Note: Descriptions are shown in the official language in which they were submitted.
kiwi
5894
HYDROGENATED POLYISOPRENE LUBRICATING COMPOSITION
This invention relates Jo compositions useful as lubricating oils
having high viscosity index, improved resistance to oxidative dog-
radiation and resistance to viscosity losses caused by permanent or
temporary shear.
According to the instant invention a lubricating composition is
provided comprising (1) an hydrogenated polyisoprene having a
viscosity of 1000 to 3500 centistokes at 100C; (2) a low viscosity
synthetic hydrocarbon, such as alkyd Bunsen so low viscosity
polyalphaolefin and/or a low viscosity ester, such as monstrous,
divesters, polyesters, and optionally (3) an additive package.
A further object of the invention is to provide a lubricating
composition with properties not obtainable with conventional polyp
metric thickeners
A further object of the invention is to provide lubricating
lo compositions exhibiting improved shear stability, oxidative stability
and excellent temperature-viscosity properties.
The viscosity-temperature relationship of a lubricating oil is
one of the critical criteria which must be considered when selecting
a lubricant for a particular application. The mineral oils colr~nonly
used as a base for single and multi graded lubricants exhibit a
relatively large change in viscosity with a change in temperature.
Fluids exhibiting such a relatively large change in viscosity with
temperature are said to have a low viscosity index. The viscosity
index of a common paraffinic mineral oil is usually given a value of
about 100. Viscosity index (VI) is determined according to ASTM
Method D 2770-74 wherein the VI is related to kinematic viscosities
measured at 40~C and 1û0C.
Lubricating oils composed mainly of mineral oil are said to be
single graded. SUE grading requires that oils have a certain
~`~
32
--2--
minimum viscosity at high temperatures and, to be multi graded, a
certain maximum viscosity at low temperatures. For instance, an oil
having a viscosity of 10 cyst. at 100C (hereinafter all viscosities
are at 100C unless otherwise noted) would be an SUE 30 and if
5 that oil had a viscosity of 3400 cup. at -OKAY, the oil would be
graded WOW. An unmodified mineral oil of 10 cyst. can no-t meet
the low temperature requirements for a 10~-30 multi grade rating,
since its viscosity index dictates that it would Howe a viscosity
considerably greater than 3500 cup. at -20C, which Is the maximum
10 allowed viscosity for a WOW rating.
The viscosity requirements for qualification as multi grade
engine oils are described by the SUE Engine Oil Viscosity Classify-
cation - SUE J300 ~EP80, which became effective April 1, 1982.
The low temperature (W) viscosity requirements are determined by
15 ASTM D 2602, Method of Test for Apparent Viscosity of Motor Oils
at Low Temperature Using the Cold Cranking Simulator, and the
results are reported in centipoise (cup). The higher temperature
(100C) viscosity is measured according to ASTM D445, Method of
Test for Kinematic Viscosity of Transparent and Opaque Liquids,
20 and the results are reported in centistokes (cyst. ). The following
table outlines the high and low temperature requirements for the
recognized SUE grades for engine oils.
SUE Viscosity (cup) at Viscosity (cyst.)
Viscosity Temperature (C) at 100C
25 Grade _ Max. _ Min. Max.
OW 3250 at -30 3.8
OW 3500 at -25 3.8
low 3500 at -20 4.1
WOW 3500 at -15 5.6
WOW 4500 a -10 5.6
WOW 6D0~ at -5 9.3
5.6 Less than 9.3
9.3 Less than 12.5
12.5 Less than 16.3
16.3 Less than 21.9
In a similar manner, SUE J306c describes the viscometric
qualifications for axle and manual transmission lubricants. High
temperature (100C) viscosity measurements are performed according
to ASTM D445. The low temperature viscosity values are deter-
5 mined according to ASTM D2983, Method of Test for Apparent Viscosity at Low Temperature Using the Brook field Viscometer and
these results are reported in centipoise (cup), where (cup) and (cyst)
are related as follows:
cyst = cup
Density, k~7dm3
The following table summarizes the high and low -temperature
requirements for qualification of axle and manual transmission tub-
recants .
SUE Maximum Temperature Viscosity at
15 Viscosity for Viscosity 100C, cyst.
Grade of 150,000 cup, cMinimum Maximum
WOW -55 --
WOW -40 4.1
WOW -26 7.0
WOW ~12 11.0
-- 13.5 24.0
140 -- 24.0 41.0
250 --
It is obvious from these tables that the viscosity index of a
25 broadly multi graded oil such as WOW or WOW will require fluids
having considerably higher viscosity index than narrowly multi-
graded lubricants such as WOW. The viscosity index require-
mints for different multi grade fluids can be approximated by the
use of ASTM Standard Viscosity-Tempearture Charts for Liquid
Petroleum Products (D 341).
If one assumes that extrapolation of the high temperature
(40C and 100C) viscosities to -40C or below is linear on chart
D 341, then a line connecting a 100C viscosity of, for example,
12.5 cyst. and a low temperature viscosity of 3500 cup at -25C would
I
--4--
give the correct 40C viscosity and permit an approximation of the
minimum viscosity index required for that particular grade of oil
(Lowe) .
The 40C viscosity estimated by linearly connecting the 100C
5 and -25~C viscosities would be about: 70 cyst. The viscosity index
of an oil having K.V.1oo = 12.5 cyst. end K.V.40 = 70 cyst. would
be about 180 (ASTM D 2270-74). Unless the -25C viscosity of a
fluid is lower than the linear relationship illustrated, then an oil
must have a viscosity index of at least 180 to even potentially
10 qualify as a WOW oil.
In actual fact, many V. I . improved oils have viscosities at
-25C which are considerably greater than predicted by linear
extrapolation of the K.V.1oo and K.V.40 values. Therefore, even
having a V. I . of 180 does not guarantee the blend would be a
15 WOW oil .
Using this technique minimum viscosity index requirements for
various grades of crankcase or gear oils can be estimated. A few
typical estimations are shown in the following table:
Estimated Required
crankcase K-V-100C V 40C Viscosity
Oil Grade cyst. cyst. Index
. _ .
Lowe 9.3 60 135
WOW 12.5 70 180
WOW 9.3 53 159
250~-50 16.3 75.5 232
Gear Oil Grade
guy 24 ~70 112
WOW 24 200 149
WOW 41 31~ 184
WOW 24 150 192
It can thus be seen that preparation of very broadly graded
lubricants, such as SW-40 or WOW requires thickeners which
produce very high viscosity indices in the final blends.
I
-5-
It has been the practice to improve the viscosity index of
mineral oils or low viscosity synthetic oils by adding a polymeric
thickener to relatively non-viscous base fluids. Polymeric thick-
enters are commonly used in the production of multi grade lubricants.
Typical polymers used as thickeners include hydrogenated styrenes
isoprene block copolymers, rubbers based on ethylene and propel-
one (COP), polymers produced by polymerizing high molecular
weight esters of the cruelty series, polyisobutylene and the like.
These polymeric thickeners are added to bring the viscosity of a
base fluid up to that required for a certain SUE grade and to
increase the viscosity index of the fluid, allowing the production of
multi graded oils. Polymeric VI improvers are traditionally high
molecular weight tubbers whose molecular weights may vary from
10,000 to 1,000,000. Since the thickening power and VI increase
are related to the molecular weight of the VI improver, most of
these polymers normally have a molecular weight of at least 100,000.
The use of these high molecular weight VI improvers, in the
production of multi graded lubricants has some serious drawbacks:
1. They are very sensitive Jo oxidation, which results
in a loss of VI and thickening power and frequently in the
formation of unwanted deposits.
I. They are sensitive to large viscosity losses from
mechanical shear when exposed to the high shear rates and
stresses encountered in crankcases or gears.
3. They are susceptible to a high degree of temporary
shear .
Temporary shear is the result of the non-Newtonian viscometrics
associated with solutions of high molecular weight polymers. It is
caused by an alignment of the polymer chains with the shear field
under high shear rates with a resultant decrease in viscosity. The
decreased viscosity reduces the wear protection associated with
viscous oils. Newtonian fluids maintain their viscosity regardless of
shear rate.
We have found that certain combinations of fluids and additives
can be used to prepare multi graded lubricants which outperform
prior art formulations and have none or a greatly decreased amount
of the above listed deficiencies found in polymerically thickened
oils .
I
--6--
Certain specific blends of high viscosity hydrogenated polyp
isoprene, low viscosity synthetic hydrocarbons and/or low viscosity
esters form base fluids from which superior crankcase or gear oils
can be produced by the addition ox the proper additive "packages".
5 The finished oils thus prepared exhibit very high stability to per-
Mennonite shear and, because of their nearly Newtonian nature, very
little, if any, temporary shear and so maintain the viscosity no-
squired for proper wear protection. The oils of this invention have
remarkably better stability toward oxidative degradation than those
10 of the prior art. The unexpectedly high viscosity indices produced
from our base fluid blends permit the preparation of broadly multi-
graded crankcase fluids, such as WOW and gear oils such as
WOW. Up to now it has been difficult if not impossible, to
prepare such lubricants without the use of frequently harmful
15 amounts of polymeric V.I. improvers.
The oligomeric polyisoprenes of this invention may be prepared
by Ziegler or, preferably, anionic polymerization. Such polymeric
ration techniques are described in United States Patent 4,060,492.
For the purposes of this invention, the preferred method of
preparation for the liquid hydrogenated polyisoprenes is by the
anionic alkyd lithium catalyzed polymerization of isoprene. Many
references are available to those familiar with this art which desk
crime the use of such catalysts and procedures. The use of alkyd
lithium catalysts such as secondary bottle lithium results in a polyp
25 isoprene oligomer having a very high (usually greater than continuity, which results in backbone unsaturation.
When alkyd lithium catalysts are modified by the addition of
ethers or amine, a controlled amount of 1,2- and 3,4- addition can
take place in the polymerization.
I
-7-
SHEA SHEA
CH2=C-CH=CH2 Eli { CH2-C=CH-CH2~-
1,4-addition
_ Eli SHEA
ROW
SCHICK-- ~CH2-CH~
OH C-CH
lo " " 3
SHEA SHEA
1,2-addition 3,4-addition
Hydrogenation of these structures gives rise to the saturated
species represented below:
SHEA SHEA
-CH2-C=CH-CH2- Ho -CH2-C-CH2-CH
H
1,4-addition (A)
SHEA SHEA
-OH -C- -I J- -SCHICK-
OH SHEA
SHEA SHEA
1,2-addition (B)
2 SHEA OH -OH-
lc,-c~3 H-C-CH3
SHEA SHEA
3,4-addition I
I
--8-
Structure (A) is the preferred structure because of its low Tug
and because it has a lower percent of its mass in the pendant
groups (SHEA-). Structure (B) is deficient in that the tetrasu~sti-
tuned carbons produced serve as points of thermal instability.
5 Structure (C) has 60% of its mass in a pendant (isopropyl) group
which, if repeated decreases the thickening power of the oligomer
for a given molecular weight and also raises the Tug of the resultant
polymer. This latter property has been shown to correlate with
viscosity index. Optimization of structure (A) is desired for the
10 best combination of thickening power, stability and V. I . improve-
mint properties.
Another feature of alkyd lithium polymers is the ease with
which molecular weight and molecular weight distribution can be
controlled. The molecular weight is a direct function of the moo-
15 men to catalyst ratio and, taking the proper precautions to exclude impurities, can be controlled very accurately thus assuring good
quality control in the production of such polymer. The alkyd lithe
I'm catalysts produce very narrow molecular weight distributions
such that Mom ratios of 1.1 are easily gained . For V . I . imp
20 provers a narrow molecular weight distribution is highly desirable since, at the given molecular weight, thickening power is maximized
while oxidative and shear instability are minimized. If desired,
broad or even polymodal MOW. distributions are easily produced by
a variety of techniques well known in the art. Star-shaped or
25 branched polymers can also be readily prepared by the inclusion of
multi functional monomers such as divinely Bunsen or by termination
of the "lovingly chains with a polyfunctional coupling agent such as
dim ethyl terephthalate .
It is well known that highly unsaturated polymers are concede-
30 drably less stable than saturated polymers toward oxidation. It isimportan~, therefore, that the ~rno~lnt of unsaturation present in the
polyisoprenes be draslicall~7 reduced. This is accomplished easily
by anyone skilled in the art using, for instance, a Pi, Pod or No
catalyst in a pressurized hydrogen atmosphere at elevated temper-
35 azure.
Regardless of the mode of preparation, isoprene oligomersrequire hydrogenation to reduce the high level of unsaturation
I
present after polymerization. For optimum oxidation stability, 90%,
and preferably 99% or more of the olefinic linkages should be
saturated .
The low viscosity synthetic hydrocarbons of the present invent
5 lion, having viscosities of from l to 10 cyst., consist primarily ofoligomers of alphaolefins and alkylated benzenes.
Low molecular weight oligomers of alphaolefins from C8 (octane)
to C12 (dodecene) or mixtures of the olefins can be utilized. Low
viscosity a]phaolefin oligomers can be produced by Ziegler catalysis,
10 thermal polymerization, free radically catalyzed polymerization and,
preferably, By catalyzed polymerization. A host of similar pro-
cusses involving BF3 in conjunction with a cocatalyst is Nina in
the patent literature. A typical polymerization technique is desk
cried in United States Patent No. 4,045,50~.
The alkylbenzenes may be used in the present invention alone
or in conjunction with low viscosity polyalphaolefins in blends with
high viscosity synthetic hydrocarbons and low viscosity esters.
The alkylbenzenes, prepared by Friedel-Crafts alkylation of Bunsen
with offense are usually predominantly dialkylbenzenes wherein the
20 alkyd chain may be 6 to 14 carbon atoms long. The alkylating
olefins used in the preparation of alkylbenzenes can be straight or
branched chain olefins or combinations. These materials may be
prepared as shown in US 3,909,432.
The low viscosity esters of this invention, having viscosities of
25 from 1 to 10 cyst. can be selected from classes of esters readily
available commercially, e . g ., monstrous prepared from monobasic
acids such as pelargonic acid and alcohols; divesters prepared from
dibasic acids and alcohols or from dills and monobasic acids or
mixtures of acids; and polyol esters prepared from dills, trios
30 (especially trimethylol propane), tutorials (such as pentaerythritol),
hexaols (such as dipentaerythritol) and the like reacted with moo-
basic acids or mixtures of acids.
Examples of such esters include tridecyl pelargonate, Dow-
ethylhexyl adipate, Dow ethylhexyl assault, trimethylolpropane
35 triheptanoate and pentaerythritol tetraheptanoate.
An alternative to the synthetically produced esters described
above are those esters and mixtures of esters derived from natural
q38~
-10-
sources, plant or animal. Examples of these materials are the fluids
produced from jujube nuts, tallows, safflowers and sperm whales.
The esters used in our blends ought to be carefully selected
to insure compatibility of all components in finished lubricants of
5 this invention. If esters having a high degree of polarity (roughly
indicated by oxygen content) are blended with certain combinations
of high viscosity synthetic hydrocarbons and low viscosity synthetic
hydrocarbons, phase separation can occur at low temperatures with
a resultant increase in apparent viscosity. Such phase separation
10 is, of course, incompatible with long term storage of lubricants
under a variety of temperature conditions.
The additive "packages" mixed with the recommended base oil
blend for the production of multi graded crankcase fluids or gear
oils are usually combination of various types of chemical add lives
15 so chosen to operate best under the use conditions which the par-
titular formulated fluid may encounter.
Additives can be classified as materials which either impart or
enhance a desirable property of the base lubricant blend into which
they are incorporated. While the general nature of the additives
20 might be the same for various types or blends of the base Libra-
cants, the specific additives chosen will depend on the particular
type of service in which the lubricant is employed and the kirk-
teristics of the base lubricants.
The main types of current day additives are:
1. Dispersals
2. Oxidation and Corrosion Inhibitors,
3. Anti-Wear Agents,
4. Viscosity Improvers,
5. Pour Point Depressants,
6. Anti-Rust Compounds, and
7. roam Inhibitors.
Normally a finished lubricant will contain several and possibly
most or all of the above types of additives in what is commonly
called an "additive package The development of a balanced add-
35 live package involves considerably more work than the casual use officio of the additive types. Quite often functional difficulties
arising from combinations of these materials show up under actual
operating conditions. On the other hand, certain unpredictable
synergistic effects of a desirable nature may also become evident.
The only methods currently available for obtaining such data are
from extensive full scale testing both in the laboratory and in the
5 field. Such testing is costly and time-consuming.
Dispersants have been described in the literature as "deter-
gents". wince their function appears to be one of effecting a
dispersion of particulate matter, rather than one of "cleaning up"
any existing dirt and debris, it is more appropriate to categorize
10 them as dispersants. Materials of this type are generally molecules
having a large hydrocarbon "tail" and a polar group head. The tail
section, an oleophilic group, serves as a solubilizer in the base
fluid while the polar group serves as the element which is attracted
to particulate contaminants in the lubricant.
The dispersants include metallic and cashless types. The
metallic dispersants include sulfonates (products of the neutralize-
lion of a sulfonic acid with a metallic base), thiophosphonates
(acidic components derived from the reaction between polybutene
and phosphorus pentasulfide) and founts and phenol sulfide salts
20 the broad class of metal founts includes the salts of alkylphen-
owls, alkylphenol sulfides, and alkyd phenol alluded products).
The cashless type dispersants may be categorized into two broad
types: high molecular weight polymeric dispersants for the formula-
lion of multi grade oils and lower molecular weight additives for use
25 where viscosity improvement is not necessary. The compounds
useful for this purpose are again characterized by a "polar" group
attached to a relatively high molecular weight hydrocarbon chain.
The "polar" group generally contains one or more of the eye-
ments--nitrogen, oxygen, and phosphorus. The solubilizing chains
30 are generally higher in molecular weight than those employed in the
metallic types; however, in some instances they may be quite
similar. Rome examples are N-substituted long chain alkenyl sue-
cinimides, high molecular weight esters, such as products formed
by the esterificatio~ of moo or polyhydric aliphatic alcohols with
35 olefin substituted succinic acid, and Mannish bases from high mole-
cuter weight alkylated phenols.
I
-12-
The high molecular weight polymeric cashless dispersants have
the general formula:
R R R R R
.
C-cH2-c-cH2~c-cH~-c-cH2-c-cH2
o o P o o
where O = Oleophilic Group
P = Polar Group
R = Hydrogen or Alkyd Group
The function of an oxidation inhibitor is the prevention of a
deterioration associated with oxygen attack on the lubricant base
fluid. These inhibitors function either to destroy free radicals
(chain breaking) or to interact with peroxides which are involved in
the oxidation mechanism. Among the widely used anti-oxidants are
the finlike types (chain-breaking) e.g., 2,6-di-tert.-butyl pane
crossly and 9,4' methylenebis(2,6-di-tert.-butylphenol), and the zinc
dithiophosphates (peroxide-destroying).
Wear is loss of metal with subsequent change in clearance
between surfaces moving relative to each other. If continued, it
will result in engine or gear malfunction. Among the principal
factors causing wear are rnetal-to-metal contact, presence of Abram
size particulate matter, and attack of corrosive acids.
Metal-to-metal contact can be prevented by the addition of
film-forming compounds which protect the surface either by physical
absorption or by chemical reaction. The zinc dithiophosphates are
widely used for this purpose. These compounds were described
under anti-oxidant and anti-bearing corrosion additives. Other
effective additives contain phosphorus, sulfur or combinations of
these elements.
Abrasive wear can be prevented by effective removal of par-
ticulate matter by filtration while corrosive wear from acidic mater-
tats can be controlled by the use of alkaline additives such as basic
founts and sulfonates.
Although conventional viscosity improvers are of ten used in
"additive packages" their use should not be necessary for the
~2~5~
-13-
practice of this invention since our particular blends of high and
low molecular weight base lubricants produce the same effect.
However, we do not want to exclude the possibility of adding some
amounts of conventional viscosity improvers. These materials are
5 usually oil-soluble organic polymers with molecular weights ranging
from approximately 10, 000 to 1, 000, 000 . The polymer molecule in
solution is swollen by the lubricant. The volume of this swollen
entity determines the degree to which the polymer increases its
viscosity .
Pour point depressants prevent the congelation of the oil at
low temperatures. This phenomenon is associated with the crystal-
ligation of waxes from the lubricants. Chemical structures of rep-
resentative commercial pour point depressants are:
COO OH
__~ _ . paraffin paraffin
paraffin SHEA C _ ¦ 1
_ n _ SHEA paraffin paraffin
n
Alkylated Wax Naphthal~ne PolymethacrylaLe Alkylated Wax Phenol
Chemicals employed as rust inhibitors include sulfonates,
alkenyl succinic acids, substituted imidazolines, amine, and amine
phosphates .
The anti-foam agents include the silicones and miscellaneous
25 organic copolymers.
Additive packages known to perform adequately for their
recommended purpose are prepared and supplied by several major
manufacturers. The percentage and type of additive to be used in
each application is recommended by the suppliers. Typically avail-
30 able packages are:
1. HAYAKAWA [Trademark E-320 for use in automotive gear oils,
2. L~brizol trademark] 5002 for use in industrial gear oils,
3. Laboriously 4856 supplied by the Laboriously Corp. for use in
gasoline crankcase oil, and
4. OLGA trademark] 8717 for use in diesel crankcase oils.
A typical additive package for an automotive gear lubricant
would normally contain antioxidant, corrosion inhibitor, anti-wear
~2~18~
-14-
agents, anti-rust agents, extreme pressure agent and foam inn-
biter .
A typical additive package for a crankcase lubricarlt would
normally be comprised of a dispers~nt, antioxidant, corrosion inn-
biter, anti-wear agent, anti-rust agent and foam inhibitor.
An additive package useful for formulating a compressor fluid
would typically contain an antioxidant anti-wear agent, an anti-
rust agent and foam inhibitor.
This invention uses blends of HI having a viscosity range of
1000 to 3500 cyst. with one or more synthetic hydrocarbon fluids
having viscosities in the range of 1 to 10 cyst. and/or one or more
comma title ester fluids having a viscosity range of 1 to 10 cyst .
Such blends, viny treated with a properly chosen additive
"package", can be formulated in broad range multi graded crankcase
or gear oils having improved shear stability, improved oxidative
stability, and nearly Newtonian viscometric properties. The blends
of this invention also find uses in certain applications where no
additive need be employed.
In discussing the constitution of the base oil blend, i-t is
convenient to normalize the percentages of HI, low viscosity
synthetic hydrocarbons, and low viscosity esters in the final Libra-
cant so that they total 100%. The actual percentages used in the
final formulation would then be decreased depending on the amount
of additive packages utilized.
Each of the ingredients, HI, low viscosity synthetic hydra-
carbons, and low viscosity esters are essential parts of this invent
lion . The HI provides thickening and V . I . improvement to the
base oil blend . The V. I . improvement produced by HI in blends
with low viscosity synthetic hydrocarbons or low viscosity esters is
shown in the examples.
The low viscosity synthetic hydrocarbon fluid is frequently the
main ingredient in the base oil blend, particularly in finished Libra-
cants having an SUE viscosity grade of 30 or 40. While certain low
viscosity esters are insoluble in (high viscosity) HI, the presence
of low viscosity synthetic hydrocarbon, being a better solvent for
low viscosity esters, permits greater variations in the type of
esters used in base oil blends of high viscosity synthetic hydrocar-
-15-
buns, low viscosity synthetic hydrocarbons, and low viscose try
esters .
Crankcase and gear oils consisting solely of hydrogenated
polyisoprene oligomers and low viscosity synthetic hydrocarbons
5 with the proper additives produce synthetic fluids having excellent
oxidative and hydroly tic stability . Such fluids are exemplified in
Example 3.
The third optional component, low viscosity esters can be used
in combination with hydrogenated polyisoprene oligomers and low
10 viscosity hydrocarbons or alone with hydrogenated polyisoprene
oligomers. In the three component blend the proper choice Or ester
and hydrogenated polyisoprene oligomers can produce crankcase and
gear oil formulations having outstanding viscosity indices and low
temperature properties. Such three component blends are thus-
treated in Examples 1 and 2.
Two component blends of hydrogenated polyisoprene oligomersand esters can be used to prepare multi graded lubricants having
outstanding viscometric properties, detergency, and oxidative
stability. While some applications present environments having high
moisture levels, which would be deleterious to certain esters, there
are other applications such as automotive gear oils where the high
ester contents found in the hydrogenated polyisoprene oligomers-
en ton blends can be used to advantage . Example 4 illustrates the
formulation of multi grade lubricants with such two component
blends.
When it is deemed advantageous to use a low viscosity ester as
part of the blend, the low viscosity hydrocarbons act as a common
solvent for the HI and the added ester. Depending on the
polarity of the ester, the latter two are frequently somewhat in-
compatible. Excellent multi graded lubricants can be formulated with
or without ester.
The third component, low viscosity esters, can be added to
produce the superior lubricants of this invention. HI and low
viscosity synthetic hydrocarbons can be used alone to produce
multi graded lubricants. The addition ox low levels of low viscosity
esters, usually 1-25% results in a base oil blend superior to blends
of high viscosity s,vnLhetic hydrocarbons and low viscosity synthetic
hydrocarbons alone in low -temperature fluidity.
.,
~2;~:~Q~3~
-16-
Low viscosity esters usually constitute 10-25% of the synthetic
base oil blend, more or less can be used in specific formulations.
When the final application involves exposure to moisture elimination
or limitation of toe amount of ester in blends may be advantageous.
The components of the finished lubricants of this invention can
be admixed in any convenient manner or sequence.
An important aspect of the present invention is in the use of
the properly constituted base oft blend in combination with the
proper compatible additive package to produce finished broad range
multi grade lubricants having:
1. Improved temporary shear stability.
2. Excellent oxidation stability.
3. High viscosity index.
The range of percentages for each of the components, i . e .,
HI, low viscosity synthetic hydrocarbons, low viscosity esters,
and additive packages, will vary widely depending on the end use
for the formulated lubricant, but the benefits of the compositions of
this invention accrue when the base oil blend contains (normalized):
From 1 to 99% HI from 1 to 9g% low viscosity synthetic
hydrocarbons esters or mixtures thereof. It is preferred to
blend from 3 to 80% HI with correspondingly 90 to 20% of at
least one low viscosity ester base fluid or hydrocarbon base
fluid. The additive package can be used in from 0 to 25% of
the total formulation, all by weight.
The lubricants of -this invention approach viscometrics of
Newtonian fluids . The t is, their viscosities are changed little over
a wide range of shear rates. While the HI of the invention may,
in themselves, display non-Newtonian characteristics, particularly at
low temperatures, the final lubricant products utilizing low viscosity
oils as delineates are nearly Newtonian.
The non-Newtonian character of currently used V.I. improvers
is well documented. An excellent discussion can be found in an
SUE: publication entitled, "The Relationship Between Engine Oil
Viscosity and Engine Performance Part III. " The papers in this
publication were preset ted at a 1978 SUE Congress and Exposition
in Detroit on February 27 to March 3, 1978.
-17-
The reference of interest is Paper 78037~:
"Temporary Viscosity Loss and its Relationship to
Journal Bearing Performance, " M . L . MacMillan and C . K .
Murphy, General Motors Research Labs.
this reference, and many others familiar to researchers in the
field, illustrates hotly commercial polymeric VI improvers of molecular
weights from 30,000 and up all show a temporary viscosity loss
when subjected to shear rates of 105 to 106 sea 1 The temporary
shear loss is greater for any shear rate with higher molecular
White polymers. for instance, oils thickened to the same viscosity
with polymethacrylates of 32,000; 157,000; and 275,000 molecular
weight show percentage losses in viscosity at a 5 x 105 sea 1 shear
rate of 10, 22 and 32%, respectively.
The His of this invention have molecular weights below 5000,
Andy shear tunneling of their solutions is minimal.
The shear rates developed in pistons and gears (equal to or
greater than 106 sea 1) is such -that, depending on the polymeric
thickener used, -the apparent viscosity of the oils approaches that
of -the unthickened base fluids resulting in loss of hydrodynamics
films. Since wear protection of moving parts has been correlated
with oil viscosity, it is apparent that the wear characteristics of a
lubricant can be downgraded as a result of temporary shear. The
nearly Newtonian fluids of this invention maintain their viscosity
under these use conditions and therefore afford more protection to
Andy longer lifetime for the machinery being lubricated.
The currently used polymeric thickeners which show temporary
(recoverable) shear are also subject to permanent shear. Extended
use of polymeric thickeners leads to their mechanical breakdown
with resultant loss in thickening power and decrease in VI. This is
illustrated in Example 5. Paper 780372 (op. aft), "Polymer Stability
in Engines" by W. Wunderlich and H. Just discusses the relation-
ship between polymer type and permanent shear. The multi grade
lubricants of -this invention are not as susceptible to mechanical
shear .
thus same paper also recognizes an often overlooked feature of
high molecular weight polymeric VI improvers, i.e., their instability
toward oxidation. Just as these polymers lose viscosity by shear
Lo
-18-
they are also readily degraded by oxygen with the resultant break
down of the polymer and decrease in viscosity index. The Libra-
acting fluids of this invention suffer much less change in viscosity
index upon oxidation.
As mentioned earlier, the smelt amount of temporary shear
exhibited by the lubricants of -this invention guarantees optimum
viscosity for the protection of moving parts where high shear rates
are encountered. The importance of this feature is widely recog-
sized . In the past, SUE grading (e . g . SUE 30) relied only on a
measurement of the viscosity of a fluid at 100C under low shear
conditions, despite the fact that in machinery such as a crankcase
high temperatures and very high shear rates are encoun toned .
This disparity has led to the adoption in Europe of a new grading
system wherein viscosities for a certain grade are those measured at
150C and 106 sea 1 shear rate. This more realistic approach is
currently being considered in the United States . The ad van taxes a
Newtonian fluid brings to such a grading system are obvious to
anyone skilled in the art. The viscosity of a Newtonian fluid can
be directly extrapolated to 150C under high shear conditions. A
polymer thickened fluid, however, will invariably have a viscosity
lower than the extrapolated value, frequently close to the base fluid
itself. In order to attain a certain grade under high shear condo-
lions, polymer thickened oils will require a more viscous base fluid.
The use of thicker base fluids will produce higher viscosities at low
temperature making it more difficult to meet the low temperature
(OW for crankcase of WOW for gear oil) requirements for broadly
multi graded oils.
Stated another way, current high molecular weight VI impure-
Yens "artificially" improve the viscosity index, since realistic high
temperature high shear measurements are not utilized in determining
VI. Viscosity index is determined by low shear viscosity measure-
mints at 40C and 100C. The n~rly Newtonian lubricants of this
invention not only produce high viscosity index multi graded fluids
which stay "in grade", but the VI and multi grade rating are real-
fistic since they are not very sensitive to shear.
While the specific compositions exemplified in this patent are
fairly precise, i-i: should be obvious to anyone skilled in -the art to
-lug-
produce even further combinations within the scope of this invent
lion which will be valuable lubricants.
The following examples illustrate some of the blends encom-
passed my our invention:
EN I E 1
This example illustrates the preparation of crankcase lubricants
using hydrogenated polyisoprene (HI) of the viscosities shown:
INGREDIENT wry %
( 100 1310) 12
POW (1) 50
Di-2-Ethylhexyl assault 20
Laboriously 3940 (2) 18
B. HI (KVloo = 3360) 9
POW 53
Di-2-Ethylhexyl assault 20
Laboriously 3940 18
The lubricants had the properties shown:
KV100'CSt KV40CS~ VI CCS, cup SUE Grade
A. 13.5 81.3 170 3010@-20C Lowe
B. 13.3 76.5 177 2215@-20C Lowe
(1) 4 cyst Polyalphaolefin
(2) Additive package made by Laboriously Corporation
EXAMPLE 2
This example illustrates the preparation of automotive gear
25 lubricants using His of the kinematic viscosities shown:
I
-20-
INGREDIENT WIT %
1 9
POW 51
Di-2-Ethylhe~yl assault 20
Anglamol 6043 (1) 10
B- HI (KVlOO = 3360) 20
POW 50
Di-2-Ethylhexyl assault 20
Anglamol 6043 10
The lubricants had the properties shown:
-100' KV40Cst VI Vis@-40C,cP SUE Grade
A. 15.1 87.4 183 27,320 WOW
B. 25.4 166.0 188 72,410 WOW
(1) Additive package made by Laboriously Corporation
EXAMPLE 3
This example illustrates the preparation of lubricants with
His of the kinematic viscosities shown in blends with only sync
Thetis hydrocarboIl and additive package:
INGREDIENT WIT %
- Crankcase -
(I.) HI (KV1oo = 1310) 11
POW 51
Dialkyl Bunsen (DN-600) 20
Laboriously 3940 18
25 (B.) HI (KV1oo = 3360) 10
POW 78
Laboriously 3940 12
I
Automotive Gear O_
(C.) HI (VOW = 3360) 19
POW 71
Anglaolol 6043 10
The lubricants had the properties shown:
- 100'-- - 40 VI Skip SUE Grade
(Aye 83.8 161 KIWI
(B.)13.4 79.0 174 KIWI
(C.)25.0 162.0 189 83,420~-40C WOW
EXAM LYE 4
This example illustrates the preparation of lubricants with
Hops of the kinematic viscosities shown in blends with only esters
and additive package:
INGREDIENT WIT %
- Crankcase -
(A.) HI (KV1oo = 1310) 13
Deciduously Adipate 75
Laboriously 3940 12
(B.) HI (KVloo = 3360) 10
Deciduously Adipate 78
Laboriously 4856 12
Automotive Gear Oil
(C.) HI (KVloo = 1310) 25
Deciduously Adipate 65
Anglamol 6043 10
(D.) HI (KV1oo = 3360) 20
Deciduously Adipate 70
Anglamol 6043 10
-22-
The lubricants had the properties shown:
-100' - _ 40, Sty VI Vis,cP -SUE Grade
(~.)13.9 74.9 192 KIWI
(B.)13.4 71.2 277 KIWI
(C.)27.1 171.g 1g5 77,470@-40C WOW
(D-)29.0 177.9 204 78,630@-40C WOW
