220.127.116.11 Structural properties of nano-TiO2 [23,34]
Nanometer TiO2 is composed of crystal elements and interface elements. The crystal elements consist of Ti and O atoms in the crystal grains. These atoms are strictly located at the lattice sites. The interface elements are composed of interfacial atoms between the crystal grains. In composition, these atoms are converted from the surface atoms of the ultrafine grains. The order atoms of the order atoms and ultrafine crystal grains inside the ultrafine crystal grains account for 50% each. Assuming that the average grain size of the nanocrystalline TiO2 lattice element is 6 nm and the average width of the interface is 2 nm, the interfacial area per unit volume of the nanocrystalline TiO2 crystal is estimated to be as high as 500 m2/cm3, and the number of interfaces per unit volume is 1019 pieces/cm3. . It can be seen that the nano-TiO2 crystal has a very strange surface structure. In this surface structure, the Ti atom lacks coordination of O atoms, so that the nanometer is in a state of severe oxygen deficiency, resulting in a large number of dangling bonds on the surface, resulting in high activity of the nano-surface. Optical properties, photochemical properties, and electrochemical properties of nano-TiO2 are examples of this high activity.
18.104.22.168 Improvement of Ink Properties by Nanometer TiO2 [5,23]
Nano TiO2 particle size is only about 1/10 of the ordinary titanium white particle size, that is, 1 ~ 100nm, has almost no scattering effect on visible light, has a strong ability to shield ultraviolet light and excellent transparency, it is also known as transparent titanium dioxide. It exhibits unique properties in optics, mechanics, electricity, catalysis, etc. As a new type of material, it has been widely used in cosmetics, food packaging materials, durable plastic films, wood moisture proof, lubricants, fine ceramics, catalysts, electronics , coatings and other fields. For example, when nano-TiO2 and mica pearlescent pigments are used together, as an effect pigment, a fascinating exquisite two-color effect can be produced. The mysterious color and unique optical performance of the effect pigment are very popular with ink manufacturers.
1. Nano-titanium dioxide as pigment improves ink performance
With nano titanium dioxide can make inks or coatings with goniochromatic effect. The floppy effect ink is the ink film observed from different angles. You can see different colors of the ink layer, which is also called the perspective flash effect. The ink is prepared by mixing nano-TiO2 with A1 powder, etc., and produces flop effect. The reason for this effect is generally believed to be that on the one hand, the nano-TiO2 has a transparent property that allows visible light to pass through; on the other hand, it covers the visible light to a certain extent. In this way, the transmitted light reflects the light reflected by the surface of the nano-TiO2 particles on the Al powder surface, and the continuous reflection of the natural light produces different visual effects. This ink is printed on the surface of substrates such as metals and plastics. Due to the flop effect, it will produce a rich variety of colors. It will look modern, stylish, and highly decorative. Therefore, nano-TiO2 has a large application market in the trademark printing ink, high-grade automotive coatings, special architectural coatings and other industries.
2. Nano TiO2 Produces Protective Substrates
Ultraviolet light is an important part of sunlight, and its energy accounts for about 6% of the total sunlight energy. More and more people are aware of the dangers of UV radiation, such as skin swelling, blisters, and strong penetration of skin cells. Ultraviolet light can degrade polymer chains in synthetic materials such as plastics, synthetic resins, and plexiglass, resulting in degradation, resulting in discoloration of the coating or ink layer. How to apply anti-aging effect on the printing ink layer or decorative film or to make it have its own anti-aging effect is a concern.
Nano TiO2, ZnO2, A12O3, SiO2, Fe2O3, etc., are all excellent anti-ultraviolet absorbers and can be used in organic coatings or inks to significantly improve the anti-aging properties of inks. Such inorganic nano-materials as nano-Al2O3 have good fluidity, if added to the ink can greatly improve the wear resistance of the ink film. Nano-TiO2 is a permanent UV absorber, which is added to the acrylic ink. A small amount of nano-TiO2 can significantly reduce the UV transmittance. If the content of nano-TiO2 is 0.5%, the transmittance of ultraviolet rays is reduced to less than 50%. When the content of nano-TiO2 is 5%, the transmittance of ultraviolet rays is reduced to less than 30%. This kind of coating has good ultraviolet protection function.
1.2.3 Nano-scale SiO2 Application in Ink
Nanoscale SiO2 is an amorphous white powder with unsaturated residual bonds and hydroxyl groups in different bonding states on its surface, and its molecular state is a three-dimensional chain structure.
In general, the force of hydrogen bonding between surfaces that are agglomerated with each other is not strong and can be easily separated by shear force. However, these hydrogen bonds quickly recover after the external shear force has been eliminated, so that their structures recombine rapidly. This time-dependent shear stress reduction reaction to the restitution of external forces is called thixotropy. The thixotropic reaction is the main factor in improving the performance of traditional inks with nano-SiO2.
Nano-SiO2 is an ultra-fine powder with a hydroxyl group on the surface. Its particle size is less than 100 nm, usually 20 to 60 nm. It has high chemical purity, good dispersibility, and a large specific surface area. In the chemical industry, it is also known as white gray black, which is currently the world's largest industrial production of a nano-powder material. Nano-SiO2 is an amorphous white powder and is a non-toxic, odorless, non-polluting inorganic non-metallic material. Nanometer SiO2 is a fine chemical product, which is conductive and has a good shielding effect against static electricity. It prevents electric signals from being disturbed by external static electricity. If it is added to ink, it can be made into conductive ink, such as large-capacity integrated circuits, modern contact type. Panel switches and so on.
At present, domestic inks generally have performance deficiencies such as suspension stability and low thixotropy, resulting in the need to import large quantities of high-grade ink each year. Nano-SiO2 can provide anti-caking, emulsification, fluidization, extinction, support, suspension, thickening, thixotropy and other functions.
1.2.4 General Nano Powder Material CaCO3
CaCO3 is a common inorganic filler widely used in paper and ink. CaCO3 with an average particle size of less than 100 nm is called nano-CaCO3. According to its particle size, there are different application objects.
Nano-CaCO3 can not only play a role in whitening, expansion, and cost reduction, but also has a role in ink reinforcement. There are many hydroxyl groups on the surface of nano-CaCO3, and it belongs to hydrophilic and oleophobic substances. At the same time, due to the size of the particle size, the specific surface energy is large, and it is easy to agglomerate, resulting in poor dispersion, and the direct application effect is not very good. Therefore, it is necessary to modify the surface of the nano-CaCO3, improve the lipophilicity of the powder, and prevent the reunion of the powder. Sex, improve powder dispersion. Surface modifiers for nano-CaCO3 include inorganic modifiers and organic modifiers. For example, condensed phosphoric acid and titanate are effective surface modifiers, which can improve the processing performance and physical mechanical properties of CaCO3 powders. The performance, through the formation of irreversible chemical bonds, can significantly improve the physical stability of CaCO3 powder, in the use of ink, has a good dispersion.
Nano-CaCO3 has different applications depending on its particle size. Nano-CaCO3 with a particle size of 80 to 100 nm is used for high-grade plastic products and common inks; nano-CaCO3 with a particle size of 15 to 30 nm is used for high-grade inks, high-grade rubber products, and car paints.
2. Status of China's Nano Packaging Printing Materials
2.1 nanometer green packaging
The so-called "nano green packaging" is the application of nanotechnology, using nano-composite (packaging) materials, so that packaging has a super-functional or singular characteristics of a kind of packaging summary. The so-called nano packaging material is nano-composite packaging material with nanometer-scale structural unit, which is made of particles or crystals with a disperse phase size of 1 to 100 nm combined with other packaging materials or added. Nanostructures may become the basis for technological improvements. Once the critical dimensions of the material can be controlled, the characteristics of the new material and the functionality of the device can be enhanced, even beyond what we believe may be achieved.
Since the nano-sized grains are finer than those of the conventional materials, the number of atoms on the grain boundary is larger than the number of atoms inside the grains, forming a high-concentration grain boundary, thereby imparting properties of many different conventional materials for nanomaterials, such as high strength. , High hardness, high resistivity, low thermal conductivity, low elastic modulus, low density, etc. These excellent properties determine its wide application prospects in the future.
Green packaging aims to change people's traditional ideas, make full use of the comprehensive characteristics of packaging materials, pay attention to ecological balance, and make it greatly beneficial to the environment and human society. Nano packaging is the use of nanotechnology to change the traditional packaging materials and packaging technology, the most effective use of atoms and molecules, giving the material high-new features, focusing on saving resources, is greatly beneficial to human society.
2.2 Development Trends of Nano Packaging Printing
The national 973-nanometer chief scientist said: "Nano-plastics will be one of the most promising nano-technologies for industrialization in China." In the field of packaging and printing: nano inks, nano-pigments, nano-papers, nano-films, food-based nanocomposites Materials (PNMC), nano-luminescent materials, nano-antibacterial packaging, nano-adhesives, nano-anti-counterfeiting printing, nano-military protective packaging, nano-green packaging, nano-lithographic printing technology, nano-magnetic printing, etc. have achieved breakthroughs, and some have been preliminary The assessment methods of nanomaterials and nanostructures are basically complete, reaching the advanced level of the international 90s in the last century.
At present, the modification of nano-packaging and printing materials in China is closer to the application trend, and the application of nano-technology is combined with the actual technology system, so that it can be quickly applied. The following examples illustrate the development of nano-ink, nano-pigment, nano-paper, and nano-film. situation.
2.2.1 Nano Ink
Currently, nano inks are still largely in the pilot stage and are still a long way from being widely used in the ink manufacturing and printing industries. However, some experts predict that nano inks will open up a vast new world for the ink industry. And printing technology has brought about a new revolution.
Nano inks can also be used for luminous graphic printing. Some nanoparticles themselves have luminescent groups that can emit light themselves. The printed matter printed with the ink added with such particles does not require the irradiation of an external light source and can be recognized by the human eye by its own light emission. If this type of ink is used for outdoor large-scale advertising printing or night-time printing of graphic prints, external light sources are no longer needed, which not only saves energy, but also greatly facilitates users.
2.2.2 Nano UV Varnish [14,17]
Paper packaging products, surface gloss processing technology is gradually developed to the direction of UV curing UV coating, nano-UV polishing oil to color corrugated box with resistance to friction, scratch resistance, moisture, high gloss and other properties. Nano-UV coating oil is mainly composed of nano-oligomer (such as epoxy-acrylic acid, etc.), reactive diluent, photoinitiator and other additives. There are many methods for UV coating, such as coating and printing, and roller coating.
It can be expected that when the ever-improving nano-high-tech is widely used in corrugated box printing, the printing of corrugated boxes will have higher resolution and better results. The manufacture of corrugated boxes is inseparable from the packaging and printing. Nanoparticles play an increasingly important role in the packaging and printing industry.
2.2.3 Nanopigment [17, 30]
Recently, the nano-scale transparent iron oxide pigments that have been recently rated as national key new products by the Ministry of Science and Technology have been successfully developed. It will have an important impact on the upgrading of traditional pigments, mainly used in nano-ink, nano-water coating materials. The typical acicular particle size of the material, the long axis is 45 nanometers, the short axis is 6 to 7 nanometers, has a good dispersion, crystallinity and weather resistance, high brightness and strong coloring characteristics. Its successful development has great significance for the replacement of traditional pigments in our country. It can be used especially for the production of nano-inks, which will greatly improve the quality of inks.
Nano-metal particles can absorb all light waves and make themselves black, while also scattering light. Adding nano-metal particles to the black ink increases the purity and density of the black ink.
Because nanoparticles have good surface wettability, they are adsorbed on the surface of the pigment particles in the ink, which can greatly improve the ink's lipophilicity and wettability, and can ensure the stability of the entire ink dispersion system. If high-tech is used to make various components in ink, such as resins, pigments, fillers, etc., into nanoscale raw materials, better dispersion, suspension and stability can be achieved.
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