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What ink is used to print food plastic packaging bags

by:Supouches Packaging     2022-07-12
At present, in the printing of food plastic packaging, the most widely used benzene-soluble chlorinated polypropylene ink series. This series of ink production and application technology is very mature, mainly used for gravure printing on BOPP (biaxially oriented polypropylene) printing, printing adaptability is very good, good processing performance, drying speed faster. But this printing method still has many shortcomings. 1. The ink contains toluene, and the residual solvent value of the printed product is high; 2. The thermal stability of chlorinated polypropylene is poor, and it is easy to release chlorine and form hydrogen chloride (commonly known as hydrochloric acid) in the air, which makes the ink exhibit a strong Acidity, which has a corrosive effect on the printing plate roller; 3. Benzene-soluble ink can also release substances that destroy the ozone layer. In the process of production and use, it will also cause harm to the body of production workers, and it is also easy to leave harmful substances in the finished product. , thus causing pollution to the food in the packaging bag; because of this, benzene-soluble chlorinated polypropylene ink has been gradually eliminated, and laws and regulations have also been issued in developed countries such as Europe to prohibit or control the use of benzene-soluble chlorinated polypropylene ink. . In order to avoid and solve various problems of benzene-soluble inks, environmentally friendly inks came into being and began to be widely used in various countries. Why is it named as environmentally friendly ink? That is because this series of inks will not pollute the environment during production and use, nor will it cause physical harm to the users, and will not contaminate the food in the food packaging bags. At present, there are generally three kinds of environmentally friendly series of inks widely used in China: 1. Ultraviolet (UV) curing ink The curing process of ultraviolet curing ink is a photochemical reaction process, that is, under the action of ultraviolet energy, the prepolymer is in a very short time. Internal curing to form a film, in addition to curing the surface of the ink, ultraviolet rays can penetrate deep into the liquid UV-curable ink and stimulate the further curing of the deep ink film. In traditional inks, oil-based inks are solidified under the action of oxidation, while solvent- or water-based inks are mainly cured by evaporation of water or solvents, and some inks can penetrate into paper. Therefore, compared with traditional inks, the polymerization and drying of UV-curable inks are more thorough, without any evaporation or solvent-based pollutants, and the ink film is 100% cured. UV-curable inks are mainly used for flexographic printing on soft substrates and consist of prepolymers, reactive diluents, pigments, additives, and photoinitiators/composites. Among them, 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, ink migration, wetting of the substrate, friction coefficient, abrasion resistance, pigment dispersion and stability) properties) and the smell of the printed matter; it is required that the spectral range of the pigment to absorb ultraviolet light is as small as possible. The characteristic of the reaction is no hindrance. When printing with UV-curable ink, attention should be paid to the inhibition of polymerization, surface tension and wetting, the correlation between ink viscosity and humidity, and the expansion of the printing plate; due to the poor adhesion of ink to plastic, it is necessary to The plastic is flame-treated or corona-discharged to improve the adhesion of the plastic surface. 2. Water-based ink Water-based ink, abbreviated as Yanhuang ink, flexo water-based ink, also known as liquid ink, is mainly made of water-soluble resin, organic pigment, solvent and related auxiliaries through compound grinding. Water-based ink is the ink used in most flexographic packaging printing at home and abroad. Water-soluble resin is the binder of water-based ink. 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. Dissolved or synthetic polymer emulsion, both show excellent performance. The water-based ink does not contain volatile organic solvents, which can not only reduce the toxicity of printed products, but also prevent fire caused by static electricity and flammable solvents. Water-based ink is not only a new“green”Printing ink, and it is the best product to replace benzene-soluble ink. Water-based ink is especially suitable for packaging and printing products with strict hygiene requirements such as tobacco, wine, food, beverage, medicine, and children's toys. 3. Electron beam curable ink (EB ink) Electron beam curable ink refers to the ink that can quickly 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, colorants, etc. The energy of the electron beam is high, and it has strong penetrating power to solid components such as pigments and fillers, and the ink will not be blocked by the pigments or fillers, and the drying inside the ink film will not be affected. The drying of the ink film layer after ordinary ink printing is generally because the binder in the ink is absorbed and volatilized by the substrate, and the solid substances remain on the surface of the substrate to form a thin layer of ink. Electron beam curing is a process of rapid drying and curing at room temperature by means of electron beam as irradiation energy, radiation chemical reaction with active liquid chemical formula. Since electron beam is a type of radiation, electron beam radiation can also be classified as radiation curing.
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