Two-stage uniaxial orientation of polyethylene terephthalate films
Abstract
Abstract A METHOD OF ORIENTING A WEB OF THERMOPLASTIC POLYMERIC FILM (I.E., POLYETHYLENE TEREPHTHALATE FILM) BY STRETCHING IT IN TWO STAGES IN MAKING FILM HAVING HIGH BIREFRINGENCE. A WEB OF SUBSTANTIALLY AMORPHOUS FILM IS HEATED TO A FIRST STRETCHING TEMPERATURE BY FIRST HEATING MEANS AND STRETCHED IN A FIRST STRETCHING SPAN BETWEEN FIRST AND SECOND SETS OF NIP ROLLS OF A FIRST STRETCHING MEANS. THE FIRST STRETCHING TEMPERATURE TO WHICH THE WEB IS HEATED IF FROM 72* TO 86*C. WHEREBY, UPON FIRST STRETCHING, COLD STRETCHING DOES NOT OCCUR. THEN, THIS STRETCHED FILM IS HEATED, FROM 91* TO 120*C., BY SECOND HEATING MEANS TO A SECOND STRETCHING TEMPERATURE AND STRETCHED AGAIN IN A SECOND STRETCHING SPAN, WHOSE LENGTH IS LESS THAN THE LENGTH OF THE FIRST STRETCHING SPAN, BETWEEN SECOND AND THIRD SETS OF NIP ROLLS OF A SECOND STRETCHING MEANS WHERE- BY TO A MAKE A FILM HAVING IMPROVED BIREFRINGENCE PROPERTIES.
Inventors
- 👤 D Blecha
Bibliographic Details
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