4. Coating amount calculation: There is a rough empirical formula for calculating the coating amount of Bumeilan and laser coating rollers for reference:
Coating amount on dry basis (g/㎡)=0.2×Working fluid concentration%×Mesh depth µ×Working fluid specific gravity
The above formula cannot be applied to the electro-engraved coating roller and the pyramid-shaped embossing coating roller. The specific gravity of the 33% working solution is 1; the specific gravity of 26% is 0.96. The specific gravity of 45% is 1.04. The proportion of calculations with low accuracy can be ignored.
5. Coating amount selection: Depending on the substrate structure and application requirements, the coating amount (dry basis) can be selected between 2.5-3.5g/㎡. The coating amount of ordinary food packaging bags can be less, and the peeling strength can be satisfied, mainly considering white spots and bubbles. The coating amount of the packaging bag that requires high peel strength should be more. The amount of glue applied is determined by the depth and working concentration of the anilox roll. The best concentration is recommended to be 25%---35%.
6. Drying: In order to make the solvent in the base film coating layer evaporate cleanly, the drying efficiency of the dryer should be improved as much as possible. The factors that affect the drying efficiency are hot air temperature, wind speed and air volume. The faster the compounding speed, the higher the drying efficiency requirements; on the contrary, when the equipment drying efficiency is low, the compounding speed can only be reduced. The wind speed and air volume of the compound machine are generally not adjusted frequently after correction, but the hot air temperature and compound speed often change. The principle of setting the hot air temperature is to low first and then high to form a temperature gradient. The purpose is to prevent the coating surface from drying too quickly and preventing the further volatilization of the internal solvent. This is often called "false drying". For example, when the nozzle wind speed of the drying box is 30 meters per second and the composite speed is about 80 meters, the hot air can be set at 50-60°C, 60-70°C, 70-80°C, depending on the substrate and coating amount.
7. Laminating: On the premise that the film is not overstretched or damaged, the temperature of the composite hot roller should be increased as much as possible, and the temperature of the hot roller can be selected between 50 and 85 ℃. Note: The temperature of the heating cylinder is not equal to the temperature of the heat roller, and the temperature of the edge of the heat roller is not equal to the temperature in the middle of the heat roller. The line pressure of the hot roller is determined by the cylinder diameter, air pressure, hardness and length of the silicone roller. The only thing that can be adjusted frequently is the air pressure. Different composite machines cannot compare the linear pressure of the heat roller with the reading of the pressure gauge.
8. Curing: The composite film from the machine should be sent to the curing chamber as soon as possible, and the composite film should be heated at 45～60℃. The uncured adhesive will melt and level, eliminate small bubbles and white spots, and continue curing for 48 hours. Able to achieve satisfactory bonding strength. The air in the maturing room is required to circulate and flow, the purpose is to make the temperature of the maturing room consistent; the air with high solvent content in the maturing room is continuously discharged, and the solvent concentration in the indoor air is reduced through convection, which is beneficial to the continued volatilization of the residual solvent in the composite film.