Talking about the influence of external conditions of offset printing on ink drying

1. The effect of paper moisture content on ink drying
We know that paper fibers are hydrophilic substances. When the water content of the paper is high, a hydrated layer will be formed on the surface, which is not conducive to the combination of the ink binder and the fiber, and even affects the penetration of the binder, so the paper absorbs ink. Especially for oil-based inks with water repellency, this effect is more prominent. At the same time, the existence of the hydration layer also hinders the absorption of oxygen by the paper, and delays the process of ink oxidative polymerization, which is extremely disadvantageous for the absorption of ink on the paper (especially the oxidized conjunctive drying ink). Therefore, the moisture content of printing paper should not be too high. Considering other factors comprehensively, the paper moisture content before printing is generally controlled at 4% to 8%.
2. The effect of the acidity and alkalinity of paper on the drying of ink
The acidity and alkalinity of the paper surface have a certain influence on the drying speed of the oxidized conjunctive drying ink. The lower the pH value of the paper surface, the slower the ink drying, that is, the worse the ink absorption of the paper. According to the experiment, when the pH value of the paper is reduced from 5.5 to 4.4, the drying speed is reduced by 3 times, so the acid paper should be more dry oil than the alkaline paper.
3. The effect of fountain solution on ink drying
The concentration of hydrogen ions in the fountain solution is high, which has a destructive effect on the drier and slows the drying of the blot. Therefore, when the fountain solution is too acidic, it will cause the printed ink to dry and cause stickiness, so we are using fountain Liquid time. Not only should we consider the ability of the fountain solution to clean the blank part of the printing plate, but also the influence on the drying of the blot. If it is the dampening liquid's influence on the drying of the printed product, it should not be mistaken for that the driers are added too little and the driers are added blindly to avoid causing the printed products to not dry-add the driers-the printed products are still not Dry results.
4. The effect of the interval time of register printing on the drying of ink
Color prints are generally multicolor overprint products. How long the printing interval of the next color is, is a factor that should be considered, especially the overprinting on the background color, lacking the conditions to absorb penetration, so the drying is slower. For a four-color product, if four machines are used to print each machine to print a color sequence flow method, if the time interval is one day, then the drying time of the driers added to the ink should be controlled at one day. If a machine is used for printing, the length of the interval between printing the second, third, and fourth hue should be taken into consideration when adding the drier.
Fifth, the impact of environmental temperature and humidity on ink drying
As the ambient temperature increases, the molecular motion is accelerated, and the imprint drying is increased. On the contrary, when the temperature is decreased, the molecular motion is slowed, and the imprint drying is slowed. As the temperature increases, the oxidative polymerization of the binder in the ink also increases, and the drying speed also increases. The ink itself is an exothermic reaction during the drying of the polymerization reaction, so it in turn promotes the drying of the blot.
The ambient temperature also has an effect on the drying of the blot. The relative humidity is large, the water molecules in the air increase, and the activity of oxygen is greatly hindered, so that the absorption of oxygen by the oil molecules will be affected. In addition, when absorbing oxygen, due to the water As the molecules increase, more or less absorb some water molecules, which act as oxygen barriers in the ink. Therefore, the relative humidity is large, the ink drying speed is slow, and the relative humidity is small, the ink drying speed is fast. Generally speaking, under the same conditions, when the relative humidity is increased by 10%, the drying time will be extended by about 1 times, so it is necessary to control the humidity of the workshop.
6. Influence of workshop ventilation conditions on ink drying
The ventilation conditions of the print placement position in the workshop also have a certain relationship with the imprint drying. The workshop has good ventilation conditions, fast air flow, and more opportunities to provide oxygen, which creates conditions for the oxidative conjunctiva of the ink layer, so the drying is fast, so Spread the printed matter to facilitate the printing and drying. The thickness of the imprinted ink layer, the size and water consumption of the printed parts, and the number of printed parts. The degree of light in the workshop, etc., also have different effects on the printing and blotting drying to varying degrees.
In summary, the influence of various factors needs to be controlled on the technical conditions of the process. It is not possible to simply add more driers as the only driers. In actual production, it is necessary to comprehensively consider the relationship between various factors such as paper, various printing process conditions, and the technical experience of the operator, and carry out overall control of all aspects according to actual needs. Only in this way can high-quality prints be obtained.

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