| 摘要 |
The sagging problem in the manufacture of thick walled pipes is solved using a polyethylene molding composition having a multimodal molecular mass distribution and comprising from 45 to 55% by weight of a first low molecular weight ethylene homopolymer A, from 20 to 40% by weight of a second high molecular weight copolymer B comprising ethylene and another olefin having from 4 to 8 carbon atoms and from 15 to 30% by weight of a third ultrahigh molecular weight ethylene copolymer C prepared in the presence of a Ziegler catalyst in a three-stage polymerization process comprising additionally an organic polyoxy compound or an organic polyhydroxy compound in an amount of from 0.01 to 0.5% by weight.
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