Non-woven fabric, non-woven fabric producing method and acoustic absorbent

Abstract

A non-woven fabric, non-woven fabric producing method and an acoustic absorbent of desirable properties are provided. The non-woven fabric is a non-woven fabric including a plurality of ultrafine fibers configured from a thermoplastic resin, and comprises: a base portion configured by entangling of some of the plurality of ultrafine fibers; and a fiber bundle configured by entangling and bundling of other ultrafine fibers in the plurality of ultrafine fibers, and that is entangled with the base portion. The fiber bundle has a lower void fraction than a void fraction of the base portion.

What is claimed is: 
     
         1 . A non-woven fabric that includes a plurality of ultrafine fibers configured from a thermoplastic resin, the non-woven fabric comprising:
 a base portion configured by entangling of a first part of the plurality of ultrafine fibers; and   a fiber bundle configured by entangling and bundling of a second part of the plurality of ultrafine fibers,   wherein the fiber bundle is entangled with the base portion, and   wherein the fiber bundle has a lower void fraction than a void fraction of the base portion.   
     
     
         2 . The non-woven fabric according to  claim 1 , wherein the plurality of ultrafine fibers has a median size of at least 0.1 μm and no greater than 1 μm. 
     
     
         3 . The non-woven fabric according to  claim 1 , wherein the fiber bundle has a width at least 0.2 mm an no greater than 7.5 mm 
     
     
         4 . The non-woven fabric according to  claim 1 , wherein a proportion of the fiber bundle in the non-woven fabric is at least 15% and no greater than 96%. 
     
     
         5 . The non-woven fabric according to  claim 1 , wherein the fiber bundle has the lower void fraction of at least 90% and no greater than 99%. 
     
     
         6 . The non-woven fabric according to  claim 1 , wherein the fiber bundle has a length of at least 10 mm and no greater than 1,000 mm. 
     
     
         7 . An acoustic absorbent comprising a layer of the non-woven fabric of  claim 1 . 
     
     
         8 . A non-woven fabric producing method comprising:
 forming a plurality of ultrafine fibers from a thermoplastic resin;   configuring a base portion by entangling a first part of the plurality of ultrafine fibers;   configuring a fiber bundle by entangling and bundling a second part of the plurality of ultrafine fibers; and   entangling the fiber bundle with the base portion to provide the fiber bundle with a lower void fraction than a void fraction of the base portion.   
     
     
         9 . The non-woven fabric producing method according to  claim 8 , further comprising:
 using a melt-blown method that blows high-speed hot air to a molten thermoplastic resin, and stretches the thermoplastic resin to form the plurality of ultrafine fibers.