Figure 1 Corrugated cardboard structure Figure 3 H / bak liner technology liner absorbs more compression Figure 4 Adopting H / bak liner technology, the liner absorbs more compression After corrugated cardboard is printed, according to the design requirements of various packaging boxes and boxes, the corresponding die cutting method and box making equipment are used to die cut, and finally the desired product is produced.
Office furniture refers to a class of appliances that are indispensable for human beings to maintain normal life, engage in production practices and carry out social activities. It means that today's living room furniture design is actually designing a new way of life, work, leisure and entertainment.
People pay attention to the coordination between the color of the living room furniture and the decoration of the room, and can reflect the owner's temperament and hobbies at the same time. Living room furniture tends to be simple, thin and practical, and some living room furniture is even made of cardboard. The product design uses the principle of mechanics to make the furniture with sufficient strength. At the same time, the surface of the furniture is coated with protective paint. After special treatment, the two weaknesses of pressure resistance and water resistance are solved, so that the paper furniture has a certain degree of moisture resistance, waterproof, anti-mildew, anti-moth and other functions.
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The structure of corrugated cardboard is shown in Figure 1. Its inner layer is a special wave-shaped structure, which cushions the vibration and enhances the impact capability. It is mainly used in the outer packaging of commodities. With the emergence of waterproof corrugated cardboard and reinforced corrugated cardboard, corrugated cardboard can also be made into special liquid packaging containers, expanding the application of corrugated cardboard. With the continuous improvement of flexographic printing technology, more and more flexo printing methods are used on corrugated paper. According to relevant statistics, the flexible printing technology is mainly used for color printing of corrugated boxes. The United States accounts for 98% and Western Europe accounts for 85%. The annual output of corrugated cardboard used for packaging in China exceeds 10 billion m2. Facing such a huge market We need to further improve the shortage of corrugated printing workers, improve printing quality, and meet the needs of the market development in the district.
1.2 The process of color flexo printing on corrugated board The process of color printing on corrugated board is as follows:
Graphic design → image processing → plate making → printing → die cutting → box making manuscript design and image processing must fully consider the characteristics of corrugated paper, avoid full-page printing and ribbon graphics in the same direction as the corrugation, the text should not be too small The color of the ink should be eye-catching. Choose an ink with strong coloring power and high saturation. The number of screen lines for color painting is generally 60 lines / in, for high-end printed products is 100-120 lines / in, and the number of colors is 3-4. There are also 5 -6 colors, and can only print up to 2% of the dots. When producing the color separation film, comprehensively consider the actual ink parameters, dot expansion and other parameters, compile excellent balance and gray balance procedures, and draw the tone replication curves of C, M, Y and BK. In addition, we must also fully consider the effect of different line numbers of the dots, the width of the flexo printing machine and the printing slotting machine, and different materials and pressures. In the plate-making process, the flexographic printing plate material selects a thick photosensitive resin plate with a thickness of about 3-7mm and a hardness of 25-50 Shore Hardness (HS). When the quality of corrugated paper is poor, use thicker plates with lower hardness. When the quality of corrugated paper is better and you need to print small prints and screen plates, choose a plate with higher hardness. When printing with thick plates, as shown in Figure 2, when the printing pressure is too small, the printed substrate is prone to corrugated and "washboard" -like patterns, which affects the printing quality of the field and the high number of screen lines; when the printing pressure is too large, the printing The substrate is easily deformed or even damaged, causing deformation of the resin plate and expansion of the dots. At the same plate thickness and speed, the printing plate with higher hardness has no obvious expansion of the imprint, but the edge parallel to the corrugation is not solid, and the soft version with lower hardness has strong imprint, but the edge parallel to the corrugation has expansion .
The main feature of the flexo printing machine is the short ink path, and the anilox roller is the key component of ink transfer and ink distribution. The structure and number of ink holes on the anilox roller determine the ink transfer performance and application range of the anilox roller. In corrugated cardboard flexo printing, the anilox roller line number is often 180-300 lines / in, and the ratio of the dot line number to the anilox roller line number is 1: 4 to 1: 5. In addition, the cylinder arrangement of most corrugated cardboard flexographic printing machines is that the impression cylinder is on top, and the plate cylinder is on the bottom, printing on the bottom surface of the cardboard, so that dust and shredded paper on the printing surface can naturally fall off.
2. Factors affecting the configuration of ink 2.1 Printing ink of corrugated cardboard The biggest feature of corrugated paper is that the paper is rough, the surface is not smooth enough, the ink penetrates quickly, and the surface is mostly dark brown. Therefore, water-based inks are required to have bright basic colors, strong tinting power, and high hiding power; and have faster penetration and drying performance; they must have good resolubility during the printing process to ensure smooth ink development; in order to meet Packaging requirements, the print should also have good abrasion resistance and water resistance.
Corrugated paper printing ink is mainly made of 5 different materials, including coloring (10-40%), resin or adhesive component (20-28%), solvent component (33-50%), alkaline Material composition (accounting for 4-6%) and additives become (accounting for 3-4%). Among them, the changes of adhesives and additives play the largest role. As the quality of corrugated packaging improves, the amount of moisture absorbed by the substrate decreases, which relies more on evaporation similar to the drying principle. After the ink is printed on the substrate, the water evaporates to the surrounding environment on the one hand, and is absorbed by the substrate on the other hand. The evaporation rate of water depends on the water content, the dehydration properties of the adhesive and the volatility of the water.
2.2 Factors affecting ink configuration (1) Colorant Colorant is the most expensive component in ink configuration. The colorant used in corrugated printing ink is mainly alkaline polymer synthetic pigment, which is characterized by insoluble in adhesive resin paint, Low toxicity and abrasion resistance, improve the wettability of the pigment. In some cases, very transparent pigment chips can also be used to color the adhesive. Originally used more chromium yellow lead and other heavy metal pigments were gradually replaced.
(2) Adhesive alkali soluble resin and dispersed phase resin are two kinds of adhesives suitable for corrugated printing ink. The alkali-soluble resin is cationic, and its polymer skeleton contains functional carboxylates, and the carboxylates and the basic base material generate water-soluble salts. That is, the reaction of acid + basic base = salt + water is reversible. When the stable pH value decreases, the resin will return to an insoluble state. As shown in Figure 5. The second resin is a dispersed phase polymer. The resin particles are controlled by the suspension force generated by the hydrophilic tension. When the steady pH value decreases, this tension dissipates and the resin coalesces. The ink layer is difficult to be re-dissolved. It can be seen that the other doors are suitable for the configuration of corrugated paper ink. The solid content is higher and the water content is less. The moisture that needs to be removed is naturally less, thereby speeding up the drying speed.
(3) Additives and other ingredients Additives account for a small proportion in the configuration, but they can change the performance of the ink, such as the addition of additives polyethylene wax, which can improve the wear resistance of printed products. In the printing process, the corrugated ink is prone to foam in the ink fountain. The foam climbs over the ink fountain, blocks the pipe, and flows onto the three-dimensional ink roller and the substrate, causing printing errors. Therefore, it is necessary to add antifoam and antifoam to the corrugated printing ink Agent, but it must be noted that the anti-foam agent and anti-foam agent should not be excessive, otherwise it will cause printing defects.
The surface tension of the coated paper substrate is 36-42 dynes / cm, and the surface tension of the water is 72 dynes / cm. The surface tension of the water is much greater than the tension of the substrate. Add a surface wetting agent to reduce the surface tension of the resin or water mixture, but choose a suitable wetting agent, otherwise, the wetting agent will cause or help produce foam. The surface tension of alcohol is very low. High-quality corrugated paper printing inks are often added with a small amount of alcohol to improve the low foam and surface wetting characteristics. At the same time, it helps to improve the drying of ink and is beneficial to the ink transfer process.
The preparation of corrugated paper ink is a complex balancing process of various materials. The reasonable configuration of the ink components can greatly improve the quality of corrugated cardboard printing. 
For many years, the printing of corrugated paperboard is just to apply the functional mark on the corrugated paperboard packaging box, or the simple line and text monochrome printing, which has backward technology, low efficiency and high cost. With the development of the market economy, people's requirements for packaging products continue to increase, and various colorful and well-designed corrugated boxes and special-shaped corrugated boxes have appeared, which not only improves the added value of the products, but also increases the competitiveness of the products. , Adapted to the development of the international packaging market.
1. Color printing of corrugated cardboard 1.1 Advantages of corrugated cardboard using flexo printing When corrugated cardboard is using flexo printing technology, due to the elastic deformation of the flexographic plate, it can make up for errors in printing thickness and unevenness of the surface, making the printing ink color uniform; foreign The color printing of corrugated cardboard tends to be E-shaped corrugated cardboard with a white paper surface. The number of high-end printing screen lines can reach 120 lines / in. It can print both field plates and screen plates, and realize four-color printing; flexible printing belongs to Light pressure printing, the printing pressure is small, to solve the slush or empty imprint caused by uneven thickness of corrugated paper; Sang Yin uses water-based ink, so it can be transferred by metal anilox roller, and the printing plate only needs to be light Light contact with corrugated cardboard, water-based ink will be fully absorbed; the flexo printing machine has a simple structure, four rollers form a color group, easy to install, adjust, and clean. The flexo printing machine can also be linked with other processes for production, such as pressing Marking, grooving, die cutting, gluing, box making, counting, etc. constitute a linked production line.
Figure 2 Schematic diagram of the effect of printing pressure
The US R / bak air cushion type lining technology is the most commonly used liner technology, as shown in Figure 3. It can effectively prevent the deformation of the printing plate and the destruction of the corrugated paper, make the ink layer more uniform, and the printing tone and gradation are better. When in use, just place the liner containing microporous air bubbles on the back of the flexographic plate and attach it to the cylinder. During printing, the air cushion liner has the function of buffering pressure and absorbs between the printing substrate, the printing plate and the printing plate roller The resulting pressure is shown in Figure 4. It can reduce or eliminate the increase of dots and the deformation and damage of corrugated paper caused by too large or too small printing pressure, and it has a unique compensation function for the plate roller that beats too much, and has a good adaptation to various corrugated paper. Sex. Therefore, the air cushion type stencil technology gradually replaces the traditional thick printing plate.
Figure 5 acid-base balance of tile printing ink resin
In order to improve the printing quality of corrugated paper, it is necessary to obtain a good remelting system, that is, a system that can realize self-wetting when anilox and three-dimensional ink roller are driven. This system can be obtained by a low molecular weight alkali-soluble polymer with excellent remelting properties. The remelting property of corrugated paper printing ink is related to the volatility of the alkali material used. Sodium hydroxide is the best material for this purpose. It is non-volatile and gives the ink permanent water solubility. In addition, monoethanolamine or triethanolamine is used to replace the ammonia in the original ink for ink configuration. The use of alkali-soluble polymers can make larger pigment particles wet. At the same color intensity, less dehydration can be applied with a smaller amount of wet coating. The drying speed is faster and a higher coloring effect can be obtained. The tone level is clearer.