GB862482A - Improvements in or relating to the treatment of polyethylene terephthalate films - Google Patents

Abstract

The surface of a polyethylene terephthalate film is contacted with an aqueous dispersion of polyvinyl chloride particles having a mean diameter of from 0.1-5 microns, the dispersion also containing a wetting agent, and the film is then dried. Preferably, at least 90% by weight of the dispersed polyvinyl chloride particles have sizes within the 0.1-5 microns range, the particles being preferably of 0.2-1 micron mean diameter. Treatment may be effected at any stage in production of the film after solidification, before or after orientation or heatsetting, and one or both surfaces may be treated. When the film has previously been drawn to its finished size, the dispersion preferably contains 0.01%-0.05% of polyvinyl chloride, by weight of the total composition. When the dispersion is applied before the film has been drawn to its finished size, the dispersion preferably contains 0.01 X X%-0.05 X X% of polyvinyl chloride on the same basis, where X is the ratio of the surface area of the finished film to its area at the time of treatment. In either case, the dispersion preferably contains from 0.1% to 2.0% of wetting agent by weight of the total composition, and the dispersion is preferably applied to the film by gravure printing rolls, although other forms of roll-coating, dipping, spraying, or brushing may be used. Specified wetting agents include the condensation product of 1 mol. of cetyl alcohol with 17 mols. of ethylene oxide, and "Mersolat 10," which is the sodium salt of a chlorosulphonated paraffin. The treatment improves the slip of the film without appreciable loss of transparency. Specifications 699,016, 707,549 and 723,490 are referred to.