Why must the dryness of the ink of the gravure printing machine be controlled?
The main printing failures caused by the improper ink drying are:
(1) At a certain printing speed, if the ink initially dries too fast, it will cause problems such as paste, scratches, ink whitening, poor gloss, and poor leveling.
(2) In continuous color printing, because the ink dries too slowly, sticking to the roller will occur in the next station printing, and it will also cause the printed product to rewind and stick. The volatilization speed of the solvent in the ink depends not only on the boiling point, vapor pressure, latent heat of evaporation and other factors of the solvent, but also on the temperature of the printing environment, relative humidity, air volume, and ink layer thickness. Therefore, the volatilization rate of the solvent in the ink should be adjusted at any time according to changes in conditions.
Under normal production conditions, if the ink dries too fast, an appropriate amount of slow-drying diluent should be added; if the ink dries too slowly, a fast-drying diluent should be added. If conditions permit, the temperature of the printing environment should be controlled between 18~25℃, and the relative humidity should be controlled below 65%, which is conducive to the stability of the ink performance.