High temperature and humidity, anti-sticking and high hair, the ink layer "surface dry" is the culprit

A large amount of practical experience shows that the phenomenon of ink back sticking caused by the "surface drying" of the ink layer of polyurethane ink is mostly. To solve this phenomenon, the ink needs to be printed at a low viscosity. In the low viscosity state, the printing ink consumption is less and the ink layer is thin. Under the action of a large amount of dilution solvent, the polyurethane ink connecting material molecules are relatively loose, and the shielding ability against solvent volatilization is weak. When the ink is transferred to the film, the solvent can be quickly and completely separated from the ink layer in the drying tunnel, and it is not easy to produce "surface dry" phenomenon. After adjusting the solvent ratio and ink viscosity, there are still the following points that our operators need to pay attention to.

Measures to avoid "surface drying" of ink layer

First, the temperature and air volume of the drying tunnel

Temperature and air volume should be proportionally balanced. When the temperature is high, the air volume is relatively large, and light or temperature can easily cause "surface drying". Maintaining a suitably high temperature and sufficient air volume can completely dry the ink layer.

Second, the cooling of the printed film

After the film is printed with the last color, it needs to be properly cooled before being rolled up. Excessive residual heat exists in the printed film, which may cause the softening of the ink layer and intensify the anti-sticking.

Third, winding tension and film roll diameter

The connection material of the polyurethane ink is similar to the molecular structure of the PET film. The affinity of the ink to the PET film is particularly good. The PET film is a rigid film and has good gas barrier properties. Even a very small amount of solvent residue in the printing ink layer may cause the adhesion effect of the ink layer and the back film. Therefore, in practical applications, the PET film is more prone to reverse adhesion than the NY film. The winding tension should be as small as possible when the film roll is not loose. At the same time, the small roll diameter also ensures that the film tightening force at the inner diameter part is not large.

The harm caused by the anti-sticking phenomenon is huge. Many color printing manufacturers may have encountered similar problems more or less. Therefore, they have accumulated a lot of experience in handling. Above, I mainly analyzed the factors that caused the anti-posting from the performance characteristics of the ink and made suggestions. I hope that I can provide some help to the friends of the color printing plant. Improvement of technical level.