The solution to the yellowing of ink film in the printing process

The major technical problems in packaging and printing have long plagued people. The problems mainly focus on ① ink migration; ② yellowing of ink film; ③ white spots of printed matter; ④ sticking back and adhesion; ⑤ discoloration and fading; ⑥ ink film floating white; ⑦ Pinholes and shrinkage holes; ⑧ No ink transfer; ⑨ Bite color (commonly known as string color) and fading; ⑩ Poor gloss (whitening). These printing technical problems have become a generally agreed production failure.

1. Ink migration. Migration is when the pigment in the ink penetrates or passes through the film to contact another type of substance (sometimes it also sticks to the goods in the package) and causes pollution. The reason is that the packaging printing inks and substrates (such as plastic films) contain excessive plasticizers, and excessive additives in the ink system may sometimes be caused by the solvent in the printing ink dissolving part of the pigments of the ink and cause the substrates (such as In the film), when the stored packaging printed matter is used in summer, the printed ink film becomes soft due to the temperature increase, which accelerates the migration speed.

The countermeasures are: use plasticizers or hydrophilic substrates as little as possible on the printing materials, especially packaging printing inks, and avoid the use of pigment inks containing plasticizers and water. In the design of the ink formula, the best conditions for the overprint processing and the final use and purpose of the second, third, fourth ...

2. Ink film yellowed. In the white ink system for printing graphic ink film, titanium white powder with high coloring power, high hiding power, good whiteness and high light scattering ability is used as the ink coloring agent. However, it is not known that the material has photochemical activity, that is, problems such as gloss loss, discoloration, powdering, and peeling will occur after printing. Yellowing is one of the most troublesome problems in recent years.

To overcome this shortcoming, the commercially available X24 can overcome this shortcoming and make up for its shortcomings with only an appropriate amount. If yellowing is found during printing, the operator needs to add X24 to the ink hopper, which not only improves the whiteness and hiding power of the original white ink, but also greatly reduces the cost of printing ink materials by as much as 10% to 30% .

In addition, the yellowing of color ink is the same as that of white ink, just add X24, 0.5% ~ 2% can also avoid yellowing. In the same way, the PH value and environment of the printed matter will also cause the graphics and ink film to turn yellow. In practice, the PH value will increase the oil absorption of the pigments and fillers in the ink system, resulting in the pseudo-thickness or dryness of the ink. In severe cases, the ink cannot be transferred or the color density after the transfer becomes lighter. Usually yellowing is excluded, and the addition of 1010 antioxidants and UV absorbers is also a temporary treatment.

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