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Alkyd coatings are still widely used today for their unique application feel, forgiving and easy to use finishes, and excellent durability features. However, metal catalysts in these formulations designed to accelerate ‘drying’ can lead to in-can skinning, forming on the paint’s surface inside the container.

To help prevent skinning on oxidative drying paints, oximes have been the go-to choice among formulators and paint manufacturers.

But in recent years, several oximes have faced regulatory scrutiny due to concerns surrounding potential toxicity. Oximes include:

• Butanone oxime (MEKO)
• 2-Pentanone oxime (MPKO)
• 4-Methyl-2-pentanone oxime (MIBKO)

In this blog, we’ll address the scrutiny these oximes are facing. We will also explore Ascinin^® Anti-Skin alternatives that are designed to be free of oximes and deliver excellent skin prevention.

Oxime Regulatory Concerns

Butanone oxime (MEKO)

Out of all oximes used for skin prevention, MEKO has faced the strictest guidelines to date.

In March 2022, the European Union (EU) harmonized the classification of MEKO with the 15th ATP of the CLP regulation and granting, among the other endpoints, the Carcinogenic 1B classification. This classification requires carcinogen GHS labeling in products containing ≥ 0.1% of MEKO and restricts their use. When used in coatings, the MEKO content is required to be higher than this limit for adequate skin prevention.

Canada has also published a Code of Practice to limit MEKO content in indoor paint applications for consumers. In recent years, the government concluded that risk management actions have not been as effective as needed. This has resulted in new actions being proposed.

2-Pentanone oxime (MPKO)

MPKO has been known as a popular substitute for MEKO in this context, indicative of its registered aggregated tonnage of >1000 tpa.

However, in the EU, MPKO is expected to soon receive a harmonized GHS Carcinogenetic 2 classification based on observations in similarly structured oximes.

4-Methyl-2-pentanone oxime (MIBKO)

In the EU, an extensive evaluation from ECHA is planned to clarify suspected Carcinogenic properties. While longer chain lengths in this substance may lead to lower or no Carcinogenic potential, authorities have not received data to validate this information.

Switching to High-Performing, Oxime-Free Anti-Skinning Agents

Many formulators have already moved away from MEKO anti-skins in alkyd formulations to reach compliance in global markets. With concerns being raised around other oxime-containing anti-skins, finding an oxime-free solution is a proactive way to avoid more impact from potential oxime regulations.

Ascinin^® Anti-Skins from Borchers are designed to be free of oximes and provide optimal performance in alkyd coatings. Performance benefits include:

• Excellent skin prevention
• Improved storage stability
• Minimal effect on dry times

To further improve performance and future-proof against other regulatory concerns, Ascinin^® Anti-Skins can be used with Borchi^® OXY-Coat and Borchi^® Dragon (including Borchi® Dragon Low VOC) high-performance catalysts. These drying solutions are designed to be free of cobalt, which has also faced regulatory concerns.

In the EU, cobalt received a harmonized classification including Carcinogen 1B through the EU’s CLP Regulation. In the United States, the EPA is conducting an assessment of cobalt and cobalt compounds.

When used together in alkyd formulations, Ascinin^® anti-skins and Borchi^® high-performance catalysts can provide fast dry times and reduced yellowing.

In order to properly reformulate your alkyd formulations with Ascinin^® anti-skins and Borchi^® high-performance catalysts, it is important to conduct a ladder study to determine the right solutions for your formulations.

Summary & Conclusion

Regulations are an ever-evolving concern for coating formulators. Staying ahead of oxime regulatory trends can help you reduce the impact from potential labeling requirements down the line.

Ascinin^® oxime-free anti-skins are optimal oxime alternatives for delivering excellent skin prevention. When used with Borchi^® high-performance catalysts, other performance benefits like dry times and yellowing reduction can be improved while also reducing impact from potential cobalt regulatory requirements.

To request samples or for more information on oxime-free anti-skins, please contact our team.