AU2004219905A1 - DOT 4 brake fluids - Google Patents

Description

IN THE MATTER of a PCT Application in the name of BASF Aktiengesellschaft filed under PCT/EP2004/002552 and IN THE MATTER OF its transfer for an Application for an Australian Patent I, Gunter Isenbruck, Dr. phil.nat., Dipl.Chem., Patentanwalt and European Patent Attorney in Mannheim (F.R.G.), do solemnly and sincerely declare that I am conversant with the English and German languages and am competent in translating thereof, and that the following is, to the best of my knowledge and belief, a true and correct translation of the International Patent Application filed under No. PCT/EP2004/002552 by BASF Aktiengesellschaft for ,,DOT 4 brake fluids" Mannheim, August 12, 2005 Ginter Isenbruck - Patentanwalt - P.F. 0000054341/Ab As ORIGINALLY FILED DOT 4 brake fluids 5 The present invention relates to novel DOT 4 brake fluids, in which the addition of borates (boric acid esters) is not necessary. The brake fluids comprise 10 (a) from 10 to 50% by weight of diethylene glycol and/or dipropylene glycol and (b) from 50 to 90% by weight of (poly)ethylene glycol monoalkyl ether and/or (poly)propylene glycol monoalkyl ether 15 and are preferably free of polyglycol dialkyl diethers. Hydraulic fluids and in particular brake fluids for motor vehicles are subject to very high requirements with respect to their chemical and physical properties. According to the existing standards and specifications for brake fluids of the US Department of 20 Transportation (DOT) in the Federal Motor Vehicle Safety Standard FMVSS No. 116 and the standard SAE J 1704 published by the Society of Automotive Engineers, modem brake fluids should on the one hand have a high equilibrium reflux boiling point (ERBP) and high wet ERBP, but on the other hand should also have a viscosity which changes only slightly within a wide temperature range. 25 Accordingly, for a DOT 4 brake fluid according to FMVSS No. 116, the specification values shown below must be complied with: ERBP: 2 230 0 C 30 Wet ERBP: 155 0 C Viscosity at -40'C: 1 800 mm 2 /s There are moreover more stringent requirements for sufficiently good protection of metals and nonferrous metals from corrosion by brake fluids, which can be achieved by corrosion 35 inhibitor additives contained therein. Commercial DOT 4 brake fluids always contain boric acid esters, for example methyltriglycol borate, which can chemically eliminate certain amounts of penetrating P.F. 0000054341/Ab -2 water from the brake fluid by hydrolysis. A disadvantage is that boric acid esters are themselves hygroscopic, with the result that such DOT 4 brake fluids, particularly in regions of high relative humidity, for example in tropical and subtropical regions, can very rapidly absorb so much moisture that, in spite of the trapping function of the boric acid 5 esters, the operability of a brake system filled therewith can be adversely affected. US 3,625,899 describes DOT 4 brake fluids which contain from 54.5 to 92% of at least one boric acid ester, up to 20% of polyalkylene glycols and from 3 to 43% of polyglycol monoalkyl or dialkyl ethers, in addition to further additives. 10 US 3,972,822 describes DOT 4 brake fluids which contain from 40 to 65% of polyglycol monoalkyl ethers, from 16 to 45% of polyglycols and from 10 to 19% of boric acid esters plus corrosion inhibitors. 15 WO 00/46325 describes DOT 4 brake fluids which contain methyltriglycol borate, glycol ethers and glycols in different amounts and an additive system. WO 02/38711, too, discloses corresponding DOT 4 brake fluids which contain different methylpolyglycol borates, polyglycol monoalkyl ethers and corrosion inhibitors. 20 DE 36 27 432 C2 describes borate-free brake fluids comprising from 30 to 80% of a glycol component and up to 70% of polyglycol alkyl ether. The glycol component in turn contains from 0 to 80, preferably from 55 to 80, % by weight of diethylene glycol and/or dipropylene glycol. The polyglycol alkyl ether component contains from 0 to 90, 25 preferably from 0 to 50, % by weight of at least one polyglycol monoalkyl ether. In selected mixing ratios, these fluids fulfill the DOT 4 specification. A disadvantage in the case of these formulations is in particular the ERBP only just above the specification limit and moreover the use of polyglycol dialkyl ethers which are more expensive to synthesize and often also lead to incompatibility reactions of rubber and sealing materials. 30 There is furthermore a need for low viscosity brake fluids which fulfill the DOT 4 specification. It is an object of the present invention to provide such a brake fluid. Preferably, this brake 35 fluid should not be very hygroscopic and should be capable of being used in regions of high relative humidity. In particular, it should be necessary to use only small amounts of boric acid esters or ideally the use of such esters should even be completely superfluous.

P.F. 0000054341/Ab -3 We have found that this object is achieved by a brake fluid comprising a) from 10 to 50% by weight of diethylene glycol and/or dipropylene glycol and 5 b) from 50 to 90% by weight of one or more monoalkyl ethers of (poly)ethylene glycol or (poly)propylene glycol. In particular, the novel fluids are free of boric acid esters. 10 Diethylene glycol or dipropylene glycol or a mixture of diethylene glycol and dipropylene glycol in any desired ratio may be used. Diethylene glycol is preferred. Diethylene glycol and/or dipropylene glycol are present in the novel brake fluids in an amount of from 10 to 50, preferably from 20 to 40, % by weight. 15 A further component of the novel brake fluid comprises one or more monoalkyl ethers of (poly)ethylene glycols and/or (poly)propylene glycols, which are present in the novel fluids in an amount of from 50 to 90, preferably from 60 to 80, % by weight. 20 Examples of suitable (poly)ethylene glycols are monoethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol and hexaethylene glycol. Examples of suitable (poly)propylene glycols are monopropylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, pentapropylene glycol and 25 hexapropylene glycol. Diethylene glycol, triethylene glycol and/or tetraethylene glycol are preferred. The alkyl radical in the monoalkyl ethers of (poly)ethylene glycol and (poly)propylene 30 glycol used according to the invention is preferably a linear or branched C 1

-C

6 -alkyl radical. It is more preferable to use a linear or branched C-C 4 -alkyl radical, for example methyl, ethyl, isopropyl, n-propyl, n-butyl, isobutyl, sec-butyl or tert-butyl. The alkyl radicals are in particular methyl, ethyl, isopropyl or n-butyl. 35 In the present invention, the use of methyldiethylene glycol, methyltriethylene glycol, methyltetraethylene glycol and/or butyltriethylene glycol is preferred.

P.F. 0000054341/Ab -4 The novel brake fluids have wet ERBPs and in particular ERBPs which are close to those which have been achieved to date with borate-free brake fluids. They are comparable with those achieved today only with borate-containing fluids. Owing to the absence of borate, however, the novel fluids are substantially less hygroscopic than borate-containing ones. 5 This is advantageous in particular during use in tropical and subtropical regions, since, although a part of the water is bound by the addition of borate, water is also relatively rapidly absorbed. This results in each case in a deterioration in the quality of the brake fluid. In particular, this loss of quality occurs frequently in the brake system of motor vehicles but also during storage and transport of the fluids. The novel brake fluids do not 10 have said disadvantages. It is true that the novel brake fluids may contain different amounts of boric acid esters. However, the advantages according to the invention of low hygroscopicity are generally not achieved thereby. This is the case in particular when boric acid esters are added in the 15 amounts customary according to the prior art. Furthermore, the novel fluids are in particular free of polyalkylene glycol dialkyl ethers. Although these too may be present in different amounts, in general the advantages of the novel brake fluids, in particular the compatibility with rubber and sealing materials, are 20 then not achieved, this too of course being dependent on the amount of any polyalkylene glycol dialkyl ethers present. Further polyglycols may be present as an optional component in the novel formulations. Relatively high-boiling reaction products of ethylene oxide and/or propylene oxide and/or 25 butylene oxide with water or diol are preferably used. In particular, reaction products of mixtures of ethylene oxide and propylene oxide with water are used. The number of alkylene oxide units in said polyglycols is usually from 2 to 10, preferably 2 or 3, and in an amount of up to 5%. 30 The effect of these high-boiling polyglycols is that of a lubricant, which is due substantially to an improvement in the temperature-viscosity behavior. The polyglycols impart sufficient viscosity to the polyglycol monoalkyl ethers, which often have low viscosity at high temperatures, and thus ensure sufficient lubrication. Sufficient lubrication is desired since, in the components of the motor vehicle brake system, rubber or elastomers 35 have to slide on metal with very little wear. In a further embodiment, the novel DOT 4 brake fluids for motor vehicles furthermore contain from 0.001 to 10, preferably from 0.005 to 4, in particular from 0.005 to 1, % by P.F. 0000054341/Ab -5 weight of one or more corrosion inhibitors, for example 1H-1,2,3-benzotriazole, 1H-1,2,3 tolutriazole, hydrogenated 1H-1,2,3-tolutriazole, benzimidazole and/or derivatives thereof, alkali metal salts of phosphoric acid and phosphorous acid, fatty acids, preferably caprylic, lauric, palmitic, stearic or oleic acid, and alkali metal salts thereof, esters of phosphoric 5 acid and of phosphorous acid, preferably ethyl phosphate, dimethyl phosphate, isopropyl phosphate, diisopropyl phosphate, butyl phosphite or dimethyl phosphite, mono- and dialkylamines which may be ethoxylated and salts thereof with mineral and fatty acids, preferably butylamine, hexylamine, octylamine, isononylamine, oleylamine, dipropylamine, diisopropylamine or dibutylamine, alkanolamines which may be 10 ethoxylated, preferably mono-, di- or triethanolamine, N,N'-di-n-butylaminoethanol or 1,1'-iminodipropan-2-ol, cyclohexylamine, and/or nitro aromatics, preferably 3 nitrobenzaldehyde. The novel brake fluids may also contain one or more of the heterocyclic compounds which 15 are described in WO 01/90281 and are of the following formula X ~N \ (R')n N z H where 20 (i) X is N, Y is CR and Z is N or (ii) X is N, Y is N and Z is N or CR or (iii) X is CR, Y is N and Z is N, R, in each case independently of further radicals R present, being a hydrogen atom or a 25 radical R1, R', in each case independently of further radicals R1 present, being alkyl, aryl, aralkyl, halogen, haloalkyl, unsubstituted or alkyl-, aryl- or aralkyl-substituted amino, a heterocyclic radical, cyano, carboxyl, alkoxycarbonyl, hydroxyl or alkoxy, said organic 30 radicals R 1 each being of 1 to 30 carbon atoms, and n being 0, 1 or 2. Examples of preferred compounds of this type include purine, adeinine, 6-chloropurine, 2,6-dichloropurine, 6-methoxypurine, 1H-1,2,3-triazolo[4,5b]pyridine, 6 histaminopurine and 6-furfurylaminopurine. 35 P.R 0000054341/Ab -6 The novel borate-free DOT 4 brake fluids may furthermore contain the formulations described in WO 02/081604 and comprising 1H-1,2,4-triazole. The novel brake fluids may additionally contain the cyclic carboxylic acid derivatives 5 which are mentioned in WO 00/65001 and are of the formula I X (A)n where 10 X is an oxygen atom or a group of the formula N-R', R' being hydrogen or a linear or branched C 1 - to C 2 0-alkyl group which additionally may be interrupted by up to 9 nonneighboring oxygen atoms and/or may carry up to 15 6 hydroxyl groups, or a cycloalkyl group or an unsubstituted or substituted phenyl group, 23 A is a group of the formula -CR R3_ 20 R2 and R3 each being hydrogen or C 1 - to Cs-alkyl groups which additionally may be interrupted by up to 4 nonneighboring oxygen atoms and/or may carry up to 3 hydroxyl groups, and n is from 2 to 7. 25 These are suitable as components for reducing the low-temperature viscosity in the presence of water. Further components and assistants in the novel brake fluids for motor vehicles are 30 conventional antioxidants, e.g. phenothiazine and/or those based on phenol, and conventional antifoams and markers. All percentages by weight stated above and below are based in each case on the total amount of the hydraulic fluid or of the brake fluid. 35 P.F. 0000054341/Ab -7 The novel borate-free DOT 4 brake fluids meet the requirements stated at the outset in an outstanding manner and moreover have generally good corrosion behavior compared with the prior art, i.e. very good corrosion prevention is ensured in the case of metals such as iron, steel, tin plate, cast iron (gray cast iron), lead, tin, chromium, zinc, aluminum, 5 magnesium and alloys thereof and in the case of solder metals, for example tin solder, and in the case of nonferrous metals such as copper and alloys thereof, for example brass. In addition to the hygroscopic properties substantially reduced owing to the freedom from borate, further advantages of the novel DOT 4 brake fluids for motor vehicles which may 10 be singled out are their advantageous low-temperature viscosity, good water compatibility, a mild pH, good low temperature, high temperature and oxidation stability and good chemical stability, advantageous behavior toward (i.e. good compatibility with) materials such as rubbers, plastics, glue joints, fiber, elastomer and rubber seals and similar materials and good lubricating behavior. 15 The examples which follow illustrate the invention without restricting it. Use examples: 20 The novel borate-free DOT 4 brake fluid BFI used had the following composition: Novel example BF 1: 31.0% of diethylene glycol 25 67.7% of a mixture of methyldiglycol, butyldiglycol, butyltriglycol and methyltetraglycol 1.3% of a mixture of 1,1'-iminodipropan-2-ol, bisphenol A, tolutriazole and 3 nitrobenzaldehyde 30 Comparative example BF 2 (corresponds to example 5 from DE 36 27 432 C2) 39% of diethylene glycol 26% of triethylene glycol 24% of triethylene glycol dimethyl ether 35 10% of methyltriglycol 1% of corrosion inhibitor (1,1' -iminodipropan-2-ol used) P.F. 0U0054341/Ab -8 Physical data: BF 1 BF 2 (comparison) ERBP [C]: 251 234 wet ERBP ['C]: 159 153 5 (Water absorption: (Water absorption: 3.27%; reference RM 71 3.73%) 3.93%; reference RM 71 3.70%) Viscosity -40*C: 1393 [mm 2 ] 1277 10 Compared with the prior art according to DE 3627432 C2, the novel borate-free DOT 4 brake fluids have in particular a substantially higher ERBP which, in the case of BF 1, easily exceeds the minimum requirement according to FMVSS No. 116 by 20*C, and a lower water absorption and, associated therewith, a higher wet ERBP. 15 The novel brake fluids moreover lead to very good corrosion prevention, as shown by the results below for BF 1: Corrosion test according to SAE J 1704, test duration 120 h/100*C: 20 Metal Weight change Appearance [mg/cm 2 ] Tin plate + 0.00 unchanged Steel + 0.01 unchanged 25 Aluminum + 0.00 unchanged Gray cast iron + 0.04 unchanged Brass - 0.05 slightly tarnished Copper - 0.05 slightly tarnished Zinc + 0.03 tarnished 30 pH before/after test: 9.9/9.6

Claims (12)

1. A brake fluid comprising 5 a) from 10 to 50, preferably from 20 to 40, % by weight of diethylene glycol and/or dipropylene glycol and b) from 50 to 90, preferably from 60 to 80, % by weight of one or more monoalkyl ethers of (poly)ethylene glycol and/or (poly)propylene glycol. 10

2. A fluid as claimed in claim 1, which contains no boric acid esters.

3. A fluid as claimed in claim 1 or 2, which contains no polyalkylene glycol dialkyl ethers. 15

4. A fluid as claimed in any of claims 1 to 3, wherein diethylene glycol is used as component a).

5. A fluid as claimed in any of claims 1 to 4, wherein, in component b), the glycols 20 are selected from monoethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, hexaethylene glycol, monopropylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, pentapropylene glycol and hexapropylene glycol. 25

6. A fluid as claimed in any of claims 1 to 5, wherein, in component b), the alkyl radical is selected from linear and branched C-C 6 -alkyl radicals, preferably linear and branched CI-C 4 -alkyl radicals, in particular methyl, ethyl, isopropyl and n butyl. 30

7. A fluid as claimed in any of claims 1 to 6, wherein component b) is selected from methyldiethylene glycol, methyltriethylene glycol, methyltetraethylene glycol and butyltriethylene glycol.

8. A fluid as claimed in any of claims 1 to 7, wherein reaction products of ethylene 35 oxide and/or propylene oxide and/or butylene oxide with water or diols, preferably reaction products of mixtures of ethylene oxide and propylene oxide with water having from 2 to 10, preferably 2 or 3, alkylene oxide units are furthermore present. P.F. 0000054341/Ab -10

9. A fluid as claimed in any of claims 1 to 8, wherein from 0.01 to 10, preferably from 0.005 to 4, in particular from 0.005 to 1, % by weight of one or more corrosion inhibitors are present. 5

10. A fluid as claimed in any of claims 1 to 9, wherein the corrosion inhibitors are selected from the group consisting of 1H-1,2,3-benzotriazole, 1H-1,2,3-tolutriazole, hydrogenated 1H-1,2,3-tolutriazole, benzimidazole and/or derivatives thereof, alkali metal salts of phosphoric acid and phosphorous acid, fatty acids, preferably caprylic, lauric, palmitic, stearic or oleic acid and alkali metal salts thereof, esters 10 of phosphoric acid and of phosphorous acid, preferably ethyl phosphate, dimethyl phosphate, isopropyl phosphate, diisopropyl phosphate, butyl phosphite or dimethyl phosphite, mono- and dialkylamines which may be ethoxylated and salts thereof with mineral and fatty acids, preferably butylamine, hexylamine, octylamine, isononylamine, oleylamine, dipropylamine, diisopropylamine or dibutylamine, 15 alkanolamines which may be ethoxylated, preferably mono-, di- or triethanolamine, N,N'-di-n-butylaminoethanol or 1,1'-iminodipropan-2-ol, cyclohexylamine, and/or nitro aromatics, preferably 3-nitrobenzaldehyde.

11. A fluid as claimed in any of claims 1 to 10, which complies with the following 20 specification values (DOT 4): ERBP: > 230 0 C Wet ERBP: > 155 0 C Viscosity at -40OC: 1 800 mm 2 /s 25

12. The use of a fluid as claimed in any of claims 1 to 11 as a brake fluid in motor vehicles, preferably in regions of high relative humidity.