Causes of foaming of pigment concentrate slurry may include uneven thickness during the painting operation, no wet jointing during application, compatibility issues, insufficient amount of additives in the paint, insufficient amount of emulsion in the paint, and not being applied in one go. In addition, the difference in surface tension between the colorant and the paint is too large, and the poor compatibility between the two is also a possible reason. The formation of bubbles in liquids is a very complex problem, usually in the form of bubble nuclei that evaporate or dissociate rapidly when the liquid flows through an area of very low absolute pressure in a very short period of time.
Aqueous colorant foaming not only makes the equipment underutilized, but also affects the production quality. The air in the foam will hinder the dispersion of the pigment or filler, affect the stirring speed, prolong the blending time, and cause the pigment and filler to not be fully wetted. This can lead to dissatisfaction and uneven weight in the continuous filling line, as well as pitting in the coating film during use.
The methods to solve these problems mainly include: first, the solution of compatibility problems, such as mechanical dispersion and the addition of wetting agents; The second is the use of defoamer, which can be added before and at the end of slurry preparation; the third is slow stirring, that is, putting the slurry in a container and stirring slowly; The fourth is the vacuum method, in which the slurry is stirred in a closed container, while the container is kept in a vacuum state (using a vacuum pump).
Pigment concentrates are prone to foaming during the grinding phase, and to prevent this problem, a defoamer is required. Silicone defoamers are the most commonly used and have good long-term and shear stability, making them particularly suitable for resin-free grinding (water slurry grinding) and water-based overprint coatings. Saiyang defoamer can be used as the preferred product of pigment concentrate slurry, and it shows excellent defoaming effect in the grinding stage. SAILYANG defoamer can effectively destroy the surface tension of the foam, so that the foam bursts and dissipates quickly, thereby reducing the formation of foam and improving the coating quality and appearance. In addition, Saiyang silicone defoamer is also widely used in water-based pigment concentrates and printing inks to prevent foaming during the grinding stage.
Overall, choosing the right defoamer and applying it correctly can not only reduce foam generation and improve the coating effect, but also improve the quality and appearance of the coating and ensure the effectiveness of the pigment concentrate.
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