Green ink in flexible packaging applications

In recent years, China's ink industry has achieved rapid development. Its output has continued to grow rapidly, and the level of application of new technologies and new equipment continues to increase. The production technology level and product quality of most enterprises have been greatly improved, and the market for environmentally-friendly ink products is rapidly increasing. Growing, people are increasingly valued. In particular packaging inks, as an important growth area of ​​the global ink, environmentally-friendly products are becoming large-scale, and the important trend of current packaging and printing materials is to improve their environmental performance, choose energy-saving, low-consumption, non-toxic, non-polluting, and easy to degrade The pollution-free packaging materials, and inks are the raw materials that cause more serious pollution. Therefore, how to reduce the environmental pollution and energy consumption of inks has become the most important development direction of the ink industry. In China's flexible packaging printing industry, environmental inks represented by water-based inks, alcohol-soluble inks, and UV inks are increasingly being favored by printing manufacturers.

Specifically, in the flexographic printing market, ink painting has been developing at a rapid rate in recent years, and has greatly surpassed the tendency of solvent ink systems, and it has advantages in terms of ease of use and simple printing. Now when the flexographic industry compares and selects ink or solvent ink, confidence in ink has risen so that more printing work has been done by aqueous flexo printing. At present, ink users require improved performance mainly in the following two aspects:

1. Obtain a stable pH ink system. The ink-manufacturing industry must develop inks with stable pH values ​​during the printing process to eliminate the need to detect and adjust the pH during printing.

Second, improving re-solubility is another important area of ​​research. In the process of volatilization of amines in the ink, the resin tends to solidify, and may even cure on the plate. Recently, ink makers have improved the properties of the resin to make it more soluble, which means that the printing system can be run longer before cleaning, thus increasing the yield. With the joint efforts of related industries, that ink suppliers provide better ink, film suppliers provide easier and water-bonded film surfaces, and printer manufacturers create better drying equipment for water-based systems, then ink The use will continue to grow and make greater contributions to reducing VOCS emissions.

In the screen printing market, UV inks and aqueous screen printing inks together occupy a large market. At present, inks for screen printing use volatile and dry inks to occupy the mainstream position in terms of output and variety. However, the production of UV inks and water-based inks has increased year by year, and the increase is large, and it is only a matter of time before the yield exceeds that of the volatile drying inks. As the types of homopolymers, prepolymers, and polymerization initiators in UV ink raw materials have increased, the application range of UV inks has become more extensive, and it can be applied to various printing materials for screen printing, and its market share is bound to increase. . At present, foreign water-based inks account for more than 50% of screen printing inks. Full-function water-based ink surface is dry for 5s, heat-hardened for 10s; ultra-fine water-based ink can be printed with 500 mesh, color can be printed with 8 colors and computer can produce 6,000 colors; water-based ink (make-up grade) with zero VOC content, per kilogram water-based ink 50m2 printed.

In the aspect of composite film flexible packaging, after years of development, the production process of the composite film has been relatively complete, so there will be no major changes in the near future. As gravure printing has the advantages of exquisite printing quality and high economical efficiency for long-term large-scale printing, it is currently used in a large number of applications in China, and since the inherent characteristics of water-based inks can only be applied to flexographic and relief printing, the cost of UV inks is high. It also makes it very limited in gravure printing. Therefore, alcohol-soluble inks with low VOC emissions are currently products that meet environmental requirements and have a very broad application prospect. As the existing production process of the composite membrane is more or less accompanied by the generation of waste, it is necessary to make some changes in the production process to meet the needs of environmental protection. This is mainly reflected in:

1. In the process of plastic gravure printing, benzene-free inks (mainly alcohol-soluble inks) are used instead of current benzene-based inks.

2. In the dry compounding process, the solvent used is ethyl acetate. Although the “Emission Standards for Integrated Air Pollutants Emissions” (G816297-1996) does not specify the emission of ethyl acetate gas, the gas has harmful effects on the human respiratory tract and liver and should be used as little as possible. Alcohol-soluble polyurethane adhesives have been developed that use industrial alcohol instead of ethyl acetate as a solvent. The adhesive uses alcohol as a solvent, is non-polluting, has good compatibility with alcohol-soluble inks, and is inexpensive, and will be widely used. application.

When using alcohol-soluble gravure inks, note the following:

1. It should be stored at a relatively low temperature, and the ink should be fully stirred before use so that it has good flow properties.

2. Alcohol-soluble ink in viscosity, thinness, dryness, etc., must meet the requirements of the machine. In general, ethanol can be used as a quick-drying diluent and butanol as a slow-drying diluent. When the speed of the printing press is high or the climate is cold and dry in winter, a quick-drying agent may be added to accelerate the drying.

3. Alcohol-soluble inks can be mixed with each other to adjust various colors, but not mixed with other types of inks, especially with chlorinated polypropylene system inks, so as to avoid resin precipitation and other phenomena.

Source: Saint Gerkan Design Print