Elimination methods and preventive measures of sta

  • Detail

The generation, elimination methods and preventive measures of static electricity in packaging printing

1. The harm of static electricity

1) affects the printing quality of products. If the surface of the substrate is charged, such as paper, polyethylene, polypropylene, cellophane, etc., they will absorb paper scraps or dust and impurities floating in the air, thus affecting the transfer of ink, flowers and dots appear on the print, resulting in the decline of print quality. If the ink is charged, when it is discharged in the process of moving, electrostatic ink spots may appear in the connection and utilization of the above aluminum alloy cables on the print, which seems to be caused by the uneven inking caused by the poor fluidity of the ink. This situation often occurs in the layered thin edition and according to the person in charge. In field printing, if the charged ink discharges at the edge of the line on the print, many other factors will affect the price of the impact tester, and ink whiskers are easy to appear

2) affect production safety. During the printing process, high-speed friction will produce high-voltage static electricity. When static electricity accumulates to a certain extent, it is easy to cause air discharge, resulting in electric shock or fire. High voltage static electricity may cause ink and solvent to catch fire, or shock workers, directly threatening the safety of operators. The generation mechanism of static electricity, friction is the main cause of static electricity. When two solid materials contact or rapidly separate, because different materials have different abilities to adsorb electrons, electrons will be transferred from one material to the surface of another material, and the surface where electrons are obtained shows negative charge, while the other surface is positively charged due to the loss of electrons

second, the main factors of static electricity include:

(1) material properties

material conductivity has a dual effect on static electricity. If the material is a conductor, the charge moves freely on its surface, and the charge tends to distribute freely on its whole surface, and will not stay in a local position. The free distribution of charge can only cause low voltage. As long as any part of this material contacts the ground, the charge on the surface can be transferred to the ground to eliminate static electricity. Insulation materials are different from conductors, such as paper and plastic film in printing materials. When static electricity is generated, a higher voltage will be formed, and it is impossible to eliminate static electricity through grounding

(2) environmental conditions

include the composition, pressure, temperature, humidity, etc. of the gas around the contact object (material)

(3) mechanical action

the contact type, contact time, contact area, separation speed, material and the nature of the force of the two materials. In general, the closer the contact between the two materials or the faster the separation speed, the stronger the static electricity generated

III. elimination methods and preventive measures

1) chemical elimination method

chemical elimination method generally applies a layer of antistatic agent on the surface of the substrate to make the substrate conductive and become a slightly conductive insulating material. Chemical elimination method has great limitations, such as chemical composition will have a negative impact on the quality of paper, reducing its strength, adhesion, tightness, tension, etc., so this method is generally not used

2) physical elimination method

physical elimination method is a method to eliminate static electricity by using electrostatic characteristics without changing the properties of materials. Physical elimination is one of the most important methods to eliminate static electricity in modern industrial production

(1) grounding

grounding is the simplest method. That is, connect the generated static electricity with the earth with a metal conductor to make it equipotential with the earth, and the charge will leak through the earth. But this elimination method has little effect on insulating objects

(2) humidity control

the surface resistance of printing materials will decrease with the increase of the relative humidity of the air. Therefore, increasing the relative humidity of the air can improve the conductivity of the paper surface and accelerate the charge leakage. Generally, the suitable environment for the printing workshop is: the temperature is about 20 ℃ and the relative humidity is more than 70%

Copyright © 2011 JIN SHI