In water-based coatings, HEC (Hydroxyethyl Cellulose) is a commonly used water-soluble polymer, mainly used as a thickener, stabilizer, film-forming aid and rheology modifier. Its unique physical and chemical properties make it have important application value in water-based coating systems.
1. Basic characteristics of HEC
HEC is a non-ionic cellulose ether generated by the reaction of natural cellulose with ethylene oxide after alkali treatment. It is easily soluble in cold water to form a transparent and stable colloidal solution with good thickening, water retention, emulsion stability and film-forming properties. Due to its non-ionic properties, HEC has a strong adaptability to the pH value and electrolyte of the system and can maintain stable performance under a wide range of formulation conditions.
2. The main role of HEC in water-based coatings
Thickening effect
The main role of HEC is to provide viscosity control of the coating system. By adjusting the amount and molecular weight of HEC, the rheological properties of the coating can be controlled, including construction viscosity, storage viscosity, and sag during brushing. Appropriate viscosity helps prevent the sedimentation of pigments and fillers, improves the construction performance and surface smoothness of the coating. The thickening mechanism of HEC is mainly to form a network structure through the expansion of its molecular chain in water, thereby improving the viscoelasticity of the system.
Stabilize pigment dispersion
HEC can improve the dispersion stability of pigments in coatings and prevent precipitation and flocculation. This is because HEC can provide appropriate viscosity and steric hindrance effects in the system, which helps to stabilize the distribution between pigment particles. At the same time, it has good adaptability to both inorganic and organic pigments.
Improve construction performance
Construction performance is an important indicator for measuring the quality of coatings. HEC can adjust the brushing, roller coating or spraying performance of the coating, so that it has good leveling, no splashing, no sag during the application process, and has a certain open time (Open Time), which is convenient for large-scale continuous construction. In addition, the improvement of HEC's leveling performance also helps to improve the surface smoothness during film formation.
Film-forming aids
Although HEC itself is not a film-forming substance, it can assist the film-forming process. For example, in latex paints, it helps to release water slowly, giving the emulsion particles more time to coalesce and form a more dense and uniform coating. This is especially important under low temperature or dry conditions.
Improved anti-sagging and anti-splashing performance
By properly selecting HEC with different degrees of substitution and viscosity grades, the anti-sagging ability of the paint can be significantly improved, preventing the paint from sliding down even when applied on a vertical surface. In addition, HEC can suppress splashing caused by brushing or roller coating, improving the cleanliness and efficiency of the construction process.
3. Precautions for the use of HEC
Although HEC has many advantages in water-based paints, the following points should also be noted when using it:
Dissolution method: The correct dissolution of HEC is crucial to the performance. It is usually recommended to slowly add HEC to stirred cold water to avoid agglomeration, and pre-wetting or dispersants can be used to assist dispersion.
Compatibility with other additives: HEC is a non-ionic cellulose ether, which is usually compatible with anionic or non-ionic surfactants and emulsions, but in some specific formulas, it is still necessary to test its compatibility with preservatives, dispersants and other ingredients.
Dosage control: The dosage of different HEC models is different, and the general usage is about 0.2%-1.0%. Excessive use may lead to excessive viscosity, construction difficulties or poor film formation.
4. HEC's advantages in green environmental protection
With the increasingly stringent environmental regulations, water-based coatings are gradually replacing traditional solvent-based coatings. HEC, as a renewable resource derived from natural cellulose, is in line with the concept of sustainable development. Its low VOC (volatile organic compound) content and the absence of harmful ingredients such as formaldehyde make it an ideal green additive.
HEC plays multiple key roles in water-based coatings, not only improving the construction, stability and appearance quality of the coating, but also providing guarantees in terms of environmental performance. With the development of water-based coating technology, the performance requirements for HEC will become more diverse and specialized, and its application potential in the field of high-performance water-based coatings is still very broad in the future.
Post time: May-06-2025