Once the paper is charged with static electricity, it will cause a lot of trouble for printing. The first is that the paper cannot be hit. Under static electricity, the paper and paper are held firmly. With unevenness, it is difficult for air to enter between papers. In order to collide, it is sometimes necessary to open them one by one and it is a waste of time. During the printing process, due to the electrostatic attraction, the sheets are firmly stuck together, sometimes two, sometimes a few, and sometimes a sheet of paper cannot be separated, resulting in a paper suction nozzle that cannot absorb the paper. Brushes are heavy and tend to break. Blank; brush pressure is light, but also produce double, multiple sheets. Multiple sheets of paper enter between the blanket cylinder and the impression cylinder, causing boring cars and crushed the blanket and liner. Paper with static electricity is not smooth when the paper is fed from the front, and it is not correct when it reaches the front gauge. Inaccurate positioning, resulting in the second overprint can not register, poor product quality, great waste. Even after passing through the embossing section, the delivery is very uneven, causing great troubles for the second entire paper and seriously affecting the production speed.

There is a certain relationship between static electricity and papermaking. Under normal circumstances, the original paper is less charged when shipped from the factory and the probability of coated paper is not high. Because printing paper (white paper, cardboard, etc.) and coated paper are reprocessed on the basis of the base paper, even if the base paper is charged, it will be eliminated during processing. Generally, paper with a basis weight of 80g/m or less has more static electricity. However, static electricity is not present before the machine is printed on the paper or static electricity is not obvious before printing. This is often caused by the sudden increase in static electricity after imprinting. In the offset printing process, due to the presence of water, it is not common to see static electricity after printing pressure. For offset printing, static electricity is mainly generated before printing.

(I) Analysis of the reasons:

The main cause of static electricity on paper is frictional electricity generation. Many objects are charged by the friction, paper and calender friction papermaking, printing paper and rubber roller. The friction between the impression cylinders is an important factor in the generation of static electricity. |

The binding forces of the electrons of different substances are not the same, or they have different affinity for electrons. When two different substances are in close contact, the electron-releasing side is weak due to the binding force to the electrons, and some electrons will adhere to the surface of the electrophilic side through the interface. As a result of this electron transfer, a double layer is formed on the interface. At this time, if the two substances are rapidly separated, the electron-releasing side is positively charged due to the loss of some electrons, and the electrophilic side is negatively charged by obtaining some electrons. This is the essence of triboelectricity generation. |

Paper in printed material. Blanket. Ink. The affinity between the plates and the electrons is different, and the pressure during the printing process makes them in close contact with each other. There is also a high speed that allows them to separate quickly, and they are fully equipped with friction and electricity. Therefore, it is understandable that thousands of volts of static electricity appear in printing. In particular, some papers are electrostatically charged before printing. Paper has generated static electricity during the manufacturing process. When it is too late to be packaged and sent to the printing plant, some static electricity remains. This is also the reason why the paper is charged before printing. When using these papers, it is necessary to take a different approach to eliminate the static electricity they carry, in light of the actual production conditions.

(B) The solution:

1, inventory method

After the paper enters the printing plant, the storage time should be longer and the storage location can be better connected with the printing shop. The best temperature is 18-25 °C and the relative humidity is 60%-70%. Make the temperature of the printing shop. The humidity is consistent with the paper bank, which helps to change the moisture content of the paper. Changing the moisture content of paper is a process of releasing static electricity.

2. Drying method (wetting method)

The main method is to eliminate static electricity by adjusting the main humidity. When the relative humidity in the workshop is less than 50%, high static electricity is easily generated during the printing or plate making process, and the relative humidity of the shop and the moisture content of the paper are increased. Especially, increasing the indoor relative humidity when paper is being dried is very effective for eliminating static electricity. The humidity control equipment can be used to increase the relative humidity in the room. When there is no humidity control equipment, sufficient water can be sprinkled on the floor. The humidity control equipment is mainly a humidifier, and a centrifugal automatic humidifier can be installed on the ceiling or wall of the workshop. When the relative humidity in the room does not meet the requirements, the humidifier can automatically spray misty water vapor, increase the indoor relative humidity, and automatically stop spraying when the relative humidity in the room reaches the required level.

3. Static eliminator method

The ions generated by the static eliminator neutralize the charge on the electrified body to eliminate static electricity. There are three types of static eliminators: one is an applied voltage type static eliminator, which applies a high voltage to acicular or thin wire electrodes and generates a corona discharge to generate ions. The transistor static eliminator used in printing machines generally belongs to this category. The second is a self-discharge type static eliminator that puts conductive fibers. Conductive rubber or conductive metal materials such as needle-shaped or thin wire electrodes and well grounded, the use of the electric field of the charged body to generate corona discharge ions, to neutralize the charge on the charged body; Third, the radioactive element in addition to static , using radioisotope electricity

Separation, ionization of air, generates ions that neutralize the electrostatic charge on the charged body.

4. Antistatic agent method

Antistatic agent is also called static elimination agent or deoxidizer. The principle is to give paper. The hygroscopic ions on the surface of the charged body such as a thin film make it hydrophilic, absorb moisture in the air, reduce the electrical resistance, and increase the electrical conductivity, so that the static charge is not easily accumulated. Antistatic agents are mainly surfactants, with hydrophilic and hydrophobic groups, or polar groups and non-polar groups. Hydrophilic groups have strong affinity for substances such as water, which are more polar, and hydrophobic groups have strong affinity for oils and other less polar objects. Antistatic agents are widely used in printing, such as the use of antistatic agents to produce anti-static soft roller and so on.

5. Process operation method

During the printing process, a damp towel may be added to the delivery section to hold the dipped towel on the pull rod so that the paper is contacted with a damp towel to eliminate static electricity. This is a temporary but effective way to eliminate static electricity. The disadvantage is that Often Ting Ding wet towels.

Reprinted from: network Author win: Real-ho song