Title of Invention:
WORKING FLUID COMPOSITION FOR REFRIGERATOR,
REFRIGERATlON OIL, AND METHOD FOR PRODUCING SAME
Technical Field
[0001] The present invention relates to a working fluid for a
refrigerating machine that uses, as a refrigerant, an environmentally
friendly hydrocarbon having an extremely low global walming potential,
such as ethane, propane, butane and isobutane, and refrigerating
machine oil (a lubricating oil for a refrigerating machine)and a method
for manufacturing the same, and more particularly, it relates to a
refrigerating machine oil that does not cause wear even if its viscosity is
lowered for power saving of a refrigeration system, has high reliability
and is compatible with the system.
Background Art
[0002] In conventional refrigerating machines, air conditioners, cold
storage chambers and the like, freon containing fluorine and chlorine
was used as a refrigerant. Examples of the freon include
chlorofluorocarbon (CFC) such as R- 1 1 (trichloromonofluoromethane)
or R-12 (dichlorodifluoromethane), and hydrochlorofluorocarbon
(HCFC) such as R-22 (monochlorodifluoromethane).
[0003] However, the production and use of the freon have been
internationally regulated due to a recent problem of ozone layer
depletion, and a novel hydrogen-containing freon refrigerant 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
refrigerant of hydrofluorocarbon (HFC) such as R410A or R407C.
[0004] Although the HFC does not deplete the ozone layer, however, it
has a high greenhouse effect, and hence is not necessarily an excellent
refrigerant from the viewpoint of global warming that has become a
recent problem.
[0005] Therefore, a lower hydrocarbon having 2 to 4 carbon atoms has
been recently gathering attention because it does not deplete the ozone
layer and causes an extremely small influence on the global warming as
compared with the aforementioned chlorine or non-chlorine
fluorocarbon refrigerants. For example, isobutane (R600a) is already
used as a refrigerant for a cold storage chmeber, and a refrigerating
machine using an isobutane refrigerant is spreading worldwide.
Besides, a lower hydrocarbon compound is now being examined to be
used, as a refrigerant, in a refrigeration system having high cooling
efficiency such as a room air conditioner or an industrial refrigerating
machine including a compressor, a condenser, a throttle device, an
evaporator and the like, which has been developed with the freon
refrigerant,. Such a hydrocarbon refrigerant has a global warming
potential (GWP) of 11100 or less and is highly efficient as compared
with R410A that is a mixed refrigerant of hydrofluorocarbon (HFC)
currently widely used as a refrigerant for a room air conditioner. In
particular, there is a possibility that use of propane (R290) having 3
carbon atoms can largely and economically reduce the influence on the
global warming without requiring large-scaled design change of a room
air conditioner.
[0006] As a refrigerating machine oil for the lower hydrocarbon
refrigerant, a mineral oil of, for example, a naphthene- or paraffin-based
mineral oil, an alkylbenzene oil, an ester oil, an ether oil and a
fluorinated oil having compatibility with the refrigerant have been
proposed (see Patent Literature 1). Among these refrigerating machine
oils, the alkylbenzene oil, that is, a synthetic hydrocarbon, is expected as
a refrigerating machine oil that can save power when used in a
reciprocating compressor (see Patent Literature 2). A polyol ester
(POE) and the like have been proposed as the ester oil (see Patent
Literature 3).
Citation List
Patent Literature
[0007] Patent Literature 1 : Japanese Patent Application Laid-Open No.
10-130685
Patent Literature 2: International Publication No.
W02007/003024 A1
Patent Literature 3: Japanese Patent Application Laid-Open No.
2003-41278
Summary of Invention
Technical Problem
[0008] However, the above-described hydrocarbon refrigerant 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 tnachine oil compatible with this refiigerant.
[0009] Meanwhile, the power saving of a refrigerating machine is
significant also from the viewpoint of global environment protection.
One of the countermeasures is reduction of a friction force on a sliding
portion of a refkigerating machine. For this purpose, it is effective to
lower the viscosity of a rekigerating machine oil, namely, viscosity
lowering is effective. If the viscosity of a refrigerating machine oil is
lowered, however, an oil film formed on the sliding portion becomes
thin, and hence, wear is easily caused and reliability is lowered.
Besides, if the viscosity of a refrigerating machine oil is lowered, the
flash point of the refrigerating machine oil is lowered, which also causes
a problem of safety.
[0010] When the compatibility with a hydrocarbon refrigerant of the
above-described conventional refrigerating machine oils is examined in
consideration of these technical problems, all of them still have room
for improvements. For example, a mineral oil-based low viscosity oil
has a low flash point, and since drying process at a high temperature,
namely, at approximately 120°C, is performed afier sealing the oil in
producing a compressor, there is a fear of a safety problem. Since the
high pressure viscosity of the alkylbenzene is small, an oil film formed
in an elastic fluid lubrication region is thin, and hence, the alkylbenzene
has a problem of lubricity. When the viscosity of the ester is lowered,
20 a fatty acid with a shol-t carbon chain is unavoidably used, -. and hence,
the ester is easily hydrolyzed and inferior in stability.
[0011] In consideration of the problems of the above-described
conventional techniques, an object is to provide a refiigerating machine
oil that has a flash point sufficiently high for ensuring safety even if the
viscosity is lowered, has appropriate compatibility with a hydrocarbon
refrigerant, can retain an oil film thickness not impairing lubricity, and
is excellent in stability and an electrical insulating property; a method
for manufacturing the same; and a working fluid composition for a
refrigerating machine using the refrigerating machine oil.
Solution to Problem
[0012] In order to achieve the aforementioned object, the present
inventor has made earnest studies, resulting in finding that a low
viscosity oil comprising, in a prescribed ratio, a specific mineral oil
containing a comparatively large number of naphthene rings and an
alkylbenzene, which is a synthetic hydrocarbon, shows no problem in
safety because their disadvantages are compensated with each other, has
proper compatibility with a hydrocarbon refrigerant, has good lubricity,
high stability and low hygroscopicity, and is excellent as a refrigerating
machine oil for a hydrocarbon rehigerant such as propane or isobutane,
and thus, the present invention was accomplished.
[0013] Specifically, the present invention provides a working fluid
composition for a refrigerating machine according to the following [I]
to [6], a refrigerating machine oil according to the following [7], and a
method for manufacturing a refrigerating machine oil according to the
following [a].
[l] A working fluid composition for a refrigerating machine
comprising: a refrigerating machine oil comprising a mineral oil and an
alkylbenzene in a mass ratio, the mineral oil/the alkylbenzene, of 8511 5
to 15/85, wherein the mineral oil has a %CN by n-d-M ring analysis of
20 to 60, a pour point of -15°C or less and a kinematic viscosity at 40°C
of 1.5 to 15 mm2/s; and a hydrocarbon refrigerant having 2 to 4 carbon
atoms, the refrigerating machine oil having a kinematic viscosity at
40°C of 2 to 12 d s and a flash point of 120°C or more.
[2] The working fluid composition for a refrigerating
machine according to [I], wherein the alkylbenzene is a linear
alkylbenzene in which a linear alkyl group is bonded to a benzene ring,
5 and wherein a kinematic viscosity at 40°C of the alkylbenzene is 2 to 10
mm2/s.
[3] The working fluid composition for a refrigerating
machine according to [l] or 121, wherein the %CN by the n-d-M ring
analysis of the mineral oil is 40 to 60.
10 [4] The working fluid composition for a refrigerating
machine according to any one of [I] to [3], further comprising at least
one glycerin derivative selected from an ester compound of glycerin and
an ether compound of glycerin, wherein a content of the glycerin
derivative is 0.005 to 1.0% by mass based on a total amount of the
15 refi-igerating machine oil.
[5] The working fluid composition for a refrigerating
machine according to any one of [I] to [4], further comprising at least
one phosphorus compound selected from a mono(alkylpheny1) diphenyl
phosphate having one alkyl group having 3 to 5 carbon atoms, a
20 di(alkylpheny1) phenyl phosphate having two alkyl groups having 3 to 5
carbon atoms, and a tri(alkylpheny1) phosphate having three alkyl
groups having 3 to 5 carbon atoms, wherein a content of the phosphorus
compound is 0.05 to 3.0% by mass based on a total amount of the
refi-igerating machine oil.
25 [6] The working fluid composition for a refrigerating
machine according to any one of [I] to [5], wherein the hydrocarbon
refrigerant is isobutane.
[7] A refrigerating machine oil comprising a mineral oil and
an alkylbenzene, in a mass ratio, the mineral oillthe alkylbenzene, of
85/15 to 15/85, wherein the mineral oil has a %CN by n-d-M ring
analysis of 20 to 60, a pour point of -15°C or less and a kinematic
viscosity at 40°C of 1.5 to 15 mm2/s, the refrigerating machine oil
having a kinematic viscosity at 40°C of 2 to 12 mm2/s and a flash point
of 120°C or more, and the refrigerating machine oil being used with a
hydrocarbon refrigerant having 2 to 4 carbon atoms.
[8] A method for manufacturing a refrigerating machine oil
comprising a step of mixing a mineral oil and an alkylbenzene in a mass
ratio, the mineral oillthe alkylbenzene, of 85/15 to 15/85, to obtain a
refrigerating machine oil comprising a mixed oil of the mineral oil and
the alkylbenzene as a base oil and having a kinematic viscosity at 40°C
of 2 to 12 rnm2/s and a flash point of 120°C or more, wherein the
mineral oil has a %CN by n-d-M ring analysis of 20 to 60, a pour point
of -15°C or less and a kinematic viscosity at 40°C of 1.5 to 15 mm2/s,
the refrigerating machine oil being used with a hydrocarbon refrigerant
having 2 to 4 carbon atoms.
Advantageous Effects of Invention
[0014] The present invention makes it possible to provide a
refrigerating machine oil that has a flash point sufficiently high for
ensuring safety even if the viscosity is lowered, has appropriate
compatibility with a hydrocarbon refrigerant, can retain an oil film
thickness not impairing lubricity, and is excellent in stability and an
electrical insulating property, a method for manufacturing the same, and
a working fluid composition for a refrigerating machine using the
refrigerating machine oil.
[0015] More specifically, according to the present invention, even if the
kinematic viscosity at 40°C of the refrigerating machine oil is lowered
to 2 to 12 mm2/s for power saving of a refrigeration apparatus, the
refrigerating machine oil has no problem of safety because of the flash
point of 120°C or more, has proper compatibility with a hydrocarbon
refrigerant, has not only excellent lubricity, that is one of significant
characteristics, but also a high electrical insulating property, low
hygroscopicity and high stability, and therefore, a remarkable effect that
the refrigerating machine oil is excellent in comprehensive
performances as a refrigerating machine oil is achieved.
Description of Embodiments
[0016] Preferred embodiments of the present invention will now be
described in detail.
[0017] [Embodiment 1: Refrigerating machine oil and method for
manufacturing the same]
A refrigerating machine oil according to Embodiment 1 of the
present invention comprises a.minera1 oil and an alkylbenzene, in a
mass ratio, the mineral oiVthe alkylbenzene, of 85/15 to 15/85, wherein
the mineral oil has a %CN by n-d-M ring analysis of 20 to 60, a pour
point of -15°C or less and a kinematic viscosity at 40°C of 1.5 to 15
mm2/s, the refrigerating machine oil has a kinematic viscosity at 40°C
of 2 to 12 mm2/s and a flash point of 120°C or more, and is used with a
hydrocarbon refrigerant having 2 to 4 carbon atoms.
[0018] A method for 'manufacturing a refiigerating machine oil
according to Embodiment 1 of the present invention comprises a step of
mixing a mineral oil and an alkylbenzene in a mass ratio, the mineral
oiVthe alkylbenzene, of 85/15 to 15/85, to obtain a refrigerating
machine oil comprising a mixed oil of the mineral oil and the
alkylbenzene as a base oil and having a kinematic viscosity at 40°C of 2
to 12 mm2/s and a flash point of 120°C or more, wherein the mineral oil
has a %CN by n-d-M ring analysis of 20 to 60, a pour point of -15°C or
less and a kinematic viscosity at 40°C of 1.5 to 15 m d s , and wherein
the refiigerating machine oil is used with a hydrocarbon refrigerant
having 2 to 4 carbon atoms.
[0019] In a refrigeration compressor, a sliding portion is an elastic fluid
lubrication region in many cases, and it is necessary to select a base
stock having a high viscosity-pressure coefficient for retaining a thick
oil film in this region. Therefore, in the present embodiment, the %CN
by the n-d-M ring analysis of the mineral oil is in a range of 20 to 60,
preferably 35 to 50, and more preferably 40 to 50. Alternatively,
the %CN is in a range of preferably 35 to 60 and krther more preferably
40 to 60. In the case where the %CN of the mineral oil falls in the
aforementioned range, if a pressure is applied to the refrigerating
machine oil due to load applied in the sliding portion, the viscosity is
increased and the oil film can be made thick. A %CN by the n-d-M
ring analysis herein means a value measured in accordance with ASTM
D3238.
[0020] The pour point of the mineral oil is -15°C or less, preferably
-25°C or less, and more preferably -40°C or less -6rom the viewpoint of a
low temperature characteristic necessary as a refiigerating machine oil.
A pour point herein means a value measured in accordance with JIS
K2269.
[0021] The kinematic viscosity at 40°C of the mineral oil is 1.5 to 15
mm2/s, preferably 3 to 10 mm2/s, and more preferably 3 to 7 r n d s
from the viewpoint of power saving. A kinematic viscosity at 40°C
herein means a value measured in accordance with JIS K2283.
[0022] Examples of the mineral oil used in the present embodiment
include mineral oils having %CN by the n-d-M ring analysis, pour points
and kinematic viscosities at 40°C respectively falling in the
aforementioned ranges, among those obtained by refining, for example,
lubricating oil hactions resulted ftom atmospheric distillation and/or
distillation under reduced pressure of csude oil by a single refining
treatment or a combination of two or more refining treatments selected
from solvent deasphalting, solvent extraction, hydrogenation refining,
hydro-cracking, hydrogenation isomerization, solvent dewaxing,
catalytic dewaxing, sulhric acid washing, a clay treatment, and the like.
With respect to the respective properties of the base oil of the
mineral oil, the aforementioned ranges can be attained for the kinematic
viscosity by adjusting the conditions of the distillation under reduces
pressure, for the %CN by the n-d-M ring analysis by adjusting the
conditions of the solvent extraction, the hydrogenation refining and the
hydro-cracking, and for the pour point by adjusting the conditions of the
hydrogenation isomerization, the solvent dewaxing and the catalytic
dewaxing.
[0023] The refrigerating machine oil of the present embodiment further
contains the alkylbenzene in addition to the above-described mineral oil.
In the present embodiment, either of a branched alkylbenzene in which
an alkyl group bonded to a benzene ring is a branched alkyl group, and
a linear alkylbenzene in which an alkyl group bonded to a benzene ring
is a linear alkyl group may be used, but a linear alkylbenzene is
preferred because the viscosity change depending on temperature of this
alkylbenzene is small. The number of carbon atoms of the alkyl group
is preferably 1 to 30 and more preferably 4 to 20 from the viewpoint of
suitable viscosity as a base oil of a lubricating oil. The number of
alkyl groups contained per molecule of the alkylbenzene depends upon
the number of carbon atoms of the alkyl group, but is preferably 1 to 4
and more preferably 1 to 3 for attaining the viscosity falling in the
above-described range.
[0024] The kinematic viscosity at 40°C of the alkylbenzene is
preferably 3 to 10 mm21s, more preferably 4 to 9 mm2/s, and further
more preferably 4 to 6 mm2/s fiom the viewpoint that the viscosity of
the refiigerating machine oil attained after adding an additive is lowered
to be used as a power saving type oil.
[0025] Besides, the mass ratio between the above-described specific
mineral oil and the alkylbenzene (mineral oillalkylbenzene) is 85/15 to
15/85, preferably 70130 to 30170, and more preferably 60140 to 40160.
When the mass ratio therebetween falls in such a range, a refiigerating
machine oil that has a flash point sufficiently high for ensuring safety
even if the viscosity is lowered, has appropriate compatibility with a
hydrocarbon refrigerant, can retain an oil film thickness not impairing
lubricity, and is excellent in stability and an electrical insulating
property can be realized. If the ratio of the alkylbenzene is smaller
than the aforementioned range, the flash point is lowered as a result of
the viscosity lowering of the refrigerating machine oil due to the
characteristic of the mineral oil having a molecular weight distsibution,
and it is apprehended that such a refi-igerating machine oil cannot be
actually used for manufacturing a refrigeration compressor. On the
other hand, if the ratio of the alkylbenzene is larger than the
aforementioned range, it is apprehended that the compatibility with an
organic material used in the compressor is lowered due to the
characteristic of the alkylbenzene.
For mixing the mineral oil and the alkylbenzene, since both of
them are hydrocarbon oils, a general lubricating oil mixing method can
be employed, and either batch process using a mixing tank or
high-throughput flow process using a cornell machine or the like in
which these oils are allowed to flow in a pipe to be stirred and mixed by
a baffle plate may be employed.
[0026] The kinematic viscosity at 40°C of the refrigerating machine oil
of the present embodiment is 2 to 12 mm2/s, more preferably 2 to 8
mm2/s, and fitsther more preferably 4 to 6 m d s from the viewpoint of
the power saving.
[0027] The flash point of the refrigerating machine oil of the present
embodiment is 120°C or more, preferably 125°C or more, and more
preferably 130°C or more from the viewpoint of the safety.
[0028] The refrigerating machine oil of the present embodiment may
consist of a mixed base oil containing the specific mineral oil and the
alkylbenzene, and may fixther comprise, if necessary, any of base oils
and additives described below. When the refrigerating machine oil
further contains any of the base oils and additives described below, the
content of the above-described mixed base oil is preferably 90% by
mass or more and more preferably 95% by mass or more based on the
total amount of the refrigerating machine oil.
[0029] The refrigerating machine oil of the present embodiment may be
appropriately mixed with an ester such as a polyol ester (POE) or a
diester, an ether such as a polyalkylene glycol (PAG) or a polyvinyl
ether (PVE), a mineral oil other than the above-described specific
mineral oil, and a hydrocarbon-based syntl~etic oil other than the
alkylbenzene such as poly-a-olefin (PAO) as long as the function as a
refrigerating machine oil can be satisfied.
[0030] The refrigerating machine oil of the present embodiment can
further comprise a compound having an oiling effect. In this manner,
even if a lubrication state in the sliding portion is in a mixed lubrication
region in which partial metallmetal contact occurs, good lubricity can be
attained. As the compound having an oiling effect, at least one type of
glycerin derivative selected from an ester compound of glycerin and an
ether compound of glycerin is preferred because such a glycerin
derivative is easily adsorbed to the surface of the sliding portion, does
not affect the safety, and has a large abrasion resistance effect.
1003 11 As the ester compound of glycerin, an ester compound in which
not all hydroxyl groups form an ester bond (namely, a partial ester) is
prefel-sed, and a carboxylic acid constituting the ester is preferably a
fatty acid, particularly a fatty acid having 12 to 20 carbon atoms.
Specific examples include glycerol monooleate and glycerol
monolaurate.
[0032] As the ether compound of glycerin, an ether compound in which
not all hydroxyl groups form an ether bond is preferred. Glycerol
alkyl ether or glycerol alkenyl ether is preferred, whose alkyl group or
alkenyl group preferably has 12 to 20 carbon atoms, and specific
examples include glycerol monooleyl ether and glycerol monolauryl
ether.
[0033] The content of the glycerin derivative is preferably 0.005 to
1.0% by mass, more preferably 0.01 to 0.5% by mass, and further more
preferably 0.02 to 0.2% by mass based on the total amount of the
refrigerating machine oil. If the content is smaller than the lower limit
of the above-described range, the abrasion resistance effect tends to be
smaller, and if it exceeds the upper limit, there is a tendency that the
additive is easily precipitated at a low temperature.
[0034] Furthermore, the refrigerating machine oil of the present
embodiment preferably further comprises a phosphorus compound from
the viewpoint of improvement of the abrasion resistance. As the
phosphorus compound, at least one phosphorus compound selected
from a mono(alkylpheny1) diphenyl phosphate having one alkyl group
having 3 to 5 carbon atoms, a di(alkylpheny1) phenyl phosphate having
two alkyl groups having 3 to 5 carbon atoms, and a tri(alkylpheny1)
phosphate having three alkyl groups having 3 to 5 carbon atoms is
particularly preferred.
[0035] Examples of the mono(alkylpheny1) diphenyl phosphate having
one alkyl group having 3 to 5 carbon atoms include isopropylphenyl
diphenyl phosphate, test.-butylphenyl diphenyl phosphate, and
n-butylphenyl diphenyl phosphate.
[0036] Examples of the di(alkylpheny1) diphenyl phosphate having two
alkyl groups having 3 to 5 carbon atoms include di(isopropylpheny1)
phenyl phosphate, di(tert.-butylphenyl) phenyl phosphate, and
di(n-butylphenyl) phenyl phosphate.
[0037] Examples of the tri(alkylpheny1) diphenyl phosphate having
three alkyl groups having 3 to 5 carbon atoms include
tri(isopropylpheny1) phosphate, tri(tert.-butylphenyl) phosphate, and
tri(n-butylphenyl) phosphate.
[0038] In the present embodiment, any one of the above-described
mono(alkylpheny1) diphenyl phosphate, di(alkylpheny1) phenyl
phosphate and tri(alkylpheny1) phosphate may be used, or a mixture of
two or more of them may be used.
[0039] The content of the phosphorus compound is preferably 0.05 to
3.0% by mass, more preferably 0.1 to 2.0% by mass, and further more
preferably 0.2 to 1.0% by mass based on the total amount of the
refrigerating machine oil. If the content is smaller than the lower limit
of the above-described range, the abrasion resistance effect tends to be
smaller, and if it exceeds the upper limit, the stability of the refrigerating
machine oil tends to be lowered.
[0040] Triphenyl phosphate (TPP) or tricresyl phosphate (TCP) may be
used as the phosphorus compound in the present embodiment, but the
TPP and the TCP are liable to increase a friction coefficient although
they show the abrasion resistance effect. On the other hand, if at least
one selected fiom the aforementioned mono(alkylpheny1) diphenyl
phosphate, di(alkylpheny1) phenyl phosphate and tri(alkylpheny1)
phosphate is used, not only the abrasion resistance effect is attained but
also the friction coefficient can be retained low, and hence such a
compound is preferred from the viewpoint of the power saving.
[0041] Besides, the refrigerating machine oil of the present embodiment
preferably contains a stability improving additive for fbrther improving
the stability of a mixture of the refrigerant and the refsigerating machine
oil in actual use. As the stability improving additive, at least one
selected from a hindered phenol compound, an aromatic amine
compound, an epoxy compound and a carbodiimide is preferred, and
addition of an epoxy compound and a carbodiimide in combination is
more preferred. These additives are added sufficiently in a content of
0.05 to 5.0% by weight in total based on the total amount of the
refrigerating machine oil.
[0042] As the hindered phenol compound, 2,6-di-test.-butyl phenol,
2,6-di-test.-butyl-p-cresol,
4,4-methylene-bis-(2,6-di-test.-butyl-p-cresoa)n d the like are suitable,
as the aromatic amine compound, a-naphthylamine,
p,p'-di-octyl-diphenylamine and the like are suitable, and as the epoxy
compound, a glycidyl ether group-containing compound, an epoxidized
fatty acid monoestel; an epoxidized fat or oil, an epoxy cycloalkyl
group-containing compound and the like are suitable.
100431 Moreover, additives such as an anti-wear agent like an organic
sulFur compound, an oiliness agent like 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.
[0044] The refrigerating machine oil of the present embodiment is
preferably used as a lubricating oil for a refrigerating machine in which
a hydrocarbon refrigerant having 2 to 4 carbon atoms is used. Here, if
the refrigerating machine oil of the present embodiment is applied to a
refrigerating machine in which isobutane is used as a refrigerant, it is
also necessary to have a characteristic suitable to a motorized (hermetic)
compressor, namely, a high electrical insulating property. Therefore,
the refrigerating machine oil of the present invention preferably has,
after adding an additive, a volume resistivity of lo9 Q.m or more. A
volume resistivity herein means a value measured in accordance with
JIS C2101. Besides, if an additive is used, the volume resistivity
means a volume resistivity of the refrigerating machine oil attained after
adding the additive thereto.
[0045] [Embodiment 2: Working fluid composition for refrigerating
machine]
A working fluid composition for a refrigerating machine
15 according to Embodiment 2 of the present invention comprises: a
refrigerating machine oil comprising a mineral oil and an alkylbenzene
in a mass ratio, the mineral oillthe alkylbenzene, of 85/15 to 15/85,
wherein the mineral oil has a %CN by n-d-M ring analysis of 20 to 60, a
pour point of -15°C or less and a kinematic viscosity at 40°C of 1.5 to
15 mm2/s; and a hydrocarbon refrigerant having 2 to 4 carbon atoms,
wherein the refrigerating machine oil has a kinematic viscosity at 40°C
of 2 to 12 m d s and a flash point of 120°C or more. The refrigerating
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 omitted.
[0046] Specific examples of the hydrocarbon refrigerant having 2 to 4
carbon atoms in the present embodiment include ethane, propane,
n-butane and isobutane. In particular, a hydrocarbon refrigerant such
as isobutane (R600a) which has been used for a cold storage chamber,
5 and propane w 9 0 ) which has been examined for practical use for a
room air conditioner can be suitably used in the present embodiment.
Particularly, the working fluid composition for a refrigerating machine
of the present embodiment can achieve the power saving by lowering
the viscosity of the refrigerating machine oil, and therefore is suitable
10 for a cold storage chamber in which a reciprocating compressor, where
this effect is largely shown, is mainly used, and more particularly, is
suitable for an isobutane refrigerant.
[0047] In the working fluid composition for a refrigerating machine of
the present embodiment, a content ratio between the refrigerant and the
15 refrigerating machine oil is not especially limited, and the
refsigerant/the refrigerating machine oil is preferably 10190 to 90110,
and more preferably 30170 to 70130.
Examples
[0048] The present invention will now be more specifically described
20 by way of examples and comparative examples, but it is noted that the
present invention is not limited to the following examples at all.
[0049] [Example 11
A mineral oil having a kinematic viscosity at 40°C of 3.4 mm2/s,
a flash point of 108"C, a %CN by the n-d-M ring analysis of 40, and a
25 pour point of -50°C or less (VG3 base oil manufactured by JX Nippon
Oil & Energy Corporation, hereinafter referred to as the "mineral oil A")
and an alkylbenzene having a kinematic viscosity at 40°C of 4.5 mm2/s
and a flash point of 158°C (linear alkylbenzene manufactured by JX
Nippon Oil & Energy Corporation, hereinafter referred to as the "LAB")
were mixed in a mass ratio of the mineral oil AILAG = 30170 to obtain a
5 refrigerating machine oil having a kinematic viscosity at 40°C of 4.1
rnm2/s, a flash point of 136°C and a pour point of -50°C.
[0050] [Examples 2 to 10 and Comparative Examples 1 to 61
In Examples 2 to 10 and Comparative Examples 1 to 6, the
above-described mineral oil A and LAB, and the following mineral oils
10 and additives were used to obtain refrigerating machine oils respectively
having compositions shown in Tables 1 to 4. The kinematic viscosities
at 40°C, the flash points and the pour points of the obtained
refrigerating machine oils are also shown in Tables 1 to 4.
(Base oil)
15 Mineral oil B: a mineral oil having a kinematic viscosity at 40°C
of 6.5 mm2/s, a flash point of 116"C, a %CN by the n-d-M ring analysis
of 47, and a pour point of -50°C or less (VG7 base oil manufactured by
JX Nippon Oil & Energy Corporation)
Mineral'oil C: a mineral oil having a kinematic viscosity at 40°C
20 of 8.7 mm2/s, a flash point of 130°C, a %CN by the n-d-M ring analysis
of 57, and a pour point of -50°C or less (VG8 base oil manufactured by
JX Nippon Oil & Energy Corporation)
PAO: poly-a-olefin having a kinematic viscosity at 40°C of 5.2
mm2/s, a flash point of 194"C, a %CN by the n-d-M ring analysis of 11,
25 and a pour point of -50°C or less
(Additive)
GMO: glycerol monooleate
GMOE: glycerol monooleyl ether
TBPP: tert.-butylphenyl phosphate (a mixture of
tert.-butylphenyl diphenyl phosphate and di(tert.-butylphenyl) phenyl
phosphate in a mass ratio of 211
[0051] [Table 11
Kinematic viscosity at
40°C, mm21s
Flash noint. "C
I Additive I "mMaUssEo' h 1 0 . l I - 1 - 1 - 1 - I
[0052] [Table 21
4.3
136
[0053] [Table 31
Item
TBPP, mass%
Kinematic viscosity at
40°C, mm2/s
Flash point, "C
Pour voint. OC
4.0
130
Example 6
Mineral oil
A M
(50150)
99.9
-
Base oil
Type(mass
ratio)
Content
GMO. mass%
-
4.0
130
-50
5.4
134
Example 7
Mineral oil
BLAB
(50150)
99.5
-
0.5
5.4
134
-50
5.5
130
Example 8
Mineral oil
CLAB
(50150)
100
-
4.2
132
-
5.9
149
-50
Example 9
Mineral oil
CLAB
(20180)
100
-
Example 1C
Mineral oil
C!LAB
(20180)
99.5
-
-
4.8
153
-50
0.5
4.8
153
-50
FPf 2-0797-00
Flash point, "C 108 116 110
Pour point, OC -50 -50 -50
Y, mass% - - -
atic viscosity at 40°C,
mm2/s 3.4 6.5 3.5
Item
[0054] [Table 41
Comparative
Example 1
Mineral oil A
(100)
100
-
-
Base oil
Additive
[0055] Next, the refrigerating machine oils of Examples 1 to 10 and
Type (mass ratio)
Content, mass%
GMO, mass%
GMOE. mass%
Comparative Examples 1 to 6 were subjected to the following
Comparative
Example 2
Mineral oil B
(100)
100
-
-
evaluation tests.
-
Comparative
Example 3
Mineral oil
AILAB
(9011 0)
100
-
-
[0056] (Lubricity)
In accordance with ASTM D-3233-73, a Falex burning load was
measured initially at 50°C and 290 spm under an atmosphere where the
blowing of a refrigerant R600a was controlled (to 70 ml/min).
Besides, a Falex wear test was performed at 50°C and 290 ipm
under a load of 50 Lbf for 5 minutes in a break-in period and under a
load of 100 Lbf for 1 hour in an actual test, and the result was shown as
a total wear amount (in mg) of a vane and a block obtained after the test.
The test load was set to be low for setting a condition ranging
5 from a mixed lubrication region to a mild boundary lubrication region.
The obtained results are shown in Tables 5 and 6.
[0057] (Thermal stability)
In accordance with ANSVASHRAE 97-1983, a stainless steel
cylinder (100 ml) was charged with each sample oil (20 g), the
10 refrigerant R600a (20 g) and a catalyst (a wire of iron, copper or
aluminum), the resulting cylinder was heated to 175OC, and after
retaining the resultant for 14 days, a color tone (according to ASTM)
and an acid value of the sample oil were measured. The obtained
results are shown in Tables 5 and 6.
15 [0058] (Electrical insulating property)
In accordance with JIS C2101, the volume resistivity at 80°C
was measured. The obtained results are shown in Tables 5 and 6.
[0059] [Table 51
machine oils of Examples 1 to 10 and Comparative Examples 1 to 6
Item
Lubricity, Falex
burning load,
Lbf
Lubricity, Falex
wear, mg
Thermal
stability (175OC,
after 14 days)
color tone
(ASTM)
total acid value,
mgKOWg
Elech'ical
insulating
property
volume
resistivity
(80°C), TC2.m
have the low-temperature characteristic corresponding to the pour point,
[0060] [Table 61
[0061] As is understood fkom Tables 1 to 6, all the refiigerating
Example
1
350
6.7
L1.0
0.01
0.017
Example
2
330
5.8
L1.0
0.01
0.018
Example
3
400
4.9
L1.0
0.01
0.016
Example
4
410
4.7
L1.0
0.01
0.018
Example
5
490
2.1
L1.0
0.01
0.011
Example
6
510
2.0
L1.0
0.01
0.011
Example
7
530
1.7
L1.0
0.01
0.010
Example
8
480
4.2
L1.0
0.01
0.018
Example
9
380
4.5
L1.0
0.01
0.019
Example
10
500
2.0
L1.0
0.01
0.010
the thermal stability and the electrical insulating property at a sufficient
level required as a refrigerating machine oil.
The refrigerating machine oils of Comparative Examples 1 to 3
have, however, a flash point, used as a target for the safety, lower than
5 120°C, and since the drying process at approximately 120°C is
performed after injecting the refrigerating machine oil in producing a
compressor, these oils are too dangerous to use. On the other hand, the
refrigerating machine oils of synthetic oil type of Comparative
Examples 4 to 6 have sufficiently high flash points but are so inferior in
the lubricity that seizure was caused in the wear test performed under a
comparatively low load. Specifically, if abrasion or seizure is caused
in a sliding portion of a refrigeration compressor, a refrigeration cycle
cannot function.
On the contrary, each of the refrigerating machine oils of
Examples 1 to 10 has a flash point of 120°C or more, has lubricity at
level of a given burning load although the viscosity is low, and the wear
amount is excellently as small as 10 mg or less. In particular, the
lubricity of Examples 5, 6 and 10 in which an abrasion resistance
additive is contained is excellent, but even if the low viscosity
refrigerating machine oil of the present invention is used, a refrigerating
machine is preferably designed, from the viewpoint of long-term
reliability, to keep a sliding portion in an elastic fluid lubrication region
so as to prevent the abrasion with the thickness of the oil film.
Industrial Applicability
[0062] The refrigerating machine oil of the present invention is used as
a lubricating oil for a refrigerating machine using a hydrocarbon
refiigerant having 2 to 4 carbon atoms, such as isobutane, and in
particular, can be used in a power saving 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
tube), an evaporator and the like are provided and a refiigerant is
circulated among these components, particularly as a lubricating oil in a
refiigerating machine including a reciprocating type, a rotary type, a
scroll type or a screw type compressor, and can be suitably used in a
cold storage chamber, a room air conditioner, an industrial refiigerating
machine and the like.

CLAIMS
1. A working fluid composition for a refrigerating machine
comprising:
a rehigerating machine oil comprising a mineral oil and an
alkylbenzene in a mass ratio, the mineral oiVthe alkylbenzene, of 85/15
to 15/85, wherein the mineral oil has a %CN by n-d-M ring analysis of
20 to 60, a pour point of -15°C or less and a kinematic viscosity at 40°C
of 1.5 to 15 mm2/s; and
a hydrocarbon refrigerant having 2 to 4 carbon atoms,
the refrigerating machine oil having a kinematic viscosity at
40°C of 2 to 12 rnm2/s and a flash point of 120°C or more.
2. The working fluid composition for a refrigerating machine
according to claim 1, wherein the alkylbenzene is a linear alkylbenzene
in which a linear alkyl group is bonded to a benzene ring, and wherein a
kinematic viscosity at 40°C of the alkylbenzene is 2 to 10 m d s .
3. The working fluid composition for a refrigerating machine
according to claim 1 or 2, wherein the %CN by the n-d-M ring analysis
of the mineral oil is 40 to 60.
4. The working fluid composition for a refrigerating machine
according to any one of claims 1 to 3, hsther comprising at least one
glycerin derivative selected hom an ester compound of glycerin and an
ether compound of glycerin, wherein a content of the glycerin derivative
is 0.005 to 1.0% by mass based on a total amount of the refrigerating
machine oil.
5. The working fluid composition for a refrigerating machine
according to any one of claims 1 to 4, further comprising at least one
phosphorus compound selected from a mono(alkylpheny1) diphenyl
phosphate having one alkyl group having 3 to 5 carbon atoms, a
di(alkylpheny1) phenyl phosphate having two alkyl groups having 3 to 5
carbon atoms, and a tri(alkylpheny1) phosphate having three alkyl
groups having 3 to 5 carbon atoms, wherein a content of the phosphorus
compound is 0.05 to 3.0% by mass based on a total amount of the
refrigerating machine oil.
6. The working fluid composition for a refrigerating machine
according to any one of claims 1 to 5, wherein the hydrocarbon
refrigerant is isobutane.
7. A refrigerating machine oil comprising a mineral oil and an
alkylbenzene, in a mass ratio, the mineral oillthe alkylbenzene, of 85/15
to 15/85, wherein the mineral oil has a %CN by n-d-M ring analysis of
20 to 60, a pour point of -15°C or less and a kinematic viscosity at 40°C
of 1.5 to 15 mm2/s,
the refrigerating machine oil having a kinematic viscosity at
40°C of 2 to 12 mm2/s and a flash point of 120°C or more, and
the refrigerating machine oil being used with a hydrocarbon
refrigerant having 2 to 4 carbon atoms.
8. A method for manufacturing a refrigerating machine oil
comprising a step of mixing a mineral oil and an alkylbenzene in a mass
ratio, the mineral oiVthe alkylbenzene, of 85/15 to 15/85, to obtain a
refrigerating machine oil comprising a mixed oil of the mineral oil and
the alkylbenzene as a base oil and having a kinematic viscosity at 40°C
of 2 to 12 mm2/s and a flash point of 120°C or more, wherein the
mineral oil has a %CN by n-d-M ring analysis of 20 to 60, a pour point
of -1 5°C or less and a kinematic viscosity at 40°C of 1.5 to 15 mrn2/s,
the refrigerating machine oil being used with a hydrocarbon
refrigerant having 2 to 4 carbon atoms.