| 摘要 |
A hot melt-extrudable composition comprising a major proportion of polyethylene of density within a range 0.91 to 0.925 and a minor proportion of a polyethylene of density at least 0.94 and containing not more than small traces of oxygen and carbonyl groups is extruded to form films of high impermeability to water vapour. The high density polyethylene preferably contains in the molecule branch chains with six or more carbon atoms and main chain segments with more than seven carbon atoms between the branch chains, and one tenth of the molecules have terminal unsaturation. The composition may be prepared by compounding the heated components in a mill or mixer and the sheet obtained by blown tube or elongated slot method. It may be coated on sheets of regenerated cellulose, cellulose acetate or ethers, paper, fabric and metals. Pigments, fillers, dyes and plasticizers may also be included in the composition.
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