On the Selection of Gravure Printing Inks

In the soft packaging printing materials, ink quality and technical performance are the most important factors affecting the quality of packaging materials. As the selection of gravure ink for technical personnel of flexible packaging companies, their applicability and economy must be considered. I. Selection of suppliers The selection of upstream suppliers shall be based on the internationally accepted IS09001 quality assurance system requirements, first trial of ink, and draw conclusions based on the opinions of technology, production personnel and customers to meet the requirements. Because the printability of inks is related to the ambient temperature and humidity, the choice of ink supply companies must also consider the differences in the climate, giving priority to companies that are geographically close. The inspection of qualified suppliers mainly includes comprehensive assessment of product quality, technical performance, price, delivery time, technical service, and customer satisfaction. In particular, it pays attention to the supplier's technical service and communication skills. When there is a problem with printing quality, Can actively participate in the settlement, and can assume its due responsibilities. We must pay attention to the importance of ink quality in packaging and printing, and strengthen the management of ink production enterprises as an upstream customer, and achieve "win-win development" in the value chain. Second, the ink's applicability In the selection of ink, we must first consider the applicability of the ink. The applicability of the ink should be based on the following aspects:

1. Printed substrates with different resin printing substrates should use inks with different resin systems. The commonly used printing substrates include BOPP film, BOPE film, BOPA film, PE film and so on. According to the "similar compatibility" principle, only the matrix resin is similar or similar, and the printing substrate and the ink will have good adhesion. In the ink system, the binder resin plays a key role in adhesion. Gravure inks currently developed are classified into benzene solvent type inks, alcohol solvent type inks, and water solvent type inks. According to the binder resin is divided into chlorinated polypropylene ink, polyurethane ink, polyamide ink and so on. The chlorinated polypropylene ink is suitable for the printing of BOPP film; the polyurethane ink is suitable for the printing of BOPET film and BOPA film, and can be used for high temperature cooking and boiling; the polyamide ink is suitable for the surface printing of BOPP film and PE film.

2. Printing process conditions The printing process conditions include printing speed (line speed), drying capacity, plate roller performance, gravure printing mode (table printing, lining printing), printing color number, printing sequence, ambient temperature, humidity, and the like. The process conditions directly affect the transfer rate of the ink, the drying speed, etc., so the ink must be selected reasonably and economically according to the process conditions. For example, when the humidity at the production site is high and the printing speed is high, high-grade inks with high transfer rates and fast drying speeds are used to prevent the film from sticking after printing. Under the conditions of air drying and high printing speed, the ink with high viscosity and antistatic agent is used to avoid quality problems caused by static electricity.

3, printing effect Printing effects include the hue, gloss, transparency, hiding, leveling, overprint accuracy of printed products. Different ink manufacturers have some differences in terms of hue, solid content, viscosity, glossiness, level expression, etc. Even inks produced by the same manufacturer and different batches are not the same. Therefore, when doing the same product, after obtaining the customer's approval of the sample draft, use the same batch of ink as much as possible to ensure consistency with the sample.

4, after the printing process conditions Plastic film after printing, but also after extrusion composite, 1000-type composite, vacuum aluminum plating, cutting, bag making and other processes, even when the customer is using high-temperature cooking, boiling, freezing, Sterilization and other treatment. Therefore, the ink should be selected according to the post-printing process conditions and application conditions of the packaging materials. For example, when performing dry compounding, the adaptability of the ink and adhesive in the ink should be taken into account so that the peel strength of the compounded product is not affected. In the process of bag making, high-temperature cooking, boiling, freezing, etc., the high and low temperature resistance of the table printing ink should be taken into account to prevent problems such as detachment and discoloration of the ink film.

5, the customer's conditions of use ink as an organic system consisting of pigments, additives, binders, fillers and solvents and other chemical substances, formed by printing ink film attached to the plastic substrate. As a packaging material for various products, not only must play a marketing role to attract eyeballs, but also play a role in ensuring product quality and protecting the lives of consumers. Therefore, the choice of ink must first consider the health and safety of the ink, and tasteless, its resistance to meet the customer's conditions of use.

Ink resistance includes light resistance, heat resistance, grease resistance, chemical resistance, and good compatibility with the packaged product. Table printing inks are resistant to friction, oxidation, water, and light, and have some antistatic properties. Can meet the resistance of the ink, while the added additives should be hygienic and non-toxic; no need to add the filler requirements do not add. Third, the economics of ink The economics of ink not only include the price, but also includes the quantity. According to the demand for materials provided by the production department and the "raw materials consumption quota" compiled by the technical department, the amount of ink purchased will be calculated. While achieving economic procurement as much as possible, it is also necessary to reduce the use cost based on actual production conditions.

Because the ink, especially the toning ink, is different from other raw materials, once it is left over, it is very difficult to use it again, and it has to be abandoned, resulting in waste. Achieving proximity to “zero inventory” not only reduces the occupation of funds, but also selects the bias of the original color ink according to the customer's requirements, ensuring consistency of the hue of the printed products. For example, the primary colors of red are partial red and purple, and the primary colors of blue are partial sky blue and partial purple. The primary yellow points are greenish and red. In the absence of artificial control of the temperature and humidity of the site environment, it is necessary to select inks containing different additives for different on-site environments, thereby reducing the increase in use costs caused by the temporary addition during the printing process. In addition, the ink is also required to have a certain anti-static performance, to prevent electrostatic adsorption of air generated by friction with the plate roller, as well as foreign matter such as hair, dust and the like in the environment, resulting in print quality problems. Flexible packaging companies should strengthen communication and understanding with ink production companies, let ink production companies fully understand their own printing equipment, including printing speed, printing substrates, drying methods and capabilities, on-site environment, composite adhesives, end-user requirements and The packaged products, etc., are conducive to the formulation of suitable inks. In order to achieve product quality controllability and traceability, each batch of ink must be tested for quality at the factory and in the factory, including items such as viscosity, fineness, solids content, and appearance.


Source: 21st Century Fine Chemicals Network

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