Highly elastic one shot thermoplastic polyurethane cpds. - contg. mainly aliphatic linear hexa:carbon units and used as food packaging films

摘要

Thermoplastic polyurethane moulding materials are made in teh 'one shot process' by reacting (a) exclusively linear aliphatic polyester diols with a molw. et. of >500, (b) diisocyanates and (c) bifunctional chain lengtheners. The starting materials contain 6C units and the wt. ratio polyesterdiols to diisocyanates is 1:1.5 to 1:3.0. The K-value of the system (NCO/OH x 100)= 97-101. The prods. are esp. suitable for the prodn. of extruded tubular films which are physiologically harmless and esp. useful for food packaging applications. Partic. due to the high elasticity of the films, they are useful for packing of goods which are to be boiled, since the casings are able to accommodate the expansion of the food during boiling and then to shrink agains on cooling as the food contracts, so that no wrinkles are formed in the casing under these circumstances.