GB1468896A - Defoaming compositions - Google Patents

Abstract

1468896 Defoaming composition for black liquor SHINETSU CHEMICAL CO 7 June 1974 [8 June 1973] 25390/74 Heading C1C [Also in Division C3] In a defoaming agent in the form of an emulsion and comprising a defoaming composition emulsified in water with an emulsifier or in the form of a solution of a defoaming composition in a water-miscible solvent, e.g. dioxane, the defoaming composition consists essentially of (a) from 50-98 p.b.w. of at least one oily fluid selected from polyorganosiloxane fluids and hydrocarbon oils having a viscosity of from 50-50,000 cs. at 25‹ C., and (b) from 50-2 p.b.w. of a finely divided silica filler having a specific surface area of at least 100 m.<SP>2</SP>/g., which has been surface treated with from 0À1 to 100 p.b.w. per 100 p.b.w. of the finely divided silica filler, of a nitrogen-containing organosilicon compound of the formula (R 3 Si) a Z, where R is a monovalent hydrocarbon group having up to 12 C atoms, a is 1 or 2, and Z is a monovalent, when a is 1, or divalent, when a is 2, group selected from -NR<SP>1</SP>X, -ONR<SP>1</SP> 2 , -NX 2 and =NX, where R<SP>1</SP> is a monovalent hydrocarbon group of up to 12 C atoms and X is hydrogen or a monovalent hydrocarbon group of up to 12 C atoms. An aliphatic acid ester of sorbitol may be added as a wetting agent in an amount of from 0À1-5 p.b.w. per 100 p.b.w. of components (a) and (b). The polyorganosiloxane fluid may be represented by the average unit formula where R<SP>2</SP> is a monovalent hydrocarbon group having up to 7 carbon atoms and n is 1À9 to 2À1. The silica filler may be silica aerogel of fumed silica. The nitrogen-containing organosilicon compound may be a silylainine, an aminoxysilane or a disilazane. The hydrocarbon oil is preferably an aliphatic hydrocarbon having a boiling point exceeding 70‹ C., or a hydrocarbon oil derived from petroleum. The defoaming agent may be added to foamable liquids, e.g. black liquor from the alkali process of pulp production. In the examples defoaming compositions are prepared from: component (a): (1) a dimethylpolysiloxane fluid (100 cs.) alone or together with spindel oil; or (2) spindel oil; and component (b): finely divided silica of surface area 200-300 m.<SP>2</SP>/g. surface-treated with trimethylsilylamine, dimethylaminooxytriethylsilane or hexamethyldisilazane; and optionally sorbitol monolaurate as wetting agent. The defoaming compositions are either emulsified in water with emulsifiers or dissolved in dioxane and the resulting defoaming agents are added to aqueous solutions containing sodium oleate or polyoxyethylene nonylphenyl ether, or to the black liquor from an alkaline pulping process, for defoaming tests (Example 4).