GB804994A - Improvements in rubbery pigments - Google Patents

Abstract

A fibre-containing white silicon dioxide, having an average particle size 5-600 mm , surface area 60-300 sq. m./grm., and index of refraction the same as arc silica, and wherein the fibres having a ratio of width to length 1 : 10 to 1 : 50, is prepared by slowly heating brown condensed silicon monoxide in an oxidizing atmosphere from a temperature in the range of 500-540 DEG C. to a temperature below the sintering temperatures of silicon and silicon dioxide, e.g. not exceeding 1000 DEG C., and at a rate insufficient to cause ignition, holding the monoxide at the maximum temperature, and cooling, the time of heating at the maximum temperature being sufficient to oxidize the particles throughout. The silicon monoxide may be prepared by the processes disclosed in Specifications 804,991 or 804,992. The oxidizing atmosphere may be air, oxygen, carbon dioxide, steam, or mixtures, and the silicon monoxide may be stirred during oxidation. In an example (I) the silicon monoxide is placed in a furnace at 540 DEG C. in a steam atmosphere, and after 1 hour the temperature is increased to 650 DEG C. for 2 hours, raised to 730 DEG C. for 2 hours, and finally maintained at 820 DEG C. for 12 hours, and the product is allowed to furnace cool. The silicon dioxide is used in amount 20-45 per cent as a reinforcing filler for rubbers. The silicon dioxide may be milled into the composition or mixed with latex, which is coagulated and dried, and the composition may include minor amounts of vulcanizing, accelerator, anti-oxidant, and pigment ingredients. The composition is vulcanized at 250-300 DEG F. The rubber may be natural rubber, e.g. caoutchouc, balata, or gutta percha, polychloroprene, polymers of conjugated dienes, e.g. butadiene-1,3, isoprene, 2, 3- or 1,4-dimethyl butadiene-1,3, copolymers of such dienes or containing at least 50 per cent conjugated diene with isobutylene, methyl or ethyl acrylates or methacrylates, 2-vinyl pyridine, styrene, acrylo- or methacrylonitriles, or mixtures of these, or polyacrylic rubbers obtained by polymerization of esters of acrylic acid, e.g. methyl, ethyl, propyl, butyl or octyl acrylates, methyl, ethyl or butyl methacrylates, or methyl ethacrylate, or mixtures thereof, or by copolymerization of acrylic esters with 5-10 per cent chloroethyl vinyl ether, acrylonitrile, vinyl chloride, dichlorodifluoroethylene or styrene. The acrylic rubbers may be mixed with 80-20 parts polychloroprene, butadiene-1,3-styrene copolymer, or natural rubber.ALSO:A fibre-containing white silicon dioxide, having an average particle size 5-600 mm , surface area 60-300 sq. m./grm., and index of refraction the same as arc silica, and wherein the fibres have a ratio of width to length 1:10 to 1:50, is prepared by slowly heating brown condensed silicon monoxide in an oxidizing atmosphere (see Group III) and is used preferably in amount of 20-45 per cent, as a reinforcing filler for rubbers. The silicon dioxide may be milled into the composition or mixed with latex, which is coagulated and dried, and the composition may include minor amounts of vulcanizing, accelerator, anti-oxidant, and pigment ingredients, e.g. sulphur, zinc oxide, zinc stearate, titanium dioxide, di-dodecylamine, pine tar, phenyl b naphthylamine, 2-mercaptobenzothiazole, diortho tolyl guanidine, N-penta-methylene ammonium penta-methylene dithiocarbonate, and stearic acid. The composition is vulcanized at 250-300 DEG F. The rubber may be natural rubber, e.g. caoutchouc, balata or gutta-percha, polychloroprene, polymers of conjugated dienes, e.g. butadiene-1,3, isoprene, 2-, 3- or 1,4-dimethyl butadiene-1,3, copolymers of such dienes or containing at least 50 per cent conjugated diene with isobutylene, methyl or ethyl acrylates or methacrylates, 2-vinyl pyridine, styrene, acrylo- or methacrylonitriles, or mixtures of these, or polyacrylic rubbers obtained by polymerization of esters of acrylic acid, e.g. methyl, ethyl, propyl, butyl or octyl acrylates, methyl, ethyl, or butyl methacrylates, or methyl ethacrylate, or mixtures thereof, or by copolymerization of acrylic esters with 5-10 per cent chloroethyl vinyl ether, acrylonitrile, vinyl chloride, dichlorodifluoroethylene, or styrene. The acrylic rubbers may be mixed with 80-20 parts polychloroprene, butadiene-1,3-styrene copolymer, or natural rubber. In examples: (II) a uniform mixture of silicon dioxide, natural rubber, zinc oxide, 2-mercaptobenzothiazyle disulphide, pine tar, phenyl b naphthylamine, stearic acid, secondary cocoamine, and sulphur is prepared; (III) a mixture of silicon dioxide, 75 : 25 butadiene : styrene copolymer, zinc oxide, stearic acid, secondary coco-amine, phenyl b naphthylamine, N-hexyl-2-mercapto benzothiazole sulphene amide, and sulphur is prepared. Specifications 804,991, [Group III], and 804,992 are referred to.