Why does floating color and flower appear during the paint production process

作者： huayang 时间：2024-08-06 00:32:26 阅读：7

Nowadays, people's living standards are getting better and better. Their demand for houses is not only for shelter from wind and rain, but also for comfortable, aesthetically pleasing, and versatile living spaces. Indoor coatings are an indispensable part of house decoration, and people's requirements for the color and performance of coatings are gradually increasing. However, the modulation of paint colors is very complex, and problems such as floating color and flower formation are often encountered during the production and application of paints.

Professionals stated that there are many factors affecting the floating color of latex paint, such as the particle size difference of pigments and fillers, the surface tension difference of various substances in the system, the hydrophilic lipophilic balance value (HLB) of various substances, and the compatibility of lotion and color paste. Please continue to look down for details.

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. Thickeners or dispersants with certain functional groups such as hydrophobic end groups have strong affinity for pigment particles, which adsorb pigment particles to form bridge flocculation and cause paint float. Strong hydrophobic associative thickeners have poor bridge flocculation and coloring properties due to the adsorption of hydrophobic groups on pigment paste particles. Alkali swelling thickeners have different amounts of ionic charges, resulting in different amounts of charge on the film-forming material during coating drying after salt thickening. They also have different affinity for strong polar pigment particles and the severity of float. Different systems also have differences in color development.