Viscosity reduction of cellulose derivatives
AssigneeThe Dow Chemical Company
InventorWen-Jiu Cheng
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Abstract
In the method of making low molecular weight cellulose ethers and esters by contacting such ethers or esters of higher molecular weight with HCl or other hydrogen halide gas, yellowing of the depolymerized or degraded product is inhibited by treating the dry material with SO.sub.2 at about ambient temperature. Residual acid in the product can be neutralized conveniently by treatment with a weak base such as ammonia or sodium bicarbonate. The low molecular weight-low viscosity product is useful in detergent compositions and in coatings for medical pills and capsules.
Claims10
In the process wherein a cellulosic ether or ester is contacted as an essentially dry powder with hydrogen halide at about ambient to 80.degree. C and is thereby converted to a corresponding ether or ester of substantially lower molecular weight, the improvement wherein the lower molecular weight product is contacted as an essentially dry powder with SO.sub.2 gas at about ambient temperature, thereby inhibiting yellowing of said product.
Dependencies are inferred from the claim text.