Cellulose nanofiber, sheet-like material obtained therefrom, and method for producing cellulose nanofiber and sheet-like material

Abstract

The present invention provides: a cellulose nanofiber enabling the provision of a high-performance sheet-like material; a method for producing the cellulose nanofiber; and a sheet-like material obtained from the cellulose nanofiber. A bamboo-derived cellulose nanofiber having a cellulose purity of at least 90%, a fiber diameter of 10-20 nm, and a crystallinity of at least 70% can be obtained by a method comprising: (1) a step for subjecting a bamboo material to an alkali treatment and a mechanical treatment to prepare bamboo fibers; (2) a step for delignificating the obtained bamboo fibers; (3) a step for mechanically spreading the delignificated bamboo fibers; (4) a step for removing hemicellulose from the spread bamboo fibers; and (5) a step for removing metal components from the bamboo fibers from which hemicellulose has been removed. A high strength sheet material having a tensile strength of 7-200 N for a basis weight of 10-210 g/m 2 or a high strength sheet material having a tensile strength of 7-200 N for a density of 0.3-1.1 g/cm 3 can be obtained by making this cellulose nanofiber into a sheet.

1 . A bamboo-derived cellulose nanofiber, wherein the bamboo-derived cellulose nanofiber has a cellulose purity of greater than or equal to 90%, a fiber diameter of 10 to 20 nm, and a crystallinity of greater than or equal to 70%. 
     
     
         2 . A suspension wherein the bamboo-derived cellulose nanofibers according to  claim 1  are dispersed in water. 
     
     
         3 . A suspension wherein the bamboo-derived cellulose nanofibers according to  claim 1  are dispersed in an organic solvent. 
     
     
         4 . A method for manufacturing bamboo-derived cellulose nanofibers, the method comprising the following steps (1) to (5):
 (1) applying alkali treatment and mechanical treatment to a bamboo material to create bamboo fibers,   (2) applying delignification treatment to the obtained bamboo fibers,   (3) mechanically defibrating the bamboo fibers having undergone the delignification treatment,   (4) removing hemicellulose from the defibrated bamboo fibers, and   (5) removing metal components from the bamboo fibers after the removal of hemicellulose.   
     
     
         5 . The method according to  claim 4 , wherein a chipped bamboo material with the inner and outer skins removed is used. 
     
     
         6 . The method according to  claim 5 , wherein the chipped bamboo material has a length of 1 to 10 cm. 
     
     
         7 . The method according to  claim 4 , wherein the alkali treatment of the bamboo material is performed using sodium hydroxide. 
     
     
         8 . The method according to  claim 4 , wherein the mechanical treatment of the bamboo material is performed using a mixer. 
     
     
         9 . The method according to  claim 4 , wherein the delignification treatment of the bamboo fibers is performed using at least one solvent of peracetic acid, chlorous acid, sodium sulfite, sulfuric acid, ozone, an enzyme, and a microorganism (bacteria). 
     
     
         10 . The method according to  claim 4 , wherein the removal of hemicellulose is performed using an aqueous solution of potassium hydroxide. 
     
     
         11 . The method according to  claim 4 , wherein the removal of the metal components is performed using an acidic solution. 
     
     
         12 . The method of  claim 11 , wherein a hydrochloric acid solution is used as the acidic solution. 
     
     
         13 . A sheet material comprising bamboo-derived cellulose nanofibers, wherein the sheet material exhibits a tensile strength of 7 to 200 N per basis weight of 10 to 210 g/m 2 . 
     
     
         14 . A sheet material comprising bamboo-derived cellulose nanofibers, wherein the sheet material exhibits a tensile strength of 7 to 200 N per density of 0.3 to 1.1 g/cm 3 . 
     
     
         15 . A method for manufacturing a sheet material comprising bamboo-derived cellulose nanofibers, wherein bamboo-derived cellulose nanofibers obtained by the method according to  claim 4  are formed into a sheet. 
     
     
         16 . The method according to  claim 15  wherein the sheet is formed by:
 (a) creating a suspension comprising bamboo-derived cellulose nanofibers dispersed in water, 
 (b) removing the water from the suspension and collecting the residue thereof, 18 and 
 (c) applying hot press treatment to the collected residue to obtain the sheet material. 
 
     
     
         17 . The method according to  claim 16 , wherein the sheet is formed by collecting cellulose nanofibers from the suspension of (a), dispersing the collected cellulose nanofibers in an alcohol to make a separate suspension, and applying hot press treatment thereto. 
     
     
         18 . The method according to  claim 15 , wherein the sheet is formed by:
 (a) creating a suspension comprising cellulose nanofibers dispersed in an alcohol,   (b) spreading the suspension on a substrate to form a film, and   (c) applying freeze-drying treatment to the film of the suspension to obtain the sheet material.   
     
     
         19 . A bamboo-derived lignocellulose nanofiber, which is manufactured by the method according to  claim 4 , and has a lignin content of 1 to 2 wt %.