"Knowing to know one another" skillfully wins ink dry "obstacle race"

Ink drying refers to the process of changing the ink from a fluid state to a solid state. The speed of the ink has a great influence on the quality of the printed matter. When the drying is too fast, the ink will be crusted and pasted on the surface of the printing plate, causing ink to accumulate in the printed matter. The phenomenon of poor gloss; drying too slowly, the back of the print may appear dirty, transfer phenomenon, is not conducive to the next process. In fact, ink drying is a relatively complex process involving many aspects such as physics, chemistry, fluid mechanics, and surface treatment. At the same time, it is affected by many factors such as the substrate, ink composition, printing conditions, printing methods, printing equipment, and printing environment. The influence needs to be grasped by many parties.

The drying speeds of different inks are also different. The key lies in the nature of ink pigments and binders. 1. Influence of temperature The temperature is an important factor affecting the ink drying speed. It is known in practice that the ink drying time is reduced by approximately 20% for each approximately 5.5°C increase in temperature. Therefore, in the absence of air conditioning device to control the temperature, the ink drying speed is greatly affected by seasonal changes: low winter room temperature, ink drying speed is slow; summer room temperature is high, the ink drying speed is faster.

2. Influence of humidity Humidity is also a major factor that affects the speed of ink drying. The higher the humidity, the slower the drying speed. Humidity factors that have a great influence on the ink drying speed include the relative humidity of the shop, the humidity of the Paper, and the humidity of the ink.

1 workshop relative humidity. The higher the relative humidity of the air, the slower the ink dries. Because the density of water vapor in the air is too large, it will affect the release of water vapor from the ink during the drying process. Therefore, in the southern rainy season, the ink drying speed is very slow, and sometimes even dry, the amount of dry oil needed to increase the drying speed.

2 paper humidity. The moisture content of paper can prevent ink penetration and reduce oxidative drying ability. If the moisture content of the paper is very high, then the fibers of the paper will be in a relaxed state, the pores will be easily blocked by the water layer film, and the absorptivity of the ink to the ink will be reduced, and the drying of the ink will be delayed.

3 ink humidity. The ink offset on paper is actually an emulsified ink. The speed of ink drying has a close relationship with the evaporation rate of water in emulsion ink. If the ink emulsification is severe when it contains much water, the evaporation speed is slow and the ink drying speed will be slowed accordingly.

3. The influence of paper The paper is interwoven with plant fibers and supplemented with raw materials such as fillers, rubber compounds and pigments. Some of its physical and chemical properties have a great influence on the drying speed of the ink.

1 paper structure. The effect of the paper structure on the ink drying speed lies in the physical conditions determined after fiber interweaving, surface sizing and packing. In general, the paper surface is rough, the structure is loose, the permeability is large, the degree of sizing is small, and the ink is easy to dry. This is because the paper with rough, loose and low degree of sizing has strong absorptivity to the link material. After the ink is printed on the paper, some mineral solvents can immediately be absorbed by the paper and lose their balance, resulting in fixation and drying speed.

2 paper pH. Paper is divided into acid and alkali. In general, the ink on acid paper dries slower than the ink on alkaline paper. Experiments have shown that the pH of general offset paper is controlled at 8-9.
4. The effect of ink properties The drying speeds of different inks are also different. The key lies in the nature of ink pigments and binders. In general, inks made with organic pigments dries faster than inks made with inorganic pigments; inks that use thinner binders dry faster than inks that use thick binders; inks that contain more oil have lower drying rates than those that contain less ink. SLOW.

1 pigment. Inorganic pigments are all metal salts, oxides, and the like. They are dispersed in a binder and act as a drying agent for dry vegetable oils. Therefore, inks made with inorganic pigments generally dry faster. However, there are special cases. Since the pigment of black ink is mainly carbon black, there is no drying effect on dry vegetable oil, so the drying speed of black ink is relatively slow. Most of the organic pigments are non-metal oxides and salts, which have no drying effect in the binder, and sometimes even have the effect of inhibiting the oxidative polymerization of the binder and delaying drying.

2 oil content. The oil content refers to the proportion of the binder and the pigment in the ink manufacturing process. According to the actual production statistics, there is a certain relationship between the oil content and the ink drying speed, that is, the oil content is large, the ink drying speed is slow, the oil content is small, and the ink drying speed is fast.

3 varnish. The main component of the varnish is dry vegetable oil, which is thick, thin, and the size of the viscosity. The ink drying speed has a great relationship with the viscosity of the varnish. The greater the viscosity, the faster the drying speed.

5. The effect of diluting agent and dissolving agent Dilute agents (white oil, maintenance oil) and release agent all have the characteristic of inhibiting ink drying.

1 white oil. White oil is a white opaque emulsion made from magnesium carbonate, stearic acid varnish, and water. It has a loose texture, moisture content, and hygroscopicity. It can easily cause ink emulsification and retard the oxidative polymerization process of the ink layer. Affects ink drying.

2-dimensional oil. One of the main components of Weili oil is aluminum hydroxide, which is an amphoteric hydroxide. Not only does it have no dryness, it also adsorbs driers, and there is a certain degree of dissociation in water, so it will be used in printing. Increase the degree of emulsification of the ink, resulting in delayed drying of the ink.

3 remover. The release agent is made of waxes and dry oils, or Vaseline and dry oils, turpentine, etc. The auxiliary materials themselves are very slow drying. If they are used in small quantities, they will not significantly affect the drying speed of the ink. However, if the wax-containing release agent is used excessively, on the one hand, the original structure of the ink will be changed, and the plasticity of the ink will be enhanced. On the other hand, it will float on the surface of the ink, retard the oxidative polymerization conjunctiva of the binder, and thus affect the ink drying speed.

6. Graphic distribution and the influence of ink layer thickness 1 Graphic distribution. The smaller the area of ​​the layout graphic, the larger the blank position, the greater the water consumption of the paper, and the greater the emulsification of the ink, the ink printed on the paper is not easy to dry. In particular, the ink at both ends of the printed sheet near the margin of the blank portion is more difficult to dry due to the large amount of emulsification.

2 ink thickness. Too thick ink layer will cause oxide film on the surface of the ink layer, slow down the speed of oxygen in the air entering the film layer, and the thick ink layer will reduce the chance of contact between the ink and the paper, thus reducing the penetration, so that it is too thick. The ink layer, the ink drying speed will be slower.

7. Influence of the fountain solution The fountain solution is generally acidic. When it is acidic enough to react with metal salts that act as driers, the drying process of the ink will be destroyed. Practice has proved that the stronger the acidity of the fountain solution, the longer the drying time of the ink.

In fact, the drying of the ink on the substrate is a very involved and relatively complicated subject. To obtain a proper drying rate, ink manufacturers and printing companies need to make unremitting efforts through practice. Only by understanding the many elements that affect ink drying, and improving or applying it properly, can we win the ink drying "obstacle race."

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