Patent ID: 8709450

Claim:
A cellulose derivative comprising the chemical structure represented by the following formula (1) as a repeating unit: wherein in formula (1), R 1 , R 2 and R 3 are each independently selected from the group consisting of the following formulas (a), (b) and (c): —H (a) —CH 2 —COOM (b) —CH 2 —CO—NH—X—CO—Y—Z (c) where in formula (b), M is hydrogen, an alkali metal or an alkaline earth metal, and in formula (c), X is a C1-10 divalent hydrocarbon group, Y is a divalent group derived from polyalkylene oxide with oxygen atoms at both ends, and Z is a C1-24 hydrocarbon group or —CO—R 4 (where R 4 is a C1-23 hydrocarbon group); wherein at least one of R 1 , R 2 and R 3 comprises formula (c); wherein substituent (c) is present in a degree of substitution of 0.001 to 0.50; and wherein the cellulose derivative has a weight-average molecular weight of from 1×10 3 to 5×10 6 .