method for preventing the formation of or destruction of foam

摘要

An anti-foam composition comprises a mixture of a silica aerogel, and a methyl siloxane polymer having defined semi-rubbery characteristics and containing an average of from 1.75 to 2 carbon atoms per atom of silicon. The polymer may be diluted with up to about 3 parts of an untreated liquid dimethyl siloxane oil. The proportions are preferably from 1.5 to 7.5 parts by weight of aerogel to 100 parts of polymer or polymer and oil. The composition may be used as such in proportions of from about 1 to 5,000 parts per million of foaming liquid or as a 0.05 to 5.0 per cent dispersion in benzene, toluene or chlorinated hydrocarbon. Excess aerogel may be removed by filtration from such a dispersion before use. Foaming liquids mentioned include aqueous alkaline and soap solutions; alkaline black liquor in paper-making; synthetic rubber latices; butadiene-styrene emulsions; cutting oil emulsions; paint emulsions; varnishes; lubrication oils. The rubbery polymer may be made by partial oxidation as by air-blowing of liquid methyl siloxane polymers; by co-hydrolysis and co-condensation of mono- and di-methyl silanes; or by acid- or alkalicatalysed polymerization of liquid methyl siloxane. In examples of the preparation of a suitable polymer (1) dimethyl diethoxy silane and methyl triethoxy silane was hydrolyzed using NaOH as catalyst and the product polymerized with HCl as catalyst to a viscosity of 50,000 centistokes; (2) a liquid dimethyl siloxane polymer obtained by hydrolysis and condensation of dimethyl diethoxy silane was air-blown to a viscosity of 55,000 centistokes; and in the production of an antifoam agent; (3) 14 parts of the product of (2) was milled with 1 part of silica aerogel, the anti-foam properties with sodium oleate being measured; (4) the product of (2) diluted with unoxidized dimethyl siloxane oil, blended with silica aerogel, and dispersed in benzene was tested with sodium oleate; (5) the composition of (4) was tested with a triethanolamine triethanolamineoleate mixture.ALSO:An anti-foam composition comprises a mixture of a silica aerogel, and a methyl siloxane polymer having defined semi-rubbery characteristics and containing an average of from 1.75 to 2 carbon atoms per atom of silicon. The polymer may be diluted with up to about 3 parts of an untreated liquid dimethyl siloxane oil. The proportions are preferably from 1.5 to 7.5 parts by weight of aerogel to 100 parts of polymer or polymer and oil. The composition may be used as such in proportions of from about 1 to 5,000 parts per million of foaming liquid or as a 0.05 to 5.0 per cent dispersion in benzene, toluene or chlorinated hydrocarbon. Excess aerogel may be removed by filtration from such a dispersion before use. Foaming liquids mentioned include aqueous alkaline and soap solutions; alkaline black liquor in paper-making; synthetic rubber latices; butadiene-styrene emulsions; cutting oil emulsions; paint emulsions; varnishes; lubrication oils. The rubbery polymer may be made by partial oxidation as by air-blowing of liquid methyl siloxane polymers; by co-hydrolysis and co-condensation of mono- and di-methyl silanes; or by acid- or alkali-catalysed polymerization of liquid methyl siloxane. In examples of the preparation of a suitable polymer (1) dimethyl diethoxy silane and methyl triethoxy silane was hydrolyzed using NaOH as catalyst and the product polymerized with HCl as catalyst to a viscosity of 50,000 centistokes; (2) a liquid dimethyl siloxane polymer obtained by hydrolysis and condensation of dimethyl diethoxy silane was air-blown to a viscosity of 55,000 centistokes; and in the production of an anti-foam agent; (3) 14 parts of the product of (2) was milled with 1 part of silica aerogel, the anti-foam properties with sodium oleate being measured; (4) the product of (2) diluted with unoxidized dimethyl siloxane oil, blended with silica aerogel, and dispersed in benzene was tested with sodium oleate; (5) the composition of (4) was tested with a triethanolamine triethanolamineoleate mixture.