At present, the “green revolution†set off by various industries around the world is also constantly impacting the packaging and printing, making flexographic printing “stand out†and making great strides, and is recognized as a “best and most promising†printing method. The reason is that the flexo printing has the wide adaptability and economy of printing, and more importantly, the flexographic printing adopts water-based ink, has good printing adaptability and excellent environmental protection performance, and accords with the development trend of modern printing.
In China, due to the late start of flexographic printing, people are accustomed to the control of solvent-based inks, and the control of water-based inks either uses inertial thinking or they do not know where to start. The result is often a lot of manpower, material resources, and financial resources. lost heavily. Therefore, it is particularly important to correctly understand the technical control indicators of water-based inks. This article discusses the main technical indicators such as water ink viscosity, PH value, thickness and fineness.
The main difference between a water-based ink and a solvent ink is that the solvent used in the ink is not an organic solvent but water. The connection material is composed of a resin and water. The main components of the water-based ink are a colorant, a water-based binder, a solvent and various additive. Usually can be configured as follows:
Colorant: 12-40% Resin: 20-28% Water + Alcohol: 33-50% Alkaline: 4-6% Additive: 3-4%
The colorant agent is usually an alkali-resistant pigment, including organic pigments and inorganic pigments, and requires good dispersibility in water. It is essentially the same as the colorant in the solvent ink, and there are a few exceptions. It is necessary to select according to the specific circumstances. Packaging materials require colorful, pigmented pigments. In order to increase the color intensity of the ink and improve the viscosity, dyes may also be used. Various pigments are subjected to anionic, non-ionic surface treatment to improve the surface tension and polarity of the water. The color toner is dispersed, and the uneven distribution of untreated toner is not conducive to printing.
There are many different types of water-based inks for connecting materials, which can be selected according to different occasions and applications. At present, domestic research and development use more alkali soluble binders. Such water-based ink binders can be dissolved in water and dried to become water-insoluble after printing. Usually, an appropriate amount of ammonium hydroxide is added to the resin solution to form a soluble resin salt. After the ammonia is volatilized, the ink becomes a substance that is insoluble in water. The performance of this kind of ink mainly depends on the type of the acid resin used. Rosin modified maleic acid resin is generally used as the connecting material. Due to its wide range of raw materials and reasonable price, it has been widely used. However, the inks produced from these types of connecting materials have relatively poor abrasion resistance, water resistance and viscosity stability. Nowadays, acrylic resin is commonly used as a connecting material in foreign countries. It has significant advantages in terms of gloss, weather resistance, water resistance, chemical resistance, and contamination resistance, and it has excellent performance when directly dissolving and dissolving or synthesizing molecular emulsions. Domestic acrylic resins and polymer emulsions are of poor quality and unstable, and most manufacturers still use imported acrylic resins and emulsions, but the supply period and prices have caused troubles for ink-jet printers. Therefore, the development of a kind of economical and reasonable, good performance and alkali-soluble binders has become the primary task of many innovations in ink-jet production plants. Sometimes to achieve some purpose. Several types of binders can also be used in combination. At this time, we must balance the impact of other ink properties.
Solvent-clean water is added with a small amount of alcohol such as ethanol, isopropanol or n-propanol. The addition of alcohols helps to increase the stability of the ink, speed up drying, and reduce surface tension. Isopropanol also reduces foaming.
The additives are mainly stabilizers, defoamers, anti-foaming agents and other additives. Stabilizers reduce ink viscosity and adjusted pH. PH value should be controlled within the range of 8.5-9.5 to improve the stability of the ink. Defoamers can break or inhibit foaming in the ink. Sometimes in order to increase the ink's performance, wax additives can be added, generally polyethylene wax. There are also some other additives that can be selected according to specific needs.
Viscosity Control Viscosity is a measure that prevents fluid flow and is the ability of fluid molecules to interact and produce their ability to impede the relative movement of their molecules, ie the resistance to fluid flow. Viscosity directly affects the transfer of ink and the quality of flexographic prints. The size of the viscosity is related to the viscosity of the resin in the vehicle and its density. Low viscosity, fast ink transfer, will cause the color light, dot distortion, uneven ink transfer and other defects; high viscosity, ink transfer slow, uneven ink, color, but sometimes not deep printing, easy to cause dirty version and paste version and other ills. Low viscosity can be adjusted with new inks; high viscosity can be diluted with water or water and ethanol (50% each), and can also be adjusted with ink stabilizers. In addition, the temperature has a great influence on the viscosity of the ink. Usually, the viscosity decreases when the temperature increases, whereas the viscosity increases when the temperature increases. Therefore, in order to maintain the consistency of the print density in the printing process, the temperature of the printing shop should be kept constant.
PH value control of the binder in the ink is mainly alkali soluble resin, PH value is controlled in the range of 8.5-9.5, the ink printing performance is best, the quality of the print is the most stable. As amines are constantly evaporating during the printing process, the operator will also add new ink and various additives to the ink from time to time, so the PH value changes at any time. When the PH value is higher than 9.5, the alkalinity is too strong, the viscosity of the ink will decrease, the drying speed will slow, and the water resistance will become worse; when the PH value is lower than 8.5, the alkalinity is too weak, the viscosity of the ink will increase and the drying The faster the speed is, the easier it is to jam the printing plate and the anilox roller, causing the layout to be dirty and bubbles to form. It is recommended to control the pH and viscosity in the actual control, especially in the case of color printing. This problem should be paid more attention. Usually, a simple pH indicator is prepared in addition to the viscosity cup so that it can be detected at any time. PH value stabilizer or a small amount of alkaline substance can be added when the PH value is low. When the PH value is high, solvent can be added or diluted for dilution.
Thickness Control The thickness of the so-called ink refers to the degree of dispersion of solid powdered substances such as pigments and fillers mixed in the binder. The thickness of the ink not only affects the color strength, hue, and stability of the ink, but also affects the rheological properties and economic benefits of the ink. The ink is too thick to cause problems such as heaping ink and stencil, and the coloring power and hue of the ink will be decreased. The ink is too fine and the flowability is too large. After the printing deposition, the dots will spread, which will affect the quality of the printed product. In addition, the thickness of the ink will also affect the dispersion of the base. When the dispersion of the ink is not satisfactory, its printing performance will not be satisfactory. The observation will produce less smooth, smooth, soft and will produce a "block". Feeling like, thus greatly reducing printing performance. Flexographic printing can select inks of different thickness according to different requirements. Printed wires with finer, more precise prints require higher fineness of the ink; when printing is not required for high precision or in-situ printing, the thickness of the ink is fine. Can be reduced, this is also considered from the perspective of economic efficiency. (School of Printing and Packaging Engineering, Xi'an University of Technology)
In China, due to the late start of flexographic printing, people are accustomed to the control of solvent-based inks, and the control of water-based inks either uses inertial thinking or they do not know where to start. The result is often a lot of manpower, material resources, and financial resources. lost heavily. Therefore, it is particularly important to correctly understand the technical control indicators of water-based inks. This article discusses the main technical indicators such as water ink viscosity, PH value, thickness and fineness.
The main difference between a water-based ink and a solvent ink is that the solvent used in the ink is not an organic solvent but water. The connection material is composed of a resin and water. The main components of the water-based ink are a colorant, a water-based binder, a solvent and various additive. Usually can be configured as follows:
Colorant: 12-40% Resin: 20-28% Water + Alcohol: 33-50% Alkaline: 4-6% Additive: 3-4%
The colorant agent is usually an alkali-resistant pigment, including organic pigments and inorganic pigments, and requires good dispersibility in water. It is essentially the same as the colorant in the solvent ink, and there are a few exceptions. It is necessary to select according to the specific circumstances. Packaging materials require colorful, pigmented pigments. In order to increase the color intensity of the ink and improve the viscosity, dyes may also be used. Various pigments are subjected to anionic, non-ionic surface treatment to improve the surface tension and polarity of the water. The color toner is dispersed, and the uneven distribution of untreated toner is not conducive to printing.
There are many different types of water-based inks for connecting materials, which can be selected according to different occasions and applications. At present, domestic research and development use more alkali soluble binders. Such water-based ink binders can be dissolved in water and dried to become water-insoluble after printing. Usually, an appropriate amount of ammonium hydroxide is added to the resin solution to form a soluble resin salt. After the ammonia is volatilized, the ink becomes a substance that is insoluble in water. The performance of this kind of ink mainly depends on the type of the acid resin used. Rosin modified maleic acid resin is generally used as the connecting material. Due to its wide range of raw materials and reasonable price, it has been widely used. However, the inks produced from these types of connecting materials have relatively poor abrasion resistance, water resistance and viscosity stability. Nowadays, acrylic resin is commonly used as a connecting material in foreign countries. It has significant advantages in terms of gloss, weather resistance, water resistance, chemical resistance, and contamination resistance, and it has excellent performance when directly dissolving and dissolving or synthesizing molecular emulsions. Domestic acrylic resins and polymer emulsions are of poor quality and unstable, and most manufacturers still use imported acrylic resins and emulsions, but the supply period and prices have caused troubles for ink-jet printers. Therefore, the development of a kind of economical and reasonable, good performance and alkali-soluble binders has become the primary task of many innovations in ink-jet production plants. Sometimes to achieve some purpose. Several types of binders can also be used in combination. At this time, we must balance the impact of other ink properties.
Solvent-clean water is added with a small amount of alcohol such as ethanol, isopropanol or n-propanol. The addition of alcohols helps to increase the stability of the ink, speed up drying, and reduce surface tension. Isopropanol also reduces foaming.
The additives are mainly stabilizers, defoamers, anti-foaming agents and other additives. Stabilizers reduce ink viscosity and adjusted pH. PH value should be controlled within the range of 8.5-9.5 to improve the stability of the ink. Defoamers can break or inhibit foaming in the ink. Sometimes in order to increase the ink's performance, wax additives can be added, generally polyethylene wax. There are also some other additives that can be selected according to specific needs.
Viscosity Control Viscosity is a measure that prevents fluid flow and is the ability of fluid molecules to interact and produce their ability to impede the relative movement of their molecules, ie the resistance to fluid flow. Viscosity directly affects the transfer of ink and the quality of flexographic prints. The size of the viscosity is related to the viscosity of the resin in the vehicle and its density. Low viscosity, fast ink transfer, will cause the color light, dot distortion, uneven ink transfer and other defects; high viscosity, ink transfer slow, uneven ink, color, but sometimes not deep printing, easy to cause dirty version and paste version and other ills. Low viscosity can be adjusted with new inks; high viscosity can be diluted with water or water and ethanol (50% each), and can also be adjusted with ink stabilizers. In addition, the temperature has a great influence on the viscosity of the ink. Usually, the viscosity decreases when the temperature increases, whereas the viscosity increases when the temperature increases. Therefore, in order to maintain the consistency of the print density in the printing process, the temperature of the printing shop should be kept constant.
PH value control of the binder in the ink is mainly alkali soluble resin, PH value is controlled in the range of 8.5-9.5, the ink printing performance is best, the quality of the print is the most stable. As amines are constantly evaporating during the printing process, the operator will also add new ink and various additives to the ink from time to time, so the PH value changes at any time. When the PH value is higher than 9.5, the alkalinity is too strong, the viscosity of the ink will decrease, the drying speed will slow, and the water resistance will become worse; when the PH value is lower than 8.5, the alkalinity is too weak, the viscosity of the ink will increase and the drying The faster the speed is, the easier it is to jam the printing plate and the anilox roller, causing the layout to be dirty and bubbles to form. It is recommended to control the pH and viscosity in the actual control, especially in the case of color printing. This problem should be paid more attention. Usually, a simple pH indicator is prepared in addition to the viscosity cup so that it can be detected at any time. PH value stabilizer or a small amount of alkaline substance can be added when the PH value is low. When the PH value is high, solvent can be added or diluted for dilution.
Thickness Control The thickness of the so-called ink refers to the degree of dispersion of solid powdered substances such as pigments and fillers mixed in the binder. The thickness of the ink not only affects the color strength, hue, and stability of the ink, but also affects the rheological properties and economic benefits of the ink. The ink is too thick to cause problems such as heaping ink and stencil, and the coloring power and hue of the ink will be decreased. The ink is too fine and the flowability is too large. After the printing deposition, the dots will spread, which will affect the quality of the printed product. In addition, the thickness of the ink will also affect the dispersion of the base. When the dispersion of the ink is not satisfactory, its printing performance will not be satisfactory. The observation will produce less smooth, smooth, soft and will produce a "block". Feeling like, thus greatly reducing printing performance. Flexographic printing can select inks of different thickness according to different requirements. Printed wires with finer, more precise prints require higher fineness of the ink; when printing is not required for high precision or in-situ printing, the thickness of the ink is fine. Can be reduced, this is also considered from the perspective of economic efficiency. (School of Printing and Packaging Engineering, Xi'an University of Technology)
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