| 摘要 |
Polyoxyalkylene-polysiloxane block copolymers are disclosed which exhibit an outstanding defoaming action and have the special advantage of not causing wetting defects when dispersions defoamed therewith are applied on a 2-dimensional substrate. Dispersions of polymeric organic substances, especially dispersions of vehicles, coating agents and adhesives are defoamed by the addition of 0.01 to 2.0% by weight, based on the dispersion to be defoamed, of a polyoxyalkylene-polysiloxane block copolymer of the formula, R1O-A-[B-A-]mR1 wherein A is a polyoxyalkylene block with the average formula CnH2nO-)y, in which n has a value of 2.8 to 4.0 and y a value of 15 to 100, B is a polysiloxane block of the average formula, <IMAGE> wherein the R2 groups are the same or different and represent an alkyl group with 1 to 4 carbon atoms or a phenyl group, with the proviso that at least 90% of the R2 groups are methyl groups and x has a value of 10 to 100, R1 groups are the same or different and represent a hydrogen atom or an alkyl group with 1 to 4 carbon atoms and m has a value of 4 to 20.
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