CA1288760C

CA1288760C - Energy transmitting fluid

Info

Publication number: CA1288760C
Application number: CA000555657A
Authority: CA
Inventors: Walter Ensign Francis Lewis
Original assignee: Union Carbide Corp
Current assignee: Union Carbide Corp
Priority date: 1986-12-30
Filing date: 1987-12-30
Publication date: 1991-09-10
Anticipated expiration: 2008-09-10
Also published as: JPH0558474B2; JPS63308086A; GR3002159T3; BR8707105A; DE3770930D1; DK690287A; AR240173A1; DK690287D0; EP0273460A2; MX169073B; EP0273460B1; ES2022294B3; ATE64612T1; KR880007705A; SG2992G; ZA879760B; EP0273460A3; KR920009624B1

Abstract

ENERGY TRANSMITTING FLUID
Abstract of the Disclosure A water-glycol energy transmitting fluid having a viscosity of from about 10 to about 200 centistokes at 40°C comprising:
(a) from about 30 to about 40 percent by weight, based upon the total weight of the fluid, of water, (b) diethylene glycol, (c) from about 0.8 to about 5.0 percent by weight, based upon the total weight of fluid, of an aliphatic carboxylic acid having 9 to 12 carbon atoms, (d) a water-soluble polymeric viscosity control agent, (e) A corrosion inhibiting amount of at lease one corrosion inhibitor, an (f) a metal deactivator.

Description

-ENEP~GY TRANSMITTING FLU~D
- Field of the Invention This invention relates to energy transmitting fluids and, more particularly, to water~glycol type energy transmitting fluids having enhanced lubricity and anti-wear propertieæ under high pressure conditions.
Backqround of the Invention Water-based fluids have been used commercially for many years a~ a means of transmitting energy in hydraulic systems. Among such water-based ~luids are the water-soluble glycol or glycol ether-containing composition~ (hereinafter "water-glycol" type fluids) disclosed, for example, in U.S. Patent Nos. 2,558,030 and 2,602,780 both to Zisman et al., and U.S. Patent No. 2,768,141 to Langer et al.
Compared to petroleum-based fluids, water-glycol type fluids generally have low fla~mibility, and good temperature stability.
Moreover, clean-up and disposal are usually more convenient when utilizing water-glycol type fluids as opposed to petroleum-based compositions.
However, water-glycol type energy transmitting fluids, such as are disclosed by the above-ci~ed patents, generally have relatively poor lubricating and anti-wear properties in high pressure applications.
~ arious lubricity and/or anti-wear additives have been _uggested in attemp~s to improve ~he performance of wa~er-glycol ~ype energy transmitting fluids.

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U.S. Patent No. 2,9~7,699 to Wasson, ~t al.
discloses the use of alkali metal soaps of an organic aliphatic acid as an anti-wear agent in water-glycol type hydraulic fluids.
U.S. Patent No. 4,4g3,77~ ~o Snyder, Jr., et al. disc~oses a water-based hydraulic fluid having incorporated therein as an a~tiwear or lubricity agent, ths me~al or amine salt of an organo ~ul~ur,;phosphorous., boron or carboxylic acid.
U.S. Patent No. 3,9g2,312 to ~enjida, et al. di~closes a watex-glycol base hydraulic fluid comprising from about 30-60 weight percent of water;
from about 5-30 weight percent of a water-soluble polymer containing (1) a xesidue of a polyamlde having active hydrogen atoms and (2) oxyalkylene groups bonded to the residue; and from about 15-60 weight percent of a glycol, said fluid being disclosed as having good lubricating and wear preventing qualities.
U.S. Patent No. 4,434,066 to ~ewis discloses a water-glycol type fluid composition having incorporated therein between about 0.1 to 10 percen~ by weight of an aci~ic lubricity agent (i.e., saturated and unsaturated carboxylic and polycarboxylic acids having at least 6 carbon atoms, aromatic carboxylic acids, alkali metal or organic amine salts of said carboxylic acids, polymerized fatty acids, oxycarboxylic acids and dicarboxylic acids), and between about 0.01 and about 10 percent by weight of an anti-wear agent (i.e., a combination of an hydroxyl-substitut0d aromatic acid componen~
and a ni~roaromatic compound component).

UcS. Paten~ No~ 4,390,439 to Schwartz et al. disclose~ ~che use o~ odec~noic acid o improv~
~o anti-wear and ~orrosion-inhibiting propcr~ies of hydraulic fluid~ having a water con~ent of from about 60 to about 99 weight percent.
Th~ disclosures of the prior art regarding the enhanced lubricity and ar~ti-wear be~efits oi~
additive c:ontaining ~luids notwithstanding, prior to this invention the lubricity and wear characteristics of water-glycol type fluids have limited the use of ~uch fluias to sy~ems operatixlg at pressures of less than about 3, 000 p~
Accordingly, this invention is directed towards the provision of a water-glycol type energy transmitting fluid having enhanced high pressure performance SummarY of the Invention This invention relates to an energy transmitting fluid, suitable for u~e i~ systems operating at pressures up to at least about 5,000 psi, comprising:
Ca) frQm about 30 to abou~ 4~, preferably from about 34 to about 37 percent by weight, based on the total weight of the f luid, of water;
(b) ~rom about 35 to about 50 percent by weight, based on the total weight o~ fluid, of diethylene glycol;
~ C) from about a.8 ~o ~bout 5.0 p~rcent by weight, ba~ed on the total weight of the fluid, of an aliphatic carhoxylic acid having 9 to 1~ carbon atoms inclusive:
(d) a wa~er-soluble polymeric viscosity control agen~;

(e) a corrosion i~hibitiny amount of at least one corrosion inhibitor; and (f) a metal deactivator, wherein (b) and (d) are presen~ in amounts sufficient to provide the ~luid with a viscosity of from about 10 to about 200 centistokes at 40C.
This invention further relates to a method of transmitting mechanical energy by fluid pressure in systems operating at pressures up ~o at least .- abou~ S,000 psi, wherein the fluids herein described are utilized as an energy transmitting medium.
It has been found that the particular combination of wa~er, diethylene glycol and carboxylic acid herein disclosed is effective in enhancing the high pressure performance of water-glycol type energy ~ransmitting fluids, rendering such fluids suitable for use in systems operating at pressures up to at least about 5,D00 psi, preferably up to at least about 7,000 psi and most preferably up to at least about 10,000 psi.
; Description of the Invention ~: In accordance with~the present invention there is provided a water-glycol composition having a viscosity of from about 10 to about 200 centistokes at 40C comprising water, diethylene glyeol, an aliphatic carboxylic acid having 9 ~o 12 carbon atoms, a water-soluble polymeric viscosity control agent, at least one corrosium inhib;tor, and a metal deactivator.
The aliphatic carboxylic acid component of the composition of this invention is selected from the group consisting of ~aturated and unsatura~ed, ;.

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linear and branch d carboxylic and polycarboxylic acids having 9 ~o 12 carbon atoms and mixtures thereof. Representative of the carboxylic acids ~uitable for use herein are nonanoic, decanoic, neodecanoic, undecanoic, and dodecanoic acids, and mixtures thereof. For purposes of ~his invention, the Cg to C12 carboxylic acid i8 generally presen~ in the above described composition in an amount of from about 0.8 to about ~.0 percent by weight, preferably f rom about 1.0 to about 2.0 percent by weight, and, most preferably, from about 1 ~o about 1.6 percent by weigh~, all based upon the total weight of the composition. At concentrations of less than about 0.~ percent by weight, ~he Cg to C12 carboxylic acids are generally unable to provide the lubricity required for high pressure applications.
For purposes of this invention linear carboxylic acids, hav~ng ten to twelve carbon atoms, inclusive, constitute a preferred class of carboxylic acids.
The polymeric viscosity control agents of the composition of this invention include psly(alkylene oxid`e) polymers, alkylene oxide adducts of alkyl phenols, polyalkyl methacryla~es, urethane polymers, polyamide esters, and polyamide alkoxylates, with poly(alkylene oxide) polymers being a preferred class of polymers.
The poly(alkylene oxide) polymers suitable for use herein contain oxyethylene groups or a random or block dis~ribution of both oxyethylene yroups and higher oxyalkylene groups such as ~ ' ' "

~ 28~ ;0 oxypropylene and oxybu~ylene sroups and have ave~age molecular weights of from about 400 to about 40,000, or even higher. The amount of oxyethylene groups in the molecule is such that the poly(alkylene oxide) polymers are soluble in water at 25C and the amount of oxypropylene or higher oxyalkylene groups is such that the poly(alkylene oxide) remains li~uid at 25C
up to an average molecular weight of 40,000 and higher. The oxypropylene/ oxyethylene ratio may vary from zero to abou~ unity. These poly(alkylene oxide) polymers may be made by processes well known in the art by reacting e~hylene oxides or mixtures of ethylene oxide and propylene oxide or higher alkylene oxide with a compound having at least one active hydrogen atom up to as many as six such active hydrogen atoms including, for example, water, monohydroxylic alcohols such as ethanol and propanol, dihydroxylic alcohols such as ethylene glycol, trihydroxylic alcohols such as glycerine and trimethylpropane, tetrahydroxylic alcohols such as pentaerythritol, hexahydroxylic alcohols such as sorbitol, and mono- or poly-func~ional amines such as butylamine and ethylene di~mine. The poly(alkylene oxide) products of such reaction will have linear or branched oxyethylene or oxyethylene-higher oxyalkylene chains and such chains will terminate with hydroxyl groups. Some or all of these hydroxyl groups may be etherified by reac~ion with a dialkyl sulfate such as diethyl sulfa~e.
Alkylene oxide adducts of alkyl phenols suitable for use herein include the adduc~s .

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disclosed, for example, in U.S. Patent No. 2,76B,141 to Langer et al. and U.S. Patent No. 3,379,644 to Ka~zenstein et al.
Polyalkyl methacrylates and polyurethanes such as may be employed herein are disclosed, for example, in U.S. Paten~ No. 3,352,783 to McCord.
These polyal~yl metharylates generally result from the polymerization of alkyl methacrylates in which the alkyl groups have an average of from abou~ 3 to about 10 carboA atoms.
Included amony the polyamide es~ers suitable for use herein are t~e polymers disclosed in U.S. Patent No. 3,341,573 to Shibe. Suitable polyamide alkoxylates are disclosed, for example, in U.S~ Patent No. 3,992,312 to Genjida et al.
For purposes of this invention, random copolymers of ethylene oxide and 1,2-propylene oxide having a viscosity of up to about 100,000 centistokes at 100C, preferably of from about 5,000 centis~okes to about 50,000 centistokes at 1~0C and comprising from about 65 to about 85 weight percent of oxyethylene groups are preferred.
It will be apparent to the art-skilled that the relative quantities of viscosity control agent and diethylene glycol provided to the energy transmitting compositions of this invention are subject to variation depending upon the desired viscosity of the energy transmitting composition and the particular viscosity control agent employed therein. Preferably, the diethylene glycol and viscosity control agent arP present in the compositions of this invention in amounts sufficient ,.

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to provide such compositions with a viscosity of from about 35 to about 80 centistokes at 40C. In general, composition viscosities within the previously described ranges of preference are achieved by utilizing a poly(alkylene oxide) viscosity control agent in an amount of from about 10 to about 20 percent by weight of the composition, and die~hylene glycol in an amount of from about 40 to about 60 percen~ by weight of the composition.
The optimum viscosity of the fluid compositions of this invention is subject to variation and depends in part on the type of pump employed in a given operation. For example, vane pumps typically operate at pressurPs up to about 3,000 psi and employ as the fluid of choice a composition having a viscosity of from abou~ 60 to about 80 centistokes at 40OC, whereas, ~he fluid of choice in axial piston pumps, which generally operate at pressures of from about 5,000 psi to about 6,000 psi typically has a ~iscosity of from about 35 to about 50 centistokes at 40C.
Included among the corrosion inhibitors suitable for use in the compo~itions of this - invention are alkyl amines such as, for example, propylarnine, butylamine, he~ylamine, n-octylamine, ~yclohexylamine, dimethylaminopropylamine, and the like; alkanolamines such as, for example, ethanolamine, diethanolamine, triethanolamine, N,N-dimethylethanolamine, arylamines su~h as aminotoluene and the like; as well as other amine-type corrosion inhibitors such as for example, ethylene diamine, isopropylaminoethanol, ~2~3~760 _ g _ tripropylamine, morpholine, pyridine, 1,4-biæ(2-aminoethyl~pyperdine, imidazoline, 2-heptadecyl-1-(2-hydro~yethyl)- imidazoline, and the like; and mixtures thereof. In addition to the amine type corro~ion inhibitors, other corro~ion inhibitors suitable fo~ use herein include alkali metal nitrites, nitrates and benzoates, alkoxylated fatty acids, and mixtures thereof..
The amount of corrosion inhibitor present in the composition of this invention is 6ubject to variation and depends in part upon factors which include choicQ of inhibitor(s~ and th~ s~verity of the application in which the fluid is employed. In generai the total amount of inhibitor present in the composition of this inven~ion ranges from about 0.4 to about 4.0 percent by weight, based upon the total weight of the composition. As used herein a "corrosion inhibiting amount" of inhibitor is at least that amount of one or more inhibitors which is effective in achieving the degree of corrosion protection required by a particular application.
The metal deactivators used herein function primarily as chela~ing agents for copper and copper alloys, Representative. of ~he metal deactivators suitable for use in the composi~ions of this invention are tolyltriazole, benzotriazole, mercaptobenzothiazole, sodium mercaptobenzothiazole, disodium 2,5-mercaptothiadiazole, mercaptobenzoimidazole, and the like, and mix~ures thereof. In general, the ~otal amoun~ o metal deactivator present in the composition of this invention is from about 0.01 to about 2.0 percent by - 128~

weight, based upon the total weight of the composition.
In addition to ~he componen~s previously described, the energy ~ransmitting fluids of this invention may further comprise one or more additional components as are conventionally used in water-based fluids. When present, the to~al amount o all such additional components typically constitutes from about 0.001 to about 2% percent of the total weight of the fluid composition.
Exemplary of such additional components are foam inhibitors, such as silicones of the emulsion type, polyoxyalkylene type nonionic surfactants, and the like; alkaline compatible dyes; sequestering agents such as aminocarboxylic acids and derivatives thereof including ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid, the sodium or copper salts thereof, and oxycarboxylic acids and derivatives thereof such as ~artaric acid ~nd sodium glyconate; and such other additives as would not interact with the previously described components to adversely affect the lubricity of ~he resultant composition.
In preparing the water-based compositions of the invention, each of the components used may be added in any order of addi~ion, or combinations of some of them may be prepared prior to incorporating same in the composition. In general, each of the components to be used should be in water-soluble form such as the alkali metal or ammonium salts thereof, or should be capable of being solubilized in situ. The compositions of this in~ention may be 7~
... .. . .

prepared from concentrates which in use are diluted to provide the water contents previously described.
In accordance with a pr~ferred embodiment this invention, there is provided an energy transmitting fluid suitable for use i~ systems operating at pressures up to at least about 5,000 psi consisting essentially of:
(a) ~rom about 34 to about 37 percent by weight, based upon the total weight of the fluid, of water, (b) from abou~ 12 to about 16 percen~
by weight, based upon the total weight of the fluid, of a water-soluble polyalkylene oxide viscosity control agent, preferably a copoIymer of ethylene oxide and propylene oxide having a viscosity of from about 40,000 centistokes to about 60,000 centistokes at 100C and comprising from about 70 to about 80 ~ percent by weight, based upon the to~al weight of the copolymer, of ~thylene oxide groups, ~ c) from about 1.0 to about 2.0 percent by weight, based upon the total weight of the fluid, of a linear aliphatic carboxylic acid having 9 to 12 carbon atoms, inclusive, preferably decanoic and/or dodecanoic acid, (d) from about 35 to about 40 percent by weight, based upon the total weight of the fluid, of diethylene glycol, (e) from about 1.4 to about 3.5 percent by weight, based upon the total weight of the fluid, of at least one amine-~ype corrosion inhibitor, preferably a combination o from about 0.6 to about 1.5 percent by weight, based on the 87~F~

total weight of the fluid, of morpholine and ~rom about 0.8 to about 2.0 per~ent by weight, based on the total weight of the fluid, of isopropylaminoethanol, and , (f) from abou~ 0.04 to about 0.1 percent by weight, based upon the total weight of the fluid, of a metal deac~ivator, preferably tolyltriazole.
Examples The following Examples are illustrative of the present invention. It is not intended, how~ver, that the scope of ~he invention b~ limited by these Examples. Unless otherwise indicated, all of the percentages referred to in the following Examples are by weight.
Examples 1 to 3 and Comparative Examples Cl to C2 The high press~re performance of the fluids formulated to the specifications of Table 1 was evaluated by means of the procedure described in ASTM D 2882-83 entitled "Standard Method for Indicating the Wear Characteristics of Petroleum and Non-Petroleum Hydraulic Fluids in a Constant Volume Vane Pump". The operational conditions employed in the test were as follows:
The procedure described in ASTM D2882-83 was repeated six times for e~ch formulatiQn.
Following each run of a given tes~ a fluid wear ra~e was obtained. Wear rates are given as the total weight loss of the pump's cam ring and vanes over the operational period of the test~

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Wear ra~es provided in Table 1 represent an average value of six replicate test runs. A
formulation was cons~dered to pass the test if each of the six replicate runs provided wear rates of less than l gram/lOO hours. If a given run provided a wear rate in.excess of 1 gram/lOO hours tes~ing was discontinued and the formulation was considered to have failed the test.

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Pump - Vickers V-10~C vane pump Pump Speed - 1200 rpm Pump Pressure - 1900 psig (134 kgfcm2) Fluid Temperature - 65C
Fluid Quantity - 2 gal lons Operational Period - 100 hours . , . .

Table 1 Formulations (we~ght ~)1 Ingredlents,Cl C~ 1 2 33 De~on~zed ~ater 35.0 40.5 36.0 38.00 40.00 Ethylene Glycol . 49.3 43.3 - - -D~ethylene Glycol - - 48.8 46.5 46.5 UCON0i 75H 380,0004 12.5 13.6 12.0 12.3 12.6 Morphol~ne 0.8 0.8 0.8 0.8 0.8 Isopropylam~noethanol 1.0 1.2 1.0 1.0 1.0 Decano~c Acld 1.3 1.2 1.3 1.3 1.3 Tolyltrlazole 0.1 - 0.1 0.1 0.1 Sod~um mercaptobenzo- -thlazole - 0.1 Wear Rate (mg/100 hrs) - - 12 12 20 Test Results Fa~l Fa~l Pass Pass Fall 1 In add~tlon to the ~ngredlents descrlbed above, each of the Formulatlons prov~ded ln Table 1 conta~ned less than 0.01 welght percent of benzoic acld.

2 ~est results for Formulations C2 were based on a s~ngle pump test run.

3 Flve of the 6 runs for Formulat~on 3 provlded wear rates of less than 1 gram/100 hours, the s~xth run provlded a wear rate in excess of 1 gram/100 hours.

4 A llnear polymer of ethylene oxlde and propylene oxlde commerc~ally avallable from Un~on Carbide Corporatlon - contalnlng 75 we~ght percent oxyethylene, 25 welght percent oxypropylene, and character~zed as having an S.U.S.
vlscos~ty of 380~000 at 100F ~37.8C).

~2~ ;0 The performa~ce of a ~luid prepared according to the speci~ications o~ Formulation 2 of Table 1 at operational pressures of 5,000 psi was evaluated by means of the following test procedure, said procedure being divided into a 2-hour start-up period, a 1 hour break-in period and 22~-hsur test period.
~ ix~een gallons of tes~ fluid was charged to a Sundstrand Model 22-2132 variable displacement pump equipped with welded pistons. Operational condi~ion employed in the test were as follows:

Input Speed 3100 + 100 l.p.m.
Load Pressure 5000 psi Change Pressure 200 + 20 psi Case Pressure ~0 psi max.
Stroke 1/2 of Fuil Reservoir Temperature 120 ~ 10F
Loop Temperature 170 + 10JF
Maximum Inlet Vacuum 10 inches Hg (5 psi~

At various times during the course of the test flow data readings we~e taken. Pursuant to this test, a degradation in flow rate is indicative of system wear (i.e. as the system wears the clearance between movable system par~s increases and the 1Ow rate of the fluid is decreased). Flow data for this test is reported in Table 2. An examination of the flow data in flow indicates that no significant degradation in flow occurred over the operational period of the ~e~t.

2 ~

At the expiration of the 222-hour test period the system was oooled to a loop temperature of 100F and shut down. After a 24-hour shut-down period ~he pump was dis~ssembled and examined for wear. Inspection of the test parts indicated that no unusual p~mp wear or distress occurred.

~able 2 Readinq Flow (qal./min.) After break-in 24.8 ; After 1 test hour 24.9 After 25 test hours 24.9 After 27 test hours 24.9 After 75 test hours 24.9 After 125 test hours 24.9 After 175 test hours 24.8 After 222 test hours 24.7 ; . , , ~ ` .~' , .

Claims

1. An energy transmitting fluid, comprising (a) from about 30 to about 40 percent by weight, based on the total weight of the fluid, of water;
(b) from about 35 to about 50 percent by weight, based on the total weight of fluid, of diethylene glycol;
(c) from about 0.8 to about 5.0 percent by weight, based on the total weight of the fluid, of an aliphatic carboxylic a~id having 9 to 12 carbon atoms inclusive;
(d) a water-soluble polymeric visoosity control agent;
(e) a corrosion inhibiting amount of at least one corrosion inhibitor; and (f) a metal deactivator, wherein (b) and (d) are present in amounts sufficient to provide the fluid with a viscosity of fram about 10 to about 200 centistokes at 40°C.

2. A fluid as in claim 1 wherein the polymeric viscosity control agent is selected from the group consisting of poly(alkylene oxide) polymers, alkylene oxide adducts of alkyl phenols, polyalkyl methacrylates, urethane polymers, polyamide esters, and polyamide alkoxylates.

3. A fluid as in claim 2 wherein the corrosion inhibitor comprises at least one amine type corrosion inhibitor.

4. A fluid as in claim 3 wherein the metal deactivator is selected from the group consisting of tolyltriazale, benzotriazole, mercaptobenzothiazole, sodium mercaptobenzothiazole, disodium 2,5-mercaptothiadiazole, mercaptobenzoimidazole and mixtures thereof.

5. A fluid as in claim 1 wherein the water-soluble polymeric viscosity control agent is a poly(alkylene oxide) polymer.

6. A fluid as in claim 5 wherein the poly(alkylene oxide) polymer is a random copolymer of ethylene oxide and 1,2-propylene oxide having a viscosity of up to about 100,000 centistokes at 100°C.

7. A fluid as in claim 1 wherein the carboxylic acid is selected from the group consisting of nonanoic, decanoic, neodecanoic, undecanoic, and dodecanoic acid, and mixtures thereof.

8. A fluid as in claim 1 wherein component (e) is present therein in an amount of from about 0.4 to about 4.0 percent by weight, based on the total weight of the fluid.

9. A fluid as in claim 1 containing a combination of morpholine and isopropylamino ethanol as an amine-type corrosion inhibitor.

10. A fluid as in claim 9 wherein the metal deactivator is present therein in an of from about 0.01 to about 2.0 percent by weight, based on the total weight of the fluid.

11. An energy transmitting fluid which comprises (a) from about 34 to about 37 percent by weight, based on the total weight of the fluid, of water, (b) from about 12 to about 16 percent by weight, based on the total weight of the fluid, of a water-soluble poly(alkylene oxide) viscosity control agent, (c) from about 1.0 to about 2.0 percent by weight, based on the total weight of the fluid, of an aliphatic carboxylic acid having 9 to

12 carbon atoms, inclusive, (d) from about 35 to about 50 percent by weight, based on the total weight of the fluid, of diethylene glycol, (e) from about 1.4 to about 3.5 percent by weight, based on the total weight of the fluid, of at least one amine-type corrosion inhibitor, and (f) from about 0.04 to about 0.1 percent by weight, based on the total weight of the fluid, of a metal deactivator.
12. A fluid as in claim 11 wherein the poly(alkylene oxide) viscosity control agent has a viscosity of from about 40, 000 centistokes to about 60,000 centistokes at 100°C and comprises from about 70 to about 80 percent by weight of ethylene oxide groups.

13. A fluid as in claim 10 containing a combination of morpholine and isopropylamino ethanol as an amine-type corrosion inhibitor.

14. A fluid as in claim 13 wherein the metal deactivator is tolyltriazole.

15. A fluid as in claim 14 wherein the aliphatic carboxylic acid is a linear carboxylic acid having ten to twelve carbon atoms, inclusive.

16. A fluid as in claim 15 wherein the aliphatic carboxylic acid is decanoic and/or dodecanoic acid.

17. A method of transmitting mechanical energy by fluid pressure in systems operating at pressures up to at least about 5,000 psi which comprises utilizing as an energy transmitting medium a fluid as described in claim 1, 4, 11 or 14.