Polyurethane adhesives for laminated packaging foils - giving improved resistance to delamination in use

摘要

One- or two-component adhesives, pref. based on reaction prods. of OH-contg. with excess isocyanate and opt. a hardener, contg. as adhesive up to 60, pref. 10-20 wt.% of =1 vinyl acetate/vinyl chloride copolymer. The copolymer additive is modified with =1 alpha, beta-unsatd. carboxylic acid or its derivs., in amt. of 0.5-10 wt.%. Pref. acids are maleic or crotonic acids. Used in mfr. of laminated metal foils coated with a heat-sealing layer, for use in flexible containers, esp. for fruit and vegetable juices. Delamination during storage, resulting in leakage or reaction of the contents with the Al foil is prevented. Use of a fourth layer, e.g. of orientated polyester, between the Al and the sealing layer is avoided.