薄壁注塑专用高熔体流动速率PP的开发进展

Development progress of high MFR PP for thin wall injection molding

综述了国内外典型高熔体流动速率、薄壁注塑成型聚丙烯(PP)的反应器特点。剖析了典型薄壁注塑成型用PP的性能,发现Unipol工艺单反应器在生产薄壁注塑成型用PP时,存在H_2需求量高、高H_2浓度条件下反应器控制困难、挤出造粒困难的问题。详细分析了引起这些问题的原因,并给出了相应解决方案:可通过升级现有邻苯二甲酸酯类催化剂体系,增加催化剂氢调敏感性;缓慢建立H_2组分,适当提高丙烯分压,保证床层温度及露点温差;降低过滤网目数并相应调整造粒机的各工艺,以避免缠刀及连锁停车。

The characteristics of the reactor of high melt flow rate(MFR)polypropylene(PP)for thin wall molding are reviewed in China and abroad.The properties of typical PP are analyzed.The results show that there exist issues such as higher demand for hydrogen,difficulties in reactor control and extruding in high H2 concentration during the production of PP by Unipol plant.The possible reasons and relevant solutions are offered:the hydrogen response can be enhanced by upgrading current phthalic acid ester catalyst system.The bed temperature and dew point temperature difference are maintained by establishing hydrogen component slowly and improving propylene partial pressure.The mesh of filter screen is enlarged and the granulator process is modified to avoid twisting knife and interlocking shutdown.