Importance

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Abstract

Cold-seal adhesives are disclosed that contain no natural rubber and are capable of forming dry coatings on flexible films which adhere to one another with commercially acceptable packaging strength at room temperature by pressure contact, but also allow such layered substrata to be reeled into rolls and stored for extended periods of time without blocking. The flexible films are usable in forming packages, particularly for comestibles and pharmaceuticals, without need for heat sealing. Such cold-seal adhesives are aqueous dispersions containing 30 to 55 percent of a polyurethane ionomer reaction product, having a T.sub.g of between about -50 to 10.degree. C., of a mixture of (a) a blend of between 0 and 40 percent polyester polyol and between 60 and 100 percent polyether polyol, (b) aliphatic diisocyanate and (c) dimethylol propionic acid and preferably containing 0.05 to 4 percent of grafted amorphous silica.

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First Claim