Room-temperature-curable organopolysiloxane composition

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 following general formula:
• (X)aR13−aSi—, wherein
• each X is independently selected from the group consisting of a hydroxyl group and a hydrolysable group,
• each R1 is independently selected from the group consisting of a monovalent hydrocarbon group and 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 group consisting of a silane and a siloxane oligomer, wherein
• the cross-linking agent has three or more silicon-bonded hydrolyzable groups per molecule;
• (C1) a platinum compound present in an amount such that metallic platinum is present in an amount of 1 to 2,000 ppm based on the weight of the composition;
• (C2) an organosiloxane oligomer, where
• the organosiloxane oligomer contains aryl and alkenyl groups,
• the organosiloxane oligomer has 8 or less silicon atoms per molecule, and
• the organosiloxane oligomer contains in each molecule at least one divalent organosiloxane group represented by the formula
• —(R2)(R3)SiO—(R2)(R3)Si—,
• where R2 is an aryl group, and R3 is an alkenyl group;
• wherein the organosiloxane oligomer is present in a quantity such that the composition contains at least 2 moles of component (C2) per 1 mole of platinum atoms in component (C1);
• and
• (D) 5 to 300 parts by weight of an inorganic powder.

A method characterized by:

• (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. %, wherein 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)aR13−aSi—, wherein
• X is selected from the group consisting of a hydroxyl group and a hydrolyzable group, R1 is selected from the group consisting of a monovalent hydrocarbon group and 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 group consisting of a silane and a siloxane oligomer, wherein 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.

A method characterized by:

• (1) adding (C1) a platinum compound, in an amount such that metallic platinum is present in an amount of 1 to 2,000 ppm based on the weight of a room-temperature-curable organopolysiloxane composition;
• to 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 following general formula:
• (X)aR13−aSi—, where
• each X is independently selected from the group consisting of a hydroxyl group and a hydrolysable group, each R1 is independently selected from the group consisting of a monovalent hydrocarbon group and 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 group consisting of a silane and a siloxane oligomer, wherein
• the cross-linking agent has three or more silicon-bonded hydrolyzable groups per molecule;
• (C2) an organosiloxane oligomer, where
• the organosiloxane oligomer contains aryl and alkenyl groups,
• the organosiloxane oligomer has 8 or less silicon atoms per molecule, and
• the organosiloxane oligomer contains in each molecule at least one divalent organosiloxane group as represented by the formula
• —(R2)(R3)SiO—(R2)(R3)Si—,
• where R2 is an aryl group, and R3 is an alkenyl group;
• where the organosiloxane oligomer is present in a quantity such that the composition contains at least 2 moles of component (C2) per 1 mole of platinum atoms in component (C1);
• and
• (D) 5 to 300 parts by weight of an inorganic powder;
• and
• (2) curing the room-temperature-curable organopolysiloxane composition.