FUNCTIONAL FLUID COMPOSITION FOR IMPROVING LUBRICITY OF A BRAKING SYSTEM

Info

Publication number: 20090099048
Type: Application
Filed: Oct 10, 2008
Publication Date: Apr 16, 2009
Applicant: Dow Global Technologies Inc. (Midland, MI)
Inventors: Jin Zhao (Midland, MI), Kenn L. Bouchard (Bay City, MI), Tina M. Killebrew (Midland, MI)
Application Number: 12/249,174

Abstract

The functional fluids of the present invention comprise about 50 parts by weight to about 99 parts by weight of a glycol component and about 0.3 parts by weight to about 10 parts by weight of one or more additives including a phosphate content. Desirably, in one aspect of this invention, the functional fluid composition exhibits an average scar width according to ASTM D 2670 (100 lb break-in for 1 min, 200 lb load for 30 minutes) that ranges from about 0.05 mm to about 0.45 mm, an average tooth count according to ASTM D 2670 (100 lb break-in for 1 min, 200 lb load for 30 minutes) of less than about 15, or both.

Description

Description

CLAIM OF PRIORITY

The present application claims the benefit of the filing date of Provisional Application No. 60/979901 (“FUNCTIONAL FLUID COMPOSITION FOR IMPROVING LUBRICITY OF A BRAKING SYSTEM” filed Oct. 15, 2007 by Zhao et. al.), the contents of which are hereby incorporated by reference in their entirety.

FIELD OF THE INVENTION

This invention relates to functional fluids that are useful in a variety of applications. The functional fluids of the present invention are particularly useful as hydraulic fluids such as brake fluids for anti-lock brake systems, stability control systems or regenerative braking systems for automotive vehicles that benefit from lower viscosity fluids for sudden movement (e.g., sudden braking), satisfactory operation, or both at low temperatures.

BACKGROUND OF THE INVENTION

Newly developed equipment such as electronic or automated anti-lock braking systems, stability control systems and regenerative braking systems have created a need for high performance hydraulic fluids (e.g., brake fluids) having appropriate physical and performance properties. In particular, there is a strong demand for high performance brake fluids having high lubricity to reduce or eliminate brake noise, while improving the life of the brake. Additionally, there is a demand for high performance brake fluids having good low temperature viscosities while meeting or exceeding the desired minimum dry equilibrium reflux boiling point (ERBP) and wet equilibrium reflux boiling point (WERBP) temperatures. Illustrations of current international standards for brake fluids are set forth in Table 1 below. Successful candidates for such fluids need to be relatively inexpensive too.

One exemplary solution to providing such desirable functional fluids was introduced in commonly owned U.S. Patent Application Publication 2007/0027039, filed Jun. 29, 2006, titled Low Viscosity Functional Fluids, and incorporated herein by reference for all purposes.

SUMMARY OF THE INVENTION

In one aspect, the invention is directed at a functional fluid composition for imparting lubricity in a fluid power system having metal/rubber contact comprising: about 50 parts by weight to about 99 parts by weight of a glycol component; and about 0.3 parts by weight to about 10 parts by weight of one or more additives including a phosphate content; wherein the functional fluid composition exhibits an average scar width as measured according to ASTM D 2670 (100 lb break-in for 1 min, 200 lb load for 30 minutes) less than about 0.35 mm, an average tooth count according to ASTM D 2670 (100 lb break-in for 1 min, 200 lb load for 30 minutes) of less than about 15, or both, and wherein the functional fluid is optionally free of silicone; wherein the one or more additives includes either or both of a first additive including an ester of phosphoric acid and/or a second additive including an ethoxylated phosphate ester.

TABLE 1 DOT 3, DOT 4 and DOT 5 Brake Fluid Standard Standard FMVSS FMVSS ISO FMVSS ISO 4925 116, SAE 116, SAE 4925 116, ISO 1703, ISO, 1704 4925 4925 Classification (FMVSS, DOT 3 DOT 4 DOT 5.1 SAE) Classification (ISO) Class 3 Class 4 Class 5.1 Class 6 ERBP Min 205° C. Min 230° C. Min Min 260° C. Min 250° C. 205° C. Wet ERBP (3.5% Min 140° C. Min 155° C. Min Min 180° C. Min 165° C. water per FMVSS 116) 155° C. KINEMATIC max. 1500 cSt max. 1800 cSt max. max. 900 cSt Max. 750 cSt VISCOSITIES 1500 cSt at 40° C.

This aspect of the invention may be further characterized by one or any combination of the following features: the first additive consists essentially of a tricresyl phosphate; the second additive includes an ethoxylated phosphate ester selected from the group consisting of a polyoxyethylene octadadecenyl ether phosphate. a polyoxyethylene lauryl ether phosphate, a linear alcohol ethoxy phosphate, a polyethylene phenyl ether phosphate, a dialkylphenol phosphate ester or any combination thereof; the second additive includes a polyethylene glycol phenyl ether phosphate; the second additive consists essentially of a polyethylene glycol phenyl ether phosphate; the first additive exhibits a melting point that ranges from about −45° C. to about −25° C., a boiling point (at 4 mm Hg) that ranges from about 230° C. to about 265° C., a flash point that is at least about 375° C., a specific gravity (at 25° C.) that ranges from about 1.1 to about 1.25, and an acid number of less than about 0.5 mg KOH/kg of the first additive; the second additive exhibits an acid number (KOH to first inflection point) that ranges from about 90 to about 115 mg KOH/kg of the second additive and a nonionic content less than about 15%; the first additive, the second additive, or both is present in the amount of about 0.005 to about 0.7 parts by weight of the fluid composition; the one or more additives includes a corrosion inhibitor that is present in the amount of about 0.5 parts by weight to about 2 parts by weight of the one or more additives; the one or more additives further comprises an antioxidant, an anti-foaming agent, a pH stabilizer, or any combination thereof; the glycol component comprises the formula:

wherein R₁is H or an alkyl group containing 1 to 8 carbon atoms or mixtures thereof, the glycol component including at least one glycol wherein at least one of R₂, R₃, R₄, and R₅is an alkyl group containing 1 to 8 carbon atoms; the glycol component includes at least one glycol wherein R₂, R₃, R₄, and R₅are each H; the glycol component includes at least one glycol having at least one first repeat unit wherein R₂, R₃, R₄, and R₅are each H and at least one second repeat unit wherein at least one (e.g., one, two, three, or all four) of R₂, R₃, R₄, and R₅are each an alkyl group containing 1 to 8 carbon atoms; the at least one glycol include glycol where n=2 is present in an amount of from about 0.25 parts by weight to about 10 parts by weight of the glycol component and glycol where n=4 or more in an amount from about 0 parts by weight to about 30 parts by weight of the glycol component; the composition is substantially free of glycol borate esters; the fluid composition further comprises from about 0.1 parts by weight to about 70 parts by weight of a glycol borate ester comprising the formula:

wherein each R₁R₂, R₃, R₄, and R₅is independently H or an alkyl group containing 1 to 8 carbon atoms or mixtures thereof, n is 1 to 4; the amount of the borate ester with n=3 is greater than about 90 parts by weight of the borate ester, an amount of the borate ester with n=2 is from about 0.5 parts by weight to about 5.0 parts by weight of the borate ester, and an amount of the borate ester with n=4 is from about 0 or 0.1 parts by weight to about 15 parts by weight of the borate ester; the amount of glycol component with n=3 is greater than about 40 parts by weight of the glycol component, an amount of glycol component with n=2 is from about 0.5 parts by weight to about 5.0 parts by weight of the glycol component, and the glycol component with n=4 or more is from about 5 parts by weight to about 15 parts by weight of the glycol component; the glycol component comprises one or more high purity glycol components; about 0.5 parts by weight to about 10 parts by weight of the glycol component has R₁contains 4 carbon atoms and n=2, about 40 parts by weight to about 60 parts by weight of the glycol component has R₁contains 1 carbon atom and n=3, about 5 parts by weight to about 15 parts by weight of the glycol component has R₁contains 4 carbon atoms and n=3, about 5 parts by weight to about 15 parts by weight of the glycol component wherein R₁contains 4 carbon atoms and n=4 or more, about 0.3 parts by weight to about 10 parts by weight of one or more additives including a phosphate content, and the functional fluid composition exhibits either or both of an average scar width according to ASTM D 2670 (100 lb break-in for 1 min, 200 lb load for 30 minutes) that ranges from about 0.1 mm to about 0.3 mm or an average tooth count according to ASTM D 2670 (100 lb break-in for 1 min, 200 lb load for 30 minutes) of less than about 8; the functional fluid composition is free of silicone; the fluid power system is a brake system; the one or more additives further includes at least one corrosion inhibitor, the at least one corrosion inhibitor is present in the amount of about 0.005 to about 5 parts by weight of the additive component.

Another aspect of the invention is directed at an additives package for imparting lubricity in a fluid power system comprising: about 5 parts by weight to about 75 parts by weight of at least one of (i) a first additive including an ester of phosphoric acid and (ii) a second additive including an ethoxylated phosphate ester; about 30 parts by weight to about 99 parts by weight of two or more corrosion inhibitors that includes at least one of (a) propanediamine and xylene, (b) hydroxyethylpiperazine, (c) dodecenyl succinic anhydride, (d) Di-(2-ethylhexyl)phosphoric acid, (e) poly(diethoxysiloxane), (e) oleic acid, and (f) propylene glycol and borax 5 mol component, wherein the first additive exhibits a melting point that ranges from about −45° C. to about −25° C., a boiling point (at 4 mm Hg) that ranges from about 230° C. to about 265° C., a flash point that is at least about 375° C., a specific gravity (at 25° C.) that ranges from about 1.1 to about 1.25, and an acid number of less than about 0.5 mgKOH/kg, wherein the second additive exhibits an acid number (KOH to first inflection point) that ranges from about 90 to about 115 and a nonionic content less than about 15%, and wherein a functional fluid composition includes the additive package, the functional fluid composition exhibits an average scar width according to ASTM D 2670 (100 lb break-in for 1 min, 200 lb load for 30 minutes) of less than about 0.35 mm, an average tooth count according to ASTM D 2670 (100 lb break-in for 1 min, 200 lb load for 30 minutes) of less than about 15, or both.

This aspect of the invention may be characterized by one or any combination of the following features: the first additive consists essentially of a tricresyl phosphate; the second additive consists essentially of a polyethylene glycol phenyl ether phosphate.

A further aspect of the invention is dericted at a functional fluid composition for imparting lubricity in a fluid power system having metal/rubber contact comprising: about 50 parts by weight to about 99 parts by weight of a glycol component; and about 0.3 parts by weight to about 10 parts by weight of one or more additives; wherein the functional fluid is further characterized either or both of the glycol component includes a polyethylene-propylene glycol monomethyl ether having an average molecular weight of about 500 at a concentration from about 10 wt. % to about 30 wt. % based on the total weight of the functional fluid; or the one or more additives includes oleic acid at a concentration from about 0.02 wt. % to about 0.5 wt. % based on the total weight of the functional fluid; wherein the one or more additives optionally contains a polyethylene phenyl ether phosphate, the functional fluid is optionally is free of silicone, the glycol component includes methoxytriglycol present a concentration greater than about 25 wt. % based on the total weight of the functional fluids, and the functional fluid has one or any combination of the following characteristics: an average scar width less than about 0.36 mm, a tooth count less than about 10, an ERBP greater than about 250° C., or a viscosity at −40° C. of less than about 800 cSt.

A process aspect of the invention is direct at method for imparting lubricity comprising the steps of: contacting one or more rubber components of a fluid power system with a functional fluid composition free of silicone and including about 0.3 parts by weight to about 10 parts by weight of one or more additives including a phosphate content, wherein the functional fluid composition exhibits either or both of an average scar width according to ASTM D 2670 (100 lb break-in for 1 min, 200 lb load for 30 minutes) that ranges from about 0.05 mm to about 0.45 mm and/or an average tooth count according to ASTM D 2670 (100 lb break-in for 1 min, 200 lb load for 30 minutes) of less than about 15.

Another aspect of the invention is directed at a braking system which includes a functional fluid composition and/or an additives package as described herein. Such a braking system may further be characterized as being free of a booster.

Yet another aspect of the invention is directed at the use of a functional fluid composition and/or an additives package as described herein in a braking system. Such a braking system may be further characterized as being free of a booster.

DETAILED DESCRIPTION OF THE INVENTION

The present invention contemplates an improved composition possessing a unique combination of attributes that make it suitable as a working fluid in a number of applications, especially in hydraulic fluids applications (e.g., a fluid which is in a sealed and/or closed system in which the fluid may be exposed to temperatures greater than about 50° C., or even greater than about 100° C., and may remain in a liquid state at those temperatures), such as brake fluids. More particularly, the fluid compositions of the present invention employ a glycolic component as its major component and preferably also include one or more additives. Surprisingly, when the compositions are employed as described herein, the fluids exhibit a high lubricity, high dry equilibrium reflux boiling point (ERBP), a low temperature viscosity, a low average scar width as measured according to ASTM D 2670 with a 45.4 kg break-in for 1 minute followed by a 90.9 kg load for 30 minutes, and/or a low average tooth count as measured according to ASTM D 2670 (with a 45.4 kg break-in for 1 minute followed by a 90.9 kg load for 30 minutes (all such properties being in accordance with the preferred properties as described herein). More specifically the present invention employs a glycol component of glycols, alkoxy glycols, or both, and an additive including a phosphate content (such as an ester of phosphoric acid and/or an ethoxylated phosphate ester) that together provide a fluid that can be used as a brake fluid, which meets the provisions for of one or both of DOT 3 or DOT 4 brake fluids under the provisions of the table above. By way of example, unexpectedly good results are believed obtainable (e.g., in a brake fluid composition that may be free of silicone) when employing as a composition of the present invention, in combination with a glycolic major component (e.g., a glycol component including an alkoxyl triglycol such as methoxytriglycol, butoxytriglycol or both, and optionally an alkoxylated polyethylene-propylene glycol and/or an alkoxylated polypropylene glycol), one or both of a first additive including (or consisting essentially of, or even consisting of) an ester of phosphoric acid (e.g., an aromatic phosphate ester such as tricresyl phosphate), or a second additive including (or consisting essentially of, or even consisting of) an ethoxylated phosphate ester (e.g., one that includes an ethoxylated phosphoric ester and/or a propoxylated phosphoric ester, such as polyoxyethylene octadadecenyl ether phosphate, polyoxyethylene lauryl ether phosphate, a linear alcohol ethoxy phosphate, a polyethylene phenyl ether phosphate, a dialkylphenol phosphate ester, or any combination thereof.

The use of an additive including a phosphate content (such as the first additive and/or the second additive), without beyond bound by theory, is believed to improve the lubricity of the fluid and reduce the average scar width and/or reduce the average tooth count. Such additives have been used as working fluids in metal working operations, such as metal rolling and metal forming which are generally performed in open systems where the fluid can expand and the fluid is not exposed to repeated operations (e.g., more than one, two or three forming steps at the same region, and/or the fluid is not exposed repeatedly to temperatures greater than about 50° C. or greater than about 100° C.). Anti-wear additives including a phosphate content have also been used in other applications, such as in refrigerant compositions, which generally contain a high concentration of a refrigerant (e.g., a fluorocarbon containing fluorine, carbon and optionally other atoms such as hydrogen and chlorine, which typically have a boiling point below 60° C., preferably below about 50° C. or even below 30° C.). Refrigerant systems typically operate at relatively low pressures, e.g., less than about 10, 4 or even 2 atmospheres). Functional fluids for systems such as brake systems are very demanding in that the fluid may be repeatedly exposed to high temperatures (e.g., greater than about 60, 80, 100, or even 120° C.) and/or high pressures, greater than about 10, 20, 50, or 100 atmospheres. This is particularly true for glycolic functional fluid compositions as compared with silicone based functional fluid compositions, as the silicone fluids are innately more stable and relatively more expansive. Brake fluids (which are generally free of refrigerants, such as a fluorocarbon containing fluorine, carbon and optionally other atoms) are typically exposed to repeated pressure and/or temperature cycles. The number of cycles may be quite high (e.g., greater than 10, 100, 1000 or even 10000), as the fluid may be replaced only once every year or even less. Additionally, the changes in pressure may be quite sudden (e.g., some or even all of the fluid may increase in pressure from less than 2 atmospheres to greater than 10 atmospheres in a time of less than 1 or even less than 0.1 second). The changes in temperature may also be quite severe, with the temperature sometimes starting near or at ambient conditions (which typically is less than about 30° C., but may be less than about 0° C., or even less than about −30° C.). It is found that the additives containing a phosphate content (as described herein) offer surprising benefits, including wear resistance properties, in a demanding application such as brake fluids which experiences repeated pressure loading and unloading, repeated thermal heating (e.g., due to the friction between a moving component and a braking component). It is believed that these results are unexpected in a glycolic functional fluid (e.g., a fluid which is substantially free, or even entirely free of a refrigerant and/or silicone) used in a brake system which is a closed, sealed system which repeatedly experiences temperature and pressure changes as described above.

Functional fluids of the present invention may comprise one or any combination of the following:

- (a) about 50 parts by weight to about 99 parts by weight, based on the total weight of the composition of a glycol component;
- (b) optionally, about 0 parts by weight to about 70 parts by weight, based on the weight of the total composition, of a glycol borate ester component; and
- (c) about 0.30 parts by weight to about 10 parts by weight, based on the weight of the total composition, of an additive component (e.g., an additive component including a phosphate content).

The glycol component can be formed partially, substantially entirely (at least 90% or at least 95% by weight) or entirely of one, two, three or more glycols, polyglycols, or both. Preferably the glycols or polyglycols of the glycol component have the formula of FORMULA I:

with repeat unit:

Each of R₁, R₂, R₃, R₄, R₅is either hydrogen (H) or an alkyl group containing 1 to 8 or more carbon atoms or mixtures thereof. For example, the glycols or polyglycols may have at least one of R₂, R₃, R₄, R₅is an alkyl group containing 1 to 8 or more carbon atoms, such as one disclosed in Provisional Application Ser. No. 60/976,010 (filed Sep. 28, 2007) titled “Functional Fluid Composition”, which is hereby incorporated by reference for all purposes. It is preferable that R₁be an alkyl group containing 1 to 8 carbon atoms such that glycol or polyglycol is an alkoxy glycol ether (e.g., an alkyl end capped alkoxy glycol ether) as opposed to being simply a glycol where R₁is (H). Typically, R₁is (H) for less than 90%, more typically less than 50% and even possibly less than 30% or 20% by weight of the glycol component, the overall fluid composition, or both. It will be understood that, as used herein, a polyglycol of FORMULA I has n of at least 2 or greater and that the term glycol includes all polyglycols. It should also be understood that the glycol component can include glycols or FORMULA I wherein R₁is an alkyl group and where R₁is H.

The glycols of FORMULA I having n of at least 2 may have repeat units which are the same (e.g., a homopolymer), repeat units which are different (e.g., a copolymer), or a combination thereof. Polyglycol copolymers may include two, three or even four or more different repeat units. A preferred copolymer may contain two different repeat units. Polyglycol copolymers may be characterized as block copolymers, random copolymers, alternating copolymer, or any combination. Block copolymers may include copolymers having one block of each repeat unit, as well as copolymers having a plurality of blocks of one or even each of the repeat units. A block may be defined as a long run of consecutive sequences (e.g., three, four, five, or more) of the same repeat units. Suitable polyglycol copolymer include random copolymers such as a copolymer which is substantially free (e.g., less than about 20 mole %, or even 10 mole % of the repeat units of the copolymer are in blocks) or even entirely free of blocks of long run of consecutive sequences (e.g., three, four, five, or more) of the same repeat units. Without limitation, exemplary glycols include those in which the repeat unit is ethylene oxide (CH₂—CH₂—O), propylene oxide (e.g., CH(CH₃)—CH₂—O or CH₂—CH(CH₃)—O), or combinations thereof.

The glycol component may include an amount of glycol where n=1. When included, such glycol is at least about 5% by weight of the glycol component. Moreover such glycol is typically less than about 30%, more typically less than about 20% and even more typically less than about 15% by weight of the of the glycol component. Preferably, glycols of the glycol component comprise glycols (e.g., alkoxy glycols) where n=2, glycols (e.g., alkoxy glycols) where n=3, glycols (e.g., alkoxy glycols) where n=4 or more, or any mixture thereof. More preferable glycol components may comprise a combination (e.g., a mixture) of glycols (e.g., alkoxy glycols) having n=2, n=3, and n=4 or more. It is also preferred for the glycols wherein n=2 or more to be present in the glycol component and/or the overall functional fluid in an amount that is at least about 50 parts by weight, more typically at least about 60 parts by weight and more typically at least about 75 parts by weight of the glycol component, the overall functional fluid or both. It is also preferred for the glycols wherein n=2 or more to be present in the glycol component and/or the overall functional fluid in an amount that is less than about 99 parts by weight, more typically less than about 90 parts by weight and even more typically less than about 85 parts by weight.

The glycol component typically includes an amount of one or more first glycol (e.g., a first polyglycol) where R₂, R₃, R₄, and R₅are each H. When included, such first glycol is at least about 3%, more typically at least about 10% and even more typically at least about 20% by weight of the glycol component. Moreover such first glycol is typically less than about 80%, more typically less than about 50% and even more typically less than about 30% by weight of the of the glycol component. For such first glycol, n is at least 1, but preferably n is 2 or more. The amount of the first glycol in which n=2 is typically from about 0.25 parts by weight to about 20.00 parts by weight by weight of the first glycol. The amount of the first glycol in which n=3 is typically from about 25.0 parts by weight to about 99.5 parts by weight of the first glycol. The amount of the first glycol in which n=4 is typically from about 0 or 0.1 parts by weight to about 15 parts by weight of the first glycol. Of course, higher or lower amounts of the overall first glycol and the particular amounts of the first glycol having different n values may be employed unless otherwise specified.

The glycol component may optionally include an amount of one or more second glycol (e.g., a second polyglycol) wherein at least one (and preferably only one), but also possibly two, three or all four of R₂, R₃, R₄, and R₅are each an alkyl group containing 1 to 8 carbon atoms. Preferable second glycols (which may be one glycol or a mixture of glycols) include an R₂or R₃group and more preferably include an R₄or R₅group comprising a methyl, an ethyl, a propyl, a butyl, or any combination thereof. Moreover, preferable second glycols include an R₂or R₃group and more preferably include an R₄or R₅group comprising a methyl or an ethyl group. Still more preferable second glycols include an R₂or R₃group and more preferably include an R₄or R₅group comprising a methyl group. When included, such second glycol is at least about 3%, more typically at least about 10% and even more typically at least about 20% by weight of the glycol component. Moreover such second glycol is typically less than about 80%, more typically less than about 50% and even more typically less than about 30% by weight of the of the glycol component. For such second glycol, n is at least 1, but preferably n is 2 or more. The amount of the second glycol in which n=2 is typically from about 0.25 parts by weight to about 10.00 parts by weight by weight of the second glycol. The amount of the second glycol in which n=3 is typically from about 25.0 parts by weight to about 99.5 parts by weight of the second glycol. The amount of the second glycol in which n=4 is typically from about 0 or 0.01 parts by weight to about 15 parts by weight of the second glycol. Of course, higher or lower amounts of the overall second glycol and the particular amounts of the second glycol having different n values may be employed unless otherwise specified.

The glycol component may optionally include an amount of one or more third glycol (e.g., a third polyglycol) that is a copolymer. Such copolymer may be a block copolymer, and/or a random copolymer. Thus, any of the third glycols (which may be one glycol or a mixture of glycols) will typically include one or more first repeat units of FORMULA I having a first configuration and one or more second repeat units having a second configuration. In particular, the third glycol typically includes at least one of first repeat unit of FORMULA I wherein R₂, R₃, R₄, and R₅are each H. The third glycol also typically includes at least one second repeat unit wherein at least one and typically only one, but also possibly two, three or all four of R₂, R₃, R₄, and R₅are each an alkyl group containing 1 to 8 carbon atoms. Preferable second repeat units of the third glycols include an R₂or R₃group and more preferably include an R₄or R₅group comprising a methyl, an ethyl, a propyl, a butyl, or any combination thereof. More preferable second repeat units of the third glycols include an R₂or R₃group and more preferably include an R₄or R₅group comprising a methyl or an ethyl group. Still more preferable second repeat units of the third glycols include an R₂or R₃group and more preferably include an R₄or R₅group comprising a methyl group. When included, such third glycol is at least about 3%, more typically at least about 10% and even more typically at least about 20% by weight of the glycol component. Moreover, such third glycol is typically less than about 80%, more typically less than about 50% and even more typically less than about 30% by weight of the of the glycol component. For such third glycol, n is at least 2 or more. The amount of the third glycol in which n=2 is typically from about 0.25 parts by weight to about 10.00 parts by weight by weight of the third glycol. The amount of the third glycol in which n=3 is typically from about 25.0 parts by weight to about 99.5 parts by weight of the third glycol. The amount of the third glycol in which n=4 is typically from about 0 or 0.01 parts by weight to about 15 parts by weight of the third glycol. Of course, higher or lower amounts of the overall third glycol and the particular amounts of the third glycol having different n values may be employed unless otherwise specified.

Advantageously, use of glycols of each of the types mentioned, but particularly the second glycols and third glycols, surprisingly assist the fluid in achieving various properties. Such properties can include, without limitation, higher boiling points, lower viscosities, greater lubricity, combinations thereof or the like. Preferably the glycol component includes a (e.g., one or more) second glycol, a (e.g., one or more) third glycol, or both. The amount of the second glycol, the third glycol, or the combination of the second glycol and third glycol may be greater than about 5 wt. %, preferably greater than 10 wt. %, and more preferably greater than about 15 wt. % based on the total weight of the fluid composition. The amount of the second glycol, the third glycol, or the combination of the second glycol and third glycol may be less than about 90 wt. %, preferably less than about 70 wt. %, more preferably less than about 50 wt. %, and most preferably less than about 35 wt. % based on the total weight of the fluid composition. Of course, higher or lower amounts of the second glycol, the third glycol, or the combination of the second and third glycol may be employed

Suitable R₁groups of the glycol component are alkyl groups containing from 1 to 8 carbon atoms. Preferable glycol components include an R₁group comprising a methyl, an ethyl, a propyl, a butyl, or any combination thereof.

Without limitation, examples of useful glycols (e.g., alkoxy glycols or otherwise) include methoxy triglycol, methoxy diglycol, methoxy polyglycol, ethoxy triglycol, ethoxy diglycol, ethoxy tetraglycol, propoxy triglycol, butoxy triglycol (e.g., triethylene glycol monobutyl ether), butoxy diglycol (e.g., diethylene glycol monobutyl ether), butoxy teteraglycol, pentoxy diglycol, pentoxy triglycol, 2-ethylhexyl diglycol or any combination thereof.

Preferable glycols (e.g., alkoxy glycols) of the glycol component include, without limitation, methoxy triglycol, methoxy diglycol, methoxy polyglycol, methoxy tetraglycol, ethoxy polyglycol, ethoxy triglycol, ethoxy diglycol, ethoxy tetraglycol, butoxy polyglycol, butoxy triglycol, butoxy diglycol, butoxy tetraglycol, triethylene glycol monohexyl ether, diethylene glycol monopropyl ether, triethylene glycol monopropyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monopropyl ether, tripropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monobutyl ether, polypropylene glycol monobutyl ether, polypropylene glycol monopropyl ether, or any combination thereof. More preferable alkoxy glycol components comprise methoxy triglycol, methoxy diglycol, methoxy polyglycol, butoxy triglycol, butoxy diglycol, butoxy polyglycol, Triethylene glycol monohexyl ether, Diethylene glycol monopropyl ether, Triethylene glycol monopropyl ether, Dipropylene glycol monomethyl ether, dipropylene glycol monopropyl ether, tripropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monobutyl ether, polypropylene glycol monopropyl ether, Polypropylene glycol monobutyl ether or any combination thereof. Most preferable alkoxy glycol components comprise a mixture of two or more of methoxy polyglycol, butoxy diglycol, butoxy triglycol, butoxy polyglycol, triethylene glycol monopropyl ether, tripropylene glycol monopropyl ether, tripropylene glycol monobutyl ether, polypropylene glycol monopropyl ether, or polypropylene glycol monobutyl ether.

Further examples of useful glycols (e.g., alkoxy glycols or the like) include, without limitation, diethylene glycol monopropyl ether, triethylene glycol monopropyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monopropyl ether, tripropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether, tripropylene glycol monobutyl ether, polypropylene glycol monopropyl ether, polypropylene glycol monobutyl ether, polybutylene glycol monopropyl ether, polybutylene glycol monobutyl ether, any combinations thereof or the like.

Without limitation, methods of preparing useful alkoxy glycols include an alkoxilation reaction that reacts an alkylene oxide with an alcohol to produce an alkyl glycol.

In one aspect, use of high purity alkoxy glycols in the glycol component is preferable. For example, by using high purity alkoxy glycol, a suitable low temperature viscosity is achievable. In particular, high purity butoxy triglycol and butoxy diglycol may individually or in combination be used to help maintain the desired low temperature viscosity. In one aspect, high purity alkoxy glycol is at least about 90% pure (i.e., the high purity alkoxy glycol consists of at least about 90 wt. % of molecules having the same molecular structure); at least about 97% pure, or at least about 98% pure. In one preferred embodiment, high purity butoxy triglycol and high purity butoxy diglycol is utilized in the fluid composition and is preferably at least 50% and more preferably at least 75% by weight of the glycol component.

The fluid composition may also include borate ester, but preferably includes no more than about 10 parts by weight of a borate ester (e.g., a glycol borate ester) based on the weight of the fluid composition. Suitable fluid compositions may also be substantially free, or even entirely free of a glycol borate ester. When utilized, the glycol borate ester component preferably includes at least one ingredient that has the formula:

with repeat unit:

where R₁, R₂, R₃, R₄, and R₅can be any of groups as specified with respect to FORMULA I and n can be as specified with respect to FORMULA I, (for example, R₁R₂, R₃, R₄, and R₅may each independently be H or an alkyl group containing 1 to 8 carbon atoms or mixtures thereof, and n may range from 1 to 4). As such, the glycol borate ester component can have any of the repeat units of the first glycol of the glycol component, the second glycol of the glycol component, the third glycol of the glycol component or any combination thereof as discussed with respect to FORMULA I herein. It is also understood that the glycol borate ester component and any borate containing compound is not considered as part of the glycol component, but rather is separate.

Examples of optional glycol borate ester components include alkoxy glycol borate ester components such as methoxy triethylene glycol borate ester, ethoxy triethylene glycol borate ester, butoxy triethylene glycol borate ester or any combination thereof disclosed in U.S. Pat. No. 6,558,569, filed Nov. 10, 2000 (see e.g., column 3, lines 13-40), hereby incorporated by reference. If a borate ester component is present in the composition, it is preferably present in an amount greater than 0.01 or greater than 1 parts by weight of the functional fluid, but it is also preferably present in an amount less than about 10 parts by weight of the functional fluid. More preferably, the borate ester component is present in the composition in an amount less than about 4 parts by weight of the functional fluid. In one embodiment, the functional fluid compositions of the present invention are substantially free (less than about 0.5% by weight of the functional fluid) or entirely free of any borate ester component.

When a glycol borate component is in the composition, it is typically the case that the glycol groups represent a substantial portion of the composition. Such glycol groups, as defined herein, are the portions of FORMULA I and FORMULA II attached to the (H) hydrogen atom or the (B) Boron atom of those formulas. Thus, such glycol groups may be as follows:

These glycol groups can represent at least about 50%, more typically at least about 60%, still more typically at least about 80% and even possibly at least about 90% by weight of the overall composition.

As indicated, the composition of the present invention further contemplates an optional additive package that includes one or more additives having a phosphate content (e.g., at least one phosphate ester) for improving lubricity of a brake system. The additive component additives thus may comprise one or more additives that typically include one or any combination, without limitation corrosion inhibitors, stabilizers such as pH stabilizers, lubricants, anti-wear agents, anti-foaming agents, and antioxidants. The additive component, when present, is typically at least about 0.05 parts by weight, more typically at least about 0.1 parts by weight and even more typically at least about 0.3 parts by weight of the functional fluid. The additive component, when present, is typically less than about 20 parts by weight, more typically less than about 15 parts by weight, and even possibly less than about 10 parts by weight of the functional fluid.

It will be appreciated from the above that the one or more additives herein may have a phosphate content. For example, one preferred approach is to have one or more additives having a phosphate content present in the amount of at least about 0.005, more specifically at least about 0.01, and still more specifically at least about 0.1 parts by weight of the additive component. It is generally expected however that the total concentration of the one or more additives including phosphate will be less than about 0.7, more specifically less than 0.5, and more specifically less than about 0.4 parts by weight of the additive component.

The additives package of the present invention may include from about 5 parts by weight to about 75 parts by weight (e.g., from about 5 wt. % to about 75 wt. % based on the total weight of the additives package) of at least one of (i) a first additive including an ester of phosphoric acid and (ii) a second additive including an ethoxylated phosphate ester and about 30 parts by weight to about 99 parts by weight (e.g., from about 30 wt. % to about 99 wt. % based on the total weight of the additives package) of two or more corrosion inhibitors that includes at least one of (a) propanediamine and xylene, (b) hydroxyethylpiperazine, (c) dodecenyl succinic anhydride, (d) di-(2-ethylhexyl)phosphoric acid, (e) poly(diethoxysiloxane), (e) oleic acid, and (f) propylene glycol and borax 5 mol component.

In one preferred example for use in the additive component, the one or more additives having a phosphate content will include a first additive having a phosphoric ester. The phosphoric ester may be an aromatic phosphate ester, an aliphatic phosphate ester, or a combination thereof, Without limitation, the phosphoric ester may be an aromatic phosphate ester such as a phosphoric acid tris(methylphenyl)ester (e.g., tricresyl phosphate). The first additive may have a specific gravity (at 20° C.) that ranges from about 1.1 to about 1.25 and a flash point of at least about 380° C. (e.g., about 390 to about 430° C. The first additive may exhibit a melting point of less than about −55, and more specifically less than about −45° C. The first additive may also exhibit a melting point of at least about −25, and more specifically at least about −30° C. For example, the melting point may range from about −55 to about −25, and more preferably from about −45 to −30° C. The first additive may exhibit a boiling point (at 4 mm Hg) of at least about 230, and more specifically at least about 240° C. The first additive may also exhibit a boiling point (at 4 mm Hg) of less than about 270, and more specifically less than about 265° C. For example, the boiling point (at 4 mm Hg) may range from about 230 to about 270, and more preferably from about 240 to 265° C. The first additive may exhibit an acid number, e.g., as measured according to ASTM D974-01, of less than about 0.5, more specifically less than about 0.1 mg KOH/kg.

In another preferred example for use in the additive component, the one or more additives having a phosphate content includes a second additive having (or consisting of) an alkoxylated phosphoric ester. Suitable alkoxylated phosphoric esters, without limitation, an ethoxylated phosphoric ester, a propoxylated phosphoric ester, and the like. The alkoxylated phosphoric ester may contain one or more aromatic groups (e.g., phenyl groups). An exemplary ethoxylated phosphoric ester is a polyethylene phenyl ether phosphate. The second additive may have a specific gravity (at 25° C.) that ranges from about 1.1 to about 1.35 and a flash point of at least about 120° C. (e.g., about 130 to about 170° C.). The second additive may exhibit a freezing point of at least about 40, and more specifically at least about 10° C. The second additive may also exhibit a freezing point of less than about −50, and more specifically less than about −20° C. For example, the freezing point may range from about 40 to about −50, and more preferably from about 10 to −20° C. The second additive may exhibit a boiling point (at 760 mm Hg) of at least about 110, and more specifically at least about 140° C. The second additive may also exhibit a boiling point (at 760 mm Hg) of less than about 190, and more specifically less than about 160° C. For example, the boiling point (at 760 mm Hg) may range from about 110 to about 190, and more preferably from about 140 to 160° C. The second additive may exhibit an acid number (KOH to first inflection point), as measured for example according to ASTM D974-01, that ranges from about 90 to about 115, and more preferably from about 90 to about 110. The second additive also may exhibit a nonionic content less than about 15, and more preferably less than about 7%. An exemplary alkoxylated phosphoric ester is a polyethylene phenyl ether phosphate.

Examples of suitable additives having a phosphate content include, without limitation, a polyoxyethylene octadadecenyl ether phosphate (e.g., CAS number 9004-98-2, CAS number 7664-38-2, or LUBRHOPHOS® LB-400 which is commercially available from Rhodia), polyoxyethylene lauryl ether phosphate (e.g., CAS number 39464-66-9 or LUBRHOPHOS® RD-510E which is commercially available from Rhodia), a linear alcohol ethoxy phosphate (e.g., LUBRHOPHOS® LK-500 which is commercially available from Rhodia), a polyethylene phenyl ether phosphate (e.g., CAS No. 39464-69-2) sold under the tradename LUBRHOPHOS® LP-700 which is commercially available from Rhodia), a dialkylphenol phosphate ester (e.g., Rhodefac® RM-510 which is commercially available from Rhodia), or any combination thereof.

It is contemplated that the one or more additives having a phosphate content (e.g., first additive, second additive, or both) may be utilized for improving lubricity (e.g., antiwear properties) for fluid power systems such as one disclosed in U.S. Pat. No. 5,152,926 (filed Sep. 10, 1990, see e.g., col. 3, line 29 to col. 4, line 29), which is hereby incorporated by reference for all purposes, and for brake systems having silicone functional components such as one disclosed in U.S. Pat. No. 4,744,915 (filed Aug. 24, 1987, see e.g., col. 2, lines 53-68), which is hereby incorporated by reference for all purposes. Accordingly, it is appreciated that the present invention may be incorporated into fluid powers systems such as systems that generate, transmit, and control applications of power by using pressurized and moving fluids within an enclosed circuit (e.g., brake systems). Furthermore, it is appreciated that the one or more additives having a phosphate content of the present invention may be incorporated into a functional fluid that includes a silicone content, is essentially free of silicone (e.g., contains silicone at a concentration less than about 5 wt. %, preferably less than about 1 wt. %, more preferably less than about 0.1 wt. %, and most preferably less than about 0.01 wt. % based on the total weight of the functional fluid) or is free of silicone.

The additives having a phosphate content may be phosphate esters, phosphate esters, or both. Examples of suitable phosphate esters include phosphate monoesters, phosphate diesters, phosphate triesters, and any combination thereof. The phosphate ester may include or consist essentially (e.g., contain at least 90 wt %, or at least 95 wt % based on the total weight of the phosphate esters or the phosphate containing additives) of one or more phosphate triesters. The phosphate ester may be substantially or totally free of phosphate triesters and contain phosphate monoesters, phosphate diesters, or both.

U.S. Pat. No. 4,755,316 (filed Oct. 23, 1987) TABLE D lists the following examples of additives having a phosphate content, which may be used in the present functional fluid: phosphates, phosphate esters (bicresyl phosphate), phosphites, thiophosphates (zinc diorganodithiophosphates) chlorinated waxes, and halogen substituted phosphorous compound. Additional examples of additives having a phosphate content include those described in U.S. Pat. No. 5,152,926 (filed Sep. 10, 1990), see e.g., col. 3, line 29 to col. 4, line 29. These additives include: organic phosphates, such as Lubrizol™ 1097 which is a zinc (dialkyl dithio) phosphate manufactured by the Lubrizol Corporation; SYN-O-AD™ 8478, a 70%/30% blend of tri(2,4,6-tri-t-butyl phenyl)phosphate/triphenyl phosphate manufactured by the Stauffer Chemical Company; an ethoxylated phosphate ester (Antara™ LP-700 type), a phosphate alcohol (ZELEC 3337 type), and a zinc dialkyldithiophosphate (e.g., Lubrizol 5139, 5604, 5178, 5186 type). Ethoxylated phosphate esters may be water soluble compositions having a phosphorus content of from about 4 to 10 percent, preferably 5 to 7 percent, such as Antara™LP-700 of GAF (polyoxyethylene phenyl ether phosphate). Additional additives having a phosphate content include those described in U.S. Pat. No. 4,744,915 (filed Aug. 24, 1987), e.g., col. 2, lines 53-68, such as phosphate acid esters, trioctyl phosphate and tricreosol phosphate.

The first additive, the second additive, or both may be present at a concentration greater than about 0.005 parts, preferably greater than 0.010 parts, and more preferably greater than about 0.03 parts by weight of the total fluid composition. The first additive, the second additive, or both may be present at a concentration less than about 2.5 parts, preferably less than 0.7 parts, and more preferably less than about 0.3 parts by weight of the total fluid composition. For example, the first additive, the second additive, or both may be present at a concentration from about 0.005 to about 0.7 parts by weight of the fluid composition.

It is further appreciated the one or more additives may include known corrosion inhibitors such as the alkanol amines or alkyl amines and other organic amines to increase low temperature viscosity of functional fluids (e.g., functional fluids containing borate esters), which in turn leads to the use of more complex and expensive additives such as those disclosed in EP0750033, filed Jun. 20, 1996, incorporated by reference (see, e.g. page 2, lines 55 to page 3, line 56) and EP0617116, filed on Mar. 9, 1994, incorporated by reference (see e.g., page 2, lines 14 to page 3, line 7 and page 4, lines 1-16). By using small amounts of borate esters, the fluid compositions may use known corrosion inhibitors and still achieve the desired low temperature viscosity. In addition, increased amounts of corrosion inhibitors and additives may be used to achieve improved stability or corrosion resistance without sacrificing low viscosity. When included, the corrosion inhibitors may be present in the amount of about 0 or about 0.005 to about 7, and more specifically from about 0.1 to about 5 (e.g., from about 2 to about 4) parts by weight of the additive component.

Examples of corrosion inhibiting agents which may be used include those disclosed in EP Patent No. 0750033 (filed Jun. 20, 1996), such as amines capable especially of neutralizing the boric ester, an amine containing at least one alkyl radical, especially from C1 to C7, or a cyclane radical, especially from C5 to C7, or, again, an alkoxy radical especially from C1 to C6; an ethoxylated amines such as di-n-butylamine, tri-n-butylamine, diisopropanolamine of general formula: HN(CH₂CHOHCH₃)₂, monocyclohexylamine, dicyclohexylamine, 2-amino-1-ethanol, diethanolamine of general formula: HN (CH₂—CH₂OH)₂, monomethanolmonopropylamine of general formula: HN(CH₂OH)(CH₂CH₂CH₃) or diisopropylamine;an N-acyl derivative of sarcosine, for example the N-oleyl acylsarcosine marketed by Ciba Geigy under the name Sarkosyl 0™, benzotriazole, tolyltriazole, triphenyl phosphite, dodecenylsuccinic anhydride, bisphenol A, or polymerized trimethylquinoline.

Additional inhibitors disclosed in EP Patent No. 0617116 (filed Mar. 9, 1994) include ether-amines having a molecular weight between 120 and 300 (preferably between 150 and 250) and having the following formula:

in which R₃is linear or branched radical having at least one ether functional group and no alcohol functional group, R is a methyl radical or a hydrogen atom, p is an integer from 1 to 3 and q is an integer from 0 to 2. The ether-amine used must contain a radical R₃which is a linear or branched radical having at least one ether functional group and no alcohol functional group. Radical R₃is not cyclic. R₃may have the following formula: R₁—O—R₂— in which R₁is a linear or branched alkyl radical preferably having from 1 to 5 carbon atoms and R₂is a linear or branched alkylene radical preferably having from 2 to 8 carbon atoms. The ether-amine comprises at least one and preferably at least 2 units derived from an epoxide. Advantageously, p+q may range from 1 to 3. Some or all of the ether-amine may have p+q=2. Furthermore, it is also advantageous to use a mixture comprising by weight from 85 to 95% of an ether amine having p+q=2 and from 15 to 5% of an ether-amine having p+q=3. The ether-amine is generally obtained by reacting a starting ether-amine, with an epoxide such as, for example, ethylene oxide, propylene oxide or a mixture of the two. The starting ether-amine can have the following general formula (A): R₁—O—R₂—NH₂in which R₁and R₂have the same meaning as above. The ether-amine obtained advantageously contains the amines having the following formula (B):

which R₁, R₂, R, p and q have the same meaning as above (i.e., as for formula (A) above). In practice, a mixture of ether-amines having the formula (B) is obtained. It is desirable to obtain essentially the which R₁, R₂, R, p and q have the same meaning as above. In practice, a mixture of ether-amines having the formula (B) is obtained. It is desirable to obtain essentially the amine having the formula (B) in which p=1 and q=1. An example of a suitable ether-amine is 2,2′-[3(methoxypropyl)imino]bisethanol amine.

Examples of classes of corrosion inhibitors that may be used in the functional fluid compositions of the present invention include fatty acids such as lauric, palmitic, stearic or oleic acids, esters of phosphorus or phosphoric acid with aliphatic alcohols, phosphates or phosphites such as ethyl phosphate, dimethyl phosphate, isopropyl phosphate, butyl phosphite, triphenyl phosphite and diisopropyl phosphite, alkenyl anhydride such as dodecenyl succinic anhydride (DDSA), di-(2-ethylhexyl)phosphoric acid (DEHPA), propanediamine and xylene component (e.g., Dupont Metal Deactivator comprising N,N′ disalicylidene-1,2-propanediamine and xylene), poly(diethoxysiloxane) (e.g., PSI-021), hydroxyethylpiperazine (e.g., dihydroxyethyl piperazine), propylene glycol and borax 5 mol component, heterocyclic nitrogen containing compounds such as benzotriazole or its derivatives or any combination, such compounds optionally with 1,2,4 triazole and/or its derivatives (see U.S. Pat. No. 6,074,992 (e.g., column 2, line 65 to column 3, line 12) filed Feb. 2, 1999 by Pierre Levesque and GB Patent No. British Patent No. 1,111,680 (e.g., page 1, line 10 to page 2, line 8) filed Dec. 1, 1965, by McPhail et. al., both hereby incorporated by reference). Other amine compounds useful as corrosion inhibitors include alkyl amines such as di-n-butylamine and di-n-amylamine, cyclohexylamine and salts thereof. Amine compounds which are particularly useful as corrosion inhibitors in the functional fluid compositions of the present invention include the alkanol amines, preferably those containing one to three alkanol groups with each alkanol group containing from one to six carbon atoms. Examples of useful alkanol amines include mono-, di- and trimethanolamine, mono-, di- and triethanolamine, mono-, di- and tripropanolamine and mono-, di- and triisopropanolamine.

Examples of 1,2,4 triazoles and its derivatives include those listed in U.S. Pat. No. 6,074,992 (column 2, line 65 to column 3, line 12) filed Feb. 2, 1999 by Pierre Levesque, such as 1,2,4 triazole or its derivatives represented by the formula:

wherein R and R′ are the same or different and can be hydrogen, an alkyl group containing from 1 to 8 carbon atoms, an amino group such as —NH, —NHR or —NR R′, an acyl group such as —COR, or an aryl group such as benzene or toluene.

Without limitation, additional examples of 1,2,4 triazoles and its derivatives include those listed in GB Patent No. British Patent No. 1,111,680 (page 1, line 10 to page 2, line 8) filed Dec. 1, 1965, by McPhail et. al. such as 1,2,4-triazoles having the formula

wherein R₁, R₂, R₃and R₄=hydrogen, alkyl, aryl, alkaryl, aralkyl, cycloalkyl, acyl or aroyl, the symbol (R₄) meaning that the substituent R₄is attached to any one of the nitrogen atoms comprising the triazole ring or is a labile substituent if R₄is hydrogen. Thus, the formula recited above embraces, for example, not only 3-substituted- and 3,5-substituted-1,2,4-triazoles, for example 3-amino-1,2,4-triazole, 3-amino-5-heptyl-1,2,4-triazole, but also acylated and aroylated-1,2,4-triazoles which may be

for example benzoylated-5-phenyl-1,2,4-triazole, which may be

The additive components may also advantageously contain, in addition to one or more corrosion inhibitors, other additive compounds such as antifoaming agents, pH stabilizers, antioxidants and the like, all well known to the skilled formulator for enhancing the performance of the functional fluid composition.

It is contemplated that other materials may be formulated into the functional fluids of the present invention so long as care is taken not to lower ERBP or WERBP temperatures and particularly lubricity below acceptable levels or to increase the low temperature viscosity above an acceptable level. For example, the functional fluids of the present invention may include from about 0 or 0.10 parts by weight to about 30 parts by weight, based on the total weight of the composition, of a diluent or a lubricant such as, for example, polyethylene oxides, polypropylene oxides, polyglycols (e.g. mixtures of monoethylene glycol, diethylene gycol, triethylene glycol tetraethylene glycol, and higher mol adducts of ethylene glycol), poly(alkylene oxides) dialkoxyglycols, borate co-esters, or any combination thereof. One preferred lubricant such as a polyalkylene glycol monobutyl ether is present in the amount from about 10 to about 30, and more preferably in an amount of about 15 to about 25 parts by weight of the functional composition. An example of a preferred polyalkylene glycol monobutyl ether (which contains two different alkylene glycol repeat units, oxyethylene and oxypropylene, at about equal weights and n is at least four) is sold under the tradename UCON™ 50-HB-260, commercially available from The Dow Company.

It is also contemplated that the teachings of the present invention could be applied to other fluids formulated to achieve lower viscosities such as those disclosed in U.S. Pat. No. 4,371,448, EP0 750033 and EP0617116 (hereby incorporated by reference for all purposes) to further lubricity while maintaining acceptable minimum ERBP and WERBP temperatures.

The functional fluids of the present invention may meets the needs in the art for high performance functional fluids having high lubricity to reduce or eliminate brake noise, while improving the life of the brake. The functional fluids of the present invention include brake fluids that meet all of the requirements for DOT 3 and DOT 4 fluids given in Federal Motor Vehicle Safety Standards 116, having high boiling points (e.g. ERBP above 203° C. and 230° C., respectively) and also having reduced kinematic viscosity at −40° C., below 1500 cSt and 1800 cSt, respectively. The novel functional fluids of the present invention may meet all of the requirements for DOT 3 and DOT 4 fluids given in Federal Motor Vehicle Safety Standards 116 and have improved lubricity (e.g., antiwear).

Fluid compositions of the present invention have an ERBP of at least about 205° C., preferably at least about 225° C., more preferably at least about 240° C., and most preferably at least about 245° C. The low temperature viscosity at −40° C. of the fluid composition is preferably less than 1500 centistokes (cSt), preferably less than about 1200 or about 1100 centistokes (cSt), more preferably less that about 1000 cSt or about 900 cSt, and possibly less than about 850 cSt.

EXAMPLE FORMULATION

The following example as shown in Table 2 is not intended to be limiting and illustrates a certain preferred embodiment of the present invention. D500 is a polyethylene-propylene glycol monomethyl ether having an average molecular weight of about 500 having n of at least 4, pusher is a mixture of polyethylene glycols having n of at least 4, PSI-021 is a poly(diethoxysiloxane) available from Gelest Inc. (Morrisville, Pa., USA), and Butyl Carbitol™ solvent is a diethylene glycol monobutyl ether available from The Dow Chemical Co. (USA). Intermediate 1 contains about 45 wt. % Butyl Carbitol™ Solvent, about 12.5% monoethylene glycol, about 9.4 wt. % Agerite Resin D, about 1.25 wt. % sodium nitrate, about 0.65 wt. % benzotriazole, and about 31.2 wt. % butyl diethanolamine. Intermediate 2 contains about 88 wt. % propylene glycol and about 12 wt. % sodium borate (e.g., Borax 5 Mol).

By way of example, the functional fluids of Table 2 which include a commercial DOT 3 brake fluid (Comparative Example 1) and newly developed functional fluids (Examples 1-3), are evaluated for lubricity. The lubricity properties of these fluids are shown in Table 3. Table 3 illustrates that Comparative Example 1 has a relatively large scar width and a relatively high average tooth count, indicating low lubricity, while the newly developed fluids (Examples 1-3) have higher lubricity than Comparative Example 1, with Example 1 having the highest lubricity (lowest scar width). Example 1 also has the lowest average tooth count.

TABLE 2 Comparative Ingredient Example 1 Example 1 Example 2 Example 3 Butyl CARBITOL ™ Solvent 2.9000% 2.8942% 2.9000% 2.8942% MTG (methoxytriglycol) 53.1450% 53.0387% 46.0400% 45.9479% BTG (butoxytriglycol) 9.0000% 8.9820% 9.0000% 8.9820% Methoxypolyglycol (MPGr) - refined 12.0000% 11.9760% 12.0000% 11.9760% not basic UCON ® 50 HB-260 20.0000% 19.9600% D500 20.0000% 19.9600% Pusher 7.0000% 6.9860% Intermediate A 1.6000% 1.5968% 1.6000% 1.5968% Intermediate B 0.5900% 0.5888% 0.5900% 0.5888% DDSA (dodecenyl succinic anhydride) 0.1500% 0.1497% 0.1500% 0.1497% DEHPA (di-2-ethyl hexyl phosphoric 0.1000% 0.0998% 0.1000% 0.0998% acid) Dupont metal deactivator 0.0100% 0.0100% 0.0100% 0.0100% PSI-021 (polydiethoxysiloxane) 0.0050% 0.0050% 0.0050% 0.0050% Hydroxyethylpiperazine 0.5000% 0.4990% 0.5000% 0.4990% (dihydroxyethyl piperazine) Oleic acid 0.1050% 0.1048% LUBRHOPHOS ® LP-700 0.2000% 0.2000% Total 100.0000% 100.0000% 100.0000% 100.0000%

TABLE 3 Average Scar Average Fluid Test Condition Width, mm Tooth Count Comparative 45.4 kg break in, 90.9 kg 0.5385 19 Example 1 load for 30 minutes Example 1 45.4 kg break in, 90.9 kg 0.1880 0 load for 30 minutes Example 2 45.4 kg break in, 90.9 kg 0.3350 8 load for 30 minutes Example 3 45.4 kg break in, 90.9 kg 0.2875 5 load for 30 minutes

Lubricity (e.g., antiwear) of functional fluids may be determined using the Falex Pin & Vee Block Test Machine according to a modified ASTM D 2670. By way of example, lubricity is evaluated for compositions of the present invention. For the purposes of this evaluation, a load of 100 lb is applied and maintained for a break in time of 1 minute. The load is increased and maintained at 200 lb for a remaining test duration of 30 minutes. Thereafter, wear is determined and recorded as the measured width of the Vee Block scaring, (e.g., average scar width), the number of teeth of the ratchet mechanism advanced to maintain a constant load during a prescribed test time interval, (e.g., average tooth count), or both. Higher reported numbers (e.g., average scar width and average tooth count) correlate to higher degrees of wear.

The functional fluid of the present invention will impart improved lubricity for a fluid power system as determined from an average scar width according to modified ASTM D 2670 (100 pounds break-in for 1 minute, 200 pounds load for 30 minutes), an average tooth count according to modified ASTM D 2670 (100 lb break-in for 1 min, 200 lb load for 30 mins), or both. The functional fluid may exhibit an average scar width of at least about 0.05, more specifically at least about 0.1 mm. The functional fluid also will exhibit an average scar width less than about 0.45, specifically less than about 0.35, and more specifically less than about 0.3 mm. For example, the average scar width may range from about 0.05 to about 0.45, more specifically from about 0.1 to about 0.3 mm. Furthermore, the functional fluid may exhibit an average tooth count of less than about 15, and more specifically less than about 8.

The formulation for the functional fluids are analyzed to measure the physical properties relating to DOT 3 brake fluid requirements. The physical properties (using the test procedures set forth in the Federal Motor Vehicle Standard 116 found at §571.116 et seq.) are shown in Table 4. It is also surprisingly seen in Example 2 and Example 3 that a polyethylene-propylene glycol monoalkyl ether (e.g., a polyethylene-propylene glycol monomethyl ether having an average molecular weight of about 500) such as D500 (e.g., at a concentration from about 10 wt. % to about 30 wt. %, more preferably from about 17 wt. % to about 23 wt. % based on the total weight of the functional fluid), a monounsaturated fatty acid such as oleic acid (e.g., at a concentration from about 0.02 wt. % to about 0.5 wt. %, preferably from about 0.08 wt. % to about 0.15 wt. % based on the total weight of the functional fluid) or both may also be used in combination with methoxy triglycol preferably at a concentration greater than about 25 wt. %, more preferably from about 40 wt. % to about 60 wt. % (and preferably in combination with an ethoxylated phosphate ester, and more preferably in combination with a polyethylene phenyl ether phosphate such as LUBRHOPHOS® LP-700) in functional fluids having one or any combination of the following characteristics: an average scar width less than about 0.36 mm, a tooth count less than about 10, an ERBP greater than about 250° C., or a viscosity at −40° C. of less than about 800 cSt (preferably less than about 780 cSt).

TABLE 4 Comparative Exam- Example 1 ple 1 Example 2 Example 3 ERBP, ° C. 249 249 253 253 Viscosity @−40° C., cSt 821 821 776.7 777

Functional fluids of the present invention are well suited for use as a hydraulic fluid for numerous mechanical systems (e.g., hydraulic lifts, cranes, forklifts, bulldozers, hydraulic jacks, brake systems, combinations thereof, or the like). The high lubricity as well as ERBP, WERBP, and low temperature viscosity of these fluid compositions are well-suited for brake systems in transportation vehicles (e.g., fixed and rotary wing aircraft, trains, automobiles in classes 1 to 8, or the like). These braking systems include anti-lock braking systems (ABS), stability control systems, or combinations thereof. Thus, the present invention includes any of these systems which include the fluid compositions disclosed herein.

Traditional automotive brake systems include a depression mechanism operably connected to a master cylinder, a pneumatic or hydraulic booster, brake lines, and a braking mechanism. To operate the brakes, an operator presses the depression mechanism and the master cylinder applies a pressure to the brake fluid that is transmitted through the brake lines to the braking mechanism that at least partially resists the motion of the wheel or wheels. Traditional brake systems require a booster pump to increase the pressure applied to the brake fluid to adequately operate the braking mechanism (e.g., to avoid a collision, when one or more wheels is slipping on a road surface, or combinations thereof due to the high viscosity of traditional brake fluids.

Brake systems of the present invention may include low viscosity functional fluids described above, traditional higher viscosity brake fluids, or any combination thereof. Preferred brake systems include brake fluids that consist essentially of the low viscosity functional fluids described above. Furthermore, brake systems of the present invention may optionally include a booster pump (e.g. a pre-charge booster pump); however, the booster pump is preferably not included in the brake system as the use of the presently disclosed brake fluid may make the booster pump extraneous. Exclusion of the booster pump would represent a cost savings over systems where a booster pump was required.

It should be understood that various ingredients may be substituted, added, or removed from the above formulations without departing from the scope of the present invention. Moreover, it is contemplated that the weight concentrations of the above ingredients and the values of the properties listed may vary up to or greater than 5%, 10%, 25%, or 50% of the values listed. For example, a value of 10 may vary by 10%, which may result in a range of about 9 to about 11.

It will be further appreciated that functions or structures of a plurality of components or steps may be combined into a single component or step, or the functions or structures of one-step or component may be split among plural steps or components. The present invention contemplates all of these combinations. Unless stated otherwise, dimensions and geometries of the various structures depicted herein are not intended to be restrictive of the invention, and other dimensions or geometries are possible. Plural structural components or steps can be provided by a single integrated structure or step. Alternatively, a single integrated structure or step might be divided into separate plural components or steps. In addition, while a feature of the present invention may have been described in the context of only one of the illustrated embodiments, such feature may be combined with one or more other features of other embodiments, for any given application. It will also be appreciated from the above that the fabrication of the unique structures herein and the operation thereof also constitute methods in accordance with the present invention. The present invention also encompasses intermediate and end products resulting from the practice of the methods herein. The use of “comprising” or “including” also contemplates embodiments that “consist essentially of” or “consist of” the recited feature.

The explanations and illustrations presented herein are intended to acquaint others skilled in the art with the invention, its principles, and its practical application. Those skilled in the art may adapt and apply the invention in its numerous forms, as may be best suited to the requirements of a particular use. Accordingly, the specific embodiments of the present invention as set forth are not intended as being exhaustive or limiting of the invention. The scope of the invention should, therefore, be determined not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. The disclosures of all articles and references, including patent applications and publications, are incorporated by reference for all purposes.

Claims

1. A functional fluid composition for imparting lubricity in a fluid power system having metal/rubber contact comprising:

about 50 parts by weight to about 99 parts by weight of a glycol component; and

about 0.3 parts by weight to about 10 parts by weight of one or more additives including a phosphate content;

wherein the functional fluid composition exhibits an average scar width as measured according to ASTM D 2670 (100 lb break-in for 1 min, 200 lb load for 30 minutes) less than about 0.35 mm, an average tooth count according to ASTM D 2670 (100 lb break-in for 1 min, 200 lb load for 30 minutes) of less than about 15, or both, and

wherein the functional fluid is optionally free of silicone;

wherein the one or more additives includes (i) a first additive including an ester of phosphoric acid, (ii) a second additive including an ethoxylated phosphate ester, or (iii) both (i) and (ii).

2. The functional fluid composition of claim 1, wherein the first additive consists essentially of a tricresyl phosphate.

3. The functional fluid composition of claim 2, wherein the second additive includes an ethoxylated phosphate ester selected from the group consisting of a polyoxyethylene octadadecenyl ether phosphate. a polyoxyethylene lauryl ether phosphate, a linear alcohol ethoxy phosphate, a polyethylene phenyl ether phosphate, a dialkylphenol phosphate ester or any combination thereof.

4. The functional fluid composition of claim 3, wherein the second additive includes a polyethylene glycol phenyl ether phosphate.

5. The functional fluid composition of claim 3, wherein the second additive consists essentially of a polyethylene glycol phenyl ether phosphate.

6. The functional fluid composition of claim 3, wherein the first additive exhibits a melting point that ranges from about −45° C. to about −25° C., a boiling point (at 4 mm Hg) that ranges from about 230° C. to about 265° C., a flash point that is at least about 375° C., a specific gravity (at 25° C.) that ranges from about 1.1 to about 1.25, and an acid number of less than about 0.5 mg KOH/kg of the first additive.

7. The functional fluid composition of claim 3, wherein the second additive exhibits an acid number (KOH to first inflection point) that ranges from about 90 to about 115 mg KOH/kg of the second additive and a nonionic content less than about 15%.

8. The functional fluid composition of claim 3, wherein the first additive, the second additive, or both is present in the amount of about 0.005 to about 0.7 parts by weight of the fluid composition.

9. The functional fluid composition of claim 3, wherein the one or more additives includes a corrosion inhibitor that is present in the amount of about 0.5 parts by weight to about 2 parts by weight of the one or more additives.

10. The functional fluid composition of claim 6, wherein the glycol component comprises the formula: wherein R1 is H or an alkyl group containing 1 to 8 carbon atoms or mixtures thereof, the glycol component including at least one glycol wherein at least one of R2, R3, R4, and R5 is an alkyl group containing 1 to 8 carbon atoms.

11. The functional fluid composition according to claim 10, wherein the glycol component includes at least one glycol having at least one first repeat unit wherein R2, R3, R4, and R5 are each H and at least one second repeat unit wherein at least one (e.g., one, two, three, or all four) of R2, R3, R4, and R5 are each an alkyl group containing 1 to 8 carbon atoms.

12. The functional fluid composition according to claim 10 wherein the at least one glycol include glycol where n=2 is present in an amount of from about 0.25 parts by weight to about 10 parts by weight of the glycol component and glycol where n=4 or more in an amount from about 0 parts by weight to about 30 parts by weight of the glycol component.

13. The functional fluid composition according to claim 10 wherein the composition is substantially free of glycol borate esters.

14. The functional fluid composition according to claim 10 further comprising from about 0.1 parts by weight to about 70 parts by weight of a glycol borate ester comprising the formula: wherein each R1 R2, R3, R4, and R5 is independently H or an alkyl group containing 1 to 8 carbon atoms or mixtures thereof, n is 1 to 4.

15. The functional fluid composition according to claim 10 wherein the glycol component comprises one or more high purity glycol components.

16. The functional fluid composition according to claim 10 wherein:

about 0.5 parts by weight to about 10 parts by weight of the glycol component has R1 contains 4 carbon atoms and n=2;

about 40 parts by weight to about 60 parts by weight of the glycol component has R1 contains 1 carbon atom and n=3;

about 5 parts by weight to about 15 parts by weight of the glycol component has R1 contains 4 carbon atoms and n=3;

about 5 parts by weight to about 15 parts by weight of the glycol component wherein R1 contains 4 carbon atoms and n=4 or more;

about 0.3 parts by weight to about 10 parts by weight of one or more additives including a phosphate content,

wherein the functional fluid composition exhibits an average scar width according to ASTM D 2670 (100 lb break-in for 1 min, 200 lb load for 30 minutes) that ranges from about 0.1 mm to about 0.3 mm, an average tooth count according to ASTM D 2670 (100 lb break-in for 1 min, 200 lb load for 30 minutes) of less than about 8, or both.

17. The functional fluid composition according to claim 10, wherein the functional fluid composition is free of silicone.

18. The functional fluid composition according to claim 10, wherein the fluid power system is a brake system.

19. An additives package for imparting lubricity in a fluid power system comprising:

about 5 parts by weight to about 75 parts by weight of at least one of (i) a first additive including an ester of phosphoric acid and (ii) a second additive including an ethoxylated phosphate ester;

about 30 parts by weight to about 99 parts by weight of two or more corrosion inhibitors that includes at least one of (a) propanediamine and xylene, (b) hydroxyethylpiperazine, (c) dodecenyl succinic anhydride, (d) Di-(2-ethylhexyl)phosphoric acid, (e) poly(diethoxysiloxane), (e) oleic acid, and (f) propylene glycol and borax 5 mol component,

wherein the first additive exhibits a melting point that ranges from about −45° C. to about −25° C., a boiling point (at 4 mm Hg) that ranges from about 230° C. to about 265° C., a flash point that is at least about 375° C., a specific gravity (at 25° C.) that ranges from about 1.1 to about 1.25, and an acid number of less than about 0.5 mgKOH/kg,

wherein the second additive exhibits an acid number (KOH to first inflection point) that ranges from about 90 to about 115 and a nonionic content less than about 15%, and

wherein a functional fluid composition includes the additive package, the functional fluid composition exhibits an average scar width according to ASTM D 2670 (100 lb break-in for 1 min, 200 lb load for 30 minutes) of less than about 0.35 mm, an average tooth count according to ASTM D 2670 (100 lb break-in for 1 min, 200 lb load for 30 minutes) of less than about 15, or both.

20. The additive package of claim 19, wherein the first additive consists essentially of a tricresyl phosphate.

21. The additive package of claim 20, wherein the second additive consists essentially of a polyethylene glycol phenyl ether phosphate.

22. A method for imparting lubricity comprising the steps of:

contacting one or more rubber components of a fluid power system with a functional fluid composition free of silicone and including about 0.3 parts by weight to about 10 parts by weight of one or more additives including a phosphate content, wherein the functional fluid composition exhibits an average scar width according to ASTM D 2670 (100 lb break-in for 1 min, 200 lb load for 30 minutes) that ranges from about 0.05 mm to about 0.45 mm, an average tooth count according to ASTM D 2670 (100 lb break-in for 1 min, 200 lb load for 30 minutes) of less than about 15, or both.

23. A functional fluid composition for imparting lubricity in a fluid power system having metal/rubber contact comprising:

about 50 parts by weight to about 99 parts by weight of a glycol component; and

about 0.3 parts by weight to about 10 parts by weight of one or more additives;

wherein the functional fluid is further characterized either or both of i) the glycol component includes a polyethylene-propylene glycol monomethyl ether having an average molecular weight of about 500 at a concentration from about 10 wt. % to about 30 wt. % based on the total weight of the functional fluid; or ii) the one or more additives includes oleic acid at a concentration from about 0.02 wt. % to about 0.5 wt. % based on the total weight of the functional fluid;

wherein the one or more additives optionally contains a polyethylene phenyl ether phosphate, the functional fluid is optionally is free of silicone, the glycol component includes methoxytriglycol present a concentration greater than about 25 wt. % based on the total weight of the functional fluids, and the functional fluid has one or any combination of the following characteristics: an average scar width less than about 0.36 mm, a tooth count less than about 10, an ERBP greater than about 250° C., or a viscosity at −40° C. of less than about 800 cSt.