U.S. patent application number 10/669763 was filed with the patent office on 2004-12-02 for continuously variable transmission fluid and method of making same.
This patent application is currently assigned to Pennzoil-Quaker State Company. Invention is credited to Chiu, I-Ching.
Application Number | 20040242441 10/669763 |
Document ID | / |
Family ID | 32069781 |
Filed Date | 2004-12-02 |
United States Patent
Application |
20040242441 |
Kind Code |
A1 |
Chiu, I-Ching |
December 2, 2004 |
Continuously variable transmission fluid and method of making
same
Abstract
A continuously variable transmission fluid comprises a
hydrogenated cyclic dimer of .alpha.-alkyl styrene and a low
temperature viscosity control agent. The fluid does not contain
more than 20 wt. % of a linear dimer of the .alpha.-alkyl styrene,
and the fluid has a kinematic viscosity of greater than about
2.5.times.10.sup.-6 m.sup.2/s at 100.degree. C., as measured
according to ASTM D-445. The dimerized .alpha.-alkyl styrene can be
made by (a) contacting an .alpha.-alkyl styrene with a supported
acid catalyst to effect oligomerization of the .alpha.-alkyl
styrene to a cyclic dimer; and (b) hydrogenating the cyclic dimer
in the presence of a hydrogenation catalyst to produce a fully
hydrogenated cyclic dimer, wherein the .alpha.-alkyl styrene is
contacted with the supported acid catalyst in the absence of a
solvent for the .alpha.-alkyl styrene and a free acid.
Inventors: |
Chiu, I-Ching; (Houston,
TX) |
Correspondence
Address: |
Shell Oil Company
P. O. Box 2463
Houston
TX
77252-2463
US
|
Assignee: |
Pennzoil-Quaker State
Company
Houston
TX
|
Family ID: |
32069781 |
Appl. No.: |
10/669763 |
Filed: |
September 24, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60414894 |
Sep 30, 2002 |
|
|
|
Current U.S.
Class: |
508/591 ;
508/579 |
Current CPC
Class: |
C10N 2030/06 20130101;
C10N 2020/065 20200501; C10M 111/04 20130101; C10M 2207/2805
20130101; C10M 2205/0206 20130101; C10M 2205/028 20130101; C10M
2203/1065 20130101; C10N 2030/02 20130101; C10N 2040/04 20130101;
C10M 2201/02 20130101; C10M 2203/065 20130101; C10M 2209/084
20130101; C10N 2020/02 20130101; C10M 111/02 20130101; C10M
2209/086 20130101; C10M 169/041 20130101; C10M 2209/103 20130101;
C10N 2040/045 20200501; C10M 2205/06 20130101; F16H 57/04 20130101;
C10M 169/04 20130101; C10M 2203/045 20130101; C10M 169/044
20130101; C10M 2203/106 20130101; C10M 2207/28 20130101; C10M
2203/0206 20130101 |
Class at
Publication: |
508/591 ;
508/579 |
International
Class: |
C10M 15/02 |
Claims
What is claimed is:
1. A continuously variable transmission (CVT) fluid, comprising or
obtained by mixing: a hydrogenated cyclic dimer of .alpha.-alkyl
styrene; and a low temperature viscosity control agent, wherein the
fluid comprises less than about 20 wt % of a linear dimer of the
.alpha.-alkyl styrene, and the fluid has a kinematic viscosity of
greater than about 2.5.times.10.sup.-6 m.sup.2/s at 100.degree. C.,
as measured according to ASTM D-445.
2. The CVT fluid of claim 1, wherein the kinematic viscosity of the
fluid is greater than about 3.0.times.10.sup.-6 m.sup.2/s at
100.degree. C.
3. The CVT fluid of claim 1, wherein the kinematic viscosity of the
fluid is from about 3.0.times.10.sup.-6 m.sup.2/s at 100.degree. C.
to about 8.0.times.10.sup.-6 m.sup.2/s at 100.degree. C.
4. The CVT fluid of claim 1, wherein the kinematic viscosity of the
fluid is greater than about 8.0.times.10.sup.-6 m.sup.2/s at
100.degree. C.
5. The CVT fluid of claim 1, wherein the fluid has a traction
coefficient (100.degree. C.) of at least about 0.08.
6. The CVT fluid of claim 1, wherein the fluid has a traction
coefficient (100.degree. C.) form about 0.08 to about 0.109.
7. The CVT fluid of claim 1, wherein the fluid has a traction
coefficient (100.degree. C.) of at least about 0.109.
8. The CVT fluid of claim 1, wherein the fluid has a Brookfield
viscosity (-30.degree. C.) of less than about 100
Pa.multidot.s.
9. The CVT fluid of claim 1, wherein the fluid has a Brookfield
viscosity (-30.degree. C.) of from about 100 Pa.multidot.s to about
5 Pa.multidot.s.
10. The CVT fluid of claim 1, wherein the fluid has a Brookfield
viscosity (-30.degree. C.) of less than about 5 Pa.multidot.s.
11. The CVT fluid of claim 1, wherein the hydrogenated cyclic dimer
of .alpha.-alkyl styrene is present in greater than about 80 wt
%.
12. The CVT fluid of claim 1, wherein the hydrogenated cyclic dimer
of .alpha.-alkyl styrene is present in greater than about 85 wt
%.
13. The CVT fluid of claim 1, wherein the hydrogenated cyclic dimer
of .alpha.-alkyl styrene is present in greater than about 90 wt
%.
14. The CVT fluid of claim 1, wherein the low temperature viscosity
control agent has a viscosity of greater than 2.5.times.10.sup.-6
m.sup.2/s at 100.degree. C.
15. The CVT fluid of claim 1, further comprising an additive
selected from dispersants, detergents, viscosity index improvers,
friction modifiers, anti-wear agents, or mixtures thereof.
16. The CVT fluid of claim 1, wherein the low temperature viscosity
control agent is selected from oligomers or polymers of linear
alpha olefins of at least 12 carbon atoms, naphthenic oils,
synthetic ester oils, polyether oils, or mixtures thereof
17. The CVT fluid of claim 1, wherein the low temperature viscosity
control agent has a viscosity of less than 2.5.times.10.sup.-6
m.sup.2/s at 100 .degree. C.
18. The CVT fluid of claim 1, wherein the low temperature viscosity
control agent comprises an oligomer or polymer of linear alpha
olefins having 12 to about 20 carbon atoms, said oligomer or
polymer having a molecular weight of about 250 to about 600.
19. The CVT fluid of claim 1, wherein the low temperature viscosity
control agent comprises a naphthenic oil.
20. The CVT fluid of claim 1, wherein the .alpha.-alkyl styrene is
.alpha.-methyl styrene.
21. A method of making dimerized .alpha.-alkyl styrene and products
thereof, comprising: contacting an .alpha.-alkyl styrene with a
supported acid catalyst under a temperature and pressure condition
to effect oligomerization of the .alpha.-alkyl styrene to produce
an oligomerization product, the oligomerization product comprising
a cyclic dimer of the .alpha.-alkyl styrene; and hydrogenating the
cyclic dimer of the .alpha.-alkyl styrene in the presence of a
hydrogenation catalyst to produce a fully hydrogenated cyclic dimer
of the .alpha.-alkyl styrene, wherein the .alpha.-alkyl styrene is
contacted with the supported acid catalyst in the absence of a
solvent for the .alpha.-alkyl styrene and a free acid.
22. The method of claim 21, further comprising mixing the fully
hydrogenated cyclic dimer with an additive to form a continuously
variable transmission fluid, wherein the continuously variable
transmission fluid comprises less than about 20 wt. % of a linear
dimer of the .alpha.-alkyl styrene.
23. The method of claim 22, wherein the transmission fluid
comprises less than about 5 wt. % of a trimer or higher oligomer of
the .alpha.-alkyl styrene.
24. The method of claim 22, wherein the .alpha.-alkyl styrene is
.alpha.-methyl styrene.
25. The method of claim 24, wherein the fully-hydrogenated dimer is
1-cyclohexyl-1,1,3-trimethylhydrindane.
26. The method of claim 25, wherein the
1-cyclohexyl-1,1,3-trimethylhydrin- dane is mixed with an oil
additive to form a continuously variable transmission fluid.
27. The method of claim 26, wherein the transmission fluid
comprises less than about 20 wt. % of a linear dimer of
.alpha.-methyl styrene.
28. The method of claim 26, wherein the transmission fluid
comprises less than about 5 wt. % of a trimer or higher oligomer of
.alpha.-methyl styrene.
29. The method of claim 22, wherein the supported acid catalyst is
a column of an acidic ion exchange resin.
30. The method of claim 29, wherein the acidic ion exchange resin
is a strongly acidic ion exchange resin.
31. The method of claim 29, wherein the .alpha.-alkyl styrene is
passed through the acidic resin exchange resin column at a
temperature from about 25.degree. C. to about 250.degree. C.
32. The method of claim 31, wherein the .alpha.-alkyl styrene has a
residence time in the acidic ion exchange column in the range of
about 1 second to about 250 minutes.
33. The method of claim 29, wherein the acidic ion exchange resin
column has a column pressure in the range from about 15 psig (103
kPa) to about 44 psig (303 kPa).
34. The method of claim 21, further comprising separating the
cyclic dimer of the .alpha.-alkyl styrene from other oligomers of
the .alpha.-alkyl styrene prior to the hydrogenation of the cyclic
dimer.
Description
PRIOR RELATED APPLICATIONS
[0001] This patent application claims priority to U.S. Provisional
Application Serial No. 60/414,894 filed on Sep. 30, 2002, entitled
"Continuously Variable Transmission Fluid and Method of Making
Same," which is incorporated by reference herein in its
entirety.
FEDERALLY SPONSORED RESEARCH STATEMENT
[0002] Not applicable.
REFERENCE TO MICROFICHE APPENDIX
[0003] Not applicable.
FIELD OF THE INVENTION
[0004] This invention relates generally to transmission fluids for
use with continuously variable transmissions (CVT), also referred
to as traction drives.
BACKGROUND OF THE INVENTION
[0005] Continuously variable transmissions (CVT), also known as
traction drives, represent a radical departure from conventional
automatic transmissions. The push belt version of the CVT was
invented by Dr. Hub Van Doorne, and since its introduction, many
cars have been equipped with the push belt CVT system. CVT push
belts are manufactured by Van Doorne's Transmissie VB of Tilburg,
the Netherlands. A more detailed description of such transmissions
and belts and lubricants employed therein is found in U.S. Pat. No.
5,750,477 and the references cited therein. In brief, a belt and
pulley system is central to the operation of this type of
transmission. The pulley system comprises a pair of pulleys with a
V-shaped cross-section, each consisting of a moveable sheave, a
fixed sheave, and a hydraulic cylinder. Between the pulleys runs a
belt which consists of a set of metal elements held together by
metal bands. In operation, the driving pulley pushes the belt to
the driven pulley, thereby transferring power from the input to the
output. The transmission drive ratio is controlled by opening or
closing the moveable sheaves so that the belt rides lower or higher
on the pulley faces. This manner of operation permits continuous
adjustment of gear ratio between the input and output shafts.
[0006] It has become clear from commercial use of CVT that the
fluids used in the CVT are just as important as the mechanical
design for satisfactory operation. The lubricant should fulfill
several functions: to lubricate the metal belt in its contacts with
the pulley assembly, the planetary and other gears, the wet-plate
clutches, and the bearings; to cool the transmission; and to carry
hydraulic signals and power. The hydraulic pressure controls the
belt traction, transmission ratio, and clutch engagement.
Accordingly, the fluid should maintain a relatively high
coefficient of friction for metal/metal contact, as well as
exhibiting a suitable degree of shear stability.
[0007] While the working elements of a traction drive are sometimes
spoken of as being in contact, it is generally accepted that a
fluid film be provided therebetween. Thus, rather than
metal-to-metal rolling contact, a film of fluid is introduced into
the load zone, and power is transmitted by shearing of the film,
which may become very viscous due to the high pressure at the
contact area. The nature and properties of the fluid, therefore,
determine to a large extent the performance and capacity of the
traction drive. Traction fluids preferably have a high shear
resistance (often measured as "traction coefficient") to maximize
the power transmission performance. Low viscosity, particularly at
low temperatures, is also desirable for efficient operation under
cold conditions. The fluid should ideally also exhibit good
lubricating properties for and compatibility with other components
of the traction drive. Such fluids also serve to remove heat and
prevent wear at the contact surfaces and to lubricate bearings and
other moving parts associated with the drive.
[0008] So far, various different traction drive fluids have been
developed and disclosed See, for example, U.S. Pat. No. 6,372,696;
No. 5,422,027; No. 6,262,000; No. 6,451,745; and No. 6,103,673.
However, it is often the case that some compounds having a high
traction coefficient at high temperatures cause a relatively large
churning loss because of the high viscosity, thus resulting in low
transmission efficiency, but also having relatively poor capability
to start traction drive units at low temperatures. On the other
hand, other compounds of low viscosity and therefore high
transmission efficiency have a relatively low traction coefficient
at high temperatures and their viscosity decreases with increasing
oil temperature too much, causing trouble with respect to
lubrication in traction drive units. Therefore, there is a need for
a traction fluid or a CVT fluid with a relatively high traction
coefficient and good low temperature properties, such as viscosity
and shear stability.
SUMMARY OF THE INVENTION
[0009] Embodiments of the invention meet the above need in one or
more of the following aspects. In one aspect, the invention relates
to a continuously variable transmission (CVT) fluid with a
relatively high traction coefficient and good low temperature
properties. The CVT fluid comprises or obtained by mixing a
hydrogenated cyclic dimer of .alpha.-alkyl styrene and a low
temperature viscosity control agent, wherein the fluid comprises
less than about 20 wt. % of a linear dimer of the .alpha.-alkyl
styrene. Preferably, the CVT fluid has a kinematic viscosity of
greater than about 2.5.times.10.sup.-6 m.sup.2/s at 100.degree. C.,
as measured according to ASTM D-445. The low temperature viscosity
control agent should be present in an amount sufficient to reduce
the viscosity of the fluid at -30.degree. C.
[0010] In another aspect, the invention relates to a method of
making a dimerized .alpha.-alkyl styrene, which can be used as a
base oil for a CVT fluid. The method comprises (a) contacting an
.alpha.-alkyl styrene with a supported acid catalyst under a
temperature and pressure condition to effect oligomerization of the
.alpha.-alkyl styrene to produce a cyclic dimer of the
.alpha.-alkyl styrene; and (b) hydrogenating the cyclic dimer of
the .alpha.-alkyl styrene in the presence of a hydrogenation
catalyst to produce a fully hydrogenated cyclic dimer of the
.alpha.-alkyl styrene, wherein the .alpha.-alkyl styrene is
contacted with the supported acid catalyst in the absence of a
solvent for the .alpha.-alkyl styrene and in the absence of a free
acid. A continuously variable transmission fluid is formulated by
mixing the fully hydrogenated cyclic dimer with an oil additive,
wherein the continuously variable transmission fluid does not
comprise more than 20 wt. % of a linear dimer of the .alpha.-alkyl
styrene. In some embodiments, the .alpha.-alkyl styrene is
.alpha.-methyl styrene and the cyclic dimer is
1-cyclohexyl-1,1,3-trimethylhydrindane. The CVT fluid formulated
according to embodiments of the invention has a relatively high
traction coefficient and good low temperature properties.
[0011] Additional aspects of the invention and characteristics and
properties of various embodiments of the invention become apparent
with the following description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Not applicable.
DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0013] In the following description, all numbers disclosed herein
are approximate values, regardless whether the word "about" or
"approximate" is used in connection therewith. They may vary by 1
percent, 2 percent, 5 percent, or sometimes 10 to 20 percent.
Whenever a numerical range with a lower limit, R.sup.L and an upper
limit, R.sup.U, is disclosed, any number falling within the range
is specifically disclosed. In particular, the following numbers
within the range are specifically disclosed:
R=R.sup.L+k*(R.sup.U-R.sup.L), wherein k is a variable ranging from
1 percent to 100 percent with a 1 percent increment, i.e., k is 1
percent, 2 percent, 3 percent, 4 percent, 5 percent, . . . , 50
percent, 51 percent, 52 percent, . . . , 95 percent, 96 percent, 97
percent, 98 percent, 99 percent, or 100 percent. Moreover, any
numerical range defined by two R numbers as defined in the above is
also specifically disclosed. Any references cited herein are hereby
incorporated by reference, in their entirety.
[0014] Embodiments of the invention provides a continuously
variable transmission (CVT) fluid with a relatively high traction
coefficient and good low temperature properties. The CVT fluid
comprises a hydrogenated cyclic dimer of .alpha.-alkyl styrene and
a low temperature viscosity control agent in an amount sufficient
to reduce the viscosity of the fluid at -30.degree. C., wherein the
fluid is comprises less than about 20 wt. % of a linear dimer of
the .alpha.-alkyl styrene. Preferably, the CVT fluid has a
kinematic viscosity of greater than about 2.5.times.10.sup.-6
m.sup.2/s at 100.degree. C., as measured according to ASTM D-445.
In some embodiments, the kinematic viscosity is greater than about
3.0.times.10.sup.-6 m.sup.2/s at 100.degree. C.,
3.5.times.10.sup.-6 m.sup.2/s at 100.degree. C.,
4.0.times.10.sup.-6 m.sup.2/s at 100.degree. C. 4.5.times.10.sup.-6
m.sup.2/s at 100.degree. C., 5.0.times.10.sup.-6 m.sup.2/s at
100.degree. C., 6.5.times.10.sup.-6 m.sup.2/s at 100.degree. C.,
7.0.times.10.sup.-6 m.sup.2/s at 100.degree. C.,
7.5.times.10.sup.-6 m.sup.2/s at 100.degree. C.,
8.0.times.10.sup.-6 m.sup.2/s at 100.degree. C.,
8.5.times.10.sup.-6 m.sup.2/s at 100.degree. C.,
9.0.times.10.sup.-6 m.sup.2/s at 100.degree. C.,
9.5.times.10.sup.-6 m.sup.2/s at 100.degree. C., or
2.5.times.10.sup.-6 m.sup.2/s at 100.degree. C. It may also be
greater than about 10.0.times.10.sup.-6 m.sup.2/s at 100.degree.
C., 11.0.times.10.sup.-6 m.sup.2/s at 100.degree. C.,
12.0.times.10.sup.-6 m.sup.2/s at 100.degree. C.,
13.0.times.10.sup.-6 m.sup.2/s at 100.degree. C., or higher. The
CVT fluid can be used as a lubricant in any design of continuously
variable transmission, such as the push belt type or the toroidal
type. These types of continuously variable transmission are
disclosed, for example, in U.S. Pat. No. 6,565,478 and No.
5,750,477.
[0015] As used herein, the term "in an amount sufficient to reduce
the viscosity of the fluid at -30.degree. C." means that the CVT
fluid contains from about 1 to about 20 wt % of a low temperature
viscosity control agent. In some embodiments, "in an amount
sufficient to reduce the viscosity of the fluid at -30.degree. C."
means from about 3 to about 15 wt %, or from about 5 to about 10 wt
%.
[0016] Preferably, the CVT fluid has a relatively high traction
coefficient. For example, in some embodiments, the traction
coefficient at 100.degree. C. is greater than about 0.07, 0.08,
0.09, or 0.10. In other embodiments, the traction coefficient at
100.degree. C. is greater than about 0.101, 0.102, 0.103, 0.104,
0.105, 0.106, 0.107, 0.108, or 0.109. In some other embodiments,
the traction coefficient at 100.degree. C. exceeds about 0.11,
0.12, 0.13, 0.14, or 0.15.
[0017] One low temperature property of the CVT fluid is the
Brookfield viscosity, which can be measured according to ASTM D
2983, entitled "Low-Temperature Viscosity of Automotive Fluid
Lubricants Measured by Brookfield Viscometer," which is
incorporated by reference herein in its entirety. Preferably, the
Brookfield viscosity at -30.degree. C. of the CVT fluid is less
than about 100 Pa.multidot.s. In some embodiments, the Brookfield
viscosity is less than about 90, 80, 70, 60, 50, 40, 30, 20, 10, or
5 Pa.multidot.s. Preferably, it is in the range from about 5 to
about 70 Pa.multidot.s.
[0018] As described above, the CVT fluid comprises a hydrogenated
dimer of .alpha.-alkyl styrene as a base oil. The method for making
the hydrogenated dimer comprises (a) contacting an .alpha.-alkyl
styrene with a supported acid catalyst under a temperature and
pressure condition to effect oligomerization of the .alpha.-alkyl
styrene to produce an oligomerization product, the oligomerization
product comprising a cyclic dimer of the .alpha.-alkyl styrene; and
(b) hydrogenating the cyclic dimer of the .alpha.-alkyl styrene in
the presence of a hydrogenation catalyst to produce a fully
hydrogenated cyclic dimer of the .alpha.-alkyl styrene, wherein the
.alpha.-alkyl styrene is contacted with the supported acid catalyst
in the absence of a solvent for the .alpha.-alkyl styrene and the
absence of a free acid. A CVT fluid is formulated by mixing the
fully hydrogenated cyclic dimer with one or more oil additives
(such as a low temperature viscosity control agent), wherein the
continuously variable transmission fluid comprises less than about
20 wt. % of a linear dimer of the .alpha.-alkyl styrene.
[0019] Although the alkyl group of the .alpha.-alkyl styrene can be
any straight, branched, or cyclic hydrocarbyl group of any carbon
number, it is preferred that the alkyl group is a straight
hydrocarbyl chain with a carbon number of less than 30. The term
"alkyl" used herein refers to an organic group comprising carbon
and hydrogen and can have a straight chain, branched chain, or
cyclic hydrocarbons from one to about twenty carbons. For example,
alkyl includes, but is not limited to, methyl, ethyl, propyl,
butyl, pentyl, hexyl, cyclopropyl, cyclobutyl, cyclopentyl,
cyclohexyl, methylcyclopentyl, ethenyl, propenyl, butenyl,
pentenyl, hexenyl, phenyl, naphthyl, anthracenyl, benzyl, and
isomers thereof In some embodiments, the alkyl group has from 1 to
4 carbon atoms, such as methyl or ethyl. The preferred dimers are
accordingly hydrogenated cyclic dimers of .alpha.-methylstyrene and
.alpha.-ethylstyrene, hydrogenated cyclic co-dimers of
.alpha.-methylstyrene and .alpha.-ethylstyrene, and mixtures
thereof Hydrogenated dimer of .alpha.-methylstyrene is also called
1-cyclohexyl- 1,1,3-trimethylhydrindane. The method of making
1-cyclohexyl-1,1,3-trimet- hylhydrindane is explained in the
following. While the synthesis of
1-cyclohexyl-1,1,3-trimethylhydrindane is exemplified herein, the
cyclic dimer of other .alpha.-alkyl styrene can also be obtained by
the following process, with or without modifications.
[0020] Dimerization of .alpha.-methyl styrene is effected by
passing .alpha.-methyl styrene, preferably in the absence of a
solvent, through a column of an acidic ion-exchange resin under
conditions which yield at least 80% of the cyclic dimer, which is
followed by fully hydrogenating the product under conditions which
convert the cyclic dimer of .alpha.-methyl styrene to
1-cyclohexyl-1,1,3-trimethylhydrindane. Optionally, before
hydrogenating, the cyclic dimer is vacuum distilled to remove a
minor amount of the trimer of .alpha.-methyl styrene. Preferably,
the acid is supported such that there is no substantial amount of
free acid (i.e., unsupported acid). In other words, the
dimerization occurs substantially free of unsupported acid (i.e.,
free acid). In some embodiments, the dimerization reaction is
completely free of free acid.
[0021] In one embodiment, the acidic resin is the strongly acidic
resin Amberlyst.RTM. 15, an acidic sulfonated
divinylbenzene/styrene copolymer. The column of resin is operated
at a temperature of about 0.degree. C. to about 150.degree. C., a
pressure of about 15 to about 44 psig (about 103 to about 303 kPa
gauge), and with a residence time of about 1 second to about 200
minutes. Preferably, the column of resin is operated at about
60.degree. C. to about 120.degree. C., a pressure of about 15 to
about 30 psig (100 to 200 kPa gauge), and a residence time of about
5 second to about 20 minutes.
[0022] Hydrogenation of the product of the dimerization column is
carried out by contact with a hydrogenation catalyst, preferably
palladium on carbon at a temperature of about 120.degree. C. to
about 220.degree. C. preferably about 160.degree. C. to about
200.degree. C., for about 4 hours to about 24 hours at a hydrogen
pressure of about 500 to about 2,000 psig (3,447 to 13,789 kPa
gauge) preferably, about 700 to about 1,000 psig (4,826 to 6,895
kPa gauge). Optionally, the hydrogenated product is vacuum
distilled at a pressure of about 0.1 to about 150 mm Hg absolute to
remove the fully hydrogenated trimer of .alpha.-methyl styrene.
[0023] Dimerization Catalyst
[0024] The acidic ion-exchange catalysts used in the process of the
invention may be considered solid super acids. Sulfonic acid groups
are attached to polymers such as divinylbenzene/styrene copolymers,
perfluorinated epoxides, and phenolformaldehyde resins. The acidity
may be increased by reacting the sulphonated polymers with Lewis
acid halides, such as AlCl.sub.3, SnCl.sub.2, TiCl.sub.4, SbF.sub.5
and BF.sub.3.
[0025] The preferred catalyst for use in the dimerization step is
the strongly acidic ion-exchange resin, Amberlyst.RTM. 15, a
product of the Rohm & Haas Company. Alternatively, other acidic
supported catalysts could be used, although not necessarily with
equivalent results. Examples of such catalysts are Nation.RTM.-H, a
copolymer of perfluorinated epoxide/vinyl/sulphonic acid made by
E.I. Dupont, and strongly acidic ion-exchange resins Dowex-50 made
by the Dow Chemical Company. Alternatively, weakly acidic
ion-exchange resin with carboxylic acid functionality could be
used, such as Amberlite CG-50 or Amberlite IRC-50S made by Rohm
& Haas.
[0026] Reactor
[0027] The acidic ion-exchange resin particles preferably are
placed in a fixed bed arrangement in a cylindrical reactor. In some
embodiments of the invention, the catalyst is in particulate form
and disposed in a fixed bed. Consequently, the mixing of the fresh
.alpha.-methyl styrene with products is minimized and the
conversion of the feed stock into a product, which is almost
completely the cyclic dimer, appears to occur by a sequential
reaction of .alpha.-methyl styrene to the linear dimer,
2,4-diphenyl-4-methyl-1-pentene or the 2-pentene isomer, followed
by a Friedel-Crafts reaction to form the cyclic dimer,
1-cyclohexyl-1,1,3-trim- ethylindane. In the example below, the
ratio of the length to the diameter of the resin bed is about 5/1,
but it is expected that ratios between about 1/10 and about 20/1
could be used. The size of the resin particles are normally be
about 200 mesh to macro-reticular beads.
[0028] The residence time in the reactor, that is the time when the
.alpha.-methyl styrene is in contact with the catalyst, is about 1
second to about 200 minutes, preferably about 5 second to about 20
minutes, depending on the desired yield of the product and the
temperature chosen for the reaction. In general, a temperature
between ambient and about 150.degree. C. are used, preferably about
60.degree. to about 120.degree. C., depending on the residence time
and desired yield of the cyclic dimer. The operating pressure is
about 15 to about 44 psig (100 to 300 kPa gauge), preferably about
15 to about 30 psig (100 to 200 kPa gauge). One familiar with the
art understands that a balancing of variables (e.g. residence time,
temperature, length/diameter) is usually made to provide the
optimum conditions for making the desired yield of the cyclic
dimer.
[0029] Hydrogenation of the Dimer
[0030] Since only .alpha.-methyl styrene need be supplied to the
reactor, the product containing a high yield of the cyclic dimer,
of at least 80%, can be immediately fed to a hydrogenation step,
although separation of the dimer from the small amount of trimer
can be done before the hydrogenation step.
[0031] Hydrogenation can be carried out using a known catalyst,
such as nickel on kieselguhr, nickel on silica/alumina, Raney
nickel, palladium on carbon, platinum and the like. In the example
below, palladium supported on carbon is used and found to be
effective. If a supported catalyst is used, it typically is placed
in a fixed bed reactor and the feed stock passed over it while
mixed with hydrogen under suitable hydrogenation conditions. The
temperature should be between about 120.degree. and about
250.degree. C., but preferably between about 160.degree. and about
200.degree. C. The pressure of the hydrogen in the reactor is about
5,000 to about 2,000 psig (3,447 to 13,789 kPa gauge), preferably
about 700 to about 1,000 psig (4,826 to 6,895 kPa gauge). After a
suitable period of time, the cyclic dimer of .alpha.-methyl styrene
is converted to the fully hydrogenated form in which the phenyl
groups of the dimer have been converted to cyclohexyl groups.
[0032] After separating the hydrogen, the product may be used
directly as the base oil for further formulating a transmission
fluid, or it may be purified by distillation to remove the
hydrogenated trimer of .alpha.-methyl styrene. As will be seen in
Example 3 below, the traction coefficient for the hydrogenated
product containing about 95% of the cyclic dimer and 5% of the
trimer is superior to that of the hydrogenated linear dimer. After
removing the trimer, the traction coefficient is further
improved.
[0033] The above process has one or more of the following
advantages. In a once-through catalytic reaction in a fixed bed
reactor, .alpha.-methyl styrene is converted to at least 80% yield
of the cyclic dimer. The product can be immediately converted to
the fully hydrogenated form and used as the base oil for further
formulating a transmission fluid, or alternatively, it can be
distilled to remove the minor portion of the trimer of
.alpha.-methyl styrene and then hydrogenated. The trimer also may
be removed by distillation after the hydrogenation step. No
diluents are needed in the dimerization step, the .alpha.-methyl
styrene being supplied in commercially pure form. Thus, separation
of diluents from the product of the dimerization reaction is not
needed and no aqueous washes are required. The hydrogenation
product containing the trimer of .alpha.-methyl styrene has a
traction coefficient greater than that of the hydrogenated linear
dimer and the traction coefficient is further improved by
separation of the trimer.
[0034] While the above processes are described in detail, the
process conditions can vary. For example, the processes can be
modified by practicing the dimerization and hydrogenation steps
disclosed in the following U.S. patents which are incorporated by
referenced herein in their entirety: U.S. Pat. Nos. 2,629,751;
3,411,369; 3,440,894; 3,595,797; 3,929,923; 3,975,278; 3,997,617;
and 4,046,703.
[0035] Formulating Traction Fluid
[0036] Another aspect of the invention relates to a traction or a
CVT fluid comprising the hydrogenated cyclic dimer of .alpha.-alkyl
styrene as the major component, which may be combined with one or
more additives, as needed to improve low temperature viscosity and
other desirable properties. Such additives include, but are not
limited to, low temperature viscosity control agents, dispersants,
detergents, viscosity index modifiers, phosphorus compounds, and
friction modifiers. Formulations of a traction or CVT fluid have
been taught in the following U.S. patents which are incorporated by
reference herein in their entirety: U.S. Pat. Nos. 3,411,369;
3,440,894; 3,595,797; 3,975,278; 4,046,703; 4,521,324; 4,525,290;
4,556,503; 5,422,027; 6,103,673; 6,262,000; 6,337,309; 6,372,696;
and 6451,745. Various additives or components disclosed in the
above patents may be used in the traction or CVT fluid.
[0037] Base Oil
[0038] The base oil for a traction fluid in accordance with
embodiments of the invention is a hydrogenated cyclic dimer of
.alpha.-methyl styrene, which is included in an amount of at least
50 percent by weight of the traction fluid. However, in some
embodiments, only about 20 wt % to about 50 wt % of the
hydrogenated cyclic dimer is present in the traction fluid. On the
other hand, in other embodiments, a higher amount, such as at least
about 60 wt %, about 70 wt %, about 80 wt %, about 85 wt %, or
about 90 wt % is used. Some traction fluids may include up to about
95 wt % to about 99 wt % of the hydrogenated cyclic dimer. In some
embodiments, the traction fluids are completely or substantially
free of a linear dimer, either hydrogenated or un-hydrogenated.
However, in other embodiments, a linear dimer may be present up to
about 10 to about 20 percent by weight of the traction fluid. In a
preferred embodiment, the linear dimer is present in less than
about 5 percent by weight of the traction fluid. In some
embodiments, hydrogenated trimers are present in the traction
fluid, in addition to the hydrogenated dimers. In other
embodiments, the traction fluid is completely or substantially free
of the trimers or higher oligomers of .alpha.-alkyl styrene.
[0039] As used herein, the term "substantially free of a linear
dimer of the .alpha.-alkyl styrene" means that the CVT fluid
contains less than about 20 wt. % of a linear dimer of the
.alpha.-alkyl styrene. In some embodiments, "substantially free of
a linear dimer of the .alpha.-alkyl styrene" means less than 15 wt.
%, less than 10 wt. %, less than 5 wt. %, less than 3 wt. %, less
than 1 wt. %, or less than 0.5 wt. %.
[0040] In some embodiments, the CVT fluid is substantially or
completely free of any trimer or higher oligomers of the
.alpha.-alkyl styrene. As used herein, the term "substantially free
of trimer or higher oligomers of the .alpha.-alkyl styrene" means
that the CVT fluid contains less than about 5 wt. % of a linear
dimer of the .alpha.-alkyl styrene. In some instances, it means
less than 1 wt. %, or less than 0.5 wt. %.
[0041] Low-Temperature Viscosity Control Agent
[0042] The second component of the traction fluids is a
low-temperature viscosity control agent. The low-temperature
viscosity control agent (which is to be distinguished from a
viscosity index modifier, an optional component described below) is
selected from among a variety of materials which are known to be
useful for this purpose. The low-temperature viscosity control
agent is selected from (a) oligomers or polymers of linear
.alpha.-olefins of at least 12 carbon atoms, (b) naphthenic oils,
(c) synthetic ester oils, or (d) polyether oils, or mixtures
thereof These materials are distinguishable from the base fluids,
described above, in that they are generally lower viscosity
materials than the base fluid, typically exhibiting a viscosity of
up to or less than about 2.5.times.10.sup.-6 m.sup.2/s (2.5 cSt),
preferably about 1.5 to about 2.5, or about 1.8 to about
2.3.times.10.sup.-6 m.sup.2/s (1.5 to 2.5 or 1.8 to 2.3 cSt) at
about 100.degree. C. These are also materials which typically
retain a measure of mobility at low temperatures (e.g., -30.degree.
C.) and can serve to reduce the low temperature viscosity of fluids
to which they are added. On the other hand, in other embodiments,
The low-temperature viscosity control agent can be materials which
have a viscosity greater than 2.5.times.10.sup.-6 m.sup.2/s (2.5
cSt), such as 3.0.times.10.sup.-6 m.sup.2/s (3 cSt),
4.0.times.10.sup.-6 m.sup.2/s (4 cSt), 5.0.times.10.sup.-6
m.sup.2/s (5 cSt), 6.0.times.10.sup.-6 m.sup.2/s (6 cSt) or
higher.
[0043] Polymers and oligomers of linear .alpha.-olefins are well
known items of commerce. A typical commercial material is
Ethylflo.TM. 162, a 2 .times.10.sup.-6 m.sup.2/s (2 cSt)
poly-.alpha.-olefin product of Ethyl Corporation. Preferred
materials are those oligomers or polymers of .alpha.-olefins
containing 12 to 40 carbon atoms, and preferably 16 to 20 carbon
atoms. Such materials do not contain a significant fraction of
.alpha.-olefin monomers of fewer than 12 carbon atoms, that is,
less than about 5 percent by weight, preferably less than about 1
percent by weight, and more preferably substantially no such
monomers. The description "oligomers or polymers" is used since
generally low molecular weight materials are desired, and there is
otherwise no clear demarcation between an oligomer and a polymer.
Materials as low as dimers (a degree of polymerization of 2) are
included. Suitable materials for the present invention typically
have a molecular weight range of about 100 to about 1000,
preferably about 150 to about 600, and most preferably about 250 to
about 600 or, about 250 to about 500 or about 250 to about 400.
[0044] Naphthenic oils are well known items of commerce, commonly
derived from petroleum. Preferred materials are hydrogenated
naphthenic oils, which are also well known. Examples include
Hydrocal.TM. 38 from Calumet Lubricants Company and 40 Pale Oil.TM.
from Diamond Shamrock. Synthetic ester oils suitable for use as low
temperature viscosity control agents include esters of polyhydroxy
compounds and predominantly monocarboxylic acylating agents; esters
of predominantly monohydroxy compounds and polycarboxylic acylating
agents; esters of monohydroxy compounds and monocarboxylic
acylating agents, and mixtures of the foregoing types. The prefix
"poly" in this context indicates at least two hydroxy groups or
carboxylic groups, as the case may be. The molecular weight of the
esters (as of any of the viscosity control agents) should be
sufficiently high that the materials are not objectionably volatile
so as to experience significant evaporative loss under operating
conditions, while retaining the above-described viscosities.
Certain synthetic ester oils and their methods of preparation are
disclosed in PCT publication WO 91/13133. Synthetic ester oils are
available as Emery.TM. synthetic lubricant basestocks from Henkel
Corporation and as Emkarate.TM. lubricant basestocks from Imperial
Chemical Industries PLC.
[0045] Polyether oils suitable for use as a low temperature
viscosity control agent include polyalkylene oxides, and in
particular, polyethylene oxides, polypropylene oxides, polybutylene
oxides, and mixtures thereof. The polyether oil typically has a
molecular weight in the ranges suitable for maintaining an
appropriate viscosity and non-volatility. Such materials are also
well known items of commerce and are available as Emkarox.TM.
polyalkylene glycols from Imperial Chemical Industries PLC.
[0046] As is the case with the base fluid, the low temperature
viscosity control agent is often a hydrogenated material. Each of
these components preferably contains fewer than about 20%, fewer
than about 15%, or more preferably fewer than about 10% molecules
containing carbon-carbon unsaturation, and in the most preferred
case is substantially free from carbon-carbon unsaturation, that is
to say, retaining at most a low level of unsaturation which does
not measurably or significantly affect its performance.
[0047] The amount of the low temperature viscosity control agent in
the traction fluid is preferably that amount suitable to provide a
viscosity at -30.degree. C. of a CVT fluid of less than or equal to
100 Pa.multidot.s (100,000 cP), such as about 2 to about 100
Pa.multidot.s (2,000 to 100,000 cP), preferably about 5 to about 80
or about 70 Pa.multidot.s (5,000 to 80,000 or 70,000 cP), and more
preferably 10 to 50 Pa.multidot.s (10,000 to 50,000 cP). As stated
previously, the amount of low temperature viscosity control agent
should preferably be about 1 to 20 percent by weight of the
traction fluid, preferably about 3 to about 15, and more preferably
about 5 to about 10 percent by weight.
[0048] Viscosity Index Improvers
[0049] To increase the viscosity at higher temperatures, viscosity
index improvers are added to the formulation. Generally speaking,
there are two types of viscosity modifiers (or viscosity index
improvers). One is the relative polar ester-type, such as LUBRIZOL
7671.TM., which is a long chain ester of maleic anhydride styrene
copolymer (see also, LUBRIZOL 7764.TM. and LUBRIZOL 7783.TM. which
are polymethacrylate copolymers). The other is the non-polar
hydrogenated olefin copolymer (OCP) type, such as LUBRIZOL
7075.TM., (also included are hydrogenated styrene-diene copolymers,
such as INFINEUM SV 200.TM. and INFINEUM SV 150.TM., etc.) which
are amorphous hydrocarbon polymers.
[0050] A preferred polar ester-type viscosity modifier is
LUBRIZOL.TM. 7671 made by LUBRIZOL (Wickliffe, Ohio). LUBRIZOL.TM.
7671 is a polymethacrylate type thickener and also acts as a pour
point depressant for vegetable oils. Other polar ester-type
viscosity modifiers include LUBRIZOL.TM. 7764, LUBRIZOL.TM. 7776,
LUBRIZOL.TM. 7785, LUBRIZOL.TM. 7786, from LUBRIZOL (Wickliffe,
Ohio) which are polymethacrylate copolymer viscosity index
improvers.
[0051] Polar ester-type viscosity modifiers having similar
properties as those in the following table are also useful:
1 Property Value Flash Point, .degree. C. 165 Specific Gravity 0.90
Viscosity, cSt 8500 @ 40.degree. C. 1500 @ 100.degree. C.
[0052] A preferred non-polar hydrogenated olefin copolymer-type
viscosity modifier is the LUBRIZOL 7075.TM. Series made by LUBRIZOL
(Wickliffe, Ohio). This series is Lubrizol's next generation
nondispersant olefin copolymer (OCP) viscosity modifier.
Hydrogenated olefin copolymers are the most widely used type of
viscosity modifier for passenger car motor oils and heavy-duty
diesel engine oils. Developed in the mid-1960s, hydrogenated olefin
copolymers differ mainly in molecular weight and the ratio of
ethylene to propylene. These polymers effectively minimize
viscosity variations over typical engine operating temperatures.
They are cost-effective and are suitable for formulating nearly any
mainline engine oil. The polymers provide a cost-effective way to
meet the latest international and original equipment manufacturer
(OEM) specifications for passenger car and heavy-duty diesel engine
oils.
[0053] Non-polar hydrogenated olefin copolymer-type viscosity
modifiers having the following characteristics may also be useful
in embodiments:
2 Property Value Flash Point, .degree. C. 190 Specific Gravity 0.87
Viscosity, cSt 825 @ 100.degree. C.
[0054] LUBRIZOL 7075D.TM. is a preferred olefin copolymer type
viscosity modifier from LUBRIZOL (Wickliffe, Ohio). Other olefin
copolymer type viscosity modifiers include the LUBRIZOL 7070.TM.
series, 7077.TM. series, 7740.TM. series; INFINEUM SV140.TM.,
SV145.TM., SV200.TM., SV205.TM., SV300.TM., SV305.TM., (EXXONMOBIL,
Tex.) and PARATONE.TM. 8900 series by (CHEVRON, Calif.).
[0055] Ester type viscosity modifiers, different from the polar
ester types described above, having the following characteristics
may also be useful in embodiments:
3 Property Value Flash Point, .degree. C. 161 Specific Gravity 0.90
Viscosity, cSt 20.5 @ 100.degree. C.
[0056] The ester type viscosity index improver may be added in an
amount from about 0 to about 3.0 wt %, more preferred from about
0.2 to about 2.5 wt %, most preferred from about 0.5 to about 2 wt
% and the hydrogenated olefin copolymer type viscosity index
improver may be added in an amount from about 0 to about 6.0 wt %,
more preferred from about 1 to about 5 wt %, most preferred from
about 2 to about 4 wt %.
[0057] Other suitable conventional viscosity index improvers, or
viscosity modifiers, are olefin polymers, such as polybutene,
hydrogenated polymers and copolymers and terpolymers of styrene
with isoprene and/or butadiene, polymers of alkyl acrylates or
alkyl methacrylates, copolymers of alkyl methacrylates with N-vinyl
pyrrolidone or dimethylaminoalkyl methacrylate. These are used as
required to provide the viscosity range desired in the finished
oil, in accordance with known formulating techniques.
[0058] Esters obtained by co-polymerizing styrene and maleic
anhydride in the presence of a free radical initiator and
thereafter esterifying the copolymer with a mixture of
C.sub.4-C.sub.18 alcohols, are also useful as viscosity modifying
additives. The styrene esters generally are considered to be
multi-functional premium viscosity modifiers. The styrene esters in
addition to their viscosity-modifying properties also are pour
point depressants and exhibit dispersancy properties when the
esterification is terminated before its completion leaving some
unreacted anhydride or carboxylic acid groups. These acid groups
can then be converted to amides by reaction with a primary amine.
The co-polymerization of styrene with maleic anhydride creates a
copolymer (SMA) which has a higher glass transition temperature
than polystyrene and is chemically reactive with certain functional
groups. Thus, SMA polymers are often used in blends or composites
where interaction or reaction of the maleic anhydride provides for
desirable interfacial effects. Some SMA polymers that are
commercially available from ROHMAX USA (Horsham, Pa.) include
VISCOPLEX.TM. 2-360, VISCOPLEX.TM. 2-500, VISCOPLEX.TM. 3-540,
VISCOPLEX.TM. 4-671, and VISCOPLEX.TM. 6-054.
[0059] Another class of suitable viscosity index improvers is
polymethacrylate(PMA)-based viscosity modifiers. For example, a
suitable viscosity modifier is a copolymer comprising units derived
from (a) methacrylic acid esters containing from about 9 to about
25 carbon atoms in the ester group, and (b) methacrylic acid esters
containing from about 7 to about 12 carbon atoms in the ester
group, said ester groups having 2-(C.sub.1-4 alkyl)-substituents,
and optionally (c) at least one monomer selected from the group
consisting of methacrylic acid esters containing from about 2 to
about 8 carbon atoms in the ester group and which are different
from methacrylic acid esters (a) and (b), vinyl aromatic compounds,
and nitrogen-containing vinyl monomers, with the proviso that no
more than about 60% by weight of the esters contain not more than
11 carbon atoms in the ester group. Such a copolymer is disclosed
in U.S. Pat. No. 6,124,249, which is incorporated by reference
herein in its entirety.
[0060] Commercial PMA-based viscosity modifiers are available from
Lubrizol Corporation under the following trade names: Lubrizol.RTM.
7776--nondispersant polymethacrylate viscosity modifier with pour
point depressing properties and an Orbahn Shear Stability Index of
0 to 2; Lubrizol.RTM. 7785--nondispersant polymethacrylate
viscosity modifier diluted in vegetable oil for environmentally
sensitive applications; Lubrizol.RTM. 7786--nondispersant
polymethacrylate viscosity modifier with pour point depressing
properties and an Orbahn Shear Stability Index of 10; and
Lubrizol.RTM. 7794--nondispersant polymethacrylate viscosity
modifier with pour point depressing properties and an Orbahn Shear
Stability Index of 20.
[0061] Another component of the lubricant formulation may be an oil
soluble zinc salt. There is no particular restriction on the type
of zinc salt; however, it should not be a zinc thiophosphate or
dithiophosphate material. While zinc dialkyldithiophosphates
(ZDDPs) are widely known in the lubricating art, they should not be
present in the CVT fluids except perhaps in small and
inconsequential amounts. Indeed, the CVT fluids should be
substantially free from any thiophosphate derivatives, in order to
provide a formulation which exhibits minimal copper corrosion. In
one embodiment, the lubricating formulation is substantially free
from compounds of all types containing active sulfur atoms. By
"active sulfur atoms" is meant sulfur atoms which are available (or
are sufficiently labile to become available) to react with metal
parts of a transmission. Besides elemental sulfur, materials which
may contain or may generate active sulfur atoms include common
anti-wear agent including sulfurized olefins, thiocarbamates, and
dithiocarbamates. By "substantially free" it is meant that the
amount of the thiophosphate material is sufficiently low as to have
no practically measurable effect on performance of the fluid, with
regard to copper corrosion. In numerical terms this would normally
correspond to an amount of zinc dialkyldithiophosphate of less than
200 parts per million in the composition, preferably less than 50
or 10 ppm.
[0062] Copper corrosion is measured by ASTM standard test number
130. The compositions are formulated to be substantially free from
thiophosphate salts, exhibits a copper corrosion rating of 1B or
better when tested for 3 hours at 149.degree. C.
[0063] Oil-soluble zinc salts are species which contain at least
one hydrocarbyl group of at least 4, and preferably at least 6,
carbon atoms. The hydrocarbyl group is generally required in order
to provide the required oil solubility, and its particular length
or other characteristics may vary depending on the type of zinc
salt involved. Suitable zinc salts include zinc phosphates,
phosphites, phosphonates, sulfonates, carboxylates, phenates, and
salicylates.
[0064] As used herein, the term "hydrocarbyl substituent" or
"hydrocarbyl group" is used in its ordinary sense, which is
well-known to those skilled in the art. Specifically, it refers to
a group having a carbon atom directly attached to the remainder of
the molecule and having predominantly hydrocarbon character.
Examples of hydrocarbyl groups include:
[0065] (1) hydrocarbon substituents, that is, aliphatic (e.g.,
alkyl or alkenyl), alicyclic (e.g., cycloalkyl, cycloalkenyl)
substituents, and aromatic-, aliphatic-, and alicyclic-substituted
aromatic substituents, as well as cyclic substituents wherein the
ring is completed through another portion of the molecule (e.g.,
two substituents together form a ring);
[0066] (2) substituted hydrocarbon substituents, that is,
substituents containing non-hydrocarbon groups which, in the
context of this invention, do not alter the predominantly
hydrocarbon substituent (e.g., halo (especially chloro and fluoro),
hydroxy, alkoxy, mercapto, alkylmercapto, nitro, nitroso, and
sulfoxy);
[0067] (3) hetero substituents, that is, substituents which, while
having a predominantly hydrocarbon character, in the context of
this invention, contain other than carbon in a ring or chain
otherwise composed of carbon atoms. Heteroatoms include sulfur,
oxygen, nitrogen, and encompass substituents as pyridyl, furyl,
thienyl and imidazolyl. In general, no more than two, preferably no
more than one, non-hydrocarbon substituent is present for every ten
carbon atoms in the hydrocarbyl group; typically, there is no
non-hydrocarbon substituents in the hydrocarbyl group.
[0068] Hydrocarbyl groups containing active sulfur may be avoided,
if desired, to the extent that they may undesirably contribute to
copper corrosion.
[0069] In one embodiment, the zinc salt is a zinc hydrocarbyl
phosphate. The phosphate can be a mono-or dihydrocarbyl phosphate.
Each hydrocarbyl groups typically independently contain 1 to 30
carbon atoms, preferably 1 to 24 carbon atoms, more preferably 1 to
12 carbon atoms, provided, as stated above, that at least one
hydrocarbyl group contains at least 6 carbon atoms. In a preferred
embodiment, each hydrocarbyl is independently an alkyl or aryl
group. When any group is an aryl group it typically contains 6 to
24 carbon atoms, more preferably 6 to 18 carbon atoms. Examples of
hydrocarbyl groups include a butyl, amyl, hexyl, octyl, oleyl or
cresyl, with octyl and cresyl being preferred.
[0070] The zinc hydrocarbyl phosphates can be prepared by reacting
phosphorus acid or anhydride, preferably phosphorus pentoxide, with
an alcohol at a temperature of 30.degree. C. to 200.degree. C.,
preferably 80.degree. C. to 150.degree. C., followed by
neutralization with a zinc base. The phosphorus acid is generally
reacted with the alcohol in a ratio of about 1:3.5, preferably 1:2.
The product of such a reaction typically comprises a mixture of
monohydrocarbyl and dihydrocarbyl zinc phosphates, typically being
present in a relative ratios of about 1:1, or more generally, 2:1
to 1:2 or 3:1 to 1:3. Mixtures of about 1:1
monohydrocarbyl:dihydrocarbyl materials can be prepared by the
simple stoichiometric reaction of alcohol with P.sub.2O.sub.5:
3ROH+P.sub.2O.sub.5.fwdarw.RO--P(.dbd.O)--(OH).sub.2+(RO).sub.2--P(.dbd.O)-
--OH
[0071] The alcohol can be any of the commercially available
alcohols having an appropriate chain length, or mixtures of such
alcohols. The alcohols can be aliphatic, cycloaliphatic, aromatic,
or heterocyclic, including aliphatic-substituted cycloaliphatic
alcohols, aliphatic-substituted aromatic alcohols,
aliphatic-substituted heterocyclic alcohols,
cycloaliphatic-substituted aliphatic alcohols,
cycloaliphatic-substituted aromatic alcohols,
cycloaliphatic-substituted heterocyclic alcohols,
heterocyclic-substituted aliphatic alcohols,
heterocyclic-substituted cycloaliphatic alcohols, and
heterocyclic-substituted aromatic alcohols. The alcohols may
contain non-hydrocarbon substituents of a type which do not
interfere with the reaction of the alcohols with the phosphorus
compound. The alcohols can be monohydric alcohols such as methanol,
ethanol, isooctanol, 2-ethylhexanol, dodecanol, and cyclohexanol.
Alternatively, the alcohols can be polyhydric alcohols, such as
alkylene polyols such as ethylene glycols, including di-, tri- and
tetraethylene glycols; propylene glycols, including di-, tri- and
tetrapropylene glycols; glycerol; and the like. Also useful
alcohols are mixed C.sub.18-C.sub.28 primary alcohols having
mostly, on an alcohol basis, C.sub.22 alcohols. A variety of
mixtures of monohydric fatty alcohols derived from naturally
occurring triglycerides and ranging in chain length of from C.sub.8
to C.sub.18 are also useful, and are available from various sources
including Procter & Gamble Company.
[0072] Another category of zinc salts includes the zinc
carboxylates. These can be seen as the neutralization product of a
zinc base and a carboxylic acid. As before, the carboxylic acid
should contain at least 6 carbon atoms, to provide appropriate
solubility. The carboxylic acids can be aliphatic or aromatic,
mono- or polycarboxylic acids (or acid-producing compounds). These
carboxylic acids include lower molecular weight carboxylic acids as
well as higher molecular weight carboxylic acids (e.g. having more
than 8 or more carbon atoms). Usually, in order to provide the
desired solubility, the number of carbon atoms in a carboxylic acid
should be at least about 8, e.g., 8 to 400, preferably 10 to 50,
and more preferably 10 to 22.
[0073] Carboxylic acids include saturated and unsaturated acids.
Examples of useful acids include dodecanoic acid, decanoic acid,
tall oil acid, 10-methyl-tetradecanoic acid, 3-ethyl-hexadecanoic
acid, and 8-methyl-octadecanoic acid, palmitic acid, stearic acid,
myristic acid, oleic acid, linoleic acid, behenic acid,
hexatriacontanoic acid, tetrapropylenyl-substituted glutaric acid,
polybutenyl-substituted succinic acid derived from a polybutene
(average Mn=200-1500), polypropenyl-substituted succinic acid
derived from a polypropene, (average Mn=200-1000),
octadecyl-substituted adipic acid, chlorostearic acid,
12-hydroxystearic acid, 9-methylstearic acid, dichlorostearic acid,
ricinoleic acid, lesquerellic acid, stearyl-benzoic acid,
eicosanyl-substituted naphthoic acid, dilauryl-decahydronaphthalene
carboxylic acid, mixtures of any of these acids, their alkali and
alkaline earth metal salts, their ammonium salts, their anhydrides,
or their esters or triglycerides. A preferred group of aliphatic
carboxylic acids includes the saturated and unsaturated higher
fatty acids containing from about 12 to 30 carbon atoms. Other
acids include aromatic carboxylic acids including substituted and
non-substituted benzoic, phthalic and salicylic acids or
anhydrides, most especially those substituted with a hydrocarbyl
group containing about 6 to 80 carbon atoms. Examples of suitable
substituent groups include butyl, isobutyl, pentyl, octyl, nonyl,
dodecyl, and substituents derived from the above-described
polyalkenes such as polyethylenes, polypropylenes,
polyisobutylenes, ethylene-propylene copolymers, and oxidized
ethylene-propylene copolymers.
[0074] An especially preferred zinc carboxylate is zinc oleate,
which can be prepared by the neutralization of oleic acid by a
basic zinc compound. Another zinc carboxylate is zinc
salicylate.
[0075] The zinc compound can be a simple (neutral) salt, generally
formed by straightforward stoichiometric acid-base neutralization
of the acid with a zinc base such as zinc oxide or zinc hydroxide.
The zinc salt can also be an overbased salt. Alternatively, the
zinc salt can be a basic salt, in which one equivalent of a zinc
base is reacted with somewhat less than one equivalent of acid, as
described, for instance, in U.S. Pat. No. 5,110,488 (columns 9 and
10). An example of such a material is a slightly "over-zinc-ed"
oleate, that is, Zn.sub.4Oleate.sub.3O.sub.1. This is a species of
overbased materials in general, which are well known to those
skilled in the art and are generally disclosed in numerous patents
such as U.S. Pat. No. 3,492,231 and especially the references cited
therein.
[0076] The amount of the oil-soluble zinc salt should be sufficient
to impart an increased steel-on-steel dynamic coefficient of
friction for the formulation of at least 0.125, preferably 0.125 or
0.127 to 0.150, more preferably 0.130 to 0.140 or 0.135. The
corresponding static coefficient of friction is 0.14 to 0.2 The
coefficients of friction are measured at 110.degree. C. by ASTM
G-77. The coefficient of friction of the formulation is improved,
that is, increased over that of the same composition without the
zinc salt.
[0077] The preferred amount of the oil soluble zinc salt,
differently stated, is 0.05 to 1.0 percent by weight of the
lubricant formulation, preferably 0.2 to 0.5 weight percent. The
zinc salt preferably contributes up to 0.15 weight percent zinc to
the formulation, more preferably 0.01 to 0.1 weight percent.
[0078] Other Additives
[0079] The fluid used in embodiments of the invention may typically
contain one or more additional additives suitable for use in a
continuously variable transmission or an automatic transmission
fluid (ATF). Such additional materials include other friction
modifiers; and antioxidants, including hindered phenolic
antioxidants, secondary aromatic amine antioxidants, oil-soluble
copper compounds, and phosphorus-containing antioxidants. Other
components include metal deactivators such as tolyltriazole,
benzotriazole, and the methylene-coupled product of tolyltriazole
and amides such as 2-ethylhexylamine. Such metal deactivators can
also be useful in adjusting the metal-to-metal friction in push
belt CVTs. Other components can include seal swell compositions,
such as isodecyl sulfolane (that is, isodecyl-3-sulfolanyl ether),
which are designed to keep seals pliable. Also permissible are pour
point depressants, such as alkyl-naphthalenes, polymethacrylates,
vinyl acetate/fumarate or /maleate copolymers, and styrene/maleate
copolymers. Also included can be corrosion inhibitors, dyes,
fluidizing agents, antifoam agents, dispersants, detergents, and
anti-wear agents. These optional materials are known to those
skilled in the art, are generally commercially available, and many
are described in greater detail in U.S. Pat. No. 6,251,840. Each of
these materials may be present in conventional and functional
amounts.
[0080] Detergents and dispersants of the types discussed in U.S.
Pat. No. 6,372,696 patent are known in the lubrication art and
reference may be made to the patent for additional information.
They are selected to improve the durability of the traction fluid
and are generally present in amounts of up to about 20 wt %.
[0081] Other potential additives which may be present in traction
fluids are phosphorus compounds. It is understood by those skilled
in the art that the additives which are used in traction fluids may
include any or all of those mentioned above. They are chosen to
optimize the performance of the traction fluid considering both
performance and cost. As will be seen in the example, the additives
can significantly affect the viscosity and traction
coefficient.
[0082] The composition of embodiments of the invention is normally
supplied as a fully formulated lubricant or functional fluid, or
initially prepared as a concentrate. In a concentrate, the relative
amounts of the various components are generally about the same as
in the fully formulated composition, except that the amount of oil
of lubricating viscosity is decreased by an appropriate amount. The
absolute percentage amounts of the remaining components are
correspondingly increased. Thus, when the concentrate is added to
an appropriate amount of oil, the final formulation of the
invention is obtained. A typical concentrate of the invention may
contain, for instance, 0.5 to 20 weight percent of the zinc salt,
that is, about 10 times the concentration typically used in a final
blend.
[0083] Measurement of Traction Coefficient
[0084] The traction coefficient is determined generally as
disclosed in U.S. Pat. No. 3,975,278 and is a well-known
measurement. In this method, coefficient of traction is determined
on a rolling disk machine. This machine is designed to predict the
performance of a fluid in variable speed drives and comprises two
hardened steel rollers which may be loaded one against the other
and driven at any required speed. The fluid is introduced between
the rollers and the relationships between applied load, roller
surface speeds, relative sliding speed between the two rollers, and
torque transmitted from one roller to the other through the contact
between them are a measure of the potential performance of the
fluid in a variable speed drive. Literature references on this
rolling disk machine include M. A. Plint [Proceedings of the Inst.
of Mech. Engrs., Vol. 180, pp 225, 313 (1965-66)]; "The Lubrication
of Rollers, I" by A. W. Crook [Phil. Trans. A 255, 281 (1963a)],
which are incorporated by reference herein in their entirety. In
addition, the traction coefficient can also be measured by a
four-roller machine described in a SAE technical paper
2002-01-1696, entitled "Development of Toroidal Traction Drive CVTF
for Automobile" by Toru Matsuoka, Noboru Ishida, Shinichi Komatsu,
and Mitsuo Matsuno of Nippon Mitsubishi Oil Corporation, which is
incorporated by referenced herein in its entirety.
[0085] To carry out the testing, a Mini Traction Machine (MTM) test
system from PCS Instruments, 78 Stanley Gardens, London W3 7SZ, UK,
can be used. The test includes evaluating the fluid behavior in an
EHD contact formed between a polished 19.1 mm (3/4 inch) steel ball
and a 46 mm diameter steel disk, each independently driven to
produce a sliding/rolling contact, lubricated with the test
specimen (each sample being about 30 g). Testing is carried out at
a Hertz contact pressure of 1.25 GPa. The temperature of the test
oil at the inlet of the contact is continuously measured and
controlled to 100.degree. C., and the system given sufficient time
to thermally stabilize. Rolling speed is maintained at 2.5 m/s. A
slide to roll ratio continuously varying from 0% to 10% is achieved
by changing the surface speeds of both specimens simultaneously.
Traction force is continuously measured during each test, and
traction coefficient is calculated therefrom. Traction coefficient,
f.sub.t, is defined by:
f.sub.T=F.sub.T/P.sub.N
[0086] where F.sub.t is the measured tangential or tractive force
exerted between the members and P.sub.n is the normal load or
contact force between the members.
[0087] The following examples are presented to exemplify
embodiments of the invention. All numerical values are approximate.
When numerical ranges are given, it should be understood that
embodiments outside the stated ranges may still fall within the
scope of the invention. Specific details described in each example
should not be construed as necessary features of the invention.
EXAMPLE 1
[0088] A 1.0 cm diameter, 5 cm long vertical steel column, wrapped
with a heating tape and thermal couples inserted inside and outside
the column to monitor the temperature, was connected to a pump with
a Tygon.RTM. tubing. The column was filled with 6 grams of
Amberlyst 15 (Rohm & Haas). Neat .alpha.-methylstyrene (i.e.
without solvents) was pumped upward into the column. The product is
collected at the other end of the column, and subjected to GC
analysis. The components of product at various residence times and
temperatures are given in the table below. An C-13 NMR analysis
reveals the product is a cyclic dimer of .alpha.-methylstyrene,
1-phenyl-1,3,3-trimethylindane. Therefore, it was concluded that
.alpha.-methyl styrene has been initially dimerized to a linear
dimer, 2,4-diphenyl-4-methyl-1-pentene or the corresponding
2-pentene isomer. The linear dimer further contacts the catalyst
while traveling through the column and an intramolecular
Friedel-Crafts alkylation occurs to give the cyclic dimer. The
process did not involve any solvent or require an aqueous wash. The
catalyst was found still active, even after one liter of
.alpha.-methylstyrene had been passed through the column. The
conversion of monomer to polymer was substantially 100%. At
120.degree. C. and a high pumping speed, the product gives almost
exclusively the cyclic dimer, 1-phenyl-1,3,3-trimethylindane. C-13
NMR: 151.86 ppm, 150.68 ppm, 148.39 ppm, 127.70 ppm, 126.93 ppm,
126.38 ppm, 125.20 ppm, 124.70 ppm, 122.25 ppm, 77.52 ppm, 76.88
ppm, 76.25 ppm, 58.95 ppm, 50.49 ppm, 42.55 ppm, 30.63 ppm, 30.40
ppm, and 30.10 ppm.
4 RESIDENCE SKIN TIME TEMP., CYCLIC LINEAR TRIAL # (MINUTES)
.degree. C. DIMER DIMER TRIMER 1 48 31 74% 18% 8% 2 15 69 93% 5% 2%
3 29 83 90% 6% 4% 4 15 120 96% 3% 1% 5 59 119 94% 5% 1%
EXAMPLE 2
[0089] The product collected from the column in Trial 4 of Example
1 was completely hydrogenated with 900 psi (6205 kPa) of H.sub.2 at
195.degree. C. for 24 hours in the presence of 2% Pd on active
carbon as a catalyst. After filtering out the catalyst, the
hydrogenated product was ready to use as continuously variable
transmissions (CVT) fluid. The pure hydrogenated cyclic dimer,
1-cyclohexyl-1,3,3-trimethylindane, is obtained by further
distillation under vacuum, boiling point at 125.degree.-140.degree.
C./0.5 mm Hg; kinematic viscosity 3.9 cSt at 100.degree. C.; 22.3
cSt at 40.degree. C. C-13 NMR: 53.2 ppm, 50.69 ppm, 48.82 ppm,
45.60 ppm, 44.87 ppm, 39.79 ppm, 31.14 ppm, 28.3-24.03 ppm
(multi-peaks), and 20.37 ppm., as compared to C-13 NMR of
hydrogenated linear dimer, 2,4-dicyclohexyl-4-methylpentane, 44.22
ppm, 42.42 ppm, 41.32 ppm, 32.62 ppm, 30.36 ppm, 27.52 ppm, 25.57
ppm, 24.45-23.86ppm (multi-peaks), 22.04 ppm, 21.94 ppm, and 15.95
ppm.
EXAMPLE 3
[0090] The traction coefficient was measured by Mini Traction
Machine (MTM), manufactured by PCS Instruments at 78 Stanley
Gardens, London, England W# 7SZ. The test conditions are briefly
described as follows: Both ball and disc speeds are 1 m/sec under
no load. Once temperature is equilibrated at 50.degree. C., a 30 N
load (.about.0.88 Gpa) is applied. Slide roll ratio is increased
stepwise in increments of 1 from 0 to 50. The traction coefficient
against slide/roll ratio is recorded, and the traction coefficient
is read at end of slide/roll ratio of 50%.
[0091] The product of Example 2 containing 95% of the hydrogenated
cyclic dimer was measured to have a traction coefficient of 0.1062.
After purification to remove the trimer of .alpha.-methyl styrene
the traction coefficient for substantially pure 1-cyclohexyl
-1,3,3-trimethylhydrindan- e was 0.1093. By contrast, a sample of
the linear dimer of .alpha.-methyl styrene was hydrogenated to
2,4-dicyclohexyl-4-methyl pentane, and measured to have a traction
coefficient of 0.1048.
EXAMPLE 4
[0092] In several experiments, traction fluids were formulated to
include one or more of an additional base oil, a viscosity index
improver, and a low temperature viscosity control agent. In Table 1
below, Emkarate 1130, a low temperature viscosity control agent
from Imperial Chemical Industries was added in varying amounts to
the hydrogenated cyclic dimer of .alpha.-methyl styrene.
5 TABLE 1 Physical Properties Kin. Kin. Formulation Vis @ Vis @
Example Emkarate 1130, 100.degree. C., 40.degree. C., Traction
Trial 2, wt % wt % cSt cSt Coefficient 1 95 5 3.74 19.63 0.10515 2
90 10 3.76 20.6 0.10221 3 80 20 3.76 19.7 0.09524
[0093] As can be seen, the viscosity at above ambient temperatures
was not adversely affected, but the traction coefficient was
decreased as the amount of the Emkarate 1130 was increased.
[0094] In a second experiment reported in Table 2 a secondary base
oil, PAO4, a 4 cSt poly (.alpha.-olefin) synthetic hydrocarbon, was
added to hydrogenated cyclic dimer of .alpha.-methyl styrene and a
viscosity index improver, Lz7075, an OCP-type VI improver from
Lubrizol was added.
6TABLE 2 Formulation Physical Properties PAO Lz Brookfield Example
4, 7075, Kin. Vis @ Vis.@ Traction Trial 2, wt % wt % wt %
100.degree. C., cSt -30.degree. C. Coefficient 1 80 20 0 3.57
20,800 0.09251 2 94 0 6 6.79 314,500 0.10293 3 94 6 0 3.63 123,400
0.10329 4 64 30 6 6.1 11,270 0.08045 5 70 30 0 3.54 6,820
0.08367
[0095] As can be seen from the results, the secondary base oil
reduced the viscosity and the traction coefficient. Adding the VI
index improver increased the viscosity and reduced the traction
coefficient below that measured with the cyclic dimer alone.
Reducing the amount of the secondary base oil in the absence of the
VI improver improved the viscosity and traction coefficient (Trial
3 relative to Trial 1). In Trial 4, adding a substantial fraction
of the secondary base oil plus the VI improver increased the
viscosity at 100.degree. C., but reduced the viscosity at
-30.degree. C., while the traction coefficient was reduced. In
Trial 5, omitting the VI improver reduced viscosity and increased
the traction coefficient relative to Trial 4.
[0096] In a third experiment, the effect of all three additives was
explored, except that the type of viscosity index improver was
changed. As can be seen from Table 3 below, the viscosity was
substantially constant except for Trial 4 where the VI improver was
omitted and the viscosity was reduced.
7TABLE 3 Formulation Physical Properties Ex- Em- Kin. Kin. Brook-
ample karate PAO Lz Vis @ Vis @ field 2, 1130, 4, 7785, 100.degree.
C., 40.degree. C., Vis. @ Trial wt % wt % wt % wt % cSt cSt
-30.degree. C. 1 90 0 8 2 4.78 27.1 48,800 cP 2 90 8 0 2 4.67 26.4
46,000 cP 3 95 4 0 11 4.7 26.9 46,400 cP 4 95 3 2 0 3.68 20.8
38,800 cP Emkarate 1130: di(decyl) sebacate (synthetic di-ester)
PAO4: 4 cSt poly(.alpha.-olefin) (synthetic hydrocarbon base oil)
Lz 7075: Lubrizol OCP-type VI improver Lz 7785: Lubrizol PMA-type
VI improver
[0097]
8 TABLE 4 Physical Properties Kin. Kin. Brookfield Formulation Vis
@ Vis @ Vis @ Traction Example PAO 100.degree. C., 40.degree. C.,
-30.degree. C., Co- Trial 2, wt % 2, wt % cSt cSt cP efficient 6 80
20 3.1 14.8 10740 0.08938 7 0 0 5.5 114 42050 0.10485 8 0 0 3.4 29
14740 0.09128 PAO2: 2 cSt poly(.alpha.-olefin) (synthetic
hydrocarbon base oil) Trial 7: Commercial CVT Fluid: Santotrac 50
Trial 8: Commercial CVT Fluid: Santotrac 2000
[0098] As demonstrated above, embodiments of the invention provide
a CVT fluid that has a traction coefficient comparable to
commercial CVT fluid but has improved low temperature performance,
as shown by the Brookfield Viscosity at -30.degree. C. As
heretofore stated, the CVT fluid is excellent with respect of
flowability at low temperatures, having a relatively high traction
coefficient in a wide temperature and range from room temperature
to high temperatures besides having a low viscosity, producing
insignificant churning loss and thus achieving high transmission
efficiency. Therefore, fuel economy should be improved by the CVT
fluid. The process of making the hydrogenated dimer of
.alpha.-alkyl styrene is relatively simple and can be easily
implemented. Therefore, the process is cost-effective. Other
properties and advantages are apparent to those skilled in the
art.
[0099] While the invention has been described with respect to a
limited number of embodiments, the specific features of one
embodiment should not be attributed to other embodiments of the
invention. No single embodiment is representative of all aspects of
the inventions. In some embodiments, the compositions may include
numerous compounds not mentioned herein. In other embodiments, the
compositions do not include, or are substantially free of, any
compounds not enumerated herein. Variations and modifications from
the described embodiments exist. The method of making the CVT fluid
is described as comprising a number of acts or steps. These steps
or acts may be practiced in any sequence or order unless otherwise
indicated. Moreover, it is known that some of the materials
described above may interact in the final formulation, so that the
components of the final formulation may be different from those
that are initially added. For instance, metal ions (of, e.g., a
detergent) can migrate to other acidic sites of other molecules.
The products formed thereby, including the products formed upon
employing the composition of the invention in its intended use, may
not susceptible of easy description. Nevertheless, all such
modifications and reaction products are included within the scope
of the invention; the invention encompasses the composition
prepared by admixing the components described above. The appended
claims intend to cover all those modifications and variations as
falling within the scope of the invention.
* * * * *