Packaging bags frequently exhibit quality issues in hot and humid summer conditions. How can this be solved?

The impact of high-temperature and high-humidity environments in summer on the gravure printing production of packaging bags is quite significant. This is because packaging bag companies currently mainly use solvent-based gravure inks. High temperatures easily accelerate the volatilization of organic solvents in the ink, while high humidity easily changes the ink viscosity, thus affecting the quality of gravure printing on packaging bags.

Below, Shunxingyuan Packaging, a professional flexible packaging manufacturer, will guide you in understanding how manufacturers with rich experience in packaging bag manufacturing take preventive measures in advance under high-temperature and high-humidity environments to reduce unnecessary quality losses.

1. Impact on shallow screen transfer

When the ambient temperature rises, the volatilization rate of organic solvents in gravure inks also increases. If diluting solvents are not added in time to adjust the solvent ratio in the ink, or slow-drying solvents are not used in time, the printed matter will exhibit shallow screen whitening and small text blocking phenomena.

However, it should be noted that the amount of slow-drying solvent added should be determined according to the actual situation. If too much is added, it will adversely affect the drying of the ink, which may lead to excessive solvent residue and ink stickiness.

2. Impact on ink drying

Ink false drying, that is, the phenomenon of the ink layer being dry on the surface but not dry inside.

This phenomenon easily leads to excessive solvent residue, poor ink layer adhesion, and ink stickiness after winding.

The phenomenon of ink false drying is more likely to occur in summer, mainly due to:

1. High temperature causes the solvent on the surface of the ink layer to volatilize too quickly;

2. High humidity causes a large amount of water in the air to enter the ink, inhibiting the volatilization rate of the solvent in the ink;

3. A large amount of slow-drying solvent is used. If this solvent does not volatilize completely, it is easy to cause residue, resulting in the phenomenon of ink false drying.

Solutions:

1. Appropriately reduce the ink viscosity;

2. Reasonably control the printing speed;

3. Adjust the matching degree of air volume and air temperature;

4. Since the drying effect of medium and low-speed gravure printing machines is not very good, flexible packaging companies can choose gravure printing machines with better drying capabilities, or modify existing gravure printing machines to improve drying capabilities;

5. When the environmental humidity is too high, flexible packaging companies with the conditions should dehumidify the workshop and maintain a constant temperature and humidity as much as possible.

3. Impact on solvent residue

Practice has shown that when the environmental humidity increases, the ink drying speed slows down.

Generally, when the ambient temperature is 20℃, when the humidity increases from 65% to 75%, the drying speed of the ink before and after can differ by 1-2 times.

In addition, most flexible packaging companies use a large amount of slow-drying solvents in summer gravure printing production, such as butyl acetate, which accounts for a large proportion in solvent-free and ketone-free inks.

Especially for low-speed gravure printing machines, to ensure the printing effect of printed matter, especially the shallow screen area, a large amount of butyl acetate must be added. However, the drying efficiency of low-speed gravure printing machines is low, which may lead to excessive solvent residue.

For high-speed gravure printing machines, due to the faster speed, 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 good drying effect can be achieved with a larger air volume and appropriate drying temperature.

In response to the phenomenon of excessive solvent residue in printed matter caused by high temperature and high humidity, flexible packaging gravure printing companies should use gas chromatography to conduct real-time monitoring to prevent problems before they occur.

4. Impact on winding

During the storage and handling of printed matter, if the ambient temperature is too high or the ventilation is poor, it is easy to cause ink stickiness, especially for printed matter with larger tension in some parts after winding (such as positions with more concentrated printing patterns).

In addition, high solvent residue, ink false drying, and poor ink layer adhesion caused by high temperature and high humidity will also aggravate the ink stickiness after winding.