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EP-4134417-B1 - REFRIGERATING MACHINE OIL, WORKING FLUID COMPOSITION FOR REFRIGERATING MACHINE, AND METHOD FOR PRODUCING REFRIGERATING MACHINE OIL

EP4134417B1EP 4134417 B1EP4134417 B1EP 4134417B1EP-4134417-B1

Inventors

  • NARA FUMIYUKI
  • SHONO Yohei
  • OGATA HIDETOSHI

Dates

Publication Date
20260513
Application Date
20210427

Claims (8)

  1. A refrigerating machine oil comprising a mixed base oil of a first hydrocarbon base oil having a kinematic viscosity at 40°C of less than 6 mm 2 /s and a second hydrocarbon base oil having a kinematic viscosity at 40°C of 10 mm 2 /s or more, wherein a (A)/(B) ratio is more than 1 and 1.25 or less, wherein (A) is a kinematic viscosity at 40°C of the mixed base oil, and (B) is the kinematic viscosity at 40°C of the first hydrocarbon base oil, wherein, when a plurality of base oil components corresponding to the first hydrocarbon base oil or the second hydrocarbon base oil are contained, (A) means the kinematic viscosity at 40°C of the mixed base oil containing all the base oil components corresponding to the first hydrocarbon base oil or the second hydrocarbon base oil, and, when a plurality of base oil components corresponding to the first hydrocarbon base oil are contained, (B) means the kinematic viscosity at 40°C of the mixed base oil containing all of the base oil components corresponding to the first hydrocarbon base oil, wherein the kinematic viscosity is measured in accordance with JIS K2283:2000, and wherein the refrigerating machine oil comprises a phosphorus-containing additive.
  2. The refrigerating machine oil according to claim 1, wherein the kinematic viscosity at 40°C of the second hydrocarbon base oil is 20 mm 2 /s or more and 1000 mm 2 /s or less.
  3. The refrigerating machine oil according to claim 1 or 2, wherein a content of the second hydrocarbon base oil in the mixed base oil is 0.5% by mass or more and 10% by mass or less.
  4. The refrigerating machine oil according to any one of claims 1 to 3, having a kinematic viscosity at 40°C of 6 mm 2 /s or less.
  5. Use of the refrigerating machine oil according to any one of claims 1 to 4 in a working fluid composition together with a hydrocarbon refrigerant.
  6. A working fluid composition for a refrigerating machine oil comprising: the refrigerating machine oil according to any one of claims 1 to 4; and a refrigerant.
  7. The working fluid composition for a refrigerating machine oil of claim 6, wherein the refrigerant comprises a hydrocarbon refrigerant.
  8. A method for producing a refrigerating machine oil comprising a mixed base oil of a first hydrocarbon base oil having a kinematic viscosity at 40°C of less than 6 mm 2 /s and a second hydrocarbon base oil having a kinematic viscosity at 40°C of 10 mm 2 /s or more, the method comprising: mixing the first hydrocarbon base oil and the second hydrocarbon base oil such that a (A)/(B) ratio is more than 1 and 1.25 or less, wherein (A) is a kinematic viscosity at 40°C of the mixed base oil, and (B) is the kinematic viscosity at 40°C of the first hydrocarbon base oil, wherein, when a plurality of base oil components corresponding to the first hydrocarbon base oil or the second hydrocarbon base oil are contained, (A) means the kinematic viscosity at 40°C of the mixed base oil containing all the base oil components corresponding to the first hydrocarbon base oil or the second hydrocarbon base oil, and, when a plurality of base oil components corresponding to the first hydrocarbon base oil are contained, (B) means the kinematic viscosity at 40°C of the mixed base oil containing all of the base oil components corresponding to the first hydrocarbon base oil, wherein the kinematic viscosity is measured in accordance with JIS K2283:2000, and wherein the refrigerating machine oil comprises a phosphorus-containing additive.

Description

Technical Field The present invention relates to a refrigerating machine oil, a working fluid composition for a refrigerating machine, and a method for producing a refrigerating machine oil. Background Art A refrigerating machine such as a refrigerator contains a refrigerant circulation system containing a compressor, a condenser, an expansion mechanism (an expansion valve, a capillary), an evaporator, and the like, and heat exchange is performed by circulating a refrigerant in the refrigerant circulation system. Compressors for refrigerating machines contains rotary compressors, piston-crank compressors, and the like. For example, in a piston-crank type compressor, a rotary motion of a motor is converted into a reciprocating motion by a connecting rod, and a piston coupled to the connecting rod is reciprocated to compress a refrigerant. The refrigerating machine oil is sealed in a compressor together with a refrigerant, and lubricates sliding members such as a connecting rod and a piston. As such a refrigerating machine oil, for example, the following Patent Document 1 discloses a refrigerating machine oil containing a mineral oil having a relatively low viscosity and a specific copolymer. EP1995299A1 and EP3521407A1 also relate to refrigerating machine oils. Citation List Patent Document [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2018-83920 Summary of Invention Technical Problem When the viscosity at 100°C of the conventional refrigerating machine oil is lowered, it is effective to some extent for lowering the friction in the fluid lubrication region, but in a low sliding speed region such as an elastic fluid lubrication region, a mixed lubrication region, or a boundary lubrication region, the opportunity of metal-to-metal contact increases, and the friction coefficient tends to increase. In addition, for example, the above-described conventional refrigerating machine oil is expected to be effective to some extent in reducing friction in a boundary lubrication region having a high friction coefficient, but is not necessarily sufficient in improving efficiency of a compressor. In particular, in a lubrication region (an elastic fluid lubrication region or a mixed lubrication region) having a relatively high sliding speed in which the friction coefficient rapidly starts to increase as the sliding speed decreases, which is focused on by the present inventors, there is a problem in that the friction coefficient rather increases. The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a refrigerating machine oil having excellent low friction characteristics even in a lubrication region where a sliding speed is relatively high as described above. Solution to Problem The present invention is concerned with a refrigerating machine oil according to claim 1. Preferred embodiments are defined in claims 2 to 4. Further, the present invention is concerned with the use of the refrigerating macghine oil according to claim 5 and to a working fluid composition according to claim 6. A perferred embodiment of the working fluid composition is defined in claim 7. Moreover, the present invention is concerned with a method for producing a refrigerating machine oil according to claim 8. Advantageous Effects of Invention According to the present invention, it is possible to provide a refrigerating machine oil having excellent low friction characteristics even in a lubrication region in which a sliding speed is relatively high. Description of Embodiments Hereinafter, embodiments of the present invention will be described in detail. The refrigerating machine oil according to the present embodiment contains a mixed base oil of a first hydrocarbon base oil having a kinematic viscosity at 40°C of less than 6 mm2/s and a second hydrocarbon base oil having a kinematic viscosity at 40°C of 10 mm2/s or more. As the first hydrocarbon base oil, for example, a mineral hydrocarbon oil, a synthetic hydrocarbon oil, or a mixture thereof can be used. Examples of the mineral oil-based hydrocarbon oil include paraffinic mineral oils and naphthenic mineral oils obtained by refining a lubricating oil fraction obtained by atmospheric distillation or vacuum distillation of a paraffinic or naphthenic crude oil by a method such as solvent deasphalting, solvent refining, hydrorefining, hydrocracking, solvent dewaxing, hydrodewaxing, clay treatment, or sulfuric acid washing. These purification methods may be used alone or in combination of two or more thereof. Examples of the synthetic hydrocarbon oil include alkylbenzenes, alkylnaphthalenes, poly α-olefins (PAO), polybutenes, and ethylene-α-olefin copolymers. The kinematic viscosity at 40°C of the first hydrocarbon base oil is less than 6 mm2/s, preferably 4 mm2/s or less, and more preferably 4 mm2/s or less. The lower limit of the kinematic viscosity at 40°C of the first hydrocarbon base oil is not particularly