Causes and elimination of static electricity during printing

In the printing production process, sometimes paper or printed products attract and stick to each other, which is difficult to separate. This phenomenon is the phenomenon of printing static electricity. In the dry climate in winter, the phenomenon of static electricity on the printed paper is particularly prominent, ranging from obstacles to normal paper feeding, paper collection and flushing, and even printing failures. Therefore, knowing the static electricity of printing and mastering the coping methods are of positive significance for promoting production.

Paper has such a property that when its water content is high, the electrical conductivity increases; conversely, when the water content is very low, the insulation performance increases. In this case, the paper is more prone to static electricity.

Discomfort in the papermaking process can easily cause static electricity on the paper. In the papermaking process, due to the low content of electrolytes (such as alum, sodium chloride, etc.), too much sizing material content, some fillers (such as kaolin, etc.) content is too small, the paper is subjected to high temperature during drying and calendering And the effect of pressure makes the paper with high voltage static electricity. Improper storage of paper can also generate static electricity. When there is a large gap between the temperature of the paper storehouse and the temperature of the printing workshop, the variation of the moisture content of the paper will not only cause expansion and contraction and affect the registration, but also easily cause static electricity. In addition, the paper placement time before printing is too short, the temperature and humidity of the paper and the printing environment lack an effective balance, and the paper stack pressure is too high and too heavy, which can also cause the paper to become static.

The friction in printing causes static electricity. When the water content of the paper is low, the paper is very dry, and the paper is subjected to friction and pressure during the paper conveying and imprinting process, which makes the paper electrostatic.

The static electricity on the paper is caused by one reason, and it is caused by several cases concurrently, and the situation is not the same. The size of static electricity carried by various papers or batches of paper is not necessarily the same. Another feature is that after the paper is charged, the polarity of the charges on both sides is opposite, and the paper that is in contact with the front and back sides is firmly adsorbed to each other and is not easy to separate. Therefore, it will bring obstacles to printing paper conveying, conveying and aligning paper, which not only affects production efficiency and product quality (such as easy to cause imprinting, overprinting and other associated failures), but also increases the loss of printed products.

In order to prevent the occurrence of printed static electricity, first of all, we must control from the source. First, the paper with static electricity can be temporarily suspended, the storage time should be properly extended, and the temperature and humidity of the paper warehouse should be well controlled. The temperature in the warehouse is directly controlled between 18 ℃ -20 ℃, and the relative humidity of the air is controlled at 60-65 %, Under this condition, it is helpful to reduce or eliminate paper static electricity. Secondly, paper drying measures can be used to remove paper static electricity. When the paper needs to be used urgently, you can use a paper dryer to hang the static paper. Attention should be paid to the coordination of machine speed and air humidity when hanging, that is, when the machine speed is fast, the relative humidity of the ambient air is controlled at 80-85%. On the contrary, when the machine speed is slow, the humidity is kept at 70-80% and the effect is better. It is worth noting that the thickness of each stack of paper should be controlled within 10mm when hanging, and the paper should be loosened as much as possible when sandwiching the paper, so that the moisture in the air can evenly enter the paper. Third, the emergency drying paper removes static electricity. For the situation that the printed paper is static and cannot be printed normally, the "steam method" can be used to quickly dry the paper to reduce the static electricity of the paper and complete the printing as soon as possible. In the production practice of a machine, when the author printed 30 grams of glossy paper at a speed of 3500 sheets per hour, the paper had a strong static electricity, which made it difficult to convey and transfer paper, and the overprint was inaccurate. Therefore, we had to stop the machine to carry out emergency drying of the charged paper, that is, each stack of paper with a thickness of about 15mm was placed on each layer of the drying rack, and then the surrounding of the drying rack was filled with steaming water, which caused the paper to increase rapidly. Water content to reduce static electricity and maintain normal printing.

A comprehensive method can also be used to eliminate paper static electricity, which combines the increase of paper temperature, the increase of water content, and the use of static electricity eliminators, which has a better effect. The main measures are:

1. Install air-conditioning equipment in the printing workshop, adjust and maintain the printing workshop at a constant temperature and humidity according to the strength of the paper static electricity. Under normal circumstances, the temperature of the workshop is adjusted between 18 ℃ -20 ℃, and the relative humidity of the air is maintained between 60-65%. If the paper is heavily charged, the relative humidity of the air can be adjusted to 80-85%.

2. Install a static eliminator on the printing machine to eliminate paper static electricity. The static eliminator is adjustable, and the paper and static electricity are eliminated by adjusting the voltage and frequency. Use high voltage and high frequency when the static electricity of the paper is large, and lower the voltage and frequency when the static electricity of the paper is not large.

3. Use isotope emitters to eliminate printed static electricity. The principle of isotope emitters and static eliminators to eliminate static electricity is basically the same, all of which ionize some air molecules into ions. Because the ions have different charges, when the paper passes through the ion space, part of the electrostatic charge will be neutralized, so that the purpose of eliminating static electricity is achieved.

In summary, static electricity has an adverse effect on printing efficiency and quality, and also increases paper consumption. Therefore, correct understanding and understanding of printing static electricity and taking corresponding measures to overcome and eliminate it can ensure the smooth progress of printing and achieve the purpose of improving production efficiency and quality.

Silicone Tong

Silicone Tong,Silicone Food Tong,Silicone Kitchen Tong,Silicone Ice Tong

Fortary Industry&Trading Co., Ltd. , https://www.kitchenset.de