What factors affect the printing products of gravure printing don't dry?

Jan 11, 2022
The gravure printing has a thick ink layer, so the problem of poor drying always exists. The printing feature of gravure printing is wet and wet. Although there is a long drying path, the ink of the previous color group is not dry when the gravure is stacked, but a film is formed on the surface of the ink layer to prevent the next color. The inks of the group reverse the stickiness of the ink of the previous color when the ink is stacked.

We would like to tell you the following summarizes the gravure printing products do not dry reasons for your reference;

1. The gravure mesh is deep, sometimes the depth reaches 60μm, the amount of ink is large, and it will be 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, resulting in a large amount of slow-drying agent retention.

4. In some inner printing processes, the last color is printed with white ink, and then it is rolled up. The distance between the drying and the winding station is too short, and the drying is difficult. In addition, the white ink base requires the ink to have good hiding power, and can only thicken the ink layer. In general, the amount of white ink is the largest of all colors.

5. During the printing of pe gravure composite film, the temperature of the drying device must not be too high, and the drying channel 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 and large air volume, and adopt the volatilization method in the drying process to abandon evaporation.

6. Dependence of solvent volatility on environmental conditions. When the ambient air pressure is relatively low, it is difficult to effectively control the drying efficiency with a mechanical exhaust device.

7. There is a boundary layer between the ink layer on the surface of the print and the contact surface with the atmosphere (foreign counterparts call it "Boundarylayer", some people translate it as "mirror film"). This layer contains hot air and solvent vapor. Mixture, the temperature is higher. When the ink is dried under the action of high temperature, the liquid solvent therein will evaporate and move to the boundary layer. If there is no solvent in the boundary layer, the solvent vapor is easily transferred to the atmosphere. However, as the concentration of the solvent vapor in the boundary layer continues to increase, the evaporation ratio of the solvent will decrease. When the solvent vapor in the boundary layer tends to be saturated, the evaporation process will stop. The traditional gravure 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 gravure drying tunnel, reducing the wind resistance and increasing the air volume, but due to this layer The existence of a boundary layer that does not follow the air, some non-volatile residual solvents in the ink will still be wrapped in it.



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