Manufacture of tempered polypropylene film

Abstract

Abstract PURPOSE: To obtain the polypropylene film having a high tensile strength in both lengthwise and widthwise directions with better productivity without cutting film by biaxially stretching and then restretching longitudinally an unstretched sheet with a specific melt-crystallization temperature under a specific condition. CONSTITUTION: The unstretched sheet of polypropylene having a melt crystallization temperature of 100W125°C is biaxially stretched to obtain the biaxially stretched polypropylene film having a [widthwise refractive index]-[lengthwise refractive index] value of 0.010W0.030. Then, the film is restretched to 1.5W3.0 times in lengthwise direction while controlling its widthwise shrinking ratio to less than 20% to obtain the objective film having the lengthwise tensile strength of 30kg/mm 2 or more and the widthwise tensile strength of 20kg/mm 2 or more. COPYRIGHT: (C)1981,JPO&Japio

Inventors

• 👤 Toshiya Yoshii
• 👤 Kenji Tsunashima
• 👤 Takashi Sumiya

Bibliographic Details