Patent ID: 7423099

Claim:
A process for producing a polyolefin comprising a combination of liquid phase polymerization of α-olefin conducted in one or more liquid phase polymerization reactors and gas phase polymerization of α-olefin conducted in one or more gas phase polymerization reactors after the liquid phase polymerization in a material flow, the process comprising: step A of polymerizing liquid α-olefin in the presence of a catalyst in a first reactor for liquid phase polymerization to produce a slurry comprising unreacted liquid α-olefin and a polymer powder containing the catalyst, step B of causing gas comprising α-olefin to flow in a second reactor for gas phase polymerization while keeping the second reactor unfilled with a seed powder, step C of transferring the slurry produced in the first reactor into the second reactor unfilled with a seed powder in which the gas comprising α-olefin is caused to flow, step D of vaporizing the liquid α-olefin included in the slurry transferred from the first reactor, polymerizing the vaporized α-olefin and the α-olefin included in the gas blown into the second reactor, and forming a fluidized bed by fluidizing a polymer powder, this step being conducted in the second reactor in which the gas comprising the α-olefin is caused to flow, and step E of bringing the temperature and the pressure in the second reactor to a temperature and a pressure high enough to polymerize the α-olefin in the second reactor while allowing the gas comprising the α-olefin to flow.