What is the role of HEC in latex paint?

There are three main methods for using hydroxyethyl cellulose (HEC) as a thickener in latex paint, along with key precautions:

1. Direct Addition Method: During the grinding and dispersion stage, HEC powder is slowly added to water under high-speed stirring. Stirring continues until it is completely dissolved and the system viscosity significantly increases. Then, other additives and pigments/fillers are added sequentially and the mixture is ground again. This method is simple to operate and suitable for continuous production.

2. Preparation of Pre-dissolved Mother Liquor: A high-concentration HEC aqueous solution is prepared in advance. During stirring, the powder should be slowly sieved in to avoid clumping, and a mildew inhibitor should be added as early as possible. The concentration of the mother liquor is generally recommended to be controlled below 2.5-3.0% (by weight) to ensure its operability and stability. This method allows for flexible adjustment of the finished product viscosity.

3. Preparation of Organic Solvent Slurry: HEC powder is pre-mixed into a slurry using an organic solvent (such as ethylene glycol or propylene glycol) or a mixture of organic solvent and ice water. HEC swells but does not completely dissolve in the slurry; it dissolves rapidly and thickens upon addition to the paint. This method effectively avoids dust and accelerates dissolution, making it particularly suitable for processes requiring rapid dissolution.

Key Precautions

Always add HEC powder slowly with thorough stirring to avoid forming insoluble lumps.

Avoid an alkaline system before dissolution is complete. Adjust the pH value only after the HEC is fully wetted to promote dissolution.

Water temperature and pH significantly affect the dissolution rate and final viscosity. It is recommended to proceed under normal temperature and neutral conditions.

Be sure to add sufficient antifungal agent as early as possible to prevent microbial degradation that leads to viscosity reduction.

By selecting appropriate methods and strictly controlling the process, the thickening, stabilizing, and rheology-modifying functions of hydroxyethyl cellulose can be fully utilized, ensuring reliable performance and storage stability of latex paint products.