Glazing quality problems and solutions

1. "Fish eyes" appear on the film layer, pinhole

If there are too many bubbles generated during the glazing process and the bubbles in the film layer are not removed in time before drying completely, there will be "fish eyes" and pinholes on the surface of the film. There are two reasons for this phenomenon: It is because the viscosity of the aqueous varnish is too high, so that the bubbles are not easily removed; the second is that the coating speed is too fast, resulting in too many bubbles. This problem can be solved by reducing the viscosity or coating speed of the aqueous varnish.

2. The film gloss is not ideal

If the film glossiness is not ideal, first check whether it is caused by incomplete drying. If the film gloss is not satisfactory after drying thoroughly, it may be due to the excessive dilution of the water-based glazing oil. The dilution of the varnish. Second, the surface roughness of the paper should be checked. If the surface roughness of the paper is too high, the paper will excessively absorb the water-based glazing oil, resulting in too little water-based glazing on the surface of the paper. The gloss of the film layer after drying is not satisfactory, and it is necessary to increase the coating amount by increasing the coating amount. The gloss of the layer. Generally, the gloss of the high-gloss water-based glazing oil on the coated paper can reach 85% to 90%.

3. The film wear resistance and scratch resistance are poor

The reasons for this phenomenon are as follows: First, due to incomplete drying of the ink layer or the aqueous glazing film layer, the binding force between the aqueous glazing film layer and the ink layer is lowered; second, the aqueous glazing oil is excessively diluted. The coating amount is insufficient, the paper absorbability is good, and the film layer is thin. The improvement of the abrasion resistance and scratch resistance of the film layer can be achieved by adding an appropriate amount of an anti-wear agent (generally a wax emulsion) to the aqueous varnish. After the addition of a high anti-wear agent, the waterborne glazing film layer can be rubbed several thousand times.

4. Cracks in the film layer

Cracks appear on the film layer, which may be due to incomplete drying of the ink layer, which may affect the surface state of the film layer during the drying process of the aqueous varnish; on the other hand, due to improper setting of the drying zone of the water-based varnish, if When the drying temperature is too low and the air volume is too large, the surface layer will be dry and the inside will be completely dry, and cracks will appear on the surface. When this problem occurs, first check if the ink layer is completely dry. If it is completely dry, it is necessary to appropriately reduce the air volume when the water-based varnish is dried or increase the drying temperature.

5. Uneven coating, shrinkage of the film

There are two reasons for the coating of water-based varnish, and the film shrinkage is caused by two reasons: one is that the surface tension of the ink layer is low; the other is that the water content of the dilution liquid in the aqueous varnish is too high, thereby improving the water repellency. The surface tension of the varnish. This can be solved by reducing the water content of the diluent in the aqueous coating, adding an appropriate amount of surfactant to the aqueous coating or replacing the aqueous coating.

6. Stripes appear on the surface of the film

Streaks appear on the surface of the film layer, which may be due to excessive coating amount of the aqueous varnish and excessive viscosity. It may also be because the surface of the coating roll is too rough and the ink layer is not dry, so that the ink layer repels the water-based glazing film layer. At this time, it is checked whether it is caused by external causes such as incomplete drying of the ink layer and rough surface of the coating roll, and if not, it is necessary to reduce the coating amount of the aqueous varnish or to lower the viscosity of the aqueous varnish.

7. Low adhesion of the film layer

The low adhesion of the film layer is caused by the incomplete drying of the aqueous varnish film layer or the ink layer, and the low adhesion of the water glazing film layer to the ink layer. This can only be solved by replacing the ink or water-based varnish.