大型中空容器级HDPE树脂的中试聚合研究

采用两段淤浆聚合工艺合成了由低摩尔质量的均聚物和高摩尔质量的共聚物组成的、具有宽峰或双峰摩尔质量分布的高密度聚乙烯大型中空容器级树脂。通过调节第一段和第二段聚合过程中聚合物的熔体质量流动速率来控制摩尔质量的大小及其分布；采用控制第二段共聚物中共聚单体数量来调节聚合物密度；控制第一段小分子数目，增加第二段摩尔质量或调整密度获得最大耐环境应力开裂性（ESCR）。随着共聚单体丁烯-1加入量的增加，反应釜共混物的密度、熔点、结晶度、拉伸屈服应力、断裂伸长率减少。随着高摩尔质量共聚物的含量增加，屈服应力、熔点、密度、结晶度减少，摩尔质量分布的双峰特性也增加，反应釜共混物的均聚物峰的高度减少，共聚物峰的高度增加。流变性能结果表明，通过改变共混物的组分可以获得力学性能和加工性能的平衡。

Study on Pilot Polymerization of HDPE Resin for Large Hollow Container

Reactor blends of polyethylene/poly(ethylene-co-1-butene)large hollow container HDPE resins with broad or bimodal molecular weight distributions were synthesized in a two-stage slurry polymerization process.These blends were composed of low molecular weight homopolymer and high molecular weight copolymer.The molecular weight and molecular weight distribution of the polymer were manipulated by varying the ratio of homopolymer/copolymer and adjusting the melt index of the first and second stages of the polymerization.The density of the polymer was tuned by controlling the addition of the comonomer in the second copolymerization stage.By decreasing the density and controlling the low molecular number of the first stage of the polymerization,the optimum environmental stress cracking(ESCR)could be obtained with increasing the molecular weight of the second stage.The density,melting point,degree of crystallinity,tensile strength at yield and percentage elongation at break of the blend decreased with the increase of the comonomer content in the blend.with the increase of the mass fraction of copolymer.With the increase of the fraction of HMWs copolymer,the tensile strength at yield,melting point,density and degree of crystallinity decreased,and the bimodal characteristics of the molecular weight distribution increased,the height of the copolymer peak increased and the homopolymer peaks decreased.The results of rheological properties showed a balance of the mechanical properties and processability could be obtained by altering the composition of the blends.