Application of nanotechnology in ink coating
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First, the concept and application of nano
The term "nano" has received much attention, but one important point is that we should not stick to the size of nanometers, but only emphasize that nanotechnology is below 100nm, but the emphasis is on the benefits of size and detail. The improvement in pigment properties by nanometers is a predictable benefit.
There are quite a lot of nano products, and they are spread all over the industry. In 2001, the global nano-industry has about 26.5 billion US dollars. Most of its applications are powder structures, which are limited by application. Therefore, how to break through this? The application of technology to disperse the powder to the fineness we need will be the focus of the current stage. From the perspective of the range of nano-specialized products, the proportion of ink coatings in the overall output value is quite large, and each product is also related to each other. Therefore, nano-ink coatings will be a very important one in nano-specialized products. field. Nano specialization unit The process is mainly dealing with powders. The processes such as grinding, manufacturing, and processing to finished products can all show the characteristics of the products. Examples include inkjet inks, coating plastics, and pharmaceutical products.
Second, nano-dispersion technology
There are two main problems in the nano-dispersion technology. The first is to break up the large particles and depolymerize them to improve the original characteristics. The second is to disperse the small nano-powders to achieve mass production, cheap and small application. effective. In the nano-dispersion of pigments, the dispersion of powder is the most difficult point, and there are technical bottlenecks that must be broken. For example, the ball milling of conventional ball milling can be quite difficult to 200 nm. To achieve smaller particles, it is necessary to rely on the grinding and dispersion technology. The particles of the grinding ball should be fine, and the energy transfer should be sufficient to increase the collision frequency and obtain smaller particles. The smaller the particles, the stronger the aggregation effect. Therefore, we must use the interface point of view to stabilize the particles, and the application formula needs to be dispersed. Stabilizer, formulated into products such as ink, paint, etc.
The traditional bead mill is a high-speed collision with beads, but the separation net will block the beads inside, and the technique of separating the net can not be overcome, because the smallest bead is about 0.05mm, the grinding ball is not small enough to divide the particles. Very thin, it limits the development of technology, and because of its expensive equipment, difficult maintenance, and can not meet the needs of more detailed, so must develop new equipment. And decentralized equipment must pay attention to:
1. The internal design of the grinding tank.
2. The grinding groove drives the material of the shaft.
3. Type of grinding media.
4. Separation mechanism and pore size of dispersion and grinding media.
5. Mode of operation.
The nanobead mill dispersion system adopts a material with wear resistance and high heat transfer effect to manufacture a tank body, a low-cost grinding medium and a high energy density stirring shaft, a blade and a tank body. The principle is to put a very fine grinding ball into a single stirring tank and transfer it into the stirring with a high blade speed of mechanical force >15~30m/s. The dispersion effect created by microbead grinding has two main points:
(1) The increase of collision point: the collision point and the diameter are closely related, and the grinding medium with small diameter will increase the collision point. Taking the grinding medium of 0.05 mm as an example, the collision point is 1000 times more than the grinding medium of 0.5 mm.
(2) The increase of the effective shear force surface: the smaller the beads, the more the number, the more the shear force will increase.
However, it must be noted that although the grinding medium is small in effect on the bead mill, if the grinding medium is not far from the volume of the powder, the powder cannot be dispersed. In general, the size of the powder is 1/3 of the grinding media –1/10 is most appropriate, and at the same time, attention should be paid to the hardness, pH, color deviation, cost and pollution of the grinding media. It is also worth noting that the nano-powder interface stabilization technique, when the particles become smaller, the distance between the particles is also reduced, and the stability is also reduced. Therefore, the amount of the dispersant must also be increased.
In the selection criteria of the dispersant, it should be from the application point of view. For example, in the application of inkjet ink, the HLB value should be considered to be similar to the HLB value of the pigment requirement in terms of the need for grinding and dispersion; and good wettability and dispersion characteristics and low foaming property of the polishing should be required. In the ink function requirements, storage and additive stability, ink stability in the ink cartridge and anti-blocking properties should be considered. The ink should be sprayed on the paper to have good water resistance and rub resistance and anti-solvent. And heat resistance and so on.
Third, pigment coating ink nanotechnology application
In the actual verification of pigment nanocrystallization, the appearance color of nano-sized pigments is far darker than that of sub-micron pigments. The main reason is that the pigment particles are large, and the light will break through the light, so the light scatters light, and a small part The light penetrates the past. The nanopigment has a small particle size, a weak light scattering, a small spectral absorption area, and a light reflectance of less than 1%, so that the appearance of the color is significantly deeper than that of the submicron pigment.
The application range of nano-sized pigments is quite extensive. Examples of life such as inkjet ink, paint, ink, photoelectric display, etc., in the manufacturing process of the product, adding a small proportion of nano pigments such as 3%-5% can improve the ink. Problems such as shielding rate, saturation, optical rotation resistance, and water resistance.