Process for coating film

A travelling web or film 9 is coated by being brought into contact with a guide surface, e.g. the surface of a stationary roll 10, while coating liquid is fed into the pocket 12 formed between the film and the guide surface. In Fig. 2, the liquid is fed through the stationary roll 10 to a longitudinal slot 11 running across the width of the film. A similar roll 13 to coat the other side of the film and doctor rollers 18, 19 may also be provided. Splash pans 20, 21 are connected to a main bath 17, surplus liquid being caught in these pans and bath. Rolls 10 and 13 may be arranged in a variety of relative positions and a rotatable guide roller may be provided to increase the wrap of the film about a roll 10 or 13, or to ensure that the film enters the doctor rolls from the required direction. In Fig. 7 roll 13 is partially immersed in the bath but the pocket 15 remains above the surface thereof. The other side of the film is prewetted by roll 10 and coated in the bath. Where gravity tends to empty the pocket the film is sprayed with liquid immediately before contacting the guide. A typical film to be treated is one of regenerated cellulose. Coating liquids may be lacquer type moisture-proofing compositions such as nitrocellulose, wax or resin dissolved in a volatile organic solvent such as an ethyl acetate-toluene mixture. Specification 541,555 is referred to.