重包装薄膜用LDPE 2320D的工业开发

Industrial development of LDPE 2320D for heavy packing film

研究了重包装薄膜对低密度聚乙烯（LDPE）分子结构的要求，结合反应温度、反应压力、相对分子质量调节剂种类对LDPE分子结构的影响，确定了重包装薄膜用LDPE2320D的关键工艺参数。反应压力为270～290MPa，反应器第一至四区的温度为280～290℃，采用丙烯和丙醛作为相对分子质量调节剂时，2320D的支化度为13．6～14．6个／1000C，密度为0．9215~0．9225g／cm2，正己烷提取物含量小于60mg／kg。用2320D吹塑的薄膜横向拉伸屈服应力约为11．0MPa，雾度小于15．0％；30gm厚的薄膜在120℃加热60s后，纵、横向收缩率分别为59．3％，29．7％，优于用进口同类产品吹塑的薄膜。

The key technological parameters for producing low density polyethylene （LDPE） 2320D for heavy packing film use were determined by exploring the requirements of molecular structure that LDPE should meet for manufacturing heavy packing film, and the effects of the reaction temperature, reaction pressure and types of relative molecular mass modifiers on the molecular structure of LDPE. LDPE 2320D had branching degree of 13.6-14.6/1 000 C, density of 0.921 5-0.922 5 g/cm3 and content of n-hexane extractives less than 60 mg/kg when the reaction pressure was 270-290 MPa, the reaction temperature from the first to the fourth zone was 280-290 ~C, and propylene and pro- panal were used as relative molecular mass modifiers. The blown film made of LDPE 2320D possessed transverse ten- sile stress at yield of 11.0 MPa or so and haze below 15.0%. The machine and transverse shrinkage of the 30 um thick film made of the resin were 59.3% and 29.7%, respectively, after the film was treated at 120℃ for 60 seconds, which was superior to those of the film made of its imported counterparts.