Heat-curable silicone rubber composition for rubber laminate

1. A rubber laminate obtained by simultaneously cross-linking and curing a heat-curable fluororubber composition and a heat-curable silicone composition, both compositions being in contact with each other during cross-linking;

the heat-curable silicone rubber composition comprising:

100 parts by mass of an alkenyl-containing diorganopolysiloxane (A) that comprises:

50 to 99 mass % of an alkenyl-containing diorganopolysiloxane (A1) that is capped at molecular terminals with alkenyl-containing organosilyl groups, is free of alkenyl groups in side molecular chains, and has a degree of polymerization in the range of 2,500 to 100,000;

1 to 50 mass % of an alkenyl-containing diorganopolysiloxane (A2) having two or more alkenyl groups in side molecular chains and having a degree of polymerization in the range of 2,500 to 100,000;

10 to 100 parts by mass of a fine silica powder (B) having specific surface area in the range of 50 m 2 /g to 400 m 2 /g;

0.1 to 10 parts by mass of an organohydrogenpolysiloxane (C) having in one molecule at least two silicon-bonded hydrogen atoms; and

0.1 to 5 part by mass of an organic peroxide (D).

2. The rubber laminate according to claim 1 , wherein the rubber laminate comprises a silicone-rubber layer and a fluororubber layer.

3. The rubber laminate according to claim 2 , wherein the content of alkenyl groups in constituent (A2) ranges from 0.4 to 1.8 mass %.

4. The rubber laminate according to claim 1 , wherein the content of alkenyl groups in constituent (A2) ranges from 0.4 to 1.8 mass %.

5. The rubber laminate according to claim 4 , wherein, in addition to the alkenyl groups, constituent (A2) contains other silicon-bonded groups which are alkyl groups.

6. The rubber laminate according to claim 5 , wherein more than 50 mole % of silicon-bonded groups in constituent (A2) are the alkyl groups.

7. The rubber laminate according to claim 6 , wherein the alkyl groups are methyl groups.

8. The rubber laminate according to claim 1 , wherein constituent (A1) is present at 60 to 98 mass %, and constituent (A2) is present at 2 to 40 mass %.

9. The rubber laminate according to claim 1 , wherein the degree of polymerization of constituent (A1) is in the range of 3,000 to 20,000.

10. The rubber laminate according to claim 1 , wherein the degree of polymerization of constituent (A2) is in the range of 3,000 to 20,000.

11. The rubber laminate according to claim 1 , wherein the alkenyl groups of constituent (A1) are vinyl.

12. A method of manufacturing a rubber laminate comprising the steps of bringing into mutual contact a heat-curable silicone composition and a heat-curable fluororubber composition and simultaneously cross-linking and curing both compositions, wherein the silicone-rubber composition comprises:

100 parts by mass of an alkenyl-containing diorganopolysiloxane (A) that comprises:

50 to 99 mass % of an alkenyl-containing diorganopolysiloxane (A1) that is capped at molecular terminals with alkenyl-containing organosilyl groups, is free of alkenyl groups in side molecular chains, and has a degree of polymerization in the range of 2,500 to 100,000;

1 to 50 mass % of an alkenyl-containing diorganopolysiloxane (A2) having two or more alkenyl groups in side molecular chains and having a degree of polymerization in the range of 2,500 to 100,000;

10 to 100 parts by mass of a fine silica powder (B) having specific surface area in the range of 50 m 2 /g to 400 m 2 /g;

0.1 to 10 parts by mass of an organohydrogenpolysiloxane (C) having in one molecule at least two silicon-bonded hydrogen atoms; and

0.1 to 5 part by mass of an organic peroxide (D).