| 摘要 |
FIELD: chemistry. ^ SUBSTANCE: invention relates to a high-density polyethylene composition, preparation method thereof, articles made therefrom and a method of making said articles. The composition contains at least a first component which is a high-molecular ethylene and alpha-olefin copolymer, and a second component which is a low-molecular ethylene polymer. The composition has flow melt index (I2) of at least 1, density in the range of 0.950-0.960 g/cm3 and g' equal to or greater than 1. The first component of the composition has density in the range of 0.915-0.940 g/cm3 and flow melt index (I21.6) in the range of 0.5-10 g/10 min. The second component has density in the range of 0.965-0.980 g/cm3 and flow melt index (I2) in the range of 50-1500 g/10 min. The method of preparing the composition comprises the following steps: feeding ethylene and one or more alpha-olefin comonomers into a first reactor; (co)polymerisation of ethylene in the presence of one or more alpha-olefin comonomers in a first reactor to obtain a first component which is a high-molecular ethylene and alpha-olefin copolymer; feeding a first component and an additional amount of ethylene into a second reactor; polymerisation of the additional amount of ethylene in the second reactor to obtain a second component which is a low-molecular ethylene polymer. Articles made from the disclosed high-density polyethylene composition can be made through compression moulding, injection moulding or high-pressure blow moulding. Closing devices such as bottle caps, made from said high-density polyethylene composition are characterised by high cracking resistance due to environmental action. ^ EFFECT: bottle caps can withstand pressure of carbonated beverages, make easier the closing and sealing of bottles, and are characterised by optimum human force applied to twist-off the cap. ^ 39 cl, 4 dwg, 4 tbl, 11 ex |
