Hydroxyethyl cellulose (HEC) is a water-soluble nonionic cellulose ether, and its main source is natural cellulose. Natural cellulose is widely present in plants and is the main component of plant cell walls. Specifically, hydroxyethyl cellulose is made by chemically reacting natural cellulose with ethylene oxide under alkaline conditions. This chemical reaction process is usually called ethoxylation, and the result is that the hydroxyl groups on the natural cellulose molecules are partially or completely replaced to form hydroxyethyl cellulose with ethoxy groups.
The following are the specific steps of the preparation process of hydroxyethyl cellulose:
Source of cellulose: Cellulose is usually extracted from plant materials such as cotton and wood. The extracted cellulose is purified and bleached to remove impurities such as lignin, hemicellulose and other non-cellulose components to obtain high-purity cellulose.
Alkalinization treatment: Mix cellulose with concentrated sodium hydroxide (NaOH) solution, and the hydroxyl groups in cellulose react with sodium hydroxide to produce sodium cellulose. In this process, the cellulose molecular structure expands to a certain extent, making it easier to react with ethylene oxide.
Ethoxylation reaction: Alkalized sodium cellulose is mixed with ethylene oxide (C2H4O) at a certain temperature and pressure. The ring structure of ethylene oxide opens to form ethoxy groups (-CH2CH2OH), which combine with the hydroxyl groups on the cellulose molecules to form hydroxyethyl cellulose. This reaction process can be carried out to varying degrees, resulting in hydroxyethyl cellulose with different degrees of substitution.
Post-treatment: The product after the reaction usually contains unreacted alkali, solvents and other by-products. In order to obtain pure hydroxyethyl cellulose, post-treatment steps such as neutralization, washing and drying are required. The goal of these treatment steps is to remove residual alkali, solvents and by-products to obtain the final purified product.
Hydroxyethyl cellulose has been widely used in various industries due to its unique chemical properties and excellent performance. Specifically, hydroxyethyl cellulose has good water solubility, thickening, stability, film-forming and lubricity, and is commonly used in the following fields:
Building materials: In building materials, hydroxyethyl cellulose is mainly used as a thickener and water retaining agent for cement-based materials and gypsum-based materials. It can effectively improve the construction performance of materials, improve the water retention, workability and anti-sagging of mortar, extend the open time and ensure the smooth progress of construction.
Paint industry: In paint, hydroxyethyl cellulose is used as a thickener, suspending agent and emulsifier to improve the rheology and stability of paint, prevent pigment sedimentation, and enhance the flatness and gloss of the coating.
Cosmetics and personal care products: In cosmetics, hydroxyethyl cellulose is often used as a thickener, film former and moisturizer. It can provide products with a good feel, improve product stability and adhesion, and enhance moisturizing effect.
Pharmaceutical industry: In the pharmaceutical field, hydroxyethyl cellulose is used as an excipient for pharmaceutical preparations. As a component of sustained-release tablets, film coatings, etc., it can control the release rate of drugs and improve the stability and bioavailability of drugs.
Food industry: In the food industry, hydroxyethyl cellulose is used as a food additive to play a role in thickening, emulsification and stabilization. It is widely used in beverages, condiments, dairy products and other foods to improve the texture and taste of products.
Hydroxyethyl cellulose also has important applications in the oil extraction, papermaking, textile printing and dyeing industries. In oil extraction, hydroxyethyl cellulose is used as a thickener and stabilizer for drilling fluids, which can improve the suspension capacity of drilling fluids and prevent well wall collapse. In the papermaking industry, it is used as a retention agent and reinforcing agent to improve the strength and durability of paper. In textile printing and dyeing, hydroxyethyl cellulose is used as a thickener to help the printing and dyeing slurry to be evenly distributed and improve the printing and dyeing quality.
Hydroxyethyl cellulose is obtained from natural cellulose through a series of chemical reactions. Its wide application is not only due to its excellent physical and chemical properties, but also because it can provide diversified solutions in many industries to meet different technical needs.