Summary of raw and auxiliary materials and spare p

Summary of raw and auxiliary materials and spare parts for cartons (consumables) (IV)

2 Characteristics of the ink transfer roller

① the holes on the ink transfer roller are the same size and evenly distributed, which can effectively transfer and control the ink volume, making the ink film thickness uniform and the ink volume consistent. And it is less difficult to ink due to the poor viscosity of the printing ink

② with high precision, the corrugated roller can ensure the transmission of ink under a small pressure and reduce the ink blotting phenomenon at the edges of graphics and texts. The inking is uniform, and it is not easy to have a stiff edge

③ ink transfer by roller is adopted, and ink transfer failures such as ghosting or bar rarely occur, and ink flying rarely occurs in high-speed printing

④ the ink volume is easy to adjust by using the corrugated roller inking device. The thickness of the transferred ink layer is thin and very uniform, which makes dot color printing possible, and the ink film density is consistent from the minimum point to the field

⑤ the corrugated roller has high durability and corrosion resistance, especially the application of laser engraving ceramic corrugated roller, which greatly improves the service life of the corrugated roller and the stability of ink transfer

people call ceramic roller the "heart" of flexographic press, which shows its importance. The reasonable matching of ceramic roller and doctor blade can transfer water-based ink accurately and stably. Therefore, ceramic roller, also known as quantitative roller or metering roller, keeps the flexographic ink layer within the selected BCM value range during ink transmission. This is also the reason why flexographic products are "achromatic"

selection of ceramic roller:

first, according to the inking area of various colors of graphics and texts of printed matter, it is estimated by daily experience that the number of lines per inch of roller can be selected to meet the general inking volume of imprinting. Secondly, according to the ink absorption of the substrate material, during the preliminary proofreading overprint process, observe the hue of each color imprint and the saturation degree of the ink volume, and then change the roller with different line numbers until it meets the requirements of the imprinted ink layer

suggestion: data recording during each printing process is an important basis for future production

the number of lines of commonly used ceramic roller is as follows:

field version: 250 lines/inch ~ 400 lines/inch

text line version: 400 lines/inch ~ 600 lines/inch

pattern plate: 550 lines/inch ~ 800 lines/inch (suitable for 133 lines/inch ~ 150 lines/inch), 700 lines/

inch ~ 1000 lines/inch (suitable for 175 lines/inch)

if selecting the embossing roller for the inking volume demand of a certain color printing plate, it is necessary not only to select the matching of the number of lines, but also to compare the BCM value in the embossing roller of the same number of lines, so as to achieve a reasonable selection. It is generally required that the number of embossing rollers is better, so that different products can be selected according to the change of imprinting ink volume. It is absolutely impossible to make do with the blending of ink hue. In this way, it is difficult to achieve the best amount of ink and ink layer, and it is also difficult to achieve the best effect of hue. It will not only waste time and ink, but also cause unqualified imprinting quality. In the long run, the losses it will bring will far exceed the price of buying a few more ceramic corrugated rollers

the maintenance of ceramic roller is also a very important work. The price of a ceramic roller is still relatively expensive at present. Taking good care of the roller is not only a problem of service life, but also a direct impact on the transmission of ink and the quality of imprinting. Tiny holes are very easy to be blocked by dry ink, so clean the wrinkle roller after each printing. For the wrinkle roll that has been blocked by ink, you can only use professional detergent to clean it, or you can restore the ink transfer effect of the original BCM value

domestic enterprises that produce and sell ceramic roller are mainly: Shanghai aokeli Printing Machinery Co., Ltd., Zhongshan Xinsheng roller factory, Changzhou Wujin Haili roller Co., Ltd., Guangzhou Yuexin Laser Technology Co., Ltd., American Praxair company (represented by Hongye Equipment Co., Ltd.), Guangdong Guangtai Laser Technology Co., Ltd., Yiming Technology Co., Ltd., etc

doctor blade

doctor blade and ceramic roller form an ink transfer system. Now flexographic printing machines are equipped with plug-in reverse doctor blade structure, which is easy to operate and has good ink scraping effect. The materials of the doctor blade are steel sheet and plastic sheet. The blade edge is ground into an inclined plane, which is conducive to clean scraping. The pressure adjustment of the doctor blade is subject to the removal of all excess ink on the surface of the corrugated roller. The pressure is not easy to be too large to avoid damaging the ceramic corrugated roller. The worn doctor blade should be replaced in time, otherwise the ink transfer quality cannot be guaranteed

it must be reminded that the doctor blade can only be installed when the ceramic roller is inked

Polish

polish is a colorless, transparent or translucent ink. It can increase the printing gloss, protect the surface of the printed matter, improve the abrasion resistance, chemical resistance and water resistance of the printed matter, and prevent the printed matter from rubbing dirty or sticking

at present, UV glazing process and solvent based glazing process are widely used, but the application of water-based glazing agent is very few. Glazing oil mainly includes solvent based and water-based. Solvent type is generally made of polyurethane, SBS (styrene butadiene styrene block copolymer), EVA (ethylene vinyl acetate copolymer), polyacrylate, etc. as the main resin, toluene, ethyl acetate, gasoline, etc. as the solvent, supplemented by tackifying resin, plasticizer, antioxidant and other additives. Due to the volatilization of organic solvents, there are shortcomings of flammability, toxicity and environmental pollution, which is no longer the focus of current research and development. Although UV glazing has the advantage of fast drying speed, it is expensive. The aqueous varnish formed by uniformly dispersing water-insoluble macromolecular substances in water through emulsifier overcomes the shortcomings of solvent based varnish, such as flammability, toxicity, high energy consumption, environmental pollution and so on, so it has become the focus of development and research in the field of paper glazing at present

water is the cheapest and pollution-free coating solvent. This water-based varnish developed rapidly in the 1990s and was widely welcomed in developed countries. For the printing industry, many health, environmental protection, labor protection and other requirements and constraints have been gradually increased, especially for food packaging and printing. Therefore, water-based varnish also meets the requirements of international health standards

classification of water-based Polish

1 Traditional water-based glazing oil with problems solved in time. The main agent of traditional water-based polish is polymer dissolved in water or suspended in water. Its water content is 50% - 70%. Due to the excessive water content, the glazing effect is not ideal, resulting in the problems of slow drying and difficult flow

2. Modern new water-based glazing oil. Adding additives (mainly surfactants) to the traditional water-based glazing oil forms a modern new type of water-based glazing oil. Among them, ethylene glycol or propylene glycol is used to replace 80% of water, and its appearance is milky white. By adjusting the solid content in the glazing oil, different glazing effects such as high gloss, ordinary gloss and sub gloss can be obtained

the new water-based glazing oil meets the requirements of health and environmental protection. It is used more and more, and is widely used in the packaging of food, medicine and other products. Moreover, the printing products using water-based glazing oil can be recycled through biodegradation

3. Catalytic waterborne polish. Catalytic waterborne Varnish is generally used in web printing machines with heating devices. It is thermosetting and will not be plasticized again when heated, so it can only be calendered by online calendering

catalytic waterborne Polish contains free formaldehyde, which is a carcinogen and harmful to human health. Therefore, from the perspective of sanitation and environmental protection, catalytic water-based glazing oil can only be used on printing materials that do not have high requirements for sanitation and environmental protection

composition and application of water-based glazing oil

water-based glazing oil is mainly composed of main agent, solvent and auxiliary agent

1. Main agent. The main agent of water-based glazing oil is film-forming resin, usually synthetic resin, which affects and dominates various physical properties of the deep layer and the glazing quality of the film, such as gloss, adhesion, dryness, etc

there are many kinds of waterborne film-forming resins, but the copolymer resin of acrylic acid system is widely used at home and abroad. The performance of its copolymer resin depends on the composition of monomer and synthesis process. Waterborne acrylic copolymer resin has a series of excellent properties, such as good film-forming property, good gloss, high transparency, fast drying speed, wear resistance, water resistance and so on. It is widely used in Waterborne Varnish

2. auxiliary. Additives are used to improve the physical and chemical properties and processing characteristics of water-based varnish. The commonly used additives include curing agent, surfactant, defoamer, desiccant, adhesion aid, wetting dispersant and other additives

there are many kinds of additives, and the use depends on the type of varnish. However, the amount of various additives should not exceed 5% of the total amount, otherwise it will affect the processing adaptability of glazing oil

3. Solvents. The main role of solvents in Hebei area is to disperse or dissolve synthetic resins and various additives

the solvent of water-based glazing oil is mainly water, which is colorless, tasteless, non-toxic, has a wide range of sources, low price, almost zero volatility, and very good leveling. However, there are also shortcomings, such as slow drying speed, easy to cause product size instability, etc. Therefore, an appropriate amount of ethanol is added during use to improve the drying performance of aqueous solvents and improve the processing adaptability of aqueous glazing oils

the application of water-based glazing oil must be comprehensively considered according to different glazing methods, paper types, product quality requirements, etc. in order to achieve good results. Attention should be paid when using:

① during the coating process, the viscosity and solid content of the glazing oil must be reasonably controlled, and the dilution can only be carried out within a certain solid content range of 10 yuan/ton in Tangshan area

② when selecting the paper type, consider the good dimensional stability of thick paper and the poor dimensional stability of thin paper

③ it should be noted that the coating amount of water-based glazing oil is not easy to control, so the control of viscosity is very important

④ when using water-based varnish, you can completely cancel or reduce the use of anti stick dirt agent, because the water-based varnish is completely cured, the surface is very smooth, and rarely sticks dirty

⑤ in terms of the control of drying time, we should make full use of the osmotic drying of water-based glazing oil. Another way to improve the drying speed is to increase the content of ethanol, but it should be combined with the actual situation and the viscosity of the glazing oil, and it cannot be adjusted at will

in a word, whether it is water-based glazing oil or other water-based materials, they are not very ideal in the printing of non absorbent substrate materials (on paper with good absorption, the printing adaptability is ideal), which needs to be further improved and perfected

the polishing of flexographic press is completed by the printing unit, so it can also be called "printing light". You can use water-based varnish, or add a UV drying system to use UV varnish. There are also special glazing devices for positive and negative glazing, which can also be used for the coating operation of non drying glue, and even machine compounding into non drying glue printing products, etc. The glazing coating is thicker than the printing ink layer to obtain better gloss or other effects

there are quite a lot of varieties of glazing (printing) materials, and choosing the appropriate varnish is a major factor to improve the quality of flexo printing products. Flexographic printing usually needs to add one color water-based printing light or UV printing light at the end of the color sequence, which is completed by the printing unit. In addition to enhancing the gloss of the imprint, it is also to enhance the physical properties of the imprinted surface to adapt to post printing