Nonwoven fabric and method for producing the same

Abstract

A nonwoven fabric including fibers that contain a polymer having a glass transition temperature of greater than or equal to 50° C. as a main component, and having a vertical strength of greater than or equal to 1 N/5 cm per 1 g/m 2 , and by satisfying both of the following conditions (1) and (2), a nonwoven fabric having sufficient strength to be handled alone and including fibers that contain a polymer having a Tg of greater than or equal to 50° C. as a main component without performing a post processing such as emboss processing, calender processing, or spunlace processing, and a method for producing the nonwoven fabric can be provided. (1) A density is 0.01 to 0.4 g/cm 3 . (2) A proportion of parts with a density exceeding 0.4 g/cm 3 is less than or equal to 3% in a cross section in a thickness direction.

1 . A nonwoven fabric, comprising:
 fibers comprising a polymer having a glass transition temperature of greater than or equal to 50° C. as a main component,   wherein the nonwoven fabric has a vertical strength of greater than or equal to 1 N/5 cm per 1 g/m 2 , and   the nonwoven fabric satisfies conditions (1) and (2):   (1) a density of 0.01 to 0.4 g/cm 3 ; and   (2) a proportion of parts with a density exceeding 0.4 g/cm 3  of less than or equal to 3% in a cross section in a thickness direction.   
     
     
         2 . The nonwoven fabric according to  claim 1 , wherein a fiber fusion rate of the nonwoven fabric in a cross section in a thickness direction is greater than or equal to 15%, and an average area of parts where the fibers are fused is less than or equal to 70 μm 2 . 
     
     
         3 . The nonwoven fabric according to  claim 1 , wherein an average fiber diameter of the nonwoven fabric is 1 to 10 μm. 
     
     
         4 . The nonwoven fabric according to  claim 1 , comprising:
 amorphous polyetherimide-based fibers.   
     
     
         5 . A method for producing the nonwoven fabric according to  claim 1 : the method comprising:
 performing a melt blown method while maintaining a temperature in at least one of,   (1) a hemispherical space of 0.5×collection distance d around a nozzle tip relative to the collection distance d between a tip of a spinning nozzle and a collection surface of spun fibers, and   (2) a point of 1 cm from the collection surface on a straight line relative to the collection distance d between the tip of the spinning nozzle and the collection surface of spun fibers,   at a temperature higher than a glass transition temperature by greater than or equal to 10° C.