GB1007183A - Improvements in and relating to coated films - Google Patents

Abstract

1,007,183. Coated polystyrene film. UNION CARBIDE CORPORATION. Aug. 23, 1962 [Aug. 25, 1961], No. 32433/62. Heading B2E. A transparent self-supporting polystyrene film resistant to fogging upon exposure to a humid environment has a coating thereon of polyethylene oxide having a molecular weight above 1500, e.g. from 1500 to 5,000,000, hydroxyethyl cellulose having a viscosity measured at 25 ‹C. as a 2% by weight aqueous solution of from 0.9 to 15,000 centipoise, or a mixture thereof. The polyethylene oxide and the hydroxyethyl cellulose may be present in the coating in approximately equal amounts by weight. The coating may be from 0.0003 to 0.0004 mils thick. The coated film may be produced by applying to the surface of a hydrophilic polystyrene film 10 a coating of a less than 2% by weight solution in a polar hydroxylated solvent, e.g. water or lower alkanols such as ethanol and isopropanol, of the polyethylene oxide, hydroxyethyl cellulose, or a mixture thereof, and evaporating off the solvent, e.g. by blower 30 and infra-red lamps 32. The polystyrene film is rendered hydrophilic by subjecting the film to flame treatment and chemical reagents, or a corona discharge by passing the film over an insulated roller while discharging a high frequency current through the film. The polyethylene oxide may be a copolymer of ethylene oxide with minor amounts of other polymerizable oxides, e.g. propylene oxide, epoxybutane, and styrene oxide. The coating may be applied by brushing, dipping, spraying and roller coating using, for example, two or preferably three rolls 16, 18, 20 to transfer the solution via wick 24 from tank 22 to the film surface.