Esters of methylolcyclohexanols/ones as synthetic base lubricants

Abstract

Purpose -The purpose of this paper is to examine the preparation of asymmetric mixed esters of methylolcyclohexanols in order to decrease the pour point and increase the thermal stability of base oils. Design/methodology/approach -The aldol condensation reaction of cyclohexanone with paraformaldehyde is modified to give mixture of alicyclic polyols. The obtained mixture was subsequently esterified by different pure and mixed linear mono carboxylic acids to give asymmetric mixture of esters of methylolcyclohexanols/ones. Findings -The obtained base lubricants showed better wear preventive characteristcs (four-ball rolling contact test) compared with previously reported and commercially available ester base lubricants. Research limitations/implications -Because of the complexity of the obtained mixture, it was impossible to study the structure and composition of the obtained products by modern techniques such as high field NMR spectroscopy. Practical implications -The obtained materials are slightly acidic and should be neutralized before use or formulation. Originality/value -The paper presents a new process for obtaining synthetic ester base lubricants from mixed polyols of neo structure, which was obtained from aldol condensation reaction of cyclohexanone and paraformaldehyde, and linear aliphatic monocarboxylic acids. The key step in this process is modifying the reaction condition for obtaining mixture of polyols, and not pure 2,2,6,6-tetramethylolcyclohexanol. This allows one to obtain asymmetrical and complex mixture of esterification products, which is favored in the production of synthetic ester base stocks, having excellent viscosity-temperature properties, decreased pour point, and increased thermal stability. The synthesized ester base lubricants also show excellent viscosity-temperature properties compared with ester base lubricants of the same family.