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The polymerization of vinyl chloride monomer

by:CSSSLD     2021-01-23
Scattered in the process of emulsion polymerization system stability, is easy to control reaction temperature, monomer uniform dispersion degree, of PVC particle is fine, high relative molecular mass. But the process is complex, high impurity content in the product. PVC resin is a linear polymer with thermoplastic. Due to the molecular chain of every other carbon atoms have a negatively charged sexual strong chlorine atom, and molecular chain with high polarity, macromolecular chain interaction force between big, hindered the relative slip between molecular chains. So the injection molding processing of PVC resin shows certain rigidity and hardness, the macro and has good resistance to chemical corrosion.

oxygen chlorination process is based on ethylene as raw materials by oxygen chlorination directly by ethylene dichloride, dichloroethane pyrolysis produce vinyl chloride. Oxygen chlorination process is with the development of oil industry appeared in the 1960 s, due to the abundant raw materials, save energy, lower cost, is the main method in the production of vinyl chloride. Use some peroxide and azo compound initiator, under the action of radiant energy, or heat, light, vinyl chloride monomer can smoothly to carry on the free radical chain reaction type into PVC resin.

emulsion polymerization using water-soluble initiator, monomer chloroethene body by emulsification dispersed emulsion in water medium, polymerization under the effect of temperature and stirring, the final reaction products to paste, can be directly used for production and application of emulsion coating. Can also be through condensation, washing, dehydration, drying processes made solid PVC powder. This kind of resin can preparation composition medium - at room temperature PVC paste plastic, used in the production of artificial leather, plastic foam, and fabric coating, etc.

in the process of the polymerization degree of polymerization control by polymerization temperature, polymerization rate by the dosage of initiator to adjust. There are four kinds of industrial aggregation methods: suspension polymerization, emulsion polymerization and bulk polymerization, solution polymerization. Suspension polymerization system is mainly composed of monomer, initiator, water, dispersant of four basic components. Commonly used initiator has two benzoyl peroxide, azodiisobutyronitrile, peroxide of isopropyl carbonate. Dispersant with polyvinyl alcohol, maleic anhydride, cellulose ethers, etc.

in the production of the first water in the reaction kettle, dispersants, eliminate air with nitrogen, then stir in vinyl chloride monomer and polymerization reactions to maintain at a certain temperature range. After polymerization suspension by alkali treatment, decomposition of hydrogen chloride in the process of neutralization reaction, remove residual impurities such as the initiator and monomer in the resin adsorption, after washing, drying, sieving getting white powder PVC resin.

acetylene and hydrogen chloride gas reaction of vinyl chloride method become the calcium carbide acetylene method, this is the first to realize industrialized production method, has the advantages of less investment, simple technology and product purity. Joint method of ethylene by petroleum cracking after chloride generated dichloroethane, then heating pyrolysis under pressurized conditions have to vinyl chloride and hydrochloric acid, the generated hydrogen chloride reacts with acetylene vinyl chloride can be obtained. This method can be directly used to hydrogen chlor-alkali industry, the cost is relatively low calcium carbide acetylene method.

suspension polymerization process in different reaction temperature and pressure control, adopt different dispersants, change polymerization conditions, such as mixing form and strength of the aggregation after take different post-processing methods, and properties of resin particles form are not the same, this is PVC with different models. In addition, the polymerization process of sticky kettle phenomenon can lead to high relative molecular mass of the component, in the resin is not easy to plasticizing and make the products appear crystal transparent, affect the quality of injection molding processing products.

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