Patent GB-848674-A (GB)
Title: Silicon dioxide pigments and preparation of same
IPC: C01B33/18
Filed: 1956-12-20
Abstract: Light coloured to white silicon dioxide pigment is prepared by treating brown, particulate, solid, disproportionated silicon monoxide (SiO2)x Siy (see Group III) with gaseous fluorine, chlorine, bromine, or iodine, to form SiO2 containing say 3% halogen and is used as a reinforcing pigment in organic polymeric compositions.  The pigment may be fibrous.  The halogen may be removed from the resulting silica by treatment with water or steam to replace halogen with -OH groups.  The halogen-free silica may be coated with alcohols, amines, or silicone resins.  A large number of organic polymers, in which the pigment may be used, are specified including natural and synthetic rubbers, such as polymers, copolymer, terpolymers, &c., of conjugated dienes, vinyl resins, acrylic resins, carboxyl-containing compounds, olefins, ester urethanes, or silicones.  The polymeric compositions contain the usual compounding ingredients, and may contain 25-45% pigment to 75-55% polymer, and are cured.  In examples:-the halogen free pigment is mixed with:-(4) natural rubber, dianilino methane, sulphur, zinc oxide, stearic acid, pine oil, phenylbeta-naphthylamine, didodecylamine, and benzylthiazyl disulphide; (5) polyvinyl chloride, lead stearate, a toughener, a stabiliser, and a processing aid; (6) methyl silicone rubber and dicumyl peroxide. Specification 828,723 is referred to.ALSO:Light coloured to white silicon dioxide pigment is prepared by treating brown, particulate, solid, disproportionated silicon monoxide (SiO2)x Siy at from 600 DEG C. to below the fusion point of the silicon monoxide with gaseous fluorine, chlorine, bromine, or iodine, in amount such as to form SiO2 containing say 3% halogen and gaseous silicon halides by reaction with Si.  To reduce the silicon halide formation, the halogen gas may contain up to 66%, but preferably not over 50%, oxidis-ing gas, e.g. oxygen, water vapour, or air, to form additional SiO2.  The halogen may be removed from the resulting silica by treatment with water or steam to replace halogen with -OH groups.  The halogen should be in excess, and is contacted with the silicon monoxide by any method at 600-1100 DEG C., preferably 700-900 DEG C.  The halogen removal is effected with steam at 100-1100 DEG C., and some bound nitrogen may also be removed, but additional steam is required to remove all bound nitrogen.  The halogen-free silica may be coated with alcohols, amines, or silicone resins. A large number of organic polymers, in which the pigment may be used, are specified including natural and synthetic rubbers, such as polymers, copolymers, terpolymers &c. of conjugated dienes, vinyl resins, acrylic resins, carboxyl-containing compounds, olefins, ester urethanes, or silicones.  The polymeric compositions contain the usual compounding ingredients, and may contain 25-45% pigment to 75-55% polymer, and are cured.  In Examples:- (1) chlorine is passed through substantially fibrous silicon monoxide in a heated silica tube and silicon tetrachloride and hexachlorodisiloxane are collected in an ice-cooled receiver; (3) the halogenated silica of (1) has steam passed therethrough in a heated tube.  The halogen free pigment is mixed with:- (4) natural rubber, dianilino methane, sulphur, zinc oxide, stearic acid, pine oil, phenylbetanaphthylamine, didodecylamine, and benzylthiazyldisulphide; (5) polyvinyl chloride, lead stearate, a toughener, a stabilizer, and a processing aid; (6) methyl silicone rubber and dicumyl peroxide.  Specifications 804,991, 804,992 and 828,723 are referred to.