Synthesis and Optimization of Oil Soluble FKM Seal Compatible Copper Passivators

Copper and its alloys are widely utilized in automotive and industrial applications because of its frictional properties and high ductility. Unfortunately, a number of additives used in these industries can be corrosive to copper. To mitigate this, copper passivators are often coupled with these additives. While there are effective copper passivators on the market, many are limited in application due to limited solubility in oil, being detrimental to commonly utilized fluoroelastomer (FKM) seals, and being reactive with numerous other components. Additionally, many of these passivators are quite costly. Due to this, we sought to develop a cost-effective and atom economical copper passivator that was both oil soluble and FKM seal compatible. Sixteen triazole derivatives were synthesized and tested for copper passivation, demulsibiltiy, and solubility. Derivatives were synthesized by alkylating the nucleophilic nitrogen on benzotriazole with a branched alkyl group. All oxygen based groups were used to minimize the presence of reactive amines, theoretically reducing FKM seal compatibility issues. Optimization of this synthesis was carried out to maximize atom economy and minimize cost. Asymmetrically branched benzotriazole derivatives provided the most favorable conversions and the best solubility. Derivatives which utilized shorter aldehydes and longer, unbranched alcohols produced the smallest quantity of by-product. Specific limitations regarding the alkyl chain length of both the alcohol and aldehyde were also identified. The cheapest derivative synthesized was estimated to cost less than 34% of that of Irgamet 39, an effective and commonly utilized copper passivator. The purity of these derivates, after optimized reaction parameters were implemented, ranged from 90-94%. These reaction parameters also halved the reaction time necessary for comparable product conversions. Optimized derivatives were determined to be completely stable, remaining within ± 3% of the derivative’s product purity at the time of synthesis. Currently, we are running static seal testing against bisphenol AF cured Type II fluoroelastomers to assess each derivatives’ seal compatibility. In the future we aim to determine mechanism behind FKM seal degradation.