During the coating process, it is important to reasonably control the viscosity of the water-based varnish. Too low viscosity can not play a protective and decorative role; too high viscosity will cause poor leveling and slow drying. For the varnish viscosity of offline polishing, the general recommendation is 18-25 seconds (din 4, 25 degrees Celsius), while the viscosity of the online polishing is generally recommended 4 0-70 seconds (din 4, 25 degrees Celsius). The specific viscosity should be adjusted according to the characteristics of the paper and equipment.
The thinner for water-based varnish is generally 1: 1 ethanol aqueous solution. When the alcohol content in the thinner is higher, the drying speed is faster, and it can be adjusted according to the specific situation. Care should be taken not to dilute too much, otherwise it will reduce the abrasion resistance and gloss of the film.
Due to the low temperature and humidity in winter, the problem of poor leveling is likely to occur when using water-based varnish. The main reasons are: First, the temperature is low and the viscosity is high, and the 1: 1 ethanol aqueous solution needs to be added to adjust to the normal use viscosity; Second, the humidity is low, the glazing oil evaporates quickly, and the water needs to slow down the evaporation rate And appropriately reduce the drying temperature and air volume. In addition, when it is used in winter, it should be put into the production workshop 24 hours in advance to increase its temperature. Stir well before use, and measure and adjust the viscosity before use.
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