Defoamer compositions

Claim 1

A defoamer composition comprising (A) 5 to 50 parts by weight of an organopolysiloxane containing an oxyalkylene group having formula (1): ##STR13## wherein Y is a monovalent hydrocarbon group having 6 to 30 carbon atoms or an alkoxy group having 6 to 30 carbon atoms, G is an oxyalkylene group of the formula: --R--O--(C.sub.2 H.sub.4 O).sub.d (C.sub.3 H.sub.6 O).sub.e --A wherein R is a divalent hydrocarbon group having 2 to 6 carbon atoms, A is a group selected from the class consisting of a hydrogen atom, an acetyl group, an alkyl group having 1 to 8 carbon atoms, and an isocyanate group, d=6 to 60, e=2 to 60, d+e=8 to 75, and e/(d+e)=0.2 to 0.8, said oxyalkylene group having an average molecular weight of 500 to 5,000, a and b are independently equal to 0, 1 or 2, c is equal to 1, 2 or 3, a+b+c=3, l is an integer of from 10 to 200, m is a number such that m+2a is equal to 1 to 50, n is a number such that n+2b is equal to 1 to 30, and (n+2b)/l=0.01 to l, (B) 100 parts by weight of an organopolysiloxane containing an oxyalkylene group having formula (2): ##STR14## wherein G' is an oxyalkylene group of the formula: --R--O--(C.sub.2 H.sub.4 O).sub.h (C.sub.3 H.sub.6 O).sub.i --A wherein R and A are as defined above, h=6 to 60, i=2 to 60, h+i=8 to 75, and i/(h+i)=0.2 to 0.8, said oxyalkylene group having an average molecular weight of 500 to 5,000, f is equal to 1, 2 or 3, g is equal to 0, 1 or 2, f+g=3, p and q are independently integers of at least 1, and (q+2g)/p=0.02 to 1, (C) 20 to 200 parts by weight of a dimethylpolysiloxane having a viscosity of 100 to 1,000,000 centistokes at 25° C. and (D) a silica filler.