Analysis of common problems in polishing process

First, the film surface appears streaks or wrinkles

Viscosity varnishes for varnishes are too late to level and prone to streaks. Depending on the suitability of the prints, a leveling, good wettability lacquer can be selected; or the proper amount of thinner can be added to reduce the viscosity of glazing oils. . If the amount of coating is too large, the amount of coating can be reduced by adjusting; sometimes, the wettability of the coating on the surface of the printed matter is not good, and the smoothness of the dried film is affected, or the leveling property of the coating oil is poor. The process conditions do not match the coating oil suitability. Other types of coating varnish may be used or the process conditions may be changed to match that of the varnish.

Second, the print adhesion to each other

The solvent in the varnish has poor volatility, and the drying performance of the coating is poor. Consider changing the solvent with high volatilization rate or changing the type of coating varnish; it may also make the coating layer too thick and the solvent inside the coating. Incomplete volatilization, high residue, can reduce the amount of coating, reduce the thickness of the film layer; or coating temperature or calendering in the low temperature, short drying time and make the coating dry, can improve the coating coating production And the working temperature in calendering, speed reduction, the coating completely dry.

Third, film formation film gloss difference

î—¥ î—¥ If it is the quality of varnishes, more consideration should be given to changing the glazing with good quality according to the process and economic requirements; if the coating is too thin, the coating amount is insufficient or the coating oil concentration is small, in the roughness If the surface of high-absorption and high-absorption printing is not easy to fill in and fill up, then the coating amount should be increased to increase the coating concentration, or a layer of polishing primer should be applied on the surface before processing, and then the coating coating may be applied. When the temperature of the optical coating drying and calendering is low and the calendering pressure is low, the process parameters should be adjusted during the operation to increase the temperature and increase the pressure; it is also estimated that the reason is the equipment itself, if the calendered steel belt is worn, The smoothness of the gloss is reduced, which is to repair and improve the surface condition of the calendered steel strip.

Fourth, after calendering, the blank part of the printed product is light-colored, and the light-colored part is discolored.

The glazing solvent has a certain dissolution effect on the ink layer, which needs to change the type of varnishes or change the solvent composition; if the ink is poorly dried and the ink layer is not resistant to dissolving solvents, the ink drying condition must be improved and the ink should be dried afterwards. Gloss coating, to reduce the amount of solvent in the coating oil to dissolve the ink; the layer is not completely dry, the residual solvent in the film layer is high, it is necessary to improve the coating drying temperature or reduce the speed, extend Drying time reduces the amount of residual solvent in the coating.

Fifth, uneven coating, bubbles, pits, etc.

Surface oil has a large surface tension value, and has poor wettability on the ink layer on the surface of the printed matter. The surface tension should be reduced, and the wetting performance of the coating on the ink layer should be improved. The solvent in the coating is poorly vaporized and the solvent in the coating layer is poor. Residue is high, you can use a high volatilization rate of the solvent or the coating is completely dried and then calendered; may also be coated in the speed is too fast, the drying temperature is low, so that the coating is completely dry, the solvent does not volatilize Completely, it is necessary to adjust the coating process conditions; the ink layer on the surface of the printed matter will also produce crystallization phenomenon, which should take effective measures, such as removing the oily surface of the ink layer or hair treatment, improve the coating The wetting of the ink by the oil reduces or eliminates the adverse effects of the crystallization of the ink layer on the coating.

Sixth, film surface foaming

In the process of calendering, the pressure is too high, the temperature of the calendered strip is too high, so that the glazed layer is partially softened, which requires a suitable reduction in the pressure and temperature of the calendering; it may also be the conditions of the coating and calendering process. Unmatched, after the glazing layer on the printed surface is cooled, the peeling force is the same as that of the upper strip, and the process conditions need to be changed to match the glazing oil, the calender speed is reduced, and the glazing layer is improved between the glazing layer and the upper strip. Peeling force.

VII. Adhesion between printed matter and glazing tape during calendering

î—¥ î—¥ coating is too thin, it should increase the amount of coating; coating viscosity is too low, to increase the viscosity of the coating oil; then the pressure is too small pressure, pressure temperature is insufficient, to increase the pressure temperature Increase the pressure of calendering.

Eight, the printed calendered, the surface easily cracked

   high temperature, so that the printed matter in the process of calendering too much dehydration, water content decreased, and paper fibers become brittle, the operating temperature should be reduced calendering, and take effective measures to maintain the print-set water content; pressure The pressure in the light is too large, the printability and plasticity of the print are reduced, and the toughness is degraded, and the pressure in the calendering can be reduced. If the post-processing of the coating oil is poor, the processing quality should be re-selected. Oil; improper selection of post-processing conditions, adjustable post-processing conditions to match the suitability of calendered presses.

Nine, after the light is not uniform on both sides of the film surface brightness

In the process of calendering, the pressure on both sides of the glazing band is not equal, and the wear on both sides of the glazing band is not caused. The pressure on both sides of the glazing band should be adjusted to make them equal, and the parallelism between the hot roller and the transfer roller is adjusted so that The glazing tapes on both sides are evenly and evenly worn, and the wear may be uniform. It may also be uneven on both sides of the varnish. This requires adjusting the glazing unit to check the parallelism and gap between the metering roller and the applicator roller. Both sides of the coating thickness as possible.