Refrigeration oil base oil, refrigeration oil and refrigeration fluid components used in refrigeration equipment

Abstract

Provided is a base oil for a refrigerator oil in which the cyclic saturated fraction is 40 mass% or less and the non-cyclic saturated fraction is 60 mass% or more of the saturated fraction, the density at 15°C is 0.805 g / cm3 or less, and the normal paraffin content is 50 mass% or less.

Description

[Technical Field]

[0001] The present invention relates to a base oil for refrigeration oil, refrigeration oil, and a working fluid composition for refrigeration machines. [Background technology]

[0002] In refrigeration systems, there is an increasing need to replace refrigerants with relatively high global warming potentials (GWP) with low-GWP refrigerants, such as those with a GWP of less than 150. Examples of low-GWP refrigerants include carbon dioxide (R744) refrigerants and hydrocarbon refrigerants.

[0003] On the other hand, energy conservation is also required for refrigeration systems. Generally, the lower the viscosity of the refrigeration oil, the lower the stirring resistance and friction of the sliding parts, so lowering the viscosity of the refrigeration oil leads to energy conservation in refrigeration systems. For example, Patent Document 1 discloses a refrigeration oil with a viscosity of VG3 to VG8. Also, for example, Patent Document 2 discloses a refrigeration oil containing a mixed base oil consisting of a low viscosity base oil and a high viscosity base oil. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2006 / 062245 [Patent Document 2] International Publication No. 2007 / 105452 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, if the viscosity of the refrigeration oil decreases, it becomes difficult to maintain an oil film in the sliding parts, which may lead to an increase in the coefficient of friction, for example. On the other hand, if one attempts to reduce the coefficient of friction, the pour point of the refrigeration oil may rise, which is undesirable from the standpoint of fluidity. Therefore, one aspect of the present invention aims to provide a base oil and refrigeration oil for refrigeration machines that can reduce the coefficient of friction while suppressing an increase in the pour point. [Means for solving the problem]

[0006] According to the inventors' studies, it has been found that in a base oil for refrigeration oil, by setting the cyclic and acyclic saturated content, the density at 15°C, and the normal paraffin content within predetermined ranges, it is possible to achieve both a reduction in the coefficient of friction and suppression of the rise in the pour point (in other words, it is possible to suppress excessive increases in the coefficient of friction or excessive increases in the pour point).

[0007] The present invention includes the following aspects. [1] The cyclic saturated content is 40% by mass or less, the acyclic saturated content is 60% by mass or more, and the density at 15°C is 0.805 g / cm³. 3 The following is a base oil for refrigeration oil, having a normal paraffin content of 50% by mass or less. [2] The base oil for refrigeration oil according to [1], wherein the content of hydrocarbons having 12 to 16 carbon atoms in the base oil is 80% by mass or more. [3] A refrigeration oil base oil according to [1] or [2], comprising a hydrocarbon base oil having a normal paraffin content of less than 5% by mass. [4] The refrigeration oil base oil according to [3], further comprising a second hydrocarbon base oil having a normal paraffin content of 5% by mass or more, in addition to the hydrocarbon base oil. [5] A refrigeration oil base oil according to [3] or [4], wherein the initial boiling point of the hydrocarbon base oil is 140°C or higher and the 90% distillation temperature is 270°C or lower.

[0008] [6] A refrigerant oil containing a base oil for refrigerant oil as described in any of [1] to [5]. [7] The refrigeration oil according to [6], further comprising a phosphorus-containing anti-wear agent. [8] The refrigerant oil according to [6] or [7], further comprising a polymer additive. [9] A refrigerant oil according to any one of [6] to [8], wherein the residual carbon content of the 10% residual oil of the refrigerant oil is 0.02% by mass or more.

[10] A refrigerant oil as described in any of [6] to [9], wherein the 90% distillation temperature of the refrigerant oil is 270°C or lower. A working fluid composition for a refrigerator, comprising a refrigerant oil as described in any of

[11] [6] to

[10] and a refrigerant.

[12] The working fluid composition for a refrigerator according to

[11] , wherein the refrigerant comprises a hydrocarbon. [Effects of the Invention]

[0009] According to one aspect of the present invention, it is possible to provide a base oil for refrigeration oil and a refrigeration oil that can reduce the coefficient of friction and suppress the rise in the pour point. In one aspect of the present invention, such effects can be obtained even when the base oil for refrigeration oil and the refrigeration oil have low viscosity. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described in detail below. One embodiment of the present invention has a cyclic saturated content of 40% by mass or less, an acyclic saturated content of 60% by mass or more, and a density of 0.805 g / cm³ at 15°C. 3 The following is a base oil for refrigeration oil, having a normal paraffin content of 50% by mass or less.

[0011] From the viewpoint of further reducing the coefficient of friction, the content of cyclic saturated components (1- to 6-ring cycloparaffins (hereinafter also simply referred to as "cycloparaffins")) in the saturated components of the base oil is preferably 30% by mass or less, 20% by mass or less, 10% by mass or less, 5% by mass or less, or 3% by mass or less, based on the total saturated components of the base oil, and may be 0% by mass or 0% by mass or more.

[0012] The content of acyclic saturates (paraffins (hereinafter, also simply referred to as "paraffins")) in the saturates of the base oil is preferably 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 97% by mass or more, and may be 100% by mass or 100% by mass or less, based on the total amount of saturates in the base oil, from the viewpoint of further reducing the friction coefficient.

[0013] The density of the base oil at 15°C is preferably 0.802 g / cm 3 or less, 0.800 g / cm 3 or less, 0.790 g / cm 3 or less, or 0.780 g / cm 3 or less, and may preferably be 0.76 g / cm 3 or more, 0.77 g / cm 3 or more, or 0.775 g / cm 3 or more. The density in this specification means the density at 15°C measured in accordance with the "vibration method" described in JIS K2249-1:2011.

[0014] The content of normal paraffins in the base oil is preferably 45% by mass or less, 40% by mass or less, 35% by mass or less, 30% by mass or less, 20% by mass or less, 10% by mass or less, 5% by mass or less, or 2% by mass or less, and may be 0% by mass or 0% by mass or more, based on the total amount of the base oil, from the viewpoint of further suppressing the increase in pour point.

[0015] The content of hydrocarbons having 12 to 16 carbon atoms in the base oil is preferably 80% by mass or more, 85% by mass or more, 90% by mass or more, or 95% by mass or more, and may be 100% by mass or 100% by mass or less, based on the total amount of the base oil, from the viewpoint of further reducing the friction coefficient.

[0016] The content of hydrocarbons having 13 to 18 carbon atoms in the base oil is preferably 80% by mass or more, 85% by mass or more, 90% by mass or more, or 95% by mass or more, and may be 100% by mass or 100% by mass or less, based on the total amount of the base oil, from the viewpoint of further reducing the friction coefficient.

[0017] The normal paraffin content of the base oil for refrigeration oil, which has 18 or more carbon atoms, is preferably 10% by mass or less, 5% by mass or less, 2% by mass or less, 1% by mass or less, or 0% by mass, in terms of the low-temperature characteristics of the refrigeration oil.

[0018] The pour point of the base oil is preferably -10°C or lower, more preferably -20°C or lower, -30°C or lower, or -40°C or lower, and may also be -80°C or higher. In this specification, the pour point refers to the pour point measured in accordance with JIS K2269:1987.

[0019] In one embodiment, the base oil for refrigeration oil contains a predetermined hydrocarbon base oil. This hydrocarbon base oil has a cyclic saturated content of 30% by mass or less and an acyclic saturated content of 70% by mass or more, and a density of 0.805 g / cm³ at 15°C. 3 The following are hydrocarbon base oils.

[0020] From the viewpoint of further reducing the coefficient of friction, the content of cyclic saturated material in the hydrocarbon base oil is 30% by mass or less, based on the total saturated material in the hydrocarbon base oil, preferably 20% by mass or less, 10% by mass or less, 5% by mass or less, or 3% by mass or less, and may be 0% by mass or 0% by mass or more.

[0021] From the viewpoint of further reducing the coefficient of friction, the content of acyclic saturated matter in the saturated matter 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, and may be 100% by mass or less.

[0022] The density of hydrocarbon base oil at 15°C is 0.805 g / cm³. 3 The following, preferably 0.802 g / cm³ 3 Below 0.800g / cm 3 Below, 0.790g / cm 3 The following, or 0.780 g / cm³ 3The following may be the case, preferably 0.76 g / cm³ 3 More than 0.77g / cm 3 Above, or 0.775 g / cm³ 3 That's all.

[0023] The normal paraffin content of the hydrocarbon base oil may be 50% by mass or less, and from the viewpoint of further reducing the coefficient of friction, it may preferably be 40% by mass or less, 35% by mass or less, or 30% by mass or less based on the total amount of hydrocarbon base oil, and from the viewpoint of further suppressing the rise in the pour point, it may more preferably be 20% by mass or less, 10% by mass or less, 5% by mass or less, less than 5% by mass, or 2% by mass or less, and may be 0% by mass or 0% by mass or more.

[0024] The aromatic hydrocarbon content of the hydrocarbon base oil is not particularly limited, but from the viewpoint of further reducing the coefficient of friction, it is preferably 10% by mass or less, 5% by mass or less, 2% by mass or less, 1% by mass or less, 0% by mass or more.

[0025] From the viewpoint of further reducing the coefficient of friction, the content of hydrocarbons having 12 to 16 carbon atoms in the hydrocarbon base oil is preferably 80% by mass or more, 85% by mass or more, 90% by mass or more, or 95% by mass or more, based on the total amount of hydrocarbon base oil, and may be 100% by mass or 100% by mass or less.

[0026] From the viewpoint of further reducing the coefficient of friction, the content of hydrocarbons having 13 to 18 carbon atoms in the hydrocarbon base oil is preferably 80% by mass or more, 85% by mass or more, 90% by mass or more, or 95% by mass or more, based on the total amount of hydrocarbon base oil, and may be 100% by mass or 100% by mass or less.

[0027] The content of hydrocarbons having fewer than 12 carbon atoms in the hydrocarbon base oil may be 5% by mass or less, preferably less than 1% by mass, based on the total amount of hydrocarbon base oil, from the viewpoint of flash point and suppression of the emission of volatile organic compounds.

[0028] In this specification, the content of cyclic saturated components (cycloparaffins), acyclic saturated components (paraffins), normal paraffins, hydrocarbons with 12 to 16 carbon atoms, hydrocarbons with 13 to 18 carbon atoms, and hydrocarbons with less than 12 carbon atoms in the base oil for refrigeration oils and hydrocarbon base oils is determined by separating the analyte sample (hydrocarbon base oil) into saturated hydrocarbon oil and aromatic hydrocarbon oil by silica gel chromatography, and then performing hydrocarbon type analysis of each by GC-TOFMS, which combines gas chromatography and mass spectrometry using FI ionization. An example of the analytical conditions is shown below. (Gas chromatography conditions) Column: Phenomenex ZB-1MS Injection temperature: 350℃ Heating conditions: 50°C to 350°C (heating rate: 5°C / min) Carrier gas: Helium Injection method: Split sample injection volume: 1 μL (10% toluene solution) (MS conditions) Counter electrode voltage: -10kV Ionization method: FI (Field Ionization) Ion source temperature: Room temperature Mass number measurement range: m / z 35~500

[0029] In the mass spectrum obtained from GC-TOFMS analysis, the type (C) for each number of carbon atoms is selected. n H 2n+z (Here, n is an integer and z is an even number between -18 and 2) The percentage of another ionic intensity can be determined from the percentage of the total ionic intensity, and in this specification, the content (mass%) of each component is considered to be approximately the same as the ionic intensity % of each component for calculation. If the aromatic hydrocarbon content of the sample is less than 1 mass%, chromatographic fractionation may be omitted and type analysis may be performed. In this case, the content of each component shall be calculated by considering all of them as saturated hydrocarbons.

[0030] Furthermore, the content of normal paraffins, hydrocarbons with 12 to 16 carbon atoms, hydrocarbons with 13 to 18 carbon atoms, and hydrocarbons with fewer than 12 carbon atoms in the hydrocarbon base oil can be determined by, for example, calculating and summarizing the peak area % corresponding to normal paraffins and non-normal paraffins for each carbon number, assuming they are approximately the same as mass %, using a hydrocarbon type analysis method (gas chromatography) by gas chromatography under the following conditions, and then integrating them. If equivalent results can be obtained, this method may be used. An example of analytical conditions is shown below. (Gas chromatography conditions) Column: Liquid-phase non-polar column (length 30m, inner diameter 0.25mmφ, liquid-phase thickness 0.1μm) Injection temperature: 350℃ Detector: FID 360℃ Heating conditions: 50°C to 350°C (heating rate: 6°C / min) Carrier gas: Helium Injection method: Split sample injection volume: 1 μL (10% toluene solution)

[0031] The initial boiling point of the hydrocarbon base oil may be 140°C or higher, and the 90% distillation temperature of the hydrocarbon base oil may be 270°C or lower. The initial boiling point and 90% distillation temperature of the hydrocarbon base oil, as well as other distillation properties described below, refer to the distillation properties measured by the atmospheric pressure distillation test method (in accordance with the atmospheric pressure method described in JIS K2254:2018).

[0032] The 90% distillation temperature (T90) of the hydrocarbon base oil is preferably 267°C or lower, 266°C or lower, 265°C or lower, 264°C or lower, 263°C or lower, 262°C or lower, or 261°C or lower, and may be, for example, 220°C or higher, 230°C or higher, 240°C or higher, 245°C or higher, or 250°C or higher.

[0033] From the viewpoint of further reducing the coefficient of friction, the initial boiling point (IBP) of the hydrocarbon base oil is preferably 140°C or higher, 170°C or higher, 190°C or higher, 200°C or higher, 210°C or higher, 220°C or higher, 230°C or higher, or 240°C or higher, and may be 260°C or lower, 255°C or lower, or 250°C or lower.

[0034] The 10% distillation temperature (T10) of the hydrocarbon base oil is preferably 200°C or higher, 210°C or higher, 220°C or higher, 230°C or higher, or 240°C or higher, and may be 260°C or lower, 255°C or lower, or 250°C or lower, from the viewpoint of further reducing the coefficient of friction.

[0035] The 50% distillation temperature (T50) of the hydrocarbon base oil is preferably 210°C or higher, 220°C or higher, 230°C or higher, 240°C or higher, or 245°C or higher, and may be 265°C or lower, 260°C or lower, 255°C or lower, or 250°C or lower, from the viewpoint of further reducing the coefficient of friction.

[0036] From the viewpoint of further reducing the coefficient of friction, the distillation endpoint (EP) of the hydrocarbon base oil is preferably 250°C or higher, 260°C or higher, and may be 320°C or lower, 300°C or lower, 280°C or lower, or 270°C or lower.

[0037] The difference between T90 and T10 of the hydrocarbon base oil (T90-T10) is preferably 5°C or higher or 6°C or higher, and may be 40°C or lower, 20°C or lower, 15°C or lower, or 10°C or lower, from the viewpoint of further reducing the coefficient of friction.

[0038] The total distillate of hydrocarbon base oil may be, for example, 95% or more by volume, 96% or more by volume, 97% or more by volume, 98% or more by volume, or 99% or more by volume, and may be 99.9% or less by volume. The residual amount of hydrocarbon base oil may be, for example, 0.1% or more by volume, and may be 6% or less by volume, 4% or less by volume, 3% or less by volume, 2% or less by volume, or 1% or less by volume. The loss of hydrocarbon base oil may be, for example, 1% or less by volume, 0.5% or less by volume, or 0.1% or less by volume, and may be 0% by volume.

[0039] The kinematic viscosity of a hydrocarbon base oil at 40°C is, for example, 1.0 mm. 2 / s or more, 1.5mm 2 / s or more, or 2.0mm 2 It may be 6.0mm or more 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 It may be less than or equal to / s. In this specification, kinematic viscosity refers to kinematic viscosity measured in accordance with JIS K2283:2000.

[0040] The kinematic viscosity of a hydrocarbon base oil at 100°C is, for example, 0.5 mm. 2 / s or more, 0.7mm 2 / s or more, or 0.8mm 2 It may be 2.0 mm or more 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 1.0 mm 2 It can be less than or equal to / s.

[0041] The flash point of the hydrocarbon base oil may be, for example, 70°C or higher, 80°C or higher, 100°C or higher, or 110°C or higher, and may be 150°C or lower, 140°C or lower, or 130°C or lower. By increasing the initial boiling point of the hydrocarbon base oil, the flash point can be increased, thereby further enhancing safety. 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.

[0042] The distillation properties, kinematic viscosity, and flash point of the hydrocarbon base oils described above can be interpreted as the distillation properties, kinematic viscosity, and flash point of base oils for refrigeration oils, respectively.

[0043] The pour point of the hydrocarbon base oil may be, for example, -10°C or below, -20°C or below, -30°C or below, or -40°C or below, and may also be -80°C or above.

[0044] Examples of hydrocarbon base oils having the above properties include mineral oil-based hydrocarbon base oils, synthetic hydrocarbon base oils, and mixed base oils thereof. Mineral oil-based hydrocarbon base oils include paraffinic or naphthenic refined mineral oils obtained by using crude oil or its distillation residue as raw material and refining them by appropriately combining conventional petroleum refining processes (solvent delamination, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, sulfuric acid washing, clay treatment, distillation, etc.). Examples of synthetic hydrocarbon base oils include poly-α-olefins or their hydrides, isoparaffins, alkylbenzenes, alkylnaphthalenes, etc. These hydrocarbon base oils can be used individually or in combination of two or more.

[0045] From the viewpoint of easily obtaining the above-mentioned properties, the hydrocarbon base oil is preferably a mineral oil-based hydrocarbon base oil. More specifically, for example, by hydrorefining a lamp / light oil fraction obtained by atmospheric distillation of crude oil, or a cracked light oil fraction obtained by cracking a residue oil raw material including atmospheric residual oil of crude oil or its vacuum residual oil, and fractionally distilling it so that hydrocarbons having 12 to 16 or 13 to 18 carbon atoms are the main components (for example, 80% by mass or more, especially 90% by mass or more), a hydrocarbon base oil having the above-mentioned properties can be easily obtained.

[0046] Furthermore, from the viewpoint of easily obtaining the above-mentioned properties, the hydrocarbon base oil is more preferably an isoparaffinic base oil. As the isoparaffinic base oil, for example, it may be an isoparaffinic base oil obtained by a combination of hydrocracking, hydroisomerization, hydrodecay, hydrorefining, distillation, etc., of a component containing normal paraffin obtained by a dewaxing process in the petroleum refining process or Fischer-Tropsch synthesis, or polymers of olefins such as ethylene, propylene, butylene, and diisobutylene.

[0047] The base oil for refrigeration oil may contain a hydrocarbon base oil having the above properties (hereinafter also referred to as "hydrocarbon base oil A") as its main component. The base oil for refrigeration oil may contain only hydrocarbon base oil A, or it may further contain other base oils in addition to hydrocarbon base oil A. 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 the base oil for 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, based on the total amount of the refrigeration oil.

[0048] In one embodiment, when the refrigeration oil base oil contains a hydrocarbon base oil (first hydrocarbon base oil) with a paraffin 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 normal paraffin content of 5% by mass or more in addition to the first hydrocarbon base oil. This allows for a synergistic low-friction effect through the combined use of the first hydrocarbon base oil and the second hydrocarbon base oil. In this case, the normal paraffin content of the first hydrocarbon base oil may be 2% by mass or less, 0% by mass or more, and the normal paraffin 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.

[0049] The second hydrocarbon base oil is, from the viewpoint of maintaining a low pour point and reducing the coefficient of friction, preferably a hydrocarbon base oil that satisfies the above-mentioned properties (distillation properties, hydrocarbons having 12 to 16 carbon atoms, hydrocarbons having 13 to 18 carbon atoms, kinematic viscosity (40°C, 100°C), flash point, density, aromatic content) for hydrocarbon base oil A, rather than one mainly composed of a single normal paraffin.

[0050] When using a second hydrocarbon base oil, the content of the second hydrocarbon base oil is preferably 50% by mass or less, 40% by mass or less, or 35% by mass or less based on the total amount of refrigeration oil base oil, and may be 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 be 30% by mass or less, 25% by mass or less, 20% by mass or less, or 15% by mass or less.

[0051] Another embodiment of the present invention is a refrigerant oil containing the above-mentioned base oil for refrigeration oil. The refrigerant oil may contain the base oil for refrigeration as its main component. The content of the base oil for refrigeration oil 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 refrigerant oil.

[0052] The refrigeration oil may contain hydrocarbon base oil A, a first hydrocarbon base oil and a second hydrocarbon base oil, a hydrocarbon base oil other than hydrocarbon base oil A, the first hydrocarbon base oil and the second hydrocarbon base oil (a third hydrocarbon base oil), and an oxygen-containing base oil.

[0053] As the third hydrocarbon base oil, for example, mineral oil-based hydrocarbon oil, synthetic hydrocarbon oil, or a mixture thereof can be used. Examples of mineral oil-based hydrocarbon oil include paraffinic mineral oil, naphthenic mineral oil, etc., obtained by distilling crude oil such as paraffinic and naphthenic oils at atmospheric pressure and under reduced pressure to obtain lubricating oil fractions, and then refining them by methods such as solvent delamination, solvent refining, hydrorefining, hydrocracking, solvent dewaxing, hydrodewaxing, clay treatment, and sulfuric acid washing. These refining methods may be used individually or in combination of two or more.

[0054] As mineral oil-based hydrocarbon oils, residual hydrocarbon base oils can also be preferably used. Examples of residual hydrocarbon base oils include residual oil from atmospheric distillation of crude oil, residual oil from vacuum distillation of the atmospheric distillation residual oil, desaturated oil from these residual oils with propane, etc., solvent-extracted extract oil from the desaturated oil with furfural, etc., solvent-extracted raffinate oil from the desaturated oil, and refined oils obtained by refining these oils through hydrocracking, hydrorefining, solvent dewaxing, or hydrodewaxing. Among these, refined oil obtained by hydrorefining the solvent-extracted raffinate from the desaturated oil of vacuum distillation residue oil, followed by solvent dewaxing or hydrodewaxing, is particularly preferred.

[0055] Examples of synthetic hydrocarbon oils include alkylbenzenes, alkylnaphthalenes, poly-α-olefins (PAOs), polybutenes, and ethylene-α-olefin copolymers.

[0056] The kinematic viscosity of the third hydrocarbon base oil at 40°C is, for example, 6 mm. 2 / s or more is acceptable, and from the viewpoint of more effectively reducing the coefficient of friction, 20mm 2 / s or more, 50mm 2 / s or more, 80mm 2 / s, or 90mm2 It may be greater than or equal to / s. The upper limit of the kinematic viscosity of the third hydrocarbon base oil at 40°C is not particularly limited, but for example, 1000 mm 2 It may be less than or equal to / s, preferably 500 mm 2 It is less than or equal to / s.

[0057] The kinematic viscosity of residual hydrocarbon base oil at 40°C is, for example, 100 mm. 2 / s or more, 200mm 2 / s or more, 300mm 2 / s or more, 400mm 2 / s or more, or 450mm 2 / s or more, and 1000mm 2 / s or less, 800mm 2 / s or less, 600mm 2 / s or less, or 500mm 2 It can be less than or equal to / s.

[0058] The kinematic viscosity of residual hydrocarbon base oil at 100°C is, for example, 10 mm. 2 / s or more, 20mm 2 / s or more, or 30mm 2 / s or more, and 100mm 2 / s or less, 50mm 2 / s or less, or 40mm 2 It can be less than or equal to / s.

[0059] The viscosity index of the residual hydrocarbon base oil may be, for example, 0 or greater, 50 or greater, or 80 or greater, and may be 300 or less, 140 or less, or 100 or less. The viscosity index as used herein refers to the viscosity index measured in accordance with JIS K2283:2000.

[0060] The flash point of the residual hydrocarbon base oil may be, for example, 200°C or higher, 250°C or higher, or 300°C or higher, and may be 500°C or lower, 450°C or lower, or 400°C or lower.

[0061] The residual carbon content of the residual hydrocarbon base oil is not particularly limited, but is preferably 0.1% by mass or more, 0.2% by mass or more, or 0.3% by mass or more, and preferably 10% by mass or less, 5% by mass or less, 1% by mass or less, or 0.8% by mass or less, in terms of further improving wear resistance.

[0062] The ASTM color of residual hydrocarbon base oil may be 6.0 or less, 4.0 or less, or 3.0 or less from the viewpoint of the hue of the refrigeration oil, and may be L0.5, 0.5 or more, or 1.0 or more.

[0063] When using a third hydrocarbon base oil, the content of the third hydrocarbon base oil may be 0.5% by mass or more, 1% by mass or more, 2% by mass or more, or 3% by mass or more, based on the total amount of base oil contained in the refrigeration oil, and may be 50% by mass or less, 30% by mass or less, 10% by mass or less, or 5% by mass or less.

[0064] Examples of oxygen-containing base oils include esters, ethers, carbonates, ketones, silicones, and polysiloxanes. Note that the term "ester" here does not include polymers, which will be discussed later. Examples of esters include monoesters, polyol esters, aromatic esters, dibasic acid esters, complex esters, carbonate esters, and mixtures thereof. Among these, monoesters of monohydric aliphatic alcohols and monohydric fatty acids are preferred, and, if necessary, a mixture of such monoesters and polyol esters of dihydric to hexahydric alcohols and monohydric fatty acids is desirable.

[0065] Examples of monohydric aliphatic alcohols constituting such esters include monohydric aliphatic alcohols having 1 to 20 carbon atoms, preferably 4 to 18, and more preferably 4 to 12 carbon atoms. Examples of monohydric fatty acids constituting such esters include monohydric fatty acids having 1 to 20 carbon atoms, preferably 4 to 18, and more preferably 4 to 12 carbon atoms. Examples of dihydric to hexahydric alcohols constituting such esters include neopentyl glycol, trimethylolpropane, pentaerythritol, and dipentaerythritol. Examples of ethers include polyvinyl ethers, polyalkylene glycols, polyphenyl ethers, perfluoroethers, and mixtures thereof.

[0066] Refrigerant oil preferably further contains an anti-wear agent as an additive to improve wear resistance. Examples of anti-wear agents include phosphorus-containing anti-wear agents. Examples of phosphorus-containing anti-wear agents include phosphate esters, thiophosphate esters, acidic phosphate esters, amine salts of acidic phosphate esters, and chlorinated phosphate esters. The anti-wear agent (preferably a phosphorus-containing anti-wear agent) is used alone or in combination of two or more. The phosphorus-containing anti-wear agent is preferably one or more selected from phosphate esters and thiophosphate esters.

[0067] Examples of phosphate esters include tributyl phosphate, tripentyl phosphate, trihexyl phosphate, triheptyl phosphate, trioctyl phosphate, trinonyl phosphate, tridecyl phosphate, triundecyl phosphate, tridodecyl phosphate, tritridecyl phosphate, tritetradecyl phosphate, tripentadecyl phosphate, trihexadecyl phosphate, triheptadecyl phosphate, trioctadecyl phosphate, trioleyl phosphate, triphenyl phosphate, tricresyl phosphate, tri(ethylphenyl) phosphate, tri(butylphenyl) phosphate, trixylenyl phosphate, cresyldiphenyl phosphate, and xylenyldiphenyl phosphate. The phosphate ester is preferably triphenyl phosphate or tricresyl phosphate.

[0068] Examples of thiophosphate esters include tributyl phosphate phosphate, tripentyl phosphate phosphate, trihexyl phosphate phosphate, triheptyl phosphate phosphate, trioctyl phosphate phosphate, trinonyl phosphate phosphate, tridecyl phosphate phosphate, triundecyl phosphate phosphate, tridodecyl phosphate phosphate, tritridecyl phosphate phosphate, tritetradecyl phosphate phosphate, tripentadecyl phosphate phosphate, trihexadecyl phosphate phosphate, triheptadecyl phosphate phosphate, trioctadecyl phosphate phosphate, trioleyl phosphate phosphate, triphenyl phosphate phosphate, tricresyl phosphate phosphate, trixylenyl phosphate phosphate, cresyl diphenyl phosphate phosphate, and xylenyl diphenyl phosphate phosphate. The thiophosphate ester is preferably triphenylphosphorothionate.

[0069] The content of the anti-wear agent (preferably a phosphorus-containing anti-wear agent) may be, for example, 0.1% by mass or more, 0.5% by mass or more, or 1% by mass or more, or 5% by mass or more, 4% by mass or less, or 3% by mass or less, based on the total amount of refrigerant oil.

[0070] The refrigeration oil may further contain polymer additives. The polymer additive may, for example, contain a polymer component having a kinematic viscosity at 40°C higher than that of the base oil for the refrigeration oil, and may contain a polymer containing an unsaturated carboxylic acid ester as a monomer unit. The polymer is obtained by polymerizing one or more monomers, including an unsaturated carboxylic acid ester which is an ester of an unsaturated carboxylic acid and an alcohol.

[0071] The polymer is not particularly limited in that it contains an unsaturated carboxylic acid ester as a monomer unit, and may further contain other monomers (monomers copolymerizable with unsaturated carboxylic acid esters). That is, the polymer may be a homopolymer of one unsaturated carboxylic acid ester, a copolymer of two or more unsaturated carboxylic acid esters, or a copolymer of one or more unsaturated carboxylic acid esters and one or more other monomers.

[0072] The unsaturated carboxylic acid constituting an unsaturated carboxylic acid ester has at least one polymerizable unsaturated bond (polymerizable carbon-carbon double bond) and at least one carboxyl group. For example, it may be an unsaturated monocarboxylic acid having one polymerizable unsaturated bond and one carboxyl group, or an unsaturated dicarboxylic acid having one polymerizable unsaturated bond and two carboxyl groups. Examples of unsaturated monocarboxylic acids include acrylic acid, methacrylic acid (hereinafter collectively referred to as "(meth)acrylic acid"), and crotonic acid. Examples of unsaturated dicarboxylic acids include maleic acid, fumaric acid, citraconic acid, mesaconic acid, and itaconic acid.

[0073] The alcohols constituting the unsaturated carboxylic acid ester may be, for example, alcohols having 1 to 40 carbon atoms, preferably including alcohols having 1 to 18 carbon atoms, and more preferably including alcohols having 1 to 8 carbon atoms. These alcohols may be linear or branched. The alcohols may include alcohols having 1 to 18 carbon atoms and alcohols having 20 to 40 carbon atoms. These alcohols may be aliphatic alcohols.

[0074] The alcohol may be 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 may be linear or branched).

[0075] The alcohol preferably comprises at least one selected from linear 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 linear alkyl groups having 1 to 18 carbon atoms and branched alkyl groups having 4 to 40 carbon atoms.

[0076] When the unsaturated carboxylic acid ester is a (meth)acrylic acid ester, the (meth)acrylic acid ester preferably includes at least one selected from (meth)acrylic acid esters having a linear alkyl group having 1 to 18 carbon atoms, and more preferably includes at least one selected from (meth)acrylic acid esters having a linear alkyl group having 1 to 18 carbon atoms and at least one selected from (meth)acrylic acid esters having a 2-position branched alkyl group having 4 to less than 20 carbon atoms or 20 to 40 carbon atoms.

[0077] A branched alkyl group with 4 or more carbon atoms and less than 20 carbon atoms is an alkyl group represented by the following formula (1). [ka] In equation (1), x and y are independent integers that are non-negative and such that x + y is less than 16.

[0078] In the above formula (1), a branched alkyl group with 20 to 40 carbon atoms is one in which x and y are independent integers of 0 or more, and x + y is an integer between 16 and 36. In particular, it is preferable that x is an integer between 5 and 18, and y is an integer between 3 and 18.

[0079] When the unsaturated carboxylic acid ester is an unsaturated dicarboxylic acid ester, the unsaturated dicarboxylic acid ester preferably includes at least one selected from unsaturated dicarboxylic acid esters having a linear alkyl group with 4 to 10 carbon atoms.

[0080] Other monomers besides unsaturated carboxylic acid esters are not particularly limited, but examples include unsaturated carboxylic acids or their anhydrides as exemplified as unsaturated carboxylic acids constituting the unsaturated carboxylic acid esters described above, and unsaturated hydrocarbon compounds having polymerizable unsaturated bonds. The unsaturated hydrocarbon may be, for example, an unsaturated hydrocarbon compound having 2 to 20 carbon atoms, and preferably an α-olefin or styrene having 2 to 20 carbon atoms. Specific examples of α-olefins include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, and 1-eicosene. The α-olefin is preferably an α-olefin having 8 to 12 carbon atoms.

[0081] The polymer is preferably a copolymer of unsaturated carboxylic acid esters (two or more unsaturated carboxylic acid esters), or a copolymer of an unsaturated carboxylic acid ester (one or more unsaturated carboxylic acid esters) and an α-olefin (one or more α-olefins). The copolymer of unsaturated carboxylic acid esters is preferably a copolymer of (meth)acrylic acid esters. The copolymer of an unsaturated carboxylic acid ester and an α-olefin is preferably at least one selected from a copolymer of (meth)acrylic acid ester and an α-olefin and a copolymer of an unsaturated dicarboxylic acid ester and an α-olefin, and more preferably a copolymer of an unsaturated dicarboxylic acid ester and an α-olefin.

[0082] 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, mesaconic acid, and itaconic acid, and aliphatic alcohols having 3 to 10 carbon atoms such as propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, and decanol. The aliphatic alcohol having 3 to 10 carbon atoms is preferably a linear aliphatic alcohol having 4 to 10 carbon atoms. The unsaturated dicarboxylic acid ester is preferably a maleic acid ester. Preferred examples of maleic acid esters include dimethyl maleate, diethyl maleate, dipropyl maleate, dibutyl maleate, dipentyl maleate, dihexyl maleate, diheptyl maleate, dioctyl maleate, and didecyl maleate.

[0083] If the polymer is a copolymer, the content of the unsaturated carboxylic acid ester may be 10 mol% or more, 30 mol% or more, or 50 mol% or more, and may be 90 mol% or less, 70 mol% or less, or 50 mol% or less, based on the total monomer units constituting the copolymer.

[0084] When the above polymer is a copolymer of an unsaturated carboxylic acid ester and an α-olefin, the molar ratio of the unsaturated carboxylic acid ester to the α-olefin is not particularly limited, but is preferably 1 / 9 or more, more preferably 3 / 7 or more, preferably 9 / 1, and more preferably 7 / 3 or less.

[0085] The number-average molecular weight (Mn) of the polymer is preferably 300 or more, more preferably 1000 or more, even more preferably 1500 or more, and may be 2000 or more, 3000 or more, or 4000 or more, preferably 500000 or less, more preferably 50000 or less, even more preferably 30000 or less, and may be 20000 or less, 15000 or less, or 10000 or less.

[0086] The weight-average molecular weight (Mw) of the polymer is preferably 400 or more, more preferably 1000 or more, even more preferably 2000 or more, and particularly preferably 3000 or more, and may also be 4000 or more, 5000 or more, 6000 or more, 7000 or more, 8000 or more, or 9000 or more, preferably 10000000 or less, more preferably 100000 or less, even more preferably 50000 or less, and particularly preferably 30000 or less, and may also be 20000 or less.

[0087] The Mw / Mn ratio of the polymer is preferably 1.2 or higher, more preferably 1.5 or higher, even more preferably 1.7 or higher, particularly preferably 2 or higher, preferably 5 or lower, more preferably 3.5 or lower, even more preferably 3 or lower, and may also be 2.5 or lower.

[0088] In this specification, "weight-average molecular weight (Mw)" and "number-average molecular weight (Mn)" refer to the weight-average molecular weight and number-average molecular weight, respectively, calculated in polystyrene equivalent by gel permeation chromatography (GPC) using a Waters APC XT column and tetrahydrofuran as the mobile phase (standard substance: polystyrene).

[0089] The kinematic viscosity of the polymer at 100°C is preferably 10 mm². 2 / s or more, more preferably 20 mm 2 / s or more, more preferably 100mm 2 The value is 1 / s or more, preferably 100,000 mm 2 / s or less or 10,000mm 2 / s or less, more preferably 1000mm 2 / s or less, more preferably 800mm 2 / s or less, 500mm 2 It may be less than / s.

[0090] The kinematic viscosity of the polymer at 40°C is preferably 100 mmHg. 2 / s or more, more preferably 200mm 2 / s or more, more preferably 400mm 2 / s or 400mm 2 It exceeds / s, and 500mm 2 / s or more or 1000mm 2 It may be 100,000 mm or more, preferably 100,000 mm 2 / s or less, more preferably 20,000 mm 2 / s or less, more preferably 15,000 mm 2 / s or less, 10000mm 2 / s or less or 5000mm 2 It can be less than or equal to / s.

[0091] The viscosity index of the polymer is preferably 80 or higher, more preferably 140 or higher, may be 180 or higher or 200 or higher, preferably 400 or lower, more preferably 300 or lower, and may be 250 or lower. The viscosity index as used herein refers to the viscosity index measured in accordance with JIS K2283:2000.

[0092] The polymer is preferably one in which the residual carbon content after evaporation and thermal decomposition falls within a predetermined range. The reason for this is unknown, but it is presumed that the presence of a precursor (polymer precursor) corresponding to the residual carbon content can further reduce the coefficient of friction in a predetermined 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, even more preferably 1.5% by mass or more, and may 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, even more preferably 4% by mass or less, and may be 3.5% by mass or less. In this specification, residual carbon content means residual carbon content measured by the micro method in accordance with JIS K 2270-2:2009.

[0093] Polymer additives may contain, in addition to the polymer, other components such as diluent oils to improve handling during synthesis, transportation, etc. The physical properties of the polymer described above (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 interpreted as the physical properties of the polymer additive in the state in which it is added to refrigeration oil. However, if the polymer additive contains other components besides the polymer, the number-average molecular weight (Mn) and weight-average molecular weight (Mw) of the polymer additive refer to the values ​​measured excluding those other components.

[0094] In calculating the average molecular weight of each polymer in a polymer additive or refrigeration oil containing the same, the average molecular weight of each polymer may be calculated by gel permeation chromatography as described above using a sample from which components attributable to other components have been separated and excluded from the polymer additive or refrigeration oil containing the same by rubber membrane dialysis or the like. Alternatively, the average molecular weight of each polymer may be calculated using the polymer additive or refrigeration oil containing the same, by excluding the peaks attributable to other components during the gel permeation chromatography calculation process described above.

[0095] More specific examples of the polymers (polymer additives) described above include those described in the examples below, but other examples of polymers (polymer additives) include the following. Polymer additive A: Copolymer of (meth)acrylic acid ester (kinematic viscosity at 100°C: 600 mm) 2 / s, Polymer Mn: 25000, Mw / Mn: 1.4, Residual carbon content: 1.1% by mass Polymer additive B: Copolymer of (meth)acrylic acid ester (kinematic viscosity at 100°C: 370 mm) 2 / s, Polymer Mn: 25900, Mw / Mn: 1.3, Residual carbon content: 1.1% by mass Polymer additive C: Copolymer of (meth)acrylic acid ester (kinematic viscosity at 100°C: 180 mm) 2 / s, Polymer Mn: 3620, Mw / Mn: 2.0, Residual carbon content: 1.3% by mass Polymer additive D: Copolymer of (meth)acrylic acid ester (kinematic viscosity at 100°C: 360 mm) 2 / s, Polymer Mn: 11000, Mw / Mn: 1.6, Residual carbon content: 0.9% by mass Polymer additive E: Copolymer of (meth)acrylic acid ester (kinematic viscosity at 100°C: 380 mm) 2 / s, Polymer Mn: 22500, Mw / Mn: 1.5, Residual carbon content: 0.1% by mass Polymer additive F: Copolymer of maleic acid ester and α-olefin (Kinematic viscosity at 40°C: 1980 mmHg) 2 kinematic viscosity at 100°C: 200 mm² / s 2 / s, viscosity index 227, polymer Mn: 4500, Mw / Mn: 2.2, residual carbon content: 3.1% by mass Polymer additive G: Copolymer of maleic acid ester and α-olefin (Kinematic viscosity at 40°C: 4100 mmHg) 2 kinematic viscosity at 100°C: 260 mm² / s 2 / s, viscosity index 190, polymer Mn: 1800, Mw / Mn: 2.7, residual carbon content: 2.8% by mass Polymer Additive H: Copolymer of maleic acid ester and α-olefin (kinematic viscosity at 40°C: 4300 mm 2 / s, kinematic viscosity at 100°C: 300 mm 2 / s, viscosity index 225, Mn of the polymer: 2000, Mw / Mn: 2.5, residual carbon content: 1.7 mass%) Polymer Additive I: Copolymer of maleic acid ester and α-olefin (kinematic viscosity at 40°C: 7000 mm 2 / s, kinematic viscosity at 100°C: 500 mm 2 / s, viscosity index 230, Mn of the polymer: 2650, Mw / Mn: 4.0, residual carbon content: 2 mass%) Polymer Additive J: Copolymer of maleic acid ester and α-olefin (kinematic viscosity at 40°C: 11000 mm 2 / s, kinematic viscosity at 100°C: 700 mm 2 / s, viscosity index 250, Mn of the polymer: 2690, Mw / Mn: 3.1, residual carbon content: 1.5 mass%) Polymer Additive K: Copolymer of maleic acid ester and α-olefin (kinematic viscosity at 40°C: 400 mm 2 / s, kinematic viscosity at 100°C: 40 mm 2 / s, viscosity index 160, residual carbon content: 0.8 mass%) Polymer Additive L: Copolymer of alkyl methacrylate (alkyl methacrylate includes alkyl methacrylates having a linear alkyl group with 1, 12 - 16, 18 carbon atoms, and alkyl methacrylates having a 2-branched alkyl group with 6, 8, 10 or more and less than 20 carbon atoms as the main components, Mn of the copolymer: 9300, Mw: 16000, Mw / Mn: 1.7) Polymer Additive M: Copolymer of dialkyl maleate and α-olefin with 8 - 10 carbon atoms (dialkyl maleate includes dialkyl maleates having a linear alkyl group with 4, 8 - 10 carbon atoms as the main components, Mn of the copolymer: 8300, Mw: 12800, Mw / Mn: 1.5) Polymer additive N: Copolymer of alkyl methacrylate and C10 α-olefin (The alkyl methacrylate mainly consists of alkyl methacrylate having a linear alkyl group with 12 to 15 carbon atoms, and alkyl methacrylate having a 2-position branched alkyl group with 6, 8, 10 or more but less than 20 carbon atoms; the copolymer has Mn: 6900, Mw: 9900, and Mw / Mn: 1.4) Polymer additive O: Copolymer containing methyl methacrylate, n-dodecyl methacrylate, n-tridecyl methacrylate, n-tetradecyl methacrylate, n-hexadecyl methacrylate, n-octadecyl methacrylate, and 2-decyl-tetradecyl (x=11, y=9) methacrylate as monomer units (Mn=10500, Mw=18000, Mw / Mn=1.7)

[0096] From the viewpoint of further improving the frictional properties of the refrigerant oil, the polymer content 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, based on the total amount of refrigerant oil. From the viewpoint of suppressing the viscosity of the refrigerant oil and achieving a lower coefficient of friction even in regions with relatively high 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 1% by mass or less, and may even be less than 1% by mass.

[0097] The refrigeration oil according to this embodiment may further contain other additives in addition to the components described above. Examples of additives include antioxidants, acid scavengers, phosphorus-free extreme pressure agents, metal deactivators, wear inhibitors, pour point depressants, detergent dispersants, and antifoaming agents. Unless otherwise specified below, the content of these additives may be 10% by mass or less or 5% by mass or less based on the total amount of refrigeration oil.

[0098] Examples of antioxidants include phenolic antioxidants and amine-based 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). Examples of amine-based antioxidants include phenyl-α-naphthylamines and dialkylated diphenylamines. These antioxidants can be used individually or in combination of two or more. The antioxidant content is, for example, 0.01 to 5% by mass, preferably 0.1 to 3% by mass, based on the total amount of refrigerant oil.

[0099] Examples of acid scavengers include epoxy compounds (epoxy acid scavengers). Examples of epoxy compounds 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. These acid scavengers can be used individually or in combination of two or more. The content of the acid scavenger is, for example, 0.01 to 5% by mass, preferably 0.1 to 3% by mass, based on the total amount of refrigerant oil.

[0100] The kinematic viscosity of refrigerant oil at 40°C should be, for example, 10 mm, from the viewpoint of more effectively reducing the coefficient of friction. 2 / s or less, preferably 6 mm 2 / s or less, more preferably 5mm 2 / s or less, more preferably 4 mm 2 / s or less, 3.5mm 2 / s or less, or 3.0mm 2 It may be less than or equal to / s. There is no particular limit to the lower limit of the kinematic viscosity of refrigerant oil at 40°C, but for example, 1 mm 2 / s or more or 2mm 2 It may be 0.5 mm² or more. The kinematic viscosity of the refrigerant oil at 100°C is preferably 0.5 mm². 2 / s or more, more preferably 0.8 mm 2 / s or more, more preferably 1 mm 2 It may be 10 mm² or more. The kinematic viscosity of the refrigerant oil at 100°C is preferably 10 mm². 2 / s or less, more preferably 5mm 2 / s or less, more preferably 3 mm 2 / s or less, particularly preferably 2 mm 2 It can be less than or equal to / s.

[0101] The viscosity index of the refrigeration oil may be -50 or higher, preferably 0 or higher, more preferably 50 or higher, and may be 200 or lower.

[0102] The pour point of the refrigeration oil is preferably -10°C or lower, and more preferably -20°C or lower, -30°C or lower, -40°C or lower, or -45°C or lower.

[0103] The volume resistivity of the refrigerant oil is preferably 1.0 × 10⁻⁶. 9 Ω·m or greater, more preferably 1.0 × 10 10 Ω·m or greater, more preferably 1.0 × 10⁻⁶ 11 It may be Ω·m or greater. Volume resistivity as used herein refers to volume resistivity measured at 25°C in accordance with JIS C2101:1999.

[0104] The moisture content of the refrigerant oil may be preferably 200 ppm or less, more preferably 100 ppm or less, and even more preferably 50 ppm or less, based on the total amount of refrigerant oil. Moisture content as used herein refers to moisture content measured in accordance with JIS K2275-2 or 3 (Karl Fischer volumetric titration method or coulometric titration method).

[0105] The density of refrigerant oil at 15°C is, for example, 0.75 g / cm³. 3 More than 0.76g / cm 3 Above, or 0.77 g / cm³ 3 The above is sufficient, and 0.85 g / cm³ 3 Below, 0.83g / cm 3 Below, 0.81g / cm 3 Below 0.80g / cm 3The following or 0.79 g / cm³ 3 The following is acceptable:

[0106] The flash point of the refrigeration oil may be, for example, 70°C or higher, 80°C or higher, 90°C or higher, 100°C or higher, or 110°C or higher, and may be 150°C or lower, 140°C or lower, or 130°C or lower.

[0107] The acid value of the refrigeration oil is preferably 1.0 mg KOH / g or less, more preferably 0.1 mg KOH / g or less. The hydroxyl value of the refrigeration oil is, for example, 10 mg KOH / g or less, preferably 5 mg KOH / g or less, more preferably 2 mg KOH / g or less. The acid value as used herein refers to the acid value measured in accordance with JIS K2501:2003. The hydroxyl value as used herein refers to the hydroxyl value measured in accordance with JIS K0070:1992.

[0108] From the viewpoint of further reducing the coefficient of friction, the initial boiling point (IBP) of the refrigeration oil is preferably 140°C or higher, 170°C or higher, 190°C or higher, 200°C or higher, 210°C or higher, 220°C or higher, 230°C or higher, or 240°C or higher, and may be 260°C or lower, 255°C or lower, or 250°C or lower.

[0109] From the viewpoint of further reducing the coefficient of friction, the 10% distillation temperature (T10) of the refrigerant oil is preferably 200°C or higher, 210°C or higher, 220°C or higher, 230°C or higher, or 240°C or higher, and may be 260°C or lower, 255°C or lower, or 250°C or lower.

[0110] From the viewpoint of further reducing the coefficient of friction, the 50% distillation temperature (T50) of the refrigerant oil is preferably 210°C or higher, 220°C or higher, 230°C or higher, 240°C or higher, or 245°C or higher, and may be 265°C or lower, 260°C or lower, 255°C or lower, or 250°C or lower.

[0111] The 90% distillation temperature (T90) of the refrigerant oil is preferably 220°C or higher, 230°C or higher, 240°C or higher, 245°C or higher, or 250°C or higher, and may be 270°C or lower, 267°C or lower, 266°C or lower, 265°C or lower, 264°C or lower, 263°C or lower, 262°C or lower, or 261°C or lower, from the viewpoint of further reducing the coefficient of friction.

[0112] From the viewpoint of further reducing the coefficient of friction, the distillation endpoint (EP) of the refrigerant oil is preferably 250°C or higher, 260°C or higher, 270°C or higher, 275°C or higher, or 280°C or higher, and may be 320°C or lower, 310°C or lower, 300°C or lower, 295°C or lower, or 290°C or lower.

[0113] The difference between T90 and T10 of the refrigeration oil (T90-T10) is preferably 5°C or higher, 6°C or higher, 7°C or higher, 8°C or higher, 9°C or higher, or 10°C or higher, and may be 40°C or lower, 30°C or lower, 20°C or lower, or 15°C or lower, from the viewpoint of further reducing the coefficient of friction.

[0114] The total distillate volume of the refrigerant oil may be, for example, 90% or more by volume, 93% or more by volume, or 95% or more by volume, and may be 99% or less by volume. The residual volume of the refrigerant oil may be, for example, 1% or more by volume, or may be 10% or less by volume, 7% or less by volume, or 5% or less by volume. The amount of refrigerant oil lost may be, for example, 1% or less by volume, 0.5% or less by volume, or 0.1% or less by volume, and may be 0% by volume.

[0115] The ash content of the refrigeration oil may preferably be 100 ppm or less, more preferably 50 ppm or less. In this specification, ash content refers to ash content measured in accordance with JIS K2272:1998.

[0116] The residual carbon content of the 10% residue of refrigerant oil may be 0.01% by mass or less, but from the viewpoint of further reducing the coefficient of friction, it is preferably 0.01% by mass or more, 0.02% by mass or more, 0.05% by mass or more, 0.1% by mass or more, 0.2% by mass or more, or 0.21% by mass or more, for example, 0.6% by mass or less, 0.5% by mass or less, or 0.4% by mass or less. In this specification, residual carbon content refers to residual carbon content measured by the micro-method in accordance with JIS K2270-2:2009. In this specification, residual carbon content of the 10% residue refers to residual carbon content measured by the same method in the residue oil after distilling refrigerant oil and removing distillate oil up to 90% by volume.

[0117] The refrigerant oil according to this embodiment may exist in the form of a working fluid composition for a refrigerator mixed with refrigerant in a refrigerator equipped with a refrigerant circulation system having a compressor, condenser, expansion mechanism and evaporator. The refrigerant oil lubricates sliding members in the compressor, for example. That is, another embodiment of the present invention is a working fluid composition for a refrigerator containing the above-mentioned refrigerant oil and refrigerant. The content of the refrigerant oil in the working fluid composition for a refrigerator may be 1 part by mass or more, 2 parts by mass or more, 500 parts by mass or less, or 400 parts by mass or less, per 100 parts by mass of refrigerant.

[0118] Examples of refrigerants include hydrocarbons, saturated fluorinated hydrocarbons, unsaturated fluorinated hydrocarbons, fluorinated ethers such as perfluoroethers, bis(trifluoromethyl) sulfide, methane trifluoride iodide, ammonia, and carbon dioxide.

[0119] The refrigerant preferably contains 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 refrigerant.

[0120] The hydrocarbon is preferably a hydrocarbon having 1 to 5 carbon atoms, more preferably a hydrocarbon having 2 to 4 carbon atoms. Specific 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 of these. Among these, the hydrocarbon is preferably a gaseous hydrocarbon at 25°C and 1 atm, and more preferably propane, n-butane, isobutane, 2-methylbutane, or mixtures thereof.

[0121] Examples of saturated fluorinated hydrocarbons include those having 1 to 3 carbon atoms, more preferably 1 to 2 carbon atoms. Examples of unsaturated fluorinated hydrocarbons (HFOs) include those having 2 to 4 carbon atoms, 1 to 5 fluorine atoms, more preferably fluoropropenes, and even more preferably fluoropropenes with 3 to 5 fluorine atoms. [Examples]

[0122] The present invention will be described in more detail below based on examples, but the present invention is not limited to the following examples.

[0123] The base oils (hydrocarbon base oils) 1 to 4 used in the examples are as follows. Since the aromatic content of these hydrocarbon base oils was less than 1% by mass, chromatographic fractionation was not performed, and all were considered saturated hydrocarbons and hydrocarbon type analysis was performed directly by the GC-TOFMS method or the gas chromatography method described above. The properties of these hydrocarbon base oils are shown in Table 1.

[0124] Base oil (hydrocarbon base oil) 1: Isoparaffin base oil obtained by hydrocracking / isomerization / purification and fractional distillation of paraffin components synthesized from carbon monoxide and hydrogen by the Fischer-Tropsch reaction (aromatic content <0.5% by mass, ASTM color: 0) Base oil (hydrocarbon base oil) 2: Normal paraffinic hydrocarbon oil (aromatic content <0.5% by mass, ASTM color: 0) obtained by adsorption separation using molecular sieves and fractional distillation from the kerosene fraction obtained by hydrodesulfurization of the atmospheric distillation oil of crude oil. Base oil (hydrocarbon base oil) 3: Mineral oil-based hydrocarbon oil obtained by hydrorefining and fractional distillation of hydrocracked diesel oil, which is a raw material containing vacuum distillation residue oil (aromatic content <0.5% by mass, ASTM color: 0). Base oil (hydrocarbon base oil) 4: Mineral oil-based hydrocarbon oil obtained by hydrorefining and fractional distillation of hydrocracked diesel oil, which is a raw material containing vacuum distillation residue oil (aromatic content <0.5% by mass, ASTM color: 0).

[0125] [Table 1]

[0126] Furthermore, the following base oils 5 to 12 were prepared using base oils 1, 2, and 4 described above. Mixture of base oil 5: base oil 1 / base oil 2 (mass ratio 80 / 20) Mixture of base oil 6: base oil 1 / base oil 2 (mass ratio 70 / 30) Mixture of base oil 7: base oil 1 / base oil 2 (mass ratio 55 / 45) Mixture of base oil 8: base oil 1 / base oil 2 (mass ratio 45 / 55) Mixture of base oil 9: base oil 1 / base oil 4 (mass ratio 80 / 20) Mixture of base oil 10: base oil 1 / base oil 4 (mass ratio 65 / 35) Mixture of base oil 11: base oil 1 / base oil 4 (mass ratio 50 / 50) Mixture of base oil 12: base oil 1 / base oil 4 (mass ratio 30 / 70)

[0127] Using each of the base oils 1 to 12 described above, 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 (both based on the total amount of refrigerant oil) to prepare the refrigerant oils for 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 refrigerant oils was all below 267°C. The residual carbon content of the 10% residue of these refrigerant oils was 0.3% by mass. The specific gravity at 15°C for the refrigerant oils of Examples 1 to 7 and the base oils used therein was 0.8017 g / cm³. 3 The following are examples, and in this respect, all of them correspond to "gasoline" as defined in Article 2, Paragraph 1 of the Japanese Gasoline Tax Law.

[0128] Phosphorus-containing anti-wear agent: A mixture of tricresyl phosphate and triphenylphosphorothionate. Polymer additive: Copolymer of dialkyl maleate and α-olefin with 8 to 10 carbon atoms (the dialkyl maleate mainly contains dialkyl maleate having a linear alkyl group with 4 or 8 to 10 carbon atoms; the copolymer has Mn: 8300, Mw: 12800, and Mw / Mn: 1.5)

[0129] [Evaluation of friction properties] The following tests were conducted to evaluate the friction characteristics of the refrigeration oils in the examples and comparative examples. The coefficient of friction (μ) in the lubrication region corresponding to the elastofluid lubrication region or mixed lubrication region was measured using an MTM (Mini Traction Machine) tester (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 properties. Balls and discs: Standard test specimens (AISI 52100 standard) Test temperature: 40℃ Sliding speed: 0.3~0.9 m / s (partial excerpt) Load capacity: 10N Slip ratio: 30% Note that the sliding speed is |U D -U BThe value in m / s was used. Here, UD is the speed of the disk in the sliding part [m / s], and UB is the speed of the ball in the sliding part [m / s].

[0130] [Table 2] [Table 3]

[0131] As described above, the cyclic saturated content is 40% by mass or less, the acyclic saturated content is 60% by mass or more, and the density at 15°C is 0.805 g / cm³. 3 In the examples using base oils with a normal paraffin content of 50% by mass or less, it was possible to reduce the coefficient of friction and suppress the rise in the pour point (the pour point became -10°C or lower). Conversely, in comparisons using base oils that did not satisfy the above properties, the coefficient of friction increased excessively, or the pour point increased excessively (the pour point exceeded -10°C).

[0132] (Low-temperature precipitation test in the presence of refrigerant) For the refrigerant oil of Example 1, a low-temperature precipitation test was conducted in accordance with Annex A of JIS K2211 (2009) using the hydrocarbon refrigerant R600a as the refrigerant. The mixed fluid of refrigerant oil and R600a did not produce any fuzzy precipitates, granular precipitates, cloudiness, or turbidity even when cooled to -40°C in the range of refrigerant oil / refrigerant ratio (mass ratio) of 1 / 99 to 99 / 1, and no tendency toward low-temperature precipitation was observed.

Claims

1. The cyclic saturated content is 40% by mass or less, the acyclic saturated content is 60% by mass or more, and the density at 15°C is 0.805 g / cm³. ３ A base oil for refrigeration oil, wherein the normal paraffin content is 50% by mass or less, the content of hydrocarbons having 12 to 16 carbon atoms in the base oil is 80% by mass or more, the initial boiling point of the base oil is 140°C or higher and 250°C or lower, and the 90% distillation temperature is 270°C or lower.

2. The base oil for refrigeration oil according to Claim 1, comprising a hydrocarbon base oil having a density of 0.780 g / cm³ or less at 15°C.

3. A refrigeration oil base oil according to claim 1 or 2, comprising a hydrocarbon base oil having a normal paraffin content of less than 5% by mass.

4. The refrigeration oil base oil according to claim 3, further comprising, in addition to the hydrocarbon base oil, a second hydrocarbon base oil having a normal paraffin content of 5% by mass or more.

5. The refrigeration oil base oil according to claim 3, wherein the initial boiling point of the hydrocarbon base oil is 140°C or higher, and the 90% distillation temperature is 270°C or lower.

6. A refrigerant oil containing the base oil for refrigerant oil described in claim 1 or 2.

7. The refrigerant oil according to claim 6, further comprising a phosphorus-containing anti-wear agent.

8. The refrigerant oil according to claim 6, further containing a polymer additive.

9. The refrigerant oil according to claim 6, wherein the residual carbon content of the 10% residual oil of the refrigerant oil is 0.02% by mass or more.

10. The refrigerant oil according to claim 6, wherein the 90% distillation temperature of the refrigerant oil is 270°C or lower.

11. The refrigerating oil described in claim 6, Refrigerant and A working fluid composition for refrigerators containing the following:

12. The working fluid composition for a refrigerator according to claim 11, wherein the refrigerant comprises a hydrocarbon.

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