| 摘要 |
<p>PURPOSE:To obtain a film which is used as the magnetic tape, etc. and has a uniform thickness by a method wherein thermoplastic resin is extruded in the form of a film from a die slit, cooled, set and nipped on a rotary cooling drum and nip rolls controlled to a constant speed. CONSTITUTION:Thermoplastic resin such as polyethylene, polypropylene, etc. is heated, fused and extruded in the form of a film from a die slit, cooled and set on a rotary cooling drum controlled to a constant speed in which the instantaneous rotation flucutution ratio given by the no load formula is within the accuracy of + or -1%. A pair of nip rolls in which the circumferential speed is controlled to be constant is used so as to prevent thickness fluctuation of a film on account of variation of a taking-up tension so that the variation of tension by a film extending device may take no effect on the cooling drum. Accordingly, the film with uniform thickness is obtained by the effect of film thickness fluctuation control added to that of constant speed control of the cooling drum.</p> |
