| abstract |
(A) Siloxane-based antifoams andn (B) silicone polyethers prepared by reacting organopolysiloxanes (1) containing 0.05% to 1.6% by weight of Si-bonded hydrogen atoms with unsaturated polyethers (3) of the formulae: nn CH 2 ═CR 1 —(CH 2 ) a O(C 2 H 4 O) b R 1 (Ia)n n CH 2 ═CR 1 —(CH 2 ) a O(C 2 H 4 O) b (C 3 H 6 O) c R 1 (Ib)n n CH 2 ═CR 1 —(CH 2 ) a O(C 3 H 6 O) c R 1 (Ic),n n wheren R 1 is a hydrogen or a C 1-6 hydrocarbon radical, a is 0 to 16, b is 1 to 50, and c is 1 to 50, wherein the sum b+c is ≧10 and at least two different polyethers (Ia), (Ib) and (Ic) are used, and optionally further reacting the reaction product with organopolysiloxanes (2) containing from 0.01% to 0.5% by weight of Si-bonded hydrogen atoms, wherein the first and second step reactions take place with a hydrosilylation catalyst, and the weight ratio of Si-bonded hydrogen in organopolysiloxane (1) to Si-bonded hydrogen in organopolysiloxane (2) is at least 1.5. |