Void-containing polyester shrink film with improved density retention

摘要

Disclosed are void-containing polyester shrink films which show excellent density retention upon exposures to high temperatures. The films have high shrinkage and retain their low density after processing under conditions of temperature and moisture used in typical recycling processes. The films are useful for sleeve label and other shrink film applications, and their lower density allows them to be readily separated from soft drink bottles, food containers and the like during recycling operations. Also disclosed is a process for void-containing polyester shrink films having high shrinkage and low density after exposure to elevated temperatures.

主权项

1. A process for making a void-containing shrink film, the process comprising steps of:
(i) mixing a copolyester and 20 to 30 weight percent of a voiding agent based on a total weight of the copolyester and voiding agent at a temperature at or above the glass transition temperature of the copolyester so as to form a uniform dispersion of the voiding agent within the copolyester; (ii) forming a film from the dispersion; (iii) orienting the film in one or more directions at a temperature above the glass transition temperature of the copolyester; and (iv) annealing the oriented film at a temperature above the orienting temperature and from about 85° C. to about 110° C., wherein after 5 seconds in a 95° C. water bath the annealed film has a shrinkage of at least 40%, and wherein after 15 minutes in a 85° C. water bath the annealed film has a density of less than 1.05 g/cc so as to float in a recycling process wash bath having a density of about 1.03-1.05 g/cc.