The principle of de-lighting of coatings and their application

The influence factors of gloss and glossthe determination of gloss and gloss
light is projected on the surface of an object and reflects light, and the ability of the surface to reflect light is called luster. The gloss of different surfaces is different, measuring the size of the surface's ability to reflect light, called gloss. Glossy is expressed as a percentage

. The higher the gloss on an object's surface, the stronger its ability to reflect light and the higher its brightness. The size of the gloss is determined by a photoelectrometer. Depending on the size of gloss, the coating can be divided into bright light, bright light, no light and so on.
gloss classification (with a reflective gloss classification of 60 degrees for example)
class
lightless
lightless
bright
bright gloss (%)
<10
15-60
>60
factors affecting gloss the roughness of the coating surface
the roughness of the surface of the object and the tightness of the surface of the object. When light hits an object's surface, part of it is absorbed, some is reflected and scattered, and some is refracted. The smaller the roughness of the surface, the more light is reflected and the greater the gloss. Conversely, if the surface of the object is uneven, the scattered light increases, resulting in a decrease in gloss. The situation is shown in Figure 1.film-forming process
the coating is applied to the surface of the object and cured into a film by the volatile solvent. The formation process of coating film is essential for the surface roughness and gloss of coating film. In the wet film stage, the evaporation rate of the solvent in the coating surface diffusion control, when the various parts of the solvent volatilization rate is not very different, it is possible to get a high gloss surface; In the dry film stage, the evaporation rate of the solvent is mainly controlled by the diffusion of the solvent in the coating body as a whole, and also affects the roughness of the coating surface. In addition, in the formation process of the coating film, with the volatile solvent, the coating film will become thinner and shrink, some suspended heavy particles in the coating will be rearranged on the coating surface, resulting in uneven coating surface.particle size and particle size distribution of pigments, fine materials
A high-gloss coating film can only be obtained when the diameter of the pigment particles is less than 0.3 m. The reason is that the pigment particles scattered in the coating in a certain thickness of the coating film, and after drying, only the top layer of pigment particles local upburst, particle diameter of less than 0.3 m pigment ions caused by the coating surface roughness will not exceed 0.1 m. When the average particle diameter of the pigment is between 3-5 m, a coating film with better light-dissipation effect can be obtained.
In addition to the above three factors can affect the gloss of the coating surface, pigment volume concentration (PVC), pigment dispersion and coating surface structure and surface reflection characteristics and other factors can also affect the gloss of the coating surface. Among them, with the increase of PVC of pigments, the gloss of the coating surface is first reduced, the limit volume concentration (CPVC) of pigments appears at a very small value, and then accompanied by the increase of PVC, gloss is also greater. When the pigment type and dosing are determined, the better the dispersion, the higher the gloss of the coating surface.
Lighting principle
combined with the coating surface gloss produced by the process and factors affecting gloss, light is the use of various means to destroy the smoothness of the coating film, increase the surface microscopic roughness of the coating film, reduce the reflection of light on the coating surface. It can be divided into physical and chemical de-lighting. Physical de-lighting is the addition of anti-lighting agent, so that the coating in the film-forming process, the surface produces uneven, increase the scattering of light and reduce reflection. Chemical de-lighting is obtained by introducing structures or substumps in coatings that absorb light, such as polypropylene things.
the method ofThe anti-light agent
(1) metal soap
metal soap is a kind of anti-lighting agent commonly used in the early days, mainly some metal stingrates, such as aluminum stingrate, zinc stingrate, calcium stingrate, magnesium stingrate, etc. The principle of de-lighting of metal soap is based on its insolubleness with the composition of the coating, it is suspended in the coating with very fine particles, and when the film is formed, it is distributed on the surface of the coating film, so that the surface of the coating film produces microscopic roughness, reducing the reflection of the surface light of the coating film and achieve the goal of de-lighting.
(2)
wax is an early application of a more widely used anti-light agent, it belongs to the organic suspended anti-light agent. After the coating construction is completed, with the evaporation of the solvent, the wax in the coating film is dissipated to a fine crystal suspended on the surface of the coating film, forming a layer of scattered light roughness surface to play a role in the lighting. Wax as an anti-light agent is characterized by simple use, can give the coating film a good feel and water resistance, moisture and heat resistance, anti-fouling. However, the wax layer formed on the surface of the coating film will also prevent the evaporation of solvents and oxygen infiltration, affecting the drying and coating of the coating film. The future development trend is to synthesize polymer wax with silicon dioxide to achieve the best light-eliminating effect.
(3) functional fine material
system pigments, such as diatom soil, kaolin soil, synthetic silica, etc. are specially used as a light-eliminating agent functional fine material, it belongs to the inorganic filler-type anti-light agent. When the coating film is dry, their tiny particles form a slightly rough surface on the coating surface, reducing the reflection of light to get a dim appearance. The anti-light effect of this kind of anti-light agent is restricted by many factors.
In the case of silicon dioxide, when it is used as an anti-light agent, the pore volume, average particle size and particle size distribution, dry film thickness and whether the particle surface has been treated, etc., will affect its light-eliminating effect.
coatings play an irreplaceable role in obtaining low gloss and anti-lighting agents. However, in the process of use, there are still many defects to be improved, such as the selection and use of anti-light agent conditions are more demanding, the price is high. Domestic anti-light agents containsubstances, coating film is easy to yellow, poor baking resistance. Production of good price-appropriate anti-lighting agent, is still a problem to be solved.anti-light resin
resin is an essential component of the coating, so it produces the anti-light resin, using it and other resins to act on the film to obtain a low gloss. The use of detergents can be avoided and coating costs can be reduced.
its structure:
(1) the use of anti-light resin in the function group and coating composition of the curing agent and the other resin curing temperature difference, resulting in successive curing, so that the coating surface produces uneven contraction, thereby destroying the smoothness of the coating surface, resulting in de-lighting.
(2) increases the surface pressure difference between the two resins, resulting in uneven coating film shrinkage to produce slight roughness.
(3) in the synthetic resin to introduce a poor solubility monosome, coating film so that these monosomes to promote the synthetic resin from the coating film, thereby increasing the microscopic roughness of the coating surface, reduce the gloss.
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