A method for lubricating aluminum sliding members with refrigeration oil, refrigeration oil, and refrigeration machine

Abstract

Provided is a method for lubricating, with refrigerator oil, an aluminum-based sliding member in a refrigerator, wherein the refrigerator oil contains: a base oil; and an additive including at least one compound selected from the group consisting of a sarcosine compound, and an alcohol compound having at least 8 carbon atoms.

Description

[Technical Field]

[0001] This disclosure relates to a method for lubricating aluminum sliding members with refrigeration oil, refrigeration oil, and a refrigeration machine. [Background technology]

[0002] Refrigeration devices such as refrigerators, car air conditioners, room air conditioners, and vending machines are equipped with a compressor for circulating a refrigerant within the refrigeration cycle. The compressor is filled with refrigeration oil to lubricate the sliding members. Refrigeration oil generally contains a base oil in addition to additives selected according to desired properties. For example, Patent Document 1 discloses a refrigeration oil containing an extreme pressure additive consisting of a tertiary phosphate for lubricating the sliding parts of a compressor in a refrigeration cycle device. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2020 / 045356 [Overview of the project] [Problems that the invention aims to solve]

[0004] As used in the refrigeration oil disclosed in Patent Document 1, tertiary phosphates (e.g., tricresyl phosphate) are additives widely known as extreme pressure agents (also called anti-wear agents) and are added to improve the wear resistance of sliding members. However, our own research has shown that the degree to which refrigeration oil improves the wear resistance of sliding members depends on the type of sliding member. Specifically, a refrigeration oil that can provide good wear resistance to a combination of iron-based sliding members does not necessarily provide good wear resistance to a combination of iron-based sliding members and aluminum-based sliding members. For example, when lubricating aluminum-based sliding members with refrigeration oil containing tertiary phosphates, sufficient wear resistance is not always obtained.

[0005] One aspect of the present invention aims to improve the wear resistance of an aluminum-based sliding member.

Means for Solving the Problems

[0006] The present inventors have found that when an aluminum-based sliding member is lubricated with a refrigerant oil containing a specific additive, excellent wear resistance can be obtained.

[0007] One aspect of the present invention is a method of lubricating an aluminum-based sliding member in a refrigerator with a refrigerant oil, wherein the refrigerant oil contains a base oil and an additive containing at least one compound selected from the group consisting of a sarcosine compound and an alcohol compound having 8 or more carbon atoms.

[0008] Another aspect of the present invention is a refrigerant oil containing a base oil and an additive containing at least one compound selected from the group consisting of a sarcosine compound and an alcohol compound having 8 or more carbon atoms, and is used for lubricating an aluminum-based sliding member.

[0009] In each of the above aspects, the additive may contain a sarcosine compound. The additive may contain an alcohol compound. The additive may contain a sarcosine compound and an alcohol compound.

[0010] Another aspect of the present invention is a refrigerator including a refrigerant circulation system having a compressor, a condenser, an expansion mechanism, and an evaporator, wherein the compressor includes an aluminum-based sliding member, and the refrigerant circulation system includes the above refrigerant oil and a refrigerant.

[0011] The refrigerant may contain an unsaturated fluorinated hydrocarbon.

Advantages of the Invention

[0012] According to one aspect of the present invention, the wear resistance of an aluminum-based sliding member can be improved.

Brief Description of the Drawings

[0013] [Figure 1] This is a schematic diagram showing one embodiment of a refrigerator. [Modes for carrying out the invention]

[0014] Embodiments of the present invention will be described in detail below. One embodiment of the present invention is a method for lubricating a sliding member in a refrigerator with refrigeration oil.

[0015] Figure 1 is a schematic diagram showing one embodiment of a refrigerator. As shown in Figure 1, the refrigerator 10 includes at least a refrigerant circulation system 6 in which a compressor (refrigerant compressor) 1, a condenser (gas cooler) 2, an expansion mechanism 3 (capillary, expansion valve, etc.), and an evaporator (heat exchanger) 4 are sequentially connected by a flow path 5. The refrigerant circulation system 6 contains refrigerant oil and refrigerant. The refrigerant circulation system 6 may further include an accumulator 7 between the evaporator 4 and the compressor 1 (on the side of the compressor 1) to suppress and prevent liquid refrigerant from flowing directly into the compressor 1.

[0016] Examples of such refrigeration devices 10 include automotive air conditioners, dehumidifiers, refrigerators, cold storage warehouses, vending machines, display cases, cooling equipment in chemical plants, residential air conditioners, packaged air conditioners, and hot water heat pumps.

[0017] In the refrigerant circulation system 6, first, the high-temperature (usually 70-120°C) refrigerant discharged from the compressor 1 into the flow path 5 becomes a high-density fluid (supercritical fluid, etc.) in the condenser 2. Subsequently, the refrigerant liquefies as it passes through the narrow flow path of the expansion mechanism 3, and then vaporizes in the evaporator 4, becoming low temperature (usually -40-0°C). The cooling by the refrigerator 10 utilizes the phenomenon that the refrigerant absorbs heat from its surroundings when it vaporizes in the evaporator 4.

[0018] Inside compressor 1, a small amount of refrigerant and a large amount of refrigerant oil coexist under high temperature conditions (typically 70-120°C). The refrigerant discharged from compressor 1 into flow path 5 is in gaseous form and contains a small amount (typically 1-10 volume%) of refrigerant oil as a mist, with a small amount of refrigerant dissolved in this mist-like refrigerant oil (point a in Figure 1).

[0019] Inside the condenser 2, the gaseous refrigerant is compressed into a high-density fluid, and under relatively high temperature conditions (usually 40-80°C), a large amount of refrigerant and a small amount of refrigerant oil coexist (point b in Figure 1). Furthermore, the mixture of the large amount of refrigerant and the small amount of refrigerant oil is sequentially sent to the expansion mechanism 3 and the evaporator 4, where it rapidly cools to a low temperature (usually -40-0°C) (points c and d in Figure 1), and is returned to the compressor 1.

[0020] Examples of compressors 1 include rotary compressors, piston-crank compressors, piston-swashplate compressors, scroll compressors, screw compressors, centrifugal compressors, and the like. In this embodiment, aluminum-based sliding members are used on the sliding surfaces of these compressors for weight reduction and other purposes. The aluminum-based sliding members may be made of aluminum alone or of an aluminum alloy. The aluminum alloy may be, for example, an aluminum alloy containing aluminum as the base material and at least one element selected from the group consisting of tin (Sn), silicon (Si), copper (Cu), and chromium (Cr). Furthermore, the mating sliding member that slides together with the aluminum-based sliding member may be an aluminum-based sliding member, an iron-based sliding member made of cast iron, steel, or various iron-based alloys, or various coated sliding members in which the surface of these sliding members is coated with a coating material.

[0021] In the method according to this embodiment, the sliding members in the compressor 1 as described above are lubricated with refrigerant oil. The refrigerant oil contains a base oil and an additive containing at least one compound selected from the group consisting of sarcosine compounds and alcohol compounds having 8 or more carbon atoms. That is, in one embodiment of the present invention, the refrigerant oil is a refrigerant oil containing a base oil and the above additive.

[0022] The base oil is at least one selected from the group consisting of oxygenated oils and hydrocarbon oils. Examples of oxygenated oils include esters and ethers. Examples of hydrocarbon oils include mineral oil, alkylbenzene, alkylnaphthalene, poly-α-olefin, polybutene, and ethylene-α-olefin copolymer.

[0023] In one embodiment, the base oil may be at least one selected from the group consisting of esters and ethers, and may be at least one selected from the group consisting of polyol esters, complex esters, polyalkylene glycols, and polyvinyl ethers.

[0024] Examples of polyol esters include esters of polyhydric alcohols and fatty acids. The polyhydric alcohol may be a polyhydric alcohol having 2 to 6 hydroxyl groups. The number of carbon atoms in the polyhydric alcohol may be 4 to 12 or 5 to 10. Examples of polyhydric alcohols include neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, di-(trimethylolpropane), tri-(trimethylolpropane), pentaerythritol, and dipentaerythritol. Preferably, the polyhydric alcohol is pentaerythritol, dipentaerythritol, or a mixture thereof.

[0025] Fatty acids may be linear or branched. Fatty acids may be saturated fatty acids. The number of carbon atoms in fatty acids may be 4-20, 4-18, 4-9, or 5-9. Examples of fatty acids include linear fatty acids with 4-20 carbon atoms such as butanoic acid, pentanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, and octadecenoic acid, and branched fatty acids with 4-20 carbon atoms such as 2-methylpropanoic acid, 2-methylbutanoic acid, 2-methylpentanoic acid, 2-methylhexanoic acid, 2-ethylpentanoic acid, 2-methylheptanoic acid, 2-ethylhexanoic acid, 3,5,5-trimethylhexanoic acid, and 2-ethylhexadecanoic acid.

[0026] Examples of complex esters include esters synthesized from at least one selected from polyhydric alcohols, at least one selected from polybasic acids, and at least one selected from monohydric alcohols and monohydric fatty acids.

[0027] Examples of polyhydric alcohols include neopentyl glycol, trimethylolpropane, and pentaerythritol. In addition to these polyhydric alcohols, the polyhydric alcohol may further contain dihydric alcohols having 2 to 10 carbon atoms other than neopentyl glycol. Examples of dihydric alcohols having 2 to 10 carbon atoms other than neopentyl glycol include ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, and 2,2-diethyl-1,3-pentanediol.

[0028] Polybasic acids may be, for example, polybasic acids having 6 to 12 carbon atoms. Examples of polybasic acids include adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, and trimellitic acid.

[0029] Monohydric alcohols may be monohydric alcohols having, for example, 4 to 18 carbon atoms. Examples of monohydric alcohols include butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, dodecanol, and oleyl alcohol.

[0030] Monounsaturated fatty acids may be monounsaturated fatty acids having 2 to 12 carbon atoms, for example, ethane acid, propanoic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, and dodecanoic acid.

[0031] Examples of polyalkylene glycols include polyethylene glycol, polypropylene glycol, and polybutylene glycol. The polyalkylene glycol may also be a polyalkylene glycol having two or more copolymer chains selected from oxyethylene, oxypropylene, and oxybutylene. One or both ends of these polyalkylene glycols may be alkylated or acylated.

[0032] Examples of polyvinyl ethers include a homopolymer selected from alkyl vinyl ethers having an alkyl group having 1 to 20 carbon atoms, and copolymers of two or more alkyl vinyl ethers having an alkyl group having 1 to 20 carbon atoms. In one embodiment, the polyvinyl ether may be a copolymer of an alkyl vinyl ether having an alkyl group having 1 to 3 carbon atoms (preferably an ethyl group) and an alkyl vinyl ether having an alkyl group having 3 to 8 carbon atoms (preferably an isobutyl group).

[0033] The base oil content may be 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more, based on the total amount of refrigerating oil, and may also be 99% by mass or less.

[0034] The additive contains either a sarcosine compound or an alcohol compound, and preferably contains both a sarcosine compound and an alcohol compound, from the viewpoint of further improving the wear resistance of the sliding member.

[0035] Sarcosine compounds are compounds or derivatives thereof having a substructure represented by the following formula (1). [ka]

[0036] The sarcosine compound is, for example, at least one of the compounds represented by the following formula (2) or its derivatives. [ka] In the formula, R 1 R represents an alkyl group. 2 represents a hydrogen atom or a chain-like hydrocarbon group.

[0037] R 1 The alkyl group represented by may be linear or branched. The number of carbon atoms in the alkyl group may be, for example, 1 or more, 10 or less, 8 or less, 6 or less, 5 or less, or 4 or less.

[0038] R 2 The chain-like hydrocarbon group represented by may be linear or branched. The hydrocarbon group may be saturated or unsaturated. The number of carbon-carbon unsaturated bonds in the unsaturated hydrocarbon group may be 1 or more, 2 or more, 4 or less, 3 or less, or 2 or less. 2 The number of carbon atoms in the chain-like hydrocarbon group represented by may be, for example, 1 or more, 5 or more, 10 or more, 12 or more, 14 or more, 15 or more, 16 or more, or 17 or more, and may be 30 or less, 28 or less, 26 or less, 24 or less, 22 or less, 20 or less, 19 or less, 18 or less, or 17 or less.

[0039] Examples of the derivatives mentioned above include salts. Examples of salts include metal salts, ammonium salts, and amine salts. Examples of metals that make up metal salts include alkali metals such as sodium, potassium, and lithium, and alkaline earth metals such as calcium and magnesium. Examples of amine compounds that make up amine salts include amine compounds having 1 to 20 carbon atoms. Preferably, the amine compounds include amine compounds having one or two alkyl groups or alkenyl groups having 4 to 18 carbon atoms, such as di-2-ethylhexylamine and oleylamine.

[0040] In one embodiment, the sarcosine compound may be a mixture of two or more compounds, specifically, R in formula (2). 2 This may be a mixture of at least two compounds selected from the group consisting of sarcosine compounds as specified below. (i) R 2 is a sarcosine compound in which R is a linear or branched saturated hydrocarbon group having 12 to 30 carbon atoms (ii) R 2 is a sarcosine compound in which R is a linear or branched unsaturated hydrocarbon group having 12 to 30 carbon atoms, preferably 15 to 20 carbon atoms, and having 1 carbon-carbon unsaturated bond (iii) R 2 is a sarcosine compound in which R is a linear or branched unsaturated hydrocarbon group having 12 to 30 carbon atoms, preferably 15 to 20 carbon atoms, and having 2 to 4 carbon-carbon unsaturated bonds

[0041] In the sarcosine compounds of (i) to (iii) above, R in formula (2) 1 is preferably a hydrocarbon group having 1 to 4 carbon atoms, for example, a methyl group, an ethyl group, a propyl group, or a butyl group, and particularly preferably a methyl group. In the sarcosine compounds of (i) to (iii) above, the number of carbon atoms of R in formula (2) 2 may preferably be 15 or more or 16 or more, and may be 20 or less or 18 or less. R in formula (2) 2 is preferably linear.

[0042] In the above embodiment, the sarcosine compound preferably contains the sarcosine compound of (ii) above as the main component. In this case, the proportion of the sarcosine compound of (ii) above may be, for example, 50% by mass or more, preferably 60% by mass or more, based on the total amount of sarcosine compounds, and may be 100% by mass if the degree of purification is increased, but from the viewpoint of diversity of manufacturing raw materials and cost, it may preferably be 95% by mass or less, 90% by mass or less, 85% by mass or less, or 82% by mass or less. The total proportion of the sarcosine compound of (i) above and the sarcosine compound of (iii) above may be, for example, 50% by mass or less, preferably 40% by mass or less, based on the total amount of sarcosine compounds, and may be 5% by mass or more, 10% by mass or more, 15% by mass or more, or 18% by mass or more. The proportions of the sarcosine compound in (i) and the sarcosine compound in (iii) above may be 25% by mass or less or 20% by mass or less, based on the total amount of sarcosine compounds, and may be 2.5% by mass or more, 5% by mass or more, 7.5% by mass or more, or 9% by mass or more.

[0043] In one embodiment, the sarcosine compound is preferably N-oleoylsarcosine (R 1 is a methyl group, R 2 It contains a linear unsaturated hydrocarbon group with 17 carbon atoms (one carbon-carbon unsaturated bond) as its main component. In this case, the proportion of N-oleoylsarcosine may be, for example, 50% by mass or more, preferably 60% by mass or more, based on the total amount of sarcosine compounds, and may be 100% by mass if the degree of purification is increased, but from the viewpoint of diversity of raw materials for production and cost, it may preferably be 95% by mass or less, 90% by mass or less, 85% by mass or less, or 80% by mass or less.

[0044] Each of the sarcosine compounds described above can be identified and quantified, for example, by LC-CAD / MS analysis using a commercially available HPLC column. The proportion (mass%) of each sarcosine compound relative to the total amount of sarcosine compounds may be calculated by considering it to be equivalent to or approximately the same as the proportion (area%) of the peak area derived from each sarcosine compound obtained in the analysis.

[0045] The sarcosine compound content may be 0.01% by mass or more, 0.05% by mass or more, or 0.08% by mass or more, based on the total amount of refrigerant oil, and may be 3% by mass or less, 1% by mass or less, or 0.5% by mass or less.

[0046] The alcohol compound is, for example, at least one compound represented as R-OH (where R represents a hydrocarbon group). The number of carbon atoms in the alcohol compound (the number of carbon atoms in the hydrocarbon group represented by R) is 8 or more, may be 10 or more, or 12 or more, and may be 32 or less, 28 or less, or 24 or less. The alcohol compound (the hydrocarbon group represented by R) may be linear or branched, and may have a cyclic structure (naphthene ring or aromatic ring), and is preferably branched. The alcohol compound may be a monohydric alcohol or a dihydric or polyhydric alcohol, and is preferably a monohydric alcohol. The alcohol compound may be a primary alcohol, a secondary alcohol, or a tertiary alcohol, and is preferably a primary alcohol.

[0047] In one embodiment of the present invention, the alcohol compound is, for example, an alcohol having an alkyl group represented by the following formula (3). [ka] In the formula, x and y are independent integers between 0 and 18, and x + y is an integer between 4 and 36.

[0048] x may preferably be an integer of 1 or more, 3 or more, 5 or more, or 7 or more, and may be an integer of 15 or less, 13 or less, 11 or less, or 9 or less. y may preferably be an integer of 1 or more, 3 or more, 5 or more, or 7 or more, and may be an integer of 15 or less, 13 or less, 11 or less, or 9 or less. x+y may preferably be 6 or more, 8 or more, 10 or more, or 12 or more, and may be 32 or less, 28 or less, 24 or less, 20 or less, or 16 or less. xy is not particularly limited, but may preferably be 0 or more or 2 or more, and may be 15 or less, 10 or less, 6 or less, or 4 or less. Note that in the above formula (3), -Cx H 2x - and -C y H 2y The groups represented by - may be linear or branched. -C x H 2x - and -C y H 2y When the group represented by - is branched, the branched group may be, for example, a methyl group, and the total number of branched methyl groups may be 0 or more, 1 or more, 2 or more, or 4 or more, or 8 or less, or 7 or less.

[0049] In one embodiment, the alcohol compound may be an alcohol represented by the following formula (4). [ka] In the equation, x and y are equivalent to x and y in equation (3) above, respectively.

[0050] A preferred example of such an alcohol compound is a so-called Guerbet alcohol, which is a β-branched alcohol synthesized by the Guerbet reaction, a dimerization reaction of a starting alcohol. The starting alcohol can be, for example, at least one selected from monoalcohols having 4 to 20 carbon atoms. The starting alcohol may be used alone or as a mixture of two or more, but from the viewpoint of efficiently obtaining a single dimerization product, it is preferable to use it alone. The carbon number of Guerbet alcohol may be, for example, 8 or more, preferably 12 or more or 16 or more, from the viewpoint of not lowering the kinematic viscosity and flash point of the refrigeration oil, and may be 40 or less, 36 or less, 30 or less, 24 or less, or 20 or less, from the viewpoint of further improving the wear resistance of aluminum sliding members. Methods for producing Guerbet alcohol are described, for example, in Japanese Patent Application Publication No. 2015-13815, WO2016-194800, etc.

[0051] Examples of such alcohol compounds include 2-methylheptanol, 2-ethylhexanol, 2-propylpentanol, 2-butylbutanol, 2-methyloctanol, 2-ethylheptanol, 2-propylhexanol, 2-butylpentanol, 2-methylnonanol, 2-ethyloctanol, 2-propylheptanol, 2-butylhexanol, 2-pentylpentanol, 2-methyldecanol, 2-ethylnonanol, 2-propyloctanol, 2-butylheptanol, 2-pentylhexanol, and 2-methylundecane. 2-ethyldecanol, 2-propylnonanol, 2-butyloctanol, 2-pentylheptanol, 2-hexylhexanol, 2-methyldodecanol, 2-ethylundecanol, 2-propyldecanol, 2-butylnonanol, 2-pentyloctanol, 2-hexylheptanol, 2-methyltridecanol, 2-ethyldodecanol, 2-propylundecanol, 2-butyldecanol, 2-pentylnonanol, 2-hexyloctanol, 2-heptylheptanol, 2-methyltetradecanol, 2-ethyltridecanol Canol, 2-propyldodecanol, 2-butylundecanol, 2-pentyldecanol, 2-hexylnonanol, 2-heptyloctanol, 2-methylpentadecanol, 2-ethyltetradecanol, 2-propyltridecanol, 2-butyldodecanol, 2-pentylundecanol, 2-hexyldecanol, 2-heptylnonanol, 2-octyloctanol, 2-methylhexadecanol, 2-ethylpentadecanol, 2-propyltetradecanol, 2-butyltridecanol, 2-pentyldodecanol, 2-hexyl Ndecanol, 2-heptyldecanol, 2-octylnonanol, 2-methylheptanol, 2-ethylhexadecanol, 2-propylpentadecanol, 2-butyltetradecanol, 2-pentyltridecanol, 2-hexyldodecanol, 2-heptylundecanol, 2-octyldecanol, 2-nonylnonanol, 2-methylnonadecanol, 2-ethyloctadecanol, 2-propylheptadecanol, 2-butylhexadecanol, 2-pentylpentadecanol, 2-hexyltetradecanol, 2-heptyltridecanol,Examples include 2-octyldodecanol, 2-nonylundecanol, 2-decyldecanol, 2-decyltetradecanol, 2-dodecylhexadecanol, 2-tetradecyloctadecanol, and 2-hexadecyleicosanol (these may also have branched structures such as methyl groups).

[0052] The alcohol compound is preferably a branched aliphatic alcohol having 16 to 18 carbon atoms. Specific examples of branched aliphatic alcohols having 16 to 18 carbon atoms include 2-hexyl-1-dodecanol, 2-hexyl-1-decanol, 2-octyl-1-decanol, 2-(4-methyl-hexyl)-8-methyl-undecanol, and 2-(4,4-dimethylpentan-2-yl)-5,7,7-trimethyl-1-octanol. The number of branched methyl groups in the branched alcohol compound may be 0 or more, 1 or more, 2 or more, or 4 or more, and may be 8 or less, or 7 or less.

[0053] The flash point of the alcohol compound is preferably 70°C or higher, 100°C or higher, 130°C or higher, or 150°C or higher, and may be 250°C or lower or 200°C or lower, in terms of safety and not lowering the flash point of the refrigeration oil. In this specification, the flash point refers to the flash point measured in accordance with the Cleveland Open-Oc (COC) method described in JIS K2265-4:2007.

[0054] The pour point of the alcohol compound may preferably be 0°C or below, -10°C or below, or -20°C or below, as it does not impede the fluidity of the refrigeration oil at low temperatures. In this specification, the pour point refers to the pour point measured in accordance with JIS K2269:1987.

[0055] The freezing point of the alcohol compound is preferably 0°C or below, -10°C or below, or -20°C or below, and may also be -30°C or below, or -50°C or below, as long as it does not impede the fluidity of the refrigeration oil at low temperatures. In this specification, the freezing point means a temperature 1°C lower than the lowest temperature at which the flow of the alcohol compound is observed, measured with the pour point measurement interval (2.5°C) in JIS K2269:1987 (method for measuring the pour point described above) set to 1°C.

[0056] The viscosity of the alcohol compound at 30°C is preferably 20 mPa·s or more, 50 mPa·s or more, 100 mPa·s or more, or 150 mPa·s or more, and may be 500 mPa·s or 300 mPa·s or less, in order to further improve the wear resistance of the aluminum sliding member. The viscosity as used herein refers to the viscosity (mPa·s) measured using a single-cylindrical rotational viscometer in accordance with JIS Z8803.

[0057] The alcohol compound content may be 0.1% by mass or more, 0.5% by mass or more, or 1% by mass or more, based on the total amount of refrigerant oil, and may be 10% by mass or less, 5% by mass or less, 4% by mass or less, or 3% by mass or less.

[0058] The additive may further contain a partial ester of a polyhydric alcohol and a carboxylic acid including an unsaturated carboxylic acid, from the viewpoint of further improving the wear resistance of the aluminum-based sliding member. This partial ester refers to an ester in which some of the hydroxyl groups of the polyhydric alcohol are esterified, while the remaining hydroxyl groups remain unesterified. In other words, the partial ester has an ester bond and hydroxyl groups.

[0059] The polyhydric alcohol may be a polyhydric alcohol having 2 to 6 hydroxyl groups. The number of carbon atoms in the polyhydric alcohol may be 4 or more or 5 or more, and 12 or less or 10 or less. Examples of polyhydric alcohols include neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, di-(trimethylolpropane), tri-(trimethylolpropane), pentaerythritol, and dipentaerythritol. From the viewpoint of further improving the wear resistance of the sliding member, the polyhydric alcohol is preferably pentaerythritol.

[0060] An unsaturated carboxylic acid is a carboxylic acid having at least one carbon-carbon unsaturated bond. The number of carbon-carbon unsaturated bonds may be 1 or 2 or more, and may be 4 or less, 3 or less, or 2 or less. An unsaturated carboxylic acid may be, for example, a monounsaturated carboxylic acid. An unsaturated carboxylic acid may be linear or branched. The number of carbon atoms in an unsaturated carboxylic acid may be 4 or more, 8 or more, or 12 or more, and may be 36 or less, 28 or less, or 20 or less.

[0061] Examples of such unsaturated carboxylic acids include pentenoic acid, hexenoic acid, heptenic acid, octenoic acid, nonenic acid, decenoic acid, undecenoic acid, dodecenoic acid, tridecenoic acid, tetradecenoic acid, pentadecenoic acid, hexadecenoic acid, heptadecenoic acid, and octadecenoic acid (all of which may be linear or branched).

[0062] The carboxylic acid may consist only of unsaturated carboxylic acids, or it may further contain saturated carboxylic acids in addition to unsaturated carboxylic acids. That is, partial esters include (I) and (II) below. (I) A partial ester in which some of the hydroxyl groups of a polyhydric alcohol are esterified with an unsaturated carboxylic acid, while the remaining hydroxyl groups remain unesterified. (II) A partial ester in which some hydroxyl groups of a polyhydric alcohol are esterified with an unsaturated carboxylic acid, some other hydroxyl groups are esterified with a saturated carboxylic acid, and the remaining hydroxyl groups remain unesterified.

[0063] The saturated carboxylic acid may be, for example, a monovalent saturated carboxylic acid. The number of carbon atoms in the saturated carboxylic acid may be 4 or more, 8 or more, or 12 or more, and may be 36 or less, 28 or less, or 20 or less. Examples of saturated carboxylic acids include pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, and octadecanoic acid.

[0064] For example, if the polyhydric alcohol is pentaerythritol, the partial ester may be a monoester in which only one of the four hydroxyl groups of pentaerythritol is esterified, a diester in which only two hydroxyl groups are esterified, or a triester in which only three hydroxyl groups are esterified, preferably including all of the monoester, diester, and triester. In this case, if the partial ester includes all of the monoester, diester, and triester, the proportion of monoester may be 0 to 15% by mass, the proportion of diester may be 20 to 40% by mass, and the proportion of triester may be 30 to 45% by mass, based on the total amount of the partial ester.

[0065] The iodine value (gI2 / 100g) of the partial ester may be 20 or more, 40 or more, or 50 or more, and may be 100 or less, 80 or less, or 70 or less. The iodine value of the partial ester is thought to originate from the carbon-carbon unsaturated bond in the unsaturated carboxylic acid. In this specification, the iodine value refers to the iodine value (gI2 / 100g) measured in accordance with JIS K0070-1992.

[0066] The partial ester content may be 0.001% by mass or more, 0.01% by mass or more, or 0.1% by mass or more, based on the total amount of refrigerant oil, and may be 10% by mass or less, 5% by mass or less, or 1% by mass or less.

[0067] The additives may further include other additives besides sarcosine compounds, alcohol compounds, and partial esters. These other additives are, for example, at least one selected from the group consisting of antioxidants, acid scavengers, anti-wear agents, defoamers, metal deactivators, viscosity index improvers, pour point depressants, and detergent dispersants. The total amount of these other additives may be 0.01% by mass or more and 5% by mass or less, based on the total amount of refrigerant oil.

[0068] Examples of antioxidants include phenolic antioxidants. Examples of phenolic antioxidants include 2,6-di-tert.-butyl-p-cresol (DBPC), 2,6-di-tert.-butyl-phenol, and 4,4'-methylenebis(2,6-di-tert.-butyl-phenol). The antioxidant content may be 0.01% by mass or more, or 0.1% by mass or more, and may be 5% by mass or less, 3% by mass or less, or 1% by mass or less, based on the total amount of refrigerant oil.

[0069] Examples of acid scavengers include epoxy-based acid scavengers. Examples of epoxy-based acid scavengers include glycidyl ether type epoxy compounds, glycidyl ester type epoxy compounds, aryl oxirane compounds, alkyl oxirane compounds, alicyclic epoxy compounds, epoxidized fatty acid monoesters, and epoxidized vegetable oils. The content of the acid scavenger may be 0.01% by mass or more, or 0.1% by mass or more, and may be 5% by mass or less, 3% by mass or less, or 1% by mass or less, based on the total amount of refrigerant oil.

[0070] Examples of anti-wear agents include phosphorus-based anti-wear agents. Examples of phosphorus-based anti-wear agents include phosphate esters, acidic phosphate esters, amine salts of acidic phosphate esters, chlorinated phosphate esters, phosphite esters, and thiophosphate esters. The content of the anti-wear agent may be 0.01% by mass or more, 0.1% by mass or more, 5% by mass or less, 3% by mass or less, or 1% by mass or less, based on the total amount of refrigeration oil. In one embodiment, the refrigeration oil does not need to contain an anti-wear agent (also called an extreme pressure agent), and does not need to contain a phosphorus-based anti-wear agent (also called a phosphorus-based extreme pressure agent). The refrigeration oil according to this embodiment can improve the wear resistance of aluminum sliding members even when it does not contain an anti-wear agent (phosphorus-based anti-wear agent).

[0071] Examples of metal deactivators include benzotriazole and benzotriazole derivatives. The content of the metal deactivator may be 0.0001% by mass or more, 0.0005% by mass or more, or 0.0008% by mass or more, based on the total amount of refrigerant oil, and may be 1% by mass or less, 0.1% by mass or less, or 0.01% by mass or less.

[0072] The kinematic viscosity of refrigerant oil at 40°C is, for example, 3 mm. 2 / s or more, 10mm 2 / s or more, or 20mm 2 / s or more, and 500mm 2 / s or less or 300mm 2 It may be less than or equal to / s. The kinematic viscosity of the refrigerant oil at 100°C is, for example, 1 mm 2 / s or more or 2mm 2 / s or more, and 100mm 2 / s or less or 50mm 2 It may be less than or equal to / s. The viscosity index of the refrigerant oil may be, for example, 10 or more, 50 or more, or 70 or more, and may be 500 or less, 300 or less, or 250 or less. In this specification, the kinematic viscosity and viscosity index of the refrigerant oil refer to the kinematic viscosity and viscosity index measured in accordance with JIS K2283:2000, respectively.

[0073] As described above, the refrigerant oil coexists with the refrigerant in the refrigerant circulation system 6. In other words, one embodiment of the present invention can also be described as a working fluid composition containing the above-mentioned refrigerant oil and refrigerant. Examples of refrigerants include saturated fluorinated hydrocarbons (also called HFCs), unsaturated fluorinated hydrocarbons (also called HFOs), hydrocarbons, fluorinated ethers, bis(trifluoromethyl) sulfide, methane trifluoride iodide, ammonia, and carbon dioxide. The refrigerant may be one of these refrigerants alone, or it may be a mixture of two or more refrigerants. In one embodiment, the refrigerant contains an unsaturated fluorinated hydrocarbon, in which case the effect of improving the wear resistance of the sliding member by the above-mentioned refrigerant oil can be more preferably obtained.

[0074] Examples of saturated fluorinated hydrocarbons include those having 1 to 3 carbon atoms, more preferably 1 to 2 carbon atoms. Examples of saturated fluorinated hydrocarbons include difluoromethane (R32), trifluoromethane (R23), pentafluoroethane (R125), 1,1,2,2-tetrafluoroethane (R134), 1,1,1,2-tetrafluoroethane (R134a), 1,1,1-trifluoroethane (R143a), 1,1-difluoroethane (R152a), and fluoroethane (R16 1) Examples include 1,1,1,2,3,3,3-heptafluoropropane (R227ea), 1,1,1,2,3,3-hexafluoropropane (R236ea), 1,1,1,3,3,3-hexafluoropropane (R236fa), 1,1,1,3,3-pentafluoropropane (R245fa), and 1,1,1,3,3-pentafluorobutane (R365mfc).

[0075] Preferred saturated fluorinated hydrocarbons include, for example, R32 alone; R23 alone; R134a alone; R125 alone; mixtures of R134a / R32 = 60-80% by mass / 40-20% by mass; mixtures of R32 / R125 = 40-70% by mass / 60-30% by mass; mixtures of R125 / R143a = 40-60% by mass / 60-40% by mass; mixtures of R134a / R32 / R125 = 60% by mass / 30% by mass / 10% by mass; mixtures of R134a / R32 / R125 = 40-70% by mass / 15-35% by mass / 5-40% by mass; and mixtures of R125 / R134a / R143a = 35-55% by mass / 1-15% by mass / 40-60% by mass. More specifically, a mixture of R134a / R32 = 70 / 30 mass%; a mixture of R32 / R125 = 60 / 40 mass%; a mixture of R32 / R125 = 50 / 50 mass% (R410A); a mixture of R32 / R125 = 45 / 55 mass% (R410B); a mixture of R125 / R143a = 50 / 50 mass% (R507C); R32 / Examples include a mixture of R125 / R134a = 30 / 10 / 60 mass%; a mixture of R32 / R125 / R134a = 23 / 25 / 52 mass% (R407C); a mixture of R32 / R125 / R134a = 25 / 15 / 60 mass% (R407E); and a mixture of R125 / R134a / R143a = 44 / 4 / 52 mass% (R404A).

[0076] Examples of unsaturated fluorinated hydrocarbons include carbon-2 to carbon-4 unsaturated fluorinated hydrocarbons having one or more carbon-carbon double bonds and containing fluorine and hydrogen. The unsaturated fluorinated hydrocarbon is preferably fluoropropene, more preferably fluoropropene with 3 to 5 fluorine atoms. Examples of unsaturated fluorinated hydrocarbons include 1,2,3,3,3-pentafluoropropene (HFO-1225ye), 1,3,3,3-tetrafluoropropene (HFO-1234ze), 2,3,3,3-tetrafluoropropene (HFO-1234yf), 1,2,3,3-tetrafluoropropene (HFO-1234ye), and 3,3,3-trifluoropropene (HFO-1243zf). The unsaturated fluorinated hydrocarbon is preferably at least one selected from HFO-1225ye, HFO-1234ze, and HFO-1234yf.

[0077] The hydrocarbon is preferably a hydrocarbon having 1 to 5 carbon atoms, more preferably a hydrocarbon having 2 to 4 carbon atoms. Examples of hydrocarbons include methane, ethylene, ethane, propylene, propane (R290), cyclopropane, n-butane, isobutane, cyclobutane, methylcyclopropane, 2-methylbutane, and n-pentane. The hydrocarbon is preferably at least one selected from the group consisting of propane, n-butane, isobutane, and 2-methylbutane.

[0078] The amount of refrigerant oil in the refrigerant circulation system 6 (the amount of refrigerant oil in the working fluid composition) may be 1 part by mass or more, or 2 parts by mass or more, and 500 parts by mass or less, or 400 parts by mass or less, per 100 parts by mass of refrigerant. [Examples]

[0079] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0080] (Examples 1-4 and Comparative Example 1) Using the components listed below, refrigerated oil with the composition shown in Table 1 (mass %) based on the total amount of refrigerated oil was produced.

[0081] (Base oil) A mixed ester obtained by mixing base oil a and base oil b below in a mass ratio of 75 / 25 (kinematic viscosity at 40°C: 83.29 mm²). 2 kinematic viscosity at 100°C: 9.63 mm² / s 2 / s) Base oil a: Complete ester of pentaerythritol and a mixed carboxylic acid of 2-ethylhexanoic acid / 3,5,5-trimethylhexanoic acid (mixing ratio (mass ratio): 48 / 52) Base oil b: Dipentaerythritol and a mixed carboxylic acid of 2-ethylhexanoic acid / 3,5,5-trimethylhexanoic acid (mixing ratio (mass ratio): 50 / 50) complete ester.

[0082] (Additives) (A) Branched octadecyl alcohol with the structure represented by the following formula (5) (2-heptyl-1-undecanol (an alcohol represented by formula (4), where x=8, y=6, and the total number of branched methyl groups is 6), which has 6 methyl branched groups): 2-(4,4-dimethylpentan-2-yl)-5,7,7-trimethyl-1-octanol, flash point (COC) 160°C, pour point <-30°C, freezing point <-90°C, viscosity at 30°C: 220 mPa·s) [ka]

[0083] (B) A mixture of sarcosine compounds mainly composed of N-oleoylsarcosine as shown below (R 1 and R 2 R in equation (2) above is 1 and R 2 This means that the proportion (mass%) of each sarcosine compound relative to the total amount of sarcosine compounds was calculated by assuming that it was approximately the same as the proportion (area%) of the peak area derived from each sarcosine compound obtained by LC-CAD / MS analysis using an ACQUITYUPLC BEH C18 column. · N-oleoyl sarcosine (R 1 is a methyl group, R 2 This is a linear unsaturated hydrocarbon group with 17 carbon atoms (one carbon-carbon unsaturated bond) (71% by mass) • N-palmitre oil sarcosine (R 1 is a methyl group, R 2 This is a linear unsaturated hydrocarbon group with 15 carbon atoms (one carbon-carbon unsaturated bond) (5% by mass) ·N-butyl-N-oleoylglycine(R 1 is a butyl group, R 2 This is a linear unsaturated hydrocarbon group with 17 carbon atoms (one carbon-carbon unsaturated bond) (4% by mass) • N-Linoleoyl Sarcosine (R 1 is a methyl group, R 2 This is a linear unsaturated hydrocarbon group with 17 carbon atoms (two carbon-carbon unsaturated bonds) (10% by mass) ·N-palmitoyl sarcosine (R1 is a methyl group, R 2 (3% by mass of a linear saturated hydrocarbon group with 15 carbon atoms) ·N-Stearoyl Sarcosine (R 1 is a methyl group, R 2 (A linear saturated hydrocarbon group with 17 carbon atoms) 7% by mass

[0084] (C) Epoxy acid scavenger (glycidyl neodecanoate) (D) Phenolic antioxidants (E) Metal deactivators (F) Phosphorus-based anti-wear agent (tricresyl phosphate)

[0085] [Evaluation of abrasion resistance] A sealed FALEX testing machine (pin: 3135 steel, V-block: 4032 Al (aluminum-based sliding member with a sliding surface formed of aluminum alloy (Al-Si system))) was used, and the test conditions were: test load 0.3 MPaG, test time 5 hours, rotation speed 290 rpm, and test temperature 25°C (room temperature). Test pieces conforming to the ASTM D2670 wear test were used, and the wear resistance test was conducted under an environment of 2,3,3,3-tetrafluoropropene refrigerant injection (refrigerant injection rate: 10 L / h). After the test, the average value (mm) of the wear width at three points on the V-block (left end, middle, and right end) was measured. The results are shown in Table 1. A smaller wear width indicates better wear resistance. In Comparative Example 1, seizing occurred in the V-block (low wear resistance), so the wear width could not be measured.

[0086] [Table 1]

[0087] When the refrigeration oils of Examples 5 to 8 were manufactured as described below, all of the refrigeration oils were able to improve the wear resistance of aluminum sliding members, similar to Examples 1 to 4.

[0088] (Example 5) Refrigerant oil was prepared in the same manner as in Example 1, except that 1% by mass of 2-hexyl-1-dodecanol (based on the total amount of refrigerant oil) was added instead of additive (A).

[0089] (Example 6) Refrigerant oil was prepared in the same manner as in Example 1, except that 1% by mass of 2-octyl-1-decanol (based on the total amount of refrigerant oil) was added instead of additive (A).

[0090] (Example 7) Refrigerant oil was prepared in the same manner as in Example 1, except that 1% by mass (based on the total amount of refrigerant oil) of 2-(4-methylhexyl)-8-methyl-undecanol was added instead of additive (A).

[0091] (Example 8) Refrigerant oil was prepared in the same manner as in Example 1, except that 1% by mass (based on the total amount of refrigerant oil) of 2-(4,4-dimethylpentan-2-yl)-5,7,7-trimethyl-1-octanol was added instead of additive (A). [Explanation of Symbols]

[0092] 1... Compressor, 2... Condenser, 3... Expansion mechanism, 4... Evaporator, 5... Flow path, 6... Refrigerant circulation system, 7... Accumulator, 10... Refrigeration unit.

Claims

1. A method for lubricating aluminum sliding members in a refrigerator with refrigeration oil, The aforementioned refrigerant oil Base oil containing esters, A method comprising an additive containing an alcohol compound represented by the following formula (4) and having 24 or fewer carbon atoms. 【Chemistry 1】 [In the formula, x and y each represent an integer greater than or equal to 5.]

2. The method according to claim 1, wherein the additive further comprises a sarcosine compound.

3. A base oil containing an ester, An additive containing an alcohol compound represented by the following formula (4) and having 24 or fewer carbon atoms, A refrigeration oil used for lubricating aluminum sliding components. 【Chemistry 2】 [In the formula, x and y each represent an integer greater than or equal to 5.]

4. The refrigeration oil according to claim 3, wherein the additive further comprises a sarcosine compound.

5. A refrigerator comprising a refrigerant circulation system having a compressor, a condenser, an expansion mechanism, and an evaporator, The compressor includes an aluminum sliding member, A refrigerator comprising the refrigerant circulation system described in claim 3 or 4 and a refrigerant.

6. The refrigerator according to claim 5, wherein the refrigerant contains an unsaturated fluorinated hydrocarbon.

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