Abstract: A multimodal polymer composition for pipes is disclosed as well as a pipes made thereof. The polymer is a multimodal polyethylene with a density of 0.930-0.965 g/cm3, and a viscosity at a shear stress of 747 Pa (&eegr;747 Pa) of at least 650 Pa.s, said multimodal polyethylene comprising a low molecular weight (LMW) ethylene homopolymer fraction and a high molecular weight (HMW) ethylene copolymer fraction, said HMW fraction having a weight ratio of the LMW fraction to the HMW fraction of (35-55):(65-45). Preferably, the multimodal polyethylene has a viscosity at a shear stress of 2.7 kPa (&eegr;2.7 kPa) of 260-450 kPa.s; and a shear thinning index (SHI) defined as the ratio of the viscosities at shear stresses of 2.7 and 210 kPa, respectively, of SHI27/210=50-150, and a storage modulus (G′) at a loss modulus (G″) of 5 kPa, of G′5 kPa≧3000 Pa. The pipe is made of the multimodal polymer composition and withstands a stress of 8.0 MPa gauge during 50 years at 20° C. (MRS8.0).

Abstract: A multimodal polymer composition for pipes is disclosed as well as a pipes made thereof. The polymer is a multimodal polyethylene with a density of 0.930-0.965 g/cm3, and a viscosity at a shear stress of 747 Pa (&eegr;747Pa) of at least 650 Pa.s, said multimodal polyethylene comprising a low molecular weight (LMW) ethylene homopolymer fraction and a high molecular weight (HMW) ethylene copolymer fraction, said HMW fraction having a weight ratio of the LMW fraction to the HMW fraction of (35-55):(65-45). Preferably, the multimodal polyethylene has a viscosity at a shear stress of 2.7 kPa (&eegr;2.7 kPa ) of 260-450 kPa.s; and a shear thinning index (SHI) defined as the ratio of the viscosities at shear stresses of 2.7 and 210 kPa, respectively, of SHI2 7/210=50-150, and a storage modulus (G′) at a loss modulus (G″) of 5 kPa, of G′5 kPa≧3000 Pa. The pipe is made of the multimodal polymer composition and withstands a stress of 8.0 MPa gauge during 50 years at 20° C. (MRS8.0).

Abstract: A procatalyst and a process for the preparation of a multimodal ethylene homopolymer or copolymer by gas-phase polymerisation is described. The procatalyst used in the process is prepared by: a) contacting the support, preferably silica with a halogenating agent, preferably ethyl aluminium dichloride to obtain a first reaction product, b) contacting the first reaction product with a compound or mixture containing hydrocarbyl and one or more of hydrocarbyloxy, monoalkylamido, dialkylamido, carboxylato and alkoxymethoxy groups linked to magnesium, thereby to obtain a second reaction product (the procatalyst precursor), and c) contacting the second reaction product with a titanium compound, preferably TiCl4. In step a) the molar ratio of the alkyl metal chloride to the surface hydroxyls of the inorganic oxide is preferably between 1:1 and 10:1. In step b) the atomic ratio of the magnesium to the chlorine of the alkyl metal chloride of step a) preferably is between 1:1.5 to 1:2.5.

Abstract: The invention relates to a process for the preparation of a high activity procatalyst for the production of ethylene polymers. The process according to the present invention comprises the following steps:(a) contacting the inorganic support with an alkyl metal chloride which is soluble in non-polar hydrocarbon solvents, and has the formula(R.sub.n MeCl.sub.3-n).sub.m (1)wherein R is a C.sub.1 -C.sub.20 aklyl group, Me is a metal of group III(13) of the periodic table, n=1 or 2 and m=1 or 2, to give a first reaction product,(b) contacting said first reaction product with a compound or mixture containing hydrocarbyl and hydrocarbyl oxide linked to magnesium which is soluble in non-polar hydrocarbon solvents, to give a second reaction product, and(c) contacting said second reaction product with a titanium compound which contains chlorine, having the formulaCl.sub.x Ti(OR.sup.IV).sub.4-x (2)wherein R.sup.IV is a C.sub.2 -C.sub.20 hydrocarbyl group and x is 3 or 4, to give said procatalyst.

Abstract: The invention relates to a procatalyst for the production of ethylene polymers, which procatalyst comprises an inorganic support, a chlorine compound carried on said support, a magnesium compound carried on said support, a titanium compound carried on said support, whereby the chlorine compound can be different from or the same as the magnesium compound and/or the titanium compound. The activity balance AB of the procatalyst in specified polymerization conditions, isAB>3.2wherein AB=?(A+A'):2!.multidot.?log (MFR.sub.2 ':MFR.sub.2):(A-A')!, A means polymerization activity expressed an kg PE/g cat .multidot.h, MFR.sub.2 means the melt flow rate in g/min units at a load of 2,16 kg, according to the standard ISO 1133, the absence of the upper index ' means low melt flow rate polymerization and the presence of the upper index ' means high melt flow polymerization. This means that the catalyst activity is relatively independent of the presence of chain transfer agents.