Composite closure for plastic containers - comprises metal foil and adhesive layer of e.g. polyisobutylene, withstanding high temp. conditioning and being easily peelable

摘要

A composite material used as closure for a container comprises a metal foil and an adhesive layer. The adhesive compsn. comprises (A) a copolymer of an aliphatic monoolefin and an unsatd. monoethylenic carboxylic acid, having good adhesion to the foil and the container and (B) a cpd. which can reduce the adhesion of (A) to the foil and/or the container, comprising polyisobutylene, polystyrene, paraffin, wax, or an EP copolymer. (A) is pref. an ethylene or propylene polymer grafted with acrylic acid, a high density polyethylene grafted with less than 5% acrylic acid being prefd. The adhesive layer is less than 20 microns thick and contains 10-90 wt.% (A) and 90-10% (B). The metal foil is Al and is 30-80 microns thick. The material is used for closing e.g. plastic bottles or tubs by thermowelding. The containers contg. e.g. yoghurts may be conditioned at high temps. without affecting the adhesion of the composite closure to the container. The closure can be easily peeled off to open the container.