It is well known that the materials used in the packaging and printing industry are insulators such as paper, plastic, ink, adhesive and guide rollers (the departments of anodized natural alumina); the processes of printing, compounding, rewinding and slitting are high-speed rubbing, Contact, separation of the "surface" project. Packaging and printing of static electricity mainly with the chemical composition of insulation materials, molecular structure, mechanical properties, smoothness, electrical and environmental temperature and humidity, mechanical conditions such as contact pressure, friction separation speed and other factors. Film type, contact type, contact time, contact area, the separation speed is different, the resulting electrostatic discharge time and voltage are different.
First- the harm of static electricity
Once the paper with static electricity, it will bring a lot of trouble printing. The first is under static electricity, paper and paper tightly sucked between, can not clean. In the printing process, because of electrostatic attraction, the sheets of paper between the close together, and sometimes two, sometimes several, and sometimes a bunch of paper is difficult to separate, resulting in suction nozzle can not afford paper, seriously affecting the printing efficiency . Plastic materials in the process of color printing, because of electrostatic discharge, often found in the edges of printed products spurt-like ink overflow, overprint deviation increases and so on; ink generated static electricity will produce shallow net or leakage phenomenon; plastic film and ink adsorption environment Dust, hair and other foreign matter prone to knives silk and other quality issues. During rewinding, slitting, bag making and other processes, electrostatic discharge will destroy the equipment optical correction system, electromagnetic control system.
Second- eliminate the static method
To combine the actual production, the use of packaging materials (packaging what products), the use of the customer's premise and so on, take a different anti-static technology to eliminate static electricity. Common anti-static technology is as follows:
1.physical elimination method
Physical elimination method is to eliminate the use of static inherent characteristics of the material without changing the function of the material. Such as "grounding" elimination method, that is, in the process of installing static electricity brush. The brush body placed in the paper or plastic coil winding or unwinding place, and make the static grounding brush grounding reliable grounding, but can not be connected to the device or guide roller. Due to equipment may be poorly grounded; sector guide rollers through the anode, the surface of natural alumina, and alumina is non-conductive.
2. chemical elimination method
Chemical elimination of static electricity that antistatic agent processing technology, mainly the antistatic agent (surfactant) by adding (filling) technology or coating technology, the resin or substrate can be modified motor method is more thorough and Perfect anti-static technology. However, because of the addition or application of antistatic agents, causing changes in the chemical composition of the material, the technology is not suitable for the treatment of paper and is only used for the modification of plastic resins.
Especially in the packaging of food, medicine, cosmetics, chemical products, etc., pay attention to safety, hygiene and compatibility with the matrix resin and so on, so the technical content is higher. With anti-static packaging materials, not only put an end to a variety of quality accidents due to static electricity, but also for customers to improve the packaging efficiency, ensuring the sealing strength, which has been recognized by customers.
3. add-type processing technology
The technology (that is, masterbatch technology) is the additive type antistatic agent according to a certain concentration (a few percent to dozens of percent) mixed with the thermoplastic resin, and add a variety of additives, by melting, mixing, granulation , Prepared antistatic masterbatch. Antistatic agent selection, pay attention to compatibility with the matrix resin. If the compatibility is poor, the prepared antistatic particles have poor performance; but the compatibility is too good, then the antistatic agent migrates to the surface too slowly, and it is difficult to form an antistatic water film. The same resin as the product resin is selected as the matrix resin. During the process of melting, kneading and granulating, the processing temperature should be kept as low as possible to prevent the antistatic agent from decomposing or even deteriorating due to poor thermal stability.
The use of antistatic particles to prepare antistatic plastic film, often using three layers (ABC) coextrusion blow molding process. Pay attention to add the proportion of antistatic masterbatch according to the concentration of its effective substance to determine, and based on test results for the appropriate adjustments to the surface resistivity ps about 1011Ω can be; increase the amount of not only increase product costs, but also later The processing operations have a negative impact.
4. coating-type processing technology
Coating antistatic agent treatment technology is made of ionic surfactant antistatic coating, coated on the plastic film surface, to prevent the effect of charge accumulation. The choice of coated antistatic agent, to be coated substrate according to the size of the work function to determine. The work function of plastic materials, it is easy to carry negative charge; its work function is small, then with a positive. Common plastic materials work function in descending order has been mentioned earlier, PP, PE easily with negative electricity, should be coated with a cationic surfactant; PET, PA is easily charged with positive, it is appropriate to use anionic surface Active agent coating. Requires plastic film surface wetting tension greater than 38dyn / cm; anti-static coating film is good, abrasion resistance, chemical resistance and lasting effect.