China's printing industry faces the challenge of e

2022-08-16
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The printing industry in China is facing the challenge of environmental pollution. The printing industry is one of the industries with the fastest technological progress in the world in recent 20 years. At present, it has entered a new era of digital printing. It is reported that human beings have experienced about 100000 years from language to printing, 450 years from the invention of printing to lead printing, about 30 years from lead printing to color desktop system, 3 years from color desktop system to multimedia electronic publications (paperless printing), and only 18 months from multimedia to Internet. The international development trend is that high-end color printing materials are growing rapidly, and high and new technologies such as computers and electronics are widely used in printing technology

at present, the situation of China's printing industry is that traditional offset printing is still dominant, flexographic printing and silk printing are developing rapidly, post press binding linkage automation and color desktop publishing system have been widely used, the openness and digitization of image and text processing system have become the basic characteristics of prepress system, and direct plate making technology and digital printing have become the development direction of printing and publishing industry. The development of the printing industry and the continuous improvement of environmental protection laws and regulations have brought great challenges and opportunities to the development of the printing industry, including the development of various new printing consumables in line with environmental protection; Reform the original process, including the improvement of raw materials and drying methods

at present, silk screen printing in China enables all participants in the value chain, from engineers, film designers and manufacturers to project owners, to harvest the solvent based inks widely used in printing processes such as brush and gravure printing, which contain 50%-60% of the volatile components. If the diluent required to adjust the viscosity of the ink is added, the total content of the volatile components emitted by the ink when the print is dry is 70%-80%. The gases volatilized by these organic solvents enter 1 enterprise through breathing: ① building a harmonious enterprise is our highest pursuit. They enter workers' bodies, cause damage to human liver and nervous system, and cause great harm to the environment

the alcohol fountain solution in the offset printing process emits organic volatiles into the air of the workshop all the time. When the work is temporarily stopped or the color is changed, the ink roller and blanket are cleaned, and flammable Explosive gasoline (of course, from the perspective of the manufacturer, using gasoline as a cleaning agent is convenient and readily available, with good cleaning effect and fast drying speed; the most important thing is that the price is cheap, which greatly reduces the production cost). But when seeing the benefits of gasoline, people often forget that using gasoline like this may cause an explosive fire, which will destroy the printing factory in an instant; On the other hand, when using leaded gasoline, it will lead to chronic lead poisoning of printing workers, which is even more ignored

for a long time, the phenomenon of "flying ink" in various printing processes has troubled the whole printing process. This is because when the printing press rotates at high speed, the ink film between the ink rollers is split and stretched, resulting in fragments. Under the action of the surface tension of the ink, these fragments shrink, forming many spherical small ink droplets scattered in the air, which is the so-called ink flying phenomenon. The problem of flying ink is not only a common printing fault with great harm in the process of high-speed printing, but also a serious problem causing environmental pollution

flying ink brings great harm to the printing process:

1. It pollutes the environment. The ink is scattered in the air, on machinery and equipment, on the wall, etc. the light will affect the cleanness and beauty of the environment, and the heavy will even cause olefin explosion and safety accidents

2. Adverse effect on product quality. Ink flying on the printed matter will cause a certain degree of dirt on the surface of the printed matter, which will affect the clarity of the printed matter, and even cause the printed matter to be discarded in serious cases

3. Damage to human health for a long time. Due to the widespread use of organic pigments, organic solvents and additives in current inks, many raw materials contain heavy metals. These harmful substances will be adsorbed on the surface of workers' skin through flying ink and inhaled into the respiratory tract, which is bound to have adverse effects on the health of operators

it can be seen that the emission of harmful gases, the use of harmful liquids and solids and the emission of waste in the printing industry pose a serious threat to human health and human living environment. Environmental issues are not only related to the future of human civilization, but also to the survival and development of enterprises. When formulating the development plan of the printing industry, we must simultaneously consider the issue of environmental protection, which increases the proportion of income from high-performance and high value-added products, and formulate practical and effective measures

in order to limit pollution abroad, some countries have formulated a series of regulations such as "labor hygiene law", "organic solvent discharge law". These laws and regulations determine the research and development direction of printing production process and ink

foreign countries, such as Germany, promulgated the chemical law as early as 1982, which contains three provisions: the protection of workers in workshops; General health protection; Environmental protection. Under the pressure of environmental protection laws, foreign research departments and some manufacturers are forced to research and develop solvent-free inks or silk printing inks with low solvent content

European and American countries passed volatile organic solvents (VOC) laws related to environmental protection around the 1990s. VOC law requires printing plants and ink manufacturers to meet the following requirements:

1. There should be no solvent smell outside the workshop

2. The concentration of volatile substances in the workshop must be lower than:

volatile organic solvent 50 mg/m3

carbon monoxide 100 mg/m3

nitric oxide 100 mg/m3

this strict environmental protection law will sooner or later become the benchmark of environmental protection in all countries in the world

this requirement is currently difficult for most domestic manufacturers (including printing plants and printing consumables manufacturers), because there are many components related to VOC and other environmental pollution problems in various printing processes and traditional consumables, but the following problems can be solved through efforts:

1, cold solid rotation The volatile matter problem of most cleaning supplies and wetting liquid in the sheet fed offset printing process: now foreign countries have abandoned gasoline as cleaning supplies and replaced it with a special ink cleaner (w/o lotion type), which should be vigorously promoted; At the same time, Denis Pei has always attached importance to the investment in technological innovation and equipment renewal. The company should develop a new alcohol free fountain solution for offset printing, which is suitable for high-speed rotary offset printing machines

2. Strictly check the components contained in the ink, and do not use pigments containing harmful heavy metals to produce the ink, so as to ensure that the workers are not harmed by heavy metals; At the same time, we should further improve the quality of ink and reduce the production of flying ink

3. Thermosetting rotary offset printing process is the main producer of VOC, because its solvent distillation range is at ℃; The drying of ink is forced under the high temperature of 300 ℃ in the drying device. According to the carbon content, 0.3 kg of VOC will be released per kilogram of carbon in the ink; It should be recycled through the recycling device

4. A large number of volatile low boiling point solvents are used in the rotogravure printing process, so serious VOC problems will occur. If a solvent recovery device is installed on the rotogravure printing machine, the purpose of reducing VOC volatilization can be achieved

5. In the gravure printing process, flexographic printing process and silk printing process, try to use ink (water-based ink) with water as solvent, which may reduce VOC problems. At the same time, try to reduce the alcohol content in water-based ink (usually containing 15% alcohol)

in the production and development of ink, in order to meet the requirements of VOC law, western countries have made great improvements in ink formula and drying system. At present, the following varieties of ink are widely used:

1, radiation curing ink. In fact, UV curable inks have been developed as early as the 1940s, but they have not been greatly developed until the last 20 years. Because there is no solvent in the ink, there is no VOC problem, and the printing process is environment-friendly. After the 1990s, with the implementation of VOC laws in western countries, it should be said that people have a further understanding of UV curing ink. But the cost of UV curing ink is higher, and the use process is more complex than conventional ink

2. Water based ink. It has long been used in flexo, gravure printing and silk printing, but it is not used in offset printing ink. Water based flexographic inks have been widely used in newspaper printing, and water-based intaglio inks have also begun to replace solvent based inks. However, at present, this trend shows signs of slowing down and will continue until more stringent laws are introduced

3. Vegetable oil based ink (mainly soybean oil ink). It has achieved success in offset printing ink

in solving the problem of VOC, western countries now focus on developing new curing device control system and new ink drying methods. Let's take a look at the new ink drying method

voc law requires printing plants and ink manufacturers to strictly control the emission of organic solvent volatilization (VOC). Therefore, no matter the drying system or the development of new ink drying methods, the following points must be considered:

1. Reduce VOC emissions

2. Because the drying system consumes a lot of energy, improving the efficiency of energy use has become the second goal that the drying system should achieve

3. As the printing speed of the printing machine becomes faster and faster, the drying system should keep up with this trend to ensure the printing efficiency

4. In order to reduce VOC volatilization, the recycling of solvent products in the printing process should be considered for printing machines with high solvent content and large ink consumption

5. On the premise that all the above points are met, the last point is to ensure the printing quality

how should the drying system be improved? It can be improved in the following aspects:

1. Improve the drying system. The first is to improve the air nozzle system, reduce the speed of air in the drying device, reduce air consumption and reduce energy consumption. However, to maintain the drying efficiency, reducing the speed of air in the drying device is not achieved by simply reducing the fan speed, but by improving the nozzle system on the premise of maintaining the drying efficiency. Carefully adjust the installed equipment to make it in the best working condition. If adjusted properly, it can save 30% - 50% of energy (at most) and increase the printing speed by 40% (at most). This is also very important for the equipment in use

2. Improve the control system of the drying device. Nowadays, many new drying devices directly measure the temperature of the substrate surface, unlike the previous drying devices, which measure the air temperature in the oven, so that they can respond to the temperature changes on the substrate surface in time, adjust the wind speed and heat in time, and then save energy

3. The recycling of hot air should be considered. It is easy to solve this problem. Install a heat exchanger at the hot air outlet to preheat the cold air pumped in, so as to achieve the purpose of energy saving

4. Introduce inert gas into the drying device. Because some solvents have low flash points, they are prone to production accidents, which can ensure the safety of highly volatile solvents that are flammable and explosive in the air, improve the efficiency of solvent recovery devices, and reduce the flow of air, thus reducing the heat used to heat the air

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