Composition for refrigerator

Abstract

Provided is a composition for refrigerators, which is a mixture of a refrigerant mixture containing carbon dioxide and a refrigerant oil having a low global warming potential value, and which has excellent thermal stability, and which contains the refrigerant mixture and the refrigerant oil containing a base oil, the mixed refrigerant contains a fluorinated hydrocarbon compound and carbon dioxide, the content of the fluorinated hydrocarbon compound is less than 25 mass% based on the total amount of the mixed refrigerant, and the base oil contains at least one selected from the group consisting of polyvinyl ethers and polyalkylene glycols.

Description

Technical Field

[0001] This invention relates to a composition for refrigeration machines comprising a mixed refrigerant and refrigeration oil. Background Technology

[0002] A refrigeration unit, such as a compression refrigeration unit, typically consists of at least a compressor, a condenser, an expansion mechanism (expansion valve, etc.), an evaporator, etc., and has a structure in which a mixture of refrigerant and refrigeration oil (hereinafter also referred to as "refrigeration unit composition") circulates within a closed system.

[0003] As refrigerants used in compression refrigeration units, fluorinated hydrocarbons (HFCs) with lower environmental impact are gradually being used instead of the previously commonly used hydrochlorofluorocarbons (HCFCs). Most of these HFCs used are saturated fluorinated hydrocarbons such as 1,1,1,2-tetrafluoroethane (R134a), difluoromethane (R32), and mixtures of difluoromethane and pentafluoroethane (R410A).

[0004] In addition, the use of unsaturated fluorinated hydrocarbon compounds (Hydro-Fluoro-Olefin; hereinafter also referred to as "HFO") such as 1,3,3,3-tetrafluoropropylene (R1234ze) and 2,3,3,3-tetrafluoropropylene (R1234yf) with low global warming potential was also studied.

[0005] Furthermore, the use of carbon dioxide, as a refrigerant with a lower global warming potential (GWP), was also studied.

[0006] For example, Patent Document 1 discloses a composition for use in a refrigerant consisting of a mixture of unsaturated fluorinated hydrocarbon compounds, saturated fluorinated hydrocarbon compounds, and carbon dioxide.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2014-177607 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] As mentioned above, Patent Document 1 investigated the practical application of mixed refrigerants containing carbon dioxide, but depending on the choice of the composition of the mixed refrigerant and the composition of the refrigeration oil, there are sometimes differences in the overall thermal stability of the refrigeration composition containing the mixed refrigerant and the refrigeration oil.

[0012] The present invention was made in view of the above-mentioned problems, and its object is to provide a refrigeration composition with excellent thermal stability, said refrigeration composition being a mixture of a mixed refrigerant and refrigeration oil, said mixed refrigerant being a refrigerant with low global warming potential and containing carbon dioxide.

[0013] means for solving problems

[0014] Through in-depth research, the inventors discovered that a refrigeration composition comprising a mixed refrigerant satisfying a specific composition and a refrigeration oil containing a specific base oil can solve the aforementioned problems. The present invention was made based on this insight. That is, according to various embodiments of the present invention, the following [1] to

[10] are provided.

[0015] [1] A composition for refrigeration equipment, comprising a mixed refrigerant and a refrigeration oil containing a base oil,

[0016] The mixed refrigerant contains fluorinated hydrocarbons and carbon dioxide.

[0017] The content of the fluorinated hydrocarbon compound is less than 25% by mass based on the total amount of the mixed refrigerant.

[0018] The base oil contains one or more selected from polyvinyl ethers and polyalkylene glycols.

[0019] [2] According to the refrigeration composition described in [1] above, the carbon dioxide content is 50% by mass or more and 97% by mass or less based on the total amount of the mixed refrigerant.

[0020] [3] According to the refrigeration composition described in [1] or [2] above, the content of the fluorocarbon compound is 3% by mass or more and less than 25% by mass based on the total amount of the mixed refrigerant.

[0021] [4] The refrigeration composition according to any one of [1] to [3] above, wherein the content of the fluorocarbon compound is 3% by mass or more and 20% by mass or less based on the total amount of the mixed refrigerant.

[0022] [5] The refrigeration composition according to any one of [1] to [4] above, wherein the fluorinated hydrocarbon compound contains 70% by mass or more and 100% by mass or less of an unsaturated fluorinated hydrocarbon compound.

[0023] [6] The refrigeration composition according to any one of [1] to [5] above, wherein the content of one or more selected from the polyvinyl ethers and polyalkylene glycols is 90% by mass or more and 100% by mass or less based on the total amount of base oil.

[0024] [7] The refrigeration composition according to any one of [1] to [6] above, wherein the content of the polyalkylene glycol is 90% by mass or more and 100% by mass or less based on the total amount of the base oil.

[0025] [8] The refrigeration composition according to any one of [1] to [7] above, wherein the total content of the mixed refrigerant and the refrigeration oil in the refrigeration composition is 90% by mass or more and 100% by mass or less.

[0026] [9] Refrigeration oil, which is used in mixed refrigerants containing fluorinated hydrocarbons and carbon dioxide, wherein the content of fluorinated hydrocarbons is less than 25% by mass.

[0027] The refrigeration oil contains base oil.

[0028] The base oil contains one or more selected from polyvinyl ethers and polyalkylene glycols.

[0029]

[10] The method for manufacturing the refrigeration composition described in any one of [1] to [8] above includes a step of mixing a mixed refrigerant and a refrigeration oil containing a base oil.

[0030] The mixed refrigerant contains fluorinated hydrocarbons and carbon dioxide.

[0031] The content of the fluorinated hydrocarbon compound is less than 25% by mass based on the total amount of the mixed refrigerant, and the base oil contains one or more selected from polyvinyl ethers and polyalkylene glycols.

[0032] Invention Effects

[0033] According to the present invention, a refrigeration composition with excellent thermal stability can be provided, the refrigeration composition being a mixture of a mixed refrigerant and refrigeration oil, wherein the mixed refrigerant is a refrigerant with low global warming potential and contains carbon dioxide. Detailed Implementation

[0034] In this specification, the lower and upper limits of the preferred numerical range (e.g., the range of content, etc.) can be combined independently. For example, based on the statement "preferably 10 to 90, more preferably 30 to 60", the "preferable lower limit (10)" and the "more preferably upper limit (60)" can be combined to set "10 to 60". Similarly, in this specification, the values ​​of "above", "below", "less than", and "exceeding" related to the description of the numerical range can be arbitrarily combined.

[0035] [Composition for Refrigeration Equipment]

[0036] The refrigeration composition of this embodiment is a refrigeration composition comprising a mixed refrigerant and a refrigeration oil containing a base oil. The mixed refrigerant contains fluorinated hydrocarbons and carbon dioxide. The content of the fluorinated hydrocarbons is less than 25% by mass based on the total amount of the mixed refrigerant. The base oil contains one or more selected from polyvinyl ethers and alkylene glycols.

[0037] The aforementioned mixed refrigerant, lacking carbon dioxide, is not ideal from the perspective of global warming potential. Furthermore, its thermal stability becomes insufficient when the base oil contains no or more of a type selected from polyvinyl ethers and polyalkylene glycols. Moreover, even when the content of fluorinated hydrocarbons in the aforementioned mixed refrigerant is 25% by mass or more, its thermal stability remains insufficient.

[0038] It should be noted that, in this specification, "hydrocarbon group" refers to a group consisting only of carbon atoms and hydrogen atoms. "Hydrocarbon group" includes: "aliphatic group" consisting of a straight chain or branched chain, "alicyclic group" having one or more non-aromatic saturated or unsaturated carbon rings, and "aromatic group" having one or more aromatic rings such as benzene rings that exhibit aromaticity.

[0039] Additionally, in this specification, "number of cyclic carbon atoms" refers to the number of carbon atoms in the atoms constituting the ring itself in a compound with a cyclic structure formed by atomic bonds. When the ring is substituted with a substituent, the carbon contained in the substituent is not included in the number of cyclic carbon atoms.

[0040] Furthermore, the number of cyclic atoms represents the number of atoms that constitute the ring itself in a compound with a cyclic structure formed by atomic bonds. Atoms that do not constitute the ring (such as hydrogen atoms terminated by bonds connecting the atoms that constitute the ring) and atoms contained in substituents when the ring is substituted are not included in the number of cyclic atoms.

[0041] Furthermore, examples of substituents described as "substituted or unsubstituted" include: alkyl groups with 1 or more and 10 or less carbon atoms (preferably 1 or more and 6 or less, more preferably 1 or more and 4 or less, and even more preferably 1 or more and 3 or less); cycloalkyl groups with 3 or more and 10 or less cyclic carbon atoms (preferably 3 or more and 8 or less, more preferably 4 or more and 6 or less, and even more preferably 5 or 6); aryl groups with 6 or more and 18 or less cyclic carbon atoms (preferably 6 or more and 12 or less); halogen atoms (fluorine atoms, chlorine atoms, bromine atoms, iodine atoms); cyano; nitro; hydroxyl; amino, etc.

[0042] These substituents can be further replaced by the aforementioned optional substituents.

[0043] In addition, the "unsubstituted" in the record "substituted or unsubstituted" means: not substituted by these substituents and bonded with hydrogen atoms.

[0044] The following describes each component contained in the composition for this refrigeration unit.

[0045] <Mixed refrigerants>

[0046] The aforementioned mixed refrigerant contains fluorinated hydrocarbons and carbon dioxide, and the content of the aforementioned fluorinated hydrocarbons is less than 25% by mass based on the total amount of the aforementioned mixed refrigerant.

[0047] The following is an explanation of this mixed refrigerant.

[0048] Specifically, saturated fluorocarbon compounds (HFCs) and unsaturated fluorocarbon compounds (HFOs) can be listed as examples of the aforementioned fluorocarbon compounds.

[0049] From the viewpoint of reducing the global warming potential of the aforementioned mixed refrigerant, the aforementioned fluorinated hydrocarbon compound preferably contains 70% to 100% by mass of unsaturated fluorinated hydrocarbon compound, more preferably 80% to 100% by mass, and even more preferably 90% to 100% by mass.

[0050] (Saturated fluorinated hydrocarbons (HFCs))

[0051] As a saturated fluorinated hydrocarbon compound (HFC), a fluoride of an alkane having 1 to 4 carbon atoms is preferred, a fluoride of an alkane having 1 to 3 carbon atoms is more preferred, and a fluoride of an alkane (methane or ethane) having 1 or 2 carbon atoms is even more preferred. Examples of such fluorides of methane or ethane include trifluoromethane (R23), difluoromethane (R32), 1,1-difluoroethane (R152a), 1,1,1-trifluoroethane (R143a), 1,1,2-trifluoroethane (R143), 1,1,1,2-tetrafluoroethane (R134a), 1,1,2,2-tetrafluoroethane (R134), and 1,1,1,2,2-pentafluoroethane (R125), among which difluoromethane and 1,1,1,2-tetrafluoroethane are preferred.

[0052] These saturated fluorinated hydrocarbon compounds can be used alone or in combination of two or more.

[0053] (Unsaturated fluorinated hydrocarbons (HFO))

[0054] Examples of unsaturated fluorinated hydrocarbon compounds (HFOs) include, for example, linear or branched chain alkenes with 2 or more but less than 6 carbon atoms, and fluorides of cyclic alkenes with 4 or more but less than 6 carbon atoms, which are compounds with carbon-carbon double bonds.

[0055] More specifically, examples include: ethylene with one or more but less than three (preferably three) fluorine atoms, propylene with one or more but less than five fluorine atoms, butene with one or more but less than seven fluorine atoms, pentene with one or more but less than nine fluorine atoms, hexene with one or more but less than eleven fluorine atoms, cyclobutene with one or more but less than five fluorine atoms, cyclopentene with one or more but less than seven fluorine atoms, and cyclohexene with one or more but less than nine fluorine atoms.

[0056] Among these HFOs, fluorinated propylene is preferred, more preferably propylene with 3 or more but less than 5 fluorine atoms, and even more preferably propylene with 4 fluorine atoms.

[0057] Suitable examples of the aforementioned HFOs include: 1,2,3,3,3-pentafluoropropene (R1225ye), 2,3,3,3-tetrafluoropropene (R1234yf), 1,3,3,3-tetrafluoropropene (R1234ze), 1,2,3,3-tetrafluoropropene (R1234ye), 1,1,2-trifluoroethylene (R1123), cis-1,2-difluoroethylene (R1132(Z)), trans-1,2-difluoroethylene (R1132(E)), and (Z)-1,1,1,4,4,4-hexafluoro-2-butene (R1336mzz(Z)). Among these HFOs, one or more selected from R1234yf, R1234ze, R1123, and R1132(E) are preferred.

[0058] These HFOs can be used individually or in combination of two or more. For example, a combination of R1234yf and R1234ze can be used as a case of combining two or more HFOs.

[0059] In the HFO contained in the aforementioned mixed refrigerant, the content of fluorinated propylene in the aforementioned propylene, based on the total HFO (100% by mass), is preferably 50% by mass or more and 100% by mass or less, more preferably 70% by mass or more and 100% by mass or less, further preferably 90% by mass or more and 100% by mass or less, and even more preferably 100% by mass.

[0060] Furthermore, the HFO contained in the aforementioned mixed refrigerant preferably includes at least one of R1234yf and R1234ze. The content of R1234yf and R1234ze in the HFO contained in the aforementioned mixed refrigerant, based on the total HFO (100% by mass), is preferably 50% by mass or more and 100% by mass or less, more preferably 70% by mass or more and 100% by mass or less, further preferably 90% by mass or more and 100% by mass or less, and even more preferably 100% by mass.

[0061] As described above, the aforementioned mixed refrigerant contains fluorinated hydrocarbon compounds and carbon dioxide, and may also contain other refrigerants. Among these other refrigerants, naturally occurring refrigerants other than carbon dioxide are preferably listed.

[0062] (Natural refrigerants other than carbon dioxide)

[0063] As natural refrigerants other than carbon dioxide, one or more can be selected from hydrocarbon refrigerants (HC) and ammonia. These natural refrigerants can be used alone or in combination of two or more.

[0064] As the aforementioned hydrocarbon-based refrigerant, hydrocarbons with 1 or more but less than 8 carbon atoms are preferred, more preferably hydrocarbons with 1 or more but less than 5 carbon atoms, and even more preferably hydrocarbons with 3 or more but less than 5 carbon atoms. If the number of carbon atoms is 8 or less, the boiling point of the refrigerant will not become too high, making it a preferred refrigerant. Examples of such hydrocarbon-based refrigerants include one or more selected from methane, ethane, ethylene, propane (R290), cyclopropane, propylene, n-butane, isobutane (R600a), 2-methylbutane, n-pentane, isopentane, and cyclopentaneisobutane. One of these can be used alone, or two or more can be used in combination.

[0065] (Mixing ratio of the refrigerant)

[0066] As mentioned above, the aforementioned mixed refrigerant needs to contain carbon dioxide from the perspective of low global warming potential.

[0067] The carbon dioxide content in the mixed refrigerant is preferably 50% by mass or more, more preferably 75% by mass or more, even more preferably 80% by mass or more, and preferably 97% by mass or less, based on the total amount of the aforementioned mixed refrigerant.

[0068] On the other hand, from the viewpoint of thermal stability, the content of the aforementioned fluorinated hydrocarbon compounds should be less than 25% by mass based on the total amount of the aforementioned mixed refrigerant, preferably less than 20% by mass, more preferably less than 15% by mass, and preferably more than 3% by mass, more preferably more than 5% by mass.

[0069] [Refrigeration oil]

[0070] The aforementioned refrigeration oil contains a base oil, which comprises one or more selected from polyvinyl ethers (hereinafter also referred to as "PVE") and polyalkylene glycols (hereinafter also referred to as "PAG").

[0071] From the viewpoint of obtaining better stability, the base oil content, based on 100% by mass of the total amount of the refrigeration oil, is preferably 90% by mass or more and 100% by mass or less, more preferably 95% by mass or more and 100% by mass or less, further preferably 97% by mass or more and 100% by mass or less, and even more preferably 98% by mass or more and 100% by mass or less.

[0072] <Base Oil>

[0073] The aforementioned refrigeration oil contains base oils selected from polyvinyl ether (PVE) and polyalkylene glycol (PAG) base oils.

[0074] From the viewpoint of obtaining better thermal stability, it is preferable that the base oil contains one or more types selected from PVE.

[0075] From the viewpoint of improving refrigerant solubility, the content of one or more selected from PVE and PAG in 100% by mass of the total base oil is preferably 80% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, further preferably 95% by mass or more and 100% by mass or less, and even more preferably 98% by mass or more and 100% by mass or less. Furthermore, the content of PAG in 100% by mass of the total base oil is preferably 80% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, further preferably 95% by mass or more and 100% by mass or less, and even more preferably 98% by mass or more and 100% by mass or less.

[0076] The following sections will explain the PVE and PAG contained in this base oil.

[0077] (Polyvinyl ethers (PVE))

[0078] Polyvinyl ethers (PVEs) as mentioned above can be categorized as polymers having one or more structural units derived from vinyl ethers. It should be noted that when the aforementioned base oil contains this PVE, the base oil may contain only this PVE, or it may contain two or more PVEs in combination.

[0079] From the viewpoint of obtaining better stability, the preferred PVE is a polymer having one or more structural units derived from vinyl ethers and having alkyl groups with 1 or more and 4 or fewer carbon atoms in its side chains.

[0080] The preferred PVE is a polymer (A1) having one or more structural units of the following general formula (A-1).

[0081] [Chemistry 1]

[0082]

[0083] In general formula (A-1), R 1a R 2a and R 3a Each can independently represent a hydrocarbon group consisting of 1 or more hydrogen atoms and 8 or fewer carbon atoms. R 4a R represents a divalent hydrocarbon group with 2 or more but less than 10 carbon atoms. 5a It represents a hydrocarbon group with 1 or more carbon atoms and less than 10 carbon atoms.

[0084] In general formula (A-1), r is OR 4a The average number of units shown represents a number greater than or equal to 0 and less than 10, preferably a number greater than or equal to 0 and less than 5, more preferably a number greater than or equal to 0 and less than 3, and even more preferably 0.

[0085] It should be noted that there are multiple ORs in the general formula (A-1). 4a In the case where r is greater than 2, multiple ORs 4a Choose either that they are the same or that they are different.

[0086] Additionally, when r is 0, the carbon atom (C) in the general formula (A-1) and -OR 5a The bond is a single bond, and the carbon atom (C) is bonded to -OR. 5a Direct bonding.

[0087] As an optional R 1a R 2a and R 3a Hydrocarbon groups with 1 to 8 carbon atoms can be listed as alkyl groups such as methyl, ethyl, various propyl, various butyl, various pentyl, various hexyl, various heptyl, and various octyl; cyclopentyl, cyclohexyl, various methylcyclohexyl, various ethylcyclohexyl, and various dimethylcyclohexyl; aryl groups such as phenyl, various methylphenyl, various ethylphenyl, and various dimethylphenyl; and arylalkyl groups such as benzyl, various phenylethyl, and various methylbenzyl.

[0088] It should be noted that in this specification, the expression "various XXX groups" includes all isomers that can be considered as XXX groups. For example, "various alkyl groups" means "straight-chain, branched, or cyclic hydrocarbon groups." For instance, if it is "various propyl groups," it means "n-propyl, isopropyl," and other propyl groups. In addition, if it is "various butyl groups," it means "n-butyl, sec-butyl, isobutyl, tert-butyl, cyclobutyl," and other butyl groups.

[0089] As an optional R 1a R 2a and R 3aThe number of carbon atoms in the hydrocarbon group is preferably 1 or more and 6 or less, more preferably 1 or more and 4 or less, and even more preferably 1 or more and 3 or less.

[0090] As R 1a R 2a and R 3a Each of the following is preferably an alkyl group having 1 or more hydrogen atoms or 8 or fewer carbon atoms, more preferably an alkyl group having 1 or more hydrogen atoms or 6 or fewer carbon atoms, even more preferably an alkyl group having 1 or more hydrogen atoms or 4 or fewer carbon atoms, and even more preferably an alkyl group having 1 or more hydrogen atoms or 3 or fewer carbon atoms.

[0091] It should be noted that R 1a R 2a and R 3a Choose either that they are the same or that they are different.

[0092] As an optional R 4a Divalent hydrocarbon groups with 2 or more but less than 10 carbon atoms include, for example, ethylene, 1,2-propylene, 1,3-propylene, various butylene, various pentylene, various hexene, various heptylene, various octylene, various nonylene, and various decylene divalent aliphatic groups; alicyclic groups as divalent residues in alicyclic compounds such as cyclohexane, methylcyclohexane, ethylcyclohexane, dimethylcyclohexane, and propylcyclohexane; various phenylene, various methylphenylene, various ethylphenylene, various dimethylphenylene, and various naphthylene divalent aromatic groups; divalent alkyl aromatic groups in alkyl aromatic hydrocarbons such as toluene, xylene, and ethylbenzene, where the alkyl and aromatic portions each have a monovalent bond; and divalent alkyl aromatic groups in polyalkyl aromatic hydrocarbons such as xylene and diethylbenzene, where the alkyl portion has a bond.

[0093] As an optional R 4a The number of carbon atoms in the hydrocarbon group is preferably 2 or more and 8 or less, more preferably 2 or more and 6 or less, and even more preferably 2 or more and 4 or less.

[0094] As R 4a Preferably, it is a divalent aliphatic group with 2 or more and 10 or less carbon atoms, more preferably a divalent aliphatic group with 2 or more and 6 or less carbon atoms, and more preferably a divalent aliphatic group with 2 or more and 4 or less carbon atoms.

[0095] As an optional R 5aHydrocarbon groups with 1 or more but less than 10 carbon atoms include, for example, alkyl groups such as methyl, ethyl, various propyl, various butyl, various pentyl, various hexyl, various heptyl, various octyl, various nonyl, and various decyl; cycloalkyl groups such as cyclopentyl, cyclohexyl, various methylcyclohexyl, various ethylcyclohexyl, various propylcyclohexyl, and various dimethylcyclohexyl; aryl groups such as phenyl, various methylphenyl, various ethylphenyl, various dimethylphenyl, various propylphenyl, various trimethylphenyl, various butylphenyl, and various naphthyl; and arylalkyl groups such as benzyl, various phenylethyl, various methylbenzyl, various phenylpropyl, and various phenylbutyl.

[0096] As an optional R 5a The number of carbon atoms in the aforementioned hydrocarbon group is preferably 1 or more and 8 or less, more preferably 1 or more and 6 or less.

[0097] As R 5a From the viewpoint of further improving stability, alkyl groups with 1 or more and 6 or less carbon atoms are preferred, and alkyl groups with 1 or more and 4 or less carbon atoms are more preferred.

[0098] In one embodiment of the invention, the polymer (A1) preferably has R 5a The structural unit (α1) is an ethyl group.

[0099] From the viewpoint of further improving refrigerant solubility, the content of structural unit (α1) is preferably 60% or more and 100% or less, more preferably 70% or more and 100% or less, further preferably 80% or more and 100% or less, even more preferably 85% or more and 100% or less, and even more preferably 90% or more and 100% or less, based on the total amount (100% by mass) of structural units (A1) of the polymer (A1), excluding terminal structural units.

[0100] In polymer (A1), the number of units (degree of polymerization) that are structural units represented by general formula (A-1) can be appropriately set in such a way that the hydroxyl value of the aforementioned base oil (P) falls within the range of 15 mg KOH / g or less.

[0101] In addition, the polymer (A1) can be a homopolymer having only one structural unit of the general formula (A-1), or a copolymer having two or more of the structural units.

[0102] It should be noted that there are no particular limitations on the copolymerization method of this copolymer; it can be a block copolymer, a random copolymer, or a graft copolymer.

[0103] The terminal portion of the polymer (A1) can be fitted with monovalent groups derived from saturated hydrocarbons, ethers, alcohols, ketones, amides, nitriles, etc.

[0104] In one embodiment of the invention, one end of the polymer (A1) is preferably a group represented by the following general formula (A-1-i).

[0105] [Chemistry 2]

[0106]

[0107] In general formula (A-1-i), * indicates the position where the carbon atom is bonded to the structural unit shown in general formula (A-1).

[0108] In the general formula (A-1-i), R 6a R 7a and R 8a Each of the groups independently represents a hydrocarbon group having 1 or more hydrogen atoms or 8 or fewer carbon atoms, preferably a hydrocarbon group having 1 or more hydrogen atoms or 6 or fewer carbon atoms, more preferably an alkyl group having 1 or more hydrogen atoms or 6 or fewer carbon atoms, and even more preferably an alkyl group having 1 or more hydrogen atoms or 4 or fewer carbon atoms.

[0109] It should be noted that R 6a R 7a and R 8a Choose either that they are the same or that they are different.

[0110] As an optional R 6a R 7a and R 8a Hydrocarbon groups with 1 to 8 carbon atoms can be listed as alternatives to R in general formula (A-1). 1a R 2a and R 3a A group that is identical to the listed groups of hydrocarbon groups with 1 or more but less than 8 carbon atoms.

[0111] In the general formula (A-1-i), R 9a The term refers to a divalent hydrocarbon group having 2 or more and 10 or less carbon atoms, preferably a divalent hydrocarbon group having 2 or more and 8 or less carbon atoms, more preferably a divalent hydrocarbon group having 2 or more and 6 or less carbon atoms, and even more preferably a divalent aliphatic group having 2 or more and 4 or less carbon atoms.

[0112] In the general formula (A-1-i), r1 is OR 9a The average number of units shown represents a number greater than or equal to 0 and less than 10, preferably a number greater than or equal to 0 and less than 5, more preferably a number greater than or equal to 0 and less than 3, and even more preferably 0.

[0113] It should be noted that there are multiple ORs in the general formula (A-1-i). 9aIn the case where r1 is 2 or more, multiple ORs 9a Choose either the same or different.

[0114] Additionally, when r1 is 0, the carbon atom (C) in the general formula (A-1-i) and -OR 10a The bond is a single bond, and the carbon atom (C) is bonded to -OR. 10a Direct bonding.

[0115] As an optional R 9a Divalent hydrocarbon groups with 2 or more but less than 10 carbon atoms can be listed as R in general formula (A-1). 4a A group that is the same as the listed group, consisting of a divalent hydrocarbon group with 2 or more but less than 10 carbon atoms.

[0116] In the general formula (A-1-i), R 10a The term refers to a hydrocarbon group having 1 or more and 10 or less carbon atoms, preferably a hydrocarbon group having 1 or more and 8 or less carbon atoms, and more preferably an alkyl group having 1 or more and 8 or less carbon atoms.

[0117] It should be noted that, as R 10a When r1 in the general formula (A-1-i) is 0, it is more preferably an alkyl group with 1 or more and 6 or less carbon atoms, and when r1 is 1 or more, it is more preferably an alkyl group with 1 or more and 4 or less carbon atoms.

[0118] As an optional R 10a Hydrocarbon groups with 1 or more but less than 10 carbon atoms can be listed as R, which is an optional component in general formula (A-1). 5a A group that is the same as the listed group and has a hydrocarbon group with 1 or more but less than 10 carbon atoms.

[0119] In addition, in the polymer (A1), it is preferred that one end is a group represented by the general formula (A-1-i), and the other end is selected from the group represented by the general formula (A-1-i), the group represented by the general formula (A-1-ii) below, the group represented by the general formula (A-1-iii) below, and a group having an olefinic unsaturated bond.

[0120] [Chemistry 3]

[0121]

[0122] In general formulas (A-1-ii) and (A-1-iii), R 11a R 12a R 13a R 18a R 19a and R 20aEach of the following groups independently represents a hydrocarbon group having 1 or more hydrogen atoms and 8 or fewer carbon atoms, preferably a hydrocarbon group having 1 or more hydrogen atoms and 6 or fewer carbon atoms, more preferably an alkyl group having 1 or more hydrogen atoms and 6 or fewer carbon atoms, and even more preferably an alkyl group having 1 or more hydrogen atoms and 3 or fewer carbon atoms. 11a R 12a R 13a R 18a R 19a and R 20a Choose either that they are the same or that they are different.

[0123] As an optional R 11a R 12a R 13a R 18a R 19a and R 20a The hydrocarbon group can be listed as R, which is an optional component of the general formula (A-1). 1a R 2a and R 3a A group that is identical to the listed groups of hydrocarbon groups with 1 or more but less than 8 carbon atoms.

[0124] In the general formula (A-1-ii), R 14a and R 16a Each group independently represents a divalent hydrocarbon group having 2 or more and 10 or fewer carbon atoms, preferably a divalent hydrocarbon group having 2 or more and 6 or fewer carbon atoms, and more preferably a divalent aliphatic group having 2 or more and 4 or fewer carbon atoms. R can be selected as an optional group. 14a and R 16a The divalent hydrocarbon group can be listed as R, which can be selected as an alternative in general formula (A-1). 4a The same group as the divalent hydrocarbon group.

[0125] In the general formula (A-1-ii), r2 and r3 are respectively OR 14a and OR 16a The average number of units shown represents a number greater than or equal to 0 and less than 10, preferably a number greater than or equal to 0 and less than 5, more preferably a number greater than or equal to 0 and less than 3, and even more preferably 0.

[0126] There are multiple ORs in the general formula (A-1-ii). 14a and OR 16a At that time, multiple ORs 14a and multiple OR 16a Choose either that they are the same or that they are different.

[0127] Additionally, when r2 is 0, the carbon atom (C) in the general formula (A-1-ii) and -OR 15a The bond is a single bond, and the carbon atom (C) is bonded to -OR. 15aDirect bonding. Similarly, when r3 is 0, the carbon atom (C) in the general formula (A-1-ii) bonds with -OR. 17a The bond is a single bond, and the carbon atom (C) is bonded to -OR. 17a Direct bonding.

[0128] In the general formula (A-1-ii), R 15a and R 17a Each group independently represents a hydrocarbon group having 1 or more and 10 or less carbon atoms, preferably a hydrocarbon group having 1 or more and 8 or less carbon atoms, and more preferably an alkyl group having 1 or more and 8 or less carbon atoms.

[0129] It should be noted that, as R 15a When r2 is 0, it is further preferred to use an alkyl group having 1 or more and 6 or less carbon atoms; when r2 is 1 or more, it is further preferred to use an alkyl group having 1 or more and 4 or less carbon atoms. Similarly, as R... 17a When r3 is 0, it is more preferably an alkyl group with 1 or more and 6 or less carbon atoms, and when r3 is 1 or more, it is more preferably an alkyl group with 1 or more and 4 or less carbon atoms.

[0130] (Polyalkylene glycols (PAGs))

[0131] The preferred polyalkylene glycol (PAG) is the compound (B1) represented by the following general formula (B-1). It should be noted that when the aforementioned base oil contains this PAG, the base oil may contain only this PAG, or it may contain two or more in combination.

[0132] R 1b -[(OR 2b ) m -OR 3b ] n (B-1)

[0133] In general formula (B-1), R 1b It can represent a hydrogen atom, a monovalent hydrocarbon group with 1 or more but less than 10 carbon atoms, an acyl group with 2 or more but less than 10 carbon atoms, a hydrocarbon group with 1 or more but less than 10 carbon atoms that is divalent or hexavalent, or a heterocyclic group with 3 or more but less than 10 substituted or unsubstituted cyclic atoms.

[0134] R 2b It refers to alkylene groups with 2 or more but less than 4 carbon atoms.

[0135] R 3b It represents a hydrogen atom, a monovalent hydrocarbon group with 1 or more but less than 10 carbon atoms, an acyl group with 2 or more but less than 10 carbon atoms, or a heterocyclic group with 3 or more but less than 10 substituted or unsubstituted cyclic atoms.

[0136] In general formula (B-1), n ​​is an integer of 1 or more and 6 or less, preferably an integer of 1 or more and 4 or less, more preferably an integer of 1 or more and 3 or less, and even more preferably 1.

[0137] n is based on R in general formula (B-1) 1b The number of bonding sites determines the number of bonding sites. For example, in R 1b When the group is alkyl or acyl, n is 1, and R 1b It is a hydrocarbon group or a heterocyclic group, and when the valence of the group is 2, 3, 4, 5 and 6, n is 2, 3, 4, 5 and 6 respectively.

[0138] In general formula (B-1), m is OR 2b The average number of units shown represents a number greater than or equal to 1, and preferably an average of m×n that is greater than or equal to 6 and less than or equal to 80. It should be noted that the value of m is not particularly limited, but preferably an average of m×n that satisfies the aforementioned range.

[0139] In the presence of multiple ORs 2b In the case of multiple ORs 2b They can be chosen to be the same or different from each other. Furthermore, when n is 2 or more, multiple Rs in one molecule... 3b Choose either that they are the same or that they are different.

[0140] As an optional R 1b and R 3b The aforementioned monovalent hydrocarbon groups can be exemplified by, for example, alkyl groups such as methyl, ethyl, various propyl, various butyl, various pentyl, various hexyl, various heptyl, various octyl, various nonyl, and various decyl; cycloalkyl groups such as cyclopentyl, cyclohexyl, various methylcyclohexyl, various ethylcyclohexyl, various propylcyclohexyl, and various dimethylcyclohexyl; aryl groups such as phenyl, various methylphenyl, various ethylphenyl, various dimethylphenyl, various propylphenyl, various trimethylphenyl, various butylphenyl, and various naphthyl; and arylalkyl groups such as benzyl, various phenylethyl, various methylbenzyl, various phenylpropyl, and various phenylbutyl.

[0141] The number of carbon atoms in the monovalent hydrocarbon group is preferably 1 or more and 10 or less, more preferably 1 or more and 6 or less, and even more preferably 1 or more and 3 or less.

[0142] Optional R 1b and R 3b The alkyl group of the aforementioned acyl group having 2 or more and 10 or fewer carbon atoms can be any of straight-chain, branched, or cyclic. Examples of alkyl groups that can be selected as the aforementioned R group include... 1b and R 3b Hydrocarbon groups that have 1 or more but less than 9 carbon atoms.

[0143] It should be noted that the number of carbon atoms in the acyl group is preferably 2 or more and 10 or less, more preferably 2 or more and 8 or less, and even more preferably 2 or more and 6 or less.

[0144] As an optional R 1b The aforementioned divalent or higher and hexavalent hydrocarbon groups can be exemplified by, for example, those selected as the aforementioned R... 1b Residues formed by further removing one or more but less than five hydrogen atoms from a monovalent hydrocarbon group; residues formed by removing hydroxyl groups from polyols such as trimethylolpropane, glycerol, pentaerythritol, sorbitol, 1,2,3-trihydroxycyclohexane, and 1,3,5-trihydroxycyclohexane, etc.

[0145] It should be noted that the number of carbon atoms in the hydrocarbon group with a valence of divalent or higher and hexavalent or lower is preferably 2 or higher and 10 or lower, more preferably 2 or higher and 8 or lower, and even more preferably 2 or higher and 6 or lower.

[0146] As an optional R 1b and R 3b The aforementioned heterocyclic group is preferably a heterocyclic group containing oxygen atoms or a heterocyclic group containing sulfur atoms. It should be noted that the heterocyclic group can be a saturated ring or an unsaturated ring.

[0147] Examples of oxygen-containing heterocyclic groups include residues formed by removing one or more but less hydrogen atoms from saturated heterocycles containing oxygen atoms, such as ethylene oxide, 1,3-epoxypropane, tetrahydrofuran, tetrahydropyran, and hexamethylene oxide, or unsaturated heterocycles containing oxygen atoms, such as ethylene oxide, furan, pyran, oxetine, isobenzofuran, and isochromene.

[0148] In addition, examples of the sulfur-containing heterocyclic group include residues formed by removing one or more but no more than six hydrogen atoms from saturated heterocycles containing sulfur atoms, such as cyclothioethane, trimethylene sulfide, tetrahydrothiophene, tetrahydrothioran, and hexamethylene sulfide, or unsaturated heterocycles containing sulfur atoms, such as cyclothioethylene, thiophene, thioran, and thiotripyridine.

[0149] Alternatively, R can be selected. 1b and R 3b The aforementioned heterocyclic group may optionally have a substituent, which may optionally be bonded to an oxygen atom in general formula (B-1). As described above, the substituent is preferably an alkyl group having 1 or more and 6 or less carbon atoms, more preferably an alkyl group having 1 or more and 4 or less carbon atoms, and even more preferably an alkyl group having 1 or more and 3 or less carbon atoms.

[0150] It should be noted that, from the viewpoint of thermal stability with the aforementioned mixed refrigerant, the number of cyclic atoms in the heterocyclic group is preferably 3 or more and 10 or less, more preferably 3 or more and 8 or less, and even more preferably 3 or more and 6 or less.

[0151] As an optional R 2b Examples of the aforementioned alkylene groups include, for instance, alkylene groups with 2 carbon atoms such as dimethylene (-CH2CH2-) and ethylene (-CH(CH3)-); alkylene groups with 3 carbon atoms such as trimethylene (-CH2CH2CH2-), propylene (-CH(CH3)CH2-), propylene (-CHCH2CH3-), and isopropylene (-C(CH3)2-); and alkylene groups with 4 carbon atoms such as tetramethylene (-CH2CH2CH2CH2-), 1-methyltrimethylene (-CH(CH3)CH2CH2-), 2-methyltrimethylene (-CH2CH(CH3)CH2-), and butylene (-C(CH3)2CH2-).

[0152] It should be noted that there are multiple Rs. 2b At that time, multiple R 2b The same can be chosen from each other, and can be a combination of two or more alkylene groups.

[0153] Among these alkylene groups, as R 2b Preferably, it is propylene (-CH(CH3)CH2-).

[0154] It should be noted that in compound (B1) represented by general formula (B-1), the content of the oxypropylidene unit (-OCH(CH3)CH2-) is expressed as the content of the oxyalkylene unit (OR) in compound (B1). 2b Based on the total amount (100 mol%), it is preferably 50 mol% or more and 100 mol% or less, more preferably 65 mol% or more and 100 mol% or less, and even more preferably 80 mol% or more and 100 mol% or less.

[0155] Among the compounds (B1), preferably one or more are selected from the following general formula (B-1-i): polyoxypropylene glycol dimethyl ether, polyoxyethylene polyoxypropylene glycol dimethyl ether, polyoxypropylene glycol monobutyl ether, and polyoxypropylene glycol diacetate.

[0156] [Chemistry 4]

[0157]

[0158] In the general formula (B-1-i), m1 is the average number of oxypropylene units, representing a number of 1 or more, preferably a number of 6 or more and 80 or less.

[0159] [Chemistry 5]

[0160]

[0161] In the general formula (B-1-ii), m2 and m3 are the average number of oxypropylene units and oxyethylidene units, respectively, each independently representing a number of 1 or more, preferably the value of m2+m3 is a number of 6 or more and 80 or less.

[0162] [Chemistry 6]

[0163]

[0164] In general formula (B-1-iii), m4 is the average number of oxypropylene units, representing a number of 1 or more, preferably a number of 6 or more and 80 or less.

[0165] It should be noted that m1 in general formula (B-1-i), m2 and m3 in general formula (B-1-ii), and m4 in general formula (B-1-iii) are values ​​appropriately set in such a way that the hydroxyl value of the aforementioned base oil (P) falls within the range of 15 mg KOH / g or less. There are no particular limitations as long as the adjustment is made in such a way that the hydroxyl value falls within the specified range, and each is preferably a number that satisfies the aforementioned range.

[0166] The number-average molecular weight (Mn) of the aforementioned PVE and PAG, and the POE described below, is preferably 300 or more and 3,000 or less.

[0167] If the number-average molecular weight (Mn) is 300 or higher, the lubricity and sealing properties become good. On the other hand, if the number-average molecular weight (Mn) is 3,000 or lower, the compatibility with mixed refrigerants becomes good.

[0168] From this perspective, the number-average molecular weight (Mn) of PVE, PAG, and POE (described later) is more preferably 350 or more, further preferably 400 or more, more preferably 2,800 or less, further preferably 2,500 or less, even more preferably 2,000 or less, and even more preferably 1,500 or less.

[0169] It should be noted that the number-average molecular weight (Mn) is a value measured by the method described in the examples below.

[0170] (Other base oils)

[0171] In addition to containing one or more base oils selected from PVE and PAG, the aforementioned base oils may also contain other base oils without impairing the effects of the present invention.

[0172] Other base oils that may be listed include mineral oils or other synthetic oils that do not conform to the aforementioned PVE and PAG, such as polyol esters (POE), polyesters, polycarbonates, hydrides of α-olefin oligomers, alicyclic hydrocarbons and alkylated aromatic hydrocarbons; or mineral oils, etc.

[0173] Examples of polyol esters (POEs) include, for example, glycols or esters of polyols and fatty acids. When the aforementioned base oil contains such a POE, the base oil may contain only that POE, or it may contain two or more in combination.

[0174] The preferred type of POE is an ester formed from a diol or a polyol having 3 or more but less than 20 hydroxyl groups and a fatty acid having 3 or more but less than 20 carbon atoms.

[0175] Examples of the aforementioned diols include ethylene glycol, 1,3-propanediol, propylene glycol, 1,4-butanediol, 1,2-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentanediol, 1,6-hexanediol, 2-ethyl-2-methyl-1,3-propanediol, 1,7-heptanediol, 2-methyl-2-propyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, and 1,12-dodecanediol.

[0176] Examples of the aforementioned polyols include, for instance, trimethylolethane, trimethylolpropane, trimethylolbutane, di(trimethylolpropane), tri(trimethylolpropane), pentaerythritol, dipentaerythritol, tripentaerythritol, glycerol, polyglycerol (2-20 polymers of glycerol), 1,3,5-pentanetriol, sorbitol, dehydrated sorbitol, sorbitol glycerol condensate, calendula alcohol, arabinitol, xylitol, mannitol, and other polyols; sugars such as xylose, arabinose, ribose, rhamnose, glucose, fructose, galactose, mannose, sorbitol, cellobiose, maltose, isomaltose, trehalose, sucrose, metriose, gentiotriose, and pinotriose; as well as their partial etherifications and methyl glucosides (glycosides).

[0177] Among these polyols, hindered alcohols such as neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, di(trimethylolpropane), tri(trimethylolpropane), pentaerythritol, dipentaerythritol, and tripentaerythritol are preferred.

[0178] The number of carbon atoms in the aforementioned fatty acid is preferably 3 or more, more preferably 4 or more, and preferably 20 or less, more preferably 16 or less, and even more preferably 9 or less.

[0179] It should be noted that the number of carbon atoms in this fatty acid also includes the carbon atoms of the carboxyl group (-COOH) present in the aforementioned fatty acids.

[0180] Furthermore, the aforementioned fatty acid can be either a straight-chain fatty acid or a branched-chain fatty acid. From the viewpoint of lubrication performance, a straight-chain fatty acid is preferred, while from the viewpoint of hydrolytic stability, a branched-chain fatty acid is preferred. The aforementioned fatty acid can also be either a saturated fatty acid or an unsaturated fatty acid.

[0181] Examples of the aforementioned fatty acids include isobutyric acid, propionic acid, butyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, nonadecanoic acid, eicosanoic acid, oleic acid, and other straight-chain or branched-chain fatty acids; or so-called new acids where the α-carbon atom is quaternary.

[0182] The aforementioned fatty acid is preferably selected from one or more of the following: isobutyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, oleic acid (cis-9-octadecenoic acid), isovaleric acid (3-methylbutyric acid), 2-methylhexanoic acid, 2-ethylvaleric acid, 2-ethylhexanoic acid, and 3,5,5-trimethylhexanoic acid.

[0183] As a POE, it can be a partial ester of a polyol where all hydroxyl groups are not esterified, or a full ester where all hydroxyl groups are esterified, or a mixture of the partial ester and the full ester, preferably the full ester.

[0184] From the viewpoint of superior hydrolytic stability, esters of hindered alcohols such as neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, di(trimethylolpropane), tri(trimethylolpropane), pentaerythritol, dipentaerythritol, and tripentaerythritol are preferred. More preferably, esters of neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, pentaerythritol, and di(pentaerythritol) are preferred. Furthermore, from the viewpoint of superior compatibility with the aforementioned mixed refrigerants and superior hydrolytic stability, esters of pentaerythritol and di(pentaerythritol) are even more preferred.

[0185] As a suitable method for POE, preferred options include: diesters of neopentyl glycol containing one or more fatty acids selected from isobutyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, oleic acid, isovaleric acid, 2-methylhexanoic acid, 2-ethylvaleric acid, 2-ethylhexanoic acid, and 3,5,5-trimethylhexanoic acid; diesters of neopentyl glycol containing one or more fatty acids selected from isobutyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, oleic acid, isovaleric acid, 2-methylhexanoic acid, 2-ethylvaleric acid, 2-ethylhexanoic acid, and 3,5,5-trimethylhexanoic acid; and diesters of neopentyl glycol containing one or more fatty acids selected from isobutyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, oleic acid, isovaleric acid, and 2,5,5-trimethylhexanoic acid. Triesters of one or more fatty acids selected from 1-methylhexanoic acid, 2-ethylpentanoic acid, 2-ethylhexanoic acid, and 3,5,5-trimethylhexanoic acid with trimethylolpropane; triesters of one or more fatty acids selected from isobutyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, oleic acid, isovaleric acid, 2-methylhexanoic acid, 2-ethylpentanoic acid, 2-ethylhexanoic acid, and 3,5,5-trimethylhexanoic acid with trimethylolbutane; tetraesters of one or more fatty acids selected from isobutyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, oleic acid, isovaleric acid, 2-methylhexanoic acid, 2-ethylpentanoic acid, 2-ethylhexanoic acid, and 3,5,5-trimethylhexanoic acid with pentaerythritol, etc.

[0186] As a type of POE, an ester of a polyol and two or more mixed fatty acids is preferred, and an ester of a polyol having two or more and 20 or fewer hydroxyl groups and two or more mixed fatty acids having three or more and 20 or fewer carbon atoms is more preferred.

[0187] Examples of the two or more types of mixed fatty acids include, preferably, a mixed fatty acid composed of two or more fatty acids selected from fatty acids with 4 or more carbon atoms and 9 or fewer carbon atoms; more preferably, a mixed fatty acid composed of one or more fatty acids selected from fatty acids composed of fatty acids with 8 or 9 carbon atoms, fatty acids composed of fatty acids with 5 or 9 carbon atoms, and fatty acids composed of fatty acids with 4, 5, and 9 carbon atoms; and even more preferably, a mixed fatty acid composed of fatty acids with 8 or 9 carbon atoms.

[0188] It should be noted that in the case of esters formed with two or more fatty acids, the ester can be an ester formed by mixing two or more esters of one fatty acid with a polyol.

[0189] Examples of the aforementioned mineral oils include: for instance, oils produced by vacuum distilling the residual oil obtained from atmospheric distillation of crude oil such as alkane-based crude oil, intermediate-based crude oil, or cycloalkane-based crude oil, and then refining the resulting lubricating oil fraction through solvent deasphalting, solvent extraction or hydrocracking, solvent dewaxing or contact dewaxing, or hydrogen refining; oils produced by isomerizing mineral oil waxes; or oils produced by hydrogen-isomerizing dewaxing of residual WAX (GTL wax) from GTL processes such as Fischer-Tropsch processes.

[0190] Synthetic oils and mineral oils that can be used as other base oils mentioned above can be used alone, or in combination of two or more.

[0191] When the aforementioned base oil contains the aforementioned other base oils, from the viewpoint of the aforementioned refrigerant solubility, the content of the other base oils is preferably more than 0% by mass and less than 10% by mass in 100% by mass of the total amount of the aforementioned base oils, more preferably more than 0% by mass and less than 5% by mass, and even more preferably more than 0% by mass and less than 2% by mass.

[0192] In the aforementioned refrigeration oil, the content of the aforementioned base oil, based on the total amount of the aforementioned refrigeration oil (100% by mass), is preferably 90% by mass or more and 100% by mass or less, more preferably 95% by mass or more and 100% by mass or less, and even more preferably 97% by mass or more and 100% by mass or less.

[0193] (Properties of base oil)

[0194] The kinematic viscosity of the aforementioned base oil at 100°C (hereinafter also referred to as "kinematic viscosity at 100°C") is preferably 2.0 mm. 2 / s or higher and 50.0mm 2 / s or less.

[0195] If the kinematic viscosity is 2.0 mm 2 At speeds above 50.0 m / s, lubrication and sealing properties become good. On the other hand, if the kinematic viscosity is 50.0 mm... 2 When the energy efficiency is below a certain value (e.g., / s), the resulting refrigeration unit composition exhibits good energy-saving performance.

[0196] From this perspective, the preferred kinematic viscosity of this base oil at 100°C is 3.0 mm. 2 / s or higher, preferably 4.0mm 2 / s or higher, further preferably 5.0mm 2 / s or higher, and preferably 40.0mm 2 / s or less, preferably 30.0mm 2 / s or less, and more preferably 25.0mm 2 / s or less, and more preferably 15.0mm. 2 / s or less.

[0197] In addition, the kinematic viscosity of the base oil at 40°C (hereinafter also referred to as "kinematic viscosity at 40°C") is preferably 10.0 mm. 2 / s or higher, more preferably 20.0mm 2 / s or higher, further preferably 25.0mm 2 / s or higher, and preferably 250.0mm 2 / s or less, more preferably 200.0 mm 2 / s or less, and more preferably 150.0mm. 2 / s or less, and more preferably 120.0mm 2 / s or less.

[0198] It should be noted that the kinematic viscosity at 100°C and the kinematic viscosity at 40°C of the base oil were measured using the methods described in the examples below.

[0199] From the viewpoint of improving thermal stability, the hydroxyl value of the aforementioned base oil is preferably below 30 mg KOH / g, more preferably below 25 mg KOH / g, even more preferably below 20 mg KOH / g, even more preferably below 15 mg KOH / g, even more preferably below 10 mg KOH / g, and even more preferably below 5 mg KOH / g. Furthermore, the hydroxyl value of base oil (A) is typically above 0.1 mg KOH / g.

[0200] In this specification, the hydroxyl value of the base oil is the value determined by neutralization titration according to JIS K0070:1992.

[0201] From a safety perspective, the flash point of the aforementioned base oil is preferably 170°C or higher. From this perspective, the flash point of the base oil is more preferably 180°C or higher, even more preferably 190°C or higher, and still more preferably 195°C or higher.

[0202] In addition, there is no specific upper limit to the flash point of this base oil, such as below 300°C.

[0203] It should be noted that the flash point of the base oil was measured using the method described in the examples below.

[0204] <Other Additives>

[0205] In addition to the aforementioned base oil, the aforementioned refrigeration oil may also contain various additives (hereinafter referred to as "other additives") that may be selected by the refrigeration oil. Examples of such other additives include one or more additives selected from antioxidants, oiliness improvers, extreme pressure agents, acid scavengers, oxygen scavengers, metal inertizers, rust inhibitors, and defoamers.

[0206] When the aforementioned refrigeration oil contains the other additives, from the viewpoint of effectiveness and economy, the total content of the other additives, based on the total amount of the aforementioned refrigeration oil (100% by mass), is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, even more preferably 0.3% by mass or more, and preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, and even more preferably 2% by mass or less.

[0207] The aforementioned refrigeration oil may not contain these other additives.

[0208] As examples of the aforementioned antioxidants, phenolic antioxidants and amine antioxidants can be listed.

[0209] Examples of phenolic antioxidants include monophenolic antioxidants and polyphenolic antioxidants.

[0210] Examples of monophenolic antioxidants include octyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 6-methylheptyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, etc. (as alkyl groups, groups with 4 or more carbon atoms and 20 or less can be listed, and groups with 8 or more carbon atoms and 18 or less are preferred); 2,6-di-tert-butyl-4-alkylphenols such as 2,6-di-tert-butyl-4-methylphenol and 2,6-di-tert-butyl-4-ethylphenol (the alkyl group has 1 or more carbon atoms and 4 or less); 2,4-dimethyl-6-tert-butylphenol and 2,6-di-tert-pentyl-p-cresol, etc.

[0211] Examples of polyphenolic antioxidants include 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'-butylidene bis(3-methyl-6-tert-butylphenol), 4,4'-isopropylidene bis(2,6-di-tert-butylphenol), and 2,2'-methylenebis(4-methyl-6-nonylphenol). 2,2'-Isobutylidene bis(4,6-dimethylphenol), 2,2'-methylene bis(4-methyl-6-cyclohexylphenol), 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, thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], etc.

[0212] Examples of amine-based antioxidants include dialkyl diphenylamines such as 4,4'-dibutyldiphenylamine and 4,4'-dioctyldiphenylamine; phenyl-α-naphthylamines such as alkylphenyl-α-naphthylamine and phenyl-α-naphthylamine; and N,N'-diphenyl-p-phenylenediamine.

[0213] The aforementioned refrigeration oil may contain one of these antioxidants alone, or it may contain two or more in combination.

[0214] When the aforementioned refrigeration oil contains this antioxidant, from the viewpoint of suppressing the increase in the acid value of the resulting refrigeration oil and more easily improving its oxidative stability at high temperatures, the content of the antioxidant, based on the total amount of the aforementioned refrigeration oil (100% by mass), is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and even more preferably 0.3% by mass or more. Furthermore, from the viewpoint of easily achieving an effect commensurate with the content, the content is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less.

[0215] Examples of oiliness modifiers include, for instance, aliphatic saturated or unsaturated monocarboxylic acids such as stearic acid and oleic acid; polymeric fatty acids such as dimer acids and hydrogenated dimer acids; hydroxy fatty acids such as castor oil and 12-hydroxystearic acid; aliphatic saturated and unsaturated monools such as lauryl alcohol and oleyl alcohol; aliphatic saturated or unsaturated monoamines such as stearylamine and oleylamine; aliphatic saturated or unsaturated monocarboxylic acid amides such as laurylamide and oleamide; and esters formed by polyols such as glycerol and sorbitol with aliphatic saturated or unsaturated monocarboxylic acids.

[0216] The aforementioned refrigeration oil may contain one type of oiliness improver alone, or it may contain two or more types in combination.

[0217] When the aforementioned refrigeration oil contains the oiliness improver, the content of the oiliness improver, based on the total amount of the aforementioned refrigeration oil (100% by mass), is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, and preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 2% by mass or less.

[0218] Examples of extreme pressure agents include, for instance, phosphorus-based extreme pressure agents. Examples of phosphorus-based extreme pressure agents include phosphate esters, phosphites, acid phosphate esters, acid phosphites, or their amine salts.

[0219] Examples of phosphate esters include triaryl phosphate esters, trialkyl phosphate esters, monoalkyl diaryl phosphate esters, dialkyl monoaryl phosphate esters, and trienyl phosphate esters. It should be noted that the term "aryl" used in relation to this extreme pressure agent is not limited to functional groups consisting solely of aromatic rings, but also includes alkylaryl and arylalkyl groups.

[0220] Examples of the aforementioned phosphate esters include, for instance, triphenyl phosphate, tricresyl phosphate, benzyl diphenyl phosphate, toluyl diphenyl phosphate, xylyl phenyl phosphate, propylphenyl diphenyl phosphate, dipropylphenyl phosphate, ethylphenyl diphenyl phosphate, diethylphenyl phosphate, triethylphenyl phosphate, tripropylphenyl phosphate, butylphenyl diphenyl phosphate, dibutylphenyl phosphate, tributylphenyl phosphate, etc., triaryl phosphate; alkyl phosphate esters such as tributyl phosphate, ethyl dibutyl phosphate, trihexyl phosphate, tri(2-ethylhexyl) phosphate, tridecyl phosphate, trilauryl phosphate, trimyristyl phosphate, tripalmityl phosphate, tristearyl phosphate, etc.; and ethyl diphenyl phosphate, trioleyl phosphate, etc.

[0221] As for the aforementioned acidic phosphate esters, various acidic alkyl phosphate esters, acidic dialkyl phosphate esters, etc. can be listed.

[0222] As for the aforementioned phosphites, various trialkyl phosphites, triaryl phosphites, monoalkyl diaryl phosphites, dialkyl monoaryl phosphites, and trienyl phosphites can be listed.

[0223] As for the aforementioned acidic phosphites, various dialkyl hydrogen phosphites, dienyl hydrogen phosphites, diaryl hydrogen phosphites, etc., can be listed.

[0224] In addition, the aforementioned phosphorus-based extreme pressure agents can be phosphate esters containing sulfur atoms, such as trithiophene phosphate. It should be noted that amine salts can be amine salts of acidic phosphate esters or acidic phosphites. The amine forming the amine salt can be any of a primary amine, secondary amine, or tertiary amine.

[0225] The aforementioned refrigeration oil may contain one of these extreme pressure agents alone, or it may contain two or more in combination.

[0226] When the aforementioned refrigeration oil contains the extreme pressure agent, the content of the extreme pressure agent, based on the total amount of the aforementioned refrigeration oil (100% by mass), is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, even more preferably 0.5% by mass or more, and preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less.

[0227] Examples of acid scavengers include, for instance, epoxy compounds. Examples of epoxy compounds include glycidyl ether compounds, cyclohexane oxides, α-olefin oxides, and epoxidized soybean oil, with glycidyl ether compounds being preferred.

[0228] Examples of the aforementioned glycidyl ether compounds include: aliphatic monools with a carbon number preferably of 3 or more and 30 or less, more preferably of 4 or more and 24 or less, and even more preferably of 6 or more and 16 or less; aliphatic polyols with a carbon number of 3 or more and 30 or less, more preferably of 4 or more and 24 or less, and even more preferably of 6 or more and 16 or less; or glycidyl ethers derived from aromatic compounds containing one or more hydroxyl groups. The aliphatic monools or aliphatic polyols can be linear, branched, or cyclic, and can be saturated or unsaturated.

[0229] It should be noted that, in the case of aliphatic polyols or aromatic compounds containing two or more hydroxyl groups, from the viewpoint of suppressing the stability of refrigeration oil and the increase of hydroxyl value, it is preferable that all hydroxyl groups are etherified with glycidyl ether.

[0230] Examples of the aforementioned glycidyl ether compounds include phenyl glycidyl ether, alkyl glycidyl ether, and alkylene glycol glycidyl ether. Examples of such glycidyl ether compounds include, for example, glycidyl ethers derived from saturated aliphatic monools with 6 or more and 16 or less carbon atoms in a linear, branched, or cyclic form (i.e., alkyl glycidyl ethers with 6 or more and 16 or less carbon atoms in the alkyl group), such as 2-ethylhexyl glycidyl ether, isononyl glycidyl ether, decyl glycidyl ether, lauryl glycidyl ether, and myristyl glycidyl ether.

[0231] The aforementioned refrigeration oil may contain one type of acid scavenger alone, or it may contain two or more types in combination.

[0232] When the aforementioned refrigeration oil contains this acid scavenger, from the viewpoint that its oxidative stability at high temperatures is more easily improved, the content of the acid scavenger, based on the total amount of the aforementioned refrigeration oil (100% by mass), is preferably 0.1% by mass or more, more preferably 0.4% by mass or more, and even more preferably 0.8% by mass or more. Furthermore, from the viewpoint that it is easier to achieve an effect commensurate with the content, it is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, and even more preferably 2% by mass or less.

[0233] Examples of oxygen scavengers include sulfur-containing aromatic compounds such as 4,4'-thiobis(3-methyl-6-tert-butylphenol), diphenyl sulfide, dioctyl diphenyl sulfide, dialkyl diphenyl sulfide, benzothiophene, dibenzothiophene, phenothiazine, benzothiaran, thiaran, thiaanthracene, dibenzothiaran, and diphenylene disulfide; various aliphatic unsaturated compounds such as alkenes, dienes, and trienes; and terpenes with double bonds.

[0234] The aforementioned refrigeration oil may contain one of the oxygen scavengers alone, or it may contain two or more in combination.

[0235] When the aforementioned refrigeration oil contains the oxygen scavenger, the content of the oxygen scavenger, based on the total amount of the aforementioned refrigeration oil (100% by mass), is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, and preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, and even more preferably 2% by mass or less.

[0236] Examples of copper inert agents, such as N-[N,N'-dialkyl (alkyl with 3 or more carbon atoms and 12 or fewer)aminomethyl]triazole, can be cited as metal inert agents.

[0237] Examples of rust inhibitors include metal sulfonates, aliphatic amines, organic phosphites, organic phosphates, metal salts of organic sulfonates, metal salts of organic phosphates, alkenyl succinates, and polyol esters.

[0238] Examples of defoamers mentioned above include silicone oils such as dimethylpolysiloxane and polymethyl methacrylates.

[0239] The aforementioned refrigeration oil may contain one of the aforementioned metal inert agents, rust inhibitors, or defoamers individually, or may contain two or more in combination.

[0240] When the aforementioned refrigeration oil contains the aforementioned metal inert agent, the aforementioned rust inhibitor, or the aforementioned defoamer, the content of each is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, and preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, and even more preferably 2% by mass or less, based on the total amount of refrigeration oil (100% by mass).

[0241] (Mixing ratio of refrigeration oil to mixed refrigerant)

[0242] In the aforementioned composition for refrigeration machines, the content ratio (refrigeration oil / mixed refrigerant) of the aforementioned refrigeration oil to the aforementioned mixed refrigerant is preferably 1 / 99 or more and 99 / 1 or less by mass, more preferably 1 / 99 or more and 90 / 10 or less, further preferably 5 / 95 or more and 88 / 12 or less, and even more preferably 10 / 95 or more and 60 / 40 or less. If the mass ratio of the aforementioned refrigeration oil to the aforementioned mixed refrigerant is set within this range, lubricity and suitable refrigeration capacity in the refrigeration machine can be obtained.

[0243] Furthermore, in the aforementioned refrigeration machine composition, the total content of the aforementioned mixed refrigerant and the aforementioned refrigeration oil, based on the total amount of the refrigeration machine composition (100% by mass), is preferably 90% by mass or more and 100% by mass or less, more preferably 95% by mass or more and 100% by mass or less, further preferably 98% by mass or more and 100% by mass or less, and even more preferably 100% by mass.

[0244] [Refrigeration oil]

[0245] The refrigeration oil described in this embodiment is used together with the mixed refrigerant in the above-mentioned refrigeration composition, and the details are the same as above.

[0246] [Method for manufacturing a composition for refrigeration equipment]

[0247] The aforementioned refrigeration composition is obtained by mixing the aforementioned mixed refrigerant with the aforementioned refrigeration oil. Specifically, the method for manufacturing the refrigeration composition according to one aspect of the present invention includes a step of mixing a mixed refrigerant with a refrigeration oil containing a base oil. The mixed refrigerant contains fluorinated hydrocarbons and carbon dioxide, the content of the fluorinated hydrocarbons is less than 25% by mass based on the total amount of the mixed refrigerant, and the base oil contains one or more selected from polyvinyl ethers (PVE) and polyalkylene glycols (PAG).

[0248] The detailed descriptions of the aforementioned mixed refrigerant and the aforementioned refrigeration oil are the same as above, therefore, their descriptions are omitted. Furthermore, the suitable range for the total content of the aforementioned mixed refrigerant and the aforementioned refrigeration oil in this refrigeration composition is also as shown above.

[0249] [Refrigeration unit]

[0250] The aforementioned refrigeration machine is used by filling the interior of the refrigeration machine with the composition.

[0251] The preferred type of refrigeration unit is a compression refrigeration unit that uses the aforementioned mixed refrigerant, and more preferably it has a refrigeration cycle having a compressor, a condenser, an expansion mechanism (expansion valve, etc.) and an evaporator; or a refrigeration cycle having a compressor, a condenser, an expansion mechanism, a dryer and an evaporator.

[0252] The aforementioned composition for refrigeration machines is used to lubricate sliding parts, such as those provided in a compressor. It should be noted that the sliding part is not particularly limited.

[0253] As for machines equipped with the above-mentioned refrigeration units, examples include open-type car air conditioners, electric vehicle air conditioners, and other car air conditioners; indoor air conditioners and cabinet air conditioners; refrigeration systems such as gas heat pumps (GHP), freezers, refrigerators, vending machines, and display cases; hot water supply systems such as water heaters and underfloor heating; and heating systems. They are preferably used in air conditioners, and more preferably in indoor air conditioners and cabinet air conditioners.

[0254] Furthermore, when the aforementioned refrigeration composition is filled into the interior of a refrigeration machine for use, the mass ratio of the aforementioned refrigeration oil to the aforementioned mixed refrigerant (refrigeration oil / mixed refrigerant) is preferably 1 / 99 or more and 99 / 1 or less, more preferably 1 / 99 or more and 90 / 10 or less, further preferably 5 / 95 or more and 88 / 12 or less, and even more preferably 10 / 95 or more and 60 / 40 or less.

[0255] This ratio refers to the ratio of the mixed refrigerant to the refrigeration oil introduced into the device, regardless of whether the mixed refrigerant and the refrigeration oil are completely or partially compatible, and is always based on their respective amounts when introduced into the system. That is, it does not mean the ratio of the amounts of the components in the aforementioned refrigeration composition.

[0256] Example

[0257] The present invention will be described in more detail below through examples, but the present invention is not limited to these examples at all.

[0258] It should be noted that the physical properties of each component and each refrigeration unit composition are determined according to the following guidelines.

[0259] [Kinematic viscosity at 40℃]

[0260] The determination was carried out in accordance with JIS K2283:2000.

[0261] [Acid Value]

[0262] The determination was performed by neutralization titration according to JIS K0070:1992 for base oil (A).

[0263] [Number-average molecular weight (Mn)]

[0264] The number-average molecular weight (Mn) of the base oil (A) was determined using gel permeation chromatography (GPC).

[0265] Regarding GPC, as a column, a column consisting of two "TSKgel SuperMultiporeHZ-M" columns manufactured by Tosoh Corporation was used in series, with tetrahydrofuran as the eluent. A refractive index detector (RI detector) was used for the determination, and polystyrene was used as the standard sample to calculate the number-average molecular weight (Mn).

[0266] <Evaluation Methods for Thermal Stability>

[0267] The refrigeration compositions (refrigeration oil composition / refrigerant = 30g / 30g, moisture content in the refrigeration composition: 500 ppm by mass, air content: 25mL) prepared in Examples 1-6 and Comparative Examples 1-9, and a metal catalyst containing iron, copper and aluminum were filled into the autoclave tube. After being kept at a temperature of 175°C for 14 days, the appearance of the oil, the presence of precipitates and the discoloration of the catalyst were visually observed.

[0268] It should be noted that the appearance of the oil is evaluated using ASTM colorimetry. Oil with a colorimetric score below 1.0 (L1.0) is judged as good, while oil with a colorimetric score above 1.0 (L1.5, L2.0, etc.) is judged as poor.

[0269] In addition, after the thermal stability test, the acid value of the refrigeration oil composition was evaluated using the method described below.

[0270] (Evaluation of the acid value of the refrigeration oil composition)

[0271] The determination was performed according to JIS K2501:2003, using the indicator photometric titration method (refer to Appendix 1 of the JIS standard below).

[0272] The physical properties of the base oils contained in the refrigeration compositions evaluated in the various embodiments and comparative examples are shown in Table 1 below.

[0273] [Table 1]

[0274] Table 1

[0275]

[0276] [Examples 1-6 and Comparative Examples 1-9]

[0277] Each refrigeration unit composition was prepared by mixing 100% by mass of the base oil shown in Table 1 and the mixed refrigerant with the composition shown in Table 2 at the mixing ratios shown in Table 2, and the aforementioned thermal stability was evaluated. The results are shown in Table 2 below.

[0278] [Table 2]

[0279] Table 2

[0280]

[0281] As shown in Table 2, it can be confirmed that the refrigeration compositions of Examples 1-6, despite containing carbon dioxide and having low global warming potential, all exhibit high thermal stability.

[0282] In contrast, as shown in Table 2, the refrigeration compositions of Comparative Examples 1, 2, 8 and 9 had a fluorinated hydrocarbon content of 25% by mass or more, poor color after thermal stability testing, or a higher acid value.

[0283] On the other hand, in the refrigeration compositions of Comparative Examples 3 to 7, which use polyol ethers as base oils for refrigeration oils, it was confirmed that the color was poor after thermal stabilization, and consequently the iron and copper catalysts changed color.

[0284] Industrial utilization

[0285] The refrigeration composition of the present invention described above is a mixture of a carbon dioxide-containing mixed refrigerant and refrigeration oil, which is a refrigerant with low global warming potential. Due to its excellent thermal stability, it is suitable for use in refrigeration applications. For example, it is particularly suitable for use in closed-type compression refrigeration units that use the mixed refrigerant. Furthermore, since it is a refrigeration composition containing the aforementioned mixed refrigerant, it is also suitable for use in, for example, refrigeration systems of open-type automotive air conditioners, electric vehicle air conditioners, indoor air conditioners and cabinet air conditioners, gas heat pumps (GHP), freezers, refrigerators, vending machines, display cases, etc., hot water supply systems such as water heaters and underfloor heating, heating systems, etc.

Claims

1. A composition for refrigeration equipment, comprising a mixed refrigerant and a refrigeration oil containing a base oil. The mixed refrigerant contains fluorinated hydrocarbons and carbon dioxide. The content of the fluorinated hydrocarbon compound is less than 25% by mass based on the total amount of the mixed refrigerant. The base oil contains one or more selected from polyvinyl ethers and polyalkylene glycols.

2. The composition for a refrigeration unit according to claim 1, wherein, The carbon dioxide content is 50% by mass or more and 97% by mass or less, based on the total amount of the mixed refrigerant.

3. The composition for a refrigeration unit according to claim 1 or 2, wherein, The content of the fluorinated hydrocarbon compound is 3% by mass or more and less than 25% by mass, based on the total amount of the mixed refrigerant.

4. The composition for a refrigeration unit according to any one of claims 1 to 3, wherein, The content of the fluorinated hydrocarbon compound is 3% by mass or more and 20% by mass or less, based on the total amount of the mixed refrigerant.

5. The composition for a refrigeration unit according to any one of claims 1 to 4, wherein, The fluorinated hydrocarbon compound contains 70% to 100% by mass of unsaturated fluorinated hydrocarbon compounds.

6. The composition for a refrigeration unit according to any one of claims 1 to 5, wherein, The content of one or more of the polyvinyl ethers and polyalkylene glycols selected from the above is 90% by mass or more and 100% by mass or less based on the total amount of base oil.

7. The composition for a refrigeration unit according to any one of claims 1 to 6, wherein, The content of the polyalkylene glycols is 90% by mass or more and 100% by mass or less, based on the total amount of the base oil.

8. The composition for a refrigeration unit according to any one of claims 1 to 7, wherein, In the composition for refrigeration machines, the total content of the mixed refrigerant and the refrigeration oil is 90% by mass or more and 100% by mass or less.

9. Refrigeration oil, which is used in mixed refrigerants containing fluorinated hydrocarbons and carbon dioxide, wherein the content of fluorinated hydrocarbons is less than 25% by mass. The refrigeration oil contains base oil. The base oil contains one or more selected from polyvinyl ethers and polyalkylene glycols.

10. A method for manufacturing a refrigeration composition according to any one of claims 1 to 8, comprising a step of mixing a mixed refrigerant and a refrigeration oil containing a base oil. The mixed refrigerant contains fluorinated hydrocarbons and carbon dioxide. The content of the fluorinated hydrocarbon compound is less than 25% by mass based on the total amount of the mixed refrigerant, and the base oil contains one or more selected from polyvinyl ethers and polyalkylene glycols.

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