FP12-0546-00
DESCRIPTION
Title of Invention
REFRIGERATING MACHINE WORKING FLUID COMPOSITION
5 AND REFRIGERANT OIL
Technical Field
[0001] The present invention relates to a working fluid composition for a refrigerating machine and a refrigerating machine oil, and more specifically, it relates to a working fluid composition for a refrigerating
10 machine containing a refrigerant composed mainly of a mixture of
difluoromethane (also known as "HFC-32" or "R32") and an unsaturated fluorinated hydrocarbon, as well as a refrigerating machine oil used in the working fluid composition for a refrigerating machine. Background Art
15 [0002] In light of the problem of ozone layer depletion that is a focus of
attention in recent years, the restrictions on CFCs (chlorofluorocarbons) and HCFCs (hydrochlorofluorocarbons) that are used as refrigerants in conventional refrigerating machines have become more stringent, and HFCs (hydrofluorocarbons) are coming into use as substitute
20 refrigerants.
[0003] Among HFC refrigerants, HFC-134a, R407C and R410A are routinely used as refrigerants for automobile air conditioners, refrigerators and room air conditioners. However, while these HFC refrigerants have ozone depletion potentials (ODP) of zero, their high
25 global warming potentials (GWP) have led to their gradual restriction.
Difluoromethane has been studied as an alternative to such refrigerants,

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but its global warming potential is not sufficiently low, while its boiling
point is too low and its thermodynamic properties cannot be directly
applied to current refrigeration systems, and it is poorly compatible with
lubricating oils (refrigerating machine oils) such as polyol esters or
5 polyvinyl ethers used with conventional HFC refrigerants. On the
other hand, unsaturated fluorinated hydrocarbons have very low ODP and GWP and may be noncombustible depending on the structure, and include HFO-1234yf which is equivalent or superior to HFC-134a in terms of thermodynamic properties, as a measure of refrigerant
10 performance, and therefore its use as a refrigerant has been proposed
(Patent Literatures 1 to 3). Citation List Patent Literature [0004] [Patent Literature 1] International Patent Publication No.
15 WO2004/037913
[Patent Literature 2] International Patent Publication No.
WO2005/105947
[Patent Literature 3] International Patent Publication No.
WO2009/057475
20 Summary of Invention
Technical Problem
[0005] When a refrigerant and refrigerating machine oil are applied in a refrigeration system, the refrigerant must have thermodynamic properties suited for refrigeration systems, without adversely affecting
25 the environment. In addition, with the co-presence of a refrigerant and
a refrigeratmg machine oil, it is desirable that both mutually dissolve

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(compatibility), that the thermal/chemical stability is excellent, and that an oil film is maintained to minimize friction between sliding members (lubricity).
[0006] In refrigeration systems using unsaturated fluorinated
5 hydrocarbons, refrigerating machine oils such as polyol esters or
polyvinyl ethers used in HFCs exhibit compatibility with unsaturated fluorinated hydrocarbons, and therefore such refrigerating machine oils are considered suitable. Research by the present inventors, however, has shown that unsaturated fluorinated hydrocarbons have inferior
10 thermal/chemical stability due to an unstable . double bond in the
molecule.
[0007] Furthermore, one reason for which compatibility between the refrigerant and refrigerating machine oil (hereunder also referred to simply as "compatibility") is desired is that in the refrigerant circulation
15 cycle of a refrigerating machine, the refrigerating machine oil that
lubricates the refrigerant compressor circulates in the cycle together with the refrigerant. That is, depending on selection of the refrigerating machine oil used in the refrigerant of a refrigerating machine, suitable compatibility between the refrigerant and refrigerating
20 machine oil may not be obtained and refrigerating machine oil
discharged from the refrigerant compressor may readily pool in the cycle. As a result, the amount of oil in the refrigerant compressor is reduced, causing problems such as friction due to poor lubrication, and occlusion of the expansion mechanism including the capillaries. Thus,
25 selection of a refrigerating machine oil suitable for the refrigerant is
essential. In a refrigeration system using difluoromethane, however,

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compatibility with the refrigerating machine oil is an issue, and the thermodynamic properties can be problematic.
[0008] The present invention has been accomplished in light of these
circumstances, and it is ah object thereof to provide a working fluid
5 composition for a refrigerating machine and a refrigerating machine oil,
that allow compatibility and thermal/chemical stability to be achieved in a refrigeration system using a refrigerant comprising difluoromethane and an unsaturated fluorinated hydrocarbon, without requiring major modifications to existing systems.
10 Solution to Problem
[0009] As a result of much diligent research directed toward achieving the object stated above, the present inventors have found that high levels of both sufficiently high compatibility and thermal/chemical stability can be achieved by using a refrigerant comprising difluoromethane and
15 an unsaturated fluormated hydrocarbon in a prescribed mass ratio, and a
refrigerating machine oil comprising a specific ester or ether as the base oil, and the invention has been completed upon this finding. [0010] In other words, the invention provides a working fluid composition for a refrigerating machine that comprises a refrigerant
20 comprising difluoromethane and an unsaturated fluorinated
hydrocarbon wherein the mass ratio of the difluoromethane/the unsaturated fluorinated hydrocarbon is 95/5 to 10/90, and a refrigerating machine oil comprising at least one base oil selected from among polyol esters with a carbon/oxygen molar ratio of 3.2 to 5.8 and polyvinyl
25 ethers with a carbon/oxygen molar ratio of 3.2 to 5.8.
[0011] According to the invention, the total of the difluoromethane and

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the unsaturated fluorinated hydrocarbon in the refi'igerant is preferably
80 mass% or greater.
[0012] AlsOj the mass ratio of the refrigerant/the refi"igerating machine
oil is preferably 90/10 to 30/70.
5 [0013] Furthermore, the mass ratio of the difluoromethane/the
unsaturated fluorinated hydrocarbon is preferably 90/10 to 50/50.
[0014] The unsaturated fluorinated hydrocarbon is preferably
fluoropropene.
[0015] When the base oil is a polyol ester with a carbon/oxygen molar
10 ratio of 3.2 to 5.8, examples of prefeiTed polyol esters include esters
synthesized from a C4 to C9 fatty acid and a C4 to CI2 polyhydric
alcohol.
[0016] Also, when the base oil is a polyvinyl ether with a
carbon/oxygen molar ratio of 3.2 to 5.8, examples of preferred
15 polyvinyl ethers include polyvinyl ethers having a structural unit
represented by the following formula (1).
[Chemical Formula 1]
(1)
C C-
R^ 0{R*'0)mR*
[In the formula, R, R and R may be the same or different and each
20 represents hydrogen or a CI to C8 hydrocarbon group, R'* represents a
CI to CIO divalent hydrocarbon group or C2 to C20 divalent ether bonded oxygen-containing hydrocarbon group, R^ represents a CI to C20 hydrocarbon group, m represents a number such that the average

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value of m for the polyvinyl ether is 0 to 10, R^ to R^ may be the same
or different for each structural unit, and when m is 2 or greater for one
structural unit, the multiple R'^O groups may be the same or different.]
[0017] The invention also provides a reMgerating machine oil,
5 comprising at least one base oil selected from among polyol esters with
a carbon/oxygen molar ratio of 3.2 to 5.8 and polyvinyl ethers with a carbon/oxygen molar ratio of 3.2 to 5.8, and being used together with a refrigerant that comprises difluoromethane and an unsaturated fluorinated hydrocarbon wherein a mass ratio of the
10 difluoromethane/the unsaturated fluorinated hydrocarbon is 95/5 to
10/90,
Advantageous Effects of Invention
[0018] According to the invention it is possible to provide a working fluid composition for a refrigerating machine and refrigerating machine
15 oil, that allow compatibility and thermal/chemical stability to be
achieved in a refrigeration system using a refrigerant comprising difluoromethane and an unsaturated fluorinated hydrocarbon, without requiring major modifications to existing systems. Description of Embodiments
20 [0019] Preferred embodiments of the invention is now described in
detail. [0020]
[Working fluid composition for a refrigerating machine] The working fluid composition for a refrigerating machine of this
25 embodiment comprises a refrigerant comprising difluoromethane and an
unsaturated fluorinated hydrocarbon wherein a mass ratio of the

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difluoromethane/the unsaturated fluorinated hydrocarbon is 95/5 to
10/90, and a refrigerating machine oil comprising at least one base oil
selected from among polyol esters with a carbon/oxygen molar ratio of
3.2 to 5.8 and polyvinyl ethers with a carbon/oxygen molar ratio of 3.2
5 to 5.8. In addition, the refrigerating machine oil of this embodiment
comprises at least one base oil selected from among polyol esters with a carbon/oxygen molar ratio of 3.2 to 5.8 and polyvinyl ethers with a carbon/oxygen molar ratio of 3.2 to 5.8, and is used together with a refrigerant that comprises difluoromethane and an unsaturated
10 fluorinated hydrocarbon wherein a mass ratio of the
difluoromethane/the unsaturated fluorinated hydrocarbon is 95/5 to 10/90.
[0021] In the working fluid composition for a refrigerating machine of this embodiment, the mixing proportion between the refrigerant and
15 refrigerating machine oil is not particularly restricted but the mass ratio
of the refrigerant^the refrigerating machine oil is preferably 90/10 to 3 0/70 and more preferably 80/20 to 40/60.
[0022] The components in the working fluid composition for a refrigerating machine is now described.
20 [0023]
[Refrigerant]
For this embodiment, the refrigerant is one containing difluoromethane and an unsaturated fluorinated hydrocarbon, with the blending ratio of the difluoromethane/the unsaturated fluorinated hydrocarbon being at a
25 mass ratio of 95/5 to 10/90 and preferably 80/20 to 20/80. It is also
preferably 90/10 to 50/50 and more preferably 90/10 to 60/40.

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[0024] Difluoromethane (R32) by itself has a low boiling point and
high pressure, and therefore cannot be considered to have favorable
thermodynamic properties as a refrigerant. In addition, its global
warming potential or GWP value is approximately 600, which is lower
5 than the value of 1300 for the typical hydrofluorocarbon refrigerant
HFC-134a but still not sufficiently low. It is also poorly compatible with refrigerating machine oils. However, its stability is satisfactory even in the copresence of refrigerating machine oils. [0025] On the other hand, the thermodynamic properties of the
10 unsaturated fluorinated hydrocarbon can be improved by selecting the
type of unsaturated fluorinated hydrocarbon. The GWP value is very low, for example, 4 for HFO-1234yf This is because of the double bond in the molecule that causes it to readily decompose in air, [0026] The unsaturated fluorinated hydrocarbon also has suitable
15 compatibility with refrigerating machine oils. Because it readily
decomposes, however, its poor stability is a problem. [0027] In this embodiment, therefore, mixing the difluoromethane and unsaturated fluorinated hydrocarbon in the proportion specified above compensates for the drawback of each refrigerant and accentuates its
20 advantages for its suitable use as a refrigerant.
[0028] The unsaturated fluorinated hydrocarbon is preferably fluoropropene having 3 to 5 fluorine atoms, and it is preferably one or a mixture of two or more from among 1,2,3,3,3-pentafluoropropene (HFO-1225ye), 1,3,3,3-tetrafluoropropene (HFO-1234ze), 2,3,3,3-
25 tetrafluoropropene (HFO-1234yf), 1,2,3,3-tetrafluoropropene (HFO-
1234ye) and 3,3,3-trifluoropropene (HFO-1243zf). From the

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viewpoint of refrigerant properties, it is preferred to use one or more
selected from among HFO-1225ye, HFO-1234ze and HFO-1234yf
[0029] The total of the difluoromethane and the unsaturated fluorinated
hydrocarbon in the refrigerant is preferably 80 mass% or greater and
5 more preferably 90 mass% or greater.
[0030] For this embodiment, the refrigerant may be one comprising difluoromethane and an unsaturated fluorinated hydrocarbon, and it may fiirther comprise another refrigerant other than the difluoromethane and unsaturated fluorinated hydrocarbon. The refrigerants other than the
10 difluoromethane and unsaturated fluorinated hydrocarbon include HFC
refrigerants, fluorine ether-based refrigerants such as perfluoroethers, dimethyl ether, and natural refrigerants such as ammonia, propane and isobutane. The refrigerant is preferably an azeotropic mixture, but so long as it has the physical properties required for a refrigerant, it does
15 not necessarily need to be an azeotropic mixture.
[0031]
[Refrigerating machine oil]
The refrigeratmg machine oil of this embodiment comprises at least one base oil selected from among polyol esters with a carbon/oxygen molar
20 ratio of 3.2 to 5.8 (hereunder also referred to simply as "polyol ester")
and polyvinyl ethers with a carbon/oxygen molar ratio of 3.2 to 5.8 (hereunder also refen"ed to simply as "polyvinyl ether"). The carbon/oxygen molar ratio can be calculated from the composition, if the chemical structure of the compounds composing the refrigerating
25 machine oil is specified. Even If the chemical structure is not specified,
organic elemental analysis of the refrigerating machine oil allows the

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content of carbon atoms and oxygen atoms to be quantified and specified.
[0032] The polyol ester of this embodiment is an ester synthesized from
a polyhydric alcohol and a carboxylic acid, having a carbon/oxygen
5 molar ratio of 3.2 to 5.8, preferably 3.2 to 5.0 and even more preferably
4.0 to 5.0.
[0033] The carboxylic acid composing the polyol ester is preferably a fatty acid (a monobasic aliphatic carboxylic acid) and especially a saturated fatty acid, preferably with 4 to 9 and especially 5 to 9 carbon
10 atoms. The polyol ester of this embodiment may be a partial ester with
a portion of the hydroxyl groups of the polyhydric alcohol remaining as hydroxyl groups without esterification, a complete ester with all of the hydroxyl groups esterified, or a mixture of the partial ester and the complete ester, but the hydroxyl value is preferably no greater than 10
15 mgKOH/g, more preferably no greater than 5 mgKOH/g and most
preferably no greater than 3 mgKOH/g.
[0034] For the difluoromethane and unsaturated fluorinated hydrocarbon in the refrigerant, when the proportion of the difluoromethane that has poor compatibility with refrigerating machine
20 oils is high, such as when the mass ratio of the difluoromethane/the
unsaturated fluorinated hydrocarbon is 95/5 to 50/50, the proportion of branched fatty acids is preferably 50 to 100 mol%, especially 70 to 100 mol% and more preferably 90 to 100 mol% based on the total carboxylic acids. Specific C5 to C9 branched fatty acids include
25 branched pentanoic acid, branched hexanoic acid, branched heptanoic
acid, branched octanoic acid and branched nonanoic acid. More
10

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specifically, fatty acids branched at the a- and/or p-position are
preferred, with 2-methylbutanoic acid, 2-methylpentanoic acid, 2-
methylhexanoic acid, 2-ethylpentanoic acid, 2-methylheptanoic acid, 2-
ethylhexanoic acid and 3,5,5-trimethylhexanoic acid being especially
5 preferred and 2-ethylhexanoic acid and/or 3,5,5-trimethylhexanoic acid
being most preferred. The carboxylic acids may also include fatty acids other than C5 to C9 branched fatty acids.
[0035] Also, for the difluoromethane and the unsaturated fluorinated hydrocarbon in the refrigerant, when the proportion of the unsaturated
10 fluorinated hydrocarbon is greater than the difluoromethane it is easier
to achieve compatibility with refrigerating machine oils, and therefore the proportion of straight-chain fatty acids among the fatty acids is preferably 50 to 95 mol%, especially 60 to 90 mol% and more preferably 70 to 85 mol%, based on the total carboxylic acids.
15 Specific C5 to C9 straight-chain fatty acids include n-pentanoic acid, n-
hexanoic acid, n-heptanoic acid, n-octanoic acid and n-nonanoic acid. Of these, n-pentanoic acid and/or n-heptanoic acid are most preferred, and especially a mixture of both. The n-pentanoic acid content is preferably at least 30 mol% based on the total carboxylic acids,
20 particularly from the viewpoint of compatibility, while it is preferably
no greater than 50 mol% and especially no greater than 45 mol%, particularly from the viewpoint of hydrolytic stability. The heptanoic acid content is preferably at least 20 mol%, especially at least 25 mol% and more preferably at least 30 mol%, based on the total carboxylic acid,
25 from the viewpoint of lubricity. On the other hand, it is no greater than
50 mol% and preferably no greater than 45 mol% based on the total
11

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carboxylic acids, particularly from the viewpoint of hydrolytic stability.
The carboxylic acids other than straight-chain fatty acids are preferably
C5 to C9 branched fatty acids and especially 2-ethylhexanoic acid
and/or 3,5,5-trimethylhexanoic acid. The content of 3,5,5-
5 trimethylhexanoic acid is preferably 5 mol% or greater and especially
10 mol% or greater based on the total carboxylic acids, particularly from the viewpoint of hydrolytic stability, while it is also preferably no greater than 30 mol% and especially no greater than 25% based on the total carboxylic acids, particularly from the viewpoint of compatibility
10 and lubricity.
[0036] A particularly preferred example of a combination of carboxylic acids is a mixture of n-pentanoic acid, n-heptanoic acid and 3,5,5-trimethylhexanoic acid. The proportion of each component in such an acid mixture is more preferably 30 to 50 mol% of n-pentanoic acid, 20
15 to 50 mol% of n-heptanoic acid and 5 to 30 mol% of 3,5,5-
trimethylhexanoic acid based on the total acid mixture. [0037] The polyhydric alcohol in the polyol ester is preferably a polyhydric alcohol with 2 to 6 hydroxyl groups. The number of carbon atoms of the polyhydric alcohol is preferably 4 to 12 and
20 especially 5 to 10. Hindered alcohols such as neopentyl glycol,
trimethylolethane, trimethylolpropane, trimethylolbutane, di-(trimethylolpropane), tri-(trimethylolpropane), pentaerythritol and di-(pentaerythritol) are preferred. Pentaerythi'itol or an ester mixture of pentaerythritol and di-(pentaerythritol) is most preferred, for particularly
25 excellent compatibility with refrigerants and hydrolytic stability.
[0038] The polyvinyl ether for this embodiment has a carbon/oxygen
12

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molar ratio of 3.2 to 5.8, preferably 4.0 to 5.8 and even more preferably 4.0 to 5.0. If the molar ratio is below this range the hygroscopicity increases, and if it exceeds this range the compatibility is reduced. The weight-average molecular weight of the polyvinyl ether of the invention is preferably 200 to 3000, and especially 500 to 1500. [0039] The polyvinyl ether to be preferably used for this embodiment has a structural unit represented by the following formula (1). [Chemical Formula 2]
R^ R^

C—^C^
I I
R3 0(R'*0)mR^

(1)

1 O 1
10 [In the formula, R , R and R may be the same or different and each
represents hydrogen or a CI to C8 hydrocarbon group, R** represents a CI to CIO divalent hydrocarbon group or C2 to C20 divalent ether bonded oxygen-containing hydrocarbon group, R^ represents a CI to C20 hydrocarbon group, m represents a number such that the average.
15 value of m for the polyvinyl ether is 0 to 10, R' to R^ may be the same
or different for each structural unit, and when m is 2 or greater for one structural unit, the multiple R^'O groups may be the same or different.] [0040] Preferably, at least one of R^ R^ and R^ in fomiula (1) is hydrogen and most preferably all are hydrogen. The value of m in
20 formula (I) is 0 to 10, especially 0 to 5 and more preferably 0. Also,
R^ in formula (1) represents a CI to C20 hydrocarbon group. The hydrocarbon group may be an alkyl, cycloalkyl, phenyl, aryl or arylalkyl group, with alkyl and especially CI to C5 alkyl groups being
13

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especially preferred.
[0041] The polyvinyl ether for this embodiment may be a homopolymer
having the same structural unit represented by formula (1) or a
copolymer composed of two or more of such structural units, but a
5 copolymer has an effect of satisfying the condition of compatibility
while allowing further improvement in lubricity, insulation and hygroscopicity. Selection of the type of monomer serving as the starting material, the type of initiator and the ratio of the copolymer allow the target level to be achieved for performance of the lubricant.
10 Thus, an effect is achieved by which it is possible to flexibly obtain a
lubricant meeting the demands for lubricity and compatibility, that differ depending on the model of compressor in the re&igeration system or air-conditioning system, the material and refrigerating performance of the lubricating sections, and the type of refrigerant. The copolymer
15 may be a block copolymer or random copolymer.
[0042] When the polyvinyl ether of the invention is a copolymer, the copolymer preferably comprises a structural unit (1-1) represented by formula (1) wherein R is a CI to C3 alkyl group, and a structural unit (1-2) represented by formula (1) wherein R^ is a C3 to C20, preferably
20 C3 to CIO and even more preferably C3 to C8 alkyl group. In the
structural unit (1-1), R^ is most preferably an ethyl group, and in the structural unit (1-2), R^ is most preferably an isobutyl group. When the polyvinyl ether of the invention is a copolymer comprising the aforementioned structural units (1-1) and (1-2), the molar ratio of the
25 structural unit (l-l)/the structural unit (1-2) is preferably 5/95 to 95/5,
more preferably 20/80 to 90/10 and even more preferably 70/30 to
14

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90/10. If the molar ratio is outside of this range, the compatibility with refrigerants is inadequate and the hygroscopicity tends to be increased. [0043] The polyvinyl ether of the invention may be composed entirely of a structural unit represented by formula (1), or it may be a copolymer further comprising a structural unit represented by the following formula (2). In this case, the copolymer may be either a block copolymer or a random copolymer. [Chemical Formula 3]
R^ R*

■C ^C-
I I
R7 R^

(2)

10
15

[In the formula, R^ to R^ may be the same or different from each other,
with each representing hydrogen or a CI to C20 hydrocarbon group.]
[0044] Polyvinyl ethers of the invention may be produced by
polymerization of their corresponding vinyl ether-based monomers, and
by copolymerization of corresponding hydrocarbon monomers having
olefmic double bonds and vinyl ether-based monomers. Preferred
vinyl ether-based monomers corresponding to the structural unit
represented by formula (1) are monomers represented by the following
formula (3).
[Chemical Formula 4] R^ R2
(3)

20

R^ 6(R'*0)mR^
[In the formula, R\ R^ R^, R'*, R^ and m each have the same definitions

15

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as R^ R^ R^ R\ R^ and m in formula (1).]
[0045] The polyvinyl ether of the invention preferably has the following
terminal structure.
(A) One end has a structure represented by formula (4) or (5), and the
other end has a structure represented by formula (6) or (7).
[Chemical Formula 5]
HC C (4)
I I
R^i 0(R'*^0)nR^''
[In the formula, R^\ R^^ and R^^ may be the same or different from each other, with each representing hydrogen or a CI to C8 hydrocarbon
10 group, R**^ represents a CI to CIO divalent hydrocarbon group or C2 to
C20 divalent ether bonded oxygen-containing hydrocarbon group, R^^ represents a CI to C20 hydrocarbon group, n represents a number such that the average value of n in the polyvinyl ether is 0 to 10, and when n is 2 or greater the multiple R'^'O groups may be the same or different.]
15 [Chemical Formula 6]
HC C v5)
I I
R81 R91
[In the formula, R^', K^\ R^^ and R^' may be the same or different from
each other, and each represents hydrogen or a CI to C20 hydrocarbon
group.]
20 [Chemical Formula 7]
16

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R^2 R22
C CH (^)
I I
[In the formula, R^^, R^"^ and R^^ may be the same or different from each other, with each representing hydrogen or a CI to C8 hydrocarbon
Art
group, R represents a CI to CIO divalent hydrocarbon group or C2 to
5 C20 divalent ether bonded oxygen-containing hydrocarbon group, R
represents a CI to C20 hydrocarbon group, p represents a number such that the average value of p in the polyvinyl ether is 0 to 10, and when p is 2 or greater the multiple R'^^O groups may be the same or different.] [Chemical Formula 8]
I I (7)
C CH t'J
I I
10 R'2 R^2
[In the formula, R^^, R^^ R^^ and R^^ may be the same or different from
each other, and each represents hydrogen or a CI to C20 hydrocarbon
group.]
[0046] (B) One end has a structure represented by formula (4) or (5),
15 and the other end has a stmcture represented by the following formula
(8).
[Chemical Formula 9] R" R=*2
C C OH W
R23 H
[In the formula, R^^ R^^ and R^^ may be the same or different from each
17

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other, and each represents hydrogen or a CI to C8 hydrocarbon group.]
[0047] Among such polyvinyl ether-based compounds, the following
are particularly preferred as main components of the refrigerating
machine oil for this embodiment.
5 (1) Compounds wherein one end has a structure represented by formula
(4) or (5) and the other end has a structure represented by formula (6) or (7), wherein R\ R^ and R"^ in formula (1) are both hydrogen, m is a number of 0 to 4, R"* is a C2 to C4 divalent hydrocarbon group and R^ is a CI to C20 hydrocarbon group.
10 (2) Compounds having only a structural unit represented by formula (1),
with one end having a structure represented by formula (4) and the other end having a structure represented by formula (6), wherein R , R and R^ in formula (1) are both hydrogen, m is a number of 0 to 4, R'* is a C2 to C4 divalent hydrocarbon group and R^ is a CI to C20 hydrocarbon
15 group.
(3) Compounds wherein one end has a structure represented by formula
(4) or (5) and the other end has a structure represented by formula (8), and wherein R, R and R in formula (1) are both hydrogen, m is a number of 0 to 4, R'* is a C2 to C4 divalent hydrocarbon group and R^ is
20 a CI to C20 hydrocarbon group.
(4) Compounds having only a structural unit represented by formula (1), with one end having a structure represented by formula (5) and the other end having a structure represented by formula (8), wherein R , R and R'' in formula (1) are both hydrogen, m is a number of 0 to 4, R'' is a C2
25 to C4 divalent hydrocarbon group, R^ is a CI to C20 divalent
hydrocarbon group and R^ is a CI to C20 hydrocarbon group.
18

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(5) Compounds of each of (1) to (4) above having a structural unit
wherein R^ in formula (1) is a CI to C3 hydrocarbon group and a
structural unit wherein R^ is a C3 to C20 hydrocarbon group.
[0048] The polyvinyl ether of this embodiment can be produced by
5 radical polymerization, cationic polymerization or radiation
polymerization of the aforementioned monomers. Upon completion of the polymerization reaction, it is subjected to ordinary separation and purification methods as necessary to obtain the desired polyvinyl ether-based compound having a structural unit represented by formula (1).
10 [0049] The polyvinyl ether of this embodiment must have a
carbon/oxygen molar ratio within a prescribed range as explained above, and adjusting the carbon/oxygen molar ratio of the starting monomers allows production of a polymer having the molar ratio within said range. Specifically, if the proportion of monomers with a high carbon/oxygen
15 molar ratio is high, a polymer with a high carbon/oxygen molar ratio is
obtained, and if the proportion of monomers with a low carbon/oxygen molar ratio is high, a polymer with a low carbon/oxygen molar ratio is obtained. By copolymerization of a vinyl ether-based monomer with a hydrocarbon monomer having an olefinic double bond, a polymer is
20 obtained having a higher carbon/oxygen molar ratio than the
carbon/oxygen molar ratio of the vinyl ether-based monomer, but this proportion can be adjusted by the ratio of hydrocarbon monomers with olefmic double bonds that are used, and their numbers of carbon atoms. [0050] In the production steps for a polyvinyl ether having a structural
25 unit represented by formula (1), secondary reactions sometimes occur
forming' unsaturated groups such as allyl groups in the molecule.
19

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When unsaturated groups are formed in the polyvinyl ether molecule,
the thermostability of the polyvinyl ether itself is lowered and polymers
are generated causing formation of sludge, or the resistance to oxidation
(antioxidation) tends to be reduced, resulting in production of peroxides.
5 Particularly when peroxides are produced, they decompose and generate
carbonyl group-containing compounds, and the carbonyl group-containing compounds are a source of sludge that can cause capillary cloggmg. Consequently, the polyvinyl ether of this embodiment preferably has a low degree of unsaturation due to unsaturated groups
10 and the like, and more specifically, a degree of unsaturation of no
greater than 0.04 meq/g, more preferably no greater than 0.03 meq/g and even more preferably no greater than 0.02 meq/g. The peroxide number is preferably no greater than 10.0 meq/kg, more preferably no greater than 5.0 meq/kg and even more preferably no greater than 1.0
15 meq/kg. The carbonyl value is preferably no greater than 100 ppm by
weight, more preferably no greater than 50 ppm by weight, and most preferably no greater than 20 ppm by weight.
[0051] The degi^ee of unsaturation, peroxide number and carbonyl value according to the invention are the values measured according to the
20 Standard Methods for the Analysis of Fats, Oils and Related Materials,
established by the Japan Oil Chemists' Society. Specifically, the degree of unsaturation is the value (meq/g) obtained by reacting Wijs solution (ICl-acetic acid solution) with a sample, allowing the reaction mixture to stand in a dark area, subsequently reducing the excess ICl to
25 iodine, titrating the iodine portion with sodium thiosulfate and
calculating the iodine value, and then converting the iodine value to
20

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vinyl equivalents; the peroxide number is the value (meq/kg) obtained
by adding potassium iodide to a sample, titrating the produced free
iodine with sodium thiosulfate, and converting the free iodine to
milliequivalents with respect to 1 kg of sample; and the carbonyl value
5 is the value (ppm by weight) obtained by allowing 2,4-
dinitrophenylhydrazine to act on a sample to produce colorable quinoid ion, measuring the absorbance of the sample at 480 nm, and converting it to carbonyl content based on a predetermined calibration curve with cinnamaldehyde as the standard substance. There are no particular
10 restrictiopis on the hydroxyl value but it is preferably 10 mgKOH/g,
more preferably 5 mgKOH/g and even more preferably 3 mgKOH/g. [0052] The content of polyol ester or polyvinyl ether in the refrigerating machine oil is preferably a total of 80 mass% or greater and especially 90 mass% or greater, for excellent lubricity, compatibility,
15 thermal/chemical stability and electrical insulating properties. Base
oils other than polyol esters and polyvinyl ethers that may be present in the refrigerating machine oil include hydrocarbon-based oils including mineral oils, olefin polymers, naphthalene compounds, alkylbenzenes and the like, and oxygen-containing synthetic oils such as polyglycols,
20 ketones, polyphenyl ethers, silicones, polysiloxanes and perfluoroethers.
Polyglycols and ketones are preferred as base oils to be used in combination with polyol esters and polyvinyl ethers. [0053] The kinematic viscosity of the refrigerating machine oil of this embodiment is not particularly restricted, but the 40°C kinematic
25 viscosity is preferably 3 to 1000 mm /s, more preferably 4 to 500 mm /s
and most preferably 5 to 400 mm /s. The 100°C kinematic viscosity is
2i

FP12-0546-00
preferably 1 to 100 mm /s and more preferably 2 to 50 mm /s. For the
purpose of the invention, the kinematic viscosity is the kinematic
viscosity measured according to JIS K 2283, "Crude Oil and Petroleum
Products - Kinematic Viscosity Test Method and Viscosity Index
5 Calculation Method".
[0054] The volume resistivity of the refrigerating machine oil of this embodiment is also not particularly restricted, but is preferably 1.0 x
11 t '^
10 Q.cm or greater, more preferably 1.0 x 10 ^-cm or gi'eater and most preferably 1.0 x lo'"^ H-cm or greater. High electrical insulating
10 properties are usually required for use in sealed refrigerating machines.
Accordmg to the invention, the volume resistivity is the value measured according to JIS C2101, "Electrical Insulation Oil Test Method", at 25°C. [0055] The moisture content of the refrigerating machme oil of this
15 embodiment is not particularly restricted but is preferably no greater
than 200 ppm, more preferably no greater than 100 ppm and most preferably no greater than 50 ppm based on the total mass of the refrigerating machine oil. A lower moisture content is desired from the viewpoint of effect on the thermal/chemical stability and electrical
20 insulating properties of the refrigerating machine oil, especially for use
in a closed refrigerating machine.
[0056] The acid value of the refrigerating machine oil of this embodiment is also not particularly restricted, but in order to prevent corrosion of metals used in the refrigerating machine or pipings, and in
25 order to prevent decomposition of the ester in the refrigerating machine
oil of this embodiment, it is preferably no greater than 0.1 mgKOH/g
22

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and more preferably no greater than 0.05 mgKOH/g. According to the
invention, the acid value is the value measured based on JIS K2501,
"Petroleum Products And Lubricant Oils - Neutralization Value Test
Method".
5 [0057] The ash content of the refi*igerating machme oil of this
embodiment is not particularly restricted, but in order to increase the thermal/chemical stability of the refrigerating machine oil of this embodiment and inhibit generation of sludge, it is preferably no greater than 100 ppm by mass and more preferably no greater than 50 ppm by
10 mass. According to the invention, the ash content is the value
measured based on JIS K2272, "Crude Oil/Petroleum Product Ash Content and Sulfated Ash Content Test Method".
[0058] If necessary, the reMgerating machine oil of this embodiment may be used in a form that further contains various additives. In the
15 explanation which follows, the additive contents are given based on the
total weight of the refrigerating machine oil composition, and the content of these components in the refrigerator fluid composition is preferably no greater than 5 mass% and especially no greater than 2 mass%, based on the total amount of the refrigerating machine oil
20 composition.
[0059] In order to further enhance the abrasion resistance and load resistance of the working fluid composition for a refrigerating machine and the refrigerating machine oil of this embodiment, the working fluid composition for a refrigerating machine and the refrigerating machine
25 oil may be added one or more phosphorus compounds selected from the
group consisting of phosphoric acid estei*s, acidic phosphoric acid esters,
23

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thiophosphoric acid esters, acidic phosphoric acid ester amine salts,
chlorinated phosphoric acid esters and phosphorous acid esters. These
phosphorus compounds are esters of phosphoric acid or phosphorous
acid with alkanols or polyether alcohols, or derivatives thereof.
5 [0060] In order to further improve the thermal/chemical stability of the
working fluid composition for a refrigerating machine and refrigerating machine oil according to this embodiment, the working fluid composition for a refrigerating machine and the refrigerating machine oil may contain one or more epoxy compounds selected from among
10 phenylglycidyl ether-type epoxy compounds, alkylglycidyl ether-type
epoxy compounds, glycidyl ester-type epoxy compounds, allyloxirane compounds, alkyloxirane compounds, allcyclic epoxy compounds, epoxidated fatty acid monoesters and epoxidated vegetable oils. [0061] The working fluid composition for a refrigerating machine and
15 refrigerating machine oil of this embodiment may contain
conventionally known additives for refrigerating machine oils as necessary, in order to further increase their performance. Examples of such additives include phenol-based antioxidants such as di-tert-butyl-p-cresol and bisphenol A, amine-based antioxidants such as phenyl-a-
20 naphthylamine and N,N-di(2-naphthyl)-p-phenyIenediamine, anti-wear
agents such as zinc dithiophosphate, extreme-pressure agents such as chlorinated paraffins and sulfur compounds, oil agents such as fatty acids, silicone-based and other types of antifoaming agents, metal inactivating agents such as benzotriazoles, viscosity index improvers,
25 pour point depressants, detergent dispersants and the like. Such
additives may be used alone or in combinations of two or more.
24

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[0062] The working fluid composition for a refrigerating machine and
refrigerating machine oil of this embodiment is preferably used in a
room air conditioner or refrigerator with a reciprocating or rotating
closed compressor, or in an open or closed automobile air conditioner.
5 The working fluid composition for a refrigerating machine and
refrigerating machine oil according to this embodiment may also be suitably used in cooling devices of dehumidifiers, hot water suppliers, freezers, freezing/refrigerating warehouses, automatic vending machines, showcases, chemical plants and the like. The working fluid
10 composition for a refrigerating machine and refrigerating machine oil
according to this embodiment may also be suitably used in devices with centrifiigal compressors. Examples [0063] The present invention is now explained in greater detail based
15 on examples and comparative examples, with the understanding that
these examples are in no way limitative on the invention. [0064]
[Refrigerating machine oil] First, refrigerating machine oils 1 to 8 were prepared using the
20 following base oils 1 to 8.
[Base oil]
Base oil 1: Ester of fatty acid mixture of 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid (mixing ratio (molar ratio): 50/50) and pentaerythritol (carbon/oxygen molar ratio: 4.8).
25 Base oil 2: Ester of fatty acid mixture of n-pentanoic acid, n-heptanoic
acid and 3,5,5-trimethylhexanoic acid (mixing ratio (molar ratio):
25

FP12-0546-00
40/40/20) and pentaerythritol (carbon/oxygen molar ratio: 3.3).
Base oil 3: Ester of 2-ethylhexanoic acid and pentaerythritol
(carbon/oxygen molar ratio: 4.6).
Base oil 4: Ester of fatty acid mixture of n-pentanoic acid and 3,5,5-
5 trimethylhexanoic acid (mixing ratio (molar ratio): 90/10) and
pentaerythritol (carbon/oxygen molar ratio: 3.3).
Base oil 5: Ester of fatty acid mixture of n~pentanoic acid and 3,5,5-trimethylhexanoic acid (mixing ratio (molar ratio): 25/75) and
pentaerythritol (carbon/oxygen molar ratio: 4.6).
10 Base oil 6: Ester of 3,5,5-trimethylhexanoic acid and trimethylolpropane
(carbon/oxygen molar ratio: 5.5).
Base oil 7: Ester of 3,5,5-trimethylhexanoic acid and pentaerythritol
(carbon/oxygen molar ratio: 5.1).
Base oil 8: Copolymer of ethylvinyl ether and isobutylvinyl ether
15 (ethylvinyl ether/isobutylvinyl ether ^ 7/1 (molar ratio), weight-average
molecular weight: 910, carbon/oxygen molar ratio: 4.3). One terminal
structure is represented by formula (4), with R^\ R^^ and R^^
representing hydrogen and R^^ representing an ethyl group, and n is 0.
The other terminal structure is represented by formula (7), with R , R ,
20 R^^ and R^^ representing hydrogen.
[0065] The properties of the obtained refrigerating machine oils 1 to 8
are shown in Tables 1 and 2.
[0066]
[Table 1] 25
26

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Refrigerating
machine oil 1 Refrigerating
machine oil 2 Re&igerating machine oil 3 Refrigerating machine oil 4
BaseoH Base oil I Base oil 2 Base oil 3 Base oil 4
Carbon/oxygen molar ratio 4.8 3.3 4.6 3.3
40°C Kinematic viM^sily fmm'/s] 68.3 28.5 45.1 18.2
IWC Kinematic \'iscosity [mmVs] 8.31 5.50 6.30 3.90
Volume resistivity [n-cm] 5 >: 10'^ 6x10" 5 X iO" 4 X 10"
Moisture content Ippm] 45 56 53 58
Acid value [mgKOH/g] 0.01 0.01 0.01 0.01
Hydroxyl value fmgKOIi/g] 2.1 1.8 1.7 2.0
Ash fmass ppml 0.1 0.1 0.1 0.1
[0067] [Table 2]

Refrigerating machine oil 5 Refrigerating machine oil 6 Refrigerating machine oil 7 Refrigerating machine oil 8
Base oil Base oil 5 Base oil 6 Base oil 7 Base oil 8
Cartxjn/oxygen molar ratio 4.6 5.5 5.1 4.3
40''C Kinematic viscosi^ fmmVs] 67.5 51.5 110.8 66.4
100°C Kinematic viscosity [mmVs] 8.20 7.10 11.0 8.15
Volume resistivity [O-cm] 6 X 10" 5 X 10" 7 X 10" 9 X 10'^
Moisture content fppm] 61 47 55 87
Acid ^'alue [mgKOH/gl 0.01 0.01 0.01 0.01
Hydroxyl value fmgKOH/gl 1.6 2.2 1.8 1.5
Ash [mass ppm] O.I 0.1 0.1 O.i
[0068]
[Examples 1 to 17, Comparative Examples 1 to 6]
For Examples 1 to 17 and Comparative Examples 1 to 6, the following
10 evaluation test was carried out with working fluid compositions for a
re&igerating machine that were combinations of refrigerating machine oils 1 to 8 above and the refrigerants listed in Tables 3 to 6. As explained below, the mass ratio of the refrigerant and refrigerating machine oil in the working fluid composition for a refrigerating
27

FP12-0546-00
machine was changed for each test. [0069]
[Compatibility evaluation]
The refrigerating machine oil was added at 2 g with respect to 18 g of
5 each of the different refrigerants listed in Tables 3 to 6, according to JIS-
K-2211, "Refrigerating machine oils", "Refrigerant compatibility test method", to produce working fluid compositions for a refrigerating machine. Next, each composition was observed to determine whether or not the refrigerant and refrigerating machine oil had mutually
10 dissolved at 0°C. The obtained results are shown in Tables 3 to 6. In
Tables 3 to 6, "compatible" means that the refrigerant and refrigerating machine oil had mutually dissolved, "separated" means that the refrigerant and refrigerating machine oil had separated into two layers, and "somewhat turbid" means that they had mutually dissolved but
15 turbidity was visible with the naked eye.
[0070]
[Thermal/chemical stability evaluation]
Following the procedure of JIS-K-2211, a catalyst (fron, copper or aluminum wire) was placed in a glass tube, and 1 g of refrigerating
20 machine oil (initial color hue: L0.5) adjusted to a moisture content of no
greater than 100 ppm and 1 g of a refrigerant as shown in Tables 3 to 6 were frirther added to prepare a working fluid composition for a refrigerating machine. The glass tube was sealed and then heated to 150°C and stored for 1 week. Next, the color tone of the refrigerating
25 machine oil and the change in catalyst color were evaluated. The color
tone was evaluated according to ASTM D156. The change in catalyst
28

FP12-0546-00
color was determined by visual observation of the outer appearance, and evaluation was made as "no change", "no gloss" or "blackening". The obtained results are shown in Tables 3 to 6. [0071] [Table 3]
29

Example 1 Example 2 Example 3 Example 4 Comp, Ex. 1
Refrigerating machine oil Refrigerating machine oil 1 Refrigerating machine oil 1 Refrigerating machine oil 1 Refrigerating machine oil 1 Refrigerating machine oil 1
Refrigerant R32 rmass%l 75 50 25 90 100

HFO-1234yfrmass%l 25 50 75 10 -

R410Armass%l - - - - -

GWP 490 330 170 590 650
Compatibility Compatible Compatible Compatible Somewhat turbid Separated
Thermal/chemical stability Color tone (ASTM D156) L0.5 L0.5 L0.5 L0.5 L0.5

Catalyst outer appearance Cu No ehange No change No change No change No change

Catalyst outer appearance Fe No change No change No change No change No change

Catalyst outer appearance Al No chanec No change No change No change No change
[0072] [Table 4]
30

Example 5 Example 6 Example 7 Example 8 Comp. Ex. 4
Refrigerating machine oii Refrigerating machine oil 2 Refrigerating machine oi! 2 Refrigerating machine oil 2 Refrigerating machine oil 2 Refrigerating machine oil 2
Refrigerant R32 rmass%l 75 50 25 90 100

HFO-I234vfrmass%l 25 50 75 10 .

R4!0Arm3SS%l - - - . -

GWP 490 330 170 590 650
Compatibility Compatible Compatible Compatible Somewhat turbid Separated
Thermal/chemical stability Color tone (ASTM Dl 56) L0.5 L0.5 L0.5 LO.S LO.S

Catalyst outer appearance Cu No change No change No change No change No change

Catalyst outer appearance Fe No change No change No change No change No change

Catalyst outer appearance Al No change No change No change No change No change
[0073] [Table 5]
31

Example 9 Example 10 Example 11 Example 12 Exampl
Refrigerating machine oil Refrigerating machine oil 3 Refrigerating machine oil 4 Refrigerating machine oil 5 Refrigerating machine oil 5 Refrige machin
Refrigerant R32 rmass%l 75 50 25 90 75

HFO-I234vfrmass%l 25 50 75 10 25

R410Armass%l - - - . -

GWP 490 330 170 590 490
Compatibility Compatible Compatible Compatible Somewhat turbid Compat
Thcnnal/chcmical stability Color tone fASTM DI56) L0.5 L0.5 L0.5 L0,5 L0.5

Catalyst outer appearance Cu No change No change No change No change No chan

Catalyst outer appearance Fe No change No change No change No change No chan

Catalyst outer appearance Al No change No change No change No change No chan
[0074] [Table 6]
32

Example 15 Example 16 Example 17 Comp. Ex. 7 Comp. Ex
Refrigerating machine oil Refrigerating machine oil S Refrigerating machine oil 8 Refrigerating machine oil 8 Refrigerating machine oil 8 Refrigerat machine o
Refrigerant R32 rmass%l 75 50 25 100 -

HFO-]234yfrmass%l 25 50 75 . 100

R410Arniass%l - . - . -

GWP 490 330' 170 650 4
Compatibility Compatible Compatible Compatible Separated Compatib
Thermal/chemical stability Color tone (ASTM D156) L0.5 L0.5 L0.5 L0.5 L0.5

Catalyst outer appearance Cu No change No change No change No change No gloss

Catalyst outer appearance Fc No change No change No change No change No gloss

Catalyst outer appearance Al No change No change No change No change No chang
33

FP12-0546-00
Industrial Applicability
[0075] The present invention is useful as a working fluid composition and a refrigerating machine oil to be used in a refrigeration system employing a refrigerant comprising difluoromethane and an unsaturated fluorinated hydrocarbon.
34

FP12-0546-00

CLAIMS
1. A working fluid composition for a refrigerating machine comprising:
a refrigerant comprising difluoromethane and an unsaturated
5 fluorinated hydrocarbon wherein a mass ratio of the
difluoromethane/the unsaturated fluorinated is 95/5 to 10/90, and
a refrigerating machine oil comprising at least one base oil
selected from among polyol esters with a carbon/oxygen molar ratio of
3.2 to 5.8 and polyvinyl ethers with a carbon/oxygen molar ratio of 3.2
10 to 5.8.
2. A working fluid composition for a refrigerating machine according to
claim I, wherein the total of the difluoromethane and the unsaturated
fluorinated hydrocarbon in the refrigerant is 80 mass% or greater.
3. A working fluid composition for a refrigerating machine according to
15 claim 1 or 2, wherein the mass ratio of the refrigerant/the refrigerating
machine oil is 90/10 to 30/70.
4. A working fluid composition for a refrigerating machine according to
any one of claims 1 to 3, wherein the mass ratio of the
difluoromethane/the unsaturated fluorinated hydrocarbon is 90/10 to
20 50/50.
5. A working fluid composition for a refrigerating machine according to
any one of claims 1 to 4, wherein the unsaturated fluorinated
hydrocarbon is fluoropropene.
6. A working fluid composition for a refrigerating machine according to
25 any one of claims 1 to 5, wherein the base oil is a polyol ester with a
carbon/oxygen molar ratio of 3.2 to 5.8, and the polyol ester is an ester
35

FP12-0546-00

synthesized from a C4 to C9 fatty acid and a C4 to C12 polyhydric alcohol.
7. A working fluid composition for a refrigerating machine according to any one of claims 1 to 5, wherein the base oil is a polyvinyl ether with a carbon/oxygen molar ratio of 3.2 to 5.8, and the polyvinyl ether is a polyvinyl ether having a structural unit represented by the following formula (1). [Chemical Formula 1]
(1)
I I
■c—c
R3 0(R'*0)n,RS

1 O Q
10 [In the formula,. R, R and R may be the same or different and each
represents hydrogen or a CI to C8 hydrocarbon group, R'* represents a CI to CIO divalent hydrocarbon group or C2 to C20 divalent ether bonded oxygen-containing hydrocarbon group, R^ represents a CI to C20 hydrocarbon group, m represents a number such that the average
15 value of m for the polyvinyl ether is 0 to 10, R^ to R^ may be the same
or different for each structural unit, and when m is 2 or greater for one structural unit, the multiple R'^O groups may be the same or different.] 8. A refrigerating machine oil, comprising at least one base oil selected from among polyol esters with a carbon/oxygen molar ratio of 3.2 to 5.8
20 and polyvinyl ethers with a carbon/oxygen molar ratio of 3.2 to 5.8, and
the refrigeratmg machine oil being used together with a refrigerant comprising difluoromethane and an unsaturated fluorinated hydrocarbon wherein a mass ratio of the difluoromethane/the
36

FP12-0546-00
unsaturated fluorinated hydrocarbon is 95/5 to 10/90.
Dated this 25.04.2014
[RANJNA MEHTA-DUTT]
OF REMFRY & SAGAR ATTORNEY FOR THE APPLICANT[S]
37