Methods for producing wet-spun non-woven fabrics

Abstract

The present invention provides a wet-spun non-woven fabric composed of inorganic fibers containing bundled inorganic fibers and a binder component for binding the fibers, wherein the average number of the fibers in each bundle is 1.5 to 20 and the average Z/X value represented by the following formula in the cross section of the non-woven fabric is 0.9 or below: (number of adjacent fibers in the thickness direction in each bundle)/(number of adjacent fibers in the plane direction in each bundle)= Z/X, and a method for producing a wet-spun non-woven fabric, which comprises the steps of dispersing inorganic fibers in an aqueous medium in the presence of an anionic dispersion stabilizer, adding a cationic compound to the obtained fiber dispersion to bundle the fibers and thereby preparing a fiber dispersion containing the resultant fiber bundles, making a sheet from the obtained fiber dispersion containing the fiber bundles by wet method and applying a binder to the obtained sheet. The non-woven fabric is a non-woven inorganic fiber fabric having a high density.

1 . A method for producing a wet-spun non-woven fabric composed of inorganic fibers containing bundled inorganic fibers and a binder component for binding the fibers, comprising dispersing inorganic fibers in an aqueous medium in the presence of an anionic dispersion stabilizer, adding a cationic compound to the obtained fiber dispersion to bundle the fibers and thereby preparing a fiber dispersion containing the resultant fiber bundles, making a sheet from the obtained fiber dispersion containing the fiber bundles by a wet method and applying a binder to the obtained sheet, wherein an average number of the fibers in each bundle is 1.5 to 20, and an average Z/X value represented by the following formula in the cross section of the non-woven fabric is 0.9 or below:
   (number of adjacent fibers in the thickness direction in each bundle)/(number of adjacent fibers in the plane direction in each bundle)= Z/X.      
   
   
       2 . The method of  claim 1 , wherein the aqueous medium for dispersing the fibers further comprises a nonionic surfactant and wherein the cationic compound comprises a polyethyleneimine. 
   
   
       3 . The method of  claim 1 , wherein the maximum number of fibers in the bundle is not larger than 100. 
   
   
       4 . The method of  claim 1 , wherein the average diameter of the inorganic fibers is 4 μm to 20 μm and the average fiber length is 1 mm to 25 mm. 
   
   
       5 . The method of  claim 1 , wherein the inorganic fibers are glass fibers. 
   
   
       6 . The method of  claim 1 , wherein the fabric has a density of 0.20 g/cm 3  to 1.20 g/cm 3 . 
   
   
       7 . The method of  claim 6 , wherein the fabric has a binder content of 3% by mass to 18% by mass and a density of 0.20 g/cm 3  to 0.50 g/cm 3 . 
   
   
       8 . The method of  claim 6 , wherein the fabric has a binder content of 50% by mass to 90% by mass and a density of 0.40 g/cm 3  to 1.20 g/cm 3 . 
   
   
       9 . A method for producing a wet-spun non-woven fabric composed of inorganic fibers containing bundled inorganic fibers and a binder component for binding the fibers, comprising dispersing inorganic fibers in an aqueous medium in the presence of a cationic dispersion stabilizer, adding an anionic compound to the obtained fiber dispersion to bundle the fibers and thereby prepare a fiber dispersion containing the resultant fiber bundles, making a sheet from the obtained fiber dispersion containing the fiber bundles by a wet method and applying a binder to the obtained sheet, wherein an average number of the fibers in each bundle is 1.5 to 20, and an average Z/X value represented by the following formula in the cross section of the non-woven fabric is 0.9 or below:
   (number of adjacent fibers in the thickness direction in each bundle)/(number of adjacent fibers in the plane direction in each bundle)= Z/X.      
   
   
       10 . The method of  claim 9 , wherein the cationic dispersion stabilizer comprises polyethyleneimine and the aqueous medium for dispersing the fibers further comprises a nonionic surfactant. 
   
   
       11 . The method of  claim 9 , wherein the maximum number of fibers in the bundle is not larger than 100. 
   
   
       12 . The method of  claim 9 , wherein the average diameter of the inorganic fibers is 4 μm to 20 μm and the average fiber length is 1 mm to 25 mm. 
   
   
       13 . The method of  claim 9 , wherein the inorganic fibers are glass fibers. 
   
   
       14 . The method of  claim 9 , wherein the fabric has a density of 0.20 g/cm 3  to 1.20 g/cm 3 . 
   
   
       15 . The method of  claim 14 , wherein the fabric has a binder content of 3% by mass to 18% by mass and a density of 0.20 g/cm 3  to 0.50 g/cm 3 . 
   
   
       16 . The method of  claim 14 , wherein the fabric has a binder content of 50% by mass to 90% by mass and a density of 0.40 g/cm 3  to 1.20 g/cm 3 . 
   
   
       17 . A method for producing a wet-spun non-woven fabric composed of inorganic fibers containing bundled inorganic fibers and a binder component for binding the fibers, comprising dispersing a first part of inorganic fibers in an aqueous medium in the presence of an anionic dispersion stabilizer to prepare an anionic fiber dispersion, dispersing a second part of inorganic fibers in an aqueous medium in the presence of a cationic dispersion stabilizer to prepare a cationic fiber dispersion and thereby preparing at least two fiber dispersions, mixing the at least two fiber dispersions together to bundle the fibers and to prepare a fiber dispersion containing the fiber bundles, making a sheet from the obtained fiber dispersion containing the fiber bundles by a wet method and applying a binder to the obtained sheet, wherein an average number of the fibers in each bundle is 1.5 to 20, and an average Z/X value represented by the following formula in the cross section of the non-woven fabric is 0.9 or below:
   (number of adjacent fibers in the thickness direction in each bundle)/(number of adjacent fibers in the plane direction in each bundle)= Z/X.      
   
   
       18 . The method of  claim 17 , wherein the maximum number of fibers in the bundle is not larger than 100. 
   
   
       19 . The method of  claim 17 , wherein the average diameter of the inorganic fibers is 4 μm to 20 μm and the average fiber length is 1 mm to 25 mm. 
   
   
       20 . The method of  claim 17 , wherein the inorganic fibers are glass fibers.