JPS5930758B2 - Improvement of hydraulic system liquid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to improvements in hydraulic fluids, and more particularly to hydraulic fluids containing novel orthosilicate esters.

Hydraulic liquids are generally used in hydraulic systems that perform various functions, and the characteristics required of the liquids differ depending on the case.

One of the most stringent requirements is for automotive brake and clutch fluids.

Car manufacturers have very strict specifications for such fluids and set very high standards for various properties.

Recently, there has been a trend toward using single hydraulic systems to operate devices that previously used separate hydraulic systems, such as power steering, shock absorbers, and brakes.

This presents significant problems in the formulation of suitable liquids.

Mineral oil-based fluids traditionally used in power steering and shock absorbers are satisfactory for nitrile and chloroprene rubbers used in seals and gaskets in such systems, but are not suitable for hydraulic brake and clutch systems. It is extremely harmful to the natural or synthetic rubber used.

This causes the seal to expand abnormally, causing the brake and clutch systems to malfunction.

On the contrary, it has been used in brake and clutch systems and works satisfactorily in those systems.

Liquids based on glycols, glycol ethers and/or glycol ether esters, etc., can damage nitrile and chloroprene rubber gaskets used in power steering and shock absorbers, rendering them inoperable.

In the case of wheel operation, this is generally required for all mechanical devices.

The feature of reliable operation is important and is an absolutely essential requirement from a safety perspective.

Accordingly, there is a growing need for liquids that can be satisfactorily used in central systems controlling many different devices.

Among the various liquids that have been proposed as base-stock for hydraulic fluids are certain orthosilicate esters.

These have been proposed and used in certain hydraulic systems where hydrolytic stability is less important.

However, such esters are not sufficiently hydrolytically stable for automotive fluids, and manufacturers have therefore refused to use them.

The present inventors have discovered a new orthosilicate ester with excellent hydrolytic stability, which has a boiling point,
Since it has a good balance of necessary properties such as hydrolytic stability and rubber swelling properties, it is suitable for use in formulating hydraulic fluids for automotive equipment, including central fluids.

Such orthosilicate esters contain at least 1
It is characterized by the presence of glycol monoether residues and at least one branched organic group.

Accordingly, the present invention provides a hydraulic fluid containing an orthosilicate ester having the following general formula: Si(ORJm((OC2H4)30CH3J.

[OC3H6)k-OCH3J4-m-n (wherein R is t-butyl or neopentyl, k is 2 or 3, m is 1 or 2, and n is 0, 1 or 2) Such an orthosilicate ester is It is useful as a liquid component in hydraulic systems and is used as a base material for this purpose.

In this case, the orthosilicate ester is present in all or substantially all of the hydraulic fluid, for example '70 or 99% (
% by weight, the same applies).

In such uses, the orthosilicate ester may be mixed with small amounts of other known base materials, if desired.

However, orthosilicate esters are particularly useful for blending with substantial amounts of other known base stocks to improve the properties of the known base stock or to provide liquids that are mixed with the properties of another component. It is.

In this case, the orthosilicate ester can be contained in a wide range of proportions, for example in the range of 1 to 70%, more preferably in the range of 10 to 60%.

Thus, for example, good rubber expansion properties for nitrile rubbers due to orthosilicate esters and good rubber expansion properties for natural and synthetic rubbers commonly used in automotive brake and clutch systems due to known synthetic base materials for brake and clutch systems. Central system fluids can be formulated that combine swelling properties.

Base materials that can be mixed with orthosilicate esters in the present invention include the known and widely used glycols, polyoxyethylene glycols, and their mono- and dialkyl esters.

These substances are commercially available, for example under the trade name ``Ucon J''.

Other examples include the trade names "Oxito" and "Cel Iosolve J."

Other base materials include the boric acid esters described in British Patent No. 1,341,901.

Further base materials which may be mixed with the orthosilicate esters of the present invention include dicarboxylic acid esters and glycol diesters (UK Patent No. 1,34
See specification No. 1,901.

Furthermore, British Patent Nos. 1,083,324 and 1,2
49,803).

Thus, the hydraulic liquids of the present invention contain at least 7 such orthosilicate esters, or mixtures of esters thereof, or mixtures of such orthosilicate esters and one or more other known hydraulic liquid base materials.
Contains 0%.

It is particularly preferred that the hydraulic fluids of the invention have a kinematic viscosity of not more than 5000 cst, preferably not more than 2000 cst, at -40°C and a boiling point of at least 230°C, especially at least 260°C.

When using the hydraulic fluids of the present invention, they are typically mixed with small amounts of various additives of the type commonly used in hydraulic fluids.

Typical additives used in the present invention include castor oil or various processed castor oils, such as primary castor oil, D
TD72 Castor Oil, Blown Castor Oil (i.e., castor oil that has been bubbled with air or oxygen while being heated), Special Pale Blossom Castor Oil (i.e., similarly bubbled castor oil), Hydricin 4 (
That is, a lubricating oil additive selected from commercially available ethylene oxide/propylene oxide treated castor oil).

Other lubricating oil additives that may be used in conjunction with the hydraulic fluids of the present invention include boric acid esters (e.g., tricresyl porate) and phosphorus-containing esters, as well as phosphates (e.g., tricresyl phosphate). be.

The hydraulic fluid of the present invention contains a small amount of polyoxyalkylene glycol or its ester, such as "Ucon J" sold by Union Carbide Company.
In particular, it may include the LB and HB series.

Preferred examples of these polyoxyalkylene glycols, ethers or esters thereof are described in British Patent No. 1,0
No. 55,641.

Other suitable lubricating oil additives are orthophosphates of primary or secondary aliphatic amines having 4 to 24 carbon atoms, or sulfate alkyl groups having an average carbon number of 31/2 to 13 carbon atoms. dialkyl citrate, aliphatic dicarboxylic acid or its ester, and specific examples thereof include cyamylamine orthophosphate, dinonylamine orthophosphate, cyamylamine sulfate, dinonyl citrate, di(2-ethylhexyl ) Citrate, polyoxyethylene sebacate derived from polyoxyethylene glycol (molecular weight 200), polyoxyethylene azelate derived from polyoxyethylene glycol (molecular weight 200), polyoxyethylene glycol (molecular weight 200) polyoxyethylene adipate derived from polyoxyethylene adipate, polyoxyethylene/polyoxypropylene glutarate derived from mixed polyoxyglycols (average molecular weight approximately 200), glutamic acid, azelaic acid, sebacic acid, succinic acid, diethyl sebacate, di(2 -ethylhexyl) sebacate, diisooctyl azelate, etc.

Unsaturated fatty acids or their esters may also be used, such as oleic acid and potassium ritylinate.

Corrosion inhibitors which can be used in the present invention include nitrogen-containing heterocyclic compounds such as benzotriazole and its derivatives or mercaptobenzothiazole as described in British Patent No. 1,06], 904.

Many amines and their derivatives are also useful as corrosion inhibitors, such as di-n-butylamine, di-n-amylamine, cyclohexylamine, morpholine, triethanolamine and its soluble salts, such as cyclohexamine carbonate. .

Phosphites are also good corrosion inhibitors, for example triphenyl phosphite, diisopropyl phosphite, and inorganic salts such as sodium nitrate may also be used.

Other additives that may be included include antioxidants such as diarylamines, e.g. diphenylamine, P, P'-
Dioctyl-diphenylamine, phenyl-α-naphthylamine or phenyl-β-naphthylamine.

Other suitable antioxidants are those commonly known as hindered phenols, such as 2,4-dimethyl-6-
1-butylphenol, 2,6-di-t-butyl-4-
Methylphenol, 2,6-di-t-butylphenol, 1,1-bis(3,5-di-t-butyl-4-hydroxyphenyl)methane, 3.3', 5°5'-tetra-
1-butyl-4,4'-dihydroxy-diphenyl, 3
-methyl-4,6-1-butylphenol and 4-methyl-2-t-butylphenol.

Still other additives include phenothiazines and their derivatives, for example compounds in which an alkyl or aryl group is attached to a nitrogen atom or an aryl group.

Still other additives are alkylene oxide/ammonia condensation products as corrosion inhibitors, such as the propylene oxide/ammonia condensation products described in GB 1,249,803.

Further usable lubricating oil additives are complex esters, such as the product name "Reoplex 641" (Reoplex 641).
No. 641) J and British Patent No. 1,24
It is described in the specification of No. 9,803.

Additionally, long chain (e.g. 10 to 18 carbon atoms) primary amine corrosion inhibitors and quinoline resin antioxidants as described in British Patent No. 1,249,803 may also be used.
Examples of such amines and resins include “
Arme-en12D (Arme-en12D)J
and “Age-rite resin D”
It is commercially available as s in D)J.

The usual additives as mentioned above are usually 0.05 to 10%,
For example, it is used in a small amount of about 0.01 to 2%.

The orthosilicate esters used in the present invention are prepared by methods commonly used for the preparation of such esters, for example, by reacting silicon tetrahalides such as 5ick4 with hydroxy compounds such as glycol monoethers and alkanols; It is obtained by transesterifying tetra(hydrocarbyl)silicate with an appropriate amount of a hydroxy compound.

Examples of suitable tetra(hydrocarbyl)silicates are tetramethylsilicate, tetraphenylsilicate and tetraethylsilicate, the last being particularly preferred.

Other suitable tetra(hydrocarbyl)silicates are described in GB 1.075,236.

The orthosilicate ester used in the present invention is 1 or 2
It has 1 to 3 t-butyl or neopentyl groups and 1 to 3 glycol monoether residues, each of which is bonded to a silicon atom via an oxygen atom, and during its production, glycol monoether residues are introduced. Preferably, the alkyl groups are introduced before the reaction, for example by reacting 5iCI4 with an amount of alkanol, such as t-butanol, necessary to introduce the desired number of alkyl groups, followed by reaction with a glycol monoether.

When these orthosilicate esters are obtained by transesterification, a suitable tetraalkyl silicate containing the desired alkyl group, such as tetra(t-butyl)silicate, is mixed 1:1 with a glycol monoether.
When reacted at a molar ratio of 2 or 1:3, 1,
Two or three glycol monoether residues can be introduced.

Alternatively, a tetra(
Hydrocarbyl) silicate can be transesterified with a suitable alcohol to introduce the desired number of alkyl groups, and the compound thus obtained can be transesterified with a glycol monoether to remove the remaining ethyl groups. can be substituted with a glycol monoether residue.

When orthosilicate esters are obtained by transesterification, the tetra(hydrocarbyl)silicate starting materials and reaction conditions are chosen such that free hydroxy compounds can be removed from the reaction mixture by distillation.

For example, the transesterification reaction of tetraethyl silicate produces ethanol with a relatively low boiling point, and by distilling off ethanol, the transesterification reaction, which is an equilibrium reaction, can proceed completely.

A preferred method for preparing the novel orthosilicate esters by transesterification may use catalysts, such as sodium metal, which accelerates the reaction by forming alkoxides of glycol monoethers, or p-)luenesulfonic acid or Known transesterification catalysts such as tetraalkyl titanate (eg, tetraisopropyl titanate) can be used.

The orthosilicate ester used in the present invention can be easily produced from silicon tetrahalide by reacting a suitable hydroxy compound with the tetrahalide at a temperature of -40 to 150°C, preferably 40 to 100°C.

If desired, the reaction can also be carried out in the presence of an inert solvent such as an alkyl ether, toluene, petroleum ether, and the like.

Additionally, acid acceptors such as tertiary amines may be used to neutralize the hydrogen halides formed in the reaction.

The reaction temperature when producing by transesterification is 8
The temperature may be 0 to 250°C, preferably 120 to 200°C, and an inert solvent may be used if desired.

A more detailed description of methods for preparing glycol monoether orthosilicates can be found in the Journal of Inorganic Nuclear Chemistry (J, of
Inorganic Nuclear Chemistry
y) 1968, Vol. 30, pp. 721-727.

Next, the present invention will be explained in more detail with reference to production examples of orthosilicate esters and compatibility tests as hydraulic fluids.

Production example 1 Tris (triethylene glycol monomethyl ether)
Production of t-butyl silicate Silicon tetrachloride and diethyl ether are
The mixture was placed in a 21J Tutle round-bottom three-necked flask equipped with a stirrer, thermometer, thermocouple, nitrogen inlet, dropping tube, condenser, and water supply tube.

t-Butanol and pyridine (the latter is used as an acid acceptor to prevent the reaction of hydrogen chloride and t-butanol produced in the reaction) were placed in a dropper and slowly added into the flask at an initial temperature of 20°C. .

Temperature was recorded by thermocouple with thermometer.

The thermometer became difficult to read due to the white precipitate.

The addition of t-butanol was completed in 1.5 hours and the temperature rose due to the exothermic reaction.

A maximum of 35°C was reached at the end of the addition. The reaction mixture was stirred for an additional half hour at room temperature and then filtered.

The apparatus was reassembled as before and the filtered reaction mixture was placed in the flask.

Triethylene glycol was added dropwise to the reaction mixture via a dropper.

The addition was carried out slowly at first to such an extent that no exothermic reaction was observed, and the addition rate was gradually increased to such an extent that an exotherm of 5° C. (maximum) occurred.

During the addition, nitrogen was bubbled vigorously to remove hydrogen chloride.

The crude product was heated to 70°C for 9.5 hours to complete the reaction, then evaporated at 170°C and 0.05ml H&
i4.95% (theoretical value 4.75%) and residual chlorine 0.
140 g of a clear brown liquid containing 17% (0% theory) (23.7% based on silicon tetrachloride) was obtained.

Production example 2 Tris (triethylene glycol monomethyl ether)
Preparation of t-butyl silicate Silicon tetrachloride and 250 ml of toluene were placed in a 2 liter round bottom 3 neck flask equipped with a dropper, stirrer, condenser, nitrogen inlet and thermocouple.

The flask was placed on a water bath and 87 g of pyridine was added over 40 minutes.

During this time, the temperature inside the flask was maintained at 15±1°C.

The flask was then removed from the water bath and stirred for 15 minutes.

During that time the temperature rose to room temperature (approximately 20°C).

Tert-butanol dissolved in 50 ml of toluene was added over half an hour.

The volume temperature was kept at 20-25°C.

The flask contents were then heated at 80° C. for 1.5 hours.

The flask contents were poured into a larger (3 liter) flask equipped with similar equipment as the original flask and an additional 500 ml of toluene was added.

The remaining pyridine (260 g) was then added over 1.5 hours.

The volume temperature was kept at 20-25°C. Triethylene glycol monomethyl ether was slowly added to the reaction mixture.

1/3 of the glycol ether in 3/4 hours at a temperature of 20
Added at ~35°C.

When the contents of the flask became too viscous for the reaction to proceed, the addition was stopped and 600 vtl of toluene was added.

Glycol ether addition was resumed and the remaining glycol ether was added at 30-40°C.

When 3/4 of the glycol ether had been added, the remaining toluene (400 ml) was added, and the glycol ether addition was completed in a total of 2.5 hours.

The reaction mixture was stirred at 90-100°C for 2.5 hours and further stirred at 80°C for 7 hours.

Finally, the crude product was filtered using diatomaceous earth filter aid, evaporated in a rotary evaporator, and then heated at 170°C, 0.4-0.5
Distilled at imH& to give Si4.86% (theoretical value 4.75
%) and residual chlorine 0.05% (theoretical 0%) of a deep yellow liquid (40% based on silicon tetrachloride).

Production Example 3 Production of tris (tripropylene glycol monomethyl ether) neopentyl silicate Toluene and silicon tetrachloride were mixed in a 5 liter flask,
Add neopentyl alcohol and pyridine 79 to this while cooling.
g mixture was added.

During this time, the reaction temperature reached a maximum of 42°C due to exothermic reaction.

The reaction mixture was heated at 100° C. for 4 hours and allowed to cool overnight.

Tripropylene glycol monomethyl ether and the remaining pyridine were then added over half an hour.

During this time, the exotherm was controlled by cooling (water bath).

The reaction mixture was heated at 112-114°C for 5 hours and 20 minutes, cooled, and the precipitated pyridine hydrochloride was filtered.

The solvent was evaporated using a rotary evaporator δ, and the product was evaporated under high vacuum (2
Distilled at 00℃, 0.1 H5') to final product 484
．． 4. ! ? (66.3%).

Analysis value: Si 3.74% (theoretical value 3.84%) Residual chlorine 0.15% Production example 4 Tris (triethylene glycol monomethyl ether)
Preparation of t-butyl silicate 5iC64 and toluene (2.5 liters) were mixed and to this was added a mixture of t-butanol and 87 g of pyridine.

During this time, the temperature was kept below 50°C.

The reaction mixture was heated at 100° C. for 4 hours, cooled, and then the remaining pyridine was added.

During this time, the temperature was kept below 50'C.

Further, 250 ml of toluene was added and stirred, and the reaction mixture was heated at 100° C. for 4 hours, cooled, and after passing through, the toluene was evaporated (100° C., 20 torr).

The obtained product was heated under high vacuum (210°C, 0.5% H, 9)
The final product 346i (70.4%) was obtained.

Analysis value: Si 4.92% (theoretical value 5.68%) Residual chlorine 0.04% Production example 5 Production of bis(dipropylene glycol monomethyl ether) bis(t-butyl) silicate Mix 5ick and toluene, A mixture of t-butanol and 174 g of pyridine was added to the solution over a period of 2 hours.

During this time, heat generation was controlled so that the reaction temperature did not exceed 41°C.

The reaction mixture was heated at 100° C. for 4 hours, allowed to cool, and then a mixture of dipropylene glycol monomethyl ether and remaining pyridine was added thereto.

The resulting mixture was heated at 100°C for 4 hours, cooled,
It is passed through, the toluene is blown off, it is passed through again offshore, and finally it is subjected to high vacuum (
Distillation at 180° C. (0.01 Hg) gave the final product 248.29 (53%) as a clear yellow liquid.

Analytical value: Si 6.02% (theoretical value 5.98%) Residual chlorine 0136% Production example 6 Production of bis(t-butyl)(dipropylene glycol monomethyl ether)()lyethylene glycol 7-methyl ether) silicate t-butanol and A mixture of 158 g of pyridine was added to the toluene and SiC114 mixture previously mixed in a 5 liter flask.

During that time, the temperature was kept below 50°C by cooling in a water bath.

The reaction mixture was heated at 80-100° C. for 4 hours, allowed to cool, and then a mixture of dipropylene glycol monomethyl ether and 79 fl of pyridine was added to it (slight exotherm).

The reaction mixture was heated at 80° C. for 4 hours, allowed to cool, and to this was added a mixture of triethylene glycol monomethyl ether and the remaining pyridine (951) while cooling in a water bath.

The reaction mixture was then heated at 100-104°C for 6 hours, allowed to cool, filtered, stripped of toluene, and then distilled under high vacuum (180°C, 0.05°C [,9]) to obtain The product was filtered to give a clear yellow liquid 413.1.9 (86
%) was obtained.

Analytical values: Si 5.85% (theoretical value 5.78%) Residual chlorine 0.24% Production example 7 Tris (dipropylene glycol monomethyl ether)
Preparation of t-butyl silicate t-Butanol and 80 g of pyridine were mixed and added to a previously prepared mixture of S t C74 and toluene (1 liter).

During the addition, exotherm was controlled by cooling with a water bath.

The mixture was then heated at 80°C for 3 hours.

To this was added the remaining pyridine and dipropylene glycol monomethyl ether.

During this time the reaction mixture became viscous and difficult to stir so toluene (3 x 200 ml and 1 x 400 ml) was added.

During the addition, exotherm was controlled by cooling with a water bath.

The reaction mixture was then transferred to a 5 liter flask, 1 liter of toluene was added, and the mixture was heated at 80° C. for 12 hours.

The resulting product was filtered, the solvent was stripped off, and the product was distilled under high vacuum (200° C., 0.1iiH9), which was refiltered to yield 399 g (73.6%) of a clear yellow liquid.

Analytical value: Si 5.48% (theoretical value 5.17%) Residual chlorine 0.15% Production example 8 Production of bis(triethylene glycol monomethyl ether) bis(t-butyl) silicate A mixture of t-butanol and pyridine (174 g) was , pre-adjusted 5
Added to a mixture of tCA'4 and 2.5 liters of toluene.

The volume temperature was kept below 50°C.

The reaction mixture was heated at 100° C. for 4 hours, cooled and to it was added a mixture of triethylene glycol monomethyl ether and the remaining pyridine.

Although there was a slight exotherm, the temperature was kept below 50°C.

The reaction mixture was heated at 100° C. for 4 hours, during which time 250 ml of toluene was added to facilitate stirring.

The crude product was cooled, filtered, stripped of toluene, and then distilled under high vacuum to give a final product of clear blue-yellow liquid 323.
1.9 (64.6%).

Analysis value: Si 5.7% (theoretical value 5.6%) Residual chlorine 0
．． A mixture of 0.05% t-butanol and pyridine 147& was added to the mixture of 5xC74 and toluene over 2 hours while cooling in a water bath.

The temperature rose to 38°C (maximum) due to a gentle heat generation.

The mixture was heated at 100° C. for 4 hours, cooled, and then a mixture of tripropylene glycol monomethyl ether and the remaining pyridine was added to it over a period of 2 hours.

During that time, the temperature rose to a maximum of 30°C due to slight heat generation.

The reaction mixture was heated at 100 °C for 4 h, cooled, filtered, the solvent was evaporated and finally heated under high vacuum (180 °C, 0.1
The final product (367.2i63%) was obtained by distillation at Yong Hg).

Analytical value: Si 4.96% (theoretical value 4.8%) Residual chlorine was not measured Production example 10 A mixture of tris (tripropylene glycol monomethyl ether) t-bunal silicate t-butanol and 80 g of pyridine was placed in a cooling water bath. 5iCA' in a flask equipped with.

and 250 m/toluene.

The temperature rose to 30°C due to exotherm.

An additional 300 ml of toluene was added to maintain fluidity, and the mixture was refluxed for 2 hours.

The reaction mixture was cooled and to it was added a mixture of tripropylene glycol monomethyl ether and remaining pyridine over 1 hour.

During that time, no fever was observed.

Furthermore, toluene 6001111 was added.

Transfer the reaction mixture to a larger flask and add toluene 20
After adding 0ml, it was heated at 90°C for 10 hours.

The crude product was filtered, the solvent was evaporated on a rotary evaporator, and finally distilled at high vacuum (180 °C, 0.1 mm H9) to give 380 g (75.9%) of the final product as a pale yellow liquid. I got it.

Analytical values: Si 3.86% (theoretical value 3.91%) Residual chlorine 0.76% The infrared absorption spectra of the products of Preparation Examples 1 to 10 each matched that of the expected product.

Suitability Test as Hydraulic Fluids To investigate the suitability of these orthosilicate esters for use as hydraulic fluids, the reflux boiling point, hydrolytic stability and rubber swelling effect of each ester were determined.

The reflux boiling point was measured according to the specifications of SAE J 1703c.

Rubber expansion was measured by placing a square of rubber (approximately 1 x 1 x 1/10 inch) in a 2 ounce bottle with a layer of glass beads in the bottom.

The bottles were filled with the test liquid and placed in an oven at constant temperature for 3 days, then the rubber squares were removed, washed with ethanol and dried.

The capacity of the square rubber was accurately measured before and after the test using a known substitution method, and the percentage increase in capacity was calculated.

In the same way, 1 square styrene-butadiene rubber was
Measured at 20 degrees Celsius, and natural rubber, which is more temperature sensitive, was measured at 7
Measurements were taken at 0°C (these temperatures are commonly used to perform these tests).

Additionally, nitrile and chloroprene rubber squares were also measured at 70°C.

It should be noted that nitrile and chloroprene rubbers do not normally come into contact with brake fluids, and such rubbers have never been tested in this way, so performing the totoshi test described above is well established practice. It's not something that was done.

Hydrolytic stability was determined by placing 1 g of water, 1 g of the orthosilicate ester to be tested and 9 g of the commercially available glycol-ether hydraulic liquid base material together with anti-pumping granules in a boiling tube and boiling the mixture on a Bunsen burner. The boiling tube and contents were then allowed to cool and then measured.

The test mixtures were observed during boiling and cooling to visually determine the hydrolytic stability, e.g. gelability of the mixture or the formation of precipitates, and the beneficial extent of the orthosilicate ester was determined according to the following criteria7: 0: The test mixture gelled with heavy precipitate formation 2: Precipitate formation 3: Small precipitate formation 4: Very little precipitate formation 5: Clear The glycol-ether base material used in these tests had a boiling point of 550° F mixed ethylene/propylene glycol ether liquid with sodium nitrite as additive,
It uses Agerite Resin D and benzotriazole.

This was selected in preliminary tests in which orthosilicate esters were boiled with (a) water and (b) water and glycol ether base stock (no additives).

These preliminary tests were found not to be sufficiently rigorous for evaluating the hydrolytic stability of orthosilicate esters.

It has been found that the presence of additives increases deposit formation.

The results of boiling point measurements, hydrolytic stability tests and rubber swelling tests for styrene-butadiene rubber and natural rubber are shown in Table 1.

The results of rubber expansion tests for nitrile rubber and fluoroprene rubber are shown in Tables 2 and 3, respectively.

These test results show that orthosilicate esters have sufficient boiling points and excellent hydrolytic stability.

Furthermore, low rubber expansion results were obtained for nitrile and chloroprene rubbers.

Although the rubber expansion value of styrene-butadiene rubber was high,
Low values for chloroprene and 2) IJ rubbers are believed to be extremely important in order to obtain liquids that are compatible with these rubbers.

Orthosilicate ester as a known automotive hydraulic liquid base material (bad for chloroprene and nitrile rubber, but good for styrene-butadiene and natural rubber)
When blended with styrene, the rubber expansion value of the blended liquid is higher than that of the orthosilicate ester.
It will be lower for butadiene and natural rubber and higher for nitrile and chloroprene rubber.

In Tables 1 to 3 below, Silica 1-A-C is a glycol monoether silicate produced in the same manner as in Production Examples 1 to 10 but not of the present invention.

Silicate A is tris(triethylene glycol monomethyl ether) i-butyl silicate (analytical value: Si5
．． 0% (theoretical value 4.74%)), and silicate B is tetra(triethylene glycol monomethyl ether) silicate (analytical value: Si3.77% (theoretical value 4.
．． Silicate C is bis(tripropylene glycol monomethyl ether) bis(triethylene glycol monomethyl ether) silicate (analytical value: Si 4.17% (theoretical value 3.78%)).

Claims (1)

[Claims] 1 General formula: % formula % (wherein R means t-butyl or neopentyl, k means 2 or 3, m means 1 or 2, and n means 0, 1 or 2. 1 to 99% by weight of at least one orthosilicate ester, the remainder being at least one known base material for hydraulic fluids and/or up to 10% by weight of known additives for hydraulic fluids. A hydraulic liquid characterized by comprising at least one of the following.