Abstract: A process for producing an .alpha.-olefin polymer which comprises polymerizing an .alpha.-olefin in the presence of a catalyst system comprising(A) a solid catalyst component containing at least titanium, magnesium, halogen, and electron donor and(B) a sterically hindered aluminum amide compound represented by the general formula ##STR1## wherein, R.sup.1 through R.sup.5 denote each a hydrocarbon group of 1 to 20 carbon atoms, L denotes an alkoxy group of 1 to 20 carbon atoms and/or halogen, l is 2 or 3, x is defined by 0<x<1, y is defined by 0.ltoreq.y<3, and z is defined by 0<z<3 with the proviso that x+y+z=3.

Abstract: A process for producing an .alpha.-olefin polymer which comprises polymerizing an .alpha.-olefin in the presence of a catalyst system comprising(A) a solid catalyst component containing at least titanium, magnesium, halogen, and electron donor and(B) a sterically hindered aluminum amide compound represented by the general formula ##STR1## wherein, R.sup.1 through R.sup.5 denote each a hydrocarbon group of 1 to 20 carbon atoms, L denotes an alkoxy group of 1 to 20 carbon atoms and/or halogen, l is 2 or 3, x is defined by 0<x<1, y is defined by 0.ltoreq.y<3, and z is defined by 0<z<3 with the proviso that x+y+z=3.

Abstract: A liquid catalyst component for copolymerization of ethylene with .alpha.-olefin comprising a titanium compound represented by the following general formula:(R.sup.1 R.sup.2 N).sub.4-(m+n) TiX.sub.m Y.sub.nwherein R.sup.1 and R.sup.2 each represents a saturated hydrocarbon group having 8 to 30 carbon atoms; X represents halogen; Y represents an alkoxy group; m represents a number satisfying 1.ltoreq.m.ltoreq.3; n represents a number satisfying 0.ltoreq.n.ltoreq.2; and (m+n) satisfies 1.ltoreq.(m+n).ltoreq.3.Said liquid catalyst component is used in combination with an organoaluminum compound as a catalyst system for copolymerization of ethylene with .alpha.-olefin.

Abstract: A liquid catalyst component for copolymerization of ethylene with .alpha.-olefin comprising a titanium compound represented by the following general formula:(R.sup.1 R.sup.2 N).sub.4-(m+n) TiX.sub.m Y.sub.nwherein R.sup.1 and R.sup.2 each represents a saturated hydrocarbon group having 8 to 30 carbon atoms; X represents halogen; Y represents an alkoxy group; m represents a number satisfying 1.ltoreq.m.ltoreq.3; n represents a number satisfying 0.ltoreq.n.ltoreq.2; and (m+n) satisfies 1.ltoreq.(m+n).ltoreq.3.Said liquid catalyst component is used in combination with an organoaluminum compound as a catalyst system for copolymerization of ethylene with .alpha.-olefin.