Sheet-shaped material and process for producing said sheet-shaped material (as amended)

Abstract

The present invention provides a process including: (i) dissolving, in water, a polyvinyl alcohol having a degree of saponification of 98% or more and a degree of polymerization of 800 to 3500 to prepare a polyvinyl alcohol aqueous solution in which the concentrations of methyl acetate, acetic acid and methanol are 50 ppm or less, (ii) adding the polyvinyl alcohol aqueous solution to a fibrous substrate having microfiber-generating fibers as its main constituent, so that the fibrous substrate has the polyvinyl alcohol in an amount of 0.1 to 50% by mass based on the mass of the fibers contained in the fibrous substrate, (iii) generating microfibers having an average single fiber diameter of 0.3 to 7 μm from the microfiber-generating fibers contained in the fibrous substrate as its main constituent, (iv) adding a waterborne polyurethane to the fibrous substrate comprising the microfibers as its main constituent and having the added polyvinyl alcohol, and (v) removing the polyvinyl alcohol from the fibrous substrate comprising the microfibers as its main constituent and having the added waterborne polyurethane.

1 . A process for producing a sheet-shaped material, the process comprising the successive steps of:
 (i) dissolving, in water, a polyvinyl alcohol having a degree of saponification of 98% or more and a degree of polymerization of 800 to 3500 to prepare a polyvinyl alcohol aqueous solution in which the concentrations of methyl acetate, acetic acid and methanol are 50 ppm or less,   (ii) adding the polyvinyl alcohol aqueous solution to a fibrous substrate comprising microfiber-generating fibers as its main constituent, so that the fibrous substrate has the polyvinyl alcohol in an amount of 0.1 to 50% by mass based on the mass of the fibers contained in the fibrous substrate,   (iii) generating microfibers having an average single fiber diameter of 0.3 to 7 μm from the microfiber-generating fibers contained in the fibrous substrate as its main constituent,   (iv) adding a waterborne polyurethane to the fibrous substrate comprising the microfibers as its main constituent and having the added polyvinyl alcohol, and   (v) removing the polyvinyl alcohol from the fibrous substrate comprising the microfibers as its main constituent and having the added waterborne polyurethane.   
     
     
         2 . The process for producing a sheet-shaped material according to  claim 1 , wherein the concentrations of methyl acetate, acetic acid and methanol in the polyvinyl alcohol aqueous solution are 0.1 to 50 ppm. 
     
     
         3 . The process for producing a sheet-shaped material according to  claim 1  or  2 , wherein the step of generating the microfibers is performed by treatment with an alkaline aqueous solution. 
     
     
         4 . The process for producing a sheet-shaped material according to  claim 1  or  2 , further comprising the step of performing heating at 80 to 170° C. after the addition of the polyvinyl alcohol. 
     
     
         5 . The process for producing a sheet-shaped material according to  claim 1  or  2 , wherein the fibrous substrate comprising microfiber-generating fibers as its main constituent is integrated with a woven fabric and/or a knitted fabric by entanglement. 
     
     
         6 . A sheet-shaped material produced by the process for producing a sheet-shaped material according to  claim 1  or  2 , the sheet-shaped material having a density of 0.2 to 0.7 g/cm 3 . 
     
     
         7 . The process for producing a sheet-shaped material according to  claim 3 , further comprising the step of performing heating at 80 to 170° C. after the addition of the polyvinyl alcohol. 
     
     
         8 . The process for producing a sheet-shaped material according to  claim 3 , wherein the fibrous substrate comprising microfiber-generating fibers as its main constituent is integrated with a woven fabric and/or a knitted fabric by entanglement. 
     
     
         9 . A sheet-shaped material produced by the process for producing a sheet-shaped material according to  claim 3 , the sheet-shaped material having a density of 0.2 to 0.7 g/cm 3 .