| 摘要 |
PROBLEM TO BE SOLVED: To obtain the subject polymer esp. useful for blow molded products with improved transparency and moldability by conducting a crosslinking under specified conditions when powdery high-density polyethylene is to be kneaded in a molten state and granulated. SOLUTION: When a powdery high-density polyethylene prepared by polymerization using a catalyst selected from Ziegler-based catalyst and chromium-based catalyst is to be kneaded in a molten state at 180-300 (pref. 200-280) deg.C and granulated, a crosslinking is conducted so as to come to 1.15-1.8 (pref. 1.2-1.7) in the ratio: MIR after corsslinking/MIR before crosslinking (MIR is defined as the ratio: HMI/MI; where, MI is the melt index under a load of 2.16kg, and HMI is the melt index under a load of 21.6kg). The crosslinking agent is pref. oxygen with a concentration of 0.5-21vol.%, diluted with an inert gas, in terms of reaction uniformity, economy and handling safety. The catalyst is pref. a mixture of the Ziegler-based one and chromium-based one. |
