Title of Invention
REFRIGERATOR OIL COMPOSITION, METHOD FOR
5 PRODUCING SAME, AND WORKING FLUID COMPOSITION
Technical Field
[0001] The present invention relates to a refrigerating machine oil
composition, a method for producing the same, and a working fluid
10 composition for refrigerating machines.
Background Art
[0002] Conventionally, as refrigerants for cold storage chambers, car
air-conditioners, room air-conditioners, industrial refrigerating
machines and the like, 1,1,1,2-tetrafluoroethane (R134a), R410A that is
15 a mixed refrigerant of 111 (mass ratio) of difluoromethane (R32) and
pentafluoroethane (R125), which are hydrofluorocarbons (HFC), and
the like have been widely used.
[0003] As refrigerating machine oils used together with the
above-described HFC refrigerants, there are those into which various
20 additives are blended so as to improve a lubricating property.
[0004] It is to be noted that, in a general field of lubricant oils, as
antiwear additives for improving a lubricating property, oiliness agents
such as alcohols, esters, and long-chain fatty acids, antiwear agents
such as phosphates and metal dithiophosphates, and extreme pressure
25 agents such as organic sulfur compounds and organic halogen
compounds are known. However, in the case of refrigerating machine
oils, only additives which do not precipitate when coexisting with
refrigerants and do not have a negative effect on stability can be used,
and thus, alcohol or ester oiliness agents, and, among phosphates,
triphenyl phosphate and tricresyl phosphate are used.
5 [0005] Moreover, Patent Literature 1 discloses a refrigerating machine
compound are added together, Patent Literature 2 discloses a
compressor lubricant oil for a HFC refrigerant, to which triphenyl
phosphate and tri(akylpheny1) phosphate are added together, -and
10 Patent Literature 3 discloses a refrigerating machine oil for a HFC
refrigerant, to which tricresyl phosphate, and an epoxy compound
consisting of glycidyl ether, or carbodiimide are added, respectively.
Citation List
Patent Literature
15 [0006] Patent Literature 1: Japanese Patent Application Laid-Open No.
5-171174
Patent Literature 2: Japanese Patent Application Laid-Open No.
8-157847
Patent Literature 3: Japanese Patent Application Laid-Open No.
20 9-1 89453
Summary of Invention
Technical Problem
[0007] By the way, the above-described HFC refrigerants have an
ozone-depleting potential (ODP) of zero, but have a high global
25 warming potential (GWP), such as 1000 or niore, and illus, the use is
limited by so-called F-Gas Regulation.
[0008] As alternative rekigerants to the above-described HFC
refrigerants, hydrofluoroolefms (Wo) such as
2,3,3,3-tetrafluoropropene (HFO-1234~0, and low GWP rekigerants
such as difluoromethane (R32) attract attention in conjunction with the
5 thermodynamic properties. For example, the GWP of HFO-1234yf is
675, R32 is examined as a likely candidate because it has a high gas
pressure and is a high efficiency refrigerant. These refrigerants are
examined to be used alone or as a mixed refrigerant with other
10 refrigerants in consideration of the balance of the GWP and various
properties.
[0009] Moreover, hydrocarbon refrigerants such as isobutane (R600a)
and propane (R290) have a low GWP, such as 20 or less, and suitable
physical property values, and thus, they have been already in practical
15 use for cold storage chambers while they are combustible.
[0010] Among the above-described rekigerants, R32, a mixed
rekigerant containing R32 or the like becomes high pressure when
being used, the compressor discharge temperature becomes high, and
an oil film of a refrigerating machine oil in which a refrigerant is
20 dissolved becomes thin, thereby resulting in severe lubrication
conditions.
[0011] Moreover, since hydrocarbon refrigerants do not contain, in a
hydrocarbon molecule, fluorine that improves a lubricating property,
the improvement of the lubricating property by the refrigerant is not
25 expected in contrasi to RFC refrigerants and the like. Furthelxiore,
since the solubility of the hydrocarbon refrigerants in a refrigerating
machine oil is high, also in this case, the viscosity of the refrigerating
machine oil is decreased and lubrication conditions become severe.
[0012] If the above-described conventional refrigerating machine oils
for HFC refrigerants are directly diverted to refrigerating machine oils
5 used together with these refrigerants having a GWP of 700 or less
cases), it is difficult to obtain a sufficient lubricating property.
[0013] For example, among additives used for the above-described
conventional refrigerating machine oils for HFC refrigerants, oiliness
10 agents form lubricating films by adsorption, and thus, while a friction
coefficient can be maintained low in the case where load conditions are
relatively mild, for example in a mixed lubrication regime, an antiwear
effect is lost as load conditions become severe.
[0014] Moreover, triphenyl phosphate and tricresyl phosphate have a
15 certain degree of an antiwear effect, but it is insufficient as an antiwear
property under coexistence of a low GWP refrigerant, in which
lubrication conditions are severe.
[0015] The present invention has been made in view of the subject of
the conventional art, and it is an object of the present invention to
20 provide a refrigerating machine oil composition for a compatible
refrigerant, which has a large antiwear effect and excels in long-time
reliability even under severe lubrication conditions, such as under
coexistence of a low GWP refrigerant, a method for producing the
same, and a working fluid composition for refrigerating machines.
25 Solution to Problem
[0016] In order to solve the above-described subject, the present
invention provides a refrigerating machine oil composition comprising
at least one ester additive selected from tetraesters of pentaerythritol
and one selected from fatty acids having 5 to 18 carbon atoms and
hexaesters of dipentaerythritol and one selected from fatty acids having
5 5 to 18 carbon atoms, and a base oil that is an ester other than the ester
based on the total amount of the refrigerating machine oil composition,
and the kinematic viscosity of the refrigerating machine oil
composition at 40°C is 3 to 500 mm2/s.
10 [0017] In this manner, by blending a predetermined amount of the
above-described specific ester additive into the base oil that is an ester
other than the ester additive, and furthermore, by making the kinematic
viscosity of the refrigerating machine oil composition at 40°C be
within the above-described range, an antiwear property of a
15 refrigerating machine oil can be drastically improved without negative
effects on other properties under coexistence of a low GWP refrigerant.
[0018] Here, a constituent fatty acid of the ester additive is, as
described above, one selected from fatty acids having 5 to 18 carbon
atoms. That is, the constituent fatty acid of the ester additive needs to
20 be a single composition.
[0019] In contrast, the base oil that is an ester other than the ester
additive includes all esters other than the above-described ester
additive. For example, if a constituent alcohol of the ester is
- -- pentaerythritol and/or dipentaerythritol and fatty acids having 5 to 18
25 carbon atoms are conpained in a consiituent fatty acid, in tile case where
the constituent fatty acid is a mixed fatty acid of two or more selected
from fatty acids having 5 to 18 carbon atoms, or in the case where the
constituent fatty acid is a mixed fatty acid of one, or two or more
selected from fatty acids having 5 to 18 carbon atoms and one, or two
or more of other fatty acids, these esters can be used as the base oil.
5 [0020] It is to be noted that, in the case where the constituent alcohol
and the constituent fatty acid is a mixed fatty acid containing fatty
acids having 5 to 18 carbon atoms, tetraesters of pentaerythritol and
one selected from fatty acids having 5 to 18 carbon atoms and/or
10 hexaesters of dipentaerythritol and one selected from fatty acids having
5 to 18 carbon atoms can be generated when synthesizing the base oil.
However, according to the examination of the present inventors, if such
an ester is used as the base oil, an antiwear property improving effect
as when the above-described ester additive is blended into the base oil
15 cannot be observed. In other words, an antiwear property effect
according to the present invention is exerted only by blending the
above-described ester additive into the base oil that is an ester other
than the ester additive, and can be said to be an unexpected remarkable
effect.
20 [0021] In the present invention, the above-described ester additive is
preferably at least one selected from
pentaerythritoltetra(2-ethylhexanoate) and
dipentaerythritolhexa(hexanoate).
[0022] Moreover, the kinematic viscosity of the refrigerating machine
25 oii composition at 4G°C is prererabiy 3 to 300 mn12/s.
[0023] Furthermore, the above-described base oil is preferably a polyol
ester.
[0024] Additionally, the above-described base oil is preferably a polyol
ester obtained from pentaerythritol and a mixed acid of a carboxylic
acid having 4 to 7 carbon atoms and 3,5,5-trimethylhexanoic acid.
5 [0025] Moreover, the above-described base oil is preferably a polyol
and 3,5,5-trimethylhexanoic acid, and whose kinematic viscosity at
40°C is 30 to 110 mm2/s.
[0026] Moreover, the content of the above-described ester additive is
10 preferably 2 to 7 mass% based on the total amount of the refrigerating
machine oil composition.
[0027] Moreover, the refrigerating machine oil composition of the
present invention preferably further comprises 0.1 to 5 mass% of a
phosphate andlor 0.01 to 2 mass% of a sulfide compound based on the
15 total amount of the refrigerating machine oil composition.
[0028] The above-described phosphate is preferably at least one
selected from triphenyl phosphate, tricresyl phosphate, and alkylphenyl
phosphates having an alkyl group having 3 or 4 carbon atoms.
[0029] Moreover, the above-described sulfide compound is preferably
20 a thiobisphenol compound.
[0030] Moreover, the present invention provides a method for
producing a refrigerating machine oil composition including a step of
blending at least one ester additive selected from tetraesters of
pentaerythritol and one selected from fatty acids having 5 to 18 carbon
25 atoms and hexaeslers of dipenlaerylhritui and one selected from fatty
acids having 5 to 18 carbon atoms into at least one base oil selected
from mineral oils and synthetic oils to obtain the refrigerating machine
oil composition, in which the content of the ester additive is 2 to 20
mass% based on the total amount of the refrigerating machine oil
composition, and the kinematic viscosity of the refrigerating machine
5 oil composition at 40°C is 3 to 500 mm2/s.
composition for refrigerating machines which comprises the
above-described refrigerating machine oil composition of the present
invention, and a refrigerant containing at least one selected from
10 hydrofluorocarbons, hydrofluoroolefins, and hydrocarbons, and whose
global warming potential (GWP) is 700 or less.
[0032] The above-described refrigerant preferably contains
difluoromethane (R32).
Advantageous Effects of Invention
15 [0033] As described above, the refrigerating machine oil composition
of the present invention can maintain a low friction coefficient along
with an antiwear effect, and exerts an excellent effect of capable of
being stably used for long periods, even under severe lubrication load
conditions with a low GWP refrigerant coexisting.
20 Description of Embodiments
[0034] Hereinafter, suitable embodiments of the present invention will
be described in detail.
[0035] [First Embodiment: Refrigerating machine Oil Composition
and Method for Producing Same]
25 A refrigerating machine oil composition according to a first
embodiment of the present invention compsises at least one ester
additive selected from tetraesters of pentaerythritol and one selected
from fatty acids having 5 to 18 carbon atoms and hexaesters of
dipentaerythritol and one selected from fatty acids having 5 to 18
carbon atoms, and a base oil that is an ester other than the ester
5 additive. In the refrigerating machine oil composition, the content of
refrigerating machine oil composition, and the kinematic viscosity of
the refrigerating machine oil composition at 40°C is 3 to 500 mm2/s.
[0036] A constituent alcohol of the ester additive is pentaerythritol
10 andlor dipentaerythritol, and the ester additive is a complete ester in the
case where either alcohol is used. It is to be noted that the constituent
alcohol may contain impurities which are inevitably contained in a
normal production process.
[0037] Moreover, a constituent fatty acid of the ester additive is one
15 selected from fatty acids having 5 to 18 carbon atoms and needs to be a
single composition. However, in the case where two or more of
tetraesters of pentaerythritol and hexaesters of dipentaerythritol are
used in combination, the constituent fatty acids of the respective
complete esters may be the same or different from each other, as long
20 as the constituent fatty acid in one molecule is a single composition.
It is to be noted that the constituent fatty acid may contain impurities
which are inevitably contained in a normal production process.
[0038] Moreover, the fatty acids having 5 to 18 carbon atoms may be
either saturated fatty acids or unsaturated fatty acids, and may be
25 sirdighi-chain faiiy acids or branched Fdiiy acids. Specificaliy,
examples of the fatty acids include saturated fatty acids such as
straight-chain or branched pentanoic acid, straight-chain or branched
hexanoic acid, straight-chain or branched heptanoic acid, straight-chain
or branched octanoic acid, straight-chain or branched nonanoic acid,
straight-chain or branched decanoic acid, straight-chain or branched
5 undecanoic acid, straight-chain or branched dodecanoic acid,
tetradecanoic acid, straight-chain or branched pentadecanoic acid,
straight-chain or branched hexadecanoic acid, straight-chain or
branched heptadecanoic acid, and straight-chain or branched
10 octadecanoic acid; and unsaturated fatty acids such as straight-chain or
branched pentenoic acid, straight-chain or branched hexenoic acid,
straight-chain or branched heptenoic acid, straight-chain or branched
octenoic acid, straight-chain or branched nonenoic acid, straight-chain
or branched decenoic acid, straight-chain or branched undecenoic acid,
15 straight-chain or branched dodecenoic acid, straight-chain or branched
tridecenoic acid, straight-chain or branched tetradecenoic acid,
straight-chain or branched pentadecenoic acid, straight-chain or
branched hexadecenoic acid, straight-chain or branched heptadecenoic
acid, and straight-chain or branched octadecenoic acid.
20 [0039] The number of carbon atoms of the constituent fatty acid of the
ester additive is 5 to 18, preferably 5 to 12, and more preferably 6 to 9.
When the number of carbon atoms of the constituent fatty acid is less
than 5, an antiwear property improving effect is insufficient, and when
it exceeds 18, solubility into a base oil at low temperature is decreased.
25 [0040J The ester additive can be obtained by a deliydration
condensation reaction of pentaerythritol and/or dipentaerythritol and
one selected fiom the fatty acids having 5 to 18 carbon atoms. It is to
be noted that although a small amount of partial esters generated in
producing the ester additive may be contained as an impurity, the acid
value of the ester additive is preferably 0.1 mgKOWg or less and the
5 hydroxyl value thereof is preferably 10 mgKOWg or less.
to 15 mass%, and more preferably 2 to 7 mass% based on the total
amount of the refrigerating machine oil composition. When the
content of the ester additive is less than 2 mass% or exceeds 20 mass%,
10 an antiwear property improving effect becomes insufficient. The
content can be appropriately selected within the range depending on the
kind of a base oil, the kinematic viscosity and the like.
[0042] Moreover, the base oil in the first embodiment is an ester other
than the above-described ester additive. Esters can be obtained by a
15 dehydration condensation reaction of alcohols and fatty acids, and in
the present embodiment, in terms of cliemical stability, examples of a
preferred base oil component include diesters of dibasic acids and
monohydric alcohols, polyol esters of polyols (in particular, neopentyl
polyols) and fatty acids, and complex esters of polyols, polybasic acids,
20 and monohydric alcohols (or fatty acids). Among them, polyol esters
which excel in stability are preferable.
[0043] Furthermore, among the polyol esters, an ester synthesized
from pentaerythritol, a carboxylic acid having 4 to 7 carbon atoms, and
3,5,5-trimethylhexanoic acid is preferable because a lubricating
25 property improving eKect due to biennding of the ester additive is large,
and a polyol ester in which the carboxylic acid having 4 to 7 carbon
atoms is a branched butanoic acid is more preferable. Furthermore,
the kinematic viscosity of the polyol ester of pentaerythritol, a
branched butanoic acid, and 3,5,5-trimethylhexanoic acid at 40°C is
preferably 30 to 110 mm2/s.
5 [0044] Moreover, as the base oil according to the present embodiment,
of fatty acids having 4 to 6 carbon atoms and branched fatty acids
having 7 to 9 carbon atoms in the above-described fatty acids is 15:85
to 90:10, the above-described fatty acids having 4 to 6 carbon atoms
10 contain 2-methylpropanoic acid, and the ratio of the sum of the fatty
acids having 4 to 6 carbon atoms and the branched fatty acids having 7
to 9 carbon atoms to the total amount of the fatty acids which constitute
the above-described ester is 20 mol% or more, (hereinafter referred to
as "polyhydric alcohol fatty acid ester (A)") can be preferably used.
15 [0045] It is to be noted that although the polyhydric alcohol fatty acid
ester (A) includes complete esters in which all of hydroxyl groups in
polyhydric alcohols are esterified, partial esters in which a part of
hydroxyl groups in polyhydric alcohols remains unesterified, and a
mixture of complete esters and partial esters, the hydroxyl value of the
20 polyhydric alcohol fatty acid ester (A) is preferably 10 mgKOWg or
less, hrther preferably 5 mgKOWg or less, and the most preferably 3
mgKOWg or less.
[0046] In the fatty acids which constitute the polyhydric alcohol fatty
acid ester (A), the molar ratio of the fatty acids having 4 to 6 carbon
25 atoms and the branched ratty acids having 7 to 9 carbon atoms is 15:85
to 90:10, preferably 15:85 to 85:15, more preferably 2030 to 80:20,
further preferably 25:75 to 75:25, and the most preferably 30:70 to
70:30. Moreover, the ratio of the sum of the fatty acids having 4 to 6
carbon atoms and the branched fatty acids having 7 to 9 carbon atoms
to the total amount of the fatty acids which constitute the polyhydric
alcohol fatty acid ester (A) is 20 mol% or more. In the case of not
composition, it becomes difficult to achieve both sufficient
compatibility with a refrigerant (in particular, difluoromethane
refrigerant) and necessary viscosity as a refrigerating machine oil in a
high level. It is to be noted that the ratio of the fatty acids herein is a
value based on the total amount of the fatty acids which constitute the
polyhydric alcohol fatty acid ester (A) contained in a refrigerating
machine oil.
[0047] Specifically, examples of the fatty acids having 4 to 6 carbon
atoms include 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 acid, and hexanoic
acid. Among them, one having a branch in an alkyl skeleton, such as
2-methylpropanoic acid, is preferable.
[0048] Specifically, examples of the branched fatty acids having 7 to 9
carbon atoms include 2-methylhexanoic acid, 3-methylhexanoic acid,
4-methylhexanoic acid, 5-methylhexanoic acid, 2,2-dimethylpentanoic
acid, 2,3-dimethylpenbnlatloic acid, 2,4-dimethylpei~tanoic acid,
3,3-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-methylbutanoica cid, 1-ethyl-2-methylbutanoic acid,octanoic
acid, 2-ethylhexanoic acid, 3-ethylhexanoic acid, 3,5-dimethylhexanoic
5 acid, 2,4-dimethylhexanoic acid, 3,4-dimethylhexanoic acid,
2-methylheptanoic acid, 3-methylheptanoic acid, 4-methylheptanoic
acid, 5-methylheptanoic acid, 6-methylheptanoic acid,
2-propylpentanoic acid, nonanoic acid, 2,2-dimethylheptanoic acid,
10 2-methyloctanoic acid, 2-ethylheptanoic acid, 3-methyloctanoic acid,
3,5,5-trimethylhexanoic acid, 2-ethyl-2,3,3-trimethylbutyric acid,
2,2,4,4-tetramethylpentanoic acid, 2,2,3,3-tetramethylpentanoic acid,
2,2,3,4-tetramethylpentanoic acid, and 2,2-diisopropylpropanoic acid.
[0049] The polyhydric alcohol fatty acid ester (A) has the molar ratio
15 of the fatty acids having 4 to 6 carbon atoms and the branched fatty
acids having 7 to 9 carbon atoms of 15:85 to 90:10, and may contain
fatty acids other than the fatty acids having 4 to 6 carbon atoms and the
branched fatty acids having 7 to 9 carbon atoms as a constituent acid
component as long as the fatty acids having 4 to 6 carbon atoms
20 contain 2-methylpropanoic acid.
[0050] Specifically, examples of the fatty acids other than the fatty
acids having 4 to 6 carbon atoms and the branched fatty acids having 7
to 9 carbon atoms include fatty acids having 2 or 3 carbon atoms, such
as acetic acid and propionic acid; straight-chain fatty acids having 7 to
25 9 carbon atoms, such as heptanoic acid, ocianoic acid, and nonanoic:
acid; and fatty acids having 10 to 20 carbon atoms, 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.
[0051] In the case where the fatty acids having 4 to 6 carbon atoms and
5 the branched fatty acids having 7 to 9 carbon atoms, and fatty acids
sum of the fatty acids having 4 to 6 carbon atoms and the branched
fatty acids having 7 to 9 carbon atoms to the total amount of the fatty
acids which constitute the polyhydric alcohol fatty acid ester (A) is
10 required to be 20 mol% or more, preferably 25 mol% or more, more
preferably 30 mol% or more, and hrthermore, more preferably 80
mol% or more. Due to this ratio of 20 mol% or more, compatibility
with a refrigerant (in particular, difluoromethane refrigerant) becomes
sufficient.
15 LO0521 Among the polyhydric alcohol fatty acid ester (A), one in which
an acid constituent component consists of only 2-methylpropanoic acid
and 3,5,5-triniethylhexanoic acid is particularly preferable in terms of
achieving both ensuring of necessary viscosity and compatibility with a
refrigerant (in particular, difluoromethane refrigerant).
20 [0053] The polyhydric alcohol fatty acid ester (A) according to the
present embodiment may be a mixture of two or more esters having
different molecular structures, and in such a case, an individual
molecule is not necessary to satisfy the above-described conditions as
long as fatty acids as a whole which constitute pentaerythritol fatty acid
25 esters contained in the refrigerating nlaci~ine oil satisfy the
above-described conditions.
[0054] As described above, the polyhydric alcohol fatty acid ester (A)
requires the fatty acids having 4 to 6 carbon atoms and the branched
fatty acids having 7 to 9 carbon atoms as an acid component which
constitutes the ester, and contains other fatty acids as a constituent
5 component if necessary. That is, although the polyhydric alcohol fatty
component, or three or more fatty acids having different structures as
an acid constituent component, it is preferable that the polyhydric
alcohol fatty acid ester contain, as an acid constituent component, only
10 fatty acids in which a carbon atom adjacent to carbonyl carbon
(a-position carbon atom) is not quaternary carbon. In the case where
a fatty acid in which an a-position carbon atom is quaternary carbon is
contained in the fatty acids which constitute the polyhydric alcohol
fatty acid ester, a lubricating property in the presence of a
15 difluoromethane refrigerant tends to be insufficient.
[0055] Moreover, as polyhydric alcohols which constitute the
polyhydric alcohol fatty acid ester (A), polyhydric alcohols having 2 to
6 hydroxyl groups are preferably used.
[0056] Specifically, examples of dihydric alcohols (diols) include
20 ethylene glycol, 1,3-propanediol, propylene glycol, 1,4-butanediol,
1,2-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl
glycol, 1,6-hexanediol, 2-ethyl-2-methyl-l,3-propanediol,
1,7-heptanediol, 2-methyl-2-propyl-l,3-propanediol,
2,2-diethyl-1,3-propanediol, 1,8-octanediol, 1,9-nonanediol,
25 I,lO-decanedioi, I,I I-undecanediol, and i,i2-dodecanedloi.
Moreover, specifically, examples of trivalent or more alcohols include
polyhydric alcohols, such as trimethylolethane, trimethylolpropane,
trimethylolbutane, di-(trimethylolpropane), tri-(trimethylolpropane),
pentaerythritol, di-(pentaerythritol), tri-(pentaerythritol), glycerin,
polyglycerin (dimer to trimer of glycerin), 1,3,5-pentanetriol, sorbitol,
5 sorbitan, sorbitol-glycerin condensate, adonitol, arabitol, xylitol, and
fructose, galactose, mannose, sorbose, and cellobiose; and partially
etherified products thereof. Among them, because of having higher
hydrolytic stability, esters of hindered alcohols, such as neopentyl
10 glycol, trimethylolethane, trimethylolpropane, trimethylolbutane,
di-(trimethylolpropane), tri-(trimethylolpropane), pentaerythritol,
di-(pentaerythritol), and tri-(pentaerythritol) are more preferable, esters
of neopentyl glycol, tiimethylolethane, trimethylolpropane,
trimethylolbutane, pentaerythritol, and di-(pentaerythritol) are further
15 more preferable, neopentyl glycol, trimethylolpropane, pentaerythritol,
and di-(pentaerythritol) are further preferable, and because of having
particularly higher compatibility with a refrigerant and hydrolytic
stability, pentaer&ritol, di-(pentaerythritol), or a mixed ester of
pentaerythritol and di-(pentaerythritol) is the most preferable.
20 [0057] Preferred examples of the constituent fatty acid of the
polyhydric alcohol fatty acid ester (A) include as follows:
(i) a combination of 1 to 13 kinds selected from butanoic acid,
2-methylpropanoic acid, pentanoic acid, 2-methylbutanoic acid,
3-methylbutanoic acid, 2,2-dimethylpropanoic acid, 2-methylpentanoic
25 acid, 3-methyipenianoic acid, 4-meihylpc~itanuic. acid,
2,2-dimethylbutanoic acid, 2,3-dimethylbutanoic acid,
3,3-dimethylbutanoic acid, and hexanoic acid, and 1 to 13 kinds
selected from 2-methylhexanoic acid, 3-methylhexanoic acid,
4-methylhexanoic acid, 5-methylhexanoic acid, 2,2-dimethylpentanoic
acid, 2,3-dimethylpentanoic acid, 2,4-dimethylpentanoic acid,
5 3,3-dimethylpentanoic acid, 3,4-dimethylpentanoic acid,
acid, and 2-ethyl-3-methylbutanoic acid;
(ii) a combination of 1 to 13 kinds selected fiom butanoic acid,
2-methylpropanoic acid, pentanoic acid, 2-methylbutanoic acid,
10 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 kinds
selected from 2-methylheptanoic acid, 3-methylheptanoic acid,
15 4-methylheptanoic acid, 5-methylheptanoic acid, 6-methylheptanoic
acid, 2,2-dimethylhexanoic acid, 3,3-dimethylhexanoic acid,
4,4-dimethylhexanoic acid, 5,5-dimethylhexanoic acid,
2,3-dimethylhexanoic acid, 2,4-dimethylhexanoic acid,
2,5-dimethylhexanoic acid, 3,4-dimethylhexanoic acid,
20 3,s-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 acid, 3-ethylhexanoic acid, 2-propylpentanoic acid,
2-methyl-2-ethylpentanoic acid, 2-methyl-3-ethylpentanoic acid, and
25 3-methyl-3-ethyipentanoic acid; and
(iii) a combination of 1 to 13 kinds selected fiom 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,
5 3,3-dimethylbutanoic acid, and hexanoic acid, and 1 to 50 kinds
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,
10 5,s-dimethylheptanoic acid, 6,6-dimethylheptanoic acid,
2,3-dimethylheptanoic acid, 2,4-dimethylheptanoic acid,
2,5-dimethylheptanoic acid, 2,6-dimethylheptanoic acid,
3,4-dimethylheptanoic acid, 3,s-dimethylheptanoic acid,
3,6-dimethylheptanoic acid, 4,s-dimethylheptanoic acid,
15 4,6-dimethylheptanoic acid, 2-ethylheptanoic acid, 3-ethylheptanoic
acid, 4-ethylheptanoic acid, 5-ethylheptanoic acid, 2-propylhexanoic
acid, 3-propylhexanoic acid, 2-butylpentanoic acid,
2,2,3-trimethylhexanoic acid, 2,2,4-trimethylhexanoic acid,
2,2,5-trimethylhexanoic acid, 2,3,3-trimethylhexanoic acid,
20 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-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,
25 2,3,4,4-tetramethylpentanoic acid, 3,3,4,4-tetramethylpenianoic 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-trimethylbutyrica cid, and 2,2-diisopropylpropionic acid.
[0058] More preferred examples of the acid constituent component
which constitutes the polyhydric alcohol fatty acid ester (A) include as
follows:
selected from 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, and 2-ethyl-3-methylbutanoic acid;
(ii) a combination of 2-methylpropanoic acid and 1 to 25 kinds
selected from 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-dimethylhexanoic acid, 5,5-dimethylhexanoic acid,
2,3-dimethylhexanoic acid, 2,4-dimethylhexanoic acid,
2,5-dimethylhexanoic acid, 3,4-dimethylhexanoic acid,
33-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 acid, 3-ethylhexanoic acid, 2-propylpentanoic acid,
2-methyl-2-ethylpentanoic acid, 2-methyl-3-ethylpentanoic acid, and
3-meihyi-3-eihyipentanoic acid; and
(iii) a combination of 2-methylpropanoic acid and 1 to 50 kinds
selected from 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 5,5-dimethylheptanoic acid, 6,6-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,
10 4,6-dimethylheptanoic acid, 2-ethylheptanoic acid, 3-ethylheptanoic
acid, 4-ethylheptanoic acid, 5-ethylheptanoic acid, 2-propylhexanoic
acid, 3-propylhexanoic acid, 2-butylpentanoic acid,
2,2,3-trimethylhexanoic acid, 2,2,4-trimethylhexanoic acid,
2,2,5-trimethylhexanoic acid, 2,3,3-trimethylhexanoic acid,
15 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-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,
20 2,3,4,4-tetramethylpentanoic 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-trimethylbutyrica cid, and 2,2-diisopropylpropionic acid.
[0059] The content of the polyhydric alcohol fatty acid ester (A) is 50
25 mass% or more, preferabiy 60 mass% or more, more preferabiy 70
mass% or more, and further preferably 75 mass% or more based on the
total amount of the refrigerating machine oil. It is to be noted that the
refrigerating machine oil composition according to the present
embodiment may contain the polyhydric alcohol fatty acid ester (A)
and other esters as a base oil, and may also hrther contain additives
5 other than the ester additive, which will be described below, but when
impossible to achieve both necessary viscosity and compatibility in a
high level at the same time.
[0060] In the case where the refrigerating machine oil composition
10 according to the present embodiment contains the polyhydric alcohol
fatty acid ester (A) as a base oil, only the polyhydric alcohol fatty acid
ester (A) may be used alone (that is, the content of the polyhydric
alcohol fatty acid ester (A) is 100 mass% based on the total amount of
the base oil), and in addition to this, to a degree not impairing its
15 excellent performance, other esters other than the polyhydric alcohol
fatty acid ester (A) may be further contained as a base oil. Examples
of the base oil other than the polyhydric alcohol fatty acid ester (A)
include polyol esters, complex esters, and alicyclic dicarboxylic acid
esters other than the ester additive and the polyhydric alcohol fatty acid
20 ester (A).
[0061] Examples of the polyol esters other than the polyhydric alcohol
fatty acid ester (A) include esters of polyhydric alcohols, such as
neopentyl glycol, trimethylolethane, trimethylolpropane,
trimethylolbutane, pentaerythritol, and dipentaerythritol, and fatty
25 acids, and esters of neopentyl glycol and Iaity acids, esters of
pentaerythritol and fatty acids, and esters of dipentaerythritol and fatty
acids are particularly preferable.
[0062] As neopentyl glycol esters, esters of neopentyl glycol and fatty
acids having 5 to 9 carbon atoms are preferable. Specifically,
examples of these neopentyl glycol esters include neopentyl glycol
5 di-3,5,5-trimcthylhexanoate, neopentyl glycol di-2-ethylhexanoate,
di-2-ethylpentanoate, an ester of neopentyl glycol and
2-methylhexanoic acid/2-ethylpentanoic acid, an ester of neopentyl
glycol and 3-methylhexanoic acids-methylhexanoic acid, an ester of
10 neopentyl glycol and 2-methylhexanoic acid2-ethylhexanoic acid, an
ester of neopentyl glycol and 3,5-dimethylhexanoic
acid4,5-dimethylhexanoic acid/3,4-dimethylhexanoic acid, neopentyl
glycol dipentanoate, neopentyl glycol di-2-ethylbutanoate, neopentyl
glycol di-2-methylpentanoate, neopentyl glycol di-2-methylbutanoate,
15 and neopentyl glycol di-3-methylbutanoate.
[0063] As pentaerythritol esters, esters of pentaerythritol and a mixed
fatty acid of two or more selected from fatty acids having 5 to 9 carbon
atoms are preferable. Specifically, examples of these pentaerythritol
esters include esters of pentaerythritol and two or more fatty acids
20 selected from 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.
[0064] As dipentaerythritol esters, esters of dipentaerythritol and a
25 mixed fatty acid of two or more selected from fatty acids having 5 to 9
carbon atoms are preferable. Specifically, examples of these
dipentaerythritol esters include esters of dipentaerythritol and two or
more fatty acids selected from pentanoic acid, 2-methylbutanoic acid,
3-methylbutanoic acid, hexanoic acid, 2-methylpentanoic acid,
2-ethylbutanoic acid, 2-ethylpentanoic acid, 2-methylhexanoic acid,
5 3,5,5-trimethylhexanoic acid, and 2-ethylhexanoic acid.
according to the present embodiment contains esters other than the
ester additive and the polyhydric alcohol fatty acid ester (A), although
there is no particular limitation of the content of oxygen-containing
10 synthetic oils other than the polyhydric alcohol fatty acid ester (A) as
long as excellent lubricating property and compatibility of the
refrigerating machine oil according to the present embodiment are not
impaired, the content of the polyol esters other than the ester additive
and the polyhydric alcohol fatty acid ester (A) is preferably less than 50
15 mass%, more preferably 45 mass% or less, further preferably 40
mass% or less, further more preferably 35 mass% or less, much more
preferably 30 mass% or less, and the most preferably 25 mass% or less
based on the total amount of the reeigerating machine oil; and in the
case where esters other than the polyol esters are blended as a base oil,
20 the content thereof is preferably less than 50 mass%, more preferably
40 mass% or less, and further preferably 30 mass% or less based on the
total amount of the refrigerating machine oil. If the content of the
polyol esters and other esters other than the pentaerythritol fatty acid
esters is too much, it becomes difficult to obtain the effect by the use of
25 the ester additive and the poiyhydric aicohoi Catty acid ester (A).
[0066] It is to be noted that the polyol esters other than the polyhydric
alcohol fatty acid ester (A) may be partial esters in which a part of
hydroxyl groups in polyhydric alcohols are not esterified and remains
as hydroxyl groups, complete esters in which all of hydroxyl groups are
esterified, or a mixture of partial esters and complete esters, and it is
5 preferable that the hydroxyl value be preferably 10 mgKOWg or less,
mgKOWg or less.
[0067] Moreover, in the case where the refrigerating machine oil
according to the present embodiment contains the polyol esters other
10 than the polyhydric alcohol fatty acid ester (A), as the polyol esters,
one consisting of one polyol ester having a single structure may be
contained, or a mixture of two or more polyol esters having different
structures may be contained.
[0068] Moreover, the polyol esters other than the polyhydric alcohol
15 fatty acid ester (A) may be any of esters of one fatty acid and one
polyhydric alcohol, esters of two or more fatty acids and one
polyhydric alcohol, esters of one fatty acid and two or more polyhydric
alcohols, and esters of two or more fatty acids and two or more
polyhydric alcohols, as long as they have different structures from the
20 ester additive and the polyhydric alcohol fatty acid ester.
[0069] Moreover, the refrigerating machine oil composition according
to the present embodiment may further contain various additives
described below.
[0070] The refrigerating machine oil composition according to the
25 present embodiment can further contain phosphates. The phosphates
in themselves have a function as an antiwear additive, and by using the
above-described ester additive and the phosphates in combination, an
antiwear property of the refiigerating machine oil composition can be
remarkably improved.
[0071] Examples of preferred phosphates include triphenyl phosphate
5 (TPP), tricresyl phosphate (TCP), and alkylphenyl phosphates (APP)
AE'P, a mixture of one having one alkylphenyl group (mono-type), one
having two alkylphenyl groups (di-type), and one having three
alkylphenyl groups (tri-type) can be used, and the mixing ratio thereof
10 is not particularly limited.
[0072] The content of the phosphates is, in terms of further antiwear
property improving effect and stability, preferably 0.1 to 3 mass%, and
more preferably 0.2 to 2 mass% based on the total amount of the
refrigerating machine oil composition.
15 [0073] Moreover, the refrigerating machine oil composition according
to the present embodiment can further contain sulfide compounds.
The sulfide compounds in themselves have a hnction as an antiwear
additive, and by using the above-described ester additive and the
sulfide compounds in combination, an antiwear property of the
20 refrigerating machine oil composition can be remarkably improved.
[0074] As the sulfide compounds, monosulfide compounds are
preferable. This is because, sulfur compounds having high activity,
such as disulfide compounds, deteriorate stability of the refrigerating
machine oil and change quality of copper commonly used inside of
25 refiigeraiing equipment.
[0075] As the sulfide compounds, in particular, thiobisphenol
compounds, which have antioxidant, that is, radical scavenging
capacity and are also a stabilizer, are preferable.
[0076] The content of the sulfide compounds is preferably 0.05 to 2
mass%, and more preferably 0.1 to 1 mass% based on the total amount
5 of the refrigerating machine oil composition. When the content of the
to obtain a further antiwear property improving effect due to the
blending of the sulfide compounds, and when it exceeds 2 mass%,
corrosive wear may occur depending on the atmosphere used.
10 [0077] Furthermore, in the present embodiment, the phosphates and
the sulfide compounds may be used in combination.
[0078] Moreover, in order to hrther improve performance, the
refrigerating machine oil composition according to the present
embodiment can contain additives which are conventionally used for a
15 lubricant oil, such as an antioxidant, a friction modifier, a wear
inhibitor, an extreme pressure agent, a rust-preventive agent, a nietal
deactivator, and an antifoamer, within a range not impairing the object
of the present invention.
[0079] Examples of the antioxidant include phenol compounds such as
20 di-tert-butyl-p-cresol and amine compounds such as
alkyldiphenylamines, examples of the friction modifier include
aliphatic amines, aliphatic amides, aliphatic imides, alcohols, esters,
amine salts of acid phosphate, and amine salts of phosphite, examples
of the wear inhibitor include zinc dialkyldithiophosphates, examples of
25 the extreme pressure agent include sulfurized oiefins and sulruri~edfa ts
and oils, examples of the rust-preventive agent include alkenyl succinic
acid esters and partial esters, examples of the metal deactivator include
benzotriazoles, and examples of the antifoamer include silicone
compounds and polyester compounds.
[0080] The kinematic viscosity of the refrigerating machine oil
5 composition according to the prescnt embodiment at 40°C is 3 to 500
mm2/s. Moreover, the viscosity index of the refrigerating machine oil
composition is preferably 10 or more. It is to be noted that the
kinematic viscosity at 40°C and the viscosity index in the present
10 invention mean values measured in conformity with JIS K2283.
[0081] Although other properties are not particularly limited, the pour
point of the refrigerating machine oil composition is preferably -10°C
or less, and more preferably -20°C or less. Moreover, the flash point
of the refrigerating machine oil composition is preferably 120°C or
15 more, and more preferably 200°C or more. It is to be noted that the
pour point can be measured in conformity with JIS K2269 "Testing
Methods for Pour Point and Cloud Point of Crude Oil and Petroleum
Products", and furthermore, the flash point can be measured in
conformity with Testing Method for Flash Point by Tag closed cup
20 method of JIS K2265 "Crude Oil and Petroleum Products-Testing
Method for Flash Point".
[0082] Moreover, the acid value of the refrigerating machine oil
composition is not particularly limited, but can be preferably 0.1
mgKOWg or less, and more preferably 0.05 mgKOWg or less so as to
25 prevent colrosion of metais used for refrigerating machines or piping
and suppress deterioration of the refkigerating machine oil itself. It is
to be noted that the acid value in the present invention means an acid
value measured in conformity with JIS K2501 "Petroleum products and
lubricants-Determination of neutralization number".
[0083] Moreover, the water content of the refrigerating machine oil
5 composition is not particularly limited, but is preferably 200 ppm or
or less. In particular, in the case of being used for sealed refrigerating
machines, from the viewpoint of stability and an electrical insulation
property of the refiigerating machine oil, the water content is required
10 to be small.
[0084] The refiigerating machine oil composition according to the
present embodiment can be obtained by blending the above-described
ester additive into the base oil that is an ester other than the ester
additive such that the content of the ester additive is 2 to 20 mass%
15 based on the total amount of the refrigerating machine oil composition
and the kinematic viscosity of the obtained refrigerating machine oil
composition at 40°C is 3 to 500 mm2/s. It is to be noted that, in the
case where the refrigerating machine oil composition contains
components other than the ester additive and the base oil (the
20 above-described phosphates, the sulfide compounds and the like), the
blending of these components into the base oil may be the same time as
the ester additive, and may be before blending or after blending of the
ester additive.
[0085] A refrigerant used together with the refrigerating machine oil
25 composition according to the present embodiment is not particularly
limited, but a refrigerant that is compatible with the refrigerating
machine oil composition, that is, a refrigerant that is compatible with
the refrigerating machine oil composition without being separated into
two layers at ordinary temperature is preferable. Furthermore, the
refrigerating machine oil composition according to the present
5 embodiment can achieve an excellent antiwear property under severe
conventional refrigerating machine oil, and is useful when being used
together with hydrofluoroolefins (HFO) such as
2,3,3,3-tetrafluoropropene (HFO-1234~0, low GWP refrigerants such
10 as difluoromethane (R32), or hydrocarbon refrigerants such as
isobutane (R600a) and propane (R290). A working fluid composition
for refrigerating machines using these refrigerants will be described in
detail in a second embodiment described below.
[0086] [Second Embodiment: Working Fluid Composition for
15 Refrigerating machines]
The working fluid composition for refrigerating machines
according to the second embodiment of the present invention contains
the refrigerating machine oil composition according to the
above-described first embodiment, and a refrigerant which contains at
20 least one selected from hydrofluorocarbons, hydrofluoroolefms, and
hydrocarbons, and whose global warming potential (GWP) is 700 or
less. It is to be noted that a refrigerating machine oil composition in
the present embodiment is the same as the case of the above-described
first embodiment, and thus, an overlapped description is omitted here.
25 [0087] Examples of hydrofluorocarbons (EFC) having a GWP of 700
or less include R32 and a mixed refrigerant containing a large amount
of R32 (R410A and the like), which are hydrofluorocarbons (HFC)
having a low boiling point and high pressure. Since these HFC
refrigerants have a feature of having a high boiling point and high
pressure, and the compressor discharge temperature when using them
5 becomes high, an oil film becomes thin, thereby resulting in severe
refrigerating machine oil, an antiwear property becomes insufficient.
In contrast, according to the present embodiment, even in the case of
using the above-described HFC refkigerants, an excellent antiwear
10 property can be achieved.
[0088] Moreover, examples of hydrofluoroolefins (HFO) having a
GWP of 700 or less include 2,3,3,3-tetrafluoropropene (HFO-1234~0,
1,3,3,3-tetrafluoropropene (HFO-1234ze), and
1,2,3,3,3-pentafluoropropene (HFO-1225ye). These HFO refrigerants
15 have, in a molecule, an olefinic structure that is easy to be decomposed,
and thus, have a feature of a low GWP but low stability. In particular,
under severe lubrication conditions, local heating at a sliding part due
to metaumetal contact facilitates decomposition of the refrigerant as
well as wear. Thus, in the case of using a conventional refrigerating
20 machine oil, a working fluid in which a refrigerant is compatible with a
refrigerating machine oil may deteriorate. In contrast, according to
the present embodiment, even in the case of using the above-described
HFO refrigerants, an excellent antiwear property can be achieved
without impairing stability of the working fluid composition for
25 refrigerating machines.
[0089] Moreover, examples of hydrocarbon refrigerants having a GWP
of 700 or less include saturated hydrocarbons having 3 to 6 carbon
atoms, in particular, isobutane (R600a) and propane (R290). These
hydrocarbon refrigerants do not contain, in a hydrocarbon molecule,
fluorine that contributes to the improvement of a lubricating property
severe lubrication conditions. Thus, in the case of using a
conventional refrigerating machine oil, an antiwear property becomes
insufficient. In contrast, according to the present embodiment, even
10 in the case of using the above-described hydrocarbon refrigerants, an
excellent antiwear property can be achieved.
Examples
[0090] Hereinafter, the present invention will be described in detail
with reference to Examples and Comparative Examples, but the present
15 invention is not limited to the following Examples.
[0091] [Examples 1 to 12, Comparative Examples 1 to 121
In Examples 1 to 12 and Comparative Examples 1 to 12,
refrigerating machine oil compositions having compositions shown in
Tables 1 to 3 were prepared, respectively, using base oils and additives
20 shown below.
[0092] (A) Ester Base Oils
(A-1) POE-1: ester of pentaerythritol and a mixed acid of
2-methylpropanoic acid and 3,5,5-trimethylhexanoic acid at the mass
ratio of 7:3 (kinematic viscosity at 40°C: 34.4 rnm2/s, viscosity index:
25 77)
(A-2) POE-2: ester of pentaelythritol and a mixed acid of
2-methylpropanoic acid and 2-ethylhexanoic acid at the mass ratio of
3:7 (kinematic viscosity at 40°C: 36.7 rnm2/s, viscosity index: 78)
(A-3) POE-3: ester of dipentaerythritol and a mixed acid of
n-butanoic acid and 3,5,5-trimethylhexanoic acid at the mass ratio of
5 7:3 (kinematic viscosity at 40°C: 65.1 mm2/s, viscosity index: 90)
n-pentanoic acid, n-heptanoic acid, and 3,5,5-trimethylhexanoic acid at
the mass ratio of 4:4:2 (kinematic viscosity at 40°C: 28.5 mm2/s,
viscosity index: 133)
10 (A-5) POE-5: ester of trimethylolpropane and oleic acid
(kinematic viscosity at 40°C: 48.3 mm2/s, viscosity index: 176)
[0093] (B) Ester Additives
(B-I) PE2EH: pentaerythritoltetra(2-ethylhexanoate) (tetraester
of pentaerythritol and 2-ethylhexanoic acid, acid value: 0.01
15 mgKOH/g, hydroxyl value: 1 mgKOWg)
(B-2) DPEH: dipentaerythritolhexa(hexanoate) (hexaester of
dipentaerythritol and n-hexanoic acid, acid value: 0.01 mgKOWg,
hydroxyl value: 1 mgKOWg)
[0094] (C) Other Additives
20 (C-1) tricresyl phosphate (TCP)
(C-2) triphenyl phosphate (TPP)
(C-3) tridecyl phosphate (TDP)
(C-4) dibenzyl sulfide
(C-5) didodecyl sulfide
25 (C-6) 4,4'-thiobis(3-methyl-6-tert-butyiphenoi)
[0095] Next, the following evaluation tests were carried out by
combining the refrigerating machine oil compositions of Examples 1 to
12 and Comparative Examples 1 to 12 with refrigerants shown in
Tables 1 to 3, respectively.
[0096] (Lubricating Property Test)
5 In a lubricating property test, a high-pressure atmosphere
and fixed disk material) manufactured by Shinko Engineering Co.,
Ltd., which can provide a refrigerant atmosphere similar to an actual
compressor, was used. Basic test conditions were oil quantity: 600
10 ml, test temperature: llO°C, rotation frequency: 500 rpm, applied load:
100 kgf, and test time: 1 hour, SKH-51 was used as the vane material,
and FC250 was used as the disk material.
The test was carried out under the following four test conditions
depending on the kind of a refrigerant.
15 Lubricating Property Test-(1): R32 was used as a refrigerant,
and the pressure in the test vessel was made to be 3.1 MPa.
Lubricating Property Test-(2): HFO-1234yf (abbreviated to yf
in Tables) was used as a refrigerant, and the pressure in the test vessel
was made to be 1.6 MPa.
20 Lubricating Property Test-(3): R410A (R32/R125=1/1 at mass
ratio) was used as a refrigerant, and the pressure in the test vessel was
made to be 3.1 MPa.
Lubricating Property Test-(4): The test was carried out by
blending 20% of n-hexane (abbreviated to n-C6 in Tables) at the
25 volume ratio with respect to rhe refrigerating maciline oil conlposition
(used as an alternative to hydrocarbon refrigerants such as R290).
The pressure became slightly higher than normal pressure.
It is to be noted that evaluation of an antiwear property was
carried out based on the wear loss of the vane material, because the
wear loss of the disk material was extremely small. The obtained
5 results are shown in Tables 1 to 3.
90 g of a sample oil whose water content was adjusted to 100
ppm was weighed in an autoclave, a catalyst (iron, copper, and
aluminum wire, all having outer diameter of 1.6 mmx50 mm) and 10 g
10 of each refrigerant (R32, HFO-1234yf, R410A, or n-hexane was used)
were sealed therein, and then, it was heated to 175OC, and the
appearance and the acid value of the sample oil after 100 hours were
measured (JIS C2101). The obtained results are shown in Tables 1 to
3.
15 It is to be noted that all acid values of the sample oils before the
stability test (new oils) were 0.01 mgKOWg.

[0099] [Table 21
Example 6
(mass%)
C-5
C-6
Appearance
Test
Test Condition
Vane Wear Loss (mg)
Thermal Stability Test
( Acid Vdue (mgKOWg) ( 0.01
(1)
2.1
No
Precipitation
0.03
Example 7
No
Precipitation
0.01
Example 8
No
Precipitation
0.01
Example 9
No
Precipitation
0.01
Example 10 1 Example 11 I Example 12
No 1 No 1 No 1 Precipitatinr Precipitation Precipitation

[0101] Regarding stability, as can be seen from Tables 1 to 3, while
there is a slight increase in the acid value in combination with
HFO-1234yf, the examples and the comparative examples were at
problem-free levels.
5 [0102] Regarding a lubricating property, according to the results shown
3 I . ' ' .. 1, 7,? 9 2, .I... .,..;. . !,~..;.. .,:. < , . . ~ <.., u. ,i-iii., i, 1 ,ti " I ) ii*" ;iri. '"00 v v u O .S.&.,.ELWLL J
compared to Comparative Examples 1 to 4, and it is found that an
antiwear effect is large.
Moreover, according to the results shown in Tables 2 and 3, in
10 Examples 5 to 12, it is found that the response of an antiwear property
improving effect by the additive is drastically improved by using the
additives (B-l), (B-2), and (C-1) to (C-6) in combination. Moreover,
according to a comparison between Example 5 and Comparative
Examples 5, 7, 8, it is found that the response for increasing the
15 addition effect is decreased when the content of the ester additive
according to the present invention is too little or too much.
Industrial Applicability
[0103] The refrigerating machine oil composition of the present
invention is a refrigerating machine oil that can maintain an antiwear
20 effect and excels in long-time reliability even under severe lubrication
conditions, and thus, can be suitably used in a
refiigerationlair-conditioning system having high cooling efficiency, in
which a compressor, a condenser, a throttle device, an evaporator and
the like are included and a refrigerant is made to circulate
25 therebetween, in particular, in a system having a rotary-type,
swing-type, or scroll-type compressor, and can be used in the field of
room air-conditioners, packaged air conditioners, cold storage
chambers, car air-conditioners, industrial refrigerating machines and
the like.

CLAIMS
1. A refrigerating machine oil composition comprising:
at least one ester additive selected from tetraesters of
5 pentaerythritol and one selected from fatty acids having 5 to 18 carbon
,- ,, , . . , , . . , , . , . ! . . .'..? . . . . .... ?...;?..' , t i" " ' ' .l-i..li- iiL U-?li.l.'.&;?'d.. '- ".ii & _,-!LC. .J,,
acids having 5 to 18 carbon atoms; and
a base oil that is an ester ot'her than the ester additive,
wherein a content of the ester additive is 2 to 20 mass% based
10 on a total amount of the refrigerating machine oil composition, and
wherein a kinematic viscosity of the refrigerating machine oil
composition at 40°C is 3 to 500 rnm2/s.
2. The refrigerating machine oil composition according to claim 1,
wherein the ester additive is at least one selected from
15 pentaerythritoltetra(2-ethylhexanoate) and
dipentaerythritolhexa(hexanoate).
3. The refrigerating machine oil composition according to claim 1
or 2, wherein the kinematic viscosity at 40°C is 3 to 300 mrn2/s.
4. The refrigerating machine oil composition according to any one
20 of claims 1 to 3, wherein the base oil is a polyol ester.
5. The refrigerating machine oil composition according to any one
of claims 1 to 4, wherein the base oil is a polyol ester obtained from
pentaerythritol and a mixed acid of a carboxylic acid having 4 to 7
carbon atoms and 3,5,5-trimethylhexanoic acid.
25 6. The refrigerating machine oil composition according to any one
of claims 1 to 5, wherein the base oil is a polyol ester obtained from
pentaerythritol, a branched butanoic acid, and 3,5,5-trimethylhexanoic
acid, wherein a kinematic viscosity of the polyol ester at 40°C is 30 to
11 0 mm2/s.
7. The refrigerating machine oil composition according to any one
5 of claims 1 to 6, wherein the content of the ester additive is 2 to 7
mass% based on the total amount of the refrigerating machine oil composition.
8. The refrigerating machine oil composition according to any one
of claims 1 to 7, further comprising 0.1 to 5 mass% of a phosphate
10 and/or 0.01 to 2 mass% of a sulfide compound based on the total
amount of the refrigerating machine oil composition.
9. The refrigerating machine oil composition according to claim 8,
wherein the phosphate is at least one selected from triphenyl phosphate,
tricresyl phosphate, and alkylphenyl phosphates having an alkyl group
1 5. having 3 or 4 carbon atoms.
10. The refrigerating machine oil composition according to claim 8
or 9, wherein the sulfide compound is a thiobisphenol compound.
11. A method for producing a refrigerating machine oil
composition comprising:
20 a step of blending at least one ester additive selected from
tetraesters of pentaerythritol and one selected from fatty acids having 5
to 18 carbon atoms and hexaesters of dipentaerythritol and one selected
from fatty acids having 5 to 18 carbon atoms into a base oil that is an
ester other than the ester additive to obtain the refrigerating machine oil
25 composition,
wherein a content of the ester additive is 2 to 20 mass% based
on a total amount of the refrigerating machine oil composition, and
wherein a kinematic viscosity of the refrigerating machine oil
composition at 40°C is 3 to 500 mm2/s.
12. A working fluid composition for refrigerating machines
5 comprising:
the refrigerating machine oil composition according to any
of claims 1 to 11; and
a refrigerant containing at least one selected from
hydrofluorocarbons, hydrofluoroolefins, and hydrocarbons, wherein a
10 global warming potential of the refrigerant is 700 or less.
13. The working fluid compositio~l for rekigerating machines
according to claitn 12, wherein the refrigerant contains
difluoromethane (R32).