Fine cellulose fiber and method for producing same

Fine cellulose fiber in which a part of hydroxy groups of cellulose fiber are substituted with a functional group represented by the following structural formula to introduce an ester of phosphorous acid, and

• substituted with a carbamate group to introduce a carbamate:
• wherein, in structural formula, α is any of none, R and NHR, R is one of a hydrogen atom, a saturated linear hydrocarbon group, a saturated branched hydrocarbon group, a saturated cyclic hydrocarbon group, an unsaturated linear hydrocarbon group, an unsaturated branched hydrocarbon group, an aromatic group and a derivative group thereof, and β is a cation of an organic substance or an inorganic substance.

The fine cellulose fiber according to claim 1, wherein the degree of substitution with the carbamate group is 0.01 to 0.38.

The fine cellulose fiber according to claim 1, wherein the degree of substitution with the functional group represented by structural formula is 0.01 to 0.64.

A method for producing fine cellulose fiber,

• the method comprising adding an additive (A) and an additive (B) including at least one of urea and a urea derivative to cellulose fiber, heating the mixture at 100 to 210° C., washing the mixture, and then fibrillating the mixture,
• the additive (A) being phosphorous acids or metal phosphites, and
• the additive (B) being added in an amount of 0.01 to 100 mol based on 1 mol of the additive (A).

The method for producing fine cellulose fiber according to claim 4, wherein the heating is performed at a pH of 3 to 12.

The fine cellulose fiber according to claim 2, wherein the degree of substitution with the functional group represented by structural formula is 0.01 to 0.64.