Technical application of aluminum paste in coating industry

To achieve excellent gloss, sparkle, brightness, hiding power, tinting power, floatability and other properties, it must be well dispersed, but the following tips and suggestions should be paid attention to when dispersing:

Aluminum flakes are easy to bend and break. If high-speed stirring or other continuous and violent processing are carried out in the coating production process, its geometric structure is easily destroyed, and bad phenomena such as coarse particles, dark color, reduced hiding power and metal migration appear. High-shear dispersing means should not be used.

It is recommended to use the pre-dispersion method: first select an appropriate solvent or a mixture of several solvents. Add the solvent to the aluminum powder slurry at a ratio of 1:1 or 1:2 with the ratio of aluminum powder slurry to solvent, stir slowly until uniform (about 10-20min), and add a wetting agent or dispersant to the system.

Resin system

Many commonly used paint binders, such as oil-based varnish binders, acrylate, alkyd, epoxy, polyurethane and water-based binders, can be used with leafing and non-leafing aluminum paste pigments. In general, any coating base material or solvent is suitable as long as it is compatible with the solvent of the aluminum paste and does not cause chemical damage to the aluminum paste. It is worth noting that aluminum is an amphoteric metal, and the acid value of the paint should be controlled below 7.

Choice of solvent

The choice of flux is mainly determined by the paint material determined by the formula. Non-leafing aluminum pastes can be widely used as polar fluxes, such as aliphatic or aromatic hydrocarbons, esters (such as butyl acetate), ketones (such as methyl ethyl ketone, methyl isobutyl ketone), and alcohols (such as ethanol). The floating aluminum paste can only use non-polar solvents, and preferably aliphatic or aromatic solvents with high surface tension, especially white spirit, diphenyl, toluene and high flash point naphtha, because they can Promote excellent floatability. Moisture will react with aluminum to generate hydrogen and cause a sounding effect. Therefore, the moisture in the coating should be strictly controlled below 0.15%. It is recommended to use Bayer dehydrating agent OF to remove excessive moisture in the coating, solvent or thinner. Aqueous solvents are not suitable for any aluminum paste pigments.

The choice of aluminum paste

The particle size and particle size distribution of aluminum paste have a vital influence on color, hiding power, floppy effect and gloss. Therefore, particle size distribution is an important parameter that cannot be ignored when choosing aluminum paste. Products with stable particle size and particle size distribution should be selected. Particle size and particle size distribution are not technical parameters for selecting aluminum paste. Even if the particle size and particle size distribution are the same, after different surface treatments or the shape of aluminum flakes are different, it will cause color tone, hue or metallic feeling, whiteness, and different angles. The difference in optical effects such as color effect. Therefore, first choose the most suitable aluminum paste, and it is best to pass the preliminary sample test.