Oval printing machine, when printing with silicone ink. The machine cannot be stopped, otherwise it is easy to solidify. What is the reason?
Once the machine stops, it is easy to solidify, which is mainly related to the characteristics of silicone ink, drying mechanism and equipment working environment.
1. Two-component reaction characteristics
Silicone ink is usually a two-component (A+B component) system, and a cross-linking reaction (such as platinum catalytic addition reaction) will occur after mixing. Even at room temperature, the reaction will proceed slowly. The longer the time, the more complete the cross-linking, which will eventually lead to solidification.
Impact of shutdown: When the machine stops, the ink stays in the screen, scraper or printing head, and the local temperature may rise due to the residual heat of the equipment, accelerating the reaction.
2. Solvent volatilization and viscosity change
The solvent in the silicone ink (such as xylene and cyclohexanone) will gradually evaporate after contact with the air, causing the viscosity of the ink to increase and eventually form a gel.
Impact of shutdown: The ink on the screen is exposed to the air for too long, and the solvent evaporates quickly, especially in a high temperature and low humidity environment.
3. Screen temperature accumulation
When the oval printing machine is running, the friction between the screen and the scraper will generate heat. After stopping, the heat cannot be dissipated in time, the local temperature rises, which may trigger the thermal curing reaction of the ink.