In the production and storage of paint, pigment particle settling is a common problem affecting product quality. It not only leads to uneven paint color and reduced application performance, but can also cause pigment agglomeration, severely impacting the appearance and protective properties of the paint film. Therefore, achieving effective anti-settling and dispersion of pigment particles is a core element in ensuring the stability and performance of paint products. The key lies in breaking particle agglomeration and constructing a stable dispersion system.
The essence of pigment particle settling is the result of an imbalance between gravity and system stability. Pigment particles generally have a higher density than the paint medium. If the particles are not dispersed uniformly, they will form agglomerates, increasing the equivalent particle size and significantly enhancing the effect of gravity, thus gradually settling and forming sediment during standing. Furthermore, insufficient paint viscosity, inappropriate dispersant selection, and abnormal application and storage temperatures can all exacerbate settling and disrupt the uniformity of the paint system.
The core principle of anti-settling and dispersion is to use physical and chemical methods to break the van der Waals forces and electrostatic attraction between pigment particles, allowing the particles to be uniformly dispersed in the paint medium and constructing a stable suspension system. This process mainly consists of three stages: wetting, deagglomeration, and stabilization. Each stage requires precise control to achieve the desired anti-settling effect.
Wetting is the foundation of dispersion. It involves adding a wetting agent to reduce the interfacial tension between the paint and pigment particles, replacing the air or moisture adsorbed on the pigment particle surface, allowing the paint to fully coat the particle surface and creating conditions for subsequent deagglomeration. Different types of pigments require corresponding wetting agents; polar pigments are suitable for anionic wetting agents, while organic pigments are more suited to nonionic wetting agents, ensuring effective wetting while avoiding adverse reactions.
The deagglomeration stage requires mechanical force to break down pigment agglomerates. Commonly used equipment includes sand mills and three-roll mills. Through the collision and shearing action of the grinding media, agglomerated particles are broken into primary particles. The efficiency of mechanical dispersion is closely related to the equipment speed, grinding media type, and dispersion time. The temperature must be controlled between 40-60℃ to avoid excessively high temperatures causing resin gelation or solvent evaporation, which would affect the dispersion effect.
Stabilization is key to preventing sedimentation. It maintains the stability of the dispersion system through charge repulsion and steric hindrance effects. In aqueous systems, adjusting the pH or adding dispersants can increase the zeta potential, enhancing electrostatic repulsion between particles. Solvent-based systems rely on the anchoring segments of polymeric dispersants adsorbing onto the pigment surface, forming a spatial barrier and preventing particle re-aggregation. Furthermore, adding thixotropic agents can construct a three-dimensional network structure, further increasing system viscosity and slowing particle settling.
In actual production, the anti-settling dispersion effect needs to be comprehensively adjusted based on pigment characteristics and paint formulation to avoid excessive or insufficient dispersant. Simultaneously, the storage temperature should be controlled between 15-25℃ to reduce the impact of environmental factors on system stability. The rational application of anti-settling dispersion technology can improve the storage stability of paints, optimize the color and protective properties of the paint film, and promote the improvement of paint product quality.
