Claims
- 1. A method of preparing silicone resin powder, comprising the steps of:
- (1) preparing a solution of an MQ silicone resin in a volatile liquid organosilicon solvent;
- said solution including no more than 5 weight percent of an aromatic organic solvent, based on the weight of said volatile liquid organosilicon solvent;
- said MQ silicone resin including M units of the general formula R.sub.3 SiO.sub.1/2 and Q units of the general formula SiO.sub.4/2 wherein R is a functional or nonfunctional, substituted or unsubstituted monovalent organic radical;
- said silicone resin having a ratio of M groups to Q groups between about 0.4 and about 1.1;
- said silicone resin having a number average molecular weight between about 2,000 and 15,000 and a polydispersity ranging from 1.0 to about 6.0;
- said solution having a resin solids content between about 5% and about 70% by weight; and
- (2) spray-drying the solution obtained in step (1) to remove the volatile liquid organosilicon solvent therefrom to produce a silicone resin powder;
- said spray-drying step (2) being carried out at a temperature between about 80.degree. C. and about 350.degree. C.
- 2. A method in accordance with claim 1 wherein said volatile liquid organosilicon solvent is an endblocker.
- 3. A method in accordance with claim 2 wherein said endblocker is functional.
- 4. A method in accordance with claim 2 wherein said endblocker is non-functional.
- 5. A method in accordance with claim 1 wherein said liquid organosilicon solvent is selected from the group consisting of cyclosiloxanes, disilazanes, linear siloxanes, alkoxysilanes, alkylhalosilanes and combinations thereof.
- 6. A method in accordance with claim 1 wherein said liquid organosilicon solvent is selected from the group consisting of hexamethyldisiloxane, hexamethyldisilazane, trimethylchlorosilane, divinyltetramethyldisiloxane, divinyltetramethyldisilazane, dimethyldichlorosilane, tetramethyldihydrogendisiloxane and mixtures thereof.
- 7. A method in accordance with claim 1 wherein said spray-drying step (2) is carried out at a temperature between about 150.degree. C. and 250.degree. C.
- 8. A spray-dried silicone resin powder made in accordance with the method of claim 1.
- 9. A spray-dried silicone resin powder in accordance with claim 8 having a residual aromatic content less than about 200 ppm.
- 10. A spray-dried silicone resin powder in accordance with claim 9 having a residual aromatic content less than about 5 ppm.
- 11. A spray-dried silicone resin powder in accordance with claim 8 having a residual volatiles content less than about 3 percent.
- 12. A spray-dried silicone resin powder in accordance with claim 8 having a mean particle size less than about 20 .mu.m.
- 13. A spray-dried silicone resin powder in accordance with claim 8 having residual volatile organic content of less than about 0.5 weight percent.
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of copending application application Ser. No. 08/497,736, filed on Jul. 3, 1995.
The present application for patent is a continuation-in-part of U.S. patent application Ser. No. 08/497,736, filed Jul. 3, 1995, both of which applications disclose inventions that were, at the time the inventions were made, subject to an obligation of assignment in a common assignee.
US Referenced Citations (8)
Continuation in Parts (1)
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Number |
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497736 |
Jul 1995 |
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