Detailed analysis of the main technical parameters of flexographic water-based ink:

Posted on 04-11-2024 by

Composition of Water-based Ink:

Water-based ink is composed of water-based high molecular resin and emulsion, organic pigments, water-soluble solvents, and related additives through physical and chemical processes, without volatile organic solvents, and without certain toxic or harmful substances found in solvent-based inks.

Viscosity:

Viscosity is the magnitude of the cohesive force within the ink and is the primary control indicator in ink application. If the viscosity of the ink is too low, it can result in light color, excessive dot gain, deformation of highlights, and uneven ink transfer. Conversely, if the viscosity is too high, it can affect the ink transfer performance of the anilox roller, causing uneven ink distribution, sometimes resulting in shallow printing, as well as potential problems such as dirty plates, plate smearing, foaming, and incomplete drying.

Viscosity sensitivity is most pronounced during large temperature fluctuations in winter and summer. In high temperatures, water evaporates quickly, leading to rapid drying. In such cases, it's necessary to extend drying time or increase machine speed during operation. Conversely, in low temperatures, water evaporates slowly, leading to slower ink drying. In this scenario, increasing ink drying speed or using a drying device may be necessary. During winter use, ink can freeze below 0°C; if this occurs, placing the ink in a warmer room to naturally dissolve and stirring it evenly allows for continued use.

An increase in ink temperature reduces viscosity, resulting in lower print density and thinner ink layers. To maintain consistent print quality, it's essential to keep ink viscosity consistent. Printers must pay close attention to the impact of ink temperature, ensuring ink temperature stabilizes at the temperature of the printing workshop before printing. This measure is crucial; otherwise, ink density during the printing process will undergo noticeable changes.

Ink pH Value:

Another parameter that needs to be controlled in water-based ink application is the pH value, with the normal range being 8.5 to 9.5. Within this range, the printing performance of water-based ink and the stability of print quality are most consistent. When the pH value exceeds 9.5, the alkalinity is too strong, leading to reduced viscosity, slower drying speed, decreased water resistance, and a higher likelihood of plate smearing. Conversely, when the pH value is below 8.5, indicating weak alkalinity, ink viscosity increases, leading to faster ink drying, blockages on plates and anilox rollers, dirty prints, and bubble formation. The impact of pH value on the suitability of water-based ink for printing is mainly reflected in ink viscosity stability, drying characteristics, and dot clarity.

Technical Parameters of Water-based Ink:

1.Color: Approximates the standard sample.

Note: Use a manual color wheel to compare the color matching of the sample with the standard sample without connecting them.

2.Fineness: Less than 20 microns.

3.Instrument: 0-50 micron scraper fineness gauge.

4.Viscosity: 20 seconds ± 5 seconds.

5.Instrument: RIGOSHA #4 Cup (25°C).

6.pH Value: 8.0-9.5.

7.Instrument: Portable pH meter (PHB-2 type).

8.Heavy Metal Content: Compliant with global packaging environmental standards.

9.Resistance Properties: Meets requirements.