Title of Invention:
WORKING FLUID COMPOSITION FOR REFRIGERATOR,
REFRIGERATION OIL, AND METHOD FOR PRODUCING SAME
5 Technical Field
[0001] The present invention relates to a working fluid composition for
a refrigerating machine using, as a refrigerant, a hydrocarbon having an
extremely low global walvring potential, such as ethane, propane,
n-butane or isobutane; a refrigerating machine oil (i.e., a lubricating oil
10 for a refrigerating machine) to be used together with the hydrocarbon
reftigerant; and a method for nianufactu~ingth e saine.
Background Art
[0002] In conventional refrigerating machines, air conditioners, cold
storage chambers and the like, freon containing fluorine and chlorine
15 was used as a refrigerant. Examples of the freon include
chlorofluorocarbon (CFC) such as R-11 (trichloromonofluoromethane)
or R-12 (dichlorodifluoromethane), and hydrochlorofluorocarbon
(HCFC) such as R-22 (monochlorodifluoromethane).
[0003] However, the production and use of the £reon have been
20 internationally regulated due to a recent problem of ozone layer
depletion, and a novel hydrogen-containing fteon rekigerant not
containing chlorine is started to be used instead of the conventional
freon nowadays. Examples of the hydrogen-containing freon
refrigerant include tetrafluoroethane (R-134 or R-134a) and a mixed
25 refrigerant of hydrofluorocarbon @FC) such as R410A or R407C.
[0004] Although the HFC does not deplete thc ozone layer, however, it
has a high greenhouse effect, and hence is not necessarily an excellent
refrigerant fioin the viewpoint of global warning that has become a
recent problem.
[0005] Therefore, a lower hydrocarbon having 2 to 4 carbon atoms has
5 been recently gathering attention because it does not deplete the ozone
layer and causes an extremely small influence on the global wasming as
compared with the aforementioned chlorine or non-chlorine
fluorocasbon refrigerants, and it is now being examined to be used, as a
refrigerant, in a refrigeration system having high cooling efficiency such
10 as a room air conditioner or an industrial refijgerating machine
including a compressor, a condenser, a throttle device, an evaporator
and the like, which has been developed with the fYeon refrigerant.
Such a hydrocarbon refrigerant has a global warming potential of 1/100
or less and is highly efficient as compared with R401A that is a mixed
15 reEcigerant of hydrofluorocarbon (HFC) currently widely used as a
refrigerant for a room air conditioner. In particular, there is a
possibility that use of propane having 3 carbon atoms (R290) can
largely and econo~nicallyr cduce the influence on the global warning
without requiring large-scaled design change of an air conditionel:
20 However, this propane is combustible, and therefore, there are a
problem of technical development for using it safely, and a problem of
selection, as a lubricant, of a refrigerating machine oil having
appropriate compatibility with this refrigerant.
[0006] As a lubricating oil for the lower hydrocarbon refrigerant, a
25 mineral oil of, for example, naphthene- or paraffin-based mineral oil, an
alkylbenzene oil, an ester oil, an ether oil and a fluorinated oil having
co~npatibility with the refrigerant have been proposed. Besides, a
polyol ester (F'OE) has been proposed as the ester oil (see Patent
Literature 1).
Citation List
5 Patent Literature
[0007] Patent Literature 1: Japanese Patent Application Laid-Open No.
2003-41278
Summary of Invention
Technical Problem
10 [0008] However, the hydrocarbon refrigerant has a small polarity, and
hence is excessively dissolved in the conventional refrigerating machine
oil such as the mineral oil, alkylbenzene or polyol ester. Therefore, the
viscosity of the lubricating oil after dissolving the refiigerant therein
(namely, the viscosity of the mixture of the refrigerant and the
15 refirigerating machine oil) is lowered, and it is difficult to retain proper
viscosity in a sliding portion of a refrigerating compressor, causing
kiction.
[0009] Besides, if the mineral oil, the alkylbenzene oil or the like is
used as a hydrocarbon refrigerating machine oil, lubricity cannot be
20 retained, because the viscosity of the lubricating oil after dissolving the
rekigerant therein is lowered, and in addition, it is necessary to increase
the filling amount of the refrigerant for attaining given cooling capacity.
Here, because the lower hydrocarbon such as propane used as the
refiigerant is combustible, it is required to minimize the filling amount
25 thereof, and therefore, it is not preferable to increase the filling amount
of the refrigerant.
1
[0010] Furtl~er~norteh,e solubility of the hydrocarbon refrigerant in the
ester oil such as the polyol ester is high although it is not as high as that
in the hydrocarbon oil. Besides, although it is necessary to increase
the viscosity by increasing the molecular weight of the refrigerating
5 machine oil itself as a countermeasure against the viscosity lowering, it
is difficult for the ester oil such as the polyol ester to increase the
viscosity while retaining a low pour point, which is an indispensable
characteristic as the refrigerating machine oil.
[0011] On the other hand, since the ether oil such as polyalkylene
10 glycol (PAG) has a large polarity, the ether oil can suppress the
solubility of the hydrocarbon refrigerant therein to low level. But the
ether oil has a disadvantage that an electrical insulating property, which
is one of indispensable characteristics as the refrigerating machine oil, is
low, and in addition, its essential lubricity derived from its structure is
15 inferior to that of the ester oil.
[0012] The fluorinated oil is difficult to be compatible with the
hydrocarbon refrigerant on the contrary, and there arises a problem of
oil return in a refrigeration cycle. Besides, the fluorinated oil is
extremely expensive, and it is not realistic to industrially use it.
20 [0013] In consideration of the aforementioned problems, an object of
the present invention is to provide a refrigerating machine oil that has
appropriate compatibility and solubility with a hydrocarbon refrigerant,
can retain viscosity not impairing lubricity, and is excellent in the
lubricity, the electrical insulating proper@ and the stability, a method for
25 manufacturing the same, and a working fluid composition for a
refrigerating machine containing the refrigerating machine oil.
Solution to Problem
[0014] In order to achieve the object, the present inventors have made
earnest examinations, resulting in finding that an ester having a vely
limited specific chemical structure, among various esters, and having a
5 comparatively large polarity, what is called a complex ester, has proper
compatibility and solubility with a hydrocarbon refrigerant, has
satisfacto~y lubricity, high stability and low hygroscopicity, and is
excellent as a refrigerating machine oil for a hydrocarbon refrigerant of
propane, isobutane or the like, and thus, the present invention was
10 accomplished.
[DO151 Specifically, the present invention provides a working fluid
composition for a refrigerating machine according to the following [I]
to [9], a refrigerating machine oil according to the following [lo] or [II],
and a method for manufacturing a refrigerating maclune oil according to
15 the following [12].
Ll] A working fluid composition for a refrigerating machine,
comprising: a refrigerating machine oil comprising a complex ester as a
base oil; and a l~ydrocarbonr efrigerant having 2 to 4 carbon atoms, the
complex ester being obtainable by hrther esterifying, with at least one
20 selected from a rnonohydric alcohol having 1 to 20 carbon atoms and a
fatty acid (a chain monocarboxylic acid) having 2 to 20 carbon atoms,
an ester intermediate obtained by reacting a neopentyl polyol with a
dibasic acid, and having an acid value of 0.5 mgKOH/g or less, the
resgerating machine oil having a kinematic viscosity at 100°C of 2 to
25 50 mm2/s.
[2] A working fluid composition for a ref?igerating machine,
I
comprising: a refiigerating machine oil comprising a complex ester as a
base oil; and a hydrocarbon refrigerant having 2 to 4 carbon atoms, the
complex ester being a complex ester of a neopentyl polyol, a dibasic
acid, and at least one selected &om a monohydric alcohol having 1 to 20
5 carbon atoms and a fatty acid having 2 to 20 carbon atoms, and having
an acid value of 0.5 mgKOH/g or less, the refiigesating machine oil
having a kinematic viscosity at 100°C of 2 to 50 mm2/s.
[3] The working fluid composition for a refrigerating machine
according to [I] or [2], wherein the neopentyl polyol is at least one
10 selected &om neopentyl glycol, trimethyl01 propane and pentaelythitol,
the dibasic acid is at least one selected &om adipic acid, pimelic acid,
suberic acid, azelaic acid and sebacic acid, and the hydrocarbon
refiigerant is at least one selected from propane, butane and isobutane.
[4] The working fluid composition for a refrigerating machine
15 according to any one of [l] to 131, wherein the monohydric alcohol is at
least one selected from linear alcohol having 4 to 18 carbon atoms,
2-ethyl hexanol and 3,5,5-trimethyl hexanol.
[5] The working fluid composition for a refiigerating machine
according to any one of [l] to [4], wherein the fatty acid is at least one
20 selected from linear fatty acid having 5 to 18 carbon atoms, 2-ethyl
hexanoic acid and 3,5,5-trimethyl hexanoic acid.
[6] The working fluid composition for a refiigesating machine
according to any one of [I] to [5], wherein the complex ester is
obtainable by hrther esterifying, with a monohydric alcohol having I to
25 20 carbon atoms, an ester intermediate obtained by reacting the dibasic
acid with trimethyl01 propane at a ratio of 1.5 moles or more and less
than 3 moles of the dibasic acid per 1 mole of trimethylol propane.
[7] The working fluid composition for a refrigerating machine
according to any one of [I] to [GI], further comprising at least one
additive selected from a hindered phenol compound, an aromatic amine
5 compound, an epoxy compound, a carbodiimide and a phosphoric acid
ester, wherein a total content of the additive is 0.05 to 5.0% by mass
based on a total amount of the refiigerating machine oil.
[8] 'The working fluid composition for a refrigerating machine
according to any one of [I] to [7], wherein a volume resistivity at 80°C
10 of the refiigcrating machine oil is 10" Ocm or more.
[9] The working fluid composition for a refrigerating machine
according to any one of [l] to [8], wherein the hydrocarbon refrigerant
is propane.
[I 01 A refrigerating machine oil comprising a complex ester as a
15 base oil, the complex ester being obtainable by further esterifying, with
a monohydric alcohol having 1 to 20 carbon atoms or a fatty acid
having 2 to 20 carbon atoms, an ester intermediate obtained by reacting
a neopentyl polyol with a dibasic acid, and having an acid value of 0.5
mgKOWg or less, the refiigerating machine oil having a kinematic
20 viscosity at 100°C of 2 to 50 mm2/s, and being used with a hydrocarbon
refrigerant having 2 to 4 carbon atoms.
[I I] A refrigerating machine oil comprising a complex ester as a
base oil, the complex ester being a complex ester of a neopentyl polyol,
a dibasic acid and at least one selected f?om a rnonohydric alcoliol
25 having 1 to 20 carbon atoms and a fatty acid having 2 to20 carbon
atoms, and having an acid value of 0.5 mgKOHlg or less, the
refiigerating machine oil having a kinematic viscosity at 100°C of 2 to
50 mm2/s, and being used with a hydrocarbon refrigerant having 2 to 4
carbon atoms.
[12] A method for manufacturing a refiigerating machine oil
5 comprising: a &st step of obtaining an ester intermediate by reacting a
neopentyl polyol with a dibasic acid; a second step of obtaining a
complex ester having an acid value of 0.5 mgKOWg or less by
esterifying the ester intermediate with at least one selected fjrom a
mo~~ohydraiclc ohol having 1 to 20 carbon atoms and a fatty acid having
10 2 to 20 carbon atoms; and a third step of preparing a refrigerating
machine oil having a kinematic viscosity at 100°C of 2 to 50 mm2/s by
using the complex ester as a base oil, the refrigerant machine oil being
used with a hydrocarbon refrigerant having 2 to 4 carbon atoms.
Advantageous Effects of Invention
15 [0016] The present invention can provide a refrigerating machine oil
that has appropriate compatibility and solubility with a hydrocarbon
refrigerant, can retain viscosity not impairing lubricity, can reduce the
filling amount of the refjrigerant, and is excellent in the lubricity, the
electrical insulating property and the stability, and also provide a
20 method for manufacturing the same, and a working fluid composition
for a refrigerating machine containing the refi?gerating machine oil.
[0017] Incidentally, the present inventors presume the reason why the
aforementioned effects can be exhibited by the present invention as
follows. The rekigerating machine oil of the present invention is
25 presumed to have an appropriately large polarity, dissolve properly a
hydrocarbon rekigerant having 2 to 4 carbon atoms, and be able to
retain a given level of viscosity also after dissolving the refrigerant
therein. Besides, the refrigerating machine oil of the present invention
is presumed to show high adsorption on the surface of a sliding portion
in the presence of the hydrocarbon refrigerant having 2 to 4 carbon
5 atoms, and hence can attain satisfactory lubricity in practical use.
Description of Embodiments
[0018] preferable embodiments of the present invention will now be
described in detail.
[0019] [Embodiment 1: Refrigerating machine oil and method for
10 manufacturing the same]
A rekigerating machine oil according to Embodiment 1 of the
present invention comprises a complex ester as a base oil, wherein the
complex ester is obtainable by further esterifying, with a monohydric
alcohol having 1 to 20 carbon atoms or a fatty acid having 2 to 20
15 carbon atoms, an ester intermediate obtained by reacting a neopentyl
polyol with a dibasic acid, and has an acid value of 0.5 mgKOWg or
less, and wherein the refrigerating machine oil has a kinematic viscosity
at 100°C of 2 to 50 mm2/s, and is used with a hydrocarbon refrigerant
having 2 to 4 carbon atoms. Alternatively, as another aspect of the
20 present embodiment, the refrigerating machine oil comprises a complex
ester as a base oil, wherein the complex ester is a complex ester of a
neopentyl polyol, a dibasic acid, and at least one selected &om a
monohydPic alcohol having 1 to20 carbon atoms and a fatty acid having
2 to 20 carbon atoms, has an acid value of 0.5 mgKOWg or less, and
25 has a kinematic viscosity at 100°C of 2 to 50 d s , and wherein the
refrigerating machine oil is used with a hydrocarbon refrigerant having
2 to 4 carbon atoms.
[0020] Examples of the neopentyl polyol used in the present
embodiment include neopentyl glycol, trimethylol propane,
pentae~ythritol, dipentaelythsitol, trimethylol ethane and trimethylol
5 butane. Among these wopentyl polyol esters, a neopentyl polyol
having 5 to 10 carbon atoms is preferred, and neopentyl glycol,
trimethylol propane and pentaerythritol are particularly preferred. If
the number of carbon atoms of the neopentyl polyol exceeds 10, the
ratio of a hydrocarbon moiety occupying in a complex ester molecule is
10 large, and hence, the solubility with the hydsocarbon refrigerant tends to
be increased.
[0021] Examples of the dibasic acid used in the present embodiment
include dicarboxylic acids, and in particular, a dibasic acid represented
by the following formula (I):
15 HOOC(CH2),COOH (1)
wherein n represents an integer of 1 or more.
[0022] In formula (I), n represents an integer of 1 or more, preferably
an integer of 2 to 10, and more preferably an integer of 4 to 8.
[0023] Preferable examples of the dibasic acid represented by formula
20 (I) include adipic acid, pimelic acid, suberic acid, azelaic acid and
sebacic acid, and among these, adipic acid, pimelic acid and suberic
acid are particularly preferred. Such a dibasic acid has at1
appropriately large polarity, and is preferably used as a material for
synthesizing the complex ester of the present embodiment.
25 [0024] The monohydric alcohol having 1 to 20 carbon atoms used in
the present embodiment may be either linear or branched. Examples
of a linear monohydric alcohol include methanol, ethanol, n-propanol,
n-butanol, n-pcntanol, n-hexanol, n-heptanol, n-octanol, n-nonanol,
n-decanol, n-dodecanol and oleyl alcohol, and among these alcohols, a
linear monohydric alcohol having 4 to 18 carbon atoms is preferred.
5 Specific examples of a branched monohydric alcohol include all the
structural isomers of the aforementioned linear monohydric alcohols,
and among these, 2-ethyl hexanol and 3,5,5-trimethyl hexanol are
preferred. A mixed alcohol of a linear monohydric alcohol and a
branched monohydric alcohol also can be suitably used, and the
10 numbers of types of the linear monohydric alcohol and the branched
monohydric alcohol used in this case may be one, or two or more.
Although an unsaturated monohydric alcohol may be used, a saturated
monohydric alcohol is preferred.
[0025] The fatty acid having 2 to 20 casbon atoms used in the present
15 embodiment may be either linear or branched. Examples of a linear
fatty acid having 2 to 20 carbon atoms include acetic acid, n-propanoic
acid, n-butanoic acid, n-pentanoic acid, n-hexanoic acid, n-heptanoic
acid, n-octanoic acid, n-nonanoic acid, n-decanoic acid and oleic acid.
A linear fatty acid having 5 to 18 casbon atoms is preferred, and a linear
20 fatty acid having 8 to 12 carbon atoms is preferred. Examples of a
branched fatty acid include all the stsuctusal isomers of the
afore~nentioned linear acids. Among these, a branched fatty acid
having 5 to 18 carbon atoms, and particularly 8 to 12 is preferred, and
2-ethyl hexanoic acid, 3,5,5-titmethyl hexanoic acid or a mixture
25 thereof is further preferably used. A mixed fatty acid of a linear fatty
acid and a branched fatty acid also may be preferably used, and the
numbers of types of the linear fatty acid and the branched fatty acid
used in this case may be one, or two or more. Although an unsaturated
fatty acid may be used, a saturated fatty acid is preferred.
[0026] In both of the rnonohydric alcohol and the fatty acid, if the
5 number of carbon atoms is smalI, the hydrolytic stability is lowered, and
on the contrary, if the number of carbon atoms is too large, the affinity
with the hydrocarbon refrigerant is increased to increase the solubility
with it, resulting that such a coinpound is unsuitable for the object of the
present invei~tion. The number of carbon atoms of each of the
10 monohydric alcohol and the fatty acid is preferably 3 to 12, and
particularly preferably 4 to 10.
[0027] The complex ester of the present embodiment can be obtained
by esterification through a dehydration reaction of the specific
neopentyl polyol and dibasic acid, and hrther with the specific
15 monohydric alcohol or fatty acid, by general esterification via a
derivative, such as an acid anhydride or an acid chloride, of a fatty acid,
or by transesteiification of respective deiivatives.
[0028] Specifically, a method for manufacturing a refrigerating machine
oil of the present embodiment comprises: a first step of obtaining an
20 ester intermediate by reacting a neopentyl polyol and a dibasic acid; a
second step of obtaining a complex ester having an acid value of 0.5
rngKOH1g or less by esterifying the ester intermediate with at least one
selected from a monohydric alcohol having 1 to 20 carbon atoms and a
fatty acid having 2 to 20 carbon atoms; and a third step of preparing a
25 refrigerating machine oil having a kinematic viscosity at 100°C of 2 to
50 mm2/s by using the complex ester as a base oil.
[0029] In the present embodiment, the complex ester of interest is
obtained through the two steps of the esterification as described above.
More specifically, through the reaction of the neopentyl polyol and the
dibasic acid performed in the first step, an intermediate in which a
5 carboxyl group or a hydroxyl group remains depending upon a molar
ratio therebetween can be arbitrarily obtained. Then, the intermediate
is further esterified with a monohydric alcohol having 1 to 20 carbon
atoms, particularly 4 to 10 carbon atoms, if a carboxyl group (-COOH)
remains in the intermediate, or hrther esterified with a fatty acid having
10 2 to 20 carbon atoms, particularly 4 to 10 carbon atoms, if a hydroxyl
group remains, so as to adjust the acid value to 0.5 mgKOWg or less.
In this mannel; the obtained complex ester can be provided with an
appropriately large polarity and adsorption on the surface of a sliding
portion. Therefore, the complex ester has appropriate compatibility
15 and solubility with the hydrocarbon refrigerant, and can retain viscosity
not impairing lubricity, and the filling amount of the refrigerant can be
reduced. Besides, the refrigerating machine oil of the present
embodiment is excellent also ui the lubricity, the electrical insulating
property and the stability.
20 [0030] In the first step, a quantitative ratio among the neopentyl polyol,
the dibasic acid, and the monohydric alcohol having 1 to 20 carbon
atoms or the fatty acid having 2 to 20 carbon atoms can be appropriately
selected in accordance with the types and a combination of these
materials.
For example, if the neopentyl polyol is trimcthylol propane, it is
preferable to further esterify, with a monohydric alcohol, an ester
intermediate obtained by reacting the dibasic acid with trimethylol
propane at a ratio of 1.5 moles or more and less than 3 moles, and
particularly 1.7 moles or more and less than 2.5 inoles, of the dibasic
acid per 1 mole of trirnethylol propane. Alten~atively, it is preferable
to further esterify, with a fatty acid, an ester intermediate obtained by
reacting dibasic acid with trimethylol propane at a ratio of 0.6 mole or
more and less than 1.5 moles, and particularly 0.8 mole or more and less
than 1.5 moles, of the dibasic acid per 1 mole of tlimethylol propane.
If the neopentyl polyol is neopentyl glycol, it is preferable to
further esterie, with a inonohydric alcohol, an ester intermediate
obtained by reacting the dibasic acid with neopentyl glycol at a ratio of
1.0 mole or more and less than 2.0 moles, and particularly 1.2 moles or
more and less than 1.7 moles, of the dibasic acid per 1 mole of
neopentyl glycol. Alternatively, it is preferable to hrther esterify, with
a fatty acid, an ester intermediate obtained by reacting dibasic acid with
neopentyl glycol at a ratio of 0.6 mole or more and less than 1.2 moles,
and particularly 0.7 inole or more and less than 1 .O mole, of the dibasic
acid per 1 mole of neopentyl glycol.
[0031] The complex ester obtained by the aforementioned
manufactt~ring inethod may have a carboxyl group and/or a hydroxyl
group remaining unreacted, but it is preferable that a carboxyl group
does not remain. If the amount of remaining carboxyl groups is large,
it is apprehended that an unpreferable pl~el~oinenon, such as
precipitation of a inetal soap and the like generated through a reaction
with a metal used inside the refrigerating machine, may occur. From
this point of view, the acid value of the complex ester of the present
embodiment is 0.5 mgKOWg or less. A preferable acid value is 0.1
mgKOH/g or less. An acid value herein means an acid value measured
in accordance with JIS K2501.
[0032] If the amount of remaining hydroxyl groups is too large, an
5 unpreferable phenomenon that the ester becomes clouded at a low
temperatwe and blocks a capillary device in a refrigeration system
occurs, and therefore, the hydroxyl value of the complex ester of the
present embodiment is preferably 100 mgKOWg or less, more
preferably 60 mgKOH1g or less, and further more preferably 30
10 mgKOWg or less. A hydroxyl value herein means a hydroxyl value
measured in accordance with JIS K0070. The acid value and the
hydroxyl value of the refrigerating machine oil of the present
embodiment can be the same as those of the complex ester.
[0033] The kinematic viscosity at 100°C of the refrigerating machime
15 oil of the present embodiment is 2 to 50 mm2/s, and preferably 5 to 40
mm2/s. If the kinematic viscosity at 100°C falls in the above range, the
refiigerating machine can be properly operated, and high efficiency can
be assured. Furthermore, if the kinematic viscosity at 100°C is 10 to
30 mm2/s, reliability in wear resistance of a compressor can be fusther
20 improved. Incidentally, a kinematic viscosity herein means a
kinematic viscosity measured in accordance with JIS K2283.
[0034] The pour point of the refrigerating machine oil of the present
embodiment is preferably -15°C or less, and more preferably -25°C or
less from the viewpoint of a low temperature characteristic necessary as
25 the refiigeratingmachine oil. A pow point herein means a pour point
measured in accordance with JIS K2269. The kinematic viscosity and
the pour point of ihe complex ester of the present embodiment can be
the same as those of the refrigerating machine oil.
[0035] Since the refrigerating machine oil of the present embodiment
contains the above-described coniplex ester as a base oil, the
5 refrigerating machine oil of the present embodiment shows appropriate
compatibility and solubility over a wide range from a low temperature
to a high temperature when used as a refrigerating machine oil with a
hydrocarbon refrigerant such as propane @290), and thus the lubricity
and thermal stability can be greatly improved. Besides, as compared
10 with polyalkylene glycol (PAG) or the like used as a refrigerating
machine oil for a HFC (hydrofluorocarbon) re&igerant, the refrigerating
machine oil of the present embodiment has much higher electrical
insulating prope~tya nd small hygroscopicity.
[0036] The refrigerating machine oil of the present embodiment may
15 consist of the above-described complex ester (namely, the content of the
complex ester may be 100% by mass), but it can further contain a base
oil other than the complex ester and an additive as long as the function
as the reEgerating machine oil is satisfied. In this case, the content of
the complex ester is preferably 60% by mass or more, more preferably
20 80% by mass or more, and further more preferably 95% by mass or
more, based on the total amount of the refrigerating machine oil.
[0037] Examples of another base oil that may be contained in the
refrigerating machine oil of the present embodiment include an ester
other than the complex ester, an ether such as polyalkylene glycol
25 (PAG) or polyvinyl ether (PVE), and alkyl benzene or a mineral oil as
hydrocarbon base.
[0038] Furthermore, the refrigerating machine oil of the present
embodiment may fiuther contain a stability improving additive for
hither improving the stability of a mixed fluid of the refrigerant and the
rekigerating machine oil in actual use. Preferable examples of the
5 additive for improving stability include one or more of a hindered
phenol compound, an aromatic amine compound, an epoxy compound
and a carbodiimide, and it is more preferable to use an epoxy compound
and a carbodiimide together. The refrigerating machine oil of the
present embodiment may further contain an anti-wear agent such as
10 phosphoric acid ester. The contents of the stability improving additive
and the anti-wear additive are, in terms of the sum of them, preferably
0.05 to 5.0% by mass based on the total amount of the refrigerating
machine oil.
[0039] Among the stability improving additives, preferable examples of
15 the hindered phenol compound include 2,6-di-tert.-butyl phenol,
2,6-di-tert.-butyl-p-cresol and
4,4-methylene-bis-(2,6-di-text.-butyl-p-creol) The content of the
hindered phenol compound is preferably 0.05 to 1.0% by mass, and
more preferably 0.1 to 0.5% by mass based on the total amount of the
20 rekigerating machine oil.
[0040] Examples of the aromatic amine compound include
a-naphthylamine and p,p'-di-octyl-diphenylainine
(di(4-octylphenyl)amine), and a di(alkylpheny1)amine having an alkyl
group having 4 to 12 carbon atoms is preferred. The content of the
25 aromatic amine compound is preferably 0.05 to 1.0% by mass, and
more preferably 0.1 to 0.5% by mass based on the total amount of the
refrigerating machine oil.
[0041] Examples of the epoxy compound include a glycidyl ether
group-containing compound, an epoxidized fatty acid monoester, an
epoxidized fat or oil, and an epoxy cycloalkyl group-containing
5 compound, and an alkyl glycidyl ether having an alkyl group having 6
to 12 carbon atoms is preferred. The content of the epoxy compound
is preferably 0.1 to 2.0% by mass, and more preferably 0.2 to 1.0% by
mass based on the total amount of the refrigerating machine oil.
[0042] Preferable examples of the phosphoric acid ester include triaryl
10 phosphates such as triphenyl phosphate or tricresyl phosphate. The
content of the phosphoric acid ester is preferably 0.2 to 5.0% by mass,
and more preferably 0.5 to 2.0% by mass based on the total amount of
the refrigerating machine oil.
LO0431 An example of a preferable combination of the above-described
15 additives includes a combination of an aromatic amine compound, an
epoxy conlpould and a phosphoric acid ester. Furthermore, a
combination of a di(alkylpheny1)amine having an alkyl group having 4
to 12 carbon atoms, an alkyl glycidyl ether having an alkyl group
having 6 to 12 carbon atoms and triaryl phosphate is particularly
20 preferred.
[0044] Moreover, additives such as an anti-wear agent like an organic
sulfur compound, an oiliness agent l i e an alcohol or a higher fatty acid,
a metal deactivator like a benzotriazole derivative, and an antifoaming
agent like silicone oil may be appropriately added to the refsigerating
25 machine oil of the present embodiment,. The total content of these
additives is preferably 0.0005 to 3.0% by mass based on the total
amount of the refrigerating machine oil.
[0045] The refrigerating machine oil of the present embodiment can be
preferably used as a lubricating oil for a refiigerating machine in which
a hydrocarbon refrigerant having 2 to 4 carbon atoms is used. Here, if
5 the refrigerating machine oil of the present embodiment is applied to a
room air conditioner or the l i e in which propane (R290) is used as a
refrigerant, it is preferable that the refiigerating machine oil have a
characteristic suitable to a motorized (hermetic) compressor, namely, a
high electrical insulating property. More specifically, the volume
10 resistivity at 80°C of the rehigerating machine oil of the present
invention is preferably lo9 0.m or more (namely, 10" TQ.m or more).
A volume resistivity herein means a value measured in accordance with
JIS C2101. If an additive is used, the volume resistivity means a
volume resistivity of the refrigerating machine oil after adding the
15 additive.
[0046] pmbodiment 2: Working fluid colnposition for refiigerating
machine]
A working fluid composition for a refiigerating machine
according to Embodiment 2 of the present invention comprises: a
20 regigerating machine oil comprising a complex ester as a base oil; and a
hydrocarbon refrigerant having 2 to 4 carbon atoms, wherein the
complex ester is obtainable by further esterifying, with at least one
selected from a monohydric alcohol having 1 to 20 carbon atoms and a
fatty acid (a chain monocarboxylic acid) having 2 to 20 carbon atoms,
25 an ester intermediate obtained by reacting a neopentyl polyol with a
dibasic acid, and has an acid value of 0.5 mgKOHlg or less, and
wherein the refrigerating machine oil has a kinematic viscosity at 100°C
of 2 to 50 mm2/s. In another aspect of the working fluid composition
for a refrigerating machine of the present embodiment, the working
fluid composition for a refrigerating machine comprises a refrigerating
5 machine oil comprising a complex ester as a base oil; and a hydrocarbon
refrigerant having 2 to 4 caxbon atoms, wherein the complex ester is a
complex ester of a neopentyl polyol, a dibasic acid and at least one
selected from a monohydric alcohol having 1 to 20 carbon atoms and a
fatty acid having 2 to 20 carbon atoms, and has an acid value of 0.5
10 mgKOIl/g or less and a kinematic viscosity at 100°C of 2 to 50 mtn2/s.
The refiigerating machine oil contained in the working fluid
composition for a refrigerating machine of the present embodiment is
the same as the refrigerating machine oil according to Embodiment 1
described above, and hence redundant description will be herein
15 omitted.
COO471 As the hydrocarbon refrigerant having 2 to 4 carbon atoms of
the present embodiment, ethane, propane, n-butane or i-butane is
specifically used, among which propane (R290) is pseferable.
[0048] In the working fluid composition for a refiigerating machine of
20 the present embodiment, a content ratio between the refrigerant andthe
refrigerating machine oil is not especially limited, but a
refrigeranurefrigerating machine oil ratio is preferably 10190 to 90110,
and more preferably 30170 to 70:30.
Examples
25 [0049] The present invention will now be more specifically described
by way of examples and comparative exatnples, but it is noted that the
present invention is not limited to the following exanlples at all.
[0050] [Example I: Manufacturing of complex ester A]
With 104 g (1.0 mole) of neopentyl glycol (NPG), 219 g (1.5
moles) of adipic acid (AA) was reacted at 220°C for 3 hours to obtain
5 an ester intermediate. To this ester intermediate, 156 g (1.2 moles) of
2-ethyl hexanol was added to cause a reaction at 220°C for 2 hours, so
as to esterify a carboxyl group remaining in the ester intermediate.
After completing the reaction, 2-ethyl hexanol remaining in the resultant
reaction mixture was removed, and a trace amount of impurities was
10 further removed by an adsorption treatment (a clay treatment), resulting
in obtaining a complex ester of interest (namely, a complex ester of
neopentyl glycol, adipic acid and 2-ethyl hexanol, hereinafter refel-red to
as the "complex ester A").
[005 11 [Example 2: Manufacturing of complex ester B]
15 With 208 g (2.0 moles) of neopentyl glycol (NPG), 219 g (1.5
moles) of adipic acid (AA) was reacted at 230°C for 4 hours to obtain
an ester intermediate. To this ester intermediate, 190 g (1.2 moles) of
3,5,5-trimethyl hexanoic acid was added to cause a reaction at 230°C
for 2 hours, so as to esterify a hydroxyl group remaining in the ester
20 intermediate. After completing the reaction, 3,5,5-trimethyl hexanoic
acid remaining in the resultant reaction mixture was removed, and a
trace amount of impurities was further removed by the adsorption
treatment (the clay treatment), resulting in obtaining a complex ester of
interest (namely, a complex ester of neopentyl glycol, adipic acid and
25 3,5,5-trimethyl hexanoic acid, hereinafter referred to as the "complex
ester B").
[0052] [Example 3: Manufacturing of complex ester C]
With 134 g (1.0 mole) of triinethylol propane (TMP), 348 g (2.0
moles) of suberic acid (SA) was reacted at 220°C for 3 hours to obtain
an ester intelmediate. To this ester intermediate, 89 g (1.2 moles) of
5 te1-t.-butanol was added to cause a reaction at 220°C for 2 hours, so as to
esterify a carboxyl group remaining in the ester intermediate. After
completing the reaction, tert.-butanol remaining in the resultant reaction
mixture was removed, and a trace amount of impurities was further
removed by the adsorption treatment (the clay treatment), resulting in
10 obtaining a conlplex ester of interest (namely, a complex ester of
trimethylol propane, suberic acid and te1-t.-butanol, hereinafter referred
to as the "complex ester C").
[0053] [Example 4: Manufacturing of complex ester Dl
With 201 g (1.5 moles) of trimethylol propane (TMP), 292 g
15 (2.0 moles) of adipic acid (AA) was reacted at 235°C for 4 hours to
obtain an ester intermediate. To this ester intermediate, 103 g (0.6
mole) of n-decanoic acid was added to cause a reaction at 230°C for 3
hours, so as to esterify a hydroxyl group remaining in the ester
intermediate. After completing the reaction, n-decanoic acid
20 remaining in the resultant reaction mixture was removed, and a trace
amount of impurities was further removed by the adsorption treatment
(the clay treatment), resulting in obtaining a complex ester of interest
(namely, a complex ester of trimethylol propane, adipic acid and
n-decanoic acid, hereinafter referred to as the "complex ester D").
25 LO0541 pxamples 5 to 12 and Comparative Examples 1 to 5:
Preparation and evaluation of refrigerating machine oil]
I
hl Examples 5 to 12 and Comparative Examples 1 to 5, i
reeigerating machine oils having compositions shown in Tables 1 to 3
were prepared by using the following base oils and additives. The i
kinematic viscosity at 100°C, the acid value and the pow point of each
5 of the obtained refrigerating machine oils are also shown in Tables 1 to
3.
[0055] (Base oil)
Base oil 1 : Complex ester A
Base oil 2: Complex ester B
Base oil 3: Complex ester C
Base oil 4: Complex ester D
Base oil 5: Ester of pentae'ythfitol (FE) and 3,5,5-trimethyl
hexanoic acid
Base oil 6: Ester of neopentyl glycol (NPG) and 2-ethyl
15 hexanoic acid
Base oil 7: Ester of trirnethylol propane (TMP) and oleic acid
Base oil 8: Polyalkylene glycol (PAG, having a butyl group and
a hydroxyl goup at the ends thereof, having an oxypropylene skeleton,
and having an average molecular weight of 1200)
20 Base oil 9: Paraffin mineral oil (manufactured by JXNippon Oil
& Energy Corporation)
Incidentally, also the base oils 5 to 7 were subjected to the
adsorption treatment at the final slage of the maiufacturing for
removing a trace amount of impurities.
25 [0056] (Additive)
Hindered phenol compound: Di-tert.-butyl-p-cresol (DBPC)
Aromatic amine compound: Dioctyldiphenyla~nine@ ODA)
Epoxy compound: 2-Ethylhexyl glycidyl ether (2-EHGE)
Carbodiimide: Diphenyl carbodiimide (DPCI)
Phosphoric acid ester: Tricresyl phosphate (TCP)
[0057] [Table 11
Base oil
Additive 1
Example 7 Example 8
Base oil 3 Base oil 4
Balance Balatlce
-
roo581 [Table 21
DPCI, mass%
TCP, mass%
Kinematic viscosity at 100°C,
d s
-.
Acid value, mgKOWg
Pour poiut, "C
/ Base oil
Additive
-
-
9.8
0.01
-35.0
1 Example 9 I Example 10 / Exanlple 11 I Example 12
Type I Base oil 1 I Base oil 2 [ Base oil 3 1 Base oil 4
. -- - . - --
-
20.2
0.03
-30.0
.
11.0
0.01
-30.0
Content
DBPC, mass%
DODA, mass%
2-EHGE,
mass%
-
-
27.4
0.03
-32.5
DPCI, mass%
TCP, mass%
~
Kinematic viscosity at 10O0C,
mm2/s
Acid value, ~ ~ ~ h g
Pour point, "C
Balance
0.2
-
.
-
9.8
0.01
-35.0
Balance
0.2
0.5
20.0
0.03
-30.0
Balance
-
0.2
0.5
Balance
-
0.2
0.5
-
1.0
10.8
0.01
-30.0
0.1
1.0
27.1
0.03
-32.5
[0060] Next, the following evaluation tests were performed on the
[0059] [Table 31
refrigerating machine oils of Examples 5 to 12 and Compasative
Kinematic
viscosity at 100°C,
mm2/s
Acid value,
mgKOWg
Pour point, "C
5 Examples 1 to 5.
[0061] [Refrigerant solubility]
Fifteen grams of each rehigerating machine oil was placed in a
glass pressuse vessel, the vessel was charged with a refrigerant R290
(propane), and with the temperature set to each of several points
10.8
0.01
-22.5
10 between room temperature and 60°C, a temperature/pressurelsolubility
curve was created by calculation on the basis of the volume of the
2.4
0.01
-50.0
rekigerating machine oil in which the propane was dissolved and the
9.2
0.03
-30.0
11.2
0.01
-42.5
9.2
0.01
-15.0
pressure applied at that time. On the basis of the thus obtained
temperature/press~re/solubility curve, the amount of the propane
dissolved in each sample oil at 60°C and 1.0 MPa (dissolved
propane/sample oil +- dissolved propane: % by mass) was obtained,
5 The obtained results are shown in Tables 4 to 6.
[0062] [Thermal stability]
In accordance with ANSIIASHRtU;, 97-1983, a stainless steel
cylinder (with an internal volume of 100 ml) was charged with 20 g of
each refrigerating machine oil, 20 g of the refrigerant R290 (propane)
10 and a catalyst (a wire of iron, copper or aluminum), the resulting
cylinder was heated to 17S°C, and after retaining the resultant for 14
days, a color tone (according to ASTM) and ah acid value of the
refrigerating machine oil were measured. The obtained results are
shown in Tables 4 to 6.
15 [0063] [Lubricity]
In accordance with ASTM D-3233-73, a Falex burning load was
measured under an atmosphere where tlie blowing of the refrigerant
R290 (propane) was controlled (to a blowing rate of 70 ml/min). The
obtained results are shown in Tables 4 to 6.
20 [0064] @lectsical insulating propelQ]
In accordance with JIS C2101, the volume resistivity at 80°C of
each refrigerating machine oil was measured. The obtained results are
shown in Tables 4 to 6.
[0065] [Table 41
refrigerant (propane)
roo661 [Table 51
-
Item Exam-ple 9-
27
L1 ,o
0.01
4100
0.7
I
-
Sol"b'ity
Thermal
stability
Lubricity
insulating
property
Amount of dissolved
refiigerant (propane)
(60°C 1.0 m a ) ,
mass%
Color tone (ASTM,
17S°C, after 14 days)
Acid value (ASTM,
17S°C, after 14 days),
mgKOWg
Falex buning load, N
Volun~ere sistivity
(80°C), TQm
Example 10
23
L1.0
0.03
4200
0.7
Example 11
26
L1.0
0.01
4800
0.6
Example 12
20
L1 .o
0.03
4860
0.8
[0068] It is understood, as shown in Tables 1 to 6, that the refrigerating
machine oil of each of Examples 5 to 12 containing the complex ester of
any of Examples 1 to 4 is appropriately dissolved with the hydrocarbon
refrigerant, and has good characteristics as a rekigerating machine oil
including lubricity, a low-temperature characteristic, thermal stability
and an electrical insulating property. On the other hand, with respect
to the refrigerating machine oils of Comparative Examples 1 to 3, it is
understood that the amount of hydrocarbon refrigerant dissolved therein
is large and that these refrigerating machine oils are inferior in the
lubricity. Besides, it is understood that although the amount of
hydrogen reeigerant dissolved in the refrigerating machine oil of
Conlparative Example 4 is small, this refrigerating machine oil is
[0067] [Table 61
Comparative
Item Example 4
Amount of
Comparative
Examp-le- 5
Comparative
Example 2
Comparative
Example 1
Comparative
Example 3
greatly poor in the electrical insulating property indicated by the volume
resistivity at 80°C and is also inferior in the lubricity. Furthermore, it
is understood that the reffigerating machine oil of Comparative
Example 5 has no polarity and hence solubility of the hydrocarbon
5 refrigerant is large and that this reffigerating machine oil is inferior also
in the lubricity.
Industrial Applicability
[0069] The working fluid composition for a refrigerating machine and
the refrigerating machine oil of the present invention can be suitably
10 used as a working fluid composition and a lubricating oil for a
reeigerating machine using a hydrocarbon refiigerant of propane or the
like. In particular, they can be used in a refrigeration system with high
cooling efficiency, in which a compressor, a condenser, a throttle device
(a refrigerant flow control unit such as an expansion valve or a capillary
15 tube), an evaporator and the like are provided and a refrigerant is
circulated among these components, particularly as a lubricating oil in a
refrigerating machine including a rotary type, a swing type or a scroll
type compressor, and can be suitably used in a room air conditioner, a
package air conditioner, an industrial reeigerating machine and the like.
20

CLAlMS
1. A working fluid composition for a refrigerating machine,
comprising:
a refrigerating machine oil comprising a complex ester as a base
5 oil; and
a hydrocarbon refrigerant having 2 to 4 carbon atoms,
the complex ester being obtainable by firthe1 esterifying, with at
least one selected ftom a monohydric alcohol having 1 to 20 carbon
atoms and a fatty acid having 2 to 20 carbon atoms, an ester
10 intermediate obtained by reacting a neopentyl polyol with a dibasic acid,
and having an acid value of 0.5 mgKOH/g or less,
the refrigerating machine oil having a kinematic viscosity at
100°C of 2 to 50 d s .
2. A working fluid composition for a refrigerating machine,
15 comprising:
a refrigerating machine oil comprising a complex ester as a base
oil; and
a hydrocarbon reftigerant having 2 to 4 carbon atoms,
the complex ester being a complex ester of a neopentyl polyol, a
20 dibasic acid, and at least one selected from a monohydric alcohol having
1 to 20 carbon atoms and a fatty acid having 2 to 20 carbon atoms, and
having an acid value of 0.5 mgKOWg or less,
the refrigerating machine oil having a kinematic viscosity at
100°C of 2 to 50 mm2/s.
25 3. The working fluid cornposition for a refrigerating machine
according to claim 1 or 2, wherein the neopentyl polyol is at least one
selected from neopentyl glycol, trimethylol propane and pentaerythritol,
the dibasic acid is at least one selected from adipic acid, pilnelic acid,
suberic acid, azelaic acid and sebacic acid, and the hydrocarbon
refrigerant is at least one seIected from propane, butane and isobutane.
5 4. The working fluid composition for a refrigerating machine
according to any one of claims I to 3, wherein the monohydric alcohol
is at least one selected from linear alcohol having 4 to 18 carbon atoms,
2-ethyl hexanol and 3,5,5-trimethyl hexanol.
5. The working fluid composition for a refrigerating machine
10 according to any one of claims 1 to 4, wherein the fatty acid is at least
one selected fiom linear fatty acid having 5 to 18 carbon atoms, 2-ethyl
hexanoic acid and 3,5,5-trimethyl hexanoic acid.
6. The working fluid composition for a refrigerating machine
accordimg to any one of claims 1 to 5, wherein the complex ester is
15 obtainable by further esterifying, with a monohydric alcohol having 1 to
20 carbon atoms, an ester intermediate obtained by reacting the dibasic
acid with trimethylol propane at a ratio of 1.5 moles or more and less
than 3 moles of the dibasic acid per 1 mole of tsimethylol propane.
7. The working fluid composition for a refrigerating machine
20 according to any one of claims 1 to 6, further comprising at least one
additive selected from a hindered phenol compound, an aromatic ainine
compound, an epoxy compound, a carbodiimide and a phosphoric acid
ester, wherein a total content of the additive is 0.05 to 5.0% by mass
based on a total amount of the refrigerating machine oil.
25 8. The working fluid composition for a refrigerating machine
according to any one of claims 1 to 7, wherein a volume resistivity at
80°C of the refrigerating machine oil is 10" Ocm or more.
9. The working fluid composition for a refrigerating machine
according to any one of claims 1 to 8, wllerein the hydrocarbon
refrigerant is propane.
5 10. A refrigerating machine oil comprising a complex ester as a base
oil,
the complex ester being obtainable by hrtller esterifying, with a
monohydric alcohol having 1 to 20 carbon atoms or a fatty acid having
2 to 20 carbon atoms, an ester intermediate obtained by reacting a
10 neopentyl polyol with a dibasic acid, and having an acid value of 0.5
mgK0Wg or less,
the refrigerating machine oil having a kinematic viscosity at
100°C of 2 to 50 d s , and being used with a hydrocarbon refrigerant
having 2 to 4 carbon atoms.
15 11. A refrigerating machine oil comprising a complex ester as a base
oil,
the complex ester being a complex ester of a neopentyl polyol, a
dibasic acid and at leas.t. o ne selected from a monohydric alcohol having
1 to 20 carbon atoms and a fatty acid having 2 to 20 carbon atoms, and
20 having an acid value of 0.5 mgKOWg or less,
the refrigerating machine oil having a kinematic viscosity at
100°C of 2 to 50 mm2/s, and being used with a hydrocarbon refrigerant
having 2 to 4 carbon atoms.
12. A method for manufacturing a refrigerating machine oil
25 comprising:
a first step of obtaining an ester intermediate by reacting a
neopentyl polyol with a dibasic acid;
a second step of obtaining a cornplex ester having an acid value
of 0.5 mgICOI-Vg or less by esterifling the ester intermediate with at
least one selected fiom a monohydric alcohol having 1 to 20 carbon
5 atoms and a fatty acid having 2 to 20 carbon atoms; and
a third step of preparing a rekigerating machine oil having a
kinematic viscosity at 100°C of 2 to 50 imn2/s by using the complex
ester as a base oil,
the refrigerant lnachii oil being used with a hydrocarbon
10 refrigerant having 2 to 4 carbon atoms.