Lubricating oil base oils, lubricating oil compositions and cooling systems

Abstract

This invention provides: a lubricating oil base oil with improved chemical stability when used for extended periods with a refrigerant blended with a lubricating oil base oil; and a lubricating oil composition comprising the aforementioned lubricating oil base oil. The lubricating oil base oil of this invention is a lubricating oil base oil mixed with a refrigerant, wherein the refrigerant comprises a hydrocarbon compound having 1 to 8 carbon atoms, the lubricating oil base oil comprises at least one selected from the group consisting of polyoxyalkylene monohydric alcohols and polyoxyalkylene polyhydric alcohols, and the metal content of the aforementioned lubricating oil base oil is 10 ppm or less.

Description

Technical Field

[0001] This invention relates to lubricating oil base oils, lubricating oil compositions, and cooling systems. Background Technology

[0002] To ensure smooth refrigerant circulation in a compression refrigeration unit, various lubricating oil base oils are used. As lubricating oil base oils, compounds such as polyalkylene glycols, polyol esters, and polyvinyl ethers can be used, depending on the type of refrigerant. For example, in an embodiment of Patent Document 1, a mixture of refrigerant and a lubricating oil base oil containing an epoxy compound such as 1,2-epoxyhexadecane and a polyalkylene glycol is disclosed. Furthermore, since the refrigerant and lubricating oil base oil are sealed and used within the refrigeration unit for extended periods, stability is required to prevent the formation of precipitates even after prolonged use.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 6-240278 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] However, prolonged use of refrigerants mixed with existing lubricating oil base oils can sometimes lead to the formation of precipitates. Therefore, there is room for improvement in the chemical stability of refrigerants mixed with lubricating oil base oils over extended periods.

[0008] The present invention provides: a lubricating oil base oil with improved chemical stability when used for a long time with a refrigerant mixed with a lubricating oil base oil; and a lubricating oil composition comprising the aforementioned lubricating oil base oil.

[0009] Solution for solving the problem

[0010] The present invention has the following features.

[0011] [1] A lubricating oil base oil, which is a lubricating oil base oil mixed with a refrigerant.

[0012] The aforementioned refrigerant contains hydrocarbon compounds with 1 to 8 carbon atoms.

[0013] The aforementioned lubricating oil base oil contains at least one selected from the group consisting of polyoxyalkylene monohydric alcohols and polyoxyalkylene polyhydric alcohols.

[0014] The metal content of the aforementioned lubricating oil base oil is less than 10 ppm.

[0015] [2] According to the lubricating oil base oil described in [1], wherein at least one of the aforementioned components selected from the group consisting of polyoxyalkylene monohydric alcohols and polyoxyalkylene polyhydric alcohols is represented by the following formula 1.

[0016] R 1 {(R 2 O) m H} n …Formula 1

[0017] In Equation 1,

[0018] R 1 For initiator residues,

[0019] R 2 Each is an independent hydrocarbon group with 2 to 4 carbon atoms.

[0020] m ranges from 1 to 200.

[0021] n is 1 to 8.

[0022] [3] According to the lubricating oil base oil described in [2], wherein the aforementioned R 2 At least one of them is a hydrocarbon group with 3 carbon atoms.

[0023] [4] The lubricating oil base oil according to any one of [1] to [3], wherein the aforementioned hydrocarbon compound of the aforementioned refrigerant comprises propane.

[0024] [5] The lubricating oil base oil according to any one of [1] to [4], wherein the aforementioned hydrocarbon compound of the aforementioned refrigerant comprises propylene.

[0025] [6] The lubricating oil base oil according to any one of [1] to [5], wherein the number average molecular weight of at least one of the groups selected from polyoxyalkylene monohydric alcohols and polyoxyalkylene polyhydric alcohols is 300 to 5000.

[0026] [7] A lubricating oil composition comprising: any one of the lubricating oil base oils described in [1] to [6]; and any one or both of a refrigerant and an additive.

[0027] [8] The lubricating oil composition according to [7], wherein the aforementioned refrigerant is propane.

[0028] [9] The lubricating oil composition according to [7] or [8], wherein the aforementioned refrigerant is propylene.

[0029]

[10] The lubricating oil composition according to any one of [7] to [9] is used in automotive air conditioning, indoor air conditioning, refrigerator, freezer, vending machine hot water supply system, display cabinet hot water supply system, refrigeration / heating system or gas heat pump system.

[0030]

[11] A cooling system comprising a compressor, a condenser, an evaporator and an expansion valve, and sealed with: a refrigerant comprising a hydrocarbon compound having 1 to 8 carbon atoms, and a lubricating oil base oil as described in any one of [1] to [6].

[0031]

[12] The cooling system according to

[11] , wherein the aforementioned cooling system is used for supplying hot water, refrigeration / heating or gas heat pump systems for automotive air conditioning, indoor air conditioning units, refrigerators, freezers, vending machines, display cabinets.

[0032] The effects of the invention

[0033] According to the present invention, the chemical stability of refrigerants mixed with lubricating oil base oils is improved during long-term use. Attached Figure Description

[0034] Figure 1 This is a diagram illustrating a schematic configuration of the cooling system according to the first embodiment. Detailed Implementation

[0035] The meanings of the terms are as follows.

[0036] "Active hydrogen" refers to hydrogen atoms based on groups containing active hydrogen and hydrogen atoms based on water-based hydroxyl groups.

[0037] The term "group containing active hydrogen" refers to at least one group selected from the group consisting of hydroxyl, carboxyl, amino, monovalent functional groups obtained by removing one hydrogen atom from a primary amine, and thiol.

[0038] "Initiator residue" is a group obtained by removing one or more active hydrogen atoms from an initiator.

[0039] A "unit" refers to an atomic group that is formed directly through the polymerization of monomers.

[0040] "Number-average molecular weight" is the converted molecular weight of polystyrene obtained by GPC measurement.

[0041] "Metal content of lubricating oil base oil" refers to the total amount of metal elements detected by elemental analysis based on ICP emission spectroscopy. The unit for metal content is ppm, which is the quality standard.

[0042] "Kinematic viscosity" refers to the value measured at 100°C according to JIS K2283:2000.

[0043] "Viscosity index" refers to the value calculated from the kinematic viscosity measured according to JIS K2283:2000.

[0044] "Volume resistivity" refers to the value measured according to the "Volume Resistivity Test Method" of JIS C2101:2010 "Electrical Insulating Oil".

[0045] The "~" signifying a numerical range refers to the values ​​before and after the "~" sign, which are considered the lower and upper limits, respectively. The numerical ranges disclosed in this specification can be arbitrarily combined with their lower and upper limits to create new numerical ranges.

[0046] [Lubricating oil base oil]

[0047] The lubricating oil base oil of the present invention, when mixed with a refrigerant, can, for example, impart lubrication to the sliding parts of a compressor in a compression refrigeration machine.

[0048] (refrigerant)

[0049] The refrigerant mixed with the lubricating oil base oil of the present invention comprises a hydrocarbon compound having 1 to 8 carbon atoms. Considering the 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, further preferably 3 or 4, and most preferably 3.

[0050] Hydrocarbon compounds that can be used as refrigerants include, for example, methane, ethane, ethylene, propane, cyclopropane, propylene, n-butane, isobutane, n-pentane, and isopentane. Among these, propane and propylene are preferred.

[0051] The hydrocarbon compounds of the refrigerant can be used alone or by mixing two or more together.

[0052] The lubricating oil base oil of the present invention comprises at least one selected from the group consisting of polyoxyalkylene monohydric alcohols and polyoxyalkylene polyhydric alcohols (also referred to as "polyether polyhydric alcohols"). The polyoxyalkylene polyhydric alcohol 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, etc. In the following description, the general term for polyoxyalkylene monohydric alcohols and polyoxyalkylene polyhydric alcohols is referred to as polyoxyalkylene alcohols.

[0053] Polyoxyalkylene alcohols are not particularly limited. In one example, polyoxyalkylene alcohols can be synthesized by addition polymerization of alkylene oxides with an initiator having a group containing active hydrogen in the presence of a catalyst.

[0054] Initiators can be any compound containing an active hydrogen group, and there are no particular limitations. An initiator may have one or more active hydrogen groups. Examples of initiators include aliphatic monohydric alcohols, aliphatic dihydric alcohols, aliphatic alcohols having 3 to 8 hydroxyl groups, amines, phenols, their salts, and their alkylene oxide adducts. However, initiators are not limited to these examples.

[0055] Initiators can be used alone or in combination with two or more.

[0056] Aliphatic monohydric alcohols can be saturated, unsaturated, or cyclic. Saturated aliphatic monohydric alcohols are preferred. Examples of saturated aliphatic monohydric alcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, isobutanol, tert-butanol, n-hexanol, octanol, and 2-ethylhexanol. However, saturated aliphatic monohydric alcohols are not limited to these examples.

[0057] Examples of aliphatic diols include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, and 1,6-hexanediol. However, aliphatic diols are not limited to these examples.

[0058] Examples of aliphatic alcohols having 3 to 8 hydroxyl groups include glycerol, trimethylolethane, trimethylolpropane, hexanetriol, pentaerythritol, dipentaerythritol, diglycerol, mesoerythritol, methylglucoside, glucose, sucrose, trehalose, and sorbitol. However, aliphatic alcohols having 3 to 8 hydroxyl groups are not limited to these examples.

[0059] Examples of amines include alkanolamines, heterocyclic amines, aliphatic amines, and aromatic amines.

[0060] Examples of alkanolamines include monoethanolamine, diethanolamine, triethanolamine, and isopropanolamine.

[0061] Examples of heterocyclic amines include N-(2-aminoethyl)piperazine and N-aminomethylpiperazine.

[0062] Examples of aliphatic amines include ethylenediamine, propylenediamine, and hexamethylenediamine.

[0063] Examples of aromatic amines include toluene diamine and diaminodiphenylmethane.

[0064] However, amines are not limited to these examples. Amines can be used alone or in combination with two or more.

[0065] Examples of phenols include bisphenol A and resorcinol.

[0066] However, phenols are not limited to these examples. A single phenol can be used alone, or two or more can be used together.

[0067] As an initiator, aliphatic monohydric alcohols, aliphatic dihydric alcohols, and aliphatic alcohols having 3 to 8 hydroxyl groups are preferred, and aliphatic dihydric alcohols and aliphatic alcohols having 3 to 8 hydroxyl groups are more preferred.

[0068] Examples of catalysts include alkali metal catalysts and bimetallic cyanide complex catalysts (hereinafter referred to as "DMC catalysts"). However, catalysts are not limited to these examples.

[0069] A single catalyst can be used alone, or two or more catalysts can be used in combination.

[0070] Examples of alkali metal catalysts include alkali metals such as sodium and potassium; alkali metal alkoxides such as sodium methoxide, sodium ethoxide, sodium propoxide, potassium methoxide, potassium propoxide, etc.; hydroxides such as sodium hydroxide, potassium hydroxide, cesium hydroxide, etc.; and carbonates such as sodium carbonate, potassium carbonate, etc.

[0071] Alkali metal catalysts can be used alone or in combination with two or more.

[0072] It is believed that DMC catalysts contain at least a metal element and an organic ligand.

[0073] Examples of metal elements that can be used as DMC catalysts include Zn, Fe, Co, Ni, Al, Sr, Mn, Cr, Cu, Sn, Pb, Mo, W, and V. However, the metal elements used in DMC catalysts are not limited to these examples.

[0074] The metal element in a DMC catalyst can be one or more.

[0075] Examples of organic ligands that can be used as DMC catalysts include, for example, tert-butanol (hereinafter referred to as "TBA"), n-butanol, isobutanol, tert-amyl alcohol, isoamyl alcohol, N,N-dimethylacetamide, ethylene glycol monotert-butyl ether, ethylene glycol dimethyl ether (glycol dimethyl ether), diethylene glycol dimethyl ether (diethylene glycol dimethyl ether), triethylene glycol dimethyl ether (triethylene glycol dimethyl ether), isopropanol, and dioxane. Dioxane can be either 1,4-dioxane or 1,3-dioxane. However, the organic ligands are not limited to these examples.

[0076] Organic ligands can be used alone or in combination with two or more.

[0077] Examples of epoxides include ethylene oxide, propylene oxide, 1,2-epoxidebutane, 2,3-epoxidebutane, 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. Ethyl oxide and propylene oxide are preferred as epoxides, and propylene oxide is more preferred. However, epoxides are not limited to these examples.

[0078] Epoxyalkane can be used alone or in combination with two or more. That is, one type of epoxyalkane can be homopolymerized with an initiator, or two or more types of epoxyalkane can be copolymerized with an initiator. In the case of copolymerization, two or more types of epoxyalkane can be block copolymerized with an initiator or random copolymerized.

[0079] As a polyoxyalkylene alcohol, the compound shown in Formula 1 is preferred.

[0080] R 1 {(R 2 O) m H} n …Formula 1

[0081] In Equation 1, R 1 These are initiator residues. Details and preferred configurations of the initiator are as described above.

[0082] In Equation 1, n (R) 2 O) m They can be the same as each other, or they can be different. Furthermore, in each (R) 2 O) m In, there can exist 1 kind of R 2 O can also have more than two types of R. 2 O. There are more than two types of R. 2 In the case of O, each R 2 The bonding order of O is not restricted. For example, there are 2 types of R. 2 In the case of O, there are 2 types of R 2 O can be configured randomly, alternately, or in segments. (R) 2 O) m It can be a random copolymer with units based on two or more epoxides, or it can be a block copolymer.

[0083] R 2 Each group is independently a hydrocarbon group with 2 to 4 carbon atoms. The hydrocarbon group preferably has 2 or 3 carbon atoms, more preferably 3. Therefore, R is preferred. 2 At least one of them is a hydrocarbon group having 3 carbon atoms, more preferably R 2 All are hydrocarbon groups with 3 carbon atoms.

[0084] R 2 The hydrocarbon group can be straight-chain or branched. R 2 In the case of branches, there are no particular restrictions on the location and number of branches.

[0085] As R 2Examples include -CH2CH2-, -CH2CH2CH2-, -CH2CH2CH2CH2-, -CH(CH3)CH2-, -CH2CH(CH3)-, -CH(CH3)CH2CH2-, and -CH2CH(CH3)CH2-. -CH2CH2- and -CH2CH(CH3)- are preferred, and -CH2CH(CH3)- is even more preferred.

[0086] 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 above the lower limit of the aforementioned numerical range, it is easy to obtain a lubricating oil base oil with a good viscosity index. When m is below the upper limit of the aforementioned numerical range, it is easy to obtain a lubricating oil base oil with good fluidity at low temperatures.

[0087] 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 above the lower limit of the aforementioned numerical range, it is easy to obtain a lubricating oil base oil with a good viscosity index. When n is below the upper limit of the aforementioned numerical range, it is easy to obtain a lubricating oil base oil with a good volume resistivity.

[0088] The number-average molecular weight of the polyoxyalkylene alcohol is preferably 300 to 5000, more preferably 500 to 3000, and even more preferably 700 to 2000. When the number-average molecular weight is above the lower limit of the aforementioned range, it is easy to obtain adequate compatibility with the refrigerant. When the number-average molecular weight is below the upper limit of the aforementioned range, it is easy to obtain a lubricating oil base oil with good kinematic viscosity.

[0089] (Physical properties of lubricating oil base oil)

[0090] The metal content of the lubricating oil base oil of the present invention is 10 ppm or less. Therefore, the chemical stability of the refrigerant containing the lubricating oil base oil is improved during prolonged use. The metal content of the lubricating oil 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 oil base oil is preferably 0.1 ppm or more.

[0091] There are no particular limitations on the metal elements contained in lubricating oil base oils. In the synthesis reaction of polyoxyalkylene alcohols, epoxides can undergo addition polymerization with an initiator in the presence of a catalyst. Metal elements introduced by the catalyst used in this synthesis reaction may sometimes remain in the lubricating oil base oil. To ensure that the metal content of the lubricating oil base oil is below 10 ppm, it is preferable to thoroughly remove the catalyst after the synthesis reaction of the polyoxyalkylene alcohol.

[0092] When determining the metal content of lubricating oil base oils, there are no particular limitations on the metal elements that are tested. The test targets all metal elements that may be present in the catalysts expected to be used in the manufacture of lubricating oil base oils.

[0093] Examples of residual metals introduced by catalysts 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 element to be detected can be one or more.

[0094] There is no particular limitation on the kinematic viscosity of the lubricating oil base oil at 100°C; for example, it can be 2–200 mm. 2 / s, which can range from 5 to 100 mm. 2 / s, or 7-50mm 2 / s. When the kinematic viscosity is above the lower limit of the aforementioned range, the sealing performance is improved, thus reducing the likelihood of refrigerant leakage. When the kinematic viscosity is below the upper limit of the aforementioned range, the viscous resistance is low, and the lubricity is improved.

[0095] From the perspective of improving viscosity characteristics, the viscosity index of the lubricating oil base oil is preferably 50 or higher, more preferably 80 or higher, and even more preferably 100 or higher. The higher the upper limit of the viscosity index of the lubricating oil base oil, the better, and there is no particular limitation; for example, it can be 140, 160, 200, etc.

[0096] There is no particular limitation on the volume resistivity of lubricating oil base oils; for example, it can be 1×10⁻⁶. 10 ~1×10 15 Ω·cm, or 6×10 10 ~1×10 14 Ω·cm, can also be 1×10 11 ~1×10 14 Ω·cm. When the volume resistivity is above the lower limit of the aforementioned range, the electrical insulation performance is improved. When the volume resistivity is below the upper limit of the aforementioned range, it is easier to prevent the generation of static electricity.

[0097] (Manufacturing method of lubricating oil base oil)

[0098] The lubricating oil base oil can be obtained by: performing addition polymerization of alkylene oxides with an initiator in the presence of a catalyst to obtain polyoxyalkylene alcohols, and then removing the catalyst from the reaction solution containing the polyoxyalkylene alcohols. Details and preferred methods of the initiator, alkylene oxides, and catalyst are as described above.

[0099] There are no particular limitations on the reaction temperature, reaction time, and reactor pressure for ring-opening addition polymerization. The reaction temperature can be, for example, 80–150°C or 90–140°C. The reaction time can be, for example, 3–30 hours or 5–20 hours. The reactor pressure can be, for example, 0.01–0.9 MPaG or 0.03–0.7 MPaG.

[0100] There are no particular limitations on the method for catalyst removal. For example, methods 1, 2, and 3 can be listed below.

[0101] Method 1: Using an adsorbent to adsorb the catalyst, followed by filtration to remove the adsorbent containing the catalyst.

[0102] Method 2: Neutralize the catalyst using a neutralizing agent, and then remove the neutralized catalyst by filtration.

[0103] Method 3: A method for removing the catalyst when using a charged filter.

[0104] In catalyst removal, any one of methods 1, 2, and 3 can be implemented individually, or any two or more methods can be combined appropriately, or all of methods 1, 2, and 3 can be implemented. When implementing two or more or all of methods 1, 2, and 3, the order of implementation is not particularly limited. From the viewpoint of further reducing metal content, methods 1 and 2 are preferred methods for catalyst removal, and method 1 is more preferred.

[0105] Examples of adsorbents include synthetic silicates, ion exchange resins, activated clay, oxidized salts, and acidic clay. Examples of synthetic silicates include magnesium silicate, aluminum silicate, and hydrotalcite. Examples of oxidized salts include magnesium oxide and aluminum oxide. However, adsorbents are not limited to these examples.

[0106] Adsorbents can be used alone or in combination with two or more.

[0107] Examples of neutralizing agents include amines, alkali metal hydroxides, organic acids, inorganic acids, and their salts. Examples of inorganic acids include sulfuric acid, phosphoric acid, and hydrochloric acid. Examples of organic acids include lactic acid. However, neutralizing agents are not limited to these examples.

[0108] Neutralizing agents can be used alone or in combination with two or more.

[0109] Commercially available products can be used as charged filters. Examples of commercially available charged filters include the Zeta Plus adsorption depth filter EC series (manufactured by 3M), RO Wound (manufactured by ORGANO), and SUPRAcap 200 (manufactured by Seitz AKSJ). However, charged filters are not limited to these examples.

[0110] [Lubricating oil composition]

[0111] The lubricating oil composition of the present invention comprises: the aforementioned lubricating oil base oil; and any one or both of a refrigerant and an additive. In one example, the lubricating oil composition may comprise a lubricating oil base oil and a refrigerant, or it may comprise a lubricating oil base oil and an additive, or it may comprise a lubricating oil base oil, a refrigerant, and an additive. The lubricating oil composition according to the present invention, for example, can impart lubrication to the sliding parts of a compressor supplied with refrigerant. Regarding the refrigerant, as described above.

[0112] Examples of additives include, for example, antioxidants, extreme pressure agents, stabilizers, copper passivators, defoamers, load-bearing additives, chlorine scavengers, oxygen scavengers, cleaning and dispersing agents, viscosity index improvers, oiliness agents, rust inhibitors, corrosion inhibitors, and pour point depressants. However, additives are not limited to these examples.

[0113] Additives can be used alone or in combination with two or more.

[0114] Examples of antioxidants include phenolic antioxidants and amine antioxidants.

[0115] Examples of phenolic 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).

[0116] Examples of amine-based antioxidants include phenyl-α-naphthylamine and N,N'-diphenyl-p-phenylenediamine.

[0117] Antioxidants can be used alone or in combination of two or more.

[0118] Examples of extreme pressure agents include phosphorus-based extreme pressure agents such as phosphate esters, acidic phosphate esters, phosphites, acidic phosphites, and their amine salts.

[0119] Examples of stabilizers include phenyl glycidyl ether, alkyl glycidyl ether, alkylene glycol glycidyl ether, cyclohexene oxide, α-olefin epoxide, and epoxidized soybean oil.

[0120] Examples of copper passivating agents include benzotriazole and its derivatives. For example, N-[N,N'-dialkyl (alkyl with 3 to 12 carbon atoms)aminomethyl]triazole can be listed.

[0121] Examples of defoamers include silicone oil and fluorinated silicone oil.

[0122] The proportion of the lubricating oil base oil can be 40-99.9% by mass, 45-90% by mass, or 50-80% by mass of the total lubricating oil composition. When the proportion of the lubricating oil base oil is above the lower limit of the aforementioned range, the chemical stability when mixed with the refrigerant is easily improved. When the proportion of the lubricating oil base oil is below the upper limit of the aforementioned range, it is preferred in terms of compatibility with the refrigerant.

[0123] When a refrigerant is included in the lubricating oil composition, the proportion of the refrigerant can be 0.1% to 80% by mass, 10% to 60% by mass, or 20% to 50% by mass of the total amount of the lubricating oil composition. A refrigerant proportion above the lower limit of the aforementioned range is preferred in terms of compatibility with the lubricating oil base oil. A refrigerant proportion below the upper limit of the aforementioned range tends to improve chemical stability when mixed with the lubricating oil base oil.

[0124] When an additive is included in the lubricating oil composition, the proportion of the additive can be 0.1 to 60% by mass, 1 to 40% by mass, or 2 to 20% by mass of the total amount of the lubricating oil composition. When the proportion of the additive is above the lower limit of the aforementioned range, the oxidation resistance of the base oil improves. When the proportion of the additive is below the upper limit of the aforementioned range, it is preferred in terms of compatibility with the refrigerant.

[0125] [Mechanism of Action]

[0126] The metal content of the lubricating oil base oil of the present invention described above is less than 10 ppm. Therefore, even under harsh conditions and prolonged use of refrigerants, precipitates are not easily formed. As a result, the chemical stability of the lubricating oil base oil according to the present invention is improved during prolonged use of refrigerants formulated with it.

[0127] [use]

[0128] Lubricating oil base oils and lubricating oil compositions can be used in various cooling systems, including automotive air conditioning, indoor air conditioning units, refrigerators, cold storage, vending machines, display cases, hot water supply systems, refrigeration / heating systems, and gas heat pump systems. Lubricating oil base oils and lubricating oil compositions are particularly preferred for use in... Figure 1 The system shown is a compression cooling system consisting of a compressor 1, a condenser 2, an expansion valve 3, and an evaporator 4.

[0129] exist Figure 1 The compression cooling system shown contains a refrigerant comprising hydrocarbon compounds with 1 to 8 carbon atoms, and a lubricating oil base oil. The lubricating oil base oil and the lubricating oil composition circulate in the compressor 1, condenser 2, expansion valve 3, and evaporator 4. The lubricating oil base oil provides lubrication to the sliding parts of the compressor 1.

[0130] The amounts of lubricating oil base oil and refrigerant used in this invention can be varied widely within the range of 99 / 1 to 10 / 90, based on the refrigerant / lubricating oil base oil mass ratio. This mass ratio is preferably in the range of 90 / 10 to 50 / 50.

[0131] Example

[0132] The following examples illustrate the implementation in more detail. However, the present invention is not limited to the following description. Examples 1-9 are examples, and Examples 10-12 are comparative examples.

[0133] [Measurement and Evaluation]

[0134] (Number average molecular weight)

[0135] Under the following conditions, the GPC of the lubricating oil base oil was determined to obtain the number-average molecular weight (Mn).

[0136] GPC measurement conditions:

[0137] Model used: HLC-8220GPC (manufactured by Tosoh Corporation)

[0138] Data processing device: SC-8020 (Tosoh Corporation product)

[0139] Column used: TSG gel G2500H (Tosoh Corporation product)

[0140] Column temperature: 40℃, detector: RI, solvent: tetrahydrofuran, flow rate: 0.6 mL / min, sample concentration: 0.25% by mass, injection volume: 10 μL

[0141] Standard sample used to prepare standard curve: polystyrene ([Easical]PS-2 [Polystyrene Standards], Polymer Laboratories product)

[0142] (Metal content)

[0143] 20g of the lubricating oil base oil containing polyoxyalkylene alcohols obtained in each example was completely ashed using a burner. The ashed powder residue was mixed with 100mL of hydrochloric acid aqueous solution to prepare the test sample. The contents of Na, K, Zn, and Co were determined using an ICP 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 oil base oil.

[0144] (Chemical stability)

[0145] The tests used to evaluate chemical stability were performed according to the sealed tube test described in JIS K2211-2009. More specifically, iron, copper, and aluminum were added to the test tube as catalysts. Then, 0.7 mL of the lubricating oil base oil containing polyoxyalkylene alcohols obtained in each example and 0.7 mL of refrigerant were added, and the opening of the test tube was sealed. After heating the sealed test tube at 175°C for 14 days, the presence of any precipitates in the solution within the test tube was confirmed. Propane was used as the refrigerant.

[0146] [Example 1]

[0147] 74 g of n-butanol and 12 g of sodium hydroxide (95% by mass purity) as a catalyst were added to a 5 L autoclave. The mixture was then heated to 100 °C, and 1200 g of propylene oxide was introduced into the autoclave over 15 hours. After confirming that the pressure inside the autoclave had stabilized and that all the propylene oxide had reacted, the contents were transferred to a removable flask. 14 g of sulfuric acid (1.0 equivalent) was added to the contents for neutralization. Then, 100 g of aluminosilicate-based adsorbent (KYOWAAD 700, manufactured by Kyowa Chemical Industry Co., Ltd.) was added as an adsorbent. The adsorbent was mixed while dehydrating under reduced pressure at 100 °C for 2 hours. After the neutralized catalyst was adsorbed onto the adsorbent, the insoluble matter was completely removed by filtration to obtain a polyether monohydric alcohol.

[0148] The residual metal content in the obtained polyether monohydric alcohol was 2.1 ppm. Additionally, the number-average molecular weight determined by GPC was 1220.

[0149] [Example 2]

[0150] 400g of propylene glycol as an initiator and 12g of potassium hydroxide (95% by mass purity) as a catalyst were added to a 5L autoclave. The autoclave temperature was then raised to 110°C, and 3600g of propylene oxide was introduced over 10 hours. After confirming that the pressure inside the autoclave had stabilized and that all the propylene oxide had reacted, the contents were transferred to a 5L removable flask. 30g of acidic sodium pyrophosphate and 20g of water were added to this flask, and the mixture was stirred at 100°C for 30 minutes. Then, the mixture was dehydrated under reduced pressure for 2 hours to insolubleen the catalyst. The catalyst was then completely removed by filtration of the insoluble matter to obtain a polyether polyol.

[0151] The residual metal content in the obtained polyether polyol was 5.2 ppm. Additionally, the number-average molecular weight determined by GPC was 580.

[0152] [Example 3]

[0153] 92g of glycerol and 5g of potassium hydroxide (95% by mass purity) as a catalyst were added to a 5L autoclave. The mixture was then heated to 110°C, and 1500g of propylene oxide was introduced into the autoclave over 12 hours. After confirming that the pressure inside the autoclave had stabilized and that all the propylene oxide had reacted, the contents were transferred to a removable flask. 100g of a synthetic hydrotalcite-based adsorbent (KYOWAAD 1000, manufactured by Kyowa Chemical Industry Co., Ltd.) was added to this flask, and the product and adsorbent were mixed at 100°C for 2 hours. After the catalyst was adsorbed onto the adsorbent, the insoluble matter was completely removed by filtration to obtain a polyether polyol.

[0154] The residual metal content in the obtained polyether polyol was 0.3 ppm. Furthermore, the number-average molecular weight determined by GPC was 1500.

[0155] [Example 4]

[0156] 550 g of pentaerythritol PO adduct (manufactured by EXCENOL 410NE AGC) and 6.3 g of potassium hydroxide (95% by mass purity) as a catalyst were added to a 5 L autoclave. The mixture was then heated to 120 °C and subjected to vacuum dehydration for 1 hour to reduce the water content. Afterward, 1500 g of propylene oxide was introduced into the autoclave over 8 hours. Once the pressure in the autoclave reached a constant level and all the propylene oxide had reacted, the contents were transferred to a removable flask. 7.0 g of phosphoric acid (2.0 equivalent) and 10 g of water were added to the contents for neutralization. The mixture was then heated to 100 °C and mixed for 30 minutes, followed by a catalyst insolubilization treatment based on vacuum dehydration for 2 hours. The insoluble catalyst was then removed by filtration to obtain the polyether polyol.

[0157] The residual metal content in the obtained polyether polyol was 8.0 ppm. Additionally, the number-average molecular weight determined by GPC was 2000.

[0158] [Example 5]

[0159] 182 g of sorbitol and 14.8 g of potassium hydroxide (95% by mass purity) as a catalyst were added to a 5 L autoclave. The mixture was then heated to 110 °C and subjected to reduced pressure dehydration for 1 hour to reduce the water content. 4500 g of propylene oxide was then introduced into the autoclave over 10 hours. After confirming that the pressure inside the autoclave had stabilized and that all the propylene oxide had reacted, the contents were transferred to a removable flask. 200 g of magnesium silicate-based adsorbent (KYOWAAD 600, manufactured by Kyowa Chemical Industry Co., Ltd.) was added to this flask, 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, yielding a catalyst-free polyether polyol.

[0160] The residual metal content in the obtained polyether polyol was 1.1 ppm. Additionally, the number-average molecular weight determined by GPC was 4600.

[0161] [Example 6]

[0162] 342 g of sucrose, 13.6 g of potassium hydroxide (95% by mass purity) 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 stirred to dissolve the sucrose and catalyst in the propylene oxide. After confirming the decrease and stabilization of the autoclave pressure caused by the reaction of the propylene oxide, 3700 g of propylene oxide was further introduced into the autoclave over 10 hours. After confirming that the pressure inside the autoclave tended to be constant and that all the propylene oxide had reacted, the contents were transferred to a removable flask. 30 g of acidic sodium pyrophosphate was added to the contents for neutralization. Then, 100 g of aluminosilicate adsorbent (KYOWAAD 700, manufactured by Kyowa Chemical Industry Co., Ltd.) was added as an adsorbent. The mixture was then stirred while undergoing dehydration under reduced pressure at 100 °C for 2 hours to adsorb the neutralized catalyst onto the adsorbent. Finally, the catalyst was completely removed by filtration of insoluble matter to obtain a polyether polyol.

[0163] The residual metal content in the obtained polyether polyol was 1.7 ppm. Additionally, the number-average molecular weight determined by GPC was 4000.

[0164] [Example 7]

[0165] 74 g of n-butanol and 12 g of sodium hydroxide (95% by mass purity) as a catalyst were added to a 5 L autoclave. The mixture of 700 g of propylene oxide and 700 g of ethylene oxide was then introduced into the autoclave over 15 hours, heated to 100 °C. After confirming that the pressure inside the autoclave had stabilized and that all the propylene oxide and ethylene oxide had reacted, the contents were transferred to a removable flask. 14 g of sulfuric acid (1.0 equivalent) was added to the contents for neutralization. Then, 100 g of aluminosilicate-based adsorbent (KYOWAAD 700, manufactured by Kyowa Chemical Industry Co., Ltd.) was added as an adsorbent. The mixture was then stirred at 100 °C for 2 hours to allow the neutralized catalyst to adsorb onto the adsorbent. The catalyst was then completely removed by filtration of insoluble matter to obtain a polyether monohydric alcohol.

[0166] The residual metal content in the obtained polyether monohydric alcohol was 2.6 ppm. Additionally, the number-average molecular weight determined by GPC was 1410.

[0167] [Example 8]

[0168] 200g of propylene glycol and 12g of potassium hydroxide (95% by mass purity) as a catalyst were added to a 5L autoclave. The autoclave temperature was then raised to 110°C, and a mixture of 2600g of propylene oxide and 1000g of ethylene oxide was introduced into the autoclave over 10 hours. After confirming that the pressure inside the autoclave had stabilized and that all the propylene oxide and ethylene oxide had reacted, the contents were transferred to a 5L removable flask. 6.6g of phosphoric acid (1.0 equivalent) was added to the contents for neutralization. Then, 120g of a magnesium silicate-based adsorbent (KYOWAAD 600S, manufactured by Kyowa Chemical Industry Co., Ltd.) was added. The catalyst, neutralized at 100°C for 2 hours, was then adsorbed onto the adsorbent. The catalyst was then completely removed by filtration of insoluble matter to obtain a polyether polyol.

[0169] The residual metal content in the obtained polyether polyol was 1.8 ppm. Additionally, the number-average molecular weight determined by GPC was 1350.

[0170] [Example 9]

[0171] Add 92g of glycerol and 0.9g of potassium hydroxide (95% purity by mass) as a catalyst to a 5L autoclave. Then, heat to 110°C and introduce a mixture of 700g of propylene oxide and 300g of ethylene oxide into the autoclave over 12 hours.

[0172] After confirming that the pressure inside the autoclave has reached a constant level and that propylene oxide and ethylene oxide have completely reacted, the contents are transferred to a removable flask. 20g of acidic sodium pyrophosphate is added to this contents as a neutralizing agent for neutralization. Then, 50g of synthetic hydrotalcite-based adsorbent (KYOWAAD 1000, manufactured by Kyowa Chemical Industry Co., Ltd.) is added as an adsorbent. The adsorbent is then mixed while undergoing reduced pressure dehydration at 100°C for 2 hours, allowing the neutralized catalyst to be adsorbed onto the adsorbent. Finally, the catalyst is completely removed by filtration of insoluble matter to obtain a polyether polyol.

[0173] The residual metal content in the obtained polyether polyol was 0.5 ppm. Furthermore, the number-average molecular weight determined by GPC was 1000.

[0174] [Example 10]

[0175] 400g of propylene glycol as an initiator and 12g of potassium hydroxide (95% by mass purity) as a catalyst were added to a 5L autoclave. The autoclave temperature was then raised to 110°C, and 3600g of propylene oxide was introduced into the autoclave over 10 hours. After confirming that the pressure inside the autoclave had stabilized and that all the propylene oxide had reacted, the contents were transferred to a 5L detachable flask. 40g of magnesium silicate-based adsorbent (KYOWAAD 600S, manufactured by Kyowa Chemical Industry Co., Ltd.) was added to this flask, and the mixture was incubated at 100°C for 2 hours to allow the product to mix with the adsorbent and for catalyst adsorption. The catalyst was then removed by filtration of insoluble matter to obtain a polyether polyol.

[0176] The residual metal content in the obtained polyether polyol was 15 ppm. Additionally, the number-average molecular weight determined by GPC was 580.

[0177] [Example 11]

[0178] Add 92g of glycerol and 0.9g of potassium hydroxide (95% purity by mass) as a catalyst to a 5L autoclave. Then, heat to 110°C and introduce 1500g of propylene oxide into the autoclave over 12 hours.

[0179] After confirming that the pressure inside the autoclave has reached a constant level and that all propylene oxide has reacted, the contents are transferred to a removable flask. An equivalent amount of 2.2 g of 2-ethylhexanoic acid is added to the removable flask to neutralize the catalyst.

[0180] The residual metal content in the obtained polyether polyol was 370 ppm. Additionally, the number-average molecular weight determined by GPC was 1500.

[0181] [Example 12]

[0182] 182 g of sorbitol and 14.8 g of potassium hydroxide (95% by mass purity) as a catalyst were added to a 5 L autoclave. After heating to 110 °C, the autoclave was subjected to dehydration under reduced pressure for 1 hour to reduce the water content. Then, 4500 g of propylene oxide was introduced into the autoclave over 10 hours. After confirming that the pressure inside the autoclave had reached a constant level and that all the propylene oxide had reacted, the contents were transferred to a detachable flask.

[0183] The contents were neutralized by adding 4.1 g of phosphoric acid (0.5 equivalent) and 10 g of water. The mixture was then heated to 100°C and mixed for 30 minutes, followed by a catalyst insolubilization treatment based on vacuum dehydration for 2 hours. The insoluble catalyst was then removed by filtration to obtain the polyether polyol.

[0184] The residual metal content in the obtained polyether polyol was 50 ppm. Additionally, the number-average molecular weight determined by GPC was 4600.

[0185] [Table 1]

[0186]

[0187] [Table 2]

[0188]

[0189] The initiator and R in Formula 1 of the compounds obtained in each example 2 O, m, and n are shown in Table 1. In Tables 1 and 2, PO represents propylene oxide and EO represents ethylene oxide.

[0190] In a refrigerant containing the base oils of Examples 10-12, precipitates are produced after heating at 175°C for 14 days.

[0191] In contrast, in Examples 1-9, the metal content was below 10 ppm. No precipitates were produced in the refrigerants containing the lubricating oil base oils from these examples after heating at 175°C for 14 days. This indicates that the chemical stability of the refrigerants containing the lubricating oil base oils improved with prolonged use in Examples 1-9.

[0192] Industrial availability

[0193] According to the present invention, the chemical stability of refrigerants mixed with lubricating oil base oils is improved during long-term use.

[0194] 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.

[0195] Explanation of reference numerals in the attached figures

[0196] 1…compressor, 2…condenser, 3…expansion valve, 4…evaporator

Claims

1. A lubricating oil base oil, which is a lubricating oil base oil mixed with a refrigerant. The refrigerant comprises hydrocarbon compounds having 1 to 8 carbon atoms. The lubricating oil base oil comprises at least one selected from the group consisting of polyoxyalkylene monohydric alcohols and polyoxyalkylene polyhydric alcohols. The metal content of the base oil for the lubricating oil is less than 10 ppm.

2. The lubricating oil base oil according to claim 1, wherein, At least one of the groups selected from polyoxyalkylene monohydric alcohols and polyoxyalkylene polyhydric alcohols is represented by the following formula 1. R 1 {(R 2 O) m H} n …Formula 1 In Equation 1, R 1 For initiator residues, R 2 Each is an independent hydrocarbon group with 2 to 4 carbon atoms. m ranges from 1 to 200. n is 1 to 8.

3. The lubricating oil base oil according to claim 2, wherein, The R 2 At least one of them is a hydrocarbon group with 3 carbon atoms.

4. The lubricating oil base oil according to claim 1, wherein, The hydrocarbon compound in the refrigerant includes propane.

5. The lubricating oil base oil according to claim 1, wherein, The hydrocarbon compound in the refrigerant includes propylene.

6. The lubricating oil base oil according to claim 1, wherein, The number average molecular weight of at least one selected from the group consisting of polyoxyalkylene monohydric alcohols and polyoxyalkylene polyhydric alcohols is 300 to 5000.

7. A lubricating oil composition comprising: Lubricating oil base oil according to any one of claims 1 to 6; and Either or both of the refrigerant and the additive.

8. The lubricating oil composition according to claim 7, wherein, The refrigerant is propane.

9. The lubricating oil composition according to claim 7, wherein, The refrigerant is propylene.

10. The lubricating oil composition according to claim 7, used in automotive air conditioning, indoor air conditioning units, refrigerators, cold storage, hot water supply systems for vending machines, hot water supply systems for display cases, refrigeration / heating systems, or gas heat pump systems.

11. A cooling system comprising a compressor, a condenser, an evaporator, and an expansion valve. It also contains: a refrigerant comprising a hydrocarbon compound having 1 to 8 carbon atoms, and a lubricating oil base oil as described in any one of claims 1 to 6.

12. The cooling system according to claim 11, wherein, The cooling system is used for supplying hot water, refrigeration / heating, or gas heat pump systems to automotive air conditioners, indoor air conditioners, refrigerators, freezers, vending machines, and display cases.

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