Curable silicone composition

1. A curable silicone composition capable of producing a flex-resistant, highly transparent cured silicone product having JIS K6253 type-A durometer hardness in the range of 77 to 95 and JIS K6251 elongation equal to or greater than 38%, the aforementioned curable silicone composition comprising:

100 parts by mass of an alkenyl-containing organopolysiloxane (A) comprising: a dialkylpolysiloxane (A-1) that constitutes 52 to 69 mass % of component (A), contains on average at least 2 alkenyl groups in one molecule and has a 25° C. viscosity in the range of 5,000 to 35,000 mPa·s; and a alkenyl-containing organopolysiloxane resin (A-2) that constitutes 31 to 48 mass % of component (A), consists essentially of SiO 4/2 units, R 1 2 R 2 SiO 1/2 units, and R 1 3 SiO 1/2 units (where R 1 designates alkyl groups with 1 to 10 carbon atoms, and R 2 designates alkenyl groups), has the content of alkenyl groups ranging from 3.5 to 5.0 mass %, and the ratio of the sum of the mole numbers of the R 1 2 R 2 SiO 1/2 units and R 1 3 SiO 1/2 units to 1 mole of the SiO 4/2 units ranges from 0.5 to 1.4;

an organopolysiloxane (B) wherein silicon-bonded hydrogen atoms are in an amount of at least 0.7 mass % and wherein silicon-bonded groups other than hydrogen atoms are alkyl groups having 1 to 10 carbon atoms, with component (B) containing silicon-bonded hydrogen atoms in the amount of 0.7 to 5 moles per 1 mole of the total amount of alkenyl groups of component (A); and

a catalytic quantity of a hydrosilylation catalyst (C).

2. The curable silicone composition of claim 1 , wherein component (B) is an organopolysiloxane comprising: an organopolysiloxane (B-1) that constitutes 50 to 100 mass % of component (B), contains at least 0.7 mass % of silicon-bonded hydrogen atoms, and consists essentially of SiO 4/2 units and HR 3 2 SiO 1/2 units, (where R 3 designates alkyl groups with 1 to 10 carbon atoms); and a linear-chain organopolysiloxane (B-2) that constitutes 0 to 50 mass % of component (B), wherein silicon-bonded hydrogen atoms are in an amount of at least 0.7 mass % and wherein silicon-bonded groups other than hydrogen atoms are alkyl groups having 1 to 10 carbon atoms.

3. The curable silicone composition of claim 2 , wherein the dialkylpolysiloxane (A-1) has a viscosity in the range of 10,000 to 35,000 mPa·s at 25° C.

4. The curable silicone composition of claim 1 , wherein the dialkylpolysiloxane (A-1) has a viscosity in the range of 10,000 to 35,000 mPa·s at 25° C.

5. A composite cured silicone product comprising an integral unit of a substrate and a cured silicone layer obtained by thermally curing the curable silicone composition of claim 1 on the substrate.

6. A composite cured silicone product obtained by applying a curable silicone composition as claimed in claim 1 on a substrate and then thermally curing the applied composition.

7. The curable silicone composition of claim 1 , wherein the dialkylpolysiloxane (A-1) constitutes 52 to 65 mass % of component (A) and wherein the alkenyl-containing organopolysiloxane resin (A-2) constitutes 35 to 48 mass % of component (A).

8. The curable silicone composition of claim 7 , wherein the dialkylpolysiloxane (A-1) has a viscosity in the range of 11,000 to 32,000 mPa·s at 25° C.

9. A flex-resistant, highly transparent cured silicone product having JIS K6253 type-A durometer hardness in the range of 77 to 95 and JIS K6251 elongation equal to or greater than 38%, the aforementioned cured silicone product being obtained by thermally curing a curable silicone composition comprising:

100 parts by mass of an alkenyl-containing organopolysiloxane (A) comprising: a dialkylpolysiloxane (A-1) that constitutes 52 to 65 mass % of component (A), contains on average at least 2 alkenyl groups in one molecule and has a 25° C. viscosity in the range of 5,000 to 35,000 mPa·s; and a alkenyl-containing organopolysiloxane resin (A-2) that constitutes 35 to 48 mass % of component (A), consists essentially of SiO 4/2 units, R 1 2 R 2 SiO 1/2 units, and R 1 3 SiO 1/2 units (where R 1 designates alkyl groups with 1 to 10 carbon atoms, and R 2 designates alkenyl groups), has the content of alkenyl groups ranging from 3.5 to 5.0 mass %, and the ratio of the sum of the mole numbers of the R 1 2 R 2 SiO 1/2 units and R 1 3 SiO 1/2 units to 1 mole of the SiO 4/2 units ranges from 0.5 to 1.4;

an organopolysiloxane (B), wherein silicon-bonded hydrogen atoms are present in an amount of at least 0.7 mass % and wherein silicon-bonded groups other than hydrogen atoms are alkyl groups having 1 to 10 carbon atoms, with component (B) containing silicon-bonded hydrogen atoms in the amount of 0.7 to 5 moles per 1 mole of the total amount of alkenyl groups of component (A)}; and

a catalytic quantity of a hydrosilylation catalyst (C).

10. The flex-resistant, highly transparent cured silicone product according to claim 9 , wherein component (B) is an organopolysiloxane comprising: an organopolysiloxane (B-1) that constitutes 50 to 100% of component (B), contains at least 0.7 mass % of silicon-bonded hydrogen atoms, and consists essentially of SiO 4/2 units and R 3 2 HSiO 1/2 units (where R 3 designates alkyl groups with 1 to 10 carbon atoms); and a linear-chain organopolysiloxane (B-2) that constitutes 0 to 50 mass % of component (B), wherein silicon-bonded hydrogen atoms are present in an amount of at least 0.7 mass % and wherein silicon-bonded groups other than hydrogen atoms are alkyl groups having 1 to 10 carbon atoms.

11. The flex-resistant, highly transparent cured silicone product according to claim 10 having type-A durometer hardness according to JIS K6253 in the range of 80 to 90.

12. The flex-resistant, highly transparent cured silicone product according claim 9 having type-A durometer hardness according to JIS K6253 in the range of 80 to 90.

13. The flex-resistant, highly transparent cured silicone product according to claim 9 , wherein the dialkylpolysiloxane (A-1) has a viscosity in the range of 11,000 to 32,000 mPa·s at 25° C.