Focus on pigments: Shining Brite! High performance aluminium effect pigments

“We cannot solve our problems with the same thinking we used to create them” – Albert Einstein. In the case of aluminium-based effect pigments, the traditional production method involves milling of high purity aluminium in large quantities of VOC hydrocarbon solvents. Metaflake took a radical approach to this sustainability problem and developed a process to produce aluminium-based effect pigments by milling in water, completely avoiding the use of VOC hydrocarbon solvents

The coatings industry has successfully embraced the need to develop and implement technologies that are more sustainable with reduced negative effects on the environment. This included the moves to water-based coatings, powder coatings and radiation curing coatings in place of the more traditional solvent-based coatings.

In the case of aluminium-based effect pigments, the traditional production method involves milling of high purity aluminium in large quantities of VOC hydrocarbon solvents. This concept no longer fits with the sustainability needs of the coatings industry, since:

1. It is inherently difficult to avoid release of VOC hydrocarbon solvent to the atmosphere from this traditional milling process (for example, one prominent producer reports via EPA their emissions from one minor production site alone of >108Mt of volatile organic compounds annually)
2. It becomes exponentially more difficult to remove all traces of VOC hydrocarbon from the solvent milled product, resulting in harmful high boiling point hydrocarbon residues remaining in solvent milled aluminium pigments, even after additional post processing.

Metaflake took a radical approach to this problem and developed a unique, safe, environmentally friendly process to produce aluminium-based effect pigments by milling in water and completely avoiding the use of VOC hydrocarbon solvents. The benefits of this unique process are multiple:

1. No use of or emission of harmful VOC hydrocarbon solvents in the product or production processes;
2. Final products are 100% free of VOC hydrocarbon solvents and residues;
3. High performance, extremely high brilliance aluminium effect pigments can be produced;
4. Water milling brings some inherent stability benefits to the pigment surface in certain applications;
5. It is relatively easier to make additional surface modifications and treatments after water milling compared with a solvent milled pigment.

Caption: Water milled silver dollar shaped aluminium-based effect pigment

As well as the unique water milling process, Metaflake has also been able to utilise renewable power sources for all production processes and buildings, as well as its own electricity generation via onsite photovoltaic installations across the whole site. These measures lead to the lowest real CO2 per kg of product produced relatively to others in the industry (Scope 1 plus 2) without any need for artificial offsetting of greenhouse gas emissions or separate CO2 “compensation” accounting. Furthermore, we work with our aluminium raw material suppliers to ensure that they are increasingly utilising renewable energy in their own processes and that of their primary aluminium supplies, with targets for continual improvement as they transition to green aluminium.

Surface treated water milled aluminium pigments – high performance applications

The use of water milled aluminium effect pigments extends into high performance coating applications, such as:

• Automotive coatings – interior, exterior, trim, OEM & refinish;
• Coil coatings;
• Wood coatings;
• Plastic coatings;
• Leather coatings;
• Decorative coatings;
• Powder coatings.

These applications necessitate the need for additional surface treatment on the pigment surface to ensure the appropriate pigment properties are achieved and maintained:

• Brilliance and flip-flop;
• Opacity, hiding power, colour strength;
• Pigment stability and formulation stability;
• Circulation (ring-line) stability;
• Repeatable application characteristics;
• Performance and durability of the final applied coating;
• 100% free of VOC hydrocarbon solvents.

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Sustainable aluminium pigment technology

To facilitate these needs, Metaflake has developed a highly efficient, state of the art silica surface treatment process for applying to the water milled aluminium pigments. This process allows multiple microscopic layers of uniform silica to be applied to the pigment to achieve an optimum balance of opacity, stability, brilliance and other properties.

The range available initially covers the main metallic effect spectrum for coatings as follows:

Aqua-Brite SCT grades in high performance coatings 

• Highest stability;
• Highest chemical resistance;
• Excellent compatibility;
• Excellent adhesion;
• Suitable for highly demanding applications in water-based and solvent-based coating formulations;
• 100% free of VOC hydrocarbon solvents and residues;
• Available with various carrier components to suit customer requirements and applications;
• Low CO2.

For more information, visit metaflake.com