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[Chemical Knowledge]：Production process and preparation method of hydroxypropyl methyl cellulose

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Hydroxypropyl methyl cellulose (HPMC) is an important polymer compound, which has good water solubility, low toxicity, tasteless and colorless characteristics, and has been widely used in construction, medicine, food, daily chemical and other industries. This article will introduce the production process and preparation method of HPMC.

1. production process

1, deacetylation process

deacetylation process is one of the most common process of HPMC production. The main steps are: pretreatment of wood cellulose and lye to turn it into a filamentous substance; then acetylation reaction with chloroacetic acid; and finally deacetylation reaction of the reaction product using lye to obtain the finished HPMC.

2. Acid Hydrolysis Process
The
acid hydrolysis process is another common HPMC production process. The main steps include: using concentrated sulfuric acid to hydrolyze wood cellulose to obtain cellulose acid; then esterifying cellulose acid with methanol to obtain methyl etherified cellulose; and finally using sodium hydroxide aqueous solution to neutralize the product to obtain HPMC.

2. preparation method

1. Gel preparation method

The gel preparation method is to react cellulose and sodium hydroxide to obtain cellulose sodium salt, and then react with chloroacetate to obtain acetylated cellulose, and finally use sodium hydroxide aqueous solution for deacetylation to obtain HPMC. The HPMC prepared by this method has the characteristics of relatively narrow molecular mass distribution and relatively stable.

2, solvent-free preparation method

solvent-free preparation method is to prepare cellulose sodium salt by reacting cellulose with sodium hydroxide under solvent-free or low solvent conditions, and then esterifying with chloroacetic acid ester to prepare HPMC by direct deacetylation reaction. The HPMC prepared by this method can avoid the pollution of organic solvent to the environment and the residue of the product.

In summary, HPMC is an important polymer compound and has been widely used in many fields. With the continuous development and progress of science and technology, its production process and preparation methods will continue to be iteratively updated and improved, in order to promote the development and progress of human society continue to inject new vitality.