| 摘要 |
PROBLEM TO BE SOLVED: To provide a new polyethylene resin composition for a bottle cap having an excellent rigidity and excellent high speed molding property without reducing environmental stress cracking resistance (stress cracking resistance) capable of enduring the inside pressure of a beverage bottle, also in the case of using as the bottle cap, without having anisotropy, excellent in dimensional stability and also excellent in required performances such as a cap-opening torque, etc. SOLUTION: This polyethylene resin composition for the bottle cap is obtained by using a specific olefin polymerization catalyst and satisfies the following requirements (a) to (f). (a) The composition consists of 70-30 wt.% ratio of a low molecular weight component (A) consisting of an ethylene homopolymer having 100 to 500 g/10 min range MFR of cord D, and 30-70 wt.% ratio of a high molecular weight component (B) consisting of a copolymer of the ethylene and a 3-20Cα-olefin, (b) The MFR of the cord D is 5.0 to 10.0/10 min, (c) Its density is 0.960 to 0.967 g/cm<SP>3</SP>, (d) Its molecular weight distribution (Mw/Mn) is 8.0 to 12.0, (e) Its environmental stress cracking resistance (ESCR) is≥20 hr, (f) The ratio of a molding shrinkage in flow direction of the resin (MD) to the molding shrinkage in right angle direction to the flow of the resin (TD), measured by a film gate plate having 150 mm square and 2 mm thickness obtained by injection molding at a cylinder temperature of 200°C and mold temperature of 50°C is 1.0 to 2.5. COPYRIGHT: (C)2008,JPO&INPIT
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