Process for increasing opacity of precipitated calcium carbonate

Patent metadata

Field	Value
Publication number	US-10604416-B2
Application number	US-201615573635-A
Country	US
Kind code	B2
Filing date	May 24, 2016
Priority date	May 28, 2015
Publication date	Mar 31, 2020
Grant date	Mar 31, 2020

Abstract

The present invention relates to a process for preparing an aqueous suspension comprising precipitated calcium carbonate. The invention further relates to an aqueous suspension comprising precipitated calcium carbonate as well as a partially dewatered or essentially completely dried precipitated calcium carbonate obtainable by the process and the use of the aqueous suspension comprising precipitated calcium carbonate and/or the partially dewatered or essentially completely dried precipitated calcium carbonate in paper making, paper coating, plastic, agricultural, adhesives, sealants and/or paint applications.

First claim

The invention claimed is:

1. A process for preparing an aqueous suspension comprising precipitated calcium carbonate, the process comprising the steps of:
a) providing at least one calcium source being essentially insoluble in water;
b) providing at least one water-soluble manganese source;
c) providing at least one carbonate source;
d) carbonating the at least one calcium source of step a) with the at least one carbonate source of step c) in the presence of the at least one water-soluble manganese source of step b) in an aqueous medium to convert the calcium source at least partially into precipitated calcium carbonate and obtain an aqueous suspension comprising precipitated calcium carbonate, wherein the at least one water-soluble manganese source of step b) is present in carbonating step d) in an amount from 10 ppm to 1000 ppm (d/d), based on the total dry weight of the at least one calcium source of step a); and
e) dewatering the obtained aqueous suspension comprising precipitated calcium carbonate to remove a portion of water to obtain a partially dewatered precipitated calcium carbonate in form of an aqueous suspension having a solids content from 20.0 to 70.0 wt.-%, based on the total weight of the aqueous suspension.

2. The process according to claim 1 , wherein the at least one calcium source of step a) is selected from the group consisting of calcium oxide, calcined dolomite, dolomite, limestone, calcium carbonate, hydrated calcium oxide, calcium arsenate, calcium arsenite, calcium benzoate, calcium chromate, calcium citrate, calcium fluoride, calcium phosphate, calcium silicate, calcium sulfate, calcium sulphide, calcium tartrate, and any mixture thereof.

3. The process according to claim 1 , wherein the at least one calcium source of step a) is hydrated calcium oxide.

4. The process according to claim 1 , wherein the at least one calcium source of step a) is provided in an aqueous environment.

5. The process according to claim 1 , wherein the at least one calcium source of step a) is provided in an aqueous environment comprising the at least one calcium source of step a) in an amount of from 1.0 to 60.0 wt.-%, based on the total weight of the aqueous environment and the at least one calcium source of step a).

6. The process according to claim 1 , wherein the at least one calcium source of step a) is provided in an aqueous environment comprising the at least one calcium source of step a) in an amount of from 5.0 to 20.0 wt.-%, based on the total weight of the aqueous environment and the at least one calcium source of step a).

7. The process according to claim 1 , wherein the at least one water-soluble manganese source of step b) is selected from the group consisting of a manganese(II) source, a manganese(III) source, and a mixture thereof.

8. The process according to claim 1 , wherein the at least one water-soluble manganese source of step b) is from a manganese(II) source.

9. The process according to claim 1 , wherein the at least one water-soluble manganese source of step b) is at least one manganese(II) source selected from the group consisting of manganese(II) sulfate, manganese(II) hydroxide, manganese(II) chloride, manganese(II) acetate, manganese(II) arsenite, manganese(II) benzoate, manganese(II) bromide, manganese(II) carbonate, manganese(II) chlorate, manganese(II) citrate, manganese(II) formate, manganese(II) iodide, manganese(II) nitrate, manganese(II) oxalate, manganese(II) phosphate, manganese(II) tartrate, manganese(II) thiocyanate, and any mixture thereof.

10. The process according to claim 1 , wherein the at least one water-soluble manganese source of step b) is manganese(II) sulfate monohydrate.

11. The process according to claim 1 , wherein the at least one carbonate source of step c) is derived from a gaseous CO 2 source in the presence of water, and/or a carbonate-comprising anion.

12. The process according to claim 1 , wherein the at least one carbonate source of step c) is derived from a CO 2 comprising gas in the presence of water, and/or a carbonate-comprising anion selected from the group consisting of sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, and any mixture thereof.

13. The process according to claim 1 , wherein the at least one calcium source of step a) is hydrated calcium oxide, the at least one water-soluble manganese source of step b) is manganese(II) sulfate monohydrate, and the least one carbonate source of step c) is derived from a CO 2 comprising gas in the presence of water.

14. The process according to claim 1 , wherein the at least one water-soluble manganese source of step b) is present in carbonating step d) in an amount from 20 ppm to 800 ppm (d/d), based on the total dry weight of the at least one calcium source of step a).

15. The process according to claim 1 , wherein the at least one water-soluble manganese source of step b) is present in carbonating step d) in an amount from 50 ppm to 600 ppm (d/d), based on the total dry weight of the at least one calcium source of step a).

16. The process according to claim 1 , wherein the at least one calcium source of step a) is added to an aqueous environment to convert the calcium source at least partially into calcium cations before carbonating step d) is carried out.

17. The process according to claim 1 , wherein the at least one water-soluble manganese source of step b) is added before and/or during and/or after adding the at least one calcium source of step a) to the aqueous medium.

18. The process according to claim 1 , wherein the at least one water-soluble manganese source of step b) is added after adding the at least one calcium source of step a) to the aqueous medium.

19. The process according to claim 1 , wherein step d) is performed at a starting temperature of between 5° C. and 80° C.

20. The process according to claim 1 , wherein step d) is performed at a starting temperature of between 10° C. and 70° C.

21. The process according to claim 1 , wherein the aqueous suspension comprising precipitated calcium carbonate obtained in step d) has a solids content from 5.0 to 40.0 wt.-%, based on the total weight of the aqueous suspension.

22. The process according to claim 1 , wherein the aqueous suspension comprising precipitated calcium carbonate obtained in step d) has a solids content from 10.0 to 20.0 wt.-%, based on the total weight of the aqueous suspension.

23. The process according to claim 1 , wherein the precipitated calcium carbonate obtained by the process:
a) comprises particles having a weight median particle size d50 value of less than 15.0 μm, and/or
b) has a specific BET surface area of 1.0 m 2 /g to 50.0 m 2 /g, and/or
c) has a degree of whiteness R457 of at least 85%, and/or
d) has a yellowness index of at least 1.5.

24. The process according to claim 1 , wherein the precipitated calcium carbonate obtained by the process:
a) comprises particles having a weight median particle size d50 value of less than 3.0 μm, and/or
b) has a specific BET surface area of 4.0 m 2 /g to 20.0 m 2 /g, and/or
c) has a degree of whiteness R457 of between 90 and 95%, and/or
d) has a yellowness index of between 2.0 and 4.0.

25. The process according to claim 1 , wherein the partially dewatered precipitated calcium carbonate is in form of an aqueous suspension having a solids content from 25.0 to 60.0 wt.-%, based on the total weight of the aqueous suspension.

Assignees

• Omya Int Ag

Inventors

• Pohl Michael

Classifications

• C01F11/182 Primary

  Preparation of calcium carbonate by carbonation of aqueous solutions and characterised by an additive other than CaCO3-seeds · CPC title

• D21H17/675

  Oxides, hydroxides or carbonates · CPC title

• C09C1/021

  Calcium carbonates · CPC title

• C01F11/185

  After-treatment, e.g. grinding, purification, conversion of crystal morphology · CPC title

• C01P2004/61

  Micrometer sized, i.e. from 1-100 micrometer · CPC title