The phenomenon of flying ink, that is, polluting the environment and damaging the health of the operators, is briefly analyzed below.
1. Reasons for flying ink
When the ink is transferred, at two or more ink rolls that are in contact with each other, the fibers are cut at two or more places, and the chips are cut when they are cut or elongated, and the surface tension becomes spherical. At this time, the electric double layer existing at the interface between the fibrous material and the fragment is destroyed, a part remains in the ink, and the other part escapes to the atmosphere with an opposite charge. When the fiber is shortened, the residual charge in the ink gradually builds up on the surface of the ink roller and the paper. The fragments have the same charge as the ink, and are repelled in the air to form flying ink when they are close to the ink roller or paper.
When the ink viscosity is large high-speed machines, with a low quality link material, easy to make the ink in the ink roller is rotated, the longwire serious ink flying phenomenon, and therefore different types of printing machines need to select the corresponding ink to match.
2. Factors affecting flying ink
(1) The viscosity of the ink is too large, the ink is elongated at the exit of the ink roller, which is easy to produce flying ink, and also causes uneven ink transfer, which makes the paper pluck and remove powder, and the paper is difficult to peel off from the blanket. If the viscosity is too small, the ink layer is not well split, it is easy to produce flying ink, and at the same time, the ink is easily emulsified, and the floating, paste, and dot enlargement are affected, which affects the quality of the printed product.
(2) The thicker the ink layer of the ink roller, the larger the flying ink. On the coated paper, when the thickness of the ink layer is 1.2 μm, the ink on the plate should be as long as 2.8 g/m 2 ; but the printing on the offset paper should be at least 4 g/m 2 . In the case that the paper performance is not good for the adhesion of the ink, it is easy to cause the ink roller to accumulate ink, thereby generating flying ink.
(3) When the surface of the ink roller is uneven and the surface is cracked, part of the ink layer is thickened, the amount of ink mist is increased, and flying ink is easily generated.
(4) The printing speed increases and the flying ink increases.
(5) The relative humidity of the air is small, which promotes the generation of flying ink; when the humidity increases, the electric charge decreases, and the amount of flying ink becomes smaller.
(6) If there is too much dampening solution in the ink, a serious W/O type emulsion ink is formed, the viscosity is drastically lowered, and the ink filament is shortened, which may cause serious flying phenomenon. At the same time, the dampening solution immersed in the ink also corrodes the metal ink roller, forming a hydrophilic layer on the surface of the ink roller to repel the ink, causing the metal ink roller to be deinked.
(7) The binder of the high molecular weight ink is easy to pull the filament when the ink is split, and the flying ink is generated.
3. How to eliminate flying ink
(1) Use high-quality alcohol-resistant inks to adapt to high-speed printing.
(2) The rubber roller is removed and cleaned regularly to make the ink roller uniform and the ink transfer performance is improved.
(3) Alcohol concentration is controlled between 10% and 15%. Too low or too high is not suitable.
(4) The amount of water bucket fluid should not be too large, otherwise the ink filament will become shorter and it will be unfavorable for printing.
(5) When the electrolyte is added to the ink, the flying ink is reduced. With the addition of the electrolyte, the conductivity increases and the flying phenomenon disappears completely.
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