Ultra-high viscosity hydroxyethyl cellulose (HEC) is a water-soluble polymer compound formed by etherification of cellulose. Due to its remarkable viscosity and stability, HEC is widely used in many fields such as cosmetics, pharmaceuticals, construction, and oil extraction.

(1), HEC structure and preparation method

1.1 Structure
HEC is an ether derivative obtained from chemical treatment of natural cellulose. Its basic structural unit is β-D-glucose, connected by β-1,4 glycosidic bonds. The hydroxyl group (-OH) in cellulose is replaced by ethylene oxide (EO) or other etherifying agent, thereby introducing an ethoxy (-CH2CH2OH) group to form hydroxyethyl cellulose. Ultra-high viscosity HEC has a higher molecular weight, usually between millions and tens of millions, which allows it to exhibit extremely high viscosity in water.

1.2 Preparation method
The preparation of HEC is mainly divided into two steps: pretreatment of cellulose and etherification reaction.

Pretreatment of cellulose: Natural cellulose (such as cotton, wood pulp, etc.) is treated with alkali to stretch and dissociate the cellulose molecular chains for subsequent etherification reactions.

Etherification reaction: Under alkaline conditions, the pretreated cellulose is reacted with ethylene oxide or other etherifying agents to introduce hydroxyethyl groups. The reaction process is affected by factors such as temperature, time, and etherifying agent concentration, and HEC with different degrees of substitution (DS) and substitution uniformity (MS) are finally obtained. Ultra-high viscosity HEC generally requires high molecular weight and a suitable degree of substitution to ensure its viscosity characteristics in water.

(2) Characteristics of HEC

2.1 Solubility
HEC dissolves in both cold and hot water, forming a transparent or translucent viscous solution. The dissolution rate is affected by factors such as molecular weight, degree of substitution, and solution temperature. Ultra-high viscosity HEC has relatively low solubility in water and requires prolonged stirring to completely dissolve.

2.2 Viscosity
The viscosity of ultra-high viscosity HEC is its most notable characteristic. Its viscosity usually ranges from several thousand to tens of thousands of milliPa·s (mPa·s), depending on the concentration, temperature, and shear rate of the solution. The viscosity of HEC not only depends on the molecular weight, but is also closely related to the degree of substitution in its molecular structure.

2.3 Stability
HEC has good stability in acids, alkalis and most organic solvents and is not easily degraded. In addition, HEC solutions have good storage stability and can maintain their viscosity and other physical and chemical properties for a long time.

2.4 Compatibility
HEC is compatible with a wide range of chemicals, including surfactants, salts and other water-soluble polymers. Its good compatibility enables it to maintain stable performance in complex formulation systems.

(3) Application of HEC

3.1 Cosmetics and personal care products
In cosmetics, HEC is widely used as a thickener, stabilizer and film-forming agent. Ultra-high viscosity HEC can provide excellent touch and long-lasting stability and is commonly used in products such as lotions, shampoos, and conditioners.

3.2 Pharmaceutical industry
As a pharmaceutical excipient, HEC is often used in the preparation of sustained-release tablets, gels and other pharmaceutical preparations. Its high viscosity property can control the drug release rate and improve the bioavailability of the drug.

3.3 Building materials
In the construction industry, HEC is used as a thickener and water-retaining agent for cement and gypsum-based materials. Its high viscosity and good water retention help improve construction performance and prevent materials from drying out and sagging.

3.4 Oil extraction
In the petroleum industry, HEC is used in drilling fluids and fracturing fluids as a thickener and drag reducer. Ultra-high viscosity HEC can improve the suspension capacity and sand-carrying capacity of liquids, improving the results of drilling and fracturing operations.

(4) Development prospects of HEC

With the advancement of technology and changes in market demand, the application scope of HEC continues to expand. Future development directions include:

4.1 Development of high-performance HEC
By optimizing the production process and raw material ratio, HEC with higher viscosity, better solubility and stability can be developed to meet higher-demand application scenarios.

4.2 Environmental protection and sustainable development
Develop environmentally friendly production processes and raw materials, reduce energy consumption and waste emissions during the production process, and improve the sustainability of HEC.

4.3 Expansion of new application fields
Explore the application potential of HEC in the fields of new materials, food industry and environmental engineering to promote its application in more industries.

Ultra-high viscosity HEC is a multifunctional polymer material with broad application prospects. Its unique viscosity characteristics and good chemical stability make it play an important role in various industries. With the advancement of technology and the expansion of application fields, the market prospects of HEC will be broader.