The main purpose of the ink dispersion machine grinding the pigment is dispersed in an aggregate link compound, so as to form a dispersion of fine particles. Since the pigment is a key determinant of the ink color and optical properties, so it not only depends on the diffusion and absorption of light, and these particles with its size is also relevant. For example, in relative terms, saturation (color strength) after diluting the ink, the hue etc. For dispersion of the pigment particles, it is well known.
Due to the different chemical composition and physical properties of the pigment, so their dispersion performance will vary. Dispersing machine into the operating process is generally divided into three stages, namely (1) the pigment aggregates start wetting, (2) a pigment aggregates broken into small particles, which are separated aggregates, (3) the replacement of air with the surface of the pigment particles binders , i.e., the surface of the pigment particles adsorbed water or gas medium to be wetted substituted - attached to the surface of the pigment particles in the wetting medium.
Pigment particles in binders in the case of the system can be described of: (A) a number of dry pigment particles due to their mutual gravitational surface "hold" together, the space between the particles of air, a phenomenon called aggregation; (B) pigment particles well dispersed in coupling compound; (the C) has a number of wetting or dispersing pigment particles due to the action of certain forces slowly and floc formation, is connected between the particulate material, this phenomenon is called flocculation . Flocculation of the dispersion depends on the nature of the link and flocculation of substances and pigments; (D) when gravity is impossible to produce small particles in the dispersion flocculation, then the orientation of the pigment particles may thus form a loose structure.
Pigment particles at the incipient wetness should first make pigments and links to material well mixed, in order to make them have a good affinity for faster wetting, so the use of surfactants is a common practice. Because surfactants can change the polarity between pigments and binders, some surfactants have a balanced polar and non-polar structure, which can be formed between the two surfaces of a bridge or link.
In order to destroy these aggregates, it would require a variety of forces, such as (1) physical impact, (2) collision between the particles and the particles, (3) by means of a fluid (e.g. binders) shear. In general, a relatively large aggregates (50-100 microns) may be dispersing device (such as a three-roll mill, a ball mill, a sand mill, etc.) is physically dispersed shearing force. The relatively small aggregates of pigment is mostly due to the paint on the outside of the binder aggregate shearing action and dispersed. Shearing the pigment binders primarily due to (1) binders for abrasive surface adhesion; (2) binders for paint adhesion to the surface; (3) binders inner adhesion (cohesion) strength, that viscosity.
When linked to material substitution (replacement) air bag on the outside of pigment wetting process is not finalized and reached the dispersion purposes. This process can improve the transparency of the pigment, the pigment particles of reduced gravity, which is due in between pigments and binders to form a physical link aggregation resistance, the pigment particles can not therefore be a gathering place.
Stability of the dispersion after the formation of the pigment dispersion depends primarily on the following three forces: (1) exclusion of static electricity - the pigment particle surface ions or charged groups and causes; (2) to attract London - van der Waals attraction - - due to the different dielectric constants between the pigment particles and binders caused; (3) Since the surface of the particles is not charged groups (like causes the grains to each other as a barrier) and "steric" stabilization caused. Since the rejection of the electrostatic force in an aqueous medium, more obvious, and attracting of London - van der Waals forces are both in organic and aqueous media, so the stability of the pigment dispersion in an organic medium, usually depends on the "steric "effect.
Since the theory of electrical power to the exclusion of that DLVO theory, which is based on when the media one ionizable substances in the form of positive or negative ions adsorbed on the surface of the pigment, the corresponding charge diffusion into the medium, it charge repulsion occurs. Therefore, these particles will get a similar charge, although the dispersion emergence of these charges, but also with its protective force due to gradually add more binders and destruction. If in the dispersion was added a large number of binders occurs "physical shock" effect. Thus, due to changes in the volume of the pigment, the pigment particle aggregation occurs again. Similarly, the addition of excess solvent in the system, will happen, since the solvent will wash away links to material from the pigment particles.
