Lubricating base oils, lubricating oils and hydraulic fluids

Abstract

To provide base oil for lubricating oil excellent in stability even when there is water contamination.SOLUTION: The base oil for lubricating oil includes esters of trihydric alcohol with C14-20 fatty acid. The esters include diester and triester. The base oil for lubricating oil has a triester content based on a total amount of the diester and the triester of 93 mol% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to lubricating base oils, lubricating oils and working fluids. [Background technology]

[0002] Refrigeration machines such as refrigerators, car air conditioners, room air conditioners, and vending machines are equipped with compressors for circulating refrigerants in a refrigeration cycle. The compressors are filled with refrigeration oil to lubricate sliding members. Refrigeration oils generally contain base oils and additives selected according to desired properties.

[0003] For example, Patent Document 1 discloses a refrigerating machine oil for hydrocarbon refrigerants that is capable of achieving both low viscosity and maintaining refrigerant dissolution viscosity, as well as refrigerating machine oil compatibility with the refrigerant and maintaining refrigerant dissolution viscosity, and that contains an ester of a fatty acid, in which the proportion of straight-chain fatty acids having 10 to 22 carbon atoms is 50 to 100 mol %, with a polyhydric alcohol. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-90284 Summary of the Invention [Problem to be solved by the invention]

[0005] As disclosed in Patent Document 1, esters of specific fatty acids and polyhydric alcohols are known as base oils used in lubricating oils such as refrigerating machine oils. However, according to the studies of the present inventors, there is room for further improvement in the stability of lubricating base oils containing such esters when water is mixed in.

[0006] Therefore, one aspect of the present invention has an object to provide a lubricating base oil that is highly stable even when water is mixed in. [Means for solving the problem]

[0007] As described in Patent Document 1, it has been thought that esters used as base oils should preferably be complete esters from the viewpoint of excellent hydrolysis stability. However, the present inventors have discovered that in an ester of a trihydric alcohol and a fatty acid having 14 to 20 carbon atoms, if the amount of a triester (a complete ester) is too large, stability is significantly reduced (peroxide value increases) when water is mixed in. They have also found that if the ester contains a diester (a partial ester) and the amount of triester is not more than a specific amount, the increase in peroxide value is suppressed and excellent stability is achieved even when water is mixed in.

[0008] One aspect of the present invention is a lubricating base oil containing an ester of a trihydric alcohol and a fatty acid having 14 to 20 carbon atoms, wherein the ester includes a diester and a triester, and the content of the triester is 93 mol % or less based on the total amount of the diester and the triester.

[0009] The fatty acids having 14 to 20 carbon atoms may include oleic acid. The content of oleic acid may be 80 mass% or more based on the total amount of fatty acids having 14 to 20 carbon atoms. The fatty acids having 14 to 20 carbon atoms may further include saturated fatty acids having 14 to 20 carbon atoms. The fatty acids having 14 to 20 carbon atoms may further include unsaturated fatty acids having 14 to 20 carbon atoms other than oleic acid.

[0010] Another aspect of the present invention is a refrigerating machine oil containing the lubricating base oil described above. The refrigerating machine oil may further contain an antioxidant. The refrigerating machine oil may further contain an acid scavenger. The refrigerating machine oil may further contain an anti-wear agent. The content of the lubricating base oil may be 80 mass% or more based on the total amount of the refrigerating machine oil.

[0011] Another aspect of the present invention is a working fluid containing the above-mentioned refrigerating machine oil and a refrigerant. The refrigerant may contain a hydrocarbon. [Effects of the Invention]

[0012] According to one aspect of the present invention, it is possible to provide a lubricating base oil that is highly stable even when water is mixed in. DETAILED DESCRIPTION OF THE INVENTION

[0013] DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention is a lubricating base oil containing an ester of a trihydric alcohol and a fatty acid having 14 to 20 carbon atoms.

[0014] A trihydric alcohol is an alcohol having three hydroxyl groups. The trihydric alcohol may be an aliphatic alcohol. Examples of trihydric alcohols include trimethylolethane, trimethylolpropane, trimethylolbutane, glycerin, and 1,3,5-pentanetriol. The trihydric alcohol is preferably trimethylolpropane.

[0015] The fatty acids having 14 to 20 carbon atoms (hereinafter also referred to as "C14 to C20 fatty acids") may be saturated fatty acids or unsaturated fatty acids. The C14 to C20 fatty acids preferably include unsaturated fatty acids, more preferably unsaturated fatty acids having 18 carbon atoms (C18 unsaturated fatty acids), and even more preferably oleic acid. The content of unsaturated fatty acids (preferably C18 unsaturated fatty acids, more preferably oleic acid) may be 70% by mass or more, 75% by mass or more, 80% by mass or more, or 85% by mass or more, and may be 95% by mass or less, 93% by mass or less, or 90% by mass or less, based on the total amount of C14 to C20 fatty acids.

[0016] In one embodiment, the C14 to C20 fatty acids further include saturated fatty acids having 14 to 20 carbon atoms (hereinafter also referred to as "C14 to C20 saturated fatty acids") in addition to the unsaturated fatty acids. Examples of C14 to C20 saturated fatty acids include tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptahexadecanoic acid, octadecanoic acid, nonadecanoic acid, and eicosanoic acid. These C14 to C20 saturated fatty acids may be linear or branched. The C14 to C20 saturated fatty acid preferably includes at least one selected from the group consisting of linear C14 to C20 saturated fatty acids, more preferably includes at least one selected from the group consisting of linear tetradecanoic acid (myristic acid), linear hexadecanoic acid (palmitic acid), and linear octadecanoic acid (stearic acid), and even more preferably includes linear tetradecanoic acid (myristic acid), linear hexadecanoic acid (palmitic acid), and linear octadecanoic acid (stearic acid).

[0017] In another embodiment, the C14 to C20 fatty acids further comprise, in addition to oleic acid, an unsaturated fatty acid having 14 to 20 carbon atoms other than oleic acid (hereinafter also referred to as "C14 to C20 unsaturated fatty acid"). The C14 to C20 unsaturated fatty acid other than oleic acid may have, for example, 1 to 4, 1 to 3, 1 to 2, or 1 carbon-carbon unsaturated bond. Examples of C14 to C20 unsaturated fatty acids other than oleic acid include physeteric acid, myristoleic acid, palmitoleic acid, heptadecenylene acid, petroselaidic acid, elaidic acid, vaccenic acid, linoleic acid, linolelaidic acid, hiragonic acid, linolenic acid, and arachidonic acid. The C14 to C20 unsaturated saturated fatty acid other than oleic acid preferably comprises at least one selected from the group consisting of unsaturated fatty acids having 16 to 18 carbon atoms, more preferably palmitoleic acid.

[0018] In another embodiment, the C14 to C20 fatty acids further include, in addition to oleic acid, both C14 to C20 saturated fatty acids and C14 to C20 unsaturated fatty acids other than oleic acid. 0 fatThe fatty acid preferably includes at least one selected from the group consisting of linear C14 to C20 saturated fatty acids and at least one selected from the group consisting of unsaturated fatty acids having 16 to 18 carbon atoms, more preferably includes at least one selected from the group consisting of myristic acid, palmitic acid, and stearic acid, and palmitoleic acid, and even more preferably includes myristic acid, palmitic acid, stearic acid, and palmitoleic acid.

[0019] The content of C14 to C20 saturated fatty acids may be 1% by mass or more, 3% by mass or more, or 5% by mass or more, and 15% by mass or less, 12% by mass or less, or 10% by mass or less, based on the total amount of C14 to C20 fatty acids. The content of C14 to C20 unsaturated fatty acids other than oleic acid may be 1% by mass or more, 3% by mass or more, or 4% by mass or more, and 10% by mass or less, 8% by mass or less, or 6% by mass or less, based on the total amount of C14 to C20 fatty acids.

[0020] The content of each of the above-mentioned fatty acids is measured by the following procedure. The esters are dissolved in ethanol, subjected to alkaline hydrolysis, and then derivatized with trimethylsilyl (TMS) using N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA). The resulting TMS derivatives of the fatty acids are analyzed by GC / MS to confirm the type of fatty acid that makes up the ester. Next, each fatty acid is quantified by GC analysis under the following GC conditions. (GC conditions) Column: DB-5, 50°C → 320°C (15°C / min) Injection: 300°C, 1 μL, split ratio 50:1 Detector: FID, 320℃ Standard samples for calibration curves: Use palmitic acid (reagent) for C14 fatty acids and C16 fatty acids, and stearic acid (reagent) for C18 fatty acids. In addition, fatty acid ethylated products may be produced during the TMS derivatization treatment, and the amount of the fatty acid is calculated by adding up the amount of the fatty acid TMS derivatized product and the amount of the fatty acid ethylated product.

[0021] Esters of trihydric alcohols and C14-C20 fatty acids include diesters and triesters. Diesters are partial esters in which two of the three hydroxyl groups of a trihydric alcohol are esterified with C14-C20 fatty acids, leaving one hydroxyl group intact. Triesters are complete esters in which all three hydroxyl groups of a trihydric alcohol are esterified with C14-C20 fatty acids.

[0022] The triester content is 93 mol% or less based on the total amount of diesters and triesters. In other words, the diester content is 7 mol% or more based on the total amount of diesters and triesters. This allows for a lubricating base oil that is highly stable even when water is mixed in.

[0023] The content of the triester, based on the total amount of the diester and triester, may be preferably 92 mol% or less, 91 mol% or less, 90 mol% or less, or 89 mol% or less, or may be 70 mol% or more, 75 mol% or more, 80 mol% or more, or 85 mol% or more.

[0024] The content of the diester may be preferably 8 mol% or more, 9 mol% or more, 10 mol% or more, or 11 mol% or more, and may be 30 mol% or less, 35 mol% or less, 20 mol% or less, or 15 mol% or less, based on the total amount of the diester and triester.

[0025] The above-mentioned diester content C2 and triester content C3 (mol % based on the total amount of diester and triester) are measured under the following conditions: 13In the C-NMR spectrum, the peak at around 40.5 ppm is considered to be the peak due to the triester (area value P3), and the peak observed at around 42.5 ppm is considered to be the peak due to the diester (area value P2), and is calculated using the following formula. C2=P2 / (P2+P3)×100 C3=P3 / (P2+P3)×100 ( 13 C-NMR conditions) Solvent: deuterated chloroform ·Temperature: Room temperature Measurement method: 1 H-inverse gated decoupling method Pulse width: 30° Waiting time: 10 seconds

[0026] The ester of a trihydric alcohol containing the above-mentioned specific amounts of diester and triester and a C14 to C20 fatty acid can be produced, for example, by the following method. First, a polyhydric alcohol and a slightly excess amount of fatty acid are reacted under a nitrogen stream at 120 to 250°C while distilling off the resulting water until the hydroxyl value reaches approximately 15 mgKOH / g, yielding a crude ester. A catalyst such as a Lewis acid catalyst or a reducing agent such as a phosphorus-based reducing agent may be used during the reaction. The resulting crude ester is purified by alkali treatment with potassium hydroxide or, if necessary, an aqueous solution of sulfite, after which the excess acid is removed. The crude ester is washed with water and dehydrated, followed by adsorption with an adsorbent such as activated clay or aluminum oxide and filtration, yielding a mixture containing diesters and triesters (and possibly monoesters). The above steps are carried out according to known methods (see, for example, JP 2002-193882 A, WO 2002 / 022548 A, JP 2007-332134 A, and JP 2013-227255 A). The mixture containing the diester and triester having a hydroxyl value of about 15 mgKOH / g obtained as described above is purified and separated from the diester and triester by utilizing the difference in boiling point between the two esters, and the diester and triester are then mixed again in the desired ratio described above, thereby obtaining a diester / triester mixture in the desired ratio. In the above production method, an ester mainly consisting of triesters can be obtained by carrying out the reaction until the hydroxyl value reaches 5 mgKOH / g or less, preferably 1 mgKOH / g or less, and an ester mainly consisting of diesters can be obtained by reacting about 2 moles of C14 to C20 fatty acid with 1 mole of trihydric alcohol, and these may also be mixed in the desired ratio described above.

[0027] The ester of a trihydric alcohol and a C14 to C20 fatty acid may further contain a monoester. A monoester is a partial ester in which one of the three hydroxyl groups of a trihydric alcohol is esterified with a C14 to C20 fatty acid, leaving two hydroxyl groups intact. From the viewpoint of the stability of the refrigerating machine oil, the smaller the content of the monoester, the better. The content may be preferably 10 mol % or less, or even 0 mol %, based on the total amount of the ester of a trihydric alcohol and a C14 to C20 fatty acid.

[0028] The base oil described above is used as a base oil for lubricating oils. That is, another embodiment of the present invention is a lubricating oil containing the above-mentioned base oil for lubricating oils.

[0029] The content of the ester of a trihydric alcohol and a C14 to C20 fatty acid may be 50 mass% or more, 60 mass% or more, 70 mass% or more, 80 mass% or more, 90 mass% or more, or 95 mass% or more based on the total amount of the lubricating oil.

[0030] The lubricating oil may further contain a base oil other than the ester of a trihydric alcohol and a C14 to C20 fatty acid. The other base oil may be, for example, a hydrocarbon oil or an oxygen-containing oil. Examples of hydrocarbon oils include mineral oils, olefin polymers, naphthalene compounds, and alkylbenzenes. Examples of oxygen-containing oils include monoesters (esters of monoalcohols), polyol esters (esters of polyols having two or more hydroxyl groups) other than esters of trihydric alcohols and C14 to C20 fatty acids, esters such as complex esters, and ethers such as polyalkylene glycols, polyvinyl ethers, polyphenyl ethers, and perfluoroethers.

[0031] The lubricating oil may further contain additives depending on the desired properties. Examples of additives include antioxidants, acid scavengers, antiwear agents, oiliness agents, antifoaming agents, metal deactivators, and viscosity index improvers. The total content of the additives is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, based on the total amount of the lubricating oil, and is preferably 5% by mass or less, or 2% by mass or less.

[0032] The lubricating oil preferably further contains an antioxidant, more preferably a phenolic antioxidant. An example of the phenolic antioxidant is 2,6-di-tert-butyl-4-methylphenol. The content of the antioxidant may be 0.1 mass % or more and 3 mass % or less based on the total amount of the lubricating oil.

[0033] The lubricating oil preferably further contains an acid scavenger, more preferably an epoxy-based acid scavenger. Examples of epoxy-based acid scavenger include glycidyl ester compounds, glycidyl ether compounds, and alicyclic epoxy compounds. The content of the acid scavenger may be 0.1% by mass or more and 3% by mass or less based on the total amount of the lubricating oil.

[0034] The lubricating oil preferably further contains an antiwear agent, more preferably a phosphorus-based antiwear agent. Examples of phosphorus-based antiwear agents include orthophosphate compounds, phosphite compounds, and thiophosphate compounds. The phosphorus-based antiwear agent is preferably an orthophosphate compound, more preferably at least one selected from tricresyl phosphate, triphenyl phosphate, trialkyl phosphate, and tri(alkylphenyl)phosphate. The content of the antiwear agent may be 0.1% by mass or more and 3% by mass or less based on the total amount of the lubricating oil.

[0035] The lubricating oil, in one embodiment, may further contain antioxidants, acid scavengers and antiwear agents, and may further contain phenolic antioxidants, epoxy acid scavengers and phosphorus-based antiwear agents.

[0036] The kinematic viscosity of lubricating oil at 40°C is 10mm 2 / s or more, 20mm 2 / s or more, 30mm 2 / s or more, or 40 mm 2 / s or more, and 2 / s or less, and 300 mm 2 / s or less, 200mm 2 / s or less, 100mm 2 / s or less, or 60 mm 2 / s or less.

[0037] The kinematic viscosity of the lubricating oil at 100°C is 4mm 2 / s or more, 6mm 2 / s or more, 8mm 2 / s or more, or 9 mm 2 / s or more, and 2 / s or less, 25mm 2 / s or less, 15mm 2 / s or less, 12mm 2 / s or less, or 10 mm 2 / s or less.

[0038] The viscosity index of the lubricating oil may be 110 or greater, 140 or greater, 150 or greater, 160 or greater, or 170 or greater, and may be 300 or less, 250 or less, or 220 or less.

[0039] The kinematic viscosity and viscosity index in this specification refer to the kinematic viscosity and viscosity index measured in accordance with JIS K2283:2000.

[0040] The use of the lubricating oil is not particularly limited, but is preferably a refrigerating machine oil. That is, another embodiment of the present invention is a refrigerating machine oil containing the above-mentioned lubricating base oil. Furthermore, the term "lubricating oil" in the above description can be read as "refrigerating machine oil."

[0041] The refrigerating machine oil is used together with a refrigerant. That is, another embodiment of the present invention is a working fluid containing a refrigerating machine oil and a refrigerant.

[0042] The refrigerant preferably contains a hydrocarbon. The hydrocarbon is preferably a hydrocarbon having 2 to 4 carbon atoms. The hydrocarbon is, for example, at least one selected from the group consisting of ethylene, ethane, propane (R290), propylene, cyclopropane, normal butane, isobutane (R600a), cyclobutane, and methylcyclopropane, preferably propane (R290) or isobutane (R600a), more preferably propane (R290).

[0043] The refrigerant may consist solely of hydrocarbons, or may further contain other refrigerants in addition to hydrocarbons. The hydrocarbon content may be 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more based on the total amount of the refrigerant. Examples of such other refrigerants include saturated fluorohydrocarbons (HFCs) such as R32, R134a, R125, R143a, and R152a, unsaturated fluorohydrocarbons (HFOs) such as R1234yf and R1234ze, fluorinated ethers such as perfluoroethers, bis(trifluoromethyl)sulfide, trifluoroiodomethane, ammonia (R717), and carbon dioxide (R744).

[0044] The content of the refrigerating machine oil in the working fluid may be 1 part by mass or more or 2 parts by mass or more, and may be 500 parts by mass or less or 400 parts by mass or less, per 100 parts by mass of the refrigerant. [Example]

[0045] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0046] Esters of trimethylolpropane and C14 to C20 fatty acids having the fatty acid compositions shown in Table 1 were used as base oils 1 to 4. The contents of diesters and triesters in each ester (base oil) measured by the above procedure are shown in Table 1.

[0047] (Stability evaluation) Stability evaluation was performed in accordance with JIS K2211-09 (autoclave test). Specifically, 30 g of base oils 1 to 4, each adjusted to a water content of less than 10 ppm or 1000 ppm, were weighed into an autoclave, and catalysts (iron, copper, or aluminum wire, each 1.6 mm outer diameter x 50 mm length) and 30 g of R290 refrigerant were added. The stability test was then performed by heating at 175°C for 168 hours. The peroxide value of the refrigerating machine oil after the stability test was measured in accordance with JPI-5S-72. Table 1 shows the peroxide value after the stability test for the cases with a water content of less than 10 ppm or 1000 ppm. If the peroxide value can be suppressed to 200 mg / kg or less without additives, stability is easily maintained.

[0048] [Table 1]

[0049] As can be seen from Table 1, when the water content in the refrigeration oil was removed as much as possible (water content less than 10 ppm by mass), the peroxide values ​​of all of base oils 1 to 4 were kept below 200 mg / kg. On the other hand, when water was mixed into the refrigeration oil (water content 1000 ppm), the peroxide values ​​of base oils 1 to 3 were kept below 200 mg / kg, while the peroxide value of base oil 4 exceeded 200 mg / kg.

[0050] For base oils 1 to 3 in Examples 1 to 3, an antioxidant (2,6-di-tert-butyl-4-methylphenol), an acid scavenger (glycidyl neodecanoate), and an antiwear agent (tricresyl phosphate) were added to prepare lubricating oils (refrigerating machine oils) in Examples 4 to 6 having the compositions shown in Table 2. The stability of each of the obtained lubricating oils was evaluated in the same manner as above. The results are shown in Table 2.

[0051] [Table 2]

[0052] As can be seen from Table 2, lubricating oils (refrigerating machine oils) containing additives in addition to base oils 1 to 3 have excellent peroxide suppression effects even when water is mixed in, and therefore are easy to maintain stability.

Claims

1. A lubricating base oil containing an ester of a trihydric alcohol and a fatty acid having 14 to 20 carbon atoms, the esters include diesters and triesters; the content of the triester is 93 mol% or less based on the total amount of the diester and the triester, A lubricating base oil used with hydrocarbon-containing refrigerants.

2. 2. The lubricating base oil according to claim 1, wherein the fatty acid having 14 to 20 carbon atoms comprises oleic acid.

3. 3. The lubricating base oil according to claim 2, wherein the content of the oleic acid is 80 mass% or more based on the total amount of the fatty acids having 14 to 20 carbon atoms.

4. 4. The lubricating base oil according to claim 2, wherein the fatty acid having 14 to 20 carbon atoms further comprises a saturated fatty acid having 14 to 20 carbon atoms.

5. The lubricating base oil according to any one of claims 2 to 4, wherein the fatty acids having 14 to 20 carbon atoms further comprise an unsaturated fatty acid having 14 to 20 carbon atoms other than oleic acid.

6. Contains the lubricating base oil according to any one of claims 1 to 5, A lubricating oil used with hydrocarbon-containing refrigerants.

7. 7. The lubricating oil of claim 6, further comprising an antioxidant.

8. 8. The lubricating oil of claim 6 or 7, further comprising an acid scavenger.

9. The lubricating oil according to any one of claims 6 to 8, further comprising an anti-wear agent.

10. The lubricating oil according to any one of claims 6 to 9, wherein the content of the lubricating base oil is 80 mass% or more based on the total amount of the lubricating oil.

11. The lubricating oil according to any one of claims 6 to 10, a refrigerant comprising a hydrocarbon; A working fluid comprising:

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