| The resin of vinylidene(VDC) and vinyl chloride(VC) copolymer with high VDC content has low permeability to oxygen, carbon dioxide and water vapor, so it is mainly used to make food preservation packaging film. This resin used in our country is mostly imported from developed countries. To synthesize VDC-VC copolymer with good processing properties, four samples produced by developed countries and our country have firstly been analyzed, then the control objectives are proposed. The VDC/VC suspension ^polymerization has been carefully studied. The characterizations of composition, molecular weight, and the crystalline, processing and thermal properties for VDC-VC copolymer have been investigated. Finally, the recipe and technology conditions, which will be used for industry production of VDC-VC suspension copolymer, have been optimized.After the analysis of the four samples, it can be found that the number average molecular weight of copolymers are in the range of 30000 to 40000, the weight average molecular weight are 85000 to 100000, the polydispersity are 2.3 to 2.7, and the intrinsic viscosity are 46 to 50 ml/g (THF, 1%, 25 癈). The composition of VC monomer unit in the Dow and Wuyu resins are about 8-10%, that of Belgium is about 5%, and that of our country is about 11%. The particle size of the four samples is about 150-240 u m, and the particle is spheroidal and its distribution size is narrow. The crystallinity of Dow, Wuyu and our country resins are about 33-37%, which is lower than that of Belgium. The maximum torque of the four samples are lower than 50Nm and the those of balance torque are about 5Nm. ATBC have been detected in the resin of Wuyu with content of 4.5-8.3%.The conversion and molecule weight decrease with the increasing of VC feed fraction. If ESO or ATBC are added before polymerization, it has not any effects on conversion, molecular weight and its distribution, and particle size and its distribution When the rotate speed of the agitator is 300 rpm, particle size and its distribution are the highest under the technology of the changing rotate speed. The particle size and its distribution increase with the decreasing dispersant concentration. Most of the copolymer beads are spheroidal.The optimum recipe and technology conditions of copolymerization are presented. The ratio ofVDC to VC is 79/21 (by weight). Initiator EHP is 6g(40% emulsion)/(kg monomer). Both of the dispersant A and K are 0.3g/(kg monomer). The temperature should be ascended about 0.5 癈 per hour from 31癈 to 55 癈. The rotate speed of agitator is 350rpm at the predispersing period, and 300rpm in the process of polymerization.As the composition of VC monomer unit in the copolymer increases, the area of peak for lower temperature increases while that of for higher temperature decreases. The crystalline temperatures of the two peaks descend With the Flory's melting point theory, the effects of copolymer composition and ESO concentration on the decreasing of crystalline temperature are predicted, and the theoretic calculation results are in good agreement with the experimental data.The maximum and balance torque decrease with the increasing of VC monomer unit in the copolymer and ESO concentration, and increase with the increasing of copolymer molecular weight The thermal stability of the copolymer increases with the adding of ESO. |
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