Abstract: A multimodal polymer composition for pipes is disclosed. The polymer is a multimodal polyethylene with a density of 0.930-0.965 g/cm3, an MFR5 of 0.2-1.2 g/10 min, an Mn of 8000-15000, an Mw of 180-330×103, and an Mw/Mn of 20-35, 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 lower molecular weight limit of 3500, and a weight ratio of the LMW fraction to the HMW fraction of (35-55):(65:45).

Abstract: A method for preventing sheeting problems in a gas phase reactor in such multi-phase polymerization process, which comprises at least one loop reactor followed by a gas phase reactor, where the polymerization is continued in the presence of added monomers, and in which process a fouling preventive agent is used to prevent fouling or sheeting in the reactors. According to the invention 30-70% of the end product is polymerized in the loop reactor, where the whole amount of the fouling preventive agent is added, the amount of the fouling preventive agent being higher than necessary to prevent the fouling in the loop reactor.

Abstract: A method and apparatus for taking a sample from a flowing suspension formed by polymer particles and hydrocarbon diluent in a olefin polymerization process including at least one filter situated at a plane of an inside surface of a transfer conduit between reactors. Each filter includes perforations or pores having a size to prevent substantially any of the catalyst used in the polymerization process from passing through the filter, e.g., smaller than the smallest particle size of a catalyst used in the polymerization process. The pore or perforation size of each filter is preferably 0.1-10 .mu.m, preferably between 0.2-1 .mu.m. A pressure difference permits at least partial vaporization of the sample as it passes through the filter.

Abstract: Process for manufacturing ethylene copolymers by polymerizing ethylene and a minor amount of C.sub.3 -C.sub.6 alphaolefins in particle form in slurry reactor in the presence of an ethylene polymerizing catalyst. According to the invention the polymerization is carried out in propane diluent by using a metallocene catalyst activated with an alumoxane compound.

Abstract: A process for producing polyethylene compositions in the presence of a catalytic system of ethylene polymerizing catalyst and cocatalyst in a multistage continuous reaction sequence consisting of successive liquid phase and gas phase polymerizations is disclosed. In the first step of the process, ethylene and optionally hydrogen and comonomer are polymerized in a first loop reactor in a low boiling hydrocarbon medium in the presence of ethylene polymerizing catalyst and cocatalyst. The reaction mixture is then removed and then transferred to a second loop reactor where polymerization is continued by addiing ethylene, hydrogen and optionally inert hydrocarbon, comonomers and cocatalysts. Thereafter, the reaction mixture is removed from the second loop reactor along with an essential part of the reaction medium and transferred to a gas phase reactor where polymerizing is continued in the presence of added ethylene and optionally hydrogen, comonomers and cocatalysts to form an end product.

Abstract: The invention concerns a multi-stage process for producing polyethylene having a bimodal and/or broad molecular weight distribution in the presence of an ethylene polymerizing catalyst system in a multistep reaction sequence, in which the first reaction step is a liquid phase polymerization step and the second reaction step is formed by one or more gas-phase polymerization steps. According to the process of the invention in the first reaction step ethylene is polymerized in a loop reactor (10) in an inert low-boiling hydrocarbon medium the residence time being at least 10 minutes, reaction mixture is discharged from the loop reactor (10) and at least a substantial part of the inert hydrocarbon mixture is separated and the polymer is transferred into one or more gas-phase reactors (30), where the polymerization is completed in the presence of ethylene and optionally hydrogen and a comonomer.

Abstract: The invention relates to a regulation method for regulating the temperature in a reactor utilized in the polymerization of olefines. A circulating gas is led to the reactor along a circulating gas flow line, and the circulating gas is cooled by leading part of the circulating gas flowing along a circulating gas flow line along a by-pass flow line through a cooler. A regulating device for the circulating gas inlet-flow temperature controls the amount of the circulating gas by-pass flow along a circulating gas by-pass flow line through the cooler such that the sum of the openings of a valve in the circulating gas flow line and a valve in the circulating gas by-pass flow line is maintained substantially constant in the range from about 90 to about 120%.