Nonwoven fabric sheet and method for producing same

Abstract

The nonwoven fabric sheet of the present invention is characterized by a porosity in the range of 0.3 to 0.7 and an average pore size in the range of 0.5 μm to 5.0 μm. The nonwoven fabric sheet of the present invention preferably has a maximum pore size (μm)/average pore size (μm) ratio of 1.30 or lower. The nonwoven fabric sheet of the present invention is obtained by press-molding a nonwoven fabric at a temperature lower than the melting point of the thermoplastic resin which constitutes the nonwoven fabric sheet. According to the present invention, there is provided a nonwoven fabric sheet that has a high porosity, small uniform pore sizes and excellent productivity, which can suitably be used in various applications such as filters, light diffusing material, liquid absorber and heat insulating materials; and a method for producing the nonwoven fabric sheet.

1 . A nonwoven fabric sheet characterized by having a porosity in the range of 0.3 to 0.7 and a maximum pore size in the range of 0.5 μm to 5.0 μm.  
   
   
       2 . The nonwoven fabric sheet according to  claim 1 , wherein the maximum pore size (μm)/average pore size (μm) ratio is 1.30 or lower.  
   
   
       3 . The nonwoven fabric sheet according to  claim 1 , wherein the fiber constituting the nonwoven fabric is a polyolefin fiber.  
   
   
       4 . The nonwoven fabric sheet according to  claim 3 , wherein the polyolefin is a polymer of 4-methyl-1-pentene.  
   
   
       5 . A laminate comprising the nonwoven fabric sheet according to  claim 1  and a strength retention material laminated thereon.  
   
   
       6 . A method of producing a nonwoven fabric sheet characterized by molding a thermoplastic resin by a melt-blown method into a resin molded article in nonwoven fabric form; and subsequently press-molding said resin molded article in nonwoven fabric form with an elastic pressing means having a Young's modulus of 20 kg/cm 2  to 600 kg/cm 2  at a temperature lower than the melting point of the thermoplastic resin.  
   
   
       7 . The method of producing the nonwoven fabric sheet according to  claim 6 , wherein the pressing means has a Young's modulus of 20 kg/cm 2  to 300 kg/cm 2 .  
   
   
       8 . A filter, a light diffusion material, a liquid absorber, or a heat insulating material comprising the nonwoven fabric according to  claim 1 .  
   
   
       9 . A laminate comprising the nonwoven fabric sheet according to  claim 2  and a strength retention material laminated thereon.  
   
   
       10 . A laminate comprising the nonwoven fabric sheet according to  claim 3  and a strength retention material laminated thereon.  
   
   
       11 . A laminate comprising the nonwoven fabric sheet according to  claim 4  and a strength retention material laminated thereon.  
   
   
       12 . A filter, a light diffusion material, a liquid absorber, or a heat insulating material comprising the laminate according to  claim 5 .  
   
   
       13 . A filter, a light diffusion material, a liquid absorber, or a heat insulating material comprising the laminate according to  claim 9 .  
   
   
       14 . A filter, a light diffusion material, a liquid absorber, or a heat insulating material comprising the laminate according to  claim 10 .  
   
   
       15 . A filter, a light diffusion material, a liquid absorber, or a heat insulating material comprising the laminate according to  claim 11.