Patent GB-563175-A (GB)
Title: Preservation of rubber
IPC: C08K5/375
Filed: 1942-09-22
Abstract: Rubber is preserved by incorporating a di-(monohydric dialkyl phenol) sulphide in which at least one alkyl group on each aryl nucleus contains at least three, and preferably less than six, carbon atoms, and at least two of the positions ortho and para to each hydroxyl group are unsubstituted except by sulphur.  Examples given include mono- and di-sulphides of di(1-hydroxy 3-methyl 4, 5 or 6-isopropyl, sec. or tert. butyl, iso or tert. amyl phenyl), di(1-hydroxy 2-tert. butyl or tert. amyl 5-methyl phenyl) and corresponding 1-hydroxy 2-methyl 5-alkyl, 1-hydroxy 3-alkyl 4-methyl, 1-hydroxy 2-methyl 3-alkyl, and 1-hydroxy 3, 6-, 2, 5- or 3, 5-dialkyl compounds. Halogen substituents may be present but strongly basic groups such as amino which discolour rubber should be absent.  The sulphides may be prepared by reaction of sulphur mono- or dichloride on the dialkyl aromatic hydroxy compound.  A solution of sulphur chloride in carbon tetrachloride may be added to a solution of the phenol in the same solvent and the product crystallized by cooling or the solvent removed by evaporation.  A mixture of several products may be obtained and can be used as such.  Thus thymol and carvacrol give crystalline solid products or, if the solvent is evaporated, a composite resinous product of about equal effectiveness.  Comparative figures are given for the tensile strengths before and after ageing of vulcanized rubber mixes containing the defined class of antioxidants, containing no antioxidant, and containing other phenol sulphides.  The antioxidant may be incorporated in the rubber by milling, by adding to the latex, or by applying to the surface of crude or vulcanized rubber.  The term "rubber" includes any sulphur vulcanizable plastic material with high elasticity such as natural rubber, balata, and gutta percha, and synthetic rubbers. Specifications 359,045, [Group V], and 496,966 are referred to.ALSO:Rubber is preserved by incorporating a di-(monohydric dialkyl phenol) sulphide in which at least one alkyl group on each aryl nucleus contains at least three, and preferably less than six, carbon atoms, and at least two of the positions ortho and para to each hydroxyl group are unsubstituted except by sulphur.  Examples given include mono- and di-sulphides of di(1-hydroxy 3-methyl 4, 5 or 6-isopropyl, sec. or tert. butyl, iso or tert. amyl phenyl), di(1-hydroxy 2-tert. butyl or tert. amyl 5-methyl phenyl) and corresponding 1-hydroxy 2-methyl 5-alkyl, 1-hydroxy 3-alkyl 4-methyl, 1-hydroxy 2-methyl 3-alkyl, and 1-hydroxy 3, 6-, 2, 5- or 3, 5-dialkyl compounds.  Halogen substituents may be present but strongly basic groups such as amino which discolour rubber should be absent.  The sulphides may be prepared by reaction of sulphur mono- or di-chloride on the dialkyl aromatic hydroxy compound.  A solution of sulphur chloride in carbon tetrachloride may be added to a solution of the phenol in the same solvent and the product crystallized by cooling or the solvent removed by evaporation.  A mixture of several products may be obtained and can be used as such. Thus thymol and carvacrol give crystalline solid products or, if the solvent is evaporated, a composite resinous product of almost equal effectiveness.  Comparative figures are given for the tensile strengths before and after ageing of vulcanized rubber mixes containing the defined class of antioxidants, containing no antioxidant, and containing other phenol sulphides.  The antioxidants may be incorporated in the rubber by milling, by adding to the latex, or by applying to the surface of crude or vulcanized rubber.  The term "rubber" includes any sulphur vulcanizable plastic material with high elasticity such as natural rubber, balata, and gutta percha, and synthetic rubbers.  Specifications 359,045 and 496,966 are referred to.