DE1644872A1 - Hydraulic fluids - Google Patents

Description

The invention "relates to power transmission in hydraulic devices suitable liquids, in particular phosphoric acid esters, which act synergistically against oxidation and corrosion effective combination of! inhibitors are protected.

Various oil-like materials have been used as power transmission media used in hydraulic devices. More recently, such hydraulic devices are used in aircraft, where the power transmission is used to carry out control operations, to control servo * brakes and other mechanical Devices of the aircraft is used. There are certain types of liquid to be used in aircraft for the purposes mentioned To make demands. The liquid must not only meet the requirements in functional terms, but must also

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In addition, it must also be relatively flame-tested in order to comply with the safety regulations for aircraft. The liquid must also have a low pour point so that it functions satisfactorily even at low temperatures. The viscosity index should be high so that good usability is guaranteed over a wide temperature range. The volatility at elevated temperatures should be low. The lubricating effect must be good so that pumps, motors, etc. are adequately lubricated; the material must have a low toxicity in order to be easy to handle. Finally, the liquid should have a relatively low density so that - which is particularly important for aircraft - it does not unnecessarily increase the weight of the machine. The numerous phosphoric acid esters are one of the most important materials which have been developed with a view to the preliminary requirements for hydraulic devices in general and in particular in aircraft. These materials have already been used with success in aircraft; In general, it can be said that they meet the requirements listed above better than all other known materials, especially when they are mixed with suitable additives to improve the viscosity index and other properties. The various phosphoric esters that have already been used for the purposes mentioned include various triaryl esters, trialkyl esters and mixed esters such as dialkyl monoaryl and diaryl monoalkyl esters. Experience has shown that the high temperatures that usually occur have virtually no effect on the liquids - they are neither oxidized nor are they corrosive to metal surfaces - if the liquids mainly consist of triary compounds such as tricresyl phosphate or triphenyl phosphate or the like. In order to achieve suitable viscosity values, however, it is generally necessary to use a considerable proportion of either mixed alkylaryl esters or trialky esters, because the viscosities of the triacyl compounds. generally sai high and the Viakoeitäts ? indicia au riieöcig are for a smooth operation. AlkyIpaospliate and avoided the alkylarylphosphates are subject to "as has been shown, at higher temperatures, o.h. at temperatures above about 60 ° 0, the

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Oxidation and become extreme against copper, cadmium, magnesium, etc. corrosive. As a result, it is generally not only advisable but rather advisable. necessary in these fluids certain antioxidants and corrosion inhibitors to use.

As has now been established, liquids can be used gain sufficient flame resistance, which is particularly suitable for use in hydraulic devices in aircraft, if you have a larger amount of a trialkyl phosphate or mixed ^ Alkylaryl phosphates or mixtures of these two materials with a minor part of a synergistic mixture of inhibitors connects, the latter consisting of an epoxy compound and a polyhydroxy compound having two or more hydroxyl groups, which are separated from one another by no more than 3 carbon atoms, exist.

The trialky! Phosphates according to the invention can be represented by the following formula being represented:

X-O

Y-O-P = O

Z-O

In this formula, X, Y and Z denote alkyl radicals or substituted ones Alkyl radicals, preferably alkyl radicals having 1 to 10 carbon atoms. The radicals can contain various numbers of carbon atoms and substituted by various groups such as hydroxyl groups, halogen atoms, and so on. Examples of suitable materials are rTri butyl phosphate, trihexyl phosphate, trioctyl phosphate ^ including branched compounds such as tri- (2-ethylhexyl) phosphate and tri- (2-ethylbutyl) phosphate, trinonyl phosphates and tridecyl phosphates. Materials with mixed alkyl radicals that can be used include ethyl dibutyl phosphate, butyl dihexyl phosphate, etc. Mixtures can also be used of the various connections are used.

The mixed alkylaryl phosphates can be either dialkyl act monoaryl compounds as well as monoalkyldiaryl compounds. The alkyl groups in these compounds can be the same act that have already been mentioned in the trialkyl compounds The aryl radicals can be phenyl, xyIyI, tolyl radicals, etc.

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Act. Phenyl and various substituted phenyl compounds are suitable.

Among the connections that serve as the basis for the hydraulic fluids which are suitable according to the invention also include such triaryl compounds which are substituted by alkaryl radicals which have at least 6 carbon atoms as substituents on the aryl ring. While tricresyl phosphate does not oxidize and does not become corrosive at high temperatures, a material such as trihexylphenyl phosphate is subject to it to the same extent against the destructive influences at high temperatures as trialky compounds and mixed alkylaryl compounds, which have been mentioned above. Materials that are suitable are those containing at least 6 alkyl carbons as substituents on each aryl ring. Accordingly, the lowest suitable compound would be a hexylphenyl compound, as above has already been mentioned, or the isomers of the same such as triethylphenyl-substituted compounds. Mixtures can also be used of these compounds with trialyl or mixed alkylaryl substituents to be used.

The epoxy or epoxy compounds that are used as part of the inhibitor mixture acting according to the invention are organic compounds which have an epoxy group. Any connections can be made can be used if they have a three-membered ring with one oxygen and two carbon atoms. Examples of suitable Epoxy compounds are aryl epoxy compounds such as styrene oxide, oc-methylstyrene oxide etc. and glycidyl ethers such as glycidyl phenyl ether. Suitable compounds also include glycidyl cyclohexyl ether and glycidyl orthocresyl ether. Alkyl glycidyl ethers such as glycidyl ethyl ether, Glycidyl propyl ethers and other higher molecular weight homologues are useful. Cycloalkyl epoxides such as pinene oxide, cyclohexene epoxide and vinyl cyclohexene diepoxide are also useful. Also suitable are olefinic oxides such as ethylene oxide, propylene oxide, butylene oxide, isoprene monoxide and isoprene dioxide, as well Butadiene monoxide and butadiene dioxide. Other epoxy compounds such as Epichlorohydrin, chloroprene oxides and various alicyclic materials such as cyclohexene oxide and cyclopentene oxide are suitable. A particularly useful class of materials are the epoxies,

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obtained by epoxidizing natural materials. Examples of such materials are epoxidized soybean oil, epoxidized castor oil, epoxidized linseed oil and others epoxidized Fats and fatty acid esters that still contain unsaturation Examples of further suitable materials are glyceryltriepoxyacetoxystearate, Butyl epoxy acetoxystearate, etc.

Epoxidized linseed oil is used with particular advantage for the purposes of the invention. A commercially available product of these Type is "Epoxol 9-5"; this product is made by Swift & Co. and has a minimum epoxy oxygen content of 9 Percent by weight.

Examples of polyhydroxy compounds useful for the purposes of the invention are suitable are sorbitol, mannitol, ethylene glycol, 1,2-propylene glycol, Glycerin, pentaerythritol, erythritol, arabitol, dipentaerythritol, iripentaerythritol, etc. The polyhydroxy compounds must have at least 2 hydroxyl groups, which are located no greater distance than in the α- ode ^ Ö-position from one another to be allowed to. The hydroxyl group must be aliphatically bound; the presence of aromatic groups in the compound is acceptable; links with phenolically bound hydroxyl are not useful. Other functional groups such as tartaric acid and so on can be present. The ratio of total number of carbon atoms to hydroxyl groups must not be greater than 2: 1. So is for example 1,2-butylene glycol is a useful compound, 1,2-pentylene glycol on the other hand not. The additional requirement of the position of the hydroxyl groups is also important. 1,3-butanediol, in which the hydroxyl groups are in ß-position to each other, is one effective compound, but 1,4-butanediol is not.

The polyol is used in the inhibitor mixture in an amount of from about 0.01 to about $ 2. The upper limit results from the Solubility in the phosphate; in general, very small ones are sufficient Amounts from about 0.05 to 0.15 percent by weight and these are preferably used.

In addition to the phosphates used as a base, the hydraulic ones contain Liquids in general viscosity index improvement.

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Examples of suitable compounds that can improve the viscosity index are the various acrylates and methacrylates. The viscosity index improvers used with particular advantage are polyalkyl acrylates. Polyalky! Methacrylates are also useful and frequently used. Trade in these materials ⁴ ; they are generally polymers with molecular weights in the range between about 5,000 and 1,000,000. Preferably the molecular weight of the materials is between about 10,000 and 250,000. The alkyl radicals of the polymerized acrylates and methacrylates are C1 to Cp radicals. Examples of monomers from which the polyalkyl acrylates and methacrylates can be produced are acrylates and methacrylates with the following alkyl substituents: ethyl; n-propyl; Isopropyl; n-, iso-, sec- and tertiary butyl; η-, iso- and tertiary amyl; Hexyls such as n-hexyl, 2-ethyl-1-butyl, etc .; n-heptyl; 1,1,3,3-tetramethylbutyl; n-octyl; 2-ethylhexyl various octyl, nonyl and deeyl radicals, etc. Various combinations of these alkyl acrylates can be present in the polymers. The viscosity index improver is used in such amounts that the viscosity index of the liquid increases to such an extent that the liquid has a satisfactory viscosity in the temperature range which will prevail in the hydraulic device during operation. In general, amounts of 1 to 10 percent by weight are used. A liquid with the appropriate properties both lubricates the device and also causes sufficient power transmission over a wide temperature range.

The resistance of the hydraulic fluid to η oxidation and to show corrosiveness, two test methods were used, namely a low-volume oxidation test used to test a large number of samples and method 5308 according to Federal Test Method Standard No. 791A.

In the test with small amounts of 7 ml of fluid were introduced into a 15 cn test tube, which was immersed in an oil bath of about 127 ⁰ O. Copper samples (1/4 "x 1/2" χ 1/64 ") and cadmium and magnesium samples (1/8" χ 1/2 "χ 1/64") were placed in the test tubes. Air was passed through the mixture with the aid of a 1 mm capillary tube which was attached to the bottom of the test tube

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blown at a rate of about 2 bubbles per second. The look the liquid and the metal were rated on the following scale:

valuation liquid metal 1 unchanged unchanged 2 yellow slightly stained 3 light brown severely blotchy or
coating 4th dark brown thick coating or
corroded

became
Ratings 1 or 2 / were considered satisfactory, while maintenance 3 or 4 was considered unsatisfactory for both the liquid and the metals. The base liquid, which was used in the majority of cases and is referred to as dibutylphenyl phosphate, consisted of a mixture which, in addition to the dibutylphenyl phosphate, contained approximately 15 $ iributyl phosphate and 20 $ butyldiphenyl phosphate.

The following epoxy type additives "were used in both series of experiments used;

A) Estynox 100 (**), polymeric plasticizer, oxygenated oxygen;

B) Estynox 140 (**),, epoxidized soybean oil, 6.9 $ epoxy oxygen; G) Estynox 300 (**), epoxidized castor oil, 2 $ epoxy oxygen;

D) Estynox 306 (**), butyl epoxy acetoxystearate, 3.3 $ epoxy acid;

E) Estynox 308 (**), Glyceryltriepoxyacetoxystearat, 3j6 $ Epoxysaueistofi

F) Estynox 408 (**), isooctyl epoxystearate, 4.5 $ epoxy oxygen;

G) Epoxol 9-5 (product of Swift & Co.), epoxidized linseed oil Epoxy oxygen $ 9 minimum;

H) Epoxol 5-2E (product from Swift & Go.), Epoxidized isooctyl tallate, Epoxy oxygen $ 5 minimum;

I) Epoxy 44 (product from Proctor & Gamble Go.), Epoxidized Fat;

J) Epoxy 45 (product of Proctor & Gamble Co.), "Fett;

K) glycidol; "

1) 1,2-epoxy-3-allyloxypropane;

M) 1,2-epoxy-3- (O-chlorophenoxy) propane;

(**) s product from Baker Gastor Oil Company)

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N) glycidyl phenyl ether;

O) Epoxol 7-4 (product from Swift & Go.), Epoxidized linseed oil, Epoxy Oxygen $ 7 minimum.

example 1

The following table summarizes the results that in the case of oxidation-corrosion treatment with small amounts (such as given above). The polyalkyl acrylate used as a viscosity index improver was a mixture des Äthyl-, 2-Äthylhexyl-, Isodecylpolyacrylaffwith a average molecular weight of about 23,000 (intersection of figures). The 1,2-bis-phenylthioethane, which in some examples used for similar purposes is a common oxidation-erosion inhibitor. The Epoxy connection was made in each IaIL in used in an amount of 1 percent by weight.

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! TABLE I.

Oxidation-corrosion test with small quantities

Bas is oil Epoxy A. (Concentr. 1 $) C. Dibutyl phenyl phosphate D. M. E. It J N TL η J N J It E. η η It 1 N 1 η i ¹ H J It F. η P. Il A. η B. η A. η A. η A. η α N It •

Polyhydroxy compound other accessories

0.1 $ sorbitol 0.1 $ mannitol

$ 0.05 mannitol

$ 0.05 sorbitol

$ 1 glycerin

1 $ 1,2,6-heptanetriol

0.1 $ pentaerythritol

1 $ diethylene glycol

$ 0.05 sorbitol

$ 0.05 sorbitol

$ 0.1 erythritol

$ 0.1 arabitol

$ 0.1 inositol

0.1 $ Dipentaerytnritole 6 $ Polyalkyl acrylate

Days to Failure

1.2

Polyalkyl acrylate

714

715 8 1 7 4 18> 16

11 17

OO NJ

TABLE I (continued)

Epoxy base oil Polyhydroxy compound other accessories days up 13th $ 0.5 BPTE > to the Vei - 5 I. t (KonjBentr. 1 $) to say V ? Dibutylphenylphoephate G. $ 0.1 tripentaerythritol 17th R H $ 0.05 sorbitol $ 6.25 polyalkyl acrylate> 14th I. "A. $ 0.05 sorbitol $ 6.25 polyalkyl acrylate? -14 18th “B $ 0.05 sorbitol $ 6.25 polyalkyl acrylate> 14th "A.
"A. $ 0.05 tartaric acid $ 6.25 polyalkyl acrylate
$ 0.5 BPTE ^ 10
11 N Y, $ 0.05 sorbitol 5.7 $ polyalkyl acrylate 12 12th ■ M $ 0.05 sorbitol 5.7 $ polyalkyl acrylate 15th $ 0.1 sorbitol 8th "N $ 0.5 BPTE 4 2 «U $ 0.5 BPTE + $ 6.25 Poly- 2 4th O alkyl acrylate ι CO * G * $ 0.05 sorbitol 10 ¹ co * 0 $ 0.05 sorbitol 6 $ polyalkyl acrylate 14th "A. $ 0.02 sorbitol 14th * "" co "Ϊ ¹ $ 0.05 sorbitol 6 $ polyalkyl acrylate 14th W Jl $ 1 neopentyl glycol 2 cn "A. $ 0.1 sorbitol 14th W 0
σ> η p 1 $ ethylene glycol 12th Tributy! Phosphate - 4th «N 7th "ί ¹ $ 0.05 sorbitol , 14 Oresyl Diphenyl Phosphate - > 14 $ 0.05 sorbitol • 14

contains approximately $ 15 tributyl phosphate and $ 20 butyl phenyl phosphate
1,2-Bi3pUeriylthioätnan

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It can be seen that a large number of epoxy compounds have different * Species as one of the most inhibiting. Ingredients according to the invention ■ are effective. While epoxides alone have only a slight inhibiting: Effect "show in the experiments, one can clearly see that they are in chewing "Bination with the polyhydroxy compounds of the type mentioned increases the resistance increase strongly against oxidation and corrosion. It can also be seen that polyhydroxy compounds in which the hydroxyl groups not arranged in the manner required according to the invention or in which the ratio of carbon to oxygen atoms is greater than 2: 1, with a view to increasing the resistance are not effective. In the example in which 1,2,6-heptanetriol was used, a lag was found to fail. The sample with leopentylglycol failed after 2 days established. The sample, the BPIEE (1,2-bisphenylthioethane), contained a well-known excellent oxidation-corrosion inhibitor, showed a lifespan of 11 days in combination with inhibitor A compared to a lifespan of more than 14 to 18 days, when A was combined with the various Poljf inhibitors.

Example 2

In order to further demonstrate the effectiveness of the epoxy-polyol combinations according to the invention, samples were subjected to the aforementioned method 5308.4. This method is described in "Federal Test Methods Standard Ho. 791A ⁿ dated December 30, 1961. In this method, which is used to test hydraulic oils for their resistance to oxidation and their tendency to corrode metals, 5 different metals are used single container with the liquid to be tested thawed at a temperature of 121 ⁰ C for 168 hours.The liquid is stirred with air; then the acid number of the liquid and the weight loss (in mg per cm) of the various metals such as aluminum, copper, magnesium, Steel and cadmium measured The base material used in the experiment was the same mixture that was also used in Example 1. This mixture consisted largely of dibutylphenyl phosphate and, to a lesser extent, of butyl dipaenyl phosphate and tributyl phosphate.

The results of this experiment are as follows. Table XI compiled. 109818/1 ß fi 0

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! TABELITB II

Oxidation and corrosion resistant (federal method 5308) (168 hours "at 121 ⁰ C)

Bas is oil

Epoxy Polyhydroxyverb.

other accessories

Change in metal weight acid number

in mg / cm
Al Ou Mg steel Od

Dibutylphenyl phosphate -

Il "~

It Il If It Il It

A. $ 0.1 sorbitol Il A. $ 0.05 sorbitol η Έ $ 0.1 sorbitol η B. $ 0.05 sorbitol It G $ 0.05 sorbitol Il H $ 0.05 sorbitol Il G $ 0.2 glycerin Il Ii $ 0.5 BPTE "
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0 -21.6 -3.1 0 -1.1

-0.02 -22.2 -0.36 -0.03 -1.44 3.54 5.5 $ polyalkyl acrylate

-0.01 -0.22 -0.02 -0.01 -0.06 0.58 l

0 -0.06 -0.05 -0.02 -0.05 0.05 "^

-0.03 -0.09 -0.09 0 -0.07 0.02

-0.02 -0.09 -0.02 -0.01 -0.07 0.24

-0.09 -0.12 -0.11 -0.09 -0.11 0.01

0 -0.02 0 0 -0.02 0.07

0 -0.04 -0.02 0 -0.01 0.16

-0.03 -0.13 -0.13 -0.06 -0.09 0.07

-0.02 -3.04 -0.02 0 -0.02 0.21

It can be seen from the data in Table II that the inhibitor combination very effective "in reducing the oxidation of the liquid itself, as evidenced by the substantial reduction of the acid number increase compared to uninhibited material. The combination is also very effective in reducing it metal corrosion, especially in the case of copper and cadmium. It can also be seen that the sample containing the BPIE in conjunction with a Epoxy, a change in weight of the copper sample of 3.04 mg / cm, indicating that it is far less effective than the polyols.

In addition to the additives mentioned, other additives can also be used. With these additives it can These are additional viscosity index improvers, pour point depressants, agents for extreme prints,! dyes, etc.

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Claims (8)

Claims 1) Hydraulic! Fluid, characterized in that this mainly from a sialkylphosphate, a mixed one Alkylary! Phosphate or mixtures of these compounds as well to a lesser extent from 0.1 Ms 5.0 percent by weight of an epoxy compound and 0.01 to 2 percent by weight of a polyhydroxy compound, the latter having at least 2 hydroxyl groups, which are separated from one another by no more than 3 aliphatic ^ carbon atoms has and in which the behavior nis from carbon atom to hydroxyl groups in the molecule is not greater than 2: 1. 2) Hydraulic fluid according to claim 1, characterized in that that the! liquid consists of a mixture of trialkyl phosphates with a mixed alkylary! phosphate. 3) Hydraulic fluid according to claim 1, characterized in that that the epoxy compound is an epoxidized fat or is epoxidized ester of an unsaturated fatty acid. 4) Hydraulic fluid according to claim 3, characterized in that that the epoxy compound is an epoxidized linseed oil or an epoxidized soybean oil. 5) Hydraulic fluid according to claim 1, characterized in that that the hydroxy compound is adjacent to 3 or more Carbon atoms has hydroxyl groups. 6) Hydraulic fluid according to claim 5, characterized in that that the polyhydroxy compound by reducing a Sugar has been obtained. 7) Hydraulic fluid according to claim 6, characterized in that that the polyhydroxy compound is sorbitol. 8) Hydraulic fluid according to claim 1, characterized in that that the polyhydroxy compound pentaerythritol, dipenta 109818/1662 - 2 - is erythritol or tripentaerythritol, Pur Chevron Research Company San Francisco, Gal., Y.St.A. Lawyer 109818/1662