Patent GB-737032-A (GB)
Title: Non-blocking film
IPC: B29C41/24
Filed: 1953-04-17
Abstract: A film-casting surface is provided with 100 to 2000 microscopic pits per square centimetre of its surface having a radius of 1-10 microns, whereby films cast thereon are provided with microscopic bumps which render them non-blocking.  The surface is prepared by coating a base, e.g. a cylinder or a flexible belt, with a dispersion of a volatile immiscible liquid in a solution of a film casting surface material, e.g. methyl or ethyl cellulose, polyvinyl alcohol or gelatine, in a volatile solvent and then evaporating the solvent and the liquid, the immiscible liquid being a non-solvent for the film-casting surface material and having a higher boiling-point than the solvent; sequential evaporation first of the solvent and then of the liquid ensures the provision of the pits.  Specified immiscible liquids are ethyl benzoate, toluene, xylene and petroleum hydrocarbon fractions boiling at 220-350 DEG  F.  A suitable solvent is a water-low boiling alcohol mixture.  In examples, the coating composition comprises a dispersion of xylene or ethyl benzoate in a solution of polyvinyl alcohol in water-ethyl alcohol, other additions to the dispersion being polyglycerol and dioctyl sodium sulphosuccinate.  The surface may be employed for casting films of rubber hydrochloride, chlorinated rubber, polyethylene, polyvinyl chloride and cellulose derivatives.ALSO:A film-casting surface is provided with 100 to 2000 microscopic pits per square centimeter of its surface having a radius of 1-10 microns and is prepared by coating a base, e.g. a cylinder, with a dispersion of a volatile immiscible liquid in a solution of a film-casting surface material, e.g. methyl or ethyl cellulose, polyvinyl alcohol or gelatine, in a volatile solvent and then evaporating the solvent and the liquid, the immiscible liquid being a non-solvent for the film-casting surface material and having a higher boiling-point than the solvent; sequential evaporation first of the solvent and then of the liquid ensures the provision of the pits. Specified immiscible liquids are ethyl benzoate, toluene, xylene and petroleum hydrocarbon fractions boiling at 220-350 DEG  F.  A suitable solvent is a water-low boiling alcohol mixture.  In examples, the coating composition comprises a dispersion of xylene or ethyl benzoate in a solution of polyvinyl alcohol in water-ethyl alcohol, other additions to the dispersion being polyglycerol and dioctyl sodium sulphosuccinate.ALSO:A surface for casting films of rubber hydrochloride or chlorinated rubber is provided with 100 to 2000 microscopic pits per square centimeter of its surface having a radius of 1-10 microns, whereby films cast thereon are provided with microscopic bumps which render them non-blocking.  The surface is prepared by coating a base, e.g. a cylinder or a flexible belt, with a dispersion of a volatile immiscible liquid in a solution of a film casting surface material, e.g. methyl or ethyl cellulose, polyvinyl alcohol or gelatine, in a volatile solvent and then evaporating the solvent and the liquid, the immiscible liquid being a non-solvent for the film-casting surface material and having a higher boiling point than the solvent; sequential evaporation first of the solvent and then of the liquid ensures the provision of the pits.  Specified immiscible liquids are ethyl benzoate, toluene, xylene and petroleum hydrocarbon fractions boiling at 220 DEG -350 DEG F.  A suitable solvent is a water-low boiling alcohol mixture.  In examples, the coating composition comprises a dispersion of xylene or ethyl benzoate in a solution of polyvinyl alcohol in water-ethyl alcohol, other additions to the dispersion being polyglycerol and dioctyl sodium sulphosuccinate.