Patent ID: 7271215
Filing Date: 2007-09-18
Classification: C08G,C08L,Y10T

Abstract:
1. An addition reaction-curable liquid silicone rubber composition capable of imparting a cured product having a high hardness comprising, (A) 80 to 90% by weight, based on the sum of component (A) and component (B), of an organopolysiloxane containing at least one Si-bonded vinyl group only at each end of a backbone thereof and having a viscosity of from 1 to 1,000 Pa·s at 25° C., (B) 10 to 20% by weight, based on the sum of component (A) and component (B), of an organopolysiloxane containing at least two Si-bonded vinyl groups only in side chains on a backbone thereof and having a viscosity of from 0.1 to 100 Pa·s at 25° C., the amount of siloxane units having the vinyl groups being from 2 to 20 mole % of the total siloxane units of organopolysiloxane (B), (D) 35 to 55 parts by weight, per 100 parts by weight of the sum of component (A) and component (B), of finely divided silica having a specific surface area of at least 50 m (E) 3 to 15 parts by weight, per 100 parts by weight of the sum of component (A) and component (B), of hexamethyldisilazane, (F) 0.5 to 5 parts by weight, per 100 parts by weight of the sum of component (A) and component (B), of water, (G) an organohydrogenpolysiloxane containing at least two Si-bonded hydrogen atoms per molecule, the organohydrogenpolysiloxane being contained in a proportion such that the number of the Si-bonded hydrogen atoms contained per molecule of component (G) becomes from 1.0 to 5.0 per each Si-bonded vinyl group contained in the organopolysiloxanes of component (A) and component (B), and (H) a catalytic amount of a hydrosilation catalyst; the silicone rubber composition being cured into a product having a hardness of at least 75 as measured by a type-A durometer and an elongation at break of at least 200%.