FIELD: production of plastics; chemistry of high molecular weight compounds. SUBSTANCE: plasticized cellulose acetate (A) comprises grafted oligomer of cyclic ester and oligomer of cyclic ester (B) which tail group is affected by esterification with alcohol and/or with its derivative having at least one free hydroxyl group, its boiling point is at least about 120 C and its melting point is not more 180 C. Mass ratio of A and B is so that 0,3 ≤ A/(A+B) ≤ 0,95.. Plasticized cellulose acetate is prepared by feeding of oligomer B as product of interaction of cyclic ester with mono- and/or polyfunctional alcohol and/or with its derivative comprising at least one free group into polymer melt comprising free hydroxyl group. The process is carried out in the presence of catalyst. Or said cellulose acetate is prepared by feeding cyclic ester and said alcohol and/or its derivative together with catalyst into melt of said polymer. EFFECT: improved quality of desired product. 26 cl, 6 tbl
