Causes and preventive measures for ink crystallization, practical!
In the packaging and printing, the background color is often printed to highlight the high quality of the pattern decoration to pursue the high added value of the product. It has been found in practice that such a printing sequence is very prone to ink crystallization. What is the cause? How to solve this problem?
Analysis of the causes of ink crystallization (crystallization)
First, in order to achieve the purpose of bright and bright background, the ink layer is usually printed thickly or reprinted once or increased in printing, and the dry oil is also added more. Although the ink layer completely covers the printing carrier, the surface of the printing ink becomes a very smooth ink film layer due to excessive drying. It is difficult to overprint as well as the glass, so that the ink printed on the back is not printed uniformly or completely. Up, the ink printed on the cover (stack) presents a bead-like shape or a weakly printed pattern on the ground color. The ink connection is poor, and some can even be wiped off. The printing industry calls it ink film crystallization, vitrification or mirroring.
In order to improve the sharpness of the edges of the graphic, in recent years, most manufacturers add silicone oil to the ink system, but too much silicone oil often causes vertical shrinkage of the ink film.
At present, there are several different opinions on the causes of crystallization of the ink film. According to crystallization theory, crystallization is the process of forming crystals from a liquid (liquid or solvate) or gaseous state. A substance whose solubility is significantly reduced as the temperature is lowered. The solution is saturated and crystallized by lowering the temperature; the substance having a small decrease in solubility with a decrease in temperature is cooled and crystallized when a part of the solvent is evaporated. Some people think that the crystallization of the package printing image (ink film layer) is recrystallization... The ink film system is evaporated (volatility) and then cooled, which is also called recrystallization.
Second, some people believe that the crystallization (crystallization) of packaging printing ink is mainly caused by the crystallization of pigments in the ink system.
We know that when the pigment crystal is anisotropic, its crystal state is needle and rod. When the ink film is formed, the longitudinal direction is easily aligned along the flow direction of the resin (linking material) in the system, and thus a large shrinkage occurs; and the spherical crystals are not aligned in the direction, so that the shrinkage is small. The inorganic pigment in the packaging printing ink system usually has a spherical crystal, for example, a packaging printing ink of a cadmium pigment, and its shrinkage (crystallization) is also small.
Also, the particle size also affects the molding shrinkage ratio and the molding shrinkage ratio. When the pigment particles are large to a certain extent or small to a certain extent, the molding shrinkage ratio and shrinkage ratio are minimized. On the other hand, the resin having a large crystal spherulitic crystal has a small shrinkage, whereas the crystal is large, and the aspherical crystal has a large shrinkage.
In short, whether it is the subtractive mixing of color pigments or the additive mixing of color shades, the correct use of pigments is not only related to the chemical structure, but also depends on its physical properties, such as crystal grain size distribution and agglomeration. Influencing factors such as solid solution; it should also make a fair evaluation of the advantages and disadvantages of inorganic pigments and organic pigments, so that the two coexist, and the latter has the primary position.
In the process of selecting packaging printing ink (pigment), it must also consider its tinting strength (the finer the dispersion, the higher the tinting strength, but there is a limit value, beyond which the coloring power will decrease), covering The force (the light absorption property of the pigment itself, the difference in the refractive index of the resin binder required for the pigment and the coloring, the pigment particle size, the crystal form of the pigment, and the higher molecular structure symmetry are lower than the symmetrical low crystal type.
The crystal form has a larger hiding power than the rod shape, and the pigment with high crystallinity has a larger hiding power than the crystallinity. Therefore, the greater the hiding power of the packaging printing ink film, the more the probability of failure of vitrification. Heat, migration resistance, weatherability, solvent resistance, and interaction with polymers (resins of ink systems) or additives added can not be underestimated.
Third, some operators believe that if improperly selected, it will also cause crystallization failure.
Because the underlying ink dries too hard (dry), the surface free energy is reduced. After the current one color printing, the storage time is too long, the workshop temperature is too high, or the printing ink desiccant is too much, especially the cobalt desiccant, which will cause crystallization if a rapid and intense drying method, such as drying, is employed.
Method for preventing ink crystallization failure
1. Cover with a quick-drying ink containing more solvent (not to wait for it to dry to print the second color, although the effect is better, but this method is laborious, time-consuming, and costly), the solvent used can be immersed And soften the underlying layer of ink film (but sometimes it doesn't help).
2, master the overprinting time, the second color should be printed as soon as possible after the previous color printing.
3. Add some slow-drying polymerization aids (such as hydroquinone) or slow-drying materials (Vaseline, lanolin, wax additives) to the ink.
4. Different basic colors that are easy to overprint can be used in the design of the packaging and printing decoration.
5. Cobalt desiccant should be used less in the ink formulation.
6. A fast drying synthetic resin type binder can be used to reduce the amount of desiccant in the ink.
7. Enhance the adhesion of the second color ink, the purpose of which is to destroy the crystallized ink film. If the use of zero varnish or alkyd resin, epoxy resin and polyamide resin is a material with high adhesion, it can enhance the adhesion by adding ink, but the miscibility of these resins with offset ink is not good, can not add more Because too much addition will often dilute the color of the printing ink, and too little effect will not be good.
8. An organic solvent is added to the printing ink to dissolve the crystallized ink film layer. This is one of the commonly used methods of the printing operator, but the smoothed ink film layer which has become the main mesh structure of the crystallized ink film layer is not easily dissolved, and the effect is not good when too much.
9. Adding alkali or soap to the printing ink to enhance the polarity, making it easier to print, but at the time it seems to be printed, but after drying it is not firmly attached and it is easy to wipe off.
Looking at the above treatment methods and preventive measures, it is possible to ensure the dryness of the ink in the printing and printing, so that it is best to start printing the second color without allowing the ink film to dry over.
Article source address: http://
Electric washbasin lifts is suitable for homes, nursing homes, hospitals, rehabilitation centers and other places. It is designed to help elderly people with mobility problems, disabled, paralyzed and postoperatively inconvenient people to solve daily washing problems, such as washing face, washing hands, cleaning teeth, combing hair or Shaving, etc. People who are sitting or standing can use this product at the same time, just use the up and down keys of the hand controller to adjust the height that suits them, the operation is simple, and the lifting is smooth.
Electric Washbasin Lifts,washbasin lifting systems,height adjustable wash basin,washbasin lift bracket,motorized washbasin lift
Suzhou Uplift Intelligent Technology Co., Ltd , https://www.officestandingdesk.com