Method for producing an olefin polymer

A method for producing an olefin polymer, which comprises polymerizing or copolymerizing olefins in the presence of a catalyst consisting essentially of:

• (A) a solid catalyst component obtained by thermally reacting (a.sub.1) a magnesium compound of the formula Mg(OR.sup.1).sub.n (OR.sup.2).sub.2-n wherein each of R.sup.1 and R.sup.2 which may be the same or different is an alkyl group, an aryl group or an aralkyl group, and n is 2.gtoreq.n.gtoreq.0, (a.sub.2) a titanium compound of the formula Ti (OR.sup.3).sub.4 wherein R.sup.3 is an alkyl group, an aryl group or an aralkyl group and (a.sub.3) a silicon compound of the formula Si(OR.sup.4).sub.4 wherein R.sup.4 is an alkyl group, an aryl group or an aralkyl group, and contacting and treating (a) the resulting thermal reaction product with (b) a halogen-containing titanium compound and (c) an electron donative compound
• of the formulas:
• ##STR2## wherein each of R.sup.6 and R.sup.7 is a hydrocarbon group which may be substituted by an alkyoxy group, or R.sup.6 and R.sup.7 may be bonded to each other to form a cyclic group,
• wherein the thermal reaction product (a) contains a solid product comprising magnesium, titanium, silicon and OR group wherein R is an alkyl group, an aryl group or an aralkyl group,
• wherein the molar ratios relative to one mol of the magnesium compound (a.sub.1) are:
• ______________________________________ Mg(OR.sup.1).sub.n (OR.sup.2).sub.2-n ] 1 Ti(OR.sup.3).sub.4 0.05-4 Si(OR.sup.4).sub.4 0.1-5, ______________________________________
• wherein the molar ratios relative to one mol of the magnesium compound in component (a) are:
• ______________________________________ Halogen-containing titanium compound (b) 0.1-100 Electron donative compound (c) 0.01-10, ______________________________________
• and (B) an organometallic compound of a metal of Groups I-III of the Periodic Table,
• wherein the molar ratio of titanium in the catalyst component (A):
• organometallic compound (B) is 1:3-500.