Lubricant base oil, lubricant oil composition, and cooling system

Abstract

The present invention provides: a lubricant base oil which enables a refrigerant containing the lubricant base oil to have improved chemical stability when used over a long period; and a lubricant oil composition including the lubricant base oil.　This lubricant base oil is for mixing with a refrigerant, the refrigerant including a hydrocarbon compound having 1-8 carbon atoms. The lubricant base oil contains a compound represented by formula 1 and has a metal content of 10 ppm or less.　Formula 1: R1\{(R2O)mR3\}n; R1 is an initiator residue; the R2 moieties are each independently a C2-C4 hydrocarbon group; the R3 moieties are each independently a hydrogen atom or a C1-C4 alkyl group, wherein at least one of the R3 moieties is a C1-C4 alkyl group; m is 1-200; and n is 1-8.

Description

Lubricating base oils, lubricating oil compositions and cooling systems

[0001] The present invention relates to lubricant base oils, lubricant compositions and cooling systems.

[0002] Various lubricating base oils are used to ensure smooth circulation of the refrigerant in compression-type refrigerators. Examples of lubricating base oils that can be used include compounds such as polyalkylene glycols, polyol esters, and polyvinyl ethers, 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.

[0003] Japanese Unexamined Patent Publication No. 6-240278

[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.

[0006] The present invention has the following aspects: [1] A lubricating base oil to be mixed with a refrigerant, wherein the refrigerant contains a hydrocarbon compound having 1 to 8 carbon atoms, and the lubricating base oil contains a compound represented by the following formula 1, and the metal content of the lubricating base oil is 10 ppm or less. 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, and R ３ are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, ３At least one of the R is an alkyl group having 1 to 4 carbon atoms, m is 1 to 200, and n is 1 to 8. [2] ２ [3] The lubricating base oil according to [1], wherein at least one of R is a hydrocarbon group having 3 carbon atoms. ３ [4] The lubricating base oil according to [1] or [2], wherein at least one of the hydrocarbon compounds in the refrigerant comprises propane. [5] The lubricating base oil according to [1] to [4], wherein the hydrocarbon compound in the refrigerant comprises propylene. [6] The lubricating base oil according to [1] to [5], wherein the compound represented by Formula 1 has a number average molecular weight of 300 to 5,000. [7] A lubricating oil composition comprising the lubricating base oil according to [1] to [6], and either a refrigerant or an additive, or both. [8] The lubricating oil composition according to [7], wherein the refrigerant is propane. [9] The lubricating oil composition according to [7] or [8], wherein the refrigerant is propylene.

[10] The lubricating oil composition according to [7] to [9], wherein the lubricating oil composition is used for 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.

[11] A cooling system comprising a compressor, a condenser, an evaporator, and an expansion valve, and containing a refrigerant containing a hydrocarbon compound having 1 to 8 carbon atoms and the lubricating base oil according to any one of [1] to [6].

[12] The cooling system according to

[11] , which is for a hot water supply system, refrigeration / heating system, or gas heat pump system for a car air conditioner, an indoor air conditioner, a refrigerator, a freezer, a vending machine, or a showcase.

[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.

[0008] 1 is a diagram illustrating a schematic configuration of a cooling system according to an embodiment.

[0009] 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. "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. "Initiator residue" refers to a group formed by removing one or more active hydrogen atoms from an initiator. "Unit" refers to an atomic group formed directly by the polymerization of a monomer. "Number average molecular weight" refers to the polystyrene-equivalent molecular weight obtained by GPC measurement. "Metal content of lubricating base oil" refers to the total amount of metal elements detected by elemental analysis using ICP atomic emission spectroscopy. The unit of metal content, ppm, is based on mass. "Kinematic viscosity" refers to a value measured at 100°C in accordance with JIS K2283:2000. "Viscosity index" refers to a value calculated from the kinematic viscosity measured 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 numerical range means that the numerical values ​​before and after "to" are included as the lower and upper limits. The numerical ranges disclosed in this specification can be combined in any way to create new numerical ranges.

[0010] [Lubricant Base Oil] The lubricant base oil of the present invention can impart lubricity to sliding parts of a compressor in a compression-type refrigerator, for example, by mixing with a refrigerant.

[0011] (Refrigerant) The refrigerant to be mixed with the lubricating base oil of the present invention contains a hydrocarbon compound having 1 to 8 carbon atoms. In consideration of a boiling point suitable for use as a refrigerant, the hydrocarbon compound of the refrigerant preferably has 1 to 5 carbon atoms, more preferably 3 to 5 carbon atoms, even more preferably 3 or 4 carbon atoms, and most preferably 3 carbon atoms.

[0012] Examples of hydrocarbon compounds that can be used as refrigerants include methane, ethane, ethylene, propane, cyclopropane, propylene, n-butane, isobutane, n-pentane, and isopentane. Of these, propane and propylene are preferred. One type of hydrocarbon compound can be used alone, or two or more types can be mixed and used in combination.

[0013] (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"). １ {(R ２ O) ｍ R ３} ｎ ...Formula 1

[0014] In formula 1, R １ is 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. One type of initiator may be used alone, or two or more types may be used in combination.

[0015] The aliphatic monoalcohol may be a saturated aliphatic monool, an unsaturated aliphatic monool, or a cyclic aliphatic monool. Among these, a saturated aliphatic monool is preferred. Examples of saturated aliphatic monools include methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, isobutanol, tert-butanol, n-hexanol, octyl alcohol, and 2-ethylhexanol. However, the saturated aliphatic monool is not limited to these examples.

[0016] 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.

[0017] 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.

[0018] 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 aliphatic amines 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.

[0019] Examples of phenols include bisphenol A and resorcinol. However, the phenols are not limited to these examples. One type of phenol may be used alone, or two or more types may be used in combination.

[0020] 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.

[0021] In Formula 1, n (R ２ O) ｍ R ３ may be the same or different. ２ O) ｍ In this case, one type of R ２ O may be present, and two or more R ２O may be present. Two or more R ２ When O is present, each R ２ The bonding order of O is not limited. For example, ２ When O is present, two types of R ２ O may be arranged randomly, alternately, or in blocks. (R ２ O) ｍ may be a random copolymer having units based on two or more types of alkylene oxide, or may be a block copolymer.

[0022] R ２ 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 Preferably, at least one of R is a hydrocarbon group having 3 carbon atoms. ２ It is more preferable that all of the groups are hydrocarbon groups having 3 carbon atoms.

[0023] R ２ The hydrocarbon group of 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.

[0024] R ２ Examples of the group include -CH ２ CH ２ -, -CH ２ CH ２ CH ２ -, -CH ２ CH ２ CH ２ CH ２ -, -CH(CH ３ ) CH ２ -, -CH2CH(CH ３ ) -, -CH(CH ３ ) CH ２ CH ２ -, -CH ２ CH (CH ３ ) CH ２ -CH ２ CH ２ -, -CH2CH(CH ３ )- is preferred, and -CHCH(CH３ )- is more preferred.

[0025] 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 of R is preferably 1 to 3, more preferably 1 or 2, and most preferably 1. ３ As the alkyl group, a methyl group is most preferred.

[0026] R ３ Among these, examples of the alkyl group having 1 to 4 carbon atoms include —CH ３ , -CH ２ CH ３ , -CH ２ CH ２ CH ３ , -CH ２ CH ２ CH ２ CH ３ , -CH(CH ３ ) CH ３ , -CH(CH ３ ) CH ２ CH ３ , -CH ２ CH (CH ３ ) CH ３ Examples include:

[0027] In Formula 1, n R ３ At least one of the n R ３ All 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.

[0028] 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.

[0029] 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.

[0030] The number average molecular weight of the compound represented by Formula 1 is preferably 300 to 5,000, more preferably 500 to 3,000, and even more preferably 700 to 2,000. 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.

[0031] (Physical properties of lubricating 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 blended with 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. From the viewpoint of production efficiency, the lower limit of the metal content of the lubricating base oil is preferably 0.1 ppm or more.

[0032] The metal elements contained in the lubricating base oil are not particularly limited. In the synthesis reaction of compound 1, alkylene oxide can be added 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 make the metal content of the lubricating base oil 10 ppm or less, it is preferable to thoroughly remove the catalyst after the synthesis reaction of compound 1.

[0033] When measuring the metal content of a lubricating base oil, the metal elements to be detected are not particularly limited. The detection targets are all metal elements that may be contained in the catalyst that is 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 may be detected are not limited to these examples. Furthermore, the metal elements to be detected may be one type or two or more types.

[0034] The kinematic viscosity of the lubricating base oil at 100°C is not particularly limited, but is, for example, 2 to 200 mm ２ / s, and 5 to 100 mm ２ / s, and 7 to 50 mm ２ When the kinematic viscosity is equal to or greater than the lower limit of the above-mentioned range, the sealing performance is improved, and refrigerant leakage is less likely to occur. When the kinematic viscosity is equal to or less than the upper limit of the above-mentioned range, the viscous resistance is small, and lubricity is improved.

[0035] 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.

[0036] The volume resistivity of the lubricating base oil is not particularly limited, but is, for example, 1×10 １０ ~1 x 10 １５ Ω cm, and 6×10 １０ ~1 x 10 １４ It may be Ω cm, and 1×10 １１ ~1 x 10 １４ 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.

[0037] (Method of Manufacturing Lubricating Base Oil) Lubricating base oil is prepared by addition polymerization of alkylene oxide to an initiator in the presence of a catalyst to form an elongated oxyalkylene chain ((R ２ O) ｍ ) to obtain Compound 1, and then remove the catalyst from the reaction solution containing Compound 1. Details and preferred embodiments of the initiator are as described above.

[0038] Examples of the catalyst include alkali metal catalysts and composite metal cyanide complex catalysts (hereinafter referred to as "DMC catalysts"). However, the catalyst is not limited to these examples. One type of catalyst may be used alone, or two or more types may be used in combination.

[0039] Examples of the alkali metal catalyst 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. One type of alkali metal catalyst may be used alone, or two or more types may be used in combination.

[0040] It is believed that the DMC catalyst has at least a metal element and an organic ligand. Examples of the metal element of the DMC catalyst include Zn, Fe, Co, Ni, Al, Sr, Mn, Cr, Cu, Sn, Pb, Mo, W, and V. However, the metal element of the DMC catalyst is not limited to these examples. The metal element of the DMC catalyst may be one type or two or more types.

[0041] Examples of organic ligands for DMC catalysts include t-butyl alcohol (hereinafter referred to as "TBA"), n-butyl alcohol, iso-butyl alcohol, t-pentyl alcohol, iso-pentyl 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), iso-propyl alcohol, and dioxane. Dioxane may be 1,4-dioxane or 1,3-dioxane. However, the organic ligand is not limited to these examples. One type of organic ligand may be used alone, or two or more types may be used in combination.

[0042] Examples of alkylene oxides 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. Preferred alkylene oxides are ethylene oxide and propylene oxide, with propylene oxide being more preferred. However, the alkylene oxide is not limited to these examples.

[0043] The alkylene oxide may be used alone or in combination of two or more. That is, one alkylene oxide may be homopolymerized using an initiator, or two or more alkylene oxides may be copolymerized using an initiator. In the case of copolymerization, two or more alkylene oxides may be block copolymerized or random copolymerized using an initiator.

[0044] 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 reactor pressure may be, for example, 0.01 to 0.9 MPaG or 0.03 to 0.7 MPaG.

[0045] There are no particular restrictions on the method for introducing an alkyl group having 1 to 4 carbon atoms. Examples include the following Method 1 and Method 2. Method 1: A method in which an alkyl halide having 1 to 4 carbon atoms is reacted with a hydroxyl group at the end of an oxyalkylene chain. Method 2: A method in which a metal alkoxide having an alkyl group having 1 to 4 carbon atoms is reacted with a hydroxyl group at the end of an oxyalkylene chain.

[0046] 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.

[0047] The details and preferred embodiments of the alkyl group of the metal alkoxide are as follows: ３ The metal of the metal alkoxide may be, for example, Na or K, but is not limited thereto.

[0048] 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.

[0049] An alkyl group having 1 to 4 carbon atoms is connected to an oxyalkylene chain ((R ２ O) ｍ The 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.

[0050] The method for removing the catalyst is not particularly limited. Examples include the following methods 3, 4, and 5. Method 3: A method in which the catalyst is adsorbed using an adsorbent, and then the adsorbent with the adsorbed catalyst is removed by filtration. Method 4: A method in which the catalyst is neutralized using a neutralizing agent, and then the neutralized catalyst is removed by filtration. Method 5: A method in which the catalyst is removed during filtration using a charged filter.

[0051] 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 of carrying them 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.

[0052] 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. One type of adsorbent may be used alone, or two or more types may be used in combination.

[0053] Examples of neutralizing agents include amines, alkali metal hydroxides, organic acids, inorganic acids, and salts thereof. Examples of inorganic acids include sulfuric acid, phosphoric acid, and hydrochloric acid. Examples of organic acids include lactic acid. However, the neutralizing agents are not limited to these examples. One type of neutralizing agent may be used alone, or two or more types may be used in combination.

[0054] Commercially available charged filters may be used. Examples of commercially available charged filters include Zeta Plus Adsorption Depth Filter Cartridge EC Series (manufactured by 3M), RO Wind (manufactured by Organo Corporation), and SupraCap 200 (manufactured by Seitz AKSJ). However, charged filters are not limited to these examples.

[0055] [Lubricant Composition] The lubricant composition of the present invention comprises the above-described lubricant base oil and either or both of a refrigerant and an additive. In one example, the lubricant composition may comprise a lubricant base oil and a refrigerant, a lubricant base oil and an additive, or a lubricant base oil, a refrigerant, and an additive. The lubricant composition of the present invention can, for example, impart lubricity to the sliding parts of a compressor to which a refrigerant is supplied. The refrigerant is as described above.

[0056] 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. However, the additives are not limited to these examples. One type of additive may be used alone, or two or more types may be used in combination.

[0057] Examples of antioxidants 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 amine-based antioxidants include phenyl-α-naphthylamine and N,N'-diphenyl-p-phenylenediamine. One type of antioxidant may be used alone, or two or more types may be used in combination.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] Examples of the antifoaming agent include silicone oil and fluorinated silicone oil.

[0062] 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.

[0063] When a lubricating oil composition contains a refrigerant, the refrigerant content 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 content 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 content 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.

[0064] When the lubricating oil composition contains an additive, the proportion of the additive 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 additive 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 additive is equal to or less than the upper limit of the above-mentioned range, it is preferable in terms of compatibility with the refrigerant.

[0065] [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.

[0066] [Uses] The lubricating base oil and the lubricating oil composition can be used in various refrigeration systems, such as car air conditioners, room air conditioners, refrigerators, freezers, vending machines, hot water supply systems for showcases, refrigeration / heating systems, and gas heat pump systems. The lubricating base oil and the lubricating oil composition are particularly preferably used in a compression refrigeration system equipped with a compressor 1, a condenser 2, an expansion valve 3, and an evaporator 4, as shown in FIG. 1. The compression refrigeration system shown in FIG. 1 contains a refrigerant containing a hydrocarbon compound having 1 to 8 carbon atoms and a lubricating base oil. The lubricating base oil and the lubricating oil composition circulate through the compressor 1, the condenser 2, the expansion valve 3, and the evaporator 4. The lubricating base oil provides lubricity to the sliding parts of the compressor 1.

[0067] The amounts of the lubricating base oil and refrigerant used in the present invention can be varied widely within the range of 99 / 1 to 10 / 90 in terms of the refrigerant / lubricating base oil mass ratio, with the mass ratio preferably being within the range of 90 / 10 to 50 / 50.

[0068] The following examples will explain the embodiments in more detail, but the present invention is not limited to the following examples. Examples 1-7 are examples, and Examples 8-10 are comparative examples.

[0069] [Measurement and Evaluation] (Number Average Molecular Weight) GPC measurement of the lubricating base oil was carried out under the following conditions to determine the number average molecular weight (Mn). GPC measurement conditions: Model used: HLC-8220GPC (product of Tosoh Corporation) Data processing device: SC-8020 (product of Tosoh Corporation) Column used: TSG gel G2500H (product of Tosoh Corporation) Column temperature: 40°C, detector: RI, solvent: tetrahydrofuran, flow rate: 0.6 mL / min Sample concentration: 0.25 mass%, injection amount: 10 μL Standard sample for creating a calibration curve: polystyrene ([Easycal] PS-2 [Polystyrene Standards], product of Polymer Laboratories).

[0070] (Metal Content) 20 g of lubricating base oil containing the compound represented by Formula 1 in each example was purified and then completely incinerated using a burner. The incinerated powder residue was mixed with 100 mL of aqueous hydrochloric acid solution to prepare a measurement sample. The contents of Na, K, Zn, and Co were measured using an ICP optical emission spectrometer (SII Nanotechnology (Hitachi High-Tech Science) "SPS3500"). The total amount of these detected metal elements was calculated as the metal content of the lubricating base oil.

[0071] (Chemical Stability) The test for evaluating chemical stability was conducted 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 a lubricating base oil containing the compound represented by Formula 1 of each example and 0.7 mL of a 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, and the presence or absence of precipitates in the solution in the test tube was confirmed. Propane was used as the refrigerant.

[0072] Example 1: 162 g of powdered sodium methoxide was added to a 5-L autoclave, then the temperature was raised to 110°C. 4,350 g of propylene oxide was introduced into the autoclave over 10 hours. After the introduction of 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. 152 g of methyl chloride was then introduced over 3 hours to carry out terminal methylation. After confirming that the pressure in the system became constant after the introduction of methyl chloride and that the methyl chloride had reacted, 2,000 g of the resulting compound was transferred to a 5-L separable flask. 2,000 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 to remove insoluble matter, yielding polyoxypropylene glycol dimethyl ether. The residual metal content in the resulting polyoxypropylene glycol dimethyl ether was 0.6 ppm. The number average molecular weight determined by GPC was 1,480.

[0073] [Example 2] 162 g of powdered sodium methoxide was added to a 5 L autoclave, and the temperature was raised to 110°C. 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 propylene oxide and ethylene oxide mixture was then introduced. After the pressure had stabilized and it was confirmed that all of the propylene oxide and ethylene oxide had reacted, the temperature in the system was cooled to 70°C. 152 g of methyl chloride was then introduced over 5 hours to carry out terminal methylation. After the pressure in the system had stabilized after the introduction of methyl chloride and it was confirmed that the methyl chloride had reacted, 2,000 g of the resulting compound was transferred to a 5 L separable flask. 2,000 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 (Kyowado 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. The catalyst was then thoroughly removed by filtration of insoluble matter, yielding polyalkylene glycol dimethyl ether. The residual metal content in the resulting polyalkylene glycol dimethyl ether was 1.8 ppm. The number average molecular weight determined by GPC was 1,480.

[0074] 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, heated to 110°C, and then subjected to vacuum dehydration for 1 hour to reduce the water content in the system. Then, 2,200 g of propylene oxide was introduced into the autoclave over 10 hours. The propylene glycol monoethyl ether used as the initiator was 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 a 28% sodium methoxide methanol solution was added. After the addition, the temperature was raised to 120°C and vacuum demethanolization was performed for 10 hours. The temperature inside the system was then 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 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. After adding 2000 g of distilled water and 40 g of 35% hydrochloric acid, the aqueous layer was removed by oil-water separation. To the polyether compound in the oil layer, 60 g of a synthetic hydrotalcite adsorbent (Kyowado 1000, manufactured by Kyowa Chemical Industry Co., Ltd.) and 10 g of phosphoric acid were added as adsorbents and 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 residual metal content in the resulting polypropylene glycol ethyl methyl ether was 6.3 ppm. The number average molecular weight determined by GPC was 1100.

[0075] [Example 4] 74 g of n-butanol and 12 g of sodium hydroxide (purity 95% by mass) as a catalyst were added to a 5 L autoclave, and the temperature was raised to 100°C. 1500 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 inside the system after the introduction of methyl chloride became constant and that the methyl chloride had reacted, the resulting compound was transferred to a 5 L separable flask. 1500 g of distilled water was then added, and the aqueous layer was removed by oil-water separation. To the polyether compound in the oil layer, 40 g of an aluminum silicate adsorbent (Kyowado 700, manufactured by Kyowa Chemical Industry Co., Ltd.) was added as an adsorbent, 20 g of phosphoric acid, and 40 g of acidic sodium pyrophosphate were added, followed by stirring at 110°C for 2 hours. The catalyst was then thoroughly removed by filtration of insoluble matter, yielding polypropylene glycol butyl methyl ether. The residual metal content in the resulting polypropylene glycol butyl methyl ether was 2.1 ppm. The number average molecular weight determined by GPC was 1,500.

[0076] Example 5: 74 g of n-butanol and 12 g of potassium hydroxide (purity 95% by mass) as a catalyst were added to a 5 L autoclave, and the temperature was raised 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, and 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 100°C, and 51 g of methyl chloride was introduced over 2 hours to carry out terminal methylation. After the pressure inside the system became constant after the introduction of methyl chloride and it was confirmed that the methyl chloride had reacted, 1,800 g of the resulting compound was transferred to a 5 L separable flask. Then, 1800 g of distilled water and 40 g of sodium acid 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 as an adsorbent to the polyether compound on the oil layer side, 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 residual metal content in the obtained polyalkylene glycol butyl methyl ether was 8.2 ppm. The number average molecular weight determined by GPC was 1800.

[0077] [Example 6] 32 g of methanol and 13 g of potassium hydroxide (purity 95% by mass) as a catalyst were added to a 5 L autoclave, and the temperature was raised to 100 °C. Then, 1,180 g of propylene oxide was introduced into the autoclave over 10 hours. A mixture of 88 g of ethylene oxide was then introduced into the autoclave over 1 hour. The pressure inside the autoclave became constant, and it was confirmed that all the components had reacted. After cooling to 50 °C, 180 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 100 °C, and 63 g of methyl chloride was introduced over 2 hours to carry out terminal methylation. After the pressure inside the system became constant after the introduction of methyl chloride and it was confirmed that the methyl chloride had reacted, 1,300 g of the resulting compound was transferred to a 5 L separable flask. Thereafter, 1300 g of distilled water and 40 g of sodium acid 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 as an adsorbent to the polyether compound on the oil layer side, 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 residual metal content in the obtained polyalkylene glycol butyl methyl ether was 1.0 ppm. The number average molecular weight determined by GPC was 1250.

[0078] [Example 7] 32 g of methanol and 13 g of potassium hydroxide (purity 95% by mass) as a catalyst were added to a 5 L autoclave and then heated to 100 °C. Then, 1,268 g of propylene oxide was introduced into the autoclave over 12 hours. The pressure inside the autoclave became constant, and it was confirmed that all the components had reacted. After cooling to 50 °C, 180 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 100 °C, and 63 g of methyl chloride was introduced over 2 hours to carry out terminal methylation. After the pressure inside the system became constant after the introduction of methyl chloride and it was confirmed that the methyl chloride had reacted, 1,300 g of the resulting compound was transferred to a 5 L separable flask. Then, 1,300 g of distilled water and 40 g of sodium acid 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 as an adsorbent to the polyether compound on the oil layer side, 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 residual metal content in the resulting polyalkylene glycol butyl methyl ether was 0.8 ppm. The number average molecular weight determined by GPC was 1,250.

[0079] [Example 8] 162 g of powdered sodium methoxide was added to a 5 L autoclave, then the temperature was raised to 110 °C, and 4,350 g of propylene oxide was introduced into the autoclave over 10 hours. After the introduction of propylene oxide, the pressure became constant and it was confirmed that all of the propylene oxide had reacted. The temperature in the system was cooled to 100 °C, and 152 g of methyl chloride was introduced over 3 hours to carry out terminal methylation. After the pressure in the system became constant after the introduction of methyl chloride and it was confirmed that the methyl chloride had reacted, 2,000 g of the resulting compound was transferred to a 5 L separable flask. 2,000 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 as an adsorbent to the polyether compound in the oil layer, 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.

[0080] [Example 9] 162 g of powdered sodium methoxide was added to a 5 L autoclave, and the temperature was raised to 110°C. 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 the temperature in the system was cooled 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. The resulting compound was then filtered to remove insoluble matter, yielding a polyalkylene glycol dimethyl ether. The residual metal content in the resulting polyalkylene glycol dimethyl ether was 500 ppm. The number average molecular weight determined by GPC was 1,480.

[0081] [Example 10] 74 g of n-butanol and 12 g of sodium hydroxide (purity 95% by mass) as a catalyst were added to a 5 L autoclave, and the temperature was raised to 100°C. 1500 g of propylene oxide was then introduced into the autoclave over 12 hours. It was confirmed that the pressure inside the autoclave became constant and 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, and 10 g of an aluminum silicate adsorbent (Kyowado 700, manufactured by Kyowa Chemical Industry Co., Ltd.) and 10 g of acidic sodium pyrophosphate were added as adsorbents, followed by stirring at 110°C for 2 hours. The insoluble matter was then filtered to obtain polypropylene glycol butyl methyl ether. The residual metal content in the resulting polypropylene glycol butyl methyl ether was 50 ppm. The number average molecular weight determined by GPC was 1,500.

[0082]

[0083] The compound obtained in each example is 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.

[0084] In the refrigerants blended with each of the lubricating base oils of Examples 8-10, precipitates occurred after heating at 175°C for 14 days. In contrast, in Examples 1-7, the metal content was 10 ppm or less. In the refrigerants blended with each of these lubricating base oils, no precipitates occurred even after heating at 175°C for 14 days. Thus, in Examples 1-7, the chemical stability of the refrigerants blended with the lubricating base oils was improved when used for a long period of time.

[0085] 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.

[0086] This application claims priority based on Japanese Patent Application No. 2024-16295, filed on February 6, 2024, the entire contents of which are incorporated herein by reference.

[0087] 1... compressor, 2... condenser, 3... expansion valve, 4... evaporator

Claims

1. A lubricating base oil for mixing with a refrigerant, the refrigerant contains a hydrocarbon compound having 1 to 8 carbon atoms; The lubricating base oil comprises a compound represented by the following formula 1: The number average molecular weight is 700 or more, A lubricating base oil having a metal content of 10 ppm or less. R １ {(R)} ２ O) ｍ R ３ } ｎ ・・・Form 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. 10. The lubricant base oil of claim 1, wherein the hydrocarbon compound of the refrigerant comprises propane.

5. 10. The lubricant base oil of claim 1, wherein the hydrocarbon compounds of the refrigerant comprise propylene.

6. 2. The lubricating base oil according to claim 1, wherein the compound represented by Formula 1 has a number average molecular weight of 700 to 5,000.

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

8. 8. The lubricating oil composition of claim 7, wherein the refrigerant is propane.

9. 8. The lubricating oil composition of claim 7, wherein the refrigerant is propylene.

10. The lubricating oil composition according to claim 7, 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.

11. a compressor, a condenser, an evaporator, and an expansion valve; A cooling system in which a refrigerant containing a hydrocarbon compound having 1 to 8 carbon atoms and the lubricating base oil according to any one of claims 1 to 6 are sealed.

12. The cooling system according to claim 11, which is for a hot water supply system, a refrigeration and heating system, or a gas heat pump system for a car air conditioner, an interior air conditioner, a refrigerator, a freezer, a vending machine, or a showcase.