GB1384791A - Laminates - Google Patents

Abstract

1384791 Laminated plastics W R GRACE & CO 27 April 1973 [28 April 1972] 19905/72 Heading B5N A laminate for use as a flexible packaging material comprises a barrier layer of substantially anhydrous polyvinyl alcohol which has at least 80% of its repeating units of formula -CH 2 CH(OH)- and which has a viscosity of 2-60 centipoises at 20‹ C. as a 4% by weight aqueous solution, and a protective layer having low moisture permeability on each side of the barrier layer, the latter being bonded to at least one protective layer by mean of a polyurethane primer. The protective layers may be uni- or bi-axially oriented and may comprise a copolymer of vinylidene chloride with acrylonitrile, an alkyl acrylate or methacrylate, acrylic acid, methacrylic acid or itaconic acid, polyethylene, polypropylene, EVA copolymer, polyethylene terephthalate, PVC, polyhexamethylene adipamide, polycaproamide, or regenerated cellulose having a nitrocellulose coating. One of the outer layers of the laminate is usually of heat-sealable material such as polyethylene or a blend thereof with polyisobutylene, polypropylene, a copolymer of ethylene with propylene, vinyl acetate or acrylic, methacrylic or ethylacrylic acids or their alkyl ester, or an ionomeric resin. The laminate may be prepared by forming a coating of an aqueous solution of polyvinyl alcohol (usually containing a surfactant), on a substrate which may have been corona treated and primer coated, drying the coating and applying the other protective layer by extrusion coating or by means of adhesive optionally after primer coating.