Ethylene-vinylacetate copolymer film with at least one rough surface and method for its production.

摘要

The ratio of the mean degree of roughness of the faces of rough appearance, expressed in microns, to the percentage by weight of units derived from vinyl acetate in the copolymer constituting the film is higher than 0.019. The film is extruded in the form of an extruded sleeve which is cooled in the die by a circulation of a coolant fluid whose temperature T satisfies the relationship: in which: Tc is the temperature at which the natural logarithm of the ratio of the elongation at break to the initial length of a specimen of the copolymer is equal to 87 % of its value at 180 DEG C Tm is the mean temperature of the copolymer as it leaves the die a is equal to 0.24 G is given by the relationship in which: rho is the density of the copolymer Cp is the specific heat of the copolymer V is the mean flow velocity of the copolymer through the extrusion die H is the height of the gap between the core and the extrusion dye lambda is the thermal conductivity of the copolymer L is the length of the refrigeration zone n is equal to 0.1688 A is equal to -0.0148 Lf is the distance between the end of the refrigeration zone and the end of the die B is equal to 0.2175. The film is particularly suitable for the production of packaging bags, especially for medical products.