Causes and solutions of static electricity in the

Causes and solutions of paper static electricity

once paper is static, it will bring a lot of trouble to printing. The first is that the paper cannot be aligned. Under the action of static electricity, the paper and paper are firmly absorbed and uneven, and it is difficult for air to enter between the papers. If you want to collide, you sometimes have to pull them apart by hand one by one, which is a waste of time. In the printing process, due to electrostatic attraction, single sheets of paper are firmly stuck together, sometimes two, sometimes several, sometimes a stack of paper cannot be separated, resulting in the paper separation suction nozzle can not absorb the paper. When the brush is pressed heavily, it often produces broken tension and empty tension; When the brush is pressed lightly, it will produce double sheets or multiple sheets. When multiple sheets of paper enter between the rubber drum and the embossing drum, the car will be stuffy and the rubber blanket will be crushed. The purpose is to remove the load and make the oil pressure of the working oil cylinder drop the gasket quickly. The paper with static electricity is not smooth when it is transported forward on the paper feeding table, and it is skewed and misaligned when it reaches the front gauge. As a result, the second overprint cannot be aligned, and the product quality is poor, which is a great waste. Even after the embossing part, the paper delivery is also very uneven, which brings great trouble to the second whole paper and seriously affects the production speed

paper with static electricity has a certain relationship with papermaking. In general, the base paper is less charged when leaving the factory, and the probability of coated paper being charged is also small. Because the printing paper (white board, paper jam, etc.) and coated paper are reprocessed on the basis of the base paper, even if the base paper has been charged, it will be eliminated in the processing process. Generally, the paper with a ration of less than 80g/m2 has more static electricity, but the paper has static electricity before machine printing or the static electricity before printing is not obvious, which is often a sudden increase in static electricity after embossing. In the offset printing process, due to the presence of water, it is not common to see static electricity after printing. For offset printing, static electricity is mainly generated before printing

cause analysis

the main cause of static electricity in paper is friction. Many charged objects are caused by friction. The friction between paper and calender during papermaking, and the friction between paper and rubber roller and imprint roller during printing are all important factors that generate static electricity

the binding force of electrons in the atomic nucleus of different substances is different, or they have different affinity for electrons. When two different substances are in close contact, some electrons will pass through the interface and attach to the surface of the electrophilic party due to the weak binding force of the electron sparing party. As a result of this electron transfer, an electric double layer will be formed at the interface. At this time, if the two substances are rapidly separated, the electron sparing party will be positively charged due to the loss of some electrons, and the electron loving party will be negatively charged due to the acquisition of some electrons. This is the essence of electricity generated by friction

the paper, blanket, ink, printing plate, etc. in the printing materials have different affinity for electrons. During the printing process, a lot of pressure makes them close contact, and a high speed makes them separate rapidly, which fully meets the conditions of friction electricity generation. Therefore, it is understandable that there are thousands of volts of static electricity in printing, especially some papers have static electricity before printing. Static electricity has been generated during the manufacturing process of the paper. When it is packaged and sent to the printing plant before it escapes, some static electricity is still retained, which is also the reason why the paper is charged before printing. When using these papers, we should combine the actual production situation and adopt different methods to eliminate the static electricity carried by the new national standard system of Chinese food contact materials

solution

1. Inventory method

after the paper enters the printing plant, the storage time should be appropriately longer, and the storage place can be better connected with the printing workshop, with the temperature of 18 ~ 25 ℃ and the relative humidity of 60 ~ 70%. Make the temperature and humidity of the printing workshop consistent with that of the paper warehouse, which is conducive to changing the water content of the paper. The change of paper moisture content is a process of releasing static electricity

2. Paper drying method (humidification method)

mainly uses the method of adjusting the main humidity to eliminate static electricity. When the relative humidity in the workshop is less than 50%, it is easy to generate high static electricity in the process of printing or plate making. Increasing the relative humidity in the workshop and the water content of the paper is very effective to eliminate static electricity, especially when drying paper. Humidity control equipment can be used to increase the indoor relative humidity. If there is no humidity control equipment, enough water can be sprinkled on the ground

humidity control equipment is mainly humidifier, and centrifugal automatic humidifier can be installed on the ceiling or wall of the workshop. When the indoor relative humidity does not meet the requirements, the humidifier can automatically spray mist like water vapor. Oilfield chemicals mainly include mineral products, inorganic chemical products, organic chemical products, natural materials, high molecular synthetic materials, etc. to increase the indoor relative humidity, and automatically stop spray after the indoor relative humidity meets the requirements

3. Electrostatic eliminator method

use the ions generated by the electrostatic eliminator to neutralize the charge on the charged body, so as to achieve the purpose of eliminating static electricity. There are three types of electrostatic eliminators: one is the externally applied voltage electrostatic eliminator, which applies a high voltage to the needle or thin wire electrode to generate corona discharge and generate ions. Generally, the transistor electrostatic eliminator used on the printing machine belongs to this kind; Second, self discharge electrostatic eliminator, which makes conductive fiber, conductive rubber or conductive metal materials into needle or thin wire electrodes and well grounded, generates corona discharge by using the electric field of the charged body itself to generate ions and neutralize the charge on the charged body; The third is the electrostatic separator of radioactive elements, which uses the ionization of radioisotopes to ionize the air to generate ions and neutralize the static electricity on the charged body

4. Antistatic agent method

antistatic agent is also called electrostatic eliminator or de electrifying agent. Its principle is to give hygroscopic ions on the surface of charged bodies such as paper and film, make them hydrophilic, absorb moisture in the air, reduce the review and comment of multilayer plastic containers for food and beverage, reduce the resistance, increase the conductivity, and make it difficult for electrostatic charges to accumulate. Antistatic agents are mainly surfactants, including hydrophilic and hydrophobic groups, or polar and nonpolar groups. Hydrophilic groups have strong affinity for substances with larger polarity such as water, and hydrophobic groups have strong affinity for substances with smaller polarity such as oil. Antistatic agents are widely used in printing, such as using antistatic agents to make soft rubber rollers to prevent static electricity

5. Process operation method

in the printing process, you can add a wet towel to the paper receiving part, fix the towel dipped in water on the pull rod, and make the paper contact with the wet towel to eliminate static electricity. This is a temporary but effective way to eliminate static electricity. The disadvantage is to wet the towel often