Selection of water-based ink pigments and additives?

First, General requirements for pigment selection

1. Alkaline

Most of the resin binders of water-based inks are alkali-soluble, and the selected pigments must be alkali-resistant. If the pigment molecules contain genes such as sulfonic acid groups and carboxylic acid groups that react with alkali, reactive condensation will occur.

2. Hiding power

High-grade water-based inks require high hiding power and high color density, and the selected pigments should have high hiding power.

3. Easy to disperse

It is easily dispersed in the selected resin liquid system.

4. Select pigments according to the use performance of the substrate, such as lightfastness, heat resistance, and chemical resistance.

Second, the selection of additives in water-based inks

In order to obtain high-quality and high-stability printing performance during the manufacture and use of water-based inks, it is necessary to use ink additives. One of the differences in the quality of water-based inks at home and abroad is also the difference in the use of additives. Different types of inks need to use different additives, but some additives have more than one function and need to be used in coordination. The printability of water-based inks is affected by objective conditions such as printing conditions, surface blood characteristics of the substrate, ambient temperature and humidity, and the length of time the water-based inks are stored. Therefore, some additives need to be used to make fine adjustments to the water-based inks during use. Get the best printing effect. There are many types of water-based ink additives, and some commonly used ones are listed below.

1. PH stabilizer

The pH value of water-based ink has a greater impact on the performance of the ink. If the pH value is too low, the viscosity of the ink is too high, and the pH value is too high.

The color depth decreases. Due to the volatilization of water and ammonia, the viscosity and pH of water-based inks change, so pH stabilizers should be used frequently in the printing process. Its main function is to balance the pH value of the water-based ink during the printing process and keep the pH value of the ink system between 8.2 and 9.5. It can also be used as a diluent. The method of use is to add 1%~2% every 30-50min for better results. Commonly used pH stabilizers are ammonia, alkyl amines and so on.

2. Diluent

The thinner can reduce the color density of the ink, increase the solid content and gloss of the ink, but does not affect the viscosity, drying speed and printing performance of the ink. Add appropriate amount according to printing requirements. Common thinners include white ink, thinner and gloss paste that are formulated with light-colored inks.

3. Thinner

4. Defoamer

Because ink has soap-like characteristics and is prone to bubbles, it needs to be improved by adding anti-foaming agents and anti-foaming agents.

5. Quick-drying agent

6. Wetting and dispersing agent

The ink manufacturing process is actually to disperse the pigment in the binder by mechanical force according to the designed formula and make it form a dispersion of fine particles, so as to obtain the ink with the expected ink properties. Due to the difference in the surface properties of the pigment and the surface tension of the binder, a small amount of surfactant is needed to improve the compatibility.

7. Thickener

8. Bactericidal and antibacterial agent

9. Anti-friction agent (slip agent)