2 The composition of waterborne varnish The aqueous varnish mainly consists of three main categories: main agent, solvent and auxiliary agent.
a. The main agent. The main agent of water-based coating oil is a film-forming resin, which is a film-forming substance of the polishing agent, and is usually a synthetic resin, which affects and supports various physical properties of the deep layer and coating qualities of the film, such as gloss, adhesion, and the like. Sex, dryness, etc.;
b. Additives. Auxiliaries are used to improve the physicochemical properties and processing characteristics of aqueous polishes. The types of additives are:
Hardener. Improve the film forming property of the aqueous main agent and increase the cohesive strength of the film; Surfactant. Reduce the surface tension of aqueous solvents and improve leveling; defoamers. Can long-term control of the blistering agent polish, eliminate fish eye, pinhole and other defects; desiccant. Increase the drying speed of water-based polish, improve the printability of paper; adhesion promoter. Improve the adhesion of the film-forming substance to the substrate; wetting and dispersing agent. Improve the dispersibility of the main agent, prevent stains and improve wear resistance; other additives are plasticizers that can improve folding resistance;
c. Solvents. The main role of the solvent is to disperse or dissolve synthetic resins and various additives.
The solvent of the aqueous coating oil is mainly water. The volatility of water is almost zero and its leveling performance is very good. However, water as a solvent for aqueous coating oils also has disadvantages such as a slow drying rate and a process defect that easily causes product dimensional instability. Therefore, ethanol is added during use to improve the drying performance of the aqueous solvent and improve the processing suitability of the aqueous coating oil.
3 Application of waterborne varnish 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, and cigarette packs. Not only are the printing requirements exquisite. Color picture, but also has a magnificent surface gloss, which is a special effect produced by applying varnish to the printed material. Applying varnishes to prints not only increases the value of printed products, but also enhances the lightfastness of inks, increases the heat and moisture resistance of inks, protects the imprints, improves the performance of printed products, and brings considerable benefits to printing houses. Economic benefits.
The coating glazing market is a diversified market. Various books and magazines printing, commercial printing, trademark printing and folding carton printing plants have varying degrees of glazing needs for various packaging products. The application of waterborne varnish must be based on a variety of factors such as different coating methods, paper types, and product quality to achieve good results.
4 Influence on the quality of glazing and several issues that should be noticed The main problems that affect the quality of glazing are paper properties, paper type, viscosity, coating amount, drying conditions, and so on.
4.1 Paper Performance The effect of paper on gloss quality is mainly reflected in the effect of paper smoothness on gloss quality. High-smoothness papers have a significant effect after polishing, while papers or paperboards with low smoothness have a poor effect when applied, because the varnish is almost completely absorbed by rough paper or paperboard. In order to solve this problem, you can use the base oil before the last light, or twice the light.
4.2 Paper Type Thick paper has good dimensional stability and poor dimensional stability. Dimensional stability is one of the key indicators of print quality. It is closely related to the amount of water used in printing, the moisture content of the paper, the drying time and method, and the control of viscosity. If the printed product is under 90g/m2 paper, please use water-based coating carefully.
4.3 Varnish Viscosity and Solids In the coating process, the viscosity and solids content of the coating must be properly controlled. Therefore, the dilution can only be performed within a certain range of viscosity and solid content. Water-based glazing oil diluents generally use ethanol and water, the ratio of 1:1 mixture, dilution of 10% to 30%, not too large, should be strictly controlled.
4.4 Coating amount The coating amount of the aqueous coating oil should be controlled at 4 to 6 g/m2. Because the evaporation rate of ethanol is very fast in the coating of varnish, the control of the viscosity is very important. Ethanol content must also be increased in time to ensure product stability.
4.5 Drying conditions
Solvent-based coating oils are almost all volatilized and dried, and the penetration and drying of aqueous coating oils have great utility value. However, in multi-color printing, if the last color is coated with glazing oil, the drying time will be slower because the paper has absorbed more ink and moist water. Must use infrared drying device. During the drying process, the coating oil is heated, the bottom layer penetrates and dries quickly, and at the same time, the moisture in the coating oil is heated and evaporated by the high temperature, and is discharged through the exhaust pipe.
Another way to increase the drying rate is to increase the ethanol content, but depending on the actual situation, depending on the viscosity of the coating, it cannot be arbitrarily adjusted.
5 Conclusion With the development of society, people’s awareness of the protection of the living environment has also increased. For the printing industry, many requirements and restrictions on hygiene, environmental protection, and labor protection have been gradually increased. In particular, the requirements for food packaging and printing have become more stringent. Only in this way can the requirements of international health standards be met. Therefore, it is imperative to develop and apply pollution-free, pollution-free “green†materials.
Waterborne varnish has the characteristics of non-toxic, odorless, high glossiness, and easy to use. In recent years, it has been widely used in the field of packaging and printing, and has achieved a rising trend.
a. The main agent. The main agent of water-based coating oil is a film-forming resin, which is a film-forming substance of the polishing agent, and is usually a synthetic resin, which affects and supports various physical properties of the deep layer and coating qualities of the film, such as gloss, adhesion, and the like. Sex, dryness, etc.;
b. Additives. Auxiliaries are used to improve the physicochemical properties and processing characteristics of aqueous polishes. The types of additives are:
Hardener. Improve the film forming property of the aqueous main agent and increase the cohesive strength of the film; Surfactant. Reduce the surface tension of aqueous solvents and improve leveling; defoamers. Can long-term control of the blistering agent polish, eliminate fish eye, pinhole and other defects; desiccant. Increase the drying speed of water-based polish, improve the printability of paper; adhesion promoter. Improve the adhesion of the film-forming substance to the substrate; wetting and dispersing agent. Improve the dispersibility of the main agent, prevent stains and improve wear resistance; other additives are plasticizers that can improve folding resistance;
c. Solvents. The main role of the solvent is to disperse or dissolve synthetic resins and various additives.
The solvent of the aqueous coating oil is mainly water. The volatility of water is almost zero and its leveling performance is very good. However, water as a solvent for aqueous coating oils also has disadvantages such as a slow drying rate and a process defect that easily causes product dimensional instability. Therefore, ethanol is added during use to improve the drying performance of the aqueous solvent and improve the processing suitability of the aqueous coating oil.
3 Application of waterborne varnish 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, and cigarette packs. Not only are the printing requirements exquisite. Color picture, but also has a magnificent surface gloss, which is a special effect produced by applying varnish to the printed material. Applying varnishes to prints not only increases the value of printed products, but also enhances the lightfastness of inks, increases the heat and moisture resistance of inks, protects the imprints, improves the performance of printed products, and brings considerable benefits to printing houses. Economic benefits.
The coating glazing market is a diversified market. Various books and magazines printing, commercial printing, trademark printing and folding carton printing plants have varying degrees of glazing needs for various packaging products. The application of waterborne varnish must be based on a variety of factors such as different coating methods, paper types, and product quality to achieve good results.
4 Influence on the quality of glazing and several issues that should be noticed The main problems that affect the quality of glazing are paper properties, paper type, viscosity, coating amount, drying conditions, and so on.
4.1 Paper Performance The effect of paper on gloss quality is mainly reflected in the effect of paper smoothness on gloss quality. High-smoothness papers have a significant effect after polishing, while papers or paperboards with low smoothness have a poor effect when applied, because the varnish is almost completely absorbed by rough paper or paperboard. In order to solve this problem, you can use the base oil before the last light, or twice the light.
4.2 Paper Type Thick paper has good dimensional stability and poor dimensional stability. Dimensional stability is one of the key indicators of print quality. It is closely related to the amount of water used in printing, the moisture content of the paper, the drying time and method, and the control of viscosity. If the printed product is under 90g/m2 paper, please use water-based coating carefully.
4.3 Varnish Viscosity and Solids In the coating process, the viscosity and solids content of the coating must be properly controlled. Therefore, the dilution can only be performed within a certain range of viscosity and solid content. Water-based glazing oil diluents generally use ethanol and water, the ratio of 1:1 mixture, dilution of 10% to 30%, not too large, should be strictly controlled.
4.4 Coating amount The coating amount of the aqueous coating oil should be controlled at 4 to 6 g/m2. Because the evaporation rate of ethanol is very fast in the coating of varnish, the control of the viscosity is very important. Ethanol content must also be increased in time to ensure product stability.
4.5 Drying conditions
Solvent-based coating oils are almost all volatilized and dried, and the penetration and drying of aqueous coating oils have great utility value. However, in multi-color printing, if the last color is coated with glazing oil, the drying time will be slower because the paper has absorbed more ink and moist water. Must use infrared drying device. During the drying process, the coating oil is heated, the bottom layer penetrates and dries quickly, and at the same time, the moisture in the coating oil is heated and evaporated by the high temperature, and is discharged through the exhaust pipe.
Another way to increase the drying rate is to increase the ethanol content, but depending on the actual situation, depending on the viscosity of the coating, it cannot be arbitrarily adjusted.
5 Conclusion With the development of society, people’s awareness of the protection of the living environment has also increased. For the printing industry, many requirements and restrictions on hygiene, environmental protection, and labor protection have been gradually increased. In particular, the requirements for food packaging and printing have become more stringent. Only in this way can the requirements of international health standards be met. Therefore, it is imperative to develop and apply pollution-free, pollution-free “green†materials.
Waterborne varnish has the characteristics of non-toxic, odorless, high glossiness, and easy to use. In recent years, it has been widely used in the field of packaging and printing, and has achieved a rising trend.