Horizontal polymerization reactor for producing propylene-based polymer and method for producing propylene-based polymer

A horizontal polymerization reactor for producing a propylene-based polymer comprising:

• a cylindrical reaction container comprising an internal space, and comprising a polymerization reaction chamber and a bearing chamber which are divided from each other by a partition wall intersecting a length direction of the internal space;
• an agitator comprising an agitator shaft rotating in a circumferential direction of the reaction container and an agitating member fixed on the agitator shaft;
• a bearing disposed at least one end side of the agitator shaft of the agitator to bear the end portion of the agitator shaft;
• a pressure equalization line connecting the polymerization reaction chamber and the bearing chamber,
• a purge gas feed line connected at least to the bearing chamber;
• and
• a catalyst feed nozzle connected to a catalyst feed port of the polymerization reaction chamber,
• wherein the agitator shaft of the agitator passes through the partition wall and is placed in the polymerization reaction chamber and the bearing chamber, and the agitating member of the agitator is placed in the polymerization reaction chamber, and the bearing is placed in the bearing chamber.