1,Alkaline methyl cellulose is a natural polymer. Each chemical fiber base ring has three hydroxyl groups, which are reflected by the most hydroxyl groups and converted into hydroxyethyl cellulose. The raw cotton linter or special pulp is infiltrated into 30% protopine, and after 30 minutes, the press is removed. Squeezed until the proportion of edible alkali is 1: 2.8, and crushed. The crushed alkali methyl cellulose was put into the reaction tank, sealed, vacuum-packed, nitrogen-filled, and repeated vacuum-packed nitrogen-filled to completely replace the gas in the kettle. The pre-cooled ethylene oxide liquid was pressed in, the collet of the reaction tank was put into the cooling circulating water, and it was manipulated to reflect up and down at 25 ° C for 2h to obtain a crude hydroxyethyl cellulose. The crude product was washed with ethanol, and formic acid was added to pH 4-6, and then glyoxal was added for chemical cross-linking and embrittlement. It was then washed with tap water, filtered off with suction, dried, and pulverized to obtain hydroxyethyl cellulose. Raw material consumption (kg / t): cotton linter or low-meal pulp: 730-780, tablet alkali (30%): 2400, ethylene oxide: 900, ethanol (95%): 4500, glacial acetic acid: 240, ethyl acetate Dialdehyde (40%): 100-300.
2. Gas phase method: The gas phase method is to add a preservative or diluent in the whole process of reflection. The alkali chemical fiber and EO are reflected in the gas phase. The flax fiber is pre-soaked and activated in 18.5% NaOH solution, and then squeezed and crushed and placed in a tube reactor. The tubular reactor was evacuated, filled with nitrogen twice, and EO was added. The vacuum value was 90.64kPa, and the temperature was 27 ～ 32 ° C. It was obtained after 3 ～ 3.5h.
3. High performance liquid phase method: High performance liquid phase method is to reflect etherification in the presence of diluent. After the cotton linter was alkalized and pressed, it was reflected with EO at 20-60 ° C for 1 to 3 hours in the presence of a diluent to obtain a crude hydroxyethyl cellulose. Common diluents are toluene, isopropanol, tert-butanol or their compounds. The substance remains insoluble in the diluent.
The gas-phase method and the high-performance liquid-phase method require the preparation of alkali methyl cellulose in advance. The methyl cellulose is pre-soaked in an 18% NaOH aqueous solution at 20 ° C for deoiling. After the etherification reaction, Closing, cleaning, dryness, and crushing to get goods.