Note: Descriptions are shown in the official language in which they were submitted.
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ruFASE COMPOSTTION
SACRGROUND OF THE INVENTION
1. Field of the Invention _ ____ _,__ ,
This invention relates to grease compositions having low
noise properties and high dropping points.
2. Descrifltion of the Related Art ~ ,~_" ,_,,., ,__ ,._. ._,
The bearings in modern automobiles and electric appliances
are typically sealed bearings. Greases for sealed bearings must
provide lubrication for the life of the bearing which places high
demands on greases used in such service. Sealed bearing greases moat
meet numerous performance requirements including extending bearing
life, high temperature performance, high dropping point, low oil
separation, oxidation stability, fretting wear protection and low
noise.
Recently, lithium complex soap based greases have been used
in sealed bearing applications. Such greases offer long service at
high temperatures but suffer from generally higher noise than simple
lithium soap based greases.
It would be desirable to have a sealed bearing grease con-
taining a lithium complex soap which does not cause high noise in
sealed bearings. For high temperature service improvement in grease
dropping point is also desirable.
f
This invention relates to a grease composition having
a
improved noise properties and high dropping point which comprises:
a) a major amount of a lubricating base oil,
WO 95135355 PCTIUS95107471
21'91481
b) from 2 to 30 wt%, based on grease, of a lithium soap
complex thickener, and
c) from 0.1 to 10 wt%, based on grease, of a polyalkenyl
succinic anhydride, a polyalkenyl succinic acid or a mixture thereof. .
The greases according.to the invention provide long bearing
life and high dropping point while providing low bearing noise.
na~marr.FD DESCRTPTION OF THE INVENTION , , a_
A wide variety of lubrication base oils can be employed in
preparing the grease compositions of the present invention. Accord-
ingly, the lubricating oil base can be any of the conventionally used
mineral oils, synthetic hydrocarbon oils or synthetic ester oils, or
mixtures thereof depending upon the particular grease being prepared.
In general these lubricating oils will have~a viscosity in the range
of about 5 to about 400 cSt at 40°C, although typical applications
will require an oil having a viscosity ranging from about IO to about
200 cSt at 40°C. Mineral lubricating oil base stocks used in prepar-
ing the greases can be any conventionally refined base stocks derived
from paraffinic, naphthenic and mixed base crudes. Synthetic lubri-
cating oils that can be used include 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 ae polyalphaolefins;
alkyl benzenes, e.g., alkylate bottoms from the alkylation of benzene
with tetrapropylene, or the copolymers of ethylene and propylene;
silicone oils, e.g., ethyl phenyl polysiloxanes, methyl polysiloxanes,
etc.; polyglycol oils, e.g., those obtained by condensing butyl
alcohol with propylene oxide; carbonate eaters, 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 S phenyl
groups. The amount of lubricating oil in the grease can also vary
W095135355 21914 81 PC'TlUS95107471
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broadly, but, typically, will range from about 5D wt% to about 98 wt%,
preferably from about 75 wt% to about 95 wt%, of the grease.
The grease composition contains a thickener dispersed in the
lubricating base oil to form a grease. Preferred thickeners are
lithium soap complex thickeners containing a lithium soap of a C12 to
C24 hydroxy fatty acid and a second lithium salt compound which is a
lithium salt of a CZ to C12 aliphatic or cycloaliphatic dicarboxylic
acid, a lithium salt of a C3 to C14 hydroxy carboxylic acid which has
the hydroxy group separated from the carboxyl group by six or leas
carbon atoms or a mixture thereof. The lithium salt of boric acid may
be added as a third thickener component. Preferred hydroxy fatty
acids include hydroxystearic, hydroxyricinoleic, hydroxybehenic and
hydroxypalmitic. Especially preferred is 12-hydroxyatearic acid. The
second lithium salt compound is preferably a C6 to Clp aliphatic
dicarboxylic acid, more preferably azelaic or sebacic acids, especial-
ly aaelaic acid. The hydroxy-carboxylic acid is preferably lactic
acid, salicylic acid or other hydroxy-benzoic acids, more preferably
salicylic acid. The amount of lithium soap complex thickeners is
preferably from 5 to 20 wt%, based on grease. The ratio of hydroxy
fatty acid to aliphatic dicarboxylic acid and/or hydroxy-carboxylic
acid is from 10:0.5 to 10:15, preferably 10:1.5 to 10:6.
The grease composition will also contain a polyalkenyl
succinic anhydride, a polyalkenyl succinic acid or mixture thereof as
dispereant. The polyalkenyl group will have a number average molecu-
lar weight of from 300 to 4,000, preferably 400 to 2,5D0. Preferred
palyalkenyl groups are poly-Cg and poly-C4 olefins, especially poly-
ieobutylene. Polyisobutylene succinic anhydride and/or acid will
hereinafter be collectively referred to as PI85A. The amount of
dispersant ie preferably from 0.1 wt% to 5 wt%, based on grease.
Lithium complex soap greases are prepared by heating hydroxy
fatty acid and base oil, adding a concentrated aqueous solution of
lithium hydroxide. Heating is continued at elevated temperature to
remove most of the water. The reaction mixture is then cooled to
about 100°C and dicarboxylic acid is added followed by a second
'WO 95135355 PCTIU595107471
X191481
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portion of concentrated lithium hydroxide. This mixture is again
heated to elevated temperature to again remove Water. After heating
is completed, the grease mixture is cooled, remaining oil and any
other additives added and the grease is worked up using conventional
techniques. The preparation may also be accomplished in a single step
process by heating, base oil, fatty acid and dicarboxylic acid, then
adding lithium hydroxide solution followed by dehydration and adding
remaining oil. '
The grease composition may contain small amounts of supple-
mental additives which include, but are not limited to, anti-corrosive
agents, extreme pressure antiwear agents, pour point depressants,
tackiness agents, oxidation inhibitors, dyes and the like, which are
incorporated for specific purposes. The total amount of these addi-
tives will typically range from about 2 wt% to about 10 wt% based on
total weight of the grease composition.
This invention will be further understood by reference to the
followinq examples which include a preferred embodiment of the inven-
tion.
This example illustrates the preparation of a low noise
grease. A laboratory kettle was charged with 70D g of refined paraf-
finic base oil having a viscosity of 90 cSt at 40°C, 139.2 g of
12-hydroxystearic acid, 69.5 q of azelaic and 12.0 g of PIBSA having a
polyisobutenyl radical of number average molecular weight of 950. The
resulting mixture was heated with stirring until the temperature
reached 90°C. At this point, heating was stopped and 345 g of a 15%
solution of lithium hydroxide (heated to 9D°C) was added with stir-
ring. When addition of the lithium hydroxide solution was complete, "
heating was resumed to remove water. An additional 1D0 g of oil was
added during the dehydration process to control grease hardening.
Aeating was continued to a temperature of 210°C at which time
heating
was discontinued and an additional 128 9 of oil was added. The heated
mixture was allowed to cool slowly to a temperature of 7D°C or leas.
WO 95/35355
2191 ~ ~ ~ PCT~S9510747I
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The cooled greases was milled at 0.005 inch clearance and deaerated.
The grease samples described 1n Table 1 of Example 3 were manufactured
c using this procedure. Component amounts were varied as described in
&les 1-3 and Comparative Samples 4-14.
Grease noise was measured according to the following proce-
dure which is more fully described in Japanese Patent 53-2357. Solid
particles in grease result in vibrations which can be converted into
an electrical signal. After correcting for race noise of bearings
under standard conditions, the electrical signal due to solid parti-
clea including soap particles in grease can be measured according to
the following procedure. A vibration detection device is attached to
the outer ring of the bearings. The detection device converts the
vibrations into an electrical signal which is amplified and sent to a
zone wave filter. The zone wave filter compares the amplified signal
received from the bearings with the known vibration frequency from the
bearings alone, filters out the vibration frequencies from the bear-
ings and sends the filtered electronic signal through an amplifier to
a clipper circuit. The clipper circuit "clips" the electrical signal
from the amplifier at a given level. This level is set so as to
measure only peak voltages which correspond to solid particle noise
from particles in the grease. The clipping level is set at a value
greater than the peak value corresponding to the race noise from the
bearings.
This example compares the noise properties and dropping point
of a grease formulated With a polyisobutenyl succinic anhydride/acid
x
diapersant according to the invention with polyisobutenyl auccinic
amide type diapersants described in Japanese Patent A2 58125794.
Greases were formulated using the procedures of Example 1. Noise was
tested using the procedure of Example 2 and dropping point was
measured according to test method ASTM D566. The results are set
forth in Table 1.
W095l35355 21914 81 PCTIUS95I07471
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W095l35355 219 i 4 81 PCTlUS9510747i
- S -
Greases formulated with a polyisobutenyl succinic anhydride/
acid type dispersant (Samples 1-3) showed significantly better noise
property and higher dropping point compared to a lithium complex
grease fozmulated without dispersant (Sample 4). Samples 1-3 also
demonstrated consistently higher dropping points compared to greases
formulated with polyisobutenyl succinic imide type dispersants (COm-
parative Samples 5-13). A commercial lithium complex grease (Sample
14) demonstrated a much inferior noise property compared to Samples
1-3 according to this invention.
