Suitable for food plastic packaging printing ink

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 printing adaptability, good post-press processing performance and fast drying, due to the relatively high relative toxicity of (1) toluene, the residual solvent value of printed matter is high; (2) the thermal stability of chlorinated polypropylene is poor. , During the production and storage process, it is easy to release chlorine to form hydrogen chloride, making the ink more acidic, producing heavy corrosion on the printing plate roller; (3) benzene-soluble ink can damage the ozone layer, in the course of use The health and safety of workers are jeopardized. 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:

1. 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) curable inks UV curable inks refer to the cross-linking reaction of the binder in the ink under the irradiation of a certain wavelength of ultraviolet light, from the liquid to the solid-state curing ink, before the binder is dissolved, The macromolecule prepolymer firmly forms the 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 Inks (EB Inks) Electron beam curing inks are inks that can rapidly change from liquid to solid state under the irradiation of high-energy electron beams, also known as EB inks. 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. The composition of EB ink is mainly composed of pigments, binders and auxiliary agents. Since the curing of ink is realized by electron beam, the choice of binder material has specific requirements. The main components of acrylic ink are acrylic resin and participate in the reaction. The active monomer. Most of the food and beverage packaging industry adopts electron beam curing printing, and the printing method is offset printing. EB inks have been adapted to the development direction of high-speed, multi-color one-time printing in the printing industry. Since electron beam curing ink saves energy, components do not contain solvent, no pollution to environment and packaging, short curing time, high processing speed, high yield, small dot gain rate, good imprinting brightness, abrasion resistance and chemical resistance With such advantages, this technology has been rapidly promoted and applied, especially in the food packaging field. The main difference between EB inks and LIV inks is the presence or absence of photoinitiators in the vehicle. UV curing is also possible when a certain amount of photoinitiator is added to the EB ink.

4. Digital Printing Ink: Digital printing technology is infiltrating into the food packaging and printing industry as people's increasing demand for personalized packaging. With digital printing technology, a sufficiently high image resolution can be achieved and the details of the image can be ideally reproduced. In addition, digital printing technology can provide faster and smaller batches of services. Digital printing inks can be divided into ink dyed inks, electrostatic printing solid toners, and digital offset electronic liquid inks according to the different printing methods used. The toner is melted and fixed on the printing material after being heated by ceramic crystals. Most printing materials are foil, metal aluminum, PET (polyester), paper, etc., and are suitable for printing webs. It is important that the toner is selected with a suitable fixing temperature, because the optimum fixing temperature can control the fixing process of the toner well. The toner should have a certain degree of flexibility to facilitate folding processing of the printing material. Solvent resistance is also very important for electrostatic digital printing. Prints with poor solvent resistance will not be able to complete the next process, such as light and film.

In today's green environmental protection has become the subject of the printing field, more and more high-quality, multi-color printing is required for food packaging. Therefore, the printing ink must adapt to the call of the development of the times, toward the direction of benzene-free, environmental protection.