JPS6455214A - Manufacture of cellulose triacetate film - Google Patents

Abstract

PURPOSE:To enhance the productivity and at the same time obtain a film having excellent surface properties by a method wherein the time to start the drying of liquid after casting, the angle between the direction of drying air and the surface of a support, the static pressure of the drying air and the gap between the outlet of the drying air and the surface of the support are specified. CONSTITUTION:In case that solution containing cellulose triacetate is cast on a support and, after that, first drying is done by feeding drying air on the surface of the solution after casting, a film is formed under the conditions that the time to start the drying is set to be 15 seconds or less after the start of casting, the direction of the drying air is directed obliquely forward to the running direction of the support and at the same time the angle between the direction of the drying air and the surface of the support is set to be 45-80 degrees, the static pressure of the drying air is set to be 5mmAq or more and the gap between the outlet of the drying air and the surface of the support is set to be 5-50mm. When the drying is done under the conditions mentioned above, favorable and fixed surface properties are obtained after the drying at early stage on a film and, as a result, an excellent film is obtained at all times without being effected by the drying conditions at late stage. Further, since the drying is started quickly after the casting, and no condition thereafter is called in question, the drying speed in the late stage drying can be heightened. Furthermore, troubles such as uneven sinking by blowing and ununiformity in film thickness, which tend to occur when the direction of the drying air flow is parallel or normal to the surface, are solved.