OA18676A - PCC with reduced portlandite content - Google Patents
PCC with reduced portlandite content Download PDFInfo
- Publication number
- OA18676A OA18676A OA1201700143 OA18676A OA 18676 A OA18676 A OA 18676A OA 1201700143 OA1201700143 OA 1201700143 OA 18676 A OA18676 A OA 18676A
- Authority
- OA
- OAPI
- Prior art keywords
- calcium carbonate
- calcium
- precipitated calcium
- precipitated
- daims
- Prior art date
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- 239000000920 calcium hydroxide Substances 0.000 title claims abstract description 101
- 235000011116 calcium hydroxide Nutrition 0.000 title claims abstract description 100
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 claims abstract description 427
- 229940088417 precipitated calcium carbonate Drugs 0.000 claims abstract description 204
- 238000000034 method Methods 0.000 claims abstract description 131
- 230000008569 process Effects 0.000 claims abstract description 101
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 claims abstract description 81
- 239000000463 material Substances 0.000 claims abstract description 80
- 239000000292 calcium oxide Substances 0.000 claims abstract description 75
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 claims abstract description 71
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 52
- 239000003623 enhancer Substances 0.000 claims abstract description 51
- 239000007900 aqueous suspension Substances 0.000 claims abstract description 43
- 238000002156 mixing Methods 0.000 claims abstract description 27
- 229910000019 calcium carbonate Inorganic materials 0.000 claims description 101
- 235000012255 calcium oxide Nutrition 0.000 claims description 74
- 239000002105 nanoparticle Substances 0.000 claims description 68
- 239000000203 mixture Substances 0.000 claims description 67
- 239000002245 particle Substances 0.000 claims description 61
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 38
- 229960005069 calcium Drugs 0.000 claims description 38
- 239000011575 calcium Substances 0.000 claims description 38
- 229910052791 calcium Inorganic materials 0.000 claims description 38
- 239000000725 suspension Substances 0.000 claims description 30
- 229920000642 polymer Polymers 0.000 claims description 26
- 239000000654 additive Substances 0.000 claims description 24
- 239000004033 plastic Substances 0.000 claims description 23
- 229920003023 plastic Polymers 0.000 claims description 23
- 230000000996 additive effect Effects 0.000 claims description 20
- ZCCIPPOKBCJFDN-UHFFFAOYSA-N calcium nitrate Chemical compound [Ca+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O ZCCIPPOKBCJFDN-UHFFFAOYSA-N 0.000 claims description 20
- 239000007787 solid Substances 0.000 claims description 20
- 238000001035 drying Methods 0.000 claims description 18
- 239000000123 paper Substances 0.000 claims description 17
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 claims description 16
- -1 organic acid salts Chemical class 0.000 claims description 16
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 claims description 12
- 238000000576 coating method Methods 0.000 claims description 12
- 239000003973 paint Substances 0.000 claims description 12
- 239000002537 cosmetic Substances 0.000 claims description 11
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 claims description 10
- 239000012756 surface treatment agent Substances 0.000 claims description 8
- ZHJGWYRLJUCMRT-UHFFFAOYSA-N 5-[6-[(4-methylpiperazin-1-yl)methyl]benzimidazol-1-yl]-3-[1-[2-(trifluoromethyl)phenyl]ethoxy]thiophene-2-carboxamide Chemical compound C=1C=CC=C(C(F)(F)F)C=1C(C)OC(=C(S1)C(N)=O)C=C1N(C1=C2)C=NC1=CC=C2CN1CCN(C)CC1 ZHJGWYRLJUCMRT-UHFFFAOYSA-N 0.000 claims description 7
- 239000001110 calcium chloride Substances 0.000 claims description 7
- 229960002713 calcium chloride Drugs 0.000 claims description 7
- 229910001628 calcium chloride Inorganic materials 0.000 claims description 7
- 150000004676 glycans Chemical class 0.000 claims description 7
- 239000005017 polysaccharide Substances 0.000 claims description 7
- 229920001282 polysaccharide Polymers 0.000 claims description 7
- WCLKSQYCWXZMGX-UHFFFAOYSA-N 1,2,3,4-tetrabromo-5,6-dimethoxybenzene Chemical compound COC1=C(Br)C(Br)=C(Br)C(Br)=C1OC WCLKSQYCWXZMGX-UHFFFAOYSA-N 0.000 claims description 6
- SIWNEELMSUHJGO-UHFFFAOYSA-N 2-(4-bromophenyl)-4,5,6,7-tetrahydro-[1,3]oxazolo[4,5-c]pyridine Chemical compound C1=CC(Br)=CC=C1C(O1)=NC2=C1CCNC2 SIWNEELMSUHJGO-UHFFFAOYSA-N 0.000 claims description 6
- 239000004154 Calcium bromate Substances 0.000 claims description 6
- 239000004301 calcium benzoate Substances 0.000 claims description 6
- 235000010237 calcium benzoate Nutrition 0.000 claims description 6
- 235000019397 calcium bromate Nutrition 0.000 claims description 6
- WGEFECGEFUFIQW-UHFFFAOYSA-L calcium dibromide Chemical compound [Ca+2].[Br-].[Br-] WGEFECGEFUFIQW-UHFFFAOYSA-L 0.000 claims description 6
- HZQXCUSDXIKLGS-UHFFFAOYSA-L calcium;dibenzoate;trihydrate Chemical compound O.O.O.[Ca+2].[O-]C(=O)C1=CC=CC=C1.[O-]C(=O)C1=CC=CC=C1 HZQXCUSDXIKLGS-UHFFFAOYSA-L 0.000 claims description 6
- RAFRTSDUWORDLA-UHFFFAOYSA-N phenyl 3-chloropropanoate Chemical compound ClCCC(=O)OC1=CC=CC=C1 RAFRTSDUWORDLA-UHFFFAOYSA-N 0.000 claims description 6
- WHQOKFZWSDOTQP-UHFFFAOYSA-N 2,3-dihydroxypropyl 4-aminobenzoate Chemical compound NC1=CC=C(C(=O)OCC(O)CO)C=C1 WHQOKFZWSDOTQP-UHFFFAOYSA-N 0.000 claims description 5
- PQBXSHPBMBTANE-UHFFFAOYSA-L [Ca+2].[O-]I=O.[O-]I=O Chemical compound [Ca+2].[O-]I=O.[O-]I=O PQBXSHPBMBTANE-UHFFFAOYSA-L 0.000 claims description 5
- VSGNNIFQASZAOI-UHFFFAOYSA-L calcium acetate Chemical compound [Ca+2].CC([O-])=O.CC([O-])=O VSGNNIFQASZAOI-UHFFFAOYSA-L 0.000 claims description 5
- 239000001639 calcium acetate Substances 0.000 claims description 5
- 229960005147 calcium acetate Drugs 0.000 claims description 5
- 235000011092 calcium acetate Nutrition 0.000 claims description 5
- NKWPZUCBCARRDP-UHFFFAOYSA-L calcium bicarbonate Chemical compound [Ca+2].OC([O-])=O.OC([O-])=O NKWPZUCBCARRDP-UHFFFAOYSA-L 0.000 claims description 5
- 229910000020 calcium bicarbonate Inorganic materials 0.000 claims description 5
- 229910001622 calcium bromide Inorganic materials 0.000 claims description 5
- YALMXYPQBUJUME-UHFFFAOYSA-L calcium chlorate Chemical compound [Ca+2].[O-]Cl(=O)=O.[O-]Cl(=O)=O YALMXYPQBUJUME-UHFFFAOYSA-L 0.000 claims description 5
- 229940095672 calcium sulfate Drugs 0.000 claims description 5
- 235000011132 calcium sulphate Nutrition 0.000 claims description 5
- 150000002016 disaccharides Chemical class 0.000 claims description 5
- 150000002772 monosaccharides Chemical class 0.000 claims description 5
- OCUCCJIRFHNWBP-IYEMJOQQSA-L Copper gluconate Chemical class [Cu+2].OC[C@@H](O)[C@@H](O)[C@H](O)[C@@H](O)C([O-])=O.OC[C@@H](O)[C@@H](O)[C@H](O)[C@@H](O)C([O-])=O OCUCCJIRFHNWBP-IYEMJOQQSA-L 0.000 claims description 4
- 239000000853 adhesive Substances 0.000 claims description 4
- 230000001070 adhesive effect Effects 0.000 claims description 4
- 239000011248 coating agent Substances 0.000 claims description 4
- 150000004677 hydrates Chemical class 0.000 claims description 4
- 239000000825 pharmaceutical preparation Substances 0.000 claims description 4
- 229940127557 pharmaceutical product Drugs 0.000 claims description 4
- 150000005846 sugar alcohols Chemical class 0.000 claims description 4
- 229920001732 Lignosulfonate Polymers 0.000 claims description 3
- ABLZXFCXXLZCGV-UHFFFAOYSA-N Phosphorous acid Chemical class OP(O)=O ABLZXFCXXLZCGV-UHFFFAOYSA-N 0.000 claims description 3
- LLSDKQJKOVVTOJ-UHFFFAOYSA-L calcium chloride dihydrate Chemical compound O.O.[Cl-].[Cl-].[Ca+2] LLSDKQJKOVVTOJ-UHFFFAOYSA-L 0.000 claims description 3
- 229940052299 calcium chloride dihydrate Drugs 0.000 claims description 3
- 150000007524 organic acids Chemical class 0.000 claims description 3
- 235000005985 organic acids Nutrition 0.000 claims description 3
- XTEGARKTQYYJKE-UHFFFAOYSA-M Chlorate Chemical compound [O-]Cl(=O)=O XTEGARKTQYYJKE-UHFFFAOYSA-M 0.000 claims 2
- SGPGESCZOCHFCL-UHFFFAOYSA-N Tilisolol hydrochloride Chemical compound [Cl-].C1=CC=C2C(=O)N(C)C=C(OCC(O)C[NH2+]C(C)(C)C)C2=C1 SGPGESCZOCHFCL-UHFFFAOYSA-N 0.000 claims 2
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 claims 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-M Bicarbonate Chemical compound OC([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-M 0.000 claims 1
- VLTRZXGMWDSKGL-UHFFFAOYSA-M perchlorate Inorganic materials [O-]Cl(=O)(=O)=O VLTRZXGMWDSKGL-UHFFFAOYSA-M 0.000 claims 1
- VLTRZXGMWDSKGL-UHFFFAOYSA-N perchloric acid Chemical compound OCl(=O)(=O)=O VLTRZXGMWDSKGL-UHFFFAOYSA-N 0.000 claims 1
- 238000001556 precipitation Methods 0.000 abstract 1
- 235000010216 calcium carbonate Nutrition 0.000 description 96
- 239000000047 product Substances 0.000 description 45
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 37
- 229910002092 carbon dioxide Inorganic materials 0.000 description 22
- 238000006243 chemical reaction Methods 0.000 description 20
- 239000013078 crystal Substances 0.000 description 18
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 16
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 16
- 239000001569 carbon dioxide Substances 0.000 description 14
- 238000000227 grinding Methods 0.000 description 13
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 12
- 235000011941 Tilia x europaea Nutrition 0.000 description 12
- 239000004571 lime Substances 0.000 description 12
- 239000000243 solution Substances 0.000 description 10
- 238000009826 distribution Methods 0.000 description 9
- 238000001238 wet grinding Methods 0.000 description 9
- 238000001354 calcination Methods 0.000 description 8
- 239000007788 liquid Substances 0.000 description 8
- 229910000514 dolomite Inorganic materials 0.000 description 7
- 238000004519 manufacturing process Methods 0.000 description 7
- 239000004579 marble Substances 0.000 description 7
- 238000005259 measurement Methods 0.000 description 7
- 239000002002 slurry Substances 0.000 description 7
- 230000015572 biosynthetic process Effects 0.000 description 6
- 239000010459 dolomite Substances 0.000 description 6
- 238000009837 dry grinding Methods 0.000 description 6
- 239000011541 reaction mixture Substances 0.000 description 6
- 239000000126 substance Substances 0.000 description 6
- 235000000346 sugar Nutrition 0.000 description 6
- 235000019738 Limestone Nutrition 0.000 description 5
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 5
- CZMRCDWAGMRECN-UGDNZRGBSA-N Sucrose Chemical compound O[C@H]1[C@H](O)[C@@H](CO)O[C@@]1(CO)O[C@@H]1[C@H](O)[C@@H](O)[C@H](O)[C@@H](CO)O1 CZMRCDWAGMRECN-UGDNZRGBSA-N 0.000 description 5
- 229930006000 Sucrose Natural products 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 239000000945 filler Substances 0.000 description 5
- 238000001914 filtration Methods 0.000 description 5
- 239000006028 limestone Substances 0.000 description 5
- 239000000843 powder Substances 0.000 description 5
- 229960004793 sucrose Drugs 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 229910021532 Calcite Inorganic materials 0.000 description 4
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 4
- 238000002441 X-ray diffraction Methods 0.000 description 4
- 239000012736 aqueous medium Substances 0.000 description 4
- 239000007864 aqueous solution Substances 0.000 description 4
- 229910001424 calcium ion Inorganic materials 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 235000014113 dietary fatty acids Nutrition 0.000 description 4
- 239000000194 fatty acid Substances 0.000 description 4
- 229930195729 fatty acid Natural products 0.000 description 4
- 239000000706 filtrate Substances 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 238000010907 mechanical stirring Methods 0.000 description 4
- 239000001509 sodium citrate Substances 0.000 description 4
- NLJMYIDDQXHKNR-UHFFFAOYSA-K sodium citrate Chemical compound O.O.[Na+].[Na+].[Na+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O NLJMYIDDQXHKNR-UHFFFAOYSA-K 0.000 description 4
- 235000011083 sodium citrates Nutrition 0.000 description 4
- KDYFGRWQOYBRFD-UHFFFAOYSA-N succinic acid Chemical class OC(=O)CCC(O)=O KDYFGRWQOYBRFD-UHFFFAOYSA-N 0.000 description 4
- 239000005720 sucrose Substances 0.000 description 4
- 238000010923 batch production Methods 0.000 description 3
- 159000000007 calcium salts Chemical class 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 3
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 3
- 238000010924 continuous production Methods 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 239000008367 deionised water Substances 0.000 description 3
- 150000004665 fatty acids Chemical class 0.000 description 3
- 239000001095 magnesium carbonate Substances 0.000 description 3
- ZLNQQNXFFQJAID-UHFFFAOYSA-L magnesium carbonate Chemical compound [Mg+2].[O-]C([O-])=O ZLNQQNXFFQJAID-UHFFFAOYSA-L 0.000 description 3
- 229910000021 magnesium carbonate Inorganic materials 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 229910001220 stainless steel Inorganic materials 0.000 description 3
- 239000010935 stainless steel Substances 0.000 description 3
- 239000003039 volatile agent Substances 0.000 description 3
- FALRKNHUBBKYCC-UHFFFAOYSA-N 2-(chloromethyl)pyridine-3-carbonitrile Chemical class ClCC1=NC=CC=C1C#N FALRKNHUBBKYCC-UHFFFAOYSA-N 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- 238000004438 BET method Methods 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 2
- 238000013019 agitation Methods 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 150000001720 carbohydrates Chemical class 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-N carbonic acid Chemical compound OC(O)=O BVKZGUZCCUSVTD-UHFFFAOYSA-N 0.000 description 2
- 238000005119 centrifugation Methods 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 239000000470 constituent Substances 0.000 description 2
- 239000002270 dispersing agent Substances 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 238000001125 extrusion Methods 0.000 description 2
- 239000012065 filter cake Substances 0.000 description 2
- 239000010419 fine particle Substances 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 125000004435 hydrogen atom Chemical group [H]* 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- GUBGYTABKSRVRQ-QKKXKWKRSA-N lactose group Chemical group OC1[C@H](O)[C@@H](O)[C@H](O[C@H]2[C@H](O)[C@@H](O)[C@@H](O)[C@H](O2)CO)[C@H](O1)CO GUBGYTABKSRVRQ-QKKXKWKRSA-N 0.000 description 2
- 238000000691 measurement method Methods 0.000 description 2
- 235000013336 milk Nutrition 0.000 description 2
- 210000004080 milk Anatomy 0.000 description 2
- 230000000877 morphologic effect Effects 0.000 description 2
- 239000012452 mother liquor Substances 0.000 description 2
- 238000001728 nano-filtration Methods 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 150000003014 phosphoric acid esters Chemical class 0.000 description 2
- 229920000371 poly(diallyldimethylammonium chloride) polymer Polymers 0.000 description 2
- 229920000058 polyacrylate Polymers 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 230000001376 precipitating effect Effects 0.000 description 2
- 239000011435 rock Substances 0.000 description 2
- 238000010008 shearing Methods 0.000 description 2
- 229910000029 sodium carbonate Inorganic materials 0.000 description 2
- 239000011343 solid material Substances 0.000 description 2
- 238000001694 spray drying Methods 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 125000001424 substituent group Chemical group 0.000 description 2
- 239000001384 succinic acid Substances 0.000 description 2
- 235000011044 succinic acid Nutrition 0.000 description 2
- 229940014800 succinic anhydride Drugs 0.000 description 2
- QNRATNLHPGXHMA-XZHTYLCXSA-N (r)-(6-ethoxyquinolin-4-yl)-[(2s,4s,5r)-5-ethyl-1-azabicyclo[2.2.2]octan-2-yl]methanol;hydrochloride Chemical compound Cl.C([C@H]([C@H](C1)CC)C2)CN1[C@@H]2[C@H](O)C1=CC=NC2=CC=C(OCC)C=C21 QNRATNLHPGXHMA-XZHTYLCXSA-N 0.000 description 1
- WKBPZYKAUNRMKP-UHFFFAOYSA-N 1-[2-(2,4-dichlorophenyl)pentyl]1,2,4-triazole Chemical compound C=1C=C(Cl)C=C(Cl)C=1C(CCC)CN1C=NC=N1 WKBPZYKAUNRMKP-UHFFFAOYSA-N 0.000 description 1
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 description 1
- NIXOWILDQLNWCW-UHFFFAOYSA-N 2-Propenoic acid Natural products OC(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 1
- 235000014653 Carica parviflora Nutrition 0.000 description 1
- KRKNYBCHXYNGOX-UHFFFAOYSA-K Citrate Chemical compound [O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O KRKNYBCHXYNGOX-UHFFFAOYSA-K 0.000 description 1
- 241000243321 Cnidaria Species 0.000 description 1
- FBPFZTCFMRRESA-FSIIMWSLSA-N D-Glucitol Natural products OC[C@H](O)[C@H](O)[C@@H](O)[C@H](O)CO FBPFZTCFMRRESA-FSIIMWSLSA-N 0.000 description 1
- FBPFZTCFMRRESA-JGWLITMVSA-N D-glucitol Chemical compound OC[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO FBPFZTCFMRRESA-JGWLITMVSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- QPCDCPDFJACHGM-UHFFFAOYSA-N N,N-bis{2-[bis(carboxymethyl)amino]ethyl}glycine Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(=O)O)CCN(CC(O)=O)CC(O)=O QPCDCPDFJACHGM-UHFFFAOYSA-N 0.000 description 1
- 101710156645 Peptide deformylase 2 Proteins 0.000 description 1
- 239000006004 Quartz sand Substances 0.000 description 1
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 238000009621 Solvay process Methods 0.000 description 1
- 235000021355 Stearic acid Nutrition 0.000 description 1
- MCMNRKCIXSYSNV-UHFFFAOYSA-N ZrO2 Inorganic materials O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 150000007933 aliphatic carboxylic acids Chemical class 0.000 description 1
- 239000012670 alkaline solution Substances 0.000 description 1
- 229910000323 aluminium silicate Inorganic materials 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 239000011324 bead Substances 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- FNAQSUUGMSOBHW-UHFFFAOYSA-H calcium citrate Chemical compound [Ca+2].[Ca+2].[Ca+2].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O.[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O FNAQSUUGMSOBHW-UHFFFAOYSA-H 0.000 description 1
- 239000001354 calcium citrate Substances 0.000 description 1
- 229920005551 calcium lignosulfonate Polymers 0.000 description 1
- RYAGRZNBULDMBW-UHFFFAOYSA-L calcium;3-(2-hydroxy-3-methoxyphenyl)-2-[2-methoxy-4-(3-sulfonatopropyl)phenoxy]propane-1-sulfonate Chemical compound [Ca+2].COC1=CC=CC(CC(CS([O-])(=O)=O)OC=2C(=CC(CCCS([O-])(=O)=O)=CC=2)OC)=C1O RYAGRZNBULDMBW-UHFFFAOYSA-L 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 150000005323 carbonate salts Chemical class 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 230000003750 conditioning effect Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 229920001577 copolymer Polymers 0.000 description 1
- 238000002447 crystallographic data Methods 0.000 description 1
- 150000004691 decahydrates Chemical class 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 235000013681 dietary sucrose Nutrition 0.000 description 1
- 150000004683 dihydrates Chemical class 0.000 description 1
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 1
- KPUWHANPEXNPJT-UHFFFAOYSA-N disiloxane Chemical class [SiH3]O[SiH3] KPUWHANPEXNPJT-UHFFFAOYSA-N 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 235000021463 dry cake Nutrition 0.000 description 1
- 238000002296 dynamic light scattering Methods 0.000 description 1
- 150000002148 esters Chemical class 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000005187 foaming Methods 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 238000005194 fractionation Methods 0.000 description 1
- 150000004688 heptahydrates Chemical class 0.000 description 1
- 150000004687 hexahydrates Chemical class 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000008101 lactose Substances 0.000 description 1
- 229910001607 magnesium mineral Inorganic materials 0.000 description 1
- 238000010297 mechanical methods and process Methods 0.000 description 1
- 230000005226 mechanical processes and functions Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
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- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 description 1
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- 229920001495 poly(sodium acrylate) polymer Polymers 0.000 description 1
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- 239000004800 polyvinyl chloride Substances 0.000 description 1
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- UJPWWRPNIRRCPJ-UHFFFAOYSA-L strontium;dihydroxide;octahydrate Chemical compound O.O.O.O.O.O.O.O.[OH-].[OH-].[Sr+2] UJPWWRPNIRRCPJ-UHFFFAOYSA-L 0.000 description 1
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- GFQYVLUOOAAOGM-UHFFFAOYSA-N zirconium(iv) silicate Chemical compound [Zr+4].[O-][Si]([O-])([O-])[O-] GFQYVLUOOAAOGM-UHFFFAOYSA-N 0.000 description 1
Abstract
The present invention is directed to a process for producing an aqueous suspension of precipitated calcium carbonate, wherein a milk of lime is prepared by mixing water, a calcium oxide containing material, and a precipitation enhancer, and subsequently, the milk of lime is carbonated to form an aqueous suspension of precipitated calcium carbonate.
Description
PCC with reduced portlandite content
The présent invention relates to a process for the production of precipitated calcium carbonate, a precipitated calcium carbonate obtained by said process, and its use.
Calcium carbonate is one of the most commonly used additives in the paper, paint and plastics industries. While naturally occurring ground calcium carbonate (GCC) is usually used as a fHier in many applications, synthetically manufactured precipitated calcium carbonate (PCC) may be tailor-made with respect to its morphology and particle size allowing PCC to fulfil additional functions.
Commonly known PCC production processes include the steps of slaking quicklime with water, whereby a suspension of fine particles of calcium hydroxide, also known as portlandite, is formed, and subsequentiy precipitating calcium carbonate by passing carbon dioxide through the resulting portlandite suspension. The carbon dioxide dissolves and dissociâtes in the water, providing carbonate ions to react with the free calcium ions from the dissolved portlandite. This leads to an oversaturation of calcium carbonate in solution, resulting in the précipitation of calcium carbonate. As calcium carbonate forms, more portlandite dissolves. Therefore, the highest point of the calcium carbonate concentration is near the surface of the portlandite particles, and consequently, in this région the oversaturation is at its maximum. As the PCC continues to grow near to the surface of the portlandite particle, some of the portlandite may get overgrown, and incorporated in or associated with the forming PCC. The resuit is a precipitated calcium carbonate containing a significant amount of residual portlandite, which can be as high as 10 wt.-%. With time, the portlandite can leach into the water phase, resulting in high alkalinity of the sample.
Depending on the field of application, such high alkalinity may hâve a négative impact. For example, the high alkalinity of the filler can promote association of volatiles, and especialiy water, with the minerai filler. If such a filler is employed in polymer or plastic applications, gas bubbles may form during the production process of the polymer or plastic. This may lead to formation of defects resulting from the gas bubbles during plastic production, for example, during the melting or extrusion step. In polymer film extrusion such gas bubbles can become elongated and “frozen” in the fabricated film, taking on the shape of a lens, a phenomenon also known as “leasing”. The afore-mentioned effects may resuit in dégradation of the quality of the
-2final mineral-comprising polymer product during the processing of such minerai filler-comprisîng products. Moreover, associated volatiles may lead to a réduction in the tensile and tear strength of a breathable film, and may dégradé its visible aspects, in particular its visible uniformity. Volatiles can also generate excessive foaming of the minerai filled polymer melt during a step of compounding, causing unwanted product build-up at the vacuum extraction, and hence, forcing a reduced output rate.
WO 99/51691 A1 describes a method of producing a precipitated calcium carbonate (PCC) product having a coarse crystalline form, which inter alia comprises the step of preparing a suspension in an aqueous medium of calcium hydroxide particles which partially dissolve, thus providing calcium ions in the aqueous medium, the aqueous medium also incorporating an agent which promotes release into solution in the aqueous medium of calcium ions from the calcium hydroxide, wherein said agent comprises a water-soluble organic compound. US 5,695,733 A discloses precipitated calcium carbonate particles in clustered form, which when used as fillers impart improved strength, opacity and other advantages to paper, and are prepared by a process involving adding lime and carbon dioxide to a reaction mixture containing seed material having a scalenohedral morphology, the lime and carbon dioxide being added simultaneously.
US 5,741,471 A relates to a process for the précipitation of discrète prismatic calcium carbonate particles by carbonation of aqueous calcium hydroxide containing a saccharide, a polysaccharide, or a saccharide or polysaccharide and a métal ion. US 5,332,564 A describes a process for producing rhombic or barrel shaped precipitated calcium carbonate. Quicklime is slaked in an aqueous solution containing about 0.1% to about 2% by weight of a sugar, based upon the weight ofthe CaCO3 to be produced. US 5,811,070 A discloses a process for producing calcium carbonate particles having an average size of 0.1 to 1.0 pm, the process comprising the steps of introducing carbon dioxide into a milk of lime containing a first reagent to prépare an aqueous suspension containing calcium carbonate particles of 0.4 pm in average size, adding a miik of lime into the aqueous suspension, and continuously reacting a carbonated solution containing a second reagent with the aqueous suspension.
-3 WO 2006/109168 A2 and WO 2006/109171 A1 are concerned with a carbonation process using a reduced flow rate of carbon dioxide, which leads to porous agglomérâtes of precipitated calcium carbonate of a very spécifie structure and unique properties, followed by an upconcentration step to increase the solids content. A process for preparing a precipitated calcium carbonate involving the use of a spécifie polymer during the carbonation step is disclosed in WO 2010/018432 A1.
In view of the foregoing, there is a continuous need for processes providing precipitated calcium carbonate, and especially for processes that allow the production of PCC with a low portlandite content.
Accordingiy, it is an object of the présent invention to provide a process for producing a PCC siurry with a low portlandite content. It is also désirable that said process does not affect the kinetics of the carbonation step in a négative way and/or does not impair the desired morphological structure of the PCC.
The foregoing and other objects are solved by the subject-matter as defined herein in the independent claims.
According to one aspect of the présent invention, a process for producing an aqueous suspension of precipitated calcium carbonate is provîded, comprising the steps of:
i) providing a calcium oxide containing material, ii) providing a précipitation enhancer selected from the group consisting of calcium carbonate nanoparticles and/or a water-soluble calcium sait, iii) preparing a milk of lime by mixing water, the calcium oxide containing material of step i), and the précipitation enhancer of step ii), and iv) carbonating the milk of lime obtained from step iii) to form an aqueous suspension of precipitated calcium carbonate.
According to a further aspect a process for producing precipitated calcium carbonate is provîded comprising the steps i) to iv) of the process according to the présent invention, and further a
-4step v) of separating the precipitated calcium carbonate from the aqueous suspension obtained from step iv).
According to still a further aspect of the présent invention, an aqueous suspension of precipitated calcium carbonate obtainable by the process according to the présent invention is provided.
According to still a further aspect of the présent invention, precipitated calcium carbonate obtainable by a process according to the présent invention is provided.
According to still a further aspect of the présent invention, a product comprising the precipitated calcium carbonate according to the présent invention is provided, wherein preferably the product is a paper, a paper product, an ink, a paint, a coating, a plastic, a polymer composition, an adhesive, a building product, a foodstuff, an agricultural product, a cosmetic product or a pharmaceutical product, and more preferably the product is a plastic or a polymer composition.
According to still a further aspect of the présent invention a use of an aqueous suspension of precipitated calcium carbonate according to the présent invention in paper, plastics, polymer compositions, paint, coatings, concrète, cosmetics, pharmaceutics and/or agriculture applications is provided.
According to still a further aspect of the présent invention a use of a precipitated calcium carbonate according to the présent invention in paper, plastics, polymer compositions, paint, coatings, concrète, cosmetics, pharmaceutics and/or agriculture applications is provided, wherein preferably a dried precipitated calcium carbonate is used in plastics and/or polymer compositions.
According to still a further aspect of the présent invention a use of calcium carbonate nanoparticles and/or a water-soluble calcium sait in a process for producing an aqueous suspension of precipitated calcium carbonate is provided.
-5Advantages embodiment of the présent invention are defined in the corresponding sub-claims.
According to one embodiment step iii) comprises the steps of: a1 ) mixing the calcium oxide containing material of step i) with water, and a2) adding the précipitation enhancer of step ii) to the mixture of step a1 ). According to another embodiment step iii) comprises the steps of: b1 ) mixing the précipitation enhancer of step ii) with water, and b2) adding the calcium oxide containing material of step i) to the mixture of step b1).
According to one embodiment the calcium carbonate nanoparticles hâve a number based médian particle size d50 of less than 150 nm, preferably from 1 to 130 nm, more preferably from 5 to 90 nm, even more preferably from 10 to 80 nm, and most preferably from 30 to 70 nm. According to one embodiment the water-soluble calcium sait is an anhydrous sait or hydrate sait, preferably selected from the group consisting of calcium nitrate, calcium sulfate, calcium acetate, calcium benzoate, calcium bicarbonate, calcium bromate, calcium bromide, calcium chlorate, calcium chloride, calcium iodite, calcium nitrite, calcium perchlorate, calcium permanganate, hydrates thereof, and mixtures thereof, more preferably selected from the group consisting of calcium nitrate, calcium sulfate, calcium acetate, calcium benzoate, calcium bicarbonate, calcium bromate, calcium bromide, calcium chlorate, calcium chloride, calcium iodite, calcium nitrite, calcium perchlorate, calcium permanganate, calcium nitrate tetrahydrate, calcium chloride dihydrate, and mixtures thereof, and most preferably selected from the group consisting of calcium nitrate, calcium nitrate tetra hydrate, calcium chloride, calcium chloride dihydrate, and mixtures thereof.
According to one embodiment the précipitation enhancer of step ii) is added in an amount from 0.01 to 25 wt.-%, based on the total weight of the calcium oxide containing material, preferably in an amount from 0.1 to 20 wt.-%, more preferably from 1 to 15 wt.-%, and most preferably from 5 to 10 wt.-%.
According to one embodiment a slaking additive is added before, during or after step iii), preferably the slaking additive is selected from the group consisting of organic acids, organic acid salts, sugar alcohols, monosaccharides, disaccharides, polysaccharides, gluconates,
-6phosphonates, lignosulfonates, and mixtures thereof. According to another embodiment the slaking additive is added in an amount from 0.01 to 2 wt-%, based on the total amount of calcium oxide containing material, preferably in an amount from 0.05 to 1 wt.-%, more preferably in an amount from 0.06 to 0.8 wt.-%, and most preferably in an amount from 0.07 to 0.5 wt.-%.
According to one embodiment the obtained suspension of precipitated calcium carbonate has a solids content of at least 5 wt.-%, preferably from 10 to 50 wt.-%, more preferably from 12 to 45 wt.-%, and most preferably from 14 to 40 wt-%, based on the total weight of the suspension.
According to another embodiment the obtained precipitated calcium carbonate has a portlandite content of less than 1 wt.-%, and preferably less than 0.1 wt.-%, based on the total weight of the dried precipitated calcium carbonate. According to still another embodiment the milk of lime is screened after step iii) and before step iv), preferably with a screen having a sieve size from 100 to 300 pm.
According to one embodiment the process for producing precipitated calcium carbonate further comprises a step vi) of drying the separated precipitated calcium carbonate obtained from step
v), and optionally a step vii) of contacting at least a part of the surface of the precipitated calcium carbonate with a surface-treatment agent. According to another embodiment the precipitated calcium carbonate obtainable by the process of the présent invention is a dried precipitated calcium carbonate, optionally comprising a treatment layer on at least a part of the surface of the precipitated calcium carbonate.
It should be understood that for the purpose of the présent invention, the following terms hâve the following meaning:
A “calcium oxide containing material” in the meaning of the présent invention can be a minerai or a synthetic material having a content of calcium oxide of at least 50 wt.-%, preferably 75 wt.%, more preferably 90 wt.-%, and most preferably 95 wt.-%, based on the total weight of the calcium oxide containing material. For the purpose of the présent invention, a “minerai material”
-7îs a solid substance having a definite inorganic Chemical composition and characteristic crystalline and/or amorphous structure.
“Ground calcium carbonate” (GCC) in the meaning of the présent invention is a calcium carbonate obtained from natural sources, such as limestone, marble, or chalk, and processed through a wet and/or dry treatment such as grinding, screening and/or fractionation, for example by a cyclone or classifier.
Throughout the présent document, the “particle size” of precipitated calcium carbonate, or other particulate materials is described by its distribution of particle sizes. The value dx représente the diameter relative to which x % by weight of the particles hâve diameters less than dx. This means that the cfeo value is the particle size at which 20 wt.-% of ali particles are smaller, and the dÿ& value is the particle size at which 98 wt.-% of ail particles are smaller. The d9& value is also designated as “top eut”. The d50 value is thus the weight médian particle size, i.e. 50 wt-% of ail grains are bigger or smaller than this particle size. For the purpose of the présent invention the particle size is specified as weight médian particle size d5o unless indicated otherwise. For determining the weight médian particle size d50 value or the top eut particle size d93 value of particles in the range of 0.2 to 100 pm a Sedigraph 5100 or 5120 device from the company Micromeritics, USA, can be used. For the purpose of the présent invention, the “particle size” of calcium carbonate nanoparticles is described as number determined particie size distribution. For determining the number based particle size distribution, e.g., the number based médian particle size (d^) or the number based top eut particle size (t/98) of calcium carbonate nanoparticles, a Malvern Zetasïzer Nano ZS can be used.
For the purpose of the présent invention, the term “nanoparticles” refers to fine particles having a number based particle size distribution in the nanometer range. For example, the nanoparticles may hâve a number based médian particle size dso of less than 150 nm in ali three dimensions of the particle. For determining the number based médian particle size d50 value or the number based top eut particle size dÿa value of nanoparticles, a Malvern Zetasïzer Nano ZS can be used.
-8“Precipitated calcium carbonate” (PCC) in the meaning of the présent invention is a synthesized material, generally obtained by précipitation following a reaction of carbon dioxide and calcium hydroxide (hydrated lime) in an aqueous environment or by précipitation of a calcium- and a carbonate source in water. Additionally, precipitated calcium carbonate can also be the product of introducing calcium and carbonate salts, calcium chloride and sodium carbonate for example, in an aqueous environment. PCC may be vaterite, calcîte or aragonite. PCCs are described, for example, in EP 2 447 213 A1, EP 2 524 898 A1,EP 2 371 766 A1, or WO 2013/142473 A1.
As used herein, the term “portlandite” refers to Ca(OH)2, which can be présent in a trigonal crystal structure, and may be formed during lime slaking.
For the purpose of the présent invention, the “solids content” of a liquid composition is a measure of the amount of material remaining after ail the solvent or water has been evaporated.
A “spécifie BET surface area” (SSA) in the meaning of the présent invention is defined as the surface area of the precipitated calcium carbonate particles divided by the mass of PCC particles. As used therein the spécifie surface area is measured by absorption using the BET isotherm (ISO 9277:1995) and is specified in m2/g.
For the purpose of the présent invention, the term “viscosity” or “Brookfield viscosity” refers to Brookfield viscosity. The Brookfield viscosity is for this purpose measured by a Brookfield (Type RVT) viscometer at 25°C ± 1°C at 100 rpm using an appropriate spindle of the Brookfield RVspindle set and is specified in mPa s. Based on his technical knowledge, the skilled person will select a spindle from the Brookfield RV-spindle set which is suitable for the viscosity range to be measured. For example, for a viscosity range between 200 and 800 mPa s the spindle number 3 may be used, for a viscosity range between 400 and 1600 mPa s the spindle number 4 may be used, and for a viscosity range between 800 and 3200 mPa-s the spindle number 5 may be used.
For the purpose of the présent application, “water-insoluble” materials are defined as materials which, when 100 g of said material is mixed with 100 g deionised water and filtered on a filter
-9having a 0.2 μη pore size at 20 °C to recover the liquid filtrate, provide less than or equal to 0.1 g of recovered solid material following évaporation at 95 to 100°C of 100 g of said liquid filtrate. “Water-soluble materials are defined as matériels which, when 100 g of said material is mixed with 100 g deionised water and filtered on a filter having a 0.2 pm pore size at 20 °C to recover the liquid filtrate, provide more than 0.1 g of recovered solid material following évaporation at 95 to 100°C of 100 g of said liquid filtrate.
A “suspension” or “slurry in the meaning of the présent invention comprises insoluble solids and water, and optionally further additives, and usually contains large amounts of solids and, thus, is more viscous and can be of higher density than the liquid from which it is formed.
Unless specified otherwise, the term “drying” refers to a process according to which at least a portion of water is removed from a material to be dried such that a constant weight of the obtained “dried” material at 120 °C is reached. Moreover, a “dried” material may be further defined by its total moisture content which, unless specified otherwise, is less than or equal to 1.0 wt.-%, preferably less than or equal to 0.5 wt.-%, more preferably less than or equal to 0.2 wt.-%, and most preferably between 0.03 and 0.07 wt.-%, based on the total weight of the dried material.
The “total moisture content” of a material refers to the percentage of moisture (i.e. water) which may be desorbed from a sample upon heating to 220°C.
Where the term “comprising” is used in the présent description and daims, it does not exclude other éléments. For the purposes of the présent invention, the term “consisting of is considered to be a preferred embodiment of the term “comprising of’. If, hereinafter, a group is defined to comprise at least a certain number of embodiments, this is also to be understood to disclose a group, which preferably consists only of these embodiments.
Where an indefinite or definite article is used when referring to a singular noun, e.g. “a”, “an” or “the”, this includes a plural of that noun unless something else is specifically stated.
-10Terms like “obtainable” or “definable” and “obtained” or “defined” are used interchangeably. This e.g. means that, unless the context clearly dictâtes otherwise, the term “obtained” does not mean to indicate that e.g. an embodiment must be obtained by e.g. the sequence of steps following the term “obtained” even though such a limited understanding is always included by the terms “obtained” or “defined” as a preferred embodiment.
The inventive process for producing an aqueous suspension of precipitated calcium carbonate comprises the steps of (i) providing a calcium oxide containing material, (ii) providing a précipitation enhancer, (iii) preparing a milk of lime by mixing water, the calcium oxide containing material of step (i), and the précipitation enhancer of step (ii), and (iv) carbonating the milk of lime obtained from step (iii) to form an aqueous suspension of precipitated calcium carbonate. The précipitation enhancer is selected from the group consisting of calcium carbonate nanoparticles and/or a water-soluble calcium sait.
In the following details and preferred embodiments of the inventive process will be set out in more details. It is to be understood that these technical details and embodiments also apply to the inventive use as well as to the inventive products and their use.
Process step i)
In step i) of the process of the présent invention, a calcium oxide containing material is provided.
The calcium oxide containing material of step i) can be obtained by calcining a calcium carbonate containing material. Calcination is a thermal treatment process applied to calcium carbonate containing materials in order to bring about a thermal décomposition resulting in the formation of calcium oxide and gaseous carbon dioxide. Calcium carbonate containing materials which may be used in such a calcinations process are those selected from the group comprising precipitated calcium carbonates; natural calcium carbonate containing minerais such as marble, limestone and chalk, and mixed alkaline earth carbonate minerais comprising calcium
- 11 carbonate such as dolomite, or calcium carbonate rich fractions from other sources. It is also possible to subject a calcium carbonate containing waste material to a calcination process in order to obtain a calcium oxide containing material.
Calcium carbonate décomposés at about 1000 °C to calcium oxide (commonly known as quicklime). The calcination step may be carried out under conditions and using equipment wellknown to the person skilled in the art. Generally, calcination may be carried out in furnaces or reactors (sometimes referred to as kilns) of various designs including shaft furnaces, rotary kilns, multiple hearth furnaces, and fluidized bed reactors.
The end of the calcination reaction may be determined, e.g. by monitoring the density change, the resîdual carbonate content, e.g. by X-ray diffraction, or the slaking reactivity by common methods.
According to one embodiment of the présent invention, the calcium oxide containing material of step i) is obtained by calcining a calcium carbonate containing material, preferably selected from the group consisting of precipitated calcium carbonate, natural calcium carbonate minerais such as marble, limestone and chalk, mixed alkaline earth carbonate minerais comprising calcium carbonate such as dolomite, and mixtures thereof.
For reasons of efficiency, it is preferred that the calcium oxide containing material has a minimum calcium oxide content of at least 75 wt.-%, preferably at least 90 wt.-%, and most preferably 95 wt-%, based on the total weight of the calcium oxide containing material.
According to one embodiment, the calcium oxide containing material consists of solely calcium oxide.
The calcium oxide containing material can consist of only one type of calcium oxide containing material. Alternatively, the calcium oxide containing material can consist of a mixture of two or more types of calcium oxide containing materials.
- 12The calcium oxide containing material can be used in the inventive process in its original form, i.e. as a raw material, for example, in form of smaller and bigger chunks. Aiternatively, the calcium oxide containing material can be ground before use. According to one embodiment of the présent invention, the calcium oxide containing material is in forms of particles having weight médian particle size d50 from 0.1 to 1000 pm, and preferably from 1 to 500 pm.
Process step ii)
In step ii) of the process of the présent invention a précipitation enhancer is provided, wherein the précipitation enhancer is selected from the group consisting of calcium carbonate nanoparticles and/or a water-soluble calcium sait.
According to one embodiment, calcium carbonate nanoparticles are selected as précipitation enhancer. Thus, in process step ii) calcium carbonate nanoparticles are provided.
The calcium carbonate may be a ground calcium carbonate, a precipitated calcium carbonate, or a mixture thereof.
Ground (or naturel) calcium carbonate (GCC) is understood to be a naturally occurring form of calcium carbonate, mined from sedimentary rocks such as limestone or chalk, or from metamorphic marble rocks, eggshelis or seashells. Calcium carbonate is known to exist as three types of crystal polymorphe: calotte, aragonite and vaterite. Calcite, the most common crystal polymorph, is considered to be the most stable crystal form of calcium carbonate. Less common is aragonite, which has a discrète or clustered needle orthorhombic crystal structure. Vaterite is the rarest calcium carbonate polymorph and is generally unstable. Ground calcium carbonate is almost exclusively of the calcitic polymorph, which is said to be trigonalrhombohedral and represents the most stable of the calcium carbonate polymorphs. The term “source of the calcium carbonate in the meaning of the présent application refers to the naturally occurring minerai material from which the calcium carbonate is obtained. The source
- 13 of the calcium carbonate may comprise further naturally occurring components such as magnésium carbonate, alumino silicate etc.
According to one embodiment of the présent invention the source of ground calcium carbonate (GCC) is selected from marble, chalk, dolomite, limestone, or mixtures thereof. Preferably, the source of ground calcium carbonate is selected from marble. According to one embodiment of the présent invention the GCC is obtained by dry grinding. According to another embodiment of the présent invention the GCC is obtained by wet grinding and subséquent drying.
“Dolomite” in the meaning of the présent invention is a carbonic calcium-magnesium-mineral having the Chemical composition of CaMg(CO3)2 (“CaCO3 MgCO3”). A dolomite minerai may contain at least 30.0 wt.-% MgCO3, based on the total weight of dolomite, preferably more than 35.0 wt.-%, and more preferably more than 40.0 wt.-% MgCO3.
According to one embodiment of the présent invention, the calcium carbonate nanoparticles comprise one ground calcium carbonate. According to another embodiment of the présent invention, the calcium carbonate nanoparticles comprise a mixture of two or more ground calcium carbonates selected from different sources.
“Precipitated calcium carbonate” (POG) in the meaning of the présent invention is a synthesized material, generally obtained by précipitation following reaction of carbon dioxide and lime in an aqueous environment or by précipitation of a calcium and carbonate ion source in water or by précipitation by combining calcium and carbonate ions, for example CaCI2 and Na2CO3, out of solution. Further possible ways of producing PCC are the lime soda process, or the Solvay process in which PCC is a by-product of ammonia production. Precipitated calcium carbonate existe in three primary crystalline forms: calcite, aragonite and vaterite, and there are many different polymorphs (crystal habits) for each of these crystalline forms. Calcite has a trigonal structure with typical crystal habits such as scalenohedral (S-PCC), rhombohedral (R-PCC), hexagonal prismatic, pinacoidal, colloïdal (C-PCC), cubic, and prismatic (P-PCC). Aragonite is an orthorhombic structure with typical crystai habits of twinned hexagonal prismatic crystals, as well as a diverse assortiment of thin elongated prismatic, curved bladed, steep pyramidal, chisel
-14shaped crystals, branching tree, and coral or worm-like form. Vaterite belongs to the hexagonal crystal System. The obtained PCC slurry can be mechanically dewatered and dried.
According to one embodiment of the présent invention, the calcium carbonate nanoparticles comprise one precipitated calcium carbonate. According to another embodiment of the présent invention, the calcium carbonate nanoparticles comprise a mixture of two or more precipitated calcium carbonates selected from different crystalline forms and different polymorphe of precipitated calcium carbonate. For example, the at least one precipitated calcium carbonate may comprise one PCC selected from S-PCC and one PCC selected from R-PCC.
According to one embodiment of the présent invention, the calcium carbonate nanoparticles are ground calcium carbonate nanoparticles. According to another embodiment of the présent invention, the calcium carbonate nanoparticles are precipitated calcium carbonate nanoparticles. According to still another embodiment of the présent invention, the calcium carbonate nanoparticles are a mixture of ground calcium carbonate nanoparticles and precipitated calcium carbonate nanoparticles.
According to one embodiment of the présent invention the calcium carbonate nanoparticles hâve a number based médian particle size d5o of less than 150 nm. According to a preferred embodiment of the présent invention the calcium carbonate nanoparticles hâve a number based médian particle size d50 from 1 to 130 nm, preferably from 5 to 90 nm, more preferably from 10 to 80 nm, and most preferably from 30 to 70 nm.
According to one embodiment of the présent invention the calcium carbonate nanoparticles hâve a number based top eut particle size d98 of less than 350 nm. According to a preferred embodiment of the présent invention the calcium carbonate nanoparticles hâve a number based top eut particle size d98 from 80 to 330 nm, preferably from 90 to 180 nm, more preferably from 100 to 170 nm.
If the calcium carbonate to be used does not yet hâve the desired or required fineness, i.e., particle size, it may be ground in one or more wet or dry grinding steps, preferably several
- 15grinding steps, e.g., two dry and/or wet steps, preferably aqueous grinding steps, to yield the corresponding spherical équivalent diameter.
The grinding may be performed in any of the known grinding equipment with which those skilled in the art are familiarfor grinding calcium carbonate. Conventional bail mills are especially suitable for dry grinding; jet plate mills as well as attritor mills are suitable for wet grinding and combinations of such mills or combinations of one or more such mills with cyclones and screens are also very suitable. Especially conventional attritor mills such as those distributed by the company Dynomill are suitable for wet grinding.
In the case of dry grinding, preferably bail mills are used and preferably iron and/or porcelain beads with a diameter of 0.5 to 10 cm are used as grinding media, especially preferably ironcylpebs with a diameter of 2.5 cm are used.
Grinding balls made of, e.g., zirconium silicate, zirconium dioxide and/or baddeleite with a diameter of 0.2 to 5 mm, preferably 0.2 to 2 mm, but also 0.5 to 5 mm, e.g., 0.5 to 2 mm, are preferred for wet grinding. Quartz sand having an équivalent spherical diameter of 0.1 to 2 mm may also be used.
The calcium carbonate particles in the nanometer range, however, are preferably produced by wet grinding and/or are brought to the desired équivalent diameter, in particular when the material is ground calcium carbonate.
Both dry and wet grinding steps may be performed one after the other, but then the last grinding step is preferably a wet grinding.
The calcium carbonate nanoparticles may hâve a low portlandite content. According to one embodiment, the calcium carbonate nanoparticles contain less than 5 wt.-% portlandite, based on the total weight of the dried calcium carbonate nanoparticles, preferably less than 3 wt.-%, more preferably less than 1 wt.-%, and most preferably less than 0.1 wt.-%.
- 16The calcium carbonate nanoparticles can be produced by any method known in the art.
According to one embodiment of the présent invention, precipitated calcium carbonate nanoparticles are obtained by a process comprising the steps of:
I) providing a calcium oxide containing material,
II) providing a sugar,
Iii) preparing a milk of lime by mixing water, the calcium oxide containing material of step I), and the sugar of step II),
IV) carbonating the milk of lime obtained from step III) to form an aqueous suspension of precipitated calcium carbonate nanoparticles, and
V) separating the precipitated calcium carbonate nanoparticles from the aqueous suspension obtained from step IV).
The sugar may be selected from monosaccharides, disaccharides, and/or polysaccharides. According to one embodiment, the sugar is added in an amount from 0.1 to 20 wt.-%, based on the total weight of the calcium oxide containing material provided in step I), preferably in an amount from 1 to 10 wt.-%, and more preferably in an amount from 2 to 5 wt.-%. Preferably, the sugar is selected from lactose or sucrose.
The calcium carbonate nanoparticles can be provided in dry form. Alternatively, the calcium carbonate nanoparticles can be suspended in water, and thus, form an aqueous suspension or slurry of the calcium carbonate nanoparticles. The obtained suspension can be ground under conditions such that autogenous grinding takes place and/or by horizontal bail milling, and/or other such processes known to the skilled man.
According to one embodiment of the présent invention, the calcium carbonate nanoparticles are in form of a suspension or a filter cake having a solids content of at least 1 wf.-%, preferably from 1 to 50 wt.-%, more preferably from 3 to 40 wt.-%, even more preferably from 5 to 30 wt%, and most preferably from 10 to 20 wt.-%, based on the total weight of the suspension or filter cake.
- 17According to another embodiment, a water-soluble calcium sait is selected as précipitation enhancer. Thus, in process step ii) a water-soluble calcium sait is provided.
The water-soluble calcium sait can be an anhydrous sait or a hydrate sait. According to a preferred embodiment the water-soluble calcium sait is selected from the group consisting of calcium nitrate, calcium sulfate, calcium acetate, calcium benzoate, calcium bicarbonate, calcium bromate, calcium bromide, calcium chlorate, calcium chloride, calcium iodite, calcium nitrite, calcium perchlorate, calcium permanganate, hydrates thereof, and mixtures thereof. As used herein, a “hydrate” is an inorganic sait containing water molécules combined in a definite ratio as an intégral part of the crystal. Depending on the number of water molécules per formula unit of sait, the hydrate may be designated as monohydrate, dihydrate, trihydrate, tetrahydrate, pentahydrate, hexahydrate, heptahydrate, octahydrate, nonahydrate, decahydrate, hemihydrate, etc.
Preferably, the water-soluble calcium sait is selected from the group consisting of calcium nitrate, calcium sulfate, calcium acetate, calcium benzoate, calcium bicarbonate, calcium bromate, calcium bromide, calcium chlorate, calcium chloride, calcium iodite, calcium nitrite, calcium perchlorate, calcium permanganate, calcium nitrate tetrahydrate, calcium chloride dihydrate, and mixtures thereof, and more preferably the water-soluble calcium sait is selected from the group consisting of calcium nitrate, calcium nitrate tetrahydrate, calcium chloride, calcium chloride dihydrate, and mixtures thereof.
According to one embodiment of the présent invention, the water-soluble calcium sait consists of one water-soluble calcium sait only. Alternatively, the water-soluble calcium sait can consist of a mixture of two or more water-soluble calcium salts.
The water-soluble calcium sait can be provided in form of a solution or as a dry materiaî. According to one embodiment, the water-soluble calcium sait is provided in form of an aqueous solution having a calcium sait concentration from 1 to 70 wt.-%, based on the total weight of the aqueous solution, and preferably from 2 to 60 wt.-%.
-18According to a preferred embodiment of the présent invention, the précipitation enhancer is a mixture of calcium carbonate nanoparticles and one or more water-soluble calcium salt(s). According to one embodiment, the précipitation enhancer comprises the calcium carbonate nanoparticles and the water-soluble salt(s) in a mass ratio from 1:10 to 10:1, preferably in a mass ratio from 1:5 to 5:1, more preferably in mass ratio from 1:2 to 2:1, and most preferably in a mass ratio of about 1:1.
According to one embodiment of the présent invention, the précipitation enhancer comprises precipitated calcium carbonate nanoparticles and calcium nitrate or hydrates thereof.
According to one embodiment of the présent invention, the précipitation enhancer of step ii) is added in an amount from 0.01 to 25 wt.-%, based on the total weight of the calcium oxide containing material, preferably in an amount from 0.1 to 20 wt.-%, more preferably from 1 to 15 wt.-%, and most preferably from 5 to 10 wt.-%.
According to one aspect of the présent invention, a use of calcium carbonate nanoparticles and/or a water-soluble calcium sait in a process for producing an aqueous suspension of precipitated calcium carbonate is provîded.
Conventional methods for preparing PCC suffer from the problem that a significant amount of portlandite is retained ortrapped during the precipitating process. The inventors surprisingly found that the addition of a précipitation enhancer selected from the group consisting of calcium carbonate nanoparticles and/or a water-soluble calcium sait during or after the lime slaking step of a process for producing PCC allows the préparation of PCC with a low portlandite content, for example, with a portlandite content of less than 1 wt. %, or less than 0.1 wt.-%, based on the total weight of the dried PCC.
Nucléation and growth of precipitated calcium carbonate may occur, when the saturation S > 1. S can be expressed as the quotient ofthe ionic activity product IP and the solubility product Ksp:
-19IP 5 = —
The ionic activity product, IP, may be defined as being directly proportional to the product of ali constituent ions for a given product, in solution. For instance, the ionic product of calcium carbonate would be directly proportional to the product of the calcium and carbonate ionic concentrations (or equal to the product of their activities). The solubility product, Ksp, would then be defined as the ionic activity product at equilibrium. Conversely, when S < 1, dissolution of calcium carbonate is favoured.
It is believed that nucléation and growth may not necessarily occur immediately after surpassing S. Rather, thermodynamic energy principals must be met, i.e., the ionic product must be sufficiently high that the energy released from précipitation surpasses the energy required for the surface liquid interactions. As used in the présent invention, the term “homogeneous nucléation” refers to the formation of clusters sufficiently large at a given saturation level to overcome the surface energy requirements, and thus, form a stable solid, without the need of other solids présent. “Heterogeneous nucléation” in the meaning of the présent invention defines as nucléation at a foreign surface, whereby the foreign surface lowers the total surface energy requirements. “Homogeneous crystal growth” in the meaning of the présent invention refers to the précipitation of the solid in question at a surface of equal composition. This may occur at its newly nucleated surface, or at surfaces of the sample composition already présent in the solution.
The înventors believe that typical slaked-lime PCC précipitation occurs by the heterogeneous nucléation of calcium carbonate at the portlandite surface, or, if still homogeneous nucléation (away from any surface), then still very near to the portiandite surface, where the calcium ion concentrations are at maximum. Without being bound to any theory, it is believed that the précipitation enhancer of the présent invention works by promoting homogeneous nucléation and/or homogeneous growth, separate from the calcium hydroxide surface.
-20For example, it is believed that calcium carbonate nanoparticles can promote homogeneous growth by providing a more favourable surface for précipitation during the carbonation step than the surface of the portlandite particles. It is also believed that the water-soluble calcium salts can promote homogeneous nucléation by încreasing the oversaturation levels in the solution. Thereby, the influences of hîgh saturation levels at the portlandite particle surface may be at least partially compensated, and thus, allowing the newly precipitated calcium carbonate to form its own nuclei and grow away from the portlandite surface. As a resuit a precipitated calcium carbonate with a significantly reduced portlandite content can be obtained. Preferably, the portlandite content of the obtained PCC is at a level, which is not détectable any more by X-ray diffraction. The inventors also found that a combination of calcium carbonate nanoparticles and a water-soluble calcium sait can be especially effective as précipitation enhancer.
Process step iii)
In step iii) of the process of the présent invention, a milk of lime is prepared by mixing water, the calcium oxide containing material of step i), and the précipitation enhancer of step ii).
The reaction of the calcium oxide containing material with water results in the formation of a milky calcium hydroxide suspension, better known as milk of lime. Said reaction is highly exothermic and is also designated as “lime slaking” in the art.
According to one embodiment of the présent invention, the température of the water, which is used in mixing step iii), i.e. the température of the water that is used to slake the calcium oxide containing material, is adjusted to be in the range from more than 0°C and less than 100°C. In other words, the water that is used to slake the calcium oxide containing material is adjusted to a température range, in which the water is in liquid form. Preferably, the température of the water, which is employed in mixing step iii) is adjusted to be from 1°C to 70°C, more preferably from 2°C to 50°C, even more preferably from 30°C to 50°C, and most preferably from 35 to 45°C. It will be apparent to the skilled person that the initial température of the water is not necessarily the same one as the température of the mixture prepared in step iii) due to the
-21 highly exothermic slaking reaction and/or due to the mixing of substances having different températures.
According to one embodiment, step iii) comprises the steps of:
a1) mixing the calcium oxide containing material of step i) with water, and a2) adding the précipitation enhancer of step ii) to the mixture of step a1 ).
Preferably, process step a2) is carried out after the reaction between the calcium oxide containing material of step i) with water is completed, i.e. after the lime has been completely slaked.
According to another embodiment, process step iii) comprises the steps of: b1 ) mixing the précipitation enhancer of step ii) with water, and b2) adding the calcium oxide containing material of step i) to the mixture of step b1).
According to still another embodiment, step iii) the calcium oxide containing material of step i), the précipitation enhancer of step ii), and water are mixed simultaneously.
The précipitation enhancer of step ii) may be added in step iii) in one portion or in several portions. According to one embodiment, in step iii) the précipitation enhancer of step ii) is mixed with the water, and the calcium oxide containing material of step i), by adding the précipitation enhancer in one portion or in two, three, four, five, or more portions.
Process step iii) may be performed at room température, i.e. at a température of 20°C ± 2°C, or at an initial température of 30 to 50°, preferably 35 to 45°C. Since the reaction is exothermic, the température typically raises to a température between 70 and 85°C during step iii).
According to a preferred embodiment, process step iii) is performed with mixing, agitation, or stirring, for example, mechanical stirring. Suitable process equipment for mixing, agitation or stirring is known to the skilled person.
-22The progress of the slaking reaction may be observed by measuring the température and/or conductivity of the reaction mixture. It can also be monitored by turbidity control. Alternatively or additionally, the progress of the slaking reaction can be inspected visually.
According to one embodiment, the calcium oxide containing material and the water are mixed in a mass ratio from 1:4 to 1:15. According to one preferred embodiment, in step iii) the calcium oxide containing material and the water are mixed in a mass ratio from 1:5 to 1:9.
According to one embodiment, the milk of lime of step iii) has a solids content from 5 to 25 wt.%, based on the total weight of the milk of lime, preferably from 10 to 20 wt.-%, and most preferably from 10 to 15 wt.-%.
According to one embodiment, the milk of lime of step iii) has a Brookfield viscosity from 1 to 1000 mPa-s at 25°C, more preferably from 5 and 800 mPa s at 25°C, and most preferably from 10 and 600 mPa s at 25°C. According to one embodiment, the Brookfield viscosity is measured at 100 rpm.
It is within the confines of the présent invention that additional water may be introduced during the slaking reaction in order to control and/or maintain and/or achieve the desired solids content or Brookfield viscosity or température of the milk of lime.
Process step iii) can be carried out in form of a batch process, a semi-continuous or a continuous process.
Process step iv)
In step iv) of the process of the présent invention, the milk of lime obtained from step iii) is carbonated to form an aqueous suspension of precipitated calcium carbonate.
-23 The carbonation is carried out by means and under conditions well-known by the person skilled in the art. The introduction of carbon dioxide into the milk of lime quickly results in the formation of the carbonate ion (CO3 2), and thus, the requisite concentration for calcium carbonate to be formed. Particularly, the carbonation reaction can be readily controlled considering the reactions involved in the carbonation process. Carbon dioxide dissolves according to its partial pressure forming carbonate ions via the formation of carbonic acid (H2CO3), which, in such an alkaline solution, dissociâtes to its constituent hydrogen and carbonate ions. Once the ionic product of calcium carbonate is sufficiently greater than the solubility product, calcium carbonate précipitâtes. At the same time, hydroxide ions are neutralized by the dissociated hydrogen ions. As a resuit the ionic product for calcium hydroxide would therefore be less than the solubility product, and it would continue to dissolve. This occurs continually, so long as CO2 is bubbled into solution, until ail calcium hydroxide is consumed, or is trapped in the calcium carbonate crystal structure. It is the inventors’ belief that the methods demonstrated in this patent application, by avoiding nucleation/growth near the calcium hydroxide surface, significantly mlnimize the trapping of calcium hydroxide, thus resulting in its near full consumption.
According to one embodiment of the présent invention, in step iv) the carbonation is carried out by feeding pure gaseous carbon dioxide or technical gases containing at least 10 vol.-% of carbon dioxide into the milk of lime.
The progress of the carbonation reaction can be readily observed by measuring the conductivity, density, turbidity and/or pH. In this respect, the pH of the milk of lime before addition of carbon dioxide will be more than 10, usually between 11 and 12.5, and will constantly decrease until a pH of about 7 is reached. At this point the reaction can be stopped.
Conductivity slowly decreases during the carbonation reaction and rapidly decreases to low levels, when the précipitation is completed. The progress of the carbonation may be monitored by measuring the pH and/or the conductivity of the reaction mixture.
According to one embodiment of the present invention, the température of the milk of lime obtained from step iii), which is used in step iv) is adjusted to be in the range from 10°C to 60°C.
-24It will be apparent to the skilled person that the initial température of the milk of lime is not necessarily the same one as the température of the mixture prepared in step iii) due to the exothermic carbonation reaction and/or due to the mixing of substances having different températures.
According to one embodiment of the présent invention, step iv) is carried out at a température from 5 to 95°C, preferably from 30 to 70°C, and more preferably from 40 to 60°C.
Process step iv) can be carried out in form of a batch process, a semi-continuous or a continuous process. According to one embodiment, the process of the présent invention involving the process steps i) to iv) is carried out in form of a batch process, a semi-continuous or a continuous process.
According to one embodiment of the présent invention, the obtained precipitated calcium carbonate has a weight médian particle size d5o from 0.1 to 100 pm, preferably from 0.25 to 50 pm, more preferably from 0.3 to 5 pm, and most preferably from 0.4 to 3.0 pm.
The precipitated calcium carbonate may hâve aragonitic, calcitic, or vateritic crystal structure, or mixtures thereof. It is a further advantage of the présent invention that the crystal structure and morphology of the precipitated calcium carbonate can be controlled, e.g. by addition of seed crystals or other structure modifÿing Chemicals. According to a preferred embodiment, the precipitated calcium carbonate obtained by the inventive process has a clustered scalenohedral crystal structure.
The morphological structure of the precipitated calcium carbonate can also be controlled by carrying out process step iv) in a spécifie température range. According to one embodiment of the présent invention, step iv) is carried out at a température from 40 to 60°C to form an aqueous suspension of scalenohedral PCC. According to another embodiment of the présent invention, step iv) is carried out at a température from 10 to 25°C to form an aqueous suspension of rhombohedral PCC.
-25The BET spécifie surface area of the precipitated calcium carbonate obtained by the process according to the present invention may be from 1 to 100 m2/g, preferably from 2 to 70 m2/g, more preferably from 3 to 50 m2/g, especially from 4 to 30 m2/g, measured using nitrogen and the BET method according to ISO 9277. The BET spécifie surface area of the precipitated calcium carbonate obtained by the process of the present invention may be controlled by the use of additives, e.g. surface active agents, shearing during the précipitation step or thereafter at high mechanical shearing rates not only leading to a low particle size, but also to a high BET spécifie surface area.
According to one embodiment of the present invention, the obtained suspension of precipitated calcium carbonate has a solids content of at least 5 wt.-%, preferably from 10 to 50 wt.-%, more preferably from 12 to 45 wt-%, and most preferably from 14 to 40 wt.-%, based on the total weight of the suspension.
According to one embodiment of the present invention, the suspension of PCC of step iv) has a Brookfield viscosity of less than or equal to 1000 mPa-s at 25°C, more preferably less than or equal to 800 mPa s at 25°C, and most preferably less than or equal to 600 mPa s at 25°C. The Brookfield viscosity may be measured at 100 rpm.
According to one embodiment of the present invention, the precipitated calcium carbonate obtained by the inventive process has a portlandite content of less than 1 wt.-%, preferably less than 0.1 wt.-%, based on the total weight of the dried precipitated calcium carbonate.
Additional process steps
The process of the present invention can comprise additional process steps.
The milk of lime may be screened in order to remove oversize particles. A suitable screen can include, for example, a screen having a sieve size from 700 to 100 pm, for example, about 100 or about 300 pm. According to one embodiment of the present invention, the milk of lime is
-26screened after step iii) and before step iv), preferably with a screen having a sieve size from 100to300 pm.
According to still another embodiment of the présent invention, at least one slaking additive is added before, during orafterstep iii) ofthe inventive process. Byadding a slaking additive, the size of the PCC particles and their crystal morphology can be controlled without affecting the viscosityofthe aqueous suspension.
The at least one slaking additive may be selected from the group consisting of organic acids, organic acid salts, sugar alcohols, monosaccharides, disaccharides, polysaccharides, gluconates, phosphonates, lignosulfonates, and mixtures thereof.
According to one embodiment of the présent invention, the at least one slaking additive is selected from the group consisting of sodium citrate, potassium citrate, calcium citrate, magnésium citrate, monosaccharides, disaccharides, polysaccharides, sucrose, sugar alcohols, meritol, citric acid, sorbitol, sodium sait of diethylene triamine pentaacetic acid, gluconates, phosphonates, sodium tartrate, sodium lignosulfonate, calcium lignosulfonate, and mixtures thereof. According to a preferred embodiment, the at least one slaking additive is sodium citrate and/or saccharose.
According to one embodiment of the présent invention, the at least one slaking additive consists of one type of slaking additive only. Altematively, the at least one slaking additive can consist of a mixture of two or more types of slaking additives.
The at least one slaking additive may be provided in an amount from 0.01 to 0.2 wt.-%, based on the total amount of calcium oxide containing material, preferably in an amount from 0.05 to 1 wt.-%, more preferably from 0.06 to 0.8 wt.-%, and most preferably from 0.07 to 0.5 wt.-%.
According to a further aspect of the présent invention, a process for producing precipitated calcium carbonate is provided, the process comprising the steps of:
i) providing a calcium oxide containing material, ii) providing a précipitation enhancer selected from the group consisting of calcium carbonate nanoparticles and/or a water-soluble calcium sait, iii) preparing a milk of lime by mixing water, the calcium oxide containing material of step
i), and the précipitation enhancer of step ii), iv) carbonating the milk of lime obtained from step iii) to form an aqueous suspension of precipitated calcium carbonate, and
v) separating the precipitated calcium carbonate from the aqueous suspension obtained from step iv).
For the purpose of the présent invention, the expression “separating” means that the PCC is removed or isolated from the aqueous suspension obtained from step iv) of the inventive process. The precipitated calcium carbonate obtained from step iv) may be separated from the mother liquor by any conventional means of séparation known to the skilled person. According to one embodiment of the présent invention, in process step v) the PCC is separated mechanically and/or thermally. Examples for mechanical séparation processes are filtration, e.g. by means of a drum filter or filter press, nanofiltration, or centrifugation. An example for a thermal séparation process is an up-concentration process by the application of heat, for example, in an evaporator. According to a preferred embodiment, in process step v) the PCC is separated mechanically, preferably by filtration and/or centrifugation.
It is also preferred that the mother liquor obtained after précipitation and/or any one of the reactants may be recycled into the process.
The obtained PCC may be further processed, e.g., may be deagglomerated or subjected to a dry grinding step. Otherwise, it may also be wet ground în form of a suspension, if the PCC is subjected to dewatering, dispersion and/or grinding steps, these steps may be accomplished by procedures known in the art. Wet grinding may be carried out in the absence of a grinding aid or in the presence of a grinding aid. One or more grinding agents can be included, such as, e.g., sodium polyacrylate, a sait of polyacrylate acid, and/or a sait of a copolymer of acrylic acid. Dispersants also can be included to préparé dispersions if desired.
-28According to still a further aspect of the présent invention, the process for producing precipitated caicium carbonate comprising steps i) to v) further comprises a step vi) of drying the separated precipitated calcium carbonate obtained from step v), and optionally a step vii) of contacting at least a part of the surface of the precipitated calcium carbonate with a surface-treatment agent.
According to one embodiment of the présent invention, a process for producing dried precipitated calcium carbonate is provided, the process comprising the steps of:
i) providing a calcium oxide containing material, ii) providing a précipitation enhancer selected from the group consisting of calcium carbonate nanoparticles and/or a water-soluble calcium sait, iii) preparing a milk of lime by mixing water, the calcium oxide containing material of step
i), and the précipitation enhancer of step ii), iv) carbonating the milk of lime obtained from step iii) to form an aqueous suspension of precipitated calcium carbonate,
v) separating the precipitated calcium carbonate from the aqueous suspension obtained from step iv), and vi) drying the separated precipitated calcium carbonate obtained from step v).
Optionally, the process for producing dried precipitated calcium carbonate further comprises a step of concentrating the separated precipitated calcium carbonate obtained from step v) before step vi). Suitable concentration methods are known to the skilled person. For example, the desired concentration may be achieved by means of a thermal process, e.g., in an evaporator under ambient, atmospheric pressure or at reduced pressure, or by means of a mechanical process, e.g., in a filter press, such as nanofiltration, and/or centrifuge.
In general, the drying step vi) may take place using any suitable drying equipment and can, for example, include thermal drying and/or drying at reduced pressure using equipment such as an evaporator, a flash drier, an oven, a spray drier and/or drying in a vacuum chamber.
According to one embodiment, drying step vi) is a spray drying step, preferably said spray drying step is carried out at a lower température ranging from 200°C to 400°C, and preferably
-29from 250°C to 350°C. By means of drying step vi), a dried precipitated calcium carbonate is obtained having a low total moisture content which is less than or equal to 1.0 wt-%, based on the total weight of the dried precipitated calcium carbonate.
According to another embodiment, the dried PCC of step vi) has a total moisture content of less than or equal to 0.5 wt.-% and preferably less than or equal to 0.2 wt.-%, based on the total weight of the dried precipitated calcium carbonate. According to still another embodiment, the dried PCC of step vi) has a total moisture content of between 0.01 and 0.15 wt.-%, preferably between 0.02 and 0.10 wt.-%, and more preferably between 0.03 and 0.07 wt.-%, based on the total weight of the dried precipitated calcium carbonate.
The precipitated calcium carbonate obtained by the inventive process can be post-treated, for example, during and/or after a drying step with an additional component. According to one embodiment the precipitated calcium carbonate is treated with a fatty acid, e.g. stearic acid, a silane, or phosphoric esters of fatty acids, or a siloxane.
According to one embodiment of the présent invention, the process for producing dried precipitated calcium carbonate comprises the steps i) to vi), and further a step vii) of contacting at least a part of the surface of the precipitated calcium carbonate with a surface-treatment agent. Suitable surface-treatment agents are, for example, fatty acids, fatty acid esters, aliphatic carboxylic acids, aliphatic carboxylic esters, polyacrylates, polydiallyldimethylammonium chloride (polyDADMAC), mono-substituted succinic anhydrides, mono-substituted succinic acids, or phosphoric acid esters.
According to one embodiment the surface-treatment agent is selected from mono-substituted succinic anhydrides, mono-substituted succinic acids, phosphoric acid esters, and mixtures thereof. The term “mono-substituted succinic anhydride” in the meaning of the présent invention refers to a succinic anhydride wherein a hydrogen atom is substituted by another substituent. The term “mono-substituted succinic acid” in the meaning of the présent invention refers to a succinic acid wherein a hydrogen atom is substituted by another substituent. Further details
-30regardîng said surface-treatment agents and methods for preparing surface-treated calcium carbonate products thereof are described in WO 2014/060286 A1 and WO 2014/128087 A1.
Products and their use
According to the présent invention, an aqueous suspension of precipitated calcium carbonate is provided, which is obtainable by a process comprising the steps of:
i) providing a calcium oxide containing material, ii) providing a précipitation enhancer selected from the group consisting of calcium carbonate nanoparticles and/or a water-soluble calcium sait, iii) preparing a milk of lime by mixing water, the calcium oxide containing material of step i), and the précipitation enhancer of step ii), and iv) carbonating the milk of lime obtained from step iii) to form an aqueous suspension of precipitated calcium carbonate.
According to a further aspect of the présent invention, a precipitated calcium carbonate is provided, which is obtainable by a process comprising the steps of:
i) providing a calcium oxide containing material, ii) providing a précipitation enhancer selected from the group consisting of calcium carbonate nanoparticles and/or a water-soluble calcium sait, iii) preparing a milk of lime by mixing water, the calcium oxide containing material of step i), and the précipitation enhancer of step ii), iv) carbonating the milk of lime obtained from step iii) to form an aqueous suspension of precipitated calcium carbonate, and
v) separating the precipitated calcium carbonate from the aqueous suspension obtained from step iv).
The PCC suspension and/or PCC obtained by the process of the présent invention may be used in various materials. According to one embodiment of the présent invention, the precipitated caicium carbonate according to the présent invention is used in paper, plastics,
-31 polymer compositions, paint, coatings, concrète, cosmetics, pharmaceutics and/or agriculture applications. Preferably a dried precipitated calcium carbonate is used in plastics and/or polymer compositions. According to another embodiment of the présent invention, the aqueous suspension of precipitated calcium carbonate according to the présent invention is used in paper, plastics, polymer compositions, paint, coatings, concrète, cosmetics, pharmaceutics and/or agriculture applications.
According to one aspect of the présent invention, a product comprising the precipitated calcium carbonate according to the présent invention is provided. According to a preferred embodiment, the product is a paper, a paper product, an ink, a paint, a coating, a plastic, a polymer composition, an adhesive, a building product, a foodstuff, an agricultural product, a cosmetic product or a pharmaceutical product, and more preferably the product is a plastic or a polymer composition.
According to still a further aspect of the présent invention, a dried precipitated calcium carbonate is provided, which is obtainable by a process comprising the steps of:
i) providing a calcium oxide containing material, ii) providing a précipitation enhancer selected from the group consisting of calcium carbonate nanoparticles and/or a water-soluble calcium sait, iii) preparing a milk of lime by mixing water, the calcium oxide containing material of step i), and the précipitation enhancer of step ii), iv) carbonating the milk of lime obtained from step iii) to form an aqueous suspension of precipitated calcium carbonate,
v) separating the precipitated calcium carbonate from the aqueous suspension obtained from step iv), and vi) drying the separated precipitated calcium carbonate obtained from step v).
Optionally, the dried precipitated calcium carbonate may comprise a treatment layer on at least a part of the surface of the precipitated calcium carbonate. According to one embodiment, a dried precipitated calcium carbonate is provided, which is obtainable by a process comprising
-32the steps i) to vi) and further a step vii) of contacting at least a part of the surface of the precipitated calcium carbonate with a surface-treatment agent.
According to one embodiment, the precipitated calcium carbonate obtainable by process steps i) to iv), i) to v), i) to vi), or i) to vii) has a portlandite content of less than 1 wt.-%, and preferably less than 0.1 wt.-%, based on the total weight of the dried precipitated calcium carbonate.
According to a preferred embodiment, the dried precipitated calcium carbonate obtainable from process steps i) to vi) is a dried powder of precipitated calcium carbonate.
The dried PCC obtainable from process steps i) to vi) may be used in paper, plastics, polymer compositions, paint, coatings, concrète, cosmetics, pharmaceutics and/or agriculture applications. According to a preferred embodiment, the dried precipitated calcium carbonate is used in plastics and/or polymer compositions. For example, said PCC may be used in thermoplastic polymers, such as polyvinyl chloride, polyolefins, and polystyrène. Moreover, the dried PCC may also be used in polymer coatings which may be applied on the surface of polymer articles, such as foils, in order to increase the hydrophobicity (e.g., reflected by an increased contact angle measured against water) of said surface.
According to one aspect of the présent invention, a product comprising dried precipitated calcium carbonate according to the présent invention, preferably a dried powder of said precipitated calcium carbonate, is provided. According to one embodiment, the product is a paper, a paper product, an ink, a paint, a coating, a plastic, a polymer composition, an adhesive, a building product, a foodstuff, an agricultural product, a cosmetic product or a pharmaceutical product. According to a preferred embodiment, a product comprising a dried precipitated calcium carbonate is provided, wherein the product is a plastic or a polymer composition.
The scope and interest of the présent invention will be better understood based on the following examples which are intended to illustrate certain embodiments of the présent invention and are non-limitative.
-33Examples
1. Measurement methods
In the following, measurement methods implemented in the examples are described.
Particle size distribution of precipitated calcium carbonate (PCC)
The particle size distribution of the prepared PCC particles was measured using a Sedigraph 5120 from the company Micromeritics, USA. The method and the instrument are known to the skilled person and are commonly used to détermine grain size of fillers and pigments. The measurement was carried out in an aqueous solution comprising 0.1 wt.-% Na4P2Û7. The samples were dispersed using a high speed stirrer and supersonics. For the measurement of dispersed samples, no further dispersing agents were added.
Particle size distribution of calcium carbonate nanoparticles
The number based particle size distribution of the calcium carbonate nanoparticles was determined by the use of a Malvern Zetasizer Nano ZS.
The samples slurry was diluted with a 0.1 wt.-% solution of Na4P2O? until 100 g of a slurry with a solids content of 0.5 wt-% was attained. 1 g of Polysalz (BASF, Germany), was added and the slurry was mixed at high shear for 5 minutes. After mixing, the sample was treated in a sonication bath for 15 to 20 minutes.
The particle size distribution was determined by adding the obtained slurry to a standard 1 cm x 1 cm cuvette. The cuvette was placed in the instrument, wherein the particle size was determined using dynamic light scattering. The values are reported in the number based
-34distribution. This means that a d5Q, by number, is defined as 50% ofthe numberof particles hâve a diameter of less than d5a in ail three dimensions.
Solids content of an aqueous suspension
The suspension solids content (also known as “dry weight”) was determined using a Moisture Analyser MJ33 from the company Mettler-Toledo, Switzerland, with the following settings: drying température of 160°C, automatic switch off if the mass does not change more than 1 mg over a period of 30 sec, standard drying of 5 to 20 g of suspension.
Spécifie surface area (SSA)
The spécifie surface area was measured via the BET method according to ISO 9277 using nitrogen, following conditioning of the sample by heating at 250°C for a period of 30 minutes. Prior to such measurements, the sample is filtered within a Büchnerfunnel, rinsed with deionised water and dried ovemight at 90 to 100°C in an oven. Subsequently the dry cake is ground thoroughly in a mortar and the resulting powder placed in a moisture balance at 130°C until a constant weight is reached.
X-ray diffraction
The purity ofthe PCC samples was analysed with a D8 Advance powder diffractometer (Bruker Corporation, USA) obeying Bragg’s law. This diffractometer consisted of a 2.2 kW X-ray tube (Cu), a sample holder, a θ-θ goniometer, and a VÂNTEC-1 detector. Nickel-filtered Cu K« radiation was employed in ail experiments (AKa-cu - 1.5406 Â). The profiles were chart recorded automatically using a Scan speed of 0.7° per minute in 2θ (XRD GV_7600). The measurement was carried out at angles from 5 to 70°.
The resulting powder diffraction pattern was classified by minerai content using the DIFFRACsuite software packages EVA and SEARCH, based on reference patterns of the ICDD PDF 2 database (XRD LTM_7603). Quantitative analysis of the diffraction data, i.e. the
-35determination of amounts of different phases in a multi-phase sample, has been performed using the DIFFRACsuite software package TOPAS (XRD LTM_7604). This involved modelling the full diffraction pattern (Rietveld approach) such that the calculated pattern(s) duplicated the experimental one.
2. Materials
A1 : Precipitated calcium carbonate nanoparticles (c/50: 0.04 pm; d98: 0.10 pm, portlandite content: < LOD).
A2: Precipitated calcium carbonate nanoparticles (c/50: 0.07 pm; d98: 0.16 pm, portlandite content: < LOD).
A3: Calcium nitrate tetrahydrate, commercially available from Riedel de Haën, Germany.
A4: Ground calcium carbonate nanoparticles (d50: 0.13 pm; d98: 0.33 pm) produced from undispersed marble obtained from Omya SPA, Carrara, Italy.
A5: Ground calcium carbonate (cf50: 3.5 pm; d98: 10.6 pm), commercially available from Omya SAS, Orgon, France.
LOD: limit of détection.
Préparation of PCC nanoparticles A1 and A2:
PCC nanoparticles A1:
A miik of lime was prepared by mixing under mechanical stirring 5 liters water with 1000 g calcium oxide (quicklime raw material from Austria) at an initial température of 50°C. The
-36obtained mixture was stirred for 30 min, wherein additional 4 iiters of water were added. Subsequently, the mixture was sieved through a 100 pm screen.
6.5 L of the obtained milk of lime were transferred into a stainless Steel reactor. After the addition of 5 wt.-% of sucrose and 2.5 wt-% of strontium hydroxide octahydrate, based on the total weight of calcium hydroxide, the milk of lime was heated to 60°C. Then the milk of lime was carbonated by introducing an air/CO2 mixture (first 15 minutes: CO2 = 1 L/min and air = 14 L/min, rest of experiment: CO2 = 3.6 L/min and air = 11.4 L/min). During the carbonation step, the reaction mixture was stirred with a speed of 1400 rpm. The reaction was monitored by online pH and conductivity measurements.
The precipitated calcium carbonate nanoparticles were obtained by filtering the suspension and rinsing the residue with water.
PCC nanoparticles A2:
A milk of lime was prepared by mixing under mechanical stirring 5 Iiters water with 800 g calcium oxide (quicklime raw material from Austria) and 0.1 wt.-%, based on the total weight of calcium oxide, dry sodium citrate as slaking additive at an initial température of 40°C. The obtained mixture was stirred for 30 min, wherein additional 4 Iiters of water were added. Subsequently, the mixture was sieved through a 100 pm screen.
L of the obtained milk of lime were transferred into a stainless Steel reactor. After the addition of 5 wt.-% of sucrose, based on the total weight of calcium hydroxide, the milk of lime was cooled down to 10°C. Then the milk of lime was carbonated by introducing an air/CO2 mixture (CO2 = 3 L/min and air = 12 L/min). During the carbonation step, the reaction mixture was stirred with a speed of 1400 rpm. The reaction was monitored by online pH and conductivity measurements.
The precipitated calcium carbonate nanoparticles were obtained by filtering the suspension and rinsing the residue with water.
-373. Example
A milk of lime was prepared by mixing under mechanical stirring 5 liters water with 1000 g calcium oxide (quicklime raw materiaî from Austria) and 0.1 wt.-%, based on the total weight of calcium oxide, dry sodium citrate as slaking additive at an initial température of 40°C. The obtained mixture was stirred for 30 min, wherein additional 4 liters of water were added. Subsequently, the mixture was sieved through a 100 pm screen.
The obtained milk of lime was transferred into a stainless Steel reactor, wherein the milk of lime was cooled down to 50°C. Subsequently, the précipitation enhancer (if présent) was added to the milk of lime (the employed précipitation enhancers are indicated in Table 1 below). Then the milk of lime was carbonated by introducing an air/CO2 mixture (20 vol-% CO2). During the carbonation step, the reaction mixture was stirred with a speed of 1400 rpm. The reaction was monitored by online pH and conductivity measurements.
The precipitated calcium carbonate was separated from the obtained suspension by filtration, rinsed with éthanol and dried in a drying cabinet at 90°C. The purity of the obtained precipitated calcium carbonate was controlled by X-ray diffraction using the method described above.
The characteristics of the prepared milks of lime and aqueous PCC suspensions are described in Tables 1 and 2 below.
| Sample | Précipitation enhancer | Amount of précipitation enhancer [wt.-%, based on total weight of calcium oxide] |
| 1 (inventive) | A2 | 1 |
| 2 (inventive) | A2 | 5 |
| 3 (inventive) | A1 | 5 |
| 4 (inventive) | A3 | 5 |
| 5 (inventive) | A3 | 10 |
| 6 (inventive) | A1 A3 | 5 5 |
| 7 (inventive) | A2 A3 | 5 5 |
| 8 (inventive) | A4 | 5 |
| 9 (comparative) | A5 | 5 |
| 10 (comparative) | — | — |
Table 1: Composition of the produced milks of lime.
| Sample | SSA [m2/g] | c/50 [ym] | [ym] | Calcite [wt.-%] | Portlandite [wt.-%] |
| 1 (inventive) | 9.30 | 1.30 | 2.40 | 99.40 | 0.6 |
| 2 (inventive) | 11.40 | 1.40 | 3.00 | 100.00 | < LOD |
| 3 (inventive) | 7.30 | 3.87 | 5.81 | 99.3 | 0.7 |
| 4 (inventive) | 5.02 | 1.32 | 3.65 | 99.3 | 0.7 |
| 5 (inventive) | 4.00 | 1.33 | 4.13 | 99.5 | 0.5 |
| 6 (inventive) | 6.90 | 1.67 | 3.78 | 100.00 | <LOD |
| 7 (inventive) | 11.80 | 1.30 | 3.20 | 100.00 | < LOD |
| 8 (inventive) | 4.70 | 1.90 | 2.50 | 99.50 | 0.5 |
| 9 (comparative) | 4.90 | 3.80 | 8.10 | 97.70 | 2.3 |
| 10 (comparative) | 4.72 | 1.62 | 4.07 | 97.20 | 2.9 |
Table 2: Characteristics of the obtained precipitated calcium carbonates (LOD: limit of détection).
The results compiled in Table 2 show that by the use of the inventive précipitation enhancer (samples 1 to 8), a PCC with a significantly reduced portlandite content can be obtained. Furthermore, no portlandite at ail was détectable in samples 6 and 7, which was produced by using a combination of calcium carbonate nanoparticles and water-soluble calcium sait as 10 précipitation enhancer.
Claims (5)
1. A process for producing an aqueous suspension of precipitated calcium carbonate comprising the steps of:
i) providing a calcium oxide containing material, ii) providing a précipitation enhancer selected from the group consisting of calcium carbonate nanoparticles and/or a water-soluble calcium sait, iii) preparing a milk of lime by mixing water, the calcium oxide containing material of step i), and the précipitation enhancer of step ii), and iv) carbonating the milk of lime obtained from step iii) to form an aqueous suspension of precipitated calcium carbonate wherein the précipitation enhancer of step ii) is added in an amount from 0.01 to 25 wt.-%, based on the total weight of the calcium oxide containing material.
2. The process of claim 1, wherein step iii) comprises the steps of:
al) mixing the calcium oxide containing material of step i) with water, and a2) adding the précipitation enhancer of step ii) to the mixture of step al).
3. The process of claim 1, wherein step iii) comprises the steps of:
bl) mixing the précipitation enhancer of step ii) with water, and b2) adding the calcium oxide containing material of step i) to the mixture of step bl).
4. The process of any one of the préviens claims, wherein the calcium carbonate nanoparticles hâve a number based médian particle size dso of less than 150 nm.
5. The process of any one of the previous claims, wherein the calcium carbonate nanoparticles hâve a number based médian particle size ¢/50 of from 1 to 130 nm.
6. The process of any one of the préviens daims, wherein the calcium carbonate nanoparticles hâve a number based médian particle size </50 of from 5 to 90 rnn.
7. The process of any one of the previous daims, wherein the calcium carbonate 5 nanoparticles hâve a number based médian particle size J50 of from 10 to 80 nm.
8. The process of any one of the previous daims, wherein the calcium carbonate nanoparticles hâve a number based médian particle size J50 of from 30 to 70 nm.
10 9. The process of any one of the previous daims, wherein the water-soluble calcium sait is an anhydrous sait or hydrate sait.
10. The process according to daim 9 wherein the water-soluble calcium sait is selected from the group consisting of calcium nitrate, calcium sulfate, calcium
15 acetate, calcium benzoate, calcium bicarbonate, calcium bromate, calcium bromîde, calcium chlorate, calcium chloride, calcium îodite, calcium nitrite, caldum perchlorate, calcium permanganate, hydrates thereof, and mixtures thereof.
11. The process according to claim 9 or 10 wherein the water-soluble caldum sait 20 is selected from the group consisting of calcium nitrate, calcium sulfate, calcium acetate, calcium benzoate, caldum bicarbonate, calcium bromate, calcium bromide, caldum chlorate, calcium chloride, calcium iodite, calcium nitrite, calcium perchlorate, calcium permanganate, calcium nitrate tetrahydrate, calcium chloride dihydrate, and mixtures thereof.
25 '
12. The process according to any one of daims 9 to 11 wherein the water-soluble calcium sait is selected from the group consisting of calcium nitrate, calcium nitrate tetra hydrate, calcium chloride, calcium chloride dihydrate, and mixtures thereof.
13. The process of any one of the préviens daims, wherein the predpitation enhancer of step ii) is added in an amount from 0.1 to 20 wt.-%, based on the total weight of the calcium oxide containing material.
14. The process of any one of the previous daims, wherein the précipitation enhancer of step ii) is added in an amount from 1 to 15 wt.-%.
15. The process of any one of the previous daims, wherein the précipitation enhancer of step ii) is added in an amount from 5 to 10 wt.-%.
16. The process of any one of the previous daims, wherein a slaking additive is added before, during or after step iii).
17. The process of any one of the previous daims, wherein the slaking additive is selected from the group consisting of organic acids, organic acid salts, sugar alcohols, monosaccharides, disaccharides, polysaccharides, gluconates, phosphonates, ligno sulfonates, and mixtures thereof.
18. The process of claim 16 or 17, wherein the slaking additive is added in an amount from 0.01 to 2 wt.-%, based on the total amount of calcium oxide containing material.
19. The process of claim 18 wherein the slaking additive is added in an amount from 0.05 to 1 wt-%.
20. The process of daim 18 or 19 wherein the slaking additive is added in an amount from 0.06 to 0.8 wt.-%.
-42.-
21. The process of any one of daims 18 to 20 wherein the slaking additive is added in an amount from 0.07 to 0.5 wt.-%.
22. The process of any one of the previous daims, wherein the obtained suspension of precipitated calcium carbonate has a solids content of at least 5 wt.-%, based on the total weight of the suspension.
23. The process of any one of the previous daims, wherein the obtained suspension of precipitated calcium carbonate has a solids content of from 10 to 50 wt.-% based on the total weight of the suspension.
24. The process of any one of the previous daims, wherein the obtained suspension of precipitated calcium carbonate has a solids content of from 12 to 45 wt.-% based on the total weight of the suspension.
25. The process of any one of the previous daims, wherein the obtained suspension of precipitated calcium carbonate has a solids content of from 14 to 40 wt.-%, based on the total weight of the suspension.
26. The process of any one of the previous daims, wherein the obtained precipitated calcium carbonate has a portlandite content of less than 1 wt.-%, based on the total weight of the dried precipitated calcium carbonate.
27. The process of any one of the previous daims, wherein the obtained precipitated calcium carbonate has a portlandite content of less than 0.1 wt.-%, based on the total weight of the dried precipitated calcium carbonate.
28. The process of any one of the previous daims, wherein the milk of lime is screened after step iii) and before step iv).
29. The process of any one of the previous daims, wherein the milk of lime is screened with a screen having a sieve size from 100 to 300 pm.
30. A process for producing precipitated calcium carbonate comprising the steps i) to iv) of the process according to any one of daims 1 to 29, and further a step v) of separating the precipitated calcium carbonate from the aqueous suspension obtained from step iv).
31. The process of claim 30, wherein the process further comprises a step vi) of drying the separated precipitated calcium carbonate obtained from step v), and optionaîly a step vii) of contacting at least a part of the surface of the precipitated caldum carbonate with a surface-treatment agent.
32. An aqueous suspension of precipitated calcium carbonate obtainable by a process according to any one of daims 1 to 29, wherein step iv) is carried out at a température from 40 to 60°C to form an aqueous suspension of scalenohedral precipitated calcium carbonate, and the precipitated calcium carbonate is scalenohedral precipitated calcium carbonate, or wherein step iv) is carried out at a température from 10 to 25°C to form an aqueous suspension of rhombohedral precipitated calcium carbonate, and the 5 precipitated calcium carbonate is rhombohedral precipitated calcium carbonate.
33. Precipitated calcium carbonate obtainable by a process according to claim 30 or 31, wherein step iv) is carried out at a température from 40 to 60°C to form an
-4Uaqueous suspension of scalenohedral precipitated calcium carbonate, and the precipitated calcium carbonate is scalenohedral precipitated calcium carbonate, or wherein step iv) is carried out at a température from 10 to 25°C to form an aqueous suspension of rhombohedral precipitated calcium carbonate, and the
5 5 precipitated calcium carbonate is rhombohedral precipitated calcium carbonate.
34. The precipitated calcium carbonate of claim 33, wherein the precipitated calcium carbonate is a dried precipitated calcium carbonate, optionally comprising a treatment layer on at least a part of the surface of the precipitated calcium carbonate.
35. A product comprising the precipitated calcium carbonate according to claim 33 or 34.
36. A product comprising the precipitated calcium carbonate according to claim
15 35 wherein the product is a paper, a paper product, an ink, a paint, a coating, a plastic, a polymer composition, an adhesive, a building product, a foodstuff, an agricultural product, a cosmetic product or a pharmaceutical product.
37. A product comprising the precipitated calcium carbonate according to claim
20 36 wherein the product is a plastic or a polymer composition.
38. Use of an aqueous suspension of precipitated calcium carbonate according to claim 32 in paper, plastics, polymer compositions, paint, coatings, concrète, cosmetics, pharmaceutics and/or agriculture applications.
39. Use of a precipitated calcium carbonate according to claim 33 or 34 in paper, plastics, polymer compositions, paint, coatings, concrète, cosmetics, pharmaceutics and/or agriculture applications.
40. Use of a precipitated calcium carbonate according to claim 39 wherein a dried precipitated calcium carbonate is used in plastics and/or polymer compositions.
5 41. Use of calcium carbonate nanoparticles and/or a water-soluble calcium sait in a process for producing an aqueous suspension of precipitated calcium carbonate.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP14190261.9 | 2014-10-24 | ||
| US62/073,071 | 2014-10-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| OA18676A true OA18676A (en) | 2019-05-17 |
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