Accelerators mercaptobenzothiazole disulphide

In sulphur cured rubbers, accelerators are generally used to reduce the dependency on sulphur in order to achieve more efficient vulcanisation, to improve heat and flex resistance due to the presence of more monosulphidic crosslinks, and to increase the cure rate of the rubber and improve production capacity. Two accelerators which have been shown to enhance bondability of rubbers are 2-mercaptobenzothiazole (MBT) and mercaptobenzothiazole disulphide (MBTS). An accelerator which is known to negatively impact on adhesion is tetramethyl thiuram disulphide (TMTD). 

With the sulphur-modified polymers cure may be brought about by zinc oxide and magnesium oxide in combination either alone or together with an accelerator such as ethylene thiourea. In the case of the homopolymers it has been common practice to support the zinc oxide/magnesium oxide/ethylene thiourea system with a further component. This component consists of a sulphide or a blend of sulphides of the type more commonly used as accelerators for the diene hydrocarbon polymers. These include mercaptobenzothiazole disulphide (MBTS), diorthotolyl guanidine (DOTG) and tetramethyl thiuram monosulphide (TMTM). In the polychloroprene homopolymers these materials appear to act as retarders of cure at processing temperatures but are accelerators at vulcanization temperatures. Their mechanism does not appear to have been fully elucidated. 

A further, important, component is an accelerator similar to those used with diene rubbers, e.g. mercaptobenzothiazole disulphide (MBTS). Its main function appears to be to prevent radical-initiated decomposition of the sulphonyl chloride grouping, a process which not only removes a sulphonyl cure site but which also generates acidic gases ... 

Journal of Applied Polymer Science 76, No.9, 31 St May 2000, p. 1413-21 BENZOTHIAZOLE-ACCELERATED SULPHUR VULCANISATION. V. 2-BISBENZOTHIAZOLE-2,2 -DISULPHIDE/ZNO AND 2-BISBENZOTHIAZOLE-2,2 -DISULPHIDE/(2-MERCAPTOBENZOTHIAZOLE)ZINC(ll) AS ACCELERATORS FOR 2,3-DEMETHYL-2-BUTENE... 

The results are reported of a study of accelerated sulphur vulcanisation using the above compounds. 2,3-Dimethyl-2-butene, was utilised as a model compound for polyisoprene and residual curatives, intermediates and products produced by heating the mixes for various times at 150C in sealed tubes were analysed using high-performance liquid chromatography. A synergistic effect was observed between bis(2-mercaptobenzothiazole) zinc(II) and 2-bisbenzothiazole-2,2 -disulphide. 23 refs. SOUTH AFRICA... 

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