Improvements in the manufacture of films, foils, ribbons and like products

摘要

A shaped film-forming composition is drawn into contact with and supported on a surface which is travelling in a gaseous medium, and a pocket of liquid which is compatible with the base of the products, is maintained in the angle between the shaped composition and the supporting surface so as to prevent air from being drawn into said angle. Suitable liquids for this purpose are solvents and plasticizers for the film-forming base, particularly a solution of a liquid plasticizer in a volatile solvent identical with that of the film-forming solution. There may be added to the liquids, colouring agents or effect materials which it is desired to introduce into the film. In an example, a solution of cellulose acetate in acetone is supplied from a casting box 10 on to a metallic band 18 passing around a drum 19 driven in the direction of the arrow. A pad of soft leather 20 resting on the band 18 is supplied with a solution of diethyl phthalate in acetone. Film formation may be carried out at speeds of 50--100 feet per minute without bubble formation. Films may be formed in a single operation or may be built up by the successive deposition of two or more layers, each layer except the last providing a supporting surface for the next layer, and a pocket of air-excluding liquid being maintained in the angle between it and the shaped composition forming the next layer. The films may have a basis of cellulose derivatives, polymerized vinyl acetate or polymerized unsaturated hydrocarbons.