Anti-scorch agent CTP_Kain Industrial Additive

Anti-scorch agent CTP, whose scientific name is N-cyclohexylthiophthalideimide, was developed by Monsanto Company in the United States in the late 1960s. Developed, it was widely recognized by the rubber products industry in the early 1980s. This product can improve the scorch time of the rubber compound containing sulfenphthalamine accelerator without having much impact on the vulcanization speed and vulcanized rubber properties. However, the anti-scorch time of the rubber compound can be improved within a wide range. Adjust it by changing its dosage. Its emergence just solves the scorch problem of modern rubber and is regarded as a revolution in the field of rubber additives since World War II.

Chemical Properties
Preparation method
—Homogeneous reaction system
—Heterogeneous reaction system
Technical indicators
Application suggestions
Purpose
Activity of CTP
Predictability of CTP dosage and processing temperature
Principle of action
Rubber processing and anti-scorch agents
Types and performance of anti-scorch agents
—Organic acids
—Nitroso compounds
—Sulfenamide anti-scorch agent

CAS registration number: 17796-82-6
Chemical name: N-cyclohexylthiophthalimide
Other names: scorch retardant; early vulcanization inhibitor; anti-scorch agent CTP; anti-scorch agent PVI
Molecular formula: C14H15O2SN
Molecular weight: 261.3

Chemical Properties

White, off-white, light yellowish brown crystalline powder. The product recrystallized from n-heptane is white crystals. 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. Temperatures and humidity that are too high or too low should be avoided during storage. Flammable, low toxicity.

Preparation method

Obtained from the reaction of phthalimide and cyclohexylsulfenyl chloride. It can also be condensed with phthalimide after chlorination of dicyclohexyl disulfide.
React cyclohexane with hydrochloric acid to form chlorinated cyclohexane. Then use sulfur for sulfurization to prepare chlorothiocyclohexane. Finally, the product is prepared by reacting phthalimide and chlorothiocyclohexane in the presence of an acid absorbing agent.

At present, the domestic production process of anti-scorch agent CTP mostly adopts a heterogeneous reaction system. This method has easy process control and high yield, but the product quality is difficult to meet the requirements of all-steel wire. Radial tire requirements.

Homogeneous reaction system

Commonly used solvents include toluene, carbon tetrachloride, etc. Since the reaction products are also soluble in such solvents, the reaction process is always in a homogeneous state. After the reaction is completed, the reaction solvent needs to be partially removed, and then another organic solvent that is miscible with it is added to separate other impurities in 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 prepare a carbon tetrachloride solution of cyclohexylsulfenphthalechloride, and added dropwise to the solution at 20~30°C. In the carbon tetrachloride solution of 0.1 mol phthalimine and 0.12 mol triethylamine, react for 1 hour. Part of the solvent was removed, and light gasoline was added to precipitate the product to obtain CTP13.89, with a purity of 99.4% and a yield of 53%.

Heterogeneous reaction system

The prepared cyclohexylsulfenphthalein chloride and phthalimide salts are respectively dissolved in two mutually immiscible solvents, react with each other, and the product It is also insoluble in the solvent used, causing it to precipitate during reaction. For example, a hexane-butane solution of cyclohexyl sulfenyl chloride reacts with an aqueous solution of sodium phthalimide at 7-8°C for 30 minutes, and the product yield is 85%. Since phthalimine is also insoluble in the reaction system, how to reduce the amount of unreacted phthalimine in the product is the key to the success of this method.

Technical indicators

Appearance: white or off-white crystal
Active substance (CTP content) ≥97%
Heating loss ≤0.30%
Ash content ≤0.10%
Toluene insoluble matter ≤0.5%
Melting point 90-94℃

Application suggestions

Anti-scorch agent CTP (PVI) (butyl oleate)
Modified with Butyl Oleate as an anti-scorch additive.
Anti-scorch agent CTP is a highly efficient vulcanization inhibitor, suitable for sulfur vulcanization systems of natural rubber SBR, BR, IIR, CR, EPM, EPDM, and NBR that use sulfenamide and thiazole accelerators. Adding a small amount can significantly improve processing safety, help speed up certain processing processes of rubber products, and save raw materials and energy. It can also improve the storage stability of the rubber and prevent natural vulcanization during storage. This product has a regeneration and recovery effect on rubber materials that have experienced high heat or scorch. The recommended dosage is 0.1-0.5 servings.

Purpose

Anti-scorch agent CTP is a very effective anti-scorch agent for all sulfur-cured dienes and low unsaturated High-density rubber, such as natural rubber, styrene-butadiene rubber, nitrile rubber, butyl rubber, chloroprene rubber, isoprene rubber, butadiene rubber, EPDM rubber, etc., all have good anti-scorch effects and are compatible with other Its activity is not affected when rubber additives are used together. There are no adverse side effects such as foaming or contamination. It can greatly improve the storage stability of the rubber and prevent natural vulcanization during storage. Compared with previous anti-scorch agents, it has good effect and less dosage. The usual dosage is 0.1-0.5 parts.A large amount is consumed, therefore, the scorch time is significantly delayed.

Rubber processing and anti-scorch agent

Due to the effect of heat during storage and processing, the rubber will undergo early vulcanization (cross-linking) and lose its fluidity and ability to be reprocessed. This is the scorch phenomenon. Scorch of the rubber compound is one of the common problems during rubber processing. Especially in the modern high-temperature, fast, and efficient processing technology and the use of compounding agents that are prone to scorch (such as reinforcing resins, methylene white system adhesives, fine particle carbon black, etc.), scorch problems are more likely to occur. . Scorch can be solved by adjusting the vulcanization system, but care must be taken to cause changes in rubber properties; rubber storage or processing conditions can be improved by cooling, but complex equipment is required. It is now widely believed that using an anti-scorch agent is the simplest and easiest way to prevent scorch. Therefore, anti-scorch agents have become an important operating aid for rubber processing safety.

Types and performance of anti-scorch agents

There are three types of rubber anti-scorch agents, namely organic acids, nitroso compounds and sulfenamides.

Organic acids

Such as salicylic acid, benzoic acid, phthalic acid benzoic acid, and phthalic anhydride. Such chemicals have weak anti-scorch ability and high selectivity for accelerator types, which will reduce the vulcanization speed and vulcanized rubber performance, and may be irritating to the skin. The most commonly used one is phthalic anhydride, which can be used in light-colored rubber products, and is only effective for alkaline accelerators DPG and MBT accelerators, but is invalid for NOBS and TMTD.

Nitroso compounds

N-Nitrosodiphenylamine, N-nitroso-phenyl-β-naphthylamine, N-nitroso-2,2,4-trimethyl-1,2-dihydroquinoline polymer. Among them, N-nitrosodiphenylamine (NDPA) is commonly used. Different from organic acids, this type of anti-scorch agent has a good anti-scorch effect on commonly used thiazole and sulfenamide accelerators.

Sulfenamide anti-scorch agent

It is a series of compounds containing S-N bonds. Depending on the R group, anti-scorch agents with different properties can be obtained. Among them, the commercial anti-scorch agent CTP or PVI is the most excellent anti-scorch agent.

Any anti-scorch agent should meet the requirements of rubber processing performance, that is, it has excellent anti-scorch performance; has little selectivity for different accelerators and coke species; is not sensitive to other compounding agents; and has no adverse effects on the vulcanization characteristics of the rubber compound and the performance of the vulcanized rubber. impact; stable storage and good operating performance; no agglomeration, no flying, easy to disperse, no blooming; meets process safety and hygiene requirements.

Keywords:Anti-scorch agent CTP

Shandong Yanggu Huatai Chemical Co., Ltd.