Abstract: A process for producing polyethylene of ultrahigh molecular weight having an intrinsic viscosity of 10-30 dl/g at 135.degree. C. in decalin is disclosed which comprises at least the following two stages of polymerization reaction: (a) a first reaction stage where in ethylene is polymerized with use of a catalyst comprising a solid component containing at least Mg, Ti and/or Va and in the absence or presence of hydrogen of reduced concentration to produce 70-99.5 weight parts of polyethylene having an intrinsic viscosity of 12-32 dl/g at 135.degree. C. in decalin; and (b) a second reaction stage wherein a fresh feed of ethylene is polymerized in the presence of hydrogen of higher concentration to produce 30-0.5 weight parts of polyethylene having an intrinsic viscosity of 0.1-5 dl/g at 135.degree. C. in decalin.

Abstract: An ultra-high molecular weight polyethylene powder easily soluble in organic solvents and suitable for use in the preparation of fibers or films having a high strength and a high elastic modulus, said polyethylene powder having an intrinsic viscosity in the range of 5 to 30 dl/g in decalin at 135.degree. C. and being obtained by at least two-step polymerization reactions which are:a first step of polymerizing ethylene in the absence of hydrogen or at a reduced hydrogen concentration, using a catalyst containing a solid catalyst component and an organometallic compound, said solid catalyst component containing at least magnesium and titanium and/or vanadium, to produce 50-99.5 parts by weight, based on 100 parts by weight of a final polyethylene product, of polyethylene having an intrinsic viscosity of 12 to 32 dl/g in decalin at 135.degree. C.; anda second step of polymerizing ethylene at a higher hydrogen concentration that in said first step to produce 50-0.5 parts by weight of polyethylene.

Abstract: Provided is a method for vapor phase polymerization of olefins. An olefin gas is fed into a horizontal cylindrical vessel having a lower curved surface corresponding to 30 to 180 degrees of the circumference of the vessel and extending substantially the length of the vessel formed by a perforated plate having a multiplicity of holes spaced at intervals in the range of from 0.5 to 50 mm, through said plate from an olefin feed chamber mounted below and covering the plate. A polymer catalyst is fed into the horizontal cylindrical vessel through a polymerization catalyst inlet port located in a portion of the vessel other than the lower curved surface formed by the perforated plate. The olefin is reacted in the presence of a catalyst with agitation to form polymer. Unreacted olefin is removed through a discharge port located in a portion of the vessel other than the lower curved surface formed by the perforated plate.

Abstract: A horizontal agitation bed type vapor phase polymerization apparatus for olefins provided on its lower curved surface with plural cells each having an opening facing on the polymerization reaction system and further having small holes formed in its side wall portion for feeding a starting olefin gas.

Abstract: A horizontal agitation bed type vapor phase polymerization apparatus for olefins, having a lower curved surface constructed by a perforated plate so as to allow a olefin gas to be fed uniformly throughout the reaction system through the said perforated plate.