Each process of flexible packaging may cause safety accidents due to static electricity, especially the two processes of printing and compounding. This is particularly because both processes use solvents. A slight negligence may cause a fire. At the same time, bag making When it comes to static electricity, it will also cause problems such as poor opening, irregularity, and sticky knives. Static electricity, a seemingly small factor, has a wide-ranging impact on our production, which should attract our attention.
I. Quality accidents caused by static electricity
1. Case 1: Air bubbles generated by static electricity
In September 2013, a packaging company in Hangzhou, Zhejiang printed on PET. When AL was compounded, it was found that there were bubbles in the edges of the color blocks of the ink immediately after the compound machine was lowered. As shown in Figure 1.
The company's compound master and technical department exhausted various methods, including increasing the amount of glue, lowering the compounding speed, and increasing the compounding pressure.
Finally, after repeated inspections, the analysis found that the root cause of this problem was that the static electricity during printing was not released. After the glue is applied, the unreleased static electricity in the ink will be released outward when it encounters glue and solvents. When releasing, push the coated glue on the edge of the pattern outwards, causing some points to be glueless at the edges, and eventually form bubbles.
In addition, PET printing will generate more static electricity than other types of films . Without static elimination facilities, it will definitely not be completely discharged.
Finally, by adding isopropyl alcohol, a solvent that can eliminate static electricity, to the diluted solvent of the ink during printing, and then printing and compounding, the bubble phenomenon was completely solved.
2. Case 2: Fire caused by static electricity
In April 2013, when a packaging company in Jiangsu printed BOPP and composite CPP film, it caused a fire due to static electricity.
It was such a composite bag that caused this electrostatic accident, as shown in Figure 2:
When printing the composite bag, there is a gold strip in the horizontal direction, and the gold is only 2 cm away from both sides of the film. Metallic substances are added to the golden ink itself, so when they are compounded, a large amount of static electricity is generated by the friction between the metal substance and the machine, which cannot be completely eliminated by the static elimination device. (If the golden ink is from the left to the right of the film, and If this is not the middle one, the static electricity will certainly be much smaller). Then, sparks generated by static electricity caused fire when they encountered glue and solvents.
One point that we should pay attention to in this case is: Don't underestimate the pre-press design of the package, it profoundly affects every step of the subsequent process.
Second, the harm of static electricity to flexible packaging production
In the printing process, because static electricity is not handled well, there may be accidents: sparks generated by static electricity cause the ink and solvent to ignite, resulting in fire. The edges of the printed pattern caused by static electricity are fluffed. Static electricity makes the ink leveling on the film worse, and the pattern is intermittent, as if it cannot be printed. The winding is uneven due to static electricity.
In the composite process, static electricity may cause accidents: sparks generated by static electricity may cause glues and solvents to catch fire, resulting in fire. Static electricity can cause the composite film to be rolled unevenly. Since the static electricity is not completely discharged during printing, air bubbles will be generated at the edges of the pattern during compounding.
3. Measures for eliminating static electricity in flexible packaging enterprises
1. It is necessary to strengthen the safety awareness of employees and provide safety training to operators.
2. When the weather is dry, increase the humidity on the production site to eliminate static electricity.
3. Strengthen the elimination of static electricity, install effective grounding devices, and install static eliminators.
4. When printing gold and silver inks, use inks produced by well-known manufacturers, because there will be antistatic agents in it, which will greatly reduce the generation of static electricity.
5. When printing polar films (NY, PET), you can consider adding a solvent to eliminate static electricity in the diluted solvent, such as isopropyl alcohol and methyl ethyl ketone to eliminate static electricity.
6. Lowering the speed of the machine and reducing the tension of unwinding and unwinding can also eliminate some static electricity.