Optimization In Production Process Of Polyvinyl Alcohol Films

PVA film is widely used in Packing, textile industry and medical industry because of its cold/hot water solubility, high light transmission, high melt point, good gas barrier property and mechanical property. In China, when PVA film can be only obtained from import, the price was as much as 270 thousand RMB per ton, even though the raw material of PVA was only 15 thousand per ton then. In 2000, the wet cast process of PVA film production was developed, but high energy cost and low production rate limit its development.The author successfully realized the industrialization of blow molding process for PVA film production after four years hard work at the PVA process study. The industrialization of molding process makes significant contribution to the company. The research point of this thesis is as follow:The formula and process of blow molding are optimized to reduce the melt point of PVA, in order to produce PVA film continuously by blow molding process. The blow film is obviously superior to wet cast film in outlook, mechanical property, thickness tolerant, heat seal property and light transmission.With DSC and TG/DTG analysis, the modifier effect of blow molding process was studied. The result shows that the modifier reduces melt point of PVA effectively and protects PVA from decomposing in high temperature, which makes the blow molding process possible. With XRD, DSC and FTIR analysis, the crystallinity of PVA film by the two processes is to calculate. The result shows that the crystallinity of blow film is higher than that of wet cast film. That is because of the high temperature, stretching after high pressure in the blow mold process. Under cross polarizing filters of a polarizing microscope, the different optical characteristics of blow molding film and wet cast film can be seen, which is caused by the difference of molecular chain orientation and crystallinity.Energy online test shows that energy consumption of blow molding process is only 30% as much as that of wet cast process. Energy cost is the main cost in PVA film production. A huge advantage of blow molding process is the low energy cost.