Modification of Pigments

Except for azo pigments, other crude pigments should be modified to different degrees in order to obtain good application performance. At present, the more commonly used modification methods are as follows.

1. Solvent treatment method

The method is to stir the pigment powder or paste in a suitable solvent and temperature for a certain period of time to achieve the purpose of improving the crystal form of the pigment.

2. Grinding treatment method

Grinding treatment is to break up the pigment aggregates by mechanical force, and use surfactants to prevent the re-aggregation of fine particles, so as to reduce the diameter of pigment particles and improve the tinting strength and vividness.

3. Treatment of rosin and its derivatives

This is a traditional modification method. Rosin is added in the early stage of pigment preparation, it can be adsorbed by the generated crystal nucleus, preventing crystal growth, making the pigment particles finer, and improving the tinting strength and transparency; adding in the later stage of preparation, rosin is adsorbed on the well-developed crystal surface to isolate the pigment particles. , to prevent its aggregation and improve the wetting and dispersibility of pigments. At present, rosin derivatives with high melting point and high anti-oxidation have attracted more and more attention.

4. Organic amine treatment

The advantage of organic amine treatment is to prevent aggregation of pigment particles. Amine treatment of pigments is usually carried out in an aqueous medium, and it can be added to the pigment suspension in the form of a water-soluble salt solution, an aqueous dispersion of free amines, or an emulsion.

5. Surfactant treatment

It can be adsorbed by pigment particles from the solution, enriched on its surface, and form a directional adsorption layer, which can reduce the interfacial tension between the pigment surface and the medium used, and improve its wettability and dispersion stability.

6. Hyperdispersant treatment

The so-called hyperdispersant is actually a polymer dispersant, which is named after its outstanding deflocculation and stabilization effects. It can reduce the mutual attraction between pigment particles in the dispersion system, increase the wettability of the particles in the medium, and improve the stability of the dispersion system.

7. Pigment Derivative Treatment

Used as a derivative of pigment modification, the chemical structure and color should be acceptable to the pigment to be treated, and can be well adsorbed on the surface of the pigment. The polar substituents of the pigment hygiene products can be combined with other treatment agents through hydrogen bonds, ionic bonds, etc., so that the latter can be adsorbed firmly on the particle surface. In addition, the addition of pigment derivatives has the effect of adjusting the shade, fluidity of the product, and improving the tinting strength, transparency and dispersibility.