Reasons and processing methods of printing paste
The term gluing is often interpreted as dirty, blocking or dyeing, and different printing forms will result in different gluing. In recent years, paste printing has appeared frequently in transparent ink printing and composite ink printing. For example, offset printing paste is often caused by the imbalance of ink and water (the difference between the pH value of the ink and the ink). The gravure paste is mostly caused by the scraping of the scraper, and it mostly occurs in the summer with high temperature. It is not difficult to find when we discuss around this fault: the ink quality of the printing ink determines the occurrence of this phenomenon. It is impractical to determine what is the cause and what is the general situation, which prevents us from remediating and eliminating it in a very short time in the actual printing operation. ?
First, the paste version of the letterpress?
The most obvious printing phenomena such as "products", "days", "mouths", etc. are filled with ink into a solid shape, and even dots are connected together, so it is often called blocking. (1) The reason is that the dryness of the ink is too large, which causes the ink to dry early or is too sticky, causing small dots of ink layer on the paper or plastic, or paper, plastic debris to concentrate on the plate or dot part; (2) The ink dries too fast, the ink in the ink fountain has skin or dry particles; (3) The ink is too thin, the ink is squeezed out under the printing pressure; (4) Too much paper or plastic absorbs the binder, resulting in the pigment in the ink Excessive content; (5) The roller is defective or unintentional; (6) The printed relief is not flat or too high; (7) It is too thick on the rubber sheet paper or smooth plastic (especially plastic woven bags) Ink; (8) Too much ink or too slow drying. ?
The exclusion methods are: (1) use reasonably dry and thick ink; (2) high-profile parts or dots to reduce printing pressure; (3) re-filter ink 15 ～ 25μm); (4) on the upper side of printing Separate or change substrates with base paper and plastic; (5) Add additives to dilute ink in thick ink to increase the flow rate of ink; (6) Make up for drying ink or solvent; (7) Dye ink should be reduced The content of resin; (8) Reduce the amount of ink supplied or add a slower ink inhibitor; (9) Do not blow the wind from the drying device onto the plate; (10) Add TM3 or silicone oil to the ink. ?
Second, the lithographic (printed) paste version?
1. Lithography (printing) is greasy (greasy) and its manifestation is: the graphic lines are spread out and not clear and complete. In the blank area, there are dirty stains of different ink weights, especially on the blanket Pieces of ink. The reason is as follows: (1) The water absorbing part on the printing plate forms an ink absorbing center, causing the surfactant in the paper or plastic ink layer to migrate to the water absorbing area. (2 The pH difference between the ink and water is too large (that is, the water-ink imbalance is often said), which causes the metal of the printing plate to be dissolved by the acid in the liquid medicine and the printing plate is not clean. (3) When using a paste containing lead to dry When the oil is used, especially when the amount is too much, the dry oil is destroyed by the highly acidic potion and is covered by the thin ink layer (which often leads to yellowing of the entire layout). This ink layer hinders the wetting The oil is dirty due to control. (4) The ink is too oily and too thick to cause insufficient water on the plate surface. (5) The non-printing area is due to the lack of inductive treatment and the pressure of the inking roller, and the desiccant and water are inappropriately added. Poor roller quality or poor installation?
The usual treatment methods are: (1) The pH of the ink should be adjusted down, close to the pH of the potion; (2) Add wax or sodium silicate to the ink; (3) Check the quality of the printing plate and water roller; ( 4) Control the printing speed; (5) The ink should be as thin as possible; (6) Choose the ink with small oiliness and thick. ?
2. The form of lithographic (printing) floating dirt is that the printing plate is full of slight ink, and it is very easy to transfer to the blanket, and then transfer to print on paper or plastic. Sometimes it is easy to wipe off, but it quickly reappears, staining in the potion. According to the phenomenon of floating dirt, people often think that it is caused by ink floating on water or dissolving in water. Therefore, some people call the disaster water or ink bleeding. The reasons are: (1) The surface active substance in the paper is leached to form an emulsion of ink in water, and then covered with the moisture absorption part of the printing plate surface. (2) The pigment in the ink has poor lipophilicity and is not fully wetted by the binder (such as ink made by Zhongluo yellow pigment can easily run into water). (3) When synthetic resin uses low temperature to dissolve binder and the content of ink oil is relatively high, it is very easy to cause emulsification of ink. ?
The usual treatment methods are: (1) The ink should be stored for a period of time after production; (2) The resin in the ink should have better wetting of the pigment; (3) The acid value of the potion should be reduced as much as possible, and the amount of water ink should be reduced ; (4) Add viscous resin solution; (5) Use pigments with large oil absorption or surface treated with hydrophobic additives. ? [next]
The dirty form of lithography (printing) is the appearance of large dots of ink in the non-printing area. The reasons are as follows: (1) The printing pressure and the operation of the printer destroy the isolation membrane on the printing plate and expose the metal, which will be immediately affected by trace surface activity, polarity, free fatty acids and other substances. The place absorbs ink and causes pollution. (2) The excessive residual ink layer left on the plate during the development of the printing plate is a dirty plate generated on the plate. (3) The ink is too thin and oily, soft, and insufficient viscosity, easy to cause the ink roller to slip and then make the water roller dirty. (4) In addition to improper induction treatment or poor glue application. (5) The insufficient water on the printing plate and the acidity of the potion are too low, which causes the water roller to absorb the ink. There are also inherent stains caused by the PS version and so on. ?
The usual treatment methods are: (1) Add ink to the ink (resin liquid); (2) Reduce the content of fat and oil in the ink as much as possible; (3) Increase the amount of water supply, especially increase the acid value of the potion ; (4) Use thick ink to make the blot as thin as possible; (5) Use a potion with higher surface tension; (6) Adjust the embossing force between the printing plate and the rubber roller; (7) Reduce the desiccant; (8) Replace the faster drying resin ink.
Third, the gravure (gravure) paste version?
In the printing of plastics, especially in the manufacture of composite inks, small prints or hierarchical patterns cannot be printed, and even ink shades of varying shades are formed on the surface of the substrate. Some people think that it is due to poor adhesion (adhesion). If we do not scientifically add adhesion-promoting (resin) agents to promote adhesion, although it can overcome the disadvantages of pull-off, excessive addition will often lead to softening of the ink film. There is no way to control paste (dyeing). The reasons are: (1) the affinity of the surface with the metal gravure and scraper due to the floating color; (2) the acid value of the composite resin is too low; (3) the ink has a strong wettability on the chrome plated surface on the gravure, resulting in The scraper scrapes the ink; (4) The scraper is slow or the angle is wrong; (5) The surface of the plate cylinder is rough; (6) The initial drying of the ink (period) is too slow (such as ethyl acetate (fast-drying solvent in the Indian ink system) ) Introduced, it is suitable to print within 1 ~ 3S on the film. (7) In the environment with high humidity, the charged ink has affinity for chromium (increasing the proportion of antistatic agent). (8) The printing speed is too slow or Confused plates caused by bad printing plates.
The method to eliminate the fault. (1) If the chrome-plated surface of the new version of the cylinder is rough, add a quick-drying solvent to the ink to form a thin layer of ink between the blade and the impression cylinder. After two or even hours, polish the chrome surface, and then Change to a normal mixed solvent (such as 7 parts of ethyl acetate, 2 parts of toluene, 1 part of butyl acetate or 8 parts of ethyl acetate, 2 parts of toluene.) (2) If there are impurities in the ink For pigment particles, paper and plastic shavings, the solvent should be increased. The best treatment is to use 250 mesh screen to filter the ink. (3) Change to a new scraper blade and adjust its angle. (4) If it is a slow-drying ink As a result, add a quick-drying solvent to dilute the ink, if it is caused by a quick-drying ink, you can add a slow-drying solvent or silicone oil to slow down the drying. (5) If the ink is dried in the plate cavity due to blowing, it should be Adjust the blowing angle, generally to increase the speed of the printer or remake the plate. (6) Add solvent to reduce the viscosity of the ink or add anti-sticking anti-soiling agent (such as waxes) etc. (7) Add gold oil or resin liquid , Or change to particle-free ink.
Fourth, stencil (silk screen) paste version?
It is often expressed in the ink drying on the screen, and the usual treatment method is to replace the slow-drying ink or adjust the ink by using a slow-drying solvent.
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