Abstract: A polyethylene molding composition having a multimodal molecular mass distribution and comprising from 45 to 55% by weight of a low molecular weight ethylene homopolymer A, from 20 to 40% by weight of a 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 an ultrahigh molecular weight ethylene copolymer C can be prepared in the presence of a Ziegler catalyst in a three-stage process and is highly suitable for producing pipes having excellent mechanical properties.

Abstract: A molding composition is suitable for the production of pipes having improved resistance to thermooxidative degradation when these pipes are in long-term contact with liquids comprising disinfectants having an oxidizing effect. Such molding composition comprises, in addition to thermoplastic polyolefins, a polyoxy compound and/or a polyhydroxy compound as additive in an amount of from 0.01 to 1.0% by weight. In addition, the molding composition can further comprise an unsaturated aliphatic hydrocarbon in an amount of up to 5% by weight. The invention also relates to a process for improving the long-term resistance of water pipes to damage caused by oxidizing disinfectants from the water by use of this molding composition.

Abstract: A polyolefinic moulding composition is suitable for producing pipes with improved resistance to thermo-oxidative degradation when these pipes are in extended contact with liquids which contain disinfectants with an oxidative action. Beside thermoplastic polyolefins, the moulding composition additionally contains specific aromatic amines which are liquid under standard conditions as an additive. The invention also relates to a pipe made from the moulding composition and to a process for improving the long-term resistance of water pipework made of plastics to damage by disinfectants with an oxidative action from the water by the use of this moulding composition.

Abstract: A polyethylene molding composition having a multimodal molecular mass distribution and comprising from 45 to 55% by weight of a low molecular weight ethylene homopolymer A, from 20 to 40% by weight of a 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 an ultrahigh molecular weight ethylene copolymer C can be prepared in the presence of a Ziegler catalyst in a three-stage process and is highly suitable for producing pipes having excellent mechanical properties.

Abstract: A molding composition is suitable for the production of pipes having improved resistance to thermooxidative degradation when these pipes are in long-term contact with liquids comprising disinfectants having an oxidizing effect. Such molding composition comprises, in addition to thermoplastic polyolefins, a polyoxy compound and/or a polyhydroxy compound as additive in an amount of from 0.01 to 1.0% by weight. In addition, the molding composition can further comprise an unsaturated aliphatic hydrocarbon in an amount of up to 5% by weight. The invention also relates to a process for improving the long-term resistance of water pipes to damage caused by oxidizing disinfectants from the water by use of this molding composition.