Heat sealing material with two adhesive layers - one of polyvinyl acetate, the other of vinyl or acrylic-olefin copolymer

Abstract

Abstract Coating material, esp. for making heat-sealing labels, consists of a support sheet, and heat-sealing layers consisting of (a) a layer of polyvinyl acetate applied to one surface of the support, and (b) on top of this a layer of vinyl-olefin or acrylic-olefin copolymer. The second layer is esp. a copolymer of (i) ethylene, propylene, butadiene, butylene etc. with (ii) vinyl acetate, acrylic acid (opt. plus an acrylate ester), vinyl chloride etc.; specifically ethylene-vinyl acetate contng. 0-60% waxy material. Used for marking or decorating heat-formed containers e.g. yoghurt pots. The adhesives have an m.pt. compatible with temps. encountered both in forming the containers from e.g. polystyrene or PVC, and in the conditioning of the container contents so do not peel off at these temps. By varying the proportions of the two layers, combined m.pts. of 80-120 degrees C. are achieved.

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