Method for producing modified cellulose fiber, and modified cellulose fiber

A method for producing modified cellulose fibers having cellulose I crystal structure, comprising:

• step A:
• introducing at least one of propylene oxide, butylene oxide, allyl glycidyl ether, and iodoethane
• to cellulose fibers via an ether bond in a solvent comprising water in the presence of a base wherein the proportion which is occupied by water in the solvent comprising water is 99% by mass or more;
• and
• step B:
• introducing at least one of 2-ethylhexyl glycidyl ether, dodecyl glycidyl ether, isostearyl glycidyl ether,
• 1-iodododecane, 1,2-epoxydodecane, stearyl glycidyl ether, and 1-iodooctadecane
• to cellulose fibers via an ether bond in a solvent comprising water in the presence of a base,
• wherein the cellulose raw materials are subjected to the step A and the step B in the order of the step A and then the step B and wherein step A and step B are performed at a temperature of 40° C. to 90° C. for a period of 10 hours to 36 hours.