Cellulose microfiber inclusions and manufacturing method thereof， and cellulose microfiber dispersion

Provided is a cellulose microfiber containing material having excellent dispersibility in water and easy to manufacture， and a method for manufacturing the cellulose microfiber dispersion. The cellulose microfiber-containing material contains cellulose microfibers in which an ester of phosphorous acid containing a cation composed of an inorganic substance is introduced， and the ratio of the cation composed of an inorganic substance to 1 g of the cellulose microfibers is 0.14 mmol or more. In addition， for the production， it is assumed that after introducing the ester of phosphorous acid into the cellulose fiber， it is decomposed to obtain a dispersion containing cellulose microfibers， and an alkali metal ion-containing material is added to the cellulose fiber in this process. Let it be concentrated. In preparing a cellulose microfiber dispersion， the cellulose microfiber content and water are mixed. [Problem] To provide: a fine cellulose fiber-containing substance that has excellent dispersibility in water and can be manufactured easily; a method for manufacturing the fine cellulose fiber-containing substance; and a method for manufacturing a fine cellulose fiber dispersion. [Solution] Provided is a fine cellulose fiber-containing substance comprising fine cellulose fibers into which phosphite containing positive ions of an inorganic substance is introduced， wherein the amount of the positive ions of inorganic substance relative to 1 g of the fine cellulose fibers is 0.14 mmol or more. Also provided is a method for manufacturing the fine cellulose fiber-containing substance including introducing the phosphite into cellulose fibers then defibrating the same to obtain a dispersion containing fine cellulose fibers， wherein in this step， an alkali metal ion-containing substance is added to the cellulose fibers and the dispersion is concentrated. Further provided is a method for manufacturing a fine cellulose fiber dispersion including mixing the fine cellulose fiber-containing substance with water. [Problem] To provide: a fine cellulose fiber-containing substance that has excellent dispersibility in water and can be manufactured easily; a method for manufacturing the fine cellulose fiber-containing substance; and a method for manufacturing a fine cellulose fiber dispersion. [Solution] Provided is a fine cellulose fiber-containing substance comprising fine cellulose fibers into which phosphite containing positive ions of an inorganic substance is introduced， wherein the amount of the positive ions of inorganic substance relative to 1 g of the fine cellulose fibers is 0.14 mmol or more. Also provided is a method for manufacturing the fine cellulose fiber-containing substance including introducing the phosphite into cellulose fibers then defibrating the same to obtain a dispersion containing fine cellulose fibers， wherein in this step， an alkali metal ion-containing substance is added to the cellulose fibers and the dispersion is concentrated. Further provided is a method for manufacturing a fine cellulose fiber dispersion including mixing the fine cellulose fiber-containing substance with water.