Decorative Paint

1. The characteristics of pearlescent pigments

       Pearlescent pigment Mica flakes are coated with metal oxides to produce pearlescent pigments. It is acid-resistant, alkali-resistant, and heat-resistant up to 900°C. It does not self-ignite, does not support combustion, and has good stability against high arcs.

Second, the formula

       The amount of pearlescent pigment added depends on the desired effect. For the solid content of pearlescent pigments, the added amount is usually about 10-25% by weight. For special effects or very thin bright coatings, the amount may be as high as 40%, but the amount of pigment addition is not recommended because they will hinder the orientation of platelet pigments and cause the loss of gloss of the coating. Sometimes only 1%-1.5% of the pearlescent pigments by weight of the solids are needed to make the varnish coating more translucent.

Three, wetting and dispersing

       In order to make it easier to disperse the pearlescent pigments, the pigments can be wetted in advance. A wetting time of 15 minutes or more is recommended for mixing powdered pigments with a part of the liquid system or a compatible solvent diluent or plasticizer to form a slurry, and then stir the slurry into the rest evenly. Pearlescent pigments can be dispersed with an ordinary stirrer similar to metal powder. The correct mixing method is to add pearl powder to a carrier that is being stirred with low shear and axial flow. The paint cannot be poured in all at once, but should be poured gradually. When the first part is fully wetted, you can continue to add it until it is fully wetted. Finally, continue to stir for 15 minutes to better disperse the pigment. You can use an axial rotating agitator to mix the amount of pigments should be less than 25%, and the speed should not be too fast. The height of the stirring paddle should be changed differently during the stirring process to prevent uneven stirring at the dead corner directly under the stirring. The lamellae state of the pigments and the corresponding brittleness only permit the use of relatively small shearing forces during dispersion. Do not use machinery used to mix conventional pigments, such as roller mills, ball mills, or stone mills, because these mechanical energy can destroy the lamellae state of the pigments and cause gloss loss. If a disperser is used, only a short mixing time is allowed. It is recommended to apply equal mixing time and speed under the same conditions to make each batch of paint.

Fourth, stability

Pearlescent pigments usually do not flocculate. There are two ways to reduce the precipitation of pigments in the paint system

1. Prevent pigment focusing through good wetting and dispersion as mentioned above

2. Make the pigments suspend well in the carrier. Adding some special additives such as thixotropic agent to the carrier can be used to improve the sedimentation performance of the pearlescent pigment in the coating. Only those that do little damage to pearlescent pigments such as organic modified bentonite, polyethylene wax and other organic thixotropic agents can be used. The use of pyrogenic silicic acid is not recommended because it is a matting agent, even if it is used in a very small amount, it will significantly reduce the gloss and color effect. Sometimes the sinking of such large and heavy pigment platelets is unavoidable to use flocculants to form a controllable flocculation phenomenon. This will become a loose, easily dispersed precipitate that is unstable under external force and can be easily stirred to return to the original uniform paint mixture.

Five, particle size selection

       Pearlescent pigments have different particle size distribution ranges. The difference in particle size will affect the gloss, hiding power and appearance of the paint. Increasing the particle size of the pigment flakes will increase the brilliance. The ideal particle size distribution is 10-60um. Larger particle size will give a glittering effect and a small covering power, while a small particle size will give a soft satin effect and great covering power.

Six, adjust the color

      Pearlescent pigments can be used in combination with ordinary pigments to create a variety of colors with bright colors and high chromatic purity. Such as phthalocyanine blue, phthalocyanine green, quinacidine red and so on. It should be noted that too much colorant should be avoided because excessive absorption of light color will cover the pearlescent color at the reflection angle.

Seven, hiding power

There are several ways in the formula to improve the hiding power

A. Pearlescent powder with fine particle size can improve hiding power. However, the pearlescent effect is a softer satin effect and the sparkle effect is not obvious. To obtain the ideal pearlescent effect and hiding power, a finer pearlescent powder can be used to replace a part of the coarser pearlescent powder.

B. Adding metal powder to the paint can improve the hiding power, such as aluminum powder, copper powder, etc. The usual amount is 5-10% of the pearlescent pigment.

C. A small amount of carbon black can provide good hiding power when blending dark colors. Adding black can improve the reflection color of pearl.

D. The use of titanium dioxide when blending light colors is also very helpful to increase the hiding power. However, the pearlescent effect will be weakened. Therefore, if you want to use titanium dioxide, you must increase the amount of pearlescent pigments to enhance the reflected light color. However, the amount of titanium dioxide should be small and just enough to cope with the hiding power. Remember that opaque pigments or dyes will reduce the pearlescent effect