Note: Descriptions are shown in the official language in which they were submitted.
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
-- 7 --
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.
6 TABIE 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
R12 R22
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.
- 12
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.
- 13 -
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.
- 14 -
~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.
- 15 -
