Focus on Cellulose ethers

Synthesis and product characteristics of hydroxypropyl methylcellulose

Hydroxypropyl methylcellulose (HPMC) is a non-ionic cellulose ether made from natural cellulose through chemical modification. It is widely used in the fields of construction, medicine, food and cosmetics. Its synthesis process and product characteristics give it unique performance and can meet a variety of industrial needs.

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1. Synthesis of hydroxypropyl methylcellulose

The preparation of KimaCell®HPMC uses natural cellulose as raw material and chemically modifies it through alkali treatment and etherification reaction. The specific synthesis process includes the following steps:

 

Alkalization of cellulose

Cellulose raw materials (such as cotton pulp or wood pulp) are mixed with sodium hydroxide solution and alkalized at a certain temperature and pressure to produce alkali cellulose. The alkalization process expands the cellulose molecular chain and increases its reactivity with the etherifying agent.

 

Etherification reaction

Alkali cellulose is reacted with formaldehyde and propylene glycol propylene oxide to produce hydroxypropyl methylcellulose. During the reaction, methylation and hydroxypropylation reactions occur simultaneously, replacing part of the hydroxyl groups on the cellulose molecular chain, thereby forming HPMC with a specific degree of substitution (DS) and molar substitution (MS).

 

Neutralization and washing

After the reaction is completed, an acidic solution is added to neutralize the reaction mixture, and then washed with water to remove unreacted raw materials and by-products to obtain pure HPMC.

 

Drying and crushing

The wet HPMC is dried to a low moisture content and crushed into powder to obtain the final product. The particle size of the product can be adjusted according to application requirements.

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2. Product characteristics of hydroxypropyl methylcellulose

HPMC has unique physical and chemical properties, which makes it excellent in a variety of applications:

Excellent water solubility

HPMC can be quickly dissolved in cold water to form a transparent colloidal solution, and its solubility is not affected by water hardness. HPMC is insoluble in hot water, but it can restore solubility after the water is cooled. This property makes it suitable for scenes that require thermal gelation performance.

Stable chemical properties

HPMC is a non-ionic substance with good tolerance to acids, alkalis and salts, and can remain stable under different pH conditions.

Good thickening and adhesion properties

The aqueous solution of HPMC has a significant thickening effect, and its viscosity increases with the increase of concentration and molecular weight. Its adhesion and film-forming properties make it perform well in coatings and adhesives.

Excellent thermal gelation properties

HPMC solution undergoes reversible gelation when heated and returns to liquid state after cooling. This thermal gelation property is widely used in building materials (such as cement mortar) to improve construction performance.

Non-toxic and biocompatible

Since HPMC is derived from natural cellulose and has good biocompatibility and safety, it is widely used in food additives and pharmaceutical excipients, such as the matrix material of drug controlled-release tablets.

Flexibility to adjust performance

The degree of substitution (DS and MS) of KimaCell®HPMC can be adjusted according to demand, thereby changing its solubility, viscosity and gelation temperature and other properties to meet the technical requirements of different applications.

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3. Application fields and prospects

HPMC can be used as a mortar thickener and water reducer in the construction field, as a drug sustained-release agent in the pharmaceutical field, and as an emulsifier and stabilizer in the food industry. With the advancement of green chemistry and sustainable development, the low-energy synthesis and high-performance development of HPMC will become the focus of future research.

 

Hydroxypropyl methylcellulose has become an indispensable and important material in modern industry and daily life with its superior performance and versatility.

 


Post time: Jan-18-2025
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