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Key points for using environmentally friendly inks
Time: 2013-05-07 Source: Cutting Edge of Packaging Read: 12370 times
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Wenzhou Junchuan Machinery Equipment Co., Ltd.

Since the 1980s, China's plastic flexible packaging industry has developed rapidly, which has promoted the rapid development of the packaging industry of food, medicine and other daily chemical products, and people's awareness of environmental protection, hygiene and safety has also been continuously enhanced. When formulating policies to promote economic development, the government also first considers protecting the environment and natural resources, and reducing pollution and harm. As for the packaging industry , how to reduce solvent residues, especially reducing or eliminating benzene solvent residues, has received widespread attention.
Now, we will introduce the different performance and application points of several flexible packaging environmental protection inks commonly used in domestic printing and packaging factories to users in order to make better use of these inks. At present, China's environmental protection inks mainly include benzene-free gravure composite inks, water-based inks, UV inks and water-based UV inks.
First, benzene-free gravure composite ink Traditional solvent-based flexible packaging composite gravure ink is generally composed of chlorinated polymers. In the ink production process, the solvents used in the ink are generally toluene, esters, ketones and other organic solvents. The role of toluene in the ink is: (1) good solubility for the resin in the ink; (2) good printability and wettability of the printing plate. Although most of these organic solvents will be eliminated after drying, the residues will still be harmful to the human body. Long-term contact will make the skin dry and rough. If it penetrates into the skin or blood vessels, it will endanger human blood cells and hematopoietic functions with blood, and may even cause Chronic poisoning of the body, organic solvents will also chemically react with some gases in the air to produce odorous chlorine and smoke, which will seriously pollute the air, have a greater impact on the growth of various plants, and disrupt ecological balance, so the ink factory has been working hard to develop environmental protection The benzene-free gravure-free composite ink with less pollution replaces the toluene ink to avoid health damage caused by benzene residue. At present, there are the following types of benzene-free composite inks:
1, Benzene-free ketone-containing polyurethane composite ink. Does not contain benzene solvents, but contains ketone solvents. Features are bright colors, good solvent release and good printability. Mainly used for printing PET film , NY film. In OPP film printing, the adhesion fastness is slightly worse, but it does not affect the composite strength.
2. Alcohol ester soluble polyurethane composite ink. Low odor, no benzene and ketone solvents. However, special attention should be paid to the reproducibility of the light-screen version when printing. It is mainly used for printing PET films and NY films. In OPP film printing, the adhesion fastness is slightly worse, but it does not affect the composite strength.
3. Alcohol-based acrylic ink, the main solvent is ethanol, and 10% water can be added as a diluent, which is cheap. At present, the ink factory mainly produces white ink, which can be used with ordinary benzene-soluble chlorinated polypropylene composite inks. The front color inks are printed with ordinary composite inks to maintain vivid colors. Finally, the white ink is used as a primer to reduce benzene. Residual solvent.
4. Alcohol-water-based polyurethane system composite ink mainly uses 95% ethanol as the diluent solvent. The ink does not contain benzene and ketone solvents. It has the characteristics of low odor, bright colors, low price and good printability. Can print PET film, NY film, OPP film. This product has been successfully launched in Zhuhai Lotong Co., Ltd. and is numbered GP39 series alcohol-soluble composite ink.
Like benzene-containing composite ink, benzene-free composite ink is also composed of a binder, a colorant, a solvent, and a small amount of auxiliary agents. Generally, a single solvent is not used in the ink, but several solvents are used to improve the solubility and drying performance. The quality control indicators of benzene-free composite inks mainly include: hue, fineness, tinting strength, gloss, viscosity, dryness, adhesion fastness, heat resistance and freeze resistance. These indicators are very important for plastic packaging printing .
Water-based inks Water-based inks use water as the main solvent and a small amount of alcohol as the co-solvent. The biggest difference between water-based inks and solvent-based inks is that the solvents used in water-based inks are water and ethanol, the VOC content is extremely low, and the environmental pollution is small. Advantages of ink painting: 1. Ink painting has environmental and safety advantages. Many inks can be designed as low VOCs or zero VOCs. 2. Ink has the advantages of stability and low flammability. Ink has better viscosity stability due to the low volatility of water. 3. The new generation of water-based products is easier to clean than the solvent system. The use of soapy water or weak alkaline washing liquid can complete the entire cleaning of the printing machine components, thereby improving production efficiency.
Compared with solvent-based inks, water-based inks have good fluidity and are easy to prepare high-pigment inks. Therefore, the color strength is generally 30% to 50% higher than that of solvent-based inks and still has good flowability. Due to the large surface tension of water, it is difficult to wet the ink, the water is not volatile, and the printing speed cannot be increased. If the printing speed and printing quality of solvent-based inks are to be obtained, not only the water-based inks need to be improved, but also the gravure printing equipment and printing plate rollers. For example: the corrosive or electric engraving roller is changed to a laser plate making roller, and the printing plate roller also needs to be made of a corrosion-resistant material. It is also necessary to retrofit more powerful and effective ink drying systems and equipment components such as ink scrapers on the printing press, which require considerable investment and long time. Therefore, in addition to printing on paper, water-based gravure inks cannot replace solvent-based inks.
Third, UV ink UV ink refers to the use of ultraviolet light of different wavelengths and energy to make ink film and dry ink under the irradiation of ultraviolet light. Utilizing different ultraviolet spectra, different energy can be generated to polymerize monomers in different ink linkers into polymers, so the color film of UV ink has good mechanical and chemical resistance.
Its main advantages are as follows:
(1) UV-curable inks do not contain VOCs, so they will not adversely affect the environment.
(2) In fact, the curing process can make the ink dry instantly (0.1s), so it can greatly shorten the curing time. In addition, UV-curable ink can adhere to the surface of the substrate without being absorbed by the substrate, so there is no need to apply a protective coating to the printed product, which allows the printed product to maintain consistent color. The improvement of the chemical composition in UV ink makes it have a longer life and stronger adhesion.
(3) UV glazing and continuous machining after UV ink printing, the printed matter obtained has high gloss, flat and uniform surface, and the packaging process can be completed immediately, which is beneficial to meet the needs of high-speed printing.
(4) Chemical substances in UV inks form high-molecular three-dimensional network polymers through cross-linking reactions. Therefore, the use of UV inks can make printed ink layers strong, quick-drying, and cross-linked. Such ink layers have higher wear resistance. Wipe performance and chemical resistance.
4. Water-based UV inks Generally, the viscosity of prepolymers in ordinary UV inks is very large, and it is necessary to add reactive diluents for dilution. The currently used diluent acrylate compounds have different degrees of skin irritation and toxicity. Water-based UV inks The ink uses water as a diluent and uses UV radiation curing technology, which greatly exerts the comprehensive effectiveness of the two. It is made by adding a certain amount of water and 5% environmentally friendly solvent to UV ink, combined with special water-based resin. Water-based UV inks combine the advantages of UV and water-based inks. Compared to traditional oil-soluble UV light-curable inks, light-curable water-based inks have the following advantages: it is not necessary to adjust the viscosity with the aid of a reactive diluent, which can solve VOC and toxicity and irritation problems; available Water or thickener controls the viscosity and rheology of the ink; extremely thin coatings can be obtained; equipment and containers are easy to clean; can be applied to screen, gravure and flexo printing.
V. Conclusion In summary, in order to adapt to the development trend of flexible packaging, it is inevitable to vigorously promote environmentally friendly inks. It is the incumbent responsibility of our ink R & D personnel to let the majority of users and consumers soberly understand and use more environmentally friendly inks for flexible packages. .

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