The additives commonly used in screen printing water-based ink are pH stabilizer, defoamer, fast drying agent and slow drying agent.
1. PH stabilizer: pH stabilizer is mainly used to adjust the pH value of ink. The problem of pH value of ink is often mentioned by ink manufacturers when they promote ink products to printing enterprises. Low pH value is easy to cause ink caking, and high pH value is relatively low viscosity.
Generally speaking, the pH change of ink should be detected in the printing process. When the pH value is lower than 8, appropriate pH value stabilizer should be added to keep the ink in good printing state.
The pH value of European water-based ink is neutral. When the pH value is adjusted to 8.5, the fluidity and glossiness of the product are in good condition. However, in the printing process (within 1 hour), due to the volatilization of amine solvent, the ink viscosity will increase rapidly, the gloss will decrease, and the fluidity will become poor, resulting in a large number of unqualified products.
If the pH value is adjusted, amine solvent is added during the printing process (within 1 hour), and continuous detection is required (with acidimeter). If you are not careful, there will be waste products, and the whole workshop is filled with a bad smell. Such products are considered to have poor printability. For example, the pH value of the ink between 7 - 8, ink stability is better. Users can add pure water as a solvent to reduce the viscosity of the ink, which will not increase the cost, but will reduce the resin smell of the ink.
Environmental protection performance of water based ink for screen printing
2. Defoamer: Ink viscosity is too high, pH value is too low, printing speed is too fast, and printing technicians add too much water, easy to produce bubbles. When the bubble ratio is large, there will be problems such as the exposure of printed matter and the amount of ink, which will seriously affect the printing quality. It is generally recommended to add defoamer and surface defoamer in ink to solve the problem of water and ink foaming, the ratio is 1-2.
3. Rapid desiccant
In the process of using ink, due to the different resin selected by the ink manufacturer or the machine speed is too fast, the ink drying speed may be slow. The speed of drying agent can be adjusted to meet the requirements of printing machine speed and improve production efficiency. The use ratio of desiccant is 2-3.
4. Slow drying agent: the slow drying agent can control and slow down the drying speed of the ink, play a role in moisturizing, prevent the ink from drying on the screen printing plate or anilox roller, and reduce the occurrence of printing faults such as printing plate blocking. The utilization rate is between 1% and 2%.