Application of the hottest water-based ink in corr

Application of water-based ink in corrugated paper printing

in the field of packaging and printing, corrugated paper printing occupies a large share. With the expansion of packaging market and the continuous improvement of printing technology, the quantity and quality of corrugated board printing have developed rapidly. However, at present, people are considering more and more environmental factors, so the ink used in corrugated board printing has become a matter of concern. In corrugated paper printing, the commonly used inks are mainly solvent based inks, water-based inks and UV inks

1. Common printing methods and inks of corrugated paper

because corrugated paperboard is composed of multi-layer wavy corrugated, the surface flatness is poor, and the printing pressure cannot be too large. The silk printing method can only print some simple patterns and words, which is difficult to print. Corrugated paperboard is generally printed by flexograph. This is mainly because: ① the elastic deformation of flexo can make up for the thickness error and uneven surface of corrugated paper in the printing process, so that the printing ink color is uniform, so as to improve the quality of finished products; ② Flexographic printing pressure is small, even after the compression deformation of the printing plate, it can better contact with the corrugated board with uneven thickness, and avoid the phenomenon of thick part of the imprint being blurred, thin part of the poor contact, and empty and untrue imprint; ③ Flexographic printing adopts corrugated roller to transfer ink, which is convenient for the transmission of water-based ink. The printing plate only needs to touch the corrugated paper gently, and the water-based ink will be almost completely absorbed by the corrugated paper; ④ The flexographic printing machine has a simple structure, which is easy to be combined with other processes, such as indentation, slotting, die cutting, gluing, box making and other corresponding machinery for online operation

when using flexography to print corrugated paper, the commonly used inks are mainly solvent based inks, water-based inks and UV inks. With people's attention to environmental factors, the proportion of solvent based inks is decreasing year by year, while water-based inks and UV inks are becoming more and more popular. At present, water-based inks have the fastest growth and a large market share. For example, about 90% of flexographic inks in the United States are water-based. In the flexible printing of corrugated boxes, water-based inks account for a larger proportion, because the words or simple patterns printed on corrugated boxes do not need high gloss, and water-based inks can meet the requirements of print quality; Moreover, the corrugated box is a loose fabric with strong water absorption. After printing water-based ink, it is mainly permeable drying, and there is no need to set a drying device; And the water-based ink is non-toxic, harmless, non flammable, easy to use, safe and low cost. Therefore, combining these factors, the main printing method of corrugated paper is flexo printing, and the most commonly used ink is water-based ink

2. Water based ink in corrugated paper printing

2.1 composition of water-based ink

(1) binder

binder in water-based ink is water-borne needle or indenter soluble resin and water-borne polymer lotion. There are many kinds of waterborne resins, such as rosin maleic acid resin, styrene maleic acid resin, acrylic acid copolymer, ethyl aminoacrylate, etc. polymer lotion, that is, waterborne dispersion resin, including vinyl acetate copolymer, acrylic acid copolymer, polyurethane resin, epoxy resin, etc. At present, water-based acrylic resin is the most commonly used binder in water-based printing ink. At present, the most successful acrylic polymers are mainly alkali soluble resin, acrylic lotion, colloidal lotion and solution, and special acrylic polymers

(2) pigments

water based inks mainly use organic or inorganic pigments with strong alkali resistance and good dispersion in water system. In addition to ordinary powders, these pigments also include pigment filter cakes, pigment aqueous dispersions and easily dispersed pigments in water. The pigments in water-based inks must have strong alkali resistance, high hiding power, high color concentration and easy dispersion

(3) cosolvent

due to the low solubility and wettability of water, corresponding cosolvent should be selected, such as ethanol, propanol (n, ISO), ethylene glycol monoacetic acid, etc. By adding cosolvent, the shortcomings of ink can be improved and its stability can be improved, the surface tension of water-based ink can be reduced, the wetting of plastic can be increased, and it also helps to dissolve resin and improve the drying speed. In addition, the resin is generally insoluble in water, and appropriate alkaline substances must be added to promote the resin to dissolve in water. Generally, amines such as ethanolamine are selected, and the dosage depends on the pH value

(4) additives

there are many kinds of additives, such as diluents, dispersants, brighteners, defoamers, diluents, electrostatic agents, etc., to improve the printability of inks

2.2 requirements for water-based ink used in corrugated paper printing

the biggest characteristics of corrugated boxes are rough paper, uneven surface, fast ink penetration, and most of the face paper is dark yellowish brown. In order to produce the printing effect of full ink layer, rich layers and bright colors unique to flexographic printing, high-quality water-based ink should be used. In addition to the requirements of ordinary water-based inks, the following points should be considered when preparing water-based inks for corrugated paper printing

(1) the basic color should be bright and strong, so as to ensure that the imprint has a high hiding power; At the same time, it can achieve the basic balance of low viscosity and high color concentration, so that the layered version and the hidden danger of improving and eliminating the white pollution caused by plastic packaging materials can be clearly printed

(2) it is necessary to maintain fast penetration and drying performance, adapt to high-speed printing, avoid back rubbing dirty, and have good leveling performance, so that the imprint is flat, bright and clean, showing full and bright color effect, and let the printing factory have the conditions to select a wide range of paper and paperboard

(3) the printing process must have good re solubility to ensure the smooth ink development process and adapt to various printing speeds

(4) imprinting has good wear resistance and water resistance, which can meet the new performance requirements of packaging materials

3. Some problems of using water-based ink in corrugated paper printing

(1) flexographic printing uses corrugated roller to transfer ink, and the hole is small. Filter the water-based ink barrel to prevent impurities from damaging the corrugated roller

(2) the water-based ink should be fine in texture, bright in color, and the viscosity of the ink should match the printing speed

(3) the water-based ink used for corrugated paper printing is an oil-water miscible system formed by resin and water under the action of surfactant, and the stability of this system is poor. The stability of water-based ink depends on its pH value. When the pH value drops to about 7.8 or lower, the ink begins to be turbid and thickened, and it is easy to form a film, which hinders the normal transmission of the ink. The alkalinity is too strong, which will affect the wrinkle roll. Generally, the pH value is controlled at 8~9. Water based ink is alkaline, similar to soap solution, and easy to bubble

(4) fully stir before use to keep the ink composition uniform; After opening and using, the ink storage should be covered and sealed immediately to prevent dust from falling and crusting; If the remaining ink contains impurities, it should be filtered first, and then used together with new ink; During storage, please avoid exposure to high temperature or hot sun. Under normal conditions, it will be stored for one year without deterioration

(5) reasonably use ink additives. There are many types of additives for water-based inks, which should be used correctly according to the instructions. Before formal printing, we should comprehensively consider printing conditions, surface characteristics of substrate, environmental temperature and humidity, storage time of water-based inks and many other factors to prepare inks

at present, water-based ink has occupied a leading position in corrugated board printing. Its printing quality has been recognized by people with the gradual serialization, matching and standardization of the varieties of plastic building materials, and its pollution is small, so it is used more and more. At present, there are still some problems to be solved, especially the problem of drying speed. However, with the development of ink technology, the development prospect of water-based ink is still bright

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