Talk about the factors that affect the gloss of water-based inks

Gloss has a great influence on the appearance quality of printed products. At present, water-based inks generally suffer from poor gloss, which seriously hinders the application of water-based inks in certain fields.

The effect of water on gloss

Water-based ink uses water as the solvent and has a high content in the ink. It can be adjusted within the range of 20% to 50%. When the water content is large, the ink absorption rate of the paper during the printing process increases, the ink viscosity increases significantly, the ink leveling process terminates prematurely, and it is difficult to form a smooth ink layer, which affects the ink glossiness.

If the water content is too low, the solid content increases and the ink viscosity increases accordingly. As for the same absorption strength of the paper, the ink absorption rate is inversely proportional to the viscosity, the greater the viscosity value, the smaller the absorption rate, the worse the leveling, the worse the ink film surface after printing.

The effect of ink fineness on glossiness

The fineness directly affects the printing quality and leveling of the ink. The fineness is good, the smoothness of the ink film is high, and the gloss of the ink film is also high. With poor fineness, it is not easy to form a high-quality ink film after printing. When the dot pattern is printed, the dot extension or emptiness is prone to occur, the dot edge is not smooth, and the gloss of the ink film is greatly reduced.

Agent and polymer monomer effect on gloss

The speed of volatilization of the cosolvent in the ink also affects the gloss of the water-based ink. When the co-solvent volatilization rate is too fast, the ink tends to flow poorly, the ink layer is less than even leveling, there are streak marks, trachoma and other phenomena, the gloss is poor. The slow evaporation of the co-solvent causes the ink to dry out poorly, the hardened conjunctiva of the binder is blocked, the leveling property is poor, and the glossiness is also affected.

The type and amount of monomers also have a certain effect on the gloss of water-based inks. When the amount of methyl methacrylate and styrene is increased, the formed ink film has high hardness and good gloss, but it is relatively brittle, has poor solubility, and is prone to cracking. When the amount of butyl acrylate is increased, the ink film has good flexibility. , Water resistance and solubility increase, but the gloss is poor.

Effect of additives on gloss

The additives in water-based inks mainly include defoamers, waxes, leveling agents, etc. They also have a certain influence on the gloss of water-based inks.

(1) Defoamer. Different types of defoamers have different effects on the gloss of the ink layer. Using S062 with good defoaming effect (with a defoaming height of 30) will reduce the gloss of the printed ink film, and the defoaming effect of CF246 (Anti-foam height of 25) can increase the gloss of the ink film.

As the content of the defoamer used increases, the gloss of the ink film gradually decreases. In the formulation of 100g water-based ink, the amount of defoamer is preferably 0.5%. Excessive amount of defoamer not only affects the gloss of the ink layer, but also affects the service life of the water-based ink.

(2) Waxy substances. In water-based inks, waxes are generally used as agents or slip agents. When using a wax of the same weight, the larger particle size has less effect on the gloss. If 1% of microcrystalline wax with an average particle size of 10 μm is used, the number of wax particles in the water-based ink system will significantly increase and the gloss will become lower when the average particle size is reduced to 5 μm. However, when the particle size of the microcrystalline wax is reduced to 1 to 2 μm, the opposite tends to occur. In high gloss applications, the combined use of polyethylene and PTFE is the most promising.

Effect of Emulsion Emulsion can make the water-based ink gloss, water resistance and friction resistance have been greatly improved, is an essential part of high-grade water-based ink.

Emulsions are polymers that are dispersed in an emulsion in an aqueous medium with the aid of an emulsifier under mechanical or vigorous shaking. Polymers such as initiators and pH modifiers are used in the polymerization. The decisive factor is the emulsifier. The emulsifier is a surfactant. Its function is to reduce the surface tension of monomer and water, and make the monomer and water form a stable and uniform system. When the water-based ink is added into the emulsion, the pigment is immersed into the pores of the aggregates of the pigment particles faster than the conventional ones. The stability of the ink system is improved, and the substrate surface has better wetting, adhesion, and soaking effects. The leveling performance is improved, the film surface is smoother, and the gloss is improved.

Reprinted from: China Design Printing Network