Hydroxyethyl cellulose (HEC) is a commonly used water-soluble cellulose derivative, widely used in coatings, adhesives, building materials, cosmetics and other fields. It serves as a thickener, stabilizer and rheology modifier in coatings, and can improve the viscosity, fluidity, spraying performance, horizontal leveling, etc. of the coating.
1. Basic properties of hydroxyethyl cellulose
Hydroxyethyl cellulose is a colorless, odorless, water-soluble cellulose derivative with a large number of hydroxyethyl (-CH2CH2OH) groups in its molecular structure. It has the following main features:
Thickening effect: It can significantly increase the viscosity of water-based coatings, giving the coatings good rheological properties.
Thickening effect: It can effectively improve the fluidity of coatings and improve construction performance at low concentrations.
Improve stability: enhance the coating performance and leveling properties of the paint, and prevent the paint from settling or agglomerating.
Water solubility: It can dissolve quickly in water and is suitable for the formulation of water-based coatings.
2. Mechanism of action of hydroxyethyl cellulose
In water-based coatings, the role of hydroxyethyl cellulose is mainly reflected in the following aspects:
Thickener: Hydroxyethyl cellulose increases the rheology of the paint through intermolecular hydrogen bonding, thereby increasing the viscosity of the paint. After adding an appropriate amount of HEC to the paint, the fluidity of the paint can be effectively controlled to prevent the paint from being too thin or dripping.
Prevent precipitation and stratification: HEC has certain suspension stability, which can prevent the solid pigments and fillers in the paint from settling and maintain the uniformity and stability of the paint.
Improve spraying performance: During the spraying process, the addition of HEC helps improve the slippery and leveling properties of the coating and ensures the smoothness of the coating.
Adjust film-forming properties: The water solubility of HEC can adjust the drying rate of water-based coatings, improve film-forming properties, and make the coating film more uniform and smooth.
3. How to add hydroxyethyl cellulose
Adding hydroxyethyl cellulose to paint is not complicated, but you need to pay attention to its dissolution process and the timing of addition. Here are a few common ways to add it:
3.1 Dissolve in water
HEC itself is water-soluble and usually needs to be dissolved in water first. The following points need to be noted when dissolving HEC:
Temperature control: Although HEC can dissolve at room temperature, the dissolution rate will accelerate as the water temperature increases. Generally speaking, the most appropriate water temperature is between 30°C and 40°C. Excessively high temperatures may cause HEC to degrade and affect its performance.
Stirring rate: To avoid clumping of HEC, sufficient stirring is required during dissolution, usually using high-shear mixing equipment or a homogenizer. HEC powder can be added gradually while stirring and make sure it is evenly dispersed.
Dissolution time: The dissolution time of HEC may vary depending on its molecular weight. Generally speaking, HEC with low molecular weight dissolves faster, while HEC with high molecular weight takes longer. Usually, the dissolution time is controlled between 15 minutes and 1 hour.
3.2 Add directly to the paint base material
Another method is to add HEC directly to other components (such as water, pigments, resins, etc.) during the mixing process of the paint. This method is generally suitable for liquid coatings, but the following matters need to be noted:
Pre-wetting: In order to prevent HEC powder from clumping when added, HEC can be mixed with a small amount of solvent (water or other solvents) to pre-wet before adding it to the coating base.
Dispersion process: After adding HEC, the paint needs to be fully dispersed to ensure that HEC is evenly distributed in the paint base. High shear mixing equipment is often used to ensure this process goes smoothly.
Pay attention to the order: The order of adding HEC should be adjusted according to the formula and production process of the coating. In some formulations, HEC should be added before other viscosity modifiers or thickeners to ensure even dispersion and optimal effectiveness.
3.3 Use pre-dissolved hydroxyethyl cellulose solution
In some large-scale production processes, a concentrated HEC solution can be prepared in advance and then added to the paint. The advantage of this method is that the dissolution process is relatively simple and can reduce the operational complexity in the production process. When using a pre-solution, usually control its concentration between 1% and 5%, and adjust it according to the needs of the coating.
4. Best time to add HEC
When producing water-based coatings, the best time to add HEC is usually in the water phase formulation, when water and other water-soluble ingredients are added. Adding it at this time can ensure that HEC is fully dissolved and dispersed, and avoid unnecessary fluctuations in the viscosity and rheology of the coating. The specific steps are as follows:
First mix water and other water-soluble ingredients (such as preservatives, dispersants) evenly.
Add hydroxyethyl cellulose and stir thoroughly to ensure even dispersion.
After HEC is dissolved, other ingredients such as pigments, fillers and resins are added.
Finally, high-shear mixing of the paint is performed to ensure the uniformity and fluidity of the paint.
5. Add the amount of HEC
The amount of HEC added usually depends on the formulation requirements of the coating and the performance goals of the final product. Generally speaking, the amount of HEC added is usually between 0.2% and 2%. The specific amount is adjusted according to the viscosity, fluidity and other requirements of the coating. Lower addition levels are used for coatings that require lower viscosity or flow properties, while higher addition levels are used for coatings that require higher viscosity and better rheological properties.
Adding hydroxyethyl cellulose to coatings can effectively improve the rheology, stability and construction performance of coatings. Through proper dissolution and dispersion methods, HEC can be ensured to be evenly distributed in the coating, allowing it to perform optimally. Adjust the addition amount according to the specific requirements of the coating to achieve the desired effect.
Post time: Nov-18-2024