Masterbatch colorant selected according to different uses of different performance organic pigments and inorganic pigments. Organic pigments Jill has a detailed introduction for everyone. So today, let's talk about the knowledge to fully inorganic pigments!

Inorganic pigments based on natural mineral pigment or an inorganic compound formed.

Inorganic pigments related presentations

English name: inorganic pigment

Inorganic pigments are non-ferrous metal oxide, or some insoluble metal salts, inorganic pigments are divided into natural and artificial inorganic pigments inorganic pigments, inorganic pigments are natural mineral pigments. Natural mineral pigment or an inorganic compound formed. Natural mineral pigments are generally lower purity, color is dark, but low prices. The synthesis of inorganic pigments varieties chromatography complete, bright color, pure, strong hiding power.

Inorganic pigments Light, heat, weather resistance, solvent resistance, hiding power, but not quite complete chromatography, low tinting strength, bright color difference, some toxic metal salts and oxides. Inorganic pigment widely used in coatings, plastics, synthetic fibers, rubber, building materials, stationery, paints, inks, paper, glass, enamel, ceramics and other industrial sectors.

Mechanism of inorganic pigments

The basic optical properties and pigment properties inorganic pigments, primarily determined by the following three aspects:
① difference between the refractive index of the pigment and the dispersion medium;
② solid absorbed light (including solid impurities);
③ particle size and particle size distribution. Where the size and size distribution can be improved by surface treatment.

In the paint production process, regardless of how fine is ground pigment powder, always contains some aggregation and flocculation of particles. Pigment in the transport, storage process, since the pressing, damp further flocculation larger particles, and the finer the pigment, the greater the surface area, surface energy higher, more easily flocculated together. If by suitable surfactant treatment, these large particles flocculated when used can easily be spread out, the dispersion mechanism is mainly as follows:

1. wetting

Inorganic pigment powder dispersed in a liquid mainly through the following three stages: wetting ① powder, wettable powder not only to the liquid surface, but also to air and moisture of the powder particles displace; ② through wettable powders and displace particles after air and water between the flocs pigment powder and aggregates are destroyed; ③ is wet and damaged and floc powder aggregates maintain a stable dispersion state in the liquid. That dispersion wetting - dispersing - maintain a stable dispersion process. In general, the inorganic pigment is rarely before use for drying of, in addition to the surface of the pigment mixed with air, but also a layer of adsorbed water film. The amount of water adsorbed on the pigment surface is usually equivalent to the amount of water required for a monomolecular film formed on the solid surface.

E.g., TiO 2 surface area per gram of 10m 2, water molecules adsorbed layer thickness 10 × 10 -10 m, the amount of water required for the monomolecular film was about 0.3% by weight of the pigment, so the moisture content of the pigment in its dispersing properties also affect one of the main factors. Moist solids are good or bad, can be judged according to their contact angle, the contact angle is 0 ° expressed complete wetting liquid is completely spread on solid surfaces; a contact angle of 180 °, said completely wet, liquid water droplets form was attached surface of the solid.

The solid in the liquid can wet well, except that the contact angle to determine the size, can also be measured to determine the size of the heat of wetting, the powder is generally hydrophilic (e.g., TiO 2) in a polar liquid in the heat of wetting large, non-small polar liquid moist heat, moist heat and hydrophobic powder in polar and non-polar liquid substantially constant.

Solid powder in a liquid settling velocity and sedimentation volume size may also determine the extent of wetting is good or bad (see Table 1), such as TiO 2 having large polarity in a small volume of solid sedimentation large polar solution, small polar solution is large; nonpolar solid powder sedimentation volume are generally large. After addition by surfactant treatment, due to the surfactant molecules are oriented strongly adsorbed on the surface of solids, helps to reduce the surface tension of the liquid, to improve their wetting and dispersing properties.

2. electrical repulsion (ξ potential)

Inorganic pigment dispersion and dispersion stability in aqueous solution, primarily dependent on its water repulsion i.e. ξ electric potential to determine the size.
Electrical repulsion is the use of a charge repulsion to maintain dispersion stability.

A surfactant capable of ionizing in aqueous solution a large number of negatively (or positively charged) ions, firmly attached to the surface of the pigment particles, so that these particles have the same charge, with other ions of opposite charge to the free diffusion of the liquid medium around, forming a diffusion layer (double layer) of charged ions. Since the potential difference between the solid surface diffusion layer to the most distant (ie, oppositely charged to 0 places) between the two ions is called ξ potential. Electrostatic repulsion between particles is resulting, these particles with the same charge repel each other upon contact you in order to maintain a stable dispersion system, known as the DLVO theory.

In the case of electrical repulsion of the surfactant must have a high ionization properties, generally used is an anionic surfactant and some inorganic dielectric, such as: tripotassium phosphate, potassium pyrophosphate, sodium polyphosphate, alkylaryl sulfonate sodium hypochlorous methylnaphthalene sulfonate, sodium polycarboxylate.

3. steric effect (or entropy effect)

When the pigment is dispersed in non-aqueous media, have significantly ruled out the possibility of the above-mentioned ion reactions, non-ionic surfactants are not ionized in water, in this case, the effect of surface active agents known as steric or entropic effects. Because surfactants can be adsorbed on the surface orientation of pigment particles, to form a monomolecular adsorption layer, this orientation of the buffer layer can be prevented from gathering between the particles, so as to maintain a stable dispersion system (also known as protective colloid or micelle).

Surfactant molecules cluster pigment surface, with the increase of surfactant concentration, which reduces the entropy, the movement will be limited, the closer the pigment particles, the more compression, which will further reduce the entropy, thereby enabling stable dispersion system.