Patent GB-390899-A (GB)
Title: Improvements in or relating to the production of films, foils, sheets or the like
IPC: B29C41/24
Filed: 1932-01-07
Abstract: The surface upon which film-forming solutions are cast, extruded, or otherwise deposited consists of hardened gelatine, glue, casein, or other proteid substance.  The film-forming solution may contain cellulose, or cellulose derivatives such as cellulose nitrate or cellulose acetate.  The casting surface may take the form of an adherent layer upon a wheel, belt, or other support.  It may consist solely of a layer of hardened proteid substance of the desired thickness or it may consist of a number of lamin , namely, a cellulose derivative priming coat, an intermediate layer, and a top layer of hardened proteid.  In examples, the priming coat is obtained from a solution containing nitrocellulose, castor oil, gum elemi, ester gum, dibutyl phthalate mixed alkylated toluene sulphonamides, alcohol, butyl and ethyl acetate, benzene, toluene and barium sulphate, or from a solution of low viscosity pyroxiline, blown rape seed oil, soft toluene-sulphonamide-aldehyde resin, phenol-aldehyde resin, tricresyl phosphate, mixed alkylated sulphonamides, ethyl ether of ethylene glycol, alcohol, toluene, benzene, butyl and ethyl acetate, magnesium carbonate.  Other ingredients which may be p incorporated in the nitrocellulose solution are dammar, shellac, butanol, denatured alcohol.  After the priming coating has thoroughly set the solution forming the intermediate layer is applied.  This solution may comprise gelatine, water, an organic acid such as acetic, salicylic, lactic, or malic acid and pure methyl alcohol. The top layer forming the actual casting surface is made from a solution of gelatine, water, glycerine and a hardening agent such as potassium dichromate, chrome alum, ammonium dichromate, formaldehyde, or tannic acid.  If desired the hardening agent may be omitted from the gelatine solution which is applied in one or more coats to the wheel or belt until the desired thickness is obtained and the final coating when set is passed through a solution of ammonium dichromate. The surface is hardened by exposure to actinic rays from the sun or from a lamp or other source.ALSO:The surface, upon which solutions of film-forming substances such as cellulose esters are deposited, consists of hardened gelatine, glue, casein, or other proteid.  The casting surface may be in the form of an adherent layer upon a wheel, belt, or other support.  It may consist solely of a layer of hardened proteid substance of the desired thickness or may consist of a cellulose derivative priming coat, an unhardened proteid intermediate layer, and a top layer of hardened proteid.  In examples, the priming coat consists of nitrocellulose, preferably of low viscosity characteristics, with gums, oils, and plasticizers, upon which coat when thoroughly set there is sprayed a solution of gelatine in water containing methyl alcohol and an organic acid such as acetic, salicylic, lactic, or malic acid.  The top layer forming the actual casting surface is made from a solution of gelatine, water, glycerine, and a hardening agent such as potassium or ammonium dichromate, chrome alum, formaldehyde, or tannic acid. If desired, the hardening agent may be omitted from the gelatine solution, which is applied in one or more coats to the wheel or belt until the desired thickness is obtained, and the final coating when set is passed through ammonium dichromate solution. The surface is hardened by exposure to actinic rays from the sun or from a lamp or other source.