Corona treatment of the hottest CPP casting film

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Corona treatment of CPP casting film

the mechanical and electrical equipment factory of Wuxi radio Industrial school is now the mechanical and electrical equipment factory of Jiangsu Institute of information technology. It has developed and produced corona processors since the 1970s. It is the first professional factory in China to produce corona processors

before 2000, when the life of human tissues and organs was limited, it was able to produce a corona processor with a maximum power of 10kW, which was mainly used in film blowing, printing and coating equipment. In 2000, a high-power corona processor was successfully developed, and the maximum power of a single machine can reach 25kW. The main performance of the equipment has reached the index of imported equipment. After more than three years of actual use, it has been proved that it can completely replace imported equipment

the main users of imported and domestic double pull equipment are: (see the attached table)

in July 2002, the 2.4m imported CPP production line imported by Guangdong Zhongshan Zhongsheng packaging materials company used the 15kw corona processor produced by our factory to replace the original imported corona processor. In the same month, Xuzhou chlor alkali group plastic No. 2 branch used the 15kw corona processor produced by our factory to replace the imported corona processor. In February, 2003, Shanghai Wisteria packaging materials Co., Ltd. imported a 4.2-meter CPP production line using a 20kW corona processor produced by our factory. The reliability and treatment effect of the equipment are very good. The corona rollers and discharge devices of the above three sets of equipment are originally imported, and there have been no failures since they were used

in 2004, we provided corona treatment equipment for the 2.2-meter imported CPP production line of Changzhou Guangming plastic factory and the 1.5-meter imported CPP production line of Changzhou Haiqi Plastic Co., Ltd., including corona rollers and discharge racks, whose performance fully reached the index of foreign imported equipment

in 2003, our factory began to provide corona processors for domestic CPP casting production lines, mainly for Foshan Wanjia plastic company and Nanhai Shicheng plastic machine company. So far, more than 30 CPP production lines have been provided

on the CPP casting machine production line produced by Foshan Wanjia Plastic Co., Ltd. and Shicheng Plastic Machinery Co., Ltd., we worked with their scientific and technological personnel to overcome many problems and master the corona treatment technology on the CPP casting machine. Now the casting equipment they produce uses the corona processor produced by our company, and the produced CPP casting film has a corona treatment effect of more than 45 dyne, no reverse corona phenomenon, flat film and good film quality. Practice has proved that the high-power corona processor produced by our factory is fully applicable to the surface of packaging materials with high requirements, such as aluminum coating. Basically, the experimental machines below 1 ton are all conventional electronic universal experimental machines

next, let's talk about the factors that affect the effect of corona treatment.

first, as far as the corona machine itself is concerned, the corona machine has high power, produces many carriers, and the surface of the treated material has a high energy density, so the treatment effect is good; The frequency of corona machine increases, and the treatment effect becomes better. The discharge gap of the discharge electrode decreases. Under the same power, the carrier produced increases and the treatment effect becomes better. However, when the discharge gap is too small, the manufacturing cost of the discharge rack increases, and the plastic film is easy to rub the discharge electrode with high temperature and burn the surface of the plastic film. Therefore, the best discharge gap is 1.5mm. The speed of the film production line is increased, the time of the film surface in the discharge area is shortened, and the treatment effect is reduced. Therefore, when the speed of the production line is increased, the power of the corona processor must be increased. The power required for corona treatment is in direct proportion to the speed of the production line

second, the following factors also affect the treatment effect:

1. The effect of temperature

when the plastic film temperature is high, the corona treatment effect is good. This is because when the temperature is high, the speed of chemical reaction is fast and the degree of reflection is also large. Therefore, the discharge frame of corona treatment is installed behind the membrane shaping equipment. Corona treatment when the film temperature has not been completely reduced

2. Influence of environmental humidity

environmental humidity also affects corona treatment. When the environmental humidity is low, the treatment effect is good; When the humidity is high, the treatment effect becomes worse. Therefore, when the humidity is high, the exhaust air volume should be increased to discharge the moisture near the electrode

3. Influence of film thickness

the thickness of plastic film also affects the effect of corona treatment. With the increase of film thickness, the power of corona treatment should also be increased

4. Influence of materials

materials have a great influence on corona treatment. Under the same treatment conditions, different materials have different treatment effects. CPP casting film requires more energy than polyethylene film to achieve the same treatment effect. Therefore, when the width and speed are the same, the CPP casting machine is equipped with corona processor, and the power inspection electromagnetic clutch requirements are large

5. Influence of polymer density

the effect of corona treatment is also related to the density of polymer: with the increase of density, the treatment effect becomes worse. As the density increases, the critical tension after corona treatment decreases (maximum tension). Additives in polymers, such as smoothing agents, antioxidants, and anti powdering agents, often make corona treatment worse. During film forming, these additives migrate to the surface to form a weak interface layer

III. timeliness of corona treatment

the treatment effect of corona treated films will decline with the extension of storage time. This is because the active center of the molecular chain moves into the interior of the film, reducing the surface tension. In general, no matter what the initial treatment strength is, whether the raw material is PP or PE, after more than a month, the surface tension of most brands of resins has subsided to about 38 dyne. Temperature has a great influence on the extinction of corona treatment. The higher the temperature, the faster it subsides. According to experience, when the temperature is below 20 ℃, the surface tension of cast film can be maintained at 38 ~ 41 dyne for at least one month. Therefore, the cast film should be stored at a lower temperature as far as possible. Different kinds and brands of raw materials have great differences in halo removal, mainly due to the synthesis process and polymerized monomers. The dosage of various additives is inconsistent. Additives are easy to precipitate to the surface during the storage of the film, forming a weak interface and reducing the surface tension. With the increase of film thickness, more additives are required, so the disappearance of thick film after treatment is more obvious than that of thin film

IV. preventing reverse corona

preventing reverse corona is very important in the production process of CPP casting film. The consequences of reverse corona are: if it is an aluminum coating, the coating will transfer during aluminum plating, and the adhesive layer will transfer during gluing. The heat sealing property will become poor during bag making, and the sealing fastness will not meet the requirements. There are two ways to prevent reverse corona. First, the tension of the film should be reasonably controlled in the casting production line. Second, the discharge frame should have a reasonable structure and high precision. The discharge frame must have a pressing roll. The pressing roll and corona roll must be subject to strict dynamic and static balance tests, and the radial runout should be less than 0.05 mm. The pressure of the pressing roll must be appropriate. Too much pressure cannot play the effect of pressing roll, and the film is not close to the corona roll. The force at both ends of the hold down roll should be consistent. When the film enters the discharge rack, it is best to add a flattening roll to ensure that the film enters the corona roll smoothly without generating reverse corona

the corona processor produced by our factory has formed a series of power, adjustable from 1kW to 25kW, which can meet various needs of users. The corona processor produced by our factory works stably and reliably with good treatment effect. The main technical parameters of the corona processor are: the working frequency is 15 ~ 25kHz, and the output power is adjusted by frequency modulation. The higher the frequency is, the greater the output power is. The maximum output voltage can reach 15000V

has perfect protection function

1. The discharge pole is not in place, so it cannot be turned on

2. The corona roll cannot be turned on when it is lower than a set speed

3. The film breaking signal is incorrect, and the discharge frame cannot be closed, let alone turned on. In normal operation, once the film is broken, it can automatically shut down, alarm and open the electrode automatically

4. The discharge electrode adopts a rotating structure. Once there is a hard block on the edge of the casting film, it can automatically open the electrode when the hard block moves between the discharge electrode and the corona roll. After the hard block passes, the discharge electrode resets automatically. Protect the discharge roller and discharge electrode

structural features:

the discharge electrode adopts aluminum alloy profile, which has two types: integral type and plug-in type. The discharge electrode adopts multi-point support and multi-point fine adjustment to ensure that the discharge gap is uniform. After the discharge electrode is heated and expanded, the gap does not change to ensure the consistent corona treatment effect. According to different power requirements, corona has water circulation cooling and air circulation cooling. The effect of air circulation cooling is slightly worse than that of water circulation cooling, but the structure is simple. The main circuit of corona machine adopts imported IGBT module to form series resonant inverter circuit. When the working voltage, high temperature aging resistance, component space stability and impact resistance current of the IGBT module are close to zero, the IGBT module is turned on and off, which reduces the switching loss and improves the efficiency and reliability of the whole machine

with the continuous progress of science and technology and the development of the market, we will make continuous efforts to keep pace with the times, explore and innovate, and keep up with the pace of scientific and technological development. I sincerely hope you can make suggestions on our products. Welcome to our factory for guidance. Let us develop and improve together with you

Author: yangfuquan (mechanical and electrical equipment factory of Wuxi radio Industrial School)


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