DE69607247T2 - Hydraulic fluid composition - Google Patents

Abstract

The present invention relates to 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 : (1) at least one constituent (A) chosen from fatty amines or the salts of one or more carboxylic acids with the said amines, and (2) 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. The composition simultaneously exhibits excellent anticorrosive properties particularly in a moist atmosphere and very high levels of brake fluid standards.

Description

The present invention relates to a hydraulic fluid composition, in particular a brake fluid composition, used in particular in the braking systems of motor vehicles, and to a process for the treatment of a hydraulic fluid for the purpose of reducing the corrosion of the ferrous alloys or metals in contact with the said fluid.

U.S. Patent 3,914,182 discloses a hydraulic fluid composition containing a borate ester of a glycol ether and an ester or mixture of esters selected from esters of formula (I) and (II). The ester of formula (I) is a dicarboxylic acid ester and the ester of formula (II) is a C2 or C3 carboxylic acid diester of glycol. In addition, the composition may contain various additives selected from lubricity additives, antioxidants, corrosion inhibitors and stabilizers such as primary or secondary aliphatic amines containing from 4 to 12 carbon atoms.

U.S. Patents 2,580,036, 5,204,102 and 3,784,474 disclose mineral lubricating oil compositions essentially containing a base oil having hydrophobic and film-forming properties.

US Patent 3,003,968 discloses a hydraulic fluid composition containing a C2-5 carboxylic acid diester of polyoxyethylene glycols.

GB patent application 1 131 263 discloses a hydraulic Chemical liquid composition based on glycol ether or on a mixture of polyalkylene glycol and a glycol ether. The composition is not based on a boric acid ester of a glycol ether.

GB Patent Application 908 291 discloses esters of ricinoleic acid and polyalkylene glycols which are particularly useful as components of a hydraulic fluid composition. However, the composition is not based on a boric acid ester of a glycol ether.

US Patent 3,206,486 discloses fatty acid monoesters of polyoxypropylene-polyoxyethylene block copolymer glycols and their use in brake fluid compositions. However, the compositions are not based on a boric acid ester of a glycol ether.

There is a hydraulic fluid composition, which is known, in particular according to US Patent 4,371,448, essentially based on a boric acid ester of a glycol ether and containing an alkylamine, optionally with corrosion inhibiting agent selected from fatty acids, esters of phosphorous or phosphoric acid with a C1-6 aliphatic alcohol and triazoles.

However, the known brake fluid compositions sometimes still leave something to be desired. The reason for this is mainly that among the requirements that a brake fluid composition should meet, there are also those that conflict due to the chemical and physical properties of the main components. Therefore, for example, it is known to be very difficult to adjust the viscosity of a brake fluid composition based on boric acid esters according to the DOT 5.1 standard and at the same time also to achieve an excellent corrosion-inhibiting system. In the formulation of known brake fluid compositions based on boric acid esters, a gain in one important property is therefore often achieved through a relatively high loss in another important property. In addition, what is required in a lubricating oil composition with hydrophobic and film-forming the properties are known, cannot be applied to a boric acid ester composition for hydraulic fluid composition with hydrophilic and hygroscopic properties, since the corrosion mechanisms are different.

It has been observed that the previously known hydraulic fluid compositions, similar to those mentioned above, do not simultaneously satisfy a number of conditions, such as extremely high boiling points, low kinematic viscosity at low temperatures and high protection against corrosion of ferrous alloys or metals, especially in a humid atmosphere. In particular, some manufacturers and/or users of motor vehicles, for example military vehicles, now require that the brake fluid compositions should be able to satisfy the following properties simultaneously:

- A dry boiling point of at least 260ºC and a wet boiling point of at least 180ºC, as defined in the US Department of Transportation Standard DOT 5.1,

- a kinematic viscosity at -40ºC of not more than 1500 mm²/s as defined in ISO Standard 4925, and

- excellent protection against corrosion of ferrous alloys or metals in a humid atmosphere, especially when it is known that some water absorption by brake fluids can occur after a long period of non-use of the vehicles.

A hydraulic fluid composition has now been found, and in particular a brake fluid composition based essentially on a boric acid ester of a glycol ether, containing a corrosion inhibitor system, allowing the above mentioned conditions to be simultaneously fulfilled. The composition, and in particular its corrosion inhibiting system, must at the same time provide good compatibility with water, causing possible water absorption of the composition and excellent anticorrosive properties in a humid atmosphere, while maintaining the boiling point. point and the kinematic viscosity properties, especially at very precise contents, required by the standards mentioned above.

The present invention therefore relates to a hydraulic fluid composition based essentially on a boric acid ester of a glycol ether, containing a corrosion-inhibiting system, characterized in that it includes:

(1) At least one component (A) selected from fatty, and optionally ethoxylated, mono-, di- or polyamines, and fatty amines containing at least one C 8 -C 22 alkyl or alkylene radical R, where the alkylene radical R may contain one or more ethylenic double bonds, or from the salts of one or more carboxylic acids with the mentioned amines in an amount of 0.05 to 2% by weight of the component(s) (A), and

(2) at least one component (B) selected 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 in an amount of 0.5 to 10% by weight of the component(s) (B), wherein the mentioned fatty acids are monocarboxylic acids having 8-22 carbon atoms.

Fatty mono-, di- or polyamines mean primary, secondary or tertiary amines containing at least one C8-22, preferably C13-22, in particular C15-18, e.g. C16- or C18-alkyl or alkylene radical R, where the alkylene radical R can contain one or more ethylenic double bonds.

The component (A) can in particular be a fatty mono-, di- or polyamine, corresponding to one of the following general formulas:

R¹-NH₂; R¹-NH-R²;

R1 -NH-(CH2 )3 -NH2 ;

R¹-[NH-(CH₂)₃]₂-NH₂: R¹-[NH-(CH₂)₃]n-NH₂

in which the general formulas R¹ and R², which are identical or different, have the above-mentioned definition of the radical R, n is a number in the range from 3 to 6 and x, y and z, which are identical or different, are numbers in the range from 1 to 3.

The component (A) is preferably the salt of one or more carboxylic fatty acids, in particular C8-22, with one of the fatty mono-, di- or polyamines, corresponding in particular to one of the above general formulas and in particular to the general formula:

R¹-NH-(CH₂)₃-NH₂

in which R¹ has the same meaning as above.

Component (A) is also preferably a fatty diamine, in particular according to the general formula:

R¹-NH-(CH₂)₃-NH₂

in which R¹ has the same meaning as above, in particular R¹ is an alkylene radical, e.g. a C₁₈-alkylene radical.

The component (B) can be the product of the reaction of one or more carboxylic fatty acids, in particular C₈₋₂₂, with a polyoxyalkylene glycol, such as diethylene glycol or preferably dipropylene glycol. It can also be the product of the transesterification reaction of one or more esters of the carboxylic fatty acids, in particular C₈₋₂₂, preferably of one or more glycerides of the mentioned carboxylic fatty acids, with a polyoxyalkylene glycol, such as diethylene glycol or preferably dipropylene glycol. The component (B) can preferably be the product of the transesterification reaction of castor oil with a polyoxyalkylene glycol, such as diethylene glycol or especially dipropylene glycol. The polyoxyalkylene glycol used as component (B) contained in the above-mentioned reaction products usually corresponds to the general formula:

HO-(CH₂CHR²O)n-H

in which R² is a hydrogen atom or a C₁₋₄-alkyl radical, preferably the methyl radical, and n is a number in the range from 1 to 4, preferably 2 or 3, in particular 2.

Fatty acids are monocarboxylic acids with 8 to 22, preferably 12 to 20, especially 15 to 18, e.g. 18 carbon atoms.

The composition according to the invention contains from 0.05 to 2%, preferably from 0.1 to 1% by weight of the component (or components) (A) and from 0.5 to 10%, preferably from 1 to 8% by weight of the component (or components) (B).

The composition is essentially based on a boric acid ester of a glycol ether in a ratio that can be in the range of 40 to 95%, preferably 65 to 95% by weight. The boric acid ester of a glycol ether is preferably a boric acid ester of an ethylene glycol monoalkyl ether, which is usually obtained when orthoboric acid and an ethylene glycol monoalkyl ether, according to the formula:

R³(OCH₂CH₂)mOH

in which R³ is an alkyl radical, e.g. having 1 to 4, preferably 1 or 2 carbon atoms, and m is a number in the range from 1 to 4, preferably 2 to 3. The preferred boric acid ester of a glycol ether is the boric acid ester of a triethylene glycol monomethyl ether. The composition can additionally advantageously contain at least one glycol ether, such as triethylene glycol monobutyl ether or monoethyl ether, or, preferably, triethylene glycol monomethyl ether in a ratio which can be in the range from 5 to 40% by weight, preferably from 10 to 30% by weight.

The composition may also contain other additives, such as corrosion inhibitors. In particular, it may contain the following additives:

- From 0.5 to 5% by weight of at least one amine capable in particular of neutralising the boric acid ester used, in particular an amine containing at least one alkyl radical, in particular of C₁₋₇, or a cycloalkane radical, in particular of C₅₋₇, or, in turn, an alkoxy radical, in particular of C₁₋₇ or one of these ethoxylated amines, for example di-n-butylamine, tri-n-butylamine, diisopropanolamine of the general formula: HN(CH₂CHOHCH₃)₂, monocyclohexylamine, dicyclohexylamine, 2-amino-1-ethanol, diethanolamine of the general formula: HN(CH₂-CH₂OH)₂, monomethanolmonopropylamine of the general formula: HN(CH₂OH)(CH₂CH₂CH₃) or diisopropylamine;

- from 0.1 to 2% by weight of an N-acyl derivative of sarcosine, for example N-oleyl acyl sarcosine, sold by Ciba-Geigy under the name "Sarkosyl 0®"

- from 0.1 to 2% by weight of corrosion-inhibiting additives, such as benzotriazole or tolyltriazole, triphenyl phosphite, dodecenyl succinic acid or an antioxidant, such as bisphenol A or polymerized trimethylquinoline.

All the percentages by weight indicated above in each case refer to the total weight of the composition and in such a way that the sum of the percentages of the composition is always equal to 100.

The composition according to the present invention can be prepared by mixing the components (A) and (B) and optionally other components and additives with the boric acid ester of a glycol ether, in any order, under an inert atmosphere such as nitrogen and a temperature which may be in the range of -20° to +50°C.

The hydraulic fluid composition according to the present invention is particularly suitable for use as a brake fluid. It can additionally meet the requirements of the standards FMVSS 116-DOT 4, and in particular the standards DOT 5.1 regarding dry and wet boiling points, the requirements of ISO standard 4925 regarding kinematic viscosity at -40ºC, and those of SAE standard J 1703 - January 1995 regarding fluidity and appearance of the brake fluid at -50ºC, while at the same time being able to demonstrate excellent anti-corrosive properties in a humid atmosphere according to the LCSEA-C-6 test procedure of the French Armies' Department of Petrols.

The present invention also relates to a process for the treatment of a hydraulic fluid composition, in particular a brake fluid composition, including a boric acid ester of a glycol ether, preferably the boric acid ester of triethylene glycol monomethyl ether, and optionally a glycol ether, such as triethylene glycol monobutyl ether or monoethyl ether, or preferably triethylene glycol monomethyl ether, a treatment for reducing the corrosion of iron(II) alloys or metals in contact with the said composition, in particular in a humid atmosphere, including the addition of a corrosion-inhibiting system, characterized in that the corrosion-inhibiting system contains:

(1) At least one component (A) selected from fatty and optionally ethoxylated mono-, di- or polyamines, or from the salts of one or more carboxylic acids with the amines mentioned, in an amount of from 0.05 to 2% by weight of the component(s) (A), and

(2) at least one component (B) selected 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, in an amount of 0.5 to 10% by weight of the component(s) (B).

In particular, components (A) and (B) may correspond to those described above and in particular have the preferred constituents (A) and (B), used in particular in the proportions mentioned above. The composition treated according to the present invention may additionally include additives such as those mentioned above and in the same proportions. The present process for the treatment of a hydraulic fluid composition, in particular a brake fluid, has the advantage of ensuring excellent protection against the corrosion of the ferrous alloys or metals, in particular in a humid atmosphere, while maintaining the dry and wet boiling points and the kinematic viscosity at -40ºC at the content of the standards mentioned above, without causing turbidity or crystallization at -50ºC under a humid atmosphere.

In the process of the invention, ingredients (A) and (B) and optionally other ingredients or additives may be mixed with the boric acid ester of a glycol ether in any order, under an inert atmosphere such as nitrogen and a temperature which may range from -20° to +50°C.

Test and measurement procedures:

- The dry boiling point, or equilibrium reflux boiling point (ERBP), is measured in ºC according to ASTM method D-1120;

- the wet equilibrium reflux boiling point (WERBP) is measured in ºC according to the procedure of SAE Standard J 1703 - January 1995;

- the fluidity and appearance at -50ºC are measured and determined according to the procedures of SAE Standard J 1703 - January 1995;

- the anti-corrosive properties in a humid atmosphere are measured according to the French Armies' Department of Petrols method LC SEA-C-6, a method which includes:

To N-oleyl of sarcosine, as an additive,

- "Duomeen 0®", sold by Akzo Nobel, corresponding to N-oleyl-1,3-diaminopropane, as component (A),

- "Inipol 002®", sold by CECA-Companie, corresponds to N-oleyl-1,3-diaminopropanedioleate, as component (A),

- "Delco A Base®", manufactured by BP Chemicals, corresponding to the ester obtained by transesterification of castor oil with dipropylene glycol, as component (B).

Comparative tests 1 to 4 and example 5

Comparative brake fluid compositions 1 to 4 and the brake fluid composition 5 according to the present invention are prepared by mixing the various ingredients mentioned in Table 1 at ambient temperature (20°C) and under a nitrogen atmosphere.

The results of the measurements and the tests carried out on these compositions are summarized in Table 2.

Analyses of Tables 1 and 2 show that:

- Only composition 5 according to the present invention, including in particular 0.4% by weight of "Inopol 002®" as component (A) and 4% by weight of "Delco A Base®" as component (B), enables to simultaneously meet the requirements of the above-mentioned standards and to exhibit excellent anticorrosive properties in a humid atmosphere;

- although comparative compositions 1 to 3 contain component (A) in proportions (0.5 wt. %, 1.0 wt. %, and 10 wt. %, respectively) which are higher than in composition 5 (0.4 wt. %) and although comparative composition 4 contains component (B) in a proportion (10.0 wt. %) which is much higher than that in composition 5 (4.0 wt. %), none of these comparative compositions exhibits satisfactory anticorrosive properties in a humid atmosphere, nor do they simultaneously satisfy all the requirements of dry or wet boiling point, kinematic viscosity at -40ºC and appearance at -50ºC.

The components (A) and (B) used simultaneously in the present invention form, by a synergistic effect, a hydraulic fluid and in particular a brake fluid composition with excellent properties which are superior to those of the comparative compositions containing only a single one of the components (A) and (B), even in proportions which are very strikingly high compared to those used in the present invention.

Example 6

The brake fluid composition 6 according to the present invention is prepared by mixing the following various components at ambient temperature (20°C) and under a nitrogen atmosphere:

% by weight

Boric acid ester of triethylene glycol monomethyl ether: 72.0

Triethylene glycol monomethyl ether: 19.9

Cyclohexylamine: 1.0

Other specific additives (see (1) in Table 1): 2.1

"Sarcosyl 0®": 0.5

"Duomeen 0®" [Component (A)]: 0.5

"Delco A Base®" [Component (B)]: 4.0

The results of the measurements and tests carried out on this composition are collected below:

- ERBP: 265ºC

- EATING TEMPERATURE: 182ºC

- Kinematic viscosity at -40ºC: 1350 mm²/s

- Fluidity and appearance at -50ºC:

Appearance: Bright and clear

Flow time: 6 s

- Test for corrosion in humid atmosphere:

Corrosion spots: 0

Comments: Very satisfactory. Table 1 Comparative compositions 1 to 4 and composition 5 according to the invention

(1) Triphenyl phosphite (0.25 wt%) + tolyltriazole (0.05 wt%) + polymerized trimethylquinoline (0.5 wt%), sold by Monsanto under the trademark "Flectol"® + triethylene glycol monobutyl ether (1.3 wt%). Table 2 Results of tests and measurements on comparative compositions 1 to 4 and composition 5 according to the invention

Claims (10)

1. Hydraulic fluid composition based essentially on a boric acid ester of a glycol ether, containing a corrosion-inhibiting system, characterized in that it includes: (1) At least one component (A) selected from fatty and optionally ethoxylated mono-, di- or polyamines and fatty amines containing at least one C 8-22 alkyl or alkylene radical R, where the alkylene radical R may contain one or more ethylenic double bonds, or from the salts of one or more carboxylic acids with the mentioned amines in an amount of 0.05 to 2% by weight of the component(s) (A), and (2) at least one component (B) selected 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 in an amount of 0.5 to 10% by weight of the component(s) (B), wherein the mentioned fatty acids are monocarboxylic acids having 8 to 22 carbon atoms. 2. Composition according to claim 1, characterized in that the component (A) is a fatty mono-, di- or polyamine, corresponding to one of the following general formulas: R¹-NH₂; R¹-NH-R²; R1 -NH-(CH2 )3 -NH2 ; R1 -[NH-(CH2 )3 ]2 -NH2 ; R1 -[NH-(CH2 )3 ]n-NH2 ; in which the general formulas R¹ and R², identical or different, denotes a C₈₋₂₂-alkyl or -alkylene radical R, where the alkylene radical R contains 1 or more ethylenic double bonds, n is a number in the range from 3 to 6 and x, y and z, identical or different, are numbers in the range from 1 to 3. 3. Composition according to claim 1 or 2, characterized in that the component (A) is the salt of one or more carboxylic fatty acids with one of the fatty mono-, di- or polyamines. 4. Composition according to claim 3, characterized in that the fatty mono-, di- or polyamine has the general formula R¹-NH-(CH₂)₃-NH₂ in which R¹ represents a C₈₋₂₂-alkyl or -alkylene radical R where the alkylene radical R contains one or more ethylenic double bonds. 5. Composition according to any one of claims 1 to 4, characterized in that component (B) is the product resulting from the reaction of one or more C8-22 carboxylic fatty acids with diethylene glycol or dipropylene glycol, or from the transesterification reaction of one or more glycerides of C8-22 carboxylic fatty acids with diethylene glycol or dipropylene glycol. 6. Composition according to any one of claims 1 to 5, characterized in that component (B) is the product of the transesterification reaction of castor oil with diethylene glycol or dipropylene glycol. 7. Composition according to any one of claims 1 to 6, characterized in that it includes from 0.1 to 1% by weight of the component(s) (A) and from 1 to 8% by weight of the component(s) (B). 8. Composition according to any one of claims 1 to 7, characterized in that it is based essentially on the boric acid ester of triethylene glycol monomethyl ether and optionally contains a glycol ether selected from triethylene glycol monobutyl ether or monoethyl ether or monomethyl ether. 9. Process for the preparation of the composition according to any of claims 1 to 8, characterized in that the components (A) and (B) and optionally other components and additives are mixed with the boric acid ester of a glycol ether under an inert atmosphere. 10. A process for treating a hydraulic fluid composition including a boric acid ester of a glycol ether to reduce corrosion of ferrous alloys or metals in contact with said composition, including the addition of a corrosion inhibiting system, characterized in that the corrosion inhibiting system includes: (I) At least one component (A) selected from fatty and optionally ethoxylated mono-, di- or polyamines, wherein the fatty amines mentioned contain at least one C8-22 alkyl or alkylene radical R, where the alkylene radical R can contain one or more ethylenic double bonds, or from the salts or from one or more carboxylic acids with the amines mentioned, in an amount of 0.05 to 2% by weight of the component(s) (A), and (2) at least one component (B) selected 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, in an amount of 0.5 to 10% by weight of the component(s) (B), wherein the fatty acids mentioned are monocarboxylic acids having 8 to 22 carbon atoms.