Patent ID: 7888437

Claim:
A process for producing an olefin polymer, comprising polymerizing an olefin having 3 or more carbon atoms in the presence of a catalyst for olefin polymerization comprising a solid titanium catalyst component (I) which comprises titanium, magnesium, halogen, and a cyclic ester compound (a) specified by the following formula (1): wherein n is an integer of 5 to 10, R 2 and R 3 are each independently COOR 1 or a hydrogen atom, and at least one of R 2 and R 3 is COOR 1 ; and R 1 's are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms, and a single bond (excluding C a —C a bonds, and a C a —C b bond in the case where R 3 is a hydrogen atom) in the cyclic backbone may be replaced with a double bond, and an organometallic compound catalyst component (II) which comprises a metal element selected from Groups I, II and XIII of the periodic table, at an internal pressure of the polymerization vessel which is 0.4 times or more as high as the saturation vapor pressure of the olefin at a polymerization temperature.