Solve the problem of gravure back tack in printing
We are a big printing company in Shenzhen China . We offer all book publications, hardcover book printing, papercover book printing, hardcover notebook, sprial book printing, saddle stiching book printing, booklet printing,packaging box, calendars, all kinds of PVC, product brochures, notes, Children's book, stickers, all kinds of special paper color printing products, game cardand so on.
For more information please visit
http://www.joyful-printing.com. ENG only
http://www.joyful-printing.net
http://www.joyful-printing.org
email: info@joyful-printing.net
After printing on plastic film or transparent paper, the print has a dry illusion, but the back side is dirty during storage after printing the roll or bag. In severe cases, the print is not broken, and the ink layer is dyed. , resulting in product retirement. This phenomenon is more likely to occur during the hot season, but high temperature is not the only cause of back tack. It is also closely related to a series of factors such as plastics, inks, solvent evaporation rate, air volume in the operating environment, and illumination.
1. The solvent in the gravure ink failed to be completely evaporated after printing.
(1) Plastic film printing is to dry the ink by solvent evaporation. Its volatilization speed is an important factor that determines the drying of the ink layer and affects the printing quality. The slower the solvent evaporates, the better the reproducibility of the plate, the more beautiful the print color, but it is easy to stick; on the contrary, it will cause whitening of the print. Therefore, choosing the solvent with the proper volatilization speed is the key to gravure printing of plastic film. In continuous color printing, the film must be completely evaporated during the running time between the two printing stations. Otherwise, the roller will stick when printing at the next station.
(2) After the film printing, the organic solvent in the ink is not completely volatilized in the drying system, and there is still residual heat after the film is wound, and the solvent remaining in the ink layer is brought to a condition of continued volatilization to form blocking.
(3) During the hot and humid season, the film is too tight or compressed after printing.
Countermeasure, the evaporation rate of the solvent in the ink depends not only on the boiling point of the solvent, vapor pressure, latent heat of vapor, but also on the temperature, humidity, wind base, solute and thickness of the ink layer in the operating environment. Therefore, the evaporation rate of the solvent in the ink should be adjusted at any time according to the change of the conditions. At normal temperatures, if the ink layer is too dry, a slow-releasing solvent should be added; otherwise, a solvent that evaporates quickly is added. It may also be diluted with a mixed solvent of xylene, ethanol and isopropanol (the three solvents are each mixed in a ratio of 1/3, and it is better to use a single solvent than the mixed solvent). If you feel too dry, you can use a little alcohol instead of some ethanol (butanol has the effect of increasing the gloss of the ink). But be sure to pay attention to the amount of addition, so as not to affect the drying of the print.
The solvent for gravure printing of plastic film is mainly composed of alcohol, benzene, alcohol, ethanol, isopropanol, benzene, toluene and dimethyl. Due to the needs of nitrocellulose, esters such as ethyl acetate and butyl acetate are also added. In short, the organic solvent in the ink is required to be completely volatilized before winding. Appropriately slow down the speed and increase the air volume. After the film is printed, it is loosely placed in the wire woven basket, so that the ink layer can be continuously ventilated and dried, and then cut and bagged after curing. After film printing, the bag is wrapped and placed vertically in the carton to reduce the film surface. The pressure between.
2. Plastic gravure ink ink is poor In some plastic gravure ink, the binder has a low melting point, and it is easy to stick when the operating environment temperature is high and the relative humidity is large.
Countermeasures:
1 When the conditions permit, install the air conditioner in the operation workshop, control the room temperature between 18 °C and 20 °C, and control the relative humidity to less than 65%;
2 Replace the ink with good ink.
3. Plastic film thin printing package is not suitable for the reasons
1 plastic film processed from non-packaging resin;
2 The opening agent in the resin is insufficient. Countermeasure: Replace the plastic film.
4. The impact of static electricity Cause: The plastic film generates static electricity, forming a film between each other. Countermeasure: Add antistatic thorns to the plastic.