US2736709A

US2736709A - Hydraulic fluids

Info

Publication number: US2736709A
Application number: US450512A
Authority: US
Inventors: Samuel A Glickman; Joseph M Wilkinson
Original assignee: General Aniline and Film Corp
Current assignee: GAF Chemicals Corp
Priority date: 1954-08-17
Filing date: 1954-08-17
Publication date: 1956-02-28
Anticipated expiration: 1973-02-28

Description

a g 2,736,709 Patented Feb-1 5i: 5

HYDRAULIC. FLUIDS Samuel A. Glickman and Joseph M. Wilkinson, Easton, Pa., assiguors to General Aniline &Fiim Corporation, New York, N. Y., a corporation of. Delaware- No Drawing. Application August 17, M54, Serial No. 450,512

4.- Claims. (c1. 252-74 This invention relates to hydraulic fluids and particularly to hydraulic brake fluids containing 3-methoxy-lbutanol and 3,5,x-polymethoxy-l alkanolsas the principal ingredients.

Many hydraulic fluid compositions are known to the art. The earliest improved. fluids contained castor oil and a high boiling diluent in conjunction with various inhibitors. Later modifications included blown castor oil and castor oil glycol reaction products. However, low temperature usefulness, gum formation, and other factors led the art to find other materials.

When one surveys the field of organic liquids which could possibly be suitable for use as'hydraulic fluidsfrom the standpoint of viscosity at'high and low temperatures, low volatility and lack of corrosive actionon metals, etc., one is immediately impressed" by the paucity of compounds which are acceptable'from-thestandpointof attack or the swelling of rubber. The vast majority'ofotherwise acceptable liquids including esters; ketones', halides, acetals, acids, amines, ethers', hydrocarbons, etc, have far too great a degree of rubber attack. As a result of many studies, it has been shown that very few organic liquids are acceptable in this respect. Outstanding among those acceptable are certain alcohols'and ether alcohols having a favorable oxygen tocarbonratio and/ or distribution-in the molecule, i. e'., structural configuration.

To be suitable for use as a hydraulic fluid; a liquid composition must have the following characteristics: It must not exhibit too great a viscosity change under wide temperature range, i. e., it must be reasonably viscousat the highest temperatures for which use it' is contemplated, and on the other hand, it must remain fluid'at the lowest temperatures likely to be encountered in automotive use, e. g., 50 F. In general, fluids which haveaviscosity of at least 5 cps. at 130 F. and a viscosityno greater than 1500 cps. at 40 F; are considered suitable; A further requirement is that the fluid must have a lubricating action on most parts'of the braking system in order to prevent undesirable wearing during-use. In this respect, fluids which allow-the moving parts to wear not more than .001 of an inch during;200,000-braking cycles are usually considered adequate.

It is an absolute prerequisitethat asuitable fluid should not unduly attack any of the rubber or metal parts in the braking system. The attack on rubber is so undesirable that extensive research has gone into=the-manufacture of fluids which show a minimum of swelling or softening action on rubber. In regard' to the attack on'the metal parts, it might be saidthat the fluid must have the correct pH value, that is, presumably in the range of 8.5 i to 9.5. In this range, protection would beobtained" against the attack of acid sensitive metals, such as iron, tin,- aluminum, zinc, etc. while this degree of alkalinity is not sufliciently high to cause the attack of alkali sensitive materials, such as aluminum and zinc.

It is a further prerequisite that the fluid: should: have as-loW-a volatility as'is practical to;v achieve,.in:.order. to eliminate the possibilities of evaporation from the brake system storage unitas well as topreventthe undesirable evaporation of. the. fluid fromzthe areas adjacent to; hot braking surfaces. In the.past,.tliese: objectionsliave been achieved through the use of .various mixtures of? aliphatic alcohols, and glycerine esters, such as castor oil,.soya.oil, etc., or with mixtures of various ether alcohols, such as fi-butoxy ethanol, the monoethyl ether ofdiethylene glycol and various polymers. of ethylene'oxide, propylene oxide, or. interpolymers. of ethylene and propylene oxides. The first-mentioned type consisting of alcohols. and natural oils: has certainshortcomings, eg., with. the lower aliphatic alcohols. The degree of attack on' rubber rapidly increases with. the increasingchain length of the alcohol used in practice. It has been found thatalcohols higher than the butyl alcohols cannotbeused because: of excessive attack on, or'swelling of, the rubber parts? in the braking system. The alcohols up to and i'ncludingthe butyl alcohols have, unfortunately, rather low boiling points and hydraulic brake fluids. prepared with them show an undesirably high degree of volatility. Inaddition,v the presence of natural. glycerine esters, such as castor oil' and/or soyaoil, etc., is undesirable because, as is well known, these substances are subject to oxidation and in time form undesirable gummy materials in. the system. Because of the disadvantages, considerable effort has been, made: to develop improved fluids for hydraulic systems- One composition. which" has been suggested to overcome these disadvantages,- comprises a mixture of the above-mentionedcomponents: Carbitol, butyl Cellosolve, andfinterpolymers of'etl'rylene oxide and propylene oxide;

While fluids of this typeare better than mixture of alcohols and natural. oils, they also: have certain. shortcomings; It'has been established that the relatively low boiling points of two of. the components used in such fluids, namely, butyl Cellosolve? and Carbitolfi prevent suchicompositions from". being considered for" high temperature applications; It has. been. further established that such compositions will be prone; to-peroxide formation, a well known: shortcoming.characteristic ofpolyoxyethylenes,. polyox-ypropylenes, and; the various: interpolymers of ethylene.oxidecand-propylene oxide;

We have. founds that the foregoing shortcomings and difliculties' of the presently utilized fluids, particularly those containing polyoxyalkylenes' andinterpolymers of alkylene' oxides are substantially overcome by'employing an alkaline buffered mixture of- 3-methoxy- 1-butanoli and 3,5.x-polymethoxy-l-alkanols': as the principal ingredients with or without the presence of minor amounts of auxiliary components, such as' antioxidants, corrosion inhibitors, viscosity regulators, andithelike'.

The 3-methoxy-1-butanol and 3,5-x-polymethoxy-1- alkanols utilizedin the mixture are-characterized byv the following general formula:

Where n represents an integer of from 1 to 10.

The alkanols characterized by the foregoing formula are' prepared by reacting, in the known manner, vinyl methyl ether with metha-nol'toyield dimethylacetal and reacting the latter with additional vinyl methyl ether. The ratio of methanol to vinyl methyl ether may vary from 210:1.0 to 20:1, preferably from. 2.0:1 to 5.011, respectively. The crude acetal is then distilled to yield individual components wwhichmaybersubjected to simultaneous hydrolysis-reduction to yield individual alkoxyalkanols such as 3-methoxy-l-butanol; 3,5-dimethoxylhexanol; 3,5,7-trimetl1oxy-1.-octanol; 3,5,7,9-tetramethoxy-l-decanol;v 3,-5,,7,9,'1l pentamethoxyal:dodecanol. and polymethoxy-l-alkanols. as. described. iii- Examples. 1,. 4, and 5 of United States Patent 2,618,663; Alternatively,

the crude acetal may be subjected to simultaneous hydrolysis-reduction as described in Example 3 of said patent and the mixture of alkanols employed as such in accordance with the present invention. The mixture of alkanols may be distilled to yield the individual components of the alkanols and the individual components blended in the ratio of 20 to 40% of 3-methoxy-1-butanol and 60 to 80% of the remaining 3,5,x-polymethoxy-lalkanols.

The alkanols are colorless liquids characterized by partial solubility in water, especially the methoxy derivatives which are completely soluble in water, and by complete miscibility in organic solvents, such as aliphatic alcohols, ketones, esters, glycol ethers, aromatic solvents, and aliphatic petroleum ethers and naphthas. The complete miscibility in aliphatic hydrocarbons is in sharp distinction to the polyethylene glycols which are virtually insoluble in these solvents.

All of the alkanols in the mixture, i. e., the 3-methoxyl-alkanol and 3,5,x-polymethoxy-l-alkanols, when in contact with rubber have a very low swelling action, considerably less than that tolerated by commercially available hydraulic fluids. In addition they possess an unusual inertness to oxidation attack. It is believed that the arrangement of atoms in the alkanols of the mixture contributes to this property. This is unexpected since it has been recognized by the art, U. S. P. 2,492,955 and 2,481,278, that polymers of ethylene and propylene oxide have one serious drawback which limits their use as lubricants because the two carbon unit between the ether linkage in the polymer chain appears to make the polymer extremely sensitive to oxidation.

The hydraulic fluids prepared in accordance with the present invention possess sufiicient lubricity under operating conditions in various climes and extremes of temperatures. Tests have indicated that the lubricity is met by the presence, even in very small amounts, of the higher members of the 3,5,x-polymethoxy-l-alkanols series which are viscous liquids resembling glycerine and the low polyethylene glycols in consistency. These materials are free from gum formation which is a serious drawback to the use of lubricants of the like of castor oil and derived compounds.

The presence in the hydraulic fluid of low boiling diluents either as solvents or decomposition products may result in vapor lock and is, therefore, to be avoided. The lowest member of the alcohol series is 3-methoxy-butanol with a boiling point of 159 C. at 760 mm. The presence of the higher members of the series increases the pot temperature at whichsuch a mixture boils and may be varied depending on needs.

The wide solvent power of the 3,5,x-polymethoxy-1- alkanols makes it possible to secure homogeneous solutions on mixing with commercial hydraulic fluids. The water tolerance of the 3,5,x-polymethoxy alkanols is excellent.

The hygroscopicity of the 3,5,x-polymethoxy-l-alkanols is of a lower order than the glycols and polyethylene glycols in the same molecular weight range. Brake fluid mixtures containing these alkanols possess advantages over materials containing the polyethylene glycols.

Inasmuch as mixtures of B-methoxy-l-alkanols and 3,5,x-polymethoxy-l-alkanols may in themselves serve as hydraulic brake fluids because of their desirable properties, it is at times desirable to fit certain needs to incorporate auxiliary substances, such as anti-oxidants, corrosion inhibitors, viscosity modifiers, buffering agents, and the like.

As anti-oxidants, there may be used any of the materials commonly used to prevent the oxidation of oxidizable organic compounds, such as unsaturated hydrocarbons, e. g., rubber, unsaturated fuels, unsaturated esters, such as oxidizable vegetable oil, ethers, vinyl compounds, etc. Examples of these anti-oxidants are para-tertiary butylg catechols, hydroquinones, and various morpholine derivatives, such as N-phenyl-morpholine, N-(p-hydroxyphenyl)morpholine, N,N diphenyl-p-phenylenediamine, diphenylamine, N phenyl-B-naphthylamine, p-phenylphenol, o-phenylphenol, di-p-methoxydiphenylarnine, mtoluylenediamine, various condensation products of aldehydes with aromatic amines: acetone-aniline and acetaldehyde aniline and butylaldehyde-aniline, aldol-[S- naphthylamine, hydroquinone monobenzyl ether, and isopropoxydiphenylamine.

As corrosion inhibitors, we may use inorganic nitrites, such as sodium nitrites, etc., organic nitrites, such as tertiary amine nitrites, chromates, such as sodium chromates and the like, inorganic boron compounds, such as sodium tetraborate, organic boron compounds, such as triethanol amine borate and the like, certain sulfur compounds, such as dialkylthiourea, mercaptans, organic disulfides, diarylamine phosphates, such as diphenylamine phosphate, long chain alkyl sulfonamide acetate sodium salt, phosphites, such as sodium phosphite, organic phosphoric acid and organic derivatives of phosphorous acids, such as benzene-phosphenic acid, etc.

In addition to the components named above, auxiliary substances, such as viscosity modifiers, bulfering agents, and coloring agents may be optionally added.

As viscosity modifiers, there may be used various polyhydroxy compounds, such as glycol, glycerine, 1,2,4- butanetriol, 1,4-butanediol, propylene glycol, etc., especially when used in conjunction with complex forming inorganic salts, such as borax, nickel and chromium salts, various polymeric materials, such as polyvinyl methyl ether, polyvinyl butyl ether, interpolymers of isobutyl vinyl ether and oleyl vinyl ether, various polyacrylates, such as polylauryl acrylate, polyolefines, such as polyisobutylene or interpolymers thereof, etc.

As buffering agents, the following inorganic compounds are useful: borates, such as sodium tetraborate, sodium metaborate, ammonium and organic borates, such as triethanolamine borates, sodium phosphite, tetraborate and the like, inorganic phosphate, such as the various sodium phosphates, such as trisodium o-phosphate, disodium hydrogen phosphate, sodium pyrophosphate, organic phosphate, e. g., triethanolamine phosphate, quinoline phosphate, salts of alkaline metals, organic acids, such as sodium acetate, sodium citrate, sodium benzoate, potassium tartrate and the like, and mixtures thereof to yield (when admixed in the brake fluid composition) a pH above 7 and not exceeding a pH of 11.

In order to dissolve sodium borate in the hydraulic brake fluid composition, it was found advantageous to use a solubilizing agent, such as ethylene glycol, in the formation. However, glycol is not essential in the hydraulic brake fluid. This agent can be omitted in compositions in which other buffers are incorporated. Also in place of ethylene glycol in borax formations, other solubilizing agents, such as Carbitol can be used.

The choice of coloring matter is not of critical importance in the finishing of the hydraulic brake fluid provided it does not cause a deleterious effect on the viscosity of the fluid or exhibit corrosive action on the rubber or metal parts of the braking system. Most dyestuffs are acceptable on these accounts since in most cases they are used only in minute quantities. Where coloring material or dyestuffs are added for identification or other purposes, the sole requirement is that the dyestuff be sufficiently soluble in the hydraulic fluid. It has been found that dyestuffs of any class may be used. These include vat dyestuffs, diphenylamine derivatives, azo dyes, triphenylmethane dyes, and the like.

From the standpoint of rubber swelling, we have found that the proportions of 3-methoxy-l-butanol in the mixture must range from 20 to 40% to yield good results. The 3-methoxy-1-butanol does not appear to give good results when employed alone or when incorporated with the foregoing auxiliary substances. The unusual and unexpected feature of the present invention is that the mixture, in addition to 20-40% of 3=methoxy-1-butanol, must contain 60 to- 80% of' at least one of the individual 3,5 ,x-polymethoxyl -alkanols-or a mixture thereof to yield good results. In these proportions the brake-fluid does not causeany swelling or disintegration of rubber and completely eliminates-brake failurethrough loss of fluid. Moreover, the blending of the individual alkanols of the mixture makes it readily possible to fit prescribed commercial needs or requirements of certain brake fluids with respect to non-volatility, viscosity, lubricity, and miscibility with auxiliary components. For general all around good results particularly in automotive hydraulic brake fluids, we.-have,foun d; that the; following blend is ideal:

The following blend may also be used for all around good results:

Percent 3-methoxy-1-butanol 20-35 3,5-dimethoxy-1-hexanol 25-35 3,5,7-trimethoxy-l-octanol 10-25 3,5,7,9-tetramethoxy-1-decanol -20 3,5,7,9,11-pentamethoxy-1-dodecanol 2:5-10

Polymethoxy-l-alkanols. characterized by the following formula:-

wherein n represents an integer-of from 6'-to 8, 05-35%.

The higher polymethoxy alcohols of the type 3,5,7,'9',- 11,13,xpolymethoxy-l-alkanols, i. e., wherein n in the above formula equals 6or greater, maybe used in the range of 60 to:80%' to 20 to 40% of'3 methoxy-l'-butanol to yield a mixture which gives excellent results with respect to prevention of'rubber swelling. A mixture of 20% of 3-methoxy-1-butanol and 80'% of 3,5-dimethoxyl-hexanol is comparable to-a mixture of 40% of- 3-methoxy-l-butanol and 60% of 3,5-dimethoxy-1-hexanol. Both mixtures'possess suflicient lubricity under operating conditions in various climatesandi extremesoftemperatures.

As illustrative of thepreparation of hydraulic brake fluids in accordance withthe present invention, the following examples are given. The parts are by weight.

EXAMPLE I To 88.6 parts of amixture of3,5,x-polymethoxy alkanol (prepared in accordance with. Example3, United States Patent 2,618,663), containing byweight the following components:

Percent S-methoxy-l-butanol 35.0 3,5-dimethoxy-l hexanol 30.0 3,5,7-trimethoxy-l-octanol 22.0 3,5,7,9-tetramethoxy-l-decanol 7.5 3,5,7,9,11-pentamethoxy-l-dodecanol 3.6

Higher homologues characterized'by the above formula wherein n equals 6' or more 2.9

cps. and at +130 F.- was 7v cps. A.tube containing thismaterial was maintained at 40 F. for 6 days and at the endrof this.period,.thetube.was tiltedfrom. a vertical to a horizontal position. It was observed that flow began immediately. This composition was maintained at -60 F. for 6 hours. Flow began immediately upon tilting. The: material: was; admixed: 1 0% by weight with water andmaintained at--60 F. for 6 hours after which, it was clear angl fluid; The boiling point asdetermined by the temperature of, the refluxwas found to be, 345. E. Flash; point by-Cleveland opencup ASTM methodwas 180 F. A sample of v the fluid was weighed into a ceramic boatand maintainedat: 210 F. for 48 hours in a location. free from drafts. Only 70% of thefluid evaporated. The pHgwas determined using a BeckmanpHmeter and found tobe: 9.3. A sample: was boiled under a reflux condenser at its, atmospheric boiling pointof, abont345 F. for 8 hours. At'the conclusion of this treatment the material showed only a very slight yellowing. No other evidence of decomposition was noted, and the sample was judged to be remarkably stable. This composition was admixed with other-commercially available brake fluids, for example, a fluid composedof'about 35% by volume of ethylene oxide-propylene oxide interpolymers, 32.5% by-volume of butyl Cellosolve and 32.5% by volume of Carbito in addition to various inhibitors and found to be completely miscible within the temperature range of--30to +60'F A 1% inch Wagner-Lockheed FC666 wheel cylinder cup was measured to the nearest thousandth inch and introducedinto this composition at a temperature of 158 F: for a' period of hours. Afterwards, the cup was againmeasured' and the increase in diameter due to the swelling eifects'of the composition was 0.018 inch. The above composition was brought in contact with all the parts of a commercial wheel brake cylinder and maintained at 158 F. for 14 days. Upon disassembly and examination, it'was found that the fluid caused no rust or corrosion. of; the-.metal parts and left no hard, dry gummy residue or 'anysubstantial amount of sludge. Test strips, ofjtinned iron, cold rolled steel, aluminum, cast iron, brass: and copper; were bolted together so that the strips were-inelectrical contact. These strips and a part of a: sample takenfrom a Wagner-Lockheed FC666 rubber wheel cylinder cup; were introduced into the above composition, diluted, with 5% by volume of distilled water, maintainedfata temperature-of 210 F. for 120 hours. At.1the end of; this period the, strips were removed, disengagedandrpolished to remove corrosion products, if any. Corrosion losses were observed by noting the weight lost (milligram per square cm.)

Loss

Tin." 0 Steel 0. Brass 0 Copper milligram per sq. cm" 0.1 Aluminum 0 Iron milligram per sq. cm 0.1

A lubrication test was carried out in a commercial hydraulic brake wheel cylinder actuated by a conventional mast cylinder driven by a cam. The assembly was operated to simulate the actual actions of a brake in normal operation and the wheel cylinder was actuated in this fashion every six seconds. The composition of Example I was introduced into this system and underwent 160,000 braking cycles at, the completion of which the moving parts were disassembled and examined for evidence of wear. Wearing was determined visually and by micrometer measurements. None of the surfaces exhibited as much as 0.001 inch wear.

EXAMPLE II To thesame solution of the composition of Example I there were added20 parts per million'of a soluble copper phthalcyaninedyestuif The performance data for this colored composition was substantially identical with that asabove indicating that the colorant had no deleterious effect. The presence of colorant is often desirable to aid in the detection of leaks in a hydraulic system.

EXAMPLE III To 99.5 parts of the mixed polymethoxyalkanol of the composition of Example I, there were added 0.4 part of copper naphthenate and 0.1 part of triethanolamine. The mixture was stirred until a homogeneous solution resulted. This composition exhibited a viscosity of 420 cps. at a temperature of 40 C. and a viscosity of 16 cps. at +25 C. When a Wagner-Lockheed FC666 wheel cylinder cup was immersed in this composition for a period of 24 hours at 158 F., the cup showed, after an alcohol rinse and drying, a weight increase of only 8.8%.

By way of comparison, B-butoxyethanol often used as a constituent in commercial brake fluid exhibited a rubber swell of 37.4%.

EXAMPLE IV A brake fluid composition was prepared by dissolving one-tenth part of triethanolamine, 0.3 part of p-hydroxyphenylmorpholine and 0.1 part of the amine nitrite described in Example I, in 99.5 parts of a mixture of polymethoxyalkanols of Example I. The compounding was carried out by stirring the constituents together at room temperature until a homogeneous mixture resulted. When test strips of cast iron, steel, tin, iron, brass, copper and aluminum were immersed in the composition for a period of days at 100 C., it was found in all cases that the weight loss of the strips due to corrosion was less than 0.3 milligram per square centimeter. An average corrosion value of 0.5 mg. per sq. cm. over the above described test condition for these metals is normally considered excellent.

EXAMPLE V A solution of 0.5 part of borax, 0.3 part of phenyl-B- naphthylamine, and .01 part of sodium nitrite in 25 parts of ethylene glycol was added with stirring to 75 parts of the mixed polymethoxyalkanols of Example I. The resul ing mixture was agitated until homogeneous. In a rubber swelling test in which a 1%. inch Wagner-Lockheed FC666 wheel cylinder rubber cup was immersed in this composition for 120 hours at 70 C., the diameter of increase of the rubber cup was 0.018 inch. In a commercially marketed fluid consisting of essentially 65% nbutanol and 35 castor oil together with suitable stabilizers, the rubber swell in the same test was found to be 0.22 inch.

EXAMPLE VI Polymetrzoxy alkanols obtained from polymethoxyacetals Vinyl Ether to Methanol Ratio of Polymethoxyacetal 2.6:1 2.8:1 2.9:1 3.0:1

Component: Percent Percent Percent Percent 3-metn0x y-i-butanol. r 34. 3 27.8 23. 2 23. 8 3,5-dimethoxy-1-hexan0l 29. 7 28. 9 31. 2 27. 5 3,5, 7-trimethoxy-l octanol 22. 2 24. 8 26. 4 21. 3 3,5,7,9-tetramethoxy-ldecanol 7. 5 12. 9 12. 1 18. 3 3,5,7,9,11-penta-1 oxydodeeanol 3. 6 4. 3 4. 5 8. 0 3,5,7,9,11,13- and higher 2. 6 3.0 3. 0 3. 2

E EXAMPLE VII To each of the first set of four samples (which were set aside) each weighing about parts, there was added a. solution of 0.6 part of borax, 0.35 part of phenyl-finaphthylamine, and 0.03 part of sodium nitrite in 30 parts of ethylene glycol. The resulting four mixtures were agitated until homogeneous. In rubber swelling tests in which a 1% inch Wagner-Lockheed FC666 wheel cylinder rubber cup was immersed in each of the four compositions for 120.hours at 70 C., the diameter of increase of the rubber cup was 0.012.

EXAMPLE VIII Example IV was repeated with the exception that 99.5 parts of the mixture of polymethoxyalkanols of Example I were replaced by parts of a mixture consisting of 40% of 3,5-dimethoxy-1-hexanol and 60% of 3,5,7,9,l1-pentamethoxy-l-dodecanol prepared in accordance with Examples 1 and 4 respectively, of U. S. P. 2,618,663. When the compounded mixture was subjected to the corrosion strip test, the weight of loss of the strips due to corrosion was less than 3.3 milligrams per cm.

EXAMPLE IX Example III was repeated with the exception that 99.5 parts of methoxyalkanols of the composition of Example I were replaced by 75 parts of a mixture consisting of 20% of 3-methoxy-1-butanol and 80% of 3,5,7-trimethoxy-1- octanol prepared in accordance with Examples 1 and 5 respectively, of U. S. P. 2,618,663. When a Wagner- Lockheed FC666 wheel cylinder rubber cup was immersed in this composition for a period of hours at 133 C.,

the cup showed, after an alcohol rinse and drying, a

wherein n represents an integer of from 6 to 10.

2. A hydraulic fluid composition consisting essentially of an alkaline buffering agent selected from the class consisting of alkaline borates, phosphites, and phosphates, and a mixture of monoand polymethoxy-l-alkanols consisting of 20 to 35% of S-methoxy-l-butanol, 25 to 35% of 3,5-dimethoxy-1-hexanol, 10 to 25% of 3,5,7- trimethoxy-l-octanol, 5 to 20% of 3,5,7,9-tetramethox*- l-decanol, 2.5 to 10% of 3,5,7,9,1l-pentamethoxy-ldodecanol, and 0.5 to 3.5% of polymethoxy-l-alkanols characterized by the following formula:

wherein n represents an integer of from 6 to 8.

3. A brake fluid composition consisting essentially of an alkaline buffering agent selected from the class consisting of alkaline borates, phosphites, and phosphates, and a mixture of monoand polymethoxy-l-alkanols consisting of 35.0% of 3-methoxy-1-butanol, 30.0% of 3,5-dimethoxy hexanol, 22.0% of 3,5,7-trimethoxy-l-octanol, 7.5% of 3,5,7,9-tetramethoxy-l-decanol, 3.6% of 9 3,5,7,9,11-pentamethoxy-l-dodecanol, and 2.9% of polymethoxy-l-alkanols having the following formula:

wherein n represents an integer of from 6 to 8.

4. A brake fluid composition consisting essentially of an alkaline bufiering agent selected from the class consisting of alkaline borates, phosphites, and phosphates, and a mixture of monoand polymethoxy-l-alkanols consisting of 20 to 40% of 3-rnethoXy-1butanol, 25 to 35% of 3,5- dimethoxy-l-hexanol, 15 to 30% of 3,5,7-trimethoxy-1- octanol, 5 to 20% of 3,5,7,9-tetramethoxy-I-decanol, 2.5 to 10% of 3,5,7,9,11-pentamethoxy-l-dodecanol, and 0.5

to 3.5% of polymethoxg l-alkanols characterized by the following formula:

0113- CHCH2 CHz-0H [(IJCH: 11: wherein n represents an integer of from 6 to 10.

References Cited in the file of this patent UNITED STATES PATENTS 2,165,962 Mueller-Cunradi July 11, 1939 2,481,278 Ballard et al Sept. 6, 1949 2,564,760 Hoaglin et a1 Aug. 21, 1951 2,564,761 Hoaglin et a1. Aug. 21, 1951 2,618,663 Glickman et a1. Nov. 18, 1952

Claims

1. A HYDRAULIC FLUID COMPOSITION CONSISTING ESSENTIALLY OF AN ALKALINE BUFFERING AGENT SELECTED FROM THE CLASS CONSISTING OF ALKALINE BORATES, PHOSPHATES AND PHOSPHITES, AND A MIXTURE OF MONO- AND POLYMETHOXY-L-ALKANOLS CONSISTING OF 20 TO 40% OF 3-METHOXY-L-BUTANOL AND 60 TO 80% OF AT LEAST ONE 1-POLYMETHOXY-ALKANOL OF THE GROUP CONSISTING OF 3.5-DIMETHOXY-L-HEXANOL, 3,5,7,TRIMETHOXY-L-OCTANOL, 3,5,7,9-TETRAMETHOXY-L-DECANOL, 3,5,7,9,11-PENTAMETHOXY-L-DODECANOL, AND POLYMETHOXY-LALKANOLS CHARACTERIZED BY THE FOLLOWING FORMULA: