Preparation of HPMC from hydroxypropyl methylcellulose

There are two technical routes to prepare HPMC, one is intermittent and the other is continuous. The batch process is that the cellulose is alkalized, pressed, crushed and matured, and then etherified with etherifying agent in autoclave to obtain crude products. In the process of etherification and alkalization, cellulose is continuously crushed in a high-pressure reactor and is not required to be crushed continuously in a reactor. After neutralization, iron removal, cooking and washing, the finished product is obtained.

Hydroxypropylmethyl HPMC was prepared by alkalization of cellulose in the presence of organic solvents, followed by etherification with methyl chloride and propylene oxide.

The conditions for preparing HPMC in laboratory are as follows. Then, 106G 50% NaOH aqueous solution was added. After heating for 30 min, the water and methanol were distilled and removed. Then 120g of chloromethane and 10g of propylene oxide were added to etherify at 60 ~ 120 ℃ for 1.5h to obtain hydroxypropylmethylcellulose HPMC. The degree of methoxy substitution of HPMC was obtained DS = 2.0, degree of substitution Ms = 0.1, soluble in water. The preparation methods of HPMC are mostly liquid phase method. The uniformity of the product is good.

The concentration of alkali liquor used in the preparation of alkali cellulose is generally in the range of 35% ~ 50%, and the mass ratio of cellulose to alkali liquor is 1: (0.5 ~ 2.6). The smaller amount of alkali liquor is that the alkali liquor is sprayed into it and etherified with cellulose without pressing. The minimum amount of alkali liquor is that 50% alkali liquor is added into a large amount of inert solvent, and then cellulose is added to prepare alkali cellulose. The inert solvent can make the heat conduction uniform and easy to control the temperature in the reaction process. After the reaction is completed, most of the water and organic compounds produced by the side reaction can be removed by azeotropy.

The method of preparing HPMC with different contents of methoxy, hydroxypropyl and different viscosity can control the ratio of cellulose to different amount of alkali and water, and different aging time and temperature. The alkali cellulose is first prepared, and then the alkali cellulose is reacted with different proportion of chloromethane and propylene oxide at different temperature and time Products. Most of the reaction temperature is raised by stages over a certain period of time, and finally rises to 60 ~ 80 ℃ or even as high as 80 ~ 90 ℃; the reaction is carried out under natural pressure (above 2MPa); the reaction time is generally about 4 ~ 10h, and the reaction time and temperature can be determined according to the requirements of the finished products.

Adding steps of etherifying agents chloromethane and propylene oxide: there are two-step adding two etherifying agents respectively, one-step adding at one time, and adding two etherifying agents at the same time. After reaction for a period of time, one of them is added. At present, most of the methods are added at the same time, which is more convenient.

For more information, please pay attention to Shandong chuangyao Biotechnology Co., Ltd www.cyhuagong.com  。