The major technical problems in packaging and printing have long plagued people. The problems mainly focus on:
â‘ Ink migration;
â‘¡Ink film yellowing;
â‘¢White spots of printed products;
â‘£ Back adhesion and adhesion;
⑤ Discoloration and fading;
â‘¥ The ink film floats white;
⑦ Pinhole and shrinkage hole;
⑧ No ink transfer;
⑨Bite color ( commonly known as string color ) and fade;
â‘© Poor gloss ( whitening ) .
These printing technical problems have become a generally agreed production failure.
1 . Printed white spots. This problem reminds people that during the storage and use of printing inks, the stability of the ink is the result of the interaction of the components of the product system. The polar strength of the ink solvent is different, which will have different effects on the absorption of the reactive ink auxiliary agent on the pigment surface. Everyone knows that the binder and the active additive will produce competitive adsorption on the surface of the pigment, which mainly depends on the affinity of the binder, the active assistant and the surface of the pigment.
Since the physical adsorption of the surface active agent of the ink particles does not affect the chemical adsorption of the polymer, the physical adsorption of the surface active substance on the pigment surface is not firm. From this point, the excessive addition of substances such as reactive dispersant, abrasion-resistant wax and even amide resin binder in the printing ink system will affect the adhesion of the packaging printing ink film. In addition, during the grinding process, the dispersing aid is too Less, especially the improper order of addition, especially when the dispersion time is too short, when a large number of pinhole white spots on the surface after printing on the machine and white faults after compounding will occur.
In order to prevent such failures, the active additives of the ink should be properly selected, or the amount of time to grind and disperse the ink should be properly extended, and the printing should be stirred after the ink is fully stirred during printing.
2 . Sticky and sticky. In recent years, in the southern Jiangsu area, the back adhesion or adhesion of Li Indian compound ink has plagued printing companies more than gravure and surface printing inks in the past. Most of the failures occurred between July and October . After packaging and printing, there is no sticking or sticking phenomenon after the ink is dried and formed into a film within a short time. However, when the film is unrolled for processing or after the printing is delivered to the user for a period of time, the ink film will not feel smooth. It triggers the serious phenomenon of sticking or sticking to one piece when cutting and packing.
The appearance of this phenomenon is actually caused by the softening point of the ink binder of the composite packaging bag being too low. When the ink is diluted and printed, it is caused by adding too much slow-drying agent or inhaling too much water and causing surface dry internal wetness ( commonly known as skin burnt bones ) .
In order to prevent the recurrence of this failure, one must strictly select the ink products with technical parameters produced by regular manufacturers; the second is to strictly follow the evaporation rate or evaporation rate of the solvent during printing, and the mixed solvent is not selected to contain water That kind; three, when packaging and printing, surface treatment should be carried out on substrates stained with oil and wax, etc .; fourth, the second overprint should be performed after the printing ink film has dried in the previous pass; Ink with a higher softening point.
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