低晶点薄膜专用低密度聚乙烯树脂2420 H的质量优化

Quality improvement of low density polyethylene resin 2420 H for low crystal point film

为解决低晶点薄膜专用低密度聚乙烯树脂2420 H晶点多的问题,对晶点产生原因及影响因素进行了分析,并进行了工艺优化。结果表明:晶点是2420 H生产过程中形成的凝胶状高分子质量聚合物,分子间链转移生成的长支链是其主要来源;通过采取降低反应温度和挤压机筒体温度,降低高/低压产品分离器液位,增大反应压力和后冷器热水流量等措施,2420 H的重均相对分子质量、支化度和长链支化度分别降低至7.86×10^4,13.8%,0.09706%,晶点数量由64个下降至16个。

In order to solve the problem of unnecessary crystal points in low crystal point thin film resin 2420 H of Lanzhou Petrochemical Company,PetroChina,the causes and influencing factors of crystal points were analyzed,and the corresponding improvement measures were put forward.The results showed that the crystal point was gelatinous polymer formed during the 2420 H production process,and the long branched chain generated by inter-molecular chain transfer was the main source of gelatinous polymer.By decreasing the temperatures of reactor and extruder cylinder,the liquid level of high and low pressure product separator,and increasing reaction pressure and the flow of hot water in the after cooler,the weight average molecular mass,branching degree and long chain branching degree of 2420 H were reduced to 7.86×10^4,13.8%and 0.09706%respectively,and the number of crystal points was also significantly decreased from 64 to 16.