Base fluid

A base fluid for metal working fluids comprising a stoichiometrically neutral salt of the esterification product, obtained by partial esterification of:

• (a) polymerized unsaturated C.sub.12 -C.sub.24 fatty acid, selected from the group consisting of dimer acid, trimer acid, hydrogenated dimer acid, hydrogenated trimer acid, and mixtures thereof,
• (b) a monohydric alkoxylated alcohol selected from the group consisting of:
• (1) straight or branched chain, saturated monohydric alcohols having from 1 to 24 carbon atoms, which are alkoxylated with from 2 to 25 moles of a C.sub.2 -C.sub.5 alkylene oxide, and
• (2) alkoxy polyalkylene glycols in which one of the two terminal hydroxyl groups is etherified with a C.sub.1 -C.sub.4 aliphatic monohydric alcohol and which is alkoxylated with from 2 to 25 moles of a C.sub.2 -C.sub.5 alkylene oxide, and mixtures of (1) and (2), and optionally,
• (c) an aliphatic, straight or branched chain, saturated or unsaturated monohydric alcohol, having from 1 to 24 carbon atoms,
• until a partial ester is obtained, having an acid number of from 10 to 120, after which said partial ester is:
• (d) converted into a stoichiometrically neutral salt by means of a neutralizing agent, selected from the group consisting of ammonium hydroxide, the alkali metal hydroxides, the alkyl amines, the alkanol amines, and mixtures thereof.