Viscosity index improvers, refrigerator oils and working fluid compositions for refrigerators

Abstract

This invention relates to viscosity index improvers, etc., which are viscosity index improvers containing a copolymer (A) comprising a monomer (a) having fluorine atoms as represented by the following general formula (1) and a monomer (b) represented by the following general formula (2) as necessary constituent monomers, wherein the solubility parameter of the copolymer (A) is 8.1 to 10.0 (cal / cm³). 3 ) 1 / 2 The mass ratio (b / a) of the monomer (b) constituting the copolymer (A) to the mass of the monomer (a) is 0.01 to 42. [In general formula (1), R 1 It is a hydrogen atom or a methyl group; R 2 It is an alkylene group with 2 to 4 carbon atoms; p is an integer of 0 or 1; q is an integer of 0 to 20, and when q is 2 or more, R 2 They can be the same or different; Y is a monovalent group in which some or all of the hydrogen atoms in a hydrocarbon group with 1 to 40 carbon atoms are replaced by fluorine atoms. [In general formula (2), R 3 It can be a hydrogen atom or a methyl group; -X 1 - is a group represented by -O- or -NH-; R 4 It is an alkylene group with 2 to 4 carbon atoms; r is an integer of 0 or 1; s is an integer of 0 to 20, and when s is 2 or more, R 4 They can be the same or different; R 5 It consists of hydrocarbon groups with 1 to 40 carbon atoms.

Description

Technical Field

[0001] This invention relates to viscosity index improvers, refrigeration oils, and working fluid compositions for refrigeration machines. Background Technology

[0002] Due to the ozone layer depletion problem in recent years, hydrofluorocarbons (HFCs) are being used as refrigerants for refrigeration engine oils to replace chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). Consequently, the development of refrigerants with lower Global Warming Potential (GWP) than HFC refrigerants has been undertaken. Because of their good compatibility with such refrigerants, POEs (polyol esters) and similar materials have been used in lubricating oils (oxygen-containing base oils) for refrigeration engine oils in recent years (e.g., Patent Documents 1 and 2).

[0003] Furthermore, in recent years, from an energy-saving perspective, there has been a demand for further improvements in the viscosity index of refrigeration oils. However, there are limitations to increasing the viscosity index by changing the composition of POE. On the other hand, refrigeration oils that use viscosity index improvers such as polyalkylene glycols and alkyl methacrylate copolymers to improve the viscosity index are known (e.g., Patent Documents 3-7). However, the compatibility of these viscosity index improvers with refrigerants is insufficient, especially at low temperatures.

[0004] On the other hand, it is known that copolymers containing monomers having fluorine atoms as constituent monomers can be used as viscosity index improvers (e.g., Patent Documents 8 and 9). However, these viscosity index improvers are insoluble in refrigeration oils containing refrigerants and lubricants, and therefore cannot be used as viscosity index improvers for refrigeration oils.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 9-302370

[0008] Patent Document 2: Japanese Patent Application Publication No. 2019-158233

[0009] Patent Document 3: Japanese Patent Application Publication No. 2017-057278

[0010] Patent Document 4: Japanese Patent No. 6925323

[0011] Patent Document 5: Japanese Patent No. 6826987

[0012] Patent Document 6: Japanese Patent No. 6793127

[0013] Patent Document 7: Japanese Patent Application Publication No. 2017-197662

[0014] Patent Document 8: Japanese Patent Application Publication No. 1-245005

[0015] Patent Document 9: Japanese Patent No. 5755469 Summary of the Invention

[0016] The problem that the invention aims to solve

[0017] The purpose of this invention is to provide a viscosity index improver suitable for use in refrigeration oils, which has excellent solubility in refrigerants and oxygen-containing base oils, and when used in refrigeration oils, it has a high viscosity index improvement effect, thereby obtaining refrigeration oils with excellent low-temperature characteristics; it also provides refrigeration oils containing the viscosity index improver and refrigeration working fluid compositions containing the refrigeration oil.

[0018] Methods for solving problems

[0019] The inventors conducted in-depth research, which resulted in the realization of this invention.

[0020] That is, the present invention provides a viscosity index improver, which is a viscosity index improver containing a copolymer (A) containing a monomer (a) having fluorine atoms represented by the following general formula (1) and a monomer (b) represented by the following general formula (2) as necessary constituent monomers, wherein the solubility parameter of the copolymer (A) is 8.1 to 10.0 (cal / cm³). 3 ) 1 / 2 The mass ratio (b / a) of the monomer (b) in the monomer constituting copolymer (A) to the mass of the monomer (a) is 0.01 to 42.

[0021] [Chemistry 1]

[0022]

[0023] In general formula (1), R 1 It is a hydrogen atom or a methyl group; R 2 It is an alkylene group with 2 to 4 carbon atoms; p is an integer of 0 or 1; q is an integer of 0 to 20, and when q is 2 or more, R 2 They can be the same or different; Y is a monovalent group in which some or all of the hydrogen atoms in a hydrocarbon group with 1 to 40 carbon atoms are replaced by fluorine atoms.

[0024] [Chemistry 2]

[0025]

[0026] In general formula (2), R 3 It can be a hydrogen atom or a methyl group; -X 1 - is a group represented by -O- or -NH-; R4 It is an alkylene group with 2 to 4 carbon atoms; r is an integer of 0 or 1; s is an integer of 0 to 20, and when s is 2 or more, R 4 They can be the same or different; R 5 It consists of hydrocarbon groups with 1 to 40 carbon atoms.

[0027] In addition, one aspect of the present invention relates to a refrigeration oil containing a lubricating oil base oil and the aforementioned viscosity index improver.

[0028] Another aspect of the present invention relates to a working fluid composition for a refrigeration machine, comprising the aforementioned refrigeration oil and refrigerant.

[0029] The effects of the invention

[0030] The viscosity index improver of the present invention exhibits the following effects: it has excellent solubility in refrigerants and oxygen-containing base oils, and when used in refrigeration oils, it has a high viscosity index improvement effect, thereby enabling the production of refrigeration oils with excellent low-temperature characteristics. Detailed Implementation

[0031] The viscosity index improver of the present invention is a viscosity index improver containing a copolymer (A) having a fluorine atom as represented by the following general formula (1) and a monomer (b) as represented by the following general formula (2) as necessary constituent monomers, wherein the solubility parameter of the copolymer (A) is 8.1 to 10.0 (cal / cm³). 3 ) 1 / 2 The mass ratio (b / a) of the monomer (b) in the monomer constituting copolymer (A) to the mass ratio (b / a) of the monomer (a) is 0.01 to 42.

[0032] [Chemistry 3]

[0033]

[0034] In general formula (1), R 1 It is a hydrogen atom or a methyl group; R 2 It is an alkylene group with 2 to 4 carbon atoms; p is an integer of 0 or 1; q is an integer of 0 to 20, and when q is 2 or more, R 2 They can be the same or different; Y is a monovalent group in which some or all of the hydrogen atoms in a hydrocarbon group with 1 to 40 carbon atoms are replaced by fluorine atoms.

[0035] [Chemistry 4]

[0036]

[0037] In general formula (2), R 3 It can be a hydrogen atom or a methyl group; -X 1- is a group represented by -O- or -NH-; R 4 It is an alkylene group with 2 to 4 carbon atoms; r is an integer of 0 or 1; s is an integer of 0 to 20, and when s is 2 or more, R 4 They can be the same or different; R 5 It consists of hydrocarbon groups with 1 to 40 carbon atoms.

[0038] The solubility parameter of the structural unit derived from the above monomer (a) is preferably 6.5 to 9.0 (cal / cm³). 3 ) 1 / 2 .

[0039] In addition, the weight-average molecular weight of the copolymer (A) is preferably 1,000 to 2,000,000.

[0040] Furthermore, the viscosity index improver of the present invention preferably contains an oxygen-containing base oil in addition to the copolymer (A) described above. It should be noted that the oxygen-containing base oil (also referred to as oxygen-containing base oil (B)) contained in the viscosity index improver of the present invention is preferably used as a polymerization solvent during copolymer synthesis or as a diluent for the copolymer, and may be the same as or different from the oxygen-containing base oil used as a lubricating oil base oil in the refrigeration oil described later.

[0041] <Copolymer(A)>

[0042] In this invention, copolymer (A) uses monomer (a) having fluorine atoms as represented by the above general formula (1) and monomer (b) represented by the above general formula (2) as necessary constituent monomers, and the solubility parameter of copolymer (A) is 8.1 to 10.0 (cal / cm³). 3 ) 1 / 2 The mass ratio (b / a) of the monomer (b) in the monomer constituting copolymer (A) to the mass of the monomer (a) is 0.01 to 42.

[0043] The monomer (a) is described.

[0044] In general formula (1), R 1 The symbol represents a hydrogen atom or a methyl group. From the perspective of improving the viscosity index, a methyl group is preferred.

[0045] In general formula (1), R 2 Examples of alkylene groups having 2 to 4 carbon atoms include ethylene, isopropylene, 1,2-propylene or 1,3-propylene, isobutylene, and 1,2-butylene, 1,3-butylene or 1,4-butylene. From the perspective of improving viscosity index, ethylene is preferred.

[0046] R 2O represents an alkylene oxide with 2 to 4 carbon atoms, such as ethoxide, 1,2-propoxide or 1,3-propoxide, as well as 1,2-butoxide, 1,3-butoxide or 1,4-butoxide, etc.

[0047] p is an integer that is either 0 or 1.

[0048] q is an integer from 0 to 20, and from the perspective of solubility in oxygen-containing base oil (B), it is preferably an integer from 0 to 4, and more preferably an integer from 0 to 2.

[0049] R when q is 2 or more 2 They can be the same or different, (R) 2 O) q Some can be segmental or random. It should be noted that segmental refers to two or more R... 2 The same parts are continuously bonded.

[0050] In general formula (1), Y is a monovalent group in which some or all of the hydrogen atoms in a hydrocarbon group with 1 to 40 carbon atoms are replaced by fluorine atoms.

[0051] As a monovalent group in which a portion of the hydrogen atoms in a hydrocarbon group are replaced by fluorine atoms, examples include monovalent groups in straight-chain or branched chain aliphatic hydrocarbon groups in which a portion of the hydrogen atoms are replaced by fluorine atoms [e.g., straight-chain partially fluorinated alkyl groups with 1 to 40 carbon atoms {2,2,2-trifluoroethyl (-CH2CF3), 2,2,3,3-tetrafluoropropyl (-CH2CF2CHF2), 2,2,3,3,3-pentafluoropropyl (-CH2CF2CF3), 1H,1H,5H-octafluoropentyl (- CH2(CF2)3CHF2), 1H,1H,2H,2H-nonafluorohexyl (-CH2CH2(CF2)3CF3), 1H,1H,2H,2H-tetrafluorooctyl (-CH2CH2(CF2)5CF3), 1H,1H,2H,2H-heptafluorooctyl (-CH2CH2(CF2)7CF3), 1H,1H-nonadecafluorodecyl (-CH2(CF2)8CF3), -CH2(CF2)9CF3, -CH2(CF2) 10 CF3, -CH2(CF2) 12 CF3, -CH2(CF2) 15 CF3, -CH2(CF2) 18 CF3, -CH2(CF2) 20 CF3, -CH2(CF2) 22 CF3, -CH2(CF2) 24 CF3, -CH2(CF2) 26 CF3, -CH2(CF2) 28CF3, -CH2(CF2) 30 CF3, -(CH2)2CF3, -(CH2)3CF3, -(CH2)4CF3, -(CH2)5CF3, -(CH2)6CF3, -(CH2)7CF3, -(CH2)8CF3, -(CH2)9CF3, -(CH2) 10 CF3、-(CH2) 12 CF3、-(CH2) 14 CF3、-(CH2) 16 CF3、-(CH2) 18 CF3、-(CH2) 20 CF3, etc.; branched partially fluorinated alkyl groups with 3 to 30 carbon atoms {1,1,1,3,3,3-hexafluoroisopropyl (-CH(CF3)2), -CH(CF3)CF2CF3, -CH2CH(CF3)2, -CH(CF3)(CF2)3CHF2, -CH(CF2CF3)(CF2)2CF3, etc.}; partially fluorinated alkylene groups with 2 to 40 carbon atoms {e.g., difluoroethylene, etc.}; partially fluorinated alicyclic hydrocarbon groups with 3 to 40 carbon atoms {e.g., 2-fluorocyclohexyl, 3-fluorocyclohexyl or 4-fluorocyclohexyl, 4-(trifluoromethyl)cyclohexyl, etc.}; partially fluorinated aromatic hydrocarbon groups with 6 to 40 carbon atoms {e.g., 2-fluorophenyl, 3-fluorophenyl or 4-fluorophenyl, 2-fluorobenzyl, 3-fluorobenzyl or 4-fluorobenzyl, etc.}.

[0052] As a monovalent group in which all hydrogen atoms in a hydrocarbon group are replaced by fluorine atoms, examples include monovalent groups in straight-chain or branched chain aliphatic hydrocarbon groups in which all hydrogen atoms are replaced by fluorine atoms [e.g., straight-chain perfluoroalkyl groups with 1 to 40 carbon atoms {trifluoromethyl (-CF3), pentafluoroethyl (-CF2CF3), heptafluoropropyl (-(CF2)2CF3), nonafluorobutyl (-(CF2)3CF3), perfluoropentyl (-(CF2)4CF3), perfluorohexyl (-(CF2)5CF3), perfluoroheptyl (-(CF2)6CF3), perfluorooctyl (-(CF2)7CF3), perfluorononyl (-(CF2)8CF3), perfluorodecyl (-(CF2)9CF3), -(CF2)...] 10 CF3, -(CF2) 11 CF3, -(CF2) 13 CF3, -(CF2) 15 CF3, -(CF2) 17 CF3, -(CF2) 19 CF3, -(CF2) 21 CF3, -(CF2) 23 CF3, -(CF2) 29 CF3, -(CF2)39 CF3, etc., branched perfluoroalkyl groups with 3 to 40 carbon atoms {-CF(CF3)2, -C(CF3)3, -CF(CF3)CF2CF3, -CF2CF(CF3)2, -CF(CF3)(CF2)2CF3, -CF(CF2CF3)CF2CF3, -CF2C(CF3)3, -CF(CF3)(CF2)3CF3, -CF(CF2CF3)(CF2)2CF3, -(CF2)2C(CF3)3, -CF(CF3)(CF2)4CF3, -CF(CF2CF2CF3)(CF2)2CF3, -(CF2)3C(CF3)3, -CF(CF3)(CF2)5CF3, -CF (CF2CF2CF2CF3)(CF2)2CF3, -(CF2)4C(CF3)3, -CF(CF3)(CF2)6CF3, -CF(CF2CF2CF2CF2CF3)(CF2)2CF3, -(CF2)5C(CF3)3, -CF(CF3)(CF2)7CF3, -CF(CF2CF2CF2CF2CF2CF3)(CF2)2CF3, -(CF2)6C(CF3)3, etc.; perfluoroalkylene groups with 2 to 40 carbon atoms (e.g., tetrafluoroethylene); perfluoroalicyclic hydrocarbon groups with 3 to 40 carbon atoms (e.g., perfluorocyclohexyl); perfluoroaromatic hydrocarbon groups with 6 to 40 carbon atoms (e.g., perfluorophenyl).

[0053] As for Y in general formula (1), from the perspective of improving the viscosity index, it is preferable to be a monovalent group in which some or all of the hydrogen atoms in a straight-chain or branched aliphatic hydrocarbon group with 1 to 24 carbon atoms are replaced by fluorine atoms, further preferably a monovalent group in which some or all of the hydrogen atoms in a straight-chain or branched aliphatic hydrocarbon group with 8 to 20 carbon atoms are replaced by fluorine atoms, and particularly preferably a monovalent group in which some or all of the hydrogen atoms in a straight-chain or branched aliphatic hydrocarbon group with 10 to 18 carbon atoms are replaced by fluorine atoms.

[0054] Furthermore, from the perspective of ease of acquisition, it is preferable to use monovalent groups in which some or all of the hydrogen atoms in a straight-chain or branched aliphatic hydrocarbon group having 2 to 8 carbon atoms are replaced by fluorine atoms.

[0055] Furthermore, considering the processability of viscosity index improvers and their solubility in oxygen-containing base oils (B), monovalent groups in straight-chain or branched aliphatic hydrocarbon groups with 1 to 4 carbon atoms in which some or all hydrogen atoms are replaced by fluorine atoms are preferred.

[0056] Monomer (a) can be used alone or in combination with two or more.

[0057] Monomer (a) can be manufactured by known methods, for example, by the following methods: esterification of aliphatic or aromatic monools having 1 to 40 carbon atoms with (meth)acrylic acid; esterification of alkyl oxides (including alkyl oxides having 2 to 4 carbon atoms, such as ethylene oxide, propylene oxide, butane oxide, etc.) adducts of aliphatic or aromatic monools having 1 to 40 carbon atoms with (meth)acrylic acid; etherification of vinyl ether compounds having hydroxyl groups (e.g., 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, 4-hydroxybutyl vinyl ether, etc.) with aliphatic or aromatic monools having 1 to 40 carbon atoms; reaction of alkyl halogenated (alkyl halogenated with 2 to 4 carbon atoms) vinyl ethers (e.g., 2-chloroethyl vinyl ether, etc.) with aliphatic or aromatic monools having 1 to 40 carbon atoms in the presence of a palladium catalyst and an aliphatic amine; etc.

[0058] In addition, in this invention, "(meth)acrylic acid" refers to "acrylic acid and / or methacrylic acid".

[0059] Additionally, monomer (a) is commercially available from the following sources: 2,2,2-trifluoroethyl acrylate (product name "Biscoat 3F"), 2,2,3,3-tetrafluoropropyl acrylate (product name "Biscoat 4F"), 1H,1H,5H-octafluoropentyl acrylate (product name "Biscoat 8F"), 1H,1H,5H-octafluoropentyl methacrylate (product name "Biscoat 8FM"), 1H,1H,2H,2H-tridecylfluorooctyl acrylate (product name "Biscoat 13F") (all manufactured by Osaka Organic Chemicals Co., Ltd.), and 2,2,2-trifluoroethyl methacrylate (product name "LIGHT ESTER"). M-3F (manufactured by Kyoei Chemical Co., Ltd.), 2,2,3,3,3-pentafluoropropyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.), 1,1,1,3,3,3-hexafluoroisopropyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.), and 1H,1H-nonadecanofluorodecyl methacrylate (product name "1H,1H-perfluoro-N-decyl methacrylate", manufactured by Fujifilm and Koh Genuine Chemicals Co., Ltd.), 2-(perfluorooctyl)ethyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.). The products manufactured by Daikin Industries, Ltd. include {2-(perfluorobutyl)ethyl methacrylate, 2-(perfluorohexyl)ethyl methacrylate, 1H,1H,3H-tetrafluoropropyl methacrylate, 1H,1H,5H-octafluoropentyl methacrylate, 1H,1H,7H-dodecylheptyl methacrylate, 1H,1-(trifluoromethyl)trifluoroethyl methacrylate, 1H,1H,3H-hexafluorobutyl methacrylate}, 2-(perfluorobutyl)ethyl methacrylate (product name "CHEMINOX FAMAC-4"), (2-perfluorohexyl)ethyl methacrylate (product name "CHEMINOX FAMAC-6", both manufactured by Unimatec Corporation), and hexafluoro-2-propyl methacrylate ("product name HFIP-M", manufactured by Central Glass Corporation).

[0060] As a monomer (a), from the perspective of the treatability of the viscosity index improver and the solubility in oxygen-containing base oil (B), a fluoroalkyl (meth)acrylamide monomer having some or all of the hydrogen atoms in a straight-chain or branched alkyl group having 2 to 4 carbon atoms replaced by fluorine atoms is preferred, and 2,2,2-trifluoroethyl (meth)acrylate is even more preferred.

[0061] As monomer (a), from the perspective of solubility in refrigerant (C), fluoroalkyl (meth)acrylamide monomers having some or all of the hydrogen atoms of a straight-chain or branched alkyl group having 2 to 8 carbon atoms replaced by fluorine atoms are preferred, and 2-(perfluorohexyl)ethyl (meth)acrylate is more preferred.

[0062] In this invention, from the perspective of solubility in oxygen-containing base oil (B), the solubility parameter (hereinafter referred to as SP value) of the structural unit of monomer (a) (the structure in which the carbon-carbon double bond of monomer (a) reacts to become a single bond) is preferably 6.5 to 9.0 (cal / cm³). 3 ) 1 / 2 More preferably, it is 8.0–9.0 (cal / cm³). 3 ) 1 / 2 .

[0063] Regarding SP values, for example, in Y of general formula (1), if the proportion of hydrogen atoms in the alkyl group that are replaced by fluorine atoms is high, the degree of branching is high, or the number of carbon atoms is large, then the SP value tends to decrease; if the proportion of hydrogen atoms replaced by fluorine atoms is low, the degree of branching is low, or the number of carbon atoms is small, then the SP value tends to increase.

[0064] It should be noted that the SP value in this invention refers to the value (heat of vaporization and molar volume of atoms or functional groups at 25°C) recorded on page 152 (Table 5) of the Fedors method (Polymer Engineering and Science, February, 1974, Vol. 14, No. 2, pp. 147-154), calculated by mathematical formula (28) (page 153). Specifically, it can be calculated based on Δe recorded in Table 1 below, which is a parameter of the Fedors method. i and v i The value is calculated by substituting the values ​​corresponding to the types of atoms and groups of atoms in the molecular structure into the following mathematical formula.

[0065] SP value = (ΣΔe) i / ΣΔv i ) 1 / 2

[0066] [Table 1]

[0067]

[0068] For example, in the case of 2,2,2-trifluoroethyl methacrylate, it is described below.

[0069] -CH2-C(CH3)-CO-O-CH2-CF3

[0070] SP value = {(1180+350+1125+4300+1180+1020) / (16.1-19.2+33.5+18.0+16.1+57.5)} 1 / 2

[0071] =8.66

[0072] In addition, when the copolymer (A) uses two or more monomers (a), the SP values ​​of the carbon-carbon double bonds of the various monomers constituting monomer (a) are calculated by the above method to form single bonds. The SP values ​​of each monomer (a) are then arithmetically averaged based on the mass fraction of the monomer units. The resulting value preferably satisfies the range of the SP values ​​of the monomer (a) described above.

[0073] Next, monomer (b) will be explained.

[0074] In the above general formula (2), R 3 The symbol represents a hydrogen atom or a methyl group. From the perspective of improving the viscosity index, a methyl group is preferred.

[0075] r is an integer of 0 or 1, and from a lubrication perspective, r = 0 is preferred.

[0076] -X 1 - represents a group represented by -O- or -NH-.

[0077] In general formula (2), R 4 Examples of alkylene groups having 2 to 4 carbon atoms include ethylene, isopropylene, 1,2-propylene or 1,3-propylene, isobutylene, and 1,2-butylene, 1,3-butylene or 1,4-butylene. From the perspective of improving viscosity index, ethylene is preferred.

[0078] R 4 O represents an alkene group having 2 to 4 carbon atoms, such as ethoxide, 1,2-propene or 1,3-propene, as well as 1,2-butene, 1,3-butene or 1,4-butene, etc. Ethoxide is preferred from the perspective of solubility in oxygen-containing base oil (B).

[0079] s is an integer from 0 to 20, and from the perspective of solubility in oxygen-containing base oil (B), 0 to 2 is preferred.

[0080] R when s is 2 or more 4 They can be the same or different, (R) 4 O) s Some can be segmental or random. It should be noted that segmental refers to two or more R... 4 The same parts are continuously bonded.

[0081] In general formula (2), R 5This refers to hydrocarbon groups with 1 to 40 carbon atoms. Examples include chain aliphatic hydrocarbon groups with 1 to 40 carbon atoms (e.g., methyl, ethyl), and straight-chain alkyl groups with 3 to 40 carbon atoms (e.g., n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecanyl, n-hexadecyl, n-octadecyl, n-eicosyl, n-eicosyl, n-eicosyl, n-hexadecyl). Alkyl groups, n-octadecyl, n-trianedecyl, n-tetradecyl, etc.; branched alkyl groups with 3 to 40 carbon atoms {e.g., isopropyl, isobutyl, tert-butyl, sec-butyl, isopentyl, 1-ethylpropyl, 1,1-dimethylpropyl, 2-methylbutyl, isohexyl, 2-methylpentyl, isoheptyl, 2-methylhexyl, isooctyl, 2-ethylhexyl, isononyl, isodecyl, isododecyl}; and groups with 20 to 40 carbon atoms branched at the 2-position [e.g., 2-dodecane]. Tridecyl, 2-alkyl (6-13 carbon atoms of alkyl) tetradecyl {e.g. 2-dodecyltetradecyl, etc.}, 2-alkyl (4-15 carbon atoms of alkyl) hexadecyl {e.g. 2-dodecylhexadecyl, 2-tetradecylhexadecyl, etc.}, 2-alkyl (2-17 carbon atoms of alkyl) octadecyl {e.g. 2-tetradecyloctadecyl, 2-hexadecyloctadecyl, etc.}, 2-alkyl (1-19 carbon atoms of alkyl) eicosyl {e.g. 2-hexadecyleicosyl, etc.}, 2-alkyl (1-18 carbon atoms of alkyl) dodecyl, 2-alkyl (1-16 carbon atoms of alkyl) tetradecyl, 2-alkyl (1-14 carbon atoms of alkyl) hexadecyl, 2-alkyl (1-12 carbon atoms of alkyl) octadecyl, 2-alkyl (1-10 carbon atoms of alkyl) triacontyl, etc.], alicyclic hydrocarbon groups [e.g. cyclohexyl, etc.], aromatic hydrocarbon groups [e.g. phenyl, etc.], etc.

[0082] As R 5 From the perspective of improving the viscosity index, alkyl groups with 8 to 20 carbon atoms are preferred, and alkyl groups with 10 to 18 carbon atoms are even more preferred.

[0083] Furthermore, from the perspective of solubility in refrigerant (C), alkyl groups having 1 to 6 carbon atoms are preferred, alkyl groups having 1 to 4 carbon atoms are more preferred, and branched alkyl groups having 3 to 4 carbon atoms are particularly preferred.

[0084] As monomers (b), specifically, examples include alkyl esters of (meth)acrylate with alkyl groups having 1 to 40 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, hexyl (meth)acrylate, n-dodecyl (meth)acrylate, n-octadecyl (meth)acrylate, 2-n-dodecylhexadecyl (meth)acrylate, 2-n-tetradecyl (meth)acrylate. Alkyl octadecyl esters, etc.; alkyl vinyl ethers with 1 to 40 carbon atoms (e.g., methyl vinyl ether, ethyl vinyl ether, etc.); etherifications of hydroxyalkyl (2 to 4 carbon atoms) vinyl ethers or hydroxyalkyl vinyl ethers with 2 to 4 carbon atoms in alkyl oxides and alcohols with 1 to 40 carbon atoms; N-alkyl (methyl)acrylamides with 1 to 40 carbon atoms (e.g., N-methyl (meth)acrylamide, N-ethyl (meth)acrylamide, etc.); AO adducts of alkyl alcohols with 1 to 40 carbon atoms and esterifications of (meth)acrylic acid, etc.

[0085] As monomer (b), from the perspective of solubility in refrigerant (C), alkyl methacrylates with 1 to 6 carbon atoms of the alkyl group are preferred, alkyl methacrylates with 1 to 4 carbon atoms of the alkyl group are more preferred {e.g., ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, and hexyl methacrylate}, alkyl methacrylates with 2 to 4 carbon atoms of the alkyl group are more preferred {e.g., ethyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, and tert-butyl methacrylate}, and isobutyl methacrylate, isopropyl methacrylate, and tert-butyl methacrylate are particularly preferred.

[0086] Monomer (b) can be used in one or more ways.

[0087] From the perspective of achieving a suitable SP value for the copolymer, the SP value of the structural unit from monomer (b) (the structure in which the carbon-carbon double bonds in monomer (b) react to become single bonds) is preferably 8.5 to 10.0 (cal / cm²). 3 ) 1 / 2 More preferably, it is 8.7–9.8 (cal / cm³). 3 ) 1 / 2 .

[0088] In this invention, the copolymer (A) may contain, in addition to monomers (a) and (b), a vinyl monomer containing a nitrogen atom (c), an aliphatic hydrocarbon vinyl monomer (d), an alicyclic hydrocarbon vinyl monomer (e), an aromatic hydrocarbon vinyl monomer (f), a vinyl ester (g), a vinyl ketone (h), a vinyl monomer containing an epoxy group (i), a vinyl monomer containing a halogen element other than monomer (a) (j), an unsaturated polycarboxylic acid ester (k), a vinyl monomer containing a hydroxyl group (l), and a vinyl monomer containing an ionic group (m) as constituent monomers.

[0089] Examples of vinyl monomers (c) containing nitrogen atoms include vinyl monomers containing amide groups (c1), monomers containing nitro groups (c2), vinyl monomers containing primary to tertiary amino groups (c3), vinyl monomers containing quaternary ammonium salt groups (c4), amphoteric vinyl monomers (c5), and monomers containing nitrile groups (c6).

[0090] (c1) Vinyl monomers containing amide groups:

[0091] Examples of monomers that have a nitrogen atom only in the amide group include (meth)acrylamide, dialkyl (1-4 carbon atoms) substituted (meth)acrylamide [N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide and N,N-di-n-butyl(meth)acrylamide, etc.], and N-vinylcarboxamide [N-vinylformamide, N-vinylacetamide, N-vinyl-n-acrylamide or N-vinylisoacrylamide, and N-vinylhydroxyacetamide, etc.].

[0092] (c2) Monomers containing nitro groups:

[0093] Examples include 4-nitrostyrene.

[0094] (c3) Vinyl monomers containing primary to tertiary amino groups:

[0095] Examples of vinyl monomers containing primary amino groups include: alkenylamines (3-6 carbon atoms, such as (meth)allylamine and crotonylamine), aminoalkyl (2-6 carbon atoms) (meth)acrylates (such as (meth)acrylate aminoethyl ester)}; vinyl monomers containing secondary amino groups include: alkyl (1-6 carbon atoms)aminoalkyl (2-6 carbon atoms) (meth)acrylates (such as tert-butylaminoethyl methacrylate and (meth)acrylate methylaminoethyl ester), diphenylamine (meth)acrylamide (such as 4-diphenylamine (meth)acrylamide and 2-diphenylamine (meth)acrylamide), dienylamines (6-12 carbon atoms, such as di(meth)allylamine)}; and vinyl monomers containing tertiary amino groups include: dialkyl (1-4 carbon atoms)aminoalkyl (2-6 carbon atoms) (meth)acrylates (such as dimethyl)methacrylates (meth)acrylates (such as dimethyl)methacrylates (meth)acrylates (such as dimethyl)methacrylates (meth)acrylates (such as dimethyl)methacrylates (meth)acrylates (such as dimethyl)methacrylates (meth)acrylates (such as dimethyl)methacrylates (meth)acrylates (such as dimethyl)methacrylates (meth)acrylates (such as dimethyl)methacrylates (meth)meth ... Acrylates [(meth)acrylate dimethylaminoethyl ethyl acrylate, (meth)acrylate diethylaminoethyl ethyl acrylate, etc.], dialkyl (carbon 1-4)aminoalkyl (carbon 2-6) (meth)acrylamides [dimethylaminoethyl (meth)acrylamide, diethylaminoethyl (meth)acrylamide, dimethylaminopropyl (meth)acrylamide, etc.]; aromatic vinyl monomers containing tertiary amino groups [N,N-dimethylaminostyrene, etc.]; vinyl monomers containing nitrogen-containing heterocycles [(meth)acrylate morpholinoethyl ethyl ester, 4-vinylpyridine, 2-vinylpyridine, N-vinylpyrrole, N-vinylpyrrolidone, and N-vinylthiopyrrolidone, etc.], and their hydrochloride, sulfate, phosphate, or lower alkyl (carbon 1-8) monocarboxylic acid (acetic acid and propionic acid, etc.) salts, etc.

[0096] (c4) Vinyl monomers containing quaternary ammonium groups:

[0097] Examples of examples include substances obtained by quaternizing the aforementioned vinyl monomers containing tertiary amino groups using quaternizing agents (alkyl chlorides, dialkyl sulfates, dialkyl carbonates, and benzyl chlorides, etc., with 1 to 12 carbon atoms). Specifically, examples include alkyl methacrylate quaternary ammonium salts [(meth)acryloyloxyethyl trimethylammonium chloride, (meth)acryloyloxyethyl triethylammonium chloride, (meth)acryloyloxyethyl dimethylbenzylammonium chloride, (meth)acryloyloxyethyl methylmorpholinoammonium chloride, etc.]; alkyl (meth)acrylamide quaternary ammonium salts [(meth)acryloylaminoethyl trimethylammonium chloride, (meth)acryloylaminoethyl triethylammonium chloride, and (meth)acryloylaminoethyl dimethylbenzylammonium chloride, etc.]; and other vinyl monomers containing quaternary ammonium groups (dimethyl diallyl ammonium methyl sulfate and trimethylvinylphenylammonium chloride, etc.).

[0098] (c5) Amphoteric vinyl monomers:

[0099] Examples include N-(meth)acryloyloxy(or amino)alkyl (1-10 carbon atoms)-N,N-dialkyl (1-5 carbon atoms)ammonium-N-alkyl (1-5 carbon atoms)carboxylates (or sulfates), [N-(meth)acryloyloxyethyl-N,N-dimethylammonium-N-methylcarboxylate, N-(meth)acryloylaminopropyl-N,N-dimethylammonium-N-methylcarboxylate, and N-(meth)acryloyloxyethyl-N,N-dimethylammoniumpropyl sulfate, etc.]

[0100] (c6) Monomers containing nitrile groups:

[0101] Examples include (meth)acrylonitrile.

[0102] (d) Aliphatic hydrocarbon vinyl monomers:

[0103] Examples include alkenes with 2 to 20 carbon atoms (ethylene, propylene, butene, isobutene, pentene, heptene, diisobutene, octene, dodecene, and octadecene, etc.) and dienes with 4 to 12 carbon atoms (butadiene, isoprene, 1,4-pentadiene, 1,6-heptadiene, and 1,7-octadiene, etc.).

[0104] (e) Alicyclic hydrocarbon vinyl monomers:

[0105] Examples include cyclohexene, (di)cyclopentadiene, pinene, limonene, indene, vinylcyclohexene, and ethimide-dicycloheptene.

[0106] (f) Aromatic hydrocarbon vinyl monomers:

[0107] Examples include styrene, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, 4-ethylstyrene, 4-isopropylstyrene, 4-butylstyrene, 4-phenylstyrene, 4-cyclohexylstyrene, 4-benzylstyrene, 4-crotonylbenzene, and 2-vinylnaphthalene.

[0108] (g) Vinyl ester:

[0109] Examples include vinyl esters of saturated fatty acids with 2 to 12 carbon atoms (vinyl acetate, vinyl propionate, vinyl butyrate, and vinyl octanoate, etc.).

[0110] (h) Vinyl ketone

[0111] Examples include alkyl or aryl vinyl ketones with 1 to 8 carbon atoms (such as methyl vinyl ketone, ethyl vinyl ketone, and phenyl vinyl ketone).

[0112] (i) Vinyl monomers containing epoxy groups;

[0113] Examples include glycidyl methacrylate and glycidyl (meth)allyl ether.

[0114] (j) Vinyl monomers containing halogen elements;

[0115] Examples include vinyl chloride, vinyl bromide, vinylidene chloride, (meth)allyl chloride, and halogenated styrene (such as dichlorostyrene).

[0116] (k) Esters of unsaturated polycarboxylic acids;

[0117] Examples include alkyl, cycloalkyl, or aralkyl esters of unsaturated polycarboxylic acids [alkyl diesters of unsaturated dicarboxylic acids (maleic acid, fumaric acid, and itaconic acid, etc.) with 1 to 8 carbon atoms (dimethyl maleate, dimethyl fumarate, diethyl maleate, and dioctyl maleate)].

[0118] (l) vinyl monomers containing hydroxyl groups;

[0119] Examples include aromatic vinyl monomers containing hydroxyl groups (such as p-hydroxystyrene), hydroxyalkyl (2-6 carbon atoms) (meth)acrylates [such as (meth)acrylate-2-hydroxyethyl ester and (meth)acrylate-2- or 3-hydroxypropyl ester], mono- or dihydroxyalkyl (1-4 carbon atoms) substituted (meth)acrylamides [such as N,N-dihydroxymethyl (meth)acrylamide, N,N-dihydroxypropyl (meth)acrylamide and N,N-di-2-hydroxybutyl (meth)acrylamide], vinyl alcohol, and enols with 3-12 carbon atoms [(meth)allyl] Alcohols, crotonol, isoctanol, 1-octenol and 1-undecenol, etc.; olefin diols with 4 to 12 carbon atoms [1-buten-3-ol, 2-buten-1-ol and 2-buten-1,4-diol, etc.]; hydroxyalkyl (1 to 6 carbon atoms) alkenyl (3 to 10 carbon atoms) ethers (2-hydroxyethylpropene ether, etc.); alkenyl (3 to 10 carbon atoms) ethers or (meth)acrylates of poly(3 to 8) alcohols (glycerol, pentaerythritol, sorbitol, sorbitan, diglycerol, sugars and sucrose, etc.) [sucrose (meth)allyl ether, etc.], etc.

[0120] Examples of vinyl monomers containing ionic groups (m) include vinyl monomers containing anionic groups (m1), vinyl monomers containing sulfonic acid groups (m2), vinyl monomers containing sulfate groups (m3), and vinyl monomers containing phosphate groups (m4).

[0121] (m1) Vinyl monomers containing anionic groups:

[0122] Examples include vinyl monomers containing monocarboxylic acid groups {unsaturated monocarboxylic acids [(meth)acrylic acid, α-meth)acrylic acid, crotonic acid, and cinnamic acid, etc.], monoalkyl (carbon number 1-8) esters of unsaturated dicarboxylic acids (monoalkyl maleate ester, monoalkyl fumarate ester, and monoalkyl itaconic acid ester, etc.)}; and vinyl monomers containing dicarboxylic acid groups (maleic acid, fumarate, itaconic acid, and citraconic acid, etc.).

[0123] (m2) Vinyl monomers containing sulfonic acid groups:

[0124] Examples include olefin sulfonic acids with 2 to 6 carbon atoms [vinyl sulfonic acid and (meth)allyl sulfonic acid, etc.], aromatic vinyl sulfonic acids with 6 to 12 carbon atoms [α-methylstyrene sulfonic acid, etc.], (meth)acrylate monomers containing sulfonic acid groups [(meth)acrylate sulfonylpropyl ester and 2-(meth)acryloyloxyethane sulfonic acid, etc.], (meth)acrylamide monomers containing sulfonic acid groups [2-(meth)acrylamide-2-methylpropane sulfonic acid, etc.], vinyl monomers containing sulfonic acid groups and hydroxyl groups [3-(meth)acrylamide-2-hydroxypropane sulfonic acid, 3-allyloxy-2-hydroxypropane sulfonic acid and 3-(meth)acryloyloxy-2-hydroxypropane sulfonic acid, etc.], and alkyl (3 to 18 carbon atoms) allyl sulfonated succinates [dodecyl allyl sulfonated succinate, etc.].

[0125] (m3) Vinyl monomers containing sulfate groups:

[0126] Examples include sulfates of poly(n=2-30) oxidized olefins (ethylene oxide, propylene oxide, and butene oxide, etc.: the addition form can be any of homopolymerization, random addition, or block addition) mono(meth)acrylates, and sulfates of poly(degree of polymerization 2-30) oxidized olefins (ethylene oxide, propylene oxide, and butene oxide, etc.: the addition form can be any of homopolymerization, random addition, or block addition) bisphenol A mono(meth)acrylates, etc.

[0127] (m4) Vinyl monomers containing phosphate groups:

[0128] Examples include (meth)acryloyloxyalkyl (2-6 carbon atoms) phosphate monoesters [(meth)acryloyloxyethyl phosphate, etc.] and (meth)acryloyloxyphosphonic acid [2-acryloyloxyethyl phosphonic acid].

[0129] From the perspective of solubility in oxygen-containing base oil (B) and solubility in refrigerant (C), the mass ratio of monomer (a) constituting copolymer (A) is preferably 2 to 99% by mass, more preferably 2 to 55% by mass, more preferably 5 to 40% by mass, and particularly preferably 10 to 30% by mass, based on the total mass of monomers constituting copolymer (A).

[0130] From the perspective of solubility in oxygen-containing base oil (B), the mass ratio of monomer (b) constituting copolymer (A) is preferably 1 to 98% by mass, more preferably 10 to 98% by mass, more preferably 30 to 95% by mass, particularly preferably 30 to 90% by mass, and most preferably 70 to 90% by mass, based on the total mass of monomers constituting copolymer (A).

[0131] In the monomers (b) constituting copolymer (A), from the perspective of solubility in refrigerant (C), R in general formula (2) 5 The mass ratio of alkyl monomers having 1 to 4 carbon atoms is preferably 10 to 98% by mass, more preferably 10 to 90% by mass, more preferably 30 to 90% by mass, particularly preferably 50 to 90% by mass, and most preferably 70 to 90% by mass, based on the total mass of the monomers constituting copolymer (A).

[0132] From the perspective of solubility in oxygen-containing base oil (B) and solubility in refrigerant (C), the total mass ratio of monomers (a) and monomers (b) constituting copolymer (A) is preferably 50 to 100% by mass, more preferably 80 to 100% by mass, and particularly preferably 90 to 100% by mass, based on the total mass of monomers constituting copolymer (A).

[0133] From the perspective of solubility in oxygen-containing base oil (B) and solubility in refrigerant (C), the total mass ratio of monomers (c) to (m) constituting copolymer (A) is preferably 50% by mass or less, more preferably 20% by mass or less, and particularly preferably 10% by mass or less, based on the total mass of monomers constituting copolymer (A).

[0134] In this invention, the mass ratio (b / a) of monomer (b) to monomer (a) in the monomer constituting copolymer (A) is 0.01 to 42, and from the perspective of improving the viscosity index, it is preferably 0.1 to 40, more preferably 0.5 to 20, and particularly preferably 0.8 to 10.

[0135] If the mass ratio is less than 0.01, the solubility in oxygen-containing atomic base oil (B) is poor; if the mass ratio is greater than 42, the solubility in refrigerant (C) is poor.

[0136] The SP value of copolymer (A) is 8.1–10.0 (cal / cm³). 3 ) 1 / 2 From the perspectives of improving viscosity index, solubility in oxygen-containing base oils (B), and solubility in refrigerants (C), a viscosity index of 8.5 to 9.8 (cal / cm³) is preferred. 3 ) 1 / 2, more preferably 8.8 to 9.5 (cal / cm 3 ). 1 / 2 .

[0137] If the SP value of the copolymer (A) is less than 8.1, its solubility in the oxygen atom-containing base oil (B) is poor; if the SP value is greater than 10.0, its solubility in the oxygen atom-containing base oil (B) and in the refrigerant (C) is poor.

[0138] It should be noted that regarding the SP value of the copolymer (A), the SP values of the monomer units (structures in which carbon-carbon double bonds react to become single bonds) constituting the copolymer (A) are calculated by the above method, and the SP values of each monomer are arithmetically averaged based on the mass fraction of the constituent monomer units, and the obtained value is the SP value of the copolymer (A).

[0139] For example, in the case of a copolymer having 20% by mass of 2,2,2-trifluoroethyl methacrylate (SP value of the structural unit: 8.66) and 80% by mass of n-butyl methacrylate (SP value of the structural unit: 9.45) as the constituent monomers, the calculation can be carried out as follows.

[0140] SP value of the copolymer = (8.66×20 + 9.45×80) / 100 = 9.29

[0141] From the aspects of solubility in the oxygen atom-containing base oil (B) and solubility in the refrigerant (C), the weight-average molecular weight of the copolymer (A) is preferably 1,000 to 2,000,000, more preferably 1,000 to 1,000,000, and particularly preferably 1,000 to 500,000.

[0142] It should be noted that in the present invention, the weight-average molecular weight (hereinafter simply referred to as Mw) and the number-average molecular weight (hereinafter simply referred to as Mn) can be measured by gel permeation chromatography (hereinafter simply referred to as GPC) under the following conditions.

[0143] <Measurement conditions for Mw and Mn>

[0144] Apparatus: "HLC-8320GPC" [manufactured by Tosoh Corporation]

[0145] Columns: "TSKgel GMHXL" [manufactured by Tosoh Corporation], 2 columns

[0146] "TSKgel Multipore H XL -M" [manufactured by Tosoh Corporation], 1 column

[0147] Measurement temperature: 40°C <00Sample solution: 0.25% by mass tetrahydrofuran solution

[0149] Solution injection volume: 10.0 μl

[0150] Detection device: Refractive index detector

[0151] Reference material: Standard polystyrene (TSKstandardPOLYSTYRENE)

[0152] 12 types (molecular weight: 589, 1,050, 2,630, 9,100, 19,500, 37,900, 96,400, 190,000, 355,000, 1,090,000, 2,110,000, 4,480,000) [Made by Tosoh Corporation]

[0153] The copolymer (A) can be obtained by known manufacturing methods, specifically, methods such as solution polymerization of the above-mentioned monomer mixture in a solvent in the presence of a polymerization catalyst.

[0154] Examples of solvents include toluene, xylene, alkyl (3-10 carbon atoms) benzene, methyl ethyl ketone, and polymeric base oils {e.g., oxygen-containing base oil (B) (e.g., at least one selected from the group consisting of ester oil (B1), polyvinyl ether (B2), and polyalkylene glycol (B3), etc.), mineral oil, etc.}. Among these, oxygen-containing base oil (B) is preferred from the perspectives of eliminating the step for solvent removal, the processability of viscosity index improvers, and compatibility with refrigerant (C).

[0155] Examples of polymerization catalysts include azo-based catalysts (such as azobisisobutyronitrile and azobispentonitrile) and peroxide-based catalysts (such as benzoyl peroxide, cumyl peroxide, and lauryl peroxide). 2,2'-azobis(2,4-dimethylpentonitrile) can also be used as a polymerization catalyst.

[0156] Furthermore, chain transfer agents (such as alkyl mercaptools with 2 to 20 carbon atoms) can be used as needed.

[0157] The polymerization temperature is preferably 50–140°C, more preferably 70–120°C. In addition to solution polymerization, copolymer (A) can also be obtained by bulk polymerization, emulsion polymerization, or suspension polymerization.

[0158] As a polymerization form of copolymer (A), it can be either a random addition polymer or an alternating copolymer, and it can also be either a graft copolymer or a block copolymer.

[0159] The Mw of copolymer (A) can be adjusted by modifying polymerization conditions such as polymerization temperature, monomer concentration (solvent concentration), catalyst amount or chain transfer dose.

[0160] The viscosity index improver of the present invention may contain only the copolymer (A) described above, or it may contain an oxygen-containing base oil (B). From the perspective of the processability of the viscosity index improver and its compatibility with the refrigerant (C), it is preferable to contain an oxygen-containing base oil (B).

[0161] As the oxygen-containing base oil (B), oxygen-containing base oils with lubricating properties that have been used as lubricants can be used. Examples include ester oils (B1), polyvinyl ethers (B2), and polyalkylene glycols (B3). Among these, ester oil (B1) is preferred from the perspectives of the processability of viscosity index improvers and compatibility with refrigerants (C).

[0162] Examples of ester oils (B1) include monoesters (B11) and polyol esters (B12) of a monohydric alcohol (x1) and a monocarboxylic acid (y1). Examples of polyol esters (B12) include diesters (B12-1) of a monohydric alcohol (x1) and a dicarboxylic acid (y2), and polyol esters (B12-2) of a poly(2- to 10-membered) alcohol (x2) and a monocarboxylic acid (y1). Among these, from the perspective of compatibility with refrigerant (C), the ester oil (B1) is preferably a monoester (B11) and / or a polyol ester (B12) of a monohydric alcohol (x1) and a monocarboxylic acid (y1), more preferably a monoester (B11) of a monohydric alcohol (x1) and a monocarboxylic acid (y1) and / or a polyol ester (B12-2) of a polyol (x2) and a monocarboxylic acid (y1), and particularly preferably a polyol ester (B12-2) of a polyol (x2) and a monocarboxylic acid (y1). It should be noted that the polyol ester (B12-2) of a polyol (x2) and a monocarboxylic acid (y1) can be a full ester in which all the hydroxyl groups of the polyol are esterified, or it can be a partial ester in which a portion of the hydroxyl groups remain, preferably a full ester. The smaller the hydroxyl value of the total ester, the more likely the polyol ester (B12-2) of the poly(2-10) alcohol (x2) and the monocarboxylic acid (y1) is to be difficult to precipitate at low temperatures.

[0163] Examples of monohydric alcohols (x1) include saturated aliphatic monools with 1 to 24 carbon atoms [straight-chain saturated aliphatic monools {e.g., methanol, ethanol, n-propanol, n-butanol, n-pentanol, n-hexanol, n-heptanol, n-octanol, n-nonanol, n-decanol, n-undecyl alcohol, n-dodecyl alcohol, n-tridecyl alcohol, n-tetradecyl alcohol, n-pentadecanyl alcohol, n-hexadecyl alcohol, n-heptadecyl alcohol, n-octadecyl alcohol, n-nonadecanyl alcohol, n-eicosyl alcohol, n-ticosyl alcohol, and n-tetradecyl alcohol, etc.} and branched-chain saturated aliphatic monools {e.g., 2-ethylhexanol, 3,5,5-trimethyl-1-hexanol} Isononol, isodecanol, isoundecylol, isoundecylol, isododecylol, isotridecylol, isotetradecylol, isopentadecanylol, isohexadecylol, isoheptadecylol, isooctadecylol, and isononadecanylol, etc.; alicyclic monools {e.g., cyclohexanol, 2-tert-butylcyclohexanol, 3-tert-butylcyclohexanol or 4-tert-butylcyclohexanol, menthol, cyclohexaneethanol, 2-isopropylcyclohexanol, 3-isopropylcyclohexanol or 4-isopropylcyclohexanol, etc.}; straight-chain unsaturated aliphatic monools; branched-chain unsaturated aliphatic monools; alicyclic unsaturated monools; and monools containing an aromatic ring with 7 to 24 carbon atoms {e.g., benzyl alcohol, etc.}, etc.

[0164] Among these, considering low-temperature viscosity, kinematic viscosity at 40°C, and compatibility with refrigerant (C), straight-chain or branched saturated aliphatic monools with 4 to 16 carbon atoms are preferred, straight-chain or branched saturated aliphatic monools with 4 to 10 carbon atoms are even more preferred, straight-chain or branched saturated aliphatic monools with 4 to 8 carbon atoms are particularly preferred, and branched saturated aliphatic monools with 4 to 8 carbon atoms are most preferred.

[0165] As polyols (x2), examples include saturated aliphatic diols with 2 to 24 carbon atoms [linear saturated aliphatic diols {e.g., ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,1... 5-Pentadecanediol and 1,16-hexadecanediol, etc., branched saturated aliphatic diols {e.g., 2-methyl-1,3-propanediol, 2-methyl-1,4-butanediol, 1,2-butanediol, neopentyl glycol, 1,2-pentanediol, 1,2-hexanediol, 3-methyl-1,5-pentanediol, 1,2-heptanediol, 1,2-octanediol, 1,2-nonanediol, 1,2-decanediol, 1,2-undecanediol, 1,2-dodecanediol, 1,2-tridecanediol} , 1,2-Tetradecanediol, 1,2-Pentadecanediol, and 1,2-Hexadecanediol, etc.; polyalkylene glycols with 4 to 24 carbon atoms (e.g., diethylene glycol, triethylene glycol, etc.); unsaturated aliphatic glycols with 2 to 24 carbon atoms; saturated aliphatic polyols (3 or more members) with 3 to 24 carbon atoms [3-membered saturated aliphatic alcohols with 3 to 24 carbon atoms (e.g., glycerol, trimethylolethane, trimethylolpropane, etc.); 4-membered saturated aliphatic alcohols with 4 to 24 carbon atoms (e.g., 1,2-tetradecanediol, 1,2-pentadecanediol, and 1,2-hexadecanediol, etc.); polyalkylene glycols with 4 ...propane, trimethylolpropane, etc.); polyalkylene glycols with 4 to 24 carbon atoms (e.g., 1,2-tetradecanediol, 1,2-pentadecanediol, and 1,2-hexadecanediol, etc.); polyalkylene glycols with 4 to 24 carbon atoms (e.g., 1,2-tetradecanediol, 1,2-pentadecanediol, and 1,2-hexadecanediol, etc.); polyalkylene glycols with Examples include pentaerythritol, xylitol, and bis(trimethylolpropane); alcohols with five or more carbon atoms (e.g., sorbitol, dipentaerythritol, tri-trimethylolpropane, disorbitol, trisorbitol, etc.); alicyclic diols (e.g., 1,2-cyclohexanediol, 1,3-cyclohexanediol, or 1,4-cyclohexanediol, etc.); unsaturated aliphatic polyols (three or more carbon atoms) with 3 to 24 carbon atoms; and diols containing an aromatic ring with 8 to 24 carbon atoms (e.g., ethylene oxide adducts of dihydroxybenzene, etc.).

[0166] Among these, considering low-temperature viscosity, kinematic viscosity at 40°C, and compatibility with refrigerant (C), straight-chain or branched saturated aliphatic diols with 2 to 24 carbon atoms or saturated aliphatic polyols (3 or more) with 3 to 24 carbon atoms are preferred, and straight-chain or branched saturated aliphatic diols with 2 to 10 carbon atoms or saturated aliphatic polyols (3 or more) with 3 to 10 carbon atoms are even more preferred. In particular, straight-chain or branched saturated aliphatic diols with 4 to 8 carbon atoms or saturated aliphatic polyols (3 or more) with 4 to 8 carbon atoms are preferred.

[0167] Examples of monocarboxylic acids (y1) include saturated aliphatic monocarboxylic acids with 2 to 25 carbon atoms [linear saturated aliphatic monocarboxylic acids {e.g., propionic acid, butyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, nonadecanoic acid, eicosanonic acid, behenic acid, and tetracosanoic acid, etc.}, with 2 to 2 Branched saturated aliphatic monocarboxylic acids with 5 carbon atoms (e.g., 2-ethylhexanoic acid, 3,5,5-trimethylhexanoic acid, isononanoic acid, isodecanonicic acid, isoundecanoic acid, isodecadecanoic acid, isotetradecanoic acid, isodepentadecananoic acid, isohexadecananoic acid, isohexadecananoic acid, isoctadecanoic acid, and isononadecananoic acid, etc.), alicyclic monocarboxylic acids (e.g., cyclohexanecarboxylic acid, etc.), unsaturated aliphatic monocarboxylic acids with 2 to 25 carbon atoms, and monocarboxylic acids containing aromatic rings (e.g., benzoic acid, etc.).

[0168] Among these, aliphatic monocarboxylic acids with 2 to 25 carbon atoms are preferred in terms of low-temperature viscosity, kinematic viscosity at 40°C, and compatibility with refrigerant (C). Straight-chain or branched saturated aliphatic monocarboxylic acids with 2 to 24 carbon atoms are even more preferred. Straight-chain or branched saturated aliphatic monocarboxylic acids with 4 to 14 carbon atoms are particularly preferred.

[0169] Examples of dicarboxylic acids (y2) include saturated aliphatic dicarboxylic acids with 2 to 24 carbon atoms [linear saturated aliphatic dicarboxylic acids {e.g., ethanedioic acid (oxalic acid), propanedioic acid (malonic acid), n-butanedioic acid (succinic acid), n-pentanedioic acid (glutaric acid), n-hexanedioic acid (adipic acid), n-heptanedioic acid, n-octanedioic acid, n-nonanedioic acid (azelic acid), n-decanedioic acid (sebacic acid), n-undecanedioic acid, n-dodecanedioic acid, n-triadecanedioic acid, n-tetradecanedioic acid, n-pentadecanedioic acid, and n-hexadecanedioic acid, etc.}, branched... Saturated aliphatic dicarboxylic acids (e.g., 2-methylglutaric acid, 3-methylglutaric acid, 3-methylhexanoic acid, etc.), alicyclic saturated dicarboxylic acids (e.g., 1,2-cyclopentanedicarboxylic acid or 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid or 1,4-cyclohexanedicarboxylic acid, etc.), unsaturated aliphatic dicarboxylic acids with 2 to 24 carbon atoms (e.g., maleic acid, fumaric acid, etc.), and dicarboxylic acids containing aromatic rings with 8 to 24 carbon atoms (e.g., phthalic acid, isophthalic acid, terephthalic acid, etc.).

[0170] Among these, aliphatic dicarboxylic acids with 2 to 24 carbon atoms are preferred in terms of low-temperature viscosity, kinematic viscosity at 40°C, and compatibility with refrigerant (C). Straight-chain or branched aliphatic dicarboxylic acids with 2 to 24 carbon atoms are even more preferred, and straight-chain or branched aliphatic dicarboxylic acids with 4 to 10 carbon atoms are particularly preferred.

[0171] As an ester oil (B1), considering its low-temperature viscosity and compatibility with the refrigerant (C), esters of saturated aliphatic alcohols (selected from at least one of the group consisting of saturated aliphatic monools, saturated aliphatic diols, and saturated aliphatic polyols) and saturated aliphatic carboxylic acids (saturated aliphatic monocarboxylic acids and / or saturated aliphatic dicarboxylic acids) are preferred. Esters of branched saturated aliphatic alcohols (branched saturated aliphatic monools and / or branched saturated aliphatic diols) and branched saturated aliphatic carboxylic acids (branched saturated aliphatic monocarboxylic acids and / or branched saturated aliphatic dicarboxylic acids) are even more preferred. Esters of branched saturated aliphatic alcohols with 4 to 10 carbon atoms and branched saturated aliphatic carboxylic acids with 4 to 10 carbon atoms are particularly preferred.

[0172] As for the ester oil (B1), from the perspective of compatibility with the refrigerant (C), an ester with 20 to 45 carbon atoms is preferred, and an ester with 20 to 40 carbon atoms is even more preferred.

[0173] Furthermore, regarding the ester oil (B1), from the perspective of improving the viscosity index brought about by the copolymer (A), an ester with 10 to 40 carbon atoms is preferred, and an ester with 10 to 25 carbon atoms is even more preferred. By keeping the number of carbon atoms within these ranges, the viscosity index improvement effect brought about by the copolymer (A) is increased without making the molecular weight too large.

[0174] Polyethylene ether (B2) (hereinafter sometimes simply referred to as PVE) can be exemplified by polymers having more than one structural unit derived from vinyl ether.

[0175] As a PVE, it is preferable to have the structural unit represented by the following general formula (3).

[0176] [Chemistry 5]

[0177]

[0178] [In the formula, R] 6 R 7 and R 8 They can be the same or different, representing hydrogen atoms or hydrocarbon groups respectively, R 9 R represents a divalent hydrocarbon group or a divalent hydrocarbon group containing an ether bond oxygen. 10 Represents a hydrocarbon group, where m represents an integer greater than or equal to 0. When m is 2 or greater, multiple R groups are represented. 9 They can be the same or different.

[0179] R in general formula (3) 6 R 7 and R 8The hydrocarbon group represented preferably has 1 to 8 carbon atoms, more preferably 2 to 7, and even more preferably 3 to 6. Additionally, R in general formula (3) 6 R 7 and R 8 At least one of them is preferably a hydrogen atom, and more preferably all of them are hydrogen atoms.

[0180] R in general formula (3) 9 The number of carbon atoms in the divalent hydrocarbon group and the hydrocarbon group containing ether bond oxygen is preferably 1 to 10, more preferably 2 to 8, and even more preferably 3 to 6. Furthermore, R in general formula (3) 9 The divalent hydrocarbon group containing an ether bond can be, for example, a hydrocarbon group having an oxygen in the side chain that forms an ether bond.

[0181] R in general formula (3) 10 Preferably, the hydrocarbon group has 1 to 20 carbon atoms. Examples of such hydrocarbon groups include alkyl, cycloalkyl, phenyl, aryl, and aralkyl groups. Among these, alkyl groups are preferred, and alkyl groups with 1 to 5 carbon atoms are more preferred.

[0182] In general formula (3), m is preferably 0 to 20, more preferably 1 to 18, and even more preferably 2 to 16. In addition, the average value of m in all structural units constituting polyvinyl ether (B2) is preferably 0 to 10.

[0183] The polyethylene ether (B2) in this invention can be a homopolymer composed of one of the structural units selected from those represented by general formula (3), a copolymer composed of two or more of the structural units selected from those represented by general formula (3), or a copolymer composed of the structural units represented by general formula (3) and other structural units. By making the polyethylene ether (B2) a copolymer, compatibility with the refrigerant (C) of the refrigeration oil can be satisfied, and lubricity, insulation, hygroscopicity, etc., can be further improved. At this time, by appropriately selecting the type of monomer as raw material, the type of initiator, the proportion of structural units in the copolymer, etc., the various properties of the aforementioned refrigeration oil can achieve the desired properties. Therefore, refrigeration oils corresponding to different lubricity, compatibility, and other requirements depending on the compressor model, lubrication material, cooling capacity, refrigerant type, etc. in the refrigeration system or air conditioning system can be freely obtained. The copolymer can be either a block copolymer or a random copolymer.

[0184] In the case that the polyvinyl ether (B2) in this invention is a copolymer, the copolymer preferably comprises structural unit (3-1) and structural unit (3-2), wherein structural unit (3-1) is represented by the above general formula (3) and R 10 It is an alkyl group having 1 to 2 carbon atoms, and the structural unit (3-2) is represented by the above general formula (3) and R 10It is an alkyl group with 3 to 20 carbon atoms, preferably 3 to 10, and more preferably 3 to 8. R is the structural unit (3-1). 10 Ethyl is particularly preferred, and R is also preferred as a structural unit (3-2). 10 Isobutyl is particularly preferred. Furthermore, when the polyvinyl ether (B2) in this invention is a copolymer comprising the above-described structural units (3-1) and (3-2), the molar ratio of structural unit (3-1) to structural unit (3-2) is preferably 5:95 to 95:5, more preferably 20:80 to 90:10, and even more preferably 70:30 to 90:10. When this molar ratio is within the above range, it tends to further improve compatibility with the refrigerant (C) and reduce hygroscopicity.

[0185] In the manufacturing process of the polyethylene ether (B2) of this invention, side reactions sometimes occur, forming unsaturated groups such as aryl groups in the molecule. From the perspectives of improving the thermal stability of the polyethylene ether itself, suppressing the formation of sludge due to polymer formation, and suppressing the formation of peroxides due to decreased antioxidant properties, the polyethylene ether (B2) of this invention preferably has a low degree of unsaturation derived from unsaturated groups. The degree of unsaturation of the polyethylene ether (B2) is preferably 0.04 meq / g or less, more preferably 0.03 meq / g or less, and even more preferably 0.02 meq / g or less. Furthermore, the peroxide value of the polyethylene ether (B2) is preferably 10.0 meq / kg or less, more preferably 5.0 meq / kg or less, and even more preferably 1.0 meq / kg. Additionally, the carbonyl value of the polyethylene ether (B2) is preferably 100 ppm by mass or less, more preferably 50 ppm by mass or less, and even more preferably 20 ppm by mass or less. In addition, the hydroxyl value of the polyvinyl ether (B2) is preferably 10 mg KOH / g or less, more preferably 5 mg KOH / g or less, and even more preferably 3 mg KOH / g or less.

[0186] It should be noted that the unsaturation degree, peroxide value, and carbonyl value in this invention refer to values ​​measured using the benchmark oil and fat analysis test method established by the Japan Oil Chemical Society. Specifically, the unsaturation degree in this invention refers to the value obtained by reacting the sample with Widmanstätten solution (ICl-acetic acid solution), allowing it to stand in the dark, then reducing excess ICl to iodine, titrating the iodine component with sodium thiosulfate, and converting this iodine value to vinyl equivalents (meq / g). Furthermore, the peroxide value in this invention refers to the value obtained by adding potassium iodide to the sample, titrating the resulting free iodine with sodium thiosulfate, and converting this free iodine to milliequivalents relative to 1 kg of sample (meq / kg). Additionally, the carbonyl value in this invention refers to the value obtained by reacting 2,4-dinitrophenylhydrazine with the sample to generate quinone ions with colorimetric properties, measuring the absorbance of the sample at 480 nm, and converting it to carbonyl content based on a calibration curve previously obtained using cinnamaldehyde as a standard (mass ppm).

[0187] Polyalkylene glycols (B3) include substances with various chemical structures, with polyethylene glycol, polypropylene glycol, and polybutane glycol as basic compounds. The unit structures are ethylene oxide, propylene oxide, and butylene oxide. They can be obtained by ring-opening polymerization using ethylene oxide, propylene oxide, and butylene oxide as monomers, respectively.

[0188] Examples of polyalkylene glycols (B3) include compounds represented by the following general formula (11).

[0189] R α -[(OR β ) f -OR γ ] g (11)

[0190] In equation (11), R α Residues representing hydrogen atoms, alkyl groups having 1 to 10 carbon atoms, acyl groups having 2 to 10 carbon atoms, or compounds having 2 to 8 hydroxyl groups, R β R represents an alkylene group having 2 to 4 carbon atoms. γ [This indicates a hydrogen atom, an alkyl group with 1 to 10 carbon atoms, or an acyl group with 2 to 10 carbon atoms; f represents an integer from 1 to 80; g represents an integer from 1 to 8.]

[0191] In the above general formula (11), R α R γ The alkyl group can be any of the following: straight-chain, branched, or cyclic. The alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 6. If the alkyl group has more than 10 carbon atoms, it tends to have reduced compatibility with the refrigerant (C).

[0192] Additionally, R α R γ The alkyl portion of the acyl group can be linear, branched, or cyclic. The number of carbon atoms in the acyl group is preferably 2 to 10, more preferably 2 to 6. If the number of carbon atoms in the acyl group is greater than 10, the compatibility with the refrigerant (C) decreases, and phase separation may occur.

[0193] R α R γ When all represented groups are alkyl or acyl groups, R α R γ The groups represented can be the same or different. Furthermore, when g is 2 or more, multiple R groups in the same molecule... α R γ The groups represented can be the same or different.

[0194] R α When the represented group is a residue of a compound having 2 to 8 hydroxyl groups, the compound can be either chain-like or cyclic.

[0195] Of the polyalkylene glycols represented by the above general formula (11), R is preferred. α R γ At least one of them is an alkyl group (more preferably an alkyl group having 1 to 4 carbon atoms), and in particular, from the viewpoint of compatibility with the refrigerant (C), methyl is preferred.

[0196] Furthermore, from the perspective of thermal / chemical stability, R is preferred. α With R γ Both are alkyl groups (more preferably alkyl groups having 1 to 4 carbon atoms), and particularly preferably both are methyl groups.

[0197] From the perspectives of ease of manufacturing and cost, R is preferred. α Or R γ One of the atoms is an alkyl group (more preferably an alkyl group having 1 to 4 carbon atoms), and the other is a hydrogen atom; particularly preferred is one being a methyl group and the other a hydrogen atom. Furthermore, from the perspective of lubricity and sludge solubility, R is preferred. α and R γ Both are hydrogen atoms.

[0198] R in the above general formula (11) β This refers to alkylene groups having 2 to 4 carbon atoms. Examples of such alkylene groups include ethylene, propyleneene, and butylene. Additionally, as OR... βExamples of alkylene oxides representing repeating units include ethylene oxide, propylene oxide, and butylene oxide. The same molecule may contain the same alkylene oxide or more than one alkylene oxide.

[0199] In the polyalkylene glycol represented by the above general formula (11), from the perspective of compatibility with refrigerant (C) and viscosity-temperature characteristics, it is preferable to include a copolymer of ethylene oxide (EO) and propylene oxide (PO). In this case, from the perspective of ablation load and viscosity-temperature characteristics, the proportion of ethylene oxide in the sum of ethylene oxide and propylene oxide (EO / (PO+EO)) is preferably in the range of 0.1 to 0.8, more preferably in the range of 0.3 to 0.6.

[0200] In addition, from the perspective of hygroscopicity and thermal / oxidative stability, the value of EO / (PO+EO) is preferably in the range of 0 to 0.5, more preferably in the range of 0 to 0.2, and most preferably 0 (i.e., propylene oxide homopolymer).

[0201] In the above general formula (11), f represents alkylene oxide OR β The repetition count (aggregation degree) is an integer from 1 to 80. Additionally, g is an integer from 1 to 8. For example, in R... α In the case of alkyl or acyl groups, g is 1. R α In the case of residues of a compound having 2 to 8 hydroxyl groups, g represents the number of hydroxyl groups present in the compound.

[0202] Furthermore, there are no particular restrictions on the product of f and g (f×g), but in order to achieve a good balance and meet the performance requirements of refrigeration oil, the average value of f×g is preferably 6 to 80.

[0203] The number-average molecular weight of the polyalkylene glycol represented by general formula (11) is preferably 500 to 3000, more preferably 600 to 2000, and even more preferably 600 to 1500, where n is preferably a number in which the number-average molecular weight of the polyalkylene glycol satisfies the above conditions. If the number-average molecular weight of the polyalkylene glycol is too low, it tends to have insufficient lubricity in the presence of refrigerant (C). On the other hand, if the number-average molecular weight is too high, the range of compositions that exhibit compatibility with refrigerant (C) at low temperatures becomes narrower, and it tends to easily cause poor lubrication of the refrigerant compressor or heat exchange obstruction in the evaporator.

[0204] The hydroxyl value of polyalkylene glycol (B3) is not particularly limited, but it is desirable to be less than 100 mg KOH / g, preferably less than 50 mg KOH / g, further preferably less than 30 mg KOH / g, and most preferably less than 10 mg KOH / g.

[0205] The polyalkylene glycol (B3) of this invention can be synthesized using known methods ("Epoxy Alkane Polymers," Mitsuta Shibata et al., Kaibundo, November 20, 1990). For example, by using one or more of the specified epoxides as an alcohol (R... α OH;R α R represents the expression in the above general formula (11). α By performing addition polymerization on polyalkylene glycols (with the same definition), and then etherifying or esterifying the terminal hydroxyl groups, the polyalkylene glycol represented by the above general formula (11) can be obtained. It should be noted that when two or more different epoxides are used in the above manufacturing process, the resulting polyalkylene glycol can be either a random copolymer or a block copolymer. From the perspective of having better oxidative stability and lubricity, a block copolymer is preferred, and from the perspective of having better low-temperature fluidity, a random copolymer is preferred.

[0206] From the perspectives of the lubricity of the refrigeration oil and its compatibility with the refrigerant (C), the kinematic viscosity of polyalkylene glycol (B3) at 100°C is preferably 5–20 mm. 2 / s, preferably 6–18 mm 2 / s, more preferably 7-16mm 2 / s, further preferably 8-15mm 2 / s, the optimal value is 10-15mm 2 / s. Furthermore, regarding the kinematic viscosity of this polyalkylene glycol (B3) at 40°C, considering the lubricity of the refrigeration oil and its compatibility with the refrigerant (C), the kinematic viscosity at 40°C is preferably 10–200 mm. 2 / s, more preferably 20-150mm 2 / s.

[0207] Furthermore, the pour point of the polyalkylene glycol represented by the above general formula (11) is preferably below -10°C, more preferably -20 to -50°C. If a polyalkylene glycol with a pour point of -10°C or higher is used, there is a tendency for the refrigeration oil to solidify easily in the refrigerant circulation system at low temperatures.

[0208] Furthermore, in the manufacturing process of polyalkylene glycols represented by the above general formula (11), alkylene oxides such as propylene oxide sometimes undergo side reactions to form unsaturated groups such as aryl groups in the molecule. If unsaturated groups are formed in the polyalkylene glycol molecule, it can easily lead to a decrease in the thermal stability of the polyalkylene glycol itself, the formation of polymers and the generation of sludge, or a decrease in antioxidant properties (antioxidant properties) and the generation of peroxides. In particular, when peroxides are generated, they decompose to generate compounds with carbonyl groups, and these compounds further generate sludge, which can easily cause capillary blockage.

[0209] Therefore, the polyalkylene glycol (B3) used in this invention preferably has a low degree of unsaturation derived from unsaturated groups, specifically, preferably 0.04 meq / g or less, more preferably 0.03 meq / g or less, and most preferably 0.02 meq / g or less. Furthermore, the peroxide value is preferably 10.0 meq / kg or less, more preferably 5.0 meq / kg or less, and most preferably 1.0 meq / kg. In addition, the carbonyl value is preferably 100 ppm by mass or less, more preferably 50 ppm by mass or less, and most preferably 20 ppm by mass or less.

[0210] In this invention, to obtain polyalkylene glycols with low unsaturation, low peroxide value, and low carbonyl value, the reaction temperature during the reaction of propylene oxide is preferably below 120°C (more preferably below 110°C). Furthermore, if an alkaline catalyst is used during manufacturing, the degree of unsaturation can be reduced by using inorganic adsorbents such as activated carbon, activated clay, bentonite, dolomite, or alumina silicates to remove it. Additionally, by minimizing contact with oxygen during the manufacture or use of the polyalkylene glycol, or by adding antioxidants, an increase in peroxide value or carbonyl value can be prevented.

[0211] The carbon / oxygen molar ratio of the polyalkylene glycol (B3) in this invention is preferably within a specified range. Polymers with this molar ratio within the above range can be manufactured by selecting and adjusting the type and mixing ratio of the raw material monomers.

[0212] In addition to containing an oxygen-containing base oil (B) {at least one selected from the group consisting of the above-mentioned ester oil (B1), polyethylene ether (B2), and polyalkylene glycol (B3)}, the viscosity index improver of the present invention may further contain hydrocarbon oils such as mineral oil, olefin polymers, naphthalene compounds, and alkylbenzenes. The total content of the ester oil (B1), polyethylene ether (B2), and polyalkylene glycol (B3) is preferably 5% by mass or more, more preferably 30% by mass or more, and even more preferably 95% by mass or more, based on the total amount of base oil contained in the viscosity index improver.

[0213] The kinematic viscosity (measured according to JIS-K2283) of oxygen-containing base oil (B) in viscosity index improvers is typically 1–200 mmHg at 40°C. 2 From the perspective of improving the viscosity index, a viscosity of 5 to 100 mm / s is preferred. 2 / s, further preferably 7-20mm 2 / s.

[0214] The kinematic viscosity (measured according to JIS-K2283) of oxygen-containing base oil (B) in viscosity index improvers is typically 1–50 mmHg at 100°C. 2From the perspective of kinematic viscosity at low temperatures, 1 to 10 mm / s is preferred. 2 / s, further preferably 1-9mm 2 / s.

[0215] The viscosity index (measured according to JIS-K2283) of the oxygen-containing base oil (B) in the viscosity index improver is usually 0 or above, and preferably 50 or above, and more preferably 50 to 180, from the perspective of improving the viscosity index of the lubricating oil composition.

[0216] From the perspective of the solubility of copolymer (A), the SP value of oxygen-containing base oil (B) is preferably 8.0 to 10.0 (cal / cm³). 3 ) 1 / 2 A further preferred value is 8.4–9.5 (cal / cm³). 3 ) 1 / 2 .

[0217] It should be noted that when the viscosity index improver contains two or more oxygen-containing base oils (B), the SP value of each oxygen-containing base oil (B) in the viscosity index improver is calculated using the above method, and the SP value of each oxygen-containing base oil (B) is arithmetically averaged based on its mass fraction. The resulting arithmetic mean is preferably within the above range.

[0218] From the perspectives of viscosity index improvement, solubility in oxygen-containing base oil (B), and solubility in refrigerant (C), the absolute value of the difference between the SP value of copolymer (A) and the SP value of oxygen-containing base oil (B) is preferably 2.0 (cal / cm³). 3 ) 1 / 2 The following, and more preferably, are 0.1 to 2.0 (cal / cm³). 3 ) 1 / 2 Further preferably, it is 0.1–1.5 (cal / cm³). 3 ) 1 / 2 A particularly preferred value is 0.1–1.0 (cal / cm³). 3 ) 1 / 2 The optimal value is 0.1–0.65 (cal / cm³). 3 ) 1 / 2 .

[0219] It should be noted that when the viscosity index improver contains two or more oxygen-containing base oils (B), the SP value of each oxygen-containing base oil (B) in the viscosity index improver is calculated using the above method, and the SP value of each oxygen-containing base oil (B) is arithmetically averaged based on its mass fraction. The absolute value of the difference between the calculated SP value of the oxygen-containing base oil (B) and the SP value of the copolymer (A) is preferably within the above range.

[0220] The mass ratio (A / B) of the copolymer (A) to the oxygen-containing base oil (B) in the viscosity index improver is usually 99 / 1 to 1 / 99, and from the perspective of viscosity index, it is preferably 99 / 1 to 10 / 90, and more preferably 99 / 1 to 20 / 80.

[0221] When two or more oxygen-containing base oils (B) are used, the SP value of each oxygen-containing base oil is calculated, and the arithmetic mean is calculated according to the mass ratio. The arithmetic mean obtained preferably satisfies the above SP value.

[0222] The viscosity index improver of the present invention has excellent solubility for refrigerants and oxygen-containing base oils. When used in refrigeration oil, it has a high viscosity index improvement effect, thereby obtaining refrigeration oil with excellent low-temperature characteristics. Therefore, it can be used as a viscosity index improver for refrigeration oil, and is particularly useful as a viscosity index improver for use in working fluid compositions for refrigeration machines containing refrigerant (C) and refrigeration oil.

[0223] <Refrigeration oil>

[0224] The refrigeration oil of the present invention comprises a lubricating oil base oil and the aforementioned viscosity index improver. Here, any base oil commonly used in lubricating oils can be used as the lubricating oil base oil; however, from the perspective of excellent compatibility with both the refrigerant and the aforementioned viscosity index improver, an oxygen-containing base oil is preferred. That is, the refrigeration oil of the present invention preferably comprises an oxygen-containing base oil. When the viscosity index improver comprises an oxygen-containing base oil (B), it can be used directly as a refrigeration oil, or it can be further formulated to contain an oxygen-containing base oil (B) or an oxygen-containing base oil other than the oxygen-containing base oil (B) contained in the viscosity index improver for use as a refrigeration oil.

[0225] Regarding the oxygen-containing base oil used as the lubricating oil base oil in the refrigeration oil of the present invention, any oxygen-containing base oil that is commonly used in lubricating oils can be used. From the perspective of use in refrigeration oils, it is preferable to select at least one selected from esters and ethers, and more preferably at least one selected from the group consisting of ester oil (B1), polyethylene ether (B2), and polyalkylene glycol (B3). One of ester oil (B1), polyethylene ether (B2), and polyalkylene glycol (B3) can be used, or two or more can be used together.

[0226] Regarding ester oils (B1), polyethylene ethers (B2), and polyalkylene glycols (B3) used as base oils for lubricating oils, the same substances as those exemplified above as oxygen-containing base oils (B) used in viscosity index improvers can be cited.

[0227] Regarding the ester oil (B1) in the oxygen-containing base oil used as a lubricating oil base oil, polyol ester (B12) is preferred, and polyol ester (B12-2) of polyol (2 to 10) alcohol (x2) and monocarboxylic acid (y1) is more preferred.

[0228] Furthermore, the refrigeration oil of the present invention may further contain other base oils besides the aforementioned oxygen-containing base oils. Other base oils may include, for example, hydrocarbon oils or other oxygen-containing oils. Examples of hydrocarbon oils include mineral oils, olefin polymers, naphthalene compounds, and alkylbenzenes. Examples of other oxygen-containing base oils include esters such as complex esters, aliphatic ethers, polyphenyl ethers, and perfluoroethers.

[0229] From the perspective of the solubility of copolymer (A), the SP value of the oxygen-containing base oil in the refrigeration oil is preferably 8.0 to 10.0 (cal / cm³). 3 ) 1 / 2 A further preferred value is 8.4–9.5 (cal / cm³). 3 ) 1 / 2 .

[0230] It should be noted that when the refrigeration oil contains two or more oxygen-containing base oils (for example, when the oxygen-containing base oil used as the lubricating oil base oil is different from the polymeric base oil used as the viscosity index improver or the oxygen-containing base oil used as the diluent), the SP values ​​of each component in the refrigeration oil are calculated using the above method, and the arithmetic mean of each SP value is calculated based on its mass fraction. The arithmetic mean obtained is preferably within the range described above.

[0231] From the perspective of its solubility and solubility in refrigerants, the absolute value of the difference between the SP value of copolymer (A) in the refrigeration oil and the SP value of the oxygen-containing base oil is preferably 2.0 (cal / cm). 3 ) 1 / 2 The following, and more preferably 1.5 (cal / cm) 3 ) 1 / 2 The following, particularly preferred, value is 1.0 (cal / cm³). 3 ) 1 / 2 the following.

[0232] It should be noted that when the refrigeration oil contains two or more oxygen-containing atomic base oils, the SP values ​​of each component in the refrigeration oil are calculated using the above method, and the SP values ​​are arithmetically averaged based on their mass fractions. The absolute value of the difference between the SP value of the calculated oxygen-containing atomic base oil and the SP value of the copolymer (A) is preferably within the above range.

[0233] The kinematic viscosity of oxygen-containing atomic base oils in refrigeration oils at 40°C (measured according to JIS-K2283) is typically 1–200 mm.2 From the perspective of improving the viscosity index and the kinematic viscosity at low temperatures, the preferred value is 5–100 mm / s. 2 / s, further preferably 7-50mm 2 / s.

[0234] From the perspectives of improving viscosity index and kinematic viscosity at low temperatures, the kinematic viscosity of oxygen-containing base oils in refrigeration oils at 100℃ (measured according to JIS-K2283) is preferably 1–10 mm. 2 / s, further preferably 1-9mm 2 / s.

[0235] The viscosity index (measured according to JIS-K2283) of oxygen-containing base oil in refrigeration oil is usually above 0. From the perspective of improving the viscosity index of refrigeration oil, it is preferably above 50, and more preferably 50 to 180.

[0236] In addition to the viscosity index improver and oxygen-containing atomic base oil (B) of this invention, the refrigeration oil of this invention may further contain various additives as needed. Examples of such additives include acid scavengers, antioxidants, extreme pressure agents, oiliness agents, defoamers, metal passivators, anti-wear agents, pour point depressants, and cleaning and dispersing agents. It should be noted that the content of the additives, based on the total amount of various additives relative to the total volume of the refrigeration oil, is preferably 5% by mass or less, more preferably 2% by mass or less.

[0237] In the refrigeration oil of the present invention, the content of oxygen-containing atomic base oil is generally 50% by mass or more, preferably 60% by mass or more, based on the total amount of refrigeration oil. In order to make the refrigeration oil have excellent properties such as lubricity, compatibility, thermal / chemical stability, and electrical insulation, the content is preferably 70% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more, based on the total amount of refrigeration oil.

[0238] Furthermore, in the case where the viscosity index improver of the present invention is contained in the refrigeration oil, the content of the viscosity index improver or copolymer (A) is generally 50% by mass or less based on the total amount of refrigeration oil, and preferably 1 to 20% by mass, more preferably 2 to 10% by mass, based on the total amount of refrigeration oil, from the perspective of viscosity index.

[0239] The kinematic viscosity of refrigeration oil at 40°C is not particularly limited, but can preferably be 3–1000 mm. 2 / s, more preferably 4 to 500 mm 2 / s, further preferably 5-400mm 2From the perspectives of maintaining a high kinematic viscosity, reducing low-temperature viscosity characteristics, and balancing compatibility with refrigerants, 15 mm is further preferred. 2 / s or above or 30mm 2 / s or higher, can be 200mm 2 / s or less, 100mm 2 / s or below or 85mm 2 / s or less.

[0240] There is no particular limitation on the kinematic viscosity of refrigeration oil at 100°C, but it can preferably be 1 to 100 mm. 2 / s, more preferably 2 to 50 mm 2 From the perspectives of maintaining a high kinematic viscosity, reducing low-temperature viscosity characteristics, and balancing compatibility with refrigerants, 5 mm is further preferred. 2 / s or above or 7mm 2 / s or higher, can be 25mm 2 / s or less, 20mm 2 / s or less or 15mm 2 / s or less.

[0241] The viscosity index of the refrigeration oil is not particularly limited, but is preferably 90 or higher, more preferably 100 or higher, more preferably 120 or higher, and even more preferably 200 or higher, 250 or higher, or 300 or higher. From the perspective of maintaining a high kinematic viscosity at 100°C, reducing low-temperature viscosity characteristics, and balancing compatibility with the refrigerant, the mixing ratio of the oxygen-containing base oil and the viscosity index improver can be freely set, for example, to be 400 or lower, 350 or lower, 300 or lower, or 250 or lower. Furthermore, for the same reason, the ratio of the viscosity index of the refrigeration oil to the viscosity index of the oxygen-containing base oil contained in the refrigeration oil can be, for example, 1.5 times or higher, preferably 2 times or higher, more preferably 2.5 times or higher, even more preferably 3 times or higher, preferably 10 times or lower, more preferably 8 times or lower, and even more preferably 6 times or lower.

[0242] There is no particular limitation on the volume resistivity of refrigeration oil, but it can preferably be 1.0 × 10⁻⁶. 9 Ω·m or more, more preferably 1.0×10 10 Ω·m or more, with the optimal value being 1.0 × 10⁻⁶. 11 Ω·m or higher. Especially in applications involving hermetic refrigeration units, there is a tendency to require high electrical insulation. It should be noted that, in this invention, volume resistivity refers to the value measured at 25°C according to JISC 2101 "Test Method for Electrical Insulating Oils".

[0243] There is no particular limitation on the water content of refrigeration oil, but it is preferably 200 ppm or less, more preferably 100 ppm or less, and most preferably 50 ppm or less, based on the total volume of the refrigeration oil. Especially when used in hermetically sealed refrigeration applications, a low water content is required from the perspective of its impact on the thermal / chemical stability and electrical insulation of the refrigeration oil.

[0244] The acid value of the refrigeration oil is not particularly limited. However, to prevent corrosion of metals used in the refrigeration unit or piping, and to prevent the decomposition of esters contained in the refrigeration oil of this invention, it is preferably below 0.1 mg KOH / g, and more preferably below 0.05 mg KOH / g. It should be noted that, in this invention, the acid value refers to the acid value measured according to JIS K2501 "Petroleum products and lubricating oils—Neutralization value test method".

[0245] The ash content of the refrigeration oil is not particularly limited. However, in order to improve the thermal / chemical stability of the refrigeration oil and inhibit the formation of sludge in this invention, it is preferably below 100 ppm, and more preferably below 50 ppm. It should be noted that the ash content in this invention refers to the ash content value determined according to JIS K 2272 "Test Method for Ash Content and Sulfuric Acid Ash Content of Crude Oil and Petroleum Products".

[0246] Refrigeration oils containing the viscosity index improver of the present invention are suitable for use in refrigeration machines such as air conditioners, refrigerators, open or closed automotive air conditioners, dehumidifiers, water heaters, cold storage, cold storage warehouses, vending machines, display cases, and chemical plants, as well as refrigeration machines with centrifugal compressors, which have reciprocating or rotary hermetically sealed compressors.

[0247] <Working fluid compositions for refrigeration machines>

[0248] When the viscosity index improver of the present invention is used as a viscosity index improver for refrigeration oil, it exists in the refrigeration machine as a working fluid composition for refrigeration machines mixed with refrigerant (C). That is, the working fluid composition for refrigeration machines of the present invention contains the refrigeration oil of the present invention (lubricating oil base oil and viscosity index improver of the present invention) and refrigerant (C). The viscosity index improver of the present invention is preferably used in a working fluid composition for refrigeration machines containing refrigerant (C) and oxygen-containing base oil (B).

[0249] Examples of refrigerants (C) include saturated fluorinated hydrocarbon refrigerants {difluoromethane (R32), trifluoromethane (R23), pentafluoroethane (R125), 1,1,2,2-tetrafluoroethane (R134), 1,1,1,2-tetrafluoroethane (R134a), 1,1,1-trifluoroethane (R143a), 1,1-difluoroethane (R152a), fluoroethane (R161), 1,1,1,2,3,3,3-heptafluoropropane (R227ea), 1,1,1,2,3,3-hexafluoropropane (R236ea), 1,1,1,3,3,3-hexafluoropropane (R236fa), 1,1,1,3,3-pentafluoropropane (R245fa), and 1,1,1,3,3-pentafluorobutane (R365mfc), etc.}, and unsaturated fluorinated hydrocarbon refrigerants. Hydrocarbon refrigerants {e.g., 2,3,3,3-tetrafluoropropylene (R1234yf), 1,2,3,3,3-pentafluoropropylene (R1225ye), 1,3,3,3-tetrafluoropropylene (R1234ze), 1,2,3,3-tetrafluoropropylene (R1234ye), 3,3,3-trifluoropropylene (HFO-1243zf), monofluoroethylene (HFO-1141), difluoroethylene (HFO-1132), 1,1,2-trifluoroethylene (R1123), (Z)-1,1,1,4,4,4-hexafluoro-2-butene (R1336mzz(Z)), 1-chloro-2,3,3,3-tetrafluoropropylene (HCFO-1224yd), etc.} and natural refrigerants {carbon dioxide, ammonia, n-propane, n-butane, and n-isobutane}, etc.

[0250] Saturated fluorinated hydrocarbon refrigerants can also be mixtures of two or more types, such as mixtures of R134a / R32 = 60–80% by mass / 40–20% by mass, R32 / R125 = 40–70% by mass / 60–30% by mass, R125 / R143a = 40–60% by mass / 60–40% by mass, R134a / R32 / R125 = 60% by mass / 30% by mass / 10% by mass, R134a / R32 / R125 = 40–70% by mass / 15–35% by mass / 5–40% by mass, and R125 / R134a / R143a = 35–55% by mass / 1–15% by mass / 40–60% by mass, etc.

[0251] More specifically, examples include mixtures with R134a / R32 = 70 / 30 wt%; mixtures with R32 / R125 = 60 / 40 wt%; mixtures with R32 / R125 = 50 / 50 wt% (R410A); mixtures with R32 / R125 = 45 / 55 wt% (R410B); mixtures with R125 / R143a = 50 / 50 wt% (R507C); R Mixtures of 32 / R125 / R134a = 30 / 10 / 60% by mass; mixtures of 23 / 25 / 52% by mass (R407C); mixtures of 25 / 15 / 60% by mass (R407E); mixtures of 44 / 4 / 52% by mass (R404A), etc.

[0252] As the refrigerant (C), from the perspective of compatibility with the copolymer (A), it is preferably at least one refrigerant or a mixture of two or more refrigerants selected from saturated fluorinated hydrocarbon refrigerants, unsaturated fluorinated hydrocarbon refrigerants and natural refrigerants. It is preferably at least one selected from the group consisting of saturated or unsaturated fluorinated hydrocarbon refrigerants with 1 to 3 carbon atoms and carbon dioxide, ammonia, n-propane, n-butane and n-isobutane. It is more preferably at least one selected from the group consisting of R32, R125, R134a, R410A, R407C, R1234yf, R1234ze, carbon dioxide, ammonia, n-propane, n-butane and n-isobutane. It is even more preferably R32, R125, R134a, R410A, R407C, R1234yf and R1234ze. It is particularly preferably R32, R125, R134a, R410A, R407C and R1234yf.

[0253] The content of copolymer (A) in the working fluid composition for refrigeration machines is preferably 0.1 to 30 parts by mass relative to 100 parts by mass of refrigerant (C), and more preferably 0.2 to 10 parts by mass.

[0254] The mass ratio of refrigerant (C) to refrigeration oil (total mass of copolymer (A) and oxygen-containing base oil (B)) in the working fluid composition for refrigeration machines (refrigerant (C) / refrigeration oil) is preferably 99 / 1 to 1 / 99, and more preferably 95 / 5 to 40 / 60.

[0255] The following matters are disclosed in this specification.

[0256] This disclosure (1) relates to a viscosity index improver, which is a viscosity index improver containing a copolymer (A) comprising a monomer (a) having fluorine atoms represented by the following general formula (1) and a monomer (b) represented by the following general formula (2) as necessary constituent monomers, wherein the solubility parameter of the copolymer (A) is 8.1 to 10.0 (cal / cm³). 3 ) 1 / 2 The mass ratio (b / a) of the monomer (b) in the monomer constituting copolymer (A) to the mass of the monomer (a) is 0.01 to 42.

[0257] [Chemistry 6]

[0258]

[0259] In general formula (1), R 1 It is a hydrogen atom or a methyl group; R 2 It is an alkylene group with 2 to 4 carbon atoms; p is an integer of 0 or 1; q is an integer of 0 to 20, and when q is 2 or more, R 2 They can be the same or different; Y is a monovalent group in which some or all of the hydrogen atoms in a hydrocarbon group with 1 to 40 carbon atoms are replaced by fluorine atoms.

[0260] [Chemistry 7]

[0261]

[0262] In general formula (2), R 3 It can be a hydrogen atom or a methyl group; -X 1 - is a group represented by -O- or -NH-; R 4 It is an alkylene group with 2 to 4 carbon atoms; r is an integer of 0 or 1; s is an integer of 0 to 20, and when s is 2 or more, R 4 They can be the same or different; R 5 It consists of hydrocarbon groups with 1 to 40 carbon atoms.

[0263] This disclosure (2) relates to the viscosity index improver described in this disclosure (1), wherein the solubility parameter of the structural unit from the monomer (a) is 6.5 to 9.0 (cal / cm³). 3 ) 1 / 2 .

[0264] This disclosure (3) relates to the viscosity index improver described in disclosure (1) or (2), wherein the weight-average molecular weight of the copolymer (A) is 1,000 to 2,000,000.

[0265] This disclosure (4) relates to any one of the viscosity index improvers in disclosures (1) to (3), wherein the improver further contains an oxygen-containing base oil.

[0266] This disclosure (5) relates to a refrigeration oil containing a lubricating oil base oil and a viscosity index improver as described in any one of disclosures (1) to (4).

[0267] This disclosure (6) relates to the refrigeration oil described in this disclosure (5), wherein the oil contains an oxygen-containing atomic base oil.

[0268] This disclosure (7) relates to the refrigeration oil described in this disclosure (6), wherein the oxygen-containing base oil is at least one selected from the group consisting of ester oil (B1), polyvinyl ether (B2) and polyalkylene glycol (B3).

[0269] This disclosure (8) relates to the refrigeration oil described in disclosure (6) or (7), wherein the absolute value of the difference between the solubility parameter of the copolymer (A) and the solubility parameter of the oxygen-containing base oil is 2.0 (cal / cm³). 3 ) 1 / 2 the following.

[0270] This disclosure (9) relates to the refrigeration oil described in any one of disclosures (6) to (8), wherein the solubility parameter of the oxygen-containing base oil is 8.0 to 10.0 (cal / cm³). 3 ) 1 / 2 .

[0271] This disclosure (10) relates to a working fluid composition for a refrigeration machine, comprising any one of the refrigeration oils (5) to (9) of this disclosure, and a refrigerant.

[0272] This disclosure (11) relates to the working fluid composition for a refrigeration machine described in this disclosure (10), wherein the refrigerant is at least one refrigerant selected from the group consisting of saturated fluorinated hydrocarbon refrigerants, unsaturated fluorinated hydrocarbon refrigerants and natural refrigerants, or a mixture of two or more refrigerants.

[0273] Example

[0274] The present invention will be described in more detail below based on embodiments, but the present invention is not limited to the embodiments.

[0275] <Example 1>

[0276] [Manufacturing of Viscosity Index Improver (R-1)]

[0277] In a reaction vessel equipped with a stirring device, heating and cooling device, thermometer, and nitrogen inlet pipe, a monomer mixture {20 parts by mass of monomer (a-1) [2,2,2-trifluoroethyl methacrylate] and 80 parts by mass of monomer (b-4) [n-butyl methacrylate]} totaling 100 parts by mass, 400 parts by mass of oxygen-containing base oil (B-1) [dieseride of neopentyl glycol and 2-ethylhexanoic acid] as the polymerization base oil, and 0.2 parts by mass of 2,2'-azobis(2,4-dimethylpentanonitrile) as the polymerization catalyst were added, followed by nitrogen purging (gas phase oxygen concentration 100 ppm). Under sealed conditions, the temperature was raised to 76°C while stirring, and the polymerization reaction was carried out at this temperature for 5 hours. After heating to 90°C, the product is cured for 2 hours. After heating to 120°C, the unreacted monomers are removed at this temperature under reduced pressure (0.027~0.040MPa) for 1 hour to obtain a viscosity index improver (R-1) containing copolymer (A-1).

[0278] <Examples 2-18, Comparative Examples 1-7>

[0279] [Manufacturing of viscosity index improvers (R-2) to (R-18), (R'-1) to (R'-7)]

[0280] In Example 1, the monomer blend and polymer base oil were replaced with the substances listed in Tables 2 to 5, and the reaction was carried out in the same manner to obtain polymer solutions (R-2) to (R-18) and (R'-1) to (R'-7) containing each polymer.

[0281] [Table 2]

[0282]

[0283] [Table 3]

[0284]

[0285] [Table 4]

[0286]

[0287] [Table 5]

[0288]

[0289] It should be noted that the composition of the monomers recorded in Tables 2 to 5 is as follows.

[0290] (a-1): 2,2,2-trifluoroethyl methacrylate, product name "LIGHT ESTER M-3F", manufactured by Kyoei Chemical Co., Ltd.

[0291] (a-2): 2,2,3,3,3-pentafluoropropyl methacrylate, manufactured by Tokyo Chemical Industry Co., Ltd.

[0292] (a-3): 2-(perfluorooctyl)ethyl methacrylate, manufactured by Tokyo Chemical Industry Co., Ltd.

[0293] (a-4): 2-(perfluorohexyl)ethyl methacrylate, manufactured by Tokyo Chemical Industry Co., Ltd.

[0294] (b-1): Methyl methacrylate

[0295] (b-2): Ethyl methacrylate

[0296] (b-3): Isopropyl methacrylate

[0297] (b-4): n-Butyl methacrylate

[0298] (b-5): Isobutyl methacrylate

[0299] (b-6): tert-butyl methacrylate

[0300] (b-7): Dodecyl methacrylate

[0301] (b-8): A mixture of straight-chain and branched alkyl methacrylates with 14 to 16 carbon atoms (an esterification of Neodol45 (manufactured by Shell Chemicals) and methacrylic acid).

[0302] (b-9) Octadecyl methacrylate

[0303] (b-10): 2-Dodecylhexadecyl methacrylate

[0304] (b-11): 2-Tetradecyl octadecyl methacrylate

[0305] In addition, the oxygen-containing atomic base oils (B) used in Tables 2-5 are described below.

[0306] (B-1) Diester of neopentyl glycol and 2-ethylhexanoic acid (kinematic viscosity at 40°C: 7.45 mm) 2 kinematic viscosity at 100℃ and per second: 2.05 mm³ / s 2 / s, viscosity index: 52, SP value: 8.79)

[0307] (B-2) Diester of neopentyl glycol and 3,5,5-trimethylhexanoic acid (kinematic viscosity at 40°C: 13.0 mm) 2 kinematic viscosity at 100℃ and per second: 3.1 mm³ / s 2 / s, viscosity index: 95, SP value: 8.52)

[0308] (B-3)2-ethylhexanol diester with adipic acid (kinematic viscosity at 40°C: 7.80 mm) 2 kinematic viscosity at 100℃ and per second: 2.40 mm³ / s 2 / s, viscosity index: 135, SP value: 8.91)

[0309] (B-4) Monoester of 2-ethylhexanol and 2-ethylhexanoic acid (kinematic viscosity at 40°C: 2.70 mm) 2 kinematic viscosity at 100℃ and per second: 1.10 mm³ 2 / s, viscosity index: 85, SP value: 8.45)

[0310] (B-5) Tetraester of pentaerythritol and 3,5,5-trimethylhexanoic acid (kinematic viscosity at 40°C: 114.1 m) 2 kinematic viscosity at 100℃ and per second: 11.5 mm³ / s 2 / s, SP value: 8.81)

[0311] (B-6) Tetraester of pentaerythritol and 2-ethylhexanoic acid (kinematic viscosity at 40°C: 45.3 mm) 2 kinematic viscosity at 100℃ and per second: 6.3 mm³ / s 2 / s, viscosity index: 81, SP value: 9.15)

[0312] <Compatibility of copolymers in viscosity index improvers with oxygen-containing base oil (B)>

[0313] The compatibility of the copolymer in the viscosity index improver with oxygen-containing base oil (B) was evaluated using the following evaluation criteria.

[0314] [Evaluation Criteria]

[0315] ○: Uniform appearance, no insoluble matter from copolymers.

[0316] ×: Uneven appearance, insoluble matter from the copolymer observed.

[0317] <Manufacturing of Refrigeration Oil>

[0318] Viscosity index improvers (R-1) to (R-18) and (R'-1) to (R'-7) and oxygen-containing base oil (B) were placed at 25°C for one day for temperature adjustment. Further, viscosity index improvers (R-1) to (R-18) and (R'-1) to (R'-7) and oxygen-containing base oil (B) were mixed and stirred (500 rpm) according to the mixing proportions listed in Tables 1 to 5 to produce refrigeration oils (1) to (18) and comparative refrigeration oils (1') to (7'). The appearance of each refrigeration oil was visually observed under a white fluorescent lamp at room temperature (25°C) at 5 minutes and 1 hour after stirring began. The solubility of viscosity index improvers (R) or (R') in oxygen-containing base oil (B) was evaluated according to the following evaluation criteria.

[0319] [Evaluation Criteria]

[0320] ◎: Dissolves within 5 minutes after stirring begins, with a uniform appearance and no insoluble copolymer material.

[0321] ○: Dissolves within 1 hour after stirring begins, with a uniform appearance and no insoluble copolymer material.

[0322] ×: One hour after stirring began, the appearance was still uneven, and insoluble matter from the copolymer was observed.

[0323] <Calculation Methods for Kinematic Viscosity and Viscosity Index of Refrigeration Oil>

[0324] The kinematic viscosity at -40℃, -20℃, 40℃, and 100℃ was determined using the method described in JIS-K2283. The viscosity index was calculated using the kinematic viscosity measurements at 40℃ and 100℃. A higher value indicates a greater improvement in the viscosity index.

[0325] <Compatibility test with refrigerant (C)R134a>

[0326] 6g of R134a (40% by mass) as a representative saturated fluorinated hydrocarbon refrigerant was mixed into 4g each of refrigeration oils 1-18 or comparative refrigeration oils 2', 3', 6', and 7', and cooled for 1 hour. The compatibility of the refrigerant and refrigeration oil was visually confirmed and evaluated according to the following criteria. Additionally, 8.5g of refrigerant R134a (15% by mass) was mixed into 1.5g of each of the above-mentioned refrigeration oils, and the compatibility was similarly evaluated. The results are shown in Tables 2-5.

[0327] [Evaluation Criteria]

[0328] ◎: When the refrigeration oil concentration is 15% by mass and 40% by mass, the appearance is uniform and there are no insoluble substances.

[0329] ○: When the refrigeration oil concentration is 15% by mass, the appearance is uneven and insoluble matter is observed. However, when the refrigeration oil concentration is 40% by mass, the appearance is uniform and no insoluble matter is observed.

[0330] ×: At refrigeration oil concentrations of 15% by mass and 40% by mass, the appearance was uneven, and insoluble matter was observed.

[0331] <Compatibility test with refrigerant (C)R1234yf>

[0332] 6g of R1234yf (40% by mass of refrigeration oil), a representative unsaturated fluorinated hydrocarbon refrigerant, was mixed with 4g each of the refrigeration oils 14-18 shown in Table 4 or the comparative refrigeration oils 2', 3', 6', and 7' shown in Table 5, and cooled at -30°C for 1 hour. The compatibility of the refrigerant and refrigeration oil was visually confirmed and evaluated according to the following criteria. Additionally, 8.5g of refrigerant R1234yf (15% by mass of refrigeration oil) was mixed with 1.5g of each of the above-mentioned refrigeration oils, and the compatibility was similarly evaluated. The results are shown in Table 6.

[0333] [Evaluation Criteria]

[0334] ◎: At refrigeration oil concentrations of 15% by mass and 40% by mass, the appearance is uniform and there are no insoluble substances.

[0335] ○: When the refrigeration oil concentration is 15% by mass, the appearance is uneven and insoluble matter is observed. However, when the refrigeration oil concentration is 40% by mass, the appearance is uniform and no insoluble matter is observed.

[0336] ×: At refrigeration oil concentrations of 15% by mass and 40% by mass, the appearance was uneven, and insoluble matter was observed.

[0337] [Table 6]

[0338]

[0339] As shown in Tables 2-6, the viscosity index improver of the present invention exhibits excellent solubility in oxygen-containing base oils and refrigerants, with a high viscosity index improvement effect and low low-temperature viscosity. On the other hand, it can be seen that the viscosity index improver of the comparative examples has low solubility in oxygen-containing base oils or refrigerants.

[0340] Industrial applicability

[0341] The viscosity index improver of the present invention exhibits excellent solubility in refrigerants and oxygen-containing base oils. When used in refrigeration oils, it significantly improves the viscosity index, resulting in refrigeration oils with excellent low-temperature characteristics. Therefore, it can be appropriately used as a viscosity index improver for refrigeration oils. Furthermore, the refrigeration oil of the present invention, when mixed with this viscosity index improver, shows a high viscosity index improvement effect, resulting in excellent low-temperature viscosity characteristics and excellent compatibility with refrigerants. Therefore, the working fluid containing the refrigeration oil and refrigerant of the present invention can circulate unimpeded in the refrigeration system, making it very useful. Additionally, the refrigeration oil or working fluid for refrigeration machines containing the viscosity index improver of the present invention is suitable for use in refrigeration machines such as air conditioners, refrigerators, open or closed automotive air conditioners, dehumidifiers, water heaters, freezers, cold storage warehouses, vending machines, display cases, and chemical plants with reciprocating or rotary hermetically sealed compressors, as well as refrigeration machines with centrifugal compressors.

Claims

1. A viscosity index improver, comprising a copolymer (A) containing a monomer (a) having fluorine atoms as represented by the following general formula (1) and a monomer (b) as represented by the following general formula (2) as essential constituent monomers, wherein, The solubility parameters of copolymer (A) are 8.1–10.0 (cal / cm³). 3 ) 1 / 2 The mass ratio (b / a) of said monomer (b) to said monomer (a) in the monomers constituting copolymer (A) is 0.01 to 42. [Chemistry 1] In general formula (1), R 1 It is a hydrogen atom or a methyl group; R 2 It is an alkylene group with 2 to 4 carbon atoms; p is 1; q is 0; Y is a monovalent group in which some or all of the hydrogen atoms in a hydrocarbon group with 1 to 40 carbon atoms are replaced by fluorine atoms; [Chemistry 2] In general formula (2), R 3 It can be a hydrogen atom or a methyl group; -X 1 - is a group represented by -O- or -NH-; R 4 It is an alkylene group with 2 to 4 carbon atoms; r is 1; s is 0; R 5 It is an alkyl group having 1 to 4 carbon atoms.

2. The viscosity index improver as described in claim 1, wherein, The solubility parameter of the structural unit from said monomer (a) is 6.5–9.0 (cal / cm³). 3 ) 1 / 2 .

3. The viscosity index improver as described in claim 1 or 2, wherein, The copolymer (A) has a weight-average molecular weight of 1,000 to 2,000,000.

4. The viscosity index improver as described in claim 1 or 2, wherein, It further contains oxygen-containing atomic base oils.

5. A refrigeration oil comprising a lubricating oil base oil and the viscosity index improver as described in claim 1.

6. The refrigeration oil as described in claim 5, wherein, It contains oxygen-containing atomic base oil.

7. The refrigeration oil as described in claim 6, wherein, The oxygen-containing base oil is selected from at least one of the group consisting of ester oil (B1), polyvinyl ether (B2), and polyalkylene glycol (B3).

8. The refrigeration oil as described in claim 6 or 7, wherein, The absolute value of the difference between the solubility parameter of the copolymer (A) and the solubility parameter of the oxygen-containing base oil is 2.0 (cal / cm³). 3 ) 1 / 2 the following.

9. The refrigeration oil as described in claim 6 or 7, wherein, The solubility parameter of the oxygen-containing base oil is 8.0–10.0 (cal / cm³). 3 ) 1 / 2 .

10. A working fluid composition for a refrigeration machine, comprising the refrigeration oil of claim 5 and a refrigerant.

11. The working fluid composition for a refrigeration machine as claimed in claim 10, wherein, The refrigerant is at least one refrigerant selected from the group consisting of saturated fluorinated hydrocarbon refrigerants, unsaturated fluorinated hydrocarbon refrigerants, and natural refrigerants, or a mixture of two or more refrigerants.

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