Ordinary insoluble sulfur products are in powder form with a particle size of approximately 150 μ m. Easy to fly, inconvenient for transportation. At the same time, it is not easy to evenly disperse in the rubber during use, which is not in line with our original intention of using this type of vulcanizing agent. It will also have a certain impact on the production environment. Therefore, oil can be filled into the powder to prevent the formation of dust, and the vulcanizing agent can be better dispersed in the rubber material, thereby avoiding frost formation and combustion of the rubber material. Oil filled sulfur powder, the types of oil are generally aromatic oil and naphthenic oil obtained from petroleum refining, and the content of oil filled is generally 10% to 34%. Refined aromatic oil and naphthenic oil have good dispersion and compatibility. However, its processing cost is relatively high, so the price of oil filled insoluble sulfur used for radial tires is also correspondingly high.
Special oil filled sulfur powder should have the following characteristics: first, the flash point should be higher than 160 degrees; second, good low-temperature fluidity; third, good thermal stability; fourth, light color; fifth, the lower the alkaline nitrogen content, the better. In order to stabilize the price of insoluble sulfur for oil filling, most sulfur filled oils today use universal aromatic oils. The fatty hydrocarbons between them are converted into aromatic hydrocarbons such as benzene through dehydrogenation cyclization using platinum rhenium catalysts, and then aromatic hydrocarbon products are extracted from them. This type of aromatic oil contains certain impurities and alkaline substances, which have a significant impact on the stability of insoluble sulfur when used as a vulcanizing agent to increase oil content. To ensure the stability, dispersibility in rubber, heat resistance and conversion resistance of oil filled insoluble sulfur during storage at room temperature, the composition of the oil can be adjusted and appropriate control agents can be added. After addition, impurities and alkaline substances can be stabilized and neutralized, making the vulcanizing agent loose, non spherical, and non flying.
Rubber sulfur powder is a commonly used vulcanizing agent for natural rubber vulcanization, and it is also a vulcanizing agent with a long history since the development of the rubber industry. The fracture elongation is high but the thermal oxidative aging performance is poor, so suitable accelerators need to be used. It should be noted that the addition of oil filled sulfur powder and increasing the amount of various additives in the vulcanization system can improve the tensile strength, tensile stress, hardness, and tear strength of natural rubber vulcanizates; When the sulfur content is high, the aging resistance of the vulcanized rubber is better. The use of calcium carbonate as a filler in natural rubber is a very good way to reduce costs and increase the volume of the product.
When using oil filled sulfur powder as a vulcanizing agent, natural rubber is filled with calcium carbonate, and generally accelerator M and accelerator DM are added. If it is a light colored natural rubber product, a small amount of Qiu Lamb accelerator can be added to improve the natural rubber. Effective crosslinking density results in better mechanical properties of vulcanized rubber. Natural rubber and calcium carbonate are used in combination with accelerators CZ/DM, CZ/TMTD, and NS/TMTD. The vulcanization speed is fast, and the tensile strength, tear strength, and aging resistance of the vulcanized rubber are high. However, the application of calcium carbonate should be noted that if the dosage is not appropriate, it is easy to cause a decrease in the elasticity, strength, and viscosity of natural rubber products.
In addition to filling with calcium carbonate, the way to reduce the application cost of natural rubber can also be to use recycled rubber in moderation, which can effectively reduce raw material costs while ensuring product quality.