NO141016B - HYDRAULIC VAESKE. - Google Patents

Description

The invention relates to hydraulic fluids which

has the ability to inhibit and regulate damage to mechanical parts that come into contact with these liquids.

A large selection of hydraulic fluids is also known

used for many purposes. Hydraulic fluids have been used as electronic coolants, nuclear reactor coolants, diffusion pump fluids, lubricants, damping fluids, grease bases, power transmission and hydraulic fluids, heat transfer fluids, heat pump fluids, fluids for cooling equipment and as filter media for air conditioning systems.

In many of the hydraulic fluids used

for the above purposes, damage has been reported to the liquid during use and to mechanical parts, especially metal parts that come into contact with the liquid, which is shown by weight loss of such parts, which is due to wear of the metal parts. Damage has been reported in aircraft hydraulic systems, in gas turbine bearings, in jet turbine control systems, in steam turbine bearings, in steam turbine control systems, electrohydraulic control systems and spacecraft control equipment. Damage has also been observed to such materials as glass, "Teflon", "Mylar", "Plexiglass" and parts constructed of other non-metallic materials.

In cases where such fluids are used in hydraulic systems in air and space systems, such systems place strict requirements on the hydraulic fluid. Not only must these hydraulic fluids meet strict application requirements, but they must also meet FAA and other government requirements regarding fire resistance. In addition, the hydraulic fluid must be able to work in the hydraulic system for a longer period of time without causing particular damage or functional deterioration in the various lines, valves, pumps etc. as the fluid flows

through when in use.

Damage caused by incoming functional fluids

in contact with valves and other parts, has been attributed to wear or erosion of the environment that comes into contact with the functional fluid in a hydraulic system. Among the many undesirable results that such damage causes is a marked reduction in the strength of the structural mechanical parts of the hydraulic system, e.g. pumps and valves, together with a change in the geometry of these parts. Such changes in the case of pumps can cause a reduction in pump efficiency, and in the case of valves, they can cause incorrect operations, excessive leakage and even dangerous conditions.

This damage necessitates expensive and time-consuming, premature overhaul of mechanical parts. Also, metal removed from metal components in mechanical parts that come into contact with the functional fluid contaminates the fluids, causes filter clogging and unnecessary filter replacement, and requires premature draining and replacement of the fluid in the system. The metal contamination can also cause changes in the physical and chemical properties of the functional fluids.

Metal contaminants can also reduce the oxidative stability of a liquid, whereby the liquid's performance is adversely affected. Furthermore, metal contamination of the liquid can manifest itself in numerous other ways, including viscosity change, increased acid number, formation of precipitation products, reduction of chemical stability and discolouration.

Another problem in the industry is the inevitable contamination of aircraft and electrohydraulic control systems with chlorinated solvents used for cleaning the systems and components.

A detailed discussion of this problem can be found in the Vickers 22nd Fluid Power Conference Report, 30 Oct. 1972, Part 4,

pp. 25-29. Contamination using chlorinated solvents reduces the life of functional fluids and accelerates damage, causing unnecessary internal leakage in hydraulic systems to the point of malfunction. No additive known to date has satisfactorily overcome the problems associated with contamination of functional fluids by chlorinated solvent.

In accordance with the invention, a hydraulic fluid is provided which exhibits improved low erosion, shear, oxidative and heat stability and which also has good fire resistance characteristics and which is particularly well suited for aircraft hydraulic purposes. The invention encompasses the incorporation of a small amount of certain ammonium salts of phosphoric acids into various base raw material mixtures to produce a hydraulic fluid capable of inhibiting damage to the metal surroundings containing the hydraulic fluid.

The ammonium salts of the phosphoric acids included in the hydraulic fluids in accordance with the invention are represented by the following formula:

where R, R', R'', R''<1> may be the same or different and represent hydrogen or an alkyl group containing 1-15 carbon atoms, Y' and Y" represent hydrogen, a lower alkyl group or a phenyl group. I in addition, the hydraulic fluid according to the invention contains phenyl-a-naphthylamine.

Below is a list of typical ammonium salts of phosphoric acids that correspond to the respective ammonium ions and phosphoric ester anions:

Each part of the ammonium ions can in turn be combined with each part of the phosphoric ester anion so that typical compounds are obtained which can be used in connection with the invention. Eksempler' på spesielt foretrukne ammoniumsalter av fosforsyrer er: Decyltrimetylammoniumdifenylfosfat Didodecyldimetylammoniumdifenylfosfat Dimetylpropyldodecylammoniumdifenylfosfat Dodecylammoniumdifenylfosfat Allyltributylammoniumdifenylfosfat Bis(dodecyltrimetylammonium)fenylfosfat Decyltrimetylammoniumdimetylfosfat Didodecyldimetylammoniumetylmetylfosfonat Bis(didodecyldimetylammonium)metylfosfonat Dodecyltrimetylammoniumdimetylfosfat Dodecyltrimetylammoniumdibenzylfosfat Dodecyltrimetylammoniummetylfenylfosfat Dodecyltrimetylammonium-bis(nonylfenyl)fosfat Dodecyltrimetylammoniumdiallylfosfat Dodesyltrimetylammoniumdifenylfosfat Didodecyldimetylammonium-di-n-dodecylfosfat Dodecyltrimetylammonium-di- n-dodecyl phosphate Dioctylmethylammonium dioctylphosphate Trioctylammonium dioctylphosphate Bis(trioctylammonium)ethyl phosphate Tridecyltrimethylammonium diphenylphosphate Trioctylmethylammonium diphenylphosphate Tris(n-tridecyl)methylammonium diphenylphosphate Tris(n-dodecyl)methylammonium diphenylphosphate Tris(isooctyl)me tylammonium diphenylphosphate Triethylmethylammonium methylmethylphosphonate 2-ethylhexyldimethyldodecylammonium diphenylphosphate Dimethylethyldodecylammonium diethylphosphate Dimethylbutyldodecylammonium dibutylphosphate Trimethyldodecylammonium dimethylmethylphosphonate Tris(dodecyl)butylammonium dibutylphosphate Tetramethylammonium methyloctylphosphonate Tetramethylammonium methylhexadecylphosphonate Tetramethylammonium methyl-tert,-butylphosphonate

The quaternary ammonium salts of diesters of phosphoric acid containing no N-H bonds can be prepared by known methods, as set forth in British Patent Document No. 1,119,015 and in Preprints of the Symposium on Deposit, Wear, and Emission Control by Lubricants and fuel Additives which is presented in the Division of Petroleum Chemistry of the American Chemical Society, N.Y. City Meeting, Sept. 7-12, 1969, pp. A-110. These methods include:

1. Reaction of an amine with a triester of phosphoric acid where the triester alkylates the amine. These reactions usually take place above 40 - 60° and can be run in the pure state or in alcohol solvents. All volatile compounds are then removed by distillation, leaving the phosphoric acid diester salt of a quaternary ammonium cation.

R<1> is preferably of benzyl-, allyl- or lower alkyl- (in particular

elt methyl-) type. R" can be alkyl, aryl, alkaryl, aralkyl, etc.

2. Reaction of the phosphoric acid diester with a quaternary ammonium hydroxide to produce the salt in a neutralization reaction and then removal of the liberated water. 3. Reaction of the quaternary ammonium halide with the sodium or potassium salt of the phosphoric acid diester and extraction of the phosphate with a solvent, e.g. acetone, so that it becomes possible to remove the sodium or potassium chloride.

Erosion exhibited by hydraulic fluids has been attributed to the electrical properties of the fluid in Boeing Scientific Research Laboratories Document Dl-82-0847. It has been suggested that erosion caused by hydraulic fluids can be controlled by eliminating ionic contaminants present in the fluid, or by significantly increasing the conductivity of the fluid.

Both measures have been explored with some degree of success. This is surprising due to the fact that removal of ionic contaminants actually lowers conductivity. This turns out to indicate two opposing solutions to the problem of ameliorating damage caused by erosion. Recent experiments have shown that removal of ionic contaminants by filtration through an activated clay will control the erosion caused by a phosphate ester hydraulic fluid. However, this is not a practical solution, as the erosion starts again soon after the filtration is stopped. In addition, filtering on aircraft is virtually impossible.

The addition of ammonium salts of phosphoric acids to various basic raw materials has proven to be effective in preventing damage. Furthermore, conductivity measurements of these liquids containing ammonium salts of phosphoric acids indicated increased conductivity. It is too early to draw the conclusion that conductivity can be considered as an explanation for the mechanism, or to assess the effectiveness of damage inhibitors. However, the conductivity actually serves as a certain indication, although further research in this area is considered necessary and desirable.

Typical conductivity values for commercial aircraft hydraulic fluids, based on phosphate esters, on the market today range from approx. 0.02 to approx. 0.05 micromhos/cm.

Functional liquid mixtures to which the ammonium salts of phosphoric acid mixtures described above can be added are called base raw materials. They include esters and amides of phosphoric acids, mineral oils and synthetic hydrocarbon oils, orthosilicates, alkoxypolysiloxanes, silicones, polyphenol ethers and polyphenol thioethers, chlorinated biphenyl compounds, monocarboxylic acid esters, esters of polyhydric compounds, polyalkylene ether glycols and alcohols as well as esters thereof.

The concentration of ammonium salts of phosphoric acids in the functional liquid is adjusted according to the particular system and

the functional fluid for preventing and managing damage. Thus, it has been shown that the additive response, i.e. the concentration of an ammonium salt of phosphoric acid which is necessary to inhibit and regulate damage of a base raw material, varies according to the base raw material or mixtures of base raw materials used.

Therefore, the concentration of ammonium salts of phosphoric acid for basic raw materials which are applicable in the practice of the invention is from 0.01 to 10% by weight, the particular concentration being the amount which will effectively prevent and control damage. The preferred additive concentration is from 0.025 to 5% by weight,

and preferably from 0.1 to 2.0% by weight. Therefore, the invention includes mixtures comprising a functional liquid and a damage-inhibiting amount of an ammonium salt of phosphoric acids, i.e. that the ammonium salt is added in a concentration that is sufficient to regulate and prevent damage. The functional liquid mixtures according to the invention can be put together in any way known to the person skilled in the field when it comes to the incorporation of an additive into a base raw material, and preferably by adding an ammonium salt of phosphoric acids to the base raw material while stirring until a liquid mixture is obtained .

As indicated above, the products according to the invention can use a large selection of basic raw materials. Suitable base raw materials shall be discussed in detail below.

The functional liquid mixtures which are suitable for use as basic raw material in connection with the invention can be esters and amides of an acid of phosphorus, represented by the structural formula:

where Y is selected from the group consisting of oxygen, sulfur and Y^ is selected from the group consisting of oxygen, sulfur and and Y2 is selected from the group consisting of oxygen, sulfur and

R, R-^, R2, R3, R^ and R^ are each selected from the group consisting of alkyl, alkoxy, aryl, substituted aryl and substituted alkyl wherein R, R^, R2, R^, R^ and R ,, may be identical or different with respect to any other radical, and a, b, and c are integers with value 0 or 1, and the sum a+b+c is from 1 to 3.

In general, the number of carbon atoms in the alkyl groups will vary from 1 to 30. Included in the alkyl groups are cycloalkyl and alkyl-substituted cycloalkyl. Also included are aralkyl groups, e.g. benzyl, α- or β-phenylethyl, α, α-dimethylbenzyl and the like. wherein the alkyl part has 1-30 carbon atoms. Also included are cyclobutyl, cyclohexyl, cycloheptyl etc. Also included are alkaryl groups, e.g. methylphenyl, ethylphenyl, etc. Also included are alkoxy-alkyl, e.g. methoxyethyl, ethoxyethyl, butoxyethyl, butoxybutyl and the like.

Typical examples of substituted alkyl radicals are the haloalkyl radicals which can be represented by structural

where Hal refers to a halogen, m is less than or equal to 2n+1, and n can have any value from 0 to 18, and R₁ and R₂ can be hydrogen, halogen, e.g. F, Cl, Br and I, or alkyl radicals. Preferred radicals are those where Hal is fluorine.

The halogenated alkyl radicals can be primary, secondary or tertiary.

Other suitable fluorine-containing radicals include fluorinated alkoxyalkyl radicals.

Also included within the scope of the invention is that the hydrogen and fluorine in the previously described haloalkyl radicals can be replaced by other halogens, e.g. chlorine or bromine.

Typical examples of aryl and substituted aryl radicals are phenyl, cresyl, xylyl, halogenated phenyl, alkoxylated phenyl, cresyl and xylyl where the available hydrogen on the aryl or substituted aryl is partially or completely replaced by halogen, 0-, m- and p-trifluoromethylphenyl , o-, m- and p-2,2,2-trifluoroethyl-phenyl, o-, m- and p-3,3,3-trifluoropropylphenyl and o-, m- and p-4,4,4-trifluorobutylphenyl . Also included are isopropylphenyl, butylphenyl, α-alkylbenzylphenyl and α,α-dialkylbenzylphenyl, e.g. α-methylbenzylphenyl, α,α-dimethylbenzylphenyl.

The orthosilicates useful as base raw materials include the tetraalkylorthosilicates, e.g. tetra(octyl)-orthosilicates, tetra(2-ethylhexyl)orthosilicates and the tetra(iso-octyl)orthosilicates and such where the isooctyl radicals are obtained from isooctyl alcohol originating from the oxo process, and the (trioxy-silico)trialkylorthosilicates, also referred to as hexa- (Alkoxy)disiloxanes, e.g. hexa(2-ethylbutoxy)disiloxane and hexa(2-ethylhexoxy)disiloxane.

The preferred tetraalkylorthosilicates and hexa-(alkoxy)disiloxanes are those where the alkyl or alkoxy radicals have 4-12 carbon atoms and where the total number of carbon atoms in the orthosilicate is 16-60.

In addition to the hexa(alkoxy)disiloxanes referred to above, other hexa(alkoxy)disiloxanes can be used where the aliphatic radical in the alkoxy groups, e.g. are 1-ethylpropyl, 1,3-dimethylbutyl, 2-methylpentyl, 1-methylhexyl, 1-ethylpentyl, 2-butylhexyl and 1-methyl-4-ethyloctyl.

The orthosilicates and alkoxypolysiloxanes can be represented by the general structural formula:

wherein Rg, Rg and R^Q may each be alkyl, substituted alkyl, aryl, substituted aryl and may be identical or different with respect to any other radical, O is oxygen, Si is silicon, X is a member of the group which consists of carbon and silicon, m is an integer with the value 0 or 1, n is an integer with a value from 1 to approx. 200 or more and when X is carbon, m is equal to 0, n is equal to 1, and R^^/ <R>^2°9 Ri3 ^an each be hydrogen, alkyl, substituted alkyl, aryl, and substituted aryl, and when X is silicon, m is equal to 1, n is an integer with a value from 1 to approx. 200 or more, and R<->^</><R>12 °9 Ri3 ^an each be alkyl, substituted alkyl, aryl and substituted aryl.

Typical examples of substituted aryl radicals are o-, m- and p-chlorophenyl, o-, m- and p-bromophenyl, o-, m- and p-fluorophenyl, a, a,a-trichlorocresyl, a, a,a- trifluorocresyl, xylyl and o-, m- and p-cresyl. Typical examples of alkyl and haloalkyl radicals are those already described above.

The siloxanes or silicones useful as base raw materials are represented by the general structural formula:

where R"L4# R15'<R>16' <R>17' <R>18'°^ R19 ^an ^ver be alkyl, substituted alkyl, aryl and substituted aryl, and n is an integer from about 0 to about 2000 or more. Typical examples of alkyl and haloalkyl radicals together with the number of carbon atoms are those described above. Typical examples of the siloxanes are poly-(methyl) siloxane, poly(methyl, phenyl) siloxane, poly(methyl, chlorophenyl )siloxane and poly(methyl, 3,3,3-trifluoropropyl)siloxane. Typical examples of substituted!aryl radicals are o-, m- and p- chlorophenyl, o-, m- and p-bromophenyl, 6-,\m- and p-fluorophenyl, a, a,a-trichlorocresyl, a,a,a-trifluorocresyl, p-,,m- and p-cresyl and xylyl. 0 0 ;.r Dicarboxylic acid esters which are suitable spm base raw materials are represented by the structural formula:|

wherein Rori and R are each selected from the group consisting of alkyl, . substituted alkyl, aryl and substituted aryl,, and R_. is a divalent radical that is selected from the group consisting of alkylene.. and substituted alkylene, and is produced by the restriction of di-, carboxylic acids such as e.g. adipic acid, azelaic acid, suberlnic acid, sebacic acid, hydroxysuccinic acid, fumaric acid, maleic acid, etc.;, with alcohols such as e.g. butyl alcohol, hexyl alcohol, 2-ethylhexyl alcohol, dodecyl alcohol, 2 , 2-dimethylheptanol, 1-methylcycl.o-■ ■< i . ,.. l . >::', hexylmethanol, etc.

, ."•.;:<-./•-•..-i-- -.- r i.-. <J. :. <■-.

Typical examples of alkyl, aryl, substituted alkyl and substituted aryl radicals are given above.

Polyesters that are suitable as basic raw materials., are

> •> , O ■ .' ; ;.'":>■• "i: J.i.' : ■ ' Si,-'--- , • > represented by the structural formula: r ...

where R2;j is selected from the group consisting- -of .h<y>dro<g>en': .and. alkyl.,-=;■< < <R>24 and R25 are each selected from the group consisting of--:of:--alkyl■-.■■ s-- >zvJ substituted alkyl, aryl and substituted aryl -, a is , a; :h'elrt :.taTl- ;-n) with a value of 0 or 1, Z is an integer^ jtal'1-With verdr..>l. ^él-1'er-'2i/ and when Z is 1, R->g is selected from the group consisting of hydrogen,

alkyl acyloxy and substituted acyloxy, and when Z is 2, R is oxygen and is produced by esterification of such polyalcohols as pentaerythritol, dipentaerythritol, trimethylolpropah, trimethylolethane and neopentylglycol with such acids as propionic acid, butyric acid, isobutyric acid , n-valeric acid, capric acid, caproic acid, n-heptyl acid, caprylic acid, 2-ethylhexanoic acid, 2,2-dimethylheptanoic acid and pelargonic acid. Typical examples of alkyl, substituted alkyl, aryl and substituted aryl radicals are given above.

Other esters which are also suitable as basic raw materials are the monoesters.

Another class of mixtures which are suitable as basic raw materials for the invention are the polyphenyl ethers, polyphenyl thioethers or mixtures thereof, as represented by the structural formula:

where A, A^, A2 and A^ are each a chalcogen of atomic number. 8-16,

X, X^, ... X^, and X^ are each selected from the group consisting of . hydrogen, alkyl, haloalkyl, halogen, arylalkyl and vsubstituted, arylalkyl, m, n and o are whole numbers, each has a value of 0 to 8, and a is an integer of value 0 or .1, provided that when a is 0, n may have a value of 1 to 2. Typical examples of alkyl and substituted alkyl radicals are granted. above. Typical examples of such base raw materials are 2- to 7-ringed ortho-,. meta- and para-polyphenyl ethers and mixtures thereof, 2- to. 7-, .. ringed ortho-, meta- and para-polyphenylthioethers and mixtures thereof, mixed polyphenyl-ether-thioether compounds where at least one of the chalcogens represented by A, A^, A2 and A^ is different with regard to to any of the other chalcogens, dihalogenated diphenyl ethers, e.g. 4-bromo-3'-chlorodiphenyl ethers and bisphenoxy-biphenyl compounds and mixtures thereof.

Hydrocarbon oils, including mineral oils derived from petroleum sources, and synthetic hydrocarbon oils are suitable base raw materials. The physical properties of functional liquids originating from a mineral oil are selected on the basis of the requirements set for liquid tanks, and the invention therefore includes as basic raw materials mineral oils that have a wide viscosity range and volatility range, such as mineral oils with naphthenic or paraffinic or mixed basis.

The synthetic hydrocarbon oils include, but are not limited to, such oils derived from oligomerization of olefins, e.g. polybutenes and oils derived from high or α-olefins of 4-20 carbon atoms, such as by acid-catalyzed dimerization and then oligomerization using mixtures of aluminum alkyl compounds and titanium halides such as. catalysts, or Friedel-Crafts catalysts, or peroxide catalysts.

Chlorinated biphenyl compounds and terphenyl compounds are also useful as base raw materials.

The liquid preparations according to the invention can, when used as a functional liquid, also contain acid acceptors, dyes, pour point depressants, thickeners, antioxidants, antifoam agents, viscosity index-improving agents, e.g. polyalkyl acrylates, polyalkyl methacrylates, polycyclic polymers, polyurethanes, polyalkylene oxides and polyesters, lubricants, water and the like.

It is also within the scope of the invention that the basic raw materials mentioned above can be utilized individually or as a mixture containing two or more basic raw materials in varying amounts. The base raw materials can also contain other liquids which, in addition to the functional liquids, include desired liquids originating from coal tar products, synthetic substances and synthetic oils, e.g. alkylene polymers (e.g. polymers of propylene, butylene, etc., and mixtures thereof), alkylene oxide-type polymers (e.g. propylene oxide polymers) and derivatives, including alkylene oxide polymers prepared by polymerization of alkylene oxide in the presence of water or alcohol, e.g. ethyl alcohol, alkylbenzenes (eg, monoalkylbenzene, eg, dodecylbenzene, tetradecylbenzene, etc.) and dialkylbenzene (eg, n-nonyl-2-ethylhexylbenzene); polyphenyl compounds (e.g. bi-

phenyl and terphenyl compounds), halogenated benzene, halogenated lower alkylbenzene and monohalogenated diphenyl ethers.

However, it is preferred when performing inventive

then the phosphoric acid ammonium salt preparation is combined

with a phosphate ester as the base raw material.

The basic raw material will primarily consist of trialkyl phosphates which are

present in amounts from 50 to 95% by weight and preferably from 60

to 90% by weight. The trialkyl phosphates which give optimal results are those where each of the alkyl groups contains 1-20 carbon atoms, preferably 3-12 carbon atoms, and more preferably 4-9 carbon atoms. The alkyl groups are preferably of the straight-chain configuration

tion. A single trialkyl phosphate may contain the alkyl group in all three positions or may have a mixture of different alkyl groups. Mixtures of different trialkyl phosphates can be used. Suitable types of trialkyl phosphates that can be used as the base raw material mixture include tripropyl phosphates, tri-butyl phosphates, trihexyl phosphates, trioctyl phosphates, dipropyl-octyl phosphates, dibutyloctyl phosphates, dipropylhexyl phosphate, dihexyloctyl phosphate, dihexylpropyl phosphate and propylbutyloctyl phosphate.

phosphate.

The trialkyl phosphates can be combined with triaryl phosphates

or mixed alkylaryl phosphates. Preferred triaryl phosphates are tricresyl phosphate, cresyl diphenyl phosphate, trixylenyl phosphate, tert.-butylphenylphenylphosphates, ethylphenyldicresylphosphate or isopropylphenyldiphenylphosphate, phenyl-bis(4-a-methylbenzylphenyl)phosphate, diphenyldecylphosphate, diphenyloctylphosphate, methyldiphenylphosphate, butyldicresylphosphate and the like. In a preferred embodiment, a base raw material is used which mainly contains trixylenyl phosphate. The triaryl phosphates function as thickeners for the trialkyl phosphates. Thus, the amount of triaryl phosphate can vary between 0 and 35% by weight. The preferred range for the triaryl phosphates will be from approx. 5 to approx. 30% by weight of the mixture.

Conventional polymeric thickeners or viscosity index (VI) improvers can be mixed with the mixture of the trialkyl and triaryl phosphate material to achieve the desired viscosity. Typical thickeners used can be polyacrylates, polymethacrylates, polyethylene oxides, polypropylene oxides, polyesters and the like.

A polyester which is based on an azelaic acid and a diol, e.g. propylene glycol and the like are preferably used as thickeners, in the range of 0.3-20% by weight.

Combinations of antioxidants and/or acid acceptors in amounts varying from 0.1 to 5% by weight can also be incorporated into the functional liquid mixture, e.g. epoxides and/or amines. The combination of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate and phenyl-a-naphthylamine has been shown to be very effective.

Corrosion inhibitors, e.g. benzotriazole, quinizarin etc. in an amount varying between 0.001 and 0.5% by weight, can be added to the mixture and thoroughly mixed with it. A dye in a concentration varying between 5 and 20 ppm can be added to the mixture and mixed with it in a conventional manner. Effective amounts of a silicone antifoam agent may also be incorporated into the mixture and are usually most effective in an amount varying between 5 and 50 ppm.

The hydraulic fluids according to the invention can contain up to 1% by weight of water. However, it is preferred to maintain water levels below 0.6% by weight, and most preferably below approx. 0.3% by weight.

The invention can be illustrated by means of the following

examples.

In the examples and throughout the description, all parts and percentages are by weight unless otherwise indicated.

Example 1

A base feedstock consisting of 78.98% by weight tributyl phosphate and 9.70% by weight mixed cresyl and xylenyl phosphates having a viscosity of approximately 220 Saybolt universal seconds at 37.8°C is combined with 9.00% by weight of a polyester thickener-- agent, "Plastolein" 9789 from Emery Industries. Next, 1.0% by weight of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate and 1.0% by weight of phenyl-α-naphthylamine are mixed into the mixture.

Then 0.02% by weight of benzotriazole is mixed in together with conventional dye and antifoam in an amount of 20 and 15 ppm, respectively. Then, dodecyltrimethylammonium diphenylphosphate is mixed into the mixture in various amounts including 0.1 and 0.3% by weight.

The preparation prepared as above was tested in an apparatus consisting of a "Boeing" 737 trailing edge flap valve pressurized by a "Vickers" axial piston pump together with related equipment necessary to ensure that the apparatus would operate in accordance with the requirements of Section 10.2 of the SAE specification AS 1241 which relates to erosion resistance of fire-resistant hydraulic fluids for aircraft. The liquids are assessed on the basis of the increase in the degree of leakage for the valve when it is in the closed or zero position. The results of the addition of the dodecyltrimethylammonium diphenyl phosphate to the phosphate ester liquor are as follows:

The test results show that the addition of an effective amount of dodecyltrimethylammonium diphenyl phosphate to a phosphate ester hydraulic fluid prevents damage to hydraulic systems.

Example 2

A similar erosion test was carried out on the phosphate ester liquid described in Example 1, with 0.3% by weight of dodecyl trimethylammonium diphenyl phosphate. In this test, the concentration of chlorinated solvents was gradually increased up to a final level of 2000 ppm chlorine.

These data are presented in the figure and illustrate the utility of dodecyltrimethylammonium diphenyl phosphate in preventing damage to a hydraulic system from chlorine-contaminated phosphate ester hydraulic fluids.

Example 3

An erosion test was performed on a Boeing Material Spee. 311C (BMS 311-C) qualified phosphate ester hydraulic fluid for aircraft that was contaminated with 1000 ppm chlorine as 1,1,1-trichloroethane. After the erosion rate was established, the phosphate ester liquid described in Example 1 with 0.3% by weight of dodecyltrimethylammonium diphenyl phosphate was added in portions to the contaminated liquid. The following data were obtained from this test:

QUALIFIED BMS 311-C PHOSPHATESTER-HYDRAULIC FLUID +1000

PPM CHLORINE AS CH3CC13

The above results illustrate the utility of a composition containing dodecyltrimethylammonium diphenyl phosphate in arresting the damage caused to hydraulic systems by chlorine-contaminated phosphate ester hydraulic fluids.

Example 4

In an erosion test similar to that described in Example 1, the damage-causing characteristics of the liquid described in Example 1 were completely stopped by the addition of 0.5% by weight of a mixed mono- and bis-(dodecylammonium) methyl phosphate. This test illustrates the usefulness of mixed mono- and bis-(dodecyl-ammonium) methyl phosphates in stopping damage caused by phosphate ester fluids in hydraulic systems. The conductivity before the addition was 0.021 mmhos/cm, and after the addition 0.24 mmhos/cm.

Example 5

A mixture similar to that described in Example 1 was prepared. Two preparations were prepared with this mixture. The first contained 0.2% by weight of dodecyltrimethylammonium diphenylphosphate and the second preparation contained 0.2% by weight of trioctylmethylphosphonium dimethylphosphate. These preparations were subjected to stability tests which are described in Boeing Material Specification 311-C. The following results were obtained in these tests:

Boeing thermal stability test

Test conditions: 121.1°C, 168 hour duration, steel, magnesium, cadmium plated steel, copper and aluminum present as catalysts.

These tests show that preparations made with dodecyltrimethylammonium diphenylphosphate as an additive show greater thermal and oxidative stability than preparations made with trioctylmethylphosphonium dimethylphosphate.

Example 6

Illustrative Embodiment No. 1

In an erosion test carried out in a similar manner to that described in example 1, a polyphenyl ether liquid consisting of mixed meta- and para-pentaphenylene tetraoxides and containing 0.2% bis(dodecylbenzyltrimethylammonium phenylphosphate) will show less metal damage than the same liquid without the bis-ammonium phosphate.

Example 7

Illustrative Embodiment No. 2

In an erosion test carried out in a similar manner to that described in example 1, a liquid which consisted of approximately 85% synthetic hydrocarbon oil, e.g. such as that produced by Royal

Lubricants for use in MIL-H-83282 hydraulic fluids,

15% trimethylolpropane triheptanoate and 0.2% didodecyldimethylammonium didodecyl phosphate show less metal damage than the same liquid without the ammonium phosphate.

Example 8

Illustrative Embodiment No. 3

In an erosion test carried out in a similar manner to that described in Example 1, a liquid consisting of approximately 50% mixed alkyl-substituted phosphate ester, 40% aromatic mineral oil, e.g. "NUSO" 95 from Sun Oil Co., 10% pentaerythritol tetraheptanoate and 0.2% nonylphenyltrimethylammonium dioctyl phosphate showed less metal damage than the same fluid without the ammonium phosphate.

Claims (4)

1. Hydraulic fluid comprising a major amount of a base raw material selected from the group consisting of esters of a phosphoric acid, amides of a phosphoric acid, mixtures of esters and amides of a phosphoric acid, and mixtures of the foregoing with one or several materials selected from the group consisting of mineral oils, synthetic hydrocarbon oils, orthosilicates, alkoxypolysiloxanes, silicones, polyphenol ethers, polyphenylthioethers, chlorinated biphenyl compounds, esters of dicarboxylic acids and monohydric alcohols, esters of monocarboxylic acids and polyhydric alcohols, polyalkylene ether alcohols and esters thereof, and mixtures thereof, characterized in that it also contains an effective erosion-inhibiting amount of an ammonium salt of a phosphoric acid which is comprised by the following formula: where R, R', R"', R<*>'' may be the same or different and represent hydrogen or an alkyl group containing 1-15 carbon atoms, Y<1> and Y" represent hydrogen, a lower alkyl group or a phenyl group , as well as phenyl-α-naphthylamine. 2. Hydraulic fluid as stated in claim 1, characterized in that the ammonium salt is present in an amount between 0.01 and 10% by weight. 3. Hydraulic fluid as stated in claim 1, characterized in that the ammonium salt is present in an amount between 0.1 and 2.0% by weight. 4. Hydraulic fluid as stated in claim 1, characterized in that the ammonium salt of a phosphoric acid is dodecyltrimethylammonium diphenylphosphate.