JPH08502769A - Working fluid composition - Google Patents

Abstract

  (57) [Summary] (A) A refrigerant consisting essentially of difluoromethane (R-32), (B) at least one neopentyl polyol, and at least one aliphatic carboxylic acid or an esterifiable derivative thereof. A working fluid composition comprising an ester-based oil consisting of a reaction product and a lubricant. A heat transfer device containing the working fluid composition is also claimed.

Description

DETAILED DESCRIPTION OF THE INVENTION The working fluid composition The present invention relates to a heat transfer device to the working fluid used (working fluid) compositions, specifically configured control means of the discharge temperature of the compressor (means clustering) Working fluid composition for use in a heat transfer device. Mechanical compression type heat transfer devices such as refrigerators, chillers, refrigerators, heat pumps and automotive air conditioners are well known. In such a device, a refrigerant liquid with a suitable boiling point evaporates at low pressure, removing heat from the surrounding zone. The vapor produced is then compressed and passed through a condenser where it condenses and gives off heat to a second zone. Then, the produced condensate is returned to the evaporator through the expansion valve, where the cooling and refrigeration cycle is completed. The mechanical energy needed to compress the vapor and pump the refrigerant may be provided by an electric motor or an internal combustion engine. Preferred properties of the refrigerant include low toxicity, nonflammability, noncorrosion, high stability and no unpleasant odor in addition to having a suitable boiling point and a high latent heat of vaporization. Traditionally, heat transfer devices include chlorofluorocarbon refrigerants such as dichlorodifluoromethane (Refrigerant R-12), chlorodifluoromethane (Refrigerant R-22), or an azeotrope of chlorodifluoromethane and chloropentafluoroethane (Refrigerant R-115). There is a tendency to use mixtures, the azeotrope being Refrigerant R-502. However, wholly or partially halogenated chlorofluorocarbons are associated with the depletion of the earth's protective ozone layer, and as a result their use and manufacture should be severely limited by international agreements. Although heat transfer devices of the type to which the present invention pertains are closed systems in nature, leakage during operation or maintenance of the device can result in loss of refrigerant to the atmosphere. Therefore, it is important to replace the wholly or partially halogenated chlorofluorocarbon refrigerants with materials that have low or no ozone depletion potential. In addition to the possibility of ozone depletion, it has been suggested that significant concentrations of chlorofluorocarbon refrigerants in the atmosphere may contribute to global warming (the so-called greenhouse effect). Therefore, it is desirable to use a refrigerant that has a relatively short atmospheric lifetime as a result of which the refrigerant can react with other atmospheric components such as hydroxyl radicals. Certain hydrofluoroalkanes, ie compounds containing only carbon atoms, hydrogen atoms and fluorine atoms in their structure, have been proposed as alternatives to chlorofluorocarbons. Hydrofluoroalkanes of particular interest are compounds with boiling points and other thermal properties comparable to the chlorofluorocarbons being replaced, but the compounds are less damaging or mild to the ozone layer. It is also a benigen. Specifically, 1,1,1,2-tetrafluoroethane (R-134a) may be mentioned. In the heat transfer device, the refrigerant becomes a constituent of the working fluid composition. The working fluid composition also contains a lubricant. The lubricant circulates around the device along with the refrigerant, constantly providing lubrication to the compressor. In addition to having good lubricity in the presence of a refrigerant, the properties desired for a lubricant include good hydrolytic stability and good thermal stability. Furthermore, in order to return the lubricant to the compressor, it should be compatible with the refrigerant, which in practice should have some degree of mutual solubility between the lubricant and the refrigerant, i.e. It means that the lubricant and the coolant should be at least partially soluble in each other. Traditionally, heat transfer devices tend to use mineral oil as a lubricant. The good solubility of the chlorofluorocarbons with the mineral oil allows the mineral oil to circulate around the heat transfer device with the chlorofluorocarbons, which in turn ensures effective lubrication of the compressor. Unfortunately, however, the above alternative refrigerants have different solubilities from the currently used chlorofluorocarbons, yet tend not to dissolve well in mineral oils, making them impossible to use as lubricants. . As a result, not only is there a problem with finding a viable alternative refrigerant that has low or no ozone deplation, and in many cases, together with an alternative refrigerant. The need to replace chlorofluorocarbon refrigerants has created very real difficulties for the industry because there are also problems with developing a lubricant that will perform well. The Applicant has proposed a working fluid composition comprising a refrigerant having no possibility of depleting ozone and a lubricant capable of imparting effective lubrication to a compressor in the presence of the refrigerant. developed. The working fluid composition of the present invention is a viable alternative for at least some of the currently used working fluid compositions comprising a chlorofluorocarbon refrigerant and a mineral oil lubricant. Can be provided. According to the present invention, a working fluid composition comprising: (A) a refrigerant consisting essentially of difluoromethane (R-32), and (B) a sufficient amount of lubricant to provide lubrication. , A lubricant comprising an ester base oil comprising a reaction product of at least one neopentyl polyol and at least one aliphatic carboxylic acid or at least one esterifiable derivative thereof. A working fluid composition comprising: A small molecule, difluoromethane, tends to result in high compressor discharge temperatures when used for high lift, single stage compression. As a result, heat transfer devices that use difluoromethane as the refrigerant preferably constitute the discharge temperature control means of the compressor from the standpoint of limiting the maximum discharge temperature achieved. Heat transfer devices capable of controlling the discharge temperature of the compressor are known in the art. Typically, this temperature control is provided by injecting a stream of lubricant into the compressor and / or by injecting a stream of liquid refrigerant into the compressor. These two methods result in efficient cooling of the compressor and thus control of the compressor discharge temperature. The heat transfer device that constitutes the means for controlling the discharge temperature of the compressor often uses a screw compressor, that is, a screw compressor (which may be a single or two screw configuration). However, reciprocating compressor type heat transfer devices that use injection of liquid refrigerant for cooling applications are also known in the art. The heat transfer device should preferably be able to maintain the discharge temperature of the compressor below 150 ° C, for example below 130 ° C. Therefore, in a preferred aspect of the present invention, a heat transfer device that constitutes the discharge temperature control means of the compressor, and (A) a refrigerant consisting essentially of difluoromethane (R-32), and (B) An ester-based oil comprising a reaction product of at least one neopentyl polyol and at least one aliphatic carboxylic acid or an esterifiable derivative thereof, which is a lubricant in an amount sufficient to provide lubrication. A heat transfer device is provided which uses a working fluid composition containing a lubricant consisting of The lubricant component of the working fluid composition of the present invention comprises an ester-based oil. The ester-based oils described above are those that are capable of sufficiently dissolving the difluoromethane refrigerant to enable the transport of lubricant around the heat transfer system and the return of lubricant to the compressor. Should be Generally, this is because the ester-based oil is capable of dissolving at least 5.0% by weight of the oil weight of difluoromethane refrigerant at 40 psi (40 pounds per square inch) and a temperature of 0 ° C. Means what it should be. Generally, the lubricant component should have a viscosity at 40 ° C within the range of 46 to 220 cSt. When the heat transfer device is of the type that controls the discharge temperature of the compressor using a liquid refringerant injection technique, the lubricant component at 40 ° C. is preferably 46-100 cSt. Viscosities in the range of 4 to 85 cSt, more preferably viscosities in the range of 46 to 68 cSt. However, if the heat transfer device is of the type that controls the discharge temperature of the compressor using the cooling effect created by injecting a stream of lubricant, then the lubricant component is preferably at 40 ° C. Has a viscosity in the range of 68 to 220 cSt, more preferably in the range of 100 to 190 cSt, especially in the range of 125 to 175 cSt. The viscosity index of the lubricant component, which is a measure of how the viscosity changes with temperature, is in the range 50 to 200, more preferably 60 to 150, and particularly preferably 90. It is in the range of ~ 130. Furthermore, preferred lubricants have a pour point below -20 ° C, more preferably below -30 ° C, particularly preferably below -40 ° C. Suitable neopentyl polyols for constituting the ester-based oils mentioned above include pentaerythritol; polypentaerythritols such as dipentaerythritol or tripentaerythritol; trimethylolalkanes such as trimethylolethane and trimethylolpropane; Mention may be made of pentyl glycol. The esters may be formed using linear and / or branched chain aliphatic carboxylic acids, such as linear and / or branched chain alkanoic acids. Small amounts of aliphatic polycarboxylic acids, such as aliphatic dicarboxylic acids, can also be used in the synthesis of the ester to increase its viscosity. However, when such an aliphatic polycarboxylic acid is used in the ester synthesis, the aliphatic polycarboxylic acid is 30% by weight or less, more preferably 10% by weight or less of the carboxylic acid used in the synthesis. It is preferable to configure. Generally, the amount of carboxylic acid (s) used in the ester synthesis is sufficient to esterify all of the hydroxyl groups contained in the polyol. However, residual hydroxyl functionality is acceptable. It will be appreciated that esterified derivatives of carboxylic acids may be used in the synthesis if desired. Lubricants preferably used in the working fluid compositions of the present invention are those wherein the ester-based oil is at least one neopentyl polyol selected from pentaerythritol, dipentaerythritol and tripentaerythritol, and a linear chain ( A lubricant comprising a reaction product of at least one aliphatic carboxylic acid selected from linear) aliphatic carboxylic acids and branched-chain aliphatic carboxylic acids. As mentioned above, esterifiable derivatives of the carboxylic acids, such as acyl halides, anhydrides and lower alkyl esters thereof, may also be used in the ester synthesis, in the following, the carboxylic acid is used in the synthesis of ester-based oils. Whenever reference is made to the use of, the use of its esterifiable derivative should not be excluded. A suitable acyl halide is an acyl chloride and a suitable lower alkyl ester is a methyl ester. The base or ester-based oil in this preferred lubricant has the formula: [In the formula, R is a hydrocarbon group remaining after removing a plurality of hydroxyl groups from pentaerythritol, dipentaerythritol, or tripentaerythritol; R ¹ is independently a linear (linear) aliphatic hydrocarbyl group; A group or a branched-chain aliphatic hydrocarbyl group; and n is an integer of 4, 6, or 8], or one or more of the ester compounds. The aliphatic hydrocarbyl group specified as R ¹ is, for example, a pendant type atom or group such as a chlorine atom, a fluorine atom and a bromine atom and / or a heteroatom in a chain such as an oxygen atom and a nitrogen atom. May be replaced with. However, such hydrocarbyl groups are preferably unsubstituted and therefore preferably contain only carbon and hydrogen atoms. Suitable base oils may consist of a single ester compound of formula I above, ie a single pentaerythritol type neopentylpolyol, and the product formed by the reaction of a single carboxylic acid. Will be recognized. Suitable base oils may also contain two or more of the compounds of formula I above. Such base oils may be prepared by utilizing two or more pentaerythritol-type neopentyl polyols and / or two or more carboxylic acids in the synthesis of said ester, or with different ester compounds. And each of them can be produced by combining a mixture of a specific pentaerythritol type neopentylpolyol and an ester compound which is a reaction product of a specific carboxylic acid. Furthermore, various hybrid ester compositions, each of which is prepared by utilizing in the synthesis two or more of the pentaerythritol type neopentyl polyols and / or two or more of the carboxylic acids. The various mixed ester compositions described above can also be blended together to form an ester-based oil. Preferred ester-based oils are those compounds of formula I above, in which each R ¹ is independently a linear alkyl group or a branched chain alkyl group and one or more thereof. Is. A preferred linear alkyl group for R ¹ is a C _4-9 linear alkyl group, and an ester compound containing such an alkyl group can be used as a pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid It can be prepared by using at least one C _5-10 linear alkanoic acid selected from nonanoic acid and decanoic acid. Particularly preferred linear alkyl groups for R ¹ are C _4-8 linear alkyl groups, especially linear C ₄ alkyl groups and linear C ₆ alkyl groups, which are derived from pentanoic acid and heptanoic acid, respectively. Linear C ₆ alkyl groups are particularly preferred linear alkyl group. Preferred branched chain alkyl group as R ¹ is a C _{6 to 9} branched chain alkyl group, an ester compound containing such alkyl groups, at least one C ₇ ~ ₁₀ branched alkanoic acid in the synthesis of the oil of the ester substrate , For example, 2-methylhexanoic acid, 3-methylhexanoic acid, 4-methylhexanoic acid, 2,2-dimethylpentanoic acid, 2,4-dimethylpentanoic acid, 2-ethylpentanoic acid, 3-ethylpentanoic acid, 2- Ethylhexanoic acid, 3,5-dimethylhexanoic acid, 2,2-dimethylhexanoic acid, 2-methylheptanoic acid, 3-methylheptanoic acid, 4-methylheptanoic acid, 2,2-dimethylheptanoic acid, 3,5, It can be prepared by using 5-trimethylhexanoic acid, 2-methyloctanoic acid, 3-methyloctanoic acid, 2-ethylheptanoic acid and isodecanoic acid. Particularly preferred branched-chain alkyl group as R ¹ is, C ₇ ~ ₉ branched alkyl group, in particular branched C ₈ alkyl radical which is derived from the branched-chain C ₉ alkanoic acid. Particularly preferred ester-based oils are obtained when a combination of linear and branched chain alkanoic acids is used in the synthesis, so that the oil is a compound of formula I above at least a portion of the number of radicals R ¹ is at least a portion of the line is an alkyl groups and a plurality of radicals R ¹ consists of one or more compounds which are branched-chain alkyl group. Of the total number of the plurality of groups R ¹ in one or more ester compounds constituting the oil of the substrate, preferably 30 to 80% (number basis), more preferably 40 to 80% (number basis). Particularly preferably, 50 to 70% (based on the number) is a branched chain alkyl group, and the remaining group R ¹ is a linear alkyl group. The ester-based oil is an ester derived from dipentaerythritol, i.e., the compound of formula I above, wherein R is a hydrocarbon group remaining after removal of multiple hydroxyl groups from dipentaerythritol. It preferably consists of one or more compounds. Further, such ester base oil is an ester compound represented by the formula I in which R in the formula is a hydrocarbon group remaining after removing a plurality of hydroxyl groups from pentaerythritol and / or tripentaerythritol. It may consist of one or more species. Preferably at least 25% by weight, more preferably at least 50% by weight and particularly preferably at least 75% by weight of the ester-based oil consists of one or more ester compounds derived from dipentaerythritol. is there. Lubricants also typically contain one or more of the additives conventional in refrigerant lubricant technology. Mention may be made of antioxidants, deacidifyuing agents, antiwear agents, and extreme pressure resistance agents. Such additives are well known to those skilled in the art. If the lubricant contains such additives, such additives may be present in amounts conventional in the art. The cumulative amount of all additives does not exceed 8% of the total weight of the lubricant, for example 5%. Preferred antioxidants are compounds containing hindered phenol in the molecule, preferred deacidifying agents are compounds containing epoxy groups in the molecule, and preferred antiwear agents and extreme pressure agents are organophosphorus compounds. In particular, organic phosphates, phosphites and thiophosphates. The following compounds are representative of preferred antioxidants, deacidifiers, antiwear agents and extreme pressure resistant agents. Antioxidants: 2-6-di-t-butyl-4-methylphenol, 2-6-di-t-butyl-4-ethylphenol, 2-6-di-t-butyl-4-hydroxyphenol, 2 2,2'-methylenebis (4-methyl-6-t-butylphenol), 2,2'-methylenebis (4-ethyl-6-t-butylphenol), 2,2'-butylidenebis (4-methyl-6-t-) Butylphenol), 4,4'-butylidene bis (3-methyl-6-t-butylphenol), 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 1,3, 5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene and the like. Deacidifying agent: phenyl glycidyl ether, butyl glycidyl ether, bisphenol A epichlorohydrin condensate, vinylcyclohexene dioxide, 2- (3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxycyclohexane) -meta- Dioxide, 3,4-epoxycyclohexylmethyl-3,4-epoxy-cyclohexanecarboxylate, polypropylene glycol diglycidyl ether, resorcin diglycidyl ether, polyethylene glycol diglycidyl ether, etc. Antiwear and extreme pressure resistant agents: tricresyl phosphate, trisnorphenyl phosphite, distearyl phosphate, tributyl phosphate, trilauryl phosphate, trilauryl phosphate, mono-di-hybrid lauryl phosphite, mono-di-hybrid Tridecyl phosphate, mono-2-ethylhexyl-2-ethylhexyl phosphate, di-2-ethylhexyl phosphate and the like. The working fluid composition of the present invention typically contains 30-99 wt% R-32, for example 77-99 wt%, and 1-70 wt%, for example 1-30 wt% lubricant. The working fluid composition of the present invention may be used to provide cooling by a method that involves condensing a refrigerant and then evaporating it in heat exchange relationship with the object to be cooled. The working fluid composition may also be used to provide heating by a method that involves condensing a refrigerant in a heat exchange relationship with the object to be heated and then evaporating it. The present invention will be described with reference to the following examples, but is not limited to the examples. Example 1 A cooling test device (rig) incorporating a screw compressor was filled with "Emkarate" (registered trademark) RL-150S refrigeration lubricant (see below) and difluoromethane (R-32) refrigerant. The performance of the resulting working fluid composition was investigated in the test device over a long test period. The test rig continued to run for 1000 hours. No serious operating problems occurred, indicating that the lubricant provided effective lubrication of the compressor in the presence of difluoromethane refrigerant. “Emkarate” ® RL-150S is available from ICI Chemicals & Polymers Ltd. The lubricant is an ester-based oil derived from the reaction of dipentaerythritol, n-heptanoic acid, and 3,5,5-trimethylhexanoic acid.

Claims (1)

[Claims] 1. A working fluid composition comprising: (A) a refrigerant consisting essentially of difluoromethane (R-32), and (B) a lubricant in an amount sufficient to impart lubrication, at least a neopentyl polyol. A working fluid composition comprising one and a lubricant consisting of an ester-based oil consisting of a reaction product of an aliphatic carboxylic acid or at least one esterifiable derivative thereof. 2. The working fluid according to claim 1, wherein the lubricant component has a viscosity in the range of 46 to 220 cSt at 40 ° C, a viscosity index in the range of 50 to 200, and a pour point of less than -20 ° C. Composition. 3. The ester-based oil is at least one neopentylpolyol selected from pentaerythritol, dipentaerythritol, tripentaerythritol, trimethylolethane, trimethylolpropane and neopentyl glycol, and linear and branched chain aliphatics. The working fluid composition according to claim 1, which comprises a reaction product of at least one aliphatic carboxylic acid selected from carboxylic acids or one or more esterifiable derivatives of such an acid. 4. The ester-based oil described above has the formula: [In the formula, R is a hydrocarbon group remaining after removing a plurality of hydroxyl groups from pentaerythritol, dipentaerythritol, or tripentaerythritol; R ¹ is independently a linear (linear) aliphatic hydrocarbyl group; Group or a branched-chain aliphatic hydrocarbyl group; and n is an integer of 4, 6, or 8], the working fluid according to claim 1. Composition. 5. The ester-based oil is one or more compounds represented by the formula I in which each R ¹ is independently a linear alkyl group or a branched chain alkyl group. The working fluid composition according to claim 4. 6. 1 of compounds wherein said ester-based oil is a compound of formula I, wherein each R ¹ is independently a C _4-9 linear alkyl group or a C _6-9 branched chain alkyl group. A working fluid composition according to claim 5 which comprises one or more species. 7. The ester-based oil is a compound of formula I in which each R ¹ is independently a linear C ₄ alkyl group, a linear C ₆ alkyl group or a C _7-9 branched chain alkyl group. 7. The working fluid composition according to claim 6, which comprises one or more of the following compounds: 8. The ester-based oil is a compound of formula I in which at least some of the plurality of groups R ¹ are linear alkyl groups and at least ^one of the plurality of groups R ¹ The working fluid composition according to any one of claims 5 to 7, which comprises one or more compounds of which a part is a branched chain alkyl group. 9. The working fluid composition according to claim 8, wherein 30 to 80% of the plurality of groups R ¹ in one or more ester compounds of the formula I constituting the oil is a branched chain alkyl group. Ten. 8. At least a portion of at least partially linear C ₆ alkyl group of the branched chain is C ₈ alkyl group and a plurality of linear alkyl group of the plurality of branched chain alkyl groups of the Alternatively, the working fluid composition according to claim 9. 11. The ester-based oil comprises one or more compounds represented by the formula I in which R ¹ is a hydrocarbon group remaining after removing a plurality of hydroxyl groups from dipentaerythritol. The working fluid composition according to claim 8 or 9, which is one. 12. 12. At least 25% by weight of said ester-based oil consists of one or more of the ester compounds of formula I, said ester compound being derived from pentaerythritol. A working fluid composition as described. 13. 13. At least 50% by weight of said ester-based oil consists of one or more of the ester compounds of formula I, said ester compound being derived from dipentaerythritol. A working fluid composition as described. 14. A heat transfer device comprising a means for controlling the discharge temperature of a compressor and using the composition according to any one of the preceding claims as a working fluid composition. 15. A heat transfer device that constitutes a means for controlling the discharge temperature of the compressor, and (A) a refrigerant consisting essentially of difluoromethane (R-32), and (B) a sufficient amount to provide lubrication. A lubricant comprising an ester-based oil comprising a reaction product of at least one neopentyl polyol and at least one aliphatic carboxylic acid or an esterifiable derivative thereof. Transfer device using the different working fluid composition as a working fluid composition.