Desirability of adding mixtures of phenols and amine antioxidants to mineral oils

Abstract

Studies have been made on the effectiveness of amine and phenolic inhibitors, including mixtures of them, in MS-8 mineral oil under conditions of high-temperature catalytic oxidation. It is found thatmineral oils containing simultaneously amine and phenolic inhibitors have oxidation rates that are determined only by the content of the amine inhibitor, while the phenolic inhibitor partially determines the secondary oxidation-destruction processes.It is usually considered that joint use of amine (A) and phenolic (P) antioxidants results in synergism of their properties and thus reduces the oxidation of the oil better than does separate use. Consequently, many lubricating oils contain antioxidants of both types, e.g., MS-8p mineral aviation oil and semisynthetic Petrim oil for gas-turbine engines (GTE). Many firms specializing in additives for lubricating oils such as the Swiss firm of Ciba provide ready-made packages of additives containing mixtures of amine and phenolic antioxidants (Irganox L64, Irganox L150, and so on).There is a study [1] of estimating the performance of various inhibitors under conditions of high-temperature catalytic oxidation (HCO) for hydrocarbon oils. Some interest attaches to the interaction of amine and phenolic antioxidants as regards the oxidation rate of mineral oil such as MS-8p under conditions of HCO, since those conditions most closely correspond to the actual working conditions of oils in GTE lubrication.As the oxidation rate we took the constant quantity obtained on testing these in the presence of a catalyst at high temperatures, which is virtually equal to the amount of O C C = > in the oxidation products formed in a fixed time interval.Lubricating oil specimens were oxidized as described in [2]. The contents of oxidation products were determined by IR spectroscopy from the integral absorption area in the region of wavelengths 1645 -1825 cm -1 in the differential spectrum obtained by subtracting the IR spectrum of the unoxidized oil from the IR spectrum of the oxidized oil. The performance of the oxidation inhibitors was estimated from the change in the amount of oxidation products formed in the oil after adding to the oil the inhibitor at various concentrations. The effectiveness coefficient K ef can be determined for each inhibitor concentration from

Synthesis and evaluation of ashless detergent/dispersant additives for lubricating engine oil

“…All these compounds form the solid asphaltic materials. For this reason, the addition of antioxidants is necessary to all lubricating oils to minimize the formation of such compounds (Fangkun et al, 2009;Jing et al, 2008), as the role of antioxidants is to protect the type of base oil by either scavenging (alkyl and peroxy) radicals or decomposing hydroperoxides into stable products (Kyunghyun, 2010;Mukhin et al, 2009). The present work aims to prepare different ashless detergent/dispersant additives based on propylene oxide (PO) and evaluation of the prepared compounds such as antioxidant and detergent/dispersant for lubricating oil.…”