Monofilament and manufacturing method therefor

Abstract

To provide a monofilament of polyamide 4 (PA4) having high tensile characteristics even when the monofilament is knotted. A monofilament of PA4, in a scattering vector in a range of 0.02 nm −1 or greater and 0.04 nm −1 or less measured by small-angle X-ray scattering, the monofilament having an average value of a ratio I2/I1 of a normalized scattering intensity I2 in an equatorial direction to a normalized scattering intensity I1 in a meridian direction of 5 or less. A birefringence of the monofilament is 50×10 −3 or greater.

1 . A monofilament of polyamide 4,
 in a scattering vector in a range of 0.02 nm −1  or greater and 0.04 nm −1  or less measured by small-angle X-ray scattering, the monofilament having an average value of a ratio I2/I1 of a normalized scattering intensity I2 in an equatorial direction to a normalized scattering intensity I1 in a meridian direction of 5 or less, and   a birefringence of the monofilament being 50×10 −3  or greater.   
     
     
         2 . The monofilament according to  claim 1 , wherein a tensile strength of the monofilament when knotted is 550 MPa or greater, and an elongation at break of the monofilament when knotted is 10% or greater. 
     
     
         3 . The monofilament according to  claim 1 , wherein a filament diameter is 400 μm or less. 
     
     
         4 . A method for manufacturing a monofilament of polyamide 4 by drawing an un-drawn monofilament of polyamide 4,
 the method comprising:   a first drawing of drawing an un-drawn monofilament of polyamide 4 by dry heat drawing at a drawing temperature of 40° C. or higher and a drawing ratio of 2.5 times or greater and 3.5 times or less; and   a second drawing of drawing a primary drawn monofilament of the polyamide 4 produced in the first drawing by wet heat drawing at a drawing temperature of 80° C. or higher and 120° ° C. or lower and a specific drawing ratio;   the specific drawing ratio being a drawing ratio that makes a total drawing ratio 3.5 times or greater, the total drawing ratio being a drawing ratio of the un-drawn monofilament caused by both the first and the second drawing, and   when the total drawing ratio is 3.5 times, the drawing ratio in the first drawing being less than 3.5 times.   
     
     
         5 . The method for manufacturing a monofilament according to  claim 4 , wherein a density of the un-drawn monofilament is 1.225 g/cm 3  or less.