RECLASSIFICATION OF 1-HYDROXYCYCLOHEXYL-PHENYL KETONE AND PATH FORWARD
September 1rst, 2025, Waalwijk, The Netherlands
Introduction
1-Hydroxycyclohexyl-phenyl ketone (CAS no. 947-19-3), commercially known as Omnirad® 184 and Omnirad® 184D in the iGM Resins portfolio, is a widely used photoinitiator in the energy curing industry, valued for its consistent performance across a wide range of applications. The product is registered in Europe by IGM Resins under Annex IX. The European Chemicals Agency (ECHA) required IGM Resins, as lead registrant, to conduct additional in vivo genotoxicity testing (OECD 414). The new toxicological results show that the product is a reprotoxic substance. As a result, Omnirad® 184 is now reclassified with immediate effect as Reproductive Toxicity Category 1B under EU REACH regulations. This regulatory shift introduces new compliance obligations for formulators and manufacturers, especially in Europe and North America. This change marks a significant transformation in the handling and usage of this product across the industry.
Our tested solutions
While a universal substitute may not suit every formulation, we recognize the importance of offering options that align with both performance needs and regulatory compliance. Thanks to our constant innovation and ongoing development of photoinitiators, iGM Resins is well positioned to offer a broad range of solutions, from standard products to advanced, high-performance alternatives.
The closest alternative is Omnirad® 1173. This is also a low molecular weight photoinitiator with good reactivity under Hg-lamp, low yellowing and excellent formulation compatibility. Its liquid nature makes it easy to handle. Its higher evaporation rate could lead to easier dirty collection on the lamps and higher perceived odor when on the press. Produced at our Mortara, Italy site, it offers reduced delivery times for customers in Europe and a complete Life Cycle Analysis.
For more sensitive applications, and if the highest reactivity and lowest yellowing level are required, Omnirad® 601 is an excellent choice. This solid photoinitiator is especially suited where very low odor is required. Its solubility is more limited than Omnirad® 184. Omnirad® 601 combines a higher molecular weight with a higher functionality, leading to significantly lower odor and emissions in general.
An intermediate option between Omnirad® 1173 and Omnirad® 601 is our economical solution Omnirad® 2509. This is a liquid photoinitiator, bringing good surface cure, low yellowing and good formulation stability for both inks and clear varnishes with an affordable cost in use too — a perfect combination of performance and economics.
Omnirad® 184 is an efficient, non-yellowing photoinitiator, used to initiate photopolymerization of (meth)acrylate monomers and oligomers under a wide variety of conditions. Chemically speaking, Omnirad® 184 belongs to the class of alpha hydroxy ketones (AHK), which are Type I photoinitiators. IGM Resins is offering a range of mono- and di-functional AHK products. The complete list can be found in our product brochure.
Tailored Support and Technical Expertise
Our technical experts are ready to support customers in identifying the most suitable alternatives to Omnirad® 184. We work case by case, ensuring each application — whether in coatings, inks, or adhesives — receives a tailored approach. This includes formulation guidance, performance testing, and regulatory advice to ensure minimal disruption during the transition.
Conclusion
The reclassification of 1-Hydroxycyclohexyl-phenyl ketone reinforces the need for safer and more sustainable solutions. iGM Resins remains committed to guiding our partners through this change with reliable alternatives, expert support, and a continued focus on regulatory alignment and product performance.
For more information or support, please contact your local iGM Resins representative or go to https://igmresins.com/en/contact