CN117616071A - Method for preparing super absorbent polymer - Google Patents
Method for preparing super absorbent polymer Download PDFInfo
- Publication number
- CN117616071A CN117616071A CN202280048139.6A CN202280048139A CN117616071A CN 117616071 A CN117616071 A CN 117616071A CN 202280048139 A CN202280048139 A CN 202280048139A CN 117616071 A CN117616071 A CN 117616071A
- Authority
- CN
- China
- Prior art keywords
- foaming
- foam stabilizer
- polymer
- mixture
- super absorbent
- 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.)
- Pending
Links
- 229920000247 superabsorbent polymer Polymers 0.000 title claims abstract description 130
- 238000000034 method Methods 0.000 title claims abstract description 119
- 238000005187 foaming Methods 0.000 claims abstract description 147
- 239000006260 foam Substances 0.000 claims abstract description 87
- 239000003381 stabilizer Substances 0.000 claims abstract description 87
- 239000000203 mixture Substances 0.000 claims description 125
- 239000000178 monomer Substances 0.000 claims description 73
- 229920000642 polymer Polymers 0.000 claims description 62
- 238000006116 polymerization reaction Methods 0.000 claims description 39
- 238000004132 cross linking Methods 0.000 claims description 38
- 239000003431 cross linking reagent Substances 0.000 claims description 37
- 239000004088 foaming agent Substances 0.000 claims description 37
- 239000004604 Blowing Agent Substances 0.000 claims description 36
- 238000001035 drying Methods 0.000 claims description 35
- 239000011148 porous material Substances 0.000 claims description 33
- 239000000017 hydrogel Substances 0.000 claims description 27
- 238000010298 pulverizing process Methods 0.000 claims description 26
- 229920005601 base polymer Polymers 0.000 claims description 25
- 239000000843 powder Substances 0.000 claims description 25
- NIXOWILDQLNWCW-UHFFFAOYSA-N acrylic acid group Chemical group C(C=C)(=O)O NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 claims description 24
- 150000001875 compounds Chemical class 0.000 claims description 22
- 239000003505 polymerization initiator Substances 0.000 claims description 21
- 239000002202 Polyethylene glycol Substances 0.000 claims description 10
- 230000002209 hydrophobic effect Effects 0.000 claims description 10
- 230000004048 modification Effects 0.000 claims description 10
- 238000012986 modification Methods 0.000 claims description 10
- 229920001223 polyethylene glycol Polymers 0.000 claims description 8
- 230000002378 acidificating effect Effects 0.000 claims description 7
- 230000005660 hydrophilic surface Effects 0.000 claims description 7
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 6
- 238000002156 mixing Methods 0.000 claims description 6
- 229920000036 polyvinylpyrrolidone Polymers 0.000 claims description 4
- 239000001267 polyvinylpyrrolidone Substances 0.000 claims description 4
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 claims description 4
- 239000011736 potassium bicarbonate Substances 0.000 claims description 4
- 235000015497 potassium bicarbonate Nutrition 0.000 claims description 4
- 229910000028 potassium bicarbonate Inorganic materials 0.000 claims description 4
- TYJJADVDDVDEDZ-UHFFFAOYSA-M potassium hydrogencarbonate Chemical compound [K+].OC([O-])=O TYJJADVDDVDEDZ-UHFFFAOYSA-M 0.000 claims description 4
- 239000004372 Polyvinyl alcohol Substances 0.000 claims description 3
- 230000000379 polymerizing effect Effects 0.000 claims description 3
- 229920001451 polypropylene glycol Polymers 0.000 claims description 3
- 229920002451 polyvinyl alcohol Polymers 0.000 claims description 3
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 3
- 235000017550 sodium carbonate Nutrition 0.000 claims description 3
- MAGFQRLKWCCTQJ-UHFFFAOYSA-M 4-ethenylbenzenesulfonate Chemical compound [O-]S(=O)(=O)C1=CC=C(C=C)C=C1 MAGFQRLKWCCTQJ-UHFFFAOYSA-M 0.000 claims description 2
- ICGLPKIVTVWCFT-UHFFFAOYSA-N 4-methylbenzenesulfonohydrazide Chemical compound CC1=CC=C(S(=O)(=O)NN)C=C1 ICGLPKIVTVWCFT-UHFFFAOYSA-N 0.000 claims description 2
- 239000004156 Azodicarbonamide Substances 0.000 claims description 2
- MWRWFPQBGSZWNV-UHFFFAOYSA-N Dinitrosopentamethylenetetramine Chemical compound C1N2CN(N=O)CN1CN(N=O)C2 MWRWFPQBGSZWNV-UHFFFAOYSA-N 0.000 claims description 2
- UIIMBOGNXHQVGW-DEQYMQKBSA-M Sodium bicarbonate-14C Chemical compound [Na+].O[14C]([O-])=O UIIMBOGNXHQVGW-DEQYMQKBSA-M 0.000 claims description 2
- 229920002125 Sokalan® Polymers 0.000 claims description 2
- XOZUGNYVDXMRKW-AATRIKPKSA-N azodicarbonamide Chemical compound NC(=O)\N=N\C(N)=O XOZUGNYVDXMRKW-AATRIKPKSA-N 0.000 claims description 2
- 235000019399 azodicarbonamide Nutrition 0.000 claims description 2
- VJRITMATACIYAF-UHFFFAOYSA-N benzenesulfonohydrazide Chemical compound NNS(=O)(=O)C1=CC=CC=C1 VJRITMATACIYAF-UHFFFAOYSA-N 0.000 claims description 2
- 229920002401 polyacrylamide Polymers 0.000 claims description 2
- 239000004584 polyacrylic acid Substances 0.000 claims description 2
- 229920001690 polydopamine Polymers 0.000 claims description 2
- 229920005606 polypropylene copolymer Polymers 0.000 claims description 2
- 229920002689 polyvinyl acetate Polymers 0.000 claims description 2
- 239000011118 polyvinyl acetate Substances 0.000 claims description 2
- 230000008569 process Effects 0.000 abstract description 71
- 238000002360 preparation method Methods 0.000 abstract description 37
- 238000010521 absorption reaction Methods 0.000 abstract description 36
- 238000009826 distribution Methods 0.000 abstract description 9
- 239000002245 particle Substances 0.000 description 64
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 28
- 239000004583 superabsorbent polymers (SAPs) Substances 0.000 description 25
- 230000000052 comparative effect Effects 0.000 description 24
- 239000000243 solution Substances 0.000 description 16
- DNIAPMSPPWPWGF-UHFFFAOYSA-N Propylene glycol Chemical compound CC(O)CO DNIAPMSPPWPWGF-UHFFFAOYSA-N 0.000 description 15
- -1 amine salt Chemical class 0.000 description 14
- VZSRBBMJRBPUNF-UHFFFAOYSA-N 2-(2,3-dihydro-1H-inden-2-ylamino)-N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]pyrimidine-5-carboxamide Chemical compound C1C(CC2=CC=CC=C12)NC1=NC=C(C=N1)C(=O)NCCC(N1CC2=C(CC1)NN=N2)=O VZSRBBMJRBPUNF-UHFFFAOYSA-N 0.000 description 13
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 13
- 239000003999 initiator Substances 0.000 description 13
- NIXOWILDQLNWCW-UHFFFAOYSA-M Acrylate Chemical compound [O-]C(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-M 0.000 description 12
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 description 12
- 238000012719 thermal polymerization Methods 0.000 description 12
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 description 11
- 239000007788 liquid Substances 0.000 description 11
- 230000000704 physical effect Effects 0.000 description 11
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 10
- 238000006243 chemical reaction Methods 0.000 description 10
- 239000000463 material Substances 0.000 description 10
- 239000002904 solvent Substances 0.000 description 10
- YMWUJEATGCHHMB-UHFFFAOYSA-N Dichloromethane Chemical compound ClCCl YMWUJEATGCHHMB-UHFFFAOYSA-N 0.000 description 9
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 9
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 9
- MTHSVFCYNBDYFN-UHFFFAOYSA-N diethylene glycol Chemical compound OCCOCCO MTHSVFCYNBDYFN-UHFFFAOYSA-N 0.000 description 9
- 238000003756 stirring Methods 0.000 description 9
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 8
- 239000006185 dispersion Substances 0.000 description 8
- 239000000499 gel Substances 0.000 description 8
- 239000011259 mixed solution Substances 0.000 description 8
- 238000006386 neutralization reaction Methods 0.000 description 8
- 229920000747 poly(lactic acid) Polymers 0.000 description 8
- 239000004626 polylactic acid Substances 0.000 description 8
- 230000000694 effects Effects 0.000 description 7
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 description 6
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 6
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 6
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 6
- WERYXYBDKMZEQL-UHFFFAOYSA-N butane-1,4-diol Chemical compound OCCCCO WERYXYBDKMZEQL-UHFFFAOYSA-N 0.000 description 6
- 229910052751 metal Inorganic materials 0.000 description 6
- 239000002184 metal Substances 0.000 description 6
- 239000000047 product Substances 0.000 description 6
- 235000017557 sodium bicarbonate Nutrition 0.000 description 6
- 229910000030 sodium bicarbonate Inorganic materials 0.000 description 6
- 239000011780 sodium chloride Substances 0.000 description 6
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 5
- 229920006037 cross link polymer Polymers 0.000 description 5
- 230000014509 gene expression Effects 0.000 description 5
- 239000002149 hierarchical pore Substances 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- 239000003607 modifier Substances 0.000 description 5
- 150000003839 salts Chemical class 0.000 description 5
- 238000001878 scanning electron micrograph Methods 0.000 description 5
- XLLIQLLCWZCATF-UHFFFAOYSA-N 2-methoxyethyl acetate Chemical compound COCCOC(C)=O XLLIQLLCWZCATF-UHFFFAOYSA-N 0.000 description 4
- YEJRWHAVMIAJKC-UHFFFAOYSA-N 4-Butyrolactone Chemical compound O=C1CCCO1 YEJRWHAVMIAJKC-UHFFFAOYSA-N 0.000 description 4
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 4
- 239000002250 absorbent Substances 0.000 description 4
- JHIVVAPYMSGYDF-UHFFFAOYSA-N cyclohexanone Chemical compound O=C1CCCCC1 JHIVVAPYMSGYDF-UHFFFAOYSA-N 0.000 description 4
- BGTOWKSIORTVQH-UHFFFAOYSA-N cyclopentanone Chemical compound O=C1CCCC1 BGTOWKSIORTVQH-UHFFFAOYSA-N 0.000 description 4
- 230000014759 maintenance of location Effects 0.000 description 4
- 238000005259 measurement Methods 0.000 description 4
- 239000003960 organic solvent Substances 0.000 description 4
- 239000002504 physiological saline solution Substances 0.000 description 4
- 239000007787 solid Substances 0.000 description 4
- 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 3
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- 238000001704 evaporation Methods 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 239000011521 glass Substances 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 229920005610 lignin Polymers 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 230000008018 melting Effects 0.000 description 3
- 235000011121 sodium hydroxide Nutrition 0.000 description 3
- 125000001424 substituent group Chemical group 0.000 description 3
- 238000012546 transfer Methods 0.000 description 3
- ZIBGPFATKBEMQZ-UHFFFAOYSA-N triethylene glycol Chemical compound OCCOCCOCCO ZIBGPFATKBEMQZ-UHFFFAOYSA-N 0.000 description 3
- 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
- SBASXUCJHJRPEV-UHFFFAOYSA-N 2-(2-methoxyethoxy)ethanol Chemical compound COCCOCCO SBASXUCJHJRPEV-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
- POAOYUHQDCAZBD-UHFFFAOYSA-N 2-butoxyethanol Chemical compound CCCCOCCO POAOYUHQDCAZBD-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
- KWOLFJPFCHCOCG-UHFFFAOYSA-N Acetophenone Chemical compound CC(=O)C1=CC=CC=C1 KWOLFJPFCHCOCG-UHFFFAOYSA-N 0.000 description 2
- 229910002016 Aerosil® 200 Inorganic materials 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 229920002430 Fibre-reinforced plastic Polymers 0.000 description 2
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 description 2
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 description 2
- 239000004793 Polystyrene Substances 0.000 description 2
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 2
- 230000002745 absorbent Effects 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
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000007664 blowing Methods 0.000 description 2
- 229930188620 butyrolactone Natural products 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 125000004386 diacrylate group Chemical group 0.000 description 2
- 235000014113 dietary fatty acids Nutrition 0.000 description 2
- XXJWXESWEXIICW-UHFFFAOYSA-N diethylene glycol monoethyl ether Chemical compound CCOCCOCCO XXJWXESWEXIICW-UHFFFAOYSA-N 0.000 description 2
- 239000000839 emulsion Substances 0.000 description 2
- HNRMPXKDFBEGFZ-UHFFFAOYSA-N ethyl trimethyl methane Natural products CCC(C)(C)C HNRMPXKDFBEGFZ-UHFFFAOYSA-N 0.000 description 2
- 230000001747 exhibiting effect Effects 0.000 description 2
- 239000000194 fatty acid Substances 0.000 description 2
- 229930195729 fatty acid Natural products 0.000 description 2
- 150000004665 fatty acids Chemical class 0.000 description 2
- 239000011151 fibre-reinforced plastic Substances 0.000 description 2
- 239000010419 fine particle Substances 0.000 description 2
- 239000004872 foam stabilizing agent Substances 0.000 description 2
- 125000000524 functional group Chemical group 0.000 description 2
- CATSNJVOTSVZJV-UHFFFAOYSA-N heptan-2-one Chemical compound CCCCCC(C)=O CATSNJVOTSVZJV-UHFFFAOYSA-N 0.000 description 2
- IPCSVZSSVZVIGE-UHFFFAOYSA-N hexadecanoic acid Chemical compound CCCCCCCCCCCCCCCC(O)=O IPCSVZSSVZVIGE-UHFFFAOYSA-N 0.000 description 2
- 230000000977 initiatory effect Effects 0.000 description 2
- HQKMJHAJHXVSDF-UHFFFAOYSA-L magnesium stearate Chemical compound [Mg+2].CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O HQKMJHAJHXVSDF-UHFFFAOYSA-L 0.000 description 2
- 235000013372 meat Nutrition 0.000 description 2
- 230000003472 neutralizing effect Effects 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 230000035699 permeability Effects 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
- 229920001432 poly(L-lactide) Polymers 0.000 description 2
- 229920002223 polystyrene Polymers 0.000 description 2
- LLHKCFNBLRBOGN-UHFFFAOYSA-N propylene glycol methyl ether acetate Chemical compound COCC(C)OC(C)=O LLHKCFNBLRBOGN-UHFFFAOYSA-N 0.000 description 2
- 229910052814 silicon oxide Inorganic materials 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
- 238000009281 ultraviolet germicidal irradiation Methods 0.000 description 2
- 239000008096 xylene Substances 0.000 description 2
- DNIAPMSPPWPWGF-VKHMYHEASA-N (+)-propylene glycol Chemical compound C[C@H](O)CO DNIAPMSPPWPWGF-VKHMYHEASA-N 0.000 description 1
- MYWOJODOMFBVCB-UHFFFAOYSA-N 1,2,6-trimethylphenanthrene Chemical compound CC1=CC=C2C3=CC(C)=CC=C3C=CC2=C1C MYWOJODOMFBVCB-UHFFFAOYSA-N 0.000 description 1
- 229940015975 1,2-hexanediol Drugs 0.000 description 1
- YPFDHNVEDLHUCE-UHFFFAOYSA-N 1,3-propanediol Substances OCCCO YPFDHNVEDLHUCE-UHFFFAOYSA-N 0.000 description 1
- 229940035437 1,3-propanediol Drugs 0.000 description 1
- IZXIZTKNFFYFOF-UHFFFAOYSA-N 2-Oxazolidone Chemical class O=C1NCCO1 IZXIZTKNFFYFOF-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
- CKSAKVMRQYOFBC-UHFFFAOYSA-N 2-cyanopropan-2-yliminourea Chemical compound N#CC(C)(C)N=NC(N)=O CKSAKVMRQYOFBC-UHFFFAOYSA-N 0.000 description 1
- NLGDWWCZQDIASO-UHFFFAOYSA-N 2-hydroxy-1-(7-oxabicyclo[4.1.0]hepta-1,3,5-trien-2-yl)-2-phenylethanone Chemical compound OC(C(=O)c1cccc2Oc12)c1ccccc1 NLGDWWCZQDIASO-UHFFFAOYSA-N 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
- SMBRHGJEDJVDOB-UHFFFAOYSA-N 2-methylpropanimidamide;dihydrochloride Chemical compound Cl.Cl.CC(C)C(N)=N SMBRHGJEDJVDOB-UHFFFAOYSA-N 0.000 description 1
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- 235000021355 Stearic acid Nutrition 0.000 description 1
- NNLVGZFZQQXQNW-ADJNRHBOSA-N [(2r,3r,4s,5r,6s)-4,5-diacetyloxy-3-[(2s,3r,4s,5r,6r)-3,4,5-triacetyloxy-6-(acetyloxymethyl)oxan-2-yl]oxy-6-[(2r,3r,4s,5r,6s)-4,5,6-triacetyloxy-2-(acetyloxymethyl)oxan-3-yl]oxyoxan-2-yl]methyl acetate Chemical compound O([C@@H]1O[C@@H]([C@H]([C@H](OC(C)=O)[C@H]1OC(C)=O)O[C@H]1[C@@H]([C@@H](OC(C)=O)[C@H](OC(C)=O)[C@@H](COC(C)=O)O1)OC(C)=O)COC(=O)C)[C@@H]1[C@@H](COC(C)=O)O[C@@H](OC(C)=O)[C@H](OC(C)=O)[C@H]1OC(C)=O NNLVGZFZQQXQNW-ADJNRHBOSA-N 0.000 description 1
- 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
- 230000002159 abnormal effect Effects 0.000 description 1
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- 238000005054 agglomeration Methods 0.000 description 1
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- 239000003570 air Substances 0.000 description 1
- 125000000217 alkyl group Chemical group 0.000 description 1
- AZDRQVAHHNSJOQ-UHFFFAOYSA-N alumane Chemical class [AlH3] AZDRQVAHHNSJOQ-UHFFFAOYSA-N 0.000 description 1
- DIZPMCHEQGEION-UHFFFAOYSA-H aluminium sulfate (anhydrous) Chemical compound [Al+3].[Al+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O DIZPMCHEQGEION-UHFFFAOYSA-H 0.000 description 1
- QGZKDVFQNNGYKY-UHFFFAOYSA-O ammonium group Chemical group [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 1
- 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
- 108010038083 amyloid fibril protein AS-SAM Proteins 0.000 description 1
- 239000003963 antioxidant agent Substances 0.000 description 1
- 230000003078 antioxidant effect Effects 0.000 description 1
- 235000006708 antioxidants Nutrition 0.000 description 1
- 239000011668 ascorbic acid Substances 0.000 description 1
- 235000010323 ascorbic acid Nutrition 0.000 description 1
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Landscapes
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
Abstract
The invention provides a preparation method of a super absorbent polymer. More particularly, the present invention provides a method for preparing a super absorbent polymer, in which a multi-step foaming process using a foam stabilizer is performed to form a hierarchical bubble distribution in the super absorbent polymer to be prepared, thereby preparing a super absorbent polymer having excellent absorption rate and absorption properties.
Description
Cross Reference to Related Applications
The present application is based on and claims priority from korean patent application nos. 10-2021-0093471 and 10-2022-0087601, filed on day 7, month 16 and day 2022, month 7, and day 15, respectively, the disclosures of which are incorporated herein by reference in their entireties.
Technical Field
The invention relates to a preparation method of a super absorbent polymer. More particularly, the present invention relates to a method for preparing a super absorbent polymer, in which a multi-step foaming process using a foam stabilizer is performed to form a hierarchical bubble distribution in the super absorbent polymer to be prepared, thereby preparing a super absorbent polymer having excellent absorption rate and absorption properties.
Background
Superabsorbent polymers (SAP) are synthetic polymeric materials capable of absorbing 500 to 1000 times their own weight of moisture. Different manufacturers refer to them as different names, such as SAM (superabsorbent material), AGM (absorbent gel material), etc. Since the actual application of such super absorbent polymers to sanitary products, they have been widely used in water-retaining soil products for gardening, water-stopping materials for civil engineering and construction, sheets for raising seedlings, antistatics for food circulation, cataplasm materials, and the like.
These superabsorbent polymers are widely used in sanitary materials such as diapers and panty liners. Inside the sanitary material, the superabsorbent polymer is typically distributed throughout the pulp. However, efforts have been recently made to provide thinner sanitary materials, such as diapers having a thinner thickness, etc., and as a part thereof, diapers having a reduced pulp content, and further, diapers without pulp, so-called pulpless diapers, are being actively developed.
In sanitary materials (e.g., pulp-free diapers) with reduced pulp content or without pulp, superabsorbent polymers need to exhibit not only high absorption properties but also high absorption rates, because they act not only as absorbents for absorbing liquids (e.g., urine, etc.), but also as pulp.
In order to produce a super absorbent polymer having such an improved absorption rate, a method of increasing the specific surface area by introducing a pore structure into the super absorbent polymer is mainly used. Specifically, in order to increase the specific surface area of the super absorbent polymer, a foaming agent may be used in the polymerization step to generate bubbles, and a gas such as carbon dioxide gas, air, or nitrogen gas may be injected.
However, since the bubbles generated from the foaming agent are unstable in the neutralizing liquid, the bubbles easily escape from the neutralizing liquid, and particularly, the size of the bubbles is difficult to control, which makes it impossible to produce a super absorbent polymer having a desired pore structure.
Accordingly, there is a continuing need to develop superabsorbent polymers that exhibit high absorption rates while maintaining the basic absorption properties of the superabsorbent polymers.
Disclosure of Invention
[ problem ]
Accordingly, the present invention provides a method for preparing a superabsorbent polymer, in which a multi-step foaming process using a foam stabilizer is performed to form a hierarchical pore distribution in the superabsorbent polymer to be prepared, thereby preparing a superabsorbent polymer having improved absorption properties and absorption rate.
[ technical solution ]
To solve the above problems, the present invention provides a method for preparing a super absorbent polymer, comprising the steps of:
preparing a monomer composition comprising a water-soluble acrylic-based monomer having an at least partially neutralized acidic group, a polymerization initiator, and a first crosslinking agent;
first foaming the mixture obtained by mixing the monomer composition with the first foaming agent and the foam stabilizer;
the mixture obtained by mixing the first foaming mixture and the second foaming agent is subjected to second foaming;
forming an aqueous gel polymer by cross-polymerizing the second foamed mixture;
forming a base polymer powder by drying, pulverizing and classifying the hydrogel polymer; and
at least part of the surface of the base polymer powder is crosslinked in the presence of a surface crosslinking agent.
[ Effect of the invention ]
According to the method for preparing a super absorbent polymer of the present invention, a multi-step foaming process using a foaming agent and a foam stabilizer is performed to easily generate bubbles of different sizes in each step, and as a result, a hierarchical pore distribution is formed inside the super absorbent polymer finally prepared through processes such as drying, pulverizing, etc., thereby increasing its specific surface area and remarkably improving the absorption properties and absorption rate of the super absorbent polymer.
Drawings
FIG. 1 shows a schematic illustration of a multi-step foaming process in a method of preparing superabsorbent polymers according to an embodiment of the present invention;
FIG. 2 shows OM images of bubbles generated under the conditions of the first foaming process and the second foaming process of example 1;
fig. 3 shows a graph showing the size of bubbles generated according to the concentration change of the foam stabilizer and the size change of the cells after curing in the multi-step foaming process of example 1;
FIG. 4 shows a graph showing pore size distribution of the inside of the super absorbent polymers prepared according to example 1 and comparative example 1;
FIG. 5 shows a schematic representation of cross-sectional images of superabsorbent polymers prepared according to example 1, comparative example 1 and comparative example 4; and
fig. 6 shows SEM images of cross sections of superabsorbent polymers prepared according to example 1, comparative example 1 and comparative example 4.
Detailed Description
The terminology used in the description presented herein is for the purpose of describing exemplary embodiments only and is not intended to be limiting of the invention. Singular expressions may include plural expressions unless the context has a different expression. It should be understood that the terms "comprises," "comprising," "includes," "including" or "having" in this specification are intended to specify the presence of stated features, steps, components, or groups thereof, but do not preclude the presence or addition of one or more other features, steps, components, or groups thereof.
The term "polymer" as used herein refers to the polymerized state of an acrylic-based monomer as a water-soluble ethylenically unsaturated monomer, and may include all ranges of water content or ranges of particle size. Among the above polymers, a polymer having a water content (moisture content) of about 40% by weight or more in a state before drying after polymerization may be referred to as a hydrogel polymer, and particles obtained by pulverizing and drying this hydrogel polymer may be referred to as a crosslinked polymer.
Furthermore, the term "superabsorbent polymer particles" as used herein refers to particulate materials comprising a crosslinked polymer obtained by polymerizing an acrylic-based monomer comprising at least partially neutralized acidic groups, which is then crosslinked by an internal crosslinking agent.
Furthermore, the term "superabsorbent polymer" as used herein refers to a crosslinked polymer obtained by polymerizing an acrylic-based monomer containing at least partially neutralized acidic groups, or a base polymer in powder form composed of superabsorbent polymer particles obtained by pulverizing the crosslinked polymer, or those forms suitable for commercialization including by subjecting the crosslinked polymer or the base polymer to additional processes (e.g., surface crosslinking, reassembly of fine particles, drying, pulverizing, classifying, etc.), depending on the context. Thus, the term "superabsorbent polymer" can be construed to include a plurality of superabsorbent polymer particles.
Furthermore, the term "cells" refers to spherical spaces formed by the foaming gas generated in the mixture during the foaming process, and the term "cells" refers to spherical spaces formed by curing the cells in the aqueous gel polymer, base polymer or superabsorbent polymer.
Furthermore, the term "average diameter" of a hole or bubble refers to the median of the longest diameter values of each hole or bubble to be measured. This is less affected by outliers than simple averages.
While the invention is susceptible of various modifications and alternative forms, specific exemplary embodiments are shown and described in detail in the following description. However, it is not intended to limit the invention to the specific exemplary embodiments, and it is to be understood that the invention includes all modifications, equivalents, or alternatives falling within the spirit and technical scope of the invention.
Furthermore, the technical terms used in the present specification are only used to illustrate specific exemplary embodiments, and are not intended to limit the present invention. As used herein, singular expressions may include plural expressions unless the context clearly indicates otherwise.
In order to produce superabsorbent polymers having a high absorption rate, the specific surface area of the superabsorbent polymer particles should be increased. Therefore, in order to realize a super absorbent polymer having a high specific surface area, a method of forming many pores in the super absorbent polymer by initiating a foaming process during a preparation process or a method of mechanically modifying the super absorbent polymer has been used. In particular, the size of the cells produced varies depending on how the foaming mechanism is controlled, and thus the final particles after comminution have different shapes. In order to increase the specific surface area, it is preferable to include a large number of micropores in the pulverized particles. However, since the bubbles generated by the conventional foaming process are unstable in the neutralization liquid, the bubbles easily escape from the neutralization liquid, and particularly, the size of the bubbles is difficult to control, which makes it impossible to prepare a super absorbent polymer having a desired pore structure.
Accordingly, the present inventors have found that when preparing a super absorbent polymer, a multi-step foaming process using a foaming agent and a foam stabilizer is performed to stably generate different-sized bubbles in each step, and thus a hierarchical pore structure can be formed inside the super absorbent polymer finally prepared by a drying, pulverizing, etc., thereby completing the present invention.
In particular, it was confirmed that in the multi-step foaming process, the size of bubbles generated in each foaming step is easily controlled by controlling the concentration of the foam stabilizer used together with the foaming agent. Accordingly, in order to form a more stable cell structure, the composition of the foam stabilizer used in the foaming process and the optimum concentration of the foam stabilizer in each foaming step are derived.
Method for producing superabsorbent polymers
Hereinafter, each step of the method for preparing superabsorbent polymer particles according to one embodiment will be described.
(step of preparing monomer composition)
First, according to one embodiment of the present invention, the method comprises the steps of: a monomer composition is prepared that includes a water-soluble acrylic-based monomer having an at least partially neutralized acidic group, a polymerization initiator, and a first crosslinking agent.
The acrylic-based monomer is a compound represented by the following formula 1:
[ 1]
R 1 -COOM 1
In the formula (1) of the present invention,
R 1 is a C2 to C5 alkyl group having an unsaturated bond, and
M 1 is a hydrogen atom, a monovalent or divalent metal, an ammonium group or an organic amine salt.
Preferably, the acrylic acid-based monomer includes one or more selected from acrylic acid, methacrylic acid and monovalent metal salts, divalent metal salts, ammonium salts and organic amine salts thereof.
The acrylic-based monomers here may be those having at least partially neutralized acidic groups. Preferably, the monomers may be those that are partially neutralized with basic substances such as sodium hydroxide, potassium hydroxide, ammonium hydroxide, and the like. In this regard, the degree of neutralization of the acrylic acid-based monomer may be 40mol% to 95mol%, preferably 40mol% or more, 60mol% or more, 70mol% or more, and 95mol% or less, 90mol% or less, 85mol% or less, or 40 to 90mol%, 60 to 85mol%,70 to 85mol%. However, an excessively high degree of neutralization causes precipitation of the neutralized monomer, and thus polymerization is less likely to occur; while too low a degree of neutralization would not only greatly reduce the absorption capacity of the polymer, but would also impart difficult to process properties to the polymer, such as an elastomeric rubber.
The concentration of the acrylic acid-based monomer with respect to the monomer composition including the raw material of the super absorbent polymer and the solvent may be 20wt% to 60wt%, preferably 20wt% or more, 40wt% or more, and 60wt% or less, 50wt% or less, or 40wt% to 50wt%, and may be selected from appropriate concentrations in consideration of polymerization time, reaction conditions, and the like. However, when the concentration of the monomer is too low, the yield of the super absorbent polymer may become low and there may be an economic efficiency problem. In contrast, when the concentration of the monomer is too high, there may be a process problem in that a part of the monomer precipitates, or the crushing efficiency of the polymerized hydrogel polymer at the time of crushing is lowered, and the physical properties of the super absorbent polymer may be deteriorated.
The term "first crosslinking agent" as used herein is used to distinguish it from a second crosslinking agent described later mainly for crosslinking the surface of the superabsorbent polymer particles, and is used to polymerize the water-soluble ethylenically unsaturated monomer by crosslinking the unsaturated bond of the above-mentioned water-soluble ethylenically unsaturated monomer. The crosslinking in the above step is performed, whether it is surface crosslinking or internal crosslinking. However, when the surface crosslinking process of the superabsorbent polymer particles described later is performed, the particle surface of the finally prepared superabsorbent polymer has a structure crosslinked by the second crosslinking agent, and the inside thereof has a structure crosslinked by the first crosslinking agent.
As the first crosslinking agent, any compound is suitable as long as it is capable of introducing crosslinking during the polymerization of the acrylic-based unsaturated monomer. Specifically, as the first crosslinking agent, a crosslinking agent having one or more functional groups reactive with the water-soluble substituent of the acrylic-based unsaturated monomer and one or more ethylenically unsaturated groups; alternatively, a crosslinking agent having two or more functional groups reactive with the water-soluble substituents of the monomer and/or the water-soluble substituents formed by hydrolysis of the monomer may be used.
Non-limiting examples of the first crosslinking agent may include polyfunctional crosslinking agents such as N, N' -methylenebisacrylamide, trimethylpropane tri (meth) acrylate, ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polypropylene glycol (meth) acrylate, butanediol di (meth) acrylate, diethylene glycol di (meth) acrylate, hexanediol di (meth) acrylate, triethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, dipentaerythritol pentaacrylate, glycerol tri (meth) acrylate, pentaerythritol tetraacrylate, triarylamine, ethylene glycol diglycidyl ether, propylene glycol, glycerol, or ethylene carbonate, which may be used alone or in combination of two or more thereof, but are not limited thereto.
The first crosslinking agent may be used in an amount of 0.01 to 5 parts by weight relative to 100 parts by weight of the water-soluble ethylenically unsaturated monomer. For example, the first crosslinking agent may be used in an amount of 0.01 parts by weight or more, 0.05 parts by weight or more, 0.1 parts by weight or more, 0.45 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, and 0.1 to 3 parts by weight, or 0.45 to 1 part by weight, relative to 100 parts by weight of the water-soluble ethylenically unsaturated monomer. When the content of the first crosslinking agent is too low, sufficient crosslinking does not occur, and thus it may be difficult to achieve strength exceeding an appropriate level, whereas when the content of the first crosslinking agent is too high, the internal crosslinking density increases, and thus it may be difficult to achieve desired water retention capacity.
The monomer composition may further include a polymerization initiator for initiating the polymerization reaction of the monomer. Those conventionally used for preparing superabsorbent polymers can be used as polymerization initiators without particular limitation.
Specifically, depending on the polymerization method, the polymerization initiator may be a thermal polymerization initiator or a photopolymerization initiator by UV irradiation. However, even in the case of the photopolymerization method, it is possible to generate a certain amount of heat by UV irradiation or the like, and a certain amount of heat is generated with the polymerization reaction (which is an exothermic reaction), and thus, a thermal polymerization initiator may be further contained.
As the photopolymerization initiator, a compound capable of forming a radical by light (e.g., UV) may be used without limitation in view of the composition.
For example, one or more selected from benzoin ether, dialkyl acetophenone, hydroxy alkyl ketone, phenyl glyoxylate, benzyl dimethyl ketal, acyl phosphine, and α -amino ketone may be used as the photopolymerization initiator. Meanwhile, as a specific example of the acylphosphine, commercially available lucirin TPO, i.e., diphenyl (2, 4, 6-trimethylbenzoyl) phosphine oxide may be used. Further different photopolymerization initiators are disclosed in detail in "UV Coatings: basic, recent Developments and New Application (Elsevier, 2007)" (page 115) written by Reinhold Schwalm, however, they are not limited to the examples described above.
The photopolymerization initiator may be included in an amount of about 0.01wt% to about 1.0wt% with respect to the monomer composition. When the concentration of the photopolymerization initiator is too low, the polymerization rate may be slow. When the concentration of the photopolymerization initiator is too high, the molecular weight of the super absorbent polymer may become low and its physical properties may become nonuniform.
In addition, one or more selected from persulfate-based initiators, azo-based initiators, hydrogen peroxide, and ascorbic acid may be used as the thermal polymerization initiator. Specific examples of persulfate-based initiators may include sodium persulfate (Na 2 S 2 O 8 ) Potassium persulfate (K) 2 S 2 O 8 ) Ammonium persulfate ((NH) 4 ) 2 S 2 O 8 ) Etc. Examples of azo-based initiators may include 2, 2-azobis (2-amidinopropane) dihydrochloride, 2-azobis- (N, N-dimethylene) isobutyramidine dihydrochloride, 2- (carbamoylazo) isobutyronitrile, 2-azobis (2- [ 2-imidazolin-2-yl)]Propane) dihydrochloride, 4-azobis- (4-cyanovaleric acid), and the like. Further different thermal polymerization initiators are disclosed in detail in "Principle of Polymerization (Wiley, 1981)" (page 203) by Odian, however, they are not limited to the above examples.
The thermal polymerization initiator may be included in an amount of about 0.001wt% to about 0.5wt% with respect to the monomer composition. When the concentration of the thermal polymerization initiator is too low, additional thermal polymerization is difficult to occur, and thus the effect of adding the thermal polymerization initiator may not be significant. When the concentration of the thermal polymerization initiator is too high, the molecular weight of the super absorbent polymer may become low and its physical properties may become nonuniform.
The total amount of these polymerization initiators may be 2 parts by weight or less with respect to 100 parts by weight of the water-soluble ethylenically unsaturated monomer. In other words, when the concentration of the polymerization initiator is too low, the polymerization rate may become slow and a large amount of residual monomer may be extracted in the final product, which is not preferable. In contrast, when the concentration of the polymerization initiator is higher than the above range, the polymer chain constituting the network becomes shorter, so the content of the water-soluble component increases and the physical properties of the polymer may deteriorate, for example, the absorbability under pressure decreases, which is not preferable.
The monomer composition may further contain additives such as a thickener, a plasticizer, a storage stabilizer, an antioxidant, and the like, as needed.
Further, the monomer composition containing the monomer may be, for example, in a solution state dissolved in a solvent (e.g., water), and the solid content (i.e., the concentration of the monomer, the first crosslinking agent, and the polymerization initiator in the monomer composition in the solution state) may be appropriately adjusted in consideration of the polymerization time, the reaction conditions, and the like. For example, the solids content in the monomer mixture may be 10wt% to 80wt%, preferably 10wt% or more, 15wt% or more, 30wt% or more, and 80wt% or less, 60wt% or less, 50wt% or less, 15wt% to 60wt%, or 30wt% to 50wt%.
When the monomer composition has a solid content within the above range, it is not necessary to remove unreacted monomers after polymerization by using a gel effect phenomenon occurring in the polymerization of a high concentration aqueous solution, and it may be advantageous in terms of control of the pulverization efficiency during pulverization of the polymer described later.
As the solvent suitable for this, any solvent may be used without limitation in consideration of the composition thereof as long as it can dissolve the above-mentioned components, and for example, one or more 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 ethyl ether, toluene, xylene, butyrolactone, carbitol, methyl cellosolve acetate and N, N-dimethylacetamide may be used in combination.
Meanwhile, as described below, the content of each component in the above-mentioned monomer composition refers to the total content of components in the monomer composition of the first foaming process and the monomer composition additionally added in the second foaming process.
(first foaming step)
Next, a method of preparing a superabsorbent polymer according to an embodiment of the present invention includes a step of performing a first foaming on a mixture obtained by mixing a monomer composition with a first foaming agent and a foam stabilizer.
In the first foaming step, bubbles are generated from the first foaming agent contained in the mixture of the monomer composition, the first foaming agent and the foam stabilizer, and the generated bubbles can be stably trapped in the mixture by the foam stabilizer used together. The bubbles generated in the first foaming step form a plurality of pores in the hydrogel polymer in the cross-linking polymerization step described later, and form a porous structure in the super absorbent polymer finally prepared by a process such as drying, pulverizing, etc., thereby increasing the specific surface area.
On the other hand, as described later, the foaming step is performed at a low temperature of about 50 ℃ or less, and thus bubbles are generated before the polymerization step, and bubbles stably trapped in the mixture by the foam stabilizer may form pores inside the hydrogel polymer formed in the polymerization step. As the first foaming agent, a low-temperature foaming agent foaming at 50 ℃ or lower may be used, and thus, the foaming process may be performed first before the polymerization step.
Specific examples of the first foaming agent may include one or more selected from sodium carbonate, sodium bicarbonate, potassium bicarbonate, azodicarbonamide, p' -oxybisbenzenesulfonyl hydrazide, dinitroso pentamethylene tetramine, p-toluenesulfonyl hydrazide and benzenesulfonyl hydrazide, preferably include one or more selected from sodium carbonate, potassium bicarbonate and the like.
In the first foaming step, the first foaming agent may be used in an amount of 200ppmw to 8,000ppmw, preferably, 200ppmw or more, 500ppmw or more, and/or 8,000ppmw or less, 6,000ppmw or less, 4,000ppmw or less, 500ppmw to 6,000ppmw, or 800ppmw to 40,000ppmw, relative to the water-soluble ethylenically unsaturated monomer in the mixture. When the first foaming agent is contained in the above content range, the generated microbubbles can be stably formed. When the content of the first foaming agent is very small, the foaming effect is insignificant, and when it is contained in excess, the gel strength of the finally produced super absorbent polymer may be lowered.
The foam stabilizer is a component that causes bubbles generated from the foaming agent to be stably trapped in the mixture without coming out of the mixture, and that is dispersed at the interface between the bubbles generated from the foaming agent and the mixture to trap and stabilize the bubbles. In addition, by changing the concentration of the foam stabilizer in the first foaming step and in the second foaming step described later, the size of the generated bubbles can be controlled.
Specifically, the higher the concentration of the foam stabilizer in the mixture, the easier it is to stably form microbubbles. In the present invention, the foam stabilizer is added at a relatively high concentration in the first foaming step, and then the foaming agent, monomer, solvent, etc. are additionally added in the second foaming step, and thus the concentration of the foam stabilizer becomes low. Thus, microbubbles having a relatively small average diameter are generated in the first foaming step, and bubbles having a relatively large average diameter are generated in the second foaming step.
The foam stabilizer may be a hydrophilic surface modifying compound located at the interface between the bubbles generated by the foaming agent and the mixture, thereby stably capturing the bubbles.
Specifically, the foam stabilizer is a particulate type material having an average diameter of about 0.05 μm to about 5 μm that is dispersible in the mixture by hydrophilic surface modification.
Foam stabilizers are compounds prepared by hydrophilic surface modification of hydrophobic compounds with specific surface modifiers, in particular hydrophilic surface modification of hydrophobic compounds by using one or more polymers selected from the following as surface modifiers: polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl acetate, polyvinylpyrrolidone, polyacrylic acid, polyacrylamide, polydopamine, poly (4-styrenesulfonate), polyethylene glycol and polypropylene glycol, or copolymers thereof.
The polymer used as surface modifier may be a homopolymer or a block copolymer.
The hydrophobic compound may include a hydrophobic synthetic high molecular compound having a melting point of 100 ℃ or more, for example, poly (L-lactide), poly (D, L-lactic-co-glycolic acid), polylactic acid, polystyrene, polymethyl methacrylate, polystyrene-polybutadiene copolymer, polystyrene-polyimide copolymer, nylon, polyester; hydrophobic natural high molecular compounds having a melting point of 100 ℃ or higher, for example, lignin, polylactic acid-lignin blends, cellulose acetate (for example, cellulose triacetate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate); solid hydrocarbons having a melting point above 100 ℃, for example, fatty acids (e.g., stearic acid, palmitic acid), fatty acid metal salts, glycerides, and sugar esters; particles (e.g., talc, etc.) capable of hydrophilic surface modification among hydrophobic compounds used as defoamers and lubricants, but are not particularly limited thereto.
Meanwhile, when the surface modification target is an insoluble hydrophobic compound, the hydrophilic surface-modified foam stabilizer may be surface-modified by dispersing and stirring the hydrophobic particles and the surface modifier in a mixed solution of water and a cosolvent (acetone, ethanol, etc.). In addition, in dissolving the surface modification target in an organic solvent, the surface modification may be performed by a method of precipitating the compound by dropping the organic solvent in which the hydrophobic compound is dissolved into water (dropping method), or a method of forming an emulsion and then evaporating the volatile organic solvent (emulsion evaporation method).
The hydrophilic surface-modified foam stabilizer may have an average diameter of about 0.05 μm to about 5 μm when dispersed in the mixture.
The concentration of the foam stabilizer relative to the total weight of the mixture in the first foaming step is greater than the concentration of the foam stabilizer relative to the total weight of the mixture in the second foaming step. This is because, in the second foaming step, the second foaming agent is additionally contained in the first foaming mixture, and thus the relative concentration (content) of the foam stabilizer becomes small.
Specifically, in the first foaming step, the foam stabilizer may be contained in an amount of 0.02wt% to 1.0wt% with respect to the total weight of the mixture, and in this case, the concentration of the foam stabilizer in the second foaming step becomes smaller than that in the first foaming step. In the first foaming step, the content of the foam stabilizer is preferably 0.02wt% or more, 0.05wt% or more, 0.1wt% or more, 0.3wt% or more, and 1.0wt% or less, 0.8wt% or less, 0.5wt% or less, and 0.05wt% to 0.8wt%, or 0.3wt% to 0.5wt%. When the foam stabilizer is contained within the above content range, bubbles to be generated can be stably formed, and in particular, the diameter of bubbles to be generated can be controlled to 100nm or less. Thus, in the first foaming step, microbubbles having a diameter of 100nm or less can be generated.
The first blowing agent and the foam stabilizer may be used as the first blowing agent composition in which they are dissolved or dispersed.
The first blowing agent composition may further comprise an additional solvent to dissolve or disperse the first blowing agent and the foam stabilizer. As the solvent, for example, 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 ethyl ether, toluene, xylene, butyrolactone, carbitol, methyl cellosolve acetate, N-dimethylacetamide, or a mixture thereof may be used, and water may be preferably used.
The first foaming step may be carried out at 35 ℃ to 50 ℃, preferably at 35 ℃ or more, 40 ℃ or more, 50 ℃ or more, and the first foaming agent foams in the corresponding temperature range, and the microbubbles are easily trapped in the mixture.
Microbubbles having a diameter of 100nm or less are generated in the first foaming step. The diameter of the microbubbles is preferably 20nm or more, and may be 100nm or less or 20nm to 100nm. Due to the high concentration of the foam stabilizer, microbubbles are stably trapped in the mixture and contribute to the formation of micropores having a diameter of 2 μm to 180 μm in the super absorbent polymer finally prepared by an additional foaming process, a crosslinking polymerization process, a surface crosslinking process, a pulverization process, or the like.
(second foaming step)
Next, a method of preparing a super absorbent polymer according to an embodiment of the present invention includes a step of performing a second foaming on a mixture obtained by mixing a first foaming mixture and a second foaming agent.
Here, the first foaming mixture means a mixture containing microbubbles by the first foaming.
After the first foaming, additional bubbles are generated by the second foaming step. The bubbles are created by the foaming agents in the mixture (the remaining first foaming agent and the further second foaming agent). The bubbles generated in the second foaming step may be stably trapped in the mixture by the foam stabilizer present in the first foaming mixture.
However, no additional foam stabilizer is added in the second foaming step, and the concentration of the foam stabilizer in the mixture becomes relatively low in the second foaming step. Thus, the bubbles generated in the second foaming step have a larger average diameter than the bubbles generated in the first foaming step. In addition, it is possible to achieve a hierarchical porous structure in the finally produced super absorbent polymer according to the sizes of the bubbles generated in the first foaming step and the bubbles generated in the second foaming step.
In the second foaming agent, the same components as in the first foaming agent described above may be used.
In addition, the amount of the second foaming agent is the same as that of the first foaming agent described above, and as described below, when the monomer is added in the second foaming step, the second foaming agent may be further added according to the amount of the monomer. Specifically, the second blowing agent may be used in an amount of 200ppmw to 8,000ppmw, preferably, 200ppmw or more, 500ppmw or more, or 8,000ppmw or less, 6,000ppmw or less, 4,000ppmw or less, 500ppmw to 6,000ppmw or 800ppmw to 40,000ppmw, relative to the water-soluble ethylenically unsaturated monomer in the mixture to be foamed. When the second foaming agent is contained in the above content range, bubbles can be stably generated.
The second blowing agent may be used as a second blowing agent composition comprising an additional solvent. Here, the same solvent as the first blowing agent composition may be used as the solvent.
On the other hand, in the second foaming step, the concentration of the foam stabilizer contained in the mixture is reduced as compared with the first foaming step, and the concentration is reduced to 0.1 to 0.5 times as compared with the first foaming step (this means that the foaming target mixture is diluted 2 to 10 times).
Specifically, the concentration of the foam stabilizer is relatively reduced according to the content of the added second foaming agent composition, and the concentration of the foam stabilizer may be reduced by additionally adding the monomer composition in the second foaming step.
In the second foaming step, the additionally added monomer composition may include a water-soluble acrylic-based monomer having an acid group that is at least partially neutralized, a polymerization initiator, and a first crosslinking agent. The components and contents of the water-soluble acrylic-based monomer, the polymerization initiator, and the first crosslinking agent are the same as described above.
The second foaming step may be performed at 35 to 50 c and the foaming agent is foamed in a corresponding temperature range so that bubbles can be easily trapped in the mixture.
In the second foaming step, bubbles having a particle size of 2 to 10 times that of the bubbles generated in the first foaming process may be generated.
Specifically, when microbubbles having a diameter of 100nm or less are generated in the first foaming step, bubbles having a diameter of 100nm to 1,000nm can be generated in the second foaming step. Preferably, the diameter of the bubbles may be 100nm or more, 150nm or more, 1,000nm or less, 500nm or less, 400nm or less, 250nm or less, and 100nm to 500nm, 100nm to 400nm, or 150nm to 250nm. The bubbles contribute to the formation of pores having an average diameter of 180 μm or more in the super absorbent polymer finally produced by a crosslinking polymerization process, a surface crosslinking process, a pulverization process, or the like.
Meanwhile, the above-described foaming step may be additionally performed a plurality of times as needed, and bubbles having different average diameters may be generated by adjusting the concentration of the bubble stabilizer in the additional foaming step.
(crosslinking-polymerization step)
Next, a method of preparing a superabsorbent polymer according to an embodiment of the present invention includes the step of forming an aqueous gel polymer by cross-polymerizing a second foamed mixture.
Here, the second foaming mixture includes classified bubbles generated in the first and second foaming steps. The air bubbles contained in the second foaming mixture are stably trapped in the foaming mixture by the foam stabilizer, and the air bubbles form pores inside the hydrogel polymer formed in the crosslinking polymerization step. Specifically, a hierarchical porous structure having different average diameters is formed in the hydrogel polymer.
The cross-linking polymerization step may be carried out at a temperature of 50℃to 100℃which is higher than the foaming step described above. When the polymerization is carried out in the above temperature range, an appropriate pore structure can be formed inside the hydrogel polymer by the bubbles generated in the foaming step.
The crosslinking polymerization method is largely classified into thermal polymerization and photopolymerization according to the polymerization energy source. When the thermal polymerization is carried out, it can be usually carried out in a reactor such as a kneader equipped with a stirring shaft. When photopolymerization is carried out, it may be carried out in a reactor equipped with a movable conveyor belt. The above polymerization method is merely an example, and the present invention is not limited to the above polymerization method.
For example, when discharged from the outlet of the reactor according to the type of stirring shaft with which the reactor is equipped, the hydrogel polymer obtained by performing thermal polymerization while supplying hot air to the above-mentioned reactor such as a kneader equipped with a stirring shaft or by heating the reactor may have a size of cm or mm. Specifically, the size of the resulting hydrogel polymer varies depending on the concentration, the feed rate, etc. of the monomer composition fed thereto, and generally, hydrogel polymers having a weight average particle diameter of 2mm to 50mm can be obtained.
Further, as described above, when photopolymerization is carried out in a reactor equipped with a movable conveyor belt, the obtained hydrogel polymer may be a sheet-like hydrogel polymer having a conveyor belt width in general. In this case, the thickness of the polymer sheet may vary according to the concentration of the monomer composition fed thereto and the feeding rate. 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 composition is supplied to such an extent that the thickness of the sheet-like polymer becomes too thin, production efficiency is low, and thus, it is not preferable, and when the thickness of the sheet-like polymer exceeds 5cm, polymerization reaction may not occur uniformly over the entire thickness due to the excessive thickness.
The hydrogel polymer obtained by the above process may have a water content of about 40wt% to about 80 wt%. Meanwhile, as used herein, "water content" refers to the weight of water relative to the total weight of the polymer, which may be a value obtained by subtracting the weight of the dry polymer from the weight of the polymer. In particular, the water content may be defined as a value calculated by measuring a weight loss measured due to evaporation of water in the polymer during a drying process that increases the temperature of the polymer by infrared heating. At this time, the water content was measured under the following drying conditions: the temperature was raised from room temperature to about 180 ℃, then the temperature was maintained at 180 ℃, and the total drying time was set to 20 minutes, including the temperature raising step for 5 minutes.
(drying, pulverizing and classifying step)
Next, according to one embodiment of the present invention, there is included the step of forming a base polymer powder by drying, pulverizing and classifying the hydrogel polymer.
Specifically, a step of drying the resulting hydrogel polymer is performed. If necessary, in order to increase the efficiency of the drying step, a step of coarsely pulverizing the hydrogel polymer may be further performed before drying.
In this regard, the shredder used herein is not limited by its configuration, and specifically, it may include any one selected from a vertical shredder (vertical pulverizer), a turbo cutter (turbo cutter), a turbo grinder (turbo grinder), a rotary cutter mill (rotary cutter mill), a cutter mill (cutter mill), a disc mill (disc mill), a shredding crusher (shred crusher), a crusher (crusher), a chopper (chopper), and a disc cutter (disc cutter), but is not limited to the above examples.
For this, a coarse pulverizing step may be performed so that the particle size of the hydrogel polymer becomes 2mm to 10mm. Due to the high water content of the hydrogel polymer, comminution to particle sizes of less than 2mm is technically not easy and agglomeration between the comminuted particles may occur. Meanwhile, when the polymer is pulverized to a particle size of more than 10mm, the effect of improving efficiency in the subsequent drying step may not be significant.
The hydrogel polymer coarsely pulverized as above or the hydrogel polymer not subjected to the coarse pulverization step immediately after polymerization is dried. In this regard, the drying may be performed at a temperature of 150℃or more for 30 minutes or more, preferably at a temperature of 150℃to 250℃or 170℃to 200 ℃. When the drying temperature is lower than 150 ℃, there is a fear that the drying time becomes too long and the physical properties of the finally formed super absorbent polymer may deteriorate. When the drying temperature is higher than 250 ℃, there is a fear that only the polymer surface is excessively dried, and thus fine particles may be generated during the subsequent pulverizing process, and the physical properties of the finally formed super absorbent polymer may be deteriorated.
Meanwhile, the drying step may be performed for more than 30 minutes. When the drying step is performed for 30 minutes or less, the drying is insufficient. Preferably, the drying step may be performed for 30 minutes to 90 minutes, but is not limited thereto.
In the drying step, any drying method may be selected and used without limitation in view of its constitution, as long as it is generally used in a process of drying an aqueous gel polymer. Specifically, the drying step may be performed by a method such as supplying hot air, infrared irradiation, microwave irradiation, or ultraviolet irradiation. When the above drying step is completed, the water content of the polymer may be about 0.1wt% to about 10wt%.
Next, a step of pulverizing the dried polymer obtained by the drying step is performed.
The polymer powder obtained by the pulverizing step may have a particle size of about 300 μm to about 800 μm. Specific examples of the pulverizer that can be used to achieve the above particle size may include, but are not limited to, pin mills (pin mills), hammer mills (hammer mills), screw mills (screen mills), roll mills (roll mills), disc mills (disk mills), or click mills (jog mills), etc.
In order to manage the physical properties of the finally commercialized super absorbent polymer powder after the pulverizing step, a separation process of classifying the polymer powder obtained after the pulverizing according to particle size may be performed. Preferably, polymers having particle diameters of 300 μm to 800 μm are classified, and only polymer powders having such particle diameters are subjected to a surface crosslinking reaction and then commercialized. More specifically, the classified base polymer powder has a particle diameter of 300 μm to 800 μm, and may contain 50wt% or more of particles having a particle diameter of 300 μm to 600 μm.
(surface Cross-linking Process)
Meanwhile, according to an embodiment of the present invention, after preparing the base polymer powder by the above-mentioned classification process, a step of crosslinking at least part of the surface of the base polymer powder in the presence of a surface crosslinking agent is included.
At least part of the surface of the base polymer powder is thermally crosslinked by subjecting the base polymer powder to a heat treatment in the presence of a second crosslinking agent, thereby forming superabsorbent polymer particles. The surface crosslinking step is to initiate a crosslinking reaction on the surface of the base polymer powder in the presence of a second crosslinking agent. By this surface crosslinking, a surface crosslinked layer can be formed on at least a part of the surface of the base polymer powder. This is to increase the surface cross-linking density of the superabsorbent polymer. As described above, when the superabsorbent polymer further includes a surface cross-linked layer, it has a structure having a higher cross-linking density on the outer side than on the inner side.
The surface crosslinking step may be performed at a temperature above about 180 ℃ for more than about 30 minutes.
As the second crosslinking agent, any second crosslinking agent conventionally used for producing superabsorbent polymers may be used without any particular limitation. For example, the second crosslinking agent may include one or more polyols 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; one or more carbonate-based compounds selected from ethylene carbonate and propylene carbonate; epoxy compounds such as ethylene glycol diglycidyl ether; oxazoline compounds such as oxazolidinones; a polyamine compound; an oxazoline compound; mono-, di-or polyoxazolidinone compounds; or a cyclic urea compound, etc. Preferably, the same ones as the above-mentioned first crosslinking agents can be used, and for example, diglycidyl ether-based compounds of alkylene glycol, such as ethylene glycol diglycidyl ether, and the like, can be used.
The second crosslinking agent may be used in an amount of 0.001 parts by weight to 2 parts by weight with respect to 100 parts by weight of the base polymer powder. Preferably, the second crosslinking agent may be used in an amount of 0.005 parts by weight or more, 0.01 parts by weight or more, or 0.02 parts by weight or more, and 0.5 parts by weight or less, 0.3 parts by weight or less. By controlling the content range of the second crosslinking agent within the above range, it is possible to produce a super absorbent polymer exhibiting comprehensive physical properties such as excellent absorption performance, liquid permeability, and the like.
Meanwhile, in order to further enhance the liquid permeability of the super absorbent polymer according to one embodiment, aluminum salts such as aluminum sulfate and other various polyvalent metal salts may be further used during the surface crosslinking. Such multivalent metal salts may be included on the surface crosslinked layer of the final superabsorbent polymer.
Meanwhile, the super absorbent polymer according to an embodiment of the present invention may have a particle size of 300 μm to 800 μm. More specifically, at least 95% by weight or more of the base polymer powder and the super absorbent polymer comprising the same have a particle diameter of 300 μm to 800 μm, and may contain 50% by weight or more of particles having a particle diameter of 300 μm to 600 μm.
(super Water-absorbent Polymer)
By the above-described multi-step foaming process of the present invention, the super absorbent polymer prepared according to the method of preparing a super absorbent polymer according to an embodiment of the present invention includes a plurality of pores, and the average diameter thereof may be 20 to 150 μm.
In addition, the super absorbent polymer includes 70% or more of micropores having a diameter of 2 μm to 180 μm in the pores. Thus, the superabsorbent polymer may comprise a hierarchical pore structure. The proportion of micropores is preferably 70% or more, 73% or more, 78% or more, 81% or more, 84% or more, and 99% or less, 95% or less, 92% or less, or 70% to 99% or 73% to 92%.
Even when a usual foaming process is performed, the generated microbubbles tend to disappear by a process such as polymerization, pulverization, or the like. As described above, in the present invention, a multi-step foaming process using a foam stabilizer is performed, as a result, many micro-pores having a diameter of 2 μm to 180 μm exist in the finally prepared super absorbent polymer, and thus the absorption rate can be significantly improved.
Meanwhile, it is difficult to introduce the desired hierarchical pore structure of the present invention during the preparation of the super absorbent polymer when the multi-step foaming process is not performed or when the foam stabilizer of the present invention is not used even if the multi-step process is performed.
At this time, the average diameter of the pores of the superabsorbent polymer can be checked by observing the internal structure of the superabsorbent polymer particles to be measured using an optical microscope (OM; magnification: X50 or X500) and an electron microscope (SEM; magnification: X200 or X5000). More specifically, the longest diameter of each hole included in the superabsorbent polymer particles is measured, and then the median value of the measured longest diameters may be determined as the average diameter. In this case, it is preferable to measure the diameters of 800 or more holes with respect to one sample of the superabsorbent polymer and determine the average diameter.
Further, the content of micropores having a diameter of 2 μm to 180 μm means that the longest diameter of each of more than 800 pores is measured with respect to one superabsorbent polymer sample, and then the ratio of the number of micropores having a diameter of 2 μm to 180 μm is determined in the pores.
On the other hand, the superabsorbent polymer may include particles having a particle size of about 300 μm to about 800 μm in an amount of 90wt% or more based on the total weight, and the particle size of the superabsorbent polymer particles may be determined according to the European Disposable and nonwoven Association (EDANA) WSP220.3 method.
Furthermore, the superabsorbent polymers may have a Centrifuge Retention Capacity (CRC) of 28g/g or more, preferably 28.8g/g or more, 29.5g/g or more, and 35g/g or less, 33g/g or less, 31.7 or less, 28 to 35g/g, or 28.8 to 31.7g/g, measured according to EDANA WSP241.3 method. The method of measuring the Centrifuge Retention Capacity (CRC) will be described in more detail in experimental examples described later.
Furthermore, according to the vortex method, the super absorbent polymer has an absorption rate (vortex time) of 40 seconds or less. The smaller the value, the more excellent the absorption rate, so the lower limit of the absorption rate is theoretically 0 seconds. For example, the absorption rate may be 5 seconds or more, 10 seconds or more, 20 seconds or more, and 40 seconds or less, 38 seconds or less, 37 seconds or less, 35 seconds or less, 33 seconds or less, 32 seconds or less, 31 seconds or less, or 10 seconds to 40 seconds. The absorption rate according to the vortex method means the time (unit: seconds) taken for the vortex of liquid to disappear by rapid absorption when the super absorbent polymer added to the physiological saline is stirred. Superabsorbent polymers can be considered to have higher initial absorption rates with shorter times. Here, physiological saline means 0.9wt% sodium chloride (NaCl) aqueous solution. The method of measuring the absorption rate will be described in more detail in experimental examples described later. On the other hand, for the base polymer powder before surface crosslinking, the absorption rate according to the vortex method can be measured in the same manner.
The present invention will be described in more detail in the following exemplary embodiments. However, the following exemplary embodiments are only for describing the present invention, and the specific description of the present invention is not limited to the following exemplary embodiments.
< preparation example >
Hereinafter, the first blowing agent composition including the foam stabilizer used in the examples was prepared as follows.
Preparation example 1-1: preparation of the first blowing agent composition (A-1)
First, PEO copolymer containing 0.25% w/v concentration was preparedF-127, sigma-Aldrich) was placed in a high shear mixer and 20% v/v methylene chloride containing 15% w/v polylactic acid (poly (L-lactide), average Mn of 20,000, sigma-Aldrich) was added thereto under stirring at 20,000rpm at room temperature (24.+ -. 1 ℃ C.) and atmospheric pressure (1 atm). After the addition of methylene chloride, stirring was further carried out at 20,000rpm for 15 minutes to form an oil-in-water emulsion.
Thereafter, the methylene chloride was evaporated under slow stirring for 20 hours to form a PLA foam stabilizer surface-modified with PEO copolymer. The foam stabilizer was recovered by centrifugation and then redispersed in water. At this time, the average particle diameter of the foam stabilizer in the aqueous dispersion was 0.3. Mu.m.
9g of the prepared foam stabilizer was added to 800g of water (here, the total water content was 800g in view of the water content in the aqueous dispersion including the foam stabilizer). Next, 1.35g of Sodium Bicarbonate (SBC) was also added as a first blowing agent, and stirred at room temperature (24.+ -. 1 ℃ C.) to prepare a first blowing agent composition.
Preparation examples 1-2: preparation of the first blowing agent composition (A-2)
In preparation example 1-1, an equivalent amount of PLA/lignin (introduced into the organic solvent in a weight ratio of 9:1) was used instead of PLA in the preparation of the aqueous dispersion of the foam stabilizer. At this time, the average particle diameter of the foam stabilizer in the aqueous dispersion was 0.3. Mu.m.
In addition, the first blowing agent composition (A-2) was prepared in the same manner as in preparation example 1-1.
Preparation examples 1-3: preparation of the first blowing agent composition (A-3)
In preparation example 1-1, the same amount of PE/PP wax (LG chemistry) was used instead of PLA. At this time, the average particle diameter of the foam stabilizer in the aqueous dispersion was 0.2. Mu.m.
In addition, the first blowing agent composition (A-3) was prepared in the same manner as in preparation example 1-1.
Preparation examples 1-4: preparation of the first blowing agent composition (A-4)
In preparation example 1-1, the same amount of cellulose ester (180955, sigma-Aldrich) was used instead of PLA. At this time, the average particle diameter of the foam stabilizer in the aqueous dispersion was 0.6. Mu.m.
In addition, the first blowing agent composition (A-4) was prepared in the same manner as in preparation example 1-1.
Preparation examples 1-5: preparation of the first blowing agent composition (A-5)
In preparation example 1-1, the same amount of magnesium stearate (415057, sigma-Aldrich) was used instead of PLA. At this time, the average particle diameter of the foam stabilizer in the aqueous dispersion was 2. Mu.m.
In addition, the first blowing agent composition (A-5) was prepared in the same manner as in preparation example 1-1.
Preparation examples 1-6: preparation of the first blowing agent composition (A-6)
In preparation example 1-1, the same amount of polyvinyl alcohol (360627, mw 9,000-10,000, sigma-Aldrich) was used instead of the surface modifier PEO copolymer. At this time, the average particle diameter of the foam stabilizer in the aqueous dispersion was 0.3. Mu.m.
In addition, the first blowing agent composition (A-6) was prepared in the same manner as in preparation example 1-1.
Preparation examples 1-7: preparation of the first blowing agent composition (A-7)
A first blowing agent composition (A-7) was prepared in the same manner as in preparation example 1-1, except that the same amount of potassium hydrogencarbonate (DUKSAN) was used in place of the blowing agent SBC in preparation example 1-1.
< examples and comparative examples >
Example 1
(step 1) to a glass vessel equipped with a stirrer and a thermometer, 5,000g of acrylic acid, 1,750g of NaOH and 2,300g of water were slowly dropped to prepare a mixture. A solution of 615g of water, 4.5g of IRGACURE819 as a photoinitiator, 9g of sodium persulfate as a thermal initiator, and 22.5g of polyethylene glycol diacrylate (PEGDA, molecular weight 400 g/mol) as a first crosslinking agent was slowly dropped thereinto to prepare a monomer composition. The degree of neutralization of acrylic acid in the resulting composition was 70mol%.
(step 2) the prepared monomer composition was introduced into a transfer tube, and also introduced into the first blowing agent composition of preparation example 1. Here, the content of SBC as the first blowing agent was introduced at 1,500ppmw based on acrylic acid (the content of the foam stabilizer of production example 1 was increased by 5.5 times). At this time, the foam stabilizer was contained in an amount of 0.36wt% with respect to the total weight of the mixture.
The mixture was heated to 50 ℃ for the first foaming. The flow rate is controlled so that the Reynolds Number (Reynolds Number) is 5,000 or more so that the monomer composition and the first blowing agent composition are easily mixed in the transfer pipe.
(step 3) the prepared monomer composition was additionally added to the first foaming mixture, followed by the addition of a second blowing agent composition in which the SBC was dispersed in water such that the SBC was 1,500ppmw relative to the total monomers in the mixture, and the second foaming mixture was heated to 50 ℃ for second foaming.
At this time, the content of the additional monomer composition was controlled so that the concentration of the foam stabilizer was 0.036wt% with respect to the total amount of the mixture (controlled so that the foam stabilizer was diluted 10 times). However, after the first foaming process, part of the foam stabilizer is adsorbed and consumed at the interface, as a result of which the concentration of foam stabilizer in the mixture is somewhat reduced.
The flow rate is controlled so that the reynolds number is 5,000 or more so that the components are easily mixed in the delivery pipe.
Meanwhile, fig. 1 shows a schematic view of a flow chart of the multi-step foaming process of example 1.
(step 4) the second foaming mixture exiting the transfer tube was fed onto a conveyor belt having a width of 10cm and a length of 2m at a rate of 500mL/min to 2000mL/min and rotated at a speed of 50 cm/min. Then, simultaneously with feeding the second foaming mixture, by feeding the second foaming mixture at 10mW/cm 2 Ultraviolet rays were irradiated to conduct polymerization for 60 seconds, thereby obtaining a sheet-like hydrogel polymer having a water content of 55 wt%.
(step 5) next, the sheet-shaped hydrogel polymer is cut into a size of about 5cm×5cm, and then introduced into a meat grinder to crush the polymer, thereby obtaining hydrogel particle chips having a size of 1mm to 10 mm. The chips are then dried in an oven capable of moving the air flow up and down. The chips were uniformly dried by blowing hot air at 180 c or higher from bottom to top for 15 minutes and then from top to bottom for 15 minutes, and as a result, the dried product had a water content of 2% or less. After drying, the crumb was pulverized with a pulverizer and then classified to prepare a base polymer powder having a size of 300 μm to 800 μm.
(step 6) to 100 parts by weight of the prepared base polymer powder, 6 parts by weight of an aqueous solution of a second crosslinking agent containing 3 parts by weight of ethylene carbonate was sprayed, and the surface crosslinking liquid was uniformly distributed on the base polymer powder by stirring at room temperature. Subsequently, the base polymer powder mixed with the surface crosslinking liquid is placed in a surface crosslinking reactor to perform a surface crosslinking reaction.
It was confirmed that the base polymer powder was gradually heated from an initial temperature of around 80℃in the surface crosslinking reactor and was manipulated after 30 minutes to reach a maximum reaction temperature of 190 ℃. After reaching the maximum reaction temperature, the reaction was further carried out for 15 minutes, and a sample of the finally prepared superabsorbent polymer was taken. After the surface cross-linking process, the samples were classified using ASTM standard mesh screens to prepare superabsorbent polymer of example 1 having a particle size of 300 μm to 800 μm.
Examples 2 to 7
Each super absorbent polymer was prepared in the same manner as in example 1, except that the first blowing agent compositions (A-2 to A-7) prepared in preparation examples 2 to 7 were used in example 1.
Comparative example 1
Superabsorbent polymers were prepared in the same manner as in example 1 except that the same foam stabilizer and blowing agent as in example 1 were used, but the first high concentration (foam stabilizer: 0.36 wt%) foaming process was not performed, and the second low concentration (foam stabilizer: 0.036 wt%) foaming process was performed under the same conditions.
Comparative example 2
Superabsorbent polymers were prepared in the same manner as in example 4 except that the same foam stabilizer and blowing agent were used as in example 4, but the first high concentration (foam stabilizer: 0.36 wt%) foaming process was not performed, and the second low concentration (foam stabilizer: 0.036 wt%) foaming process was performed under the same conditions.
Comparative example 3
Super absorbent polymer was prepared in the same manner as in example 1 except that in example 1, when the first foaming agent composition of preparation example 1 was prepared, polystyrene (LG chemistry, 0.3 μm latex beads) was used as a foam stabilizer, but the first high concentration (foam stabilizer: 0.36 wt%) foaming process was not performed, and the second low concentration (foam stabilizer: 0.036 wt%) foaming process was performed under the same conditions.
Comparative example 4
Superabsorbent polymers were prepared in the same manner as in example 1 except that the foam stabilizer in example 1 was not used.
Comparative example 5
A solution (solution a) was prepared in which 8.6g (80 ppmw relative to the monomer) of IRGACURE 819 initiator diluted with acrylic acid at 0.5wt% and 12.3g of polyethylene glycol diacrylate diluted with acrylic acid at 20wt% (PEGDA, mw=400) were mixed. 540g of acrylic acid and the above solution A were introduced into a glass reactor of 2L capacity surrounded by a jacket in which a heat medium precooled to 25℃was circulated. Then, 832g of 25wt% caustic soda solution (solution C) was slowly dropped and mixed into the glass reactor. After confirming that the temperature of the mixed solution was raised to about 72 ℃ or higher due to the heat of neutralization, the mixed solution was left until it was cooled. The degree of neutralization of acrylic acid in the thus-obtained mixed solution was about 70mol%. Solution D was prepared separately, wherein bubbles were generated by introducing water into a microbubble generator (O2 Bubble, OB-750S) circulating at a flow rate of 500 kg/h. Silicon oxide was added thereto and placed in an ultrasonic apparatus (O2 Bubble, OB-750S) to prepare a solution F. Then, when the temperature of the neutralized mixed solution is cooled to about 45 ℃, the previously prepared F solution is injected into the mixed solution and then mixed. At this time, silicon oxide was prepared in 0.05 parts by weight with respect to 100 parts by weight of the mixed solution.
Subsequently, the solution prepared above was poured into a cylinder-type (Vat-type) tray (width 15 cm. Times.length 15 cm) installed in a square polymerization reactor, on which a light irradiation device was installed, and the inside thereof was preheated to 80 ℃. Then, the mixed solution is subjected to light irradiation. It was confirmed that gel was formed from the surface about 20 seconds after the light irradiation, and that polymerization and foaming occurred simultaneously at about 30 seconds after the light irradiation. Subsequently, the polymerization was carried out for an additional 2 minutes, and the polymerized sheet was taken and cut into 3cm×3cm sizes. The slices are then subjected to a chopping process using a meat chopper to produce chips. The average particle size of the chips produced was 1.5mm. The chips are then dried in an oven capable of converting the air flow up and down. The chips were uniformly dried by blowing hot air at 180 ℃ or higher from bottom to top for 15 minutes and then from top to bottom for 15 minutes, whereby the water content of the dried chips was about 2wt% or less. The dried chips were pulverized with a pulverizer, and then classified to obtain a base polymer having a size of 150 μm to 850 μm.
Thereafter, 100 parts by weight of the prepared base polymer was mixed with a crosslinking agent solution in which 4.5g of water, 1g of ethylene carbonate, 0.05g of Aerosil 200 (Evonik), 0.25g of a 20wt% water-dispersible silica (Snowtex, ST-O) solution were mixed, and then surface crosslinking reaction was performed at 190 ℃ for 30 minutes. The resulting product was crushed and sieved to obtain a surface-crosslinked super absorbent polymer having a particle diameter of 150 μm to 850 μm. 0.1g of Aerosil 200 was dry-mixed with the obtained super absorbent polymer to prepare the super absorbent polymer.
Experimental example ]
Experimental example 1: measurement of bubble size in a multi-step foaming process
(1-1) in order to examine the structure of bubbles generated in the multi-step foaming process during the preparation process of example 1, the foaming mixture of each foaming step was photographed at a magnification of 50 to 500 times using an optical microscope (product name: ti-U, manufacturer: nikon). Specifically, OM images of bubbles in the first foaming mixture and the second foaming mixture are shown in fig. 2 in the following manner.
Fig. 2A shows bubbles generated after a first foaming process (foaming under high concentration of foam stabilizer conditions), and fig. 2B shows bubbles generated after a second foaming process (foaming under low concentration of foam stabilizer conditions). Referring to fig. 2A, a relatively high concentration of the foam stabilizer is included in the first foaming process and thus small-sized microbubbles are trapped in the foaming mixture, and referring to fig. 2B, a relatively low concentration of the foam stabilizer is included in the second foaming process and thus relatively large-sized bubbles are trapped in the foaming mixture, as compared to the first foaming process.
(1-2) during the preparation process of example 1, the concentration of the foam stabilizer in the multi-step foaming process was changed, the size of bubbles generated in the foaming process was measured by OM map of experimental example 1 (1-1), and the size of pores after curing was measured by SEM image of experimental example 2 described later, and the change thereof is shown in the graph of fig. 3.
Referring to fig. 3, it was confirmed that the higher the concentration of the foam stabilizer during the foaming process, the significantly smaller the size of the generated bubbles.
Experimental example 2: measurement of pore size of superabsorbent polymers
To examine the pore structure of the superabsorbent polymers prepared in examples and comparative examples, internal images of superabsorbent polymer particles were taken at a magnification of 200 to 5,000 times using a scanning electron microscope (SEM, product name: JCM-6000, manufacturer: JEOL). Specifically, the average diameter of the pores of the super absorbent polymer was measured as follows. Thus, the pore size distribution of example 1 and comparative example 1 is shown in fig. 4. In addition, cross-sectional images of example 1, comparative example 1, and comparative example 4 are shown in fig. 5 and 6, respectively.
1) First, the super absorbent polymer of the example was classified at 1.0 amplitude for 1 minute by using a Retsch particle classifier, thereby preparing a 2g sample by preparing individual particles having a particle size of 200 μm to 500 μm without damaging the particles.
2) The prepared sample particles were then randomly arranged and placed in an SEM stage.
3) Next, sample particles arbitrarily arranged on the SEM stage were fixed with a carbon tape, and the size of pores formed on the surface of the super-absorbent particles was measured at 200 to 5000 times. At this time, an average of 1000 or more particles of the super absorbent polymer was targeted, and among them, the sizes of 800 or more particles in which the pores were clearly visible were measured. Here, it is assumed that "clearly visible holes" are identified by forming spherical bubbles. The superabsorbent polymer particles were determined to be most clearly visible when approximately hemispherical shapes were present on their surfaces by the comminution process.
4) Next, the pore diameters of 800 or more particles finally measured were obtained and the respective diameters were measured, and the proportion of micropores having a pore diameter of 2 μm to 180 μm in the pores was calculated and shown in table 1.
5) Further, the average diameter was obtained from the statistical median of the measured particle diameters, and the results are shown in table 1. In this regard, a quartile range is used to examine the pore size distribution in order to exclude measurement errors due to a measurer and abnormal values.
Fig. 5A shows a schematic view of a cross-sectional view of a super absorbent polymer prepared by the multi-step foaming process of example 1, in which a plurality of micropores exist inside the super absorbent polymer particles finally prepared by polymerization, drying, pulverization, etc., and thus the absorption rate can be significantly improved. Fig. 5B shows a schematic view of a cross-sectional view of a super absorbent polymer prepared by the one-step foaming process of the comparative example, in which pores having a relatively large average diameter are present inside the super absorbent polymer particles finally prepared by polymerization, drying, pulverization, etc., and thus the effect of improving the absorption rate may be reduced as compared with the example. Fig. 5C shows a schematic view of a cross-sectional view of the super absorbent polymer prepared by the one-step foaming process of comparative example 4, in which pores having the largest average diameter are present inside the super absorbent polymer particles finally prepared by polymerization, drying, pulverization, etc., and the number of pores is minimized, so that the effect of improving the absorption rate may be reduced as compared with the example.
Fig. 6A shows a cross-sectional SEM image of the super absorbent polymer prepared by the multi-step foaming process of example 1, and fig. 6B shows a cross-sectional SEM image of the super absorbent polymer prepared by the one-step foaming process of comparative example 1, and fig. 6C shows a cross-sectional SEM image of the super absorbent polymer prepared by the one-step foaming process of comparative example 4. Referring to fig. 6, the examples show that a large number of micropores are formed in the super absorbent polymer, and thus the absorption rate can be significantly improved.
Experimental example 3: measurement of physical Properties of superabsorbent polymers
The physical properties of the super absorbent polymers prepared in examples and comparative examples were evaluated by the following methods, respectively, and are shown in table 1 below.
Unless otherwise indicated, the following physical properties were evaluated at room temperature (24.+ -. 1 ℃ C.), and physiological saline or saline refers to a 0.9wt% aqueous sodium chloride (NaCl) solution.
(1) Centrifuge Retention Capacity (CRC)
The centrifuge retention capacity of each polymer by absorption capacity under no load was measured according to EDANA WSP 241.3.
Specifically, W is 0 (g) (about 0.2 g) after uniformly introducing the super absorbent polymer into a nonwoven fabric bag and sealing it, it was immersed in physiological saline (0.9 wt%) at room temperature. After 30 minutes, the bag was dehydrated at 250G for 3 minutes using a centrifuge, and then the weight W of the bag was measured 2 (g) A. The invention relates to a method for producing a fibre-reinforced plastic composite In addition, after the same operation was performed without using the polymer, the weight W of the bag was measured 1 (g) A. The invention relates to a method for producing a fibre-reinforced plastic composite The CRC (g/g) was calculated according to the following equation using each obtained weight:
[ equation 1]
CRC(g/g)＝{[W 2 (g)-W 1 (g)]/W 0 (g)}-1
(2) Absorption Rate (vortex time)
The absorption rate (vortex time) of the super absorbent polymers of examples and comparative examples was measured by the following method.
(1) First, 50mL of 0.9% brine was placed in a 100mL flat bottom beaker using a 100mL mass cylinder.
(2) Next, the beaker was placed in the center of a magnetic stirrer, and then a circular magnetic rod (diameter 30 mm) was placed in the beaker.
(3) Then, the stirrer was operated so that the magnetic bar was stirred at 600rpm, and the lowest part of the vortex generated by the stirring was brought into contact with the tip of the magnetic bar.
(4) After confirming that the saline temperature in the beaker reached 24.0 ℃, a 2±0.01g sample of superabsorbent polymer was added, while a stopwatch was timed. The time taken for the vortex to disappear and the liquid surface to be completely level was measured in seconds and determined as the absorption rate.
[ Table 1]
Referring to table 1, the examples show that by performing a multi-step foaming process using foam stabilizers, a hierarchical cell distribution is formed in the prepared superabsorbent polymer, thus exhibiting improved absorption properties and absorption rate.
Comparative examples 1 to 3, in which a multi-step foaming process was not performed although a foam stabilizer was used, showed that it was difficult to form a hierarchical cell distribution, and thus the vortex time was improved, as compared with the examples.
Comparative example 4, in which a multi-step foaming process was performed but a foam stabilizer was not used, showed that it was difficult to generate microbubbles, compared with the examples, and thus the vortex time was significantly increased.
Further, comparative example 5, in which a physical foaming process was performed although a multi-step foaming process was performed, showed that it was difficult to generate microbubbles, compared with the examples, and thus the vortex time was significantly increased.
Claims (12)
1. A method of preparing a superabsorbent polymer, the method comprising the steps of:
preparing a monomer composition comprising a water-soluble acrylic-based monomer having an at least partially neutralized acidic group, a polymerization initiator, and a first crosslinking agent;
first foaming the mixture obtained by mixing the monomer composition with the first foaming agent and the foam stabilizer;
the mixture obtained by mixing the first foaming mixture and the second foaming agent is subjected to second foaming;
polymerizing the second foamed mixture by cross-linking to form an hydrogel polymer;
Forming a base polymer powder by drying, pulverizing and classifying the hydrogel polymer; and
at least part of the surface of the base polymer powder is crosslinked in the presence of a surface crosslinking agent.
2. The method of claim 1, wherein the concentration of the foam stabilizer relative to the total weight of the mixture in the first foaming step is greater than the concentration of the foam stabilizer relative to the total weight of the mixture in the second foaming step.
3. The method according to claim 1, wherein in the first foaming step the foam stabilizer is contained in an amount of 0.02 to 1.0wt% relative to the total weight of the mixture, and the concentration of the foam stabilizer in the second foaming step is smaller than in the first foaming step.
4. The method of claim 1, wherein the foam stabilizer is a hydrophilic surface modified compound.
5. The method of claim 1, wherein the foam stabilizer is a compound obtained by hydrophilic surface modification of a hydrophobic compound with one or more polymers selected from the group consisting of: polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl acetate, polyvinylpyrrolidone, polyacrylic acid, polyacrylamide, polydopamine, poly (4-styrenesulfonate), polyethylene glycol and polypropylene glycol, or copolymers thereof.
6. The method of claim 1, wherein the first blowing agent and the second blowing agent each independently foam below 50 ℃.
7. The method of claim 1, wherein the first blowing agent and the second blowing agent are each independently one or more selected from the group consisting of: sodium carbonate, sodium bicarbonate, potassium bicarbonate, azodicarbonamide, p' -oxybisbenzenesulfonyl hydrazide, dinitroso pentamethylene tetramine, p-toluenesulfonyl hydrazide, and benzenesulfonyl hydrazide.
8. The method of claim 1, wherein a monomer composition comprising a water-soluble acrylic-based monomer having at least partially neutralized acidic groups, a polymerization initiator, and a first crosslinking agent is further mixed in a second foaming step.
9. The method of claim 1, wherein the first foaming step and the second foaming step are each independently performed at 35 ℃ to 50 ℃.
10. The method according to claim 1, wherein microbubbles having a diameter of 100nm or less are generated in the first foaming step, and
bubbles having a diameter of 100nm to 300nm are generated in the second foaming step.
11. The method of claim 1, wherein the cross-linking polymerization step is performed at 50 ℃ to 100 ℃.
12. The method of claim 1, wherein the superabsorbent polymer comprises a plurality of pores,
the plurality of pores having an average diameter of 20 μm to 150 μm, an
Of the plurality of pores, micropores having a diameter of 2 μm to 180 μm are 70% or more.
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| KR10-2022-0087601 | 2022-07-15 | ||
| PCT/KR2022/010412 WO2023287262A1 (en) | 2021-07-16 | 2022-07-18 | Preparation method of super absorbent polymer |
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