U.S. patent application number 10/332987 was filed with the patent office on 2004-08-12 for lubricating oil for refrigerators and hydraulic fluid composition for refrigerator using the same.
Invention is credited to Mogami, Kenji, Tazaki, Naoko, Tazaki, Toshinori, Yamazaki, Hirotaka.
Application Number | 20040157753 10/332987 |
Document ID | / |
Family ID | 27531616 |
Filed Date | 2004-08-12 |
United States Patent
Application |
20040157753 |
Kind Code |
A1 |
Tazaki, Toshinori ; et
al. |
August 12, 2004 |
Lubricating oil for refrigerators and hydraulic fluid composition
for refrigerator using the same
Abstract
The present invention proposes a lubricating oil for
refrigerators comprising, as the base oil, a polyester-based
derivative or a polyvinyl ether derivative and a
polycarbonate-based oxygenated compound; a polyoxyalkylene glycol
derivative; or a polyester-based derivative or a polyvinyl ether
derivative and a polyoxyalkylene glycol derivative. The lubricating
oil exhibits excellent miscibility with a refrigerant having one
carbon atom and no chlorine atoms and, in particular, with
difluoromethane and provides a hydraulic fluid composition
exhibiting excellent antiwear, lubricity and stability.
Inventors: |
Tazaki, Toshinori; (Chiba,
JP) ; Tazaki, Naoko; (Chiba, JP) ; Mogami,
Kenji; (Chiba, JP) ; Yamazaki, Hirotaka;
(Chiba, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Family ID: |
27531616 |
Appl. No.: |
10/332987 |
Filed: |
November 24, 2003 |
PCT Filed: |
July 23, 2001 |
PCT NO: |
PCT/JP01/06333 |
Current U.S.
Class: |
508/462 ;
508/465; 508/579 |
Current CPC
Class: |
C10M 171/008 20130101;
C10N 2030/02 20130101; C10M 2209/104 20130101; C10M 2209/1033
20130101; C10M 2209/043 20130101; C10M 2209/103 20130101; C10N
2020/02 20130101; C10M 2207/301 20130101; C10M 2209/108 20130101;
C10M 2209/107 20130101; C10M 2209/1085 20130101; C09K 5/045
20130101; C10N 2030/06 20130101; C10M 2207/325 20130101; C10N
2020/101 20200501; C10M 2209/105 20130101; C09K 2205/24 20130101;
C10M 111/04 20130101; C10M 2209/04 20130101; C10M 2209/1045
20130101; C10M 2209/1075 20130101; C10N 2040/30 20130101; C10M
2209/1055 20130101 |
Class at
Publication: |
508/462 ;
508/465; 508/579 |
International
Class: |
C10M 17/32; C10M
17/24 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 26, 2000 |
JP |
2000-224842 |
Jul 26, 2000 |
JP |
2000-224843 |
Aug 8, 2000 |
JP |
2000-239830 |
Aug 23, 2000 |
JP |
2000-252279 |
Aug 23, 2000 |
JP |
2000-252280 |
Claims
1. A lubricating oil for refrigerators which comprises, as a base
oil, (a) a polyvinyl ether-based derivative with a kinematic
viscosity of 3 to 500 mm.sup.2/s at 40.degree. C. and (b) a
polycarbonate-based oxygenated compound with a kinematic viscosity
of 3 to 2,000 mm.sup.2/s at 40.degree. C. in an amount of 0.1% by
weight or more and less than 60% by weight based on an amount of
the entire base oil, wherein a temperature of phase separation at a
low temperature side of a mixture comprising the lubricating oil
and a refrigerant having one carbon atom and no chlorine atoms is
5.degree. C. or lower in at least any one of the case where the
lubricating oil is contained within a range of 3 to 50% by weight
based on an amount of the entire mixture.
2. A lubricating oil for refrigerators which comprises, as a base
oil, (a) a polyester-based derivative with a kinematic viscosity of
3 to 500 mm.sup.2/s at 40.degree. C. and (b) a polycarbonate-based
oxygenated compound with a kinematic viscosity of 3 to 2,000
mm.sup.2/s at 40.degree. C. in an amount of 0.1% by weight or more
and less than 60% by weight based on an amount of the entire base
oil, wherein a temperature of phase separation at a low temperature
side of a mixture comprising the lubricating oil and a refrigerant
having one carbon atom and no chlorine atoms is 10.degree. C. or
lower in at least any one of the case where the lubricating oil is
contained within a range of 3 to 50% by weight based on an amount
of the entire mixture.
3. The lubricating oil for refrigerators according to claim 1 or
claim 2, wherein a kinematic viscosity at 40.degree. C. of said
lubricating oil is 7 to 200 mm.sup.2/s and a viscosity index of
said lubricating oil is 40.degree. C. or greater.
4. The lubricating oil for refrigerators according to any one of
claims 1 to 3, wherein said polycarbonate-based oxygenated compound
is a polycarbonate having at least two carbonate bonds in one
molecule which is at least one compound selected from: (i)
compounds represented by general formula (I): 26 wherein Z
represents a residue group obtained by eliminating hydroxyl group
from an alcohol having 1 to 12 carbon atoms and a functionality of
n, R.sup.1 represents a linear or branched alkylene group having 2
to 10 carbon atoms, R.sup.2 represents a monovalent hydrocarbon
group having 1 to 12 carbon atoms or a group having ether bond
represented by R.sup.4(O--R.sup.3).sub.p--, R.sup.4 representing
hydrogen atom or a monovalent hydrocarbon group having 1 to 12
carbon atoms, R.sup.3 representing a linear or branched alkylene
group having 2 to 10 carbon atoms and p representing an integer of
1 to 20, k represents an integer of 1 to 30, m represents an
integer of 1 to 50 and n represents an integer of 1 to 6; and (ii)
compounds represented by general formula (II): 27 wherein R.sup.5
represents a linear or branched alkylene group having 2 to 10
carbon atoms, q represents an integer of 1 to 20 and Z, R.sup.1,
R.sup.2, k, m and n are the same as described for general formula
(I).
5. The lubricating oil for refrigerators according to claim 4,
wherein said compound represented by general formula (I) is a
compound represented by general formula (I-a): 28wherein R.sup.6
represents a residue group obtained by eliminating hydroxyl group
from a monohydric alcohol having 1 to 12 carbon atoms and R.sup.1,
R.sup.2, k and m are as described for general formula (I); and/or
said compound represented by general formula (II) is a compound
represented by general formula (II-a): 29wherein R.sup.1, R.sup.2,
R.sup.5, R.sup.6, k, m and q are the same as described for general
formulae (I), (II) and (I-a).
6. The lubricating oil for refrigerators according to claim 5,
wherein R.sup.1 in general formula (I-a) and general formula (II-a)
represents an alkylene group having 2 to 6 carbon atoms.
7. The lubricating oil for refrigerators according to claim 6,
wherein R.sup.1 represents ethylene group or propylene group.
8. The lubricating oil for refrigerators according to any one of
claims 5 to 7, wherein, in general formula (I-a) and general
formula (II-a), R.sup.2 and/or R.sup.6 represents a linear or
branched alkyl group having 1 to 6 carbon atoms.
9. A lubricating oil for refrigerators used for a refrigerant
having one carbon atom and no chlorine atoms which comprises, as a
base oil, a polyoxyalkylene glycol derivative with a kinematic
viscosity of 3 to 2,000 mm.sup.2/s at 40.degree. C. and, as a main
component thereof, having at least one constituting unit
represented by general formula (III): 30wherein R.sup.7 to R.sup.10
each independently represent hydrogen atom, a monovalent
hydrocarbon group having 1 to 10 carbon atoms or a group
represented by general formula (IV): 31wherein R.sup.11 and
R.sup.12 each independently representing hydrogen atom, a
monovalent hydrocarbon group having 1 to 20 carbon atoms or an
alkoxyalkyl group having 2 to 20 carbon atoms, R.sup.13
representing an alkylene group having 2 to 5 carbon atoms, a
substituted alkylene group having an alkyl group as a substituent
and 2 to 5 carbon atoms in an entire group or a substituted
alkylene group having an alkoxyalkyl group as a substituent and 4
to 10 carbon atoms in an entire group, R.sup.14 representing a
monovalent hydrocarbon group having 1 to 10 carbon atoms and n
representing an integer of 0 to 20; and at least one of R.sup.7 to
R.sup.10 represents a group represented by general formula
(IV).
10. A lubricating oil for refrigerators which comprises, as a base
oil, (a) a polyvinyl ether-based derivative with a kinematic
viscosity of 3 to 500 mm.sup.2/s at 40.degree. C. and (b) a
polyoxyalkylene glycol derivative with a kinematic viscosity of 3
to 2,000 mm.sup.2/s at 40.degree. C. in an amount of 0.1% by weight
or more and less than 60% by weight based on an amount of the
entire base oil, and having at least one constituting unit
represented by general formula (III): 32wherein R.sup.7 to R.sup.10
each independently represents hydrogen atom, a monovalent
hydrocarbon group having 1 to 10 carbon atoms or a group
represented by general formula (IV): 33wherein R.sup.11 and
R.sup.12 each independently representing hydrogen atom, a
monovalent hydrocarbon group having 1 to 20 carbon atoms or an
alkoxyalkyl group having 2 to 20 carbon atoms, R.sup.13
representing an alkylene group having 2 to 5 carbon atoms, a
substituted alkylene group having an alkyl group as a substituent
and 2 to 5 carbon atoms in an entire group or a substituted
alkylene group having an alkoxyalkyl group as a substituent and 4
to 10 carbon atoms in an entire group, R.sup.14 representing a
monovalent hydrocarbon group having 1 to 10 carbon atoms and n
representing an integer of 0 to 20; and at least one of R.sup.7 to
R.sup.10 represents a group represented by general formula (IV);
characterized that a temperature of phase separation at a low
temperature side of a mixture comprising the lubricating oil and a
refrigerant having one carbon atom and no chlorine atoms is
5.degree. C. or lower in at least any one of the case where the
lubricating oil is contained within a range of 3 to 50% by weight
based on an amount of the entire mixture.
11. A lubricating oil for refrigerators which comprises, as a base
oil, (a) a polyester-based derivative with a kinematic viscosity of
3 to 500 mm.sup.2/s at 40.degree. C. and (b) a polyoxyalkylene
glycol derivative with a kinematic viscosity of 3 to 2,000
mm.sup.2/s at 40.degree. C. in an amount of 0.1% by weight or more
and less than 60% by weight based on an amount of the entire base
oil, having at least one constituting unit represented by general
formula (III): 34wherein R.sup.7 to R.sup.10 each independently
represent hydrogen atom, a monovalent hydrocarbon group having 1 to
10 carbon atoms or a group represented by general formula (IV):
35wherein R.sup.11 and R.sup.12 each independently representing
hydrogen atom, a monovalent hydrocarbon group having 1 to 20 carbon
atoms or an alkoxyalkyl group having 2 to 20 carbon atoms, R.sup.13
representing an alkylene group having 2 to 5 carbon atoms, a
substituted alkylene group having an alkyl group as a substituent
and 2 to 5 carbon atoms in an entire group or a substituted
alkylene group having an alkoxyalkyl group as a substituent and 4
to 10 carbon atoms in an entire group, R.sup.14 representing a
monovalent hydrocarbon group having 1 to 10 carbon atoms and n
representing an integer of 0 to 20; and at least one of R.sup.7 to
R.sup.10 represents a group represented by general formula (IV);
characterized that a temperature of phase separation at a low
temperature side of a mixture comprising the lubricating oil and a
refrigerant having one carbon atom and no chlorine atoms is
10.degree. C. or lower in at least any one of the case where the
lubricating oil is contained within a range of 3 to 50% by weight
based on an amount of the entire mixture.
12. The lubricating oil for refrigerators according to any one of
claims 9 to 11, wherein a kinematic viscosity at 40.degree. C. of
said lubricating oil is 7 to 200 mm.sup.2/s and a viscosity index
of said lubricating oil is 40 or greater.
13. The lubricating oil for refrigerators according to any one of
claims 1 to 12, which further comprises an acid catcher.
14. The lubricating oil for refrigerators according to any one of
claims 1 to 13, which further comprises at least one additive
selected from a group consisting of extreme pressure agents,
oiliness agents and antioxidants.
15. The hydraulic fluid composition for refrigerators which
comprises (A) a refrigerant having one carbon atom and no chlorine
atoms and (B) a lubricating oil for refrigerators described in any
one of claims 1 to 14.
16. The hydraulic fluid composition for refrigerators according to
claim 15, which comprises said (A) and said (B) in amounts such
that a ratio of an amount by weight of said (A) to an amount by
weight of said (B) is in a range of 5:95 to 99:1.
17. The hydraulic fluid composition for refrigerators according to
claim 15 or claim 16, wherein said (A) is difluoromethane.
Description
TECHNICAL FIELD
[0001] The present invention relates to a lubricating oil for
refrigerators and a hydraulic fluid composition for refrigerators
using the lubricating oil. More particularly, the present invention
relates to a lubricating oil for refrigerators which exhibits
excellent miscibility with a refrigerant having one carbon atom and
no chlorine atoms and, in particular, with difluoromethane. The
present invention also relates to a hydraulic fluid composition for
refrigerators comprising the lubricating oil for refrigerators and
the refrigerant that exhibits excellent antiwear, lubricity and
stability.
BACKGROUND ART
[0002] In general, refrigerators such as compression-type
refrigerators comprises a compressor, a condenser, an expansion
mechanism like an expansion valve, an evaporator and, where
necessary, a dryer and has a structure in which a mixed fluid of a
refrigerant and a lubricating oil is circulated in the closed
system. In the compression-type refrigerator, in general,
temperature is high in the compressor and low in the refrigerating
chamber although the conditions may be different depending on the
type of the apparatus and it is required, in general, that the
refrigerant and the lubricating oil be circulated in the system
without causing phase separation in a wide temperature range.
[0003] In general, there are two areas of phase separation between
a refrigerant and a lubricating oil, i.e., at the lower temperature
side and at the high temperature side. It is preferable that the
maximum temperature in the area of phase separation at the low
temperature side is 10.degree. C. or lower, more preferably
5.degree. C. or lower, still more preferably 3.degree. C. or lower,
still more preferably 0.degree. C. or lower and most preferably
-2.degree. C. or lower. When the phase separation takes place
during the operation of refrigeration, the lifetime and the
efficiency of the apparatus are adversely affected to a great
extent. For example, when the phase separation of the refrigerant
and the lubricating oil takes place in the compressor, lubrication
of moving parts deteriorates and seizure occurs to cause a great
decrease in the lifetime of the apparatus. When the phase
separation takes places in the evaporator, the efficiency of heat
exchange decreases because of the presence of lubricating oil of
high viscosity.
[0004] As the refrigerant for the compression-type refrigerators
and, in particular, for air conditioners, heretofore,
chlorodifluoromethane (referred to as R22, hereinafter) and a
mixture of chlorodifluoromethane and chloropentafluoroethane in
weight ratio of 48.8:51.2 (referred to as R502, hereinafter) have
been mainly used. As the lubricating oil, various types of mineral
oils and synthetic oils that satisfy the foregoing requirement have
been used. However, R22 and R502 are more rigorously restricted
worldwide because there is the anxiety of causing environmental
pollution such as destruction of the ozonosphere present in the
stratosphere. As the novel type of the refrigerant,
hydrofluorocarbons such as 1,1,1,2-tetrafluoroethane,
difluoromethane, pentafluoroethane and 1,1,1-trifluoroethane
(occasionally referred to as R134a, R32, R125 and R143a,
respectively) are attracting attention. These hydrofluorocarbons
and, in particular, R134a, R32, R125 and R143a have little anxiety
of causing the ozonosphere destruction and are preferable as the
refrigerant for the compression-type refrigerators.
[0005] Further improvements are required from the standpoint of the
energy saving and difluoromethane (R32) among the foregoing novel
refrigerants is attracting attention. However, the refrigerant R32
is used at a higher pressure and a higher temperature than those of
conventional refrigerants and there is the great possibility that
problems arise on lubrication. It is the actual present situation
that no lubricating oils exhibiting sufficient miscibility with R32
are found among the lubricating oils for refrigerants that have
been examined for the use in combination with the foregoing novel
refrigerants. Development of a lubricating oil exhibiting
miscibility with R32 at the same level as that with R134a, R407c (a
mixture of R32, R125 and R134a in the weight ratio of 23:24:52) and
R410A (a mixture of R32 and R125 in the weight ratio of 50:50) has
been desired.
[0006] Under the above circumstances, the present invention has an
object of providing a lubricating oil for refrigerators which
exhibits excellent miscibility with a refrigerant having one carbon
atom and no chlorine atoms and, in particular, with difluoromethane
(R32). Another object of the present invention is to provide a
hydraulic fluid composition for refrigerators comprising the
lubricating oil for refrigerators and the refrigerant and
exhibiting excellent antiwear, lubricity and stability.
[0007] The present inventors have been studying miscibility in the
presence of the refrigerant R32 regarding oxygenated compounds such
as polyether compounds, examples of which include polyoxyalkylene
glycol derivatives and polyvinyl ether derivatives, and polyol
ester derivatives. However, these compounds do not always exhibit
the sufficient miscibility with the refrigerant R32.
DISCLOSURE OF THE INVENTION
[0008] As the result of intensive studies by the present inventors
to achieve the above-described object, it was found that a mixture
obtained by mixing a polyvinyl ether-based derivative or a
polyester-based derivative each having a specific viscosity with a
specific relative amount of a polycarbonate-based oxygenated
compound and, in particular, a polycarbonate compound having two or
more carbonate bonds in one molecule exhibited excellent
miscibility with refrigerants having one carbon atom and no
chlorine atoms and, in particular, with R32 at low temperatures and
it was also found that a mixture containing the compound and the
refrigerant could be used as the hydraulic fluid composition for
refrigerators achieving the above-described object. The present
invention has been completed based on the knowledge.
[0009] As the first aspect, the present invention provides:
[0010] (A-1) A lubricating oil for refrigerators which comprises,
as a base oil, (a) a polyvinyl ether-based derivative with a
kinematic viscosity of 3 to 500 mm.sup.2/s at 40.degree. C. and (b)
a polycarbonate-based oxygenated compound with a kinematic
viscosity of 3 to 2,000 mm.sup.2/s at 40.degree. C. in an amount of
0.1% by weight or more and less than 60% by weight based on an
amount of the entire base oil, wherein a temperature of phase
separation at a low temperature side of a mixture comprising the
lubricating oil and a refrigerant having one carbon atom and no
chlorine atoms is 5.degree. C. or lower in at least any one of the
case where the lubricating oil is contained within a range of 3 to
50% by weight based on an amount of the entire mixture; and
[0011] (A-2) A lubricating oil for refrigerators which comprises,
as a base oil, (a) a polyester-based derivative with a kinematic
viscosity of 3 to 500 mm.sup.2/s at 40.degree. C. and (b) a
polycarbonate-based oxygenated compound with a kinematic viscosity
of 3 to 2,000 mm.sup.2/s at 40.degree. C. in an amount of 0.1% by
weight or more and less than 60% by weight based on an amount of
the entire base oil, wherein a temperature of phase separation at a
low temperature side of a mixture comprising the lubricating oil
and a refrigerant having one carbon atom and no chlorine atoms is
10.degree. C. or lower in at least any one of the case where the
lubricating oil is contained within a range of 3 to 50% by weight
based on an amount of the entire mixture.
[0012] In the first aspect of the present invention, it is
preferable that (b) the polycarbonate-based oxygenated compound is
a polycarbonate having at least two carbonate bonds in one molecule
which is at least one compound selected from:
[0013] (i) compounds represented by general formula (I): 1
[0014] wherein Z represents a residue group obtained by eliminating
hydroxyl group from an alcohol having 1 to 12 carbon atoms and a
functionality of n, R.sup.1 represents a linear or branched
alkylene group having 2 to 10 carbon atoms, R.sup.2 represents a
monovalent hydrocarbon group having 1 to 12 carbon atoms or a group
having ether bond represented by R.sup.4(O--R.sup.3).sub.p--,
R.sup.4 representing hydrogen atom or a monovalent hydrocarbon
group having 1 to 12 carbon atoms, R.sup.3 representing a linear or
branched alkylene group having 2 to 10 carbon atoms and p
representing an integer of 1 to 20, k represents an integer of 1 to
30, m represents an integer of 1 to 50 and n represents an integer
of 1 to 6; and
[0015] (ii) compounds represented by general formula (II): 2
[0016] wherein R.sup.5 represents a linear or branched alkylene
group having 2 to 10 carbon atoms, q represents an integer of 1 to
20 and Z, R.sup.1, R.sup.2, k, m and n are the same as described
for general formula (I).
[0017] As the result of further intensive studies by the present
inventors to achieve the above-described object, it was found that
a polyoxyalkylene glycol derivative having a specific viscosity and
a specific substituent by itself or a mixture of the
polyoxyalkylene glycol and a polyvinyl ether-based derivative
having a specific viscosity or a polyester-based derivative having
a specific viscosity in specific relative amounts exhibited
excellent miscibility with refrigerants having one carbon atom and
no chlorine atoms and, in particular, with R32 and it was also
found that a mixture containing the compound or the mixture and the
refrigerant could be used as the hydraulic fluid composition for
refrigerators achieving the above-described objects. The second
aspect of the present invention has been completed based on the
knowledge.
[0018] As the second aspect, the present invention provides:
[0019] (B-1) A lubricating oil for refrigerators used for a
refrigerant having one carbon atom and no chlorine atoms which
comprises, as a base oil, a polyoxyalkylene glycol derivative with
a kinematic viscosity of 3 to 2,000 mm.sup.2/s at 40.degree. C.
and, as a main component thereof, having at least one constituting
unit represented by general formula (III): 3
[0020] wherein R.sup.7 to R.sup.10 each independently represent
hydrogen atom, a monovalent hydrocarbon group having 1 to 10 carbon
atoms or a group represented by general formula (IV): 4
[0021] wherein R.sup.11 and R.sup.12 each independently
representing hydrogen atom, a monovalent hydrocarbon group having 1
to 20 carbon atoms or an alkoxyalkyl group having 2 to 20 carbon
atoms, R.sup.13 representing an alkylene group having 2 to 5 carbon
atoms, a substituted alkylene group having an alkyl group as a
substituent and having 2 to 5 carbon atoms in an entire group or a
substituted alkylene group having an alkoxyalkyl group as a
substituent and having 4 to 10 carbon atoms in an entire group,
R.sup.14 representing a monovalent hydrocarbon group having 1 to 10
carbon atoms and n representing an integer of 0 to 20; and at least
one of R.sup.7 to R.sup.10 represents a group represented by
general formula (IV);
[0022] (B-2) A lubricating oil for refrigerators which comprises,
as a base oil, (a) a polyvinyl ether-based derivative with a
kinematic viscosity of 3 to 500 mm.sup.2/s at 40.degree. C. and (b)
a polyoxyalkylene glycol derivative with a kinematic viscosity of 3
to 2,000 mm.sup.2/s at 40.degree. C. in an amount of 0.1% by weight
or more and less than 60% by weight based on an amount of the
entire base oil, and having at least one constituting unit
represented by general formula (III); wherein a temperature of
phase separation at a low temperature side of a mixture comprising
the lubricating oil and a refrigerant having one carbon atom and no
chlorine atoms is 5.degree. C. or lower in at least any one of the
case where the lubricating oil is contained within a range of 3 to
50% by weight based on an amount of the entire mixture; and
[0023] (B-3) A lubricating oil for refrigerators which comprises,
as a base oil, (a) a polyester-based derivative with a kinematic
viscosity of 3 to 500 mm.sup.2/s at 40.degree. C. and (b) a
polyoxyalkylene glycol derivative with a kinematic viscosity of 3
to 2,000 mm.sup.2/s at 40.degree. C. in an amount of 0.1% by weight
or more and less than 60% by weight based on an amount of the
entire base oil, having at least one constituting unit represented
by general formula (III); wherein a temperature of phase separation
at a low temperature side of a mixture comprising the lubricating
oil and a refrigerant having one carbon atom and no chlorine atoms
is 10.degree. C. or lower in at least any one of the case where the
lubricating oil is contained within a range of 3 to 50% by weight
based on an amount of the entire mixture.
[0024] The present invention also provides a hydraulic fluid
composition for refrigerators which comprises, as the essential
components, (A) a refrigerant having one carbon atom and no
chlorine atoms and (B) a lubricating oil for refrigerators
according to the first aspect or the second aspect of the present
invention.
[0025] It is considered that the advantageous effect of the present
invention is exhibited in the following manner. The lubricating
oils for refrigerators as the first aspect and the second aspect of
the present invention are used in combination with a refrigerant
having one carbon atom and no chlorine atoms and, in particular,
with a fluorohydrocarbon-based refrigerant having no chlorine
atoms. There is the tendency that the inner pressure is higher and
the temperature during the use is also higher. Therefore, when the
difference in the hardness between the parts constituting the metal
sliding portion of the compression mechanism is set at a value
greater than 10 as expressed by H.sub.RC, where necessary, the
antiwear of the part having a greater hardness is sufficiently
improved while the antiwear of the part having a smaller hardness
is surely kept at a current value with the hardness at the ordinary
value. In this manner, antiwear of the necessary parts in the metal
sliding portion can be improved and the adverse effect of the
absence of the lubricating effect of chlorine atom due to the
absence of chlorine atom in the fluorohydrocarbon refrigerant can
be compensated. As for the tendency that the sliding part having a
greater hardness accelerates wear of the sliding part having a
smaller hardness, at least one compound selected from esters of
orthophosphoric acid, esters of phosphorous acid and esters of
acidic phosphoric acid is added to the lubricating oil as the
extreme pressure agent and the insufficiency of lubricity due to
the absence of chlorine atom in the fluorohydrocarbon refrigerant
can be compensated by the working of the extreme pressure
agent.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 shows a flow diagram that exhibits an example of the
compression type refrigerating cycle of the
"compressor-condenser-expansi- on valve-evaporator" system having
an oil separator and a hot gas line.
[0027] FIG. 2 shows a flow diagram that exhibits an example of the
compression type refrigerating cycle of the
"compressor-condenser-expansi- on valve-evaporator" system having
an oil separator.
[0028] FIG. 3 shows a flow diagram that exhibits an example of the
compression type refrigerating cycle of the
"compressor-condenser-expansi- on valve-evaporator" system having a
hot gas line.
[0029] FIG. 4 shows a flow diagram which exhibits an example of the
compression type refrigerating cycle of the
"compressor-condenser-expansi- on valve-evaporator" system.
[0030] In the Figures, numerical symbol 1 means a compressor,
numerical symbol 2 means a condenser, numerical symbol 3 means an
expansion valve, numerical symbol 4 means an evaporator, numerical
symbol 5 means an oil separator, numerical symbol 6 means a hot gas
line and numerical symbol 7 means a valve for a hot gas line.
THE MOST PREFERRED EMBODIMENT TO CARRY OUT THE INVENTION
[0031] The lubricating oil for refrigerators of the present
invention will be described below.
[0032] The lubricating oil for refrigerators as the first aspect of
the present invention comprises, as a base oil, (a) a polyvinyl
ether-based derivative with a kinematic viscosity of 3 to 500
mm.sup.2/s at 40.degree. C. and (b) a polycarbonate-based
oxygenated compound with a kinematic viscosity of 3 to 2,000
mm.sup.2/s at 40.degree. C. in an amount of 0.1% by weight or more
and less than 60% by weight based on an amount of the entire base
oil.
[0033] In a mixture comprising the lubricating oil and a
refrigerant having one carbon atom and no chlorine atoms such as
R32, the lubricating oil is miscible with the refrigerant (in other
words, the liquid phase is homogeneous) at a temperature of
5.degree. C. or lower in the case of the polyvinyl ether-based
derivative in (A-1) and at a temperature of 10.degree. C. or lower
in the case of the polyester-based derivative (A-2) in at least any
one of the case where the lubricating oil is contained within the
range of 3 to 50% by weight based on the amount of the entire
mixture. The content of the lubricating oil exhibiting the
miscibility with the refrigerant at a temperature of 5.degree. C.
or lower or at a temperature of 10.degree. C. or lower is within
the range of 3 to 50% by weight as described above. It is
preferable that the range is 10 to 15% by weight. It is more
preferable that the lubricating oil is miscible with the
refrigerant in the entire range of the content of 3 to 50% by
weight. When the temperature exhibiting the miscibility, i.e., the
temperature of phase separation at the low temperature side,
exceeds 5.degree. C. or 10.degree. C., there is the anxiety that
phase separation takes place during the operation of refrigeration.
When the phase separation takes place during the operation of
refrigeration, the lifetime and the efficiency of the apparatus are
adversely affected to a great extent. For example, when the phase
separation of the refrigerant and the lubricating oil takes place
in the compressor, lubrication of moving parts deteriorates and
seizure occurs to cause a great decrease in the lifetime of the
apparatus. When the phase separation takes places in the
evaporator, the efficiency of heat exchange decreases due to the
presence of lubricating oil of high viscosity.
[0034] Based on the foregoing reasons, it is necessary that the
maximum temperature in the area of phase separation at the low
temperature side be 5.degree. C. or lower for (A-1) and 10.degree.
C. or lower for (A-2). It is preferable that the maximum
temperature is 3.degree. C. or lower for (A-1) and 8.degree. C. or
lower for (A-2); more preferably 0.degree. C. or lower and
5.degree. C. or lower, respectively; still more preferably
-2.degree. C. or lower and 2.degree. C. or lower, respectively; and
most preferably -5.degree. C. or lower for both of (A-1) and
(A-2).
[0035] Examples of (a) the polyvinyl ether-based derivative of
lubricating oil (A-1) as the first aspect of the present invention
include polyvinyl ether-based compounds (1) having a constituting
unit represented by general formula (V): 5
[0036] wherein R.sup.13, R.sup.14 and R.sup.15 each represent
hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms,
the atom and the groups represented by R.sup.13, R.sup.14 and
R.sup.15 may be the same with or different from each other,
R.sup.16 represents a divalent hydrocarbon group having 1 to 10
carbon atoms, R.sup.17 represents a hydrocarbon group having 1 to
20 carbon atoms, a represent numbers giving an average value of 0
to 10, the atom and the groups represented by R.sup.13 to R.sup.17
may be the same or different among different constituting units
and, when a plurality of R.sup.16O are present, the plurality of
R.sup.16O may represent the same group or different groups.
[0037] Polyvinyl ether compounds (2) comprising block or random
copolymers comprising the constituting units represented by the
general formula (V) and constituting units represented by the
following general formula (VI): 6
[0038] can also be used wherein R.sup.18 to R.sup.21 each represent
hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms
that may be the same with or different from each other and the atom
and the groups represented by R.sup.18 to R.sup.21 may be the same
or different among different constituting units.
[0039] In the general formula (V), R.sup.13, R.sup.14 and R.sup.15
each represent hydrogen atom or a hydrocarbon group having 1 to 8
carbon atoms and preferably 1 to 4 carbon atoms. The atom and the
groups represented by R.sup.13, R.sup.14 and R.sup.15 may be the
same with or different from each other. Specific examples of the
hydrocarbon group include alkyl groups such as methyl group, ethyl
group, n-propyl group, isopropyl group, n-butyl group, isobutyl
group, sec-butyl group, tert-butyl group, various types of pentyl
groups, various types of hexyl groups, various types of heptyl
groups and various types of octyl groups; cycloalkyl groups such as
cyclopentyl group, cyclohexyl group, various types of
methylcyclohexyl groups, various types of ethylcyclohexyl groups
and various types of dimethylcyclohexyl groups; aryl groups such as
phenyl group, various types of methylphenyl groups, various types
of ethylphenyl groups and various types of dimethylphenyl groups;
and arylalkyl groups such as benzyl group, various types of
phenylethyl groups and various types of methylbenzyl groups. It is
preferable that R.sup.13, R.sup.14 and R.sup.15 represent hydrogen
atom.
[0040] Next, R.sup.16 in the general formula (V) represents a
divalent hydrocarbon group having 1 to 10 carbon atoms and
preferably having 2 to 10 carbon atoms. Specific examples of the
divalent hydrocarbon group having 1 to 10 carbon atoms include
divalent aliphatic groups such as methylene group, ethylene group,
phenylethylene group, 1,2-propylene group, 2-phenyl-1,2-propylene
group, 1,3-propylene group, various types of butylene groups,
various types of pentylene groups, various types of hexylene
groups, various types of heptylene groups, various types of
octylene groups, various types of nonylene groups and various types
of decylene groups; alicyclic groups having two bonding portions on
alicyclic hydrocarbons such as cyclohexane, methyl-cyclohexane,
ethylcyclohexane, dimethylcyclohexane and propylcyclo-hexane;
divalent aromatic hydrocarbon groups such as various types of
phenylene groups, various types of methylphenylene groups, various
ethylphenylene groups, various types of dimethylphenylene groups
and various types of naphthylene groups; alkylaromatic groups
having one monovalent bonding portion on each of the alkyl portion
and the aromatic portion of alkylaromatic hydrocarbons such as
toluene, xylene and ethylbenzene; and alkylaromatic hydrocarbon
groups having bonding portions on alkyl group portions of
polyalkylaromatic hydrocarbons such as xylene and diethylbenzene.
Among the examples, aliphatic groups having 2 to 4 carbon atoms are
preferable.
[0041] Additionally, a in the general formula (V) represent numbers
showing the repeating numbers of the group represented by R.sup.16O
and giving an average value in the range of 0 to 10 and preferably
in the range of 0 to 5. When a plurality of R.sup.19O are present,
the plurality of R.sup.16O may represent the same group or
different groups.
[0042] Further, R.sup.17 in the general formula (V) represents a
hydrocarbon group having 1 to 20 carbon atoms and preferably having
1 to 10 carbon atoms. Examples of the hydrocarbon group represented
by R.sup.17 include alkyl groups such as methyl group, ethyl group,
n-propyl group, isopropyl group, n-butyl group, isobutyl group,
sec-butyl group, tert-butyl group, various types of pentyl groups,
various types of hexyl groups, various types of heptyl groups,
various types of octyl groups, various types of nonyl groups and
various types of decyl groups; cycloalkyl groups such as
cyclopentyl group, cyclohexyl group, various types of
methylcyclohexyl groups, various types of ethylcyclohexyl groups,
various types of propylcyclohexyl groups and various types of
dimethylcyclohexyl groups; aryl groups such as phenyl group,
various types of methylphenyl groups, various types of ethylphenyl
groups, various types of dimethylphenyl groups, various types of
propylphenyl groups, various types of trimethylphenyl groups,
various types of butylphenyl groups and various types of naphthyl
groups; and arylalkyl groups such as benzyl group, various types of
phenylethyl groups, various types of methylbenzyl groups, various
types of phenylpropyl groups and various types of phenylbutyl
groups.
[0043] The atom and the groups represented by R.sup.13 to R.sup.17
may be the same or different among different constituting
units.
[0044] In the general formula (VI), R.sup.18 to R.sup.21 each
represent hydrogen atom or a hydrocarbon group having 1 to 20
carbon atoms and the atom and the groups represented by R.sup.18 to
R.sup.21 may be the same with or different from each other.
Examples of the hydrocarbon group having 1 to 20 carbon atoms
include the groups described above as the examples of the
hydrocarbon group represented by R.sup.17 in the general formula
(V). The atom and the groups represented by R.sup.18 to R.sup.21
may be the same or different among different constituting
units.
[0045] In lubricating oil (A-1) as the first aspect of the present
invention, a mixture of the above polyvinyl ether-based compound
(1) and the polyvinyl ether-based compound (2) may also be
used.
[0046] Polyvinyl ether-based compounds (1) and (2) used in the
present invention can be produced by polymerization of the
corresponding vinyl ether monomer and copolymerization of the
corresponding hydrocarbon monomer having an olefinic double bond
and the corresponding vinyl ether monomer, respectively.
[0047] As the polyvinyl ether-based compound used in the aspect of
the present invention, polyvinyl ether-based compounds that have
one chain end with the structure represented by general formula
(VII) or (VIII) are preferable: 7
[0048] wherein R.sup.22, R.sup.23 and R.sup.24 each represent
hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms,
the atoms and the groups represented by R.sup.22, R.sup.23 and
R.sup.24 may be the same with or different from each other,
R.sup.27, R.sup.28, R.sup.29 and R.sup.30 each represent hydrogen
atom or a hydrocarbon group having 1 to 20 carbon atom, the atoms
and the groups represented by R.sup.27, R.sup.28, R.sup.29 and
R.sup.30 may be the same with or different from each other,
R.sup.25 represents a divalent hydrocarbon group having 1 to 10
carbon atoms, R.sup.26 represents a hydrocarbon group having 1 to
20 carbon atoms, b represent numbers giving an average value of 0
to 10 and, when a plurality of R.sup.25O are present, the plurality
of R.sup.25O may represent the same group or different groups, and
the other chain end having the structure represented by general
formula (IX) or (X): 8
[0049] wherein R.sup.31, R.sup.32 and R.sup.33 each represent
hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms,
the atoms and the groups represented by R.sup.31, R.sup.32 and
R.sup.33 may be the same with or different from each other,
R.sup.36, R.sup.37, R.sup.38 and R.sup.39 each represent hydrogen
atom or a hydrocarbon group having 1 to 20 carbon atom, the atoms
and the groups represented by R.sup.36, R.sup.37, R.sup.38 and
R.sup.39 may be the same with or different from each other,
R.sup.34 represents a divalent hydrocarbon group having 1 to 10
carbon atoms, R.sup.35 represents a hydrocarbon group having 1 to
20 carbon atoms, c represent numbers giving an average value of 0
to 10 and, when a plurality of R.sup.34O are present, the plurality
of R.sup.34O may represent the same group or different groups.
[0050] As the polyvinyl ether-based compound used in the aspect of
the present invention, polyvinyl ether-based compounds that have
one chain end with the structure represented the general formula
(VII) or (VIII) and the other chain end having the structure
represented by general formula (XI) are also preferable: 9
[0051] wherein R.sup.40, R.sup.41 and R.sup.42 each represent
hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms and
the atoms and the groups represented by R.sup.40, R.sup.41 and
R.sup.42 may be the same with or different from each other.
[0052] Among the above polyvinyl ether-based compounds, the
following compounds are preferable for lubricating oil (A-1) as the
first aspect of the present invention:
[0053] (1) Compounds which have one chain end having the structure
represented by general formula (VII) or (VIII) and the other chain
end having the structure represented by general formula (IX) or (X)
and comprise the structural unit represented by general formula (V)
in which R.sup.13, R.sup.14 and R.sup.15 each represent hydrogen
atoms, a represent numbers of 0 to 4, R.sup.16 represents a
divalent hydrocarbon group having 2 to 4 carbon atoms and R.sup.17
represents a hydrocarbon group having 1 to 20 carbon atoms;
[0054] (2) Compounds which comprise the structural unit represented
by general formula (V) alone and have one chain end having the
structure represented by general formula (VII) and the other chain
end having the structure represented by general formula (IX),
wherein R.sup.13, R.sup.14 and R.sup.15 in general formula (V) each
represent hydrogen atom, a represent numbers of 0 to 4, R.sup.16
represents a divalent hydrocarbon group having 2 to 4 carbon atoms
and R.sup.17 represents a hydrocarbon group having 1 to 20 carbon
atoms;
[0055] (3) Compounds which have one chain end having the structure
represented by general formula (VII) or (VIII) and the other chain
end having the structure represented by general formula (XI) or (X)
and comprise the structural unit represented by general formula (V)
in which R.sup.13, R.sup.14 and R.sup.15 each represent hydrogen
atom, a represent numbers of 0 to 4, R.sup.16 represents a divalent
hydrocarbon group having 2 to 4 carbon atoms and R.sup.17
represents a hydrocarbon group having 1 to 20 carbon atoms;
[0056] (4) Compounds which comprise the structural unit represented
by general formula (V) alone and have one chain end having the
structure represented by general formula (VII) and the other chain
end having the structure represented by general formula (X),
wherein R.sup.13, R.sup.14 and R.sup.15 in general formula (V) each
represent hydrogen atom, a represent numbers of 0 to 4, R.sup.16
represents a divalent hydrocarbon group having 2 to 4 carbon atoms
and R.sup.17 represents a hydrocarbon group having 1 to 20 carbon
atoms; and
[0057] (5) mixtures of the compounds (1) to (4).
[0058] In lubricating oil (A-1) as the first aspect of the present
invention, polyvinyl ether-based compounds which comprise the
structural unit represented by the general formula (V) and have one
chain end having the structure represented by the general formula
(VII) and the other chain end having the structure represented by
the following general formula (XIII): 10
[0059] wherein R.sup.43, R.sup.44 and R.sup.45 each represent
hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms and
the atoms and the groups represented by R.sup.43, R.sup.44 and
R.sup.45 may be the same with or different from each other;
R.sup.46 and R.sup.48 each represent a divalent hydrocarbon group
having 2 to 10 carbon atoms and may represent the same group or
different groups; R.sup.47 and R.sup.49 each represent a
hydrocarbon group having 1 to 10 carbon atoms and may represent the
same group or different groups; d and e each represent numbers
giving an average value of 0 to 10 and may represent the same
number or different numbers; when a plurality of R.sup.46O are
present, the plurality of R.sup.46O may represent the same group or
different groups; and, when a plurality of R.sup.48O are present,
the plurality of R.sup.48O may represent the same group or
different groups can also be used.
[0060] Further, in lubricating oil (A-1) as the first aspect of the
present invention, polyvinyl ether-based compounds which are
homopolymers and copolymers of alkyl vinyl ethers comprising
structural units represented by the following general formula (XIV)
or (XV): 11
[0061] wherein R.sup.50 represents a hydrocarbon group having 1 to
8 carbon atoms; and having a weight-average molecular weight of 300
to 5,000 and one chain end having the structure represented by the
following general formula (XVI) or (XVII): 12 --CH.dbd.CHOR.sup.52
(XVII)
[0062] wherein R.sup.51 represents an alkyl group having 1 to 8
carbon atoms and R.sup.52 represents a hydrocarbon group having 1
to 8 carbon atoms; can also be used.
[0063] Further examples of the polyvinyl ether-based derivative
described above include the compounds described in detail in
Japanese Patent Application Laid-Open Nos. Heisei 6(1994)-128578,
Heisei 6(1994)-234814, Heisei 6(1994)-234815 and Heisei
8(1996)-193196.
[0064] The (a) polyvinyl ether-based derivative in lubricating oil
(A-1) as the first aspect of the present invention has a kinematic
viscosity at 40.degree. C. in the range of 3 to 500 mm.sup.2/s,
preferably in the range of 5 to 200 mm.sup.2/s and more preferably
in the range of 5 to 150 mm.sup.2/s.
[0065] Examples of (a) the polyester-based derivative of the base
oil in lubricating oils for refrigerators (A-2) as the first aspect
and in lubricating oil for refrigerators (B-3) as the second aspect
of the present invention include aromatic esters, esters of dibasic
acids, polyol esters, complex esters, esters of carbonic acid and
mixtures of these esters.
[0066] As the aromatic ester, esters obtained from aromatic
carboxylic acids having a functionality, in general, in the range
of 2 to 6, preferably in the range of 2 to 4 and more preferably of
2 or 3 and aliphatic alcohols having, in general, 1 to 18 carbon
atoms and preferably 1 to 12 carbon atoms are used. Examples of the
aromatic carboxylic acid having a functionality of 2 to 6 include
phthalic acid, isophthalic acid, terephthalic acid, trimellitic
acid, pyromellitic acid and mixtures of these acids. The aliphatic
alcohol having 1 to 18 carbon atom may be a linear alcohol or a
branched alcohol. Examples of such an alcohol include methanol,
ethanol, linear and branched propanols, linear and branched
butanols, linear and branched pentanols, linear and branched
hexanols, linear and branched heptanols, linear and branched
octanols, linear and branched nonanols, linear and branched
decanols, linear and branched undecanols, linear and branched
dodecanols, linear and branched tridecanols, linear and branched
tetradecanols, linear and branched pentadecanols, linear and
branched hexadecanols, linear and branched heptadecanols, linear
and branched octadecanols and mixtures of these alcohols. Examples
of the aromatic ester include dibutyl phthalate, di(2-ethylhexyl)
phthalate, dinonyl phthalate, didecyl phthalate, didodecyl
phthalate, ditridecyl phthalate, trisbutyl trimellitate,
tris(2-ethylhexyl) trimellitate, trisnonyl trimellitate, trisdecyl
trimellitate, trisdodecyl trimellitate and tristridecyl
trimellitate. When a carboxylic acid having a functionality of two
or greater is used, naturally, the ester may be a simple ester
obtained from a single type of aliphatic alcohol or a complex ester
obtained from two or more types of aliphatic alcohols.
[0067] As the ester of a dibasic acid, esters of dibasic acids
having 5 to 10 carbon atoms such as glutaric acid, adipic acid,
pimellic acid, suberic acid, azelaic acid and sebacic acid with
monohydric alcohols having 1 to 15 carbon atoms and linear and
branched alkyl groups such as methanol, ethanol, propanol, butanol,
pentanol, hexanol, heptanol, octanol, nonanol, decanol, undecanol,
dodecanol, tridecanol, tetradecanol and pentadecanol and mixtures
of these esters are preferable. Specific examples of the ester
include ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl
adipate, ditridecyl adipate, di-2-ethylhexyl sebacate and mixtures
of these esters.
[0068] As the polyol ester, esters of diols and polyols having 3 to
20 hydroxyl groups with fatty acids having 6 to 20 carbon atoms are
preferable. Examples of the diol include ethylene glycol,
1,3-propanediol, propylene glycol, 1,4-butanediol, 1,2-butanediol,
2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol,
1,6-hexanediol, 2-ethyl-2-methyl-1,3-propanediol, 1,7-heptanediol,
2-methyl-2-propyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol,
1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol
and 1,12-dodecanediol. Examples of the polyol include polyhydric
alcohols such as trimethylolethane, trimethylolpropane,
trimethylolbutane, di(trimethylolpropane), tri(trimethylolpropane),
pentaerythritol, di(pentaerythritol), tri(pentaerythritol),
glycerol, polyglycerols (2- to 20-mers of glycerol),
1,3,5-pentanetriol, sorbitol, sorbitane, condensates of sorbitol
and glycerol, adonitol, arabitol, xylitol and mannitol; sugars such
as xylose, arabinose, ribose, rhamnose, glucose, fructose,
galactose, mannose, sorbose, cellobiose, maltose, isomaltose,
trehalose, sucrose, raffinose, gentianose and melezitose; partial
esterification products of these compounds; and methyl glucosides.
Among these compounds, hindered alcohols such as neopentyl glycol,
trimethylolethane, trimethylolpropane, trimethylolbutane,
di(trimethylol)propane, tri(trimethylolpropane), pentaerythritol,
di(pentaerythritol) and tri(pentaerythritol) are preferable as the
polyol.
[0069] The number of carbon atoms in the fatty acid is not
particularly limited. In general, fatty acids having 1 to 24 carbon
atoms are used. Among the fatty acids having 1 to 24 carbon atoms,
fatty acids having 3 or more carbon atoms are preferable, fatty
acids having 4 or more carbon atoms are more preferable, fatty
acids having 5 or more are still more preferable, and fatty acids
having 5 to 9 carbon atoms are most preferable from the standpoint
of the lubricity. From the standpoint of the miscibility with the
refrigerant, fatty acids having 18 or less carbon atoms are
preferable, fatty acids having 12 or less carbon atoms are more
preferable and fatty acids having 9 or less carbon atoms are most
preferable.
[0070] Any of linear fatty acids and branched fatty acids can be
used. From the standpoint of the lubricity, linear fatty acids are
preferable. From the standpoint of the stability to hydrolysis,
branched fatty acids are preferable. Any of saturated fatty acids
and unsaturated fatty acids can be used.
[0071] Examples of the fatty acid include pentanoic acid, hexanoic
acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid,
undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic
acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid,
octadecanoic acid, nonadecanoic acid, icosanoic acid and oleic
acid, which may be linear, branched or so-called neo-acids having a
quaternary .alpha.-carbon atom. Specifically, valeric acid
(n-pentanoic acid), caproic acid (n-hexanoic acid), enanthoic acid
(n-heptanoic acid), caprylic acid (n-octanoic acid), peralgonic
acid (n-nonanoic acid), capric acid (n-decanoic acid), oleic acid
(cis-9-octadecenoic acid), isopentanoic acid (3-methylbutanoic
acid), 2-methylhexanoic acid, 2-ethylpentanoic acid,
2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid are
preferable.
[0072] The polyol ester may be a partial ester in which a portion
of hydroxyl groups are remaining without being esterified, a
complete ester in which the entire hydroxyl groups are esterified
or a mixture of a partial ester and a complete ester. It is
preferable that the polyol ester is a complete ester.
[0073] The complex ester is an ester obtained from a combination of
a monobasic acid and a dibasic acid and a combination of a
monohydric alcohol and a polyol. As the fatty acid, the dibasic
acid, the monohydric alcohol and the polyol, the compounds
described above as the examples of the corresponding compounds for
the esters of dibasic acids and polyol esters can be used.
[0074] The ester used in the present invention may be, naturally, a
single ester having a single structure or a mixture of two or more
types of esters having different structures.
[0075] Among the above various esters, polyol esters and complex
esters are preferable due to the excellent miscibility with the
refrigerant.
[0076] Among the polyester polyols, due to the more excellent
stability to hydrolysis, esters of hindered alcohols such as
neopentyl glycol, trimethylolethane, trimethylolpropane,
trimethylolbutane, di(trimethylol-propane),
tri(trimethylolpropane), pentaerythritol, di(pentaerythritol) and
tri(pentaerythritol) are more preferable and esters of neopentyl
glycol, trimethylolethane, trimethylolpropane, trimethylolbutane
and pentaerythritol are still more preferable. Esters of
pentaerythritol and trimethylolpropane are most preferable due to
the remarkably excellent miscibility with the refrigerant and
stability to hydrolysis.
[0077] Specific examples of the polyol ester include diesters of
neopentyl glycol with one or more types of fatty acids selected
from valeric acid, caproic acid, enanthoic acid, caprylic acid,
peralgonic acid, capric acid, oleic acid, isopentanoic acid,
2-methylhexanoic acid, 2-ethylpentanoic acid, 2-ethylhexanoic acid
and 3,5,5-trimethylhexanoic acid; triesters of trimethylolethane
with one or more fatty acids selected from valeric acid, caproic
acid, enanthoic acid, caprylic acid, peralgonic acid, capric acid,
oleic acid, isopentanoic acid, 2-methylhexanoic acid,
2-ethylpentanoic acid, 2-ethylhexanoic acid and
3,5,5-trimethylhexanoic acid; triesters of trimethylolpropane with
one or more fatty acids selected from valeric acid, caproic acid,
enanthoic acid, caprylic acid, peralgonic acid, capric acid, oleic
acid, isopentanoic acid, 2-methylhexanoic acid, 2-ethylpentanoic
acid, 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid;
triesters of trimethylolbutane with one or more fatty acids
selected from valeric acid, caproic acid, enanthoic acid, caprylic
acid, peralgonic acid, capric acid, oleic acid, isopentanoic acid,
2-methylhexanoic acid, 2-ethylpentanoic acid, 2-ethylhexanoic acid
and 3,5,5-trimethylhexanoic acid; and tetraesters of
pentaerythritol with one or more fatty acids selected from valeric
acid, caproic acid, enanthoic acid, caprylic acid, peralgonic acid,
capric acid, oleic acid, isopentanoic acid, 2-methylhexanoic acid,
2-ethylpentanoic acid, 2-ethylhexanoic acid and
3,5,5-trimethylhexanoic acid.
[0078] The ester of two or more types of fatty acids may be a
mixture of two or more types of esters each obtained from a single
fatty acid and a polyol or esters of a mixture of two or more types
of fatty acids and a polyol. The esters of a mixture of two or more
types of fatty acids and a polyol are preferable due to the
excellent properties at low temperatures and miscibility with the
refrigerant.
[0079] As esters other than those described above, esters disclosed
in Japanese Patent Application Laid-Open Nos. Heisei
4(1992)-183788, 5(1993)-17792, 8(1996)-226717, 8(1996)-231972,
8(1996)-240352, 8(1996)-240362, 8(1996)-253779 and 8(1996)-259975
are preferable.
[0080] The (a) polyester-based derivative has a kinematic viscosity
at 40.degree. C. in the range of 3 to 500 mm.sup.2/s, preferably in
the range of 5 to 300 mm.sup.2/s and more preferably in the range
of 8 to 150 mm.sup.2/s.
[0081] It is preferable that (b) the polycarbonate-based oxygenated
compound used as the base oil in lubricating oils (A-1) and (A-2)
as the first aspect of the present invention is a polycarbonate
having at least two carbonate bonds in one molecule, which is at
least one compound selected from:
[0082] (i) compounds represented by general formula (I): 13
[0083] wherein Z represents a residue group obtained by eliminating
hydroxyl group from an alcohol having 1 to 12 carbon atoms and a
functionality of n, R.sup.1 represents a linear or branched
alkylene group having 2 to 10 carbon atoms, R.sup.2 represents a
monovalent hydrocarbon group having 1 to 12 carbon atoms or a group
having ether bond represented by R.sup.4(O--R.sup.3).sub.p--,
R.sup.4 representing hydrogen atom or a monovalent hydrocarbon
group having 1 to 12 carbon atoms, R.sup.3 representing a linear or
branched alkylene group having 2 to 10 carbon atoms and p
representing an integer of 1 to 20, k represents an integer of 1 to
30, m represents an integer of 1 to 50 and n represents an integer
of 1 to 6; and
[0084] (ii) compounds represented by general formula (II): 14
[0085] wherein R.sup.5 represents a linear or branched alkylene
group having 2 to 10 carbon atoms, q represents an integer of 1 to
20 and Z, R.sup.1, R.sup.2, k, m and n are as described for the
general formula (I).
[0086] In the general formulae (I) and (II), Z represents a residue
group obtained by eliminating hydroxyl group from an alcohol having
1 to 12 carbon atoms and a functionality of 1 to 6. It is
preferable that Z represents a residue group obtained by
eliminating hydroxyl group from a monohydric alcohol having 1 to 12
carbon atoms.
[0087] Examples of the alcohol having 1 to 12 carbon atoms and a
functionality of 1 to 6 from which the residue group represented by
Z is derived include the following alcohols. Examples of the
monohydric alcohol include aliphatic monohydric alcohols such as
methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol,
various types of butyl alcohol, various types of pentyl alcohol,
various types of hexyl alcohol, various types of octyl alcohol,
various types of decyl alcohol and various types of dodecyl
alcohol; alicyclic monohydric alcohols such as cyclopentyl alcohol
and cyclohexyl alcohol; aromatic alcohols such as phenol, cresol,
xylenol, butylphenol and naphthol; and aromatic aliphatic alcohols
such as benzyl alcohol and phenetyl alcohol. Examples of the
dihydric alcohol include aliphatic alcohols such as ethylene
glycol, propylene glycol, butylene glycol, neopentylene glycol and
tetramethylene glycol; alicyclic alcohols such as cyclohexanediol
and cyclohexanedimethaonol; aromatic alcohols such as catechol,
resorcinol, hydroquinone and dihydroxydiphenyl. Examples of the
trihydric alcohol include aliphatic alcohols such as glycerol,
trimethylolpropane, trimethylolethane, trimethylolbutane and
1,3,5-pentanetriol; alicyclic alcohols such as cyclohexanetriol and
cyclohexane-trimethanol; and aromatic alcohols such as pyrogallol
and methyl-pyrogallol. Examples of the alcohol having a
functionality of 4 to 6 include pentaerythritol, digylcerol,
triglycerol, sorbitol and dipentaerythritol.
[0088] The compound represented by general formula (I) as the
example of the polycarbonate compound can be compounds represented
by general formula (I-a): 15
[0089] wherein R.sup.6 represents a residue group obtained by
eliminating hydroxyl group from a monohydric alcohol having 1 to 12
carbon atoms and R.sup.1, R.sup.2, k and m are as described for
general formula (I). The compound represented by general formula
(II) as the example of the polycarbonate compound can be
represented by general formula (II-a): 16
[0090] wherein R.sup.1, R.sup.2, R.sup.5, R.sup.6, k, m and q are
as described for general formulae (I), (II) and (I-a).
[0091] In the general formula (I-a) and the general formula (II-a),
examples of the residue group represented by R.sup.6 which is
obtained by eliminating hydroxyl group from a monohydric alcohol
having 1 to 12 carbon atoms include aliphatic hydrocarbon groups
such as methyl group, ethyl group, n-propyl group, isopropyl group,
various types of butyl group, various types of pentyl group,
various types of hexyl group, various types of octyl group, various
types of decyl group and various types of dodecyl group; alicyclic
hydrocarbon groups such as cyclopentyl group, cyclohexyl group,
methylcyclohexyl group, dimethylcyclohexyl group and
decahydronaphthyl group; aromatic hydrocarbon groups such as phenyl
group, various types of tolyl group, various types of xylyl group,
mesityl group and various types of naphthyl group; and aromatic
aliphatic hydrocarbon groups such as benzyl group, methylbenzyl
group, phenetyl group and various types of naphthylmethyl group.
Among these groups, linear and branched alkyl groups having 1 to 6
carbon atoms are preferable.
[0092] R.sup.1 represents a linear or branched alkylene groups
having 2 to 10 carbon atoms, preferably a linear or branched
alkylene group having 2 to 6 carbon atoms and more preferably
ethylene group or propylene group from the standpoint of the
properties and the easiness of production. R.sup.2 represents a
monovalent hydrocarbon group having 1 to 12 carbon atoms or a group
having ether bond represented by R.sup.4(O--R.sup.3).sub- .p--,
wherein R.sup.4 represents hydrogen atom or a monovalent
hydrocarbon group having 1 to 12 carbon atoms and preferably 1 to 6
carbon atoms, R.sup.3 represents a linear or branched alkylene
group having 2 to 10 carbon atoms and p represents an integer of 1
to 10. Examples of the monovalent hydrocarbon group having 1 to 12
carbon atoms described above include the groups described as the
examples of the group represented by R.sup.6. As the linear or
branched alkylene group having 2 to 10 carbon atoms which is
represented by R.sup.3, linear and branched alkylene groups having
2 to 6 carbon atoms are preferable and ethylene group and propylene
group are more preferable from the same standpoint as that
described above for R.sup.1.
[0093] As the group represented by R.sup.2, linear and branched
alkyl groups having 1 to 6 carbon atoms are preferable.
[0094] As the linear or branched alkylene group having 2 to 10
carbon atoms which is represented by R.sup.5 in general formula
(II-a), linear and branched alkylene groups having 2 to 6 carbon
atoms are preferable and ethylene group and propylene groups are
more preferable from the same standpoint as that described above
for R.sup.1.
[0095] The above polycarbonate compound can be produced in
accordance with various processes. In general, the aimed
polycarbonate compound can be produced by reacting a diester of
carbonic acid or a derivative forming an ester of carbonic acid
such as phosgene with an alkylene glycol or a polyoxyalkylene
glycol in accordance with a conventional process.
[0096] The lubricating oil as the first aspect of the present
invention may comprise a single type or a plurality of types of the
polycarbonate compound represented by general formula (I) and may
comprise a single type or a plurality of types of the polycarbonate
compound represented by general formula (II). The lubricating oil
may comprise one or more type of the polycarbonate compound
represented by general formula (I) and one or more types of the
polycarbonate compound represented by general formula (II). The
lubricating oil may further comprise oxygenated compounds such as
polyether compounds, examples of which include polyoxyalkylene
glycol derivatives and polyvinyl ether derivatives, and polyester
derivatives in combination with the polycarbonate compound
described above as long as the object of the present invention is
not adversely affected.
[0097] The (b) polycarbonate compound has a kinematic viscosity at
40.degree. C. in the range of 3 to 2,000 mm.sup.2/s, preferably in
the range of 5 to 1,500 mm.sup.2/s and more preferably in the range
of 10 to 1,000 mm.sup.2/s.
[0098] The lubricating oil for refrigerators as the first aspect of
the present invention comprises, as the base oil, (a) the foregoing
polyvinyl ether-based derivative in lubricating oil (A-1) or the
foregoing polyester-based derivative in lubricating oil (A-2) and
(b) the foregoing polycarbonate-based oxygenated compound in an
amount of 0.1% by weight or more and less than 60% by weight,
preferably 0.5 to 55% by weight and more preferably 1.0 to 50% by
weight, based on the amount of the entire base oil. The base oil
may further comprise polyoxyalkylene glycol, polyesters such as
polyol esters, esters of carbonic acid and hydrocarbons such as
poly-.alpha.-olefins in addition to the above components.
[0099] It is preferable that the lubricating oil for refrigerators
as the first aspect of the present invention has a kinematic
viscosity at 40.degree. C. in the range of 7 to 200 mm.sup.2/s and
more preferably in the range of 8 to 150 mm.sup.2/s and a viscosity
index of 40 or greater, more preferably in the range of 50 to 130
and still more preferably in the range of 60 to 120.
[0100] Lubricating oil for refrigerators (B-1) as the second aspect
of the present invention is used for refrigerators using a
refrigerant having one carbon atom and no chlorine atoms and
contains a base oil which comprises as a main component thereof a
polyoxyalkylene glycol derivative with a kinematic viscosity of 3
to 2,000 mm.sup.2/s at 40.degree. C. and having at least one
constituting unit represented by the general formula (III): 17
[0101] In the general formula (III), R.sup.7 to R.sup.10 each
independently represents hydrogen atom, a monovalent hydrocarbon
group having 1 to 10 carbon atoms or a group represented by the
general formula (IV): 18
[0102] The monovalent hydrocarbon group having 1 to 10 carbon atoms
which is represented by R.sup.7 to R.sup.10 is, in general, an
alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2
to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms,
an aryl group having 6 to 10 carbon atoms or an aralkyl group
having 7 to 10 carbon atoms. Specific examples of the monovalent
hydrocarbon group include alkyl groups such as methyl group, ethyl
group, n-propyl group, isopropyl group, various types of butyl
group, various types of pentyl group, various types of hexyl group,
various types of heptyl group, various types of octyl group,
various types of nonyl group and various types of decyl group;
alkenyl groups such as vinyl group, allyl group, propenyl group,
isopropenyl group, various types of butenyl group, various types of
pentenyl group, various types of hexenyl group, various types of
heptenyl group, various types of octenyl group, various types of
nonenyl group and various types of decenyl group; cycloalkyl groups
such as cyclopentyl group and cyclohexyl group; aryl groups such as
phenyl group, various types of tolyl group, various types of xylyl
group and naphthyl group; and aralkyl groups such as benzyl group,
1-phenylethyl group and 2-phenylethyl group. Among these groups,
monovalent hydrocarbon groups having 6 or less carbon atoms are
preferable and alkyl groups having 3 or less carbon atoms are more
preferable.
[0103] In the general formula (IV), R.sup.11 and R.sup.12 each
independently represent hydrogen atom, a monovalent hydrocarbon
group having 1 to 20 carbon atoms or an alkoxyalkyl group having 2
to 20 carbon atoms. As the monovalent hydrocarbon group having 1 to
20 carbon atoms, monovalent hydrocarbon groups having 1 to 10
carbon atoms are preferable. Examples of the monovalent hydrocarbon
groups having 1 to 10 carbon atoms include the groups described as
the examples of the monovalent hydrocarbon groups having 1 to 10
carbon atoms represented by R.sup.7 to R.sup.10. As the monovalent
hydrocarbon group, monovalent hydrocarbon groups having 6 or less
carbon atoms are preferable and alkyl groups having 3 or less
carbon atoms are more preferable. Examples of the alkoxyalkyl group
having 2 to 20 carbon atoms include methoxymethyl group,
ethoxymethyl group, n-propoxymethyl group, isopropoxymethyl group,
various types of butoxymethyl groups, various types of
pentoxymethyl groups, various types of hexoxymethyl groups, various
types of heptoxymethyl groups, various types of octoxymethyl
groups, various types of nonyloxymethyl groups, 1-methoxyethyl
group, 2-methoxyethyl group, 1-ethoxyethyl group, 2-ethoxyethyl
group, various types of propoxyethyl groups, various types of
butoxyethyl groups, various types of pentoxyethyl groups, various
types of hexoxyethyl groups, various types of heptoxyethyl groups,
various types of octoxyethyl groups, various types of methoxypropyl
groups, various types of ethoxypropyl groups, various types of
propoxypropyl groups, various types of butoxypropyl groups, various
types of pentoxypropyl groups, various types of hexoxypropyl
groups, various types of heptoxypropyl groups, various types of
methoxybutyl groups, various types of ethoxybutyl groups, various
types of pentoxybutyl groups, various types of hexoxybutyl groups,
various types of methoxypentyl groups, various types of
ethoxypentyl groups, various types of propoxypentyl groups, various
types of butoxypentyl groups, various types pentoxypentyl groups,
various types of methoxyhexyl groups, various types of ethoxyhexyl
groups, various types of propoxyhexyl groups, various types of
butoxyhexyl groups, various types of methoxyheptyl groups, various
types of ethoxyheptyl groups, various types of propoxyheptyl
groups, various types of methoxyoctyl groups, various types of
ethoxyoctyl groups and various types of methoxynonyl groups. Among
these groups, alkoxyalkyl groups having 6 or less carbon atoms are
preferable.
[0104] Next, R.sup.13 represents an alkylene group having 2 to 5
carbon atoms, a substituted alkylene group having an alkyl group as
a substituent and 2 to 5 carbon atoms in the entire group or a
substituted alkylene group having an alkoxyalkyl group as a
substituent and 4 to 10 carbon atoms in the entire group.
[0105] Examples of the alkylene group include ethylene group,
1-methylethylene group, ethylethylene group, 1,1-dimethylethylene
group, 1,2-dimethylethylene group, n-propylethylene group,
isopropylethylene group, 1-ethyl-2-methylethylene group,
1-ethyl-1-methylethylene group, trimethylene group, tetramethylene
group, pentamethylene group, (methoxymethyl)ethylene group,
(ethoxymethyl)ethylene group, (methoxyethyl)ethylene group,
1-methoxymethyl-2-methylethylene group,
1,2-(bismethoxymethyl)ethylene group,
1,1-(bismethoxymethyl)ethylene group, (ethoxyethyl)ethylene group,
1,2-(bisethoxyethyl)ethylene group and 2-methoxy-1,3-propylene
group. Ethylene group and substituted ethylene groups having 6 or
less carbon atoms are preferable. R.sup.14 represents a monovalent
hydrocarbon group having 1 to 10 carbon atoms. Examples of the
group represented by R.sup.14 include the groups described as the
examples of the monovalent hydrocarbon groups having 1 to 10 carbon
atoms which are represented by R.sup.7 to R.sup.9. As the group
represented by R.sup.14, hydrocarbon groups having 6 or less carbon
atoms are preferable and alkyl groups having 3 or less carbon atoms
are more preferable. n represents an integer of 0 to 20.
[0106] The atoms or groups represented by R.sup.7 to R.sup.9 may be
the same with or different from each other. At least one of R.sup.7
to R.sup.9 represents a group represented by the general formula
(IV). In particular, it is preferable that one of R.sup.7 and
R.sup.9 represents a group represented by the general formula (IV)
and the other of R.sup.7 and R.sup.9, R.sup.8 and R.sup.10 each
represent hydrogen atom or a monovalent hydrocarbon group having 1
to 10 carbon atoms.
[0107] In lubricating oil for refrigerators (B-1) as the second
aspect of the present invention, the polyoxyalkylene glycol
derivative used as the main component of the base oil comprises at
least one constituting unit represented by the general formula
(III). The polyalkylene glycol derivatives can be divided into the
following three types of compounds: homopolymers comprising a
single type of the constituting unit represented by the general
formula (III); copolymers comprising two or more types of the
constituting units represented by the general formula (III); and
copolymers comprising the constituting units represented by the
general formula (III) and other constituting units such as
constituting units represented by general formula (XVIII): 19
[0108] wherein R.sup.63 to R.sup.66 each represent hydrogen atom or
an alkyl group having 1 to 3 carbon atoms.
[0109] Preferable examples of the homopolymer described above
include homopolymers comprising 1 to 200 constituting units A
represented by the general formula (III) and having hydroxyl group,
an acyloxyl group having 1 to 10 carbon atoms, an alkoxyl group
having 1 to 10 carbon atoms or an aryloxyl group at each chain
end.
[0110] Preferable examples of the copolymer include copolymers
which comprise two types of constituting units A and B each
represented by the general formula (III) each in a number of 1 to
200 and copolymers which comprise 1 to 200 constituting units A
represented by general formula (III) and 1 to 200 constituting
units C represented by general formula (XVIII), each copolymer
having hydroxyl group, an acyloxyl group having 1 to 10 carbon
atoms, an alkoxyl group having 1 to 10 carbon atoms or an aryloxyl
groups at each chain end.
[0111] The above copolymers include alternating copolymers, random
copolymers and block copolymers comprising constituting units A and
constituting units B (or constituting units C) and graft copolymers
comprising the main chain comprising constituting units A to which
constituting units B are grafted.
[0112] The above polyoxyalkylene glycol derivative used as the main
component in lubricating oil for refrigerators (B-1) as the second
aspect of the present invention can be prepared, for example, in
accordance with the following process.
[0113] (X) Process
[0114] The polyoxyalkylene glycol derivative can be obtained by
homopolymerization of an oxirane compound represented by general
formula (XIX): 20
[0115] wherein R.sup.7 to R.sup.10 are the same as those described
above, or copolymerization of two or more types of the above
oxirane compound.
[0116] The polyoxyalkylene glycol derivative can be produced also
by copolymerization of the oxirane compound represented by the
above general formula (XIX) and an alkylene oxide having 2 to 8
carbon atoms which is represented by general formula (XX): 21
[0117] wherein R.sup.63 to R.sup.66 are the same as those described
above; such as ethylene oxide and propylene oxide.
[0118] The oxirane compound represented by general formula (XIX)
include various compounds since R.sup.7 to R.sup.10 represent
various atom and groups. Examples of the oxirane compound include
glycidyl methyl ether, ethyl glycidyl ether, propyl glycidyl ether,
butyl glycidyl ether, 2-ethylhexyl glycidyl ether, 2-methyloctyl
glycidyl ether, vinyl glycidyl ether, allyl glycidyl ether, phenyl
glycidyl ether, sec-butylphenyl glycidyl ether,
4,7-dioxa-1,2-epoxyoctane, 1,2-epoxy-4,7,10-trioxatetrade- cane,
1,2-epoxy-4,7,10,13-tetraoxatetradecane,
4,7-dioxa-1,2-epoxy-5-methy- loctane,
4,7-dioxa-1,2-epoxy-6-methyloctane, 6,9-dimethyl-1,2-epoxy-4,7,10-
-trioxa-undecane,
1,2-epxoy-4,7,10,13-tetraoxa-6,9,12-trimethyltetradecane- ,
1,2-epoxy-5-methyl-4,7,10-trioxaundecane,
1,2-epoxy-8-methyl-4,7,10-trio- xa-undecane,
2,7-dioxa-4,5-epoxyoctane, 4,5-epoxy-9-methyl-2,7,10-trioxa-u-
ndecane, 4,5-epoxy-2,7,10,13-tetraoxatetradecane,
7,8-epoxy-2,5,10,13-tetr- aoxatetradecane,
3,12-dimethyl-7,8-epoxy-2,5,10,13-tetraoxatetra-decane,
1,2-epoxy-3-methoxy-5-oxahexane,
4,8-dioxa-1,2-epoxy-6-methoxy-nonane,
4,7-dioxa-1,2-epoxy-5-(2-oxapropyl)octane,
3,5-bis(2-oxapropyl)-4,7-dioxa- -1,2-epoxyoctane,
3,6-bis(2-oxapropyl)-4,7-dioxa-1,2-epoxyoctane and
6,9-bis(2-oxapropyl)-1,2-epoxy-4,7,10-trioxaundecane.
[0119] As the initiator of the polymerization, conventional
compounds such as water, alkali hydroxides, alcohols having a
functionality of 1 to 6, alkoxides, thiols, 2,2'-thiodiethanol,
sodium alkoxides of 2,2'-thiodiethanol, phenol, phenoxides and
amines can be used.
[0120] (Y) Process
[0121] The aimed polyoxyalkylene glycol derivative can be produced
by polymerization of at least one homopolymer of the oxirane
compound represented by general formula (XIV) which is obtained in
accordance with (X) process with another type of oxirane compound
represented by general formula (XIV) or an alkylene oxide having 2
to 8 carbon atoms which is represented by general formula (XV). In
this process, the two types of the reaction can be conducted
continuously in a single reactor.
[0122] (Z) Process
[0123] The aimed polyoxyalkylene glycol derivative can be produced
by obtaining a polyoxyalkylene glycol by polymerization of an
alkylene oxide having 2 to 8 carbon atoms which is represented by
general formula (XX), followed by polymerizing the obtained
polyoxyalkylene glycol with an oxirane compound represented by
general formula (XIX) or with an oxirane compound represented by
general formula (XIX) and an alkylene oxide represented by general
formula (XX). In this process, the two types of the reaction can be
conducted continuously in a single reactor.
[0124] Further improvements in the properties as the oil for
refrigerators such as improvement in solubility, decrease in
hygroscopicity, improvement in the viscosity index and improvement
in the lubricity can be achieved by converting entire hydroxyl
groups or a portion of hydroxyl groups at the chain ends of the
polyoxyalkylene glycol derivative obtained in accordance with
processes (X) to (Z) into esters or ethers. It is preferable that
the hydrocarbon group in the residue group of the ester or the
ether has 1 to 10 carbon atoms.
[0125] In lubricating oil for refrigerators (B-1) as the second
aspect of the present invention, the above polyoxyalkylene glycol
derivative used as the main component of the base oil has a
kinematic viscosity at 40.degree. C. in the range of 3 to 2,000
mm.sup.2/s, preferably in the range of 3 to 500 mm.sup.2/s, more
preferably in the range of 3 to 300 mm.sup.2/s and most preferably
in the range of 5 to 200 mm.sup.2/s.
[0126] Lubricating oils for refrigerators (B-2) and (B-3) as the
second aspect of the present invention will be described in the
following.
[0127] Lubricating oil for refrigerators (B-2) as the second aspect
of the present invention comprises, as the base oil, (a) a
polyvinyl ether-based derivative with a kinematic viscosity of 3 to
500 mm.sup.2/s at 40.degree. C. and (b) a polyoxyalkylene glycol
derivative with a kinematic viscosity of 3 to 2,000 mm.sup.2/s at
40.degree. C. in an amount of 0.1% by weight or more and less than
60% by weight based on an amount of the entire base oil, and having
at least one constituting unit represented by the general formula
(III).
[0128] As the polyvinyl ether-based derivative used as component
(a) of the base oil in lubricating oil for refrigerators (B-2) as
the second aspect of the present invention, the same polyvinyl
ether-based derivatives as those described for component (a) of the
base oil in lubricating oil for refrigerators (A-1) as the first
aspect of the present invention is used.
[0129] Lubricating oil for refrigerators (B-3) as the second aspect
of the present invention comprises, as the base oil, (a) a
polyester-based derivative with a kinematic viscosity of 3 to 500
mm.sup.2/s at 40.degree. C. and (b) a polyoxyalkylene glycol
derivative with a kinematic viscosity of 3 to 2,000 mm.sup.2/s at
40.degree. C. in an amount of 0.1% by weight or more and less than
60% by weight based on an amount of the entire base oil, having at
least one constituting unit represented by the general formula
(III).
[0130] As the polyester-based derivative used as component (a) of
the base oil in lubricating oil for refrigerators (B-3) as the
second aspect of the present invention, the same polyvinyl
ether-based derivatives as those described for component (a) of the
base oil in lubricating oil for refrigerators (A-1) as the first
aspect of the present invention.
[0131] The above lubricating oils for refrigerators are miscible
with a refrigerant having one carbon atom and no chlorine atoms
such as R32 (which means that the liquid phase is homogeneous) at a
temperature of 5.degree. C. or lower for (B-2) and at a temperature
of 10.degree. C. or lower for (B-3) in at least any one of the case
where the lubricating oil is contained within the range of 3 to 50%
by weight based on the amount of the entire mixture comprising the
lubricating oil and the refrigerant. The content of the lubricating
oil exhibiting the miscibility with the refrigerant at a
temperature of 5.degree. C. or lower for (B-2) or at a temperature
of 10.degree. C. or lower for (B-3) is within the range of 3 to 50%
by weight as described above. It is preferable that the range is 10
to 15% by weight. It is more preferable that the lubricating oil is
miscible with the refrigerant in the entire range of the content of
3 to 50% by weight. When the temperature exhibiting the
miscibility, i.e., the temperature of phase separation at the low
temperature side, exceeds 5.degree. C. for (B-2) or 10.degree. C.
for (B-3), there is the anxiety that phase separation takes place
during the operation of refrigeration. When the phase separation
takes place during the operation of refrigeration, the lifetime and
the efficiency of the apparatus are adversely affected to a great
extent. For example, when the phase separation of the refrigerant
and the lubricating oil takes place in the compressor, lubrication
of moving parts deteriorates and seizure occurs to cause a great
decrease in the lifetime of the apparatus. When the phase
separation takes places in the evaporator, the efficiency of heat
exchange decreases due to the presence of lubricating oil of high
viscosity.
[0132] Based on the above reasons, it is necessary that the maximum
temperature in the area of phase separation at the low temperature
side is 5.degree. C. or lower for (B-2) and 10.degree. C. or lower
for (B-3). It is preferable that the maximum temperature is
3.degree. C. or lower and 8.degree. C. or lower, respectively, more
preferably 0.degree. C. or lower and 5.degree. C. or lower,
respectively, and most preferably -2.degree. C. or lower or
2.degree. C. or lower, respectively.
[0133] As component (b) of the base oil in (B-2) and (B-3), the
same polyoxyalkylene glycol derivatives as those described for the
main component of the base oil in lubricating oil for refrigerators
(B-1) are used. The polyoxyalkylene glycol derivative has a
kinematic viscosity at 40.degree. C. in the range of 3 to 2,000
mm.sup.2/s, preferably in the range of 3 to 500 mm.sup.2/s, more
preferably in the range of 3 to 300 mm.sup.2/s and most preferably
in the range of 5 to 200 mm.sup.2/s.
[0134] It is preferable that the base oil in the lubricating oil
for refrigerators as the second aspect of the present invention has
a kinematic viscosity in the range of 7 to 200 mm.sup.2/s and more
preferably in the range of 8 to 150 mm.sup.2/s and a viscosity
index of 40 or greater, more preferably in the range of 50 to 130
and most preferably in the range of 60 to 120.
[0135] It is preferable that the lubricating oils for refrigerators
as the first aspect and the second aspect of the present invention
further comprise acid catchers, extreme pressure agents, oiliness
agents and antioxidants.
[0136] Examples of the acid catcher include compounds having
glycidyl ether group, epoxidized monoesters of fatty acids,
epoxidized oils and fats and compounds having epoxycycloalkyl
group. Examples of the extreme pressure agent include organic
sulfur compound-based agents such as monosulfides, polysulfides,
sulfoxides, sulfones, thiosulfinates, vulcanized oils and fats,
thiocarbonates, thiophenes, thiazoles and esters of methanesulfonic
acid; phosphoric acid ester-based agents such as monoesters of
phosphoric acid, diesters of phosphoric acid and triesters of
phosphoric acid such as tricresyl phosphate; phosphorous acid
ester-based agents such as monoesters of phosphorous acid, diesters
of phosphorous acid and triesters of phosphorous acid;
thiophosphoric acid ester-based agents such as triesters of
thiophosphoric acid; higher fatty acid-based agents; hydroxyaryl
fatty acid-based agents; ester-based agents such as esters of
polyhydric alcohols and esters of acrylic acid; organic chlorine
compound-based agents such as chlorinated hydrocarbons and
chlorinated derivatives of carboxylic acids; organic fluorine
compound-based agents such as fluorinated aliphatic carboxylic
acids, fluorinated ethylene resins, fluorinated alkylpolysiloxanes
and fluorinated graphite; alcohol-based agents such as higher
alcohols; naphthenic acid salt-based agents such as lead
naphthenate; fatty acid salt-based agents such as lead salts of
fatty acids; thiophosphoric acid salt-based agents such as zinc
dialkyl-dithiophosphates; thiocarbamic aid salt-based agents; and
metal compound-based agents such as organomolybdenum compounds,
organotin compounds, organogermanium compounds and esters of boric
acid. Examples of the antioxidant include phenol-based antioxidants
such as 2,6-di-tert-butyl-p-cresol and amine-based antioxidants
such as .alpha.-naphthylamine.
[0137] Preferable examples of the oiliness agent include (x)
compounds obtained by etherification of aliphatic polyhydric
alcohols having a functionality of 3 to 6 and (y) compounds
obtained by etherification of condensates of two or three molecules
of aliphatic polyhydric alcohols having a functionality of 3 to
6.
[0138] The above component (x) and component (y) will be described
in the following. As the compound obtained by etherification of an
aliphatic polyhydric alcohol having a functionality of 3 to 6 of
component (x), compounds represented by the following general
formulae (XVIII-a) to (XVIII-f) are preferable: 22
[0139] wherein R.sup.53 to R.sup.58 each represent hydrogen atom or
an alkyl group, an aryl group or an aralkyl group which has 1 to 18
carbon atoms and may be linear or branched. The atoms or the groups
represented by R.sup.53 to R.sup.58 may be the same with or
different from each other. R.sup.53 to R.sup.58 may each represent
a glycol ether residue group represented by
--(R.sup.aO).sub.x--R.sup.b, wherein R.sup.a represents an alkylene
group having 2 to 6 carbon atoms, R.sup.b represents an alkyl
group, an aryl group or an aralkyl group which has 1 to 20 carbon
atoms and x represents an integer of 1 to 10.
[0140] Examples of the aliphatic polyhydric alcohol having a
functionality of 3 to 6 include glycerol, trimethylolpropane,
erythritol, pentaerythritol, arabitol, sorbitol and mannitol.
Examples of the group represented by R.sup.53 to R.sup.58 in the
general formulae (XVIII-a) to (XVIII-f) include methyl group, ethyl
group, n-propyl group, isopropyl group, various types of butyl
group, various types of pentyl group, various types of hexyl group,
various types of heptyl group, various types of octyl group,
various types of nonyl group, various types of decyl group, various
types of undecyl group, various types of dodecyl group, various
types of tridecyl group, various types of tetradecyl group, various
types of pentadecyl group, various types of hexadecy group, various
types of heptadecyl group, various types of octadecyl group, phenyl
group and benzyl group. R.sup.53 to R.sup.58 may also represent
hydrogen atom and, in this case, the above compound is a partial
ether.
[0141] As for the compound obtained by etherification of a
condensate of two or three molecules of aliphatic polyhydric
alcohols having a functionality of 3 to 6 of component (y), for
example, compounds obtained by etherification of alcohols
corresponding to general formula (XVIII-a) are represented by
general formulae (XVIII-g) and (XVIII-h) and compounds obtained by
etherification of alcohols corresponding to general formula
(XVIII-d) are represented by general formulae (XVIII-i) and
(XVIII-j): 23
[0142] wherein R.sup.53 to R.sup.60 are the same as those described
for R.sup.53 to R.sup.58 and the atoms or groups represented by
R.sup.53 to R.sup.60 may be the same with or different from each
other.
[0143] Examples of the condensate of two or three molecules of an
aliphatic polyhydric alcohols having a functionality of 3 to 6
include diglycerol, ditrimethylolpropane, dipentaerythritol,
disorbitol, triglycerol, tritrimethylolpropane, tripentaerythritol
and trisorbitol.
[0144] Examples of components (x) and (y) represented by the
general formulae (XVIII-a) to (XVIII-j) include trihexyl ether of
glycerol, dimethyl octyl triether of glycerol,
di(methyloxyisopropylene) dodecyl triether of glycerol, diphenyl
octyl triether of glycerol, di(phenyloxy-isopropylene) dodecyl
triether of glycerol, trihexyl ether of trimethylol-propane,
dimethyl octyl triether of trimethylolpropane,
di(methyloxy-isopropylene) dodecyl triether of trimethylolpropane,
tetrahexyl ether of pentaerythritol, trimethyl octyl tetraether of
pentaerythritol, tri(methyloxyisopropylene) dodecyl tetraether of
pentaerythritol, hexapropyl ether of sorbitol, tetramethyl octyl
pentaether of sorbitol, hexa(methyloxyisopropylene) ether of
sorbitol, tetrabutyl ether of diglycerol, dimethyl dioctyl
tetraether of diglycerol, tri(methyloxy-isopropylene) dodecyl
tetraether of diglycerol, pentaethyl ether of triglycerol,
trimethyl dioctyl pentaether of triglycerol,
tetra(methyloxy-isopropylene) decyl pentaether of triglycerol,
tetrabutyl ether of ditrimethylolpropane, dimethyl dioctyl
tetraether of ditrimethylolpropane, tri(methyloxyisopropylene)
dodecyl tetraether of ditrimethylolpropane, pentaethyl ether of
tritrimethylolpropane, trimethyl dioctyl pentaether of
tritrimethylolpropane, tetra(methyloxyisopropylene) decyl
pentaether of tritrimethylolpropane, hexapropyl ether of
dipentaerythritol, pentamethyl octyl hexaether of
dipentaerythritol, hexa(methyloxyisopropylene) ether of
dipentaerythritol, octapropyl ether of tripentaerythritol,
pentamethyl octyl hexaether of tripentaerythritol,
hexa(methyloxyisopropylene) ether of tripentaerythritol, octamethyl
dioctyl decaether of disorbitol and deca(methyloxyisopropylene)
ether of disorbitol. Among these compounds, diphenyl octyl triether
of glycerol, di(methyloxyisopropylene) dodecyl triether of
trimethylolpropane, tetrahexyl ether of pentaerythritol, hexapropyl
ether of sorbitol, dimethyl dioctyl tetraether of diglycerol,
tetra(methyloxyisopropylene) decyl pentaether of triglycerol,
hexapropyl ether of pentaerythritol and pentamethyl octyl hexaether
of tripentaerythritol are preferable.
[0145] The kinematic viscosity of components (x) and (y) at
40.degree. C. is in the range of 5 to 200 mm.sup.2/s and preferably
in the range of 10 to 100 mm.sup.2/s. When the kinematic viscosity
is smaller than 5 mm.sup.2/s, the effect of improving the lubricity
and preventing clogging of capillaries is small. When the kinematic
viscosity exceeds 200 mm.sup.2/s, it is unfavorable because the
miscibility with the refrigerant decreases (i.e., the temperature
of phase separation is elevated). In the lubricating oil
composition for refrigerators of the present invention, the above
components (x) and (y) may be used singly or in combination of two
or more. It is preferable that the amount of components (x) and (y)
are in the range of 0.1 to 30% by weight based on the amount of the
entire composition. When the amount is less than 1% by weight, the
object of the present invention is not sufficiently achieved. When
the amount exceeds 30% by weight, the effect is not exhibited to
the degree expected from the amount and solubility into the base
oil occasionally decreases. It is more preferable that the amount
is in the range of 0.1 to 15% by weight and most preferably in the
range of 0.5 to 10% by weight.
[0146] The lubricating oil for refrigerators of the present
invention may further comprise other additives conventionally used
for lubricating oils such as metal inactivators, defoaming agents,
detergent dispersants, viscosity index improvers, antiwear
additives, rust preventives, corrosion inhibitors and pour pint
improvers, where desired.
[0147] Examples of the metal inactivator include benzotriazole
derivatives. Examples of the defoaming agent include silicone oils
such a dimethylpolysiloxane and polymethacrylates. Examples of the
detergent dispersant include sulfonates, phenates and succinimide.
Examples of the viscosity index improver include polymethacrylates,
polyisobutylene, ethylene-propylene copolymers and hydrogenated
styrene-diene copolymers.
[0148] The hydraulic fluid composition for refrigerators of the
present invention comprises (A) a refrigerant having one carbon
atom and no chlorine atoms and (B) a lubricating oil for
refrigerators of the present invention described above.
[0149] Examples of the refrigerant having one carbon atom and no
chlorine atoms include difluoromethane (R32). The amounts of
component (A) and component (B) are selected in a manner such that
the ratio of the amount by weight of component (A) to the amount by
weight of component (B) is, in general, in the range of 5:95 to
99:1 and preferably in the range of 10:90 to 99:1. When the amount
of the refrigerant is smaller than the above range, the
refrigerating ability decreases. When the amount of the refrigerant
exceeds the above range, the lubricity decreases. Therefore, such
amounts are not preferable.
[0150] The lubricating oil for refrigerators of the present
invention can be applied to various types of refrigerators. In
particular, the lubricating oil for refrigerators of the present
invention is advantageously applied to compression-type
refrigerating cycles of compression-type refrigerators. For
example, the lubricating oil can be advantageously applied to
refrigerators disclosed in Japanese Patent Application Laid-Open
Nos. Heisei 4(1992)-183788, Heisei 8(1996)-259975, Heisei
8(1996)-240362, Heisei 8(1996)-253779, Heisei 8(1996)-240352,
Heisei 5(1993)-17792, Heisei 8(1996)-226717 and Heisei
8(1996)-231972. For example, the advantageous effects can be
exhibited when the lubricating oil of the present invention is
applied to compression-type refrigerating cycles having an oil
separator and/or a hot gas line such as the refrigerating cycles
shown in FIGS. 1 to 3.
[0151] FIG. 1 shows a flow diagram that exhibits an example of the
compression type refrigerating cycle of the
"compressor-condenser-expansi- on valve-evaporator" system having
an oil separator and a hot gas line. FIG. 2 shows a flow diagram
that exhibits an example of the compression type refrigerating
cycle of the "compressor-condenser-expansion valve-evaporator"
system having an oil separator. FIG. 3 shows a flow diagram that
exhibits an example of the compression type refrigerating cycle of
the "compressor-condenser-expansion valve-evaporator" system having
a hot gas line. In the Figures, numerical symbol 1 means a
compressor, numerical symbol 2 means a condenser, numerical symbol
3 means an expansion valve, numerical symbol 4 means an evaporator,
numerical symbol 5 means an oil separator, numerical symbol 6 means
a hot gas line and numerical symbol 7 means a valve for a hot gas
line. In general, a compression-type refrigerating cycle comprises
a compressor, a condenser, an expansion valve and an evaporator as
shown in FIG. 4. As the lubricating oil for a refrigerator, a
lubricating oil exhibiting excellent miscibility with the
refrigerant used for the refrigerator is used. However, when a
refrigerant comprising component (A) as the main component is used
for the above refrigerating cycle and the refrigerator is
lubricated with a conventional refrigerating oil, antiwear is poor
and a stable operation for a long period time cannot be achieved
due to insufficient stability. In particular, the drawbacks are
marked when a capillary tube is used as the expansion valve in the
refrigerating cycle of a refrigerator such as an electric
refrigerator and a small air conditioner. The lubricating oil of
the present invention can be effectively used as the lubricating
oil composition even when a compression-type refrigerating cycle
having an oil separator and/or a hot gas line is operated using a
refrigerant comprising component (A) as the main component.
[0152] The hydraulic fluid composition for refrigerators of the
present invention exhibits remarkably excellent miscibility between
component (A) and component (B). The maximum temperature in the
area of phase separation at the low temperature side is 5.degree.
C. or lower, more preferably 3.degree. C. or lower, still more
preferably 0.degree. C. or lower and most preferably -2.degree. C.
or lower.
[0153] The hydraulic fluid composition of the present invention
does not cause phase separation at the low temperature side during
operation of the refrigerator since the maximum temperature in the
area of phase separation at the low temperature side is low and
enables stable operation of the refrigerator.
EXAMPLES
[0154] The present invention will be described more specifically
with reference to examples in the following. However, the present
invention is not limited to the examples.
[0155] The kinematic viscosity and the viscosity index of a base
oil and the properties of a lubricating oil were evaluated in
accordance with the following methods.
[0156] <Base Oil>
[0157] (1) Kinematic Viscosity
[0158] The kinematic viscosity was measured in accordance with the
method of Japanese Industrial Standard K2283-1983 using a glass
capillary viscometer at 40.degree. C. and at 100.degree. C.
[0159] <Lubricating Oil>
[0160] (2) Kinematic Viscosity
[0161] The kinematic viscosity was measured in accordance with the
method of Japanese Industrial Standard K2283-1983 using a glass
capillary viscometer at 40.degree. C.
[0162] (3) Test of Miscibility
[0163] A prescribed amount of a sample was placed into a
pressure-resistance glass ampoule. The glass ampoule was connected
to a vacuum piping and a piping of the refrigerant of
difluoromethane (R32). After the ampoule was evacuated to remove
gasses at the room temperature, the ampoule was cooled and a
prescribed amount of the refrigerant of difluoromethane (R32) was
taken into the ampoule. Then, the ampoule was sealed. To examine
the miscibility at the low temperature side, the ampoule was cooled
slowly from the room temperature to -50.degree. C. in a
thermostatted chamber and the temperature at which the phase
separation started was measured. The lower the temperature of phase
separation, the more preferable the property at the low temperature
side.
[0164] (4) Lubricity
[0165] The load of seizure was obtained in accordance with the
method of ASTM D-3233 using a Falex friction tester of the closed
type. The condition of the test was as follows: the amount of oil:
300 ml; the refrigerant: R32; the pressure: 0.8 MPaG; and the
temperature: 50.degree. C.
[0166] (5) Stability (Autoclave Test)
[0167] Into an autoclave having an inner volume of 200 ml, 40 g of
a sample oil, 40 g of the refrigerant of R32 gas and a metal
catalyst containing copper, aluminum and iron were placed and water
was added to the system in an amount such that the content of water
in the system was adjusted to 2,000 ppm. After the autoclave was
closed and kept at 175.degree. C. for 21 days, the sample of the
lubricating oil was analyzed.
Preparation Example 1
[0168] In a four-necked glass flask having a capacity of 1 liter
and equipped with a stirrer, a thermometer, an inlet for nitrogen
and a distillation head for concentrating the distillate, 360.6 g
(4.0 moles) of dimethyl carbonate, 268.8 g (2.0 moles) of
dipropylene glycol and 3.9 g (0.02 moles) of a 28% by weight
methanol solution of sodium methoxide as the catalyst were placed
and the resultant mixture was heated at 120.degree. C. for 5 hours
in an oil bath while nitrogen gas was passed at a rate of 50
ml/minute. When distillation of methanol did not take place any
more, the heating was stopped and 500 ml of toluene was added to
the mixture. The obtained toluene solution of the product was
washed with 300 ml of pure water and the washing water was not
alkaline after the washing was repeated five times. Toluene was
completely removed by distillation using a rotary evaporator under
evacuation by an aspirator at 120.degree. C. for 30 minutes,
followed by evacuation by a vacuum pump at 133 Pa for 30 minutes
and 295 g of a polycarbonate of dipropylene glycol (methyl group at
the chain ends) of the aimed compound expressed as: 24
[0169] was obtained. This compound will be referred to as PC-1.
Preparation Example 2
[0170] In accordance with the same procedures as those conducted in
Preparation Example 1 except that 236.3 g (2.0 moles) of
3-methyl-1,5-pentanediol was used in stead of 268.8 g of
dipropylene glycol, 255 g of a polycarbonate of
3-methyl-1,5-pentanediol (methyl group at the chain ends) of the
aimed compound expressed as: 25
[0171] was obtained. This compound will be referred to as PC-2.
[0172] In Table 1, the kinematic viscosity and the viscosity index
of PC-1 and PC-2 obtained above are shown together with the
corresponding data of PVE-1, PVE-2 and PVE-3.
1TABLE 1 Kinematic Kinematic viscosity at 40.degree. C. viscosity
at 100.degree. C. Sample (mm.sup.2/s) (mm.sup.2/s) Viscosity index
PVE-1 70.33 8.20 85 PVE-2 33.74 5.21 76 PVE-3 70.71 8.51 88 PC-1
141.7 10.30 20 PC-2 88.47 11.15 113 Notes: PVE-1 Copolymer [ethyl
vinyl ether/isobutyl vinyl ether (ratio by mole: 9/1)] PVE-2
Copolymer [ethyl vinyl ether/isobutyl vinyl ether (ratio by mole:
8/2)] PVE-3 Polyethyl vinyl ether PC-1 Polycarbonate obtained in
Preparation Example 1 PC-2 Polycarbonate obtained in Preparation
Example 2
Preparation Example 3
[0173] With reference to the process described in Japanese Examined
Patent Application Publication Heisei 7(1995)-119430,
polyoxyalkylene glycol derivatives MIPPO-1 and MIPPO-2 were
prepared.
[0174] MIPPO-1: poly[methoxyisopropoxypropylene oxide] (methyl
groups at both chain ends)
[0175] MIPPO-2: copoly[methoxyisopropoxypropylene oxide/ethylene
oxide] (methyl groups at both chain ends)
[0176] In Table 2, the kinematic viscosity and the viscosity index
of MIPPO-1 and MIPPO-2 obtained above are shown together with the
corresponding data of POE-1, POE-2 and POE-3.
2TABLE 2 Kinematic Kinematic viscosity at 40.degree. C. viscosity
at 100.degree. C. Sample (mm.sup.2/s) (mm.sup.2/s) Viscosity index
POE-1 67.90 8.27 98 POE-2 50.20 6.98 94 POE-3 31.40 5.23 95 MIPPO-1
130.50 20.05 177 MIPPO-2 68.70 12.62 186 Notes: POE-1 Complete
ester from pentaerythritol and 2-ethylhexanoic
acid/3,5,5-trimethylhexanoic acid (ratio by mole: 0.5/0.5) POE-2
Complete ester from trimethylolpropane and 3,5,5-trimethylhexanoic
acid POE-3 Complete ester from pentaerythritol and 2-ethylhexanoic
acid/2-methylhexanoic acid (ratio by mole 0.5/0.5) MIPPO-1
Poly[methoxyisopropoxypropylene oxide] (methyl groups at both chain
ends) MIPPO-2 Copolymer [methoxyisopropoxypropylene oxide/ethylene
oxide] (methyl groups at both chain ends)
Examples 1 to 5
[0177] Base oil (a) and base oil (b) shown in Table 3 are mixed in
relative amounts also shown in Table 3 to prepare lubricating oils
and the properties of the prepared lubricating oils were evaluated.
The results are shown in Table 3.
Comparative Examples 1 to 3
[0178] The properties of lubricating oils composed of a polyvinyl
ether alone shown in Table 3 were evaluated. The results are shown
in Table 3.
3 TABLE 3 Example Comparative Example 1 2 3 4 5 1 2 3 Base oil (a)
type PVE-1 PVE-1 PVE-2 PVE-3 PVE-3 PVE-1 PVE-1 PVE-2 amount (% by
wt.) 90 80 90 95 85 100 100 100 Base oil (b) type PC-1 PC-2 PC-1
PC-1 PC-2 -- -- -- amount (% by wt.) 10 20 10 5 15 -- -- --
Kinematic viscosity 75.09 73.57 38.18 73.04 73.08 70.33 33.74 70.71
at 40.degree. C. (mm.sup.2/s) Temperature of phase separation
(.degree. C.) 15% by weight 0 -4 -2 -3 -9 sepa- 23 10 ration 20% by
weight -8 -12 -16 -10 -18 sepa- 21 8 ration Autoclave test
appearance of oil good good good good good good good good
precipitates none none none none none none none none metal catalyst
no no no no no no no no change change change change change change
change change Lubricity [load 3550 3670 3210 3470 3500 3180 2890
3190 of seizure] (N) Note: In the temperature of phase separation,
% by weight shows the following value: [sample/(sample + R32)]
.times. 100 (Similarly, in the following Tables)
Examples 6 to 10
[0179] Base oil (a) and base oil (b) shown in Table 4 are mixed in
relative amounts also shown in Table 4 to prepare lubricating oils
and the properties of the prepared lubricating oils were evaluated.
The results are shown in Table 4.
Comparative Examples 4 to 6
[0180] The properties of lubricating oils composed of a polyester
alone shown in Table 4 were evaluated. The results are shown in
Table 4.
4 TABLE 4 Example Comparative Example 6 7 8 9 10 4 5 6 Base oil (a)
type POE-1 POE-1 POE-2 POE-3 POE-3 POE-1 POE-2 POE-3 amount (% by
wt.) 90 80 90 95 85 100 100 100 Base oil (b) type PC-1 PC-2 PC-1
PC-1 PC-2 -- -- -- amount (% by wt.) 10 20 10 5 15 -- -- --
Kinematic viscosity 72.7 71.5 55.1 35.5 36.1 67.9 50.2 31.4 at
40.degree. C. (mm.sup.2/s) Temperature of phase separation
(.degree. C.) 15% by weight 5 10 2 -5 -8 sepa- sepa- 15 ration
ration 20% by weight -2 0 -8 -9 -15 sepa- sepa- 12 ration ration
Autoclave test appearance of oil good good good good good light
light light yellow yellow yellow precipitates none none none none
none none none none metal catalyst no no no no no no no no change
change change change change change change change Lubricity [load
3780 3880 3640 3600 3490 3690 3580 3720 of seizure] (N)
Examples 11 to 17
[0181] Base oil (a) and base oil (b) shown in Table 5 are mixed in
relative amounts also shown in Table 5 to prepare lubricating oils
and the properties of the prepared lubricating oils were evaluated.
The results are shown in Table 5.
5TABLE 5 Example 11 12 13 14 15 16 17 Base oil (a) type PVE-1 PVE-1
PVE-2 PVE-3 PVE-3 -- -- amount (% by wt.) 80 70 90 95 85 -- -- Base
oil (b) type MIPPO MIPPO MIPPO MIPPO MIPPO MIPPO MIPPO -2 -1 -1 -1
-2 -1 -2 amount (% by wt.) 20 30 10 5 15 100 100 Kinematic
viscosity 70.0 83.96 37.95 72.28 70.40 130.5 68.7 at 40.degree. C.
(mm.sup.2/s) Temperature of phase separation (.degree. C.) 15% by
weight 4 0 -34 -1 -32 -50> -50> 20% by weight 0 -3 -38 -4 -36
-50> -50> Autoclave test appearance of oil good good good
good good good good precipitates none none none none none none none
metal catalyst no no no no no no no change change change change
change change change Lubricity [load 3650 3910 3330 3760 3900 4220
3910 of seizure] (N)
Examples 18 to 22
[0182] Base oil (a) and base oil (b) shown in Table 6 are mixed in
relative amounts also shown in Table 6 to prepare lubricating oils
and the properties of the prepared lubricating oils were evaluated.
The results are shown in Table 6.
6TABLE 6 Example 18 19 20 21 22 Base oil (a) type POE-1 POE-1 POE-2
POE-3 POE-3 amount (% by wt.) 90 80 90 90 80 Base oil (b) type
MIPPO-1 MIPPO-2 MIPPO-1 MIPPO-1 MIPPO-2 amount (% by wt.) 10 20 10
10 20 Kinematic viscosity at 72.20 68.06 54.76 35.50 36.30
40.degree. C. (mm.sup.2/s) Temperature of phase separation
(.degree. C.) 15% by weight 10 5 7 2 -1 20% by weight 2 -3 0 -5 -12
Autoclave test appearance of oil good good good good good
precipitates none none none none none metal catalyst no no no no no
change change change change change Lubricity [load 3810 3930 3690
3880 4020 of seizure] (N)
INDUSTRIAL APPLICABILITY
[0183] The lubricating oil for refrigerators of the present
invention exhibits excellent miscibility with a refrigerant having
one carbon atom and no chlorine atoms and, in particular, with
difluoromethane.
[0184] The hydraulic fluid composition for refrigerators of the
present invention comprising the lubricating oil for refrigerators
and the refrigerant of the present invention exhibits excellent
antiwear, lubricity and stability.
* * * * *