Patent ID: 8742040

Claim:
A solid titanium catalyst component (I) comprising titanium, magnesium, halogen, a cyclic ester compound (a) represented by the following formula (1) and a cyclic ester compound (b) represented by the following formula (2), wherein the combining molar ratio of the cyclic ester compound (a) to the cyclic ester compound (b) ((cyclic ester compound (a)/(cyclic ester compound (a)+cyclic ester compound (b)))×100 (% by mol)) is 50-90% by mol: wherein n is an integer of 5 to 10, R 2 and R 3 are each independently COOR 1 or R, at least one of R 2 and R 3 is COOR 1 , and a single bond (except C a —C a bond, and C a —C b bond in the case where R 3 is R) in the cyclic skeleton may be replaced with a double bond, R 1 is each independently a monovalent hydrocarbon group of 1 to 20 carbon atoms, plural R are each independently an atom or a group selected from a hydrogen atom, a hydrocarbon group of 1 to 20 carbon atoms, a halogen atom, a nitrogen-containing group, an oxygen-containing group, a phosphorous-containing group, a halogen-containing group and a silicon-containing group, and they may be bonded to one another to from a ring, but at least one R is not a hydrogen atom, and in a skeleton of the ring formed by bonding of plural R to one another may be contained a double bond, and when two or more C a to each of which COOR 1 is bonded are contained in the skeleton of the ring, the number of carbon atoms to constitute the skeleton of the ring is 5 to 10; wherein n is an integer of 5 to 10, and R 4 and R 5 are each independently COOR 1 or a hydrogen atom, at least one of R 4 and R 5 is COOR 1 , R 1 is each independently a monovalent hydrocarbon group of 1 to 20 carbon atoms, and a single bond (except C a —C a bond and C a —C b bond in the cyclic skeleton may be replaced with a double bond).