1. Printing process
The printing process includes pre-press service design, printing and post-press processing. Pre-press service design refers to the original manuscript made of digital files or printing plates; printing refers to the graphic information from the printing plates or digital files transferred to the surface of the substrate; post-press processing refers to the printed matter to obtain the required shape and use of performance, such as processing into a book or made into a box and so on.
1.1 Traditional printing
Traditional printing can be divided into lithography, letterpress, intaglio and perforated printing according to the different printing plates. Lithographic printing is the use of ink and water to complete the principle of printing, offset printing process is widely used. The printing plate used in offset printing is a precoated photopolymerized plate (PS plate). Letterpress printing plates currently include aluminum alloy, lead alloy, copper plate, zinc plate, plastic plate, etc. However, due to the toxicity of lead lettering and lead alloy plates, letterpress printing was once in decline. With the emergence of flexographic printing, letterpress printing rose again. Flexo plates use such as rubber letterpress, photopolymerized resin plates and other elastic solids made of letterpress.
1.2 Digital Printing
Digital printing refers to the reproduction process in which a colorant/colorant (e.g., ink) is transferred directly to the substrate using data files to control the appropriate equipment. The digital printing system is mainly composed of pre-press systems and digital printing presses, some systems are also equipped with binding and cutting equipment.
1.3 Screen Printing
Screen printing technology is screen printing technology, which means that it is based on the screen, and then through the photopolymerization plate making method, made with the graphic screen printing plate. To screen print, the technology is five main elements, which are screen printing plate, squeegee, ink, printing table and substrate. Screen printing will produce paint, ink cleaning wastewater, plate washing wastewater, waste empty containers, waste rags and so on.
Packaging and printing industry hazardous waste treatment
2. Printing process hazardous waste generation node analysis
Hazardous waste generated by the printing industry mainly comes from the pre-press process and printing two sections.
2.1 Hazardous waste generated by the pre-press process
Hazardous wastes generated by the pre-press process include photographic material wastes, surface treatment wastes, distillation residues and organic resin wastes.
2.1.1 Photographic material waste
The pre-press processes used in different printing processes are very different. As far as traditional printing is concerned, offset printing and flexographic printing use similar traditional pre-press processes. -The traditional pre-press process represented by the laser typesetting machine, -by the laser typesetting machine output film, film processing, plate composition, the hazardous wastes generated include waste film, film processing process of waste developer and waste fixing solution, plate tanning process of waste developer, all belong to the “National Hazardous Wastes Directory” in the HW16 All belong to HW16 of “National Hazardous Waste List”, “Photographic Material Waste”. At present, the digital pre-press process represented by direct plate making (Computer toPlate, or CTP for short) has begun to replace the traditional process represented by the laser typesetting machine, CTP is more than 30min faster than the traditional plate making time, and it has taken the lead in obtaining the application in the field of newspaper printing in our country (using offset printing), but has not yet gained the practical application in the field of flexo printing.The CTP plate making process CTP plate making process does not need to output film, which only produces waste developer in the plate making process.
Screen printing process prints due to the large format (up to 3m × 4m), its film can be output through large printers, no longer need to film development process. However, in the solar plate before the need to coat the surface of the screen photopolymer, solar plate after the use of water rinse to complete the development process, so that there will be a small amount of photopolymer into the liquid phase.
Digital printing presses include toner-based digital printing presses and inkjet printing presses. Compared with traditional printing, digital printing does not require plate making, it is made of photographic material by the printing cylinder (no plate) by the sensitivity of the formation of ink or toner can be adsorbed graphics, and then transferred to paper and other substrates. Toner-based digital printing presses produce waste photoconductive drums in the course of their use, which are photopolymerized material waste. Inkjet presses do not produce photographic material waste.
In summary, in offset printing, flexographic printing, screen printing and toner-based digital printing press pre-press process, will produce photographic material waste, only, for different processes, the type of hazardous waste generated and the characteristics of the differences.
2.1.2 Surface treatment waste
The plate making of gravure printing process is still dominated by electronic engraving, which is accomplished by engraving the cylinder of the gravure plate directly by an electronic engraving machine. The plate roller of the electronically engraved gravure plate is made of steel, and its surface is plated with nickel and copper before it is used for engraving. The plating residue and bath solution generated from the plating process belongs to HW17 “Surface Treatment Waste” in the “National Hazardous Waste List”.
2.1.3 Distillation residue
In offset printing plate making, flexographic printing plate making and CTP plate making process, it is necessary to develop the photographic coating on the surface of the plate base by developing liquid. For different printing processes
