Exploration to Enhance Grinding Dispersion Efficiency in Paint Manufacturing

In the current paint production process, pigments, fillers, base materials, and solvents are generally mixed uniformly using high-speed dispersers and then mechanically dispersed (using sand mills) to achieve specific fineness targets, forming a homogeneous and stable dispersion. However, in recent years, significant increases in raw material costs have led to rising costs for various types of paints, adversely affecting the economic efficiency of companies. Additionally, the paint industry faces intense competition, wherein timely supply confers a competitive advantage. Therefore, exploring methods to reduce production costs and increase production efficiency in paint manufacturing could be beneficial. Based on my years of experience in paint production, controlling the grinding dispersion process is crucial for both quality and efficiency. This article focuses on discussing the grinding dispersion efficiency of solvent-based paints.

1. Factors Affecting Grinding Dispersion Efficiency:

1.1 Pigment-to-Binder Ratio:The appropriate dispersion of pigments, fillers, base materials, and solvents is essential regardless of the grinding dispersion equipment used, such as sand mills. Designing a reasonable dispersion process requires consideration of the base material's wetting performance on pigments, the oil absorption of pigments and fillers, and the viscosity of the mixed paint slurry. These factors directly influence the efficiency of grinding dispersion. For instance, experiments using iron blue powder with a solid content of 50% long oil alkyd resin and 200# solvent gasoline achieving a fineness of 20 microns were conducted (see Table 1).

From Table 1 (keeping other grinding conditions constant), the following conclusions can be drawn:

• A very high pigment-to-binder ratio leads to insufficient wetting of pigment particles, causing operational difficulties. Conversely, a very low ratio results in excessive materials, leading to time-consuming trials.

• Pigment powders with lower oil absorption are more challenging to disperse, requiring longer grinding times to achieve similar fineness levels compared to powders with higher oil absorption.

• When the viscosity of the mixed paint slurry reaches a certain level, dispersion becomes challenging.

• Higher efficiency in grinding dispersion is achieved when the mixed paint slurry attains a specific pigment-to-binder ratio.

1.2 Pre-dispersion Effect:Complete wetting plays a crucial role in dispersion and stability in the paint production process. Operational methods, pre-dispersion time, and shear forces are pivotal. The rate at which the mixed paint slurry infiltrates the capillaries of pigment particles is directly proportional to factors such as the pore size, surface tension of the mixed paint, and the cosine of the liquid-solid contact angle. However, excessive viscosity of the mixed paint slurry can adversely impact stability and dispersion efficiency.

1.3 Grinding Media:In the operation of sand mills, the grinding efficiency of different paint types is related to factors such as the type, density, hardness, and loading of zirconia beads used. Typically, finer product requirements necessitate smaller diameter zirconia beads. Paints with higher pigment content benefit from larger diameter and relatively denser zirconia beads. The selection of zirconia bead density, type, and loading should also consider factors such as dispersion material, speed, paint viscosity, and density of pigments/fillers. Mismatched density, hardness, and particle size of dispersion media significantly reduce grinding dispersion efficiency, potentially failing to achieve the required fineness.

1.4 Operating Temperature:The operating temperature of sand mills is usually maintained between 40-60 degrees Celsius. Higher temperatures accelerate solvent evaporation, leading to thinner double-layer thickness and reduced stability. Moreover, increased temperature accelerates particle movement, increasing agglomeration chances and enlarging particle size, affecting grinding efficiency.

1.5 Operator Quality:The quality of operators is pivotal among the three elements—man, machine, and materials—in production. Skilled operators significantly affect production efficiency, especially in labor-intensive processes in large and medium-sized enterprises. A competent operator requires not only technical skills but also a strong sense of responsibility. The experience and work attitude of the operator closely relate to factors such as zirconia bead addition, control of paint slurry flow, basic equipment troubleshooting, and maintenance.

1.6 Equipment Operation:Efficient equipment operation is vital for ensuring grinding efficiency. The wear of disperser impellers, lubrication of mechanical parts, and unobstructed inlet and outlet pipelines for paint slurry significantly affect grinding dispersion efficiency. Factors like loose motor belts, severe wear of sand mill disperser impellers, or blockages in paint slurry pipelines impact efficiency and should be addressed through proper maintenance.

2. Conclusion:Through experimental exploration of paint grinding dispersion efficiency, adjustments to the original grinding process were made, resulting in improved dispersion efficiency, reduced energy consumption, alleviation of electricity shortages, and an annual increase in enterprise profitability by 400,000 yuan (refer to Table). The enhanced dispersion efficiency shortened product production cycles, meeting customer demands significantly, thereby enabling companies to gain credibility and competitive advantage in a fierce market competition.