摘要:
Finely divided ethene polymers are prepared by means of a Ziegler catalyst system composed of (1) a titanium-containing catalyst component obtained by precipitation in an organic liquid from (1.1) a solution of titanium tetrachloride in a hydrocarbon, (1.2) a solution of a certain organoaluminum compound in a hydrocarbon, and a catalyst component which contains (1.3) an alpha-monoalkene and (2) aluminum, wherein the (1) used has been precipitated at relatively low temperatures in an organic liquid which, at the precipitation temperature has a relatively high viscosity and comprises (a) a liquid hydrocarbon and (b), dissolved therein, relatively small amounts of polymer of an alpha-monoalkene, with the provisos that (i) for every gram-mole of the total amount of titanium tetrachloride used specific amounts of the organic liquid, of the organoaluminum compound and of the alpha-monoalkene are used and (ii) for every mole unit of the total amount of titanium tetrachloride used specific amounts are precipitated per minute and specific amounts of the alpha-monoalkene are introduced per minute.
摘要:
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.
摘要:
The invention pertains to a method for the preparation of ultra high molecular mass polyethylene by polymerization in suspension or in gas phase in the presence of a chromium catalyst sitting on an alumosilicate support material. The chromium catalyst has been subjected to a fluorinating treatment and the polymerization is performed under low temperature conditions within a temperature range of from 50 to 100° C. The invention pertains also to ultra high molecular mass polyethylene prepared by that method and having a density in the range of from 0.930 to 0.950 g/cm3.
摘要:
The invention relates to a polyethylene molding composition which has a multimodal molar mass distribution and is particularly suitable for producing protective coatings on steel pipes. The molding composition has a density at a temperature of 23° C. in the range from 0.94 to 0.95 g/cm3 and an MFI190/5 in the range from 1.2 to 2.1 dg/min. It comprises from 45 to 55% by weight of a low molecular weight ethylene homopolymer A, from 30 to 40% by weight of a high molecular weight copolymer B of ethylene and another olefin having from 4 to 8 carbon atoms and from 10 to 20% by weight of an ultra high molecular weight ethylene copolymer C.
摘要:
Plastics pipes comprise polyolefins which can be prepared by means of a fluorine-modified chromium catalyst and are used for transporting gases and liquids.
摘要:
Plastics pipes comprise polyolefins which can be prepared by means of a fluorine-modified chromium catalyst and are used for transporting gases and liquids.
摘要:
Ethylene/.alpha.-olefin copolymers are prepared by catalytic dry-phase copolymerization of the monomers in a stirred or fluidized polymerization zone, transfer of the resulting mixture of solid copolymer and unconverted gaseous monomer into a let-down zone and separation of the mixture, after pressure reduction, into a gaseous phase and a solid phase, by a continuous process in which the solid phase is continuously flushed beforehand with gaseous ethylene and then flushed with a mixture of nitrogen and steam. The ethylene copolymers are very substantially free of residual monomers and odor and flavor substances.
摘要:
A catalyst for the copolymerization of ethylene by the gas-phase fluidized-bed method is prepared by a process in which a titanium-containing and magnesium-containing active component, reacted with an alcohol as a complexing agent, is applied to a finely divided silica from homogeneous solution, in the presence of a polysiloxane, by evaporating the solvent, and the resulting homogeneous catalyst intermediate is then preactivated by treatment with the alkylaluminum compound and the Lewis base in an inert hydrocarbon solution, and the copolymers prepared using the above catalyst are employed for the production of films exhibiting little blocking.
摘要:
The invention relates to a polyethylene molding composition which has a multimodal molar mass distribution and is particularly suitable for producing external sheathing of electric or information transmission cables. The molding composition has a density at a temperature of 23° C. in the range from 0.94 to 0.95 g/cm3 and an MFI190/5 in the range from 1.2 to 2.1 dg/min. It comprises from 45 to 55% by weight of a low molecular weight ethylene homopolymer A, from 30 to 40% by weight of a high molecular weight copolymer B of ethylene and another olefin having from 4 to 8 carbon atoms and from 10 to 20% by weight of an ultra high molecular weight ethylene copolymer C. The invention also relates to an electric or information transmission cable having an external sheath of the polyethylene molding composition which has a thickness in the range from 0.2 to 3 cm.
摘要:
A process for producing a pipe having improved resistance to thermooxidative degradation, the process comprising melting a polyolefinic molding composition in an extruder, extruding the molten molding composition through an annular die and subsequently cooling it, wherein the inner surface of the pipe is exposed to the action of a halogen-comprising treatment gas before or after cooling.