Some Issues on Printed Materials (11)

What are the ink drying methods?
The process of changing the ink from liquid to solid state is dry. Under ideal circumstances, the printing ink should be stable in the container or on the ink fountain or ink roller of the printing machine. When the printing ink is transferred from the printing plate to the surface of the substrate At that time, the ink quickly turned into a solid film.

There are physical ways to promote ink drying. There are also chemical ways. The way the ink is dried is determined by the type of ink, which is determined by the ink's binder and its formulation. The drying methods of inks are: drying of oxidized conjunctiva, penetration drying, volatile drying and some special drying methods, such as ultraviolet drying, infrared drying, condensation drying, electron beam drying, precipitation drying and so on.

Oxidative conjunctiva drying is the reaction of unsaturated fatty acids in the binder with oxygen in the air to polymerize the original straight chain structure into a network structure, thereby turning the ink into a solid film. Osmosis drying is when the ink is transferred to the porous paper surface, due to the effect of capillaries, the ink quickly penetrates into the gap on the surface of the paper, of course, mainly the binder penetrates into the paper fibers until the pigment particles in the ink become between Close enough, the space between them shrinks until the resulting capillary pull force is equal to the pull of the paper fiber to the web. Volatile drying refers to the fact that the printing ink contains volatile solvents. After printing on the surface of the printing material, the solvent evaporates into the atmosphere, leaving the remaining resin and fixing agent in the ink together with the color material to form a solid film layer and fixed on the substrate. On the surface.

Oxidative conjunctiva drying, osmotic drying and volatilization drying are commonly used drying methods, in addition to some special drying methods. Condensation drying is the drying method of the ink used in the printing of the carton. The ink is solid at room temperature. The ink is heated and melted at the time of printing. After being printed on the substrate, the temperature decreases, and the ink naturally changes to a solid state and “drys”. . With this ink, the printing machine must be heated. Ultraviolet drying, infrared drying and electron beam drying are all using special inks. After special irradiation, photopolymerization takes place and the ink is dried. The ink used in the precipitation drying method is ethyl cellulose dissolved in a high-boiling solvent and used as a binder. After being transferred onto paper, the printed product is immersed in a molten wax solution, and the binder is immediately precipitated to form a hard and flat ink. Film, generally used to print food packaging paper, such as bread packaging paper.

In most cases, the ink contains two or more drying methods. If the ink is transferred from the printing plate to the surface of the paper, some of the ink in the ink penetrates into the fibers of the paper. At the same time, the solvent begins to volatilize, and the binder on the surface of the paper begins to oxidize, resulting in the viscosity of the surface ink film. Hardness continues to increase, completing the drying process. Among them, there are both the effect of oxidized conjunctiva and the effect of infiltration and volatilization. However, the general ink is a drying method to complete the drying process. In addition, different types of inks are used for different printing methods to adapt to different types of printing plates and substrates. For example, the substrates used in plain printing are mostly offset paper and coated paper, and the resin type inks mainly include oxidized conjunctiva drying methods, while the gravure printing and flexographic printing using non-absorbable substances as substrates are generally used. The volatile solvent resin ink, the drying method is mainly volatile drying.