How to Choose the Right Filter for Paint Manufacturing Process

As industrial consumers, we hold specific expectations for paints. They should firmly adhere to the painting substrate, exhibit a consistent texture, and offer a smooth coverage free of craters or surface irregularities. Additionally, it is essential for the color to remain uniform across every drum we employ.

Filters play a crucial role in ensuring that the final product in various industries adheres to industry standards and meets the expectations of industrial users. One such industry is the paint industry. In this detailed guide, we will provide you with a comprehensive overview of filtration in the paint industry, and how to choose the right filter for this industry.

Paint Manufacturing Process

To put it simply, paints consist of resins, solvents, and pigments, and additional ingredients are incorporated to meet specific application requirements. These ingredients are carefully measured and mixed in a controlled environment using a mixing reactor. The entire process can be completed in as little as 30 minutes to produce the paint.

Once mixed, the paint is continuously filtered to eliminate any impurities that could affect its surface properties. Selected samples of the paint are then sent to a laboratory for rigorous quality control checks before being approved for release. Some of the quality control checks conducted in the laboratory include:

Draw Down Test

The draw down test involves spreading the paint on a glass plate using a wire-wrapped rod. After the paint has dried, the surface is inspected for any irregularities such as craters, gels, and particles of grit. Additionally, properties like gloss and adhesion are also evaluated. Based on these observations, the surfaces are classified as either acceptable or unacceptable.

Hegman Grind Test

The Hegman grind test utilizes a Hegman gauge, which is a rectangular stainless steel block with a wide, inclined groove on its top surface. The gauge is marked with graduations that indicate its depth. During the test, the paint is placed at the deepest part of the groove and then spread towards the shallow end using a scraper bar.

As the paint encounters contaminants larger than the space between the groove and the scraper bar, scratches are formed along the surface of the groove. Each paint formulation has a specific requirement for the position and number of these scratches. If the paint fails to meet the specifications in either of these areas, it continues to circulate through the filters until subsequent tests yield positive results. Only then is the paint considered suitable for packaging.

Types of Filters Used

In the complex world of paint manufacturing, filters can maintain the quality and consistency of the final product. There are multiple types of filters used in this industry, each with its unique characteristics and applications. Here are three types of filters commonly utilized in the paint manufacturing sector.

Bag Filters

Bag filters stand out as a popular choice in paint manufacturing, especially when dealing with large volumes and high flow rates. Their design and structure make them well-suited for capturing coarse particles effectively. The ample surface area of the bag filter facilitates efficient filtration, making it an ideal option for processes that demand robust particle removal capabilities. Additionally, the versatility of bag filters extends to their ability to accommodate different production scales, ensuring reliability in diverse manufacturing settings.

Cartridge Filters

Cartridge filters offer a versatile solution to filtration challenges in the paint manufacturing industry. Their adaptability to various particle sizes makes them indispensable for applications with smaller batch sizes. Cartridge filters can effectively capture contaminants and particles, providing a tailored approach to filtration based on the specific requirements of the manufacturing process. This flexibility makes them suitable for a range of paint formulations, contributing to the precision and efficiency of the production line.

Depth Filters

Depth filters carve a niche in the paint manufacturing landscape by offering comprehensive filtration across a wide range of particle sizes. Their unique design enables effective contaminant capture throughout the entire depth of the filter. This characteristic makes depth filters particularly efficient in maintaining the purity and quality of the paint by addressing particles at different levels. The versatility of depth filters makes them valuable in scenarios where a diverse range of particle sizes needs to be managed, ensuring a thorough and reliable filtration process.

The common types of filters used in paint filtration are bags and resin bonded cartridges. These filters should possess the following properties:

• Silicone-free: The filtration media must not contain any silicone, as it can contaminate the paint.
• Effective gel removal: The filters should be able to effectively remove gels from the paint.
• Minimize circulation time: The filtration media should reduce the time required for circulation before packaging the paint.
• Batch filtration capability: The filters should be capable of filtering an entire batch of paint.
• No collapse or fiber migration: The filtration media should not collapse or allow any fiber material to migrate into the paint.
• Consistent pigment particle removal: The efficiency of pigment particle removal should not increase during the filtration process.

How to Choose the Right Filter for Paint Industry

Selecting the appropriate filter for the paint industry requires a comprehensive consideration of multiple factors. The following explores the dimensions of filter selection within different stages of the paint manufacturing process to make an informed decision and optimize filtration performance.

Why Silicone-Free Filter Media is Essential

Silicone, which is a release agent, can have negative effects on the appearance and adhesion of paint. Even trace amounts of silicone in paint can cause it to peel and create craters in otherwise smooth surfaces. Filters have the potential to be a source of silicone contamination. The threads on filter bags and the fiber additives and dyes used in filter media may contain silicone.

Lubricants used in the filter media production equipment and cleaning materials can also contain silicone. To ensure that paint is free from silicone contamination, filter manufacturers must take precautions and remove all potential sources of silicone in their production processes.

Filtration of Gels in Paint Process

Gels, which are highly cross-linked polymer webs formed during polymerization, can pose challenges during the filtration process. These gels have a high molecular weight and do not dissolve in the solvent. When subjected to stress, they can deform and cause issues during filtration. To effectively remove gels, it is recommended to use rigid, resin bonded filters as they offer a stable fiber matrix.

Additionally, to enhance the efficiency of gel removal, it is advisable to lower the flow rates below normal levels. This allows the filter media to effectively capture and remove the gels from the paint formulation.

Maintaining Consistent Color in Paint Manufacturing

To ensure consistent color in paint manufacturing, it is important to use filters that effectively remove large particles and agglomerates while allowing dispersed pigments to pass through. This can be achieved through proper classification and clarification of particles based on size.

Classifying filters capture large particles while allowing smaller particles like pigments to pass through the cartridge. On the other hand, clarifying filters remove particles of all sizes. As filters begin to plug and form a cake, their efficiency can shift towards functioning more like clarifying filters. High-quality classifying filters have uniform fiber structures and a controlled graded density construction in their efficiency control layer.

Cartridges with low resin content tend to compress under increasing pressure drop, resulting in increased efficiency and potential pigment removal. However, wound type filters tend to form filter cakes rapidly, requiring frequent changes and disrupting the batch process.

While resin bonded cartridges have been widely used in the past due to their durability and low fiber migration, their manufacturing process has faced environmental concerns and has been rarely used. Alternative methods such as stainless steel metal cartridges and bag filters are being adopted. Stainless steel metal elements have the advantage of being reusable after cleaning.

Conclusion

By understanding the nuances of your manufacturing process and considering key factors in filter selection, you can navigate the complexities and enhance the precision of your paint manufacturing journey.

Brother Filtration provides comprehensive solutions for paint filtration, specifically designed to meet the needs of paint manufacturers. Our team is available to assist you in implementing the right filtration solution for your paint manufacturing process. To learn more about our solutions, please reach out to our application support teams at [email protected].