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Which inks are needed for the printing of food packaging bags

In the printing of food plastic packaging bags, how to choose the printing ink is very important. Now the requirements for food packaging are becoming more and more strict, and the ink can not have any residual environmental protection ink. In Europe and other developed countries and regions, laws and regulations have been introduced to prohibit or control the use of benzene-soluble chlorinated polypropylene ink.

Why is it named environment-friendly ink? That is because this series of inks will not pollute the environment, cause physical harm to the users, and will not pollute the food in the food packaging bag during the production and use process.

At present, there are three kinds of environmentally friendly ink widely used in China:

1. Ultraviolet (UV) curing ink

The curing process of UV curing ink is a photochemical reaction process, that is, under the action of UV energy, the prepolymer is solidified into a film in a very short time. In addition to causing the surface curing of the ink, UV can penetrate into the liquid UV curing ink and stimulate the further curing of the deep ink film. In traditional ink, the ink based on oil is solidified under oxidation, while the ink based on solvent or water is solidified mainly by evaporation of water or solvent, and part of the ink can penetrate into the paper. Therefore, compared with traditional ink, the polymerization and drying of UV-curable ink is more thorough, without any evaporation or solvent pollutants, and the ink film is 100% cured. UV-curable ink is mainly used for flexible printing on soft substrates. It consists of prepolymer, reaction diluent, pigment, additive, photoinitiator/composite. The choice of reactive diluent has an impact on the migration reaction in the ink formula; The additives adjust the performance of the ink (printability, migration of the ink, wetting of the substrate, friction coefficient, abrasion resistance, dispersion and stability of the pigment) and the smell of the printed matter; It is required that the spectral range of ultraviolet absorption of pigment should be as small as possible. The ideal pigment should have the characteristics of good dispersion, good leveling, strong coloring power, small ultraviolet absorption under light irradiation, and no harm to polymerization. When printing with UV-curable ink, attention should be paid to the inhibition of polymerization, surface tension and wetting, the correlation between viscosity and humidity of ink, and the expansion of printing plate; Due to the poor adhesion of the ink to the plastic, it is necessary to conduct flame treatment or corona discharge treatment on the printed plastic to improve the adhesion of the plastic surface.

2. Water-based ink

Water-based ink, which is also referred to as flaming yellow ink for short, and flexographic water-based ink, which is also referred to as liquid ink, is mainly made of water-soluble resin, organic pigment, solvent and related additives through composite grinding.

Water-based ink is currently used by most flexographic packaging printing at home and abroad.

Water soluble resin Water based ink binder, water soluble acrylic modified resin is often used as binder in China. Its heat resistance, weather resistance, chemical resistance, pollution resistance and gloss have significant advantages. Whether directly dispersed and dissolved or synthetic polymer lotion, it shows excellent performance. Water based ink does not contain volatile organic solvents, which can not only reduce the residual toxicity of printed products, In addition, it can prevent fire due to contact between static electricity and flammable solvent.

Water-based ink is not only a new type of "green" printing ink, but also the best product to replace benzene soluble ink. Water-based ink is especially suitable for packaging and printing products with strict sanitary conditions, such as cigarettes, alcohol, food, beverages, drugs, children's toys, etc.

3. Electron beam curing ink (EB ink)

Electron beam curing ink refers to the ink that can rapidly change from liquid to solid under the irradiation of high-energy electron beam, also known as EB ink.

Electron beam curing ink is mainly composed of pigments, binders, auxiliary agents, pigments, etc. The electron beam has high energy and strong penetration to solid components such as pigments and fillers. The ink will not be blocked and absorbed by pigments or fillers, and the drying inside the ink film will not be affected.

The drying of the ink film after the printing of ordinary ink is generally due to the absorption and volatilization of the binder in the ink by the substrate, while the solid substance remains on the surface of the substrate, forming a thin layer of ink.

The electron beam curing is a process of rapid drying and curing at room temperature by using the electron beam as the irradiation energy and reacting with the active liquid chemical formula.

Because electron beam is a kind of radiation, it can also be classified as radiation curing.

Radiation curing is a new technology developed on the basis of existing science and technology. It mainly uses a scanning electron accelerator. During radiation curing, the electron beam of the electron accelerator scans the surface of the substrate to achieve curing processing. Its basic meaning is to use ultraviolet light or electron beam as the energy source to initiate a chemically active liquid formula and realize a rapid reaction curing process on the surface of the substrate. The biggest advantage of UV curing and electron beam curing technology, which is different from traditional technology (such as thermal curing), is that radiation curing uses high-efficient ultraviolet light or electron beam as the initiation means to quickly realize coating curing. Among them, electron beam radiation is composed of a group of accelerated electron flows. Under the action of high-energy electron beams, free radicals or ionic radicals are generated. Free radicals or ionic radicals are then cross-linked with other substances to form a network polymer. Compared with ultraviolet light, particle energy is much higher than ultraviolet light, which can ionize the air. In addition, electron beam curing generally does not require photoinitiator and can directly initiate chemical reactions, The penetration of matter is also greater than that of ultraviolet light.

With the improvement of national requirements and standards for the printing industry, the importance of environmental awareness and the continuous development of environmental protection printing technology, consumers have higher requirements for food packaging, which also puts forward higher requirements for the use of ink materials in printing. Therefore, environmentally friendly ink will become one of the mainstream printing materials in the future food packaging industry.