The present invention intends to provide an acid type carboxylated cellulose nanofiber having a high viscosity in a low shear region, or to provide an acid type carboxylated cellulose nanofiber having a very short fiber length, and the acid type carboxylated cellulose nanofiber has a carboxy group at least in part of a constituent unit constituting a cellulose molecular chain, wherein a viscosity of water dispersion with a content from 0.95 to 1.05% by mass is 400 Pa.Math.s or higher at a shear velocity from 0.003 to 0.01 s.sup.−1 at 30° C., or an average fiber length is from 50 to 500 nm and a ratio of fibers having a fiber length of 300 nm or shorter is 50% or higher.

The present invention intends to provide an acid type carboxylated cellulose nanofiber having a high viscosity in a low shear region, or to provide an acid type carboxylated cellulose nanofiber having a very short fiber length, and the acid type carboxylated cellulose nanofiber has a carboxy group at least in part of a constituent unit constituting a cellulose molecular chain, wherein a viscosity of water dispersion with a content from 0.95 to 1.05% by mass is 400 Pa.Math.s or higher at a shear velocity from 0.003 to 0.01 s.sup.−1 at 30° C., or an average fiber length is from 50 to 500 nm and a ratio of fibers having a fiber length of 300 nm or shorter is 50% or higher.

A process for producing an oxidized nanofibrillar cellulose hydrogel is disclosed, wherein the process comprises oxidizing cellulose pulp fibers in the presence of hypochlorite as an oxidant and a heterocyclic nitroxyl radical as a catalyst; and disintegrating the oxidized cellulose pulp fibers to obtain a nanofibrillar cellulose hydrogel; wherein all steps of the process after oxidizing are performed under aseptic conditions. An oxidized nanofibrillar cellulose hydrogel and a system for producing the same are also disclosed.

A process for producing an oxidized nanofibrillar cellulose hydrogel is disclosed, wherein the process comprises oxidizing cellulose pulp fibers in the presence of hypochlorite as an oxidant and a heterocyclic nitroxyl radical as a catalyst; and disintegrating the oxidized cellulose pulp fibers to obtain a nanofibrillar cellulose hydrogel; wherein all steps of the process after oxidizing are performed under aseptic conditions. An oxidized nanofibrillar cellulose hydrogel and a system for producing the same are also disclosed.

Disclosed is a dispersion of metal-containing oxidized cellulose nanofibers with superior dispersibility, which is applicable to various uses. The disclosed metal-containing oxidized cellulose nanofiber dispersion comprises a dispersion medium, and metal-containing oxidized cellulose nanofibers containing a metal other than sodium in salt form, wherein the metal-containing oxidized cellulose nanofibers have a number-average fiber diameter of 100 nm or less.

Disclosed is a dispersion of metal-containing oxidized cellulose nanofibers with superior dispersibility, which is applicable to various uses. The disclosed metal-containing oxidized cellulose nanofiber dispersion comprises a dispersion medium, and metal-containing oxidized cellulose nanofibers containing a metal other than sodium in salt form, wherein the metal-containing oxidized cellulose nanofibers have a number-average fiber diameter of 100 nm or less.

An object of the present invention is to provide an efficient method for producing cellulose nanofibers, without N-oxyl compounds such as TEMPO remaining in the cellulose nanofibers. Provided is a method for producing cellulose nanofibers, the method including: oxidizing a cellulose raw material with hypochlorous acid, or a salt thereof, having an available chlorine concentration of from 14% by mass to 43% by mass, to produce an oxidized cellulose; and fibrillating the oxidized cellulose into nanofibers.

An object of the present invention is to provide an efficient method for producing cellulose nanofibers, without N-oxyl compounds such as TEMPO remaining in the cellulose nanofibers. Provided is a method for producing cellulose nanofibers, the method including: oxidizing a cellulose raw material with hypochlorous acid, or a salt thereof, having an available chlorine concentration of from 14% by mass to 43% by mass, to produce an oxidized cellulose; and fibrillating the oxidized cellulose into nanofibers.

A composition comprising nanocellulose is disclosed, wherein the nanocellulose contains very low or essentially no sulfur content. The nanocellulose may be in the form of cellulose nanocrystals, cellulose nanofibrils, or both. The nanocellulose is characterized by a crystallinity of at least 80%, an onset of thermal decomposition of 300° F. or higher, and a low light transmittance over the range 400-700 nm. Other variations provide a composition comprising lignin-coated hydrophobic nanocellulose, wherein the nanocellulose contains very low or essentially no sulfur content. Some variations provide a composition comprising nanocellulose, wherein the nanocellulose contains about 0.1 wt % equivalent sulfur content, or less, as SO.sub.4 groups chemically or physically bound to the nanocellulose. In some embodiments, the nanocellulose contains essentially no hydrogen atoms (apart from hydrogen structurally contained in nanocellulose itself) bound to the nanocellulose. Various compositions, materials, and products may incorporate the nanocellulose compositions disclosed herein.

A composition comprising nanocellulose is disclosed, wherein the nanocellulose contains very low or essentially no sulfur content. The nanocellulose may be in the form of cellulose nanocrystals, cellulose nanofibrils, or both. The nanocellulose is characterized by a crystallinity of at least 80%, an onset of thermal decomposition of 300° F. or higher, and a low light transmittance over the range 400-700 nm. Other variations provide a composition comprising lignin-coated hydrophobic nanocellulose, wherein the nanocellulose contains very low or essentially no sulfur content. Some variations provide a composition comprising nanocellulose, wherein the nanocellulose contains about 0.1 wt % equivalent sulfur content, or less, as SO.sub.4 groups chemically or physically bound to the nanocellulose. In some embodiments, the nanocellulose contains essentially no hydrogen atoms (apart from hydrogen structurally contained in nanocellulose itself) bound to the nanocellulose. Various compositions, materials, and products may incorporate the nanocellulose compositions disclosed herein.