CA2181387A1

CA2181387A1 - Refrigeration working fluid compositions for use in recompression type cooling systems

Info

Publication number: CA2181387A1
Application number: CA002181387A
Authority: CA
Inventors: Martin Anthony Krevalis; Carolyn Boggus Duncan; Richard Henry Schlosberg
Original assignee: Individual
Current assignee: ExxonMobil Chemical Patents Inc
Priority date: 1994-11-17
Filing date: 1995-11-16
Publication date: 1996-05-18
Also published as: IL116043A0; CN1177371A; EP0804517A1; BR9509790A; AU4164296A; NZ296904A; AR000158A1; WO1997019144A1; ZA959743B

Abstract

A refrigeration working fluid composition which is miscible or partially miscible at temperatures of less than 120°C and which is immiscible at temperatures of at least about 120-180°C, the refrigeration working fluid comprising:
(i) about 65 to 95 weight % of a refrigerant, based on the total weight of the working fluid composition, the refrigerant comprising a blend of pentafluoroethane, 1,1,1-trifluoroethane, and 1,1,1,2-tetrafluoroethane, wherein the tetrafluoroethane is present in an amount of between about 0.5 to 10 weight %, based on the total weight of the refrigerant, and (ii) about 5 to 35 weight % of a polyol ester lubricant, based on the total weight of the working fluid composition.

Description

2i8~87 \
REFRTI'-~R~ WORKING FLUID Ir 0~
FOR USE IN _ nl!~SSION TYPE COOLING S'~STE~S
This is a continuation-in-part of U.S. Patent Application, Serial ~o. 08/340,961. Tlle invention relates to ref rigeration working f luid compositions uniquely designed for efficient operation in recompression type cooling system. More particularly this invention relates to refrigeration working fluid compositions ~- ,r;cing fluorocarbon (l~FC) refrigerant blends and certain polyol ester lubricants having suitaole viscosities and which are miscible with the refrigerant at low temperatures (i.e., below 120C) while immiscible at higher temperatures ( i . e ., about 120-180C or greater), thereby exhibiting reversible micr~;h; l ;ty.
R~(CR~ P - - OF THE INVENITION
Cooling systems of the -h_n; c~l vapor recompression type, including refrigerators, freezers, heat pumps, air conditioning systems, and the like, are well known. In such devices, a refrigerant of suitable boiling point t:V~rLLeS at low pressure, taking heat from the ~ulL~,ullding zone. The resulting vapor is then compressed and pagged to a rnnCi~n~r where it cr n~lrnF:r~s and gives off heat to a second zone. ~he r t~nrl~ncate is then returned through an expansion valve to the evaporator, so completing the cycle.
It is recognized that currently used refrigerants which contain chlorine, such as dichlorodifluoromethane, will be replaced by chlorine-free refrigerant fluids because of the adverse effect of the r~hlr~rin;-ted materials upon the atmospheric ozone 21~387 l -- 2 --layer . Tetraf luoroethane isomers and in particular "Refrigerant 134a", which is 1,1,1,2-tetrafluoroethane, are now rrlnc; ~f~red desirable fluids for use in refrigeration systems.
s Refrigeration working fluids are required to have a lubricant which i8 compatible and miscible with the refrigerant so that moving parts of the system are properly lubricated. Heretofore, such lllhr;~ Ints have 10 been ~ - s ~ ~ of 1~YdLOC~I1LOn mineral oils which are miscible with the chlorine-cont~;nin~ refrigerant fluids and which provide effective lubrication.
The use of chlorine-free, HFC (hydrofluorocarbon) 15 refrigerants has create~ a need for new lubricants, since mineral oils are not compatible with these materials. This need i3 well recognized in the art and there are numerous recent publications and patents r.~ l nsi n~ various type3 of synthetic lubricants which 20 are said to be compatible with tetraf luoroethane refrigerznt fluids~ Esters of polyols are being particularly ~nrh~q; 7ed as being suitable for use with the tetrafluoroethane r~frigerants, especially refrigerant R134a~
U.S. Patent 5,021,179, issued June 4, 1991 to Zehler et al., disclose~ esters of polyols in which the acyl groups have at least 22% of (a) branched acyl groups or ( b ) acyl groups which contain no more than 30 six carbon atoms. This patent also indicates that the esters have a certain ratio of the number percent of acyl groups that have 8 or more carbon atoms and are unbranched to the number percent of acyl groups that are branched and contaill not more than 6 carbon atoms, 35 and that this ratio is 110t greater than 1~56~ Also, ~1387 1~ ~

the patent requires that the number percent of acyl groups having at least 9 carbon atoms, branched or not branched, will be not greater than 81.
PCT Application WO 90/12849 published 17~v~
1990 by Jolley et al. discloses generally liquid compositions containing a major amount of at least one fluorine containing hyd]-ocarbon containing one or two carbon atoms and a minor amount of at least one soluble organic lubricant comprising at least one carboxylic ester of a polylly~llu~sy compound containing at least- two hydroxy groups and having the formula R[OC(O)R']n where R is hydrocarbyl, each l~' is ; n,l~p~n~l~ntly ~IydLu~
straight chain lower hydrocarbyl, a branched chain hydrocarbyl group, or a straight chain hydrocarbyl group rrn~ining from 8 to about 22 carbon atoms, provided that at least one R' group is IIYdLU~ a lower straight chain hydrocarbyl or a branched chain hydrocarbyl group, or a carboxylic acid-containing or carboxylic acid ester-containing hydrocarbyl group, and n is at least 2.
U.K. Patent 2,216,541, issued October 23, 1991, to Imperial Chemical Industries and published october 11, 1989, discloses the use of any ester of molecular weight 250 or greater as being suitable for use as compatible lubricants with Refrigerant 134a (R-134a and some related refrigerant fluids. The patent exemplifies adipates, ~y~l -l l itates and ben20ates.
European Published Patent Application 440069 published August 7, 1991, ~y Kao Corporation discloses refrigeration working fluids composed of fluoroethanes and esters prepared by reacting an aliphatic polyol and a straight or branched chain alcohol with an aliphatic polycarboxylic acid having 2 to 1o carbon atoms.
European p-lhl; ~::hPrl Application 415778 puhl i ~2hr~rl 5 March 6, 1991, by Rao Corporation discloses refrigeration working fluid compositio~s containing hydrogenated f luoroethane and an ester ~ ~ ul.d obtained from an aliphatic polyhydric alcohol, a saturated aliphatic ~; c~rhn~rylic acid and a saturated lO aliphatic monncArhn~ylic acid.
-European Published Application 406479 p-lhl i ~:h~-l January 9, 1991, by Ryodo Oil T~nhnicAl Research Center Co., Ltd., discloses lLbricants which are said to be l5 , ;hle with Rl34a. Suitable lubricants are:
esters of neopentyl glycol and a straight or branched-chain monovalent fatty acid having 3-lô carbon atoms;
esters of pentaerythritol, dipentaerytllritol and tripentaerythritol with straigllt or branched chain C2-20 C18 monovalent fatty acids; esters of a trihydroxypolyvalent alcohol of the formula RC~CX20H)3 where R is C1-C3 alkyl with a straight or branched-chain monovalent fatty acid having 2-18 carbon atoms and not more than 25 mol% per total fatty acid of at least one 25 polybasic acid having carbon number of 4-36.
European pl-hl i F:h~d Application 435253 published July 3, 1991, by NLppon oil co., 1td. discloses a number of esters said to be compatible with R134a, the 30 esters being def ined as having specif ic structures and being esters of mono-, di- and tri-pentaerythritol and other polyols such as trimethylolethane, trimethylolpropane, trimethylolbutane or dimers or trimers thereof with monocarbo~ylic acids having 2-15 35 carbon atoms and dicarboxylic acids having 2-lo carbon . . .

3~?

atoms. The esters are generally said to have molecular weights of about 200-3000.
European Published Application 430657 published S June 5, 1991, by Ashai Denka Kogyo Kabushiki ~ Cln~;
lubricants compatible with R134a which are characterized at being neopentyl polyol ester of a fatty acid having 2 to 6 carbon atoms. It is said in this publication that the use of acids having 7 or more 10 carbon atomg will resu]~t in incompatibility if the amount of C2-C6 acids is not 20 mol96 or greater such that the average number of carbon atoms of the fatty acids per hydro~yl group of the neopentylpolyol i5 6 or below. Suitable neopentyl polyols include mono-, di-15 and tri- pentaerythritol, trimethylolpropane, and trimethylolethane. The polyols muæt have at least 3 OE~
groups .
In the operation of a typical refrigeration 20 system, the working fl~id composition comprising a mi~ture of refrigerant and lubricant i5 passed from the compressor, where the temperatures are highest and where the lubricant is needed, to the cnnr~pncpr~ where t ~ ul~S are reduced. Thereafter, the working 25 fluid composition is then sent on to the ~vel~OL~Or~
where temperatures are coldest and where the lubricant is not needed. Thereafter the working fluid composition, in vapor form, is returned to the compressor for repetition of the cycle.
The refrigerant working fluid compositions of this invention will e~hibit partial or complete homogeneity and miscibility of the ester lubricant and the HFC
refrigerant blends when the working fluid composition 35 is in the evaporator, but when the working fluid compoæition is in the compressor, where tempt:LelLuL~i are high and lubricant is needed, the ester lubricant in a very concentrated form is available for lubrication of the compressor since the ester lubricant 5 and the refrigerant blends exhibit complete ;qr~hility at high temperatureS, i.e., about 120C
to 180C or greater. Thus, separation of the ester lubricant from the refrigerant blends in the ., -~s,,or iS h~lnrf i r; A 1 .
The working fluid compositions of this invention may also be partially miscible or semi-h~ -, eous at lower temperatures, i.e., the blend of ester and refrigerant may exhibit partial m;cr;hility, but this l5 partial miscibility or semi-homogeneity does not prevent their use in refrigeration equipment, and such semi-homogeneous compositions also exhibit subst~nti~l ly complete immiscibility at higher temperatures, i.e., at about 120C to 180C or greater, 20 thereby capable of achieving the objectives of this invention .
Therefore, the present inventors have discuv~ d that miccihil; ty/i cc; hil; ty can be significantly 25 influenced by blending refrigerants. More importantly, however, is the fact that the present inventors have discovered that the tem~erature/immiscibility relationship of refrigerant blends such as R125, R143a and R134a, or R125 and R143a, is inverse to that of 30 conventionally known sillgle ~ u nn~nt refrigerants with polyol esters.
The present inventors have found that when the specific refrigerant blends of the present invention 35 are mixed with polyol ester lubricants, the lubricants 2~ 3~7 become i i¢c;hle at high temperatures allowing for.
separation of refrigerant and lubricant in the compressor section of a cooling system which op~rAt~
at high t~ ~_LaLu~t:s, t:hereby allowing a certain 5 portion of the lubricant to remain behind in the compressor section rather than cycling through the entire cooling system ~here the lubricant is not needed .
To the contrary, single refrigerants such as R134a and R143a are immiscible at lower temperatures allowing for separation of refrigerant and lubricant in the t:V~OLc-Lur section of the cooling system which operates at low temperatures, th.ereby allowing a certain portion of the lubricant to rer.ain behind in the ~vcl~oLclLoL
section where the lubricant is not needed and thereby depriving the compressor section of the much needed lubricant ( See Figs . 3 and 4 ) .
A single refrigerant such as R125 is also undesirable since it is miscible at all temperatures which the cooling sygtem operates, thereby causing the lubricant to pass from evaporator to compressor to con~ r, in series, without the benefit of nnnan~ration and separation of an immiscible polyol ester lubricant in the compressor section which is sought by using the refrigerant blends of the present invention ( See Fig. 5 ) .
Still other refrigerants such as R32 are undesirable since they are miscible at high temperatures and immiscible at low temperatures ( See Fig. 6). Such refrigerants cause the lubricant to separate out of the wor]cing f luid composition while in 2 1 ~ 7 ~,=, the evaporator section, thereby depriving the compressor section of the much needed lubricant.
European Patent Publication No. 0 536 940, S published on April 14, 1993, and assigned to T ,-r;Al Chemical Industries PLC ~ zclo~pc a working fluid comprising a heat trangfer fluid comprising a mixture of at least two compounds selected from the group consisting of hydrofluornnlkAnP~ and fluorn~lk~nP~; and 10 a lubricant. The heat trangfer fluid may comprise two, three or more components selected from the group consisting of: R32, R134, Rl34a, R125, R152a, R143a and R143. One suitable heat transfer fluid comprises a mixture of R32 and R125.
However, as demonstrated in Fig. 7, attached hereto, working f luid compositions which include a blend of R32 and R125 are not; ~rihle at higher temperatures, except for the composition having a 20 lubricant of technical grade pentaerythritol, cekanoic 9 and cekonic 8 which exhibited; qr;h; 1 i ty in the temperature range of between 100-130C~ If, however, you refer to Example E on Fig~ 1, this lubricant is nnnf:; ~Pred miscible at all temperatures in the 25 refrigerant blend according to the present invention and in Example I on Fig. 2, this lubricant is con, ic~Pred i ;~n;hle from 120-180C. Therefore, it quite clear that not all refrigerant blends act the same and that each blend of refrigerants exhibits its 30 own unique mi8cibility and; i~-;h;lity properties.
Thus, it would not be obvious to one of ordinary skill in the art what affect one combination of refrigerant blends would have on the miscibility of a particular polyol ester lubricant, based upon the teaching of H~ 87 other refrigerant blends such as that demonstrated in the Flg. 7.
Therefore, since E~lropean Patent Publication No. 0 536 940 does not disclose the specific weight p~ ~;e~L
of the unique refrigera]lt blends ( especially that of R134a) recited in the present invention nor the ~perifir lubricants admixed with such blends, it cannot be conclusively gtated ~hat they would exhibit the same mi~rihility and i ~ ril~jlity properties of the refrigeration working fluid composition of the pre&ent invention. one cannot readily determine from the mi~rihi 1 ity data of a 8ingle refrigerant and lllhricAnt what affect the blending of another refrigerant together with that gingle refrigerant would have on the mi ~::r~ hi 1 i ty properties of the resulting working fluid without the benefit of l:he extensive research efforts of the present inventors.
Leaving the luhricant behind in the, tzSSUL
maximizes the lubricant~s effect while leaving it behind in the evaporato]- minimizes its effect.
Therefore, it wag completely unexpected that when blending selected refrigerant8, which by themselves do not behave in such a way that the lubricant is i qri hl e in high temperature environments such as a compressor and miscible in low temperature environments such as an evaporator, ~nh~nr~-i lubrication of a cooling system can occu]-.
STTM~TA~V QF TT~ INYENTION
In accordance with the present invention there have been discovered blends of HFC refrigerants and ~$i387 polyol esters of certaill monocarboxylic acids useful. as refrigeration working fluids exhibiting reverse mi ~r; h; l; ty which provide improved lubrication of refrigeration equipment containing such compositions.
The pref erred working f luid compositions according to the present invention are as follows:
~a) A refrigeration working fluid composition which is miscible or paLtially miscible at t~ Lu.~:Y
of less than 120C and ~hich is; qr; hl e at temperatures of at least about 120-180C or greater, the refrigeration working fluid c ~; n~:
~i) about 65 to 95 weight % of a refrigerant, based on the total weight of the working f luid composition, the refrigerant comprising a blend of pentaf luoroethane, 1, 1, ~.-trif luoroethane, and 1, 1, 1, 2-tetraf luoroethane, wherein the tetraf luoroethane is present in an amount of between about 0 . 5 to 10 weight %, based on the total weight of the refrigerant, and (ii) about 5 to 35 weight 96 of a polyol ester lubricant, based on the total weight of the working f luid composition .
( b ) A ref rigeration working f luid composition which is miscible or partially miscible at t~ LuLe:s of less than 120C and which is immiscible at temperatures of at least about 120-180C, the refrigeration working fluid comprising:
(i) about 65 to 95 weight 96 of a refrigerant, based on the total weight of the working f luid composition, the refrigerant comprising a blend of 1, 1, 1-trif luoroethane and pentaf luoroethane, and (ii) about 5 to 35 weight % of a polyol ester lubricant, based on the total weight of the working fluid composition.

21~1387 It is a further object of the present invention wherein a - ~h~n;r~l v~por recompression type cooling system comprising an ~va~oLa~or~ a compressor, and a r~n~lPn~or has refrigeration working fluid compositions S (a) and (b) cycling therethrough, wherein the refrigeration working fluid composition is miscible or partially miscible in ~:he evaporator at temperatures of less than 120C and i ~r; h] e in the ~ S~UL at temperatures of at least about 120-180C, whereby the 10 polyol ester lubricant is separated from the refrigerant in the ~ ~ ~ x~or when lubricant the is most needed and the po] yol ester lubricant is miscible or partially miscible ~ n the refrigerant while the refrigeration worki~g fluid compositio}l is contained in 15 the evaporator such that the polyol ester lubricant can be readily transported from the evaporator to the compressor .
.~
20 BRIEF D~ . lO.~ OF T~E Lr ~
Fig. 1 is a chart which show the reversible miscibility exhibited by the refrigeration working f luid composition of th.e present invention comprising a refrigerant of 44% R125, 52% R143a and 4~6 R134a and the 25 selected polyol ester lubricants verses refrigeration working f luid compositions which do not exhibit reversible miscibility;
Fig. 2 is a chart which show the reversible 30 mi ~::r; h; 1 i ty exhibited by the refrigeration working fluid composition of the present invention comprising a refrigerant of 55% R143a and 45% R125 and the selected polyol ester lubricants verses refrigeration working f luid compositions which do not e~Lhibit reversible 35 miscibility;
.. . .

~1~13~7 Fig. 3 is a chart ~hich shows the relative i ~r; hi l; ty of various polyol ester lubricants in R143a at any t~ Lure;
S Fig. 4 is a chart which shows the relative m; ~::r; h; l; ty of various polyol ester lubricants in R134a at any temperature;
Fig. 5 is a chart o~hich shows the relative m;~l-;hil;ty of various polyol ester lubricants in R125 at an~ temperature and the relative immiscibility of other polyol egter lubricants in R125 at any temperature;
lS Fig. 6 is a chart which shows the reversible miscibility of various polyol ester lubricants in R32, wherein these lubricants are im,miscible at low temperatures and miscible at higher temperatures which is completely; n~-proS; te to the present invention; and Fig. 7 is a chart which shows the relative m; ~::r; h; l; ty of various polyol ester lubricants in a refrigerant blend of 60 weight 96 R32 and 40 weight R125 at any temperature, except for working fluids which are formed using TPE/CK9/CK8 which e~hibited ; ~r; h; l; ty in the narrow temperature range of between about 100-130C.
D~!T~TT~n r.~ ~. QF T~ INVIÇNTION
The polyol esters are present in an amount effective to provide iubrication, which is generally over the range of about 5-35~ by weight based on the total weight or the ref rigeration working f luid O ~ 87 composition. Preferred amounts are 10%, 25% and 35%
ester .
The refrigeration working fluid compositions of S this invention are prei~erably either:
(a) a refrigeratlon working fluid composition which is essentially a hl ,g~n~ouS or semi ~ eous one phase composition at low temperatures but which exhibits i ~cih;lity at temperatures of about 120-180C comprising (i) a refrigerant ~ of a blend of 44 wt.% R-125, 52 wt.% R-143a, and 4 wt.% R-134a, and an effective amount of (ii) a polyol ester lubricant being ( 1 ) a trimethylolpropane ester of (a) IS 3,5,5-trimethylht~An~ ic acid, (b) a mixture of 6? % by weight n-heptanoic acid with 24 % by weight 2-methylhexanoic acid, 7 % by weight 2-ethyl rPntAn~ic acid and 2 % by weight mixed isomers of C7 Al kAnf~i .
acids or (c) a mixture of heptanoic acids I sed of about 25 wt.% 3,4-dimethylpentanoic, 51% 3,4 and 5-methylhexanoic, 8% n-heptanoic, 5% 3-ethylrPntAn~ic and the balance a mixture of other branched heptanoic acids, or ( 2 ) a technical grade pentaerythritol ester of (a) branched C7 aci~,s being a mixture of 27 wt.% 2-ethylrPntAn-lic acid, 74 wt.% 2-methylpentanoic acid and the balance mixed C7 acid isomers or (b) n-pentanoic acid; or (b) a refrigeration working fluid which is eæsentially a homogenecus or semi-homogeneous one phase composition at low temperatures but which exhibits immiscibility at temperature o~ 120-180C comprising (a) a refrigerant comp~sed of a mixture of 5s-50 wt.%
R-143a, and 45-50 wt.% R-125, and an ef~ective amount of (b ~ a polyol ester lubricant being ( 1 ) a .

2~81~7 O, ~, - 14 trimethylolpropane ester of (a) 2-ethyl hPY~nn;c acid, ~ b ) 3, s, S-trimethylhe_anoic acid or ( c ) a mi~ture of branched heptanoic acids composed of 25 wt . % 3, 4-dimethylpentanoic, 51% 3,4 and 5-methylhPyAnnic~ 8% n-S heptanoic, 5% 3-ethylpentanoic and the balance a mixture of other branched heptanoic acids; (2) a tP~hnir~l grade pentaerythritol ester of (a) a mi_ture of about 75 wt.~ 3~5~5-trimethylhpy~nn;~ acid and about 25 wt . % of a branched chain C8 carboYylic acid mi_ture ~ of 25 wt.% 3~s-dimethylhpy;~nnic acid, 19 wt.%
4, 5-dimethyl-he_anoic a~id, 17% 3, 4-dimethyl h~Y;:lnn;
acid, 11% 5-methylheptanoic acid, 5 wt.% 4-methylheptanOic acid and the balance mixed methylheptanoic and dim~ethylhe_anoic acids, (b) n-15 pentanoic acid, or (c) a mixture of heptanoic acids composed of about 25% 3,4-dimethylpentanoic, 51% 3,4 and 5-methylhe_anoic, 8~ n-heptanoic, 5% 3-ethylpentanoic and the halance a miYture of other branched heptanoic acid~.
As used herein, Rl~5 refers to pentafluoroethane, R143a refers to l,1,1-trifluoroethane and R134a refers to 1, 1,1, 2-tetraf luoroethane .
M;~r;h;l;ty and; ;qnihility is detPrmin~d in the following manner. A measured quantity of ester lubricant is poured into a valved glass tube of 12 mm I.D. The tube is connected to a R-134a refrigerant charging unit, where air is evacuated and a set volume of refrigerant i8 condensed into the glass tube until a desired refrigerant gas pressure drop is obtained. The composition of ~he lubricant/ref rigerant miYture is calculated from weight measurements taken of the tube, tube plus lubricant, and tube plus lubricant plus 35 ref rigerant . The tube containing the 3~

lubricant/refrigerant is visually obsel:ved for m;s-;h;lity at room te~lperature, in a high temperature viEibility bath where the temperature is ~hP Latically controlled up to +180C, and in a low S temperature visibility bath where the t~ _LC~LUL~: is thermostatically controlled down to -80C. The mi~ture is conci ~Pred miscible to a given temperature if one clear layer is observed. The mixture is c~nc;~Pred c~ ;hle if two separate layers are observed.
10 Partial m;cr;h;l;ty is any state between m;CC;hil;ty and; c~;h;lity.
In the data included in the examples, miscibility temperature ref ers to the lowest temperature at which 15 m; cr; h; 1; ty is observed at the given composition. The highest of these t ~ ules is the m;-cr;h; 1 ;ty value for working fluid compositions having that ester lubricant .
EXAMPLES
This invention is illustrated by Figures 1 and 2 which show the reversible m;cr;h;l;ty exhibited by the compositions of the invention in plots which are composites for data obtained over three compositional ranges for each ester, i.e., 10~, 25% and 35% by weight ester. All percPn~qPc are by weight. T ~LCILUl~S
are in degrees centigrade.
These examples produce an interesting rhPn~ .on.
Instead of having immiscibility in the lower temperatures ranges, as is often seen with the single components such as R143a, immiscibility now tends to occur in the higher temperature ranges which is highly desira~le for cooling systems. The below e~amples produced a variety of working fluids which e~hibited 2181~1~7 f' -' 1 6 miscibility at low temperatures and im~niscihility at high temperatures. LO~J temperature ~iR-;h;lit-y means that the lubricant will not separate out in the coldest parts of a cooling syst:em, i.e., parts of the system S where lubricant build-up could be detrimental to performance. Likewise, high temperature; ~::r;hi 1 ;ty means that the lubricant/refrigerant will separate in high tl ,~ .UL~ regions of the cooling system, such as the compressor, precisely where lubricant/refrigerant 10 separation is most desirable.
Figs. 1 a~d 2 also demonstrate that increased m; ~r; h; 1 i ty can be achieved by mixing refrigerants in the same way that it i5 achieved by mixing lubricants.
5 The ;n~ -t;hility Rl43 with polyol esters is almost ~limin;lt~.A when it is mixed with R125, even when R125 i8 the minority (i.e., less than 50%) component.
In Figure 1, the compositions of the present 20 invention, i.e., Examples s, C, and D, contain the esters i~lPnt;f iecl below: -B: T~5P/CK9 -- trimethylolpropane ester of 3,5,5-trimethylhexanoic acid ( ~Cekanoic g acid" ) ZS
C: TMP/1770 - trimethylolpropane ester of a mixture of acids being 67% n-heptanoic; 2496 2-methyl h2xanoic, 7% 2-ethylpentanoic and 2% mixed isomers of C7 acids.
D: ~PE/CK7 - trimethylolpropane ester of mixed heptanoic acids ( ~Cekanoic 7 acid~ ) which is a mixture of 23% 2-ethylpentanoic acid, 74% 2-methylhexanoic acid and the balance other C 7 acid isomers .

Comparative compositions A and E contain refrigerant blends of 44% R125, S2% R143a and 4% R134a admixed with the following esters:
A: ~eopentyl glycol ester of 3, 5, 5-trimethyl hl~Ann; c acid.
E: technical grade pentaerythritol ester of a mixture of (a) 85 wt.% 3,s,5-trimethyl h~ nnic and (b) 15 wt . % isooctanoic acids which is a mi~ture of 26 wt. %
3,5-dimethyl-, 19% 4,s-dimethyl, 17% 3,4-dimethylhexanoic acid, 11% S-methylheptanoiC, 5% 4-methylheptanOic and the balance mixed methylheptanoic and dimethylhexanoic ac.i~ds.
In Figure 2, the compositions of the invention are compositions F, G and I containing these esters:
F: is the trimethylolpropane ester of 2-ethyl hexanoic acid.
G: Is same ester as in composition a.
I: is same ester as in composition E except there is used 7s wt. % of 3, 5, s-trimetllylhexanoic acid and 25% of the same mixture of isooctanoic acids.
Comparative composition H contains refrigerant blends of s5% R143a and 45% R125 admi ~ed with the following ester:
H: TMP/1770 - trimethylolpropane ester of a mixture of acids being 67% n-heptanoic; 24% 2-methyl hexanoic, 7% 2-ethylpentanoic and 2% mixed isomers of C7 acids.

All esters were evaluated at the concentration levels of 10%, 25% and 35% by weight ester, based on the total weight of ester and refrigerant by weight based on the total weight of the refrigeration working S fluid composition.
The following additional comeositions were evaluated over compositional ranges of 10%, 25% and 35%
by weight ester with similar results:
Composition J: The trimethylol propane ester of a mixture of heptanoic acids (25% 3,4-dimethylpantAnn;~, 51% 3,4 and S-methy7ha~nn;c acids, 896 n-heptanoic, s%
3-ethylpantAnni c and the balance a mixture of other 15 branched heptanoic acids ) was mixed with a blend of 44%
R-125, s2% R-143a and 4% R-134a and was found to be miscible at -50C to +58C and ; i ~c; hle at higher temperatures .
.~
Composition ~: The technical grade pentaerythritol ester of n-pentanoic acid was evaluated with the same refrigerant blend as was Ester J and was found to be miscible at -50C to +63C and immiscible at higher temperatures .
Composition L: The same ester used in Composition J was mixed with a blenc of 50% by weight 143a and 50%
by weight R-12s and was found miscible at -50C to +55C
and immiscible at higher temperatures.
Composition M: The same ester used in Composition E~ was mixed with the same refrigerant blend of Composition I, and found to be miscible at -50C and +61C but; i~-;hle at higher temperatures.

.

~ 3 ~ ~3~?7 ?

Composition ~: The technical grade pentaerythritol ester of the acid mixture of Composition J was mi~ed with the same refrigerant hlend of Composition 1 and found to be miscible at -50C and +32C, but i i ~rih~
5 at higher temperatures.

Claims

What is Claimed is:

1. A refrigeration working fluid composition which is miscible or partially miscible at temperatures of less than 120°C and which is immiscible at temperatures of at least about 120-180°C, said refrigeration working fluid comprising:
(i) about 65 to 95 weight % of a refrigerant, based on the total weight of said working fluid composition, said refrigerant comprising a blend of pentafluoroethane, 1,1,1-trifluoroethane, and 1,1,1,2-tetrafluoroethane, wherein said tetrafluoroethane is present in an amount of between about 0.5 to 10 weight %, based on the total weight of the refrigerant, and (ii) about 5 to 35 weight % of a polyol ester lubricant, based on the total weight of said working fluid composition.

2. The composition according to claim 1 wherein said refrigerant comprises a blend of 44 weight %
pentafluoroethane, 52 weight % 1,1,1-trifluoroethane.
and 4 weight % 1,1,1,2-tetrafluoroethane.

3. The composition according to claim 1 wherein said polyol ester lubricant is selected from the group consisting of:
(1) an esterification reaction product of trimethylolpropane and at least one acid or acid mixture selected from the group consisting of:
(a) 3,5,5-trimethylhexanoic acid, (b) a mixture of 67 % by weight n-heptanoic acid with 24 % by weight 2-methylhexanoic acid, 7 % by weight 2-ethylpentanoic acid and 2 % by weight mixed isomers of C7 alkanoic acids, and (c) a mixture of heptanoic acids composed of about 25 wt.% 3,4-dimethylpentanoic, 51%
3,4 and 5-methylhexanoic, 8% n-heptanoic, 5% 3-ethylpentanoic and the balance a mixture of other branched heptanoic acids; and (2) an esterification reaction product of technical grade pentaerythritol ester and at least one acid or acid mixture selected from the group consisting of:
(a) branched C7 acids being a mixture of 27 wt.% 2-ethylpentanoic acid, 74 wt.% 2-methylpentanoic acid and the balance mixed C7 acid isomers, and (b) n-pentanoic acid.

4. A refrigeration working fluid composition which is miscible or partially miscible at temperatures of less than 120°C and which is immiscible at temperatures of at least about 120-180°C, said refrigeration working fluid comprising:
(i) about 65 to 95 weight % of a refrigerant, based on the total weight of said working fluid composition, said refrigerant comprising a blend of 1,1,1-trifluoroethane and pentafluoroethane, and (ii) about 5 to 35 weight % of a polyol ester lubricant, based on the total weight of said working fluid composition.

5. A composition according to claim 4 wherein said refrigerant comprises a blend of 50-55 wt. %
1,1,1-trifluoroethane and 45-50 weight %
pentafluoroethane.

6. The composition according to claim 4 wherein said polyol ester lubricant is selected from the group consisting of:
(1) an esterification reaction product of trimethylolpropane and at least one acid or acid mixture selected from the group consisting of:
(a) 2-ethyl hexanoic acid, (b) 3,5,5-trimethylhexanoic acid, and (c) a mixture of branched heptanoic acids comprising 25 weight % 3,4-dimethylpentanoic, 51 weight % 3,4 and 5-methylhexanoic, 8 weight % n-heptanoic, 5 weight % 3-ethylpentanoic and the balance a mixture of other branched heptanoic acids; and (2) an esterification reaction product of technical grade pentaerythritol ester and at least one acid or acid mixture selected from the group consisting of:
(a) a mixture of about 75 weight %
3,5,5-trimethylhexanoic acid and about 25 weight % of a branched chain C8 carboxylic acid mixture composed of 25 weight % 3,5-dimethylhexanoic acid, 19 weight % 4,5-dimethylhexanoic acid, 17 weight % 3,4-dimethylheptanoic acid, 11 weight % 5-methylheptanoic acid, 5 weight % 4-methylheptanoic acid and the balance mixed methylheptanoic and dimethylhexanoic acids, (b) n-pentanoic acid, and (c) a mixture of heptanoic acids comprising: about 25 weight % 3,4-dimethylpentanoic, 51 weight % 3,4 and 5-methylhexanoic, 8 weight % n-heptanoic, 5 weight % 3-ethylpentanoic and the balance a mixture of other branched heptanoic acids.

7. A mechanical vapor recompression type cooling system comprising an evaporator, a compressor, and a condensor, wherein said cooling system includes a refrigeration working fluid composition which cycles therethrough, said refrigeration working fluid composition is miscible or partially miscible in said evaporator at temperatures of less than 120°C and immiscible in said compressor at temperatures of at least about 120-180°C, said refrigeration working fluid comprising: (i) about 65 to 95 weight % of a refrigerant, based on the total weight of said working fluid composition, said refrigerant comprising a blend of pentafluoroethane, 1,1,1-trifluoroethane, and 1,1,1,2-tetrafluoroethane, wherein said tetrafluoroethane is present in an amount of between about 0.5 to 10 weight %, based on the total weight of the refrigerant, and (ii) about 5 to 35 weight % of a polyol ester lubricant, based on the total weight of said working fluid composition, whereby said polyol ester lubricant is separated from said refrigerant in said compressor when lubricant is most needed and said polyol ester lubricant is miscible or partially miscible in said refrigerant while said refrigeration working fluid composition is contained in said evaporator such that said polyol ester lubricant can be readily transported from said evaporator to said compressor.

8. The cooling system according to claim 7 wherein said refrigerant comprises a blend of 44 weight % pentafluoroethane, 52 weight % 1,1,1-trifluoroethane, and 4 weight % 1,1,1,2-tetrafluoroethane.

9. The cooling system according to claim 7 wherein said polyol ester lubricant is selected from the group consisting of:
(1) an esterification reaction product of trimethylolpropane and at least one acid or acid mixture selected from the group consisting of:
(a) 3,5,5-trimethylhexanoic acid, (b) a mixture of 67% by weight n-heptanoic acid with 24% by weight 2-methylhexanoic acid, 7% by weight 2-ethylpentanoic acid and 2% by weight mixed isomers of C7 alkanoic acids, and (c) a mixture of heptanoic acids composed of about 25 wt.% 3,4-dime thylpentanoic, 51%
3,4 and 5-methylhexanoic, 8% n-heptanoic, 5% 3-ethylpentanoic and the balance a mixture of other branched heptanoic acids; and (2) an esterification reaction product of technical grade pentaerythritol ester and at least one acid or acid mixture selected from the group consisting of:
(a) branched C7 acids being a mixture of 27 wt.% 2-ethylpentanoic acid, 74 wt.% 2-methylpentanoic acid and the balance mixed C7 acid isomers, and (b) n-pentanoic acid.

10. A mechanical vapor recompression type cooling system comprising an evaporator, a compressor, and a condensor, wherein said cooling system includes a refrigeration working fluid composition which cycles therethrough, said refrigeration working fluid composition is miscible or partially miscible in said evaporator at temperatures of less than 120°C and immiscible in said compressor at temperatures of at least about 120-180°C, said refrigeration working fluid comprising: (i) about 65 to 95 weight % of a refrigerant, based on the total weight of said working fluid composition, said refrigerant comprising a blend of 1,1,1-trifluoroethane and pentafluoroethane, and (ii) about 5 to 35 weight % of a polyol ester lubricant, based on the total weight of said working fluid composition, whereby said polyol ester lubricant is separated from said refrigerant in said compressor when lubricant is most needed and said polyol ester lubricant is miscible or partially miscible in said refrigerant while said refrigeration working fluid composition is contained in said evaporator such that said polyol ester lubricant can be readily transported from said evaporator to said compressor.

11. A cooling system according to claim 10 wherein said refrigerant comprises a blend of 50-55 wt.
% 1,1,1-trifluoroethane and 45-50 weight %
pentafluoroethane.

12. The cooling system according to claim 10 wherein said polyol ester lubricant is selected from the group consisting of:
(1) an esterification reaction product of trimethylolpropane and at least one acid or acid mixture selected from the group consisting of:
(a) 2-ethyl hexanoic acid, (b) 3,5,5-trimethylhexanoic acid, and (c) a mixture of branched heptanoic acids comprising 25 weight % 3,4-dimethylpentanoic, 51 weight % 3,4 and 5-methylhexanoic, 8 weight % n-heptanoic, 5 weight % 3-ethylpentanoic and the balance a mixture of other branched heptanoic acids; and (2) an esterification reaction product of technical grade pentaerythritol ester and at least one acid or acid mixture selected from the group consisting of:
(a) a mixture of about 75 weight %
3,5,5-trimethylhexanoic acid and about 25 weight % of a branched chain C8 carboxylic acid mixture composed of 25 weight % 3,5-dimethylhexanoic acid, 19 weight % 4,5-dimethylhexanoic acid, 17 weight % 3,4-dimethylheptanoic acid, 11 weight % 5-methylheptanoic acid, 5 weight % 4-methylheptanoic acid and the balance mixed methylheptanoic and dimethylhexanoic acids, (b) n-pentanoic acid, and (c) a mixture of heptanoic acids comprising: about 25 weight % 3,4-dimethylpentanoic, 51 weight % 3,4 and 5-methylhexanoic, 8 weight % n-heptanoic, 5 weight % 3-ethylpentanoic and the balance a mixture of other branched heptanoic acids.