DESCRIPTION
Title of Invention
REFRIGERATING MACHINE OIL AND WORKING FLUID
COMPOSITION FOR REFRIGERATING MACHINES
5 Technical Field
[0001] The present invention relates to a refrigerating machine oil and a
working fluid composition for refrigerating machines, and specifically it
relates to a refrigerating machine oil that is usefiil when used in
combination with difluoromethane refrigerants (HFC-32), unsaturated
10 fluorinated hydrocarbons and the like, as well as a working fluid
composition for refrigerating machines that employs the refiigerating
machine oil.
Background Art
[0002] In light of the problem of ozone layer depletion that has become
15 a focus of attention in recent years, the restrictions on CFCs
(chlorofluorocarbons) and HCFCs (hydrochlorofluorocarbons) that are
used as refiigerants in conventional refrigerating machines have become
more stringent, and HFCs (hydrofluorocarbons) are coming into use as
substitute refrigerants.
20 [0003] Mineral oils or hydrocarbon oils such as alkylbenzenes have
been preferred for use as refrigerating machine oils when CFCs or |
HCFCs are used as refrigerants, but since changing the refrigerant can
cause the refrigerating machine oil used with it to exhibit unpredictable
behavior in terms of its compatibility with the refrigerant, its lubricity,
25 its dissolved viscosity with the refrigerant and its thermal and chemical
stability, it has been necessary to develop different refrigerating
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machine oils for different refrigerants. Examples of refrigerating
machine oils that have been developed for HFC refrigerants include
polyalkylene glycols (see Patent document 1), esters (see Patent j
document 2), carbonic acid esters (see Patent document 3) and 1
5 polyvinyl ethers (see Patent document 4). Of the refrigerating machine
oils mentioned above, esters are most widely used for refrigerators and
air conditioning units.
[0004] Among HFC refrigerants, HFC-134a, R407C and R410A are
routinely used as refrigerants for automobile air conditioners,
10 refrigerators and room air conditioners. However, while these HFC
refrigerants have ozone depletion potentials (ODP) of zero, their high
global warming potentials (GWP) have led to their gradual restriction.
It has therefore become an urgent issue to develop refrigerants as
substitutes for such HFCs.
15 [0005] In light of this background it has been proposed to use, as
substitute refrigerants for HFCs, fluoropropene refrigerants which have
very low ODP and GWP, are noncombustible and are comparable or
superior to HFCs in terms of their thermodynamic properties, as a
measure of refrigerant performance. There has also been proposed the
20 use of refrigerant mixtures of fluoropropene with saturated
hydrofluorocarbons, C3-5 saturated hydrocarbons, dimethyl ether,
carbon dioxide, bis(trifluoromethyl)sulfide or trifluoroiodomethane (see
Patent document 5). In addition, difluoromethane refrigerants (HFC-
32) are attracting attention as HFC refrigerants with relatively low
25 global warming potential and high refrigerating efficiency.
[0006] Incidentally, one of the performance aspects required for a
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refrigerating machine oil is compatibility with refrigerants used in I
combination. Advances are therefore proceeding in the development j
of refrigerating machine oils suited for difluoromethane refrigerants or I
unsaturated fluorinated hydrocarbon refrigerants, when such refrigerants
5 are to be used.
[0007] For example, a refrigerating machine oil serving to lubricate a
refrigerant compressor generally must have compatibility with
refrigerants in order for the refrigerating machine oil to be circulated in
the cycle together with the refrigerant. However, when refrigerating
10 machine oils that are conventionally employed as HFC refrigerants are
used with difluoromethane refrigerants, the compatibility between the
refrigerant and refrigerating machine oil is not sufficient, and the
refrigerating machine oil ejected from the refrigerant compressor tends
to pool in the cycle, resulting in a reduced amount of refrigerating
15 machine oil in the refrigerant compressor and thus poor lubrication, and
blocking of the expansion mechanism including capillaries.
Refrigerating machine oils for difluoromethane refrigerants are being
developed with the goal of avoiding this phenomenon, and for example,
ester-based refrigerating machine oils have been proposed, including the
20 refrigerating machine oils for difluoromethane refrigerants disclosed in
Patent documents 6 to 12.
Citation List
Patent Literature
[0008] [Patent document 1] Japanese Unexamined Patent Application
25 Publication HEI No. 02-242888
[Patent document 2] Japanese Unexamined Patent Application
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Publication HEX No. 03-200895
[Patent document 3] Japanese Unexamined Patent Application
Publication HEI No. 03-217495
[Patent document 4] Japanese Unexamined Patent Application
5 Publication HEI No. 06-128578
[Patent document 5] International Patent Publication No.
WO2006/094303
[Patent document 6] Japanese Unexamined Patent Application
Publication HEI No. 6-17073
10 [Patent document 7] Japanese Unexamined Patent Application
Publication HEI No. 10-298572
[Patent document 8] Japanese Unexamined Patent Application
Publication No. 2002-060771
[Patent document 9] Japanese Unexamined Patent Application
15 Publication No. 2002-105471
[Patent document 10] Japanese Unexamined Patent Application
Publication No. 2002-129177
[Patent document 11] Japanese Unexamined Patent Application
Publication No. 2002-129178
20 [Patent document 12] Japanese Unexamined Patent Application
Publication No. 2002-129179
Summary of Invention
Technical Problem
[0009] Even conventional ester-based refrigerating machine oils,
25 however, cannot always exhibit adequate performance when used in {
combination with difluoromethane refrigerants and unsaturated !
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fluorinated hydrocarbons. When conventional ester-based
refrigerating machine oils are used in combination with difluoromethane
refrigerants, in particular, it is extremely difficult to both achieve
compatibility with the difluoromethane refrigerants while ensuring the
5 viscosity necessary as a refrigerating machine oil. Among
conventional ester-based refrigerating machine oils, for example, those
that exhibit satisfactory compatibility with difluoromethane refrigerants
tend to have unsatisfactory lubricity in the presence of difluoromethane
refrigerants.
10 [0010] The present invention has been accomplished in light of the
aforementioned problems of the prior art, and its object is to provide a
refrigerating machine oil that allows high levels to be achieved for
refrigerant compatibility, lubricity and low-temperature flow properties
when it is used together with difluoromethane refrigerants, unsaturated
15 fluorinated hydrocarbons and the like, as well as a working fluid
composition for a refrigerating machine using the same.
Solution to Problem
[0011] In order to solve the problems described above, the invention
provides a refrigerating machine oil comprising an ester of a polyhydric
20 alcohol and a fatty acid, wherein the molar ratio of C4-C6 fatty acid and
C7-C9 branched fatty acid in the fatty acid is between 15:85 and 90:10,
the C4-C6 fatty acid includes 2-methylpropanoic acid, and the ratio of
the total C4-C6 fatty acid and C7-C9 branched fatty acid in the total fatty
acid composing the ester is at least 20 mol%.
25 [0012] In the refrigerating machine oil of the invention, the ratio of 2-
methylpropanoic acid in the C4-C6 fatty acid is preferably at least 20
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mol%.
[0013] Also, in the refrigerating machine oil of the invention, the C4-C6
fatty acid preferably is 2-methylpropanoic acid.
[0014] Also preferably, the polyhydric alcohol in the refrigerating
5 machine oil of the invention is pentaerythritol and the 40°C kinematic
viscosity of the refrigerating machine oil is 20 to 80 mm /s.
[0015] Even more preferably, the C7-C9 branched fatty acid in the
refrigerating machine oil of the invention is 3,5,5-trimethylhexanoic
acid.
10 [0016] The invention fiirther provides a working fluid composition for a
refrigerating machine that comprises the refrigerating machine oil of the
invention and a difluoromethane refrigerant.
[0017] The invention still fijrther provides a working fluid composition
for a refrigerating machine that comprises the refiigerating machine oil
15 of the invention and an unsaturated fluorinated hydrocarbon refrigerant.
[0018] The invention still fiirther provides a working fluid composition
for a refrigerating machine that comprises the refrigerating machine oil
of the invention, a difluoromethane refiigerant and an unsaturated
fluorinated hydrocarbon refrigerant. The mass ratio of the
20 difluoromethane refrigerant and unsaturated fluorinated hydrocarbon
refrigerant in this case is between 95:5 and 50:50.
Advantageous Effects of Invention
[0019] According to the invention there is provided a refrigerating
machine oil that allows high levels to be achieved for refrigerant
25 compatibility, lubricity and low-temperature flow properties when it is
used together with difluoromethane refiigerants, unsaturated fluorinated
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hydrocarbons and the like, as well as a working fluid composition for a
refrigerating machine using the same.
Description of Embodiments
[0020] Preferred embodiments of the invention will now be described
5 in detail.
[0021] The refrigerating machine oil of this embodiment is a
refrigerating machine oil comprising an ester of a polyhydric alcohol
and a fatty acid, which is an ester wherein the molar ratio of C4-C6 fatty
acid and C7-C9 branched fatty acid in the fatty acid is between 15:85 and
10 90:10, the C4-C6 fatty acid includes 2-methylpropanoic acid, and the
ratio of the total of C4-C6 fatty acid and C7-C9 branched fatty acid in the
total fatty acid composing the ester is at least 20 mol% (hereunder
referred to as "polyhydric alcohol fatty acid ester (A)").
[0022] The polyhydric alcohol fatty acid ester (A) includes complete
15 esters wherein the all of the hydroxyl groups of the polyhydric alcohol
are esterified, partial esters wherein some of the hydroxyl groups of the
polyhydric alcohol remain without being esterified, and mixtures of
complete esters and partial esters, but the hydroxyl value of the
polyhydric alcohol fatty acid ester (A) is preferably no greater than 10
I
20 mgKOH/g, more preferably no greater than 5 mgKOH/g and most preferably no greater than 3 mgKOH/g.
[0023] Of the fatty acids composing the polyhydric alcohol fatty acid
ester (A), the molar ratio of C4-C6 fatty acid and branched C7-C9 fatty j
acid is 15:85 to 90:10, preferably 15:85 to 85:15, more preferably 20:80 |
25 to 80:20, even more preferably 25:75 to 75:25 and most preferably j
30:70 to 70:30. The ratio of the total of C4-C6 fatty acid and branched
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C7-C9 fatty acid with respect to the total fatty acids composing the
polyhydric alcohol fatty acid ester (A) is at least 20 mol%. If this
condition for the fatty acid composition is not satisfied, it will be
difficult to achieve high levels for both adequate compatibility with
5 difluoromethane refrigerants and the viscosity necessary as a
refrigerating machine oil. The ratio of fatty acids, for the purpose of
the invention, is the value based on the total fatty acids composing the
polyhydric alcohol fatty acid ester in the refrigerating machine oil.
[0024] Specific examples of C4-C6 fatty acid include butanoic acid, 2-
10 methylpropanoic acid, pentanoic acid, 2-methylbutanoic acid, 3-
methylbutanoic acid, 2,2-dimethylpropanoic acid, 2-methylpentanoic
acid, 3-methylpentanoic acid, 4-methylpentanoic acid, 2,2-
dimethylbutanoic acid, 2,3-dimethylbutanoic acid, 3,3-dimethylbutanoic
acid and hexanoic acid. Acids with branching in the alkyl backbone,
15 such as 2-methylpropanoic acid, are preferred.
[0025] Specific examples of branched C7-C9 fatty acid include 2-
methylhexanoic acid, 3-methylhexanoic acid, 4-methylhexanoic acid, 5-
methylhexanoic acid, 2,2-dimethylpentanoic acid, 2,3-
dimethylpentanoic acid, 2,4-dimethylpentanoic acid, 3,3-
20 dimethylpentanoic acid, 3,4-dimethylpentanoic acid, 4,4-
dimethylpentanoic acid, 2-ethylpentanoic acid, 3-ethylpentanoic acid,
1,1,2-trimethylbutanoic acid, 1,2,2-trimethylbutanoic acid, 1-ethyl-1- j
methylbutanoic acid, l-ethyl-2-methylbutanoic acid, octanoic acid, 2- !
ethylhexanoic acid, 3-ethylhexanoic acid, 3,5-dimethylhexanoic acid,
25 2,4-dimethylhexanoic acid, 3,4-dimethylhexanoic acid, 4,5-
dimethylhexanoic acid, 2,2-dimethylhexanoic acid, 2-methylheptanoic
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acid, 3-methylheptanoic acid, 4-methylheptanoic acid, 5-
methylheptanoic acid, 6-methylheptanoic acid, 2-propylpentanoic acid,
nonanoic acid, 2,2-dimethylheptanoic acid, 2-methyloctanoic acid, 2-
ethylheptanoic acid, 3-methyloctanoic acid, 3,5,5-trimethylhexanoic
5 acid, 2-ethyl-2,3,3-trimethylbutyric acid, 2,2,4,4-tetrainethylpentanoic
acid, 2,2,3,3-tetramethylpentanoic acid, 2,2,3,4-tetrainethylpentanoic
acid and 2,2-diisopropylpropanoic acid.
[0026] The polyhydric alcohol fatty acid ester (A) has a molar ratio of
C4-C6 fatty acid and branched C7-C9 fatty acid of 15:85 to 90:10, and it
10 may include fatty acids other than C4-C6 fatty acid and branched C7-C9
fatty acid as constituent acid components, so long as the C4-C6 fatty acid
include 2-methylpropanoic acid.
[0027] Specific fatty acids other than C4-C6 fatty acid and branched C7-
C9 fatty acid include C2-C3 fatty acid such as acetic acid and propionic
15 acid; C7-C9 straight-chain fatty acid such as heptanoic acid, octanoic
acid and nonanoic acid; and C10-C20 fatty acid such as decanoic acid,
undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid,
pentadecanoic acid, hexadecanoic acid, heptadecanoic acid,
octadecanoic acid, nonadecanoic acid, eicosanoic acid and oleic acid.
20 [0028] When a C4-C6 fatty acid and a branched C7-C9 fatty acid are to
be used in combination with a fatty acid other than such fatty acids, the
ratio of the total of C4-C6 fatty acid and C7-C9 branched fatty acid with
respect to the total fatty acids composing the polyhydric alcohol fatty
acid ester (A) must be at least 20 mol%, but it is preferably at least 25
25 mol% and more preferably at least 30 mol%. If this ratio is at least 20
mol%, the compatibility with difluoromethane refrigerants will be
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sufficient.
[0029] A polyhydric alcohol fatty acid ester (A) wherein the acid
components are 2-methylpropanoic acid and 3,5,5-trimethylhexanoic
acid is particularly preferred from the viewpoint of both ensuring the
5 necessary viscosity and obtaining compatibility with difluoromethane
refrigerants.
[0030] The polyhydric alcohol fatty acid ester of this embodiment may
be a mixture of 2 or more different esters with different molecular
structures, in which case the individual molecules do not necessarily
10 have to satisfy the aforementioned conditions, and it is sufficient if the
conditions are satisfied comprehensively by the fatty acids composing
the pentaerythritol fatty acid ester in the refrigerating machine oil.
[0031] As mentioned above, the polyhydric alcohol fatty acid ester (A)
comprises a C4-C6 fatty acid and a branched C7-C9 fatty acid as essential
15 acid components of the ester, and if necessary may comprise other fatty
acids as constituent components. That is, the polyhydric alcohol fatty
acid ester (A) may comprise only 2 different fatty acids as constituent
acid components, or it may have 3 or more different fatty acids with
different structures as constituent acid components, but the constituent
20 acidcomponentsofthepolyhydricalcoholfatty acid ester are preferably
only fatty acids in which the carbon atom adjacent to the carbonyl
carbon (the a-position carbon atom) is not a quaternary carbon. When
the fatty acids composing the polyhydric alcohol fatty acid ester include
a fatty acid wherein the a-position carbon atom is a quaternary carbon,
25 the lubricity in the presence of difluoromethane refrigerants will tend to
be inadequate.
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[0032] The polyhydric alcohol composing the polyol ester of this
embodiment is preferably a polyhydric alcohol with 2-6 hydroxyl
groups.
[0033] Specific examples of dihydric alcohols (diols) include ethylene
5 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, 1,12-
10 dodecanediol and the like. Specific examples of trihydric and greater
alcohols include polyhydric alcohols such as trimethylolethane,
trimethylolpropane, trimethylolbutane, ditrimethylolpropane,
tritrimethylolpropane, pentaerythritol, dipentaerythritol,
tripentaerythritol, glycerin, polyglycerin (glycerin 2-3mers), 1,3,5-
15 pentanetriol, sorbitol, sorbitan, sorbitolglycerin condensation products,
adonitol, arabitol, xylitol, mannitol and the like, saccharides such as
xylose, arabinose, ribose, rhamnose, glucose, fiuctose, galactose, |
mannose, sorbose and cellobiose, and partial etherified forms thereof
Of these, esters of hindered alcohols such as neopentyl glycol,
20 trimethylolethane, trimethylolpropane, trimethylolbutane,
ditrimethylolpropane, tritrimethylolpropane, pentaerythritol,
dipentaerythritol and tripentaerythritol are preferred, esters of neopentyl
glycol, trimethylolethane, trimethylolpropane, trimethylolbutane,
pentaerythritol and dipentaerythritol are more preferred, and neopentyl
25 glycol, trimethylolpropane, pentaerythritol and dipentaerythritol are
even more preferred for more excellent hydrolytic stability, while
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pentaerythritol, dipentaerythritol or mixed esters of pentaerythritol and
dipentaerythritol are most preferred for particularly excellent
compatibility with refrigerants and hydrolytic stability.
[0034] Preferred examples of constituent acid components of the
5 polyhydric alcohol fatty acid ester (A) of the invention include the
following.
(i) Combinations of 1 to 13 acids selected from among butanoic acid, 2-
methylpropanoic acid, pentanoic acid, 2-methylbutanoic acid, 3-
methylbutanoic acid, 2,2-dimethylpropanoic acid, 2-methylpentanoic
10 acid, 3-methylpentanoic acid, 4-methylpentanoic acid, 2,2-
dimethylbutanoic acid, 2,3-dimethylbutanoic acid, 3,3-dimethylbutanoic
acid and hexanoic acid, and 1 to 13 acids selected from among 2-
methylhexanoic acid, 3-methylhexanoic acid, 4-methylhexanoic acid, 5-
methylhexanoic acid, 2,2-dimethylpentanoic acid, 2,3-
15 dimethylpentanoic acid, 2,4-dimethylpentanoic acid, 3,3-
dimethylpentanoic acid, 3,4-dimethylpentanoic acid, 4,4-
dimethylpentanoic acid, 2-ethylpentanoic acid, 3-ethylpentanoic acid
and 2-ethyl-3-methylbutanoic acid;
(ii) Combinations of 1 to 13 acids selected from among butanoic acid,
20 2-methylpropanoic acid, pentanoic acid, 2-methylbutanoic acid, 3-
methylbutanoic acid, 2,2-dimethylpropanoic acid, 2-methylpentanoic
acid, 3-methylpentanoic acid, 4-methylpentanoic acid, 2,2-
dimethylbutanoic acid, 2,3-dimethylbutanoic acid, 3,3-dimethylbutanoic
acid and hexanoic acid and 1 to 25 acids selected from among 2-
25 methylheptanoic acid, 3-methylheptanoic acid, 4-methylheptanoic acid,
5-methylheptanoic acid, 6-methylheptanoic acid, 2,2-dimethylhexanoic
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acid, 3,3-dimethylhexanoic acid, 4,4-dimethylhexaiioic acid, 5,5-
dimethylhexanoic acid, 2,3-dimethylhexanoic acid, 2,4-
dimethylhexanoic acid, 2,5-dimethylhexanoic acid, 3,4-
dimethylhexanoic acid, 3,5-dimethylhexanoic acid, 4,5-
5 dimethylhexanoic acid, 2,2,3-trimethylpentanoic acid, 2,3,3-
trimethylpentanoic acid, 2,4,4-trimethylpentanoic acid, 3,4,4-
trimethylpentanoic acid, 2-ethylhexanoic acid, 3-ethylhexanoic acid, 2-
propylpentanoic acid, 2-methyl-2-ethylpentanoic acid, 2-methyl-3-
ethylpentanoic acid and 3-methyl-3-ethylpentanoic acid; and
10 (iii) Combinations of 1 to 13 acids selected from among butanoic acid,
2-methylpropanoic acid, pentanoic acid, 2-methylbutanoic acid, 3-
methylbutanoic acid, 2,2-dimethylpropanoic acid, 2-methylpentanoic
acid, 3-methylpentanoic acid, 4-methylpentanoic acid, 2,2-
dimethylbutanoic acid, 2,3-dimethylbutanoic acid, 3,3-dimethylbutanoic
15 acid and hexanoic acid, and 1 to 50 acids selected from among 2-
methyloctanoic acid, 3-methyloctanoic acid, 4-methyloctanoic acid, 5-
methyloctanoic acid, 6-methyloctanoic acid, 7-methyloctanoic acid, 8-
methyloctanoic acid, 2,2-dimethylheptanoic acid, 3,3-dimethylheptanoic
acid, 4,4-dimethylheptanoic acid, 5,5-dimethylheptanoic acid, 6,6-
20 dimethylheptanoic acid, 2,3-dimethylheptanoic acid, 2,4-
dimethylheptanoic acid, 2,5-dimethylheptanoic acid, 2,6-
dimethylheptanoic acid, 3,4-dimethylheptanoic acid, 3,5-
dimethylheptanoic acid, 3,6-dimethylheptanoic acid, 4,5-
dimethylheptanoic acid, 4,6-dimethylheptanoic acid, 2-ethylheptanoic
25 acid, 3-ethylheptanoic acid, 4-ethylheptanoic acid, 5-ethylheptanoic
acid, 2-propylhexanoic acid, 3-propylhexanoic acid, 2-butylpentanoic
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acid, 2,2,3-trimethylhexanoic acid, 2,2,3-trimethylhexanoic acid, 2,2,4-
trimethylhexanoic acid, 2,2,5-trimethylhexanoic acid, 2,3,4-
trimethylhexanoic acid, 2,3,5-trimethylhexanoic acid, 3,3,4-
trimethylhexanoic acid, 3,3,5-trimethylhexanoic acid, 3,5,5-
5 trimethylhexanoic acid, 4,4,5-trimethylhexanoic acid, 4,5,5-
trimethylhexanoic acid, 2,2,3,3-tetramethylpentanoic acid, 2,2,3,4-
tetramethylpentanoic acid, 2,2,4,4-tetramethylpentanoic acid, 2,3,4,4-
tetramethylpentanoic acid, 3,3,4,4-tetrainethylpentanoic acid, 2,2-
diethylpentanoic acid, 2,3-diethylpentanoic acid, 3,3-diethylpentanoic
10 acid, 2-ethyl-2,3,3-trimethylbutyric acid, 3-ethyl-2,2,3-trimethylbutyric
acid and 2,2-diisopropylpropionic acid.
[0035] More preferred examples of constituent acid components of the
polyhydric alcohol fatty acid ester of the invention include the following,
(i) Combinations of 2-methylpropanoic acid and 1 to 13 acids selected
15 from among 2-methylhexanoic acid, 3-methylhexanoic acid, 4-
methylhexanoic acid, 5-methylhexanoic acid, 2,2-dimethylpentanoic
acid, 2,3-dimethylpentanoic acid, 2,4-dimethylpentanoic acid, 3,3-
dimethylpentanoic acid, 3,4-dimethylpentanoic acid, 4,4-
dimethylpentanoic acid, 2-ethylpentanoic acid, 3-ethylpentanoic acid
20 and 2-ethyl-3-methylbutanoic acid;
(ii) Combinations of 2-methylpropanoic acid and 1 to 25 acids selected
from among 2-methylheptanoic acid, 3-methylheptanoic acid, 4-
methylheptanoic acid, 5-methylheptanoic acid, 6-methylheptanoic acid,
2,2-dimethylhexanoic acid, 3,3-dimethylhexanoic acid, 4,4-
25 dimethylhexanoic acid, 5,5-dimethylhexanoic acid, 2,3-
dimethylhexanoic acid, 2,4-dimethylhexanoic acid, 2,5-
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dimethylhexanoic acid, 3,4-dimethylhexanoic acid, 3,5-
dimethylhexanoic acid, 4,5-dimethylhexanoic acid, 2,2,3-
trimethylpentanoic acid, 2,3,3-trimethylpentanoic acid, 2,4,4-
trimethylpentanoic acid, 3,4,4-trimethylpentanoic acid, 2-ethylhexanoic
5 acid, 3-ethylhexanoic acid, 2-propylpentanoic acid, 2-methyl-2-
ethylpentanoic acid, 2-methyl-3-ethylpentanoic acid and 3-methyl-3-
ethylpentanoic acid; and
(iii) Combinations of 2-methylpropanoic acid and 1 to 50 acids selected
from among 2-methyloctanoic acid, 3-methyloctanoic acid, 4-
10 methyloctanoic acid, 5-methyloctanoic acid, 6-methyloctanoic acid, 7-
methyloctanoic acid, 8-methyloctanoic acid, 2,2-dimethylheptanoic acid,
3,3-dimethylheptanoic acid, 4,4-dimethylheptanoic acid, 5,5-
dimethylheptanoic acid, 6,6-dimethylheptanoic acid, 2,3-
dimethylheptanoic acid, 2,4-dimethylheptanoic acid, 2,5-
15 dimethylheptanoic acid, 2,6-dimethylheptanoic acid, 3,4-
dimethylheptanoic acid, 3,5-dimethylheptanoic acid, 3,6-
dimethylheptanoic acid, 4,5-dimethylheptanoic acid, 4,6-
dimethylheptanoic acid, 2-ethylheptanoic acid, 3-ethylheptanoic acid, 4-
ethylheptanoic acid, 5-ethylheptanoic acid, 2-propylhexanoic acid, 3-
20 propylhexanoic acid, 2-butylpentanoic acid, 2,2,3-trimethylhexanoic
acid, 2,2,3-trimethylhexanoic acid, 2,2,4-trimethylhexanoic acid, 2,2,5-
trimethylhexanoic acid, 2,3,4-trimethylhexanoic acid, 2,3,5-
trimethylhexanoic acid, 3,3,4-trimethylhexanoic acid, 3,3,5-
trimethylhexanoic acid, 3,5,5-trimethylhexanoic acid, 4,4,5-
25 trimethylhexanoic acid, 4,5,5-trimethylhexanoic acid, 2,2,3,3-
tetramethylpentanoic acid, 2,2,3,4-tetramethylpentanoic acid, 2,2,4,4-
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tetramethylpentanoic acid, 2,3,4,4-tetrainethylpentanoic acid, 3,3,4,4-
tetramethylpentanoic acid, 2,2-diethylpentanoic acid, 2,3-
diethylpentanoic acid, 3,3-diethylpentanoic acid, 2-ethyl-2,3,3-
trimethylbutyric acid, 3-ethyl-2,2,3-trimethylbutyric acid and 2,2-
5 diisopropylpropionic acid.
[0036] The content of the polyhydric alcohol fatty acid ester (A) is 50
mass% or greater, preferably 60 mass% or greater, more preferably 70
mass% or greater and even more preferably 75 mass% or greater, based
on the total mass of the refrigerating machine oil. The refrigerating
10 machine oil of this embodiment may contain a lubricant base oil other
than the polyhydric alcohol fatty acid ester (A) and additives, as
explained below, but if the polyhydric alcohol fatty acid ester (A)
content is less than 50 mass%, it will not be possible to achieve high
levels for both the necessary viscosity and compatibility.
15 [0037] The polyhydric alcohol fatty acid ester (A) in the refrigerating
machine oil of this embodiment is used primarily as a base oil. The
base oil used for the refrigerating machine oil of this embodiment may
be the polyhydric alcohol fatty acid ester (A) alone (that is, a polyhydric
alcohol fatty acid ester (A) content of 100 mass%), but a base oil other
20 than the polyhydric alcohol fatty acid ester (A) may also be included in
an amount that does not impair the excellence of performance. Base
oils other than the polyhydric alcohol fatty acid ester (A) include
mineral oils, hydrocarbon-based oils such as olefin polymers |
alkyldiphenylaUcanes, alkylnaphthalenes and alkylbenzenes; and
25 oxygen-containing synthetic oils (hereunder also referred to as "other
oxygen-containing synthetic oils") such as esters other than the
16
^ FPl 1-0356-00
polyhydric alcohol fatty acid ester (A), including polyol esters, complex
esters and alicyclic dicarboxylic acid esters, polyglycols, polyvinyl
ethers, ketones, polyphenyl ethers, silicones, polysiloxanes and
perfluoroethers.
5 [0038] The oxygen-containing synthetic oil is preferably an ester other
than the polyhydric alcohol fatty acid ester (A), or a polyglycol or
polyvinyl ether, and most preferably it is a polyol ester other than the
polyhydric alcohol fatty acid ester (A), Polyol esters other than the
polyhydric alcohol fatty acid ester (A) include esters of fatty acids and
10 polyhydric alcohols such as neopentyl glycol, trimethylolethane,
trimethylolpropane, trimethylolbutane, pentaerythritol and
dipentaerythritol, and most preferably esters of neopentyl glycol and
fatty acids, esters of pentaerythritol and fatty acids and esters of
dipentaerythritol and fatty acids.
15 [0039] Preferred neopentyl glycol esters are esters of neopentyl glycol
and C5-C9 fatty acid. Specific examples of such neopentyl glycol
esters include neopentylglycol di-3,5,5-trimethylhexanate,
neopentylglycol di-2-ethylhexanate, neopentylglycol di-2-
methylhexanate, neopentyl glycol di-2-ethylpentanate, esters of
20 neopentyl glycol and 2-methylhexanoic acid and 2-ethylpentanoic acid,
esters of neopentylglycol and 3-methylhexanoic acid and 5-
methylhexanoic acid, esters of neopentyl glycol and 2-methylhexanoic
acid and 2-ethylhexanoic acid, esters of neopentyl glycol and 3,5-
dimethylhexanoic acid, 4,5-dimethylhexanoic acid and 3,4-
25 dimethylhexanoic acid, neopentylglycol dipentanate, neopentylglycol
di-2-ethylbutanate, neopentylglycol di-2-methylpentanate,
17
^ FPl 1-0356-00
neopentylglycol di-2-methylbutanate, neopentylglycol di-3-
methylbutanate, and the like.
[0040] Pentaerythritol esters are preferably esters of pentaerythritol and
C5-C9 fatty acid. Specific examples of such pentaerythritol esters
5 include esters of pentaerythritol with one or more fatty acids selected
fi"om among pentanoic acid, 2-methylbutanoic acid, 3-methylbutanoic
acid, hexanoic acid, 2-methylpentanoic acid, 2-ethylbutanoic acid, 2-
ethylpentanoic acid, 2-methylhexanoic acid, 3,5,5-trimethylhexanoic |
acid and 2-ethylhexanoic acid.
10 [0041] Dipentaerythritol esters are preferably esters of dipentaerythritol
and C5-C9 fatty acid. Specific examples of such dipentaerythritol
esters include esters of dipentaerythritol with one or more fatty acids
selected fi*om among pentanoic acid, 2-methylbutanoic acid, 3-
methylbutanoic acid, hexanoic acid, 2-methylpentanoic acid, 2-
15 ethylbutanoic acid, 2-ethylpentanoic acid, 2-methylhexanoic acid, 3,5,5-
trimethylhexanoic acid and 2-ethylhexanoic acid.
[0042] When the refiigerating machine oil of this embodiment contains
an oxygen-containing synthetic oil other than the polyhydric alcohol
fatty acid ester (A), the content of the oxygen-containing synthetic oil
20 other than the polyhydric alcohol fatty acid ester (A) is not particularly
restricted so long as it does not impair the excellent lubricity and
compatibility of the refiigerating machine oil of this embodiment, but
when a polyol ester other than the polyhydric alcohol fatty acid ester
(A) is added, the amount is preferably less than 50 mass%, more
25 preferably no greater than 45 mass%, even more preferably no greater
than 40 mass%, yet more preferably no greater than 35 mass%, even yet
18
^ FPl 1-0356-00
more preferably no greater than 30 mass% and most preferably no
greater than 25 mass%, based on the total mass of the refrigerating
machine oil; and when an oxygen-containing synthetic oil other than a
polyol ester is added, the amount is preferably less than 50 mass%,
5 more preferably no greater than 40 mass% and even more preferably no
greater than 30 mass% based on the total mass of the refrigerating
machine oil. If the addition amount of polyol ester other than a
pentaerythritol fatty acid ester or another oxygen-containing synthetic
oil is too large, the features of the invention may not be obtained.
10 [0043] A polyol ester other than the polyhydric alcohol fatty acid ester
(A) 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 a partial ester and a complete ester, but the hydroxyl value is
15 preferably no greater than 10 mgKOH/g, even more preferably no
greater than 5 mgKOH/g and most preferably no greater than 3
mgKOH/g.
[0044] When the refrigerating machine oil and working fluid
composition for a refrigerating machine according to this embodiment
20 contains a polyol ester other than the polyhydric alcohol fatty acid ester
(A), the polyol ester may contain one type of polyol ester with a single
structure, or a mixture of two or more polyol esters with different
structures.
[0045] The polyol ester other than the polyhydric alcohol fatty acid
25 ester (A) may be an ester of one fatty acid and one polyhydric alcohol,
an ester of two or more fatty acids and one polyhydric alcohol, an ester
19
g^ FPl 1-0356-00 I
of one fatty acid and two or more polyhydric alcohols, or an ester of two
or more fatty acids and two or more polyhydric alcohols.
[0046] The refrigerating machine oil of this embodiment may consist
entirely of the polyhydric alcohol fatty acid ester (A), or it may
5 comprise the polyhydric alcohol fatty acid ester (A) and another base oil,
but the additives mentioned below are further added. The working
fluid composition for a refrigerating machine according to this
embodiment, as well, may fiirther contain various additives. In the
explanation which follows, the additive contents are given based on the
10 total mass of the refrigerating machine oil, and the contents of these
components in the working fluid composition for a refrigerating
machine are preferably selected to be within the preferred ranges
specified below, based on the total amount of the refrigerating machine
oil.
15 [0047] In order to further enhance the abrasion resistance and load
resistance of the refrigerating machine oil and the working fluid
composition for a refrigerating machine according to this embodiment,
there may be added one or more phosphorus compounds selected from
the group consisting of phosphoric acid esters, acidic phosphoric acid
20 esters, 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.
25 [0048] Specific examples of phosphoric acid esters include tributyl
phosphate, tripentyl phosphate, trihexyl phosphate, triheptyl phosphate,
20
| l FPl 1-0356-00
trioctyl phosphate, trinonyl phosphate, tridecyl phosphate, triundecyl
phosphate, tridodecyl phosphate, tritridecyl phosphate, tritetradecyl
phosphate, tripentadecyl phosphate, trihexadecyl phosphate,
triheptadecyl phosphate, trioctadecyl phosphate, trioleyl phosphate,
5 triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate,
cresyldiphenyl phosphate and xylenyldiphenyl phosphate.
[0049] Acidic phosphoric acid esters include monobutyl acid phosphate,
monopentyl acid phosphate, monohexyl acid phosphate, monoheptyl
acid phosphate, monooctyl acid phosphate, monononyl acid phosphate,
10 monodecyl acid phosphate, monoundecyl acid phosphate, monododecyl
acid phosphate, monotridecyl acid phosphate, monotetradecyl acid
phosphate, monopentadecyl acid phosphate, monohexadecyl acid
phosphate, monoheptadecyl acid phosphate, monooctadecyl acid
phosphate, monooleyl acid phosphate, dibutyl acid phosphate, dipentyl
15 acid phosphate, dihexyl acid phosphate, dUieptyl acid phosphate, dioctyl
acid phosphate, dinonyl acid phosphate, didecyl acid phosphate,
diundecyl acid phosphate, didodecyl acid phosphate, ditridecyl acid
phosphate, ditetradecyl acid phosphate, dipentadecyl acid phosphate,
dihexadecyl acid phosphate, diheptadecyl acid phosphate, dioctadecyl
20 acid phosphate and dioleyl acid phosphate.
[0050] Thiophosphoric acid esters include tributyl phosphorothionate,
tripentyl phosphorothionate, trihexyl phosphorothionate, triheptyl
phosphorothionate, trioctyl phosphorothionate, trinonyl
phosphorothionate, tridecyl phosphorothionate, triundecyl
25 phosphorothionate, tridodecyl phosphorothionate, tritridecyl
phosphorothionate, tritetradecyl phosphorothionate, tripentadecyl
21
Il FPl 1-0356-00
phosphorothionate, trihexadecyl phosphorothionate, triheptadecyl
phosphorothionate, trioctadecyl phosphorothionate, trioleyl
phosphorothionate, triphenyl phosphorothionate, tricresyl
phosphorothionate, trixylenyl phosphorothionate, cresyldiphenyl
5 phosphorothionate and xylenyldiphenyl phosphorothionate.
[0051] Acidic phosphoric acid ester amine salts include amine salts of
acidic phosphoric acid esters, and C1-C24 and preferably C5-C18 primary
to tertiary straight-chain or branched alkyl group amine.
[0052] Amines composing amine salts of acidic phosphoric acid esters
10 include straight-chain and branched amines such as methylamine,
ethylamine, propylamine, butylamine, pentylamine, hexylamine,
heptylamine, octylamine, nonylamine, decylamine, undecylamine,
dodecylamine, tridecylamine, tetradecylamine, pentadecylamine,
hexadecylamine, heptadecylamine, octadecylamine, oleylamine,
15 tetracosylamine, dimethylamine, diethylamine, dipropylamine,
dibutylamine, dipentylamine, dihexylamine, diheptylamine, j
dioctylamine, dinonylamine, didecylamine, diundecylamine,
didodecylamine, ditridecylamine, ditetradecylamine, dipentadecylamine,
dihexadecylamine, diheptadecylamine, dioctadecylamine, dioleylamine,
20 ditetracosylamine, trimethylamine, triethylamine, tripropylamine,
tributylamine, tripentylamine, trihexylamine, triheptylamine,
trioctylamine, trinonylamine, tridecylamine, triundecylamine,
tridodecylamine, tritridecylamine, tritetradecylamine,
tripentadecylamine, trihexadecylamine, triheptadecylamine,
25 trioctadecylamine and trioleylamine, tritetracosylamine. The amine
may be a simple compound or a mixture of two or more different
22
g FPl 1-0356-00
compounds.
[0053] As chlorinated phosphoric acid esters there may be mentioned
tris(dichloropropyl) phosphate, tris(chloroethyl) phosphate,
tris(chlorophenyl) phosphate, and polyoxyalkylene bis[di(chloroalkyl)]
5 phosphate. Phosphorous acid esters include dibutyl phosphite,
dipentyl phosphite, dihexyl phosphite, diheptyl phosphite, dioctyl
phosphite, dinonyl phosphite, didecyl phosphite, diundecyl phosphite,
didodecyl phosphite, dioleyl phosphite, diphenyl phosphite, dicresyl
phosphite, tributyl phosphite, tripentyl phosphite, trihexyl phosphite,
10 triheptyl phosphite, trioctyl phosphite, trinonyl phosphite, tridecyl
phosphite, triundecyl phosphite, tridodecyl phosphite, trioleyl phosphite,
triphenyl phosphite and tricresyl phosphite. Mixtures of the above
compounds may also be used.
[0054] When the refrigerating machine oil and working fluid
15 composition for a refrigerating machine according to this embodiment
contains such phosphorus compounds, the phosphorus compound
content is not particularly restricted but is preferably 0.01-5.0 mass%
and more preferably 0.02-3.0 mass% based on the total mass of the
refrigerating machine oil (the total mass of the base oil and all of the
20 additives). A single phosphorus compound may be used, or two or
more may be used in combination.
[0055] The refrigerating machine oil and working fluid composition for
a refrigerating machine of this embodiment may also contain added
terpene compounds for further improved thermal and chemical stability.
25 A "terpene compound" according to the invention is a compound
obtained by polymerization of isoprene or a derivative thereof, and
23
j | FPl 1-0356-00
isoprene 2-8mers are preferably used. Teipene compounds include,
specifically, monoterpenes such as geraniol, nerol, linalool, citrals
(including geranial), citronellol, menthol, limonene, terpinerol, carpone,
ionone, thujone, camphor and bomeol, sesquiterpenes such as famesene,
5 famesol, nerolidol, juvenile hormone, humulene, caryophyllene, elemen,
cadinol, cadinene and tutin, diterpenes such as geranylgeraniol, phytol,
abietic acid, pimaradiene, daphnetoxin, taxol and pimaric acid,
sestaterpenes such as geranylfamesene, triterpenes such as squalene,
limonin, camelliagenin, hopane and lanosterol, and tetraterpenes such as
10 carotenoids.
[0056] Preferred among these terpene compounds are monoterpenes,
sesquiterpenes and diterpenes, with sesquiterpenes being more preferred
and a-famesene (3,7,ll-trimethyldodeca-l,3,6,10-tetraene) and/or pfamesene
(7,11 -dimethyl-3 -methylidenedodeca-1,6,10-triene) being
15 especially preferred. According to the invention, a single type of
terpene compound may be used alone, or two or more different ones
may be used in combination.
[0057] There are no particular restrictions on the content of terpene
compounds in the refrigerating machine oil of this embodiment, but it is
20 preferably 0.001-10% by mass, more preferably 0.01-5% by mass and
even more preferably 0.05-3%) by mass based on the total mass of the
refrigerating machine oil. A terpene compound content of less than
0.001%) by mass will tend to result in an insufficient improving effect
on the thermal and chemical stability, while a content of greater than
25 10% by mass will tend to result in insufficient lubricity. The content
of terpene compounds in the working fluid composition for a ;.
7
i\l J
f
24 [
i
^ FPl 1-0356-00
9
refrigerating machine according to this embodiment is preferably
selected so as to fall within the aforementioned preferred range based on
the total mass of the refrigerating machine oil.
[0058] In order to fiirther improve the thermal and chemical stability of
5 the refrigerating machine oil and working fluid composition for a
refrigerating machine according to this embodiment, it may contain one
or more epoxy compounds selected from among phenyl glycidyl ethertype
epoxy compounds, alkyl glycidyl ether-type epoxy compounds,
glycidyl ester-type epoxy compounds, allyloxirane compounds,
10 alkyloxirane compounds, alicyclic epoxy compounds, epoxidated fatty
acid monoesters and epoxidated vegetable oils.
[0059] Specific examples of phenyl glycidyl ether-type epoxy
compounds include phenyl glycidyl ethers and alkylphenyl glycidyl
ethers. The alkylphenyl glycidyl ethers referred to here may have 1 to
15 3 Ci-Ci3 alkyl groups, preferred examples of which include those with
one C4-C10 alkyl group such as n-butylphenyl glycidyl ether, ibutylphenyl
glycidyl ether, sec-butylphenyl glycidyl ether, tertbutylphenyl
glycidyl ether, pentylphenyl glycidyl ether, hexylphenyl
glycidyl ether, heptylphenyl glycidyl ether, octylphenyl glycidyl ether,
20 nonylphenyl glycidyl ether and decylphenyl glycidyl ether.
[0060] Specific examples of alkyl glycidyl ether-type epoxy
compounds include decyl glycidyl ether, undecyl glycidyl ether,
dodecyl glycidyl ether, tridecyl glycidyl ether, tetradecyl glycidyl ether,
2-ethylhexyl glycidyl ether, neopentyl glycol diglycidyl ether,
25 trimethylolpropanetriglycidyl ether, pentaerythritoltetraglycidyl ether,
1,6-hexanediol diglycidyl ether, sorbitolpolyglycidyl ether,
25
^ FPl 1-0356-00
polyalkyleneglycol monoglycidyl ether and polyalkyleneglycol
diglycidyl ether.
[0061] Specific examples of glycidyl ester-type epoxy compounds
include phenylglycidyl esters, alkylglycidyl esters and alkenylglycidyl
5 esters, among which preferred examples include glycidyl-2,2-dimethyl
octanoate, glycidyl benzoate, glycidyl acrylate and glycidyl
methacrylate.
[0062] Specific examples of allyloxirane compounds include 1,2-
epoxystyrene and alkyl-l,2-epoxystyrenes.
10 [0063] Specific examples of alkyloxirane compounds include 1,2-
epoxybutane, 1,2-epoxypentane, 1,2-epoxyhexane, 1,2-epoxyheptane,
1,2-epoxyoctane, 1,2-epoxynonane, 1,2-epoxydecane, 1,2-
epoxyundecane, 1,2-epoxydodecane, 1,2-epoxytridecane, 1,2-
epoxytetradecane, 1,2-epoxypentadecane, 1,2-epoxyhexadecane, 1,2-
15 epoxyheptadecane, 1,1,2-epoxyoctadecane, 2-epoxynonadecane and
1,2-epoxyeicosane.
[0064] Specific examples of alicyclic epoxy compounds include 1,2-
epoxycyclohexane, 1,2-epoxycyclopentane, 3,4-
epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate, bis(3,4-
20 epoxycyclohexylmethyl)adipate, exo-2,3-epoxynorbomane, bis(3,4-
epoxy-6-methylcyclohexylmethyl)adipate, 2-(7-oxabicyclo[4.1.0]hept-
3-yl)-spiro(l,3-dioxane-5,3'-[7]oxabicyclo[4.1.0]heptane, 4-(rmethylepoxyethyl)-
l,2-epoxy-2-methylcyclohexane and 4-epoxyethyl-
1,2-epoxycyclohexane.
25 [0065] Specific examples of epoxidated fatty acid monoesters include
epoxidated esters of C12-C20 fatty acid and Ci-Cg alcohol or phenols or
26
^ FPl 1-0356-00
alkylphenols. Most preferably used are butyl, hexyl, benzyl,
cyclohexyl, methoxyethyl, octyl, phenyl and butylphenyl esters of
epoxystearic acid.
[0066] Specific examples of epoxidated vegetable oils include epoxy
5 compounds of vegetable oils such as soybean oil, linseed oil and
cottonseed oil.
[0067] Preferred among these epoxy compounds are phenyl glycidyl
ether-type epoxy compounds, alkyl glycidyl ether-type epoxy
compounds, glycidyl ester-type epoxy compounds, and alicyclic epoxy
10 compounds.
[0068] When the refrigerating machine oil and working fluid
composition for a refrigerating machine according to this embodiment
contain such epoxy compounds, the epoxy compound content is not
particularly restricted but is preferably 0.01-5.0 mass% and more
15 preferably 0.1-3.0 mass% based on the total mass of the refrigerating
machine oil. A single epoxy compound may be used, or two or more
may be used in combination.
[0069] Conventionally known refrigerating machine oil additives may
be included as necessary, in order to fiirther increase the performance of
20 the refrigerating machine oil and working fluid composition for a
refrigerating machine of this embodiment. 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-naphthylamine
and N,N-di(2-naphthyl)-p-phenylenediamine, anti-wear agents such as
25 zinc dithiophosphate, extreme-pressure agents such as chlorinated
parafFms and sulfiir compounds, oil agents such as fatty acids, silicone-
27
FPl 1-0356-00
based and other types of antifoaming agents, metal inactivating agents
such as benzotriazoles, acid scavengers such as carbodiimides, viscosity
index improvers, pour point depressants, detergent dispersants and the
like. Such additives may be used alone or in combinations of two or
5 more. There are no particular restrictions on the content of such
additives, but it is preferably no greater than 10 mass% and more
preferably no greater than 5 mass% based on the total mass of the
refrigerating machine oil.
[0070] The kinematic viscosity of the refrigerating machine oil of this
10 embodiment is not particularly restricted, but the 40°C kinematic
viscosity is preferably 20-80 mmVs, more preferably 25-75 mmVs and
most preferably 30-70 mm Is. The 100°C kinematic viscosity is
preferably 2-20 mm Is and more preferably 3-10 mm Is. If the
kinematic viscosity is below this lower limit it will not be possible to
15 obtain the necessary viscosity as a refrigerating machine oil, while if it
is above the upper limit, the compatibility with difluoromethane
refrigerants will tend to be insufficient.
[0071] The volume resistivity of the refrigerating machine oil of this
embodiment is also not particularly restricted, but is preferably 1.0 x
20 10^^ Qcm or greater, more preferably 1.0 x 10^^ Qcm or greater and
most preferably 1.0 x 10^"* Q-cm or greater. High electrical insulating
properties will usually be required for use in sealed refrigerating
machines. According to the invention, the volume resistivity is the
value measured according to JIS C 2101, "Electrical Insulating Oil Test
25 Method", at 25°C.
[0072] The moisture content of the refrigerating machine oil of this
28
^ FPl 1-0356-00
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
5 the viewpoint of effect on the thermal and chemical stability and
electrical insulating properties of the refrigerating machine oil,
especially for use in a closed refrigerating machine.
[0073] The acid value of the refrigerating machine oil of this
embodiment is also not particularly restricted, but in order to prevent
10 corrosion of metals used in the refrigerating machine or pipings, it is
preferably no greater than 0.1 mgKOH/g 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".
15 [0074] The ash content of the refrigerating machine oil of this
embodiment is not particularly restricted, but in order to increase the
thermal and chemical stability of the refrigerating machine oil and
inhibit generation of sludge, it is preferably no greater than 100 ppm
and more preferably no greater than 50 ppm. According to the
20 invention, the ash content is the value measured based on JIS K 2272,
"Crude Oil/Petroleum Product Ash Content and Sulfated Ash Content
Test Method".
[0075] The refrigerating machine oil of this embodiment exhibits
sufficiently high lubricity and sufficiently high compatibility when used
25 together with difluoromethane refrigerants, and it may be widely used
as a refrigerating machine oil for a refrigerating machine for
29
FPl 1-0356-00
difluoromethane refrigerants. Specific refrigerating machines in which |
the refiigerating machine oil of this embodiment may be used include |
cooling devices in room air conditioners, package air conditioners, i
refrigerators, automobile air conditioners, dehumidifiers, freezers,
5 freezing/refrigerating warehouses, automatic vending machines,
showcases, chemical plants and the like, among which refrigerating
machines with closed compressors are particularly preferred. The
refiigerating machine oil for a difluoromethane refiigerant according to |
1 the invention may also be used in a compressor with a reciprocating,
10 rotating or centrifiigal system. The refiigerating machine oil of the
invention in such a refiigerating machine may be used as a working
fluid composition for a refiigerating machine, in combination with a j
I
refiigerant, as described hereunder. j
[0076] Specifically, the working fluid composition for a refiigerating
15 machine according to this embodiment comprises a refiigerating |
machine oil according to this embodiment as described above, and a |
refiigerant. There are no particular restrictions on the mixing ratio of
the refiigerating machine oil and the refiigerant in the working fluid
composition for a refiigerating machine according to this embodiment,
20 but the refiigerating machine oil content will usually be 1-1000 parts by
mass and preferably 2-800 parts by mass with respect to 100 parts by I
I I
mass of the refiigerant. j
}
[0077] From the viewpoint of obtaining both sufficiently high lubricity j
and sufficiently high compatibility which have not been obtainable |
25 usmg conventional refiigerating machine oils, the working fluid |
composition for a refiigerating machine according to this embodiment I
30 I
^ FPl 1-0356-00
exhibits its utility most prominently when it comprises only a
difluoromethane refrigerant as the refrigerant component, but it may |
also comprise an HFC refrigerant other than a difluoromethane |
refrigerant, an unsaturated fluorinated hydrocarbon (HFO) refrigerant, a i
5 trifluoroiodomethane refrigerant, a fluorinated ether-based refrigerant
such as a perfluoroether, a non-fluorine-containing ether-based
refrigerant such as dimethyl ether, or a natural refrigerant such as
ammonia, carbon dioxide (CO2) or a hydrocarbon.
[0078] HFC refrigerants other than difluoromethane include C1-C3 and
10 preferably C1-C2 hydrofluorocarbons. Specific examples include
trifluoromethane (HFC-23), pentafluoroethane (HFC-125), 1,1,2,2-
tetrafluoroethane (HFC-134), 1,1,1,2-tetrafluoroethane (HFC-134a),
1,1,1-trifluoroethane (HFC-143a), 1,1-difluoroethane (HFC-152a),
fluoroethane (HFC-161), 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea),
15 1,1,1,2,3,3-hexafluoropropane (HFC-236ea), 1,1,1,3,3,3-
hexafluoropropane (HFC-23 6fa), 1,1,1,3,3-pentafluoropropane (HFCi
245fa) 1,1,1,3,3-pentafluorobutane (HFC-365mfc), and mixtures of two j
or more of the foregoing. These refrigerants may be appropriately
selected depending on the purpose of use and the required performance,
20 but preferred examples include HFC-32 alone; HFC-23 alone; HFC-
134a alone; HFC-125 alone; HFC-134a/HFC-32 = 60-80 mass%/40-20
mass% mixture; HFC-32/HFC-125 = 40-70 mass%/60-30 mass%
mixture: HFC-125/HFC-143a = 40-60 mass%/60-40 mass% mixture;
HFC-134a/HFC-32/HFC-125 = 60 mass%/30 mass%/10 mass% I
I
25 mixture; HFC-134a/HFC-32/HFC-125 = 40-70 mass%/15-35 mass%/5- I
40 mass% mixture; and HFC-125/HFC-134a/HFC-143a = 35-55 I
31 I
I
^ FPl 1-0356-00
mass%/l-15 mass%/40-60 mass% mixture. More specifically, these
include HFC-134a/HFC-32 = 70/30 mass% mixture; HFC-32/HFC-125
= 60/40 mass% mixture; HFC-32/HFC-125 = 50/50 mass% mixture
(R410A); HFC-32/HFC-125 = 45/55 mass% mixture (R410B); HFC-
5 125/HFC-143a = 50/50 mass% mixture (R507C); HFC-32/HFC-
125/HFC-134a = 30/10/60 mass% mixture; HFC-32/HFC-125/HFC-
134a = 23/25/52 mass% mixture (R407C); HFC-32/HFC-125/HFC-
134a = 25/15/60 mass% mixture (R407E); and HFC-125/HFC-
134a/HFC-143a = 44/4/52 mass% mixture (R404A).
10 [0079] The unsaturated fluorinated hydrocarbon (HFO) refrigerant is
preferably a fluoropropene with 3-5 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-tetrafluoropropene (HFO-1234yf), 1,2,3,3-
15 tetrafluoropropene (HFO-1234ye) and 3,3,3-trifluoropropene (HFO-
1243zf). Among these, HFC-32 and HFO-1234yf are preferred as
refrigerants, with an HFC-32:HFO-1234yf mass ratio of 95:5 to 50:50.
From the viewpoint of refrigerant properties, it is preferred to use one or
more selected from among HFO-1225ye, HFO-1234ze and HFO- I
20 1234yf
[0080] As hydrocarbon refrigerants there are preferred C1-C5 I
hydrocarbon, and specific examples include methane, ethylene, ethane,
propylene, propane (R290), cyclopropane, normal-butane, isobutane,
cyclobutane, methylcyclopropane, 2-methylbutane, normal-pentane, and
25 mixtures of two or more of the foregoing. Preferred among these are
refrigerants that are gases at 25°C, 1 atmosphere, such as propane, I
32 I
^ FPl 1-0356-00
normal-butane, isobutane, 2-methylbutane, and mixtures thereof.
[0081] Specific examples of fluorinated ether-based refrigerants include
HFE-134p, HFE-245mc, HFE-236mf, HFE-236me, HFE-338mcf, HFE-
365mcf, HFE-245mf, HFE-347mmy, HFE-347mcc, HFE-125, HFE-
5 143m, HFE-134m, HFE-227me and the like, and these refrigerants may
be appropriately selected depending on the purpose of use and the
required performance.
[0082] The refrigerating machine oil of this embodiment will usually be
in the form of a working fluid composition for a refrigerating machine j
10 in admixture with a refrigerant, in a refrigerating air conditioner. !
There are no particular restrictions on the mixing proportion of the |
?
(
refrigerating machine oil and refrigerant in the composition, or on the |
mixing proportion of the refrigerating machine oil and refrigerant in the |
I
working fluid composition for a refrigerating machine according to the |
|-
15 invention, but the refrigerating machine oil content is preferably 1-500 I
parts by mass and more preferably 2-400 parts by mass with respect to I
100 parts by mass of the refrigerant. I
[0083] The refrigerating machine oil and working fluid composition for |
a refrigerating machine of this embodiment is preferably used in an air I
20 conditioner or refrigerator with a reciprocating or rotating closed |
i
compressor, or in an open or closed automobile air conditioner. The I
refrigerating machine oil and working fluid composition for a I
refrigerating machine according to this embodiment may also be I
suitably used in cooling devices of dehumidifiers, hot water suppliers, I
25 freezers, freezing/refrigerating warehouses, automatic vending |
machines, showcases, chemical plants and the like. The refrigerating f
i 33 I
1^ FPl 1-0356-00
machine oil and working fluid composition for a refrigerating machine
according to this embodiment may also be suitably used in devices with
centrifugal compressors. j
[0084] The working fluid composition for a refrigerating machine
5 according to this embodiment may be suitably used in refrigerating
machines for difluoromethane refrigerants, as mentioned above, and a
typical construction of a refrigerant circulation cycle comprising the
refrigerating machine is provided with a compressor, a condenser, an
expansion mechanism and an evaporator, and if necessary a desiccator,
10 [0085] Examples of compressors include high-pressure container-type
compressors housing a motor comprising a rotor and a stator in a sealed
container storing a refrigerating machine oil, a rotation axis fitted in the
rotor, and a compressor part linked to the motor via the rotation axis, j
wherein high-pressure refrigerant gas discharged by the compressor part j
15 is retained in the sealed container, and low-pressure container-type j
compressors housing a motor comprising a rotor and a stator in a sealed j
j
container storing a refrigerating machine oil, a rotation axis fitted in the |
rotor, and a compressor part linked to the motor via the rotation axis,
wherein high-pressure refrigerant gas discharged by the compressor part
20 is directly ejected out of the sealed container.
[0086] As insulating films for use as electrical insulating system |
1
materials in motor parts, it is preferred to use crystalline plastic films i
with glass transition points of 50°C or higher, and specifically one or I
more insulating films selected from the group consisting of !
25 polyethylene terephthalate, polybutylene terephthalate, polyphenylene j
sulfide, polyetheretherketone, polyethylene naphthalate, |
34 j
I
^ FPl 1-0356-00 I
I
polyamideimide and polyimide films, or composite films comprising a i
resin layer with a high glass transition temperature covering a film with
a low glass transition temperature, because they are resistant to i
degradation of tensile strength properties and electrical insulation
5 properties. Magnet wires used in motor parts are preferably ones
having an enamel coating with a glass transition temperature of 120°C
or higher, such as a single polyester, polyesterimide, polyamide or
polyamideimide layer, or an enamel coating that is a composite coating
comprising a layer with a low glass transition temperature as the lower
10 layer and a layer with a high glass transition temperature as the upper I
layer. Enamel wires with composite coatings include those comprising r
a polyesterimide coated as the lower layer and a polyamideimide coated I
as the upper layer (AI/EI), and those comprising a polyester coated as I
the lower layer and a polyamideimide coated as the upper layer (AI/PE). I
15 [0087] As desiccants for packing into desiccators, there are preferably |
used synthetic zeolites comprising silicic acid and alkali aluminate »
metal complex salts, having a carbon dioxide gas absorption volume of
no greater than 1.0%, with a pore size of no greater than 3.3 angstrom |
and a carbon dioxide gas partial pressure of 250 mmHg at 25°C. I
20 Specific examples include XH-9, XH-10, XH-11 and XH-600, trade I
names of Union Showa,KK. I
Examples I
[0088] The present invention will now be explained in greater detail j
based on examples and comparative examples, with the understanding I
25 that the invention is in no way limited to the examples. |
[0089] j
35 I
^ FPl 1-0356-00
[Examples 1 to 36 and Comparative Examples 1 to 15]
Sample oils were prepared for Examples 1 to 36 and Comparative
Examples 1 to 15, by combining base oils 1 to 36 and additives 1 to 5,
indicated below, in the compositional ratios listed in Tables 1 to 10.
5 The properties of the obtained sample oils are shown in Tables 1 to 10.
[0090]
(Base oils)
Base oil 1: Tetraester of pentaerythritol and a fatty acid mixture (2-
methylpropanoic acid: 30 mol%, 3,5,5-trimethylhexanoic acid: 70
10 mol%).
Base oil 2: Tetraester of pentaerythritol and a fatty acid mixture (2- |
I
methylpropanoic acid: 35 mol%, 3,5,5-trimethylhexanoic acid: 65
mol%). j
Base oil 3: Tetraester of pentaerythritol and a fatty acid mixture (2- I
15 methylpropanoic acid: 50 mol%, 3,5,5-trimethylhexanoic acid: 50 i
mol%). I
Base oil 4: Tetraester of pentaerythritol and a fatty acid mixture (2- j
methylpropanoic acid: 60 mol%, 3,5,5-trimethylhexanoic acid: 40 j
mol%). 1
20 Base oil 5: Tetraester of pentaerythritol and a fatty acid mixture (2- I
methylpropanoic acid: 70 mol%, 3,5,5-trimethylhexanoic acid: 30 [
mol%). I
Base oil 6: Tetraester of pentaerythritol and a fatty acid mixture (2- I
methylpropanoic acid: 30 mol%, 2-ethylhexanoic acid: 70 mol%). j
25 Base oil 7: Tetraester of pentaerythritol and a fatty acid mixture (2- j
methylpropanoic acid: 35 mol%, 2-ethylhexanoic acid: 65 mol%). |
36
^ FPl 1-0356-00
:
:
Base oil 8: Tetraester of pentaerythritol and a fatty acid mixture (2-
methylpropanoic acid: 70 mol%, 2-ethylhexanoic acid: 30 mol%).
Base oil 9: Tetraester of pentaerythritol and a fatty acid mixture (2-
I
methylpropanoic acid: 30 mol%, 2-methylhexanoic acid: 35 mol%, 2- j
5 ethylpentanoic acid: 35 mol%). j
Base oil 10: Tetraester of pentaerythritol and a fatty acid mixture (2- |
methylpropanoic acid: 70 mol%, 2-methylhexanoic acid: 15 mol%, 2- |
ethylpentanoic acid: 15 mol%). I
Base oil 11: Tetraester of pentaerythritol and a fatty acid mixture (2- Ii
10 methylpropanoic acid: 30 mol%, 3,5,5-trimethylhexanoic acid: 60 I
mol%, 2-methylbutanoic acid: 10 mol%). I
Base oil 12: Tetraester of pentaerythritol and a fatty acid mixture (2- |
methylpropanoic acid: 60 mol%, 3,5,5-trimethylhexanoic acid: 30 ^
I
mol%, 2-methylbutanoic acid: 10 mol%).
15 Base oil 13: Tetraester of pentaerythritol and a fatty acid mixture (2-
methylpropanoic acid: 15 mol%, 3,5,5-trimethylhexanoic acid: 35
mol%, 2-methylbutanoic acid: 50 mol%).
Base oil 14: Tetraester of pentaerythritol and a fatty acid mixture (2-
methylpropanoic acid: 35 mol%, 3,5,5-trimethylhexanoic acid: 15 I
20 mol%, 2-methylbutanoic acid: 50 mol%). |
Base oil 15: Tetraester of pentaerythritol and a fatty acid mixture (2- i
methylpropanoic acid: 20 mol%, 3,5,5-trimethylhexanoic acid: 30 I
mol%, 2-methylpentanoic acid: 50 mol%). I
Base oil 16: Tetraester of pentaerythritol and a fatty acid mixture (2- f
25 methylpropanoic acid: 20 mol%, 3,5,5-trimethylhexanoic acid: 30 |
j
mol%, 2-ethylpentanoic acid: 25 mol%, 2-methylhexanoic acid: 25 I
37 I
I
i
^ FPl 1-0356-00
]
I
mol%).
Base oil 17: Tetraester of pentaerythritol and a fatty acid mixture (2-
methylpropanoic acid: 30 mol%, 2-ethylhexanoic acid: 50 mol%, 2-
methylpentanoic acid: 20 mol%).
5 Base oil 18: Tetraester of pentaerythritol and a fatty acid mixture (2-
methylpropanoic acid: 25 mol%, 2-ethylhexanoic acid: 45 mol%, 2-
ethylpentanoic acid: 15 mol%, 2-methylhexanoic acid: 15 mol%).
Base oil 19: Triester of trimethylolpropane and a fatty acid mixture (2-
methylpropanoic acid: 30 mol%, 3,5,5-trimethylhexanoic acid: 70 i
10 mol%). I
Base oil 20: Hexaester of dipentaerythritol and a fatty acid mixture (2- I
methylpropanoic acid: 70 mol%, 3,5,5-trimethylhexanoic acid: 30 I
mol%). j
Base oil 21: Tetraester of pentaerythritol and 2-methylpropanoic acid, I
15 Base oil 22: Tetraester of pentaerythritol and propionic acid. I
Base oil 23: Tetraester of pentaerythritol and n-butanoic acid. I
Base oil 24: Tetraester of pentaerythritol and 2-ethylhexanoic acid.
Base oil 25: Tetraester of pentaerythritol and a fatty acid mixture (2-
ethylhexanoic acid: 50 mol%, 3,5,5-trimethylhexanoic acid: 50 mol%).
20 Base oil 26: Tetraester of pentaerythritol and 3,5,5-trimethylhexanoic I
acid. I
Base oil 27: Tetraester of pentaerythritol and a fatty acid mixture
(propionic acid: 30 mol%, 3,5,5-trimethylhexanoic acid: 70 mol%).
Base oil 28: Tetraester of pentaerythritol and a fatty acid mixture (ni
25 butanoic acid: 25 mol%, 3,5,5-trimethylhexanoic acid: 75 mol%).
Base oil 29: Tetraester of pentaerythritol and a fatty acid mixture (n- |
L :
!
38
^ FPl 1-0356-00 I
I
i
butanoic acid: 65 mol%, 3,5,5-trimethylhexanoic acid: 35 mol%).
Base oil 30: Tetraester of pentaerythritol and a fatty acid mixture (2-
methylpropanoic acid: 10 mol%, 3,5,5-trimethylhexanoic acid: 90
mol%).
5 Base oil 31: Tetraester of pentaerythritol and a fatty acid mixture (2-
methylbutanoic acid: 90 mol%, 3,5,5-trimethylhexanoic acid: 10 mol%).
Base oil 32: Tetraester of pentaerythritol and a fatty acid mixture (2-
methylbutanoic acid: 30 mol%, 3,5,5-trimethylhexanoic acid: 70 mol%).
Base oil 33: Tetraester of pentaerythritol and a fatty acid mixture (2-
10 methylbutanoic acid: 60 mol%, 3,5,5-trimethylhexanoic acid: 40 mol%).
Base oil 34: Tetraester of pentaerythritol and a fatty acid mixture (2-
methylpentanoic acid: 30 mol%, 3,5,5-trimethylhexanoic acid: 70
mol%).
Base oil 35: Diester of neopentyl glycol and 2-ethylhexanoic acid.
15 Base oil 36: Hexaester of dipentaerythritol and a fatty acid mixture (2-
ethylhexanoic acid: 50 mol%, 3,5,5-trimethylhexanoic acid: 50 mol%); i
40°C kinematic viscosity: 249.9 mm /s, 100°C kinematic viscosity: l
19.58 mm^/s. |
[0091]
20 (Additives)
Additive 1: Tricresyl phosphate I
i
i
Additive 2: Triphenyl phosphorothionate i
Additive 3: Glycidyl-2,2-dimethyl octanoate |
Additive 4: p-t-Butylphenyl glycidyl ether j
25 Additive 5: di-t-Butyl-p-cresol ii
[0092] Each of the refrigerating machine oils obtained in Examples 1 to i
39 I
I
I
^ FPl 1-0356-00
i
I
36 and Comparative Examples 1 to 15 was subjected to the following
tests. I
[0093]
(Refrigerant compatibility test)
5 Following the "Test method of refrigerant compatibility" for
"Refrigerating machine oils" according to JIS K2211, mixtures of 18 g I
of each refrigerant listed in Tables 1 to 8 and 2 g of sample oil were i
slowly cooled from 20°C to -40°C, and the phase separation or opacity |
temperature of each mixture was evaluated as the phase separation |
10 temperature. An evaluation of "<-40" indicates that no phase f
I
separation or opacity was observed in the measuring temperature range I
of the test. An evaluation of "separation" in the tables indicates that I
phase separation or opacity had already taken place at 20°C. f
[0094] 1
15 (Stability test) |
After placing 90 g of sample oil prepared to a moisture content of 1000 I
ppm, 10 g of difluoromethane refrigerant and an Al, Cu or Fe catalyst in f
a 200 ml autoclave, the mixture was heated at 175°C for 168 hours, and j
the acid value was measured upon completion of the test. I
20 [0095] [Table 1] |
I
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^ FPl 1-0356-00
I
[0104] [Table 10] f
Units Comp. Ex. 13 Comp. Ex. 14 Comp. Ex. IS I
Base oil No. ^3 3A _35 |
40°C mmVs 32.5 68.1 7.3 I
Kinematic viscosity :; I
100°C mmVs 5.23 ^^58 _2:02 |
Viscosity index J7 ^6 ^6 I
Phase separation HFC-32 ^C J 2 ^ |
temperature |R410A | °C |-29 |-32 |- |
Industrial Applicability
i
[0105] According to the invention it is possible to provide a 5 refrigerating machine oil that allows high levels to be achieved for
-
refrigerant compatibility, lubricity and low-temperature flow properties
when it is used together with difluoromethane refrigerants, unsaturated
I fluorinated hydrocarbons and the like, as well as a working fluid
composition for a refrigerating machine using the same.

CLAIMS
1. A refrigerating machine oil comprising an ester of a polyhydric
alcohol and a fatty acid, wherein the molar ratio of C4-C6 fatty acid and
C7-C9 branched fatty acid in the fatty acid is between 15:85 and 90:10,
5 the C4-C6 fatty acid includes 2-methylpropanoic acid, and
the ratio of the total C4-C6 fatty acid and C7-C9 branched fatty
acid in the total fatty acids composing the ester is at least 20 mol%.
2. The refrigerating machine oil according to claim 1, wherein the ratio
of 2-methylpropanoic acid in the C4-C6 fatty acid is at least 20 mol%.
10 3. The refrigerating machine oil according to claim 1 or 2, wherein the
C4-C6 fatty acid is 2-methylpropanoic acid.
4. The refrigerating machine oil according to any one of claims 1 to 3,
wherein the polyhydric alcohol is pentaerythritol and the 40°C
I kinematic viscosity of the refrigerating machine oil is 20 to 80 mm /s.
I
'i 15 5. The refrigerating machine oil according to any one of claims 1 to 4,
wherein the C7-C9 branched fatty acid is 3,5,5-trimethylhexanoic acid.
i 6. A working fluid composition for a refrigerating machine, comprising
i the refrigerating machine oil according to any one of claims 1 to 5 and
a difluoromethane refrigerant.
20 7. A working fluid composition for a refrigerating machine comprising
the refrigerating machine oil according to any one of claims 1 to 5 and
an unsaturated fluorinated hydrocarbon refrigerant.
8. A working fluid composition for a refrigerating machine comprising
the refrigerating machine oil according to any one of claims 1 to 5, a
25 difluoromethane refrigerant and an unsaturated fluorinated
hydrocarbon refrigerant.
i 51
^ FPl 1-0356-00
9. A working fluid composition for a refrigerating machine comprising
the refrigerating machine oil according to any one of claims 1 to 5, a
difluoromethane refrigerant and an unsaturated fluorinated
hydrocarbon refrigerant, wherein the mass ratio of the difluoromethane
5 refrigerant and the unsaturated fluorinated hydrocarbon refrigerant is
between 95:5 and 50:50.