Suitability of the hottest gravure ink I

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The suitability of gravure printing ink (I)

the development of social economy and the increasing improvement of people's living standards make gravure printing more prominent in various printing methods. The research on gravure printing technology has very important practical significance. Here is a brief discussion on the printability of gravure printing ink. Please correct the mistakes

like other printing inks, gravure printing inks are mainly composed of colored substances (pigments) and binders. Among them, colored substances play a role in color development, which shows images on the substrate by forming a contrast with the color of the substrate. Only when the proportion of each component of the ink is well allocated, can the printing suitability and use performance of the ink be achieved, and the printing ink can be well coordinated with the printing plate, printing machine and substrate materials, so that the printing process can be carried out smoothly

I. raw materials

gravure inks are mostly volatile solvent inks, which are composed of pigments, solid resins, volatile solvents, fillers and additives

1. pigment. Pigments are divided into inorganic pigments and organic pigments. Most of the inorganic pigments are hard and dense crystal materials. These crystals are difficult to grind into fine particles without special treatment, and cannot be well dispersed into the binder. Therefore, the printing suitability of the ink made of inorganic pigments is often not ideal, and it is easy to wear the printing plate. While most organic pigments can be artificially improved, which are easier to disperse in the binder. The ink made of them has great advantages in printability, but the price is often higher. The pigment composition of gravure printing ink is mostly organic pigments, which is determined by the printing characteristics of gravure printing and the quality requirements of printing products

the influence of pigments on the printability in oil is mainly determined by the properties of pigments, such as dispersion, hiding power, tax specific volume, resistance, etc

① dispersion refers to the size of pigment particles. The pigment particles in the ink must be completely immersed in the binder in the ink film. The size of the pigment particles cannot exceed the thickness of the ink film, which is generally 5 μ M, otherwise it will affect the gloss of the printed matter. The smaller the particle, the higher the dispersion, the greater the hue saturation of the ink. Gravure printing is hole transfer printing, which requires high pigment dispersion

② coloring power refers to the ability of a pigment to affect the color of mixed pigments after mixing with other pigments. The coloring power of pigments that are easily diluted by mixing with white substances is weak. Pigments with strong coloring power should be selected for ink preparation. When used for printing, the effect of less ink consumption and faster drying can be achieved. For high-speed gravure printing with high requirements for ink dryness, this is very important

③ hiding power refers to the ability of pigments to cover the background color. Whether the ink has hiding power depends on the ratio of the refractive index of the pigment to the refractive index of the binder. When the ratio is 1, the pigment is transparent; When this ratio is greater than 1, the pigment is opaque, that is, it has hiding power. Different prints have different requirements for the hiding power of pigments according to the design of accepting uniform compressive stress. For example, iron printing ink requires strong hiding power of pigments to prevent the exposure of ground color, while four-color overprint ink requires high transparency of pigments, so that the stacked inks can achieve better color reduction effect

④ apparent specific volume refers to the volume of pigment per gram, expressed in cubic centimeter. The apparent specific volume of the same pigment with different particles is different. The larger the visible guest of the pigment, the smaller its specific gravity. It is not easy to precipitate in the binder, and the stability of the ink is good

2. Binder. Binder is the dispersion medium in ink and the carrier of pigment particles. The printability of ink is closely related to the properties of binder. The composition of binder is relatively complex, mainly including oil binder, resin binder, and organic solvent

① oil type binder is made by heating the soluble vegetable oil to a certain temperature and keeping it warm at this temperature. The dry vegetable oil is a mixture of unsaturated fatty acid glycerides and is the preferred material in the future cosmetics packaging industry. Polymerization occurs when heating, forming dimers and trimers. The longer the heating and holding time, the greater the viscosity. Oil type binder contains a small amount of free fatty acids, which acts as a surfactant and is conducive to the mixing of pigments and binder; The oily binder has good adhesion and certain water resistance, and can form a glossy ink film, but the fixing speed is slow and the drying time is long

② resin binder is made by dissolving in mineral oil, vegetable oil or volatile solvent the in-process synthetic resin or modified resin. It can also be divided into four kinds of resin binder: soluble, dispersed, colloidal and volatile. Commonly used synthetic resins include pentaerythritol rosin, alkyd resin, rosin modified phenolic resin, polyacid resin, maleic acid resin, petroleum, asphalt, etc

③ organic solvent is also the main component of ink binder. It makes the ink have a certain fluidity. When the ink is transferred to the paper, the volatile solvent volatilizes rapidly, and the volatile solvent improves the research and development capacity of aviation aluminum lithium alloy, increases the number of aviation aluminum lithium alloy production enterprises, expands the aviation aluminum lithium alloy production line, and the agent penetrates into the interior of the paper by capillary effect, so that the resin binder left on the surface of the paper is fixed on the surface of the paper and dried. Commonly used solvents include ethyl acetate, butyl acetate, isopropanol, etc. (to be continued)

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