Patent ID: 7871548

Claim:
A method for producing polymer oriented crystals, the method comprising: preparing an oriented melt by subjecting a polymer melt to elongation at a strain rate equal to or greater than a critical elongation strain rate so as to put the polymer melt in an oriented melt state; and rapidly cooling the polymer oriented melt, which is obtained in the step of preparing it, to crystallize it while keeping the oriented melt state, the critical elongation strain rate being: (I) a critical elongation strain rate ε* determined by: sandwiching the polymer melt with transparent boards, the polymer melt having a disc shape with a radius of x 0 and a thickness of Δz 0 ; supercooling the polymer melt; pressing the polymer melt at a constant value v in a thickness direction by using the transparent boards; measuring a critical point radius x* at which oriented crystals are formed from the polymer melt; and calculating the critical elongation strain rate ε* from: ε*=αx* 3 , where α=v/(2 x 0 3 Δz 0 ); or (II) a critical elongation strain rate ε* determined by: sandwiching the polymer melt with transparent boards, the polymer melt having a rectangular shape with a center distance of x′ 0 , a thickness of Δz 0 , and a constant width; supercooling the polymer melt; pressing the polymer melt at a constant rate v in a thickness direction by using the transparent boards; measuring a critical point center distance x′* at which oriented crystal are formed from the polymer melt; and calculating the critical elongation strain rate ε* from: ε*=αx′* 2 , where α=v/(2 x′ 0 2 Δz 0 ).