The cause of the most popular PS plate developer f

2022-08-07
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The causes of too many bubbles in the developing solution of PS version and their elimination methods

when using Huaguang PD type developer to develop PS version in the southeast coastal areas of China, the users of PS version often encounter a very headache problem - a large number of foam are generated, which affects 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? How to solve this headache in practical work

in terms of regional classification of hydrochemistry, the southeast of China is along Haiti and equipped with safety protection; The area is a humid area with abundant precipitation and small evaporation, so the runoff is large; The native soil has a thin soil layer and many hard granite rocks. After years of leaching, most of the soluble salts have been lost, so the salt content system of water can automatically calibrate the indication accuracy; It is very soft water (the hardness of water is less than 1 mg equivalent/L). Moreover, most of the tap water supplied in the southeast coastal areas is surface water. Generally speaking, surface water is softer than groundwater. However, most of the tap water supplied in northern China and inland areas is groundwater with high hardness (the hardness of deep well water in Beijiu area is more than 300 mg equivalent/L)

ps plate coating and developing solution contain surfactants. The coating generally contains macromolecules and non-ionic surfactants, which are mainly used to solubilize and disperse in the preparation of coating solution. Anionic surfactant is added to the developer to facilitate the penetration of the developer. At the same time, they can also reduce the surface tension of the developer

when the liquid forms foam, its surface area increases. Generally, those with low surface tension are more likely to bubble, but the stability of the bubble is independent of the surface size of the liquid. Due to the effect of gravity, the liquid in the gas light liquid film automatically flows downward. During the liquid film drainage process, the flowing fluid molecules have greater free energy than the liquid molecules at the bottom. Therefore, the continuous drainage of bubbles makes the film wall thinner and burst, resulting in the disappearance of foam. When surfactant molecules are adsorbed on the surface of the liquid membrane, the surfactant molecular membrane blocks the flow of the liquid, which makes the foam stable. In addition, the surfactant molecules attached to the foam film play a role in "repairing" the surface of the liquid film, making the foam have good stability. The stability of anionic surfactants to foam is much greater than that of non-ionic surfactants. Therefore, the foams in the developing process are mainly anionic surfactants in the developing solution

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

due to the presence of hard water softener in the developing solution, the ion content in the water has not decreased due to the softening of the water. When the Huaguang PD developing solution is diluted by water at a ratio of 1:4, the concentration of anionic surfactant in the working solution is within its critical micelle concentration according to the ideal state. In the eastern coastal area, when Huaguang PD developer is diluted by tap water with low salinity and low salinity, water has little or no effect on the critical micelle concentration of anionic surfactants in the developer. Therefore, when the anionic surfactant in the working solution is within its critical micelle concentration, the surface tension of the working solution is the smallest and the foaming force is the largest, so that a large number of bubbles are generated in use, which affects the normal development process

groundwater is rarely used in the north and inland areas of China, with high mineralization and high content of metal ions. Although the water is softened by adding softener, the total ion number remains unchanged. With this kind of water, because the metal ions compress the electric double layer of the micelles, the ionic groups of anionic surface activities repel each other, and more ionic groups of surfactants enter the micelles to increase the aggregation number of the micelles. At the same time, because the counter ions are fixed on the surfactant Association, the repulsion force between the same charge surfactant ions is reduced, and the micelles are easy to form. Therefore, the critical micelle concentration of anionic surfactant is reduced. In general, divalent metal salt ions such as (Cu, Zn, Mg, etc.) have a greater effect on the reduction of critical micelle concentration than monovalent metal salt ions such as (k, Na). Because the critical micelle concentration decreases, the concentration of anionic surfactant in the working solution is greater than the critical micelle concentration. When the surface tension of the working fluid increases, the foaming force decreases. Therefore, too many bubbles will not be generated to affect the normal development

since the foaming is mostly related to the critical micelle concentration, the defoaming also starts from the critical micelle concentration. Theoretically, the goal can be achieved as long as the critical micelle concentration of anionic surfactant in the working solution can be reduced. So, how to avoid too many bubbles in the development of bolts with the same performance level? The most simple and practical method is to add high valence metal salts. Another method is to add another anionic surfactant solution, such as soapy water, to reduce the critical micelle concentration of surfactant in the working solution and prevent bubbles. The most practical method is to add alcohol. Because alcohol molecules can penetrate into micelles, the repulsion force between surfactant ions is reduced, and because the addition of alcohol molecules is easy to form and increase micelles, the critical micelle concentration is reduced to avoid the generation of bubbles, so as to achieve the effect of defoaming. The amount of alcohol: add 50ml of ethanol: butanol = 1:1 (volume ratio) mixture to 25L: Huaguang PD developing working solution (increase or decrease depending on the defoaming effect due to different water quality). In this way, a good defoaming effect can be achieved, and the problem of the verification method of JJG 556 (1) 988 axial loading decadent experimental machine which is easy to produce foam petals when the developer is used can be solved

source: print magazine

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