Sticker Waterproof Paper PS Version Of The Developer Foaming Reasons

Sticker Waterproof Paper PS version of the developer foaming reasons

PS version users in southeast coastal areas of China often encounter a very headache when using Huaguang PD developer for PS version development - produce a large number of bubbles, affecting the normal development processing of PS version. This phenomenon is rarely encountered in the north. Why is it easy to produce bubbles in the southeast coast, and how to solve this headache in actual work?

In the classification of hydrochemistry, the southeast coastal area of China is a humid area with abundant precipitation and small evaporation, so the runoff is large. Therefore, the soil layer is thin, more hard granite rock, the soil has been eluviated for many years, and most of the soluble salt has been lost, so the water salt content is small, the salinity is low, the hardness is correspondingly low, and it is very soft water (the hardness of water is < 1 mg equivalent/l). In addition, most of the tap water supplied in the southeast coastal areas is surface water, which is generally softer than groundwater. The tap water supplied in the north and inland areas of China is mostly groundwater, and the hardness is higher (the hardness of deep well water in the north is > 300 mg equivalent/L).

The PS plate coating and developer both contain surfactants. The coating generally contains macromolecules and non-ionic surfactants, which are mainly used for solubilization and dispersion in the preparation of the coating solution. The anionic surfactant is added to the developer to facilitate the developer penetration. At the same time, they can also reduce the surface tension of the developer.

When a liquid forms a foam, its surface area increases. Generally, small surface tension is more likely to foam, but the stability of the bubble is independent of the surface size of the liquid. Due to the action of gravity, the liquid in the gas-light liquid film automatically flows downward, and the fluid molecules flowing down during the liquid film drainage process have greater free energy than the liquid molecules at the bottom, so the bubble continues to discharge the liquid, making the membrane wall thin and burst, resulting in the disappearance of the foam. When the surfactant molecules are adsorbed on the surface of the liquid film, the foam is stable because the surfactant molecular film impedes the liquid flow. In addition, the surfactant molecules attached to the foam film play a role in the surface "repair" of the liquid film, so that the foam has good stability. The stability of anionic surfactants to foam is much greater than that of non-ionic surfactants. Therefore, the foamers in the development process are mainly anionic surfactants in the developer.

The type of surfactant is the main factor that determines the foaming force, but the different environmental conditions, such as humidity, water hardness, pH value of the developer and additives, have a certain impact on the foaming force.

Because the development contains a hard water softener to soften the water, although the water is softened, the ion content in the water is not reduced because of the softening of the water, when the PD developer is diluted by water at 1:4, according to the ideal state, the concentration of anionic surfactant in the working liquid is in its critical micellar concentration. In the eastern coastal areas, when Huagang PD developer was diluted with tap water with low salinity and salt content, the critical micelle concentration of anionic surfactant in the developer was little or no affected by water. Therefore, the anionic surfactant in the working liquid is in its critical micelle concentration range, the surface tension of the working liquid is minimum, and the foaming force is maximum, so that a large number of bubbles are produced in use and affect the normal development process.

In the north and inland areas of China, the water used is not much groundwater, high salinity, metal ion content, although the softening agent softeners the water, but the total number of ions is unchanged. The metal ions compress the double layer of the micelle, so that the anionic surface active ion groups repulsion each other, and more surfactant ion groups enter the micelle to increase the aggregation number of micelles. At the same time, because the counter ion is fixed on the surfactant association, the repulsion between the ions of the same charge surfactant is reduced, and the micelle is easy to form. Therefore, the critical micelle concentration of anionic surfactant is reduced. In general, bivalent metal salt ions (Cu, Zn, Mg, etc.) have a greater effect on the reduction of critical micelle concentration than univalent metal salt ions (K, Na). Because the critical micelle concentration decreases, the concentration of anionic surfactant in the working solution is greater than the critical micelle concentration. As the surface tension of the working fluid increases, the foaming force becomes smaller. So there will not be too many bubbles and affect the normal development.

Since foaming is mostly related to the critical micelle concentration, the critical micelle concentration is also used for defoaming. Theoretically, the goal can be achieved as long as the critical micelle concentration of anionic surfactant in the working liquid can be reduced.

So, how to avoid producing too many bubbles in the development? The simplest and most practical method is to add high-priced metal salts. Another method is to add another anionic surfactant solution such as soapy water, so that the critical micelle concentration of surfactant in the working solution is reduced to prevent the formation of bubbles. The most practical way is to add alcohol. Because alcohol molecules can penetrate into micelles, the repulsive force between surfactant ions is reduced, and because the addition of alcohol molecules to micelles is easy to form and increase, the critical micelle concentration is reduced to avoid the formation of bubbles, so as to achieve the effect of defoaming. The amount of alcohol is: add ethanol: butanol = 1:1 (volume ratio) mixture of 50ml in 25L: Huagang PD development working liquid (depending on the water quality, the defoaming effect can be increased or decreased as appropriate).

In this way, good defoaming effect can be achieved, and the problem of foam flap easily produced when the developer is used can be solved.