BR112019021097B1 - COMPOSITION OF COOLING OIL - Google Patents

Abstract

The present invention relates to a refrigeration oil for a mixed refrigerant that contains less than 40% by mass of an unsaturated fluorinated hydrocarbon (HFO) compound based on the total amount of the mixed refrigerant, which contains a base oil ( P) containing one or more substances selected from the group consisting of polyvinyl ethers (PVE), a polyalkylene glycol (PAG), copolymers (ECP) of a polyvinyl ether and poly(oxy)alkylene glycol or a monoether thereof, and esters of polyol (POE), and wherein the base oil has a hydroxyl value of 15 mg KOH/g or less; and a composition for refrigerators which contains the foregoing refrigeration oil and a specific refrigerant.

Description

Technical Field

[001] The present invention relates to a refrigeration oil and a refrigeration oil composition containing the refrigeration oil.

Background of the Technique

[002] In general, a compression-type refrigerator has a structure in which it is not only configured with at least one compressor, a condenser, an expansion mechanism (an expansion valve), an evaporator, etc., but also a mixture of refrigerant and refrigerant oil (hereinafter also referred to as "refrigerator oil composition") is circulated within a closed system.

[003] As the refrigerant that is used for compression type refrigerators, fluorinated hydrocarbon compounds with a low environmental charge have been used instead of the often conventionally used hydrochlorofluorocarbon (HCFC). As the fluorinated hydrocarbon compounds, a saturated fluorinated hydrocarbon compound (HydroTluorCarbon; hereinafter also abbreviated as "HFC", such as 1,1,1,2-tetrafluoroethane (R134a), difluoromethane (R32) and a mixture of difluoromethane and pentafluoroethane (R410A) is often used.

[004] In addition, the use of unsaturated fluorinated hydrocarbon compounds (HydroTluorOlefin; hereinafter also abbreviated as "HFO") that have a low potential on global warming, such as 1,3,3,3- tetrafluoropropene (R1234ze) and 2,3,3,3-tetrafluoropropene (R1234yf).

[005] Thus, in view of the fact that a refrigerant that has lower global warming potential is required, for example, every air conditioner manufacturer uses R32 refrigerant (difluoromethane) for room air conditioners or packaged air conditioners instead of R410A. Furthermore, in low temperature equipment, a refrigerant is required as an alternative to the current R404A.

[006] Therefore, particularly in such applications, the practical implementation of a refrigerant containing the aforementioned HFO has recently begun to be investigated.

[007] For example, PTL 1 describes a working fluid composition for refrigerators that contains a refrigerant that contains hydrofluorethane having a specific structure, difluoroethane and tetrafluoropropene; and a refrigerator oil containing at least one selected from a polyol ester, a polyvinyl ether and a polyalkylene glycol compound as an oil base, wherein the carbon/oxygen molar ratio of the oil base is 2.5 or plus and 5.8 or minus.

Citation List Patent Literature

[008] PTL 1: WO 2013/147048A

Summary of the Invention

[009] In compression-type refrigerators that have the structure mentioned above, depending on the type of equipment, in general, the temperature becomes high inside the compressor, while it becomes low inside the condenser and, therefore, the refrigerant and refrigeration oil are required to be circulated within this system without causing phase separation over a wide temperature range from low temperatures to high temperatures. If phase separation occurs between the refrigerant and the refrigerating oil during the operation of the compression type refrigerator, a significant decrease in the durability and refrigeration efficiency of the compression type refrigerator is caused. Consequently, the refrigeration oil is required to have excellent compatibility with the refrigerant to be used.

[0010] Here, as mentioned above, the practical implementation of a mixed refrigerant containing HFO is investigated recently, and currently some mixed refrigerants have been used. However, among such mixed refrigerants, many mixed refrigerants contain HFO in low proportion. In the case where the proportion occupied by HFO in the mixed refrigerant is low, it has been confirmed that the compatibility between the mixed refrigerant and the refrigerating oil is lower (the separation temperature on the side with high temperature decreases, while the separation temperature on the side with low temperature increases, such that the temperature region in which the mixed refrigerant and refrigerant oil are not separated from each other becomes narrow), as compared, for example, with a mixed refrigerant in which the proportion of HFO in the refrigerant mixed is relatively high as in the refrigerant specifically described in the working examples of PTL 1.

[0011] Consequently, as for a refrigerant oil to be used in a mixed refrigerant that has a low proportion in HFO content, it has been observed that the development of a refrigerant oil that has excellent compatibility with the mixed refrigerant in a range of Wider temperature range from low temperature to high temperature is required.

[0012] Additionally, from the point of view of preventing current leakage in equipment, for the refrigerant oil, electrical properties are required on the occasion of use as a refrigerant oil composition, specifically a high volumetric resistivity. However, it has been confirmed that when the proportion of HFO occupying the mixed refrigerant is low, the volumetric resistivity decreases as well.

[0013] Consequently, it was also observed that for a refrigerant oil to be used for a mixed refrigerant having a low proportion of HFO content, on the occasion of use as a refrigerant oil composition, a higher volumetric resistivity is required.

[0014] Taking into account the above problems, a problem of the present invention is to provide a refrigeration oil that has excellent compatibility with a mixed refrigerant that contains less than 40% by weight of HFO based on the total amount of the mixed refrigerant and that a composition of the refrigerating oil which has excellent electrical properties is obtainable therefrom.

Solution to the Problem

[0015] The present inventor and others have made extensive and intensive investigations. As a result, it was found that a refrigeration oil containing a base oil (P), including a compound specified as a base oil, with a base oil hydroxyl value (P) being 15 mg KOH/g or less, is able to solve the above mentioned problem. The present invention was carried out on the basis of such a finding. Specifically, in accordance with each of the embodiments of the present invention, the following [1] to [5] are provided. [1] A refrigerant oil for a mixed refrigerant that contains less than 40% by mass of an unsaturated fluorinated hydrocarbon (HFO) compound based on the total amount of the mixed refrigerant, the refrigerant oil containing a base oil ( P), which includes at least one selected from the group consisting of a polyvinyl ether (PVE), a polyalkylene glycol (PAG), a copolymer (ECP) of a poly(oxy)alkylene glycol or a monoether thereof, and a polyvinyl ether and a polyol ester (POE), with a base oil hydroxyl value (P) being 15 mg KOH/g or less. [2] A refrigerating oil composition containing a mixed refrigerant containing less than 40% by mass of a fluorinated unsaturated hydrocarbon (HFO) compound based on the total amount of the mixed refrigerant and refrigerating oil as set forth in [ 1] above. [3] A method of producing a refrigerating oil composition as set forth in [2] above, including a step of mixing the refrigerating oil as described in [1] above and a mixed refrigerant containing less than 40% in mass of an unsaturated fluorinated hydrocarbon (HFO) compound based on the total amount of the mixed refrigerant. [4] A refrigerator which contains the refrigerating oil as described in [1] above or the refrigerating oil composition as described in [2] above added thereto. [5] An air conditioner which has the refrigerating oil as described in [1] above or the refrigerating oil composition as described in [2] above added to it.

Advantageous Effects of the Invention

[0016] According to the present invention, it is possible to provide a refrigeration oil that has excellent compatibility with a mixed refrigerant that contains less than 40% by mass of an HFO based on the total amount of mixed refrigerant and that a composition of refrigeration oil having excellent electrical properties is obtainable therefrom.

Description of Modalities Cooling Oil

[0017] The refrigeration oil according to an embodiment of the present invention (hereinafter also referred to simply as the "refrigeration oil") is a refrigeration oil for a mixed refrigerant that contains less than 40% by mass of a fluorinated unsaturated hydrocarbon (HFO) compound based on the total amount of refrigerant (hereinafter also referred to as "low HFO containing refrigerant"), wherein the refrigerant oil contains a base oil (P), including at least one selected from the group consisting of a polyvinyl ether (hereinafter also referred to as "PVE"), a polyalkylene glycol (hereinafter also referred to as "PAG"), a copolymer of a poly(oxy)alkylene glycol or a monoether thereof and a polyvinyl ether (hereinafter also referred to as "ECP"), and a polyol ester (hereinafter referred to as "POE") and a base oil hydroxyl value (P) is 15 mg KOH/g or less.

[0018] In view of the fact that the refrigeration oil contains the base oil (P) with a hydroxyl value of 15 mg KOH/g or less, it has excellent compatibility with the aforementioned low-HFO-containing refrigerant.

[0019] In this application, the expression "hydrocarbon group" means a group consisting of only one carbon atom and one hydrogen atom. The "hydrocarbon group" includes an "aliphatic group" consisting of a straight chain or a branched chain, an "alicyclic group" having one or more rings of saturated or unsaturated carbon without aromaticity, and an "aromatic group" having one or more more aromatic rings with aromaticity, such as a benzene ring.

[0020] In this application, the expression "ring carbon atoms" indicates a number of carbon atoms between the atoms constituting the ring itself of a compound having a structure in which the atoms are connected in a ring shape. In the case where the previous ring is replaced by a substituent, the carbon(s) contained in the substituent is/are not included in the carbon atoms of the ring.

[0021] The expression "ring atoms" denotes a number of atoms constituting a ring itself of a compound having a structure in which the atoms are connected in a ring shape. An atom that does not make up the ring (for example, a hydrogen atom that terminates a bond of atoms that make up the ring), or atoms contained in a substituent, in which case the previous ring is replaced with the substituent, are not included in the ring atoms.

[0022] Examples of the substituent in the description of "substituted or unsubstituted" include an alkyl group having 1 or more and 10 or less (preferably 1 or more and 6 or less, more preferably 1 or more and 4 or less, and further more preferably 1 or more and 3 or less) carbon atoms; a cycloalkyl group having 3 or more and 10 or fewer (preferably 3 or more and 8 or fewer, more preferably 4 or more and 6 or fewer, and even more preferably 5 or 6) ring carbon atoms; an aryl group having 6 or more and 18 or fewer (preferably 6 or more and 12 or fewer) ring carbon atoms; a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom); a cyano group; a nitro group; a hydroxyl group; and an amino group.

[0023] These substituents can be further substituted with the above mentioned arbitrary substituent.

[0024] The expression "unsubstituted" in the description of "substituted or unsubstituted" means that the compound is not substituted by such a substituent and the hydrogen atom is attached to it.

[0025] Each of the components that are contained in the refrigeration oil is described below.

Base Oil (P)

[0026] The base oil (P) that the refrigeration oil contains is a base oil that includes at least one selected from the group consisting of a polyvinyl ether (PVE), a polyalkylene glycol (PAG), a copolymer ( ECP) of a poly(oxy)alkylene glycol or a monoether thereof and a polyvinyl ether and a polyol ester (POE).

[0027] From the point of view of the compatibility of the refrigeration oil with the refrigerant with low HFO content as well as from the point of view of an improvement in the volumetric resistivity of the resulting composition of refrigeration oil, the base oil (P) preferably includes at least at least one selected from the group consisting of PVE, POE and ECP, more preferably it includes at least one selected from the group consisting of PVE and POE, and even more preferably it includes PVE.

[0028] From the point of view of providing a refrigeration oil that has excellent compatibility with the refrigerant with low HFO content, the total content of at least one of those selected from the group consisting of PVE, POE, ECP and PAG 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, even more preferably 90% by mass or more and 100% by mass or less, but even more preferably 98% by mass or more and 100% by mass, and even more preferably 100% by mass based on 100% by mass of the total amount of base oil (P).

[0029] PVE, PAG, ECP, and POE that are contained in the base oil (P) contains are described herein successively.

(Polyvinyl Ether (PVE))

[0030] Examples of polyvinyl ether (PVE) include polymers with at least one structural unit derived from a vinyl ether. In the case where the PVE is included in the base oil (P), the base oil (P) can contain the PVE alone or it can contain a combination of two or more of them.

[0031] Of such PVEs, from the point of view of compatibility with the low HFO content refrigerant, polymers having at least one structural unit derived from a vinyl ether and having an alkyl group having 1 or more and 4 or fewer carbon atoms in a side chain are preferred.

[0032] Of the PVEs, a polymer (A1) having at least one structural unit represented by the following general formula (A-1) is preferred.

[0033] In the general formula (A-1), R1a, R2a and R3a each independently represent a hydrogen atom or a hydrocarbon group having 1 or more and 8 or fewer carbon atoms; R4a represents a divalent hydrocarbon group having 2 or more and 10 or less carbon atoms; and R5a represents a hydrocarbon group having 1 or more and 10 or fewer carbon atoms.

[0034] In the general formula (A-1), r is an average value of the number of units represented by OR4a and represents a number of 0 or more and 10 or less, and is preferably a number of 0 or more and 5 or less , more preferably a number of 0 or more and 3 or less, and even more preferably 0.

[0035] In the general formula (A-1), in the case where OR4a exists in the plural (ie, in the case where r is a number of 2 or more), OR4a in the plural may be the same or different from one another.

[0036] In the case where r is 0, the bond between the carbon atom (C) and -OR5a in the general formula (A-1) is a single bond and the carbon atom (C) bonds directly to -OR5a.

[0037] Examples of the hydrocarbon group having 1 or more and 8 or less carbon atoms, which may be selected for R1a, R2a and R3a, include alkyl groups such as a methyl group, an ethyl group, various propyl groups, various butyl groups, various pentyl groups, various hexyl groups, various heptyl groups and various octyl groups; cycloalkyl groups such as a cyclopentyl group, a cyclohexyl group, various methylcyclohexyl groups, various ethylcyclohexyl groups and various dimethylcyclohexyl groups; aryl groups, such as one phenyl group, several methylphenyl groups, several ethylphenyl groups and several dimethylphenyl groups; and arylalkyl groups, such as a benzyl group, various phenylethyl groups and various methylbenzyl groups.

[0038] In this application, the expression "various XXX groups" is to include all isomers that are considered to be XXX groups. For example, the term "various alkyl groups" represents "linear, branched, or cyclic hydrocarbon groups." For example, the expression "various propyl groups" represents several propyl groups, such as an n-propyl group and an isopropyl group; the term "various butyl groups" represents various butyl groups, such as an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group and a cyclobutyl group.

[0039] The number of carbons of the hydrocarbon group that can be selected for R1a, R2a and R3a 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 .

[0040] R1a, R2a and R3a are each independently preferably a hydrogen atom or an alkyl group having 1 or more and 8 or fewer carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 or more and 6 or less carbon atoms, even more preferably a hydrogen atom or an alkyl group having 1 or more and 4 or less carbon atoms and even more preferably a hydrogen atom or an alkyl group having 1 or more and 3 or fewer atoms of carbon.

[0041] R1a, R2a, and R3a may be the same or different from each other.

[0042] Examples of the divalent hydrocarbon group having 2 or more and 10 or less carbon atoms, which may be selected for R4a, include divalent aliphatic groups such as an ethylene group, a 1,2-propylene group, a 1 group ,3-propylene, various butylene groups, various pentylene groups, various hexylene groups, various heptylene groups, various octene groups, various nonylene groups and various decylene groups; alicyclic groups which are a divalent residue of an alicyclic compound such as cyclohexane, methylcyclohexane, ethylcyclohexane, dimethylcyclohexane and propylcyclohexane; divalent aromatic groups such as various phenylene groups, various methylphenylene groups, various ethylphenylene groups, various dimethylphenylene groups and various naphthylene groups; divalent alkyl aromatic groups having a monovalent attachment site on each of the alkyl group moieties and the aromatic moiety of an alkyl aromatic hydrocarbon such as toluene, xylene and ethylbenzene; and divalent aromatic alkyl groups having a site of attachment on the alkyl group portion of an aromatic polyalkyl hydrocarbon such as xylene and diethylbenzene.

[0043] The number of carbons of the hydrocarbon group that can be selected for R4a 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.

[0044] R4a is preferably a divalent aliphatic group having 2 or more and 10 or less carbon atoms, preferably a divalent aliphatic group having 2 or more and 6 or less carbon atoms, and even more preferably a divalent aliphatic group having 2 or plus and 4 or fewer carbon atoms.

[0045] Examples of the hydrocarbon group having 1 or more and 10 or less carbon atoms, which may be selected for R5a, include alkyl groups such as a methyl group, an ethyl group, various propyl groups, various butyl groups, various groups pentyl, various hexyl groups, various heptyl groups, various octyl groups, various nonyl groups and various decyl groups; cycloalkyl groups, such as a cyclopentyl group, a cyclohexyl group, various methylcyclohexyl groups, various ethylcyclohexyl groups, various propylcyclohexyl groups and various dimethylcyclohexyl groups; aryl groups, such as one phenyl group, several methylphenyl groups, several ethylphenyl groups, several dimethylphenyl groups, several propylphenyl groups, several trimethylphenyl groups, several butylphenyl groups and several naphthyl groups; and arylalkyl groups, such as a benzyl group, various phenylethyl groups, various methylbenzyl groups, various phenylpropyl groups and various phenylbutyl groups.

[0046] The carbon number of the hydrocarbon group that can be selected for R5a is preferably 1 or more and 8 or less, and more preferably 1 or more and 6 or less.

[0047] From the point of view of further improving the compatibility with the low HFO content refrigerant, R5a is preferably an alkyl group with 1 or more and 6 or less carbon atoms, more preferably an alkyl group with 1 or more and 4 carbon atoms and even more preferably a methyl group or an ethyl group.

[0048] In one embodiment of the present invention, preferably, the polymer (A1) has a structural unit (α1) in which R5a is an ethyl group.

[0049] The content of the structural unit (α1) is preferably 30% by mass or more and 100% by mass or less, more preferably 40% by mass or more and 100% by mass or less, and even more preferably 50% by mass mass or more and 100% by mass or less based on the total amount (100% by mass) of the structural units that the polymer (A1) has.

[0050] In one embodiment of the present invention, the copolymer (A1) may be a copolymer with a structural unit (α1) in which R5a is an ethyl group and a structural unit (α2) in which R5a is a methyl group.

[0051] In the foregoing copolymer, the mass ratio of structural unit (α1) to structural unit (α2) [α1/α2] is preferably 30/70 or more and 99/1 or less, more preferably 40/60 or more and 95/5 or less and even more preferably 50/50 or more and 90/10 or less.

[0052] The total content of structural units (α1) and (α2) in the polymer (A1) is preferably 70% by mass or more and 100% by mass or less, more preferably 80% by mass or more and 100% by mass or less, even more preferably 90% by mass or more and 100% by mass or less, and even more preferably 95% by mass or more and 100% by mass or less based on the total amount (100% by mass) of the units structural features that the polymer (A1) has.

[0053] In the polymer (A1), the number of units of the structural unit (degree of polymerization) represented by the general formula (A-1) can be suitably defined such that a base oil hydroxyl value (P) falls within range of 15 mg KOH/g or less.

[0054] The polymer (A1) may be a homopolymer having only one type of structural unit represented by the general formula (A-1), or it may be a copolymer having two or more types of structural units.

[0055] The copolymerization morphology of the copolymer is not particularly limited, and it may be a block copolymer, it may be a random copolymer, or it may be a graft copolymer.

[0056] In the terminal part of the polymer (A1), a monovalent group derived from saturated hydrocarbons, ethers, alcohols, ketones, amides, nitriles and the like can be introduced.

[0057] In one embodiment of the present invention, a termination of the polymer (A1) is preferably a group represented by the following general formula (A-1-i):

[0058] In the general formula (A-1-i), indicates the bonding position for the carbon atom in the structural unit represented by the general formula (A-1).

[0059] In the general formula (A-1-i), R6a, R7a and R8a each independently represent a hydrogen atom or a hydrocarbon group having 1 or more and 8 or fewer carbon atoms, preferably a hydrogen atom or a hydrocarbon group having 1 or more and 6 or less carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 or more and 6 or less carbon atoms, and even more preferably a hydrogen atom or an alkyl group having 1 or more and 3 or less carbon atoms.

[0060] R6a, R7a and R8a may be the same or different from each other.

[0061] As the hydrocarbon group having 1 or more and 8 or less carbon atoms, which may be selected for R6a, R7a and R8a, the same as those enumerated as the hydrocarbon group having 1 or more and 8 are exemplified or less carbon atoms, which can be selected for R1a, R2a and R3a in the general formula (A-1).

[0062] In the general formula (A-1-i), R9a represents a divalent hydrocarbon group with 2 or more and 10 or less carbon atoms, and is preferably a divalent hydrocarbon group with 2 or more and 8 or fewer carbon atoms carbon, more preferably a divalent hydrocarbon group having 2 or more and 6 or fewer carbon atoms, and even more preferably a divalent aliphatic group having 2 or more and 4 or fewer carbon atoms.

[0063] In the general formula (A-1-i), r1 is an average value of the number of units represented by OR9a and represents a number of 0 or more and 10 or less and is preferably a number of 0 or more and 5 or least, more preferably a number of 0 or more and 3 or less, and even more preferably 0.

[0064] In the general formula (A-1-i), in the case where there is more than one OR9a (that is, in the case where r1 is a number of 2 or more), the more than one OR9a can be equal to or different from each other.

[0065] In the case where r1 is 0, the bond between the carbon atom (C) and -OR10a in the general formula (A-1-i) is a single bond and the carbon atom (C) bonds directly to -OR10a.

[0066] As the divalent hydrocarbon group with 2 or more and 10 or less carbon atoms, which can be selected for R9a, the same as those enumerated as the divalent hydrocarbon group with 2 or more and 10 or less are exemplified carbon atoms, which can be selected for R4a in the general formula (A-1).

[0067] In the general formula (A-1-i), R10A represents a hydrocarbon group having 1 or more and 10 or fewer carbon atoms, and is preferably a hydrocarbon group having 1 or more and 8 or fewer carbon atoms , and more preferably an alkyl group having 1 or more and 8 or fewer carbon atoms.

[0068] In the case where r1 in the general formula (A-1-i) is 0, R10A is more preferably an alkyl group having 1 or more and 6 or less carbon atoms and in the case where r1 is 1 or more, R10A is more preferably an alkyl group having 1 or more and 4 or less carbon atoms.

[0069] As the hydrocarbon group having 1 or more and 10 or less carbon atoms, which may be selected for R10A, the same as those enumerated as the hydrocarbon group having 1 or more and 10 or fewer carbon atoms are exemplified , which can be selected for R5a in the general formula (A-1).

[0070] Preferably, in the polymer (A1), one terminus is the group represented by the general formula (A-1-i), and the other terminus is the one selected from the group constituted by the group represented by the general formula (A-1 -i), a group represented by the following general formula (A-1-ii), a group represented by the following general formula (A-1-iii), and a group having an unsaturated olefinic bond.

[0071] In the general formulas (A-1-ii) and (A-1-iii), R11a, R12A, R13a, R18a, R19a and R20A each independently represent a hydrogen atom or a hydrocarbon group with 1 or more and 8 or fewer carbon atoms, preferably a hydrogen atom or a hydrocarbon group having 1 or more and 6 or fewer carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 or more and 6 or fewer carbon atoms and even more preferably a hydrogen atom or an alkyl group having 1 or more and 3 or less carbon atoms. R11a, R12A, R13a, R18a, R19a and R20A can be the same or different from each other.

[0072] As the hydrocarbon group that can be selected for R11a, R12A, R13a, R18a, R19a and R20A, the same as those enumerated as the hydrocarbon group having 1 or more and 8 or less carbon atoms, which can be selected for R1a, R2a and R3a in the general formula (A-1).

[0073] In the general formula (A-1-ii), R14a and R16A each independently represent 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 less than carbon atoms, and more preferably a divalent aliphatic group having 2 or more and 4 or less carbon atoms. As the divalent hydrocarbon group selectable for R14a and R16A, the same as those enumerated as the divalent hydrocarbon group selectable for R4a in the general formula (A-1) are exemplified.

[0074] In the general formula (A-1-ii), r2 and r3 are each an average value of the number of units represented by OR14a and OR16A and each independently represents a number of 0 or more and 10 or less, and they are each preferably a number from 0 or more to 5 or less, more preferably a number from 0 or more to 3 or less, and even more preferably 0.

[0075] In the general formula (A-1-ii), in case there is more than one OR14a and OR16a, more than one OR14a and OR16a may be the same or different from each other.

[0076] In the case where r2 is 0, the bond between the carbon atom (C) and -OR15a in the general formula (A-1-ii) is a single bond and the carbon atom (C) bonds directly to -OR15a. Likewise, in the case where r3 is 0, the bond between the carbon atom (C) and -OR17a in the general formula (A-1-ii) is a single bond and the carbon atom (C) bonds directly a -OR17a.

[0077] In the general formula (A-1-ii), R15a and R17a each independently represent a hydrocarbon group having 1 or more and 10 or fewer carbon atoms, preferably a hydrocarbon group having 1 or more and 8 or fewer carbon atoms, and more preferably an alkyl group having 1 or more and 8 or fewer carbon atoms.

[0078] In the case where r2 is 0, R15a is even more preferably an alkyl group with 1 or more and 6 or less carbon atoms and in the case where r2 is 1 or more, R15A is even more preferably an alkyl group with 1 or more and 4 or fewer carbon atoms. Likewise, in the case where r3 is 0, R17a is even more preferably an alkyl group having 1 or more and 6 or less carbon atoms, and in the case where r3 is 1 or more, R17a is even more preferably a group alkyl with 1 or more and 4 or fewer carbon atoms.

(Polyoxyalkylene Glycol (PAG))

[0079] Polyoxyalkylene glycol (PAG) is preferably a compound (B1) represented by the following general formula (B-1). In the case where PAG is included in the base oil (P), PAG can be contained singly or it can be contained in combination of two or more of them. R1b-[(OR2b)m-OR3b]n (B-1)

[0080] In the general formula (B-1), R1b represents a hydrogen atom, a monovalent hydrocarbon group having 1 or more and 10 or fewer carbon atoms, an acyl group with 2 or more and 10 or fewer carbon atoms, carbon, a hydrocarbon group having a valency of 2 or more and 6 or less and having 1 or more and 10 or fewer carbon atoms, or a substituted or unsubstituted heterocyclic group having 3 or more and 10 or fewer ring atoms .

[0081] R2b represents an alkylene group having 2 or more and 4 or less carbon atoms.

[0082] R3b represents a hydrogen atom, a monovalent hydrocarbon group having 1 or more and 10 or fewer carbon atoms, an acyl group having 2 or more and 10 or fewer carbon atoms, or a substituted or unsubstituted heterocyclic group with 3 or more and 10 or fewer atoms in the ring.

[0083] In the general formula (B-1), n represents 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 less, and even more preferably 1.

[0084] n is defined according to the number of binding sites of R1b in the general formula (B-1). For example, in the case where R1b is an alkyl group or an acyl group, n is 1, and in the case where R1b is a hydrocarbon group or a heterocyclic group and the valency of the preceding group is 2, 3, 4, 5 , or 6, n is 2, 3, 4, 5 or 6, respectively.

[0085] In the general formula (B-1), m is an average value of the number of units represented by OR2b and represents a number of 1 or more and is preferably a number that makes the average value of (m x n) within from a range of 6 or more to 80 or less. The value of m is a value that is properly adjusted such that the base oil hydroxyl (P) value is within a range of 15 mg KOH/g or less, and is not particularly limited as long as it is adjusted such that the preceding hydroxyl value is within the predetermined range.

[0086] In case there is more than one OR2b, the more than one OR2b may be the same or different from each other. Furthermore, in the case where n is 2 or more, more than one R3b in a molecule can be the same or different from each other.

[0087] Examples of monovalent hydrocarbon group that can be selected for R1b and R3b include alkyl groups such as a methyl group, an ethyl group, various propyl groups, various butyl groups, various pentyl groups, various hexyl groups, various heptyl groups, several octyl groups, several nonyl groups and several decyl groups; cycloalkyl groups, such as a cyclopentyl group, a cyclohexyl group, various methylcyclohexyl groups, various ethylcyclohexyl groups, various propylcyclohexyl groups and various dimethylcyclohexyl groups; aryl groups, such as one phenyl group, several methylphenyl groups, several ethylphenyl groups, several dimethylphenyl groups, several propylphenyl groups, several trimethylphenyl groups, several butylphenyl groups and several naphthyl groups; and arylalkyl groups, such as a benzyl group, various phenylethyl groups, various methylbenzyl groups, various phenylpropyl groups and various phenylbutyl groups.

[0088] From the point of view of compatibility with the low HFO content refrigerant, the number of carbons of 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.

[0089] The portion of the hydrocarbon group having the acyl group having 2 or more and 10 or less carbon atoms and capable of being selected for R1b and R3b may be any one of a linear, branched or cyclic portion. Examples of the alkyl group moiety include those having 1 or more and 9 or fewer carbon atoms from the hydrocarbon group that may be selected for R1b and R3b.

[0090] From the point of view of compatibility with the low HFO content refrigerant, the number of carbons of 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.

[0091] Examples of the hydrocarbon group having a valence of 2 or more and 6 or less, which may be selected for R1b, include residues obtained by further removing 1 or more and 5 or less hydrogen atoms from the monovalent hydrocarbon group that can be selected for R1b; and residues obtained by removing a hydroxyl group from a polyhydric alcohol, such as trimethylolpropane, glycerin, pentaerythritol, sorbitol, 1, 2,3-trihtrihydroxycyclohexane and 1,3,5-trihtrihydroxycyclohexane -hexane.

[0092] From the point of view of compatibility with the low HFO content refrigerant, the number of carbons of the hydrocarbon group having a valence of 2 or more and 6 or less 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.

[0093] The heterocyclic group that can be selected for R1b and R3b is preferably a heterocyclic group containing an oxygen atom or a heterocyclic group containing sulfur atoms. The heterocyclic group can have a saturated ring or it can have an unsaturated ring.

[0094] Examples of heterocyclic group containing an oxygen atom include residues obtained by removing 1 or more and 6 or less hydrogen atoms from a saturated heterocyclic ring containing the oxygen atom, such as ethylene oxide, 1,3- oxide propylene, tetrahydrofuran, tetrahydropyran and hexamethylene oxide, or an unsaturated heterocyclic ring containing the oxygen atom, such as acetylene oxide, furan, pyran, oxycycloheptatriene, isobenzofuran and isochromene.

[0095] Examples of the heterocyclic group containing a sulfur atom include residues obtained by removing 1 or more and 6 or less hydrogen atoms from a saturated heterocyclic ring containing the sulfur atom, such as ethylene sulfide, trimethylene sulfide , tetrahydrothiophene, tetrahydrothiopyran and hexamethylene sulfide, or an unsaturated heterocyclic ring containing the sulfur atom, such as acetylene sulfide, thiophene, thiopyran and thioterpyridine.

[0096] The heterocyclic group that can be selected for R1b and R3b can have a substituent and the substituent can bind to the oxygen atom in the general formula (B-1). The substituent is as mentioned above and 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 1 or more and 3 or fewer carbon atoms.

[0097] From the point of view of compatibility with the low HFO content refrigerant, the ring atoms of the heterocyclic group are 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.

[0098] Examples of the alkylene group that may be selected for R2b include an alkylene group having 2 carbon atoms, such as a dimethylene group (-CH2CH2-) and an ethylene group (-CH(CH3)-); an alkylene group having 3 carbon atoms, such as a trimethylene group (-CH2-CH2-CH2), a propylene group (-CH(CH3)CH2-), a propylidene group (-CHCH2CH3-) and an isopropylidene group ( -C(CH3)2); and an alkylene group having 4 carbon atoms, such as a tetramethylene group (-CH2CH2CH2CH2), a 1-methyltrimethylene group (CH(CH3)CH2CH2), a 2-methyltrimethylene group (-CH2CH(CH3)CH2-), and a butylene group (-C(CH3)2 Ch2-).

[0099] In the case where there is more than one R2b, the more than one R2b may be the same or different and may be a combination of two or more alkylene groups.

[00100] Of these alkylene groups, R2b is preferably a propylene group (-CH(CH3)CH2-).

[00101] In the compound (B1) represented by the general formula (B-1), the content of oxypropylene units (-OCH(CH3)CH2-) 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 based on the total amount (100 mol%) of the oxyalkylene moiety (OR2b) in the compound (B1).

[00102] Compound (B1) is preferably at least one selected from the group consisting of polyoxypropylene glycol dimethyl ether represented by the following general formula (B-1-i), polyoxyethylene polyoxypropylene glycol dimethyl ether represented by the following general formula (B-1 -ii), polyoxypropylene glycol monobutyl ether represented by the following general formula (B-1-iii) and polyoxypropylene glycol diacetate.

[00103] In the formula (B-1-i), m1 is an average value of the number of oxypropylene units and represents a number of 1 or more, and is preferably a number of 6 or more and 80 or less.

[00104] In formula (B-1-ii), m2 and m3 are each an average value of the number of oxypropylene units and oxyethylene units, respectively, and each independently represents a number of 1 or more, and they are preferably a number that makes the value of (m2 + m3) fall within a range of 6 or more and 80 or less.

[00105] In the formula (B-1-iii), m4 is an average value of the number of oxypropylene units and represents a number of 1 or more, and is preferably a number of 6 or more and 80 or less.

[00106] m1 in the general formula (B-1-i), m2 and m3 in the general formula (B-1-ii) and m4 in the general formula (B-1-iii) are each an appropriately adjusted value such that the hydroxyl value of the base oil (P) is within a range of 15 mg KOH/g or less and these are not particularly limited as long as they are adjusted in such a way that the preceding hydroxyl value is within the predetermined range .

[00107] (Copolymer (ECP) of Poly(oxy)alkylene Glycol or its Monoether and Polyvinyl Ether)

[00108] (Copolymer (ECP) of Poly(oxy)alkylene Glycol or its Monoether and Polyvinyl Ether)

[00109] The copolymer (ECP) of a poly(oxy)alkylene glycol or its monoether and a polyvinyl ether may be a copolymer having a structural unit derived from a poly(oxy)alkylene glycol or its monoether and a structural unit derived from a polyvinyl ether.

[00110] The expression "poly(oxy)alkylene glycol" indicates both a polyalkylene glycol and a polyoxyalkylene glycol.

[00111] In the case where ECP is included in the base oil (P), the base oil (P) may contain the ECP alone or may contain a combination of two or more of them.

[00112] The ECP is preferably a copolymer (C1) represented by the following general formula (C-1) or a copolymer (C2) represented by the following general formula (C-2).

[00113] In the general formulas (C-1) and (C-2), R1c, R2c and R3c each independently represent a hydrogen atom or a hydrocarbon group with 1 or more and 8 or fewer carbon atoms.

[00114] Each R4c independently represents a hydrocarbon group having 1 or more and 10 or fewer carbon atoms.

[00115] Each R5c independently represents an alkylene group having 2 or more and 4 or fewer carbon atoms.

[00116] Each R6c independently represents a hydrogen atom, an alkyl group having 1 or more and 20 or fewer carbon atoms, a substituted or unsubstituted alicyclic group having 3 or more and 20 or fewer carbon atoms in the ring, a substituted or unsubstituted aromatic group that has 6 or more and 24 or fewer carbon atoms in the ring, an acyl group that has 2 or more and 20 or fewer carbon atoms, or an oxygen-containing hydrocarbon group that has 2 or more and 50 or fewer carbon atoms.

[00117] In case there are more than one R1c, R2c, R3c, R4c, R5c and R6c, respectively, these may be the same or different from each other in all structural units.

[00118] XC and YC independently represent a hydrogen atom, a hydroxyl group, or a hydrocarbon group that has 1 or more and 20 or fewer carbon atoms.

[00119] v in general formulas (C-1) and (C-2) is an average value of the number of units represented by OR5c and represents a number of 1 or more and is preferably a number of 1 or more and 50 or less . In case there is more than one OR5c, the OR5c can be the same or different from each other. "OR5c" denotes a structural unit derived from a poly(oxy)alkylene glycol or its monoether.

[00120] u in the general formula (C-1) represents a number of 0 or more, and is preferably a number of 0 or more and 50 or less; and w represents a number from 1 or more, and is preferably a number from 1 or more and 50 or less.

[00121] x and y in the general formula (C-2) each independently represent a number of 1 or more and they are each preferably a number of 1 or more and 50 or less.

[00122] The values of v, u, w, x and y are each a value defined such that the hydroxyl value of the base oil is within a range of 15 mg KOH/g or less, and they are not particularly limited , provided they are adjusted in such a way that the above hydroxyl value is within the predetermined range.

[00123] The copolymerization morphology of each copolymer (C1) and the copolymer (C2) is not particularly limited, and it can be a block copolymer, it can be a random copolymer, or it can be a graft copolymer.

[00124] As the hydrocarbon group having 1 or more and 8 or less carbon atoms, which can be selected for R1c, R2c and R3c, the same as those enumerated for the monovalent hydrocarbon group having 1 or more and 8 or fewer carbon atoms, which can be selected for R1a, R2a and R3a in the general formula (A-1).

[00125] The number of carbons of the hydrocarbon group that can be selected for R1c, R2c and R3c is preferably 1 or more and 8 or less, more preferably 1 or more and 6 or less, and even more preferably 1 or more and 3 or less .

[00126] Preferably, R1c, R2c and R3c are independently a hydrogen atom or an alkyl group with 1 or more and 8 or less carbon atoms, more preferably a hydrogen atom or an alkyl group with 1 or more and 6 or less carbon atoms, and even more preferably a hydrogen atom or an alkyl group having 1 or more and 3 or less carbon atoms.

[00127] Also preferably, at least one of R1c, R2c and R3c is a hydrogen atom and more preferably, all of R1c, R2c and R3c are hydrogen atoms.

[00128] As the hydrocarbon group having 1 or more and 10 or less carbon atoms, which can be selected for R4c, the same as those enumerated for the hydrocarbon group having 1 or more and 10 or less carbon atoms are exemplified carbon, which can be selected for R5a in the general formula (A-1).

[00129] The number of carbons of the hydrocarbon group that can be selected for R4c is preferably 1 or more and 8 or less, more preferably 1 or more and 6 or less, and even more preferably 1 or more and 4 or less.

[00130] As the alkylene group that can be selected for R5c, the same as those enumerated for the alkylene group having 2 or more and 4 or less carbon atoms, which can be selected for R2b in the general formula are exemplified. 1) and the alkylene group is preferably a propylene group (-CH(CH3)CH2-).

[00131] In the copolymer (C1) or the copolymer (C2), the content of oxypropylene unit (-OCH(CH3)CH2-) 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 based on the total content (100 mol%) of oxyalkylene (OR5c) which is a structural unit derived from poly(oxy)alkylene glycol or its monoether in the copolymer (C1) or the copolymer (C2).

[00132] Examples of alkyl group with 1 or more and 20 or less carbon atoms, which can be selected for R6C, include a methyl group, an ethyl group, various propyl groups, various butyl groups, various pentyl groups, various hexyl groups , several heptyl groups, several octyl groups, several nonyl groups, and several decyl groups.

[00133] The number of carbons of the alkyl 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.

[00134] Examples of alicyclic group having 3 or more and 20 or less ring carbon atoms, which can be selected for R6c, include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group and a cyclodecyl group.

[00135] The number of carbon atoms in the ring of the alicyclic 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.

[00136] The alicyclic group may have any substituent mentioned above, and as the substituent, an alkyl group is preferred.

[00137] Examples of aromatic group having 6 or more and 24 or less carbon atoms in the ring, which can be selected for R6c, include a phenyl group, a naphthyl group, an anthracenyl group and a phenanthryl group.

[00138] The number of carbon atoms in the ring of the aromatic group is preferably 6 or more and 18 or less, and more preferably 6 or more and 12 or less.

[00139] The aromatic group can have any substituent mentioned above, and as the substituent, an alkyl group is preferable.

[00140] Examples of the acyl group with 2 or more and 20 or less carbon atoms in the ring, which can be selected for R6c, include an acetyl group, a propionyl group, a butyryl group, an isobutyryl group, a valeryl group, a isovaleryl group, a pivaloyl group, a benzoyl group and a toluoyl group.

[00141] The number of carbons of 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.

[00142] Examples of the oxygen-containing hydrocarbon group having 2 or more and 50 or less carbon atoms, which can be selected for R6c, include a methoxymethyl group, a methoxyethyl group, a methoxypropyl group, a 1,1- group bismethoxypropyl, a 1,2-bismethoxypropyl group, an ethoxypropyl group, a (2-methoxyethoxy)propyl group and a (1-methyl-2-methoxy)propyl group.

[00143] The number of carbons of the oxygen-containing hydrocarbon group is preferably 2 or more and 20 or less, more preferably 2 or more and 10 or less, and even more preferably 2 or more and 6 or less.

[00144] The hydrocarbon group with 1 or more and 20 or less carbon atoms, which can be selected for XC and YC, includes an alkyl group with 1 or more and 20 or less (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) carbon atoms, a substituted or unsubstituted cycloalkyl group with 3 or more and 20 or less (preferably 3 or more and 10 or least, more preferably 3 or more and 8 or less, and even more preferably 3 or more and 6 or less) ring carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted naphthyl group and an arylalkyl group with 7 or more and 20 or less (preferably 7 or more and 13 or less) carbon atoms.

(Polyol Ester (POE))

[00145] Examples of polyol ester (POE) include esters of a diol or a polyol and a fatty acid. In the case where the POE is included in the base oil (P), the base oil (P) can contain the POE alone or it can contain a combination of two or more of them.

[00146] Of such POE, an ester of a diol or a polyol having 3 or more and 20 or less hydroxyl groups and a fatty acid having 3 or more and 20 or less carbon atoms is preferred.

[00147] Examples of diol include ethylene glycol, 1,3-propanediol, propylene glycol, 1,4-butanediol, 1,2-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 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.

[00148] Examples of polyol include polyhydric alcohols such as trimethylolethane, trimethylolpropane, trimethylolbutane, di-(trimethylolpropane), tri-(trimethylolpropane), pentaerythritol, di-(pentaerythritol), tri-(pentaerythritol), glycerin, a polyglycerin (for example, glycerin dimer to icosamer), 1,3,5-pentanetriol, sorbitol, sorbitan, a sorbitol-glycerin condensate, adonitol, arabitol, xylitol and mannitol; saccharides, such as xylose, arabinose, ribose, rhamnose, glucose, fructose, galactose, mannose, sorbose, cellobiose, maltose, isomaltose, trehalose, sucrose, raffinose, gentianose, and melenzitose; as well as partially esterified derivatives and methyl glycosides (glycosides) thereof.

[00149] Of these polyols, hindered alcohols, such as neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, di-(trimethylolpropane), tri-(trimethylolpropane), pentaerythritol, di-(pentaerythritol), and tri-(pentaerythritol), are preferred .

[00150] The number of carbons of the fatty acid is preferably 3 or more, and more preferably 4 or more from the point of view of lubrication performance; and is preferably 20 or less, more preferably 16 or less, and even more preferably 9 or less from the point of view of compatibility with the low HFO refrigerant.

[00151] The number of carbons of the fatty acid also includes the carbon atom of the carboxyl group (-COOH) that the fatty acid has.

[00152] Although the fatty acid may be a linear fatty acid or it may be a branched fatty acid, a linear fatty acid is preferred from a lubrication performance point of view, whereas a branched fatty acid is preferred from a stability point of view of hydrolysis. Furthermore, the fatty acid can be a saturated fatty acid or it can be an unsaturated fatty acid.

[00153] Examples of fatty acid include linear fatty acids or branched fatty acids such as isobutyric acid, propionic acid, butanoic acid, pentanoic 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 and oleic acid, as well as so-called neoacids in which the α-carbon atom is quaternized.

[00154] The fatty acid is preferably at least one selected from the group consisting of isobutyric acid, valeric acid (n-pentanoic acid), caproic acid (n-hexanoic acid), enanthoic acid (n-heptanoic acid), caprylic acid (n-heptanoic acid), n-octanoic acid), pelargonic acid (n-nonanoic acid), capric acid (n-decanoic acid), oleic acid (cis-9-octadenoic acid), isopentanoic acid (3-methylbutanoic acid), 2-methylhexanoic acid, 2 -ethylpentanoic acid, 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid.

[00155] The POE can be a partial ester in which all hydroxyl groups of a polyol are not esterified but remain as such, or a complete ester in which all hydroxyl groups are esterified; or it can also be a mixture of the preceding partial ester and the preceding complete ester. POE is preferably a complete ester.

[00156] From the POE, from the point of view of excellent hydrolysis stability, an ester of a hindered alcohol, such as neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, di-(trimethylolpropane), tri-(trimethylolpropane), pentaerythritol, di-( pentaerythritol), and tri-(pentaerythritol), is preferred; and a neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, pentaerythritol or di-(pentaerythritol) ester is more preferred; and from the point of view of excellent compatibility with the low HFO content refrigerant and hydrolysis stability, a pentaerythritol ester and a di-(pentaerythritol) ester are even more preferred.

[00157] As a suitable embodiment of POE, examples thereof include a diester of neopentyl glycol with at least one fatty acid selected from the group consisting of isobutyric acid, valeric acid, caproic acid, enantic acid, caprylic acid, pelargonic acid, capric acid, oleic acid, isopentanoic acid, 2-methylhexanoic acid, 2-ethylpentanoic acid, 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid; a triester of trimethylolethane with at least one fatty acid selected from the group consisting of isobutyric acid, valeric acid, caproic acid, entoic acid, caprylic acid, pelargonic acid, capric acid, oleic acid, isopentanoic acid, 2-methylhexanoic acid, 2-ethylpentanoic acid, 2-ethylhexanoic acid, and 3,5,5-trimethylhexanoic acid; triester of trimethylolpropane with at least one fatty acid selected from the group consisting of isobutyric acid, valeric acid, caproic acid, entoic acid, caprylic acid, pelargonic acid, capric acid, oleic acid, isopentanoic acid, 2-methylhexanoic acid, 2-methylhexanoic acid -ethylpentanoic acid, 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid; triester of trimethylolbutane with at least one fatty acid selected from the group consisting of isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, oleic acid, isopentanoic acid, 2-methylhexanoic acid, 2 -ethylpentanoic acid, 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid; and a pentaerythritol tetraester with at least one fatty acid selected from the group consisting of isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, oleic acid, isopentanoic acid, 2-methylhexanoic acid , 2-ethylpentanoic acid, 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid.

[00158] Of the POE, from the point of view of compatibility with the refrigerant with low HFO content, an ester of a polyol with a mixture of two or more fatty acids is preferable, and an ester of a polyol that has 2 or more esters 20 or fewer hydroxyl groups with a mixture of two or more fatty acids each having 3 or more and 20 or fewer carbon atoms.

[00159] As examples of mixing two or more fatty acids, a mixed fatty acid of a combination of two or more fatty acids selected from the group consisting of fatty acids having 4 or more and 9 or less carbon atoms is preferable; at least one mixed fatty acid selected from the group consisting of a mixture of fatty acids of a combination of fatty acids with 8 and 9 carbon atoms, respectively, a mixed fatty acid of a combination of fatty acids with 5 and 9 atoms of carbon, respectively, and a mixed fatty acid of a combination of fatty acids with 4, 5, and 9 carbon atoms, respectively, is more preferred; and a mixed fatty acid of a combination of fatty acids having 8 and 9 carbon atoms, respectively, is even more preferred.

[00160] In the case of an ester with two or more fatty acids, the ester may be a mixture of two or more esters of a fatty acid and a polyol.

[00161] Preferably, the number average molecular weights (Mn) of PVE, PAG, ECP and POE are each independently 300 or more and 3000 or less.

[00162] When the number average molecular weight (Mn) is 300 or more, the performance of lubrication and sealing becomes favorable. On the other hand, when the number average molecular weight (Mn) is 3000 or less, the compatibility with low HFO content refrigerant becomes favorable.

[00163] From the above point of view, the number average molecular weights (Mn) of PVE, PAG, ECP and POE are each independently more preferably 350 or more, and even more preferably 400 or more, and more preferably 1500 or less, and even more preferably 1,200 or less.

[00164] The number average molecular weight (Mn) is a value measured by the method described in the Examples section as mentioned later.

Other Base Oil

[00165] The base oil (P) may also contain another base oil, in addition to at least one base oil selected from the group consisting of PVE, PAG, ECP and POE within a range where the effects of the present invention are not harmed.

[00166] Examples of other base oil include a mineral oil or other synthetic oil not corresponding to the above-mentioned PVE, PAG, ECP and POE, such as a polyester, a polycarbonate, an α-olefin oligomer hydride, a compound of alicyclic hydrocarbons, and an alkylated aromatic hydrocarbon compound.

[00167] Examples of mineral oil include refined oils obtained by submitting the lubricating oil fractions obtained by atmospherically distillation of an intermediate base, paraffinic or naphthenic crude oil, or by vacuum distillation of an atmospheric residual oil obtained by distillation from crude oil to at least one of solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing and hydrorefining; oils produced by the isomerization of a mineral oil-based wax; and oils produced by isomerization of GTL WAX (gas-to-liquid wax) which is produced by the Fischer-Tropsch process or the like.

[00168] Mineral oil and other synthetic oil can be used alone or in combination with two or more of them.

[00169] In the case where the base oil (P) contains the other base oil, from the point of view of providing a refrigeration oil with excellent compatibility with the refrigerant with low HFO content, the content of the other base oil is preferably 0% by mass or more and 50% by mass or less, more preferably 0% by mass or more and 30% by mass or less, even more preferably 0% by mass or more and 10% by mass or less, and even more preferably 0% by mass or more and 2% by mass or less based on 100% by mass of the total base oil content (P).

[00170] In the refrigeration oil which is an embodiment of the present invention, the content of the base oil (P) 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 based on the total content (100% by mass) of the refrigerating oil.

Base Oil Properties (P)

[00171] The base oil hydroxyl value (P) is 15 mg KOH/g or less.

[00172] When the hydroxyl value of the base oil (P) is greater than 15 mg KOH/g, the compatibility of the refrigeration oil with the refrigerant with low HFO content and the favorable electrical properties of the refrigeration oil composition resulting are not obtained.

[00173] From the above point of view, the hydroxyl value of the base oil (P) is preferably 10 mg KOH/g or less, more preferably 9 mg KOH/g or less, even more preferably 8 mg KOH/g or less, even more preferably 5 mg KOH/g or less, and even more preferably 3 mg KOH/g or less.

[00174] The base oil hydroxyl value (P) is a value measured by the method described in the Examples section, as mentioned later.

[00175] On the occasion of the synthesis of various base oils, the hydroxyl value of the base oil (P) can be, for example, regulated by adjusting the charged amounts of the raw materials and/or a hydrogenation treatment condition after the polymerization.

[00176] The kinematic viscosity at 100°C (hereinafter referred to as "kinematic viscosity 100°C") of the base oil (P) is preferably 2.0 mm2/s or more and 50.0 mm2/s or less.

[00177] When the kinematic viscosity is 2.0 mm2/s or more, the lubrication and sealing performance becomes favorable. On the other hand, when the kinematic viscosity is 50.0 mm2/s or less, the compatibility with low HFO content refrigerant becomes favorable.

[00178] From the above point of view, the kinematic viscosity at 100°C of the base oil (P) is preferably 3.0 mm2/s or more, more preferably 4.0 mm2/s or more, and even more preferably 5.0 mm2/s or more, and is preferably 40.0 mm2/s or less, more preferably 30.0 mm2/s or less, even more preferably 25.0 mm2/s or less, and even more preferably 15 .0 mm2/s or less.

[00179] The kinematic viscosity 100°C of the base oil (P) is a value measured by the method described in the Examples section, as mentioned later.

[00180] From a safety point of view, the base oil flash point (P) is preferably 180°C or higher. From the above point of view, the flash point of the base oil (P) is more preferably 190°C or higher, and even more preferably 195°C or higher.

[00181] Although an upper limit of the base oil flash point (P) is not particularly limited, it is, for example, 300°C or lower.

[00182] The base oil flash point (P) is a value measured by the method described in the Examples section, as mentioned later.

Other Additives

[00183] The refrigeration oil may contain, in addition to the base oil (P), various additives (hereinafter also referred to as "other additives") that a refrigeration oil may contain. Like the other additives, at least one additive selected from the group consisting of an antioxidant, an oil improver, an extreme pressure agent, an acid scavenger, an oxygen scavenger, a metal deactivator, a rust inhibitor and a antifoaming agent are exemplified.

[00184] In the case where the refrigeration oil contains the above-mentioned other additives, from the point of view of effects, economy and etc., the total content of the above-mentioned other additives 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, and is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less, based on the total content (100% by mass) of the refrigerating oil.

[00185] However, the refrigeration oil may not contain the other additives mentioned above.

[00186] Examples of the antioxidant include a phenol-based antioxidant and an amine-based antioxidant.

[00187] Examples of phenol-based antioxidant include a monophenol-based antioxidant and a polyphenol-based antioxidant.

[00188] Examples of the monophenol-based antioxidant include alkyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionates (alkyl group examples include those with 4 or more and 20 or less carbon atoms , and preferably 8 or more and 18 or fewer carbon atoms), such as n-octyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl propionate), 6-methylheptyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) and n-octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate; 2,6-di-tert-butyl-4-alkylphenols (the alkyl group has 1 or more and 4 or fewer carbon atoms), such as 2,6-di-tert-butyl-4-methylphenol and 2,6-di -tert-butyl-4-ethylphenol; 2,4-dimethyl-6-tert-butylphenol, and 2,6-di-tert-amyl-p-cresol.

[00189] Examples of the polyphenol-based antioxidant 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'-butylidenebis(3-methyl-6-tert-butylphenol), 4,4'-isopropyllidenebis(2,6-di-tert-butylphenol), 2,2'-methylenebis(4-methyl-6-nonylphenol) ), 2,2'-isobutylidenebis(4,6-dimethylphenol), 2,2'-methylenebis(4-methyl-6-cyclohexylphenol), 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), bis(3,5-di-tert-butyl-4-hydroxybenzyl) sulfide, and thiodiethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate].

[00190] Examples of the amine-based antioxidant include dialkyl diphenylamines such as dibutyl 4,4'-diphenylamine and dioctyl 4,4'-diphenylamine; phenyl-α-naphthylamine, such as an alkylphenyl-α-naphthylamine and phenyl-α-naphthylamine; and N,N'-diphenyl-p-phenylenediamine.

[00191] The cooling oil may contain the antioxidant alone or it may contain a combination of two or more of them.

[00192] The antioxidant content 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 based on the total content (100% by mass) of the refrigerating oil from the point of view that an acid number increase of the resulting refrigerating oil is suppressed, and that the high temperature oxidation stability is improved more easily. The aforementioned content is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less from the point of view of making it easy to display an effect corresponding to the content.

[00193] Examples of the oiliness improver include saturated or unsaturated aliphatic monocarboxylic acids such as stearic acid and oleic acid; polymerized fatty acids, such as an acid dimer and a hydrogenated acid dimer; hydroxy fatty acids, such as ricinoleic acid and 12-hydroxystearic acid; saturated or unsaturated aliphatic monoalcohols, such as lauryl alcohol and oleyl alcohol; saturated or unsaturated aliphatic monoamines, such as stearylamine and oleylamine; saturated or unsaturated aliphatic monocarboxylic acid amides such as lauric acid amide and oleic acid amide; and partial esters between a polyhydric alcohol, such as glycerin and sorbitol, and a saturated or unsaturated aliphatic monocarboxylic acid.

[00194] The cooling oil may contain the oiliness enhancer alone or it may contain a combination of two or more thereof.

[00195] The oiliness improver content is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 0.1% by mass or more, and it is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 2% by mass or less, based on the total content (100% by mass) of the refrigeration oil.

[00196] Examples of the extreme pressure agent include a phosphorus-based extreme pressure agent. Examples of the phosphorus-based extreme pressure agent include a phosphoric acid ester, a phosphorous acid ester, a phosphoric acid ester, an acid phosphorous ester and amine salts.

[00197] Examples of the phosphoric acid ester include a triaryl phosphate, a trialkyl phosphate, a monoalkyl diaryl phosphate, a dialkyl monoaryl phosphate and a trialkenyl phosphate. The "aryl" mentioned in connection with the extreme pressure agent is a concept that includes not only a functional group composed of only one aromatic ring, but also an alkylaryl and an arylalkyl.

[00198] Examples of the phosphoric acid ester include triaryl phosphates such as triphenyl phosphate, tricresyl phosphate, benzyl diphenyl phosphate, cresyl diphenyl phosphate, dicresyl phenyl phosphate, propylphenyl diphenyl phosphate, dipropylphenyl phenyl phosphate, ethylphenyl diphenyl phosphate, diethylphenyl phenyl phosphate, triethylphenyl phosphate, tripropylphenyl phosphate, butylphenyl diphenyl phosphate, dibutylphenyl phenyl phosphate and tributylphenyl phosphate; alkyl phosphates, such as tributyl phosphate, ethyldibutyl phosphate, trihexyl phosphate, tri(2-ethylhexyl) phosphate, tridecyl phosphate, trilauryl phosphate, trimyristyl phosphate, tripalmityl phosphate, and tristearyl phosphate; ethyl diphenyl phosphate and trioleyl phosphate.

[00199] Examples of the acidic phosphoric acid include various alkyl acid phosphates and dialkyl acid phosphates.

[00200] Examples of the phosphorous acid ester include various trialkyl phosphites, triaryl phosphites, monoalkyl diaryl phosphites, monoaryl dialkyl phosphites and trialkenyl phosphites.

[00201] Examples of the acidic phosphoric acid ester include various dialkyl hydrogen phosphite, dialkenyl hydrogen phosphite and diaryl hydrogen phosphite.

[00202] The phosphorus-based extreme pressure agent can also be a phosphoric acid ester containing sulfur atom, such as trithiophenyl phosphate or the like. Examples of the amine salt include amine salts of an acid phosphoric acid ester or an acid phosphorous ester. The amine forming the amine salt can be a primary, secondary or tertiary amine.

[00203] The refrigeration oil may contain the extreme pressure agent alone or it may contain a combination of two or more of these.

[00204] The content of the extreme pressure agent is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more and is preferably of 5% by mass or less, more preferably 3% by mass or less and even more preferably 2% by mass or less, on a total content basis (100% by mass) of the refrigerating oil.

[00205] Examples of the acid scavenger include an epoxy compound. Examples of the epoxy compound include a glycidyl ether compound, cyclohexene oxide, dα-olefin oxide and epoxidized soybean oil. Of these, a glycidyl ether compound is preferred.

[00206] Examples of the glycidyl ether compound include an aliphatic monoalcohol that preferably has 3 or more and 30 or less carbon atoms, more preferably 4 or more and 24 or less carbon atoms, and even more preferably 6 or more and 16 or fewer carbon atoms; an aliphatic polyhydric alcohol having 3 or more and 30 or fewer carbon atoms, more preferably 4 or more and 24 or fewer carbon atoms, and even more preferably 6 or more and 16 or fewer carbon atoms; and a glycidyl ether derived from aromatic compounds containing 1 or more hydroxyl groups. The aliphatic monoalcohol or the aliphatic polyhydric alcohol can be linear, branched or cyclic and can also be saturated or unsaturated.

[00207] In the case of an aliphatic polyhydric alcohol or in the case of an aromatic compound containing two or more hydroxyl groups, it is preferable that all hydroxyl groups are etherified glycidyl from the point of view of the stability of the cooling oil and the suppression of an increase in a hydroxyl value.

[00208] Examples of the glycidyl ether compound include phenyl glycidyl ether, an alkyl glycidyl ether and an alkylene glycol glycidyl ether. Examples of the glycidyl ether compound include a glycidyl ether derived from a linear, branched, or cyclic saturated aliphatic monoalcohol having 6 or more and 16 or fewer carbon atoms (i.e., an alkyl glycidyl ether in which an alkyl group has 6 or more and 16 or fewer carbon atoms). Examples of such glycidyl ether include 2-ethylhexyl glycidyl ether, isononyl glycidyl ether, decyl glycidyl ether, glycidyl lauryl ether and glycidyl myristyl ether.

[00209] The refrigerating oil may contain the acid scavenger alone or it may contain a combination of two or more thereof.

[00210] The acid scavenger content 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 based on the total content (100% by mass) of the refrigeration oil. The foregoing content is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less from the point of view of facilitating the display of an effect that matches the content.

[00211] Examples of the oxygen scavenger include sulfur-containing aromatic compounds such as 4,4'-thiobis(3-methyl-6-tert-butylphenol), diphenyl sulfide, dioctyl diphenyl sulfide, dialkyl diphenylene sulfide, benzothiophene, dibenzothiophene, phenothiazine, benzothiapyran, thiapyran, thianthrene, dibenzothiapyran and diphenylene disulfide; aliphatic unsaturated compounds such as various olefins, dienes and trienes; and terpenes that contain a double bond.

[00212] The refrigerant oil may contain the oxygen scavenger alone or it may contain a combination of two or more thereof.

[00213] The content of the oxygen scavenger is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 0.1% by mass or more, and is preferably 10 % by mass or less, more preferably 5% by mass or less and even more preferably 3% by mass or less, based on the total content (100% by mass) of the refrigeration oil.

[00214] Examples of the metal deactivator include an N-[N,N'-dialkyl (alkyl group having 3 or more and 12 carbon atoms) aminomethyl]triazole.

[00215] Examples of the rust inhibitor include a metal sulfonate, an aliphatic amine, an organic phosphoric acid ester, an organic phosphorous acid ester, an organic sulfonic acid metal salt, an organic phosphoric acid metal salt, an organic ester of alkenyl succinic acid and a polyhydric alcohol ester.

[00216] Examples of the antifoaming agent include silicone oils such as dimethyl polysiloxane and polymethacrylates.

[00217] The refrigeration oil may contain the metal deactivator, the oxidation inhibitor or the antifoam agent, respectively alone or it may contain a combination of two or more of these.

[00218] In the case where the refrigeration oil contains the metal deactivator, the rust inhibitor, or the antifoaming agent, the content of each of them is preferably 0.1% by mass or more, more preferably 0. 5% by mass or more and even more preferably 0.1% by mass or more and is preferably 10% by mass or less, more preferably 5% or less and even more preferably 3% by mass or less, with based on the total content (100% by mass) of the refrigerating oil.

Mixed Soda

[00219] Refrigeration oil is a refrigeration oil for a mixed refrigerant (low HFO content refrigerant) that contains less than 40% by mass of an unsaturated fluorinated hydrocarbon compound (HFO) based on the total content (100% by mass) of the mixed soda.

[00220] As mentioned above, as the HFO content in the mixed refrigerant is low, there is a tendency for the compatibility between the refrigerant oil and the mixed refrigerant to be worse.

[00221] Consequently, from the point of view of ensuring a wider temperature region, where the refrigerant oil and the mixed refrigerant are able to be matched with each other in the resulting refrigerant oil composition, the content of HFO mixed refrigerant is preferably of 15% by mass or more, more preferably 20% by mass or more and even more preferably 25% by mass or more based on the total content (100% by mass) of the mixed refrigerant.

[00222] Meanwhile, the refrigeration oil has excellent compatibility even with a mixed refrigerant which has a low HFO content as a refrigerant with a preceding low HFO content. Accordingly, in the case where it is intended to control the minor HFO content in the mixed refrigerant, the HFO content in the mixed refrigerant is preferably 37% by mass or less, more preferably 35% by mass or less, even more preferably 32 % by mass or less and even more preferably 28% by mass or less based on the total content (100% by mass) of the mixed refrigerant.

[00223] The mixed refrigerant is described here.

(Compound of Unsaturated Fluorinated Hydrocarbon (HFO))

[00224] Examples of the unsaturated fluorinated hydrocarbon (HFO) compound include compounds with a carbon-carbon double bond such as fluorides of a straight or branched chain olefin having 2 or more and 6 or fewer carbon atoms; and a cyclic olefin having 4 or more and 6 or fewer carbon atoms.

[00225] More specifically, examples thereof include an ethylene having 1 or more and 3 or less (preferably 3) fluorine atoms introduced into it; a propene having 1 or more and 5 or less fluorine atoms introduced therein; a butene having 1 or more and 7 or fewer fluorine atoms introduced therein; a pentene having 1 or more and 9 or fewer fluorine atoms introduced therein; a hexene having 1 or more and 11 or fewer fluorine atoms introduced therein; a cyclobutene having 1 or more and 5 or less fluorine atoms introduced therein; a cyclopentene having 1 or more and 7 or fewer fluorine atoms introduced therein; and a cyclohexene having 1 or more and 9 or fewer fluorine atoms introduced therein.

[00226] Of these unsaturated fluorinated hydrocarbon compounds, a propene fluoride is preferred; a propene having 3 or more and 5 or less fluorine atoms introduced is more preferred; and a propene having 4 fluorine atoms introduced is even more preferred.

[00227] Suitable examples of the unsaturated fluorinated hydrocarbon compound 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 (R1234yz), 1,1,2-trifluoroethylene (R1123), and (Z)-1,1,4,4,4-hexafluoro-2-butene (R1336mzz( Z)). Of these unsaturated fluorinated hydrocarbon compounds, at least one selected from the group consisting of R1234yf, R1234ze, R1123 and R1336mzz (Z) is preferred; at least one selected from the group consisting of R1234yf, R1234ze, and R1336mzz (Z) is more preferred; and at least one selected from the group consisting of R1234yf and R1234ze) is even more preferred.

[00228] These unsaturated fluorinated hydrocarbon compounds (HFOs) can be used singly or can be used in combination of two or more of them. Here, in case of using a combination of two or more HFOs, examples of these include a combination of R1234yf and R1234ze.

[00229] In the unsaturated fluorinated hydrocarbon compound containing the low HFO content refrigerant, the fluorine content of a propylene 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, even more preferably 90% by mass or more and 100% by mass or less, and even more preferably 100% by mass on a total content basis (100% by mass) of the fluorinated hydrocarbon compound unsaturated.

[00230] A refrigerant with a low HFO content is one that contains yet another refrigerant in addition to the HFO. As the other refrigerant, at least one selected from the group consisting of a saturated fluorinated hydrocarbon compound (HFC) and a natural refrigerant is preferably exemplified; and at least one selected from the group consisting of a saturated fluorinated hydrocarbon (HFC) compound, a hydrocarbon (HC) based refrigerant, carbon dioxide (CO2) and ammonia (NH3) is most preferably exemplified.

[00231] That is, the low HFO content refrigerant is preferably a mixed refrigerant that contains less than 40% by mass of the unsaturated fluorinated hydrocarbon compound (HFO) based on the total amount of mixed refrigerant and at least one selected from the group consisting of a saturated fluorinated hydrocarbon (HFC) compound and a natural refrigerant; and, more preferably, a mixed refrigerant that contains less than 40% of the unsaturated fluorinated hydrocarbon compound (HFO) based on the total amount of the mixed refrigerant and at least one selected from the group consisting of a hydrocarbon compound (HFC), a refrigerant based on hydrocarbon (HC), carbon dioxide and ammonia.

Saturated fluorinated hydrocarbon compound (HFC)

[00232] The saturated fluorinated hydrocarbon compound (HFC) is preferably an alkane fluoride having 1 or more and 4 or less carbon atoms, more preferably an alkane fluoride having 1 or more and 3 or fewer carbon atoms , and even more preferably a fluoride of an alkane having 1 or 2 carbon atoms (methane or ethane). Examples of methane or ethane fluoride 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). Of these saturated fluorinated hydrocarbon compounds, at least one selected from the group consisting of R32, R134a and R125 is preferred; and R32 is more preferred.

[00233] These saturated fluorinated hydrocarbon compounds (HFCs) can be used singly or can be used in combination of two or more of them. Here, case examples of using a combination of two or more of them include a combination of R32 and R125 and a combination of R32, R125, and R134a, with a combination of R32, R125, and R134a being preferred.

natural soda

[00234] As the natural refrigerant, at least one selected from the group consisting of a hydrocarbon-based refrigerant (HC), carbon dioxide (CO2 or carbonic acid gas) and ammonia is exemplified. These natural coolants can be used alone or they can be used in combination with two or more of them.

[00235] The hydrocarbon-based refrigerant is preferably a hydrocarbon having 1 or more and 8 or less carbon atoms, more preferably a hydrocarbon having 1 or more and 5 or less carbon atoms, and even more preferably a hydrocarbon having has 3 or more and 5 or fewer carbon atoms. When the carbon number is 8 or less, the boiling point of the soda does not become excessively high, and therefore it is preferable as the soda. As the hydrocarbon-based refrigerant, at least one selected from the group consisting of methane, ethane, ethylene, propane (R290), cyclopropane, propylene, n-butane, isobutane (R600a), 2-methylbutane, n-pentane are exemplified , isopentane, cyclopentane, isobutane and n-butane and these can be used singly or can be used in combination of two or more of them.

[00236] Like low HFO refrigerant, a mixed refrigerant, which includes less than 40% by mass of the above-mentioned fluorinated unsaturated hydrocarbon compound (HFO), based on the total amount of the mixed refrigerant and the hydrocarbon compound (HFC) is exemplified even more preferably.

[00237] As a suitable mixed refrigerant, a mixed refrigerant that contains less than 40% by mass of the above-mentioned fluorinated unsaturated hydrocarbon compound (HFO), on a basis of the total amount of the mixed refrigerant, more than 40% by mass of at least one selected from the group consisting of 1,1,1,2,2-pentafluoroethane (R125) and 1,1,1,2-tetrafluoroethane (R134a) based on the total amount of mixed refrigerant and difluoromethane (R32) ; or a mixed refrigerant containing less than 40% by mass of the above-listed fluorinated unsaturated hydrocarbon (HFO) compound, based on the total amount of the mixed refrigerant, and 60% by mass or more of difluoromethane (R32), based on the amount total mixed refrigerant is exemplified even more preferably.

[00238] As the mixed refrigerant that contains less than 40% by mass of HFO based on the total amount of mixed refrigerant, more than 40% by mass of at least one selected from the group consisting of R125 and R134a based on the total amount of mixed refrigerant and R32, a mixed refrigerant containing less than 40% by mass of HFO based on the total amount of mixed refrigerant, more than 40% by mass in the total of at least one selected from the group consisting of R125 and R134a based on total amount of mixed refrigerant and more than 10% by mass of R32 based on total amount of mixed refrigerant is even more preferably exemplified; and a mixed refrigerant that contains less than 40% by mass of HFO based on the total amount of the mixed refrigerant, more than 40% by weight based on the total amount of at least one selected from the group consisting of R125 and R134a based on the total amount of mixed refrigerant and more than 20% by mass of R32 based on the total amount of mixed refrigerant is further preferably exemplified.

[00239] As a mixed refrigerant that contains less than 40% by mass of HFO based on the total amount of mixed refrigerant and 60% by mass or more of R32 based on the total amount of mixed refrigerant, a mixed refrigerant that contains less than 40% by mass of the HFO based on the total amount of mixed refrigerant and 65% by mass or more of R32 based on the total amount of mixed refrigerant is even more preferably exemplified; and a mixed refrigerant that contains less than 40% by mass of HFO based on the total amount of mixed refrigerant and 70% by mass or more of R32 based on the total amount of mixed refrigerant is further more preferably exemplified.

[00240] With respect to the HFO in the mixed refrigerant described as each of the combinations of refrigerants in such a mixed refrigerant (low HFO content refrigerant), the suitable modalities and the suitable HFO content are the same as those HFO modalities and content of HFO in said mixed refrigerant.

Cooling Oil Properties

[00241] The refrigeration oil has excellent compatibility with the refrigerant with low HFO content under either a high temperature environment and a low temperature environment.

[00242] A temperature of the separation of two layers on the high temperature side of the low HFO refrigerant refrigerant oil is preferably 35°C or more, more preferably 45°C or more, even more preferably 50°C or more and even more preferably 55°C or more.

[00243] A two-layer separation temperature on the low temperature side of the low HFO refrigerant refrigerant oil is preferably -15°C or less, more preferably -20°C or less, even more preferably -30° C or below, even more preferably -40°C or below and even more preferably -45°C or below.

[00244] In this order, "the two-layer separation temperature on the high temperature side of the refrigerant oil of the low HFO content refrigerant" and "the two-layer separation temperature on the low temperature side of the refrigerant oil low HFO refrigerant" above each means a value measured by the method described in the Examples section as mentioned later.

[00245] The volumetric resistivity of the refrigerant oil composition as a mixture of low HFO refrigerant and refrigerant oil, which is measured by the method described in the Examples section as mentioned later, is preferably 3.0 10x6 Q-m or more, more preferably 1.0 10x7 Q-m or more, even more preferably 5.0 10x7 Q-m or more, even more preferably 1.0 10x8 Q-m or more, and even more preferably 2.0 10x8 Q-m or more.

Refrigeration Oil Production Method

[00246] The aforementioned method of producing the refrigerating oil according to an embodiment of the present invention is a method of producing a refrigerating oil, the refrigerating oil being one that contains less than 40% by mass of a compound of fluorinated unsaturated hydrocarbon (HFO) based on the total amount of the mixed refrigerant and that it contains a base oil (P), which includes at least one selected from the group consisting of a polyvinyl ether (PVE), a polyalkylene glycol (PAG) , a copolymer (ECP) of a poly(oxy)alkylene glycol or its monoether and a polyvinyl ether and a polyol ester (POE), with a base oil hydroxyl value (P) being 15 mg KOH/g or less .

[00247] The aforementioned production method is a method of producing a refrigerant oil for a mixed refrigerant (low HFO content refrigerant) that contains less than 40% by mass of an unsaturated fluorinated hydrocarbon compound (HFO) based on the total amount of the mixed refrigerant, the refrigeration oil being obtained by mixing a base oil (P) which includes at least one selected from the group consisting of a polyvinyl ether (PVE), a polyalkylene glycol (PAG), a copolymer (ECP) of a poly(oxy)alkylene glycol or its monoether and a polyvinyl ether and a polyol ester (POE), with a base oil hydroxyl value (P) being 15 mg KOH/g or less.

[00248] In the foregoing production method, the above-mentioned other additives can be mixed in addition to the base oil (P).

[00249] Detailed explanations of the base oil (P) and the other additives are the same as those mentioned above, and therefore the explanations are omitted.

[00250] Low HFO refrigerant is also the same as the one mentioned above.

Composition of refrigeration oil

[00251] The refrigeration oil to be used is the one resulting from the mixture with the aforementioned low HFO content refrigerant. That is, the refrigeration oil composition according to an embodiment of the present invention contains the low HFO refrigerant and the refrigeration oil. Detailed explanations of low HFO refrigerant and refrigerant oil are the same as mentioned above, so the explanations are omitted.

[00252] A proportional content of refrigerant oil and low HFO refrigerant ((refrigerant oil)/(low HFO refrigerant)) in the refrigerant oil composition is preferably 1/99 or more and 99 /1 or less, more preferably 1/99 or more and 90/10 or less, even more preferably 5/95 or more and 70/30 or less, and even more preferably 5/95 or more and 60/40 or less in terms of a mass proportion. By allowing the foregoing mass ratio of refrigerating oil and low-HFO refrigerant to be within the foregoing range, it is possible to obtain proper lubricity and cooling capacity in a refrigerator.

[00253] The total content of the refrigerant oil and low HFO refrigerant in the refrigerant oil composition 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, even more preferably 98% by mass or more and 100% by mass or less, and even more preferably 100% by mass based on the total content of (100% by mass) of the refrigeration oil composition.

Properties of refrigeration oil composition

[00254] The refrigerant oil composition has excellent compatibility with the refrigerant with low HFO content under either a high temperature environment and a low temperature environment.

[00255] A two-layer separation temperature on the high temperature side of the refrigerant oil composition is preferably 35°C or more, more preferably 45°C or more, even more preferably 50°C or more, and even more preferably 55°C or more.

[00256] A two-layer separation temperature on the low temperature side of the refrigeration oil composition is preferably -15°C or less, more preferably -20°C or less, even more preferably -30°C or less, even more more preferably -40°C or less and even more preferably -45°C or less.

[00257] In this application, above mentioned "the two-layer separation temperature on the high temperature side of the refrigerant oil composition" and "the two-layer separation temperature on the low temperature side of the refrigerant oil composition" means , each a value measured by the method described in the Examples section, as mentioned later.

[00258] The "two layer separation temperature on the high temperature side of the refrigerant oil composition" and "two layer separation temperature on the low temperature side of the refrigerant oil composition" are the same as those mentioned in "two-layer separation temperature on the high-temperature refrigerant oil side of the low-HFO refrigerant" and "two-layer separation temperature on the low-temperature refrigerant oil side of the low-HFO refrigerant", respectively.

[00259] From the point of view of improving insulation, the volumetric resistivity of the cooling oil composition is preferably 3.0 x 106 Q-m or more, more preferably 1.0x107 Q-m or more, even more preferably 5, 0x107 Q-m or more, but even more preferably 1.0x108 Q-m or more, and even more preferably 2.0x108 Q-m or more.

Refrigeration Oil Composition Production Method

[00260] The composition of the refrigeration oil is obtained by mixing the above-mentioned refrigeration oil and the above-mentioned low HFO content refrigerant. That is, the method of producing the refrigerating oil composition according to an embodiment of the present invention is a method of producing a refrigerating oil composition that includes a step of mixing the above-mentioned refrigerating oil and the low content refrigerant. of HFO mentioned above.

[00261] Detailed explanations of low HFO refrigerant and refrigerant oil are the same as mentioned above, and therefore the explanations are omitted.

fridge

[00262] The refrigerating oil or refrigerating oil composition is charged inside the refrigerator and used.

[00263] The refrigerator is preferably a compression type refrigerator that uses the aforementioned low HFO refrigerant, and more preferably one that has a refrigeration cycle that includes a compressor, a condenser, an expansion mechanism (e.g. , an expansion valve) and an evaporator or that has a refrigeration cycle, which includes a compressor, a condenser, an expansion mechanism, a dryer and an evaporator.

[00264] Refrigeration oil is, for example, used for the lubrication of a sliding portion to be supplied in a compressor or the like. The sliding portion is not particularly limited.

[00265] All refrigerators are those that use refrigerant with low HFO content. Although refrigerator is applied to, for example, a car air conditioner such as an open type car air conditioner and an electric car air conditioner, an air conditioner such as a room air conditioner and a packaged air conditioner, a gas heat pump (GHP), a refrigeration system such as a freezer, a refrigerator, a vending machine and a display stand, a hot water system such as a water heater and a floor heater and a heating system, it is preferably applied in an air conditioning application, and more preferably applied to a room air conditioner or a packaged air conditioner.

EXAMPLES

[00266] The present invention is more specifically described herein with reference to the Examples, but it should be understood that the present invention is in no way limited by these examples.

[00267] The respective physical properties of each refrigeration oil and each refrigeration oil composition were determined as follows.

Hydroxyl Value

[00268] Measured by neutralization titration in accordance with JIS K0070:1992.

Kinematic viscosity at 100°C

[00269] Measurement in accordance with JIS K2283:2000.

Number average molecular weight (Mn)

[00270] Measured with a gel permeation chromatograph (GPC). As for GPC, two columns of "TSKgel SuperMultipore HZ-M", manufactured by Tosoh Corporation successively connected to each other were used; tetrahydrofuran was used as an eluent; the measurement was performed using a refractive index detector (IR detector) for detection; and the number average molecular weight (MN) was determined using polystyrene as a standard sample.

Ignition point

[00271] Measured in accordance with JIS K2265-4:2007 (Cleveland Open Cup Method).

Refrigerant Compatibility

[00272] A refrigeration oil composition that contains 10% by mass of a refrigeration oil on a basis of the total amount of the refrigeration oil composition and 90% by mass of a mixed refrigerant (refrigerant with low HFO content) that contains less than 40% by mass of a fluorinated unsaturated hydrocarbon compound (HFO) based on the total amount of mixed refrigerant [refrigerant oil composition (refrigerant oil)/( low HFO content refrigerant) = 10/90 ( mass ratio)] was prepared in each of the combinations shown in Tables 3 to 7 below.

[00273] Using the resulting refrigeration oil composition as an evaluation sample, the separation temperature in two layers on each of the high temperature sides and low temperature sides was measured by a method mentioned below, which thus evaluates the compatibility of the refrigerant oil with the low HFO content refrigerant.

[00274] Separation temperature in two layers on the high temperature side of the refrigerant with low HFO content: separation temperature on the high temperature side

[00275] The resulting composition of the refrigeration oil was charged into a pressure-resistant glass ampoule and the ampoule was connected to a vacuum pipe and a refrigerant pipe and then subjected to vacuum deaeration at room temperature (25°C ). Subsequently, the ampoule was cooled with liquid nitrogen and a predetermined amount of the low HFO content refrigerant was collected in the ampoule through the refrigerant tube, followed by sealing the ampoule, thus preparing an ampoule that has a measurement sample captured there.

[00276] Thereafter, the ampoule was kept in a thermostat; the ampoule was irradiated with a laser; the temperature of the thermostat was raised from room temperature (25°C) to 70°C at a rate of 1°C/min while the luminous transmittance of the bulb was measured; and the temperature of the thermostat, when the light transmittance of the light bulb reached 50% of the light transmittance of the light bulb at room temperature, was designated as a temperature of separation into two layers on the high temperature side of the refrigerant oil, as a measurement object to from the low HFO content refrigerant (in Tables 3 to 7 below, referred to simply as "separation temperature on the high temperature side"). It is indicated that the higher the two-layer separation temperature on the high temperature side of the refrigerant oil from the low HFO refrigerant, the better the compatibility with the low HFO refrigerant at a high temperature.

[00277] A refrigerating oil composition that does not undergo separation into two layers up to 70°C is expressed as "70 or more" in Tables 3 to 7 below.

[00278] A refrigeration oil composition that has already undergone separation into two layers at a time point of 25°C is expressed as "Separated" in Tables 3 to 7 below.

[00279] Separation temperature in two layers on the low temperature side of the refrigerant with low HFO content: separation temperature on the low temperature side

[00280] A two-layer low-temperature side separation temperature (in Tables 3 to 7 below referred to simply as "low-temperature side separation temperature") was measured by adopting the same method as the temperature measurement method of separation into two layers on the high temperature side of the low HFO content refrigerant, except that at the time of measurement, the ampoule was cooled from ambient temperature at a rate of -1°C/min. It is indicated that the lower temperature of the two-layer separation on the low temperature side of the refrigerant oil of the low HFO content refrigerant, the better the compatibility with the low HFO content refrigerant at low temperature.

[00281] A refrigeration oil composition that does not undergo separation into two layers down to -50°C is expressed as "-50 or less" in Tables 3 to 7 below.

[00282] A refrigeration oil composition that has already undergone separation into two layers at a time point of 25°C is expressed as "Separated" in Tables 3 to 7 below.

Electrical Properties

[00283] A refrigerating oil composition that contains 50% by mass of a refrigerant oil and 50% by mass of a refrigerant with low HFO content based on the total amount of the refrigerating oil composition [cooling oil composition (oil of refrigeration)/(low HFO refrigerant) = 50/50 (mass ratio)] was prepared in each of the combinations shown in Tables 3 to 7 below.

[00284] Using the composition of the resulting refrigeration oil as an evaluation sample, the volumetric resistivity was measured using a method mentioned below, thus evaluating the electrical properties. It is indicated that the higher the volumetric resistivity, the better the insulation.

Volumetric Resistivity

[00285] Measure in accordance with JIS C2101: 2010.

[00286] The physical properties of the base oil (P) that the refrigeration oil composition shows in each of the tables 3 to 7, as evaluated in the respective examples and respective comparative examples and the composition of the refrigerant with low HFO content used on the occasion of preparing the composition of the refrigeration oil in the evaluation of the above mentioned properties is shown in tables 1 and 2 respectively. Table 1 Table 2 *: The value in the table expresses the content (% by mass) of each refrigerant in the low HFO refrigerant

Examples 1 to 15

[00287] A refrigeration oil composition was prepared by mixing the refrigeration oil containing 100% by mass of the base oil (P) and the low HFO content refrigerant shown in each of the aforementioned tables 1 and 2 were mixed in a combination shown in each of Tables 3 to 7 below and evaluated according to the above mentioned evaluation methods. The results obtained are shown in Tables 3 to 7, respectively.

Comparative Examples 1 to 15

[00288] A refrigeration oil composition was prepared by mixing the refrigeration oil containing 100% by mass of base oil (P) and the low HFO content refrigerant shown in each of the aforementioned tables 1 and 2 were mixed in a combination shown in each of Tables 3 to 7 below and evaluated according to the above mentioned evaluation methods. The results obtained are shown in Tables 3 to 7, respectively. Table 3 Table 4 Table 5 : na: not measured Table 6 Table 7

[00289] As shown in Tables 3 to 7, it was confirmed that the compositions for refrigerators of Examples 1 to 15 that each use the refrigeration oil that contains 100% by mass of the base oil (P) that has a value of hydroxyl of 15 mg KOH/g or less are not only excellent in compatibility with each of the mixed refrigerants that contain less than 40% by mass of the unsaturated fluorinated hydrocarbon compound (HFO) based on the total amount of the mixed refrigerant, but also have excellent electrical properties compared to the refrigerator compositions of Comparative Examples 1 to 15, which use refrigeration oil which contains 100% by mass of the base oil which has the same molecular structure and which has a higher hydroxyl value than 15 mg KOH/g.

Industrial Applicability

[00290] The refrigeration oil that is an embodiment of the present invention has excellent compatibility with a mixed refrigerant that contains less than 40% by mass of the unsaturated fluorinated hydrocarbon compound (HFO) based on the total amount of the refrigerant mixture. Accordingly, the refrigerating oil is one which is suitably used as a refrigerating oil to be mixed in the refrigerating oil composition which uses the above-mentioned mixed refrigerant and is more preferably used for an air conditioning application and even more preferably applied in ambient air conditioners or packaged air conditioners.

[00291] Furthermore, the above-mentioned refrigeration oil which is an embodiment of the present invention is capable of providing a refrigeration oil composition with excellent electrical properties, and therefore, for example, is one that is most appropriately used as a refrigeration oil of a closed-type compression-type refrigerator using the above-mentioned mixed refrigerant.

Claims (4)

1. Refrigerating oil composition, characterized in that it comprises a mixed refrigerant and a refrigerating oil, wherein the mixed refrigerant comprises less than 40% by mass of an unsaturated fluorinated hydrocarbon compound based on the total amount of the refrigerant mixed, greater than 40% by mass of at least one selected from the group consisting of 1,1,1,2,2-pentafluoroethane and 1,1,1,2-tetrafluoroethane based on the total amount of the mixed refrigerant and difluoromethane , wherein the unsaturated fluorinated hydrocarbon compound is at least one selected from the group consisting of 2,3,3,3-tetrafluoropropene and 1,3,3,3-tetrafluoropropene, the refrigerant oil comprising a base oil including at least at least one selected from the group consisting of a polyvinyl ether, and a polyol ester, with a base oil hydroxyl value measured by neutralization titration in accordance with JIS K0070:1992 being 15 mg KOH/g or less. 2. Composition of refrigeration oil according to claim 1, characterized in that the hydroxyl value of the base oil is 10 mg KOH/g or less. 3. Refrigeration oil composition according to claim 1 or 2, characterized in that it further comprises at least one additive selected from the group consisting of an antioxidant, an oil improver, an extreme pressure agent, a acid, an oxygen scavenger, a metal deactivator, a rust inhibitor and an antifoaming agent. 4. Composition of refrigeration oil according to claim 3, characterized in that the additive is contained in an amount of 0.1% by mass or more and 10% by mass or less based on the total amount of the cooling oil. refrigeration.