Why do ordinary corrugated boxes need to pursue colorization? The first is the needs of the market. Consumers increasingly prefer high-quality printed packaging. High quality printed packaging makes consumers feel happy when shopping and have a sense of recognition and trust in goods. Secondly, the design of corrugated box is changing. The designer requires that the packaging can show more product content and beautify the goods.Experience Of Ink For Color Flexo Carton Printing

      Now more and more corrugated box designs have used high-quality patterns to better express the creativity and content of the design through the perfect embodiment of the pattern level. Publicize the enterprise culture, make the goods have affinity to consumers, and stimulate consumers’ purchase desire. Third, improve the positioning of commodities in the market through the design of high-quality patterns. High quality pattern printing is indirectly reflected in high-quality products, which paves the way for the product positioning of merchants, organically unifies the inner packaging, outer packaging and transportation packaging of products, and strengthens the awareness of the product market.Experience Of Ink For Color Flexo Carton Printing

       Fourth, the colorization of corrugated boxes helps to improve the anti-counterfeiting function of product packaging. The high-quality color corrugated boxes produced through the cooperation of professional design companies and professional plate making companies to produce printing plates and high-level carton printing manufacturers are very unlikely to be counterfeited if the counterfeiter obtains plate making data by scanning the cartons, and then printed by small corrugated carton manufacturers. Domestic counterfeiting is still rampant, causing huge losses to many enterprises. Experience Of Ink For Color Flexo Carton Printing

      Most enterprises make a fuss on the small packaging of products to prevent fake and shoddy products. However, small packages are mostly offset or gravure printing, which has a greater chance of being counterfeited for technical reasons. If technical measures are also taken in the printing of outer packaging cartons, it is bound to increase the difficulty of counterfeiting.Experience Of Ink For Color Flexo Carton Printing

      Flexographic printing has the advantages of green and environmental protection. The use of water-based ink printing has no pollution to the working environment and substrate, which is absolutely beneficial to on-site operators and end consumers. The carton industry has introduced and developed a large number of high screen flexographic printing machines, mainly including boster, Matian, tcy, Nanhai Oriental, Jingshan light machinery and other brand models. Experience Of Ink For Color Flexo Carton Printing

      The carton screen printing easily exceeds 50 lines, and the fineness directly catches up with offset printing. The carton packaging is mainly logistics and transportation function, and the commodity display function is at least one meter away from consumers.Experience Of Ink For Color Flexo Carton Printing

     Flexographic printing can completely replace offset printing to meet the colorization of cartons. In addition, because flexo printing is generally printed directly on the formed paperboard, the corrugated comprehensive strength of the same quantitative paper distribution is better than offset printing, which brings a lot of room for price reduction to the carton cost.Experience Of Ink For Color Flexo Carton Printing

Development of flexible ink

     Whether white paper or box board paper is used for flexible ink printing, the color effect can be reflected. With the ever-changing flexographic printing technology, the ink products are based on high-quality ink, and continuously develop UV / EB curing flexible ink with higher scientific and technological content, which improves the ink absorption and diffusion between ink and paperboard, making the ink color of flexographic printing products thicker, more saturated, distinct levels and beautiful feeling on paper. Experience Of Ink For Color Flexo Carton Printing

     With the continuous development of flexographic printing machines, the demand for water-based ink and various new flexible inks in the packaging and printing industry will be more urgent, and the demand will be further increased.Experience Of Ink For Color Flexo Carton Printing

     At present, China has nearly 1000 flexographic printing machines for various cartons, mainly using water-based ink for printing, with an annual consumption of more than 50000 tons, accounting for 25% of the total consumption of ink. There are two reasons why water ink is suitable for carton printing: first, corrugated board is a fabric with loose fibers and strong water absorption. Experience Of Ink For Color Flexo Carton Printing

     The water-based ink is easy to penetrate and dry after being transferred to the surface of paperboard, so there is no need to set up a drying device; Second, because the water-based ink is non-toxic, harmless, non flammable, safe and convenient to use and low cost.Experience Of Ink For Color Flexo Carton Printing

Characteristics of water-based ink

      Waterborne inks are made up of waterborne polymer resins and emulsions, organic pigments, water solvents and related auxiliaries by physical and chemical processes. They do not contain volatile organic solvents, and do not contain any toxic or harmful substances in solvent based inks. The main difference between it and solvent based ink is that the solvent used is not organic solvent but water, that is, the binder is composed of resin and water. Its environmental protection is more suitable for products with strict health requirements such as food, beverage and medicine. The composition configuration of water-based ink is as follows:Experience Of Ink For Color Flexo Carton Printing

     Pigment is the coloring material of ink. Organic pigments with complete chromatography, high color concentration and easy to achieve high hiding power are mostly selected, such as magenta ink, yellow ink and green ink; White ink multi-purpose titanium dioxide; Black ink uses carbon black.Experience Of Ink For Color Flexo Carton Printing

     Water soluble or water dispersible resin is the binder of ink and is an important factor affecting the quality of ink. The printability such as viscosity, adhesion, gloss and drying all depend on the resin composition. There are many kinds of water-based ink binders, which can be selected according to different occasions and functions. Experience Of Ink For Color Flexo Carton Printing

     At present, the research and development of ink by domestic ink companies mostly focus on the research of binder, including water-soluble binder based on polyvinyl alcohol, hydroxyethyl cellulose and polyvinylpyrrolidone, salt alkali soluble binder of soluble resin and diffusion binder commonly known as latex containing propylene, ethylene or styrene butadiene polymer.Experience Of Ink For Color Flexo Carton Printing

     From the perspective of formula, the capacity of domestic ink blending oil packaging color paste is poor, which can only reach 50%, and the capacity of imported resin packaging color paste can reach 80%. Due to the coarse particle size of domestic ink, it is easy to damage the printing anilox roller, and the particle size of imported ink is finer, forming a good affinity with the anilox roller, which will not scratch the surface of printing materials and affect the printing effect.Experience Of Ink For Color Flexo Carton Printing

      The solvent of water-based ink is mainly water. A very small amount of alcohols can be added when using, such as ethanol, isopropanol or polypropanol. The addition of alcohols helps to improve the stability of the ink, accelerate the drying speed and reduce the surface tension. Experience Of Ink For Color Flexo Carton Printing

     Isopropanol also plays the role of defoaming. The additives of water-based ink include amine stabilizer, defoamer and slow drying agent, which are used to adjust pH value, eliminate bubbles and adjust curing and drying time respectively. Pigment and ink blending oil are important raw materials for ink manufacturing. Imported color paste and ink blending oil are used for ink blending in China.Experience Of Ink For Color Flexo Carton Printing

When selecting water-based ink, pay attention to the viscosity, concentration, fineness, drying speed, wear resistance, water resistance and stability of the ink.

viscosity

   Viscosity is not only the cohesion of ink, but also the main control index in ink application. If the viscosity of ink is too low, it will cause some disadvantages, such as light color, large dot expansion, high gloss point deformation, uneven ink transmission and so on; The ink viscosity is too high, which will affect the ink transfer performance of anilox roller. The ink color is uneven, and sometimes the color is not deep. At the same time, it is easy to cause dirty version, paste version, blistering, non drying and other disadvantages.Experience Of Ink For Color Flexo Carton Printing

■ temperature has a great influence on ink viscosity.

The influence of workshop temperature on printing quality is shown in Table 5, and the relative humidity of 60% – 85% is better.

     When the temperature difference between winter and summer is large, the performance of viscosity is the most sensitive. When the temperature is high, the water evaporates quickly and dries quickly. During operation, pay attention to prolonging the drying time or increasing the machine speed; When the temperature is low, the water evaporation is slow and the ink drying is also slow. During operation, the ink drying speed can be improved or the drying device can be added.

      When used in winter, because the ink is easy to freeze below 0 ℃, if the ink freezes, it can be placed in a room with high temperature to dissolve naturally. It can be used again after stirring evenly.

      In actual production, when using a printing press with an ink scraper, the ink transfer capacity of the ink when the temperature is too low is not as stable as that when the temperature is slightly high. The increase of ink temperature will reduce the viscosity, resulting in the decrease of print density and the thinning of ink layer. To maintain the consistency of printing quality, we must maintain the consistency of ink viscosity.Experience Of Ink For Color Flexo Carton Printing

      Printers must attach great importance to the influence of ink temperature. Before printing, the temperature of ink should be stabilized at the temperature of printing workshop. This measure is very important, otherwise the ink density will change significantly during the printing process.Experience Of Ink For Color Flexo Carton Printing

■ effect of thixotropy on ink viscosity

     Thixotropy refers to the performance that the fluidity of ink increases under the action of external stirring, and gradually decreases and returns to the original state after stopping stirring. After the ink has been placed for a long time, some inks with poor stability are easy to precipitate and layer. Others have false thickening. At this time, it can be fully stirred. After stirring for a certain time, the above problems will disappear naturally. Experience Of Ink For Color Flexo Carton Printing

     When using fresh ink, be sure to stir it evenly in advance, and then make dilution adjustment. Or it is expected that after a certain amount of ink is put on the machine, the viscosity will decrease, because the water content in the machine and the thixotropy of ink can improve the fluidity of ink. When printing is normal, the ink bucket should also be stirred regularly, especially the ink with high white pulp content.Experience Of Ink For Color Flexo Carton Printing

PH value of ink

■ effect of pH value on ink viscosity

     The pH value of another index that needs to be controlled in the application of water-based ink is in the normal range of 8.5-9.5. At this time, the printing performance of water-based ink is the best and the printing quality is the most stable. Due to the continuous volatilization of ammonia in the printing process, operators will add new ink and various additives to the ink from time to time, so the pH value of the ink may change at any time. Experience Of Ink For Color Flexo Carton Printing

     Using a standard pH meter, the pH value of ink can be easily measured. When the pH value is higher than 9.5, the alkalinity is too strong, the viscosity of water-based ink decreases, the drying speed slows down, the water resistance becomes poor, and it is easy to paste; When the pH value is lower than 8.5, that is, the alkalinity is too weak, the viscosity of water-based ink will increase,.

     The ink is easy to dry, block the plate and anilox roller, cause dirt on the plate and produce bubbles. The influence of pH value on the printability of water-based ink is mainly reflected in the viscosity stability and dryness of ink and dot clarity. With the increase of pH value, the ink viscosity decreases and the drying speed slows down.Experience Of Ink For Color Flexo Carton Printing

Application experience

Water based ink often encounters some problems in the process of paperboard printing. The cause analysis and solutions can be referred to as follows:

◆ the adjustment of printing pressure is very important, including the pressure between printing plate and substrate and the pressure between anilox roller and printing plate. If the ink viscosity is too high and the ink dries too fast, the solution is to adjust the pressure, dilute the ink and add slow drying agent.Experience Of Ink For Color Flexo Carton Printing

◆ if the ink dries on the printing plate and the printing edge is blurred, it may be that the hot air blows on the printing plate and the paper fiber mixes with the ink, resulting in electrostatic reaction. The elimination method is to dilute the ink and gradually increase the speed, cover the inking system, or replace the ink and install a de electrostatic device.

◆ flexo is especially suitable for field printing. If the field is not real, the cause may be low ink viscosity and uneven substrate surface. The countermeasures are to use high viscosity ink and substrate materials with good surface quality.Experience Of Ink For Color Flexo Carton Printing

◆ the ink accumulates on the printing plate or the dot is full. The reasons include too much ink, too much printing pressure, too fast ink drying or too weak ink. The solution is to replace the anilox roller, adjust the pressure, add slow drying agent or use high-color strong ink.Experience Of Ink For Color Flexo Carton Printing