Refrigerating apparatus and refrigerant compressor

A regrigerating apparatus comprising a refrigeration cycle comprising at least a compressor, a condenser, a dryer, an expansion mechanism and an evaporator, a refrigerant composed mainly of a fluorocarbon type refrigerant containing no chlorine and having a critical temperature of 40.degree. C. or higher, and a refrigerating machine oil comprising as base oil an ester oil of one or more fatty acids which contains at least two ester linkages ##STR1## in the molecule and has a viscosity at 40.degree. C. of 2 to 70 cSt and a viscosity at 100.degree. C. of 1 to 9 cSt.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a refrigeration cycle and refrigerant 
compressor, and it relates to, in particular, a 
refrigeration-cycle-constituting material system comprising a 
refrigerating machine oil composition suitable for a flon type refrigerant 
containing no chlorine and having a critical temperature of 40.degree. C. 
or higher, for example, flon 134a, and electrical insulating materials and 
a drying agent which are hardly deteriorated by the refrigerating machine 
oil composition. 
2. Prior Art 
In recent years, chlorine-containing flons (chlorofluorocarbons, 
abbreviated as CFC) have been included in the list of compounds under 
regulation in use, all over the world because of the problems of 
environmental pollution, in particular, the ozone depletion and the global 
warming. 
All of flons included in the list of compounds under regulation in use are 
chlorine-containing flons such as flon 11, flon 12, flon 113, flon 114, 
flon 115, etc. Flon 12 which has been exclusively used as a refrigerant in 
refrigerating apparatus such as refrigerators, dehumidifiers, etc., has 
also been included in the list. 
Therefore, a refrigerant usable in place of flon 12 is required. 
Hydrofluorocarbon (HFC) having a low reactivity with ozone and a short 
decomposition period in the air has recently been noted as a substitute 
refrigerant. Flon 134a (1,1,1-tetrafluoroethane, CH.sub.2 FCF.sub.3) is a 
typical example of such a refrigerant. In detail, when the ozone depletion 
potential (ODP) of flon 12 (dichlorodifluoromethane CCl.sub.2 F.sub.2) is 
taken as 1, that of flon 134a is zero. When the global warming potential 
(GWP) of flon 12 is taken as 1, that of flon 134a is 0.3 or less. Flon 
134a is noncombustible and similar to flon 12 in thermal properties such 
as temperature-pressure characteristics. Therefore, flon 134a has been 
said to be advantageous in that it can be put into practical use without 
greatly changing the structures of refrigerating apparatus such as 
refrigerators and dehumidifiers and refrigerant compressors in which flon 
12 has heretofore been used. 
Flon 134a however, has a unique chemical structure and hence very 
characteristic properties. Therefore, it has a very poor compatibility 
with refrigerating machine oils such as mineral oils and alkylbenzene oils 
which have been used in conventional refrigeration system using flon 12, 
and hence it cannot be put into practical use at all. In addition, the 
suitability including the improving effect on the lubrication and the 
resistance to frictional wear of the sliding portions of compression 
mechanical parts, the influence on electrical insulating materials, the 
influence on drying agents, etc. is a problem, and there has been an eager 
desire for the development of a novel material system constituting a 
compressor and a refrigerating apparatus. 
Therefore, before referring to the problem of the miscibility of a 
refrigerant with a refrigerating machine oil, conventional refrigerant 
compressor and refrigeration apparatus which use a flon type refrigerant 
are first explained with reference to FIG. 7 to FIG. 9. 
FIG. 7 is a vertical cross-sectional view of the principal part of a 
conventional closed rotary compressor. FIG. 8 is a cross-sectional view 
for explaining the displacement volume of the compressor section of the 
compressor. FIG. 9 is a diagram showing the structure of an ordinary 
refrigeration cycle. 
In FIG. 7, numeral 1 shows a case used both as a closed container and as a 
oil pan. In the case 1, an electric motor section 22 and a compressor 
section 23 are accommodated. 
The electric motor 22 is composed of a stator 19 and a rotor 20, and a 
rotating shaft 4A made of cast iron is fitted in the rotor 20. The 
rotating shaft 4A has an eccentric portion 3 and an shaft hole 17 is 
formed in hollow form on the one side of the eccentric portion 3. 
The core wire of the winding wire portion 19a of the stator 19 is coated 
with an ester imide film, and an electrical insulating film of a 
polyethylene terephthalate is inserted between the core portion and the 
winding wire portion of the stator. The rotor 4A has a surface finished by 
grinding. 
The compressor 23 has as its chief mechanism components a cylinder 2 made 
of an iron-based sintered product; a roller 7 made of cast iron which is 
fitted in the eccentric portion 3 of the rotating shaft 4A and 
eccentrically rotated along the inside of the cylinder 2; a high-speed 
steel vane which is reciprocated in the groove 8 of the cylinder 2 while 
one side of the vane is in contact with the roller 7 and the other side is 
pushed by a spring 9; and a main bearing 5 and a sub-bearing 6 which are 
made of cast iron or an iron-based sintered product, are provided on both 
ends of the cylinder, and serve both as bearings for the rotary shaft 4A 
and as the side wall of the cylinder 2. 
The sub-bearing 6 has a discharge valve 27, and a discharge cover 25 is 
attached thereto so as to form a silencer 28. The main bearing 5, the 
cylinder 2 and the sub-bearing 6 are fastened with a bolt 21. 
A pump chamber 12 is composed of a space and parts surrounding the space, 
i.e., the back of the vane 10, the groove 8 of the cylinder 2, the main 
bearing 5 and the sub-bearing 6. 
The main bearing 5 has a suction piece 14 which can suck a naphthene type 
or alkylbenzene type refrigerating machine oil 13A in which a refrigerant 
flon gas stored in the bottom of the case 1 has been dissolved, into the 
pump chamber 12. The sub-bearing 6 has a discharge port 16 which can 
discharge the refrigerating machine oil 13A to an oil tube 15 from the 
pump chamber 12. The oil tube 15 is designed to be able to supply the 
refrigerating machine oil 13A to the shaft hole 17 of the rotating shaft 
4A and then to predetermined sliding portions from the shaft hole 17 
through a branch opening 18. 
The action of the rotary compressor thus composed is explained below with 
reference to FIGS. 7 and 8. When the compressor is operated to rotate the 
rotating shaft 4A made of cast iron, a roller 7 made of tempered cast iron 
is rotated with the rotation of rotating shaft 4A, and the high-speed 
steel vane 10 is reciprocated in the groove 8 of the cylinder 2 made of 
cast iron or a iron-based sintered product while the vane 10 is pushed by 
the spring 9 and its end is in contact with the roller 7. Thus, the vane 
10 compresses a refrigerant (flon 12) which has flown in through a 
refrigerant suction opening (not shown), and the refrigerant is discharged 
outside the compressor from a discharge pipe 29 through a refrigerant 
discharge opening 24. The winding wire portion 19a and the electrical 
insulating film (not shown) of the stator 9 are immersed in the 
refrigerating machine oil containing flon dissolved therein, or they are 
exposed to circumstances of spraying with mist of the refrigerant oil. 
In the case of a combination of a conventional refrigerating machine oil 
consisting of a mineral oil or an alkylbenzene and flon 12, flon 12 is 
completely miscible with the refrigerating machine oil in all use ranges, 
so that it has been not necessary at all to care about the various 
problems concerning the miscibility of flon 134a with a refrigerating 
machine oil which are hereinafter described in detail, namely, the 
separation into two layers between the refrigerating machine oil and the 
refrigerant in a compressor, and the residence of the refrigerating 
machine oil in a heat exchanger. However, in the case of fluorohydrocarbon 
type refrigerants containing no chlorine which have unique 
characteristics, for example, flon 134a the miscibility of the refrigerant 
with a refrigerating machine oil is the most serious problem in practice 
because there is no practical refrigerating machine oil which can easily 
dissolve the refrigerant. 
In general, for improving the performance characteristics of a compressor, 
namely, the coefficient of performance (COP) which indicates the energy 
efficiency, it has been necessary to minimize the mechanical loss of the 
compressor and maximize its volumetric efficiency. 
The mechanical loss of a refrigerant compressor mainly includes the 
friction loss at the journal bearing and thrust bearing in the mechanical 
part and the power for agitating oil. In general, it has been said that 
the best means is to minimize the value of the coefficient of friction 
(.mu.) defined by the following equation on the basis of the hydrodynamic 
lubrication theory of a journal bearing: 
EQU .mu.=2 .pi..sup.2 (D/C).eta.N/P (9) 
wherein 
N: revolution rate, 
P: pressure on surface, 
.eta.: viscosity, 
D: diameter of shaft, 
C: diametral clearance. 
This fact indicates that in a refrigerant compressor operated under 
hydrodynamic lubrication conditions, not only the structural factors 
regarding dimensions and shapes but also the actual viscosity of a 
refrigerating machine oil containing flon disolved therein which is a 
factor influenced by operation circumstances, have a close relationship to 
the mechanical loss of the compressure. 
On the other hand, for keeping the volumetric efficiency highest, it is 
necessary that in a mechanical chamber for compressing a refrigerant gas, 
the leakage of the refrigerant gas from the high pressure side to the low 
pressure side should be prevented by carrying out sealing between parts 
which works to compress the refrigerant gas. It should be noted that also 
in this case, the actual viscosity of a refrigerating machine oil 
containing the refrigerant dissolved therein has an important function. 
As described above, in a refrigerant compressor heretofore used by the use 
of flon 12 and a refrigerating apparatus using the refrigerant compressor, 
it is important for the improvement of performance characteristics of the 
compressor to optimize the actual viscosity of a refrigerating machine oil 
containing the refrigerant dissolved therein, at a rated operation point 
under usual operation conditions. 
A refrigerating apparatus such as a refrigerator or a dehumidifier is 
operated, though in rare cases, in a high-temperature circumstance much 
more severe than usual operation conditions. In this case, the lubrication 
in the apparatus gets into a so-called boundary lubrication region in 
which a lubricating oil layer is thined, so that the metal surfaces of 
sliding portions of a bearing are brought into contact with each other. 
Consequently, the coefficient of friction is increased at once, resulting 
in heat generation. Therefore, scoring or seizing-and-adhesion phenomenon 
occurs between the bearing and a rotating shaft and deteriorates the 
reliability of a refrigerant compressor. Therefore, some consideration is 
needed for preventing a fatal problem from occuring even under boundary 
lubrication conditions. In a conventional refrigerant compressor using 
flon 12, chlorine in flon 12 acts effectively as an extreme pressure 
agent. In detail, when scoring or seizing-and-adhesion phenomenon takes 
place between a bearing and a rotating shaft, the refrigerant flon 12 
dissolved in a refrigerating machine oil as bearing-lubricating oil is 
decomposed by frictional heat generated by the scoring or the phenomenon, 
and chlorine, i.e., the decomposition product, reacts with iron on the 
surface of the bearing to form iron chloride which acts as a lubricant. 
As described above, in the case of a refrigerating apparatus using a 
high-pressure vessel type rotary compressor, for example, a refrigerator, 
a refrigerant compressor and a refrigerating apparatus which satisfy the 
operation conditions at an ambient temperature of 30.degree. C. described 
below are satisfactory in the coefficient of performance indicating energy 
efficiency and the reliability of a product, and most products have been 
used in such ranges. The discharge pressure of the compressor: about 10 
kg/cm.sup.2 abs, oil temperature: about 100.degree. C., refrigerating 
machine oil: an alkylbenzene oil or a mineral oil having a viscosity at 
40.degree. C. of 56 cSt and a viscosity at 100.degree. C. of 6 cSt, the 
actual viscosity of which becomes 1 to 4 cSt. 
On the other hand, in the case of a refrigerating apparatus using a 
low-pressure vessel type reciprocating compressor (the explanation of the 
structure and operation is omitted), for example, a refrigerator, there 
have been used a refrigerant compressor and a refrigerating apparatus 
which satisfy the following operation conditions at an ambient temperature 
of 30.degree. C.; the suction pressure of the compressor: about 1.6 
kg/cm.sup.2 abs, oil temperature: 85.degree. C., refrigerating machine 
oil: a mineral oil having a viscosity at 40.degree. C. of 8 to 15 cSt and 
a viscosity at 100.degree. C. of 1.8 to 4.2 cSt, the actual viscosity of 
which becomes 2 to 6 cSt. 
Next, a fundamental refrigeration cycle provided with a refrigerant 
compressor which thus sucks, compresses and then discharge a flon type 
refrigerant, is explained below with reference to FIG. 9. 
As shown in FIG. 9, a compressor 40 compresses a low-temperature, 
low-pressure refrigerant gas, discharges the resulting high-temperature, 
high-pressure refrigerant gas and send the same to a condenser 41. The 
refrigerant gas sent to the condenser 41 becomes a high-temperature, 
high-pressure refrigerant fluid while releasing its heat to the air, and 
then it is sent to an expansion mechanism (e.g. an expansion valve or a 
capillary tube) 42 while being freed from water by a dryer 45. The 
high-temperature, high-pressure refrigerant fluid which passes the 
expansion mechanism becomes low-temperature, low-pressure wet vapor owing 
to squeezing effect and is sent to an evaporator 43. The refrigerant 
introduced into the evaporator 43 is evaporated while absorbing heat from 
the surroundings, and the low-temperature, low-pressure gas which has come 
out of the evaporator 43 is sucked into the condenser 40. Thereafter, the 
above cycle is repeated. 
As there frigerant, flon 12 has heretofore been used. However, the 
employment of flon 12 is under regulations, as described above. The 
employment of flon 134a in place of flon 12 involves many problems because 
conventional mineral oil type or alkylbenzene type refrigerating machine 
oils for flon 12 are very poor in miscibility with flon 134a. Therefore, 
refrigerating machine oils having a good miscibility with flon 134a have 
been vigorously developed and various refrigerating machine oils have been 
proposed. As typical examples of such refrigerating machine oils, there 
are known the compounds having ether linkages exemplified below. 
For example, Japanese Patent Application Kokai No. 1-259093 discloses "a 
refrigerating machine oil for a flon compressor" which comprises as base 
oil a propylene glycol monoether represented by the general formula: 
##STR2## 
wherein R is an alkyl group having 1 to 8 carbon atoms, and n is an 
integer of 4 to 19; Japanese Patent Application Kokai No. 1-259094 
discloses a diether type compound obtained by etherifying one end of 
propylene glycol which is represented by the general formula: 
##STR3## 
wherein each of R.sub.1 an R.sub.2 is an alkyl group having 1 to 8 carbon 
atoms, and n is an integer (average molecular weight: 300 to 600); and 
Japanese Patent Application Kokai No. 1-259095 discloses a monoether type 
compound which is a copolymer of propylene glycol and ethylene glycol and 
is represented by the general formula: 
##STR4## 
wherein R is an alkyl group having 1 to 14 carbon atoms, and m and n are 
integers, the ratio m: n being 6:4 to 1:9 (average molecular weight: 300 
to 2,000). 
The difference of these polyalkylene glycols from conventional mineral oils 
and alkylbenzene oils have been reported as follows. By the introduction 
of ether linkages into the molecule, the affinity for flon 134a is 
enhanced to improve the miscibility with flon 134a greatly, refrigerant 
lubrication due to the phenomenon of separation into two layers (a 
phenomenon that the refrigerant and the refrigerating machine oil are 
insoluble in each other and separate; hereinafter referred to merely as 
"two-layer separation") in the sliding portions of a compressor can be 
prevented, the return of the oil to the compressor which is induced by 
residence phenomenon due to the adhesion of the oil to the inner wall of a 
heat exchanger can be suppressed, and there can be solved the problems 
concerning the reliability of the compressor and a refrigerating 
apparatus, for example, seizing and scoring in the sliding portions of the 
compressor. 
Such compounds thus containing a large number of ether linkages (C--O--C), 
however, are disadvantageous in that, 
(1) they have a saturation water absorption rate is high (they tend to 
absorb water). 
(2) they have a low volume resistivity. 
(3) they have a low oxidation stability, so 
that the total acid value is apt to be increased. Therefore, the compounds 
have been not suitable for refrigerant compressors and refrigerating 
apparatus in which a hermetic motor is used as an electric motor. That is, 
although the compounds have an improved miscibility with the refrigerant, 
they are disadvantageous in that they attack the insulating materials of 
the motor to deteriorate the electrical insulating characteristics. In all 
of the above compounds, the end group having an ether linkage is capped 
with hydrogen, and the hydrogen further increases the hygroscopicity. 
Therefore, it has been proposed to replace the hydrogen by an ester group 
to obtain a refrigerating machine oil represented by the following formula 
(see Japanese Patent Application Kokai No. 2-132178): 
##STR5## 
wherein R is a hydrocarbon group, R.sup.1 is an alkylene R.sup.2 is an 
alkyl group, and n is an integer which is such that the viscosity of this 
compound becomes 10 to 300 (at 40.degree. C.). 
However, the improved miscibility with the refrigerant of this compound is 
also brought about by a large number of ether linkages in the molecule, 
like that of the above compounds, and hence this compound involves the 
same problems as in the case of the above compounds. 
Thus, the compounds having ether linkages tend to absorb water because of 
the above problem (1), and the compounds themselves are hydrolyzed by the 
water to become unstable. Furthermore, the water freezes, chokes the 
capillary of a refrigeration cycle, and disturbs the pressure balance. The 
volume resistivity of the compounds is low as described as the problem 
(2), so that the electrical insulating properties are deteriorated. When 
the total acid value is increased as described as the problem (3), the 
compounds are hydrolyzed to become unstable. 
As described above, flon 134a which is used as a substitute refrigerant for 
conventional refrigerant flon 12 involves the following fatal problem. 
Because of its unique molecular structure, flon 134a has a low affinity 
for mineral oil type and alkylbenzene oil type refrigerating machine oils 
which have heretofore been used, and hence it lacks miscibility with the 
refrigerating machine oils which is essential in a refrigerant compressor 
and a refrigerating apparatus. 
Attempts have been made to improve the miscibility, but have been 
accompanied with, for example, the deterioration of the electrical 
insulating properties, the water problem, and the unstability problems, 
such as the hydrolysis and the decomposition of the compound by an acid. 
Each problem is described below in more detail. 
SUMMARY OF THE INVENTION 
(1) A refrigerating machine oil having a bad miscibility cannot be put into 
practical use in a refrigerant compressor and a refrigerating apparatus 
from the viewpoint of performance characteristics and reliability, as 
described below. 
In general, when the solubility of a refrigerating machine oil in a 
refrigerant is low, oil discharged from a compressor is separated in a 
heat exchanger and the oil component adheres to the wall surface to 
remain, so that the amount of oil which returns to the compressor is 
decreased. Consequently, the oil surface in the compressor is lowered and 
a so-called oil drying-up phenomenon takes place, so that the oiling level 
is lowered. 
When a compressor is exposed to a low-temperature circumstance in a 
refrigerating apparatus enclosing a large amount of a refrigerant, the 
following trouble is caused. In a so-called lying-idle state in which 
liquid refrigerant is present preferentially in the bottom of the 
compressor, low-viscosity liquid refrigerant which is present in the 
bottom as a result of two-layer separation is supplied to the sliding 
surface of a rotating shaft, so that the assurance of a lubricating oil 
film becomes difficult, resulting in damage to the compressor. 
On the other hand, as to the refrigerating apparatus, a refrigerating 
machine oil which has separated adheres to the inner wall of an evaporator 
having a low temperature, to form a heat-insulating layer, and therefore 
it inhibits the heat-transfering capability seriously. Moreover, when this 
refrigerating machine oil of wax form chokes an expansion mechanism (a 
capillary tube) or a piping, the amount of the refrigerant circulated is 
greatly decreased, resulting in a lowered cooling power. As to the 
compressor, the pressure of sucked gas is lowered and the pressure of 
discharged gas is increased. Therefore, the heat deterioration of the 
refrigerating machine oil and damage to bearings are caused, so that the 
long-term reliability of the refrigerant compressor and the refrigerating 
apparatus is greatly deteriorated. 
Accordingly, a first object of the present invention is to solve such 
conventional problems and provide a refrigerating apparatus and a 
refrigerant compressor which are provided with a refrigerating machine oil 
which is highly miscible with and hence suitable for flon type 
refrigerants containing no chlorine a typical example of which is flon 
134a. More specifically, the present invention is fundamentally intended 
to make improvements with respect to, for example, (1) water absorption 
properties, (2) volume resistivity, and (3) oxidative deterioration, and 
seek for a novel refrigerating machine oil composition which is miscible 
with flon 134a under all operation conditions of a refrigerant compressor 
and a refrigerating apparatus. It is also intended to provide a 
refrigeration system having excellent performance characteristics, 
efficiency and reliability in refrigerating apparatus and refrigerant 
compressors which are different in purposes, by developing at least the 
following two refrigeration oils: a refrigeration oil for 
moderate-temperature refrigerating apparatus such as dehumidifiers which 
achieves a first aim, i.e., attainment of a critical solution temperature 
of 0.degree. C. or lower; and a refrigeration oil for low-temperature 
refrigerating apparatus such as refrigerators which achieves a second aim, 
i.e., attainment of a critical temperature of -30.degree. C. or lower. 
(2) In the long run, it is beneficial to the prevention of global warming 
(GWP) to enhance the coefficient of performance (COP) (which indicates the 
energy efficiency, i.e., the ratio of the cooling power of a refrigerant 
compressor to an input) under usual use conditions under which refrigerant 
compressors and refrigerating apparatus are usually operated. 
For reducing the input to a compressor in order to improve the performance 
characteristics of the compressor, it is necessary to reducve the 
coefficient of friction on the basis of the hydrodynamic lubrication 
theory of coaxial bearing. For the reduction, it is necessary to measure 
the solubility of flon 134a in the refrigerating machine oil used in the 
present invention and thereby determine the optimum value of the actual 
viscosity of the oil used in the compressor. When the actual viscosity is 
thus optimized, the coefficient of friction of a bearing becomes minimum 
and the coefficient of performance of the compressor and a refrigerating 
apparatus using the compressor becomes maximum. 
Therefore, a second object of the present invention is to attain high 
performance characteristics and a high reliability by specifying a 
viscosity range of the refrigerating machine oil which is most suitable 
for a refrigerating apparatus using a high-pressure vessel type rotary 
compressor or a low-pressure vessel type reciprocating compressor, on the 
basis of the above bearing theory. 
(3) However, although very rarely in practice, there is carried out an 
extremely severe operation such as operation in a high-temperature 
circumstance or overload operation which are more severe than expected by 
a designer. Also in this case, a sufficient reliability should be assured. 
In a compressor using flon 134a scoring or seizing of the sliding portion 
of a bearing of the compressor tends to take place more often than in a 
compressor using a conventional refrigerant flon 12, in a so-called 
boundary lubrication region (in which contact between metal surfaces 
occurs) beyond the hydrodynamic lubrication region of a coaxial bearing. 
When contact between metal surfaces takes place in the sliding portion of a 
bearing, flon 12 dissolved in an oil is decomposed to form a conversion 
coating of iron chloride on an iron-based sliding frictional surface. This 
iron chloride acts as an extreme pressure agent to suppress the adhesion 
and seizing. 
On the other hand, since flon 134a is a refrigerant containing no chlorine, 
chlorine cannot possibly be supplied to a compressor using flon 134a. 
Therefore, unlike flon 12, flon 134a is hardly expected to have the above 
action as extreme pressure agent. 
Accordingly, a third object of the present invention is to provide a 
refrigerating apparatus and a refrigerant compressor in which by using a 
flon type refrigerant containing no chlorine represented by flon 134a and 
a refrigerating machine oil containing an extreme pressure agent, the 
prevention of scoring and seizing of the sliding portions and the 
assurance of sufficient reliability can be achieved even when the oil runs 
out in the sliding bearing of the compressor and extremely severe 
operation is carried out. 
(4) A fourth object of the present invention is to provide a refrigerant 
compressor and a refrigerating apparatus which use a composition 
comprising a flon type refrigerant containing no chlorine represented by 
flon 134a and a refrigerating machine oil, and have an electrical 
insulating system wherein electrical insulating materials such as an 
electrical insulating film and an insulation-coated winding wire which 
constitute an electric motor section have a sufficient long-term 
reliability. 
(5) Flon 134a has a high water absorption rate and refrigerating machine 
oils miscible with flon 134a are relatively hydrophilic though fairly 
improved. Therefore, both of them tend to carry water into a refrigeration 
cycle. Water in a refrigerating apparatus is frozen in an evaporator on 
the low-temperature side and chokes a pipe having a small diameter, such 
as a capillary tube to lower the refrigerating capability. Furthermore, in 
the long run, the refrigerating machine oil, the refrigerant, electribcal 
insulating materials, etc. undergo hydrolysis reaction, so that minus 
characteristics are brought about, for example, the production of an 
acidic substance and a lowering of the mechanical strength are induced. 
Accordingly, a fifth object of the present invention is to provide a 
refrigerating apparatus in which a flon type refrigerant containing no 
chlorine represented by flon 134a and a refrigerating machine oil 
coexists, and which has a dryer packed with a drying agent effective in 
improving the reliability of the refrigerating apparatus by separating and 
adsorbing only water without absorbing the refrigerant.

PREFERRED EMBODIMENT OF THE INVENTION 
1. The above first object of the present invention can be achieved by a 
refrigerating apparatus comprising a refrigeration cycle comprising at 
least a compressor, condensor, dryer, expansion mechanism and evaporator, 
a refrigerant compomsed mainly of a fluorocarbon type refrigerant 
containing no chlorine and having a critical temperature of 40.degree. C. 
or higher, and a refrigerating machine oil comprising as base oil an ester 
oil of one or more fatty acids which contains at least two ether linkages 
##STR6## 
in the molecule and has a viscosity at 40.degree. C. of 2 to 70 cSt and a 
viscosity at 100.degree. C. of 1 to 9 cSt. 
As described above, it is absolutely necessary for the ester oil to be an 
ester of one or more fatty acids which contains at least two ester 
linkages in the molecule. Ester oils of one or more fatty acids which have 
one ester linkage have a bad miscibility with the refrigerant and hence 
cannot be used. The usable ester oil of one or more fatty acids can be 
obtained by the esterification reaction of an alcohol with one or more 
fatty acids. As the alcohol, a polyhydric alcohol is preferable. As the 
fatty acids, those having 6 to 8 carbon atoms are preferable. The fatty 
acids may be either monobasic or polybasic. The ester oils include 
hindered ester oils and complex ester oils. From the viewpoint of the 
miscibility with the refrigerant, ester oils having a branched-chain 
structure tend to be preferable to ester oils having a straight-chain 
structure. Examples of practical ester oils of one or more fatty acids are 
given below by the general formulas (1) to (5). 
The ester oils represented by the formulas (1) to (4) are hindered ester 
oils, and the ester oils represented by the formula (5) are complex ester 
oils. 
These ester oils may be used singly or in combination of two or more 
thereof. The refrigerating machine oil comprise at least 50 wt % of these 
ester oils as base oil, and the balance may be made up by other well-known 
refrigerating machine oils. 
EQU (R.sub.1 CH.sub.2).sub.2 C(CH.sub.2 OCOR.sub.2).sub.2 (1) 
(examples of esters of neopentyl glycol (abbreviated as NPG) type alcohols 
which contain two ester linkages in the molecule). 
EQU R.sub.1 CH.sub.2 C(CH.sub.2 OCOR.sub.2).sub.3 (2) 
(examples of esters of trimethylolalkylpropanes (abbreviated as TMP) which 
contain three ester linkages in the molecule). 
EQU C(CH.sub.2 OCOR.sub.2).sub.4 (3) 
(examples of esters of pentaerythritol (abbreviated as PET) which contain 4 
ester linkages in the molecule). 
EQU (R.sub.2 COOCH.sub.2).sub.3 CCH.sub.2 OCH.sub.2 C(CH.sub.2 
OCOR.sub.2).sub.3(4) 
(examples of esters of dipentaerythritol (abbreviated as DPET) which 
contain 6 ester linkages in the molecule). 
##STR7## 
(examples of complex esters containing 4 or more ester linkages in the 
molecule). 
In the above general formulas, R.sub.1 is H or an alkyl group having 1 to 3 
carbon atoms, R.sub.2 is a straight or branched-chain alkyl group having 5 
to 12 carbon atoms, R.sub.3 is an alkyl group having 1 to 3 carbon atoms, 
R.sub.3 is an alkyl group having 1 to 3 carbon atoms, and n is an integer 
of 0 to 5. 
The esters represented by the above general formulas (1) to (4) are esters 
of polyhydric alcohols and monocarboxylic acids. As such esters, esters 
having a desired viscosity grade can be obtained by optionally choosing a 
combination of the alcohol and one or a plurality of the monocarboxylic 
acids and proportions of these components. 
As the complex esters represented by the general formula (5), esters having 
a high viscosity and a wide critical solution temperature range can be 
obtained by selecting the chemical structure of the central dibasic acid 
(dicarboxylic acid) component from various chemical structures derived 
from succinic acid (n=2), glutaric acid (abbreviated as Glut), adipic acid 
(abbreviated as AZP), pimelic acid, suberic acid, azelaic acid, and 
sebacic acid (n=8), selecting the polyhydric alcohol component and the 
terminal monocarboxylic acid component from various compounds, and varying 
the blending proportions (molar fraction). 
The monocarboxylic acids represented by the formula R.sub.2 COOH may be 
straight- or branched-chain ones. The latter includes 2-ethylhexanoic acid 
(2EH), 2-methylhexanoic acid (i-C.sub.7), 3,5,5-trimethylhexanoic acid, 
3,5-dimethylhexanoic acid (i-C.sub.8), 2-methylheptanoic acid. The 
monocarboxylic acids may be used singly or in combination of two or more 
thereof. 
The base oil of the refrigerating machine oil is prepared by adjusting the 
viscosity by using such hindered ester oils and complex ester is singly or 
in combination of two or more thereof. 
The refrigerant composed mainly of a fluorocarbon type refrigerant 
containing no chlorine and having a critical temperature of 40.degree. C. 
or higher which is used in the present invention includes 
hydrofluorocarbons and fluorocarbons. Specific examples of the 
hydrofluorocarbons are difluoromethane (R32), pentafluoroethane (R125), 
1,1,2,2-tetrafluoroethane (R134), 1,1,1,2-tetrafluoroethane (R134a), 
1,1,2-trifluoroethane (R143), 1,1,1-trifluoroethane (R143a), 
1,1-difluoroethane (R152a) and monofluoroethane (R161). Specific examples 
of the fluorocarbons are hexafluoropropane (C216) and 
octafluorocyclobutane (C318). Of these, 1,1,2,2-tetrafluoroethane (R134), 
1,1,1,2-tetrafluoroethane (R134a), 1,1,2-trifluoroethane (R143), 
1,1,1-trifluoroethane (R143a) and hexafluoropropane (C216) have a boiling 
point close to that of a conventional refrigerant, dichlorodifluoromethane 
(R12), and are preferable as substitute refrigerants. The 
above-exemplified hydrofluorocarbon or fluorocarbon type refrigerants can 
be used singly or as a mixture thereof. 
The reason for the adjustment of critical temperature of the refrigerant to 
40.degree. C. or higher is that there was required a refrigerating 
apparatus in which the condensation temperature in a condenser was 
40.degree. C. 
1) The above second object of the present invention is, for one thing, 
achieved by a high-pressure vessel type refrigerant compressor used in a 
refrigeration cycle that comprises a closed vessel stored with a 
refrigerating machine oil which accommodates a motor composed of a rotor 
and a stator, a rotating shaft fitted in the rotor, and a compressor 
section connected to the motor through the rotating shaft, and in which a 
high-pressure refrigerant gas discharged from the compressor section 
resides, said refrigerant being composed mainly of a fluorocarbon type 
refrigerant containing no chlorine and having a critical temperature of 
40.degree. C. or higher, and said refrigerating machine oil comprising as 
base oil an ester oil of one or more fatty acids which contains at least 
two ester linkages 
##STR8## 
in the molecule and has a viscosity at 40.degree. C. of 2 to 70 cSt and a 
viscosity at 100.degree. C. of 1 to 9 cSt. 
The constitution of the ester oil of one or more fatty acids which contains 
at least two ester linkages in the molecule is as described above in 
detail. 
In a high-pressure vessel type rotary compressor, for example, is 
previously enclosed the aforesaid refrigerating machine oil having a 
viscosity at 40.degree. C. of 2 to 70 cSt, preferably 5.0 to 32 cSt, so 
that the actual viscosity (at a gas pressure of 9 to 11 kg/cm.sup.2 abs 
and an oil temperature of about 100.degree. C.) of the oil which contains 
flon 134a dissolved therein may be 1.0 to 4.0 cSt. 
2) In addition, the above second object of the present invention is 
achieved by a low-pressure vessel type refrigerant compressor that 
comprises a closed vessel stored with a refrigerating machine oil which 
accommodates a motor composed of a rotor and a stator, a rotating shaft 
fitted in the rotor, and a compressor section connected to the motor 
through the rotating shaft, and from which a high-pressure refrigerant gas 
discharged from the compressor section is directly exhausted, said 
refrigerant being composed mainly of a fluorocarbon type refrigerant 
containing no chlorine and having a critical temperature of 40.degree. C. 
or higher, and said refrigerating machine oil comprising as base oil an 
ester of one or more fatty acids which contains at least two ester 
linkages 
##STR9## 
in the molecule and has a viscosity at 40.degree. C. of 2 to 70 cSt and a 
viscosity at 100.degree. C. of 1 to 9 cSt. 
The constitution of the ester oils of one or more fatty acids which 
contains at least two ester linkages in the molecule is as described 
above. 
In a low-pressure vessel type reciprocating compressor, for example, is 
previously enclosed the aforesaid refrigerating machine oil having a 
viscosity at 40.degree. C. of 5.0 to 15 cSt and a viscosity at 100.degree. 
C. of 2.0 to 4.0 cSt, so that the actual viscosity (at a sucked gas 
pressure of 1.0 to 2.0 kg/cm abs and an oil temperature of 85.degree. C.) 
of the oil which contains flon 134a dissolved therein may be 2.0 to 4.5 
cSt. 
3) The above third object can be achieved by adding an extreme pressure 
agent to the aforesaid refrigerating machine oil. 
The extreme pressure agent serves as an abration-preventing agent in 
sliding portions and includes, for example, alkylpolyoxyalkylene phosphate 
esters represented by the general formulas (6) and (7) and dialkyl 
phosphate esters represented by the general formula (8): 
##STR10## 
wherein R.sub.4 is an alkyl group having 1 to 8 carbon atoms, and R.sub.5 
is H or an alkyl group having 1 to 3 carbon (molecular weight: 400 to 
700). 
##STR11## 
wherein R.sub.6 is an alkyl group having 8 to 16 carbon atoms. 
These phosphoric esters may be added singly or in combination of two or 
more thereof. The practical amount of the phosphoric esters added to the 
refrigerating machine oil is 0.05 to 10 wt %. 
It is also effective to add an acid-capturing agent, antioxidant, defoaming 
agent, etc. together with the extreme pressure agent (the 
abrasion-preventing agent). 
When an acid component is present in the refrigerating machine oil, the 
ester oil is decomposed by the acid component to become unstable. 
Therefore, the acid-capturing agent is added for removing the acid 
component. For example, compounds such as epoxy compounds reactive with 
acids are preferable as the acids-capturing agent. Particularly preferable 
examples of the acid-capturing agent are compounds having an epoxy group 
and an ether linkage, for example, diglycidyl ether compounds such as 
polyalkylene glycol diglycidyl ethers; monoglycidyl ether compounds such 
as phenyl glycidyl ether; and aliphatic cyclic epoxy compounds. The reason 
is that the epoxy group of such a compound captures an acid and that the 
ether linkage contributes to the improvement of the miscibility of the 
refrigerating machine oil with the refrigerant to a certain extent. 
The other additives described above are, for example, chlorine-capturing 
agents for preventing the influence of residues of, for instance, a 
chlorine-containing detergent used for producing the compressor or the 
refrigerating apparatus, additives for preventing oxidative deterioration 
during the circulation and storage of the oil, and additives for 
preventing foaming. These additives may be selected from those used in the 
conventional general techniques and are not critical in the present 
invention. 
4) For achieving the fourth object, the insulating film constituting an 
electric motor section and the insulation-coated winding wire which are 
described below are used in a refrigerating apparatus and a refrigerant 
compressor which simultaneously use a flon type refrigerant containing no 
chlorine represented by flon 134a and a refrigerating machine oil 
comprising as base oil the above-exemplified ester oil of one or more 
fatty acids. As the insulating film, there is used a crystalline plastics 
film having a glass transition temperature of 50.degree. C. or higher, or 
a composite film obtained by coating a film having a low glass transition 
temperature with a resin layer having a high glass transition temperature. 
As the insulation-coated winding wire, there is used an enameled wire 
having the enamel coating of a glass transition temperature of 120.degree. 
C. or higher, or an enameled wire having a composite coating consisting of 
a lower layer having a low glass transition temperature and a upper layer 
having a high glass transition temperature. 
As the insulating film, for practical purposes, it is preferable to use at 
least one kind of insulating film selected from the group consisting of 
films of polyethylene terephthalates, polybutylene terephthalates, 
polypenylene sulfides, polyether ether ketones, polyethylene naphthalates, 
polyamide-imides and polyimides. As an enamel coating, it is preferable to 
use at least one kind of insulating layer selected from the group 
consisting of insulating layers of polyester imides, polyamides and 
polyamide-imides. 
5) For achieving the fifth object, a synthetic zeolite composed of a 
composite salt consisting of alkali metal silicates and alkali metal 
aluminates which has a pore diameter of 3.3 angstrom or less and a carbon 
dioxide gas absorption capacity (at 25.degree. C. and at a partial 
pressure of carbon dioxide gas of 250 mmHg) of 1.0% or less, is used as a 
drying agent to be packed into the dryer, in the aforesaid refrigerating 
apparatus which simultaneously uses a flon type refrigerant containing no 
chlorine represented by flon 134a and a refrigerating machine oil 
comprising as base oil the above-exemplified ester oil of one or more 
fatty acids. 
In a refrigerating apparatus comprising at least a compressor, condenser, 
expansion mechanism and evaporator, and using a flon type refrigerant 
containing no chlorine represented by flon 134a the refrigerating machine 
oil according to the present invention which comprises at least one ester 
selected from the group consisting of hindered or complex esters 
containing two or more ester linkages in the molecule, and has a viscosity 
at 40.degree. C. of 2 to 70 cSt, preferably 5 to 32 cSt, and a viscosity 
at 100.degree. C. of 1 to 9 cSt, preferably 2 to 6 cSt, has a good 
miscibility with the refrigerant in the whole temperature ranges of the 
parts used in the refrigerating apparatus. Therefore, there is no 
two-layer separation between the refrigerant and the refrigerating machine 
oil. Accordingly, no two-layer separation is present in the oil-storing 
space in the compressor, so that the supply of the oil to the sliding 
portions of hearings is assured, and flon gas discharged from the 
compressor is in a liquefied state by the condenser, namely, in a state in 
which the oil is always dissolved in flon 134a with a low viscosity in a 
low-temperature circumstance of -30.degree. C. or lower in the evaporator. 
Thus, on the whole, the flon gas is in a low-viscosity state, so that the 
return of the oil to the compressor is improved. 
Therefore, the lowering of oil surface in the compressor is prevented and 
hence the supply of the oil to the sliding portions of hearings can be 
assured. Thus, the problems causing scoring and seizing can be solved. 
Furthermore, unlike conventional polyoxyalkylene glycol oils, the aforesaid 
refrigerating machine oil has a low saturated water-content of one-tenth 
or less as large as that of the conventional oils, a large improving 
effect on the stability to oxidative deterioration, and a volume 
resistivity of 10.sup.13 .OMEGA.cm which is as high as that of an 
electrical insulating oil. Therefore, in a refrigerant compressor 
comprising a pressure vessel accommodating a motor section and a 
refrigerating apparatus using the refrigerant compressor, the 
refrigerating machine oil according to the present invention do not 
separate from flon 134a and has excellent characteristics with respect to 
both the performance characteristics and reliability of the compressor. 
Since the refrigerating machine oil has an excellent miscibility also with 
conventional chlorine-containing flon refrigerants such as flon 12 and 
flon 22, such conventional chlorine-containing refrigerants can, if 
necessary, be used in place of a portion of flon 134a in admixture with 
flon 134a. 
When the refrigerating machine oil according to the present invention which 
had an oil viscosity at 40.degree. C. of 5 to 32 cSt was enclosed in a 
high-pressure vessel type rotary compressor and the coefficient of 
performance of the compressor was measured, the coefficient of performance 
reached a peak in the case of using the oil which had a viscosity of 15 
cSt. When the oil which had a viscosity of 5 to 32 cSt was used, the 
coefficient of performance was about 1.4 or more which corresponds to a 
value of 0.95 to 0.93 when the coefficient of performance in the case of 
using a conventional combination of a flon 12 and an alkyl-benzene oil is 
taken as 1. Such a value indicates that the oil involves no practical 
problem. The refrigerating machine oil according to the present invention 
which had a viscosity at 40.degree. C. of 56 cSt was found to be superior 
in the coefficient of performance of the compressor to polyoxypropylene 
glycol oils. The reason for this superiority is as follows. The ester 
linkages contained in the oil itself undergoes molecular orientation 
mainly on the surfaces of iron-based sliding portions of the shaft and 
bearings of the compressor to improve the lubrication. Moreover, the oil 
is decreased in actual viscosity owing to its high solubility in flon 134a 
to reduce the mechanical loss. These effects are synergistically brought 
about to improve the coefficient of performance of the compressor. 
On the other hand, in the case of a low-pressure vessel type reciprocating 
compressor, the amount of flon 134a dissolved and the actual viscosity 
vary only in narrow ranges because the compressor is operated at a low 
pressure in the vessel of 1 to 2 kg/cm.sup.2 abs. Therefore, 
characteristics of a refrigerant and a refrigerating machine oil are 
hardly dependent on their kinds, and it was found that the oil which had a 
viscosity at 40.degree. C. of 5 to 15 cSt and a viscosity of 100.degree. 
C. of 2 to 4 cSt was good in reliability and performance characteristics. 
When the refrigerating machine oil according to the present invention is 
blended with an adequate amount (0.05 to 10 wt %) of an extreme pressure 
agent such as a strong primary or secondary phosphoric ester retaining OH 
groups in the molecule, for example, an alkylpolyoxyalkylene phosphate 
ester or a dialkyl phosphate ester, the resulting blend can push away a 
lubricating oil film having ester linkages undergoing molecular 
orientation on the surfaces of iron-based sliding portions constituting 
the shaft and bearings of the compressor, and form a stronger chemical 
adsorption film of the phosphoric ester. Therefore, the blend can further 
improve the lubrication of the sliding portions to prevent scoring and 
seizing. 
When the lubricating properties of the refrigerating machine oil according 
to the present invention containing the extreme pressure agent were 
examined, the critical seizing pressure on surface was greatly increased 
in a FALEX test (a seizing test on the oil) carried out without the 
dissolution of flon 134a in the oil. In addition, when there was measured 
the abrasion loss of an iron-based sliding member in the case of 
employment of the refrigerating machine oil containing the extreme 
pressure agent which further contained 50% of flon 134a dissolved therein, 
as simulation of the dissolution of a high concentration of flon 134a the 
abrasion loss could be reduced to one-fifth or less as large as that 
caused in the case of the oil which did not contain the extreme pressure 
agent. The suitable range of the amount of the extreme pressure agent 
added is 0.05 to 10 wt % as described above. The results of the abrasion 
loss test are as shown in FIG. 6 though specifically described in the 
examples hereinafter given. As shown in FIG. 6, the reducing effect of the 
addition of the extreme pressure agent on the abrasion loss is remarkable. 
Conventional additives such as an acid-capturing agent, antioxidant, 
defoaming agent, etc. can be blended together with the extreme pressure 
agent. 
Next, there are explained below electrical insulating materials for the 
refrigerant compressor using flon 134a together with the refrigerating 
machine oil according to the present invention. As an insulating film used 
as electrical insulating material for the motor section, a crystalline 
plastics film having a glass transition temperature of 50.degree. C. or 
higher is used. The insulating film includes films of polyethylene 
terephthalates, polybutylene terephthalates, polyphenylene sulfides, 
polyether ether ketones, polyethylene naphthalates, polyamide-imides and 
olyimides; and composite films obtained by coating a film having a low 
glass transition temperature with a resin layer having a high glass 
transition temperature. These films are hardly deteriorated in tensile 
strength characteristics and electrical insulating characteristics and 
involve no practical problem. This is because the films carry in a much 
smaller amount of water and produce a much smaller amount of an acid than 
do conventional polyoxyalkylene glycol oils, and hence are hardly 
deteriorated by hydrolysis of the films themselves. 
An enamel coating having a glass transition temperature of 120.degree. C. 
or higher is used on a magnet wire used in the motor section. The enamel 
coating includes, for example, monolayers of polyester imides, polyamides, 
polyamide-imides and the like, and composite enamel coating films obtained 
by forming an upper layer having a high glass transition temperature on a 
lower layer having a low glass transition temperature. Like the 
above-mentioned films, these enamel coatings hardly show deterioration by 
hydrolysis, cracking, softening, swelling, a lowering of breakdown 
voltage, etc. and hence are useful for improving the reliability in 
practical. In some cases, a self-lubricating agent or an external 
lubricating agent is included in the enamel coating on the magnet wire, 
for imparting self-lubricating properties to improve the electrical 
workability. Fundamentally, the above characteristics of the enamel 
coating itself before the inclusion are retained. 
Lastly, a drying agent packed into the dryer of the refrigerating apparatus 
in which flon 134a and the aforesaid refrigerating machine oil according 
to the present invention coexist is explained below. In this invention, it 
is preferable to use a synthetic zeolite composed of a composite salt 
consisting of alkali metal silicates and alkali metal aluminates which has 
a pore diameter of 3.3 angstrom or less, a carbon dioxide absorption 
capacity at 25.degree. C. and at a carbon dioxide partial pressure of 250 
mmHg of 1.0% or less. As such a synthetic zeolite, XH-9 and XH-600 (trade 
names, mfd. by UNION SHOWA K.K.) can be exemplified. Both of them have a 
small fluorine ion adsorption. The same synthetic zeolite as above except 
for having a carbon dioxide gas adsorption capacity of 1.5% or more has a 
fluorine adsorption of as large of 0.24% or more and hence possesses 
deteriorated adsorption characteristics and breaking strength as molecular 
sieves. Moreover, corroded crystal disintegration product of such a 
synthetic zeolite chokes the piping of the refrigeration cycle or injures 
the sliding portions of bearings of the compressor. When the pore diameter 
in the present invention is specified in relation to the above carbon 
dioxide adsorption capacity in consideration of such conditions, the 
troubles described above are not caused and it becomes possible to compose 
a highly reliable refrigerating apparatus. 
Examples of the present invention are explained below with reference to 
FIGS. 1 to 6 and Tables 1 to 4. 
EXAMPLES 1 to 17 
These examples show embodiments for achieving the above first object of the 
present invention. In a closed rotary compressor concerned with a 
refrigeration cycle and a refrigerant compressor, flon 134a was used as a 
refrigerant, and as a refrigerating machine oil, there was used each ester 
oil listed in Table 1 which contained two or more ester groups in the 
molecule and had a viscosity at 40.degree. C. of 2 to 70 cSt and a 
viscosity at 100.degree. C. of 1 to 9 cSt. For comparison, data on 
conventional refrigerating machine oils are also shown in Table 1. 
FIG. 1 is a graph showing two-layer separation temperature which 
illustrates the miscibility of flon 134a with each refrigerating machine 
oil. The graph was obtained by enclosing flon 134a and the refrigerating 
machine oil in a high-pressure glass vessel, observing visually the 
two-layer separation state at each temperature and at each concentration 
of the refrigerating machine oil, and summarizing the observation results. 
The axis of abscissa refers to the concentration of the oil in flon 134a 
and the axis of ordinate to temperature. The first target value shown in 
FIG. 1 is a lower critical solution temperature necessary for a 
refrigerating apparatus such as a dehumidifier, which has a moderate 
evaporator temperature (0.degree. C. or lower). The second target value is 
a lower critical solution temperature necessary for a refrigerating 
apparatus such as a refrigerator, which has a low evaporator temperature 
(-30.degree. C. or lower). Both of the evaporator temperatures are 
specified values. 
From Table 1, it can be seen that SUNISO 4GSD (a trade name, naphthene 
type) and Z300A (a trade name, alkylbenzene type) both manufactured by 
JAPAN SUN OIL Co., Ltd. were not dissolved. A polyalkylene glycol, PAG56 
(a trade name, mfd. by JAPAN SUN OIL Co., Ltd.) had a lower critical 
solution temperature (shown by L1) of -60.degree. C. and an upper critical 
solution temperature (shown by U1) of 35.degree. C. The ester oils 
containing two or more ester groups in the molecule according to the 
present invention are so excellent in critical solution temperatures that 
their lower critical solution temperature (shown by L2) is -70.degree. C. 
and their upper critical solution temperature (shown by U2) 70.degree. C. 
or higher. The lower critical solution temperatures is an important factor 
for practical purposes in the heat exchanger of a refrigerating apparatus, 
and the upper critical solution temperature is an important factor for 
practical purposes in a refrigerant compressor. 
FIG. 9 is a diagram showing the structure of the refrigeration cycle of a 
refrigerating apparatus. The refrigerating apparatus comprising a 
refrigerant compressor 40, a condenser 41, a dryer 45, an expansion 
mechanism 42 and an evaporator 43 was operated by using each of the 
above-mentioned refrigerating machine oils together with flon 134a. 
Consequently, in the case of SUNISO 4GSD (a naphthenic mineral oil) and 
Z300A (an alkylbenzene oil) (trade names, mfd. by JAPAN SUN OIL Co., 
Ltd.), when the refrigerant was present in a large amount and lay idle in 
the compressor, a refrigerant layer having a high density and a 
refrigerating machine oil layer having a low density were present merely 
as a lower layer and an upper layer, respectively, owing to two-layer 
separation. Therefore, as shown in FIG. 7, i.e., the vertical 
cross-sectional view showing the principal part of a refrigerant 
compressor (an example of closed rotary compressor), oil supply to a shaft 
4A, a main bearing 5 and a sub-bearing 6 is carried out by suction of the 
refrigerant layer present merely as the lower layer through the suction 
opening 14 of a pump. The refrigerant layer has a lower viscosity than 
does the refrigerating machine oil. Therefore, when the refrigerant layer 
is supplied to the bearings, the resulting oil film is thin, so that 
contact between metal surfaces tends to occur. In addition, since the 
temperature of sliding frictional surfaces rises at once, the refrigerant 
was gasified, resulting in more severe conditions. When this phenomenon is 
repeated, damages due to scoring and seizing are caused in the shaft and 
the bearings, so that the performance characteristics of the refrigerant 
compressor are lost. 
When the conventional refrigerating machine oil is used in the heat 
exchanger of the refrigerating apparatus shown in FIG. 9, for example, the 
evaporator 43 used at 0.degree. to -60.degree. C., the refrigerating 
machine oil which has been discharged together with gas of the refrigerant 
from the compressor 40 undergoes two-layer separation in the evaporator 43 
and adheres to the inner wall of the piping of the heat exchanger, and 
there is caused the residence of the refrigerating machine oil or the heat 
insulation of the heat exchanger. Therefore, the conventional 
refrigerating machine oils greatly deteriorate the cooling capability of 
the refrigerating apparatus and are of no practical use. In this point, 
the polyalkylene glycol listed as Conventional Example 3 in Table 1 is 
advantageous because it has a lower critical solution temperature of 
-60.degree. C. and hence does not undergo two-layer separation in the 
evaporator 43. But, owing to its upper critical solution temperature of 
35.degree. C., it completely undergoes two-layer separation because the 
temperature of the compressor 40 during operation becomes at least 
80.degree. C. As in the case of Conventional Examples 1 and 2, when the 
polyalkylene glycol is supplied to the bearings, damages due to scoring 
and seizing are caused in the shaft and the bearing, so that the 
refrigerant compressor loses its performance characteristics. 
In a refrigerant compressor having a hermetic motor, for example, the 
rotary compressor shown in FIG. 7, a refrigerating machine oil is, of 
course, required to have characteristics as an electrical insulating oil. 
FIG. 2 shows the relationship between the water absorption and the volume 
resistivity of each of the ester oils according to the present invention 
and conventional mineral oil and polyalkylene glycol. Even in a condition 
in which the water content is controlled to be 500 ppm or less, the 
polyalkylene glycol as conventional example has a low volume resistivity 
of 10.sup.12 .OMEGA.cm or less owing to the ether linkages in the molecule 
and hence is not preferable. 
On the other hand, the refrigerating machine oil having ester linkages 
introduced thereinto according to the present invention has a high volume 
resistivity (a high insulating capability) of 10.sup.13 .OMEGA.cm or more 
which is in accordance with the standard value of electrical insulating 
oil prescribed in JIS C2320. Therefore, it can be sufficiently put to 
practical use. Although the mineral oil as conventional example has a high 
insulating capability, it has a bad miscibility with flon 134a and cannot 
be put to practical use. 
Next, the relationship among the kind, chemical structure and lower 
critical solution temperature of ester oils suitable for flon 134a is 
explained below in detail with reference to Table 1. 
The ester oil containing two or more ester groups in the molecule which is 
used in the present invention includes esters of monobasic or polybasic 
organic acids and polyhydric alcohols. Typical examples of the ester oil 
are hindered ester oils and complex ester oils which are represented by 
esters of neophentyl glycol, esters of trimethylolpropane or 
trimethylolethane, and esters of pentaerythritol. Table 1 shows the 
relationship amount the name, viscosity and critical solution temperatures 
of typical chemically synthesized products. 
TABLE 1 
______________________________________ 
Critical solution 
Viscosity temperature (.degree.C.) 
Sample refrigerating 
(cst) U L 
machine oil 40.degree. C. 
100.degree. C. 
(upper) 
(lower) 
______________________________________ 
Con- 
ventional 
Example 
1 Naphthenic mineral oil 
55.1 5.9 -- &gt;40 
(SUNISO 4GSD) 
2 Alkylbenzene oil 
60.1 6.0 -- &gt;40 
(SUNISO Z300A) 
3 Propylene glycol 
54.0 10.0 35 -60 
monoether (PAG56) 
Example 
1 Note 1 NPG/n-C.sub.8 
4.8 1.7 -29 
2 NPG/n-C.sub.7 
2.8 1.2 -61 
3 NPG/2EH 7.0 2.1 &gt;80 -60 
4 NPG/i-C.sub.7 
5.5 1.8 &gt;80 -70 
5 NPG/i-C.sub.11 
14.9 3.8 &gt;80 -40 
6 Note 2 TMP/n-C.sub.7 
13.9 3.4 -20 
7 TMP/n-C.sub.6 
10.8 2.8 -62 
8 TMP/i-C.sub.8 
32.2 5.2 -27 
9 TMP/2EH 22.0 4.2 -33 
10 TMP/i-C.sub.7 
14.9 3.4 &gt;80 -60 
11 Note 3 PET/n-C.sub.6 
17.5 3.7 -44 
12 PET/2EH 52.0 6.7 -8 
13 PET/i-C.sub.7 
28.0 4.8 -40 
14 Note 4 NPG/Glut/ 32.6 5.9 &gt;80 &lt;-75 
n-C.sub.6 
15 NPG/i-C.sub.7 + 
AZP/NPG/ 29.5 5.0 &gt;80 -45 
n-C.sub.10 
16 AZP/NPG/ 54.5 7.3 &gt;80 -60 
n-C.sub.10 
17 Glut/NPG/ 56.6 8.6 &gt;80 -60 
i-C.sub.6 
______________________________________ 
Note 1 
##STR12## 
Note 2 
##STR13## 
Note 3 
PTE: esters of pentaerythritol 
Note 4: 
complex esters, nC.sub.10 : CH.sub.3 (CH.sub.2).sub.8 COOH, iC.sub.6 : 
CH.sub.3 (CH.sub.3)CH(CH.sub.2).sub.2 COOH 
Of the sample names in Table 1, the names of chemically synthesized ester 
oils are abbreviated. For example, in the case of NPG/n-C.sub.8, NPG is an 
abbreviation of neopentyl glycol, n-C.sub.8 is an abbreviation of a normal 
organic acid (a straight-chain fatty acid) having 8 carbon atoms, and 
NPG/n-C.sub.8 denotes an ester of neopentyl glycol and the normal organic 
acid (the straight-chain fatty acid) having 8 carbon atoms. In the case of 
NPG/2EH, 2EH is an abbreviation of 2-ethylhexanoic acid and NPG/2EH 
denotes an ester of neopentyl glycol and 2-ethylhexanoic acid. 
1) As shown in Examples 1 to 4, the esters of neopentyl glycol (NPG) are 
esters of neopentyl glycol as dihydric alcohol and a monocarboxylic acid 
as monobasic organic acid, and are characterized by containing two ester 
groups in the molecule. Such a chemical structure has an important bearing 
on the miscibility with flon 134a and the viscosity characteristics of the 
oils. 
That is, ester oils of a monocarboxylic acid having 7 to 8 carbon atoms 
were satisfactory and had a lower critical solution temperature of 
-29.degree. C. to -70.degree. C. and a viscosity at 40.degree. C. of 2.8 
to 7.0 cSt. 
The smaller the number of carbon atoms of the monocarboxylic acid (the 
fatty acid), the lower the lower critical solution temperature. It was 
found that the lower critical solution temperature of the ester of 
2-ethylhexanoic acid (2EH) of Example 3 and the ester of isoheptanoic acid 
(i-C.sub.7) of Example 4 which have a branched chain in the molecule is 
advantageously lower than that of the esters of Examples 1 and 2, 
respectively. The case of increasing the number of carbon atoms of the 
carboxylic acid to 11 for increasing the viscosity is Example 5. The ester 
of Example 5 was found to have a viscosity at 40.degree. C. of 14.9 cSt 
and a lower critical solution temperature of -40.degree. C. at the lowest. 
2) Next, the esters of trimethylolpropanol (TMP) containing three ester 
linkages in the molecule are explained below with reference to Examples 6 
to 10. 
The ester oils obtained by the condensation of trimethylolpropane (TMP) as 
trihydric alcohol and a monocarboxylic acid as monobasic organic acid 
contain three ester groups in the molecule, and the monocarboxylic acid 
has 6 to 8 carbon atoms. The ester oils have a viscosity at 40.degree. C. 
of 10.8 to 32.2 cSt and a lower critical solution temperature of 
-20.degree. C. to -60.degree. C. Of these ester oils, ester oils having a 
lower critical solution temperature of -20.degree. C. or lower are the 
ester oil of heptanoic acid (n-C.sub.7) of Example 6, the ester oil of 
octanoic acid (n-C.sub.8) of Example 8 and the ester oil of 
2-ethylhexanoic acid (2EH) of Example 9. Ester oils having a lower 
critical solution temperature of -60.degree. C. or lower are the ester oil 
of hexanoic acid (n-C.sub.6) of Example 7 and the ester oil of 
isoheptanoic acid (i-C.sub.7) of Example 10. The ester oils of Examples 6 
to 10 are also characterized in that the smaller the number of carbon 
atoms, the lower the lower critical solution temperature, and that the 
lower critical solution temperature of the ester oils containing a 
branched chain is lower than that of the ester oils containing no branched 
chain even when the former ester oils and the latter ester oils have the 
same number of cabon atoms. 
3) As shown in Examples 11 to 13, the ester oils obtained by the 
condensation of pentaerythritol (PET) as tetrahydric alcohol and a 
monocarboxylic acid contain 4 ester groups in the molecule, and the 
monocarboxylic acid has 6 to 8 carbon atoms. The ester oils have a high 
viscosity at 40.degree. C. of 17.5 to 52.0 cSt and a lower critical 
solution temperature of -8.degree. C. to -44.degree. C. Thus, the lower 
critical solution temperature is shifted to higher temperatures, as 
compared with the above-mentioned ester oils of dihydric alcohols and 
trihydric alcohols. Of the ester oils of Examples 11 to 13, ester oils 
having a lower critical solution temperature of -40.degree. C. or lower 
are the ester oil of hexanoic acid (n-C.sub.6) of Example 11 and the ester 
oil of isoheptanoic acid (i-C.sub.7) of Example 13. The ester oils of 
Examples 11 to 13 are also characterized in that the smaller the number of 
carbon atoms, the lower the lower critical solution temperature, and that 
the lower critical solution temperature of the ester oils containing a 
branched chain is lower than that of the ester oil containing no branched 
chain. 
4) As a method for introducing 4 ester groups into the molecule, there is a 
method in which esterification is carried out by condensing a polyhydric 
alcohol and a monocarboxylic acid with a dicarboxylic acid (i.e. a typical 
dibasic organic acid) as the central constituent. By this method, the 
lower critical solution temperature can easily be lowered and the 
viscosity can easily be increased. Esters obtained by such a molecular 
design are complex esters and are explained with Examples 14 to 17 of the 
present invention. 
Example 14 shows a complex ester of glutaric acid (abbreviated as Glut) as 
dicarboxylic acid, neopentyl glycol (NPG) as dihydric alcohol, and 
hexanoic acid (C.sub.6) as monocarboxylic acid. This complex ester had a 
viscosity at 40.degree. C. of 32.6 cSt, a viscosity at 100.degree. C. of 
5.9 cSt, and a lower critical solution temperature of -75.degree. C. or 
lower. 
Example 15 shows the case where an ester having moderate viscosity grade 
was prepared by mixing the esters of Examples 4 and 16. This ester was 
also found to possess a lower critical solution temperature not much 
changed. 
Example 16 shows a complex ester of adipic acid (abbreviated as AZP) as 
dicarboxylic acid, neopentyl glycol (NPG) as dihydric alcohol, and 
decanoic acid (n-C.sub.10) as monocarboxylic acid. Example 17 shows a 
complex ester of glutaric acid (Glut) as dicarboxylic acid, neopentyl 
glycol (NPG) as dihydric alcohol, and isohexanoic acid (i-C.sub.6) as 
monocarboxylic acid. These complex esters were found to be so excellent 
that they had a viscosity at 40.degree. C. of 54.5 to 56.6 cSt, a 
viscosity at 100.degree. C. of 7.3 to 8.6 cSt, and a lower critical 
solution temperature of -60.degree. C. These results indicate that a 
complex ester having a suitable viscosity can be synthesized by 
determining properly the number of carbon atoms (C.sub.2 to C.sub.10) of a 
dicarboxylic acid as dibasic organic acid and the number of carbon atoms 
(C.sub.5 to C.sub.15) of a monocarboxylic acid as monobasic acid, and 
condensing the dicarboxylic acid, the monocarboxylic acid, and a 
polyhydric alcohol in a properly chosen molar ratio. 
When these Examples are arranged, the esters can be represented as follows 
by general formulas: 
Esters of neopentyl glycol: 
EQU (R.sub.1 --CH.sub.2).sub.2 --C--(CH.sub.2 OCOR.sub.2).sub.2(1) 
Esters of trimethylolalkane: 
EQU R.sub.1 --CH.sub.2 --C--(CH.sub.2 OCOR.sub.2).sub.3 (2) 
Esters of pentaerythritol: 
EQU C--(CH.sub.2 --OCOR.sub.2).sub.4 (3) 
Complex esters: 
##STR14## 
In addition, examples of easily obtainable esters are esters of 
dipentaerythritol: 
EQU (R.sub.2 COOCH.sub.2).sub.3 C--CH.sub.2 --O--CH.sub.2 --C(CH.sub.2 
--OCOR.sub.2).sub.3 (5) 
In the above formulas (1) to (5), R.sub.1 is H or an alkyl group having 1 
to 3 carbon atoms, R.sub.2 is a straight-or branched-chain alkyl group 
having 5 to 12 carbon atoms, R.sub.3 is an alkyl group having 1 to 3 
carbon atoms, and n is an integer of 0 to 5. 
The viscosity could be optionally determined by choosing the kinds of the 
polyhydric alcohol and the carboxylic acid(s). 
A moderate viscosity could easily be attained by blending a low-viscosity 
oil and a high-viscosity oil. 
In the case of a refrigerating apparatus using a flon type refrigerant 
containing no chlorine, for example, flon 134a a refrigerating machine oil 
capable of imparting fundamentally satisfactory performance 
characteristics and reliability to a compressor and the refrigerating 
apparatus can be obtained by selecting an oil having a lower critical 
solution temperature of 0.degree. C. or lower (the first target value) or 
an oil having a lower critical solution temperature of -30.degree. C. or 
lower (the second target value) both of which have a viscosity at 
40.degree. C. of 2 to 70 cSt, preferably 5 to 32 cSt and a viscosity at 
100.degree. C. of 1 to 9 cSt, preferably 2 to 6 cSt, from the hindered 
esters and the complex esters which contain two or more ester linkages in 
the molecule. 
It was confirmed that these ester type refrigerating machine oils have a 
good miscibility not only with flon 134a but also with all flon type 
refrigerant gases containing no chlorine, for example, flon 152a 
(difluoroethane CH.sub.3 CHF.sub.2). The refrigerating machine oils were 
effective in imparting high performance characteristics and a high 
reliability to a refrigerating apparatus. 
In addition, it was confirmed that since these ester oils according to the 
present invention are highly soluble also in conventional 
chlorine-containing flon type refrigerants (chlorofluorohydrocarbon type 
refrigerants) such as flon 12 and flon 22, they are effective also when 
used in part in admixture with these refrigerants. 
However, since the conventional chlorine-containing flon type refrigerants 
are included in the list of compounds under regulation in use because of 
the problem of environmental disruption, it is preferable to adjust the 
proportion of the refrigerants to 50% or less and that of the ester oil 
according to the present invention to 50% or more. 
Next, an example of refrigerating apparatus for achieving the second object 
of the present invention is given below. 
EXAMPLE 18 
The rotary compressor shown in FIG. 7 which was a refrigerant compressor 
was incorporated into a refrigerating apparatus having the constitution 
shown in FIG. 9. At a compressor temperature of 100.degree. C. and a 
discharged gas pressure of 9.5 to 10 kgf/cm.sup.2 G which were conditions 
of examining the reliability of a refrigerator, a relationship between the 
viscosity of a refrigerating oil stored in the compressor and the 
coefficient of performance (COP), i.e., the ratio of the refrigerating 
capacity of the compressor to an input, was measured by using some of the 
ester oils with a typical viscosity grade exemplified in Table 1. The 
results obtained are shown in FIG. 3. 
FIG. 3 shows a relationship between the actual viscosity of each 
refrigerating machine oil and the coefficient of performance (COP) which 
was determined for the ester oils according to the present invention 
having a viscosity at 40.degree. C. of 5 to 56 cSt and conventional 
examples, i.e., a polyalkylene glycol and an alkylbenzene oil (SUNISO 
Z-300A) used in combination with flon 12. In FIG. 3, the axis of abscissa 
refers to the actual viscosity of each refrigerating machine oil stored in 
the rotary compressor, and the axis of ordinate to the coefficient of 
performance (expressed in terms of a relative value) of the compressor. 
According to FIG. 3, when refrigerating machine oils are compared in the 
coefficient of performance by taking the coefficient of performance 
attained by the conventional combination of flon 12 and Z-300A (an 
alkylbenzene oil) having a viscosity at 40.degree. C. of 56 cSt, as 1.0, 
the coefficient of performance attained for the combination of the 
polyalkylene glycol (PAG56) of Conventional Example 3 and flon 134a is as 
small as 0.859, indicating that the energy efficiency is lowered by about 
14%. 
On the other hand, the complex ester according to the present invention 
with a viscosity at 40.degree. C. of 56.6 cSt of Example 17 gave a 
satisfactory coefficient of performance of 0.906. It can be speculated 
that this result is attributable to a reducing effect on friction loss 
caused on the basis of the journal bearing theory represented by the 
theory of the formula (9), a reducing effect on oil-agitating power, a 
heat-dissipating effect, etc. which are brought about because the 
viscosity of the refrigerating machine oil which contains flon 134a 
dissolved therein becomes as low as 4.35 cSt under the same operation 
conditions. 
When the ester oils according to the present invention which had a still 
lower viscosity of 5 to 32 cSt (at 40.degree. C.) were compared in the 
coefficient of performance under the same conditions, the ester oil with a 
viscosity of 32.6 cSt (at 40.degree. C.) of Example 14, the ester oil with 
a viscosity of 14.9 cSt (at 40.degree. C.) of Example 5 and the ester oil 
with a viscosity of 14.9 cSt (at 40.degree. C.) of Example 10 gave 
coefficient values of 0.926, 0.966 and 0.973, respectively. Thus, the 
coefficient of performance was increased in that order. On the other hand, 
in the case of the ester oil with a viscosity of 5.5 cSt (at 40.degree. 
C.) of Example 4, the coefficient of performance was 0.953, namely, it 
showed a tendency to be decreased a little. 
From these results, it can be seen that an ideal ester oil suitable for the 
rotary compressor is an ester oil which has a viscosity at 40.degree. C. 
in the range of 5 to 32 cSt (exactly, 5.5 to 32.6 cSt), i.e., a range 
around the most suitable value of 14.9 cSt, and contains two or more ester 
linkages in the molecule, as described above. 
EXAMPLE 19 
Flon 134a and each of the refrigerating machine oils according to the 
present invention exemplified in Table 1 were used in a low-pressure 
vessel type reciprocating compressor, and the compressor was incorporated 
into a refrigerator, i.e., a refrigerating apparatus. The refrigerator was 
then subjected to a high-temperature reliability test (pressure in case 
1.6 kg/cm.sup.2 abs, case temperature 85.degree. C., 100 V, 50 Hz). 
FIG. 4 shows the test results. In this graph, the axis of abscissa refers 
to the measured value of viscosity of the refrigerating machine oil, and 
the axis of ordinate to the coefficient of performance (COP). The graph 
was obtained by plotting the coefficient of performance against the actual 
viscosity in actual operation of each of the sample refrigerating machine 
oils with a viscosity at 40.degree. C. of 5.5, 14.9, 22.0, 32.6 and 56.6 
cSt, respectively, shown in Examples in Table 1. The coefficient of 
performance is in linear relation with the actual viscosity. 
From the results shown in FIG. 4, it can be seen that the lower the 
viscosity of the refrigerating machine oil, the larger the coefficient of 
performance of the low-pressure vessel type reciprocating compressor. The 
refrigerating machine oils having an actual viscosity of 2 to 4.2 cSt and 
a viscosity at 40.degree. C. of 5.5 to 14.9 cSt can be said to be 
excellent. When the actual viscosity is less than 2 cSt, a decrease of the 
coefficient of performance and a lowering of the reliability of bearings 
tend to be caused because in the case of using a conventional material 
such as cast iron or an iron-based sintered material for producing the 
sliding parts of the compressor, the precision of finishing the surfaces 
of the sliding parts is limited, and therefore at too low an actual 
viscosity, the lubrication on the surfaces gets into the so-called 
boundary lubrication region in which the contact between metal surfaces 
occurs. 
EXAMPLE 20 
The lubrication in a refrigerating machine and a refrigerant compressor for 
achieving the third object of the present invention is explained below 
with reference to the following example. 
For evaluating the lubrication, there were carried out a FALEX test in 
which a seizing load was measured in the air, and a high-pressure 
atmosphere friction test in which a seizing load was measured in a 
refrigerating machine oil containing 50% of flon 134a dissolved therein. 
FIG. 5 is a graph showing the correlation between the results of the two 
tests. The seizing load is as follows. An increasing load was applied to a 
rotating sample pin from both sides and a load at which seizing was caused 
was expressed in pound (lb). 
In the present example, the ester oil of trimethylolpropane (TMP) and 
isoheptanoic acid (i-C.sub.7) of Example 10 exemplified in Table 1 was 
employed as a typical example of a refrigerating machine oil used in the 
refrigerating apparatus of the present invention, and there was determined 
a relationship between the kind and amount of an extreme pressure agent 
added to the ester oil and the lubricating characteristics. As to 
materials for test pieces used for the evaluation of the lubrication, the 
materials for the pin and a block were standard materials, i.e., SNC-21 
(nickel chrome steel) according to the standard of JIS and SUM 41 
(resulfurized free-cutting steel) according to the standard of JIS, 
respectively. On the other hand, in the high-pressure atmosphere friction 
test, there was measured a load at which seizing was caused by friction 
between cylinders made of a material for shaft (eutectic graphite cast 
iron) and a material for roller (eutectic graphite cast iron tempered 
material), respectively, which had given satisfactory results in rotary 
compressors. 
As shown in the case of sample No. 1 in FIG. 5, the ester oil (the oil of 
Example 10) containing no extreme pressure agent gave a FALEX seizing load 
of 700 lb and a seizing load of as low as 90 kgf/cm.sup.2 in a flon 134a 
atmosphere. On the other hand, in the case of sample No. 2 and sample No. 
3, the FALEX seizing load was further increased by 400 lb to reach 1100 lb 
and the seizing load in a flon 134a atmosphere was increased by 90 
kg/cm.sup.2 to reach 180 kg/cm.sup.2, owing to addition of each of the 
following extreme pressure agents. In the case of sample No. 2, CHELEX 
H-10 (a trade name, mfd. by SAKAI CHEMICAL INDUSTRY Co., Ltd.) which was 
an acidic phosphoric acid containing an active OH group in the molecule, 
was added in an amount of 1%. In the case of sample No. 3, an ester 
compound of an alkylene glycol and phosphoric acid (butylpolyoxypropylene 
phosphate ester) was added in an amount of 1%. 
That is, it was actually proved that the phosphorus-containing compounds 
such as the acidic phosphoric ester and the alkylene glycol phosphate 
ester compound act effectively as extreme pressure agents for preventing 
seizing, regardless of the presence of flon 134a. 
Next, a FALEX test was carried out continuously for a maximum time of 120 
minutes while keeping an applied load constant at 100 lb, and the abrasion 
loss of a pin, i.e., an iron-based test piece, was measured. The results 
obtained are shown in FIG. 6. In the case of the oil of sample No. 4 which 
contained no extreme pressure agent, the pin was worn in an amount of 25 
mg. On the other hand, in the case of both of the oils containing each of 
the above-mentioned phosphorus-containing compounds, the abrasion loss was 
as small as 0.4 mg as shown for sample No. 7 and sample No. 8, namely, the 
abrasion loss could be reduced to one-fifth or less. The amount of the 
phosphorus-containing compound added is effective from about 0.05 wt % as 
shown for sample No. 5. The effect of the compound is increased with an 
increase of the amount. But when the amount exceeds 10 wt %, the improving 
effect on the lubrication hits the ceiling, so that the addition of the 
compound becomes economically disadvantageous and hence becomes 
unpractical. 
The abrasion loss could be reduced by increasing the viscosity of oil from 
14.9 cSt (at 40.degree. C.) of sample No. 4 to 56.6 cSt (40.degree. C.) of 
sample No. 6. 
From the facts described above, it was found that the seizing load, 
abrasion resistance and lubrication of the iron-based sliding members 
could be greatly improved by adding a phosphorus-containing compound such 
as an acidic phosphoric ester, phosphoric ester, alkylene glycol phosphate 
ester or the like as an extreme pressure agent to the refrigerating 
machine oil used in the present invention, in an amount of 0.05 to 10 wt 
%, or by adjusting the viscosity of the oil to a high value instead of 
adding the extreme pressure agent. The refrigerating machine oil which 
contains the extreme pressure agent exhibits excellent performance 
characteristics particularly in the presence of a flon type refrigerant 
containing no chlorine, such as flon 134a. 
EXAMPLE 21 
An example for achieving the fourth object of the present invention is 
described below. The behaviors of electrical insulating materials used in 
the hermetic motor of a compressor, in the presence of both flon 134a and 
the refrigerating machine oil according to the present invention were 
evaluated. The results obtained are explained below with reference to 
Table 2 and Table 3. 
Flon 134a and refrigerating machine oils were evaluated by observing the 
degree of deterioration of characteristics of a magnet wire (an enameled 
wire) and an insulating film material by a sealed tube test, for 
preventing external influence. 
(1) Insulating characteristics of a magnet wire (an enameled wire) 
As magnet wire test pieces, two kinds of test pieces, i.e., 5% elongated 
products and twisted-pair test pieces were subjected to a sealed tube test 
at 150.degree. C. for 40 days. An explanation is given below with 
reference to the results shown in Table 2. 
As a result of the sealed tube test carried out for a combination of flon 
134a and the polyalkylene glycol listed as Conventional Example 3 in Table 
1 which is a refrigerating machine oil said to be suitable for flon 134a 
5% elongated products of both the polyester wire (PEW) of sample No. 9 and 
the ester imide wire (EIW-R) of sample No. 10 in Table 2 were crazed, and 
the retention of the dielectric breakdown voltage of twisted-pair test 
pieces of these two kinds of wires was greatly lowered to 30 to 32%. 
On the other hand, the same evaluation as above was carried out for a 
combination of flon 134a and the composite ester oil composed of glutaric 
acid (Glut), neopentyl glycol (NPG) and isohexanoic acid (i-C.sub.6) which 
is a refrigerating machine oil used in the present invention and is 
exemplified in Table 1. Consequently, the same polyester wire (whose glass 
transition temperature is shown in Table 2) and polyester imide wire as 
the wires which were described above and deteriorated as conventional 
examples sample No. 9 and sample No 10, showed no abnormality in 
appearance, as shown for sample No. 11 and sample No. 12. The retention of 
the dielectric breakdown voltage of these samples was as high as 95% or 
more, indicating that the degree of deterioration of the magnet wires was 
very low. The reason is as follows. The refrigerating machine oil 
according to the present invention has a low water content in the early 
stages and a high thermal stability, and hardly produce an acidic 
substance capable of accelerating hydrolysis, and these characteristics 
bring about the improving effects. 
Sample No. 13 was obtained by coating the ester imide wire of sample No. 12 
with a polyimide layer to form a composite. Sample No. 14 was a wire 
coated with a polyamide-imide alone (AIW). Both samples had satisfactory 
characteristics. It was found that such a magnet wire obtained by thus 
coating a layer with a high glass transition temperature on a layer with a 
low glass transition temperature contributes to the improvement of the 
reliability of a compressor because the upper coating layer is effective 
as protective layer against an attack of flon 134a and the refrigerating 
machine oil. 
(2) Insulating characteristics of insulating films 
As a sealed tube test on insulating films for motor, an insulating strength 
test at 130.degree. C. for 40 days was carried out, whereby the films were 
evaluated with respect to the appearance and the retention of tensile 
strength. The results obtained are shown in Table 3. 
When a polyester film (Lumilar X.sub.10, a trade name, mfd. by Toray 
Industries, Inc.) conventionally used in the hermetic motor of a 
compressor was used in the conventional polyalkylene glycol oil shown for 
sample No. 15, its oligomer component was precipitated in the oil and the 
retention of tensile strength was 83%. 
On the other hand, in a combination of the complex ester oil of Example 17 
according to the present invention and flon 134a no oligomer was 
precipitated and the retention of tensile strength was as high as 89% or 
more in the case of all of Lumilar X.sub.10 of sample No. 16, PA-61M (a 
trade name, mfd. by Hitachi Kasei Co., Ltd.), i.e., the 
polyamide-imide-coated polyester of sample No. 17, the polyphenylene 
sulfide (PPS) film of sample No. 18, and the polyether ether ketone (PEEK) 
film of sample No. 19. Thus, it was found that the electrical insulating 
system of a compressor using flon 134a can be markedly improved in 
reliability. 
That is, it was found that the insulation system of a hermetic motor can be 
completed by properly selecting a film from the group consisting of 
polyester films, polyamide-imide-coated polyester films, PPS films and 
PEEK films which have a glass transition temperature of 65.degree. C. or 
higher, and using the same in the presence of both flon 134a and the 
refrigerating machine oil containing two or more ester groups in the 
molecule according to the present invention. It was found that when the 
insulation system is thus completed, there can be solved the problem of 
precipitation of an oligomer component (the problem described above for 
the oil of Conventional Example 3 shown for sample No. 15), the problems 
in the performance characteristics of a compressor and a refrigerating 
apparatus which are caused by the lowering of the film strength, and the 
practical problems in the long-term reliability. 
TABLE 2 
__________________________________________________________________________ 
Results of evaluating performance 
characteristics with respect to resistance to 
Glass an oil and flon 134a 
transition Appearance 
Retention of 
Sample 
Insulation-coated 
temperature change 
dielectric breakdown 
No. winding wire 
(.degree.C.) 
Oil tested 
(Note 1) 
voltage (Note 2) 
__________________________________________________________________________ 
9 PEW 120-140 
Conventional 
Clazed 
30 
(Polyester) Example 3 
10 EIW-R 190-210 
Conventional 
Clazed 
32 
(Polyester imide) 
Example 3 
11 PEW 120-140 
Example 17 
No 95 
(Polyester) abnormality 
12 EIW-R 190-210 
" No 98 
abnormality 
13 RFW-V (Upper layer 
Lower layer 
" No 
polyamide/lower layer 
190-210 abnormality 
98 
polyester imide) 
Upper layer 
250-310 
14 AIW 250-310 
" No 98 
(Polyamide imide) 
abnormality 
__________________________________________________________________________ 
Sealed tube test: 150.degree. C. .times. 40 days 
Note 1: 5% elongated wire 
Note 2: A relative value obtained for a twisted pair test piece by 
dividing a value after the test by a value before the test (taken as 100) 
TABLE 3 
__________________________________________________________________________ 
Results of evaluating performance 
Glass characteristics with respect to resistance to 
transition 
an oil and flon 134a 
Sample temperature Appearance 
Retention of tensile 
No. Insulating film 
(.degree.C.) 
Oil tested 
change strength (Note 1) 
__________________________________________________________________________ 
15 Lumilar .times. 10 
65 Conventional 
Oligomer was 
89 
(polyester) Example 3 
precipitated 
16 Lumilar .times. 10 
65 Example 17 
None 89 
17 PA-61M 65 " None 90 
(Polyamide-imide- 
coated polyester) 
18 PPS (Polyphenylene 
85 " None 95 
sulfide) 
19 PEEK (Polyether ether 
143 " None 98 
ketone) 
__________________________________________________________________________ 
Sealed tube test; 130.degree. C. .times. 40 days 
Note 1: A relative value obtained by dividing a value after the test by a 
value before the test(taken as 100). 
EXAMPLE 22 
An example for achieving the fifth object of the present invention is 
described below. 
It is known that particularly in refrigerating apparatus using a heat 
exchanger at 0.degree. C. or lower, the control of water content in the 
refrigerating apparatus has an important influence on the cooling 
capability and the assurance of the quality of an electrical insulating 
material. Therefore, the establishment of a technique for removing water 
is indispensable for the system of the refrigerating apparatus. 
In a refrigeration cycle composed as shown in FIG. 9, flon 134a gas 
discharged from a compressor 40 is condensed into a liquid refrigerant by 
heat dispersion in a condenser 41. This high-temperature, high-pressure 
liquid refrigerant is transformed into low-temperature, low-pressure wet 
vapor by an expansion mechanism 42 and sent to an evaporator 43. In this 
series of steps, the water in the refrigerating apparatus is adsorbed and 
removed by a drying agent represented by synthetic zeolite in a dryer 45 
provided between the condenser 41 and the expansion mechanism 42. It is 
important to choose the kind of the drying agent in consideration of a use 
environment in which the refrigerating machine oil according to the 
present invention and flon 134a coexist. The suitability of the drying 
agent is explained below with reference to Examples shown in Table 4. 
Drying agents tested are synthetic zeolites having trade names of Molecular 
Sieves all manufactured by UNION SHOWA K.K. These synthetic zeolites are 
classified according to the adsorption capacity (%) at 25.degree. C. and 
at a carbon dioxide gas partial pressure of 250 mmHg which is used as an 
indication of the distribution of the diameter of pores for adsorption. 
As to the suitability of the synthetic zeolites for flon 134a and the 
refrigerating machine oil according to the present invention, the results 
of a sealed tube test shown in Table 4 are explained below. 
It was found that the synthetic zeolite composed mainly of sodium aluminate 
and sodium silicate shown as sample No. 20 (a conventional example; trade 
name 4ANRG) has a fluorine ion adsorption of as large as 1.05%, so that 
problems due to the lowering of the strength or formation into powder are 
caused by the reaction of the synthetic zeolite. Sample No. 21 (a 
comparative example; trade name 4AXH-6) and sample No. 22 (a comparative 
example; trade name XH-7) which are composed mainly of sodium aluminate, 
potassium aluminate, sodium silicate and potassium silicate have a carbon 
dioxide gas adsorption capacity of 4.5 to 1.5% and a reduced fuorine ion 
adsorption of 0.24%. But, they cannot put into practical use because their 
fluorine ion adsorption is still too large. 
Sample No. 23 (an example; trade name XH-600) and sample No. 24 (an 
example; trade name XH-9) which consist of a synthetic zeolite composed 
mainly of potassium aluminate, sodium aluminate, potassium silicate and 
sodium silicate have a carbon dioxide gas adsorption capacity of 0.2% and 
a greatly reduced fluorine adsorption of 0.04%. Since a fluorine ion 
adsorption which permits practical use is 0.1% or less, the value of 0.2% 
indicates that these samples are sufficiently usable. 
The deterioration of characteristics of a synthetic zeolite itself by the 
adsorption of molecules of flon 134a is dependent on the distribution of 
pore diameter of the synthetic zeolite. It has been confirmed that for 
adjusting the fluorine ion adsorption to 0.1% or less, the employment of a 
synthetic zeolite whose carbon dioxide gas adsorption capacity has been 
adjusted to 1.0% or less is sufficient. That is, the following was found. 
When a synthetic zeolite composed of alkali metal silicates and alkali 
metal aluminates whose carbon dioxide gas adsorption at 25.degree. C. and 
at a carbon dioxide gas partial pressure of 250 mmHg has been adjusted to 
1.0% or less, for example, Molecular Sieves XH-600 or XH-9 (trade names, 
mfd. by UNION SHOWA K.K.), is used as a drying agent in a refrigerating 
apparatus using flon 134a and the refrigerating machine oil containing two 
or more ester linkages in the molecule according to the present invention, 
which are placed together, only water can be effectively removed and 
fluorine ion adsorption hardly produce influences such as formation into 
powder or a lowering of the strength of beads, and therefore such a drying 
agent is very excellent for practical purposes. 
TABLE 4 
______________________________________ 
Sealed tube test* 
Drying CO.sub.2 adsorption 
Decomposition 
agent capacity (%) rate of Fluorine ion 
Sample 
Name of CO.sub.2 partial pressure 
refrigerant 
adsorption 
No. sample 250 mmHg (25.degree. C.) 
(%) (%) 
______________________________________ 
20 4ANRG 12.0 0.028 1.05 
21 4AXH-6 4.5 0.032 0.24 
22 XH-7 1.5 0.035 0.24 
23 XH-600 0.2 0.042 0.04 
24 XH-9 0.2 0.04 0.04 
______________________________________ 
Sealed tube test: 150.degree. C., 7 days 
The carbon dioxide gas adsorption capacity at 25.degree. C. and at a carbon 
dioxide gas partial pressure of 250 mmHg should be 1.0% or less, and it is 
preferably as small as possible. When it is zero %, the drying agent 
absorbs water alone selectively but not fluorine ions, so that the drying 
agent becomes ideal molecular sieves. The present invention is constituted 
as explained above and hence has the following effects. 
(1) By using the refrigerating machine oil described below, in a 
refrigerating apparatus comprising a compressor, condenser, dryer, 
expansion mechanism and evaporator and using a flon type refrigerant 
containing no chlorine and having a critical temperature of 40.degree. C. 
or higher which is represented by flon 134a the performance 
characteristics and reliability of the compressor and the refrigerating 
apparatus can be markedly improved because the refrigerating machine oil 
and the refrigerant are highly miscible with each other without their 
separation into two layers in the whole temperature range where the 
compressor and the refrigerating apparatus are used, and hence a 
lubricating oil film on the shaft and bearings of the compressor and the 
refrigerant-heat-transferring capability of a heat exchanger are assured. 
The refrigerating machine oil comprises as base oil an ester oil according 
to the present invention which contains two or more ester linkages in the 
molecule and has a refrigerating machine oil viscosity at 40.degree. C. of 
2 to 70 cSt, preferably 5 to 32 cSt and a refrigerating machine oil 
viscosity at 100.degree. C. of 1 to 9 cSt, preferably 2 to 6 cSt. The 
refrigerating machine oil has a lower critical solution temperature of 
0.degree. C. or lower or -30.degree. C. or lower, and is used in the first 
target, i.e., a moderate-temperature refrigerating apparatus such as a 
dehumidifier, or the second target, i.e., a low-temperature refrigerating 
apparatus such as a refrigerator, respectively. 
(2) Moreover, the performance characteristics and the reliability can be 
improved by an improving effect on the lubrication in the sliding portions 
of bearings of the refrigerant compressor which is obtained by adding a 
phosphoric ester type extreme pressure agent having OH groups in the 
molecule and other additives such as an abrasion-preventing agent, 
acid-capturing agent, antioxidant, defoaming agent, etc. to the 
above-mentioned refrigerating machine oil. 
(3) By simultaneous use of the refrigerating machine oil containing two or 
more ester linkages in the molecule according to the present invention 
described below and flon 134a the so-called performance characteristics 
can be improved, namely, the coefficient of performance indicating the 
performance characteristics of the compressor can be increased, the power 
consumption of the refrigerating apparatus using the compressor can be 
reduced, and the refrigerating capacity can be increased. In a 
high-pressure vessel type rotary compressor, the refrigerating machine oil 
is one which has a viscosity at 40.degree. C. of 2 to 70 cSt, preferably 5 
to 32. In a low-pressure vessel type reciprocating compressor, the 
refrigerating machine oil is one which has a viscosity at 40.degree. C. of 
2 to 70 cSt, preferably 5 to 15 cSt. 
(4) The electrical insulating performance and long-term reliability of the 
refrigerating apparatus can be markedly improved by using an 
insulation-coated winding wire with a glass transition temperature of 
120.degree. C. or higher and an insulating film with a glass transition 
temperature of 70.degree. C. or higher as insulating materials for a 
motor, and a refrigerating machine oil comprising as base oil the ester 
oil according to the present invention, in a refrigerant compressor using 
a flon type refrigerant containing no chlorine represented by flon 134a. 
(5) By using a synthetic zeolite composed of alkali metal silicates and 
alkali metal aluminates having a carbon dioxide gas adsorption capacity at 
25.degree. C. and at a carbon dioxide gas partial pressure of 250 mmHg of 
1.0% or less, in the dryer constituting the refrigerating apparatus, water 
in the refrigeration cycle can be efficiently separated and adsorbed, and 
there can be prevented troubles caused by formation of the drying agent 
into powder by detedioration of the drying agent itself, namely, the 
problems caused by clogging of a piping for refrigerant with the drying 
agent and abnormal abrasion due to intrusion of the drying agent into the 
sliding portions of the compressor. Therefore, the employment of the 
synthetic zeolite has a marked improving effect on the performance 
characteristics and the long-term reliability. 
(6) The refrigerating apparatus having the constitution explained above can 
reduce the ozone depletion potential (ODP) and the global warming 
potential (GWP) which are in question in the terrestrial environment to 
zero and 0.3 or less, respectively, relative to values attained when a 
conventional chlorine-containing flon type refrigerant gas (e.g. flon 12) 
is used.