5,214,929 [IMAGE AVAILABLE]   Jun. 1, 1993             L1: 1 of 2         Drop-in substitute for dichlorodifluoromethane refrigerant INVENTOR:       George H. Goble, 286 W. Navajo, West Lafayette, IN 47906APPL-NO:       07/900,424DATE FILED:    Jun. 18, 1992REL-US-DATA:   Division of Ser. No. 638,350, Jan. 7, 1991, Pat. No. 5,151,207.INT-CL:        [5] C09K 5/04US-CL-ISSUED:  62/114; 252/67US-CL-CURRENT: 62/114; 252/67SEARCH-FLD:    252/67; 62/114REF-CITED:                             U.S. PATENT DOCUMENTS     4,303,536   12/1981   Orfeo et al.                   252/67     4,482,465   11/1984   Gray                           252/67     4,510,064    4/1985   Ermak                          252/67     4,810,403    3/1989   Bivens et al.                  252/67                           FOREIGN PATENT DOCUMENTS       2716834    10/1977  Federal Republic of Germany     61-287979    12/1986  Japan       2228739     9/1990  United Kingdom                              OTHER PUBLICATIONSW. R. Woolrich, "Handbook of Refrigerating Engineering," Appendix II, Avis  Publishing Company, Inc., 1965."Hawley's Condensed Chemical Dictionary" (11th ed. 1987), p. 265.1988-1989 Aldrich Chemical Company, Inc. catalog, p. 334.ART-UNIT:      115PRIM-EXMR:     Christine SkaneLEGAL-REP:     Woodard, Emhardt, Naughton, Moriarty & McNett ABSTRACT: A novel ternary mixture of refrigerants that can be drop-in substituted fordichlorodifluoromethane (R-12), but that, unlike dichlorodifluoromethane,causes very little ozone damage, comprising approximately 2 to 20 % by weightisobutane (R-600a), approximately 41 to 71% by weight chlorodifluoromethane(R-22), and approximately 21 to 51 by weight chlorodifluoroethane (R-142b),with the weight percentages being of the overall mixture.               4 Claims, No DrawingsEXMPL-CLAIM:   1 PARENT-CASE:   This application is a division of application Ser. No. 07/638,350, filedJan. 01, 1991, now U.S. Pat. No. 5,151,207. SUMMARY:   The present invention relates to refrigerants generally, and morespecifically to a mixture of refrigerants that may be substituted for theenvironmentally damaging refrigerant dichlorodifluoromethane (R-12).                          BACKGROUND OF THE INVENTION  Butane, isobutane, propane, and other hydrocarbons were commonly used asrefrigerants prior to World War II. The introduction of the family ofFREON.RTM. fluorocarbon products in the early 1930s provided nonflammable,nontoxic, and what were believed to be environmentally safe substituterefrigerants for hydrocarbons. Fluorocarbons largely supplanted hydrocarbonsas refrigerants of choice in most applications following World War II.Hydrocarbons are still in use today in special low temperature refrigerationsystems (-100 degree Fahrenheit) due to the relatively high boiling points offluorocarbons.  Certain chlorine containing fluorocarbon refrigerants, known aschlorofluorocarbons (CFC's), have been causally linked to the well-documenteddepletion of the earth's ozone layer. The Montreal Protocol and the UnitedStates Environmental Protection Agency (EPA) have thus called for a phase outof the use of the CFCs that are known to be contributing to the degradationof the environment, and specifically to ozone layer depletion.Dichlorodifluoromethane (CCl.sub.2 F.sub.2), also known as CFC-12,Refrigerant-12, or simply R-12, is one of the most commonly used CFCrefrigerants in automobile air conditioners and elsewhere. It is also the CFCrefrigerant with the highest ozone depletion potential of any knownrefrigerant. R-12 has an "ozone depletion units" (ODU) measure of 1.0, andserves as the yardstick of ozone depletion potential against which all otherrefrigerants are measured.  New automobile air conditioners built in 1989 consumed 20 million pounds ofR-12. An additional 80 million pounds of R-12 were consumed that year inreplenishing the R-12 refrigerant that leaked from existing automobile airconditioners. Leaking of R-12 from automobile air conditioning systems is infact a major source of the R-12 that escapes into the atmosphere each year.  Since the discovery in the 1970's that CFC refrigerants escaping into theatmosphere were depleting the earth's ozone layer, many companies have spentlarge sums of money trying to develop a non-toxic, nonflammable replacementfor R-12 that could be "dropped into" existing automobile air conditioningsystems as a substitute for R-12 without requiring any equipment changes. Todate, no such "drop in" substitutes for R-12 have been announced.Consequently, the automobile industry plans to develop and market newautomobile air conditioning systems by the 1995 model year that use an ozonesafe refrigerant, tetrafluoroethane (CH.sub.2 FCF.sub.3), also known as FC134a, Refrigerant-134a, or simply R-134a. Fortunately, R-134a has an ozonedepletion factor (ODF) of zero. Unfortunately, R-134a cannot be drop-insubstituted for R-12 in existing air conditioning systems due to compressorlubrication problems inherent in the use of R-134a in present systems, theinadequacy of the hoses used in Present systems to handle R-134a, and thenecessity of using a larger compressor than is now in use with R-12refrigerant to properly utilize R-134a.  Most automobiles that will be built through the 1994 model year will stillrequire the use of an R-12 refrigerant, or an acceptable drop-in substitute.With the environmental efforts to phase out, or ban, the use ofozone-depleting CFC's gaining momentum, it appears that an R-12 drop-insubstitute for use in existing air conditioning systems must be found.                           SUMMARY OF THE INVENTION  The present invention provides a novel ternary mixture of refrigerants thatcan be substituted for R-12, but that, unlike R-12, causes very little ozonedamage. It is free of R-12. The novel mixture of refrigerants of the presentinvention provides an acceptable level of cooling in medium and hightemperature applications where R-12 is now in use, such as in coolers and airconditioners operating at evaporating temperatures of 25 degrees Fahrenheitand higher, i.e., automobile air conditioners. It also mixes well withcompressor oils, thereby Providing for adequate lubrication of existingcompressors that utilize R-12. The novel ternary mixture of refrigerants ofthe present invention is therefore a "drop-in" substitute for R-12.  One embodiment of the present invention comprises a ternary mixture ofrefrigerants that is a drop-in substitute for dichlorodifluoromethane (R-12),comprising about 2 to 20 weight percent isobutane (R-600a), about 21 to 51weight percent chlorodifluoroethane (R-142b), and about 41 to 71 weightpercent chlorodifluoromethane (R-22), with the weight percentages of thecomponents being weight percentages of the overall mixture.  Another embodiment of the present invention comprises a method for producingrefrigeration in a refrigeration system designed for a dichlorofluoromethane(R-12) refrigerant, comprising drop-in substituting for thedichlorofluoromethane (R-12) a ternary mixture of about 2 to 20 weightpercent isobutane (R-600a), about 21 to 51 weight percentchlorodifluoroethane (R-142b), and about 41 to 71 weight percentchlorodifluoromethane (R-22), with the weight percentages of the componentsbeing weight percentages of the overall mixture; condensing the ternarymixture; and thereafter evaporating the ternary mixture in the vicinity of abody to be cooled.  It is an object of the present invention to provide a "drop in" substitutefor R-12 that causes very little ozone damage.  It is also an object of the present invention to provide a substituterefrigerant for R-12 that has an ozone depletion factor (ODF) ofapproximately 0.05.  It is also an object of the present invention to provide a drop-insubstitute refrigerant for R-12 that provides an acceptable level of coolingin medium and high temperature applications where R-12 is now in use, andthat mixes well with compressor oils that are miscible with R-12 to providefor adequate lubrication of existing compressors that utilize R-12.  Related objects and advantages of the present invention will be apparentfrom the following description. DETDESC:                     DESCRIPTION OF THE PREFERRED EMBODIMENT  For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments described below, andspecific language will be used to describe the same. It will nevertheless beunderstood that no limitation of the scope of the invention is therebyintended, such alterations and further modifications in the describedembodiments, and such further applications of the principles of the inventionas described therein being contemplated as would normally occur to oneskilled in the art to which the invention relates.  The novel ternary mixture of refrigerants of the present invention includesa mixture of approximately 2 to 20% by weight isobutane (R-600a),approximately 21 to 51% by weight chlorodifluoroethane (R-142b), andapproximately 41 to 71% by weight chlorodifluoromethane (R-22), with theweight percentages totalling 100%. This novel mixture of refrigerants is adrop-in substitute for R-12 in medium or high temperature applications, suchas coolers and air conditioners operating at evaporating temperatures of 25degrees Fahrenheit and higher.  Compared with R-12's ozone depletion factor (ODF) of 1.0, however, thisnovel mixture has an ozone depletion factor of about 0.05, and will beclassified as an EPA CLASS-II substance under the Federal Clean Air Act, asamended. R-12 is a CLASS-I substance. R-22 and R-142b are not productioncontrolled or taxed by the EPA or under the Montreal Protocol at this time.  Typical air conditioning compressor operation produces a "fog" consisting ofabout 10% compressor lubrication (mineral) oil mixed in the refrigerantdischarge hot gas stream leaving the compressor. The refrigerant typicallycondenses to liquid at temperatures of about 100 to 180 degrees Fahrenheit.The warm refrigerant liquid lowers the viscosity of the oil it is carrying,so oil build up in the high pressure (liquid) side of the refrigerationcircuit is not a problem. However, after passing through the expansiondevice, the refrigerant temperature drops to the 32 to 35 degree Fahrenheitrange and boils back to the gas phase in the evaporator. The oil will thickenand tend to become trapped in the evaporator if it is not readily miscible inthe refrigerant. The refrigerant leaves the evaporator as a gas, leaving muchof the oil behind, which then starves the compressor of oil and leadsultimately to compressor failure.  On the the other hand, an oil miscible refrigerant, such as R-12, causes theoil and refrigerant to mix during the condensation phase. This greatly lowersthe viscosity of the oil during the evaporation phase. Since the oil containslarge amounts of dissolved refrigerant, which is now boiling and foaming, andis still low in viscosity, the oil gets carried out of the evaporator by thegas stream. Now in the warm suction line, most of the remaining refrigerantleaves the oil. Since the gas velocity is higher and the suction line is muchwarmer than the evaporator, the oil can find its way back to the compressorby creeping along the walls of the warm suction line.  R-22 and R-142b are polar substances that have limited miscibility with thecompressor lubrication oils typically used in air conditioning systemscharged with R-12 refrigerant. In testing done to date with samples of R-142band R-22 mixed with approximately 10% by volume of a 525 viscosity automotiverefrigeration oil typically used in R-12 systems, both R-142b and R-22 didnot stay mixed with the 525 viscosity oil at evaporation temperatures (35degrees Fahrenheit). Testing has also shown that R-12 refrigerant and thenovel ternary mixture of the present invention stayed mixed with the 525viscosity oil, even at 0 degrees Fahrenheit.  It would be possible to use a binary mix of R-22 and R-142b in existing R-12automobile systems, but the 525 viscosity oil used in R-12 systems would haveto be changed and replaced with an oil designed for use with an R-22refrigerant. Oils designed for R-22 systems are usually of a viscosity of 150to 300. To date, no commercially marketed 525 viscosity oil is known to bemiscible with R-22 refrigerants. Due to the extreme conditions automotive airconditioners sometimes encounter, the use of 150 to 300 viscosity oils maycause lubrication problems if the oil becomes too thin.  Changing the oil in an existing R-12 system is also time consuming andcostly. Oil is spread out over the entire refrigeration circuit, so drainingthe compressor will only get part (usually just 1/2) of the oil in the entiresystem. A common method of cleaning the oil from an R-12 system is flushingthe system with trichlorofluoromethane (CCl.sub.3 F), also known as R-11.This requires the inconvenience of disconnecting the system piping. Also,R-11 has the same ozone depletion factor as R-12, and it is becomingexpensive and hard to find. Using several pounds of R-11 to flush an existingR-12 system is therefore environmentally unsound.  The isobutane component of the ternary mixture of the present inventionkeeps 525 viscosity oil miscible with the novel mixture of the presentinvention at evaporator temperatures, and also provides refrigeration effectnear the output side of the evaporator. Thus, the isobutane component aids inthe oil return from the evaporator back to the compressor, and, in fact, is anecessary component to prevent lubrication-related compressor failures inR-12 designed systems.  The small amount by weight of isobutane utilized in the mixture of thePresent invention does not appear to cause flammability problems. Incomparison testing with a binary mixture of isobutane and R-22, the R-22component of the ternary mixture of the invention appeared to leave theternary mixture more slowly when a system leak occurred, and did notconcentrate the isobutane to flammable limits. In the binary isobutane/R-22mixture, by contrast, the R-22 left the binary mixture quickly, concentratingthe isobutane to flammable limits at the leak location.  Table I sets forth examples of ternary mixtures of the invention with knowntolerances to date. Percentages are weight percentages, and components totalabout 100%.              TABLE I                                                     ______________________________________                                    Mixture Isobutane    R-142b      R-22                                     ______________________________________                                    A       8% +/- 2%    36% +/- 2%  56% +/- 2%                               B       8% + 10% - 5%                                                                          36% +/- 10% 56% +/- 2%                               C       8% + 12% - 6%                                                                          36% +/- 15%  56% +/- 15%                             D       8% +/- 2%    28% +/- 7%  64% +/- 7%                               ______________________________________                                      Mixture A has been the most preferred mixture to date. Mixture B would workin most instances. However, mixtures at the high end of the isobutane range,and/or the high end of the R-142b range may lead to flammability problems instandard automobile air conditioning systems designed for R-12. Also,mixtures at the low end of the isobutane range, and/or the low end of theR-142b range, may lead to compressor oil starvation (poor oil return) andexcessive system pressures when used in an automobile air conditioning systempowered by an engine that is being revved while the automobile is not inmotion on very hot days (90 degrees Fahrenheit or hotter).  Mixture C will cause flammability problems in standard automobile airconditioning systems designed for R-12 when the R-142b and/or isobutanecomponents are at the maximum weight percentages. Low performance or liquidslugging may also occur. If the weight percentage for R-22 is at the maximum,high system pressures will occur and lead to hoses bursting or other standardautomobile air conditioning system failures. However, Mixture C may work wellat the high and low ends of the component limits in non automotive systems,such as household air conditioning systems or heatpumps, in R-22 systems, orin modified automobile air conditioning systems designed for R-12. Mixture Cmay also work well at the high and low ends of the component limits instandard automobile air conditioning systems designed for R-12 that areoperated only under special conditions, such as at 60 degree Fahrenheitambient temperature or lower.  Mixture D represents a high performance mixture that would deliver 50 to100% more cooling at higher temperatures. Mixture D would require minorequipment changes to the standard automobile air conditioning system to add ahigh pressure cutoff switch to the high side (liquid) line gauge serviceport. The recommended cutoff pressure would be 375 to 400  PSIG, with a cutin pressure of 250 PSIG. Such a switch needs to be installed in series withthe compressor clutch circuit to disable the compressor when the cut outpressure is reached. Revving an automobile engine while not in motion at anambient temperature of over approximately 90 degrees Fahrenheit would causethe cut out to operate. Engine idle speeds probably will not cause a highpressure cut out if the condenser is clean. When the vehicle is in motion,ram air should provide adequate condenser heat dissipation to prevent overpressure cut outs.  In testing completed to date, the ternary mixture of the invention hasexhibited much better cooling than R-12 at temperatures above ambienttemperatures (70-75 degrees Fahrenheit). On nonexpansion valve airconditioning systems found in most U.S. made vehicles (orifice only), headpressure of the ternary mixture of the present invention falls off below70-75 degrees Fahrenheit, reducing the system capacity to what would beprovided by R-12.  For the purpose of promoting a better understanding of and to furtherillustrate the invention, reference will now be made in the Examples below topreferred ternary mixtures of refrigerants of the invention.  EXAMPLE 1  A mixture of 8.4% by weight isobutane, 35.7% by weight R-142b, and 55% byweight R-22 was provided in the following manner (the weight percentages addup to 99.1% due to a measurement error). TIF electronic refrigerant"charging" scales were used to weigh in the charge. A vacuum was pulled on aRoninair 4 lb. capacity "dial-a-charge" refrigerant measuring cylinder. Theisobutane (liquid) was weighed into the vacuum in the dial-a-charge. Thepressure was about 26 PSIG at 73 degrees Fahrenheit. The R-142b was thenweighed into the dial-a-charge. R-22 was then weighed in slowly withintermittent shaking of the dial-a-charge to mix the isobutane and R-22 andnoting of the pressure. R-22 was added in this fashion until the Pressurereading on the dial-a-charge was approximately 7 to 8 PSIG higher than whatR-12 would have been at the temperature of mixing. For this example, at 73degrees Fahrenheit the pressure of 80 PSIG was used as the stopping point foradding R-22. R-22 was added over a period of about 20 minutes to allowtemperatures to stabilize within the dial-a-charge.  The dial-a-charge was then removed from the charging manifold/gauges and wasconnected to the air conditioning system of a 1978 Datsun 810 and the systemwas charged in the conventional manner. The oil in this system alreadycontained a red dye for leak detection. Samples, under pressure, were takenwith a vizi-charge from the liquid line during operation. The vizi-charge wasthen switched to the low (suction line), and the valve slowly opened to boiloff the working fluid in order to observe the amount of oil carried in thesample. About 10 to 12% by volume of oil was observed after the refrigerantboiled off. Oil was observed to be still mixed evenly in the vizi-chargeafter setting for 3 days.  The mixture within the dial-a-charge was tested for flammability, but couldnot be ignited.  Cooling in the 1978 Datsun 810 seemed slightly better than that obtainedpreviously with R-12, although no detailed BTU measurements were taken.Suction (low side) and discharge (high side) pressures were close to thoseobtained with R-12. At ambient temperatures in the low 70's, low sidepressure was about 11 to 13 PSIG (at 2000 rpm; R-12 would be about 18 PSIG),and high side pressure was about 150 PSIG. Momentary high side pressures wereobtained around 200 PSIG with a hot engine, stopped at traffic lights, withthe ambient temperature in the high 70's. This is close to the high sidepressures of R-12.  The air outlets within the automobile were emitting chilled air in the 38 to40 degrees Fahrenheit range, and the compressor was cycling on and off due tothe low temperature cut out being reached. The 1978 Datsun 810 has thereceiver (storage tank) in the high pressure side rather than in the low sideas found in typical General Motors systems. The lower suction pressuresseemed to be due to the evaporator being colder by 5 to 7 degrees Fahrenheitthan was the case with R-12.                                   EXAMPLE 2     Additional testing of the mixture of Example 1 was done in a 1990 PontiacTranssPort equipped with a Harrison (GM) "V-5" variable displacementcompressor. This compressor reduces its displacement (capacity) when thesuction pressure drops below 28 PSIG. Compressor gas discharge temperaturesappeared to be close at idle with an ambient temperature of 87 degreesFahrenheit to those of an identical model 1990 Pontiac Transsport at a newcar dealer that utilized standard R-12 refrigerant. The R-12 system idled at150 degrees Fahrenheit and the mixture of Example 1 idled at 154 degreesFahrenheit.  Head (high side) pressures for the mixture of Example 1 were lower than inthe R-12 system when the vehicles were in motion (30 to 65 MPH), ranging from220 to 150 PSIG at an ambient temperature in the low 90's. Racing the engine(2000 to 3000 RPM) while parked caused slightly higher head pressures thanthe R-12 system. The R-12 system with MAX-AIR engaged was able to reach 400PSIG at an ambient temperature of 100 degrees Fahrenheit, but the mixture ofExample 1 reached 400 PSIG at an ambient temperature in the low 90's. Thisappears to be due to the fact that more heat is transferred and the condenseris less able to get rid of the heat with no ram air. At normal idle speedsand an ambient temperature of 95 degrees Fahrenheit, head pressures of around250 to 260 PSIG were observed, well within system limits.  Increasing the weight percentage of R-22 in the mixture of Example 1 tendsto drive up head pressures and also moves more heat, leading to coolerdischarge air. Idle performance with a higher R-22 weight percentage producedpressures approaching design limits at ambient temperatures of 95 degreesFahrenheit or above. A pressure limiting cut out switch that would beconnected to the high side service valve and would be used to disengage thecompressor if high idle or racing the engine while parked raised pressure toohigh (i.e., 375 PSIG) would provide much superior cooling performance duringnormal operation. Cooling would be between 50% to 100% more than a comparableR-12 system.  Lowering the weight percentages of R-22 in the mixture of Example 1 reducedthe cooling capacity and lowered head pressure while raising suctionpressure. On nonvariable displacement compressors, the suction pressure wouldbe expected to decrease instead of increase in this case. This moved themixture toward increased flammability as well. Head pressures droppedsignificantly with the vehicle in motion to the point of reducing refrigerantflow through the expansion device, which greatly reduced cooling.  While the invention has been described in the Examples and foregoingdescription, the same is to be considered as illustrative and not restrictivein character, it being understood that only preferred embodiments have beendescribed and that all changes and modifications that come within the spiritof the invention are desired to be protected. CLAIMS:   What is claimed is:  1. A method for producing refrigeration in a refrigeration system designedfor a dichlorodifluoromethane refrigerant, comprising drop-in substitutingfor said dichlorodifluoromethane a ternary mixture of about 2 to 20 weightpercent isobutane, about 21 to 51 weight percent 1-chloro-1,1-difluoroethane,and about 41 to 71 weight percent chlorodifluoromethane, with the weightpercentages of said components being weight percentages of the overallmixture; condensing said ternary mixture; and thereafter evaporating saidternary mixture in the vicinity of a body to be cooled.  2. The method of claim 1 wherein said substituting step consists of drop-insubstituting a ternary mixture of about 6 to 10 weight percent isobutane,about 21 to 35 weight percent 1-chloro-1,1-difluoroethane, and about 57 to 71weight percent chlorodifluoromethane, the weight percentages of saidcomponents being weight percentages of the overall mixture.  3. The method of claim 1 wherein said substituting step consists of drop-insubstituting a ternary mixture of about 3 to 18 weight percent isobutane,about 26 to 46 weight percent 1-chloro-1,1-difluoroethane, and about 46 to 66weight percent chlorodifluoromethane, the weight percentages of saidcomponents being weight percentages of the overall mixture.  4. The method of claim 3 wherein said substituting step consists of drop-insubstituting a ternary mixture of about 6 to 10 weight percent isobutane,about 34 to 38 weight percent 1-chloro-1,1-difluoroethane, and about 54 to 58weight percent chlorodifluoromethane, the weight percentages of saidcomponents being weight percentages of the overall mixture.