Common faults and troubleshooting methods for waterborne glazing
1. The gloss is not good, the brightness is not enough
1. Cause of failure
â‘ The paper is too thick, the penetration and absorption is too strong;
â‘¡ The coating amount is insufficient, the coating is too thin;
â‘¢ Varnish has low viscosity and insufficient solid content;
â‘£ The ink on the surface of the printed matter is not dry;
⑤Low coating environment temperature and high humidity;
â‘¥ The inherent quality of the varnish is poor.
2. Exclusion method
â‘ Properly increase the viscosity of varnish;
â‘¡ Increase the coating amount;
â‘¢ The ink should be fully dried before polishing;
â‘£The quality of the paper is too coarse, you should apply a layer of primer first;
⑤ Increase the ambient temperature and drying temperature;
â‘¥Replace water-based varnish with good gloss;
⑦ A small amount of leveling aid can be added.
Second, the drying is not good, the surface is sticky
1. Cause of failure
â‘ The water-based varnish is coated too thick;
â‘¡Viscosity of varnish is too high;
â‘¢The drying tunnel temperature and hot air are insufficient;
â‘£ Varnish PH value is too high;
⑤ The coating pressure is uneven, and the local coating is too thick;
â‘¥ The machine speed is too fast, especially when the printing carrier is a non-absorbing surface.
2. Exclusion method
â‘ Adjust to reduce the viscosity of the varnish, the diluent uses a 1: 1 mixed solution of ethanol and water
â‘¡Appropriately reduce the coating amount;
â‘¢ Adjust the pressure to make the coating even and consistent;
â‘£Enhance the temperature and hot air of the drying tunnel;
⑤ The PH value of varnish should generally be controlled at 8-9;
â‘¥According to the product situation, adjust the machine speed;
⑦A quick-drying emulsion can be added in an appropriate amount;
⑧ Replace with quick-drying water-based varnish.
3. Uneven coating on the surface, streaks and orange peel
1. Cause of failure
â‘ The viscosity of varnish is excessive;
â‘¡ The coating amount of varnish is too large;
â‘¢ The coating pressure is not adjusted properly;
â‘£ The surface of the coating roller is too rough and not smooth;
⑤ Varnish dries too fast;
â‘¥ Varnish leveling is poor;
⑦ The ink is not dry and repels varnish.
2. Exclusion method
â‘ Ink should be fully dried and dust removed before glazing;
â‘¡Adjust the coating pressure to make the coating uniform;
â‘¢ If the coating roller is rough, aging or deformed, it should be reground or remade;
â‘£ Appropriately reduce the viscosity of varnish;
⑤ Appropriately reduce the coating amount;
â‘¥Slow drying aid or PH stabilizer is added in a small amount.
4. There are many bubbles in the glazing process
1. Cause of failure
â‘ The viscosity of varnish is too high;
â‘¡ The PH value of varnish is low;
â‘¢ Excessive circulation stirring;
â‘£ The amount of varnish in the rubber disc and rubber drum is insufficient;
⑤ The speed is too fast.
2. Exclusion method
â‘ Reduce varnish viscosity;
â‘¡ Add appropriate amount of PH stabilizer to increase PH value;
â‘¢Appropriate amount of water-based defoamer should be mixed well, and the maximum amount should not exceed 1%
â‘£ Increase the supply of varnish;
⑤ Appropriately reduce the coating speed.
5. Difficult to clean varnish and easy skinning
1. Cause of failure
â‘ The water-based varnish dries too fast;
â‘¡ The PH value of varnish is low;
â‘¢Poor oil solubility is poor;
â‘£ Long downtime, not cleaned in time;
⑤ The ambient temperature is too high.
2. Exclusion method
â‘ Add slow drying agent to reduce the drying speed;
â‘¡Add PH stabilizer to increase PH value and improve water solubility of water-based varnish;
â‘¢It should be cleaned in time when shutting down;
â‘£ Temporary shutdown, varnish circulation system should continue to operate;
⑤When cleaning is difficult, you can use water detergent or ethanol for cleaning.
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