Process to prepare precipitated calcium carbonate implementing low charge acrylate a/o maleinate-containing polymer
Process to prepare a precipitated calcium carbonate (PCC) comprising the following steps: (i) providing CaO, which is optionally partially or fully slaked (hereafter “calcium source”); ({umlaut over (υ)}) providing a CO 2 -comprising gas; ({umlaut over (υ)}i) contacting said calcium source of step (i) and said CO 2 -comprising gas of step (ii) in an aqueous environment in a reactor, in one or more steps; (iv) obtaining a PCC-comprising suspension; (v) optionally concentrating said PCC-comprising suspension of step (iv); (vi) optionally adding dispersing additives to the suspension of step (iv) and/or (v); (vii) optionally grinding the product of step iv, v or vi.
1. A process for preparing a precipitated calcium carbonate (PCC) comprising the following steps:
(i) providing CaO, which is optionally partially or fully slaked;
(ii) providing a CO 2 -comprising gas;
(iii) contacting the CaO of step (i) and the CO 2 -comprising gas of step (ii) in an aqueous environment in a reactor, in one or more steps, in the presence of a polymer to obtain a PCC-comprising suspension;
(iv) obtaining the PCC-comprising suspension from step (iii);
(v) optionally concentrating the PCC-comprising suspension of step (iv); and
(vi) optionally adding dispersing additives to the suspension of step (iv) and/or (v);
wherein the polymer results from the polymerization of the following monomers present in the polymer in the following % monomer units relative to the total monomer units forming said polymer:
a) from 50% to 98% of at least one vinyl group-comprising monomer not comprising Formula (I),
b) from 2% to 50% of at least one vinyl group-comprising monomer having at least one substituent comprising Formula (I):
wherein:
m, n, p and q are whole numbers having a value of less than 150, and at least one of m, n, p and q has a value of greater than 0, such that 25≦(m+n+p)q≦150;
R represents a functional linking group selected from ethers, esters or amides,
R 1 and R 2 are the same or different, and represent hydrogen or alkyl groups having 1 to 4 carbon atoms,
R′ represents hydrogen or a hydrocarbon radical having 1 to 40 carbon atoms, the sum of the monomer unit percentages of monomers a) and b) being equal to 100%.
2. The process according to claim 1 , wherein the polymer results from polymerization of a) from 80% to 97% of at least one vinyl group-comprising monomer not comprising Formula (I), and b) from 3% to 20% of at least one vinyl group-comprising monomer having at least one substituent comprising Formula (I).
3. The process according to claim 1 , wherein the polymer results from polymerization of a) from 85% to 95% of at least one vinyl group-comprising monomer not comprising Formula (I), and b) from 5% to 15% of at least one vinyl group-comprising monomer having at least one substituent comprising Formula (I).
4. The process according to claim 1 , wherein in Formula (I), at least one of m, n, p and q has a value of greater than 0, such that 50≦(m+n+p)q≦150.
5. The process according to claim 1 , wherein in Formula (I), R′ represents hydrogen or a hydrocarbon radical having 1 to 3 carbon atoms.
6. The process according to claim 1 , wherein in Formula (I), R′ is a methyl radical or hydrogen.
7. The process according to claim 1 , wherein monomer a) is selected from the group consisting of an anionic monomer, acrylic acid, methacrylic acid, maleic acid, a cationic monomer, an acrylamide, a methacrylamide, a neutral monomer, an acrylic acid ester, a methacrylic acid ester, a maleic acid esters, and any mixture thereof.
8. The process according to claim 1 , wherein monomer a) is a mixture of an anionic monomer and a neutral monomer.
9. The process according to claim 1 , wherein monomer a) is a mixture of an anionic monomer and a neutral monomer at a monomer unit ratio of anionic monomers:neutral monomers is from 50:50 to 2:1.
10. The process according to claim 1 , wherein monomer a) is a mixture of an anionic monomer and a neutral monomer at a monomer unit ratio of anionic monomers:neutral monomers is from 8:1 to 12:1.
11. The process according to claim 1 , wherein monomer a) is a mixture of an anionic monomer and a neutral monomer at a monomer unit ratio of anionic monomers:neutral monomers is 10:1.
12. The process according to claim 1 , wherein monomer a) is a mixture of an anionic and a neutral monomer(s) selected from among acrylic and/or methacrylic acids and esters thereof.
13. The process according to claim 1 , wherein monomer a) is a cationic monomer(s) selected from the group consisting of cationic (meth)acrylic esters, and chloride and/or sulfate salts of one or more of the following: [2-(methacryloyloxy)ethyl]trimethyl ammonium, [3-acrylamido)propyl]trimethylammonium, dimethyl diallyl ammonium, [3-(methacrylamido)propyl]trimethylammonium.
14. The process according to claim 1 , wherein monomer b) includes additional substituents not comprising Formula (I) selected from one or more of the following functional groups: alkyl, aryl, alkyl ester, hydrogen, alkyl amide, carboxyl and allyl.
15. The process according to claim 14 , wherein the additional substituents is at least one methyl substituent.
16. The process according to claim 1 , wherein monomer b) has a methyl group in trans-position relative to the substituent comprising Formula (I) in which the functional group linking is an ester.
17. The process according to claim 1 , wherein the polymer is added in an amount totaling 0.01% to 0.5% by dry weight relative to the dry weight of PCC obtained in step (iv).
18. The process according to claim 1 , wherein the polymer is added in an amount totaling 0.05% to 0.2% by dry weight relative to the dry weight of PCC obtained in step (iv).
19. The process according to claim 1 , wherein the polymer has an intrinsic viscosity of less than or equal to 100 ml/g.
20. The process according to claim 1 , wherein the polymer is fractionated in doses added over time prior to and/or during step (iii).
21. The process according to claim 1 , wherein the polymer is added during more than one of steps (i), (ii) and (iii).
22. The process according to claim 1 , wherein more than 80% by weight of the polymer is added prior to reaching an aqueous environment maximum viscosity during step (iii).
23. The process according to claim 1 , wherein more than 80% of the polymer is added prior to reaching an aqueous environment conductivity drop associated with a conductivity curve inflection point slope of more than 45° during step (iii).
24. The process according to claim 1 , wherein more than 80% by weight of the polymer is added prior to reaching a pH value of less than 7.2 during step (iii).
25. The process according to claim 1 , wherein more than 80% of the polymer is added prior to step (iii).
26. The process according to claim 1 , wherein the CaO of step (i) is partially or fully slaked by addition of slaking water to form a slaked lime suspension prior to step (iii).
27. The process according to claim 26 , wherein more than 80% of the polymer is added to the slaking water.
28. The process according to claim 26 , wherein 100% of the polymer is added to the slaking water.
29. The process according to claim 26 , wherein 100% by weight of the polymer is added to the slaked lime suspension prior to step (iii).
30. The process according to claim 1 , wherein the contacting of the CaO and the CO 2 -comprising gas in step (iii) is performed until the conductivity of the aqueous environment drops.
31. The process according to claim 1 , wherein the contacting of the CaO and the CO 2 -comprising gas in step (iii) until an aqueous environment pH of 7.5 is reached.
32. The process according to claim 1 , wherein the contacting of the CaO and the CO 2 -comprising gas in step (iii) until an aqueous environment pH of 7.2 is reached.
33. The process according to claim 1 , wherein the CO 2 -comprising gas is provided in step (iii) at an overpressure of at least 0.1 bar relative to the pressure in said reactor.
34. The process according to claim 1 , wherein the CO 2 -comprising gas is provided in step (iii) at an overpressure of at least 0.6 bar relative to the pressure in said reactor.
35. The process according to claim 1 , wherein the PCC-comprising suspension of step (iv) is concentrated by mechanical and/or thermal concentration.
36. The process according to claim 1 , wherein the PCC of step (iv) is dried.
37. The process according to claim 1 , wherein monomer a) comprises methacrylic acid and ethyl acrylate, and monomer b) comprises (i) a first substituent consisting of Formula (I), wherein R is an ester function, R′ is a methyl group, m is 0, p is 0, n is 45, and q is 1; and (ii) a second substituent consisting of a methyl group, and wherein the first and second substituents of monomer b) are in trans-position relative to one another.