Method for producing multifilament

Abstract

A method for producing a multifilament including 50 or more single filaments by melt spinning is provided. The method includes the steps of (A) obtaining 50 or more raw filaments in a molten state by discharging a composition including a poly(3-hydroxyalkanoate) resin from a spinning nozzle, and (B) cooling the raw filaments by blowing gas onto the raw filaments in the molten state. The spinning nozzle includes a nozzle surface including 50 or more discharge holes. The nozzle surface is segmented into a central region and a peripheral region surrounding the central region. An outer edge of the central region and an outer edge of the peripheral region are similar in shape to each other and share a same area centroid. A similarity ratio between the outer edge of the central region and the outer edge of the peripheral region is 1:2.

1 . A method for producing a multifilament including 50 or more single filaments by melt spinning, the method comprising:
 obtaining 50 or more raw filaments in a molten state by discharging a composition comprising a poly(3-hydroxyalkanoate) resin from a spinning nozzle; and   cooling the raw filaments by blowing gas onto the raw filaments in the molten state, wherein:
 the spinning nozzle includes a nozzle surface including 50 or more discharge holes; 
 the nozzle surface is segmented into a central region and a peripheral region surrounding the central region; 
 an outer edge of the central region and an outer edge of the peripheral region are similar in shape to each other and share a same area centroid; 
 a similarity ratio between the outer edge of the central region and the outer edge of the peripheral region is 1:2; 
 the number of the discharge holes present in the peripheral region exceeds 75% of the number of the discharge holes present on the nozzle surface; 
 a temperature of the gas is from (Tc-45)° C. to (Tc-20)° C. where Tc is a crystallization temperature of the composition comprising the poly(3-hydroxyalkanoate) resin; 
 a speed of the gas is 0.01 m/s or greater and less than 0.10 m/s; and 
 an average value of fineness of the single filaments is from 3.0 dtex to 15.0 dtex. 
   
     
     
         2 . The method for producing the multifilament according to  claim 1 , wherein no discharge holes are present in the central region. 
     
     
         3 . The method for producing the multifilament according to  claim 1 , wherein each of the outer edge of the central region and the outer edge of the peripheral region has a circular shape, an ellipsoidal shape, or a regular polygonal shape. 
     
     
         4 . The method for producing the multifilament according to  claim 3 , wherein each of the outer edge of the central region and the outer edge of the peripheral region has the circular shape. 
     
     
         5 . The method for producing the multifilament according to  claim 1 , wherein a temperature of the composition immediately after the composition is discharged from the spinning nozzle is from 150° C. to 168° C. 
     
     
         6 . The method for producing the multifilament according to  claim 1 , wherein the poly(3-hydroxyalkanoate) resin comprises a poly(3-hydroxybutyrate) resin. 
     
     
         7 . The method for producing the multifilament according to  claim 2 , wherein each of the outer edge of the central region and the outer edge of the peripheral region has a circular shape, an ellipsoidal shape, or a regular polygonal shape. 
     
     
         8 . The method for producing the multifilament according to  claim 7 , wherein each of the outer edge of the central region and the outer edge of the peripheral region has the circular shape. 
     
     
         9 . The method for producing the multifilament according to  claim 2 , wherein a temperature of the composition immediately after the composition is discharged from the spinning nozzle is from 150° C. to 168° C. 
     
     
         10 . The method for producing the multifilament according to  claim 2 , wherein the poly(3-hydroxyalkanoate) resin comprises a poly(3-hydroxybutyrate) resin.