One pre-volatile drying mechanism
Pre-drying is a necessary process before photo-curing. Failure to perform pre-drying will result in unsatisfactory final results of photo-curing. UV-curable water-based inks generally adopt appropriate heating methods, such as infrared baking or hot air drying, to shorten the initial moisture evaporation process. With the gradual volatilization of water, the dispersed polymer particles gradually move closer, but they can still move freely. Then as the water volatilizes further, the polymer particles reach close packing and become irreversible contact with each other. It is generally believed that the theoretical volume solid content is 74% at this time.
Two UV curing film forming mechanism
In the later stage, the dispersed phase particles begin to condense, and about 3% moisture remains at this time. At the same time, the curing reaction of the functional group-containing curing group molecules is initiated by the photoinitiator at the interface and inside of the dispersed phase particles.
The curing process can generally be divided into four stages: ①The interaction between light and the photoinitiator, which may include the absorption of light and the interaction between the photoinitiator; ②The photoinitiator molecules are rearranged to form free radicals Intermediate; ③The reaction of free radicals with the unsaturated groups in the oligomer initiates a chain or polymerization reaction; ④The polymerization reaction continues, and the liquid component is transformed into a solid polymer.
Three advantages of UV light curing equipment:
1. Fast curing speed: Ordinary offset printing needs several hours or even more time to completely dry the ink and enter the next processing procedure. UV offset printing can be completely cured in 1 second to several seconds, so it is especially suitable for printing some non-absorbent substrates.
2. Strong abrasion resistance: After the UV ink is cured into a film, its friction resistance is good, which reduces the loss caused by friction during the use and transportation of packaging products.
3. Green printing: UV ink does not contain solvents, there is no solvent volatilization, and will not pollute the atmosphere. It belongs to green printing.
4. No powder spraying: Because it can be cured and dried in time after UV irradiation, there is no need to spray powder, which greatly improves the working environment. At the same time, it is also conducive to post-press processing techniques, such as laminating, glazing, etc.
5. High efficiency and good quality: UV offset printing has a short production cycle, high production capacity, and the printed dots are clear and of good quality. However, because the packaging UV offset printing process is more complicated, and the application time is not long, the application of the printing process still needs to be summarized continuously, to see the shortcomings in the UV offset printing, and continue to improve.
