Patent Description:
The low viscosity functional fluid composition according to the present invention is useful in a variety of applications and in particular as a brake fluid, especially for new electronic or automated anti-lock brake systems which require lower viscosity fluids for satisfactory operation at low temperatures.

Functional fluid compositions based on borate esters are well known in the art. To be useful for example as DOT <NUM> or DOT <NUM> brake fluids, these borate ester based compositions must meet stringent physical properties and performance requirements particularly with respect to minimum dry equilibrium reflux boiling point ("ERBP"), minimum wet equilibrium reflux boiling point ("WERBP") and maximum low temperature kinematic viscosity (e.g. determined at -<NUM>) while maintaining adequate resistance to corrosion, stability and meeting other physical property requirements such as pH, reserve alkalinity, corrosion protection and rubber swelling.

While borate esters are advantageous to meet the DOT <NUM> and DOT <NUM> criteria according to Federal Motor Vehicle Safety Standards (FMVSS) No <NUM>, especially a very high wet boiling point (wERBP), borate containing brake fluids are associated with problems. Federal Motor Vehicle Safety Standards (FMVSS).

No <NUM> refers to <NUM> CFR § <NUM> in the <NUM>-<NUM>-<NUM> edition and will be referred to as FMVSS in this specification.

<CIT> describes hydraulic fluids comprising alkoxy glycol borate esters, alkoxy glycols and corrosion inhibitors, additionally containing cyclic carboxylic acid derivatives.

<CIT> describes low viscosity functional fluid compositions comprising alkoxy glycol borate esters, alkoxy glycol components and additives such as corrosion inhibitors, wherein the alkoxylation degrees of the alkoxy glycol borate esters and the alkoxy glycols are restricted to a certain narrow pattern.

<CIT> teaches a hydraulic fluid which formally fulfils the specification DOT <NUM>. This hydraulic fluid essentially consists of (A) about <NUM> to <NUM>% by weight of at least one boric acid ester obtained from orthoboric acid, diethylene glycol and an ethylene glycol monoalkyl ether; (B) <NUM> to <NUM>% by weight of at least one ethylene glycol monoalkyl ether; (C) <NUM> to <NUM>% by weight of at least one bis-(ethylene glycol monoalkyl ether)-formal; (D) <NUM> to <NUM>% by weight of at least one alkylamine; and (E) <NUM> to <NUM>% by weight of at least one stabilizer and/or inhibitor; the percentages by weight in each case being relative to the total weight of the fluid.

<CIT> teaches a hydraulic fluid composition, especially a brake fluid composition, based on a boric ester of a glycol ether and comprising a corrosion-inhibiting system which includes: (<NUM>) at least one constituent (A) chosen from fatty amines or the salts of one or more carboxylic acids with the said amines, and (<NUM>) at least one constituent (B) chosen from the products resulting from the reaction of one or more carboxylic fatty acids with a polyoxyalkylene glycol, or from the transesterification reaction of one or more esters of carboxylic fatty acids with a polyoxyalkylene glycol.

<CIT> teaches a hydraulic fluid composition having a high boiling point, in particular a high equilibrium reflux boiling point and a low viscosity. The composition contains, as additive, at least one ether amine having a molecular weight between <NUM> and <NUM> and having the formula
<CHM>
in which.

<CIT> discloses a functional fluid composition comprising.

<CIT> teaches hydraulic fluids with a boron content of from <NUM> to <NUM> % by weight, and consisting essentially of.

<CIT> teaches a brake fluid based on glycols and glycol ethers, consisting essentially of.

<CIT> describes brake fluid compositions containing orthoesters of the formulae A and B in combination with polyoxyalkyleneglycol esters of dicarboxylic acids and/or alkyl esters of glycols or polyglycols
<CHM>.

Such compounds were applied in <NUM> wt. -% in base fluid, consisting of mainly conventional esters, such as propionates and nylonates and minor amounts of alkyl glycols. The addition of <NUM>% of various ortho esters resulted in a less pronounced reduction of boiling point in the presence of <NUM> wt. -% water (minus <NUM> and less, compared to -<NUM> reduction in the absence of ortho esters). Yet, the impact on water uptake and in the standardized WERBP test according to FMVSS no. <NUM> was not known. In addition, the viscosity of the functional fluids according to Castrol <CIT> was rather high with around <NUM> cSt at - <NUM>.

There is a strong demand for improved high performance hydraulic fluid compositions and brake fluids having low temperature viscosity at -<NUM> while meeting or exceeding at the same time the minimum ERBP and especially the WERBP temperature requirements, as fulfilled by the hydraulic fluid compositions and brake fluids commonly used.

Examples of borate-free brake fluids are described in the literature.

These developments allow for high ERBP but suffer from a still too high viscosity at -<NUM> and from a low WERBP. The problem to be solved by the instant invention is to provide a hydraulic fluid having the properties mentioned below and being essentially or entirely borate free.

Yet, a borate-free composition, fulfilling these criteria is not known.

According to the present invention, a functional fluid composition being essentially free from borates has been found which exhibits superior values of ERBP and of WERBP and for low temperature kinematic viscosity, while maintaining excellent resistance to corrosion, high stability and meeting other physical property requirements such as pH, reserve alkalinity and rubber swell. Especially very high WERBP values are achieved by using ortho esters as a replacement for borate esters.

In a first aspect, this invention relates to a functional fluid, comprising.

In a second aspect, this invention provides the use of the functional fluid of the first aspect as a brake fluid for vehicular brakes.

In a third aspect, this invention provides for a method of operating a vehicular brake that transmits braking force through a hydraulic system, the method comprising filling the hydraulic system with a functional fluid according to the first aspect.

The functional fluid will be referred to as fluid in the following.

The orthoester used as component (A) corresponds to one or more components according to formula (I).

In formula (I), R1, R2, R3 are independently selected from H or C<NUM> to C<NUM> alkyl groups preferably from H or C<NUM> to C<NUM> alkyl groups. In a preferred embodiment, R1, R2, R3 are independently selected from methyl or butyl. In a more preferred embodiment, R1, R2, R3 mean methyl. In a preferred embodiment, only one out of R1, R2, R3 takes the meaning of H. In another preferred embodiment, the amount of orthoester according to formula (I) wherein at least one of R1, R2, R3 takes the meaning H is less than <NUM> wt. -%, more preferably less than <NUM> wt. -%, particularly less than <NUM> wt. -%, on a basis of <NUM> wt. -% being the total amount of all orthoester according to formula (I). In a preferred embodiment, the orthoester used as component (A) corresponds to two or more components according to formula (I).

It is preferred, that the two or more orthoesters of formula (I) differ in one out of R1, R2, R3. This may mean e.g. that one out of R1, R2, R3 is methyl in one of the orthoesters, and one out of R1, R2, R3 is butyl in the other of the orthoesters.

In formula (I), R4 means H or C<NUM> to C<NUM> alkyl. In a preferred embodiment, R4 means H or methyl.

In formula (I), a, b, c are independently numbers from <NUM> to <NUM>, with the proviso that a+b+c is at least <NUM>, i.e. not all of a, b, c may equal zero. In a preferred embodiment, a, b, c are independently <NUM> or <NUM>. In another preferred embodiment, a+b+c is at least <NUM>, more preferably at least <NUM>. In a preferred embodiment, the orthoester used as component (A) corresponds to two or more components according to formula (I). It is preferred, that the two or more orthoesters of formula (I) differ in one out of a, b, c. , meaning that a, b, c are not all the same in the two or more orthoesters. For example, one out of a, b, c may be <NUM> in one of the orthoesters, and one out of a, b, c may be <NUM> in the other of the orthoesters.

The orthoester should be clear, homogeneous, and substantially free of salt or suspended components, e.g. such as residues of insoluble catalysts, to render a clear, homogenous functional fluid.

In a further preferred embodiment, the orthoester used as component (A) is not a single compound, but a mixture of at least two orthoesters according to formula (I) and (Ia). This means that in one embodiment, the fluid according to the first aspect not only comprises an orthoester according to formula (I), but in addition a bridged orthoester according to formula (Ia)
<CHM>
wherein R1, R2, R4, a and b have the same meaning as provided for formula (I), and d is a number from <NUM> to <NUM>, preferably <NUM> or <NUM>.

In formula (Ia), R1, R2 are independently selected from H or C<NUM> to C<NUM> alkyl groups preferably from H or C<NUM> to C<NUM> alkyl groups. In a preferred embodiment, R1, R2 are independently selected from methyl or butyl. In a more preferred embodiment, R1, R2 mean methyl. In a preferred embodiment, only one out of R1, R2 takes the meaning of H. In another preferred embodiment, the amount of orthoester according to formula (Ia) wherein at least one of R1, R2 takes the meaning H is less than <NUM> wt. -%, more preferably less than <NUM> wt. -%, particularly less than <NUM> wt. -%, on a basis of <NUM> wt. -% being the total amount of all orthoester according to formula (Ia). In a preferred embodiment, the orthoester used as component (A) corresponds to two or more components according to formula (Ia).

It is preferred, that the two or more orthoesters of formula (Ia) differ in one out of R1, R2. This may mean e.g. that one out of R1, R2 is methyl in one of the orthoesters, and one out of R1, R2 is butyl in the other of the orthoesters.

In formula (Ia), R4 means H or C<NUM> to C<NUM> alkyl. In a preferred embodiment, R4 means H or methyl.

In formula (Ia), a, b are independently numbers from <NUM> to <NUM>, with the proviso that a+b is at least <NUM>, i.e. not all of a, b, c may equal zero. In a preferred embodiment, a, b are independently <NUM> or <NUM>. In another preferred embodiment, a+b is at least <NUM>, more preferably at least <NUM>. In a preferred embodiment, the orthoester used as component (A) corresponds to two or more components according to formula (Ia). It is preferred, that the two or more orthoesters of formula (Ia) differ in one out of a, b, meaning that a, b are not all the same in the two or more orthoesters according to formula (Ia). For example, one out of a, b may be <NUM> in one of the orthoesters, and one out of a, b may be <NUM> in the other of the orthoesters.

If a bridged orthoester according to formula (Ia) is present, its amount is preferably at most <NUM> wt. -%, more preferably less than <NUM> wt. -%, particularly less than <NUM> wt. -%, on a basis of <NUM> wt. -% being the total amount of all orthoester according to formula (I). For the purposes of this invention, the bridged orthoester according to formula (Ia) is to be regarded as part of component A). The amount of orthoester according to formula (Ia) is to be counted within the amount of component (A).

The bridging of orthoester by polyalkylene glycols has the technical effect of increasing the viscosity of the orthoester component, and therefore increasing the viscosity of the fluid of the first aspect. A larger proportion of bridged orthoesters of the formula (Ia) provides a higher viscosity of the fluid.

Orthoesters according to formula (I) and (Ia) can be synthesized according to procedures known in the art from alkyl glycols and commercially available alkyl ortho esters, according to
<CHM>.

Useful alkyl ortho esters are selected from R4 being a H or C<NUM>- to C<NUM>-akyl residues and Rx being C<NUM>- bis C<NUM>-alkyl residues.

The alkyl glycol reactant of formula (IV) comprises species of ethoxylation degree of from y = <NUM> to y = <NUM>, preferably of from y = <NUM> to y = <NUM>, more preferably of y = <NUM> to y = <NUM>. It is to be understood that the alkyl glycol reactant may be a single species, or a mixture of different species with regards to their ethoxylation degree y and/or to radicals R1, R2 and R3.

Radicals R1, R2 and R3 are preferably C<NUM>- to C<NUM>-alkyl groups and may be methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, preferably n-butyl or methyl.

Examples of useful alkoxy glycols as starting material for component (A) of the present invention wherein R1, R2 or R3 is not H include methyldiglycol, methyltriglycol, methyltetraglycol, methylpentaglycol, methylhexaglycol, ethyldiglycol, ethyltriglycol, ethyltetraglycol, ethylpentaglycol, ethylhexaglycol, n-propyl-diglycol, n-propyltriglycol, n-propyltetraglycol, n-propylpentaglycol, n-propylhexaglycol, n-butyldiglycol, n-butyltriglycol, n-butyltetraglycol, n-butylpentaglycol, n-butylhexaglycol, n-pentyldiglycol, n-pentyltriglycol, n-pentyltetraglycol, n-pentylpentaglycol, n-pentyl-hexaglycol, n-hexyldiglycol, n-hexyltriglycol, n-hexyltetraglycol, n-hexylpentaglycol, n-hexylhexaglycol, <NUM>-ethylhexyldiglycol, <NUM>-ethylhexyltriglycol, <NUM>-ethylhexyltetraglycol, <NUM>-ethylhexylpentaglycol, <NUM>-ethylhexylhexaglycol and mixtures thereof. For the avoidance of doubt, "glycol" herein always means "ethylene glycol".

Example for useful glycols as starting material for component (A) of the present invention wherein R1, R2 or R3 is H include preferably diethyleneglycol, triethyleneglycol and tetraethylene glycol and mixtures thereof.

In general, hydraulic fluids require the presence of agents providing reserve alkalinity. Such agents are e.g. amines. The required amount of the amine component is dependent on the required reserve alkalinity and the required pH value of the final functional fluids. Both reserve alkalinity and pH contribute to corrosion inhibition.

Borate-ester containing brake fluids require higher amounts of amine, usually above <NUM> wt. -%, in order to maintain a pH value in the range of <NUM> to <NUM>, even upon hydrolysis of borate esters into the triprotic boric acid and the corresponding glycols.

In contrast, ortho-ester based brake fluids require reduced amounts of amine. Hydrolysis of ortho esters results in the formation of two equivalents of the corresponding alcohols, and one equivalent of the corresponding ester. As an example, the hydrolysis of an orthoacetate to the corresponding alcohol, and the acetic acid ester, follows this reaction path:
<CHM>.

In a subsequent hydrolysis step, the ester (e.g. acetic acid ester) may be cleaved into the corresponding alcohol and one equivalent of the mono protic acid, e.g. acetic acid. The requirement of orthoester based fluids for reserve alkalinity is therefore reduced when compared to borate based fluids.

Component (B) of the functional fluid composition according to general formula (II) comprises species of ethoxylation degree of from m = <NUM> to m = <NUM>, preferably of from m = <NUM> to m = <NUM>, more preferably of m = <NUM> to m = <NUM>. Component (B) may be a single species or a mixture of different species with regards to the ethoxylation degree, and/or to R5. R5 is a C<NUM>- to C<NUM>-alkyl group and may be methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl and <NUM>-ethylhexyl, ethyl. More preferably, R5 is ethyl, n-butyl or methyl, most preferably n-butyl or methyl.

Examples of useful alkoxy glycols for component (B) of the present invention include methyldiglycol, methyltriglycol, methyltetraglycol, methylpentaglycol, methylhexaglycol, ethyldiglycol, ethyltriglycol, ethyltetraglycol, ethylpentaglycol, ethylhexaglycol, n-propyl-diglycol, n-propyltriglycol, n-propyltetraglycol, n-propylpentaglycol, n-propylhexaglycol, n-butyldiglycol, n-butyltriglycol, n-butyltetraglycol, n-butylpentaglycol, n-butylhexaglycol, n-pentyldiglycol, n-pentyltriglycol, n-pentyltetraglycol, n-pentylpentaglycol, n-pentyl-hexaglycol, n-hexyldiglycol, n-hexyltriglycol, n-hexyltetraglycol, n-hexylpentaglycol, n-hexylhexaglycol, <NUM>-ethylhexyldiglycol, <NUM>-ethylhexyltriglycol, <NUM>-ethylhexyltetraglycol, <NUM>-ethylhexylpentaglycol, <NUM>-ethylhexylhexaglycol and mixtures thereof. For the avoidance of doubt, "glycol" always means "ethylene glycol". From the list above, methyltriglycol, methyltetraglycol, methylpentaglycol, ethyldiglycol, ethyltriglycol, ethyltetraglycol, n-butyldiglycol, n-butyltriglycol, n-butyltetraglycol, n-butylpentaglycol, are preferred for component (B).

In a preferred embodiment, component (B) comprises a mixture of alkoxy glycols of general formula (II) comprising solely or predominantly species with m = <NUM> and/or <NUM>. Predominantly shall mean that at least <NUM>% by weight, more preferably at least <NUM>% by weight, most preferably at least <NUM>% by weight, of component (B) comprises species with m = <NUM> and/or <NUM>. In the last case, alkoxy glycol species with m being lower than <NUM>, e.g. with m = <NUM>, and/or with m being higher than <NUM>, e.g. with m = <NUM> and/or m = <NUM>, may be present in minor amounts, preferably less than <NUM>% by weight, more preferably less than <NUM>% by weight and even more preferably less than <NUM>% by weight. Percentages of species of component (B) are given in wt. -% with the total amount of component (B) being <NUM> wt.

In a preferred embodiment, the proportion of component (B) is <NUM> - <NUM> wt. -% of the total fluid weight.

Component (C) is a polyethylene glycol according to formula (III). In formula (III), k is a number of <NUM>, or higher. It is preferred, that k is a number from <NUM> - <NUM>. More preferably, k is <NUM> or <NUM>. In one preferred embodiment, component (C) is a mixture of compounds according to formula (III) wherein k is <NUM> or <NUM>.

If component (C) is present, it is required that in at least <NUM> wt. -% of all compounds according to formula (III) k is <NUM> or <NUM>, the wt. -% being relative to the total weight of all compounds according to formula (III). This means that compounds according to formula (III) wherein k is <NUM> or <NUM> make up to <NUM> wt. -%, preferably <NUM> to <NUM> wt. -% of the fluid, the total fluid weight being <NUM> wt.

The total amount of component (C) in the fluid is from <NUM> to <NUM> wt. -%, preferably <NUM>-<NUM> wt. -% of the weight of the fluid, i.e. the total weight of the fluid being <NUM> wt. In one other preferred embodiment, component (C) is absent, i.e. the amount is <NUM>%. In one other preferred embodiment, the amount of species of formula (III) wherein k = <NUM> is <NUM> - 10wt. In one other preferred embodiment, the amount of species of formula (III) wherein k = <NUM> is <NUM> - <NUM> wt. In one other preferred embodiment, the total amount of species according to formula (III) wherein k is <NUM> or higher than <NUM> is at most <NUM> wt. -%, more preferably at most <NUM> wt. Said weight percentages provided for species according to formula (III) are provided as weight percentages of the fluid, i.e. the total weight of the fluid is <NUM> wt. They are not provided as weight percentages of the total weight of component (C).

Component (D) is an additive that is required to impart particular properties to the functional fluid for performing on specifications to be fulfilled for brake fluids according to the current norms and standards FMVSS, SAE J <NUM> and ISO <NUM>. The total amount of all components (D) in the fluid is from <NUM> to <NUM> wt. -%, preferably from <NUM> to <NUM> wt.

Component (D) comprises one or more additives selected from the group consisting of corrosion inhibitors, amines as reserve alkalinity agents, stabilizing antioxidants, defoamers, lubricants and dyes.

Component (D) may comprise an amine or mixtures of amines as alkalinity agent. Amines are preferably alkyl or cycloalkyl amines, alkanol amines, alkyl amine ethoxylates and their mixtures. Preferred alkyl amines are mono- and di-(C<NUM>- to C<NUM>-alkyl)amines. Examples of suitable alkyl or cycloalkyl amines are n-butylamine, n-hexylamine, n-octylamine, <NUM>-ethylhexylamine, isononylamine, n-decylamine, n-dodecylamine, oleylamine, d-n-propylamine, di-isopropylamine, din-butylamine, tri-n-butylamine, di-n-amylamine, cyclohexylamine, and salts of such amines. Examples of suitable alkanolamines are mono-, di- and trimethanolamine, mono-, di- and triethanolamine, mono-, di- and tri-n-propanolamine and mono-, di- and tri-isopropanolamine. Examples of suitable alkyl amine ethoxylates are such linear, cyclic or branched alkylamine ethoxylates carrying <NUM> to <NUM> EO moieties and an alkyl chain having <NUM> to <NUM> carbon atoms.

Component (D) of the present functional fluid composition may comprise, besides the Amine, at least one additive with corrosion inhibition action, although the alkylamine ethoxylates exhibit corrosion inhibition properties themselves. Suitable customary additives with corrosion inhibition properties include fatty acids such as lauric, palmitic, stearic or oleic acid; esters of phosphorus or phosphoric acid with aliphatic alcohols or aliphatic alcohol ethoxylates; such as ethyl phosphate, dimethyl phosphate, isopropyl phosphate, n-butyl phosphate, <NUM>-ethylhexyl phosphate, triphenyl phosphite and diisopropyl phosphite; heterocyclic nitrogen containing organic compounds such as benzotriazole, tolyltriazole, <NUM>,<NUM>,<NUM>-triazole, benzoimidazole, purine, adenine and derivatives of such heterocyclic organic compounds. Of course, mixtures of the above additives with corrosion inhibition action can be used.

Defoamers may be selected from groups of oil based defoamers, such as natural oils, glycerides, waxes, powdered silica, alkoxylates such es EO/PO block copolymers, silicone based defoamers, preferably modified polyether or silicone derivatives and mixtures thereof.

The fluid may include from <NUM> to <NUM>% by weight, based on the total weight of the fluid, of a lubricant. Suitable lubricants are for example, propylene oxide containing alkylene oxide polymers that are optionally substituted with a C<NUM> to C<NUM> alkyl group, triglycerides, castor oil, ricinoleic acid, and ethoxylates of castor oil or ricinoleic acid and mixtures thereof. In a preferred embodiment, the lubricants are homopolymers of propylene oxide, copolymers of propylene oxide with ethylene oxide and/or butylene oxide, mono C<NUM> to C<NUM> alkyl substituted homopolymers of propylene oxide, mono C<NUM> to C<NUM> alkyl substituted copolymers of propylene oxide with ethylene oxide and/or butylene oxide, triglycerides, castor oil, ricinoleic acid, and ethoxylates of castor oil or ricinoleic acid and mixtures thereof. In case of such ethoxylates, <NUM> to <NUM> ethoxy units are preferred. In another preferred embodiment, the propylene oxide containing alkylene oxide polymers that are optionally substituted with a C<NUM> to C<NUM> alkyl group have a number average molecular weight in the range of <NUM> to <NUM>/mol.

Suitable age protecting agents or antioxidants are phenolic stabilizers like Bisphenols (e,g. Bisphenol A or Bisphenol M), butyl hydroxytoluene, methoxy phenols, butylated hydroxy anisole, hydroquinone derivatives; sterically hindered amines such as benzylated, alkylated or styrenated diphenylamine, styrenated phenylamine, substituted piperidine derivatives, phenothiazine derivatives or quinoline derivatives and mixtures thereof. In general, any literature known glycol stabilizing or age protecting agents could be used herein.

In one preferred embodiment, the % values (A) - (D) add up to <NUM>% by weight.

The total content of the fluid in boric acid esters is at most <NUM> wt. -%, preferably less than <NUM> wt. Most preferably, the fluid is free of boric acid esters.

In a preferred embodiment, the combined amount of components (A) and (B) adds up to at least <NUM>% of the fluid weight.

The functional fluid composition of the present invention exhibits superior behavior in ERBP and WERBP temperature and simultaneously in low temperature viscosity performance. It exhibits an ERBP of at least <NUM>, more preferably of at least <NUM> and a WERBP of at least <NUM>, more preferably at least <NUM>. The functional fluid composition of the present invention exhibits a low temperature kinematic viscosity of less than <NUM> centistokes ("cSt") (= mm<NUM>/s), more preferably of less than <NUM> cSt, each determined at a temperature of -<NUM>. All analytical methods are described in FMVSS to which reference is made. For the purpose of this specification, ERBP and WERBP are to be determined according to FMVSS no <NUM>.

The low viscosity functional fluid composition of the present invention is especially useful as a brake fluid, for example for vehicles such as passenger cars and trucks, especially for new electronic or automated anti-lock brake systems which require lower viscosity fluids for satisfactory operation at low temperatures.

Besides its superior behavior in ERBP and WERBP temperature and its low temperature viscosity performance, the functional fluid composition of the present invention exhibits a good corrosion protection, a good water compatibility, a mild pH value, a good stability with regard to low and high temperatures, a good oxidation stability, a good chemical stability, a good behavior towards rubber and elastomers, a good lubrication performance and good foaming behavior.

A mixture of <NUM> (<NUM> mol) trimethyl orthoacetate and <NUM> (<NUM> mol) methyl triglycol is placed under nitrogen in a <NUM> liter four-necked flask equipped with a stirrer and a distillation attachment including a Vigreux column and heated to <NUM> within <NUM>. After the constant reaction temperature had been reached, a first portion of methanol was distilled off over the course of <NUM> minutes. The reaction temperature was increased to <NUM> and held for a further <NUM> minutes, a total of about <NUM>% (<NUM>, <NUM> mol) of the theoretical amount of methanol being distilled off. Thereafter, a further <NUM> (<NUM> mol) of methyl triglycol were metered in at constant heating power, and after one hour the reaction temperature was increased to <NUM> and held for one hour, further methanol being distilled off. A further <NUM> (<NUM> mol) of methyl triglycol were then metered in at constant heating power, and <NUM> of benzoic acid were added. After <NUM> hours, a further <NUM> and finally another <NUM> of benzoic acid were added after a further hour. Finally, the mixture was stirred at a reaction temperature of <NUM> for a further <NUM>. A total of <NUM> / <NUM> of methanol (<NUM> mol) were distilled off, which corresponds to a conversion of <NUM>%. A similar conversion rate was observed by <NUM>H-NMR analysis.

In analogy to the synthesis procedure of OE-A, Triethylorthoacetate (<NUM> mol) was reacted with MTG (<NUM> mol) and MTeG (<NUM> mol), resulting in the corresponding product with <NUM>% conversion according to <NUM>-NMR.

In analogy to the synthesis procedure of OE-A, Trimethylorthoformiate (<NUM> mol) was reacted with MTG (<NUM> mol) and MTeG (<NUM> mol), resulting in the corresponding product with <NUM>% conversion of the starting orthoformiate according to <NUM>-NMR.

In analogy to the synthesis procedure of OE-A, Trimethylorthoformiate (<NUM> mol) was reacted with MTG (<NUM> mol), resulting in the corresponding product with <NUM>% conversion of the starting orthoformiate according to <NUM>-NMR.

In analogy to the synthesis procedure of OE-A, Trimethyl ortho acetate (<NUM> mol) was reacted with a mixture of <NUM>% triethyleneglycolmonobutylether and <NUM>% tetraethyleneglycolmonobutylether (combined <NUM> mol), resulting in the corresponding product with <NUM>% conversion according to NMR.

In analogy to the synthesis procedure of OE-A, Trimethyl ortho acetate (<NUM> mol) was reacted with a mixture of <NUM> wt. -% triethyleneglycolmonomethylether, <NUM> wt. -% diethyleneglycol and <NUM> wt. -% triethyleneglycol (combined <NUM> mol), using phosphoric acid as a catalyst, resulting in the corresponding product with <NUM>% conversion according to NMR.

Table with physical-chemical data (viscosity, boiling point, stability at repeated boiling, even in presence of amine).

Table <NUM> shows functional fluid compositions and their performance. Percentages are wt. -% with respect to the total fluid weight, unless otherwise noted.

Claim 1:
A functional fluid, comprising
(A) from <NUM> to <NUM>% by weight, based on the total composition, of one or more ortho-ester according to formula (I)
<CHM>
wherein
R1, R2, R3 are independently selected from H or C<NUM> to C<NUM> alkyl groups,
R4 means H or C<NUM> to C<NUM> alkyl,
a, b, c are independently numbers from <NUM> to <NUM>,
with the proviso that a+b+c is at least <NUM>,
(B) from <NUM> to <NUM>% by weight, based on the total composition, of one or more alkoxy glycol according to formula (II)

        R<NUM> - O - (CH<NUM> - CH<NUM> - O)m - H     (II)

wherein
R<NUM> is a C<NUM> to C<NUM> alkyl residue,
m is a number from <NUM> to <NUM>,
(C) from <NUM> to <NUM> wt.-% of at least one compound according to formula (III)

        H -O- (CH<NUM> - CH<NUM> - O)k - H     (III)

wherein k is a number of <NUM> or higher, with the proviso that in at least <NUM> wt.-% of all compounds according to formula (III) k is <NUM> or <NUM>,
(D) at least one additive, selected from the group consisting of corrosion inhibitor, alkalinity agents, aging protection agents, defoamers and lubricants,
the fluid comprising at most <NUM> wt.-% of an ester between boric acid and a glycol or polyglycol compound, and
with the proviso that the combined amount of component (A) and component (B) adds up to at least <NUM> % of the total fluid weight.