Production of surface-reacted calcium salts by grinding induced conversion

Patent metadata

Field	Value
Publication number	US-12331200-B2
Application number	US-202017420308-A
Country	US
Kind code	B2
Filing date	Jan 31, 2020
Priority date	Feb 1, 2019
Publication date	Jun 17, 2025
Grant date	Jun 17, 2025

Abstract

The present invention relates to a process for producing an aqueous suspension of surface-reacted calcium salt particles by mixing a calcium salt excluding monocalcium phosphate and dicalcium phosphate, a calcium phosphate selected from monocalcium phosphate and/or dicalcium phosphate, with water, and grinding the obtained aqueous suspension at a pH value of at least 4.2 to form an aqueous suspension of surface-reacted calcium salt particles.

First claim

The invention claimed is:

1. A process for producing an aqueous suspension of surface-reacted calcium salt particles comprising the steps of:
a) providing a calcium salt excluding monocalcium phosphate and dicalcium phosphate,
b) providing a calcium phosphate, wherein the calcium phosphate is dicalcium phosphate and is produced by contacting a calcium ion source and a phosphate ion source,
c) forming an aqueous suspension by mixing the calcium salt of step a), and the calcium phosphate of step b) with water, and
d) grinding the aqueous suspension of step c) at a pH value from 4.2 to 14 and at a temperature of 0° C. to 100° C. to form an aqueous suspension of surface-reacted calcium salt particles,

wherein the calcium salt of step a) and the calcium phosphate of step b) in combination have a calcium ion to a phosphate ion molar ratio (Ca 2+ : PO 4 3− ) in the range from 2.2:1 to 100:1;
wherein grinding of step d) is carried out:
(1) in a ball mill, a rod mill, a vibrating mill, a centrifugal impact mill, a vertical bead mill, an attrition mill, a sand mill, or combinations thereof; and
(2) at a specific grinding energy from 50 to 500 kWh per dry metric ton of (2) surface-reacted calcium salt particles.

2. The process of claim 1 , wherein the calcium salt of step a) is selected from a calcium carbonate-comprising material, calcium oxide, calcium hydroxide, calcium chloride, calcium nitrate, calcium chlorate, calcium bromide, calcium iodide, calcium acetate, calcium sulphate, calcium citrate, or mixtures thereof.

3. The process of claim 2 , wherein the calcium carbonate-comprising material is selected from natural ground calcium carbonate, precipitated calcium carbonate, dolomite, or mixtures thereof.

4. The process of claim 1 , wherein the calcium salt of step a) is in form of particles having a weight median particle size d 50 (wt) from 0.05 to 500 μm.

5. The process of claim 1 , wherein the calcium salt of step a) and the calcium phosphate of step b) in combination have a calcium ion to phosphate ion molar ratio (Ca 2+ : PO 4 3− ) in the range from 2.5:1 to 10:1.

6. The process of claim 1 , wherein the calcium phosphate of step b) is dicalcium phosphate dihydrate and is provided in an amount from 1.7 to 230 wt.-%, based on the total weight of the calcium salt excluding monocalcium phosphate and dicalcium phosphate.

7. The process of claim 1 , wherein the calcium phosphate of step b) is anhydrous dicalcium phosphate and is provided in an amount from 1.4 to 181 wt.-%, based on the total weight of the calcium salt excluding monocalcium phosphate and dicalcium phosphate.

8. The process of claim 1 , wherein the aqueous suspension formed in step c) has a solids content from 1 to 90 wt.-%, based on the total weight of the aqueous suspension.

9. The process of claim 1 , wherein step d) is carried out at a pH value from 4.5 to 14.

10. The process of claim 1 , wherein the dicalcium phosphate of step b) is produced by the following steps:
i) providing the calcium ion source excluding dicalcium phosphate,
ii) providing the phosphate ion source selected from phosphoric acid, a salt thereof, or a mixture thereof, and
iii) contacting the calcium ion source of step i) and the phosphate ion source of step ii) in the presence of water to form dicalcium phosphate,
wherein the calcium ion source of step i) and the phosphate ion source of step ii) in combination are provided in a calcium ion to phosphate ion molar ratio from 1:2 to 5:1.

11. The process of claim 10 , wherein the calcium ion source of step i) is the same as the calcium salt of step a) of claim 1 and/or the phosphate ion source of step ii) is phosphoric acid.

12. The process of claim 10 , wherein the phosphate ion source is phosphoric acid, a hydrogen-free salt of phosphoric acid, a monohydrogen salt of phosphoric acid, Na 2 HPO 4 , or a dihydrogen salt of phosphoric acid, or a mixture thereof.

Assignees

• Omya Int Ag

Inventors

• Gerard Daniel E
• Karvonen Lassi

Classifications

• C09C3/041

  Grinding · CPC title

• C01P2006/12

  Surface area · CPC title

• C01P2004/51

  Particles with a specific particle size distribution · CPC title

• C01B25/327 Primary

  After-treatment · CPC title

• C09C1/021

  Calcium carbonates · CPC title