Cooling method of bulk PVC resin polymerization

Abstract

The invention discloses a method for cooling down polymerization system in the polymerization process of PVC resin, which comprises letting normal temperature recirculated water into polymerization still jacket and still top condenser, then cooling down the polymerization system with circulated water, and letting 5-15 deg C circulate chilled water into the polymerization stirrer. The invention can substantially improve the heat-transfer capability for polymerization agitation.

Description

technical field [0001] The invention relates to a method for cooling a polymerization system during the polymerization of bulk polyvinyl chloride resin, in particular to a method for cooling by a polymerization stirrer. Background technique [0002] The method of bulk polymerization is used to produce polyvinyl chloride, because water is not used as a medium during the polymerization process, and no dispersant is used, and only vinyl chloride monomer and initiator are used. The bulk polymerization is carried out in two steps. The first step is pre-polymerization, which is carried out in a pre-polymerization tank. Add 30-50% of the total amount of monomers and the corresponding initiator, and the polymerization conversion rate is controlled at 8-12%. The second step For the polymerization, it is carried out in the polymerization tank. After transferring all the pre-polymerized materials, all the remaining monomers are added to supplement the initiator, an...

AI Technical Summary

Problems solved by technology

The circulating water is water at normal temperature, and the circulating water is passed into the condenser on the jacket of the polymerization kettle, mainly to cool the material, which can basically achieve the purpose of cooling, but the circulating water is passed into the polymerization stirrer, and the The main cooling object is the medium that is in close contact with the polymerization agitator, such as: vinyl chloride monomer, PVC powder, due to the small temperature difference between the reaction medium and the circulating water, the heat exchange effect during the polymerization reaction is poor, and cannot Effectively control the temperature of the reaction medium within the suitable temperature range of the polymerization reaction, and at the same time, due to the difference in local temperature of the locally overheated particles, there is a large difference between the internal and external quality, and the molecular chains are intertwined and cross-linked to form very tight resin particles. , this kind of particles are not easy to plasticize during processing, and become permanent "fish eyes"; if the kettle is not cleaned, it will also increase the "fish eyes" of the resin, thereby reducing product quality, such as the number of "fish eyes" increases, the number of impurities increases, The particle size range becomes wider, etc.; in addition, due to the frequent occurrence of the phenomenon of sticking, it is necessary to maintain a high frequency of cleaning the kettle. Generally, three batches of materials are produced and the kettle is cleaned once, which delays the production cycle and prevents the polymerization production from running smoothly for a long time. , increasing production costs

The root cause is that there is no suitable cooling medium for the polymerization stirrer