WO2004081155A1 - Dot 4 brake fluids - Google Patents

Abstract

The invention relates to a brake fluid that comprises a) 10 to 50 % by weight, preferably 20 to 40 % by weight, of diethylene glycol and/or dipropylene glycol, b) 50 to 90 % by weight, preferably 60 to 80 % by weight, of one or more monoalkylethers of (poly)ethylene glycol and/or (poly)propylene glycol. The inventive fluids are especially borate-free and owing to their low hygroscopicity are suitable for use in areas with high atmospheric humidity.

Description

 DOT 4 brake fluids

The present invention relates to new DOT 4 brake fluids in which the addition of borates (boric acid esters) is not necessary. The brake fluids included

(a) 10 to 50% by weight of diethylene glycol and / or dipropylene glycol and

(b) 50 to 90% by weight of (poly) ethylene and / or (poly) propylene glycol monoalkyl ether

and are preferably free of polyglycol dialkyl ethers.

Hydraulic fluids and in particular brake fluids for motor vehicles are subject to very high requirements with regard to their chemical and physical properties. According to the existing standards and specifications for brake fluids from the US Department of Transportation (DOT) in the Federal Motor Vehicle Saftey Standard FMVSS-No. 116 and the SAE J 1704 standard published by the Society of Automotive Engineers, modern brake fluids are said to have high dry boiling points (reflux boiling points, dry [Equilibrium reflux boiling point, "ERBP"]) and high wet boiling points (reflux boiling points, moist ["wet ERBP"]) have, on the other hand, but also have a viscosity that changes only slightly within a wide temperature range.

For a DOT 4 brake fluid according to FMVSS no. 116 the specification values listed below must therefore be observed:

Dry boiling point "ERBP":> 230 ° C

Wet boiling point "wet ERBP":> 155 ° C viscosity at -40 ° C: <1800 mm ² / s

In addition, there are further requirements for a sufficiently good corrosion protection for metals and non-ferrous metals by brake fluids, which can be achieved by the corrosion protection additives contained therein.

Commercial DOT 4 brake fluids always contain boric acid esters such as methyl triglycol borate, which can chemically eliminate penetrating water from the brake fluid in certain quantities by hydrolysis. The disadvantage here is that boric acid esters themselves are hygroscopic, which means that such DOT 4 brake fluids are particularly useful in regions with high air humidity, for example in tropical and subtropical regions. areas can absorb so much moisture very quickly that the functionality of a brake system filled with it can be adversely affected despite the boric acid ester's collection function.

US Pat. No. 3,625,899 describes DOT 4 brake fluids which contain 54.5 to 92% of at least one boric acid ester, up to 20% polyalkylene glycols and 3 to 43% polyglycol monoalkyl or dialkyl ether in addition to other additives.

No. 3,972,822 describes DOT 4 brake fluids which contain 40 to 65% polyglycol monoalkyl ether, 16 to 45% polyglycols and 10 to 19% boric acid ester plus corrosion inhibitors.

WO 00/46325 describes DOT 4 brake fluids which contain methyl triglycol borate, glycol ethers and glycols in different amounts and an additive system.

Corresponding DOT 4 brake fluids are also disclosed in WO 02/38711, which contain different methylpolyglycol borates, polyglycol monoalkyl ethers and corrosion inhibitors.

DE 36 27 432 C2 describes borate-free brake fluids of 30 to 80% of a glycol component and up to 70% polyglycol alkyl ethers. The glycol component in turn contains 0 to 80% by weight, preferably 55 to 80% by weight, of diethylene glycol and / or dipropylene glycol. The polyglycol alkyl ether component contains 0 to 90% by weight, preferably 0 to 50% by weight, of at least one polyglycol monoalkyl ether. These liquids meet the DOT 4 specification in selected mixing ratios. A disadvantage of these formulations is, in particular, the dry boiling point “ERBP”, which is just above the specification limit, and also the use of complex polyglycol dialkyl ethers which are difficult to synthesize and which often also lead to incompatibility reactions of rubber and sealing materials.

There is still a need for low viscosity brake fluids that meet the DOT 4 specification.

The object of the present invention is to provide such a brake fluid. This brake fluid should preferably be less hygroscopic and usable in regions with high air humidity. In particular, the conversion should only require small amounts of boric acid esters or, ideally, even be completely unnecessary. This object is achieved by containing a brake fluid

a) 10 to 50% by weight of diethylene glycol and / or dipropylene glycol and b) 50 to 90% by weight of one or more monoalkyl ethers of (poly) ethylene glycol or (poly) propylene glycol.

In particular, the liquids according to the invention are free from boric acid esters.

Diethylene glycol or dipropylene glycol or a mixture of diethylene glycol and dipropylene glycol can be used in any ratio. Diethylene glycol is preferred.

Diethylene glycol and / or dipropylene glycol are present in the brake fluids according to the invention in an amount of 10 to 50% by weight, preferably 20 to 40% by weight.

Another component of the brake fluids according to the invention are one or more monoalkyl ethers of (poly) ethylene glycols and / or (poly) propylene glycols, which are present in the fluids according to the invention in an amount of 50 to 90% by weight, preferably 60 to 80% by weight, available. ,

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 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 glycol used according to the invention is preferably a linear or branched - - alkyl radical. It is more preferred to use a linear or branched C4-alkyl radical, for example methyl, ethyl, i-propyl, n-propyl, n-butyl, i-butyl, sec-butyl or tert-butyl.

In particular, the alkyl radicals are methyl, ethyl, i-propyl or n-butyl. In the context of the present invention, the use of methyldiethylene glycol, methyltriethylene glycol, methyltetraethylene glycol and or butyltriethylene glycol is preferred.

The brake fluids according to the invention have wet boiling points and, in particular, dry boiling points which are those which have hitherto been achieved with borate-free brake fluids. They are comparable to those that have so far only been achieved with liquids containing borate. Due to the absence of borate, the liquids according to the invention are significantly less hygroscopic than those containing borate. This is particularly advantageous when used in tropical and subtropical areas, since part of the water is bound by the addition of borate, but water is also absorbed relatively quickly. This results in a deterioration in the quality of the brake fluid. In particular, this loss of quality often occurs in the braking system of motor vehicles, but also during the storage and transportation of the liquids. The brake fluids according to the invention do not have the disadvantages mentioned.

The brake fluids according to the invention can contain boric acid esters in different amounts. However, the advantages of low hygroscopicity according to the invention are generally not achieved in this way. This is especially the case when the amounts of boric acid esters customary according to the prior art are added.

Furthermore, the liquids according to the invention are in particular free from polyalkylene glycol dialkyl ethers. Although these may also be present in different amounts, the advantages of the brake fluids according to the invention, in particular the compatibility with rubber and sealing materials, are generally not achieved, this of course also depending on the amount of polyalkylene glycol dialkyl ethers that may be present ,

Further polyglycols can be contained in the formulation bars according to the invention as an optional component. Higher-boiling reaction products of ethylene oxide and / or propylene oxide and / or butylene oxide with water or diols 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 the polyglycols mentioned is generally 2 to 10, preferably 2 to 3 and in an amount of up to 5%.

The effect of these high-boiling polyglycols is that of a reducing agent, which is essentially due to an improvement in the temperature-viscosity behavior. The polyglycols give the polyglycols, which are often thin at high temperatures, colmonoalkyl ethers have sufficient viscosity and thus ensure adequate lubrication. Adequate lubrication is desirable since rubber or elastomers on metal in the components of the motor vehicle brake system must slide as wear-free as possible.

In a further embodiment, the DOT 4- according to the invention contain

Brake fluids for motor vehicles, further 0.001 to 10% by weight, preferably 0.005 to 4% by weight _5, in particular 0.005 to 1% by 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 their derivatives, alkali metal salts of phosphoric acid and phosphorous acid, fatty acids, preferably caprylic, lauric, palmitic, stearic or oleic acid and their alkali metal salts, Esters of phosphoric acid and phosphorous acid, preferably ethyl phosphate, dimethyl phosphate, isopropyl phosphate, disopropyl phosphate, butyiphosphite or dimethyl phosphite, optionally ethoxylated mono- and dialkylamines and their salts with mineral and fatty acids, preferably butylamine, hexylamine, octylamine, isononylamine, oleylamine, oleylamine , Diisopropylamine or dibutylamine, optionally ethoxylated alkanolamines, preferably mono-, di- or triethanolamine, N, N'-di-n-butylaminoethanol or l , l'-Iminodipropan-2-ol, cyclohexyl laminate, and / or nitroaromatics, preferably 3-nitrobenzaldehyde.

Also one or more of the heterocyclic compounds of the following general formula described in WO 01/90281

in the

(i) x for N, Y for CR and Z for N or

(ii) X for N, Y for N and Z for N or CR or

(iii) X is CR, Y is N and Z is N,

in which

R, atom in each case independently of other radicals R present, a hydrogen or denotes a radical R ^1, R ¹ , each independently of other radicals R ¹ , alkyl, aryl, aralkyl, halogen, haloalkyl, optionally alkyl-, aryl- or aralkyl-substituted amino, denotes a heterocyclic radical, cyano, carboxyl, alkoxycarbonyl, hydroxyl or alkoxyl, the abovementioned organic radicals for R ¹ each have 1 to 30 carbon atoms, and

n stands for 0, 1 or 2, can be contained in the brake fluids according to the invention. Examples of preferred compounds of this type include purine, adenine, 6-chloropurine, 2,6-dichloropurine, 6-methoxypurine, 1H-1, 2,3-triazolo (4,5B) pyridine, 6-histaminopurine and 6-furrarylaminopurine.

The borate-free DOT 4 brake fluids according to the invention can furthermore contain the formulations described in WO 02/081604 with 1H-1,2,4-triazole.

In addition, the brake fluids according to the invention can contain the cyclic carboxylic acid derivatives of the general formula I listed in WO 00/65001

included in the

X represents an oxygen atom or a grouping of the formula NR ¹ , where

R ¹ denotes hydrogen or a linear or branched Q- to C ₂ o-alkyl group, which can additionally be interrupted by up to 9 non-adjacent oxygen atoms and / or can carry up to 6 hydroxyl groups, or a cycloalkyl group or an optionally substituted phenyl group designated,

A denotes a grouping of the formula -CR ² R ³ -, wherein

R and R represent hydrogen or C 1 -C ₈ -alkyl groups, which can additionally be interrupted by up to 4 non-adjacent oxygen atoms and / or can carry up to 3 hydroxyl groups, and

n represents a number from 2 to 7. These are suitable as components for lowering the low-temperature viscosity in the presence of water.

Other components and auxiliaries in the brake fluids for motor vehicles according to the invention can include conventional antioxidants such as e.g. Phenothiazine and / or those based on phenol, and conventional defoamers and dyes.

All of the above and following percentages by weight relate to the total amount of hydraulic fluid or brake fluid.

The borate-free DOT 4 brake fluids according to the invention excellently meet the requirements mentioned at the outset and also have a generally good corrosion behavior compared to the prior art, i.e. Excellent protection against corrosion is achieved with metals such as iron, steel, tinplate, cast iron (gray cast iron), lead, tin, chromium, zinc, aluminum, magnesium and their alloys and with soldering metals, for example solder, as well as with non-ferrous metals such as copper and their alloys, for example Brass.

In addition to the hygroscopic properties which are significantly reduced by the absence of borate, further advantages of the DOT 4 brake fluids for motor vehicles according to the invention are their favorable low-temperature viscosity, good water compatibility, a gentle pH value, good low-temperature, high-temperature and oxidation stability and good chemical stability, to emphasize favorable behavior (ie good compatibility) towards materials such as rubbers, plastics, glue joints, fiber, elastomer and rubber seals and similar materials as well as good lubricating behavior.

The following examples are intended to illustrate the present invention without restricting it.

Application examples:

The borate-free DOT 4 brake fluid BF1 used according to the invention had the following composition:

Example BF 1 According to the Invention:

31.0% diethylene glycol 67.7% mixture of methyl diglycol, butyl diglycol, butyl triglycol and. Methyl tetraglycol 1.3% mixture of l, -Iminodipropan-2-ol, bisphenol A, tolutriazole and. 3

nitrobenzaldehyde

Comparative example BF 2 (corresponds to example 5 from DE 36 27 432 C2) 39% diethylene glycol

26% triethylene glycol 24% triethylene glycol dimethyl ether

10% methyl triglycol

1% corrosion inhibitor (used: l, l'-iminodipropan-2-ol)

Physical data: BF 1 BF 2 (comparison)

ERBP [° C]: 251 234 wet ERBP [° C]: 159 153

(Water intake: (Water intake:

3.27%; Reference RM 71 3.73%) 3.93%; Reference RM 71 3.70%) Viscosity -40 ° C: 1393 1277

[mm ² / s]

The borate-free DOT 4 brake fluids according to the invention are distinguished from the prior art according to DE 3627432 C2 in particular by a significantly higher dry boiling point “ERBP”, which in BF 1 exceeds the minimum requirement according to FMVSS No. 116 by a good 20 ° C., and by a lower water absorption and associated higher wet boiling point "wet ERBP". The brake fluids according to the invention also lead to very good corrosion protection, as the following results for BF 1 show:

Corrosion test according to SAE J 1704, test duration 120h / 100 ° C:

Metal weight change appearance [mg / cm ² ]

Tinplate ± 0.00 unchanged

Steel + 0.01 unchanged Aluminum ± 0.00 unchanged

Gray cast iron +0.04 unchanged

Brass -0.05 slightly tarnished

Copper -0.05 slightly tarnished

Zinc +0.03 tarnished

pH before / after test: 9.9 / 9.6

Claims

claims 1. Brake fluid containing a) 10 to 50% by weight, preferably 20 to 40% by weight, diethylene glycol and / or dipropylene glycol b) 50 to 90% by weight, preferably 60 to 80% by weight, one or more Monoalkyl ether of (poly) ethylene glycol and / or (poly) propylene glycol. 2. Liquid according to claim 1, characterized in that it contains no boric acid esters. 3. Liquid according spoke 1 or 2, characterized in that it contains no polyalkylene glycol dialkyl ether. 4. Liquid according to one of claims 1 to 3, characterized in that as Component a) diethylene glycol is used. 5. Liquid according to one of claims 1 to 4, characterized in that in component b) the glycols 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. 6. Liquid according to one of claims 1 to 5, characterized in that in component b) the alkyl radical is selected from linear or branched Ci-C ₆ - Alkyl radicals, preferably linear and branched C ₁ -C ₄ alkyl radicals, in particular methyl, ethyl, i-propyl or n-butyl. 7. Liquid according to one of claims 1 to 6, characterized in that component b) is selected from methyldiethylene glycol, methyltriethylene glycol, Methyl tetraethylene glycol and butyltriethylene glycol. 8. Liquid according to one of claims 1 to 7, characterized in that further reaction products of ethylene 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 with 2 to 10, preferably 2 up to 3 alkylene oxide units are present. , Liquid according to one of claims 1 to 8, characterized in that 0.01 to 10 wt .-%, preferably 0.005 to 4 wt .-%, in particular 0.005 to 1 wt .-%, one or more corrosion inhibitors are present. 10. Liquid according to one of claims 1 to 9, characterized in that the Corrosion inhibitors are selected from the group 1H-1, 2,3-benzotriazole, 1H-1,2,3-tolutriazole, hydrogenated 1H-1, 2,3-tolutriazole, benzirnidazole and / or their derivatives, alkali metal salts of phosphoric acid and phosphorous acid , Fatty acids, preferably caprylic, lauric, palmitic, stearic or oleic acid and their alkali metal salts, esters of phosphoric acid and phosphorous acid, preferably Ethyl phosphate, dimethyl phosphate, isopropyl phosphate, diisopropyl phosphate, butyl phosphite or dimethyl phosphite, optionally ethoxylated mono- and dialkylamines and their salts with mineral and fatty acids, preferably butylamine, hexylamine, octylamine, isononylamine, oleylamine, dipropylamine, diutopropylamine, optionally ethoxylated amine or diisopropylamine Alkanolamines, preferably mono-, di- or triethanolamine, N, N'-di-n-butylaminoethanol or l, -iminodipropan-2-ol, cyclohexylamine, and / or nitroaromatics, preferably 3-nitrobenzaldehyde. 11. Liquid according to one of claims 1 to 10, characterized in that it meets the following specification values (DOT 4): Dry boiling point "ERBP":> 230 ° C Wet boiling point "wet ERBP":> 155 ° C Viscosity at -40 ° C: <1800mm ² / s 12. Use of a liquid according to one of claims 1 to 11 as a brake fluid in motor vehicles, preferably in areas with high humidity.