Requirements and selection of printing ink for the

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Requirements and selection of printing ink for flexible packaging

printing ink for flexible packaging refers to the process ink that uses the printing machine to print on "soft" packaging materials such as plastic film, woven bags, aluminum foil and roll packaging paper. According to the different types of printing plates, they can be divided into intaglio ink, relief ink and flexographic ink; According to the main components of ink, it can be divided into solvent ink, alcohol soluble ink and water-based ink; Root mm; According to the different surface of the printed object, it can be divided into surface printing ink and internal printing ink

requirements of ink for flexible packaging

the application scope of flexible packaging products is mainly people's daily life, which generally requires multiple transportation and long use time. Moreover, with the increasing improvement of consumer aesthetic standards, the printing quality must also be improved. In the process of daily use, the ink should not fade or change color due to light; The adhesion should have a certain fastness, and it will not fall off under the bending and general friction during the packaging process; In the printing process, it should have good printing overprint adaptability. When the printing surface is in roll shape, it is mainly for aerospace, automobile, public transportation, oil and natural gas and other industrial end markets with harsh environment, and does not bond with other surfaces; In terms of stability, it is required to be able to withstand the solvent in the adhesive during compounding and the acid-base, oily and other components in the packaging, as well as the heat during later processing; Suitable for cold 78 elastomer modified asphalt waterproof coiled material areas and frozen storage; In addition, there are many other testing items about viscosity, volatility, fineness and so on. The relevant contents have national standards, which will not be repeated here

in recent years, with the continuous improvement of productivity, printing machines have higher and higher requirements for the performance, quality and function of inks in the process of improving printing quality and speed. High requirements are put forward for flexible packaging inks in improving the purity and saturation of color, reducing the thickness of ink film, improving the adhesion and gloss, reducing energy consumption and using pollution-free and recyclable materials. Especially in environmental protection, solving the environmental pollution problem in the process of ink manufacturing and use is the most urgent topic at present. Many developed countries have formulated strict laws and regulations, established strong control and monitoring institutions, and constantly studied and developed various effective solutions, such as the use of environmental protection materials, the suppression and recycling of the discharge of harmful pollutants, etc. In the past, because the plastic film is difficult to adhere, the binder of the gravure printing ink used on it is generally made of chlorinated polymers, but in the production process, chlorinated polymers need to use strong solvents (such as aromatic solvents such as toluene) to dissolve and adjust the viscosity, which will be harmful to the health and safety of workers in the production process, and the residual solvents in the packaging will also be toxic to the human body, In addition, chlorofluorocarbons volatilized from chlorinated polymers will destroy the ozone layer. Therefore, their use has been restricted in many developed countries. In order to meet the requirements of environmental protection regulations, flexible packaging inks have developed new systems to meet the requirements of environmental protection, such as water-based inks and alcohol soluble inks. Among them, water-based inks are products that meet the requirements of environmental protection. However, due to the high surface tension of water, up to 72 dyne/cm, the inks are difficult to wet and dry slowly. According to the current technical level, they cannot fully meet the standards of flexible packaging inks. In addition, in order to use water-based ink in gravure printing machine, not only ink and resin need more advanced technology, gravure printing equipment also need to be improved. For example, it is necessary to change the etching roller with a groove of about 38 ~ 42 microns into a laser plate making roller with a groove depth of 24 ~ 28 microns, and to have more effective and powerful drying equipment, which requires a lot of investment. So far, flexible packaging water-based ink has not been widely used in Europe and the United States and other major countries. Because water-based inks can not fully replace toluene inks, the ink industry has developed alcohol soluble inks that are easy to be accepted by the environment. Using alcohol and other low toxic alcohols removed from the VOC list as solvents can solve the health damage caused by toluene inks and the problem that solvent residues affect the quality of packaged food. In developed countries, alcohol soluble inks have fully replaced benzene inks. It can be predicted that alcohol soluble inks will also be widely used in flexible packaging in China in the near future

selection of ink for flexible packaging

before selecting ink, it is necessary to first determine the printing substrate type of ink. Even if it is the same kind of material, you should also understand in detail the material composition, manufacturer, grade, additives, pretreatment process, etc. of the substrate, and then select the applicable ink type according to the above characteristics. When selecting ink, you should also pay attention to the following four influencing factors:

1 Printing conditions. Including printing speed, capacity of drying equipment, shape and number of lines of printing plate, number of printing colors, printing sequence, temperature and humidity conditions of printing workshop, etc. The drying of ink is the most important link that affects the printing quality, and the drying speed is affected by various factors such as printing machine and environment, which is the main factor that leads to the instability of printing effect and the defects of printing quality

2. Printing effect. Including printing color, hue saturation, transparency, gloss, surface printing or internal printing, whether there is additional printing gloss surface, etc. The printing effect is directly related to the dispersion degree of pigment particles in the ink. When the pigment particles are reduced, the color intensity will increase rapidly, that is, better gloss and transparency can be achieved. In order to prevent the condensation of organic pigments, it is necessary to add a suitable dispersant

3. Processing conditions. Most printed products become finished products after one-time processing. For this processing condition, we must judge whether it adapts to the characteristics of ink, which is also an important part of ensuring product quality. Especially in the subsequent compounding process, the compatibility with adhesive, compounding strength, heat sealing strength, etc. are closely related to the type of ink and the resin binder therein, which need to be tested and investigated in advance

4. Purpose. Before printing, we should also know the final use and use status of the product, which should be paid special attention. For example, the packaging of daily chemical products must have certain acid and alkali resistance, oil resistance of oily food packaging, low temperature resistance of frozen packaging, etc. for some special packaging that requires high-temperature cooking, not only the connecting resin of the ink must have high temperature resistance, but also the pigment in the ink needs good high-temperature decomposition resistance. For packages with special requirements, sufficient tests should be carried out after full consultation with customers, otherwise it is easy to cause quality problems

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