The aluminum paste production process is generally a wet process, which is under the protection of solvent oil. The sprayed aluminum powder is ground into a sheet-like structure with a suitable size and diameter-to-thickness ratio, and then classified, solid-liquid separation, and surface treatment are performed to make Different specifications and models of metallic pigment products.

The aluminum paste production process can be roughly divided into four processes:

◆ Ball milling process

According to the process regulations of each product, put the specified variety and quantity of aluminum powder, solvents, and grinding aids into the ball mill of the specified size and quantity. Under certain temperature conditions, grind at the specified speed for a certain period of time, using the ball mill The impact force and shear force generated between the rotating steel ball and the mill and between the steel balls stretch the spherical aluminum powder into a sheet structure. According to the requirements of different products, further grinding is carried out to make it into an aluminum sheet with a certain surface condition, shape, particle size and diameter-thickness ratio.

Then use a large amount of mineral spirits to remove it from the ball mill. In the grinding process, the replacement of one fatty acid by another will give the aluminum paste a completely different characteristic and appearance. Because the appearance of each type of aluminum sheet is different from other types, the technical parameters that affect the product application formula and end use will also change according to the desired effect.

◆ Grading process

The finely ground aluminum flakes are passed through a different number of screens and divided into aluminum flakes with different particle size distributions. The aluminum flakes with too large particle size are re-grinded, and the aluminum flakes with medium particle size are processed into a product variety. The aluminum flakes with small particle size are one type, and they are processed separately.

◆ Solid-liquid separation process

Use polypropylene box or plate and frame compressors to compress the separated aluminum flakes or filter cake with a solid content of about 80% to remove solvents and additives that are not conducive to the coating system.

After the solvent is clarified by pressure filtration again, it is returned for grinding or use out of the machine, and the filter cake is subjected to surface treatment. Some flash products use a centrifugal separator to centrifugally separate the sieve to achieve a solid content of more than 80% of the filter cake.

◆ Kneading process

In the kneader, perform the necessary surface treatment on the filter cake, add a certain amount of high boiling point aromatic solvent oil to adjust the solid content of the product; according to different products, add the specified variety and amount of dispersant to ensure that the product has good dispersion performance; add different The positioning and arrangement aids ensure that the product has a good positioning and arrangement state in the paint film. Through surface treatment, the product has the specified technical performance and application performance.

The choice of solvent for floating and non-floating aluminum pastes is different: non-floating aluminum pastes can be widely used in polar and non-polar solvents; while floating aluminum pastes can only use polar solvents, and the best is high surface Aliphatic or aromatic hydrocarbon solvents with tension (at least 27 dyne/cm). Polar solvents including ketones and alcohols will affect and eliminate the fatty acid lubricants on the aluminum flakes, resulting in a decrease in the floatability of the floating aluminum paste.