From the perspective of environmental protection, the progress of printing ink

In the industrial society where industrial production flourishes and people’s living standards have generally improved, the printing industry has played an important role in the national economy. Brilliant and colorful prints have brought about civilization while also causing environmental pollution. Progress and market development, China's printing industry has made considerable progress in recent years, but compared with developed countries, whether it is the printing equipment research and development, production, or the printing shop's environmental pollution and printing supplies, especially the most used There is still a big gap in the environmental issues of printing inks, all of which have brought tremendous challenges and opportunities to the development of China's printing industry. For printing consumables, especially printing inks, it is a great opportunity to develop and produce various new materials that meet environmental protection requirements. What is gratifying is that in the field of printing inks, the transformation of the original formula, production technology, raw materials, and drying methods has now been mentioned on the agenda. However, from an environmental point of view, there is still huge room for development in printing inks.

Status: The domestic printing workshop environment is not optimistic

At present in China, the inks used in large quantities in the printing process are basically solvent-based inks. The organic volatiles of these solvent-based inks are not processed and are directly discharged into the air of the workshop. This not only affects the production environment, but also affects the health of workers. There will be great harm. This is because these solvent-based inks contain 50% to 60% of organic volatile substances. In addition, in the actual production process, diluents for adjusting the viscosity of the ink are usually added. When the printed materials are dried, the ink is emitted. The total content of volatile components is even as high as 70% to 80%.

The benzene compounds in these printing plants have exceeded the standards. According to the requirements of the national standard, the maximum allowable concentration of benzene in industrial workshops is 10 mg/m 3, toluene is 100 mg/m 3, and xylene is 100 mg/m 3 . The average concentration of benzene in these printing plants exceeds the national standard by 2.2 times, toluene exceeds the national standard by 4.2 times, and the average concentration of xylene exceeds the national standard. From a medical point of view, this will bring a great deal of irreversible harm to the health of printing workers.

In addition, the latest research results show that excessive levels of other heavy metals in actual production will also lead to deterioration of the printing environment and even affect the health of operators.

In a word, the emission of harmful gases, the use of hazardous liquids and solids, and the discharge of wastes in the printing industry pose a serious threat to human health and the living environment. This environmental issue not only involves the future of human civilization, but also involves the survival and development of the enterprise. Therefore, we must consider the issue of environmental protection in the printing industry and draw up feasible and effective measures.

Hope: The latest development direction of ink

In the production and development of ink, in order to meet the requirements of the VOC law, Western countries have made great improvements in the ink formulation and drying system. The more types of ink used today are the following types and are also the future printing inks. Research and development of new directions.

First, UV curing ink

UV ink is an environment-friendly ink that has rapidly developed in recent years. It quickly captures the market with instant curing (dry), free of volatile solvents, and simple application. UV inks include UV frosting, UV ice, and UV foam. UV wrinkles, UV embossing, UV refraction, UV gemstones, UV light fixing inks, UV varnish, and other specialty packaging inks. On the surface of the substrate with metallic mirror gloss, the UV ink is printed on the surface of the substrate with a screen printing process. After being treated with ultraviolet light, the device produces a unique visual effect that is elegant, dignified, and luxurious. Products are mainly used in high-end and exquisite chic tobacco, wine, cosmetics, health products, food, medicine and other packaging and printing.

Make up

UV inks are cross-linked polymerization reactions under the irradiation of UV light, and instantly cure into film. It is mainly composed of photopolymerizable prepolymers, photosensitive monomers, photopolymerization initiators, organic pigments and additives. Among them, the photopolymerization initiator is the most important component of the entire UV ink and is the start of photopolymerization.

2. Application Features

1) Instant curing, high production efficiency.

2) It does not contain volatile solvents; there will be no solvent erosion to destroy the print; it will not pollute the human body and the environment.

3) The ink will not clog the web, so a fine mesh can be used to print the best quality lines.

4) The ink concentration is stable and will not cause unevenness due to different concentrations.

5) The ink will not dry out and there will be no foul odor of solvent.

6) The speed of light curing is extremely fast, and the UV equipment is small in size and takes up less space in the factory building.

7) The heat emitted by the UV lamp will not damage the printed material.

8) Transparent or translucent ink, fast curing, good color effect.

Although UV inks have so many advantages. However, at present, there are also deficiencies. UV curable inks have higher costs and are more complicated to use than conventional inks.

Curing mechanism

UV inks are selective to UV light and its drying is affected by the total energy of the UV light source and the distribution of light energy at different wavelengths. Under the irradiation of UV light, the photopolymerization initiator in the UV ink absorbs photons of a certain wavelength and is excited to an excited state to form radicals or ions. Then, a polymer such as a polymerizable prepolymer and a photosensitive monomer is brought into an excited state by energy transfer between molecules, and a charge transfer complex is produced. These complexes continuously crosslink and polymerize to form a film.

4. Looking ahead

At present, there are still some defects in the printing of UV inks, which still need to be improved. The main development directions are: the development of low-stimulating reactive monomers, to avoid allergic reactions or burns to ink producers and users; to develop photoinitiators for UV-curable inks, to improve the efficiency of initiation, and to facilitate the deep curing of color inks; Cationic and cationic free radical UV light curing systems, because the cationic light curing system is not affected by oxygen inhibition, surface curability is good, the skin irritation to the human body is small, the internal stress of the ink layer after curing is small, the volume shrinkage is small, flexibility and adhesion Advantages such as good performance; development of non-irritating, non-polluting and safer water-based UV inks; improved adhesion of inks to substrates; research and development of UV inks with small curing shrinkage and strong adhesion.

From a production point of view, currently there are not many manufacturers that can actually produce UV-cured inks in the country. In particular, high-end UV-curable inks are scarce, and many high-end users choose to use imported inks for high-end printing jobs. This is also a new direction for domestic ink manufacturers. If more domestic manufacturers conduct research and production in this area, the market potential and market potential are great.

Water-based UV-curing inks are at the forefront of this field. At present, there are relatively few manufacturers involved in this field in China.

Second, water-based ink

Water-based ink is a printing ink made of water-soluble resin as a binder, mainly made of water as a solvent. It has long been used in flexo printing, gravure printing and screen printing, and has recently begun to be used in waterless offset printing.

The environmental performance of ink and wash is unquestionable. Some international companies' printing products require the use of ink as printing ink. For ink painting, study its various formulations to achieve the best printability, meet various resistance requirements of the final printing products, minimize ink production costs, develop new waterborne resin binders, and even develop a The new additives, etc., have become a new topic for R&D at home and abroad.

Various problems in the existing inks, such as wettability of pigments, dispersion of pigments during production, ink storage stability (no delamination, no precipitation, no flocculation), printing inks during printing Problems such as rapid drying and adhesion on the non-absorbent plastics and metal surfaces, dilution of inks, etc. are still being solved.

As far as China is concerned, at present, high-end ink is basically occupied by imported ink, and some of our manufacturers produce some low-grade ink. In other words, the development and production of ink painting is still in its infancy in China. Both the developer and the manufacturer are promising because there is a huge business opportunity here.

in conclusion

For the latest ink technology, traditional ink research and development also has a lot of work to do, for example, the further improvement of the resin binder in traditional ink; further increase the brightness without affecting the drying; improve the color of the ink, making the ink film more vivid, etc. . In addition, there are a variety of special ink research and development, such as conductive ink, magnetic ink, lottery cover ink, passive light ink and so on.

With the progress of the times and the development of science and technology, the printing industry and ink production industry will face a series of new challenges. At the same time, these new challenges will also bring new opportunities for the printing ink industry, rely on science and technology to continuously develop new inks, better adapt to new demands, create better print products, and promote the further development of printing companies.

In the next few years, the environmental protection of ink will become the focus of attention. The current testing standards used will be more stringent. The main manifestations are: further reduction of heavy metal content, reduction of residual solvents in printed matter, prevention of air pollution, sewage treatment, etc. Therefore, green ink is a major trend in the future development of ink, and will also win a larger market.

Author: Wang Color Printing

Reprinted from: Screen Printing