Influence of ink resolubility on the quality of flexible packaging Gift Boxes

Influence of ink resolubility on the quality of flexible packaging Gift Boxes

The resolubility of ink is an important indicator of ink quality. It has a non-negligible impact on the printing and composite quality of flexible packaging composite materials. Many colleagues in the industry have paid attention to this, but it is difficult to make a clear theoretical explanation. The author Write down the problems and understandings related to ink resolubility encountered in many years of work, in order to attract more attention and discussion.

1. The concept of ink resolubility

The resolubility of the ink refers to the redissolving ability of the printed and dried ink after encountering the solvent. Usually, the following methods can be used to compare and judge the degree of ink resolubilization: Cut out two printing films (printed with different inks) Lay it flat on the desktop, add two drops of ethyl acetate on the printing ink layer respectively, after 3 or 4 seconds, stand the two films upright, the ink that flows down more means the resolubility is stronger, and the ink flows down. A lower value indicates a weaker resolubility.

There is currently no clear quantitative index for the resolubility of ink, and the resolubility of inks from different manufacturers may have obvious differences. Since the resolubility of the ink has a certain impact on the quality of printed and compounded products, flexible packaging companies may wish to use the resolubility of the ink as a reference index for the selection of inks, and select inks with moderate resolubility to reduce adverse effects on product quality.

Since the influence of the resolubility of the ink on printing and compounding is the same or similar to some phenomena that occur when the printing ink is not completely dried, the problems discussed below exclude the incomplete drying of the printing ink.

2. Influence of ink resolubility on Gift Boxes printing process

For inks with strong resolubility, the ink remaining at the bottom of the cell during printing will be redissolved by the ink in the ink tank, so the plate blocking phenomenon is relatively lighter, and the reproducibility of the shallow screen part will be better (of course, with the ink The fineness is also directly related).

For inks with weak resolubility, it is difficult for the ink remaining at the bottom of the cell to be redissolved by the ink in the ink tank, so it is easy to block the plate, and the reproduction of the shallow screen part is poor.

The ink with strong resolubility is also prone to "bite color" during printing (that is, the color in the back dissolves the color in the front a little). In severe cases, the pattern will be transferred to the printing film again, causing pollution to the product. And the color of the latter group of inks will change due to the mixing of the previous inks, thus affecting the hue of printing.

The solution to the "bite color" of the ink is to increase the printing speed, reduce the pressure of the embossing roller to reduce the contact time, and it will be better if the scraper is withdrawn a little bit. solvent.

3. Influence of ink resolubility on composite process

The resolubility of the ink is strong, and the solvent and glue will penetrate into the ink together during compounding. First, the apparent glue amount will be insufficient. Second, the curing agent will connect with the ink binder and printing residual solvents (such as isopropyl alcohol and water). ) react, resulting in the glue not drying.

For this kind of ink, the amount of glue can be increased to ensure the composite strength, and the working concentration of the glue can be increased to reduce the dissolution and penetration of the ink. In addition, more curing agent should be added to ensure that the glue is dry.

If the resolubility of the ink is too strong, the phenomenon of "bite color" will also occur during gluing, which is manifested as a fuzzy printing pattern on the surface of the gluing roller. product and affect transparency.

The solution is to increase the compounding speed, and reduce the pressure of the embossing roller to reduce the contact time.

When doing peel strength inspection, composite products processed with inks with too strong resolubility are often easily separated from the middle of the ink layer, resulting in low peel strength of the product.

For inks with too strong reconstituted properties, the printing film cannot use a glue roller when compounding, because the ink is easily reconstituted after gluing, and the reconstituted ink will be scratched by the glue roller.

The white ink with too strong resolubility will become uneven or the coverage rate will decrease due to the redissolving of the white ink after gluing.

In the case of solvent-free compounding, due to the strong fluidity of the solvent-free adhesive, the ink with strong resolubility is more likely to appear "inking" phenomenon with the flow of the glue, that is, the printing boundary of the ink of this color becomes jagged shape, and into other colors beyond the boundaries of the print.

The resolubility of ink is only one of the factors that affect the quality of printed composite products. I hope the above discussion can be helpful for flexible packaging companies to find the cause of the problem.

In the process of material organization, I have received help from the technical staff of many ink production enterprises. I would like to express my gratitude here! Some inappropriate opinions should also be corrected by colleagues in the industry.

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