The influence of high temperature and high humidity environment on flexible packaging gravure production in summer is obvious, because at present, flexible packaging enterprises still focus on solvent gravure printing ink. High temperature is easy to promote the rapid volatilization of organic solvent in the ink, and high humidity is easy to change the ink viscosity, which affects the quality of flexible packaging gravure printing. At present, it is the season of two volts high temperature. Understanding the impact of high temperature and high humidity environment on flexible packaging gravure production and how to make countermeasures to reduce unnecessary quality loss has become the most concerned problem of flexible packaging enterprises.
1. Anti white dot on shallow screen and blocking of small text
When the ambient temperature rises, the volatilization rate of organic solvents in gravure ink accelerates, and the printing products will have the phenomenon of shallow screen anti white spots and small text blocking.
Countermeasures:
At this time, slow drying solvent should be added in time, but the amount should be determined according to the actual situation, otherwise excessive addition will cause problems such as excessive solvent residue and ink anti adhesion.
2. False drying of ink
Ink false dry, that is, the ink layer does not dry in the surface. This phenomenon can easily lead to excessive solvent residue, poor adhesion of ink layer, anti adhesion of ink after winding, etc.
Countermeasures:
Reduce ink viscosity properly; Reasonably control the printing speed; Adjust the matching degree of air volume and air temperature; Improve drying capacity; Maintain constant temperature and humidity.
3. The solvent residue exceeds the standard
When the ambient humidity increases, the ink drying speed will slow down. Generally, if the ambient temperature is 20 ℃, when the humidity rises from 65% to 75%, the drying speed before and after the ink can differ by 1 ~ 2 times. In addition, most flexible packaging enterprises will use a large number of slow drying solvents in gravure production in summer. Especially for low-speed gravure printing machines, a large amount of butyl must be added to ensure the printing effect, especially in the shallow screen area. However, the drying efficiency of low-speed gravure printing machines is low, which will lead to excessive solvent residue.
Countermeasures:
For the high-speed gravure press, due to the fast machine speed, there is no need to add too many slow drying solvents to adjust the ink drying speed. At this time, the ink viscosity is low, the ink layer is thin after transfer, and a good drying effect can be achieved with large air volume and appropriate drying temperature. In view of the excessive residue of printing solvent that may be caused by high temperature and high humidity environment, flexible packaging gravure printing enterprises should use gas chromatograph to do real-time monitoring, so as to prevent accidents.
4. Anti adhesion of ink
In the process of printing storage and handling, if the ambient temperature is too high or the ventilation is not smooth, it is easy to cause ink anti adhesion, especially for the printing with large tension in individual parts after winding (such as the position where the printing patterns are concentrated). In addition, factors such as high solvent residue, false drying of ink and poor adhesion of ink layer caused by high temperature and high humidity environment will also aggravate the anti adhesion of ink after winding.
5. Effect on ink stability of ink tray
At present, because the closed or semi closed ink scraping system has not been popularized and applied in gravure production, most flexible packaging enterprises still use open ink trays, that is, the ink in the ink trays is directly exposed to the air. However, in the environment of high temperature and high humidity, the stability of ink in open ink tray will gradually deteriorate: high temperature is easy to lead to "solvent imbalance", resulting in a series of printing faults; High humidity is easy to increase ink viscosity, resulting in blocking.
Countermeasures:
In view of the phenomenon of "solvent imbalance", the actual proportion of solvent components in ink tray can be analyzed by gas chromatograph to avoid the change of ink solvent proportion caused by improper design of solvent volatilization gradient.
6. Impact on nylon film printing quality
Nylon film is a product that is easy to absorb moisture. The change of size after moisture absorption will easily lead to inaccurate overprint in the printing process. The slower the printing speed, the more inaccurate the overprint. In the process of bag making, it is easy to have problems such as dislocation of front and back patterns and inability to align. In addition, the water film accumulated on the surface of nylon film will also lead to insufficient composite strength and blistering.
Countermeasures:
Before use, put the nylon film into the curing room for drying for 2 ~ 3 hours, and do not open the package too early; During printing, the first color group is not printed on the plate roller, and pre drying is also required; Nylon film shall be used up at one time as far as possible; Moisture proof and drying measures shall be taken for unused nylon film; The workshop shall maintain reasonable and constant temperature and humidity.
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