论文部分内容阅读
采用一种含二酯类内给电子体的氯化镁负载Ziegler-Natta催化剂和三异丁基铝(TIBA)助催化剂,在同一反应器中经常压丙烯预聚和加压下的乙烯与少量丙烯淤浆共聚合两步反应,高效地合成了外径为0.4~3 mm的中空球形聚乙烯粒子,其球形粒子的外表面和内部空腔的内表面均较为平滑,壳层厚度均匀.聚合反应的催化剂效率最高达到7.49 kg/g Ti·h·MPa(6.5 kg PE/g Cat.).研究了助催化剂种类、助催化剂浓度(Al/Ti摩尔比)和乙烯聚合阶段的丙烯共单体添加量对聚合物粒子形貌的影响,发现采用三乙基铝(TEA)或TEA/TIBA混合物为助催化剂时,虽然聚合物粒子仍呈中空球形形态,但其内部空腔的形状极不规则.以TIBA为助催化剂时,在一定范围内提高Al/Ti比和丙烯添加量均可显著提高催化效率,聚合反应动力学曲线由衰减型变为增长型,但聚合物粒子的中空形貌得以保持.对比丙烯预聚产物的粒子形貌发现,助催化剂含TEA时所得预聚物粒子结构较松散,内部有较多孔隙和裂纹,而改为TIBA后预聚物粒子内部相对致密.
A Ziegler-Natta catalyst and a triisobutylaluminum (TIBA) cocatalyst were loaded with a magnesium chloride-containing electron donor in the diester. In the same reactor, propylene was pre-polymerized and pressurized with a small amount of propylene Slurry copolymerization two-step reaction, the external diameter of 0.4 ~ 3 mm hollow spherical polyethylene particles synthesized, the outer surface of the spherical particles and the inner surface of the inner cavity are relatively smooth, uniform thickness of the shell. The catalyst efficiency was up to 7.49 kg / g Ti · h · MPa (6.5 kg PE / g Cat.) The effects of the type of promoter, the concentration of cocatalyst (Al / Ti molar ratio) and the amount of propylene comonomer The effects of TEA or TEA / TIBA mixture on the morphology of the polymer particles were observed. Although the polymer particles were still hollow spherical morphology, the shape of the internal cavity was very irregular When TIBA is a cocatalyst, both the Al / Ti ratio and the propylene content can increase the catalytic efficiency remarkably in a certain range. The kinetic curve of polymerization reaction changes from decaying to growthing, but the hollow morphology of the polymer particles is maintained. Comparing the particles of propylene prepolymer Appearance found, the resulting prepolymer when less structured particles containing cocatalyst TEA, more internal voids and cracks, and the interior of the particle to TIBA prepolymer relatively dense.