EP2099885A2

EP2099885A2 - A fluid composition having excellent fire-resistance

Info

Publication number: EP2099885A2
Application number: EP07874159A
Authority: EP
Inventors: John N Sherman
Original assignee: BASF Corp
Current assignee: BASF Corp
Priority date: 2006-12-05
Filing date: 2007-12-03
Publication date: 2009-09-16
Also published as: WO2008143648A4; WO2008143648A2; KR20090096452A; CN101573432A; JP2010511774A; US20080132436A1; CA2671287A1; WO2008143648A3

Abstract

A fluid composition includes a poly(alkylene glycol) present in an amount of greater than 85 parts by weight based on the total weight of the fluid composition, and a sterically hindered ester present in an amount of from 0.5 up to 15 parts by weight based on the total weight of the fluid composition. The sterically hindered ester, present in the amount of from 0.5 up to 15 parts by weight based on the total weight of the fluid composition, provides the fluid compositions with excellent fire resistance, without adversely affecting other physical properties of the fluid compositions such as hydrolytic stability. More specifically, the sterically hindered ester has a higher fire point (Fp) than the poly(alkylene glycol), which typically sufficiently lowers the S.F.P. of the fluid composition to allow the fluid composition to rate as a Factory Mutual Approved Fluid.

Description

A FLUID COMPOSITION HAVING EXCELLENT FIRE-RESISTANCE

1. Field of the Invention

[0001] The present invention generally relates to a fluid composition for use in industrial fluid applications. More specifically, the present invention relates to a fluid composition for use as hydraulic, compressor, gear, bearing or turbine fluid compositions where excellent fire resistant is required.

2. Background of the Invention [0002] In many industry segments fires caused by the ignition and subsequent combustion of fluid compositions used in the industry are a serious hazard. This typically occurs where the fluid compositions are subjected to sufficiently high temperatures exist so as to ignite the fluid compositions. [0003] Fire-resistant fluid compositions are used in industries where the fluid compositions are in close proximity to high temperature surfaces or other sources of ignition, and thereby a danger to human life. These specialized fluids are also used where mechanical fire suppression measures are not practical or in combination with mechanical fire suppression systems for more comprehensive protection. In general industrial applications where fire hazards exist, the use of fire-resistant fluid compositions at some level is typically a requirement for obtaining insurance for the industrial facility.

[0004] A major category of fluid compositions requiring excellent fire-resistance are hydraulic fluid compositions due to the fact that these fluids are under pressure in hydraulic systems and may contact ignition sources while in the form of an atomized spray, which is a highly combustable liquid form. Fire-resistant fluid compositions are also required for other categories of fluid compositions including gear, compressor, and turbine fluid compositions.

[0005] Common basestocks used for fire-resistant fluid compositions include esters, poly(alkylene glycols), vegetable oils, and phosphate esters. Fluid compositions including poly(alkylene glycols) find particular use in lubrication applications for compressors, gears, bearings, hydraulic and turbine systems. The fluid compositions typically include the poly(alkylene glycols) in amounts greater the 85 parts by weight of the fluid compositions, based on the total weight of the fluid compositions. Esters are another class of components that are known for use in lubrication applications for compressors, pumps, and hydraulic machinery. The esters have been used as an alternative to the fluid compositions including poly(alkylene glycols). [0006] Several industries have created their own standards regarding the fire resistance of hydraulic fluid compositions, including Factory Mutual Research Corporation (FMRC), which is now known as FM Global. FM Global certifies fluids as fire-resistant according to their approval standard CN 6930, and FM Global certification is a widely accepted standard within industry. For example, FM Global certification of a fire-resistant hydraulic fluid composition is generally a requirement for sale to most industrial facilities in the U.S.A. with potential fire hazards. If applicable, the use of FM Global certified fire-resistant hydraulic fluid compositions is generally a requirement for obtaining insurance for the facility.

[0007] The standard by which FM Global certifies fire-resistant hydraulic fluid compositions has recently changed. The original FMRC, in their standard CN 6930 - 1975, required the hydraulic fluid composition to pass a spray flammability test and a hot channel ignition. In response to the revised FM Global approval standard CN 6930 - 1975, formulators of ester based compositions determined that addition of a viscosity modifier additives to a ester-based formulation would enable the fluid

composition to be approved according to the CN 6930 standard, whereas the same

formulation without the viscosity modifier would not be approved. However,

improvement in fire resistance due to the viscosity modifier additive was contingent

on the viscosity modifier additive maintaining relatively high molecular weight,

which was impossible in industrial applications for more than a short period due to the

mechanical shearing of the fluid composition under normal usage, which the viscosity

modifier was particularly sensitive to. The use of anti-mist additives to obtain FM

Global approval according to CN 69230 with poly(alkylene glycol) based

compositions was demonstrated in U.S. Patent 5,141,663 Miller. Anti-mist additives,

like viscosity index modifiers, are high molecular weight compounds that increase the

droplet size of the fluid composition under the conditions of the CN 6930 - 1975

standard, which allowed the fluid to pass the tests and obtain the approval. [0008] In 2002 FM Global published the revised CN 6930 standard, which replaced

the old standard and redefined the requirements for the flammability classification

rating of industrial fluids intended for use as, but not limited to, lubricants, hydraulic power transmission, turbine governor control, transformer insulation and cooling.

The revised standard classified the fire resistance of fluids by their Spray

Flammability Parameter (S.F.P.) value. S.F.P. is a calculated value derived by

evaluation of the flammability characteristics of the fluid. The S.F.P. is calculated

according to equation (1) as follows:

c_{F P} _ (11.02 ^χ l0⁶) x (g_c,) .

° ^• " ^•* ^•! Normalized) ~ _{/ \ / \ / \} ^ '

(p_f ) ^χ (q_cr) ^χ (^mf )

wherein Q_ch is a chemical heat release rate,

Pf is a density of the fluid composition, q_cr is a critical heat flux for ignition, and nif is a fluid mass flow rate during measurement of the chemical heat release rate.

[0009] The S.F.P. is obtained by determination of the chemical heat release rate (Q_Ch) of a finely atomized spray of the fluid composition using a Factory Mutual

10,00OkW- Scale Fire Products Collector located at FM Global. The critical heat flux for ignition (q_cr ) for the fluid composition is obtained through determination of a fire point of the fluid composition using the fire point value obtained from equation 2 as follows: q_cr = a x σ x T_f ⁴ (2)

wherein q_cr is the same as set forth above, a is absorptivity of the fluid composition (assumed to be 1 ), σ is the Stefan-Boltzmann constant (5.67 x 10"¹ * kW/m²K⁴), and Tf is the fire point of the fluid composition (° K). [0010] The spray flammability parameter (S.F.P.) may be estimated, as stated in the FM Global approval standard; CN 6930 (revised January 2002), by using equation 3 as follows:

_ 1.94 χ l0¹⁷ χ ΔH_r ,

° -^r -^r -(Estimated) ~ _ 4 V P)

P/ ^{x T}f

wherein S.F.P., p/, and 7/are the same as set forth above, and ΔΗj is the net heat of combustion.

[0011] Using the S.F.P. values determined for fluid compositions, FM Global categorizes fluids as Group 0, 1, and 2, with Group 0 being the most fire-resistant and Group 2 the least fire-resistant. The specific standards, as of January of 2002, are illustrated in greater detail below in Table 1.

Table 1

[0012] Calculations for determining S.F.P. are rounded to the nearest whole number. For example, an S.F.P. of 5.8 X 10 ⁴ is rounded up and reported as 6 X 10⁴. An S.F.P. of 5.5 X 10⁴ is rounded down and reported as 5 X 10⁴.

[0013] The new CN6930 standard of 2002 eliminated the means by which anti-mist and viscosity modifier additives had been used to obtain approval under the previous CN 6930 - 1975 standard. Due to their high carbon contents and low fire points, many poly(alkylene glycol) and ester-based compositions that were approved under the previous CN 6930 - 1975 standard could only obtain the Group 2 rating under the new CN 6930 standard of 2000. Although the density of the fluid composition remains a factor, the two key properties upon which the S.F.P. is mainly derived are the chemical heat release rate (Q_Ch) and the critical heat flux (q_cr), as set forth above. The chemical heat release rate (Q_Ch) is based on the carbon content of the fluid and therefore difficult to change, whereas the critical heat flux (q_cr) is directly related the fire point (Tf) of the fluid composition and can be modified.

[0014] As such, it became advantageous to lower the S.F.P. of the fluid compositions including the poly(alkylene glycols) by adding other components to the fluid compositions to increase the fire point (Tf), resulting in an increase in critical heat flux

(q_cr) and decrease in S.F.P. For example, PCT Application No. WO 01/90232 to Totten et al. discloses the addition of antioxidants to a fluid composition including poly(alkylene glycol) in order to decrease the S.F.P. It is well known in the art that poly(alkylene glycol)s have very limited thermal oxidative stability and that antioxidants are required for all high performing fluid compositions based on poly(alkylene glycol), regardless of whether or not the fluid compositions are to be used in applications where fire-resistance is important. Although the antioxidants are able to decrease the S.F.P. of the poly(alkylene glycol) to a certain point, it must be noted that the equation used in Totten et al. to obtain the reported S.F.P. s, and also the S.F.P. ranges used to classifiy the groups, have been changed by FM Global, with the result that the reported fire points of all but one of the examples given in Totten et al. resulting in a less fire-resistant classification than reported in Totten et al.

[0015] In May of 2004 FM Global changed the S.F.P. classifications for Standard CN 6930 to two categories; "FM Approved", which is more fire resistant, and "specification tested", which is less fire resistant. The new classifications are illustrated in greater detail in Table 2. Table 2

[0016] Limited applications have combined poly(alkylene glycols) and sterically hindered esters together in the same fluid composition. More specifically, sterically hindered esters have been used in poly(alkylene glycol)-based compressor lubricants as a sludge inhibitor. For example, U.S. Patent No. 4,302,343 to Carswell et al. discloses a compressor lubricant including from 15 to 45 parts by weight of a hindered ester, and from 55 to 85 parts by weight of a poly(alkylene glycol). The ester has sufficient high temperature stability to inhibit the formation of sludge and thus to extend the useful life of the compressor lubricant. However, esters are subject to hydrolytic instability, and the presence of esters in the compressor fluid in the amounts set forth in Carswell et al. would cause an increase in the blend viscosity, thus necessitating the use of a lower viscosity poly(alkylene glycol) to maintain the same viscosity grade for the fluid composition. The lower viscosity and thus lower molecular weight poly(alkylene glycol) will have a lower fire point, thus counteracting any improvement in fire point gained by the inclusion of the ester. Therefore, such high amounts of ester in fluid compositions would be undesirable for many applications, especially applications in which hydrolytic stability and fluid viscosity are important. [0017] Due to the deficiencies of the prior art, it would be desirable to provide a fluid composition having greater than 85 parts by weight of a poly(alkylene glycol) that is formulated to reduce the S.F.P. of the fluid compositions to levels that, to date, have not been attainable with such high amounts of poly(alkylene glycol), even with the addition of antioxidants.

SUMMARY OF THE INVENTION AND ADVANTAGES

[0018] The subject invention provides a fluid composition comprising a poly(alkylene glycol) present in an amount of greater than 85 parts by weight based on the total weight of the fluid composition, and a sterically hindered ester present in an amount of from 0.5 up to 15 parts by weight based on the total weight of the fluid composition.

[0019] The sterically hindered ester, present in the amount of from 0.5 up to 15 parts by weight based on the total weight of the fluid composition, provide the fluid compositions with excellent fire resistance without materially affecting other physical properties of the fluid compositions such as viscosity and hydrolytic stability. More specifically, the sterically hindered ester has a higher fire point (F_p) than the poly(alkylene glycol) to provide the fluid composition with excellent fire resistance, which allows the fluid composition to rate as a Factory Mutual Approved Fluid under the current standards. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT [0020] A fluid composition is provided that is particularly useful in lubrication applications for compressors, pumps, and hydraulic machinery. The fluid composition includes a novel combination of poly(alkylene glycol) and a sterically hindered ester in specific amounts that provide the fluid composition with excellent fire resistance to allow the fluid composition to rate as a Factory Mutual (FM) Approved Fluid, as described in further detail below. Due to the fact that the S.F.P. of the fluid composition is so low, the fluid composition is ideal for lubrication applications where the risk of fire is present. As a result, the low S.F.P. of the fluid composition may lead to lower insurance premiums and, thus, lower operational costs. [0021] As set forth above, the fluid composition includes poly(alkylene glycol). More specifically, the fluid composition is based on poly(alkylene glycol), which provides many beneficial lubrication properties that are known in the art. 2.) The poly(alkylene glycol) is typically of the formula: wherein R7 comprises a Cj to Cg carbon group, Rg is a C2 to C4 carbon chain, and n is at least 1, more typically from 4 to 24. R7 and Rg may be either straight chain or branched molecules, and it is to be appreciated that when n is greater than 1, Rg may be the same or different within the poly(alkylene glycol). For example, the polyalkylene glycol may be a homopolymer with Rg being the same in each unit, or may be a random polymer with different combinations of Rg being either a C2, C3, or C4 carbon chain throughout the poly(alkylene glycol). [0022] The fluid composition of the present invention may include poly(alkylene glycols) of various number average molecular weights (M_w) based on the desired application and viscosity grade. More specifically, poly(alkylene glycols) having different M_w may be preferred for different lubrication applications. For example, some applications may call for poly(alkylene glycols) having a specific viscosity. Viscosity is directly proportional to M_w, with lower M_w correlating to lower viscosity. As known in the art, S.F.P. increases for poly(alkylene glycols) as M_w decreases. Although the poly(alkylene glycol) that is included in the fluid composition may be any poly(alkylene glycol) that satisfies the above formula, and may further be any poly(alkylene glycol) with any value greater than 1 for n in the above formula, the present invention is particularly suitable for fluid compositions including poly(alkylene glycol) that has a low M_w of less than or equal to 1500 g/mol, more typically from 1000 to 1500 g/mol. The presence of the sterically hindered ester in the fluid composition may be more significant in terms of adjusting the S.F.P. for fluid compositions including poly(alkylene glycols) of the low M_w.

However, it is to be appreciated that the present invention is suitable for any fluid composition including poly(alkylene glycol) of any molecular weight. [0023] The poly(alkylene glycols) that are suitable for the present invention typically comprise the reaction product of an alcohol and an alkylene oxide; however, it is to be appreciated that the present invention is not limited to any particular manner of forming the poly(alkylene glycol).

[0024] The alcohol serves as an initiator compound onto which the alkylene oxide is added, as is evident from the above formula that is representative of poly(alkylene glycols) that are suitable for the present invention. The alcohols are typically monofunctional alcohols and may be straight chain or branched molecules. However, it is to be appreciated that, in certain embodiments, di or polyfunctional alcohols may also be used. The alcohols typically have from 1 to 8 carbon atoms. Suitable monofunctional alcohols include, but are not limited to, those selected from the group of methanol, ethanol, propanol, butanol, hexanol, and combinations thereof. Butanol is particularly suitable for purposes of the present invention. Difunctional alcohols that may be suitable for purposes of the present invention include dihydric phenols such as saligenin, catechol, resorcinol, hydroquinone, and combinations thereof. [0025] Alkylene oxides that are suitable for purposes of the present invention may be selected from the group of ethylene oxide, propylene oxide, butylene oxide, and combinations thereof. More specifically, mixtures of ethylene oxide, propylene oxide, and/or butylene oxide may be used. Most preferably, the alkylene oxide is about 100% propylene oxide. [0026] An example of a poly(alkylene glycol) that comprises the reaction product of the alcohol and the alkylene oxide include a propylene oxide adduct of butanol, specific examples of which include Plurasafe WI- 165 and Plurasafe WI-285 propoxylate polymers, which are both commercially available from BASF Corporation of Florham Park, NJ. Most preferably, the poly(alkylene glycol) is the propylene oxide adduct of butanol. [0027] As set forth above, the fluid composition is based on poly(alkylene glycol). More specifically, the poly(alkylene glycol) is present in the fluid composition in an amount of greater than 85 parts by weight, more typically at least 90 parts by weight, most typically from about 91 to about 96 parts by weight, based on the total weight of the fluid composition. [0028] The sterically hindered ester is present in the fluid composition in order to increase the fire point and thus lower the S.F.P. of the fluid composition. By "sterically hindered", it is meant that the ester has at least one carbon atom chosen from the group of a tertiary carbon atom and a quaternary carbon atom. More specifically, the sterically hindered ester includes at least one carbon atom that is attached to either three or four other carbon atoms, and may include both a tertiary carbon atom and a quaternary carbon atom, multiple quaternary carbon atoms, or multiple tertiary carbon atoms. Alternatively, the sterically hindered ester may include a single tertiary or quaternary carbon atom. The steric hindrance of the ester renders the ester more stable and less prone to decomposition, as opposed to unhindered esters that do not include the tertiary and/or quaternary carbon atoms. The sterically hindered esters, due to the steric hindrance, elevate a fire point of the fluid composition including the poly(alkylene glycol) when present in the amounts specified below, thereby reducing the S.F.P. of the fluid composition. [0029] In one embodiment, the sterically hindered ester is of the formula:

wherein R1-R4 are each selected from the group of: a Cj to Ci g carbon group, an ester group having the formula:

wherein R5 comprises a Ci to C5 carbon group and R^ comprises a C4 to Ci g carbon chain optionally comprising ethylenic unsaturation, provided that at least two of R1-R4 comprise the ester group, and combinations thereof. More specifically, the sterically hindered ester of the above formula typically has the quaternary carbon atom, with an ester group present in at least three out of four branches that extend from the quaternary carbon atom. When the tertiary carbon is present, an ester group is also present in three branches that extend from the tertiary carbon atom.

[0030] Specific examples of sterically hindered esters that are suitable for purposes of the present invention may be selected from the group of, but are not limited to, trimethylol propane trioleate, pentaerythritol tetraoleate, neopentyl glycol octanoate, and combinations thereof. [0031] The sterically hindered ester represented by the formula above typically comprises the reaction product of a sterically hindered polyol and a fatty acid; however, it is to be appreciated that the present invention is not limited to any particular method of making the sterically hindered ester. The sterically hindered polyol has at least two hydroxyl functional groups, and may have four or more hydroxyl functional groups, each of which provides a situs for forming ester linkages when reacted with the fatty acid. More specifically, the quaternary carbon atom has at least one hydroxyl group pending from at least two of four branches that extend from the quaternary carbon atom, and may have a hydroxyl group pending from each of the four branches. When the tertiary carbon atom is present, a hydroxyl group may pend from at least two of the branches, and may pend from each of the branches. Typically, the hydroxyl group is a primary hydroxyl group; however, secondary hydroxyl groups may also be suitable for purposes of the present invention. [0032] Specific examples of sterically hindered polyols that are suitable for purposes of the present invention may be selected from the group of neopentyl glycol, trimethylol propane, trimethylol butane, pentaerythritol, dipentaerythritol, and combinations thereof. Most preferred sterically hindered polyols include trimethylol propane, pentaerythritol, and combinations thereof.

[0033] The fatty acid typically has at least 4 carbon atoms, more typically from 4 to 18 carbon atoms, and may include ethylenic unsaturation. Specific examples of fatty acids that are suitable for purposes of the present invention include, but are not limited to, saturated fatty acids such as butyric acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid, and eicosanoic acid; ethylenically unsaturated fatty acids such as alpha-linolenic acid, docosahexaenoic acid, eicosapentaenoic acid, linoleic acid, arachidonic acid, oleic acid, and erucic acid; and combinations thereof.

[0034] Alternatively, the sterically hindered ester may comprise the reaction product of a sterically hindered polycarboxylic acid and an alcohol. Specific examples of suitable polycarboxylic acids include phthalic acid and trimellitic acid. The resulting sterically hindered ester may be selected from the group of, but is not limited to, trimellitates, dimerates, and combinations thereof. Examples of suitable trimellitates are those that have the following formula:

wherein RJO, Rn, and Rj2 are independently selected from the group of branched C 7 to C\Q carbon chains, linear C 7 to CI Q carbon chains, and combinations thereof. It is to be appreciated that the groups pending from the benzene ring may be arranged different from the positions as shown, with the above formula merely providing an example of a suitable trimellitate for purposes of the present invention, and that any trimellitate is suitable for purposes of the present invention. An example of a suitable dimerate is di-2-ethylhexyl dimerate. However, it is also to be appreciated that any dimerate is suitable for purposes of the present invention.

[0035] The sterically hindered ester is present in the fluid composition in an amount of from 0.5 up to 15 parts by weight, more typically from 0.5 to 10 parts by weight, most typically from 1 to 5 parts by weight, based on the total weight of the fluid composition. [0036] The sterically hindered ester is present in the fluid composition in the amounts as set forth above in order to lower a S.F.P. of the fluid composition, typically to a point where the S.F.P. of the fluid composition is low enough for the fluid composition to be rated as a Factory Mutual (FM) Approved Fluid, while still allowing the fluid composition to maintain acceptable hydrolytic stability. However, it is to be appreciated that the present invention is not limited to any particular S.F.P., and covers fluid compositions having the poly(alkylene glycol) and ester present in the claimed amounts regardless of the S.F.P. of the fluid composition. [0037] In order to be rated as a FM approved fluid, the fluid composition must currently have a S.F.P. of less than or equal to 5.5 as measured in accordance with CN 6930. The S.F.P. is calculated as set forth in the Background of the Invention section above.

[0038] The chemical heat release rate (Q_Ch) of the fluid composition is based on the amount of carbon in the poly(alkylene glycol) and the ester. As such, for the fluid compositions of the present invention that include relatively high amounts of greater than 85 parts by weight of the poly(alkylene glycol), the chemical heat release rate (Q_ch) of the fluid composition typically cannot be significantly modified without changing the components of the fluid composition altogether. However, the fire point (Tf) of the fluid composition is typically significantly modified by including the sterically hindered ester in the fluid composition in the amounts set forth above. [0039] The fluid composition of the present invention including the poly(alkylene glycol) and the ester, in the amounts set forth above, has a fire point (Tf) of greater than or equal to 550 °F, more typically greater than or equal to 600 °F. As known in the art, fire point fire point (Tf) is a temperature at which the fluid composition will continue to burn, after ignition, for at least 5 seconds. The fluid composition having the fire point (Tf) as specified, especially those having a fire point (Tf) greater than or equal to 600 °F, typically have the S.F.P. that is less than or equal to 5.5. More specifically, the S.F.P. can be approximated through determination of the fire point (Tf) of the fluid composition and a net heat of complete combustion of the fluid composition. [0040] The fluid composition of the present invention is typically substantially free of water, and may be referred to in the art as an anhydrous fluid composition. More specifically, the fluid composition of the present invention typically includes less than 0.1 percent by weight of water, based on the total weight of the fluid composition. The fluid composition, by being substantially free of water, provides resistance to oxidation and thermal degradation that is not available with fluid compositions that have higher water contents. Further, due to the presence of the ester in the fluid composition, which is prone to hydrolysis, the substantial absence of water in the fluid composition substantially prevents the ester from hydrolyzing, thereby maximizing a useful life of the fluid composition of the present invention. [0041] In addition to the poly(alkylene glycol) and the ester, the fluid composition may further include an antioxidant in order to provide thermal oxidative stability to the composition and aid in decreasing the S.F.P. of the fluid composition. Specific examples of the antioxidants include, but are not limited to, propyl gallate, 2,6-di-tert- butyl-4-methylphenol (or butylated hydroxytoluene (BHT), vitamin E, hindered phenolic antioxidants (such as phenothiazine), amine-based antioxidants (such as Irganox L06 and Irganox L57, both sold by Ciba Specialty Chemicals Corporation), phosphates, and combinations thereof. Preferably, the antioxidant comprises the amine-based antioxidant. When used, the antioxidant is typically present in an amount of at least 0.1 parts by weight, more typically from 0.1 to 10, most typically from 0.3 to 2 parts by weight based on the total weight of the fluid composition. [0042] The fluid composition of the present invention may also include additives that provide various functions within the fluid composition. The additives may be selected from the group of, but are not limited to, lubricity additives such as boundary agents, anti-wear agents and extreme pressure agents; corrosion inhibitors; metal passivators; anti-foam additives; dyes; perfumes; detergents; and combinations thereof.

[0043] Examples of lubricity additives include, but are not limited to, organic acids having from 4 to 18, more typically from 7 to 12, carbon atoms; dithiophosphates; organic amine/phosphate blends such as Irgalube 349, commercially available from Ciba Specialty Chemicals Corporation; organo-molybdenum compounds; phosphorothionates; alkylated phosphate esters; triphenyl phosphates; alkylated triphenyl phosphates; fatty amines such as Amine-0 and Sarkosyl-O, commercially available from Ciba Specialty Chemicals Corporation; and combinations thereof. When used, the lubricity additive is typically present in the fluid composition in an amount of from 0.1 to 10, more typically from 0.1 to 5, parts by weight based on the total weight of the fluid composition.

[0044] Examples of corrosion inhibitors include, but are not limited to, organic amines, amine-organic acid complexes, organic diacids, sarcosine and succinic acid derivatives, alkyl and aryl phosphites. When used, the corrosion inhibitors are typically present in the fluid composition in an amount of from 0.1 to about 10, more typically from 0.1 to 5, parts by weight based on the total weight of the fluid composition.

[0045] Examples of metal passivators include, but are not limited to, tolyltriazole and its derivatives, and benzotriazole and its derivatives. When used, the metal passivators are typically present in the fluid composition in an amount of from 0.05 to

5, more typically from 0.05 to 2, parts by weight based on the total weight of the fluid composition.

[0046] Anti-foam additives, dyes, perfumes and detergents that are suitable for the fluid composition are known in the art and, when used, are typically present in a combined amount of from 0.1 to 2 parts by weight based on the total weight of the fluid composition.

[0047] The following examples are meant to illustrate the present invention and are not to be view in any way as limiting to the scope of the invention. EXAMPLES

[0048] Fluid compositions of the present invention are provided, and relevant physical properties of those fluid compositions are shown below in Table 1.

Comparative Examples of fluid compositions are also included in Table 1, with the relevant physical properties of the comparative fluid compositions also included in Table 1. Table 1

[00491 Ester A is trimethylol propane trioleate.

[0050] Ester B is pentaerythritol tetraoleate.

[0051] Ester C is a pentaerythritol ester of linear and branched fatty acids, CAS No.

118685-24-8. [0052] Ester D is a dipentaerythritol ester of valeric, caprylic, and capric acids, CAS

No. 68441-66-7.

[0053] Ester E is a mixture of trimethylolpropane esters, CAS No. 11138-60-6.

[0054] Ester F is a pentaerythritol ester of caprylic and capric acids, CAS No. 68441- 68-9.

[0055] Ester G is trioxtyl trimellitic ester, CAS nNo. 3319-31-1.

[0056] Ester H is triisodecyl tridecyl trimellitic ester, CAS No. 70225-05—7.

[0057] Ester J is di-2-ethylhexyl dimerate.

[0058] Ester K is ditridecyl adipate, CAS No. 16958-92-2. [0059] Ester L is di-2-ethylhexyl sebacate, CAS No. 122-62-3.

[0060] Antioxidant is phenothiazine.

[0061] Additive A is a phosphorous-based anti-wear additive commercially available from Ciba Specialty Chemical Corporation of Tarrytown, NY.

[0062] Additive B is another phosphorous-based anti-wear additive commercially available from Ciba Specialty Chemical Corporation.

[0063] Additive C is a yellow metal passivators commercially available from Ciba

Specialty Chemical Corporation.

[0064] PAG is a 67/33 blend of butanol-initiated propylene oxide polymers having a number average molecular weight of 1200 and 700 respectively. RESULTS

[0065] With reference to the Examples and the Comparative Examples above, it is apparent that most of the fire points of the Examples, each of which include a ester present in an amount that is in accordance with the present invention, are above 600

°F. For the Examples whose fire points fall below 600 °F, the fire points are sufficiently close to 600 ⁰F to be within experimental error and are still suitable for purposes of the present invention. For the Comparative Examples that have fire points above 600 ⁰F and S.F.P.s of less than 5.5, hydrolytic stability is unacceptably poor when tested in accordance with ASSTM D 943-99 entitled "Standard Test Method for Oxidation Characteristics of Inhibited Mineral Oils". Further, the remaining Comparative have fire points that are significantly less than 600 °F, and each have a S.F.P. unacceptably in excess of 5.5.

[0066] The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Obviously, many modifications and variations of the present invention are possible in light of the above teachings, and the invention may be practiced otherwise than as specifically described.

Claims

CLAIMSWhat is claimed is:

1. A fluid composition comprising: a poly(alkylene glycol) present in an amount of greater than 85 parts by weight based on the total weight of said fluid composition, and a sterically hindered ester present in an amount of from 0.5 up to 15 parts by weight based on the total weight of said fluid composition.

2. A fluid composition as set forth in claim 1 that is substantially free of water.

3. A fluid composition as set forth in any preceding claim wherein said ester is present in an amount of from 0.5 to 5 parts by weight based on the total weight of said fluid composition.

4. A fluid composition as set forth in any preceding claim wherein said poly(alkylene glycol) has a number average molecular weight of less than or equal to about 1500 g/mol.

5. A fluid composition as set forth in any preceding claim wherein said sterically hindered ester is of the formula:

wherein R1-R4 are each selected from the group of: a Ci to C] g carbon group, an ester group having the formula:

wherein R5 comprises a C^ to C5 carbon group and Rg comprises a C4 to C\$ carbon chain optionally comprising ethylenic unsaturation, provided that at least two of Ri - R4 comprise said ester group, and combinations thereof.

6. A fluid composition as set forth in any preceding claim wherein said sterically hindered ester comprises the reaction product of a sterically hindered polyol and a fatty acid.

7. A fluid composition as set forth in claim 6 wherein said sterically hindered polyol has at least one carbon atom chosen from of the group of a tertiary carbon atom and a quaternary carbon atom.

8. A fluid composition as set forth in claim 6 or 7 where said sterically hindered polyol has at least three hydroxyl functional groups.

9. A fluid composition as set forth in any one of claims 6-8 wherein said fatty acid has at least 4 carbon atoms.

10. A fluid composition as set forth in any one of claims 6-9 wherein said ester is selected from the group of trimethylol propane trioleate, pentaerythritol tetraoleate, and combinations thereof.

11. A fluid composition as set forth in any preceding claim wherein said ester comprises the reaction product of a hindered polycarboxylic acid and an alcohol.

12. A fluid composition as set forth in any preceding claim wherein said poly(alkylene glycol) is of the formula:

wherein R7 comprises a Ci to Cs carbon group, Rg is a C2 to C4 carbon chain, and n is at least 1.

13. A fluid composition as set forth in any preceding claim wherein said poly(alkylene glycol) comprises the reaction product of an alcohol and an alkylene oxide.

14. A fluid composition as set forth in any preceding claim wherein said alcohol is selected from the group of monofunctional alcohols, difunctional alcohols, polyfunctional alcohols, and combinations thereof.

15. A fluid composition as set forth in claim 13 or 14 wherein said alcohol comprises a monofunctional alcohol.

16. A fluid composition as set forth in claim 15 wherein said monofunctional alcohol comprises butanol.

17. A fluid composition as set forth in any one of claims 13-16 wherein said alkylene oxide is selected from the group of ethylene oxide, propylene oxide, butylene oxide, and combinations thereof.

18. A fluid composition as set forth in any one of claims 13-17 wherein said alkylene oxide comprises about 100% propylene oxide.

19. A fluid composition as set forth in any preceding claim wherein said poly(alkylene glycol) comprises a propylene oxide adduct of butanol.

20. A fluid composition as set forth in any preceding claim further comprising an antioxidant.

21. A fluid composition as set forth in claim 20 wherein said antioxidant is further defined as an amine-based antioxidant.

22 A fluid composition as set forth in claim 20 or 21 wherein said antioxidant is present in an amount of at least 0.1 parts by weight based on the total weight of said fluid composition.

23. A fluid composition as set forth in any preceding claim further comprising an additive selected from the group of lubricity additives, corrosion inhibitors, metal passivators, anti-foam additives, dyes, perfumes, detergents, and combinations thereof.

24. A fluid composition as set forth in any preceding claim having a fire point of greater than or equal to 550 ⁰F.

25. A fluid composition as set forth in claim 24 having a fire point of greater than or equal to 600 ⁰F.

26. A fluid composition as set forth in any preceding claim having a spray flammability parameter of less than or equal to 5.5 as measured in accordance with

CN 6930.

27. A fluid composition as set forth in any preceding claim further defined as a lubricating composition.