Patent ID: 7985315

Claim:
A process for producing an unstretched film comprising heating and melting thermoplastic resins and ejecting and extruding them through an extrusion T-die onto a casting roll, wherein a thermoplastic resin A and another thermoplastic resin B to form an unstretched film are separately heated and melted, the other thermoplastic resin B is led to both edges of an extrusion T-die, wherein the melt viscosity of thermoplastic resin A is lower than the melt viscosity of the other thermoplastic resin B, the difference in the melt viscosity between the thermoplastic resin A and the other thermoplastic resin B is at most 3000 poises at a shear rate of from 20 to 500 sec−1, the two resins are ejected and extruded onto the casting roll in such a manner that the other thermoplastic resin B melt can coexist on both sides of the heated and melted thermoplastic resin A to thereby form an unstretched film where the other thermoplastic resin B coexists on both sides of thermoplastic resin A, wherein, in a feed block, the cross section of the lower part of a resin melt supply duct to which thermoplastic resin A is fed is rectangular, and the cross section of holes to be formed on both sides of the lower part of the resin melt supply duct to which the thermoplastic resin B is fed is rectangular, the cross-sectional shape of the unstretched film is so formed is formed by thermoplastic resin A and thermoplastic resin B, wherein thermoplastic resin B coexists on both sides of thermoplastic resin A and the width of thermoplastic resin B is substantially uniform in the cross direction of the unstretched film, and thereafter the other thermoplastic resin part is cut off.