Patent ID: 8378091

Claim:
A cellulose derivative having a molecular weight of 5×10 3 to 5×10 6 Daltons and comprising a repeating unit represented by the following formula (1): wherein R 1 , R 2 and R 3 are each independently selected from the group consisting of the following formulas (a), (b), (c) and (d): (X in the formula (c) is an alkali metal, and R 4 CO and R 5 CO in the formula (d) are each an oleoyl group, with the proviso that when the equivalents of (a), (b), (c) and (d) per monosaccharide unit are represented by E(a), E(b), E(c) and E(d), respectively, E(a)+E(b)+E(c)+E(d)=3, E(b)+E(c)+E(d)=0.3 to 3 and E(d)/{E(b)+E(c)+E(d)}=0.001 to 1).