Green printing faces process improvement problems
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The industrial development in the world today is staggering, and the industrial pollution generated is also shocking. Toxic industrial waste water, waste gas, solid waste, etc. are gradually consuming our homes. At the same time, more and more people are beginning to care about our living environment and become aware of the importance of environmental protection for sustainable development. Today, environmental protection has been deeply rooted in the hearts of the people.
Use environmentally friendly inks
Ink in the printing industry is indispensable and uses a lot, but it is also the most serious harm to human health and the environment. The first is volatile organic compounds (VOCs). The volatilization of ink solvents can cause serious greenhouse effects, which can cause photochemical smog and damage the human nervous system. Secondly, heavy metal elements such as clamps, chromium and mercury in ink pigments, if they contain these heavy metals. The use of ink for food packaging or close contact with the human body is unimaginable. In order to reduce the damage of the ink to the environment, it is necessary to use a new type of non-polluting ink.
UV curable ink
UV-curable ink refers to the use of ultraviolet light of different wavelengths to make the ink change from liquid to solid, and film and dry. Since this ink does not contain any volatile solvent, it is free of VOC or other harmful substances, and the pollution is almost zero. It is a truly environmentally friendly ink. It also has the advantages of good gloss, bright colors and fast drying speed. It is an ideal ink. At present, UV ink technology has been mature, but it should be used to prevent ultraviolet rays from harming operators and avoiding ozone. These problems can be solved by ventilating the UV lamp around the UV lamp by providing the operator with UV-protective overalls and rubber gloves.
Water-based ink
This ink uses water and ethanol as solvents, has very low VOC emissions, is less polluting to the environment, and does not endanger human health. It is the only ink of all printing inks approved by the American Food and Drug Association. In the United States, 95% of flexo prints are printed with water-based inks. In addition, it also has the characteristics of non-flammable, bright colors, non-corrosive plates, good adhesion, and strong water resistance. It should be noted that the aqueous ink is generally alkaline. Therefore, the waste water such as the cleaning ink tank, the ink roller and the printing plate should be added to the acidic substance for precipitation before it can be discharged, otherwise the water body will be polluted.
Waterborne UV ink
This thinner is to be improved since the diluent of the currently used UV ink is toxic and irritating to the skin. Water-based Uv inks were born in this context, using ethanol and water as thinners. This ink has good environmental characteristics of the above two inks.
New environmentally friendly ink
For example, vegetable oil inks, the most commonly used is soybean oil. The American Soybean Oil Association standard stipulates that the sheet-fed offset ink has a soybean oil content of more than 20%, and the rotary offset ink has a soybean oil content of 7% or more. Japan's Osaka Printing Ink Company has also recently introduced a new environmentally friendly ink, which is a sheetfed offset ink, which is a 100% vegetable oil ink based on soybean oil, which meets environmental protection requirements.
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R&D and use
Non-polluting film and developer
Since not all companies now have the ability to use CTP and digital proofing processes, laser imagesetters are everywhere, and the use of silver-containing film has become an inevitable problem. In the case of fixing, the waste water contains silver ions, which may cause damage to the environment. The harm of the developer can not be ignored. The developer is generally a drug harmful to the human body such as hydroquinone. Long-term contact may cause hair loss, redness of the skin, and serious eye diseases.
There is now a dry film imaging technique that uses a special film to solve the above problems. It does not have the exposure and development process of traditional film and can be imaged without any chemicals, so it is called "green film".
Use CTP and digital proofing
The computer direct plate-making technology directly outputs the graphic information after RIP to the printing plate through the computer, removes the film as the intermediate link, reduces the steps of film output, development, fixing and printing in the plate making, greatly reducing the silver content, The discharge of waste liquids such as hydroquinone, which is harmful to the human body and the environment, also reduces the damage of ultraviolet light to the human body and the pollution of the air, which brings good news to the environment.
The digital proofing technology corresponding to CTP is gradually phasing out the traditional proofing process for film-making. Digital proofing and CTP technology together announced the advent of the digital printing era, and also announced that the use of film for many years, the environmental pollution hazard will soon exit the printing market. Heavy metals and toxic developers that are harmful to the human body and the environment will no longer be used. This technology will undoubtedly accelerate the pace of printing towards environmental protection.
However, CTP and digital proofing techniques are not perfect. At present, because CTP has not been mass-produced, the price is relatively high, and the cost of use is also large. Only a few large enterprises are willing to purchase, while many other small and medium-sized enterprises still use the traditional method of lower cost. The same is true for digital proofing. Not only is the machine expensive, but the proofing cost is about twice that of the traditional one. These factors have constrained the development of environmentally friendly printing technology.
Promote flexographic printing
Due to its good printing quality, wide printing materials, low investment and high efficiency, and good environmental performance, flexo printing has developed rapidly in developed countries such as Europe and America. An important reason for flexo printing in the packaging field is that it uses water-based inks and does not contain toxic organic substances, which is in line with the green development trend of modern packaging printing. The biggest feature of water-based inks is the significant reduction in VOC emissions, which reduces air pollution and improves the working environment in the pressroom. Due to its environmental characteristics, it is especially suitable for packaging and printing of food, beverages, medicines and other items.
Flexo printing can also use solvent-free UV inks, so there is no solvent emissions and no environmental pollution. In short, due to the use of environmentally-friendly green materials, flexographic printing is expanding its range of applications and is the leader in packaging and printing. Therefore, in order to achieve green printing, we must vigorously promote flexographic printing.
Try waterless offset printing and alcohol-free printing
Waterless offset printing uses an ink-repellent silicone resin coated printing plate to remove the coating in the image to absorb the ink and realize the transfer of the graphic, so that the fountain solution is not required to achieve the ink balance. The dampening solution contains volatile organic substances such as isopropyl alcohol, which are inhaled by the human body for a long time, which may affect the function of the kidney and lungs, and may even cause dermatitis or damage to the nervous system. The inks commonly used in waterless offset printing are soy oil inks and aromatic-free inks, which are not produced by VOC and therefore do not affect the human body and the environment. Therefore, the removal of dampening solution and the use of non-solvent inks can be said to be a major contribution to environmental protection by waterless offset printing.
In addition to removing the dampening solution in the production process, we can also find alternatives to reduce the harm of IPA to workers' health and the environment. Alcohol-free printing meets the requirements. This substitute is mainly composed of one or two chemicals of ethylene glycol and ether and other additives, and has good environmental performance. Of course, the use of substitutes will also bring some new problems, such as the new dampening solution is too slow to volatilize, which is not conducive to the machine cooling, and the replacement of the product does not have the effect of disinfecting the dampening system.
Open up the digital printing market
Since digital printing is directly from the computer to the print, no film or printing plate is required, eliminating many intermediate steps of conventional printing and avoiding the use of toxic chemicals such as developer. Digital printing uses a new imaging technology that can largely avoid a series of problems caused by the evaporation of organic solvents in the traditional printing process. The main imaging principles of digital printing are as follows:
Electrophotographic
Its basic principle is to form an electrostatic latent image on the photoconductor by laser scanning, and then use the Coulomb force between the charged toner and the electrostatic latent image to realize the visualization of the latent image, and finally transfer the toner to the substrate. . Since electrostatic photography uses toner, no volatile organic matter is produced throughout the printing process, which is a non-polluting imaging technique.
Inkjet printing
The ink is ejected from the fine nozzle onto the substrate at a certain speed, and finally the ink image is reproduced by the interaction of the ink and the substrate. According to the way of inkjet, it is divided into continuous inkjet and drop-on-demand inkjet.
Magnetic recording imaging
This technology relies on the magnetic material to form a latent image under the action of an external magnetic field, and then uses the interaction between the magnetic toner and the magnetic field force of the latent image to complete the visualization of the latent image. Finally, the magnetic toner is transferred to the substrate to complete the printing. .
Electrocoagulation imaging
The ink is agglomerated by the electrochemical reaction, so that the ink is fixed on the surface of the image forming roller to form an image, and the ink which is not reacted in the non-image portion is still liquid and can be scraped off. Finally, the ink fixed on the surface of the drum is transferred to the substrate by the action of pressure.
Elimination of film, plastic molding process
For the sake of beauty and protection of the mountain, many printed materials are now covered with plastic film, but this process will cause serious environmental pollution. First of all, it will cause white pollution like the plastic products we usually use. The film covering the surface of the printed matter is as difficult to degrade as other plastic products, and benzene is involved in the processing, which is harmful to human body. In addition, the coated paper is not recycled and wastes resources. The source of cellulose in China's papermaking is the recycling of old paper, which is made into pulp after deinking and recycled. However, coated paper cannot be recycled. On the contrary, if it is simply incinerated, it will cause secondary pollution. The laminating process also frequently causes problems such as foaming, wrinkles, and film peeling. Therefore, the film coating and plastic molding process is a technology that damages the environment, and we should avoid using this post-press process.
Environmentally friendly glazing coating
Post-press glazing, like the film, also protects the cover and improves the gloss of the print, but the process is simpler and less expensive than the film. In the past, solvent-based varnish was used, and VOC volatilization during use was very unsafe and caused great damage to the environment. The new waterborne varnishes and UV varnishes contain no solvents and can be used in a wide range of applications. Especially in the field of packaging and printing, water-based varnish has been widely used in the packaging of products such as cigarettes, wine labels and food packaging bags because it does not cause harm to the human body.
In addition to the above-mentioned main ways, as long as we are a caring person in production practice, we will find more ways to improve the printing process and achieve green printing. In short, print is everywhere, and printing is closely related to people. Green printing is not only related to the long-term interests of the printing industry, but also to the coordinated development of the whole society. How to achieve green printing, each company should develop a reasonable plan according to their actual situation. Only in this way can we achieve sustainable development in the printing industry and make the printing industry prosper.