Gasket/packing material with excellent adhesiveness and resistance to coolants

Claim 1

A room temperature-curing composition consisting essentially of a product obtained by mixing (i) 100 weight parts of an essentially linear polydimethylsiloxane having silicon-bonded hydroxyl group at the molecular terminals and having a viscosity of 0.005 to 0.05 m 2 /s at 25° C., (ii) 10 to 45 weight parts organopolysiloxane composed of R' 3 SiO 0 .5, R' 2 SiO, and SiO 2 units where each R' represents methyl, and in which the R' 3 SiO 0 .5 unit/R' 2 SiO/SiO 2 unit molar ratio is 0.7-1:0.01-0.5:1, (iii) 10 to 150 weight parts inorganic filler, (iv) 1 to 3 weight parts alkoxysilane selected from the group consisting of methyltrimethyoxysilane, vinyltrimethyoxysilane, gamma-glycidoxypropyltrimethyoxysilane, di(methyl ethyl ketoxime)diethoxysilane, and gamma-mercaptopropyltrimethoxysilane, and (v) 10 to 25 weight parts of a silicon compound selected from the group consisting of vinyltris(methyl ethyl ketoxime)silane, methyltris(methyl ethyl ketoxime)silane, tetrakis(methyl ethyl ketoxime)silane, and mixtures thereof to make compositions curable at room temperature to elastomeric solids which exhibit resistance to loss of properties upon exposure to radiator coolant.