Views: 0 Author: Site Editor Publish Time: 2022-09-21 Origin: Site
Hydroxypropyl methyl cellulose (HPMC), also known as hypromellose, cellulose hydroxypropyl methyl ether, is made of highly pure cotton cellulose as raw material and specially etherified under alkaline conditions. have to.
Hydroxypropyl methylcellulose has thermal gel properties, easily soluble in cold water, but difficult to dissolve in hot water. But its gelation temperature in hot water is significantly higher than that of methyl cellulose. The dissolution in cold water is also greatly improved compared with methyl cellulose.
The aqueous solution forms gel and precipitates after heating, and dissolves again after cooling. The gel temperature of products with different specifications is different. The solubility changes with the viscosity. The lower the viscosity, the greater the solubility. The properties of HPMC of different specifications are different. The dissolution of HPMC in water is not affected by the pH value. Bulk density: 0.25-0.70g/ (usually about 0.4g/), specific gravity 1.26-1.31. Discoloration temperature: 180-200℃, carbonization temperature: 280-300℃. The methoxy value is 19.0% to 30.0%, and the hydroxypropyl value is 4% to 12%. Viscosity (22℃, 2%) 5～200000mPa.s. Gel temperature (0.2%) 50-90 ℃. HPMC has the characteristics of thickening ability, salt expulsion, pH stability, water retention, dimensional stability, excellent film-forming properties, and a wide range of enzyme resistance, dispersibility and cohesiveness.
Hydroxypropyl methylcellulose is stable to acid and alkali, and its aqueous solution is very stable in the range of pH=2~12. Caustic soda and lime water have little effect on its performance, but alkali can speed up its dissolution and increase the viscosity. Hydroxypropyl methylcellulose is stable to common salts, but when the concentration of the salt solution is high, the viscosity of the hydroxypropyl methylcellulose solution tends to increase.