Screen printing of plastic parts generally adopts solvent volatilization and drying ink. The solvent in the ink volatilizes (part of the solvent penetrates into the surface of the plastic part first, and then volatilizes slowly), leaving the solid resin component to form a film to achieve drying. The drying speed is the same as the following factors.
(1) dry environment
temperature, humidity and ventilation conditions. With low temperature, high humidity and good ventilation, the drying speed is fast.
(2 ) Influence of ink
The solvent in the ink volatilizes fast, and the drying speed is fast; otherwise, it is slow. When some retarder-type slow-drying solvents are added to the ink in excess, it will remain in the ink film layer for a long time and make the printed matter smelly . The solvent absorption ability of the resin pigment in the ink also affects the drying speed. The absorption capacity is strong, the solvent release is difficult, and the drying speed of the ink is slow. If the resin used in the binder in the ink does not dry well, the surface is sticky or the softening point is too low, it will also cause poor drying of the ink.
(3 ) The influence of the thickness and area of the printing ink layer
If the printing area is large, the ink layer is thick, and the solvent evaporates slowly, the drying speed will be slow; on the contrary, when printing fine lines and characters, the ink layer is thin, the area is small, and the solvent evaporates quickly, so the drying speed is fast.
There is a pair of contradictions in the screen printing of plastic parts: on the one hand, in order to avoid the phenomenon of ink scraping back and forth on the screen, and the phenomenon of screen blocking and wire drawing due to the drying of the oil pin, it is hoped that the ink will dry slowly; and in order to improve production efficiency, From the perspective of shortening the production cycle, it is hoped that the ink will dry faster after screen printing. Therefore, the solvent component in the ink is generally a mixed solvent composed of various solvents (main solvent, co-solvent and thinner) with different volatilization speeds to solve the contradiction between slow drying during printing and fast drying after printing .
Usually the ink factory has corresponding supporting ink standard solvent supply, which can basically meet the drying and anti-netting requirements at the same time. Some manufacturers' ink solvents are also equipped with fast-drying, slow-drying, slow- drying and extra-slow-drying solvents, which can fully adapt to various screen printing requirements and environmental conditions.
