Problems of Static Electricity in BOPP Film Production and Solutions

To solve the above problems, it is essential to understand the specific causes of static electricity generation in films. In summary, the main reasons for static electricity in films are as follows:

1. Static Electricity Generated During Film Production  

Static electricity arises during film production due to friction between plastic pellets, friction between the melt and the die head, and friction between the film and guide rollers during winding. As a result, films may already carry static electricity when leaving the factory. Therefore, antistatic agents must be added during the production process to eliminate this static charge, and this method has proven highly effective.  

Antistatic agents are surfactants containing polar hydrophilic groups and nonpolar lipophilic groups in their molecules. The lipophilic groups have some compatibility with plastics, while the hydrophilic groups can ionize or absorb moisture from the air, forming a thin conductive layer on the film surface to discharge charges and eliminate static electricity. This is a commonly used method. However, excessive addition of antistatic agents may cause troubles in subsequent production processes (such as lamination and heat sealing).  

2. Static Electricity Generated During Printing, Lamination, Slitting, and Bag Making  

Static electricity is generated in films due to friction with guide rollers, friction between high-speed moving films and dry air, etc. This type of static electricity has the greatest impact on production, and if not effectively eliminated, it can also significantly affect post-processing operations. Generally, using superconducting static electricity brushes (contact-type elimination) is a relatively effective solution. This method involves grounding the static charge through low-resistance brushes that make direct contact with the film, conducting the charge away. Alternatively, ion generators can be used to blow ions onto the film as air currents (non-contact type). However, in practice, while ionized air eliminates the static charge on the film, the moving film may also carry some airborne ions into the winding process, leaving the film with residual static electricity. Therefore, the former method is more cost-effective, safer, and more efficient. However, during installation, it is crucial to strictly follow the installation drawings and ensure reliable grounding.  

3. Static Electricity Generated by Finished Films on Automatic Packaging Machines  

Static electricity may occur due to friction between finished films and equipment guide rollers, or incomplete elimination of static charge on the film itself. This can cause difficulties in automatic packaging, especially when the contents are sensitive to static electricity. The same solutions mentioned above can be applied, with the most effective method being the use of superconducting static electricity brushes.  

It is particularly important to note that most manufacturers mistakenly believe that since guide rollers are typically made of metal, static electricity generated by friction with films should be completely grounded and discharged. In reality, this is a misunderstanding. Generally, the materials selected for these guide rollers require surface treatment (even anodizing) during production. After treatment, the surface of the guide roller is actually aluminum oxide (a non-conductive material), not metallic aluminum, so static electricity cannot be discharged. Additionally, equipment is not always reliably grounded (in terms of electrical requirements) during installation. Therefore, this factor must be considered when installing static electricity brushes. Specifically, the grounding end of the brush must be reliably grounded (it is recommended to connect the ground wire to the grounding terminal of the equipment's power distribution cabinet) to effectively utilize its function.