1. Principle
When the water-based resin is coated on the surface of the substrate, a part of the wetting agent is at the bottom of the coating, which is in contact with the surface to be wetted, the lipophilic segment is adsorbed on the solid surface, and the hydrophilic group extends outward to the water. The contact between the water and the substrate becomes the contact between the water and the hydrophilic group of the wetting agent, forming a sandwich structure with the wetting agent as the intermediate layer. Make it easier to spread the water phase, so as to achieve the purpose of wetting. Another part of the water-based wetting agent exists on the surface of the liquid, its hydrophilic group extends to the liquid water, and the hydrophobic group is exposed to the air to form a monomolecular layer, which reduces the surface tension of the coating and promotes better wetting of the coating. substrate, so as to achieve the purpose of wetting.
2. Some experience in the use of water-based wetting agents
In actual production, when considering the wetting ability of resin, not only the size of its static surface tension, but also the size of dynamic surface tension needs to be considered, because in the process of coating the resin, under the action of stress, at this time The lower the dynamic surface tension, the better the wetting. At this time, the faster the wetting agent forms a monomolecular layer on the surface of the coating, that is, the faster the formation of an oriented molecular layer, the more conducive to wetting. The fluorine-containing wetting agent mainly reduces the static surface tension, and the silicone-based wetting agent can reduce the dynamic surface tension very well. Therefore, in the process of practical application, it is very important to choose a suitable wetting agent according to the actual situation. important
3. The role of water-based dispersants
The function of water-based dispersants is to use wetting and dispersing agents to reduce the time and energy required to complete the dispersion process, stabilize the dispersed pigment dispersion, modify the surface properties of pigment particles, and adjust the mobility of pigment particles. Specifically reflected in the following aspects:
1. Improve the gloss and increase the leveling effect. The gloss actually mainly depends on the scattering of light on the surface of the coating (that is, a certain level of flatness. Of course, it is necessary to determine whether it is flat enough with a testing instrument, not only the number and shape of the primary particles, but also their combination. method), when the particle size is less than 1/2 of the incident light (this value is uncertain), it will appear as refracted light, and the gloss will not increase. Similarly, the covering power that relies on scattering to provide the main covering power will not increase (except Carbon black mainly absorbs light, forget about organic pigments). Note: The incident light refers to the range of visible light and the leveling is not good; but pay attention to the reduction of the number of primary particles, which reduces the structural viscosity, but the increase of the specific surface will reduce the number of free resins. Whether there is a balance point is not good. But in general, the leveling of powder coatings is not as fine as possible.
2. Prevent floating color from blooming.
3. Improve the tinting strength Note that the tinting strength is not as high as possible in the automatic toning system.
4. Reduce viscosity and increase pigment loading.
5. Reducing flocculation is like this, but the finer the particle, the higher the surface energy, and
the dispersant with higher adsorption strength is required, but the dispersant with too high adsorption strength may cause adverse effects on the performance of the coating film.
6. The reason for increasing the storage stability is similar to the above. Once the stability of the dispersant is not enough, the storage stability will become worse.
7. Increase color development, increase color saturation, increase transparency (organic pigments) or hiding power (inorganic pigments).
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