Donald W Calvin

US Patent:

40081303, Feb 15, 1977

Filed:

Feb 23, 1976

Appl. No.:

5/660294

Inventors:

Joel F. M. Leathers - Midland MI
Donald W. Calvin - Zachary LA

Assignee:

The Dow Chemical Company - Midland MI

International Classification:

B01D 336

US Classification:

203 6

Abstract:

Fluorosilicic acid solutions, which normally undergo decomposition when distilled, thereby creating unwanted forms of SiO. sub. 2, are rendered stable during distillation by providing in the fluorosilicic acid solution an amount of HF which is at least about 10 parts of HF per 36 parts of H. sub. 2 SiF. sub. 6 and an amount of H. sub. 2 O which is at least about 54 parts of H. sub. 2 O per 36 parts of H. sub. 2 SiF. sub. 6. The mixture is distilled to remove any excess H. sub. 2 O and excess HF that is present, without encountering formation of SiO. sub. 2, until an azeotropic solution containing about 36% H. sub. 2 SiF. sub. 6, about 10% HF and about 54% H. sub. 2 O is reached. The ternary azeotrope, being of constant quality and concentration, is more suitable for use in various processes, such as processes for making fumed SiO. sub. 2, than H. sub. 2 SiF. sub. 6 solutions which are not of constant quality or concentration.

US Patent:

45085382, Apr 2, 1985

Filed:

Dec 4, 1980

Appl. No.:

6/212762

Inventors:

Joel F. M. Leathers - Midland MI
Donald W. Calvin - Midland MI

Assignee:

The Dow Chemical Company - Midland MI

International Classification:

C01B 3312

US Classification:

23313R

Abstract:

A method of recovering fumed hydrophobic SiO. sub. 2, produced by the flame hydrolysis of a ternary azeotrope of H. sub. 2 SiF. sub. 6, HF, and H. sub. 2 O, is disclosed. The method involves passing the fumed hydrophobic silica, as it leaves the combustion chamber, through a nonclassifying agglomerator at a residence (travel) time of from about 0. 5 to several seconds, preferably about 1. 0 to about 5. 0 seconds, then separating the fumed silica from the product stream in a cyclone separator or other means for collecting dispersoids.

US Patent:

40596800, Nov 22, 1977

Filed:

Sep 20, 1976

Appl. No.:

5/724683

Inventors:

Joel F. M. Leathers - Midland MI
Donald W. Calvin - Zachary LA

Assignee:

The Dow Chemical Company - Midland MI

International Classification:

C01B 3312
C01B 722

US Classification:

423337

Abstract:

Fluorosilicic acid solutions, which normally undergo decomposition when distilled, thereby creating unwanted forms of SiO. sub. 2, are rendered stable during distillation by providing in the fluorosilicic acid solution an amount of HF which is at least about 10 parts of HF per 36 parts of H. sub. 2 SiF. sub. 6 and an amount of H. sub. 2 O which is at least about 54 parts of H. sub. 2 O per 36 parts of H. sub. 2 SiF. sub. 6. The mixture is distilled to remove any excess H. sub. 2 O and excess HF that is present, without encountering formation of SiO. sub. 2, until an azeotropic solution containing about 36% H. sub. 2 SiF. sub. 6, about 10% HF and about 54% H. sub. 2 O is reached. The ternary azeotrope, being of constant quality and concentration, is more suitable for use in various processes, such as processes for making fumed SiO. sub. 2, than H. sub. 2 SiF. sub. 6 solutions which are not of constant quality or concentration.