Some packaging printing manufacturers and ink production companies sometimes encounter the following two situations:
One is that there is no problem in the printing or during the use of packaging and printing products in the cold season, while the printing ink films adhere to each other in the printing or use during the high humidity season.
Second, there is no problem in the printing or laminating of packaging and printing products in high humidity seasons. When used in the low temperature season, there is no adhesiveness in the upper and lower films of printed products.
For this reason, after reviewing a large number of relevant printing faults and processing method information, and after seeing and testing the above two distinct printing faults, the author thinks that the former is the ink in which the thermoplastic resin in the system has a low softening point or the ink system An excessive amount of slow-drying solvent remains in the printed ink film. Once the ambient temperature rises, it will soften and return to stick due to the release of the solvent.
The latter is due to the improper or excessive use of dispersion aids in the ink or compounding system. Such simple conclusions do not seem to be convincing enough. For this reason, this article briefly discusses some of the technical issues of adhesion problems, ie, ink adhesion and lamination, in order to discuss with the printing and ink industry colleagues.
1, using pressure to solve the ink layer, adhesive layer caused by excessive adhesion problems.
The pressurization of the printing machinery and the compound glue coating machine can make the adhesion between the printing ink film layer and the coating composite glue layer tight and complete, and make the ink and glue flow under pressure, which is beneficial to The molecules of the ink system and the molecules of the glue system diffuse and permeate, thereby increasing the adhesive strength of the ink and the substrate, the glue, and the printed ink film.
Of course, the pressure should be such that the ink ink film and the glue lamination film do not deform into degrees. In other words, after the pressurization, the purpose is also to discharge excess ink or rubber to reduce the thickness of the ink layer and the adhesive layer, so as to ensure that the entire ink layer and the adhesive layer are uniform and dense in thickness and prevent partial under ink or glue from being etched. Create voids. It can also prevent certain inks and adhesives from generating bubbles due to volatiles during heat curing or cooling and maturation.
2, using a hair dryer to solve the problem of solvent residues
Usually we use infrared drying in the packaging and printing process, in addition to drying, blow drying or even drying drying, the purpose of letting ink and glue system solvent volatilization, viscosity increase, easy to ink film, glue composite operation. At the same time, ink and glue can also allow the surface of the substrate to be fully wetted, which facilitates its diffusion, penetration and adsorption. Therefore, inks and glues with solvents need to be fully blown, infrared-baked, etc., forcing the solvent to evaporate and evaporate completely. Solvent-free, it can be printed and glued immediately after coating.
Infrared, ultraviolet, air blow, bake, etc. depend on the volatilization rate and evaporation rate of the solvent, while the UV class depends on the light energy intensity, so that a photon absorbs one minute and the self-study of the ink and glue is achieved during the film formation and drying time. Sexual period and so on. Should not be too long, so as not to harden the ink film and film (curing), poor adhesion, adhesion is not strong; not too short, so that solvent evaporation, evaporation or cross-linking is not enough, resulting in poor adhesion of ink and The laminating strength of the glue is reduced.
We know that printing and laminating can be performed at outdoor temperatures, under infrared, ultraviolet, heat curing, or cold air curing, or alternatively with infrared heating and cold air blowing. Alternating infrared and ultraviolet light can also be used. . This depends on the curing (curing) temperature of the ink and glue. In particular, it is reasonable to remove the film after ink film formation and compound glue curing (curing).