GB396424A - Improvements in the production of films and foils - Google Patents

Abstract

Apparatus for the manufacture of foils and films by dry or wet methods comprises a drum provided with a tough corrosion-resistant and substantially - permanent surface of stainless steel or cold-worked nickel on which the film or foil is formed. The surface may be formed by shrinking an endless tyre of stainless steel or cold-worked nickel on to a drum or spider of other material. A length of nickel band may be hammer welded into endless form, the joint being rolled and ground to the thickness of the rest of the band, and the band is then cold-worked to impart the necessary toughness and to make the joint uniform in its properties with the rest of the band. The band after slight stretching is shrunk on a spider and a final polishing is given to ensure concentricity and smoothness. Very glossy foils are produced by deposition of solutions upon such surfaces, and the deposition of gelatine or like coatings to receive the solutions may be dispensed with. Although the stainless steel or cold-worked nickel surface has high resistance to corrosive influences, it may be protected by a coating of wax. For the production of cellulose acetate foils, the drum may be enclosed in a casing through which evaporative medium is caused to flow, preferably in the opposite direction to that of the film. The casing and the evaporative medium may be heated. The solution may be deposited from a hopper which s supplied by gravity, or by pumps or other pressure devices. Alternatively, the solution may be transferred to the drum surface by a resilient roller. Specification 396,398 is referred to.