Green Printing Ink (1)

A. The harm of ink to the environment

Ink is the largest source of pollution in the printing industry. The annual output of ink in the world has reached 3 million tons. Annual global emissions of organic volatile compounds (VOC) caused by ink have reached hundreds of thousands of tons. These organic volatiles can form a more serious greenhouse effect than carbon dioxide, and they can form oxides and photochemical smog under the irradiation of the sun, seriously polluting the atmosphere and affecting people's health. In addition, foods, toys and other packaging and printing ordinary ink heavy metals and other harmful components of the human body will also directly harm the health of consumers.

(1) Impact on human health

Printing inks consist of pigments, binders, solvents, and adjuvants. Among them, organic solvents and heavy metal elements cause serious damage to the human body. There are two kinds of pigments in the ink - inorganic and organic, both are insoluble in water and other media, and has a distinctive color and stability. Some inorganic pigments contain lead, chromium, copper, mercury and other heavy metal elements, which have certain toxicity and can not be used for printing food packaging and children's toys. Some organic pigments contain biphenyl rubber and have carcinogenic components and should be strictly prohibited. Organic solvents can dissolve many natural resins and synthetic resins. They are important components of various inks, but some of them can damage human and subcutaneous fats. Long-term exposure can make skin dry and rough. If it penetrates skin or blood vessels, it can endanger people with blood. Hematocrit and hematopoietic function; being sucked into the airway, bronchus, lungs, or through blood vessels, lymphatic vessels to other organs, and may even cause chronic body poisoning. Some inks have the toxicity problem of heavy metal ions. Pigments and dyes contain carcinogenic ingredients, which are harmful to human health. In the printing of composite packaging materials, a large amount of ink, organic solvents and adhesives are used. Although these accessories do not have direct contact with the food, some toxic substances will migrate into the food during the process of food packaging and storage and endanger people's health. Ethanol, isopropyl alcohol, butanol, propanol, butanone, ethyl acetate, butyl acetate, toluene, xylene and other organic solvents are often used in printing inks. Although most of these solvents can be removed by drying, residual solvents can migrate into foods and harm the human body. Solvents used in gravure inks typically include butanone, xylene, toluene, butanol, and the like. Especially butanone, the residual odor is very strong. Because the pigment particles in the ink are very small and have strong adsorption power, they are heated and dried during printing, but due to short time and high speed, they often do not dry completely, especially the printed matter with large inked area and thick ink layer. Its residual solvent is more. These residual solvents are brought into the compounding process. After compounding, it is more difficult to run away and the permeation will slowly migrate. Therefore, the solvent residue must be controlled to a minimum.

(2) Impact on environmental quality

The problem of air pollution caused by the volatilization of solvents in the ink is the most serious with gravure ink, because it uses more VOC as a solvent. Long-term exposure to high concentrations of VOCs will cause significant damage to the human body, especially the nervous system. VOCs will also react photochemically with nitrogen oxides in the air to produce ozone and fumes, causing atmospheric pollution. To reduce VOCs, there are two solutions for recovering and burning the discharged solvent, but many gravure machines are not equipped with such devices. In addition, the discharge of water-based cleaning ink and offset fountain solution can contaminate the water quality. The disposal of industrial waste such as printed materials and ink containers is also very tricky.

Two. The current major environmental protection ink

To meet the environmental protection requirements of inks, we must first change the ink composition, that is, use environmentally friendly materials to formulate new inks. At present, environmental protection inks mainly include water-based inks, UV inks, water-based UV inks, and some alcohol-soluble inks.

(1) Water-based ink

The biggest difference between water-based inks and solvent-based inks is that the solvent used is water instead of organic solvents, which significantly reduces VOC emissions, prevents air pollution, does not affect human health, is not easy to burn, ink is stable, colorful, and does not corrode Plate material, simple operation, low price, good adhesion after printing, strong water resistance, rapid drying, it is especially suitable for food, beverages, pharmaceuticals and other packaging printed matter, is the world recognized environmental protection printing material, is also the current all printing ink The only ink approved by the U.S. Food and Drug Association. At present, 40% of U.S. plastic printing uses water-based ink, and other economically developed countries (such as Japan, Germany, France, etc.) use more water-based ink in plastic film printing. In June this year, the United Kingdom enacted legislation to prohibit the printing of food films using solvent-based inks. According to relevant data, in the United States, water-based inks complying with the VOC regulations must reach the state of use of the ink composition, the proportion of volatile components is below 25%, the moisture content is above 75%, and the water with less moisture is in use, the non-volatile components are used. Above 60% of these two standards. Water-based inks are usually used for printing paper products including paper-plastic composite products. Characteristic is to meet the paper printing ink absorption, so that the print color full, more rare is the solvent is water and ethanol, the environment is small, known as green ink.