Lubricant base oil, lubricant composition, and cooling system

Abstract

The present invention provides: a lubricant base oil that improves chemical stability when a refrigerant mixed with the lubricant base oil is used for an extended period of time; and a lubricant composition containing the lubricant base oil.　A lubricant base oil according to the present invention is mixed with a refrigerant. The refrigerant includes a hydrocarbon compound having 1 to 8 carbon atoms. The lubricant base oil includes at least one substance selected from the group consisting of polyoxyalkylene monools and polyoxyalkylene polyols, and the metal content of the lubricant base oil is 10 ppm or less.

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 at least one selected from the group consisting of polyoxyalkylene monools and polyoxyalkylene polyols, and the metal content of the lubricating base oil is 10 ppm or less. [2] The lubricating base oil according to [1], wherein the at least one selected from the group consisting of polyoxyalkylene monools and polyoxyalkylene polyols is represented by the following formula 1. R １ {(R ２ O) ｍ H} ｎ ...Formula 1 In Formula 1, R １ is the initiator residue, R ２are each independently a hydrocarbon group having 2 to 4 carbon atoms, m is 1 to 200, and n is 1 to 8. [3] The R ２ [2] The lubricating base oil according to [2], wherein at least one of the hydrocarbon groups has 3 carbon atoms. [4] The lubricating base oil according to any one of [1] to [3], wherein the hydrocarbon compound of the refrigerant comprises propane. [5] The lubricating base oil according to any one of [1] to [4], wherein the hydrocarbon compound of the refrigerant comprises propylene. [6] The lubricating base oil according to any one of [1] to [5], wherein the number average molecular weight of at least one selected from the group consisting of polyoxyalkylene monools and polyoxyalkylene polyols is 300 to 5,000. [7] A lubricating oil composition comprising the lubricating base oil according to any one of [1] to [6], and either a refrigerant or an additive. [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 any one of [7] to [9], which is used in a car air conditioner, an indoor air conditioner, a refrigerator, a freezer, a hot water supply system in a vending machine, a hot water supply system in a showcase, a refrigeration / heating system, or a gas heat pump system.

[11] A cooling system equipped with a compressor, a condenser, an evaporator, and an expansion valve, and filled with 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 used in a car air conditioner, an indoor air conditioner, a refrigerator, a freezer, a vending machine, a hot water supply system in a showcase, a refrigeration / heating system, or a gas heat pump system.

[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] The lubricating base oil of the present invention contains at least one selected from the group consisting of polyoxyalkylene monools and polyoxyalkylene polyols (also referred to as "polyether polyols"). The polyoxyalkylene polyol may be a polyoxyalkylene diol having two hydroxyl groups, a polyoxyalkylene triol having three hydroxyl groups, or a polyoxyalkylene tetraol having four or more hydroxyl groups. In the following description, polyoxyalkylene monools and polyoxyalkylene polyols will be collectively referred to as polyoxyalkylene alcohols.

[0014] The polyoxyalkylene alcohol is not particularly limited. In one example, the polyoxyalkylene alcohol can be synthesized by addition polymerization of an alkylene oxide to an initiator having an active hydrogen-containing group in the presence of a catalyst.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] The polyoxyalkylene alcohol is preferably a compound represented by the following formula 1: １ {(R ２ O) ｍ H} ｎ ...Formula 1

[0029] In formula 1, R １is a residue of an initiator. Details and preferred embodiments of the initiator are as described above.

[0030] In Formula 1, n (R ２ O) ｍ 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 ２ O 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.

[0031] R ２ are each independently a hydrocarbon group having 2 to 4 carbon atoms. The hydrocarbon group preferably has 2 or 3 carbon atoms, and more preferably 3 carbon atoms. 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.

[0032] 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.

[0033] 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(CH３ ) -, -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(CH ３ )- is more preferred.

[0034] 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 fluidity at low temperatures is likely to be obtained.

[0035] 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.

[0036] The number-average molecular weight of the polyoxyalkylene alcohol 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.

[0037] (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.

[0038] The metal elements contained in the lubricating base oil are not particularly limited. In the synthesis reaction of polyoxyalkylene alcohol, alkylene oxide 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 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 polyoxyalkylene alcohol.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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 10１４ When the volume resistivity is equal to or greater than the lower limit of the above-mentioned range, the electrical insulation properties are improved. When the volume resistivity is equal to or less than the upper limit of the above-mentioned range, the generation of static electricity is easily prevented.

[0043] (Method for producing lubricating base oil) The lubricating base oil is obtained by addition polymerizing an alkylene oxide to an initiator in the presence of a catalyst to obtain a polyoxyalkylene alcohol, and then removing the catalyst from the reaction solution containing the polyoxyalkylene alcohol. The details and preferred embodiments of the initiator, alkylene oxide, and catalyst are as described above.

[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] The method for removing the catalyst is not particularly limited. Examples include the following methods 1, 2, and 3. Method 1: A method in which the catalyst is adsorbed using an adsorbent, and then the adsorbent with the adsorbed catalyst is removed by filtration. Method 2: A method in which the catalyst is neutralized using a neutralizing agent, and then the neutralized catalyst is removed by filtration. Method 3: A method in which the catalyst is removed during filtration using a charged filter.

[0046] In removing the catalyst, any one of Method 1, Method 2, and Method 3 may be carried out alone, or two or more of them may be appropriately combined, or all of Methods 1, 2, and 3 may be carried out. When two or more or all of Methods 1, 2, and 3 are carried out, the order of carrying them out is not particularly limited. As the method for removing the catalyst, Methods 1 and 2 are preferred, and Method 1 is more preferred, from the viewpoint of further reducing the metal content.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] [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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] Examples of the antifoaming agent include silicone oil and fluorinated silicone oil.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] [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.

[0061] [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.

[0062] 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.

[0063] The following examples will explain the embodiments in more detail, but the present invention is not limited to the following examples. Examples 1-9 are examples, and Examples 10-12 are comparative examples.

[0064] [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).

[0065] (Metal Content) 20 g of the lubricating base oil containing polyoxyalkylene alcohol obtained in each example was 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.

[0066] (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 the lubricating base oil containing the polyoxyalkylene alcohol obtained in each example 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, and the presence or absence of precipitates in the solution in the test tube was confirmed. Propane was used as the refrigerant.

[0067] Example 1: 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. The temperature was then raised to 100°C, and 1,200 g of propylene oxide was introduced into the autoclave over 15 hours. After confirming that the pressure inside the autoclave had stabilized and all of the propylene oxide had reacted, the contents were transferred to a separable flask. 1.0 equivalent of 14 g of sulfuric acid was added to the contents to neutralize them. Then, 100 g of an aluminum silicate adsorbent (Kyowado 700, manufactured by Kyowa Chemical Industry Co., Ltd.) was added as an adsorbent. The adsorbent was then mixed while dehydrating under reduced pressure at 100°C for 2 hours. The neutralized catalyst was adsorbed onto the adsorbent, and the catalyst was thoroughly removed by filtration of insoluble matter to obtain a polyether monool. The residual metal content in the resulting polyether monool was 2.1 ppm. The number average molecular weight determined by GPC was 1,220.

[0068] [Example 2] 400 g of propylene glycol as an initiator and 12 g of potassium hydroxide (purity 95% by mass) as a catalyst were added to a 5 L autoclave. The autoclave was then heated to 110°C, and 3,600 g of propylene oxide was introduced into the autoclave over 10 hours. After confirming that the pressure inside the autoclave had stabilized and all of the propylene oxide had reacted, the contents were transferred to a 5 L separable flask. 30 g of acidic sodium pyrophosphate and 20 g of water were added to the contents and mixed at 100°C for 30 minutes. The catalyst was then insolubilized by dehydration under reduced pressure for 2 hours. The catalyst was then thoroughly removed by filtration of insoluble matter, yielding a polyether polyol. The residual metal content in the resulting polyether polyol was 5.2 ppm. The number average molecular weight determined by GPC was 580.

[0069] [Example 3] 92 g of glycerin and 5 g of potassium hydroxide (purity 95% by mass) as a catalyst were added to a 5 L autoclave. The temperature was then raised to 110°C, and 1,500 g of propylene oxide was introduced into the autoclave over 12 hours. After confirming that the pressure inside the autoclave had stabilized and all of the propylene oxide had reacted, the contents were transferred to a separable flask. 100 g of a synthetic hydrotalcite-based adsorbent (Kyowado 1000, manufactured by Kyowa Chemical Industry Co., Ltd.) was added to the contents, and the product and adsorbent were mixed at 100°C for 2 hours. After the catalyst was adsorbed onto the adsorbent, the catalyst was thoroughly removed by filtration of insoluble matter to obtain a polyether polyol. The residual metal content in the resulting polyether polyol was 0.3 ppm. The number average molecular weight determined by GPC was 1,500.

[0070] [Example 4] 550 g of a pentaerythritol PO adduct (EXCENOL 410NE, manufactured by AGC) and 6.3 g of potassium hydroxide (purity 95% by mass) as a catalyst were added to a 5-L autoclave. The temperature was then raised to 120°C, and the system was subjected to vacuum dehydration for 1 hour to reduce the water content in the system. Then, 1,500 g of propylene oxide was introduced into the autoclave over 8 hours. After confirming that the pressure inside the autoclave had stabilized and all of the propylene oxide had reacted, the contents were transferred to a separable flask. 2.0 equivalents of 7.0 g of phosphoric acid and 10 g of water were added to the contents for neutralization. The temperature was then raised to 100°C, and the mixture was mixed for 30 minutes, followed by vacuum dehydration for 2 hours to insolubilize the catalyst. The insolubilized catalyst was then removed by filtration to obtain a polyether polyol. The residual metal content in the resulting polyether polyol was 8.0 ppm. The number average molecular weight determined by GPC was 2,000.

[0071] [Example 5] 182 g of sorbitol and 14.8 g of potassium hydroxide (purity 95% by mass) as a catalyst were added to a 5 L autoclave. The temperature was then raised to 110°C, and the system was subjected to reduced pressure dehydration for 1 hour to reduce the water content in the system. Then, 4,500 g of propylene oxide was introduced into the autoclave over 10 hours. After the pressure inside the autoclave became constant and it was confirmed that all of the propylene oxide had reacted, the contents were transferred to a separable flask. 200 g of a magnesium silicate-based adsorbent (Kyowado 600, manufactured by Kyowa Chemical Industry Co., Ltd.) was added to the contents, and the product and adsorbent were mixed at 100°C for 2 hours. After the catalyst was adsorbed onto the adsorbent, insoluble matter was removed by filtration to obtain a polyether polyol from which the catalyst had been removed. The residual metal content in the resulting polyether polyol was 1.1 ppm. The number average molecular weight determined by GPC was 4,600.

[0072] Example 6: 342 g of sucrose, 13.6 g of potassium hydroxide (purity 95% by mass) as a catalyst, and 300 g of propylene oxide were added to a 5 L autoclave. The mixture was then heated to 100°C and mixed to dissolve the sucrose and catalyst in the propylene oxide. After confirming that the autoclave pressure had decreased and stabilized due to the reaction of the propylene oxide, 3700 g of propylene oxide was added to the autoclave over 10 hours. After confirming that the pressure inside the autoclave had stabilized and all of the propylene oxide had reacted, the contents were transferred to a separable flask. The contents were neutralized by adding 30 g of sodium acid pyrophosphate as a neutralizing agent. Then, 100 g of an aluminum silicate-based adsorbent (Kyowado 700, manufactured by Kyowa Chemical Industry Co., Ltd.) was added as an adsorbent. The mixture was then mixed while dehydrating under reduced pressure at 100°C for 2 hours, allowing the neutralized catalyst to be adsorbed onto the adsorbent. The catalyst was then thoroughly removed by filtration to remove insoluble matter, yielding a polyether polyol. The residual metal content in the resulting polyether polyol was 1.7 ppm. The number average molecular weight determined by GPC was 4,000.

[0073] [Example 7] 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. The temperature was then raised to 100°C, and a mixture of 700 g of propylene oxide and 700 g of ethylene oxide was introduced into the autoclave over 15 hours. After confirming that the pressure inside the autoclave had stabilized and all of the propylene oxide and ethylene oxide had reacted, the contents were transferred to a separable flask. The contents were neutralized with 14 g of sulfuric acid (1.0 equivalent). Then, 100 g of an aluminum silicate adsorbent (Kyowado 700, manufactured by Kyowa Chemical Industry Co., Ltd.) was added as an adsorbent. The mixture was then mixed at 100°C for 2 hours, and the neutralized catalyst was adsorbed onto the adsorbent. The catalyst was then thoroughly removed by filtration of insoluble matter, yielding a polyether monool. The residual metal content in the resulting polyether monool was 2.6 ppm. The number-average molecular weight determined by GPC was 1,410.

[0074] [Example 8] 200 g of propylene glycol and 12 g of potassium hydroxide (purity 95% by mass) as a catalyst were added to a 5 L autoclave. The autoclave was then heated to 110°C, and a mixture of 2600 g of propylene oxide and 1000 g of ethylene oxide was introduced into the autoclave over 10 hours. After confirming that the pressure inside the autoclave had stabilized and all of the propylene oxide and ethylene oxide had reacted, the contents were transferred to a 5 L separable flask. 6.6 g of 1.0 equivalent of phosphoric acid was added to the contents for neutralization. 120 g of a magnesium silicate adsorbent (Kyowado 600S, manufactured by Kyowa Chemical Industry Co., Ltd.) was then added. The catalyst was neutralized at 100°C for 2 hours and adsorbed onto the adsorbent. The catalyst was then thoroughly removed by filtration of insoluble matter, yielding a polyether polyol. The residual metal content in the resulting polyether polyol was 1.8 ppm. The number average molecular weight determined by GPC was 1,350.

[0075] [Example 9] 92 g of glycerin and 0.9 g of potassium hydroxide (purity 95% by mass) as a catalyst were added to a 5-L autoclave. The temperature was then raised to 110°C, and a mixture of 700 g of propylene oxide and 300 g of ethylene oxide was introduced into the autoclave over 12 hours. After confirming that the pressure inside the autoclave had stabilized and all of the propylene oxide and propylene oxide had reacted, the contents were transferred to a separable flask. 20 g of acidic sodium pyrophosphate was added as a neutralizing agent to neutralize the contents. 50 g of a synthetic hydrotalcite adsorbent (Kyowado 1000, manufactured by Kyowa Chemical Industry Co., Ltd.) was then added as an adsorbent. The adsorbent was then mixed while the mixture was dehydrated under reduced pressure at 100°C for 2 hours, allowing the neutralized catalyst to be adsorbed onto the adsorbent. The catalyst was then thoroughly removed by filtration of insoluble matter, yielding a polyether polyol. The residual metal content in the resulting polyether polyol was 0.5 ppm. The number average molecular weight determined by GPC was 1,000.

[0076] [Example 10] 400 g of propylene glycol as an initiator and 12 g of potassium hydroxide (purity 95% by mass) as a catalyst were added to a 5 L autoclave. The autoclave was then heated to 110°C, and 3,600 g of propylene oxide was introduced into the autoclave over 10 hours. After confirming that the pressure inside the autoclave had stabilized and all of the propylene oxide had reacted, the contents were transferred to a 5 L separable flask. 40 g of a magnesium silicate adsorbent (Kyowado 600S, manufactured by Kyowa Chemical Industry Co., Ltd.) was added to the contents, and the product and adsorbent were mixed at 100°C for 2 hours to adsorb the catalyst onto the adsorbent. The catalyst was then removed by filtration of insoluble matter, yielding a polyether polyol. The residual metal content in the resulting polyether polyol was 15 ppm. The number average molecular weight determined by GPC was 580.

[0077] [Example 11] 92 g of glycerin and 0.9 g of potassium hydroxide (purity 95% by mass) as a catalyst were added to a 5 L autoclave. The temperature was then raised to 110°C, and 1,500 g of propylene oxide was introduced into the autoclave over 12 hours. After confirming that the pressure inside the autoclave had stabilized and all of the propylene oxide had reacted, the contents were transferred to a separable flask. An equivalent amount of 2.2 g of 2-ethylhexanoic acid was added to the separable flask to neutralize the catalyst. The residual metal content in the resulting polyether polyol was 370 ppm. The number average molecular weight determined by GPC was 1,500.

[0078] [Example 12] 182 g of sorbitol and 14.8 g of potassium hydroxide (purity 95% by mass) as a catalyst were added to a 5 L autoclave. After heating to 110°C, the system was dehydrated under reduced pressure for 1 hour to reduce the water content, and then 4,500 g of propylene oxide was introduced into the autoclave over 10 hours. After confirming that the pressure inside the autoclave had stabilized and all of the propylene oxide had reacted, the contents were transferred to a separable flask. The contents were neutralized with 0.5 equivalents of 4.1 g of phosphoric acid and 10 g of water. The mixture was then heated to 100°C, mixed for 30 minutes, and then dehydrated under reduced pressure for 2 hours to insolubilize the catalyst. The insolubilized catalyst was then removed by filtration to obtain a polyether polyol. The residual metal content in the resulting polyether polyol was 50 ppm. The number average molecular weight determined by GPC was 4,600.

[0079]

[0080]

[0081] The initiator in formula 1, R ２ O, m and n are shown in Table 1. In Tables 1 and 2, PO represents propylene oxide and EO represents ethylene oxide.

[0082] In the refrigerants mixed with each of the lubricating base oils in Examples 10-12, precipitates occurred after heating at 175°C for 14 days. In contrast, in Examples 1-9, the metal content was 10 ppm or less. In the refrigerants mixed with each of these lubricating base oils, no precipitates occurred even after heating at 175°C for 14 days. Thus, in Examples 1-9, the chemical stability of the refrigerants blended with the lubricating base oils was improved when used for a long period of time.

[0083] 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.

[0084] This application claims priority based on Japanese Patent Application No. 2024-16254, filed on February 6, 2024, the entire contents of which are incorporated herein by reference.

[0085] 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 contains at least one selected from the group consisting of polyoxyalkylene monools and polyoxyalkylene polyols represented by the following formula 1: A lubricating base oil having a metal content of 10 ppm or less. R 1 {(R 2 O) m H} n...Formula 1 In formula 1, R 1 is an initiator residue; R 2 s each independently represent a hydrocarbon group having 2 to 4 carbon atoms; m is 1 to 200; n is 1 to 8; The initiator residue is a group obtained by removing one or more active hydrogen atoms from at least one initiator selected from the group consisting of aliphatic diols, aliphatic alcohols having 3 to 8 hydroxyl groups, amines, phenols, salts thereof, and alkylene oxide adducts thereof.

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. 10. The lubricant base oil of claim 1, wherein the hydrocarbon compound of the refrigerant comprises propane.

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

5. 2. The lubricating base oil according to claim 1, wherein the at least one selected from the group consisting of polyoxyalkylene monools and polyoxyalkylene polyols 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. 7. The lubricating oil composition of claim 6, wherein the refrigerant is propane.

8. 7. The lubricating oil composition of claim 6, wherein the refrigerant is propylene.

9. 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.

10. 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 5 are sealed.

11. The cooling system according to claim 10, which is used 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.