| 摘要 |
Compositions suitable for making films resistant to passage of water vapour comprise a copolymer of vinyl chloride and 40-80 per cent by weight of vinylidene chloride in intimate mixture with polyvinyl chloride or a copolymer of at least 70 per cent of vinyl chloride and up to 30 per cent of other olefinic compounds or mixtures thereof. Preferably, the composition comprises 10-90 per cent by weight of the vinyl chloride-vinylidene chloride copolymer. The other olefinic compounds specified include vinyl acetate, vinylidene chloride, alkyl maleates, chloromaleates and fumarates, alkyl acrylates, a -alkyl acrylates and a -chloroacrylates. The compositions may be cast from solutions in ethylene dichloride, benzene, toluene or cyclohexanone. Other materials such as plasticisers, curing agents and pigments may also be incorporated; the addition of carnauba wax or lecithin facilitates removal of the film from the casting surface. |
