Preparation of hydroxyethyl cellulose

1. Alkaline cellulose is a natural polymer. Each fiber base ring contains three hydroxyl groups. The most active hydroxyl groups react to produce hydroxyethyl cellulose. Soak the raw cotton linters or refined pulp in 30% liquid caustic soda, take it out and squeeze after half an hour. Squeeze until the ratio of alkaline water reaches 1:2.8, then crush. The pulverized alkali cellulose is put into the reaction kettle, sealed, evacuated, filled with nitrogen, and vacuum filled with nitrogen is repeated to completely replace the air in the kettle. Press into the pre-cooled ethylene oxide liquid, and pass cooling water into the jacket of the reactor, and control the reaction at about 25°C for 2 hours to obtain crude hydroxyethyl cellulose. The crude product is washed with alcohol, neutralized with acetic acid to pH 4-6, and then cross-linked with glyoxal for aging. Then it is washed with water, dewatered by centrifugation, dried and pulverized to obtain hydroxyethyl cellulose. Raw material consumption (kg/t): cotton linters or low pulp: 730-780, liquid caustic soda (30%): 2400, ethylene oxide: 900, alcohol (95%): 4500, acetic acid: 240, ethylene two Aldehydes (40%): 100-300.

2. Gas phase method: In the gas phase method, additives or diluents are added during the reaction, and the alkali fiber and EO react in the gas phase. The cotton fiber is immersed in 18.5% NaOH solution, activated, squeezed, crushed, and placed in the reactor. The reactor is evacuated into a vacuum, nitrogen is filled twice, EO is added, and the reaction is carried out at a vacuum of 90.64 kPa and 27-32°C for 3 to 3.5 hours.

3. Liquid phase method: The liquid phase method is to carry out etherification reaction in the presence of diluent. After being alkalized and squeezed, the cotton linters are reacted with EO at 20-60°C for 1 to 3 hours in the presence of a diluent to obtain crude hydroxyethyl cellulose. Commonly used diluents are acetone, isopropanol, tert-butanol or their mixtures. The product remains insoluble in the diluent.

The two production processes of gas phase method and liquid phase method need to prepare alkali cellulose in advance, that is, the cellulose is immersed in 18% NaOH solution at about 20°C for degreasing, after etherification, it is neutralized, washed, dried, and pulverized to obtain Final product.