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The reason why gravure products are not dry

Update time : 2020-10-09

Source : Zhejiang Deguang Machinery Co.,Ltd

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The reason why gravure products are not dry

gravure printing machines

The gravure product is not completely dry, and it is easy to produce back sticking, which has a great influence on the quality of printing. The following is a summary of the 7 reasons why gravure products are not dry, for your reference.

1. The gravure cell is deep, sometimes the depth reaches 60μm, the ink is large, and it is difficult to dry.
2. In order to ensure the transfer of high-gloss small dots, a slow drying agent must be added in the gravure process, which will also affect the drying effect of the ink.
3. The comprehensive balance of mixed solvents is not easy to grasp, causing a large amount of slow-drying agent to stay.
4. In some lining process, the last color is printed with white ink, and then it is reeled. The distance between the drying and rewinding station is too short and it is difficult to dry. Moreover, the white ink base requires the ink to have good hiding power, so it can only thicken the ink layer. Generally speaking, the ink loading of white ink is the largest among all colors.
5. During film printing, the temperature of the drying device should not be too high, and the drying tunnel should not be too long, otherwise the film will be stretched and deformed, which will affect the overprint accuracy and product length. The commonly used method is to use low temperature, high air volume, and volatilization in the drying process, instead of evaporation.
6. The dependence of solvent volatilization on environmental conditions. When the air pressure of the environment is relatively low, it is difficult to effectively control the drying efficiency with mechanical exhaust devices.
7. There is a boundary layer on the contact surface of the ink layer on the surface of the printed matter with the atmosphere. This is a layer containing a mixture of hot air and solvent vapor at a higher temperature. When the ink is dried under the action of high temperature, the liquid solvent in it will evaporate and move to the boundary layer. If there is no solvent in the boundary layer, the solvent vapor can easily be transferred to the atmosphere. But as the concentration of solvent vapor in the boundary layer continues to increase, the evaporation rate of the solvent will decrease. When the solvent vapor in the boundary layer becomes saturated, the evaporation process will stop. The traditional gravure printing drying process does not pay attention to the existence of the boundary layer, and ignores the role of evaporation in drying. Although the industry has made some improvements to the curve of the drying tunnel of the gravure printing machine, the wind resistance is reduced and the air volume is increased, but because of this layer With the existence of the boundary layer that does not flow with the air, some unvolatile residual solvents in the ink will still be wrapped in it.

Zhejiang Deguang provides high-quality gravure printing machines that can be used for gravure printing of various products. If you have any questions when using the printing machine for gravure products, you can contact us.

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