The problem of solving the problem of printing ink in packaging printing

Major technical problems in packaging and printing have long plagued people. The problems are mainly focused on 1 ink migration; 2 ink film yellowing; 3 white spots on printed products; 4 back sticking and adhesion; 5 discoloration and fading; 6 ink film floating white; Pin holes and shrink holes; 8 transfer without ink; 9 bite color (commonly known as cross-color) and fade; 10 gloss difference (white). These printing technology problems have become a commonly agreed production failure.

1. Pinholes and shrinkage holes. In the packaging printing process, due to the operation of the machine, especially the rotation of the printing plate and the printing roller, the ink film often forms a pinhole. These small holes of different sizes and different sizes are often referred to as chemical pinholes. In the same area, holes of the same size are often distinguished as mechanical pinholes, but occasionally, the pinholes of the dot type a white circle are often shrinkage holes due to impurities or ink micro-resin particles after drying.

The chemical pinhole failure is caused by too rapid evaporation of solvent in the wet ink film and overflow of air bubbles in the printing ink film, so that the wet film cannot be leveled, resulting in drying of the packaging printing ink film and leaving needle-like holes. Of course, there are also ink bubbles produced when the ink is produced and blended or ink dilution is excessively generated, and the ink film has lost the fluidity resulting from the pinhole type when the air bubbles overflow during the printing and drying process. When the ink contains a trace amount of water or a high temperature, especially in a high-temperature environment, the above pinhole phenomenon is more likely to occur.

The solution is to strictly select inks, strictly select thinner materials, control the viscosity of inks, and use moderately selected solvents with slow evaporation rate to improve the leveling of the printing ink film, prevent the mixing of moisture and impurities, and check the air cleanliness of the vacuum pump and the substrate. The degree of surface contamination. For two-component inks and two-component adhesives, they should be used for a period of time. Printing inks that have generated surface or inherent flocculation should be prohibited.

2. Transfer does not ink. In the normal printing process, the ink occasionally does not rotate with the ink fountain roller, and even the ink accumulates on the printing press. In particular, after the printing speed is increased, the color tone of the printing ink is relatively light or shaded.

This failure was mostly caused by too high a pigment content, a too thick ink, a too high yield value, or a short ink head. The appearance of the above phenomenon is caused by the excessively high acid value in the ink system or the binder, the pigment, or the ingestion of acidic water or the addition of a single solvent.

Once this fault occurs, the TM-27 coupling agent should be added in an appropriate amount. In severe cases, the TM-3 coupling agent should be added or the basic solvent should be added for dilution, or the moistening agent or gold saturating oil should be added, or the printing pressure can be increased. If it is a defective roller, replace the roller or put a stirrer in the ink fountain.

Reprinted from: Printed in China