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In the last article we list the problem made by solvent EA, and also explain how it influences the quality of lamination. And now we will discuss the quality requirement of solvent EA, also how to check the water content of solvent EA.
From the first article analysis, we can know the quality of solvent EA is important for dry lamination.
In China, the standard GB37728-91 "industrial ethyl acetate" classifies the solvent EA to 3 grades: Superior Quality Grade with water lower than 1000ppm, Top Quality Grade with water lower than 2000ppm, and Accepts Quality Grade with water lower than 4000ppm.
But dry lamination needs more strict quality: the water in solvent EA should be lower than 300ppm. Water and alcohol total content should be lower than 1000ppm. And in the market we call it urethane grade Solvent EA. And it’s better to keep the water and alcohol total content lower than 500ppm, especially for the high end application.
There are three methods to check the water content in solvent EA
Prepare a few solvent EA, then add some indicator into it, judge the water content according to the indicator’s color change. Though this method is simple and easy, but it only can roughly check the water content, can’t get an accurate date.
The popular indicators include potassium permanganate (KMnO₄) and copper chloride. The potassium can be added into solvent EA directly, but copper chloride should be dried in oven before test.
Karl-Fischer moisture meter can accurately check the water content of solvent EA, and its operation is also easy and quick. So it is suitable for printing and laminating factories. But it can't check the alcohol and impurity content, and now we need the GC to get the confirmed information.
GC can accurately check the purity, alcohol and water contents of solvents. But now most of the factories only have hydrogen flame detector for GC to detect the solvent residual and purity of solvent, it can't detect the water content in solvent. The GC needs thermo conductivity detector and chromatographic column to detect the water content.
The GC operation and analysis is complicated, the operator should be trained professionally. COMENS install some GCs and Karl-Fischer moisture meters, we can analysis the solvent EA quality for the customer.
1) The original EA quality is not accepted, water content is over standard.
2) The solvent EA directly contact with air, and moisture in air condenses into droplets and goes into solvent. For example, in one factory the solvent EA is stored in tank, when solvent EA came into factory, the initial water content is lower than 400ppm, but after store and using half month, the water content of solvent EA near exit of tank is high to 4000ppm! The main reason is the tank is not closed well, the breathing valve doesn’t change the Silica desiccant regularly, the installed one quality already changed.
