Patent ID: 8530401

Claim:
A defoamer composition comprising (A) at least one substantially linear organopolysiloxane having a viscosity of 50-200 mm 2 /s at 25° C. and 1013 hPa, of the formula R 2 3-g (R 3 O) g Si—[OSiR 2 2 ] n —OSi(OR 3 ) g R 2 3-g (IV), in which R 2 are identical or different and denote a monovalent, optionally halogenated hydrocarbon radical having 1-30 carbon atoms or hydrogen, R 3 are identical or different and denote hydrogen or a monovalent hydrocarbon radical having 1-4 carbon atoms, n is an integer and has an average value such that the viscosity of the organopolysiloxane (A) is 50-200 mm 2 /s at 25° C. and 1013 hPa, g is 0 or 1, with the proviso that the organopolysiloxanes of the formula (IV) have on average an Si-bonded OH group content of 30-500 ppm by weight, (B) at least one organopolysiloxane having a viscosity of 500-200,000 mm 2 /s at 25° C. and 1013 hPa, comprising units of the formula R 2 c (R 3 O) d SiO (4-c-d)/2 (II), in which R 2 and R 3 have the definition indicated for them above, c is 0, 1, 2 or 3, and d is 0, 1, 2 or 3, with the proviso that the sum c+d is ≦3 and in more than 50% of all the units of the formula (II) in the organopolysiloxane (B), the sum c+d is 2, (C) at least one precipitated silica having a BET surface area of 20-500 m 2 /g, (D) at least one fumed silica having a BET surface area of 100-500 m 2 /g (E) at least one polyethersiloxane having a cloud point of less than 50° C., (F) optionally, one or more organopolysiloxane resins which consist substantially of R 2 3 SiO 1/2 (M) units and SiO 4/2 (Q) units, where the molar ratio of M units to Q units is in the range of from 0.5 to 2.0, (G) optionally, one or more organopolysiloxanes different from (A) and (B), and (H) optionally, one or more water-insoluble organic compounds.