JP7717637B2 - Refrigerating machine oil composition and mixed composition for refrigerators - Google Patents

Description

The present invention relates to a refrigerator oil composition and a mixed composition for a refrigerator.
In this specification, the term "mixture composition for a refrigerator" refers to a composition obtained by mixing a "refrigerating machine oil composition" and a "refrigerant."

Refrigerators, such as compression-type refrigerators, generally include at least a compressor, a condenser, an expansion mechanism (e.g., an expansion valve), and an evaporator, and are structured so that a refrigerant mixture composition circulates within a sealed system.

As refrigerants for freezers such as compression freezers, fluorocarbon compounds with a lower environmental impact are increasingly being used in place of the hydrochlorofluorocarbons (HCFCs) that have been widely used up until now. As such fluorocarbon compounds, saturated fluorocarbon compounds (hydro-fluoro-carbons; hereinafter also referred to as "HFCs") such as 1,1,1,2-tetrafluoroethane (R134a), difluoromethane (R32), and 1,1-difluoroethane (R152a) are increasingly being used.
In addition, the use of unsaturated fluorinated hydrocarbon compounds (hydro-fluoro-olefins; hereinafter, also referred to as "HFOs"), such as 1,3,3,3-tetrafluoropropene (R1234ze), 2,3,3,3-tetrafluoropropene (R1234yf), and 1,2,3,3-tetrafluoropropene (R1234ye), which have low global warming potential (GWP), has also been investigated (see, for example, Patent Document 1).

Special Publication No. 2006-503961

However, while unsaturated fluorocarbon compounds (HFOs) have the advantage of having a low global warming potential (GWP), they have the disadvantage of being less thermally stable at high temperatures than saturated fluorocarbon compounds (HFCs). Therefore, an increase in the content of unsaturated fluorocarbon compounds (HFOs) in a refrigerant can easily increase the acid value of the refrigerating machine oil composition, which is a problem.

Furthermore, in recent years, refrigeration machines have become more compact and sophisticated, and their operating conditions have become more severe than ever before. This has led to demands for higher quality refrigeration oil compositions. For example, while the amount of refrigeration oil composition used within equipment has decreased as refrigeration machines have become more compact, harsher operating conditions have made it more likely that localized high-temperature areas will occur due to frictional heat in the sliding parts of the compressor, etc. If a refrigeration mixture composition is exposed to such areas, the acid value of the refrigeration oil composition will be more likely to increase.

Therefore, there is a need to develop a refrigeration oil composition that can effectively suppress an increase in acid value even when the content of unsaturated fluorocarbon compounds (HFOs) in the refrigerant is increased.

The present invention has been made in light of this need, and aims to provide a refrigerating machine oil composition that can effectively suppress an increase in acid value even when the content of unsaturated fluorocarbon compounds (HFOs) in the refrigerant is increased, as well as a mixed composition for refrigerating machines that contains the refrigerating machine oil composition.

The present inventors conducted extensive research to solve the above-mentioned problems. As a result, they discovered that a refrigerator oil composition that combines a modified silicone compound (B) with an epoxy compound (C) that satisfies specific requirements, and in which the content of the modified silicone compound (B) is adjusted to a specific range, can solve the above-mentioned problems, leading to the completion of the present invention.

That is, the present invention relates to the following [1] to [3].
[1] The following general formula (1)
C _x F _y H _z ...(1)
[In the general formula (1), x is an integer of 2 to 6, y is an integer of 1 to 11, and z is an integer of 1 to 11, and the molecule has one or more carbon-carbon unsaturated bonds.]
a base oil (A) containing at least one selected from the group consisting of polyalkylene glycols, copolymers of poly(oxy)alkylene glycols or monoethers thereof with polyvinyl ethers, and polyol esters;
a modified silicone compound (B);
and an epoxy compound (C) that satisfies the following requirements (α) and (β),
A refrigerator oil composition, wherein the content of the modified silicone compound (B) is more than 0.10 mass% based on the total amount of the refrigerator oil composition.
Requirement (α): The molecule has at least one divalent group represented by the following formula (2):

Requirement (β): The molecule has at least one ester group.
[2] The following general formula (1)
C _x F _y H _z ...(1)
[In the general formula (1), x is an integer of 2 to 6, y is an integer of 1 to 11, and z is an integer of 1 to 11, and the molecule has one or more carbon-carbon unsaturated bonds.] and the refrigerating machine oil composition according to the above [1].
[3] The following general formula (1)
C _x F _y H _z ...(1)
[In the general formula (1), x is an integer of 2 to 6, y is an integer of 1 to 11, and z is an integer of 1 to 11, and the molecule has one or more carbon-carbon unsaturated bonds.]
a base oil (A) containing at least one selected from the group consisting of polyalkylene glycols, copolymers of poly(oxy)alkylene glycols or monoethers thereof with polyvinyl ethers, and polyol esters;
a modified silicone compound (B);
an epoxy compound (C) that satisfies the following requirements (α) and (β);
mixing the
In the step, the modified silicone compound (B) is blended in an amount of more than 0.10 mass% based on the total amount of the refrigerator oil composition.
Requirement (α): The molecule has at least one divalent group represented by the following formula (2):

Requirement (β): The molecule has at least one ester group.

The present invention makes it possible to provide a refrigerating machine oil composition that can effectively suppress an increase in acid value even when the content of unsaturated fluorocarbon compounds (HFOs) in the refrigerant is increased, and a mixed composition for refrigerating machines that contains the refrigerating machine oil composition.

The upper and lower limits of the ranges described herein can be combined in any way. For example, when ranges "A to B" and "C to D" are described, the ranges "A to D" and "C to B" are also included in the scope of the present invention.
Furthermore, unless otherwise specified, the numerical range "from the lower limit to the upper limit" described in this specification means that the range is equal to or greater than the lower limit and equal to or less than the upper limit.
In this specification, the numerical values in the examples are numerical values that can be used as upper or lower limit values.

[Embodiments of Refrigerating Machine Oil Composition]
The refrigerator oil composition of the present embodiment comprises a refrigerant represented by the following general formula (1):
C _x F _y H _z ...(1)
The refrigerator oil composition is used for a refrigerant containing one or more unsaturated fluorohydrocarbon compounds selected from compounds represented by the general formula (1): [in which x is an integer of 2 to 6, y is an integer of 1 to 11, and z is an integer of 1 to 11, and the molecule has one or more carbon-carbon unsaturated bonds].
The refrigerator oil composition of the present embodiment contains a base oil (A) containing one or more selected from the group consisting of polyalkylene glycols, copolymers of poly(oxy)alkylene glycols or monoethers thereof with polyvinyl ethers, and polyol esters; a modified silicone compound (B); and an epoxy compound (C) that satisfies the following requirements (α) and (β):
Requirement (α): The molecule has at least one divalent group represented by the following formula (2):

Requirement (β): The molecule has at least one ester group.
In the refrigerator oil composition of this embodiment, the content of the modified silicone compound (B) is more than 0.10 mass % based on the total amount of the refrigerator oil composition.

The present inventors conducted extensive research based on the idea that one of the factors that causes the acid value of a refrigerating machine oil composition to easily increase when the content of unsaturated fluorohydrocarbon compounds (HFOs) in a refrigerant increases is fluorine content that is generated by decomposition of the unsaturated fluorohydrocarbon compounds (HFOs) in a high-temperature environment.
As a result, it was found that a refrigerating machine oil composition having the above-mentioned configuration can suppress an increase in the fluorine concentration in the refrigerating machine oil composition that is caused by fluorine content generated by decomposition of unsaturated fluorohydrocarbon compounds (HFOs) in a high-temperature environment, and can suppress an increase in the acid value of the refrigerating machine oil composition.

Although the details of the mechanism by which the effects of the present invention are achieved are not clearly understood, it is presumed, for example, as follows.
That is, it is presumed that the refrigerator oil composition of the present embodiment, having the above-described configuration, suppresses an increase in the acid value of the refrigerator oil composition through at least one of the following actions (i) and (ii):
(i) The effect of inhibiting the decomposition of unsaturated fluorocarbon compounds (HFOs) in high-temperature environments.
(ii) The effect of capturing fluorine (F ⁻ ) that has dissolved into the refrigerating machine oil composition as a result of the decomposition of unsaturated fluorocarbon compounds (HFOs) in a high-temperature environment, thereby reducing the amount of fluorine (F ⁻ ) in the refrigerating machine oil composition.

In the following explanation, "base oil (A)," "modified silicone compound (B)," and "epoxy compound (C)" will also be referred to as "component (A)," "component (B)," and "component (C)," respectively.

The refrigerating machine oil composition of the present embodiment may be composed only of component (A), component (B), and component (C), but may also contain components other than component (A), component (B), and component (C) within the scope of the present invention.
In the refrigerator oil composition of the present embodiment, the total content of component (A), component (B), and component (C) is preferably 80 mass % or more, more preferably 85 mass % or more, and even more preferably 90 mass % or more, based on the total amount of the refrigerator oil composition.

The components contained in the refrigerator oil composition of this embodiment are described in detail below.

<Base oil (A)>
The refrigerator oil composition of the present embodiment contains a base oil (A).
In the refrigerator oil composition of this embodiment, the content of base oil (A) is preferably 85.0 mass% or more, more preferably 90.0 mass% or more, and even more preferably 92.0 mass% or more, based on the total amount of the refrigerator oil composition, from the viewpoint of the long-term stability required of a refrigerator oil composition. Also, from the viewpoint of easily ensuring the contents of components (B) and (C) in the refrigerator oil composition and further from the viewpoint of easily ensuring the contents of additives other than components (B) and (C), the content of base oil (A) is preferably 99.0 mass% or less, more preferably 98.5 mass% or less, and even more preferably 98.0 mass% or less.
The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, the range is preferably 85.0% by mass to 99.0% by mass, more preferably 90.0% by mass to 98.5% by mass, and even more preferably 92.0% by mass to 98.0% by mass.

The refrigerating machine oil composition of the present embodiment contains, as base oil (A), one or more selected from the group consisting of polyalkylene glycols (hereinafter also referred to as "PAG"), copolymers of poly(oxy)alkylene glycols or their monoethers with polyvinyl ethers (hereinafter also referred to as "ECP"), and polyol esters (hereinafter also referred to as "POE").
PAG, ECP, and POE will be described in detail below.

(Polyalkylene glycols (PAGs))
As the PAG, any PAG used as a base oil in a refrigerator oil composition can be used without particular limitation, but it is preferably a polymer (A-1) represented by the following general formula (A-1):
R ^13a −[(OR ^14a ) _pa −OR ^15a ] _qa (A-1)
When the base oil (A) contains a PAG, the PAG may be used alone or in combination of two or more.

In the general formula (A-1), R ^13a represents a hydrogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms, an acyl group having 2 to 10 carbon atoms, a divalent to hexavalent hydrocarbon group having 1 to 10 carbon atoms, or a substituted or unsubstituted heterocyclic group having 3 to 10 ring atoms; R ^14a represents an alkylene group having 2 to 4 carbon atoms; and R ^15a represents a hydrogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms, an acyl group having 2 to 10 carbon atoms, or a substituted or unsubstituted heterocyclic group having 3 to 10 ring atoms.
Examples of the substituent that the heterocyclic group may have include an alkyl group having 1 to 10 carbon atoms (preferably 1 to 6, more preferably 1 to 3); a cycloalkyl group having 3 to 10 ring carbon atoms (preferably 3 to 8, more preferably 5 or 6); an aryl group having 6 to 18 ring carbon atoms (preferably 6 to 12); a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, an iodine atom); a cyano group; a nitro group; a hydroxy group; and an amino group.
These substituents may be further substituted with any of the above-mentioned substituents.

qa is an integer of 1 to 6, preferably an integer of 1 to 3, and more preferably 1.
Here, qa is determined depending on the number of bonding sites of R ^13a in the above general formula (A-1). For example, when R ^13a is an alkyl group or an acyl group, qa is 1. When R ^13a is a hydrocarbon group or a heterocyclic group and the valence of the group is di-, tri-, tetra-, penta-, or hexa-, qa is 2, 3, 4, 5, or 6, respectively.
pa is the number of repeating units of OR ^14a and is usually 1 or more, and preferably a number such that pa × qa is 6 to 80. The value of pa is a value that is appropriately set in order to adjust the kinematic viscosity of the base oil (A) within an appropriate range, and is not particularly limited as long as the kinematic viscosity is adjusted to be within an appropriate range.
In addition, multiple R ^14a may be the same or different from each other. When qa is 2 or more, multiple R ^15a in one molecule may be the same or different from each other.

Examples of the monovalent hydrocarbon group represented by R ^13a and R ^15a include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, various butyl groups, various pentyl groups, various hexyl groups, various heptyl groups, various octyl groups, various nonyl groups, and various decyl groups; cycloalkyl groups such as cyclopentyl, cyclohexyl, various methylcyclohexyl groups, various ethylcyclohexyl groups, various propylcyclohexyl groups, and various dimethylcyclohexyl groups; aryl groups such as phenyl, various methylphenyl groups, various ethylphenyl groups, various dimethylphenyl groups, various propylphenyl groups, various trimethylphenyl groups, various butylphenyl groups, and various naphthyl groups; and arylalkyl groups such as benzyl, various phenylethyl groups, various methylbenzyl groups, various phenylpropyl groups, and various phenylbutyl groups. The alkyl groups may be linear or branched.
Here, "various types" refers to "linear, branched, or cyclic" hydrocarbon groups, and for example, "various butyl groups" refers to various butyl groups such as "n-butyl group, sec-butyl group, isobutyl group, tert-butyl group, cyclobutyl group, etc. Furthermore, groups having a cyclic structure include positional isomers such as ortho-, meta-, and para-isomers, and the same applies hereinafter.
The monovalent hydrocarbon group represented by R ^13a and R ^15a preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, and even more preferably 1 to 3 carbon atoms, from the viewpoint of compatibility with the refrigerant.

The hydrocarbon group moiety of the acyl group having 2 to 10 carbon atoms represented by R ^13a and R ^15a may be linear, branched, or cyclic. Examples of the alkyl group moiety include the hydrocarbon groups represented by R ^13a and R ^15a above, which have 1 to 9 carbon atoms.
The number of carbon atoms in the acyl group represented by R ^13a and R ^15a is preferably 2 to 8, more preferably 2 to 6, from the viewpoint of compatibility with the refrigerant.

Examples of the divalent to hexavalent hydrocarbon group represented by R ^13a include residues in which 1 to 5 hydrogen atoms have been removed from the monovalent hydrocarbon group represented by R ^13a , and residues in which hydroxyl groups have been removed from polyhydric alcohols such as trimethylolpropane, glycerin, pentaerythritol, sorbitol, 1,2,3-trihydroxycyclohexane, and 1,3,5-trihydroxycyclohexane.
The carbon number of the divalent to hexavalent acyl group represented by R ^13a is preferably 2 to 10, more preferably 2 to 6, from the viewpoint of compatibility with the refrigerant.

The heterocyclic group represented by R ^13a and R ^15a is preferably an oxygen atom-containing heterocyclic group or a sulfur atom-containing heterocyclic group, which may be a saturated or unsaturated ring.
Examples of the oxygen atom-containing heterocyclic group include oxygen atom-containing saturated heterocycles such as ethylene oxide, 1,3-propylene oxide, tetrahydrofuran, tetrahydropyran, and hexamethylene oxide; and residues in which 1 to 6 hydrogen atoms have been removed from oxygen atom-containing unsaturated heterocycles such as acetylene oxide, furan, pyran, oxycycloheptatriene, isobenzofuran, and isochromene.
Examples of the sulfur atom-containing heterocyclic group include residues in which 1 to 6 hydrogen atoms have been removed from sulfur atom-containing saturated heterocycles such as ethylene sulfide, trimethylene sulfide, tetrahydrothiophene, tetrahydrothiopyran, and hexamethylene sulfide, and sulfur atom-containing unsaturated heterocycles such as acetylene sulfide, thiophene, thiapyran, and thiotripyridene.

The heterocyclic group represented by R ^13a and R ^15a may have a substituent, and the substituent may be bonded to the oxygen atom in the general formula (A-1). As the substituent, as described above, an alkyl group having 1 to 6 carbon atoms is preferable, and an alkyl group having 1 to 3 carbon atoms is more preferable.
The number of ring atoms in the heterocyclic group is preferably 3 to 10, more preferably 3 to 6, from the viewpoint of compatibility with the refrigerant.

The alkylene group represented by R ^14a includes alkylene groups having two carbon atoms, such as dimethylene (-CH ₂ CH ₂ -) and ethylene (-CH(CH ₃ )-); alkylene groups having three carbon atoms, such as trimethylene (-CH ₂ CH ₂ CH ₂ -), propylene (-CH(CH ₃ )CH ₂ -), propylidene (-CHCH ₂ CH ₃ -) and isopropylidene (-C(CH ₃ ) ₂ -); tetramethylene (-CH ₂ CH ₂ CH ₂ CH ₂ -), 1-methyltrimethylene (-CH(CH ₃ )CH ₂ CH ₂ -), 2-methyltrimethylene (-CH ₂ CH(CH ₃ )CH ₂ -), butylene (-C(CH ₃ ) ₂ CH ₂ -); Among these, R ^14a is preferably a propylene group (—CH(CH ₃ )CH ₂ —).

In the polymer (A-1) represented by the general formula (A-1) above, the content of oxypropylene units (—OCH(CH ₃ )CH ₂ —) is preferably 50 mol % or more, more preferably 65 mol % or more, and even more preferably 80 mol % or more, based on the total amount (100 mol %) of oxyalkylene units (OR ^{14a ) in the polymer (A-1} ).

Among the polymers (A-1) represented by the general formula (A-1) above, one or more selected from the group consisting of polyoxypropylene glycol dimethyl ether represented by the following general formula (A-1-i), polyoxyethylene polyoxypropylene glycol dimethyl ether represented by the following general formula (A-1-ii), polyoxypropylene glycol monobutyl ether represented by the following general formula (A-1-iii), polyoxypropylene glycol monomethyl ether represented by the following general formula (A-1-iv), and polyoxypropylene glycol diacetate are preferred.

(In formula (A-1-i), p1 represents a number of 1 or more, and preferably a number of 6 to 80.)

(In formula (A-1-ii), p2 and p3 each independently represent a number of 1 or more, and preferably a number such that the value of p2+p3 is 6 to 80.)

(In formula (A-1-iii), p4 represents a number of 1 or more, and preferably a number of 6 to 80.)

(In formula (A-1-iv), p5 represents a number of 1 or more, and preferably a number of 6 to 80.)

Note that p1 in the general formula (A-1-i), p2 and p3 in the general formula (A-1-ii), p4 in the general formula (A-1-iii), and p5 in the general formula (A-1-iv) may be selected appropriately depending on the kinematic viscosity required for the base oil (A).

(Poly(oxy)alkylene glycol or its monoether and polyvinyl ether copolymer (ECP))
The copolymer (ECP) of poly(oxy)alkylene glycol or its monoether with polyvinyl ether may be a copolymer having a structural unit derived from poly(oxy)alkylene glycol or its monoether and a structural unit derived from polyvinyl ether.
The term "poly(oxy)alkylene glycol" refers to both polyalkylene glycol and polyoxyalkylene glycol.
When the base oil (A) contains an ECP, the ECP may be used alone or in combination of two or more.
Among such ECPs, copolymers (A-3-i) represented by the following general formula (A-3-i) or copolymers (A-3-ii) represented by the following general formula (A-3-ii) are preferred.

In formulae (A-3-i) and (A-3-ii), R ^1c , R ^2c , and R ^3c each independently represent a hydrogen atom or a hydrocarbon group having from 1 to 8 carbon atoms.
Each R ^4c independently represents a hydrocarbon group having 1 to 10 carbon atoms.
Each R ^5c independently represents an alkylene group having 2 to 4 carbon atoms.
Each R ^6c independently represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted alicyclic group having 3 to 20 ring carbon atoms, a substituted or unsubstituted aromatic group having 6 to 24 ring carbon atoms, an acyl group having 2 to 20 carbon atoms, or an oxygen-containing hydrocarbon group having 2 to 50 carbon atoms.
When a plurality of R ^1c , R ^2c , R ^3c , R ^4c , R ^5c , and R ^6c are present, they may be the same or different in each structural unit.
X 1 ^C and Y 1 ^C each independently represent a hydrogen atom, a hydroxyl group, or a hydrocarbon group having 1 to 20 carbon atoms.

In general formulas (A-3-i) and (A-3-ii), v represents the average value of the number of units represented by OR ^5c , and is a number of 1 or more, preferably 1 to 50. When a plurality of OR ^5c is present, the plurality of OR ^5c may be the same or different. Here, "OR ^5c " represents a structural unit derived from poly(oxy)alkylene glycol or a monoether thereof.
In formula (A-3-i), u is a number of 0 or more, preferably a number from 0 to 50, and w is a number of 1 or more, preferably a number from 1 to 50.
In formula (A-3-ii), x and y each independently represent a number of 1 or more, preferably a number of 1 to 50.
The values of v, u, w, x, and y are not particularly limited as long as they are adjusted according to the hydroxyl value required for the base oil (A).

The copolymerization form of copolymer (A-3-i) and copolymer (A-3-ii) is not particularly limited, and may be a block copolymer, a random copolymer, or a graft copolymer.

Examples of the hydrocarbon group having 1 to 8 carbon atoms that can be selected as R ^1c , R ^2c , and R ^3c include the same monovalent hydrocarbon groups having 1 to 8 carbon atoms that can be selected as R ^1a , R ^2a , and R ^3a in general formula (A-1).
The hydrocarbon group that can be selected as R ^1c , R ^2c , and R ^3c preferably has 1 to 8 carbon atoms, more preferably 1 to 6 carbon atoms, and even more preferably 1 to 3 carbon atoms.
R ^1c , R ^2c , and R ^3c each independently represent preferably a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and even more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.
It is also preferable that at least one of R ^1c , R ^2c , and R ^3c is a hydrogen atom, and it is more preferable that all of R ^1c , R ^2c , and R ^3c are hydrogen atoms.

Examples of hydrocarbon groups having 1 to 10 carbon atoms that can be selected as R ^4c include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, various butyl groups, various pentyl groups, various hexyl groups, various heptyl groups, various octyl groups, various nonyl groups, and various decyl groups; cycloalkyl groups such as cyclopentyl, cyclohexyl, various methylcyclohexyl groups, various ethylcyclohexyl groups, various propylcyclohexyl groups, and various dimethylcyclohexyl groups; aryl groups such as phenyl, various methylphenyl groups, various ethylphenyl groups, various dimethylphenyl groups, various propylphenyl groups, various trimethylphenyl groups, various butylphenyl groups, and various naphthyl groups; and arylalkyl groups such as benzyl, various phenylethyl groups, various methylbenzyl groups, various phenylpropyl groups, and various phenylbutyl groups.
The hydrocarbon group that can be selected as R ^4c preferably has 1 to 8 carbon atoms, more preferably 1 to 6 carbon atoms, and even more preferably 1 to 4 carbon atoms.

The alkylene group that can be selected as R ^5c includes the same alkylene groups having 2 to 4 carbon atoms that can be selected as R ^14a in general formula (A-1), and preferably a propylene group (—CH(CH ₃ )CH ₂ —).
In the copolymer (A-3-i) or the copolymer (A-3-ii), the content of oxypropylene units (—OCH(CH ₃ )CH ₂ —) is preferably 50 mol % or more and 100 mol % or less, more preferably 65 mol % or more and 100 mol % or less, and even more preferably 80 mol % or more and 100 mol % or less, based on the total amount (100 mol %) of oxyalkylene (OR ^5c ) which is a structural unit derived from poly(oxy)alkylene glycol or its monoether in the copolymer (A-3-i) or the copolymer (A-3-ii).

Examples of the alkyl group having 1 to 20 carbon atoms that can be selected as R ^6c include a methyl group, an ethyl group, various propyl groups, various butyl groups, various pentyl groups, various hexyl groups, various heptyl groups, various octyl groups, various nonyl groups, and various decyl groups.
The alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, and even more preferably 1 to 3 carbon atoms.

Examples of the alicyclic group having 3 to 20 ring carbon atoms that can be selected as R ^6c include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, and a cyclodecyl group.
The alicyclic group preferably has 3 to 10 ring carbon atoms, more preferably 3 to 8 ring carbon atoms, and even more preferably 3 to 6 ring carbon atoms.
The alicyclic group may have the aforementioned substituent, and the substituent is preferably an alkyl group.

Examples of aromatic groups having 6 to 24 ring carbon atoms that can be selected as R ^6c include a phenyl group, a naphthyl group, an anthracenyl group, and a phenanthryl group.
The aromatic group preferably has 6 to 18 ring carbon atoms, and more preferably 6 to 12 ring carbon atoms.
The aromatic group may have the aforementioned substituent, and the substituent is preferably an alkyl group.

Examples of the acyl group having 2 to 20 ring carbon atoms that can be selected as R ^6c include an acetyl group, a propionyl group, a butyryl group, an isobutyryl group, a valeryl group, an isovaleryl group, a piperoyl group, a benzoyl group, and a toluoyl group.
The acyl group preferably has 2 to 10 carbon atoms, more preferably 2 to 8 carbon atoms, and even more preferably 2 to 6 carbon atoms.

Examples of the oxygen-containing hydrocarbon group having 2 to 50 carbon atoms that can be selected as R ^6c include a methoxymethyl group, a methoxyethyl group, a methoxypropyl group, a 1,1-bismethoxypropyl group, a 1,2-bismethoxypropyl group, an ethoxypropyl group, a (2-methoxyethoxy)propyl group, and a (1-methyl-2-methoxy)propyl group.
The carbon-containing hydrocarbon group preferably has 2 to 20 carbon atoms, more preferably 2 to 10 carbon atoms, and even more preferably 2 to 6 carbon atoms.

Examples of hydrocarbon groups having 1 to 20 carbon atoms that can be selected as X ^C and Y ^C include alkyl groups having 1 to 20 carbon atoms (preferably 1 to 10, more preferably 1 to 6, and even more preferably 1 to 3), substituted or unsubstituted cycloalkyl groups having 3 to 20 ring carbon atoms (preferably 3 to 10, more preferably 3 to 8, and even more preferably 3 to 6), substituted or unsubstituted phenyl groups, substituted or unsubstituted naphthyl groups, and arylalkyl groups having 7 to 20 carbon atoms (preferably 7 to 13).

(Polyol esters (POE))
Examples of POE include esters of diols or polyols with fatty acids. When POE is contained in base oil (A), one POE may be used alone, or two or more POEs may be used in combination.
The POE is preferably an ester of a diol or a polyol having 3 to 20 hydroxyl groups with a fatty acid having 3 to 20 carbon atoms.

Diols include ethylene glycol, 1,3-propanediol, propylene glycol, 1,4-butanediol, 1,2-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 2-ethyl-2-methyl-1,3-propanediol, 1,7-heptanediol, 2-methyl-2-propyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, and 1,12-dodecanediol.

Examples of polyols include polyhydric alcohols such as trimethylolethane, trimethylolpropane, trimethylolbutane, di-(trimethylolpropane), tri-(trimethylolpropane), pentaerythritol, di-(pentaerythritol), tri-(pentaerythritol), glycerin, polyglycerin (a dimer to 20-mer of glycerin), 1,3,5-pentanetriol, sorbitol, sorbitan, sorbitol glycerin condensates, adonitol, arabitol, xylitol, and mannitol; sugars such as xylose, arabinose, ribose, rhamnose, glucose, fructose, galactose, mannose, sorbose, cellobiose, maltose, isomaltose, trehalose, sucrose, raffinose, gentianose, and melenitose; and partially etherified products thereof, methyl glucosides (glycoside).
Among these, preferred are hindered alcohols such as neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, di-(trimethylolpropane), tri-(trimethylolpropane), pentaerythritol, di-(pentaerythritol), tri-(pentaerythritol), etc. The term "hindered alcohol" refers to an alcohol having a quaternary carbon atom bonded to four carbon atoms.

The number of carbon atoms of the fatty acid is preferably 3 or more, more preferably 4 or more, even more preferably 5 or more, and still more preferably 8 or more, from the viewpoint of lubrication performance, and is preferably 20 or less, more preferably 16 or less, even more preferably 12 or less, and still more preferably 10 or less, from the viewpoint of compatibility with the refrigerant.
The carbon number of the fatty acid includes the carbon atom of the carboxy group (—COOH) of the fatty acid.
The fatty acid may be either a linear fatty acid or a branched fatty acid, but from the viewpoint of lubrication performance, a linear fatty acid is preferred, and from the viewpoint of hydrolysis stability, a branched fatty acid is preferred. Furthermore, the fatty acid may be either a saturated fatty acid or an unsaturated fatty acid.

Examples of fatty acids include straight-chain or branched-chain fatty acids such as isobutyric acid, propionic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, nonadecanoic acid, icosanoic acid, and oleic acid, as well as so-called neo acids in which the α-carbon atom is quaternary.
More specifically, isobutyric acid, valeric acid (n-pentanoic acid), caproic acid (n-hexanoic acid), enanthic acid (n-heptanoic acid), caprylic acid (n-octanoic acid), pelargonic acid (n-nonanoic acid), capric acid (n-decanoic acid), oleic acid (cis-9-octadecenoic acid), isopentanoic acid (3-methylbutanoic acid), 2-methylhexanoic acid, 2-ethylpentanoic acid, 2-ethylhexanoic acid, 3,5,5-trimethylhexanoic acid, and the like are preferred.

The POE may be a partial ester in which some of the hydroxyl groups of the polyol remain unesterified, or a complete ester in which all of the hydroxyl groups are esterified. The POE may also be a mixture of partial esters and complete esters, but complete esters are preferred.

As POE, from the viewpoint of superior hydrolytic stability, esters of hindered alcohols such as neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, di-(trimethylolpropane), tri-(trimethylolpropane), pentaerythritol, di-(pentaerythritol), and tri-(pentaerythritol) are preferred, with neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, and pentaerythritol esters being more preferred, and with the viewpoint of particularly superior compatibility with refrigerants and hydrolytic stability, pentaerythritol esters being even more preferred.

Specific examples of preferred POE include diesters of neopentyl glycol and one or more fatty acids selected from the group consisting of isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, oleic acid, isopentanoic acid, 2-methylhexanoic acid, 2-ethylpentanoic acid, 2-ethylhexanoic acid, and 3,5,5-trimethylhexanoic acid; diesters of trimethylolethane and isobutyric acid, valeric acid, caproic acid, Triesters of one or more fatty acids selected from the group consisting of enanthic acid, caprylic acid, pelargonic acid, capric acid, oleic acid, isopentanoic acid, 2-methylhexanoic acid, 2-ethylpentanoic acid, 2-ethylhexanoic acid, and 3,5,5-trimethylhexanoic acid; triesters of trimethylolpropane and isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, oleic acid, isopentanoic acid, 2-methylhexanoic acid, 2-ethylpentanoic acid, and 3,5,5-trimethylhexanoic acid; triesters of one or more fatty acids selected from the group consisting of 2-methylhexanoic acid, 2-ethylpentanoic acid, 2-ethylhexanoic acid, and 3,5,5-trimethylhexanoic acid; triesters of trimethylolbutane and one or more fatty acids selected from the group consisting of isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, oleic acid, isopentanoic acid, 2-methylhexanoic acid, 2-ethylpentanoic acid, 2-ethylhexanoic acid, and 3,5,5-trimethylhexanoic acid; tetraesters of pentaerythritol and one or more fatty acids selected from the group consisting of isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, oleic acid, isopentanoic acid, 2-methylhexanoic acid, 2-ethylpentanoic acid, 2-ethylhexanoic acid, and 3,5,5-trimethylhexanoic acid.

Note that the ester of two or more fatty acids may be a mixture of two or more esters of one fatty acid and a polyol. Among POEs, esters of two or more mixed fatty acids and polyols are preferred from the standpoint of improving low-temperature properties and compatibility with refrigerants.

(Preferred embodiment of base oil (A))
In the refrigerator oil composition of the present embodiment, from the viewpoint of making it easier to improve the effects of the present invention, the content of one or more selected from the group consisting of PAG, ECP, and POE in the base oil (A) is preferably 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, even more preferably 70% by mass to 100% by mass, still more preferably 80% by mass to 100% by mass, even more preferably 90% by mass to 100% by mass, and still more preferably 100% by mass, based on the total amount of the base oil (A).

Here, from the viewpoint of making it easier to improve the effects of the present invention, in the refrigerator oil composition of the present embodiment, it is preferable that the base oil (A) contains alone one selected from the group consisting of PAG, ECP, and POE.
From the viewpoint of making it easier to further improve the effects of the present invention, the content of one selected from the group consisting of PAG, ECP, and POE is preferably 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, even more preferably 70% by mass to 100% by mass, still more preferably 80% by mass to 100% by mass, even more preferably 90% by mass to 100% by mass, and still more preferably 100% by mass, based on the total amount of base oil (A).

(Other base oils)
The base oil (A) may further contain other base oils within the range that does not impair the effects of the present invention.
The other base oils include one or more selected from the group consisting of mineral oils and synthetic oils that do not fall under the aforementioned PAG, ECP, and POE.

Examples of mineral oils include atmospheric residues obtained by atmospheric distillation of crude oils such as paraffinic crude oil, intermediate crude oil, or naphthenic crude oil; distillates obtained by vacuum distillation of these atmospheric residues; and mineral oils obtained by subjecting the distillates to one or more refining treatments such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining.
When a mineral oil is contained in the base oil (A), the mineral oil may be used alone or in combination of two or more kinds.

Examples of synthetic oils that do not fall under the category of the aforementioned PAG, ECP, and POE include polyvinyl ethers, polyesters, polycarbonates, hydrogenated α-olefin oligomers, alicyclic hydrocarbon compounds, alkylated aromatic hydrocarbon compounds, and oils produced by isomerizing GTL wax (gas-to-liquid wax) produced by the Fischer-Tropsch process or the like.
When the base oil (A) contains a synthetic oil that does not fall under the above-mentioned PAG, ECP, and POE, one type of synthetic oil may be used alone, or two or more types may be used in combination.

In the refrigerator oil composition of this embodiment, the content of mineral oil is preferably small from the viewpoint of the solubility of components (B) and (C). Specifically, the content of mineral oil is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less, still more preferably 0.1% by mass or less, based on the total amount of base oil (A), and even more preferably no mineral oil is contained.
Furthermore, in the refrigerator oil composition of this embodiment, from the viewpoint of facilitating the improvement of the effects of the present invention, it is preferable that the content of synthetic oils other than PAG, ECP, and POE is small. Specifically, the content of synthetic oils other than PAG, ECP, and POE is preferably 10 mass% or less, more preferably 5 mass% or less, even more preferably 1 mass% or less, still more preferably 0.1 mass% or less, based on the total amount of base oil (A), and even more preferably no synthetic oils other than PAG, ECP, and POE are contained.

(Kinematic viscosity of base oil (A) at 100°C)
The kinematic viscosity of the base oil (A) at 100°C is preferably 3 ^mm2 /s or more, more preferably 4 ^mm2 /s or more, and even more preferably 5 ^mm2 /s or more from the viewpoint of improving lubrication performance (load-bearing performance) and sealing performance, and is preferably 50 ^mm2 /s or less, more preferably 40 ^mm2 /s or less, and even more preferably 30 ^mm2 /s or less from the viewpoint of improving compatibility with refrigerants.
The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, the flow rate is preferably 3 mm ² /s to 50 mm ² /s, more preferably 4 mm ² /s to 40 mm ² /s, and even more preferably 5 mm ² /s to 30 mm ² /s.
In this specification, the 100°C kinematic viscosity of the base oil (A) is a value measured in accordance with JIS K2283:2000.

(Hydroxyl value of base oil (A))
From the viewpoint of improving the thermal stability of the refrigerating machine oil composition, the hydroxyl value of the base oil (A) is preferably 30 mgKOH/g or less, more preferably 25 mgKOH/g or less, even more preferably 20 mgKOH/g or less, still more preferably 15 mgKOH/g or less, even more preferably 10 mgKOH/g or less, and even more preferably 5 mgKOH/g or less. The hydroxyl value of the base oil (A) is usually 0.1 mgKOH/g or more.
In this specification, the hydroxyl value of the base oil (A) is a value measured by neutralization titration in accordance with JIS K0070:1992.

(Number average molecular weight (Mn) of base oil (A))
From the viewpoint of improving lubricating performance (load-bearing performance) and sealing performance, the number average molecular weight (Mn) of the base oil (A) is preferably 300 or more, more preferably 400 or more, and even more preferably 500 or more. From the viewpoint of improving compatibility with the refrigerant, the number average molecular weight (Mn) is preferably 10,000 or less, more preferably 7,000 or less, and even more preferably 5,000 or less.
The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, the range is preferably 300 to 10,000, more preferably 400 to 7,000, and even more preferably 500 to 5,000.
In this specification, the number average molecular weight (Mn) of the base oil (A) is a value measured by the method described in the examples below.

<Modified Silicone Compound (B)>
The refrigerator oil composition of the present embodiment contains a modified silicone compound (B).
The modified silicone compound (B), when used in combination with the epoxy compound (C), can effectively suppress the elution of fluorine components into the refrigerator oil composition due to the decomposition of the unsaturated fluorohydrocarbon compound (HFO), and can effectively suppress an increase in the acid value of the refrigerator oil composition.
If the refrigerator oil composition does not contain the modified silicone compound (B), the increase in the acid value of the refrigerator oil composition cannot be sufficiently suppressed.

In the refrigerator oil composition of this embodiment, the content of the modified silicone compound (B) must be more than 0.10 mass % based on the total amount of the refrigerator oil composition.
If the content of the modified silicone compound (B) is 0.10 mass% or less, it is not possible to sufficiently suppress the elution of fluorine components into the refrigerating machine oil composition due to the decomposition of the unsaturated fluorohydrocarbon compound (HFO), and it is not possible to sufficiently suppress an increase in the acid value of the refrigerating machine oil composition.
From the viewpoint of further improving the effect of suppressing an increase in the acid value of the refrigerator oil composition, the content of the modified silicone compound (B) is preferably 0.20 mass% or more, more preferably 0.30 mass% or more, even more preferably 0.40 mass% or more, and still more preferably 0.45 mass% or more, based on the total amount of the refrigerator oil composition. There are no particular restrictions on the upper limit of the content of the modified silicone compound (B), but from the viewpoint of obtaining an effect commensurate with the amount added, it is preferably 5.0 mass% or less, more preferably 4.0 mass% or less, even more preferably 3.0 mass% or less. Still more preferably 2.0 mass% or less.
The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, the content is preferably 0.20% by mass to 5.0% by mass, more preferably 0.30% by mass to 4.0% by mass, even more preferably 0.40% by mass to 3.0% by mass, and still more preferably 0.45% by mass to 2.0% by mass.

The modified silicone compound (B) can be used without any particular limitation as long as it is a silicone compound in which at least one of the side chains and terminals of the polysiloxane skeleton of an unmodified silicone compound has been modified.
The unmodified silicone compound is a silicone compound in which all of the side chains and terminals of the polysiloxane skeleton are composed of alkyl groups, and no functional groups other than the alkyl groups have been introduced into the side chains and terminals of the polysiloxane skeleton. Preferred examples of the unmodified silicone compound include compounds represented by the following general formula (b1-1):

In the general formula (b1-1), R ^b1 and R ^b2 each independently represent an alkyl group having 1 to 10 carbon atoms. nb is an integer of 1 or greater. The number of carbon atoms in the alkyl group that can be selected as R ^b1 and R ^b2 is preferably 1 to 6, more preferably 1 to 3, even more preferably 1 to 2, and most preferably 1.
In the following description, R ^b1 will be referred to as an alkyl group on the side chain of the polysiloxane skeleton, and R ^b2 will be referred to as an alkyl group at the end of the polysiloxane skeleton.

Here, the above-mentioned phrase "at least one of the side chains and terminals of the polysiloxane skeleton is modified" means that at least one of the alkyl groups on the side chains of the polysiloxane skeleton in the unmodified silicone compound (R ^b1 in the general formula (b1-1) below) and the alkyl groups on the terminals (R ^b2 in the general formula (b1-1) above) is substituted with a functional group other than the alkyl group.

Examples of side-chain-modified modified silicones include monoamine-modified silicones, diamine-modified silicones, special amino-modified silicones, epoxy-modified silicones, alicyclic epoxy-modified silicones, carbinol-modified silicones, mercapto-modified silicones, carboxyl-modified silicones, hydrogen-modified silicones, amino-polyether-modified silicones, epoxy-polyether-modified silicones, epoxy-aralkyl-modified silicones, polyether-modified silicones, aralkyl-modified silicones, fluoroalkyl-modified silicones, long-chain alkyl-modified silicones, higher fatty acid ester-modified silicones, higher fatty acid amide-modified silicones, polyether-long-chain alkyl-aralkyl-modified silicones, long-chain alkyl-aralkyl-modified silicones, and phenyl-modified silicones.
These may be used alone or in combination of two or more.

Examples of terminally modified silicones include modified silicones that are modified at both ends, such as amino-modified silicone, epoxy-modified silicone, alicyclic epoxy-modified silicone, carbinol-modified silicone, methacryl-modified silicone, polyether-modified silicone, mercapto-modified silicone, carboxyl-modified silicone, phenol-modified silicone, silanol-modified silicone, acrylic-modified silicone, and carboxylic anhydride-modified silicone; and modified silicones that are modified at one end, such as epoxy-modified silicone, carbinol-modified silicone, diol-modified silicone, methacryl-modified silicone, and carboxyl-modified silicone.

Examples of side chain terminal-modified modified silicones include side chain amino-modified, both-terminal methoxy-modified silicones, side chain epoxy-modified, both-terminal epoxy-modified silicones, etc.

Here, in this embodiment, from the viewpoint of making it easier to improve the effects of the present invention, the modified silicone compound (B) preferably contains a side-chain-modified silicone (B1) in which at least the side chain of the polysiloxane skeleton is modified.
From the viewpoint of making it easier to improve the effects of the present invention, the content of the side chain-modified silicone (B1) in the modified silicone compound (B) is preferably 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, even more preferably 70% by mass to 100% by mass, still more preferably 80% by mass to 100% by mass, even more preferably 90% by mass to 100% by mass, and even more preferably 95% by mass to 100% by mass, based on the total amount of the modified silicone compound (B).

Furthermore, from the viewpoint of further enhancing the effects of the present invention, it is preferable that the side chain-modified silicone (B1) contains one or more types selected from side chain-modified silicone (B1a) having one or more epoxy groups in the side chain and side chain-modified silicone (B1b) having one or more polyether groups in the side chain.

Examples of side-chain-modified silicones (B1a) having one or more epoxy groups in the side chain include side-chain-modified epoxy-modified silicones, side-chain-modified alicyclic epoxy-modified silicones, side-chain-modified epoxy-polyether-modified silicones, side-chain-modified epoxy-aralkyl-modified silicones, and side-chain-end-modified side-chain epoxy-modified/both-ends epoxy-modified silicones.

The side chain-modified silicone (B1a) having one or more epoxy groups in the side chain may be a commercially available product.
Commercially available side chain-modified epoxy-modified silicones include X-22-343, KF-101, KF-1001, and X-22-2000 manufactured by Shin-Etsu Chemical Co., Ltd.; and SF8411 Fluid and SF8413 Fluid manufactured by Dow-Toray Industries, Inc.
Commercially available side-chain modified alicyclic epoxy-modified silicones include X-22-2046 and KF-102 manufactured by Shin-Etsu Chemical Co., Ltd.; and BY16-839 Fluid and L-9300 manufactured by Dow-Toray Industries, Inc.
Commercially available side chain-modified epoxy-polyether-modified silicones include X-22-4741 and KF-1002 manufactured by Shin-Etsu Chemical Co., Ltd.; and BY16-876 and FZ-3736 Fluid manufactured by Dow Toray Industries, Inc.
Examples of commercially available side-chain modified epoxy-aralkyl-modified silicones include KF-1005 manufactured by Shin-Etsu Chemical Co., Ltd.
An example of a commercially available side chain terminal modified type side chain epoxy-modified/both terminal epoxy-modified silicone is X-22-9002 manufactured by Shin-Etsu Chemical Co., Ltd.

Among these, from the standpoint of availability and effectiveness, the side-chain-modified silicone (B1a) having one or more epoxy groups in the side chain is preferably a side-chain-modified epoxy-modified silicone.

The side-chain-modified silicone (B1a) having one or more epoxy groups in the side chain may be used alone or in combination of two or more.

Examples of the side chain-modified silicone (B1b) having one or more polyether groups in the side chain include side chain-modified polyether-modified silicone, side chain-modified amino-polyether-modified silicone, and side chain-modified polyether-long-chain alkyl-aralkyl-modified silicone.
In this specification, silicone compounds having both an epoxy group and a polyether group in the side chain, such as side-chain-modified epoxy-polyether-modified silicones, are classified as side-chain-modified silicones (B1a) having one or more epoxy groups in the side chain.

The side chain-modified silicone (B1b) having one or more polyether groups in the side chain may be a commercially available product.
Commercially available side chain-modified polyether-modified silicones include KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640, KF-642, KF-643, KF-644, KF-6020, KF-6204, X-22-4515, KF-6011, KF-6012, KF-6015, and KF-6015 manufactured by Shin-Etsu Chemical Co., Ltd., and FZ-2110 manufactured by Dow-Toray Industries, Inc.
Examples of commercially available side chain modified amino-polyether modified silicones include X-22-3939A manufactured by Shin-Etsu Chemical Co., Ltd.
Examples of commercially available side-chain modified polyether/long-chain alkyl/aralkyl modified silicones include X-22-2516 manufactured by Shin-Etsu Chemical Co., Ltd.

Among these, from the standpoint of availability and effectiveness, the side-chain-modified silicone (B1b) having one or more polyether groups in the side chain is preferably a side-chain-modified polyether-modified silicone.

The side-chain-modified silicone (B1b) having one or more polyether groups in the side chain may be used alone or in combination of two or more.

The content of one or more types selected from side-chain-modified silicones (B1a) having one or more epoxy groups in the side chain and side-chain-modified silicones (B1b) having one or more polyether groups in the side chain in the side chain, based on the total amount of side-chain-modified silicone (B1), is preferably 50% to 100% by mass, more preferably 60% to 100% by mass, even more preferably 70% to 100% by mass, still more preferably 80% to 100% by mass, even more preferably 90% to 100% by mass, and even more preferably 95% to 100% by mass.

<Epoxy Compound (C)>
The refrigerator oil composition of the present embodiment contains an epoxy compound (C) that satisfies the following requirements (α) and (β).
(α) The molecule has at least one divalent group represented by the following formula (2):

(β) The molecule has at least one ester group.

The epoxy compound (C), when used in combination with the modified silicone compound (B), can effectively suppress the elution of fluorine components into the refrigerator oil composition resulting from the decomposition of the unsaturated fluorohydrocarbon compound (HFO), and can effectively suppress an increase in the acid value of the refrigerator oil composition.
If the refrigerator oil composition does not contain the epoxy compound (C), an increase in the acid value of the refrigerator oil composition cannot be sufficiently suppressed.

The epoxy compound (C) preferably has a molecular weight of 300 or more, since this can appropriately suppress the reactivity of the epoxy group, inhibit the decomposition of the unsaturated fluorohydrocarbon compound, and improve the solubility in the base oil; more preferably, it has a molecular weight of 320 or more, and even more preferably, it has a molecular weight of 350 or more.
Furthermore, the molecular weight of the epoxy compound (C) is preferably 2,000 or less, more preferably 1,500 or less, and even more preferably 1,000 or less, from the viewpoints of solubility in refrigerating machine oil and sludge formation after stability evaluation.

In the refrigerator oil composition of this embodiment, from the viewpoint of further improving the effects of the present invention, the content of the epoxy compound (C) is preferably 0.05 mass% or more, more preferably 0.07 mass% or more, and even more preferably 0.08 mass% or more, based on the total amount of the refrigerator oil composition. The upper limit of the content of the epoxy compound (C) is not particularly limited, but from the viewpoint of obtaining an effect commensurate with the amount added, it is preferably 5.0 mass% or less, more preferably 4.0 mass% or less, and even more preferably 3.0 mass% or less.
The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, the content is preferably 0.05% by mass to 5.0% by mass, more preferably 0.07% by mass to 4.0% by mass, and even more preferably 0.08% by mass to 3.0% by mass.

In the present embodiment, the epoxy compound (C) can be one or more selected from the group consisting of compounds satisfying the above two requirements (α) and (β), without any particular limitation.
Here, from the viewpoint of making it easier to improve the effects of the present invention, it is preferable that the epoxy compound (C) contains one or more selected from the group consisting of epoxidized fatty acid esters (C1), epoxidized vegetable oils (C2), and epoxidized alicyclic carboxylic acid esters (C3).
The content of one or more selected from the group consisting of epoxidized fatty acid esters (C1), epoxidized vegetable oils (C2), and epoxidized alicyclic carboxylic acid esters (C3) in the epoxy compound (C) is preferably 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, even more preferably 70% by mass to 100% by mass, still more preferably 80% by mass to 100% by mass, still more preferably 90% by mass to 100% by mass, and even more preferably 95% by mass to 100% by mass, based on the total amount of the epoxy compound (C).
The epoxidized fatty acid ester (C1), the epoxidized vegetable oil (C2), and the epoxidized alicyclic carboxylic acid ester (C3) will be described below.

(Epoxidized fatty acid ester (C1))
Examples of the epoxidized fatty acid ester (C1) include an epoxidized ester of a fatty acid having 8 to 30 carbon atoms (preferably 12 to 20 carbon atoms) with an alcohol having 1 to 10 carbon atoms, a phenol, or an alkylphenol having 7 to 14 carbon atoms.

As the epoxidized fatty acid ester (C1), one represented by the following general formula (c1) is preferably used, from the viewpoint of being able to effectively suppress an increase in the acid value of the refrigerator oil composition.

(In formula (c1), R ^c1 is a hydrocarbon group having 4 to 20 carbon atoms, R ^c2 is a hydrocarbon group having 1 to 10 carbon atoms, p is an integer of 1 to 3, n is an integer of 0 to 12, and m is an integer of 1 to 3. When m is 2 or more, multiple structures within [ ] may be the same or different.)
Examples of the hydrocarbon group include alkyl groups such as methyl group, ethyl group, n-propyl group, isopropyl group, various butyl groups, various pentyl groups, various hexyl groups, various heptyl groups, various octyl groups, various nonyl groups, and various decyl groups; cycloalkyl groups such as cyclopentyl group, cyclohexyl group, various methylcyclohexyl groups, various ethylcyclohexyl groups, various propylcyclohexyl groups, and various dimethylcyclohexyl groups; aryl groups such as phenyl group, various methylphenyl groups, various ethylphenyl groups, various dimethylphenyl groups, various propylphenyl groups, various trimethylphenyl groups, various butylphenyl groups, and various naphthyl groups; and arylalkyl groups such as benzyl group, various phenylethyl groups, various methylbenzyl groups, various phenylpropyl groups, and various phenylbutyl groups; and the like, each having a corresponding number of carbon atoms.
In the epoxidized fatty acid ester represented by (c1) above, it is preferable that R ^c1 is an alkyl group having 5 to 12 carbon atoms, R ^c2 is an alkyl group having 1 to 6 carbon atoms, p is 1, n is an integer of 1 to 10, and m is 1 or 2.

Specific examples of the epoxidized fatty acid ester (C1) include those obtained by epoxidizing the butyl ester, hexyl ester, 2-ethylhexyl ester, benzyl ester, cyclohexyl ester, methoxyethyl ester, octyl ester, phenyl ester, or butylphenyl ester of linoleic acid, oleic acid, palmitic acid, linolenic acid, or stearic acid.
Examples of commercially available epoxidized fatty acid esters (C1) include Sanso Cizer E-6000 manufactured by New Japan Chemical Co., Ltd. and Chemicizer T-5000 manufactured by Sanwa Synthetic Chemical Industry Co., Ltd.

The epoxidized fatty acid ester (C1) may be used alone or in combination of two or more.

(Epoxidized Vegetable Oil (C2))
Examples of the epoxidized vegetable oil (C2) include those obtained by epoxidizing vegetable oils such as soybean oil, linseed oil, rice bran oil, and cottonseed oil.

As the epoxidized vegetable oil (C2), from the viewpoint of making it easier to improve the effects of the present invention, one having a group represented by the following general formula (c2) is preferably used. More specifically, a glycerin ester having one or more groups represented by the following general formula (c2) is preferred, a triglyceride having one or more groups represented by the following general formula (c2) is more preferred, and a triglyceride having two or more groups represented by the following general formula (c2) is even more preferred.

(In formula (c2), R ^c1 is a hydrocarbon group having 4 to 20 carbon atoms, p is an integer of 1 to 3, n is an integer of 0 to 12, and m is an integer of 1 to 3. When m is 2 or more, the structures in [ ] may be the same or different.)
The details of R ^c1 are the same as those in the formula (c1) above.
In the group represented by (c2) above, it is preferred that R ^c1 is an alkyl group having 4 to 12 carbon atoms, p is 1, n is an integer of 1 to 10, and m is 1 or 2.

Commercially available epoxidized vegetable oils (C2) include Sanso Cizer E-2000H manufactured by New Japan Chemical Co., Ltd.; Chemicizer SE-80, Chemicizer SE-100, Chemicizer T-3000N, Chemicizer LE-3000, and Chemicizer T-2000 manufactured by Sanwa Synthetic Chemical Industry Co., Ltd.; New Cizer 510R manufactured by NOF Corporation; and Adeka Cizer O-180A manufactured by ADEKA Corporation.

The epoxidized vegetable oil (C2) may be used alone or in combination of two or more types.

(Epoxidized alicyclic carboxylic acid ester (C3))
Examples of the epoxidized alicyclic carboxylic acid ester (C3) include an epoxidized ester of an alicyclic carboxylic acid having 5 to 12 ring carbon atoms with an alcohol having 1 to 8 carbon atoms, a phenol, or an alkylphenol having 7 to 14 carbon atoms, and the alicyclic carboxylic acid may be a monocarboxylic acid or a dicarboxylic acid.

As the epoxidized alicyclic carboxylic acid ester (C3), one represented by the following general formula (c3) is preferably used, from the viewpoint of being able to effectively suppress an increase in the acid value of the refrigerator oil composition.

(In formula (c3), R ^c3 and R ^c4 each independently represent a hydrocarbon group having 4 to 20 carbon atoms.)
Specific examples of the hydrocarbon group include those having the same number of carbon atoms as those exemplified as the hydrocarbon group in formula (c1).
In the epoxidized alicyclic carboxylic acid ester represented by (c3) above, R ^c3 and R ^c4 are preferably each independently an alkyl group having 6 to 12 carbon atoms.

Specific examples of the epoxidized alicyclic carboxylic acid ester include epoxidized alicyclic dicarboxylic acid esters, and more specific examples include di-2-ethylhexyl 4,5-epoxycyclohexane-1,2-dicarboxylate.
Examples of commercially available epoxidized alicyclic carboxylic acid esters include Sanso Cizer E-PS manufactured by New Japan Chemical Co., Ltd.

The epoxidized alicyclic carboxylic acid ester (C3) may be used alone or in combination of two or more.

Here, from the viewpoint of further improving the effects of the present invention, it is more preferable that the epoxy compound (C) contains one or more compounds selected from the group consisting of epoxidized fatty acid esters (C1) and epoxidized vegetable oils (C2), and it is even more preferable that the epoxy compound (C) contains epoxidized fatty acid esters (C1).

<Content Ratio of Modified Silicone Compound (B) and Epoxy Compound (C)>
In the refrigerator oil composition of this embodiment, from the viewpoint of further improving the effects of the present invention, the content ratio of the modified silicone compound (B) to the epoxy compound (C) [(B)/(C)], in mass ratio, is preferably 0.10 or more, more preferably 0.50 or more, even more preferably 1.0 or more, and still more preferably more than 1.0. Also, it is preferably 10 or less, more preferably 9.0 or less, and even more preferably 8.0 or less.
The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, the range is preferably 0.10 or more and 10 or less, more preferably 0.50 or more and 9.0 or less, even more preferably 1.0 or more and 8.0 or less, and still more preferably more than 1.0 and 8.0 or less.

<Antioxidant (D)>
The refrigerator oil composition of the present embodiment may further contain an antioxidant (D).
The antioxidant (D) is preferably at least one selected from the group consisting of phenol-based antioxidants and amine-based antioxidants.
Examples of phenol-based antioxidants include 2,6-di-tert-butyl-p-cresol (DBPC), 2,6-di-tert-butyl-4-ethylphenol, and 2,2'-methylenebis(4-methyl-6-tert-butylphenol).
Examples of the amine antioxidant include phenyl-α-naphthylamine and N,N'-diphenyl-p-phenylenediamine.
Of these, phenol-based antioxidants are preferred, and of the phenol-based antioxidants, 2,6-di-tert-butyl-p-cresol (DBPC) is preferred.
From the viewpoints of stability and antioxidant performance, the content of the antioxidant (D) is preferably 0.01 mass % or more, more preferably 0.05 mass % or more, and even more preferably 0.1 mass % or more, based on the total amount of the refrigerator oil composition, and is preferably 5 mass % or less, more preferably 3 mass % or less, and even more preferably 1 mass % or less.
The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, the range is preferably 0.01% by mass to 5% by mass, more preferably 0.05% by mass to 3% by mass, and even more preferably 0.1% by mass to 1% by mass.
The antioxidant (D) may be used alone or in combination of two or more kinds.

(Ratio of Modified Silicone Compound (B) to Antioxidant (D))
When the refrigerator oil composition of the present embodiment contains an antioxidant (D), from the viewpoint of further improving the effects of the present invention, the content ratio of the modified silicone compound (B) to the antioxidant (D) [(B)/(D)], in mass ratio, is preferably 0.10 or more, more preferably 0.20 or more, even more preferably 0.30 or more, and is preferably 5.0 or less, more preferably 3.5 or less, even more preferably 2.0 or less.

(Ratio of Epoxy Compound (C) to Antioxidant (D))
When the refrigerator oil composition of the present embodiment contains the antioxidant (D), from the viewpoint of further improving the effects of the present invention, the content ratio of the epoxy compound (C) to the antioxidant (D) [(C)/(D)], in mass ratio, is preferably 0.05 or more, more preferably 0.10 or more, even more preferably 0.20 or more, and is preferably 5.0 or less, more preferably 2.0 or less, even more preferably 1.0 or less.

<Glycidyl Ether Compound (E)>
The refrigerator oil composition of the present embodiment may further contain a glycidyl ether compound (E).
Examples of the glycidyl ether compound (E) include glycidyl ethers derived from aliphatic mono- or polyhydric alcohols or aromatic compounds containing one or more hydroxyl groups, each having a carbon number of typically 3 to 30, preferably 4 to 24, and more preferably 6 to 16. The aliphatic mono- or polyhydric alcohol may be linear, branched, or cyclic, and may be saturated or unsaturated, but is preferably a saturated aliphatic monoalcohol.
In the case of an aliphatic polyhydric alcohol or an aromatic compound containing two or more hydroxyl groups, it is preferred that all of the hydroxyl groups are glycidyl etherified from the viewpoint of the stability of the refrigerator oil composition.
Examples of glycidyl ether compounds include phenyl glycidyl ether, alkyl glycidyl ether, and alkylene glycol glycidyl ether. Among these, glycidyl ethers derived from linear, branched, or cyclic saturated aliphatic monoalcohols having 6 to 16 carbon atoms (i.e., alkyl glycidyl ethers in which the alkyl group has 6 to 16 carbon atoms) are more preferred. Examples of such glycidyl ethers include 2-ethylhexyl glycidyl ether, isononyl glycidyl ether, decyl glycidyl ether, lauryl glycidyl ether, and myristyl glycidyl ether. 2-Ethylhexyl glycidyl ether is the most preferred. The use of an alkyl glycidyl ether such as 2-ethylhexyl glycidyl ether appropriately prevents an increase in the acid value of the refrigerating machine oil composition, making it easier to improve oxidation stability at high temperatures.

The content of the glycidyl ether compound (E) is preferably 0.10 to 10.00 mass% based on the total amount of the refrigerating machine oil composition. By setting the content of the glycidyl ether compound (E) to 0.10 mass% or more, the acid in the refrigerating machine oil composition can be appropriately captured, effectively preventing an increase in the acid value of the refrigerating machine oil composition and facilitating an improvement in high-temperature stability. Furthermore, by setting the content to 10.00 mass% or less, it is possible to achieve effects commensurate with the content.
The content of the glycidyl ether compound (E) is more preferably 0.4% by mass or more, even more preferably 0.5% by mass or more. It is more preferably 5% by mass or less, even more preferably 4% by mass or less, and even more preferably 3% by mass or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is more preferably 0.4% by mass to 5% by mass, even more preferably 0.5% by mass to 4% by mass, and even more preferably 0.5% by mass to 3% by mass.
The glycidyl ether compound (E) may be used alone or in combination of two or more.

(Ratio of modified silicone compound (B) to glycidyl ether compound (E))
When the refrigerator oil composition of this embodiment contains the glycidyl ether compound (E), from the viewpoint of further improving the effects of the present invention, the content ratio of the modified silicone compound (B) to the glycidyl ether compound (E) [(B)/(E)], in mass ratio, is preferably 0.01 or more, more preferably 0.05 or more, even more preferably 0.08 or more, and is also preferably 5.0 or less, more preferably 2.0 or less, even more preferably 1.0 or less.

(Ratio of epoxy compound (C) to glycidyl ether compound (E))
When the refrigerator oil composition of the present embodiment contains the glycidyl ether compound (E), from the viewpoint of further improving the effects of the present invention, the content ratio of the epoxy compound (C) to the glycidyl ether compound (E) [(C)/(E)], in mass ratio, is preferably 0.01 or more, more preferably 0.03 or more, even more preferably 0.04 or more, and is preferably 5.0 or less, more preferably 2.0 or less, even more preferably 1.0 or less.

<Stabilizer (F)>
The refrigerator oil composition of the present embodiment may further contain a stabilizer (F).
Examples of the stabilizer (F) include aliphatic unsaturated compounds and terpenes having a double bond.
The aliphatic unsaturated compound is preferably an unsaturated hydrocarbon, and specific examples thereof include olefins and polyenes such as dienes and trienes. As the olefin, α-olefins such as 1-tetradecene, 1-hexadecene, and 1-octadecene are preferred from the viewpoint of reactivity with oxygen.
As the aliphatic unsaturated compound other than those mentioned above, from the viewpoint of reactivity with oxygen, unsaturated aliphatic alcohols having conjugated double bonds, such as vitamin A ((2E,4E,6E,8E)-3,7-dimethyl-9-(2,6,6-trimethylcyclohex-1-yl)nona-2,4,6,8-tetraen-1-ol) represented by the molecular formula C ₂₀ H ₃₀ O, are preferred.
As the terpenes having a double bond, terpene hydrocarbons having a double bond are preferred, and from the viewpoint of reactivity with oxygen, α-pinene, β-pinene, α-farnesene (C ₁₅ H ₂₄ : 3,7,11-trimethyldodeca-1,3,6,10-tetraene) and β-farnesene (C ₁₅ H ₂₄ : 7,11-dimethyl-3-methylidendodeca-1,6,10-triene) are more preferred.

The content of the stabilizer (F) is preferably 0.10 mass% or more, more preferably 0.20 mass% or more, even more preferably 0.30 mass% or more, based on the total amount of the refrigerator oil composition, and is preferably 8.0 mass% or less, more preferably 5.0 mass% or less, even more preferably 3.0 mass% or less.
The upper and lower limits of these numerical ranges can be combined in any combination. Specifically, the content is more preferably 0.10% by mass to 8.0% by mass, even more preferably 0.20% by mass to 5.0% by mass, and even more preferably 0.30% by mass to 3.0% by mass.
The stabilizer (F) may be used alone or in combination of two or more.

(Ratio of modified silicone compound (B) to stabilizer (F))
When the refrigerator oil composition of the present embodiment contains a stabilizer (F), from the viewpoint of further improving the effects of the present invention, the content ratio of the modified silicone compound (B) to the stabilizer (F) [(B)/(F)], in mass ratio, is preferably 0.01 or more, more preferably 0.04 or more, even more preferably 0.06 or more, and is preferably 5.0 or less, more preferably 3.0 or less, even more preferably 1.0 or less.

(Ratio of epoxy compound (C) to stabilizer (F))
When the refrigerator oil composition of the present embodiment contains the stabilizer (F), from the viewpoint of further improving the effects of the present invention, the content ratio of the epoxy compound (C) to the stabilizer (F) [(C)/(F)], in mass ratio, is preferably 0.01 or more, more preferably 0.04 or more, even more preferably 0.06 or more, and is preferably 5.0 or less, more preferably 3.0 or less, even more preferably 1.0 or less.

<Other additives>
The refrigerator oil composition of the present embodiment may contain other additives (hereinafter also referred to as "other additives") in addition to the modified silicone compound (B), the epoxy compound (C), the antioxidant (D), the glycidyl ether compound (E), and the stabilizer (F).
Examples of other additives include extreme pressure agents and antifoaming agents.
That is, the refrigerating machine oil composition of the present embodiment may consist only of the base oil (A), the modified silicone compound (B), and the epoxy compound (C), or may further contain, in addition to the base oil (A), the modified silicone compound (B), and the epoxy compound (C), one or more selected from the group consisting of an antioxidant (D), a glycidyl ether compound (E), a stabilizer (F), an extreme pressure agent, and an antifoaming agent.

(extreme pressure agent)
As the extreme pressure agent, phosphorus-based extreme pressure agents, metal salts of carboxylic acids, and sulfur-based extreme pressure agents are preferred.
Examples of phosphorus-based extreme pressure agents include phosphate esters, acid phosphate esters, phosphites, acid phosphites, and amine salts thereof.
Among these, from the viewpoint of improving extreme pressure properties and friction characteristics, one or more selected from tricresyl phosphate (TCP), trithiophenyl phosphate, tri(nonylphenyl) phosphite, dioleylhydrogen phosphite, and 2-ethylhexyldiphenyl phosphite are preferred, and tricresyl phosphate (TCP) is more preferred.
Examples of the metal salts of carboxylic acids include metal salts of carboxylic acids having 3 to 60 carbon atoms (preferably 3 to 30 carbon atoms).
Among these, at least one selected from metal salts of fatty acids having 12 to 30 carbon atoms and metal salts of dicarboxylic acids having 3 to 30 carbon atoms is preferred.
As the metal constituting the metal salt, alkali metals and alkaline earth metals are preferred, and alkali metals are more preferred.
Examples of sulfur-based extreme pressure agents include sulfurized fats and oils, sulfurized fatty acids, sulfurized esters, sulfurized olefins, dihydrocarbyl polysulfides, thiocarbamates, thioterpenes, and dialkylthiodipropionates.

(Antifoaming agent)
Examples of the antifoaming agent include silicone oil and silicone-based antifoaming agents such as fluorinated silicone oil.
The silicone compound used as the defoaming agent is an unmodified silicone compound that is not classified as the modified silicone compound (B).

[Method of producing refrigerator oil composition]
The method for producing the above refrigerator oil composition is not particularly limited.
For example, the method for producing the refrigerating machine oil composition of the present embodiment comprises adding a compound represented by the following general formula (1)
C _x F _y H _z ...(1)
[In the general formula (1), x is an integer of 2 to 6, y is an integer of 1 to 11, and z is an integer of 1 to 11, and the molecule has one or more carbon-carbon unsaturated bonds.]
a base oil (A) containing at least one selected from the group consisting of polyalkylene glycols, copolymers of poly(oxy)alkylene glycols or monoethers thereof with polyvinyl ethers, and polyol esters;
a modified silicone compound (B);
an epoxy compound (C) that satisfies the following requirements (α) and (β);
mixing the
In the step, the modified silicone compound (B) is blended in an amount of more than 0.10 mass% based on the total amount of the refrigerator oil composition.
Requirement (α): The molecule has at least one divalent group represented by the following formula (2):

Requirement (β): The molecule has at least one ester group.
The method for mixing the above components is not particularly limited, and examples thereof include a method including a step of blending a modified silicone compound (B) and an epoxy compound (C) into a base oil (A). The antioxidant (D), the glycidyl ether compound (E), the stabilizer (F), and other additives may be blended into the base oil (A) at the same time as blending the modified silicone compound (B) and the epoxy compound (C) into the base oil (A), or may be blended separately. Note that each component may be blended after being made into a solution (dispersion) by adding a diluent oil or the like. After blending the components, it is preferable to stir them uniformly by a known method.

[Physical properties of refrigerator oil composition]
In this embodiment, the refrigerating machine oil composition has the following physical property values after the thermal stability test described in the examples below.

<Acid value>
The acid value of the refrigerator oil composition after the thermal stability test described in the Examples below is preferably less than 0.18 mgKOH/g, more preferably 0.17 mgKOH/g or less, and even more preferably 0.16 mgKOH/g or less.

<Fluorine content>
The amount of fluorine in the refrigerating machine oil composition after the thermal stability test described in the Examples below is preferably less than 17 ppm by mass, more preferably 15 ppm by mass or less, and even more preferably 14 ppm by mass or less, based on the total amount of the refrigerating machine oil composition.

[Mixed composition for refrigerator]
The above-mentioned refrigerating machine oil composition is mixed with a refrigerant and used as a mixed composition for a refrigerating machine.
That is, the mixed composition for a refrigerator contains the above-mentioned refrigerator oil composition and a refrigerant.
The refrigerant will be described below.

<Refrigerant>
The refrigerant used in this embodiment is represented by the following general formula (1):
C _x F _y H _z ...(1)
The refrigerant contains one or more unsaturated fluorohydrocarbon compounds selected from compounds represented by the general formula (1): [in which x is an integer of 2 to 6, y is an integer of 1 to 11, and z is an integer of 1 to 11, and the molecule has one or more carbon-carbon unsaturated bonds].

The above general formula (1) represents the type and number of elements in the molecule, and specifically represents an unsaturated fluorohydrocarbon compound having 2 to 6 carbon atoms C. An unsaturated fluorohydrocarbon compound having 2 to 6 carbon atoms C has the physical and chemical properties required for a refrigerant, such as boiling point, freezing point, and latent heat of vaporization.
In the above general formula (1), the bonding form of the x carbon atoms represented by _Cx includes unsaturated bonds such as a carbon-carbon single bond and a carbon-carbon double bond. From the viewpoint of stability, the carbon-carbon unsaturated bond is preferably a carbon-carbon double bond, and the unsaturated fluorohydrocarbon compound has one or more unsaturated bonds such as a carbon-carbon double bond in the molecule, and the number thereof is preferably one. In other words, it is more preferable that at least one of the bonding forms of the x carbon atoms represented by _Cx is a carbon-carbon double bond.

Preferred examples of the unsaturated fluorinated hydrocarbon compound include fluorides of linear or branched chain olefins having 2 to 6 carbon atoms and cyclic olefins having 4 to 6 carbon atoms.
Specific examples include fluorides of ethylene having 1 to 3 fluorine atoms introduced, fluorides of propene having 1 to 5 fluorine atoms introduced, fluorides of butene having 1 to 7 fluorine atoms introduced, fluorides of pentene having 1 to 9 fluorine atoms introduced, fluorides of hexene having 1 to 11 fluorine atoms introduced, fluorides of cyclobutene having 1 to 5 fluorine atoms introduced, fluorides of cyclopentene having 1 to 7 fluorine atoms introduced, and fluorides of cyclohexene having 1 to 9 fluorine atoms introduced.
Among these, propene fluorides are preferred, and propene having 3 to 5 fluorine atoms introduced is more preferred. Specifically, one or more selected from 1,3,3,3-tetrafluoropropene (R1234ze), 2,3,3,3-tetrafluoropropene (R1234yf), and 1,2,3,3-tetrafluoropropene (R1234ye) are preferred, and 2,3,3,3-tetrafluoropropene (R1234yf) is more preferred.
The unsaturated fluorohydrocarbon compounds may be used alone or in combination of two or more thereof. Thus, only one selected from 1,3,3,3-tetrafluoropropene (R1234ze), 2,3,3,3-tetrafluoropropene (R1234yf), and 1,2,3,3-tetrafluoropropene (R1234ye) may be used alone.

(Other refrigerants)
In the present embodiment, the refrigerant may be a mixed refrigerant containing, in addition to the unsaturated fluorohydrocarbon compound represented by the general formula (1) above, other compounds as necessary, and may contain, for example, a saturated fluorohydrocarbon compound.
The saturated fluorinated hydrocarbon compound is preferably a fluoride of an alkane having 1 to 4 carbon atoms, more preferably a fluoride of an alkane having 1 to 3 carbon atoms, and even more preferably a fluoride of an alkane (methane or ethane) having 1 or 2 carbon atoms. Examples of the fluoride of methane or ethane include trifluoromethane (R23), difluoromethane (R32), 1,1-difluoroethane (R152a), 1,1,1-trifluoroethane (R143a), 1,1,2-trifluoroethane (R143), 1,1,1,2-tetrafluoroethane (R134a), 1,1,2,2-tetrafluoroethane (R134), and 1,1,1,2,2-pentafluoroethane (R125). Of these, difluoromethane and 1,1,1,2,2-pentafluoroethane are preferred.
These saturated fluorohydrocarbon compounds may be used alone or in combination of two or more.

The refrigerant may also include a natural refrigerant. Examples of natural refrigerants include hydrocarbon refrigerants (HC), carbon dioxide (CO ₂ , carbon dioxide gas), and ammonia. These natural refrigerants may be used alone or in combination of two or more.
The hydrocarbon refrigerant is preferably a hydrocarbon having from 1 to 8 carbon atoms, more preferably from 1 to 5 carbon atoms, and even more preferably from 3 to 5 carbon atoms. If the carbon number is 8 or less, the boiling point of the refrigerant does not become too high, which is preferable as a refrigerant. Examples of the hydrocarbon refrigerant include one or more selected from the group consisting of methane, ethane, ethylene, propane (R290), cyclopropane, propylene, n-butane, isobutane (R600a), 2-methylbutane, n-pentane, isopentane, cyclopentane isobutane, and normal hexane. These refrigerants may be used alone or in combination of two or more.

(Content of unsaturated fluorohydrocarbon compounds in refrigerants)
In this embodiment, the refrigerant contains the unsaturated fluorohydrocarbon compound represented by the general formula (1) above.
The content of the unsaturated fluorohydrocarbon compound represented by the general formula (1) is preferably 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, even more preferably 70% by mass to 100% by mass, still more preferably 80% by mass to 100% by mass, even more preferably 90% by mass to 100% by mass, and even more preferably 100% by mass (i.e., a refrigerant consisting solely of the unsaturated fluorohydrocarbon compound), based on the total amount of the refrigerant.
The refrigerating machine oil composition of the present embodiment is excellent in the effect of suppressing an increase in acid value even in a refrigerant having such a high content of unsaturated fluorohydrocarbon compounds.

(Amount of refrigerant and refrigerating machine oil composition used)
In the mixed composition for a refrigerator of this embodiment, the amounts of the refrigerant and the refrigerator oil composition used, expressed as a mass ratio of the refrigerator oil composition to the refrigerant [(refrigerant oil composition)/(refrigerant)], are preferably 1/99 to 90/10, more preferably 5/95 to 70/30. When the mass ratio of the refrigerator oil composition to the refrigerant is within this range, lubricity and suitable refrigeration capacity in the refrigerator can be obtained.

[Uses of refrigerating machine oil composition and mixed composition for refrigerating machine]
The refrigerating machine oil composition and the mixed composition for a refrigerating machine are preferably used in, for example, air conditioners, refrigerators, vending machines, showcases, refrigeration systems, hot water supply systems, or heating systems. Examples of the air conditioners include car air conditioners such as open-type car air conditioners and electric car air conditioners; gas heat pump (GHP) air conditioners; and the like.

[One aspect of the present invention provided]
In one aspect of the present invention, the following [1] to [14] are provided.
[1] The following general formula (1)
C _x F _y H _z ...(1)
[In the general formula (1), x is an integer of 2 to 6, y is an integer of 1 to 11, and z is an integer of 1 to 11, and the molecule has one or more carbon-carbon unsaturated bonds.]
a base oil (A) containing at least one selected from the group consisting of polyalkylene glycols, copolymers of poly(oxy)alkylene glycols or monoethers thereof with polyvinyl ethers, and polyol esters;
a modified silicone compound (B);
and an epoxy compound (C) that satisfies the following requirements (α) and (β):
A refrigerator oil composition, wherein the content of the modified silicone compound (B) is more than 0.10 mass% based on the total amount of the refrigerator oil composition.
Requirement (α): The molecule has at least one divalent group represented by the following formula (2):

Requirement (β): The molecule has at least one ester group.
[2] The refrigerator oil composition according to [1], wherein the modified silicone compound (B) includes a side-chain-modified silicone (B1) in which at least a side chain of a polysiloxane skeleton is modified.
[3] The refrigerator oil composition according to [2], wherein the side chain-modified silicone (B1) comprises at least one selected from the group consisting of side chain-modified silicones (B1a) having one or more epoxy groups in the side chain and side chain-modified silicones (B1b) having one or more polyether groups in the side chain.
[4] The refrigerator oil composition according to any one of [1] to [3], wherein the content of the modified silicone compound (B) is 0.20 mass% or more based on the total amount of the refrigerator oil composition.
[5] The refrigerator oil composition according to any one of [1] to [4], wherein the molecular weight of the epoxy compound (C) is 300 or more.
[6] The refrigerator oil composition according to any one of [1] to [5], wherein the epoxy compound (C) is at least one selected from the group consisting of an epoxidized fatty acid ester (C1) and an epoxidized vegetable oil (C2).
[7] The refrigerator oil composition according to [6], wherein the epoxidized fatty acid ester (C1) is represented by the following general formula (c1):

[In formula (c1), R ^c1 is a hydrocarbon group having 4 to 20 carbon atoms, R ^c2 is a hydrocarbon group having 1 to 10 carbon atoms, p is an integer of 1 to 3, n is an integer of 0 to 12, and m is an integer of 1 to 3. When m is 2 or more, the multiple structures in [ ] may be the same or different.]
[8] The refrigerating oil composition according to any one of [1] to [7], wherein the content of the epoxy compound (C) is 0.05 mass% or more based on the total amount of the refrigerating oil composition.
[9] The refrigerator oil composition according to any one of [1] to [8], wherein the content ratio [(B)/(C)] of the modified silicone compound (B) to the epoxy compound (C) is 0.10 or more in mass ratio.
[10] The refrigerator oil composition according to any one of [1] to [9], further comprising one or more additives selected from the group consisting of an antioxidant (D), a glycidyl ether compound (E), a stabilizer (F), an extreme pressure agent, and an antifoaming agent.
[11] The refrigerator oil composition according to any one of [1] to [10], wherein the unsaturated fluorinated hydrocarbon compound comprises one or more selected from the group consisting of R1234ze, R1234yf, and R1234ye.
[12] The refrigerator oil composition according to any one of [1] to [11], wherein the refrigerant consists solely of the unsaturated fluorohydrocarbon compound.
[13] The following general formula (1):
C _x F _y H _z ...(1)
[In the general formula (1), x is an integer of 2 to 6, y is an integer of 1 to 11, and z is an integer of 1 to 11, and the molecule has one or more carbon-carbon unsaturated bonds.] and the refrigerating machine oil composition according to any one of [1] to [12].
[14] The following general formula (1):
C _x F _y H _z ...(1)
[In the general formula (1), x is an integer of 2 to 6, y is an integer of 1 to 11, and z is an integer of 1 to 11, and the molecule has one or more carbon-carbon unsaturated bonds.]
a base oil (A) containing at least one selected from the group consisting of polyalkylene glycols, copolymers of poly(oxy)alkylene glycols or monoethers thereof with polyvinyl ethers, and polyol esters;
a modified silicone compound (B);
an epoxy compound (C) that satisfies the following requirements (α) and (β);
mixing the
In the step, the modified silicone compound (B) is blended in an amount of more than 0.10 mass% based on the total amount of the refrigerator oil composition.
Requirement (α): The molecule has at least one divalent group represented by the following formula (2):

Requirement (β): The molecule has at least one ester group.

The present invention will be explained in more detail with reference to the following examples. However, the present invention is not limited to the following examples.

[Methods for measuring various physical properties]
The properties of the raw materials used in each Example and Comparative Example and the refrigerator oil compositions of each Example and Comparative Example were measured according to the procedures shown below.
(1) Kinematic Viscosity at 100°C The kinematic viscosity at 100°C of the base oil (A) was measured in accordance with JIS K2283:2000.
(2) Hydroxyl Value The hydroxyl value of the base oil (A) was measured by neutralization titration in accordance with JIS K0070:1992.
(3) Number average molecular weight (Mn)
The number average molecular weight (Mn) of the base oil (A) was measured using a gel permeation chromatography (GPC) device.
GPC was performed using two "TSKgel SuperMultipore HZ-M" columns connected in series, manufactured by Tosoh Corporation, with tetrahydrofuran as the eluent and a refractive index detector (RI detector) as the detector, and the number average molecular weight (Mn) was determined using polystyrene as a standard sample.

[Details of each component used in preparing the refrigerator oil composition]
Details of each component used in preparing the refrigerator oil composition are shown below.

<Base oil (A)>
(PAG)
"Polyoxypropylene glycol dimethyl ether": kinematic viscosity at 100°C = 10.3 ^{mm 2} /s, hydroxyl value = 1 mg KOH/g, number average molecular weight = 1,020
(ECP)
"Copolymer of polypropylene glycol (PPG) and polyethyl vinyl ether (PEV) (PPG/PEV=5/5 (molar ratio))": kinematic viscosity at 100° C.=10.5 mm ² /s, hydroxyl value=1 mgKOH/g, number average molecular weight=870
(POE)
"Ester of pentaerythritol with a mixture of octanoic acid (C8 acid) and nonanoic acid (C9 acid) (C8 acid/C9 acid=1/1.1 (molar ratio))": kinematic viscosity at 100° C.=8.5 mm ² /s, hydroxyl value=1 mgKOH/g, number average molecular weight=670

<Modified Silicone Compound (B)>
・ "Epoxy-modified silicone": KF-101 (manufactured by Shin-Etsu Chemical Co., Ltd.)
The epoxy-modified silicone is a modified silicone corresponding to the side-chain-modified silicone (B1a) having one or more epoxy groups in the side chain.
"Polyether-modified silicone": KF-945 (manufactured by Shin-Etsu Chemical Co., Ltd.), HLB value = 4
The polyether-modified silicone is a modified silicone corresponding to the side-chain-modified silicone (B1b) having one or more polyether groups in the side chain.

<Epoxy Compound (C)>
"Epoxy compound 1": epoxidized soybean oil represented by the following formula, molecular weight: 933, Sanso Cizer E-2000H (manufactured by New Japan Chemical Co., Ltd.)

The epoxidized soybean oil represented by the above formula is an epoxy compound corresponding to the epoxidized vegetable oil (C2).
"Epoxy compound 2": epoxidized fatty acid ester represented by the following formula, molecular weight: 411, Sanso Cizer E-6000 (manufactured by New Japan Chemical Co., Ltd.)

The epoxidized fatty acid ester represented by the above formula is an epoxy compound corresponding to the epoxidized fatty acid ester (C1).

<Antioxidant (D)>
Di-tert-butyl-p-cresol (DBPC)

<Glycidyl Ether Compound (E)>
2-Ethylhexyl glycidyl ether

<Stabilizer (F)>
β-pinene

<Other additives>
Extreme pressure agent (tricresyl phosphate), silicone-based antifoaming agent *Silicone-based antifoaming agents are unmodified silicone compounds that are not classified as modified silicone compounds (B).

[Examples and Comparative Examples]
The above components were mixed to prepare refrigerator oil compositions having the compositions shown in Tables 1 to 3, and the following thermal stability tests were carried out.
The numerical units of the blending compositions in Tables 1 to 3 are "mass %."
The content of the modified silicone compound (B) in Tables 1 to 3 means the content calculated as solid content.

<Thermal stability test>
The test was carried out in accordance with Appendix C of JIS K2211:2009.
Specifically, a 200 mL autoclave tube was charged with a mixed composition for refrigerators (water content: 500 ppm by mass, air content: 25 mL) prepared by mixing 30 g of the refrigerating machine oil compositions of the Examples and Comparative Examples with 30 g of R1234yf, and a metal catalyst composed of iron, copper, and aluminum. The tube was then evacuated and sealed, and held at 175°C for 14 days. The appearance of the oil and the presence or absence of precipitates (and the color of precipitates, if any) were then visually observed.
The oil appearance was evaluated by ASTM color, and oils judged to have a good appearance were those judged to be 0.5 or less (L0.5), and oils judged to have a poor appearance were those judged to be greater than 0.5 (L1.0, L1.5, etc.).
After the thermal stability test, the acid value of the refrigerator oil composition and the amount of fluorine in the refrigerator oil composition were evaluated by the methods described below.

(Evaluation of acid value of refrigerator oil composition)
Measurement was carried out by indicator photometric titration method in accordance with JIS K2501:2003 (see Appendix 1 of the JIS standard).

(Evaluation of fluorine content in refrigerator oil composition)
The amount of fluorine in the refrigerating machine oil composition was measured by separating the refrigerant from the mixed composition for a refrigerating machine after the autoclave test and detecting fluorine ions (F ⁻ ) in the refrigerating machine oil composition in accordance with JIS K 0127:2013 (General rules for ion chromatography analysis).

From Table 1, the following can be seen.
It can be seen that the refrigerator oil compositions of Examples I-1 to I-4 have an excellent effect of suppressing an increase in the acid value of the refrigerator oil composition after the thermal stability test, and the amount of fluorine in the refrigerator oil composition after the test is also small.
In contrast, the refrigerating machine oil compositions of Comparative Examples I-1 to I-10 were found to have an insufficient effect of suppressing the increase in the acid value of the refrigerating machine oil composition after the thermal stability test, and the fluorine content in the refrigerating machine oil composition after the test was also high.

From Table 2, the following can be seen.
It can be seen that the refrigerator oil composition of Example II-1 has an excellent effect of suppressing an increase in the acid value of the refrigerator oil composition after the thermal stability test, and the amount of fluorine in the refrigerator oil composition after the test is also small.
In contrast, the refrigerating machine oil compositions of Comparative Examples II-1 to II-4 were found to have an insufficient effect of suppressing the increase in the acid value of the refrigerating machine oil composition after the thermal stability test, and the fluorine content in the refrigerating machine oil composition after the test was also high.

From Table 3, the following can be seen.
It is clear that the refrigerator oil composition of Example III-1 has an excellent effect of suppressing an increase in the acid value of the refrigerator oil composition after the thermal stability test.
In contrast, it is clear that the refrigerator oil compositions of Comparative Examples III-1 to III-4 are insufficient in their effect of suppressing the increase in acid value of the refrigerator oil composition after the thermal stability test.
In Example III-1 and Comparative Examples III-1 to III-2, the amount of fluorine in the refrigerating machine oil composition after the test was small. This is thought to be because, in Example III-1 and Comparative Examples III-1 to III-2, the iron and copper used as the metal catalysts were slightly discolored, and fluorine adhered to the iron and copper used as the metal catalysts, resulting in a small amount of fluorine eluted into the refrigerating machine oil composition after the test.
In the other examples and comparative examples, no discoloration of the metal catalyst was observed.

These results demonstrate that a refrigerator oil composition containing a modified silicone compound (B) and an epoxy compound (C), in which the content of the modified silicone compound (B) is adjusted to greater than 0.10 mass%, is effective in suppressing an increase in the acid value of the refrigerator oil composition after a thermal stability test.

Claims (14)

The following general formula (1)
C _x F _y H _z ...(1)
[In the general formula (1), x is an integer of 2 to 6, y is an integer of 1 to 11, and z is an integer of 1 to 11, and the molecule has one or more carbon-carbon unsaturated bonds.]
a base oil (A) containing at least one selected from the group consisting of polyalkylene glycols, copolymers of poly(oxy)alkylene glycols or monoethers thereof with polyvinyl ethers, and polyol esters;
a modified silicone compound (B);
and an epoxy compound (C) that satisfies the following requirements (α) and (β):
A refrigerator oil composition, wherein the content of the modified silicone compound (B) is more than 0.10 mass% based on the total amount of the refrigerator oil composition.
Requirement (α): The molecule has at least one divalent group represented by the following formula (2):

Requirement (β): The molecule has at least one ester group. The refrigerator oil composition according to claim 1, wherein the modified silicone compound (B) includes a side-chain-modified silicone (B1) in which at least the side chain of the polysiloxane skeleton is modified. The refrigerator oil composition according to claim 2, wherein the side chain-modified silicone (B1) comprises one or more selected from the group consisting of side chain-modified silicones (B1a) having one or more epoxy groups in the side chain and side chain-modified silicones (B1b) having one or more polyether groups in the side chain. The refrigerator oil composition according to any one of claims 1 to 3, wherein the content of the modified silicone compound (B) is 0.20 mass% or more based on the total amount of the refrigerator oil composition. The refrigerator oil composition according to any one of claims 1 to 4, wherein the molecular weight of the epoxy compound (C) is 300 or more. The refrigerator oil composition according to any one of claims 1 to 5, wherein the epoxy compound (C) is one or more selected from the group consisting of epoxidized fatty acid esters (C1) and epoxidized vegetable oils (C2). The refrigerator oil composition according to claim 6, wherein the epoxidized fatty acid ester (C1) is represented by the following general formula (c1):

[In formula (c1), R ^c1 is a hydrocarbon group having 4 to 20 carbon atoms, R ^c2 is a hydrocarbon group having 1 to 10 carbon atoms, p is an integer of 1 to 3, n is an integer of 0 to 12, and m is an integer of 1 to 3. When m is 2 or more, the multiple structures in [ ] may be the same or different.] The refrigerator oil composition according to any one of claims 1 to 7, wherein the content of the epoxy compound (C) is 0.05 mass% or more based on the total amount of the refrigerator oil composition. The refrigerator oil composition according to any one of claims 1 to 8, wherein the content ratio [(B)/(C)] of the modified silicone compound (B) to the epoxy compound (C) is 0.10 or more in mass ratio. The refrigerator oil composition according to any one of claims 1 to 9 further contains one or more additives selected from the group consisting of an antioxidant (D), a glycidyl ether compound (E), a stabilizer (F), an extreme pressure agent, and an antifoaming agent. The refrigerator oil composition according to any one of claims 1 to 10, wherein the unsaturated fluorinated hydrocarbon compound comprises one or more compounds selected from the group consisting of R1234ze, R1234yf, and R1234ye. The refrigerator oil composition according to any one of claims 1 to 11, wherein the refrigerant consists solely of the unsaturated fluorohydrocarbon compound. The following general formula (1)
C _x F _y H _z ...(1)
[In the general formula (1), x is an integer of 2 to 6, y is an integer of 1 to 11, and z is an integer of 1 to 11, and the molecule has one or more carbon-carbon unsaturated bonds.]; and a mixed composition for a refrigerator, comprising the refrigerator oil composition according to any one of claims 1 to 12. The following general formula (1)
C _x F _y H _z ...(1)
[In the general formula (1), x is an integer of 2 to 6, y is an integer of 1 to 11, and z is an integer of 1 to 11, and the molecule has one or more carbon-carbon unsaturated bonds.]
a base oil (A) containing at least one selected from the group consisting of polyalkylene glycols, copolymers of poly(oxy)alkylene glycols or monoethers thereof with polyvinyl ethers, and polyol esters;
a modified silicone compound (B);
an epoxy compound (C) that satisfies the following requirements (α) and (β);
mixing the
In the step, the modified silicone compound (B) is blended in an amount of more than 0.10 mass% based on the total amount of the refrigerator oil composition.
Requirement (α): The molecule has at least one divalent group represented by the following formula (2):

Requirement (β): The molecule has at least one ester group.