CN113748156A - Method for preparing super absorbent polymer - Google Patents
Method for preparing super absorbent polymer Download PDFInfo
- Publication number
- CN113748156A CN113748156A CN202180003060.7A CN202180003060A CN113748156A CN 113748156 A CN113748156 A CN 113748156A CN 202180003060 A CN202180003060 A CN 202180003060A CN 113748156 A CN113748156 A CN 113748156A
- Authority
- CN
- China
- Prior art keywords
- superabsorbent polymer
- preparing
- polymer
- particles
- weight
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 229920000247 superabsorbent polymer Polymers 0.000 title claims abstract description 210
- 238000000034 method Methods 0.000 title claims abstract description 83
- 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 96
- 238000001035 drying Methods 0.000 claims abstract description 88
- 230000000996 additive effect Effects 0.000 claims abstract description 86
- 238000010298 pulverizing process Methods 0.000 claims abstract description 62
- 239000000843 powder Substances 0.000 claims abstract description 29
- 238000002156 mixing Methods 0.000 claims abstract description 18
- 239000002245 particle Substances 0.000 claims description 204
- 150000001732 carboxylic acid derivatives Chemical class 0.000 claims description 63
- 239000000178 monomer Substances 0.000 claims description 51
- 239000000126 substance Substances 0.000 claims description 50
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 40
- -1 alkali metal salts Chemical class 0.000 claims description 37
- 239000003431 cross linking reagent Substances 0.000 claims description 37
- 150000001875 compounds Chemical class 0.000 claims description 21
- 239000003505 polymerization initiator Substances 0.000 claims description 19
- 238000004132 cross linking Methods 0.000 claims description 18
- 230000002378 acidificating effect Effects 0.000 claims description 14
- 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 5
- 125000004429 atom Chemical group 0.000 claims description 4
- 125000004051 hexyl group Chemical group [H]C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])* 0.000 claims description 2
- 229910044991 metal oxide Inorganic materials 0.000 claims 3
- 150000004706 metal oxides Chemical class 0.000 claims 3
- 239000004583 superabsorbent polymers (SAPs) Substances 0.000 abstract description 23
- 230000008569 process Effects 0.000 abstract description 22
- 239000000047 product Substances 0.000 description 52
- NIXOWILDQLNWCW-UHFFFAOYSA-M Acrylate Chemical compound [O-]C(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-M 0.000 description 29
- 238000006116 polymerization reaction Methods 0.000 description 29
- DNIAPMSPPWPWGF-UHFFFAOYSA-N Propylene glycol Chemical compound CC(O)CO DNIAPMSPPWPWGF-UHFFFAOYSA-N 0.000 description 27
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 22
- 238000005054 agglomeration Methods 0.000 description 22
- 239000000203 mixture Substances 0.000 description 21
- 230000002776 aggregation Effects 0.000 description 18
- 239000000463 material Substances 0.000 description 18
- 230000000052 comparative effect Effects 0.000 description 16
- 239000011148 porous material Substances 0.000 description 15
- 230000002829 reductive effect Effects 0.000 description 14
- 235000013372 meat Nutrition 0.000 description 12
- 239000000243 solution Substances 0.000 description 12
- 238000012719 thermal polymerization Methods 0.000 description 12
- 125000000524 functional group Chemical group 0.000 description 11
- 239000003999 initiator Substances 0.000 description 11
- 238000010438 heat treatment Methods 0.000 description 10
- 230000000704 physical effect Effects 0.000 description 10
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 9
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 9
- 230000002209 hydrophobic effect Effects 0.000 description 9
- 238000003756 stirring Methods 0.000 description 9
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 8
- 238000010521 absorption reaction Methods 0.000 description 8
- 238000004519 manufacturing process Methods 0.000 description 8
- 238000001179 sorption measurement Methods 0.000 description 8
- 230000001965 increasing effect Effects 0.000 description 7
- 238000006386 neutralization reaction 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
- 239000002253 acid Substances 0.000 description 5
- 239000003795 chemical substances by application Substances 0.000 description 5
- 230000003472 neutralizing effect Effects 0.000 description 5
- 229920001223 polyethylene glycol Polymers 0.000 description 5
- 238000002360 preparation method Methods 0.000 description 5
- 239000011780 sodium chloride Substances 0.000 description 5
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 4
- 239000002202 Polyethylene glycol Substances 0.000 description 4
- 150000001340 alkali metals Chemical class 0.000 description 4
- 150000001342 alkaline earth metals Chemical class 0.000 description 4
- 239000007864 aqueous solution Substances 0.000 description 4
- 230000008901 benefit Effects 0.000 description 4
- WERYXYBDKMZEQL-UHFFFAOYSA-N butane-1,4-diol Chemical compound OCCCCO WERYXYBDKMZEQL-UHFFFAOYSA-N 0.000 description 4
- 150000001768 cations Chemical class 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 239000000499 gel Substances 0.000 description 4
- 238000005259 measurement Methods 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- 238000012986 modification Methods 0.000 description 4
- 230000004048 modification Effects 0.000 description 4
- 239000004745 nonwoven fabric Substances 0.000 description 4
- 239000007787 solid Substances 0.000 description 4
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 description 3
- IZXIZTKNFFYFOF-UHFFFAOYSA-N 2-Oxazolidone Chemical compound O=C1NCCO1 IZXIZTKNFFYFOF-UHFFFAOYSA-N 0.000 description 3
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
- 239000002585 base Substances 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 238000007796 conventional method Methods 0.000 description 3
- 238000005520 cutting process Methods 0.000 description 3
- 235000011187 glycerol Nutrition 0.000 description 3
- 239000007924 injection Substances 0.000 description 3
- 238000002347 injection Methods 0.000 description 3
- 238000009434 installation Methods 0.000 description 3
- 230000000670 limiting effect Effects 0.000 description 3
- 230000014759 maintenance of location Effects 0.000 description 3
- 230000000379 polymerizing effect Effects 0.000 description 3
- 239000011802 pulverized particle Substances 0.000 description 3
- 239000011347 resin Substances 0.000 description 3
- 229920005989 resin Polymers 0.000 description 3
- 235000011121 sodium hydroxide Nutrition 0.000 description 3
- 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
- CERQOIWHTDAKMF-UHFFFAOYSA-N Methacrylic acid Chemical compound CC(=C)C(O)=O CERQOIWHTDAKMF-UHFFFAOYSA-N 0.000 description 2
- 239000002250 absorbent Substances 0.000 description 2
- 230000002745 absorbent Effects 0.000 description 2
- 238000013019 agitation Methods 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
- 150000007942 carboxylates Chemical group 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
- 230000003247 decreasing effect Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 230000018109 developmental process Effects 0.000 description 2
- 238000010586 diagram Methods 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
- 230000014509 gene expression Effects 0.000 description 2
- 238000000227 grinding Methods 0.000 description 2
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 2
- 239000003960 organic solvent Substances 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
- 239000011164 primary particle Substances 0.000 description 2
- 239000011734 sodium Substances 0.000 description 2
- CHQMHPLRPQMAMX-UHFFFAOYSA-L sodium persulfate Substances [Na+].[Na+].[O-]S(=O)(=O)OOS([O-])(=O)=O CHQMHPLRPQMAMX-UHFFFAOYSA-L 0.000 description 2
- ODFAPIRLUPAQCQ-UHFFFAOYSA-M sodium stearoyl lactylate Chemical compound [Na+].CCCCCCCCCCCCCCCCCC(=O)OC(C)C(=O)OC(C)C([O-])=O ODFAPIRLUPAQCQ-UHFFFAOYSA-M 0.000 description 2
- 239000003724 sodium stearoyl-2-lactylate Substances 0.000 description 2
- 235000010956 sodium stearoyl-2-lactylate Nutrition 0.000 description 2
- 238000005507 spraying Methods 0.000 description 2
- 239000003381 stabilizer Substances 0.000 description 2
- 239000002562 thickening agent Substances 0.000 description 2
- ZIBGPFATKBEMQZ-UHFFFAOYSA-N triethylene glycol Chemical compound OCCOCCOCCO ZIBGPFATKBEMQZ-UHFFFAOYSA-N 0.000 description 2
- 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
- PUPZLCDOIYMWBV-UHFFFAOYSA-N (+/-)-1,3-Butanediol Chemical compound CC(O)CCO PUPZLCDOIYMWBV-UHFFFAOYSA-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
- YPFDHNVEDLHUCE-UHFFFAOYSA-N 1,3-propanediol Substances OCCCO YPFDHNVEDLHUCE-UHFFFAOYSA-N 0.000 description 1
- 229940035437 1,3-propanediol Drugs 0.000 description 1
- RRQYJINTUHWNHW-UHFFFAOYSA-N 1-ethoxy-2-(2-ethoxyethoxy)ethane Chemical compound CCOCCOCCOCC RRQYJINTUHWNHW-UHFFFAOYSA-N 0.000 description 1
- SBASXUCJHJRPEV-UHFFFAOYSA-N 2-(2-methoxyethoxy)ethanol Chemical compound COCCOCCO SBASXUCJHJRPEV-UHFFFAOYSA-N 0.000 description 1
- 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
- POAOYUHQDCAZBD-UHFFFAOYSA-N 2-butoxyethanol Chemical compound CCCCOCCO POAOYUHQDCAZBD-UHFFFAOYSA-N 0.000 description 1
- 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 group [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
- AUZRCMMVHXRSGT-UHFFFAOYSA-N 2-methylpropane-1-sulfonic acid;prop-2-enamide Chemical compound NC(=O)C=C.CC(C)CS(O)(=O)=O AUZRCMMVHXRSGT-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
- SVYPQURSUBDSIQ-UHFFFAOYSA-N 4-methyl-3-oxopent-4-ene-1-sulfonic acid Chemical compound CC(=C)C(=O)CCS(O)(=O)=O SVYPQURSUBDSIQ-UHFFFAOYSA-N 0.000 description 1
- 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
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- KWIUHFFTVRNATP-UHFFFAOYSA-N Betaine Natural products C[N+](C)(C)CC([O-])=O KWIUHFFTVRNATP-UHFFFAOYSA-N 0.000 description 1
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- 239000004593 Epoxy Substances 0.000 description 1
- ZMDDERVSCYEKPQ-UHFFFAOYSA-N Ethyl (mesitylcarbonyl)phenylphosphinate Chemical compound C=1C=CC=CC=1P(=O)(OCC)C(=O)C1=C(C)C=C(C)C=C1C ZMDDERVSCYEKPQ-UHFFFAOYSA-N 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 1
- 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 1
- KWIUHFFTVRNATP-UHFFFAOYSA-O N,N,N-trimethylglycinium Chemical compound C[N+](C)(C)CC(O)=O KWIUHFFTVRNATP-UHFFFAOYSA-O 0.000 description 1
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 description 1
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- LXEKPEMOWBOYRF-UHFFFAOYSA-N [2-[(1-azaniumyl-1-imino-2-methylpropan-2-yl)diazenyl]-2-methylpropanimidoyl]azanium;dichloride Chemical compound Cl.Cl.NC(=N)C(C)(C)N=NC(C)(C)C(N)=N LXEKPEMOWBOYRF-UHFFFAOYSA-N 0.000 description 1
- GUCYFKSBFREPBC-UHFFFAOYSA-N [phenyl-(2,4,6-trimethylbenzoyl)phosphoryl]-(2,4,6-trimethylphenyl)methanone Chemical compound CC1=CC(C)=CC(C)=C1C(=O)P(=O)(C=1C=CC=CC=1)C(=O)C1=C(C)C=C(C)C=C1C GUCYFKSBFREPBC-UHFFFAOYSA-N 0.000 description 1
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- 239000000908 ammonium hydroxide Substances 0.000 description 1
- 229910001870 ammonium persulfate Inorganic materials 0.000 description 1
- 150000003863 ammonium salts Chemical class 0.000 description 1
- 239000002280 amphoteric surfactant Substances 0.000 description 1
- 108010038083 amyloid fibril protein AS-SAM Proteins 0.000 description 1
- 239000011668 ascorbic acid Substances 0.000 description 1
- 235000010323 ascorbic acid Nutrition 0.000 description 1
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- 230000000903 blocking effect Effects 0.000 description 1
- 239000012267 brine Substances 0.000 description 1
- 239000001273 butane Substances 0.000 description 1
- CDQSJQSWAWPGKG-UHFFFAOYSA-N butane-1,1-diol Chemical compound CCCC(O)O CDQSJQSWAWPGKG-UHFFFAOYSA-N 0.000 description 1
- 125000000484 butyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])C([H])([H])[H] 0.000 description 1
- 229930188620 butyrolactone Natural products 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- LDHQCZJRKDOVOX-NSCUHMNNSA-N crotonic acid Chemical compound C\C=C\C(O)=O LDHQCZJRKDOVOX-NSCUHMNNSA-N 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- ISAOCJYIOMOJEB-UHFFFAOYSA-N desyl alcohol Natural products C=1C=CC=CC=1C(O)C(=O)C1=CC=CC=C1 ISAOCJYIOMOJEB-UHFFFAOYSA-N 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 125000004386 diacrylate group Chemical group 0.000 description 1
- 229940019778 diethylene glycol diethyl ether Drugs 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 125000001495 ethyl group Chemical group [H]C([H])([H])C([H])([H])* 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
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Images
Classifications
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- 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
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- 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
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- 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
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- 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
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- 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
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- 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
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- 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
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- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
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Abstract
The present disclosure relates to a method of preparing superabsorbent polymers. More particularly, the present disclosure relates to a method for preparing such a superabsorbent polymer, which is capable of significantly reducing the amount of fine powder generated during the 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
This application claims the benefit of korean patent application No. 10-2020-.
The present disclosure relates to a method of preparing superabsorbent polymers. More particularly, the present disclosure relates to a method of preparing superabsorbent polymers in which the amount of fines generated is significantly reduced.
Background
Superabsorbent Polymer (SAP) is a synthetic polymeric material that is capable of absorbing 500 to 1000 times its own weight of moisture. Each manufacturer names them differently, such as SAM (Super Absorbent Material), AGM (Absorbent Gel Material), etc. Such super absorbent polymers are beginning to be put into practical use in sanitary products, and are now widely used not only in sanitary products but also in water-retentive soil products for gardening, water-stopping materials for civil engineering and construction, sheets for growing seedlings, freshness-retaining agents for the field of food circulation, materials for cataplasms, 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. However, in recent years, continuous efforts have been made to provide sanitary materials such as diapers having a thinner thickness. As part of such efforts, development of so-called pulp-free diapers and the like in which the content of pulp is reduced or no pulp is used at all is being actively advanced.
As described above, in the case of a sanitary material in which the content of pulp is reduced or pulp is not used, superabsorbent polymers are contained at a relatively high ratio, and these superabsorbent polymer particles are inevitably contained in multiple layers in the sanitary material. In order for all the superabsorbent polymer particles contained in the multiple layers to absorb a large amount of liquid such as urine more effectively, the superabsorbent polymer needs to exhibit substantially high absorption performance and a fast absorption rate.
Meanwhile, such superabsorbent polymers are generally prepared by a method including: a step of polymerizing the 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 pulverized 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 the 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 equipment may occur, and thus the productivity of preparing the superabsorbent polymer may be reduced.
Therefore, there is a continuing need to develop a technology capable of manufacturing superabsorbent polymers without generating fine powder to fundamentally solve the problem.
Disclosure of Invention
Technical problem
Accordingly, the present disclosure relates to a method for preparing a super absorbent polymer capable of significantly reducing the amount of fine powder generated during the process by mixing a hydrogel polymer with an additive having a specific structure, pulverizing it, and drying it with a paddle dryer.
Technical scheme
In order to solve the above problems, there is provided a method of preparing a superabsorbent polymer, the method comprising:
1) a step of forming a hydrogel polymer 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 (step 1);
2) a step of mixing the hydrogel polymer with the carboxylic acid-based additive, followed by pulverization to prepare a pulverized product containing the aqueous superabsorbent polymer particles (step 2);
3) a step of drying the pulverized 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 first and second,
a is an alkyl group having 5 to 21 carbon atoms,
B1is-OCO-, -COO-or-COOCH (R)1)COO-，
B2is-CH2-、-CH2CH2-、-CH(R2) -, -CH-or-C.ident.C-,
wherein R is1And R2Each independently an alkyl group having 1 to 4 carbon atoms,
n is an integer of 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 pulverizing the hydrogel polymer in the presence of the carboxylic acid-based additive. Further, even in the drying process using the paddle dryer, agglomeration between particles is suppressed to obtain a granular dried product, so that the amount of dry crumbs after drying can be greatly reduced. Thus, a superabsorbent polymer in which the amount of fine powder is significantly reduced can be manufactured.
Drawings
FIG. 1 is a flow chart illustrating a conventional method of preparing superabsorbent polymers.
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 water content of each pulverized 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. The singular is intended to include the plural unless the context clearly dictates otherwise. It will be further understood that the terms "comprises," "comprising," "has," "having," or "having," when used in this specification, specify the presence of stated features, steps, components, or combinations 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 have been shown by way of example and will herein be described in detail. However, it is not intended to limit the invention to the particular forms disclosed, and it should be understood that the invention includes 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 have been shown by way of example and will herein be described in detail. However, it is not intended to limit the invention to the particular forms disclosed, and it should be understood that the invention includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.
Hereinafter, a method of preparing a superabsorbent polymer and a superabsorbent polymer prepared therefrom will be described in more detail according to 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 disclosure. Unless the context dictates otherwise, singular expressions of the present disclosure may include plural expressions.
According to one embodiment of the present disclosure, there is provided a method of preparing a superabsorbent polymer, the method comprising:
1) a step of forming a hydrogel polymer 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 (step 1);
2) a step of mixing the hydrogel polymer with the carboxylic acid-based additive, followed by pulverization to prepare a pulverized product containing the aqueous superabsorbent polymer particles (step 2);
3) a step of drying the pulverized 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 first and second,
a is an alkyl group having 5 to 21 carbon atoms,
B1is-OCO-, -COO-or-COOCH (R)1)COO-，
B2is-CH2-、-CH2CH2-、-CH(R2) -, -CH-or-C.ident.C-,
wherein R is1And R2Each independently an alkyl group having 1 to 4 carbon atoms,
n is an integer of 1 to 3, and
c is carboxyl.
The term "polymer" in this disclosure is in a state in which the 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.
Further, the term "superabsorbent polymer particles" refers to particulate materials comprising a crosslinked polymer in which water-soluble ethylenically unsaturated monomers having at least partially neutralized acidic groups are polymerized and crosslinked by an internal crosslinking agent.
Furthermore, the term "superabsorbent polymer" is used to include all of the following, depending on the context: 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 a powder composed of superabsorbent polymer particles in which the crosslinked polymer is pulverized, and a crosslinked polymer or a base resin which is further processed (e.g., dried, pulverized, classified, surface-crosslinked, etc.) in a state suitable for commercialization. Thus, the term "superabsorbent polymer" may be construed to include compositions comprising a superabsorbent polymer, i.e., a plurality of superabsorbent polymer particles.
Further, the term "conventional superabsorbent polymer particles" refers to particles having a particle size of 150 μm to 850 μm among 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 (EDANA).
Further, the term "chopping" means that the hydrogel polymer is cut into small pieces to improve drying efficiency, and is used separately from being crushed into a conventional particle size.
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 facilitate the drying of the hydrogel polymer and to improve the efficiency of the crushing process, a process of chopping the hydrogel polymer is performed before the drying process. However, due to the viscosity of the hydrogel polymer during this chopping process, the hydrogel polymer cannot be crushed into micron-sized particles but 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 multistage pulverization process is required for pulverizing it into micrometer-sized particles. Therefore, there is a problem that many fine powders are generated in the process.
Specifically, FIG. 1 shows a flow diagram 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.
(polymerization) cross-linking polymerizing a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups in the presence of an internal cross-linking agent and a polymerization initiator to form a hydrogel polymer;
(chopping) the hydrogel polymer;
(drying) drying the minced hydrogel polymer; and
(coarse pulverizing/classifying/fine pulverizing) pulverizing the dried polymer, and then classifying the pulverized polymer into conventional particles and fine powder;
as noted 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 with a perforated plate at the bottom and dried in a fixed bed manner by hot air supplied from the bottom or top. Since the polymer dried by the above drying method has a sheet shape instead of a particle shape, the step of pulverization and subsequent classification is performed as a step of coarse pulverization, subsequent classification and then fine pulverization, and subsequent classification again, so that the produced particles become conventional particles, i.e., particles having a particle diameter of 150 to 850 μm. However, since the coarse pulverization and the fine pulverization after the drying are performed in a dry manner, a large amount of fine powder is generated in the pulverization process. Specifically, the amount of the fine powder separated in the final classification step by the preparation method is up to 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 added before the drying step.
However, when the fine powder reassembled body mixed with water is reinjected into a pulverizing or drying process for reuse of the fine powder, problems such as an increase in load on equipment and/or energy consumption arise. In addition, the physical properties of the superabsorbent polymer are deteriorated due to the fine powder that is not classified and remains.
Accordingly, the present inventors have recognized that the amount of fine powder generated in the conventional production method is largely affected by the particle size introduced into the pulverization process, and have determined that if the hydrogel polymer can be pulverized to the micrometer scale in the chopping process without agglomeration occurring between the hydrogel polymers, the amount of fine powder generated during the process can be reduced. Therefore, 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 was mixed with the carboxylic acid-based additive and then pulverized, the viscosity of the hydrogel polymer was reduced due to the carboxylic acid-based additive, and thus the pulverization into micrometer-level particles was possible. The present invention has been accomplished in view of the above. 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. Furthermore, since the drying process is performed in the form of micron-sized particles, the drying may be efficient.
Specifically, the carboxylic acid-based additive has both a hydrophobic functional group and a hydrophilic functional group. Meanwhile, since the water-soluble ethylenically unsaturated monomer contains an acidic group (-COOH) and/or a neutralized acidic group (-COO-), a large number of hydrophilic moieties are present on the surface of the hydrogel polymer prepared by polymerization due to the acidic group (-COOH) and/or the neutralized acidic group (-COO-) that remain without participating in the polymerization. Therefore, 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 portion present on the surface of the hydrogel polymer, and the surface of the polymer on which the additive is adsorbed becomes hydrophobic due to the hydrophobic functional group located at the other end of the additive. Therefore, agglomeration between polymer particles can be suppressed.
More specifically, in the carboxylic acid-based additive, the hydrophobic functional group is an alkyl group having from 5 to 21 carbon atoms (moiety a), and the hydrophilic functional group is a moiety C, in particular a carboxyl group (COOH) or, in the case of a salt, a carboxylate group (-COO)-). The hydrophobic functional group and the hydrophilic functional group are respectively positioned at both ends of the additive. In particular, the carboxylic acid-based additive comprises a part (B) in addition to a part A and a part C at both ends1-B2) And part (B)1-B2) The adsorption property to the polymer surface is improved, and the adsorption property to the polymer surface may be insufficient in the case of having only the portion C. Thus, and has an A-C structure without a moiety (B)1-B2) Has excellent adsorption property to the surface of the polymer exhibiting hydrophilicity, and thus effectively inhibits the agglomeration of the water-containing super absorbent polymer particles, compared to the compound of (1).
Furthermore, the comminuted product comprising aqueous superabsorbent polymer particles is preferably dried in a mobile manner. In this context, mobile drying is classified as fixed bed drying, depending on whether the 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 bottom plate through which air can pass, such as a porous iron plate, and hot air passes through the material from bottom to top to perform drying.
When the pulverized product containing the aqueous superabsorbent polymer particles is dried in a traveling manner, an agglomeration phenomenon between the aqueous superabsorbent polymer particles is prevented, so that a granular dried product can be obtained. Therefore, there is an advantage in that the drying can be completed in a short time without a process of coarsely pulverizing or pulverizing the agglomerated particles after the drying.
As an apparatus capable of performing drying by such a mobile drying method, a paddle dryer, a horizontal mixer, a rotary kiln, or a steam pipe dryer can be used. Among them, it is preferable to use a paddle dryer to dry the pulverized product in terms of installation cost, throughput per unit volume, and heat transfer efficiency. In particular, the paddle dryer has advantages in that an area required for installation is small, installation is simple, and a yield per unit volume is high. However, in order to dry the pulverized product at 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 an excellent effect 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 chopped hydrogel polymers not mixed with the carboxylic acid-based additive are agglomerated with each other during drying, drying using a paddle dryer is impossible. Further, even when a conventionally known surfactant other than the carboxylic acid-based additive, for example, a betaine-based amphoteric surfactant, is polymerized with the hydrogel polymer and then pulverized, the effect of suppressing agglomeration between particles is not good. Thus, drying in a rotary heating device, such as a steam pipe dryer, with low throughput per unit volume may be possible, but it is difficult to dry by a paddle dryer with high density between the pulverized particles because of the large throughput per unit volume.
Specifically, FIG. 2 shows a flow diagram of a method of making a superabsorbent polymer composition according to one embodiment. Referring to fig. 2, unlike the conventional method of preparing superabsorbent polymers, superabsorbent polymers can be prepared by a step of finely pulverizing only particles having a particle size of more than 850 μm among superabsorbent polymer particles after preparing a hydrogel polymer and then pulverizing and drying. Therefore, since the coarse pulverizing process, which is a dry pulverizing process after drying, can be omitted, considering that the 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 the manufacturing cost can also be reduced.
Further, according to the method of preparing the superabsorbent polymer, when the hydrogel is crushed in a state where the hydrogel polymer is mixed with the carboxylic acid-based additive, adhesion between particles is weakened due to the hydrophobic functional groups 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 contents (E/C) having a short chain that participate in polymerization but are not bonded to the main chain may be present in the superabsorbent polymer. These extractable contents are not preferred because they may lead to rewetting. Specifically, when the hydrogel polymer, in which the carboxylic acid-based additive is not mixed, is chopped, the hydrogel polymer is granular and agglomerated again due to viscosity. As a result, the hydrogel polymer is subjected to mechanical shear in the chopper, which results in damage to the polymer chains, resulting in increased extractable content. However, in the case of the method for preparing the superabsorbent polymer, the re-agglomeration of the formed particulate hydrogel is prevented by the hydrophobic functional group of the carboxylic acid-based additive, and thus the particulate hydrogel can easily pass through the porous plate of the chopper. Thus, excessive mechanical shear on the hydrogel can be prevented, so that the extractable content present in the superabsorbent polymer can be reduced.
Hereinafter, a method of preparing the superabsorbent polymer composition of one embodiment will be described in more detail with respect to each component.
(step 1)
The above steps form the hydrogel polymer by cross-linking polymerizing the water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups in the presence of the internal cross-linking agent and the polymerization initiator, 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 or photopolymerizing the monomer composition.
The water-soluble ethylenically unsaturated monomer can be any of the monomers 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 first and second organic solvents,
r is a C2 to C5 hydrocarbon group having an unsaturated bond, and
m' is a hydrogen atom, a monovalent 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 the acids.
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) acrylate, 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.
Herein, the water-soluble ethylenically unsaturated monomer may have an acidic group, and at least some of the acidic group may be neutralized by a neutralizing agent. Specifically, at least some of the acid groups of the water-soluble ethylenically unsaturated monomer may be neutralized in the step of mixing the water-soluble ethylenically unsaturated monomer having the acid groups, the internal crosslinking agent, the polymerization initiator, and the neutralizing agent. In this case, basic substances capable of neutralizing acidic groups, such as sodium hydroxide, potassium hydroxide, and ammonium hydroxide, may be used as the neutralizing agent.
Further, the water-soluble ethylenically unsaturated monomer may have a neutralization degree of 50 to 90 mol%, 60 to 85 mol%, 65 to 85 mol%, or 65 to 75 mol%, wherein the neutralization degree refers to a degree to which an acidic group contained in the water-soluble ethylenically unsaturated monomer is neutralized by a neutralizing agent. The range of neutralization may vary depending on the final physical properties. Too high a degree of neutralization causes precipitation of the neutralized monomer, and thus polymerization may not easily occur. Conversely, too low a neutralization degree not only deteriorates the absorption rate of the polymer but also imparts a characteristic that the polymer is difficult to handle such as a characteristic 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 unsaturated bonds of the water-soluble ethylenically unsaturated monomer by crosslinking. The crosslinking in the above step is performed either on the surface or inside, but when a surface crosslinking process of the superabsorbent polymer particles, which will be described later, is performed, the surface of the particles of the finally prepared superabsorbent polymer has a structure crosslinked by a surface crosslinking agent, and the inside of the particles has a structure crosslinked by an internal crosslinking agent.
As the internal crosslinking agent, any compound may be used as long as it allows introduction of a crosslinking bond during polymerization of the water-soluble ethylenically unsaturated monomer. As non-limiting examples, the internal crosslinking agent may be a polyfunctional 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 glycol 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 di (meth) acrylate, butylene glycol di (meth) acrylate, propylene glycol tri (meth) acrylate, propylene glycol tetra (meth) acrylate, ethylene glycol tetra (meth) acrylate, propylene glycol tetra (meth) acrylate, ethylene glycol tetra (meth) acrylate, propylene glycol tetra (meth) acrylate, ethylene glycol tetra (meth) acrylate, propylene glycol, glycerin or ethylene carbonate, and these may be used alone or in a 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 carried out by thermal polymerization, photopolymerization, or hybrid polymerization in the presence of a polymerization initiator with or without a thickener, a plasticizer, a storage stabilizer, an antioxidant, or the like, but specific details will be described later.
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 in the monomer composition. 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 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.
Further, the polymerization initiator may be appropriately selected depending on 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 the thermal polymerization initiator and the photopolymerization initiator may be used. However, even by the photopolymerization method, a certain amount of heat is generated by UV irradiation or the like, and some heat is generated as the polymerization reaction (exothermic reaction) proceeds. Accordingly, the composition may further comprise a thermal polymerization initiator.
Herein, any compound that can form radicals by light (e.g., UV rays) may be used without limitation as the photopolymerization initiator.
For example, the photopolymerization initiator may be one or more compounds selected from the group consisting of: benzoin ethers, dialkyl acetophenones, hydroxy alkyl ketones, phenyl glyoxylates, benzyl dimethyl ketals, acyl phosphines and alpha-amino ketones. Further, specific examples of acylphosphines 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 well disclosed on page 115 of "UV Coatings: bases, Recent Developments and New Application (Elsevier, 2007)" written by Reinhold Schwalm, and the disclosure is not limited thereto.
Further, as the thermal polymerization initiator, one or more initiators selected from the group consisting of: persulfate-based initiators, azo-based initiators, hydrogen peroxide, and ascorbic acid. Specifically, sodium persulfate (Na) may be used2S2O8) Potassium persulfate (K)2S2O8) Ammonium persulfate ((NH)4)2S2O8) And the like as examples of the persulfate-based initiator; and 2, 2-azobis (2-amidinopropane) dihydrochloride, 2-azobis- (N, N-dimethylene) isobutylamidine dihydrochloride, 2- (carbamoylazo) isobutyronitrile, 2-azobis- [2- (2-imidazolin-2-yl) propane]Dihydrochloride, 4-azobis- (4-cyanovaleric acid), and the like are examples of the azo-based initiator. More different thermal Polymerization initiators are well disclosed on page 203 of "principles of Polymerization (Wiley, 1981)" written 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 monomers may be extracted from the final product. In contrast, when the concentration of the polymerization initiator is higher than the above range, polymer chains forming the network are shortened, so that the content of extractable components is increased and the absorption rate under pressure is decreased, thereby decreasing the physical properties of the polymer.
If necessary, the monomer composition may further include additives such as a thickener, a plasticizer, a preservation stabilizer, an antioxidant, and the like.
Further, the monomer composition comprising the monomer may be, for example, in the form of a solution dissolved in a solvent (e.g., water). The solid content of the monomer composition in a solution state, that is, 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 solid 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 solid content within the above range, it may be advantageous for: the pulverization efficiency during pulverization of a polymer, which will be described later, is controlled while eliminating the need to remove unreacted monomers after 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 at least partially neutralized may be performed without any particular limitation as long as the hydrogel polymer may be formed by thermal polymerization, photopolymerization, or hybrid polymerization.
Specifically, polymerization methods are roughly classified into thermal polymerization and photopolymerization according to the energy source of polymerization. In the case of thermal polymerization, it is usually carried out in a reactor equipped with a stirring shaft, such as a kneader. In the case of photopolymerization, it is generally carried out in a reactor equipped with a movable conveyor belt or in a container with a flat bottom. However, the above polymerization method is only an example, and the present disclosure is not limited thereto.
For example, the hydrogel polymer can be obtained by supplying hot air into a reactor having a stirring shaft, such as a kneader, or heating the reactor to perform thermal polymerization. The hydrogel polymer thus obtained may have a size of several centimeters to several millimeters, depending on the shape of the stirring shaft provided in the reactor. Specifically, the size of the obtained hydrogel polymer may vary depending on the concentration of the monomer composition injected thereto and the injection speed, and a hydrogel polymer having a weight-average particle diameter of 2mm to 50mm may be obtained.
Further, when the photopolymerization is carried out in a reactor equipped with a movable conveyor belt or in a vessel 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 of the injected monomer composition, the injection speed, or the injection amount, 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 an excessively thick thickness.
At this time, the hydrogel polymer thus obtained may have a water content of 30 to 70% by weight. For example, the hydrogel polymer can have a water content of 35 wt.% or more, 40 wt.% or more, 45 wt.% or more, or 50 wt.% or more, 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 ensure 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 received in the subsequent pulverization step increases, and thus pulverization may be difficult to proceed to a desired particle size.
Meanwhile, "water content" in the present specification is the content of moisture 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 moisture evaporation of the polymer during the process of raising the temperature of the crumb polymer by infrared heating for drying. At this time, the drying conditions for measuring the moisture content were 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 through 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 retention capacity and the absorption rate under pressure, which are general physical properties of the superabsorbent polymer, can be significantly improved, as compared to the case of having a two-dimensional linear structure that is not further crosslinked by an internal crosslinking agent.
(step 2)
The above step is mixing the hydrogel polymer with the carboxylic acid-based additive, followed by pulverization to prepare a pulverized product comprising the aqueous superabsorbent polymer particles and the additive. In this step, the hydrogel polymer is not chopped, but rather is comminuted into particles that can be applied to the final product, thereby producing 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: a carboxylic acid represented by chemical formula 1, an alkali metal salt of a carboxylic acid represented by chemical formula 1, and an alkaline earth metal salt of a carboxylic acid represented by chemical formula 1. More specifically, the carboxylic acid based additive is one of the following: a carboxylic acid represented by chemical formula 1, an alkali metal salt of a carboxylic acid represented by chemical formula 1, and an alkaline earth metal salt of a 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 terms of suppressing agglomeration of 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 increase due to the increase in the 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-heneicosyl.
More specifically, a may be a linear alkyl group having 6 to 18 carbon atoms. For example, A may be-C6H13、-C11H23、-C12H25、-C17H35or-C18H37。
Further, a moiety of chemical formula 1 (B)1-B2) The adsorption performance to the polymer surface is improved, and the adsorption performance to the polymer surface with only the portion C may be insufficient. When B is present2When the number of carbon atoms of (B) is 3 or more, the moiety B1The distance from the portion C increases and the adsorption performance to the hydrogel polymer may deteriorate.
In this context, R1And R2May each independently be a C1 to C4 linear or branched alkyl group having 1 to 4 carbon atoms. More specifically, R1And R2And 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, it is advantageous that the molecular structure of the additive is not bulky, and therefore R1And R2Both may be methyl.
In addition, n of chemical formula 1 may be 1,2, or 3. More specifically, consider part (B)1-B2) Is for enhancing the adsorption property for the moiety C and how long a molecular length is required for the carboxylic acid-based additive to be effectively adsorbed on the hydrogel polymer, means (B)1-B2) N is preferably 1.
Specifically, in chemical formula 1, B1Can be that
Wherein is the bonding site to the adjacent atom.
For example, B1Can be that
Further, in chemical formula 1, B2Can be that
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, B2Preferably, it 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, the first and second,
m is H+A monovalent cation of an alkali metal or a divalent cation of an alkaline earth metal,
if M is H+Or a monovalent cation of an alkali metal, then k is 1, if M is a divalent cation of an alkaline earth metal, then k is 2, and
A、B1、B2and n is described 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', the reaction mixture is,
M1is an alkali metal such as sodium or potassium, and
A、B1、B2and n is described 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', M2Is an alkaline earth metal such as calcium, and
A、B1、B2and n is described 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 any alkali metal salt selected from the group consisting of:
in the above-mentioned context, it is preferred that,
M1each independently an alkali metal.
Alternatively, the carboxylic acid-based additive may be any one of alkaline earth metal salts selected from:
in the above-mentioned context, it is preferred that,
M2each independently an alkaline earth metal.
For example, the carboxylic acid-based additive may be any one of the 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 particles after pulverization, and when too much additive is used, the overall physical properties of the final superabsorbent polymer may be degraded. 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 the easiness of drying and the cost of the solvent recovery system. Further, a method of putting the additive in the form of a solution and the hydrogel polymer into a reaction tank to be mixed; a method of spraying the solution after placing the hydrogel polymer in a mixer; a method of continuously supplying the hydrogel polymer and the solution to a continuously operated mixer for mixing; and so on.
The comminuted product comprising aqueous superabsorbent polymer particles and additives can be prepared by mixing the hydrogel polymer with the additives followed by comminution. Specifically, the pulverization step may be performed such that the pulverized aqueous superabsorbent polymer particles have a conventional particle size.
In this context, comminution may be carried out in a wet manner. Specifically, 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 pulverized into a desired particle size under wet conditions without generating fine powder.
Further, any one selected from the following may be used as the pulverizer: vertical mills, turbo cutters, turbo grinders, rotary shredders (rotary mill), shredders (chopper mill), disc mills, chip breakers, crushers, shredders (choppers), and disc cutters.
Wherein the comminution may be performed by a chopper, more particularly by 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 additives such that the hydrogel polymer is pulverized while passing through the fine-cut holes of the perforated plate.
In other words, the pulverization may be performed by pushing the hydrogel polymer mixed with the carboxylic acid-based additive into a perforated 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 multi-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 mincing module in which two or more perforated plates are connected in series may be used, or two or more meat grinders including one perforated plate may be connected in series and used.
For example, in the case of using a meat chopper having two or more perforated plates, the perforated plates may be arranged in series in the order of screw-knife-perforated plate, in which case the distance between the perforated plates and the knives is preferably 1mm or less to improve chopping efficiency.
Further, the pore size of the fine cut pores in the multiwell plate (meaning the diameter of the pores) may be 0.2mm to 6 mm. For example, it may be 0.5mm or greater, 0.7mm or greater, or 1mm or greater, 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 perforated plate, the smaller the size of the pulverized aqueous super absorbent polymer particles, so that the drying speed is increased, thereby increasing the drying efficiency. When the pore size of the fine cutting holes 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 be stopped.
Thus, the term "aqueous superabsorbent polymer particles" as used herein may be understood to mean a hydrogel polymer that is comminuted while passing through fine-cut holes provided in the perforated plate of a meat grinder, i.e., a hydrogel polymer that is comminuted while passing through fine-cut holes having a hole size of 0.2mm to 5 mm.
Herein, the aqueous superabsorbent polymer particles contained in the comminuted product are particles having a water content of about 30% by weight or greater. Since they are particles in which the hydrogel polymer is pulverized into particles without being subjected to a drying process, their water content may be 30 to 70% by weight, like the hydrogel polymer.
Meanwhile, at least some of the additives contained in the pulverized product may be present on the surface of the aqueous superabsorbent polymer particles. Herein, "at least some of the additives are present on the surface of the aqueous superabsorbent polymer particles" means that at least some of the additives adsorb or bond on the surface of the aqueous superabsorbent polymer particles. Specifically, 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 on the hydrophilic portion of the surface of the superabsorbent polymer through intermolecular forces, such as dipole-dipole interactions. In this way, the hydrophilic part of the additive is physically adsorbed on the surface of the superabsorbent polymer particles to surround the surface, while the hydrophobic part of the additive is not adsorbed on the surface of the polymer particles, so that 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 is added after the polymer is formed. Therefore, the re-agglomeration phenomenon between the aqueous superabsorbent polymer particles can be further suppressed, as compared to the case where the additive is added during the polymerization process and is present inside the polymer.
(step 3)
The above step is to dry the pulverized product with a paddle dryer to prepare superabsorbent polymer particles. The above drying step may be performed such that the water content of the aqueous superabsorbent polymer particles prepared in step 2 is about 10% by weight or less, specifically, about 0.01% by weight to about 10% by weight. Thus, the dried product prepared 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, the drying of the pulverized product is performed using a paddle dryer.
The paddle dryer is an agitation dryer having one or more rotating shafts arranged in a horizontal direction, and a plurality of paddles attached to the rotating shafts. As the rotary shaft rotates, the material injected into the dryer is dried. In this case, the plate-shaped blades horizontally positioned at the end of each paddle may stir the dried product up and down as well as 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 rotary shaft attached to a jacket of the dryer and the paddle. Thus, drying in paddle dryers is carried out in an indirect drying mode, in which heat is supplied from the dryer jacket or paddle walls to the material to be dried by heat transfer. This has an advantage of preventing deterioration that may occur due to rapid temperature increase or uneven drying of the material to be dried and preventing deformation of the product, compared to direct drying in which hot air is directly supplied to the material to be dried and then dried in a belt dryer.
Thus, compared to a product prepared by drying in a direct drying manner in which gas or hot air is directly supplied into the dryer, a dried product in the form of particles uniformly dried to the inside with suppressing thermal variation can be obtained by drying the water-containing superabsorbent polymer particles prepared in step 2 in an indirect drying manner with a paddle dryer.
For example, a paddle dryer may have two rotating shafts. Each of the two rotational axes may rotate at the same or different speeds.
Preferably, the rotary shafts provided in the paddle dryer may be rotated at 1rpm to 120rpm, respectively. When the rotating shaft of the paddle dryer rotates too slowly, it may be difficult to suppress agglomeration between particles, and when the rotating shaft of the paddle dryer rotates too fast, excessive stirring occurs, and thus particles may be crushed into an undesired size, which is not desirable.
Further, the production per unit volume of the pulverized product in the paddle dryer may be 40% to 80%. This is significantly higher than the throughput per unit volume of dryers such as steam tube dryers or rotary kiln dryers with a throughput per unit volume of 10% to 30%.
Further, the drying using the paddle dryer may be performed at a temperature of 80 ℃ to 250 ℃ for 10 minutes to 3 hours.
Specifically, the temperature in the paddle dryer may be about 80 ℃ to about 250 ℃. When the temperature in the dryer is too low, the drying time may become excessively long, and 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. Thus, the drying process may preferably be carried out at a temperature in the dryer of about 100 ℃ to about 240 ℃, more preferably at a temperature of about 110 ℃ to about 220 ℃.
In addition, 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.
Further, the dried product prepared in step 3 may contain 90% by weight or more, preferably 93% by weight or more, of the superabsorbent polymer particles having a particle size of 2000 μm or less, based on the total weight. Further, among others, the 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 moisture from aqueous superabsorbent polymer particles that are comminuted in step 2 while passing through finely cut holes having a hole size of 0.2mm 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 did not have a large change in particle size compared to the aqueous superabsorbent polymer particles comminuted in step 2.
In particular, in the case of using fine cut holes having a hole size of more than 1mm and 2mm or less in step 2, the dried product prepared in step 3 may include 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 of using fine-cut holes having a hole size of 0.2mm to 1mm in step 2, the dried product prepared 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 size of 1400 μm or less, based on the total weight.
By the method for producing a superabsorbent polymer according to an embodiment in which step 2 of pulverizing the hydrogel polymer after mixing with the carboxylic acid-based additive and step 3 of drying the pulverized product containing the aqueous superabsorbent polymer particles produced in step 2 using a paddle dryer are combined, it is possible to dry the pulverized product at a high throughput per unit volume in a short time without agglomeration between the aqueous superabsorbent polymer particles, thereby producing a dried product in the form of particles, not in the form of flake or block 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 using ASTM standard sieves into conventional particles having a particle size of from about 150 μm to about 850 μm, fine powders having a particle size of less than about 150 μm, and particles having a particle size of greater than about 850 μm. 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 pulverize particles having a particle size of more than 850 μm among the superabsorbent polymer particles contained in the dried product prepared in step 3. In the above step, particles having a particle size of more than 850 μm are pulverized to have a particle size of about 150 μm to about 850 μm.
The fine comminution may be carried out in a dry manner. That is, in the superabsorbent polymer particles prepared in step 3, particles having a particle size of more than 850 μm may be pulverized into small particles by mechanical energy.
Herein, the pulverizer for pulverization may be a pin mill, a hammer mill, a screw mill, a roll mill, a disc mill, or a jog mill, but the present disclosure is not limited thereto.
The superabsorbent polymer prepared as described above may include 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.
Further, the superabsorbent polymer may comprise less than about 10 wt%, specifically less than about 8 wt%, more specifically less than about 7 wt%, based on total weight, of fine powders having a particle size of less than 150 μm.
(surface crosslinking step)
Thereafter, if necessary, a step of preparing a superabsorbent polymer having a surface crosslinked layer formed on at least a portion of the surface by crosslinking the surface of the prepared superabsorbent polymer in the presence of a surface crosslinking agent may also be included.
As the surface cross-linking agent, any surface cross-linking agent generally used for preparing superabsorbent polymers may be used without any particular limitation. Examples of the surface crosslinking agent may include: at least one polyol 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 glycerol; 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;
azoline compounds, e.g.
An oxazolidinone; a polyamine compound;
an oxazoline compound; sheet
Oxazolidinone, di
Oxazolidinones or polypeptides
An oxazolidinone compound; a cyclic urea compound; and so on.
Such a surface cross-linking agent may be used in an amount of about 0.001 parts by weight to about 5 parts by weight, based on 100 parts by weight of the 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 prepared.
Further, a method of mixing the surface cross-linking agent with the superabsorbent polymer is not particularly limited. For example, a method of adding the surface cross-linking agent and the super absorbent polymer in a reactor for mixing; 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 crosslinking process may be performed at a temperature of about 80 ℃ to about 250 ℃. More specifically, the surface crosslinking 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 surface of the superabsorbent polymer particles is sufficiently crosslinked to increase the absorption rate under pressure.
The heating means for surface crosslinking is not particularly limited. It may be provided with a thermal medium or a heat source directly. At this time, a usable heat medium may be a heated fluid such as steam, hot air, hot oil, etc., but the present invention is not limited thereto. Further, the temperature of the heat medium supplied thereto may be appropriately selected in consideration of the manner of the heat medium, the heating speed, and the target temperature of heating. Meanwhile, an electric heater or a gas heater may be used as a heat source directly provided, but the present invention is not limited thereto.
Further, the superabsorbent polymer prepared by the above method may further comprise, in addition to the superabsorbent polymer particles and the carboxylic acid-based additive, a process of crushing the additive with the hydrogel polymer followed by drying B1The ester bond of (a) is decomposed to form a compound.
In particular, when the additive is one in which n is 1 and B1When the compound is-OCO-, the superabsorbent polymer may also comprise an alcohol having an A-OH structure and a compound having a HOOC-B structure2-a compound of structure C.
Furthermore, when the additive is one in which n is 1 and B1When the compound is-COO-, the superabsorbent polymer may also comprise a carboxylic acid having an A-COOH structure and a compound having HO-B2-a compound of structure C.
Furthermore, when the additive is one in which n is 1 and B1is-COOCH (R)1) COO-Compound, the superabsorbent polymer may also comprise a carboxylic acid having an A-COOH structure and a compound having a HOCH (R)1)COO-B2-a compound of structure C.
Since the superabsorbent polymer also contains a compound formed by decomposing ester bonds in the molecules of the additive, the fluidity of the additive is increased, and the phenomenon of re-agglomeration after pulverization can be further prevented.
Further, the superabsorbent polymer may have a 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.
Further, the extractable content of the superabsorbent polymer can 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% by weight, but may be 5% by weight or more, 8% by weight or more, or 10% by weight or more.
Further, the superabsorbent polymer may have a vortex time of 70 seconds or less, 68 seconds or less, or 66 seconds or less at 24 ℃. Further, a shorter vortex time may be evaluated as better, and the vortex time may be 40 seconds or longer, or 50 seconds or longer.
Further, the superabsorbent polymer can 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 present invention is not intended to be limited by these examples.
EXAMPLE-preparation of superabsorbent polymers
Example 1
(step 1)
100g (1.388mol) 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: 70 mol%; 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. This is achieved byFurther, while supplying the monomer composition, the irradiation intensity was 10mW/cm2To perform a polymerization reaction for 60 seconds, thereby obtaining a hydrogel polymer having a water content of 55% by weight.
(step 2)
Subsequently, sodium stearoyl-2-lactylate (Almax-6900, manufactured by Ilshinwells) represented by the following chemical formulae 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. Then, the mixture was pulverized using a meat chopper including a plurality of fine-cut holes having a size of 3 mm. Herein, the water content of the aqueous superabsorbent polymer particles contained in the pulverized product was 55% by weight.
[ chemical formulas 1 to 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 1.7m2In a twin-shaft paddle dryer (product name: paddle dryer NPD-1.6W, manufacturer: NARA MACHINERY co., LID), and then continuously dried while stirring a rotating shaft at 30 rpm. At this time, the temperature inside the paddle dryer was maintained at 200 ℃ during drying, and the production amount 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)
Particles having a particle size of more than 850 μm classified by a sieve of more than #20 among the superabsorbent polymer particles prepared in step 3 were finely pulverized using a roll mill (66F Gran-U-sizer, 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 classified again using an ASTM standard sieve, and then the particle size distribution of the finally prepared superabsorbent polymer particles including all the superabsorbent polymer particles having a particle size of 850 μm or less prepared in step 3 was determined. The results are shown in Table 1. Referring to Table 1, it can be seen that the superabsorbent polymer finally prepared contained 96.2% by weight of conventional particles (superabsorbent polymer particles having a particle size of 150 μm to 850 μm) based on the total weight.
Example 2
A super absorbent polymer was prepared in the same manner as in example 1, except that a meat chopper including a perforated plate having a plurality of fine-cut holes having 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 contains 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. Further, it can be seen that the superabsorbent polymer finally prepared in example 2 contained 94.7 wt% of conventional particles based on the total weight.
Example 3
A super absorbent polymer was prepared in the same manner as in example 1, except that a meat chopper including a perforated plate having a plurality of fine-cut holes having 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 contains 99.7% by weight of superabsorbent polymer particles having a particle size of 2000 μm or less, and 98.1% by weight of particles having a particle size of 1400 μm or less, based on the total weight. Further, it can be seen that the superabsorbent polymer finally prepared in example 3 contained 97.2 wt% of conventional particles based on the total weight.
Example 4
A superabsorbent polymer was prepared in the same manner as in example 1 except that sodium stearoyl-2-lactylate represented by chemical formula 1-6 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 chopper including a perforated plate having 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 contains 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. Further, it can be seen that the superabsorbent polymer finally prepared in example 4 contained 93.8 wt% of conventional particles based on the 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.
(chopping) subsequently, the hydrogel polymer obtained by the polymerization reaction was mixed with the same amount of water as in example 1, and chopped using a meat chopper comprising a perforated plate having a plurality of fine-cut holes with a hole size of 16 mm.
(drying) thereafter, the chopped hydrogel polymer was dried for 40 minutes while being supplied at a flow rate of 200 kg/hour to a belt dryer (manufactured by Okawara) having a width of 1600mm and a length of 6200mm, which was 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. Further, the dried product prepared in the above step is prepared in the form of a single sheet, and since there is no dried product prepared in the form of particles, classification is impossible.
(coarse grinding/classification/fine grinding) the dried polymer was coarsely ground to a particle size of about 2mm using a chopper (PULVERISETTE 19, manufactured by Fritsch). After the coarse pulverization was completed, the obtained granules were classified using ASTM standard sieves, and the results are shown in table 1 below. Thereafter, of the classified particles, particles having a particle size of more than 850 μm classified by a sieve of more than #20 were finely pulverized 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 classified again 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 contained 79.4 wt% of the conventional particles based on the total weight.
Comparative example 2
An attempt was made to prepare a superabsorbent polymer 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 the inside of the dryer is agglomerated, 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 having a width of 1600mm and a length of 6200mm, which was capable of changing the wind direction up and down, was used in place of the paddle dryer in step 3 of example 3. However, since the inside of the dried product is not dried, the fine pulverization process cannot be performed.
Comparative example 4
An attempt was made to prepare a superabsorbent polymer in the same manner as in example 3, except that a fluidized bed dryer (drying temperature 210 ℃ and superficial velocity 1.2 m/sec) provided with a perforated plate having a diameter of 0.8mm and having a diameter of 300mm and an open pore ratio of 8% was used in place of the paddle dryer in step 3 of example 3. However, superabsorbent polymers cannot be prepared because of the occurrence of blocking during drying.
Test example 1
The results of classifying 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 examples in which superabsorbent polymer was prepared by adding a carboxylic acid-based additive during pulverization of hydrogel polymer, agglomeration/agglomeration between aqueous superabsorbent polymer particles was suppressed during drying, and thus drying in a paddle dryer having high throughput per unit volume was possible. Further, the dried product dried by the paddle dryer is in the form of unagglomerated primary particles, so that conventional particles can be obtained only by fine pulverization without coarse pulverization, thereby significantly reducing the amount of fine powder generated 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 the hydrogel polymer was pulverized, it was impossible to use the paddle dryer as in the examples due to the agglomeration/agglomeration between the chopped hydrogel polymers during the drying process. Further, in the case of comparative example 1 in which the carboxylic acid-based additive was not used when the hydrogel polymer was pulverized, as in the conventional process, it was possible to perform drying with a belt dryer as a fixed bed dryer. However, since the dried product is in the form of a sheet, a coarse pulverizing process is required, and thus, a large amount of fine powder is generated in the final superabsorbent polymer due to a two-stage dry pulverizing process including coarse pulverizing and fine pulverizing.
Further, in the case of using a belt dryer or a fluidized bed dryer in place of comparative examples 3 and 4 in which a moving dryer (e.g., a paddle dryer) in which the particles can be dried by mechanical agitation, there is a problem in that, even if the carboxylic acid-based additive is added during pulverization of the hydrogel polymer to prepare the aqueous superabsorbent polymer particles, the interior of the particles cannot be effectively dried, or lumps are generated during drying.
Therefore, 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 the paddle dryer in the 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 the drying efficiency through the high throughput per unit volume of the paddle dryer.
Test example 2: comparison of drying rates based on pore size of the fine cut pores
In order to check the drying speed according to the pore size of the fine cut pores of the meat chopper 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 positions (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 pulverized 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 the drying in the direction of the arrow, TR-1, TR-2, TR-3, TR-4 and TR-5 refer to the points where 11.6%, 27%, 42.4%, 62.9% and 78.3% of the drying is performed, respectively.
[ equation 1]
Water content (wt%) { [ H ]0(g)-H1(g)]/H0(g)}*100
In the case of the equation 1, the,
H0(g) is the initial weight of the collected sample, an
H1(g) Heating while raising the temperature from room temperature to 180 deg.C and maintaining at 180 deg.C by using infrared moisture meterThe weight of the sample measured after 40 minutes (5 minutes including the temperature raising step).
The water content versus residence time was calculated for the samples collected at 7 points for each of examples 1 to 3 and is shown in the graph in fig. 4. Referring to fig. 4, it can be seen that the drying speed increases as the pore size of the mincer's fine cutting pores decreases during comminution. Therefore, it can be seen that, since the hydrogel polymer is pulverized by passing through the fine-cut pores having a smaller pore size, not only can a dried product having a smaller particle size be prepared, but also the 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. All steps were performed in a constant temperature and humidity chamber (temperature 23. + -. 0.5 ℃ C., relative humidity 45. + -. 0.5%) unless otherwise stated. To prevent measurement errors, the average of three measurements was taken as measurement data. In addition, the physiological saline or saline used in the evaluation of the following physical properties means a 0.9 wt% sodium chloride (NaCl) aqueous solution.
(1) Centrifuge Retention Capacity (CRC)
The centrifuge retention capacity according to the absorbance under no load conditions of each polymer was measured according to the EDANA WSP 241.3 method.
Specifically, when W is0(g, about 0.2g) after the polymer was uniformly inserted into the nonwoven fabric encapsulate and sealed, it was immersed in saline (0.9 wt%) at room temperature. After 30 minutes, the encapsulates were centrifuged at 250G for 3 minutes to drain and the weight W of the encapsulates was measured2(g) In that respect Further, after the same operation was performed without using the resin, the weight W of the envelope was measured1(g) In that respect Then, CRC (g/g) was calculated according to the following equation 2 by using the obtained weight value.
[ equation 2]
CRC(g/g)＝{[W2(g)-W1(g)]/W0(g)}-1
(2) Extractable content (16 hours E/C)
The extractable content of the superabsorbent polymers prepared in the examples and comparative examples was measured according to the EDANA (european disposables and nonwovens association) WSP 270.2 method.
Specifically, 1.0g of the superabsorbent polymer was added to 200g of a 0.9 wt% NaCl solution, the soaking was maintained for 16 hours while stirring at 500rpm, and the aqueous solution was filtered through filter paper. The filtered solution was first titrated with 0.1N caustic soda solution to pH 10.0 and then back titrated with 0.1N hydrogen chloride solution to pH 2.7. 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.
First, 50mL of 0.9% saline was added to a 100mL beaker with a flat bottom using a 100mL Mass Cylinder.
② Next, after placing the beaker in the center of the magnetic stirrer, a magnetic rod (diameter 8mm, length 30mm) was put into the beaker.
③ thereafter, the stirrer was operated so that the magnetic rod stirred at 600rpm and the lowest part of the vortex generated by the stirring reached the top of the magnetic rod.
After determining that the temperature of the brine in the beaker reached 24.0 ℃,2 ± 0.01g of a 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) Water 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 size of 150 μm to 850 μm was taken out of the prepared superabsorbent polymer and its weight was measured as H0(g) (initial weight of sample). Thereafter, the temperature was raised from room temperature using an infrared moisture meterThe weight of the sample was measured as H after heating for 40 minutes (5 minutes including the temperature raising step) while being up to 180 ℃ and maintained at 180 ℃1(g) In that respect The water content was then calculated according to equation 1 above.
[ Table 3]
As shown in table 3, in the case of the superabsorbent polymer prepared in the examples, the extractable content was mostly reduced and the vortex time was significantly improved while having a similar water content and a higher water retention capacity, compared to the superabsorbent polymer of comparative example 1, which was dried with a belt dryer after pulverizing the hydrogel polymer without adding any additive.
Accordingly, it can be seen that when a carboxylic acid-based additive is added to pulverize a hydrogel polymer and the pulverized product is dried in a paddle dryer to prepare a superabsorbent polymer, a superabsorbent polymer having a significantly reduced fine powder content without deteriorating water retention capacity, and simultaneously exhibiting improved water retention capacity and short vortex time, can be manufactured.
Claims (20)
1. A method of preparing a superabsorbent polymer comprising:
1) a step of forming a hydrogel polymer 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 (step 1);
2) a step of mixing the hydrogel polymer with a carboxylic acid-based additive, followed by pulverization to prepare a pulverized product containing aqueous superabsorbent polymer particles (step 2);
3) a step of drying the pulverized product with a paddle dryer to prepare superabsorbent polymer particles (step 3); and
4) a step of finely pulverizing particles having a particle size of more than 850 μm among the superabsorbent 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 first and second,
a is an alkyl group having 5 to 21 carbon atoms,
B1is-OCO-, -COO-or-COOCH (R)1)COO-，
B2is-CH2-、-CH2CH2-、-CH(R2) -, -CH-or-C.ident.C-,
wherein R is1And R2Each independently an alkyl group having 1 to 4 carbon atoms,
n is an integer of 1 to 3, and
c is carboxyl.
2. The method of preparing a superabsorbent polymer of claim 1,
wherein the hydrogel polymer has a water content of 30 to 70 wt.%.
3. The method of preparing a superabsorbent polymer of claim 1,
wherein in the chemical formula 1, the metal oxide,
a is-C6H13、-C11H23、-C12H25、-C17H35or-C18H37。
4. The method of preparing a superabsorbent polymer of claim 1,
wherein in the chemical formula 1, the metal oxide,
B1is composed of
Wherein is the bonding site to the adjacent atom.
5. The method of preparing a superabsorbent polymer of claim 1,
wherein in the chemical formula 1, the metal oxide,
B2is composed of
Wherein is the bonding site to the adjacent atom.
6. The method of preparing a superabsorbent polymer of 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 of preparing a superabsorbent polymer of 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 of preparing a superabsorbent polymer of claim 1,
wherein the carboxylic acid-based additive is used in an amount of 0.01 to 1 part by weight based on 100 parts by weight of the hydrogel polymer.
9. The method of preparing a superabsorbent polymer of claim 1,
wherein the carboxylic acid-based additive is mixed in the form of a solution dissolved in a solvent.
10. The method of preparing a superabsorbent polymer of claim 1,
wherein the comminution is carried out in a wet manner.
11. The method of preparing a superabsorbent polymer of claim 1,
wherein the pulverization is performed by pushing the hydrogel polymer mixed with the carboxylic acid-based additive into a perforated plate provided with a plurality of fine-cut holes having a certain size.
12. The method of preparing a superabsorbent polymer of claim 11,
wherein the fine cut holes have a hole size of 0.2mm to 6 mm.
13. The method of preparing a superabsorbent polymer of claim 1,
wherein the paddle dryer has two rotating shafts.
14. The method of preparing a superabsorbent polymer of claim 13,
wherein the rotating shaft is rotated at 1rpm to 120rpm during the drying of the pulverized product.
15. The method of preparing a superabsorbent polymer of claim 1,
wherein the drying is performed at a temperature of 80 ℃ to 250 ℃ for 10 minutes to 3 hours.
16. The method of preparing a superabsorbent polymer of 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 of preparing a superabsorbent polymer of claim 1,
further comprising the step of classifying said superabsorbent polymer particles after said step 3 and before said step 4.
18. The method of preparing a superabsorbent polymer of claim 1,
wherein the superabsorbent polymer is prepared to contain 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 of preparing a superabsorbent polymer of claim 1,
wherein the superabsorbent polymer is prepared to contain less than 10% by weight of fine powder having a particle size of less than 150 μm, based on the total weight.
20. The method of preparing a superabsorbent polymer of claim 1,
further comprising the step of preparing a superabsorbent polymer having a surface crosslinked layer formed on at least a portion of the surface by crosslinking the surface of the prepared superabsorbent polymer in the presence of a surface crosslinking agent.
Applications Claiming Priority (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR10-2020-0007114 | 2020-01-20 | ||
| KR20200007114 | 2020-01-20 | ||
| KR1020210007622A KR20210093786A (en) | 2020-01-20 | 2021-01-19 | Preparation method of super absorbent polymer |
| KR10-2021-0007622 | 2021-01-19 | ||
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| 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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| 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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