Studies On Quality Improvement Of VDC-VC Suspension Polymerization Resin

Concerning the disadvantages of domestic vinylidene chloride-vinyl chloride (VDC-VC) copolymer, such as low tensile strength and percentage of film forming in the blow moulding, higher heat shrinking of film, and easiness of blowing-out, VDC-VC suspension copolymerizations were carried out in conditions of temperature increasing, and constant temperature and pressure, to investigate the copolymerization variables on the kinetics of copolymerization, molecular weight and particle properties of copolymers.The kinetics of VDC/VC (molar ratio 80/20) suspension copolymerization in conditions of temperature increasing in the range of 30-50癈, and using initiators of EHP and CPN, were studied. It showed that using of the initator with high activity would lead to the high reaction rate in the early stage of polymerization, early termination of polymerization, and low conversion of copolymerization. Using of the initator with suitable activity would lead to almost constant reaction of polymerization, and high conversion of polymerization. The regression equation for temperature increasing copolymerization is as follows:For CNP initiator: For EHP initiator: The kinetics of VDC/VC (molar ratio 70/30, 75/25, and 78/22) suspension copolymerizalion were also investigated in the polymerization temperature of 40 癈, and using of EHP initiator. It showed that the polymerization period was longer and copolymers with low viscosity would be obtained. But copolymers with homogeneous composition distribution could be prepared. The kinetic equation for constant temperature and pressure copolymerization is as follows:For temperature increasing copolymerization, the viscosity of VDC-VC copolymers decreased with the increase of average polymerization temperature.polymerization conversion and VC feeding concentration. For constant temperature copolymerization, the influence of conversion on the viscosity of copolymer was not obvious. The mean particle si/e of VDC-VC copolymer decreased with the increase of agitation rate, concentration of dispersants and VC feeding concentration. The bulk density of VDC-VC copolymer increased, and the plasticiser absorption decreased, with the increase of conversion and VDC feeding concentration. The influence of water/oil ratio on the plasticizer absorption was not obvious.The VDC-VC suspension recipe and process conditions were optimized through the above research. The results were applied to instruct the production of VDC-VC copolymer in 5m reactor, and VDC-VC copolymer with required molecular structure and particle properties were obtained. The blow moulding propertoes of copolymer was improved.