Packaging ink development

Since the 1970s, as snack foods have become more popular, many flexible substrates have been developed to package and protect consumer foods such as PE, PP, OPP, PET and NYLON.

Compared with traditional paper and cellophane, most newly developed plastic films are more difficult to attach. Previously, gravure inks used on packaging films that were more difficult to attach were generally made from 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.

In Europe, especially in Germany, aromatic solvents like toluene have been banned for food packaging inks. Similar to Europe, the United States has stricter environmental laws to control the release of volatile organic compounds. This has prompted chemists working in polymers and inks to work harder to develop more environmentally friendly systems for food packaging inks.

Although aqueous gravure inks have attracted much attention as an alternative to toluene-based inks, printability and quality still fall short of the standard for solvent-based gravure inks. This is mainly due to the higher surface tension of water, up to 72 dyne/cm, which makes the ink difficult to wet and dry slowly. In order that water-based inks can be used in gravure printing presses, not only inks and resins require advanced technology, but gravure printing equipment also needs improvement. For example, changing an etching drum with a groove depth of about 38-42 μm to a laser pattern making drum with a groove depth of about 24-28 μm also requires more efficient and powerful drying equipment and components such as rollers, pumps, and scrapers made from corrosion-resistant materials. . Because all these require a lot of investment, water-based gravure inks are still not widely available in Europe and the United States. The water-based flexographic printing inks currently used in the market are mainly used for the printing of paper and corrugated paper. The quality requirements are general and relatively easy to accept. They are widely used in Europe and America.

Since water-based gravure inks are not yet fully capable of replacing toluene inks, the ink industry has been working hard to develop environmentally acceptable alcohol-soluble inks. Alcohol-soluble ink can help us to solve the health problems caused by toluene ink and solvent residues affect the quality of packaged foods 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. It is foreseeable that in the near future, China's packaging inks will be the market for alcohol-soluble inks.