Room temperature curable silicone rubber composition

摘要

The invention provides an improvement of a room temperature-curable silicone rubber composition cured by the mechanism of the condensation reaction between terminal silanolic hydroxy groups of a diorganopolysiloxane and an organosilicon compound having at least three alkoxy groups per molecule in the presence of an organotin compound as a catalyst to form crosslinks in respect of the remarkably small permanent compression set as well as excellent heat resistance of the cured rubbery elastomer thereof. Different from conventional compositions of the above mentioned type containing some organotin compound as the curing catalyst, the inventive composition preferably contains very specific organotin compound as the curing catalyst, which is represented by the general formula R2R1Sn-O-SnR1R2 or R2SnR21, in which R is a monovalent hydrocarbon group and R1 is an acid residue of a monoalkyl ester of a dibasic carboxylic acid such as MeOCOCH=CHCOO- and the like, in a limited amount. The composition may further contain an inorganic filler, of which the neutral surface condition is important in order that the composition may have good curability to give a cured rubbery elastomer exhibiting a small permanent compression set. A limited content of silicon-bonded vinyl group in the diorganopolysiloxane, the balance being methyl groups, is effective to improve the heat resistance of the cured rubber.