Abstract: A base fluid for hydraulic or metal working fluids comprises the esterification product having a hydroxyl number below 15 and an acid number below 10 of polymerized fatty acids and a monohydric alkoxylated alcohol, selected from (a) straight or branched chain saturated monohydric C.sub.1 -C.sub.24 alcohols, alkoxylated with 2-25 moles of C.sub.2 -C.sub.5 alkylene oxide and (b) alkoxy poly(alkylene) glycol etherified with C.sub.1 -C.sub.4 aliphatic monohydric alcohol and which is alkoxylated with 2-25 moles of C.sub.2 -C.sub.5 alkylene oxide, optionally the alcohol component also comprises (c) a straight or branched chain C.sub.1 -C.sub.24 aliphatic monohydric alcohol. The acid number of the crude ester is preferably reduced by reacting it with a glycidyl ester of a C.sub.5 -C.sub.22 aliphatic monocarboxylic acid, preferably a C.sub.6 -C.sub.12 branched chain, aliphatic monocarboxylic acid.

Abstract: A base fluid for metal working fluids comprises a stoichiometrically neutral salt of the partial esterification product having an acid number of 10-120, preferably 20-100 of polymerized fatty acids and a monohydric alkoxylated alcohol, selected from (a) straight or branched chain saturated monohydric C.sub.1 -C.sub.24 alcohols, alkoxylated with 2-25 moles of C.sub.2 -C.sub.5 alkylene oxide, (b) alkoxy poly(alkylene) glycol etherified with C.sub.1 -C.sub.4 aliphatic monohydric alcohol and which is alkoxylated with 2-25 moles of C.sub.2 -C.sub.5 alkylene oxide, (c) an aliphatic, straight or branched chain, saturated or unsaturated C.sub.1 -C.sub.24 monohydric alcohol, and mixtures thereof, which partial ester is converted into a stoichiometrically neutral salt by neutralizing it by ammonium hydroxide, or an alkali metal hydroxide or an alkyl amine or an alkanol amine. Also the novel stoichiometrically neutral alkali metal and alkanol amine salts of the partial esters have been claimed.