Polyethylene compositions and closures for bottles

摘要

A dual reactor solution process gives high density polyethylene compositions containing a first ethylene copolymer and a second ethylene copolymer and which have good processability, toughness, and environmental stress crack resistance combined with good organoleptic properties. The polyethylene compositions are suitable for compression molding or injection molding applications and are particularly useful in the manufacture of caps and closures for bottles.

主权项

1. A closure for bottles, said closure comprising a bimodal polyethylene composition comprising:
(1) 10 to 70 wt % of a first ethylene copolymer having a melt index I2, of less than 0.4 g/10 min; a molecular weight distribution Mw/Mn, of less than 3.0; and a density of from 0.920 to 0.955 g/cm3; and (2) 90 to 30 wt % of a second ethylene copolymer having a melt index I2, of from 100 to 10,000 g/10 min; a molecular weight distribution Mw/Mn, of less than 3.0; and a density higher than the density of said first ethylene copolymer, but less than 0.967 g/cm3;
wherein the density of said second ethylene copolymer is less than 0.037 g/cm3 higher than the density of said first ethylene copolymer; the ratio (SCB1/SCB2) of the number of short chain branches per thousand carbon atoms in said first ethylene copolymer (SCB1) to the number of short chain branches per thousand carbon atoms in said second ethylene copolymer (SCB2) is greater than 0.5; and wherein said bimodal polyethylene composition has a molecular weight distribution Mw/Mn, of from 3 to 11; a density of at least 0.949 g/cm3; a melt index I2, of from 0.4 to 5.0 g/10 min; an MZ of less than 400,000; a stress exponent of less than 1.50; and an ESCR Condition B (10% IGEPAL) of at least 20 hrs.