New technology in the field of paper packaging and printing
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1. Paper packaging development trends and technical requirements
In recent years, the global paper product packaging industry has developed rapidly, and the production capacity of cartons and cartons has increased significantly. Among the world's packaging industry, paper packaging products accounted for more than 32%. In Europe, paper and paperboard consumption is as high as 41%. The per capita consumption of paper and paperboard in 2000: 331.7 kg in the United States, 249.9 kg in Japan, 229.4 kg in Taiwan, and 28.4 kg in mainland China. In 2000, China imported 13.03 million tons of paper, cardboard and pulp (about 6 billion US dollars), accounting for 66.7% of China's paper and paperboard consumption. In recent years, the growth rate of the packaging industry in Hong Kong is about twice that of the printing industry. In 2000, the sales of packaging industry in Guangdong Province reached 50 billion yuan, including 18 billion yuan for paper packaging products and 14 billion yuan for packaging and printing.
With the further enhancement of people's environmental awareness, cartons, cartons, paper bags, paper cups, paper tubes and other packaging containers are widely used in Europe, and are used in various juices, milk, cooked food, fast food, snacks and other beverages. The carton pack of food is visible everywhere. According to relevant information from the China Tobacco Department, the proportion of domestic hard-packed cigarettes has reached 56%.
With the continuous improvement of people's living standards and the automation of packaging of goods, not only the demand for carton/carton has increased greatly, but also the printing quality and processing precision of color folding carton/multi-color carton have been put forward. . It is necessary to avoid the rabbits from discharging the waste on the automatic folding folder-gluer, so that the folding carton can automatically complete the processes of opening, molding, filling and sealing on the high-speed packaging machine, which not only requires the design of the carton structure to be reasonable, but also ensures that the film has sufficient mold. Cutting accuracy and folding paste box accuracy. Multi-color printing, short-run jobs, improved printing quality and processing accuracy, and reduced processing costs are also the market pressures and problems faced by carton packaging and printing companies. Therefore, only the application of modern processing methods and new technologies, in the process of paper packaging printing and post-press processing, continuously improve the automation of equipment, reduce the adjustment time of equipment and the auxiliary preparation time of the work, constantly adapt to the new changes in the market, to meet different The requirements of users can enhance the competitiveness of packaging and printing enterprises.
2. Paper packaging container CAD technology
The more popular carton structure CAD software on the international market, in addition to the basic functions of common interactive graphics software (high quality, rapid completion of graphics generation, editing, modification, dimensioning, etc.), should also meet the carton design Special requirements, convenient to call the box graphics library and select a satisfactory box structure, input box size (length, width, height) and cardboard thickness, you can immediately display or print the box structure diagram, automatic discharge, and Output sheet die-cutting map, printing outline drawing and backing (bottom mold) processing drawing; when the user designs or calls the required box structure drawing, as long as the cardboard web size and discharge gap are input, the material can be discharged. And compare different discharge schemes, showing optimized die-cutting discharge map and related parameters (such as the number of discharges, cardboard utilization, etc.).
In addition to selecting the standard box type and changing the shape of the carton, it is also possible to arbitrarily design the special box type, the rotating carton stereo view, and the display carton opening and closing process; for different cutting edges, creasing lines and slotted broken parts should be selected Corresponding line types, to control the carton sample, die-cutting plate, bottom mold (backing) version and die-cutting tool to improve the processing accuracy of the die-cut and backing plates and the accuracy of the carton.
3. Paper packaging printing technology
In the field of paper packaging printing, lithographic offset printing, letterpress flexo printing, gravure printing, and screen printing are all coexisting, each having its own characteristics. In the single-sheet printing, most of them use offset printing, but also use flat-press screen printing and sheet-fed gravure printing. In web printing, most of them use gravure and flexo printing, and also use offset printing and silk. In the form of web printing, there are also several combinations of printing methods on one printing production line. The color of the carton is generally between 2-8 colors, of which 4-6 colors are used most. Folding cartons, especially the pillboxes, use more spot colors, so the number of printing color groups is mostly 6-8 colors. The number of color groups of sheetfed offset presses is generally 4 colors, basically no more than 5-6 colors, and the use of multicolor web presses (including gravure, flexo and screen printing) has increased rapidly. The number of printing color groups has reached 8-10 colors.
3.1 Offset printing technology
(1) Digital printing and CTP technology
Digital printing technology prints on the basis of personalized database information, providing paper bags, cartons and corrugated boxes with the option of individualized packaging printing, which can change the design and processing parameters of paper packaging containers by region or product. With a special process, the folding carton can have a variable printing color and hot stamping effect, in order to meet the needs of the market packaging carton (box) specifications and the number of short-running jobs.
Agfa's high-definition CTP technology provides high-quality outlets for modern packaging printing. The unique laser and optical imaging system, intelligent multi-beam simultaneous imaging method, IntelliSpot intelligent network and other technologies increase the security of the system, simplify the system structure, and improve the automation degree and overall efficiency of the system.
(2) FM screening technology
The quality of printed matter depends mainly on the number of dots on the unit area and the number of successive changes in the number of dots from small to large. The more the number of Internet access points, the higher the definition of the printed matter, the more the number of changes in the dot, the stronger the performance of the printed matter, and the more delicate it looks.
In order to improve the quality of printed products, amplitude modulation screening, frequency modulation (FM) screening and hybrid screening technology are often used.
The network of AM modulation is a regular arrangement, depending on the size of the dot to change the amount of printing ink, and the size of the dot of the FM screening is fixed, the distance between the dots can be changed, and the printing is adjusted according to the change of the dot distance and the number of dots. The amount of ink on the paper to achieve a change in color. The amplitude modulation screening has three elements: the number of screen lines, the shape of the dot and the angle of the screen. The FM screen has only one element of the dot size. The smaller the dot, the finer the print, the better the visual effect, which is equivalent to the number of high-screen lines in the amplitude-modulated screen. However, the smaller the point of the FM screen, the higher the requirements for printing conditions. Hybrid screening is a hybrid screening technology that combines amplitude modulation and FM screening technology to form the same image. In the uniform color zone, especially in the highlight zone, conventional screening can produce a smoother appearance than FM screening. But for the high detail part, the FM screening effect is better. Advanced screening software analyzes images to determine where to use the appropriate screening geometry, and combines FM and conventional screening to achieve the best overall results.
Using FM screening technology, it can eliminate moiré, improve the uniformity of horizontal reproduction, improve the resolution and sharpness of images, and easily realize Hi-Fi printing. Although FM screening is demanding on printing conditions, it is suitable for waterless printing. High-definition FM dots can significantly improve the clarity and level of presentation of prints. The FM network point arrangement is not like the AM screen point, and is limited by the dot spacing and arrangement angle. In the printing and copying, the frequency modulation dot is selected, which can show more detailed changes, improve the definition and have anti-counterfeiting function.
(3) Printing color management technology
The CP2000 integrated offset printing machine center control system developed by Heidelberg Company adopts TFT ultra-thin screen display technology, and is equipped with prepress interface technology, image control technology, printing color management system, online help system and information management system to form printing. Quality control mode under integrated conditions. The multi-level printing color management system PCM includes consulting, standardization, prepress and printing optimization, and generates and implements Icc color profile files. In order to optimize the color process and improve the production efficiency of the printing house, the pre-press and printing equipment can be effectively coordinated. Not only can you get high fidelity color, but also save time, reduce waste, and achieve efficient production.
(4) Waterless offset printing technology
Waterless offset printing is a lithographic offset printing method that uses special silicone rubber coated plates and inks to print, eliminating the need for isopropyl alcohol or other chemical fountain solutions that are required in traditional lithographic offset printing. The printing process is simple to operate, and the ink balance is not adjusted, and the ink is transferred to the printing plate within a certain temperature range.
The printing plate used for waterless offset printing is a flat intaglio plate, and the graphic portion is lower than the surface of the printing plate. Although the plate making process is the same as the PS plate, it is different from the PS plate. Therefore, waterless offset printing plates have unique processing difficulties. Plate, ink and temperature control are the key to waterless offset printing technology, which directly affects the development speed of waterless offset printing. The printing plate is the core of waterless offset printing. The waterless offset printing plate has the advantages of easy operation, good image quality, high printing density, beautiful color and good quality of printed products, but the printing durability of the printing plate is easy to operate. Conditions and the impact of special prints. The special ink used in waterless offset printing has the characteristics of low viscosity, high viscosity, large thixotropy and stable performance. Since different colors of ink react differently to temperature changes, it is necessary to control the temperature of different printing color groups. Although the cost of consumables in waterless offset printing itself is high, the reject rate of printed products is low and the production efficiency is high. It can be seen that with the advancement of technology and the increase of labor productivity costs, especially for high-quality fine paper packaging, waterless offset printing technology has certain advantages and will be further developed and promoted.
3.2 Flexo printing technology
New flexible plate and thin plate process, sleeve plate and computer direct plate making technology, environmentally friendly UV ink, high wire ceramic anilox laser engraving technology, closed doctor blade system, gearless transmission technology, no stop change The development and application of related technologies such as roll device and automatic control technology have promoted the rapid development of flexo printing.
(1) The improvement of the quality of the thin plate and CDI technology photosensitive resin plate and the appearance of the thin plate process have laid a good foundation for improving the quality of the printing plate, the application of CTP technology and the emergence of digital flexographic plate making technology (CDI). It can effectively overcome the phenomenon of dot enlargement, ensure the quality of printed products, shorten the production cycle and reduce the cost.
The digital thin sleeve plate has good stability, can effectively control the expansion of the dot, reduce the photopolymer, and improve the image quality and registration accuracy. Not only can it improve the quality of printed products in paper packaging, so that the quality of flexo printing can reach the level of offset printing and gravure printing. It also reduces printing pressure, reduces plate cleaning times, extends plate life (10-25% over time), further reduces setup time, reduces downtime, and IT at downtime (10-20%).
The CDI system jointly developed by DuPont and DuPont Seri can transfer digital information directly to the laser photosensitive plate. Spark XT, a CDI platesetter developed by Esko-Graphics, is aimed at the packaging and printing market, especially for small and medium-sized labels and folding carton flexographic printing companies. As technology continues to advance and the cost of various systems for the development of flexographic digital imaging platemaking systems is decreasing, the proportion of paper products such as cartons, paper bags, and multi-layer bags is increasing.
(2) Sleeve type high mesh ceramic anilox roller
The laser-engraved ceramic anilox roll is sprayed on the surface of the treated base roll as a primer layer, and then the plasma powder is sprayed with plasma at a high temperature. After being polished and polished by diamond, the laser beam is accurately engraved with a high-energy laser beam. Steep cellars, and finally fine polishing. The number of mesh lines and the amount of cell ink are the most important parameters for making laser-engraved ceramic mesh. The anilox roller with a high number of screen lines can form a thinner and more uniform ink layer, which can meet the requirements of printing with rich printing layers, especially to meet the needs of its high-gloss portion, which can reduce the expansion of the dot during printing and maintain a constant and uniform The amount of ink transferred.
Sleeve type high mesh ceramic enamel anilox roller. The ultra-high-energy laser beam engraving technology and the sleeve-type anilox roller structure consisting of a mandrel, a gas-supporting roller and a sleeve simplify the quality of the high-precision anilox roller and the quick change of the anilox roller. The plate roller and the anilox roller adopt the sleeve structure and the direct drive technology (that is, the rotation of the anilox roller is directly driven by the plate rolling), which solves the problem that the repeat length of the flexographic printing product is limited by the gear pitch. . Therefore, when replacing printed products of different circumferences, it is not necessary to replace the plate cylinder and the mandrel of the anilox roller and the gear, which greatly shortens the time taken for the printing plate to be rolled and the anilox roll when the product is replaced.
The carbon dioxide laser engraved ceramic anilox roller line can reach l000LPI, and the special ceramic layer or super-hard ceramic layer can improve the service life of the ceramic anilox roller and reduce the use cost.
The ceramic anilox roller processed by YAG laser engraving technology has smooth wall of mesh hole, neat mesh wall, high smoothness, accurate ink transfer and small blade loss. Not only the ceramic anilox roller has long service life, but also can extend the printing plate. Service life. The high-power, high-precision YAG laser engraving machine can engrave 16001pi anilox rolls.
(3) Closed double scraper cavity inking system
The two-roller, forward-squeegee-type, and reverse-squeegee-type structure can realize quantitative ink supply, but the ink is often exposed to the atmosphere in a large area, and the solvent of the solvent ink is volatilized into the surrounding air, resulting in ink characteristics. Changes and environmental pollution problems: If water-based inks are used, bubbles will be generated and the quality of the print will be affected.
The closed double-blade cavity inking system consists of a ceramic anilox roller, two scrapers, a sealing strip, an ink storage container, an ink pump, an inking hose and the like. In a fully enclosed system, the scraper, seal, gasket, and pressure plate are mounted on a hollow bracket and mechanically (or pneumatically or hydraulically) pushed toward the ceramic anilox roller and applied with a certain pressure. The ink supply tube and the return tube are respectively connected to the ink pump and the ink storage container to realize the quantitative ink supply. The reverse scraper structure is suitable for high-speed operation, which reduces the volatilization and environmental pollution of the solvent in the solvent ink. The system can also be quickly docked with an automated cleaning system for quick cleaning to reduce ink change times and downtime.
(4) Environmentally friendly flexo ink
Today, people pay more and more attention to environmental protection, water-based inks and UV inks adapt to market demand, and promote the application of flexographic printing in the field of packaging and printing. It can be used not only for the printing of various coated papers, offset papers and whiteboard papers, but also for printing carriers such as gold and silver cardboard, synthetic paper, self-adhesive paper and corrugated boxes.
Water-based (or water-based) inks use water as the main solvent, which is non-toxic, non-polluting and has no residual odor. It completely eliminates the harm of certain toxic substances in solvent inks to the human body and the pollution of packaged goods, effectively reducing air pollution. Improve environmental quality and printing environment, especially suitable for pharmaceutical, food, beverage, tea, tobacco and alcohol, and daily necessities in contact with human body.
Under ultraviolet irradiation, the photoinitiator in the UV ink is excited to decompose into a radical, and the radical causes the crosslinking reaction to occur rapidly, so that the colloidal component instantaneously becomes a solid. Because UV ink is mainly composed of pigment, photosensitive resin, reactive diluent, photoinitiator and auxiliary agent, it does not contain volatile organic solvent, which can greatly reduce the emission of VOC, and it has less energy consumption, small equipment footprint and easy drying. high productivity. Since the UV ink has no problem of volatilization of water or solvent, the transfer and reduction of the dots are good, and the color is more vivid, which greatly promotes the quality of the flexo print. Although the drying cost of the UV ink is significantly higher than that of the water-based ink, the UV ink has good photocuring efficiency and ink layer properties, and can well protect the surface of the printed product.