3,770,640 United States Patent Office Patented Nov. 6, 1973 2 bility to heat and decompose under conditions of normal 3,770,640 use. Additionally, some azo dyes do not have the requisite REFRGERANTS COLORED FOR LEAK solubility, e.g., in refrigeration oil-dichlorodifluoro ENDICATION Philip Lee Bartlett, Wilmington, Del, assignor to E. I. du . Pont de Nemours and Company, Wilmington, Del. 5 In addition to these problems, some of the dyes utilized Filed Nov. 22, 1971, Ser. No. 201,120 in the art severely stain acrylic finishes such as those nor nt. C. CO9k 3/02 mally used in automobiles thus making it impractical to U.S. C. 252-68 15 Claims use containing such dyes in automobile air conditioners. O Alburger in U.S. 3,489,898 discloses solutions and dis ABSTRACT OF THE DISCLOSURE persions of various fluorescent whitening agents in mix Refrigerants, refrigeration oils and -refrigera tures of non-volatile fluorotelomers and volatile trichloro tion oil mixtures containing anthraquinone dyes having the fluoromethane of 1,1,2-trichloro-1,2,2-trifluoroethane and Structure fluoromethane of 1,1,2-trifluoroethane and NORO,)(tlo 5 the application of the solutions to the surfaces of contain ers intended for the storage of liquid oxygen. Surface de fects in the containers are made visible by evaporating the R R8 surface solution leaving some solution entrapped in the sur face cracks. Alburger also discloses, for this use, the dye 20 1,4-bis(4-methylanilino)anthraquinone. The same dye is disclosed as suitable in the process of U.S. 3,399,025 wherein the dye is tranfered from suspended trichloroflu oromethane to polymer granules in an aqueous slurry. The process is carried out under pressure and at temperatures 25 up to about 275 F. for times up to one hour. It has now been discovered that by incorporating antha wherein R, R2, R3 and R4 are each H or an anilino group, quinone dyes, having a designated structure, into fluoro substituted by from 1 to 3 saturated alkyl groups having carbon refrigerants, refrigeration oils and mixtures thereof, a total of from 4 to 24 carbon atoms, and wherein at least the resultant compositions provide positive indication of 30 leaks anywhere in a vapor compression heat transfer sys 2 and no more than 3 of R, R2, R3 and R are H. tem; possess adequate stability to the highest temperatures normally encountered in refrigeration systems in the pres BACKGROUND OF THE INVENTION ence of fluorinated refrigerants, refrigeration oils and materials of construction; do not interfere with the normal (1) Field of the invention 35 operation of such a heat transfer system and are easily The invention relates to refrigerants, refrigeration oils removed from painted surfaces, as for example, automo and refrigerant-refrigeration oils colored with anthraqui bile finishes, or refrigerator cabinets. none dyes for leak detection. They are particularly useful in the field of vapor compression heat transfer processes SUMMARY OF THE INVENTION wherein fluorocarbon refrigerants, at least in part in the 40 liquid phase, are subjected to elevated temperature, e.g., A composition which comprises in conventional home refrigeration, in freezing, air con (A) a refrigeration liquid selected from the group ditioning, heat pumping, and in heat engines employing consisting of power turbines. (a) a fluorocarbon refrigerant selected from the 45 group consisting of (2) Description of the prior art , Various dyes have been employed to indicate the pres , ence and location of leaks in vapor compression heat chlorodifluoromethane, transfer systems such as refrigeration systems employing 1,1,2-trichloro-1,2,2-trifluoroethane, fluorocarbon refrigerants and refrigeration oils. Escaping 50 1,2-dichloro-1,1,2,2-tetrafluoroethane, refrigerant and/or oil containing dissolved dye are 1,1-difluoroethane/dichlorodifluoromethane intended to deposit easily visible dye indications on the aZeotrope, outside of the device, thus facilitating recognition and chloropentafluoroethane/chlorodifluoro location of a leak. None of the dyes of the art employed 55 methane azeotrope, for this purpose satisfy all of the stringent requirements chlorotrifluoromethane, of the refrigeration field. chlorotrifluoromethane/trifluoromethane U.S. 1,915,965 discloses the use of basic dyes such as azeotrope, methyl violet base, crystal violet, Auramine B, Rhodamine bromotrifluoromethane, B, etc., as leak indicators in refrigeration systems. The 60 basic dyes as a class are generally too unstable for use at trifluoromethane, the temperatures often encountered in modern refrigera chloropentafluoroethane tion, i.e., temperatures as high as 300' F. and even about /chloropentafluoroethane 400 F. at the compressor outlet valve. The color is azeotrope, destroyed and the dye is converted to tars which may plug chloropentafluoroethane/1,1-difluoroethane the system. Further, such dyes generally possess inade 65 azeotrope, quate solubility in the refrigeration oils. For example, dichlorofluoromethane, methyl violet base dissolves to the extent of less than 1 wt. dichlorodifluoromethane/chlorofluoro percent in well known “Suniso' 3GS refrigeration oil. methane azeotrope, U.S. 3,370,013 discloses the use of oil soluble azo dyes 70 chlorofluoromethane/1,2-dichlorotetra as leak indicators in fluorocarbon refrigerants. Like the fluoroethane azeotrope, basic dyes, the azo dyes generally possess inadequate sta difluoromethane, 3,770,640 3 4. 1,2-dibromotetrafluoroethane, dichlorodifluoromethane/chlorofluoromethane azeo 1,1,1-trifluoroethane, trope (British Pat. 1,218,917), 1,1-difluoro-1-chloroethane, chlorofluoromethane/1,2-dichlorotetrafluoroethane azeo 1,1-difluoroethane, trope (U.S. Pat. 3,505,232), bromotrifluoromethane/difluoromethane difluoromethane, azeotrope, 1,2-dibromotetrafluoroethane, 1,2-dichlorotetrafluoroethane/dichloro 1,1,1-trifluoroethane, fluoromethane azeotrope, and 1,1-difluoro-1-chlorethane, hexafluoroethane/trifluoromethane 1,1-difluoroethane, azeotrope, O bromotrifluoromethane/difluoromethane azeotrope (b) a refrigeration oil and (U.S. Pat. 3,418,242), (c) a mixture of (a) and (b) and 1,2-dichlorotetrafluoroethane/dichlorofluoromethane (B) an anthraquinone dye or mixture of anthraqui azeotrope (U.S. Pat. 2,630,686), and none dyes having the structure hexafluoroethane/trifluoromethane azeotrope (Hadley et 5 al. Journ. Amer. Chem. Soc. 62 3302 (1940)). Trichlorofluoromethane, dichlorodifluoromethane, Ri O R3 chlorofluoromethane, 1,1,2-trichloro-1,2,2-trifluoroethane, /N 20 1,2-dichloro-1,1,2,2-tetrafluoroethane, 1,1-difluoroethane/dichlorodifluoromethane azeo trope, chloropentafluoroethane/chlorodifluoromethane azeo R2 s R4 trope 25 are preferred, dichlorodifluoromethane being most pre ferred. Useful refrigeration oils include any of the oils which wherein R, R2, R2 and R4 are each H or an anilino are well known in the art and are commonly used in group substituted by from 1 to 3 saturated alkyl heat transfer apparatus, e.g., naphthenic oils, paraffinic groups having a total of from 4 to 24 carbon atoms, 30 oils, alkylated benzene oils and polyalkyl silicate oils. and wherein at least 2 and no more than 3 of R Useful illustrative oils include for example R, R3 and R are hydrogen, and wherein the anthraquinone dye is soluble in the refriger ation liquid, the concentration of said dye being at least about 0.007 gram per 100 cc. of said refrigeration liquid. 35 The process aspect of this invention is a process for Trade name Oil type Manufacturer indicating leaks in a vapor compression heat transfer 'Suniso'3GS.------Naphthenic------Sun Oil Co. "Suniso' 4GS------do------Do. system which comprises circulating through said system 'Sunis0'5GS- ----do------D0. 40 'Capella' D------do--- - Texaco Oil Co. a composition of this invention as described above. 'Delco' 15-117------Paraffinic Do.

DESCRIPTION OF THE INVENTION "Zerice'CE (General S-41.------Electric) Alkylated---do---- benzene--- HygieDQ. g. Co. ace). The present invention is directed to a composition 'Fluicil' S-55K.------Polyisobutyl silicate.-- Farbenfabriken which is particularly useful in the detection of leaks oc Bayer A.G. curring in vapor compression heat transfer systems. The 45 "Sometimes called Alaska Bleu. composition comprises a refrigeration liquid containing at least about 0.007 gram of a dissolved anthraquinone dye per 100 cc. of refrigeration liquid at 77 F., from about 0.007 to about 1.3 grams of dye per 100 cc. of When the refrigeration liquid is a mixture of fluorocarbon refrigeration oil being preferred in most instances. By 50 refrigerant and refrigeration oil, the ratio of one to the the term "refrigeration liquid” as used herein is meant other is not critical; however, about a 1:1 weight ratio a fluorocarbon refrigerant, a refrigeration oil or a mix is preferred. ture of a fluorocarbon refrigerant and refrigeration oil. The dyes useful in this invention include an anthra Useful fluoocarbon refrigerants include quinone dye or mixture of anthraquinone dyes having the 55 trichlorofluoromethane, Structure dichlorodifluoromethane, chlorodifluoromethane, 1,1,2-trichloro-1,2,2-trifluoroethane, 1,2-dichloro-1,1,2,2-tetrafluoroethane, 60 1,1-difluoroethane/dichlorodifluoromethane azeo trope (U.S. Pat. 2,479,259, Re. 23,358), chloropentafluoroethane/chlorodifluoromethane azeo trope (U.S. Pat. 2,641,579), chlorotrifluoromethane, 65 chlorotrifluoromethane/trifluoromethane azeo trope (British Pat. 1,063,416), bromotrifluoromethane, trifluoromethane, chloropentafluoroethane, wherein one or two of the substituents R, R2, R3 or R4 difluoromethane/chloropentafluoroethane azeo 70 are anilino, the anilino group being substituted by 1 to 3 trope (British Pat. 1,026,336), Saturated alkyl groups having a total of 4 to 24 carbon chloropentafluoroethane/1,1-difluoroethane azeo atoms in the alkyl groups. These dyes may be prepared trope (U.S. Pat. 2,641,580), by various art-known methods, e.g., by reacting halo dichlorofluoromethane, 75 anthraquinones with alkyl substituted anilines as dis 3,770,640 5 6 closed, for example, in U.S. Pats. 2,101,094 and 2,091,- creases with the number of carbon atoms in the alkyl 812; by reacting diaminoanthraquinones with alkyl sub groups Substituting the anilino group. With one C-alkyl stituted bromobenzenes as disclosed in U.S. Pat. 2,596,- group Substituting a single anilino group the solubility is 820, or by reacting dihydroxyanthraquinones with alkyl as high as would normally be needed, for example, in a substituted anilines as disclosed in British Pat. 248,874. 5 concentrate not intended to constitute the entire charge The following dyes are illustrative of the dyes useful to the System. Since the difficulty of purification of the in this invention: dye increases with the carbon content of the alkyl groups, it is preferred not to exceed about 12 carbon atoms in 1,4-bis(2,4,6-triethylanilino)anthraquinone, any one alkyl group or 24 total carbon atoms in the alkyl 1-(2,4,6-triethylanilino) anthraquinone, 10 groups substituting the anilino group of the dye, Since 1,4-bis(4-dodecylanilino)anthraquinone, solubility is adequate in dyes containing 4 carbon atoms 1-(4-dodecylanilino) anthraquinone, in the alkyl group substituting a single anilino group and 1,8-bis(4-dodecylanilino)anthraquinone, because preparation and purification is relatively simple, 1,5-bis(4-dodecylanilino) anthraquinone, 15 the red dye, 1-(4-butylanilino)anthraquinone, is most pre 1,4-bis(4-butylanilino) anthraquinone, ferred, 1,8-bis(4-butylanilino)anthraquinone, It should be noted that the anthraquinone dyes utilized 1,5-bis(4-butylanilino)anthraquinone, in this invention do not raise the pour point of the com 1-(2,6-bis(2-propyl)anilino) anthraquinone, mon refrigeration oils above that point found for the pure 1-(4-cyclohexylanilino) anthraquinone and 20 oil. 1,5-bis(4-cyclohexylanilino) anthraquinone. The compositions of this invention can be prepared and incorporated into a refrigeration systems in several Although dyes meeting the criteria set out in the present Ways. For example, the pure dye could be added to the invention are satisfactory in their performance, closely System before charging of refrigerant and refrigeration related dyes are unsatisfactory. For example, dyes having 25 oil. Alternatively, the dye can be dissolved in either the free hydroxyl, halogen, or amino groups on the anthra refrigerant or the refrigeration oil in a mixture of the two quinone nucleus decompose under the contemplated use before charging to the system in any art-known anner. conditions and aromatic mono-substitution of amino Further, should one wish to introduce into the refrigera groups present on the anthraquinone nucleus to yield 30 tion liquid amounts of dye in excess of the normal solu aniline derivatives confers adequate stability on the mole bility of the dye, inert cosolvents such as Xylene can be cule whereas alkyl substitution of the amino groups, such employed. as 2-propyl substitution, does not. The compositions of this invention are circulated There should be at least about 4 carbon atoms in the through vapor compression heat transfer Systems and in alkyl group or groups substituting the anilino group on 35 addition to fulfilling their normal use, e.g., heat transfer, the dye molecule in order to confer adequate solubility they simultaneously detect leaks in the System. Special of the dye in the refrigeration liquid especially in the utility of the compositions of this invention is COntem fluorocarbon refrigerants. plated in the original charging of new refrigeration devices Intermediates should be removed from the final dye to especially in automobile air conditioning and in the adding avoid generally deleterious effects on the stability of the 40 of make-up refrigerant to these devices. dye mixture. For example, in dyes of the class utilized in this invention which have been prepared by reacting 1 EXAMPLES chloroanthraquinone with nuclearly substituted alkyl ani The following examples are intended to be merely ill lines, it is highly important that the aniline be removed 45 lustrative of the invention and not in limitation thereof. at least to the extent that less than about 0.5 wt. percent Unless otherwise indicated, all quantities are by weight. remains in the dye mixure. If this is not done, tarring can occur in less than a day when the impure dye is heated Example 1 to 400° F. in the presence of refrigerant dichlorodifluoro methane, refrigeration oil and materials of vapor com 50 The solubilities of various dyes useful in this inven pression heat transfer apparatus construction such as cop tion were measured in refrigeration oil. Useful refrigera per, aluminum and iron. tion oils must possess several properties including sta The dyes may be purified by any art-known means bility at high temperatures on compression of the re which will be readily apparent to one skilled in the art frigerant which temperatures may approach 400 F.; com depending on the particular dye and synthesis method in patibility with the refrigerant employed; pour and floc volved. For example, the removal of unreacted 4-dodecyl culation points below the evaporator temperature; high aniline from the dye, 1-(4-dodecylanilino) anthraquinone dielectiric strength sufficient to insulate an enclosed pump prepared by reaction between the aniline and 1-chloroan motor; and sufficient viscosity to seal the valves and pis thraquinone, is best accomplished by precipitation of the 60 ton of the pump. "Suniso"3GS refrigeration oil was used dye from HCl-acidified methanol solution by addition of in the following tests and is a commonly used refrigera water, followed by silica gel chromatography to remove tion oil manufactured by the Sun Oil Company. The man the last traces of the aniline. ufacturer reports the following properties. The red anthraquinone dyes are preferred for use in the compositions and process of this invention because 65 Aromatics, percent ------38 the red color deposited at the site of a leak is more easily Viscosity, SUS/210 F. by ASTM Method D161 - 40.8 recognized than are the blue and green dyes of the inven Pour point, F. ------45 tion class. Red dyes are produced on mono-substitution Floc, point, F. ------68 and by 1,5- and 1,8-disubstitution of the anthraquinone nucleus. Because of greater ease of preparation, dyes ob 70 Solubility was estimated by suspending a series of tained by 1-mono-substitution are preferred. The red dye weighed amounts of dye in measured volumes of "Suniso" 1-(4-butylanilino)anthraquinone is most preferred. 3GS oil and stirring the mixtures. Solubilities reported The solubility of the dyes, utilized in this invention, are those corresponding to the largest sample which dis in fluorocarbon refrigerants and in refrigeration oils in Solved completely. The results are shown in Table I. 3,770,640

TABLE Solubility of dyes in refrigeration oil R.N/N/ O. R3

Solubility in refrig. oil 1 Substituents (G/100 cc.) Dye number R1 R2 R3 R4 Color at 77 F. I- 2,4,6-triethylamiino---- 2.5 2.------do------1.5 3- 4-dodecylanilino. >10 4------do------rail 5.-- --do---- 4-dodecylanilino----H------Red.------>0 6------do------H------dodecylanilino.-- Red.------>10 7. 4-butylanilino. -H---- - Blue-green 5 8. d -H-... -H. 1.5 9. 4-butyla -H ra-3.0 10 a re-E.--- 4-butyla 1.5 11--- 2,6-di-(2-propyl)anilino. -H...-- -H...-- ra.0 12.-- ---, 2-methylanilino------2-methylanilino------H------H... 1.0 13--- -- 4-methoxyanilino------4-methoxyanilino------H ... --E.-- ras 14------4-methylphenylsulfamido.---- 4-methylphenylsulfamido... --H------. -E <1.5 1 'Suniso' 3GS, room temp. NoTE-Dyes 1-11 together with arefrigerant, refrigeration oil or refrigerant-refrigeration oil, are within the scope of this invention. Dyes 12-14 are not. The solubility of 1 - (4 - butylanilino)anthraquinone 1,1,2-trichloro - 1,2,2 - trifluoroethane (and trichloro tested in other refrigeration oils in addition to "Suniso' fluoromethane at 0° F. and 30 F.) being a liquid at the 3GS and the solubilities thus determined are shown in indicated temperature was not confined, but was simply Table II below. 30 stirred with the dye and filtered. The weight of the residue TABLE was determined as above. Solubility in refrigerant oil Other refrigerants, being normally gaseous but having Oil: (g/100 cc, 77 F.) lower vapor pressures than those refrigerants treated in "Suniso" 4GS5GS ------1.5is 8 containersstainless steel similarly cylinders, equipped were treatedand the in weight 200 ml, of aerosolresidue 1.5 was determined as above. See 1. 117III-III 0.75 The solubility desired will vary depending on the tinc “Zeric" sai-III-III 3.8 torial quality of the dye used; however, a solubility of at ------least about 0.05 g/100 cc. of refrigerant is normally pre Fluicil' S-55K ------1.3 40 ferred. As 1-(4-butylanilino) anthraquinone iss the least The presence of at least up to 1 g of 1-(4-butylanilino) soluble dye in fluorinated refrigerants of the refrigera anthraquinone of 1-(4-dodecylanilino)anthraquinone in tion compositions of this invention, it follows that all 100 ml, of “Suniso' 3GS and similar refrigeration oils, other dyes are sufficiently soluble in the refrigerants of i.e., “Suniso".5GS (Sun Oil Company) and "Capella” E 45 the invention. (Texaco Inc.), did not affect the pour points of the oils It is recognized that the refrigeration oil in which the as measured by the ASTM D97-66 method. subject dyes are soluble passes at least in small amounts Example 2 Egy, 8, figye fly therefore E.g.The solubilities i. ofvarious the preferred fluorinated dye-(4-butylaniling). refrigerants are catorNTS," dye will be ii. carried toAREFERA. all parts of the system. Also it tropeSlity of chloropentafluoroethane/chlorodifluoromethane chlorodifluoromethane and in the azeo- isstantial Fhat, degree, miscible S.E.E.S.E with refrigeration oils and thus, at least in part, a single refrigeration oil-refrigerant phase refrigerantwas measured to aby 140 charging mi. stainless 1.00 g. steel of dyegas andcylinder 50 ml. fitted of formed wherein the subject dyes are more soluble than Wii di leg and fitted glass filter at the open end of in the refrigerant alone. For example, on a weight per the dip leg. After equilibrating at the indicated tempera- cent basis 1-(4-butylanilino) anthraquinone was found to tures, the liquid contents were discharged through the dip be soluble to the extent of 0.43% at 77 F. and 0.29% leg to a tared beaker. After drying, the residue was at 0 F. in a 10 to 1 by wt. mixture of the azeotrope of weighed. By measuring the difference in weight, the 60 chloropentafluoroethane/chlorodifluoromethane and "Ze amount of dissolved dye was calculated. rice' S-41 alkylated benzene oil.

TABLE II Solubility of 1-(4-butylanilino) anthraquinone i in fluorinated refrigerants at various temperatures Solubility (giiO0 cc. of refrigerant) Refrigerant O° E. 30° E. 50° E. 770 F. Trichlorofluoromethane------i. 1.2 1.3 13 Dichlorodifluoromethane.---- 0.1 ------0.23 0.03 Chlorodifluoromethane------1.1 ------1.3 1,1,2-trichloro-1,2,2-trifluoroethane.-- 0.38 O4. 1,2-dichloro-1,1,2,2-tetrafluoroethane------0.16 0.24 idioroethinefdichlorodifluoromethane 2 0.31 0.38 Chloropentafluoroethanelchlorodifluoromethane ------...-- O.03 0.08 0.14 1 Dye No. 8 in Table I. 2Azeotrope: U.S. Pat. 2,479,259, Re.23,358. Azeotrope: U.S. Pat. 2,641,579. 3,770,640 10 Example 3 oil. In a second test utilizing the same dye and refrigerant oil mixture as above but having a leak rate of 1.2 oz./yr., The thermal stability of various dyes in a refrigerant a substantial amount of easily visible red oil was observed refrigerant oil mixture was measured under conditions at the leak site after 3% days. analogous to the most severe conditions which would be The same solution deposited no undissolved dye on encountered under practical refrigeration conditions. The 5 a 35 micron nylon filter. degree of degradation shown in Table IV is probably sev Molecular sieves appear to be generally operable as an eral hundred times the degree of degradation which efficient drying means for mixtures of the dyes utilized would be observed in practice under normal operating in this invention with refrigeration oil and fluorinated conditions. In the tests of this example the entire sample refrigerants. was continuously exposed to high temperatures whereas 0. The dyes utilized in this invention may be easily re in practice only a small portion of the mixture is exposed moved from automobile finishes with aromatic solvents, at any one time to high temperatures, i.e., on compres for example xylene. The preferred method of dye removal SO. is to place a xylene soaked cloth over the spot for 10-15 The tests consisted of sealing in glass tubes, in the minutes thus to remove the absorbed dye. absence of air as is customary in the stability tests in this 5 The foregoing detailed description has been given for field (ASHRAE Transactions, Jan. 25-28, 1965), a mix clarity of understanding only and no unnecessary limita ture consisting of tions are to be understood therefrom. The invention is 0.05 wt. percent of dye based on the weight of the oil not limited to exact details shown and described for ob and dichlorodifluoromethane mixture, vious modifications will occur to one skilled in the art. Mixture, as indicated, of dichlorodifluoromethane and 20 The embodiments of the invention in which an exclu "Suniso'3GS refrigeration oil, sive property or privilege is claimed are defined as fol One coupon each of: lows: cold rolled steel No. 1010 1. A leak detecting refrigeration composition which TS aluminum No. 1100 consists essentially of purified copper. 25 (A) a refrigeration liquid selected from the group con The sealed tubes were heated in an oven at the tem sisting of peratures and for the times indicated. The volatile ma (a) a fluorocarbon refrigerant selected from the terials were removed and the residual material was taken group consisting of up in benzene. Aliquot portions were analyzed by visible 30 trichlorofluoromethane, light spectroscopy. Comparison of the heights of the prin dichlorodifluoromethane, cipal absorption peaks permitted calculation of the chlorodifluoromethane, amount, expressed in percent, of dye destroyed. The re 1,1,2-trichloro-1,2,2-trifluoroethane, sults are shown in Table TV. 1,2-dichloro-1,1,2,2-tetrafluoroethane, TABLE IV Stability of dyes in refrigeration oil 1 and dichlorodifluoromethane in the presence of Fe, Cu, Al a

Ratio Substituents Prin. abs. CCFafoil Temp. Time Decomp. Dye No. R1 R2 peak (mu) (vol.) (o F.) (days) (percent)

a - as saw a - - - - 2,4,6-triethylanilino. 2,4,6-triethylanilino. 630 1. 400 6.7 ------ado------do------630 400 2 6.5 50 1. 400 1 0.0 510 1. 400 2 0.0 50 4 300 5 0.0 510 4 300 5 0.0 8------do------H------510 1. 300 5 0.05 2-propylamino------2-propylamino- 630 400 2 >80 DuPont Oil Red A3 400 a. 100 ----do------1 300 2 100 ----do ------1 250 6 10 i 'Sinis0' 3GS, 2 Normal materials of construction of refrigeration apparatus. 8Bisazo dye prepared from methyl anilines and 2-maphthol. Example 4 1,1-difluoroethane/dichlorodifluoromethane The solubility of dyes useful in this invention in refrig azeotrope, eration oil appears to be insensitive to low temperatures. chloropentafluoroethane/chlorodifluoro For example, 0.25 wt. percent 1-(4-butylanilino) anthra methane azeotrope, quinone in "Suniso" 5GS and "Capella” E refrigeration 65 chlorotrifluoromethane, oil was not precipitated even at -58 F. chlorotrifluoromethane/trifluoromethane A simulated leak was created passing 0.3 ounce of azeotrope, dichlorodifluoromethane per year, a typical specification bromotrifluoromethane, leakage rate in air conditioners in the automobile indus trifluoromethane, try (except at the shaft seal where 3.2 to 5 oz./yr. loss is 70 chloropentafluoroethane, normally permitted). The leak was detectable on wiping difluoromethane/chloropentafluoroethane with a white cloth after eight hours. The mixture Sub azeotrope, jected to the test consisted of 0.05 g. of 1-(4-butylanilino) chloropentafluoroethane/1,1-difluoroethane anthraquinone in 100 ml. of a 5/1 (vol.) mixture of azeotrope, dichlorodifluoromethane and "Suniso' 3GS refrigeration 75 dichlorofluoromethane, 3,770,640 11 12 dichlorodifluoromethane/chlorofluoro 12. A composition according to claim 4 wherein the methane azeotrope, anthaquinone dye is 1-(4-butylanilino) anthraquinone. chlorofluoromethane/1,2-dichloroetetra 13. A composition according to claim 5 wherein the fluoroethane azeotrope, anthraquinone dye is 1-(4-butylanilino) anthraquinone. difluoromethane, 14. A composition according to claim 6 wherein the 1,2-dibromotetrafluoroethane, anthraquinone dye is 1-(4-butylanilino) anthraquinone. 1,1,1-trifluoroethane, 15. A process for detecting leaks in a vapor compres 1,1-difluoro-1-chloroethane, sion heat transfer system which process comprises cir 1,1-difluoroethane, culating through said heat transfer system a composi bromotrifluoromethane/difluoromethane O tion consisting essentially of azeotrope, (A) a refrigeration liquid selected from the group con 1,2-dichlorotetrafluoroethane/dichloro sisting of fluoromethane azeotrope, and (a) a fluorocarbon refrigerant selected from the hexafluoroethane/trifluoromethane group consisting of azeotrope, 5 trichlorofluoromethane, (b) a refrigeration oil selected from the group dichlorodifluoromethane, consisting of naphthenic oils, paraffinic oils, al chlorodifluoromethane, kylated benzene oils and polyalkyl silicate oils, 1,1,2-trichloro-1,2,2-trifluoroethane, and 1,2-dichloro-1,1,2,2-tetrafluoroethane, (c) a mixture of (a) and (b) and 1,1-difluoroethane/dichlorodifluoromethane (B) an anthraquinone dye or mixture of anthraquinone 20 azeotrope, dyes having the structure chloropentafluoroethane/chlorodifluoro methane azeotrope, chlorotrifluoromethane, chlorotrifluoromethane/trifluoromethane 25 azeotrope, bromotrifluoromethane, trifluoromethane, chloropentafluoroethane difluoromethane/chloropentafluoroethane 30 azeotrope, chloropentafluoroethane/1,1-difluoroethane azeotrope, dichlorofluoromethane, wherein R, R2, R3 and R4 are each H or an anilino dichlorodifluoromethane/chlorofluoro group substituted by from 1 to 3 saturated alkyl 35 methane azeotrope, groups having a total of from 4 to 24 carbon atoms, chlorofluoromethane/1,2-dichlorotetrafluoro and wherein at least 2 and no more than 3 of R, ethane azeotrope, R, R8 and R are hydrogen, and difluoromethane, wherein the anthaquinone dye is soluble in the refrigera 1,2-dibromotetrafluoroethane, tion liquid, the concentration of said dye being at least 40 1,1,1-trifluoroethane, about 0.007 gram per 100 cc. of said refrigeration liquid. 1,1-difluoro-1-chloroethane, 2. A composition according to claim 1 wherein the 1,1-difluoroethane, refrigeration liquid is a fluorocarbon refrigerant selected bromotrifluoromethane/difluoromethane from the group consisting of trichlorofluoromethane, di azeotrope, chlorodifluoromethane, chlorodifluoromethane, 1,1,2-tri 45 1,2-dichlorotetrafluoroethane/dichlorofluoro chloro-1,2,2-trifluoroethane, 1,2-dichloro-1,1,2,2-tetrafluo methane azeotrope, and roethane, 1,1 - difluoroethane/dichlorodifluoromethane hexafluoroethane/trifluoromethane azeotrope, azeotrope, and chloropentafluoroethane/chlorodifluoro (b) a refrigeration oil selected from the group methane azeotrope. consisting of naphthenic oils, paraffinic oils, al 3. A composition according to claim 2 wherein the flu 50 kylated benzene oils and polyalkyl silicate oils, orocarbon refrigerant is dichlorodifluoromethane. and 4. A composition according to claim 1 wherein the (c) a mixture of (a) and (b) and refrigeration liquid is a refrigeration oil. (B) an anthraquinone dye or mixture of anthraquinone 5. A composition according to claim 1 wherein the dyes having the structure refrigeration liquid is a mixture of a refrigeration oil and 55 a fluorocarbon refrigerant selected from the group con sisting of trifluorofluoromethane, dichlorodifluorometh ane, chlorodifluoromethane, 1,1,2-trichloro-1,2,2-trifluoro ethane, 1,2-dichloro-1,1,2,2-tetrafluoroethane, 1,1-diflu oroethane/dichlorodifluoromethane azeotrope, and chlo 60 ropentafluoroethane/chlorodifluoromethane azeotrope. 6. A composition according to claim 5 wherein the flu orocarbon refrigerant is dichlorodifluoromethane. 7. A composition according to claim 5 wherein the weight ratio of refrigeration oil to fluorocarbon refriger 65 antis about 1:1. 8. A composition according to claim 6 wherein the wherein R, R2, R3 and R are each H or an anilino weight ratio of refrigeration oil to dichlorodifluorometh group substituted by from 1 to 3 saturated alkyl ane is about 1:1. groups having a total of from 4 to 24 carbon atoms, 9. A composition according to claim 1 wherein the and wherein at least 2 and no more than 3 of R, R2 anthraquinone dye is 1-(4-butylanilino) anthraquinone. 70 R3 and R are hydrogen, and 10. A composition according to claim 2 wherein the wherein the anthraquinone dye is soluble in the refrigera anthraquinone dye in 1-(4-butylanilino)anthraquinone. tion liquid, the concentration of said dye being at least 11. A composition according to claim 3 wherein the about 0.007 gram per 100 cc. of said refrigeration liquid. anthraquinone dye is 1-(4-butylanilino) anthraquinone. 75 (References on following page) 3,770,640 13 14 References Cited 579,519 8/1946 Great Britain. UNITED STATES PATENTS 1,137,595 12/1968 Great Britain. 1915,965 6/1933 Williams ------252- .408 LEON D. ROSDOL, Primary Examiner E. E. E. I. S. 5 H. A. PITLICK, Assistant Examiner 3,399,025 8/1968 Nicholson ------8-4 U.S. C. XR 3,489,898 1/1970 Alburger ----- 252-301.2 P X As W. A. Y.Y.8 FOREIGN PATENTS 8-39; 252-408; 260-378 1,567,508 5/1969 France. O