Physical properties and modification of pigments

1. density

The density of organic pigment is 1 - 2.0g/m and inorganic pigment is 1.8 - 8.8g/m.

2. specific surface area

In general, organic pigments and inorganic pigments are 10 100m /g and 5 50m /g respectively.

3. granularity

As the size of the pigment particles has an impact on its color, light fastness, covering power and color intensity, the size of the different kinds of pigment particles should be controlled in a suitable range, although the size of the different kinds of pigment particles is different. The size range of pigment can be obtained from very small colloidal particles (about 0.01Pm) to larger particles (about 100 Hong m). It can be seen that the pigment is a fine granular material.

4. crystal

Commercial pigments mostly exist in crystalline state, and isocrystalline phenomena are very common.

5. dispersion and dispersion stability

The pigment is dispersed in the medium with a solid state, and it is insoluble in its dispersed medium, and the physical and chemical properties of the pigment are basically not changed by the dispersive medium. The degree of dispersion and the stability of dispersion system directly affect the performance of inks, coatings, plastic products and textile fibers.

Two. The modification of pigment

In addition to azo pigment, other crude pigments should be modified to different degrees to obtain good application performance. At present, the commonly used modification methods are as follows.

1. solvent treatment

The method is to mix the pigment powder or paste in proper solvent and temperature for a certain time to improve the crystal form of the pigment.

2. grinding treatment

The grinding treatment is to break the pigment aggregates by the effect of mechanical force, and use the surface active agent to prevent the fine particles from gathering again, in order to reduce the diameter of the pigment particles and improve the coloring force and brightness.

Treatment of 3. rosin and its derivatives

This is a traditional method of modification. When adding rosin at the early stage of preparation of the pigment, it can be adsorbed by the generated nucleus, prevent the growth of the crystal, make the pigment particles fine, and improve the coloring force and transparency. In the later preparation, the rosin is adsorbed on the well developed crystal surface, isolating the pigment particles, preventing its aggregation and improving the wettability and dispersity of the pigment. . At present, rosin derivatives with high melting point and high oxidation resistance have attracted more and more attention.

4. organic amine treatment

The advantage of organic amine treatment is to prevent the aggregation of pigment particles. I Amine Treatment pigments are usually carried out in water medium. It can be added into the pigment suspension form in water soluble salt solution, free amine aqueous dispersion, or emulsion.

5. surfactants treatment

It can be adsorbed by pigment particles from the solution and enriched on the surface to form a directional arrangement of adsorption layer, which can play a role in reducing the interfacial tension between the pigment surface and the medium, and improving its wettability and dispersion stability.

6. hyper dispersant treatment

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

7. pigment derivative treatment

Derivatives used to modify pigments, chemical structures and colors should be acceptable to the treated pigments and can be adsorbed very well on the surface of the pigments. The polar substituents of pigment sanitary products can be combined with other treatment agents by hydrogen bonding, ionic bonding and so on, so that the latter can be firmly adsorbed on the surface of particles. In addition, the addition of pigment derivatives can adjust the color and fluidity of products, improve the coloring power, transparency and dispersion.