Method for producing pulp fibers for cellulose nanofiberization, and pulp fibers for cellulose nanofiberization

Abstract

The purpose of the present invention is to provide a method which is for producing pulp fibers for cellulose nanofiberization from pulp fibers of used sanitary products, and which can produce pulp fibers for cellulose nanofiberization that have low lignin content and a low distribution thereof and that have excellent cellulose nanofiberization properties. This method is described below. The method is characterized by involving: a step for supplying, from a mixed solution supply port (32) to a treatment tank (31), a mixed solution (51) which contains superabsorbent polymers and pulp fibers derived from used sanitary products; a step for supplying an ozone-containing gas (53) from an ozone-containing gas supply port (43) to a treatment solution (52) inside of the treatment tank (31); a step in which, by raising the ozone-containing gas (53) while lowering the superabsorbent polymers and pulp fibers in the treatment tank (31), the ozone-containing gas (53) is brought into contact with the superabsorbent polymers and the pulp fibers, and pulp fibers for cellulose nanofiberization are formed from the pulp fibers; and a step for discharging the treatment solution (52) from a treatment solution discharge port (33), wherein the pulp fibers for cellulose nanofiberization have a lignin content of less than or equal to 0.1 mass %.

1 . A method of manufacturing pulp fibers for cellulose nanofiberization from pulp fibers of used hygiene products, comprising steps of:
 a preparation step of preparing a treatment tank which includes a liquid mixture supply port, and a treatment liquid discharge port and an ozone containing gas supply port that are arranged below the liquid mixture supply port,   a liquid mixture supply step of supplying a liquid mixture which includes super absorbent polymers and the pulp fibers that derive from the used hygiene products and water, from the liquid mixture supply port to the treatment tank,   an ozone containing gas supply step of supplying ozone containing gas from the ozone containing gas supply port to a treatment liquid in the treatment tank,   a pulp fibers for cellulose nanofiberization formation step of forming the pulp fibers for cellulose nanofiberization from the pulp fibers while dissolving at least a portion of the super absorbent polymers in the treatment liquid, by, in the treatment tank, raising the ozone containing gas while lowering the super absorbent polymers and the pulp fibers so as to make the ozone containing gas come into contact with the super absorbent polymers and the pulp fibers, and   a treatment liquid discharge step of discharging the treatment liquid which includes the pulp fibers for cellulose nanofiberization from the treatment liquid discharge port, wherein   the pulp fibers for cellulose nanofiberization have a lignin content ratio of 0.1 mass % or less.   
     
     
         2 . The method according to  claim 1 , wherein the pulp fibers for cellulose nanofiberization have a beating degree reduction speed of 300 mL/h or more. 
     
     
         3 . The method according to  claim 1 , wherein in the pulp fibers for cellulose nanofiberization formation step, the ozone containing gas is supplied from the ozone containing gas supply port as microbubbles or nanobubbles. 
     
     
         4 . The method according to  claim 1 , wherein the treatment liquid is acidic. 
     
     
         5 . The method according to  claim 1 , further comprising an inactivation step of inactivating the super absorbent polymers by an acid, before the liquid mixture supply step. 
     
     
         6 . The method according to  claim 5 , wherein the acid is an acid which can form a complex with metal ions included in an excrement. 
     
     
         7 . The method according to  claim 1 , wherein the pulp fibers for cellulose nanofiberization have an ash content ratio of 0.65 mass % or less. 
     
     
         8 . The method according to  claim 1 , wherein in the liquid mixture supply step, the liquid mixture is supplied continuously from the liquid mixture supply port to the treatment tank in a first flow rate, and in the treatment liquid discharge step, the treatment liquid is discharged continuously from the treatment liquid discharge port in a second flow rate. 
     
     
         9 . The method according to  claim 1 , further comprising a cellulose nanofibers formation step of forming cellulose nanofibers from the pulp fibers for cellulose nanofiberization, after the treatment liquid discharge step. 
     
     
         10 . Pulp fibers for cellulose nanofiberization which derive from used hygiene products that include pulp fibers and super absorbent polymers, wherein the pulp fibers for cellulose nanofiberization have a lignin content ratio of 0.1 mass % or less. 
     
     
         11 . The pulp fibers for cellulose nanofiberization according to  claim 10 , wherein the pulp fibers for cellulose nanofiberization have a beating degree reduction speed of 300 mL/h or more. 
     
     
         12 . The pulp fibers for cellulose nanofiberization according to  claim 10 , wherein the pulp fibers for cellulose nanofiberization have an ash content ratio of 0.65 mass % or less.