Surface crust
In the printing process, when adding a new ink, sometimes the surface of the ink around the ink drum is found to have different degree of conjunctiva phenomenon. If these ink films are added to the ink fountain, the ink supply performance of the machine will be seriously affected.
Cause
The binders in offset printing inks consist of synthetic resins, vegetable oils, and high-boiling point mineral oils. The linseed oils commonly used in offset printing rotary inks are dry oils because they contain more unsaturated fatty acids. Base, can evenly absorb the oxygen in the air, oxidize and polymerize into a tough solid film, so the offset printing rotary ink has better drying in the air. At the same time, due to the use of certain inorganic pigments (such as iron blue, etc.) in the ink formulation, the surface of the ink is prone to surface crusting during storage.
2. Solution
Some anti-drying agents (anti-skinning agents) can be added in an appropriate amount during the ink production process, since most of them are strong reducing agents and can be preferentially oxidized, so it is possible to retard the oxidative polymerization of drying oils. In addition, try to avoid exposing the ink to the air for a long time.
The above is a common fault in the production of ink for printing. In the printing process, no matter what faults are encountered, we must carefully observe the system analysis in combination with the appearance, and then find out the solution to the problem. We can eliminate the problems that cannot be solved at the moment and eventually solve the problems completely.
Source: 21st Century Fine Chemicals Network