Specific use of metallic color powder dispersant

In coating production, what is the specific use of metallic color powder dispersant?

1. Selection of dispersant

Based on the characteristics of metallic color powder: Different metallic color powders, such as aluminum powder, copper powder, etc., have different surface properties and particle sizes, and need to be matched with corresponding dispersants. For example, aluminum powder has high surface activity and is easily oxidized, so a dispersant with anti-oxidation and strong dispersing ability should be selected; nano-scale metallic color powder has a small particle size and a large specific surface area, so a dispersant with strong steric hindrance effect is required to prevent agglomeration.

Combined with the coating system: solvent-based coatings use oil-soluble dispersants, and water-based coatings use water-soluble dispersants. For example, for acrylic solvent-based coatings, select a dispersant with good compatibility with acrylic resin; for water-based latex paints, select a dispersant suitable for water-based systems that can stably disperse metallic color powders.

2. Determine the dosage

Reference product description: The dispersant product manual will provide an approximate dosage range for different systems, which is generally a certain proportion of the metal color powder mass, such as 5%-15%. Initially, the test can be carried out within this range.

Experimental optimization: Prepare small samples of paint with different dispersant dosages to test the dispersion effect. For example, use a scraper fineness meter to measure the dispersion fineness of the color powder, or observe the storage stability, leveling of the paint, and the gloss and color uniformity of the coating after drying. Adjust the dosage according to the results until the best dispersion effect is achieved.

3. Addition method

Pre-dispersion: First mix the metal color powder with an appropriate amount of dispersant and solvent, and pre-disperse it with a high-speed mixer or grinding equipment. For example, in a high-speed mixer, stir at 1000-1500 rpm for 15-30 minutes to allow the dispersant to initially adsorb on the surface of the color powder to reduce agglomeration.

Gradual addition: After pre-dispersion, slowly add the mixture containing metal color powder and dispersant during the mixing process of the paint preparation. For example, first stir the base resin and other additives of the coating at a low speed, and then slowly pour in the pre-dispersed liquid to avoid excessive local concentration affecting dispersion.

Synchronize with grinding: If the coating needs to be ground and refined, the dispersant can be added to the grinding equipment together with the metal color powder, such as a sand mill. During grinding, the dispersant continues to act, making the color powder particle size smaller and evenly dispersed. Generally, it is ground to a particle size that meets the coating requirements.

4. Dispersion process control

Stirring speed and time: Stirring speed and time are key in the dispersion process. High-speed stirring at the beginning is conducive to the rapid adsorption and dispersion of the dispersant and the color powder, such as stirring at 2000-3000 rpm for 15-30 minutes; then stirring at a low speed to prevent the color powder from reaggregating, such as stirring at 500-1000 rpm for 10-15 minutes.

Temperature control: Temperature affects the dispersion effect. Some dispersants are highly active in a specific temperature range, such as 25-40℃. The temperature should be controlled during dispersion to avoid excessively high temperatures that may cause the dispersant to decompose or the coating system to change performance, and too low temperatures that may result in low dispersion efficiency. The temperature can be adjusted by a jacketed reactor or temperature control equipment.