GB1001313A - Packaging material and method for its production - Google Patents

Abstract

Packaging material in the form of a flexible and pliable film or foil having good mechanical strength and good sealing tightness characteristics is produced by a method which includes the steps of moving a flexible supporting band over a predetermined path, successively applying to the band at different places in its path at least one coating of a plastic material in fluid condition to form a flexible component layer of good mechanical strength and applying at least one coating of another plastic material of the polyvinylidene chloride type in fluid condition to form a component layer of good sealing tightness characteristics, the surfaces of each coating being still tacky or adhesive when the following coating is applied thereon. The polyvinylidene chloride may be applied to a thickness less than that required to form a self-supporting film of the material. The band may be a temporary support, e.g. an endless non-adhesive band of metal, natural or synthetic rubber or cloth, metallized and/or silicone-treated rubber or cloth or silicone-treated metal, and the first coating applied thereon is non-adhesive with respect to the band and the packaging material formed thereon is finally separated from the band; or the band may be a permanent support to which the first coating adheres, e.g. a continuous band of paper or cardboard, cloth, metal foil or cellulose film. The film of good mechanical strength may be formed from at least one material selected from polyvinyl resins e.g. polyvinyl chloride, polyolefins e.g. polyethylene, polystyrene, polyamides and polyesters. The film of good sealing-tightness characteristics may be of polyvinylidene chloride, preferably modified with an acrylic resin. A first coating of polyamide may be applied to the support, a second coating of polyvinyl chloride applied over the first coating, a third coating of polyvinylidene chloride applied and a fourth coating of polyamide applied thereover. The layer being applied may be subjected to an orientation operation. The film or foil may be subjected to heating during its formation. The coatings may be applied as emulsions, granules, powder pastes or solutions with a doctor, or by means of cylinders, or air brush or by extrusion. The expression "polyvinylidene chloride type" is defined as meaning polyvinylidene chloride and copolymers of vinylidene chloride and vinyl chloride, which may be modified by one or more acrylic resins.