Patent GB-848673-A (GB)
Title: Halogen-free silica pigments, cured products containing same, and method of preparation thereof
IPC: C09C1/30
Filed: 1956-12-20
Abstract: Light coloured to white, particulate solid amorphous or fibrous silica, containing up to 3% by weight halogen is treated (see Group III) with a liquid or gaseous alcohol free of amine groups to remove substantially all the halogen without causing sintering of the silica or decomposition of the alcohol, and the product is used as a reinforcing pigment in organic polymeric compositions. The alcohol forms surface-bound ester groups, which give the pigment hydrophobic properties.  The treated silica may be subsequently treated with steam at 100 DEG -350 DEG  C and 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, carboxylcontaining compounds, olefins, ester urethanes, or silicones.  The polymeric compositions contain usual compounding ingredients, and may contain 25-45% pigment to 75-55% polymer and are cured.  In examples the silica pigment is mixed with:-(6) natural rubber, dianilino methane, sulphur, zinc oxide, stearic acid, pine oil, phenylbeta-naphthylamine, didodecylamine, and benzyl thiazyl disulphide; (7) polyvinyl chloride, 75/25 styrene/acrylonitrile, lead stearate, and organic tin compound stabiliser, and 60/20/20 butadiene 1,3/acrylonitrile/styrene; (8) methyl silicone rubber and dicumyl peroxide.  Specifications 804,991, 804,992, 828,723 and 848,674 are referred to.ALSO:Light coloured to white, particulate solid amorphous silica, containing up to 3% by weight halogen, obtained by halogenating silicon monoxide (SiO2)x Siy to remove Si, is treated with a liquid or gaseous alcohol free of amine groups in an amount, and at a temperature and pressure, such as to remove substantially all the halogen without causing sintering of the silica or decomposition of the alcohol.  The halogenated silicon monoxide, which is preferably substantially fibrous, is prepared according to Specification 848,674 and the resulting silica may contain 1-8% bound nitrogen.  The alcohol forms surface bound ester groups, which give the pigment hydrophobic properties. Suitable alcohols, which include esters containing at least one free -OH group and chlorinated and fluorinated alcohols, are ethanol, 1-propanol, 1- or 2-butanol, 1-hexanol, 1-heptanol, cyclohexanol, 2-methyl cyclohexanol, 1,2-pentanediol, 2-ethyl hexanol, 3-methyl-3-buten-1-ol, allyl alcohol, phenyl trimethylol methane, 1,1,1, - trimethylol, - 2,4,4, - trimethyl pentane, 1,1,1, - trimethylol hexane, 1,1 - dimethylol heptane, pentaerythritol mono-oleate, or dioleate, or glyceryl mono-ricinoleate, -laurate, or -stearate.  Where polyhydric alcohols are used the -OH groups should be near each other and at one end of the chain.  The alcohol, preferably as gas or vapour, should be in excess, and is contacted by any method under anhydrous conditions (using anhydrous reactants) at not above 1100 DEG C., preferably 100-600 DEG C. under atmospheric, reduced, or elevated pressure. Nitrogen, argon, or helium, may be used as carrier for the alcohol. The treated silica may be subsequently treated with steam at 100-350 DEG C. and 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 usual compounding ingredients, and may contain 25-45% pigment to 75-55% polymer and are cured.  In examples (1) halogenated silicon monoxide is heated at 160 DEG C. in an autoclave with n-butyl alcohol while agitating, and (2) halogenated silicon monoxide in a silica tube is heated at 160-200 DEG C. while a mixture of n-butyl alcohol vapour and N2 is passed through.  The silica pigment is mixed with:- (6) natural rubber, dianilino methane, sulphur, zinc oxide, stearic acid, pine oil, phenylbeta-naphthylamine, didodecylamine, and benzyl thiazyl disulphide; (7) polyvinyl chloride, 75/25 styrene/acrylonitrile, lead stearate, and organic tin compound stabilizer, and 60/20/20 butadiene 1,3/acrylonitrile/styrene; (8) methyl silicone rubber and dicumyl peroxide.  Specifications 804,991, 804,992 and 828,723 also are referred to.