| 摘要 |
The present inventions relates to a process for producing polyethylene compositions comprising polymerising polyethylene resins in a cascaded multi-stage reaction in which the reaction steps are performed in at least two slurry phase reactors (A) and (B) and at least one gas phase reactor (C) which are arranged in series in any order wherein in reactor (A) a low molecular weight ethylene homo- or copolymer fraction having a MFR2 of 100 to 2000 g/10 min, in reactor (B) a low molecular weight ethylene homo- or copolymer fraction having an MFR2 of 100 to 2000 g/10 min, and in reactor (C) a high molecular weight ethylene copolymer fraction are polymerised, and further comprising a compounding step after polymerisation, wherein the final polyethylene composition has a MFR21 of 3 to 50 g/10 min, the melt flow rates being determined according to ISO 1133, a multimodal polymer composition comprising a polyethylene resin comprising (i) a first low molecular weight ethylene homo- or copolymer fraction having a MFR2 of 100 to 2000 g/10 min, (ii) a second low molecular weight ethylene homo- or copolymer fraction having a MFR2 of 100 to 2000 g/10 min, and (iii) a high molecular weight ethylene copolymer fraction, wherein the polyethylene resin has a MFR21 of 3 to 50 g/10 min and white spots are dispersed within the final composition with a white spot dispersion of less than 4.5 after a single compounding step, the melt flow rates being determined according to ISO 1133 and the white spot test according to ISO 18553, and the use of at least two slurry phase reactors for the polymerisation of a low molecular weight polyethylene fraction for improving the homogeneity of a multimodal polyethylene resin. |
