Lubricating oil base oil, lubricating oil composition, and cooling system

Abstract

The present invention relates to a lubricating oil base oil that is mixed with a refrigerant containing a C1-8 hydrocarbon compound. The lubricating oil base oil contains an oxyalkylene polymer having a hydroxyl group. The oxyalkylene polymer having a hydroxyl group contains a unit based on ethylene oxide and a unit based on propylene oxide, and satisfies the formula X×Y≥80, where X mass% is the amount of the unit based on ethylene oxide relative to the total amount of the unit based on ethylene oxide and the unit based on propylene oxide, and Y is the number of functional groups of the oxyalkylene polymer having a hydroxyl group.

Description

Lubricating base oils, lubricating oil compositions, and cooling systems

[0001] This application claims priority from Japanese Patent Application No. 2024-016186, filed February 6, 2024, the contents of which are incorporated herein by reference.

[0002] Various lubricating base oils are used to ensure smooth circulation of the refrigerant in compression-type refrigerators. Compounds such as polyalkylene glycol, polyol ester, and polyvinyl ether can be used as lubricating base oils depending on the type of refrigerant. For example, Patent Document 1 discloses, in an example, that a lubricating base oil containing polypropylene glycol is mixed with a refrigerant containing a hydrocarbon compound having 1 to 8 carbon atoms.

[0003] JP 2012-233091 A

[0004] However, when a conventional lubricating base oil is mixed with a refrigerant, if the content of the lubricating base oil is high, there are cases where the lubricating base oil becomes completely miscible with the refrigerant, and there is room for improvement.

[0005] An object of the present invention is to provide a lubricating base oil that has low compatibility with refrigerants containing hydrocarbon compounds having 1 to 8 carbon atoms, a lubricating oil composition containing the lubricating base oil, and a cooling system containing the lubricating base oil.

[0006] The present invention provides the following means. [1] A lubricating base oil to be mixed with a refrigerant containing a hydrocarbon compound having 1 to 8 carbon atoms, the lubricating base oil comprising an oxyalkylene polymer having a hydroxyl group, the oxyalkylene polymer having a hydroxyl group comprising units based on ethylene oxide and units based on propylene oxide, wherein the content of ethylene oxide-based units relative to the total amount of units based on alkylene oxide is X% by mass, and Y is the number of functional groups in the oxyalkylene polymer having a hydroxyl group, and the lubricating base oil satisfies the following formula 1: X×Y≧80 Formula 1 [2] The lubricating base oil of [1], wherein X×Y is 80 to 200, 80 to 180, 80 to 150, 90 to 150, or 80 to 120. [3] The lubricating base oil of [1] or [2], wherein the hydrocarbon compound has 1 to 5 carbon atoms, 3 to 5, 3 to 4, or 3 carbon atoms. [4] The lubricating base oil of any of [1] to [3], wherein X is 5 to 80, 10 to 70, or 35 to 60. [5] The lubricating base oil of any of [1] to [4], wherein the number of functional groups of the hydroxyl-containing oxyalkylene polymer is 2 or more. [6] The lubricating base oil of any of [1] to [5], wherein the number of functional groups of the hydroxyl-containing oxyalkylene polymer is 3 or more. [7] The lubricating base oil of any of [1] to [4], wherein the number of functional groups of the hydroxyl-containing oxyalkylene polymer is 1 to 8, 1 to 6, 1 to 4, or 1 to 3. [8] The lubricating base oil of any of [1] to [7], wherein the number average molecular weight of the hydroxyl-containing oxyalkylene polymer is 500 to 5,000. [9] The lubricating base oil of any one of [1] to [8], wherein the number average molecular weight of the oxyalkylene polymer having a hydroxyl group is 500 to 5,000, 500 to 3,000, or 700 to 2,000.

[10] The lubricating base oil of any one of [1] to [9], wherein the refrigerant is propane.

[11] The lubricating base oil of any one of [1] to [9], wherein the refrigerant is propylene.

[0007]

[12] A lubricating oil composition comprising the lubricating base oil of any one of [1] to

[11] and either a refrigerant or an additive, or both.

[13] The lubricating oil composition of

[12] , wherein the number average molecular weight of the hydroxyl group-containing oxyalkylene polymer is 500 to 5,000.

[14] The lubricating oil composition of

[12] or

[13] , wherein the refrigerant is propane.

[15] The lubricating oil composition of

[12] or

[13] , wherein the refrigerant is propylene.

[16] The lubricating oil composition of any one of

[12] to

[15] , for use in a hot water supply system, refrigeration or heating system, or gas heat pump system of a car air conditioner, an indoor air conditioner, a refrigerator, a freezer, a vending machine, or a showcase.

[0008]

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

[11] .

[18] The cooling system of

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

[0009] According to the present invention, it is possible to provide a lubricating base oil having low compatibility with refrigerants containing hydrocarbon compounds having 1 to 8 carbon atoms, a lubricating oil composition containing the lubricating base oil, and a cooling system containing the lubricating base oil.

[0010] 1 is a diagram illustrating a schematic configuration of a cooling system according to an embodiment.

[0011] The following terms used in this specification and claims are defined as follows. A numerical range represented by "to" means a numerical range with the numbers before and after "to" as the lower and upper limits. A "hydrocarbon compound" is a compound composed of carbon and hydrogen. An "oxyalkylene polymer" is a polymer having a polyoxyalkylene chain formed from units based on alkylene oxide. An "active hydrogen-containing group" is 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. An "active hydrogen" is a hydrogen atom derived from the active hydrogen-containing group and a hydrogen atom derived from a hydroxyl group of water. An "initiator" is a compound having the above-mentioned active hydrogen. The "number of functional groups" is the number of hydroxyl groups at the terminal of an oxyalkylene polymer having a hydroxyl group.

[0012] The number-average molecular weight (hereinafter referred to as "Mn") and weight-average molecular weight (hereinafter referred to as "Mw") of a polymer are polystyrene-equivalent molecular weights obtained by GPC measurement. The molecular weight distribution is a value calculated from Mw and Mn, and is the ratio of Mw to Mn (hereinafter referred to as "Mw / Mn"). "Kinematic viscosity" is a value measured at 100°C 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." In this specification, the lower and upper limits of preferred numerical ranges (e.g., Mn, etc.) described in stages can be independently combined. For example, the description "preferably 10 to 90, more preferably 30 to 60" can be combined with the "preferable lower limit (10)" and the "more preferable upper limit (60)" to form "10 to 60."

[0013] The lubricating base oil of the present embodiment can impart lubricity to the sliding parts of a compressor in a compression-type refrigerator, for example, by mixing with a refrigerant.

[0014] (Refrigerant) The refrigerant to be mixed with the lubricating base oil of this embodiment 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.

[0015] 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.

[0016] <Oxyalkylene polymer having a hydroxyl group> The oxyalkylene polymer having a hydroxyl group can be obtained by anionic ring-opening addition polymerization of an alkylene oxide to the active hydrogen of an initiator having an active hydrogen-containing group in the presence of a ring-opening addition polymerization catalyst.

[0017] 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, and 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] Examples of organic ligands for DMC catalysts include t-butyl alcohol, 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. t-butyl alcohol and ethylene glycol dimethyl ether (glyme) are preferred, and t-butyl alcohol is more preferred. 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.

[0028] 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. However, the alkylene oxide is not limited to these examples. Among these, the alkylene oxide includes ethylene oxide and propylene oxide, and preferably includes only ethylene oxide and propylene oxide.

[0029] 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.

[0030] The oxyalkylene polymer having a hydroxyl group is preferably a compound represented by the following formula 2: １ {(R ２ O) ｍ H} ｎ ...Formula 2

[0031] In formula 2, R １ is the initiator residue obtained by removing active hydrogen from the initiator. Details and preferred embodiments of the initiator are as described above.

[0032] In Formula 2, 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 ２O 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.

[0033] R ２ are each independently a hydrocarbon group having 2 to 4 carbon atoms. ２ at least one of R is a hydrocarbon group having 2 or 3 carbon atoms; ２ It is more preferable that all of the groups have 2 or 3 carbon atoms.

[0034] 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.

[0035] R ２ Examples of the group include -CH ２ CH ２ -, -CH ２ CH ２ CH ２ -, -CH ２ CH ２ CH ２ CH ２ -, -CH(CH ３ ) CH ２ -, -CH2CH(CH ３ ) -, -CH(CH ３ ) CH ２ CH ２ -, -CH ２ CH (CH ３ ) CH ２ -, and -CH ２ CH ２ - or -CHCH(CH ３ )- is preferred.

[0036] In Formula 2, 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.

[0037] In formula 2, n is 1 or more, preferably 2 or more, and more preferably 3 or more. In another aspect of the present invention, n is preferably 1 to 8, more preferably 1 to 6, even more preferably 1 to 4, and particularly preferably 1 to 3. In yet another aspect of the present invention, the number of functional groups in the oxyalkylene polymer having a hydroxyl group is preferably 2 to 8, more preferably 2 to 6, and even more preferably 2 to 4. When n is equal to or greater than the lower limit of the above-mentioned numerical range, a lubricating base oil having a good viscosity index is likely to be obtained. When n is equal to or less than the upper limit of the above-mentioned numerical range, a lubricating base oil having a good volume resistivity is likely to be obtained.

[0038] The Mn of the hydroxyl group-containing oxyalkylene polymer is preferably 500 to 5,000, more preferably 500 to 3,000, and even more preferably 700 to 2,000. When the Mn 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 Mn 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.

[0039] (EO Unit Content, PO Unit Content) The oxyalkylene polymer having a hydroxyl group contains units based on propylene oxide (oxypropylene groups) and units based on ethylene oxide (oxyethylene groups), and the content of oxyethylene groups relative to the total amount of units based on alkylene oxide in the oxyalkylene polymer having a hydroxyl group (also referred to as the "EO unit content") is preferably 5 to 80 mass%, more preferably 10 to 70 mass%, and particularly preferably 35 to 60 mass%. The content of oxypropylene groups relative to the total amount of units based on alkylene oxide in the oxyalkylene polymer having a hydroxyl group (also referred to as the "PO unit content") is preferably 20 to 99 mass%, more preferably 70 to 90 mass%. The total content of oxypropylene groups and oxyethylene groups relative to the total amount of units based on alkylene oxide in the oxyalkylene polymer having a hydroxyl group is preferably 50 to 100 mass%, more preferably 70 to 100 mass%.

[0040] (Number of Functional Groups) The number of functional groups of the oxyalkylene polymer having a hydroxyl group is preferably 2 or more, and preferably 3 or more. In another aspect of the present invention, the number of functional groups of the oxyalkylene polymer having a hydroxyl group is preferably 1 to 8, more preferably 1 to 6, even more preferably 1 to 4, and particularly preferably 2 or 3. In yet another aspect of the present invention, the number of functional groups of the oxyalkylene polymer having a hydroxyl group is preferably 2 to 8, more preferably 2 to 6, and even more preferably 2 to 4.

[0041] (EO Unit Content (X) × Number of Functional Groups (Y)) The hydroxyl group-containing oxyalkylene polymer satisfies the formula X × Y ≧ ​​80, where X is the content of oxyethylene groups relative to the alkylene oxide-based units and Y is the number of functional groups in the hydroxyl group-containing oxyalkylene polymer. X × Y is 80 or greater, preferably 80 to 200, more preferably 80 to 180, even more preferably 80 to 150, even more preferably 90 to 150, and particularly preferably 80 to 120. When X × Y is within the above range, the hydroxyl group-containing oxyalkylene polymer is likely to become hydrophilic, its compatibility with refrigerants is likely to decrease, and a better lubricating effect is likely to be obtained. The hydroxyl group-containing oxyalkylene polymer preferably contains a residue obtained by removing active hydrogen from an initiator and a unit based on alkylene oxide, and is preferably composed only of a residue obtained by removing active hydrogen from an initiator and a unit based on alkylene oxide.

[0042] The content of the oxyalkylene polymer having a hydroxyl group satisfying X×Y≧80 relative to the total mass of the lubricating base oil is preferably 50 to 100 mass%, more preferably 80 to 100 mass%, and even more preferably 90 to 100 mass%. The lubricating base oil may contain components other than the oxyalkylene polymer having a hydroxyl group satisfying X×Y≧80.

[0043] The lubricating base oil containing the hydroxyl group-containing oxyalkylene polymer is incompatible in a temperature range of 90°C to -60°C in a compatibility test according to JIS K2211:2009, where the ratio of the mass of the lubricating base oil to the mass of the propane is 20 / 80 (lubricating base oil / propane (mass ratio)). In a compatibility test where the ratio of the mass of the lubricating base oil to the mass of the propane is 50 / 50 (lubricating base oil / propane (mass ratio)), it is preferably partially compatible in a temperature range of 90°C to -60°C. Partial compatibility refers to two states, complete compatibility and incompatibility, within the temperature range of 90°C to -60°C. The temperature range in which it is incompatible is -60 to 90°C. Lubricating base oils that are incompatible with refrigerants over all or part of this range reduce equipment wear and have good lubricating effects.

[0044] The kinematic viscosity at 100°C of the lubricating base oil containing the hydroxyl group-containing oxyalkylene polymer of this embodiment is 2 to 200 mm ２ When the kinematic viscosity is equal to or greater than the lower limit, the sealability is excellent. In addition, when the kinematic viscosity is equal to or less than the upper limit, the viscosity resistance is small and the lubricity is excellent. Preferably, the kinematic viscosity at 100°C is 5 to 100 mm ２ / s.

[0045] Furthermore, the volume resistivity of the lubricating base oil containing the oxyalkylene polymer having a hydroxyl group is 1×10 １０ Preferably, it is Ω cm or more, and more preferably 6×10 １０ Ω cm or more, most preferably 1×10 １１ The volume resistivity is 1×10 Ω·cm or more. １０ On the other hand, in terms of preventing the generation of static electricity, a volume resistivity of 1×10 １５ Preferably, it is Ω cm or less, and more preferably 1×10 １４ It is Ω·cm or less.

[0046] (Method for producing lubricating base oil) The lubricating base oil may include a step of obtaining an oxyalkylene polymer having hydroxyl groups by ring-opening addition polymerization of an alkylene oxide to an initiator in the presence of a catalyst, and then removing the catalyst from the reaction solution containing the oxyalkylene polymer having hydroxyl groups. The details and preferred embodiments of the initiator, alkylene oxide, and catalyst are as described above.

[0047] 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.

[0048] 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.

[0049] In removing the catalyst, any one of Method 1, Method 2, and Method 3 may be carried out alone, any two or more of them may be carried out in appropriate combination, or all of Method 1, Method 2, and Method 3 may be carried out. When two or more or all of Method 1, Method 2, and Method 3 are carried out, the order of carrying them out is not particularly limited. As the method for removing the catalyst, Method 1 or Method 2 is preferred, and Method 1 is more preferred, from the viewpoint of further reducing the metal content.

[0050] 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.

[0051] 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 agent is not limited to these examples. One type of neutralizing agent may be used alone, or two or more types may be used in combination.

[0052] 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.

[0053] [Lubricant Composition] The lubricant composition of this embodiment contains the lubricant base oil described above and either or both of a refrigerant and an additive. In one example, the lubricant composition may contain a lubricant base oil and a refrigerant, a lubricant base oil and an additive, or a lubricant base oil, a refrigerant, and an additive. In one embodiment, the lubricant composition preferably contains a lubricant base oil and a refrigerant, and optionally an additive. The lubricant composition of this embodiment can, for example, impart lubricity to the sliding parts of a compressor supplied with a refrigerant. The refrigerant is as described above. Examples of additives include antioxidants, extreme pressure agents, stabilizers, copper deactivators, antifoaming agents, load-bearing additives, chlorine scavengers, oxygen scavengers, detergents and 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] Examples of the antifoaming agent include silicone oil and fluorinated silicone oil.

[0059] The proportion of the lubricating base oil containing the hydroxyl group-containing oxyalkylene polymer 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.

[0060] 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.

[0061] 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 lubricating 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.

[0062] The amounts of the lubricating base oil and the refrigerant used in this embodiment can be varied widely in the range of 99 / 1 to 10 / 90 as the refrigerant / lubricating base oil mass ratio, with the mass ratio preferably being in the range of 90 / 10 to 50 / 50.

[0063] [Uses] The lubricating base oil or lubricating oil composition of this embodiment can be used in various refrigeration systems, such as hot water supply systems for car air conditioners, room air conditioners, refrigerators, freezers, vending machines, and showcases, refrigeration or heating systems, and gas heat pump systems. The lubricating base oil and lubricating oil composition are particularly preferably used in a compression-type refrigeration system equipped with a compressor 1, a condenser 2, an expansion valve 3, and an evaporator 4 shown in FIG. 1. The compression-type 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 or lubricating oil composition of this embodiment circulates through the compressor 1, the condenser 2, the expansion valve 3, and the evaporator 4 shown in FIG. 1. It provides lubricity to the sliding parts of the compressor 1.

[0064] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0065] <Molecular Weight> GPC measurement of the lubricating base oil was carried out under the following conditions to determine Mn and Mw. [GPC Measurement Conditions] Model used: HLC-8220GPC (manufactured by Tosoh Corporation) Data processing device: SC-8020 (manufactured by Tosoh Corporation) Column used: TSG gel G2500H (manufactured by Tosoh Corporation) Column temperature: 40°C, detector: RI, solvent: tetrahydrofuran, flow rate: 0.6 ml / min, sample concentration: 0.25 mass%, injection volume: 10 μl Standard sample for creating a calibration curve: polystyrene ([Easycal] PS-2 [Polystyrene Standards], Polymer Laboratories

[0066] Production Examples 1 to 7 are working examples, and Production Examples 8 to 11 are comparative examples.

[0067] <Production Example 1> 92 g of glycerin and 5 g of potassium hydroxide (purity 95% by mass) as a catalyst were added to a 5-L autoclave, and the temperature was raised to 110°C. A mixture of 720 g of propylene oxide and 480 g of ethylene oxide was introduced over 12 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. 90 g of a synthetic hydrotalcite 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 to adsorb the catalyst onto the adsorbent. After removing insoluble matter by filtration and removing the catalyst, a hydroxyl-containing oxyalkylene polymer was obtained. Table 1 shows the Mn, Mw / Mn, number of functional groups, EO unit content, and X × Y in Formula 1 of the hydroxyl-containing oxyalkylene polymer. The results of Production Examples 2 to 11 are similarly shown in Tables 1 and 2.

[0068] <Production Example 2> 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. After heating to 120°C, the system was dehydrated under reduced pressure for 1 hour to reduce the water content, and then a mixture of 535 g of propylene oxide and 465 g of ethylene oxide was introduced over 8 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 7.0 g of 2.0 equivalents of phosphoric acid and 10 g of water, and then heated to 100°C. The mixture was 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, and a hydroxyl-containing oxyalkylene polymer was obtained.

[0069] Preparation Example 3: 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 a mixture of 3200 g of propylene oxide and 800 g of ethylene oxide was introduced 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. 200 g of a magnesium silicate 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 to allow the catalyst to adsorb onto the adsorbent. After that, insoluble matter was removed by filtration, and the catalyst was removed to obtain an oxyalkylene polymer having hydroxyl groups.

[0070] <Production Example 4> 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. After the addition, the temperature was raised to 100°C and mixed. After the sucrose and catalyst were dissolved in the propylene oxide and the autoclave pressure decreased due to the reaction of the propylene oxide and then stabilized, a mixture of 3300 g of propylene oxide and 400 g of ethylene oxide was introduced over 10 hours. After the pressure inside the autoclave stabilized and it was confirmed that all of the propylene oxide had reacted, the contents were transferred to a separable flask. To the content, 30 g of acidic sodium pyrophosphate was added as a neutralizing agent to neutralize the mixture, and then 100 g of an aluminum silicate-based adsorbent (Kyowad 700, manufactured by Kyowa Chemical Industry Co., Ltd.) was added as an adsorbent. The mixture was then dehydrated under reduced pressure at 100°C for 2 hours while the adsorbent was mixed in to allow the neutralized catalyst to be adsorbed onto the adsorbent. Insoluble matter was then removed by filtration, and the catalyst was removed to obtain an oxyalkylene polymer having a hydroxyl group.

[0071] <Production Example 5> 74 g of normal butanol and 12 g of sodium hydroxide (purity 95% by mass) as a catalyst were added to a 5 L autoclave, and the temperature was raised to 100 ° C. A mixture of 200 g of propylene oxide and 800 g of ethylene oxide was introduced over 8 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. After neutralizing the contents with 14 g of 1.0 equivalent of sulfuric acid, 100 g of an aluminum silicate adsorbent (Kyowado 700, manufactured by Kyowa Chemical Industry Co., Ltd.) was added as an adsorbent. The mixture was dehydrated under reduced pressure at 100 ° C. for 2 hours, and the adsorbent was mixed to adsorb the neutralized catalyst. After that, insoluble matter was removed by filtration, and the catalyst was removed to obtain an oxyalkylene polymer having hydroxyl groups.

[0072] <Production Example 6> 76 g of propylene glycol as an initiator and 6 g of potassium hydroxide (purity 95% by mass) as a catalyst were added to a 5 L autoclave, and the temperature of the autoclave was raised to 110 °C. A mixture of 1,060 g of propylene oxide and 870 g of ethylene oxide was introduced over 12 hours. After the pressure inside the autoclave became constant and it was confirmed that all of the propylene oxide and ethylene oxide had reacted, the contents were transferred to a 5 L separable flask. 15 g of sodium acid pyrophosphate and 10 g of water were added to the contents and mixed at 100 °C for 30 minutes. The mixture was then dehydrated under reduced pressure for 2 hours to insolubilize the catalyst. The insoluble matter was then removed by filtration, and the catalyst was removed to obtain an oxyalkylene polymer having hydroxyl groups.

[0073] <Production Example 7> 92 g of glycerin and 5 g of potassium hydroxide (purity 95% by mass) as a catalyst were added to a 5 L autoclave, and the temperature was raised to 110 ° C., and 1,000 g of propylene oxide was introduced over 10 hours. After confirming that the pressure inside the autoclave had become constant and all of the propylene oxide had reacted, 500 g of ethylene oxide was then introduced over 6 hours. After confirming that the pressure inside the autoclave had become constant and all of the ethylene 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 to adsorb the catalyst onto the adsorbent. After that, insoluble matter was removed by filtration, and the catalyst was removed to obtain an oxyalkylene polymer having hydroxyl groups.

[0074] <Production Example 8> 74 g of normal butanol and 12 g of sodium hydroxide (purity 95% by mass) as a catalyst were added to a 5 L autoclave, and the temperature was raised to 100 ° C., and 1,000 g of propylene oxide was introduced 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. 14 g of 1.0 equivalent of sulfuric acid was added to the contents to neutralize them, and 100 g of an aluminum silicate adsorbent (Kyowado 700, manufactured by Kyowa Chemical Industry Co., Ltd.) was added as an adsorbent. The adsorbent was mixed and the neutralized catalyst was adsorbed onto the adsorbent while dehydrating under reduced pressure at 100 ° C. for 2 hours. After that, insoluble matter was removed by filtration, and the catalyst was removed to obtain an oxyalkylene polymer having hydroxyl groups.

[0075] <Production Example 9> 76 g of propylene glycol as an initiator and 6 g of potassium hydroxide (purity 95% by mass) as a catalyst were added to a 5 L autoclave, and the temperature of the autoclave was raised to 110 ° C., and 1950 g of propylene oxide was introduced 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 5 L separable flask. 15 g of sodium acid pyrophosphate and 10 g of water were added to the contents and mixed at 100 ° C. for 30 minutes. After 2 hours of dehydration under reduced pressure to insolubilize the catalyst, the insoluble matter was removed by filtration to obtain a catalyst-free oxyalkylene polymer having hydroxyl groups.

[0076] <Production Example 10> 76 g of propylene glycol as an initiator and 6 g of potassium hydroxide (purity 95% by mass) as a catalyst were added to a 5 L autoclave, and the temperature of the autoclave was raised to 110°C. A mixture of 1,737 g of propylene oxide and 193 g of ethylene oxide was introduced over 12 hours. After the pressure inside the autoclave became constant and it was confirmed that all of the propylene oxide and ethylene oxide had reacted, the contents were transferred to a 5 L separable flask. 15 g of sodium acid pyrophosphate and 10 g of water were added to the contents and mixed at 100°C for 30 minutes. The mixture was then dehydrated under reduced pressure for 2 hours to insolubilize the catalyst. The insoluble matter was then removed by filtration, yielding a catalyst-free oxyalkylene polymer having hydroxyl groups.

[0077] <Production Example 11> 304 g of propylene glycol and 12.3 g of potassium hydroxide (purity 95% by mass) as a catalyst were added to a 5 L autoclave, and after heating, 2552 g of propylene oxide and 1232 g of ethylene oxide were introduced at 110°C over 10 hours. After confirming that the pressure had become constant and all of the propylene oxide and ethylene oxide had reacted, the contents were removed. 15 g of acid sodium pyrophosphate and 10 g of water were added to the contents and mixed at 100°C for 30 minutes. After that, the catalyst was insolubilized by dehydration under reduced pressure over 2 hours, and the insoluble matter was removed by filtration to obtain an oxyalkylene polymer having hydroxyl groups from which the catalyst had been removed.

[0078] <Compatibility with Refrigerants> Based on the "Test method for compatibility with refrigerants" of JIS K2211:2009 "Refrigerating machine oil", a mixture of 20% by mass of a lubricating base oil containing an oxyalkylene polymer having hydroxyl groups obtained in each example and 80% by mass of a refrigerant (propane), or a mixture of 50% by mass of a lubricating base oil containing an oxyalkylene polymer having hydroxyl groups obtained in each example and 50% by mass of a refrigerant (propane), was gradually cooled from room temperature to -60 ° C. in a thermostatic bath, and the temperature at which phase separation began was measured using an optical sensor. The temperature at which phase separation began was gradually increased from room temperature to +90 ° C. In the table, "partial compatibility" indicates that partial two-phase separation was observed under these conditions (from -60 ° C. to 90 ° C.), "complete compatibility" indicates that the mixture was always dissolved, and "incompatibility" indicates that the mixture was always separated into two layers. The evaluation results are shown in Tables 1 and 2.

[0079]

[0080]

[0081] As shown in Tables 1 and 2, in the case of lubricating base oils containing oxyalkylene polymers having hydroxyl groups satisfying the specific formula of Production Examples 1 to 7, the mass ratio of the refrigerant to the refrigerant was "incompatible" when it was 20 / 80, and "partially compatible" when it was 50 / 50. On the other hand, in the case of lubricating base oils containing oxyalkylene polymers having hydroxyl groups that do not satisfy the specific formula of Production Examples 8 to 11, the mass ratio of the refrigerant to the refrigerant was "incompatible" when it was 20 / 80, and "completely compatible" when it was 50 / 50. In other words, it was shown that the compatibility was lower in the case of lubricating base oils containing oxyalkylene polymers having hydroxyl groups that satisfy the specific formula.

[0082] According to the present invention, there are provided a lubricating base oil having low compatibility with refrigerants containing hydrocarbon compounds having 1 to 8 carbon atoms, a lubricating oil composition containing the lubricating base oil, and a cooling system containing the lubricating base oil.

[0083] 1...compressor, 2...condenser, 2...expansion valve, 4...evaporator

Claims

1. A lubricating base oil to be mixed with a refrigerant containing a hydrocarbon compound having 1 to 8 carbon atoms, the lubricating base oil comprising an oxyalkylene polymer having a hydroxyl group, the oxyalkylene polymer having a hydroxyl group comprising units based on ethylene oxide and units based on propylene oxide, the content of units based on ethylene oxide relative to the total amount of units based on alkylene oxide is X mass%, and the number of functional groups of the oxyalkylene polymer having a hydroxyl group is Y, satisfying the following formula 1: X x Y ≥ 80 Formula 1 2. The lubricating base oil according to claim 1, wherein the functionality of the hydroxyl-containing oxyalkylene polymer is 2 or more.

3. The lubricating base oil according to claim 2, wherein the functionality of the hydroxyl-containing oxyalkylene polymer is 3 or more.

4. The lubricating base oil according to any one of claims 1 to 3, wherein the number average molecular weight of the hydroxyl group-containing oxyalkylene polymer is 500 to 5,000.

5. The lubricating base oil according to any one of claims 1 to 3, wherein the refrigerant is propane.

6. The lubricating base oil according to any one of claims 1 to 3, wherein the refrigerant is propylene.

7. A lubricating oil composition comprising the lubricating base oil according to any one of claims 1 to 3, and either or both of a refrigerant and an additive.

8. The lubricating oil composition according to claim 7, wherein the number average molecular weight of the hydroxyl group-containing oxyalkylene polymer is 500 to 5,000.

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

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

11. The lubricating oil composition according to claim 7, which is used in hot water supply systems, refrigeration or heating systems, or gas heat pump systems in car air conditioners, room air conditioners, refrigerators, freezers, vending machines, and showcases.

12. A cooling system comprising a compressor, a condenser, an evaporator, and an expansion valve, 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 3 are enclosed.

13. The cooling system of claim 12, wherein the cooling system is for a hot water system, refrigeration or heating system in a car air conditioner, a room air conditioner, a refrigerator, a freezer, a vending machine, a showcase, or a gas heat pump system.

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