GB757764A - Stable despersible accelerator masterbatch for use in the vulcanization of natural or synthetic rubber - Google Patents

Abstract

A stable vulcanization accelerator master batch for addition to natural or synthetic rubber during compounding comprises an unmasticated, unvulcanized polymer or copolymer of a conjugated diolefinic compound of less than 8 aliphatic carbon atoms and at least one water-insoluble organic thiuram polysulphide. The batch is prepared by mixing a latex of the polymer or copolymer with an aqueous slurry of the polysulphide, coagulating the mixture, and drying the coagulum while maintaining a temperature below the melting point of the thiuram polysulphide, and maintaining the coagulum in an unmasticated condition. The polysulphide may comprise tetramethyl thiuram disulphide, pentamethylene thiuram tetrasulphide or tetramethyl thiuram tetrasulphide. The latex may comprise natural rubber or a polymer or copolymer of butadiene, isoprene, or chloroprene, or a copolymer of one or more of such diolefinic compounds and an olefine or substituted olefine such as styrene, a -methyl styrene, vinyl toluene, or chlorinated styrene, acrylo- and methacrylonitrile, methyl methacrylate and other esters and amides of acrylic and methacrylic acids, methyl vinyl and methyl isopropenyl ketones, or vinyl pyridine.ALSO:A vulcanization accelerator master batch for addition to natural or synthetic rubber during the compounding of the same comprises an unmasticated, unvulcanized polymer or copolymer of a conjugated diolefinic compound of less than 8 aliphatic carbon atoms and at least one water insoluble organic thiuram polysulphide, said batch being further characterized by being stable for extended periods of storage at normal temperatures. The batch is prepared by mixing a latex of a vulcanizable polymer or copolymer of a conjugated diolefinic compound of less than 8 carbon atoms with an aqueous slurry of the polysulphide, coagulating the mixture, and drying the coagulum while maintaining a temperature below the melting point of the thiuram polysulphide, and maintaining the coagulum in an unmasticated condition. The polysulphide may comprise tetra-methyl thiuram disulphide, pentamethylene thiuram tetrasulphide, or tetramethyl thiuram tetrasulphide. The latex may comprise natural rubber or a polymer or copolymer of butadiene, isoprene, or chloroprene, or a copolymer of one or more of such diolefinic compounds and an olefine or substituted olefine such as styrene, a methyl styrene, vinyl toluene, or chlorinated styrene, acrylo and methaacrylonitrile, methyl methacrylate and other esters and amides of acrylic and methacrylic acids, methyl-vinyl and methyl isopropenyl ketones, or vinyl pyridene. The master batch preferably comprises 25 to 75 parts by weight of the polymer or copolymer and 75 to 25 parts of the polysulphide. In an example 300 parts by weight of a wet filler cake of tetramethyl-thiuram disulphide is mixed with water to form a slurry which is mixed with 600 parts of butadiene-styrene latex, and sodium chloride solution is added. Coagulation is effected by adding sulphuric acid solution, and the coagulum is filtered, washed, and dried at 80 DEG C. under reduced pressure. In a further example the slurry is formed by adding water containing a wetting agent to pulverized tetramethyl thiuram disulphide.