The invention belongs to the field of
polymer chemistry, and relates to a preparation method of
cellulose acetate. The
cellulose acetate obtained by the method has low
turbidity and high
viscosity. The method comprises the following steps of: A, activating 1 weight part of
cellulose by using 8 to 20 weight parts of glacial
acetic acid at the temperature of between 20 and 60 DEG C; B, adding 0.005 to 0.05 weight part of catalyst and 3 to 6 weight parts of
acetic anhydride; C, adding 0.5 to 1.5 weight parts of high-concentration
acetic acid solution at the temperature of between 10 and 25 DEG C, and reacting till the content of the
acetic acid is 60.5 to 62.5 percent, wherein the high-concentration
acetic acid solution is 80
mass percent acetic acid; D, adding 0.5 to 1.5 weight part of 5 to 15 weight percent
aqueous solution of acetate, and reacting for 1 to 3 hours at the temperature of between 20 and 50 DEG C; and E, filtering,
settling and granulating. The preparation method is simple and convenient in the production process and easy in operation; the reaction time is shortened; the prepared product has high substitution degree, namely the content of the acetic acid is more than or equal to 60.0 percent; the product has high
viscosity, namely the falling ball
viscosity is more than or equal to 70 seconds; and the
cellulose acetate is particularly suitable for manufacturing polarizing films in optical elements.