TiCl_4/Ni(acac)_2复合催化剂烯烃聚合与共聚合反应的研究

Studies on TiCl_4/Ni (acac)_2 Supported Catalysts for Ethylene Polymerization and Copolymerization

制备 ＴｉＣｌ４／Ｎｉ（ａｃａｃ）２复合催化剂．研究给电子体三苯基朕（ＰＰｈ３）对乙烯聚合的影响．当ｎ（ＰＰｈ３）／ｎ（Ｎｉ）为 ０．７时，催化效率为 １９００ ｇ·ｇ－１，相对分子质量为 ５３．６ × １０４，熔点 １３１．９ ℃，结晶度为４２．５％。用 ＤＳＣ，１３Ｃ ＮＭＲ等对聚合产物进行了结构性能的分析和表征．结果表明，所得聚合物熔点、结晶度、密度降低，获得一定支化度的聚乙烯．表明催化剂具有一定的齐聚和原位共聚功能．研究发现，对乙烯／１－丁烯共聚合，随／１－丁烯摩尔百分比增加，催化效率下降，相对分子质量、熔点、结晶度下降，密度减少，支化度增加．用ＤＳＣ等研究乙烯／１－丁烯共聚物的性能，共聚物的熔点。结晶度、密度明显较低，当ｘ（１－丁烯）为１０％时分别达到 １２３．５ ℃、２０．８％、０．９１１ｇ·ｃｍ－３．ＤＳＣ出现熔融双峰．支化度明显提高，达３２．８支链数／１０００ Ｃ．用１３Ｃ ＮＭＲ研究了共聚物的组成、三元序列分布、平均链长度，表明共聚物分子链有嵌段结构．

The complex catalyst TiCl4/Ni (acac )2was prepared and the effects of electron donor triphenyl phasphine (PPh3) on the gas-phase polymerization of ethylene was investigated. The polymeric products were characterized by means of DSC, 13C NMR and so on. The results showed that polyethylene products with a certain branching degree were obtained by using the catalyst system featured by their low melting point, low crystallinity and low density, indicating the catalyst has oligomerization and in situ copolymerization in some extent. When n(PPh3 )/n( Ni) = 0. 7, the catalytic efficiency reached the maximum of 1 900 g· g-1 and the molecular weight, melting point and crys tallinity of the product were 53.6 × 104, 131 .9 ℃ and 42.5% respectively. The catalyst system was applied to the copolymerization of ethylene with 1-butene and found that the branching degree of the copolymer products increased with increasing the feed ratio of 1-butene whereas the catalytic efficiency, the molecular weight, the melting point, the cytstallinity and the density decreased. All the products have two melting peaks in its DSC curves and have higher branching degree. The peak temperature of the low temperature peak, crystallinity and density of the copolymer prod ucts are obviously lower than that of the homopolymer, and are 123.5 ℃ ,20.8% and 0.911 g· cm-1 respectively for the product prepared with x = 10% 1-butene feed ratio. Its branching degree reaches 32. 8 branching number/ 1000C. The composition, thiad sequence distribution, run number and average sequence length were characterized ac- cording to the 13C NMR data. Its was found that the copolymer molecular chains exist block chain structure.