RU2295560C2 - Braking fluid and a method for preparation thereof - Google Patents

Abstract

FIELD: special-destination fluids.

SUBSTANCE: invention relates to compositions of braking fluids used in automobile brake and clutch hydraulic circuits. Braking fluid according to invention is composed of, wt %: polycondensate of boric acid and poly(alkylene glycols) or monoethers thereof 38-45, diethyleneglycol monomethyl ether 2-7, ionol 0.3-0.6, benzotriazole 0.05-0.50, morpholine 0.05-0.30, plasticizer 4-7, poly(propylene glycol) with average molecular weight 500, 2-5, tripropylene glycol monobutyl ether - the balance. Braking fluid is prepared by mixing boric acid polycondensate with poly(propylene glycol) and solution of additives: ionol, plasticizer, benzotriazole, and morpholine in poly(alkylene glycol) monoalkyl ethers. Polycondensate of boric acid and poly(alkylene glycols) or monoethers thereof is prepared by esterification of reaction mixture including, wt %: boric acid 14-16, di- or triethyleneglycol 11-20, diethyleneglycol monomethyl ether 60-70, N-methyldiethanolamine 0.05-3.00, and tripropylene glycol monobutyl ether 1-15. In addition, 0.15-0.30% of saturated sodium hydroxide solution.

EFFECT: improved low-temperature properties and improved anticorrosive properties and stability on storage and during operation.

3 cl, 6 tbl, 5 ex

Description

The invention relates to compositions of brake fluids used in hydraulic brakes and clutches of vehicles, and to methods for their preparation.

For guaranteed and safe operation of the brakes in extreme working and climatic conditions, brake fluids (ТЖ) must withstand high mechanical and thermal loads for a long time, provide protection against wear, corrosion and the formation of deposits that interfere with the normal operation of the brake system. A serious danger to the operation of the brakes is the formation of vapor bubbles in the fluid during high-temperature operation due to the low boiling point of the fluid itself and the presence of water in it.

Of greatest importance as the basis of modern brake fluids are compositions based on organic esters of boric acid. Borates are characterized by a sufficiently high boiling point, good lubricating properties, and high thermal oxidative stability. They do not destroy rubber and have anti-corrosion properties. Easy hydrolysis of boric esters allows you to bind free water and prevent the negative effects of its influence.

Depending on the actual characteristics in accordance with the requirements of international safety standards FM USS 116 a, brake fluids are divided into classes DOT-3, DOT-4 and DOT-5. The boiling point of the “dry” liquid for the classes DOT-3, DOT-4 and DOT-5, ° C, is respectively: not less than 205, 230 and 260, the boiling point of the “moistened” liquid containing 3.5% water, ° C , - not less than 140, 155 and 180, kinematic viscosity at minus 40 ° С, mm ² / s, - not more than 1500, 1800 and 900, viscosity at 100 ° С, mm ² / s, - not less than 2.0, 2.0 and 1.5, viscosity at 50 ° C, mm ² / s, for all types - at least 5.

Known brake fluid and method for its production (RF patent No. 2144043, publ. 27.12.98). The brake fluid contains esters of boric acid and monoalkyl esters of polyalkylene glycols of the general formula B [O (R ¹ CHCH ₂ O] _n R] ₃ , where R = CH ₃ or C ₂ H ₅ , R ¹ = H or CH ₃ , n is an integer 3-6, monoalkyl ethers of polyalkylene glycols of the general formula R ² (OCH ₂ CHR ¹ ) _m OH, where R ² is an alkyl radical C ₃ -C ₅ , m is a number 2-3, a buffer component based on alkali metal borate, antioxidant and anticorrosive additives - diphenylol propane, tolyl triazole, benzotriazole in the following ratio of components, wt.%: boric acid esters - 40-89, polyalkylene glycol monoalkyl esters kalya - 10-54, buffer component - 0.5-5.0, anticorrosive additive - 0.01-0.20. Brake fluid is obtained by the interaction of alkylene oxide with methyl or ethyl alcohol in the presence of an alkaline catalyst After alcohol hydroxyalkylation from the resulting mixture glycol ethers distill low molecular weight components The remaining mixture of methyl (or ethyl) polyalkylene glycol ethers is reacted with a boron-containing reagent. Boron acid, boric anhydride or trimethyl borate are used as a boron-containing reagent. The resulting mixture of boric esters after distillation of low-boiling components is mixed with monoalkyl ethers of polyalkylene glycols containing C ₃ to C ₅ alkyl radicals as a substituent. The properties of the resulting brake fluid meet the requirements of the DOT-4 specification.

The disadvantage of the described method for producing brake fluid is that the process of obtaining TJ, in addition to the esterification of boric acid with oxyalkylated alcohols, additionally includes the stage of oxyalkylation of alcohols, as a result of which a mixture of products of uncertain composition is formed. Known liquid, in addition, is characterized by high viscosity at minus 40 ° C (1437 mm ² / s).

Closest to the proposed composition and method of obtaining is brake fluid according to the patent of the Russian Federation 2176664 (publ. 10.12.2001). Known liquid contains a mixture of borates of glycols and their monoethyl ethers, (43-48) wt.%, Polypropylene glycol with a molecular weight of 1000, (10-14) wt.%, Morpholine, (0.5-0.9) wt.%, benzotriazole, (0.0-0.1) wt.%, diethylene glycol monoethyl ether - up to 100 wt.%. The liquid is characterized in that it contains boron esters of a mixture of glycols and their monoethyl ethers of the following composition as a mixture of borates, wt.%: Diethylene glycol monoethyl ether - (0-7), the sum of tri- and tetraethylene glycols monoethyl ethers (80-100), including including monoethyl ether of triethylene glycol (75-99), the sum of di- and triethylene glycols (0-20). A disadvantage of a liquid of known composition is the low boiling point of the “dry” and “moistened” liquids, corresponding to the performance properties of the DOT-3 class

The present invention is to provide a brake fluid that meets the requirements of the class DOT-4, ensuring uninterrupted operation of the brakes at low ambient temperatures, stable during storage and operation due to increased hydrolytic stability, having high anticorrosion properties due to high pH values and a minimum content of buffer additives in as free amines.

This object is achieved in that the brake fluid, including boric acid esters, monoalkyl ethers of polyalkylene glycols, one of which is diethylene glycol monoethyl ether, polypropylene glycol, plasticizer and additives: ionol, benzotriazole, morpholine, additionally contains tripropylene glycol monobutyl ether, medium molecular weight polypropylene glycol 500, polypropylene glycol and as boric acid esters - polycondensate of boric acid of polyalkylene glycols and their monoesters in the following ratio of components, wt.%:

Polyalkylene Glycols Boric Acid Polycondensate and their monoesters 38-45 Diethylene glycol monoethyl ether 2-7 Ionol 0.30-0.60 Benzotriazole 0.05-0.50 Morpholine 0.05-0.30 Plasticizer 4-7 Medium molecular weight polypropylene glycol weighing 500 2-5 Tripropylene glycol monobutyl ether up to 100

The problem is also achieved by the fact that in the method of producing brake fluid by mixing boric acid esters with polypropylene glycol, a plasticizer and additives: ionol, benzotriazole, morpholine and monoalkyl ethers of polyalkylene glycols, one of which is diethylene glycol monoethyl ether, with stirring and elevated temperature, as esters boric acid use a polycondensate of boric acid of polyalkylene glycols and their monoesters, which is obtained by esterification from the reaction mixture, including (14-16) wt. % boric acid, (11-20) wt.% di- or triethylene glycol, (60-70) wt.% monoethyl ether of diethylene glycol, (1-15) wt.% monobutyl ether of tripropylene glycol and (0.05-3.0) wt.% N-methyldiethanolamine, and additives before introduction into the polycondensate are pre-dissolved in monoalkyl ethers of polyalkylene glycols. In addition, (0.15-0.30) wt.% A saturated aqueous solution of sodium hydroxide can be added to the reaction mixture.

The inventive composition of the brake fluid and the method for its preparation allow the creation of a liquid fuel that meets the requirements of the DOT-4 class, which ensures uninterrupted operation of the brakes at low ambient temperatures and has high anti-corrosion properties.

In the study of the prior art, no similar compositions and methods for producing brake fluids were identified that would be characterized by an identical set of essential features with the same technical result as obtained in the proposed technical solution, which allows us to conclude that it meets the criteria of "novelty" and " inventive step ". The inventive brake fluid can be obtained using known materials and technical means and used in the automotive industry, which indicates that the proposed technical solution meets the criterion of "industrial applicability".

The invention is illustrated by examples of its implementation.

Example 1

In a round-bottomed flask with a capacity of 500 ml, load 35.3 g (14.12 wt.%) Boric acid (according to GOST 9656-75), 27.5 g (11.00 wt.%) Diethylene glycol (according to TU 18-16 -136-83), 3.4 g (1.36 wt.%) N-methyldiethanolamine, 150.0 g (60.00 wt.%) Diethylene glycol monoethyl ether (according to TU 6-01-5757583-89), 33 8 g (13.52 wt.%) Tripropylene glycol monobutyl ether. The reaction is carried out with vacuum distillation of the reaction water at a temperature of 140 ° C, a residual pressure of 70 kPa for 3 hours. Exposure of the reaction mixture for a specified period of time under the selected conditions allows 15.25 g (6.1) to be removed together with the reaction water in the form of condensate wt.%) diethylene glycol monoethyl ether added to the reaction mixture to complete the esterification of boric acid. The yield of polycondensate is 202.0 g, which is 99% of the calculated amount. The obtained polycondensate is characterized by a boiling point of a “dry” liquid of 267 ° C, a boiling point of a “moistened” liquid of 201 ° C, a viscosity at 50 ° C of 9.58 mm ² / s, and at 100 ° C of 3.38 mm ² / s the pH value is 5.83.

To 200 g of the obtained polycondensate add a solution containing 26.3 g (5 wt.%) Of the LZ-EK plasticizer (according to TU 38.101525-75), 26.3 g (5 wt.%) Of polypropylene glycol with an average molecular weight of 500 ( Laprol-502, according to TU 2226-012-0576-6801-93), 1.05 g (0.2 wt.%) Morpholine (according to GOST 19433-88), 0.26 g (0.05 wt. %) benzotriazole, 2.63 g (0.5 wt.%) ionol (according to TU 38.59011237-90), 243.4 g (46.25 wt.%) tripropylene glycol monobutyl ether and 26.3 g (5.0 wt. .%) diethylene glycol monoethyl ether (according to TU 6-01-5757583-89). The mixture was incubated for 1 h at atmospheric pressure at a temperature of 60 ° C with stirring. The characteristics of the obtained liquid containing 38% polycondensate are shown in table 6, example 1.

Examples 2 and 3 are similar to example 1. They differ in the different ratio of reagents in the synthesis of polycondensates and components in the composition of TJ. In examples 4 and 5, in the synthesis of boric acid polycondensate, a saturated aqueous solution of sodium hydroxide was added to the reaction mixture in the amount of 0.15 and 0.30 wt.%, Respectively.

The reagent ratio data for the synthesis of boric acid polycondensates are shown in Table 1. Polycondensates are light yellow liquids with a boiling point at atmospheric pressure (264-270) ° С and a kinematic viscosity level at 50 ° С (8.79-11, 23) mm ² / s, necessary and sufficient to obtain a brake fluid with the required viscosity-temperature properties by mixing with a solvent (monoalkyl ethers of polyalkylene glycols) and additives (table 2).

The introduction of polyalkylene glycols and N-methyldiethanolamine into the polycondensate increases the hydrolytic stability of the product. The hydrolytic stability test was carried out according to the research methodology (Yao Y., Dong Y. Improvement of hydrolitic stability of borate esters used as lubricant additives // Lubrication Engineering. - 1995. - T.51, No. 6. - S.475-479). The condition of the products was evaluated 2 times a day. The comparison was made in time before the appearance of turbidity and the amount of precipitate released after two weeks of aging in a desiccator saturated with water vapor. The results are shown in table 3.

The synthesis of a polycondensate containing N-methyldiethanolamine, as well as the introduction of a saturated aqueous solution of sodium hydroxide into the reaction medium, makes it possible to obtain a brake fluid with the required pH value (7-11) without additional buffer additives (table 4).

The resulting polycondensates in an amount of (38-45)% are mixed with a solution of additives, polypropylene glycol and a plasticizer in monoalkyl ethers of polyalkylene glycols (solvent) with stirring under atmospheric pressure at a temperature of (60-80) ° С. A decrease in the polycondensate content below 38% reduces the boiling point of the humidified liquid; an increase in concentration above 45% requires an increased amount of buffer components.

It is proposed to use “LZ-EC”, a diethylene glycol monoethyl ester and C ₇ -C ₉ fatty acid fractions, as a plasticizer that improves the compatibility of brake fluid with rubber seals, and to add thermal oxidative stability, add an antioxidant additive — ionol or diphenylolpropane. Protection of metals from corrosion is carried out by introducing anti-corrosion additives, for example a mixture of benzotriazole with morpholine, into the brake fluid. You can use other anti-corrosion additives known from the prior art.

The composition of the obtained fluid samples is shown in table 5, and their physico-chemical characteristics are shown in table 6. For comparison, table 6 shows the requirements for brake fluids formulated in the DOT-4 specification. As follows from the data of table 6, the proposed brake fluids meet the requirements of the specified specification, differ gently viscous-temperature dependence and low viscosity at minus 40 ° C.

Increased hydrolytic stability, the ability to control pH values with minimal use of corrosion-aggressive free amines as buffer additives and improved low-temperature characteristics expand the possibilities of using the proposed brake fluids in changing temperature conditions, i.e. provides a new technical result.

Table 1
The ratio of reagents in the synthesis of polycondensates of boric acid, wt.% Reagent Example one 2 3 four 5 Boric acid 14.12 16.00 14.36 15.00 14.00 Diethylene glycol 11.00 17.90 - 13.00 12.00 Triethylene glycol - - 20.00 - - Diethylene glycol monoethyl ether 60.00 58.10 63,99 70.00 58.65 Tripropylene glycol monobutyl ether 13.52 5.00 1.00 1.80 15.00 N-methyldiethanolamine 1.36 3.00 0.65 0.05 0.05 Saturated aqueous solution of caustic soda - - - 0.15 0.30

table 2
Physico-chemical characterization of boric acid polycondensates of polyalkylene glycols and their monoesters Indicators Example one 2 3 four 5 The boiling point of the liquid, ° C "dry" 267 265 270 264 266 “Hydrated” 201 196 202 194 200 Kinematic viscosity, mm ² / s, at temperature, ° С +50 9.58 11.18 11.23 8.78 9.34 +100 3.38 3.37 3.80 3.10 3.41 The transit time of the air bubble through the liquid layer after holding for 6 hours at -50 ° C 47 fifty 49 39 46 The fluidity after holding for 6 h at -40 ° C in the presence of water 33 38 40 31 35 PH value 5.83 6.95 4.96 5.17 5.45

Table 3
Hydrolytic stability of boric acid polycondensates of various compositions The composition of the reaction mixture in the synthesis of polycondensate, wt.% Time before the appearance of turbidity, h Fluid condition after two weeks Boric acid Diethylene glycol monoethyl ether Diethylene glycol N-methyldiethanolamine 13 87 - - 12 Very large sediment 16 70 fourteen - 36 Large sediment 16 70 9 3 48 A small amount of crystals on the walls of the box

Table 4
The pH value of brake fluids containing polycondensate of boric acid esters of various compositions (at a concentration of polycondensate in the brake fluid of 38%) The composition of the reagents in the reaction mixture in the synthesis of polycondensate, wt.% pH Boric acid Diethylene glycol monoethyl ether Tripropylene glycol monobutyl ether Diethylene glycol N-methyldiethanolamine Saturated aqueous NaOH solution 15.00 70.00 2.00 13.00 - - 4.41 15.00 69.75 2.00 13.00 - 0.25 6.73 15.00 69.75 2.00 11.50 1,50 0.25 7.41

Table 5
Composition of brake fluid samples Component The content of the examples, mass fraction,% one 2 3 four 5 Polycondensate 38.00 38.00 38.00 43.00 45.00 Tripropylene glycol monobutyl ether 46.25 56.55 48.25 44.10 37.80 Diethylene glycol monoethyl ether 5.00 - 7.00 2.00 4.00 Plasticizer ("LZ-EK") 5.00 5.00 4.00 5.00 7.00 Polypropylene glycol (Laprol-502) 5.00 - 2.00 5.00 5.00 Morpholine 0.20 0.05 0.20 0.20 0.30 Benzotriazole 0.05 0.10 0.05 0.10 0.50 Ionol 0.50 0.30 0.50 0.60 0.40

Table 6
Physico-chemical characteristics of brake fluids Indicators Units DOT-4 standards of FM USS standard No. 116a Example one 2 3 four 5 Liquid boiling point ° C "dry" > 230 244 243 240 243 246 “Hydrated” > 155 162 163 162 164 165 Kinematic viscosity at mm ² / s temperature, ° С: +50 > 5.0 5.69 5.96 6.74 6.10 6.49 +100 > 2.0 2.20 2.10 2,35 2.10 2.20 -40 <1800 1115 1125 1092 980 1043 Thermal stability ° C <3 1,0 1,0 1,0 2.0 1,0

Continuation of table 6 Indicators Units DOT-4 standards of FM USS standard No. 116a Example one 2 3 four 5 Low temperature properties (after keeping for 6 hours at minus 50 ° С): Appearance Transparent, without sediment Compliant Travel time of an air bubble through a layer of liquid when capsizing a vessel from <35 eighteen twenty 19 eighteen 21 Compatible with water at minus 40 C for 6 hours: Appearance Transparent, without sediment Compliant Fluidity from <10 6 7 7 6 7 Appearance after aging at plus 60 ° C for 24 hours Transparent, without sediment Compliant PH 7-11 7.7 8.5 7.7 7.8 7.9

Claims (3)

1. Brake fluid, including boric acid esters, monoalkyl ethers of polyalkylene glycols, one of which is diethylene glycol monoethyl ether, polypropylene glycol, ionol, benzotriazole, morpholine and a plasticizer, characterized in that it additionally contains tripropylene glycol monobutyl ether 500 and medium polypropylene glycol the quality of boric acid esters is boric acid polycondensate of polyalkylene glycols and their monoesters in the following ratio of components, wt.%: Polyalkylene Glycols Boric Acid Polycondensate and their monoesters 38-45 Diethylene glycol monoethyl ether 2-7 Ionol 0.3-0.6 Benzotriazole 0.05-0.50 Morpholine 0.05-0.30 Plasticizer 4-7 Polypropylene glycol with medium molecular weight 500 2-5 Tripropylene glycol monobutyl ether Up to 100 2. The method of producing brake fluid according to claim 1 by mixing esters of boric acid with monoalkyl ethers of polyalkylene glycols, one of which is diethylene glycol monoethyl ether, with stirring and elevated temperature with polypropylene glycol, a plasticizer and additives: ionol, benzotriazole, morpholine, characterized in that as boric acid esters, a polycondensate of boric acid of polyalkylene glycols and their monoesters is used, which is obtained by esterification from a reaction mixture comprising 14-16 wt.% boric acid, 11-20 m wt% of diethylene or triethylene glycol, 60-70 wt.% diethylene glycol monoethyl ether, 0.05-3.00 wt.% N-methyldiethanolamine, 1-15 wt.% tripropylene glycol monobutyl ether, and the additives are pre-dissolved before introduction into the polycondensate in monoalkyl ethers of polyalkylene glycols. 3. The method according to claim 2, characterized in that the reaction mixture is additionally injected with 0.15-0.30 wt.% Saturated aqueous sodium hydroxide solution.