The "green" of printing production is still difficult - the safe disposal of waste products in printing (on)

(It's not easy-Safe Disposal of Printshop Waste Is a Job in ofself)

If you ask a printer about the problem of harmful waste, you may get a blank expression. The other person's answer may be "What waste? We do not have any waste." This is often heard.

Whether it is due to misdirection by inexperienced dealers, or because it is difficult to tell whether waste is harmful, printers are in fact surrounded by such harmful waste products.

We can imagine that each chemical entering the printing production process must have its final outlet. If chemicals do not become part of the product, they will evaporate or become waste water and become harmful substances.

Chemicals that enter the production chain are generally toxic, and they are finally emitted as harmful emissions. When chemicals are discharged from the production process in liquid or solid state and enter landfills or are burned, they will enter soil and natural reference water and food systems, potentially causing harm to human health.

It is the responsibility of the printer manager to identify and manage hazardous waste streams so as not to contaminate soil and water.

What is hazardous waste?
Any chemical waste that has one of the following characteristics can be called hazardous waste:

Combustible (D001): Liquid with a flash point of less than 60°C and 140°F.
Corrosive (D002): Liquid with a pH below 2.0 (acid) or above 12.5 (base).
Reactive (D003): Objects that are unstable at room temperature and are prone to violent changes.
Toxic (D004-D017): Contains chromium, lead and silver.

In addition, there are some special chemicals that are also harmful to the environment and society. The following is a series of numbers beginning with F, such as F005 for toluene, F003 for acetone, and F002 for perchloroethylene.

Once a chemical has been used or will soon be used, it will certainly produce waste, which means that waste should be under full control from the stage of generation of hazardous waste to the final dissolution of the waste. Waste from any production process, if it is not harmful, but is not conducive to a normal waste sorting system, should be marked as non-hazardous waste. If hazardous waste is mixed with harmless waste, the result is that all waste is harmful.

If you walk through the press, you will find many chemicals. "Material Safety Data Sheet (MSDS)" is a major tool for determining if a chemical is toxic and how toxic it is. The harmful ingredients and percentages will be listed on the MSDS. The identification of the composition of the printed matter and the origin of the waste will help determine the composition of the waste and the potential release hazard. It must be noted that many suppliers, in order to protect their own interests, tend to make their own description of the composition of the waste. MSDS often advises printers to consult with regional agents to determine if the final waste of their chemicals is harmful and to take appropriate measures.

Laboratory testing of waste products will facilitate more detailed categorization, such as quantity, type, content of each source, and the relationship between its maximum and minimum values ​​and safety standards. Usually called TCLP test.

In printing and post-press processing plants, waste products can come from every production step. The printing shop and the darkroom of the plate making will produce a lot of waste products, some of which have been classified as hazardous waste. Some of these wastes enter the production process as chemicals, and other wastes form an integral part of the production process.

Darkrooms produce photo-sensitive waste, and the fixer washes silver off the film or paper during exposure. If the fixer fluid displaced from the development system contains more than 5 ppm of silver, the liquid is a hazardous waste. Some manufacturers have restricted the use of silver salts to diffuse the plates to reduce the concentration of silver in the waste. In practical applications, this waste water can be discharged into the sewer, but it is not allowed to enter the collection tank or the sink.

The highly toxic, silver-containing waste developer is corrosive and is only hazardous when its pH is above 2.5. Photoresponsive film and paper products contain a certain amount of silver in the emulsion. When developing, silver is not completely removed from the photosensitive paper and film. Undeveloped waste paper and film will be carried along with silver. In the soil.

Due to the different printing processes, the composition of the ink is also different. Therefore, the classification of ink waste can also be classified as toxic and non-toxic. Offset inks have always been classified as non-toxic items and are strictly managed. Liquid inks, such as gravure inks and flexo inks, contain solvents, are flammable, and are often toxic, so they are recommended to be classified as hazardous waste and care must be taken to separate them from each other. Mixing ink and other toxic chemicals with the printing press may make all the mixed ink wastes harmful.

The fountain solution consists of a series of chemicals that are flammable if the fountain solution contains a high level of isopropyl alcohol. If the fountain solution is alcohol-free, it often contains vinyl glycol, propylene glycol, n-butyl carbitol, and other safer but still toxic chemicals.

Chemicals from various plates and plates may also contain toxic chemicals. They may be used as substrates or as a basic raw material for plates. It may also be the chemicals used in the processing of the plates.

In the cleaning process of printing presses and blankets, the cleaning liquid contains a large amount of solvents. These solvents, in addition to being flammable, also pose a hazard to human health. Various kinds of cleaning methods will generate waste more or less. Because the printing machine cleaning devices are also different from each other, the toxicities of waste generated are also very small.

Various oils (such as lubricants) used to maintain the printing presses and other equipment also contain various solvents, which may also be toxic. If the oil contains toxic chemicals, such as combustible alcohols, methyl chloride or methyl ethyl ketone, this waste oil cannot be buried in soil with other wastes.

Containers that have been loaded with ink, solvents, and other chemicals, if not completely emptied, may cause contamination of toxic waste. Measures must be taken and the container cleaned.

Finding Safer Substitutes The key to managing hazardous waste is to designate relevant procedures to eliminate or minimize the use of chemicals, which is a well-known key to environmental protection.

In order to achieve the same production efficiency or quality, it is also a simple measure to seek safer alternatives or other methods. In addition, some kind of technology can be used to reduce waste, recycle waste, or harmless before waste is removed. deal with.

Darkroom operation Silver salt diffusion is a major contaminant in the prepress process. The silver in the solution can be easily removed using a silver filter or an ion exchange system. Fundamentally, silver is collected in the filter and stays there. Finally, it can accumulate less and become one of the financial resources.

The key to this optimal management plan is to operate a filter device that can recover 95% or more of silver, and the device's silver collection efficiency must meet the requirements of local regulations.

The silver content of the filtered waste water is very low, and it is even possible to discharge the waste water directly into the sewer. In those places where collection tanks or sinks are used, the water discharged from the filtration device should have a lower silver content, ie, be cleaner, so as not to make the waste water a hazardous waste.

Fountain solution: Every effort should be made to extend the use of the fountain solution as long as possible to ensure quality. This effort may require the use of a filter in a recovery unit to filter out particles from paper and ink, and a cooler must be installed in the recovery unit. In addition, operators must be trained to change some of their work habits.

The non-alcoholic fountain solution is environmentally friendly and should be used with priority, and although new chemical formulations are used, the adjustment of the rollers is not large. Gradually reduce the concentration of the fountain solution, or to reduce the content of harmful substances in the fountain solution (such as vinyl glycol), the use of safer, less toxic chemicals, but also a solution. As long as we continue to work hard to develop new safety chemicals, change our methods of operation and our attitude towards environmental protection, we will eventually succeed.

We can always use the fountain solution until the light is used, or do not adjust the fountain solution to the optimal concentration before replacing the fountain solution. This will reduce the evaporation of the volatile solvent in the fountain solution and also reduce the residual liquid. The content of organic solvent makes it not become harmful waste liquid. Solutions with low levels of isopropanol or similar solvents are flammable and must be discharged to comply with relevant regulations.