GB953944A - Reduction of viscosity of water-soluble non-ionic cellulose ethers - Google Patents

Abstract

The viscosities of water-soluble non-ionic cellulose ethers is reduced by treating the cellulose ether, without substantial dissolution, with an aqueous solution of hydrogen peroxide, the duration and temperature of the treatment being controlled in accordance with the amount of reduction in viscosity desired. The cellulose ether may be suspended as a slurry in a liquid in which it is insoluble at the treatment temperature and the aqueous solution of hydrogen peroxide added to the slurry. Alternatively, the cellulose ether, either dry or moistened with a liquid in which it is insoluble at the treatment temperature, may be sprayed evenly with a proportion of an aqueous solution of hydrogen peroxide insufficient to dissolve the ether and may thereafter be subjected to sufficient heat treatment to effect the required viscosity reduction. The cellulose ether may be soluble both in hot water and in water at ordinary temperatures. In the slurry method the cellulose ether may be suspended in an aqueous alcohol of sufficient alcohol concentration to prevent gelling of the ether. If the ether is soluble in water at room temperature and insoluble in hot water, it may be suspended for treatment in water maintained at a temperature above the gel point. In this case the ether may be methyl, ethyl, ethyl methyl-, hydroxyethyl methyl-, hydroxyethyl ethyl, hydroxypropyl methyl, or hydroxypropyl ethyl-cellulose. The treatment may be effected at a pH of between 5 and 9. The viscosity of the cellulose ether may be determined in a 2% aqueous solution of the ether at 20 DEG C., by the method of BSS 188 (1957). If ethyl alcohol is present with the mass of ether being treated the treatment temperature must be sufficiently high to evaporate off the alcohol before the peroxide becomes effective. The process is applicable to ethers which, although insoluble in neutral aqueous solutions, are soluble in alkaline aqueous solutions.