Water-soluble ink adhesion characteristics in printing

Water-soluble inks are not always environmentally friendly inks, and water-soluble inks are diverse when dissolved in water. It is not only that the multiphase equilibrium emulsion system can be compatible with water, the homogeneous equilibrium system in which the mixed surfactant forms a micelle can also be miscible, and the ink mixed with a large amount of certain organic solvents can also be miscible with the aqueous phase. After these organic compounds volatilize, they naturally pollute the ecological environment and endanger human health. It has been seen that some water-soluble inks are not environment-friendly inks, which contain excessive amounts of organic volatiles, or even organic solvents that are seriously polluting the environment and endanger the health of producers, operators, and consumers (benzenes, etc.). People favor environmentally-friendly inks based on a consensus that human beings need to cherish and protect the ecological environment of the earth for a long time to survive and develop. The green products of ink and wash ink are also adapted to this rising demand for environmental protection and are increasingly valued and developed. Applied.

With the rapid development of simple and efficient flexographic printing technology and processing production lines, ink-jet manufacturing and ink-and-wash printing will all have a broader development market. Such as corrugated box printing, paper bags, paper cups, carton printing, newspaper printing, decorative printing and so on. However, with regard to the current number of ink and ink prints, the water-based varnishes are much larger than the water-based inks, which is related to the high price of water-based inks. Although the price of UV varnish is higher than that of waterborne varnish, the gloss of its printing products is high. Its excellent physicochemical mechanical properties and decorative effects make it occupy a certain market share. The price of water-based color ink is also reasonable. Due to the high concentration of color ink pigments, the price of new materials is slightly higher. The development and design of products need to invest manpower and time, consume more research funding, and should also be compensated. From the point of view of the ink manufacturers, always putting the quality of the customer's printed matter first is the glorious mission of R&D and manufacturing of ink. It is normal that good-quality environment-friendly ink and wash should meet the following requirements:
1. Adhere to the substrate firmly. 2, low odor or tasteless. 3, good fluidity, PH value and viscosity stability, suitable for printing.

4, ink film resistance to water, scratches and other high resistance, its bright color feel good, decorative and beautiful.

The author has also seen that the imported ink-and-seal printed plastic bags are easy to peel off. It is believed that the solution to the good adhesion of the ink to the substrate is still the basic requirement for ink printing. We selected different macromolecule polymer resin binders and special auxiliaries, and used electronic peeling testers and transparent materials manufactured by Shandong Jinan Languang Electromechanical Technology Development Center for different substrates of paper, tobacco packets, aluminum foil and plastic films. The plastic tape was used as a comparative test to better solve the problem of enhanced paint adhesion of paper and ink and artificial marble handicrafts. Improve the application of water-based fluorescent security inks and water-based temperature-change security inks on non-absorbent materials.

Substrate substrates have different surfaces, and the paper material has countless fiber capillary pore structures. These untreated paper surfaces have a large number of holes to absorb ink. After printing, the ink penetrating into the fiber and the surface ink film form a kind of embedded mechanical riveting force, which is relatively difficult to occur with respect to the plastic film substrate. This type of mechanical staking force is related to the inner diameter of the hole. The area of ​​the attached interface varies with the type of paper, which directly affects the speed and depth of the final infiltration, resulting in differences in adhesion and the difference in surface gloss of the ink film. And some paper's flexural deformability.

If the surface of the paper is subjected to special sealing treatment, the capillary cavity is completely blocked, and the ink cannot penetrate, and no riveting force can be used. Like the polyolefin film material, the surface is very smooth and cannot absorb ink. The original brand of ink may cause serious damage. Shedding phenomenon. At this time, through experiments, the use of suitable special additives (including pigment dispersants, coupling agents, defoamers), and their strong surface activity have greatly reduced the surface free energy of water. The overall surface tension of the ink is lower than the critical surface tension of the substrate, and the ink wets the substrate more easily, and then diffuses to form the interfacial force. According to the Lewis acid-base theory, the interfacial forces include van der Waals forces and chemical bonding forces. The formation of chemical bonds contributes the most to the adhesion. Generally, the covalent bond force is 100 to 1000 KJ/mol, while the van der Waals interaction and hydrogen bond generally do not exceed 50 KJ/ Mol. The use of coupling agents facilitates the formation of chemical bonds and improves the ability to adapt to the environment. Everyone said that benzene-based organic solvents are harmful, but one has never heard anyone say that benzene-based organic solvents are useless, so alcohol-soluble inks with low VOC emissions in place of benzene-solvent inks are also conducive to environmental protection in the process of plastic film gravure printing. There will be quite a wide range of applications. Therefore, we study the ink wash in the absence of benzene solvents and other organic solvents, try to reduce the surface tension of the ink, only the good wettability can weak the surface of the substrate, showing good adhesion, leveling and Dryness. It is the first time that the paper material is still immersed in the surface layer and then diffused into the interior, so that it can form a mechanical riveting force or a chemical bond force, leaving a smooth and bright ink layer on the surface.

The practice shows that the high color concentration and non-corrosiveness of the ink increases its application method, so that the temperature change effect of the water-based temperature-change security ink becomes more pronounced and more prominent, and the adhesive strength on the aluminum-plated plastic film outperforms the solvent. Ink. It is often the case that the ink is used as the primer and then the solvent ink is printed to avoid the defect that the latter bites the coating and is not firmly attached. Ink binders are critical to adhesion and affect the ink's viscosity, gloss, and printability. When selecting ink polymer binders, it is not impossible to use rosin modified maleic acid resin or polyvinyl alcohol resin. The key is to see the application and use occasions. In order to improve the adhesion, diffusion type acrylic emulsion, liquid styrene-acrylic emulsion and alkali-melting acrylic resin can be used as the linking material. Generally, the adhesion of macromolecules and emulsions with lower glass transition temperature is better. Of course, we cannot ignore the printability when we study the properties of ink adhesion.

Source: 21st Century Fine Chemicals Network