Working fluid for traction drive

The working fluid for traction drive use has a particularly high traction coefficient at high temperatures and the principal ingredient thereof is a decahydronaphthalene compound substituted, on either one or both of the decahydronaphthalene rings, with two or three substituent groups which may be cyclohexyl groups, cyclohexyl alkyl groups, e.g. cyclohexyl methyl, cyclohexyl ethyl, 1-methyl-1-cyclohexyl ethyl and 1-methyl-1-(methylcyclohexyl) ethyl groups, or a combination thereof. The working fluid can be a mixture of a base oil of various types and the above mentioned decahydronaphthalene compound in an amount of 5 to 250 parts by weight per 100 parts by weight of the base oil.

BACKGROUND OF THE INVENTION 
The present invention relates to a novel working fluid for traction drive 
or, more particularly, to a working fluid for traction drive having a high 
traction coefficient at high temperatures. 
A working fluid for traction drive as usually meant is an oily fluid used 
in various kinds of traction drive apparatuses, i.e. friction drive 
apparatuses utilizing rolling contact, such as continuously variable 
transmission for automobiles and industrial machines, hydraulic 
instruments and the like. Working fluids for traction drive should satisfy 
several requirements including a high traction coefficient and stability 
against heat and oxidation as well as inexpensiveness as a matter of 
course. 
As a trend in recent years, studies in the machinery are directed to a 
design of smaller and smaller or lighter and lighter traction drive 
apparatuses with automobiles as a main object of the application thereof. 
Such a smaller and lighter traction drive apparatus is necessarily 
operated under operating conditions of increasingly high velocity and high 
load so that a working fluid for traction drive use also should have 
greatly improved performance accordingly and development of such an 
improved working fluid is eagerly desired. 
Various compounds have hitherto been proposed as useful for the service as 
a working fluid for traction drive use including, for example, those 
disclosed in Japanese Patent Publication Nos. 46-338, 36-339, 47-35763, 
48-42067, 48-42068 and 53-36105 and Japanese Patent Kokai No. 55-43108 and 
55-40726. These compounds, however, are not free from the problem that the 
traction coefficient thereof is greatly decreased at a high temperature 
of, for example, 100.degree. to 160.degree. C. 
Several compounds are known to have a high traction coefficient at high 
temperatures including those proposed in Japanese Patent Publication Nos. 
60-1353, 60-1354 and 60-43392 and Japanese Patent Kokai No. 60-35095. 
These compounds, however, are still not quite satisfactory when the 
traction drive apparatus is to be operated under severer operating 
conditions or at still higher temperatures. Therefore, it is an important 
technical problem to develop a working fluid for traction drive use 
capable of exhibiting greatly improved performance at high temperatures. 
SUMMARY OF THE INVENTION 
Accordingly, the present invention has an object to provide a working fluid 
for traction drive use suitable for use in traction drive apparatuses 
operated at particularly high temperatures without the above described 
problems and disadvantages in the conventional working fluids. 
Thus, the working fluid for traction drive use provided by the invention 
comprises a decahydronaphthalene compound having, in a molecule, 
(i) at least two cyclohexyl alkyl groups, 
(ii) at least two cyclohexyl groups, or 
(iii) at least one cyclohexyl alkyl group and at least one cyclohexyl 
group, bonded to the decahydronaphthalene rings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As is understood from the above given summary of the invention, the 
pricipal ingredient in the inventive working fluid for traction drive use 
is a decahydronaphthalene compound substituted with at least two 
substituent groups each selected from the class consisting of cyclohexyl 
alkyl groups and cyclohexyl group. 
Various kinds of compounds can be named as the examples of the above 
defined decahydronaphthalene compound, of which particularly preferable 
are those represented by the general formula: 
##STR1## 
in which R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7 and 
R.sup.8 each denote a hydrogen atom or an alkyl group having 1 to 4 carbon 
atoms, the subscripts p, q, r and s are each 1, 2 or 3 and the subscripts 
m and n are each zero, 1, 2 or 3 with the proviso that m+n is equal to 2 
or 3. The characteristic feature of these compounds is that two or three 
cyclohexyl alkyl groups are bonded to one or both of the 
decahydronaphthalene rings and the bonding therebetween is formed at the 
.alpha.-carbon atom of the cyclohexyl alkyl group relative to the 
cyclohexane ring. In other words, the carbon atom bonded to the 
cyclohexane ring should simultaneously be bonded to one of the 
decahydronaphthalene rings. 
Particular examples of the decahydronaphthalene compounds of such a type 
include: 
bis(cyclohexyl methyl)decahydronaphthalenes expressed by the formula: 
##STR2## 
bis(1-cyclohexylethyl)decahydronaphthalenes expressed by the formula 
##STR3## 
bis(1-methyl-1-cyclohexyl ethyl)decahydronaphthalenes expressed by the 
formula 
##STR4## 
bis(cyclohexyl methyl)methyl decahydronaphthalenes expressed by the 
formula 
##STR5## 
bis(1-cyclohexyl ethyl)methyl decahydronaphthalenes expressed by the 
formula 
##STR6## 
bis(1-methyl-1-cyclohexyl ethyl)methyl decahydronaphthalenes expressed by 
the formula 
##STR7## 
bis(methylcyclohexyl methyl)decahydronaphthalenes expressed by the formula 
##STR8## 
bis[1-(methylcyclohexyl)ethyl]decahydronaphthalenes expressed by the 
formula 
##STR9## 
bis[1-methyl-1-(methylcyclohexyl)ethyl]decahydronaphthalenes expressed by 
the formula 
##STR10## 
bis(methylcyclohexyl methyl)methyl decahydronaphthalenes expressed by the 
formula 
##STR11## 
bis[1-(methylcyclohexyl)ethyl]methyl decahydronaphthalenes expressed by 
the formula 
##STR12## 
bis[1-methyl-1-(methylcyclohexyl)ethyl]methyl decahydronaphthalenes 
expressed by the formula 
##STR13## 
tris(cyclohexyl methyl)decahydronapthalenes expressed by the formula 
##STR14## 
tris(1-cyclohexyl ethyl)decahydronaphthalenes expressed by the formula 
##STR15## 
and the like. 
Although the cyclohexylalkyl group should be bonded to the 
decahydronaphthalene rings preferably at the .alpha.-carbon atom relative 
to the cyclohexane ring, usable cyclohexylalkyl-substituted 
decahydronaphthalene compounds include those in which the cyclohexylalkyl 
group is bonded to the decahydronaphthalene rings at the .beta.- or 
.gamma.-carbon atom relative to the cyclohexane ring. In other words, the 
decahydronaphthalene rings and the cyclohexane ring may be bonded together 
through a link of two or three carbon atoms intervening therebetween. 
In addition to the above described decahydronaphthalene compounds having 
two or three cyclohexylalkyl groups in a molecule, the principal 
ingredient in the inventive working fluid for traction drive use can be a 
decahydronaphthalene compound having two or more cyclohexyl groups or a 
combination of one or more cyclohexylalkyl groups and one or more of 
cyclohexyl groups in a molecule. It is optional that the 
decahydronaphthalene and cyclohexane rings are substituted with 1 to 3 
alkyl groups having 1 to 4 carbon atoms. Particular examples of these 
compounds include dicyclohexyl decahydronaphthalenes expressed by the 
formula 
##STR16## 
1-cyclohexylethyl cyclohexyl decahydronaphthalenes expressed by the 
formula 
##STR17## 
and the like. 
The inventive working fluid for traction drive use may comprise either a 
single kind or a combination of two kinds or more of the above described 
decahydronaphthalene compounds. 
The above described decahydronaphthalene compounds can be prepared by 
various known methods without particular limitations. For example, the 
cyclohexylalkyl-substituted decahydronaphthalenes represented by the 
general formula [I] can be synthesized most conveniently from naphthalene 
or a substituted naphthalene represented by the general formula 
##STR18## 
or tetrahydronaphthalene or a substituted tetrahydronaphthalene 
represented by the general formula 
##STR19## 
in which R.sup.4, R.sup.5, q and r each have the same meaning as defined 
for the general formula [I], as the starting material. Namely, these 
naphthalene or tetrahydronaphthalene compounds are reacted with a 
halogenated alkylbenzene or a derivative thereof represented by the 
general formula 
##STR20## 
or styrene or a derivative thereof represented by the general formula 
##STR21## 
in which R.sup.1, R.sup.2, R.sup.3, R.sup.6, R.sup.7, R.sup.8, p and s 
each have the same meaning as defined for the general formula [I], R.sup.9 
and R.sup.10 are each an alkyl group having carbon atoms smaller in number 
by one than R.sup.3 and R.sup.7, if R.sup.3 and/or R.sup.7 are hydrogen or 
methyl, R.sup.9 and/or R.sup.10 are hydrogen) respectively, and X is a 
halogen atom, in the presence of a catalyst. Though dependent on the type 
of the desired decahydronaphthalene compound, the catalyst used in this 
reaction should usually be selected from the group consisting of ordinary 
Friedel-Crafts catalysts such as sulfuric acid, aluminum chloride and the 
like, heteropolyacids such as phosphotungstic acid, silicotungstic acid, 
phosphomolybdic acid, silicomolybdic acid and the like and salts thereof, 
activated clay, acid clay, silica alumina, solid phosphoric acid, 
ion-exchange resins, titanium dioxide, zeolites and the like. The reaction 
product thus obtained is then subjected to fractionation by, for example, 
distillation under reduced pressure and the fractions containing the 
compounds represented by the general formula 
##STR22## 
in which R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, 
R.sup.8, p, q, r, s, m and n each have the same meaning as defined for the 
general formula [I] and n' is 2 or 3, are subjected to a hydrogenation 
treatment to give the desired decahydronaphthalene compounds of the 
general formula [I]. The hydrogenation treatment can be performed 
according to a known procedure using a catalyst which may be any of 
conventional ones containing a noble metal, e.g. ruthenium, platinum, 
rhodium, iridium and palladium, nickel, molybdenum and the like. 
The thus obtained compounds or, in particular, the substituted 
decahydronaphthalene compounds of the general formula [I] can be used as 
such as a working fluid for traction drive use although it is optional to 
admix the same with various kinds of known additives according to need. 
The inventive working fluid for traction drive use described above has a 
high traction coefficient at a high temperature of, for example, 
100.degree. to 160.degree. C. in addition to the excellent general 
properties in other respects so that it is quite satisfactory as a working 
fluid used in traction drive apparatuses operated under a condition of 
particularly high temperatures. Accordingly, the applicability of the 
inventive working fluid for traction drive use covers a wide variety of 
machinery including continuously variable transmissions for automobiles 
and industrial machines, hydraulic instruments and so on. 
When the working fluid for traction drive use should desirably have a high 
traction coefficient over a wide temperature range from low to high 
temperatures in addition to the excellent general properties without the 
problems of poor flowability at low temperatures and discontinuity of oil 
film at high temperatures, the working fluid should be formulated by 
combining a decahydronaphthalene compound having, in a molecule, (i) at 
least two cyclohexyl alkyl group, (ii) at least two cyclohexyl groups, or 
(iii) at least one cyclohexyl alkyl group and at least one cyclohexyl 
group, bonded to the decahydronaphthalene rings with a base oil having a 
kinematic viscosity of 8 centistokes or below or, preferably, 7 
centistokes or below at 100.degree. C. 
Preferable base oils suitable for the purpose include naphthenic base oils, 
aromatic base oils, paraffinic base oils, silicone-based base oils, 
esteric base oils and the like as well as mixtures thereof. Particularly 
preferable among them are the naphthenic ones, of which examples include: 
1-(2-decahydronaphthyl)-1-cyclohexyl ethane; 
1-(1-decahydronaphthyl)-1-cyclohexyl ethane; 1-(2-methyl 
decahydronaphthyl)-1-cyclohexyl ethane; 1-(1-methyl 
decahydronaphthyl)-1-cyclohexyl ethane; 
1-dimethyl-decahydronaphthyl-1-cyclohexyl ethane; 
2-(2-decahydronaphthyl)-2-cyclohexyl propane; 
2-(1-decahydronaphthyl)-2-cyclohexyl propane; 1-cyclohexyl-1,4-dimethyl 
decahydronaphthalene; 1,2-di(methyl cyclohexyl)-2-methyl propane; 
2,3-di(methyl cyclohexyl) butane; 1,3-dicyclohexyl-3-methyl butane; 
2,4-dicyclohexyl pentane; 2,4-dicyclohexyl-2-methyl pentane; 
1,3-dicyclohexyl-1-methyl cyclopentane; tercyclohexyl; cyclohexylmethyl 
decahydronaphthalene; 1-dicyclohexyl-1-cyclohexyl ethane; naphthenic 
mineral oils and the like. 
The aromatic base oil is exemplified by the hard-type alkyl benzenes 
obtained by the reaction of a propylene polymer and benzene, soft-type 
alkyl benzenes obtained by the reaction of an .alpha.-olefin and benzene, 
alkyl naphthalenes such as diisopropyl naphthalene and the like, alkyl 
biphenyls such as diethyl biphenyl and the like, diaryl alkanes such as 
phenyl xylyl ethane, benzyl naphthalene and the like, and others. The 
paraffinic base oil is exemplified by poly-.alpha.-olefins, paraffinic 
mineral oils, polybutenes, propylene oligomers, squalane and the like. 
The silicone-based base oil includes silicone fluids such as dimethyl 
silicones and phenyl methyl silicones and the esteric base oil includes 
polyol esters and diesters, cyclohexane carboxylic acid esters of 
cycloalkanols such as cyclohexane carboxylic acid esters of cyclohexanol 
and cyclododecanol, phosphate esters such as tricyclohexyl phosphate and 
others. 
These base oils can be used either singly or as a combination of two kinds 
or more according to need. Any of such combinations can be used provided 
that the kinematic viscosity of the mixture does not exceed 8 centistokes 
at 100.degree. C. even when one of the component compounds has a kinematic 
viscosity higher than 8 centistokes at 100.degree. C. 
The use of the above described base oil in combination with a 
decahydronaphthalene compound having, in a molecule, (i) at least two 
cyclohexyl alkyl group, (ii) at least two cyclohexyl groups, or (iii) at 
least one cyclohexyl alkyl group and at least one cyclohexyl group, bonded 
to the decahydronaphthalene rings has a remarkable synergistic effect in 
respect of the improvement of the traction coefficient of the mixture to 
give a working fluid for traction drive use having excellent properties. 
It is taught in ASLE Trans., volume 13, pages 105 to 116 (1969) that the 
rule of additivity is held for the traction coefficient according to the 
equation 
##EQU1## 
in which C.sub.i is the weight fraction of the i-th component, f.sub.i is 
the traction coefficient of the i-th component and f is the traction 
coefficient of the mixture of the i components. 
Although it is reported in SAE 710837 (1971) that a slight synergistic 
effect is obtained in the traction coefficient of a mixture of components, 
the reported increment over the additivity rule is only 2 to 3% so that it 
is a quite novel discovery that the traction coefficient of a mixture 
exceeds the value of any one of the components before blending or the 
traction coefficient of a mixture is larger by at least 10% than the value 
expected from the rule of additivity. 
When the working fluid for traction drive use is prepared by mixing the 
above described base oil and a decahydronaphthalene compound having, in a 
molecule, (i) at least two cyclohexyl alkyl group, (ii) at least two 
cyclohexyl groups, or (iii) at least one cyclohexyl group and at least one 
cyclohexyl group, bonded to the decahydronaphthalene rings, the mixing 
ratio is not particularly limitative provided that the mixture has a 
kinematic viscosity of at least 3.0 centistokes or, preferably, in the 
range from 3.6 to 10.0 centistokes at 100.degree. C. Though dependent on 
the particular types of the respective component compounds, it is a 
general guideline that 100 parts by weight of the base oil should be 
admixed with from 5 to 250 parts by weight or, preferably, from 8 to 150 
parts by weight of a decahydronaphthalene compound having, in a molecule, 
(i) at least two cyclohexyl alkyl group, (ii) at least two cyclohexyl 
groups, or (iii) at least one cyclohexyl alkyl group and at least one 
cyclohexyl group, bonded to the decahydronaphthalene rings. Even when the 
mixing ratio of the components is within the above mentioned range, it is 
a further requirement that the mixture should have a kinematic viscosity 
of at least 3 centistokes at 100.degree. C. since otherwise the traction 
drive apparatus using the mixture as the working fluid cannot withstand a 
continuous running over a long period of time to ensure the rating life of 
the apparatus due to the fatigue by rolling. 
As is known, rolling-element fatigue life largely depends on the surface 
roughenss of each of the rolling contact surfaces and the thickness of the 
oil film formed therebetween and can be estimated in relation to the value 
of the oil film parameter .LAMBDA.. In connection with the relationship 
between the value of .LAMBDA. and surface fatigue, it is taught in Machine 
Design, volume 7, page 102 (1974) that the rating life or longer of the 
surface can be ensured when it is larger than 0.9. 
When a calculation is made by applying the above described criterion to an 
actual bearing as an example of the rolling-contact surface, a conclusion 
is made that the life of the surface due to fatigue by rolling can exceed 
the rating value or the value expected by design when the working fluid 
has a viscosity of at least 3.0 centistokes or, preferably, at least 3.6 
centistokes at 100.degree. C. In other words, a working fluid for traction 
drive use, when it is prepared by blending two or more components, should 
be formulated so as to have a viscosity of at least 3.0 centistokes, or 
preferably, at least 3.6 centistokes at 100.degree. C. In addition, a 
working fluid for traction drive use to be used in automobiles should 
preferably have a pour point of -30.degree. C. or lower in order to 
facilitate smooth starting of the engine in a cold district. 
In the following, the inventive working fluids for traction drive use and 
the performance thereof are illustrated in more detail by way of examples 
and comparative examples. 
In the Examples and Comparative Examples described below, the traction 
coefficient of the working fluids was measured using a two roller machine. 
The machine had two rollers each having a diameter of 52 mm and a 
thickness of 6 mm contacting each other at the side faces with a 
contacting load of 7 kg by means of a spring in such a manner that one of 
the wheels could drive the other. The side face of the driving roller was 
straightly cylindrical without crowning while the side face of the driven 
roller had a barrel-shaped form with a crown radius of 10 mm. One of the 
rollers was rotated at a constant velocity of 1500 rpm while the other 
roller was continuously rotated at a velocity of 1500 rpm to 1750 rpm so 
as to determine the tangential force, i.e. traction force, generated 
between the rollers, from which the traction coefficient was calculated. 
The rollers were made of a steel for rolling bearing SUJ-2 and the surface 
thereof was polished as smooth as a mirror. 
The maximum Hertzian contact pressure was 112 kgf/mm.sup.2. 
The relationship between the traction coefficient and the temperature of 
the working fluid was determined at a slip ratio of 5% by varying the 
temperature of the fluid in the oil reservoir equipped with a heater in 
the range from 30.degree. C. to 160.degree. C. 
EXAMPLE 1 
Into a four-necked flask of 3-liter capacity equipped with a reflux 
condenser, thermometer and stirrer were introduced 896 g (7 moles) of 
naphthalene and 44.8 g of a silica gel-supported heteropolyacid catalyst 
containing 17% by weight of phosphotungstic acid and the mixture was 
heated at 150.degree. C. Then, 1092 g (10.5 moles) of styrene were added 
dropwise into the mixture in the flask kept at 150.degree. C. under 
agitation over a period of 8 hours and, after completion of the dropwise 
addition of styrene, the mixture was further agitated for additional 30 
minutes at 150.degree. C. to complete the reaction. After completion of 
the reaction, the solid catalyst was immediately removed from the mixture 
by filtration and the filtrate was subjected to distillation under reduced 
pressure to give about 800 g of a fraction boiling at 230.degree. to 
250.degree. C. under a pressure of 0.6 mmHg. This fraction was analyzed by 
the gas chromatographic-mass spectrometric analysis and proton NMR 
analysis to find that the main constituent thereof was bis(1-phenyl 
ethyl)naphthalene as an addition product of 2 moles of styrene to 1 mole 
of naphthalene. 
In the next place, a 500 g portion of this fraction was introduced into an 
autoclave of 1-liter capacity together with 25 g of a hydrogenation 
catalyst containing 5% by weight of ruthenium supported on carbon carrier 
(a product by Nippon Engelhard Co.) and the hydrogenation reaction of the 
naphthalene compound was performed for 4 hours at a reaction temperature 
of 200.degree. C. under a hydrogen pressure of 100 kg/cm.sup.2. After 
cooling, the reaction mixture was filtered to remove the catalyst and the 
filtrate was analyzed by the NMR analysis to find that more than 99% of 
the starting naphthalene compound had been hydrogenated and the main 
constituent of the filtrate was bis(1-cyclohexyl 
ethyl)decahydronaphthalene as the nucleus-hydrogenated compound of 
bis(1-phenyl ethyl)naphthalene. This product had a kinematic viscosity of 
60 centistokes at 100.degree. C. and a refractive index n.sub.D.sup.20 of 
1.5084. This product had a very high traction coefficient at high 
temperatures with a value of 0.102 at 140.degree. C. FIG. 1 of the 
accompanying drawing shows the traction coefficient of the product as a 
function of temperature. 
COMATIVE EXAMPLE 1 
Into a glass-made flask of 3-liter capacity were introduced 1000 g of 
.alpha.-methyl styrene, 50 g of acid clay and 50 g of ethylene glycol and 
the mixture was agitated for 2 hours at 140.degree. C. to effect the 
reaction. After cooling, the reaction mixture was filtered to remove the 
acid clay and then the filtrate was distilled to remove the unreacted 
.alpha.-methyl styrene and ethylene glycol and to give 900 g of a fraction 
boiling at 125.degree. to 130.degree. C. under a pressure of 0.2 mmHg. 
This fraction was identified by the NMR and gas chromatographic analyses 
to be a mixture of 95% of a linear dimer and 5% of a cyclic dimer of 
.alpha.-methyl styrene. 
The thus obtained fraction was subjected to a hydrogenation reaction and 
post-treatment in the same manner as in Example 1 to give a hydrogenation 
product usable as a working fluid for traction drive use, of which the 
main constituent was 2,4-dicyclohexyl-2-methyl pentane. This product had a 
refractive index n.sub.D.sup.20 of 1.4902, specific gravity (15/4.degree. 
C.) of 0.90 and kinematic viscosity of 3.7 centistokes at 100.degree. C. 
The traction coefficient thereof was 0.063 at 140.degree. C. 
EXAMPLE 2 
(1) Preparation of base oil 
Into a glass-made flask of 3-liter capacity were introduced 1000 g of 
tetrahydronaphthalene and 300 g of concentrated sulfuric acid and the 
mixture was chilled at 0.degree. C. by keeping the flask in an ice bath. 
Then, 400 g of styrene were added dropwise into the mixture in the flask 
under agitation over a period of 3 hours followed by further continued 
agitation for additional 1 hour to complete the reaction. The mixture was 
kept standing still with the stirrer turned off so that the mixture was 
separated into two layers. The organic phase taken by phase separation was 
washed first with 500 ml of a 1N aqueous solution of sodium hydroxide and 
then with 500 ml of a saturated aqueous solution of sodium chloride each 
three times followed by drying over anhydrous sodium sulfate and, after 
stripping of the unreacted tetrahydronaphthalene by distillation, 
subjected to distillation under reduced pressure to give 750 g of a 
fraction boiling at 135.degree. to 148.degree. C. under a pressure of 0.17 
mmHg. This fraction could be identified by analysis to be a mixture of 
1-(2-tetrahydronaphthyl)-1-phenyl ethane and 
1-(1-tetrahydronaphthyl)-1-phenyl ethane. 
A 500 g portion of this fraction was taken in an autoclave of 1-liter 
capacity together with 25 g of a hydrogenation catalyst containing 5% by 
weight of ruthenium supported on carbon (a product by Nippon Engelhard 
Co.) and the hydrogenation reaction was performed for 4 hours at a 
reaction temperature of 200.degree. C. under a hydrogen pressure of 50 
kg/cm.sup.2. After cooling, the reaction mixture was filtered to remove 
the catalyst and the filtrate was stripped of the low boiling matter. The 
thus obtained product had a specific gravity (15/4.degree. C.) of 0.94, 
refractive index n.sub.D.sup.20 of 1.5040 and the kinematic viscosity 
thereof was 35.76 centistokes at 40.degree. C. and 4.709 centistokes at 
100.degree. C. Analysis of the product by the NMR method indicated that 
more than 99.9% of the starting compounds had been hydrogenated and it 
could be identified to be a mixture of 
1-(2-decahydronaphthyl)-1-cyclohexyl ethane and 1-(1-decahydronaphthyl)- 
1-cyclohexyl ethane. 
(2) Preparation of a mixed fluid for traction drive use 
A mixed working fluid for traction drive use, which is referred to as the 
mixed fluid-1 hereinbelow, was prepared by blending 78 parts by weight of 
the fluid prepared in (1) above and mainly composed of 
1-(2-decahydronaphthyl)-1-cyclohexyl ethane, which is referred to as the 
fluid A-1 hereinbelow, and 22 parts by weight of the fluid prepared in 
Example 1 and mainly composed of bis(1-cyclohexyl 
ethyl)decahydronaphthalene, which is referred to as the fluid B-1 
hereinbelow. Properties of this mixed fluid-1 are shown in Table 1 below 
and the traction coefficient thereof is shown in FIG. 2 as a function of 
temperature. 
EXAMPLE 3 
A mixed working fluid for traction drive use, which is referred to as the 
mixed fluid-2 hereinbelow, was prepared by blending 90 parts by weight of 
the fluid A-1 and 10 parts by weight of the fluid B-1. Properties of this 
mixed fluid-2 are shown in Table 1 below and the traction coefficient 
thereof is shown in FIG. 2 as a function of temperature. 
COMATIVE EXAMPLE 2 
Properties of the fluid A-1 used in Example 2 are shown in Table 1 and the 
traction coefficient thereof is shown in FIG. 2 as a function of 
temperature. 
COMATIVE EXAMPLE 3 
Properties of the fluid B-1 used in Example 2 are shown in Example 2 are 
shown in Table 1 and the traction coefficient thereof is shown in FIG. 2 
as a function of temperature. 
TABLE 1 
______________________________________ 
Item 
Kinematic viscosity, 
Vis- Pour 
centistokes, at 
cosity point, 
No. Fluid 40.degree. C. 
100.degree. C. 
index .degree.C. 
______________________________________ 
Example 2 
Mixed 80.47 6.769 -29 -25.0 
fluid-1 
Example 3 
Mixed 55.38 5.678 -18 -27.5 
fluid-2 
Comparative 
Fluid A-1 35.76 4.709 -5 -30.0 
Example 2 
Comparative 
Fluid B-1 -- 59.75 -- -- 
Example 3 
______________________________________ 
EXAMPLE 4 
(1) Preparation of base oil 
Into a glass-made flask of 3-liter capacity were introduced 1000 g of 
.alpha.-methyl styrene, 40 g of acid clay and 50 g of mesityl oxide and 
the mixture was heated at 140.degree. C. for 2 hours under agitation to 
effect the reaction. After cooling, the reaction mixture was filtered to 
remove the acid clay as the catalyst and the filtrate was stripped of the 
unreacted .alpha.-methyl styrene and mesityl oxide and distilled under 
reduced pressure to give 900 g of a fraction boiling at 125.degree. to 
130.degree. C. under a pressure of 0.2 mmHg. This fraction was identified 
by the NMR and gas chromatographic analyses to be a mixture of 97% and 3% 
of a linear dimer and a cyclic dimer, respectively, of .alpha.-methyl 
styrene. 
This fraction was subjected to the hydrogenation reaction and 
post-treatment in substantially the same manner as in (1) of Example 2 to 
give a fluid mainly composed of 2,4-dicyclohexyl-2-methyl pentane and 
suitable for use as a working fluid for traction drive use. This product 
had a specific gravity (15/4.degree. C.) of 0.90 and the kinematic 
viscosity thereof was 20.27 centistokes at 40.degree. C. and 3.580 
centistokes at 100.degree. C. with a viscosity index of 13. 
(2) Preparation of a mixed fluid for traction drive use 
A mixed working fluid for traction drive use, which is referred to as the 
mixed fluid-3 hereinbelow, was prepared by blending 73 parts by weight of 
the product obtained in (1) above and mainly composed of 
2,4-dicyclohexyl-2-methyl pentane, which is referred to as the fluid A-2 
hereinbelow, and 27 parts by weight of the fluid B-1. Properties of the 
mixed fluid-3 are shown in Table 2 below and the traction coefficient 
thereof is shown in FIG. 3 as a function of temperature. 
COMATIVE EXAMPLE 4 
Properties of the fluid A-2 obtained in (1) of Example 4 are shown in Table 
2 and the traction coefficient thereof is shown in FIG. 3 as a function of 
temperature. Table 2 and FIG. 3 also contain the data for the fluid B-1 to 
facilitate comparison. 
TABLE 2 
______________________________________ 
Item 
Kinematic viscosity, 
Vis- Pour 
centistokes, at 
cosity point, 
No. Fluid 40.degree. C. 
100.degree. C. 
index .degree.C. 
______________________________________ 
Example 4 
Mixed 69.62 6.215 -36 -27.5 
fluid-3 
Comparative 
Fluid A-2 20.27 3.580 13 below 
Example 4 -35 
Comparative 
Fluid B-1 -- 59.75 -- -- 
Example 3 
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EXAMPLE 5 
Reaction of naphthalene and styrene was performed in substantially the same 
manner as in Example 1 except that 150 g of an acid clay calcined 
beforehand at 220.degree. C. for 20 hours were used as the catalyst. After 
completion of the reaction, the reaction mixture was filtered to remove 
the catalyst and the filtrate was stripped of the unreacted naphthalene. 
The resultant reaction product was analyzed and identified to be a mixture 
composed of 32% by weight of 1-phenyl-1-naphthyl ethane, 43% by weight of 
bis(1-phenethyl)naphthalene and 23% by weight of 
tris(1-phenethyl)naphthalene. This mixture was subjected to a 
hydrogenation reaction in the same manner as in Example 1 using a Raney 
nickel catalyst (Raney Nickel NDH, a product by Kawaken Fine Chemical Co.) 
to give a fluid which contained 32% by weight of 
1-cyclohexyl-1-decahydronaphthyl ethane, 43% by weight of bis(1-cyclohexyl 
ethyl)decahydronaphthalene and 23% by weight of tris(1-cyclohexyl 
ethyl)decahydronaphthalene. 
EXAMPLE 6 
A mixed working fluid for traction drive use, which is referred to as the 
mixed fluid-4 hereinbelow, was prepared by blending 73 parts by weight of 
the fluid A-1 obtained in (1) of Example 2 and 27 parts by weight of the 
fluid obtained in Example 5, which is referred to as the fluid B-2 
hereinbelow. Properties of this mixed fluid-4 are shown in Table 3 below 
and the traction coefficient thereof is shown in FIG. 4 as a function of 
temperature. Table 3 also shows the properties of the fluid B-2 obtained 
in Example 5. Table 3 and FIG. 4 also show the data for the fluid A-1 to 
facilitate comparison. 
TABLE 3 
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Item 
Kinematic viscosity, 
Vis- Pour 
centistokes, at 
cosity point, 
No. Fluid 40.degree. C. 
100.degree. C. 
index .degree.C. 
______________________________________ 
Example 6 
Mixed 81.24 6.893 -20 -25.0 
fluid-4 
Comparative 
Fluid A-1 35.76 4.709 -5 -30.0 
Example 2 
Example 5 
Fluid B-2 4471 34.11 -407 +10.0 
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EXAMPLE 7 
(1) Preparation of base oil 
Into a mixture in a four-necked flask of 2-liter capacity composed of 500 
ml of toluene, 158 g (2 moles) of pyridine and 396 g (2 moles) of 
cyclododecanol were added dropwise 293 g (2 moles) of cyclohexane carbonyl 
chloride at a temperature of 45.degree. to 75.degree. C. over a period of 
2.5 hours under agitation followed by further continued agitation for 
additional 1 hour at the same temperature to complete the reaction. After 
cooling to room temperature, the reaction mixture was filtered using a 
Buchner funnel to remove the precipitates of pyridine hydrochloride. The 
filtrate was stripped of toluene and then subjected to distillation under 
reduced pressure to give 445 g of a fraction boiling at 160.degree. to 
170.degree. C. under a pressure of 0.2 mmHg, which could be identified by 
analysis to be an ester of cyclododecanol and cyclohexane carboxylic acid. 
(2) Preparation of a mixed fluid for traction drive use 
A mixed fluid, which is referred to as the mixed fluid-5 hereinbelow, was 
prepared by blending 86 parts by weight of the product obtained in (1) 
above and mainly composed of the ester of cyclododecanol and cyclohexane 
carboxylic acid, which is referred to as the fluid A-3 hereinbelow, and 14 
parts by weight of the fluid B-2 prepared in Example 5. Properties of this 
mixed fluid-5 are shown in Table 4 below and the traction coefficient 
thereof is shown in FIG. 5 as a function of temperature. 
COMATIVE EXAMPLE 5 
Properties of the fluid A-3 are shown also in Table 4 and the traction 
coefficient thereof is shown also in FIG. 5 as a function of temperature. 
Table 4 and FIG. 5 also show the data for the fluid B-2 to facilitate 
comparison. 
TABLE 4 
______________________________________ 
Item 
Kinematic viscosity, 
Vis- Pour 
centistokes, at 
cosity point, 
No. Fluid 40.degree. C. 
100.degree. C. 
index .degree.C. 
______________________________________ 
Example 7 
Mixed 81.82 7.4020 15 -25.0 
fluid-5 
Comparative 
Fluid A-3 52.02 6.055 34 -27.5 
Example 5 
Example 5 
Fluid B-2 4471 34.11 -407 +10.0 
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