HEAT-ACTIVATABLE POLYURETHANE COATINGS AND THEIR USE AS ADHESIVES

摘要

A coated sheet has a heat-activatable adhesive coating of thermoplastic polyurethane having a melting point of 40 to 100 ~C. The coating may be crystalline and have an average crystal size below 10 .mu.m. The coating, wh en molten, may remain tacky for a period of from 2 to 50 seconds. Preferred processes comprise heat activating the coating and subsequently cold or cool sealing, for instance to form a packet around a heat-sensitive material.