Polyglycol lubricants for refrigeration compressors and process for preparing the same

Abstract: A refrigeration fluid compositions for compression refrigeration which have an upper solution critical temperature equal to or greater than 60°C are composed of (A) selected hydrochlorofluorocarbons and hydrofluorocarbons and (B) polyether polyols having viscosities of greater than 80 centistokes (8 x 10⁻⁵ m²/s) at 38°C and having a number average molecular weight of from 400 to 2000 wherein the polyols are the residue of an active hydrogen compound such as glycerine or ethylene diamine.

Description: This invention relates to compositions of polyglycols with hydrofluorocarbon and hydrochlorofluorocarbon refrigerants which are useful for lubricating heat pumps and air conditioning compressors. Refrigerant R12 (dichlorodifluoromethane) is used in automotive air conditioners and many other types of refrigeration and air conditioning compressors. It is a chlorofluorocarbon that has been identified as depleting atmospheric ozone. The Montreal Accord restricts the production of R12 by 1990. Refrigerant R134a (1,1,1,2-tetrafluoroethane) has a vapor pressure that is very similar to R12 and it has the advantage that it does not deplete atmospheric ozone. R134a can replace R12 in most refrigeration systems without major redesign of present equipment. It could be used in automotive air conditioners without any or with minor re-tooling by the automotive companies. The major problem of using R134a is that conventional lubricants such as naphthenic mineral oils are not soluble over the temperature range of from -20 to 80°C, the operating temperatures encountered in the different refrigeration applications. Some polyglycols are soluble in R134a at 25°C and below but phase separate below 60°C. Phase separation of the lubricant from the refrigerant can cause poor lubrication of the compressor which results in increased wear and decreased compressor life. It is well known in the refrigeration industry that lubricant concentration in the refrigerant is limited to the preferred range of from 10 to 20 weight percent due to thermodynamic considerations. However, a range of from 1 to 25 weight percent is considered to be useful in this invention. The usefulness of this invention is that it will enable compressor manufacturers to substitute R134a and other hydrofluorocarbons or hydrochlorofluorocarbons for chlorofluorocarbons such as R12 in most compressors without mechanical modification to existing compressors and be able to operate over a broad temperature range. The fundamentals of lubrication in air conditioners are set forth by H.H. Kruse et al. in "Fundamentals of Lubrication in Refrigeration Systems and Heat Pumps" pages 763-783; ASHRAE Transactions Vol 90 part 2B (1984). Lubricants for various refrigeration compressors are known from U.S. Patent 4,248,726. This patent shows polyether polyols or polyglycols with functionalities of 1 to 6 are useful as refrigeration lubricants with various refrigerants such as, for example, and R11, R12, and R22. The polyglycols can have free OH groups or can be ether or ester capped and they contain an acid scavenging additive package. These fluids must have a viscosity of from 50 to 200 cs (5 x 10⁻⁵ to 2 x 10⁻⁴ m²/s) at 98.8°C and a viscosity index of at least 150. The focus of this patent is an additive package that prevents the degradation of the high viscosity polyglycols in a rotary type refrigerators. The high molecular weight polyglycols of this patent are insoluble in R134a at 25°C. U.S. Patent 4,267,064 shows essentially the same invention as the above 4,248,726 patent except that the '064 patent discloses and teaches the use of polyether polyols having viscosities of from 25 to 50 cs (25 x 10⁻⁶ to 5 x 10⁻⁵ m²/s) at 98.8°C. The high molecular weight polyglycols of this patent are insoluble in R134a at 25°C. EP-A-0 378 176, which has to be considered prior art only according to Art. 54(3) EPC, discloses lubricant base compositions which are miscible with R134a in the temperature range of from -20°C to greater than 65°C, wherein said base compositions comprise from 95 to 5 percent by weight of polyether polyols and from 5 to 95 percent of esters made from polyhydric alcohols with alkanoic acids or esters made from alkanedioic acids with alkanols. In EP-A-0 377 122, which also constitutes prior art according to Art. 54(3) EPC, various lubricating oils which are miscible with R134a throughout the temperature range of the application are described. In one embodiment, the lubricant oil contains polyoxyalkylene polyol initiated from glycol, and fluorinated oil as a further component. However, lubricant oils which are composed of a polyether polyol having a viscosity of greater than 80 cs (8 x 10⁻⁵m²/s) at 38°C and which are miscible with the refrigerant up to at least 60°C are not disclosed in EP-A-0 377 122. U.S. Patent 4,755,316 discloses compositions containing one or more polyether polyols for lubricating refrigeration compressors using R134a. However, it has been found (control D) that the polypropylene glycol based on trimethylolpropane mentioned in the patent is unexpectedly inferior to the polyglycols used herein. Lubricants for various refrigeration compressors are also known from Japanese Patent J57051795. This patent suggests that a high molecular weight polypropylene glycol based on glycerine might be useful as a refrigeration lubricant. However, the upper solution critical temperature of this glycol is not adequate as can be seen from Control E herein. The invention comprises polyether polyol lubricant compositions with hydrofluorocarbon and hydrochlorofluorocarbon refrigerants which have upper solution critical temperatures equal to or greater than 60°C. In general, the compositions consist of (A) a refrigerant selected from hydrofluorocarbons and hydrochlorofluorocarbons, and (B) a polyether polyol which has a viscosity of greater than 80 centistokes (8 x 10⁻⁵ m²/s) at 38°C and the formula Z-[(CH₂-CH(R₁)-O-) n -(CH₂-CH(CH₃)-O-) m -H] p where Z is the residue of an active hydrogen compound selected from the group consisting of glycerine, pentaerythritol, sorbitol, ethylene diamine, diethylene triamine, hydrazine, ethanolamine, diethanolamine, triethanolamine, isopropanolamine, diisopropanolamine and triisopropanolamine, R₁ is hydrogen, ethyl, or mixtures thereof, n is 0 or a positive number, m is a positive number, n+m is a number having a value which will give a polyether polyol with a number average molecular weight range of from 400 to 2000, p is an integer having a value equal to the the number of active hydrogens of Z with the proviso that the composition does not contain an ester selected from (1) esters made from polyhydric alcohols with alkanoic acids and (2) esters made from alkanedioic acids with alkanols, and that the composition does not contain fluorinated oils when Z is glycerine. The polyol lubricant compositions have a preferred upper solution critical temperatures in the range of from 65°C to 110°C. The polyether polyols have a preferred viscosity in the range of from 90 to 800 centistokes (9 x 10⁻⁵ to 8 x 10⁻⁴ m²/s) at 38°C. Examples of the polyether polyols or polyoxyalkylene polyols used in this invention are those derived from ethylene oxide, propylene oxide, 1-2, or 2-3 butylene oxide. The above oxides may be polymerized alone, i.e., homopolymerized or in combination. The combined oxides may also be combined in a random or block addition. While some of the above compounds may be of a hydrophilic nature, those of a hydrophobic nature are preferred, such as those derived from propylene oxide, butylene oxides or combinations thereof. Examples of suitable polyoxyalkylene glycols are those derived from ethylene, propylene, and butylene oxides wherein the alkylene oxides are initiated from a compound having from 3 to 6 active hydrogens in a known manner. These polyether polyols and their preparation are well known from the book "Polyurethanes" by Saunders and Frisch, Interscience Publishers (1962), pages 33-39. Examples of suitable initiator compounds which are employed to prepare the above polyether polyols are compounds having from 3 to 6 active hydrogens such as, for example, glycerine, pentaerythritol, sorbitol, ethylene diamine, diethylene triamine, hydrazine, ethanolamine, diethanolamine, triethanolamine, isopropanolamine, diisopropanolamine and triisopropanolamine. The foregoing polyether polyols should have a number average molecular weight range of from 400 to 2000 and preferably in the range of from 400 to 1500. The final lubricant compositions of this invention may contain effective amounts of ashless additives, such as antioxidants, corrosion inhibitors, metal deactivators, lubricity additives, extreme pressure additives and viscosity index improvers as may be required. Examples of useful ashless antioxidants which can be used herein are phenyl naphthylamines, i.e., both alpha and beta-naphthyl amines; diphenyl amine; iminodibenzyl; p,p-dibutyl-diphenylamine; p,p′-dioctyldiphenylamine; and mixtures thereof. Other suitable antioxidants are hindered phenolics such as 6-t-butylphenol, 2,6-di-t-butylphenol and 4-methyl-2,6-di-t-butylphenol and the like. Examples of suitable ashless metal corrosion inhibitors are commercially available, such as Irgalube 349 from Ciba-Geigy. This inhibitor compound is an aliphatic amine salt of phosphoric acid monohexyl ester. Other useful metal corrosion inhibitors are NA-SUL DTA and NA-SUL EDS from the White Chemical Company (diethylenetriamine dinonylnapthalene sulfonate and ethylene diamine dinonylnaphthalene sulfonate) and N-methyl oleosarcosine, respectively. Examples of suitable ashless cuprous metal deactivators are imidazole, benzimidazole, pyrazole, benzotriazole, tolutriazole, 2-methyl benzimidazole, 3,5-dimethyl pyrazole, and methylene bis-benzotriazole. An effective amount of the foregoing additives for use in a air conditioning compressor is generally in the range of from 0.1 to 5.0 percent by weight for the antioxidants, from 0.1 to 5.0 percent by weight for the corrosion inhibitors, and from 0.001 to 0.5 percent by weight for the metal deactivators. The foregoing weight percentages are based on the total weight of the polyether polyols. It is to be understood that more or less of the additives may be used depending upon the circumstance for which the final composition is to be used. Examples of refrigerants useful in this invention are hydrochlorofluorocarbons such as chlorodifluoromethane, chlorofluoromethane, 2,2-dichloro-1,1,1-trifluoroethane, 1-chloro-1,2,2,2-tetrafluoroethane, 2-chloro-1,1,2,2-tetrafluoroethane, 1-chloro-2,2,2-trifluoroethane, 1,1-dichloro-1-fluoroethane and 2-chloro-2,2-difluoroethane. Other examples of refrigerants useful in this invention are hydrofluorocarbons such as 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, 1,1,1-trifluoroethane, 2,2-difluoroethane, trifluoromethane, methylene fluoride, methyl fluoride, difluoroethylene and pentafluoroethane. The general procedure for the preparation of the controls and the examples of present invention with the refrigerant R134a is set forth below. The data is given in the following Table. The selected polyol is vacuum stripped. Glass ampules are washed with acetone and vacuum dried at 110°C. The empty ampule or tube is weighed and the mixture to be evaluated is syringed into the tube. The tube is re-weighed to determine the weight of lubricant. The tube is evacuated to remove air and then immersed in a dry ice/methylene chloride slurry in a Dewar flask. The R134a is transferred at a pressure of 8 psig into the tube to give the desired lubricant concentration. The filled ampule was then disconnected and allowed to equilibrate at room temperature, 25°C. The ampules were placed in a controlled temperature bath and the temperature varied from -20 to 85°C while observing for phase separation. The temperature of phase separation is called the upper solution critical temperature (USCT) and is reported in degrees C. Temperatures above 85°C were not investigated because of pressure limitations of the glass ampule apparatus. Systems with USCT's above this temperature measurement limit are denoted as greater than 85°C. R134a Upper Solution Critical Temperature Data Run Number Lubricant--Neat Viscosity-- in cs @ 100°F or 38°C (m²/s) Lubricant Wt % in R134a USCT °C Control A n-butanol + PO to 1170 Mol Wt--57 cs (57 x 10⁻⁶) 16 60 Control B Propylene glycol + PO to 2000 Mol Wt--160 cs (16 x 10⁻⁵) 12 <25 Control C Propylene glycol + PO to 1000 Mol Wt--73 cs (73 x 10⁻⁶) 25 70 Control D Trimethylol propane + PO to 720 Mol Wt--133 cs (133 x 10⁻⁶) 16 52 Control E Glycerine + PO to 3000 Mol Wt-230 cs viscosity index 180 (23 x 10⁻⁵) 22 <25 Example 1 Glycerine + PO to 700 Mol Wt--108 cs (108 x 10⁻⁶) 16 78-80 Example 2 Ethylene diamine + PO to 511 Mol Wt--753 cs (753 x 10⁻⁶) 15 >85 Example 3 Ethylene diamine + PO to 951 Mol Wt--263 cs (263 x 10⁻⁶) 15 70

Claims: Fluid compositions for use in compression refrigeration which have an upper solution critical temperature equal to or greater than 65°C comprising (A) a refrigerant selected from hydrofluorocarbons and hydrochlorofluorocarbons, and (B) a polyether polyol which has a viscosity of greater than 80 centistokes (8 x 10⁻⁵ m²/s) at 38°C and the formula Z-[(CH₂-CH(R₁)-O-) n -(CH₂-CH(CH₃)-O-) m -H] p where Z is the residue of an active hydrogen compound selected from glycerine, pentaerythritol, sorbitol, ethylene diamine, diethylene triamine, hydrazine, ethanolamine, diethanolamine, triethanolamine, isopropanolamine, diisopropanolamine and triisopropanolamine, R₁ is hydrogen, ethyl, or mixtures thereof, n is 0 or a positive number, m is a positive number, n+m is a number having a value which will give a polyether polyol with a number average molecular weight range of from 400 to 2000. p is an integer having a value equal to the the number of active hydrogens of Z with the proviso that the composition does not contain an ester selected from (1) esters made from polyhydric alcohols with alkanoic acids and (2) esters made from alkanedioic acids with alkanols, and that the composition does not contain fluorinated oils when Z is glycerine. Fluid compositions for use in compression refrigeration which have an upper solution critical temperature equal to or greater than 60°C comprising (A) a refrigerant selected from hydrochlorofluorocarbons and hydrofluorocarbons, and (B) a lubricant composition which comprises a polyether polyol which has a viscosity of greater than 80 centistokes (8 x 10⁻⁵ m²/s) at 38°C and which has the formula Z-[-(CH₂-CH(CH₃)-O-) n -H] p where Z is the residue of an active hydrogen compound selected from the group consisting of pentaerythritol, sorbitol, ethylene diamine, diethylene triamine, hydrazine, ethanolamine, diethanolamine, triethanolamine, isopropanolamine, diisopropanolamine and triisopropanolamine, n is a number having a value which will give a polyether polyol with a number average molecular weight range of from 400 to 2000. p is an integer having a value equal to the the number of active hydrogens of Z with the proviso that the composition does not contain an ester selected from (1) esters made from polyhydric alcohols with alkanoic acids and (2) esters made from alkanedioic acids with alkanols. A composition as claimed in Claim 1 or 2 wherein said lubricant composition has an upper solution critical temperature of from 65°C to 110°C. A composition as claimed in Claim 1 or 2 wherein said polyether polyols have a viscosity in the range of from 90 to 800 centistokes (9 x 10⁻⁵ to 8 x 10⁻⁴ m²/s) at 38°C. A composition as claimed in Claim 1 or 2 wherein said fluid composition contains a concentration of about 1 to about 25 percent by weight of lubricant composition. A composition as claimed in Claim 1 or 2 wherein said hydrochlorofluorocarbons are selected from chlorodifluoromethane, chlorofluoromethane, 2,2-dichloro-1,1,1-trifluoroethane, 1-chloro-1,2,2,2-tetrafluoroethane, 2-chloro-1,1,2,2-tetrafluoroethane, 1-chloro-2,2,2-trifluoroethane, 1,1-dichloro-1-fluoroethane and 2-chloro-2,2-difluoroethane and said hydrofluorocarbons are selected from 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, 1,1,1-trifluoroethane, 2,2-difluoroethane, trifluoromethane, methylene fluoride, methyl fluoride, difluoroethylene and pentafluoroethane. A composition as claimed in Claim 2 for use in compression refrigeration which has an upper solution critical temperature of from 65°C to 110°C, wherein component (A) is 1,1,1,2-tetrafluoroethane, and component (B) is a lubricant composition which comprises a polyether polyol which has a viscosity from 90 to 800 centistokes (9 x 10⁻⁵ to 8 x 10⁻⁴ m²/s) at 38°C and which has the formula Z-[-(CH₂-CH(CH₃)-O-) n -H] p where Z is glycerine, n is a number having a value which will give a polyether polyol with a number average molecular weight range of from 400 to 2000. p is 3. A fluid composition as claimed in Claim 2 for use in compression refrigeration which have an upper solution critical temperature of from 65°C to 110°C, wherein component (A) is 1,1,1,2-tetrafluoroethane, and (B) is a lubricant composition which comprises a polyether polyol which has a viscosity of from 90 to 800 centistokes (9 x 10⁻⁵ to 8 x 10⁻⁴ m²/s) at 38°C and which has the formula Z-[-(CH₂-CH(CH₃)-O-) n -H] p where Z is ethylene diamine, n is a number having a value which will give a polyether polyol with a number average molecular weight range of from 400 to 2000. p is 4. A process for preparing fluid compositions for use in compression refrigeration which have an upper solution critical temperature equal to or greater than 65°C comprising mixing: (A) a refrigerant selected from hydrofluorocarbons and hydrochlorofluorocarbons, and (B) a polyether polyol which has a viscosity of greater than 80 centistokes (8 x 10⁻⁵ m²/s) at 38°C and the formula Z-[(CH₂-CH(R₁)-O-) n -(CH₂-CH(CH₃)-O-) m -H] p where Z is the residue of an active hydrogen compound selected from glycerine, pentaerythritol, sorbitol, ethylene diamine, diethylene triamine, hydrazine, ethanolamine, diethanolamine, triethanolamine, isopropanolamine, diisopropanolamine and triisopropanolamine, R₁ is hydrogen, ethyl, or mixtures thereof, n is 0 or a positive number, m is a positive number, n+m is a number having a value which will give a polyether polyol with a number average molecular weight range of from 400 to 2000, and p is an integer having a value equal to the the number of active hydrogens of Z with the proviso that the composition does not contain an ester selected from (1) esters made from polyhydric alcohols with alkanoic acids and (2) esters made from alkanedioic acids with alkanols, and that the composition does not contain fluorinated oils when Z is glycerine. A process for preparing fluid compositions for use in compression refrigeration which have an upper solution critical temperature equal to or greater than 60°C comprising mixing: (A) a refrigerant selected from hydrochlorofluorocarbons and hydrofluorocarbons, and (B) a lubricant composition which comprises a polyether polyol which has a viscosity of greater than 80 centistokes at 38°C and which has the formula Z-[-(CH₂-CH(CH₃)-O-) n -H] p where Z is the residue of an active hydrogen compound selected from the group consisting of pentaerythritol, sorbitol, ethylene diamine, diethylene triamine, hydrazine, ethanolamine, diethanolamine, triethanolamine, isopropanolamine, diisopropanolamine and triisopropanolamine, n is a number having a value which will give a polyether polyol with a number average molecular weight range of from 400 to 2000 with the proviso that the composition does not contain an ester selected from (1) esters made from polyhydric alcohols with alkanoic acids and (2) esters made from alkanedioic acids with alkanols.

Inventors: MCGRAW PHILIP W, MCGRAW, PHILIP W.
Applicants: DOW CHEMICAL CO, THE DOW CHEMICAL COMPANY
Application year: 1990
Main classification: C10M107
IPC codes: C10M105, C10N40, C09K5, C10N20, C10M169, C10M171, C10M107