The modulation of paint colors is very complex. During the production and construction process of paint, the problem of floating color and flower formation is often encountered. When the paint has floating color and flower formation, there is a color difference between the color and the standard plate, making it difficult to adjust the color. This not only wastes pigments but also results in inaccurate color adjustment. At the same time, the opening effect of the paint is poor, and the color of the coating film deviates after drying, making it difficult to apply uniformly. One of the dynamic separation phenomena of pigments in the genus Phasia: pigments experience separation barriers in the horizontal direction, resulting in uneven coating color and the appearance of Phasia. Floating color refers to a change in color in the vertical direction, where one or more pigments separate during the film-forming and drying process of a coating. One pigment floats to the surface, while the other remains in place or sinks to the bottom

How to observe and judge the phenomenon of floating color and blooming in the laboratory

We can start from two aspects:

Static floating color in the tank: After the paint is evenly dispersed and left to stand in the tank for a period of time, one or more pigments that appear in the tank separate and float on the surface. For example, after being stored for a period of time, black, phthalocyanine, or white can be seen on the surface of the tank when opened

Dynamic floating color of coating film: The phenomenon of pigment particles separating during the drying process of coating film is called dynamic floating color. The pigment separation of dynamic floating color can be divided into two situations: one is uneven color on the surface of the coating film, and the other is that the surface color of the coating film is uniform, but there is a difference in color between the surface and bottom layers. To identify floating colors using finger rubbing, first pour or apply the coating onto a glass plate or black and white cardboard. When in a flat state, rub the fingers until the coating begins to become viscous and the pigment particles no longer migrate and separate. If there is floating color in the coating, there will be a difference in color between the surface that has not been rubbed and the surface that has been rubbed. During the rubbing process, the pigment is easily separated and filamentous stripes appear. After the coating dries, the surface that has been rubbed will show angular vortex patterns. The degree of color change during finger rubbing varies with the rubbing conditions. The length of rubbing time, the intensity of rubbing action, and the drying speed of the coating have a significant impact on the degree of color change

There are many factors affecting the floating color and blooming of paint. The difference in particle size of pigments and fillers, the difference in surface tension of various substances in the system, the hydrophilic lipophilic balance value (HLB) of various substances, and the compatibility of lotion and color paste have a great impact on the floating color and blooming of latex paint, which is discussed in detail below

1. The influence of particle size of pigment fillers on the floating color and blooming of coatings

During the drying process of coatings, as the volatile components in the coating evaporate, these volatile components also carry some pigments and fillers onto the coating. When these pigments and fillers particles are transported to the surface, finer particles with higher surface area are easier to transport, while coarse particles with relatively lower surface area hinder movement. During the drying of latex paint coatings, more hydrophilic substances tend to evaporate quickly. If the white pigment is more hydrophilic than the pigment particles in the pigment, they are more easily carried to the surface by strongly polar volatile substances. Due to the large difference in particle size between the pigment and filler, the miscibility between the pigment and filler becomes poor. As a result, paints made with this pigment are difficult to apply, and during the application process, there is severe whitening of the coating, leading to color floating in the coating. Floating white is difficult to adjust to dark paint and can cause waste of pigments. The solution is to carefully select the color and filler, so that the particle size of the selected color and filler matches; Thus avoiding the phenomenon of floating color and blooming

2. The Effect of Surface Tension Difference on Paint Floatation and Blossoming

During regular color adjustment, it is often found that some colorants are difficult to disperse evenly in white base paint. After a period of rest, the dispersed paint quickly experiences color separation or floating, or the opening effect of the coating is not good. In the process of making paint, the production process formula of white paste is different from that of color paste. Anionic dispersants or ionic polyelectrolyte dispersants are often used to make white paste, while non-ionic dispersants or some anionic dispersants are often used in color paste. Therefore, white pigments and colored pigment particles have different surface properties due to the adsorption of a layer of different wetting and dispersing agents, with different hydrophilic and oleophilic values and surface tension. Ionic surfactants generally have higher surface tension than non-ionic surfactants. They are all non-ionic surfactants, and due to their different hydrophobic end molecular structures, their surface tension also varies. Moreover, the outermost chain link in the hydrophobic end structure of the molecule contributes the most to the surface tension. Molecules with low surface energy mean that the forces between molecules are small and the surface tension is also low. From a thermodynamic perspective, substances with low surface tension are prone to adsorption and transfer to the interface, which stabilizes the system. The decrease in surface tension weakens the tendency of liquid contraction surface and droplet coalescence, reducing the additional pressure difference on the curved liquid surface, thus facilitating the stability of the liquid surface and dispersion system. So, if the surface tension between the white paste or color paste is significantly different from the surface tension of the system, coatings prepared with this paste are more prone to color floating

3. Compatibility between systems

If the lotion is compatible with the color paste, the floating and blooming of the paint and film will be much better. If the lotion is well wetted with the color paste, the color spread of the paint will also be good. Anionic and non-ionic surfactants are often used as wetting and dispersing agents in water-based coatings. Inorganic pigments with polar and ionic surfaces in water-based coatings can interact with the polar groups or ions of the added ionic surfactants to form a two-layer adsorption layer. Surfactants are adsorbed on the surface of pigment particles in the water system pigment paste to form a protective layer, but the forces between the protective layers can be divided into intermolecular forces and electrostatic forces, so the forces between them are different. When the above color paste is mixed with various lotion or latex paints, the dispersion stability of the color paste is different. When the affinity between the surfactant on the surface of the pigment particles and the surfactant adsorbed on the surface of the lotion particles, namely, the emulsifier or water, is large, the surfactant adsorbed by the pigment particles is stripped, making the protective layer on the surface of the pigment particles thinner, causing the flocculation of the pigment, thus causing the floating color of the coating film. Of course, when the emulsifier outside the lotion particles has good compatibility with the surfactant outside the pigment and filler particles in the color paste, the lotion will have good wetting of these pigments and filler particles, and the overall color paint will have good color exhibition, bright color, and no floating color

4. The influence of hydrophilic and oleophilic equilibrium values on floating color and flowering

Hydrophilic lipophilic balance (HLB) is a very sensitive issue. Many materials are often used in the production of coatings: lotion, pigment, filler, solvent, cosolvent and various additives. These materials all have their own hydrophilic and lipophilic balance values (HLB values). If the hydrophilic and lipophilic balance values of each material match, the performance of the entire coating system will be excellent, and phenomena such as floating color, blooming, and water separation will be overcome. Of course, after the selection of the lotion, pigments and fillers we use, the hydrophile lipophilic balance value (HLB value) cannot be changed, but the HLB value of the whole system can be adjusted by carefully selecting additives, namely wetting dispersants, thickening agents, etc., to balance the HLB value of the whole system. We know that lipophilic substances have low surface tension at their lipophilic end. When coatings are stored in containers and tanks, these lipophilic substances are prone to float to the surface. From a thermodynamic perspective, the energy of the entire system decreases and the system becomes stable. When the latex paint produced floats statically in the container, not only is the can opening effect poor, but the construction performance is also poor, and the coating state is also poor. If the coating appears white, it indicates that the HLB value of the white paste is relatively small and the white paste is more oil friendly. Therefore, when producing white paste, it is necessary to make it more hydrophilic; If the paint floats in the color of the color paste, it indicates that the HLB value of the white paste is relatively high and hydrophilic. Therefore, when producing the white paste, it is necessary to make it more oil friendly to prevent the paint from floating

The matching of hydrophilic lipophilic balance (HLB) values can be achieved by carefully selecting wetting and dispersing agents. Ammonium salt dispersants with hydrophobic groups in anionic dispersants are more oleophilic than sodium carboxylate dispersants, with lower HLB values. Additionally, ammonium salt dispersants with hydrophobic groups greatly improve the float color of latex paint coatings. Because when the pigment particles are coated with this type of dispersant, there is not only electrostatic resistance but also steric hindrance around the pigment particles. In addition, during the drying process of the coating, as the water evaporates, the ammonia in the ammonium salt also evaporates, making this type of dispersant more hydrophobic. Therefore, the pigment particles coated with this type of dispersant have better compatibility with the film-forming material. In addition, steric hindrance makes the structure very loose, which suppresses the floating color of the coating during the drying process, that is, the floating color during the dynamic process is also suppressed

5. The Effect of Thickener on the Floating Color and Blossoming of Latex Paint

Some pseudo plastic binding thickeners have a strong affinity with surfactants with high HLB values, causing them to desorb from the surface of pigments, resulting in pigment aggregation and flocculation, which in turn reduces the coloring power of the system and generates floating colors and flowers. In systems where organic and inorganic pigments are mixed, especially when titanium dioxide is used in conjunction with blue, green, and carbon black pastes, the use of weakly pseudoplastic associative thickeners can result in latex paints with satisfactory color and good leveling properties