Elastic Relief - Water Based Ink

Flexible flexo printing ink

PH value and viscosity control

Today, most flexible letterpress printers understand the color matching of a color. During the use of the entire aqueous ink, it is necessary to pay attention to and maintain a certain viscosity. In the laboratory, detecting the viscosity is the most common task for the operator each time using the Zahn cup and the meter. If the viscosity of the ink is higher than the expected value, some amount of water is generally added. Time will happen.

If water is used alone to control the viscosity of the ink, the acid value of the ink will decrease as the viscosity becomes smaller each time water is added. The pH of the water is 7, while the pH of the flexographic water-based ink is generally supplied by the supplier, usually between 8.5 and 9.5. When the PH value decreases, the effects of the ink components will begin to change, and the lower PH value will have a significant loss of color intensity. Even more, the ink components begin to separate or split and produce a muddy phenomenon. The same is true for high pH values. It will result in loss of structure and composition.

Today, the PH value is considered to be the most critical factor in controlling the mid-range of flexographic printing. Is pH more important than viscosity? The answer is correct. However, in establishing and maintaining the most suitable ink, the pH and viscosity are inseparable and the two are controlled with each other.

● Use the correct viscosity adjustment fluid

How to control the pH and viscosity? First, you must use the PH meter to detect the pH, understand the ink values ​​of all the ink components and additives, and record the changes at any time. Urban water usage may vary by more than one unit at different times of the month. In addition to adjusting the viscosity with water, another premixed conditioning solution can also be used. This conditioning solution contains some amount of amines and other ingredients. Usually the ink supplier provides adjustment solution that can increase the pH of the ink by 1 to 1.5. At this time, it is impossible to adjust the ink with water.

Both the pH and the viscosity are the key to the success of the printing. In the establishment of printing, pump, roller, measuring system, printing plate, binding back work, materials and drying environment, the ink has only the best viscosity / PH value to get the best color. Many letterpress printers have found that colors in contact with each other during overprinting, plate liners, or color overprinting occur. Therefore, the most useful way to achieve this is to increase the viscosity and lower the pH, which helps the drying process and avoid post-printing. The color is moistened by the pre-printing color, for example: This method obviously requires more than one type of adjusting liquid to be added to each ink machine table to adjust the required viscosity. In addition, these adjustment liquids must be higher than the pH of each ink by 1.0 to 1.5.

Does the automated system make sense?

In the use of printing ink, the use of automated viscosity/PH value control system can effectively detect the stability of the ink on the line, thereby reducing the loss of ink film and ink, while reducing the volatile organic compounds (VOC) (amines, alcohols Or the use of other solvents, it can save the printers valuable time to do other important work.

Today's newer generation of automatic control systems have excellent accuracy and reliability. They can be easily operated and maintained. Both multi-unit or single-unit control systems can be purchased at a lower price than before, and some even provide SPC/ISO report.

Finally, it must be mentioned that, whether using an automated system or manual operation, the most important thing is to adjust the use of liquid, not water.