Corrugated Card Color Printing and Factors Affecting Ink Configuration Continued

2, the factors that affect the ink configuration

2,1 Corrugated board printing ink

Corrugated paper is characterized by rough paper, the surface is not smooth enough, the ink penetration, the surface is mostly dark brown. Therefore, it is required that the basic color of the water-based ink is bright, the coloring power is strong, and the hiding power is high; and the ink has a fast penetration and drying performance; in the printing process, it must have good redissolvability to ensure smooth ink-discharging process; in order to satisfy Packaging requirements, the imprint should also have good abrasion resistance and water resistance.

Corrugated printing inks are mainly made of 5 different materials, including coloring (10-40%), resin or adhesive (20-28%), solvent (33-50%), alkaline Material composition (4-6%) and additives (3-4%). Among them, changes in adhesives and additives play the largest role. As the quality of corrugated packaging increases, the amount of moisture absorbed by the substrate decreases, and it is more dependent on evaporation that resembles the drying principle. After the ink is printed on the substrate, moisture evaporates on the one hand to the surrounding environment and on the other hand it is absorbed by the substrate. The rate of evaporation of water depends on the moisture content, the dehydration characteristics of the binder and the volatility of the water.

2.2 Factors Affecting Ink Configuration

(1) Colorant

The colorant is the most expensive component in the ink configuration. The colorant used in corrugated paper printing inks is mainly a basic polymer synthetic pigment, which is characterized by insolubility in the binder resin paint, low toxicity and abrasion resistance, and improved pigments. Wetness. In some cases, the adhesive can also be colored with very transparent pigment chips. The original chrome yellow lead and other heavy metal pigments were gradually replaced.

(2) Adhesives

Alkali-soluble resins and disperse-phase resins are two types of adhesives that are suitable for corrugated paper printing inks. The alkali soluble resin is cationic, its polymer backbone contains functional carboxylate groups, and the carboxylates react with the basic base to generate water soluble salts. Ie acid + alkaline binder = salt + water

This reaction is reversible. When the steady pH value decreases, the resin will return to an insoluble state. As shown in Figure 5. The second resin is a disperse phase polymer. The resin particles are controlled by the levitation force generated by the hydrophilic tension. When the steady pH value decreases, this tension dissipates and the resin coalesces. This reaction is non-reversible. Once it is dried, The ink layer is hardly redissolved. From this, it can be seen that his door is suitable for the configuration of corrugated paper inks, containing high solids content and less water, and naturally requiring less water to be removed, thereby accelerating the drying speed.

Figure 5 Corrugated printing ink resin acid-base balance

In order to improve the printing quality of corrugated paper, it is necessary to obtain a good remelting property system, that is, a system capable of realizing self-rewetting during the transmission of anilox and solid ink rollers. This system can be obtained from a low molecular weight alkali soluble polymer with excellent remelting properties. The remeltability of corrugated printing inks is related to the volatility of the base material used, and sodium hydroxide is the best material for this purpose, it is non-volatile and imparts permanent water solubility to the ink. An ink configuration was also performed using monoethanolamine or triethanolamine instead of ammonia in the original ink. Alkali-solubilized polymers allow the wetting of larger pigment particles. With the same color intensity, less dehydration can be achieved with less wet coating, faster drying, and a higher coloring effect. The tone level is clearer.

(3) Additives and other ingredients

Additives account for a small proportion of the configuration, but they can change the properties of the ink, such as the addition of additive polyethylene wax, which can improve the abrasion resistance of prints. In the printing process, corrugated paper ink is prone to foaming in the ink fountain. The foam crawls through the ink fountain and blocks the pipe. It flows onto the three-dimensional ink roller and the substrate and causes printing errors. Therefore, anti-foaming agent and defoaming agent must be added to the corrugated printing ink. Agent, but must pay attention to anti-foaming agent and defoamer can not be excessive, otherwise it will cause printing defects.

The surface tension of the coated paper substrate is 36-42 dyne/cm, the surface tension of water is 72 dyne/cm, and the surface tension of water is much greater than the substrate tension. In order to obtain the flat coating effect, the ink is applied to the ink. Add a surface humectant to reduce the surface tension of the resin or water mixture, but choose a suitable humectant, otherwise, the humectant will cause or contribute to foaming. The surface tension of alcohol is very low, and high quality corrugated printing inks often add a small amount of alcohol to improve the low foam and surface wetting properties, and at the same time help to improve the drying of the ink and benefit the transfer process.

The preparation of corrugated paper inks is a complex balancing process of various materials. The proper configuration of ink components can greatly improve the quality of corrugated board printing.