If the viscosity of the solvent-based gravure printing ink is too high, it will cause printing defects such as scratches, bite, paste, and "orange peel".
In summary, when designing and manufacturing solvent-based gravure printing inks, it is necessary to select suitable pigments, resins, and solvents to match, so that the ink reaches a suitable initial viscosity. The printing plant should use the appropriate mixed solvent, preferably the thinner provided by the original ink manufacturer, and adjust the original ink to an appropriate "working viscosity" before it can be printed on the machine, so that high-quality prints will be obtained.
In addition, the viscosity of the ink in the printing process is also related to the printing speed. In general, the faster the printing speed, the lower the viscosity of the ink, otherwise the ink transfer effect is not ideal.
Solvent-based gravure printing inks are volatile dry inks, that is, when the solvent overflows from the wet ink film, the ink film will change from liquid to solid. Therefore, the speed of solvent volatilization has a direct impact on the drying properties of the ink.
When designing and producing solvent-based gravure printing inks, the solvent mixture of medium-boiling point, low-boiling point and high-boiling point is generally selected to meet the drying requirements of the ink. If the resin is improperly selected, the resin softening point is low, the resin does not remove the solvent well, the pigment release to the solvent is not good, too much high boiling point solvent will soften the ink film, etc., will affect the solvent volatilization rate, resulting in solidification Too much solvent remains in the ink film afterwards.
When preparing solvent-based gravure printing inks, the resin is generally selected first, followed by the solvent. The dissolution parameter of the mixed solvent is similar to the dissolution parameter of the dissolved substance, so it is easy to dissolve and the faster the volatilization rate. Due to the addition of pigments in the finished ink, the volatilization rate of the mixed solvent will be greatly reduced, and the larger the pigment particles, the slower the volatilization rate of the solvent, the worse the drying property of the ink. At the same time, the greater the amount of pigment, the slower the volatilization rate of the mixed solvent. This is due to the mutual traction between the solvent and the pigment surface, which resists the removal rate of the solvent.
In addition, the higher the room temperature, the lower the relative temperature of the air and the faster the air circulation, the faster the volatilization rate of the mixed solvent, and the slower the converse.
The printing failures caused by improper drying of the ink mainly include:
(1) At a certain printing speed, the initial drying of the ink will cause problems such as paste, scratches, ink whitening, poor gloss, and poor leveling.
(2) In continuous register printing, because the ink is too slow to dry, sticking rollers will occur when printing at the next station, and it will also cause the printed product to rewind and stick. The evaporation rate of the solvent in the ink depends not only on the solvent's boiling point, vapor pressure, latent heat of evaporation and other factors, but also on the temperature, relative humidity, air volume and ink layer thickness of the printing environment, so it should be adjusted at any time according to the changes in conditions The evaporation rate of the solvent in the ink.
Under normal production conditions, if the ink dries too fast, an appropriate amount of slow-drying thinner should be added; if the ink dries too slowly, the fast-drying thinner 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 ink performance.
Backpacks,Rucksack,Jansport Backpack,Mini Backpack
Ningbo Happiness Stationery Industrial & Trading Co Ltd , https://www.cnhappiness.com