Preparation Method of Hydroxypropyl Methyl Cellulose
Production method one:
The industrial production method of hydroxypropyl methylcellulose is to cook plant raw materials with a sulfite solution or an alkali solution, mainly to remove lignin, which are called a sulfite method and an alkali method, respectively. The resulting materials are called sulfite pulp and alkaline pulp.
The residual lignin is then further removed by bleaching, and the resulting bleached pulp can be used in papermaking. Further removal of hemihydroxypropyl methyl cellulose can be used as a raw material for hydroxypropyl methyl cellulose derivatives.
Production method two: mashing fiber plant material and inorganic acid into a slurry to make α-hydroxypropyl methylcellulose and then treating to partially depolymerize the hydroxypropyl methylcellulose and then removing the non-crystalline portion and purified.
Production method three: decocting the selected industrial wood pulp board and then sending it to
a reaction kettle to which 1% to 10% hydrochloric acid (amount of 5% to 10%) has been added for temperature hydrolysis and the temperature is 90 to 100 ° C and the hydrolysis The time is 0.5 to 2 hours. After the reaction is completed, it’s cooled and sent to the neutralization tank, adjusted to neutrality with liquid alkali. After filtration, the filter cake is dried at 80 to 100 ° C and finally crushed to obtain the product.
Production method four: hydroxypropyl methyl cellulose made from wood pulp or cotton pulp. Refined after bleaching and mechanical dispersion.
At normal temperature, hydroxypropyl methylcellulose is neither soluble in water nor in common organic solvents, such as alcohol, ether, acetone, benzene, etc. It’s also insoluble in dilute alkali solutions.
Therefore, it’s relatively stable at room temperature due to the existence of hydrogen bonds between the hydroxypropyl methylcellulose molecules. Hydroxypropyl methylcellulose is insoluble in water, organic solvents such as ethanol and ether and can be dissolved in copper ammonia Cu (NH3) 4 (OH) 2 solution and copper ethylenediamine [NH2CH2CH2NH2] Cu (OH) 2 solution.