Application of Corona Treatment Equipment on Dry Laminating Machine

Plastic flexible packaging is now widely used in various areas of commodity packaging. The most commonly used non-polar films such as polyethylene and polypropylene in flexible packaging are non-polar materials. The surface is dense and smooth. It is an inert surface and its surface free energy is only 2.9-3.0×10ˉ6J/cm2. In theory, films with a surface free energy below 3.3 × 10 ˉ 6 J/cm2 will not be able to wet any of the currently used adhesives. Therefore, the surface free energy of the film must be 3.8-4.0×10ˉ6J/cm2 before surface treatment to obtain good composite strength. There are many commonly used thin film surface treatment methods, of which corona treatment is a commonly used method.

The three intaglio printing machines used in our factory are equipped with corona treatment equipment. When the treatment is required, it is only necessary to pass the film sequentially between the electrode rollers. The treated film directly enters the printing unit, and the ink has good adhesion on the film. The installation of corona treatment equipment on the dry laminating machine is an aspect of our technical transformation. The purpose is to increase the surface tension value of the polyethylene hydrocarbon film and improve the attachment fastness of the composite product. Our plant has been equipped with a corresponding point spark treatment equipment on the dry laminating machine in accordance with the actual situation, and achieved very good results. The processing equipment is DCD16-2-10 plastic surface treatment machine produced by Dalian Radio 9 Factory. After corona treatment, the surface tension of the film can reach 3.8~10ˉ2N/cm2, which greatly improves the peeling strength of the composite film and can completely meet the quality requirements. For the aluminized film, especially BOPP aluminized film is very helpful, but in the installation of the device to be changed. The corona treatment principle, surface tension detection method, equipment installation wiring and common troubleshooting are discussed below.

1 Corona treatment principle

Electric shock or breakdown, under the action of a high-voltage electric field, the strong impact of the electron flow on the plastic film can make the surface of the film fluffy, become rough, and increase the surface area. When the adhesive is in contact with its surface, it can produce good wetting, the adhesive will penetrate into the furrowed groove, relying on the "anchoring" effect to make the film firmly bonded, which is a physical effect, observed under high magnification magnifying glass After the film compared to the untreated film, the surface is obviously uneven and very rough, and the electric impact strength can be enhanced with the increase of voltage and current.

2 increase the polarity of the film

Under the action of a high-voltage electric field, oxygen in the air turns into ozone, and ozone decomposes into oxygen and new ecological oxygen atoms. The new eco-oxygen atom is a fortifier that oxidizes the a-carbon atoms in the polyethylene or polypropylene molecules to form carbonyl groups and hydroxyl groups. With this structure, the molecular properties of the film increase and surface tension increases. The affinity of the adhesive increases, and the adhesion fastness between the composite films increases. In addition, due to the generation of hydroxyl groups and the appearance of new a-carbon atoms in the molecular chain, the active hydrogen appears to chemically react with the active group isocyanate (-NCO) in the polyester adhesive. A strong chemical bond is formed between the adhesive material and the adhesive, which further increases the adhesive fastness. From the detection of infrared light, it was found that there was a carbonyl absorption peak on the surface of the treated polyolefin film on the line, which proved that the above chemical action was present.

3 Commonly used detection methods

1. The BOPP single-sided transparent tape was used for peeling test. The BOPP single-sided adhesive tape was affixed on the surface of the film to be tested, and then it was pressed and then torn. If the surface tension of the film meets the requirements for use, then the peeling force is very strong and the sound is small; on the contrary, it is easy to peel off and is mixed with “rustle” sound.
2. Using the Dyne pen for testing: BOPP: 3.8×10ˉ2N/m; PET: 5.0×10ˉ2N/m; nylon: 5.2×10ˉ2N/m when the surface tension of the film meets the requirements. The liquid marks in the places where the strokes were tested were uniform, without breaking or shrinking. If one part shrinks and one part does not shrink, it means that the treatment is not enough. It is worth mentioning that when testing PET and nylon, a large-scale test pen must be used. Common specifications for surface tension test pens are: 3.8×10ˉ2N/m; 4.0×10ˉ2N/m; 4.2×10ˉ2N /m;4.4×10ˉ2N/m;4.8×10ˉ2N/m5(for aluminum foil).

3. Prepare a surface tension test solution as shown in Table 1:

After treatment, the film should not be placed for a long time, up to 7 days, the longer the time, the more obvious the surface tension value decreases. If it takes a long time, the initial value of the surface tension increases when the film is processed.

4 Common Faults and Troubleshooting Methods

The SDCD16-Z-10 corona treatment equipment sometimes has some failures during its use, including electrical failures and mechanical failures. I will categorize and analyze the problems encountered in my actual work for reference.

1. The device does not generate sparks, the anode on the cradle and the aluminum ribs do not discharge. Such failures often occur during the rainy season. Due to the high humidity in the room, there is water in the discharge aluminum row on the impact rack and the insulator silicon rubber roller, which causes the positive electrode to discharge and the aluminum row cannot discharge. The treatment method is: the total power is turned off, and all rollers of the impact frame (including the traction roller and the insulating silicone rubber roller) and the discharge aluminum row are wiped dry with a dry cloth. And the electric fan is used for heat treatment. Without water, the discharge equipment can work normally. After encountering the above situation, the impact machine should be started from small to large. While observing the spark condition, the normal spark is continuous, without red spots, and uniform.

2. The discharge aluminum row does not discharge, the voltage does not rise (refer to the KV meter) and the current (A) indicates too large. Causes: parallel connection of processing equipment, diode damage, or series connection, breakdown of capacitors; breakdown of high-voltage transformers; breakage of thyristor damage in processing equipment; poor contact of high-voltage transformer carbon brush or oil contamination on the slip ring; The over-current switch is damaged; the transistor on the circuit board is damaged and cannot be amplified; the high-voltage transformer winding is broken or the insulating porcelain bottle is damaged; the output of the high-voltage transformer is connected to the positive and negative electrodes, and leakage or breakdown occurs. Countermeasures: Measure the capacitance and resistance of the diode. Replace it if it is damaged. Correct the wiring. The green line is in the middle and the red line is on both sides. Replace the thyristor. Check the carbon brush and grind it with 1000# water-resistant sandpaper. Until clean; replace the over-current switch; replace the transistor; carefully check the winding, replace the insulating porcelain; replace the same model, the connection with the specifications; replace the new AC contactor.

3. When discharging BOPP and PE films, the discharged aluminum discharges electricity. When VMOPP and VMCPP films are processed, the discharged aluminum row does not discharge. Cause: The diodes of the processing equipment were broken down; the silicone rubber insulating roller on the impact frame was broken down; when the VMOPP was processed, it was heard that the “buzz” sounds, the spark was only a little; the positive and negative wires of the output terminal of the high voltage transformer touched Conductors, as well as leakage or breakdown; positive and negative wiring incorrectly; oil or dirt on the discharge aluminum row. Countermeasures: Replace the diodes; replace the silicone rubber insulation roller; the connection line should be suspended in the air, can not touch the conductor, if it should be replaced should be replaced; replace the positive and negative pole wiring; wipe the oil and Other clean.

In the process of using the SDCD16-2-10 corona treatment equipment, the discharge aluminum row can be arbitrarily adjusted according to the width and width of the material, but it is forbidden to touch by hand to ensure safety. After the treated film is tested, the surface tension value is sufficient, not the bigger the better, it is worth mentioning is: in the impact VMOPP, VMCPP film, the high and low voltage transformer and the impact of the negative and positive wiring connections, that is That is, the positive pole of the impact frame is connected to the negative pole, and the negative pole is connected to the positive pole or the live line.

The application of point spark processing equipment on the dry laminating machine greatly improves the product's composite strength and quality. In the actual use of the installation process, it must be operated by professional personnel and pay attention to the use of safety.