Hydroxypropyl methyl cellulose HPMC , also known as hydroxypromellose, is a white to off-white cellulose ether powder or granule that has cold water solubility and hot water insolubility similar to methyl cellulose. Hydroxypropyl group and methyl group are ether bond and anhydrous glucose ring of cellulose combined, is a kind of non-ionic cellulose mixed ether. It is a semi-synthetic, inactive, viscoelastic polymer commonly used as a lubricant in ophthalmology, or as an excipient or excipient in oral medicines.

1. The production process

Kraft pulp with αcellulose content of 97%, intrinsic viscosity of 720mL /g and average fiber length of 2.6mm was soaked in 49% NaOH solution at 40℃ for 50 seconds. Then the pulp was extruded to remove the excess 49% NaOH solution to get alkali cellulose. The weight ratio of (49% NaOH aqueous solution) to (solid component of pulp) in the impregnation step was 200. The weight ratio of NaOH in alkali cellulose to solid in pulp is 1.49. The alkali cellulose thus obtained (20kg) is placed in a jacked pressure reactor with internal agitation, then vacuumized and purged with nitrogen to adequately remove oxygen from the reactor. Then, the temperature in the reactor was controlled at 60℃ while the internal stirring was carried out.

Then 2.4kg dME was added and the temperature in the reactor was controlled to 60℃. After the addition of dimethyl ether, methylene chloride was added to make the molar ratio of methylene chloride to NaOH in alkaline cellulose 1.3, propylene oxide was added to make the weight ratio of propylene oxide to solid in pulp 1.97, and the temperature in the reactor was controlled from 60℃ to 80℃. After adding chloromethane and propylene oxide, the temperature in the reactor was controlled from 80℃ to 90℃. In addition, the reaction lasted for 20 minutes at 90℃.

The gas is then drained from the reactor and the crude hydroxypropyl methyl cellulose is removed from the reactor. The temperature of crude hydroxypropyl methyl cellulose was 62℃. Measure the cumulative 50% particle size in the cumulative weight based particle size distribution based on the ratio of crude hydroxypropyl methyl cellulose through the openings of the five sieving, each having a different opening size.

As a result, the average particle size of coarse particles was 6.2mm. The obtained crude hydroxypropyl methyl cellulose was introduced into a continuous biaxial kneader (KRC kneader S1, L/D = 10.2, internal volume 0.12 L, rotation speed 150rpm) at a speed of 10kg/hr, and decomposed crude hydroxypropyl methyl cellulose was obtained. As a result of similar measurements using 5 screens with different opening sizes, the average particle size was 1.4mm. Adding 80℃ hot water to the decomposed crude hydroxypropyl methyl cellulose in the tank with temperature control of the jacket. the amount of the weight ratio of the decomposed crude hydroxypropyl methyl cellulose to the total amount of the slurry is 0.1, and the slurry is obtained. The slurry was stirred at a constant temperature of 80℃ for 60 minutes.

?Then, the slurry is supplied to the rotating speed of 0.5 RPM and pre-heated rotary pressure filter (BHS Sonthofen products). The temperature of grout is 93℃. Use a pump to supply slurry, pump discharge pressure is 0.2mpa. The opening size of the rotary pressure filter is 80μm, and the filter area is 0.12m2. The slurry supplied to the rotary pressure filter is filtered through the filter and converted into filter cake. The resulting filter cake is supplied with 0.3mpa steam and 95℃ hot water with a weight ratio of 10.0 to the solid component of the washed HYDROXYpropyl methyl cellulose, which is then filtered through a filter.

Hot water is supplied through a pump at a discharge pressure of 0.2mpa. After hot water is supplied, 0.3mpa steam is supplied. Then, after washing products are removed from the filter surface by a scraper and discharged out of the washing machine. The steps from supplying slurry to discharging washed products are carried out continuously. As measured using a heat – drying hygrometer, the water content of the washed product thus discharged was 52.8%. The washed products discharged from the rotary pressure filter were dried by an air dryer at 80℃, and crushed in the Victory mill to obtain hydroxypropyl methyl cellulose.

2.Application

HPMC?product is used as thickener, dispersant, binder, emulsifier and stabilizer in textile industry. Also widely used in synthetic resin, petrochemical, ceramic, paper, leather, medicine, food, cosmetics and other industries.