POLYOLEFIN COMPOSITION FOR INJECTION MOLDING

摘要

Compsn. comprises a super-high molecular weight polyolefin (1) (having a critical viscosity measured in decalin soln. at 135 deg. C of 10-40 dl/g (better 15-35 dl/g)) and a low and high molecular weight polyolefin (2) (having a critical viscosity measured in decalin at 135 deg. C of less than 10 dl/g (better 0.1-5 dl/g, best 0.5-3 dl/g)). Polyolefin (1) makes up 15-40 wt.% (better 20-35 wt.%) of the total amount of polyolefins (1) and (2). The critical viscosity (etc.) of the compsn. measured in decalin soln. at 135 deg. C lies between 4.0-10 dl/g (better 4-9 dl/g), the melting torque (T1) of the compsn. is 4.5 Kg cm or less. Polyethylene is used as a typical polyolefin. The compsn. is produced in a multi-stage polymerisation process consisting of (i) a process to produce (1) and (ii) a process to produce (2). Process (i) is carried out in the presence of Ziegler catalyst comprising: (A) a highly active component contg. Mg, Ti and a halogen, (B) organic aluminium compounds. Process (ii) is carried out in the presence of hydrogen molecules.