Study On Cross-Linking Modification Of PVC Resins

Since excess production capacity of ordinary homogenized PVC, low operationrate of polymerization plants, and massive losses in chemical plants, combined withexisting market requirement and tendency, investigation and production of specialresins have been done in order to re-adjust product mix. The present paper hasinvestigated cross-linking modification of PVC, through cross-linking modification,extinction resin and resins with high polymerization degree have been prepared.At first, through experiments and investigations of various cross-linking reactionby adding cross-linking agent into vinyl chloride, acting laws of differentcross-linking agents and vinyl chloride, and related effect on resins’ quality have beenexplored, meanwhile cross-linking agents have been optimized. By selection ofsuitable type of cross-linking agent, addition amount and addition method, destructiveeffect of cross-linking agent upon dispersing agent and adverse effect upon resins’quality can be overcome. Experiments have been done by a gradually magnifyingmethod. That is to investigate by using firstly small-scale experiment (30L ofpolymerization reactor), then middle-scale experiment (13.5m3of polymerizationreactor), finally industrial-scale production (70m3of polymerization plant).Through experiment and investigation of different systems of cross-linking agent,dispersing agent, initiator, as well as process control conditions, extinction PVCspecial resin containing21±2%of gel has been prepared, with stable industrialproduction and qualified resin. As a result, regular particle morphology, porousinternal structure, good extinction performance and plasticizing performance wereobtained.Next step, using cross-linking agent B as cross-linking chain extender, throughexperiments, relationship between amount of chain extender and reaction temperaturehas been explored, suitable amount of chain extender and reaction temperature underpractical production conditions also determined. Experiments have been done by agradually magnifying method. That is to investigate by using firstly small-scaleexperiment (30l of polymerization reactor), then middle-scale experiment (13.5m3of polymerization reactor), finally industrial-scale production (70m3ofpolymerization plant). Through experiment and investigation of different systems ofcross-linking agent, dispersing agent, initiator, as well as process control conditions,extinction PVC special resin containing21±2%of gel has been prepared, with stable batch production and qualified resin. As a result, regular particle morphology, porousinternal structure, good plasticizing performance and mechanical property wereobtained.Both extinction PVC special resin and resin with high polymerization degreehave higher additional value. Compared to ordinary PVC resin, they have bettereconomic and social benefit. In the present case, due to overall market depression ofPVC industry, it is of great importance to investigate and produce special-use resin.