DE2400914C2 - Orthosilicic acid esters, process for their preparation and their use - Google Patents

Description

- ^ CH- CH-

(H)

mean in which R is an alkyl radical with 1 to 2 carbon atoms, η is an integer from 2 to 4 and R ⁵ and R ^{6 are} each a hydrogen atom or a methyl radical. with the proviso that at least one of the radicals R ⁵ and R ^{6 is} a hydrogen atom, with the proviso that the radicals R ¹ , R ² , R ³ and R * together contain at least 15 to 60 carbon atoms.

2. Orthosilicic acid esters of the general formula I, in which

a) R ^{1 is} a tert-butyl radical and —OR ² . —OR ³ and —OR ^{4 are} each a triethylene glycol monome- (hylätherrest, otter

b) R ^{1 is} a neopentyl radical and —OR ² . —OR ³ and —OR * each represent a tripropylene glycol monomethyl ether radical. or

c) R ¹ and R ^{2 are} each a tert-butyl radical and —OR ^{3 and —OR 4 are} each a dipropylene glycol monomethyl ether radical. or

d) R ¹ and R ² each represent a tert-butyl radical, —OR ³ a dipropylene glycol monomethyl ether ^{radical and —OR 4} a triethylene glycol monomethyl ether radical. or

e) R ^{1 is} a tert-butyl radical and —OR ² . —OR ³ and —OR ⁴ each represent a dipropylene glycol monomethyl ether radical. or

f) R 'and R ^{2 are} each a tert-butyl radical and —OR ^{3 and —OR 4 are} each a triethylene glycol monomethyl ether radical, or

g) R ¹ and R ^{2 are} each a tert-butyl radical and —OR 'and —OR ^{4 are} each a tripropylene glycol monomethyl ether radical, or

h) R ^{1 is} a tert-butyl radical and —OR ³ , —OR ³ and —OR ^{4 are} each a tripropylene glycol monomethyl ether radical.

3. Process for the preparation of orthosilicic acid ester η according to one of claims 1 and 2, characterized in that one known per se Way a silicon tetrahalide or an orthosilicic acid ester with one or more of the Formula I reacts corresponding hydroxy compounds.

4. Use of orthosilicic acid esters according to one of claims I and 2 as a component for Hydraulic fluids that also contain at least one common hydraulic fluid additive and / or base material.

The invention relates to the objects characterized in the speeches.

Hydraulic fluids are widely used in hydraulic systems, which are many different Perform functions. The combination of properties which a hydraulic fluid must have differs from case to case. Among the toughest requirements ; include those that are used in brake and clutch fluids in motor vehicles. The vehicle manufacturers and other relevant bodies have very strict specifications for such liquids in which very high quality standards with regard to numerous properties are required will.

Recently there has been a tendency in vehicle construction to operate or actuate * aggregates. like power steering. Shock absorbers and brakes, which were previously each equipped with their own hydraulic systems to use a single hydraulic system. This has serious problems in making the formulation more suitable Hydraulic fluids out. The mineral oil-based hydraulic fluids heretofore used in power steering systems and shock absorbers show with regard to the nitrile and chloroprene rubbers used for the seals and sleeves in such System used to have satisfactory properties. but damage the construction of hydraulic Brake and clutch systems made significant use of synthetic rubbers and natural rubbers. This leads to excessive swelling of this sealing material, which leads to serious malfunctions of the brake or clutch system. Conversely, they are usually based on glycols. Hydraulic fluids composed of glycol ethers and / or glycol ether esters, which were previously used in and coupling systems have been used and have worked satisfactorily in such systems, a damaging effect on the nitrile and chloroprene rubber sleeves. those in power steering systems and shock absorbers are used, which can also lead to malfunctions. When operating vehicles is the operational safety and reliability, which is very important for all mechanical devices Dimensions is desirable, a property that is made up. The importance of security is absolutely essential Claim is due.

There was therefore a need for a hydraulic fluid in a central system; .ti. which controls the operation or the operation of a number of different units ^r , can be used in a satisfactory manner.

Under the. numerous different types of fluids used as base materials or oils for hydraulic fluids have been proposed, certain orthosilicic acid esters are also found. These connections have been proposed and used in some cases for certain types of hydraulic fluids, where the hydrolysis resistance is of comparatively little importance. From the vehicle manufacturers However, these hydraulic fluids were completely inadequate for these purposes because of their Resistance to hydrolysis rejected across the board.

The invention was now based on the object of creating new orthosilicic acid esters that can be used as the base material or oil can be used for hydraulic fluids and not with the above disadvantages of for this purpose known compounds are afflicted, i.e. in particular not too strong Swelling of the most varied in hydraulic systems

3 4

The types of rubber that are commonly used give the orthosilicic acid ester a sufficient hound which also has good hydrolysis resistance at the boiling point.

point. The orthocisic acid esters according to the invention are suitable

It has now been found that hydraulic fluid components and can do this

can be dissolved by certain new orthosilicic acid esters, 5 for this purpose as a base material or as base oils

which have superior resistance to hydrolysis and are used. In this case, the invented

due to the good balance of their proper Qrthocteselsäureester the entire, or

shafts, such as boiling point, resistance to hydrolysis and essentially all of the hydraulic fluid, e.g.

Rubber swelling, for use in manufacturing 70 or 99 percent by weight of hydraulic fluid,

management of hydraulic fluids for vehicle aggregates io. If the orthosilicic acid according to the invention

and in particular hydraulic fluids for esters can also be used for this purpose

central hydraulic systems are suitable. if desired with small amounts of other known ones

The orthosilicic acid esters according to the invention are base materials or base oils are mixed,

those of the general formula I are the orthosilicic acid esters according to the invention

₃ 15 but especially for mixing with considerable people

^OR gene suitable from other known base materials,

_R , _n L _OR 4 _n to modify their properties or to create a flow

K U j> i υ κ WJ gokelt produce a mixture of properties

j WJ gokelt produce a mixture of properties

Q £ 2, p fi di

The orthosilicic acid esters according to the invention can be used

(I)

of the individual components. In this case I

wherein R ^{1 contains} a tertiary carbon atom in a wide range of proportions

tend alkyl group having 4 to 8 carbon atoms or wesend seim, z. B. in quantities from 1 to 70 and ins-

is the neopentyl group, the radical R ^{2 is} a tert-butyl group, especially 10 to 60 percent by weight. In this way

group means or the radicals R ² , R ³ and R ^- * can be used, for example, hydraulic fluids for

or are different and, independently of one another, formulate 25 central hydraulic systems which are the good ones

a radical of the general formula II rubber swelling properties of the or-

thosilicic acid esters in relation to nitrile rubbers and the

I 1 known synthetic base materials or base oils

r pu ppj oil · R (ΙΠ * " ^{r Brcms} " ^{un <} ^ coupling systems in relation to the in

30 the brake and clutch systems of motor vehicles, in which R is an alkyl radical with 1 to 2 carbon atoms, synthetic chewing atoms commonly used, η an integer from 1 to 4 and R ^s and R ^{6 have} chuke and natural rubbers,
each is a hydrogen atom or a Nietüylrest, with the To the base materials or base oils, with the proviso that at least one of the radicals. R ⁵ and R ^6, the orthosilicic acid esters according to the invention are mixed a hydrogen atom, with the proviso that they can be 35, the radicals R ¹ , R ² , R ³ and R ⁴ known for this purpose belong together at least 15 up to and often used glycols. Polyoxyalkyiengly contain 60 carbon atoms. kole and their mono- and dialkyl esters, which are commercially available Preferred orthosilicic acid esters of the general. Further basic materials Hiw. Base oils formula I are those in which the boric acid known from GB-PS 1341901

a) R ^{1 is} a tert-butyl radical and —OR ² , —OR ³ and 40 esters. Further examples of known base oils which are ^{or can be mixed with the —OR 4, in} each case a triethylene glycol monomethyl orthosilicic acid ester according to the invention, are those mentioned in GB-PS 1341 901

b) R ^{1 is} a neopentyl radical and —OR ² , —OR ³ and and in GB-PSs 1083324 and 1249803 executes — OR ⁴ each a tripropylene glycol monomethyl dicarboxylic acid ester and glycol ether radical described, or 45 diesters.

c) R ¹ and R ² each represent a tert-butyl radical and —OR ^3. It is generally desirable that the dipropylene glycol mono-application of the orthosilicic acid ester according to the invention or the hydraulic fluids obtained ^{under Ver and —OR 4 each have a kinematic vis-}

d) R ¹ and R ² each have a tert-butyl radical, —OR ³ a cosile of at most 50 and in particular no more dipropylene glycol monomethyl ether ^{radical and — OR 4} 50 than 20 cm ² / s at -40 ° C and a boiling point of min in triethylene glycol monomethyl ether, or at least 230 ° and preferably at least 260 ⁰ C

e) R ^{1 is} a tert-butyl radical and —OR ² , —OR ³ and sit.

—OR ⁴ each have a dipropylene glycol monomethyl den using the ortho according to the invention

ether residue, or hydraulic fluids obtained from silicic acid esters

f) R ¹ and R ^{2 are} each a tert-butyl radical and —OR ³ 55 are usually small amounts of various additives and —OR ^{4 are} each a triethylene glycol mono of the methyl ether radical commonly used in hydraulic fluids. or species mixed in.

g) R ¹ and R ² each have a tert-butyl radical and —OR ^3, typical additives that can be used are the sciimizing active and —OR ^4, each a tripropylene glycol monosamic additive from the castor oil group or in a methyl ether radical. or 60 differently treated castor oilc. e.g.

H h) R ^{1 is} a tert-butyl radical and —OR ² , —OR ³ and “Firsts” castor oil.

—OR ⁴ each a tripropylene glycol monomethyl castor oil according to specification DTD 72.

{£ · ätherrest is. blown castor oil. i.e. a castor oil. the unler

fii. The boiling point of the orthosilicic acid ester of the invention was heated with air or oxygen blown.

p is generally the higher the larger the b "> special hclles. blown castor oil. i.e. an on

"'Molecule is where the number of carbon atoms in the molecule is similar to blown castor oil

ψ. is a convenient parameter for its size. Dem and a commercially available one with ethylene oxide and II

;! ■ at least 15 carbon atoms are required accordingly. Castor oil treated with propylene oxide. ||

Other lubricating additives that can be incorporated into the hydraulic fluids obtained using the orthocoils according to the invention are, inter alia, boric acid esters, tl. B. tricresyl borate. and phosphorus-containing esters, especially phosphates. e.g. tricresyl phosphate.

Using the orthosilicic acid esters according to the invention The hydraulic fluids obtained can also contain smaller amounts of polyoxyalkylene glycols or contain polyoxyalkylene glycol ethers. Appropriate Examples of such polyoxyalkylene glycols and their Ethers and esters are given in GB-PS 1055641. Other suitable chemical additives are orthophosphates or sulfates of primary or secondary aliphatic Amines with a total of 4 to 24 carbon atoms, the alkyl citrates with an average of 3j to 13 carbon atoms in the alkyl radicals, aliphatic dicarboxylic acids and their esters. Specific examples of such additives are:

Diamylamine orthophosphate,
Dinonylamine orthophosphate,
Diamylamine sulfate.
Dinonyl citrate.
Di- (2-ethyhexyl) citrate.

Polyoxyethylene sebacate, azelate or adipate derived from a polyoxyethylene glycol with a molecular weight of 200,
Polyoxyethylene / polyoxypropylene giarate. derived from a polyoxyglycol mixture with an average molecular weight of about 200.
Glutaric acid,
Azelaic acid,
Sebacic acid,
Succinic acid,
Diethyl sebacate,
Di- (2-ethylhexyl) sebaeate and
Di (isooctyl) azelate.

Unsaturated aliphatic acids or their salts, e.g. oleic acid or potassium ricinoleate. can also be used.

Usable corrosion inhibitors can be selected from heterocyclic. Compounds containing nitrogen. e.g., benzotriazole and benzotriazole derivatives such as those in US Pat GB-PS 1061904 described, or mercaptobenzthiazoien, to be selected. Many amines or amine derivatives are also suitable as corrosion inhibitors. E.g. hydraulic fluids can be used as corrosion inhibitors

Di- (n-butylamine),
Di- (n-amylamine),
Cyclohexylamine,
Morpholine,
Triethanulamine,

and their soluble salts, e.g., cyclohexylamine carbonate.

Phosphites, ζ. B. triphenyl phosphite and
Di- (isopropyl) -phosphite, which are also good corrosion inhibitors,

and certain inorganic salts, e.g. B. Sodium Nitrate,

can be added.

Other additives that make use of the inventive · Orthosilicic acid esters can be added to hydraulic fluids obtained are antioxidants, like dialylamines, e.g. diphenylamine. p.p'-dioctyl-diphenylamine, Phenyl-a-naphthylamine or phenyl-ß-miphthykimin. Other useful antioxidants

are the compounds commonly known as "hindered phenols"; B.

2,4-dimethyl-6-tert-butylphenol,
2,6-di-tert-butyI-4-methylphenol,
2,6-di-tert-butylphenol.

1,1-bis (3,5-di-tert-butyI-4-hydroxyphenyl) methane, S.S'.S.S'-tetra-tert.-butyM ^ '- dihydroxy-di-phenyl. 3-methyl-4,6-di-tert-butylphenol and
4-methyl-2-tert-butylphenol.

Still other additives that can be used are phenothiazine and its derivatives. e.g. those with on the nitrogen atom or the aryl groups in the Phenothiazine molecule bonded alkyl or aryl radicals.

Other additives that can be used include alkylene oxide / ammonia condensation products. for example the propylene oxide / ammonia condensation product described in GB-PS 1249803. can be used, and rA-ar as corrosion inhibitors: As lubricant additives, commercially available complex esters and also the products described in GB-PS 1249803 can be used. In addition, long-chain (e.g. C _{) 10- lg} primary amine corrosion inhibitors and polymerized quinoline resin antioxidants can be used as additives. as described in GB-PS 1249803).

Common additives such as dvi described above are usually used in small amounts. e.g.

3e 0.05 to 10 and in particular 0.1 to 2 percent by weight, used.

The orthosilicic acid esters of the invention can be refined by, for example, in a manner known per se a silicon tetrahalide or an orthosilicic acid

J5 ester with one or more of the formula I corresponding hydroxy compounds.

For the production of in-situ hosilicates. which contain cfcvcn or two alkyl radical (s), for example, SiCl ₄ or an orthosilicic acid ester can be added stepwise with the

4C convert the desired glycol monohydric alcohol in the appropriate stoichiometric ratio (eg 1: 2) and then react the reaction product with alkenol ( e.g. in a ratio 1: 2). An orthosilicic acid ester, such as tetraethyl silicic acid, can preferably also be transesterified with a corresponding alcohol. to introduce the desired number of alkyl radicals required and further transesterify the compound obtained with a glycol monoether. to exchange the remaining ethyl residues for glycol monoether residues.

In the preparation of the orthosilicic acid esters according to the invention by transesterification, a Catalyst used. E.g. sodium metal, which the reaction via the formation of the alkoxide of the glycol monoether crj: ichtert, or a known transesterification catalyst, such as p-Toluolsulfonsäuie or a Telraalkyl-, e.g. tetraisopropyl titanate.

Can iliciumtetrahalogeniden The preparation of the invention Orthokieselsäureester from ^ by reacting the corresponding hydroxy compound mil tetrahalide the VCN at a temperature -40 ° to l50 ^a C. preferably from 40 ° to 100 ° C. without difficulty, optionally in the presence of an inert solvent such as alkyl ethers. Toluene and petroleum ether. be performed. In addition, an acid acceptor, for example a tertiary amine. can be used to trap the hydrogen halide formed during the reaction.

In the production of the inventive ortho

Reak I converters: 17Og SiCI ₄ 326 and Dipropylene glycol monomelhy lather 14Xg tert-butanol 34Xg Pyridine 2.5 liters toluene

Siücium'.o'.rachlorUi 174 ι » Tripropylene glycol monomelhyl ether 679 β Neopentyl alcohol XSg Pyridine .140 u toluene 2.5 liters

7 8

Silicic acid esters can cause a reaction when converted * - Analysis: 4.92% Si (theory 5.68%); Residual chlorine content:

temperature from, for example, XO to 250 and before 0.04%.

/ possibly 120 'to 200 "C applied and desired-".... ^

if an inert solvent is also used. '"

Further details of the preparation of glycol mono- 5 bis (dipropylene glycol monomethyl ether) bis (tert.-butyl) ether sulfate esters are from the »Journal of Inor- silicic acid esters

aanic Nuclear Chemistry ". I96X. Volume 30. Pages 721 to 727 / u.

The following examples serve to illustrate the invention.

Example I.

Tris (propylene glycol monomers, ethyl ether) -neo _P entylkie-

sels.iurcester _{); GemjSL} . _{h of} tert-butanol and 174 g of pyridine in the

Reaction component: run for 2 hours, the heat development being regulated so that the temperature does not exceed ^{41 3 C.} The reaction mixture is then heated to KX) ¹ C for 4 hours, allowed to cool, and a mixture of dipropylene glycol monomethyl ether and the remainder of the pyridine is then added. The resulting mixture is heated for 4 hours in a 5 liter flask, the toluene and SiI-100 C, cooled and filtered, whereupon the cium tetrachloride is mixed and the mixture is stripped under toluene, the reaction product is filtered again, cooling with a mixture of neopentyl alcohol 25 and finally in a high vacuum (180 ³ CzO ₁ OI3 mbar) and 79 g of pyridine are added, the reaction temperature stripping off. 248.2 g (53%) of the end product temperature are obtained as a result of the exothermic reaction to a maximum of clear gVibe of liquid.

42 "C. Then the reaction mixture becomes 4 hours analysis: 6.02% Si (theory 5.98%); residual chlorine content:

the heated to 100 C for a long time and cool overnight 0.36%.

calmly. Then tripropylene glycol mono- 30 Example 4

methyl ether and the rest of the pyridine in the course of a

added half an hour, the exothermic Rcak bis (tert-butyl) - (dipropylene glycol monomethyl ether) - (trition is controlled by cooling with a water bath. Ethylene glycol monomethyl ether) silicic acid ester
The reaction mixture is heated to 112 ° to 114 ° C. for 5 hours and 20 minutes of reactants, then cools and J5. . _{] 7f)}
nitrates the precipitated pyridine hydrochloride. Then ^blC ' ^a j ^ g jj
is the solvent in a rotary evaporator tert-butano ..... , _1O "
stripped and the product finally in a high vacuum D.propylenglykolmonomethylalher 48 g
(200 C / 0.1333 mbar) stripped. 484.4 g of potassium glycol monomethyl ether 197 g are obtained
(66.3%) of the final product. 40 toluene 2 5 liters

Analysis: 3.74% Si (theory 3.84%): residual chloride pyndin S3- g

stop: 0.15%. A mixture placed in a 5 liter flask

from toluene and SiCl ₄ is mixed with a mixture of tert-Example 2 butanol and 158 g of pyridine, the temperature

...., · .. ,, ι ·· ι. , -. ". ,, ■ 45 temperature by cooling with a water bath to below

Tris (ethylene glycol monomethyl ether) -tert-butyl- _{kie | th is held. The reaction mixture is then}

selsdureester _{4 hours} , _{ang to 80} » _bjs , _{0 (rc heated} , cool

Reactants: left and with a mixture of dipropylene glycol

monomethyl ether and 79 g of pyridine were added. A very weak exothermic reaction takes place. The reaction mixture is heated to 80 ° C for 4 hours, allowed to cool again and with a mixture of triethylene glycol monomethyl ether and the remainder of pyridine (95 g) was added, thereby using a water bath a mixture of SiCl ₄ and 2.5 liters of toluene cooled with 55 will.

a mixture of tert-butanol and 87 g of pyridine. The reaction mixture is then heated for 6 hours

sets, keeping the temperature below 50 ^: C. to 100 ° to 104 ° C, then allowed to cool, filtered, stripped The reaction mixture is then stripped for 4 hours on the toluene and finally stripped the reaction mixture 100 ⁼ C, cooled and then with a mixture in a high vacuum (180 ° C / 0.0667 mbar). The product obtained from triethylene glycol monomethyl ether and the remainder 60 is filtered and 413.1 g of the pyridine are obtained, the temperature in turn (86%) of a clear, yellow liquid,
is kept below 50 ⁼ C. To make stirring easier. Analysis: 5.85% Si (theory 5.78%); Residual chlorine content:

more toluene (250 ml) is added and the 0.24% is heated.
The reaction mixture then stands up for a total of 4 times
100 ° C. It is then cooled, filtered and the toluene 65

(100 ^a C / 26.66 mbar) stripped. The product obtained Example D

Tris (dipropylene glycol monomethyl ether) tert-butyl kiestrip is then removed in a high vacuum (210 ° C./0.667 mbar). 346 g (70.4%) of the end product are obtained. selsic acid ester

SiCI ₄ 170 e tert-butanol 74 a Triethylene glycol monomethyl ether 542 "s Pyridine 347 e toluene 2.5 liters + 250 ml

Reaction participants:

SiCl ₄ 170 g

tert-Butiinol 74 g

Dipropyleneglycol monomethylitlier 488 g Pyridine "'348 g

Toli'ol 1 liter + 2IX) ml + 20 «ml

200 ml +4 (K) i «l +1 liter

A premix; ius SiCl ₄ and 1 lithium toluene is mixed with a mixture of tert-bulanol and 80 g of pyridine. During the addition, the exothermic reaction is regulated by cooling with a water bath. The reactants are then heated to 80 ° C. for 3 hours and then a mixture of the remainder of the pyridine and the dipropylene glycol monomethyl ether is added. During the addition, the reaction mixture becomes viscous and difficult to stir, so that further aliquots of Toliic! {3 * 300 m! and then 1x400 ml) can be added as required. The heat development during the addition is regulated by cooling with a water bath. When the addition is complete, the reaction mixture is transferred to a 5 liter flask, a further liter of toluene being added, and the mixture is then heated to 80 ° C. for 12 hours. The product obtained is filtered, then the solvent is stripped off and the product is then removed under high vacuum stripped (mbar 200 ⁰ C / 0.1333). Finally, the product is filtered and is obtained 399 g (73.6%) of a clear yellow liquid.

Analysis: 5.48% Si (theory 5.17%); Residual chlorine content: JO 0.15%.

24 00 -f- 914 JO Reaction participants: 170 G SiCI ₄ 148 G tert-butanol 453 G Tripropylcnglykolmonomct hy lather 348 G Pyridine 2.S liter C. toluene J OmI

Example 6

Bis (triethylene glycol monomethyl ether) - bis (tert-butyl) silicic acid ester

Reaction participants:

SiCl ₄ 170 g tert-butanol 148 e Triethylene glycol monomethyl ether 361g Pyridine 348 g toluene 2.5 liters + 250 ml

A premix of SiCl ₄ and 2.5 liters of toluene is mixed with a mixture of tert-butanol and 174 g of pyridine, the temperature being kept ^{below 50 ° C. during the addition.} The reaction mixture is then heated to 100 ° C. for 4 hours. it cools down and a mixture of triethylene glycol monomethyl ether and the rest of the pyridine is added. A slightly exothermic reaction takes place, the temperature being kept below 50 ° C. The reaction mixture is then heated for 4 hours at 10O ⁰ C. During this time, a further 250 ml of toluene are added. to make stirring easier. The crude product obtained is cooled and filtered, whereupon toluene is stripped off and the product is then stripped off in a high vacuum, the end product being a clear, light yellow liquid in a yield of 323.1 g (64.6%).

Analysis: 5.7% Si (theory 5.6%); Residual chlorine content: 0.05%.

Example 7

Bis (tripropylene glycol monomethyl ether) bis (tert-butyl) silicic acid ester

A mixture of SiCl ₄ and toluene is mixed with a mixture of terl-Bulanol and 74 g of pyridine over the course of 2 hours, while cooling with a water bath, the temperature of the reduction gas rising to a maximum of 38 ° C. as a result of the moderately strong development of heat. The reaction mixture is then heated to 100 ° C. for 4 hours, cooled and then a mixture of the tripropylene glycol monomethyl ether and the remaining pyridine is added over the course of 2 hours, with a slight evolution of heat which is the part of the reason 'can be "ULTRASONIC to a maximum of 30" C rise ^T emi. Then the reaction mixture 4 hours at 1OO' ^J C heated, cooled and filtered, the solvent stripped and finally stripped off the product in high vacuo (0.1333 mbar 180'C). 367.2 g (63%) of the end product are obtained.

Analysis: 4.96% Si (theory 4.8%); Residual chlorine content: Not determined.

Example 8

Tris (tripropylene glycol monomethyl ether) tert-butyl silicic acid ester

Reaction participants:

SiCl ₄ 119 g

tert-butanol 51.8g

Tripropylene glycol monoinethyl ether 474 g
Pyridine 237 g

Toluene 250 ml + 300 ml + 600 ml + 200 ml

In a flask equipped with a water bath for cooling, a mixture of SiCl ₄ and 250 ml of toluene is mixed with a mixture of tert-butanol and 80 g of pyridine. The exothermic reaction increases the temperature to 30 ^° C. To keep the reaction mixture flowing, a further 300 ml of toluene are added, whereupon the mixture is refluxed for 2 hours. The reaction mixture is then cooled and the tripropylene glycol monomethyl ether and the remaining pyridine are added over the course of one hour, a slight evolution of heat being observed. A further 600 ml of toluene are also added. The reaction mixture is transferred to a larger flask with the aid of a further 200 ml of toluene and then heated ^{to 90 ° C. for 10 hours.} The crude product is then worked up by filtering, stripping off the solvent in a rotary evaporator and finally stripping in a high vacuum (180 ° C./0.1333 mbar), 380 g (75.9%) of a pale yellow liquid being obtained as a by-product.

Analysis: 3.86% Si (theory 3.91%): residual chlorine content: 0.76%.

The infrared spectra of the products of Examples 1 to 8 above confirm in each case that the expected product was obtained.

The usefulness of the orthosilicic acid esters according to the invention for use in hydraulic fluids was determined by measuring the reflux point, hydrolysis resistance and the rubber swelling effect of various esters.

The return message was included in the specification SAE J 1703c specified manner.

The rubber swelling was determined as follows:

A square rubber plate with dimensions of about 2.54 by 2.54 by 0.254 cm was placed in a 56.8262 cm ^{1 bottle with a glass bead layer on the bottom.} Then, the bottle was filled with the test liquid and placed in an oven at a constant temperature for 3 days, after which the rubber sheet was taken out, washed with ethanol and dried. The volume of the rubber sheet was measured precisely before and after the test using the known displacement method, and the change in volume in percent was then calculated from the measured values. Styrene-butadiene rubber sheets were tested at I2O "C, natural rubber sheets, which are temperaüirempfin'Jüchcr, hpi 70 ° C, ie at the temperatures customary for carrying out these tests.

In addition, nitrile and chloroprene rubber sheets were also made used, each of which was tested at a temperature of 70 C. It should be noted that. since nitrile and chloroprene rubber have not usually come into contact with brake fluids until now came and these rubbers were therefore not tested in this way, it was not recognized in this regard or common practice there.

The resistance to hydrolysis was determined by adding 1 g of water to 1 g of the orthosilicic acid ester to be tested and 9 g of a commercially available glycol ether hydraulic fluid base material, as well as boiling stones placed in a boiler pipe and over a Bunsen burner to simmer were heated. Then you left the boiler pipe together

I abeiie i

Cool contents, t'is mixture to be tested was during of boiling and subsequent cooling visually detectable signs of unstability to hydrolysis, such as gelling of the mixture or formation of a ■> Precipitation or desiments. observed. After this The result of the visual assessment was then the silicic acid ester with regard to its resistance to hydrolysis rated according to the following rating scale:

0 = Tesa mixture gelled 3 = Low

Sedimentation

1 = Heavy sedimentation 4 = Very weak

Sedimentation

2 = sediment formation 5 = clear

The glycol ether base oil used in these investigations one with additives (presumably sodium nitrite. Agerite Resin D and benzotriazole) partially inhibited Ethylene / propylene glycol ether mixture liquid with a boiling point of 288 "C used. This base oil was selected after preliminary tests in which the orthosilicic acid ester with

a) water and

b) Water and glycol ether base oil without additives
was heated to boiling.

These preliminary tests did not prove to be sharp enough to make the hydrolysis-resistant wedge of the tested. To determine orthosilicic acid ester. It has been found that the presence of the additives stimulates the formation of precipitates increased.

The results of boiling point determination, hydrolysis resistance tests and rubber swell tests on styrene-butadiene rubber and natural rubber are in of Table I, the results of rubber swell tests on nitrile rubber and chloroprene rubber in Tables II and III reproduced.

Tested orthosilicic acid ester

Boiling point ( ⁰ C)

(% (, »Uellung) nature
rubber Styrene
Butadiene
rubber 3.9 0.5 23.7 34.2 55.5 51.7 41.8 51.2 36.5 47.1 19.2 44.4 44.1 39.9 37.6
5.5
-0.7
8.0 60.9
9.3
2.4
14.2

Tris (triethylene glycol monomethyl ether) tert-butyl silicic acid ester Tris (tripropylene glycol monomethyl ether) neopentyl silicic acid ester *

Bis (dipropylene glycol monomelhyl ether) bis (tert-butyl) siliceous acid ester *

Bis (tert-butyl) - (dipropylene glycol monomethyl ether) - (triethylene glycol monomethyl ether) silicic acid ester *

Tris (dipropylene glycol monomethyl ether) -terL-butyl-silicic acid ester Bis (triethylene glycol monomethyl ether) -bis (tert-butyl) -silicic acid ester Bis (tripropylene glycol monomethyl ether) -bis (tert-butyl) -silicate ester A.

Orthosilicic acid ester B

Orthosilicic acid ester C

* \ Not determined

3 4th

4th
4th
5
5

5
0
1
1

From the test results given in the tables it can be seen that the orthosilicic acid esters examined have satisfactory boiling points and a superior hydrolysis-resistant wedge. In addition, low rubber swell values were found for nitrile and chloroprene rubber. The rubber swell values for styrene-butadiene and natural rubber were high, but this is not of great importance, since the low rubber swell values for chloroprene and nitrile rubber are far more important if hydraulic fluids are to be produced that are compatible with all of the rubbers mentioned. When the orthosilicic acid esters of the invention are used with known vehicle hydraulic fluid base oils. which have very poor properties with respect to chloroprene and nitrile rubbers, but good properties with respect to styrene-butadiene and natural rubber, the mixture has lower values compared with the values of the pure orthosilicic acid ester with respect to styrene-butadiene rubbers and natural rubbers, compared with nitrile - and chloroprene sleeves, on the other hand, have higher rubber swelling values.
The silica esters A to C mentioned in Tables 1 to III are not in accordance with the teaching of the invention, but are prepared in the manner described in Examples I to 8, glycol monoether-orthocisic acid esters. which have been checked for comparison. The Orthokieselsäurccstcr A was tris (triithylene glycol monomethyl ether) isobutyl kieselsäu ester with an analytically determined silicon concentration of 5.0 percent by weight (theory 4.74%). [5er orthosilicic acid ester /? was tetra (triethylene glycol monomethyl ether) silicic acid ester with a silicon content of 3.77 percent by weight (theory 4.1%). The othosilicic acid ester C \ varBis (tripropylene glycol monomethyl ether) bis (triethylene glycol monomethyl ether) silicic acid ester with a silicon content of 4.17 percent by weight (theory 3.78%).

Table II

Tested orthosilicic acid ester

3-day rubber source yeast
Nitrile rubber ( X !, 'cure)

Bis (dipropylene glycol monomethyl ether) bis (tert.-bytulosilicic acid ester 0 Bis (tert-butyl) - (dipropylene glycol monomethyl ether) -

(triethylene glycol monomethylL (her) silicic acid ester 2,6

Tris (dipropylene glycol monomethyl ether) tert-butyl silicic acid ester - 0.01

Bis (triethylene glycol monomethyl ether) bis (tert-butyl) silicic acid ester 7.2

BisCtripropyleneglykolmonomethylätheO-bisdert.-butyO-Kieselsäureestcr -0.34

Orthosilicic acid ester A 20.8

Orthosilicic acid ester C 6.5

Table III

Tested orthosilicic acid ester

3-day rubber quelltesl
Chloroprene rubber (% Quelluni!)

Tris (triethylene glycol monomethyl ether) tert-butyl silicic acid ester 1.5

TrisUripiOpyleneglykolmonomethylätheO-neopentyl-Silicic acid ester 0.2

Orthosilicic acid ester A 17.4

Orthosilicic acid ester C 11.3

Claims (1)

Patent claims: I. Orthosilicic acid esters of the general formula I OR ³ R ¹ O-Si-OR " ¹ (D wherein R ^{1 is} a tertiary carbon atom-containing alkyl group having 4 to 8 carbon atoms or the neopentyl group. the radical R ² denotes a teru-buty group or the radicals R ² , R ³ and R ^{4 are} identical or different and. independently of one another, a radical of the general formula II R ⁵ R ⁶