Process for continuously producing an aromatic polyimide film

Abstract

An aromatic polyimide film having excellent mechanical, thermal and electrical properties, is continuously produced by the steps of: preparing a dope solution having a rotation viscosity of 500-10.sup.5 poises at 100.degree. C. by uniformly dissolving aromatic polyimide in a solvent consisting of at least one phenol compound; extruding the dope solution through a T-die at 50.degree. C. or more, but at least 30.degree. C. below the boiling point of the solvent, under conditions which cause the apparent viscosity and shear stress of the dope solution to be 500-5.times.10.sup.4 poises and 10.sup.4 -10.sup.6 dyne.multidot.cm.sup.-2, respectively, to form a filmy stream of the dope solution; placing the filmy stream of the dope solution on a surface of a supporting means while heating the surface at a temperature of 50.degree. C. or more and continuously moving it along its endless path, maintaining the placed filmy stream of the dope solution on the moving, heating surface of the supporting means until the filmy stream forms a film having a uniform thickness and then the film is solidifed by evaporating the solvent therefrom to an extent that the concentration of the solvent is 50% by weight or less; continuously peeling off the solidified film from the moving heating surface of the supporting means; and drying the peeled film at a temperature of 200.degree. C. to 600.degree. C. to provide an aromatic polyimide film free from the solvent.