Ink goes green new trend

The environmental protection of commodity packaging has become a trend in the future development of packaging, and the corresponding requirements also apply to packaging printing inks without pollution. Traditional solvent inks secrete toxins during volatilization, which is particularly detrimental to food packaging. This article describes several commonly used environmentally friendly inks: water-based inks, UV light-curable inks and water-based UV inks in three categories, of which water-based UV inks is a new research direction, with broad prospects.

At present, China's ink industry already has a considerable scale, with more than 300 production companies, of which more than 30 have considerable scale and production and research and development capabilities. The total production capacity of ink is approximately 220,000 tons per year, ranking fourth in the world. It accounts for 5% to 6% of the world's total production. Generally speaking, although China's inks can basically meet the needs of the domestic printing and packaging industry, there is still a considerable gap compared with the advanced level in foreign countries. After joining the WTO, China's ink industry needs rapid development and narrowing the gap with the world's advanced level.

The important development trend of current packaging printing materials is to improve their environmental performance, choose energy-saving, low-cost, non-toxic, non-polluting, and easily degradable pollution-free packaging materials, and ink is a raw material that causes more serious pollution, therefore, how to reduce the ink The environmental pollution and energy consumption have become the most important development direction of the ink industry.

To fundamentally improve the impact of ink on the environment, we must start from changing the composition of the ink, that is to use environmentally friendly materials as far as possible to formulate a new type of environmentally friendly ink, in order to reduce VOC emissions and improve energy efficiency. At present, environmental-friendly inks mainly include water-based inks, UV-curable inks, and water-based UV inks.

Water-based ink

The biggest difference between water-based inks and solvent-based inks is that the solvents used in water-based inks are water and ethanol, with very low VOC content and low environmental pollution. In the flexible packaging industry, since solvent-based inks are based on volatile drying, the lower the boiling point of the solvent, the more volatile it is and the toxic gas is released to pollute the environment. After the printing is completed, there are residual toxic substances on the surface. Water The solvent used in the base ink is water and ethanol excluded from the VOC list, which can greatly reduce VOC emissions. At present, more than 40% of U.S. plastic film printing uses water-based inks, and other developed countries use more and more water-based inks in flexible packaging. In the United States, water-based inks that comply with VOC regulations must meet the following two criteria:
1. In use ink composition, the proportion of volatile components is 25%, moisture is above 75%;
2. When the ink with less water is used, the non-volatile content is more than 60%. In recent years, China has also made some provisions for food packaging. The status of “green” printing is continuously improving in China. At present, China's water-based ink for flexible packaging ranks first among other printing inks with 35% of its usage.

UV ink

UV inks are inks that use ultraviolet light of different wavelengths and energies to form and dry inks under ultraviolet light. Utilizing different UV spectra, different energy can be generated to polymerize monomers in different ink binders into polymers, so the UV ink film has good mechanical and chemical UV inks The main advantages are:

1. Without solvent, fundamentally avoiding the pollution of VOC to the environment;
2, drying speed, low energy consumption;
3, good gloss, colorful;
4, water resistance, solvent resistance, good wear resistance. The main components of UV inks include pigments, photopolymerizable prepolymers, photopolymerization initiators and additives. The prepolymer is the main functional ingredient. The commonly used prepolymers have three major categories: epoxy acrylates, amine ester acrylates, and polyester acrylates. At present, UV ink has become a relatively mature ink technology. Its pollutant emission is almost zero, and it has a reputation as an energy-saving and environment-friendly "green" product. According to statistics, the annual output of UV inks is approximately 16,000 tons in Japan, approximately 18,000 tons in Europe, and approximately 19,000 tons in North America, of which flexo inks and offset inks are the most rapidly growing.

Water based UV ink

Water-based UV inks are a new research direction in the field of UV inks. Since the viscosity of the prepolymer in the general UV ink is generally very large, it is necessary to add a reactive diluent to dilute, and the currently used diluent acrylate compounds have different degrees of skin irritation and toxicity, so in the development of low viscosity pre At the same time as polymer and low-toxicity reactive diluents, another development direction is to study water-based UV inks, ie, UV inks using water and ethanol as diluents, which can achieve lower VOC emissions while still being low. toxicity. According to reports, water-based UV solder mask inks have been developed, and the United States has also successfully developed water-based UV inks for printing.

Only by continuously using advanced technologies and developing “green packaging printing inks” and other functional ink products that meet the requirements of environmental protection can we bring new development opportunities to the packaging industry in China.