New Generation of REACH Compliant Ketamine Epoxy Curing Agents

Here at Alpine, we like to keep you informed of trending news in the paint and coatings industry. Gaining massive attention and all the rage is a new generation of ketamine epoxy hardeners. These curing agents are outperforming their analogous predecessors, and offering a unique combination of long pot-life, reduced hazard and fast thin-film cure speeds.

Traditionally, ethylene amines have been used as epoxy curing agents and can cross-link epoxy resins to form an infusible mass. However, their poor compatibility with conventional aromatic epoxy, inherent toxicological properties and low active hydrogen equivalent weights with subsequent low stoichiometric loading levels negates their use in modern formulated systems.

Many modification techniques are employed to enhance their performance, including reaction with carboxylic acids to generate amido-amine and polyamides, mannich bases, association salts, adduction, and for applications requiring high latency and fast thin film cure, ketamines.

Reversible Reaction

Ketamines are formed through the dehydration of a primary amine group with a ketone. A former industry standard ketamine was withdrawn due to REACH (Registration, Evaluation, Authorization and Restriction of Chemicals) restrictions. This withdrawal and the resultant void in the marketplace led to Bitrez recently developing a new range of REACH-compliant ketamines to satisfy the market demand. In addition to generating REACH-compliant products, it was opportune to rectify some of the other less-favorable characteristics and refine the products while maintaining the desirable pot-life/reactivity features associated with this class of curing agent. The new series of ketamines are offered as solvent cut or solvent-free materials, although all of them liberate some solvent during the hydrolysis process.

Concern over their toxicity and the costs attributed to REACH registration of each new ketamine species essentially led to the withdrawal of these conventional ketamines from circulation in Europe.

New Ketamine Grades

The new series of ketamine grades was developed to be REACH compliant and available for use in Europe. Additionally, improvements in the following properties were achieved:

• Reduced free amine in supply product. New ketamine label requirements are now available.

• Reduced free amine during application (when hydrolyzed). The new ketamine curing agents have low-supply free amine levels and low free amine levels following hydration, so they remain more consistent in terms of the hazards associated with corrosive amines.

• Improved compatibility. Through reaction with atmospheric humidity, this new generation of ketamine curing agents is less prone to the problems associated with humidity during cure.

• Improved surface appearance. The new generation of ketamine grades offer enhanced compatibility and vary in terms of their surface appearance from a moderate improvement to the surface film to a significant advance based on selected grades from within the range. The new ketamine grades are offered in several supply forms with some high solid-content grades diluted with ketone and/or aromatic solvents, or supplied free from any supplementary solvent – meaning they are supplied solvent free but acknowledging the solvent inherently generated following hydration.

• Maintain pot-life and cure properties. The new generation of ketamine curing agents offers significant improvement of working time/pot-life while maintaining desirable high thin-film reactivity. Alteration and extension to pot-life is the main design driver for this generic product group, and the new ketamines satisfy that particular aspect as expected.

The new generation of ketamines warrant all the fanfare as they are REACH compliant and also outperform their conventional counterparts both during and after cure. Additionally, they offer both long pot-life and reduced hazard, making them the ideal curing agents for the paint and coatings industry.

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(Adapted from PCI article https://www.pcimag.com/articles/106938-a-new-generation-of-reach-compliant-ketamine-epoxy-curing-agents)