Some enterprises have ignored the role of antistatic agents for a long time, or are worried about reducing profits due to the addition of auxiliaries. As a result, they have not added or added proper amount of antistatic agents into the plastic substrate, ink, varnish and composite adhesive system, resulting in some failures, such as print mottling, ink whiskers, similar scraper line marks (printing defects), and image edge biting after register printing Edge, ink film wrinkling and warping after coating adhesive, breakdown and combustion during corona treatment after polishing These faults not only increase the waste rate of printed products, but also affect the economic benefits of enterprises. Therefore, it is very important to prevent and eliminate static electricity, and adding antistatic agent can solve these problems.
Causes of static electricity
When the electrical neutral ink, varnish, composite adhesive or substrate lose electrons, it will have a positive charge, otherwise, it will carry a negative charge. For example, copper powder is often used in gold ink system. However, copper powder is easy to oxidize, which leads to electrical instability. Especially after gold ink printing, when the printing surface needs to be corona treated, static electricity will be generated in the process of charge accumulation and the substrate will be broken down.
The resistivity of plastic substrate is very high, about 1010-1020 Ω· cm, which is good only as electrical insulation material. However, since we want to process it into fixed cylinder, sheet and bag, especially after decoration design, printing, polishing, coating and compounding, the surface of plastic substrate is easy to generate static electricity once it is rubbed, which leads to the continuous accumulation of electric charge, and then it can be used as electrical insulation material The dust in the air is adsorbed on the product and the value of the product is reduced.
Common faults caused by static electricity
1. Breakdown phenomenon
A printing factory in Nanyang City, Henan Province, used OPP film surface printing, coating varnish, and then corona treatment. As a result, two gold ink lines under the printing pattern appeared intermittent electrostatic breakdown fault. When the factory bought the second batch of gold ink again, printing, polishing, corona treatment, the breakdown phenomenon did not appear again. The reason is that when the static electricity exceeds a certain value, corona discharge occurs and sparks are emitted. Although the substrate breakdown is rare, these sparks can ignite flammable materials in serious cases, causing fire.
2. Similar to blade marks
When a printing factory in Weifang City of Shandong Province was printing OPP film, the full page appeared a serious fault similar to scraper line mark. Immediately return the ink to the original factory, add antistatic agent to reprocess, and then print again. The similar scratch mark does not appear again.
3. Wrinkling and deformation of pictures and texts
After a printing factory in Xiangfan City, Hubei Province, the plastic packaging bags were coated with adhesive compound. The results showed that the parts with printed pictures and texts were wrinkled and deformed, which led to the reduction of the flatness of the packaging bags. Later, by adding antistatic agent and using different polarity of different solvents to increase the ink surface tension, the fault was fundamentally suppressed.
When the above-mentioned faults occur, the thinking mode of technicians is: hard damage of printing drum, double line caused by swing of scraper, impurity (i.e. foreign matter) mixed in ink, high viscosity of ink, serious corrosion of gravure cylinder, and so on. However, it is seldom considered that static electricity will also produce similar scraper marks, spots, ink whiskers, color biting and edge drawing, breakdown, wrinkling deformation (warping edge) ）And so on.

As packaging and decoration printing ink, varnish, composite adhesive and substrate, antistatic agent should be added to improve the antistatic effect of ink, varnish, adhesive and substrate in high-speed printing, varnish coating and high-speed coating adhesive compound, and avoid the occurrence of the above-mentioned failures.

Methods of preventing and eliminating static electricity
Introduction of antistatic agents into packaging and printing ink, varnish, composite adhesive, substrate system, the following methods to prevent and eliminate static electricity.
For inner printing ink, potassium sulfate ester antistatic agent is added; for surface printing ink, nitrate antistatic agent is added at the dosage of 0.50% ～ 0.90%, which can completely prevent the printing ink layer from speckles and ink whiskers. When it is increased to 1% ～ 2%, it will prevent the similar scratch, color biting, edge drawing and deformation (warping) of graphic ink film, but excessive addition of antistatic agent often affects the product Adhesion fastness, because antistatic agents are mainly surfactants.
For solvent based varnish, composite adhesive, and PE, PP, PVC, PC, PA, PS, ABS, CN, acrylic resin, polyvinyl acetate and other plastic products, 1% - 10% quaternary ammonium salt antistatic agent can be added. The antistatic treatment by mixing method is only suitable for acrylic resin, PVC and ABS, and its dosage is generally between 0.5% and 2%.
The anti-static methods of plastics should also include: (1) direct conduction through the circuit; (2) increasing the relative humidity of the environment.
Selection requirements of antistatic agent
Antistatic agents can be divided into internal antistatic agents and external antistatic agents according to different use methods. The selection of antistatic agent should be based on the following principles.
1. External antistatic agent
The ideal external antistatic agents are usually formulated as 0.5% to 2% antistatic solutions. They are printed, coated, sprayed, impregnated, and mixed (stirring, grinding, etc.), so that they can be integrated in plastic, ink, varnish, adhesive system, or on the surface of the substrate. Therefore, the selection requirements can be summarized as follows: (1) firmly bonded to the surface of the binder; (2) non dispersing, washable and friction resistant; (3) soluble or dispersible with solvent; (4) good electrostatic removal effect regardless of high temperature or low temperature; (5) no change of printing ink and printing color; (6) low toxicity and no skin irritation; (7) good hand feeling And the price is low.
2. Internal antistatic agent
The ideal internal antistatic agent should meet the following conditions: (1) in the process of forming plastic substrate or in the process of polymerization or mixing with ink, varnish, adhesive and other binders, it can be integrated smoothly and the product has good transparency; (2) it can resist high temperature of 120-300 ℃; 3) it is compatible with plastic, ink, varnish, adhesive and other binders, It can be used together with other additives; (4) it does not cause back adhesion and adhesion of packaging and printing products; (5) low toxicity, low price and wide source of materials.
The general requirements of antistatic agent are as follows: the obtained printing ink film, varnish film and adhesive coating are uniform, with good decoration and high production efficiency, which are suitable for mass production. The utilization rate of ink, varnish and adhesive is high, and the solvent diffusion pollution and residual amount of solvent can be reduced.
Dongguan Beite packaging materials Co., Ltd. - located in Dongguan City, the world's manufacturing city, is a subsidiary of Beite packaging (China) Co., Ltd., with a plant area of 6000 square meters. It is a flexible packaging enterprise integrating R & D, production and sales. It has a complete set of domestic advanced production equipment, a scientific and humanized management system and a group of experienced technical personnel For backing, to provide customers with quality products and first-class service.
The company produces composite bags, roll film, fruit bags, aluminum foil bags, suction mouth bags, self-supporting bags, zipper bags, anti-static bags, special-shaped bags, etc., which are suitable for the internal and external packaging of food, daily chemicals, electronics, toys, medicine, cosmetics, industrial products and other industries.
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