U.S. patent application number 09/791628 was filed with the patent office on 2001-09-27 for lubricants.
This patent application is currently assigned to Imperial Chemical Industries PLC. Invention is credited to Corr, Stuart.
Application Number | 20010023934 09/791628 |
Document ID | / |
Family ID | 26299685 |
Filed Date | 2001-09-27 |
United States Patent
Application |
20010023934 |
Kind Code |
A1 |
Corr, Stuart |
September 27, 2001 |
Lubricants
Abstract
A working fluid composition comprising: (A) a heat transfer
fluid comprising a mixture of at least two compounds selected from
the group consisting of hydrofluoroalkanes and fluoroalkanes; and
(B) sufficient to provide lubrication of a lubricant which is at
least partially soluble in each component of the heat transfer
fluid.
Inventors: |
Corr, Stuart; (Runcorn,
GB) |
Correspondence
Address: |
Intellectual Property Group
Pillsbury Winthrop LLP
Ninth Floor
East Tower 1100 New York Avenue, N.W.
Washington
DC
20005-3918
US
|
Assignee: |
Imperial Chemical Industries
PLC
|
Family ID: |
26299685 |
Appl. No.: |
09/791628 |
Filed: |
February 26, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09791628 |
Feb 26, 2001 |
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08976658 |
Nov 24, 1997 |
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08976658 |
Nov 24, 1997 |
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07957080 |
Oct 7, 1992 |
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Current U.S.
Class: |
252/68 ;
252/67 |
Current CPC
Class: |
C10M 2211/022 20130101;
C10M 171/008 20130101; C10N 2040/36 20130101; C10N 2040/44
20200501; C09K 2205/22 20130101; C10M 2209/105 20130101; C10M
2207/286 20130101; C09K 5/045 20130101; C10N 2040/30 20130101; C10N
2040/38 20200501; C10M 2211/06 20130101; C10M 2209/104 20130101;
C10N 2040/34 20130101; C10N 2040/42 20200501; C10N 2040/40
20200501; C10N 2020/01 20200501; C10M 2207/283 20130101; C10N
2040/50 20200501; C10M 2207/281 20130101; C10N 2040/32 20130101;
C10M 2209/107 20130101; C10M 2207/282 20130101; C10N 2040/00
20130101 |
Class at
Publication: |
252/68 ;
252/67 |
International
Class: |
C09K 005/00; F25D
001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 11, 1991 |
GB |
9121657.2 |
Jul 22, 1992 |
GB |
9215602.5 |
Claims
1. A working fluid composition comprising: (A) a heat transfer
fluid comprising a mixture of at least two compounds selected from
the group consisting of hydrofluoroalkanes and fluoroalkanes; and
(B) sufficient to provide lubrication of a lubricant which is at
least partially soluble in each component of the heat transfer
fluid.
2. A working fluid composition as claimed in claim 1 wherein the
heat transfer fluid (A) comprises at least two hydrofluoroalkanes
selected from the group consisting of difluoromethane,
1,1,2,2-tetrafluoroethane, 1,1,1,2-tetrafluoroethane,
pentafluoroethane, 1,1-difluoroethane, 1,1,1-trifluoroethane and
1,1,2-trifluoroethane.
3. A working fluid composition as claimed in claim 1 or claim 2
wherein the heat transfer fluid (A) comprises a mixture of: (1)
tetrafluoroethane; (2) at least one hydrofluoroalkane selected from
the group consisting of difluoromethane and 1,1,1-trifluoroethane;
and optionally (3) pentafluoroethane.
4. A working fluid composition as claimed in claim 3 wherein the
tetrafluoroethane is 1,1,1,2-tetrafluoroethane.
5. A working fluid composition as claimed in claim 4 wherein the
heat transfer fluid (A) is a binary mixture consisting essentially
of 1,1,1,2-tetrafluoroethane and difluoromethane.
6. A working fluid composition as claimed in any one of claims 1 to
3 wherein the heat transfer fluid (A) comprises a ternary or higher
mixture of: (1) 1,1,1,2-tetrafluoroethane or
1,1,2,2-tetrafluoroethane; (2) at least one hydrofluoroalkane
selected from the group consisting of difluoromethane and
1,1,1-trifluoroethane; and optionally (3) pentafluoroethane.
7. A working fluid composition as claimed in claim 6 wherein the
heat transfer fluid (A) comprises a mixture of: (1)
1,1,1,2-tetrafluoroethane or 1,1,2,2-tetrafluoroethane; (2)
difluoromethane or 1,1,1-trifluoroethane; and (3)
pentafluoroethane.
8. A working fluid composition as claimed in claim 7 wherein the
heat transfer fluid (A) comprises a mixture of: (1)
1,1,1,2-tetrafluoroethane; (2) difluoromethane; and (3)
pentafluoroethane.
9. A working fluid composition as claimed in any one of the
preceding claims wherein the lubricant (B) comprises at least one
polyoxyalkylene glycol.
10. A working fluid composition as claimed in claim 9 wherein the
lubricant (B) comprises at least one polyoxyalkylene glycol having
the general formula:
A[--O--(CH.sub.2CH(CH.sub.3)O).sub.1(CH.sub.2CH.sub.2O).-
sub.m-Q].sub.x I wherein A is the residue remaining after removing
the hydroxyl groups from a hydroxyl containing organic compound; Q
represents an optionally substituted alkyl, aralkyl or aryl group;
l and m are independently 0 or an integer provided that at least
one of l or m is an integer; and x is an integer, said at least one
polyoxyalkylene glycol having an average molecular weight in the
range of from about 150 to about 3000.
11. A working fluid composition as claimed in any one of claims 1
to 8 wherein the lubricant (B) comprises at least one neopentyl
polyol ester.
12. A working fluid composition as claimed in claim 11 wherein the
lubricant (B) comprises at least one neopentyl polyol ester
selected from the esters of pentaerythritol, dipentaerythritol,
tripentaerythritol, trimethylol ethane, trimethylol propane and
neopentyl glycol.
13. A working fluid composition as claimed in claim 11 or claim 12
wherein the lubricant (B) comprises one or more compounds of
general formula: 3wherein R is the hydrocarbon radical remaining
after removing the hydroxyl groups from pentaerythritol,
dipentaerythritol, tripentaerythritol, trimethylol ethane,
trimethylol propane or neopentyl glycol, or the hydroxyl containing
hydrocarbon radical remaining after removing a proportion of the
hydroxyl groups from pentaerythritol, dipentaerythritol,
tripentaerythritol, trimethylol ethane, trimethylol propane or
neopentyl glycol; each R.sup.1 is, independently, H, a straight
chain (linear) aliphatic hydrocarbyl group, a branched aliphatic
hydrocarbyl group, or an aliphatic hydrocarbyl group (linear or
branched) containing a carboxylic acid or carboxylic acid ester
substituent, provided that at least one R.sup.1 group is a linear
aliphatic hydrocarbyl group or a branched aliphatic hydrocarbyl
group; and n is an integer.
14. A working fluid composition as claimed in claim 13 wherein the
linear and branched hydrocarbyl groups specified for R.sup.1 are
unsubstituted and the carboxylic acid or carboxylic acid ester
containing hydrocarbyl group specified for R.sup.1 contains no
other substituents.
15. A working fluid composition as claimed in claim 13 or claim 14
wherein the lubricant (B) comprises one or more compounds of
Formula II in which R is the hydrocarbon radical remaining after
removing the hydroxyl groups from pentaerythritol,
dipentaerythritol, tripentaerythritol, trimethylol ethane,
trimethylol propane or neopentyl glycol.
16. A working fluid composition as claimed in claim 15 wherein the
lubricant (B) comprises one or more compounds of Formula II in
which R is the hydrocarbon radical remaining after removing the
hydroxyl groups from pentaerythritol, dipentaerythritol,
trimethylol propane or neopentyl glycol.
17. A working fluid composition as claimed in claim 16 wherein the
lubricant (B) comprises one or more compounds of Formula II in
which R is the hydrocarbon radical remaining after removing the
hydroxyl groups from pentaerythritol, dipentaerythritol or
trimethylol propane.
18. A working fluid composition as claimed in any one of claims 13
to 17 wherein the lubricant (B) comprises one or more compounds of
Formula II in which each R.sup.1 is, independently, a linear alkyl
group or a branched alkyl group.
19. A working fluid composition as claimed in claim 18 wherein the
lubricant (B) comprises one or more compounds of Formula II in
which each R.sup.1 is, independently, a C.sub.5-8 linear alkyl
group or a C.sub.8-10 branched alkyl group.
20. A working fluid composition as claimed in claim 18 or claim 19
wherein at least one R.sup.1 group is a linear alkyl group.
21. A working fluid composition as claimed in any one of claims 18
to 20 wherein at least one R.sup.1 group is a linear alkyl group
and at least one R.sup.1 group is a branched alkyl group.
22. A working fluid composition as claimed in claim 11 of claim 12
wherein the lubricant (B) comprises one or more esters of general
formula: 4wherein R.sup.2 is the hydrocarbon radical remaining
after removing the hydroxyl groups from pentaerythritol,
dipentaerythritol or trimethylol propane; each R.sup.3 is,
independently, a linear alkyl group or a branched alkyl group; and
p is an integer of 3, 4 or 6, wherein one or more of the named
polyols, one or more linear alkanoic acids, or esterifiable
derivatives thereof, and optionally one or more branched alkanoic
acids, or esterifiable derivatives thereof, are utilised in the
synthesis of the ester.
23. A working fluid composition as claimed in claim 22 wherein a
mixture of one or more linear alkanoic acids, or esterifiable
derivatives thereof, and one or more branched alkanoic acids, or
esterifiable derivatives thereof, are utilised in the synthesis of
the ester.
24. A working fluid composition as claimed in claim 22 or claim 23
wherein the lubricant comprises one or more compounds of Formula
III in which R.sup.2 is the hydrocarbon radical remaining after
removing the hydroxyl groups from pentaerythritol or
dipentaerythritol.
25. A working fluid composition as claimed in any one of claims 22
to 24 wherein the lubricant (B) comprises one or more compounds of
Formula III in which each R.sup.3 is, independently, a C.sub.5-8
linear alkyl group or a C.sub.8-10 branched alkyl group.
26. The use of the working fluid composition claimed in any one of
claims 1 to 25 in a heat transfer device.
27. A heat transfer device containing the working fluid composition
claimed in any one of claims 1 to 25.
Description
[0001] The present invention relates generally to lubricants and
more particularly to working fluid compositions contained in heat
transfer devices which comprise the lubricant and a heat transfer
fluid.
[0002] Heat transfer devices of the mechanical compression type
such as those used in refrigerators, freezers, heat pumps and
automobile air conditioning systems are well known. In such devices
a heat transfer fluid of a suitable boiling point evaporates at low
pressure taking heat from a surrounding zone. The resulting vapour
is then compressed and passes to a condenser where it condenses and
gives off heat to a second zone. The condensate is then returned
through an expansion valve to the evaporator so completing the
cycle. The mechanical energy required for compressing the vapour
and pumping the fluid is provided by, for example, an electric
motor or an internal combustion engine.
[0003] The heat transfer fluids used in these heat transfer devices
include chlorine containing fluoroalkanes such as
dichlorodifluoromethane (R-12), chlorodifluoromethane (R-22) and
mixtures thereof with, for example, fluoroalkanes such as
1,1-difluoroethane (R-152a). However, such chlorine containing
fluoroalkanes have been implicated in the destruction of the ozone
layer and as a result the use and production thereof is to be
severely limited by international agreement. The use of certain
fluoroalkanes and hydrofluoroalkanes in place of the chlorine
containing fluoroalkanes has been proposed. The fluoroalkanes and
hydrofluoroalkanes of particular interest are those compounds which
have comparable boiling points and other thermal properties to the
chlorine containing fluoroalkanes which they are replacing, but
which are also less damaging or benign to the ozone layer. Thus,
R-12 is generally being replaced by a new refrigerant,
1,1,1,2-tetrafluoroethane (R-134a).
[0004] Hitherto, heat transfer devices have tended to use mineral
oils as lubricants. The good solubility of chlorine containing
fluoroalkanes with mineral oils allows the mineral oil to circulate
around the heat transfer device together with the chlorine
containing fluoroalkane, and this in turn ensures proper
lubrication of the compressor. Unfortunately, however, the
replacement fluoroalkane and hydrofluoroalkane heat transfer fluids
such as R-134a have different solubility characteristics to the
chlorine containing fluoroalkanes presently in use and tend to be
insufficiently soluble in mineral oils to allow the latter to be
used as lubricants. Consequently, numerous alternative lubricants
such as polyoxyalkylene glycols terminating in hydroxyl and other
groups, esters of polyols with mono- and polyfunctional acids, and
halo substituted esters and ethers have been proposed as lubricants
for use with the replacement heat transfer fluids.
[0005] Unfortunately, R-134a cannot be used as a direct replacement
for certain of the refrigerants which are presently in use such as
R-22 and R-502 (an azeotropic mixture of R-22 and
chloropentafluoroethane R-115) since it does not possess comparable
boiling characteristics and thermal properties. It has thus been
proposed that existing refrigerants such as R-22 and R-502 be
replaced by refrigerant mixtures comprising two or more
refrigerants selected from the fluoroalkanes and
hydrofluoroalkanes. Particular mention may be made of binary
mixtures of refrigerants such as R-134a and difluoromethane (R-32)
or R-32 and pentafluoroethane (R-125). Unfortunately, these
refrigerant mixtures are also not sufficiently soluble in mineral
oils to allow the latter to be used as lubricants. Moreover, the
miscibility and solubility of an alternative lubricant with one
component of the mixture, for example with R-134a, does not mean
that such a lubricant will also be miscible and soluble with the
refrigerant mixture itself. In consequence, the development of a
lubricant which exhibits acceptable lubricating properties in a
heat transfer device utilising a refrigerant mixture presents a
very real problem.
[0006] It has now been found that if a prospective lubricant is at
least partially soluble in each component of the refrigerant
mixture then it will be at least partially soluble in the
refrigerant mixture itself, thereby enabling its use as a lubricant
with that mixture. Such a lubricant may provide an acceptable
lubricating action even if it is immiscible with one or more of the
components of the refrigerant mixture or with the refrigerant
mixture itself.
[0007] According to the present invention there is provided a
working fluid composition comprising (A) a heat transfer fluid
comprising a mixture of at least two compounds selected from the
group consisting of hydrofluoroalkanes and fluoroalkanes; and (B)
sufficient to provide lubrication of a lubricant which is at least
partially soluble in each component of the heat transfer fluid.
[0008] The heat transfer fluid may comprise two, three or more
components. Preferred hydrofluoroalkanes and fluoroalkanes are
selected from the group consisting of difluoromethane (R-32),
1,1,2,2-tetrafluoroethane (R-134), 1,1,1,2-tetrafluoroethane
(R-134a), pentafluoroethane (R-125), 1,1-difluoroethane (R-152a),
1,1,1-trifluoroethane (R-143a) and 1,1,2-trifluoroethane
(R-143).
[0009] One suitable heat transfer fluid comprises a mixture of R-32
and R-125. Such a mixture may comprise equal proportions of each
component on a weight basis.
[0010] The present invention is particularly concerned with the
provision of a working fluid composition which provides a useful
replacement for the working fluids presently in use which comprise
R-22 or R-502 as the refrigerant and a mineral oil lubricant. A
particularly desirable working fluid composition in this respect is
one which comprises
[0011] (A) a heat transfer fluid comprising a mixture of:
[0012] (1) tetrafluoroethane;
[0013] (2) at least one hydrofluoroalkane selected from the group
consisting of difluoromethane (R-32) and 1,1,1-trifluoroethane
(R-143a); and optionally
[0014] (3) pentafluoroethane (R-125); and
[0015] (B) sufficient to provide lubrication of a lubricant which
is at least partially soluble in each component of the heat
transfer fluid.
[0016] The tetrafluoroethane may be 1,1,1,2-tetrafluoroethane
(R-134a) or 1,1,2,2-tetrafluoroethane (R-134) or a mixture of these
two isomers. Preferably, however, the tetrafluoroethane is a single
isomer, and more preferably is R-134a.
[0017] Although the heat transfer fluid may comprise more than
three components, it is preferably a binary or ternary mixture. The
mixture may be an azeotrope or near-azeotrope, but will normally be
zeotropic.
[0018] In one preferred embodiment of the present invention, the
heat transfer fluid is a binary mixture consisting essentially of
R-134a and R-32. Such a mixture provides a particularly suitable
replacement for the R-22 refrigerant which has been used hitherto
in commercial refrigeration systems and related heat transfer
devices. Preferably, such a mixture comprises from 45 to 75% by
weight, more preferably from 65 to 75% by weight of R-134a and from
25 to 55% by weight, more preferably from 25 to 35% by weight of
R-32. A particularly preferred binary mixture comprises about 70%
by weight of R-134a and about 30% by weight of R-32.
[0019] In a further preferred embodiment of the present invention,
the heat transfer fluid comprises a ternary or higher mixture
of:
[0020] (1) R-134a or R-134;
[0021] (2) at least one hydrofluoroalkane selected from the group
consisting of R-32 and R-143a; and optionally
[0022] (3) R-125.
[0023] Such a heat transfer fluid provides a suitable replacement
for the R-22 and R-502 refrigerants which have been used hitherto
in commercial refrigeration systems and related heat transfer
devices.
[0024] Particularly suitable ternary heat transfer fluids may be
selected from:
[0025] (a) R-134a+R-32+R-143a;
[0026] (b) R-134+R-32+R-143a;
[0027] (c) R-134a+R-32+R-125;
[0028] (d) R-134+R-32+R-125;
[0029] (e) R-134a+R-143a+R-125; and
[0030] (f) R-134+R-143a+R-125.
[0031] A particularly preferred heat transfer fluid comprises a
mixture of:
[0032] (1) R-134a or R-134, especially R-134a;
[0033] (2) R-32 or R-143a, especially R-32; and
[0034] (3) R-125.
[0035] Such heat transfer fluids provide a particularly suitable
replacement for R-22 and R-502.
[0036] One particularly preferred ternary heat transfer fluid for
replacing R-22 is a mixture consisting of:
[0037] (1) 55 to 65% by weight, particularly about 60% by weight of
R-134a;
[0038] (2) 25 to 35% by weight, particularly about 30% by weight of
R-32; and
[0039] (3) 5 to 15% by weight, particularly about 10% by weight of
R-125.
[0040] Another particularly preferred ternary heat transfer fluid
for replacing R-22 is a mixture consisting of:
[0041] (1) 25 to 35% by weight, particularly about 30% by weight of
R-134a;
[0042] (2) 45 to 55% by weight, particularly about 50% by weight of
R-32; and
[0043] (3) 15 to 25% by weight, particularly about 20% by weight of
R-125.
[0044] One particularly preferred ternary heat transfer fluid for
replacing R-502 is a mixture consisting of:
[0045] (1) 45 to 55% by weight, particularly about 50% by weight of
R-134a;
[0046] (2) 25 to 35% by weight, particularly about 30% by weight of
R-32; and
[0047] (3) 15 to 25% by weight, particularly about 20% by weight of
R-125.
[0048] Another particularly preferred ternary heat transfer fluid
for replacing R-502 is a mixture consisting of:
[0049] (1) 45 to 55% by weight, particularly about 50% by weight of
R-134a;
[0050] (2) 35 to 45% by weight, particularly about 40% by weight of
R-32; and
[0051] (3) 5 to 15% by weight, particularly about 10% by weight of
R-125.
[0052] All the percentages by weight quoted above are based on the
total weight of the ternary heat transfer fluid.
[0053] Suitable lubricants may be selected from those currently
used with R-134a provided that the requirement of partial
solubility is met.
[0054] Lubricants satisfying the requirement of partial solubility
may, in particular, be selected from the class known in the art as
polyoxyalkylene glycols. Suitable polyoxyalkylene glycol lubricants
include hydroxyl group initiated polyoxyalkylene glycols, e.g.
ethylene and/or propylene oxide oligomerslpolymers initiated on
mono- or polyhydric alcohols such as methanol, butanol,
pentaerythritol and glycerol. Such polyoxyalkylene glycols may also
be end-capped with suitable terminal groups such as alkyl, e.g.
methyl groups.
[0055] A preferred polyoxyalkylene glycol lubricant is one having
an average molecular weight in the range of from about 150 to about
3000 and comprising one or more compounds of general formula:
A[--O--(CH.sub.2CH(CH.sub.3)O).sub.1(CH.sub.2CH.sub.2O).sub.m-Q].sub.x
I
[0056] wherein
[0057] A is the residue remaining after removing the hydroxyl
groups from a hydroxyl containing organic compound;
[0058] Q represents an optionally substituted alkyl, aralkyl or
aryl group;
[0059] l and m are independently 0 or an integer provided that at
least one of l or m is an integer; and
[0060] x is an integer.
[0061] The polyoxyalkylene glycol lubricant may be prepared using
conventional techniques. Such techniques are well known to those
skilled in the art. Thus, in one method a hydroxyl containing
organic compound such as an alcohol is reacted with ethylene oxide
and/or propylene oxide to form an ethylene oxide and/or propylene
oxide oligomer/polymer containing terminal hydroxyl groups which is
subsequently etherified to give a polyoxyalkylene glycol of Formula
I. The polyoxyalkylene glycol lubricant which is finally formed
will not usually consist of a single compound of Formula I, but
will usually comprise a mixture of such compounds which vary from
one another in respect of the degree of polymerisation, i.e. the
number of ethylene and/or propylene oxide residues. Moreover, a
mixture of alcohols and/or phenols may be used as initiators in the
formation of the polyoxyalkylene glycol lubricant, and a mixture of
etherifying agents which provide different Q groups may also be
used. The molecular weight of a polyoxyalkylene glycol lubricant
comprising a mixture of compounds of Formula I will represent the
average molecular weight of all the compounds present, so that a
given lubricant may contain specific polyoxyalkylene glycols which
have a molecular weight outside the range quoted above, providing
that the average molecular weight of all the compounds is within
that range.
[0062] The moiety A in the polyoxyalkylene glycol of Formula I is
the residue remaining after removing the hydroxyl groups from a
hydroxyl containing organic compound. Such compounds include the
mono- and polyhydric alcohols and phenols. Where the hydroxyl
containing organic compound which is used as an initiator in the
formation of the polyoxyalkylene glycol is a monohydric alcohol or
phenol, A is preferably a hydrocarbyl group and more preferably is
an alkyl, aryl, alkaryl or aralkyl group, especially alkyl.
Suitable alkyl groups for A may be selected from the straight chain
(linear), branched or cyclic alkyl groups. Preferably, A is a
C.sub.1-12, particularly a C.sub.1-10 and especially a C.sub.1-6
alkyl group. Specific examples of alkyl groups include methyl,
ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,
tert-butyl, the various pentyl groups, the various hexyl groups,
cyclopentyl, cyclohexyl and the like. Particularly preferred alkyl
groups for A are the C.sub.1-12, particularly the C.sub.1-10 and
especially the C.sub.1-6 straight chain alkyl groups, examples of
which have been listed above. An especially preferred alkyl group
for A is methyl or n-butyl.
[0063] Other suitable hydrocarbyl groups for A are those which
remain after removing a hydroxyl group(s) from benzyl alcohol and
phenols such as phenol, cresol, nonylphenol, resorcinol and
bisphenol A.
[0064] Where a polyhydric alcohol is used in the formation of the
polyoxyalkylene glycol, A is preferably a hydrocarbon radical.
Suitable hydrocarbon radicals for A are those which remain after
removing the hydroxyl groups from polyhydric alcohols such as
ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol,
diethylene glycol, dipropylene glycol, cyclohexane dimethanol,
glycerol, 1,2,6-hexane triol, trimethylolpropane, pentaerythritol,
dipentaerythritol and sorbitol. A particularly preferred
hydrocarbon radical for A is that remaining after removing the
hydroxyl groups from glycerol.
[0065] The moiety Q in the polyoxyalkylene glycol of Formula I is
an optionally substituted alkyl, aralkyl or aryl group. A preferred
optionally substituted aralkyl group for Q is an optionally
substituted benzyl group. Preferred optionally substituted aryl
groups for Q include phenyl and alkyl substituted phenyl groups.
Preferably, Q is an optionally substituted, for example halogen
substituted, alkyl group, particularly an optionally substituted
C.sub.1-12 alkyl group and more particularly an optionally
substituted C.sub.1-4 alkyl group. Suitable alkyl groups for Q may
be selected from the straight chain (linear), branched or cyclic
alkyl groups, especially the linear alkyl groups. Although the
alkyl groups for Q are described as being optionally substituted,
they are preferably unsubstituted. Accordingly, particularly
preferred alkyl groups for Q are selected from methyl, ethyl,
propyl, isopropyl and the various butyl groups. An especially
preferred alkyl group for Q is methyl.
[0066] The polyoxyalkylene glycol of Formula I may be a
polyoxyethylene glycol, a polyoxypropylene glycol or a
poly(oxyethylene/oxypropylene) glycol. In the latter case, the
ethylene and propylene oxide residues may be arranged randomly or
in blocks along the polymer chain. Preferred polyoxyalkylene
glycols are the polyoxypropylene glycols and the
poly(oxyethylene/oxypropylene) glycols.
[0067] Particularly preferred lubricants for use in the working
fluid compositions of the invention are those selected from the
class known as neopentyl polyol esters due, inter alia, to their
generally high level of thermal stability. Suitable neopentyl
polyol esters include the esters of pentaerythritol,
polypentaerythritols such as di- and tripentaerythritol,
trimethylol alkanes such as trimethylol ethane and trimethylol
propane, and neopentyl glycol. Such esters may be formed with
linear and/or branched aliphatic carboxylic acids, such as linear
and/or branched alkanoic acids, or esterifiable derivatives
thereof. A minor proportion of an aliphatic polycarboxylic acid,
e.g. an aliphatic dicarboxylic acid, or an esterifiable derivative
thereof may also be used in the synthesis of the ester lubricant in
order to increase the viscosity thereof. However, where such an
aliphatic polycarboxylic acid (or esterifiable derivative thereof)
is employed in the synthesis, it will preferably constitute no more
than 30 mole %, more preferably no more than 10 mole % of the total
amount of carboxylic acids (or esterifiable derivatives thereof)
used in the synthesis. Usually, the amount of the carboxylic
acid(s) (or esterifiable derivative thereof) which is used in the
synthesis will be sufficient to esterify all of the hydroxyl groups
contained in the polyol, but in certain circumstances residual
hydroxyl functionality may be acceptable.
[0068] A preferred neopentyl polyol ester lubricant is one
comprising one or more compounds of general formula: 1
[0069] wherein
[0070] R is the hydrocarbon radical remaining after removing the
hydroxyl groups from pentaerythritol, dipentaerythritol,
tripentaerythritol, trimethylol ethane, trimethylol propane or
neopentyl glycol, or the hydroxyl containing hydrocarbon radical
remaining after removing a proportion of the hydroxyl groups from
pentaerythritol, dipentaerythritol, tripentaerythritol, trimethylol
ethane, trimethylol propane or neopentyl glycol;
[0071] each R.sup.1 is, independently, H, a straight chain (linear)
aliphatic hydrocarbyl group, a branched aliphatic hydrocarbyl
group, or an aliphatic hydrocarbyl group (linear or branched)
containing a carboxylic acid or carboxylic acid ester substituent,
provided that at least one R.sup.1 group is a linear aliphatic
hydrocarbyl group or a branched aliphatic hydrocarbyl group;
and
[0072] n is an integer.
[0073] The aliphatic hydrocarbyl groups specified for R.sup.1 above
may be substituted, e.g. by pendant atoms or groups such as chloro,
fluoro and bromo, and/or by in chain hetero atoms such as oxygen
and nitrogen. Preferably, however, such hydrocarbyl groups are
unsubstituted and, except in the case where R.sup.1 is an aliphatic
hydrocarbyl group containing a carboxylic acid or carboxylic acid
ester substituent, contain only carbon and hydrogen atoms.
[0074] The ester lubricants of Formula II may be prepared by
reacting the appropriate polyol or mixture of polyols with the
appropriate carboxylic acid or mixture of acids. Esterifiable
derivatives of the carboxylic acids may also be used in the
synthesis, such as the acyl halides, anhydrides and lower alkyl
esters thereof. Suitable acyl halides are the acyl chlorides and
suitable lower alkyl esters are the methyl esters. Aliphatic
polycarboxylic acids, or esterifiable derivatives thereof, may also
be used in the synthesis of the ester lubricant. Where an aliphatic
polycarboxylic acid is used in the synthesis of the ester
lubricant, the resulting lubricant will comprise one or more
compounds of Formula II in which at least one of the R.sup.1 groups
is an aliphatic hydrocarbyl group (linear or branched) containing a
carboxylic acid or carboxylic acid ester substituent. The ability
of polycarboxylic acids to react with two or more alcohol molecules
provides a means of increasing the molecular weight of the ester
formed and so a means of increasing the viscosity of the lubricant.
Examples of such polycarboxylic acids include maleic acid, adipic
acid and succinic acid, especially adipic acid. Generally, however,
only monocarboxylic acids (or esterifiable derivatives thereof)
will be used in the synthesis of the ester lubricant, and where
polycarboxylic acids are used they will be used together with one
or more monocarboxylic acids (or esterifiable derivatives thereof)
and will constitute only a minor proportion of the total amount of
carboxylic acids used in the synthesis. Where an aliphatic
polycarboxylic acid (or an esterifiable derivative thereof) is
employed in the synthesis, it will preferably constitute no more
than 30 mole %, more preferably no more than 10 mole % of the total
amount of carboxylic acids used in the synthesis, with one or more
monocarboxylic acids (or esterifiable derivatives thereof)
constituting the remainder.
[0075] Usually, the amount of the carboxylic acid(s) (or
esterifiable derivative thereof) which is used in the synthesis
will be sufficient to esterify all of the hydroxyl groups contained
in the polyol(s), in which case the resulting lubricant will
comprise one or more compounds of Formula II in which R is the
hydrocarbon radical remaining after removing the hydroxyl groups
from pentaerythritol, dipentaerythritol, tripentaerythritol,
trimethylol ethane, trimethylol propane or neopentyl glycol.
However, in certain circumstances ester lubricants which comprise
residual hydroxyl functionality may be acceptable. Such lubricants
comprise one or more ester compounds of Formula II in which R is
the hydroxyl containing hydrocarbon radical remaining after
removing a proportion of the hydroxyl groups from pentaerythritol,
dipentaerythritol, tripentaerythritol, trimethylol ethane,
trimethylol propane or neopentyl glycol. Esters containing residual
(unreacted) hydroxyl functionality are often termed partial esters,
and lubricants containing them may be prepared by utilising an
amount of the carboxylic acid or acids which is insufficient to
esterify all of the hydroxyl groups contained in the polyol or
polyols.
[0076] It will be appreciated that the preferred neopentyl polyol
ester lubricants may comprise a single compound of Formula II, i.e.
the reaction product which is formed between a single polyol and a
single monocarboxylic acid. However, such ester lubricants may also
comprise a mixed ester composition comprising two or more compounds
of Formula II. Such mixed ester compositions may be prepared by
utilising two or more polyols and/or two or more carboxylic acids
(or esterifiable derivatives thereof) in the synthesis of the
ester, or by combining a mixture of different esters each of which
is the reaction product of a particular polyol and a particular
carboxylic acid. Furthermore, different mixed ester compositions,
each of which has been prepared by utilising two or more polyols
and/or two or more carboxylic acids (or esterifiable derivatives
thereof) in their synthesis, may also be blended together.
[0077] The preferred neopentyl polyol ester lubricants comprise one
or more compounds of Formula II in which R is the hydrocarbon
radical remaining after removing the hydroxyl groups from
pentaerythritol, dipentaerythritol, trimethylol propane or
neopentyl glycol. Particularly preferred alcohols for the synthesis
of the ester are pentaerythritol, dipentaerythritol and trimethylol
propane.
[0078] Preferably, each R.sup.1 in Formula II is, independently, a
linear aliphatic hydrocarbyl group or a branched aliphatic
hydrocarbyl group.
[0079] Preferred-linear aliphatic hydrocarbyl groups for R.sup.1
are the linear alkyl groups, particularly the C.sub.3-10 linear
alkyl groups, more particularly the C.sub.5-10 linear alkyl groups
and especially the C.sub.5-8 linear alkyl groups. Examples of
suitable linear alkyl groups include n-pentyl, n-hexyl, n-heptyl,
n-octyl, n-nonyl and n-decyl. Esters containing such alkyl groups
can be prepared by utilising a linear alkanoic acid in the
synthesis of the ester.
[0080] Preferred branched aliphatic hydrocarbyl groups for R.sup.1
are the branched alkyl groups, particularly the C.sub.4-14 branched
alkyl groups, more particularly the C.sub.6-12 branched alkyl
groups and especially the C.sub.8-10 branched alkyl groups.
Examples of suitable branched alkyl groups include isopentyl,
isohexyl, isoheptyl, isooctyl, isononyl, isodecyl, 2-ethylbutyl,
2-methylhexyl, 2-ethylhexyl, 3,5,5-trimethylhexyl, neopentyl,
neoheptyl and neodecyl. Esters containing such alkyl groups can be
prepared by utilising a branched alkanoic acid in the synthesis of
the ester.
[0081] In a particularly preferred embodiment of the present
invention, the ester lubricant comprises one or more esters of
general formula: 2
[0082] wherein
[0083] R.sup.2 is the hydrocarbon radical remaining after removing
the hydroxyl groups from pentaerythritol, dipentaerythritol or
trimethylol propane;
[0084] each R.sup.3 is, independently, a linear alkyl group or a
branched alkyl group; and
[0085] p is an integer of 3, 4 or 6,
[0086] wherein one or more of the named polyols, one or more linear
alkanoic acids, or esterifiable derivatives thereof, and optionally
one or more branched alkanoic acids, or esterifiable derivatives
thereof, are utilised in the synthesis of the ester lubricant.
[0087] Preferably, a mixture of two or more linear alkanoic acids,
in particular two, or esterifiable derivatives thereof, are
utilised in the synthesis of the ester. More preferably, a mixture
of one or more linear alkanoic acids, or esterifiable derivatives
thereof, and one or more branched alkanoic acids, or esterifiable
derivatives thereof, are utilised in the synthesis. Thus,
particularly preferred ester lubricants of the invention are mixed
ester compositions which comprise a plurality of compounds of
Formula III.
[0088] Where a mixture of linear and branched alkanoic acids (or
esterifiable derivatives thereof) are utilised in the synthesis of
the ester, as is preferred, the linear alkanoic acid(s) preferably
constitutes at least 25 mole %, e.g from 25 to 75 mole %, of the
total amount of carboxylic acids used. In this way, at least 25
mole %, e.g. from 25 to 75 mole %, of the hydroxyl groups contained
in the polyol or mixture of polyols may be reacted with the said
linear alkanoic acid(s).
[0089] Ester based lubricants comprising one or more compounds of
Formula III provide a particularly good balance between the
properties desired of a lubricant and, in particular, exhibit good
thermal stability, good hydrolytic stability and acceptable
solubility and miscibility with the heat transfer fluid. As stated
previously, the present invention is particularly concerned with
the provision of a working fluid composition which can replace the
existing working fluid compositions comprising R-22 or R-502 as the
refrigerant. Refrigeration systems which contain replacements for
R-22 and R-502 typically operate at temperatures above those using
R-134a as the sole replacement refrigerant. Thus, it is
particularly desirable that the lubricant which is used in a
working fluid composition designed to replace the existing
compositions based on R-22 and R-502 exhibits good thermal
stability.
[0090] Preferably, R.sup.2 is the hydrocarbon radical remaining
after removing the hydroxyl groups from pentaerythritol or
dipentaerythritol.
[0091] Preferred linear and branched alkyl groups for R.sup.3 are
those described above in connection with R.sup.1 and are derived by
utilising the corresponding alkanoic acids or esterifiable
derivatives thereof.
[0092] An especially preferred ester based lubricant comprises a
mixed ester composition which comprises a plurality of esters of
Formula III and which is the reaction product of pentaerythritol,
heptanoic acid and a mixture of branched C.sub.8-.sub.10 alkanoic
acids. Preferably, the heptanoic acid will constitute from 25 to 75
mole % of the total amount of acids utilised in the synthesis, with
the branched C.sub.8-.sub.10 acids constituting the remainder.
Esterifiable derivatives of the acids may also be used in the
synthesis of the ester.
[0093] The lubricant will typically be part of a lubricant
composition which also comprises one or more of the additives which
are conventional in the refrigeration lubricants art. Specific
mention may be made of oxidation resistance and thermal stability
improvers, corrosion inhibitors, metal deactivators, viscosity
index improvers, anti-wear agents and extreme pressure resistance
additives. Such additives are well known to those skilled in the
art. Where the lubricant is part of a lubricant composition
containing one or more additives, such additives may be present in
the amounts conventional in the art. Preferably, the cumulative
weight of all the additives will not be more than 8%, e.g. 5%, of
the total weight of the lubricant composition.
[0094] Suitable oxidation resistance and thermal stability
improvers may be selected from the diphenyl-, dinaphthyl-, and
phenylnaphthyl-amines, the phenyl and naphthyl groups of which may
be substituted. Specific examples include N,N'-diphenyl
phenylenediamine, p-octyldiphenylamine, p,p-dioctyldiphenylamine,
N-phenyl-1-naphthyl amine, N-phenyl-2-naphthyl amine,
N-(p-dodecyl)-phenyl-2-naphthyl amine, di-1-naphthyl amine, and
di-2-naphthyl amine. Other suitable oxidation resistance and
thermal stability improvers may be selected from the phenothiazines
such as N-alkylphenothiazines, and the hindered phenols such as
6-(t-butyl) phenol, 2,6-di-(t-butyl) phenol,
4-methyl-2,6-di-(t-butyl) phenol and
4,4'-methylenebis(-2,6-di-[t-butyl] phenol).
[0095] Suitable cuprous metal deactivators may be selected from
imidazole, benzamidazole, 2-mercaptobenzthiazole,
2,5-dimercaptothiadiazole, salicylidine-propylenediamine, pyrazole,
benzotriazole, tolutriazole, 2-methylbenzamidazole, 3,5-dimethyl
pyrazole, and methylene bis-benzotriazole. Examples of more general
metal deactivators and/or corrosion inhibitors include organic
acids and the esters, metal salts and anhydrides thereof, such as
N-oleyl-sarcosine, sorbitan monooleate, lead naphthenate,
dodecenyl-succinic acid and its partial esters and amides, and
4-nonylphenoxy acetic acid; primary, secondary and tertiary
aliphatic and cycloaliphatic amines and amine salts of organic and
inorganic acids, such as oil soluble alkylammonium carboxylates;
heterocyclic nitrogen containing compounds, such as thiadiazoles,
substituted imidazolines, and oxazolines; quinolines, quinones and
anthraquinones; ester and amide derivatives of alkenyl succinic
anhydrides or acids, dithiocarbamates, dithiophosphates; and amine
salts of alkyl acid phosphates and their derivatives.
[0096] Suitable viscosity index improvers include polymethacrylate
polymers, copolymers of vinyl pyrrolidone and methacrylates,
polybutene polymers, and copolymers of styrene and acrylates.
[0097] Examples of suitable anti-wear and extreme pressure
resistance agents include sulphurised fatty acids and fatty acid
esters, such as sulphurised octyl tallate; sulphurised terpenes;
sulphurised olefins; organopolysulphides; organo phosphorous
derivatives including amine phosphates, alkyl acid phosphates,
dialkyl phosphates, aminedithiophosphates, trialkyl and triaryl
phosphorothionates, trialkyl and triaryl phosphines, and
dialkylphosphites, e.g., amine salts of phosphoric acid monohexyl
ester, amine salts of dinonylnaphthalene sulphonate, triphenyl
phosphate, trinaphthyl phosphate, diphenyl cresyl and dicresyl
phenyl phosphates, tricresyl phosphate, naphthyl diphenyl
phosphate, triphenylphosphorothionate; dithiocarbamates, such as an
antimony dialkyl dithiocarbamate; chlorinated and/or fluorinated
hydrocarbons, and xanthates.
[0098] The working fluid compositions of the invention will
typically comprise a major amount of the heat transfer fluid and a
minor amount of the synthetic lubricant. Preferably, the working
fluid compositions of the invention will comprise from 50 to 99% by
weight, more preferably from 70 to 99% by weight, of the heat
transfer fluid and from 1 to 50% by weight, more preferably from 1
to 30% by weight, of the lubricant based on the total weight
thereof.
[0099] The working fluid compositions are useful in all types of
compression cycle heat transfer devices. Thus, they may be used to
provide cooling by a method involving condensing the heat transfer
fluid and thereafter evaporating it in a heat exchange relationship
with a body to be cooled. They may also be used to provide heating
by a method involving condensing the heat transfer fluid in a heat
exchange relationship with a body to be heated and thereafter
evaporating it.
[0100] The working fluid compositions of the invention provide a
good compromise between performance and low or zero ozone
depletion. They are especially suitable for applications currently
satisfied by refrigerants R-22 and R-502.
[0101] The present invention is now illustrated, but not limited,
with reference to the following Examples.
[0102] The working fluid compositions of the invention which were
investigated in the following Examples comprised a lubricant and a
heat transfer fluid which was either a binary mixture of
1,1,1,2-tetrafluoroethane (R-134a) and difluoromethane (R-32) or a
ternary mixture of 1,1,1,2-tetrafluoroethane (R-134a),
difluoromethane (R-32) and pentafluoroethane (R-125).
[0103] 1,1,1,2-tetrafluoroethane, difluoromethane and
pentafluoroethane are at least partially soluble in each of the
lubricants tested which means the converse is true, i.e. each of
the lubricants tested will be at least partially soluble in each of
these hydrofluoroalkanes. Moreover, each lubricant tested is at
least partially soluble in the binary or ternary mixtures
themselves.
EXAMPLE 1
[0104] In this Example various working fluid compositions were
prepared comprising 15% w/w of a lubricant and the complementary
percentage of a heat transfer fluid comprising (by weight) equal
proportions of R-134a and R-32. The lower miscibility temperature
of each composition, i.e. the lowest temperature at which the
lubricant remained miscible with the heat transfer fluid, was
determined. The method employed was as follows:
[0105] A set amount of the lubricant to be tested was placed in a
previously evacuated thick walled test tube and the tube was then
placed in a cooling bath regulated at the desired temperature. Once
the tube was sufficiently cold, a set amount of the heat transfer
fluid was condensed into the test tube. The tube was then removed
from the cooling bath and the contents allowed to warm to room
temperature. After the contents had been allowed to equilibriate at
room temperature, they were agitated and visually examined for
evidence of phase separation (the mixture looks cloudy). If there
was no evidence of phase separation, the temperature of the mixture
was lowered in a cooling bath at a rate of 1.degree. C. per minute
until phase separation was observed. The temperature at which phase
separation was first observed was recorded as the lower miscibility
temperature.
[0106] The results are shown in Table 1. Each lubricant is at least
partially soluble in each of the components of the heat transfer
fluid and also in the fluid itself.
[0107] The lower miscibility temperatures of a series of
compositions comprising 15% w/w of a lubricant and the
complementary percentage of a single hydrofluoroalkane selected
from R-134a, R-32 and R-125 were also determined. The compositions
were prepared and the lower miscibility temperatures determined
using the procedure described above. The results are shown in Table
1A. In Table 1A it will be noticed that the lower miscibility
temperatures are in some cases quoted as being less than
-60.degree. C. This means that at -60.degree. C. phase separation
was not observed.
1TABLE 1 LOWER MISCIBILITY TEMPERATURE LUBRICANT (.degree. C.) PE6
-27 "EMKARATE" .TM. RL-212 -3 "EMKARATE" .TM. RL-184 >10
"EMKAROX" .TM. RL-118 I
[0108]
2 TABLE 1A LOWER MISCIBILITY TEMPERATURE (.degree. C.) LUBRICANT
R-134a R-32 R-125 PE6 <-60 0 <-60 "EMKARATE" .TM. RL-212 -25
>20 <-60 "EMKARATE" .TM. RL-184 10 >20 <-60 "EMKAROX"
.TM. RL-118 <-60 I <-60
[0109] I--denotes immiscibility over the temperature range
-50.degree. C. to +20.degree. C.
[0110] PE6 is an ester of pentaerythritol and n-hexanoic acid.
[0111] "EMKARATE" .TM. RL-212 is a commercially available ester
based lubricant for use with R-134a obtainable from ICI Chemicals
& Polymers Ltd. Specifically, the lubricant comprises an ester
of trimethylol propane and heptanoic acid.
[0112] "EMKARATE" .TM. RL-184 is a commercially available ester
based lubricant for use with R-134a obtainable from ICI Chemicals
& Polymers Ltd. Specifically, the lubricant comprises an ester
of pentaerythritol, heptanoic acid and a mixture of branched
C.sub.8-10 alkanoic acids.
[0113] "EMKAROX" .TM. RL-118 is a commercially available
polyoxyalkylene glycol based lubricant for use with R-134a
obtainable from ICI Chemicals & Polymers Ltd. Specifically, the
lubricant comprises an end-capped polyoxyalkylene glycol.
[0114] "EMKARATE" and "EMKAROX" are trademarks of ICI Chemicals
& Polymers Ltd.
EXAMPLE 2
[0115] In this Example a series of working fluid compositions were
prepared comprising varying proportions of a lubricant comprising
an ester of pentaerythritol and n-hexanoic acid and a heat transfer
fluid comprising 70% by weight of R-134a and 30% by weight of R-32.
The lubricant is at least partially soluble in each of the
components of the heat transfer fluid and also in the fluid itself.
The lower miscibility temperature of each composition was
determined. The compositions were prepared and the lower
miscibility temperatures determined using the procedure described
in Example 1.
[0116] The results are shown in Table 2. In Table 2 it will be
noticed that the lower miscibility temperature of one of the
compositions is quoted as being less than -50.degree. C. This means
that at -50.degree. C. phase separation was not observed.
3 TABLE 2 Working fluid composition % by weight of % by weight of
heat Lower miscibility lubricant transfer fluid temperature
(.degree. C.) 10.8 89.2 -30 20.3 79.7 -25 27.5 72.5 -32 36.9 63.1
-38 46.0 54.0 -47 68.0 32.0 <-50
EXAMPLE 3
[0117] In this Example a series of working fluid compositions were
prepared comprising varying proportions of a lubricant and a heat
transfer fluid comprising 70% by weight of R-134a and 30% by weight
of R-32. The lubricant comprised an ester of dipentaerythritol,
n-hexanoic acid and a branched C.sub.6 carboxylic acid, i.e. a
branched acid comprising 6 carbon atoms, and is at least partially
soluble in each of the components of the heat transfer fluid and
also in the fluid itself. The lower miscibility temperature of each
composition was again determined. The compositions were prepared
and the lower miscibility temperatures determined using the
procedure described in Example 1.
[0118] The results are shown in Table 3. In Table 3 it will be
noticed that the lower miscibility temperature of one of the
compositions is quoted as being less than -55.degree. C. This means
that at -55.degree. C. phase separation was not observed.
4 TABLE 3 Working fluid composition % by weight of % by weight of
heat Lower miscibility lubricant transfer fluid temperature
(.degree. C.) 10.0 90.0 -32 17.3 82.7 -28 38.0 62.0 -35 46.2 53.8
-41 57.8 42.2 Slightly immiscible at -55 68.8 31.2 <-55
EXAMPLE 4
[0119] In this Example a series of working fluid compositions were
prepared comprising varying proportions of a lubricant and a heat
transfer fluid comprising 70% by weight of R-134a and 30% by weight
of R-32. The lubricant comprised a mixture of the lubricants used
in Examples 2 and 3, i.e. a mixture comprising an ester of
pentaerythritol and n-hexanoic acid and an ester of
dipentaerythritol, n-hexanoic acid and a branched C.sub.6
carboxylic acids and is at least partially soluble in each of the
components of the heat transfer fluid and also in the fluid itself.
The lower miscibility temperature of each composition was again
determined. The compositions were prepared and the lower
miscibility temperatures determined using the procedure described
in Example 1.
[0120] The results are shown in Table 4. In Table 4 it will be
noticed that the lower miscibility temperature of one of the
compositions is quoted as being less than -50.degree. C. This means
that at -50.degree. C. phase separation was not observed.
5 TABLE 4 Working fluid composition % by weight of % by weight of
heat Lower miscibility lubricant transfer fluid temperature
(.degree. C.) 10.5 89.5 -31 19.7 80.3 -27 28.9 71.1 -29 41.1 58.9
-32 48.0 52.0 -39 55.2 44.8 -46 69.7 30.3 <-50
EXAMPLE 5
[0121] In this Example a series of working fluid compositions were
prepared comprising varying proportions of a lubricant comprising
an ester of pentaerythritol and n-hexanoic acid and a heat transfer
fluid comprising 50% by weight of R-134a, 30% by weight of R-32 and
20% by weight of R-125. The lubricant is at least partially soluble
in each of the components of the heat transfer fluid and also in
the fluid itself. The lower miscibility temperature of each
composition was again determined. The compositions were prepared
and the lower miscibility temperatures determined using the
procedure described in Example 1.
[0122] The results are shown in Table 5. In Table 5 it will be
noticed that the lower miscibility temperature of some of the
compositions is quoted as being less than -50.degree. C. This means
that at -50.degree. C. phase separation was not observed.
6 TABLE 5 Working fluid composition % by weight of % by weight of
heat Lower miscibility lubricant transfer fluid temperature
(.degree. C.) 10.2 89.8 <-50 22.0 78.0 -48 29.7 70.3 <-50
41.6 58.4 <-50 48.6 51.4 <-50 60.7 39.3 <-50
[0123] It will be appreciated that the binary mixtures of R-134a
and R-32 and the ternary mixtures of R-134a, R-32 and R-125 which
form the subject of the above Examples can also be used in
combination with other neopentyl polyol ester type lubricants to
yield viable working fluid compositions. Moreover, binary mixtures
of R-134a and R-32 and ternary mixtures of R-134a, R-32 and R-125
comprising different proportions of the constituent
hydrofluoroalkanes to the mixtures exemplified above can also be
used in combination with neopentyl polyol ester type lubricants to
yield viable working fluid compositions.
* * * * *