Production method of special resin for low-polymerization-degree gas-solid-phase chlorinated polyvinyl chloride

Abstract

The invention relates to a production method of special resin for low-polymerization-degree gas-solid-phase chlorinated polyvinyl chloride (PVC). The production method sequentially comprises the following steps: preparation of an auxiliary agent, feeding of a polymerization kettle, material activation, continuous supplementation of an initiator during polymerization, discharging of PVC slurry, steam stripping and drying. According to the method, part of an initiator is added in a one-time decrement mode during feeding, the low-concentration and high-activity initiator is continuously supplemented in the middle and later periods of the reaction, and the rate of the free radical initiation reaction is adjusted. The method can be widely applied to the production process of the special polyvinyl chloride resin for gas-solid phase method chlorination.

Description

technical field [0001] The invention relates to the technical field of chemical engineering, in particular to a production method of a special resin for gas-solid phase chlorinated polyvinyl chloride with a low degree of polymerization. Background technique [0002] Chlorinated polyvinyl chloride (CPVC) is obtained by further chlorination of polyvinyl chloride (PVC), and is a new type of polymer elastomer material between rubber and plastic. After the PVC resin is chlorinated, the irregularity of the molecular bond increases, the polarity increases, the solubility of the resin increases, and the chemical stability improves, thereby improving the material's heat resistance, acid, alkali, salt, oxidant, etc. Corrosion. Compared with PVC, CPVC has greatly improved its heat resistance, corrosion resistance, flame retardant and self-extinguishing properties, and mechanical properties. It is widely used in building materials, electrical, chemical, metallurgy, medicine, coatings an...

AI Technical Summary

Problems solved by technology

In the chlorinated polyvinyl chloride process produced by the gas-solid phase method, the chlorine gas molecules in the gas phase enter through the internal pores of the particles and undergo grafting reactions with the PVC molecular chains. The grafting rate and grafting uniformity are affected by the abundance of pores and the uniformity of pores. At the same time, the heat of grafting reaction is removed by circulating vulcanized chlorine gas to produce polyvinyl chloride resin. By adjusting the stirring speed of the polymerization tank and the type and amount of dispersant, the polyvinyl chloride resin can be significantly changed macroscopically. The particle shape of vinyl resin can adjust the particle size distribution and the roundness of the shape, and the internal void structure is also improved, but it is difficult to complete the regulation of the deep micro-nano structure of the resin. The specificity of ethylene production and application is not strong, especially when the gas-solid phase chlorination process is adopted, it is difficult to remove heat, which will cause poor thermal stability of chlorinated polyvinyl chloride resin

[0009] The production temperature of polyvinyl chloride resin with low degree of polymerization is high, the molecular thermal movement is violent, and the growth rate of polyvinyl chloride molecular chain is fast. It is necessary to control the number of free radicals required for chain initiation to reduce the initiation rate. Usually, the process of adding initiator at one time will cause initial The high concentration of free radicals decomposed by the initiator causes the reaction rate to be too fast, and the precipitation is too fast to form compact particles, which reduces the porosity of PVC particles, increases the apparent density of PVC particles, and affects the vulcanization of materials and the concentration of chlorine in the gas-solid phase chlorination process. diffusion