Water-based ink pigments (five)

3, yellow pigment

Diphenylamine Yellow (PY12, PY13, PY14) and Hansa Yellow (PY3) pigments can be used in water-based inks with excellent color strength, gloss, and leveling, but poor rheological properties in individual acrylic systems. .

Chromium yellow pigments have good flowability, opacity, color strength and leveling in most aqueous inks, but are active in individual acrylic systems and do not disperse when they are easy to thicken after storage.

Although color inks for aqueous inks are primarily pigments, individual fuels are also useful, for example, alkaline fuels and metal complex fuels.

4, white pigment (P, W6 titanium dioxide)

Both rutile and anatase titanium dioxide can be used in water-based inks.

The American Kerr-Megee company has studied the performance of four kinds of rutile titanium dioxide in the water type ink, as shown in Table 3.

As can be seen from Table 3, although the titanium dioxide contents of C and D are relatively low, they have high hiding power and excellent wettability and dispersion stability. D is white with blue light, which has the highest opacity and excellent light scattering ability. Through analysis of its particle size and distribution, it has been found that it has a narrow particle distribution range.

5, black pigment (PB7, carbon black)

Carbon black is the king of pigment and has excellent properties such as heat resistance, light resistance, and chemical resistance. Factors that affect the application performance of carbon black include:

(1) Primary particle size. The smaller the particles, the higher the coloring power, but the hue is red-brown and hard to disperse, while the carbon black of the medium particles has a blue phase, so the suitable particle size for the ink carbon black is 20-75μ.

(2) Primary particle structure. The primary particles are fused into aggregates by chemical bonds during the production process. The aggregates of the low-structure carbon black are composed of smaller primary particles, exhibit low dibutyl phthalate absorption, have low oil absorption, low Viscosity, high gloss, high color strength, high density and other application properties.

(3) The degree of surface oxidation. After surface oxidation treatment, the oil absorption can be reduced, the blackness and gloss can be improved, and the wettability and dispersibility can be improved.

U.S. companies believe that anionic and non-ionic dispersants can be used in the preparation of aqueous carbon black dispersions. There are two methods of selection:

(1) DAR value. DAR refers to the minimum amount of dispersion needed to obtain a flowing carbon black dispersion, and the smaller the DAR, the more effective the dispersant. The factors that affect DAR are:

Carbon black ion size - The smaller the particles, the greater the DAR.

Surface oxidation - has a low DAR value compared to unoxidized carbon black.

• Degree of Surface Oxidation - As the degree of oxidation increases, the DAR value increases.

• System pH - The lowest DAR value when PH is 9 to 11.5.

Carbon black loading - As the carbon black content of the system increases, the DAR value increases.

(2) HLB value. The HLB value of a non-ionic dispersant suitable for aqueous ink low-structure carbon blacks (eg, Regal 3001) should be greater than 14.5.

6, metal pigments

Metallic pigments include gold powder (copper powder) and silver powder (aluminum powder). In general, such pigments cause a lot of troubles when used in aqueous inks. In particular, the presence of surfactants tends to chemically react with metal pigments and reduce dispersions. The stability and brightness of the prints. Therefore, when preparing aqueous metallic ink, it is necessary to repeatedly adjust the ink formulation.

Emulsion-type aqueous resin liquids have good drying and anti-friction properties, and due to the presence of surfactants such as emulsifiers that are reactive with metallic pigments, produce dim spots and instability. Emulsion-based aqueous resin liquids are the opposite, have excellent dispersion stability, good printing properties, and high brightness, but have poor drying and rubbing resistance.

An American company believes that an effective method for preparing water-based metallic inks is to use an enhanced emulsification system, that is, to use a solution-type resin liquid and an emulsified-type resin liquid, and the aqueous metallic ink thus produced has high brightness and good dispersion. Body stability and rub fastness.

When preparing water-based metallic inks, pay attention to:

(1) The particle size and shape of the metallic pigment are the main factors that affect ink properties such as opacity and brightness.

(2) The smaller the solid content of the resin in the ink system, the higher the brightness.

(3) Different resin systems have different brightness, which may be caused by the interfacial tension between the binder and the metallic pigment.

(4) Individual water-based resin systems affect the orientation of metallic pigments in the ink film, thereby affecting the print quality. In general, the stability of the automatic orientation of metallic pigments in the form of flakes is more important than suspensibility.

(5) Factors influencing the stability of the dispersion: Surfactant, water/alcohol solvent ratio, solid content, pH, final surface tension of the ink.

(6) The metal pigment is added last at the time of mixing, and it is slowly stirred.

(7) Adjust the pH of the ink to about 7 to 8.5 to reduce the chemical reactivity of the metal pigments and other components of the system.

Source: 21st Century Fine Chemicals Network