The greening of the printing process of foamed flexible packaging

(1) Greening process of gravure printing

The gravure ink contains a large amount of volatile organic solvents, accounting for almost 50% of the gravure ink. Among them, xylene, toluene, ethyl acetate, butanone and other low-boiling, highly volatile solvents contain aromatic hydrocarbons that are toxic and flammable, and are the main factors of environmental pollution. In addition, the gravure printing speed is extremely high, and it is necessary to use fast-drying inks with extremely strong volatility. External drying (gravure printing with a drying process) is also required by electricity or infrared heating to meet the printing requirements, resulting in large gravure exhaust emissions. Gravure printing is particularly prominent in the environmental issues of all printing processes. Many authorities in the printing industry believe that gravure printing will lose its competitiveness in the market and will eventually be replaced by other printing technologies unless practical measures are taken to solve the gravure problem of gravure printing and improve the environmental performance of gravure printing.

1, reduce the impact of organic solvents on the production environment

The use of large amounts of solvents during the gravure printing process is an important cause of solvent contamination in the gravure printed flexible packaging industry. The discharge of solvent-laden exhaust gas from the gravure printing machine and the exhaust system of the composite machine caused environmental pollution, and the volatilization of the solvent during use also caused indoor pollution and safety problems.

The entire printing unit can be fully enclosed, reducing the spread of solvents in the workshop.

Ultrasonic gravure roll cleaning system is used to reduce the amount of solvent used. By setting up the printing plate pre-cleaning device of the printing plate, the printing plate roller is automatically cleaned on the machine at the end of the printing, which can effectively prevent the ink from drying on the printing plate. This type of cleaning device can complete most of the cleaning of the printing plate rollers, significantly reducing the amount of manual cleaning work and also improving the operating environment.

In the gravure discharge system, the solvent is treated by means such as solvent recovery treatment to reduce the discharge of solvent into the air; some printing plants have begun to use a single solvent ink in order to make the solvent more convenient for recycling. At the same time, the explosive lower limit control system with volatile solvent concentration is adopted, and through part of the hot gas circulation, the energy consumption for drying is maximally saved.

In order to reduce the total amount of solvents, the development of high-concentration, low-viscosity inks suitable for shallow printing is an important research direction. Even solvent-free solid inks are likely to be on the market. People from S iegwerk Ink believe that the HotTech ink technology they are developing has application potential. This patented HotTech ink technology is a solvent-free, solid gravure ink that dissolves immediately before being transferred to a printing plate roll and is expected to be on the market within a few years.

2. Development and application of benzene-free solvent inks and water-based inks to achieve solvent-free benzene and water-based gravure ink printing

Currently used gravure printing inks are generally made of chlorinated polymers. In the ink production process, the chlorinated polymer needs to be dissolved using a strong solvent (such as toluene and other aromatic solvents), and the viscosity of the ink needs to be adjusted during the printing process using toluene. Chlorinated polymer ink systems are now considered unsuitable for environmental protection. This is because the chlorofluorocarbons that are volatilized during production can damage the ozone layer. The use of aromatic solvents (toluene) can cause injury to the health and safety of workers during ink production and printing. In addition, the solvent residue in the packaging ink is another important issue to pay attention to. Since toluene is a slow-drying solvent, it easily remains in the dried ink film layer, corrupting the food in the package and causing harmful odors.

The production of plastic gravure inks is under the control of fire laws, labor safety laws, and health laws and regulations. Therefore, it is an inevitable trend to actively develop and apply green gravure inks and water-based inks that meet environmental protection requirements.

(2) Water-based gravure film packaging material

Although water-based gravure inks have attracted much attention as an alternative to toluene-based inks, the inks in packaging film printing are still water-based and have not yet reached a truly practical stage. On the whole, the important reason why water-based gravure inks have not been popularized further is that the printing performance and quality are still not up to the standard for solvent-based gravure inks. This is mainly due to the higher surface tension of water, which makes it difficult for the ink to wet. If the printing speed and the printing quality of the gravure solvent ink are to be obtained, not only the aqueous ink itself requires advanced technology, but also the gravure printing apparatus and the printing plate roller need to be improved. For example, changing a corrugated or engraved drum with a groove depth of approximately 38-42 micrometers to a laser-made plate roll with a groove depth of approximately 24 - 28 micrometers also requires more effective and powerful drying equipment and printing that must be manufactured using corrosion-resistant materials. Roller, ink pump and scraper components. These improvements require considerable investment.

(3) Develop and apply intaglio alcohol-soluble composite plastic ink

Since water-based gravure inks are not yet fully capable of replacing toluene inks, the ink industry has been working hard to develop alcohol-soluble inks that can be accepted by the environment. Alcohol-soluble ink can effectively solve the health problems caused by toluene ink and solvent residue affect the quality of packaged food and other issues. In Europe and the United States, this development has become a trend. In Asia, such as Singapore, South Korea and other countries, toluene ink is being eliminated, will be replaced by alcohol-soluble gravure ink. Alcohol-soluble inks are now widely used in the domestic gravure printing industry. It can be predicted that in the near future, alcohol-soluble inks will occupy a major share of the high-grade food and pharmaceutical flexible packaging ink market in China.

The gravure alcohol-soluble composite plastic ink has the characteristics of low odor, benzene-free, and the use of such environmentally-friendly inks will certainly increase the competitiveness of gravure printing in the field of packaging printing.

Source: Guangzhou Printing Network