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Solution to Bubble Formation in Protective Film Production Process

Protective film is the most common material used in die-cutting production. However, many manufacturers may encounter bubble issues during the production process, which can be quite troublesome. Let's take a look at the reasons why bubbles may form in protective films:

1. Poor film wetting:

   - Main reason: The slip agents and antistatic agents added by the manufacturers during film production gradually infiltrate the film's surface during storage, reducing its surface tension. Inadequate corona treatment intensity or prolonged storage time can also contribute to poor film wetting.

2. Low temperature causing poor wetting:

   - Main reason: The decrease in adhesive temperature due to low temperature causes an increase in adhesive viscosity and poor wetting. The impact of low temperature on the film can also result in poor flow after adhesive coating, leading to blockages and poor wetting.

3. Insufficient coating:

   - Main reason: Inadequate coating due to excessively high or low adhesive viscosity.

4. Foaming of adhesive:

   - Main reason: Excessive drying oven temperature causing foaming of the adhesive.

So, what are the solutions to these problems?

1. Choose suitable ink and increase the coating volume, paying special attention to the selection of dry composite white ink as it has a significant impact.

2. Enhance the adhesive's wetting ability on the film, improve poor adhesion in certain areas; increase the coating volume; increase the temperature and pressure of the composite roller, use smooth rollers; reduce the composite speed to increase immersion and coating time; select adhesives with good wetting properties and preheat them.

3. Preheat the adhesive and film, and increase the temperature of the composite pressure roller.

4. Clean the coating roller, and strengthen the management of coating volume and roller. Generally, after a new coating roller has been used for around 5 million meters (5000 R/S), aluminum plating treatment should be applied. After three re-chrome treatments, re-engraving should be performed. This management procedure can prevent issues such as poor appearance and low peel strength due to insufficient coating roller. Static elimination should be implemented on the film, and machine hygiene management should be maintained. The adhesive solvents should be tightly sealed and filtered during use.

5. Adjust the viscosity and replace the coating roller. Within the suitable viscosity range according to the process requirements, the coating volume can be achieved by adjusting the solid content of the adhesive and its compatibility with the coating roller.

6. Adjust the drying conditions. Lower air volume can result in solvent residue. The airspeed at the nozzle of the drying chamber must reach 30-35 meters/second. The temperature in Zone I should be set at 50-60°C, in Zone II at 60-70°C, and in Zone III at 70-80°C. The temperature of the first zone's entrance should not exceed 60°C.

7. Increase the coating volume and the temperature and pressure of the composite pressure roller; increase the hardness of the rubber on the pressure roller to 80-85°C. Adjust the entry angle of the film into the composite roller to align with the tangent direction as much as possible.

8. Implement moisture prevention measures, such as avoiding moisture absorption in materials like nylon and cellulose acetate, which react with NCO base to produce CO2. Maintain a dry environment and seal the curing agent packaging.

9. Increase the coating volume for manufacturing protective film, increase the temperature and pressure of the composite pressure roller, and increase the hardness of the pressure roller's rubber to 80-85°C. Adjust the entry angle of the film into the composite roller to align with the tangent direction as much as possible.

10. Implement moisture prevention measures, such as maintaining a dry environment and sealing the curing agent packaging during the formation process of protective film. This can also have a positive effect on improving bubble issues and greatly improve the quality and effectiveness of the protective film.



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