The Influence of Zirconia Beads, Aluminum Beads, and Glass Beads on the Dispersion and Grinding Performance of Sand Mills

Material grinding is an important process in ink production, and the degree of dispersion of materials represents the quality of grinding. Factors such as grinding equipment, grinding media, grinding time, and the number of grinding cycles influence the grinding effect and efficiency of materials. To apply the grinder effectively in ink dispersion and grinding, this article analyzes the impact of grinding media (including different media types and different diameters of the same type), grinding time and cycles, and different grinding equipment like horizontal sand mill, basket mill, ball mill, and electric stirrer on the dispersion and grinding of solvent-based and water-based inks.

In ink production, materials need to be pre-dispersed and then ground using grinding equipment until the fineness meets the process requirements. Pigment grinding is a crucial step in the production of solvent-based and water-based inks. Grinding equipment relies on grinding media such as balls, zirconia beads, and others to impact, friction, and shear materials through different movements, thereby breaking down and dispersing the materials. Grinding machines are commonly used in ink pigment grinding. Grinding machines can be divided into vertical and horizontal grinding machines. Compared to other equipment like roller mills and colloid mills, grinding machines have the advantages of high production efficiency, lower operating costs, and finer particle size of materials.

The quality of ink production depends on the dispersion of materials, which is closely related to factors such as grinding equipment, grinding media, grinding time, and the number of grinding cycles. Various studies have explored the influence of factors like pigment-to-binder ratio, feed rate, and the number of grinding cycles on ink pre-dispersion properties. Additionally, research has investigated the grinding effects under different types of sanding machines and grinding methods, as well as the impact of the diameter of grinding media and grinding time on ink grinding results.

To effectively apply grinding machines in ink dispersion and grinding, this study examined the grinding effects of various factors. The study first outlined the materials, instruments, and testing methods used in the experiments. Then, it analyzed the impact of grinding media (including different media types and different diameters of the same type), grinding time and cycles, and various grinding equipment such as horizontal sand mills, basket mills, ball mills, and electric stirrers on the dispersion and grinding of solvent-based and water-based inks.

Research Methodology

Materials and Instruments

• Materials: Water-based ink pigments, acrylic resin AZR (Atos company), and additives like dispersants and defoamers.

• Grinding equipment: High-speed stirrer (Shanghai Sile Instruments), Buhler horizontal sand mill (Swiss Buhler), basket mill.

• Grinding media: Zirconia beads (diameters of 1.0-1.2mm, 1.6-1.8mm, and 2.2-2.4mm from Pingxiang Jinrui New Materials Co., Ltd.), alumina beads (from Shandong Shengri Co., Ltd.), glass beads (from Hebei Chiyego Glass Bead Co., Ltd.).

• Measurement instruments: MicrotracS-3500 laser particle size analyzer (Microtrac Corporation), electronic balance (Mettler-Toledo).

Experimental Content and Methods

• Testing content: Measurement of pigment particle size distribution after grinding with different grinding media (zirconia beads, alumina beads, and glass beads), different diameters of zirconia beads, and various grinding times and cycles using different grinding equipment (horizontal sand mill, basket mill, ball mill, and electric stirrer).

• Testing methods: Mixing pigments, dispersants, and additives at room temperature in specific pigment-to-binder ratios, pre-dispersing the mixture, placing it in the respective grinding equipment, adding grinding media, and grinding at a certain speed for a specified time. Samples of ink pigments were taken within the specified time and tested using a laser particle size analyzer to analyze the grinding effects.

Experimental Results and Analysis

The study analyzed the impact of grinding media, grinding time and cycles, and different grinding equipment on the dispersion and grinding of solvent-based and water-based inks.

1. Grinding Media

1.1 Different Types of Grinding Media

• When using grinding media with a higher density, the pigment particle size is smaller, leading to better grinding results. Zirconia beads with a density of 6 outperformed glass beads (density 2.4) and alumina beads (density 3.85) in grinding. Zirconia beads achieved a pigment particle size of less than 1μm, alumina beads less than 2μm, and glass beads less than 3μm.

• The grinding effect and particle size are related to the type of grinding media, primarily due to differences in density and surface smoothness. Zirconia beads have a higher density than glass beads and a smoother surface. Under the same grinding media speed and diameter conditions, higher-density and larger-sized grinding media generate greater dispersing shear forces during collision and friction with pigment particles, resulting in higher dispersion efficiency and better grinding effects.

1.2 Different Diameters of Grinding Media

• Smaller-diameter zirconia beads led to smaller pigment particle sizes and better grinding results. Zirconia beads with diameters of 1.0-1.2mm resulted in pigment particles of less than 1μm, while those with diameters of 1.6-1.8mm led to particles of less than 1.52μm. Zirconia beads with diameters of 2.2-2.4mm resulted in particles of less than 1.6μm. Smaller-diameter grinding media had a higher probability of collision and shear within the grinding mill, leading to narrower particle size distribution and better grinding efficiency.

2. Grinding Time and Cycles

2.1 Grinding Time

• Longer grinding times led to smaller pigment particle sizes and better grinding results. After 30 minutes of grinding, 95% of pigment particles were less than 1.58μm, and this decreased to 0.76μm after 120 minutes of grinding.

2.2 Grinding Cycles

• Increasing the number of grinding cycles resulted in smaller pigment particle sizes and better grinding effects. After one cycle of grinding, 95% of pigment particles were less than 1.16μm, and this decreased to 0.88μm after four cycles of grinding.

3. Different Grinding Equipment

• The choice of grinding equipment significantly influenced the grinding effect, with horizontal sand mills providing the best results, followed by basket mills, ball mills, and electric stirrers. After 2 hours of grinding, horizontal sand mills achieved a pigment particle size of less than 1.38μm, while electric stirrers achieved less than 12.12μm.

In conclusion, grinding equipment, grinding media, grinding time, and the number of grinding cycles directly affect the dispersion performance of materials, specifically the particle size distribution of pigments. This study, conducted under controlled conditions using specific materials, instruments, and testing methods, demonstrated that using high-density zirconia beads as grinding media resulted in better grinding effects than glass beads and alumina beads. Smaller-diameter grinding media and longer grinding times and cycles also improved grinding efficiency. Among different grinding equipment, horizontal sand mills provided the best grinding results.