The presently claimed invention is directed to novel polyesters which are obtainable by reacting a mixture comprising at least one C8-C20 Guerbet alcohol, at least one aliphatic or cycloaliphatic dicarboxylic acid and at least one polyol with a hydroxyl functionality in the range of ?2 to ?6 and the use of these polyesters as a component of lubricating oil compositions.

The present invention provides a working fluid composition for a refrigerating machine containing: a refrigerating machine oil containing, as a base oil, a mixed ester of (A) a complex ester synthesized from a polyhydric alcohol such as neopentyl glycol, a polybasic acid having 6 to 12 carbon atoms, a monohydric alcohol having 4 to 18 carbon atoms and the like, and (B) a polyol ester synthesized from a polyhydric alcohol such as neopentyl glycol and a monocarboxylic fatty acid having 4 to 18 carbon atoms, in a mass ratio of (A) the complex ester/(B) the polyol ester of 5/95 to 95/5; and a refrigerant such as carbon dioxide.

Provided are a lubricant composition in which low friction and low abrasion are compatible in various temperatures and loads, and a manufacturing method of a lubricant composition. A lubricant composition of the present invention contains at least trivalent or more polyol a1; a mixture b1 of at least one of a polymerization reaction mixture of an unsaturated fatty acid having 18 to 22 carbon atoms which contains at least 75 mass % of a divalent carboxylic acid having 36 to 44 carbon atoms or a mixture obtained by performing hydrogenation with respect to the polymerization reaction mixture; and composite ester A containing polyester in which monool c1 represented by General Formula (1) described below is condensed, in which a feed ratio of the number of moles of a hydroxyl group of a1/the number of moles of a carboxylic acid of b1/the number of moles of a hydroxyl group of c1 is 1/1.5 to 2.0/0.7 to 1.5, and a content of the composite ester A is 0.1 to 5 mass % with respect to the total mass of the lubricant composition.

ROHGeneral Formula (1):

The present invention provides a working fluid composition for a refrigerating machine containing: a refrigerating machine oil containing, as a base oil, a mixed ester of (A) a complex ester synthesized from a polyhydric alcohol such as neopentyl glycol, a polybasic acid having 6 to 12 carbon atoms, a monohydric alcohol having 4 to 18 carbon atoms and the like, and (B) a polyol ester synthesized from a polyhydric alcohol such as neopentyl glycol and a monocarboxylic fatty acid having 4 to 18 carbon atoms, in a mass ratio of (A) the complex ester/(B) the polyol ester of 5/95 to 95/5; and a refrigerant such as carbon dioxide.