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(1) Ink roll deinking caused by ink problems, black ink is more common. The ink produced from the soot lime has a large oiliness and does not cause deinking. The black ink with carbon powder as the raw material is poor in oil and deinking phenomenon may occur. It is possible to dilute some thin inks. If the image contrast of the product is large, when the ink cannot be thinned, some oleic acid can be added to the ink. .
(2) The ink has low viscosity and short ink. It is commonly used in light-colored inks formulated with a lighter. This type of ink is easily emulsified. The acid in the water bucket invades the ink, corrodes the surface of the ink roller, and causes the surface of the ink roller to pro The water layer can be used to remove oil from the ink. In this case, thicken ink can be added to the ink to increase the viscosity.
(3) After the occurrence of deinking of the ink roller, the moisture of the plate should be reduced as much as possible and the acidity of the water bucket should be reduced to remove the gum arabic.
(4) The ink is too thick and too hard, add No. 6 varnish to increase its fluidity.
(5) Intensively agitate the ink fountain and remove the inner skin and impurities from the ink fountain to prevent the ink from drying or gelling and prevent deinking.
5. Ink emulsification phenomenon and causes: Water is divided into fine droplets dispersed in the ink called emulsification, in the printing process, oil and water are not absolutely not harmonized, due to the ink and the constant contact of moisture, and the role of mechanical force And the participation of other factors will have different degrees of emulsification. When printing yellow ink and pale blue ink, this phenomenon often occurs, and most of them occur on both ends of the ink roller. The emulsification of ink is very harmful to the printing, diluting the ink color, affecting the drying of the imprinting, creating a dirty surface, the ink being “slackâ€, the ink roller being deinked, the imprinting color discoloring, the paper becoming yellow or blue, affecting the product quality, etc. Adverse consequences. The cause of ink emulsification is mainly due to the decrease of the surface tension between oil and water. In addition to the fact that the surface water is too large, the water of the water bucket is too strong, the content of the resin is too much, and the active material on the surface of the paper is detached, the common ink The reasons for emulsification are:
(1) The acid value of the ink is too high. The surface tension at the interface between ink and water depends on their polarity. The polarity of the ink is usually measured by the acid value. The more free fatty acid in the ink, the higher the acid value. The stronger the polarity, the greater the possibility of emulsification. A certain acid value can ensure the dispersion of the pigment in the ink and the adhesion of the ink in the transfer process, but the high acid value is the biggest cause of ink emulsification.
(2) Ink pigments have poor water resistance, especially pigments for offset inks, which are insoluble in both water and acid, but also have water-resistance properties. Since ordinary lake pigments are often hydrophilic, they are often hydrophilic powders. When the dye components in the pigment encounter acidic water, the dye will precipitate out of the dissolved water quickly, causing emulsification failure. If the pigment of the ink pigment is coarse, the viscosity is not enough, and the binding with the binder is not strong enough during the rolling process, the moisture is easily absorbed by the contact with the acid during the printing process and swells by itself and gradually separates from the binder to generate emulsification.
(3) There are no pictures on both sides of the plate, and the water content is large, which causes emulsification on both ends.
(4) To add too much diluting agent in ink, the commonly used auxiliary oil is carbonic acid, Weili oil is aluminum hydroxide, and it is an emulsifier, so the more the auxiliary material is added, the more the ink will be emulsified. . Too much dripping agent in the ink, the printing process is bound to increase the acidity of the water bucket syrup, too strong acid can easily cause ink emulsification, in addition to the driers itself is a strong emulsifier, so the ink in the dryer to increase and release more The more the ink can cause emulsification failure.
Treatment method: It is impossible to completely solve the problem of emulsification of ink, because oil and water will produce emulsification under the action of machinery. Trace emulsification has little effect on printing. If emulsification is serious, it must be solved.
(1) Replace the new ink.
(2) Add concentrated ink to the ink to reduce the acidity of the syrup and the amount of gum arabic.
(3) Add less oleic acid, white oil, and Weili oil.
(4) Reduce the amount of driers.
6. The phenomenon of pulling the paper and its causes: The pulling of paper hair means that the ink and the paper cannot be well adapted to each other. The fibers on the paper surface are pulled up, and the pattern marks appear white. The reason for the generation of naps is that due to the looseness of the paper fiber structure, the following causes are caused by the ink:
(1) The ink viscosity is too strong.
(2) Ink flow is too small.
(3) Add too much dry oil, so that the ink becomes thicker and thicker. The viscosity of the ink is too high or too thick (too much dry oil, and thickening occurs) The cohesive force is large, and the tension on the blanket when the ink is transferred to the paper also increases, if the cohesion between the paper fibers (Coupling force) is less than the cohesion between the ink, the paper fiber structure will be destroyed and pull paper phenomenon appears.
Approach:
(1) The viscosity of the ink is too strong, and can be increased by using Kangbang and Vaseline to change the ink viscosity.
(2) The ink is too thick and has poor fluidity, and can be diluted with No. 6 varnish.
(3) Too much dry oil or the ink becomes sticky and thick, and it can be properly added to solve the new ink.
(4) If the ink is adjusted after the ink has been adjusted and the phenomenon of pulling the paper is still serious, it can be solved by overprinting the white oil.
Ink-induced printing failure (below)
Approach: