Drying principle and drying skills of the hottest

The drying principle and drying skills of ink 14

the most frequently asked questions from sales personnel in the printing industry, technical service representatives and printing staff in the sheet fed printing process are mainly about the drying of ink on coated paper and uncoated paper. In order to find the answer to these problems that light cannot pass through these structures, we must understand the ink drying process of ink and sheet fed paper. The drying process of ink includes two steps. The first step, oxidation, is a process through which oxygen combines with the oil in the ink and inking oil to form a solid. The second step is absorption. Through this process, the solvent penetrates into the paper and allows oxygen to come into contact with oil or inking oil. If the speed of solvent penetrating into the paper or coating is not fast enough, the reaction speed of oxygen with oil and inking oil will be reduced, and finally the drying time will be extended. With this in mind, let's pay more attention to the drying process. When the ink is first printed on the substrate, the solvent in the ink will penetrate into the gap of the fiber or coating of the substrate. The pigment is retained in the dry oil part, which fixes the pigment on the printing surface. However, this is not completely dry. Due to the loss of solvent, the ink film becomes sticky and cannot be misjudged. In this way, everything has two sides. The ink loses its fluidity and stops there to prepare for conversion. With the loss of solvent, oxygen reacts with oil and the resin begins the drying phase. At this stage, the ink surface is fixed and will not be transferred to another piece of paper in the stack. However, the ink in the center of the ink film still remains liquid. According to the composition of the ink, the thickness of the printing ink film, the nature of paper or other materials and environmental conditions, it takes two minutes to more than one and a half hours for the ink to be completely fixed. After printing, oxidation occurs in alkyd resin or dry oil, and may also occur in resin. This polymerization results in the formation of a three-dimensional, like structure of the chemical binder. Oxygen reacts with all the oils and resins in the ink to convert the liquid materials in the ink film into solids, so that the ink is completely dry. If you leave linseed oil open, the same reaction will happen. Oxygen will react with linseed oil and cross combine to finally harden. A paper or coating with a very tight surface will make the penetration of solvent very slow. Therefore, there will be solvent residues in the ink, and will interfere with the reaction between oxygen and oil and inking oil. Of course, this will also increase the ink drying time. In order to speed up drying, desiccants are used in the ink to speed up the oxidation process. The two desiccants most widely used and longest used in industry include the following: * cobalt: it can accelerate the surface drying process (fixation). Because cobalt is blue, it turns brown during drying and is easy to fade white. Moreover, it is easily soluble in organic acids, so acidic fountain solution with too low pH value (lower than 4.0) has an impact on it* Manganese: it can accelerate the internal drying process and is a more powerful desiccant than cobalt. This desiccant is brown, but it has less effect on white than cobalt, and it is not easy to penetrate into the fountain solution. During the printing operation, a mixture of these desiccants is generally used to accelerate the surface and internal drying at the same time in order to complete the drying process. According to some of the following steps, the printer can overcome the ink drying problem: 1 Discuss the work with the ink supplier before printing, including the paper used. The best solution to the drying problem is prevention. All papers are different. For example, the drying of ink on paper is completely different from that on paper such as Springhill opera smooth. 2. When printing on paper with dense surface, avoid using soybean oil-based ink. Soybean oil is semi dry (slow) oil. 3. Keep the pH value of the fountain solution within the range of 4.0 to 5.0. The higher the acidity (the lower the pH value), the slower the drying process of the ink. 4. When printing a large area of the field, overprint with ink mixing oil containing desiccant or transparent size. 5. Use the recommended amount of desiccant for the ink being used. Too much desiccant will plasticize the ink, making it not dry. 6. Mixing additional desiccant in the fountain solution can improve the drying performance of the ink. Graf o SIEC is an example of additional desiccant, which can be added in an amount of 1% to 3%. 7. Lower the stack at the receiving end of the printer. 8. Use large particles of powder to help separate the printed paper, and allow more oxygen to enter and react with oil and resin. 9. Let the supplier increase the strength of the ink, so that it can be printed with a thinner ink layer, which can be easier to fix and dry. 10. Because the temperature of the printing machine or paper may be too low and will delay the drying of the ink, pretreat the paper before printing. 11. Remember that the ink composed of reflex blue extends the drying time. Discuss with the ink supplier. 12. There should be enough drying time before operation or replacement. 13. Use infrared drying to accelerate ink drying. 14. Remember that the ink used for film printing will fix and harden on the tough film within a few hours. Moreover, the best action plan is to discuss the operation and the paper to be used with the ink supplier. Some ink drying problems are the result of improper carriers, which leads to a low oxidation process or the lack of available catalysts. The oxidation rate can be increased by combining more oil or alkyd resin in the catalyst, or by using completely dry materials, such as flaxseed oil or tung oil, instead of semi dry oil, such as soybean oil

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