Green printing ink and green printing

With the vigorous development of industrial production in various countries and the general improvement of people’s living standards, the increasingly polluted environment of the Earth and the atmosphere that mankind lives on is threatening the quality of human life and even the survival of mankind itself. The printing industry occupies an important position in the national economy. Brilliant and colorful prints bring civilization to people, but also cause environmental pollution, reduce or completely eliminate the pollution of printing to the environment, make printing into green printing, will become the next generation Even the historical mission of several generations of printers.

The development of the printing industry is closely related to the development of printing inks. The environmental pollution of traditional solvent inks is obvious to all. Therefore, all countries in the world have paid great attention to the development of environmentally friendly inks. China is no exception. New printing ink printing materials and Accessories without pollution and pollution are increasingly being developed and applied. Green printing is increasingly becoming the consensus and joint action of the printing industry.

First, the composition and classification of ink

It is well known that printing is the process of transferring graphics on a printing plate to a substrate via ink, so the role of the ink is extremely important. The main components of inks are pigments and binders. There are also additives.
The pigment plays a role in color development. Its main properties such as the degree of dispersion and the hiding power of the tinctorial force have a direct influence on the performance of the ink. Ink pigments are divided into organic pigment inorganic pigments and special pigments used for special printing (such as gold powder, silver fluorescent pigments, phosphorescent pigments), etc. The use of special pigments in packaging and printing is currently on a linear upward trend.

The complex composition of the binders plays a key role in the inks, and there is an oil type binder resin type binder. The oil type binder has good adhesion and certain resistance properties to form a good gloss ink film. The resin type binder is made by dissolving synthetic resin or modified resin in mineral oil vegetable oil or volatile agent. The organic solvent is one of the main components in the binder, and its role is to make the ink have a certain degree of fluidity. After the ink is transferred to the substrate, the volatile solvent quickly evaporates and the less volatile solvent penetrates into the substrate so that the pigment particles and the binder adhere to the surface of the substrate and dry. Commonly used ink solvents are petroleum solvents, alcohol solvents and ester solvents. Additives, or additives, are auxiliary components of the ink and are used to adjust the printability of the ink. The auxiliary agent is divided into a color adjuster fluidity adjuster dryness adjuster and the like, and is used to adjust the hue, fluidity, and drying speed of the ink, respectively.

The ink classification method is various and one of the main classification methods according to the use classification can be divided into letterpress (including flexography) offset gravure, special ink and new ink.

Toppan inks have dramatically decreased with changes in the proportion of letterpress prints, but Flexo Toppan inks have stood out, and the share of flexographic printing is gradually increasing. Flexo printing can be divided into solvent inks, inks and UV inks. The latter two inks are becoming the focus of development due to their excellent environmental performance.

Offset printing inks have strong coloring power and certain resistance to nature. Most of them use resin type binders. Offset inks have quick-drying bright offset inks and rotary offset inks. The former is suitable for high-speed color printing of sheetf Used for web offset rotary presses with speeds of 250-300,000 rpm, divided into two types, thermosetting and cold-setting. Thermosetting offset inks are suitable for color printing. Coldset offset inks have low viscosity and are suitable for printing newsprint and offset paper.

Intaglio printing ink is divided into two types: engraved gravure and gravure. Engraving gravure printing ink is mainly used for the printing of securities. The linking material is made of oil type linking material with lower viscosity. The gravure printing ink is dried by solvent evaporation, and it is low viscosity ink and divided into benzene type, gasoline type, alcohol type and Water-based five kinds. Benzene-based gravure printing ink uses toluene and xylene as solvents. Cosolvent benzene is added during printing to adjust the drying speed. The advantages are strong adhesion, good film formation, high glossiness of the ink film, but high toxicity, and toxicity to humans and the atmosphere. Big pollution. Gasoline gravure inks use gasoline as a solvent and are low toxicity inks. Mixed gravure inks and alcohol gravure inks are less toxic or less toxic, have less pollution to the environment, and their usage is increasing dramatically. The solvent of the water-based gravure ink is water and a small amount of alcohol, and the quality of printing products is gradually increasing. It is generally favored by people and has broad development prospects. Special ink refers to ink specially formulated for special printing. New ink refers to ink newly developed according to market demand. At present, UV ink is recognized as an ideal green ink due to its excellent environmental protection.

Second, the composition and nature of environmentally friendly ink

Eco-friendly inks, also known as green inks, are UV-curable inks and inks that are environmentally friendly alternatives to ink.

Ultraviolet curing ink is also called UV ink. UV inks consist of binders, pigments, reactive diluents, photoinitiators, and auxiliaries. The linking material is one of the main components and its content is about 30%~50%. It is the main ink film forming material, and determines the nature of the ink generally using saturated or unsaturated dibasic acid esters and acrylic resins. The reactive diluent is a relatively high molecular weight active monomer compound, and the content of 40% to 60% is mainly used to adjust the ink viscosity. The photoinitiator is an organic compound that excites the characteristic group of the crosslinking reaction of the photocurable resin, and its content is only 1% to 5%. It absorbs ultraviolet light energy to generate radical or ion-induced photosensitive resin (linking material) and active diluent monomer. A polymerization reaction occurs so that the molecules crosslink and polymerize and solidify.

At present, UV inks are mainly used for flexographic offset printing. Gravure printing and screen printing have different printing methods for different substrates, and their performance requirements for UV inks are also different. Therefore, the specific distribution ratio of UV ink is also different. The main characteristics of UV ink are: no solvent is volatile and pollution-free, and it meets the requirements of environmental protection. It is widely used in food packaging and printing, and the printability is suitable for paper cardboard plastic products, metal, textiles, etc. Printed materials have a short curing time and consume less energy, resulting in good quality prints.

Ink is composed of color materials, additives, and the like. The colorant is the colorant, which is the coloring matter of the ink. The linking material of the ink is mainly composed of an aqueous polymer emulsion or a water-dispersible resin amine compound and other organic detergents (a very small amount of ethanol). Resin is the main component of the binder. Water-soluble acrylic copolymer resin is commonly used. It directly affects the chemical stability, water resistance, and heat resistance of the ink. Amine compounds make the inks weakly alkaline while water and a small amount of ethanol are used to dissolve the resin to adjust the ink viscosity and drying speed. Auxiliaries are regulators, including stabilizer defoamers, diluting agents, etc., to adjust the PH value of the ink viscosity drying speed, eliminate bubble lightening ink color.

The ink does not contain volatile organic compounds. It is non-polluting to the environment and per capita. Non-toxic The ink has good stability, high brightness, and strong adhesion. Drying speed can be adjusted, water resistance is good, printing performance is excellent, and the plate is not corroded.
The use of ink in flexo printing is also used in gravure printing.

Third, the development of green ink is a prerequisite for achieving green printing

In order to reduce environmental pollution, the development of green inks to develop green prints is gradually becoming known. Laws and regulations also encourage people to buy green inks. European environmental laws and regulations have added provisions relating to printing, which imposes clear restrictions on the emission of volatile organic compounds in the printing industry. This not only increases the content of waste disposal, but also provides a way to reduce the loss of ink. The United Kingdom back in 2000 Month legislation forbidding the use of solvent-based ink printing food packaging film. According to statistics, 60% of prints in the UK are printed with non-alcoholic or low-alcohol inks. The United States Environmental Protection Administration (EPA) strongly opposes the use of solvent-based ink flexo ink is currently the only non-toxic ink approved by the United States Food and Drug Association, widely used in food and drug packaging printing. In addition to offset printing in developed countries such as Europe, the United States and Japan, ink is gradually replacing traditional solvent-based inks. In the United States, for example, 95% of flexo and 80% of gravure prints are printed in ink.

Among all kinds of printing methods, offset printing is the main force of offset printing inks as printing inks. In recent years, the mainstay of printing inks has developed very rapidly. Its varieties, specifications and quality have reached a very high level. There have been many improvements in terms of low toxicity or non-toxic pollution. The development speed of UV ink is even more alarming. China's domestic offset printing ink has also made considerable progress. Some ink production enterprises have passed the ISO 9000 series quality system certification, and some have also passed the ISO 9001 series of environmental management system certification. Compared with foreign countries, we have the stability of ink quality. There is still a certain gap between the development of new product series (especially the development of environment-friendly offset printing inks). Flexo can use ink and ink, which has great advantages in environmental protection. It is called the best and most promising printing method in the world. In recent years, it has developed very rapidly. The quality of ink produced by developed countries in the world has reached a fairly high level. The quality of Yongping's domestic ink and wash inks can basically meet the needs of the domestic market. However, domestic ink and wash inks are still not as good as foreign high-grade inks in terms of color saturation, gloss, and stability. Small gaps, especially in the high-line cable printing gap.

With the enhancement of people's environmental awareness, green printing is an inevitable trend in the development of the printing industry. To demonstrate green printing, the use of green ink is a prerequisite. At present, green ink mainly refers to UV ink and ink. We have reason to believe that more and better green inks will continue to be developed in the future. Green environmental printing will certainly be realized and will surely be realized.