How to do PS plate developer foaming
We are a big printing company in Shenzhen China . We offer all book publications, hardcover book printing, papercover book printing, hardcover notebook, sprial book printing, saddle stiching book printing, booklet printing,packaging box, calendars, all kinds of PVC, product brochures, notes, Children's book, stickers, all kinds of special paper color printing products, game cardand so on.
For more information please visit
http://www.joyful-printing.com. ENG only
http://www.joyful-printing.net
http://www.joyful-printing.org
email: 860681365@qq.com
PS users in the southeastern coastal areas of China often encounter a very headache when using the Huaguang PD type developing machine for PS plate development - a large amount of foam is generated, which affects the normal development of the PS plate. This phenomenon is rarely encountered in the north. Why is it easy to produce bubbles on the southeast coast, and how to solve this headache in actual work?
In the classification of water chemical areas, the southeast coastal areas of China are humid areas with abundant precipitation and small evaporation, so the runoff is large; therefore, the soil layer is thin, and there are many hard granite rocks. The soil has been leached for many years, and most of the soluble salts have been lost. Therefore, the water has less salt content, low salinity and low hardness, and is extremely soft water (water hardness <1 meq/liter). Moreover, the tap water supplied in the southeastern coastal areas is mostly surface water. Generally speaking, surface water is softer than ground water. The tap water supplied in northern and inland areas of China is mostly groundwater with high hardness (hardness of deep well water in Beijing area >300 meq/liter).
Surfactants are included in both the PS coating and the developer. The coating generally contains macromolecular and nonionic surfactants, and the main function is to solubilize and disperse in the preparation of the coating liquid. An anionic surfactant is added to the developer to facilitate developer penetration. At the same time, they also reduce the surface tension of the developer.
When the liquid forms a foam, its surface area increases. Generally, the surface tension is small and foaming is more likely, but the stability of the bubble is independent of the surface tension of the liquid. The formed bubbles, due to the action of gravity, the liquid in the bubble liquid film automatically flows downward, and the fluid molecules flowing in the liquid film discharge process have a larger free energy than the liquid molecules at the bottom, so the bubbles are continuously drained. The film wall is thinned and broken, causing the foam to disappear. When a surfactant molecule is adsorbed on the surface of the liquid film, the foam is stabilized because the surfactant molecular film hinders the flow of the liquid. In addition, the surfactant molecules adsorbed on the foam film act as a surface "repair" to the liquid film, so that the foam has good stability. Anionic surfactants are much more stable to foam than nonionic surfactants. Therefore, the foaming material at the time of development processing is mainly an anionic surfactant in the developing solution.
The type of surface active agent is the main factor determining the foaming power, but the environmental conditions, such as temperature, water hardness, developer pH and additives, have a certain impact on the foaming power.
Since the developer contains a hard water softener to soften the water, although the water is softened, the ion content in the water is not reduced by the softening of the water. When the Huaguang PD developer is diluted 1:4 by water, it is ideal. The concentration of anionic surfactant in the working fluid is calculated to be within its critical micelle concentration range. In the southeast coastal area, when the Huaguang PD developer is diluted by tap water with low salinity and low salt content, the water has little effect on the critical micelle concentration of the anionic surfactant in the developer, or has no effect at all. Therefore, the anionic surfactant in the working fluid is in the range of its critical micelle concentration, the surface tension of the working fluid is the smallest, and the foaming force is the largest, so that a large amount of bubbles are generated during use to affect the normal progress of the development process.
The tap water used in northern China and inland areas is mostly groundwater, with high salinity and high metal ion content. Although the softener is added to soften the water, the total ion number remains unchanged. With this water, since the metal ions compress the electric double layer of the micelle, the mutual repulsion between the ionic groups of the anionic surfactant is reduced, and more of the ionic groups of the surfactant enter the micelle to make the glue The number of clusters of the bundle increases. At the same time, since the counter ion is immobilized on the surfactant association, the repulsive force between the ions of the same charge is reduced, and the micelle is easily formed. The critical micelle concentration of the anionic surfactant is thus reduced. In general, divalent metal salt ions such as (Cu2, Zn2+, Mg2+, etc.) have a greater effect on the reduction of the critical micelle concentration than monovalent metal salt ions such as (K+, Na+). Just because the critical micelle concentration decreases, the concentration of anionic surfactant in the working fluid is greater than the critical micelle concentration.