1. Problem Overview
Hydroxyethyl cellulose (HEC) is a thickener and rheology modifier widely used in latex paint, which can improve the viscosity, leveling and storage stability of the paint. However, in practical applications, HEC sometimes precipitates to form crystals, affecting the appearance, construction performance and even storage stability of the paint.
2. Analysis of the causes of crystal formation
Insufficient dissolution: The dissolution of HEC in water requires specific stirring conditions and time. Insufficient dissolution may lead to local oversaturation, thus forming crystalline precipitation.
Water quality problem: Using hard water or water with more impurities will cause HEC to react with metal ions (such as Ca²⁺, Mg²⁺) to form insoluble precipitates.
Unstable formula: Some additives in the formula (such as preservatives, dispersants) may react incompatiblely with HEC, causing it to precipitate and form crystals.
Improper storage conditions: Excessive temperature or long-term storage may cause HEC to recrystallize or condense, especially in high temperature and high humidity environments.
pH value changes: HEC is sensitive to pH, and extremely acidic or alkaline environments may destroy its dissolution balance and cause crystal precipitation.
3. Solutions
In response to the above problems, the following measures can be taken to avoid or reduce the phenomenon of HEC producing crystals in latex paint:
Optimize the dissolution method of HEC
Use the pre-dispersion method: first slowly sprinkle HEC into the water under low-speed stirring to avoid agglomeration caused by direct input; then let it stand for more than 30 minutes to fully wet it, and finally stir it at high speed until it is completely dissolved.
Use hot water dissolution method: dissolving HEC in warm water at 50-60℃ can accelerate the dissolution process, but avoid excessively high temperatures (over 80℃), otherwise it may cause HEC degradation.
Use appropriate co-solvents, such as a small amount of ethylene glycol, propylene glycol, etc., to promote the uniform dissolution of HEC and reduce crystallization caused by excessive local concentration.
Improve water quality
Use deionized water or softened water instead of ordinary tap water to reduce the interference of metal ions.
Adding an appropriate amount of chelating agent (such as EDTA) to the latex paint formula can effectively stabilize the solution and prevent HEC from reacting with metal ions.
Optimize formula design
Avoid additives that are incompatible with HEC, such as certain high-salt preservatives or certain specific dispersants. It is recommended to perform compatibility testing before use.
Control the pH value of latex paint between 7.5-9.0 to prevent HEC from precipitating due to drastic pH fluctuations.
Control storage conditions
The storage environment of latex paint should maintain a moderate temperature (5-35℃) and avoid long-term high or low temperature environments.
Keep it sealed to prevent moisture evaporation or contamination, avoid local increases in HEC concentration due to solvent volatilization, and promote crystallization.
Choose the right HEC variety
Different types of HEC have differences in solubility, viscosity, etc. It is recommended to choose HEC with high degree of substitution and low viscosity to reduce its tendency to crystallize at high concentrations.
By optimizing the dissolution mode of HEC, improving water quality, adjusting the formula, controlling the storage environment and selecting the appropriate HEC variety, the formation of crystals in latex paint can be effectively avoided or reduced, thereby improving the stability and construction performance of latex paint. In the actual production process, targeted adjustments should be made according to specific circumstances to ensure product quality and user experience.
Post time: Mar-26-2025