Hydraulic fluid composition

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

[0001] The present invention relates to a hydraulic fluid composition, especially a brake fluid composition employed in particular in the braking systems of motor vehicles, and to a process for the treatment of a hydraulic fluid with a view to reducing the corrosion of the ferrous alloys or metals in contact with the said fluid.

[0002] US Patent No. 3,914,182 discloses a hydraulic fluid composition comprising a borate ester of a glycol ether and an ester or a mixture of esters selected amongst 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 di-ester of glycol. Furthermore the composition may comprise various additives selected amongst lubricity additives, antioxidants, corrosion inhibitors and stabilizers such as primary or secondary aliphatic amines containing from 4 to 12 carbon atoms.

[0003] US Patents No. 2,580,036, No. 5,204,102 and No. 3,784,474 disclose mineral lubricating oil compositions essentially comprising a base oil which exhibits hydrophobic and film-forming properties.

[0004] US Patent No. 3,003,968 discloses a hydraulic fluid composition comprising a C₂ to C₅ carboxylic acid di-ester of polyoxyethylene glycols.

[0005] GB Patent Application No. 1,l3l,263 discloses a hydraulic fluid composition based on glycol ether or a mixture of a polyalkylene glycol and a glycol ether. The composition is not based on a boric ester of a glycol ether.

[0006] GB Patent Application No. 908,291 discloses esters of ricinoleic acid and polyalkylene glycols which are particularly useful as constituents of hydraulic fluid composition. However the composition is not based on a boric ester of a glycol ether.

[0007] US Patent No. 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 ester of a glycol ether.

[0008] There is a hydraulic fluid composition which is known, especially according to US Patent No. 4,371,448, essentially based on a boric ester of a glycol ether and comprising an alkylamine optionally with corrosion-inhibiting agent chosen from fatty acids, esters of phosphorous or phosphoric acid with a C₁-C₆ aliphatic alcohol and triazoles.

[0009] However, the known brake fluid compositions still leave something to be desired. The reason for this is, above all, that amongst the requirements which a brake fluid composition should fulfil, there are also those which are conflicting because of the chemical and physical properties of the main components. Thus, for example, it is known to be very difficult to adjust the viscosity of a brake fluid composition based on a boric acid esters in accordance with the DOT-5. 1 standard and at the same time also to achieve an excellent corrosion inhibiting system. When formulating known brake fluid compositions based on boric acid esters, a gain in an important property is thus frequently brought by a relatively high sacrifice in another important property. Furthermore, what is known in a lubricating oil composition having hydrophobic and film-forming properties cannot be applied to a boric acid ester composition for hydraulic fluid composition having hydrophilic and hygroscopic properties, since the corrosion mechanismes are different.

[0010] It has been observed that the hydraulic fluid compositions known hitherto, like that mentioned above, do not simultaneously satisfy a number of requirements such as extremely high boiling points, a low kinematic viscosity at low temperature and a high protection against corrosion of ferrous alloys or metals, especially in a moist atmosphere. In particular, some manufacturers and/or users of motor vehicles such as military vehicles now demand that the brake fluid compositions should be capable of simultaneously satisfying the following characteristics :

• a dry boiling point of at least 260°C and a wet boiling point of at least 180°C, as defined in the US Department of Transportation standard DOT 5.1,
• a kinematic viscosity at - 40°C of not more than 1500 mm²/s, as defined in ISO standard 4925, and
• an excellent protection against the corrosion of ferrous alloys or metals in a moist atmosphere, especially when it is known that some water uptake by brake fluids may appear after a long period of nonutilization of the vehicles.

[0011] A hydraulic fluid composition has now been found, and especially a brake fluid composition based essentially on a boric ester of a glycol ether comprising a corrosion-inhibitor system, allowing the abovementioned requirements to be satisfied simultaneously. The composition and in particular its corrosion-inhibiting system, must ensure at the same time good compatibility with water originating a possible water uptake of the composition and excellent anticorrosive properties in a moist atmosphere, while maintaining the boiling point and kinematic viscosity characteristics, especially at the very severe levels demanded by the abovementioned standards.

[0012] The present invention therefore relates to a hydraulic fluid composition based essentially on a boric ester of a glycol ether, comprising a corrosion-inhibiting system, characterized in that it includes :

(1) at least one constituent (A) chosen from fatty and optionally ethoxylated mono-, di- or polyamines or from 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.

[0013] Fatty mono-, di- or polyamines are generally understood to mean primary, secondary or tertiary amines containing at least one C₈-C₂₂, preferably C₁₃-C₂₂, especially C₅-C₁₈, e.g. C₁₆ or C₁₈ alkyl or alkylene radical R, the alkylene radical R which may contain one or more ethylenic double bonds.

[0014] The constituent (A) may be especially a fatty mono-, di- or polyamine corresponding to one of the following general formulae :

        R¹-NH₂ ; R¹-NH-R² ;









in which general formulae R¹ and R², being identical or different, have the definition of the abovementioned radical R, n is a number ranging from 3 to 6, and x, y and z, being identical or different, are numbers ranging from 1 to 3.

[0015] The constituent (A) is preferably the salt of one or more carboxylic fatty acids, especially C₈-C₂₂, with one of the fatty mono-, di- or polyamines corresponding especially to one of the preceding general formulae and in particular to the general formula :

        R¹-NH-(CH₂)₃-NH₂

in which R¹ has the same definition as above.

[0016] Also the constituent (A) is preferably a fatty diamine, in particular corresponding to general formula :

        R¹-NH-(CH₂)₃-NH₂

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

[0017] The constituent (B) may be the product of the reaction of one or more carboxylic fatty acids, especially C₈-C₂₂, with a polyoxyalkylene glycol such as diethylene glycol or preferably dipropylene glycol. It may also be the product of the transesterification reaction of one or more esters of carboxylic fatty acids, especially C₈-C₂₂, preferably of one or more glycerides of the said carboxylic fatty acids, with a polyoxyalkylene glycol such as diethylene glycol or preferably dipropylene glycol. The constituent (B) may be preferably the product of the transesterification reaction of castor oil with a polyoxyalkylene glycol such as diethylene glycol or especially dipropylene glycol. The polyoxyalkylene glycol involved in the above-mentioned reaction products used as constituent (B) generally corresponds to the general formula :

        HO-(CH₂CHR²O)_n-H

in which R² represents a hydrogen atom or a C₁ - C₄ alkyl radical, preferably the methyl radical, and n is a number ranging from 1 to 4, preferably equal to 2 or 3, especially equal to 2.

[0018] Fatty acids are generally understood to mean monocarboxylic acid with 8 to 22, preferably 12 to 20, especially 15 to 18, e.g. 18 carbon atoms.

[0019] The composition according to the invention may include from 0.05 to 2 %, preferably from 0. 1 to 1 % by weight of the constituent(s) (A) and from 0.5 to 10 %, preferably from 1 to 8 % by weight of the constituent(s) (B).

[0020] The composition is based essentially on a boric ester of a glycol ether in a proportion that can range from 40 to 95 %, preferably from 65 to 95 % by weight. The boric ester of a glycol ether preferably is a boric ester of an ethylene glycol monoalkyl ether which is generally obtained when reacting orthoboric acid and an ethylene glycol monoalkyl ether corresponding to the formula :

        R³(OCH₂CH₂)_mOH

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

[0021] The composition may also include other additives such as corrosion-inhibiting agents. In particular it may include the following additives :

• from 0.5 to 5 % by weight of at least one amine capable especially of neutralizing the boric ester employed, in particular an amine containing at least one alkyl radical, especially from C₁ to C₇, or a cyclane radical, especially from C₅ to C₇, or, again, an alkoxy radical especially from C₁ to C₆, or one of these ethoxylated amines, for example di-n-butylamine, tri-n-butylamine, diisopropanolamine of general formula :
  
          HN(CH₂CHOHCH₃)₂,
  
  monocyclohexylamine, dicyclohexylamine, 2-amino-1-ethanol, diethanolamine of general formula :
  
          HN (CH₂-CH₂OH)₂,
  
  monomethanolmonopropylamine of general formula :
  
          HN(CH₂OH)(CH₂CH₂CH₃)
  
  or diisopropylamine ;
• from 0. 1 to 2 % by weight of an N-acyl derivative of sarcosine, for example the N-oleyl acylsarcosine marketed 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, dodecenylsuccinic anhydride or an antioxydant such as bisphenol A or polymerized trimethylquinoline.

[0022] All the percentages by weight given in each case above relate to the total weight of the composition and so that the sum of the percentages of the composition is always equal to 100.

[0023] The composition according to the present invention may be prepared by mixing the constituents (A) and (B) and optionally other constituents and additives with the boric ester of a glycol ether, in any order, under an inert atmosphere such as nitrogen, and at a temperature that can range from - 20 to + 50°C.

[0024] The hydraulic fluid composition according to the present invention is particularly suitable for being employed as brake fluid. It may additionally satisfy the requirements of the standards FMVSS 116-DOT 4 and in particular of the standards DOT 5.1 relating to the dry and wet boiling points, the requirements of the ISO standard 4925 relating to kinematic viscosity at - 40°C and those of the SAE standard J 1703 - January 1995, relating to the fluidity and the appearance of the brake fluid at - 50°C, and may simultaneously exhibit excellent anticorrosive properties in a moist atmosphere according to the LCSEA-C-6 test method of the French Armies' Department of Petrols.

[0025] The present invention also relates to a process for the treatment of a hydraulic fluid composition, especially of a brake fluid composition including a boric ester of a glycol ether, preferably the boric 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 ferrous alloys or metals in contact with the said composition, especially in a moist atmosphere, including the addition of a corrosion-inhibiting system, characterized in that the corrosion-inhibiting system includes :

(1) at least one constituent (A) chosen from fatty and optionally ethoxylated mono-, di- or polyamines, or from 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.

[0026] In particular, the constituents (A) an (B) may correspond to those described above and especially to the preferred constituents (A) and (B), employed in particular in the abovementioned proportions. 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 treatment of a hydraulic fluid composition, in particular of brake fluid, has the advantage of ensuring an excellent protection against the corrosion of ferrous alloys or metals especially in a humid atmosphere, while maintaining the dry and wet boiling points and the kinematic viscosity at - 40°C at the level of the abovementioned standards, without causing turbidity or crystallization at - 50°C under a moist atmosphere.

[0027] In the process of the invention the constituents (A) and (B) and optionally other constituents or additives may be mixed with the boric ester of a glycol ether in any order, under an inert atmosphere such as nitrogen and a temperature that can range from - 20° to + 50°C.

Test and measurement methods :

[0028] 

• the dry boiling point, or equilibrium reflux boiling point (ERBP), is measured in °C according to the ASTM method D-1120 ;
• the wet equilibrium reflux boiling point (WERBP) is measured in °C according to the method of the SAE standard J 1703 - January 1995 ;
• the fluidity and the appearance at - 50°C are measured and assessed according to the methods of the SAE standard J 1703 - January 1995 ;
• the anticorrosive properties in a moist atmosphere are measured according to the method LC SEA-C-6 of the French Armies' Department of Petrols, a method which includes :

  1. Objective
  The test is intended to verify the ability of the synthetic liquid for auto brake H-542 to ensure the protection of metal components against oxidation and corrosion, especially when the vehicles are being stored.

  2. Principle
  Test pieces are immersed in the liquid to be tested and are then drip-drained and placed in a moist oven. The performance of the product is judged according to the rust spots which have or have not appeared on the test pieces.

  3. Apparatus

  3.1.

  A controllable-humidity oven of internal dimension L x 1 x h:55 x 52 x 64.5 cm (or similar dimensions).

  3.2.

  Three test pieces of pig iron produced by cutting out strips 10 mm in width from the wheel cylinders of a brake circuit, 31.75 mm or 38.1 mm (1.25 or 1.50 inch) in diameter, along a generatrix not including any protuberance or orifice ; the test pieces are employed as they are without any other polishing or treatment.

  4. Procedure

  4.1.

  Handle test pieces only with pincers ; any contact with bare hands may distort the test results.

  4.2.

  Verify the test pieces before the test (any trace of pitting or corrosion is unacceptable and any doubtful test piece must be rejected).

  4.3.

  The test pieces are suspended for 15 min in the vapour phase of boiling trichloroethylene and are then left do dry in the open air.

  4.4.

  Each test piece is then immersed in the liquid to be tested for one minute and then left to drip-drain for one minute. The three test pieces are then placed for 150 hours in a moist oven in a perfectly horizontal position on glass rods positioned 13 cm from the bottom of the oven, the concavity facing upwards, the oven being controlled at 95 ± 4 % relative humidity and at a temperature of 30 ± 0.5°C.

  4.5.

  At the end of the period of 150 hours, withdraw the test pieces with pincers and examine them. Note the corrosion, pits, changes in colour and any raised deterioration on the concave surface of the test piece. Disregard anything that appears less than 1.5 mm from the cutting lines or less than 7 mm from the ends of the test piece.

  5. Expression of the results
  The test is considered to be satisfactory if at least two test pieces out of three show not more than three corrosion spots less than one millimetre in diameter.

Constituents and additives employed by way of example in the composition according to the invention :

[0029] 

• «Sarkosyl 0» ® marketed by the company Ciba Geigy, corresponding to N-oleyl of sarcosine, as additive,
• «Duomeen 0» ® marketed by the company Akzo Nobel, corresponding to N-oleyl-1,3-diaminopropane, as constituent (A),
• «Inipol 002» ® marketed by the company CECA, corresponding to N-oleyl-1,3-diaminopropane dioleate, as constituent (A),
• «Delco A Base» ® manufactured by BP Chemicals, corresponding to the ester obtained by transesterification of castor oil with dipropylene glycol, as constituent (B).

Comparative tests 1 to 4 and Example 5

[0030] Brake fluid comparative compositions 1 to 4 and the brake fluid composition 5 according to the present invention are prepared by mixing the various constituents mentioned in Table 1 at ambient temperature (20°C) and under a nitrogen atmosphere.

[0031] The results of the measurements and tests performed on these compositions are collated in Table 2.

[0032] Analysis of Tables 1 and 2 shows that :

• only composition 5 according to the present invention, including especially 0.4 % by weight of «Inopol 002» ® as constituent (A) and 4 % by weight of «Delco A Base» ® as constituent (B) makes it possible simultaneously to satisfy all the requirements of the abovementioned standards and to exhibit excellent anticorrosive properties in a moist atmosphere ;
• although the comparative compositions 1 to 3 contain the constituent (A) in proportions (0.5 %, 1.0 %, 1.0 % by weight respectively) which are higher than that in composition 5 (0.4 % by weight), and although comparative composition 4 contains the constituent (B) in a proportion (10.0 % by weight) which is much higher than that in composition 5 (4.0 % by weight), none ofthese comparative compositions exhibits satisfactory anticorrosive properties in a moist atmosphere, nor do they satisfy simultaneously all the requirements of dry or wet boiling point, of kinematic viscosity at - 40°C and of appearance at - 50°C.

[0033] The constituents (A) and (B) employed simultaneously in the present invention form, through a synergy effect, a hydraulic fluid and especially brake fluid composition with excellent properties which are superior of those of the comparative compositions containing only a single one of the constituents (A) and (B), even in proportions that are very markedly high than those employed in the present composition.

Example 6

[0034] Brake fluid composition 6 according to the present invention is prepared by mixing the following various constituents at ambient temperature (20°C) and under a nitrogen atmosphere :
   % by weight

• boric ester of triethylene glycol monomethyl ether :    72.0
• triethylene glycol monomethyl ether :    19.9
• cyclo-hexylamine :    1.0
• other specific additives (see (1) in Table 1) :    2.1
• «Sarkosyl 0» ® :    0.5
• «Duomeen 0» ® [constituent (A)] :    0.5
• «Delco A Base» ® [constituent (B)] :    4.0

[0035] The results of the measurements and tests performed on this composition are collected hereafter :

• ERBP : 265°C
• WERBP: 182°C
• kinematic viscosity at - 40°C : 1350 mm²/s
• fluidity and appearance at - 50°C :

  . appearance : bright and clear

  . flow time : 6 s

• test for corrosion in moist atmosphere :

  . corrosion spots : 0

  . comments : very satisfactory.
  
  
  
  

Claims

1. Hydraulic fluid composition based essentially on a boric ester of a glycol ether, comprising a corrosion-inhibiting system, characterized in that it includes :

(1) at least one constituent (A) chosen from fatty and optionally ethoxylated mono-, di- or polyamines or from 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.

2. Composition according to Claim 1, characterized in that the constituent (A) is a fatty mono-, di- or polyamine corresponding to one of the following general formulae:

        R¹-NH₂ ; R¹-NH-R² ;









in which general formulae R¹ and R², being identical or different, denote a C₈-C₂₂ alkyl or alkylene radical R, the alkylene radical R containing 1 or more ethylenic double bonds, n is a number ranging from 3 to 6, and x, y and z, being identical or different, are numbers ranging from 1 to 3.

3. Composition according to Claim 1 to 2, characterized in that the constituent (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 corresponds to the general formula

        R¹-NH-(CH₂)₃-NH₂

in which R¹ denotes a C₈-C₂₂ alkyl or alkylene radical R, the alkylene radical R containing one or more ethylenic double bonds.

5. Composition according to any one of Claims 1 to 4, characterized in that the constituent (B) is the product resulting from the reaction of one or more C₈-C₂₂ carboxylic fatty acids with diethylene glycol or dipropylene glycol or from the transesterification reaction of one or more glycerides of C₈-C₂₂ carboxylic fatty acids with diethylene glycol or dipropylene glycol.

6. Composition according to any one of Claims 1 to 5, characterized in that the constituent (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 0.05 to 2 % by weight of the constituent(s) (A) and from 0.5 to 10 % by weight of the constituent(s) (B).

8. Composition according to any one of Claims 1 to 7, characterized in that it is based essentially on the boric ester of triethylene glycol monomethyl ether and optionally comprised a glycol ether chosen from triethylene glycol monobutyl ether or monoethyl ether or monomethyl ether.

9. Process for the preparation of the composition according to any one of Claims 1 to 8, characterized in that the constituents (A) and (B) and optionally other constituents and additives are mixed with the boric ester of a glycol ether under an inert atmosphere.

10. Process for the treatment of a hydraulic fluid composition including a boric ester of a glycol ether, in order to reduce the corrosion of ferrous alloys or metals in contact with the said composition, including the addition of a corrosion-inhibiting system, characterized in that the corrosion-inhibiting system includes:

(1) at least one constituent (A) chosen from fatty and optionally ethoxylated mono-, di- or polyamines or from the salts or 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 polyoxyalkylene glycol.