Patent GB-998991-A (GB)
Title: Siloxane antifoam compositions
IPC: C08G77/392
Filed: 1962-11-16
Abstract: An antifoam composition consists essentially of an intimate admixture of (1) from 90 to 99% (by wt.) of a siloxane copolymer containing an average of from 1.75 to 2.1 organic radicals and Si-bonded H atoms when present per Si atom, the copolymer consisting essentially of (A) from 0.04 to 4.5 mol per cent of units of the formula <FORM:0998991/C3/1> wherein M is an ammonium ion, an alkali metal or a hydrogen atom, R is alkylene radical of 2 to 30 C atoms, a cycloalkylene radical of 4 to 18 C atoms or an aralkylene radical of 7 to 18 C atoms, wherein the S atom is attached to the C atom in R which is at least the second C atom away from the Si atom, a is 1, 2 or 3, b is 0, 1 or 2 and a+b is 1, 2 or 3, and (B) from 95.5 to 99.96 mol. per cent of units of the formula <FORM:0998991/C3/2> wherein c is 1, 2 or 3 and in the polymer has an average value of from 1 to 2.1, d is 0 or 1, the average value of c+d in the polymer is from 1.75 to 2.1, and (2) from 1 to 10% of finely divided silica or C black.  The S-containing siloxanes are described in Specification 998,993 and in U.S.A.  Specification 2,968,643.  The silica filler can be silica aerogel, fume silica or precipitated silica, or it can be a treated silica as described in Specification 699,759.  The composition is made by mixing the ingredients together, and preferably by mixing them with a liquid methylpolysiloxane. Pigments, rust inhibitors and antioxidants may also be added. Examples are given describing the preparation of the copolymers and compositions and the antifoaming efficiency of the compositions.ALSO:An antifoam composition consists essentially of an intimate admixture of (1) from 1-10% of finely divided silica or carbon black, and (2) from 90-99% by weight of a siloxane copolymer containing an average of from 1,75-2,1 organic radicals and Si-bonded H atoms when present per Si atom, the copolymer consisting essentially of (A) from 0,04-4,5 mol per cent of units of the formula <FORM:0998991/B1-B2/1> wherein M is an ammonium ion, an alkali metal or a H atom, R is an alkylene radical of 2-30 C atoms, a cycloalkylene radical of 4-18 C atoms or an aralkylene radical of 7-18 C atoms, wherein the S atom is attached to the C atom in R which is at least the second C atom away from the Si atom, a is 1, 2 or 3, b is 0, 1 or 2 and a+b is 1, 2 or 3, and (B) from 95,5-99,96 mol per cent of units of the formula <FORM:0998991/B1-B2/2> wherein c is 1, 2 or 3 and in the polymer has an average value of from 1 to 2,1, d is 0 or 1, the average value of c+d in the polymer is from 1,75 to 2,1 (see Division C3).  The sulphur-containing siloxanes are described in Specification 998,993 and in U.S.A.  Specification 2,968,643.  The silica filler can be silica aerogel, fume silica, precipitated silica or a treated silica as described in Specification 699,759.  The composition is made merely by mixing the ingredients together and preferably with a liquid methylpolysiloxane.  Pigments, rust inhibitors and antioxidants may also be added.  Examples are given describing the preparation of the copolymers and compositions and the antifoaming efficiency of the compositions.  The compositions are used by adding them to any foaming aqueous system.