Treat the refined cotton cellulose with lye at 35-40 ℃ for half an hour, press, crush the cellulose, and properly age at 35 ℃, so that the average polymerization degree of the alkali fiber obtained is within the required range. Put the alkali fiber into the etherification kettle, add propylene oxide and methyl chloride in turn, etherify at 50-80 ℃ for 5h, and the maximum pressure is about 1.8MPa. Then add proper amount of hydrochloric acid and oxalic acid to wash the material in 90 ℃ hot water to make the volume expand. Dehydrate with a centrifuge and wash to neutral. When the water content in the material is less than 60%, dry it to less than 5% with a hot air flow of 130 ℃, and finally crush it through a 20-mesh sieve to obtain the finished product.
