Problems in the application and development of the

Problems in the application and development of pearlescent pigments

with the rapid development, pearlescent pigments have been more and more widely used in the packaging, printing and publishing industries, from cosmetics, cigarette cases, alcohol, gift packaging, to business cards, greeting cards, calendars, book covers, to painting and newspaper printing, textile printing, pearlescent pigments are everywhere. In particular, the market demand for pearlescent film used in food packaging is increasing day by day. For example, in ice cream, soft drinks, biscuits, candy, napkin packaging and other fields, the use of pearlescent film gives consumers a pleasing feeling

the promotion of pearlescent pigments encountered obstacles

although there is a great demand for pearlescent pigments in various fields, pearlescent pigments still encounter certain resistance in terms of market promotion

first, the production process of several kinds of pearlescent pigments (mica titanium pearlescent pigments) sold on the market at present is very complex, and the requirements for process accuracy and equipment are high, which makes the manufacturing cost remain high, limiting the wide application of such pigments. For example, many paint manufacturers and ink manufacturers have been very interested in this kind of pigment, but they are deterred due to its high price in practical application. Therefore, reducing production costs and realizing large-scale production is a key step to expand the market

second, the application research of pearlescent pigments is still in a very weak link. At present, the research and development of the application technology of pearlescent pigments in coatings, plastics, printing inks, artificial leather, building materials, cosmetics, paper, packaging materials, textile printing and dyeing and other aspects is just beginning. Because most people still know little about the characteristics of this new decorative pigment, coupled with the lagging application technology and low technical level, The poor decorative effect restricts the application and promotion of pearlescent pigments. So that many products that could have been decorated with this kind of pigment to enhance the added value of products lose excellent competitive opportunities. However, people have never stopped pursuing pearlescent pigments, because people clearly understand a truth: a breakthrough in application technology will often promote the upgrading of products in an industry, and will bring inestimable economic benefits to an industry

third, the pearlescent pigment production process seems simple, but the actual production technology is complex, involving many disciplines. Therefore, countries all over the world have strictly kept this technology confidential and blocked. In order to keep business secrets, many companies have never announced their annual sales performance so far. Compared with some industrialized countries, the scientific research, production and application of mica titanium pearlescent pigments in China are still in the primary stage of development. Regardless of product quality, variety and application technology, they are at a low level. Many key technical issues have not made breakthrough progress, so that the products of German and Japanese pigment companies are still unified

factors affecting pearlescent gloss

although pearlescent pigments encounter various obstacles in application, the industry still calls for the advantages of pearlescent pigments to be reflected in all links of printing

let's first analyze some situations of mica titanium pearlescent pigment in use: pearlescent pigment is a kind of gloss pigment, and its flashing effect is passive luminescence, that is to say, it can show flashing effect only under light receiving conditions. The pearlescent effect of pearlescent ink prepared with it mainly depends on the pearlescent gloss of the pigment, and the gloss depends on the content and shape of the pearlescent pigment in the ink

content of pearlescent pigments

under the condition of ensuring that the pigments in the ink are evenly dispersed, someone has studied the influence of the amount of pearlescent pigments in the textile silk printing ink on the pearlescent gloss. The method is to change the amount of pearlescent pigment in the same ink formula, and evaluate the pearlescent gloss effect by visual method. In the study, the proportion of pearlescent pigment in the ink is continuously increased. When the amount of pigment is 5%, the gloss effect is poor; When used, the refueling speed will be very slow; When the amount reaches 12%, the pearlescent effect is better; When the dosage is 15%, the pearlescent effect is the best and the fastness is also good; When the amount of pigment is increased to 17%, the pearlescent effect is similar to that when the amount of pigment is 15%; If you continue to increase the dosage, the pearlescent effect will no longer increase. This shows a truth. Blindly seeking to increase the amount of pearlescent pigment can not significantly improve the pearlescent effect. When the amount of pigment reaches a certain value, the pearlescent effect will no longer play its role. The result of blindly adding pigment dosage: first, the cost of ink increases; The second is to reduce the printing fastness of the ink. In order to ensure the printing adaptability of ink, it is suggested that the amount of pearlescent pigment should be controlled at 12% - 15%

shape of pearlescent pigment

in addition to the amount of pearlescent pigment, the pearlescent effect is related to the shape of the pigment. Flat crystal should be the basic structural form of pearlescent pigment. Only such a form can strongly reflect pearlescent luster like a lens, and the diameter thickness ratio of flat crystal is best around 200, and the substances that meet this condition are very rare. At present, pearlescent pigments, which are produced most and used most widely in the world, are micro powders formed by coating one or more layers of titanium or other metal oxides on the surface of natural mica flakes through special chemical processes. So measuring the quality of pearlescent ink depends on whether flake pigments are used in ink preparation

how to reduce the amount of pearlescent pigment

if the amount of pearlescent pigment is reduced, the ink cost will be lower, and people will be more motivated to adopt pearlescent ink, but is there a good way to reduce the amount of pearlescent pigment in the ink? The answer is yes. To reduce the amount of pearlescent pigments, in fact, the main thing is to make the flake pearlescent pigments achieve parallel orientation. If the flake pearlescent pigments can be evenly and parallel arranged on the surface of the ink layer, even if there are no pigment particles in the middle or bottom layer of the ink layer, the pearlescent effect will not be affected, because the light is intercepted by the flake particles of the upper surface layer, and the pigment particles of the middle and bottom layers are not affected by light, so they cannot reflect or refract light, which has little impact on the pearlescent gloss. The following is to realize the uniform arrangement of flake pearlescent pigments on the surface of the ink layer from all links, and finally reduce the amount of pearlescent pigments

preparation process of pearlescent ink

the quality of pearlescent pigment ink largely depends on the wettability and dispersion of the resin carrier to the flake pigment and the degree of parallel orientation in the ink film. The former is determined by the structure and characteristics of the selected resin itself, while the latter depends on the ink design formula and the correct implementation of the printing process. Resin carrier is the foundation, formula design and printing technology are the key. The ideal ink should have a low solid content. Therefore, the amount of pearlescent pigment should not be too much, because too many pigments are easy to be dense, will be in an irregular state, and it is very easy to be poorly arranged. During the drying process of the printed ink layer, the volume of the ink layer should have a large shrinkage force. Using the shrinkage force and the self gravity of the flake powder, the flake mica titanium pearlescent pigment is compressed to make it parallel, which is different from the proportion of the color paste, paint, ink Viscosity and many other factors are closely related. The more the flake pigments can be arranged 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

selection of pearlescent pigment flake diameter

the selection of flake pigment should grasp the relationship between flake size and flash effect: the larger the flake diameter is, the greater the distance between flash sources (spacing between flakes) is, and the more dispersed the flash effect is. This is because the larger the film diameter, the more opportunities for multiple reflection and refraction of light on the surface, so the flash intensity is stronger; If the film diameter is small, the flash source spacing will be small, the flash effect will be concentrated, and the repeated reflection and refraction opportunities will be less, and the flash intensity will become weak. In addition to the relationship between the size of the chip and light, it is also related to the state of the pigment in the ink. Generally, the smaller the chip size is, the easier it is to condense and settle in the binder; The smaller the aspect ratio of particles, the easier it is to be suspended in the binder

when mixing ink, thickener can be added to prevent sedimentation or pre wetting the pigment, and then dispersed in the binder to avoid condensation or sedimentation. Because mica titanium pearlescent pigment has good dispersion ability, it creates superior conditions for ink manufacturing. In low viscosity ink media, good dispersion effect can be obtained only by low-speed stirring. At the same time, it can avoid using other equipment such as three roller machine, high-speed mixer or ball mill in ink manufacturing, because it will cause mica titanium pearlescent pigment particles to be broken and lose luster. Even if the above equipment must be used to disperse in the production, it should also be arranged in the final stage of the ink production process, and the mica pearlescent pigment should be added and mixed evenly

influence of printing process on pearlescent effect

pearlescent ink is suitable for various printing methods, but various printing processes will have a certain impact on the quality of printed matter. In order to ensure the printing quality, the printing process should match the performance of pearlescent ink. Therefore, it is necessary to put forward some requirements for the printing process to meet the performance of printing ink. For example, in the pearlescent offset printing process, the printing speed is fast, and the ink viscosity is required to be small. In order to produce pearlescent effect, when the pearlescent pigment particle size is large, the ink roller transmission effect is not very good, the speed is fast, and the friction between the ink rollers is too large, so it is easy to grind the flake pigment, and the pearlescent effect cannot be displayed. If the vehicle speed is too slow, it will cause stacking roller failure; In order to pursue the flash effect, when the pearl pigment particle size is large, in order to increase the ink fluidity, make the printing ink thinner, dry too slowly, affect the printing speed, and be forced to stop, which is a thorny problem in offset printing

in the intaglio printing process with pearlescent ink, although the surface of printed matter has enough gloss and a large number of pearlescent pigments, it is difficult to show the glittering effect of pearlescent ink. This is because in the printing plate of the engraving cylinder, only the smaller pearlescent powder with weak reflective ability will be transferred to the substrate, while the larger flake particles will still remain in the groove of the printing plate, and the amount of pearlescent pigment transferred to the paper is insufficient, so it is difficult to produce a flashing effect

the silk 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 particle size of the pigment in the pearlescent ink is large, it has multi-faceted reflection performance, which will form a very uniform equal intensity diffusion and produce good pearlescent luster

but special attention should be paid to when selecting the mesh number of silk. The pore diameter of silk is related to the particle size of pearlescent pigment used in printing ink. In order to make the ink can be used after being broken, and it can smoothly pass through the printing plate and miss printing on the substrate without blocking on the plate, it is generally required that the pore diameter of the wire should be 1.5 ~ 2.5 times larger than the maximum particle of the pigment, but the foreign trade order is negative, and the larger the hole is, the better, because the wire with too low mesh will affect the accuracy of the graphics, and the printed image will be too rough, so the mesh number should be appropriate. The manufacturer of pearlescent ink shall indicate the particle size of pearlescent pigment in the ink product package for the reference of users when selecting. Generally, it is concluded from the experiment that the particle size is 20 ~ 180 μ The ink prepared with m pearlescent pigment should be 40 ~ 60 mesh/inch yarn. Enterprises pay more attention to the domestic market, and can print some prints with low precision. If the pearlescent particle size is 5 ~ 100 μ The ink made of M pigment can be printed with 60 ~ 100 mesh/inch yarn