Field of the Invention
[0001] 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
[0002] 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.
[0003] 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.
[0004] International Application No.
WO0063325 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.
[0005] 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 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
[0006] 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 C
14 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.
[0007] 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 C
14 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.
[0008] 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).
Detailed Description of the Invention
[0009] 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.
[0010] 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
[0011] 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 (mm
2/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 C
6 to C
12 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
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.
[0012] 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
[0013] 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).
[0014] 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 C
14 or greater, such as C
14-C
40, C
14-C
35, C
14-C
30, or C
14-C
25,. 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 less, 10% or less,
5% or less, or even 1% or less) of the alkyl groups contained within the detergent
to be C
8 or greater (such as C
8-C
14, C
10-C
14, or even C
12-C
14). 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% C
20 or greater normal alpha-olefins.
[0015] 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).
[0016] 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.
[0017] 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.
[0018] 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 %.
[0019] 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
[0020] 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
[0021] 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.
[0022] The Carboxylate Index (CI) of the detergent additive can then be calculated from
the following formula:

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;
MW
KOH is the molecular weight of KOH; and
W is the weight of the alkyl-substituted hydroxybenzoate detergent additive.
[0023] 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-substituted
hydroxybenzoate detergent additive present in the composition. This is expressed by
the following formula:

[0024] 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
[0025] 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 100C. 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
[0026] 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 posttreatment
with ethylene carbonate or boric acid, pentaerythritols, phenate-salicylates 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.
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'-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-tert-butylphenol),
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'-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 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 trichlorostearate,
chlorinated naphthalene, fluoroalkylpolysiloxane, and lead naphthenate. A preferred
EP agent is zinc dialkyl dithiophosphate (ZnDTP) as one of the co-additive components
for the antiwear hydraulic fluid composition of the present invention, and is shown
by the general formula:

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.
10. Pour point depressants: polymethacrylate type polymers.
11. Foam inhibitors: alkyl methacrylate polymers and dimethyl silicone polymers
Examples
Emulsification Performance
[0027] 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
[0028] 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 C
20 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
[0029] 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
[0030] 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 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
[0031] 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
[0032] 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
[0033] 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
[0034] 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
[0035] 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.
Table 1
|
Comp. Ex. 1 |
Comp. Ex. 2 |
Comp. Ex. 3 |
Comp. Ex. 4 |
Comp. Ex. 5 |
Ex.1 |
Ex.2 |
56 Cl Ca alkyl-substituted hydroxybenzoate detergent (wt.%) |
- |
0.075 |
0.075 |
0.15 |
0.15 |
0.225 |
0.225 |
28 Cl Ca alkyl-substituted hydroxybenzoate detergent |
0.041 |
- |
- |
- |
- |
- |
- |
(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 at minutes after stirring) |
9 min |
30 min |
40 min |
25 min |
40 min |
40 min |
40 min |
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 |
1CI of antiwear hydraulic fluid composition = (CI of alkyl-substituted hydroxybenzoate
detergent) x (wt. % alkyl-substituted hydroxybenzoate detergent in fluid) |
Rust Inhibition Performance
[0036] 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.
Example 3
[0037] 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
[0038] 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
[0039] 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 C
14 - C
18. The detergent has a TBN of 168 and a CI of 51.
Comparative Example 8
[0040] 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 C
20 - C
28. The detergent has a TBN of 230 and a CI of 46.
Comparative Example 9
[0041] 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 C
20 - C
28. The detergent has a TBN of 325 and a CI of 36.
Comparative Example 10
[0042] 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 C
20 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
[0043] 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.
Table 2
|
Ex.3 |
Comp. Ex. 6 |
Comp. Ex. 7 |
Comp. Ex. 8 |
Comp. Ex. 9 |
Comp. Ex. 10 |
56 Cl alkyl-substituted hydroxybenzoate detergent |
0.075 |
- |
- |
- |
- |
- |
(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 (ASTM D 665B) |
Pass |
Pass |
Fail |
Fail |
Fail |
Fail |
1CI of antiwear hydraulic fluid composition = [CI of alkyl-substituted hydroxybenzoate
detergent] x [wt.% alkyl-substituted hydroxybenzoate detergent in fluid] |
[0044] 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.
[0045] 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 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.
[0046] For the avoidance of doubt, the subject-matter of the present invention includes
subject-matter as defined in the following numbered paragraphs (hereafter "para."):
- 1. An antiwear hydraulic fluid composition comprising (a) a major amount of a base
oil of lubricating viscosity and (b) a minor amount of at least one oil soluble detergent
additive comprising 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 further wherein said antiwear hydraulic fluid composition has a Carboxylate Index
of greater than 0.084.
- 2. The antiwear hydraulic fluid composition according to para. 1, wherein said alkyl-substituted
hydroxybenzoic acid comprises a linear or branched alkyl group or a mixture of linear
and branched alkyl groups.
- 3. The antiwear hydraulic fluid composition according to para. 1 wherein at least
90% of the alkyl groups of said alkyl-substituted hydroxybenzoic acid are C14 or greater.
- 4. The antiwear hydraulic fluid composition according to para. 1 wherein said antiwear
hydraulic fluid composition is able to achieve an emulsion of 0-0-80 at 40 minutes
in the ASTM D 1401 water separability test method.
- 5. The antiwear hydraulic fluid composition according to para. 1, wherein said salt
comprises a calcium salt.
- 6. The antiwear hydraulic fluid composition according to para. 1, wherein said hydraulic
fluid composition comprises no added rust inhibitors.
- 7. The antiwear hydraulic fluid composition according to para. 1, wherein said oil
soluble detergent additive comprises a TBN of less than 200 mg KOH/g.
- 8. The antiwear hydraulic fluid composition according to para. 1, wherein said oil
soluble detergent additive comprises a TBN of less than 160 mg KOH/g.
- 9. The antiwear hydraulic fluid composition according to para. 1, wherein said oil
soluble detergent additive comprises greater than 0.1 weight percent of the total
weight of said antiwear hydraulic fluid composition.
- 10.The antiwear hydraulic fluid composition according to para. 1, wherein said oil
soluble detergent additive comprises greater than 0.2 weight percent of the total
weight of said antiwear hydraulic fluid composition.
- 11.The antiwear hydraulic fluid composition of para. 1 further comprising at least
one of these co-additives: (a) an ashless dispersant; (b) an oxidation inhibitor;
(d) a demulsifier; (e) an extreme pressure agent; (f) a friction modifier; (g) a multifunctional
additive; (h) a viscosity index improver; (i) a pour point depressant; (j) a foam
inhibitor; and (k) an emulsifier..
- 12. An antiwear hydraulic fluid composition comprising (a) a major amount of a base
oil of lubricating viscosity and (b) a minor amount of at least one oil soluble detergent
additive comprising 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 further wherein said antiwear hydraulic fluid composition has a Carboxylate Index
of greater than 0.034.
- 13.The antiwear hydraulic fluid composition according to para. 12, wherein said alkyl-substituted
hydroxybenzoic acid comprises a linear or branched alkyl group or a mixture of linear
and branched alkyl groups.
- 14.The antiwear hydraulic fluid composition according to para. 12 wherein at least
90% of the alkyl groups of said alkyl-substituted hydroxybenzoic acid are C14 or greater.
- 15.The antiwear hydraulic fluid composition according to para. 12 wherein said antiwear
hydraulic fluid composition is able to achieve a pass result in the ASTM D 665 rust
inhibition method.
- 16.The antiwear hydraulic fluid composition according to para. 12, wherein said salt
comprises a calcium salt.
- 17.The antiwear hydraulic fluid composition according to para. 12, wherein said hydraulic
fluid composition comprises no added rust inhibitors.
- 18.The antiwear hydraulic fluid composition according to para. 12, wherein said oil
soluble detergent additive comprises a TBN of less than 200 mg KOH/g.
- 19.The antiwear hydraulic fluid composition according to para. 12, wherein said oil
soluble detergent additive comprises a TBN of less than 160 mg KOH/g.
- 20. The antiwear hydraulic fluid composition according to para. 12, wherein said oil
soluble detergent additive comprises greater than 0.05 weight percent of the total
weight of said antiwear hydraulic fluid composition.
- 21.The antiwear hydraulic fluid composition according to para. 12, wherein said oil
soluble detergent additive comprises greater than 0.07 weight percent of the total
weight of said antiwear hydraulic fluid composition.
- 22.The antiwear hydraulic fluid composition of para. 12 further comprising at least
one of these co-additives: (a) an ashless dispersant; (b) an oxidation inhibitor;
(d) a demulsifier; (e) an extreme pressure agent; (f) a friction modifier; (g) a multifunctional
additive; (h) a viscosity index improver; (i) a pour point depressant; (j) a foam
inhibitor; and (k) an emulsifier.