U.S. patent application number 15/746533 was filed with the patent office on 2018-08-02 for use of polyclycerin esters as friction modifiers in lubricant formulations.
This patent application is currently assigned to Evonik Oil Additives GmbH. The applicant listed for this patent is Evonik Oil Additives GmbH. Invention is credited to Thomas DAMASKE, Jennifer HOLTZINGER, Stefan MAIER, Klaus SCHIMOSSEK, Oliver SPRINGER, Marcus STEPHAN, Jan Marian VON HOF.
Application Number | 20180216023 15/746533 |
Document ID | / |
Family ID | 53761989 |
Filed Date | 2018-08-02 |
United States Patent
Application |
20180216023 |
Kind Code |
A1 |
MAIER; Stefan ; et
al. |
August 2, 2018 |
USE OF POLYCLYCERIN ESTERS AS FRICTION MODIFIERS IN LUBRICANT
FORMULATIONS
Abstract
The present invention relates to a lubricating oil composition
comprising polyglycerol partial esters of polyfunctional carboxylic
acids and saturated or unsaturated, linear or branched fatty acids
and/or poly(hydroxystearic acid) and the use thereof to lubricate
an engine and reduce friction.
Inventors: |
MAIER; Stefan; (Darmstadt,
DE) ; SPRINGER; Oliver; (Wesel, DE) ;
HOLTZINGER; Jennifer; (Frankfurt am Main, DE) ;
SCHIMOSSEK; Klaus; (Bensheim, DE) ; DAMASKE;
Thomas; (Otzberg, DE) ; STEPHAN; Marcus;
(Pfungstadt, DE) ; VON HOF; Jan Marian; (Bochum,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Evonik Oil Additives GmbH |
Darmstadt |
|
DE |
|
|
Assignee: |
Evonik Oil Additives GmbH
Darmstadt
DE
|
Family ID: |
53761989 |
Appl. No.: |
15/746533 |
Filed: |
July 6, 2016 |
PCT Filed: |
July 6, 2016 |
PCT NO: |
PCT/EP2016/065904 |
371 Date: |
January 22, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10M 2203/1025 20130101;
C10M 2207/30 20130101; C10M 2205/0285 20130101; C10M 2207/283
20130101; C10N 2020/01 20200501; C10M 2207/281 20130101; C10M
129/78 20130101; C10N 2040/25 20130101; C10M 105/42 20130101; C10N
2030/06 20130101; C10M 2205/028 20130101; C10M 169/04 20130101;
C10M 2207/282 20130101; C10N 2030/02 20130101; C10N 2020/04
20130101; C10M 169/044 20130101 |
International
Class: |
C10M 129/78 20060101
C10M129/78; C10M 105/42 20060101 C10M105/42; C10M 169/04 20060101
C10M169/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 24, 2015 |
EP |
15178187.9 |
Claims
1. A lubricating oil composition comprising (a) 0.2 to 5% by weight
of one or more polyglycerol partial esters, based on a total weight
of the lubricating oil composition, wherein the polyglycerol
partial esters are obtained by esterification of a polyglycerol
mixture with (i) one or more polyfunctional carboxylic acids and
(ii) one or more saturated or unsaturated, linear or branched fatty
acids and/or (ii) poly(hydroxystearic acid), wherein a degree of
esterification of the poly-glycerol mixture is between 30 and 75%
of the OH goups; (b) 85 to 99.8% by weight of an apolar base stock
selected from the group consisting of API Group II, III and IV and
mixtures thereof, based on the total weight of the lubricating oil
composition; and (c) 0 to 10% by weight of a polar ester oil of API
Group V, based on the total weight of the lubricating oil
composition.
2. The lubricating oil composition according to claim 1, wherein
the polyglycerol has a mean degree of condensation of from 3 to
6.
3. The lubricating oil composition according to claim 1, wherein
the fatty acids are saturated or unsaturated, linear or branched
having 8 to 22 carbon atoms.
4. The lubricating oil composition according to claim 1, wherein
the saturated fatty acids are one or more selected from the group
consisting of caprylic acid, capric acid, lauric acid, tridecanoic
acid, myristic acid, palmitic acid, margaric acid, stearic acid,
isostearic acid, arachidic acid, behenic acid, and 12-hydroxy
stearic acid.
5. The lubricating oil composition according to claim 1, wherein
the unsaturated fatty acids are one or more selected from the group
consisting of hexadecenoic acids, octadecenoic acids, eicosenoic
docosenoic acids, octadecadienoic acids, octadecatrienoic acids,
and ricinoleic acid.
6. The lubricating oil composition according to claim 1, wherein
the polyfunctional carboxylic: acids have 4 to 54 carbon atoms, and
a mean functionality of from 2 to 2.5.
7. The lubricating oil composition according to claim 1, wherein
the polyfunctional carboxylic acids are aliphatic dicarboxylic
acids which are selected from the group consisting of malonic acid,
succinic acid, furmaric acid, maleic acid, dimethylgiutaric acid,
adipic acid, trimethyladipic acid, azelaic acid, sebacic acid,
dodecanedioic acid and their anhydrides.
8. The lubricating oil composition according to claim 1, wherein
the polyglycerol partial esters have HLB values of from 3 to 7.
9. The lubricating oil composition according to claim 1, wherein
the polyglycerol partial esters have an OH-number in the range of
50 to 180 mg KOH/g.
10. The lubricating oil composition according to claim 1, further
comprising an additive.
11. The lubricating oil composition according to claim 10, wherein
the additive is at least one selected from the group consisting of
viscosity index (VI) improvers, pour point depressants,
dispersants, detergents, defoamers, corrosion inhibitors,
antioxidants, antiwear and extreme pressure additives and fiction
modifiers.
12. The lubricating oil composition according to claim 1, wherein
the polyglycerol partial esters have a weight-average molecular
weight of 2,000 to 15,000 g/mol.
13. A method of lubricating an engine, comprising adding the
lubricating oil composition according to claim 1 to the engine.
14. A method of reducing friction in an engine, comprising applying
the lubricating oil composition according to claim 1 to the engine.
Description
[0001] The present invention relates to a lubricating oil
composition comprising polyglycerol partial esters of
polyfunctional carboxylic acids and saturated or unsaturated,
linear or branched fatty acids and/or poly(hydroxystearic acid) and
the use thereof to lubricate an engine and reduce friction.
[0002] Energy losses due to friction in lubricated contacts can be
reduced by adding friction modifiers to the lubricant formulation.
Friction modifiers are used especially in gear and engine oil
formulations where lower viscosity formulations are applied in
order to save energy. While reducing the energy losses in the
fluid, lubricants with low viscosities struggle to keep the sliding
surfaces completely apart from each other and require a friction
modifier to maintain a lubricant film on the surfaces.
[0003] Friction modifiers work by forming adsorption layers on the
metal surface. They are of high importance under mixed lubrication
conditions when the sliding surfaces are not always separated by a
lubricant film of sufficient thickness. Such conditions can be
simulated with a mini traction machine (MTM) that is able to
measure the friction coefficient over a broad range of
conditions.
[0004] Friction reducing additives that have been used to improve
fuel economy fall into three main chemically-defined categories,
which are organic, metal organic and oil insoluble. The organic
friction reducing additives themselves fall within four main
categories which are (i) carboxylic acids or their derivatives,
including partial esters, (ii) nitrogen-containing compounds such
as amides, imides, amines and their derivatives, (iii) phosphoric
or phosphonic acid derivatives and (iv) organic polymers.
[0005] In current commercial practice examples of friction reducing
additives are glycerol monooleate and oleylamide, which are both
derived from unsaturated fatty acids, or molybdenum
dialkyldithiocarbamate. Also used are copolymers with blocks of
polyethyleneglycol (WO 2011/107739 and WO 2015/065801) or other
alkoxide polymers (WO 2014/139935). It is further known that
polyglycerol solubilized by a long alkyl chain attached via an
ether function (U.S. Pat. No. 7,803,745) or an ester function (WO
2015/044639) can be applied as a friction modifier.
[0006] It was now surprisingly found that polyglycerol partial
esters of polyfunctional carboxylic acids and saturated or
unsaturated, linear or branched fatty acids and/or
poly(hydroxystearic acid) show superior performance as friction
modifiers for lubricants. Superior means a larger reduction of the
friction coefficient and/or more efficient friction reduction due
to a lower treat rate and/or a better combination of oil
compatibility and friction reducing performance.
[0007] In a first embodiment, the present invention is directed to
a lubricating oil composition comprising a lubricating base oil and
polyglycerol partial esters, characterized in that the polyglycerol
partial esters are obtainable by esterification of a polyglycerol
mixture with [0008] (i) polyfunctional carboxylic acids and [0009]
(ii) saturated or unsaturated, linear or branched fatty acids
and/or [0010] (ii) poly(hydroxystearic acid).
[0011] Polyglycerol esters were found to work especially in apolar
formulations containing mainly API Group II, Ill and/or IV as
lubricating base oils.
[0012] The American Petroleum Institute (API) currently defines
five groups of lubricant base stocks (API Publication 1509). Groups
I, II and III are mineral oils which are classified by the amount
of saturates and sulphur they contain and by their viscosity
indices. The table below illustrates these API classifications for
Groups I, II and III.
TABLE-US-00001 Group Saturates Sulphur content Viscosity Index (VI)
I <90% >0.03% 80-120 II at least 90% not more than 0.03%
80-120 III at least 90% not more than 0.03% at least 120
[0013] Group I base stocks are solvent refined mineral oils, which
are the least expensive base stock to produce, and currently
account for the majority of base stock sales. They provide
satisfactory oxidation stability, volatility, low temperature
performance and traction properties and have very good solvency for
additives and contaminants.
[0014] Group II base stocks are mostly hydroprocessed mineral oils,
which typically provide improved volatility and oxidation stability
as compared to Group I base stocks.
[0015] Group III base stocks are severely hydroprocessed mineral
oils or they can be produced via wax or paraffin isomerisation.
They are known to have better oxidation stability and volatility
than Group I and II base stocks but have a limited range of
commercially available viscosities.
[0016] Group IV base stocks differ from Groups I, II and III in
that they are synthetic base stocks comprising e.g.
polyalphaolefins (PAOs). PAOs have good oxidative stability,
volatility and low pour points. Disadvantages include moderate
solubility of polar additives, for example antiwear additives.
[0017] Group II, II and IV oils are known for their exceptional
stability towards oxidation and high temperatures, but they provide
only limited solubility for polar additives such as friction
modifiers. For this reason the lubricating oil compositions
according the present invention may contain up to 10% of an ester
base oil according to API Group V as solubilizer.
[0018] Group V base stocks are all base stocks that are not
included in the other Groups. Examples include alkyl naphthalenes,
alkyl aromatics, vegetable oils, esters (including polyol esters,
diesters and monoesters), polycarbonates, silicone oils and
polyalkylene glycols.
[0019] The friction modifier performance of polyglycerol partial
esters according to the present invention can be achieved in
formulations with and without the additional ester base stock.
[0020] In a preferred embodiment, the lubricating oil compositions
according to the present invention are characterized in that they
comprise [0021] (a) 90-100% by weight of an apolar oil selected
from the group consisting of API Group II, III and IV and/or
mixtures thereof and [0022] (b) 0-10% of a polar ester oil of Group
V according to the definition of the American Petroleum Institute
(API), based on the total weight of the lubricating oil
composition.
[0023] Polyglycerol partial esters of poly(hydroxystearic acid) and
polyfunctional carboxylic acids are known as W/O emulsifiers in
cosmetic or pharmaceutical formulations and as auxiliaries for
dispersing inorganic micropigments in oily dispersions (EP 1 500
427 B1 and EP 1 683 781 B1). For best performance as friction
modifiers the parameters surface activity or polarity and oil
solubility have to be balanced and adjusted to the polarity of the
respective oil mixture used as base stock. The balance of polar and
apolar parts in the polymer is described by the HLB value that is
calculated. This can be done by selection of a polyglycerol
characterized by a certain degree of polymerization and selection
of carboxylic acids and polycarboxylic acids. Especially the amount
of polycarboxylic acids has a major influence on the molecular
weight (measured by SEC) of the resulting component. The ratio of
acid and alcohol functions is important as it determines the degree
of esterification and thus the amount of unreacted OH-functions
(described by the OH-number determined by titration). Free acid
functions are unwanted and should be kept at a minimum level
(described by the acid value, determined by titration).
[0024] The superior performance relative to other friction
modifiers is attributed to the high polarity of the polyglycerol
moieties, the free OH-functions due to the partial esterification
and the polymeric nature of the substances which provides multiple
interaction sites between the surface and the friction reducing
component. The polymeric nature of the described friction modifiers
is especially important for the solubility of the component as very
polar moieties in the molecule have to be kept in solution.
[0025] These polyglycerol partial esters of polyfunctional
carboxylic acids and saturated or unsaturated, linear or branched
fatty acids and/or poly(hydroxystearic acid) are obtainable by
esterification of a polyglycerol mixture with saturated or
unsaturated, linear or branched fatty acids having 8 to 22 carbon
atoms, preferably 12 to 18 carbon atoms, and polyfunctional
carboxylic acids having 4 to 54 carbon atoms, preferably 6 to 36
carbon atoms, more preferably 6 to 18 carbon atoms and even more
preferably 6 to 12 carbon atoms, and a mean functionality of from 2
to 4, preferably 2 to 3 and more preferably 2 to 2.5, the degree of
esterification of the polyglycerol mixture being between 30 and 75%
of the OH groups.
[0026] The mean functionality of a mixture of polyfunctional
carboxylic acids can be determined using the following formula:
N _ = i x i 100 N i ##EQU00001##
with N=mean functionality of a mixture of polyfunctioal carboxylic
acids [0027] x.sub.i=mass fraction [%] of individual polyfunctional
carboxylic acid i [0028] N.sub.i=functionality of individual
polyfunctional carboxylic acid i
[0029] Particularly suitable linear or branched saturated fatty
acid components are selected from the group consisting of caprylic
acid, capric acid, lauric acid, tridecanoic acid, myristic acid,
palmitic acid, margaric acid, stearic acid, isostearic acid,
arachidic acid, behenic acid and mixtures thereof. A suitable
saturated fatty acid is also 12-hydroxy stearic acid. Naturally
occurring mixtures are, for example, the coconut fatty acids, which
contain lauric acid as the main constituent and also contain
saturated C14- to C18-fatty acids and possibly small amounts of
saturated C8- to C18-fatty acids and unsaturated fatty acids, and
tallow fatty acids, which are essentially a mixture of palmitic
acid and stearic acid.
[0030] Suitable unsaturated fatty acid components are
monoolefinically unsaturated acids, for example hexadecenoic acids,
octadecenoic acids, such as oleic acid (cis-9-octadecenoic acid) or
eladidic acid (trans-9-octadecenoic acid), eicosenoic acids and
docosenoic acids, such as erucic acid (cis-13-docosenoic acid) or
brassidic acid (trans-13-docosenoic acid), poly-unsaturated fatty
acids, for example octadecadienoic acids and octadecatrienoic
acids, such as linoleic acid and linolenic acid, ricinoleic acid
and mixtures thereof.
[0031] The liquid fatty acids which contain 18 to 22 carbon atoms,
namely oleic, ricinoleic, erucic and isostearic acids, are
particularly suitable. Because of branching solidification points
are below 35 DEG C. It is also possible to use fatty acid mixtures,
which can also contain wax-like components, such as hydrogenated
ricinoleic acid.
[0032] The poly(hydroxystearic acids) co-used according to the
invention are prepared, for example, by polycondensation of
hydroxystearic acid, preferably 12-hydroxystearic acid, which is
obtained by hardening of ricinoleic acid or technical-grade castor
oil fatty acid, by known processes. They have a mean degree of
polymerization of 1 to 10 units, preferably 2 to 8 units and in
particular 2 to 5 units.
[0033] The polyfunctional carboxylic acids can be dicarboxylic
acids, tricarboxylic acids or polycarboxylic acids. The
polyfunctional carboxylic acids may be unsubstituted or optionally
substituted by one, two or three hydroxyl groups, preferably by one
hydroxyl group.
[0034] The aliphatic dicarboxylic acids used for the esterification
should have a chain length of 3 to 18 carbon atoms. They can be
straight-chain or branched, such as, for example, malonic acid,
succinic acid, fumaric acid, maleic acid, dimethylglutaric acid,
adipic acid, trimethyladipic acid, azelaic acid, sebacic acid,
dodecanedioic acid, hecadecanedioic acid, octadecanedioic and their
anhydrides.
[0035] The dicarboxylic acids used can also be dimeric fatty acids.
As is known, these are mixtures of acyclic and cyclic dicarboxylic
acids which are obtained by a catalyzed dimerization reaction of
unsaturated fatty acids having 12 to 22 carbon atoms.
[0036] For the preparation and use of dimer acids and their
physical and chemical properties, reference is made to the
publication "The Dimer Acids: The chemical and physical properties,
reactions and applications", Ed. E. C. Leonard; Humko Sheffield
Chemical, 1975, Memphis, Tenn.
[0037] The dicarboxylic acids can also contain, to a lesser extent,
tri-and polyfunctional carboxylic acids. The functionality of the
mixture should not exceed a value of 2 to 2.5 molar average.
[0038] Furthermore, as polyfunctional carboxylic acids can be used
phthalic acid, trimellitic acid and pyromellitic acid.
[0039] Under the term "polyglycerol" according to the present
invention encompasses a polyglycerol comprising glycerol.
Therefore, for the calculation of amounts, masses etc. the glycerol
content has to be taken into account. The term glycerol oligomers
or polyglycerol(s) encompasses linear as well as cyclic
structures.
[0040] Suitable polyglycerols are in particular those having a mean
degree of condensation of >2, preferably from 3 to 6. These are
technical-grade polyglycerol mixtures which are obtained, for
example, by alkali-catalyzed condensation of glycerol at elevated
temperatures and from which fractions with the desired degree of
condensation can be obtained if desired by distillation methods.
Also suitable are polyglycerols obtained by other methods, e.g.
from epichlorohydrin or glycidol. Commercial polyglycerols can be
obtained from companies like Solvay, Spiga Nord, Daicel or
Lonza.
[0041] In the polyglycerol partial esters according to the
invention, from 30 to 75%, preferably from 50 to 65%, of the
hydroxyl groups of the polyglycerol are esterified. They are
initially esterified to a degree of esterification of from 25 to
60%, preferably from 35 to 50%, using fatty acid and in a second
step, using dicarboxylic acids to an overall degree of
esterification of from 30 to 75%, preferably from 50 to 65%.
Through suitable selection of the hydrophilic and lipophilic
molecular proportions, an HLB value of from 3 to 7 is aimed at in
order to obtain favorable products.
[0042] The HLB value is a measure of the degree to which the
molecule is hydrophilic or lipophilic, determined by calculating
values for the different regions of the molecule. For the purpose
of the present invention, the HLB value of the polyglycerol partial
esters is calculated as follows:
HLB=(mp/(mp+ma))*20,
where mp is the mass of polyglycerol, and ma is the mass of
carboxylic acid mixture comprising mono-, di- and polycarboxylic
acids as well as polyhydroxy fatty acids used in the synthesis of
the polyglycerol ester. For example, esterification of 100 g
polyglycerol with 90 g mono-carboxylic acid and 10 g dicarboxylic
acid would result in an HLB of (100 g 1(90 g+10 g+100 g))*20=10,
independent of the degree of polymerization of the polyglycerol and
the type of carboxylic acids used.
[0043] For the present invention it is essential that the
polyglycerol backbone of the polyglycerol partial ester comprises
an average degree of polymerization of from 2 to 8, preferred from
2.5 to 6, particularly preferred from 3 to 4.5. A suitable method
for determining the oligomer distribution of the polyglycerol in a
given polyglycerol partial ester comprises hydrolysis or
alcoholysis of the partial ester, separation of the resulting
polyglycerol from the formed carboxylic acid compounds, and
analysis by gas chromatography after derivatization.
[0044] The polyglycerol partial esters according to the invention
can be prepared in a manner known per se by heating the reaction
components and removing the resultant water of reaction by
distillation. The reaction can be accelerated by means of acidic
catalysts such as sulfonic acids, phosphoric acid or phosphorous
acid or basic catalysts such as alkali metal or alkaline earth
metal oxides or hydroxides, alcoholates or salts, or Lewis acids,
such as tin salts,. However, the addition of a catalyst is not
absolutely necessary. The polyglycerol partial esters are
preferably prepared in a two-step process, which again is carried
out in a manner known per se. In a first step, the polyglycerol is
esterified using the monofunctional fatty acid or some of the fatty
acid. After most, or all, of the fatty acid has reacted, the
polyfunctional carboxylic acid is then added and the esterification
reaction is continued. The progress of the reaction can be
monitored, for example, via the water of reaction removed, by
measuring the acid number or by infrared spectroscopy. In general,
an acid number in the end product of <20, preferably <10, is
desired. Products with an acid number of <5 are particularly
preferred. The acid number is measured according to DIN EN ISO
2114.
[0045] The weight average molecular weight M.sub.w of the claimed
polyglycerol partial esters determined via SEC versus
polymethylmethacrylate (PMMA) standard is in the range of 2,000 to
15,000 g/mol, preferably in the range of 4,000 to 10,000 g/mol,
with a polydispersity index of 1.5 to 5, preferably 2 to 4.
[0046] The OH-number of the polyglycerol partial esters according
to the present invention is in the range of 50 to 180 mg KOH/g,
preferably 80 to 170 mg KOH/g and most preferred in the range of
110 to 150 mg KOH/g. The OH-number is measured according to DIN 53
240-2.
[0047] For engine oils the organic polymeric friction reducing
additive is present at levels of 0.2 to 5% by weight, preferably
0.3 to 3% by weight, and even more preferably 0.5 to 2% by weight
in an automotive engine oil, based on the total weight of the
lubricating oil composition.
[0048] Accordingly, a preferred embodiment of the present invention
is directed to a lubricating oil composition, comprising [0049] (a)
0.2 to 5% by weight, preferably 0.3 to 3% by weight, even more
preferably 0.5 to 2% by weight, of a polyglycerol partial ester,
based on the total weight of the lubricating oil composition,
[0050] (b) 85 to 99.8% by weight, preferably 87 to 99.7% by weight,
even more preferably 88 to 99.5% by weight, of an apolar base stock
selected from the group consisting of API Group II, III and IV
and/or mixtures thereof, based on the total weight of the
lubricating oil composition, and [0051] (c) 0 to 10% by weight of a
polar ester oil of Group V according to the definition of the
American Petroleum Institute (API), based on the total weight of
the lubricating oil composition.
[0052] In a preferred embodiment (a), (b) and (c) add up to 100% by
weight.
[0053] In addition to the polyglycerol partial esters in accordance
with the invention, the lubricant oil compositions detailed herein
may also comprise one or more further additive(s). These additives
include viscosity index (VI) improvers, pour point depressants and
dispersant inhibitor (DI) additives selected from the group
consisting of dispersants, detergents, defoamers, corrosion
inhibitors, antioxidants, antiwear and extreme pressure additives
and further friction modifiers.
[0054] Suitable viscosity index improvers are, for example,
polyalkyl(meth)acrylate polymers, ethylene-propylene copolymers,
styrene-isoprene copolymers, hydrogenated styrene-isoprene
copolymers, polyisobutylene, and dispersant type viscosity index
improvers.
[0055] Suitable pour point depressants are, for example,
polyalkyl(meth)acrylate polymers.
[0056] Suitable dispersants are, for example, alkenyl succinimides,
alkenyl succinate esters, alkenyl succinimides modified with other
organic compounds, alkenyl succinimides modified by post-treatment
with ethylene carbonate or boric acid, pentaerythritols,
phenatesalicylates and their post-treated analogs, alkali metal or
mixed alkali metal, alkaline earth metal borates, dispersions of
hydrated alkali metal borates, dispersions of alkaline-earth metal
borates, polyamide ashless dispersants and the like or mixtures of
such dispersants.
[0057] Suitable detergents are, for example, metal detergents which
include oil-soluble neutral and overbased sulfonates, phenates,
sulfurized phenates, thiophosphonates, salicylates, and
naphthenates and other oil-soluble carboxylates of a metal,
particularly the alkali or alkaline earth metals, as for example
barium, sodium, potassium, lithium, calcium, and magnesium. The
most commonly used metals are calcium and magnesium, which may both
be present in detergents used in a lubricant, and mixtures of
calcium and/or magnesium with sodium. Particularly convenient metal
detergents are neutral and overbased calcium sulfonates having TBN
of from 20 to 450, neutral and overbased calcium phenates and
sulfurized phenates having TBN of from 50 to 450 and neutral and
overbased magnesium or calcium salicylates having a TBN of from 20
to 450. Combinations of detergents, whether overbased or neutral or
both, may be used as well.
[0058] Suitable defoamers are, for example, selected from the group
consisting of alkyl (meth)acrylate polymers, silicone oil and
dimethyl silicone polymers.
[0059] Suitable corrosion inhibitors are, in many cases, divided
into antirust additives and metal passivators/deactivators. The
antirust additives used may, inter alia, be sulphonates, for
example petroleumsulphonates or (in many cases overbased) synthetic
alkylbenzenesulphonates, e.g. dinonylnaphthenesulphonates;
carboxylic acid derivatives, for example lanolin (wool fat),
oxidized paraffins, zinc naphthenates, alkylated succinic acids,
4-nonylphenoxy-acetic acid, amides and imides (N-acylsarcosine,
imidazoline derivatives); amine-neutralized mono- and dialkyl
phosphates; morpholine, dicyclohexylamine or diethanolamine. The
metal passivators/deactivators include benzotriazole,
tolyltriazole, tolutriazole (such as Vanlube.RTM. 887 or 887E),
2-mercaptobenzothiazole, dialkyl-2,5-dimercapto-1,3,4-thiadiazole;
N,N'-disalicylideneethylenediamine,
N,N'-disalicylidenepropylenediamine; zinc dialkyldithiophosphates
and dialkyl dithiocarbamates.
[0060] Suitable anti-oxidants are, for example, phenol type
(phenolic) oxidation inhibitors, such as
4,4'-methylene-bis(2,6-di-tert-butylphenol),
4,4'-bis(2,6-di-tert-butylphenol),
4,4'-bis(2-methyl-6-tert-butylphenol),
2,2'-methylene-bis(4-methyl-6-tert-butyl-phenol),
4,4'butylidene-bis(3-methyl-6-tert-butylphenol),
4,4'-isopropylidene-bis(2,6-di-tertbutylphenol),
2,2'-methylene-bis(4-methyl-6-nonylphenol),
2,2'-isobutylidene-bis(4,6-dimethylphenol),
2,2'-methylene-bis(4-methyl-6-cyclohexylphenol),
2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol,
2,6-di-tert-butylphenol, 2,4-dimethyl-6-tert-butyl-phenol,
2,6-di-tert-1-dimethylamino-p-cresol,
2,6-di-tert-4-(N,N'dimethylamino-methylphenol),
4,4'-thiobis(2-methyl-6-tert-butylphenol),
2,2'-thiobis(4-methyl-6-tert-butylphenol),
bis(3-methyl-4-hydroxy-5-tert-butylbenzyl)-sulfide, and
bis(3,5-di-tert-butyl-4-hydroxybenzyl). Other types of oxidation
inhibitors include alkylated diphenylamines (e.g., Irganox L-57
from BASF), metal dithiocarbamate (e.g., zinc dithiocarbamate) and
methylenebis(dibutyldithiocarbamate).
[0061] Suitable antiwear additives are, for example, phosphates,
phosphites, carbamates, esters, sulfur containing compounds and
molybdenum complexes.
[0062] Suitable extreme pressure additives are, for example, zinc
dialkyldithiophosphate (primary alkyl, secondary alkyl, and aryl
type), sulfurized oils, diphenyl sulfide, methyl trichlorostearate,
chlorinated naphthalene, fluoroalkylpolysiloxane and lead
naphthenate.
[0063] A second embodiment of the present invention is directed to
an engine oil comprising the lubricating oil composition as
described hereinbefore.
[0064] A third embodiment of the present invention is directed to a
method of lubricating an engine using the lubricating oil
composition as described hereinbefore.
[0065] A fourth embodiment of the present invention is directed to
a method of reducing friction in an engine by applying/by the
addition of the lubricating oil composition as described
hereinbefore.
[0066] The invention has been illustrated by the following
non-limiting examples.
EXPERIMENTAL PART
EXAMPLE 1
Polycarboxylic Acid Ester Prepared from polyglycerol, isostearic
acid, sebacic acid and poly(hydroxystearic acid) according to
synthesis example 2 of EP 1 500 427 B1
[0067] A mixture of isostearic acid (91.1 g, 0.320 mol) and
poly(hydroxystearic acid) (141.7 g, 0.120 mol, acid number of 47 mg
KOH/g) was esterified with polyglycerol (61.9 g, 0.121 mol,
hydroxyl value of 950 mg KOH/g) at 240.degree. C. while nitrogen
flowing through. After 2 h at this temperature, the acid number of
the reaction mixture was <10. Then, the mixture was cooled to
130.degree. C., sebacic acid (20.2 g, 0.100 mol) was added and the
mixture was heated again to 240.degree. C. After 3 h at this
temperature, a viscous product having an acid number of <5 was
obtained.
COMPARATIVE EXAMPLE 1
Polycarboxylic Acid Ester Prepared from Ethoxylated Soybean Oil,
Oleic Acid and Dimer Acid
[0068] A mixture of epoxidized soybean oil (300 g, 0.302 mol) with
an oxirane-[O] content of 6.3%, oleic acid (331 g, 1.18 mol) and
dimer acid (57.5 g; 0.101 mol, comprising about 2% monobasic acids,
about 96% dimer acids and about 2% trimer acids and higher
polyacids) was heated to 240.degree. C. until the acid value was
<10 mg KOH/g.
[0069] The structure of this polymer is different to polyglycerol
partial ester according to the present invention and therefore not
encompassed by the present invention.
COMPARATIVE EXAMPLE 2
Polycarboxylic Acid Ester Prepared from Polyglycerol, Isostearic
Acid and Sebacic Acid
[0070] A mixture of 72 g isostearic acid and 11 g sebacic acid was
esterified with 17 g polyglycerol (average degree of
polymerization=3) at 240.degree. C. while nitrogen flowing through.
Reaction was cooled down when an acid number of 12 was reached.
[0071] The OH-value of this polymer is much lower than the
favorable range according to the present invention.
COMPARATIVE EXAMPLE 3
[0072] Polymeric friction modifier Perfad.TM. 3006, which is
commercially available by Croda Inc. (see US 2013/0079536, WO
2011/107739 A1 for structure and Lube Magazine No. 120, April 2014,
page 27 for physical properties).
[0073] The structure of this polymer is different to polyglycerol
partial ester according to the present invention and therefore not
encompassed by the present invention.
COMPARATIVE EXAMPLE 4
[0074] Polymeric friction modifier Perfad.TM. 3057, diluted form of
Perfad.TM. 3050, which is commercially available by Croda Sucursal
Colombia (see US 2013/0079536, WO 2011/107739 A1 for structure and
Lube Magazine No. 120, April 2014, page 27 for physical
properties).
[0075] The structure of this polymer is different to polyglycerol
partial ester according to the present invention and therefore not
encompassed by the present invention.
TABLE-US-00002 TABLE 1 physical data of examples and comparative
examples HLB acid number OH-number M.sub.n M.sub.w value [mg KOH/g]
[mg KOH/g] [g/mol] [g/mol] Ex 1 ~5 .ltoreq.5 125-145 2600 6100
Comp. Ex 1 -- 9 24 4600 16000 Comp. Ex. 2 -- 12 10-20 3200 10600
Comp. Ex. 3 -- 1.2 -- -- -- Comp. Ex. 4 -- 4*.sup.) -- -- --
M.sub.n and M.sub.w are measured via GPC using PMMA (polymethyl
methacrylate) as standard *.sup.)value given for Perfad .TM. 3050;
Perfad .TM. 3057 is a diluted form of Perfad .TM. 3050
[0076] All polymers were diluted in Nexbase 3043 which is a Group
III oil according to the American Petroleum Institute (API). The
final blends have a similar kinematic viscosity at 100.degree. C.
(KV.sub.100) of about 4.45 cSt.
[0077] For Comparative Examples 3 and 4 treat rates of 0.5% are
recommended by the manufacturer.
TABLE-US-00003 TABLE 1 Viscosity values of the tested blends
Comparative Example 1 [% wt] 1 Comparative Example 2 [% wt] 1
Comparative Example 3 [% wt] 0.5 Comparative Example 4 [% wt] 0.5
Example 1 [% wt] 1 Reference Nexbase 3043 [% wt] 99 99 99.5 99.5 99
KV.sub.100 mm.sup.2/s 4.49 4.45 4.48 4.43 4.48 (KV.sub.100 =
Kinematic Viscosity @ 100.degree. C.)
[0078] Determination of Friction-Reducing Action:
[0079] The measurements of the coefficient of friction at
100.degree. C. were performed on a Mini Traction Machine (MTM) from
PCS Instruments. The test consist of evaluating the friction level
occurring in a lubricated contact formed by a steel ball and a
steel disc. The speeds of the ball and the disc are driven
independently. The ball is loaded and rubbed in rolling sliding
conditions against the steel disc, the contact being fully immersed
in oil.
[0080] For each sample, the test was performed in two steps:
[0081] 1) Run In phase
[0082] For this phase, the conditions described in Table 2 below
have been applied, SRR referring to Sliding Roll Ratio. This
parameter was maintained constant during the 2 hours testing and is
defined as:
U Ball - U Disc U ##EQU00002##
where U Ball-U Disc represents the sliding speed and U the
entrainment speed, given by U=(U Ball+U Disc)/2
TABLE-US-00004 TABLE 2 test parameters for run in phase Test Rig
MTM 2 von PCS Instruments Disc Highly polished stainless Steel AISI
52100 Disc diameter 46 mm Ball Highly polished stainless Steel AISI
52100 Ball diameter 19.05 mm Mean Speed 100 mm/s Temperature
100.degree. C. Duration 2 hours Load 30 N SRR 50%
[0083] 2) Stribeck Curve Evaluation
[0084] A Stribeck was then obtained by measuring the friction
coefficient under the conditions shown in Table 3.
TABLE-US-00005 TABLE 3 conditions for Stribeck curve evaluation
Test Rig MTM 2 von PCS Instruments Disc Highly polished stainless
Steel AISI 52100 Disc diameter 46 mm Ball Highly polished stainless
Steel AISI 52100 Ball diameter 19.05 mm Mean Speed from 5 to 2500
mm/s Temperature 100.degree. C. Load 30 N SRR 50%
[0085] The Stribeck curves are plotted in FIG. 1. The curve
NB3043-Ref refers to the formulation containing 100% of Group III
oil named Nexbase 3043.
[0086] FIG. 1: Stribeck curve measurements after two hours of run
in phase
[0087] To express in % the friction reduction obtained by working
Example 1, a quantifiable result can be expressed as a number is
obtained as follows:
[0088] Integration of the friction value curves in the range of
sliding speed 0.005-2.5 m/s using the trapezoidal rule. The area
corresponds to the "total friction" over the entire speed range
examined. The smaller the area, the greater the friction-reducing
effect of the polymer examined.
[0089] The percentage friction reductions calculated therefrom in
relation to the reference oil are compiled in Table 4 below.
TABLE-US-00006 TABLE 4 Quantitative evaluation of the reduction in
friction Comp. Comp. Comp. Comp. Reference Ex. 1 Ex. 1 Ex. 2 Ex. 3
Ex. 4 Area in 99.239 51.079 62.675 71.354 65.109 86.581 mm/s
reduction in 0 48.53 36.84 28.10 34.39 12.75 friction relative to
reference [%]
[0090] The data in Table 4 and FIG. 1 show clearly that the
inventive polymers have a much better effect with regard to the
reduction in friction than the corresponding comparative polymers
of the prior art using different chemistry. The effect is even more
pronounced in the low speed regime as revealed in Table 5
below.
[0091] Since the low speeds are of particular economic interest for
the use of the lubricant compositions in accordance with the, Table
5 shows the integration data of the friction value curves within
the sliding speed range from 0.005 to 0.090 m/s.
[0092] The areas determined and the percentage reductions in
friction calculated therefrom in relation to the reference oil are
compiled in Table 5 in an analogous manner to Table 4.
TABLE-US-00007 TABLE 5 Quantitative evaluation of the reduction in
friction at low frequency (from 0.005 to 0.090 m/s) Comp. Comp.
Comp. Comp. Reference Ex. 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Area 7.863
1.855 4.429 5.464 3.405 4.025 [mm/s] reduction in 0 76.41 43.67
30.51 56.70 48.81 friction relative to reference in low speed
regime [%]
[0093] The data in Table 5 show clearly that the inventive polymers
have a much better effect once again with regard to the reduction
in friction than the corresponding comparative polymers of the
prior art.
[0094] Compared to the results as shown in Table 4, it is found
that the friction-increasing action of lubricant composition for
use in accordance with the invention is very clearly marked
specifically within the range of low sliding speeds.
* * * * *