Green ink printing technology

At present, China's printing industry is facing a great deal of environmental pressure. Since most of the inks used in printing contain organic solvents, and organic solvents are discharged into the atmosphere almost without any treatment, the annual organic emissions to the atmosphere are volatilized. The substance (VOC) is as high as hundreds of thousands of tons. In addition, the ink contains harmful heavy metal elements such as lead, chromium, cadmium, mercury, arsenic and antimony, which are extremely harmful to the human body and the environment. These substances have caused major pollution to the environment we produce and live in. After seeing all the above, people can't help asking where the green ink is, why not develop and use green ink?

First, define the green ink

At present, China has not established the criteria for the determination of green inks or environmentally friendly inks, but the general understanding of green inks should be viewed in a narrow sense and in a broad sense. In a narrow sense, green ink refers to the use of raw materials that are almost harmless to the human body for the manufacture of inks. There is almost no pollution during the production and printing of inks, and it poses almost no harm to human production and living environments. Ink varieties. In a broad sense, green ink is a relatively environmentally friendly product and it contains the following three layers of meaning.

(1) To significantly reduce the harmful components of ink, mainly include reducing the content of aromatic hydrocarbons and ketones, reducing the content of heavy metals, and reducing other harmful components to the human body.

(2) To significantly reduce the hazards to the operators and the environment during the production and use of the ink, and to improve the first-line production environment. At the same time, the energy consumed by the ink during its manufacture and use is not significantly increased.

(3) It must be conducive to the recovery and disposal of packaging waste, and there should be no "secondary pollution".

Although at present, the research and development of China's environment-friendly ink is still constrained by many factors, but for the Chinese ink industry, the ultimate realization of the broad-based green ink is its ultimate goal, and the manufacture and promotion of narrow-defined green ink is the current development goal. And the ultimate pursuit. With the development of technology, people began to consider factors such as ease of use, cost of use, and environmental performance. What are the green inks currently on the market? Here are some of them.

Second, energy curing ink

Energy-curable inks use UV light or accelerated high-energy electron beams (EB) to polymerize the monomers in the ink into a polymer. Currently, energy-curable inks mainly include UV inks and EB inks.

Compared with common inks, the main advantages of energy-curable inks are: they do not contain harmful VOCs to the human body and the environment, do not pollute the environment, have fast drying and curing speeds, consume less energy, and have a large cross-link curing density, and a degree of cure of 100%. %, can be printed on a variety of substrates, with excellent mechanical properties and physicochemical properties. Therefore, once energy-curable inks are available, they are sought after by the market.

The UV ink is mainly composed of a prepolymer resin, a diluent monomer, a photoinitiator, a photosensitizer, a photosensitizer, a polymerization inhibitor, and a pigment. UV inks mainly include offset UV inks, letterpress UV inks, gravure UV inks, screen printing UV inks, UV inkjet inks, and UV printed circuit board inks. The environmental protection of UV inks is only relative to the ordinary printing process, and there are also many problems.

(1) Some components of UV inks come in contact with the skin and may cause some irritating effects and may even cause skin irritation.

(2) UV light has some damage to the human body.

(3) The cured ink layer is very hard to degrade due to the high density of cross-linking, and the ink residue is also difficult to handle.

For this reason, people are actively researching and developing water-based UV inks and expect to solve the problems existing in UV inks.

EB ink is a kind of ink with great development potential. It can be used for web offset and flexo printing. Compared to UV inks, they do not use photoinitiators, have no odor, do not release ozone, do not require cold curing of the heat source, and are not affected by the color of the ink during curing. The curing is more thorough and the quality is more stable. However, the high cost of EB ink curing equipment is the biggest obstacle in the promotion and application. At the same time, EB inks also have degradation problems after they are discarded.

At present, most of the inks used for gravure printing contain benzene solvents. Due to volatilization, the exhaust gas emitted by gravure printing is a major source of pollution in the packaging and printing industry. Although water-based gravure inks have been received as a substitute for solvent-based gravure inks and have received high expectations, the water-based process of gravure inks is still slow.

The following are some of the factors that prevent the gravure ink from becoming water-based.

(1) Poor print quality: At present, water-based inks have poor adhesion and rub resistance to plastics, poor printability, and poorer printability than solvent inks.

(2) Dryness is not good: The water-based ink has poor drying properties, resulting in low printing speed during printing, which increases energy consumption and costs. It is necessary to reconstruct the original drying equipment or use a special printing press suitable for water-based gravure ink.

(3) The printing plate must be reconstructed: In order to improve the drying property of the water-based gravure ink and to strengthen the printing effect, the printing plate must be reconstructed to achieve a shallow plate.

At present, water-based gravure printing inks are still under research and development. Although there have been reports of successful research and development, they have only stayed at the laboratory level and a process is still needed to achieve industrialization. However, water-based gravure inks have already begun trials on some special substrates. If the above problem is solved, the water-based gravure ink can achieve a wide range of applications.