1. Reasons for Flying Ink
When ink transfers, at two or more contact rollers, the fibers are cut off or elongated to produce fragments, which become spherical due to external tension. At this time, the electric double layer existing at the interface between the fibre and the fragment is destroyed, one part is left in the ink, and the other part escapes to the atmosphere with opposite charges. When the fibre is shortened, the residual charges in the ink gradually pile up on the surface of the ink roll and paper. Fragments, with the same charge as ink, are squeezed into the air to form flying ink when they are near the ink roll or paper.
When high-speed press uses high-viscosity ink and low-quality linking material, it is easy to make ink rotate in the ink roll, drawing filament produces serious flying ink phenomenon, so different types of printers need to choose the appropriate ink to match.
2. Elements Affecting Flying Ink
(1) Ink stickiness is too large, ink is elongated at the outlet of ink roll, which is easy to produce flying ink. At the same time, it will make the ink transfer uneven, making the paper dehairing and dedusting, paper peeling from rubber cloth difficult, easy to pattern, offset and so on; too small stickiness, poor ink layer unity, easy to produce flying ink, and easy to emulsify ink, float dirt, paste plate, dot expansion, affecting the quality of printing.
(2) The thicker the ink layer on the roller, the larger the flying ink. When the thickness of the ink layer is 1.2 micron, the printing ink only needs to reach 2.8 g/m2, but when printed on offset paper, the printing ink on offset paper should reach at least 4 g/m2. When the paper performance is not good for the adhesion of ink, it is easy to compose ink roller stacking, thus producing flying ink.
(3) When the outer surface of the ink roller is rough and cracked, the local ink layer becomes thicker and the amount of ink mist increases, which is easy to produce flying ink.
(4) The printing speed increases and the flying ink increases.
(5) The relative humidity of air is small, which promotes the production of flying ink. When the humidity increases, the charge decreases and the quality of flying ink decreases.
(6) It is assumed that too much embossing liquid in the ink constitutes a serious W/O emulsified ink, and the viscosity drops sharply and the ink filament becomes shorter, which will cause serious ink flying phenomenon. At the same time, the embossing solution immersed in the ink will corrode the metal ink roll, forming a hydrophilic layer on the surface of the ink roll and extruding the ink, forming a metal ink roll deinking.
(7) The binder of high molecular weight ink is easy to pull the growing filament and produce flying ink when the ink is united.
3. How to eliminate flying ink
(1) Select high-quality alcohol-resistant ink to adapt to high-speed printing.
(2) Remove the cots regularly and thoroughly clean them, so that the ink layer of the roller is averaged and the ink transmission performance is improved.
(3) The concentration of alcohol should be controlled between 10% and 15%, too low or too high is not suitable.
(4) The amount of bucket liquid should not be too large, otherwise the ink filament will become shorter, which is not conducive to printing.
(5) When electrolyte is involved in ink, the flying ink will decrease. With the participation of electrolyte, the conductivity will increase, and the flying ink phenomenon will disappear intact.
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