Method of concurrently-biaxially drawing polyvinyl alcohol film

摘要

A concurrent-biaxially drawn polyvinyl alcohol film is prepared by fabricating a molten hydrate polyvinyl alcohol into a film; drying it under preventing an orientation thereof to form a substantially non-orientated substrate film having a water content of 3 to 20 wt. %; coating an aqueous dispersion of a macromolecular compound on at least one surface of the substrate film to form a coated film having an average water content of 5 to 30 wt. % with an increased water content of 2 to 10 wt. %; concurrent-biaxially drawing the coated film at an area elongation percent of 600 to 1300% to form a drawn film; drying the drawn film under releasing stress at a water content of less than 3 wt. % to form a dried film; and heat-treating continuously the dried film at higher than 160 DEG C. and lower than a decomposition temperature for a short time.