Talking about a New Type of Green Packaging Printing Ink--Water Based Ink (I)

With the continuous improvement of human environmental awareness, green environmental protection has become the theme of development in the 21st century. In recent years, many countries have added a lot of requirements and restrictions on packaging and printing in terms of hygiene and environmental protection. Especially for food packaging and printing, due to the use of organic solvent inks and coating oils, hydrocarbons are emitted and the air is contaminated. Detrimental to health, so far the food packaging and printing in developed countries has basically no longer use solvent-based printing materials. Research and development and application of small pollution, less pollution, and even pollution-free green packaging and printing materials become an inevitable requirement for the development of green packaging, environmentally friendly green packaging and printing materials will be more attention and development.

First, the composition of water-based ink

Water-based inks are inks prepared from a combination of specific aqueous polymer resins, pigments, and water, and the addition of co-solvents via physical and chemical processes, referred to as ink. The difference between solvents is the biggest difference between water-based inks and solvent inks. Water-based inks use water as the solvent. After the ink is transferred to the substrate, the water evaporates into the environment or penetrates into the substrate. The ink dries with the evaporation of moisture. Water-based polymer resin is the most important component of water-based ink. It mainly acts as a linker in the ink. It allows the pigment to be uniformly dispersed, so that the ink has a certain degree of fluidity, and provides adhesion with the substrate material. The ink can form a uniform ink layer after printing. At present, most of the research and development use of alkali-soluble resin, this type of resin can be dissolved in water, made of water-based link material, printing and drying into insoluble substances. The hue of the ink depends mainly on the pigment. The pigment is distributed uniformly in the binder in the state of particles. The pigment particles can absorb, reflect, refract, and transmit light, and thus can exhibit a certain color. General requirements Pigments have a bright color, suitable coloring power and hiding power, and a high degree of dispersion. In addition, depending on the purpose of use, it is also possible to select specific solvents that are resistant to different resistances. The role of the solvent is to dissolve the resin so that the ink has a certain degree of fluidity, and can be smoothly transferred during the printing process, and the viscosity and drying performance of the ink are adjusted. Auxiliaries have a great influence on ink performance and are an indispensable part of ink painting. Commonly used additives in inks are pH stabilizers, slow drying agents, defoamers, dilutants, and the like.

Second, the characteristics of water-based ink

1, environmental characteristics

Water-based ink as a new type of packaging printing material, its biggest advantage is that it does not contain volatile organic solvents, its use reduces the amount of organic volatiles (VOC), will not harm the health of ink manufacturers and printing operators, improve The environmental quality, so it is known as environmentally friendly ink. The biggest feature of water-based ink is no pollution to the environment, no impact on human health, not easy to burn, and good safety. It can not only reduce the residual toxicity on the surface of the printed matter, make the printing equipment easy to clean, but also reduce the risk of fire due to static electricity and flammable solvents. Therefore, in this sense, the water-based ink is a new type of “green” packaging printing material. .

2, printing characteristics

In addition to the advantages of environmental characteristics, water-based inks also have better printing properties. The ink is stable, does not corrode the plate, is easy to operate, is inexpensive, has good post-print adhesion, is strong in water resistance, and is relatively quick to dry (printing speeds up to 150-200 m/min). In addition to the use of water-based ink gravure, but also for the development of a great potential for flexo and screen printing. However, due to the high boiling point of water in the water-based ink, the heat of evaporation is large, the drying of the printed matter is slow, and the hot air drying device is required. In addition, the printed matter of some inks may also be hygroscopic and anti-adhesive due to the excessively high humidity, and the gloss of the printed matter is relatively poor.

In short, current water-based inks still have some problems in the process and materials that need to be solved. For example: dryness, glossiness, the problem of print deformation caused by the absorption of water by the substrate, and the occurrence of air bubbles after the film is applied, especially the drying problem becomes the biggest problem in the application of water-based ink.

Third, the application of water-based ink

From a printing point of view, water-based inks are not yet suitable for offset printing, and its main application areas are flexographic printing and gravure printing.

1. Application in flexo printing

We know that most flexo and gravure products are packaged products, and food packaging, tobacco and wine packaging, children's toys, etc., account for a large proportion of packaging materials that require strict sanitary conditions. Therefore, there is an urgent need for “green” printed materials. Water-based ink is undoubtedly one of the best choices. Under the impact of the “green revolution” set off in the world, flexo printing has developed rapidly. The main reason is that the vast majority of flexographic inks use water-based inks, have excellent environmental performance, and are in line with the development trend of modern packaging and printing. In the U.S., 95% of flexographic products use water-based inks. In Japan, 70% of flexographic plates are used for printing on corrugated cardboard, and 95% of them use water-based inks. In China, the proportion of flexo printing is increasing day by day. There are nearly 200 narrow-width flexographic printing production lines in China, which require more than 100,000 tons of water-based ink annually.