White spots and tackiness of packaging products

Major technical problems in packaging and printing have long plagued people. The problems are mainly focused on 1 ink migration; 2 ink film yellowing; 3 white spots on printed products; 4 back sticking and adhesion; 5 discoloration and fading; 6 ink film floating white; Pin holes and shrink holes; 8 transfer without ink; 9 bite color (commonly known as cross-color) and fade; 10 gloss difference (white). These printing technology problems have become a commonly agreed production failure.

1. Print white spots. This problem reminds people that during the storage and use of printing ink, the stability of the ink is the result of the interaction of the various components of the product system. The polarity of the ink solvent is different, which also has different effects on the absorption of the active ink additive on the surface of the pigment. It is well known that binders and coagents will produce competitive adsorption on the surface of the pigments, depending on the affinity of the binder, coagent, and the pigment surface.

Because the physical adsorption of the surface active agent of the ink particle does not affect the chemical adsorption of the polymer, the physical adsorption of the surface active substance on the surface of the pigment is not strong. From this point, the addition of excessive amounts of active dispersants, abrasion-resistant waxes, and even amide-based resin binders in the printing ink system can affect the adhesion of ink films for packaging printing inks. In addition, due to the fact that the dispersing agents are too Less, especially in the wrong order of addition, especially if the dispersion time is too short, a large number of pinhole white spots on the surface after printing on the machine and complex white defects after printing will occur.

In order to prevent such failures, it is necessary to rationally screen the ink's coagent, or extend the time to grind and disperse the ink in an appropriate amount, and then stir the ink sufficiently before printing.

2. Stick back and stick together. In recent years, in the southern part of Jiangsu Province, the back-adhesion or adhesion of India-Indian composite ink has been trapped around the printing companies more than gravure and surface printing inks in the past. Most of the failures occurred in July to October. After the package is printed, the ink does not return to stick or stick within a short period of time after the film is dried. However, the ink film does not feel smooth when the film is processed after being printed or delivered to the user for a period of time. The phenomenon of sticking together when triggering sticking or slitting and packing.

The appearance of this phenomenon is actually caused by the low softening point of the ink binder of the packaged printed matter. When the ink is diluted in printing, it is caused by the addition of too much slow-drying agent or inhalation of excessive moisture and the appearance of dampness (commonly referred to as skin coke bones).

In order to prevent the recurrence of the failure, one must strictly select the ink products with the technical parameters produced by the regular manufacturers; the second is to strictly follow the volatilization rate or evaporation rate of the solvent during the printing, and the mixed solvent is not selected to contain moisture. The third is when the packaging and printing, should be stained with oil and wax and other substances on the substrate surface treatment; Fourth, in the previous printing ink film dry after the second overprint; five is to use as much as possible link material Softer ink.