Three kinds of environmentally friendly ink for food packaging and printing

With the improvement of living standards, people have put forward higher requirements for food packaging. As a printing material, ink must comply with the principle of no transfer when it is used in food packaging. Food packaging should not use conventional inks. The printer manufacturers must ensure that the solvents in the inks are completely evaporated after printing. The inks are required to be completely cured and meet the applicable standards of the application industry.

In the current food plastic packaging printing, benzene-soluble chlorinated polypropylene ink is the most widely used. The production and use of this type of ink technology have been mature, mainly used in the printing of BOPP (biaxially oriented polypropylene) materials, and the use of gravure printing. Although this ink has excellent printability, good after-press processing performance and fast drying, it is due to:
(1) The relative toxicity of toluene is relatively high, and the residual solvent value of printed matter is high;
(2) The thermal stability of chlorinated polypropylene is poor. During the production and storage process, chlorine is easily released to form hydrogen chloride, making the ink more acidic and producing heavy-weight corrosion on the printing plate roll;
(3) Benzene-soluble ink can damage the ozone layer, and it will also cause harm to the health and safety of workers during use. Residues remaining in the packaging products will cause certain levels of contamination of the food in the package under certain conditions. . This kind of ink is tending to be eliminated. In Europe and some developed countries, regulations for prohibiting or controlling the use of this ink have been formulated.

Due to various problems with benzene-soluble inks, environmental-friendly inks have emerged. The use of environmentally friendly inks does not cause any pollution to the environment, nor does it cause any physical harm to the operators, and it does not cause damage to the interior foods.

The green inks that are already on the market include:

Water-based ink

Water-based ink is the ink used in most flexographic packaging and printing at home and abroad. It is mainly composed of water-soluble resin, organic pigments, solvents and related additives through compound grinding. Water-soluble resin is the link material of water-based ink, and water-soluble acrylic modified resin is often used as the linking material in China, and its heat resistance, weather resistance, chemical resistance, pollution resistance and glossiness have significant advantages, regardless of direct dispersion. Dissolving or synthesizing polymer emulsions, all show excellent performance. Water-based inks do not contain volatile organic solvents, which can not only reduce the toxicity of printed products, but also prevent them from catching fire due to contact with static electricity and flammable solvents. Water-based ink is not only a new type of "green" printing ink, but also the best alternative to benzene-soluble ink.

2. Ultraviolet (UV) curing ink

UV-curing ink is a kind of ink that undergoes cross-linking reaction in the ink under irradiation of a certain wavelength of ultraviolet light, and changes from liquid to solid-state curing ink. Before the linking material is dissolved, the macromolecule prepolymer is firmly fixed. Form ink film. UV-curing inks are mainly used for flexible printing of flexible substrates. They consist of prepolymers, reactive diluents, pigments, additives, photoinitiators/composites. The choice of reactive diluent has an impact on the migration reaction in the ink formulation; the performance of the additive on the ink (printability, migration of the ink, wetting of the substrate, coefficient of friction, abrasion resistance, dispersion and stabilization of the pigment) Adjust the odor of the product and the printed matter; require the pigment to absorb the ultraviolet light in a spectral range that is as small as possible. The ideal pigment should have good dispersibility, good leveling property, strong coloring power, small UV absorption under light irradiation, and polymerization Responsive features. When printing with UV-curing inks, attention should be paid to the inhibition of polymerization reaction, surface tension and wetting, the dependence of the viscosity and humidity of the ink, and the swelling of the printing plate; due to the poor adhesion of the ink to the plastic, it is necessary to print. Plastics are treated by flame or corona discharge to increase the adhesion of the plastic surface.

3. Electron beam curing ink (EB ink)

Electron beam curing ink is an ink that can rapidly change from a liquid to a solid state under the irradiation of a high-energy electron beam, which is also called EB ink. The electron beam energy is high, and it has strong penetrability for solid components such as pigments and fillers, and the ink will not be hindered from being absorbed by the pigment or filler, and the internal drying of the ink film will not be affected.