U.S. patent application number 12/172618 was filed with the patent office on 2010-01-14 for thermally stable zinc-free antiwear agent.
Invention is credited to Patricia Corbett, Helen T. RYAN.
Application Number | 20100009881 12/172618 |
Document ID | / |
Family ID | 41119753 |
Filed Date | 2010-01-14 |
United States Patent
Application |
20100009881 |
Kind Code |
A1 |
RYAN; Helen T. ; et
al. |
January 14, 2010 |
THERMALLY STABLE ZINC-FREE ANTIWEAR AGENT
Abstract
There is disclosed a lubricant additive composition comprising a
thermally stable, zinc-free, phosphorous-containing antiwear agent.
Moreover, a lubricant composition comprising the disclosed additive
composition is also disclosed. Methods for making and using the
disclosed compositions are disclosed.
Inventors: |
RYAN; Helen T.; (London,
GB) ; Corbett; Patricia; (Bracknell, GB) |
Correspondence
Address: |
MH2 TECHNOLOGY LAW GROUP (Cust. No. w/NewMarket)
1951 KIDWELL DRIVE, SUITE 550
TYSONS CORNER
VA
22182
US
|
Family ID: |
41119753 |
Appl. No.: |
12/172618 |
Filed: |
July 14, 2008 |
Current U.S.
Class: |
508/440 |
Current CPC
Class: |
C10M 2223/04 20130101;
C10M 137/105 20130101; C10M 2223/047 20130101; C10N 2030/42
20200501; C10M 2203/1006 20130101; C10N 2030/06 20130101; C10M
2223/041 20130101; C10M 2203/1025 20130101; C10M 2209/084 20130101;
C10M 161/00 20130101; C10N 2040/08 20130101; C10N 2030/08 20130101;
C10N 2030/12 20130101; C10N 2030/40 20200501; C10N 2030/04
20130101 |
Class at
Publication: |
508/440 |
International
Class: |
C10M 137/10 20060101
C10M137/10 |
Claims
1. A lubricant additive composition comprising at least one
thermally stable dithiophosphate prepared by reacting a
dithiophosphoric acid with an alkene; and at least one
polyalkylmethacrylate viscosity index improver, wherein the
additive composition provides a phosphorus content ranging from
about 300 to about 700 parts per million when used in a lubricating
composition.
2. The additive of claim 1, wherein the alkene is a
dicyclopentadiene or ethyl acrylate.
3. A method of controlling sludge formation in a multigrade
lubricating composition, said method comprising providing a major
amount of a base oil, and a minor amount of an additive composition
comprising at least one thermally stable dithiophosphate prepared
by reacting a dithiophosphoric acid with an alkene; and at least
one polyalkylmethacrylate viscosity index improver, wherein the
lubricating composition has a phosphorus content ranging from about
300 to abut 700 parts per million.
4. The method of claim 3, wherein the phosphorus content in the
lubricating composition ranges from about 400 to about 500 parts
per million.
5. The method of claim 3, wherein the lubricating composition
further comprises thermally unstable metal-free antiwear agents,
with the proviso that the thermally unstable metal-free antiwear
agents are present in an amount that does not contribute to sludge
formation.
6. The method of claim 5, wherein the metal-free antiwear agent is
selected from the group consisting of thermally unstable
dithiophosphates prepared by reacting a dithiophosphoric acid with
an alkenoic acid, amine salts of sulfurized phosphate, and mixtures
thereof.
7. The method of claim 3, wherein the composition further comprises
one or more materials selected from the group consisting of
antioxidants, dispersants, detergents, rust inhibitors, corrosion
inhibitors, demulsifiers, and supplemental viscosity index
improvers.
8. A method of controlling sludge formation in a monograde
lubricating composition, said method comprising providing a base
oil, and adding thereto at least one thermally stable
dithiophosphate prepared by reacting a dithiophosphoric acid with
an alkene, wherein the composition has a phosphorus content ranging
from about 300 to abut 700 parts per million.
9. The method of claim 8, wherein the phosphorus content in the
composition ranges from about 400 to about 500 parts per
million.
10. The method of claim 8, wherein the composition further
comprises thermally unstable metal-free antiwear agents, with the
proviso that the thermally unstable antiwear agents are present in
an amount that does not contribute to sludge formation.
11. The method of claim 10, wherein the thermally unstable
metal-free antiwear agent is selected from the group consisting of
thermally unstable dithiophosphates prepared by reacting a
dithiophosphoric acid with an alkenoic acid, amine salts of
sulfurized phosphate, and mixtures thereof.
12. The method of claim 8, wherein the composition further
comprises one or more materials selected from the group consisting
of antioxidants, dispersants, detergents, rust inhibitors,
corrosion inhibitors, demulsifiers, and supplemental viscosity
index improvers.
13. A lubricant additive composition comprising at least one
thermally stable triarylphosphate or dilaurylphosphate; and at
least one polyalkylmethacrylate viscosity index improver, wherein
the additive composition provides a phosphorus content ranging from
about 300 to about 700 parts per million when used in a lubricating
composition.
14. The additive composition of claim 13, wherein the
triarylphosphate is tricresylphosphate.
15. A lubricating composition comprising: a major amount of a base
oil; and a minor amount of the additive composition of claim 1.
16. The lubricating composition of claim 15, wherein the base oil
is chosen from a Group I, Group II, and a Group III base oil.
17. The lubricating composition of claim 15, wherein the phosphorus
content in the composition ranges from about 400 to about 500 parts
per million.
18. The lubricating composition of claim 15, wherein the
composition further comprises one or more materials selected from
the group consisting of antioxidants, dispersants, detergents, rust
inhibitors, corrosion inhibitors, demulsifiers, and viscosity index
improvers.
19. The lubricating composition of claim 15, wherein the
composition is a hydraulic fluid.
20. A method of improving the thermal stability of a lubricating
composition, said method comprising formulating the lubricating oil
comprising a major amount of a base oil and a minor amount of the
additive composition of claim 1.
21. A method of lubricating a hydraulic machine having a
lubrication system, said method comprising adding to the
lubrication system the lubricating composition of claim 1.
Description
FIELD OF THE DISCLOSURE
[0001] The present disclosure relates to a thermally stable,
zinc-free antiwear agent, compositions containing same, and methods
of use thereof.
BACKGROUND OF THE DISCLOSURE
[0002] The use of ashless and zinc-free antiwear hydraulic
technology is known. However some ashless or zinc free, antiwear
multigrade oils containing polyalkylmethacrylate viscosity index
improvers (PMA VIIs) with very low phosphorus levels, such as
between 50 and 150 ppm, have borderline failing performance in
current industry pump tests; T6H20C and 35VQ25. This negative
result is because the PMA VIIs compete with the thin phosphorous
tribolayer in the ashless system. It is noted that this result does
not occur when using ZDDP-based fluids because the tribolayer they
form is thicker. One of the problems with adding more antiwear
species to overcome the borderline failing pump performance is that
not all the antiwear additives are thermally stable and so at the
required higher levels they will contribute to sludge/varnish
formation in use. Moreover, the antiwear species break down to form
acidic species that can lead to the blockage of filters.
[0003] It is a requirement of hydraulic fluids that they exhibit
acceptable hydraulic performance, i.e. power transmission, as well
as other important characteristics such as thermal stability, rust
inhibition and antiwear performance. These latter properties are
usually achieved by incorporating specific additives in a base oil.
Further, to maintain good power transmission and to avoid damaging
hydraulic equipment, in which they are used, hydraulic fluids
should be kept meticulously clean and free of contaminants
[0004] Antiwear agents such as zinc dihydrocarbyl dithiophosphates
(ZDDPs) are commonly used. One factor against use of ZDDP's as an
antiwear agent in hydraulic fluids is the environmental one
associated with use of zinc, and for this reason, zinc-based
hydraulic fluids have been banned from some applications. It is
therefore desirable to provide a zinc-free multigrade hydraulic oil
with performance matching or exceeding that of a zinc-based
multigrade fluid by using thermally stable antiwear additives at
high phosphorus levels
[0005] What is needed is an antiwear agent for a multigrade
hydraulic fluid that can provide the following properties/solutions
at high phosphorus levels: passing pump performance, acceptable
varnish/sludge control, tolerance to water, thermal stability, and
environmental acceptability.
SUMMARY OF THE DISCLOSURE
[0006] In accordance with the disclosure, there is disclosed a
lubricant additive composition having at least one thermally stable
dithiophosphate prepared by reacting a dithiophosphoric acid with
an alkene and at least one polyalkylmethacrylate viscosity index
improver.
[0007] Further disclosed is a lubricant additive composition having
at least one thermally stable triarylphosphate or
dilaurylphosphate; and at least one polyalkylmethacrylate viscosity
index improver.
[0008] There is also disclosed a lubricating composition comprising
a major amount of base oil, and a minor amount of the additive
compositions.
[0009] Yet also disclosed is a method of controlling sludge
formation in a multigrade lubricating composition, said method
comprising providing a major amount of a base oil, and a minor
amount of the lubricant additive compositions.
[0010] There is further disclosed a method of controlling sludge
formation in a monograde lubricating composition, said method
comprising providing a major amount of a base oil, and a minor
amount of the lubricant additive compositions.
[0011] Also disclosed is a method of improving the thermal
stability of a lubricating composition comprising formulating a
lubricating oil having a major amount of a base oil and a minor
amount of the lubricant additive compositions.
[0012] Additional objects and advantages of the disclosure will be
set forth in part in the description which follows, and/or can be
learned by practice of the disclosure. The objects and advantages
of the disclosure will be realized and attained by means of the
elements and combinations particularly pointed out in the appended
claims.
[0013] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory only and are not restrictive of the disclosure, as
claimed.
DESCRIPTION OF THE EMBODIMENTS
[0014] The present disclosure relates to a thermally stable,
zinc-free lubricant additive composition. Moreover, there is
disclosed a lubricant composition comprising a major amount of a
base oil and a minor amount of an additive composition.
[0015] By "thermally stable" herein is meant that acceptable
varnish or sludge is formed in bench or pump tests that are run to
evaluate functional fluids, such as hydraulic fluids. These bench
tests include the Cincinnati Milacron procedure A (a thermal
stability test), the Nippon oil color test at various temperatures,
the ASTM D2619 hydrolytic stability test, the ASTM D4310 1000-hr
TOST test, the ASTM D943 Life TOST test, the Eaton 35VQ25, a pump
test, the Parker Denison T6H20C hybrid pump test, modifications of
these tests, as well as non-standard industry tests.
[0016] By "zinc-free" herein is meant that no zinc has been added
to the composition, but the composition can have trace levels of
zinc due to contamination.
[0017] The compositions can comprise at least one thermally stable,
zinc-free, antiwear agent. Suitable antiwear agents can include the
reaction products of an alkene, such as a dicyclopentadiene,
acrylate, or methacrylate, and a dithiophosphoric acid, and/or
dicyclopentadiene dithioates. Thiophosphoric acids suitable for use
in preparing the antiwear agents can have formula (I):
##STR00001##
wherein R is a hydrocarbyl group having from about 2 to about 30,
for example about 3 to about 18 carbon atoms. In an aspect, R
comprises a mixture of hydrocarbyl groups containing from about 3
to about 18 carbon atoms.
[0018] As used herein, the term "hydrocarbyl group" or
"hydrocarbyl" is used in its ordinary sense, which is well-known to
those skilled in the art. Specifically, it refers to a group having
a carbon atom directly attached to the remainder of a molecule and
having a predominantly hydrocarbon character. Examples of
hydrocarbyl groups include:
[0019] (1) hydrocarbon substituents, that is, aliphatic (e.g.,
alkyl or alkenyl), alicyclic (e.g., cycloalkyl, cycloalkenyl)
substituents, and aromatic-, aliphatic-, and alicyclic-substituted
aromatic substituents, as well as cyclic substituents wherein the
ring is completed through another portion of the molecule (e.g.,
two substituents together form an alicyclic radical);
[0020] (2) substituted hydrocarbon substituents, that is,
substituents containing non-hydrocarbon groups which, in the
context of the description herein, do not alter the predominantly
hydrocarbon substituent (e.g., halo (especially chloro and fluoro),
hydroxy, alkoxy, mercapto, alkylmercapto, nitro, nitroso, and
sulfoxy);
[0021] (3) hetero-substituents, that is, substituents which, while
having a predominantly hydrocarbon character, in the context of
this description, contain other than carbon in a ring or chain
otherwise composed of carbon atoms. Hetero-atoms include sulfur,
oxygen, nitrogen, and encompass substituents such as pyridyl,
furyl, thienyl, and imidazolyl. In general, no more than two, or as
a further example, no more than one, non-hydrocarbon substituent
will be present for every ten carbon atoms in the hydrocarbyl
group; in some embodiments, there may be no non-hydrocarbon
substituent in the hydrocarbyl group.
[0022] The thermally stable, zinc-free antiwear agents can be
prepared by mixing an alkene, for example a dicyclopentadiene,
acrylate, or methacrylate, and a dithiophosphoric acid for a time
and temperature sufficient to react the thioacid with the alkene.
Typical reaction times range from about 30 minutes to about 6
hours, although suitable reaction conditions can readily be
determined by one skilled in the art. The reaction product can be
subjected to conventional post-reaction work up, including vacuum
stripping and filtering.
[0023] In an embodiment, the thermally stable, zinc-free antiwear
agents can be dicylopentadiene dithioates. In another embodiment,
the thermally stable, zinc free antiwear agents can be represented
by formula (II):
##STR00002##
[0024] wherein R' is a hydrocarbyl group having from about 1 to
about 6 carbon atoms.
[0025] In a further embodiment, the thermally stable, zinc-free
antiwear agents can be dilaurylphosphates or triarylphosphates,
such as tricresylphosphates.
[0026] The additive composition can comprise any effective amount
of the thermally stable, zinc-free antiwear agents. In particular,
the additive composition can comprise from about 10% to about 45%
by weight, and for example from about 25% to about 40%, by weight
of the thermally stable, zinc-free antiwear agents, relative to the
total weight of the composition. In an aspect, the thermally
stable, zinc-free antiwear agents can be present in a lubricant
composition in an amount ranging from about 0.001% to about 1% by
weight, for example from about 0.1% to about 0.7% by weight
relative to the total weight of the lubricant composition.
[0027] The lubricant composition can further comprise a viscosity
index improver (VII). Examples of VIIs include, but are not limited
to, polyalkylmethacrylate VIIs. The viscosity index improver can be
supplied in the form of a solution in an inert solvent, such as a
mineral oil solvent, which usually is a severely refined mineral
oil. The viscosity index improver solution often will have a
boiling point above 200.degree. C., and a specific gravity of less
than 1 at 25.degree. C. On an active ingredient basis (i.e.,
excluding the weight of inert diluent or solvent associated with
the viscosity index improver), the finished lubricant compositions
of this invention can comprise in the range of about 0 to about 25
wt % of the polymeric viscosity index improver.
[0028] Suitable materials for use a VII herein include
polyalkylmethacrylate VIIs such as those available from Rohmax
Additives GmbH (Darmstadt, Germany) under the trade designations:
VISCOPLEX.RTM. 8-129, VISCOPLEX.RTM. 8-200, VISCOPLEX.RTM. 8-226,
VISCOPLEX.RTM. 8-251, VISCOPLEX.RTM. 8-310, VISCOPLEX.RTM. 8-300,
VISCOPLEX.RTM. 8-350, VISCOPLEX.RTM. 8-400, and VISCOPLEX.RTM.
8-440; from Rohm & Haas Company (Philadelphia, Pa.) under the
trade designations ACRYLOID.RTM. 1277, ACRYLOID.RTM. 1265 and
ACRYLOID.RTM. 1269; and from Afton Chemical Corporation (Richmond,
Va.) under the trade designations: HiTEC.RTM. 5708 and HiTEC.RTM.
5785H. Mixtures of the foregoing products can also be used as well
as dispersant and dispersant/antioxidant VIIs. In an embodiment,
the VII is a viscosity index improver such as HiTEC.RTM. 5708 or
HiTEC.RTM. 5785H. Shear stable OCP VII's can also be used.
[0029] In an aspect, the additive composition is ashless. In
another aspect, the additive composition is zinc free. Examples of
commercially available thermally stable, zinc-free,
phosphorus-containing antiwear agents include, but are not limited
to, HiTEC.RTM. 511, available from Afton Chemical Corporation of
Richmond, Va.; Irgablube.RTM. 63, available from Ciba Specialty
Chemicals Corporation of Tarrytown, N.Y.; and Durad.RTM. 125,
available from Chemtura Corporation of Middlebury, Conn.
[0030] Typically, the lubricating compositions can contain a major
amount of a base oil and a minor amount of the disclosed additive
composition. A "major amount" is understood to mean greater than or
equal to 50% by weight relative to the total weight of the
lubricating composition. For example, the base oil can be present
in the lubricating composition in an amount ranging from about 60
to about 99 percent by weight, and as a further example from 80 to
98 percent by weight. A "minor amount" is understood to mean less
than 50% by weight, for example 0.005 to about 49%, and as a
further example from about 1 to about 30% by weight relative to the
total amount of the lubricant composition.
[0031] In an aspect, the lubricating composition can comprise a
phosphorous content ranging from about 100 to about 1000 parts per
million, for example from about 300 to about 700 parts per million,
and as a further example from about 400 to about 500 parts per
million.
[0032] The lubricant compositions of this disclosure can be based
on natural or synthetic oils, or blends thereof, provided the
lubricant has a suitable viscosity for use in lubricant
composition, such as hydraulic applications. The base oil can have
a viscosity in the range of ISO 10 to ISO 460, and for example from
ISO 22 to ISO 150. Suitable oils also can have a grade of ISO 32,
46, and 68.
[0033] Mineral oils include animal oils and vegetable oils (e.g.,
castor oil, lard oil) as well as other mineral lubricating oils
such as liquid petroleum oils and solvent treated or acid-treated
mineral lubricating oils of the paraffinic, naphthenic or mixed
paraffinic-naphthenic types. Oils derived from coal or shale are
also suitable. Further, oils derived from a gas-to-liquid process
are also suitable.
[0034] Non-limiting examples of synthetic oils include hydrocarbon
oils such as polymerized and interpolymerized olefins (e.g.,
polybutylenes, polypropylenes, propylene isobutylene copolymers,
etc.); polyalphaolefins such as poly(1-hexenes), poly-(1-octenes),
poly(1-decenes), etc. and mixtures thereof; alkylbenzenes (e.g.,
dodecylbenzenes, tetradecylbenzenes, di-nonylbenzenes,
di-(2-ethylhexyl)benzenes, etc.); polyphenyls (e.g., biphenyls,
terphenyl, alkylated polyphenyls, etc.); alkylated diphenyl ethers
and alkylated diphenyl sulfides and the derivatives, analogs and
homologs thereof and the like.
[0035] Alkylene oxide polymers and interpolymers and derivatives
thereof where the terminal hydroxyl groups have been modified by
esterification, etherification, etc., constitute another class of
known synthetic oils that can be used. Such oils are exemplified by
the oils prepared through polymerization of ethylene oxide or
propylene oxide, the alkyl and aryl ethers of these polyoxyalkylene
polymers (e.g., methyl-polyisopropylene glycol ether having an
average molecular weight of about 1000, diphenyl ether of
polyethylene glycol having a molecular weight of about 500-1000,
diethyl ether of polypropylene glycol having a molecular weight of
about 1000-1500, etc.) or mono- and polycarboxylic esters thereof,
for example, the acetic acid esters, mixed C.sub.3-8 fatty acid
esters, or the C.sub.13 Oxo acid diester of tetraethylene
glycol.
[0036] Another class of synthetic oils that can be used includes
the esters of dicarboxylic acids (e.g., phthalic acid, succinic
acid, alkyl succinic acids, alkenyl succinic acids, maleic acid,
azelaic acid, suberic acid, sebacic acid, fumaric acid, adipic
acid, linoleic acid dimer, malonic acid, alkyl malonic acids,
alkenyl malonic acids, etc.) with a variety of alcohols (e.g.,
butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl
alcohol, ethylene glycol, diethylene glycol monoether, propylene
glycol, etc.) Specific examples of these esters include dibutyl
adipate, di(2-ethylhexyl)sebacate, di-n-hexyl fumarate, dioctyl
sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl
phthalate, didecyl phthalate, dieicosyl sebacate, the 2-ethylhexyl
diester of linoleic acid dimer, the complex ester formed by
reacting one mole of sebacic acid with two moles of tetraethylene
glycol and two moles of 2-ethylhexanoic acid and the like.
[0037] Esters useful as synthetic oils also include those made from
C.sub.5-12 monocarboxylic acids and polyols and polyol ethers such
as neopentyl glycol, trimethylol propane, pentaerythritol,
dipentaerythritol, tripentaerythritol, etc.
[0038] Hence, the base oil used which can be used to make the
compositions as described herein can be selected from any of the
base oils in Groups I-V as specified in the American Petroleum
Institute (API) Base Oil Interchangeability Guidelines. Such base
oil groups are as follows:
[0039] Group I contain less than 90% saturates and/or greater than
0.03% sulfur and have a viscosity index greater than or equal to 80
and less than 120; Group II contain greater than or equal to 90%
saturates and less than or equal to 0.03% sulfur and have a
viscosity index greater than or equal to 80 and less than 120;
Group III contain greater than or equal to 90% saturates and less
than or equal to 0.03% sulfur and have a viscosity index greater
than or equal to 120; Group IV are polyalphaolefins (PAO); and
Group V include all other basestocks not included in Group I, II,
III or IV.
[0040] The test methods used in defining the above groups are ASTM
D2007 for saturates; ASTM D2270 for viscosity index; and one of
ASTM D2622, 4294, 4927 and 3120 for sulfur.
[0041] Group IV basestocks, i.e. polyalphaolefins (PAO) include
hydrogenated oligomers of an alpha-olefin, the most important
methods of oligomerisation being free radical processes, Ziegler
catalysis, and cationic, Friedel-Crafts catalysis.
[0042] The polyalphaolefins typically have viscosities in the range
of 2 to 100 cSt at 100.degree. C., for example 4 to 8 cSt at
100.degree. C. They can, for example, be oligomers of branched or
straight chain alpha-olefins having from about 2 to about 30 carbon
atoms, non-limiting examples include polypropenes, polyisobutenes,
poly-1-butenes, poly-1-hexenes, poly-1-octenes and poly-1-decene.
Included are homopolymers, interpolymers and mixtures.
[0043] Basestocks suitable for use herein can be made using a
variety of different processes including but not limited to
distillation, solvent refining, hydrogen processing
oligomerisation, esterification, and re-refining.
[0044] The base oil can be an oil derived from Fischer-Tropsch
synthesized hydrocarbons. Fischer-Tropsch synthesized hydrocarbons
can be made from synthesis gas containing H.sub.2 and CO using a
Fischer-Tropsch catalyst. Such hydrocarbons typically require
further processing in order to be useful as the base oil. For
example, the hydrocarbons can be hydroisomerized using processes
disclosed in U.S. Pat. No. 6,103,099 or 6,180,575; hydrocracked and
hydroisomerized using processes disclosed in U.S. Pat. No.
4,943,672 or 6,096,940; dewaxed using processes disclosed in U.S.
Pat. No. 5,882,505; or hydroisomerized and dewaxed using processes
disclosed in U.S. Pat. No. 6,013,171; U.S. Pat. No. 6,080,301; or
U.S. Pat. No. 6,165,949.
[0045] Unrefined, refined and rerefined oils, either mineral or
synthetic (as well as mixtures of two or more of any of these) of
the type disclosed hereinabove can be used in the base oils.
Unrefined oils are those obtained directly from a mineral or
synthetic source without further purification treatment. For
example, a shale oil obtained directly from retorting operations, a
petroleum oil obtained directly from primary distillation or ester
oil obtained directly from an esterification process and used
without further treatment would be an unrefined oil. Refined oils
are similar to the unrefined oils except they have been further
treated in one or more purification steps to improve one or more
properties. Many such purification techniques are known to those
skilled in the art such as solvent extraction, secondary
distillation, acid or base extraction, filtration, percolation,
etc. Rerefined oils are obtained by processes similar to those used
to obtain refined oils applied to refined oils which have been
already used in service. Such rerefined oils are also known as
reclaimed or reprocessed oils and often are additionally processed
by techniques directed to removal of spent additives, contaminants,
and oil breakdown products.
[0046] Gas to liquid (GTL) hydrocarbons, such as gasoline fraction,
kerosene fraction, and light oil fraction, can also be used as base
oils.
[0047] The lubricant compositions of this disclosure can further
comprise thermally unstable phosphorus-containing antiwear
additives as secondary antiwear agents, so long as such additives
are present in an amount that does not contribute to sludge
formation, such as from about 1 to about 500 parts per million, for
example from about 150 to about 300 parts per million. In an
aspect, the thermally unstable antiwear additives can be thermally
unstable metal-free antiwear agents. In an embodiment, the
thermally unstable metal-free antiwear agent is a thermally
unstable dithiophosphate prepared by reacting a dithiophosphoric
acid with an alkenoic acid or an amine salt of sulfurized
phosphate; and mixtures thereof.
[0048] The disclosed lubricant compositions can comprise optional
additional additives known to those of ordinary skill in the art.
Non-limiting examples of optional additional additives include
antioxidants, dispersants, detergents, rust inhibitors, corrosion
inhibitors, demulsifiers, and supplemental viscosity index
improvers. The optional additional additives can be present in the
disclosed compositions in any effective amount, which can readily
be determined by one of ordinary skill in the art.
[0049] In an aspect, the lubricating compositions disclosed herein
can be multigrade lubricating compositions. In another aspect, the
lubricating compositions can be monograde lubricating compositions.
In an embodiment, the lubricant compositions can be functional
fluids for power transmission applications, such as a hydraulic
fluid for use in hydraulic machines.
[0050] By "hydraulic machine" herein is meant any pump, machine,
device having a hydraulic system and in which a lubrication system
can be employed to improve the functional life of the machine. The
lubricant compositions disclosed herein can be used in vane-,
piston-, and gear-type pumps of mobile and stationary hydraulic
equipment, including in environmentally sensitive areas. Typical
machines can include cars, paper machine circulating systems, dryer
bearings, calendar stacks, and turbines.
[0051] A method of improving the thermal stability of a lubricating
composition, said method comprising formulating the lubricating
composition comprising a major amount of a base oil and a minor
amount of the disclosed additive composition is disclosed.
[0052] A method of lubricating a hydraulic machine having a
lubrication system, said method comprising adding to the
lubrication system the disclosed lubricating composition is also
disclosed.
[0053] Further, there is disclosed a method of controlling sludge
formation in a lubricating composition (e.g., a multigrade or
monograde lubricating composition) comprising providing a major
amount of a base oil and a minor amount of the disclosed lubricant
additive composition.
EXAMPLES
Example I
[0054] A lubricating composition, such as a hydraulic fluid, was
formulated with the treat rates as shown in Table 1 and subjected
to the FZG test. HiTEC.RTM. 511, Irgalube 63 and Irgalube 353 are
liquid ashless dithiophosphates from Afton Chemical Corporation and
from Ciba Specialty Chemicals Corporation.
[0055] HiTEC.RTM. 833 is an amine salt of sulfurized phosphate and
is available from Afton Chemical Corporation.
[0056] In the FZG test, two steel spur gears are rotated together
with oil dip lubrication for a series of 15 minute stages. The
relative torque between the gears is increased by a fixed amount
after each stage and the gears are run together for a given period
after which they are examined for wear or damage. The result of the
test is quoted in terms of the final pass stage and the first fail
stage. To be satisfactory, the pass stage must be higher than
10.
[0057] The results are shown in Table 1 below.
TABLE-US-00001 TABLE 1 FZG Example Treat Rate RATING 1 HiTEC .RTM.
511 (0.5%) Pass 11 2 HiTEC .RTM. 511 (0.5%) and HiTEC .RTM. 833
(0.05%) Pass 12 3 HiTEC .RTM. 833 at 0.05% Pass 7 4 HiTEC .RTM. 511
(0.5%) and Pass 12 Irgalube .RTM. 353 (0.05%)
[0058] In this table, the FZG result was given as a load stage
result (in the stepwise phase). Examples 1 and 2 gave "pass 11" and
"pass 12" results, respectively, which are satisfactory results.
Example 3, on the other hand, gave an FZG result of "pass 7," which
is not satisfactory. To improve the FZG performance of thermally
unstable antiwear agents like HiTEC.RTM. 833 and Irgalube.RTM. 353
and to give FZG performance greater than 10 Fail and passing pump
performance in multigrade formulations, an increase in treat rate
of these antiwear additives would be required. However, this
increase in treat rate for HiTEC.RTM. 833 and Irgalube.RTM. 353
would result in poor performance in the thermal stability tests,
whereas thermally stable antiwear additives like HiTEC.RTM. 511 can
be used at high treat rates to give good pump and FZG results with
good thermal stability in multigrade formulations. This variation
in thermal stability at higher treat is shown in the tables
below.
Example II
[0059] An additive composition, such as a hydraulic fluid additive,
was formulated with the treat rates as described in Table 2a below.
Irgalube.RTM. 353 is the reaction product of dithiophosphoric acid
and acrylic or methacrylic acid and is available from Ciba
Specialty Chemicals Corporation of Tarrytown, N.Y. Durad.RTM. 125
is a tricresylphosphate, available from Chemtura Corporation of
Middlebury, Conn. The antiwear additives were added at treat level
to give 500 ppm of phosphorous in the finished oil approximately.
All antiwear additives were tested in the same formulation
containing corrosion inhibitors, rust inhibitors, detergents,
dispersant and demulsfiers.
[0060] The thermal stability performance of the composition was
demonstrated by results of the Cincinnati Milacron Thermal
Stability Test Procedure "A" (CCMA) (see Cincinnati Milacron
Lubricants Purchase Specification Approved Products Handbook, pages
3-1 to 3-3). In this test, a beaker of the lubricating composition
containing copper and steel rods is heated to 135.degree. C. for
168 hours. At the end of the test, the rods are rated visually for
discoloration. Appearance ratings range on a scale from 1 to 10,
where the lower the numerical rating, the better the result.
Additionally, the change in viscosity of the oil, the amount of
sludge formed in the oil, and the weight loss of the copper and
steel rods are determined. Results are provided in Table 2b
below.
TABLE-US-00002 TABLE 2a Example Treat Rate 4 HiTEC .RTM. 511 (0.5%)
5 HiTEC .RTM. 511 (0.1%) 6 HiTEC .RTM. 833 (0.1%) 7 HiTEC .RTM. 833
(0.649%) 8 Irgalube .RTM. 353 (0.44%) 9 Durad .RTM. 125 (0.47%) 10
Irgalube .RTM. 63 (0.52%)
TABLE-US-00003 TABLE 2b Ex. Property Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8
Ex. 9 10 Sludge, mg/100 mL 5.07 0.93 1.96 221.29 76.26 0.44 1.18
Copper Rod Rating 2 2 2 6 6 2 5 Copper Weight 0.23 -0.13 0.17 -6.18
0.8 0 0.88 Loss, mg/100 mL Steel Rod Rating 1 1 1 3 2 1 1 Steel
Weight Loss, 0.19 -0.27 0.11 0.49 0.54 -0.20 -0.03 mg/100 mL
[0061] In the CCMA test, Examples 7 and 8 demonstrated sludge
contents of 221.29 mg and 76.26 mg, respectively, thereby
demonstrating poor thermal stability. Examples 4, 5, 9, and 10, on
the other hand, demonstrated sludge contents of 5.07 mg, 0.93 mg,
0.44 mg, and 1.18 mg, respectively, thereby demonstrating good
thermal stability. Additionally, Examples 7 and 8 demonstrated
copper rod ratings of 6, whereas examples 4, 5, 9, and 10
demonstrated lower copper rod ratings of 2 and 5. Thus, it can be
seen that the zinc-free, phosphorous-containing antiwear agents
disclosed herein are thermally stable at high treat rates, as
compared to thermally unstable antiwear systems at high treat
rates.
[0062] The corrosion and sludge formation properties of the
composition were also determined using the Nippon Oil Color Test
(NOC) Test. The method is as follows: A 50 mL beaker is filled with
45 g of the composition. Iron and copper coil catalysts (use for
ASTM D 943) are added to the beaker. The beaker is stored at
135.degree. C. for 210 hours. Thereafter, the beaker is removed and
analyzed for color (ASTM D 1500) and sludge content. Low color
results score less than 5.0 and acceptable sludge results are less
than 10 milligrams of sludge after 210 hours of oil aging. Results
are shown in Table 3 below.
TABLE-US-00004 TABLE 3 Property Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9
Ex. 10 Color 3 3.5 3.5 8 7 4 2.5 Sludge content, 1.1 1.03 1.18
155.31 0.48 1.07 2.19 mg
[0063] In the NOC test, Examples 4, 5, 9 and 10 demonstrated
acceptable color and sludge results at high treat rates. However,
although Example 6 demonstrated acceptable color and sludge at a
low treat rate, the same antiwear agent demonstrated poor color and
sludge results at a high treat rate. For instance, Example 7
demonstrated an unacceptable color rating of 8 and 155.31 mg of
sludge, clearly exceeding the maximum sludge content. Example 8
also demonstrated a high color rating of 7 (and thus poor color
results) at a high treat rate. Thus, it can be seen that the
thermally stable, zinc-free, phosphorous-containing antiwear agents
disclosed herein have improved corrosion properties and reduced
sludge formation properties at high treat rates, as compared to
thermally unstable antiwear systems at high treat rates.
[0064] The filterability of the lubricant composition was also
evaluated using the ISO 13357 Filtration Test (Filtration Test).
The test method is as follows: For the dry phase of the test, the
sample is mixed for one minute at 30 times to the snap. For the wet
phase of the test, the sample is mixed and allowed to stand for 24
hours. 350 mL of the sample is then mixed with 0.7 mL Analar water
(0.2% v/v) and placed in an oven for 2 hours at 70.degree. C. The
sample is removed from the oven and stirred at 1500 rpm for 5
minutes. The sample is returned to the oven for 70 hours, removed
from the oven, and placed in a dark cupboard for 24 hours. The
sample is removed from the cupboard and mixed for one minute at 30
times to the snap.
[0065] Prior to filtering, a 0.8 .mu.m filter is preheated for 10
minutes at 70.degree. C. and wetted with the sample composition.
The sample composition is filtered through the filter under
positive pressures of 1 bar (ISO viscosity grades 32 and 46) and 2
bar (ISO viscosity grades 68 and 100). This method is conducted in
triplicate, and the results of the runs are averaged.
[0066] Filterability is expressed as a dimensionless number which
is a ratio (expressed as a percentage) between volumes (Stage 1) or
flow rates (Stage 2) at specified intervals during the test. During
Stage 1, filterability is calculated as a ratio (expressed as a
percentage) between 240 mL and the volume of oil actually filtered
at the time that 240 mL would have theoretically taken to filter
with no plugging of the filter media. Good filterability indicates
that the composition is unlikely to give performance problems in
use, unless fine systems filters are being used.
[0067] During Stage 2, filterability is calculated as a ratio
(expressed as a percentage) between the flow rate near the start of
filtration (between 10 mL and 50 mL) and the flow rate near the end
of filtration (between 200 mL and 300 mL). Stage 2 is considered
the more severe part of the test, as it is sensitive to the
presence of gels and fine silts in the lubricating composition.
Good filterability indicates that the composition is unlikely to
give filtration problems even in the most extreme conditions.
[0068] The minimum values to meet the ISO 13357 Filtration Test are
described in Table 4 below. The results of the ISO 13357 Filtration
Test are shown in Table 4a below.
TABLE-US-00005 TABLE 4 Stage 1 Stage 2 DRY 80% 60% WET 70% 50%
TABLE-US-00006 TABLE 4a Property Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex.
9 Ex. 10 DRY (Stage 1) 85 85.8 91.7 88.6 65.6 91.9 85.8 DRY (Stage
2) 73.7 74.5 78.8 74.8 29 77.8 74.5 WET (Stage 1) 81.1 87.4 82.5
53.1 58.8 82.9 54.7 WET (Stage 2) 59.4 70.4 65.9 *** 32.3 68.7 8.1
*** Test was aborted and no result was obtained.
[0069] As can be seen above, Examples 4, and 5 demonstrated
acceptable Stage 1 and Stage 2 values during both the dry and wet
phases of the Filtration Test. Examples 9 and 10 also demonstrated
acceptable Stage 1 and Stage 2 results during the dry phases, and
Example 9 demonstrated acceptable Stage 1 during the wet phases.
These Examples thus demonstrate that lubricating compositions
comprising the thermally stable, zinc-free, phosphorous-containing
antiwear agents disclosed herein at both low and high treat rates
are not likely to give performance problems.
[0070] However, thermally unstable antiwear systems do not give
acceptable values at high treat rates, as can be seen in Examples 7
and 8. For example, Example 7 failed the wet phase, Stage 1 and
Stage 2 minimum requirements. Moreover, Example 8 failed both
stages of the wet and dry phases, except dry phase, Stage 1.
Therefore, it can be seen that lubricating compositions comprising
the thermally stable, zinc-free, phosphorous-containing antiwear
agents disclosed herein at low and high treat rates are unlikely to
give filtration problems, even in the most extreme conditions, as
compared to thermally unstable antiwear systems.
[0071] For the purposes of this specification and appended claims,
unless otherwise indicated, all numbers expressing quantities,
percentages or proportions, and other numerical values used in the
specification and claims, are to be understood as being modified in
all instances by the term "about." Accordingly, unless indicated to
the contrary, the numerical parameters set forth in the following
specification and attached claims are approximations that can vary
depending upon the desired properties sought to be obtained by the
present disclosure. At the very least, and not as an attempt to
limit the application of the doctrine of equivalents to the scope
of the claims, each numerical parameter should at least be
construed in light of the number of reported significant digits and
by applying ordinary rounding techniques.
[0072] It is noted that, as used in this specification and the
appended claims, the singular forms "a," "an," and "the," include
plural referents unless expressly and unequivocally limited to one
referent. Thus, for example, reference to "an antioxidant" includes
two or more different antioxidants. As used herein, the term
"include" and its grammatical variants are intended to be
non-limiting, such that recitation of items in a list is not to the
exclusion of other like items that can be substituted or added to
the listed items.
[0073] While particular embodiments have been described,
alternatives, modifications, variations, improvements, and
substantial equivalents that are or can be presently unforeseen can
arise to applicants or others skilled in the art. Accordingly, the
appended claims as filed and as they can be amended are intended to
embrace all such alternatives, modifications variations,
improvements, and substantial equivalents.
* * * * *