PROCEDE DE PREPARATION D'ARTICLES A DEUX OU PLUSIEURS COUCHES COMBINEES ET COEXTRUDEES

摘要

Multilayer articles are made by moulding sheets prepd. by co-extruding >=2 different thermoplastic polymers. One polymer is a strongly hydrolysed PVA contg. water and plasticisers, and is fed to an extruder connected with a coextrusion head. The polymer is heated under pressure to form a plastisol which is then subjected to rapid decompression with opt. venting prior to being introduced into the extrusion head and while its temp. is at least equal to and pref. higher than that of the extrusion head. At least another thermoplastic polymer melt is separately fed to the extrusion head and the temps. of the polymers are adjusted before they come into contact so that the temp. of the PVA at least that of the other polymer(s). The feed rate of the polymers is so adjusted that their linear exit speed are equal or differ by is not >10%. The composite sheet is impermeable to gases, vapours and odours is resistant to water and chemical agents. The sheet is partic. useful for prodn. of bottles and containers for beverages, e.g. by blow moulding, or for forming inner pockets for containers.