Use of calcium carbonate in an acidic aqueous media

• US 6,228,161 B1
• Filed: 12/30/1996
• Issued: 05/08/2001
• Est. Priority Date: 12/30/1996
• Status: Expired due to Term

• Current Assignee: Minerals Technologies Incorporated
• Original Assignee: Minerals Technologies Incorporated
• Inventors: Drummond, Donald Kendall
• Primary Examiner(s): Chin, Peter
• Application Number:
  US08/774,662
• Time in Patent Office: 1,590 Days
• Field of Search: 106/464, 106/465, 162/135, 162/181.2, 162/168.1, 162/158
• US Class Current: 106/464
• CPC Class Codes: C01F 11/18 Carbonates
• CPC Class Codes: C01F 11/185 After-treatment, e.g. grinding, purification, conversion of crystal morphology
• CPC Class Codes: C01P 2006/22 Rheological behaviour as dispersion, e.g. viscosity, sedimentation stability
• CPC Class Codes: C01P 2006/60 Optical properties, e.g. expressed in CIELAB-values
• CPC Class Codes: C09C 1/021 Calcium carbonates
• CPC Class Codes: D21H 17/07 Nitrogen-containing compounds
• CPC Class Codes: D21H 17/65 Acid compounds
• CPC Class Codes: D21H 17/66 Salts, e.g. alums
• CPC Class Codes: D21H 17/67 Water-insoluble compounds, e.g. fillers, pigments
• CPC Class Codes: D21H 17/675 Oxides, hydroxides or carbonates
• CPC Class Codes: D21H 17/71 Mixtures of material D21H17/69 takes precedence; Pulp or paper comprising several different materials not incorporated by special processes D21H23/10, D21H23/70, D21H23/76 take precedence

Abstract

The present invention relates to an acid-stabilized calcium carbonate slurry having a pH of less than 7, preferably between about 6 and about 7, containing water, calcium carbonate, preferably precipitated calcium carbonate, and an acid-stabilizer of a water soluble calcium salt, a weak acid, a chelating agent, a weak acid capable of chelating calcium ion, or a mixture thereof. The acid-stabilizer is present in an amount sufficient to provide an aqueous calcium carbonate slurry having an increased calcium ion concentration and an acidic pH. In a typical acid-stabilized calcium carbonate slurry of the invention, the acid-stabilizer is present in an amount sufficient to provide a calcium ion concentration of about 1 millimolar to about 5 molar, preferably from about 1 to about 120 millimolar. The invention also relates to a method of making the acid-stabilized calcium carbonate slurry of the invention, to a method of forming a filled paper, that includes the step of adding the acid-stabilized calcium carbonate slurry of the invention to a papermaking pulp in a process for making acid paper, and to a filled paper produced according to the method of the invention.

Claims

1. An acid-stabilized calcium carbonate slurry for use in making acid paper, consisting of water, calcium carbonate, and a water soluble calcium salt wherein the water soluble calcium salt is present in an amount sufficient to provide an aqueous calcium carbonate slurry having a calcium ion concentrate from about 1 millimolar to about 5 molar sufficient to impart a pH of less than 7.

2. The acid-stabilized calcium carbonate slurry of claim 1, wherein the calcium carbonate is present in an amount of from about 1 to about 40 percent by weight.

3. The acid-stabilized calcium carbonate slurry of claim 1, wherein the calcium carbonate is precipitated calcium carbonate.

4. The acid-stabilized calcium carbonate slurry of claim 1, wherein the water soluble calcium salt is present in an amount sufficient to provide a calcium ion concentration of from about 1 millimolar to about 5 molar.

5. The acid-stabilized calcium carbonate slurry of claim 4, wherein the water soluble calcium salt is present in an amount sufficient to provide a calcium ion concentration of from about 1 to about 120 millimolar.

6. The acid-stabilized calcium carbonate slurry of claim 4, wherein the calcium salt is calcium sulfate, calcium acetate, calcium nitrate, calcium citrate, a calcium halide, or a mixture thereof.

7. The acid-stabilized calcium carbonate slurry of claim 6, wherein the calcium halide is calcium chloride.

8. The acid-stabilized calcium carbonate slurry of claim 1, additionally comprising a weak acid present in an amount sufficient to provide a weak acid concentration of from about 0.1 to about 1000 millimolar.

9. The acid-stabilized calcium carbonate slurry of claim 8, wherein the weak acid is added in an amount sufficient to provide a weak acid concentration of from about 0.2 to about 100 millimolar.

10. The acid-stabilized calcium carbonate slurry of claim 8, wherein the water soluble calcium salt is present in an amount sufficient to provide a calcium ion concentration of from about 1 millimolar to about 5 molar.

11. The acid-stabilized calcium carbonate slurry of claim 10, wherein the water soluble calcium salt is present in an amount sufficient to provide a calcium ion concentration of from about 1 to about 120 millimolar.

12. The acid-stabilized calcium carbonate slurry of claim 8, wherein the weak acid is carbonic acid, phosphoric acid, sulfurous acid, or a carboxylic acid.

13. The acid-stabilized calcium carbonate slurry of claim 1, wherein the water soluble calcium salt is present in an amount sufficient to provide a calcium ion concentration of from about 1 millimolar to about 5 molar and additionally comprising a chelating agent in a concentration of from about 0.01 to about 1000 millimolar.

14. The acid-stabilized calcium carbonate slurry of claim 13, wherein the water soluble calcium salt is present in an amount sufficient to provide a calcium ion concentration of from about 1 to about 120 millimolar and the chelating agent is present in a concentration of from about 0.1 to about 100 millimolar.

15. The acid-stabilized calcium carbonate slurry of claim 13, wherein the chelating agent is a polycarboxylate.

16. The acid-stabilized calcium carbonate slurry of claim 15, wherein the polycarboxylate is sodium ethylenediaminetetraacetic acid (EDTA) or sodium polyacrylate.