The hottest factors affecting the drying speed

2022-08-18
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Factors affecting drying speed

I. Influence of ambient temperature and humidity

1 Influence of ambient temperature

when the temperature rises, the movement speed of molecules accelerates, and the internal energy of molecules increases, which is easy to generate more peroxides with activated genes, thus accelerating the polymerization of oil molecules. Therefore, with the increase of temperature, the oxidation polymerization reaction of ink will be accelerated, so as to speed up the drying of ink

the drying process of ink film is an exothermic reaction, and the heat released during printing drying will also accelerate the drying speed of imprinting. The influence of temperature on the speed of imprinting drying is obvious. When the temperature of the environment rises, the ink drying is fast, and vice versa. For example, in hot summer weather, bright and fast drying inks do not need to be added, accounting for 13.9%; Equipment with a journey of 400 ~ 700mm can also be dried quickly. However, in cold winter, it is necessary to add dry oil

2. The influence of environmental humidity

in the offset printing process, it is necessary to wet the printing plate with water. Water is a polar molecule and oil is a non-polar molecule. Because wetting 3 with water is a water absorption printing plate, there will be different buttons and control keys in the pressure testing machine, and the ink emulsification will be controlled within the range of 10 to 30%. The rate of water condensation and evaporation is closely related to the drying of the imprint. Because water molecules are highly polar substances, the existence of water can hinder the oxidation and polymerization of oil molecules to form a film, which will affect the drying speed of imprinting. The level of environmental humidity will play a certain role in the evaporation speed of water. With the increase of environmental humidity, the activity of oxygen in the air will also be weakened, which reduces the absorption of oxygen by the ink. At the same time, the emulsified water in the inner layer of the ink film also softens the ink film, thus slowing down the drying speed of the ink. Therefore, in the offset printing process, we should control the balance of water and ink, and use as little water as possible on the premise of not dirty version, so as to reduce the emulsification of the ink. The amount of water in the ink is closely related to the drying of the imprint

second, the influence of ink auxiliary materials

transparent diluents, white oil, debonding agents, etc. have the property of inhibiting the drying of ink, making the drying of imprints slow down. Diluent, viride oil, white ink, white oil and other main components are binder and aluminum hydroxide. In the process of calibration, as long as the levelness of the lever and the perpendicularity of the force axis at the end of the lever force point are effectively controlled, aluminum oxide often exists, which is insoluble in water. Because aluminum hydroxide is easy to dissociate with water, the emulsification degree of ink will be increased in printing, so the drying of imprinting is slow. Viride oil is generally used as a diluent for multicolor overprint inks of ordinary products. The diluted ink color basically has no effect, but the brightness is general and the drying is slow. White oil is a kind of white translucent emulsion. Diluting the ink color with it can reduce the viscosity of the ink, and the color matching is uniform. The white oil is non drying, loose and contains water, which accelerates the emulsification of the ink. The water is absorbed into the ink layer and then evaporates gradually, blocking the oxidation and polymerization process of the ink, which will seriously affect the drying speed of the imprint

in the process of offset printing, in order to change the printability of the ink, or reduce the viscosity of the ink, non drying auxiliary materials such as debonding agents are often added, which basically does not affect the gloss and fluidity of the ink color. However, do not use too much. Because of its non drying and permeable substances, it is easy to cause the disadvantage of slow drying of the imprint. The content in the ink is less than 5%

generally speaking, if the ink needs to be diluted and debond, the amount of drier should be increased in the ink accordingly. Such as: red and white dry oil

third, the impact of bucket solution

the bucket solution is inseparable from acidic substances, such as phosphoric acid, citric acid, etc. first, the gravure needs to supplement the inorganic salt layer lost in the printing process. Phosphoric acid and other acidic substances have the function of cleaning ink dirt, and acidity will destroy the drying of ink. The stronger the acidity of the bucket solution, the slower the drying time of the ink. Therefore, it is necessary to control the pH value of the bucket solution and follow the instructions of wetting powder when mixing the bucket solution. Add some Arabic gum to the wetting liquid to enhance the ability of hydrophilic and dirt removal, and reduce the influence of drying after emulsification of ink

IV. influence of paper

paper has a great influence on imprinting drying

influence of pH value of paper. The paper should be neutral, that is, the pH value is 7. However, most of the paper is weakly alkaline, and the paper is often acidic, which has a great impact on the drying of the imprint. The paper is acidic, which can make the ink layer unable to dry for several days, affecting the timely delivery, and the fiber structure of the paper affects the drying of the imprint. The paper with rough surface, loose structure, high permeability and less sizing will dry quickly; On the contrary, the surface smoothness is high, and the imprinting of coated paper and card paper with dense and tough fiber dries slowly

v. the influence of image and text distribution and ink layer thickness

in the offset printing process, the image and text area is large, the distribution is uniform, and the water consumption on the printing plate surface is large. Because the water consumption is uniform, the emulsification value of ink on each part of the ink roller surface is relatively average. Generally, the imprint with both ends close to the edge of the blank part is not easy to dry due to the large amount of emulsification. The smaller the area of the graphic part of the layout, the greater the emulsification value of the ink. It is necessary to prevent the phenomenon of non drying. In addition to adding driers, it is more important to strictly control the moisture of the layout, reduce the introduction of ink, and ensure the timely drying of the imprint

excessive thickness of the imprinted ink layer will reduce the contact between the ink layer and the air. When a film is formed on the surface of the ink layer, the speed of oxygen in the air entering the ink film is slowed down. With the thickness of the ink layer, the contact opportunity between the imprinted ink and the paper is reduced, and the penetration effect is correspondingly reduced. Therefore, the drying speed of the excessively thick ink layer can only be very slow, and the amount of drying agent can be adjusted according to the thickness of the ink layer. We should control the thickness of the imprinted ink layer to avoid the disadvantages of excessive thickness of the ink layer caused by offset printing, such as large ink and water, one-sided emphasis on thickness and bright colors, and excessive increase of ink volume

VI. impact of paper receiving and stacking

the stacking of printing sheets has a great impact on the drying speed of imprints. Offset printing ink is oxidized on paper, and the drying of ink film depends on the reaction of oxidation and polymerization exothermic with oxygen in the air. If the paper surface is smooth, the stacking is high, and the air is difficult to contact with imprints, there will inevitably be a thick stacking in the middle of a sheet of paper, and the drying of printing sheets is slow

in order to speed up the drying of the imprinted ink film, it is often used to separate the printing sheets in multiple layers on the paper receiving table with wooden splints to reduce the stacking thickness and speed up the drying, or wait for a certain time after the printing of the printing sheets, and ventilate the printing semi-finished products, in order to increase the contact between the imprint and the air and speed up the drying of the imprint

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