AN IMPROVED HIGH PERFORMANCE LUBRICATING GREASE COMPOSITION
FOR HIGH LOAD AND HIGH TEMPERATURE APPLICATION IN HOT ROLLING MILL
FIELD OF THE INVENTION
The present invention relates to an improved high performance lubricating
grease composition useful for preventing seizure of work roll bearings in the finishing
stands of hot strip mill by effective lubrication and protection of the mating surfaces of
the rolling elements in actual practice through lowering of bearing temperature and
minimizing friction and wear. The improved high performance lubricating grease
composition of the invention comprises at least 75% by weight of base oil, from about
7% to about 15% by weight of lithium-calcium 12-hydroxy stearate soap thickener, from
about 6% to about 12% by weight extreme pressure, anti wear and friction modifier
additives, from about 0.2% to about 3% by weight of a water resistant, high temperature,
non-corrosive thermally stable, adherence-imparting, high performance polymeric
additive fully compatible with said EP-AW additives for substantially resisting
displacement by water spray without any adverse effect on mobility of the grease, from
about 0.2% to about 2% by weight of rust/corrosion inhibitors and from about 0.50 % to
about 2 % by weight of oxidation inhibitors for enhancing the performance and longevity
of said grease.
BACKGROUND OF THE INVENTION
Grease is a lubricant that under certain loads and within its range of temperature
application exhibits the properties of a solid body, undergoes plastic strain and starts to
flow like a fluid should the load reach the critical point, and regains solid-body properties
after the removal of the stress. Lubricating grease is best described as a thickener or
gellant diluted by a lubricating fluid. To improve certain properties and functions,
additional components are sometimes included (often called "additives"). This
unconventional way to define the thickener as being diluted by a lubricating fluid, rather
than the more common way to describe it as thickening the fluid, comes from recent
research. This work shows the active part the gellant, at least when being a metal soap,
plays a major role in the actual lubrication contact zone. Lubricating grease properties
depend on both its composition and the manufacturing process used.

It is known in the art various lubricating grease compositions adapted for
particular uses. The document CN 1252434 described composite lithium- and calcium-
base lubricating grease contains base oil, condensed oil and additives. The condensed
oil is compound metallic soap produced through the reaction of 12-hydroxy stearic acid, decanedioic acid, boric acid and naphthenic acid with lithium and calcium hydroxides,
where the weight proportions among 12-hydroxy stearic acid, decanedioic acid, boric
acid and naphthenic acid.
The document WO 2008065158 relates to an improvement to lubricating
compositions, and in particular relates to a semi-solid lubricating composition with
excellent heat resistance, mechanical stability, load resistance, water resistance,
corrosion resistance and flame resistance.
The document EP 0995790 discloses titanium complex grease compositions
having performance additives and a process and compositions thereof The additives
envisaged by the invention include anti-oxidants, extreme pressure and antiwear
additives, rust inhibitors, friction modifiers, structural modifiers, polymers, solid
lubricants, biodegradable additives/ashless additives, multifunctional additives, etc.
In prior art, the concept of thickening oils by soaps for lubrication purpose is well
known. The usage of metallic soaps or their complex soaps as thickeners still dominates
in lubricating greases. These metallic or complex metallic soap base greases are
generally derived from metals such as lithium, calcium, sodium, barium, aluminium, etc.
Lithium base greases are mainly used for their better performance, easy availability and
cost factors etc. Metallic soaps based on other metals have also been reported in prior
art (C.J. Boner. Ind.Eng.Chem, 29,59,1937).
The prior art greases are associated with one or other disadvantages and are not
able to meet fully the various requirements of modern machinery. These greases require
addition of certain performance additives, which are costly, and many of them are
environmentally unsafe.
Over the years, a variety of greases and processes have been suggested for use
in steel mills and other applications. Typifying such greases and processes are those

found in U.S. Pat Nos. 2,964,475; 2,987,151; 3,344,065; 3,843,528; 3,846,314;
3,920,571; 4,107,058; 4,305,831; 4,431,552, 4,440,658 and 4,514,312. These prior art
greases and processes have met with varying degrees of success. None of these prior
art greases and processes, however, has been successful in simultaneously providing
all the above stated properties at the high performance levels required in steel mills.
Hence, the invention pertains to an improved high performance lubricating
grease composition useful for preventing seizure of work roll bearings in the finishing
stands of hot strip mill by effective lubrication and protection of the mating surfaces of
the rolling elements in actual practice through lowering of bearing temperature and
minimizing friction and wear.
OBJECT OF THE INVENTION
A primary object of this invention is to propose an improved high performance
lubricating grease composition incorporating certain performance additives.
Another object of this invention is to propose an improved high performance
lubricating grease composition useful for preventing seizure of work roll bearings in the
finishing stands of hot strip mill.
Another object of this invention is to propose an improved high performance
lubricating grease composition with improved properties of protection of the mating
surfaces of the rolling elements.
Another object of this invention is to propose an improved high performance
lubricating grease composition with improved wear and friction properties.
Another object of this invention is to propose an improved high performance
lubricating grease composition for preventing rust and corrosion in presence of water
spray and be un-reactive with the bearing materials.

Another object of this invention is to propose an improved high performance
lubricating grease composition with good adherence properties as well as resistance to
displacement by water spray.
Still another object of this invention is to propose novel improved high
performance lubricating grease composition to retain all these above mentioned
properties during use without exhibiting any adverse effect such as lacquer deposition
on the tapered roller bearing parts due to oxidation, thermal breakdown and
polymerization of the lubricating grease.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to an improved high performance lubricating
grease composition useful for preventing seizure of work roll bearings in the finishing
stands of hot strip mill by effective lubrication and protection of the mating surfaces of
the rolling elements in actual practice through lowering of bearing temperature and
minimizing friction and wear.
The bearings used in the finishing stands of hot rolling mill are 4-row tapered
roller type and the mill operates under high loads and at medium to high speed. The
bearing and grease used to lubricate the components experience a very large load at a
high speed and also a thermal stress due to friction of bearing elements and to some
extent from radiated heat from red-hot steel plate surface during rolling process. To
minimize the effect of radiated heat on bearings and the heat generated due to high-
speed rotation of bearings under heavy load, cooling is accomplished by high velocity
water spray on the bearing housing from all directions. With such water spray force,
even well sealed bearings will not totally exclude water. Therefore, the bearing grease
will experience water contamination with a physical force that tends to wash the grease
out of the bearings.
High performance grease is important to minimize failure of bearings used in
work roll. Such bearing failures cause sudden break down of the mill that can endanger
operating personnel, interrupt steel mill operations, cause damage or loss and raise
lubricant consumption.

The improved-high performance grease used to lubricate such bearings under
such operating conditions of hot strip mill has:
a) reduce wear and friction;
b) prevent rust and corrosion in presence of water spray and be un-reactive
with the bearing materials;
c) have good adherence properties as well as resist displacement by water
spray;
d) retain these properties during use without exhibiting any adverse effect such
as lacquer deposition on the tapered roller bearing parts due to oxidation,
thermal breakdown and polymerization of the lubricating grease.
The developed improved high performance grease has:
a) a substantial proportion of a base oil;
b) a thickener, such as lithium soap of fatty acids or a mixture of lithium-calcium
soap of fatty acids;
c) a sufficient amount of an additive package to impart extreme pressure and
anti wear properties along with anti corrosion, anti-oxidation characteristics;
d) a sufficient amount of a high temperature, non-corrosive, oxidatively and
thermally stable, water resistant, hydrophobic, adherence-imparting
polymeric additive. The polymeric additive to-operates and is compatible
(non-interfering) with the extreme pressure anti-wear additive package to
minimize water contamination in the grease as well as resist displacement by
water spray while not adversely affecting mobility properties of the grease.
An improved high performance lubricating grease composition for high load and
high temperature application in hot rolling mill, wherein the ration by weight of
each component are as follows:
a) 75% to 90% by weight of a base oil;
b) 7% to 15% by weight of thickener;
c) 6% to 12% by weight of an additive package to impart extreme pressure
and anti-wear properties along with, metal deactivation characteristics;
d) 0.5 to 2% by weight of anti-oxidant;
e) 1 to 5 % by weight of solid lubricants;
f) 0.2 to 2% by weight of anti-rust and anti-corrosion agents;

g) 1 to 3% by weight of friction modifier;
h) 0.5 to 2 % by weight of lime;
i) 0.2% to 3% by weight of polymeric additive.
The preferred improved lubricating grease composition comprising by weight at '.'..
least 75% base oil, from about 7% to about 15% lithium-calcium 12-hydroxy stearate "
soap thickener, from about 6% to about 12% extreme pressure, anti wear and friction
modifier additives, from about 0.2% to about 3% of a water resistant, high temperature,
non-corrosive thermally stable, adherence-imparting, high performance polymeric
additive fully compatible with said EP-AW additives for substantially resisting
displacement by water spray without any adverse effect on mobility of the grease, from
about 0.2% to about 2% of rust/corrosion and oxidation inhibitors for enhancing the
performance and longevity of said grease.

The lubricating grease composition has been prepared consisting of the
ingredients with proportions as described below in Table 1:

The improved lubricating grease prepared according to the above composition
exhibited the physico chemical characteristics indicated in the table 2.



Base Oil
The base oil can be naphthenic oil, paraffinic oil, aromatic oil, or a synthetic oil
such as a polyalphaolefin, polyolester, diester, polyalkyl ethers, polyaryl ethers, silicone
polymer fluids, or combinations thereof.
Other hydrocarbon oils can also be used, such as: (a) oil derived from coal
products, (b) alkylene polymers, such as polymers of propylene, butylene, etc., (c) olefin
(alkylene) oxide-type polymers, such as olefin (alkylene) oxide polymers prepared by
polymerizing alkylene oxide (e.g., propylene oxide polymers, etc., in the presence of
water or alcohols, e.g., ethyl alcohol), (d) carboxylic acid esters, such as those which are
prepared by esterifying such carboxylic acids as adipic acid, azelaic acid, sebacic acid,
alkenyl succinic acid, fumaric acid, maleic acid, etc., with alcohols such as butyl alcohol,
hexyl alcohol, 2-ethylhexyl alcohol, etc., (e) liquid esters of acids of phosphorus, (f) alkyl
benzenes, (g) polyphenols such as biphenols and terphenols, (h) alkyl biphenyl ethers,
and (i) polymers of silicon, such as tetraethyl silicate, tetraisopropyl silicate, tetra(4-

•methyl-2-tetraethyl) silicate, hexyl(4-methol-2-pentoxy) disilicone, poly(methyl)siloxane, and
poly(methyl)phenylsiloxane.
The preferred base oil comprises a mixture of a refjned solvent extracted hydrogenated
dewaxed base stock derived from paraffinic, naphthenic or mixed base crudes and having
viscosity of 300 cSt to 350 cSt at 40°C.
Thickener
Ideally, the thickener improves the lubricating properties, by building a thicker film at the
lubricated surfaces than can be achieved with the included fluid alone. At the same time, its
necessary to have lubricating grease that can replenish itself into the contact area through
microscopic flow behavior. When using lubricating greases that are subjected to very high
centrifugal acceleration forces, it becomes evident that the density of the thickener is important
for the degree of separation. The smaller the difference between thickener and fluid, the less the
separation will be, even at extreme conditions.
The preferred thickener in the present composition is lithium-calcium 12-hydroxy
stearate soap thickener, 12-hydroxy stearic acid, in its refined fatty acid form or as the
triglyceride (hydrogenated castor oil), is the most commonly used anion, several other anions
are used. Tallow, lard, stearic acid, oleic acid and many other fatty acids or fats are used either
as the major anion or as modifiers for the desired soap structure.
Inhibitors
The additive package may be complemented by the addition of small amounts of an
antioxidant, a corrosion-inhibiting agent, and a metal deactivator. Oxidation inhibitor prevents
varnish and sludge formation and oxidation of metal parts. The anti oxidant used in this
invention is of aminic type, alkylated phenyl or diphenylamine.
Corrosion inhibiting agent prevents rusting of iron by water, suppress attack by acidic
bodies and form protective film over metal surfaces to diminish corrosion of exposed metallic
parts. Anti-rust and anti-corrosion agents used are neutral metallic salt of dinonyl naphthalene
sulphonate and metal alkyl dithiocarbamate.

Metal deactivator prevents or diminishes copper corrosion and counteracts the
effects of metal on oxidation by forming catalytically inactive compounds with soluble or
insoluble metal ions. Typical metal deactivators used include mercaptobenzothiazole
and complex organic amines.
Polymer
Polymer, which is used in the above-developed grease to attain the desired
characteristics described in the table, has molecular weight in the range of 3,00,000 to
5,00,000. Acceptable polymers for attaining many of the grease characteristics
described above include: polyolesters (polyesters), polyamides, polyurethanes,
polyoxides, polyamines, polyacrylamide, polyvinyl alcohol, ethylene vinyl acetate and
polyvinyl pyrrolidone. Co-polymers with mpnomeric units comprising the monomelic
units of the preceding polymers and combinations thereof may also be used. Also,
boronated polymers or boronated compounds comprising the borated or boronated
analogs of the preceding polymers (i.e., any of the preceding polymers reacted with
boric acid, boric oxides, or boron inorganic oxygenated material) may also be used when
nucleophilic sites are available for boration. The preferred polymer comprises:
polyethylene, polypropylene, poly isobutylene and ethylene-propylene copolymers.
Performance Additives
The extreme pressure and anti wear additives, friction modifier and solid lubricant
additives can be selected from one or more of the following:
1)Sulfurized oxymolybdenum organo phosphorodithioate;
2) Organomolybdenum dithiocarbamate;
3) Zinc or other metal dialkyl dithiophosphate or carbamate;
4) Colloidal Graphite;
5) Molybdenum disulphide.
Different embodiments of the invention are possible to achieve the best method
of performance and to obtain the product as stated above to meet the object of the
invention. It will be understood that skilled persons with many modifications, variations
and adaptations may carry out the invention into practice without departing from its spirit
or exceeding the scope of claims in describing the invention for the purpose of
illustration.

WE CLAIM:
1. An improved high performance lubricating grease composition for high load and high
temperature application in hot rolling mill, wherein the ration by weight of each
component are as follows:
a) 75% to 90% by weight of a base oil;
b) 7% to 15% by weight of thickener;
c) 6% to 12% by weight of an additive package to impart extreme pressure and anti-
wear properties along with, metal deactivation characteristics;
d) 0.5 to 2% by weight of anti-oxidant;
e) 1 to 5 % by weight of solid lubricants;
f) 0.2 to 2% by weight of anti-rust and anti-corrosion agents;
g) 1 to 3% by weight of friction modifier;
h) 0.5 to 2 % by weight of lime; and
i) 0.2% to 3% by weight of polymeric additive.
2. An improved high performance lubricating grease composition as claimed in claim 1,
wherein said base oil comprises a mixture of a refined solvent extracted hydrogenated
dewaxed base stock derived from paraffinic, naphthenic or mixed base crudes.
3. An improved high performance lubricating grease composition as claimed in claim 1,
wherein said base oil is having viscosity of 300 cSt to 350 cSt at 40°C.
4. An improved high performance lubricating grease composition as claimed in claim 1,
wherein said thickener is lithium soap of fatty acids or a mixture of lithium-calcium soap
of fatty acids.
5. An improved high performance lubricating grease composition as claimed in claim 1,
wherein said thickener is lithium-calcium 12-hydroxy stearate soap.
6. An improved high performance lubricating grease composition as claimed in claim 1,
wherein said additives are extreme pressure additives, anti-wear additives, friction
modifiers, solid lubricants, anticorrosion additives, metal deactivators and anti oxidants.
7. An improved high performance lubricating grease composition as claimed in claim 6,
wherein the said anti-oxidant is selected from the group of aminic type, alkylated phenyl
or diphenylamine.

8. An improved high performance lubricating grease composition as claimed in
claim 1 and 6, wherein the said additives can be selected from one or more of the
following: Sulfurized oxymolybdenum organo-phosphorodithioate, Organomolybdenum
dithiocarbamate, Zinc or other metal dialkyl dithiophosphate or carbamate, Colloidal
Graphite, Molybdenum disulphide.
9. An improved high performance lubricating grease composition as claimed in claim 6,
wherein the said anti-rust and anti-corrosion agents are selected from the group of
neutral metallic salt of dinonyl naphthalene sulphonate and metal alkyl dithiocarbamate.
10. An improved high performance lubricating grease composition as claimed in claim 6,
wherein the said metal deactivators are selected from mercaptobenzothiazole and
complex organic amines.
11. An improved high performance lubricating grease composition as claimed in claim 1,
wherein said friction modifier is lithium-hydroxide monohydrate.
12. An improved high performance lubricating grease composition as claimed in claim 1,
wherein said polymeric additives are selected from the group of polyethylene,
polypropylene, poly isobutylene and ethylene-propylene copolymers.

ABSTRACT

AN IMPROVED HIGH PERFORMANCE LUBRICATING GREASE COMPOSITION FOR HIGH
LOAD AND HIGH TEMPERATURE APPLCIATION IN HOT ROLLING MILL
The present invention relates to an improved high performance lubricating grease composition
for high load and high temperature application in hot rolling mill, wherein the ration by weight of
each component are as follows: 75% to 90% by weight of a base oil; 7% to 15% by weight of
thickener; 6% to 12% by weight of an additive package to impart extreme pressure and anti-
wear properties along with, metal deactivation characteristics; 0.5 to 2% by weight of anti-
oxidant; 1 to 5 % by weight of solid lubricants; 0.2 to 2% by weight of anti-rust and anti-
corrosion agents; 1 to 3% by weight of friction modifier; 0.5 to 2 % by weight of lime; and 0.2%
to 3% by weight of polymeric additive.