EP0011730B1 - Brake fluids having a conserving activity and an amount of oleic acid - Google Patents

Description

The invention relates to brake fluids containing em fatty acids.

Commercial brake fluids that comply with the US standards of the Federal Motor Vehicle Safety Standard FMVSS 116, DOT 3 and the Handbook of the Society of Automotive Engineers SAE J 1703 consist essentially of glycol ethers as basic components, polyglycols as lubricant components and contain inhibitors for corrosion protection and antioxidants.

These DOT-3 brake fluids generally have good corrosion protection against tinplate, steel, cast iron, brass, copper and aluminum. Corrosion protection is only guaranteed if the metals are completely immersed in the liquid or otherwise well wetted by it.

In order to be able to store brake parts, in particular cast iron wheel brake cylinders, after manufacture and functional test, they are impregnated with special brake pastes.

A major disadvantage of this brake pastes is that they greatly increase in re-filling of the brake system with brake fluid, the viscosity, so that the viscosity of the filled fluid under circumstances, the maximum viscosities of 1,500 - exceed 10- ³ m ^z / s at -40 ° C substantially . Such mixtures then no longer meet the requirements of FMVSS 116, DOT3.

The task was therefore to propose brake fluids that can be used simultaneously for impregnation and that allow the components to be stored for longer periods without corrosion.

Simply increasing the inhibitor concentration or using other inhibitors, e.g. B. of fatty acids can increase the anti-corrosion effect on the wetted part. However, fluids are not obtained that meet the requirements placed on brake protection fluids. In addition, the concentration of fatty acids or fatty acid derivatives can only be increased slightly because these components tend to precipitate at low temperatures or cause increased rubber swelling of the SBR cuffs.

• A) 10 bis 40 Gew.-%, bezogen auf die Bremsflüssigkeit von Polyalkylenglykoien in Form von einheitlichen Verbindungen oder Gemischen von Verbindungen dar Formel
  
  in der R einen 1,2-Äthylen- und/oder 1,2-Propylenrest, wobei, bezogen auf die einzelne Verbindung oder das Gemisch, die Zahl der Prooylenreste überwiegt und n eine Zahl von 10 oder mehr bedeutet, und wobei das durchschnittliche Molekulargewicht 500 bis 3000 beträgt, und
• B) 0,1 bis 3 Gew.-% einer an sich als Korrosionsinhibitor bekannten Fettsäure, sowie als Ergänzung zu 100% die folgenden Bestandteile,
• C) Polyglykoläther der Formel
  
  in der R¹ Methyl oder Äthyl, R² Wasserstoff oder Methyl und n die Zahlen 2 bis 4 bedeuten,
• D) ggf. Polyglykole des Äthylenoxids und/oder Propylenoxids mit einem Molekulargewicht im Molekulargewichtsbereich üblicher Schmiermittel in Bremsflüssigkeiten, und/oder
• E) ggf. 20 bis 50 Gew.-% von Borsäureestern von Glykoiäthern der Formel 11 und
• F) geringe Mengen an sich bekannter Antioxydantien und Inhibitoren

aufweisen.It has now surprisingly been found that brake fluids based on polyglycol ethers as basic components, polyglycols as lubricant components containing a fatty acid as corrosion inhibitor, if appropriate further inhibitors and antioxidants meet the stated requirement if they contain

• A) 10 to 40 wt .-%, based on the brake fluid of polyalkylene glycols in the form of uniform compounds or mixtures of compounds of the formula
  
  in which R is a 1,2-ethylene and / or 1,2-propylene radical, where, based on the individual compound or the mixture, the number of prooylene radicals predominates and n represents a number of 10 or more, and wherein the average molecular weight 500 to 3000, and
• B) 0.1 to 3% by weight of a fatty acid known per se as a corrosion inhibitor, and as a supplement to 100% the following constituents,
• C) Polyglycol ether of the formula
  
  in which R ^{1 is} methyl or ethyl, R ^{2 is} hydrogen or methyl and n is the numbers 2 to 4,
• D) optionally polyglycols of ethylene oxide and / or propylene oxide with a molecular weight in the molecular weight range of conventional lubricants in brake fluids, and / or
• E) optionally 20 to 50% by weight of boric acid esters of glyco ether of the formula 11 and
• F) small amounts of known antioxidants and inhibitors

exhibit.

The high molecular weight polyalkylene glycols are carrier substances that have low water solubility and are characterized by high lipophilicity. As a result, they can dissolve the fatty acids more, so that the concentration of the fatty acids can be up to 3% in the brake fluid.

The polyalkylene glycols of the formula I contained in the brake fluids according to the invention can consist solely of polypropylene glycols, by mixing predominantly polypropylene glycols with polyethylene glycols or by reacting mixtures of ethylene oxide and (in excess) propylene oxide are produced, statistical mixtures of compounds being formed which on average contain more propylene oxide than ethylene oxide residues and have molecular weights in the range specified.

However, polyethylene glycols can also be reacted with propylene oxide or polypropylene glycols with ethylene oxide, the starting polyglycols the amount of alkylene oxides and the polymerization conditions being selected, consisting of polyalkylene glycols according to the formula with the molecular weights specified there from 500 to 3000, preferably 1800 to 2200.

Appropriately, the procedure for the preparation of the polyalkylene glycols of the formula is such that an epoxy mixture consisting of the desired molar ratios of ethylene oxide and propylene oxide is polymerized by methods known per se.

Fatty acids to be added as corrosion inhibitors are in particular C ₁₂ to C ₂₄ monocarboxylic acids or their derivatives.

In particular, fatty acids with and without olefinic double bonds, in particular C ₁₈ fatty acids, come into consideration. Suitable fatty acids are e.g. As oleic acid, ricinoleic acid, stearic acid, linoleic acid or linolenic acid.

in Betracht, in der R¹ einen niedermolekularen Alkylrest, vorzugsweise Methyl, R² Wasserstoff oder Methyl und n die Zahlen 2 bis 4 bedeutet. Im einzelnen seien genannt:

The basic components are the polyglycol ethers of formula II that are common in brake fluids

into consideration, in which R ^{1 is} a low molecular weight alkyl radical, preferably methyl, R ^{2 is} hydrogen or methyl and n is the numbers 2 to 4. The following may be mentioned in detail:

• Benzotriazol, Imidazol, Imidazolin, prim., sek. Amine, Äthanolamine, Bisphenol A, Triphenylphosphit oder 2,4-Di-tert.-butyl-kresol.

As further inhibitors and as antioxidants, compounds known per se are also suitable, such as, for. B. in US Pat. No. 3,711,410, columns 9 to 11, are listed in detail. The following should be mentioned in particular:

• Benzotriazole, imidazole, imidazoline, prim., Sec. Amines, ethanolamines, bisphenol A, triphenyl phosphite or 2,4-di-tert-butyl-cresol.

The brake fluids according to the invention can also contain boric acid esters of glycol ethers of the formula II, for. B. in amounts of 20 to 50 wt .-%. Suitable boric acid esters are e.g. B. methyl tri glycol ortho borate, ethyl tri glycol ortho borate, methyl / ethyl di / tri ortho borate.

Further borester compounds are described in detail in US Pat. No. 3,711,410.

To investigate the impregnating effect of the brake fluids according to the invention, wheel brake cylinders made of gray cast iron are halved on the long side, cleaned with isopropanol ... and well dried. The halved brake cylinder is then immersed for 5 seconds each in the commercially available brake fluid or in the brake fluids. improved corrosion protection, drains for 5 seconds and stores them in a closed container over a water vapor-saturated atmosphere. This shows that when using commercially available brake fluids, severe rusting of the cast iron parts can be observed after only a few hours. In the case of the liquids according to the invention, on the other hand, the build-up of rust is avoided, even after storage for 30 days above the water vapor-saturated atmosphere at room temperature.

• 1. Feuchtigkeitskorrosionstest mit der SAE RM 1 Reference-Fluid: Bereits nach wenigen Tagen war starke Korrosion der Graugußbremszylinder festzustellen.
• 2. Verwendung einer handelsüblichen Bremsflüssigkeit gemäß DOT 3 der folgenden Zusammensetzung: 20% Polyglykol, Mol-Verh. EO/PO 2 : 4 (EO = Ethylenoxid, PO = Propylenoxid), Mol-Gew. 300, 20% Triäthylenglykol, 5% Butyltriglykol, 25% Äthyltriglykol, 29,4% Äthyldiglykol, 0,25% Dibutylamin, 0,30% Bisphenol A, 0,05% Benzotriazol. Nach wenigen Stunden bis zwei Tagen war starker Rostansatz auf den Graugußteilen zu beobachten.
• 3. Verwendung von einer Bremsflüssigkeit, bestehend aus ca. 70 Gewichtsteilen Glykoläther, 25% eines handelsüblichen Schmiermittels auf EO/PO-Basis (Molverhältnis 2 : 1, Molgewicht 1100), 3% einer Mischung von Korrosionsinhibitoren aus Benzotriazol, Dodecylamin, Triäthanolamin und 2% Ölsäure. (Die Ölsäure scheidet sich beim Abkühlen teilweise aus; es tritt eine Trübung ein.) Nach ca. 8 Stunden konnte Rostansatz beobachtet werden.
• 4. Es wurde die gleiche Mischung wie unter 3. angegeben verwendet, nur wurden anstelle der 25% Schmiermittel nur 15% Schmiermittel verwendet und 10% eines PO-Adduktes in Kombination mit einem PO/EO-Addukt (Zusammensetzung 90% PO/10% EO, mittlerer MG 2000). Im Korrosionsversuch zeigte sich nach 30 Tagen keinerlei Rostansatz.
• 5. 25% Polypropylenglykol mit Molgewicht 900, 20% Äthyltriglykol, 30% Äthyldiglykol, 2% Ölsäure, 1,5% Dibutylamin, 4% eines Glycerin-Borsäureadduktes, 0,05% Benzotriazol und 17,45% Methyltriglykol. Die Viskosität bei -40°C betrug 1,276. 10-³ m²/s, der Kochpunkt 215°C, pH-Wert 9,3. Die Flüssigkeit entspricht SAE J 1703. Im Feuchtigkeitskorrosionstest nach 30 Tagen kein Rostansatz.
• 6. Im Feuchtigkeitskorrosionstest ergab eine Bremsflüssigkeit, bestehend aus: 10% eines Polypropylenglykols vom Molgewicht ca. 1000, 7,5% eines Polypropylenglykols, ca. Molgewicht 2000; 7,5% eines Schmiermittels, bestehend aus ca. 3 Mol Äthylenoxid und 3 Mol Propylenoxid, 20% Äthyltriglykol, 30% Äthyldiglykol, 0,5% Rizinolsäure, 0,05% Benzotriazol, 4,3% Korrosionsinhibitor (Umsetzungsprodukt aus Glycerin mit Borsäureester), 1% Dibutylamin, ca. 20% Methyltrilglykol. Das Produkt weist eine Viskosität von 1,175 - 10-³ m³/s bei -40°C auf, einen Kochpunkt von 218°C, pH-Wert 9,7; nach 30 Tagen keinen Rostansatz. Wird anstelle des Polypropylenglykols mit Molgewicht ca. 1000 + Polypropylenglykol mit Molgewicht ca. 2000 und dem EO/PO-Addukt ein handelsübliches Schmiermittel eingesetzt, so tritt bereits nach wenigen Tagen starker Korrosionsansatz ein.

The following tests were carried out for comparison with conventional brake fluids:

• 1. Moisture corrosion test with the SAE RM 1 Reference-Fluid: After just a few days, the cast iron brake cylinder showed severe corrosion.
• 2. Use of a commercially available brake fluid according to DOT 3 of the following composition: 20% polyglycol, mole ratio. EO / PO 2: 4 (EO = ethylene oxide, PO = propylene oxide), mol. 300, 20% triethylene glycol, 5% butyl triglycol, 25% ethyl triglycol, 29.4% ethyl diglycol, 0.25% dibutylamine, 0.30% bisphenol A, 0.05% benzotriazole. After a few hours to two days, heavy rust formation was observed on the gray cast iron parts.
• 3.Use of a brake fluid consisting of approx. 70 parts by weight of glycol ether, 25% of a commercially available lubricant based on EO / PO (molar ratio 2: 1, molecular weight 1100), 3% of a mixture of corrosion inhibitors made of benzotriazole, dodecylamine, triethanolamine and 2 % Oleic acid. (The oleic acid is partially eliminated on cooling; it becomes cloudy.) After about 8 hours, rust formation could be observed.
• 4. The same mixture was used as stated under 3., only instead of the 25% lubricant only 15% lubricant was used and 10% of a PO adduct in combination with a PO / EO adduct (composition 90% PO / 10% EO, medium MG 2000). In the corrosion test, there was no rust formation after 30 days.
• 5. 25% polypropylene glycol with a molecular weight of 900, 20% ethyl triglycol, 30% ethyl diglycol, 2% oleic acid, 1.5% dibutylamine, 4% of a glycerol-boric acid adduct, 0.05% benzotriazole and 17.45% methyl triglycol. The viscosity at -40 ° C was 1.276. 10- ³ m ² / s, the boiling point 215 ° C, pH 9.3. The liquid corresponds to SAE J 1703. No rust formation in the moisture corrosion test after 30 days.
• 6. In the moisture corrosion test, a brake fluid consisting of: 10% of a polypropylene glycol with a molecular weight of about 1000, 7.5% of a polypropylene glycol, about a molecular weight of 2000; 7.5% of a lubricant, consisting of approx. 3 moles of ethylene oxide and 3 moles of propylene oxide, 20% ethyl triglycol, 30% ethyl diglycol, 0.5% ricinoleic acid, 0.05% benzotriazole, 4.3% corrosion inhibitor (reaction product of glycerol with boric acid ester ), 1% dibutylamine, approx. 20% methyltrilglycol. The product has a viscosity of 1,175 - to 10- ³ m ³ / s at -40 ° C, a boiling point of 218 ° C, pH 9.7; no rust formation after 30 days. If a commercially available lubricant is used instead of the polypropylene glycol with a molecular weight of approx. 1000 + polypropylene glycol with a molecular weight of approx. 2000 and the EO / PO adduct, severe corrosion begins to develop after only a few days.

Brake fluids containing corrosion-inhibiting fatty acids based on polyglycol ethers and polyglycols are already known from British patent specification 1,081,294. In contrast to the present brake fluids, which contain 10 or more alkylene oxide units in the polyalkylene glycol, di- or trialkylene glycols should be used according to the teaching of the patent mentioned. However, these brake fluids give insufficient rust protection in moisture corrosion tests compared to the brake fluids of the invention.

Claims (7)

1. Brake fluids based on polyglycol ethers and polyglycols and containing fatty acids, characterized in that they contain
2. A) 10 to 40% by weight, based on the brake fluid, of polyalkylene glycols, in the form of uniform compounds or mixtures of compounds, of the formula I

   

   where R is a 1,2-ethylene and/or 1,2 propylene radical, the number of propylene radicals, based on the individual compound or the mixture, predominating, and n being a number of 10 or more, and the average molecular weight being 500 to 3000,
3. B) 0.1 to 3% by weight of a fatty acid known to be a corrosion inhibitor, and, to make up 100%, the following constituents
4. C) polyglycol ethers of the formula

   

   where R¹ is methyl or ethyl, R² is hydrogen or methyl, and n is a number from 2 to 4,
5. D) if desired, polyglycols of ethylene oxide and/or propylene oxide having a molecular weight in the molecular weight range of lubricants usually used in brake fluids, and/or
6. E) if desired, 20 to 50% by weight of boric acid esters of glycol ethers of the formula II, and
7. F) small amounts of conventional antioxidants and inhibitors.