Polyester based thermally adhesive composite short fiber

Abstract

Polyester-based heat-bonding conjugate staple fibers capable of giving a high grade fiber structure which has good dimensional stability and is hardly deformed, even when used under a high temperature atmosphere, comprises an amorphous polyester having a glass transition point of 50 to 100° C. and not having a crystal-melting point as a heat-bonding component and a polyalkylene terephthalate having a melting point of not less than 220° C. as a fiber-forming component, have characteristics comprising the number of crimps of 3 to 40 crimps/25 mm, a crimp percent of 3 to 40% and a web area shrinkage percent of not more than 20%. Herein, the web area shrinkage percent (%) is represented by the expression: (A 0 −A 1 )/A 0 ×100, wherein a card web nonwoven fabric comprising 100% of the heat-bonding conjugate staple fibers and having an area of A 0 and a basis weight of 30 g/m 2 is left in a hot air dryer maintained at 150° C. for two minutes, and the area of the left nonwoven fabric is A 1 .

1 . Polyester-based heat-bonding conjugate staple fibers comprising an amorphous polyester having a glass transition point of 50 to 100° C. and not having a crystal-melting point as a heat-bonding component and a polyalkylene terephthalate having a melting point of not less than 220° C. as a fiber-forming component, characterized by having the number of crimps of 3 to 40 crimps/25 mm, a crimp percent of 3 to 40%, and a web area shrinkage percent of not more than 20% defined as described below.  
       <Web Area Shrinkage Percentage>
 A card web nonwoven fabric comprising 100% of the heat-bonding conjugate staple fibers and having an area of A 0  and a basis weight of 30 g/m 2  is left in a hot air dryer maintained at 150° C. for two minutes, and then the area A 1  of the nonwoven fabric is measured. The web area shrinkage percentage is determined by the following expression.  
 Web area shrinkage percentage (%)=( A   0   −A   1 )/ A   0 ×100  
 
     
     
         2 . The polyester-based heat-bonding conjugate staple fibers according to  claim 1 , wherein a polyether polyester block copolymer is applied to the surfaces of the fibers in an amount of not less than 0.03 percent by weight on the basis of the weight of the fibers.  
     
     
         3 . The polyester-based heat-bonding conjugate staple fibers according to  claim 1  or  2 , wherein the heat-bonding component is an amorphous copolyester comprising isophthalic acid component, terephthalic acid component, ethylene glycol component, and diethylene glycol component.  
     
     
         4 . The polyester-based heat-bonding conjugate staple fibers according to  claim 1  or  2 , wherein the fiber-forming component is polyethylene terephthalate.  
     
     
         5 . A method for producing polyester-based heat-bonding conjugate staple fibers, characterized by melting and conjugationally extruding an amorphous polyester having a glass transition point of 50 to 100° C. and not having a crystal-melting point and a polyalkylene terephthalate having a melting point of not less than 220° C., cooling and solidifying the conjugationally extruded fibers, taking off the fibers at a rate of not more than 1,500 m/minute to form the undrawn conjugate fibers, applying a polyether polyester block copolymer to the undrawn conjugate fibers in an amount of not less than 0.03 percent by weight on the basis of the weight of the fibers, drawing the undrawn conjugate fibers in a draw ratio of 0.72 to 1.25 times the cold maximum draw ratio at a temperature of T 1  to (T 2 +30° C.), and further crimping the drawn fibers so as to give the number of crimps of 3 to 40 crimps/25 mm and a crimp percent of 3 to 40%. Herein, T 1  is either higher temperature among the glass transition point of the amorphous polyester and the glass transition point of the polyalkylene terephthalate, and T 2  is the glass transition point of the amorphous polyester.  
     
     
         6 . The method for producing the polyester-based heat-bonding conjugate staple fibers according to  claim 5 , wherein the drawing is a two step drawing comprising drawing in a draw ratio of 0.70 to 1.00 time the cold maximum draw ratio at a temperature of T 1  to (T 1 +10° C.) and further in a draw ratio of 1.03 to 1.25 at a temperature of (T 1 +10° C.) to (T 2 +30° C.).  
     
     
         7 . The method for producing the polyester-based heat-bonding conjugate staple fibers according to  claim 5  or  6 , wherein a heating medium used for the drawing is hot water.  
     
     
         8 . The method for producing the polyester-based heat-bonding conjugate staple fibers according to  claim 5  or  6 , wherein the polyether polyester block copolymer is a block copolymer comprising terephthalic acid component and isophthalic acid component and/or an alkali metal salt sulfoisophthalic acid component in a molar ratio of 40:60 to 100:0 as the acid component and ethylene glycol as the glycol component and copolymerized with 20 to 95 percent by weight of a polyalkylene glycol having a number-average molecular weight of 600 to 10,000.