Factors affecting blot dryness

First, the impact of environmental temperature and humidity

1. Influence of ambient temperature

When the temperature rises, the speed of the molecules increases, the intramolecular energy increases, and more peroxides are easily generated with the activated genes, thereby accelerating the polymerization of oil molecules. Therefore, as the temperature rises, the oxidative polymerization of the ink will increase, thereby accelerating the drying of the ink.

The drying process of the ink ink film is an exothermic reaction, and the heat released when the print sheet is dried also accelerates the drying of the print. The effect of temperature on the speed of the drying of the blot is obvious. The temperature of the environment increases, the ink dries quickly, and vice versa. For example, in the hot summer weather, bright fast-drying inks can dry quickly without adding dry oil, but in the cold winter season, dry oil is needed.

2. Impact of environmental humidity

During the offset printing process, we need to moisten the printing plate surface with water. Water is a polar molecule and oil is a non-polar molecule. Since wetting the plate with water, the phenomenon of ink emulsification occurs, and the ink emulsification is controlled between 10% and 30%. In the range, the concentration and evaporation rates of water are closely related to the drying of the blot. Because water molecules are very polar substances, the presence of water can hinder the oxidation polymerization of oil molecules to form a film, which will affect the drying speed of the imprinting. The level of the environmental humidity will play a role in the evaporation rate of the water. Increased ambient humidity, oxygen in the air will also reduce the activity, reducing the ink to the suction of oxygen, while the ink ink film emulsified layer of moisture to make the ink film softened, so that the ink drying speed slows down. Therefore, in the offset printing process, we must control the balance of ink and water, and use less water as much as possible to avoid ink emulsification. The amount of water in the ink is very close to the drying of the print.

Second, the impact of ink auxiliary materials

Transparent dilutants, white oils, detackifiers, etc. all have the property of inhibiting the drying of the ink and slow drying of the print. The main components of diluting agent, weili oil, white ink, white oil and the like are the presence of aluminum oxide in the link material and aluminum hydroxide. It is insoluble in water. Since aluminum hydroxide is easily dissociated by water, the degree of emulsification of the ink is increased during printing, so that the print is dried more slowly. Wiley oil is generally used as a dilute agent for multi-color overprint inks for common products. Dilute ink colors have no effect basically, but the brightness is generally low and drying is slow. White oil is a white translucent emulsion, use it to dilute the ink can reduce the viscosity of the ink, color uniformity, white oil has no dryness, pine contains water, so that the ink accelerates the emulsification, water intake after the ink layer gradually Evaporation removes the oxidative polymerization process of the ink and can severely affect the drying rate of the print.

In the offset printing process, in order to change the printability of the ink, or to reduce the viscosity of the ink, non-dried auxiliary materials such as a detackifier are often added, and the gloss and fluidity of the ink color are not substantially affected. However, it cannot be used in excessive amounts. Because of its non-dry and penetrating substances, it is easy to cause the disadvantages of slow drying of the imprint, and the content in the ink is less than about 5%.

In general, if the ink needs to be diluted and de-bonded, the amount of driers should be increased accordingly in the ink. Such as: red, white dry oil.

Third, the impact of the water bucket solution

The water tank solution can not be separated from the acidic substances, such as: phosphoric acid, citric acid, etc. First, the gravure plate needs to supplement the inorganic salt layer lost during the printing process. Phosphoric acid and other acidic substances have the function of cleaning the ink dirty, and the acidity will make The drying of the ink is destroyed. The stronger the acidity of the hopper solution, the slower the drying time of the ink. Therefore, to control the PH value of the hopper solution, when the hopper solution is formulated, the wetting powder instructions are used. Add some gum arabic in the dampening solution to enhance the ability of hydrophilic degreasing, reducing the emulsification of the ink and affecting the drying.

Fourth, the impact of paper

Paper is very influential on the drying of blots.

The pH of the paper pH effect. The paper is preferably neutral, that is, the pH is 7, but most of the paper is weakly alkaline, and often the acidity of the paper has a great influence on the drying of the print. The acidity of the paper can make the ink layer unable to print for a few days. Drying, affecting timely delivery, the fiber structure of the paper affects the drying of the imprint. The surface is rough, the structure is loose, and the permeability is large. The paper blot with less sizing is dried faster; on the contrary, the surface smoothness is high, and the imprinted paper and card paper with dense and tough fibers are dried slowly.

Fifth, the distribution of graphic and ink layer thickness

In the offset printing process, the graphic area is large and evenly distributed. The surface of the printing plate has a large amount of water. Because the water consumption is even, the emulsification values ​​of the inks on the ink roller surface are relatively even. In general, the edges of the edges near the edges of the blank portions are not easily dried due to the large amount of emulsification. The smaller the layout area, the greater the ink emulsification value. To prevent quits. In addition to increasing the driers, it is more important to strictly control the layout of water, reduce the ink to promote the timely drying of the imprint.

Imprinting the ink layer too thick will reduce the contact between the ink layer and the air. When the film is formed on the surface of the ink layer, the speed of the oxygen in the air entering the ink film is reduced. With thick ink layers, the chance of contact between blotting ink and paper is reduced, and the permeation is reduced accordingly. Therefore, the excessively thick ink layer drying speed can only be very slow, and the different ink layer thickness can adjust the amount of barium dry agent. It is necessary to control the thickness of the imprinted ink layer to avoid the occurrence of ink-jet printing and ink-jet printing. The thick and bright colors on the one-sided surface, and the excessively large thickness of the ink layer caused by the excessively large amount of ink.

Sixth, the impact of paper stacking

The stacking of imprinting sheets and the speed of imprinting drying have a great influence. Offset printing inks are on oxidized knotted paper. The ink film drying depends on oxygen oxidation in the air and polymerization exothermic reaction. If the paper surface is smooth, the stacking height is high. The air is difficult to contact with the imprints. It will inevitably appear that the middle part of a sheet of paper is thick and the sheets are dry slowly.

In order to speed up the drying of the blotting ink film, it is often adopted to use wooden plywood to separate the printed sheets on the delivery table in multiple layers, to reduce stacking and thicken, to speed up drying, or to wait for a certain period of time after the printing of the printed sheets is completed, to make the semi-finished printing products transparent. The purpose is to increase the contact between the print and the air and speed up the drying of the print.

After the ink is transferred from the printing plate to the surface of the printed material, part of the binder in the ink penetrates; at the same time, the solvent in the binder material starts to volatilize, and the main part of the binder material undergoes a chemical reaction and a physical reaction, thereby making the surface of the printed material. The ink film gradually increased its viscosity and hardness, and finally finally formed a solid film layer.