Propylene-based polymer, method for its production, composition thereof, catalyst component for polymerization, and method for its production

A method for producing a solid catalyst component for propylene polymerization, which comprises the steps of:

• 1) forming a solid catalyst component for polymerization comprising a magnesium compound, a titanium compound, a halogen compound and an electron-donating compound, wherein the molar ratio of the electron-donating compound (D) and the titanium content (T) incorporated therein is (D/T)i, and
• 2) treating said solid catalyst component for polymerization to make a modified solid catalyst component for polymerization, said treating comprising:
• i) treating said solid catalyst component with an electron-donating compound for its incorporation or with a titanium compound represented by the general formula TiXa·Yb, where X is a halogen atom:
• a is 3 or 4:
• Y is an electron-donating compound, and 0<b≦3, for its incorporation;
• ii) then treating and washing said solid catalyst component with a halogenous compound, and
• iii) further washing said solid catalyst component with a hydrocarbon,
• wherein the molar ratio of the electron-donating compound (D) and the titanium content (T) incorporated in said solid catalyst component thus treated is (D/T)m, such that (D/T)m/(D/T)i>1.