Abstract: To provide novel ultrahigh molecular weight polyethylene particles having a high melting point and exhibiting high crystallinity, thus capable of providing a molded product excellent in mechanical strength, thermal resistance and abrasion resistance. Ultrahigh molecular weight polyethylene particles which satisfy that (1) the intrinsic viscosity (?) is at least 15 dL/g and at most 60 dL/g, (2) the bulk density is at least 130 kg/m3 and at most 700 kg/m3, and (3) ?Tm (?Tm=Tm1?Tm2) i.e. the difference between a melting point (Tm1) in 1st scan and a melting point (Tm2) in 2nd scan, measured by a differential scanning calorimeter (DSC), is at least 11° C. and at most 30° C.

Abstract: To provide novel ultrahigh molecular weight polyethylene particles having a high melting point and exhibiting high crystallinity, thus capable of providing a molded product excellent in mechanical strength, thermal resistance and abrasion resistance. Ultrahigh molecular weight polyethylene particles which satisfy that (1) the intrinsic viscosity (?) is at least 15 dL/g and at most 60 dL/g, (2) the bulk density is at least 130 kg/m3 and at most 700 kg/m3, and (3) ?Tm (?Tm=Tm1?Tm2) i.e. the difference between a melting point (Tm1) in 1st scan and a melting point (Tm2) in 2nd scan, measured by a differential scanning calorimeter (DSC), is at least 11° C. and at most 30° C.

Abstract: A process for production of an olefin polymer is provided which comprises polymerization of ethylene and/or &agr;-olefin of three of more carbons at a polymerization temperature of not lower than 120° C. with a catalyst comprising a specific metallocene compound having a substituted fluorenyl group, and a compound which reacts with the metallocene compound to form a cationic metallocene compound. The olefin polymer or copolymer produced by the process has narrow composition distribution, narrow molecular weight distribution, and a high molecular weight.

Abstract: A process for production of an olefin polymer is provided which comprises polymerization of ethylene and/or &agr;-olefin of three of more carbons at a polymerization temperature of not lower than 120° C. with a catalyst comprising a specific metallocene compound having a substituted fluorenyl group, and a compound which reacts with the metallocene compound to form a cationic metallocene compound. The olefin polymer or copolymer produced by the process has narrow composition distribution, narrow molecular weight distribution, and a high molecular weight.

Abstract: A process for producing an ethylene/&agr;-olefin copolymer is provided in which ethylene is copolymerized with an &agr;-olefin having three or more carbons by use of an olefin polymerization catalyst at a polymerization temperature of not lower than 120° C. The olefin polymerization catalyst comprises, as constitutional components, a) a metallocene compound comprising hafnium, b) an ionizing ionic compound, and c) an organoaluminum compound, the ionizing ionic compound (b) being a compound which is capable of changing the metallocene compound (a) into a cationic form and does not further react the cationic form of the metallocene compound.

Abstract: An ethylene/&agr;-olefin copolymer of a weight-average molecular weight of not less than 40000 is produced by copolymerization of ethylene with an &agr;-olefin having three or more carbons by use of an olefin polymerization catalyst at a polymerization temperature of not lower than 120° C., the olefin polymerization catalyst comprising, as constitutional components, a) a metallocene compound, b) an ionizing ionic compound, and c) an organoaluminum compound, the ionizing ionic compound (b) being a compound which is capable of changing the metallocene compound (a) into a cationic form and does not further react the cationic form of the metallocene compound. This process produces an ethylene/&agr;-olefin copolymer of high molecular weight in high efficiency.

Abstract: A catalyst for polymerization of an olefin is provided which comprises a metallocene compound having a specified substituted fluorenyl group, and a compound capable of reacting the metallocene compound to form a cationic metallocene compound. With this compound, a high-molecular olefin polymer having narrow composition distribution and narrow molecular-weight distribution can be obtained at a polymerization temperature of not lower than 120.degree. C.

Abstract: A catalyst for olefin polymerization is provided which comprises, as the components, a) a metallocene compound, b) an ionizing ionic compound, c) an organoaluminum compound, and d) a Lewis base compound. This catalyst has a stable active species and improves productivity of an olefin polymer without deterioration of the catalytic activity the metallocene is represented by General Formula (1) or (2) where Cp-containing ligands may be Cp, fluorenyl, indenyl or tetrahydroindenyl and where the metal is a group 4 metal of the periodic table.

Abstract: A catalyst for olefin polymerization is provided which comprises, as the components, a) a metallocene compound, b) an ionizing ionic compound, c) an organoaluminum compound, and d) a Lewis base compound. This catalyst has a stable active species and improves productivity of an olefin polymer without deterioration of the catalytic activity.

Abstract: Novel catalysts for polymerization of ethylene or .alpha.-olefins, comprising a metallocene, an organoaluminum compound an ionic compound, and a boron compound, or comprising an ionic metallocene, an organoaluminum compound and a boron compound. Process for polymerization of ethylene or .alpha.-olefins by use of the above catalysts.