Drawn composite fiber, non-woven fabric, and method of producing drawn composite fiber

Abstract

Embodiments relate to a drawn composite fiber having a low thermal shrinkage, and a high single yarn strength, a non-woven fabric using the same, and a method of producing the same. The drawn composite fiber has a fineness of 0.6 dtex or less, a ratio between the cross-sectional areas of a sheath material and a core material (sheath material/core material) of 50/50 to 10/90, and a single yarn elastic modulus of 70 cN/dtex or more. The drawn composite is obtained by melt-spinning and a drawing treatment of an undrawn fiber having a sheath-core structure, in which the core material includes a resin containing a crystalline propylene-based polymer and having a melt flow rate of 10 to 30 g/10 min at a load of 21.18 N at 230° C., and the sheath material includes a resin containing an olefinic polymer where the melting point is lower than that of the core material.

1 . A drawn composite fiber comprising a sheath-core structure in which a resin containing a crystalline propylene-based polymer as a main component is a core material, and a resin containing, as a main component, an olefinic polymer of which a melting point is lower than that of the core material is a sheath material, wherein
 the drawn composite fiber has a fineness of 0.6 dtex or less,   a melt flow rate of the core material at a load of 21.18 N at 230° C. is 10 to 30 g/10 min,   a ratio between cross-sectional areas of the sheath material and the core material (sheath material/core material) is 50/50 to 10/90, and   the drawn composite fiber has a single yarn elastic modulus of 70 cN/dtex or more.   
     
     
         2 . The drawn composite fiber according to  claim 1 , wherein a ratio between a melt flow rate of the core material at a load of 21.18 N at 230° C. and a melt flow rate of the sheath material at a load of 21.18 N at 230° C. (core material/sheath material) is 0.3 to 1. 
     
     
         3 . A non-woven fabric formed using the drawn composite fiber according to  claim 1 . 
     
     
         4 . A method of producing a drawn composite fiber, comprising:
 a spinning step of obtaining, by melt-spinning, an undrawn fiber including a sheath-core structure in which a resin containing a crystalline propylene-based polymer as a main component is a core material, and a resin containing, as a main component, an olefinic polymer of which a melting point is lower than that of the core material is a sheath material; and   a drawing step of obtaining a drawn composite fiber of 0.6 dtex or less by drawing treatment of the undrawn fiber, wherein   the undrawn fiber has a fineness of 4.0 dtex or less, and has a ratio between cross-sectional areas of the sheath material and the core material (sheath material/core material) of 50/50 to 10/90,   the core material has a melt flow rate of 10 to 30 g/10 min at a load of 21.18 N at 230° C., and   the spinning step and the drawing step are consecutively performed.   
     
     
         5 . The method of producing a drawn composite fiber according to  claim 4 , wherein a ratio between a melt flow rate of the core material at a load of 21.18 N at 230° C. and a melt flow rate of the sheath material at a load of 21.18 N at 230° C. (core material/sheath material) is 0.3 to 1. 
     
     
         6 . The method of producing a drawn composite fiber according to  claim 4 , wherein the undrawn fiber is drawn at a draw magnification of 2 to 7 times in the drawing step. 
     
     
         7 . The method of producing a drawn composite fiber according to  claim 5 , wherein the undrawn fiber is drawn at a draw magnification of 2 to 7 times in the drawing step. 
     
     
         8 . The non-woven fabric according to  claim 3 , wherein a ratio between a melt flow rate of the core material at a load of 21.18 N at 230° C. and a melt flow rate of the sheath material at a load of 21.18 N at 230° C. (core material/sheath material) is 0.3 to 1.