Room-temperature-curable organopolysiloxane composition

1. A room-temperature-curable organopolysiloxane composition comprising:

(A) 100 parts by weight of an organopolysiloxane having a viscosity from 100 to 500,000 mPa·s at 25° C. and having in one molecule 1.5 or more end groups represented by the general formula:

(X) a R 1 3-a Si—, where

each X is independently a hydroxyl group or a hydrolyzable group,

each R 1 is independently a monovalent hydrocarbon group or a halogen-substituted monovalent hydrocarbon group, and

a is 1, 2, or 3;

(B) 0.01 to 40 parts by weight of a cross-linking agent selected from a silane or a siloxane oligomer, where

the cross-linking agent has three or more silicon-bonded hydrolyzable groups per molecule; and

(C) microparticles of a thermoplastic resin containing a platinum compound in such an amount that the content of metallic platinum in component (C) is within the range of 0.01 to 5 wt. %, where

the microparticles have an average diameter from 0.1 to 20 μm,

component (C) is present in an amount sufficient to provide 1 to 2,000 ppm of metallic platinum in the composition; and

(D) 5 to 300 parts by weight of an inorganic powder.

2. The composition of claim 1 , where each X in component (A) is independently an alkoxy group, and each hydrolyzable group in component (B) is independently an alkoxy group.

3. The composition of claim 1 , where the thermoplastic resin of component (C) has a glass transition point from 40 to 250° C.

4. The composition of claim 1 , where the thermoplastic resin of component (C) is a silicone resin or a polycarbonate resin.

5. The composition of claim 1 , where component (D) is selected from the group consisting of a reinforcing silica powder, quartz powder, cerium oxide powder, titanium oxide powder, carbon black, aluminum hydroxide powder, calcium carbonate powder, aluminum oxide powder, magnesium hydroxide powder, magnesium carbonate powder, zinc carbonate powder, or mixtures thereof.

6. The composition of claim 5 , where the reinforcing silica powder is a dry-process silica.

7. The composition of claim 6 , where the surface of the dry-process silica is treated with a hydrophobic agent selected from the group consisting of a trimethylchlorosilane, dimethylchlorosilane, hexamethyldisilazane, and octamethylcyclotetrasiloxane.

8. The composition of claim 1 , where component (D) is a mixture of a reinforcing silica powder, quartz powder, cerium oxide powder, and carbon black.

9. The composition of claim 1 , where component (D) is a mixture of a reinforcing silica powder, quartz powder, cerium oxide powder, titanium oxide powder, and carbon black.

10. A method comprising the steps of:

(1) admixing an amount sufficient to provide 1 to 2,000 ppm of metallic platinum in a room-temperature-curable organopolysiloxane composition of (C) microparticles of a thermoplastic resin containing a platinum compound in such an amount that the content of metallic platinum in component (C) is 0.01 to 5 wt. %, where the microparticles have an average diameter from 0.1 to 20 μm;

with a composition comprising

(A) 100 parts by weight of an organopolysiloxane having a viscosity from 100 to 500,000 mPa·s at 25° C. and having in one molecule 1.5 or more end groups represented by the general formula:

(X) a R 1 3-a Si—, where

each X is independently a hydroxyl group or a hydrolyzable group,

each R 1 is independently a monovalent hydrocarbon group or a halogen-substituted monovalent hydrocarbon group, and

a is 1, 2, or 3;

(B) 0.01 to 40 parts by weight of a cross-linking agent selected from a silane or a siloxane oligomer, where

the cross-linking agent has three or more silicon-bonded hydrolyzable groups per molecule; and

(D) 5 to 300 parts by weight of an inorganic powder; and

(2) curing the room-temperature-curable organopolysiloxane composition.

11. A product prepared by the method of claim 10 .

12. The product of claim 11 , where the product is selected from coatings, seals, or adhesives used in electric and electronic devices.