Reasons for the analysis and elimination of static electricity

In the printing production process, there sometimes occurs paper or printing products that adhere to each other and stick together, as if the paper surface has a strong vacuum suction and it is difficult to separate. This phenomenon is the printing of static electricity, in the dry climate in winter, the printing paper with electrostatic phenomenon is particularly prominent, ranging from normal to the normal paper, paper and paper to create obstacles, the weight can not automatically feed or frequent double, empty The adverse consequences such as confusing sheets, collecting paper, and increased loss not only reduce production efficiency but also affect product quality. Therefore, a correct understanding of printing static electricity and mastering coping methods have positive significance for promoting production.
When the moisture content of the paper is high, it can become an electrical conductor; conversely, when the moisture content is very low, it has an insulating property, and in this case, the paper is more likely to have an electrostatic phenomenon. The cause of static electricity First of all, the papermaking process is not easy to statically charge the paper. In the papermaking process, due to the low content of electrolytes (adding alum, sodium chloride, etc.), excessive content of sizing material, and low content of certain fillers (such as kaolin, etc.), the paper is dried and calendered. In the middle, it will be subjected to the use and influence of high temperatures and pressures, causing the paper to be charged with high voltage static electricity. Second, improper storage of paper can also generate static electricity. If there is a great disparity between the temperature of the paper warehouse and the temperature of the printing shop, due to the variation in the moisture content of the paper, not only will there be a telescopic change affecting the registration, but also it will easily cause the inconvenience caused by the static electricity. In addition, the paper placement time before printing is too short or the paper stack is too high, which results in a lack of effective balance time between the temperature and humidity of the paper and the printing environment, and the stack pressure is too heavy, causing the paper to be electrostatically charged. Third, print static electricity caused by friction. For example, when the water content of the paper is significantly lower, the paper will be excessively dry, so that during the printing process, due to the friction and pressure in the paper feeding and the printing, the electronic gain and loss of the paper's atomic nuclei will occur, and the paper belt Electrostatic phenomenon.
There is a cause for static electricity on paper, and there are several adverse conditions that make up the situation. The situation is not the same. All kinds of paper are even the same kind of paper. The size of the electrostatic charge between this batch and the previous batch of paper is not necessarily the same, that is, there will be differences in voltage levels. Another feature is that when the paper is charged, the two sides are electrically opposite. When printing, the front and back sides of the paper are stacked in a consistent manner. That is, the front or back side of the paper is firmly attached to each other. It is not easy to separate, which brings certain obstacles to printing, paper feeding, conveying and aligning paper. At the same time, not only affects the production efficiency and product quality (such as easy to cause the bottom of the imprint, misalignment of overprinting chain failure), but also increase the loss of printed products, it should take measures to eliminate static electricity printing, ensure normal printing.
To prevent the occurrence of printed static electricity, it is first necessary to control it from the source. The paper with static electricity can be put on hold, the time of stocking is properly extended, and the temperature and humidity of the paper storehouse must be controlled. The temperature in the storeroom should be controlled between 18°C ​​and 20°C, and the relative humidity should be between 60-65%. In this condition, it is helpful to weaken or eliminate static electricity on paper. Second, use paper to remove static electricity from the paper. When encountering paper urgently, you can use hanging paper machine to suspend electrostatically charged paper. Hanging should pay attention to speed and air humidity coordination, that is, when the speed is faster, the relative humidity of the ambient air is controlled at 80-85%. On the contrary, when the speed is slow, the humidity is maintained at 70-80%, and the hanging effect is better. It is worth noting that: when hanging, the thickness of each stack of paper should be within 10mm, and the paper should be loosened as much as possible when paper is clamped, so as to facilitate uniform air moisture into the paper. Third, the emergency paper removes static electricity. If the static electricity cannot be properly printed during the printing of the cut paper, the paper can be quickly “steamed” to dry the paper to reduce the static electricity of the paper and finish the printing as soon as possible. If the author used to print 30 grams of glossy paper at a speed of 3,500 sheets per hour in the previous production practice, the static electricity of the sheet was so severe that it was difficult to convey paper and convey paper, and the equipment was inaccurate. Then we had to shut down the emergency paper for the live paper. We used a paper holder to put each stack of paper about 15mm thick on each shelf, and then sprinkled hot water around the paper holder for an hour. The airing, so that the paper quickly increase the moisture content, in order to achieve the effect of weakening static electricity to maintain normal printing.
Elimination of paper static electricity can also adopt a comprehensive elimination method, that is to improve the paper temperature, moisture content and the use of static eliminator combination, the effect is better. Its main measures are:
1. Install air-conditioning equipment in the printing shop, adjust or maintain a constant temperature and humidity in the printing shop according to the strength of paper electrostatics. Under normal circumstances, the workshop temperature is adjusted between 18°C ​​and 20°C, and the relative humidity of the air is maintained at 60-65%. If the paper is charged more severely, the relative humidity of the air can be adjusted to between 80-85%;
2. Install a static eliminator on the printing press to eliminate paper static electricity. The static eliminator is adjustable to eliminate static electricity from the paper by adjusting the voltage or high frequency, that is, when the static electricity of the paper is large, high voltage or high frequency is used. If paper static electricity is not large, turn down the voltage and high frequency;
3. Use an isotope emitter to eliminate printed static electricity. Isotope emitters and static eliminators basically have the same principle of eliminating static electricity. They ionize all molecules in the air into ions. Because ions have different electrical properties, the air becomes an ion layer and becomes a good conductor of electricity. When the paper passes through the ion space, part of the electrostatic charge carried is neutralized, and part of it is guided by air ions, so that the purpose of eliminating static electricity is achieved.