Lubricating oil base oil and lubricating oil composition

Abstract

To provide: a lubricating oil base oil which causes a refrigerant having the lubricating oil base oil blended therewith to have an improved chemical stability when used for a long period; and a lubricating oil composition including the lubricating oil base oil.SOLUTION: The lubricating oil base oil according to the present invention is blended with a refrigerant. The refrigerant includes one or more unsaturated fluorohydrocarbon compounds selected from a compound represented by the following formula i, the lubricating oil base oil includes a compound represented by the following formula 1, and the lubricating oil base oil has a metal content of 10 ppm or less: the formula i CxFyHz (in the formula i, x is an integer of 2 to 6, y is an integer of 1 to 11, z is an integer of 1 to 11, and one or more carbon-carbon unsaturated bonds are present in its molecule); and the formula 1 R1{(R2O)mR3}n (R1 is an initiator residue, R2s are each independently a 2-4C hydrocarbon group, R3s are each independently a hydrogen atom or a 1-4C alkyl group, at least one of the R3s is a 1-4C alkyl group, m is 1 to 200, and n is 1 to 8.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a lubricating base oil and a lubricating oil composition. [Background technology]

[0002] Various lubricating base oils are used to ensure smooth circulation of the refrigerant in compression-type refrigerators. Compounds such as polyalkylene glycols, polyol esters, and polyvinyl ethers can be used as lubricating base oils depending on the type of refrigerant. For example, Patent Document 1 discloses, in its working examples, the mixing of a lubricating base oil containing an epoxy compound such as 1,2-epoxyhexadecane and a polyalkylene glycol with a refrigerant. Furthermore, because the refrigerant and lubricating base oil are sealed and used in the refrigerator for long periods of time, they are required to be stable enough to prevent the formation of precipitates even after long-term use. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-240278 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when refrigerants containing conventional lubricating base oils are used for a long period of time, precipitates may occur. Thus, there is room for improvement in the chemical stability of refrigerants containing lubricating base oils when used for a long period of time.

[0005] The present invention provides a lubricating base oil that improves the chemical stability of a refrigerant blended with the lubricating base oil when used for an extended period of time, and a lubricating oil composition containing the lubricating base oil. [Means for solving the problem]

[0006] The present invention has the following aspects. [1] A lubricating base oil that can be mixed with a refrigerant, The refrigerant contains one or more unsaturated fluorohydrocarbon compounds selected from the group consisting of compounds represented by the following formula i: The lubricating base oil comprises a compound represented by the following formula 1: A lubricating base oil having a metal content of 10 ppm or less. CxFyHz...Formula i In formula i, x is an integer of 2 to 6, y is an integer of 1 to 11, and z is an integer of 1 to 11, and the compound has one or more carbon-carbon unsaturated bonds in the molecule. R 1 {(R 2 O) m R 3} n ...Formula 1 In formula 1, R 1 is the initiator residue, R 2 are each independently a hydrocarbon group having 2 to 4 carbon atoms, R 3 are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R 3 at least one of is an alkyl group having 1 to 4 carbon atoms, m is 1 to 200; n is 1 to 8. [2] R 2 The lubricating base oil according to [1], wherein at least one of the above is a hydrocarbon group having 3 carbon atoms. [3] R 3 The lubricating base oil according to [1] or [2], wherein at least one of the groups is a methyl group. [4] The lubricating base oil according to any one of [1] to [3], wherein the unsaturated fluorohydrocarbon compound of the refrigerant comprises one or more selected from 2,3,3,3-tetrafluoropropene (R1234yf), 1,3,3,3-tetrafluoropropene (R1234ze), and 1,2,3,3-tetrafluoropropene (R1234ye). [5] The lubricating base oil according to any one of [1] to [4], wherein the compound represented by formula 1 has a number average molecular weight of 300 to 5,000. [6] A lubricating oil composition comprising the lubricating base oil according to any one of [1] to [5], and either or both of a refrigerant and an additive. [7] The lubricating oil composition according to [6], which is used in a car air conditioner, an indoor air conditioner, a refrigerator, a freezer, a hot water supply system for a vending machine, a hot water supply system for a showcase, a refrigeration / heating system, or a gas heat pump system. [Effects of the Invention]

[0007] According to the present invention, the chemical stability of a refrigerant blended with a lubricating base oil is improved when used for a long period of time. DETAILED DESCRIPTION OF THE INVENTION

[0008] The meanings of the terms are as follows: "Active hydrogen" refers to a hydrogen atom derived from an active hydrogen-containing group and a hydrogen atom derived from a hydroxyl group of water. The "active hydrogen-containing group" refers to at least one group selected from the group consisting of a hydroxyl group bonded to a carbon atom, a carboxyl group, an amino group, a monovalent functional group formed by removing one hydrogen atom from a primary amine, and a sulfanyl group. The term "initiator residue" refers to a group obtained by removing one or more active hydrogens from an initiator. "Unit" means an atomic group formed directly by polymerization of a monomer. The "number average molecular weight" is a polystyrene-equivalent molecular weight obtained by GPC measurement. The "metal content of lubricating base oil" is the total amount of metal elements detected by elemental analysis using ICP atomic emission spectrometry. The unit of metal content, ppm, is based on mass. "Kinematic viscosity" is a value measured at 100°C in accordance with JIS K2283:2000. The "viscosity index" is a value calculated from the measured value of kinematic viscosity in accordance with JIS K2283:2000. "Volume resistivity" is a value measured in accordance with the "Volume resistivity test method" of JIS C2101:2010 "Electrical insulating oil." The symbol "to" indicating a range of values means that the values before and after the symbol "to" are included as the lower and upper limits. The ranges of values disclosed in this specification can be combined in any way to create new ranges of values.

[0009] [Lubricant base oil] The lubricating base oil of the present invention can impart lubricity to the sliding parts of a compressor in a compression-type refrigerator, for example, by mixing with a refrigerant.

[0010] (refrigerant) The refrigerant to be mixed with the lubricating base oil of the present invention contains one or more compounds selected from the compounds represented by the following formula i. Two or more compounds may be used in combination. CxFyHz...Formula i In formula i, x is an integer of 2 to 6, y is an integer of 1 to 11, and z is an integer of 1 to 11, and the compound has one or more carbon-carbon unsaturated bonds in the molecule. The compound represented by formula i is a fluoride (unsaturated fluorohydrocarbon compound) in which y hydrogen atoms of an unsaturated hydrocarbon compound having x carbon atoms and one or more carbon-carbon unsaturated bonds have been substituted with fluorine atoms. The carbon chain constituting the compound represented by formula (i) may be linear, branched, or cyclic. The number of carbon-carbon unsaturated bonds is preferably 1 to 5, more preferably 1 to 3, and particularly preferably 1.

[0011] Examples of the compound represented by formula i include a compound in which some of the hydrogen atoms of a linear or branched chain olefin having 2 to 6 carbon atoms have been substituted with fluorine atoms, and a compound in which some of the hydrogen atoms of a cyclic olefin having 4 to 6 carbon atoms have been substituted with fluorine atoms. Specific examples include ethylene fluoride having 1 to 3 fluorine atoms introduced, propene fluoride having 1 to 5 fluorine atoms introduced, butene fluoride having 1 to 7 fluorine atoms introduced, pentene fluoride having 1 to 9 fluorine atoms introduced, hexene fluoride having 1 to 11 fluorine atoms introduced, cyclobutene fluoride having 1 to 5 fluorine atoms introduced, cyclopentene fluoride having 1 to 7 fluorine atoms introduced, and cyclohexene fluoride having 1 to 9 fluorine atoms introduced. Among these, ethylene or propene fluorides are preferred, and propene having 3 to 5 fluorine atoms introduced therein is more preferred. Specifically, 1,1,2-trifluoroethylene (HFO-1123), 2,3,3,3-tetrafluoropropene (R1234yf), 1,3,3,3-tetrafluoropropene (R1234ze), Examples include 1,2,3,3-tetrafluoropropene (R1234ye). In particular, it is preferred that the compound represented by formula i includes one or more selected from 2,3,3,3-tetrafluoropropene (R1234yf), 1,3,3,3-tetrafluoropropene (R1234ze), and 1,2,3,3-tetrafluoropropene (R1234ye).

[0012] (Compound represented by formula 1) The lubricating base oil of the present invention contains a compound represented by the following formula 1 (hereinafter referred to as "compound 1"). R 1 {(R 2 O) m R 3} n ...Formula 1

[0013] In formula 1, R 1is an initiator residue. The initiator is not particularly limited as long as it is a compound having an active hydrogen-containing group. The initiator may have one or more active hydrogen-containing groups. Examples of initiators include aliphatic monoalcohols, aliphatic diols, aliphatic alcohols having 3 to 8 hydroxyl groups, amines, phenols, salts thereof, and alkylene oxide adducts thereof. However, the initiator is not limited to these examples. The initiator may be used alone or in combination of two or more.

[0014] The aliphatic monoalcohol may be a saturated aliphatic monoalcohol, an unsaturated aliphatic monoalcohol, or a cyclic aliphatic monoalcohol. Among them, a saturated aliphatic monoalcohol is preferred. Examples of saturated aliphatic monoalcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, isobutanol, tert-butanol, n-hexanol, octyl alcohol, and 2-ethylhexanol. However, the saturated aliphatic monoalcohol is not limited to these examples.

[0015] Examples of aliphatic diols include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, and 1,6-hexanediol, but the aliphatic diols are not limited to these examples.

[0016] Examples of aliphatic alcohols having 3 to 8 hydroxyl groups include glycerin, trimethylolethane, trimethylolpropane, hexanetriol, pentaerythritol, dipentaerythritol, diglycerin, meso-erythritol, methyl glucoside, glucose, sucrose, trehalose, and sorbitol, but the aliphatic alcohols having 3 to 8 hydroxyl groups are not limited to these examples.

[0017] Examples of amines include alkanolamines, heterocyclic amines, aliphatic amines, and aromatic amines. Examples of alkanolamines include monoethanolamine, diethanolamine, triethanolamine, and isopropanolamine. Examples of heterocyclic amines include N-(2-aminoethyl)piperazine and N-aminomethylpiperazine. Examples of the aliphatic amine include ethylenediamine, propylenediamine, and hexamethylenediamine. Examples of aromatic amines include tolylenediamine and diaminodiphenylmethane. However, the amines are not limited to these examples. One type of amine may be used alone, or two or more types may be used in combination.

[0018] Examples of phenols include bisphenol A and resorcinol. However, the phenol is not limited to these examples. One type of phenol may be used alone, or two or more types may be used in combination.

[0019] As the initiator, aliphatic monoalcohols, aliphatic diols, and aliphatic alcohols having 3 to 8 hydroxyl groups are preferred, and aliphatic diols and aliphatic alcohols having 3 to 8 hydroxyl groups are more preferred.

[0020] In formula 1, n (R 2 O) m R 3 may be the same or different. 2 O) m In this case, one kind of R 2 O may be present, and two or more R 2 O may be present. Two or more R 2 If O is present, then each R 2 The bonding order of O is not limited. For example, two types of R 2 When O is present, two types of R 2 O may be arranged randomly, alternately, or in blocks. (R 2 O) mmay be a random copolymer having units based on two or more types of alkylene oxide monomers, or may be a block copolymer.

[0021] R 2 R are each independently a hydrocarbon group having 2 to 4 carbon atoms. 2 The number of carbon atoms in the hydrocarbon group is preferably 2 or 3, and more preferably 3. 2 At least one of R is preferably a hydrocarbon group having 3 carbon atoms, 2 It is more preferable that all of the groups are hydrocarbon groups having 3 carbon atoms.

[0022] R 2 The hydrocarbon group R may be a straight chain or may have a branched chain. 2 When has a branched chain, the branched position and number of branches are not particularly limited.

[0023] R 2 Examples of such groups include -CH2CH2-, -CH2CH2CH2-, -CH2CH2CH2CH2-, -CH(CH3)CH2-, -CH2CH(CH3)-, -CH(CH3)CH2CH2-, and -CH2CH(CH3)CH2-.

[0024] In formula 1, R 3 are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. 3 The number of carbon atoms in the alkyl group is preferably 1 to 3, more preferably 1 or 2, and most preferably 1. That is, R 3 As the alkyl group, a methyl group is most preferred.

[0025] R 3 Examples include -CH3, -CH2CH3, -CH2CH2CH3, -CH2CH2CH2CH3, -CH(CH3)CH3, -CH(CH3)CH2CH3, and -CH2CH(CH3)CH3.

[0026] In formula 1, n R 3 At least one of the n R is an alkyl group having 1 to 4 carbon atoms. 3All of the n R 3 may be the same or different. That is, n (R 2 O) m R attached to the end of the chain 3 may be the same as or different from each other.

[0027] In formula 1, m is 1 to 200, preferably 5 to 100, more preferably 7 to 60, and even more preferably 8 to 50. When m is equal to or greater than the lower limit of the above-mentioned range, a lubricating base oil with a good viscosity index is likely to be obtained. When m is equal to or less than the upper limit of the above-mentioned range, a lubricating base oil with good low-temperature fluidity is likely to be obtained.

[0028] In formula 1, n is 1 to 8, preferably 1 to 6, more preferably 1 to 4, and even more preferably 1 to 3. When n is equal to or greater than the lower limit of the above-mentioned range, a lubricating base oil with a good viscosity index is likely to be obtained. When n is equal to or less than the upper limit of the above-mentioned range, a lubricating base oil with a good volume resistivity is likely to be obtained.

[0029] The number average molecular weight of the compound represented by formula 1 is preferably 300 to 5000, more preferably 500 to 3000, and even more preferably 700 to 2000. When the number average molecular weight is equal to or greater than the lower limit of the above-mentioned range, it is easy to obtain a suitable compatibility with the refrigerant. When the number average molecular weight is equal to or less than the upper limit of the above-mentioned range, it is easy to obtain a lubricating base oil with good kinematic viscosity.

[0030] (Physical properties of lubricant base oil) The metal content of the lubricating base oil of the present invention is 10 ppm or less. Therefore, the chemical stability of a refrigerant containing the lubricating base oil is improved when used for a long period of time. The metal content of the lubricating base oil is preferably 8 ppm or less, more preferably 5 ppm or less, and even more preferably 3 ppm or less. The lower limit of the metal content of the lubricating base oil is the better, and is not particularly limited, but may be, for example, 1 ppm, 0.5 ppm, 0.3 ppm, etc.

[0031] The metal elements contained in the lubricating base oil are not particularly limited. In the synthesis reaction of Compound 1, an alkylene oxide monomer can be addition polymerized to an initiator in the presence of a catalyst. Metal elements derived from the catalyst used in this synthesis reaction may remain in the lubricating base oil. In order to keep the metal content of the lubricating base oil at 10 ppm or less, it is preferable to thoroughly remove the catalyst after the synthesis reaction of Compound 1.

[0032] When measuring the metal content of a lubricating base oil, there is no particular limitation on the metal elements to be detected, and the detection targets are all metal elements that may be contained in a catalyst expected to be used in the production of the lubricating base oil. Examples of residual metals derived from the catalyst include Na, K, Zn, Co, Fe, Ni, Al, Sr, Mn, Cr, Cu, Sn, Pb, Mo, W, and V. However, the metal elements that can be detected are not limited to these examples. Furthermore, the metal elements that can be detected may be one type or two or more types.

[0033] The kinematic viscosity of the lubricating base oil at 100°C is not particularly limited, but may be, for example, 2 to 200 mm 2 / s, 5 to 100 mm 2 / s, 7 to 50 mm 2 / s. When the kinematic viscosity is equal to or greater than the lower limit of the above-mentioned range, the sealing performance is improved, making it less likely for the refrigerant to leak. When the kinematic viscosity is equal to or less than the upper limit of the above-mentioned range, the viscous resistance is small, improving the lubricity.

[0034] From the viewpoint of improving viscosity characteristics, the viscosity index of the lubricating base oil is preferably 50 or more, more preferably 80 or more, and even more preferably 100 or more. The upper limit of the viscosity index of the lubricating base oil is the higher the better, and is not particularly limited, but may be, for example, 140, 160, 200, etc.

[0035] The volume resistivity of the lubricating base oil is not particularly limited, but for example, it is 1×10 10 ~1×10 15 Ω cm, may be 6 x 10 10 ~1×10 14Ω cm may be 1×10 11 ~1×10 14 The volume resistivity may be Ω·cm. When the volume resistivity is equal to or greater than the lower limit of the above-mentioned range, electrical insulation properties are improved. When the volume resistivity is equal to or less than the upper limit of the above-mentioned range, generation of static electricity is easily prevented.

[0036] (Method of manufacturing lubricating base oil) Lubricant base oils are prepared by addition polymerization of alkylene oxide monomers to initiators in the presence of a catalyst to form elongated oxyalkylene chains ((R 2 O) m ) to obtain compound 1, and then remove the catalyst from the reaction solution containing compound 1. The details and preferred embodiments of the initiator are as described above.

[0037] Examples of the catalyst include alkali metal catalysts and double metal cyanide complex catalysts (hereinafter referred to as "DMC catalysts"), but the catalyst is not limited to these examples. The catalyst may be used alone or in combination of two or more.

[0038] Examples of alkali metal catalysts include alkali metals such as sodium and potassium; alkali metal alkoxides such as sodium methoxide, sodium ethoxide, sodium propoxide, potassium methoxide, potassium ethoxide, and potassium propoxide; hydroxides such as sodium hydroxide, potassium hydroxide, and cesium hydroxide; and carbonates such as sodium carbonate and potassium carbonate. The alkali metal catalysts may be used alone or in combination of two or more.

[0039] The DMC catalyst is believed to have at least a metal element and an organic ligand. Examples of metal elements in the DMC catalyst include Zn, Fe, Co, Ni, Al, Sr, Mn, Cr, Cu, Sn, Pb, Mo, W, and V. However, the metal elements in the DMC catalyst are not limited to these examples. The DMC catalyst may contain one or more metal elements.

[0040] Examples of organic ligands for DMC catalysts include t-butyl alcohol (hereinafter referred to as "TBA"), n-butyl alcohol, isobutyl alcohol, t-pentyl alcohol, isopentyl alcohol, N,N-dimethylacetamide, ethylene glycol mono-t-butyl ether, ethylene glycol dimethyl ether (glyme), diethylene glycol dimethyl ether (diglyme), triethylene glycol dimethyl ether (triglyme), isopropyl alcohol, and dioxane. Dioxane may be 1,4-dioxane or 1,3-dioxane. However, the organic ligand is not limited to these examples. The organic ligands may be used alone or in combination of two or more.

[0041] Examples of alkylene oxide monomers include ethylene oxide, propylene oxide, 1,2-butylene oxide, 2,3-butylene oxide, methyl glycidyl ether, 2,3-epoxy-1-propanol, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, lauryl glycidyl ether, hexyl glycidyl ether, tetrahydrofuran, epichlorohydrin, styrene oxide, and cyclohexene oxide, although the alkylene oxide monomer is not limited to these examples.

[0042] The alkylene oxide monomer may be used alone or in combination of two or more. That is, one alkylene oxide monomer may be homopolymerized using an initiator, or two or more alkylene oxide monomers may be copolymerized using an initiator. In the case of copolymerization, two or more alkylene oxide monomers may be block copolymerized using an initiator, or may be random copolymerized.

[0043] The reaction temperature, reaction time, and reactor pressure of the ring-opening addition polymerization reaction are not particularly limited. The reaction temperature may be, for example, 80 to 150°C or 90 to 140°C. The reaction time may be, for example, 3 to 30 hours or 5 to 20 hours. The pressure in the reactor may be, for example, 0.01 to 0.9 MPaG or 0.03 to 0.7 MPaG.

[0044] The method for introducing an alkyl group having 1 to 4 carbon atoms is not particularly limited, and examples thereof include the following Method 1 and Method 2. Method 1: Reacting an alkyl halide having 1 to 4 carbon atoms with the hydroxyl group at the end of the oxyalkylene chain. Method 2: A method in which a metal alkoxide having an alkyl group having 1 to 4 carbon atoms is reacted with the hydroxyl group at the end of an oxyalkylene chain.

[0045] The details and preferred embodiments of the alkyl group of the alkyl halide are as follows: R 3 The same applies as described above for Example 1. Examples of halogen include, but are not limited to, fluorine, chlorine, bromine, and iodine.

[0046] The details and preferred embodiments of the alkyl group of the metal alkoxide are as follows: 3 The content is the same as that explained for 1. Examples of metals in metal alkoxides include Na and K, but are not limited to these.

[0047] The reaction temperature, reaction time, and reactor pressure of Method 1 and Method 2 are not particularly limited. The reaction temperature may be, for example, 30 to 150°C or 40 to 140°C. The reaction time may be, for example, 1 to 20 hours or 2 to 10 hours. The reactor pressure may be, for example, 0.01 to 5 MPaG or 0.05 to 2 MPaG.

[0048] The alkyl group having 1 to 4 carbon atoms is connected to an oxyalkylene chain ((R 2 O) mThe conversion rate in the reaction of introducing n R 3 At least one of these is likely to be an alkyl group having 1 to 4 carbon atoms. When the conversion rate in the reaction is equal to or less than the upper limit of the above-mentioned range, compound 1 is easily synthesized.

[0049] The method for removing the catalyst is not particularly limited, and examples thereof include the following methods 3, 4, and 5. Method 3: The catalyst is adsorbed using an adsorbent, and then the adsorbent with the adsorbed catalyst is removed by filtration. Method 4: Neutralizing the catalyst with a neutralizing agent and then removing the neutralized catalyst by filtration. Method 5: A method of removing the catalyst during filtration using a charged filter.

[0050] In removing the catalyst, any one of Method 3, Method 4, and Method 5 may be carried out alone, or two or more of them may be appropriately combined, or all of Methods 3, 4, and 5 may be carried out. When two or more or all of Methods 3, 4, and 5 are carried out, the order in which they are carried out is not particularly limited. As the method for removing the catalyst, Methods 3 and 4 are preferred, and Method 3 is more preferred, from the viewpoint of further reducing the metal content.

[0051] Examples of adsorbents include synthetic silicates, ion exchange resins, activated clay, oxide salts, and acid clay. Examples of synthetic silicates include magnesium silicate, aluminum silicate, and hydrotalcite. Examples of oxide salts include magnesium oxide and aluminum oxide. However, the adsorbents are not limited to these examples. The adsorbent may be used alone or in combination of two or more kinds.

[0052] Examples of the neutralizing agent include amines, alkali metal hydroxides, organic acids, inorganic acids, and salts thereof. Examples of the inorganic acid include sulfuric acid, phosphoric acid, and hydrochloric acid. Examples of the organic acid include lactic acid. However, the neutralizing agent is not limited to these examples. The neutralizing agent may be used alone or in combination of two or more kinds.

[0053] A commercially available product may be used as the charged filter. Examples of commercially available charged filters include Zeta Plus Adsorption Depth Filter Cartridge EC Series (manufactured by 3M), RO Wind (manufactured by Organo), and SupraCap 200 (manufactured by Seitz AKSJ). However, the charged filter is not limited to these examples.

[0054] [Lubricating oil composition] The lubricating oil composition of the present invention comprises the above-described lubricating base oil and either or both of a refrigerant and an additive. In one example, the lubricating oil composition may comprise a lubricating base oil and a refrigerant, a lubricating base oil and an additive, or a lubricating base oil, a refrigerant, and an additive. The lubricating oil composition of the present invention can, for example, impart lubricity to the sliding parts of a compressor supplied with a refrigerant. The refrigerant is as described above.

[0055] Examples of additives include antioxidants, extreme pressure agents, stabilizers, copper deactivators, antifoaming agents, load-bearing additives, chlorine scavengers, oxygen scavengers, detergent-dispersants, viscosity index improvers, oiliness agents, rust inhibitors, corrosion inhibitors, and pour point depressants, but the additives are not limited to these examples. The additives may be used alone or in combination of two or more.

[0056] Examples of the antioxidant include phenol-based antioxidants and amine-based antioxidants. Examples of phenol-based antioxidants include 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, and 2,2'-methylenebis(4-methyl-6-tert-butylphenol). Examples of the amine antioxidant include phenyl-α-naphthylamine and N,N'-diphenyl-p-phenylenediamine. The antioxidants may be used alone or in combination of two or more. The oxygen scavengers may be used alone or in combination of two or more.

[0057] Examples of extreme pressure agents include phosphorus-based extreme pressure agents such as phosphate esters, acid phosphate esters, phosphites, acid phosphites, and amine salts thereof.

[0058] Examples of the stabilizer include epoxy compounds such as phenyl glycidyl ether, alkyl glycidyl ether, alkylene glycol glycidyl ether, cyclohexene oxide, α-olefin oxide, and epoxidized soybean oil.

[0059] Examples of copper deactivators include benzotriazole and its derivatives, such as N-[N,N'-dialkyl (alkyl group having 3 to 12 carbon atoms) aminomethyl]triazole.

[0060] Examples of the antifoaming agent include silicone oil and fluorinated silicone oil.

[0061] The proportion of the lubricating base oil may be 40 to 99.9 mass%, 45 to 90 mass%, or 50 to 80 mass% of the total amount of the lubricating oil composition. When the proportion of the lubricating base oil is equal to or greater than the lower limit of the above-mentioned range, chemical stability when mixed with a refrigerant is likely to be improved. When the proportion of the lubricating base oil is equal to or less than the upper limit of the above-mentioned range, compatibility with the refrigerant is favorable.

[0062] When a lubricating oil composition contains a refrigerant, the proportion of the refrigerant may be 0.1 to 80 mass%, 10 to 60 mass%, or 20 to 50 mass% of the total amount of the lubricating oil composition. A refrigerant proportion equal to or greater than the lower limit of the aforementioned range is preferable in terms of compatibility with the lubricating base oil. A refrigerant proportion equal to or less than the upper limit of the aforementioned range is likely to improve chemical stability when mixed with the lubricating base oil.

[0063] When the lubricating oil composition contains additives, the proportion of the additives may be 0.1 to 60 mass%, 1 to 40 mass%, or 2 to 20 mass% of the total amount of the lubricating oil composition. When the proportion of the additives is equal to or greater than the lower limit of the above-mentioned range, the antioxidant properties of the base oil are improved. When the proportion of the additives is equal to or less than the upper limit of the above-mentioned range, it is preferable in terms of compatibility with the refrigerant.

[0064] [Mechanism of action] The metal content of the lubricating base oil of the present invention described above is 10 ppm or less. Therefore, even when the refrigerant is used for a long period of time under severe conditions, deposits are less likely to occur. Thus, the lubricating base oil of the present invention improves the chemical stability of refrigerants blended with the lubricating base oil when used for a long period of time.

[0065] [Application] The lubricating base oil and lubricating oil composition of the present invention can be used in various cooling systems, such as car air conditioners, room air conditioners, refrigerators, freezers, hot water supply systems for vending machines, hot water supply systems for showcases, refrigeration / heating systems, and gas heat pump systems, but the uses of the lubricating base oil and lubricating oil composition are not limited to these examples.

[0066] The amounts of the lubricating base oil and refrigerant used in the present invention can be varied widely within a range of 99 / 1 to 10 / 90 in terms of the refrigerant / lubricating base oil mass ratio, preferably within a range of 90 / 10 to 50 / 50. [Example]

[0067] The following examples will explain the embodiments in more detail, but the present invention is not limited to the following examples. Examples 1-5 are examples, and Examples 6-8 are comparative examples.

[0068] [Measurement and Evaluation] (number average molecular weight) The lubricating base oil was subjected to GPC measurement under the following conditions to determine the number average molecular weight (Mn). GPC measurement conditions: Model used: HLC-8220GPC (Tosoh product) Data processing device: SC-8020 (Tosoh Corporation product) Column used: TSG gel G2500H (Tosoh Corporation) Column temperature: 40°C, detector: RI, solvent: tetrahydrofuran, flow rate: 0.6 mL / min Sample concentration: 0.25% by mass, injection volume: 10 μL Standard sample for creating a calibration curve: Polystyrene (Easical PS-2 Polystyrene Standards, Polymer Laboratories)

[0069] (metal content) After refining 20 g of each lubricating base oil, it was completely incinerated using a burner. The incinerated powder residue was mixed with 100 mL of aqueous hydrochloric acid to prepare a measurement sample. The Na, K, Zn, and Co contents were measured using an ICP optical emission spectrometer (SPS3500, SII Nanotechnology (Hitachi High-Tech Science)). The total amount of these detected metal elements was calculated as the metal content of the lubricating base oil.

[0070] (chemical stability) The test for evaluating chemical stability was performed in accordance with the sealed tube test described in JIS K2211-2009. More specifically, iron, copper, and aluminum were placed in a test tube as catalysts. Then, 0.7 mL of each lubricating base oil and 0.7 mL of the refrigerant were placed in the test tube, and the opening of the test tube was sealed. The sealed test tube was heated at 175°C for 14 days, after which the presence or absence of precipitates in the solution in the test tube was confirmed. 2,3,3,3-tetrafluoropropene (R1234yf) was used as the refrigerant.

[0071] [Example 1] After adding 162 g of powdered sodium methoxide to a 5 L autoclave, the temperature was raised to 110°C, and 4,350 g of propylene oxide was introduced into the autoclave over 10 hours. After introducing the propylene oxide, the pressure became constant, and after confirming that all of the propylene oxide had reacted, the temperature in the system was cooled to 100°C. Thereafter, 152 g of methyl chloride was introduced over 3 hours to carry out terminal methylation. After confirming that the pressure in the system had stabilized after the introduction of methyl chloride and that the methyl chloride had reacted, 2000 g of the resulting compound was transferred to a 5 L separable flask. 2000 g of distilled water and 20 g of phosphoric acid were added, and the aqueous layer was removed by oil-water separation. 60 g of a magnesium silicate-based adsorbent (Kyowado 600S, manufactured by Kyowa Chemical Industry Co., Ltd.) was added to the polyether compound in the oil layer as an adsorbent, and the mixture was stirred at 110 °C for 2 hours. The catalyst was then thoroughly removed by filtration of insoluble matter, yielding polyoxypropylene glycol dimethyl ether. The amount of residual metal in the obtained polyoxypropylene glycol dimethyl ether was 0.6 ppm, and the number average molecular weight determined by GPC was 1,480.

[0072] [Example 2] After adding 162 g of powdered sodium methoxide to a 5 L autoclave, the temperature was raised to 110°C, and a mixture of 3,000 g of propylene oxide and 1,350 g of ethylene oxide was introduced into the autoclave over 10 hours. The mixture of propylene oxide and ethylene oxide was then introduced. After confirming that the pressure had stabilized and all of the propylene oxide and ethylene oxide had reacted, the temperature in the system was cooled to 70°C. Then, 152 g of methyl chloride was introduced over 5 hours to carry out terminal methylation. After confirming that the pressure in the system had stabilized and that the methyl chloride had reacted, 2000 g of the resulting compound was transferred to a 5 L separable flask. 2000 g of distilled water and 10 g of sulfuric acid were added, and the aqueous layer was removed by oil-water separation. To the polyether compound on the oil layer side, 100 g of an aluminum silicate adsorbent (Kyowad 700, manufactured by Kyowa Chemical Industry Co., Ltd.) and 20 g of acidic sodium pyrophosphate were added as adsorbents, and the mixture was stirred at 110° C. for 2 hours. Thereafter, the catalyst was thoroughly removed by filtration of insoluble matter, yielding polyalkylene glycol dimethyl ether. The amount of residual metal in the obtained polyalkylene glycol dimethyl ether was 1.8 ppm, and the number average molecular weight determined by GPC was 1,480.

[0073] [Example 3] 208 g of propylene glycol monoethyl ether and 12 g of potassium hydroxide (purity 95% by mass) as an addition polymerization catalyst were added to a 5 L autoclave, and the temperature was raised to 110°C. After that, the system was dehydrated under reduced pressure for 1 hour to reduce the water content, and then 2200 g of propylene oxide was introduced into the autoclave over 10 hours. The propylene glycol monoethyl ether used as an initiator is an ethanol-propylene oxide adduct. The pressure inside the autoclave became constant, and it was confirmed that all of the propylene oxide had reacted. After cooling to 50°C, 350 g of 28% sodium methoxide methanol solution was added. After the addition, the temperature was raised to 120°C and a reduced pressure methanol removal treatment was carried out for 10 hours. After that, the temperature inside the system was cooled to 100°C, and 101 g of methyl chloride was introduced over 2 hours to carry out terminal methylation. After confirming that the pressure in the system had stabilized after the introduction of methyl chloride and that the methyl chloride had reacted, 2000 g of the resulting compound was transferred to a 5 L separable flask. 2000 g of distilled water and 40 g of 35% hydrochloric acid were added, and the aqueous layer was removed by oil-water separation. 60 g of a synthetic hydrotalcite adsorbent (Kyowado 1000, manufactured by Kyowa Chemical Industry Co., Ltd.) and 10 g of phosphoric acid were added to the polyether compound in the oil layer as adsorbents, and the mixture was stirred at 110 °C for 2 hours. The catalyst was then thoroughly removed by filtration of insoluble matter, yielding polypropylene glycol ethyl methyl ether. The amount of residual metal in the resulting polypropylene glycol ethyl methyl ether was 6.3 ppm, and the number average molecular weight determined by GPC was 1,100.

[0074] [Example 4] A 5-L autoclave was charged with 74 g of n-butanol and 12 g of sodium hydroxide (purity 95% by mass) as a catalyst, and then heated to 100°C. 1,500 g of propylene oxide was then introduced into the autoclave over 12 hours. The pressure inside the autoclave became constant, and it was confirmed that all of the propylene oxide had reacted. After cooling to 50°C, 140 g of a 28% sodium methoxide methanol solution was added. After the addition, the temperature was raised to 120°C, and a reduced-pressure methanol removal treatment was carried out for 10 hours. The temperature inside the system was then cooled to 80°C, and 51 g of methyl chloride was introduced over 4 hours to carry out terminal methylation. After confirming that the pressure in the system after the introduction of methyl chloride had stabilized and that the methyl chloride had reacted, the resulting compound was transferred to a 5 L separable flask. Then, 1500 g of distilled water was added, and the aqueous layer was removed by oil-water separation. To the polyether compound in the oil layer, 40 g of aluminum silicate adsorbent (Kyowad 700, manufactured by Kyowa Chemical Industry Co., Ltd.) was added as an adsorbent, along with 20 g of phosphoric acid and 40 g of sodium acid pyrophosphate, and the mixture was stirred at 110 °C for 2 hours. The catalyst was then thoroughly removed by filtration of insoluble matter, yielding polypropylene glycol butyl methyl ether. The amount of residual metal in the resulting polypropylene glycol butyl methyl ether was 2.1 ppm, and the number average molecular weight determined by GPC was 1,500.

[0075] [Example 5] A 5-L autoclave was charged with 74 g of n-butanol and 12 g of potassium hydroxide (purity 95% by mass) as a catalyst, and then heated to 100°C. A mixture of 1,200 g of propylene oxide and 600 g of ethylene oxide was then introduced into the autoclave over 15 hours. The pressure inside the autoclave became constant, and it was confirmed that all of the propylene oxide had reacted. The autoclave was then cooled to 50°C, after which 140 g of a 28% sodium methoxide methanol solution was added. After the addition, the temperature was raised to 120°C, and a reduced-pressure demethanol treatment was carried out for 10 hours. The temperature inside the system was then cooled to 100°C, and 51 g of methyl chloride was introduced over 2 hours to carry out terminal methylation. After confirming that the pressure in the system had stabilized after the introduction of methyl chloride and that the methyl chloride had reacted, 1800 g of the resulting compound was transferred to a 5 L separable flask. Then, 1800 g of distilled water and 40 g of sodium pyrophosphate were added, and the aqueous layer was removed by oil-water separation. 50 g of magnesium silicate adsorbent (Kyowado 600S, manufactured by Kyowa Chemical Industry Co., Ltd.) was added to the polyether compound in the oil layer as an adsorbent, and the mixture was stirred at 110 °C for 2 hours. The catalyst was then thoroughly removed by filtration of insoluble matter, yielding polyalkylene glycol butyl methyl ether. The amount of residual metal in the resulting polyalkylene glycol butyl methyl ether was 8.2 ppm, and the number average molecular weight determined by GPC was 1,800.

[0076] [Example 6] After adding 162 g of powdered sodium methoxide to a 5 L autoclave, the temperature was raised to 110°C, and 4,350 g of propylene oxide was introduced into the autoclave over 10 hours. After introducing the propylene oxide, the pressure became constant and it was confirmed that all of the propylene oxide had reacted. After cooling the temperature in the system to 100°C, 152 g of methyl chloride was introduced over 3 hours to carry out terminal methylation. After confirming that the pressure in the system after the introduction of methyl chloride had stabilized and that the methyl chloride had reacted, 2000 g of the resulting compound was transferred to a 5 L separable flask. 2000 g of distilled water was then added, and the aqueous layer was removed by oil-water separation. 15 g of a magnesium silicate-based adsorbent (Kyowado 600S, manufactured by Kyowa Chemical Industry Co., Ltd.) was added to the polyether compound in the oil layer as an adsorbent, and the mixture was stirred at 110 °C for 2 hours. The catalyst was then thoroughly removed by filtration of insoluble matter, yielding polypropylene glycol dimethyl ether. The amount of residual metal in the resulting polypropylene glycol dimethyl ether was 15 ppm, and the number average molecular weight determined by GPC was 1,480.

[0077] [Example 7] After adding 162 g of powdered sodium methoxide to a 5 L autoclave, the temperature was raised to 110°C, and a mixture of 3,000 g of propylene oxide and 1,350 g of ethylene oxide was introduced into the autoclave over 10 hours. After the introduction of the propylene oxide and ethylene oxide mixture, the pressure became constant and it was confirmed that all of the propylene oxide and ethylene oxide had reacted. After cooling the temperature in the system to 70°C, 152 g of methyl chloride was introduced over 5 hours to carry out terminal methylation. After the introduction of methyl chloride, the pressure in the system became constant, and it was confirmed that the methyl chloride had reacted. After that, the obtained compound was filtered to remove insoluble matter, and polyalkylene glycol dimethyl ether was obtained. The amount of residual metal in the obtained polyalkylene glycol dimethyl ether was 500 ppm, and the number average molecular weight determined by GPC was 1,480.

[0078] [Example 8] A 5-L autoclave was charged with 74 g of n-butanol and 12 g of sodium hydroxide (purity 95% by mass) as a catalyst, and then heated to 100°C. 1,500 g of propylene oxide was then introduced into the autoclave over 12 hours. The pressure inside the autoclave became constant, and it was confirmed that all of the propylene oxide had reacted. After cooling to 50°C, 140 g of a 28% sodium methoxide methanol solution was added. After the addition, the temperature was raised to 120°C, and a reduced-pressure methanol removal treatment was carried out for 10 hours. The temperature inside the system was then cooled to 80°C, and 51 g of methyl chloride was introduced over 4 hours to carry out terminal methylation. After confirming that the pressure in the system after the introduction of methyl chloride had become constant and that the methyl chloride had reacted, the resulting compound was transferred to a 5 L separable flask, and 10 g of an aluminum silicate adsorbent (Kyowad 700, manufactured by Kyowa Chemical Industry Co., Ltd.) and 10 g of acidic sodium pyrophosphate were added as adsorbents, followed by stirring for 2 hours at 110° C. Thereafter, insoluble matter was filtered off to obtain polypropylene glycol butyl methyl ether. The amount of residual metal in the resulting polypropylene glycol butyl methyl ether was 50 ppm, and the number average molecular weight determined by GPC was 1,500.

[0079] [Table 1]

[0080] R in Formula 1 of the compound obtained in each example 1 , R 2 O, R 3 , m and n are shown in Table 1. In Table 1, PO represents propylene oxide and EO represents ethylene oxide.

[0081] In the refrigerants blended with each of the lubricating base oils in Examples 6-8, precipitates were formed after heating at 175°C for 14 days. In contrast, in Examples 1-5, the metal content was 10 ppm or less. In the refrigerants blended with these lubricating base oils, no precipitates were formed even after heating at 175°C for 14 days. Thus, in Examples 1-5, the chemical stability of the refrigerants blended with the lubricating base oils was improved when used for a long period of time. [Industrial Applicability]

[0082] According to the present invention, the chemical stability of a refrigerant blended with a lubricating base oil is improved when used for a long period of time.

Claims

1. A lubricating base oil for mixing with a refrigerant, The refrigerant contains one or more unsaturated fluorohydrocarbon compounds selected from compounds represented by the following formula i: The lubricating base oil comprises a compound represented by the following formula 1: A lubricating base oil having a metal content of 10 ppm or less. CxFyHz...Formula i In formula i, x is an integer of 2 to 6, y is an integer of 1 to 11, z is an integer of 1 to 11, and the compound has one or more carbon-carbon unsaturated bonds in the molecule. R １ {(R ２ O) ｍ R ３ } ｎ Formula 1 In formula 1, R １ is the initiator residue, R ２ are each independently a hydrocarbon group having 2 to 4 carbon atoms, R ３ are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, The R ３ at least one of is an alkyl group having 1 to 4 carbon atoms, m is 1 to 200; n is 1 to 8.

2. The R ２ 2. The lubricating base oil of claim 1, wherein at least one of the following is a hydrocarbon group having 3 carbon atoms:

3. The R ３ 2. The lubricating base oil of claim 1, wherein at least one of the following is a methyl group:

4. 2. The lubricating base oil of claim 1, wherein the unsaturated fluorohydrocarbon compound of the refrigerant comprises one or more selected from 2,3,3,3-tetrafluoropropene (R1234yf), 1,3,3,3-tetrafluoropropene (R1234ze), and 1,2,3,3-tetrafluoropropene (R1234ye).

5. 2. The lubricating base oil according to claim 1, wherein the compound represented by Formula 1 has a number average molecular weight of 300 to 5,000.

6. The lubricating base oil according to any one of claims 1 to 5, a refrigerant and / or an additive; 1. A lubricating oil composition comprising:

7. The lubricating oil composition according to claim 6, which is used in a car air conditioner, an interior air conditioner, a refrigerator, a freezer, a hot water supply system for a vending machine, a hot water supply system for a showcase, a refrigeration / heating system, or a gas heat pump system.

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