Patent ID: 6750279
Filing Date: 2004-06-15
Classification: C08G,C08K,C08L

Abstract:
A curable composition comprising:(a) an alkenyl terminated linear diorganopolysiloxane gum; (b) an alkenyl containing diorganopolysiloxane gum; (c) a precipitated silica reinforcing filler with surface area of from about 90 to 300 m2/g; (d) a hydroxy terminated polysiloxane fluid; (e) an organohydrogenpolysiloxane; (f) an effective amount of a low compression set additive; and (g) an effective amount of an addition-cure catalyst wherein the alkenyl terminated linear diorganopolysiloxane gum has the formula:MviDxDviyMvi where Mvi is R1R22SiO3/2 D is R32SiO2/2; Dvi is R4R5SiO2/2; where R1 and R4 are each independently (C2-C6)alkenyl, R2, R3 and R5 are each independently (C1-C6)alkyl or (C2-C6)alkenyl, and x and y are chosen so that the viscosity of the gum is in the range of from about 1,000,000 to about 200,000,000 centipoise at 25Â° C., and having an alkenyl concentration of about 0.001 to about 0.01 mole percent of siloxy units and wherein the low compression set additive is an acetylene alcohol having the formula:Hâ€”Câ‰¡Câ€”R10â€”OH wherein R10 is a divalent hydrocarbon radical comprising 6 to 40 carbon atoms where the structure of R10 may be any combination of linear, branched, aliphatic, aromatic, and olefinic, with the limitation that the alcohol is always &agr; to the acetylene group.