Method for producing cellulose nanofibers

In the production method of obtaining cellulose nanofibers by miniaturizing pulp fibers， there is provided a method for producing cellulose nanofibers capable of obtaining cellulose nanofibers capable of exhibiting excellent strength and the like in which a decrease in molecular weight of cellulose is suppressed. The present invention comprises a step of performing a pretreatment on the pulp fibers in a slurry and a step of micronizing the pulp fibers in the pretreated slurry with a high pressure homogenizer， with respect to the weight average molecular weight of cellulose of the pulp fibers before the pretreatment step， This is a method for producing cellulose nanofibers having a weight average molecular weight of cellulose of 65% or more of the cellulose nanofibers obtained through the micronization process. Provided is a manufacturing method for obtaining cellulose nanofibers by refining pulp fibers， the cellulose nanofiber manufacturing method making it possible to obtain cellulose nanofibers in which a decrease in the molecular weight of cellulose is suppressed and which provide excellent strength and the like. The present invention provides a cellulose nanofiber manufacturing method comprising: a step of subjecting pulp fibers in a slurry to preprocessing; and a step of refining， using a high-pressure homogenizer， the pulp fibers in the slurry that has been subjected to preprocessing. A weight-average molecular weight of the cellulose of the cellulose nanofibers obtained through the refining step to a weight-average molecular weight of the cellulose of the pulp fibers prior to the preprocessing step is not less than 65%. Provided is a manufacturing method for obtaining cellulose nanofibers by refining pulp fibers， the cellulose nanofiber manufacturing method making it possible to obtain cellulose nanofibers in which a decrease in the molecular weight of cellulose is suppressed and which provide excellent strength and the like. The present invention provides a cellulose nanofiber manufacturing method comprising: a step of subjecting pulp fibers in a slurry to preprocessing; and a step of refining， using a high-pressure homogenizer， the pulp fibers in the slurry that has been subjected to preprocessing. A weight-average molecular weight of the cellulose of the cellulose nanofibers obtained through the refining step to a weight-average molecular weight of the cellulose of the pulp fibers prior to the preprocessing step is not less than 65%.