Patent GB-954209-A (GB)
Title: Improvements in or relating to a defoaming composition and method
IPC: B01D19/04
Filed: 1960-07-19
Abstract: Silica is treated to render the surface thereof hydrophobic by (a) spraying with 15% by weight of dimethypolysiloxane oil (Ex. 1), (b) exposing to the vapours of dichlorodimethyl silane (Ex. 2), (c) treating with an alcohol, e.g. butanol, under high temperature and pressure, or (d) coating with a polymerization initiator and contacting the coated particles with a gaseous monomer to produce a polymer coated silica. The silica is employed in defoaming compositions (see Division B1).ALSO:A defoaming composition comprises 80-97 parts of a water-insoluble, hydrophobic, non-polar organic liquid, e.g. 20-3 parts of hydrophobic silica suspended therein and 0,5-5% of a spreading agent, based on said organic liquid, silica and spreading agent.  Organic liquids specified are naphthenic and paraffinic mineral oils, kerosene, trifluoro vinyl chloride polymer and chloronaphthalenes.  In an example methyl cellulose is used.  The silica (preferably having a particle size of 0,03-1 micron, may be prepared as an aerogel by removing the organic phase from a silica organo gel, as fume silica by combustion of silicon tetrachloride or as a precipitate from sodium silicate. The particle size may be reduced, if desired, in an air mill.  The silica may be made hydrophobic by treatment with a silicone, e.g. by spraying with 5-100% of dimethylpolysiloxane followed by heating at 250-350  DEG C.; by treatment with 5-15% of the vapours of an organo-silicon halide, e.g. methyl phenyl, tolyl and phenyl methyl silicon halides, dimethyldichlorosilane being specified; or by dispersion in a silicone oil, heating at 250-350  DEG C. and centrifuging after dilution with a solvent, e.g. hexane; or by treating with an alcohol, e.g. butanol under high temperature and pressure; or by coating with a polymer, e.g. by coating with a polymerization initiator and contacting the coated silica with gaseous monomer.  The spreading agent may be anionic (alkali metal, alkaline earth metal, aluminium, ammonium, or amine salts of fatty acids having 12-22 carbon atoms, e.g. sodium and triethanolamine stearates, or the acids themselves, and rosin soaps; these may be formed in situ: alkali metal salts of alkyl aryl sulphonic acids, soduim dialkyl sulphosuccinate, sulphated castor oil, sulphonated tallow, alkali metal salts of short chain petroleum sulphonic acids), cationic (salts of amines having 8-35 carbon atoms, e.g. acetates of oleylamine, cetylamine, di(aminoethyl) stearamide, dilauroyl triethylene tetramine, 1-aminoethyl-2-heptadecenyl imidazoline and didodecylamine lactate; quaternary salts, e.g. morpholinium ethyl sulphate, cetylpyridinium bromide, hexadecyl ethyl morpholinium chloride and diethyl didodecyl ammonium chloride), or nonionic (ethylene oxide condensation products with fatty alcohols having 8-35 carbon atoms, alkyl phenols, higher fatty acid amides, polyhydric alcohol (or the inner anhydride thereof), partial fatty acid esters, e.g. glycerol palmitate, pentaerythritol monooleate, sorbitan mono- and tri-stearate, mannitan monopalmitate; polyethylene glycol mono-and di-esters, e.g. of palmitic, lauric, stearic, oleic, arachidic, or behenic acids; polyethylene glycol mono-ester mono-ethers, e.g. methoxypolyethyleneglycol monostearate) or a mixture of nonionic and anionic or cationic spreading agents may be used.  Additional spreading agents disclosed in examples are sorbitan tri-oleate and sorbitan mono-stearate.  The compositions are prepared by dispersing the hydrobic silica in the organic liquid, the spreading agent being added before, during or after dispersion; a colloid mill, homogenizer or ball mill may be used to assist dispersion.  The composition may if desired be formed into an emulsion with water using an emulsifying agent, e.g. a mixture of sorbitan mono-stearate and polyoxyethylene sorbitan mono-stearate and using a colloid mill or homogenizer.  In examples emulsions comprising hydrophobic silica, methyl cellulose, sorbitan tristearate and water, with polyvinyl alcohol or gelatine as optional additional ingredients are mixed and homogenized.