Compositions containing lubricating oil, compositions containing refrigeration oil, refrigeration compressors, and refrigeration systems.

Abstract

The present invention provides a composition containing a lubricating oil with a high energy-saving rate, and in particular, a refrigeration oil-containing composition that enables energy savings for use in refrigeration machines. [Solution] A composition containing a lubricating oil and fine particles in a polydisperse state. In the polydisperse state, the D90 of the fine particles (the particle diameter at which the proportion of particles with a particle diameter of D90 or less accounts for 90% by volume of the total fine particles) is preferably 80 nm or larger.

Description

Technical Field

[0001] The present invention relates to a composition containing an energy-saving lubricating oil, a refrigerant oil-containing composition, a refrigeration compressor, and a refrigeration device.

Background Art

[0002] Patent Document 1 discloses a refrigerant compressor including a sealed container, an electric element housed in the sealed container, and a compression element housed in the sealed container, driven by the electric element, having a sliding portion, and compressing a refrigerant. Refrigerant oil for lubricating the sliding portion is stored in the sealed container. The refrigerant oil is obtained by adding and dissolving fullerene having a diameter of 100 pm to 10 nm in an amount less than the saturated solubility in the refrigerant oil, and the fullerene in the refrigerant oil remains uniformly dispersed even when the refrigerant compressor stops. Patent Document 2 describes a refrigerant working fluid including a refrigerant oil and a refrigerant composition containing fluororesin particles having D of 2.0 μm to 10.0 μm and D of 4.0 to 14.0 and D / D. 50 and 4.0 to 14.0 of D 90 / D 10 A refrigerant working fluid including a refrigerant oil and a refrigerant composition containing fluororesin particles having D of 2.0 μm to 10.0 μm and D of 4.0 to 14.0 and D / D is described.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, the proportion of refrigerators and air conditioning systems in the world's energy consumption has been increasing, and energy regulations in the refrigeration and freezing fields have been strengthened in various countries. In order to comply with energy regulations, the development of technologies with low cost and high energy-saving efficiency has been promoted. From a materials perspective, technological development aimed at energy conservation in refrigeration cycles has primarily focused on developing materials with high thermal insulation properties and heat exchanger structures with high thermal conductivity. However, improvements to compressor oils for refrigeration cycles, even within the realm of energy conservation, have mainly involved the development of new refrigerants aimed at viscosity adjustment, additive development, and improved thermal conductivity, and have not led to the development of next-generation refrigeration oils that would result in technological innovation. The present invention aims to provide a composition containing a lubricating oil with a high energy-saving rate, and in particular to provide a refrigeration oil-containing composition that is energy-saving for use in refrigeration machines. [Means for solving the problem]

[0005] The invention of claim 1 of the present invention, completed with this objective in mind, is a composition comprising a lubricating oil and fine particles present in a polydisperse state. The invention of claim 2 is the composition according to claim 1, wherein in the polydisperse state, the D90 of the fine particles (the particle diameter at which the proportion of particles with a particle diameter of D90 or less accounts for 90% by volume of the total fine particles) is 80 nm or more. The invention of claim 3 is the composition according to claim 2, wherein, in the polydisperse state, the D10 of the fine particles (the particle diameter at which the proportion of particles with a particle diameter of D10 or less accounts for 10 volume% of the total fine particles) is 30 nm or more, and the D90 of the fine particles is 1000 nm or less. The invention of claim 4 is the composition according to claim 1, wherein the fine particles consist of an inorganic compound or an organic compound. The invention of claim 5 is the composition according to claim 4, wherein the inorganic compound is one or more selected from the group consisting of titanium dioxide, silicon dioxide, aluminum oxide, iron oxide, copper oxide, and aluminum nitride. The invention of claim 6 is the composition according to claim 1, wherein the composition further comprises a dispersant having a hydrophobic portion and a hydrophilic portion. The invention of claim 7 is a refrigerant oil-containing composition in which the lubricating oil is a refrigerant oil, in any one of claims 1 to 6. The invention of claim 8 is the refrigerant oil-containing composition according to claim 7, further comprising a refrigerant. The invention of claim 9 is a refrigeration compressor comprising the refrigeration oil-containing composition described in claim 8. The invention of claim 10 is a refrigeration apparatus including the refrigeration compressor described in claim 9. [Effects of the Invention]

[0006] According to the invention of claim 1, it is possible to provide an energy-saving composition compared to a case in which fine particles exist in a monodisperse state. According to the invention of claim 2, it is possible to provide a composition in which the coefficient of friction is reduced when the composition is used as a lubricant, compared to the case in which the D90 of the fine particles present in the composition is small. According to the invention of claim 3, 4, or 5, a composition with a reduced coefficient of friction can be provided. According to the invention of claim 6, it is possible to provide a composition that can reduce the coefficient of friction and improve energy saving efficiency. According to the invention of claim 7 or 8, an energy-saving composition for a refrigerator can be provided. According to the invention of claim 9 or 10, an apparatus with improved energy saving efficiency can be provided. [Brief explanation of the drawing]

[0007] [Figure 1] This is a particle size distribution diagram of fine particles in a fine particle dispersion oil. (a) is the particle size distribution diagram in Example 1, and (b) is the particle size distribution in Comparative Example 2. [Figure 2] This is a schematic diagram of the state of fine particles in the composition of this embodiment. (a) is a schematic diagram of the state of the relatively smaller particles in fine particles 1, and (b) is a schematic diagram of the state of the relatively larger particles in fine particles 1. [Figure 3] This graph shows the relationship between the dispersed particle sizes D10, D50, and D90 and the energy saving rate in Examples 1 to 12 and Comparative Example 2. [Modes for carrying out the invention]

[0008] Hereinafter, embodiments of the present invention will be described in detail. The embodiments shown below are examples and do not limit the technical scope of the present invention to the following aspects. In the present disclosure, the description of "XX or more and XX or less" or "XX to XX" representing a numerical range means a numerical range including the described upper and lower limits, unless otherwise specified.

[0009] The composition according to this embodiment is a composition containing lubricating oil and fine particles present in a polydisperse state. The lubricating oil is not particularly limited and can be any commonly used lubricating oil. Lubricating oils are mainly classified into industrial lubricating oils and automotive lubricating oils, and either of them can be used in the present invention. Among industrial lubricating oils, since it is suitable for applications using a refrigeration cycle and particularly suitable for refrigeration machine oil, hereinafter, refrigeration machine oil will be described in this embodiment.

[0010] Refrigeration machine oil is the lubricating oil for compressors used in refrigeration and air conditioning. Different from other lubricating oils, it has the characteristic of directly contacting the refrigerant that is responsible for heat energy transfer in refrigeration and air conditioning equipment. Specific refrigeration machine oils include, among general lubricating oils, for example, paraffinic or naphthenic mineral oils, alkylbenzenes, polyalkyl glycols, polyol esters, polyvinyl alcohol, polyalphaolefins, etc. One or more selected from these are used.

[0011] Examples of refrigerant systems used together with refrigeration machine oil include CFC, HCFC, HC, HFC, HFO, NH3, CO2, HF, etc. A suitable combination of refrigeration machine oil and refrigerant system is selected and used. Although the general combinations of refrigeration machine oil and the refrigerant systems suitable for them are as follows, there may be cases where a refrigeration machine oil is not suitable for a specific refrigerant. "Refrigeration machine oil: Suitable refrigerant system" · Mineral oil: CFC, HCFC, HC, NH3 · Alkylbenzene: HCFC · Polyalkyl glycol: HCFC, HFC, HFO, CO2, NH3 · Polyol ester: HFC, HFO · Polyvinyl alcohol: HFC, HFO · Polyalphaolefin: HFC, HFO, HF For example, in the examples of this application, paraffin-based mineral oil is used as the refrigeration oil, and HC is used in combination as the refrigerant. The refrigerant specifically used is usually selected from those with a refrigerant number (ASHRAE number) starting with R. The particularly suitable refrigerants are listed below according to the refrigerant system. · HFC series: R134a, R23, R32, R404A, R407C, R407H, R410A, R448A, R449A · HFO series: R1234yf · HCFC series: R22 · Others: R600a, R744, R290

[0012] [[ID=二十]]The composition according to this embodiment includes fine particles present in a polydisperse state together with the lubricating oil. Particles are a general term for relatively small objects, and there are various shapes and densities. Fine particles specifically refer to the finer ones among the particles, and there are objects of various sizes in nature. The "fine particles" in this embodiment refer to particles with a primary particle diameter of less than 1 μm in the solution measured by the dynamic light scattering method. This embodiment is characterized in that the fine particles exist in a polydisperse state in a liquid such as a lubricating oil. Due to the fine particles existing in a polydisperse state, the static friction coefficient and dynamic friction coefficient of the entire composition become small, and it becomes possible to provide a composition that can save energy particularly when used in a refrigerator. As a result, it becomes possible to provide a highly reliable refrigerant compressor and a refrigeration device using the same using an existing refrigeration cycle, so it can be widely applied to equipment and products using a refrigeration cycle.

[0013] A polydisperse state is a state that is contrasted with a monodisperse state in which the particle size of the fine particles is not distributed but is almost uniform. Even in a monodisperse state, it is not theoretically a completely identical state. In this embodiment, as an index for measuring the degree of dispersion of fine particles in a liquid, a polydisperse state is defined as a state in which the difference between D10 and D90 is 30 nm or more. The difference between D10 and D90 is determined by dynamic light scattering measurement. First, the cumulative distribution function of the dispersed particle size distribution is determined for the fine particles dispersed in the liquid, and D10, D50, and D90 are determined from this cumulative distribution function. D10 is the particle size at which the proportion of particles with a particle size of D10 or less accounts for 10 volume percent of the total fine particles. D50 is the particle size at which the proportion of particles with a particle size of D50 or less accounts for 50 volume percent of the total fine particles, and is also called the median diameter. And D90 is the particle size at which the proportion of particles with a particle size of D90 or less accounts for 90 volume percent of the total fine particles. The measured particle size is the dispersed particle size present in the composition. Therefore, the measured dispersed particle size is not necessarily the diameter of the primary particles, but may also be secondary or tertiary particles formed by the aggregation of primary particles. In addition, particles with a smaller particle size distribution may be measured as primary particles, while particles with a larger particle size distribution may be measured as secondary or tertiary particles. If the aggregated particles form a desirable particle size distribution, the primary particle size can be anything. Figure 1 shows an example of a particle size distribution map when fine particles are present in a polydisperse state. The horizontal axis represents the dispersed particle diameter, and the vertical axis represents the frequency. Figure 1(a) is a particle size distribution map of fine particles in a fine particle dispersion oil of Example 1, where the difference between D10 and D90 is a large 407 nm. Figure 1(b) is a particle size distribution map of fine particles in a fine particle dispersion oil of Comparative Example 2, where the difference between D10 and D90 is a small 27 nm, representing a monodisperse state.

[0014] As mentioned above, the presence of fine particles in a polydisperse state reduces the friction coefficient of the composition, improving the energy efficiency of refrigeration equipment using the composition and achieving energy savings. The mechanism is explained below. In the case of the refrigeration oil of this embodiment, the friction between the cylinder and piston in the compressor of the refrigeration unit greatly affects the efficiency of the equipment. On the other hand, since the fine particles exist in a polydisperse state, the particle size of the fine particles is widely distributed. Figure 2(a) shows a schematic diagram of the situation of the relatively smaller particles in the fine particles 1. As shown in Figure 2(a), it is presumed that the relatively smaller particles in the fine particles 1 adhere to the irregularities of the grooves on the wall surface 2 of the cylinder and piston, smoothing the surface and reducing the coefficient of friction of the entire composition. Figure 2(b) also shows a schematic diagram of the situation of the relatively larger particles in the fine particles 1. As shown in Figure 2(b), it is presumed that the relatively larger particles in the fine particles 1 get stuck between the walls of the cylinder and piston, reducing the surface area and producing an effect similar to a bearing, thereby reducing friction. In particular, in this embodiment, as the cylinder and piston slide, the aggregated particles deaggregate into primary particles and become smaller, resulting in a particle size suitable for smoothing the roughness of the sliding part between the cylinder and piston. Furthermore, the relatively large particles in the pre-smoothing stage exhibit the same effect as bearings, as described above. As a result, the overall friction coefficient of the composition is reduced, achieving energy savings.

[0015] In this embodiment, the fine particles reduce the overall friction coefficient of the composition and enable energy saving when used as refrigerant oil. Therefore, the D90 of the refrigerant oil is preferably 80 nm or more, more preferably 100 nm or more, and particularly preferably 200 nm or more. Furthermore, the combination of D10 and D90, which is the range in which the most desirable fine particles are mainly distributed, reduces the overall friction coefficient of the composition and enables energy saving when used as a refrigeration oil, D10 is preferably 30 nm or more, and D90 is preferably 1000 nm or less. In particular, D10 is preferably 40nm or greater, and D90 is preferably 590nm or less. Furthermore, D10 is preferably 145nm or greater, and D90 is preferably 410nm or less. To achieve energy savings, a broad distribution of fine particles is preferable, and a difference of 40 nm or more between D10 and D90 is preferable. In particular, when the difference between D10 and D90 is 100 nm or more, it is possible to easily achieve an energy saving rate of 2.5% or more, which is preferable. However, a D90 that is too large is also unsuitable, so a difference of 900 nm or less between D10 and D90 is practical. A distribution of polydisperse particles with a preferred particle size may be composed of fine particles of two or more materials. Alternatively, multiple monodisperse particles may be used to create a polydisperse state overall.

[0016] The material of the fine particles in this embodiment is not particularly limited as long as it can maintain a desirable dispersed particle size in a polydisperse state in refrigerant oil. Fine particles made from inorganic compounds, organic compounds, etc., can be appropriately selected and used. Examples of microparticles using inorganic compounds include those made from metal oxides, carbonates, sulfates, hydroxides, metals, metal nanotubes, smectite, glass beads, talc, and carbon-based fillers. Examples of microparticles using organic compounds include those made from polymer resins and organic pigments. In addition, microparticles using inorganic-organic composite compounds are also possible. Examples of inorganic compounds used in specific fine particles include metal oxides, and specific examples of inorganic compounds including metal oxides include titanium dioxide (TiO2), silicon dioxide (SiO2), aluminum oxide (Al2O3), iron oxide (Fe2O3), copper oxide (CuO), and aluminum nitride (AlN). Among these, titanium dioxide is the most preferred. In the case of titanium dioxide, the crystal system can be either anatase or rutile, or a mixed crystal system. When using metal oxides, including titanium dioxide, it is preferable to modify the surface of the fine particles with hydrophobic substituents to improve the dispersibility of the fine particles. Examples of hydrophobic substituents include hydrophobic alkyl groups such as isobutyl groups and octyl groups.

[0017] If there are too many fine particles in the refrigerant oil, the dispersibility will be poor. Therefore, it is preferable to include 5% by mass or less in the composition, and a more preferable content is 0.5% by mass or more and 2% by mass or less.

[0018] The composition according to this embodiment preferably includes a dispersant to further improve the dispersibility of the fine particles. The dispersant is generally a substance called a surfactant or dispersant, and it is preferable that it has substituents or molecular structures that have affinity for both the refrigerant oil and the fine particles. In other words, when the fine particles are hydrophilic, such as metal oxides represented by titanium dioxide, as in this embodiment, it is preferable that the dispersant has a hydrophilic portion that has affinity for the fine particles and a hydrophobic portion that has affinity for the refrigerant oil. When using metal oxides such as titanium dioxide as fine particles, preferred dispersants include low-molecular-weight compounds equivalent to monomers, such as compounds having polar groups such as carboxyl groups or amino groups in an alkyl group. Specific examples of such compounds are given below. • Carboxylic acid compounds such as oleic acid, stearic acid, and linoleic acid • Amino compounds such as oleylamine • Phosphate compounds such as octadecylphosphonic acid • Phosphine oxide compounds such as trioctylphosphine oxide Furthermore, polyoxyethylene(10) octylphenyl ether is another preferred example of a compound having polyethylene oxide in the aromatic alkyl group. When using metal oxides such as titanium dioxide, preferred dispersants include polymers having polar groups such as carboxyl groups and amino groups. As a dispersant, polymers with polar groups are preferred over low-molecular-weight compounds. If the amount of dispersant in the refrigerant oil is too much, the dispersibility will be poor. Therefore, the preferred content is 5% by mass or less in the composition, a more preferred content is 0.5% by mass or more and 2% by mass or less, and an even more preferred content is 0.5% by mass or more and 1.0% by mass or less.

[0019] In addition, in the composition according to this embodiment, it is also possible to add, as needed, at least one selected from the group consisting of load-bearing additives, chlorine scavengers, detergent dispersants, viscosity index improvers, heat resistance improvers, stabilizers, chlorine scavengers, detergent dispersants, corrosion inhibitors, pour point lowering agents, and rust inhibitors to the refrigerant oil. Furthermore, in addition to or in addition to the above-mentioned addable substances, it is also possible to add at least one selected from the group consisting of compatibilizers, ultraviolet fluorescent dyes, polymerization inhibitors, antioxidants, extreme pressure agents, acid scavengers, oxygen scavengers, copper deactivators, rust inhibitors, oiliness agents, and defoaming agents.

[0020] The method for preparing the composition according to this embodiment is not particularly limited. Methods for dispersing fine particles and other additives such as dispersants into refrigeration oil, as needed, include conventional dispersion techniques such as mixing and stirring with stirrers and agitators, de-agglutination techniques using ultrasound, and bead mills using microbeads, which can be used as appropriate.

[0021] An example of a method for preparing the composition according to this embodiment is described below in the order of (1), (2), etc. (1) Preparation and weighing of raw materials: Prepare refrigerant oil, fine particles, and additives such as other dispersants as needed, and weigh out the required amounts. (2) Preparation of refrigeration oil: If a dispersant is used, add the dispersant to the refrigeration oil and dissolve it thoroughly. (3) Filling with fine particles: Add the fine particles to the refrigerant oil obtained in (2), disperse them in the refrigerant oil to some extent, and then transfer them to a reaction vessel equipped with a magnetic stirrer. (4) Adding beads: For example, add stirring beads with a diameter of 50 micrometers to the reaction vessel from (3) in an amount of approximately 20% by volume relative to the liquid volume of the refrigerant oil. (5) De-aggregation: The refrigerant oil to which the beads have been added is stirred at room temperature at a speed of, for example, 1000 revolutions per minute for a time appropriate to the amount, materials used, etc., to de-aggregate the fine particles. (6) Let stand: Let stand for a few minutes, for example, until the agitation beads have completely sunk. (7) Separation and recovery: The refrigerant oil containing fine particles in a polydisperse state is recovered from the reaction vessel by decantation, and the stirring beads are separated.

[0022] The present invention is not limited to the embodiments described above, and other embodiments are possible as long as they are within the spirit of the present invention. For example, while lubricating oil has been explained primarily in the context of refrigeration oil, it can also be used as other industrial lubricants such as bearing oil, turbine oil, and hydraulic fluid, as well as automotive lubricants such as engine oil, gear oil, and automatic transmission oil. [Examples]

[0023] The embodiments of the invention will be described in detail below with reference to examples, but the embodiments of the invention are not limited to these examples. In the following description, unless otherwise specified, "%" refers to mass.

[0024] (Examples 1-12, Comparative Examples 1-2) <Preparation of finely dispersed oil> Using refrigeration cycle compressor base oil (FREOL S5P) as the refrigeration oil, a particulate dispersion oil was prepared by blending fine particles and a dispersant into this refrigeration cycle compressor base oil according to the following procedure. Fine particles and dispersant were weighed and prepared in amounts that constituted 1% of the compressor base oil for the refrigeration cycle. The particle type, crystal form, and primary particle size of the fine particles are listed in Table 1 or Table 2. The fine particles in Comparative Example 2 and Example 6 had their surfaces modified with isobutyl groups, while the other fine particles were unmodified. The crystal forms of aluminum oxide, copper oxide, and aluminum nitride are unknown and are therefore indicated as "—" in the table. The dispersants used were either high-molecular-weight or low-molecular-weight dispersants as described below. As shown in Tables 1 and 2, high-molecular-weight dispersants were used in the comparative examples and examples in Table 1 and are labeled "high-molecular-weight," while low-molecular-weight dispersants were used in the examples in Table 2 and are labeled "low-molecular-weight." * Dispersant • Polymeric dispersant: Organically modified polymer containing amino groups. Amine value approximately 30 mg KOH / g. • Low molecular weight dispersant: Trioctylphosphine oxide A dispersant was added to the compressor base oil for the refrigeration cycle, and the dispersant was allowed to dissolve completely. Next, the fine particles were added to the compressor base oil in which the dispersant had dissolved, and after the particles were dispersed to some extent, the mixture was transferred to a glass container equipped with a magnetic stirrer. Zirconia (ZrO2) beads with a diameter of 50 μm were added in an amount that occupied approximately 20% of the volume relative to the liquid volume of the compressor base oil, and the mixture was stirred at a speed of 1000 rpm for 360 minutes at room temperature to disperse the fine particles in the compressor base oil. After stirring, the oil was allowed to stand for several minutes to allow the zirconia beads to settle completely, and the supernatant was separated by decantation to obtain the particulate dispersion oils of Examples 1-12 and Comparative Example 2. In Comparative Example 1, no particulates or dispersants were used, and only base oil for refrigeration cycle compressors (hereinafter abbreviated as "Base oil") was used as a control. To understand the dispersion state of the particulate matter in each particulate dispersion, D10, D50, and D90 were measured using a dynamic light scattering photometer (DLS-8000) manufactured by Otsuka Electronics Co., Ltd., and the measured values ​​are listed in Tables 1 and 2. The measurement conditions were a measurement angle of 90 degrees and a measurement temperature of 25°C, and D10, D50, and D90 were calculated using the values ​​of refractive index 1.467, dielectric constant 2.2, and viscosity 6.3.

[0025] <Refrigerator power consumption evaluation> The evaluation method for refrigerator power consumption was conducted in accordance with the IEC62552 standard. A built-in freezer (a refrigerator integrated into a built-in cabinet or shelf) model number RZ38B98C5AP manufactured by Samsung Electronics Co., Ltd., which is a refrigeration unit for R600a, was used as the evaluation refrigerator. For the initial evaluation, a refrigerator was modified to install a temperature sensor and refrigerant pressure gauge. Vacuuming and refrigerant charging were then performed, followed by an evaluation of power consumption using the base oil from Comparative Example 1. The initial evaluation was conducted 72 hours after the refrigerator started operation. After the initial evaluation, the refrigeration cycle was cleaned. This cleaning involved first removing the compressor, then flushing a special refrigeration cycle cleaning solution (manufactured by Asahi Kasei Corporation; product name: AMOLEA AS-300) through the discharge pipe connection on the freezer side of the refrigeration cycle, and draining it through the suction pipe connection on the freezer side of the refrigeration cycle. After the cleaning, a vacuum pump was used to create a vacuum, which evaporated any remaining cleaning solution from the refrigeration circuit. Next, the oil accumulated inside the compressor was discharged from the process pipe connection. At this time, in order to thoroughly discharge the accumulated oil, new base oil was introduced multiple times through the process pipe to dilute and discharge the base oil accumulated inside the compressor. After the cleaning process, the particulate dispersion oils of Examples 1-12 and Comparative Example 2 were replaced, and evaluations were performed under the same conditions as when the base oil was measured. For the evaluation of the particulate dispersion oil, stable data for 10 cycles was obtained for each particulate dispersion oil, the annual power consumption was calculated, and compared with the annual power consumption when using the base oil of Comparative Example 1. The annual energy saving rate was calculated using the following formula and is shown in Tables 1 and 2. In the tables, the ▲ symbol next to the energy saving rate indicates a negative value.

[0026]

number

[0027] Here, the meaning of each character is as follows: Φ Energy saving rate (%) P n Annual power consumption (kWh / year) when using particulate dispersed oil. P BASE Annual power consumption (kWh / year) when using base oil.

[0028] [Table 1]

[0029] [Table 2]

[0030] Figure 3 shows graphs illustrating the relationship between the dispersed particle sizes D10, D50, and D90 and the energy saving rate in Examples 1 to 12 and Comparative Example 2. In Figure 3, the horizontal axis represents the energy saving rate (more precisely, the negative value), and the vertical axis represents the dispersed particle size. As is clear from Figure 3, there is a roughly positive relationship between the dispersed particle size and the energy saving rate, with the energy saving rate increasing as the dispersed particle size increases. Furthermore, the higher the degree of dispersion of the fine particles and the larger the difference between D10 and D90, the more significantly the energy saving rate increases. Furthermore, it was found that the energy saving rate is not affected by the type of fine particles, crystal system, or primary particle size.

[0031] <Friction Test> Friction tests were performed on the base oil of Comparative Example 1 and the fine particle dispersion oil of Example 1. The tests were conducted using a stainless steel SUS304 plate thoroughly cleaned with anhydrous ethanol and a SUS304 ball indenter with a diameter of 10 mm, using a friction and wear testing machine "Tribogear" (TYPE: 40, manufactured by Shinto Kagaku Co., Ltd.). The static friction coefficient was measured after dropping 10 drops (approximately 60 μL) of the test oil onto the sliding surface of a stainless steel plate and starting the test. The dynamic friction coefficient was measured under the following conditions: load of 500 g, sliding speed of 800 mm / s, sliding distance of 10 mm, and environmental conditions of 25.5°C and 61% humidity, after 50 reciprocating slides. The results are shown in Table 3.

[0032] [Table 3]

[0033] It was confirmed that the coefficient of friction was significantly lower for the finely dispersed oil compared to the base oil, both in terms of static and dynamic friction. [Explanation of symbols]

[0034] 1…microparticles, 2…walls

Claims

1. A composition containing a lubricating oil and fine particles present in a polydisperse state.

2. The composition according to claim 1, wherein in the polydisperse state, the D90 of the fine particles (the particle diameter at which the proportion of particles with a particle diameter of D90 or less accounts for 90% by volume of the total fine particles) is 80 nm or more.

3. The composition according to claim 2, wherein in the polydisperse state, the D10 of the fine particles (the particle diameter at which the proportion of particles with a particle diameter of D10 or less accounts for 10% by volume of the total fine particles) is 30 nm or more, and the D90 of the fine particles is 1000 nm or less.

4. The composition according to claim 1, wherein the fine particles consist of an inorganic compound or an organic compound.

5. The composition according to claim 4, wherein the inorganic compound is one or more selected from the group consisting of titanium dioxide, silicon dioxide, aluminum oxide, iron oxide, copper oxide, and aluminum nitride.

6. The composition according to claim 1, further comprising a dispersant having a hydrophobic portion and a hydrophilic portion.

7. A refrigerant oil-containing composition according to any one of claims 1 to 6, wherein the lubricating oil is a refrigerant oil.

8. The refrigerant oil-containing composition according to claim 7, further comprising a refrigerant.

9. A refrigeration compressor comprising the refrigeration oil-containing composition according to claim 8.

10. A refrigeration apparatus including the refrigeration compressor described in claim 9.

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