Patent ID: 7387746

Claim:
A method of producing an ester for a refrigeration lubricant, comprising: reacting a mixed alcohol and a mixed monocarboxylic acid, and obtaining the mixed ester that has a hydroxyl value of 5.0 mgKOH/g or less and an acid value of 0.05 mgKOH/g or less, wherein the mixed alcohol consists of 65 to 99.95 mol % of pentaerythritol and 0.05 to 35 mol % of dipentaerythritol, the mixed monocarboxylic acid consists of 25 to 55 mol % of monocarboxylic acid having 5 to 8 carbon atoms and 45 to 75 mol % of isononanoic acid, and the mixed monocarboxylic acid and the mixed alcohol satisfy the following relation: 1.09 ⁢ ≤ { ∑ ( A × B ) ⁢ - ( C × D ) } E ⁢ ≤ 1.33 ( 1 ) A: number of carbon atoms of main chain of a monocarboxylic acid in the mixed monocarboxylic acid B: molar fraction of the monocarboxylic acid of item “A” C: number of carbon atoms of the longest side chain of branched monocarboxylic acids in the mixed monocarboxylic acid D: molar fraction of monocarboxylic acid having the longest side chain E: average number of hydroxyl groups of each alcohol in the mixed alcohol.