Adding color paste dispersants: those details that cannot be ignored

In the production of colorful coatings, inks, cosmetics and other products, color paste dispersants play a key role in evenly distributing pigments and improving product quality. However, adding color paste dispersants is not simply pouring them into the color paste and stirring them. There are many issues that need to be paid attention to. Ignoring these details may lead to poor dispersion effect, affect product quality, and even cause production accidents. Now, let us learn about the things that need to be paid attention to when adding color paste dispersants.

Accurately control the amount

Determined according to the instructions and experiments

The amount of color paste dispersant directly affects the dispersion effect. If the amount is too small, the pigment particles cannot be fully wrapped, and it is easy to aggregate and precipitate, resulting in uneven color of the color paste and reduced hiding power; if the amount is too large, it will not only increase the cost, but also may produce foam, affect the viscosity and stability of the color paste, and even have adverse reactions with the pigment or matrix. Therefore, it is necessary to add it strictly according to the recommended amount in the product manual. At the same time, due to the differences in pigment types, particle sizes, contents and dispersion media of different color pastes, it is best to conduct a small test first. Take a small amount of color paste and dispersant, mix and stir in different proportions, observe the pigment dispersion, color paste stability, etc., and determine the most suitable dispersant dosage for the color paste.

Consider environmental factors for adjustment

Environmental factors will also affect the amount of dispersant. For example, when the temperature is high, the activity of the dispersant is enhanced, and it may be possible to achieve a good dispersion effect by appropriately reducing the dosage; while in a low temperature environment, the activity of the dispersant is reduced, and the dosage may need to be increased. In addition, conditions such as humidity and air pressure may also indirectly affect the dispersion process, and fine-tuning is required according to actual conditions.

Strictly control the order of addition

Dispersant and pigment are mixed first

The correct order of addition helps improve dispersion efficiency and quality. Generally speaking, the dispersant and pigment should be pre-mixed first. Dispersant molecules can preferentially adsorb on the surface of pigment particles to form a protective film to prevent aggregation between pigment particles. For example, when preparing water-based color paste, first add the dispersant to the pigment powder, stir it at a low speed with a stirrer for a period of time to evenly cover the pigment particles with the dispersant, and then add the dispersion medium (such as water) for further dispersion.

Avoid premature reaction with other ingredients

If the color paste contains other additives, such as defoamers, preservatives, thickeners, etc., pay attention to the order of addition to avoid premature reaction between the dispersant and these ingredients, which will affect their respective efficacy. For example, defoamers may interact with dispersants and reduce the dispersing ability of dispersants, so defoamers are usually added after the dispersion process is basically completed.

Reasonable control of the addition speed

Slowly add to prevent agglomeration

When adding dispersants, the speed should not be too fast. If a large amount of dispersant is poured into the color paste at one time, it may cause excessive local concentration, causing the pigment particles to quickly aggregate and agglomerate, making it difficult to disperse evenly. Especially for some high-viscosity color pastes or pigments with finer particles, the dispersant should be added slowly. You can add it dropwise or in batches, stirring while adding to ensure that the dispersant can fully contact and mix with the pigment.

Combined with stirring speed adjustment

The addition speed should also match the stirring speed. In the process of adding dispersants, the stirring speed should be appropriately increased to promote the mixing of dispersants and pigments. However, the stirring speed should not be too fast to avoid excessive bubbles or excessive shearing and damage of pigment particles. Generally speaking, you can start with a lower stirring speed, and increase the stirring speed appropriately as the dispersant is gradually added. After the dispersant is added, adjust to the appropriate stirring speed and continue stirring for a period of time to fully disperse the pigment.

Pay attention to the environmental conditions for addition

Appropriate temperature and humidity

Temperature and humidity are important factors affecting the performance and dispersion effect of dispersants. Most dispersants can only work best within a certain temperature range. Generally speaking, the appropriate dispersion temperature is between 20-40℃. If the temperature is too low, the activity of the dispersant will decrease and the dispersion effect will deteriorate; if the temperature is too high, the dispersant may decompose or the pigment may denature. Excessive humidity may cause the pigment to absorb moisture and agglomerate, affecting the adsorption and dispersion of the dispersant. Therefore, when adding dispersants, it should be carried out in a constant temperature and humidity environment, or appropriate measures should be taken to control the environmental conditions.

Avoid impurity contamination

The place and tools for adding dispersants should be kept clean to prevent impurities from entering the color paste. Impurities may react with pigments or dispersants, affecting the quality and stability of the color paste. For example, impurities such as dust and metal particles may cause spots and precipitation in the color paste. During the addition process, use clean containers, stirrers, droppers and other tools, and clean and dry the tools before operation.

Pay close attention to the phenomenon of the addition process

Observe the dispersion state

During the process of adding dispersants, pay close attention to the dispersion state of the color paste. Under normal circumstances, with the addition and stirring of dispersants, the pigment particles will gradually disperse evenly, and the viscosity and fluidity of the color paste will also change. If it is found that the pigment particles are still aggregated and the color paste is layered or agglomerated, it may be caused by insufficient dispersant dosage, improper addition order or insufficient stirring, and timely adjustment is required.

Monitor foam generation

Some dispersants may generate foam during stirring. The right amount of foam helps to improve the dispersion effect, but too much foam will affect production operations and product quality. If too much foam is found, measures such as adding defoamers, reducing stirring speed or changing stirring methods can be taken to control the generation of foam.

Adding color paste dispersants is a process that requires carefulness and patience. Only by accurately controlling the dosage, strictly following the order of addition, reasonably controlling the addition speed, paying attention to environmental conditions and paying close attention to the phenomena during the addition process can the role of the dispersant be fully exerted and high-quality color paste products be prepared.