Hoechst Aktiengesellschaft

Basell Polyolefine Gmbh

Ulrich Schulte

Joachim Berthold

Heinz Vogt

Elke Damm

Ludwig Bohm

Johannes-Friedrich Enderle

Hartmut Luker

Rainer Lecht

Ludwig B&ouml;hm

Werner Breuers

Walter Albert

Gunter Kohaut

Werner Rothhöft

Hansjörg Nitz

Manfred Fleissner

Heiner Bromstrup

Johannes Friedrich Enderle

Herbert Borchert

Bruno Rapp

A polyethylene molding material has a bimodal molecular weight distribution with an overall density of &gE;0.948 g/cm and a melt flow index MFI of &lE;0.2 dg/min. The molding material comprises from 35 to 65% by weight of low-molecular-weight ethylene hompolymer A having a viscosity number VN in the range from 40 to 90 cm /g, a melt flow index MFI in the range from 40 to 2000 dg/min and a density d of &gE;0.965 g/cm . Also included is from 35 to 65% by weight of high-molecular-weight ethylene copolymer B having a viscosity number VN in the range from 500 to 2000 cm /g, a melt flow index MFI in the range from 0.02 to 0.2 dg/min and a density d in the range from 0.922 to 0.944 g/cm .

Polyethylene molding material and pipe produced therewith with improved mechanical properties

The process according to the invention for producing large-bore thick-walled pipes made of polyethylene comprises extruding the polymer composition out of an annular die 3 and subsequently cooling the melt 7 emerging from the die 3 using water as the coolant from the outside, the melt 7 emerging from the die being additionally also cooled with water from the inside. In order to ensure the internal cooling, according to the invention floating plugs 11 and 12 are inserted, which plugs are fixed in their physical position relative to the extrusion die 3 by means of retaining elements.

Hollow extrusion using internal coolant

The invention relates to a high strength pipe of ethylene polymer having a bimodal molecular weight distribution. Such pipe has a stress cracking resistance of .gtoreq.1400 h, a fracture toughness of .gtoreq.7 mJ/mm.sup.2 and a modulus of creep in flexure, measured according to DIN 54852-Z4, of .gtoreq.1100 N/mm.sup.2. The pipe according to the invention is produced from an ethylene polymer in which the ratio of weight of the low molecular weight fraction to the weight of the higher molecular weight fraction is in the range from 0.5 to 2.0 and which has a melt flow index MFI.sub.5/190.degree. C. of .ltoreq.0.35 g/10 min. It is particularly suitable for the transportation of gases and water.

Pipe of polyethylene having improved mechanical properties

The invention provides foamed plastics particles having a star-like shape the three legs of which are on the same plane. The ratio of particle thickness to particle height is from 1:2.75 to 1:3.3, that of leg width to particle height is from 1:2.2 to 1:2.5, and the particle height is from 10 to 60 mm. The particles of the invention are suitable as free-flowing packing material having a good flow and simultaneously a good interlocking capacity.

Free-flowing packing material of foamed plastics particles

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Kelkheim, Germany

Ulrich Schulte