Heat-bondable composite fiber, method for producing same and nonwoven fabric using heat-bondable composite fiber

Abstract

A heat-bondable composite fiber includes a first component that contains a polyester-based resin and a second component that contains a polyolefin-based resin having a melting point that is lower than a melting point of the polyester-based resin by 15° C. or more, and which has an eccentric sheath-core structure wherein, in a cross-section of a fiber orthogonal to a lengthwise direction, the second component occupies an outer periphery of the fiber. This heat-bondable composite fiber has an elongation at break of 200% or more, a three-dimensional apparent crimp, and a crimp elastic modulus of 85% to 100%.

1 . A heat-bondable composite fiber which comprises a first component containing a polyester-based resin and a second component containing a polyolefin-based resin having a melting point that is lower than a melting point of the polyester-based resin by 15° C. or more, and which has an eccentric sheath-core structure in which, in a cross-section of a fiber orthogonal to a lengthwise direction of the fiber, the second component occupies an outer periphery of the fiber,
 wherein the heat-bondable composite fiber has an elongation at break of 200% or more, a three-dimensional apparent crimp, and a crimp elastic modulus of 85% to 100%. 
 
     
     
         2 . The heat-bondable composite fiber according to  claim 1 , 
 wherein a ratio of the elongation at break to fineness is 80%/dtex or more.   
     
     
         3 . The heat-bondable composite fiber according to  claim 1 , 
 wherein a breaking strength is 0.5 to 1.5 cN/dtex.   
     
     
         4 . The heat-bondable composite fiber according to  claim 1 ,
 wherein a dry heat shrinkage at 120° C. is 0% to 15%.   
     
     
         5 . A method for producing a heat-bondable composite fiber, comprising:
 a process of melt spinning a first component containing a polyester-based resin and a second component containing a polyolefin-based resin having a melting point that is lower than a melting point of the polyester-based resin by 15° C. or more to form an eccentric sheath-core cross-sectional shape in which the second component occupies an outer periphery of a fiber to obtain an undrawn fiber;   a process of drawing the undrawn fiber to obtain a drawn fiber; and a process of heat-treating the drawn fiber,   wherein drawing efficiency represented by an equation below is 40% to 75%:   drawing efficiency (%)={fineness (dtex) of undrawn fiber/draw magnification (times)/fineness (dtex) of heat-bondable composite fiber}×100.   
     
     
         6 . The method for producing a heat-bondable composite fiber according to  claim 5 ,
 wherein the process of obtaining the drawn fiber is a process of drawing the undrawn fiber at a draw magnification of 1.5 times or more.   
     
     
         7 . The method for producing a heat-bondable composite fiber according to  claim 5 ,
 wherein the process of heat-treating is a process in which a heat treatment is performed in a temperature range higher than a glass transition temperature of the polyester-based resin constituting the first component by 10° C. to 70° C. and lower than the melting point of the polyolefin-based resin constituting the second component.   
     
     
         8 . The method for producing a heat-bondable composite fiber according to  claim 5 , further comprising:
 a process of imparting two-dimensional mechanical crimps to the drawn fiber after the process of drawing.   
     
     
         9 . A nonwoven fabric obtained using the heat-bondable composite fiber according to  claim 1 . 
     
     
         10 . The nonwoven fabric according to  claim 9 ,
 wherein elongation is 90% to 150%, and specific volume is 30 to 75 cm 3 /g.   
     
     
         11 . The heat-bondable composite fiber according to  claim 2 ,
 wherein a breaking strength is 0.5 to 1.5 cN/dtex.   
     
     
         12 . The method for producing a heat-bondable composite fiber according to  claim 6 ,
 wherein the process of heat-treating is a process in which a heat treatment is performed in a temperature range higher than a glass transition temperature of the polyester-based resin constituting the first component by 10° C. to 70° C. and lower than the melting point of the polyolefin-based resin constituting the second component.