Multimodal polyethylene molding composition for producing pipes having improved mechanical properties
AssigneeBasell Polyolefine GmbH
InventorHeinz Vogt
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Abstract
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.
Claims10
A polyethylene molding composition having a multimodal molecular mass distribution for producing pipes, which comprises from 45 to 55% by weight of a first ethylene homopolymer A, from 20 to 40% by weight of a second copolymer B comprising ethylene and another olefin having from 4 to 8 carbon atoms and from 15 to 30% by weight of a third ethylene copolymer C, where all percentages are based on the total weight of the molding composition and comprising additionally an amount of from 0.01 to 0.5% by weight, based on the total weight of the molding composition, of an organic polyoxy compound having the general chemical formula:
- R—[(CH2)n—O]m—H
- where n is an integer in the range from 1 to 10,
- m is an integer in the range from 3 to 500 and
- R is a hydrogen atom or an OH group or an alkyl group which has from 1 to 10 carbon atoms and may bear further substituents such as —OH, —COOH, —COOR, —OCH3 or —OC2H5,
- or an organic polyhydroxy compound having the general chemical formula:
- RO—CH2—C—(CH2—OR)3
- where R can be a hydrogen atom or an alkyl group which has from 1 to 5 carbon atoms and may bear further substituents such as —OH, —COOH, —COOR, —OCH3 or —OC2H5,
- or a combination of the two.
Dependencies are inferred from the claim text.