How to choose matting agent
Choosing the right matting agent depends on many factors. Such as dry film properties, requires transparency, paint film smooth, scratch resistance and weather resistance. Another example is the application characteristics, such as viscosity, sinking resistance, redispersion degree and gloss consistency. In the paint processing, anti-excessive grinding, decentralized is good or bad, but also take seriously.
First, the performance requirements of different matting agent choice
1, the ideal extinction efficiency
1) Select the larger average particle size of the product. The greater the average particle size of the matting agent, the higher the extinction efficiency. However, if the particles are too large, the surface of the paint film will be too rough, affecting the feel and appearance.
2) Select products with high porosity (pore volume). The greater the porosity, the higher the weight per unit weight of powder, the better the extinction performance.
2, the ideal of transparency
1) Choose a product with a smaller average particle size. In the case of the same amount added in the formula, the smaller the average particle size of the matting agent, the better the transparency of the paint film, but the corresponding extinction efficiency will also be reduced. It should be pointed out that the content of the fine powder is too high and the transparency will be negative influences.
2) Surface treatment. As matting agent surface treatment of different types, it will affect the wetting and dispersion of the binder, which will affect the transparency of the film. Therefore, it is necessary to adjust the matte and base material matching, if necessary, by adding wetting and dispersing aids to improve. At the same time also need to pay attention to whether there are other factors that lead to deterioration of the transparency of the film, such as less compatible additives or poor pigments.
3, the ideal smooth effect
1) Normally matte finish with organic finish will feel better than untreated.
2) particle size and particle size distribution. In general, the finer particles matting agent, the more delicate feel in the paint film. The narrower particle size distribution, the smaller the larger particles, feel better to some extent.
4, the ideal suspension
In general, matting agent with the paint storage time, will be layered and precipitation to some extent, the surface of the organic anti-settling performance of the product will be better. Therefore, formula design, should consider how to avoid the problem of precipitation of matting powder, add appropriate anti-sediment additives.
5, the ideal surface scratch, wear resistance
Matting agent surface organic treatment, the film surface scratch resistance and wear resistance have a certain improvement.
Second, different systems of paint on matting agent choice
1, solvent-based paint
1) In clear varnishes, the addition of matting agents must not cause hard deposits during storage or affect the clarity of the final film. Therefore, as mentioned above, organic-treated matting agents are the best choice. Matting agents treated with organic substances can also bring other benefits such as smooth surface and increased scratch resistance.
2) In the paint system, the precipitation of the matting agent is not a problem due to the addition of the pigment, the proportion of the pigment being much larger than that of the matting agent. For cost savings, there is no choice but to use matting agent without surface treatment, but sometimes, in order to improve the feel of the paint film and scratch resistance, you can also use organic matting agent.
In the solvent-based system, the matting agent particle size according to the coating system of dry film thickness and the desired surface properties of the paint film, relatively thin matting agent paint film surface will be relatively smooth, feel better, but its extinction efficiency is not as good Coarser matting agent. The closed-hole wood lacquer, feel higher, so we should use a thinner matting agent.
The amount of matting agent added depends on the resin system, the solids content, the dry film thickness, the type of matting agent, the drying method and the desired gloss. The choice of the best matting agent and calculation of the required amount of paint system to be drawn in the approximate actual use of the extinction curve.
2, water-based paint system
With the increasingly prominent environmental issues, the traditional solvent-based coatings are gradually being replaced by some environmentally friendly coatings, water-based coatings, especially for the development of water-based coatings for wood, the demand for silica matting agent is also increasing . Traditional matting agent can extinction water-based paint, but there are many drawbacks. Water-based paint system viscosity is low, so the matting agent is required to its system as little as possible, that is, silica oil absorption as small as possible, but also must be conducive to the dispersion in the aqueous system.
3, UV curing coating system
Compared with water-based coatings, UV-curable coatings is difficult to extinction. Extinction capacity depends on the nature of the formulation, the reactivity of the resin and the curing conditions. In general, low reactivity and slow cure conditions favor extinction and high reaction cure systems are difficult to quench. The vast majority of UV curing coating system requirements for matting agents should not affect the viscosity of the system, so the oil absorption of silica should be as small as possible. This matting agent manufacturing process is different from the traditional sense of silica matting agent. At the same time, the matting agent with smaller oil absorption tends to have a larger proportion of the heap and is easy to sediment and can only be used after being specially treated.
Extinction of unsaturated polyester UV-curable coatings is relatively easy, with the same matting agent mechanism. Acrylic UV-curable coatings and the traditional paint system, the opposite, often organic matter and small particle matting agent has better matting effect. It is harder to extinction in paint formulations where there is a component that may accelerate surface cure.
4, high solids coating system
High solid content coating high solids content, need to increase the amount of matting agent formulations. Ordinary matting agents tend to cause significant viscosity increases. Therefore, should use high porosity and acceptable diameter of the coarsest matting agent. Usually use a high average particle size as thick as 11μm matting agent. In addition, in order to get better extinction effect, often with a particle size and coating dry film thickness equivalent matting agent.
5, powder coating system
Powder coating curing shrinkage due to the coating is very small, the use of traditional particulate silica is difficult to dull, even if the coarse particle size matting agent, it can only reach half-light. To achieve a lower gloss, this can be done by adding gel silica and a special blend of resins.
Select matting agent is to make the paint surface micro-roughness, without affecting the appearance of coatings and mechanical properties of the film. Gel method of silica matting agent is a simple, efficient, cost-effective matting agent, as a coating has become an important additive, so that the paint showed a unique luster. The proper choice of matting agents is the key to matt coating production.