Introduction to CTP concept and chemical properties of scorch retarder

The scorch retarder CTP, scientific name N-cyclohexylthiophthalimide, was developed by Monsanto Company of the United States in the late 1960s and widely recognized by the rubber products industry in the early 1980s. The product can improve the scorch time of the rubber in the rubber compound containing the sulfenamide accelerator, but has no significant effect on the vulcanization speed and the vulcanizate performance, and the anti-scorch time of the rubber compound can be in a wide range. It is adjusted by the change in its amount. Its appearance just solved the scorch problem of modern rubber and was regarded as a revolution in the field of rubber additives since the Second World War.

Chemical properties

White, off-white, light yellow-brown crystalline powder. The product recrystallized from n-heptane is a white crystal. Soluble in acetone, benzene, toluene, ether and ethyl acetate, insoluble in kerosene and water, slightly soluble in gasoline, soluble in hot carbon tetrachloride, ethanol and heptane. Store too high temperature and humidity after too high. Combustible, low toxicity.

Preparation

It is obtained by reacting a phthalimide with cyclohexylsulfenyl chloride. It can also be condensed with a phthalimide by chlorination of dicyclohexyl disulfide.

The cyclohexane is reacted with hydrochloric acid to form a cyclohexane chloride. Sulfur is further sulfurized to obtain chlorothiocyclohexane. Finally, the product is obtained by reacting phthalimide with chlorothiocyclohexane in the presence of an acid acceptor.

At present, the production process of domestic Coke inhibitor CTP mostly adopts heterogeneous reaction system. This method is easy to control and high in yield, but the product quality is difficult to meet the requirements of all steel radial tires.

Homogeneous reaction system

Commonly used solvents are toluene, carbon tetrachloride, etc., since the reaction product is also soluble in such a solvent, the reaction process is always in a homogeneous state. After the reaction is completed, the reaction solvent is partially removed, and another organic solvent which is mutually miscible is added to separate other impurities of the product. For example, 0.05 mol of dicyclohexyl disulfide is dissolved in a certain amount of carbon tetrachloride, and a certain amount of chlorine is introduced to obtain a carbon tetrachloride solution of cyclohexyl sulfenyl chloride, which is added dropwise at 20 to 30 ° C. 0.lmol of phthalic acid imine and 0.12 mol of triethylamine in carbon tetrachloride solution, reacted for 1 h. Part of the solvent was removed, and light gasoline was added to precipitate the product to obtain CTP13.89, the purity was 99.4, and the yield was 53%.

Heterogeneous reaction system

The prepared cyclohexyl sulfenyl chloride and the phthalic acid imide salt are respectively dissolved in two solvents which are incompatible with each other, react with each other, and the product is also insoluble in the solvent used, and is precipitated while reacting. For example, a hexane-butane solution of cyclohexyl sulfenyl chloride is reacted with an aqueous solution of sodium phthalimide at 7-8 ° C for 3 min, and the product yield is 85%. Since o-phthalimide is not soluble in the reaction system, how to reduce the amount of unreacted phthalic acid imide in the product is the key to the success of the process.