PROCESS OF PREPARING ALKYLHYDROXYALKYLCELLULOSE

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 DEG 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 cellul ose 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. Se describe un procedimiento para la obtencion de alquilhidroxial-quilcelulosas, a partir de la reaccion de la celulosa en presencia de alcalis con agentes de alquilacion y agentes de hidroxialquilacion, caracterizado porque a) la celulosa se alcaliniza con 0,9 hasta 2,9 eq. de hidroxido alcalino I/AGU, empleado como lejia acuosa, en presencia de un agente de suspension, que contiene, como minimo, 0,2 eq./AGU de agente de alquilacion I, b) la celulosa alcalinizada se hace reaccionar con agentes de alquilacion y con el agente de hidroxialquilacion a una temperatura mayor que 65 degree C y c) nuevamente se dosifica hidroxido alcalino, empleado en forma de lejia acuosa, y d) se dosifica agente de alquilacion en una cantidad correspondiente al menos a la diferencia entre los eq., ya dosificados, de agente de alquilacion VAGU y los eq. dosificados en total de hidroxido alcalino/AGU, no llevandose a cabo ninguna dosificacion en el caso en que la cantidad de eq. de