The effect of high temperature and high humidity environment in summer on the production of flexible packaging gravure printing is obvious, because soft packaging enterprises still mainly use solvent-based gravure ink, high temperature tends to promote the rapid evaporation of organic solvent in the ink, and high humidity easily changes the viscosity of the ink. It affects the quality of gravure printing in flexible packaging. At present, the high temperature and high humidity environment will affect the production of flexible packaging gravure printing, and how to take countermeasures and reduce unnecessary quality loss has become the most concerned issue for soft packaging enterprises.
1. Shallow network anti-white point and small text blocking phenomenon
When the ambient temperature rises, the volatilization rate of the organic solvent in the gravure ink is accelerated, and the printed product may have a phenomenon of shallow whitening and small text blocking.
At this time, it is necessary to add a slow-drying solvent in time, but the amount of addition should be determined according to the actual situation, otherwise excessive addition may cause problems such as excessive solvent residue and ink anti-adhesion.
2. Ink dry phenomenon
The ink is dry and dry, and the ink layer does not dry in the surface. This phenomenon can easily lead to excessive solvent residue, poor adhesion of the ink layer, and anti-sticking of the ink after winding.
Appropriately reduce the viscosity of the ink; reasonably control the printing speed; adjust the matching of the air volume and the air temperature; improve the drying capacity; maintain a constant temperature and humidity.
3. Solvent residue exceeds the standard
When the ambient humidity rises, the ink drying speed will be slower. Under normal circumstances, if the ambient temperature is 20 ° C, when the humidity is raised from 65% to 75%, the drying speed of the ink before and after can vary by 1 to 2 times. In addition, most flexible packaging companies use a large amount of slow-drying solvent in the gravure printing production in summer. Especially for low-speed gravure printing machines, in order to ensure the printing effect of printed products, especially in the shallow mesh area, a large amount of butyl ester must be added. Low-speed gravure presses have lower drying efficiencies, which in turn can lead to excessive solvent residues.
For high-speed gravure printing machines, because the machine speed is faster, it is not necessary to add too much slow-drying solvent to adjust the ink drying speed. At this time, the ink viscosity is low, the ink layer is thin after transfer, and the larger air volume and appropriate Drying temperature can achieve good drying results. For the high temperature and high humidity environment, the residual solvent residue of the printing product may be exceeded. The flexible packaging gravure printing enterprise should use the gas chromatograph to do real-time monitoring work in order to prevent it from happening.
4. Ink anti-stick phenomenon
In the process of storage and handling of printed products, if the ambient temperature is too high or the ventilation is not smooth, it is easy to cause the ink to stick to the sticky phenomenon, especially for the printed products with large tension in individual parts after winding (such as the position where the printed pattern is concentrated) . In addition, factors such as high solvent residual amount, ink dry-drying phenomenon, and poor adhesion of the ink layer caused by high temperature and high humidity environment may also increase the ink anti-stick phenomenon after winding.
5. Influence on ink tank ink stability
At present, because closed or semi-closed squeegee systems have not been popularized in gravure production, most flexible packaging companies still use open ink trays, that is, the ink in the ink tray is directly exposed to the air. However, in high temperature and high humidity environments, the stability of the ink in the open ink tray will gradually deteriorate: high temperature easily leads to "solvent imbalance", resulting in a series of printing failures; high humidity tends to increase the viscosity of the ink, leading to blockage.
For the phenomenon of “solvent imbalance”, the actual proportion of the solvent component in the ink in the ink can be analyzed by gas chromatography to avoid improper design of the solvent evaporation gradient, resulting in a change in the ratio of the ink solvent.
6. Influence on the printing quality of nylon film
Nylon film is a product that is very easy to absorb moisture. The change of the size after moisture absorption may lead to inaccurate overprinting and slower printing speed. The more inaccurate the overprinting, the prone to misalignment of the front pattern during the bag making process. Unable to align and other problems, in addition, the water film on the surface of the nylon film can also cause insufficient composite strength, foaming and the like.
Before use, put the nylon film in the curing chamber and dry it for 2 to 3 hours. Do not open the package too early. When printing, the first color group is not printed on the plate, and pre-drying is required; the nylon film is used up as much as possible; The nylon film should be well protected against moisture and dryness; the workshop maintains a reasonable and constant temperature and humidity.