U.S. patent application number 13/522645 was filed with the patent office on 2012-11-22 for lubricant with enhanced energy efficiency.
This patent application is currently assigned to Cognis IP Management GmbH. Invention is credited to Dirk Rettemeyer, Markus Scherer.
Application Number | 20120295827 13/522645 |
Document ID | / |
Family ID | 42289490 |
Filed Date | 2012-11-22 |
United States Patent
Application |
20120295827 |
Kind Code |
A1 |
Scherer; Markus ; et
al. |
November 22, 2012 |
Lubricant With Enhanced Energy Efficiency
Abstract
Lubricant compositions useful especially for the lubrification
of gears, having a boundary loss coefficient X.sub.LG of 0.6 to 0.8
measured at temperatures of 40 to 120.degree. C. with a modified
method according to DIN 51354, whereby the lubricant composition
contains of a base oil a optional additives, whereby the base oil
is selected from complex ester, said, said complex ester having a
kinematic viscosity at 40.degree. C. of greater than 400 and up to
50 000 mm.sup.2/s.
Inventors: |
Scherer; Markus; (Lebach,
DE) ; Rettemeyer; Dirk; (Huckelhoven, DE) |
Assignee: |
Cognis IP Management GmbH
Dusseldorf
DE
|
Family ID: |
42289490 |
Appl. No.: |
13/522645 |
Filed: |
January 12, 2011 |
PCT Filed: |
January 12, 2011 |
PCT NO: |
PCT/EP2011/000095 |
371 Date: |
July 17, 2012 |
Current U.S.
Class: |
508/512 |
Current CPC
Class: |
C10N 2030/02 20130101;
C10M 2203/1006 20130101; C10M 2219/00 20130101; C10M 111/00
20130101; C10M 2205/0285 20130101; C10N 2020/02 20130101; C10M
2223/00 20130101; C10M 105/42 20130101; C10M 2209/1033 20130101;
C10M 2207/301 20130101; C10N 2040/04 20130101; C10N 2030/06
20130101 |
Class at
Publication: |
508/512 |
International
Class: |
C10M 105/42 20060101
C10M105/42 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 18, 2010 |
EP |
10000403.5 |
Claims
1. A lubricant composition having a boundary loss coefficient
X.sub.LG of 0.6 to 0.8 measured at temperatures of 40 to
120.degree. C. with a modified method according to DIN 51354,
whereby the lubricant composition comprises a base oil and optional
additives, whereby the base oil comprises complex esters, said
complex esters having a kinematic viscosity at 40.degree. C. of
greater than 400 and up to 50,000 mm.sup.2/s and being obtained by
reaction of: a) polyols and monocarboxylic acids and dicarboxylic
acids, or b) polyols and monoalcohols and dicarboxylic acids, or c)
polyols and monoalcohols and monocarboxylic acids and dicarboxylic
acids.
2. The lubricant composition according to claim 1, wherein the
ester is obtained by reaction of a).
3. The lubricant composition according to claim 1, wherein the acid
part of the ester comprises a blend of at least two different
dibasic acids.
4. The lubricant composition according to claim 3, wherein the
dibasic acids independently contain from 8 to 18 C-atoms.
5. The lubricant composition according claim 1, wherein the acid
part of the esters is selected from at least one branched dibasic
acid.
6. The lubricant composition according to claim 1, wherein the acid
part of the esters comprises sebacic acid, adipic acid, succinic
acid, glutaric acid, isostearic acid, or mixtures thereof.
7. The lubricant composition according to claim 1, wherein the
alcohol part of the ester comprises glycerol, neopentylglycol, an
oligo-polyglycerol, a polyglycerol, trimethylolpropane,
pentaerythritol, or mixtures thereof.
8. The lubricant composition according to claim 7, wherein the
alcohol part of the ester comprises pentaerythritol or
trimethylolpropane or mixtures thereof.
9. The lubricant composition according to claim 1, comprising from
0.01 to 5 wt % of additives, based on the total weight of the
lubricant composition.
10. The lubricant composition according to claim 1, comprising the
complex ester in an amount in the range of 1 to 99.9 wt % based on
the total weight of the lubricant.
11. The lubricant composition according to claim 1, further
comprising as additional oils in an amount in the range of 1 to 60
wt %, based on the total weight of the lubricant, an oil selected
from the group consisting of esters that are not complex,
polyalphaolefins, mineral oils, polymers, polyalkylene glycols, and
mixtures thereof.
12. A method of lubricating gears, the method comprising using the
lubricant composition according to claim 1 as an energy efficient
lubricant for the lubrication of gears.
13. The lubricant composition according to claim 10, comprising the
complex ester in an amount in the range of 10 to 80 wt %, based on
the total weight of the lubricant.
14. The lubricant composition according to claim 13, comprising the
complex ester in an amount in the range of 50 to 75 wt %, based on
the total weight of the lubricant.
15. The lubricant composition according to claim 11, comprising the
additional oils in an amount in the range of 5 to 45 wt %, based on
the total weight of the lubricant.
16. The method of claim 12 wherein the gears are gears of wind
turbines.
Description
[0001] The present invention pertains to lubricants, in particular
to industrial lubricants, including hydraulic oils, lubricants for
engines and turbine oils, and especially for lubricants for wind
turbines.
[0002] The most important function of lubricants is the reduction
of friction and wear. Apart from important applications in internal
combustion engines, vehicle and industrial gearboxes, compressors,
turbines, or hydraulic systems, there are a vast number of other
applications which mostly require specifically tailored
lubricants.
[0003] Gear lubrication oils are of particular significance for the
transmission. Apart from the important function of lubricating the
sliding rolling contacts, the oils also fulfil the task of cooling
and removing the friction heat generated in the sliding rolling
contacts. There are significant differences between the tribology
of gear drives and the tribology of journal and roller bearings,
since the lubrication conditions characterizing the sliding rolling
contacts in toothed wheels differ from those in journal or roller
bearings.
[0004] Gear boxes are widespread in all kind of machines, and
accordingly a huge number of different gears are known. With regard
to the different kinds of gears different properties of the used
lubricants must be fulfilled. An important field of application for
gears, as well as for the respective lubricants are wind
turbines.
[0005] Wind turbine applications, such as those used in wind farms
or wind plants as an alternative renewable source of energy, are
increasingly attracting more interest. Wind-electric turbine
generators, also known as wind turbines, use the energy contained
in the wind to spin a rotor (i.e., blades and hub). As the air
flows past the rotor of a wind turbine, the rotor spins and drives
the shaft of an electric generator to produce electricity.
[0006] To create this energy using a conventional wind turbine, a
gear-box is typically placed between the rotor of the wind turbine
and the rotor of a generator. More specifically, the gear-box
connects a low-speed shaft turned by the wind turbine rotor at
about 30 to 60 rotations per minute to a high speed shaft that
drives the generator to increase the rotational speed up to about
1200 to 1600 rpm, the rotational speed required by most generators
to produce electricity. This geared solution can result in a torque
through the system of close to 2 million Nm. This high torque can
put a large amount of stress on the gears and bearings in the
geared wind turbine. Wind turbine oils are desired that will
enhance the fatigue life of both the bearings and gears in the wind
turbines. Gearless direct drive wind turbines have been developed,
which have the advantage of having less moving parts to maintain,
but have their own drawbacks of generally being heavier and
generally being open models allowing cold air to pass through,
which may pose an increased risk of corrosion, especially in
offshore installations. In any event, it is expected that both
types of wind turbines will co-exist for some time. Therefore, wind
turbine oils that would enhance the fatigue life of bearings and
gears in gear-boxes used in geared wind turbines would increase the
opportunities to use the geared solution in the most efficient,
reliable and cost-effective manner.
[0007] Lubricants for such applications have therefore to fulfill
several different roles. They must work at higher operating loads
while helping in reducing temperatures in the gearboxes. They need
to avoid fatigue-related damages (e.g. pitting) and wear (adhesion,
abrasion, polishing and scuffing) on the gears, while also
remaining fitter-friendly (no leaks), non-foaming, water-resistant,
and harmless to operators. Also, inasmuch as lubricants in wind
turbines gearboxes are often subjected to prolonged periods of use
between any maintenance and service intervals, a long lasting
lubricant stability is required, so as to provide outstanding
service performance over lengthy durations of time. Finally, wind
turbines can be located all over the world, on mountain tops,
off-shore or along coastlines, in deserts: in addition to longevity
issues, said lubricants must also be able to withstand a variety of
environmental conditions, including temperature extremes and
moisture, in addition to being able to resist oxidation and prevent
corrosion.
[0008] Furthermore, there is a constant need to enhance lubricity
properties of said lubricants, to lower friction, and also lower
energy consumption in devices, equipped with such lubricants.
[0009] It was found, that specific selected ester oils will meet
all of the above requirements.
[0010] A first embodiment of this invention is therefore a
lubricant composition having a boundary loss coefficient X.sub.LG
of 0.5 to 0.9, and preferably from 0.6 to 0.8 measured at
temperatures of 40 to 120.degree. C. with a modified method
according to DIN 51354, whereby the lubricant composition contains
of a base oil a optional additives, whereby the base oil is
selected from esters, said, said esters having a kinematic
viscosity at 40.degree. C. of greater than 400 and up to 50 000
mm.sup.2/s and being obtained by reaction of: a) polyols and
monocarboxylic acids and dicarboxylic acids or of b) polyols and
monoalcohols and dicarboxylic acids or of c) polyols and
monoalcohols and monocarboxylic acids and dicarboxylic acids.
[0011] The said method for the measurement of the boundary loss
coefficient X.sub.LG is described in detail in the FVA Information
Sheet for the Research Project No. 345, Status June 2003, Annex B
to Report No. 3781 and Annex C to Report 3416.
[0012] The lubricants of the present invention are characterized in
their specific behavior under load, and especially due to their low
frictional losses. The total power loss of a gearbox P.sub.V can be
split into losses of gears P.sub.VZP and P.sub.VZ0, the losses of
bearings (P.sub.VLP and P.sub.VL0) and auxiliary loss sources
(P.sub.VX0) like seals or pumps. They can also split into load
dependent and no-load losses. According to the following equation
1:
##STR00001##
[0013] The loss coefficients indicate the relative losses of oils
compared to reference oil. Of greatest importance is the boundary
loss coefficient. This coefficient describes the relative load
dependent loss compared with a reference at conditions where
usually boundary lubrication occurs. The boundary loss coefficient
is an indicator for the frictional behavior of especially high
viscous oils. Therefore the above mentioned selection criterion of
a certain boundary loss coefficient X.sub.LG is vital for carrying
out the present invention. A figure of for example 0.6 for the
X.sub.LG means that this lubricant shows a 40% enhancement of
energy consumption towards the reference oil.
[0014] If oils are selected which the above given boundary loss
coefficient the energy consumption under running conditions will be
lowered. Thus, the use of those esters will enhance the energy
efficiency of devices, equipped with these lubricants, preferably
of gears in wind turbines.
[0015] The kinematic viscosity of the ester for use is preferably
from 800 to 25 000 mm2/s, especially from 1200 to 10 000
mm.sup.2/s, more preferably from 1300 to 5000 mm.sup.2/s and most
preferably from 1500 to 3000 mm.sup.2/s. It has been found that,
surprisingly, the use of these esters leads to very low losses in
the kinematic viscosity of the lubricant composition after
permanent shear. This property makes possible use in lubricants
which are exposed to high shear stress.
[0016] It is vital for the present teaching to select only those
ester oils which fulfill both the structural as well as the
theological properties as given in the above description.
[0017] The esters as described above are in principal known to the
skilled man. Reference is made to European patent application no.
2027234 or international publication pamphlet WO 05/019395 of the
applicant where these esters and their application as lubricants
are described in more detail.
[0018] Although all of the mentioned structures, as far as the
other selection criterions are fulfilled will be useful in lowering
energy consumption especially preferred are esters of type a). In a
preferred embodiment, the lubricant compositions are characterized
in that the monocarboxylic acids used in the reaction according to
a) are branched monocarboxylic acids or mixtures of linear and
branched monocarboxylic acids, each of which has a carbon number of
from 5 to 40 carbon atoms, where the content of branched monoacid
is preferably greater than 90 mol % based on the total content of
the acid mixture.
[0019] The monocarboxylic acids preferably have from 8 to 30 carbon
atoms and especially from 10 to 18 carbon atoms. In particular, the
monocarboxylic acids are selected from the group formed by the
following branched acids: 2,2-dimethylpropanoic acid, neoheptanoic
acid, neooctanoic acid, neononanoic acid, isohexanoic acid,
neodecanoic acid, 2-ethylhexanoic acid, 3-propylhexanoic acid,
3,5,5-trimethylhexanoic acid, isoheptanoic acid, isooctanoic acid,
isononanoic acid, isostearic acid, isopalmitic acid, Guerbet acid
C32, Guerbet acid C34 or Guerbet acid C36, and isodecanoic acid.
The linear acids are preferably selected from the group formed by
valeric acid, caproic acid, heptanoic acid, caprylic acid,
pelargonic acid, capric acid, undecanoic acid, lauric acid,
tridecanoic acid, tetradecanoic acid, pentadecanoic acid, palmitic
acid, margaric acid, stearic acid, nonadecanoic acid, arachic acid,
behenic acid, lignoceric acid, myristic acid, cerotic acid,
mellissic acid, tricosanoic acid and pentacosanoic acid,
2-ethylhexanoic acid, isotridecanoic acid, myristic acid,
palmitoleic acid, oleic acid, elaidic acid, petroselic acid,
linoleic acid, linolenic acid, elaeostearic acid, gadoleic acid and
erucic acid, and the technical-grade mixtures thereof. Preferred
branched monocarboxylic acids are isononanoic acid, isostearic acid
and 2-ethylhexanoic acid.
[0020] Preferred esters are blends of esters containing more than
one acid, preferably, the esters according to the present invention
contains dibasic acids, and more preferred mixtures of two or more
different dibasic acids.
[0021] In this regard are those dibasic acids preferred which
contain 8 to 18 C-atoms. It is a further preferred embodiment in
this context to choose branched dibasic acids for the synthesis of
the esters. Suitable dibasic acids are oxalic acid, malonic acid,
succinic acid, glutaric acid, adipic acid, pimelic acid, suberic
acid, azelaic acid, sebacic acid, brassylic acid, thapsic acid and
perlagonic acid. Preferred dibasic acids are selected from the
group sebacic acid, adipic acid, succinic acid, glutaric acid and
isostearic acid. As mentioned above esters based one more then one
different acids are preferred. The anhydrides of the dicarboxylic
acids are also suitable in accordance with the invention for the
reaction
[0022] The alcohol part of the esters is broadly selected from
mono- di- or poly alcohols. The alcohols might be linear or
branched, saturated or unsaturated, as well as cyclic or aromatic
ones too.
[0023] Alkyl alcohols might be in a preferred embodiment being
selected from the group of linear or branched, saturated or
unsaturated alkyl mono alcohols with 1 to 31 C-atoms, diols with 2
to 25 C-atoms or polyols. Linear mono alcohols are for example are
methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol,
octanol, nonanol, decanol, undecanol, dodecanol, tridecanol,
tetradecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol,
nonadecanol, eicosanol, heneicosanol, docosanol, tricosanol,
tetracosanol, pentacosanol, hexacosanol, heptacosanol, octacosanol,
nonacosanol tricontanol or hentriacontasol. In these alcohols the
OH-functionality is located in the "1" position, but all isomers
thereof are also suitable. The same applies in accordance with all
kind of branched isomers of the above alcohols. Preferred branched
alcohols are the so called Guerbet-alcohols. Unsaturated mono
alcohols are for example oleic alcohol, linoleic alcohol, 9Z- and
9E-octadec-9-en-1-ol, (9Z,12Z,15Z)-octadeca-9,12,15-trien-1-ol,
(9Z)-eicos-9-en-1-ol, or 13E- or 13Z-docosen-1-ol. Furthermore,
diols, preferable glycols, including their oligomers or polymers
are suitable alcohols for preparing esters according to the present
invention. Ethylene glycol or diethylene glycol, or their oligomers
and propane and butane diols are preferred members. Polyols are
also suitable alcohol components. Preferred examples are glycerol,
oligo- or polyglycerol, trimethylolpropane and pentaerythritol, as
well as oligomers or polymers thereon. The most preferred alcohols
are pentaerythritol and trimethylolpropane and mixtures thereof, as
well as oligomers of these alcohols.
[0024] The present invention is preferably directed to polyol
esters and blends thereof having as essential constituents esters
of sterically hindered polyols with linear and/or branched
alkanols, known as "complex esters".
[0025] The conversion to the reaction products of the complex
esters proceeds in syntheses known per se for preparing esters. The
preparation of the esters can also be carried out in accordance
with the invention by known processes such that free carboxyl
groups and/or free hydroxyl groups are present in a controlled
manner, and these products with free carboxyl and/or free hydroxyl
groups are used in the lubricant composition. According to the
invention, the free carboxyl groups present may be reacted further
with amines to give amides, and the resulting compounds may be
present in the lubricant composition as complex esters in the
context of the invention.
[0026] The lubricants according to the teaching of this invention
contains a base oil and one or more additives. The base oil
contains of up to 100% from esters according to the above
description. In general, the complex esters should be present in
major amounts, based on the weight of the lubricant, as well as the
weight of the total lubricant compositions (including all other
ingredients).
[0027] However, certain other known base oil materials may be used
also. It is preferred, that the base oil contains from 10 to 98 wt
%, preferably from 50 to 95 wt % based on the total weight of the
base oil from the ester oils as described before. Based on the
total weight of the lubricant the complex ester are preferably
present in amounts of 1 to 99.9 wt %, preferably from 10 to 80 wt
%, and most preferred from 50 to 75 wt %,
[0028] In the context of the invention, the base oil present in the
lubricant composition is understood to mean an oil which is
selected also from the group formed by mineral oils, highly refined
mineral oils, alkylated mineral oils, poly-.alpha.-olefins,
polyalkylene glycols, phosphate esters, silicone oils, esters, and
also mineral oils of the Solvent Neutral class and mineral oils of
the XHVI, VHVI, group II and group III and GTL basestock
(gas-to-liquid base oil) classes. The poly-.alpha.-olefins may
preferably be formed from C6 to C18-.alpha.-olefins and mixtures
thereof. Especially preferred are poly-.alpha.-decenes.
[0029] In addition to the further components mentioned, the
inventive lubricant composition may comprise further additives
which are selected from the group formed by polymer thickeners,
solvents, viscosity index (VI) improvers, antioxidants, corrosion
inhibitors, detergents, dispersants, demulsifiers, defoamers, dyes,
wear protection additives, EP (extreme pressure) and AW (antiwear)
additives and friction modifiers. Such additives may be present in
amounts from 0.001 to 15 wt %, based on the total weight of the
lubricant. Preferred ranges are from 0.01 to 5 wt %.
[0030] In further preferred embodiments, the inventive lubricant
compositions could comprise, as a further component, a polar
polymer in a concentration of from 0.5 to 30% by weight based on
the total amount of lubricant composition. Preference is given to a
concentration of from 1 to 18% by weight and more preferably from 2
to 12% by weight. The polar polymers for use in accordance with the
invention are preferably selected from the group formed by alkyl
fumarate-.alpha.-olefin copolymer, alkyl maleate-.alpha.-olefin
copolymer, polyalkyl methacrylate, propylene oxide polymer,
ethylene oxide-propylene oxide copolymer and alkyl
methacrylate-.alpha.-olefin copolymer.
[0031] A certain embodiment of the present invention is a lubricant
containing as additional oils 1 to 60 wt %, preferably 5 to 45 wt
%, based on the total weight of the lubricant, of ester oils,
different of those described in claim 1, polyalphaolefins, mineral
oils, polymers, polyalkylene glycols, or any mixtures thereof.
[0032] The invention further provides for the use of the inventive
lubricant composition, especially in the preferred embodiments, as
a vehicle transmission oil, axle oil, industrial transmission oil,
compressor oil, turbine oil or motor oil. The present lubricant
oils are preferably useful in such applications, where mechanical
forces are transferred via direct contact of metal parts of a
machine or a gear. Particular preference is given to use as axle
oil, clutch oil or industrial and particularly to gear oil
applications.
[0033] But most preferred is the use of the lubricants as wind
turbine oil, in particular as lubricant for gears in wind
turbines.
EXAMPLES
[0034] Tests have been conducted to show the enhanced energy
efficiency of the lubricants according to the current teaching. In
this regard the frictional losses of cylindrical gears were
measured in a modified back-to-back gear test rig (see FIG. 1)
according to DIN 51354. The test pinion at the test gear and the
test gear are mounted on two parallel shafts which are connected to
the slave gear stage. In the slave gear stage, two identical gears
to test gears are mounted, so that two equal stages are closing in
the power circle. The pinion shaft consists of two separate parts,
which are connected by the load clutch. By twisting the load clutch
using defined weights on the load lever a defined static torque is
applied. The electric motor has only to compensate the frictional
losses in the power circle. For the measurement of the loss torque
a torque meter shaft is mounted between the electric engine and the
slave gear box. The applied load is measured with a load torque
meter shaft next to the lead clutch. During the test different
operating conditions are applied, the circumferential speed is
varied from 0.5 to 20 m/s, the load is varied from no load up to a
Herzian stress of 1720 N/mm.sup.2, and the temperature is varied
from 40 to 120.degree. C. The test method uses dip lubrication.
[0035] In the test equipment as described before, two different
lubricants have been tested. Lubricant 1 is a commercial available
PAO product and is used as comparison, lubricant 2 is an ester
according to the present invention, comprising of pentaerythritol
as alcohol, and a blend from sebacic acid and isostearic acid.
[0036] The reference oil, used in the test method according to DIN
51354 contains 4% of an sulphur phosphorous additive (Anglamol.RTM.
99) and based on mineral oil.
[0037] As could be seen from FIGS. 2 and 3 the inventive ester oil
composition show always better performance according to the loss
coefficient under load, as well as to the boundary loss coefficient
over a broad temperature range from 40 to 120.degree. C.
* * * * *