CA1098892A

CA1098892A - Refrigeration or heat pump apparatus containing stable wear-inhibiting working fluid

Info

Publication number: CA1098892A
Application number: CA294,361A
Authority: CA
Inventors: Sven A. Olund
Original assignee: Chevron Research and Technology Co
Current assignee: Chevron USA Inc
Priority date: 1977-02-14
Filing date: 1978-01-05
Publication date: 1981-04-07
Also published as: FR2380514A1; BR7800843A; JPS53104608A; GB1594190A; GB1594189A; AR226277A1; DE2805604A1; IT7820216A0; IT1092690B

Abstract

ABSTRACT OF THE DISCLOSURE
Refrigeration or heat pump apparatus containing working fluid consisting essentially of refrigerant and lubricant, said refrigerant being a halo-substituted hydrocarbon of 1 to 3 carbon atoms and preferably at least 40% by weight fluorine, and said lubricant being m mineral lubricating oil, poly-alpha-olefin lubricating oil, synthetic alkylbenzene lubricating oil or mixtures thereof containing the combination of higher fatty acid and arylphosphate in a minor amount, sufficient to improve the wear-inhibiting properties of said lubricant and to improve the resistance of said lubricant to decomposition.

Description

BACKGROUND OF THE I~1VENTION
_______________._ __ ___ _

2 Field _f th~ I_vention

3 This invention relates ~o refrigeration or heat pump

4 apparatus containin~7 stable wear-inhibiting working flu- d consisting essentiaily of a refrigerant and a chemically inert 6 wax-fre~ lubricant. More particularly, the invention concerns 7 such apparatus and ~orking fluids ln which the reriyerart is a 8 halo~substituted hydrocarbon and the lubricant contains the 9 combina~ion of high~r fatty acid and arylphosphate to improve w~ar-inhibiting properties and to improve resistance to 11 decomposition.
1 2 p r ~ or ArL
13 Mineral lubricating oils have been developed containing 14 the combination of triarylphosphate such as tricresylphosphate and higher fatty acids such as oleic acld in order to inprove 16 lubricating properties~ See 7 ~or instanceg U.S. Patents 17 2,241,531~ 2~,431,008 and 2,730t499.
18 Refrigeration apparatuC and working fluids in such 19 apparatus have be~ developed in which Inineral lubricating oil is used as lubrican~ and various ad2itives such as ethylene diamlne 21 tetraacetic acid, or a salt +hereof and nitrous oxide are used to 22 inhibit chemical instability of the cil-refrigerant mixture.
23 See, for instance, U.S. Patents 3r532~631 and 3t812,040, the 24 forner of which also notes that tricrecylphosphate additive accelerates oil-refrigerant reac~ion.
26 Refrigeration apparatus and working fluids in such 27 apparatus have also been deY~loped in whlch synth~tic alkyl-28 benzene lubricating oil is used as lubricant, but it appears that 29 ~ear inhibiting and stabilizing additives for such fluids have not been suggested. See, for instance, U.S. Palents 3,092,891r 31 3,169,923 and 3,642,634.
f~

~e39~

THE INVENTION
In accordance with the present invention, an improved refrigera-tion or heat pump apparatus is provided in which said apparatus contains a working fluid consisting essentially of a refrigerant and a chemically inert, wax-free lubricant, said refrigerant being a halo-substituted hydrocarbon having from 1 to 3 carbon atoms and said lubricant being an oil of lubricating vis-cosity selected from the group consisting of mineral lubricating oil, poly-alpha-olefin lubricating oil alkylbenzene lubricating oil and mixtures there-of, the improvement comprising incorporating in said oil the combination of higher fa-tty acid and arylphospha-te in minor amounts sufficient to improve the wear-inhibiting properties of said lubricant and to improve -the resis-tance of said lubricant to decomposition.
The refrigeration or heat pump apparatus and worl~ing fluid of the invention exhibit wear-inhibiting properties and resistance -to decomposition due to the use of the particular combination of higher fatty acid and aryl-phosphate.
EMBODIMENT
The refrigerant is a fluorinated, chlorinated methane, ethane or propane of the Freon* type. The more suitable fluorinated halogenated hydro-carbon refrigerants contain at least about 40% by weight of fluorine. Ex-amples of satisfactory compounds are:

difluoromonochloromethane, difluorodichloromethane, monofluoro-trichloromethane, 1,2-dichloro-1,1,2~2-tetrafluoromethane, l,l-difluoroethane, trifluorochloromethane, pentafluorobromoethane, and mixtures thereof.
The chemically inert, wax-free lubricant is a typical refrigeration oil. Such refrigeration oils are classified on the ~Trademark - 3 -~L~98~9Z

basis of viscosity a-t lOnF~. Grades having normal viscosities of 80, 100, 150, 200, 300 and 500 SUS (Saybolt universal seconds) at 100 F are provided.
Most refrigeration equipment requires the grades covering the range from 150 to 500 SUS.
The mineral lubricating oil may be any suitable refined hydrocarbon oil of lubricating viscosity known for use as "refrigera-tion oils"~ Such oils include paraffinic or na-phthenic base oils having viscosities in -the range of from about 50 to 2000 SUS at 100F. Commercially available oils of this type include "Suniso" *3GS, white oil and "Capella" ~B oil.
The polyalpha-olefin lubricating oils are hydrogenated oligomers of alpha-olefins having about 8 to 12, preferably 10, carbon a-toms. The final oligomer may have fr~m 20 to 100 carbon atoms. The preferred polyalpha-ole:fin lubricants are those having a viscosity of 50 to 2000 SUS at 100 F. These are the compounds having about 30 to 60 carbon atoms per molecule.
The alkylbenzene lubricating oils are superior to conventional oils in compatability with the refrigerant and in thermal stability, and are thus preferred. Such oils consist essentially of alkylbenzenes having one or more side chains of 1 to 25 carbon atoms and containing a total of from 10 to 25 carbon atoms in the alkyl groups. Suitable alkylbenzene refrigeration oils, as in the case of the mineral lubricating oils, have viscosities in the range of from about 50 to 2000 SUS at 100 F.
The alkylbenzene lubricants are particularly suitable by reason of their superior compatibility with the high-fluorine-content halogenated hydro-carbons containing at least 40% by weight of fluorine.
The alkyl group of the more preferred alkylbenzenes in the composi-tions of the invention must be branched, having a-t least one branch per every five, preferably four, carbon atoms.

~Trademarks - 4 -.~c ., .

1 The most preerrPd alkyl group ic one having one branch per e~ery 2 three carbon atoms and is prepared ~y Folymerization of 3 propylene. ~n the alkyl chaln, branching is determined by 4 dividing +he number of carbon atcms ccnnected to +hree other carbon atoms plus two times the numher of carbon atoms connected 6 to four other carbon atoms by the total number of carbon atoms in 7 the alkyl group.
8 Alkylbenzenes for this use are prepared ~y ~lkylating 9 benzena with an alkylating agent in the presence of z catalyst.
Typical alkylating ager.ts are the branched-chain olefins or 11 ~ranched-chain halides, preLerably chlorides. The preferred 12 method of preparation is by the HF-catalyzed reaction of benzene 13 with a branchsd-chain olefin.
14 Satisfactory alkylbenzenes have an average molecular weight in the range of 300 to 470 and can be prepared from the 16 following branched-chain olefins:
17 hexapropylene;
18 pentaisobutyl~ne;
19 a mixed Cl8-z8 polypropylene-polyisobutylQne blend;
oligomers of Propylene and the 4 to 9 carbon atom 1-olefins 21 in a mol ratio greater than 75~25, res~ectively;
22 4,6-dime~hyl-8 isobutyl-3-dcdecene;
23 2,4-dimethyl-5-isobuty~-5 dodecene;
24 4,6,8,12-tetramethyl-10-ethyl-9-tridecene;
2,4,6,8v10-pentamethyl-2-tridecene;
26 2,4,6,8,10,12-hexamethyl-2-~entad~cene;
27 4,6/8,10-tetram2thyl-2-hexadecena;
28 4,6,8,10,12~14-hexamethyl-2-nonadacen~;
29 2r4,6,8,10912-hexam~thyl-12-eiccsene;
2,4,6,6,8,10,10,12-octamethyl-2-tridecene, etc.
31 The Freferred olefin is a blend of polypropylene ha~ing from 18 32 to 24 carbor atoms. The preferred alkylbenzenes have a molecular 33 weight in the range of 325 to 41~.
34 The alkylbenzene mixtures of this irvention have viscositi~s in the range of 80 to 800 SUS (measured a+ 100F), 36 prefarably in the range of 150 tc 500~ ~hree vlscositv grades of 37 lubricants 2L e con~entionally supplied for use in refrigeration ~1i9~

1 apparatus: l50 SUS, 300 SUS and 500 SUs. The mixtures of 2 alkylbenzenes herein described may be tailored to any or.e of 3 these three gradest but the 150 SUS grade is preferred and is 4 ob ai~ed from branched-chain alkylbenzenes produced by HF
alkylation of benzene with mixed pclypropylenes hav~ng an average 6 molecular weight in the range of 330 to 350. The alkylbonzenes 7 are primarily monosubstituted alkylbenzene, but may con~ain minor 8 proportions of polyalkylaryl hydrocarbons within the aforesaid 9 molecular weight ranges. The alkylbenzenes preferably are dried to contain not more than 30 part~ per million of water. Such 11 drying may be accomplished by conventicnal means such as blowing 12 with an inert gas, including airr nitrogen, helium, e c., and may 13 be accomplished in connection with other treatment -- for 14 examFle, clay treatment, preferably acid-trea~ed clay, used to remove various impurities.
1~ In the refrigeration or heat pump apparatus as a whole, 17 there will be from 10 to 100 parts of refrigerant per part of 18 lubricant. However, in the evaporator, the relative amount~ of 19 refrigerant and lubricant undergc a large change as ~he refrigerant is vapori~ed. ConseguQntly, it is hore that 21 incompatibility becomes a problem. It has been found that 22 maximum incompatibility occurs at about 10~ to 20~ by weight of 23 lubrican~. (Ses U.S. Paten' 3,092,981, Figure 3; U.S. ~atent 24 3,169,928, Figure 1)~ As a result, potential lubricants are usually tested for compatibility at concent~ations in this range 26 at ever-lower temperatures. Two measurements can be made: (1) 27 the temperature at which separation first occurs, and ~2~ the 28 quantity present in the oil-rich phase at successively lower 29 temperaturos. 8Oth values are important; a high temper~ture, voluminous separation would be wholly inoperative, whereas a 31 relatively high~.empeIature separation of a minute amoun of oil ~g8~

1 which did not change upon going to even lower temperatures may be 2 operative. In general; the s~paration of more ~han 5 volume 3 percent oil phase is considered ~nacceptabl2.
4 The highe~ fatty acld ~mployed in the oil of S lubricating viscosity is a monocarboxylic aliphatic acid of at 6 least 8 carbon atoms~ ~oth saturated and unsaturated acids may 7 be used. ~rom the standpoint of compatibility, the fatty acils 8 prsferably contain from about 10 to 20 carbon atoms. Examples of 9 suitable acids include caprylic aci~, p~largonlc acld, undecylic acid, lauric acid, myristic acid~ pal~itic acid~ stearic acid~
11 oleic acid, linoleic acid, etc. Oleic acid is preferred. Minor 12 amounts of fatty acid are sufficient tc improve the wear-13 inhibiting propsrtiss of the lubricant and to improve Ihe 14 resistance of said lubricant to decomposltion, usually from abou~
0.01% to 0.5~ based on the weight of the lubricant.
16 The aryl phosphat~ employed in the oil of lubricating 17 viscosity is a hydrocarbyl phosphate ester having at least one 18 aryl group, preferably a mononoclear aryl group. Such esters 19 contaln from about 10 to 25 carbons in the hydroca.bon portion.
Acid as well as neutral phosphat~s may be used, such as dlphenyl-21 phosphate. ExamplPs of neu~ral aryl phosphates, which are the 22 preferred phospha~es, incluae butyldiphenylphosphate, dibutyl-23 naphthylphosphate, and triarylphcsphates such as triphenyl-24 phosphate, and tricresylFhosphat~. For present purposes, tricresylphosphate is preferred. Minor amounts of arylphosphate 26 are sufficient to improve thG wear-inhibiting properties of the 27 lubricant and to improve the resistance of said lubricant to 28 decomposition, usually from about 0.1~ to about 2.0% based on he 29 weight of the lubricant.
In addition to thP afore~entioned higher fatty acid and 31 aryl phosphate, the refrigeration lubricant of the working fluld B~

of the invention may contain additives of the types conventionally used.
These include viscosity improvers such as polybutene having viscosi-ties in the range of from about 3000 SUS to 1,000,000 SUS at 100F; foam inhibitors such as silicone polymers; metal deactivators such as alizarine, quinizarine, zinc dithiocarbamates, and mercaptobenzothiazole; oxida-tion in~ibitors such as dibutyl-p-cresol and scavengers for hydrogen chloride such as epoxides~
EXPE~IME~TAL
The following examples further illus-trate the improved refrigera-tion or heat pump apparatus and working fluid therefor according to the pres-ent invention. Unless otherwise indicated, -the proportions of compositions are on a weight basis.
Experiments were carried out to illustrate the lubricating-enhance-ment or wear-inhibiting properties of the lubricant compositions employed in the invention. The widely accepted Falex wear test procedures were carried out to show wear-reducing qualities of the lubricants. The Falex test, briefly described, consists of running a ro-tating steel journal against two stationary steel ~-blocks immersed in the lubricant sample. Load is supplied to the V-blocks and maintained by a rachet loading mechanism. Wear is deter-mined by measuring the weight loss of the journal after the test and by re-cording the number of teeth of the ratchet mechanism advanced to maintain loadconstant d~ring the prescribed time. The present tests were carried out in accordance with ASTM D-2670 except that the duration of the tests was 30 min-utes. The lubricant was alkylbenzene lubricant derived from the HF-catalyzed alkylation of benzene with polypropylene having a viscosity of about 150 SUS
at 100F. For the purposes of the test, the oil was saturated with Refriger-ant 12*, namely: dichlorodifluoromethane. In the ~Trademark - 8 -. ~ . .

~ 8~3~%

1 tests the load was increased to 200 pounds in 30 seconds, 2 maintained at 200 pounds for 30 ~econds, followed by an increase 3 in load at a 'ate of 200 pounds per minute until 400 or 600 4 pounds was reached~ ~he Falex ~ear test data are summarized in Table I.

7 Jaw Te~h 8 Load, T~mP.~_F _ Pickup ~ear, 9 N_.__ Additive Lb. Start* End ~ No. Mq.
1. None 400 85 194 10913 23~4 11 2 93 196 10314 32.
12 3 100 214 11426 34.6 13 4 0.5~ TCP 400 88 174 ~6 4 14.7 14 5 104 203 99 12 34.0 6 124 210 86 22 44~0 16 7 1% TCP 400 88 174 86 3 15.3 17 8 122 208 86 12 19.0 18 9 2% TCP 400 88 184 96 0 2.7 19 1Q 0.1~O Myristlc Acid 400 86 160 74 0 4.3 11 0.1% MA + 0.5~ TCP 85 150 65 0 0.8 21 12 0.1~. oleic Acid 400 87 166 79 5 4.0 22 13 0.1% OA ~ 0~5% TCP 85 156 71 0 0.4 23 14,15 0.1~ MA 600 Shaft broke after 4-5 minutes 24 16 0~1% MA ~ 0.5% TCP 92 180 88 6 4.1 17 0.2% MA ~ 0.5~0 TCP 90 179 89 4 4.8 26 18 0.1~ OA 600Shaft broke aFter 6 minutes 27 19 0.1~ OA + 0.5~ ~CP 95 180 85 5 4.8 28 20~21 2% TCP 600 Sha~t broke aftsr 19-20 minutes 29 *TemFerature after 400 (600) lb. jaw load was reached.
~CP = Tricresylphosphate 31 MA = Myristic Acid 32 OA = Oleic ACid 33 Th~ aboYe test data sho~ that the combination of higher 34 fatty âcid and arylphosphate in accordance with the present invention greatly improves the wear-inhibiting properties of the 36 lubricant~ Although the hlgher fatty acid and arylphosphate 37 individually provide improved wear-inhibiting properties~ a 38 synergistic effect is obtained by ~he combination of fa~ty acid g _ 8~

and arylphosphate which provides exceptional improvemen-t. It is significant that when the severity of the tests was increased by increasing the load from 400 to 600 pounds, failure occurred and the journal broke with samples con-taining fatty acids or tricresylphosphate alone, whereas wear was still low with the combination of fat-ty acid and tricresylphosphate, as shown by runs 16, 17 and 19.
Stability tests were also carried out to illustra-te the resistance of the lubricant to decomposition in a re-frigeration or heat pump working fluid. The stability tests were carried out in accordance with the so-called Elsey Test described in the ar-ticle entitled "A method of Evaluating Refrig-erator Oils" by Elsey et al published July 1952 in Refrigeration Engineering, Vol. 60, No. 7, page 737. In this test, R12* Refrigerant (dichlorodifluoro-methane) reacts with the hydrocarbon (HC) to form an equal amount of R22~-(chlorodifluoromethane) and HCl. The amount of R22 is readily determined by mass spectrometry in accordance with the method of Spauchus et al in the ar-ticle entitled "Reaction of Refrigerant 12 with Petroleum Oils", published 1961 in the ASHRAE Journal, Vol. 3 (2), page 65. The test mixture is heated for 14 days at 175 C in the presence of copper and steel. The results are expressed as the ratio of R22 to R12 (R22/R12) a-t the end of the test. The test oil again was aIkylben~ene lubricant having a viscosity of 150 SUS at 100F. The stability test results are summari~ed in Table II.

~raaema:r ks - 10 -~9~

TABLE II

CC12F2 -~ (HC)l -~ CHClF2 ~ ~ICl + (HC)2 Copper Additive R22/R12 Plating None o.ooo6 ~ormal 0.5% TCP + 0.1% MA 0.0005 Trace O.5% TCP ~ O.1% MA O.0007 Trace 2% TCP ~ 0.1% MA O. ooo8 Some 0.5% TCP + 0.1% OA 0.0002 None 0.5% TCP + 0.1% OA 0.0000 None 2% TCP ~ 0.1% OA 0. ooo8 Some (HC)l = Hydrocarbon bef'ore reac-tion (HC)2 = Hydrocarbon after reaction TCP = Tricresylphosphate MA = ~yristic Acid OA = Oleic Acid The above test data show that the formation of Refrigerant 22* by decomposition is reduced and copper plating is substantially eliminated wi-th the combination of higher fatty acid and triarylphosphate. This is surpris-ing since, as already noted, tricresylphosphate by itself has been reportedto be detrimental to stability.
In addition to the above tests, a typical mineral lubricating oil, namely: Suniso 3GS*, was evaluated in The Falex and Elsey Tests. The mineral lubricating oil alone sustained wear of 10.5 and 15.6 milligrams in the Falex Test, while with the combination of 0.1% myristic acid and 0.5~ tricresylphos-phate the wear was reduced to 1.2 milligrams. In the Elsey Test, the ratio R22/R12 for mineral lubricating oil was 0.003, while with the combination of 0.1% oleic acid and 0.5% tricresylphosphate -the R22/R12 ratio was reduced to 0.0005-Elsey Tests were also carried out on white oil (150 SUS) and onpolyalpha-olefin lubricating oil. ~ith white oil, the presence of 0.5% TCP
and 0.1% oleic acid reduced the R22/R12 ratio from 0.0025 to 0.0014. For polyalpha-olefin lubricating oil, the same additive concentration reduced the R22/R12 ratio from 0.0033 to 0.0024.

~Trademarks - 11 1 Tests carried out on the miscibility of alkylbenzens 2 and highly fluorinated refrigerant, namcly: difluorochloro 3 methane, and a blend of diflucrochloromethane and penta1uoro-4 ethane showed that the preferred branched-chain alkylbenzenes prepared by HF alkylation of benzene with polypropylene according 6 to the pressnt in~ention were superior to ]inear alkylbsnzenQs at 7 temperatures as low as -40F, -80F and -115~F. In these tssts 8 it was found that the linear alkylbenzenes, although superior to 9 mineral lubricating oils in general, wc~ld no~ be suitable lubri-cants for use in refrigeration apparatus at 'emperaturss below 11 about -40F due to the separating out o an unmovable solid phase 12 ~hich causes plugging problems in refrigera~ion apparatus.
13 The presence of a fa ty acid and an arylphosphate in 14 th~ guantiti~s specified herein did not affec~ the miscibility of 1~ tne refrigerant and lubricant at low temperatures. Thsse 16 additiYes did not cause foaming in refrigerant use.
17 ~dditional wear tests for lcnger periods of time were 18 carried out. The basis for thsse tests and the results thereo~
19 are given in the following table.

1 TABLE~
2 FALEX ~EAR TESTS - ASIM D-2670 3 JAW_LOAD - 400 LB, DURAIION OF_TEST -_4.5 HOURS
4 Re- Testh Test frig- _ T~mp.~ F Plckup, Wear, 6 No._ _~ _ Qrant ~___Add_tiv~____ St__tz End ~T No m~
7 22 Alkyl- R12 Non~ 90 234 1443 753 93~83 8 23 ~enzene R12 None 88 216 12888 102.2 9 24 R22 None 84 211 12750 50.5 R12 2% TCP 90 240 15031 36.2 11 26 R12 0~5~ TCP40d1~ OA 82201 119 0 1~6 12 27 R22 0.5~ TCP+0.1~ OA 81160 79 0 0O4 13 28 Mlneral R12 None 8~ 2304 1434 734 236. 94 14 29 lub. oil R22 None 822215 139 41 156.8 R12 2% TCP 82 223 141 2530.9 16 31 R12 0.5~ ~CP~0.1% OA 80 177 97 0 0.3 17 32 R22 0.5~ TCP~0~1$ OA 86 164 78 0 0.3 18 IOil saturated with refrigerant~ Lnad incr~ased to 200 lb in 30 19 sec, maiDtained at 200 lb for 30 sec. Followsd by an increase in load at a rate of 200 lb~min. until 400 lb was reached.
21 2Temperature after 400-lb Jaw load reached.
22 3At 175 min, test discontinued, could not maintain 400-lb load.
23 4At 195 min, could not maintain 400 lb load.
24 5At 150 min, could not maintain 400-lb load.
In other t~sts the effectiveness of compositions of the 26 invention containing 50/50 m~xtures of mineral lubricating oil 27 and synthetic alkylbenzene lubrica~ing oil was demonstrated. The 28 mineral lubricating oil ~as S~niso 3GS, as noted above, and the 29 synthetic alkylbenzene lubricating oil was 150 SUS branched-chain alkylbenzenes produced by HF alkylation of benzene with mixed 31 polyFolypropylenes having an average mol~cular weight in the 32 range 330 to 350. ~he test oil ~as sa~urated with refrigerant 33 R12. With the combination of 0~05~ by weight of oleîc acid and 34 0.25~ by weight tricresylphosphate, wear of only 0.1 milligram w~s obtained in the Falex Test oFerating at 400 pounds for 4.5 3~ hours. In ths Els3y ~sst the ratio for R22/R12 for the same 37 mixed oils containing oleic acid and tricr~sylphosphate was 38 0.0005 ana thers was no copper plating. By comparison~ the mixed 39 oils without .he oleic acid and tricre~ylphosphate gave an R22/R12 ratio of 0.0019 and there was ccpper plating.

1 As disclosed, ~his inv~ntion ~ela+es +o apparatuses of 2 the r~frigeration, heat pump or heat engine type including 3 compressor, condenser, evaporator and, ir. con~act with the movirg 4 parts ol said apparatus, 2 working fluid comprising nalogenated alkanes ar.d a lubricant combinaticn of a lubricating oil, a 6 higher fatty acid and an arylphosphate. For those knowl~dgeable 7 in the art, it is well known that these apparatusss are 8 variations in the operation of the same cycllc system 9 r~h~n applied to refrig~raticD or heat ~umps, ~crk is added to the system through a motor-driven compressor which 11 comprasses the refrig~rant befor~ it ic condensed. HQat from ~hs 12 system at this point may be employed fcr heating purposes. ~hs 13 system is then operating as a heat ~um~. The condensed 14 refrigerant is partly cr complet~ly vaFcrized in th~ evaporator.
The heat added to the system at this ~oint or extracted from the 16 surroundings causes ccoli~g (refrigeration of the heat source).
17 In heat pumps the heat source is usually outside air, whereas in 18 refrig~ration systsms it is normally a relatively confined space 19 to b~ cooled.
~hen the system is operat~d as a heat er.glr.e, useful 21 work is delivered by the sy~tem. Heat is added to the evapora~or 22 from, for instance, hot gases obtained from combustlon oï a 23 suitable fuel. This Iesults in ~vaForation and expansion of the 24 "refrigerant" which drives a comEre~sor. ~he "refrige~an+" is +hen condansed to comFlete the cycle. ~he useful work can, -n 26 turn, be used in driving other d~vices. This ty~e of heat engine 27 is of particular importance because cf its possible adaptation to 28 anti-pollution automo~ile engiDes employlng ex-errlal combustion.
29 The same ~orking fluids are uced in all three types of 3Q +he aboYe-described aFparatus.

~D91~ 2 1 ~hile the character o~ this invention has been 2 described in detail with numerou~ exam~les, this has been don~ by 3 way of illustration only and without limita~ion of the inv~ntion.
4 It will be apparentlto those skilled in the art that modifications and variations of the illustrative examples may be 6 ~ad~ in the practice of the invention within the scope of the 7 follo~ing claims.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In a refrigeration or heat pump apparatus containing a working fluid consisting essentially of a refrigerant and a chemically inert, wax-free lubricant, said refrigerant being a halo-substituted hydrocarbon having from 1 to 3 carbon atoms and said lubricant being an oil of lubricat-ing viscosity selected from the group consisting of mineral lubricating oil, polyalphaolefin lubricating oil, alkylbenzene lubricating oil and mixtures thereof, the improvement which comprises incorporating into said oil the combination of a monocarboxylic aliphatic acid having at least 8 carbon atoms and an arylphosphate having at least one aryl group and containing from 10 to 25 carbon atoms in an amount sufficient to improve the wear-inhibiting properties of said lubricant and to improve the resistance of said lubricant to decomposition.

2. Improved refrigeration or heat pump apparatus in accordance with claim 1 in which the lubricant is an alkylbenzene lubricating oil.

3. Improved refrigeration or heat pump apparatus in accordance with claim 2 in which the alkylbenzene is a mixture of mono-substituted branched-chain alkylbenzenes having an average molecular weight in the range of from about 300 to about 470.

4. Improved refrigeration or heat pump apparatus in accordance with Claim 3 in which the higher fatty acid is oleic acid and the arylphosphate is tricresylphosphate.

5. A refrigeration or heat pump working fluid consisting essentially of a refrigerant and a chemically inert, wax-free lubricant, said refrigerant being a halo-substituted hydrocarbon having 1 to 3 carbon atoms and said lubricant being selected from the group consisting of mineral lubricating oil, polyalpha-olefin lubricating oil, alkylbenzene lubricating oil and mixtures thereof containing the combination of a monocarboxylic aliphatic acid having at least 8 carbon atoms and an arylphosphate having at least one aryl group and containing from 10 to 25 carbon atoms in minor amounts sufficient to improve the wear-inhibiting properties of said lubricant and to improve the resistance of said lubricant to decomposition.

6. A refrigeration or heat pump working fluid in accordance with claim 5 in which the lubricant is alkylbenzene lubricating oil.

7. A refrigeration or heat pump working fluid in accordance with claim 6 in which the alkylbenzene is a mixture of mono-substituted branched-chain alkylbenzenes having an average molecular weight in the range of from about 300 to 470.

8. A refrigeration or heat pump working fluid in accordance with claim 7 in which the higher fatty acid is oleic acid and the arylphosphate is tricresylphosphate.

9. Lubricant suitable for refrigeration or heat pump apparatus comprising a major proportion of alkylbenzene lubricating oil and a minor amount of the combination of a monocarboxylic aliphatic acid having at least 8 carbon atoms and an arylphosphate having at least one aryl group and containing from 10 to 25 carbon atoms sufficient to improve the wear inhibiting properties of said lubricant and to improve the resistance of said lubricant to decomposition.