How to effectively control the pH and viscosity of flexographic inks

Flexo workers all know that in the process of printing with water-based printing inks, it must be noted that the viscosity of the ink remains constant. In the laboratory, the operator uses the Zahn cup and meter to observe that checking viscosity is a common job. If the viscosity of the ink is high, some water is added, but the problem occurs at this time. If water is used to control the viscosity of the ink, the pH of the ink drops with decreasing viscosity each time water is added. The pH of the water is 7 and the pH of the flexo water ink is generally controlled by the supplier, usually at 8.5-9.5.

When the pH drops, the effects of the ink components begin to change, the lower pH values ​​have a significant loss of color intensity, the ink begins to separate or split, and high pH also results in loss of structure and composition.

The pH is considered to be the most critical factor in controlling flexo printing. In the establishment and maintenance of ink, pH and viscosity are inseparable and the two are mutually controlled.

How to control the pH and viscosity? First, use a pH meter to measure the pH, understand the ink composition, the pH of the additive, and record changes at any time. In addition to adjusting the viscosity with water, another pre-mixed conditioning solution can also be used. This conditioning solution contains amines and other components. The printing ink provided by the printer can increase the pH of the ink by 1-1.5. Do not use ink to adjust the ink.

pH and viscosity are the keys to printing success. In printing, roller, measuring systems, printing plates, binding jobs, materials, and drying environments, printing inks are only best at optimum viscosity and pH. color. Colors will be in contact with each other during overprinting, platen liners, or color overprinting. The most useful method at this time is to increase the viscosity and lower the pH, which aids in the drying process and prevents the postprint color from being wetted by the preprinted color.

In the process of ink printing, the automatic viscosity and pH control system can effectively detect the stability of the ink on the wire, thereby reducing the loss of ink film and printing ink, and also reducing the volatile organic compounds (VOC) (amines, alcohols). Or the use of other solvents, printers can save time.

The latest generation of automatic control systems has excellent accuracy and reliability. It can be operated and maintained simply, and multi-unit or single-unit control systems can be purchased at lower prices than before. What's more, regardless of the automatic system or manual operation, the adjustment fluid is used instead of water.

Reprinted from: Taiwan Printing Think Tank