Title of Invention: WORKING FLUID COMPOSITION FOR
REFRIGERATOR
Technical Field
5 [OOOl] The present invention relates to a workiig fluid composition for
a refrigerating machine, and more specifically relates to a working fluid
composition for a refrigerating machine which comprises a mixed
refrigerant which contains components such as a hydrocarbon having 3
to 4 carbon atoms, difluoromethane (also referred to as "EFC-32" or
10 "R32") and tetrafluoropropene, and has global warming potential
(GWP) of 500 or less.
Background Ant
[OOOZ] CFC (chlorofluorocarbon) and HCFC
(hydrochlorofluorocarbon), which have been conventionally used as
15 refrigerants for refrigeration equipment, have been subject to regulation
due to the problem of recent ozone depletion, and WFC
(hydrofluorocarbon) has come to be used as a rehigerant instead of
them.
[0003] Among HFC refrigerants, HFC-134a, R407C, and R410A are
20 normally used as refrigerants for car air-conditioners, cold storage
chambers, or room air-conditioners. Although the ozone depletion
potential (ODP) of these WC refrigerant is zero, these come to be
subject to regulation, because the global warming potential (GWP)
thereof is high. While difluoromethane has been studied as one of
25 alternate candidates of these refrigerants, difluoromethane has the
following problems: the global warming potential thereof is not
suficiently low; the boiling point thereof is so low that thermodynamic
characteristics cannot be applied to a current refrigeration system
directly; and difluoromethane is not easily compatible with lubricating
oils (refrigerating machine oils) used for conventional NOFC refi-igerants,
such as polyol esters and polyvinyl ethers. On the other hand,
unsaturated hydrofluorocarbons have been proposed to be used as a
refiigerant due to the following reasons; both of its ODP and GWP are
very low; unsaturated hydrofluorocarbons are non-flammable
depending on structures; and in particular with respect to HFO-1234yf,
thermodynamic characteristics as measures of refiigerant performances
are comparable with or better than those of KFC-134a (Patent
Literatures 1 to 3).
Citation List
Patent Literature
[0004] patent Literature 11 International Publication WO20041037913
[Patent Literature 21 International Publication WO2005l105947
[Patent Literature 31 International Publication WO2009/057475
Summary of In~enGon
Technical Problem
[0005] In the case where a refrigerant and a refrigerating machine oil
are applied to a refrigeration system, it is demanded for the refrigerant
that the refrigerant does not have any adverse influences on the
environment and thatthermodynamics characteristics are adapted to the
refrigeration system. In addition, in a circumstance of coexistence of
the rehigerant and the refrigerating machiie oil it is demanded that they
are soluble in each other (compatibility) and are excellent in
thermallchemical stability, and that an oil film is maintained in order to
suppress wear of a sliding member (lubricity).
[0006] With respect to a refrigeration system using unsaturated
hydrofluorocarbons, it has been considered that since refrigerating
5 machine oils used in EFC, such as polyol esters and polyvinyl ethers,
exhibit compatibility with unsaturated hydrofluorocarbons, these
refrigerating machine oil can be applied. According to the studies by
the present inventors, however, the following problem has been
revealed: unsaturated hydrofluorocarbons have unstable double bonds in
10 their molecules and thus are poor in thermaL'chemica1 stability.
[0007] In addition, one reason why the compatibility between the
refrigerant and the refrigerating machine oil (hereinafter, sometimes
simply referred to as "compatibility".) is demanded is because a
refrigerating machine oil for lubricating a refrigerant compressor
15 circulates together with a refrigerant in the refrigerant circulation cycle
of refrigeration equipment. That is, in the refkigeration equipment,
sufficient compatibility between the refrigerant and the refrigerating
machine oil is not achieved depending on the selection of the
refigerating machine oil used to the refiigerant, and the refrigerating
20 machine oil discharged from the refrigerant compressor easily remains
in the cycle. As a result, there occur problems of wear due to
lubrication failure by the reduction in amount of the oil in the refigerant
compressor and of blockage of an expansion mechanism such as a
capillary. Therefore, it is important to select the refrigerating machine
25 oil adapted to the refrigerant. Pn a refrigeration system using
difluoromethane, however, a problem is that difluoromethane is not
easily compatible with the refrigerating machine oil, and there is also
the problem of thermodynamics characteristics.
[0008] The present invention has been made in view of such problems,
and an object thereof is to provide a working fluid composition for a
5 refrigerating machine which can achieve compatibility and
thermal/chernical stability in a refrigeration system using a refrigerant
such as a hydrocarbon, difluoromethane, and an unsaturated
hydrofluorocarbon without requiring for a significant modification of an
existing system.
10 Solution to Problem
[0009] The present inventors have made intensive studies in order to
solve the above object, and as a result, have found that a specific
refigerant, and a refrigerating machine oil containing a specific ester or
ether as a base oil can be used to allow both of sufficiently high
15 compatibility and thennaI/chemical stability to be achieved at high
levels, leading to the completion of the present invention.
[0010] That is, the present invention provides a working fluid
composition for a refrigerating machine, shown in any of the following
111 to ~91.
20 [I] A working fluid composition for a reggerating machine,
comprising:
a refrigerant comprising a first refrigerant component and a
second refrigerant component, and having a global warming potential
(GWP) of 500 or less, wherein the first refrigerant component is at least
25 one selected from difluoromethane and tetrafluoropropene, and the
second refkigerant component is at least one selected from carbon
dioxide and a hydrocarbon having 3 to 4 carbon atoms; and
a refrigerating machine oil comprising at least one selected from
a polyol ester, a polyvinyl ether and a polyallylene glycol compound as
a base oil, wherein a carbonloxygen molar ratio of the base oil is 2.5 or
5 more and 5.8 or less.
[2] The working fluid composition for a refrigerating machine
according to [I], wherein the rekigerant comprises the hydrocarbon
having 3 to 4 carbon atoms, difluoromethane and tetrafluoropropene,
and has a global warming potential of 400 or less.
I0 [3] The working fluid composition for a refiigerating machine
according to [I] or [2], wherein the refiigerant contains 3 to 40 parts by
mass of the hydrocarbon having 3 to 4 carbon atoms, 20 to 60 parts by
mass of difluoromethane and 20 to 70 parts by mass of
tetrafluoropropene based on 100 parts by mass of the refrigerant.
15 [4] The working fluid composition for a refrigerating machine
according to any one of [I] to [3], wherein the hydrocarbon having 3 to
4 carbon atoms is propane or isobutane, and a global wmlning potential
of the refiigerant is 300 or less.
[5] The working fluid composition for a refrigerating machine
20 according to [I], wherein the refrigerant comprises at least one selected
from difluoromethane and tetrafluoropropene, and carbon dioxide, and
has a global warming potential of 500 or less.
[6] The working fluid composition for a refrigerating machine
according to any one of [I] to 151, wherein a mass ratio of the
25 refrigerant to ihe refrigerating machine oil is 90 : 10 to 30 : 70.
171 The working fluid composition for a refrigerating machine
according to any one of [I] to [6], wherein the base oil comprises a
polyol ester having a carbodoxygen molar ratio of 2.5 or more and 5.8
or less, and the polyol ester is a polyol ester obtainable by synthesis
from a fatty acid having 4 to 9 carbon atoms and a polyhydric alcohol
5 having 4 to 12 carbon atoms.
[8] The working fluid composition for a refrigerating machine
according to any one of [l] to [6], wherein the base oil contains a
polyalkylene glycol compound having a carbodoxygen molar ratio of
2.5 or more and 5.8 or less, and the polyakylene glycol compound is a
10 compound having a homopolymerization chain of propylene oxide or a
copolymerization chain of propylene oxide and ethylene oxide, at least
one of both ends of the chain being blocked by an ether bond.
(91 The working fluid composition for a refrigerating machine
according to any one of [I] to [6], wherein the base oil comprises a
15 polyvinyl ether having a carbodoxygen molar ratio of 2.5 or more and
5.8 or less, and the polyvinyl ether is a polyvinyl ether having a
structural unit represented by the following formula (I).
[Chemical Formula I]
20 g, and ?R3 may be the same or different and each represent a
hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, lX4
represents a divalent hydrocarbon group having I to 10 carbon atoms or
an ether bond oxygen-containing divalent hydrocarbon group having 2
to 20 carbon atoms, It5 represents a hydrocarbon group having 1 to 20
carbon atoms, m represents a number such that an average value of m in
the polyvinyl ether is 0 to 10, R' to R5 may be the same or different in
each occunence of the structural units, and when m represents 2 or
5 more in one structural unit, a plurality of R~Om ay be the same or
different.]
Advantageous Effects of Invention
[0011] The present invention can provide a working fluid composition
for a refrigerating machine which can achieve compatibility and
10 thermal/chemical stability in a refrigeration system using a refrigerant
such as a hydrocarbon, difluoromethane, and an unsaturated
hydrofluorocarbon without requiring for a significant modification of an
existing system.
Descrip~ono f Embodiments
15 [0012] Hereinafter, a preferable embodiment of the present invention is
described in detail.
[0013] A working fluid composition for a refrigerating machine
according to an cmbodment of the present invention comprises
a refrigerant comprising a first refrigerant component and a
20 second refrigerant component, wherein the first re6igerant component
is at least one selected from difluoromethane and tetrafluoropropene,
and the second refrigerant component is at least one selected from
carbon dioxide and a hydrocarbon having 3 to 4 carbon atoms, and
having a global warming potential (GWP) of 500 or less, and
25 a refkigerating machine oil comprising at least one selected from
a polyol ester, a polyvinyl ether and a polyalkylene glycol compound as
a base oil, wherein a carbonloxygen molar ratio of the base oil is 2.5 or
more and 5.8 or less.
[0014] In the working fluid composition for a refi-igerating machine
according to the present embodiment, the proportions of the refrigerant
I
5 and the refrigerating machine oil blended are not particularly limited,
but the mass ratio of the refkigerant to the refrigerating machine oil is
1 preferably 90 : 10 to 30 : 70 and more preferably 80 : 20 to 40 : 60.
[0015] Then, the components contained in the working fluid for a
refrigerating machine are described in detail.
I 10 [OO 161 [Refrigerant]
The refrigerant in the present embodiment contains a first
refrigerant component that is at least one selected from difluoromerhane
and tetrafluoropropene, and a second refrigerant component that is at
least one selected from carbon dioxide and a hydrocarbon having 3 to 4
15 carbon atoms, and the global warming potential thereof is 500 or less.
[0017] Herein, since difluoromerhane (R32) has a low boiling point and
a high pressure by itself, thermodynamic characteristics thereof as the
refrigerant cannot be said to be suitable. In addition, the global
warming potential thereof, namely, the GWP value is about 600 and is
20 Lower than that of HFC-134a that is a typical hydrofluorocarbon, 1300,
but cannot be said to be sufficiently low. In addition, difluoromethane
OP32) is not easily compatible with the refi-igerating machine oil.
Difluoromethane (R32), however, is good in stability even if coexisting
with the rehigerating machine oil.
25 [0018] In addition, thermodynamic characteristics of tetrafluoropropene
such as 2,3,3,3-tetrafluoropropene (HF0-1234yf) are almost
comparable with those of WC-134a. Furthermore, for example, the
GWP value of EFO-1234yf is 4 and is extremely low as compared with
that of WC-134a. The reason for this is because tetrafluoropropene
has a double bond in its molecule and thus is easily decomposed in the
5 atmosphere. In addition, tetrafluoropropene such as
2,3,3,3-tetrafluoropropene has proper compatibiIity with the
refrigerating machine oil. Tetrafluoropropene, however, is easily
decomposed and thus has the problem of being poor in stability.
[0019] In addition, while the hydrocarbon having 3 to 4 carbon atoms
10 has a low global warming potential (GW) of about 3 and is good in
thermodynamics characteristics as the refrigerant, it has a problem of
safety due to its highly flammability, and is so high in solubility in the
refrigerating machine oil that the viscosity of the oil is reduced to
thereby cause a problem of a significant reduction in lubricity* Thus, it
15 is difficult to singly use the hydrocarbon having 3 to 4 carbon atoms,
except for a special case.
[0020] Then, in the present embodiment, a first refrigerant component
that is at least one selected from difluoromethai~e and
tetrafluoropropene, and a second refrigerant component that is at least
20 one selected from carbon dioxide and a hydrocarbon having 3 to 4
carbon atoms are mixed, and the resulting mixed refrigerant can be used
as a suitable refrigerant, in which disadvantages of each rehigerants are
compensated and advantages thereof are utilized.
[0021] The first refrigerant component may include only any one of
25 difluoromethane and tetrafluoropropene, or may include both of
difluoromethane and tetrafluoropropene.
[0022] Tetrafluoropropenes include 2,3,3,3-tetrafluoropropene
(HFO-1234yf), 1,3,3,3-tetrafluoropropene m0-1234ze), and
1,2,3,3-tetrafluoropropene (WO-1234ye). Among them, HFO-1234yf
and HFO-1234ze are preferable, and in particular W0-1234yf is
5 preferable in terms of physical properties of the refkigerant.
Tetrafluoropropenes may be used singly or in combination of two or
more thereof.
[0023] The second refrigerant component may include only any one of
carbon dioxide and a hydrocarbon having 3 to 4 carbon atoms, or may
10 include both of carbon dioxide and a hydrocarbon having 3 to 4 carbon
atoms.
[0024] Hydrocarbons having 3 to 4 carbon atoms include propane
(R290), propylene (R1270), n-butane @600), and isobutane @6QOa),
and the GWP of all of them is as extremely low as about 3, as described
15 above. Among them, propane and isobutane are preferable in terms of
thermodynamics characteristics and stability.
[0025] Whiie the refrigerant in the present embodiment can firither
contain a component other than the first and second components, the
sum of the first refrigerant component and the second refrigerant
20 component is preferably 80% by mass or more and more preferably
90% by mass or more based on the total amount of the refrigerant.
[0026] The component other than the first and second components
includes a hydrofluorocarbon (FnjC) refrigerant and fluorine-containing
ether-based refrigerants such as perfluoroethers.
25 [0027] In addition, the refrigerant in the present embodiment can
further contain unsaturated hydrofluorocarbons other than
tetrafluoropropenes. As such unsaturated hydrofluorocarbons,
Ruoropropenes containing 3 or more and 5 or less fluorine atoms are
preferable, and any one of 1,2,3,3,3-pentafluoropropene (HFO-1225ye)
and 3,3,3-trifluoropropene (WO-1243zf) or a mixture of two or more of
thereof is preferable. From the viewpoint of physical properties of the
refrigerant, HFO-1225ye is preferable.
[0028] Preferable examples of the refrigerant in the present
embodiment include mixed refrigerants A and B described later.
to0291 [Mixed refrigerant A]
The mixed refrigerant A in the present embodiment contains a
hydrocarbon having 3 to 4 carbon atoms, difluoromethane and
tetrafluoropropene, and the global warming potential thereof is 400 or
less.
[0030] With respect to the mixed refrigerant A, hydrocarbons having 3
to 4 carbon atoms include propane (R290), propylene @1270), n-butane
(R600) and isobutane @600a), and the GWP thereof is as extremely
low as about 3, as described above. Among them, propane and
isobutane are preferable in terms of thermodynamics characteristics and
stability. Hydrocarbons having 3 to 4 carbon atoms may be used
singly or in combination of two or more.
[0031] With respect to the mixed refrigerant A, tetrafluoropropenes
include 2,3,3,3-tetrafluoropropene @33?0-1234yf),
1,3,3,3 -tetrafluoropropene P O - 1 234ze) and
1,2,3,3-tetrafluoropropene (WO-1234ye). Among them, HFO-1234yf
and WO-1234zc are preferable, and in particular HFO-1234yf is
preferable in terms of physical properties of the regigerant.
Tetrafluoropropenes may be used singly or in combination of two or
more thereof.
[0032] The content of each of the refrigerants in the mixed refrigerant A
based on 100 parts by mass of the mixed refrigerant is preferably as
5 follows: the content of the hydrocarbon having 3 to 4, carbon atoms is 3
to 40 parts by mass, the content of difluoromethane is 20 to 60 parts by
mass, and the content of tetrafluoropropene is 20 to 70 paris by mass;
and more preferably as follows: the content of the hydrocarbon having 3
to 4 carbon atoms is 5 to 30 parts by mass, the content of
10 difluoromethane is 20 to 60 parts by mass, and the content of
tetrafluoropropene is 30 to 70 parts by mass. Hercin, difluoromethane
is a high-pressure gas, and therefore when the content thereof is high,
the efficiency of the refrigerating machine is increased. But when the
content thereof is high, the GWP is increased, and also the compatibility
15 between the refigerant and the refrigerating machine oil is deteriorated.
On the other hand, tetrafluoropropene, whose GWP is low, contributes
environmental-friendliness when the content thereof is high. But it is
poor in stability and thus the stability of the working fluid is
deteriorated when the content thereof is high.
20 [0033] The global warming potential of the mixed refrigerant A is 400
or less, preferably 300 or less, and more preferably 150 or less. Herein,
the global warming potential can also be reduced by mixing only
difluoromethane and tetrafluoropropene without using the hydrocarbon
having 3 to 4 carbon atoms, but in such a case, the content of
25 tetrafluoropropene whose pressure is low is high. As a result, the
efficiency of the refrigerating machine cannot be increased and the
stability is also poor.
[0034] While the mixed refrigerant A can firther contain a component
other than the above three components, the sum of the hydrocarbon
having 3 to 4 carbon atoms, difluoromethane and tetrafluoropropene is
5 preferably 80% by mass or more and more preferably 90% by mass or
more based on the total amount of the refrigerant.
[0035] [Mixed refrigerant B]
A mixed refrigerant B in the present embodiment contains at
least one selected from difluoromethane and tetrafluoropropene, and
10 carbon dioxide, and the global warming potential thereof is 500 or less.
[0036] With respect to the mixed refrigermt B, tetrafluoropropenes
include 2,3,3,3-tetrafluoropropene (HFO-l234yf),
1,3,3,3-tetrafluoropropene (HFO-1234ze) and
1,2,3,3-tetrafluoropropene (WO-1234ye). Among them, HFO-1234yf
15 and HFO-1234ze are preferable, and in particular IIFCd-1234yf is
preferable in terms of physical properties of the refrigerant.
Tetrafluoropropenes may be used singly or in combination of two or
more thereof.
[0037] The content of each of the rehigerants in the mixed refiigerant B
20 based on 100 pasts by mass of the mixed refrigerant is preferably as
follows: the content of difluoromethane and/or tetrafluoropropene is 30
to 90 parts by mass, and the content of carbon dioxide is 10 to 70 parts
by mass; and more preferably as follows: the content of
difluoromethane a d o r tetrafluoropropene is 40 to 80 parts by mass,
25 and the content of carbon dioxide is 20 to 60 parts by mass. Herein,
difluoromethane is a high-pressure gas, and therefore when the content
thereof is high, the efficiency of the refrigerating machine is increased.
But when the content thereof is high, the GWP is increased, and also the
compatibility between the refkigerant and the refrigerating machine oil
is deteriorated. On the other hand, tetrafluoropropene, whose GWP is
low, contributes environmental-fkiendliness when the content thereof is
high. But it is poor in stability and thus the stability of the working
fluid is deteriorated when the content thereof is high.
[0038] In addition, in file case where the mixed refrigerant B contains
all of difluoromethane, tetrafluoropropene and carbon dioxide, the
proportions of difluoromethane and tetrafluoropropene contained are
not particularly limited, but it is preferable from the viewpoints of GWP
and thermodynamic characteristics that
difluoromethane/tetrafluoropropene ratio (mass ratio) he in a range from
30/70 to 70130.
[0039] The global warming potential of the mixed refrigerant B is 500
or less, preferably 300 or less, and more preferably 150 or less, from the
viewpoint of the global environment protection.
[0040] While the refrigerant in the present embodiment can further
contain a component other than the above three components, the sum of
difluoromethane andlor tetrafluoropropene, and carbon dioxide is
preferably 80% by mass or more and more preferably 90% by mass or
more based on the total amount of the refrigerant.
[0041] [Refrigerating machine oil]
The refrigerating machine oil in the present embodiment
conlains at least one selected from a polyol ester, a polyvinyl ether and a
polyalkylene glycol compound as a base oil, and the carbonloxygen
molar ratio of the base oil is 2.5 or more and 5.8 or less. Carbon and
oxygen in the base oil can be quantitatively analyzed by a common
elemental analysis method. While a carbon analysis includes a thenma1
conductivity method after conversion into carbon dioxide by burning,
and a gas chromatography method, an oxygen analysis is commonly a
carbon reduction method in which carbon monoxide derived by carbon
is quantitatively analyzed. and a Shutze-Unterzaucher method is widely
put into practical use.
[0042] En the case where the base oil is a mixed base oil including two
or more components, the carbodoxygen molar ratio of each of the
components included in the mixed base oil is not particularly limited as
long as the carbodoxygen molar ratio of ihe mixed base oil is 2.5 or
more and 5.8 or less, but it is preferable that the carbodoxygen molar
ratio of each of the polyol ester, the polyvinyl ether and the
polyalkylene glycol compound is 2.5 or more and 5.8 or less. These
preferable examples are described later.
[0043] [Polyol ester]
The polyol ester is an ester obtainable by synthesis &om a
polyhydric alcohol and a carboxylic acid, and the carbodoxygen molar
ratio is preferably 2.5 or more and 5.8 or less, more preferably 3.2 or
more and 5.0 or less, and further preferably 4.0 or more and 5.0 or less.
As the carboxylic acid, fatty acids (aliphatic monocarboxylic acids), in
particular saturated fatty acids are preferably used, and the number of
carbon atoms thereof is preferably 4 or more and 9 or less and
particularly preferably 5 or more and 9 or less. The polyol ester may
be a partial ester in which some of hydroxyl groups in the polyhydric
alcohol remains as hydroxyl groups without being esterified, may be a
complete ester in which all of hydroxyl groups are esterified, or may be
a mixture of the partial ester and the complete ester; but the hydroxyl
value is preferably 10 mgKOWg or less, further preferably 5 mgKOWig
5 or less, and most preferably 3 mgKOWg or less.
[0044] [Fatty acid]
(a-1) In the mixed refrigerant A, in the case where the proportion
of difluoromethane that is poor in compatibility with the refi-igerating
machine oil is high among main components of the refxigerant, i.e., the
10 hydrocarbon having 3 to 4 carbon atoms, difluoromethane and
tetrafluoropropene, for example, in the case where the proportion of
difluoromethane in the refrigerant is 40% by mass or more, the
proportion of branched fatty acids of fatty acids forming the polyol ester
is preferably 50 to 100% by mol, particularly preferably 70 to 100% by
15 mol, a d further preferably 90 to 100% by mol.
[0045]
(a-2) In the mixed refxigerant B, in the case where the proportion
of difluoromcthane that is poor in compatibility with the refiigcrating
machine oil is 40% by mass or more among main components of the
20 refrigeranl, i.e.,difluoromethane andlor tetrafluoropropene, and carbon
dioxide, the proportion of branched fatty acids of fatty acids forming the
polyol ester is preferably 50 to 100% by mol, particularly preferably 70
to 100% by mol, and further preferably 90 to 100% by mol.
[0046] Specific examples of branched fatty acids having 4 to 9 carbon
25 atoms include branched butanoic acids, branched pentanoic acids,
branched hexanoic acids, branched heptanoic acids, branched octanoic
acids, and branched nonanoic acids. More specifically, fatty acids
branched at a-position andlor p-position are preferable, isobutanoic acid,
2-methylbutanoic acid, 2-methylpentanoic acid, 2-methylhexanoic acid,
2-ethylpentanoic acid, 2-methyllieptanoic acid, 2-ethylhexanoic acid,
5 3,5,5-trimethylhexanoic acid, and the like are preferable, and among
them, 2-ethylhexanoic acid and/or 3,5,5-trimethylhexanoic acid is most
preferable. Herein, fatty acids other than branched fatty acids having 4
to 9 carbon atoms m2y be included.
COO471 (b-1) In the mixed refrigerant A, in the case where the total of
10 the contents of the hydrocarbon having 3 to 4 carbon atoms and
tehafluoropropene among main components of the ~ekigerantis higher
than the content of difluoromethane, specifically, the total content of
both the components is 60% by mass or more, in particular, 70% by
mass or more, the proportion of straight fatty acids of fatty acids is
15 preferably 50 to 95% by mol, particularly preferably 60 to 90% by mol,
and further preferably 70 to 85% by mol in view of high compatibility
with the refrigerating machine oil.
[0048] (b-2) In the mixed refrigerant B, in the case where the
proportion of difluoromethane among main components of the
20 refrigerant is less than 40% by mass, the proportion of straight fatty
acids of fatty acids is preferably 50 to 95% by mol, particularly
preferably 60 to 90% by mol, and further preferably 70 to 85% by mol
in view of high compatibility with the refrigerating machine oil.
[0049] Specific examples of straight fatty acids having 4 to 9 carbon
25 atoms include butanoic acid, pentanoic acid, hexanoic acid, heptanoic
acid, octanoic acid, and nonanoic acid. Among them, pentanoic acid
and/or heptanoic acid is preferable, and in particular a mixed acid
thereof is most preferable. The content of straight pentanoic acid is
preferably 30% by rnol or more in particular in terms of compatibility,
and on the other hand, is preferably 50% by rnol or less and particularly
preferably 45% by rnol or less in particular in terms of hydrolytic
stability. The content of heptanoic acid is preferably 20% by mol or
more, particularly preferably 25% by rnol or more, and further
preferably 30% by mol or more, in terms of lubricity. On the other
hand, the content is 50% by rnol or less and preferably 45% by rnol or
less in particular in tenm of hydrolytic stability. As branched fatty
acids other than straight fatty acids, branched fatty acids having 5 to 9
carbon atoms, in particular, 2-ethylhexanoic acid and/or
3,5,5-trimethylhexanoic acid is preferable. The content of
3,5,5-trimethylhexanoic acid is preferably 5% by mol or more and
particularly preferably 10% by rnol or more in particular in terms of
hydrolytic stability, and on the other hand, the content is preferably 30%
by rnol or less and particularly preferably 25% by mol or less in
particular in terms of compatibility and lubricity.
[0050] As preferable fatty acids in the cases (b-1) and (b-2), specifically,
a mixed acid of straight pentanoic acid, straight heptanoic acid and
3,5,5-trimethylhexanoic acid is preferable, and this mixed acid is more
preferably one containing 30 to 50% by rnol of straight pentanoic acid,
20 to 50% by rnol of straight heptanoic acid and 5 to 30% by mol of
3,5,5-trimethylhexanoic acid.
[005 11 [Polyhydric alcohol]
As the polyhydric alcohol forming the polyol ester, polyhydric
alcohols having 2 to 6 hydroxyl groups are prefaably used. The
number of carbon atoms of polyhydric alcohols is preferably 4 to 12 and
particularly preferably 5 to 10. Hindered alcohols such as neopcntyl
glycol, trimethylolethane, trimethylolpropane, trirnethylolbutane,
5 di-(trimethylolpropane), tri-(trimethylolpropane), pentaerythritol and
di-(pentaerythritol) are preferable. Since being particularly excellent
in compatibility with the refrigerant and in hydrolytic stability,
pentaerythritol or a mixed ester of pentaerythritol and
di-(pentaexythritol) is most preferable.
10 [0052] [Polyvinyl ether]
The carbonloxygen molar ratio of the polyvinyl ether is
preferably 2.5 or more and 5.8 or less, more preferably 3.2 or more and
5.8 or less, and further preferably 4.0 or more and 5.0 or less. If the
carbonfoxygen molar ratio is less than this range, hygroscopicity is
15 higher, and if the ratio is more than this range, compatibility i s
deteriorated. In addition, the wei@ average molecular weight of the
polyvinyl ether is preferably 200 or more and 3000 or less and more
preferably 500 or more and 1500 or less.
[0053] The polyvinyl ether preferably used in the present embodiment
20 has a structural unit represented by the following formula (1).
[Chemical Formula 21
[R', It2 and It3 may be the same or diEerent and each represent a
hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, R4
represents a divalent hydrocarbon group having 1 to 10 carbon atoms or
an ether bond oxygen-containing divalent hydrocarbon group having 2
to 20 carbon atoms, R5 represents a hydrocarbon group having 1 to 20
carbon atoms, m represents a number such that an average value of m in
the polyvinyl ether is 0 to 10, R' to R5 may be the same or different in
each occurrence of the structural units, and khen m represents 2 or
more in one structural unit, a plurality of R40 may be the same or
different.]
[0054] At least one of R', R2 and lX3 in the above formula (1) is
preferably a hydrogen atom, and all thereof are particularly preferably a
hydrogen atom. m in the formula (1) is preferably 0 or more and 10 or
less, particularly preferably 0 or more and 5 or less, and further
preferably 0. R5 in the formula (1) represents a hydrocarbon group
having 1 to 20 carbon atoms. This hydrocarbon group includes an
alkyl group, a cycloalkyl group, a phenyl group, an atyl group, an
arylalkyl group, and an alkyl group, and in particular an alkyl group
having 1 to 5 carbon atoms is preferable.
I00551 The polyvinyl ether in the present embodiment may be a
homopolymer constituted by one type of the structural unit represented
by the formula (1) or a copolymer constituted by 2 or more type of the
structural units, but the copolymer brings about the effect of fLu-ther
enhancing lubricity, insulation property, hygroscopicity, and the like
while satisfying compatibility. In this case, the types of monomers
serving as raw materials, the type of an initiator, and the rate of a
copolymer can be selected to thereby adapt the performances of an oil
agent to the intended levels. Accordingly, the following effect is
exerted: an oil agent can be obtained at will according to requirements
such as lubricity and compatibility that vary depending on the type of a
compressor in a refrigeration system or an air-conditioning system, the
material of a lubrication porlion, refrigeration ability, the type of a
refrigerant, and the like. The copolymer may be any of a block
copolymer and a random copolymer.
100561 In the case where the polyvinyl ether in the present embodiment
is a copolymer, it is preferable that the copolymer include a structural
unit (1-1) represented by the above formula (1) wherein R~ represents
an alkyl group having 1 to 3 carbon atoms, and a structural unit (1-2)
represented by the abovc formula (1) wherein R~ represents an alkyl
group having 3 to 20 carbon atoms, preferably 3 to 10 carbon atoms,
further preferably 3 to 8 carbon atoms. IX5 in the structural unit (1-1) is
particularly preferably an ethyl group, and R~ in the structural unit (1 -2)
is particularly preferably an isobutyl group. Furthermore, in the case
where the polyvinyl ether in the present embodiment is the copolymer
including the structural units (1-1) and (1-2), the molar ratio of the
structural unit (1-1) to the structural unit (1-2) is preferably 5 : 95 to 95 :
5, more preferably 20 : 80 to 90 : 10, and firther preferably 70 : 30 to
90 : 10. In the case where the molar ratio departs from the above range,
there is a tendency toward insufficient compatibility with the refrigerant
and heigher hygroscopicity.
[0057] The polyvinyl ether in the present embodiment may be one
constituted by only the structural unit represented by the above formula
(I), but may be a copolymer further including a structural unit
represented by the following formula (2). In this case, the copolymer
may be any of a block copolymer and a random copolymer.
[Chemical Formula 31
5 [R6 to R' may be the same as or different &om one another and each
represent a hydrogen atom or a hydrocarbon group having 1 to 20
carbon atoms.]
[0058] [End structure of polyvinyl ether]
The polyvinyl ether in the present embodiment can be produced
10 by polymerization of each corresponding vinyl ether-based monomer,
and copolymerization of a corresponding hydrocarbon monomer having
an olefinic double bond with a corresponding vinyl ether-based
monomer. As the vinyl ether-based monomer corresponding to the
structural unit represented by the foimula (I), a monomer represented
15 by the following formula (3) is suitable.
[Chemical Formula 41
[$, R2, R3, R4, RS and m represent the same meaning as in R', lX2, lX3,
R ~R,5 a nd m in the formula (11, respectively.]
20 [0059] As the polyvinyl ether in the present embodiment, ethers having
the following end structures are suitable.
(A) Those having a structure in which one end is represented by formula
(4) or (5) and other end is represented by formula (6) or (7).
[Chemical Formula 51
5 [R", R" and IX3' may be the same as or different from one another and
each represent a hydrogen atom or a hydrocarbon group having 1 to 8
carbon atoms, R4' represents a divalent hydrocarbon group having 1 to
I 10 carbon atoms or an ether bond oxygen-containing divalent
hydrocarbon group having 2 to 20 carbon atoms, R5' represents a
10 hydrocarbon group having 1 to 20 carbon atoms, m represents a number
I I such that an average value of m in the polyvinyl ether is 0 to 10, and
when m represents 2 or more, a plurality of R4'0 may be the same or
different.]
[Chemical Formula 61
[R6', R ~R's' ~an d R~~m ay be the same as or different fiom one another
and each represent a hydrogen atom or a hydrocarbon group having 1 to
20 carbon atoms.]
[Chemical Formula 71
[R'~R, 2' axld may be the same as or different &om one another and
each represent a hydrogen atom or a hydrocarbon group having 1 to 8
carbon atoms, R4' represents a divalent hydrocarbon group having 1 to
10 carbon atoms or an ether bond oxygen-containing divalent
hydrocarbon group having 2 to 20 carbon atoms, R5' represents a
hydrocarbon group having 1 to 20 carbon atoms, m represents a number
such that an average value of m in the polyvinyl ether is 0 to 10, and
when m represents 2 or more, a plurality of R4'0 may be the same or
different.]
[Chemical Formula 81
[R6', R"', Rs2 and R~~ may be the same as or different hom one another
and each represent a hydrogen atom or a hydrocarbon group having I to
20 carbon atoms.
[0060] (B) Those having a structure in which one end is represented by
the above formula (4) or (5) and other end is represented by the
following formula (8).
[Chemical Formula 91
@I3, R~~ and R~~ may be the same as or different fi-om one another and
each represent a hydrogen atom or a hydrocarbon group having 1 to 8
carbon atoms.]
[0061] Among such polyvinyl ether-based compounds, in particular the
following is suitable as a main component of the refi-igerating machine
oil according to the present embodiment.
(1) Those having a structure in which one end is represented by the
5 formula (5) or (6) and other end is represented by the formula (7) or (8),
wherein in the formula (I), R', R2 and R3 are each a hydrogen atom, rn
represents a number of 0 to 4, R4 represents a divalent hydrocarbon
group having 2 to 4 carbon atoms, and R5 represents a hydrocarbon
group having 1 to 20 carbon atoms.
10 (2) Those having only the structural unit represented by the formula (I),
having a structure in which one end is represented by the formula (5)
and other end is represented by the formula (7), wherein in the fonnula
(I), R', R2 and R3 are each a hydrogen atom, m represents a number of 0
to 4, R~ represents a divalent hydrocarbon group having 2 to 4 carbon
15 atoms, and R~ represents a hydrocarbon group having 1 to 20 carbon
atoms.
(3) Those having a structure in which one end is represented by the
formula (5) or (6) and other end is represented by the formula (9),
wherein in the formula (I), R', R2 and R3 are each a hydrogen atom, m
20 represents a number of 0 to 4, R4 represents a divalent hydrocarbon
group having 2 to 4 carbon atoms, and R5 represents a hydrocarbon
group having 1 to 20 carbon atoms.
(4) Those that are each of the (I) to (3), having a structural unit in which
It5 in the formula (1) represents a hydrocarbon group having 1 to 3
25 carbon atoms, and a structural unit in which such R' represents a
hydrocarbon group having 3 to 20 carbon atoms.
[0062] [Production of polyvinyl ether]
The polyvinyl ether in the present embodiment can be produced
by subjecting the above monomer to radical polymerization, cation
polymerization, radiation polymerization, or the like. After
5 completion of the polymerization reaction, a usual
separatiodpurification method is if necessary conducted, and thus the
intended polyvinyl ether-based compound having the structural unit
represented by the formula (1) is obtained.
[0063] As described above, it is required for the polyvinyl ether in the
10 present embodiment that the carbodoxygen molar ratio is in the
predetermined range, and the carbodoxygen molar ratio of a raw
material monomer can be regulated to thereby produce a polymer whose
molar ratio is in the above range. That is, when the rate of a monomer
whose carbodoxygen molar ratio is high is high, a polymer whose
15 carbodoxygen molar ratio is high is obtained, and when the rate of a
monomer whose carbodoxygen molar ratio is low is high, a polymer
whose carbodoxygen molar ratio is low is obtained. Herein, in the
case where a vinyl ether-based monomer and a hydrocarbon monomer
having an olefmic double bond are copolymerized, a polymer whose
20 carbodoxygen molar ratio is higher than the carbodoxygen molar ratio
of the vinyl ether-based monomer is obtained, but the proportion thereof
can be regulated by the rate and the number of carbon atoms of the
hydrocarbon monomer having an olefinic double bond to be used.
[0064] In addition, in a production step of the polyvinyl etlier
25 represented by the above formula (I), a side reaction may be caused and
thus an unsaturated group such as an aryl group may be formed in the
molecule. If the unsaturated group is formed in the polyvinyl ether
molecule, the following phenomenon easily occurs: the thermal stability
of the polyvinyl ether itself is deteriorated, a polymerized produce is
generated to generate sludge, or antioxidative property (oxidation
5 preventing property) is deteriorated to generate peroxide. In particular,
if peroxide is generated, it is decomposed .to generate a compound
having a carbonyl group, and the compound having a carbonyl group
further generates sludge to easily cause blockage of a capillary.
Therefore, as the polyvinyl ether according to the present embodiment,
10 those in which the degree of unsaturation due to an unsamrated group
and the like is low is preferable, and specifically, the degree of
unsaturation is preferably 0.04 meqlg or less, more preferably 0.03
meqlg or less, and most preferably 0.02 meqlg or less. In addition, the
peroxide value is preferably 10.0 meqkg or less, more preferably 5.0
15 meqtkg or less, and most preferably 1.0 meqkg. Furthermore, the
carbonyl value is preferably 100 ppm by weight or less, more preferably
50 pprn by weight or less, and most preferably 20 ppm by weight or
less.
[0065] Herein, the degree of unsaturation, the peroxide value and the
20 carbonyl value in the present invention are each the value measured by
the Standard Methods for the Analysis of Fats, Oils and Related
Materials, established by the Japan Oil Chemists' Society. That is, the
degree of unsaturation in the present invention is the value (rneqlg)
obtained by reacting a Wijs solution (ICl-acetic acid solution) with a
25 sample, leaving the resul.tant to stand in a dark area, thereafter reducing
the excess ICl to iodine, titrating the iodine content with sodium
thiosulfate to calculate the iodine vaIue, and converting the iodine value
to the vinyl equivalent; the peroxide value in the present invention is the
value (meqlkg) obtained by adding potassium iodide to a sample,
titrating the free iodine generated with sodium thiosulfate, and
converting the free iodine to the number of milliequivalents with respect
to 1 kg of the sample; and the cartsonyl value in tile present invention is
the value (ppm by weight) obtained by allowing
2,4-dinitrophenylhydrazine to act on a sample to yield a colorable
quinoid ion, measuring the absorbance of the sample at 480 lun, and
converting the absorbance to the carbonyl content based on a
predetermined calibration curve with cinnamaldehyde as the standard
substance. The hydroxyl value is not particularly limited, but it is
desirable that the hydroxyl value be 10 nigKOWg, preferably 5
mgKoWg and further preferably 3 mgKOWg.
[0066] [Polyalkylene glycol compound]
The cafbodoxygen molar ratio of the polyalkylene glycol PAG)
compound in the present embodiment is preferably 2.5 or more and 5.8
or less, preferably 2.5 or more and 4.0 or less, and further preferably 2.7
or more and 3.5 or less. If the molar ratio is less than this range,
hygroscopicity is high and electrical insulation property is deteriorated,
and if the molar ratio is more than this range, compatibility is
deteriorated. The weight average molecular weight of the
polyalkylene glycol compound is preferably 200 or more and 3000 or
less, and more preferably 500 or more and 1500 or less.
100671 [Structural unit of polyalkylene glycol]
Polyalkylene glycols include those of various chemical
structures, but a basic compound thereof is polyethylene glycol,
polypropylene glycol, polybutylene glycol, or the like. The unit
structure thereof is oxyethylene, oxypropylene, or oxybutylene, and
polyalkylene glycols can be obtained by subjecting each monomer,
5 ethylene oxide, propylene oxide, or butylene oxide, as a raw material, to
ring-opening polymerization.
[0068] Examples of the polyalkylene glycol include a compound
represented by the following formula (9):
R'~'-[(OR~~')~OR~~(~9)] ~
10 [R'" represents a hydfogen atom, an allcyl group having 1 to 10 carbon
atoms, an acyl group having 2 to 10 carbon atoms or a residue of a
compound having 2 to 8 hydroxyl groups, ltIo2 represents an allcylene
group having 2 to 4 carbon atoms, lt103 represents a hydrogen atom, an
alkyl group having 1 to 10 carbon atoms or an acyl group having 2 to 10
15 carbon atoms, f represents an integer of 1 to 80, and g represents an
integer of 1 to 8.1
[0069] In the above formula (9t,he alkyl group represented by each of
R'" and R103m ay be any of straight, branched and cyclic alkyl groups.
The number of carbon atoms of the alkyl group is preferably 1 to 10 and
20 more preferably 1 to 6. If the number of carbon atoms of the alkyl
group is more than 10, compatibility with a working medium tends to be
deteriorated.
[0070] In addition, the alkyl group portion of the acyl group represented
by each of R"' and lt103 may be any of straight, branched and cyclic
25 alkyl group portions. The number of carbon atoms of the acyl group is
preferably 2 to 10 and more preferably 2 to 6. If the number of carbon
atoms of the acyl group is more than 10, compatibility with a working
medium may be deteriorated to cause phase separation.
[0071] ]in the case where both of the groups represented by R"' and
R103 are akyl groups or acyl groups, the groups represented by R"' and
R103 may be the same or different. Furthermore, when g represents 2
or more, a plurality of R"' and R103 in the same molecule may be the
same or different.
[0072] In the case where the group represented by R"' is a residue of a
compound having 2 to 8 hydroxyl groups, this compound may be a
chain group or may be a cyclic group.
[0073] In the polyalkylene glycol represented by the above formula (9),
at least one of R"' and R103 is preferably an alkyl group (more
preferably an alkyl group having 1 to 4 carbon atoms) and particularly
preferably a methyl group in terms of compatibility with a working
medium.
[0074] Furthermore, both of R'" and 5t103 are preferably an alkyl group
(more preferably alkyl groups having 1 to 4 carbon atoms) and
particularly prererably a methyl group in terms of thermal/cl~emical
stability.
[0075] Preferably, any one of R"' and Rlo3 is an alkyl group (more
preferably an alkyl group having 1 to 4 carbon atoms) and other thereof
is a hydrogen atom, and particularly preferably, one is a methyl group
and other is a hydrogen atom, in terms of easiness of production aud
cost. In addition, both of R'" and R103 are preferably a hydrogen atom
in terms of lubricity and solubility of sludge.
[0076] R1 02 m. the above formula (9) represents an alkylene group
IFlsl2-0798-00
having 2 to 4 carbon atoms, and specific examples of such an alkylene
group include an ethylene group, a propylene group, and a butylene
group. In addition, an oxyalkylene group as a repeating unit
represented by OR' includes an oxyethylene group, an oxypropylene
group, and an oxybutylene group. Oxyalkylene groups in the same
molecule may be the same, and 2 or more oxyalkylene groups may be
included.
[0077] With respect :o the polyalkylene glycol represented by the above
formula (9, a copolymer including an oxyethylene group (EO) and an
oxypropylene group (PO) is preferable from the viewpoints of
compatibility with a working medium and viscosity-temperature
characteristics, and in this case, the proportion (EO/(PO+EO)) of the
oxyethylene group in the sum of the oxyethylene group and the
oxypropylene group is preferably in a range from 0.1 to 0.8 and more
preferably in a range from 0.3 to 0.6 in terms of baking load and
viscosity-temperature characteristics.
[0078] In addition, the value of EO/(E'O+EO) is preferably in a range
fiom 0 to 0.5, more preferably in a range from O to 0.2, and most
preferably 0 (namely, propylene oxide homopolymer), in terms of
hygroscopicity and thermal and oxidation stability.
[0079] In the above formula (9, f represents the number of repetitions
of the oxyallcylene group OR' (degree of polymerization), and
represents an integer of 1 to 80. In addition, g represents an integer of
1 to 8. For example, in the case where R' represents an alkyl group or
an acyl group, g represents 1. In the case where R"' represents a
residue of a compound having 2 to 8 hydroxyl groups, g represents the
number of hydroxyl groups in the compound.
[0080] In addition, the product (f x g) of f and g is not particularly
limited, but it is preferable that the average value off x g be 6 to 80 in
order to satisfjr the above-described requirements and performances as
the lubricating oil for a refrigerating machine in a well-balanced
manner.
[0081] The number average molecular weight of the polyalkylene
glycol represented by the formula (9) is preferably 500 to 3000, fiuther
preferably 600 to 2000 and more preferably 600 to 1500, and it is
preferable that n represent a number so that the number average
molecular weight of the polyalkylene glycol satisfies the above
conditions. In the case where the number average molecular weight of
the polyalkylene glycol is too low, lubricity under coexistence with the
refrigerant is insufficient. On the other hand, in the case where the
number average molecular weight is too high, a composition range in
which compatibility with the refrigerant is exhibited under low
temperature conditions is narrow, and lubrication failure in a refrigerant
compressor and inhibition of heat exchange in an evaporator easily
occur.
[0082] The hydroxyl value of the polyalkylene glycol is not particularly
limited, but it is desirable that the hydroxyl value be100 mgKOWg or
less, preferably 50 mgKOWg or less, fiurther preferably 30 mgI(OWg
or less, and most preferably 10 mgMOWg or less.
[0083] The polyalkylene glycol according to the present embodiment
can be synthesized using a conventionally lmom method ("Alkylene
Oxide Polymers", Shibata, M. et al., Kaibundo, issued on November 20,
1990). For example, the polyalkylene glycol represented by the above
formula (9) is obtained by performing addition polymerization of one or
more predetermined alkylene oxides to an alcohol (R"'oN[; R"'
101 - represents the same meaning as in R m the above formula (9)), and
subjecting the hydroxyl group at the end to etherification or
esterification. Herein, in the case where two or more different alkylene
oxides are used in the production step, the resulting polyalkylene glycol
may be any of a random copolymer and a block copolymer, but it is
preferably a block copolymer because of tending to be more excellent in
oxidation stability and lubricity, and preferably a random copolymer
because of tending to be more excellent in low-temperature fluidity.
[0084j The kinematic viscosity at 100°C of the polyalkylene glycol
according to the present embodiment is preferably 5 to 20 mm2/s,
preferably 6 to 18 mm2/s, more preferably 7 to 16 d s , further
preferably 8 to 15 m2/s, and most preferably 10 to 15 mm2/s. If the
kinematic viscosity at 100°C is less than the above lower limit, lubricity
under coexistence with the refrigerant is insufficient, and on the other
hand, if the kinelmtic viscosity at 100°C is more than the above upper
limit, a composition range in which compatibility with the recgerant is
exhibited is narrow, and lubrication failure in a refiigerant compressor
and inhibition of heat exchange in an evaporator easily occur. In
addition, the kinematic viscosity at 40°C of the polyalkylene glycol is
preferably 10 to 200 mm2/s and more preferably 20 to 150 d s . If
the kinematic viscosity at 40°C is less than 10 mm2/s, lubricity and
sealability of a compressor tend to be deteriorated, and if the kinematic
viscosity at 40°C is more than 200 rnm2/s, a composition range in which
compatibility with the refrigerant is exhibited under low temperature
conditions tends to be narrow, and lubrication failure in a refrigerant
compressor and inhibition of heat exchange in an evaporator tend to
easily occur.
5 [0085] In addition, the pour point of the polyalkylene glycol
represented by the above formula (9) is preferably -10°C or lower and
more preferably -20 to -50°C. If a polyallcylene glycol having a pour
point of -10°C or higher is used, the refigerating machine oil tends to
be solidified at a low temperature in the refrigerant circulation system.
10 [0086] In addition, in the production step of the polyalkylene glycol of
the above formula (9), alkylene oxides such as propylene oxide may
cause a side reaction and thus an unsaturated group such as an aryl
group may be formed in the molecule. If an unsaturated group is
formed in the polyalkylene glycol molecule, the following phenomenon
15 easily occurs: the thermal stability of the polyallcylene glycol itself is
deteriorated, a polymerized produce is generated to generate sludge, or
antioxidative property (oxidation prevention property) is deteriorated to
generate peroxide. In particular, if peroxide is generated, it is
decomposed to generate a compound having a carbonyl group, and the
20 compound having a carbonyl group M e r generates sludge to easily
cause blockage of a capillary.
[0087] Accordingly, as the polyalkylene glycol according to the present
embodiment, one in which the degree of unsaturation due to an
unsaturated group and the like is low is preferable, and specifically, the
25 degree of unsaturation is preferably 0.04 meqlg or less, more preferably
0.03 meqlg or less, and most preferably 0.02 meqlg or less. In addition,
the peroxide value is preferably 10.0 meqtkg or less, more preferably
5.0 meqkg or less, and most preferably 1.0 meqkg. Furthermore, the
carbonyl value is preferably 100 ppm by weight or less, more preferably
50 ppm by weight or less, and most preferably 20 ppm by weight or
5 less.
[0088] In the present embodiment, in ordcr to obtain a polyalkylene
glycol in which the degree of unsaturation, the peroxide value and the
carbonyl value are low, it is preferable that the reaction temperature at
which propylene oxide is reacted be 120°C or lower (more preferably
10 llO°C or lower ). In addition, if an alkali catalyst is used during the
production, an inorganic adsorbent such as activated carbon, activated
white earth, bentonite, dolomite, or aluminosilicate can be used for
removing the catalyst, to thereby reduce the degree of unsaturation. In
addition, it is possible to prevent the increase in peroxide value or
15 carbonyl value also by avoiding the polyalkylene glycol being in contact
with oxygen as much as possible during its production or use, or by
adding an antioxidant.
[0089] While it is required for the polyalkylene glycol compound in the
present embodiment that the carbon/oxygen molar ratio is in a
20 predetermined range, a polymer whose molar ratio is in the above range
can be produced by selecting and regulating the types and the mixing
ratio of the raw material monomers.
[0090] The content of the polyol ester, the polyvinyl ether or the
polyalkylene glycol compound in the refrigerating machine oil is
25 preferably 80% by mass or more and particularly preferably 90% by
mass or more in total based on the total amount of the refrigerating
machine oil in order that the refrigerating mac!kx oil is excellent in
characteristics demanded, such as lubricity, compatibility,
thermal/chemical stability, and electrical insulation property. As the
base oil, a mineral oil, a hydrocarbon-based oil such as an olefin
polymer, a naphthalene compound and alkyibenzenes, and an
oxygen-containing synthetic oil such as carbonates, ketones, polyphenyl
ethers, silicones, polysiloxanes and perfluoroethers can be used in
combination but the polyol ester, thc polyvinyl ether and the
polyalkylene glycol compound described later,. As the
oxygen-containing synthetic oil, among them, carbonates or ketones are
preferably used.
[0091] The kinematic viscosity of the refrigerating machine oil is not
particularly limited, but the kinematic viscosity at 40°C can be
preferably set to 3 to 1000 d s , more preferably 4 to 500 mrn2/s, and
most preferably 5 to 400 mm2/s. In addition, the kinematic viscosity at
100°C can be preferably set to 1 to 100 mm2/s and more preferably 2 to
5 0 mm2/s.
[0092] The volume resistivity of the refrigerating machine oil is not
particularly limited, but it can be preferably set to 1.0 x lo9 Om or
more, more preferably 1.0 x 10" Om or more, and most preferably 1.0
x 10" Om or more. In particular, in the case where the refrigerating
machime oil is used for a closed type refrigerating machine, a high
electrical insulation property tends to be required. In the present
invention, the volume resistivity means the value at 25°C measured
according to JIS C 2101 "Electrical Insulation Oil Test Method".
[0093] The moisture content in the refrigerating machine oil is not
particularly limited, but it can be preferably set to 200 ppm or less, more
preferably 100 ppm or less, and most preferably 50 ppm or less based
on the total amount of the refrigerating machine oil. In particular, in
the casc where the refrigerating machine oil is used for a closed type
refrigerating machine, the moisture content is demanded to be low from
the viewpoint of the influence on themaUchemical stability and the
electrical insulation property of the refrigerating machine oil.
[0094] The acid valuc of the refrigerating machine oil is not particularly
limited, but it can be preferably set to 0.1 mgKOWg or less and more
preferably 0.05 mgKOWg or less in order to prevent corrosion of a
metal used for a refrigerating machine or a pipe, and to prevent
decomposition of the ester contained in the refrigerating machine oil
according to the present embodiment. In the present invention, the
acid value means the acid value measured according to JIS 1C2501
"Petroleum Products And Lubricating Oils-Neutralization Value Test
Method".
[0095] The ash content of the re&igerating machine oil is not
particularly limited, but it can be preferably set to 100 ppm or less and
more preferably 50 ppm or less in order to increase the
thermal/chemical stability of the refrigerating machine oil according to
the present embodiment and to suppress the occurrence of sludge or the
like. In the present invention, the ash content means the value of the
ash content measured according to JIS K2272 "Crude OilPetroleum
Product Ash Content and Sulfated Ash Content Test Method".
[0096] The working fluid composition for a refrigerating machine
according to the present embodiment can also be used in the form of
being blended with various additives, if necessary. While the content
of the additives is shown based on the total amount of a refrigerating
machine oil composition, the content of these components in the fluid
composition for a refrigerating machine is preferably 5% by mass or
less and particularly preferably 2% by mass or less based on the total
amount of a refrigerating machine oil composition.
[0097] In order to fbrther improve the wear resistance and the load ,
carPying capacity of the working fluid composition for a refrigerating
machine according to the present embodiment, it is possible to blend at
least one phosphorus compound selected from the group consisting of
phosphates, acidic phosphatesest,h iophosphates, arnine salts of acidic
phosphates, chlorinated phosphates, and phosphites. These
phosphorus compounds are esters of phosphoric acid or phosphorous
acid and an alkanol or a polyether type alcohol, or derivatives thereof.
[0098] In addition, the working fluid composition for a refrigerating
machine according to the present embodiment may contain at least one
epoxy compound selected from a phenylglycidylether type epoxy
compound, an alkylglycidylether type epoxy compound, a glycidylester
type epoxy compound, an allyloxysilane compound, an alkyloxysilane
compound, an alicyclic epoxy compound, an epoxidated fatty acid
monoester and an epoxidated vegetable oil in order to further improve
the theimallchemical stability thereof.
[0099] In addition, the working fluid composition for a refrigerating
machine according to the present embodiment may if necessary contain
conventionally known additives for a refrigerating machine oil in order
to further enhance the performances thereof. Examples of such
additives includes a phenol-based antioxidant such as
di-tert-butyl-p-cresol and bisphenol A, an amine-based antioxidant such
as phenyl-a-naphthylamine and
N,N-di(2-naphthy1)-p-phenylenediamine, an antiwear agent such as zinc
5 dithiophosphate, an extreme pressure agent such as chlorinated paraffins
and a sulh compound, an oilness agent sucl~ as fatty acids, a
antifoaming agent such as silicones, a metal deactivator such as
benzotriazole, a viscosity index improver, a pour point depressant, and a
detergent dispersant. These additives may be used singly or in
10 combination of two or more.
[0100] The working fluid composition for a refrigerating machine
according to the present embodiment is preferably used for a room
air-conditioner and a cold storage chamber having a closed type
reciprocating or rotating compressor, or an open-type or closed type car
15 air-conditioner. In addition, the working fluid composition for a
reikigerating machine and the refrigerating machine oil according to the
present embodiment are preferably used for a cooling apparatus or the
like of a dehumidifier, a water heater, a refkigerator, a refi+igeratian and
cooling warehouse, a vending machine, a showcase, a chemical plant, or
20 the like. Furthermore, the working fluid composition for a
rei%gerating machine and the refrigerating machine oil according to the
present embodiment are also preferably used for one having a
centrifugal compressor.
Examples
25 [O 10 11 Hereinafter, the present invention is more specifically described
based on Examples and Comparative Examples, but the present
invention is not limited to the following Examples at all.
[O 1021 [Refrigerating machine oil]
First, 0.1% by mass of di-ter.-butyl-p-cresol (DBPC) as an
antioxidant was added to each of base oils 1 to 6 shown below to
prepare each of refrigerating machine oils 1 to 6. Various properties of
refrigerating machine oils 1 to 6 are shown in Table 1.
[Base oil]
Base oil 1: ester of mixed fatty acid of 2-ethylhexanoic acid and
3,5,5-trimethylhexanoic acid (mixing ratio (molar ratio): 50150) with
pentaerythritol. Carbodoxygen molar ratio: 4.8
Base oil 2: ester of mixed fatty acid of n-pentanoic acid, n-heptanoic
acid and 3,5,5-trimethylhexanoic acid (mixing ratio (molar ratio):
40/40/20) with pentaerythritol. Carbon/oxygen molar ratio: 3.3
Base oil 3: ester of oleic acid and trimethylolpropane. Carbodoxygen
molar ratio: 9.8
Base oil 4: copolymer of ethyl vinyl ether and isobutyl vinyl ether (ethyl
vinyl etherlisobutyl vinyl ether = 711 (molar ratio)). Weight average
molecular weight: 910; carbodoxygen molar ratio: 4.3
Base oil 5: compound in which both ends of polypropylene glycol were
methyl-etherified. Weight average molecular weight: 1100;
carbodoxygen molar ratio: 2.9
Base oil 6: compound being copolymer of polyoxyethylene glycol and
polyoxypropylene glycol, wherein one end was methyl-etherified.
Weight average molecular weight: 1700; carbodoxygen molar ratio: 2.7
[0103] [Table 11
[Table 11 (continued)
-
Kinematic viscosity at
40°C [&Is]
Kinematic viscosity at
100°C [mm2/s]
Volume resistivity [ Q ]
Moisture content [ppm]
Acid value [mgKOWg]
5 [0104] [Examples 1 to 8 and Comparative Examples 1 to 121
Refjigerafig
machine oil 6
Base oil 6
2.7
Hydroxyl group
twKOWg1
Ash content
( P Pb~y mass)
In each of Examples 1 to 8 and Comparative Examples 1 to 12,
Reiiigerating
machine oil 5
Base oil 5
2.9
Base oil
Carbonloxygen
molar ratio
66.4
8.15
with respect to each working fluid compositioll for a refrigerating
Refrigerating
machine oil 4
Base oil 4
4.3
1.5
0.1
46.5
9.70
73.2
15.3
4.8
0.1
1x10~
97
0.01
9x1 0"
87
0.01
7.5
0.1
I
1x10~
95
0.01
machine in which each of refrigerating machine oils 1 to 6 was
combined with each refrigerant shown in Tables 2 to 4, evaluation tests
shown below were performed. As described later, the mass ratio of the
refrigerant to the refrigerating machine oil in the worlhg fluid
5 composition for a refrigerating machine was changed with respect to
each test.
[0105] As the reFrigerant, the followings were used. Mixed refrigerant
A-1 was set in favor of refrigerant characteristics for the increase in
efficiency, and the GWP thereof was 300 or less, specifically 272.
10 Mixed refkigerant A-2 was set for a further reduction in GWP, and the
GWP thereof was 150 or less, specifically 138. Herein, HFC-134a,
whose GWP was as high as 1300, was currently used widely as a
refigerant, and therefore used for comparison.
[Refrigerant]
15 Mixed refrigerant A-1: R290mC-32mO-1234yf = 10/40/50 (mass
ratio, GWP: 272)
Mixed refi-igerant A-2: r600aMFC-32kIFO-1234yf = 20/20/60 (mass
ratio, GW: 138)
WFC-32: difluoromethane (GWP: 675)
20 JSO-1234yf: 2,3,3,3-tetrafluoropropene (GWP: 4)
WC- 134a: 1,1,1,2-tetrduoroethane (GWP: 13 00)
R290: propane (GWP: 3)
R600a: isobutane (GW: 3)
[0106] Then, with respect to each ofthe working fluid compositions for
25 a re~geratingm achine in Examples 1 to 8 and Comparative Examples
1 to 12, evaluation tests shown below were performed. The results are
shown in Tables 2 to 4.
[0 1071 [Evaluation of compatibility]
According to JIS-K-2211, "Test Method of Compatibility of
Refrigerating machine Oil with Refrigerant", 2 g of each refrigerating
5 machine oil was blended with 18 g of each of the above refrigerants
including the mixed refrigerants, and whether the refrigerant and the
refrigerating machine oil were dissolved in each other at O°C or not was
observed. The results obtained are shown in Tables 2 to 4. In Tables,
"Compatible" means that the refrigerant and the refrigerating machine
10 oil were dissolved in each other and "Separated" means that the
reeigerant and the refrigerating machine oil were separated to two
layers.
[0 1081 [Evaluation of themallchemical stability]
According to JIS-K-2211, 1 g of a rehigerating machine oil
15 (initial AS334 color L: 0.5) in which the moisture content was adjusted
1
to 100 ppm or less, 1 g of each of various refrigerants described above,
and a catalyst (wire of each of iron, copper and aluminum) were
enclosed into a glass tube, and then the resultant was placed in a
protective tube made of iron, and heated to 175°C and kept therein for
20 one week. After the test, the ASTM color of the refrigerating machine
oil and the change in color of the catalyst color were evaluated. The
ASTM color was evaluated according to ASTM D156. In addition, the
change in color of the catalyst was evaluated by visually observing the
appearance for rating as no change, no gloss, or blackened. In the case
25 of no gloss or blaclcened, the mixed liquid of the refrigerating machine
oil and the refigerant, namely, a working fluid can be said to be
deteriorated. The results obtained are shown in Tables 2 to 4.
[O 1091 [Table 21
I~efri~eratminac~h ine oil
ASTM color
(ASTM
D156)
Mixed
Example 3
Refrigeratin?
machine oil i
Mixed
rekigerant
A- 1
272
Compatible
[Table 21 (continued)
Appearance of
catalyst A1
I Mixed / Mixed I Mixed /
No change
. - .
l~efri~erant I refrigerant 1 refrigerant I refrigerant /
No change
Refrigerating machine oil
1 I (ASTM / L0.5 I L0.5 I L0.5 I
No change
Example 5
Refrigcrating
machine oil 4
Example 4
Refrigerating
machine oil 2
G W
Compatibility
/ ASTM color
~ 1 5 6 )
Themaw Appearance Of No change No change No change
chemical catalyst Cu
Appearance Of No change No change No change
catalyst Fe r
--Example 6
Refiigerating
machine oil 4
A-2
138
Compatible
Appearance of
catalyslA1
A- 1
272
Compatible
A-2
138
Compatible
No change No change No change
[0 1 l 1] [Table 41
f No change 1 No changr / No change I No changr
catalyst A1
chemical
stability
Appearance of
catalyst cu
Appearance of
catalyst Fe
[Table 41 (continued)
Appearance of 1 1 No change 1 . No gloss 1 No change
catalyst ~u
chemical
stability Appearance of
catalyst Fe
No change No gloss No change
Comparative
Exam~le1 0
Re'igerating
Rekigerant
GWP
Compatibility
ASTM color
(ASTM D156)
No change
No change
[0112] [Examples 9 to 18 and Comparative Examples 13 to 201
Ln each of Examples 9 to 18 and Comparative Examples 13 to
20, the above evaluation tests ([Evaluation of refkigerant compatibility],
[Evaluation of thermal/chemical stability]) were performed with respect
to each working fluid composition for a refrigerating machine in which
Comparative
Examule 11
Rekigerating
machine 4
HFC-32
675
Separated
L0.5
Appearance of
catalyst A1
No gloss
No gloss
Comparative
Examvle 12 A
Refrigerating
machine oil 5
EFO-1234yf
4
Compatible
L2.0
No change
No change
No change
Reiiigerating
machine oil 6
HFC-32
675
Separated
L0.5
No gloss
No gloss
No change No change
any of refi-igerating machine oils 1 to 5 and any of refrigerants shown in
Tables 5 to 7 are combined. As described later, the mass ratio of the
refi-igerant to the refi-igerating machine oil in the working fluid
composition for a refrigerating machine was changed with respect to
each of the tests.
[0113] As the refrigerant, the following three mixed refrigerants B-1,
B-2, and B-3, in which HFC-32, HFO-1234yf itself and R744 were
mixed, were used. Mixed refrigerant B-1 was a mixed refrigerant of
three refrigerants, WFC-32, FIFO-1234yf and R744, and thc GWF
thereof was 300 or less. While no test method for discriminating the
boundary between "non-flammable" and "low flammable" is established
with respect to burning property, burning property is decreased as the
proportion of non-flammable R744 is increased. Mixed refrigerant
B-2 was a mixed refrigerant of WO-1234yf and R744, and the GWF
thereof was as extremely low as 3. Mixed refrigerant B-3 was a
refrigerant in which the proportion of HFC-32 for the increase in
efficiency was increased and R744 was mixed to thereby intend to
achieve "non-flammable", and the GWP thereof was 405.
~efi-igerant]
HFC-32: difluoromethane (GWP: 675)
HFQ-1234yf: 2,3,3,3-tetrafluoropropene (GWP: 4)
R744: carbon dioxide (GWP: 1)
Mied refrigerant B-1: WFC-32/HFQ-l234yfR744 = 40140120 (mass
ratio, GWP: 272)
Mixed refi-igerant B-2: IIFO-1234yfE744 = 70130 (mass ratio, GWP:
3)
Mixed refiigerant B-3: HFC32R744 = 60140 (mass ratio, GmP: 405)
[0114] [Table 51
Refrigerating machine oil
Refrigerant
GWP
Compatibility
ASTM color
IASTM D156)
Example 9 .
Refrigerating
machine oil
Thermd
chemical
stability
5 [Table 51 (continued)
Mixed
refrigerant B-1
272
Compatible
L0.5
Appearance of
catalyst A1
Example 10
Refigeraling
machine oil
Appearance of
catalyst cu
Appearance of
catalyst Fe
Example 11
Refrigerating
machine oil 1
Mixed
refiigerant B-2
3
Compatible
L1.0
No change
Refiigerating machine oil
lAppeaimw I No change / No change I No change I catalyst A1
Mixed
refrigerant B-3
405
Compatible
L0.5
No change
No change
chemical
Stability
No change
Example 12
Refiigerating
machine oil 2
No change
No change
No change
Appearance of
catalyst cu
Appearance of
catalyst Fe
No change
No change
Example 13
Refrigerating
machme oil 2
Example 14
Refiigerating
machine oil 4
No change
No change
No change
No change
No change
No change
[O 1 161 [Table 71
1 / Com~arative / Comparative / Comparative 1
Refrigerating
Rekigermt
GWP
Compatibility
ASTM color
(ASW D156)
~cataalynst Ac1 e o f I Nochange I No change I No change 1
~xample15
Refrigerating
machine oil 3
Appearance of
TnermaV catalyst cu
chemical
Appearance of
catalvst Fe I
[Table 71 (continued)
Mixed
refrigerant B-3
405
Separated
LO.5
~ x & n ~1l6e
Refrigerating
machine oil 1
No change
No change
~ x a i p l e17
Refrigerating
machine oil 1
HFC-32
675
Separated
L0.5
Refrigerating machme oil
Refrigerant
-GWP -
Compatibility
HFO-1234yf
4
Compatible
L1.5
No change
No change
I
po1 i No change 1 No change No change 1 catalyst A1
No gloss
No gloss
Refrigerating
machine oil 2
HFC-32
675
Separated
ThermaY
chemical
stability
[0117] With respect to the working fluid composition for a refrigerating
ASTM color
(ASTM D156)
machine in each of Examples 1 to 8 shown in Tables 2 and 3 and
Examples 9 to 18 shown in Tables 5 and 6, the GWP of all the
Refrigerating
machine oil 4
NFC-32
675
Sepmated
Appeararlce of
-catalyst cu -
Appearance of
catalyst Fe
refrigerants was as low as 500 or less, the compatibility of the
Refrigerating
machine oil 5
HFO-1234yf
4
Comyatible
L0.5
No change
L0.5 L2.0
No change No change No gloss
No change No gloss
refrigerant with the refiigerating machine oil was also no problematic,
the thermal/chemical stability was also good, and the working fluid for a
1 refrigerating machine could be said to be an excellent working fluid for
1
!
a refrigerating machine.
1
5 On the other hand, with respect to the working fluid composition
for a refiigerating machine in each of Comparative Examples 1 and 2
shown in Table 3 and Comparative Examples 13 to 15 shown in Tables
6 and 7, while rekigerating machine oil 3 in Table 1, whose
carbontoxygen molar ratio was out of the range of the present invention,
was used, it was not compatible with the rekigerant, and thus the
working fluid composition for a refrigerating machine is difficult to use
as a refrigerating machine oil.
In addition, with respect to the working fluid composition for a
resgerating machine in each of Comparative Examples 3 to 6,8, 10, 12,
16, 18 and 19, the compatibility of the refi-igeraat with the refkigerating
machine oil was not satisfactory. Furthermore, in each of Comparative
Examples 3,4, 6, 10, 12, 16, 18 and 19, the GWP of the reftigerant was
also slightly high.
With respect to the working fluid composition for a refiigerating
machine in each of Comparative Examples 5,7,9, 11, 17 and 20, since
deterioration due to change in color of each oil tested and change of
properties of the catalyst were observed, and thermallchemical stability
was poor, the working fluid composition for a refrigerating machine
could not be said to be a suitable working fluid for a reeigerating
machine.
Industrial Applicabiliw
[0118] The present invention provides a worlting fluid composition for
use in a refrigerating machine which contains a refrigerant having a low
GMrP and containing a refrigerant such as a hydrocarbon,
difluoromethane, and an unsaturated hydrofluorocarbon is used, and the
5 composition can be used as a working fluid at a high efficiency in a
refrigeration system having a compressor, a condenser, a throttle device,
an evaporator, and the l i e among which the rcfligerant is circulated, in
particular, in a refrigerating machine having a compressor such as a
rotary-type, swing-type, or scrolling-type compressor, and can be
10 suitably used in the fields of a room air-conditioner, an all-in-one air
conditioner, a cold storage chamber, a car air-conditioner, an industrial
refrigerating machine, and the like.
C L m S
1. A working fluid composition for a refigerating machine,
comprising:
a refrigerant comprising a first reffigerant component and a
5 second refrigerant component, and having a global warming potential
(GWP) of 500 or less, wherein the first refrigerant component is at least
one selected from difluoromethane and tetrafluoropropene, and the
second refrigerant component is at least one selected from carbon
dioxide and a hydrocarbon having 3 to 4 carbon atoms; and
10 a refrigerating machine oil comprising at least one selected from
a polyol ester, a polyvinyl ether and a polyalkylene glycol compound as
a base oil, wherein a carbontoxygen molar ratio of the base oil is 2.5 or
more and 5.8 or less.
2. The working fluid composition for a refiigerating machine
15 according to claim 1, wherein the rekigerant comprises the hydrocarbon
having 3 to 4 carbon atoms, difluoromethane and tetrafluoropropene,
and has a global warming potential of 400 or less.
3. The working fluid composition for a refrigerating n~achine
according to claim 1 or 2, wherein the rehigeranl comprises 3 to 40
20 parts by mass of the hydrocarbon having 3 to 4 carbon atoms, 20 to 60
parts by mass of difluoromethane and 20 to 70 parts by mass of
tetrafluoropropene based on 100 parts by mass of the refrigerant.
4. The working fluid composition for a refrigerating machine
according to any one of claims 1 to 3, wherein the hydrocarbon having 3
to 4 carbon atoms is propane or isobutane, and a global warming
potential of the refrigerant is 300 or less.
5. The working fluid composition for a refrigerating machine
according to claim 1, wherein the refrigerant comprises at least one
selected from difluoromethane and tetrafluoropropene, and carbon
dioxide, and has a global warming potential of 500 or less.
5 6. The working fluid composition for a reliigerating machine
according to any one of claims 1 to 5, wherein a mass ratio of the
refrigerant to the refrigerating machine oil is 90 : 10 to 30 : 70.
7. The working fluid composition for a refrigerating machine
according to any one of claims 1 to 6, wherein the base oil comprises a
polyol ester having a carbodoxygen molar ratio of 2.5 or more and 5.8
or less, and the polyol ester is a polyol ester obtainable by synthesis
from a fatty acid having 4 to 9 carbon atoms and a polyhydric alcohol
having 4 to 12 carbon atoms.
8. The worlcing fluid composition for a refrigerating machine
according to any one of claims 1 to 6, wherein the base oil comprises a
polyalkylene glycol compound having a carbodoxygen molar ratio of
2.5 or more and 5.8 or less, and the polyalkylene glycol compound is a
compound having a homopolymerization chain of propylene oxide or a
copolymerization chain of propylene oxide and ethylene oxide, at least
one of both ends of the chain being blocked by an ether bond.
9. The working fluid composition for a refrigerating machine
according to any one of claims 1 to 6, wherein the base oil comprises a
polyvinyl ether having a carbodoxygen molar ratio of 2.5 or more and
5.8 or less, and the polyvinyl ether is a polyvinyl ether having a
structural unit represented by the following formula (1).
[Chemical Formula I]
[R', R2 and R3 may be the same or different and each represent a
hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, R4
represents a divalent hydrocarbon group having 1 to 10 carbon atoms or
5 an ether bond oxygen-containing divalent hydrocarbon group having 2
to 20 carbon atoms, R5 represents a hydrocarbon group having 1 to 20
carbon atoms, m represents a number such that an average value of m in
the polyvinyl ether is 0 to 10, R' to R~ may be the same or different in
each occurrence of the structural units, and when m represents 2 or
10 more in one structural unif a plurality of R40 may be the same or
different.]