Synthesis process for preparing polyvinyl chloride by aid of suspension methods

Abstract

The invention provides a synthesis process for preparing polyvinyl chloride by the aid of suspension methods. The synthesis process includes particular steps of adding vinyl chloride liquid into composition systems with alkaline aqueous solution, initiators, macromolecular surfactants, relative molecular mass regulators and heat stabilizers; keeping the vinyl chloride liquid and the composition systems under the conditions of certain vacuum degrees; initiating polymerization reaction under illumination and pressurization conditions; carrying out vacuumizing again after the reaction is completely carried out; adding water into reaction products during post-treatment, stirring the water and the reaction products, carrying out centrifugal filtration and washing on the reaction products and drying the reaction products in a drum type drying oven to obtain polyvinyl chloride resin. Compared with the prior art, the synthesis process has the advantages that the synthesis process is reasonable in design, post-treatment is easy to implement, products are high in conversion rate, purity and physical and mechanical properties, quality defects such as fisheye can be prevented, and finished products are uniform in molecular weight distribution and good in heat stability; the products are good in appearance and optimal in physical and chemical properties, various physical and mechanical property indexes of the products are similar, and accordingly the synthesis process has a broad application prospect.

Description

technical field [0001] The invention relates to the technical field of polyvinyl chloride preparation, in particular to a synthesis process for preparing polyvinyl chloride by a suspension method. Background technique [0002] Polyvinyl chloride, English abbreviation PVC (Polyvinyl chloride), is a polymer formed by the polymerization of vinyl chloride monomer according to the mechanism of free radical polymerization. It is a white powder with an amorphous structure, with a small degree of branching and a relative density of about 1.4. Glass The melting temperature is 77~90°C, and the stability to light and heat is poor. In practical applications, stabilizers must be added to improve the stability to heat and light. The molecular weight of industrially produced PVC is generally in the range of 50,000 to 110,000. It has a large polydispersity. The molecular weight increases with the decrease of the polymerization temperature. There is no fixed melting point. It starts to softe...

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Problems solved by technology

However, the polymerization process is carried out in a pure water medium, and the generated hydrochloric acid and hydrogen chloride gas are mixed in the product, which reduces the purity and quality of the product; bubbles and foam are easily generated during the feeding and reaction process, resulting in quality defects such as fish eyes in the product; In addition, the molecular weight distribution of polyvinyl chloride is not uniform, and the thermal stability is poor, resulting in large differences in the physical and mechanical properties of the product, which affects its application range.