RU2802813C1 - Brake fluid and method for its production - Google Patents

Abstract

FIELD: automotive systems

SUBSTANCE: methods for producing brake fluids based on glycol, intended for use in hydraulic brake systems and clutch drives of cars and trucks. Brake fluid is obtained by separating from the product of methanol oxyethylation at a molar ratio of alcohol: ethylene oxide equal to 1: (2.3-3.0), a fraction of tri- and tetraethylene glycol monomethyl ethers, which has boiling ranges at atmospheric pressure with an initial boiling point of 220-230°C and end boiling point 280-290°C, in which alkanolamines are dissolved in an amount of 1-1.5 wt%, the resulting product is treated with boric acid in an amount of 3.5-5.7 wt%, an antioxidant additive is added in an amount of 0.05-0.10 wt%. and an anti-corrosion additive in the amount of 0.05-0.10 wt%, after which drying is carried out from the reaction moisture.

EFFECT: increase in the boiling point of the liquid and a decrease in viscosity at low temperatures.

2 cl, 5 ex, 3 tbl

Description

The invention relates to methods for producing glycol-based brake fluids intended for use in hydraulic brake systems and clutch drives of cars and trucks that meet the requirements of the ISO 4925 standard in the following classes: class 4, class 5-1, class 6, as well as high-boiling brake liquids class - 4 with a boiling point of more than 300°C.

Brake fluid is an integral part of most modern cars, the main task of which is to transmit braking force from the master cylinder to the wheel cylinders. Modern brake fluid must simultaneously possess a whole range of physical and chemical properties that ensure trouble-free operation of the braking system: have a high boiling point in an anhydrous and moistened state to prevent the formation of vapor locks in the system during intense braking, good fluidity at low temperatures to ensure efficient operation of electronic systems braking aids such as ABS and ESP, be compatible with rubber parts of brake systems - at the same time do not have a destructive effect on the sealing elements and at the same time cause a certain swelling of the rubber elements to maintain the tightness of the system, do not have a corrosive effect on metal parts of the brake system , since the substances formed during the corrosion process will cause abrasive wear of the brake system elements and can serve as catalysts that accelerate oxidative processes in the brake fluid, maintain uniformity during operation, have good lubricity, as well as a number of other characteristics.

To satisfy the entire set of requirements for brake fluids, compositions based on glycols, their alkyl and boron ethers are currently most widespread. The set of requirements for the performance characteristics of brake fluids is established by various international specifications. Among them, the following main documents should be noted: FMVSS No. 116: Motor Vehicle Brake Fluids, ISO 4925: Road vehicles - Specification of non-petroleum-base brake fluids for hydraulic systems, SAE J1703: Motor vehicle brake fluid, SAE J1704: Motor vehicle brake fluid based upon glycols, glycol ethers and the corresponding borates, SAE J1705: Low water tolerant brake fluids, as well as a number of regional standards JIS K 2233: Non-petroleum base motor vehicle brake fluids, Australian Standard: Motor vehicle brake fluids, GB12981-2012 : Motor vehicle brake fluids and others. Despite such a variety of regulatory documents relating to the quality of brake fluids, they all have much in common and, in essence, describe the same characteristics mentioned above. According to these standards, all liquids are divided into several classes, differing from each other in boiling points in the “dry” and “wet” states, as well as kinematic viscosity at a temperature of -40 ° C. In the Russian Federation there are no domestic standards establishing a set of minimum requirements for brake fluids. In this regard, Russian manufacturers produce products according to their own technical specifications, developed taking into account the requirements of international standards.

The main requirements using the example of FMVSS No. 116 and ISO 4925 standards are shown in Table 1.

Table 1 Basic requirements of international standards Indicators FMVSS 116 - DOT 3 ISO 4925 - Class 3 FMVSS 116 - DOT 4 ISO 4925 - Class 4 FMVSS 116 - DOT 5 (DOT 5.1) ISO 4925 - Class 5-1 ISO 4925 - Class 6 T _boil of dry liquid (ERBP), °С,
no less 205 230 260 250 T _boil of moistened liquid (WERBP), °С, not less 140 155 180 165 Kinematic viscosity at
-40 °С (V _-40 ), mm ² /s, no more 1500 1800 1500 900 750 pH 7.0-11.5 Impact on metals:
- steel, tinned iron, cast iron
- aluminum
- brass, copper Change in mass of plates,
mg/cm ² , no more
0.2
0.1
0.4 Impact on rubber:
- cuff swelling, mm,
no more
- appearance of rubber 0.15-1.40
No stickiness or flaking Liquid mobility after exposure at -50°С, s, no more 35

From the current level of technology it is known that among domestic inventions, the requirements of international standards for classes 5.1 and 6 are met only by one development RU2345125C2, where, according to example 1, a liquid of class 5.1 with ERBP = 270 ° C, WERBP = 182 ° C and V _-40 = 795 is obtained mm ² /s, according to example 2, a liquid of class 5.1 with ERBP = 271 ° C, WERBP = 191 ° C and V _-40 = 846 mm ² / s is also obtained, according to example 3, a liquid of class 6 is obtained with ERBP = 269 ° C , WERBP = 169 °C and V _-40 = 667 mm ² /s, according to this development, the oxyethylation process is carried out until a reaction mixture with an average molecular weight of 85-120 units is obtained, which is subjected to rectification to obtain a distillate and a bottom product with an average molecular weight of 170- 180 units, which is then treated with boric acid in an amount of 5-7 wt.%, water is distilled off from the resulting borated product in the presence of an antioxidant additive, after which an anti-corrosion additive is introduced to obtain a liquid with the following ratio of components, wt.%:

monomethyl ethers of polyethylene glycols: 45-54.9 full esters of boric acid and the above monomethyl ethers of polyethylene glycols: 45-54.9 anti-corrosion additive: 0.05-0.2 antioxidant additive: 0.05-0.2

In this case, monomethyl ethers of polyethylene glycols have the following composition:

Diethylene glycol monomethyl ether 1-5 triethylene glycol monomethyl ether 60-75 Tetraethylene glycol monomethyl ether 18-26 pentaethylene glycol monomethyl ether 3-7.5 hexaethylene glycol monomethyl ether 0.6-1.5.

Brake fluids obtained in accordance with this invention have a low boiling point in the anhydrous state, not exceeding 271°C. In addition, a small amount of alkali is indicated as the only acidity regulator, which is used to catalyze the oxyethylation process. This amount may not be sufficient to achieve the required pH values with a system content of 5% water, which is achieved in corrosion tests.

The closest in essence is the invention RU2052493C1, where from the product of oxyalkylation of alcohols at a molar ratio of alcohol and ethylene oxide equal to 1: (3.0-4.0), by rectification at a residual pressure of 10-20 mm Hg. isolate a fraction of mono(C1-C4) alkyl ethers of ethylene glycols with boiling limits of 195-250°C at atmospheric pressure. The final brake fluid contains mono-C1-C4-alkyl ethers of ethylene glycol, esters of boric acid and mono-C1-C4-alkyl ethers of ethylene glycol, a plasticizer, antioxidant and anti-corrosion additives, characterized in that the liquid additionally contains the product of oxypropylation of mono- and/or diethylene glycol with a degree of oxypropylation of 2-8 at the following ratio of components, wt.%:

Esters of boric acid and mono-C1-C4 alkyl ethers of ethylene glycol: 25.0 - 50.0 Product of oxypropylation of mono- and/or diethylene glycol with degree of oxypropylation 2 - 8: 5.0 - 20.0 Plasticizer: 1.0 - 5.0 Antioxidant additive: 0.1 - 0.5 Anti-corrosion additive: 0.4 - 1.0 Mono-C1 - C4 alkyl ethers of ethylene glycol: up to 100

The brake fluid obtained in accordance with this invention has low performance indicators, allowing it to be classified only in classes 3 and 4 of fluids.

The objective of the present invention is to improve the performance characteristics, in particular, the boiling point of the brake fluid while maintaining the necessary viscosity reserve, allowing it to be classified as classes 4, 5-1 and 6.

This problem is solved due to the fact that the brake fluid is obtained by vacuum rectification of the fraction of tri- and tetraethylene glycol monomethyl ethers from the methanol oxyethylation product, characterized in that the oxyethylation of methanol is carried out at a molar ratio of alcohol: ethylene oxide in the range of 1: (2.3- 3.0), the isolated fraction of monomethyl ethers of tri- and tetraethylene glycol has boiling limits at atmospheric pressure with the beginning of boiling at 220-230°C and the end of boiling at 280-290°C, treatment of the isolated fraction with boric acid is carried out in an amount of 3.5-5, 7% wt., and also additionally include in the brake fluid alkanolamines in the amount of 1.0-1.5% wt., an antioxidant additive in the amount of 0.05-0.10% wt. anti-corrosion additive in an amount of 0.05-0.10% wt. The brake fluid obtained in accordance with this method may additionally contain a dye, which simultaneously performs the function of an acid-base indicator.

The technical result is an increase in the boiling point of the “anhydrous” liquid to 271-302°C, depending on the produced class, while maintaining the boiling point of the “moistened” liquid at least 178-197°C and low-temperature viscosity in the range of 657-1442 mm ² /s.

Our studies have shown that the presence of pentaethylene glycol monomethyl ether and its higher homologues in the system negatively affects the low-temperature viscosity of the resulting product, the presence of diethylene glycol monomethyl ether in the system negatively affects the boiling point of the resulting liquid, and the target components are tri- and tetraethylene glycol monomethyl ethers, which and provide high performance.

According to the developed technology, it is proposed to carry out ethoxylation of methanol at a molar ratio of alcohol to ethylene oxide in the range of 1:(2.3-3.0). The resulting ethoxylation product is subjected to rectification at a residual pressure of 10-20 mm. Hg isolating the target fraction of monomethyl ethers of tri- and tetraethylene glycol, containing only a small amount of impurities of monomethyl ethers of di- and pentaethylene glycol. The isolated fraction of tri- and tetraethylene glycol monomethyl ethers has boiling limits at atmospheric pressure with a starting boiling point of 220-230°C and a final boiling point of 280-290°C, which indicates a significantly heavier fractional composition compared to the analogue. Next, alkanolamines are dissolved in the resulting fraction in an amount of 1-1.5% by weight, which act as an acidity regulator and anti-corrosion additive. Then boric acid is added to this mixture in an amount of 3.5-5.7% wt., after dissolving which 0.05-0.1% wt. is added. diphenylolpropane, which acts as an antioxidant additive, and 0.05-0.1 wt.% 1,2,3 - benzotriazole, which acts as an antioxidant additive. After dissolving all components, drying from reaction moisture is carried out, and in some cases, triethylene glycol monomethyl ether is additionally partially removed in order to increase the “dry” boiling point (example No. 5).

As alkanolamines, it is preferable to use a mixture of diisopropanolamine, diethanolamine and triethanolamine. A study of the anti-corrosion properties of these components showed that diisopropanolamine has a high inhibitory activity against steel and tinplate, diethanolamine inhibits corrosion of steel, aluminum and cast iron, triethanolamine and 1,2,3-benzotriazole are effective for inhibiting corrosion of cast iron, brass and copper.

The light fraction of monomethyl ethers of ethylene glycol and diethylene glycol obtained during the rectification process can be sent for repeated oxyethylation as a recycle stream similar to the invention RU 2345125 C2, and the heavy bottom residue can be used in dust suppressant compositions similar to the invention RU 2690925C1, in the composition of cutting fluids or other petrochemical products.

The brake fluids obtained by the described method are superior to the specified analogue RU2052493 C1 and brake fluids obtained in accordance with the invention RU 2345125 C2 in terms of boiling points, and also have a reduced viscosity at negative temperatures, as illustrated by examples 1-5.

The claimed invention meets the criterion of “industrial applicability”, since it contains components known at the date of filing the application, and will find wide application in the implementation of the import substitution policy in the field of high-quality brake fluids.

The developed brake fluid does not contain alkali metals, which significantly impair the hydrolytic stability of the system, and due to the presence of amino alcohols in the composition, the activity indicator of hydrogen ions meets the standard requirements at all measurement points provided for in regulatory documentation: when diluting the brake fluid with an equal volume of a mixture of water and alcohol , taken in a ratio of 20:80 parts by volume, as well as with a content of about 5% water by mass after testing the brake fluid for corrosion activity.

An additional advantage of brake fluids obtained from fractions isolated by rectification and not containing alkali metals is the absence of color, which allows the use of indicator dyes, for example, 4-nitrophenol, which changes color at a pH below 7.5 units, to give the product the desired color. This property of brake fluids can be very useful, since when water enters the system, the pH value of all glycol brake fluids decreases sharply. A decrease in pH can also be facilitated by the natural consumption of acidity regulators during operation, which simultaneously serve as corrosion inhibitors. The change in color will alert the driver to the need to replace the brake fluid in the system.

The flexibility of the technology is ensured by the fact that it allows the production of various classes of brake fluids without changing the hardware design of the process. Thus, according to examples 1, 2 and 3, brake fluids of class 6 are obtained, according to example 4, a fluid of class 5.1 is obtained, according to example 5, a brake fluid of class 4 with a boiling point exceeding 300°C is obtained. Additionally, using the equipment involved, it is possible to obtain brake fluids of classes 3 and 4 if, at the rectification stage, not the middle fraction of tri- and tetraethylene glycol monomethyl ethers is isolated, but only low-boiling components are removed from the mixture of polymer homologues obtained during the oxyethylation of methanol under the specified conditions. Thus, the approaches used make it possible to obtain all modern classes of glycol brake fluids.

Example 1

Technical methanol poison in the amount of 974.6 kg is loaded into a reactor with a volume of 6.3 m ³ , equipped with an electric stirrer, a steam jacket for heating the reaction mass, and a coil for removing excess heat of the oxyethylation reaction. Loading of technical potassium hydroxide in the amount of 4.9 kg is carried out with the mixer turned on after loading the technical methanol poison at ambient temperature. Upon completion of loading the components, the reactor is sealed and stirred for 0.5 hours.

Before the start of the oxyethylation process, steam is supplied to the jacket of the synthesis reactor with the stirrer running, the contents of the reactors are heated to a temperature of 80-90°C, and the pressure in the reactors rises to 2.5 kgf/cm ² due to the vapors of the technical methanol poison. Next, they begin to feed ethylene oxide in portions, followed by a transition to a constant supply mode. The process of oxyethylation of an alkaline solution of methanol poison is carried out in an atmosphere of inert gas - nitrogen at a temperature of 120-130 ° C and a pressure of no more than 4.0 kgf/cm ² (up to 0.4 MPa), the total mass of supplied ethylene oxide is 4020.5 kg .

The resulting mixture in an amount of 900 g is subjected to rectification in a laboratory installation at a residual pressure of 10 mm Hg. with the release of 406.27 g of the target fraction of the following composition (wt.%):

Diethylene glycol monomethyl ether: 0.73 Triethylene glycol monomethyl ether: 50.16 Tetraethylene glycol monomethyl ether: 47.72 Pentaethylene glycol monomethyl ether: 1.39

Next, the resulting fraction of tri- and tetraethylene glycol monomethyl ethers is heated to 50°C and the following components are sequentially added at intervals of 10 minutes: 2.5 g of diisopropanolamine, 0.82 g of diethanolamine, 0.82 g of triethanolamine, 14.65 g of boric acid. After all components are dissolved, 0.4 g of diphenylolpropane and 0.4 g of 1,2,3-benzotriazole are added, after which the reaction moisture is dried at temperatures up to 150°C and a residual pressure of 20 mm Hg. The brake fluid obtained in this way has the characteristics shown in Table 2.

Example 2

The oxyethylation process is carried out similarly to example 1 with the difference that technical methanol poison is taken in the amount of 1199.8 kg, potassium hydroxide is loaded in the amount of 6 kg, and the mass of supplied ethylene oxide is 3794.2 kg.

The resulting mixture in an amount of 900 g is subjected to rectification in a laboratory installation at a residual pressure of 10 mm Hg. with the release of 407.41 g of the target fraction of the following composition (wt.%):

Diethylene glycol monomethyl ether: 1.08 Triethylene glycol monomethyl ether: 56.67 Tetraethylene glycol monomethyl ether: 41.33 Pentaethylene glycol monomethyl ether: 0.92

Next, the resulting fraction of tri- and tetraethylene glycol monomethyl ethers is heated to 50°C and the following components are sequentially added at intervals of 10 minutes: 2.53 g of diisopropanolamine, 0.83 g of diethanolamine, 0.83 g of triethanolamine, 17.00 g of boric acid. After all components are dissolved, 0.41 g of diphenylolpropane and 0.41 g of 1,2,3-benzotriazole are added, after which the reaction moisture is dried at a temperature of up to 150°C and a residual pressure of 20 mm Hg. The brake fluid obtained in this way has the characteristics shown in Table 2.

Example 3

The oxyethylation process is carried out similarly to example 1 with the difference that technical methanol poison is taken in the amount of 1091.7 kg, potassium hydroxide is loaded in the amount of 5.5 kg, and the mass of supplied ethylene oxide is 3902.8 kg.

The resulting mixture in an amount of 900 g is subjected to rectification in a laboratory installation at a residual pressure of 10 mm. Hg with the release of 415.32 g of the target fraction of the following composition (wt.%):

Diethylene glycol monomethyl ether: 0.91 Triethylene glycol monomethyl ether: 53.70 Tetraethylene glycol monomethyl ether: 44.27 Pentaethylene glycol monomethyl ether: 1.12

The resulting fraction of tri- and tetraethylene glycol monomethyl ethers is heated to 50°C and the following components are sequentially added at intervals of 10 minutes: 2.59 g of diisopropanolamine, 0.85 g of diethanolamine, 0.85 g of triethanolamine, 17.40 g of boric acid. After dissolving all components, 0.42 g of diphenylolpropane and 0.42 g of 1,2,3 - benzotriazole are added, after which the reaction moisture is dried at a temperature of up to 150 ° C and a residual pressure of 20 mm Hg. The brake fluid obtained in this way has the characteristics shown in Table 2.

Example 4

In 400 g of the fraction of monomethyl ethers of tri- and tetraethylene glycol, similar to example 3, after heating to 50°C, the following components are added: 3.9 g of diisopropanolamine, 1.28 g of diethanolamine, 1.28 g of triethanolamine, 24.56 g of boric acid , 0.65 g of diphenylolpropane and 0.65 g of 1,2,3 - benzotriazole, after which drying from reaction moisture is carried out at temperatures up to 155 ° C and a residual pressure of 20 mm Hg. The resulting system is cooled to a temperature of 80-100°C, after which 0.01 g of 4-nitrophenol is dissolved. The brake fluid obtained in this way has the characteristics given in tables 2 and 3.

Example 5

In 400 g of the fraction of monomethyl ethers of tri- and tetraethylene glycol, similar to example 3, after heating to 50°C, the following components are added: 1.22 g of diethanolamine, 1.22 g of triethanolamine, 16.95 g of boric acid, after dissolving which, first drying from reaction moisture in an amount of 14.06 g, and then by changing the receiver, partial removal of triethylene glycol monomethyl ether and impurities of diethylene glycol monomethyl ether is carried out in a total amount of 153.27 g at a temperature of 160-170 ° C and a residual pressure of 10-20 mm Hg. Art. 232.67 g of the intermediate product are obtained, which is cooled to a temperature of 80-100°C, after which 1.22 g of diisopropanolamine, 0.25 g of diphenylolpropane and 0.25 g of 1,2,3-benzotriazole are dissolved in the resulting system.

The finished brake fluid has the characteristics shown in Table 2.

table 2 Main characteristics of the obtained brake fluids Indicators ISO 4925 - Class 3 ISO 4925 - Class 4 ISO 4925 - Class 5-1 ISO 4925 - Class 6 Example 1 Example 2 Example 3 Example 4 Example 5 Example 1 - RF No. 2345125 Example 2 - RF No. 2345125 Example 3 - RF No. 2345125 ERBP, °C 205 230 260 250 275 271 274 280 302 270 271 269 WERBP, °C 140 155 180 165 178 179 180 191 197 182 191 169 V _-40 , mm ² /s 1500 1500 900 750 690 657 662 849 1442 795 846 667 Table 3 Additional brake fluid characteristics according to example 4 Index: Meaning: pH 7.94 Change in mass of plates, mg/cm ² :
- tinned iron
- steel
- aluminum
- cast iron
- brass
- copper +0.09
+0.08
+0.09
+0.11
-0.10
-0.08 Liquid mobility after exposure at -50°C, seconds: 25

Claims (2)

1. A method for producing brake fluid by vacuum rectification of the monomethyl ether fraction of tri- and tetraethylene glycol from the methanol oxyethylation product, characterized in that the oxyethylation of methanol is carried out at a molar ratio of alcohol: ethylene oxide in the range of 1: (2.3-3.0), the isolated fraction of monomethyl ethers of tri- and tetraethylene glycol has boiling limits at atmospheric pressure with the beginning of boiling at 220-230°C and the end of boiling at 280-290°C; treatment of the isolated fraction with boric acid is carried out in an amount of 3.5-5.7% wt., and also additionally include alkanolamines in the brake fluid in an amount of 1.0-1.5 wt.%, an antioxidant additive in an amount of 0.05-0.10 wt.%. and an anti-corrosion additive in an amount of 0.05-0.10 wt%. 2. The method for producing brake fluid according to claim 1, characterized in that after removing the reaction moisture, a dye, which is an acid-base indicator, is additionally introduced into the brake fluid composition.