1, Base cellulose is a natural polymer, each fiber base ring contains three hydroxyl groups.
The most active hydroxyl group reaction, to produce hydroxythyl cellulose.
Soak the raw cotton staple or refined pulp in 30% liquid alkali and extract it after half an hour.
Press press to alkali water ratio of 1:2.8 for crush.
The crushed alkali cellulose is put into the reactor, closed, vacuum pumped, nitrogen filled, and repeated vacuum and nitrogen filling will completely replace the air in the kettle.
Press into the pre-cooled ethylene oxide liquid, the reaction kettle jacket into the cooling water, control the reaction of about 25℃ for about 2h, get hydroxyethyl cellulose crude products.
Crude products were washed with alcohol, neutralized with acetic acid to pH4-6, and then glyoxal was crosslinked for aging.
It was then washed with water, dehydrated by centrifugation, dried, ground, and obtained hydroxyethyl cellulose.Raw material consumption (kg / t): cotton staple or low pulp: 730-780, liquid alkali (30%): 2400, ethylene oxide: 900, alcohol (95%): 4500, acetic acid: 240, glyoxal (40%): 100-300.
2. Gas phase method:
The gas phase method is to add additives or diluents in the reaction process, and the alkali fiber and EO react in the gas phase.
The cotton fibers were impregnated and activated in 18.5% NaOH solution, then pressed, crushed and placed in the reactor.
The reactor was pumped into vacuum, nitrogen was filled 2 times, and EO was added.
The reaction 3~3.5h was available at vacuum degree 90.64kPa, 27~32℃.
3. Liquid phase method: Liquid phase method is an etherification reaction in the presence of a diluent.After alkalization and pressing.
The cotton staple was reacted with EO at 20 to 60℃ for 1~3h in the presence of dilution to obtain crude hydroxythyl cellulose.
Commonused diluents are acetone, isopropanol, tert-butanol or a mixture of them.The product remained insoluble in the dilution agent.
The two production processes of gas phase method and liquid phase method should prepare alkali cellulose in advance, which is impregnated in 18%NaOH solution at about 20℃.
After etherification reaction, neutralization, washing, drying, and crushing to obtain the final product.