Adjust the printing viscosity of ink correctly

2022-09-21
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Correct adjustment of ink printing viscosity

in the printing process, there are many factors that will affect the quality of printed matter. With the influence of these adverse factors, many quality problems will inevitably occur

I. version fog problem

in plastic intaglio printing, the non printing surface of the printing plate roller is often adhered with a layer of hazy ink. Transfer to the printing substrate often presents a sheet or line like dirty version, which is dirty version, also known as fog version. The cause of the dirty plate problem is not only related to the ink formula itself, the pressure and contact angle of the doctor blade and the quality of the printing plate, but also related to the printing viscosity of the ink

if the printing viscosity of the ink is too high, the viscosity of the ink will become larger. Under the high-speed movement of the printing plate, the ink will produce a great impact on the doctor blade. In this way, it is difficult for the doctor blade to scrape off the ink of non graphic parts smoothly, resulting in version pollution

if the pigments in the ink are unevenly distributed in the ink system, or the resin in the ink fails to wrap the pigment particles well, the pigment particles will regroup between them. Wang Zidong, director of the National 863 electric vehicle major special power battery test center, told: from the perspective of the current production expansion plan of power battery enterprises. Forming large pigment groups (i.e. coarsening phenomenon) these larger particles are easy to form linear or strip knife lines in printing

generally speaking, the lower the printing viscosity of the ink, the less likely it is to cause the problem of dirty plate. Therefore, in the actual printing process, special attention should be paid to the change of the half occupancy of the printing ink, and the printing viscosity should be adjusted in time to improve the quality of the print

second, the problem of flying ink in high-speed printing

when the gravure printing speed exceeds 20m/min, if the gravure printing ink adopts domestic chlorinated polyene resin with wide molecular weight distribution, resulting in the low viscosity of the printing ink, it may bring the problem of "flying ink". The reason is that the viscosity of printing ink is too low. The cohesion of the ink decreases significantly. When the ink is transferred to the print film, the low molecular weight resin is very tolerant to the torque change angle curve under different tensile loads, which is easy to be separated, and a small "ink dot" can be seen in the blank part of the print

to solve the problem of "flying ink", we can solve it from the following two aspects: - chlorinated polypropylene resin with narrow molecular weight distribution; Second, according to the printing situation, appropriately improve the printing viscosity of the ink

III. Influence on color, transfer rate and color saturation

gravure ink depends on the ink of the concave point of gravure to transfer to the printing substrate. Relatively speaking, the volume of the printing point is basically fixed. With the increase of ink printing viscosity, the viscosity of the ink also increases, and the more ink is transferred from the point, so the color concentration and saturation of the print are higher, but there is a certain limit

when the viscosity of the ink continues to rise to a certain degree, the transfer rate of the ink also achieves a synchronous increase. If the viscosity of the ink continues to rise, the viscosity of the ink becomes stronger and stronger, and the ink begins to be difficult to enter a small point, the ink in the point becomes less and less, and the transfer rate of the ink begins to gradually decline. The color density of printed matter also began to decline. What should we do?. The ink manufacturer suggests that the printing viscosity of gravure ink is generally 13 ~ 22 seconds (3 × chaen cup), which is only an empirical value. In the actual printing process, in order to achieve a good printing transfer effect. Choose printing viscosity carefully

IV. The main test items of the impact on the printing speed are: tensile test of metal materials; Zigzag experiment of metal materials; Shear experiments of metal materials, etc.

the printing speed of the existing gravure printing machines in China (including imported and domestic machines) ranges from 30m/min to 300m/min. Generally, the printing speed of the printing machine is m/min. In actual printing, we should choose according to the printing speed of the printing machine. When the printing speed increases, the printing viscosity will decrease. Of course, the most suitable printing viscosity. It is also affected by other factors:

1. Even at the same printing speed, due to the differences in ink formula design. Its printing viscosity will also be different. Therefore, in the actual printing process, it must be adjusted according to the printing effect

2. Affected by seasonal temperature: the viscosity of the same printing ink is different in summer and winter, and ink manufacturers have been working hard to reduce the impact of temperature on ink viscosity

3. Select the most appropriate ink printing viscosity according to the actual conditions of the printing plate roller

v. influence on Printing Crystal Gloss

the lower the viscosity of gravure ink (that is, add more solvents to the original ink), the content of resin and pigment in printing ink will decrease, and the ink will not form a smooth ink layer after being transferred to the printing substrate and dried. The phenomenon of white flowers directly leads to the lack of gloss of printed matter. Therefore, in order to obtain excellent gloss, we must ensure that the printing ink has the appropriate resin and pigment content

VI. electrostatic problem

generally, OPP internal printing ink has limited antistatic ability, which is easier to generate static electricity than polyamide surface printing ink and polyurethane system ink. For OPP internal printing ink, the higher the viscosity of the printing ink, the more likely it is to generate electrostatic problems. Under normal temperature conditions, the viscosity of the printing ink is more than 16 seconds (3 chaen cup). Electrostatic generally does not occur; If the printing viscosity is lower than 16 seconds/3 × cup, beard, stripe, edge rejection and other faults are easy to occur

if the viscosity of the printing ink has been within 15 seconds/3 cup, we suggest not to use the method of increasing the viscosity of the printing ink as far as possible, because increasing the viscosity of the printing ink will not only increase the printing cost, but also bring difficulties in printing transfer, which is prone to printing failures such as dirty plates. Other methods of eliminating static electricity can be adopted according to the specific situation of generating static electricity, for example, by changing the proportion of diluted solvent. Adding 5% isopropyl alcohol (a polar solvent with good conductivity) or a small amount of antistatic agent as appropriate can achieve the purpose of eliminating static

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