Polyol ester lubricants, especially those compatible with mineral oils, for refrigerating compressors operating at high temperatures

A process comprising the steps of (I) draining a refrigerant heat transfer fluid made of molecules containing at least one chlorine atom per molecule and mineral oil lubricant dissolved therein from an unflushable compressor and associated piping in a vehicle air conditioner leaving a mineral oil residue and (II) replacing the refrigerant heat transfer fluid in all parts of the vehicle air conditioner designed to contain such fluid with a replacement heat transfer fluid consisting essentially of 1,1,1,2-tetrafluoroethane and a composition of matter suitable for serving as a lubricant or lubricant base stock, said composition being capable of forming a soluble clear solution with mineral oil residue in a weight ratio of the mineral oil to the composition of at least 25:100 and forming a single phase with 1,1,1,2-tetrafluoroethane between −55° C. and +71° C., said composition being a liquid with a viscosity between about 51 and about 145 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 derived from PE 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 10% of the acyl groups in the mixture are acyl groups of i-C5 acid;

• (b) the ratio of the percent of acyl groups in the mixture that contain 8 or more carbon atoms and are unbranched to the percent 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 percent of acyl groups in the mixture that contain at least nine carbon atoms, whether branched or not, is not greater than about 67;
• (e) a total of at least about 29% of the acyl groups in the mixture are monobasic acids selected from the group consisting of acids with eight carbon atoms and at least one alkyl substituent branch per molecule of acid, acids with nine carbon atoms and at least one alkyl substituent branch per molecule of acid and mixtures thereof;
• (f) at least about 5.1% but not more than about 10% of the acyl groups in the ester mixture are from adipic acid;
• and (g) the ratio of the percent of acyl groups with 8 or 9 carbon atoms to the percent of acyl groups with 5 carbon atoms is at least about 0.63:1.00.

A process comprising the steps of (I) draining a refrigerant heat transfer fluid made of molecules containing at least one chlorine atom per molecule and mineral oil lubricant dissolved therein from an unflushable compressor and associated piping in a vehicle air conditioner and leaving a mineral oil residue of at least 25% by weight of the mineral oil before draining (II) replacing the refrigerant heat transfer fluid in all parts of the vehicle air conditioner designed to contain such fluid with a replacement heat transfer fluid consisting essentially of 1,1,1,2-tetrafluoroethane and a composition of matter suitable for serving as a lubricant or lubricant base stock, said composition being capable of forming a soluble clear solution with mineral oil residue in a weight ratio of mineral oil to composition of at least 25:100, and forming a single phase with 1,1,1,2-tetrafluoroethane between −55° C. and +71° C., said composition being a liquid with a viscosity between about 64 and about 134 centistokes at 40° C. and consisting essentially of a mixture of polyol ester molecules in which at least about 95% of the alcohol moieties are derived from PE and at least about 95% 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 14% of the acyl groups in the mixture are acyl groups of i-C5 acid;

• (b) the ratio of the percent of acyl groups in the mixture that contain 8 or more carbon atoms and are unbranched to the percent of acyl groups in the mixture that are both branched and contain not more than six carbon atoms is not greater than about 1.21:
• (c) the percent of acyl groups in the mixture that contain at least nine carbon atoms, whether branched or not, is not greater than about 67;
• (d) not more than 1% of the acyl groups in the esters contain more than two carboxyl groups each;
• (e) a total of at least about 35% of the acyl groups in the mixture are from 3,5,5-trimethylhexanoic acid;
• (f) at least about 5.5% but not more than about 9.0% of the acyl groups in the ester mixture are from adipic acid;
• and (g) the ratio of the percent of acyl groups with 9 carbon atoms to the percent of acyl groups with 5 carbon atoms is at least about 0.69:1.00.