Polyol ester lubricants for hermetically sealed refrigerating compressors

A composition of matter suitable for serving as a lubricant or lubricant base stock, said composition being a liquid with a viscosity between about 22.5 and about 44 centistokes at 40° C. and consisting essentially of a mixture of polyol ester molecules in which at least about 92% of the alcohol moieties are selected from the group consisting of the alcohol moieties derived from TMP, DTMP, PE, and DPE and at least about 92% of the acyl groups are selected from the group consisting of the acyl groups of all the straight and branched chain monobasic and dibasic carboxylic acids with from four to twelve carbon atoms each, said alcohol moieties and acyl groups being further selected subject to the constraints that (a) a total of at least about 3% of the acyl groups in the mixture are acyl groups of i-C5 acid;

• (b) the ratio of the % of acyl groups in the mixture that contain 8 or more carbon atoms and are unbranched to the % of acyl groups in the mixture that are both branched and contain not more than six carbon atoms is not greater than about 1.56;
• (c) the % of acyl groups in the mixture that contain at least nine carbon atoms, whether branched or not, is not greater than about 81;
• and (d) not more than about 2% of the acyl groups in the ester mixture are part of acid molecules with more than two carboxyl groups each;
• and either (d)(1) a total of at least about 20% of the acid molecules in the mixture are one of the trimethylhexanoic acids;
• at least about 90% of the alcohol moieties in the esters are those of PE;
• and not more than about 7.5% of the acyl groups in the ester mixture are dibasic;
• or (d)(2) at least about 2.0%, but not more than about 13%, of the acyl groups in the ester mixture are dibasic;
• and a total of at least about 82% of the monobasic acyl groups in the acid mixture have either five or six carbon atoms each.