Patent GB-451501-A (GB)
Title: Improvements in or relating to the vulcanization of rubber
IPC: C08K5/00
Filed: 1935-02-01
Abstract: Tetra-aryl substituted thiuram sulphides are used as vulcanization accelerators.  Thiuram sulphides specified are the tetraphenyl, tetratolyl (o-, m-, p or mixed), tetranaphthyl (a  or b ), diphenyl - ditolyl, diphenyl - dicumyl, diphenyl-di-isopropenylphenyl, diphenyl-dixenyl, diphenyl-dinaphthyl substituted compounds and compounds containing substituted aryl groups containing non-acid substituents such as alkoxy-aryl, aryloxy-aryl, nitro-aryl, chloraryl, dialkylaminoaryl and acylamido - aryl groups. Symmetrically substituted disulphides may be obtained by treating the corresponding diarylamines with metallic sodium or potassium to form the alkali metal compound, treating the alkali metal compound with carbon disulphide to form the alkali metal salt of the diaryl dithiocarbamic acid and oxidizing this salt in water or alcohol solution, e.g. with iodine, to form the tetra-aryl thiuram disulphide.  Thus tetraphenylthiuram disulphide may be prepared from diphenylamine and the diphenyldi-b -naphthyl-thiuram disulphide from phenyl-b -naphthylamine.  The mono-sulphides may be obtained by heating the disulphides with an alkali metal cyanide.  The tri- and tetrasulphides may be obtained by treating the alkali metal salts of the diaryl dithiocarbamic acids with sulphur dichloride and sulphur monochloride respectively.ALSO:Tetra-aryl substituted thiuram sulphides are used as vulcanization accelerators.  The sulphides may be used in as low a proportion as 0,1 per cent of the rubber in which case 3-4 per cent sulphur is usually required or as high as 5 per cent with a much reduced quantity of sulphur; the tri- and tera-sulphides may be used in the absence of free sulphur.  The sulphides exhibit their maximum activity only in the presence of inorganic bases such as zinc oxide or magnesia and organic nitrogenous bases such as those which are used to activate other sulphur containing accelerators, e.g. aliphatic amines, aldehyde-amines, heterocyclic bases, amides or amidines such as urea, thiocarbanilide and substituted guanidines.  Thiuramsulphides specified are the tetraphenyl, tetratolyl (o-, m, p, or mixed), tetranaphthyl (a  or b ), diphenylditolyl, diphenyl-dicumyl, diphenyl di - isopropenylphenyl, diphenyl - dixenyl, diphenyl-dinaphthyl substituted compounds and compounds containing substituted aryl groups containing non-acid substituents such as alkoxy-aryl, aryloxy-aryl, nitro-aryl, chlor-aryl, dialkylaminoaryl and acylamido-aryl groups.  Symmetrically substituted disulphides may be obtained by treating the corresponding diarylamines with metallic sodium or potassium to form the alkali metal compound, treating the alkali metal compound with carbon disulphide to form the alkali metal salt of the diaryl di-thiocarbamic acid and oxidizing this salt in water or alcohol solution, e.g. with iodine, to form the tetra-aryl thiuram di-sulphide.  The mono-sulphides may be obtained by heating the disulphides with an alkali metal cyanide.  The tri- and tetra-sulphides may be obtained by treating the alkali metal salt of the diaryl di-thiocarbamic acid with sulphur dichloride and sulphur monochloride respectively.  Thus, tetraphenyl thiuram sulphides may be prepared from diphenylamine and the diphenyl di-b -naphthyl thiuram sulphides from phenyl-b -naphthyl amine.  Unsymmetrically substituted sulphides may be obtained by similar methods by suitable choice of diarylamines.