We know that the interaction between printing paper and ink is based on the form of adhesion and adsorption. This feature shows that the adhesion, cohesion and gloss of the ink and other factors have a great influence on the printing quality of the product. The temperature change in the production environment directly affects the viscosity and cohesion of the ink. In the printing production practice, we can find that when the printing environment temperature is too low, the molecular movement of the ink binder material is slow, and the ink tends to be in a solidified state, so that its cohesion l is large, and the ink fluidity is poor, and during the printing process, Inconveniences such as poor ink transfer and uneven ink distribution may occur, which may affect the uniform coating of the ink layer. On the other hand, due to the cohesion of the ink, its consistency is also large. The viscosity of large consistency ink is also large, so that the printing process is very easy to cause the paper powder, paper hair and coating layer and other defects, and cause chain printing quality problems such as paste printing, roughing of the print, etc. phenomenon. If the temperature is too high, the ink will be thinned, the coloring power will be reduced, the ink color of the printed product will appear pale, and the color is not bright. The printing quality is degraded.

In addition to the effect of the temperature of the production environment on the characteristics of the ink, the printing speed of the machine also affects the characteristics of the ink. This is because the ink has the characteristic of "thixotropy". When the printing press is running at a high speed, the friction coefficient of each ink roller (including the ink roller) rotates at a high speed, and the heat generated from the roller body can make the ink thin. , Increased fluidity, markedly decreased coloring power. Based on this situation, we should take full account of the level of printing speed used in the deployment of ink, a reasonable adjustment of the ink thick degree, in order to better ensure the quality of printing ink. Obviously, only maintaining a proper and constant temperature is an effective measure to prevent the change of ink consistency and viscosity. As a result of the change in printing temperature, in addition to the above-mentioned effects, there are operational factors, such as the appropriateness of the ink roller and pad pressure adjustment, which are often ignored by operators who lack production experience. According to the author's past experience in the process, the contact pressure between the rubber roller and the stringer iron roller is too tight, the overprint plate pad is too high and the ink roller contact is too tight, and the clearance between the ink fountain plate and the iron roller is too small. If the rotation of the ink fountain roller is too large, the heat of printing friction will increase greatly, and the fluidity of the ink will increase. Therefore, in order to reduce the temperature rise caused by abnormal friction and reduce the chance of ink variability, the rubber roller body must maintain a good degree of circle. The roller head and bearing should be repaired in time if worn or damaged, so that the roller and the string In order to maintain a uniform and moderate contact pressure between the iron roller, a 0.05mm thick plug gauge can be used to check whether the contact is appropriate at the production site. That is, a slight sense of resistance is applied when the plug is inserted between the rubber roller and the chain iron roller for drawing. For degree. The adjustment of the height of the printing plate cannot obviously exceed the technical parameters of the equipment specification so that it can maintain a uniform and moderate contact condition with the ink roller. If the layout is not under very large printing conditions, do not turn the ink roller rotation stroke to “maximize” to transfer ink. Through the control of these operating technologies, the abnormal temperature rise during the printing of the machine can be well prevented, and the ink characteristics can be stabilized.

It can be seen from the above situation that the influence of temperature on the ink is mainly manifested in that it can change the thick degree, fluidity, and coloring power of the ink. The effect of humidity on ink performance is reflected in the dryness of the print. The production process shows that the humidity of the printing environment is high and the ink layer of the printing ink is slow. On the contrary, the humidity of the environment is low, and the printing ink layer is dried quickly. Because the air humidity of the printing environment is high, the moisture content of the printing paper is also high, and these will be one of the reasons that affect the drying of the ink layer. Here, when the ambient temperature is between 20°C and 25°C, the relative humidity is 65 and 75% respectively, and the printing results of the two production conditions show that the difference in the drying speed of the ink layers is up to 1-2 times. It can be seen that the influence of temperature on the ink is greater than the effect of temperature on the ink. Therefore, it is particularly important to control the humidity at the production site.

In view of the influence of changes in temperature and humidity in the production environment on the printing ink and ink, in the absence of air-conditioner production conditions, it is necessary to reduce the influence of changes in temperature and humidity on the ink, and to ensure the quality of ink and the accuracy of overprinting of color prints. The best measure is to A few days before printing, the ink to be prepared will be placed at a temperature of between 20 and 25° C. to allow the ink to equilibrate at a temperature and humidity suitable for the printing conditions for a period of time so that the printing thixotropy of the ink is controlled to be “minimized”. In order to improve the product's printing quality and process results.

In summary, correct understanding of the effects of changes in temperature and humidity on the characteristics of inks, and adopting appropriate process technologies and operational techniques to control them, is effective in avoiding blindness in production and preventing the appearance of various quality problems or defects. Improving the quality of products is of great significance.

Reprinted from: "Printing World" Author: Kai Kang