There are frequent measures to limit VOCs (Volatile Organic Compounds) emissions, The environmental protection situation in the printing industry is increasingly severe. Although compared with the petroleum and petrochemical industries, even compared with the gravure printing process, the traditional offset printing production has very few VOCs emissions, but with the refinement and comprehensiveness of the greening work in the printing industry, as well as the printing Considering the health of workers, some industry professionals have already paid attention to the reduction of VOCs in the traditional offset printing field and began to actively fight VOCs.
Below, the author will start from the identification of VOCs in the offset printing process and the currently feasible VOCs emission reduction measures, and summarize some of the experiences of our company in the reduction of traditional offset VOCs for many years. The VOCs emission reduction effects described in the paper are mostly According to the actual use of our company, the calculation is for the reference of the industry.
Offset process VOCs source identification
In order to do a good job in reducing VOCs, the first issue is to find out the source of VOCs. Let us discuss the source of VOCs in the offset printing process.
1. Chemicals used in prepress plating
The traditional use of color separation film to make the PS plate requires two steps of development and water washing, and it is also necessary to apply a protective glue on the printing plate. These processes produce a large amount of chemicals and waste solutions that are harmful to the human body and the environment, and also generate a large amount of VOCs.
2. Ink
The printing ink is composed of a pigment, a binder, a solvent, and an auxiliary agent. Alcohol solvents such as isopropyl alcohol (IPA) are used in offset inks. During use, most of these solvents will volatilize into the air, posing a hazard to the working environment and the ecological environment.
3. Run solution
The dampening solution ensures that the blank portion of the printing plate forms a hydrophilic layer, and the main components of the dampening solution are usually isopropanol and phosphoric acid. Isopropanol can reduce the surface tension of water and avoid the emulsification of ink and dampening solution, but it is also a photochemical oxidant. It will form ozone when exposed to sunlight, irritating human eyes and respiratory system, endangering human health and affecting plant growth. . The higher the isopropanol content in the dampening solution, the more VOCs are emitted.
4. Car wash water
The components of the printing press must be cleaned frequently. Common cleaning solvents include n-heptane, gasoline, kerosene, glycol ethers, alcohols, toluene, ethane and specially formulated mixtures. When the printer wipes the parts of the printing machine with a rag to pick up the car wash water, the cleaning solvent in the car wash water will volatilize into the air and escape to the atmosphere with the ventilation system of the plant. This is the VOCs discharge caused by the car wash water. It is worth mentioning that although the conventionally used solvents such as n-heptane, gasoline and kerosene have an ideal cleaning effect, they have a certain corrosive effect on the printing machine ink roller and blanket.
5. Adhesive
The adhesive in a broad sense also includes a film adhesive, but the adhesive mentioned herein mainly refers to the material used in the post-printing process of the book, excluding the film adhesive.
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