| 摘要 |
Propylene polymers (PP) consisting of 25-97 wt% PP-1containing 0-15 wt% 2-10C alk-1-ene comonomer (alkene) units and 3-75 wt% of another PP (PP-2) containing 15-80 wt% alkene units as above. The PP are obtained by 2-stage polymerisation of propylene and alkene in presence of a Ziegler-Natta catalyst containing a titanium-containing solid component (a) containing a magnesium compound, a halogen, a silica support and a carboxylate ester as electron donor, with an aluminium compound (b) and another electron donor (c) as cocatalysts. The silica gel support has an average particle diameter (d-1) of 5-200 microns and an average primary particle diameter (d-2) of 1-10 microns, and contains 5-20 vol% of pores or channels with an average diameter (d-3) of 1-10 microns. Stage 1 comprises the polymerisation of propylene, optionally in the presence of alkene, at 50-100 degrees C and 15-40 bar with a mean residence time of 0.5-5 hours, and stage 2 comprises polymerisation of propylene and alkene at 30-100 degrees C and 15-40 bar with a residence time of 0.5-5 hours in the presence of the stage 1 polymer. Also claimed is the above process for the production of polypropylene. |
