On the drying of printing ink and its influence on

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On the problem of ink drying and its impact on printing quality (II)

it is worth mentioning that the water content of paper has a certain impact on ink penetration and oxidation drying. Assuming that the water content of paper is very high, the fibers or coatings on the paper surface are in a loose state, the attraction between molecules is reduced, and the pores are blocked by water film, which not only reduces the absorption of ink binder, but also reduces the absorption capacity of oxygen, Obviously, they slow down the drying speed of the ink

III. drying performance of ink from the perspective of ink composition

we know that ink is mainly composed of the following four parts: binder (or resin), solvent (or water), pigment and additives. The solvent plays a direct and obvious role in the drying performance of the ink, and different resins, pigments and additives also have a certain impact on the drying performance

for a single solvent, the lower the boiling point, the faster the volatilization rate. However, there are exceptions. For example, the boiling points of ethyl acetate and ethanol are similar, but the volatilization rate of ethyl acetate is almost twice that of ethanol. The boiling point of water is not high, but the volatilization speed is very slow. Generally, medium, low and high solvents are used together to meet the dryness requirements of the ink. However, the volatilization rate of mixed solvents is restricted by various solvent molecules, which is not a simple arithmetic mean. Table 2 lists the boiling points and volatilization rates of different solvents for reference

when the resin is dissolved in organic solvent, the volatilization rate of the solvent decreases, and different resins slow down the volatilization rate of the solvent differently. The greater the solubility of the resin, the more difficult it is for the solvent to be removed from it, and the lower the volatilization rate, that is, the worse the release of the resin to the solvent. In the preparation of volatile dry ink, the selected resin should put a certain amount of energy into the dissolving demand to consider that the agent has a certain release, otherwise, poor solvent removal is easy to cause the back to rub dirty. In the oxidized conjunctiva drying ink, dry vegetable oil is used as the connecting material. The more double bonds in the molecules of unsaturated fatty acids, that is, the higher the degree of unsaturation, the slower the drying speed. For water-based ink, the higher the content of lotion resin, the faster the drying speed

when pigments are added to make ink, the volatilization rate is greatly reduced. The smaller the pigment particle, the larger the surface area, the faster the drying, and vice versa. And the larger the proportion of pigments in the ink, the lower the volatilization rate of the solvent and the slower the drying. At the same time, different kinds of pigments have different solvent stripping properties, such as black and blue recovery: the main body is not installed horizontally, and the solvent stripping property of the color is poor, and the volatilization speed is low. Table 3 lists the effect of pigment particle size on solvent volatilization rate

in addition to special driers, other additives have little effect on the drying performance of ink due to their small amount and different functions

IV. influence of printing environment and printing conditions on ink drying. This can be explained by the fact that the temperature rises and the movement of material molecules accelerates, thus promoting the penetration, volatilization and oxidative polymerization. Similarly, the increase of printing drying temperature is also conducive to ink drying. At the same time, slow down the printing speed to make the drying sufficient. The humidity of the printing environment also has a significant impact on the drying of the ink control system software based on the Windows XP operating system platform. The higher the relative humidity, the slower the drying speed of the ink. For example, under normal conditions, when the air relative humidity is 65%, the ink drying time is 6.7 hours. When the humidity rises to 75%, the same ink takes 23.3 hours to dry, delaying the ink drying time by more than three times

in the next five years v. conclusion to sum up, the drying problem of ink on the substrate is a very wide and relatively complex problem. To obtain an appropriate drying rate, ink manufacturers and printing manufacturers need to make joint unremitting efforts

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