Thermally conductive condensation reaction curable polyorganosiloxane composition and methods for the preparation and use of the composition

1. A curable composition comprising:

(A) a condensation reaction catalyst,

(B) a polyorganosiloxane having an average, per molecule, of at least two hydrolyzable substituents,

(C) a crosslinker having formula (R 1 2 R 2 SiO 1/2 ) f (R 1 R 2 SiO 2/2 ) g (R 2 SiO 3/2 ) h (R 1 3 SiO 1/2 ) i (R 1 2 SiO 2/2 ) j (R 1 SiO 3/2 ) k (SiO 4/2 ) l , where

each R 1 is independently a monovalent organic group,

each R 2 has formula

where each D is independently a divalent organic group, each R is independently a monovalent hydrocarbon group, each X is independently a hydrolyzable substituent, subscript a is 0, 1, or 2, subscript b≧0, subscript c is 0, 1, 2, or 3, with the proviso that a quantity (a+c)≧1; and subscript d≧1, subscript e is 0 or 1, subscript f≧0, subscript g≧0, subscript h≧0, with the proviso that a quantity (f+g+h)≧2, subscript i≧0, subscript j≧0, subscript k≧0, subscript l≧0, with the proviso that a quantity (g+j)≧2, and with the proviso that when a quantity (a+c)=1, then a quantity (f+g+h)≧3, and

(D) a thermally conductive filler, where ingredient (D) is present in an amount of from 30% to 80% by volume of the curable composition.

2. The curable composition of claim 1 , where at least one of the following conditions is satisfied:

(i) ingredient (A) comprises an organotin compound, or

(ii) ingredient (A) comprises a dimethyltin compound.

3. The curable composition of claim 1 , where at least one of the following conditions is satisfied:

(i) ingredient (B) comprises a silanol-functional polyorganosiloxane; or

(ii) ingredient (B) comprises a silanol-terminated polydiorganosiloxane of formula R 4 R 3 2 SiO—(R 3 2 SiO) p —SiR 3 2 R 4 , where

each R 3 is independently a monovalent hydrocarbon group or a monovalent halogenated hydrocarbon group,

each R 4 is a hydrolyzable substituent, and

subscript p has an average value of 50 to 200,000; or

(iii) ingredient (B) comprises a silanol-terminated polydimethylsiloxane.

4. The curable composition of claim 1 , where at least one of the following conditions is satisfied:

(i) ingredient (C) comprises a crosslinker of formula (i)

where each D is independently a divalent hydrocarbon group, each X is independently a hydrolyzable substituent, each subscript a is independently 0, 1, or 2, each subscript b≧0, each subscript c is independently 0, 1, 2, or 3, each subscript d≧1, each subscript e is independently is 0 or 1, with the proviso that subscripts a, b, and c are selected such that the crosslinker has an average, per molecule, of at least three X, and subscript m has an average value of at least 100; or

(ii) ingredient (C) comprises a crosslinker of formula (ii)

where each D is independently an alkylene group, each X is independently an alkoxy group, each subscript b≧0, each subscript 2≧d≧1, and subscript m has an average value of 150 to 500; or

(iii) ingredient (C) comprises an alkoxysilylhydrocarbylene functional polyorganosiloxane.

5. The curable composition of claim 1 , where the curable composition further comprises at least one additional ingredient selected from (E) a spacer, (F) a pigment, (G) a treating agent, (H) an adhesion promoter, or (J) a drying agent.

6. A method comprising (i) mixing ingredients comprising:

(A) a condensation reaction catalyst,

(B) a polyorganosiloxane having an average, per molecule, of at least two hydrolyzable substituents,

(C) a crosslinker having unit formula (R 1 2 R 2 SiO 1/2 ) f (R 1 R 2 SiO 2/2 ) g (R 2 SiO 3/2 ) h (R 1 3 SiO 1/2 ) i (R 1 2 SiO 2/2 ) j (R 1 SiO 3/2 ) k (SiO 4/2 ) l , where

each R 1 is independently a monovalent organic group,

each R 2 has formula

where each D is independently a divalent organic group, each R is independently a monovalent hydrocarbon group, each X is independently a hydrolyzable substituent, subscript a is 0, 1, or 2, subscript b≧0, subscript c is 0, 1, 2, or 3, with the proviso that a quantity (a+c)≧1; subscript d≧1, subscript e is 0 or 1, subscript f≧0, subscript g≧0, subscript h≧0, with the proviso that a quantity (f+g+h)≧2, subscript i≧0, subscript j≧0, subscript k≧0, subscript l≧0, with the proviso that a quantity (g+j)≧2, and with the proviso that when a quantity (a+c)=1, then a quantity (f+g+h)≧3, and

(D) a thermally conductive filler;

thereby preparing a curable composition; where ingredient (D) is present in an amount of from 30% to 80% by volume of the curable composition.

7. The method of claim 6 , where the method further comprises adding to the curable composition at least one additional ingredient selected from (E) a spacer, (F) a pigment, (G) a treating agent, (H) an adhesion promoter, or (J) a drying agent.

8. The method of claim 6 , further comprising: (ii) contacting the curable composition with water.

9. A thermally conductive reaction product prepared by the method of claim 8 .

10. The curable composition of claim 1 , where ingredient (D) comprises alumina.

11. The curable composition of claim 2 , where condition (ii) is satisfied: ingredient (A) comprises a dimethyltin compound.

12. The curable composition of claim 4 , where condition (ii) is satisfied: ingredient (C) comprises a crosslinker of formula (ii)

where each D is independently an alkylene group, each X is independently an alkoxy group, each subscript b≧0, each subscript 2≧d≧1, and subscript m has an average value of 150 to 500.

13. The curable composition of claim 5 , where the curable composition further comprises (H) the adhesion promoter.

14. The method of claim 6 , where ingredient (D) comprises alumina.

15. The method of claim 7 , further comprising: (ii) contacting the curable composition with water.

16. A thermally conductive reaction product prepared by the method of claim 15 .

17. The curable composition of claim 5 , where the curable composition is stored under substantially anhydrous conditions, alternatively is stored in a sealed container.

18. The method of claim 6 , further comprising: (i-b) sealing the curable composition in a container to prevent exposure to moisture.