The elimination of printing failures of single gravure pearl ink

The gravure pearlescent ink is composed of pearl powder, gravure ink connecting material, organic solvent and additives. With the development of the printing industry, especially in the printing of cigarette labels and wine labels, pearlescent ink has been increasingly favored by packaging users for its unique visual effects. Pearlescent inks often have some unexpected printing problems when they are used on flat sheet gravure printing machines. Now two examples are shared with colleagues in the industry.

The author commissioned pearlescent ink in a printing factory in the south. The printing equipment was made in Shanghai. The printing speed was 6000 sheets/hour. The ink binder was nitrocellulose and a small amount of polyketone resin. The diluent used was ethyl acetate and iso Mixed solvent of propanol. In the process of debugging, there are always phenomena such as poor pearl ink and poor leveling. Careful observation with a 23x magnifier reveals that the ink is drying too quickly. If the gravure gravure printing machine is compared with the gravure gravure printing machine, we will know a machine with a normal opening of 6,000 sheets/hour. Its actual linear velocity formula is: V=6000×∏×D/60 The plate diameter of the printer is 0.375 meters, and the line speed is 118 meters. Obviously, the speed is very fast. Why does the phenomenon of fast ink drying occur? It has been demonstrated that due to the large diameter of the plate in the gravure printing machine, the angular velocity is very slow, although the line speed is very high. Most of the printing plate is exposed to the air. The ink has not yet fully leveled and has dried in the printing plate. , there is a blockage phenomenon. Solution: Add slow-drying solvent, ethyl acetate, isopropyl alcohol, propylene glycol methyl ether ratio of 3:3:4, ink viscosity is adjusted to 24 seconds (2 # Chaun Cup), machine speed is 6000 / hour, to achieve Customer requirements.

In batch printing, unexpected things often happen. The ink film after printing is peeled off by hand with a large area. Reduce the amount of slow-drying agent, pearlescent effect is not good, there is a blockage phenomenon. Is it a paper issue? For another white cardboard, the problem remains the same. Pearl ink problem? We continue to inquire boldly: Pearlescent powder is flaky, it is difficult to form a smooth and dense film; ink drying is too slow, a large amount of binder material penetrates into the paper or solvent residue in the ink film of the flexible packaging substrate, resulting in suspension of pearl powder It falls off on the surface. According to this idea, we replaced the nitrocellulose with acrylic resin and redesigned the formula. Test machine again, the problem solved.

Due to the special nature of pearlescent, pearlescent inks are difficult to thoroughly mix with flexible packaging substrates and plain paper gravure inks. A printing factory in Wuhan appeared when printing pearl ink. Due to the large amount of common ink in the pearlescent ink, the surface of the printed product is always uneven and dirty. At first, we thought that the quality of pearlescent ink was not good, but some of the inks could not solve the problem. It was suspected that there was a problem with the ink returning. The ink inlet of the ink tank was placed under the ink tank, and the return pipe was installed on it. No, stretching the scraper to increase the area of ​​miscibility between pearlescent ink and common ink has solved the problem of dirtiness, but it has also caused troubles such as unclean scraping and tailing. In order to increase the dispersion of pearlescent ink, installing a uniform ink roller under the gravure plate roller can also eliminate dirt problems. However, the parallel lines on the uniform ink roller are occasionally printed on the product, and the reject rate is greatly increased. We had to stop for reasons. At the bottom of the gravure platen ink tank, an even roller is added to make the dispersion of the pearl ink enhanced, but the ink roller is not fixed. With the high speed operation of the plate, the buoyancy of the ink on the roller is also unstable Therefore, the contact pressure between the uniform ink roller and the printing plate is constantly changing and cannot be normally printed. According to the fact that the ink groove of the gravure press is closed, it is difficult to change this feature. I would like to be able to make an open ink tank. Like the rotogravure machine, the uniform ink roller works with the printing plate directly in front of the printing plate. What? Under the enthusiastic support of the gravure printing machine manufacturer, around the issue of the printer, and in accordance with the above-mentioned problems frequently occurred in the production of a single gravure printing machine overnight technical changes. After the first few trial printing and printing, the above problems no longer occur, and printing is normal.

Source: Zhengzhou Baodeli Paint Co., Ltd. Ink R&D Center Liu Jiaju Wang Baoshan Yang Huiyu