Batchwise prodn. of sodium carboxymethyl cellulose - from cellulose, sodium hydroxide and sodium chloroacetate

摘要

Batchwise prodn. of sdoium carboxymethyl cellulose is carried out by homogenising with shearing forces and heating at 60-90 degrees C a mixt. contg. (in pts. wt.): cellulose 1, NaOH 0.2-0.6, CH2ClCOONa 0.5-1.75, diluting agent (pref. isopropano) 7-22, with addition of water in an amt. not exceeding 50 wt. % of the diluting agent. This process is improved in that the formation of the alkali cellulose and admixture of CH2ClCOONa is carried out at a temp. below 40 degrees C with continuous circulation through a homogenising compartment, where the residence time is less than 1/10 of the residence time if the reaction zone. The mixt. is then heated at 60-90 degrees C, while the circulation through the homogenising compartment is continued as described above. After the completion of the reaction, the sodium carboxymethyl cellulose is sepd., and the liquid components of the mixt. are used in the prepn. of the next batch. The reaction proceeds evenly through the whole mixt. so that a uniform degree of substitution is attained.