Improvements in the manufacture of films, foils, coatings and the like

摘要

Fancy films, foils, and the like are formed on a surface by evaporation of a volatile solvent from a solution of a film-forming base in said solvent, and during evaporation, numerous small bubbles are caused to form in said solution with the aid of a powder adapted to provide nuclei for said bubbles and previously applied to said surface. The film-forming base may comprise cellulose esters or ethers, or natural or artificial resins. The powder and the film-forming solution may be applied to a surface travelling along a closed path through a heated atmosphere. In a modification, the powder is applied to, and the solution is extruded on to, an at least partially dried layer of said solution supported on an endless band and applied during a previous revolution of the band. Suitable powders are cellulose derivatives, natural and synthetic resins, organic substances of high melting point, dyestuffs, pigments, and metal powders, and a number of these are specified. It is preferable that the powder should be compatible with the film-forming base. The powder 9 contained in the hopper 8 is measured out by means of the perforated rotating disc 13, and allowed to fall into the duct 30 through which flows a stream of air from the fan 29. The mouth of the duct opens on to the endless band 32 to which is subsequently applied the film-forming solution. The fan 29 and the measuring disc 13 are connected by suitable gearing 24, 26 and 27. In examples, ground cellulose acetate, which may be plasticized with diethyl phthalate, is distributed on to a surface to which is subsequently applied a solution of cellulose acetate in acetone. The temperature at which drying takes place may be from 30 to 60 DEG C., according to the bubble size desired. Specifications 396,424 and 396,723 are referred to.