METHOD OF IMPROVING THE SHEAR STABILITY OF LITHIUM GREASES

METHODE POUR AMELIORER LA RESISTANCE AU CISAILLEMENT DES GRAISSES AU LITHIUM

English Abstract

The shear stability of a multipurpose grease
comprising
(i) a lubricating oil,
(ii) a lithium soap of an hydroxy fatty acid,
(iii) a polyhydric alcohol having at least
three hydroxy groups, and
(iv) at least two metal hydrocarbylthiophosphate
compounds in which the metal is
different in at least two compounds,
is enhanced by incorporating at least a major portion
of the polyhydric alcohol into the mixture of lubricating
oil and lithium soap of an hydroxy fatty acid and
before the metal hydrocarbylthiophosphate compounds are
added during the grease preparation process. Preferred
ingredients are 12-hydroxystearic acid, glycerol,
antimony dialkyldithiophosphate, and zinc
dialkyldithiophosphate.

Claims

-17-
THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVELEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a method for preparing a grease
containing
(i) a lubricating oil,
(ii) a lithium soap of an hydroxy fatty acid,
(iii) a polyhydric alcohol having at least
three hydroxy groups, and
(iv) at least two metal hydrocarbylthiophosphate
compounds in which the metal is
different in at least two compounds,
by the steps comprising
(a) forming a mixture of the lubricating oil
and the lithium soap at a temperature
between 150° and 220° F,
(b) increasing the temperature of the
product from step (a) to between
350° and 400°F for a period of
time sufficient to improve crystallization
of the lithium soap in the oil,
(c) cooling the product from step (b) to a
temperature between 150° and 200°F,
and
(d) adding the polyhydric alcohol and the
metal hydrocarbylthiophosphate to the
product from step (c),

-18-
the improvement which comprises adding at least a major
portion of the polyhydric alcohol to the mixture of
lubricating oil and lithium soap of an hydroxy fatty
acid before step (b) to increase the shear stability of
the grease.
2. The method of claim 1 wherein the lithium
soap in (a) is formed in the lubricating oil by
contacting an hydroxy fatty acid with at least a
stoichiometric amount of a lithium base.
3. The method of claim 2 wherein a
dicarboxylic acid is added to the lithium soap thus formed
and then contacted with at least a stoichiometric
amount of lithium base to convert the dicarboxylic acid
to its dilithium soap.
4. The method of claim 1, 2, or 3 wherein
the polyhydric alcohol is selected from the group
consisting of glycerol, pentaerythritol, and mixtures
thereof.
5. The method of claim 1, 2, or 3 wherein
the metal hydrocarbylthiophosphate compounds have the
formula:
<IMG>
wherein n is 1-6; x is 1-3; R1 and R2 may each be
hydrogen or a hydrocarbyl group having from 1 to 30

-19-
carbon atoms; and M is a metal selected from the group
consisting of aluminum, antimony, cadmium, copper,
lead, tin, zinc, and mixtures thereof in which the
metal is different in at least two compounds.
6. The method of claim 5 wherein the
hydrocarbyl group is alkyl, aryl, alkaryl, aralkyl, their
unsaturated counterparts, or mixtures thereof.
7. The method of claim 5 wherein the metal
hydrocarbylthiophosphate compounds are metal
alkylthiophosphate compounds.
8. In a method for preparing a grease
containing
(i) a lubricating oil,
(ii) a lithium soap of a C12-C24 hydroxy
fatty acid,
(iii) a polyhydric alcohol selected from the
group consisting of glycerol,
pentaerythritol, and mixtures thereof, and
(iv) at least two metal hydrocarbylthiophosphate
compounds having the formula:
<IMG>

-20-
wherein n is 1-6: x is 1-3; R1 and R2
may each be hydrogen or a hydrocarbyl
group having from 1 to 30 carbon atoms;
and M is a metal selected from the group
consisting of aluminum, antimony,
cadmium, copper, lead, tin, zinc, and
mixtures thereof; in which the metal is
different in at least two compounds,
by the steps comprising
(a) forming a mixture of the lubricating oil
and the lithium soap at a temperature
between 150° and 220°F
(b) increasing the temperature of the
product from step (a) to between
350° and 400°F for a period of
time sufficient to improve dispersion of
the lithium soap in the oil,
(c) cooling the product from step (b) to a
temperature between 150° and 200°F,
and
(d) adding the polyhydric alcohol and the
metal hydrocarbylthiophosphate to the
product from step (c),
the improvement which comprises adding at least a major
portion of the polyhydric alcohol to the mixture of
lubricating oil and lithium soap of a C12-C24 hydroxy
fatty acid before step (b) to increase the shear
stability of the grease.
9. The method of claim 8 wherein the lithium
soap is formed in the lubricating oil by contacting a

-21-
C12-C24 hydroxy fatty acid with at least a stoichiometric
amount of lithium hydroxide.
10. The method of claim 9 wherein a C2-C12
dicarboxylic acid is added to the lithium soap thus
formed and then contacted with at least a stoichiometric
amount of lithium hydroxide to convert the
dicarboxylic acid to its dilithium soap.
11. The method of claim 8, 9, or 10 wherein
the polyhydric alcohol comprises glycerol.
12. The method of claim 8, 9, or 10 wherein
n is 2-4.
13. The method of claim 12 wherein n is 2-3.
14. The method of claim 8, 9, or 10 wherein
x is 1-2.
15. The method of claim 14 wherein x is 1.
16. The method of claim 8, 9, or 10 wherein
the metal hydrocarbylthiophosphate compounds comprise
at least two metal alkylthiophosphate compounds.
17. The method of claim 16 wherein the metal
is selected from the group consisting of antimony,
lead, zinc, and mixtures thereof.
18. The method of claim 16 wherein the metal
alkylthiophosphate compounds comprise two metal
dialkyldithiophosphate compounds.
19. The method of claim 18 wherein the metal
dialkyldithiophosphate compounds are antimony
dialkyldithiophosphate and zinc dialkyldithiophosphate.

-22-
20. In a method for preparing a grease
containing
(i) a lubricating oil,
(ii) a lithium soap of a C12-C24 hydroxy
fatty acid,
(iii) a lithium soap of a C2-C12 dicarboxylic
acid,
(iv) from 0.1 to 5 wt.% glycerol, and
(v) from 0.2 to 10 wt.% of at
least two metal dialkyldithiophosphate
compounds in which the metal is different
in at least two compounds,
by the steps comprising:
(a) forming a mixture of the lubricating oil
and the lithium soap of a C12-C24
hydroxy fatty acid at a temperature
between 150° and 220° F,
(b) substantially dehydrating the product
from step (a) at a temperature between
220° and 350°F,
(c) cooling the product from step (b) to a
temperature between 200° and 260°F,
(d) adding a C2-C12 dicarboxylic acid to the
product formed in step (c),

-23-
(e) contacting the mixture formed in step
(d) with at least a stoichiometric
amount of lithium hydroxide, the
contacting occurring at a temperature
between about 200° and about 240°F,
(f) substantially dehydrating the product
from step (e) at a temperature between
about 220° and about 350°F,
(g) increasing the temperature of the
product from step (f) to between about
350° and about 400°F for a period of
time sufficient to improve dispersion of
the lithium soap in the oil,
(h) cooling the product from step (g) to a
temperature between about 150° and about
200°F, and
(i) adding the glycerol and the metal
dialkyldithiophosphate compounds to the
product from step (h),
the improvement which comprises adding at least a major
portion of the glycerol to the mixture formed in step
(a), adding at least a major portion of the glycerol to
the mixture formed in step (e), or adding at least a
major portion of the glycerol to the mixtures formed in
steps (a) and (e) to increase the shear stability of
the grease.
21. The method of claim 20 wherein the
lithium soap of a C12-C24 hydroxy fatty acid is formed
in the lubricating oil by contacting a C12-C24 hydroxy
fatty acid with at least a stoichiometric amount of
lithium hydroxide.

-24-
22. The method of claim 21 wherein the
hydroxy fatty acid comprises 12-hydroxystearic acid.
23. The method of claim 22 wherein the
dicarboxylic acid comprises azelaic acid.
24. The method of claim 20, 21, or 23
wherein the total amount of glycerol added ranges from
0.2 to 1.0 wt%.
25. The method of claim 24 wherein the
amount of metal dialkyldithiophosphate compounds added
ranges from 0.5 to 4 wt.%.
26. The method of claim 20, 21, or 23
wherein the metal is selected from the group consisting
of antimony, lead, zinc, and mixtures thereof.
27. The method of claim 20, 21, or 23
wherein the metal dialkyldithiophosphate compounds are
antimony dialkyldithiophosphate and zinc
dialkyldithiophosphate.

Description

W 200 1 875
- 1 -
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention concerns the preparation of
high load-carrying lithium soap greases having improved
shear stability.
2. Description of Related Art
Various methods have been suggested for
preRaring lithium soap greases (see, for example, C.J.
Boner, Manufacture and Application of Lubricating
Greases, Reinhold Publishing Corp., New York (1954);
NLGI Lubricating Grease Guide, Second Edition, Published
by NLGI, Kansas City, Missouri (1987); as well as U.S.
Patents 2,898,296; 2,940,930; and 3,791,973). In all of
these methods, conventional additives (e.cr:
anticorrosive agents, pour point depressants, dyes, and
the like) are usually added to the grease in the final
steps of its preparation to form a fully formulated
grease.
More recently, copending patent application
Canadian Serial No. 571,453 filed July 07, 1988,
discloses that the load-carrying capability of greases
containing a lubricating oil and a thickener can be
significantly enhanced by incorporating therein a
polyhydric alcohol having at least three hydroxy groups
and at least two metal hydrocarbylthiophosphate com-
pounds in which the metal is different in at least two
compounds. The alcohol and the phosphate compounds are
added to the grease during the final steps of its
preparation.
l
_J

A
20~018'~S
- 2 -
However, none of these disclosures suggest
that the shear stability of the high load-carrying
lithium soap greases described in Serial No. 571,453
can be improved by modifying the point at which the
polyhydric alcohol is added during preparation of the
grease.
SUMMARY OF THE INVENTION
This invention concerns a method of preparing
high load-carrying lithium soap greases (specifically,
simple lithium and lithium complex soap greases) having
enhanced shear stability by modifying the usual proce-
dure for preparing these greases.
Briefly, lithium soap greases are convention-
ally prepared by first forming a mixture of a lubricat-
ing oil and a lithium soap of an hydroxy fatty acid.
If a lithium complex soap grease is to be prepared, a
dicarboxylic acid would normally be added at this point
and neutralized with a lithium base. The temperature
of the resulting mixture is then increased to between
about 350° and about 400°F (_i.e., the so-called "cook-
out"). Thereafter, the mixture is cooled to a tempera-
ture between about 150° and about 200°F, at which time
any additives may be incorporated into the mixture to
form a fully~formulated grease.
However, we have discovered that the shear
stability of a grease comprising
(i) a lubricating oil,
(ii) a lithium soap of an hydroxy fatty acid,
(iii) a polyhydric alcohol having at least
three hydroxy groups, and

- 3 -
(iv) at least two metal hydrocarbylthiophos-
phate compounds in which the metal is
different in at least two compounds
will be enhanced if conventional preparation procedures
are modified by adding at least a major portion of the
polyhydric alcohol to the mixture of lubricating oil
and lithium soap of an hydroxy fatty acid before the
high temperature "cookout" -- i.e., the alcohol is
added after the lithium soap has been dispersed in the
lubricating oil but before "cookout", while the phos-
phate compounds (and other additives) are added after
"cookout". For a lithium complex soap grease, the
polyhydric alcohol is also added before "cookout";
i.e., the alcohol is added after the lithium soap of an
hydroxy fatty acid has been dispersed in the lubricat-
ing oil, after neutralization of the dicarboxylic acid,
or both. Preferred ingredients are 12-hydroxystearic
acid, azelaic acid, glycerol, antimony dialkyldithio-
phosphate, and zinc dialkyldithiophosphate.
DETAILED DESCRIPTION OF THE INVENTION
A wide variety of lubricating oils can be
used to prepare the high load-carrying, shear stable
greases of this invention. For example, the lubri-
cating oil base can be any of the conventionally used
mineral oils, synthetic hydrocarbon oils or synthetic
ester oils, depending upon the particular grease being
prepared. In general these lubricating oils will have
a viscosity in the range of about 5 to about 10,000 cSt
at 40°C, although typical applications will require an
oil having a viscosity ranging from about 10 to about
1,000 cSt at 40°C. Mineral lubricating oil base stocks
used in preparing the greases can be any conventionally
refined base stocks derived from paraffinic, naph-
thenic, and mixed base crudes. Synthetic lubricating

z~o~.~s~s
- 4 -
oils that can be used include esters of dibasic acids,
such as di-2-ethylhexyl sebacate, esters of glycols
such as a C13 oxo acid diester of tetraethylene glycol,
or complex esters such as one formed from 1 mole of
sebacic acid and 2 moles of tetraethylene glycol and 2
moles of 2=ethylhexanoic acid. Other synthetic oils
that can be used include synthetic hydrocarbons such as
polyalphaolefins,~ _alkyl benzenes, e.g. alkylate bottoms
from the alkylation of benzene with tetrapropylene, or
the copolymers of ethylene and propylene: silicon oils,
e_.g. ethyl phenyl polysiloxanes, methyl polysiloxanes,
etc..~ _polyglycol oils, e.g. those obtained by condens-
ing butyl alcohol with propylene oxide: carbonate
esters, e.g. the product of reacting Cg oxo alcohol
with ethyl carbonate to form a half ester followed by
reaction of the latter with tetraethylene glycol, etc.
Other suitable synthetic oils include the polyphenyl
ethers, e.g. those having from about 3 to 7 ether
linkages and about 4 to 8 phenyl groups. (See U.S.
Patent 3,424,678, column 3.) The amount of lubricating
oil in the grease can also vary broadly, but, typical-
ly, will range from about 50 to about 98 wt.%, prefer-
ably from about 75 to about 95 wt.%, of the grease.
The grease will also contain a lithium soap
of an hydroxy fatty acid. The hydroxy fatty acid
employed will have from about 12 to 24, or more usually
about 16 to 20, carbon atoms and will preferably be a
hydroxy stearic acid, _e.g., 9-hydroxy, 10-hydroxy, or
12-hydroxystearic acid, more preferably the latter.
Ricinoleic acid, which is an unsaturated form for
12-hydroxy stearic acid (having a double bond in the
9-10 position), can also be used. Other hydroxy fatty
acids include 12-hydroxy behenic acid and 10-hydroxy
palmitic acid.

~- 2~40~8'~S
- 5 -
The lithium soap used in this invention
includes not only a simple lithium soap prepared from
the hydroxy fatty acid described above, but also a
lithium complex soap prepared from the hydroxy fatty
acid and a dicarboxylic acid as described in U.S.
Patent 3,791,973. The particular dicarboxylic acid
used will have from 2 to 12, preferably from 4 to 12
and most preferably from 6 to 10, carbon atoms.
Suitable dicarboxylic acids include oxalic, malonic,
succinic, glutaric, adipic, suberic, pimelic, azelaic,
dodecanedioic, and sebacic acids. Sebacic acid and
azelaic acid are particularly preferred. The propor-
tion of dicarboxylic acid to hydroxy fatty acid in the
lithium complex grease should range from about 0.2 to
about 1.0, preferably from about 0.5 to about 0.8,
moles of dicarboxylic acid per mole of hydroxy fatty
acid.
The total soap content of the shear stable
grease of this invention should be sufficient to
thicken the grease to the desired consistency. Nor-
mally, the total soap content will range from about 1
to about 30 wt.% of the grease. For most purposes, the
total soap content should be between about 5 to about
20 wt.%, preferably between about 10 to about 15 wt.%,
of the grease.
The polyhydric alcohol used herein can be any
of the aliphatic polyhydric alcohols having at least 3
hydroxy groups. Alcohols containing 3 or 4 hydroxy
groups are preferred. Specific examples of alcohols
which may be used include glycerol, pentaerythritol,
and the like. Alcohols containing 3 hydroxy groups are
more preferred, glycerol being particularly preferred.

-- 2t~~18'~S
- 6 -
The metal hydrocarbylthiophosphate compounds
used in preparing the greases of this invention may be
represented by the formula:
R1~ S
0
Mx
-S-
/0
R /2
n
wherein n is 1-6, preferably 2-4 and more preferably
2-3: and x is 1-3, preferably 1-2, and preferably 1.
R1 and R2 may each individually be hydrogen or a
hydrocarbyl group of from 1 to 30, preferably from 1 to
20, and more preferably from 1 to 10, carbon atoms.
More particularly, the hydrocarbyl group may be an
alkyl, aryl, alkaryl, or aralkyl group, and the unsatu-
rated counterparts thereof, or mixtures thereof. The
groups as defined for R1 and R2 may include hetero-
oxygen, nitrogen, sulfur, or phosphorus atoms inter-
spersed therein. Preferred hydrocarbylthiophosphate
compounds are the alkylthiophosphates, with dialkyldi-
thiophosphates being most preferred.
M can be any metal selected from the group of
aluminum, antimony, cadmium, copper, lead, tin, and
zinc. Preferred metals are antimony, lead, and zinc,
with antimony and zinc being most preferred. Thus,
preferred metal hydrocarbylthiophosphates include
antimony dialkyldithiophosphates, lead dialkyldithio-
phosphates, and zinc dialkyldithiophosphates. Accord-
ingly, preferred metal hydrocarbylthiophosphate groups
include antimony dialkyldithiophosphates in combination

-- 2'OU 18'~S
with lead dialkyldithiophosphates, zinc dialkyldithio-
phosphates or their mixtures, with antimony dialkyldi-
thiophosphates and zinc dialkyldithiophosphates being
most preferred.
Although very minor amounts of the polyhydric
alcohol and the metal hydrocarbylthiophosphate com-
pounds can be used, these additives will normally be
employed within certain ranges. In the case of the
polyhydric alcohol, from about 0.1 to about 5 wt.%,
preferably from about 0.2 to 1.0 wt.%, based on weight
of the grease, will be employed. The total amount of
metal hydrocarbylthiophosphate compounds used will
range from about 0.2 to about 10 wt.%, based on weight
of the grease. Methods of preparing the polyhydric
alcohol and metal hydrocarbylthiophosphate compounds
used herein are well known to one skilled in the art.
To prepare the high load-carrying and shear
stable greases of this invention, the lithium soap of
an hydroxy fatty acid could be preformed and then dis-
persed in the lubricating oil for both the simple
lithium and lithium complex soaps. (In contrast, the
dicarboxylic acid cannot be preformed for the lithium
complex soap.) However, it is generally more expedient
to prepare the lithium soap in situ in the lubricating
oil by neutralizing the hydroxy fatty acid with lithium
base, which generally will be lithium hydroxide.
When the lithium soap of an hydroxy fatty
acid is prepared in situ, the usual procedure is to
charge into the grease kettle from about one-fourth to
about one-half of the total amount of lubricating oil
base that will be finally incorporated into the final
grease and to then add the hydroxy fatty acid. The
mixture of fatty acid and oil is heated sufficiently to
dissolve the acid into the oil, e.g., at a temperature

,- 2~018~5
_8_
between about 150° to about 220°F, preferably between
about 180° to about 200°F. Normally, the fatty acid
will be dissolved in the oil fairly rapidly such that
dissolution can be nearly completed in from about 0.5
to about 1 hour, although times outside this range
could be used. Then a concentrated aqueous solution of
lithium hydroxide is added, usually in an amount
slightly in excess of the stoichiometric amount re-
quired to neutralize the acid, the temperature at this
stage usually being between about 150° to about 220°F,
preferably between about 200° to about 210°F. The rate
of lithium hydroxide addition is not critical, although
from 30 minutes to about 2 hours may be required
depending on the facilities at the grease plant. (If a
lithium complex rather than a simple lithium soap were
to be prepared, the dicarboxylic acid could be added
and subsequently neutralized to its dilithium soap at
this point, but this would require neutralizing the
acid very slowly or stepwise to ensure complexing of
the two types of soaps with each other before complete
neutralization of the dicarboxylic acid has occurred.)
Once neutralization of the hydroxy fatty acid
is nearly complete, the temperature of the lubricating
oil/lithium soap of an hydroxy fatty acid mixture is
increased to between about 220° to about 350°F, prefer-
ably between about 250° to about 320°F, and more pre-
ferably between about 280° to about 300°F, for a period
of time sufficient to complete the neutralization and
to effect a substantial dehydration of the mixture,
i.e., the removal of 70 to 100% of the water. (In the
case of a lithium complex grease, substantial dehydra-
tion at this point also promotes the subsequent com-
plexing reaction during neutralization of the dicar-
boxylic acid.) For a simple lithium soap, the next
step is to continue increasing the temperature of the
mixture until it is between about 350° to about 400°F,

20018'~S
- 9 -
preferably between about 380° to about 400°F, as
described hereinafter.
If, however, the lithium soap of an hydroxy
fatty acid had been preformed, the next step following
dispersion of the soap into the oil (typically at
temperatures between about 150° and about 220°F) would
be to increase the temperature of the mixture to
between about 350° and about 400°F. Dehydration is not
required because water would not normally be present
since aqueous lithium base is not needed with the
preformed soap.
If a lithium complex soap instead of a simple
lithium soap were to be prepared, the next step follow-
ing dehydration would be to cool the lubricating
oil/lithium soap of an hydroxy fatty acid mixture to a
temperature between about 200° to about 260°F, prefer-
ably between about 220° and about 240°F, as rapidly as
possible, the speed of cooling being primarily to save
time. A dicarboxylic acid is then added to the lubri-
cating oil/hydroxy fatty acid mixture thus formed.
This mixture is stirred for a short time (e.g. 30
minutes or less) to ensure proper dispersion throughout
the mixture. A concentrated aqueous solution of
lithium hydroxide is then added to convert the dicar-
boxylic acid to its dilithium soap. Normally, the
amount of lithium hydroxide added is slightly in excess
of the amount stoichiometrically required to neutralize
both acid groups of the dicarboxylic acid. During the
addition of the lithium hydroxide (which will ordi-
narily take from about 30 minutes to about 2 hours) the
temperature will be maintained within the range of
about 200° to about 240°F, preferably between about
210° to about 230°F. After all of the lithium hydro-
xide has been added and neutralization of the dicar-
boxylic acid is nearly complete, the temperature of the

2b~1$'~5
- to -
grease mixture is raised to between about 220° to about
350°F, preferably between about 250° to about 320°F,
and more preferably between about 280° and about 300°F,
for a period of time sufficient to complete the
neutralization and to effect a substantial dehydration
of the mixture as described above.
The critical aspect of this invention is the
recognition that a simple lithium soap grease having
improved shear stability will be obtained only if at
least a major portion, preferably at least 75%, more
preferably at least 90%, and most preferably essen-
tially all of the polyhydric alcohol is added to the
lubricating oil/ lithium soap of an hydroxy fatty acid
mixture before the high temperature "cookout" discussed
below, regardless of whether the lithium soap is
preformed or obtained in situ by acid neutralization.
For a lithium complex soap grease, the polyhydric
alcohol must be added before the high temperature
"cookout" as above, but the addition may be made after
the lithium soap of an hydroxy fatty acid (whether
preformed or obtained in situ) has been dispersed (or
dissolved if in situ) in the lubricating oil, after the
dicarboxylic acid has been neutralized, or both. The
high load-carrying capability of this grease (as
described in U.S. Serial No. 080,454) will also be
retained. Thus, the lithium soap greases of this
invention will have both enhanced load-carrying capa-
bility and shear stability.
Following acid neutralization (neutralization
of the hydroxy fatty acid for a simple lithium soap
grease, and the hydroxy fatty acid and the dicarboxylic
acid for a lithium complex soap grease) and alcohol
addition, the temperature of the grease mixture is
increased to between about 350° to about 400°F, prefer-
ably between about 380° to about 400°F, and maintained

1
.~. z~oQlB~s
- 11 -
at that level for about 15 minutes to about 1 hour to
ensure optimum soap crystallization and improved
yields. This increase in temperature (or "cookout") is
effected as rapidly as possible to save time and to
minimize oxidation.
The soap stock is then cooled as rapidly as
possible. This cooling is aided by incorporating the
remaining quantity of lubricating oil into the mixture.
Mixing can be continued until the grease reaches
ambient temperatures. The grease may be passed through
a conventional grease mill at this point to obtain a
somewhat improved yield and appearance. Suitable
grease mills include a Morehouse mill, a Charlotte
mill, and a Gaulin homogenizes.
When the temperature has been lowered to
between about 150° to about 200°F, preferably between
about 150° to about 170°F, the metal hydrocarbylthio-
phosphate compounds and other grease additives, if any,
that are desired in the grease can be introduced. Such
additives include, but are not limited to, anticorro-
sive agents, pour point depressants, tackiness agents,
viscosity improvers, oxidation inhibitors, dyes and the
like, which are incorporated for specific purposes.
The grease may also be passed through a grease mill
again to obtain a further improvement in yield and
appearance.
Although in most instances the lithium
hydroxide used in forming the hydroxy fatty acid soap
(and the dicarboxylic acid soap for a lithium complex
grease) is most conveniently introduced into the grease
kettle as a saturated aqueous solution, dry lithium
hydroxide can also be used. Ordinarily, however, the
average grease plant will not have proper facilities
for convenient handling of dry lithium hydroxide.

~~ss~s
- 12 -
Normally a slight excess of lithium hydroxide
is used during the soap formation stage(s), i._e., above
the stoichiometric amount theoretically required for
complete neutralization of the acid(s). Typically,
this excess will range from about 0.2 to 0.4 wt.% of
free alkali expressed as sodium hydroxide (ASTM D128).
During the various steps in its preparation,
the ingredients may be mixed or blended in any number
of ways which can readily be selected by one skilled in
the art. Suitable mixing means include angers, screw
extruders, stirred kettles, Stratco contacters, and the
like.
The multipurpose grease of this invention has
a variety of uses and may be suitably employed in
essentially any application requiring a high load-
carrying shear stable grease, including use in wheel
bearing, industrial equipment, and the like.
This invention will be further understood by
reference to the following Examples which are not in-
tended to restrict the scope of the claims appended
hereto.
Example 1 - Improved Shear Stability
Three samples of a lithium complex grease
were prepared as follows:
Stage 1 - 12-hydroxystearic acid and lubricating
oil were combined with mild heating (about 180°F)
until the acid was dissolved. When dissolution of
the acid into the oil was nearly complete, an
equivalent amount (plus slight excess) of lithium
hydroxide dissolved in water was added while the
temperature of the grease was maintained at

zooi8~s
- 13 -
between 200° and 210°F. Once the lithium had been
added, the mixture was heated quickly to about
300°F to evaporate the water and complete the
neutralization. The grease was then cooled to
about 220°F.
Stage 2 - At about 220°F, the desired amount of
azelaic acid was added and allowed to dissolve in
the mixture. When solution was complete, an
equivalent amount (plus slight excess) of lithium
hydroxide dissolved in water was added over a 45
minute period while the temperature was maintained
at about 210° to about 230°F. The alkalinity of
the mixture was then checked by a standard titra-
tion to ascertain whether the reaction was com-
plete. (If not complete, small make-up amounts of
azelaic acid or lithium hydroxide may be added at
this point if required.) Once acid addition was
complete, the mixture was heated to about 300°F to
evaporate the water and complete the neutraliza-
tion.
Stage 3 - The grease mixture was heated to about
380° to about 400°F and held for about 20 minutes.
At this point, the grease was cooled by slow
addition of the remaining portion of the lubricat-
ing oil. Once the mixture reaches about 160° to
about 180°F, the product was removed from the lab
kettle and passed through a colloid mill set at
about 5 to 10 thousandths of an inch clearance.
Staqe 4 - The milled product was then returned to
the kettle and maintained at about 150°F with
stirring. At this point, the additives are
incorporated slowly and thoroughly mixed into the
grease. Once this is completed, the product was

2001875
- 14 -
milled a second time and the consistency deter-
mined by ASTM D217.
However, in Sample 1, glycerol was added to the grease
at Stage 4; in Sample 2, glycerol was added at Stage 1,
and in Sample 3, glycerol was added at Stage 2.
The shear stability of each sample was then
determined by the procedure described in ASTM D217.
First, the consistency of the grease was measured using
a grease pentrometer after working the grease sixty
double strokes in a standard grease worker. Next, the
grease was worked at room temperature for an additional
100,000 double strokes. When the extended working was
completed, the grease was allowed to cool to room
temperature and the consistency again determined as per
ASTM D217 (i.e., after an additional sixty double
strokes). The difference in the two measurements is the
shear stability of the product. The results of these
tests are shown in Table 1 below:
Table 1
Shear Stability ll)
Sample Glycerol Base Grease (2) Final Product 131
No. Added X60 X100,000 Delta X60 X100.000 Delta
1 Stage 4 273 304 31 274 339 65
2 Stage 1 275 299 24 295 305 10
3 Stage 2 268 290 22 295 303 8
(1) Expressed as mm/10 per ASTM D217. Shear stability
given as Delta.
(2) No conventional grease additives added except that
glycerol was added to Samples 2 and 3, but not to
Sample 1.

'"~' 20 0 1 875
- 15 -
(3) All samples include glycerol and the same conven-
tional grease additives.
The data in Table 1 show that the shear
stability of a lithium based grease is enhanced when a
polyhydric alcohol is added following neutralization of
the hydroxy fatty acid or after neutralization of the
dicarboxylic acid, but before the high temperature
"cookout". As such, enhanced shear stability would
also be expected to be obtained if a portion of the
alcohol were after neutralization of the hydroxy fatty
acid and a portion were added after neutralization of
the dicarboxylic acid.
Example 2 - Retained High Load-Carrying Capability
The load-carrying capability of the final
product for Samples 2 and 3 from Example 1 were deter-
mined using a Timken test machine. In the Timken test,
a hardened steel ring or "cup" is rotated against a
hardened steel test block while being lubricated with
the grease under test. A test grease is deemed a
"failure" if the test block is damaged during the test,
and a "pass" if the test block is not damaged. Further
details regarding the Timken test procedure may be
found in ASTM D2782. The results of these tests are
shown in Table 2 below:
S.
~~ fl i :'>..

- 16 -
Table 2
Load-Carrying
Final Product
Sample No. Glvcerol Added Pass, lbs
1 Stage 4 (1)
Stage 1 60
3 Stage 2 60
(1) Not measured, but Sample 1 will have a load-
carrying capability comparable to that of Samples
2 and 3 because all samples contain the same
ingredients responsible for high load-carrying
capability (see Canadian Application Serial No.
571,453).
The data in Table 2 show that a lithium based
grease prepared according to this invention will have a
load-carrying capability comparable to the same grease
prepared by the conventional methods disclosed in
Serial No. 571,453.