Importance of surface tension of aldehyde ketone resin printing ink

The importance of surface tension of aldehyde ketone resin printing ink: at the same time, the surface tension of ink is an unavoidable factor, which is completely different from solvent based ink.

Compared with solvent ink, the surface tension of ink is much higher; However, too high surface tension will cause the ink to not well wet the surface of the substrate material and the ink holes of the gravure printing roller, which will cause the uneven printing ink film; Due to the high surface tension of the ink, the ink film will form a contracted state on the surface of the substrate, causing the ink film to show an obvious network, and also causing the ink to not be uniformly transferred from the ink holes to the surface of the substrate. However, the surface tension can be reduced, which requires careful selection of appropriate surfactants or a small amount of alcohol. Although it takes a lot of labor to develop printing ink, it is still a difficult challenge to completely reduce the VOC emission of ink in gravure printing while maintaining the printing quality of printing ink (like the printing quality of solvent based ink). Some common problems often occur in the process of gravure printing with water-based ink. This article will introduce the processing now.

Question 1: plate blocking

During the use of water-based ink, blocking is a problem that z is prone to occur, mainly because the water-based ink of gravure printing has poor re solubility, so it is very easy to cause blocking once the operation is improper. The blocking will also cause a series of printing quality problems, such as pinholes on the surface of the printed product, small text missing strokes, uneven ink color, and bottom leakage. The causes and solutions of plate blocking are as follows.

(1) Stop printing intermittently, and the ink is dried and fixed in the mesh cavity due to the volatilization of the diluent. At this time, special tools and cleaning agents shall be used to clean the printing plate. If necessary, the printing plate shall be removed and cleaned with organic solvent (ethyl acetate). Therefore, in case of intermittent shutdown, it is recommended to stop the printing without stopping to avoid ink drying in the mesh.

(2) The ink dries too quickly and dries in the mesh hole. For this, first, a small amount of slow drying agent can be added to the ink. The slow drying agent can inhibit and slow down the drying time of the ink and prevent the skin on the surface of the ink. The general dosage is controlled at 3% ~ 5%; Secondly, consider whether the diluent ratio is appropriate. If necessary, adjust the diluent ratio. Generally, the ratio of alcohol and water in the aqueous ink diluent is between 1:1 and 4:1. However, the amount of water needs to be considered when increasing the ratio of water. If the amount of water is too large, on the one hand, too many bubbles will be generated, and on the other hand, the ink will not be completely dried, causing the printing product to be sticky or the ink to be pulled back.

(3) The ink viscosity is too high. At this time, the ink viscosity should be properly reduced, but the printing speed and leveling must be taken into account. Because the viscosity of the ink is too low, too many bubbles will be generated, which will lead to problems such as white spots on the surface of the printed product, too light color of the printed text or thick thin lines and small words.

(4) The printing plate mesh hole is too shallow. At this time, the depth of the printing plate net hole should be properly deepened, but the quality problems that may occur when the printing plate net hole is too deep must be considered, such as the coarseness of the handwriting, the blurring of the small text, and the unclear pattern.