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Reverse sticking phenomenon in flexible packaging printing

In flexible packaging printing, the phenomenon of sticking on the reverse side of the printed matter often occurs, that is, when the printed matter enters the next process (the surface-printed product is usually a slitting process; the inner-printed product is usually a composite process), the graphic part of the printed matter is stuck to the printing process. The back of the substrate, the pattern and the text are damaged, this phenomenon is called adhesion.The reverse side blocking of printed matter is the most deadly quality problem in flexible packaging printing, which will lead to product scrap and bring heavy losses. In the high temperature season, reverse adhesion is more likely to occur, but there are many reasons for reverse adhesion, and high temperature is not the only reason. Therefore, in actual production, we should consider and analyze from various aspects, and find out the root cause based on the specific situation, so as to avoid the occurrence of such failures, ensure smooth production, and reduce unnecessary economic losses.The author will analyze the reasons and preventive measures for the reverse adhesion of flexible packaging printed matter from the following aspects.Improper selection of inkSome printing plants often only pay attention to the price of ink, blindly choose low-cost ink to reduce costs, and neglect the printing suitability of ink. If the ink used has poor printability, it will often lead to poor ink adhesion or poor drying, resulting in the natural fall of the ink after winding or the reverse side of the printed matter sticking. Therefore, when selecting ink, pay attention to the instructions for use of the ink to ensure that the performance of the selected ink meets the printing requirements. In addition, the adhesion of the ink should be tested during printing to ensure that the batch printing can only be done after the requirements are met.Poor ink dryingPoor drying of the ink is one of the reasons for the sticking of the reverse side of the printed matter, and the phenomenon is more obvious. Poor ink drying mainly includes two aspects: one is that the drying speed of the ink is too slow; the other is that the ink is fake dry, that is, the surface of the ink is dry, but the interior of the ink has not been completely dried.Plastic flexible packaging printing generally uses volatile drying ink, which is achieved by solvent evaporation. Therefore, the speed of solvent evaporation is an important factor that determines the drying of the ink layer and affects the printing quality. The slower the solvent volatilizes, the better the layer reproducibility of the printed matter, the brighter and more beautiful the color is, but it is easy to stick; Therefore, choosing a solvent with an appropriate volatilization rate is the key to plastic flexible packaging printing.When performing drying analysis and identification of printed matter, you can touch the ink part by hand. If the imprint is not dry, it means that the drying speed of the ink is too slow. You can replace the diluting solvent with a faster volatilization speed to adjust the ink, and increase the hot air temperature and increase the hot air. amount to speed up the drying of the ink. If the surface of the ink is dry, but the drying is not complete, it indicates that the ink is false-drying. The solvent ratio must be adjusted, the content of the fast-drying solvent must be reduced, the content of the solvent with a slower drying speed should be appropriately increased, and the hot air temperature should be increased. hot wind

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