acids
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J3/00—Processes of treating or compounding macromolecular substances
- C08J3/12—Powdering or granulating
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- B29B9/00—Making granules
- B29B9/12—Making granules characterised by structure or composition
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J3/00—Processes of treating or compounding macromolecular substances
- C08J3/02—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques
- C08J3/03—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques in aqueous media
- C08J3/075—Macromolecular gels
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J3/00—Processes of treating or compounding macromolecular substances
- C08J3/24—Crosslinking, e.g. vulcanising, of macromolecules
- C08J3/245—Differential crosslinking of one polymer with one crosslinking type, e.g. surface crosslinking
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- B29B9/00—Making granules
- B29B9/12—Making granules characterised by structure or composition
- B29B2009/125—Micropellets, microgranules, microparticles
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2333/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers
- C08J2333/02—Homopolymers or copolymers of acids; Metal or ammonium salts thereof
Landscapes
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Dispersion Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Processes Of Treating Macromolecular Substances (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
Abstract
The present disclosure relates to a method of making superabsorbent polymers. More particularly, the present disclosure relates to a method of preparing a superabsorbent polymer capable of significantly reducing the amount of fine powder generated during a process by mixing a hydrogel polymer with an additive having a specific structure, pulverizing it, and then drying it with a paddle dryer.
Description
Technical Field
Cross Reference to Related Applications
The present application claims the benefits of korean patent application No. 10-2020-0007114 filed on 1 month 20 in 2020 and korean patent application No. 10-2021-0007622 filed on 1 month 19 in 2021, the disclosures of which are incorporated herein by reference in their entireties.
The present disclosure relates to a method of making superabsorbent polymers. More specifically, the present disclosure relates to a method of preparing superabsorbent polymers in which the amount of fines produced is significantly reduced.
Background
Superabsorbent polymers (Super Absorbent Polymer, SAP) are synthetic polymeric materials capable of absorbing 500 to 1000 times their own weight of moisture. Each manufacturer names it a different name, such as SAM (Super Absorbency Material, superabsorbent material), AGM (Absorbent Gel Material ), etc. Such super absorbent polymers have been practically used for sanitary products, and are now widely used not only for sanitary products but also for water-retaining soil products for gardening, water-stopping materials for civil engineering and construction, sheets for raising seedlings, antistatics for food circulation, materials for cataplasm, and the like.
These superabsorbent polymers have been widely used in the field of sanitary materials, such as diapers or sanitary napkins. In such sanitary materials, the superabsorbent polymer is generally contained in a state of being distributed in the slurry. In recent years, however, continuous efforts have been made to provide sanitary materials such as diapers with a thinner thickness. As part of such efforts, development of so-called no-pulp diapers or the like in which pulp content is reduced or pulp is not used at all is being actively advanced.
As described above, in the case of a sanitary material in which the pulp content is reduced or no pulp is used, the superabsorbent polymer is contained in a relatively high ratio, and these superabsorbent polymer particles are inevitably contained in a plurality of layers in the sanitary material. In order for all of the superabsorbent polymer particles contained in the plurality of layers to more effectively absorb a large amount of liquid such as urine, the superabsorbent polymer needs to exhibit substantially high absorption performance and a fast absorption rate.
Meanwhile, such superabsorbent polymers are generally prepared by a process comprising: a step of polymerizing a monomer to prepare a hydrogel polymer containing a large amount of moisture; and a step of drying the hydrogel polymer and then pulverizing the dried hydrogel polymer into polymer particles having a desired particle diameter. However, when the hydrogel polymer is dried and then crushed as described above, a large amount of fine powder is generated, and thus there is a problem in that physical properties of the finally produced superabsorbent polymer are deteriorated.
Further, in order to reuse such fine powder, a fine powder reassembled body obtained by mixing fine powder with water to agglomerate, and then drying/pulverizing/classifying is generally used. However, due to the water used at this time, problems such as an increase in energy consumption during the drying process and an increase in load on the apparatus may occur, and thus productivity in preparing the super absorbent polymer may be lowered.
Accordingly, there is a continuing need to develop techniques that can produce superabsorbent polymers without producing fines to fundamentally solve this problem.
Disclosure of Invention
Technical problem
Accordingly, the present disclosure relates to a method of preparing a super water-absorbent polymer, which is capable of significantly reducing the amount of fine powder generated during a process by mixing a hydrogel polymer with an additive having a specific structure, pulverizing it, and drying it with a paddle dryer.
Technical proposal
In order to solve the above problems, there is provided a method for producing a superabsorbent polymer, the method comprising:
1) A step (step 1) of crosslinking polymerizing a water-soluble ethylenically unsaturated monomer having an at least partially neutralized acidic group in the presence of an internal crosslinking agent and a polymerization initiator to form a hydrogel polymer;
2) A step of mixing the hydrogel polymer with a carboxylic acid-based additive, followed by pulverization to prepare a pulverized product comprising aqueous superabsorbent polymer particles (step 2);
3) A step of drying the crushed product with a paddle dryer to prepare superabsorbent polymer particles (step 3); and
4) A step of finely pulverizing particles having a particle diameter of more than 850 μm among the super absorbent polymer particles (step 4),
wherein the carboxylic acid-based additive is at least one selected from the group consisting of carboxylic acids represented by the following chemical formula 1 and salts thereof:
[ chemical formula 1]
In the chemical formula 1, the chemical formula is shown in the drawing,
a is an alkyl group having 5 to 21 carbon atoms,
B 1 is-OCO-, -COO-or-COOCH (R) 1 )COO-，
B 2 is-CH 2 -、-CH 2 CH 2 -、-CH(R 2 ) -, -CH=CH-or-C≡C-,
wherein R is 1 And R is 2 Each independently is an alkyl group having 1 to 4 carbon atoms,
n is an integer from 1 to 3, and
c is carboxyl.
Advantageous effects
According to the method of preparing the superabsorbent polymer of the present disclosure, the aqueous superabsorbent polymer particles may be prepared by comminuting the hydrogel polymer in the presence of a carboxylic acid-based additive. Furthermore, even in the drying process using a paddle dryer, agglomeration between particles is suppressed to obtain a granular dried product, so that the amount of dry pulverization after drying can be greatly reduced. Thus, a superabsorbent polymer in which the amount of fines is significantly reduced can be produced.
Drawings
Fig. 1 is a flow chart showing a conventional method of preparing a superabsorbent polymer.
Fig. 2 is a flow chart illustrating a method of preparing a superabsorbent polymer according to one embodiment.
Fig. 3 shows the positions of temperature sensors installed in the paddle dryers used in examples 1 to 3.
Fig. 4 is a graph showing the moisture content of each crushed product prepared in step 2 of examples 1 to 3 with respect to the residence time in the paddle dryer.
Detailed Description
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Singular forms also are intended to include plural forms unless the context clearly indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes" or "having," when used in this specification, specify the presence of stated features, steps, components, or groups thereof, but do not preclude the presence or addition of one or more other features, steps, components, or groups thereof.
While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example and will herein be described in detail. It should be understood, however, that there is no intention to limit the invention to the specific forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.
While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example and will herein be described in detail. It should be understood, however, that there is no intention to limit the invention to the specific forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.
Hereinafter, a method of preparing the superabsorbent polymer and the superabsorbent polymer prepared therefrom will be described in more detail according to specific embodiments of the present invention.
Unless explicitly stated, the terms are used to refer to specific embodiments only and are not intended to limit the present disclosure. The singular forms of the present disclosure may include plural forms unless the context indicates otherwise.
According to one embodiment of the present disclosure, there is provided a method of preparing a superabsorbent polymer, the method comprising:
1) A step (step 1) of crosslinking polymerizing a water-soluble ethylenically unsaturated monomer having an at least partially neutralized acidic group in the presence of an internal crosslinking agent and a polymerization initiator to form a hydrogel polymer;
2) A step of mixing the hydrogel polymer with a carboxylic acid-based additive, followed by pulverization to prepare a pulverized product comprising aqueous superabsorbent polymer particles (step 2);
3) A step of drying the crushed product with a paddle dryer to prepare superabsorbent polymer particles (step 3); and
4) A step of finely pulverizing particles having a particle diameter of more than 850 μm among the super absorbent polymer particles (step 4),
wherein the carboxylic acid-based additive is at least one selected from the group consisting of carboxylic acids represented by the following chemical formula 1 and salts thereof:
[ chemical formula 1]
In the chemical formula 1, the chemical formula is shown in the drawing,
a is an alkyl group having 5 to 21 carbon atoms,
B 1 is-OCO-, -COO-or-COOCH (R) 1 )COO-，
B 2 is-CH 2 -、-CH 2 CH 2 -、-CH(R 2 ) -, -CH=CH-or-C≡C-,
wherein R is 1 And R is 2 Each independently is an alkyl group having 1 to 4 carbon atoms,
n is an integer from 1 to 3, and
c is carboxyl.
The term "polymer" in the present disclosure is in a state in which a water-soluble ethylenically unsaturated monomer is polymerized, and may include all ranges of water content or all ranges of particle size. Among the polymers, a polymer having a water content of about 30% by weight or more after pulverization and before drying may be referred to as a hydrogel polymer, and particles in which the hydrogel polymer is pulverized and dried may be referred to as a crosslinked polymer.
Furthermore, the term "superabsorbent polymer particles" refers to particulate materials comprising a crosslinked polymer in which a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups is polymerized and crosslinked by an internal crosslinking agent.
Furthermore, depending on the context, the term "superabsorbent polymer" is used to include all of the following: a crosslinked polymer in which a water-soluble ethylenically unsaturated monomer having an acid group at least partially neutralized is polymerized or a base resin in the form of powder composed of superabsorbent polymer particles in which the crosslinked polymer is pulverized, and a crosslinked polymer or base resin which is further processed (e.g., dried, pulverized, fractionated, surface crosslinked, etc.) to be in a state suitable for commercialization. Thus, the term "superabsorbent polymer" can be construed to include compositions comprising superabsorbent polymers, i.e. a plurality of superabsorbent polymer particles.
Furthermore, the term "conventional superabsorbent polymer particles" refers to particles having a particle size of 150 μm to 850 μm in the superabsorbent polymer particles.
Furthermore, the term "fines" refers to particles of superabsorbent polymer particles having a particle size of less than 150 μm. The particle size of these polymer particles can be measured according to EDANA WSP 220.3 of the European disposables and nonwovens Association (European Disposables and Nonwovens Association, EDANA).
In addition, the term "shredding" refers to cutting the hydrogel polymer into small pieces to increase drying efficiency and is used separately from comminuting to conventional particle sizes.
Superabsorbent polymers are typically prepared by drying a hydrogel polymer and then comminuting it to the desired particle size. At this time, in order to promote the drying of the hydrogel polymer and to improve the efficiency of the pulverizing process, the process of cutting the hydrogel polymer is performed before the drying process. However, due to the tackiness of the hydrogel polymer during this shredding process, the hydrogel polymer cannot be crushed into micrometer-sized particles but rather becomes an agglomerated gel. When the agglomerated gel-like hydrogel polymer is dried in a fixed bed manner, a sheet-like dried body is formed, and a multi-stage pulverization process is required for pulverizing it into micrometer-sized particles. Therefore, there is a problem in that many fine powders are generated in the process.
Specifically, FIG. 1 shows a flow chart of a conventional method of preparing superabsorbent polymers. Referring to fig. 1, in the related art, a superabsorbent polymer has been prepared, including the following steps.
(polymerizing) cross-linking a water-soluble ethylenically unsaturated monomer having an at least partially neutralized acidic group in the presence of an internal cross-linking agent and a polymerization initiator to form a hydrogel polymer;
(shredding) the hydrogel polymer;
(drying) drying the minced hydrogel polymer; and
(coarse pulverization/classification/fine pulverization) pulverizing the dried polymer, and then classifying the pulverized polymer into conventional particles and fine powder;
as described above, the minced hydrogel polymer has an agglomerated gel shape with a size of about 1cm to 10 cm. This minced hydrogel polymer was laminated on a belt having a porous plate at the bottom and dried in a fixed bed manner by hot air supplied from the bottom or the top. Since the polymer dried by the above drying method has a sheet shape instead of a particle shape, the step of pulverizing, followed by classification is performed as a step of coarse pulverizing, followed by classification, followed by fine pulverizing, followed by classification again, so that the produced particles become conventional particles, i.e., particles having a particle diameter of 150 μm to 850 μm. However, since coarse pulverization and fine pulverization after drying are performed in a dry manner, a large amount of fine powder is generated during the pulverization. Specifically, the amount of fine powder separated in the final fractionation step by this preparation method is as much as about 15 to about 25% by weight based on the total weight of the finally prepared superabsorbent polymer, and thus the separated fine powder is mixed with an appropriate amount of water for reassembly and added to the chopping step or before the drying step.
However, when the fine powder reassembly body mixed with water is re-injected into the pulverizing or drying process for re-use of the fine powder, problems such as an increase in load on equipment and/or energy consumption occur. Further, since fine powder is not classified and remains, physical properties of the super absorbent polymer deteriorate.
Accordingly, the present inventors have recognized that the amount of fine powder produced in the conventional production method is largely affected by the particle size introduced into the pulverization process, and determined that if the hydrogel polymers can be pulverized to the micrometer-sized in the pulverization process without agglomeration between the hydrogel polymers, the amount of fine powder produced during the process can be reduced. Thus, as a result of experiments with various types of additives that can reduce the viscosity of the hydrogel polymer during the chopping process, it was determined that when the hydrogel polymer is mixed with a carboxylic acid-based additive and then crushed, the viscosity of the hydrogel polymer is reduced due to the carboxylic acid-based additive, and thus crushing into micrometer-level particles is possible. The present invention has been completed accordingly. This is because the carboxylic acid-based additive mixed with the hydrogel polymer is adsorbed on the surface of the hydrogel polymer, thereby preventing agglomeration of the crushed hydrogel polymer. In addition, since the drying process is performed in the form of micron-sized particles, the drying can be efficient.
Specifically, the carboxylic acid-based additive has both hydrophobic and hydrophilic functional groups. Meanwhile, since the water-soluble ethylenically unsaturated monomer contains an acidic group (-COOH) and/or a neutralized acidic group (-COO-), a large amount of hydrophilic moieties exist on the surface of the hydrogel polymer prepared by polymerization due to the acidic group (-COOH) and/or the neutralized acidic group (-COO-), which remain without participating in polymerization. Thus, when the additive is mixed with the hydrogel polymer, the hydrophilic functional group of the additive is adsorbed onto at least a part of the hydrophilic moiety present on the surface of the hydrogel polymer, and the surface of the polymer to which the additive is adsorbed becomes hydrophobic due to the hydrophobic functional group located at the other end of the additive. Thus, agglomeration between polymer particles can be suppressed.
More specifically, in the carboxylic acid based additive, the hydrophobic functional group is an alkyl group having 5 to 21 carbon atoms (moiety a), the hydrophilic functional group is a moiety C, specifically a carboxyl group (COOH) or in the case of a salt, a carboxylate group (-COO) - ). The hydrophobic and hydrophilic functional groups are located at the two ends of the additive, respectively. In particular The carboxylic acid-based additive comprises, in addition to part a and part C at both ends, part (B 1 -B 2 ) And part (B) 1 -B 2 ) Improving the adsorption properties to the polymer surface, which may be insufficient with only part C. Thus, with a structure having an A-C structure without a portion (B 1 -B 2 ) The additive having the structure of chemical formula 1 has excellent adsorption properties to the surface of the polymer exhibiting hydrophilicity, and thus effectively inhibits agglomeration of the aqueous superabsorbent polymer particles.
Furthermore, the comminuted product comprising the aqueous superabsorbent polymer particles is preferably dried in a mobile manner. Herein, mobile drying is classified from fixed bed drying according to whether or not a material flows during drying. More specifically, the mobile drying refers to a method of mechanically stirring a material to be dried or a method of drying while flowing a particle layer by a gas. On the other hand, fixed bed drying refers to a method in which a material to be dried is placed on a base plate, such as a porous iron plate, through which air can pass, and hot air is passed through the material from bottom to top to perform drying.
When the crushed product containing the aqueous superabsorbent polymer particles is dried in a mobile manner, agglomeration phenomenon between the aqueous superabsorbent polymer particles is prevented, so that a granular dried product can be obtained. Accordingly, there is an advantage in that drying can be completed in a short time without a process of coarsely pulverizing or pulverizing agglomerated particles after drying.
As the equipment capable of drying by such a mobile drying method, a paddle dryer, a horizontal mixer, a rotary kiln, or a steam tube dryer can be used. Among them, it is preferable to dry the pulverized product using a paddle dryer in terms of installation cost, throughput per unit volume, and heat transfer efficiency. In particular, the paddle dryer has advantages in that the area required for installation is small, installation is simple, and production per unit volume is high. However, in order to dry the crushed product with a high throughput per unit volume, agglomeration between the aqueous superabsorbent polymer particles should not occur during drying. The aqueous superabsorbent polymer particles mixed with the above carboxylic acid-based additive have excellent effects of inhibiting agglomeration between particles, and thus can be dried using a paddle dryer having a high throughput per unit volume.
On the other hand, since the minced hydrogel polymers, which are not mixed with the carboxylic acid-based additive, agglomerate with each other during drying, drying using a paddle dryer is not possible. Further, even when conventionally known surfactants other than carboxylic acid-based additives, such as betaine-based amphoteric surfactants, are polymerized with a hydrogel polymer and then crushed, the effect of suppressing agglomeration between particles is not good. Thus, drying in a rotary heating apparatus such as a steam tube dryer at low throughput per unit volume may be possible, but drying by a paddle dryer having a high density between crushed particles is difficult due to the large throughput per unit volume.
Specifically, fig. 2 shows a flow chart of a method of preparing a superabsorbent polymer composition according to an embodiment. Referring to fig. 2, unlike the conventional preparation method of the super absorbent polymer, the super absorbent polymer may be prepared by a step of finely pulverizing only particles having a particle diameter of more than 850 μm among the super absorbent polymer particles after the preparation of the hydrogel polymer and the subsequent pulverization and drying. Therefore, since the coarse pulverizing process as the dry pulverizing process after drying can be omitted, it is considered that coarse pulverizing is a step of increasing the amount of fine powder, the amount of fine powder generated during the process can be significantly reduced and also the manufacturing cost can be reduced.
Further, according to the method of preparing the superabsorbent polymer, when the hydrogel is crushed in a state in which the hydrogel polymer is mixed with the carboxylic acid-based additive, adhesion between particles is weakened due to the hydrophobic functional group of the carboxylic acid-based additive, and excessive agglomeration between the particulate hydrogels is prevented, thereby increasing the specific surface area, and thus the vortex time of the superabsorbent polymer can be improved.
Meanwhile, extractable content (E/C) participating in polymerization but not bonded to the main chain and having short chains may be present in the superabsorbent polymer. These extractable contents are not preferred because they may cause rewet. Specifically, when the hydrogel polymer in which the carboxylic acid-based additive is not mixed is chopped, the hydrogel polymer is granular and re-agglomerated due to tackiness. Thus, the hydrogel polymer is subjected to mechanical shearing in the chopper, which results in damage to the polymer chains, resulting in an increase in extractable content. However, in the case of the method of producing a superabsorbent polymer, reagglomeration of the formed particulate hydrogel is prevented by the hydrophobic functional groups of the carboxylic acid-based additive, and thus the particulate hydrogel can easily pass through the porous plate of the chopper. Thus, excessive mechanical shearing action on the hydrogel can be prevented, so that extractable content present in the superabsorbent polymer can be reduced.
Hereinafter, a method for preparing the superabsorbent polymer composition of one embodiment will be described in more detail with respect to each component.
(step 1)
The above step is carried out by crosslinking polymerizing a water-soluble ethylenically unsaturated monomer having an at least partially neutralized acidic group in the presence of an internal crosslinking agent and a polymerization initiator to form a hydrogel polymer, and may consist of: a step of preparing a monomer composition by mixing a water-soluble unsaturated monomer, an internal crosslinking agent, and a polymerization initiator, and a step of forming a hydrogel polymer by thermally polymerizing or photopolymerizing the monomer composition.
The water-soluble ethylenically unsaturated monomer may be any monomer commonly used in the preparation of superabsorbent polymers. As a non-limiting example, the water-soluble ethylenically unsaturated monomer may be a compound represented by the following chemical formula 2:
[ chemical formula 2]
R-COOM'
In the chemical formula 2, the chemical formula is shown in the drawing,
r is a C2 to C5 hydrocarbon group having an unsaturated bond, and
m' is a hydrogen atom, a monovalent metal or divalent metal, an ammonium group or an organic amine salt.
Preferably, the monomer may be at least one selected from the group consisting of: (meth) acrylic acid, and monovalent (alkali) metal salts, divalent metal salts, ammonium salts and organic amine salts of said acid.
When (meth) acrylic acid and/or a salt thereof is used as the water-soluble ethylenically unsaturated monomer, it is advantageous to obtain a superabsorbent polymer having improved absorption properties. In addition, the following may be used as monomers: maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethanesulfonic acid, 2-methacryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid, 2- (meth) acrylamide-2-methylpropanesulfonic acid, (meth) acrylamide, N-substituted (meth) acrylic acid esters, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate, (N, N) -dimethylaminoethyl (meth) acrylate, (N, N) -dimethylaminopropyl (meth) acrylamide, and the like.
In this context, the water-soluble ethylenically unsaturated monomer may have acidic groups, and at least some of the acidic groups may be neutralized by a neutralizing agent. Specifically, in the step of mixing the water-soluble ethylenically unsaturated monomer having an acidic group, the internal crosslinking agent, the polymerization initiator, and the neutralizing agent, at least some of the acidic groups of the water-soluble ethylenically unsaturated monomer may be neutralized. In this case, a basic substance capable of neutralizing an acidic group, such as sodium hydroxide, potassium hydroxide, and ammonium hydroxide, may be used as the neutralizing agent.
Further, the degree of neutralization of the water-soluble ethylenically unsaturated monomer may be 50mol% to 90mol%, 60mol% to 85mol%, 65mol% to 85mol%, or 65mol% to 75mol%, where the degree of neutralization refers to the degree to which the acidic groups contained in the water-soluble ethylenically unsaturated monomer are neutralized by the neutralizing agent. The extent of neutralization may vary depending on the final physical characteristics. Too high a degree of neutralization results in precipitation of the neutralized monomer and thus polymerization may not easily occur. Conversely, too low a degree of neutralization not only deteriorates the absorptivity of the polymer but also imparts properties that are difficult to handle to the polymer, such as properties of an elastic rubber.
Further, the term "internal crosslinking agent" used herein is different from a surface crosslinking agent for crosslinking the surface of the superabsorbent polymer particles, which will be described later, and the internal crosslinking agent polymerizes the unsaturated bonds of the water-soluble ethylenically unsaturated monomer by crosslinking. The crosslinking in the above step is performed either at the surface or inside, but when the surface crosslinking process of the superabsorbent polymer particles to be described later is performed, the surfaces of the particles of the superabsorbent polymer finally prepared have a structure crosslinked by a surface crosslinking agent, and the inside of the particles have a structure crosslinked by an internal crosslinking agent.
As the internal crosslinking agent, any compound may be used as long as it allows the introduction of a crosslinking bond during the polymerization of the water-soluble ethylenically unsaturated monomer. As non-limiting examples, the internal crosslinking agent may be a multifunctional crosslinking agent such as N, N' -methylenebisacrylamide, trimethylolpropane tri (meth) acrylate, ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polypropylene glycol (meth) acrylate, butane diol di (meth) acrylate, butanediol di (meth) acrylate, diethylene glycol di (meth) acrylate, hexanediol di (meth) acrylate, triethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, dipentaerythritol pentaacrylate, glycerol tri (meth) acrylate, pentaerythritol tetraacrylate, triarylamine, ethylene glycol diglycidyl ether, propylene glycol, glycerol, or ethylene carbonate, and these may be used alone or in combination of two or more. However, the present disclosure is not limited thereto. Preferably, polyethylene glycol di (meth) acrylate may be used.
The crosslinking polymerization of the water-soluble ethylenically unsaturated monomer in the presence of the internal crosslinking agent may be performed by thermal polymerization, photopolymerization, or hybrid polymerization in the presence of a polymerization initiator with or without a thickener, plasticizer, storage stabilizer, antioxidant, or the like, but specific details will be described later.
In the monomer composition, the internal crosslinking agent may be used in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer. For example, the internal crosslinking agent may be used in an amount of 0.01 parts by weight or more, 0.05 parts by weight or more, or 0.1 parts by weight or more, and 5 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, or 0.7 parts by weight or less based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer. When too little internal crosslinking agent is used, crosslinking does not sufficiently occur, and thus it may be difficult to achieve a strength higher than an appropriate level, whereas when too much internal crosslinking agent is used, the internal crosslinking density increases, and thus it may be difficult to achieve a desired level of water holding capacity.
In addition, the polymerization initiator may be appropriately selected according to the polymerization method. In the case of thermal polymerization, a thermal polymerization initiator is used, and in the case of photopolymerization, a photopolymerization initiator is used. Further, in the case of a hybrid polymerization method (a method using both heat and light), all of a thermal polymerization initiator and a photopolymerization initiator may be used. However, even by the photopolymerization method, a certain amount of heat is generated by UV radiation or the like, and some heat is also generated as the polymerization reaction (exothermic reaction) proceeds. Thus, the composition may additionally comprise a thermal polymerization initiator.
Herein, any compound that can form radicals by light (e.g., UV rays) may be used as the photopolymerization initiator without limitation.
For example, the photopolymerization initiator may be one or more compounds selected from: benzoin ethers, dialkyl acetophenones, hydroxy alkyl ketones, phenyl glyoxylates, benzyl dimethyl ketals, acyl phosphines, and alpha-amino ketones. Further, specific examples of the acylphosphine include diphenyl (2, 4, 6-trimethylbenzoyl) phosphine oxide, phenylbis (2, 4, 6-trimethylbenzoyl) phosphine oxide, ethyl (2, 4, 6-trimethylbenzoyl) phenylphosphinate, and the like. Further different photopolymerization initiators are fully disclosed in "UV Coatings: basic, recent Developments and New Application (Elsevier, 2007)" page 115, written by Reinhold Schwalm, and the disclosure is not limited thereto.
Further, as the thermal polymerization initiator, one or more initiators selected from the following may be used: persulfate-based initiators, azo-based initiators, hydrogen peroxide and ascorbic acid. Specifically, sodium persulfate (Na 2 S 2 O 8 ) Potassium persulfate (K) 2 S 2 O 8 ) Ammonium persulfate ((NH) 4 ) 2 S 2 O 8 ) Etc. as examples of persulfate-based initiators; 2, 2-azobis (2-amidinopropane) dihydrochloride, 2-azobis- (N, N-dimethylene) isobutyl amidine dihydrochloride, 2- (carbamoylazo) isobutyronitrile, 2-azobis- [2- (2-imidazolin-2-yl) propane may be used ]Dihydrochloride, 4-azobis- (4-cyanovaleric acid), and the like are examples of azo-based initiators. Further different thermal polymerization initiators are fully disclosed in "Principle of Polymerization (Wiley, 1981)" page 203 by Odian, and the disclosure is not limited thereto.
The polymerization initiator may be used in an amount of 2 parts by weight or less based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer. When the concentration of the polymerization initiator is too low, the polymerization rate becomes slow, and a large amount of residual monomer may be extracted from the final product. In contrast, when the concentration of the polymerization initiator is higher than the above range, the polymer chain forming the network shortens, so that the content of extractable components increases and the absorption under pressure decreases, thereby decreasing the physical properties of the polymer.
The monomer composition may further contain additives such as a thickener, a plasticizer, a storage stabilizer, an antioxidant, and the like, if necessary.
Furthermore, the monomer composition comprising the monomer may, for example, be in the form of a solution dissolved in a solvent (e.g. water). The solid content of the monomer composition in the solution state, i.e., the concentrations of the monomer, the internal crosslinking agent and the polymerization initiator, may be appropriately adjusted in consideration of the polymerization time and the reaction conditions. For example, the solids content of the monomer composition may be 10 to 80 wt%, 15 to 60 wt%, or 30 to 50 wt%.
When the monomer composition has a solids content within the above range, it may be advantageous for: the pulverization efficiency during pulverization of a polymer to be described later is controlled while eliminating the need to remove the monomer unreacted after the polymerization by utilizing the gel effect phenomenon occurring in the polymerization reaction of a high-concentration aqueous solution.
At this time, any solvent that can dissolve the above components may be used without limitation. For example, the solvent may be a combination of at least one selected from the group consisting of: water, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, 1, 4-butanediol, propylene glycol, ethylene glycol monobutyl ether, propylene glycol monomethyl ether acetate, methyl ethyl ketone, acetone, methyl amyl ketone, cyclohexanone, cyclopentanone, diethylene glycol monomethyl ether, diethylene glycol diethyl ether, toluene, xylene, butyrolactone, carbitol, methyl cellosolve acetate, and N, N-dimethylacetamide.
Meanwhile, the crosslinking polymerization of the water-soluble ethylenically unsaturated monomer having an acid group which is at least partially neutralized may be performed without any particular limitation as long as the hydrogel polymer can be formed by thermal polymerization, photopolymerization or hybrid polymerization.
Specifically, polymerization methods are broadly classified into thermal polymerization and photopolymerization according to the energy source of polymerization. In the case of thermal polymerization, it is generally carried out in a reactor equipped with a stirring shaft, such as a kneader. In the case of photopolymerization, it is usually carried out in a reactor equipped with a movable conveyor belt or in a vessel having a flat bottom. However, the above polymerization method is merely an example, and the present disclosure is not limited thereto.
For example, the hydrogel polymer may be obtained by supplying hot air to a reactor having a stirring shaft such as a kneader or heating the reactor to perform thermal polymerization. Depending on the shape of the stirring shaft provided in the reactor, the hydrogel polymer thus obtained may have a size of several centimeters to several millimeters. Specifically, the size of the obtained hydrogel polymer may vary depending on the concentration of the monomer composition injected thereinto and the injection speed, and a hydrogel polymer having a weight-average particle diameter of 2mm to 50mm may be obtained.
Further, when photopolymerization is carried out in a reactor equipped with a movable conveyor belt or in a container having a flat bottom as described above, the obtained hydrogel polymer may be generally a sheet-like hydrogel polymer having a width of a belt. In this case, the thickness of the polymer sheet may vary depending on the concentration, injection speed or injection amount of the injected monomer composition, but in general, it is preferable to feed the monomer composition so that a sheet-like polymer having a thickness of about 0.5cm to about 5cm can be obtained. When the monomer mixture is fed so that the thickness of the sheet-like polymer becomes too thin, the production efficiency is low, which is not desirable. When the thickness of the sheet-like polymer is more than 5cm, the polymerization reaction cannot be uniformly performed over the entire thickness due to the excessively thick thickness.
At this time, the water content of the hydrogel polymer thus obtained may be 30 to 70% by weight. For example, the hydrogel polymer may have a water content of 35 wt% or greater, 40 wt% or greater, 45 wt% or greater, or 50 wt% or greater, and 70 wt% or less, 65 wt% or less, or 60 wt% or less. When the water content of the hydrogel polymer is too low, it is difficult to secure an appropriate surface area in the subsequent pulverization step, and thus pulverization may not be effective. When the water content of the hydrogel polymer is too high, the pressure to be accepted in the subsequent pulverization step increases, and thus pulverization may be difficult to proceed to a desired particle size.
Meanwhile, the "water content" in the present specification is the content of water in the total weight of the hydrogel polymer, and it means a value obtained by subtracting the weight of the dried polymer from the weight of the hydrogel polymer. Specifically, the water content is defined as a value calculated by weight loss due to evaporation of water of the polymer in the process of raising the temperature of the crumb polymer via infrared heating to perform drying. At this time, the drying conditions for measuring the water content are as follows: the temperature was raised to about 180 ℃ and maintained at 180 ℃ and the total drying time was 40 minutes (5 minutes including the heating step).
The hydrogel polymer formed by step 1 may have a three-dimensional network structure in which a main chain formed by polymerization of a water-soluble ethylenically unsaturated monomer is crosslinked by an internal crosslinking agent. When the hydrogel polymer has a three-dimensional network structure, the water holding capacity and the absorption under pressure, which are general physical properties of the superabsorbent polymer, can be significantly improved as compared with the case of having a two-dimensional linear structure that is not further crosslinked by an internal crosslinking agent.
(step 2)
The above steps are mixing the hydrogel polymer with a carboxylic acid-based additive followed by comminution to produce a comminuted product comprising the aqueous superabsorbent polymer particles and the additive. In this step, the hydrogel polymer is not chopped, but rather crushed into particles that can be applied to the final product, thereby producing the aqueous superabsorbent polymer particles.
At this time, the carboxylic acid-based additive is at least one selected from the group consisting of carboxylic acids represented by chemical formula 1 and metal salts thereof. Specifically, the carboxylic acid-based additive is at least one selected from the group consisting of: carboxylic acid represented by chemical formula 1, alkali metal salt of carboxylic acid represented by chemical formula 1, and alkaline earth metal salt of carboxylic acid represented by chemical formula 1. More specifically, the carboxylic acid-based additive is one of the following: carboxylic acid represented by chemical formula 1, alkali metal salt of carboxylic acid represented by chemical formula 1, and alkaline earth metal salt of carboxylic acid represented by chemical formula 1.
In chemical formula 1, a is a hydrophobic moiety and may be a linear or branched alkyl group having 5 to 21 carbon atoms. However, the case where a is a linear alkyl group is more advantageous in suppressing agglomeration of the pulverized particles and improving dispersibility. When a is an alkyl group having less than 5 carbon atoms, there is a problem in that the chain is short, so that agglomeration of the pulverized particles cannot be effectively controlled. When a is an alkyl group having more than 21 carbon atoms, the fluidity of the additive may be reduced, so that the carboxylic acid-based additive may not be effectively mixed with the hydrogel polymer, and the cost of the composition may be increased due to the increased cost of the additive.
Specifically, in chemical formula 1, a may be a linear alkyl group having 5 to 21 carbon atoms, such as n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl, n-eicosyl, or n-eicosyl.
More specifically, a may be a linear alkyl group having 6 to 18 carbon atoms. For example, A may be-C 6 H 13 、-C 11 H 23 、-C 12 H 25 、-C 17 H 35 or-C 18 H 37 。
In addition, part (B) of chemical formula 1 1 -B 2 ) Improving the adsorption properties to the polymer surface, only part C may be insufficient for the adsorption properties to the polymer surface. When B is 2 When the number of carbon atoms of (2) is 3 or more, part B 1 The distance from the portion C increases, and the adsorption property to the hydrogel polymer may deteriorate.
Herein, R 1 And R is 2 May each independently be a C1 to C4 linear or branched alkyl group having 1 to 4 carbon atoms. More specifically, R 1 And R is 2 May each independently be methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl or tert-butyl. Since the additive can be adsorbed on the superabsorbent polymer particles, the molecular structure of the additive is not voluminous and therefore R is advantageous 1 And R is 2 Both may be methyl groups.
Further, n of chemical formula 1 may be 1, 2 or 3. More specifically, consider the part (B 1 -B 2 ) Is for enhancing the adsorption performance for part C and how long the molecular length is required for the carboxylic acid-based additive to adsorb efficiently on the hydrogel polymer, meaning (B) 1 -B 2 ) N of the number of (2) is preferably 1.
Specifically, in chemical formula 1, B 1 May be Wherein is the bonding site to the adjacent atom. / >
For example, B 1 May be
Further, in chemical formula 1, B 2 May be Wherein is the bonding site to the adjacent atom. At this time, in order to improve the adsorption property of the additive to the crosslinked polymer together with the part C, B 2 Preferably is
Further, in chemical formula 1, the moiety C is a carboxyl group (COOH) as a hydrophilic moiety, and when the carboxylic acid-based additive is a salt, the hydrophilic moiety is a carboxylate group (COO - )。
In other words, the carboxylic acid-based additive may be a compound represented by the following chemical formula 1 a:
[ chemical formula 1a ]
In the chemical formula 1a, a radical of formula 1a,
m is H + Monovalent cations of alkali metals or divalent cations of alkaline earth metals,
if M is H + Or a monovalent cation of an alkali metal, k is 1, k is 2 if M is a divalent cation of an alkaline earth metal, and
A、B 1 、B 2 and n is as defined in chemical formula 1.
More specifically, when the carboxylic acid-based additive is an alkali metal salt of a carboxylic acid represented by chemical formula 1, the additive may be represented by the following chemical formula 1':
[ chemical formula 1 ]
In the chemical formula 1' described above, a compound having the formula 1,
M 1 is an alkali metal such as sodium or potassium, and
A、B 1 、B 2 and n is as defined in chemical formula 1.
Further, when the carboxylic acid-based additive is an alkaline earth metal salt of a carboxylic acid represented by chemical formula 1, the additive may be represented by the following chemical formula 1″:
[ chemical formula 1')
In chemical formula 1', M 2 Is an alkaline earth metal such as calcium, and
A、B 1 、B 2 and n is as defined in chemical formula 1.
For example, the carboxylic acid-based additive may be any carboxylic acid selected from the group consisting of:
alternatively, the carboxylic acid-based additive may be an alkali metal salt selected from any one of the following:
in the above, the above-mentioned steps,
M 1 each independently an alkali metal.
Alternatively, the carboxylic acid-based additive may be any alkaline earth metal salt selected from the group consisting of:
in the above, the above-mentioned steps,
M 2 each independently is an alkaline earth metal.
For example, the carboxylic acid-based additive may be any one of compounds represented by the following chemical formulas 1-1 to 1-7, but is not limited thereto:
meanwhile, the carboxylic acid-based additive may be used in an amount of about 0.01 parts by weight to about 1 part by weight based on 100 parts by weight of the hydrogel polymer. When too little additive is used, the additive may not be uniformly adsorbed on the surface of the hydrogel polymer, resulting in re-agglomeration of the particles after pulverization, while when too much additive is used, the overall physical properties of the final superabsorbent polymer may be reduced. For example, the carboxylic acid-based additive may be used in an amount of 0.01 parts by weight or more, 0.015 parts by weight or more, or 0.1 parts by weight or more, and 1 part by weight or less, 0.7 parts by weight or less, 0.5 parts by weight or less, or 0.4 parts by weight or less, based on 100 parts by weight of the hydrogel polymer.
The method of mixing the additive with the hydrogel polymer is not particularly limited, and may be appropriately selected as long as it is a method capable of uniformly mixing the additive with the hydrogel polymer. Specifically, the additives may be dry blended, dissolved in a solvent and then mixed, or melted and then mixed.
For example, the additives may be mixed in the form of a solution dissolved in a solvent. At this time, any type of inorganic solvent or organic solvent may be used without limitation, but water is most preferably used for the solvent in view of ease of drying and cost of the solvent recovery system. In addition, a method of placing the additive in the form of a solution and the hydrogel polymer into a reaction tank to mix them may be used; a method of spraying the solution after placing the hydrogel polymer in the mixer; a method of continuously supplying the hydrogel polymer and the solution to a continuously operated mixer for mixing; etc.
The comminuted product comprising the aqueous superabsorbent polymer particles and additives can be prepared by mixing the hydrogel polymer with the additives, followed by comminution. In particular, the comminuting step may be performed such that the comminuted aqueous superabsorbent polymer particles have a conventional particle size.
In this context, comminution can be carried out in a wet manner. In particular, since the carboxylic acid-based additive is mixed in a solution state dissolved in a solvent such as water, the hydrogel polymer can be uniformly crushed to a desired particle size under wet conditions without generating fine powder.
Further, as the pulverizer, any one selected from the following may be used: vertical crushers, turbine cutters, turbine grinders, rotary choppers (rotary cutter mill), chopper mills, disc mills, chip crushers, choppers (choppers), and disc cutters.
Wherein the comminution may be carried out by means of a chopper, more particularly a meat grinder.
At this time, the meat grinder includes a perforated plate, and the perforated plate may have a plurality of fine cutting holes having a certain size. In other words, it can be seen that the pulverization is performed by advancing the hydrogel polymer mixed with the additive so that the hydrogel polymer is pulverized while passing through the fine cut holes of the porous plate.
In other words, the pulverization can be performed by pushing the hydrogel polymer mixed with the carboxylic acid-based additive into a porous plate provided with a plurality of fine cut holes having a certain size. At this time, an extruder may be used to push out the hydrogel polymer. For example, a single screw extruder or a multiple screw extruder may be used.
Further, the pulverization may be performed while passing through two or more porous plates. For this purpose, a meat grinder including a chopping module in which two or more porous plates are connected in series may be used, or two or more meat grinders including one porous plate may be connected in series and used.
For example, in the case of using a meat grinder having two or more porous plates, the porous plates may be arranged in series in the order of screw-knife-porous plate, and at this time, the distance between the porous plate and the knife is preferably 1mm or less to improve the chopping efficiency.
Further, the pore size (meaning the diameter of the pores) of the fine cut pores in the porous plate may be 0.2mm to 6mm. For example, it may be 0.5mm or more, 0.7mm or more, or 1mm or more, and 5mm or less, 4mm or less, 3.5mm or less, 3mm or less, or 2mm or less. The smaller the pore size of the fine cut pores provided in the porous plate, the smaller the size of the crushed aqueous superabsorbent polymer particles, so that the drying speed is increased, thereby improving the drying efficiency. When the pore size of the fine cut pores is too small, excessive pressure is generated inside the chopper, so that the hydrogel polymer cannot be discharged through the porous plate and the apparatus may stop.
Thus, the term "aqueous superabsorbent polymer particles" as used herein is understood to mean hydrogel polymers which are crushed while passing through fine cut holes provided in a perforated plate of a meat grinder, i.e. hydrogel polymers which are crushed while passing through fine cut holes having a hole size of 0.2 to 5 mm.
The aqueous superabsorbent polymer particles contained in the crushed product herein are particles having a water content of about 30% by weight or more. Since they are particles in which the hydrogel polymer is crushed into particles without performing a drying process, their water content may be 30 to 70% by weight as in the hydrogel polymer.
At the same time, at least some of the additives contained in the crushed product may be present on the surface of the aqueous superabsorbent polymer particles. Herein, "at least some of the additive is present on the surface of the aqueous superabsorbent polymer particles" means that at least some of the additive is adsorbed or bonded on the surface of the aqueous superabsorbent polymer particles. In particular, the additive may be physically or chemically adsorbed on the surface of the superabsorbent polymer. More specifically, the hydrophilic functional groups of the additive may be physically adsorbed onto the hydrophilic portions of the surface of the superabsorbent polymer by intermolecular forces, such as dipole-dipole interactions. In this way, the hydrophilic portion of the additive is physically adsorbed on the surface of the superabsorbent polymer particles to surround the surface, while the hydrophobic portion of the additive is not adsorbed on the surface of the polymer particles, so the polymer particles may be coated with the additive in the form of a micelle structure. This is because the carboxylic acid-based additive is not added during the polymerization process of the water-soluble ethylenically unsaturated monomer, but after the polymer is formed. Therefore, the reagglomeration phenomenon between the aqueous superabsorbent polymer particles can be further suppressed as compared with the case where the additive is added during the polymerization process and is present inside the polymer.
(step 3)
The above step is drying the crushed product with a paddle dryer to produce superabsorbent polymer particles. The above drying step may be performed such that the aqueous superabsorbent polymer particles prepared in step 2 have a water content of about 10 wt.% or less, specifically, about 0.01 wt.% to about 10 wt.%. Thus, the dried product produced by the above drying step comprises a plurality of superabsorbent polymer particles having a water content of about 10% by weight or less.
Meanwhile, as described above, drying of the crushed product was performed using a paddle dryer.
The paddle dryer is a kind of agitation dryer having one or more rotation shafts arranged in a horizontal direction, and a plurality of paddles attached to the rotation shafts. As the rotating shaft rotates, the material injected into the dryer is dried. At this time, the plate-like blades horizontally positioned at the end of each paddle may agitate the dried product up and down and left and right.
Further, in the paddle dryer, gas or hot air is not supplied into the dryer, but a heating medium such as a heat transfer fluid is supplied to a rotating shaft attached to a jacket and a paddle of the dryer. Drying in a paddle dryer is thus carried out in an indirect drying manner, wherein heat is supplied to the material to be dried from the dryer jacket or the paddle wall by heat transfer. This has advantages in that deterioration, which may occur due to rapid temperature increase or uneven drying of the material to be dried, is prevented and deformation of the product is prevented, as compared with direct drying in which hot air is directly supplied to the material to be dried and then dried in a belt dryer.
Thus, in comparison with a product produced by drying in a direct drying manner in which a gas or hot air is directly supplied into a dryer, a dried product in the form of particles uniformly dried to the inside with suppressing a heat change can be obtained by drying the aqueous superabsorbent polymer particles produced in step 2 in an indirect drying manner with a paddle dryer.
For example, a paddle dryer may have two axes of rotation. Each of the two rotation shafts may rotate at the same or different speeds.
Preferably, the rotation shafts provided in the paddle dryer may be rotated at 1rpm to 120rpm, respectively. When the rotation of the rotation shaft of the paddle dryer is too slow, it may be difficult to suppress agglomeration between particles, and when the rotation shaft of the paddle dryer is too fast, excessive stirring occurs, and thus particles may be crushed into an unnecessary size, which is undesirable.
Further, the throughput per unit volume of crushed product in the paddle dryer may be 40% to 80%. This is significantly higher than the throughput per unit volume of a dryer such as a steam tube dryer or rotary kiln dryer which has a throughput per unit volume of 10% to 30%.
In addition, the drying using the paddle dryer may be performed at a temperature of 80 to 250 ℃ for 10 minutes to 3 hours.
In particular, the temperature in the paddle dryer may be from about 80 ℃ to about 250 ℃. When the temperature in the dryer is too low, the drying time may become too long, whereas when the drying temperature is too high, only the surface of the polymer is dried and the physical properties of the final superabsorbent polymer may be degraded. Accordingly, the drying process may preferably be conducted at a temperature in the dryer of about 100 ℃ to about 240 ℃, more preferably at a temperature of about 110 ℃ to about 220 ℃.
Further, the drying time may be about 10 minutes to about 3 hours in consideration of process efficiency. For example, drying may be performed for about 10 minutes to about 150 minutes, about 10 minutes to about 140 minutes, or about 10 minutes to about 120 minutes.
Furthermore, the dried product prepared in step 3 may contain 90% by weight or more, preferably 93% by weight or more of superabsorbent polymer particles having a particle size of 2000 μm or less, based on the total weight. Further, wherein superabsorbent polymer particles having a particle size of 1400 μm or less may be included in an amount of 40% by weight or more based on the total weight of the dried product.
More specifically, the superabsorbent polymer particles are obtained by drying the moisture from the aqueous superabsorbent polymer particles crushed in step 2 while passing through the fine-cut holes having a hole size of 0.2 to 5mm, and may be in the form of primary particles in which a plurality of particles are not physically or chemically agglomerated or attached. Thus, it can be seen that the superabsorbent polymer particles prepared in step 3 do not have a large change in particle size compared to the aqueous superabsorbent polymer particles crushed in step 2.
In particular, in the case where fine cut pores having a pore size of more than 1mm and 2mm or less are used in step 2, the dried product prepared in step 3 may contain 60% by weight or more of superabsorbent polymer particles having a particle size of 1400 μm or less based on the total weight. In the case where finely cut pores having a pore size of 0.2mm to 1mm are used in step 2, the dried product produced in step 3 may contain 90% by weight or more, 95% by weight or more, preferably 98% by weight or more of superabsorbent polymer particles having a particle diameter of 1400 μm or less, based on the total weight.
By the method for producing a superabsorbent polymer according to one embodiment in which step 2 of pulverizing a hydrogel polymer after mixing with a carboxylic acid-based additive and step 3 of drying the pulverized product comprising aqueous superabsorbent polymer particles produced in step 2 using a paddle dryer, the pulverized product can be dried in a short time with a high throughput per unit volume without agglomeration between the aqueous superabsorbent polymer particles, thereby producing a dried product in the form of particles instead of in the form of flakes or bulk particles.
Meanwhile, a step of classifying the superabsorbent polymer particles according to particle size may also be included after step 3 and before step 4, which will be described later. The superabsorbent polymer particles may be classified into conventional particles having a particle size of from about 150 μm to about 850 μm, fines having a particle size of less than about 150 μm, and particles having a particle size of greater than about 850 μm using ASTM standard sieves. In this case, the particle size may be measured according to EDANA WSP 220.3 of the European disposables and nonwovens Association (EDANA).
(step 4)
The above step is to finely crush particles having a particle diameter of more than 850 μm among the superabsorbent polymer particles contained in the dried product prepared in step 3. In the above step, the particles having a particle diameter of more than 850 μm are crushed to have a particle diameter of about 150 μm to about 850 μm.
The fine comminution can be carried out in dry form. That is, in the superabsorbent polymer particles prepared in step 3, particles having a particle diameter of more than 850 μm may be pulverized into small particles by mechanical energy.
Herein, the pulverizer for pulverizing may be a pin mill, a hammer mill, a screw mill, a roller mill, a disc mill, or a click mill, but the present disclosure is not limited thereto.
The superabsorbent polymer prepared as described above may comprise 90 wt% or more, 92 wt% or more, or 93 wt% or more of superabsorbent polymer particles having a particle size of 150 μm to 850 μm, i.e., conventional particles, based on the total weight.
Furthermore, the superabsorbent polymers may comprise less than about 10 wt%, specifically less than about 8 wt%, more specifically less than about 7 wt% of fines having a particle size of less than 150 μm, based on total weight.
(surface crosslinking step)
Thereafter, if necessary, a step of preparing a superabsorbent polymer having a surface cross-linked layer formed on at least a portion of the surface by cross-linking the surface of the prepared superabsorbent polymer in the presence of a surface cross-linking agent may be further included.
As the surface cross-linking agent, any surface cross-linking agent commonly used for producing superabsorbent polymers may be used without any particular limitation. Examples of the surface cross-linking agent may include: at least one polyhydric alcohol selected from the group consisting of ethylene glycol, propylene glycol, 1, 3-propanediol, 1, 4-butanediol, 1, 6-hexanediol, 1, 2-hexanediol, 1, 3-hexanediol, 2-methyl-1, 3-propanediol, 2, 5-hexanediol, 2-methyl-1, 3-pentanediol, 2-methyl-2, 4-pentanediol, tripropylene glycol, and glycerin; at least one carbonate-based compound selected from the group consisting of ethylene carbonate, propylene carbonate and glycerol carbonate; epoxy compounds such as ethylene glycol diglycidyl ether; Oxazoline compounds, e.g.>Oxazolidinones; a polyamine compound;An oxazoline compound; singly (I)>Oxazolidinone, di->Oxazolidinone or poly->An oxazolidinone compound; a cyclic urea compound; etc.
Such surface cross-linking agents may be used in amounts of about 0.001 parts by weight to about 5 parts by weight, based on 100 parts by weight of superabsorbent polymer particles. For example, the surface cross-linking agent may be used in an amount of 0.005 parts by weight or more, 0.01 parts by weight or more, or 0.05 parts by weight or more, and 5 parts by weight or less, 4 parts by weight or less, or 3 parts by weight or less, based on 100 parts by weight of the superabsorbent polymer particles. By adjusting the content of the surface cross-linking agent within the above range, a superabsorbent polymer having excellent absorption characteristics can be produced.
In addition, the method of mixing the surface cross-linking agent with the superabsorbent polymer is not particularly limited. For example, a method of adding a surface cross-linking agent and a super absorbent polymer to a reactor and mixing them can be used; a method of spraying a surface cross-linking agent onto a superabsorbent polymer; or a method of mixing the superabsorbent polymer and the surface cross-linking agent while continuously supplying them to a continuously operating mixer.
The surface cross-linking process may be performed at a temperature of about 80 ℃ to about 250 ℃. More specifically, the surface cross-linking process may be performed at a temperature of about 100 ℃ to about 220 ℃, or about 120 ℃ to about 200 ℃ for about 20 minutes to about 2 hours, or about 40 minutes to about 80 minutes. When the above surface crosslinking conditions are satisfied, the surfaces of the superabsorbent polymer particles are sufficiently crosslinked to improve the absorption under pressure.
The heating means for surface crosslinking is not particularly limited. The heat medium may be provided thereto or the heat source may be provided directly thereto. In this case, the usable heat medium may be a heated fluid such as steam, hot air, hot oil, or the like, but the present invention is not limited thereto. Further, the temperature of the heat medium to be supplied thereto may be appropriately selected in consideration of the manner of the heat medium, the heating rate, and the target temperature of heating. Meanwhile, an electric heater or a gas heater may be used as a directly supplied heat source, but the present invention is not limited thereto.
In addition, the super absorbent polymer prepared by the above method may further comprise, in addition to the super absorbent polymer particles and the carboxylic acid-based additive, a step of pulverizing the additive with the hydrogel polymer, followed by subjecting the B to a drying process 1 A compound formed by the decomposition of an ester bond.
Specifically, when the additive is one in which n is 1 and B 1 In the case of compounds of the formula-OCO-, the superabsorbent polymer may also comprise alcohols having the structure A-OH and alcohols having the structure HOOC-B 2 -a compound of structure C.
Furthermore, when the additive is one wherein n is1 and B 1 In the case of-COO-compounds, the superabsorbent polymer may also comprise carboxylic acids having an A-COOH structure and HO-B 2 -a compound of structure C.
Furthermore, when the additive is one in which n is 1 and B 1 is-COOCH (R) 1 ) In the case of COO-compounds, the superabsorbent polymer may also comprise carboxylic acids having an A-COOH structure and HOCH (R 1 )COO-B 2 -a compound of structure C.
Since the super absorbent polymer further contains a compound formed by decomposing ester bonds in the additive molecule, the fluidity of the additive increases, and the phenomenon of reagglomeration after pulverization can be further prevented.
Furthermore, the superabsorbent polymer may have a centrifuge retention capacity (centrifuge retention capacity, CRC) of 50g/g or greater, 53g/g or greater, or 54g/g or greater, and 60g/g or less, as measured according to EDANA method WSP 241.3.
Furthermore, the extractable content of the superabsorbent polymer may be 15 wt.% or less, 14.5 wt.% or less, or 12 wt.% or less, as measured according to EDANA method WSP 270.2. Further, since a lower extractable content can be evaluated as better, the lower limit is theoretically 0 wt% or more, but may be 5 wt% or more, 8 wt% or more, or 10 wt% or more.
Further, the superabsorbent polymer may have a vortex time at 24 ℃ of 70 seconds or less, 68 seconds or less, or 66 seconds or less. Further, a shorter vortex time may be evaluated as better, and the vortex time may be 40 seconds or more, or 50 seconds or more.
Further, the superabsorbent polymer may have a water content of 3 wt.% or less, 2.5 wt.% or less, or 2 wt.% or less.
Hereinafter, the present invention will be described in more detail with reference to examples. However, these examples are for illustrative purposes only, and the invention is not intended to be limited by these examples.
EXAMPLE-preparation of superabsorbent polymers
Example 1
(step 1)
100g (1.388 mol) of acrylic acid, 0.16g of polyethylene glycol diacrylate (Mn=508) as an internal crosslinking agent, 0.008g of diphenyl (2, 4, 6-trimethylbenzoyl) phosphine oxide as a photopolymerization initiator, 0.12g of sodium persulfate as a thermal polymerization initiator, and 123.5g of a 32% caustic soda solution were mixed at room temperature in a 3L glass vessel equipped with a stirrer and a thermometer to prepare a monomer composition (neutralization degree of acrylic acid: 70mol%; solid content: 45 wt%).
Thereafter, the monomer composition was supplied at 500 mL/min to 2000 mL/min onto a conveyor belt in which a belt having a width of 10cm and a length of 2m was rotated at a speed of 50 cm/min. Furthermore, while the monomer composition was supplied, the irradiation intensity was 10mW/cm 2 For 60 seconds to obtain a hydrogel polymer having a water content of 55% by weight.
(step 2)
Subsequently, sodium stearoyl-2-lactate (Almax-6900, manufactured by Ilshinwells) represented by the following chemical formulas 1 to 6 was added to the hydrogel polymer obtained by the above polymerization reaction in the form of an aqueous solution in hot water so that the content was 0.3 parts by weight based on 100 parts by weight of the hydrogel polymer. The mixture was then crushed using a meat grinder comprising a plurality of fine cut holes having a hole size of 3 mm. In this context, the water content of the aqueous superabsorbent polymer particles contained in the comminuted product is 55% by weight.
[ chemical formulas 1-6]
(step 3)
Thereafter, the pulverized product was put into a paddle having a diameter of 160mm, a total length of 1860mm, an effective volume of 77L and a heat transfer area of 1.7m 2 Is dried continuously while stirring the rotating shaft at 30 rpm. At this time, atThe temperature inside the paddle dryer was maintained at 200 ℃ during drying and the throughput per unit volume was 80%. The superabsorbent polymer particles obtained after drying were classified using ASTM standard sieves and the results are shown in table 1 below. Referring to table 1, it can be seen that the dried product contained 93 wt% of superabsorbent polymer particles having a particle size of 2000 μm or less, and 42.4 wt% of particles having a particle size of 1400 μm or less, based on the total weight.
(step 4)
The super absorbent polymer particles prepared in step 3 were finely pulverized with particles having a particle diameter of more than 850 μm classified by a sieve of more than #20 using a roll mill (66F Gran-U-Lizer manufactured by MPE) having a roll gap of 0.08mm/0.04mm between the first stage and the second stage, and then the final super absorbent polymer was prepared. The prepared particles were classified again using ASTM standard sieves, and then the particle size distribution of the finally prepared superabsorbent polymer particles including all the superabsorbent polymer particles prepared in step 3 having a particle size of 850 μm or less was determined. The results are shown in Table 1. Referring to table 1, it can be seen that the finally prepared superabsorbent polymer comprises 96.2 wt.% of conventional particles (superabsorbent polymer particles having a particle size of 150 μm to 850 μm) based on total weight.
Example 2
Superabsorbent polymers were prepared in the same manner as in example 1 except that a meat grinder comprising a perforated plate having a plurality of fine cut holes with a hole size of 2mm was used in step 2. At this time, classification was performed in step 3 and step 4 as in example 1 to determine the particle size of the obtained superabsorbent polymer particles, and the results are shown in table 1.
Referring to table 1, the dried product prepared in step 3 of example 2 contained 98.5 wt% of superabsorbent polymer particles having a particle size of 2000 μm or less, and 66.8 wt% of particles having a particle size of 1400 μm or less, based on the total weight. Furthermore, it can be seen that the superabsorbent polymer finally prepared in example 2 comprises 94.7% by weight of conventional particles, based on the total weight.
Example 3
Superabsorbent polymers were prepared in the same manner as in example 1 except that a meat grinder comprising a perforated plate having a plurality of fine cut holes with a hole size of 1mm was used in step 2. At this time, classification was performed in step 3 and step 4 as in example 1 to determine the particle size of the obtained superabsorbent polymer particles, and the results are shown in table 1.
Referring to table 1, the dried product prepared in step 3 of example 3 contained 99.7 wt% of superabsorbent polymer particles having a particle size of 2000 μm or less, and 98.1 wt% of particles having a particle size of 1400 μm or less, based on the total weight. Furthermore, it can be seen that the superabsorbent polymer finally prepared in example 3 comprises 97.2% by weight of conventional particles, based on the total weight.
Example 4
Superabsorbent polymers were prepared in the same manner as in example 1 except that sodium stearyl-2-lactate represented by chemical formulas 1 to 6 was used in an amount of 0.2 parts by weight based on 100 parts by weight of the hydrogel polymer in step 2, and a meat grinder including a perforated plate having a plurality of fine cut holes with a hole size of 2mm was used. At this time, classification was performed in step 3 and step 4 as in example 1 to determine the particle size of the obtained superabsorbent polymer particles, and the results are shown in table 1.
Referring to table 1, the dried product prepared in step 3 of example 4 contained 99.2 wt% of superabsorbent polymer particles having a particle size of 2000 μm or less, and 82.1 wt% of particles having a particle size of 1400 μm or less, based on the total weight. Furthermore, it can be seen that the superabsorbent polymer finally prepared in example 4 comprises 93.8 wt.% of conventional particles, based on total weight.
Comparative example 1
(polymerization) a hydrogel polymer having a water content of 55% by weight was obtained in the same manner as in example 1.
(shredding) the hydrogel polymer obtained by the polymerization reaction was then mixed with the same amount of water as in example 1 and shredded using a meat grinder comprising a multi-well plate having a plurality of fine cutter holes with a hole size of 16 mm.
(drying) thereafter, the minced hydrogel polymer was dried for 40 minutes while being supplied at a flow rate of 200 kg/hour to a belt dryer (manufactured by okawa) having a width of 1600mm and a length of 6200mm capable of changing the wind direction up and down. At this time, the temperature of the hot air supplied to the inside of the dryer was maintained at 180 ℃, and the hot air was supplied at 2.0 m/sec. Furthermore, the dried product prepared in the above step is prepared in the form of a single sheet, and fractionation is impossible because there is no dried product prepared in the form of particles.
(coarse/classification/fine pulverization) the dried polymer was coarsely pulverized to a particle size of about 2mm with a chopper (PULVERISETTE 19, manufactured by Fritsch). After the coarse pulverization was completed, the obtained particles were classified using an ASTM standard sieve, and the results are shown in table 2 below. Thereafter, the particles having a particle diameter of more than 850 μm classified by passing through a sieve of more than #20 were finely crushed using a roll mill (66F Gran-U-Lizer manufactured by MPE) having a roll gap of 0.08mm/0.04mm between the first stage and the second stage, and then the final superabsorbent polymer was prepared. The prepared particles were again classified using ASTM standard sieves, and then the particle size distribution of the final prepared superabsorbent polymer particles including all particles after pulverization was determined. And the results are shown in table 2. Referring to table 2, it can be seen that the superabsorbent polymer finally prepared in comparative example 1 comprises 79.4 wt.% of conventional particles, based on total weight.
Comparative example 2
The preparation of superabsorbent polymers was attempted in the same manner as in comparative example 1, except that the paddle dryer used in example 1 was used instead of the belt dryer in the drying step of comparative example 1. However, since caking occurs inside the dryer, the dryer cannot be operated.
Comparative example 3
An attempt was made to prepare a superabsorbent polymer in the same manner as in example 3, except that a belt dryer capable of changing the wind direction up and down, having a width of 1600mm and a length of 6200mm, was used instead of the paddle dryer in step 3 of example 3. However, since the inside of the dried product is not dried, the fine pulverizing process cannot be performed.
Comparative example 4
Preparation of a superabsorbent polymer was attempted in the same manner as in example 3, except that a fluidized bed dryer (drying temperature 210 ℃ C. And superficial velocity 1.2 m/sec) having a diameter of 300mm and an open cell content of 8% provided with a perforated plate having a diameter of 0.8mm was used instead of the paddle dryer in step 3 of example 3. However, superabsorbent polymers cannot be prepared because of the agglomeration that occurs during drying.
Test example 1
The results of fractionation of the superabsorbent polymers prepared in examples and comparative examples are shown in tables 1 and 2.
TABLE 1
TABLE 2
Referring to tables 1 and 2, in the case of the examples in which the superabsorbent polymer was prepared by adding the carboxylic acid-based additive during pulverization of the hydrogel polymer, agglomeration/aggregation between the aqueous superabsorbent polymer particles was suppressed during drying, and thus it was possible to perform drying in a paddle dryer having a high throughput per unit volume. Furthermore, the dried product dried by the paddle dryer is in the form of unagglomerated primary particles, so that conventional particles can be obtained by fine pulverization alone without coarse pulverization, thereby significantly reducing the amount of fines produced in the final superabsorbent polymer.
On the other hand, in the case of comparative example 2 in which the carboxylic acid-based additive was not used when crushing the hydrogel polymer, it was impossible to use a paddle dryer as in the example because of the agglomeration/aggregation between the crushed hydrogel polymers during the drying. In addition, in the case of comparative example 1 in which the carboxylic acid-based additive was not used when pulverizing the hydrogel polymer, it was possible to dry with a belt dryer as a type of fixed bed dryer as in the conventional process. However, since the dried product is in the form of a sheet, a coarse pulverizing process is required, and thus, since a two-stage dry pulverizing process including coarse pulverizing and fine pulverizing is included, a large amount of fine powder is generated in the final super absorbent polymer.
Further, in the case of using a belt dryer or a fluidized bed dryer instead of comparative examples 3 and 4 in which the particles can be dried by mechanical agitation (e.g., a paddle dryer), there is a problem in that the inside of the particles cannot be dried efficiently or a lump is generated during drying even if the aqueous superabsorbent polymer particles are prepared by adding the carboxylic acid-based additive during pulverization of the hydrogel polymer.
Thus, in the case where both the step of mixing the hydrogel polymer with the carboxylic acid-based additive, followed by pulverization, and the step of drying the pulverized product using a paddle dryer in a mobile dryer are performed in the preparation of the superabsorbent polymer, it is possible to significantly reduce fine powder in the superabsorbent polymer while improving drying efficiency through a high throughput per unit volume of the paddle dryer.
Test example 2: comparison of drying speed according to pore size of fine cut pores
In order to examine the drying speed according to the pore size of the fine cut pores of the meat grinder for the preparation of hydrogel polymer, the water content was measured in the following manner in the drying steps of examples 1 to 3.
First, as shown in FIG. 3, temperature sensors are installed at a total of five locations (TR-1, TR-2, TR-3, TR-4, and TR-5) in the paddle dryer. Thereafter, a certain amount of samples were collected from the inlet of the crushed product, TR-1 to TR-5 and the outlet in the dryer (seven positions in total), and the water content was calculated for each sample according to the following equation 1. At this time, when the point of adding the pulverized product is set to 0% and the point of discharging the dried product is set to 100% during drying in the direction of the arrow, TR-1, TR-2, TR-3, TR-4 and TR-5 refer to the dried points passing 11.6%, 27%, 42.4%, 62.9% and 78.3%, respectively.
[ equation 1]
Moisture content (% by weight) = { [ H 0 (g)-H 1 (g)]/H 0 (g)}*100
In the case of the equation 1,
H 0 (g) For the initial weight of the collected sample, and
H 1 (g) The weight of the sample was measured after heating for 40 minutes (including 5 minutes of the heating step) while raising the temperature from room temperature to 180 ℃ and maintaining 180 ℃ using an infrared moisture meter.
The moisture content relative to residence time of the samples collected at 7 points for each of examples 1 to 3 was calculated and is shown in the graph in fig. 4. Referring to fig. 4, it can be seen that the drying speed increases as the size of the fine cut holes of the meat grinder decreases during the pulverization. Thus, it can be seen that since the hydrogel polymer is crushed through fine cut holes having a smaller hole size, not only can a dried product having a smaller particle size be prepared, but also drying efficiency can be improved.
Test example 3: measurement of physical Properties of superabsorbent polymers
The physical properties of the superabsorbent polymers prepared in examples and comparative examples were evaluated in the following manner, and the results are shown in table 3 below. Unless otherwise indicated, all steps were performed in a constant temperature and humidity chamber (temperature 23.+ -. 0.5 ℃ C., relative humidity 45.+ -. 0.5%). In order to prevent measurement errors, an average value of three measurements is taken as measurement data. In addition, physiological saline or saline used in the following evaluation of physical properties means 0.9 wt% aqueous sodium chloride (NaCl).
(1) Centrifuge Retention Capacity (CRC)
The centrifuge retention capacity as a function of the absorption rate under unloaded conditions of the respective polymers was measured according to the EDANA WSP 241.3 method.
In particular, the method comprises the steps of,at the moment W 0 (g, about 0.2 g) after the polymer was uniformly inserted into the nonwoven fabric envelope and sealed, it was immersed in brine (0.9 wt%) at room temperature. After 30 minutes, the envelope was centrifuged at 250G for 3 minutes to drain water, and the weight W of the envelope was measured 2 (g) A. The invention relates to a method for producing a fibre-reinforced plastic composite In addition, after the same operation was performed without using the resin, the weight W of the envelope was measured 1 (g) A. The invention relates to a method for producing a fibre-reinforced plastic composite Then, CRC (g/g) is calculated according to the following equation 2 by using the obtained weight value.
[ equation 2]
CRC(g/g)＝{[W 2 (g)-W 1 (g)]/W 0 (g)}-1
(2) Extractable content (16 hours E/C)
The extractable content of the superabsorbent polymers prepared in examples and comparative examples was measured according to EDANA (European disposables and nonwovens Association) WSP 270.2 method.
Specifically, 1.0g of the super absorbent polymer was added to 200g of 0.9 wt% NaCl solution, kept immersed for 16 hours while stirring at 500rpm, and the aqueous solution was filtered through filter paper. The filtered solution was first titrated to a pH of 10.0 with 0.1N caustic soda solution and then back titrated to a pH of 2.7 with 0.1N hydrogen chloride solution. At this time, the uncrosslinked polymer material was calculated from the amount required for neutralization and measured as extractable content.
(3) Vortex time
The vortex time of the superabsorbent polymers prepared in examples and comparative examples was measured in the following manner.
(1) First, 50mL of 0.9% saline was added to a 100mL beaker with a flat bottom using a 100mL Mass Cylinder.
(2) Next, after the beaker was placed at the center of the magnetic stirrer, a magnetic bar (diameter 8mm, length 30 mm) was placed in the beaker.
(3) Thereafter, the stirrer was operated such that the magnetic bar was stirred at 600rpm, and the lowermost portion of the vortex generated by the stirring was brought to the top of the magnetic bar.
(4) After determining that the temperature of the brine in the beaker reached 24.0 ℃, 2±0.01g of superabsorbent polymer sample was added and a stopwatch was run simultaneously. Then, the time taken until the vortex disappeared and the liquid surface became completely horizontal was measured in seconds, and regarded as the vortex time.
(4) Moisture content
The water content of the superabsorbent polymers prepared in examples and comparative examples was measured by determining the weight loss due to evaporation of water in the samples during drying as follows.
First, a sample having a particle diameter of 150 μm to 850 μm was taken out of the prepared super absorbent polymer, and its weight was measured as H 0 (g) (initial weight of sample). Thereafter, the weight of the sample was measured as H after heating for 40 minutes (including 5 minutes of the heating step) while raising the temperature from room temperature to 180℃and maintaining 180℃using an infrared moisture meter 1 (g) A. The invention relates to a method for producing a fibre-reinforced plastic composite Then, the water content is calculated according to the above equation 1.
TABLE 3
As shown in table 3, in the case of the superabsorbent polymer prepared in examples, the extractable content was largely reduced and the vortex time was significantly improved while having a similar water content and a higher water retention capacity, as compared with the superabsorbent polymer of comparative example 1 dried with a belt dryer after crushing the hydrogel polymer without any additives.
Thus, it can be seen that when a carboxylic acid-based additive is added to crush the hydrogel polymer and the crushed product is dried in a paddle dryer to prepare a superabsorbent polymer, a superabsorbent polymer having a significantly reduced fine powder content without deteriorating the water retention capacity and simultaneously exhibiting improved water retention capacity and short vortex time can be manufactured.
Claims (20)
1. A method of making a superabsorbent polymer comprising:
step 1: a step of crosslinking polymerizing a water-soluble ethylenically unsaturated monomer having an acid group that is at least partially neutralized in the presence of an internal crosslinking agent and a polymerization initiator to form a hydrogel polymer;
step 2: a step of mixing the hydrogel polymer with a carboxylic acid-based additive, followed by comminution to produce a comminuted product comprising aqueous superabsorbent polymer particles;
step 3: a step of drying the crushed product with a paddle dryer to prepare superabsorbent polymer particles; and
step 4: a step of finely pulverizing particles having a particle diameter of more than 850 μm among the super absorbent polymer particles,
wherein the carboxylic acid-based additive is at least one selected from the group consisting of carboxylic acids represented by the following chemical formula 1 and salts thereof:
[ chemical formula 1]
In the chemical formula 1, the chemical formula is shown in the drawing,
a is an alkyl group having 5 to 21 carbon atoms,
B 1 is-OCO-, -COO-or-COOCH (R) 1 )COO-，
B 2 is-CH 2 -、-CH 2 CH 2 -、-CH(R 2 ) -, -CH=CH-or-C≡C-,
wherein R is 1 And R is 2 Each independently is an alkyl group having 1 to 4 carbon atoms,
n is an integer from 1 to 3, and
c is carboxyl.
2. The method for producing a superabsorbent polymer according to claim 1,
wherein the hydrogel polymer has a water content of 30 to 70% by weight.
3. The method for producing a superabsorbent polymer according to claim 1,
wherein in the chemical formula 1,
a is-C 6 H 13 、-C 11 H 23 、-C 12 H 25 、-C 17 H 35 or-C 18 H 37 。
4. The method for producing a superabsorbent polymer according to claim 1,
wherein in the chemical formula 1,
B 1 is that
Wherein is the bonding site to the adjacent atom.
5. The method for producing a superabsorbent polymer according to claim 1,
wherein in the chemical formula 1,
B 2 is that
Wherein is the bonding site to the adjacent atom.
6. The method for producing a superabsorbent polymer according to claim 1,
wherein the carboxylic acid-based additive is at least one selected from the group consisting of carboxylic acids represented by chemical formula 1, alkali metal salts thereof, and alkaline earth metal salts thereof.
7. The method for producing a superabsorbent polymer according to claim 1,
Wherein the carboxylic acid-based additive is any one of compounds represented by the following chemical formulas 1-1 to 1-7:
8. the method for producing a superabsorbent polymer according to claim 1,
wherein the carboxylic acid-based additive is used in an amount of 0.01 to 1 parts by weight based on 100 parts by weight of the hydrogel polymer.
9. The method for producing a superabsorbent polymer according to claim 1,
wherein the carboxylic acid-based additive is mixed in the form of a solution dissolved in a solvent.
10. The method for producing a superabsorbent polymer according to claim 1,
wherein the comminution is carried out in a wet manner.
11. The method for producing a superabsorbent polymer according to claim 1,
wherein the comminution is carried out by pushing the hydrogel polymer mixed with the carboxylic acid-based additive into a porous plate provided with a plurality of fine cut holes having a certain size.
12. The method for producing a superabsorbent polymer according to claim 11,
wherein the fine cut holes have a hole size of 0.2mm to 6mm.
13. The method for producing a superabsorbent polymer according to claim 1,
wherein the paddle dryer has two axes of rotation.
14. The method for producing a superabsorbent polymer according to claim 13,
wherein the rotation shaft rotates at 1rpm to 120rpm during drying of the pulverized product.
15. The method for producing a superabsorbent polymer according to claim 1,
wherein the drying is performed at a temperature of 80 ℃ to 250 ℃ for 10 minutes to 3 hours.
16. The method for producing a superabsorbent polymer according to claim 1,
wherein the dried product prepared in step 3 comprises 90% by weight or more of superabsorbent polymer particles having a particle size of 2000 μm or less, based on the total weight.
17. The method for producing a superabsorbent polymer according to claim 1,
further comprising the step of classifying the superabsorbent polymer particles after said step 3 and before said step 4.
18. The method for producing a superabsorbent polymer according to claim 1,
wherein the superabsorbent polymer produced comprises 90% by weight or more of superabsorbent polymer particles having a particle size of 150 μm to 850 μm based on the total weight.
19. The method for producing a superabsorbent polymer according to claim 1,
wherein the superabsorbent polymer produced comprises less than 10 wt.% of fines having a particle size of less than 150 μm, based on the total weight.
20. The method for producing a superabsorbent polymer according to claim 1,
further comprising a step of preparing a superabsorbent polymer having a surface cross-linked layer formed on at least a portion of the surface by cross-linking the surface of the prepared superabsorbent polymer in the presence of a surface cross-linking agent.
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| KR1020210007622A KR20210093786A (en) | 2020-01-20 | 2021-01-19 | Preparation method of super absorbent polymer |
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| WO2024136394A1 (en) * | 2022-12-23 | 2024-06-27 | 주식회사 엘지화학 | Preparation method of super absorbent polymer |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1997038740A1 (en) * | 1996-04-18 | 1997-10-23 | Minnesota Mining And Manufacturing Company | Compressed absorbent aggregate |
| CN105814088A (en) * | 2013-12-10 | 2016-07-27 | 株式会社Lg化学 | Method for preparing super-absorbent resin |
| CN106661235A (en) * | 2015-07-10 | 2017-05-10 | 株式会社Lg化学 | Method for preparing superabsorbent resin and superabsorbent resin prepared thereby |
| CN107922630A (en) * | 2015-10-14 | 2018-04-17 | 株式会社Lg化学 | Superabsorbent polymer particles body and preparation method thereof |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1997038740A1 (en) * | 1996-04-18 | 1997-10-23 | Minnesota Mining And Manufacturing Company | Compressed absorbent aggregate |
| CN105814088A (en) * | 2013-12-10 | 2016-07-27 | 株式会社Lg化学 | Method for preparing super-absorbent resin |
| CN106661235A (en) * | 2015-07-10 | 2017-05-10 | 株式会社Lg化学 | Method for preparing superabsorbent resin and superabsorbent resin prepared thereby |
| CN107922630A (en) * | 2015-10-14 | 2018-04-17 | 株式会社Lg化学 | Superabsorbent polymer particles body and preparation method thereof |
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| KR20210093742A (en) | 2021-07-28 |
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