A process of preparing alkylhydroxyalkylcellulose (e.g.,
methylhydroxyethylcellulose and methylhydroxypropylcellulose) by reaction
of cellulose in the presence of alkali metal hydroxide with an alkylating
agent and a hydroxyalkylating agent is described. The process includes:
(a) alkalizing cellulose by means of 0.9 to 2.9 equivalents of an alkali
metal hydroxide I/AGU of the cellulose in the form of an aqueous alkali
metal hydroxide solution, in the presence of a suspension medium
containing at least 0.2 equivalents of an alkylating agent I/AGU of the
cellulose; (b) reacting the alkalized cellulose of step (a) with
alkylating agent I and a hydroxyalkylating agent at a temperature above
65.degree. C.; (c) adding additional alkali metal hydroxide 11 in the
form of an aqueous alkali metal hydroxide solution; and (d) adding
additional alkylating agent 11 in an amount of at least the absolute
value of the difference between (i) the number of equivalents of
alkylating agent I/AGU of the cellulose already added, and (ii) the total
number of equivalents of alkali metal hydroxide/AGU of the cellulose
added. Additional alkylating agent 11 is not added in step (d) if (i) the
number of equivalents of alkylating agent I/AGU of the cellulose already
added exceeds (ii) the total number of equivalents of alkali metal
hydroxide/AGU of the cellulose already added. In a further step (e), the
alkylhydroxyalkylcellulose is isolated from the reaction mixture. The
isolated alkylhydroxyalkylcellulose may be optionally purified.