With rapid development, pearlescent pigments have been used more and more widely in the packaging, printing, and publishing industries, from cosmetics, cigarette cases, alcohol, gift packaging, to business cards, greeting cards, calendars, cover books, and graphic printing, textiles Printing, pearlescent pigments are everywhere. Especially the pearl film used in food packaging, its market demand is increasing day by day, such as in the ice cream, soft drinks, biscuits, candy, napkins, packaging and other fields, the use of pearlescent film to give consumers a pleasing sensation.
Pearlescent pigments promote resistance
Although the demand for pearlescent pigments in various fields is very large, pearlescent pigments still encounter certain resistance in marketing.
First, the production process of several types of pearlescent pigments (titanium series pearlescent pigments) currently sold on the market is very complicated, the process precision and equipment requirements are relatively high, and the manufacturing cost remains high, which limits the wide application of such pigments. For example, many paint shops and ink manufacturers have been very interested in this kind of pigment, but they have been deterred from their high prices in practical applications. Therefore, reducing production costs and realizing large-scale production are very crucial steps in expanding the market.
Second, the application of pearlescent pigments is still in a very weak link. The current research and development of pearlescent pigments in coatings, plastics, printing inks, artificial leather, construction materials, cosmetics, paper, packaging materials, textile printing and dyeing, etc. Just started, because most people know little about the characteristics of the new decorative pigments, coupled with lagging application technology, low technical level, poor decoration, restricting the application and promotion of pearlescent pigments. Many of the products that could have been decorated with this kind of pigment to enhance the added value of the product have lost an excellent opportunity for competition. However, for the pursuit of pearlescent pigments, people have never stopped, because people are clearly aware of the truth: an application of technology breakthroughs will often promote the upgrading of an industry's products, will bring an incalculable economic benefits to an industry.
Third, the pearlescent pigment production process seems simple, but the actual production technology is complex, involving many disciplines. Therefore, all countries in the world have kept the technology strictly confidential and blocked. To keep trade secrets, many companies have never disclosed their annual sales performance. Compared with some industrially developed countries, the research, production and application of mica titanium pearlescent pigments in China are still in the primary development stage. No matter whether the product quality, variety, or application technology are at a relatively low level, many key technical problems have not yet been achieved. Breakthrough progress made the products of German and Japanese paint companies still dominate the world.
Factors affecting pearl luster
Although pearlescent pigments encounter various resistances in application, the industry still calls for the advantages of pearlescent pigments to be reflected in all aspects of printing.
Let us first analyze the use of mica titanium pearlescent pigments. Pearlescent pigment is a glossy pigment. Its glittering effect is passive luminescence, which means that it must be exposed to light under the light conditions. It is formulated into a pearlescent ink, and its pearlescent effect mainly depends on the pearl luster of the pigment, which in turn depends on the content and shape of the pearlescent pigment in the ink.
Pearlescent pigment content
While ensuring that the pigments in the ink are uniformly dispersed, some people have studied the effect of the amount of pearlescent pigment in the textile screen printing ink on pearl luster. The method is to change the amount of pearlescent pigment in the ink in the same ink formulation, and evaluate the pearl gloss effect by visual inspection. The proportion of the pearlescent pigment in the ink is continuously increased in the study. When the amount of pigment is 5%, the gloss is The effect is poor; when the amount is up to 12%, the pearlescent effect is better; when the amount is 15%, the pearlescent effect is the best, and the fastness is also good; when the amount of pigment is further increased to 17%, the pearlescent effect and amount is 15% Similar; if you continue to increase the amount, the pearlescent effect no longer increases. This shows that one reason, blindly seeking to increase the amount of pearlescent pigments, can not significantly improve the effect of pearlescent, when the amount of pigment reaches a certain value, the pearlescent effect will no longer play its role. The result of blindly adding additional amounts of pigments is that the cost of the ink is increased. Second, the printing fastness of the ink is reduced. In order to ensure the ink's printing adaptability, it was suggested that the amount of pearlescent pigment should be controlled at 12% to 15%.
Pearlescent pigment shape
In addition to the amount of pearlescent pigments, the pearlescent effect is related to the shape of the pigments. The flat flaky crystals should be the basic structural form of the pearlescent pigments. Only in this way can the pearlescent luster be reflected as strongly as the lens, and the diameter of the platy crystals The thickness ratio is preferably around 200, and the substances that satisfy this condition are very rare. At present, the most widely used and widely used pearlescent pigments in the world are natural micro mica flakes as the core, and they are coated with one or more layers of titanium or other metal oxides through special chemical processes. Therefore, to measure the quality of pearl ink, it depends on whether the use of flake pigment ink preparation.
How to reduce the amount of pearlescent pigments
If the amount of pearlescent pigment is used less, the cost of the ink will be lower, and the power to use pearlescent ink will be greater, but is there a good way to lower the amount of pearlescent pigment in the ink? The answer is yes. To reduce the amount of pearlescent pigment, in fact, mainly to make the flaky pearlescent pigments to parallel orientation, if the flaky pearlescent pigment can be evenly arranged on the surface of the ink layer, even if there is no pigment particles in the middle layer or the bottom layer of the ink layer, it will not affect the pearlescent effect. Because the light is intercepted by flake particles on the surface layer, the pigment particles in the middle and bottom layers are not affected by light, and therefore they cannot reflect or refract light, which has little effect on pearl luster. The following will be achieved from all aspects of flaky pearlescent pigments in the ink surface evenly arranged, eventually reducing the amount of pearlescent pigments.
Pearl ink preparation process
The quality of the pearlescent pigment ink depends to a large extent on the wetting and dispersion of the flake pigment by the resin carrier and the degree of parallel orientation in the ink film. The former is determined by the structure and properties of the selected resin itself, and the latter depends on the ink design recipe and the correct implementation of the printing process. The resin carrier is the basis, and the recipe design and printing process are the key.
The ideal ink should have a low solid content. For this reason, the amount of pearlescent pigment used should not be too much, because the pigments are too apt to be dense, they may be irregular, and they are easily misaligned, and the ink is dried during the drying of the printed ink layer. The layer volume should have a large shrinkage force. Using the shrinkage force and the self-gravity effect of the flake particles, the mica titanium pearlescent pigment is compressed so that it tends to be parallel. This corresponds to the specific gravity and viscosity of the color paste, coating, and ink. And many other factors are closely related. The more the flake pigments are aligned parallel to the substrate, the better the pearlescent effect of the pigments. Adding a certain amount of polyethylene wax dispersion to the ink can improve its orientation performance.
Pearlescent pigment film diameter selection
For the selection of flake pigments, the relationship between the flake size and the flicker effect should be well understood: The larger the flake diameter, the greater the distance between the flicker sources (the distance between the flake and the flake) and the more scattered the flicker effect. This is because the larger the film diameter, the more chances are for multiple reflections and refractions of light on the surface, so the flash intensity will be strong; if the film diameter is small, the flash source spacing will be small, the flash effect will be concentrated, and the repetitive reflection and refraction will be concentrated. With less chance, the flash intensity will weaken. In addition to the relationship between the size of the film and the light, it is also related to the state of the pigment in the ink. Generally, the smaller the film diameter is, the easier it is to agglomerate, and it is easier to settle in the link material; the smaller the aspect ratio of the particles, the easier it is in the link material. Suspended.
When inks are formulated, thickeners can be added to prevent settling or pre-wetting of the pigments, which can then be dispersed in the binder to avoid coagulation or settling. Because of the good dispersion ability of titanium pearlescent pigments, the mica titanium pearlescent pigments create excellent conditions for the manufacture of ink. In low viscosity ink media, only low-speed stirring can be used to obtain good dispersion effects. At the same time, the use of three-roller machines, high-speed mixers, or ball mills in the manufacture of other inks can be avoided because it will cause the mica titanium pearlescent pigment particles to be shattered and lose luster. Even if the above equipment must be used for dispersion in production, it should be arranged in the final stage of the ink production process, and the mica pearl pigment can be added by mixing.
Effect of Printing Process on Pearlescent Effect
Pearlescent ink is suitable for all kinds of printing methods, but various printing processes will have a certain influence on the quality of printed matter. In order to ensure the printing quality, the printing process should match the performance of pearlescent ink. To do this, some requirements on the printing process are required to satisfy the properties of the printing ink. Such as pearlescent offset printing process, the printing speed is faster, requires ink viscosity is small, in order to produce pearlescent effect, the use of pearlescent pigment particle size is larger, the ink roller transfer effect is not very good, fast, friction between the roller is too large, It is easy to grind the flake pigments and the pearlescent effect cannot be displayed. If the speed is too slow, it will produce stack roller failure; in order to pursue the flash effect, when the pearlescent pigment is selected to have a large particle size, in order to increase the ink fluidity, the printing ink becomes thinner and dries too slowly, which affects the printing speed and is forced to stop. This is a thorny issue in offset printing.
In the pearlescent ink gravure printing process, although the print surface has sufficient luster and a large amount of pearlescent pigments, it is difficult to exhibit a pearlescent glitter effect. This is due to the fact that in the printing plate of the engraving cylinder, only finer, less reflective pearl powder is transferred to the substrate, while the larger flaky particles remain in the groove of the printing plate. The pearlescent pigment is transferred to If there is not enough paper on the surface, it will be difficult to produce a flash effect.
The screen printing process requirements of Pearlescent ink are also different from other ink printing. In order to match the printing process with the printing ink performance, when the pigment particle size of the pearlescent ink is large, it will have a multi-faceted reflection property, and will form a very uniform and strong diffusion, resulting in a good pearl luster.
