Methods of Pigmentation of Organic Pigment

Pigment orange 64 manufacturer says that pigmentation of organic pigments is the adjustment of the size of pigment particles through appropriate processes, with the aim of adjusting the particle size and surface charge of organic pigments and designing methods for the production of pigment varieties of the desired particle size before production. The pigmentation methods of organic pigments mainly include: kneading method, ball milling method, organic solvent treatment method, surface treatment method and so on.

Kneading method
Use of kneading machine, its principle is to rely on mechanical stirring in organic solvents on the water-containing organic pigments to exert energy, change the crystal lattice of the organic pigment or change the surface shape of the pigment, and then remove the water contained in the pigment, the process is also known as extrusion of water to the phase.

Ball milling method
In the case of mechanical grinding of organic pigments, the pigment particles are subject to shear force, and the original larger particles are refined. During the grinding process, the addition of grinding aids can prevent the fine particles from aggregating again, so as to achieve the purpose of reducing the size of the pigment particles, and to improve the coloring power and vividness of the pigments.

In the process of ball milling method, organic pigment obtains the external energy, the solid particle crystal structure overcomes the potential energy barrier, and can be transformed from the crystal state of high internal energy to the crystal state of low internal energy, so as to achieve the purpose of adjusting the crystalline form of the pigment. After grinding, the color and light of the pigment will be changed.

Organic solvent treatment
Organic pigment will have trace solubility in specific solvents, and dissolution and recrystallization will happen in the process of treatment, so that the original particle size distribution of wider particle size becomes narrower, and at the same time, relying on the solubility of the solvent to remove part of the soluble impurities, and make the particles fluffy through the permeability of the solvent.

In this process, there can be both changes in the crystalline form and the crystal particles can be made larger, so as to improve the covering performance of the pigment.
The organic pigment varieties obtained after treatment with solvent will be very bright in color and light, and the distribution of pigment particle size will become narrower, but the average particle size will not become smaller, so the organic pigment varieties with good transparency can not be obtained by this method, but only the organic pigment varieties with very good covering property.

Surface treatment
Surface treatment has two meanings:
●  For the treatment of varieties with low added value of pigment, surfactant is added in advance in the synthesis process of organic pigment, so that the synthesis of pigment and pigmentation are carried out at the same time, such as most of the production of azo pigment is the synthesis of pigment and pigmentation carried out at the same time.

● When treating the varieties with higher added value of pigment, usually the crude pigment is made first, and then the crude pigment is treated like solvent in the water containing processing aids on the surface, sometimes it is necessary to be carried out under a certain pressure in order to strengthen the dispersing effect, so that the pigment can be treated at a higher temperature.