Hoechst Aktiengesellschaft

Clariant Corporation

Hostalen Polyethylen Gmbh

Rainer Lecht

Ludwig Bohm

Werner Breuers

Joachim Berthold

Gerd Hohner

Hans-Friedrich Herrmann

Hartmut Luker

Ulrich Schulte

Manfred Fleissner

Hans Joachim Vetter

Heiner Bromstrup

Johannes Friedrich Enderle

Ludwig B Ohm

A catalyst formed by the reaction of a magnesium alkoxide dispersion having a particle size of from 100 to 3000 nm with a compound of a metal selected from the group comprising titanium, zirconium, vanadium and chromium and then with a chlorine-containing organoaluminum compound possesses a very good hydrogen responsiveness and a high activity even in the presence of molecular-weight regulators such as hydrogen. The catalyst is therefore outstandingly suitable for the production of low molecular-weight polyolefins. The catalyst makes possible the production of waxes having a reduced residual ash content. The large particle diameter and the low fines content of the polymer powder produced by suspension polymerization with this catalyst enables easy removal of the suspension medium and drying. The catalyst is furthermore advantageously used in solution polymerization and, because of the large particle diameter, in gas phase polymerization for producing low molecular-weight poly-1-olefins.

Process for producing low molecular-weight poly-1-olefins

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

Process for preparing a poly-1-olefin By means of a highly active spherical Ziegler catalyst based on a dialkylmagnesium, spherical polymers can be obtained in the polymerization of alpha-olefins. A further advantage of the catalyst of the invention lies in the high catalyst activity, so that only very small amounts of the catalyst are required for the polymerization. The residual titanium and/or zirconium content in the polymers prepared according to the invention is less than 10 ppm. Owing to its good responsiveness to hydrogen, the catalyst is particularly suited to two-stage processes for preparing polymers having a broad bimodal molecular weight distribution. The replacement of sulfur-containing electron donors such as diethyl sulfite by alcohols such as ethanol leads to less odor problems and broadened opportunities for use of the polymer. Owing to the spherical shape of the particles and the associated very good flow behavior of the polymers and copolymers, considerable simplification and advantages in handling, drying and processing are achieved.

Process for preparing a poly-1-olefin

A particularly uniform Ziegler catalyst in the form of spherical particles is obtained by using shock waves instead of a stirrer for the thorough mixing of the reactants. By means of this highly active catalyst based on a magnesium dialkyl, it is possible to obtain polymers in the form of spherical particles in the polymerization of alpha-olefins. A further advantage of the catalyst according to the invention is its high activity, which is such that only very small amounts of the catalyst are required for the polymerization. The residual content of titanium and/or zirconium in the polymers prepared according to the invention is less than 10 ppm. By virtue of its good responsiveness to hydrogen, the catalyst is suitable for the preparation of polymers with a broad bimodal molar mass distribution, particularly in two-stage processes. The replacement of sulfur-containing electron donors such as diethyl sulfite with alcohols such as ethanol has the effect of reducing the odor nuisance and increasing the number of possible uses of the polymer. Considerable simplifications and advantages in handling, drying and processing are achieved as a result of the spherical shape of the particles and the very good flowability of the polymers and copolymers which is associated therewith.

Process for the preparation of a poly-1-olefin

Growing community of inventors

Kelkheim, Germany

Rainer Lecht