Hydroxypropyl methylcellulose (Hypromellose), also known as hypromellose, is a white to off-white cellulose powder or granule, which has the characteristics of being soluble in cold water and insoluble in hot water similar to methyl cellulose. The hydroxypropyl group and the methyl group are combined with the anhydrous glucose ring of the cellulose by ether bond, which is a kind of non-ionic cellulose mixed ether. It is a semisynthetic, inactive, viscoelastic polymer commonly used as a lubricant in ophthalmology, or as an excipient or vehicle in oral medicines.
preparation
The sheet pulp of kraft paper pulp obtained from pine wood with an alpha cellulose content of 97%, an intrinsic viscosity of 720 ml/g, and an average fiber length of 2.6 mm was immersed in a 49% NaOH aqueous solution at 40°C 50 seconds; the resulting pulp was then squeezed to remove excess 49% aqueous NaOH to obtain alkali cellulose. The weight ratio of (49% NaOH aqueous solution) to (solid content in pulp) in the impregnation step was 200. The weight ratio of (the NaOH content in the alkali cellulose thus obtained) and (the solid content in the pulp) was 1.49. The alkali cellulose thus obtained (20 kg) was placed in a jacketed pressure reactor with internal stirring, then evacuated and purged with nitrogen to sufficiently remove oxygen from the reactor. Next, internal stirring was performed while controlling the temperature in the reactor to 60°C. Then, 2.4 kg of dimethyl ether was added, and the temperature in the reactor was controlled to be kept at 60°C. After adding dimethyl ether, add dichloromethane so that the molar ratio of (dichloromethane) to (NaOH component in alkaline cellulose) is 1.3, and add propylene oxide to make (propylene oxide) and (in pulp) The weight ratio of the solid content) was changed to 1.97, while the temperature in the reactor was controlled from 60°C to 80°C. After the addition of methyl chloride and propylene oxide, the temperature in the reactor was controlled from 80°C to 90°C. Furthermore, the reaction was continued at 90°C for 20 minutes. Then, the gas was vented from the reactor, and then the crude hydroxypropyl methylcellulose was taken out from the reactor. The temperature of the crude hydroxypropyl methylcellulose at the time of taking out was 62 degreeC. The cumulative 50% particle size in the particle size distribution based on cumulative weight determined based on the ratio of crude hydroxypropyl methylcellulose passing through the openings of five sieves, each sieve having a different opening size, was measured. As a result, the average particle size of the coarse particles was 6.2 mm. The thus obtained crude hydroxypropyl methylcellulose was introduced into a continuous biaxial kneader (KRC kneader S1, L/D=10.2, internal volume 0.12 liters, rotational speed 150 rpm) at a rate of 10 kg/hr, and decomposition was obtained. of crude hydroxypropyl methylcellulose. The average particle size was 1.4 mm as measured similarly using sieves of 5 different opening sizes. To the decomposed crude hydroxypropyl methylcellulose in the tank with jacket temperature control, add hot water at 80°C in an amount such that ( The weight ratio of the amount of cellulose) to (total amount of the slurry) was changed to 0.1, and a slurry was obtained. The slurry was stirred at a constant temperature of 80°C for 60 minutes. Next, the slurry was fed into a preheated rotary pressure filter (product of BHS-Sonthofen) with a rotation speed of 0.5 rpm. The temperature of the slurry was 93°C. The slurry was supplied using a pump, and the discharge pressure of the pump was 0.2 MPa. The opening size of the filter of the rotary pressure filter was 80 μm, and the filtration area was 0.12 m 2 . The slurry supplied to the rotary pressure filter is converted to a filter cake by filter filtration. After supplying steam of 0.3 MPa to the cake thus obtained, hot water at 95°C was supplied in such an amount that the weight ratio of (hot water) to (solid content of hydroxypropyl methylcellulose after washing) was 10.0, Then, filter through the filter. Hot water was supplied by a pump at a discharge pressure of 0.2 MPa. After the hot water was supplied, steam of 0.3 MPa was supplied. Then, the washed product on the filter surface is removed by a scraper and discharged out of the washing machine. The steps from feeding the slurry to discharging the washed product are carried out continuously. As a result of measurement using a heat drying type hygrometer, the water content of the washed product thus discharged was 52.8%. The washed product discharged from the rotary pressure filter was dried using an air dryer at 80° C., and pulverized in an impact mill Victory mill to obtain hydroxypropyl methylcellulose.
application
This product is used as thickener, dispersant, binder, emulsifier and stabilizer in textile industry. It is also widely used in synthetic resin, petrochemical, ceramics, paper, leather, medicine, food, cosmetics and other industries.
Post time: Nov-15-2022