Focus on Cellulose ethers

Product characteristics and synthesis method of hydroxypropyl methylcellulose

1. Product characteristics

Chemical structure and composition Hydroxypropyl methylcellulose (HPMC) is a cellulose derivative obtained by chemical modification. It is made from natural cellulose through ethylation, methylation and hydroxypropylation reactions. In its molecular structure, the cellulose skeleton is connected by β-D-glucose units through β-1,4 glycosidic bonds, and the side groups are composed of methyl (-OCH3) and hydroxypropyl (-C3H7OH).

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Physical properties

Solubility: KimaCell®HPMC is insoluble in water and organic solvents, but can form a transparent colloidal solution in cold water. Its solubility is proportional to the content of hydroxypropyl and methyl in the molecule.

Viscosity: The solution of HPMC has a certain viscosity, which usually increases with the increase of molecular weight. Its viscosity range is wide and can be adjusted according to demand to meet the use requirements of different fields.

Thermal stability: HPMC has high thermal stability, can withstand high temperature environments, and is not easy to decompose during heating.

Functional properties

Film-forming property: HPMC has good film-forming property and can form a transparent and uniform film structure in aqueous solution, so it is often used as a matrix material in drug controlled release systems.

Emulsification and stability: Due to its surface activity, HPMC is often used in emulsions, suspensions, gels and other formulations to improve the stability of the formulation.

Thickening and water retention: HPMC has good thickening properties and can increase the viscosity of the solution at low concentrations. In addition, it can effectively retain water, thereby improving the water retention capacity of the product, and is commonly found in cosmetics and daily chemicals.

Nonionicity: As a nonionic surfactant, HPMC can remain stable in acid, alkali or salt solutions and has strong adaptability.

Application areas

Pharmaceutical industry: As a drug carrier, it is used to prepare controlled-release, sustained-release and extended-release preparations; it is also used in the preparation of tablets, capsules and topical ointments for drugs.

Construction industry: As an additive, it improves the construction performance of building materials such as mortar and coatings, and improves adhesion, fluidity and water retention.

Food industry: used as thickener, emulsifier and gelling agent in seasoning, jelly, ice cream and other products.

Cosmetics industry: used in lotions, skin creams, shampoos and other products to provide viscosity and stability.

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2. Synthesis method

Cellulose extraction The synthesis process of HPMC first needs to extract cellulose from natural plant fibers (such as wood, cotton, etc.). Generally, impurities and non-cellulose components such as lignin in the raw materials are removed by chemical or mechanical methods. The cellulose extraction process mainly includes soaking, alkali treatment, bleaching and other steps.

Etherification reaction of cellulose The extracted cellulose undergoes etherification reaction and adds substituents such as methyl and hydroxypropyl. Etherification reaction is usually carried out in alkaline solution, and commonly used etherifying agents include methyl chloride (CH3Cl), propylene oxide (C3H6O), etc.

Methylation reaction: Cellulose is reacted with a methylating agent (such as methyl chloride) so that some hydroxyl groups (-OH) in the cellulose molecules are replaced by methyl groups (-OCH3).

Hydroxypropylation reaction: Introducing hydroxypropyl (-C3H7OH) groups into cellulose molecules, the commonly used reagent is propylene oxide. In this reaction, some of the hydroxyl groups in the cellulose molecules are replaced by hydroxypropyl groups.

Reaction condition control

Temperature and time: The etherification reaction is usually carried out at a temperature of 50-70°C, and the reaction time is between a few hours and more than ten hours. Too high a temperature may cause cellulose degradation, and too low a temperature will result in low reaction efficiency.

pH value control: The reaction is usually carried out under alkaline conditions, which helps to improve the efficiency of the etherification reaction.

Etherification agent concentration: The concentration of the etherification agent has an important influence on the properties of the reaction product. A higher etherification agent concentration can increase the degree of hydroxypropyl or methylation of the product, thereby adjusting the performance of KimaCell®HPMC.

Purification and drying After the reaction is completed, the product usually needs to be washed with water or extracted with a solvent to remove unreacted reagents and by-products. The purified HPMC is dried to obtain a powder or granular final product.

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Molecular weight control During the synthesis process, the molecular weight of HPMC can be controlled by adjusting the reaction conditions (such as temperature, time, and reagent concentration). HPMC with different molecular weights differ in solubility, viscosity, application effect, etc., so in practical applications, the appropriate molecular weight can be selected according to needs.

As a multifunctional polymer material, HPMC is widely used in medicine, construction, food and cosmetics. Its excellent thickening, emulsification, water retention and film-forming properties make it an important industrial raw material. The synthesis method of HPMC is mainly through the etherification reaction of cellulose. The specific reaction conditions (such as temperature, pH value, reagent concentration, etc.) need to be finely controlled to obtain products that meet the requirements. In the future, the functions of HPMC may be further expanded in many fields.


Post time: Jan-27-2025
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