With the prevalence of green printing, water-based varnishes have developed rapidly. But there are also precautions:
1. The influence of the smoothness and thickness of the paper on the glazing quality
1. Smoothness of paper:
Water-based glazing oil has a strong adsorption, because the surface of the paper is rough, which is easy to cause poor glazing effect. At this time, it is necessary to increase the coating amount when glazing. If the paper is smoother, the glazing effect is better.
2. Paper thickness:
Water-based glazing oil with water as a solvent will affect the moisture content of the paper during the glazing and drying process, which will affect the stability of the paper size and the quality of the printed matter.
2. The coating quality will be affected by the printing ink
The ink used in the printed products that need to be polished after printing must be resistant to solvents and heat, otherwise the graphics of the printed products will change color or cause wrinkling and ink formation problems.
3. The effect of the viscosity of the water-based glazing oil on the glazing quality
When the viscosity of the water-based varnish is too high:
The fluidity of water-based varnish will be poor, and it is not easy to level when coating.
When the viscosity of the water-based varnish is too low:
1. When coated with highly absorbent paper, the paper will absorb the water in the water-based polishing oil, resulting in excessive changes in the viscosity of the water-based polishing oil and uneven coating on the surface of the printed matter, which will affect the drying speed of the glossy oil film Influence smoothness.
2. When coating poorly absorbent paper, sagging will occur, resulting in problems such as uneven film layer and poor drying.
4. The influence of coating amount on the glazing quality
1. If it is too low, the varnish cannot form a continuous film, which reduces the gloss of the film;
2. If it is too large, it will make the film thicker, on the one hand increase the production cost, on the other hand also affect the drying speed.
The control of the coating amount is related to factors such as the adsorption of the printing material to the varnish used and the application of the glazing.
Before using water-based varnish, you should confirm the substrate's adsorption performance of water-based varnish.
5. The effect of drying speed on the glazing quality
1. The drying speed is too slow, which will cause the film layer to not dry well, and even scratches and sticking on the back;
2. If the drying speed is too fast, the paper will lose too much water and become brittle, and it will easily break.
The drying speed of the water-based glazing oil can be adjusted by adjusting the drying temperature, drying time, content and proportion of the water-based glazing oil diluent, so as to achieve the ideal drying effect.
6. Effect of storage conditions on coating quality
The suitable storage temperature of water-based glazing oil is 20 ～ 25 ℃, and the storage period is up to half a year. It can be sealed and stored at normal temperature without avoiding light. It should be noted that it is necessary to prevent the temperature from being too low (below 0 ° C) to freeze it. Even if it is frozen, it cannot be restored to a good state, and the gloss and wear resistance after film formation will decrease.
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