Color dyeing system for plastic films

Abstract

A process for the continuous dyeing of plastic films, such as polyethylene terephthalate, is characterized by passing the film through a dye bath comprised of dye stuffs dissolved, suspended or dispersed in a liquid carrier comprised at least in part of a polymer, preferably a polyol, having at least one free hydroxyl group and a molecular weight within the range of from about 200 to about 600. The hydrogen bonding provided by the hydroxyl group, together with the high molecular weight and high boiling point of the polyol, mitigate against migration of the dye stuff out of the film, i.e., fading of the film, and impart long lasting color fastness to the film. Rapid diffusion of the dye bath into the film is enhanced by thermal and ultrasonic energization of the bath.

Dependencies are inferred from the claim text.