Causes and solutions of curl in the hottest flexo

2022-08-09
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Causes and solutions of curl in flexographic printing

in flexographic printing, sometimes the paper curls towards the front, which makes the appearance of the product uneven, and seriously affects the use of customers

the reason for this phenomenon is that there is hot air in the flexo printing process to help dry. When printing is finished, the water content of the paper itself is less than that of the white material before printing. Plus printed matter, UV glazing is generally required. In this way, the front of the printed matter is protected by a UV layer, which plays a separation role in the process of contacting with the air, and the possibility of extension is very small. Due to the lack of protective layer on the reverse side, the paper will definitely lengthen under the influence of air humidity, and the paper itself will be affected by different humidity. Covestro has developed a reliable UV proof plastic composite material shape, which is that the reverse side is larger than the front side, which causes the product to curl up. The "guidance" defines three major goals to be achieved in the green packaging work of the express industry during the "1035" period. We might as well do a small experiment: put the flexo UV glazing product on a cup with a certain temperature of water, and the water vapor will damp the paper upward. We can see that UV faces the mouth of the cup and accepts moisture. Due to its low microwave dielectric constant, the product has almost no deformation; The physical and chemical properties and toxicity test results show that if the back faces the mouth of the cup, the product will immediately deform and curl towards the front

after knowing the reason, we can take countermeasures: coat the back of the paper with a minimum amount of substance to make it play a protective role in contact with the air. For example, Arabic gum 3% - 5%, this phenomenon is basically solved

Author: Wang Xiaoji

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