How can gravure printing enterprises quickly enter the ranks of green printing? Ελλάδα

       【Abstract】Gravure printing, as a kind of printing process, has the advantages of thick ink layer, bright color, high saturation, high printing plate durability, stable printing quality, and fast printing speed in printing, packaging and graphics. The field of publishing occupies an important position. So, how can gravure printing companies keep up with the pace of the times and quickly enter the ranks of green printing? I hope this article can give some references to relevant enterprises.

        On October 8, 2011, the General Administration of Press and Publication and the Ministry of Environmental Protection jointly issued the "Announcement on the Implementation of Green Printing", which sent an important signal to printing companies across the country: companies without green printing qualifications cannot participate in the development of textbooks in the first place. After that, they will be excluded from printing candidates such as bills, food and drug packaging, etc., and may be forced to transform or be eliminated in the end.

        As a kind of printing process, gravure printing has the advantages of thick ink layer, bright color, high saturation, high printing plate durability, stable printing quality and fast printing speed, and occupies an important position in the fields of printing, packaging and graphic publishing. important position. So, how can gravure printing companies keep up with the pace of the times and quickly enter the ranks of green printing? I hope this article can give some references to relevant enterprises.

Trace the source of pollution

        The process of gravure printing is less, but there are also some raw material usage and process technology that are not in line with green environmental protection. The common pollution sources in the production process mainly include the following three types.

1. Gravure plate making

        Gravure plate-making includes two methods of corrosion plate-making and engraving plate-making. Corrosion plate making uses chemical solvents and corrosion treatment technology, which needs to go through pickling, copper plating, chrome plating, ferric chloride corrosion and other processes, and discharges a large amount of chemical substances. Although the engraving plate-making reduces the corrosion of ferric chloride, it still needs to go through the steps of pickling, copper plating, and chrome plating in the pre-plate-making and post-processing processes, which also produces harmful waste liquid and pollutes the environment.

2. gravure ink

        In gravure printing, the largest VOC emission is gravure printing ink. Gravure printing ink is composed of solid resin, volatile solvent, pigment, filler and additives, does not contain vegetable oil, and its drying method is mostly volatile. According to different printing substrates, gravure inks are divided into paper gravure inks, plastic gravure inks, alcohol-soluble gravure inks, etc. Paper gravure printing ink contains solvents such as toluene, xylene, gasoline, etc., and there is an environmental pollution problem caused by solvent volatilization. Plastic gravure printing ink contains polyamide resin, xylene, isopropanol, chlorinated polypropylene resin, toluene, ethyl ketone, methyl ethyl ketone, ethyl acetate, etc. The chlorofluorocarbons volatilized during the printing process of this ink will Destroy the ozone layer, and toluene, xylene will cause harm to the health and safety of workers. Toluene is a slow-drying solvent that easily remains in the dry ink layer, posing a direct threat to consumers.

3. detergent

        The cleaning agent used in gravure printing usually contains chemical substances such as toluene, xylene, propyl acetate, butyl ester, and chlorofluorocarbons, which are highly volatile and will cause great pollution to the environment. In addition, chlorofluorocarbons can destroy ozone while causing bodily harm to operators.

Implement "Green" Behaviors

        At present, the green concept has been integrated into all aspects of gravure printing. According to the "5R+1D" principle summed up from the experience of enterprises in the industry, it has certain practical significance for improving the utilization rate of enterprise resources, reducing emissions, preventing pollution, and making traditional gravure printing a new type of green and environmental protection industry.

        Reduce principle (Reduce): reduce the consumption of energy and resources, reduce the discharge of waste water, waste gas and solid waste that are harmful to human health and the environment, and reduce noise pollution. The principle of repeated use (Reuse): materials can be reused in their original form, thereby reducing costs and reducing waste emissions. Renewal principle (Renew): After the product has been used, it should be treated accordingly to restore its original function. The principle of recycling (Recycle): After the product has completed its function, it can become a usable resource again. Replacement principle (Replace): Use new materials to replace previously harmful materials to reduce harm to nature and the human body, or use new processes and methods to replace original low-efficiency production processes and methods to improve efficiency and save energy and resources. Degradable principle (Degradable): Under the action of microorganisms (bacteria, mold, algae), biochemical reactions occur, and finally form substances that are common in nature such as carbon dioxide and water.

        Based on the above principles, some gravure printing companies started from their own production links and launched a series of green measures to improve their own environmental protection, mainly including the following points.

1. Use environmentally friendly gravure ink

        Environment-friendly gravure ink refers to water-based ink and alcohol-soluble ink with less pollution and less pollution.

        Water-based inks are processed and ground from water-soluble resins, advanced pigments, solvents and additives. Since the solvent used in water-based ink is mainly water and does not contain other organic solvents, its biggest feature is that it does not pollute the environment and can avoid the harm of certain toxic substances in solvent-based inks to the human body and the pollution of printed products, and the product has glossiness. High, bright ink color, high concentration, wear resistance, excellent smoothness and other advantages. In the field of flexible packaging, since water-based inks cannot completely replace solvent-based inks in a short period of time, efforts to develop alcohol-soluble inks that are easy to handle in the environment are still the leading direction for the development of environmentally friendly inks. Alcohol-soluble ink is composed of alcohol-soluble synthetic resin, solvent and organic pigment. It has good fluidity and printability, fast drying, bright luster, and bright colors. It is also a volatile drying ink and can be widely used in plastic film printing. Alcohol-soluble ink products currently on the market include alcohol-soluble surface printing inks and alcohol-soluble interior printing composite inks.

2. Use environmentally friendly adhesives

        Traditional adhesives contain free TDI and solvent residues, which are flammable, explosive, VOC emissions and other safety and pollution hazards. Therefore, the development of water-based, solidified, solvent-free and low-toxic environmental protection adhesives has become inevitable. Direction of development. Environmentally friendly adhesives include hot melt, solvent-free and water-based adhesives. Hot-melt adhesives are solid at room temperature and melt when heated to a certain temperature. They are adhesives with a certain bonding strength. It can be made into blocks, films, sticks or granules for easy packaging and storage. Its bonding speed is fast, which is suitable for automatic operation and high efficiency requirements. There is no solvent volatilization during use, and it will not pollute the environment, which is conducive to resource regeneration and environmental protection. Solvent-free adhesive is to apply two groups of substrates that can undergo chemical reactions on the surface of the bonded materials respectively. Under certain conditions, they are in close contact to carry out chemical reactions to achieve the purpose of crosslinking. Water-based adhesive is an environmentally friendly adhesive made of water as a solvent or dispersion medium. Since it does not contain organic solvents, it reduces environmental pollution and has the advantages of less glue and high bonding strength.

3. Improve Heating Efficiency of Gravure Printing Drying Device

        In the traditional gravure printing drying process, the heat energy generated by the heating element is transferred to the substrate through the radiator, so as to realize the drying of the substrate. Therefore, improving the heating efficiency of the heating element, strengthening heat preservation, and reducing heat loss are important ways for the drying oven to save energy. The specific measures are as follows: change the resistance wire of the radiator to a resistance band, and apply infrared paint, which can not only strengthen the radiation heat transfer, but also protect the resistance band; the box wall adopts a light insulation layer and pastes ceramic fiber felt, Reflects heat to prevent heat loss.

4. Treatment of gravure plate-making waste liquid

        In the process of traditional gravure printing corrosion plate making, the waste liquid contains a large amount of heavy metal ions, and direct discharge will cause huge pollution to the environment. The redox reaction can be used to recycle the waste liquid and save resources. The specific measures are as follows: detect the content of copper ions in the waste liquid, calculate the amount of iron powder and hydrogen peroxide needed to treat the waste liquid; add iron powder to the waste liquid for full reaction, filter after the reaction, and separate the solid phase and the liquid phase Separation, the solid phase is used to extract copper for reuse; hydrogen peroxide is added to the liquid phase in the previous step for a full reaction, and hydrogen peroxide is added after the reaction to make the solution saturated, which can be reused for copper washing.

5. On-line recovery of solvents

        In the gravure printing process, the ink is forcibly dried at a high temperature of 300°C in a drying device, and every kilogram of carbon will release 0.3kg of VOC substances. In order to reduce VOC emissions, for gravure printing machines with high solvent content and large ink consumption, enterprises should consider recycling solvent products online during the printing process; for collected waste solvents, consider using heating distillation to recover solvents.

        Absorption method: According to the principle of homogeneity, let the mixed gas of solvent and air enter the equipment from the bottom, pass through the packing layer of oily liquid with high boiling point and low viscosity, the gas-liquid reverse convection, and the solvent molecules are absorbed and dissolved by the oily liquid in. By adjusting the height of the packing layer and the flow rate of the dripping oily liquid, the final exhaust gas can meet the environmental protection requirements. The oily liquid that has absorbed the solvent can be separated from the oily liquid by fractional distillation.

        Solid adsorption method: Molecular sieves, activated carbon and activated carbon fibers can be used as solid adsorbents. Molecular sieves are mostly used for gas drying due to their small pores and high price, but are rarely used for solvent recovery production on a large scale. Activated carbon is an adsorbent widely used in solvent recovery. It has a good effect of intercepting solvent gas from solvent mixed air and is easy to regenerate, so it has been widely used.