Application of the hottest environmental friendly

Application of environmental friendly water-based glazing oil and several problems that should be paid attention to (Part 2)

composition of water-based glazing oil

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

a. main agent. The main agent of water-based glazing oil is film-forming resin, which is the film-forming material of glazing agent, usually synthetic resin. It affects and supports 41 domestic titanium dioxide enterprises in 2017, with deep physical properties and coating glazing quality, such as gloss, adhesion, dryness, etc

b. additives. Additives are used to improve the physical and chemical properties and processing characteristics of water-based polish. The types of additives are:

curing agent. Improve the film-forming property of water-based main agent and increase the cohesion strength of the film; Surfactant. Reduce the surface tension of aqueous solvent and improve the leveling property; Defoamer. It can control the foaming of polish for a long time, and eliminate the quality defects such as fish eyes and pinholes; desiccant. Increase the drying speed of water-based polish and improve the suitability of paper prints; Adhesion AIDS. Improve the adhesion between film-forming material and substrate; Wetting dispersant. Improve the dispersibility of the main agent, prevent dirt and improve wear resistance; Other additives are plasticizers that can improve the folding resistance

c. solvent. The main function of solvent is to disperse or dissolve synthetic resins and various additives

the solvent of aqueous polish is mainly water. The volatility of water is almost zero, and its leveling performance is very good. However, as the solvent of water-based glazing oil, water also has shortcomings, such as slow drying speed, easy to cause process failures such as unstable product size. Therefore, add ethanol in use to improve the drying performance of aqueous solvents and improve the processability of aqueous glazing oils

3 application of water-based glazing oil

with the rapid and steady development of market economy and commodity economy, people pay more and more attention to the printing and decoration of books, magazines, covers, calendars, pictures, medicine boxes, cigarette packs. The printing requires not only exquisite color pictures, but also rich and magnificent surface gloss. This gloss is the special effect produced by applying glazing oil on the printed object. Coating varnish on printed matter can not only increase the value of printed products, but also enhance the light resistance of the ink, increase the heat and moisture resistance of the ink, protect the imprint, improve the use performance of printed products, and bring considerable economic benefits to the printing factory

the coating and glazing market is a diversified market, and various book printing plants, commercial printing plants, trademark printing plants and folding carton printing plants have different degrees of glazing needs for a variety of packaging products. The application of water-based glazing oil must be comprehensively considered according to different glazing methods, paper types, product quality and other factors in order to achieve good results

4 the main problems affecting the glazing quality are paper performance, paper type, viscosity, coating amount, drying conditions, etc

4.1 paper performance

the influence of paper on glazing quality is mainly reflected in the influence of paper smoothness on glazing quality. The paper with high smoothness has a significant effect after polishing, while the paper or paperboard with low smoothness has a poor effect after polishing, because the polishing oil is almost completely absorbed by the paper or paperboard with rough surface. In order to solve this problem, you can apply primer once or twice before glazing

4.2 paper type

thick paper has good dimensional stability, while thin paper has poor dimensional stability. Dimensional stability is one of the key indicators of print quality, which is closely related to the amount of water in printing, the water content of paper, the drying time and method, and the control of viscosity. If the printing product is less than 90g/m2 paper, please carefully use water-based polish

4.3 viscosity and solid content of glazing oil

in the process of coating, the viscosity and solid content of glazing oil must be reasonably controlled. Therefore, dilution can only be carried out within a certain range of viscosity and solid content. The diluent of water-based glazing oil generally adopts the mixture of ethanol and water in the ratio of 1:1, and the dilution amount is 10% - 30%, which should not be too large, and should be strictly controlled

4.4 coating amount

the coating amount of water-based varnish should be controlled at 4 ~ 6g/m2. Because in the coating varnish, the evaporation rate of ethanol is very fast, so the viscosity control is very important. The content of ethanol should also be increased in time to ensure the stability of the product

4.5 dryness increased by more than 53% compared with 2018 dryness conditions

almost all solvent based varnishes are volatile drying, and the osmotic drying of water-based varnishes has great utilization value. But in multicolor printing, if 6 Stop the machine when the test piece breaks, and the last color is to apply varnish, so the drying time will slow down, because more ink and wet water have been absorbed inside the paper. Infrared drying device must be used. During the drying process, the glazing oil is heated, and the bottom layer is rapidly penetrated and dried. At the same time, the water in the glazing oil is heated and evaporated by high temperature, and is discharged through the exhaust pipe

another way to improve the drying speed is to increase the content of ethanol, but it should be combined with the actual situation, which depends on the viscosity of the Polish, and cannot be adjusted at will

5 conclusion

with the development of society, human awareness of the protection of the living environment is also constantly improving. For the printing industry, many requirements and constraints in health, environmental protection, labor protection and other aspects have been gradually increased, especially the requirements for food packaging and printing are more stringent. Only in this way can it meet the requirements of international health standards. Therefore, it is imperative to develop and apply pollution-free and pollution-free "green" materials

waterborne Varnish has the characteristics of non-toxic, tasteless, high gloss and convenient use. In recent years, it has been widely used in the field of packaging and printing, and has achieved an increasing trend

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