Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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ANTIWEAR HYDRAULIC FLUID COMPOSITION WITH USEFUL EMULSIFYING
AND RUST PREVENTION PROPERTIES
Field of the Invention
The present invention relates to detergents utilized in antiwear hydraulic
fluid
compositions. In particular, the present invention relates to antiwear
hydraulic fluid
compositions which can be useful for certain mobile equipment applications
(e.g.,
hydraulic fluids for construction equipment).
Background of the Invention
Hydraulic fluids need to protect equipment from rust. To achieve this they are
formulated with rust inhibitors. Typical rust inhibitors are metal sulfonates
or succinic
acid derivatives. Hydraulic fluids are also typically designed to separate
readily from
water (demulsify). Often, metallic rust inhibitors act to improve the
demulsifying
characteristics of the fluids.
Japanese Patent Publication No. JP1999311187A describes a composition
containing (A) a base fluid of a sulfur content of up to 100 ppm, (B) 0.2-1
wt. % of zinc
dithiophosphate, (C) 0.2-1 wt. % of an alkaline earth metal salt of salicylic
acid and
(D) 0.001-0.5 wt. % of a water-separating agent.
International Application No. W00063325 describes a hydraulic fluid
comprising lubricant base fluid, 0.001-5 wt.% of magnesium salicylate and 0.01-
8
wt.% of zinc dithiophosphate. The hydraulic fluid composition also comprises a
rust
inhibitor. This publication also discloses the combination of a calcium
salicylate, zinc
dithiophosphate, and a rust inhibitor.
The above publications describe compositions incorporating a metal salt of an
alkyl salicylate, zinc dithiophosphate, and a rust inhibitor. Typically such
compositions
also include demulsifiers to facilitate the separation of water from the
fluid. However,
there is a need in some cases to have hydraulic fluids which emulsify, rather
than
demulsify, water.. These include fluids with enhanced detergent and dispersant
characteristics (e.g., so called HLPD and HVLPD fluids as defined by the
German DIN
51 502 standard) and hydraulic fluids for certain mobile equipment
applications (e.g.,
hydraulic fluids for Caterpillar equipment, building machinery, excavators,
hydraulic
hoists, lifting platforms, presses, and the like), wherein water separated
from the fluid
may not be adequately removed from the equipment leading to poor lubrication.
Engine
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fluids, which are typically formulated with large amounts of dispersants, are
a way to
provide these emulsifying characteristics. Hydraulic fluids with certain
sulfonate
detergents can also have these characteristics.
Summary of the Invention
One aspect of this invention is an antiwear hydraulic fluid composition
comprising a major amount of a base fluid of lubricating viscosity and a minor
amount
of at least one oil soluble detergent additive. This detergent additive
comprises a salt
of an alkyl-substituted hydroxybenzoic acid or a sulfurized derivative
thereof, wherein
said salt is selected from the group consisting of alkali metal salts,
alkaline earth
metal salts, ammonium salts or substituted ammonium salts, and wherein at
least
90% of the alkyl groups of said alkyl-substituted hydroxybenzoic acid are C14
or
greater. Furthermore, the antiwear hydraulic fluid composition is able to able
to
achieve an emulsion of 0 ml of fluid, 0 ml of water and 80 ml of emulsion
(abbreviated
0-0-80) for 30 minutes or more, preferably 40 minutes or more in the ASTM D
1401
water separability test method, and the antiwear hydraulic fluid composition
has a
Carboxylate Index of greater than 0.084.
Another aspect of this invention is an antiwear hydraulic fluid composition
comprising a major amount of a base fluid of lubricating viscosity and a minor
amount
of at least one oil soluble detergent additive. This detergent additive
comprises a salt
of an alkyl-substituted hydroxybenzoic acid or a sulfurized derivative
thereof, wherein
said salt is selected from the group consisting of alkali metal salts,
alkaline earth
metal salts, ammonium salts or substituted ammonium salts, and wherein at
least
90% of the alkyl groups of said alkyl-substituted hydroxybenzoic acid are C14
or
greater. Furthermore, the hydraulic fluid composition is able to achieve a
"pass"
result in the ASTM D 665 rust inhibition test method, and the antiwear
hydraulic fluid
composition has a Carboxylate Index of greater than 0.034.
Surprisingly, we have found that salts as described above exhibit excellent
emulsifying and rust inhibition characteristics. This combined performance is
unexpected when compared to other detergents. One advantage of the present
invention is the reduction or removal of conventional rust inhibitors, such as
metallic
naphthalene sulfonic acid salts, (e.g., NA-SUL from King Industries).
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Detailed Description of the Invention
Antiwear hydraulic fluids are used in hydraulic systems to prevent wear in
mechanical equipment in hydraulic systems, for example, to prevent wear on
moving
metal on metal surfaces, such as steel on steel surfaces. Antiwear hydraulic
fluids
are useful, for example, in preventing wear in a variety of pumps, including
but not
limited to, vane pumps, piston pumps, and gear pumps, commonly used in
hydraulic
systems. Antiwear hydraulic fluids also provide protection for other parts of
the
hydraulic system such as motors, actuators, and pistons. Antiwear hydraulic
fluids
typically contain antiwear additves or extreme pressure agents, such as zinc
dialkyl
dithiophosphate.
The antiwear hydraulic fluid of the present invention exhibits several
performance features in addition to antiwear protection, in particular
emulsification
and rust protection. In addition, the antiwear hydraulic fluid of the present
invention
exhibits good oxidation stability, good filterability, good thermal stability,
low internal
friction, and good hydrolytic stability.
Base Oil of Lubricating Viscosity
The base oil of lubricating viscosity employed in the present invention may be
mineral oil or synthetic oils. A base oil having a viscosity of at least 10
cSt (mm2/s) at
40 C. and a pour point below 20 C., preferably at or below 0 C. is desirable.
The base
oils may be derived from synthetic or natural sources. Mineral oils for use as
the base
oil in this invention include, for example, paraffinic, naphthenic and other
fluids that
are ordinarily used in lubricating oil compositions. Synthetic oils include,
for example,
both hydrocarbon synthetic oils and synthetic esters and mixtures thereof
having the
desired viscosity. Hydrocarbon synthetic oils may include, for example, liquid
polymers having the proper viscosity prepared from the polymerization of
ethylene or
higher alpha olefins (polyalphaolefin or PAO), or from hydrocarbon synthesis
procedures using carbon monoxide and hydrogen gases such as in a Fisher-
Tropsch
process. Especially useful are the hydrogenated liquid oligomers of C6 to C12
alpha
olefins such as 1 -decene trimer. Likewise, alkyl benzenes of proper
viscosity, such as
didodecyl benzene, can be used. Useful synthetic esters include the esters of
monocarboxylic acids and polycarboxylic acids, as well as mono-hydroxy
alkanols
and polyols. Typical examples are didodecyl adipate, pentaerythritol
tetracaproate, di-
2-ethylhexyl adipate, dilaurylsebacate, and the like. Complex esters prepared
from
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mixtures of mono and dicarboxylic acids and mono and dihydroxy alkanols can
also
be used. Blends of mineral oils with synthetic oils are also useful. For
example,
blends of 10 wt % to 25 wt % hydrogenated 1-decene trimer with 75 wt % to 90
wt %
150 SUS (100F.) mineral oil make excellent lubricating oil bases.
The base oil of the present invention is present in a "major amount." A "major
amount" of a base oil of lubricating viscosity refers to a concentration of
the oil within
the hydraulic fluid composition of at least about 40 wt %. In some
embodiments, "a
major amount" of a base oil of lubricating viscosity refers to a concentration
of the oil
within the hydraulic fluid composition of at least about 50 wt %, at least
about 60 wt
%, at least about 70 wt %, at least about 80 wt %, or at least about 90 wt %.
Detergent additive
As discussed previously, the antiwear hydraulic fluid composition employed in
the present invention comprises at least one suitable detergent additive that
is oil
soluble. Such detergent additives comprise any suitable carboxylate-containing
detergents, including alkyl-substituted hydroxybenzoates and sulfurized
derivatives
thereof, wherein the Total Base Number ("TBN") of the detergent additive is
typically
less than 200 mg KOH/g, and preferably less than 160 mg KOH/g. The term "Total
Base Number" or "TBN" refers to the equivalent number of milligrams of KOH
needed
to neutralize 1 gram of a product. Therefore, a high TBN reflects strongly
overbased
products and, as a result, a higher base reserve for neutralizing acids. The
TBN of a
product can be determined by ASTM Standard No. D 2896 or equivalent procedure.
An overbased detergent can be any detergent in which the TBN of the additive
has
been increased by a process such as the addition of a base source (such as
lime)
and an acidic overbasing compound (such as carbon dioxide).
It is preferred that for at least 75% (such as at least 80%, at least 85%, at
least
90%, at least 95%, or at least 99%) of the alkyl groups contained within the
detergent
(such as the alkyl groups of a carboxylate-containing detergent, or of an
alkyl-
substituted hydroxybenzoic acid) to be C14 or greater, such as C14-C40, C14-
C35, C14-
C30, or C14-C25,. In some embodiments, at least 75% (such as at least 80%, at
least
85%, at least 90%, at least 95%, or at least 99%) of the alkyl groups
contained within
the detergent, with the remainder (such as 25% or less, about 20% or less, 15%
or
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less, 10% or less, 5% or less, or even 1 % or less) of the alkyl groups
contained within
the detergent to be C8 or greater (such as C8-C14, C10-C14, or even C12-C14).
In one
preferred embodiment, the detergent comprises a salt of an alkyl-substituted
hydroxybenzoic acid that is derived from an alkyl-substituted hydroxybenzoic
acid in
which the alkyl groups are the residue of normal alpha-olefins containing at
least 90%
C20 or greater normal alpha-olefins.
In another embodiment, the detergent comprises a carboxylate salt, such as a
salt (e.g., an overbased salt) of an alkyl-substituted hydroxybenzoic acid, or
even an
alkali metal or an alkaline earth metal salt, or an ammonium and substituted
ammonium salt of an alkyl-substituted hydroxybenzoic acid. In another
embodiment,
the detergent comprises an overbased salt (such as an overbased alkaline earth
metal salt) of a mixture of alkyl-substituted hydroxybenzoic acid and alkyl-
substituted
phenol. In another embodiment, the detergent comprises an overbased salt of an
alkyl-substituted hydroxybenzoic acid and/or an overbased salt of an alkyl-
substituted
phenol, in combination or mixture with a non-overbased salt of one or more of:
an
alkyl-substituted hydroxybenzoic acid and an alkyl-substituted phenol. In
another
embodiment, the antiwear hydraulic fluid composition comprises one or more
detergents comprising an overbased salt of an alkyl-substituted hydroxybenzoic
acid
and no other overbased salts (other than the salt of the detergent). The
detergent
additive, in this regard, can comprise any suitable concentration of anion
(e.g.,
organic anion) associated with the carboxylate salt (or salt of the alkyl-
substituted
hydroxybenzoic acid).
Some non-limiting examples of other suitable detergents which may be used in
combination with alkyl-substituted hydroxybenzoates include alkyl or alkenyl
aromatic
sulfonates, borated sulfonates, sulfurized or unsulfurized metal salts of
multi hydroxy
alkyl or alkenyl aromatic compounds, alkyl or alkenyl hydroxy aromatic
sulfonates,
sulfurized or unsulfurized alkyl or alkenyl naphthenates, metal salts of
alkanoic acids,
metal salts of an alkyl or alkenyl multiacid, and chemical and physical
mixtures
thereof. Other non-limiting examples of suitable detergent additives include
metal
sulfonates, salicylates, phosphonates, thiophosphonates and combinations
thereof.
The metal can be any metal suitable for making sulfonate, salicylate or
phosphonate
detergents. Non-limiting examples of suitable metals include alkali metals,
alkaline
metals and transition metals. In some embodiments, the metal is Ca, Mg, Ba,
Sr, K,
Na, Li or the like.
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The detergent additive employed in the present invention is generally soluble
in oil as characterized by the following test: A mixture of a 600N oil and the
additive at
a content of 10% by weight with respect to the total weight of the mixture is
centrifuged at a temperature of 60 C and for 30 minutes, the centrifugation
being
carried out under the conditions stipulated by the standard ASTM D2273 (it
should be
noted that centrifugation is carried out without dilution, i.e. without adding
solvent);
immediately after centrifugation, the volume of the deposit which forms is
determined;
if the deposit is less than 0.05% v/v (volume of the deposit with respect to
the volume
of the mixture), the product is considered as soluble in oil.
The aforementioned oil soluble detergent additive in the antiwear hydraulic
fluid composition of the present invention has a TBN typically less than 200
mg
KOH/g, and preferably less than 160 mg KOH/g. In the antiwear hydraulic fluid
composition of the present invention, the concentration of the oil soluble
detergent
additive itself will generally range from an amount of between about 0.05 wt %
to
about 0.3 wt%, and preferably about 0.07 wt% to about 0.25 wt %, based on the
total
weight of the hydraulic fluid composition. Alternatively speaking, the
detergent
additive of the present invention is present in a "minor amount." A "minor
amount" of
detergent additive refers to a concentration of the detergent additive within
the
hydraulic fluid composition of less than about 60 wt %. In some embodiments, a
"minor amount" of detergent additive refers to a concentration of the
detergent
additive within the hydraulic fluid composition of less than about 50 wt%, of
less than
about 30 wt %, of less than about 10 wt %, of less than about 1 wt %, or of
less than
about 0.5 wt %.
Generally speaking, detergents help control varnish, ring zone deposits, and
rust by keeping insoluble particles in colloidal suspension. Metal-containing
(or ash-
forming detergents) function both as detergents to control deposits, and as
acid
neutralizers or rust inhibitors, thereby reducing wear and corrosion and
extending
equipment life. Detergents generally comprise a polar head with a long
hydrophobic
tail; with the polar head comprising a metal salt of an acidic organic
compound. The
salts may contain a substantially stoichiometric amount of the metal in which
case
they are usually described as normal or neutral salts.
Alkyl-substituted hydroxybenzoate detergent additive component
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The detergent additives in the antiwear hydraulic fluid composition of the
present invention can be characterized by the amount of potassium hydroxide
equivalent to the amount of alkyl-substituted hydroxybenzoate (also referred
to herein
as a salt of an alkyl substituted hydroxybenzoic acid), or a sulfurized
derivative
thereof, present in the detergent expressed as mg KOH/g detergent and referred
to
as the Carboxylate Index (CI). Thus, a detergent additive with 56 mg KOH
equivalent
hydroxyphenyl carboxylate per gram of detergent would have a CI of 56 and
would be
referred to as 56 CI alkyl-substituted hydroxybenzoate.
Determination of the Carboxylate Index of a Detergent Additive and of an
Antiwear
Hydraulic Fluid Composition
The alkyl-substituted hydroxybenzoate detergent additive is dissolved in an
organic solvent and washed three times with equal volumes of a dilute, strong
acid
solution. The aqueous layers are collected. The combined aqueous layers are
washed with an organic solvent. The aqueous layer is removed and the organic
layers are combined and subsequently washed with distilled water. The aqueous
layer is decanted. The acidified extract is treated with pyridine and titrated
with dilute,
standardized base.
The Carboxylate Index (CI) of the detergent additive can then be calculated
from the
following formula:
CI = (V1 X C X MWKOH)/W
wherein
V1 is the volume required to reach the first end point in the titration curve;
C is the concentration of the dilute, standardized base;
MWKOH is the molecular weight of KOH; and
W is the weight of the alkyl-substituted hydroxybenzoate detergent additive.
Once the CI of the detergent additive has been calculated, the CI of the
antiwear
hydraulic fluid composition can be readily determined from the amount of the
alkyl-
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substituted hydroxybenzoate detergent additive present in the composition.
This is
expressed by the following formula:
CI of antiwear hydraulic fluid composition = (CI of alkyl-substituted
hydroxybenzoate
detergent) x (wt. % alkyl-substituted hydroxybenzoate detergent in fluid)
In one embodiment of the invention, the CI of the antiwear hydraulic fluid
composition
is greater than 0.084, preferably greater than 0.10, and more preferably
greater than
0.12. In another embodiment of the invention, the CI of the antiwear hydraulic
fluid
composition is greater than 0.034, and more preferably greater than 0.04.
Concentrate Formulation
The oil soluble detergent additive of the present invention can be employed as
a concentrate which will typically contain a sufficient amount of an organic
liquid
diluent and the oil soluble detergent additive employed in the present
invention. The
concentrates contain sufficient organic liquid diluent to make them easy to
handle
during shipping and storage. Typically, the concentrate will contain from
about 10 wt
% to 90 wt %; preferably, from about 20 wt % to 70 wt %; and more preferably,
from
about 20 wt % to 35 wt %, of a compatible organic liquid diluent. Suitable
organic
liquid diluents which can be used include, for example, paraffinic base oils
such as
solvent refined 100N, e.g., Cit-Con 100N, and hydrotreated 100N, e.g., Chevron
100N, and the like. The organic liquid diluent preferably has a viscosity of
from about
1 to 20 cSt at 1000. From about 10 wt % to 90 wt %; preferably, from about 30
wt %
to 80 wt % of the concentrate is the oil soluble additive employed in the
present
invention.
Other Additive Components
The following additive components are examples of some of the components
that can be favorably employed in the present invention. These examples of
additives
are provided to illustrate the present invention, but they are not intended to
limit it:
1. Dispersants: 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, phenate-
salicylates
and their post-treated analogs, alkali metal or mixed alkali metal, alkaline
earth metal
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borates, dispersions of hydrated alkali metal borates, dispersions of alkaline-
earth
metal borates, polyamide ashless dispersants and the like or mixtures of such
dispersants.
2. Anti-oxidants: Anti-oxidants reduce the tendency of mineral oils to
deteriorate in
service which deterioration is evidenced by the products of oxidation such as
sludge
and varnish-like deposits on the metal surfaces and by an increase in
viscosity.
Examples of anti-oxidants useful in the present invention include, but are not
limited
to, phenol type (phenolic) oxidation inhibitors, such as 4,4'-methyl ene-
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'-butyl idene-bis(3-
methyl-6-tert-
butylphenol), 4,4'-isopropyl idene-bis(2,6-d i-tert-butyl phenol), 2,2'-
methylene-bis(4-
me- thyl-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-I-
dimethylamino-p-cresol, 2,6-di-tert-4-(N,N'-dimethylamino- methylphenol), 4,4'-
thiobis(2-methyl-6-tert-butylphenol), 2,2'-th iobis(4-methyl-6-tert-butyl
phenol), 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 Ciba-Geigy), metal dithiocarbamate (e.g., zinc
dithiocarbamate), and methylenebis(dibutyldithiocarbamate).
3. Antiwear agents: As their name implies, these agents reduce wear of moving
metallic parts. Examples of such agents include, but are not limited to,
phosphates,
phosphites, carbamates, esters, sulfur containing compounds, and molybdenum
complexes.
4. Emulsifiers: Linear alcohol ethoxylates, including TERGITOL 15-S-3
available
from the Dow Chemical Company.
5. Demulsifiers: addition product of alkylphenol and ethylene oxide,
polyoxyethylene
alkyl ether, and polyoxyethylene sorbitan ester.
6. Extreme pressure agents (EP agents): zinc dialkyldithiophosphate (primary
alkyl,
secondary alkyl, and aryl type), sulfurized oils, diphenyl sulfide, methyl
trichIorostearate, chlorinated naphthalene, fluoroalkylpolysiloxane, and lead
naphthenate. A preferred EP agent is zinc dialkyl dithiophosphate (ZnDTP) as
one
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of the co-additive components for the antiwear hydraulic fluid composition of
the
present invention, and is shown by the general formula:
R1 S
\11
P- S Zn
R2 /
2
wherein, R1 and R2 are each a primary or secondary alkyl group having a carbon
number of 1 to 18, and may be the same or different. The primary or secondary
alkyl
groups of R1 and R2 having a carbon number of 1 to 18, shown by the general
formula, include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, 2-ethyl
hexyl, octyl,
nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl,
heptadecyl, and octadecyl. However, the preferable zinc dialkyl
dithiophosphate for
the antiwear hydraulic fluid of the present invention has a mixed alkyl group
of
primary and secondary alkyl groups having a carbon number of 3 to 12. A more
preferable zinc dialkyl dithiophosphate for the antiwear hydraulic fluid
composition of
the present invention has a primary alkyl group having a carbon number of 3 to
12.
The zinc dialkyl dithiophosphates having a mixed alkyl group of primary and
secondary alkyl groups may be used either individually or in combination for
the
antiwear hydraulic fluid composition of the present invention. The zinc
dialkyl
dithiophosphate is incorporated at 0.01 to 0.50 wt. % as phosphorus derived
therefrom, based on the whole composition, preferably 0.02 to 0.04 wt. %.
7. Friction modifiers: fatty alcohol, fatty acid, fatty ester amine, borated
ester, and
other esters.
8. Multifunctional additives: sulfurized oxymolybdenum dithiocarbamate,
sulfurized
oxymolybdenum organo phosphorodithioate, oxymolybdenum monoglyceride,
oxymolybdenum diethylate amide, amine-molybdenum complex compound, and
sulfur-containing molybdenum complex compound.
9. Viscosity index improvers: polymethacrylate type polymers, ethylene-
propylene
copolymers, styrene-isoprene copolymers, hydrogenated styrene-isoprene
copolymers, polyisobutylene, and dispersant type viscosity index improvers.
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10. Pour point depressants: polymethacrylate type polymers.
11. Foam inhibitors: alkyl methacrylate polymers and dimethyl silicone
polymers
Examples
Emulsification Performance
A base-line formulation was prepared and used for assessing the performance
of the detergent in Example 1 in the ASTM D 1401 water separability test. The
base-
line formulation contained 0.31 wt. % of a zinc dialkyldithiophosphate, 0.15
wt. % of a
hindered phenol antioxidant, 0.044 wt. % of a succinate ester dispersant,
0.044 wt. %
of a fatty ester friction modifier, 0.013 wt. % of an arylpolyol demulsifier
and 0.008 wt.
% of a foam inhibitor in a base fluid containing Shell HVI basestocks. All
finished
fluids in these Examples are ISO VG 46 with 8 wt. % of a polyalkyl
methacrylate
viscosity index improver.
Example 1
An antiwear hydraulic fluid composition was prepared consisting of the
baseline formulation above with the addition of 0.225 wt. % of an overbased
calcium
alkyl-substituted hydroxybenzoate detergent wherein at least 90% of the alkyl
groups
are C20 or greater and 0.06 wt. % of the succinate ester dispersant. The
overbased
calcium alkyl-substituted hydroxybenzoate detergent was prepared according to
the
method described in Example 1 of US Patent Application 2007/0027043 and has a
calcium content of 5.35 wt. %, a TBN of 150 and a CI of 56.
Example 2
An antiwear hydraulic fluid composition was prepared in accordance with the
formulation of Example 1 except that 0.01 wt. % of a linear alcohol ethoxylate
emulsifier and 0.16 wt% zinc dialkyl dithiophosphate was added.
Comparative Example 1
An antiwear hydraulic fluid composition was prepared consisting of the base-
line formulation above with the addition of 0.041 wt. % of an overbased,
sulfurized
alkyl-substituted hydroxybenzoate-containing detergent, 0.024 wt. % of an
overbased
calcium phenate, 0.027 wt. % of a naphthalene sulfonic acid zinc salt rust
inhibitor
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and 0.008 wt. % of a phenolic resin demulsifier. The overbased, sulfurized
carboxylate-containing detergent was prepared according to the method
described in
Example 16 of US Patent Number 5808145 and has a calcium content of 9.3 wt. %,
a
sulfur content of 2.4 wt. %, a TBN of 260 and a CI of 28.
Comparative Example 2
An antiwear hydraulic fluid composition was prepared consisting of the
baseline formulation above with the addition of 0.075 wt. % of the 56 CI
overbased
calcium alkyl-substituted hydroxybenzoate as described in Example 1.
Comparative Example 3
An antiwear hydraulic fluid composition was prepared in accordance with the
formulation of Comparative Example 2 except that 0.06 wt. % of the succinate
ester
dispersant was added.
Comparative Example 4
An antiwear hydraulic fluid composition was prepared consisting of the
baseline formulation above with the addition of 0.15 wt. % of the 56 CI
overbased
calcium alkylhydroxybenzoate as described in Example 1.
Comparative Example 5
An antiwear hydraulic fluid composition was prepared in accordance with the
formulation of Comparative Example 4 except that 0.06 wt. % of the succinate
ester
dispersant was added.
Results for emulsification performance test
The water separability of antiwear hydraulic fluids is characterized in the
ASTM
D 1401 test method. In this method, a 40 mL volume of the sample material was
emulsified with a 40 mL volume of distilled water by stirring the combined
liquids in a
graduated cylinder at 54 C for 5 minutes. The separation of the emulsion into
organic
and aqueous layers was characterized by monitoring the relative volumes of the
respective fluid, water and emulsion layers after cessation of stirring.
Results are set
forth below in Table 1 as the respective mL fluid-mL water-ml- emulsion
observed at
minutes after cessation of stirring.
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Comp. Comp. Comp. Comp. Comp. Ex.1 Ex.2
Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex.5
56 Cl Ca alkyl-substituted hydroxybenzoate - 0.075 0.075 0.15 0.15 0.225 0.225
detergent (wt.%)
28 Cl Ca alkyl-substituted hydroxybenzoate 0.041 - - - - - -
detergent
(wt. %)
Cl of antiwear hydraulic fluid composition 0.011 0.042 0.042 0.084 0.084 0.126
0.126
Dispersant 0.044 0.044 0.1 0.044 0.1 0.1 0.1
Zinc dialkyl dithiophosphate 0.31 0.31 0.31 0.31 0.31 0.31 0.47
Rust inhibitor 0.027 - - - - - -
Demulsifier 0.008 - - - - - -
Emulsifier - - - - - - 0.01
ASTM D 665B 40-40-0 44-36-0 40-32-8 42-38-0 0-10-70 0-0-80 0-0-80
(mL fluid-mL water-mL emulsion 9 min 30 min 40 min 25 min 40 min 40 min 40 min
at minutes after stirring) 40-40-0 46-34-0 40-38-2 43-37-0 0-16-64 0-0-80 0-0-
80
9 min 35 min 40 min 27 min 40 min 40 min 40 min
Table 1
1CI of antiwear hydraulic fluid composition = (CI of alkyl-substituted
hydroxybenzoate
detergent) x (wt. % alkyl-substituted hydroxybenzoate detergent in fluid)
Rust Inhibition Performance
A base-line formulation was prepared and used for assessing the performance
of various detergents in the ASTM D 665 rust prevention test. The base-line
formulation contained 0.31 wt. % of a zinc dialkyldithiophosphate, 0.15 wt. %
of a
hindered phenol antioxidant, 0.044 wt. % of a succinate ester dispersant,
0.044 wt. %
of a fatty ester friction modifier, 0.013 wt. % of an arylpolyol demulsifier,
0.008 wt. %
of a phenolic resin demulsifier, 0.2 wt. % of a pour point depressant and
0.008 wt. %
of a foam inhibitor in a base oil containing ExxonMobil AP/E CORE basestocks.
All
finished fluids in these Examples are ISO VG 68.
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Example 3
An antiwear hydraulic fluid composition was prepared consisting of the
baseline formulation above with the addition of 0.075 wt. % of the 56 CI
overbased
calcium alkyl-substituted hydroxybenzoate detergent as described in Example 1.
Comparative Example 6
An antiwear hydraulic fluid composition was prepared consisting of the
baseline formulation above with the addition of 0.041 wt. % of the 28 CI
overbased,
sulfurized, alkyl-substituted hydroxybenzoate-containing detergent as
described in
Comparative Example 1, 0.024 wt. % of an overbased calcium phenate and 0.027
wt.
% of a naphthalene sulfonic acid zinc salt rust inhibitor.
Comparative Example 7
An antiwear hydraulic fluid composition was prepared consisting of the
baseline formulation above with the addition of 0.067 wt. % of an overbased
calcium
alkyl-substituted hydroxybenzoate detergent wherein at least 90% of the alkyl
groups
are C14 - C18 . The detergent has a TBN of 168 and a CI of 51.
Comparative Example 8
An antiwear hydraulic fluid composition was prepared consisting of the
baseline formulation above with the addition of 0.049 wt. % of an overbased
calcium
alkyl-substituted hydroxybenzoate detergent wherein at least 90% of the alkyl
groups
are C20 - C28. The detergent has a TBN of 230 and a CI of 46.
Comparative Example 9
An antiwear hydraulic fluid composition was prepared consisting of the
baseline formulation above with the addition of 0.035 wt. % of an overbased
calcium
alkyl-substituted hydroxybenzoate detergent wherein at least 90% of the alkyl
groups
are C20 - C28. The detergent has a TBN of 325 and a CI of 36.
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Comparative Example 10
An antiwear hydraulic fluid composition was prepared consisting of the
baseline formulation above with the addition of 0.032 wt. % of an overbased
calcium
alkyl-substituted hydroxybenzoate detergent wherein at least 90% of the alkyl
groups
are C20 or greater. The overbased calcium alkyl-substituted hydroxybenzoate
detergent is prepared according to the method described in Example 1 of US
Patent
Application 2007/0027043 and has a calcium content of 12.5 wt. %, a TBN of 350
and
a CI of 37.
Results for rust inhibition performance test
Rust inhibition of antiwear hydraulic fluids was determined using ASTM D 665,
which is incorporated herein by reference. ASTM D 665 is directed at a test
for
determining the ability of fluid to aid in preventing the rusting of ferrous
parts should
water become mixed with the fluid. For the determining the rust prevention
properties
in the instant invention, Procedure B of ASTM D 665 was employed. In this
test, a
mixture of 300 mL of the test fluid is stirred with 30 mL of synthetic sea
water at a
temperature of 60 C with a cylindrical steel specimen completely immersed
therein
for 24 hours. The rust test results are reported as either a "pass" or a
"fail." The
results are presented in Table 2.
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Table 2
Ex.3 Comp. Comp. Comp. Comp. Comp.
Ex.6 Ex.7 Ex.8 Ex.9 Ex.10
56 Cl alkyl-substituted hydroxybenzoate 0.075 - - - - -
detergent
(wt. %)
28 Cl alkyl-substituted hydroxybenzoate - 0.041 - - - -
(wt. %)
51 Cl alkyl-substituted hydroxybenzoate - - 0.067 - - -
(wt. %)
46 Cl alkyl-substituted hydroxybenzoate - - - 0.049 - -
(wt. %)
36 Cl alkyl-substituted hydroxybenzoate - - - - 0.035 -
(wt. %)
37 Cl alkyl-substituted hydroxybenzoate - - - - - 0.032
(wt. %)
Cl of antiwear hydraulic fluid composition 0.042 0.011 0.034 0.023 0.013 0.012
Rust Inhibitor (wt. %) - 0.027 - - - -
Rust Inhibition Result Pass Pass Fail Fail Fail Fail
(ASTM D 665B)
'Cl of antiwear hydraulic fluid composition = [CI of alkyl-substituted
hydroxybenzoate
detergent] x [wt.% alkyl-substituted hydroxybenzoate detergent in fluid]
The alkyl-substituted hydroxybenzoate from Example 3 demonstrated
unexpected rust inhibiting performance when compared to other
carboxylate/salicylate detergents (Comparative Examples 2-5) and also
demonstrated unexpected rust inhibiting performance when compared to a
formulation containing a rust inhibitor (Comparative Example 6). The
formulation of
Example 3 advantageously does not require the addition of a rust inhibitor in
order to
pass this test.
As discussed previously, it is advantageous in certain hydraulic fluid
applications, such as hydraulic fluids for certain mobile equipment
applications and
HLPD and HLVPD fluids, to emulsify water, rather than to demulsify water.
Since the
alkyl-substituted hydroxybenzoate from Example 1 also demonstrated good rust
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inhibition without the need for a metal sulfonate rust inhibitor and since
metal
sulfonate rust inhibitors are known to demulsify water, the alkyl-substituted
hydroxybenzoate used in Example 1 provides additional performance advantages
for
such emulsifying hydraulic fluids.
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