Preparation method of hydroxyethyl cellulose

1. Alkali methyl cellulose is a natural polymer with three hydroxyl groups on each chemical fiber ring, which react with hydroxyl groups to form hydroxyethyl cellulose. Soak the raw material cotton short fibers or specially made pulp in 30% caustic soda, remove and press after thirty minutes. Squeeze until the proportion of edible alkali reaches 1:2.8, and then carry out crushing. The broken alkali methyl cellulose is invested in a reaction tank, sealed, vacuum packed, nitrogen filled, and repeatedly vacuum packed to completely replace the gas inside the reactor. Inject pre cooled ethylene oxide liquid, clamp the reaction tank barrel into the cooling circulating water, and adjust the temperature to around 25 ℃ for 2 hours to obtain crude hydroxyethyl cellulose. Wash the crude product with ethanol, add formic acid to pH 4-6, and then chemically crosslink and brittleness it with formaldehyde. Subsequently, clean with tap water, filter and dehydrate, dry vigorously, grind into powder, and obtain hydroxyethyl cellulose. Raw material consumption (kg/t): Cotton short fibers or low pulp: 730-780, caustic soda (30%): 2400, ethylene oxide: 900, ethanol (95%): 4500, glacial acetic acid: 240, formaldehyde (40%): 100-300.

2. Gas phase method: The gas phase method involves adding preservatives or diluents throughout the entire process, with alkali chemical fibers and EO reflected in the gas phase. Pre soak and activate linen fibers in 18.5% NaOH solution, then press and crush them before placing them in a tubular reactor. Vacuum the tubular reactor, fill it with nitrogen twice, add EO, and reflect it at a vacuum value of 90.64kPa and 27-32 ℃ for 3-3.5 hours.

3. High performance liquid phase method: High performance liquid phase method carries out etherification reaction in the presence of diluent. After alkalization and pressing, cotton short fibers are reacted with EO in the presence of a diluent at 20-60 ℃ for 1-3 hours to obtain crude hydroxyethyl cellulose. Common diluents include toluene, isopropanol, tert butanol, or their compounds. Substances remain insoluble in diluents.

The two production processes of gas-phase method and 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 around 20 ℃ for degreasing, etherification reaction, and then subjected to neutralization, cleaning, drying, and crushing to obtain the product.