Base oils for refrigeration oils, refrigeration oils, and working fluid compositions for refrigerators

Abstract

A refrigerant oil base oil in which the content of cyclic saturated components in saturated components is 40 mass% or less, the content of acyclic saturated components is 60 mass% or more, and the density at 15°C is 0.805 g / cm 3 Hereinafter, the normal paraffin content is 50 mass% or less.

Description

Technical Field

[0001] This invention relates to base oils for refrigeration oils, refrigeration oils, and working fluid compositions for refrigeration machines. Background Technology

[0002] In refrigeration equipment, there is an increasing need to replace refrigerants with relatively high Global Warming Potential (GWP) values ​​with low-GWP refrigerants, such as those below 150. Examples of low-GWP refrigerants include carbon dioxide (R744) and hydrocarbon refrigerants.

[0003] On the other hand, energy efficiency is also required for refrigeration equipment. Generally, the lower the viscosity of refrigeration oil, the lower the stirring resistance and friction of sliding parts, thus lowering the viscosity of refrigeration oil leads to energy savings in refrigeration equipment. For example, Patent Document 1 discloses refrigeration oils with a VG3 or higher and a VG8 or lower. In addition, Patent Document 2 discloses refrigeration oils containing a mixed base oil composed of low-viscosity base oil and high-viscosity base oil.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2006 / 062245

[0007] Patent Document 2: International Publication No. 2007 / 105452 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] However, if the viscosity of the refrigeration oil decreases, it becomes difficult to maintain the oil film in the sliding parts, thus raising concerns about, for example, an increase in the coefficient of friction. On the other hand, if a reduction in the coefficient of friction is desired, the pour point of the refrigeration oil increases, which is sometimes undesirable from a flowability point of view. Therefore, an objective of this invention is to provide a base oil and refrigeration oil for refrigeration oil that can reduce the coefficient of friction and suppress the rise in pour point.

[0010] Solution for solving the problem

[0011] According to the research of the inventors, it has been found that by setting the cyclic and non-cyclic saturated components, the density at 15°C, and the n-alkane content in the base oil for refrigeration oil within a specified range, it is possible to balance the reduction of the coefficient of friction and the suppression of the rise in pour point (in other words, it is possible to suppress excessive rise in the coefficient of friction or excessive rise in the pour point).

[0012] The present invention includes the following solutions.

[0013] [1] A base oil for refrigeration equipment, wherein the cyclic saturated component accounts for less than 40% by mass, the non-cyclic saturated component accounts for more than 60% by mass, and the density at 15°C is 0.805 g / cm³. 3 The following are examples of n-alkane content below 50% by mass.

[0014] [2] The base oil for refrigeration oil according to [1], wherein the content of hydrocarbons with carbon number 12 to 16 in the base oil is 80% by mass or more.

[0015] [3] The base oil for refrigeration oil according to [1] or [2] contains a hydrocarbon base oil with a n-alkane content of less than 5% by mass.

[0016] [4] The base oil for refrigeration oil according to [3] contains, in addition to the hydrocarbon base oil, a second hydrocarbon base oil with a n-alkane content of 5% by mass or more.

[0017] [5] The base oil for refrigeration oil according to [3] or [4], wherein the initial boiling point of the hydrocarbon base oil is above 140°C and the 90% distillation temperature is below 270°C.

[0018] [6] A refrigeration oil containing any one of the base oils for refrigeration oils described in any one of [1] to [5].

[0019] [7] The refrigeration oil according to [6] also contains phosphorus-containing anti-wear agents.

[0020] [8] The refrigeration oil according to [6] or [7] also contains polymer additives.

[0021] [9] The refrigeration oil according to any one of [6] to [8], wherein the residual carbon content of 10% of the residual oil of the refrigeration oil is 0.02% by mass or more.

[0022]

[10] The refrigeration oil according to any one of [6] to [9], wherein 90% of the refrigeration oil has a distillation temperature of 270°C or less.

[0023]

[11] A working fluid composition for a refrigeration machine, comprising any one of [6] to

[10] refrigeration oil and refrigerant.

[0024]

[12] The working fluid composition for a refrigeration machine according to

[11] , wherein the refrigerant comprises a hydrocarbon.

[0025] The effects of the invention

[0026] According to one aspect of the present invention, a base oil and a refrigeration oil for refrigeration oil can be provided that can reduce the coefficient of friction and suppress pour point rise. In one aspect of the present invention, this effect can also be achieved when the base oil and the refrigeration oil for refrigeration oil are of low viscosity. Detailed Implementation

[0027] The embodiments of the present invention will be described in detail below. One embodiment of the present invention is a base oil for refrigeration oil, wherein the cyclic saturated component accounts for less than 40% by mass, the non-cyclic saturated component accounts for more than 60% by mass, and the density at 15°C is 0.805 g / cm³. 3 The following are examples of n-alkane content below 50% by mass.

[0028] Regarding the content of cyclic saturated components (cycloalkanes of 1 to 6 rings (hereinafter also referred to as "cycloalkanes")) in the saturated components of the base oil, from the viewpoint of further reducing the coefficient of friction, the content of cyclic saturated components in the base oil is preferably 30% or less by mass, 20% or less by mass, 10% or less by mass, 5% or less by mass, or 3% or less by mass, or 0% or more by mass, based on the total amount of saturated components in the base oil.

[0029] Regarding the content of non-cyclic saturated components (alkanes (hereinafter also referred to as "alkanes")) in the saturated components of the base oil, from the viewpoint of further reducing the coefficient of friction, the total amount of saturated components in the base oil is used as a benchmark, preferably 70% or more by mass, 80% or more by mass, 90% or more by mass, 95% or more by mass, or 97% or more by mass, or 100% or less by mass.

[0030] The preferred density of the base oil at 15°C is 0.802 g / cm³. 3 Below, 0.800g / cm 3 Below, 0.790g / cm 3 The following, or possibly 0.780 g / cm 3 The preferred value is 0.76 g / cm³. 3 The above, or 0.77 g / cm³, is also possible. 3 Above or 0.775 g / cm 3 That's all. The density in this specification refers to the density at 15°C measured according to the "vibration method" as described in JIS K2249-1:2011.

[0031] From the viewpoint of suppressing pour point rise, the n-alkane content of the base oil is preferably 45% or less, 40% or less, 35% or less, 30% or less, 20% or less, 10% or less, 5% or less, or 2% or less, or 0% or more, based on the total amount of base oil.

[0032] From the viewpoint of further reducing the coefficient of friction, the content of hydrocarbons with 12 to 16 carbons in the base oil is preferably 80% or more by mass, 85% or more by mass, 90% or more by mass, or 95% or more by mass, or 100% or less by mass, based on the total amount of base oil.

[0033] From the viewpoint of further reducing the coefficient of friction, the content of hydrocarbons with 13 to 18 carbons in the base oil is preferably 80% or more by mass, 85% or more by mass, 90% or more by mass, or 95% or more by mass, or 100% or less by mass, based on the total amount of base oil.

[0034] From the viewpoint of the low-temperature characteristics of refrigeration oil, the content of n-alkanes with a carbon number of 18 or more in the base oil for refrigeration oil is preferably 10% by mass or less, 5% by mass or less, 2% by mass or less, 1% by mass or less, or may be 0% by mass.

[0035] The pour point of the base oil is preferably below -10°C, more preferably below -20°C, and can be below -30°C, below -40°C, or above -80°C. The pour point in this specification refers to the pour point measured according to JIS K2269:1987.

[0036] In one embodiment, the base oil for refrigeration oil comprises a specified hydrocarbon base oil. This hydrocarbon base oil has the following characteristics: the cyclic saturated component accounts for less than 30% by mass, the non-cyclic saturated component accounts for more than 70% by mass, and the density at 15°C is 0.805 g / cm³. 3 the following.

[0037] From the viewpoint of further reducing the coefficient of friction, the content of cyclic saturated components in the saturated components of the hydrocarbon base oil is 30% by mass or less, preferably 20% by mass or less, 10% by mass or less, 5% by mass or less, or 3% by mass or more, based on the total amount of saturated components in the hydrocarbon base oil.

[0038] From the viewpoint of further reducing the coefficient of friction, the content of non-cyclic saturated components in the saturated components of the hydrocarbon base oil is 70% by mass or more, preferably 80% by mass or more, 90% by mass or more, 95% by mass or more, or 97% by mass or more, or 100% by mass or less.

[0039] The density of the hydrocarbon base oil at 15°C is 0.805 g / cm³. 3 The preferred value is 0.802 g / cm³. 3 Below, 0.800g / cm 3 Below, 0.790g / cm 3 The following, or possibly 0.780 g / cm 3 The preferred value is 0.76 g / cm³. 3 Above, 0.77g / cm 3 The above, or possibly 0.775 g / cm³ 3 above.

[0040] The n-alkane content of the hydrocarbon base oil can be less than 50% by mass. From the viewpoint of further reducing the coefficient of friction, based on the total amount of hydrocarbon base oil, it is preferably less than 40% by mass, less than 35% by mass, or less than 30% by mass. From the viewpoint of suppressing the rise in pour point, it is more preferably less than 20% by mass, less than 10% by mass, less than 5% by mass, less than 5% by mass, or less than 2% by mass, or 0% by mass or more than 0% by mass.

[0041] There is no particular limitation on the content of aromatic hydrocarbons in the hydrocarbon base oil. From the viewpoint of further reducing the coefficient of friction, it is preferred to be less than 10% by mass, less than 5% by mass, less than 2% by mass, or less than 1% by mass, or 0% by mass or more than 0% by mass.

[0042] From the viewpoint of further reducing the coefficient of friction, the content of hydrocarbons with 12 to 16 carbons in the hydrocarbon base oil is preferably 80% or more by mass, 85% or more by mass, 90% or more by mass, or 95% or more by mass, or 100% or less by mass, based on the total amount of hydrocarbon base oil.

[0043] From the viewpoint of further reducing the coefficient of friction, the content of hydrocarbons with 13 to 18 carbons in the hydrocarbon base oil is preferably 80% or more by mass, 85% or more by mass, 90% or more by mass, or 95% or more by mass, or 100% or less by mass, based on the total amount of hydrocarbon base oil.

[0044] For the content of hydrocarbons with fewer than 12 carbon atoms in the hydrocarbon base oil, from the viewpoint of flash point and the viewpoint of suppressing the emission of volatile organic compounds, the content can be less than 5% by mass, preferably less than 1% by mass, based on the total amount of hydrocarbon base oil.

[0045] It should be noted that in this specification, the content of cyclic saturated components (cycloalkanes), acyclic saturated components (alkanes), n-alkanes, hydrocarbons with 12-16 carbon atoms, hydrocarbons with 13-18 carbon atoms, and hydrocarbons with fewer than 12 carbon atoms in the refrigeration oil base oil and hydrocarbon base oil is separated into saturated hydrocarbon oil and aromatic hydrocarbon oil by silica gel column chromatography. The saturated hydrocarbon oil and aromatic hydrocarbon oil are then determined by hydrocarbon type analysis using GC-TOFMS, a mass spectrometry method combining gas chromatography and FI ionization. An example of the analytical conditions is shown below.

[0046] (Gas Chromatography Conditions)

[0047] Column: Phenomenex ZB-1MS

[0048] Injection temperature: 350℃

[0049] Heating conditions: 50℃~350℃ (heating rate: 5℃ / minute)

[0050] Carrier gas: Helium

[0051] Injection method: Injection volume for split sample: 1 μL (10% toluene solution)

[0052] (MS conditions)

[0053] Counter electrode voltage: -10kV

[0054] Ionization method: FI (electro-induced ionization)

[0055] Ion source temperature: room temperature

[0056] Mass number measurement range: m / z 35~500

[0057] In the mass spectra obtained from GC-TOFMS analysis, the carbon number can be determined according to its type (C). n H 2n+z (Here, n represents an integer, and z represents an even number from -18 to 2.) The percentage of different ionic strengths (%) can be determined from the percentage of the total ionic strength. In this specification, the content (mass%) of each component is calculated as approximately the same as the ionic strength (%) of each component. It should be noted that if the amount of aromatic hydrocarbons in the sample is less than 1% by mass, chromatographic separation can be omitted for type analysis. In this case, the content of each component is calculated as the total amount of saturated hydrocarbons.

[0058] It should be noted that for the content of n-alkanes, hydrocarbons with 12-16 carbons, hydrocarbons with 13-18 carbons, and hydrocarbons with fewer than 12 carbons in hydrocarbon base oils, for example, by gas chromatography (GC) based on the following conditions, the peak area % of n-alkanes and non-n-alkanes according to each carbon number is considered to be approximately the same as the mass % and then calculated / statistically accumulated separately. If equivalent results can be obtained, this method can be used. An example of analytical conditions is shown below.

[0059] (Gas Chromatography Conditions)

[0060] Column: Non-polar liquid-phase column (length 30m, inner diameter 0.25mmφ, liquid phase thickness 0.1μm)

[0061] Injection temperature: 350℃

[0062] Detector: FID 360℃

[0063] Heating conditions: 50℃~350℃ (heating rate: 6℃ / minute)

[0064] Carrier gas: Helium

[0065] Injection method: Split sample injection volume: 1 μL (10% toluene solution)

[0066] The initial boiling point of hydrocarbon base oil can be above 140°C, and the 90% distillation temperature of hydrocarbon base oil can be below 270°C. The initial boiling point and 90% distillation temperature of hydrocarbon base oil, as well as other distillation properties described below, refer to distillation properties measured by atmospheric distillation test method (according to the atmospheric method described in JIS K2254:2018).

[0067] From the viewpoint of further reducing the coefficient of friction, the 90% distillation temperature (T90) of the hydrocarbon base oil is preferably below 267°C, below 266°C, below 265°C, below 264°C, below 263°C, below 262°C, or below 261°C. For example, it can also be above 220°C, above 230°C, above 240°C, above 245°C, or above 250°C.

[0068] From the viewpoint of further reducing the coefficient of friction, the initial boiling point (IBP) of the hydrocarbon base oil can preferably be above 140°C, above 170°C, above 190°C, above 200°C, above 210°C, above 220°C, above 230°C, or above 240°C, or below 260°C, below 255°C, or below 250°C.

[0069] From the viewpoint of further reducing the coefficient of friction, the 10% distillation temperature (T10) of the hydrocarbon base oil can preferably be above 200°C, above 210°C, above 220°C, above 230°C, or above 240°C, or below 260°C, below 255°C, or below 250°C.

[0070] From the viewpoint of further reducing the coefficient of friction, the 50% distillation temperature (T50) of the hydrocarbon base oil can preferably be above 210°C, above 220°C, above 230°C, above 240°C, or above 245°C, or below 265°C, below 260°C, below 255°C, or below 250°C.

[0071] For the distillation endpoint (EP) of hydrocarbon base oil, from the viewpoint of further reducing the coefficient of friction, it is preferably above 250°C or above 260°C, or below 320°C, below 300°C, below 280°C or below 270°C.

[0072] From the perspective of further reducing the coefficient of friction, the difference between T90 and T10 of hydrocarbon base oil (T90-T10) can preferably be above 5°C or above 6°C, or below 40°C, below 20°C, below 15°C, or below 10°C.

[0073] The total distillate of the hydrocarbon base oil can be, for example, 95% by volume or more, 96% by volume or more, 97% by volume or more, 98% by volume or more, or 99% by volume or more, or less than 99.9% by volume. The residual oil content of the hydrocarbon base oil can be, for example, 0.1% by volume or more, or less than 6% by volume, less than 4% by volume, less than 3% by volume, less than 2% by volume, or less than 1% by volume. The weight loss of the hydrocarbon base oil can be, for example, less than 1% by volume, less than 0.5% by volume, less than 0.1% by volume, or 0% by volume.

[0074] The kinematic viscosity of hydrocarbon base oil at 40°C can be, for example, 1.0 mm. 2 / s or more, 1.5mm 2 / s or higher, or 2.0mm 2 / s or higher, or 6.0mm 2 / s or less, 5.0mm 2 / s or less, 4.5mm 2 / s or less, 4.0mm 2 / s or less, 3.5mm 2 / s or less, or 3.0mm 2 / s or less. The kinematic viscosity in this specification refers to the kinematic viscosity measured according to JIS K2283:2000.

[0075] The kinematic viscosity of hydrocarbon base oils at 100°C can be, for example, 0.5 mm. 2 / s or more, 0.7mm 2 / s or higher, or 0.8mm 2 / s or higher, or 2.0mm. 2 / s or less, 1.5mm 2 / s or less, 1.4mm 2 / s or less, 1.3mm 2 / s or less, 1.2mm 2 / s or less, 1.1mm 2 / s or less or 1.0mm 2 / s or less.

[0076] The flash point of hydrocarbon base oils can be, for example, above 70°C, above 80°C, above 100°C, or above 110°C, or below 150°C, below 140°C, or below 130°C. Increasing the initial boiling point of the hydrocarbon base oil can raise the flash point and further improve safety. The flash point in this specification refers to the flash point measured according to the Cleveland open cup (COC) method as described in JIS K2265-4:2007.

[0077] The distillation properties, kinematic viscosity, and flash point of the hydrocarbon base oils mentioned above can be understood as the distillation properties, kinematic viscosity, and flash point of the base oils used in refrigeration oils, respectively.

[0078] The pour point of hydrocarbon base oil can be, for example, below -10°C, below -20°C, below -30°C, or below -40°C, or above -80°C.

[0079] Examples of hydrocarbon base oils possessing the aforementioned properties include mineral oil-based hydrocarbon base oils, synthetic hydrocarbon base oils, and blends thereof. Mineral oil-based hydrocarbon base oils include refined alkane or cycloalkane mineral oils obtained by refining crude oil or its distillation residues using a suitable combination of conventional petroleum refining processes (solvent consumption, solvent extraction, hydrocracking, solvent dewaxing, contact dewaxing, hydrogenation refining, sulfuric acid washing, clay treatment, distillation, etc.). Synthetic hydrocarbon base oils include, for example, polyalphaolefins or their hydrides, isoalkanes, alkylbenzenes, alkylnaphthalenes, etc. These hydrocarbon base oils can be used individually or in combination of two or more.

[0080] From the viewpoint that the aforementioned properties are readily obtained, hydrocarbon base oils are preferably mineral oil-based hydrocarbon base oils. More specifically, for example, by hydrogenating and refining kerosene / light oil fractions obtained from atmospheric distillation of crude oil, or decomposed light oil fractions obtained from decomposing atmospheric residue oil or residue oil feedstock containing vacuum residue oil of crude oil, in a manner that results in the aforementioned distillation properties, particularly hydrocarbons with carbon numbers of 12 to 16 or 13 to 18, as the main components (e.g., 80% by mass or more, particularly 90% by mass or more), hydrocarbon base oils having the aforementioned properties can be readily obtained.

[0081] Furthermore, from the viewpoint that the aforementioned properties are readily obtained, isoparaffinic base oils are more preferably preferred. For example, isoparaffinic base oils can also be obtained by combining and refining polymers containing n-alkanes (obtained through dewaxing in petroleum refining processes, Fischer-Tropsch synthesis, etc.) or olefins such as ethylene, propylene, butene, and diisobutene through suitable combinations of hydrocracking, hydrogenation isomerization, hydrogenation dewaxing, hydrogenation refining, distillation, etc.

[0082] Base oils for refrigeration oils may also contain hydrocarbon base oils (hereinafter also referred to as "hydrocarbon base oil A") with the above-mentioned properties as a main component. Base oils for refrigeration oils may contain only hydrocarbon base oil A, or may contain other base oils in addition to hydrocarbon base oil A. Based on the total amount of base oil for refrigeration oils, the content of hydrocarbon base oil A may be 50% by mass or more, 70% by mass or more, 90% by mass or more, or 95% by mass or more. Based on the total amount of refrigeration oil, the content of hydrocarbon base oil A may be 50% by mass or more, 70% by mass or more, 90% by mass or more, or 95% by mass or more.

[0083] In one embodiment, when the refrigeration oil base oil contains a hydrocarbon base oil (first hydrocarbon base oil) with an alkane content of less than 5% by mass as hydrocarbon base oil A, the refrigeration oil base oil may further contain a second hydrocarbon base oil with a n-alkane content of 5% by mass or more in addition to the first hydrocarbon base oil. This results in a synergistic low-friction effect based on the combined use of the first and second hydrocarbon base oils. In this case, the n-alkane content of the first hydrocarbon base oil may be less than 2% by mass, or 0% by mass or more, and the n-alkane content of the second hydrocarbon base oil may be 10% by mass or more, 20% by mass or more, 30% by mass or more, 50% by mass or more, 80% by mass or more, or 90% by mass or more.

[0084] From the viewpoint of maintaining a lower pour point and reducing the coefficient of friction, the second hydrocarbon base oil is preferred to be a hydrocarbon base oil that satisfies the above-mentioned range of properties (distillation properties, hydrocarbons with 12 to 16 carbons, hydrocarbons with 13 to 18 carbons, kinematic viscosity (40°C, 100°C), flash point, density, aromatic composition) with respect to hydrocarbon base oil A, compared to those with a single n-alkane as the main component.

[0085] When using a second hydrocarbon base oil, the content of the second hydrocarbon base oil, based on the total amount of base oil used in refrigeration oils, is preferably 50% by mass or less, 40% by mass or less, 35% by mass or less, 0% by mass or more, or 10% by mass or more, 15% by mass or more, 20% by mass or more, or 25% by mass or more. In another embodiment, the content of the second hydrocarbon base oil may also be 30% by mass or less, 25% by mass or less, 20% by mass or less, or 15% by mass or less.

[0086] Another embodiment of the present invention is a refrigeration oil containing the above-mentioned refrigeration oil base oil. The refrigeration oil may also contain a refrigeration oil base oil as a main component. Based on the total amount of the refrigeration oil, the content of the refrigeration oil base oil may be 50% by mass or more, 70% by mass or more, 90% by mass or more, or 95% by mass or more.

[0087] Refrigeration oil may contain hydrocarbon base oil A, hydrocarbon base oil 1 and hydrocarbon base oil 2, hydrocarbon base oil other than hydrocarbon base oil A, hydrocarbon base oil 1 and hydrocarbon base oil 2 (hydrocarbon base oil 3), or oxygenated base oil.

[0088] As a third hydrocarbon base oil, mineral oil-based hydrocarbon oils, synthetic hydrocarbon oils, or mixtures thereof can be used, for example. Examples of mineral oil-based hydrocarbon oils include alkane-based mineral oils and naphthenic mineral oils obtained by refining lubricating oil fractions from atmospheric and vacuum distillation of crude oils such as alkane and naphthenic series using methods such as solvent consumption, solvent refining, hydrogen refining, hydrocracking, solvent dewaxing, hydrogen dewaxing, clay treatment, and sulfuric acid washing. These refining methods can be used individually or in combination of two or more.

[0089] As a mineral oil-based hydrocarbon oil, a residual oil-based hydrocarbon base oil is also preferred. Examples of residual oil-based hydrocarbon base oils include, for instance, atmospheric distillation residues of crude oil, vacuum distillation residues of the atmospheric distillation residues, deasphalted oils from these residues using propane or the like, solvent-extracted oils from deasphalted oils using furfural or the like, solvent-extracted raffinate oils from deasphalted oils, and refined oils obtained by refining these oils through hydrocracking, hydrogenation refining, solvent dewaxing, or hydrogenation dewaxing. Among these, refined oils obtained by hydrogenation refining, solvent dewaxing, or hydrogenation dewaxing of the solvent-extracted raffinate oil from vacuum distillation residue oils are particularly preferred.

[0090] Synthetic hydrocarbon oils include alkylbenzenes, alkylnaphthalenes, polyalphaolefins (PAO), polybutene, and ethylene-alpha olefin copolymers.

[0091] The kinematic viscosity of the third hydrocarbon base oil at 40°C can be, for example, 6 mm. 2 From the perspective of more effectively reducing the coefficient of friction, a value of 20 mm is also possible, with a speed of 0.05 or higher. 2 / s or higher, 50mm 2 / s or higher, 80mm 2 / s, or 90mm 2 / s or higher. There is no specific upper limit to the kinematic viscosity of the third hydrocarbon base oil at 40°C; for example, it can be 1000 mm³ / s. 2 / s or less, preferably 500mm 2 / s or less.

[0092] The kinematic viscosity of residual hydrocarbon base oil at 40°C can be, for example, 100 mm. 2 / s or higher, 200mm 2 / s or higher, 300mm 2 / s or higher, 400mm 2 / s or higher, or 450mm 2 / s or higher, or 1000mm 2 / s or less, 800mm 2 / s or less, 600mm 2 / s or less, or 500mm 2 / s or less.

[0093] The kinematic viscosity of residual hydrocarbon base oil at 100°C can be, for example, 10 mm. 2 / s or higher, 20mm 2 / s or higher, or 30mm 2 / s or higher, or 100mm 2 / s or less, 50mm 2 / s or less, or 40mm 2 / s or less.

[0094] The viscosity index of residual hydrocarbon base oil can be, for example, above 0, above 50, or above 80, or below 300, below 140, or below 100. The viscosity index in this specification refers to the viscosity index measured according to JIS K2283:2000.

[0095] The flash point of residual hydrocarbon base oil can be, for example, above 200°C, above 250°C, or above 300°C, or below 500°C, below 450°C, or below 400°C.

[0096] There is no particular limitation on the residual carbon content of the residual hydrocarbon base oil. From the viewpoint of further improving wear resistance, it is preferable to have a content of 0.1% or more by mass, 0.2% or more by mass, or 0.3% or more by mass, or preferably less than 10% by mass, less than 5% by mass, less than 1% by mass, or less than 0.8% by mass.

[0097] From the perspective of the color of refrigeration oil, the ASTM color of residual hydrocarbon base oil can be below 6.0, below 4.0, or below 3.0, or it can be above 0.5, or above 0.5 or above 1.0.

[0098] When using a third hydrocarbon base oil, the content of the third hydrocarbon base oil can be based on the total amount of base oil contained in the refrigeration oil. It can be more than 0.5% by mass, more than 1% by mass, more than 2% by mass, or more than 3% by mass, or less than 50% by mass, less than 30% by mass, less than 10% by mass, or less than 5% by mass.

[0099] Examples of oxygenated base oils include esters, ethers, carbonates, ketones, organosilicones, and polysiloxanes. It should be noted that the term "ester" here may not include the polymers described later. Examples of esters include monoesters, polyol esters, aromatic esters, diesters, complex esters, carbonates, and mixtures thereof. Among these, monoesters of monoaliphatic alcohols and monobasic fatty acids are preferred; mixtures of these monoesters with polyol esters of 2- to 6-hydrone alcohols and monobasic fatty acids are desirable, depending on the specific requirements.

[0100] Examples of monoaliphatic alcohols constituting this ester include monoaliphatic alcohols having 1 to 20 carbon atoms, preferably 4 to 18, and more preferably 4 to 12. Examples of monoaliphatic fatty acids constituting this ester include monoaliphatic fatty acids having 1 to 20 carbon atoms, preferably 4 to 18, and more preferably 4 to 12. Examples of 2 to 6-hydroxyols constituting this ester include neopentyl glycol, trimethylolpropane, pentaerythritol, and dipentaerythritol. Examples of ethers include polyethylene ether, polyalkylene glycol, polyphenylene ether, perfluoroether, and mixtures thereof.

[0101] For refrigeration oils, from the viewpoint of improving wear resistance, it is preferable to further contain anti-wear agents as additives. Examples of anti-wear agents include phosphorus-containing anti-wear agents. Examples of phosphorus-containing anti-wear agents include phosphate esters, thiophosphate esters, acid phosphate esters, amine salts of acid phosphate esters, and chlorinated phosphate esters. The anti-wear agent (preferably a phosphorus-containing anti-wear agent) can be used alone or in combination of two or more. The phosphorus-containing anti-wear agent is preferably selected from one or more of phosphate esters and thiophosphate esters.

[0102] Examples of phosphate esters include tributyl phosphate, tripentyl phosphate, trihexyl phosphate, triheptyl phosphate, trioctyl phosphate, trinonyl phosphate, tridecyl phosphate, tri(undecyl) phosphate, tri(dodecyl) phosphate, tri(tridecyl) phosphate, tri(tetradecyl) phosphate, tri(pentadecanyl) phosphate, tri(hexadecyl) phosphate, tri(heptadecanyl) phosphate, tri(octadecyl) phosphate, trioleenyl phosphate, triphenyl phosphate, tricresyl phosphate, tri(ethylphenyl) phosphate, tri(butylphenyl) phosphate, tri(xylyl) phosphate, toluene diphenyl phosphate, and xylyl diphenyl phosphate. Triphenyl phosphate or tricresyl phosphate is preferred.

[0103] Examples of thiophosphate esters include tributyl thiophosphate, tripentyl thiophosphate, trihexyl thiophosphate, triheptyl thiophosphate, trioctyl thiophosphate, trinonyl thiophosphate, tridecyl thiophosphate, tri(undecyl) thiophosphate, tri(dodecyl) thiophosphate, tri(tetradecyl) thiophosphate, tri(pentadecanyl) thiophosphate, tri(hexadecyl) thiophosphate, tri(heptadecanyl) thiophosphate, tri(octadecyl) thiophosphate, trioleenyl thiophosphate, triphenyl thiophosphate, trimethyl thiophosphate, tri(xylyl) thiophosphate, toluene diphenyl thiophosphate, and xylyl diphenyl thiophosphate. Triphenyl thiophosphate is preferred.

[0104] The content of anti-wear agent (preferably phosphorus-containing anti-wear agent) can be, for example, based on the total amount of refrigeration oil, 0.1% or more by mass, 0.5% or more by mass, or 1% or more by mass, or 5% or more by mass, less than 4% by mass, or less than 3% by mass.

[0105] Refrigeration oils may further contain polymer additives. These polymer additives may, for example, contain a high molecular weight component with a kinematic viscosity at 40°C higher than that of the base oil for refrigeration oil, or a polymer containing unsaturated carboxylic acid esters as monomer units. This polymer can be obtained by polymerizing one or more monomers comprising unsaturated carboxylic acid esters that are esters of unsaturated carboxylic acids and alcohols.

[0106] There are no particular restrictions on the polymer as long as it contains unsaturated carboxylic acid esters as monomer units, and it can further contain other monomers (monomers that can copolymerize with unsaturated carboxylic acid esters). That is, the polymer can be a homopolymer of one type of unsaturated carboxylic acid ester, a copolymer of two or more types of unsaturated carboxylic acid esters, or a copolymer of one or more types of unsaturated carboxylic acid esters with one or more other monomers.

[0107] The unsaturated carboxylic acids constituting unsaturated carboxylic acid esters have at least one polymerizable unsaturated bond (polymerizable carbon-carbon double bond) and at least one carboxyl group. For example, they can be unsaturated monocarboxylic acids with one polymerizable unsaturated bond and one carboxyl group, or unsaturated dicarboxylic acids with one polymerizable unsaturated bond and two carboxyl groups. Examples of unsaturated monocarboxylic acids include acrylic acid, methacrylic acid (hereinafter also collectively referred to as "(meth)acrylic acid"), and crotonic acid. Examples of unsaturated dicarboxylic acids include maleic acid, fumaric acid, citraconic acid, succinic acid, and itaconic acid.

[0108] The alcohols constituting the unsaturated carboxylic acid esters can be, for example, alcohols with 1 to 40 carbon atoms, preferably alcohols with 1 to 18 carbon atoms, and more preferably alcohols with 1 to 8 carbon atoms. These alcohols can be straight-chain or branched-chain. The alcohols can include alcohols with 1 to 18 carbon atoms and alcohols with 20 to 40 carbon atoms. These alcohols can also be aliphatic alcohols.

[0109] Alcohols can be either monohydric or polyhydric. Examples of such alcohols include methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, heptadecanol, and octadecanol (these can be linear or branched).

[0110] The alcohol preferably comprises at least one type selected from straight-chain aliphatic monohydric alcohols having 1 to 18 carbon atoms and branched aliphatic monohydric alcohols having 4 to 40 carbon atoms. In other words, the unsaturated carboxylic acid ester preferably has at least one alkyl group selected from straight-chain alkyl groups having 1 to 18 carbon atoms and branched alkyl groups having 4 to 40 carbon atoms.

[0111] When the unsaturated carboxylic acid ester is a (meth)acrylate, the (meth)acrylate preferably contains at least one type selected from (meth)acrylates having a straight-chain alkyl group having 1 to 18 carbon atoms, more preferably it contains at least one type selected from (meth)acrylates having a straight-chain alkyl group having 1 to 18 carbon atoms and at least one type selected from (meth)acrylates having a branched alkyl group at the 2-position having 4 or more carbon atoms and less than 20 carbon atoms or having 20 or more carbon atoms and less than 40 carbon atoms.

[0112] The 2-position branched alkyl group having 4 or more carbon atoms and less than 20 carbon atoms is an alkyl group represented by the following formula (1).

[0113]

[0114] In equation (1), x and y are each independent integers greater than or equal to 0, and x+y is an integer less than 16.

[0115] In the above formula (1), the branched alkyl group at the 2-position with 20 or more carbon atoms and 40 or less has x and y each being an integer of 0 or more independently, and x+y being an integer of 16 or more and 36 or less. In particular, it is preferred that x is an integer of 5 to 18 and y is an integer of 3 to 18.

[0116] When the unsaturated carboxylic acid ester is an unsaturated dicarboxylic acid ester, the unsaturated dicarboxylic acid ester preferably includes at least one type selected from unsaturated dicarboxylic acid esters having a straight-chain alkyl group having 4 to 10 carbon atoms.

[0117] There are no particular limitations on the monomers other than unsaturated carboxylic acid esters, and examples include unsaturated carboxylic acids or their anhydrides, and unsaturated hydrocarbon compounds having polymerizable unsaturated bonds, which are examples of unsaturated carboxylic acids constituting the aforementioned unsaturated carboxylic acid esters. The unsaturated hydrocarbon can be, for example, an unsaturated hydrocarbon compound having 2 to 20 carbon atoms, and is preferably an α-olefin or styrene having 2 to 20 carbon atoms. Specifically, examples of such α-olefins include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tetracene, 1-tetradecene, 1-pentadecadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecadecene, and 1-eicosene. The α-olefin is preferably an α-olefin having 8 to 12 carbon atoms.

[0118] The polymer is preferably a copolymer of unsaturated carboxylic acid esters (two or more types of unsaturated carboxylic acid esters), or a copolymer of unsaturated carboxylic acid esters (one or more types of unsaturated carboxylic acid esters) and α-olefins (one or more types of α-olefins). The copolymer of unsaturated carboxylic acid esters is preferably a copolymer of (meth)acrylates. The copolymer of unsaturated carboxylic acid esters and α-olefins is preferably at least one selected from copolymers of (meth)acrylates and α-olefins and copolymers of unsaturated dicarboxylic acid esters and α-olefins, more preferably a copolymer of unsaturated dicarboxylic acid esters and α-olefins.

[0119] Preferred examples of unsaturated dicarboxylic acid esters in copolymers of unsaturated dicarboxylic acid esters and α-olefins include monoesters or diesters of unsaturated dicarboxylic acids such as maleic acid, fumaric acid, citraconic acid, mesoconic acid, and itaconic acid, and aliphatic alcohols with 3 to 10 carbon atoms such as propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, and decanol. The aliphatic alcohol with 3 to 10 carbon atoms is preferably a straight-chain aliphatic alcohol with 4 to 10 carbon atoms. The unsaturated dicarboxylic acid ester is preferably a maleic ester. Preferred examples of maleic esters include dimethyl maleate, diethyl maleate, dipropyl maleate, dibutyl maleate, dipentyl maleate, dihexyl maleate, diheptyl maleate, dioctyl maleate, and didecyl maleate.

[0120] When the above polymer is a copolymer, the content of unsaturated carboxylic acid esters is based on all monomer units constituting the copolymer, and can be more than 10 mol%, more than 30 mol%, or more than 50 mol%, or less than 90 mol%, less than 70 mol%, or less than 50 mol%.

[0121] When the polymer is a copolymer of unsaturated carboxylic acid ester and α-olefin, the molar ratio of unsaturated carboxylic acid ester to α-olefin is not particularly limited, but is preferably 1 / 9 or more, more preferably 3 / 7 or more, more preferably 9 / 1, and more preferably 7 / 3 or less.

[0122] The number average molecular weight (Mn) of the polymer is preferably 300 or more, more preferably 1000 or more, and even more preferably 1500 or more. It can be 2000 or more, 3000 or more, or 4000 or more, preferably 500000 or less, more preferably 50000 or less, and even more preferably 30000 or less. It can also be 20000 or less, 15000 or less, or 10000 or less.

[0123] The weight-average molecular weight (Mw) of the polymer is preferably 400 or more, more preferably 1000 or more, further preferably 2000 or more, particularly preferably 3000 or more, and can be 4000 or more, 5000 or more, 6000 or more, 7000 or more, 8000 or more, or 9000 or more, preferably 10,000,000 or less, more preferably 100,000 or less, further preferably 50,000 or less, particularly preferably 30,000 or less, and can also be 20,000 or less.

[0124] The Mw / Mn ratio of the polymer is preferably 1.2 or more, more preferably 1.5 or more, even more preferably 1.7 or more, particularly preferably 2 or more, preferably 5 or less, more preferably 3.5 or less, even more preferably 3 or less, and may also be 2.5 or less.

[0125] It should be noted that the "weight-average molecular weight (Mw)" and "number-average molecular weight (Mn)" in this specification refer to the weight-average molecular weight and number-average molecular weight of polystyrene obtained by gel permeation chromatography (GPC) using a Waters APC XT column and tetrahydrofuran as the mobile phase (standard substance: polystyrene).

[0126] The kinematic viscosity of the polymer at 100°C is preferably 10 mm. 2 / s or higher, more preferably 20mm 2 / s or higher, more preferably 100mm 2 / s or higher, preferably 100000mm 2 / s or less or 10000mm 2 / s or less, more preferably 1000mm 2 / s or less, preferably 800mm 2 Below / s, it can also be 500mm 2 / s or less.

[0127] The kinematic viscosity of the polymer at 40°C is preferably 100 mmHg. 2 / s or higher, more preferably 200mm 2 / s or higher, further preferably 400mm 2 / s or more than 400mm 2 / s, which can be 500mm 2 / s or above or 1000mm 2 / s or higher, preferably 100000mm 2 / s or less, more preferably 20000mm 2 / s or less, preferably 15000mm 2 Below / s, it can also be 10000mm 2 / s or less or 5000mm 2 / s or less.

[0128] The viscosity index of the polymer is preferably 80 or higher, more preferably 140 or higher, and can be 180 or higher or 200 or higher, preferably 400 or lower, more preferably 300 or lower, and can also be 250 or lower. The viscosity index in this specification refers to the viscosity index measured according to JIS K 2283:2000.

[0129] As a polymer, the amount of residual carbon during evaporation and thermal decomposition is preferably within a specified range. The reason for this is not clear, but it is speculated that having a precursor (polymer precursor) with a residual carbon content equivalent to this can further reduce the coefficient of friction in a specified sliding speed range. The residual carbon content of the polymer is, for example, 0.2% by mass or more, preferably 0.5% by mass or more, more preferably 1% by mass or more, further preferably 1.5% by mass or more, and can be 2% by mass or more or 2.5% by mass or more, preferably 10% by mass or less, more preferably 5% by mass or less, further preferably 4% by mass or less, and can also be 3.5% by mass or less. The residual carbon content in this specification refers to the residual carbon content measured by the micro-method according to JIS K 2270-2:2009.

[0130] In addition to polymers, polymer additives may also contain other components besides polymers, such as diluent oils, to improve workability during synthesis and transportation. The aforementioned polymer properties (number-average molecular weight (Mn), weight-average molecular weight (Mw), Mw / Mn, kinematic viscosity at 100°C, kinematic viscosity at 40°C, viscosity index, and residual carbon content) can also be understood as the properties of the polymer additive in its added state to refrigeration oil. Where the polymer additive contains other components besides polymers, the number-average molecular weight (Mn) and weight-average molecular weight (Mw) of the polymer additive refer to values ​​measured excluding those other components.

[0131] When calculating the average molecular weight of polymers in polymer additives or refrigeration oils containing them, a sample obtained by separating / excluding components belonging to other components from the polymer additives or refrigeration oils containing them through methods such as rubber membrane dialysis can be used, and the average molecular weight of the polymer can be calculated by the gel permeation chromatography described above. Alternatively, the average molecular weight of the polymer can be calculated by excluding peaks belonging to other components in the calculation of average molecular weight based on the gel permeation chromatography described above, using polymer additives or refrigeration oils containing them.

[0132] As more specific examples of the polymers (polymer additives) described above, the polymers described in the examples described later can be listed, but the following polymers (polymer additives) can also be listed.

[0133] Polymer Additive A: Copolymer of (meth)acrylate (kinematic viscosity at 100°C: 600 mmHg) 2 / s, Mn of the polymer: 25000, Mw / Mn: 1.4, Residual carbon content: 1.1% by mass)

[0134] Polymer Additive B: Copolymer of (meth)acrylate (kinematic viscosity at 100°C: 370 mmHg) 2 / s, Mn of the polymer: 25900, Mw / Mn: 1.3, Residual carbon content: 1.1% by mass)

[0135] Polymer Additive C: Copolymer of (meth)acrylate (kinematic viscosity at 100°C: 180 mmHg) 2 / s, polymer Mn: 3620, Mw / Mn: 2.0, residual carbon content: 1.3% by mass)

[0136] Polymer Additive D: Copolymer of (meth)acrylate (kinematic viscosity at 100°C: 360 mmHg) 2 / s, Mn of the polymer: 11000, Mw / Mn: 1.6, Residual carbon content: 0.9% by mass)

[0137] Polymer Additive E: Copolymer of (meth)acrylate (kinematic viscosity at 100°C: 380 mmHg) 2 / s, polymer Mn: 22500, Mw / Mn: 1.5, residual carbon content: 0.1% by mass)

[0138] Polymer additive F: Copolymer of maleate and α-olefin (kinematic viscosity at 40°C: 1980 mmHg) 2 kinematic viscosity at 100℃: 200 mm³ / s 2 / s, viscosity index 227, polymer Mn: 4500, Mw / Mn: 2.2, residual carbon content: 3.1% by mass)

[0139] Polymer Additive G: Copolymer of maleate and α-olefin (kinematic viscosity at 40°C: 4100 mmHg) 2 kinematic viscosity at 100℃ / s: 260 mm³ / s 2 / s, viscosity index 190, polymer Mn: 1800, Mw / Mn: 2.7, residual carbon content: 2.8% by mass)

[0140] Polymer additive H: Copolymer of maleate and α-olefin (kinematic viscosity at 40°C: 4300 mmHg) 2 kinematic viscosity at 100℃ / s: 300 mm³ 2 / s, viscosity index 225, polymer Mn: 2000, Mw / Mn: 2.5, residual carbon content: 1.7% by mass)

[0141] Polymer Additive I: Copolymer of maleate and α-olefin (kinematic viscosity at 40°C: 7000 mmHg) 2 kinematic viscosity at 100℃ / s: 500 mm³ 2 / s, viscosity index 230, polymer Mn: 2650, Mw / Mn: 4.0, residual carbon content: 2% by mass)

[0142] Polymer Additive J: Copolymer of maleate and α-olefin (kinematic viscosity at 40°C: 11000 mm⁻¹) 2 kinematic viscosity at 100℃ / s: 700 mm³ 2 / s, viscosity index 250, polymer Mn: 2690, Mw / Mn: 3.1, residual carbon content: 1.5% by mass)

[0143] Polymer additive K: Copolymer of maleate and α-olefin (kinematic viscosity at 40°C: 400 mmHg) 2 kinematic viscosity at 100℃ / s: 40mm 2 / s, viscosity index 160, residual carbon content: 0.8% by mass)

[0144] Polymer additive L: A copolymer of alkyl methacrylates (alkyl methacrylates comprising alkyl methacrylates having straight-chain alkyl groups with 1, 12-16, or 18 carbon atoms, and alkyl methacrylates having branched alkyl groups at the 2-position with 6, 8, or 10 or more carbon atoms but less than 20 carbon atoms as the main components; the copolymer has Mn: 9300, Mw: 16000, and Mw / Mn: 1.7).

[0145] Polymer additive M: A copolymer of dialkyl maleate and α-olefins having 8 to 10 carbon atoms (the dialkyl maleate contains dialkyl maleate with straight-chain alkyl groups having 4, 8 to 10 carbon atoms as the main component; the copolymer has Mn: 8300, Mw: 12800, and Mw / Mn: 1.5).

[0146] Polymer additive N: A copolymer of alkyl methacrylate and α-olefin with 10 carbon atoms (alkyl methacrylate includes alkyl methacrylate with straight-chain alkyl groups having 12 to 15 carbon atoms, and alkyl methacrylate with branched alkyl groups at the 2-position having 6, 8, or 10 or more carbon atoms but less than 20 carbon atoms as the main components; the copolymer has Mn: 6900, Mw: 9900, and Mw / Mn: 1.4).

[0147] Polymer Additive O: A copolymer comprising methyl methacrylate, n-dodecyl methacrylate, n-tridecyl methacrylate, n-tetradecyl methacrylate, n-hexadecyl methacrylate, n-octadecyl methacrylate, and 2-decyl-tetradecyl methacrylate (x=11, y=9) ester as monomer units (Mn=10500, Mw=18000, Mw / Mn=1.7).

[0148] From the viewpoint of further improving the frictional properties of refrigeration oil, the polymer content, based on the total amount of refrigeration oil, is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 0.8% by mass or more. From the viewpoint of suppressing the viscosity of refrigeration oil and achieving a lower coefficient of friction even in areas with high relative sliding speeds, the polymer content is preferably 5% by mass or less, more preferably 2% by mass or less, even more preferably less than 2% by mass, particularly preferably less than 1% by mass, and may also be less than 1% by mass.

[0149] In addition to the components described above, the refrigeration oil of this embodiment may further contain other additives. Examples of additives include antioxidants, acid scavengers, phosphorus-free extreme pressure agents, metal deactivators, wear-resistant agents, pour point depressants, cleaning and dispersing agents, and defoamers. Unless otherwise specified below, the content of these additives, based on the total amount of the refrigeration oil, may be 10% by mass or less or 5% by mass or less.

[0150] Examples of antioxidants include phenolic antioxidants and amine antioxidants. Examples of phenolic antioxidants include 2,6-di-tert-butyl-p-cresol (DBPC), 2,6-di-tert-butylphenol, and 4,4'-methylenebis(2,6-di-tert-butyl-phenol). Examples of amine antioxidants include phenyl-α-naphthylamines and dialkylated diphenylamines. These antioxidants can be used alone or in combination of two or more. The antioxidant content, for example, is 0.01 to 5% by mass, preferably 0.1 to 3% by mass, based on the total amount of refrigeration oil.

[0151] Examples of acid scavengers include epoxy compounds (epoxy-based acid scavengers). Examples of epoxy compounds include glycidyl ether type epoxy compounds, glycidyl ester type epoxy compounds, aryl ethylene oxide compounds, alkyl ethylene oxide compounds, alicyclic ethylene oxide compounds, epoxidized fatty acid monoesters, and epoxidized vegetable oils. These acid scavengers can be used alone or in combination of two or more. The content of the acid scavenger, for example, is 0.01 to 5% by mass, preferably 0.1 to 3% by mass, based on the total amount of refrigeration oil.

[0152] From the perspective of more effectively reducing the coefficient of friction, the kinematic viscosity of refrigeration oil at 40°C can be, for example, 10 mm. 2 Below / s, preferably 6mm 2 / s or less, more preferably 5mm 2 / s or less, preferably 4mm 2 Below / s, it can also be 3.5mm. 2 / s or less, or 3.0mm 2Below / s. There is no particular limitation on the lower limit of the kinematic viscosity of refrigeration oil at 40°C; for example, it can be 1 mm. 2 / s or more or 2mm 2 / s or higher. The kinematic viscosity of the refrigeration oil at 100°C can preferably be 0.5 mm. 2 / s or more, preferably 0.8mm 2 / s or higher, more preferably 1mm 2 / s or higher. The kinematic viscosity of the refrigeration oil at 100°C can also preferably be 10 mm. 2 / s or less, more preferably 5mm 2 / s or less, preferably 3mm 2 / s or less, especially preferably 2mm 2 / s or less.

[0153] The viscosity index of the refrigeration oil can be above -50, preferably above 0, more preferably above 50, or below 200.

[0154] The pour point of the refrigeration oil is preferably below -10°C, more preferably below -20°C, below -30°C, below -40°C, or below -45°C.

[0155] The volume resistivity of the refrigeration oil can preferably be 1.0 × 10⁻⁶. 9 Ω·m or more, preferably 1.0 × 10 10 Ω·m or higher, more preferably 1.0×10 11 Ω·m or higher. The volume resistivity in this specification refers to the volume resistivity measured at 25°C according to JIS C2101:1999.

[0156] The moisture content of the refrigeration oil, based on the total volume of the refrigeration oil, is preferably 200 ppm or less, more preferably 100 ppm or less, and even more preferably 50 ppm or less. The moisture content referred to in this specification is the moisture measured according to JIS K2275-2 or 3 (Kal Fischer volumetric titration or electrophoretic titration).

[0157] The density of refrigeration oil at 15°C can be, for example, 0.75 g / cm³. 3 Above, 0.76 g / cm 3 Above, or 0.77 g / cm 3 The above can also be 0.85 g / cm³. 3 Below, 0.83g / cm 3 Below, 0.81g / cm 3 Below, 0.80g / cm 3 Below or 0.79 g / cm 3 the following.

[0158] The flash point of refrigeration oil can be, for example, above 70°C, above 80°C, above 90°C, above 100°C, or above 110°C, or below 150°C, below 140°C, or below 130°C.

[0159] The acid value of the refrigeration oil is preferably below 1.0 mg KOH / g, more preferably below 0.1 mg KOH / g. The hydroxyl value of the refrigeration oil is, for example, below 10 mg KOH / g, preferably below 5 mg KOH / g, more preferably below 2 mg KOH / g. The acid value in this specification refers to the acid value measured according to JIS K2501:2003. The hydroxyl value in this specification refers to the hydroxyl value measured according to JIS K0070:1992.

[0160] From the viewpoint of further reducing the coefficient of friction, the initial boiling point (IBP) of refrigeration oil can preferably be above 140°C, above 170°C, above 190°C, above 200°C, above 210°C, above 220°C, above 230°C, or above 240°C, or below 260°C, below 255°C, or below 250°C.

[0161] From the viewpoint of further reducing the coefficient of friction, the 10% distillation temperature (T10) of refrigeration oil can preferably be above 200°C, above 210°C, above 220°C, above 230°C, or above 240°C, below 260°C, below 255°C, or below 250°C.

[0162] From the viewpoint of further reducing the coefficient of friction, the 50% distillation temperature (T50) of refrigeration oil can preferably be above 210°C, above 220°C, above 230°C, above 240°C, or above 245°C, below 265°C, below 260°C, below 255°C, or below 250°C.

[0163] From the viewpoint of further reducing the coefficient of friction, the 90% distillation temperature (T90) of the refrigeration oil can preferably be above 220°C, above 230°C, above 240°C, above 245°C, or above 250°C, or below 270°C, below 267°C, below 266°C, below 265°C, below 264°C, below 263°C, below 262°C, or below 261°C.

[0164] From the viewpoint of further reducing the coefficient of friction, the distillation endpoint (EP) of refrigeration oil can preferably be above 250°C, above 260°C, above 270°C, above 275°C, or above 280°C, or below 320°C, below 310°C, below 300°C, below 295°C, or below 290°C.

[0165] From the perspective of further reducing the coefficient of friction, the difference between T90 and T10 of refrigeration oil (T90-T10) can preferably be above 5°C, above 6°C, above 7°C, above 8°C, above 9°C, or above 10°C, or below 40°C, below 30°C, below 20°C, or below 15°C.

[0166] The total distillate of the refrigeration oil can be, for example, 90% or more by volume, 93% or more by volume, or 95% or more by volume, or less than 99% by volume. The residual oil content of the refrigeration oil can be, for example, 1% or more by volume, or less than 10% by volume, less than 7% by volume, or less than 5% by volume. The weight loss of the refrigeration oil can be, for example, less than 1% by volume, less than 0.5% by volume, less than 0.1% by volume, or 0% by volume.

[0167] The ash content of the refrigeration oil is preferably below 100 ppm, more preferably below 50 ppm. The ash content in this specification refers to the ash content measured according to JIS K2272:1998.

[0168] The residual carbon content of 10% residual oil in refrigeration oil can be less than 0.01% by mass. From the viewpoint of further reducing the coefficient of friction, it is preferably more than 0.01% by mass, more than 0.02% by mass, more than 0.05% by mass, more than 0.1% by mass, more than 0.2% by mass, or more than 0.21% by mass. For example, it can also be less than 0.6% by mass, less than 0.5% by mass, or less than 0.4% by mass. It should be noted that the residual carbon content in this specification refers to the residual carbon content measured by the micro-method according to JIS K2270-2:2009. The residual carbon content of 10% residual oil in this specification refers to the residual carbon content measured by the same method for the residual oil after removing up to 90% by volume of distillate from the refrigeration oil.

[0169] The refrigeration oil of this embodiment can exist in a refrigeration machine equipped with a refrigerant circulation system having a compressor, condenser, expansion mechanism, and evaporator, as a working fluid composition for refrigeration machines mixed with refrigerant. The refrigeration oil lubricates, for example, sliding components in a compressor. That is, another embodiment of the present invention is a working fluid composition for refrigeration machines containing the aforementioned refrigeration oil and refrigerant. The content of refrigeration oil in the working fluid composition for refrigeration machines can be 1 part by mass or more, or 2 parts by mass or more, or 500 parts by mass or less, or 400 parts by mass or less, relative to 100 parts by mass of refrigerant.

[0170] Examples of refrigerants include hydrocarbons, saturated fluorinated hydrocarbons, unsaturated fluorinated hydrocarbons, fluorinated ethers such as perfluoroethers, bis(trifluoromethyl) sulfides, trifluoroiodomethane, ammonia, and carbon dioxide.

[0171] The refrigerant preferably contains hydrocarbons. Based on the total amount of refrigerant, the hydrocarbon content can be 50% or more by mass, 60% or more by mass, 70% or more by mass, 80% or more by mass, 90% or more by mass, or 95% or more by mass.

[0172] The hydrocarbon is preferably a hydrocarbon with 1 to 5 carbon atoms, and more preferably a hydrocarbon with 2 to 4 carbon atoms. Examples of hydrocarbons include methane, ethylene, ethane, propylene, propane (R290), cyclopropane, n-butane, isobutane (R600a), cyclobutane, methylcyclopropane, 2-methylbutane, n-pentane, or mixtures of two or more thereof. The hydrocarbon is preferably a gaseous hydrocarbon at 25°C and 1 atmosphere, and more preferably propane, n-butane, isobutane, 2-methylbutane, or mixtures thereof.

[0173] Saturated fluorinated hydrocarbons include, preferably, 1 to 3 carbon atoms, more preferably 1 to 2 carbon atoms. Unsaturated fluorinated hydrocarbons (HFO) include, preferably, 2 to 4 carbon atoms and 1 to 5 fluorine atoms, more preferably fluoropropylene, and even more preferably fluoropropylene with 3 to 5 fluorine atoms.

[0174] Example

[0175] The present invention will be further described in detail below based on the embodiments, but the present invention is not limited to the following embodiments.

[0176] The base oils (hydrocarbon base oils) 1-4 used in the examples are described below. These hydrocarbon base oils had aromatic content below 1% by mass, therefore no chromatographic separation was performed; they were all considered saturated hydrocarbons and directly analyzed for hydrocarbon type using either the aforementioned GC-TOFMS method or the aforementioned gas chromatography method. The properties of these hydrocarbon base oils are shown in Table 1.

[0177] Base oil (hydrocarbon base oil) 1: An isoparaffinic base oil (aromatic content < 0.5% by mass, ASTM color: 0) obtained by hydrocracking / isomerizing / refining alkane components synthesized from carbon monoxide and hydrogen using the Fischer-Tropsch reaction.

[0178] Base oil (hydrocarbon base oil) 2: The kerosene fraction obtained by hydrogenation and desulfurization of crude oil distillate under atmospheric pressure is obtained by adsorption separation through molecular sieves and fractionation to obtain n-alkane hydrocarbon oil (aromatic content <0.5% by mass, ASTM color: 0).

[0179] Base oil (hydrocarbon base oil) 3: Mineral oil-based hydrocarbon oil (aromatic content < 0.5% by mass, ASTM color: 0) obtained by fractional distillation of hydrocracked light oil from feedstock containing vacuum distillation residue.

[0180] Base oil (hydrocarbon base oil) 4: Mineral oil-based hydrocarbon oil (aromatic content < 0.5% by mass, ASTM color: 0) obtained by fractional distillation of hydrocracked light oil from feedstock containing vacuum distillation residue.

[0181] [Table 1]

[0182]

[0183] In addition, using base oils 1, 2, and 4 mentioned above, the following base oils 5 to 12 were prepared. Base oil 5: a mixture of base oil 1 and base oil 2 (mass ratio 80 / 20).

[0184] Base oil 6: A mixture of base oil 1 and base oil 2 (mass ratio 70 / 30)

[0185] Base oil 7: A mixture of base oil 1 and base oil 2 (mass ratio 55 / 45)

[0186] Base oil 8: A mixture of base oil 1 and base oil 2 (mass ratio 45 / 55)

[0187] Base oil 9: A mixture of base oil 1 and base oil 4 (mass ratio 80 / 20)

[0188] Base oil 10: A mixture of base oil 1 and base oil 4 (mass ratio 65 / 35)

[0189] Base oil 11: A mixture of base oil 1 and base oil 4 (mass ratio 50 / 50)

[0190] Base oil 12: A mixture of base oil 1 and base oil 4 (mass ratio 30 / 70)

[0191] Using base oils 1 to 12, 97.3% by mass of each base oil was mixed with 1.7% by mass of the phosphorus-containing anti-wear agent and 1.0% by mass of the polymer additive (all based on the total volume of the refrigeration oil) as described below to prepare the refrigeration oils of the Examples and Comparative Examples. The properties of each base oil are shown in Tables 2 and 3. The 90% distillation temperature (T90) of these refrigeration oils is below 267°C. In addition, the residual carbon content of the 10% residual oil of these refrigeration oils is 0.3% by mass. Furthermore, the specific gravity of the refrigeration oils of Examples 1 to 7 and the base oils used therein at 15°C is 0.8017 g / cm³. 3 In the following points, all references are made to "volatile oils" as defined in Article 2, Paragraph 1 of the Japanese Volatile Oil Tax Law.

[0192] Phosphorus-containing anti-wear agent: a mixture of tricresyl phosphate and triphenyl thiophosphate.

[0193] Polymer additive: Copolymer of dialkyl maleate and α-olefin with 8 to 10 carbon atoms (dialkyl maleate contains dialkyl maleate with straight-chain alkyl groups having 4, 8 to 10 carbon atoms as the main component, and the copolymer has Mn: 8300, Mw: 12800, and Mw / Mn: 1.5).

[0194] [Evaluation of Friction Properties]

[0195] To evaluate the frictional characteristics of the refrigeration oils in the examples and comparative examples, the following tests were conducted.

[0196] The coefficient of friction (μ) in the lubrication zone, equivalent to the elastohydrodynamic lubrication zone or the hybrid lubrication zone, was determined using an MTM (Mini Traction Machine) (manufactured by PCS Instruments) under the following conditions. The results are shown in Tables 2 and 3. A smaller coefficient of friction indicates better frictional characteristics.

[0197] Ball and disc: Standard test piece (AISI 52100 standard)

[0198] Test temperature: 40℃

[0199] Sliding speed: 0.3~0.9m / s (partial excerpt)

[0200] Load capacity: 10N

[0201] Slip rate: 30%

[0202] It should be noted that the sliding speed is expressed using |U D -U B The value of [m / s]. Here, U D U is the velocity of the disk in the sliding part [m / s]. B Let be the velocity of the ball in the sliding part [m / s].

[0203] [Table 2]

[0204]

[0205] [Table 3]

[0206]

[0207] As described above, the saturated component used contained 40% or less of cyclic saturated component by mass, 60% or more of non-cyclic saturated component by mass, and had a density of 0.805 g / cm³ at 15°C. 3In the examples of base oils with a n-alkane content of 50% by mass or less, the coefficient of friction was reduced and the pour point rise was suppressed (pour point below -10°C). Conversely, in the comparative examples using base oils that did not meet the above properties, the coefficient of friction increased excessively or the pour point increased excessively (pour point exceeding -10°C).

[0208] (Low-temperature exudation test under refrigerant coexistence)

[0209] Regarding the refrigeration oil of Example 1, hydrocarbon refrigerant R600a was used as the refrigerant, and a low-temperature exudation test was conducted according to Annex A of JIS K2211 (2009). The mixture of refrigeration oil and R600a, within a refrigeration oil / refrigerant ratio (mass ratio) range of 1 / 99 to 99 / 1, did not produce hairy exudates, granular exudates, fogging, or turbidity even when cooled to -40°C, confirming no tendency for low-temperature exudation.

Claims

1. A base oil for refrigeration oil, wherein, The cyclic saturated component accounts for less than 40% by mass, and the acyclic saturated component accounts for more than 60% by mass. The density at 15°C is 0.805 g / cm³. 3 The following conditions apply: the n-alkane content is less than 50% by mass, and the content of hydrocarbons with 12 to 16 carbons in the base oil is more than 80% by mass. The base oil for the refrigeration oil contains only hydrocarbon base oil A. The kinematic viscosity of the hydrocarbon base oil A at 40°C is 3.5 mm. 2 / s or less.

2. The base oil for refrigeration oil according to claim 1, wherein, The hydrocarbon base oil A contains a first hydrocarbon base oil with a n-alkane content of less than 2% by mass.

3. The base oil for refrigeration oil according to claim 2, wherein, In addition to the first hydrocarbon base oil, the hydrocarbon base oil A also contains a second hydrocarbon base oil with a n-alkane content of 5% by mass or more.

4. The base oil for refrigeration oil according to claim 1 or 2, wherein, The initial boiling point of the hydrocarbon base oil A is above 140°C, and the 90% distillation temperature is below 270°C.

5. A refrigeration oil comprising the refrigeration oil base oil as described in claim 1 or 2.

6. The refrigeration oil according to claim 5 further contains a phosphorus-containing anti-wear agent.

7. The refrigeration oil according to claim 5, further comprising polymer additives.

8. The refrigeration oil according to claim 5, wherein, The residual carbon content of the 10% residual oil of the refrigeration oil is more than 0.02% by mass.

9. The refrigeration oil according to claim 5, wherein, The refrigeration oil has a 90% distillation temperature below 270°C.

10. A working fluid composition for a refrigeration unit, comprising: The refrigeration oil as described in claim 5, and refrigerant.

11. The working fluid composition for a refrigeration unit according to claim 10, wherein, The refrigerant contains hydrocarbons.

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