Reasons and elimination of gluing in different printing processes (2)

Second, the lithographic version (print) paste version 

1. Lithography (Indian) Oil (greasy) The form of its performance is: the lines of the graphic lines spread out without being clear and complete. In the blank areas, there are grungy marks of different ink levels, especially on the blankets. A piece of ink. The reason is:

(1) The water-absorbing portion on the printing plate forms an ink-absorbing center, resulting in migration of the surfactant in the paper or plastic ink layer to the water-absorbing zone.

(2) The pH difference between the ink and water is too large (that is, the ink and ink is often unbalanced), which results in the printing plate being discolored by the acid in the solution.

(3) When using dry syrup containing lead, especially when the amount is too much, the dry oil is destroyed by the highly acidic syrup, which is covered by a thin layer of ink (usually also leads to yellowing of the entire plate). ). This oil layer is dirty because the ink layer hinders the control of wetting.

(4) The ink is too oily and too thick, resulting in insufficient amount of water on the plate.

(5) The non-printing area is deficient in induction processing and the pressure of the ink roller is large, the desiccant is unduly added, and the water roller is poor in quality or poor in installation. 

The usual approach is:

(1) The pH of the ink should be lowered to approach the pH of the syrup;

(2) adding wax or sodium silicate to the ink;

(3) Check the quality of printing plates and water rollers;

(4) Control the printing speed;

(5) The ink is as thin as possible;

(6) Choose a small, thick oily ink. 

2. Limb (print) Dirty manifestations are that the printing plate is full of light ink and can be easily transferred to the blanket and then transferred to paper or plastic. Sometimes it is easy to wipe off, but it quickly reappears. According to the floating phenomenon, people often think that the ink is floating on water or dissolved in water. Therefore, some people call the disaster water or ink bleeding. Because:

(1) The surface active material in the paper is leached to form an emulsion of the ink in water, which is then filled with moisture-absorbing parts of the printing plate.

(2) The pigment in the ink is poor in lipophilicity and is not sufficiently wetted by the binder (such as the ink produced by the medium yellow pigment can easily run into the water).

(3) When the synthetic resin uses a low-temperature dissolving binder and the content of the ink oil is relatively high, the ink emulsification is easily caused. 

The usual approach is:

(1) The ink should be stored for a period of time after it has been produced;

(2) The resin in the ink should have good wettability to the pigment;

(3) reduce the acid value of the medicine as much as possible, and reduce the amount of ink given to it;

(4) adding a viscous resin solution;

(5) Pigments treated with oil-absorbing or surface-treated hydrophobic additives, etc. 

3. The lithographic (printed) form of dingy appearance is the appearance of large dots of ink in non-printed areas. The reason is:

(1) The printing pressure and the printer's operation damage the sensitive film on the printing plate to expose the metal except the sensitive film, and then it will be immediately affected by trace surface activity, polarity, free fatty acid, etc. create pollution.

(2) Excessive ink layer remaining on the plate during development leaves a dirty plate produced on the plate.

(3) The ink is too thin and the oiliness, softness, and viscosity are insufficient, and it is easy to cause the ink roller to slip and then make the water roller dirty.

(4) Inadequate sensor processing or gluing is not good.

(5) The lack of water on the printing plate and the low acidity of the syrup cause the water roller to absorb the ink. There are also the inherent dirtiness of the PS plate. 

The usual approach is:

(1) Adding ink varnish (resin solution) to the ink;

(2) The content of grease and oil in the ink should be reduced as much as possible;

(3) increase the amount of water supply, especially to increase the acidity of the medicine;

(4) Use a high density ink to make the print as thin as possible;

(5) Use a high surface tension syrup;

(6) Adjust the embossing force between the printing plate and the squeegee;

(7) reduce desiccant;

(8) Replace the faster dry resin ink.

Third, gravure (gravure) paste version 

In plastic printing, especially for the manufacture of composite inks, small-size or hierarchical layouts do not appear, and even the surface of the substrate forms indistinct ink. Some people think that it is due to poor adhesiveness. Adding adhesion-promoting tackifying (resin) agents without scientific knowledge can overcome the disadvantages of delamination. However, overdosing often results in softening of the ink after film formation. It is impossible to control the paste (staining). Because:

(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 strong wettability on the chrome plated surface of the gravure plate, resulting in scraping and scraping of the ink;

(4) The blade is dull or the angle is not correct;

(5) rough surface of the plate cylinder;

(6) Ink drying (period) is too slow (such as the introduction of ethyl acetate (fast-drying solvent) in the printing ink system, suitable for printing on the film 1 ~ 3S. (7) in a high humidity environment The charged ink has an affinity for chromium (increase the proportion of antistatic agent).

(8) The stencils caused by slow printing or poor printing plates.

How to troubleshoot this fault:

(1) If the chrome-plated surface of the new drum is rough, add a quick-drying solvent to the ink to form a dry thin layer of ink between the scraper and the impression cylinder. After two hours or even hours, polish the surface of the chromium. Use 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, and 2 parts of toluene.

(2) If the ink contains impurities such as pigment particles and paper, plastic shavings, the solvent should be increased. The best method is to filter the ink with a 250 mesh screen.

(3) Use a new doctor blade and adjust its angle.

(4) If it is caused by slow-drying ink, add a quick-drying solvent to dilute the ink, and if it is caused by fast-drying ink, add a slow-drying solvent or silicone oil to slow the dryness.

(5) If the ink is dried in the plate cavity due to blowing, the blowing angle should be adjusted, generally to increase the speed of the printing machine or to re-plate.

(6) Add additional solvent to reduce the viscosity of the ink or add anti-adhesion agent (such as waxes, etc.) and so on.

(7) Add oil or resin liquid, or change to no-particle ink. 