A cellulose fine fiber and its manufacturing method

Provided is a method for producing fine cellulose fibers which are nano-sized， which have a high crystallinity degree， and which are less vulnerable to fiber shape damage， by impregnating cellulose with a defibrillation solution to defibrate the cellulose without mechanical pulverization， and modifying the cellulose. The fine cellulose fiber production method according to the present invention comprises a step for impregnating cellulose with a fibrillation solution that contains a carboxylic acid vinyl ester or an aldehyde and an aprotic solvent having a donor number of 26 or higher to defibrate the cellulose. This aldehyde is at least one selected from the group consisting of aldehydes represented by formula (1)， paraformaldehyde， cinnamaldehyde， perillaldehyde， vanillin， and glyoxal. R 1―CHO (1) (Wherein， R1 represents a hydrogen atom， an alkyl group having 1-16 carbon atoms， an alkenyl group， a cycloalkyl group or an aryl group.) Provided is a method for producing fine cellulose fibers which are nano-sized， which have a high crystallinity degree， and which are less vulnerable to fiber shape damage， by impregnating cellulose with a defibrillation solution to defibrate the cellulose without mechanical pulverization， and modifying the cellulose. The fine cellulose fiber production method according to the present invention comprises a step for impregnating cellulose with a fibrillation solution that contains a carboxylic acid vinyl ester or an aldehyde and an aprotic solvent having a donor number of 26 or higher to defibrate the cellulose. This aldehyde is at least one selected from the group consisting of aldehydes represented by formula (1)， paraformaldehyde， cinnamaldehyde， perillaldehyde， vanillin， and glyoxal. R1―CHO (1) (Wherein， R1 represents a hydrogen atom， an alkyl group having 1-16 carbon atoms， an alkenyl group， a cycloalkyl group or an aryl group.)