ω-Alkenylmethyldichlorosilane-assisted propylene polymerization with Ziegler-Natta catalyst to long chain-branched polypropylene
ω-Alkenylmethyldichlorosilane-assisted propylene polymerization with Ziegler-Natta catalyst to long chain-branched polypropylene
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DOI：
10.1016/j.polymer.2020.122737
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发表时间：
2020-08
期刊：
影响因子：
4.6
通讯作者：
Kang Li;Hangsheng Zhou;Qin Yawei;Ying Zhao;Dujing Wang;Jin‐Yong Dong
中科院分区：
文献类型：
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作者：
Kang Li;Hangsheng Zhou;Qin Yawei;Ying Zhao;Dujing Wang;Jin‐Yong Dong
长链支化聚丙烯（LCB-PP）具有高熔体强度的特点，是一类在线性原型基础上进行改性的高端PP材料。催化剂技术的最新进展使得使用茂金属/非茂金属催化剂通过非共轭α，ω-二烯烃/丙烯共聚直接合成LCB-PP成为可能。然而，对于主导商业PP生产的Ziegler-Natta催化剂（MgCl2/ ticl4催化剂）来说，用于LCB-PP合成的化学物质仍然很少。为了解决这一难题，本文报道了一种基于Ziegler-Natta催化剂技术的LCB-PP合成化学方法。该新化学方法使用ω-烯基甲基二氯硅烷作为LCB试剂来帮助丙烯聚合，在主聚合（使用Ziegler-Natta催化剂）和聚合物加工（与水）过程中利用α-烯烃和烷基甲基二氯硅烷的两种不同功能在PP链之间构建二烷基硅氧烷低聚物相互连接，从而合成h形LCB-PP。通过完全抛弃大单体共聚作为LCB结构形成的必要条件，新的化学反应大大降低了空间位垒，适用于Ziegler-Natta催化剂。加入一定量的ω-烯基甲基二氯硅烷可以防止凝胶化。合成的LCB- pp样品在流变学测试中表现出较强的LCB特性。LCB密度由丙烯主聚合中ω-烯基甲基二氯硅烷掺入率控制。在不同的ω-烯基甲基二氯硅烷衍生物中，一种与丙烯共聚反应较强的衍生物合成LCB-PP效率更高。所得的3种ω-烯基甲基二氯硅烷的LCB-PP合成效率依次为：5-己烯基甲基二氯硅烷b> 7-辛烯基甲基二氯硅烷b> 3-丁烯基甲基二氯硅烷。
Long chain-branched polypropylene (LCB-PP) with high melt strength characteristics has long been a class of high-end PP materials modified from their linear prototypes. Recent advances in catalyst technology has enabled direct synthesis of LCB-PP using metallocene/non-metallocene catalysts via, among others, non-conjugatedα,ω-diolefin/propylene copolymerization. However, for Ziegler-Natta catalysts (MgCl2/TiCl4catalysts) which dominate commercial PP production, chemistries for LCB-PP synthesis are still rare. To resolve the dilemma, this paper reports a new LCB-PP synthetic chemistry based on Ziegler-Natta catalyst technology. The new chemistry usesω-alkenylmethyldichlorosilane as an LCB reagent to help with propylene polymerization, where it leverages its two distinct functionalities ofα-olefin and alkylmethyldichlorosilane in main polymerization (with Ziegler-Natta catalyst) and during polymer workup (with water) to construct dialkylsiloxane oligomer interlinkages between PP chains, thus synthesizing H-shape LCB-PP. By completely ditching macromonomer copolymerization as being essential for LCB structure formation, the new chemistry is greatly reduced of steric barrier and suits Ziegler-Natta catalysts. Gelation can be prevented by containing the addition dosage ofω-alkenylmethyldichlorosilane. The synthesized LCB-PP samples exhibit strong LCB characteristics in rheology test. LCB densities are controlled byω-alkenylmethyldichlorosilane incorporation rates in main propylene polymerization. Of differentω-alkenylmethyldichlorosilane derivatives, one that is more reactive for copolymerization with propylene is more efficient for LCB-PP synthesis. For the three synthesizedω-alkenylmethyldichlorosilanes their efficiencies for LCB-PP synthesis follow the order of 5-hexenylmethyldichlorosilane > 7-octenylmethyldichlorosilane > 3-butenylmethyldichlorosilane.