KR20050107607A - 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 a novel DOT 4 brake oil which does not require the addition of borate (boric acid ester). The brake oil may comprise (a) 10 to 50% by weight of diethylene glycol and / or dipropylene glycol and (b) 50 to 90% by weight of (poly) ethylene glycol monoalkyl ether and / or (poly) propylene glycol monoalkyl Ethers and are preferably free of polyglycol dialkyl diethers.

Hydraulic fluids and in particular automotive brake fluids require quite demanding requirements with regard to their chemical and physical properties. Existing standards and specifications for the DOT brake fluid, section 116 of the Federal Motor Vehicle Safety Standard (FMVSS), and Regulation SAE J 1704, compiled by the Society of Automotive Engineers. Modern brake fluids, on the one hand, must have a high Equilibrium Reflux Boiling Point (ERBP) and a high wet ERBP, on the one hand, but also have a very small change in viscosity over a wide temperature range.

Accordingly, DOT 4 brake fluid according to Article 116 of FMVSS must meet the following numerical values of the following criteria:

ERBP: ≥ 230 ℃

Wet ERBP: ≥ 155 ° C

Viscosity at -40 ° C: ≤ 1800 mm ² / s

There is also a more stringent requirement for sufficiently good protection of metals and nonferrous metals from corrosion by brake oil, which can be achieved by anti-corrosion additives.

Commercial DOT 4 brake oils always contain boric acid esters, such as methyltriglycol borate, which can chemically remove a certain amount of water permeated from the brake oil by hydrolysis. One drawback is that the boric esters themselves are hygroscopic, so that the DOT 4 brake fluid is very rapidly absorbing large amounts of moisture despite the trapping function of the boric esters in areas with particularly high relative humidity, such as tropical and subtropical areas. With absorbable results, the operability of the filled brake system can be adversely affected.

US 3,625,899 describes, in addition to additional additives, DOT 4 brake oil comprising from 54.5 to 92% of at least one boric acid ester, up to 20% polyalkylene glycol and from 3 to 43% polyglycol monoalkyl or dialkyl ether have.

US 3,972,822 describes a DOT 4 brake oil comprising 40 to 65% polyglycol monoalkyl ether, 16 to 45% polyglycol and 10 to 19% boric ester in addition to the corrosion inhibitor.

WO 00/46325 describes DOT 4 brake oils comprising different amounts of methyltriglycol borate, glycol ethers and glycols and additive systems.

WO 02/38711 also discloses a corresponding DOT 4 brake oil comprising different methylpolyglycol borates, polyglycol monoalkyl ethers and corrosion inhibitors.

DE 36 27 432 C2 describes a borate-free brake oil consisting of 30 to 80% glycol component and up to 70% polyglycol alkyl ether. The glycol component alternately comprises diethylene glycol and / or dipropylene glycol at 0 to 80% by weight, preferably 55 to 80% by weight. The polyglycol alkyl ether component comprises 0 to 90% by weight, preferably 0 to 50% by weight of one or more polyglycol monoalkyl ethers. At selected mixing ratios, these brake fluids meet the DOT 4 criterion. One drawback with such formulations is that they often lead to incompatible reactions of rubber and sealing materials, in particular, in addition to the use of ERBP, which is just above the standard limits and also very expensive polyglycol dialkyl ethers to synthesize.

There is also a need for low viscosity brake fluids that meet the DOT 4 criteria.

It is an object of the present invention to provide such a brake oil. Preferably, such brake oil should not be hygroscopic and should be able to be used in high relative humidity areas. In particular, the use of boric acid esters in small amounts is essential or ideally the use of such esters should be completely unnecessary.

The inventors have found that the object is (a) from 10 to 50% by weight of diethylene glycol and / or dipropylene glycol and (b) from 50 to 90% by weight of at least one (poly) ethylene glycol or (poly) propylene glycol monoalkyl. It has been found to be achieved with brake oil comprising ether.

In particular, the novel brake oil is free of boric esters.

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

Diethylene glycol and / or dipropylene glycol are present in the new brake oil in amounts of 10 to 50% by weight, preferably 20 to 40% by weight.

Additional components of the novel brake oils comprise at least one monoalkyl ether of (poly) ethylene glycol and / or (poly) propylene glycol, which is novel in an amount of 50 to 90% by weight, preferably 60 to 80% by weight. Present in brake fluid.

Suitable examples of (poly) ethylene glycols are monoethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol and hexaethylene glycol.

Suitable examples of (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 radicals in the monoalkyl ethers of (poly) ethylene glycol and (poly) propylene glycol used according to the invention are preferably linear or branched C ₁ -C ₆ -alkyl radicals. Preference is given to using linear or branched C ₁ -C ₄ -alkyl radicals, for example methyl, ethyl, isopropyl, n-propyl, n-butyl, isobutyl, sec-butyl or tert-butyl.

Alkyl radicals are especially methyl, ethyl, isopropyl or n-butyl.

In the present invention, it is preferable to use methyldiethylene glycol, methyltriethylene glycol, methyltetraethylene glycol and / or butyltriethylene glycol.

The novel brake oils of the present invention have wet ERBPs and especially ERBPs close to those achieved with no-borate brake oils to date. These are compared with those achieved with borate-containing brake fluid today. However, because there is no borate, the novel brake oil of the present invention is actually less hygroscopic than the borate-containing brake oil. This is particularly advantageous for use in tropical and subtropical areas, although part of the water is bound by the addition of borate, but water is also absorbed relatively rapidly. This results in deterioration of the brake fluid in each case. In particular, such qualitative losses often occur in automotive brake systems, but also during storage and transportation of brake oil. The novel brake oil of the present invention does not have the above disadvantages.

It is a fact that the novel brake oils of the present invention may comprise different amounts of boric acid esters. However, the advantage of low hygroscopicity according to the invention is not generally achieved thereby. This is especially the case when the boric acid ester is added in conventional amounts according to the prior art.

In addition, the novel brake oils of the invention are particularly free of polyalkylene glycol dialkyl ethers. They can also be present in different amounts, so that generally the advantages of the novel brake oils of the invention, in particular, are not achieved with rubber and sealing materials, but of course this is the amount of any polyalkylene glycol dialkyl ethers present. Also depends on.

Additional polyglycols may be present as optional ingredients in the new formulations. Relatively high boiling reaction products of ethylene oxide and / or propylene oxide and / or butylene oxide with water or diols are preferably used. In particular, the reaction product of a mixture of ethylene oxide and propylene oxide with water is used. The number of alkylene oxide units in the polyglycol is usually 2 to 10, preferably 2 or 3, and is present in an amount of up to 5%.

Such high boiling polyglycols have the effect of a lubricant, which is substantially due to the improvement of the temperature-viscosity profile. Polyglycols give sufficient viscosity to polyglycol monoalkyl ethers, which often have a low viscosity at high temperatures, to ensure sufficient lubricity. Within the accessory components of the automobile brake system, sufficient lubricity is desirable because the rubber or elastomer should slip on the metal with little wear.

In a further embodiment, the novel automotive DOT 4 brake oil further comprises from 0.001 to 10% by weight, preferably from 0.005 to 4% by weight, in particular from 0.005 to 1% by weight of at least one corrosion inhibitor, for example 1H-1. , 2,3-benzotriazole, 1H-1,2,3-tolutriazole, hydrogenated 1H-1,2,3-tolutriazole, benzimidazole and / or derivatives thereof, alkalis of phosphoric acid and phosphorous acid Metal salts, fatty acids, preferably caprylic acid, lauric acid, palmitic acid, stearic acid or oleic acid, and alkali metal salts thereof, esters of phosphoric acid and phosphorous acid, preferably ethyl phosphate, dimethyl phosphate, isopropyl phosphate, diiso Propyl phosphate, butyl phosphite or dimethyl phosphite, mono- and dialkylamines which may be ethoxylated and salts with inorganic acids and fatty acids thereof, preferably butylamine, hexylamine, octylamine, isononylamine, oleylamine , Di Lofilamine, diisopropylamine or dibutylamine, 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.

The novel brake oils of the invention may also comprise one or more heterocyclic compounds described in WO 01/90281 and represented by the formula:

Wherein X is N, Y is CR, Z is N, or

(Ii) X is N, Y is N, Z is N or CR, or

(Iii) X is CR, Y is N, Z is N,

Independently R in each instance of a further radical R is a hydrogen atom or a radical R ¹ ,

Independently, R ¹ in each case of adding the radical R ¹ of is selected from alkyl, aryl, aralkyl, halogen, haloalkyl, unsubstituted or alkyl-, aryl-, or aralkyl-substituted amino, a heterocyclic radical, a cyano Furnace, carboxyl, alkoxycarbonyl, hydroxyl or alkoxy, the organic radicals R ¹ each having 1 to 30 carbon atoms, n is 0, 1 or 2;

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-histamino And purine and 6-furfurylaminopurine.

The new muborate DOT 4 brake oil may further comprise the formulation described in WO 02/081604 and comprises 1H-1,2,4-triazole.

The novel brake oils may further comprise cyclic carboxylic acid derivatives mentioned in WO 00/65001 and represented by the formula (I).

[Formula I]

In the formula,

X is an oxygen atom or a group of the formula NR ¹ ,

R ¹ is hydrogen or a linear or branched C ₁ -C ₂₀ -alkyl group, or cycloalkyl group or unsubstituted, which may be further interrupted by up to 9 non-adjacent oxygen atoms and / or may have up to 6 hydroxyl groups Ring or substituted phenyl group,

A is a group of the formula -CR ² R ^3- ,

R ² and R ³ are each hydrogen or a C ₁ -to C ₈ -alkyl group which may be interrupted by up to 4 nonadjacent oxygen atoms and / or may have up to 3 hydroxyl groups,

n is 2 to 7;

These are suitable as components for reducing the low temperature viscosity in the presence of water.

Additional components in the novel automotive brake oils of the present invention include conventional antioxidants such as phenothiazine and / or phenolic, and conventional antifoams and markers.

All weight percentages mentioned above and below are in each case based on the total amount of hydraulic or brake oil.

The novel no-borate DOT 4 brake oil of the present invention meets the aforementioned requirements in a remarkable manner and also generally exhibits a good corrosion pattern compared to the prior art, such as iron, steel, tin plate, cast iron (gray cast iron). In the case of metals such as lead, tin, chromium, zinc, aluminum, magnesium and alloys thereof and in the case of solder metals such as tin solder and in the case of nonferrous metals such as copper and alloys thereof such as brass Very good corrosion protection is guaranteed.

In addition to the substantial reduction in hygroscopicity due to the absence of borate, the additional advantages of the novel automotive DOT 4 brake oils of the present invention are advantageous low viscosity, good water miscibility, mild pH, good low temperature, high temperature and oxidative stability. And good chemical stability, favorable aspects (ie good miscibility) and good lubrication for rubber, plastics, glue joints, fibers, elastomers and rubber seal materials and similar materials.

The following examples illustrate the invention but are not limited thereto.

Example usage:

The novel no-borate DOT 4 brake oil BF1 used has the following composition:

New  Yes BF1 :

31.0% diethylene glycol

67.7% Mixture of methyldiglycol, butyldiglycol, butyltriglycol and methyltetraglycol

1.3% 1,1'-Iminodipropan-2-ol, bisphenol A, tolutriazole and 3-nitrobenzaldehyde

Comparative example BF2

(Corresponds to Example 5 of DE 36 27 432 C2)

39% diethylene glycol

26% Triethylene Glycol

24% Triethyl Glycol Dimethyl Ether

10% Methyltriglycol

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

physical Data :

BF1 BF2 (Compare) ERBP [℃] 251 234 Wet ERBP [℃] 159 (Water absorption: 3.27%; Reference RM 71 3.73%) 153 (water absorption: 3.93%; reference RM 71 3.70%) Viscosity at -40 ° C [mm ² / s] 1393 1277

Compared with the prior art according to DE 3627432 C2, the novel non-borate DOT 4 brake oil of the present invention is actually higher ERBP, and lower, which easily exceeds the minimum requirement according to Article 116 of FMVSS up to 20 ° C., especially in the case of BF1. Water absorption and, in this regard, higher wet ERBP.

The novel brake oil of the present invention also yields very good corrosion protection, as shown in the results of the following BF1:

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

metal Change in weight [mg / cm 2] Exterior Tin ± 0.00 No change steel +0.01 No change aluminum ± 0.00 No change Gray cast iron +0.04 No change Brass -0.05 Slightly discolored Copper -0.05 Slightly discolored zinc +0.03 Discolored PH before / after test 9.9 / 9.6

Claims (12)

(a) 10 to 50% by weight, preferably 20 to 40% by weight of diethylene glycol and / or dipropylene glycol and (b) 50-90% by weight, preferably 60-80% by weight of brake oil comprising at least one monoalkyl ether of (poly) ethylene glycol and / or (poly) propylene glycol. 2. The brake oil of claim 1, which does not contain a boric acid ester. The brake oil according to claim 1 or 2, which does not contain polyalkylene glycol dialkyl ether. The brake oil according to any one of claims 1 to 3, wherein diethylene glycol is used as the component (a). The method according to any one of claims 1 to 4, wherein in component (b), the glycol is monoethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, hexaethylene glycol, monopropylene glycol, Brake oil selected from dipropylene glycol, tripropylene glycol, tetrapropylene glycol, pentapropylene glycol, and hexapropylene glycol. 6. The component according to claim 1, wherein in component (b) the alkyl radical is a linear or branched C ₁ -C ₆ -alkyl radical, preferably a linear or branched C ₁ -C ₄ -alkyl Radicals, in particular brake oils selected from methyl, ethyl, isopropyl, and n-butyl. The brake oil according to any one of claims 1 to 6, wherein the component (b) is selected from methyldiethylene glycol, methyltriethylene glycol, methyltetraethylene glycol, and butyltriethylene glycol. 8. The reaction product according to claim 1, wherein the reaction product of ethylene oxide and / or propylene oxide and / or butylene oxide with water or diol, preferably a mixture of ethylene oxide and propylene oxide with water Brake product, further 2 to 10, preferably 2 or 3, alkylene oxide units. The brake oil according to claim 1, wherein the at least one corrosion inhibitor is present at 0.01 to 10% by weight, preferably 0.005 to 4% by weight, in particular 0.005 to 1% by weight. The corrosion inhibitor according to any one of claims 1 to 9, wherein the corrosion inhibitor is 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 acid, lauric acid, palmitic acid, stearic acid or oleic acid, and alkali metal salts thereof, phosphoric acid And esters 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 with inorganic acids and fatty acids thereof , Preferably butylamine, hexylamine, octylamine, isononylamine, oleylamine, dipropylamine, diisopropylamine or dibutylamine, alkanolamines which may be ethoxylated, preferably mono-, di -Or tree Group consisting of ethanolamine, N, N'-di-n-butylaminoethanol or 1,1'-iminodipropan-2-ol, cyclohexylamine, and / or nitro aromatics, preferably 3-nitrobenzaldehyde Brake oil selected from. The brake oil according to any one of claims 1 to 10, wherein the brake oil satisfies the following reference value DOT 4. ERBP: ≥ 230 ℃ Wet ERBP: ≥ 155 ° C Viscosity at −40 ° C .: ≦ 1800 mm ² / s. Use as an automobile brake oil according to any one of claims 1 to 11, preferably in high relative humidity areas.