How to use ink in gravure printing

Editor's note: In recent years, the printing industry has become increasingly demanding for environmental protection, and the demand for environmentally friendly inks (ink and UV inks) has become higher and higher. However, there are not many manufacturers who really know how to print ink and ink, and the price and cost Failed to compare and analyze objectively, I hope this article will enable the printing manufacturers to have a certain understanding of ink and wash, truly use both the environmental protection printing technology, and ensure the printing quality.

Intaglio printing is the largest printing method in China's printing industry with the largest market share except offset printing. It is popular for its advantages such as clear marking, clear gradation, and high-speed printing, especially when using solvent-based inks. Reaching 40 to 300 meters/minute is undoubtedly a major breakthrough in printing technology.

Daily supplies, food, medicines, tobacco, alcohol, etc. are inseparable from packaging, and most of these packages use gravure printing. According to China's annual output of 260,000 tons of ink, gravure ink accounts for about 30% of the share, that is, China's gravure The printing consumes more than 70,000 tons of ink and is mainly used for packaging printing. But it is beautifying people's lives, bringing visual enjoyment to people, but it also pollutes the environment more or less. Taking 1kg ink printing as an example, the solvent it volatilizes, including the solvent in the ink and the diluent added during printing, is also about 1kg, that is, we consume 70,000 tons of gravure ink each year, and also 7 million tons of organic ink. The solvent evaporated into the atmosphere, causing direct damage to the environment and the printing operator's body.

No matter what kind of printing method is used, what is the substrate, as long as the solvent type ink is used, there must be solvent residue. From the state's maximum limit on the amount of solvent residues in packaging materials (from 2 mg/m2 for the drug standard to 8 mg/m2 for plastic composite bags), the presence of residual solvents should be limited.

How can we achieve both high quality printing and environmental protection? The answer is to use water-based printing to fundamentally solve the problem. Water-based inks can be referred to as environmentally-friendly inks. We must use ink printing correctly to understand and understand the characteristics of ink.

The difference between ink and solvent ink

1. Ink prints are solvent-free and odorless. They have no pollution to the environment during the printing process. They are harmless to the human body. They meet the hygiene standards and can be produced safely.

2. Low consumption of ink. The amount of ink used for each full square meter of ink printing is much less than that of solvent type inks, and only 50% of solvent type inks.

3. It occupies a small amount of funds and is suitable for printing a variety of substrates. Whether it is printing non-woven fabrics, PE film, BOPP film, PA film, PVC soft film, PVC hard film, aluminum foil or vacuum aluminum film, only one type of ink is purchased. Can, and can be printed, printed in India, composite printing. Solvent-based inks require 4 to 5 types, and the associated solvents are as many as 8 to 10 types.

4. Safety stock. Ink and fire will not burn in case of fire. The thinner required for ink and wash is tap water.

5. Low printing costs. Printing companies often ignore the loss of ink when calculating the cost of printing. For example, printing a variety of different substrates or using different printing methods to print the remaining ink will not only occupy the place but also cause great security risks. In addition, the used ink is likely to absorb impurities, and a gelation reaction occurs, resulting in waste. The ink storage period is long, so long as the ink tank is sealed after printing, there will not be any change.

Ink printing should have the conditions

1. Printing plate

The printing plate uses electronic engraving gravure or laser engraved gravure, the depth of the network hole is 15 ~ 25μm, shallower than solvent ink gravure. This is because the ink is produced using tap water. The boiling point of water is higher than that of the solvent. Therefore, the ink is not volatile. The shallow version can increase printing speed and avoid water ripples. If solvent inks are used for printing, the plate depth is 35-40μm, which is easy to generate water ripples. However, when using ink printing, the depth of the plate is more than 25μm, there will be water ripple phenomenon, so choose the right one. Plates are crucial.

2. Good drying equipment

Drying temperature should be based on the different substrates, the size of the printing area. Such as aluminum foil label printing, drying temperature above 100 °C; plastic film printing, drying temperature of 50-60 °C is appropriate. The wind power should be stronger than using solvent inks because hot air can quickly dry the ink after it has been transferred to the substrate.

3. Surface treatment

Except for aluminum foil, vacuum aluminized film and paper, all plastic films need to be treated by electric discharge before ink printing, so that the surface tension can reach 0.04N/m or more. The water-based solvent produced by the ink, because the surface tension of water is about 0.072N/m, the surface tension of the visible ink and the surface tension of the film have a large gap, which will affect the adhesion of the ink on the substrate, and improve the plastic film. The surface tension can improve the adhesion of the printed pattern on the film.

Flexible packaging ink printing process requirements

Many fresh milk and milk products commonly used in the market today are packaged in multi-layer co-extruded films. There are many forms of sterilization after packaging. Ink printing is used. As long as the above printing conditions are met, all indicators of the print can satisfy the milk. Flexible packaging requirements, and the printing cost is only 50% -6% of solvent-based ink. This not only reduces the cost, but also leaves no residual solvent on the packaging film, which meets the hygienic standards for food packaging.

Printing notes:

1) For printing milk packaging film, we must first select the co-extruded film that has undergone surface treatment. For example, if we use more black and white co-extruded film, the surface tension of the treated film should reach 0.042 N/m.

2) Before printing, after pouring ink into the ink tank, the plate cylinder should idle for 2-3 minutes in order to moisten the plate and stir. In the printing process, when it is necessary to stop temporarily, the plate cylinder should not be stopped to prevent the ink film on the printing plate from being solid and the plate blocking failure occurs.

3) Before printing, adjust the ink viscosity according to the depth of the printing plate. Do not add tap water during the printing process. Simply add new ink. Because the ink is not easy to evaporate, at the temperature of 32°C, the volatilization amount of the ink for one hour is only 1.2%, and no water is added to keep the color of the print product consistent, and the pass rate of the printed matter is improved.

4) After the printing is completed, immediately clean the printing plate, pour the ink into the bucket, place the clean water in the ink tank, rotate the plate cylinder to clean it, or transfer the 3% detergent solution for cleaning.

5) When blockage occurs, use glycol ether, ethanolamine, ethanol, and water in a certain proportion to mix and form the platewashing solution to moisten and clean the plate cylinder. Wastewater generated from washing plates should be set up to be filtered in order to avoid contamination of groundwater sources.

Reprinted from: Ink Information