Silica pigment particulates

• US 6,013,234 A
• Filed: 06/07/1995
• Issued: 01/11/2000
• Est. Priority Date: 04/13/1979
• Status: Expired due to Term

• Current Assignee: Rhodia Chimie (Solvac SA)
• Original Assignee: Rhodia Chimie (Solvac SA)
• Inventors: Ray, Jean-Louis, Coudurier, Maurice
• Primary Examiner(s): Koslow, C. Melissa
• Application Number:
  US08/479,530
• Time in Patent Office: 1,679 Days
• Field of Search: 423/335, 423/339, 106/482, 106/287.34
• US Class Current: 423/335
• CPC Class Codes: C01P 2004/01 depicted by an image
• CPC Class Codes: C01P 2004/60 Particles characterised by their size
• CPC Class Codes: C01P 2006/11 Powder tap density
• CPC Class Codes: C01P 2006/12 Surface area
• CPC Class Codes: C01P 2006/22 Rheological behaviour as dispersion, e.g. viscosity, sedimentation stability
• CPC Class Codes: C08K 3/36 Silica
• CPC Class Codes: C09C 1/28 Compounds of silicon C09C1/0009, C09C1/0015, C09C1/0078 take precedence
• CPC Class Codes: C09C 1/30 Silicic acid
• CPC Class Codes: C09C 1/309 Combinations of treatments provided for in groups C09C1/3009 - C09C1/3081
• CPC Class Codes: C09C 1/42 Clays

Abstract

Dry, freely-flowing, water-insoluble but readily dispersible, solid and homogeneous silica pigment particulates essentially spheroidal in geometrical configuration and having a mean particle size in excess of 80μ, preferably in excess of 150μ, are prepared by atomizing to dryness a pulverulent aqueous suspension of silica having a solids contact in excess of 18%. Such silica pigment particulates, advantageously comprised of precipitated silica, are well adapted as reinforcing fillers for elastomeric matrices.

Claims

1. Dry, dust-free and non-dusting, solid and homogeneous atomized precipitated silica particulates essentially spheroidal in geometrical configuration, said particulates having a mean particle size in excess of 150 microns, a fill density in compacted state in excess of 0.200, a BET surface area ranging from 100 to 350 m² /g, and a CTAB surface area ranging from 100 to 350 m² /g.

2. The precipitated silica particulates as defined by claim 1, said particulates having a specific volume in the range of from about 0.7 to 1.1.

3. The precipitated silica particulates as defined by claim 1, said particulates having a fill density in compacted state from about 0.28 to 0.32.

4. The precipitated silica particulates as defined by claim 1, wherein the mean particle size of said particulates is in the range of from about 200 to 300 microns.

5. A shaped article comprising an elastomeric matrix, said elastomeric matrix having well dispersed therein an effective reinforcing amount of dry, dust-free and non-dusting, solid and homogeneous atomized precipitated silica particulates essentially spheroidal in geometrical configuration, said particulates having a mean particle size in excess of 150 microns, a fill density in compacted state in excess of 0.200, a BET surface area ranging from 100 to 350 m² /g, and a CTAB surface area ranging from 100 to 350 m² /g.

6. The shaped article as defined by claim 5, said elastomeric matrix comprising a rubber.

7. The shaped article as defined by claim 5, said precipitated silica particulates having a specific volume in the range of from about 0.7 to 1.1.

8. The shaped article as defined by claim 5, said precipitated silica particulates having a fill density in compacted state from about 0.28 to 0.32.

9. Dry, dust-free and non-dusting, solid and homogeneous atomized precipitated silica particulates essentially spheroidal in geometrical configuration, said particulates having a mean particle size in excess of 150 microns, being free flowing to an extent of at least 10 times greater than in powder form, and said particulates having a fill density in compacted state in excess of 0.200, a BET surface area ranging from 100 to 350 m² /g, and a CTAB surface area ranging from 100 to 350 m² /g.

10. The precipitated silica particulates as defined in claim 9, said particulates having a specific volume in the range of from about 0.7 to 1.1.

11. The precipitated silica particulates as defined in claim 9, said particulates having a fill density in compacted state from about 0.28 to 0.32.

12. A shaped article comprising an elastomeric matrix, said elastomeric matrix having well dispersed therein an effective reinforcing amount of dry, dust-free and non-dusting, solid and homogeneous atomized precipitated silica particulates essentially spheroidal in geometrical configuration, said particulates having a mean particle size in excess of 150 microns, being free flowing to an extent of at least 10 times greater than in powder form, and said particulates having a fill density in compacted state in excess of 0.200, a BET surface area ranging from 100 to 350 m² /g, and a CTAB surface area ranging from 100 to 350 m² /g.

13. The shaped article as defined by claim 12, said elastomeric matrix comprising a rubber.

14. The shaped article as defined by claim 12, said precipitated silica particulates having a specific volume in the range of from about 0.7 to 1.1.

15. The shaped article as defined by claim 12, said precipitated silica particulates having a fill density in compacted state from about 0.28 to 0.32.

16. A process for the preparation of precipitated silica particulates which are essentially spheroidal in geometrical configuration, said particulates having a mean particle size in excess of 150 microns, a fill density in compacted state in excess of 0.200, a BET surface area ranging from 100 to 350 m² /g, and a CTAB surface area ranging from 100 to 350 m² /g, comprising:

(i) formulating an aqueous slurry of precipitated silica having a content in dry solids in excess of 18% and said aqueous slurry having a pH of at least 4, and

(ii) spraying to dryness said aqueous slurry by use of a liquid pressure nozzle, with the liquid pressure nozzle spraying being conducted at a pressure ranging from about 20 to 40 bars.

17. The process of claim 16, wherein the aqueous slurry is pulverized prior to atomization in order to reduce the particle size of the solids comprising a slurry such that no solids have a particle size of greater than 150 micron.

18. The process of claim 16, wherein the aqueous slurry of precipitated silica has a solids content in the range of from about 20 to 25%.

19. The process of claim 16, wherein the aqueous slurry of precipitated silica comprises precipitated silica filter cake.

20. The process of claim 19, wherein the precipitated silicate filter cake comprises recycled solids.

21. The process of claim 16, wherein the aqueous slurry has a pH of at least 4.5.

22. The process of claim 21, wherein the aqueous slurry has a pH in the range of from 4.5 to about 6.

23. A process for the preparation of precipitated silica particulates which are essentially spheroidal in geometrical configuration, said particulates having a mean particle size in excess of 150 microns, a fill density in compacted state in excess of 0.200, a BET surface area ranging from 100 to 350 m² /g, and a CTAB surface area ranging from 100 to 350 m² /g, comprising:

(i) formulating an aqueous slurry of precipitated silica having a content in dry solids in excess of 18% and said aqueous slurry having a pH of at least 4.5, and

(ii) spraying to dryness said aqueous slurry by use of a liquid pressure nozzle.

24. The process of claim 23, wherein the aqueous slurry is pulverized prior to atomization in order to reduce the particle size of the solids comprising a slurry such that no solids have a particle size of greater than 150 microns.

25. The process of claim 23, wherein the aqueous slurry of precipitated silica has a solids content in the range of from about 20 to 25%.

26. The process of claim 23, wherein the aqueous slurry of precipitated silica is comprised of precipitated silica filter cake.

27. The process of claim 26, wherein the precipitated silica filter cake is comprised of recycled solids.

28. The process of claim 23, wherein the precipitated silica filter cake is comprised of recycled solids.