| Owing to easy availability, excellent properties and low price of PVC resin, its output has remained very large in the polymer industry, but it is still in great need. At present, the vessel for polymerization is developing larger and larger in the world. However, there are a lot of 30m3 ones in our country. According to our national status, it is a very important and urgent task to increase the output of PVC by 50% with no change of quality and with lower cost.This subject is one of the Key National Projects for the ninth five-year planning. The relationships of molecular weight and its distribution, particle character and processing rheological properties of suspension PVC resins with optimization of polymerization recipe and technology were studied. The results showed that novel four-unit dispersing system could acquire good particle character and processing rheological property. In the novel dispersing system, middle sapond PVA was substituted for some of HPMC and high sapond PVA, which reduced the cost and improved the quality of resin. Besides, the components in the novel system can greatly influence the quality above. The optimized 6# resin had good particle character and rheological property, which convinced the feasibility of the route for four -unit compound dispersing system. At the same time, the output will go up by 50% after the technology optimization.The molecular weight and melt time were optimized and quantified by random design method and SAS regression analysis. And the regression equations were also acquired. Results showed that initiators and dispersants could affect the molecular weight, but the effect of the former was stronger. As for melt time of resin, HPMC, PVA, polymerization vessel may affect it. And there was interaction among HPMC and PVAs with different saponds. By means of regression analysis, the relationships of polymerization condition, particle character and processing rheological property were discussed and the optimized recipes were achieved, which will play an important role in the preparation of PVC resins with high quality and low cost.The effect of the molecular weight and its distribution, defect structures on the static and dynamic thermal stability and initial coloring was also studied. It was found that the thermal stability of jin-1 was superior to jin-2 and jin-3. But the initial coloring of former was inferior to jin-3. Therefore, the thermal stability was not consistent with initial coloring. 6# resin employed four-unit dispersing system, high efficient initiating system and improved technology, which were responsible for its low amount of defect structures, good stability and initial coloring.The stability of layered double hydroxide (LDH) on PVC was firstly studied in our nation. It was found that LDH had the layered crystal structure. After calcination at 500 the layered structure was destroyed and LDH became LDO. As to the stabilization of LDH on PVC, the one calcinated at 180 was better, but it was not recommended to use it separately. When it was combined with organic stannum in proper proportion, it may achieve good stabilization on PVC. But it was not so effective as lead salts and organic stannum. Therefore the further study is necessary. Because of the advantages of this novel thermal stabilizer on PVC, such as its safety, innocuity, low price, lubrication and peculiar structure, it was especially suitable for the application in the food packaging industry and it will bring out great benefit for environmental protection and economy. |
PDF Full Text Request