The Optimal Composition for Grinding Paint with Sanding Machines

In the world of paint production, achieving the perfect color and texture involves a delicate balance of various raw materials. While color standards specify the name, specifications, and the percentage of each raw material, it's not always practical to follow these standards during the paint production process. Grinding paint, in particular, is a critical stage in the manufacturing process. The ideal composition for grinding paint varies depending on the type of paint being produced and the specific machinery used. In this article, we'll explore the importance of a well-balanced paint grinding mixture and delve into the composition of grinding paint for sanding machines.

1. The Significance of a Well-Balanced Paint Grinding Mixture

When it comes to paint production, applying standards directly to the grinding process is challenging for a couple of reasons. First, production scales and equipment sizes often require adjustments to the standard feed batch. Second, the composition of grinding paint has a profound effect on the efficiency of the grinding process. For example, paint with a higher pigment content is generally more efficient on the same grinding machine compared to one with a lower pigment content. This is because the pigment content needs to reach a specific concentration for effective shear, impact, and friction between pigment particles. These interactions are crucial for achieving the desired fineness during grinding.

In practice, pigments, some paint, solvents, and additives to be added during the grinding stage are typically mixed in a batching tank. This mixture is then pre-mixed and dispersed during the grinding process to create the grinding paint. Following this, the remaining paint, solvents, and additives for color adjustment are introduced into the qualified grinding paint. The entire process involves expanding the feed quantity, adjusting it based on equipment size and production requirements, and splitting the raw materials into different categories based on their role in the grinding and color adjustment stages.

2. Composition of Grinding Paint with Sanding Machines

The equipment used for grinding paint includes high-speed dispersers, sanding machines, and three-roll mills. In this section, we'll focus on the composition of grinding paint used for sanding machines with zirconia beads as the grinding media.

2.1. Determining the Composition Using the Daniel Flow Point

To determine the ideal composition for grinding paint with sanding machines, the Daniel Flow Point method is often employed. This method, developed by Daniel in 1946, is based on the flow point of pigments and is somewhat cumbersome but practical. The Daniel Flow Point takes into account the fact that sanding machines are hybrid grinding and dispersing equipment. The composition of the grinding paint is a combination of paint viscosity and the volume fraction of pigments. For effective grinding, the paint must be in a plastic flow state with a relatively high pigment content. The Daniel Flow Point method relies on measurements and observations.

During the measurement, a specific quantity of pigment is added to paint, and a resin solution with a certain solid content is introduced gradually. The pigment starts as a loose powder and gradually transforms into a dense ball when a specific quantity of resin solution is added, without excess resin solution. This point is known as the "ball point." Adding more resin solution causes the paint to transition to a liquid state. By continuing to add resin solution, stirring with a paint mixing knife, and periodically lifting the paint off the knife at a 45° angle to allow it to flow freely, a specific point is reached. At this point, the paint composition is in a plastic flow state with a high pigment content, referred to as the Daniel Flow Point.

2.2. Using the "Triangle Coordinate Chart" for Composition Determination

The Daniel Flow Point method is accurate but can be complex in practice. To simplify the process, the "triangle coordinate chart" was developed. This chart is a practical and efficient way to determine the composition of grinding paint for sanding machines.

The triangle in the chart represents the composition of grinding paint. One side of the triangle indicates the mass percentage of pigments, another side represents the mass percentage of solvents, and the base denotes the mass percentage of solid resin in the grinding paint. The triangle is divided into 11 regions, each corresponding to specific pigment classes. Each region covers various specific pigment varieties. For example, Region 11 encompasses several colors, such as lemon yellow, light chrome yellow, medium chrome yellow, deep chrome yellow, molybdate chrome orange, and chrome green. Regions 8 and 10 can also include multiple fillers. This makes the chart versatile.

Inside the triangle, four lines are present: Line 1 runs parallel to the base and intersects the left side of the triangle; Line 2 runs parallel to the left side and intersects the right side; Line 3 runs parallel to the right side and intersects the base; Line 4 originates from the vertex of the triangle and intersects the base. Here's how to use the "triangle coordinate chart" to determine the composition for a specific pigment, such as iron red oxide:

• Choose a point within the midpoint of the region of interest and draw a line parallel to Line 1, intersecting the left side of the triangle. The reading shows the mass percentage of the pigment in the grinding paint, e.g., "46%."

• Using the same midpoint, draw a line parallel to Line 2, intersecting the right side of the triangle. This reading represents the mass percentage of solvents, e.g., "34%."

• Repeat the process by drawing a line parallel to Line 3, intersecting the base. This reading corresponds to the mass percentage of solid resin, e.g., "20%."

• Connect the vertex of the triangle to the midpoint of the region for the specific pigment and extend the line towards the base. The reading gives the solid content of the grinding paint, e.g., "37%."

By following these steps, you can easily determine the suitable composition for grinding paint for a specific pigment, such as iron red oxide.

2.3. Practical Efficiency of Grinding Paint Composition

To illustrate the practical efficiency of the composition determined using the "triangle coordinate chart," let's consider the example of iron red oxide paint. If a 50% solid content alkyd resin is used for grinding on a sanding machine, the composition determined by the chart yields the following results:

• First Pass (Fineness): 20–25 µm

• Second Pass (Fineness): Below 10 µm

These results demonstrate that the determined composition for iron red oxide paint, when used with a 50% solid content alkyd resin, leads to excellent dispersion and high production efficiency.

2.4. Composition of Grinding Paint for Various Pigments

The "triangle coordinate chart" can be used to determine the composition of grinding paint for various pigments. The chart's versatility allows it to accommodate different paint varieties. However, it's crucial to remember that this chart serves as a general guideline for "medium oil-length alkyd resin." When working with resin paints or medium oil-length alkyd resin paints with varying wetting properties, you may need to adjust the chart positions accordingly. For epoxy resin and acrylic resin paints, which have different wetting properties, different positions within the regions should be selected. In all cases, experimental validation is essential to ensure the accuracy of the determined composition.

3. Conclusion

The "triangle coordinate chart" provides a simplified and efficient method for determining the optimal composition of grinding paint for sanding machines. It streamlines the process, making it practical and accurate. Experimentation has consistently validated the accuracy of the determined compositions, ensuring that the method is reliable for paint production. This approach equips the paint industry with a valuable tool for enhancing the quality and efficiency of paint manufacturing.

In conclusion, understanding the optimal composition for grinding paint is crucial for the paint manufacturing industry. By using the "triangle coordinate chart," manufacturers can easily determine the ideal paint composition, resulting in more efficient production and better quality paint products. This method simplifies the complex process of composition determination, making it a valuable tool for the industry.

Understanding the ideal composition for grinding paint, especially when used with sanding machines, is crucial in the paint manufacturing industry. A well-balanced composition not only ensures the desired fineness but also improves the efficiency of the grinding process. To simplify this complex task, a practical tool known as the "triangle coordinate chart" has been developed. This chart simplifies the determination of grinding paint composition, making it a valuable asset in the industry. It accommodates various pigments, allowing manufacturers to optimize their grinding paint composition for different types of paints and achieve high production efficiency.