Detailed description of the types and properties of new scorch inhibitors

Category and performance of scorch inhibitors

There are three types of chemicals that can be used as rubber scorch retarders, namely organic acids, nitroso compounds, and sulfenamides.

(1) Organic acids: such as salicylic acid, benzoic acid, o-acetic acid benzoic acid, phthalic anhydride. The chemical anti-coke ability of such chemicals is weak, and the selectivity to the accelerator is large, which will reduce the vulcanization speed and the properties of the vulcanizate, and have a stimulating effect on the skin. Among them, phthalic anhydride is more commonly used, which can be used for light-colored rubber products, and is only effective for alkaline accelerators DPG and MBT accelerators, and is ineffective for NOBS and TMTD.

(2) Nitroso compounds: N-nitrosodiphenylamine, N-nitroso-phenyl-β-naphthylamine, N-nitroso-2,2,4-trimethyl-1,2 - Dihydroquinoline polymer. Often used is N-nitrosodiphenylamine (NDPA). Unlike organic acids, such scorch retarders have good anti-coke effects on commonly used thiazoles and sulfenamide accelerators.

(3) sulfenamide type scorch inhibitor: a series of compounds containing S-N bonds, the molecular structure is as follows:

R1(R2)-N-S-R3

Different properties of the scorch retarder can be obtained depending on the R group. Among them, the product CTP or PVI is the most excellent scorch retarder.

Any scorch retarder should meet the rubber processing performance requirements, that is, it has excellent anti-coke performance; it has low selectivity to different accelerators and coke species; it is not sensitive to other compounding agents; it has no bad vulcanization properties and vulcanized rubber properties. Impact; stable storage and good performance; no agglomeration, no flying, easy to disperse, no frosting; meet process safety and hygiene requirements.

New scorch retarder: N-cyclohexyl thiophthalimide

N-cyclohexylthiophthalimide [N-(cyclohexylthio)phthalimide]

CAS No.: 17796-82-6

Other names: scorch retarder; early vulcanization inhibitor; scorch retarder CTP; scorch retarder PVI

Physical and chemical properties: light yellow-brown crystal. The product recrystallized from n-heptane is a white crystal. Soluble in acetone, benzene, toluene, ether and ethyl acetate, insoluble in water. Soluble in hot carbon tetrachloride, ethanol and heptane. Avoid excessive or excessive temperature and humidity during storage. Combustible, low toxicity.

Manufacturing method: cyclohexane is reacted with hydrochloric acid to form chlorocyclohexane. Sulfur is further sulfurized to obtain chlorothiocyclohexane. Finally, the product is obtained by reacting phthalimide with chlorothiocyclohexane in the presence of an acid acceptor.

Application: It can be used in natural rubber and synthetic rubber, which can effectively prevent the scorch in the processing process and improve production efficiency. At the same time, it has a rejuvenating effect on the rubber which has been subjected to high heat or slight scorch. N-cyclohexylthiophthalimide is widely used in sulfur-vulcanizable elastomers, and has good anti-coke effect in combination with various general accelerators. Equipped with the scorch retarder CTP, whether it is open or high temperature and rapid refining, a mixing process can be used to effectively prevent scorch. It can be used in combination with accelerators M, DM, TMTD and effective or semi-effective vulcanization systems to improve the properties of the compound. The production efficiency of calendering and extrusion can be improved. It is beneficial to improve the adhesion of rubber and brass-plated steel wire. It is widely used in various general-purpose rubbers and special rubbers including nitrile rubber, ethylene-propylene or ethylene propylene diene monomer, butyl rubber and neoprene. Avoid excessive or too low temperature and humidity during storage, and keep it in a dry and ventilated place to avoid heat and moisture.