Waterborne coating common faults and troubleshooting

First, the gloss is not good, the brightness is not enough

1, the cause of the failure

1 paper is too thick, too strong penetration absorption;

2 coating amount is insufficient, the coating is too thin;

3 coating oil viscosity is small, solid content is insufficient;

4 Printed surface ink is not dry;

5 coating environment temperature is low, humidity is high;

6 The inherent quality of Varnish is poor.

2, elimination method

1 Appropriately increase the viscosity of coating oil;

2 increase the coating amount;

3 The ink should be fully dried before glazing;

4 paper quality is too thick, it should be coated with a primer;

5 increase the ambient temperature and drying temperature;

6 change the gloss of a good water-based varnish;

7 A small amount of leveling aids can be added.

Second, dry, surface is sticky

1, the cause of the failure

1 water-based gloss coating too thick;

2 Varnish viscosity is high;

3 Drying temperature and lack of hot air;

4 Varnish PH value is too high;

5 uneven coating pressure, partial coating too thick;

6 Machine speed is too fast, especially when the print carrier is a non-absorbent surface.

2, elimination method

1Adjust to reduce the viscosity of varnish. Diluent uses a 1:1 mixture of ethanol and water.

2 appropriately reduce the amount of coating;

3 adjust the pressure so that uniform coating;

4 to strengthen the drying temperature and hot air;

5 PH value of varnish oil should generally be controlled at 8-9;

6Adjust the machine speed according to the product condition;

7 can add moderately quick-drying emulsion;

8 Replace with quick-drying water-based varnish.

Third, uneven surface coating, striped and orange peel phenomenon

1, the cause of the failure

1 Overgloss viscosity;

2 Varnish coating is too large;

3 coating pressure adjustment is not suitable;

4 coating roller surface is too rough, not smooth;

5 Varnish drying too fast

6 Poor oil leveling;

7 Ink does not dry, repels varnish.

2, elimination method

1 The ink should be fully dried and removed before polishing.

2 Adjust the coating pressure so that the coating is uniform;

3 The coating roll is rough, aged or deformed and should be reground or rebuilt;

4 appropriately reduce the viscosity of varnish;

5 appropriately reduce the amount of coating;

6 Add a small amount of slow drying aid or PH stabilizer.

Fourth, the glazing process more bubbles

1, the cause of the failure

1 Varnish viscosity is high;

2 Varnish PH value is low;

3 cycle over stirring;

4The amount of light oil in the plastic plate and glue barrel is insufficient;

5 speed too fast.

2, elimination method

1 reduce the viscosity of varnish;

2 appropriate amount of PH stabilizer, increase PH value;

3 appropriate amount of water defoamer, to be fully mixed, and the maximum amount added should not exceed 1%;

4 increase the supply of light oil;

5 properly reduce the coating speed.

V. Varnish is difficult to clean, easy to crust

1, the cause of the failure

1 Waterborne varnish dries too fast;

2 PH value of varnish oil is low;

3 Varnish is poor in water solubility;

4 Long downtime, not cleaned in time;

5 The ambient temperature is too high.

2, elimination method

1 Add slow drying agent to reduce the drying speed;

2 Add PH stabilizer to increase the PH value and improve the water solubility of waterborne varnish;

3 It should be cleaned in time when shutting down;

4 Temporary shutdown, the varnish circulation system should continue to operate;

5 When cleaning is difficult, use water cleaner or ethanol to clean.

Source: Ink Technology Network