U.S. patent application number 13/992114 was filed with the patent office on 2014-01-09 for polymer thickened grease compositions and their use.
The applicant listed for this patent is Dick Meijer, Dries Muller. Invention is credited to Dick Meijer, Dries Muller.
Application Number | 20140011718 13/992114 |
Document ID | / |
Family ID | 44370590 |
Filed Date | 2014-01-09 |
United States Patent
Application |
20140011718 |
Kind Code |
A1 |
Meijer; Dick ; et
al. |
January 9, 2014 |
POLYMER THICKENED GREASE COMPOSITIONS AND THEIR USE
Abstract
The invention provides a grease composition comprising: (a) a
polymer thickened grease; (b) an acid having a pKa in the range of
2-7 wherein the pKa is measured in water at 25.degree. C.; and (c)
a metal salt. The invention further provides a mechanical component
having a metal surface onto which a layer of the grease composition
according to the invention has been applied. In addition, the
invention relates to the use of the present grease composition for
reconditioning the lubrication of a mechanical component having a
metal surface; and the use of the present grease composition for
protecting a mechanical component having a metal surface against
corrosion, wear or anti-fretting. The invention also relates to a
method for preparing the present grease composition.
Inventors: |
Meijer; Dick; (Wageningen,
NL) ; Muller; Dries; (Nijmegen, NL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Meijer; Dick
Muller; Dries |
Wageningen
Nijmegen |
|
NL
NL |
|
|
Family ID: |
44370590 |
Appl. No.: |
13/992114 |
Filed: |
December 6, 2010 |
PCT Filed: |
December 6, 2010 |
PCT NO: |
PCT/EP2010/007386 |
371 Date: |
August 15, 2013 |
Current U.S.
Class: |
508/100 ;
508/110; 508/163; 508/164 |
Current CPC
Class: |
C10N 2030/06 20130101;
C10M 2215/12 20130101; C10M 2205/0213 20130101; C10N 2050/10
20130101; C10M 169/06 20130101; C10N 2010/08 20130101; C10M
2207/126 20130101; C10N 2010/14 20130101; C10M 2207/128 20130101;
C10M 2201/085 20130101; C10M 2219/04 20130101; C10M 2215/10
20130101; C10N 2010/10 20130101; C10N 2040/02 20130101; C10M
2207/16 20130101; C10N 2010/04 20130101; C10N 2010/02 20130101;
C10M 2207/128 20130101; C10N 2010/14 20130101; C10M 2207/128
20130101; C10N 2010/14 20130101 |
Class at
Publication: |
508/100 ;
508/164; 508/163; 508/110 |
International
Class: |
C10M 169/06 20060101
C10M169/06 |
Claims
1. A grease composition comprising: (a) a polymer thickened grease;
(b) an acid having a pKa in the range of 2 7 with the pKa being
measured in water at 25.degree. C.; and (c) a metal salt.
2. The grease composition according to claim 1, further comprising
the step of applying the grease composition to a metal surface of a
mechanical component, the metal salt reacting with the acid and the
acid or the acid so obtained etches the metal surface, thereby
forming on the metal surface a layer including the metal of the
metal salt.
3. The grease composition according to claim 2, wherein the metal
of the metal salt is selected from the group consisting of Group
1A, 1B, 2A, 2B, 4A, 5A, 7B and 8B elements of the Periodic
Table.
4. The grease composition according to claim 3 comprising: (a) 1-99
wt % of the lubricating base oil; (b) 1-20 wt % of the polymeric
thickener; (c) 0.01-10 wt % of the acid; and (d) 0.01-40 wt % of
the metal containing compound, wherein all weight percentages are
based on the total weight of the grease composition.
5. The grease composition according to claim 4 further comprising a
polymeric ester in an amount in the range of from 0.1-40 wt %,
based on the total weight of the grease composition.
6. The grease composition according to claim 5, wherein the acid is
a polyprotic acid having two pKa values in the range of from
2-10.
7. The grease composition according to claim 6, wherein the acid is
phosphoric acid.
8. The grease composition according to claim 7, wherein the
polymeric thickener includes at least one component selected from
the group consisting of natural rubber, polypropylene,
polyisoprene, polybutadiene, poly(styrene-butadiene),
poly(ethylene-propylene-diene), polyurethane, polymethacrylate,
polyisobutylene, poly(isobutylene-succinic acid),
poly(isobutylene-succinic acid-polyacrylamide), polyurea and
polyethylene.
9. The grease composition according to claim 8, wherein the
polymeric thickener comprises a first component and a second
component, with the first component having a higher weight average
molecular weight than the second component.
10. The grease composition according to claim 9, wherein the
polymeric thickener includes a high molecular weight component and
a low molecular weight component, and wherein the thickener further
comprises a mixture of (1) a (co- or homo-)polymer of propylene
with a weight average molecular weight of more than 200.000 and (2)
a (co- or homo-)polymer of propylene with a weight average
molecular weight of less than 200.000.
11. The grease composition according to claim 10, wherein the
weight ratio between the high molecular weight component and the
low molecular weight component is 1:40-1:5, preferably 1:25-1:15,
more preferably 1:18-1:20.
12. The grease composition according to claim 11, wherein the low
molecular weight component is a polypropylene homopolymer.
13. The grease composition according to claim 12, wherein the low
molecular weight component has an average molecular weight between
20.000 and 100.000 and a melt flow rate of 500-1500, preferably
750-1250.
14. The grease composition according to claim 13, wherein the high
molecular weight component is a polypropylene homopolymer or a
propylene/ethylene-copolymer.
15. The grease composition according to claim 14, wherein the high
molecular weight component has an average molecular weight of
200.000-350.000 and a melt flow rate of 1.5-15, preferably
1.5-7.
16. The grease composition according to claim 15, wherein the metal
salt is selected from the group consisting of naphtenates, octoate,
carbamate, carboxamides, sulfonamides, stearates, hydroxystearates
and any mixture thereof.
17. The grease composition according to claim 16, wherein the metal
salt is a stearate, a hydroxystearate or a mixture thereof.
18. The grease composition according to claim 17, wherein the metal
in the metal salt is selected from the group consisting of bismuth,
zinc, sodium, calcium, magnesium, antimony, barium, manganese,
silver, gold, copper and lead.
19. The grease composition according to claim 18, wherein the metal
in the metal salt is bismuth or zinc.
20. The grease composition according to claim 19, further
comprising an ester oil in an amount in the range of from 1-40 wt
%, based on the total weight of the grease composition.
21. The grease composition according to claim 20 further comprising
an inert powder in an amount in the range of from 1-10 wt %, based
on the total weight of the grease composition.
22. The grease composition according to claim 21 further comprising
at least one additive component which is selected from the group
consisting of antioxidants, corrosion inhibitors, anti-wear agents
and pressure tolerance-increasing additives, and wherein the total
content of the additive component(s) is in the range between 0.2
and 15% by weight, and preferably between 1 and 8% by weight, based
on the total weight of the grease composition.
23. A mechanical component having a metal surface onto which a
layer of a grease composition has been applied, the grease
composition comprising: (a) a polymer thickened grease; (b) an acid
having a pKa in the range of 2-7 with the pKa being measured in
water at 25.degree. C.; and (c) a metal salt.
24. The mechanical component according to claim 23, further
comprising providing a metal surface onto which a layer has formed
comprising the metal of the metal salt.
25. The mechanical component according to claim 23 further
comprising a bearing, bearing component or bearing application
system.
26. Use of a grease composition for reconditioning the lubrication
of a mechanical component having a metal surface, the grease
composition comprising: (a) a polymer thickened grease; (b) an acid
having a pKa in the range of 2 7 with the pKa being measured in
water at 25.degree. C.; and (c) a metal salt.
27. Use of the grease composition according to claim 26, further
comprising for protecting a mechanical component having a metal
surface against corrosion.
28. Use of the grease composition according to claim 26, further
comprising for protecting a mechanical component having a metal
surface against wear.
29. Use of the grease composition according to claim 26, further
comprising for protecting a mechanical component having a metal
surface against fretting.
30. Use of the grease composition according to claim 29, wherein
the mechanical component comprises a bearing, bearing component or
bearing application system.
31. A method for preparing a grease composition having a polymer
thickened grease; an acid having a pKa in the range of 2-7 with the
pKa is measured in water at 25.degree. C.; and a metal salt, the
method comprising the following steps: a) mixing the polymer
thickened grease with the metal salt; and b) adding to the mixture
obtained in step (a) the acid.
32. The method for preparing a grease composition according to
claim 31, wherein in step (a) the metal salt is heated above its
melting point.
33. The method according to claim 31, further comprising
additionally mixing during step (a) one or more anti-wear
additives, anti-corrosion additives, anti-oxidants, inert powder(s)
and/or other additives.
34. The method according to claim 33, wherein a final mixing in
step (a) is carried out using a three-roll mill or ball-mill.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a grease composition; a
bearing, bearing component or bearing application system having a
metallic surface onto which a layer of the grease composition has
been applied; the use of the present grease composition for
reconditioning the lubrication in mechanical components; the use of
the present grease composition for protecting mechanical components
against corrosion, wear or fretting, and a method for preparing the
present grease composition.
BACKGROUND OF THE INVENTION
[0002] Polymer thickened lubricating greases and their preparation
are known in the art. In U.S. Pat. No. 3,392,119, a grease is
described comprising a white mineral oil that has been thickened by
means of a copolymer of ethylene and a homopolymer of
polypropylene. In U.S. Pat. No. 3,850,828, a lubricating grease
composition has been described which is thickened with a polymeric
mixture comprising a polyethylene and an atactic polypropylene. In
EP 0700986 A2, a polymeric thickener for lubricating grease
compositions is disclosed comprising containing a mixture of
copolymers or homopolymers of polypropylene having a high molecular
weight and a copolymer or homopolymer of propylene having a low
molecular weight. Further, In EP 0942063, a lubricating grease
composition is described comprising at least one polyolefin
component, at least one base oil component and at least one rubber
component.
[0003] These known polymer thickened lubricating grease
compositions still leave room for improvement in respect of various
applications, such as for instance off-shore applications and wind
turbine applications.
SUMMARY OF THE INVENTION
[0004] Object of the present invention is to provide a new set of
polymer thickened grease compositions for protecting mechanical
components against corrosion, wear or fretting.
[0005] Another object is to provide new polymer thickened grease
compositions for reconditioning the lubrication in mechanical
components.
[0006] Surprisingly, it has now been found that grease compositions
can be prepared that form a highly attractive protection layer on
mechanical components such as bearings by mixing a polymer
thickened grease with an acid and a metal salt.
[0007] Accordingly, the present invention relates to a grease
composition comprising:
(a) a polymer thickened grease; (b) an acid having a pKa in the
range of 2-7 wherein the pKa is measured in water at 25.degree. C.;
and (c) a metal salt.
[0008] The present invention also relates to a mechanical component
such as a bearing, bearing component or bearing application system
having a metallic surface onto which a layer of the grease
composition has been applied.
[0009] In addition, the present invention relates to the use of the
present grease composition for reconditioning the lubrication in
mechanical components, and to the use of the present grease
composition for protecting mechanical components against corrosion,
wear or fretting.
[0010] Further, the present invention provides a method for
preparing the present grease composition.
DETAILED DESCRIPTION OF THE INVENTION
[0011] The present invention also provides a grease composition
comprising: (a) a polymer thickened grease; (b) an acid having a
pKa in the range of 2-7 wherein the pKa is measured in water at
25.degree. C.; and (c) a metal salt, wherein upon applying the
grease composition to a metal surface of a mechanical component,
the metal salt reacts with the acid and the acid or the acid so
obtained etches the metal surface, thereby forming on the metal
surface a layer comprising the metal of the metal salt.
[0012] The metals of the metal salt to be used in accordance with
the present invention can be chosen from a wide variety of metals.
Suitably, the metal of the metal salt is selected from the group
consisting of Group 1A, 1B, 2A, 2B, 4A, 5A, 7B and 8B elements of
the Periodic Table. Preferably, the metal in the metal salt is
selected from the group consisting of bismuth, zinc, sodium,
calcium, magnesium, antimony, barium, manganese, silver, gold,
copper and lead. More preferably, the metal in the metal salt is
bismuth or zinc.
[0013] Suitably, the metal salt is selected from the group
consisting of naphtenates, octoate, carbamate, carboxamides,
sulfonamides, stearates, hydroxystearates and any mixture thereof.
Preferably, the metal salt is a stearate, a hydroxystearate or a
mixture thereof.
[0014] In the grease composition according to the present invention
use can be made of a variety of acids, provided that they have at
least one pKa in the range of 2-7 wherein the pKa is measured in
water at 25.degree. C. Preferably, the acid to be used is a
polyprotic acid. The polyprotic acid to be used in accordance with
the present invention has suitably two pKa values in the range of
from 2-10, preferably two pKa values in the range of from 2-8,
wherein the pKa is measured in water at 25.degree. C. More
preferably the polyprotic acid is a triprotic acid having three pKa
values in the range of from 2-13 wherein the pKa is measured in
water at 25.degree. C. Most preferably the triprotic acid is
phosphoric acid.
[0015] The polymer thickened grease to be used in accordance with
the present invention comprises a lubricating base oil and a
polymeric thickener. In the present grease composition preferably
only use is made of a polymeric thickener, not a conventional
soap-metal salt thickener. However, such a conventional thickener
may be incorporated in the present grease composition as long as it
does not adversely affect the overall properties of the grease
composition.
[0016] It is observed that the metal salt to be used in accordance
with the present invention does not act as a thickener. The metal
salt to be used in accordance with the present invention is added
to a grease composition that has already adequately been thickened
by means of a polymer. The metal salt serves a different purpose,
namely to react with the acid to form on the metal surface a layer
comprising the metal of the metal salt.
[0017] The present grease composition suitably comprises:
(a) 1-99 wt % of the lubricating base oil; (b) 1-30 wt % of the
polymeric thickener; (c) 0.01-10 wt % of the acid; and (d) 0.01-40
wt % of the metal containing compound, all weight percentages based
on the total weight of the grease composition.
[0018] The weight percentage of the acid is based on a 85%
concentration of the acid concerned.
[0019] Preferably, the present grease composition comprises:
(a) 10-95 wt % of the lubricating base oil; (b) 5-15 wt % of the
polymeric thickener; (c) 0.5-5 wt % of the acid; and (d) 1-10 wt %
of the metal containing compound, all weight percentages based on
the total weight of the grease composition.
[0020] In one embodiment of the present invention, the grease
composition preferably comprises in addition a polymeric ester in
an amount in the range of from 0.1-40 wt %, based on the total
weight of the grease composition. Polymeric esters are copolymers
of olefins and dicarboxylic acids which are esterified with various
kinds of alcohols. Their viscosities suitably range from 5
mm.sup.2/s up to 700 mm.sup.2/s. Suitably, the average molecular
weights (Mw) do not exceed 7,000 Dalton, ensuring that the
polymeric esters are shear stable. Suitable examples of polymeric
esters that can be used in accordance with the present invention
include di-esters, polyol esters, mono esters, glycol esters and
PEG esters. The polymeric ester is preferably high polar or low
polar polymer ester
[0021] The polymeric thickener to be used in the polymer thickened
grease suitably comprises at least one component selected from the
group consisting of natural rubber, polypropylene, polyisoprene,
polybutadiene, poly(styrene-butadiene),
poly(ethylene-propylene-diene), polyurethane, polymethacrylate,
polyisobutylene, poly(isobutylene-succinic acid),
poly(isobutylene-succinic acid-polyacrylamide), polyurea and
polyethylene.
[0022] The polymeric thickener preferably comprises a first
component and a second component, with the first component having a
higher weight average molecular weight than the second component.
Preferably, the polymeric thickener comprises a high molecular
weight component and a low molecular weight component,
characterized in that the thickener comprises a mixture of (1) a
(co- or homo-)polymer of propylene with a weight average molecular
weight of more than 200.000 and (2) a (co- or homo-)polymer of
propylene with a weight average molecular weight of less than
200.000.
[0023] The polymeric thickener to be used in accordance with the
present invention contains a high molecular weight component
comprising a (co- or homo-)polymer of propylene with a weight
average molecular weight of more 200.000, preferably
200.000-350.000 and a low molecular weight component comprising a
(co- or homo-) polymer of propylene with a weight average molecular
weight of less than 100.000, preferably 50.000-100.000.
[0024] The weight ratio between the high molecular weight component
and the low molecular weight component in the polymeric thickener
can be 1:40-3:1, suitably 1:40-1:1, preferably 1:40-1:5, more
preferably 1:25-1:15, and most preferably 1:18-1:20. Outside this
preferred range for the weight ratio between the high and low
molecular weight components the final lubricating grease
composition will generally not have desired application properties,
in particular mechanical stability and consistency, i.e. be too
"rubbery/elastic" and/or too "buttery". However, as the properties
of the final composition are also dependent on the lubricant base
oil and additives incorporated in grease compositions, as well as
on the way the composition is prepared, other ratios may also be
used for obtaining the desired properties of the final composition,
as is well known to a man skilled in the art.
[0025] According to the present invention, the low molecular weight
component is preferably a polypropylene homopolymer, more
preferably a polypropylene homopolymer with a melt flow rate of
500-1500 dg/min, especially 750-1250 dg/min as determined by test
ASTM D 1238 L.
[0026] The high molecular weight component preferably has a melt
flow rate (ASTM D-1238) of 1.5-15, more preferably 1.5-7,
especially 3-5. The low molecular weight component is preferably a
polypropylene homopolymer. Preferably, the high molecular weight
component is a polypropylene homopolymer or a
propylene/ethylene-copolymer.
[0027] The polymer thickener according to the invention is
generally used in the lubricating grease composition in
conventional amounts, i.e. from 1-20, preferably 5-15, especially
about 10 percent by weight of the total grease composition. Other
amounts can be used if desired.
[0028] Apart from the polymeric thickeners mentioned in detail
hereinabove, the present grease composition may also contain other
polymeric thickeners.
[0029] As the lubricating base oil any lubricating oil known per se
may be used, such as mineral oils, synthetic hydrocarbons, ester
oils, vegetable oils and mixtures thereof, of different viscosity.
The type of base oil and viscosity can be selected to suit specific
applications.
[0030] Furthermore, additives known per se may be incorporated in
the lubricant grease composition, as long as they do not have a
detrimental effect on the thickener composition, the base oil
and/or the final grease composition. The grease composition may
additionally comprise at least one additive component which is
selected from the group consisting of antioxidants, corrosion
inhibitors, anti-wear agents and pressure tolerance-increasing
additives, and wherein the total content of the additive
component(s) is in the range between 0.2 and 15% by weight, and
preferably between 1 and 8% by weight, based on the total weight of
the grease composition.
[0031] In one embodiment of the present invention the present
grease composition additionally comprises an ester oil in an amount
in the range of from 1-40 wt %, based on total weight of the grease
composition.
[0032] Suitably, the present grease composition may additionally
comprises an inert powder, preferably diamond powder, in an amount
in the range of from 0.01-10 wt %, based on total weight of the
grease composition.
[0033] The present invention also relates to a bearing, bearing
component or bearing application system having a metallic surface
onto which a layer of the grease composition in accordance with the
present invention has been applied.
[0034] The present invention further provides a bearing, bearing
component or bearing application system having a metallic surface
onto which a layer has formed comprising the metal of the metal
salt.
[0035] The bearing, bearing components or bearing application
system may be pre-treated with the grease composition ensuring that
it carries a protective layer against wear, fretting or corrosion
before use, or such a protective metal layer will be formed on the
bearing, bearing component or bearing application system during
operation when the present grease composition is used for
lubricating purposes.
[0036] It is also an object of the invention is to provide grease
compositions which prevent fretting, wear and corrosion. Another
object of the invention is to provide a polymer-thickened grease
composition for reconditioning the lubrication of a mechanical
component having a metal surface.
[0037] Hence, the present invention also relates to the use of the
grease composition according to the present invention for
reconditioning the lubrication of a mechanical component having a
metal surface. Preferably, the present invention relates to the use
of the grease composition according to the present invention for
reconditioning the lubrication of a bearing, bearing component or
bearing application system. When the grease composition is used for
reconditioning the lubrication of a mechanical component having a
metal surface, the metal of the metal salt is preferably bismuth.
The present grease composition will be used for this purpose in
emergency and accidental circumstances before operation of the
device in question is interrupted. In that case the grease
composition can suitably be injected by means of a device involving
pyrotechnic means. Such devices are as such known. In US
2010.0101442 A1 such a device has for instance been described. Said
document is hereby incorporated by reference.
[0038] The present invention further relates to the use of the
grease composition according to the present for protecting a
mechanical component having a metal surface against corrosion.
Preferably, the present invention relates to the use of the grease
composition according to the present for protecting a bearing,
bearing component or bearing application system.
[0039] The present invention in addition relates to the use of the
grease composition according to the present invention for
protecting a mechanical component having a metal surface against
wear. Preferably, the present invention relates to the use of the
grease composition according to the present for protecting a
bearing, bearing component or bearing application system against
wear.
[0040] Moreover, the present invention relates to the use of the
grease composition according to the present invention for
protecting a mechanical component having a metal surface against
fretting. Preferably, the present invention relates to the use of
the grease composition according to the present invention for
protecting a bearing, bearing component or bearing application
system against fretting.
[0041] When the grease composition is used for protecting a
mechanical component having a metal surface against wear, the metal
of the metal salt is preferably bismuth. In case the grease
composition is used for protecting a mechanical component having a
metal surface against wear and fretting, the metal of the metal
salt is preferably bismuth and/or zinc. In case the grease
composition is used for protecting a mechanical component having a
metal surface against corrosion the metal of the metal salt is
preferably zinc, whereas the acid applied is preferably an acid
having a pKa in the range of 2-7, preferably three pKa values in
the range of from 2-13. Preferably, the acid then used is
phosphoric acid. For anti-corrosion purposes such a grease
composition can suitably be applied in corrosion sensitive
applications, transport and storage.
[0042] In addition, the present invention relates to a method for
preparing a grease composition according to the present invention
comprising the following steps:
(a) mixing the polymer thickened grease with the metal salt; and
(b) adding to the mixture obtained in step (a) the acid.
[0043] Preferably, in step (a) the metal salt is heated above its
melting point.
[0044] Suitably, during step (a) one or more anti-wear additives,
anti-fretting additives, anti-corrosion additives, anti-oxidants,
inert powder(s) and/or other additives are additionally mixed with
the other components.
[0045] Preferably, a final mixing is carried out in step (a) using
a three-roll mill or a ball-mill
[0046] The polymeric thickener composition according to the
invention can be prepared by mixing the polymers in a manner known
per se, which can optionally involve heating and/or the use of
suitable solvents.
[0047] The polymers of the subject invention are mixed with a
lubricating base oil and optional additives by means of
conventional techniques known per se resulting in the grease
composition according to the invention.
[0048] The preparation of the grease composition is preferably be
carried out under a protective atmosphere, such as a nitrogen
gasflow, for avoiding oxidation of the oils during heating.
[0049] According to a preferred embodiment the solid polymeric
components and the lubricating base oil are heated together
(preferably under stirring) to a temperature above the melting
point of polypropylene, preferably 190-210.degree. C., although
other temperatures may be used if required.
[0050] After the polymers are dissolved in the lubricating base oil
and optionally additives have been added, the grease is cooled from
the mixing temperature to room temperature.
[0051] According to an especially preferred embodiment of the
invention this cooling is carried out in a period of time between 1
sec.-3 min, preferably 10 sec.-1 min, more preferably about 25-35
sec. This rapid cooling process, which forms an important aspect of
the invention, will be indicated hereinbelow as "quenching". The
quenching of the lubricant grease composition can be carried out,
for instance, by pouring the grease composition on a metal plate,
although any other suitable rapid cooling method may also be used,
such as spraying.
[0052] The quenching process according to the invention has a major
influence on the grease structure, giving significant improvement
of the properties of the final grease compositions compared to both
conventional lubricating greases, as well as lubricating greases
according to the invention which are cooled slowly, e.g. in
approximately 1 degree per minute by the use of conventional
cooling methods, such as simply keeping the grease in the reaction
vessel with external/internal cooling. This results, for the
polymer grease, in a lubricant lacking any mechanical
stability.
[0053] In the grease composition according to the invention, the
polymeric thickener forms a sponge-like structure, which gives the
grease its appearance and structure. The lubricating base oil is
kept within the pore-like spaces within the thickener structure,
and bleeds out during service of the grease. The
thickener-structure is very irregular with large pores as well as
very small pores. The above indicated quenching of the lubricant
grease composition provides a grease according to the invention
with a smoother and more uniform structure of the polymeric
thickener, with more uniformly distributed spaces for keeping the
lubricant oil.
[0054] During service of the lubricant grease, the oil bleeds out
of the oil/thickener-structure onto the surfaces of the bearing,
thereby providing the lubricating action. The oil bleeding
characteristics at the service temperature of the lubricant grease
composition (i.e. the running temperature of the bearing, as well
as the "start up" temperature) are therefore critical for obtaining
the lubricating action of the composition.
[0055] The mechanical stability of the grease is dependent on the
polymer thickener used, the lubricating base oil used, as well as
the additives used. Further, the mechanical properties of the
grease can be influenced by "working" the grease after the
thickener is mixed with the lubricating base oil, as is well known
to a man skilled in the art of lubricants. Preferably, the grease
is "worked" to a consistency desired and/or required for its
intended use.
[0056] The mechanical stability of the grease can be ascertained by
means of tests known in the art, such as the Shell roll stability
test. Preferably, the grease will have a penetration after the
Shell roll stability test (24 hrs at 80.degree. C., 165 rpm), of
max. 430.
[0057] The consistency of the grease can be classified by means of
the NLGI-class. According to the present invention the grease can
usually be prepared to a NLGI-class range 00 to 4. An NLGI-class of
0 or 00 can be made, resulting in a lubricant composition. Also,
the viscosity of the separated oil must be acceptable, and
preferably be constant.
[0058] The polymer-thickened grease composition according to the
present invention can be used for all conventional applications for
lubricant grease compositions, so long as these are compatible with
the components of the lubricant grease composition. The present
grease composition can be used for lubricating bearings, couplings,
toothed transmission gears, chutes or other instruments.
[0059] The mechanical component having a metal surface to be
treated with the grease composition according to the present
invention is preferably a bearing, bearing component or a bearing
application system. The bearing component may be inner rings, outer
rings, cages, rollers, balls and seal-counter faces. The bearing
application system in accordance with the present invention
comprises bearing housings, mounting axles, shafts, bearing joints
and shields.
[0060] Further uses of the lubricant grease compositions according
to the present invention are e.g. agricultural machinery, bearings
in dam-gates, low noise electric motors, large size electric
motors, fans for cooling units, machine tool spindles, screw
conveyor, and off-shore and wind turbine applications.
[0061] The present invention further relates to a grease
composition obtainable according to the method of the
invention.
[0062] The grease composition in accordance with the present
invention may have the form of a lubricant composition having an
oily character or a paste, depending on the viscosity of the final
grease composition.
[0063] The invention will now be further illustrated by the
following Examples, which do not limit the invention in any
way.
EXAMPLES
Example 1
[0064] A number of greases were used in 4-ball wear scar test
experiments according to DIN 51350/5 (1 minute at 1400 N). The
grease compositions used in these test experiments are shown in
Table 1. The results of these experiments are shown in Table 2,
whereby it is observed that in experiment No. 5 use is made of
grease No. 4 but on the balls a pre-coating of grease No. 3 was
applied. The pre-coating was formed by degreasing the balls with a
solvent; immersing the balls in the grease No. 3; heating the balls
at 85.degree. C. for 2 hours; cooling and storing the balls for 16
hours at ambient temperature; and cleaning/washing the balls with a
solvent. From the test results shown in Table 2 it is evident that
the use of the grease compositions according to the present
invention (Grease Nos. 3 and 4) brings about considerably improved
wear properties when compared with conventional greases (Grease
Nos. 1, 2, and 4).
TABLE-US-00001 TABLE 1 Grease composition Composition of grease
Grease No. 1 11% polymer, 89% lubricating oil Grease No. 2 11%
polymer, 82% lubricating oil, 6% EP/anticorrosion additives, 1%
antioxidant additive Grease No. 3 41.5% polymer, 1% anti-oxidant,
6% anticorrosion/EP additives, 20% polymer ester, 20% ester-oil,
1.5% phosphoric acid (conc. 85%), 10% bismuth hydroxystearate
Grease No. 4* SKF factory fill grease MT33 with metal- based
thickener *commercially available grease
TABLE-US-00002 TABLE 2 Wear scar (load 1400 N, Experiment No.
Grease composition 1 minute) in mm Experiment No. 1 Grease No. 1
2.5 Experiment No. 2 Grease No. 2 1.8 Experiment No. 3 Grease No. 3
0.4 Experiment No. 4 Grease No. 4 2.3 Experiment No. 5 Grease Nos.
3 (pre-coating) and 4 0.85
Example 2
[0065] In this example greases were subjected to the Fafnir test in
accordance with ASTM D4170 wherein the balls in a trust bearing are
oscillated for 22 hrs and the wear in the ball-ring contact point
is a measure of false brinelling (friction oxidation). The test
results are shown in Table 3. In experiment No. 6 a grease No. 5 is
used having the following composition: 69% polymer grease (9%
polypropylene and 91% base lubricating oil), 20% anti-friction
additive, 5% anti-corrosion, 5% anti-wear additive, 1% interne
further standard additives.
[0066] In experiment No. 7 use is the same grease No. 5 but on the
rings a pre-coating of grease No. 3 (see Table 1) was applied. The
pre-coating was formed by degreasing the rings with a solvent;
immersing the rings in the grease No. 3; heating the rings at
85.degree. C. for 2 hours; cooling and storing the rings for 16
hours at ambient temperature; and cleaning/washing the rings with a
solvent. From Table 3 it is clear that the pre-treatment of the
test bearing rings in accordance with the present invention
(experiment No. 7) brings about much less friction oxidation weight
loss when compared with the grease without the pre-treament with
the layer building grease No. 3 (experiment No. 6).
TABLE-US-00003 TABLE 3 Experiment No. Weight loss of rings (mg)
Experiment No. 6 3 Experiment No. 7 1
Example 3
[0067] A number of greases as specified in Table 4 were used in
reconditioning experiments. In this respect it is first noted that
in some applications the failure of a bearing can result in high
costs due to damaging of vital parts of machine, e.g. paper mills.
Also the failure of a lubricated bearings can results in fatal
accidents, one can think of a helicopter which will come down very
fast and will crash. Hence, it could be life and costs saving when
the bearing and lubrication can be reconditioned in case of an
imminent failure for a certain period during which a helicopter can
land/touchdown safely, or in case of a paper mill which is about to
fail to allow the operator enough time to stop the production in a
controlled procedure.
[0068] The greases were tested in a laboratory aircraft simulation
test set-up. The aim is to recondition the bearing for at least 60
minutes. The following conditions were applied: [0069] Bearing
speed: 10 000 rpm (inner ring) [0070] Load: 400 daN; balls/IR: 2000
MPa; balls/OR: 1600 MPa [0071] Initial grease (running in): Thin
film of running-in grease, <0.1 g [0072] Injection grease for
reconditioning at failure: Manual at approximately 150.degree. C.
(reading from recorder). Upon an indication of a failure the grease
in question was added to the lubricant system initially
present.
[0073] The results of the experiments are shown in Table 5. From
Table 5 it is clear that the grease composition according to the
present invention (experiment No. 10) is able to recondition the
original lubricant system in a considerably improved manner when
compared to conventional greases (experiments Nos. 8 and 9) because
it is allows the lubricant system to survive for a much longer
time, whereas at the same time a much less amount of grease is
required.
TABLE-US-00004 TABLE 4 Grease composition Composition of grease
Grease No. 6* Shell Aeroshell G14 with metal-based thickener Grease
No. 7* Klueber Isoflex NBU15 with metal-based thickener Grease No.
8 42% polymer, 1% anti-oxidant, 6% anticorrosion/EP additives, 20%
polymer ester, 20% ester-oil, 1.0% phosphoric acid (conc. 85%), 10%
bismuth hydroxystearate *commercially available grease
TABLE-US-00005 TABLE 5 Survival time after Grease moment of failure
Grease fill Experiment No. composition (minutes) (mg) Experiment
No. 8 Grease No. 6 51 2 Experiment No. 9 Grease No. 7 35 4
Experiment No. 10 Grease No. 8 82 0.9
* * * * *