WO1992018580A1

WO1992018580A1 - Refrigeration compositions of hydrofluorocarbon refrigerant and lubricant

Info

Publication number: WO1992018580A1
Application number: PCT/US1992/002401
Authority: WO
Inventors: Raymond Hilton Percival Thomas; Hang Thanh Pham; John Walter Pelava; David Paul Wilson
Original assignee: AlliedSignal Inc
Current assignee: Honeywell International Inc
Priority date: 1991-04-19
Filing date: 1992-03-25
Publication date: 1992-10-29
Anticipated expiration: 1993-10-19
Also published as: AU1987392A

Abstract

The present invention provides a composition for use in refrigeration and air-conditioning. The composition comprises: (a) a hydrofluorocarbon refrigerant selected from the group consisting of difluoromethane, pentafluoroethane, and mixtures thereof; and (b) a sufficient amount to provide lubrication of at least one lubricant selected from the group consisting of: (i) polyoxyalkylene glycol which is at least difunctional with respect to the hydroxyl groups, (ii) polyoxyalkylene glycol having a cap of a fluorinated alkyl group on at least one end thereof, (iii) fluorinated silicone having units therein selected from the group consisting of fluoroalkyl and alkyl wherein if both of the units are present, at least 25 % of the siloxane units have a fluoroalkyl substituent thereon, and mixtures thereof. The lubricant has a molecular weight of about 300 to about 6,000, a viscosity of about 5 to about 300 centistokes at 37 °C, and is miscible in combination with the refrigerant (a) in the range between about 25 °C and at least about 30 °C.

Description

REFRIGERATION COMPOSITIONS OF HYDROFLUOROCARBON REFRIGERANT AND LUBRICANT

The present invention relates to novel refrigeration compositions. More particularly, the present invention relates to novel refrigeration compositions wherein the refrigerant is difluoromethane (known in the art as R32) or pentafluoroethane (known in the art as R125) . Each of R32 and R125 is a refrigerant which may replace dichlorodifluoromethane (known in the art as R12) or chlorodifluoromethane (known in the art as R22) in many applications because environmental concerns over the use of R12 and R22 exist.

R32 has been mentioned as a possible replacement for R22 because concern over potential depletion of the ozone layer exists. See Allied Chemical's Product Data Sheet on Genetron ^® 32, 1963. Currently, R22 is used in closed loop refrigeration systems and in particular, in commercial food refrigeration systems. Both R32 and R125 have properties similar to those of R22 so that it is possible to substitute R32 or R125 for R22 with minimal changes in equipment being required.

A unique problem arises in such a substitution. R22 refrigeration systems have been considered for use with mineral oils for lubrication of the compressor. Mineral oil is typically paraffin oil or naphthenic oil. The present discussion does not apply to absorption refrigeration equipment. See for example the discussion in Chapter 32 of the 1980 ASHRAE Systems Handbook.

R32 is immiscible with mineral oil as shown in Comparative A below and R125 is immiscible with mineral oil as shown in Comparative E below. Also, blends of R32 and R125 are immiscible with mineral oil as shown in Comparative G below.

When lack of oil return becomes a problem, the art has considered the use of alkyl benzene lubricants with R22 because they are miscible. Consequently, oil which dissolves in the refrigerant travels around the refrigeration loop and generally returns with the refrigerant to the compressor. The oil does not separate during condensation, although it may accumulate because low temperatures exist when the refrigerant is evaporated. At the same time, the oil which lubricates the compressor contains some refrigerant which may affect its lubricating property.

Alkyl benzene lubricants are immiscible in R32 as shown in Comparatives B through D below and are not useful therewith. Also, alkyl benzene lubricants are immiscible with blends of R32 and R125 as shown in Comparative F below.

Another solution has been the use of extra equipment such as oil separators. Under all circumstances, sufficient oil solubility must exist so that the oil returns to the compressor.

It would be advantageous to avoid the use of oil separators by having lubricants which are miscible with R32 or R125. However, as mentioned above, no major changes to equipment should be necessary when the refrigerant substitution is made. If the lubricant separates from the refrigerant, it is expected that ■ serious operating problems could result. For example, the compressor could be inadequately lubricated if refrigerant replaces the lubricant. Significant problems in other equipment also could result if a lubricant phase separates from the refrigerant during condensation, expansion, or evaporation. These problems are expected to be serious in commercial food refrigeration systems where feed lines between the evaporator and the compressor are very long.

Small amounts of lubricants may be soluble in R32, or R125 over a wide range of temperatures, but as the concentration of the lubricant increases, the temperature range over which complete miscibility occurs, i.e., only one liquid phase is present, narrows substantially. For any composition, two consolute temperatures, i.e., a lower and a higher temperature, may exist. That is, a relatively low temperature below which two distinct liquid phases are present and above which the two phases become miscible and a higher temperature at which the single phase disappears and two phases appear again may exist. A diagram of such a system for R502 refrigerant is shown as FIG. 2 in the Kruse et al. paper mentioned above. A range of temperatures where one phase is present exists and while it would be desirable that a refrigeration system operate within such a range, it has been found that for typical compositions, the miscible range of lubricants with R32 or R125 is not wide enough to encompass the typical refrigeration temperatures.

Some disclosures which are concerned with the choice of lubricants when 1,1,1,2-tetrafluoroethane (known in the art as R134a) is used as a refrigerant exist. .S. Sanvordenker, "Materials Compatibility of R134a in Refrigerant Systems", ASHRAE Winter Meeting, 211 (January 1989) and K.S. Sanvordenker, "Durability of R-134a Compressors: The Role of the Lubricant", ASHRAE Journal. 42 (February 1991) teach that dibasic acid esters, neopentyl esters, and polyol esters are miscible with R134a and thus, suitable as lubricants for R134a. See Comparatives H and J below.

In contrast, we tested short chain fatty acid ester of trimethylolpropane with R32 as shown in Comparative I below and found that the ester was immiscible with R32 and thus, unsuitable as lubricant for R32. We also tested neopentyl dipelargonate with R32 as shown in Comparative K below and found that the ester was immiscible with R32 and thus, unsuitable as lubricant for R32.

U.S. Patent 4,971,712 teaches that monofunctional polyoxyalkylene glycols having 50% ethylene oxide and 50% propylene oxide, such as 50HB400 (registered trademark) from Union Carbide, are miscible with R134a. Japanese 2,283,797 published November 21, 1990 teaches compositions of pentafluoroethane and monofunctional polyoxyalkylene glycols.

As demonstrated by Comparative L below, the monofunctional polyoxyalkylene glycol 50HB400 (registered trademark) which is a copolymer of ethylene oxide and propylene oxide and has a butyl group on one end thereof is miscible with R134a. In contrast as shown in Comparative M below, the monofunctional polyoxyalkylene glycol 50HB400 (registered trademark) which is a copolymer of ethylene oxide and propylene oxide and has a butyl group on one end thereof is immiscible with R32.

Also as demonstrated by Comparative N below, the monofunctional polyoxyalkylene glycol which is polypropylene oxide having a butyl group on one end thereof is miscible with R134a. In contrast as shown in Comparative 0 below, the monofunctional polyoxyalkylene glycol which is polypropylene oxide having a butyl group on one end thereof is immiscible with R32.

As such, a need exists in the art for lubricants which are miscible with R32, R125, and blends thereof so as to avoid refrigerant and lubricant separation.

SUMMARY OF THE INVENTION

Considering that polyol esters and polyoxyalkylene glycols having an alkyl group on at least one end thereof are immiscible with R32, R125, and blends thereof, we were surprised to find that certain lubricants are miscible with R32, R125, and blends thereof. The miscible lubricant is selected from the group consisting of polyoxyalkylene glycol which is at least difunctional with respect to the hydroxyl groups; polyoxyalkylene glycol having a fluorinated alkyl group on at least one end thereof; fluorinated silicone having units therein selected from the group consisting of fluoroalkyl and alkyl wherein if both units are present, at least 25% of the siloxane units have a fluoroalkyl substituent thereon; and mixtures thereof.

Thus, the present invention provides a composition for use in refrigeration and air-conditioning comprising: (a) hydrofluorocarbon refrigerant selected from the group consisting of difluoromethane, pentafluoroethane, and mixtures thereof and (b) a sufficient amount to provide lubrication of at least one lubricant selected from the group consisting of: (i) polyoxyalkylene glycol which is at least difunctional with respect to the hydroxyl groups, (ii) polyoxyalkylene glycol having a cap of a fluorinated alkyl group on at least one end thereof, (iii) fluorinated silicone having units therein selected from the group consisting of fluoroalkyl and alkyl wherein if both units are present, at least 25% of the siloxane units have a fluoroalkyl substituent thereon; and mixtures thereof. The lubricant has a molecular weight of about 300 to about 6,000, a viscosity of about 5 to about 300 centistokes at 37°C, and is miscible in combination with the hydrofluorocarbon refrigerant in the range between about 25°C and at least about 30°C.

The present invention also provides a method for improving lubrication in refrigeration and air- conditioning equipment using hydrofluorocarbon refrigerant selected from the group consisting of difluoromethane, pentafluoroethane, and mixtures thereof. The method comprises the step of: employing a lubricant selected from the group consisting of polyoxyalkylene glycol which is at least difunctional with respect to the hydroxyl groups, polyoxyalkylene glycol having a cap of a fluorinated alkyl group on at least one end thereof, fluorinated silicone having units therein selected from the group consisting of fluoroalkyl and alkyl wherein if both units are present, at least 25% of the units have a fluoroalkyl substituent thereon; and mixtures thereof. The lubricant has a molecular weight of about 300 to about 6,000 and has a viscosity of about 5 to about 300 centistokes. The lubricant is miscible in combination with the fluorine-containing refrigerant in the range between about 25°C and at least about 30°C.

Other advantages of the present invention will become apparent from the following description and the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Refrigerants

The hydrofluorocarbon refrigerant of the present invention is selected from those listed in Table I below.

TABLE I

The above hydrofluorocarbon refrigerants are commercially available. R32 may also be blended with R134a. R125 may also be blended with 1,1,1- trifluoroethane (known in the art as HFC-143a) .

R22 is used in very large quantities in air- conditioning and commercial food refrigeration systems Since we have found that R32 and R125 differ in being much less miscible than R134a with lubricants, substitution for R22 becomes more difficult. Lubricants

It is characteristic of some refrigerant-lubricant mixtures that there is a temperature above which the lubricant separates. Since this phenomenon occurs also at some low temperatures, there may be a limited range of temperatures within which the two fluids are miscible. Ideally, this range should span the operating temperature range in which the refrigerant is to operate, but often this is not possible.

In the typical air conditioning or refrigeration system, the condensation of hot refrigerant gases in the condensing heat exchanger can be affected if the exchanger is coated with lubricant preferentially so that condensation of the refrigerant occurs by contact with the lubricant film. Thereafter, the two-phase must pass through a pressure reduction to the low temperature stage where the refrigerant evaporates and absorbs the heat given up in cooling air and condensing moisture. If lubricant separates at the condenser, then the performance of the evaporator stage can be affected if separate phases persist as the two-phase mixture passes through the pressure reduction step. As with the condenser, accumulation of lubricant on the evaporator coils can affect heat exchange efficiency. In addition, the low evaporator temperatures may result in excessive cooling of the lubricant resulting in a more viscous liquid and trapping of the lubricant resulting in the evaporator. These problems can be avoided if the lubricant and the refrigerant are fully miscible throughout the operating temperature ranges. R32 and R125, with their limited ability to dissolve lubricants, present a problem which must be solved. We have found a first class of lubricants which is miscible with R32; R125; blends of R32 and R125; blends of R32 and R134a; and blends of R125 and R143a. These are the lubricants of commonly assigned U.S. Patent 4,755,316 which is incorporated herein by reference. Commonly assigned U.S. Patent 4,755,316 teaches a lubricant of at least one polyoxyalkylene glycol which is at least difunctional with respect to hydroxyl groups, has a molecular weight between about 300 and about 2,000, has a viscosity of about 15 to about 150 centistokes at 37°C, and has a viscosity index of at least 20. The polyoxyalkylene glycols preferably have at least 80 percent propylene oxide units; the remaining units may be ethylene oxide, butylene oxide, or other units such as esters and olefins which may be polymerized with propylene oxide.

We believe that a second class of lubricants is miscible with R32; R125; blends of R32 and R125; blends of R32 and R134a; and blends of R125 and R143a. These lubricants are the lubricants of commonly assigned U.S. Patent 4,900,463 which is incorporated herein by reference. Commonly assigned U.S. Patent 4,900,463 teaches a lubricant which is a single phase blend of (i) at least one polyoxyalkylene glycol which has a molecular weight between about 300 and about 2000, a viscosity of about 10 to about 157 centistokes at 37°C, and a viscosity index of at least 20 and (ii) chlorotrifluoroethylene oil having a viscosity of about 0.8 to about 1000 centistokes at 25°C.

The term "polyoxyalkylene glycol" as used herein refers to compounds produced by addition polymerization of alkylene oxides, initiated by a molecule having one or more active hydrogens. Commonly, these compounds have terminal hydroxyl groups. The compound may be a copolymer of two or more alkylene oxides and the copolymer may be random or block copolymer. Examples of initiators include water, alcohols, polyalcohols, glycols, and amines. Preferably, the weight percentage of oxyalkylene groups in the chain is at least 80% and the remaining 20% may be other units including but not limited to polyester, polyamide, and polyvinyl chloride units.

More preferably, the polyoxyalkylene glycol has the formula

R₁-[(R₂0)_nR₃]_m wherein R_x is a residue of a compound having 1 to 8 hydroxyl groups or a hydroxyl group, R₂ is an alkylene moiety having 2 to 4 carbon atoms, R₃ is hydrogen or an alkyl group with 1 to 10 carbon atoms, and n and m are numbers such that the molecular weight of the polyoxyalkylene glycol is 300 to 3,000.

Many polyoxyalkylene glycols are commercially available. The polyoxyalkylene glycols may be random or block polymers or copolymers of ethylene oxide, propylene oxide, butylene oxide, or other alkylene oxides. Most preferably, the polyoxyalkylene glycols are random or block copolymers of ethylene oxide and propylene oxide or a polymer of propylene oxide. Blends of polyoxyalkylene glycols having different molecular weights may also be used in the present invention.

Chlorotrifluoroethylene oils having viscosities from about 0.8 to about 1000 centistokes at 25°C are available commercially. Preferred chlorotrifluoroethylene oils have a viscosity of about 100 to about 1,000 centistokes at 25°C.

Preferably, the weight ratio of polyoxyalkylene glycol used to chlorotrifluoroethylene oil used is about 99:1 to about 1:99. More preferably, the weight ratio is about 10:90 to about 56:44.

We have found a third class of lubricants which is miscible with R32; R125; blends of R32 and R125; blends of R32 and R134a; and blends of R125 and R143a. These are the lubricants of commonly assigned U.S. Patent 4,975,212 which is incorporated herein by reference. Commonly assigned U.S. Patent 4,975,212 teaches a lubricant of polyoxyalkylene glycols having a cap of a fluorinated alkyl group on at least one end thereof.

These glycols have a molecular weight between about 300 and about 3,000, a viscosity of about 5 to about 150 centistokes at 37°C, and a viscosity index of at least 20.

Preferably, the foregoing fluorinated lubricants comprise the formula (I)

R,OR₂[AO]_m(BO)_nR₄ wherein m is 4 to 36, n is 0 to 36, R₂ is -CH(CH₃)CH₂- or a direct bond, R_! and R₄ are independently selected from the group consisting of hydrogen, alkyl group, and fluorinated alkyl group, Rj can also be a residue of a compound having 1 to 8 active hydrogens, and A and B are the same or different and selected from the group consisting of methyl, ethyl, propyl, or butyl. At least one of R₁ and R₄ is a fluorinated alkyl group. Examples of alkyl groups include methyl, ethyl, propyl, and butyl. The lubricant may be terminated by a hydrogen at one end and a fluorinated alkyl group at the other end, by an alkyl group at one end and a fluorinated alkyl group at the other end, or by a fluorinated alkyl group at both ends. The fluorinated alkyl group may be branched or straight chain as long as fluorine atoms are attached thereto.

The foregoing fluorinated lubricants may be formed by fluorinating polyoxyalkylene glycols. The polyoxyalkylene glycols used may have primary carbons at both ends, a primary carbon at one end and a secondary carbon at the other end, or secondary carbons at both ends. Preferably, the polyoxyalkylene glycols used have a primary carbon at one end and a secondary carbon at the other end or secondary carbons at both ends.

In a more preferred embodiment, at least one of Rj and R< is a fluorinated alkyl group of the formula

(II) :

-(CH₂)_x(CF₂)_yCF₃ wherein x is 1 to 4 and y is 0 to 15. More preferably, x is 1 and y is 0 so that at least one of Rj and R₄ is a fluorinated alkyl group of the formula -CH₂CF₃ or x is 1 and y is 2 so that at least one of R_x and R₄ is a fluorinated alkyl group of the formula -CH₂(CF₂)₂CF₃. Even more preferably, both R_t and are fluorinated alkyl groups, m is 7 to 34, and n is 0.

The most preferred lubricating compositions are

CF₃CH₂0[CH₂CH(CH₃0) ]_mCH₂CF₃

CF₃(CF₂)₂CH₂0[CH₂CH(CH₃)0]_mCH₂(CF₂)₂CF₃ CF₃CH_jOCH(CH₃)CH₂0[CH₂CH(CH₃)0]_mCH₂CF₃ CF₃(CF₂)₂CH₂0CH(CH₃) CH₂0[CH₂CH(CH₃)0]_mCH₂(CF₂)₂CF₃ where m is 7 to 34. Generally, the foregoing fluorinated lubricating compositions may be formed by capping a polyoxyalkylene glycol with at least one fluorinated alkyl group. The lubricating compositions may be formed by copolymerizing ethylene and propylene oxides and terminating the resulting copolymer with at least one fluorinated alkyl group.

Preferably, the foregoing fluorinated lubricants wherein one end has an alkyl group and the other end has a fluorinated alkyl group or both ends have fluorinated alkyl groups are formed as follows. The polyoxyalkylene glycol is converted to the tosylate by treatment with p-toluenesulfonyl chloride in a suitable base such as pyridine and then the tosylated polyglycol is reacted with the sodium alkoxide of the appropriate fluorinated alcohol.

Preferably, the foregoing fluorinated lubricants wherein one end has a hydroxyl group and the other has a fluorinated alkyl group are formed as follows. An a _*lcohol initiator such as the sodium alkoxide of trifluoroethanol is used in the polymerization of polypropylene oxide.

Most preferably, the fluorinated lubricant is a fluorinated copolymer of butylene oxide and propylene oxide or is a mixture of fluorinated butylene oxide and fluorinated propylene oxide. A mixture of any of the above three classes of lubricants may also be used.

We believe that a fourth class of lubricants is miscible with R32; R125; blends of R32 and R125; blends of R32 and R134a; and blends of R125 and R143a. These lubricants are fluorinated silicones having units 14 therein selected from the group consisting of fluoroalkyl and alkyl; if both fluoroalkyl and alkyl units are present, at least 25% of the siloxane units have a fluoroalkyl substituent thereon. The 5 fluorinated silicone has a molecular weight between about 280 and about 6,000 and a viscosity of about 10 to about 300 centistokes at 38°C (0.1 to 3.0cm²/sec) .

Preferably, the fluorinated silicone is of the 10 formula

(R₃)₃Si[OSi (R₂) (CI^CHA) ]_m[OSi (R₂) (R₂) ]_π0Si (R₃)₃ wherein R_t is a partially or fully fluorinated alkyl group having 1 to 3 carbon atoms; each of R₂ is the same or different and is hydrogen, methyl, ethyl, or 15 propyl; each of R₃ is the same or different and is a methyl, ethyl, vinyl, phenyl, or CH₂CH₂R wherein R is a partially or fully fluorinated alkyl group having l to 3 carbon atoms; m is about 2 to 40; and n is about 0 to about 40. 20

A fluorinated silicone which may be useful is disclosed in U.S. Patent 3,642,626. The silicone has the following formula

CF₃(CH₂)₂Si(CH₃)₂0[ (CH₃)SiO(CH₂)₂CF₃)0]_nSi(CH₃)₂(CH₂)₂CF₃ 25 The reference teaches that the silicone has a viscosity of 50 to 100 centistokes (0.5 to 1 cm²/sec) .

More preferably, the fluorinated silicone is of the formula 30 (CH₃)₃Si [OSi (CH₃) (CK_jCH_jCFa) ]_m[OSi (CH₃) (CH₃) ]_n0Si (CH₃)₃ wherein m is about 2 to about 40 and n is 0 to about 40.

In an even more preferred embodiment, n is equal 35 to 0 and m is 2 to 40 so that the fluorinated silicone is of the formula

(CH₃)₃Si [OSi(CH₃) (CH₂CH₂CF₃) ]_mOSi(CH₃)₃

In another more preferred embodiment, wherein n is not equal to 0, at least 50% of the units are methyltrifluoropropyl.

The fluorinated silicones may be formed by any known method such as those disclosed in U.S. Patents 2,961,425 and 4,818,423.

The range of miscibility is not the only factor to be considered when one is selecting a lubricant for air conditioning service or other refrigeration application. Lubricating properties also must be satisfactory for the intended application. Practically, this means that for these applications, the viscosity of the lubricant will be about 10-150 centistokes, preferably about 32 centistokes (CS) at 37°C. with a viscosity index of at least 20 in order that the lubricant is sufficiently viscous at high temperatures to lubricate while remaining sufficiently fluid to circulate around the refrigeration circuit at low temperatures. The range of viscosity may also be expressed as about 2-24 centistokes at 98.9°C. In addition, the lubricant should be chemically stable and not cause corrosion or other problems in long-term service. Other factors which should be considered in selecting lubricant are compatibility, lubricity, safety, and the like.

Stabilizers may also be added to the present refrigeration compositions. The stabilizers of commonly assigned U.S. Patents 4,755,316; 4,900,463; and 4,975,212 may be used herein. Preferably, the stabilizer comprises: (i) at least one component selected from the group consisting of phenol and trivalent phosphorus compounds and (ii) at least one epoxide selected from the group consisting of aromatic epoxide and fluorinated alkyl epoxide.

Preferably, the phenol is phenol selected from the group consisting of:

4,4' -methylenebis(2,6-di-tert-butylphenol) ; 4,4' -bis(2,6-di-tert-butylphenol) ;

4,4* -bis(2-methyl-6-tert-butylphenol) ;

2,2' -methylenebis(4-ethyl-6-tert-butylphenol) ;

2,2' -methylenebis(4-methyl-6-tert-butylphenol) ;

4,4'-butylidenebis(3-methyl-6-tert-butylphenol) ; 4,4'-isopropylidenebis(2,6-di-tert-butylphenol) ;

2,2'-methylenebis(4-methyl-6-nonylphenol) ;

2,2' -isobutylidenebis(4,6-dimethylphenol) ;

2,2'-methylenebis(4-methyl-6-cyclohexylphenol) ;

2,6-di-tert-butyl-4-methylphenol; 2,6-di-tert-butyl-4-ethylphenol;

2,4-dimethyl-6-tert-butylphenol;

2,6-di-tert-butyl-α-dimethylamino-p-cresol;

2,6-di-tert-butyl-4(N,N' -dimethylaminomethylphenol) ;

4,4'-thiobis(2-methyl-6-tert-butylphenol) ; 4,4' -thiobis(3-methyl-6-tert-butylphenol) ;

2,2^• -thiobis(4-methyl-6-tert-butylphenol) ; bis(3-methyl-4-hydroxy-5-tert-butylbenzyl) sulfide; bis(3,5-di-tert-butyl-4-hydroxybenzyl)sulfide; 2,2- or

4,4-biphenyldiols and derivatives thereof; hydroquinone; t-butyl hydroquinone; and other derivatives of hydroquinone.

The most preferred phenols are hydroquinone and 2,6-di-tert-4-methylphenol. The foregoing phenols are commercially available. As mentioned earlier, mixtures of phenols may be used in addition to the use of a single phenol in the present invention.

The term "phenol" as used herein includes sterically hindered phenols.

Preferably, the trivalent phosphorus compound is trivalent phosphorus compound selected from the group consisting of tris(4-nonylphenyl)phosphite; tris(2,4-di-tert-butylphenyl)phosphite;

3,9-dioctadecyloxy-2,4,8,10-tetraoxa-3,9-diphospha-

[5,5] -spiroundecane;

3,9-bis(2,4-di-tert-butylphenyloxy) -2,4,8,10-tetraoxa-

3,9-diphospha- [5,5] -spiroundecane; and tetrakis(2,4-di-tert-butylphenyl) -4,4' - biphenylenediphosphonite and mixture thereof.

The preferred trivalent phosphorus compound is tris(2,4-di-tert-butylphenyl)phosphite. The foregoing phosphorus compounds are commercially available. As mentioned earlier, mixtures of phosphorus compounds may be used in addition to the use of a single phosphorus in the present invention.

Preferred aromatic epoxides are of the formula

wherein R₂ is OCH₂CHCH₂-0; Rj is hydrogen, alkyl having 1 to 20 carbon atoms, fluoroalkyl having 1 to 20 carbon atoms, aryl having 6 to 28 carbon atoms, or fluoroaryl having 1 to 28 carbon atoms; M is aryl selected from the group consisting of phenyl, naphthyl, anthracyl, and phenanthrenyl, or alkylaryl; and each n and m is from 1 to 10. More preferably, the aromatic epoxide is arorr__ic epoxide selected from the group consisting of butylphenylglycidyl ether; pentylphenylglycidyl ether; hexylphenylglycidyl ether; heptylphenylglycidyl ether; octylphenylglycidyl ether; nonylphenylglycidyl ether; glycidyl methyl phenyl ether; decylphenylglycidyl ether; 1,4-diglycidyl phenyl ether and derivatives thereof; 1,4-diglycidyl naphthyl ether and derivatives thereof; 2,2' [[ [5- heptadecafluorooctyl]1,3phenylene]bis[[2,2,2trifluorome thyl]ethylidene]oxymethylene]bisoxirane and derivatives thereof; naphthyl glycidyl ether; 4-methoxyphenyl glycidyl ether; and derivatives of naphthyl glycidyl ether.

The most preferred aromatic epoxide is naphthyl glycidyl ether. Some of the foregoing aromatic epoxides are commercially available. As mentioned earlier, mixtures of aromatic epoxides may be used in addition to the use of a single aromatic epoxide in the present invention.

Preferred fluorinated alkyl epoxides are of the formula

wherein R is fluorinated or perfluorinated alkyl group having 1 to 20 carbon atoms. More preferably, the fluorinated alkyl epoxide is fluorinated alkyl epoxide selected from the group consisting of glycidyl trifluoromethyl ether; glycidyl pentafluoroethyl ether; glycidyl heptafluoropropyl ether; and glycidyl monofluorobutyl ether.

The most preferred fluorinated alkyl epoxide is glycidyl pentafluoroethyl ether. The foregoing fluorinated alkyl epoxides are commercially available.

As mentioned earlier, mixtures of fluorinated alkyl epoxides may be used in addition to the use of a single fluorinated alkyl epoxide.

The ratio of phenol or phosphorus to epoxide in the stabilizing polyoxyalkylene glycols can be varied from 1:99 to 99:1. Preferably, the amount of phenol and aromatic or fluorinated alkyl epoxide used is about 0.01 to about 5 percent by weight based on the amount of the polyoxyalkylene glycols.

The present invention is more fully illustrated by the following non-limiting Examples.

COMPARATIVES A THROUGH G

The Comparatives in Table II below show that R32, R125, and blends thereof are immiscible with mineral oils and alkylbenzene. Sunisco 3GS (registered trademark) is a mineral oil available from Witco. Zerol (registered trademark) is an alkylbenzene available from Shrieve.

In Table II below, C-A stands for Comparative A, C-B stands for Comparative B, C-C stands for Comparative C, C-D stands for Comparative D, C-E stands for Comparative E, C-F stands for Comparative F, and C- G stands for Comparative G. In Comparatives F and G, the weight percent of R32 to R125 is 75:25. Ref stands for refrigerant and Lub stands for lubricant. The viscosity was taken at 37°C and is expressed in centistokes. MW means molecular weight. Immis means immiscible. TABLE II

COMPARATIVES H THROUGH K

The Comparatives in Table III below show that R32 is immiscible with esters. Emery 2930A (registered trademark) is a short chain fatty acid ester of trimethylolpropane available from Emery. Emery 2917 (registered trademark) is neopentyl dipelargonate available from Emery.

In Table III below, C-H stands for Comparative H, C-I stands for Comparative I, C-J stands for Comparative J, and C-K stands for Comparative K. Ref stands for refrigerant and Lub stands for lubricant. The viscosity was taken at 37°C and is expressed in centistokes. MW means molecular weight. Misc means miscible. Immis means immiscible.

COMPARATIVES L THROUGH 0

The Comparatives in Table IV below show that R32 is immmiscible with polyoxyalkylene glycols having an alkyl group on one end thereof. Ucon 50HB400 (registered trademark) is copolymer of ethylene oxide and propylene oxide having a butyl cap on one end thereof from Union Carbide. LB 385 (registered trademark) is polyoxypropylene oxide having a butyl cap on one end thereof from Union Carbide.

In Table IV below, C-L stands for Comparative L, C-M stands for Comparative M, C-N stands for

Comparative N, and C-0 stands for Comparative 0. Ref stands for refrigerant and Lub stands for lubricant. The viscosity was taken at 37°C and is expressed in centistokes. MW means molecular weight. Misc means miscible. Immis means immiscible.

EXAMPLES 1 THROUGH 12

The Examples of Table V below show that R32, R125, and blends of R125 and R143a show good miscibility with polyoxyalkylene glycols having a fluorinated alkyl group on one end thereof. P425 is difunctional polypropylene oxide available from Dow Chemical. Lub B is bis(trifluoroethyl ether) of polypropylene glycol. Lub C is dimethyl/methyltrifluoropropyl siloxane with 50% methyltrifluoropropyl units. FS 1265 (registered trademark) is methyltrifluoropropyl siloxane available from Dow-Corning.

In Table V below, E-l stands for Example 1, E-2 stands for Example 2, E-3 stands for Example 3, E-4 stands for Example 4, E-5 stands for Example 5, E-6 stands for Example 6, E-7 stands for Example 7, E-8 stands for Example 8, E-9 stands for Example 9, E-1^'0 stands for Example 10, E-ll stands for Example 11, and E-12 stands for Example 12. In Example 6, the weight percent ratio of R32 to R125 is 75:25. In Examples 7 through 9, the weight percent ratio of R125 to R143a is 50:50. Ref stands for refrigerant and Lub stands for lubricant. The viscosity was taken at 37°C and is expressed in centistokes. MW means molecular weight. Immis means immiscible.

TABLE V

Having described the invention in detail and by reference to preferred embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims.

Claims

What is claimed is:

1. A composition for use in refrigeration and air-conditioning comprising:

(a) a hydrofluorocarbon refrigerant selected from the group consisting of difluoromethane, pentafluoroethane, and mixtures thereof; and

(b) a sufficient amount to provide lubrication of at least one lubricant selected from the group consisting of: (i) polyoxyalkylene glycol which is at least difunctional with respect to the hydroxyl groups,

(ii) polyoxyalkylene glycol having a cap of a fluorinated alkyl group on at least one end thereof, (iii) fluorinated silicone having units therein selected from the group consisting of fluoroalkyl and alkyl wherein if both of said units are present, at least 25% of the siloxane units have a fluoroalkyl substituent thereon, and mixtures thereof, wherein said lubricant has a molecular weight of about 300 to about 6,000, a viscosity of about 5 to about 300 centistokes at 37°C, and is miscible in combination with said refrigerant (a) in the range between about 25°C and at least about 30°C.

2. The composition of claim 1 wherein said refrigerant is difluoromethane.

3. The composition of claim 2 wherein said refrigerant additionally comprises 1,1,1,2- tetrafluoroethane.

4. The composition of claim 1 wherein said refrigerant is pentafluoroethane.

5. The composition of claim 4 wherein said refrigerant additionallly comprises 1,1,1- trifluoroethane.

6. The composition of claim 1 wherein said lubricant is polyoxyalkylene glycol which is at least difunctional with respect to the hydroxyl groups.

7. The composition of claim 6 wherein said lubricant additionally comprises chlorotrifluoroethylene oil.

8. The composition of claim 1 wherein said lubricant is polyoxyalkylene glycol having a cap of a fluorinated alkyl group on at least one end thereof.

9. The composition of claim 1 wherein said lubricant is fluorinated silicone having units therein selected from the group consisting of fluoroalkyl and alkyl wherein if both of said units are present, at least 25% of the siloxane units have a fluoroalkyl substituent thereon.

10. A method for improving lubrication in refrigeration and air-conditioning equipment using the composition of claim 1.