聚酯切片结晶行为与固相缩聚过程新流程方案

PET Chips Crystallization Behavior and Novel Process of Solid State Polymerization

研究了聚酯基础切片在氮气环境、水相环境以及热台偏光显微镜中的结晶特性。发现．氮气环境中90℃及以下聚酯切片的结晶度很小（约6％），温度高于100℃结晶度明显增加，二次高温结晶的结晶度与一次低温结晶温度有关；水相环境中80℃～90℃的结晶度（25％～35％）明显比氮气环境中的结晶度高；球晶生长速率在180℃～190℃范围内最大。创新提出“聚酯热水介质造粒与结晶集成”的新方法并确定了基本工艺条件：热水温度90℃～95℃，切片在热水中的停留时间2S左右；气相结晶的热空气温度175℃～185℃，停留时间约5min。

Poly（ethylene terephthalate） （PET） solid state polymerization （SSP） with high inherent viscosity has been widely used in the production of bottles, industrial fibers and engineering plastics. The crystallization behavior of PET chips in N2 or water at different temperature was investigated by densitometer for crystallinity measuring, differential scanning calorimetry （D~） and polarizing optical microscopy （POM）. It shows that： （1） almost no crystallization can be detected bellow 100℃ in N2. Crystallinity increases with the temperature between 100℃ and 140 ℃, but inherent viscosity doesn＇t increase under such conditions. （2） The crystallinity of PET crystallized in water at 80℃～140℃ respectively is significantly higher than that of PET in N2 at the same temperature, which indicates that water can notably accelerate the crystallization of PET. （3） PET crystallizes fastest at 180 ℃ 190 ℃ in POM. Based on the results of crystallization behavior, a novel PET SSP process and the condition of crystallization in hot water has been brought forward.