Patent ID: 7776929

Claim:
A method for the production of defoamer formulations using hydrophilic silicas, comprising (i) mixing (A) 100 parts of at least one polyorganosiloxane comprising units of the formula R a (R 1 O) b SiO (4-a-b)/2 (I), in which R are identical or different and are hydrogen or a monovalent, substituted or unsubstituted, saturated or unsaturated hydrocarbon radical having 1 to 30 carbon atoms per radical, R 1 are identical or different and are a hydrogen atom or a monovalent, substituted or unsubstituted, saturated or unsaturated hydrocarbon radical having 1 to 30 carbon atoms per radical, a is 0, 1, 2 or 3, b is 0 or 1, the sum a+b being ≦3, with the proviso that in 0.01% to 0.15% of all the units of the formula (I), based on the total number of units of formula (I), b is other than 0, while in the remaining units of the formula (I) b is 0, and the polyorganosiloxane (I) has a viscosity of 100 to 20,000 mPa·s at 25° C., with (B) 0.1 to 100 parts of at least one amorphous, hydrophilic, precipitated or fumed silica having a BET surface area of 20-1000 m 2 /g, (C) 0 to 50 parts of silicone resin(s) composed substantially of units of the general formula R 3 SiO 1/2 and SiO 4/2 , R having the definition indicated above, (D) 0 to 200 parts of one or more polyorganosiloxanes comprising units of the formula (R a′ R 2 O) b′ SiO (4-a′-b′)/2 (II), where R has the definition indicated for it above, R 2 are identical or different and are a hydrogen atom or a monovalent, substituted or unsubstituted, saturated or unsaturated hydrocarbon radical having 1 to 30 carbon atoms per radical, a′ is 0, 1, 2 or 3, b′ is 0 or 1, the sum a′+b′ being ≦3, with the proviso that in less than 0.01% or in more than 1% of all the units of the formula (II), based on the total number of units of the formula (II), b′ is other than 0, while in the remaining units of the formula (II) b′ is 0, (E) optionally 0-5.0 parts of an alkaline or acidic catalyst and (F) optionally 0-1000 parts of an organic compound containing no silicon, and (ii) heating this mixture to a temperature of 50 to 250° C., heating being continued at least until the viscosity has a value of less than 50% of the viscosity, as measured using a cone/plate viscometer at a temperature of 25° C. and a shear rate of 1/s, of the same mixture prepared without heating.