In the current digital printing plate technology, in addition to the thermal abrasive (thermal abrasive) printing plate does not need to be processed, all types of digital printing plates (including heat sensitive, photopolymerization, silver salt) need to go through the step of syrup washing, will There is no justification for one printing plate to be more environmentally friendly than another printing plate when chemical waste is generated. In fact, many countries and regions in the world attach great importance to environmental protection and prohibit the discharge of waste liquid to public drains. Therefore, whether it is thermal, photopolymerization or silver salt version, the waste liquid needs to be recycled. As we all know, Europe has very high requirements for environmental protection, but its newspaper industry uses photosensitive CTP, and the use of photosensitive plates after recycling has basically no impact on the environment.
Regarding the environmental protection of the CTP version, there is a view that the photosensitive silver salt version will cause pollution to the environment, while the thermal version has little impact on the environment. The main reason is that the silver salt version will bring the silver halide to the process of processing In the waste liquid, the discharge will cause damage to the environment, so some people think that the silver salt plate (including the purple laser printing plate) does not meet the environmental protection requirements. Is this the case?
Therefore, our focus should be on two areas of improvement:
1. Minimize waste liquid production
In the market, some suppliers have made a lot of efforts, either through product improvement or launching new products, to minimize the generation of waste liquid. For example, Mitsubishi Corporation of Japan has designed an environmentally friendly plate-making machine, which does not need to be connected to a drain pipe, which greatly reduces the treatment cost of waste liquid. Agfa also improved its processing system. The amount of waste produced by the new plate processor has been reduced by 40%. Under normal circumstances, the processing of every square meter of printing plate produces no more than 300 ml of waste (including developer) , The amount of replenishing liquid, fixing agent and water), in addition to making the treatment of waste liquid easier, at the same time saving the amount of water and chemical agents, to achieve the purpose of environmental protection.
2. Select some printing plates whose main components can be recovered from the waste liquid
CTP plates with reliable quality, reasonable prices and environmental protection will be welcomed by the market. The silver salt version provides the highest exposure speed, easy processing, and the feasibility of silver recycling, so it is used by thousands of printers around the world. The purple laser printing plate in the silver salt plate can be operated under the yellow light of the nearly bright room environment. It has high tolerance and does not require preheating or baking. It provides an ideal choice for printers.
One of the main components of the silver salt coating is silver, and silver can be completely recovered from the waste liquid. The current recovery methods such as precipitation, filtration, centrifugal treatment, etc., further concentrate the metallic silver. These methods have proved to be very effective. Many processing machines combine three different waste liquids into a single container for storage, which facilitates the collection and transportation of waste liquids. The waste liquid of the processing machine can be mixed and stored with the waste liquid of the filming machine without causing safety problems, and the unified recovery is more convenient. The waste liquid generated by the general silver salt plate flushing system has a PH value of 6-7, a metallic silver concentration of 6 to 10 grams per liter, and an aluminum content of less than 0.5 grams per liter. This silver concentration is sufficient to allow waste disposal companies to recycle under economic conditions. Due to the high concentration of silver and recycling technology is not difficult, waste disposal companies in many places provide free collection of waste liquids, customers do not need to pay any fees. Now that the production of silver salt waste liquid has been reduced to a minimum, the harmful substances in the waste liquid have also been recovered, and there will be no pollution to the environment. On the contrary, the waste liquid generated by the thermal version of the flushing system cannot be recovered. The general practice is to discharge it after alkaline neutralization. Its ingredients still contain harmful substances, which will also have a certain impact on the environment and ecology.
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