Cellulose ether (CE) is a class of derivatives obtained by chemically modifying cellulose. Cellulose is the main component of plant cell walls, and cellulose ethers are a series of polymers generated by etherification of some hydroxyl groups (–OH) in cellulose. They are widely used in many fields such as building materials, medicine, food, cosmetics, etc., and are widely used in various industries due to their unique physical and chemical properties and versatility.
1. Classification of cellulose ethers
Cellulose ethers can be divided into different types according to the types of substituents in the chemical structure. The most common classification is based on the difference in substituents. Common cellulose ethers are as follows:
Methyl cellulose (MC)
Methyl cellulose is generated by replacing the hydroxyl part of the cellulose molecule with methyl (–CH₃). It has good thickening, film-forming and bonding properties and is commonly used in building materials, coatings, pharmaceuticals and food industries.
Hydroxypropyl methylcellulose (HPMC)
Hydroxypropyl methylcellulose is a common cellulose ether, which is widely used in building materials, medicine, daily chemicals and food fields due to its better water solubility and chemical stability. HPMC is a nonionic cellulose ether with the properties of water retention, thickening and stability.
Carboxymethyl cellulose (CMC)
Carboxymethyl cellulose is an anionic cellulose ether generated by introducing carboxymethyl (–CH₂COOH) groups into cellulose molecules. CMC has excellent water solubility and is often used as a thickener, stabilizer and suspending agent. It plays an important role in food, medicine and cosmetics.
Ethyl cellulose (EC)
Ethyl cellulose is obtained by replacing the hydroxyl group in cellulose with ethyl (–CH₂CH₃). It has good hydrophobicity and is often used as a film coating agent and controlled release material in the pharmaceutical industry.
2. Physical and chemical properties of cellulose ethers
The physical and chemical properties of cellulose ethers are closely related to factors such as the type of cellulose ether, the type of substituent and the degree of substitution. Its main properties include the following:
Water solubility and solubility
Most cellulose ethers have good water solubility and can be dissolved in cold or hot water to form a transparent colloidal solution. For example, HPMC, CMC, etc. can be quickly dissolved in water to form a high-viscosity solution, which is widely used in application scenarios with functional requirements such as thickening, suspension, and film formation.
Thickening and film-forming properties
Cellulose ethers have excellent thickening properties and can effectively increase the viscosity of aqueous solutions. For example, adding HPMC to building materials can improve the plasticity and workability of mortar and enhance anti-sagging properties. At the same time, cellulose ethers have good film-forming properties and can form a uniform protective film on the surface of objects, so they are widely used in coatings and drug coatings.
Water retention and stability
Cellulose ethers also have good water retention capacity, especially in the field of building materials. Cellulose ethers are often used to improve the water retention of cement mortar, reduce the occurrence of mortar shrinkage cracks, and extend the service life of mortar. In the food field, CMC is also used as a humectant to delay food drying.
Chemical stability
Cellulose ethers show good chemical stability in acid, alkali and electrolyte solutions, and can maintain their structure and function in a variety of complex chemical environments. This allows them to be used in a variety of industries without interference from other chemicals.
3. Production process of cellulose ether
The production of cellulose ether is mainly prepared by etherification reaction of natural cellulose. The basic process steps include alkalization treatment of cellulose, etherification reaction, purification, etc.
Alkalization treatment
First, natural cellulose (such as cotton, wood, etc.) is alkalized to convert the hydroxyl part in cellulose into highly active alcohol salts.
Etherification reaction
The cellulose after alkalization reacts with an etherifying agent (such as methyl chloride, propylene oxide, etc.) to generate cellulose ether. Depending on the reaction conditions, different types of cellulose ethers can be obtained.
Purification and drying
The cellulose ether generated by the reaction is purified, washed and dried to obtain a powder or granular product. The purity and physical properties of the final product can be controlled by subsequent processing technology.
4. Application fields of cellulose ether
Due to the unique physical and chemical properties of cellulose ethers, they are widely used in many industries. The main application fields are as follows:
Building materials
In the field of building materials, cellulose ethers are mainly used as thickeners and water retaining agents for cement mortar and gypsum-based products. Cellulose ethers such as HPMC and MC can improve the construction performance of mortar, reduce water loss, and thus enhance adhesion and crack resistance.
Medicine
In the pharmaceutical industry, cellulose ethers are widely used as coating agents for drugs, adhesives for tablets, and controlled-release materials. For example, HPMC is often used to prepare drug film coatings and has a good controlled-release effect.
Food
CMC is often used as a thickener, emulsifier, and stabilizer in the food industry. It is widely used in beverages, dairy products, and baked goods, and can improve the taste and moisturizing properties of food.
Cosmetics and daily chemicals
Cellulose ethers are used as thickeners and emulsifiers and stabilizers in cosmetics and daily chemicals, which can provide good consistency and texture. For example, HPMC is often used in products such as toothpaste and shampoo to give them a viscous feel and a stable suspension effect.
Coatings
In the coatings industry, cellulose ethers are used as thickeners, film formers, and suspending agents, which can enhance the construction performance of coatings, improve leveling, and provide good paint film quality.
5. Future development of cellulose ethers
With the increasing demand for environmental protection, cellulose ether, as a derivative of natural renewable resources, has broad development prospects. Its biodegradability, renewability and versatility make it expected to be more widely used in the fields of green materials, degradable materials and smart materials in the future. In addition, cellulose ether also has further research and development potential in high value-added fields such as biomedical engineering and advanced materials.
As an important chemical product, cellulose ether has a wide range of application value. With its excellent thickening, water retention, film-forming and good chemical stability, it plays an irreplaceable role in many fields such as construction, medicine, and food. In the future, with the continuous advancement of technology and the promotion of environmental protection concepts, the application prospects of cellulose ether will be broader and make greater contributions to promoting the sustainable development of various industries.
Post time: Sep-24-2024