Antistatic Coating of Thermoplastic Films

1,173,759. Coated films. IMPERIAL CHEMICAL INDUSTRIES Ltd. 17 Nov., 1967 [9 Dec., 1966], No. 55304/66. Heading B2E. [Also in Division B5] A film of an organic thermoplastic material having an antistatic coating is produced by treating the uncoated film to a chemical or physical treatment resulting in oxidation of the film surface to improve the bonding properties of its surface, coating with a solution comprising a water soluble cellulose derivative, a water soluble thermosetting resin and an acid catalyst, evaporating off the solvent and heating the coated film so that under the influence of the catalyst it is cured; the coating becoming adhesively bonded to the thermoplastic film. The film may be of an orientable thermoplastic material which is stretched to orient it before or after application of the coating. Examples of thermoplastic polymeric materials, water soluble cellulose derivatives and thermosetting resins are given. The thermoplastic film may be treated with chromic acid in sulphuric acid or with hot nitric acid; exposure of the surface to ozone e.g. while at a temperature above 100‹ Centigrade; exposure of the surface to high voltage electric stress accompanied by corona discharge; exposure of the surface to ionizing radiation such as ultra violet, x, alpha, beta, or gamma radiation particularly of temperatures above 100‹ Centigrade; or exposure of the surface to a flame. The coating may contain antistatic agents, release agents, pigments, fillers, dyes, and ultraviolet light stabilizers. The uncoated surface of the film may be coated with adhesive to produce an adhesive tape. The coated film may be overcoated with a heat sealable coating. The coating may have a surface resistivity of less than 109 oms: per sq. and a coat adhesion to the base film of at least 250 grams per inch.