US3711411A

US3711411A - Low water-sensitive hydraulic fluids containing borate esters and monoethanolamine

Info

Publication number: US3711411A
Application number: US00134456A
Authority: US
Inventors: A Sawyer; D Csejka
Original assignee: Olin Corp
Current assignee: Olin Corp
Priority date: 1967-04-13
Filing date: 1971-04-15
Publication date: 1973-01-16
Anticipated expiration: 1990-01-16
Also published as: CA987656A; DE2141441C3; DE2141441B2; FR2307970A1; US3711410A; GB1531096A; DE1768933C3; US3625899A; US3637794A; DE2147416A1; GB1232369A; FR2132617B2; DE1768133B2; DE2141441A1; US3729497A; GB1384685A; FR2132617A2; DE1768933A1; GB1232370A; US3711412A

Abstract

Low water-sensitive hydraulic fluid compositions which contain at least one borate ester as the base fluid and from about 0.1 to about 8 percent by weight of monoethanolamine as an alkaline buffering agent. Such low water-sensitive hydraulic fluids are high boiling and have a low rate of corrosivity.

Description

Unite States Patent 1 Sawyer et a]. 51 *Jan. 16, 1973 LOW WATER-SENSITIVE HYDRAULIC [56] References Cited FLUIDS CONTAINING BORATE NITED S T ATE S PATENTS ESTERS AND MONOETHANOLAMINE U [75] Inventors: Arthur w. y Hamden; David Sawyer et all ..252/75 A. Csejka, Orange, both of Conn. 3:377:288 4/1968 [73] Assignee: Olin Corporation Notice: The portion of the term of this p n s q e to De 7, 1 8, Primary Examiner-Leon D. Rosdol has n d C a d- Assistant ExaminerD. Silverstein Attorne -Eu' ene Za arella Jr. Gordon D. B rkit 22 Fld. A 1151971 Y g g 1 y t 1 16 p" Donald F. Clements, F. A. Iskander and Thomas P. [21] Appl. No.: 134,456 ODay Related US. Application Data 57] ABSTRACT [63] Continuation-impart of Ser. No. 717,996 April 1 Low water sensitive h d 1' f] i y rau 10 m compositions zg g g iig g gg i i 'fg iggf g g g which contain at least one borate ester as the base p u y an one fluid and from about O.l to about 8 percent by weight of monoethanolamine as an alkaline buffering agent. 8 Such low water-sensitive hydraulic fluids are high boil- I 1 n a s no 'l t [58] Field of Search ..252/74, 75, 77, 78, 49.6 mg and have How We of comm y 10 Claims, No Drawings 3,7ll,4ll

LOW WATER-SENSlTll/E HYDRAULHC lFLlJlEDS CONTAINING BORATE ESTERS AND MONGETHANOLAMENE This application is a continuation-in-part of co-pending application Ser. No. 7 l 7,996 filed Apr. 1, 1968 and now US. Pat. No. 3,625,899 which in turn was a continuation-in-part of application Ser. No. 653,338 filed July 14, 1967 and now abandoned.

This invention relates to new and improved, low water-sensitive hydraulic pressure transmission fluids for use in fluid pressure operating devices such as hydraulic brake systems, hydraulic steering mechanisms, hydraulic transmissions, hydraulic jacks, hydraulic lifts, etc. More particularly this invention relates to hydraulic fluids having a low sensivity to water which employ one or more borate esters as the base fluid and monoethanolamine as an alkaline buffering agent. The term base fluid as used throughout the specification and claims means the major active in gredient (not necessarily present in the major or largest proportion) of the hydraulic fluid, i.e., that ingredient which is most active in maintaining the desired properties of the hydraulic fluid especially in the face of aqueous contamination.

A great number of hydraulic fluid compositions have been suggested in the art. Commonly, the hydraulic pressure transmission fluids, such as brake fluids are made up of three principal units. The first is a base or lubricant for the system which may include heavy 30 bodied fluids such as polyglycols, castor oil, mixtures of these materials, etc. Diluents, which are employed for the purpose of controlling the viscosity of the fluid as represented by glycol ethers, glycols, alcohols, etc., form the second basic unit. Finally, the third basic unit is represented by an additive or inhibitor package comprising small quantities of materials which are added to control or modify various chemical and physical properties of the fluid, e.g., to reduce oxidation, to improve wetting and flow and to maintain the pH of the hydraulic system above 7 in order to minimize corrosion. By varying the composition, particularly desired properties can generally be attained. However, hydraulic fluids have been subject to increasingly stringent requirements with regard to many properties, e.g., boiling point, viscosity, corrosiveness, lubricity, pour point and rubber swell. This had made it extremely difficult to produce a desirable fluid since very often a change in composition which improves one or more of these or other essential properties will detrimentally affect some other property. This problem is magnified when water gets into the hydraulic fluid since many of the properties are affected, some to a substantial extent.

Hydraulic fluids, as exemplified by the commercial motor vehicle brake fluids, are hygroscopic by nature and therefore, absorb moisture from ambient atmospheres with resulting degradation of their boiling point. An article by C. F. Pickett entitled Automotive Hydraulic Brake Fluids and published as part of the 51st Mid-Year Meeting Proceedings of the Chemical Specialties Manufacturing Association, Inc, New York (1965) disclosed that small amounts of water, e.g., 3.5 percent by weight, added to commercial brake fluids significantly dropped the boiling point of the hydraulic fluids to temperatures which were below or perilously close to safe operating levels.

Consequently, the need for a hydraulic fluid which has a low sensitivity to water and] thus can maintain a high boiling point is readily apparent. ln addition to having a low water sensitivity, it is generally desirable to maintain the pH of the hydraulic fluid on the alkaline side to help inhibit corrosion and maintain other desired properties. Prior formulating experience has led to the conclusion that high boiling alkanolamines which are preferred as an alkaline buffering agent could be used in combination with a borate ester base fluid to provide a low water-sensitive hydraulic fluid that meets the minimum pH requirement of at least 7.0 and also maintains a high reflux boiling point than about 450-500F.). It was expected that the higher boiling alkanolamines (b.p. 450-500F.) such as diethanolamine (b.p. 515F.) would have to be used to maintain the desired boiling point. However, it was found that when using diethanol-amine as the alkaline buffering agent, introduction of small amounts of water (7.5 percent by volume) caused a crystalline precipitate or sediment to form in the hydraulic fluid within a few days. This was objectionable since hydraulic fluids have been known to accumulate even greater amounts of water and formation of a precipitate could block passages or ports in the hydraulic system causing a malfunction.

Now it gas been found that the hydraulic fluids of this invention which contain monoethanolamine as an alkaline buffering agent and a borate ester as the base fluid surprisingly do not result in the formation of a precipitate after introduction or accumulation of water (0 to 25 percent by volume). Additionally, it was surprising to find that the use of monoethanolamine, which has a boiling point of 339F., did not significantly lower the reflux boiling point of the hydraulic fluid.

The hydraulic fluids of this invention are especially desirable because they have a low water sensitivity and are particularly useful as brake fluids since they can 0 retain to a high degree the original properties of the fluid after water is accumulated. Additionally, the hydraulic fluids of this invention are able to maintain a pH of at least 7.0 and thus exhibit a very low rate of corrosivity, possess a high boiling point, are of low cost, are essentially odorless and colorless and possess a high degree of compatibility with other fluids.

The hydraulic fluids of this invention generally comprise from about 20 to about 96 percent by weight, based on the total hydraulic fluid weight, of at least one borate ester of a glycol monoether as the base fluid and from about 0.1 to about 8.0 percent by weight, based on the total weight of the hydraulic fluid, of monoethanolamine. Generally the remainder of the hydraulic fluid is comprised of a diluent and one or more additives. Additionally a b is(glycol ether) formal may be incorporated into the hydraulic fluid to give the fluid a desired viscosity-temperature relationship over a wide range of climatic and operational conditions. Details of these components and the desired proportion thereof are given below.

BASE FLUID The base fluid employed in the novel hydraulic fluids of this invention generally comprises at least one borate ester. There are many known borate esters which may be used and several are described in co-pending application Ser. No. 717,996, noted above.

More particularly, the hydraulic fluids of this invention will comprise from about 20 to about 96 percent by weight,- based on the total hydraulic fluid weight, of at least one borate ester of a glycol monoether. Preferably, the amount of borate ester will vary from about 30 to about 92 percent and more preferably from about 54.5 to about 92 percent by weight, based on the total hydraulic fluid weight. When using hydraulic fluids which can safely operate under somewhat lower temperature conditions, the range of borate ester used may vary from about 20 to about 54.4 percent and preferably from about 30 to about 54 4 percent by weight, based on the total weight of the hydraulic fluid.

Although a wide variety of borate esters can be employed as the base fluid in the novel hydraulic fluids of this invention, an especially useful class of borate esters are the so-called tri borate esters of glycol monoethers having the general formula:

wherein R, is a lower alkyl radical containing from one to four carbon atoms preferably one to two, R, is alkylene of from two to four carbon atoms, preferably two to three, and y is an integer from 2 to 4 inclusive. The R and R groups may be either straight or branched chain structures. Borates of the above-mentioned type include, for example: [CH (OCH CH O] 3 2 5( 2 2)a is [C3H7(OCH2CH2)4 O] B, [CH (OCH CHCH O] B [CH,,(OCl-l 3)aQ]3 3( HZ H3)4 ]3 2- H (OCH CHCH O] B, [C2H5(OCHZCI'ICH3)3 O] -B, [C H (OCH CHCH O] B, [C H OCH CI ICH O] B, [C H (OCH CHCH O] -B, [CH- O(OCHCH CH ,O],B, [C l-l,-,(OCl-lCH Cll ups- 3 3 3)2-4 ]3 d- 5 (OCHCH CHCl-l O] B, [CH (OCl-I CHCH CH While any of the borate esters defined by formula (1) may be used, the following borate esters are particularly useful: [CH (OCH CH O] -B, [C l- (OCH2CH2)2O]3B, 2 s( 2 2)a ]a 2- 5( 2 2)4 ]3 a 1( 2 2)s ]a-B, [C4H9(OCH CH2)zO]3B and [C4H9(OCH2CH2)3 Borates of the above-mentioned type can be conveniently prepared by reacting orthoboric acid and the glycol monoether while in the presence of a waterazeotrope forming solvent. Water formed in the esterification reaction is continuously removed as the azeotrope. At first, the temperature of the reaction mixture is maintained between about C. and about 190C. and desirably at the distillation temperature of the water-solvent azeotrope. After essentially complete removal of the water formed during esterification, the excess solvent is conveniently removed from the reaction mixture by distillation. The borate ester product, which is left in a residue, may then be recovered by distilling under reduced pressure or by extraction with a suitable solvent followed by evaporation of the solvent. For example, the compound [C l-l (OCl-l Cl-l O] B can be prepared by reacting 2 moles of.

CzH5(OCHzCHz)2O-H. 0.67 mole of orthoboric acid and 700 ml. of ethylbenzene with heating and mixing to yield 198 grams of the ester, a water-white liquid boiling at 222 223C. (5 mm. Hg. It is noted that in the preparation of these esters, a small proportion of concomitant reaction products may be formed and other minor impurities may also be present. Generally, the predominant portion of such other reaction products formed is a boroxine type compound having the following general structure:

Wherein R, is derived from the particular glycol ether being used, e.g., CH (OCl-l CH- O-, C H (OCH C H O-, etc. The amount of such concomitant reaction products formed and other impurities present may be up to about 10 percent by weight if the reacted mixture is not distilled. Distillation will reduce the amount of other reaction products and impurities to about 1 percent or less, however, either the distilled or undistilled product can be used provided the reaction medium or solvent is stripped off. The term borate ester as used in the specification and claims is intended to include relatively pure borate ester as well as crude borate ester which contains impurities and other by-products formed during preparation as described above. The preparation of the tri-borate esters per se is more completely described in U.S. Pat. No. 3,080,412 issued to D. M. Young on Mar. 5, 1963. It is of interest to note that this patent (U.S. Pat. No. 3,080,412) discloses the use of tri-borate esters, such as tris [2-(2- ethoxyethoxy)ethyl] borate, as stabilizers and corrosion inhibitors for lubricants and non-aqueous hydraulic fluids. However, use of these esters for such purposes, i.e., as a stabilizer or corrosion inhibitor, would not impart satisfactory low water sensitivity to the hydraulic fluid since such usage would generally be in very small or minor proportions (e.g., from 0.5 to 2 percent) in accordance with the generally accepted practice in the art (e.g., see U.S. Pat. No. 3,403,104 issued to P.B. Sullivan on Sept. 24, 1968).

A second highly useful class of borate esters includes compounds of the general formula: 9

Wherein R and R are independently selected from the group consisting of hydrogen and methyl, m and n are positive integers whose sum is from 2 to 20 and R, is alkyl of from one to four carbon atoms and with proviso that one of R and R is methyl and one of R and R is hydrogen. R, may be straight chain or branched alkyl. Borate esters of Type 11 can be prepared in the general way as those esters previously described (Type I) above, utilizing the so-called block type glycol monoethers. The preparation of esters of Type 11 is described in detail in U.S. Pat. No. 3,316,287

issued to L. G. Nunn, Jr. et al. on Apr. 25, 1967.

Type II borate esters useful in preparing the novel fluids of this invention include, for example: [CH3(OCH2CH2)(OCH2CHCH3)O]3B 3,7lll/til positions of this invention include esters having heteric oxyalkylene chains, that is, oxyalltylene chains in which oxyethylene and oxypropylene units are distributed randomly throughout the chain. These Type lll esters have the general formula:

1[ gl )a Rg represents a heteric oxyalkylene chain having the formula: (0Cl-l Cl-l ocn cncn where the sum of r and s is not more than 20 and wherein the weight percent of oxyethylene units in the said chain is not less than 20 based on the total weight of all the oxyalkylene units in the chain and R, is alkyl of from one to four carbon atoms and may be straight or branched chain. The preparation of Type III esters can be accomplished in the same general manner as the preparation of Types l and II described above by reacting orthoboric acid in the presence of toluene with a heteric glycol monoether of the formula:

where R, and Rg have the same meaning as previously set forth. Glycol monoethers of this class can be conveniently prepared by methods well known in the art such as the process described in U.S. Pat. No. 2,425,845 issued to W. .l. Toussaint et al. on Aug. 19, 1947.

A fourth type of borate esters suitable for use in the fluid compositions of this invention have the general formula:

wherin'T T; anargareeach an independently selected alkyl group having from one to four carbon atoms, R,,, R R R R and R are independently selected from the group consisting of hydrogen and methyl, n and m are positive integers independently selected in each chain and whose sum in each chain is from 2 to 20, and with the proviso that in no more than two of the chains is the sum of n and m the same. it is also noted that T,, T and T may be a straight or branched chain alkyl group.

Borate esters of this type can be prepared in the same way as the process described for Type II esters previously mentioned.

Type IV. borate esters suitable for use in the fluids of this invention include, for example:

It is further noted that borate esters of Types it, ill and IV may include concomitant reaction products and other impurities of the type as described above for Type I esters. Reference to these types of borate esters in the specification and claims is intended to include relatively pure borate ester as well as crude borate ester which contains impurities and other by-products formed during preparation as described above for Type I.

The amount of monoethanolamine which can be employed as an alkaline buffering agent generally must be sufiicient enough to maintain alkaline conditions in the hydraulic fluid composition, e.g., a pH value of from about 7.0 to about 1 1.5. Generally about 0.1 to about 8 percent by weight, based on the total weight of the hydraulic fluid, of monoethanolamine may be used. However, about 0.5 to about 5 percent by weight is preferred and more preferably from about 1 to about 3 percent by weight, based on the total weight of the hydraulic fluid composition.

The diluent portion of the hydraulic fluid composition of this invention generally will comprise one or more compounds selected from the group consisting of (a) glycol monoethers or diethers(b) glycols and polyglycols and (c) aliphatic saturated alcohols.

More particularly, the glycol monoethers or diethers have the formula:

R[O-R"],,O1R' v wherein R is alkyl of from one to four carbon atoms preferably one to two, R is hydrogen or alkyl of from one to four carbon atoms, preferably one to two, R" is alltylene of two to four carbon atoms, preferably two to three, and y is twoto four. The R, R and R" groups may be straight chained or branched. It is also intended that the alkylene oxide group [OR"] in the above formula (V) include mixtures of said alkylene oxides.

Illustrative of the diluents of this type (V) are the following compounds: diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol rnonoisopropyl ether, diethylene glycol monoisobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol mono-n-butyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol mono-n-butyl ether, tetrapropylene glycol monomethyl ether, tetrapropylene glycol monoethyl ether, dibutylene glycol monomethyl ether, dibutylene glycol monoethyl ether, tributylene glycol monomethyl ether, tributylene glycol monoethyl ether, tributylene glycol mono-npropyl ether, tetrabutylene glycol monomethyl ether, tetrabutylene glycol monoethyl ether, tetrabutylene glycol mono-n-butyl ether and! the corresponding diethers thereof. it is further noted that the above diluents include the various isomers of the respective compounds.

While any of the above glycol ethers defined by formula (V) may be used, the following glycol ethers are particularly useful: diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether and tetraethylene glycol monobutyl ether.

The glycol ethers are the most preferred diluent since their use will result in a fluid having a desirably high boiling point with good viscosity and water solubility properties. Most preferred of the glycol ethers are the ethylene glycols.

The second group of useful diluents are the glycols and polyglycols, including alkylene, polyalkylene and polyoxyalkylene glycols, having a molecular weight of from about 60 to about 450 and preferably from about 100 to about 300. Illustrative of such type diluents are the following compounds: ethylene glycol, propylene glycol, hexylene glycol, diethylene glycol, dipropylene glycol, triethylene I glycol, tripropylene glycol, polyethylene glycol and polypropylene glycol.

The use of the glycols and polyglycols as diluents is not as desirable as the glycol ethers since their use may result in some loss of fluidity at very low temperatures, however, they may be used in conditions where the requirements are not as demanding.

The third type of useful diluents are aliphatic, saturated monohydric alcohols containing'from six to l3 carbon atoms, preferably from eight to 10. Illustrative of such diluents are the following alcohols: hexanol, octanol, isooctanol, decanol, isodecanol, dodecanol, and tridecanol.

Since the use of the aliphatic alcohols in a high boiling hydraulic fluid may result in some loss of water solubility, they are not as desirable as the glycol ethers. However, they may be used in conditions where the requirements are not as stringent.

The diluent portion of the hydraulic fluids of this invention generally will comprise from about 79.9 percent by weight, preferably from about 3 to about 70 and more preferably from about 3 to about 45 percent by weight, based on the total weight of the hydraulic fluid composition.

While the above diluents, especially the glycol ethers, are particularly preferred, other diluents may be used if the desired properties and characteristics of the hydraulic fluid can be attained. For example, certain diesters derived from organic aliphatic acids and aliphatic alcohols might be usefully employed. Examples of diesterswhich might be used include dibutyl adipate, bis(methoxyethyl) a zelate, diisopropyl succinate, dipropylene glycol diproprionate and triethylene glycol dibutyrate.

Formal The hydraulic fluid composition of this invention may additionally contain one or more bis(glycol ether) formals having the formula:

b a )1]Z 2 I) wherein R, is alkyl of one to six carbon atoms, preferably one to four, R, is alkylene of two to four carbon atoms, preferably two to three and x is an integer of l to 5, preferably 1 to 3. The R and R, groups may be straight or branched chained and it is also intended that the alkylene oxide group (R,,()) in the above formula (VI) include mixtures of said alkylene oxides.

Illustrative of the above type formals (VI) are the following compounds: [CI-I O(C,H O)] CH While any of the above formals defined by formula (VI) may be used, the following bis(glycol ether) formals are particularly useful:

The above formals may be prepared by reacting the appropriate glycol with paraformaldehyde and removing the water of condensation which forms. Preparative techniques are commonly known in the art, e.g., British Pat. No. 506,6l3 (June I, 1939); Chemical Abstracts, 33, 9325 (1939) discloses a process for the preparation of condensation products of aldehydes with polyhydric alcohols or partial ethers thereof. Other known methods of preparation are disclosed in Canadian Pat. No. 390,733 (Aug. 13, 1940); Chemical Abstracts, 34, 6948 (1940), and in J.Am.Chem.Soc., Formaldehyde bis(B-ethoxyethyl) and bis(}8-ethoxyethoxyethyl) acetal by M. Sulzbacher, 72, 2795-6, (1950).

Generally the amount of formal (VI) which may be used in the hydraulic fluid composition of this invention may vary from 0 to about 40 percent by weight, based on the total weight of the hydraulic fluid composition. Preferably the amount of formal (VI) will vary from 0 about 15 percent and more preferably from about 2 to about 10 percent by weight, based on the total weight'of the hydraulic fluid composition.

The use of these formals in the hydraulic fluids of this invention enable such fluids to function over a wide range of climatic and operational conditions particularly'because of the desired temperature-viscosity relationship at both high and subfreezing temperatures.

Additives I When desired, variousadditives may be added to the hydraulic fluids of this invention to control or modify various chemical and physical properties of the fluids. Among the various types of additiveswhich can be added to the hydraulic fluids of this invention are included: inhibitors for pH and corrosion control, antioxidants, rust inhibitors, viscosity index improvers, pour point depressants, lubricating additives, antifoamants, stabilizers, demulsiflers, dyes and odor suppressants. Generally, the total amount of additives which may be incorporated into the fluid composition will vary depending on the particular composition and the desired properties. More particularly, the total amount of additives will comprise from 0 to about 10 percent and preferably from about 0.1 to about 8.0 percent by weight based on the total weight of the hydraulic fluid composition.

Generally, the monoethanolamine alkaline buffering agent incorporated in the hydraulic fluid composition of this invention will be sufficient to maintain the desired pH, however, supplementary inhibitors for pH and corrosion control may be included if desired. For example, inhibitors for pH and corrosion control, such as the alkali metal borates, can be employed to maintain the desired alkaline conditions, e.g., a pH value of from about 7.0 to about ll.5. These inhibitors are generally added in an amount of from to about 8.0 percent by weight based on the total weight of the hydraulic fluid composition and preferably from about 0.2 to about 6.0 percent by weight on the same basis. Useful inhibitors include alkali metal borates, such as sodium borate, potassium tetraborate, etc; sodium meta arsenite; alkali metal salts of fatty acids, such as potassium oleate, the potassium soap of rosin or tall oil; alkylene glycol condensates with alkali metal borates, such as the ethylene glycol condensate of potassium tetraborate; phosphites, such as triphenyl phosphite, tri(tert.amylphenyl)phosphite, diisopropyl phosphite, etc.; mercaptobenzotriazole; morpholine compounds including alkyl morpholines having from one to four carbon atoms in the alkyl group such as N-ethyl morpholine, N-isopropyl morpholine, N-butyl morpholine; N-phenyl morpholine, N-(Z-aminoethyl) morpholine, N-(Z-hydroxyethyl) morpholine, etc.; phosphates, including the alkali metal phosphates, dibutyl amine phosphates, the dialltyl acid 0- phosphates and amine salts thereof; triazoles including benzotriazole, l ,2'naphthotriazole, 4- nitrobenzotriazole, aminobenzotriazoles, such as 5- acylaminobenzotriazole, and alkyl triazoles having one to carbon atoms in the alkyl group as exemplified by methyl triazole, ethyl triazole, n-propyl triazole, tertiary butyl triazole, hexyl triazole, isodecyl triazole,etc. Other useful corrosion inhibitors include adenine, 4- methylimidazole, 3,5-dimethyl pyrazole, 6- nitroidazole, imidazole, benzimidazole, quanine, in-

dazole, ammonium dinonylnaphthaline sulfonate, dioleyl thiodipropionate, ethylbenzoate, ethyl-paminobenzoate, cyclohexyl ammonium nitrite,

diisopropyl ammonium nitrite, butynediol, glycerin, 1,3,5trimethyl-2,4,6tris(3,5-di-tert. butyl-4-hydroxybenzoyl), 4,4-methylene bis(2,6-di-tert. butylphenol), 4-hydroxymethyl-2,6-di-tert. butylphenol, 4,4'-methylene bis(4-methyl-6-tert. butylphenol), salicylal-o-aminophenol, 2,6-di-tert. butyl-Z- dimethylamino-p-cresol, 4,4-thio bis(6-tert. butyl-ocresol). Mixtures of the above-mentioned inhibitors can be employed if desired.

An antioxidant may be used as an additive in the hydraulic fluid compositions of this invention if desired. Generally the amount of antioxidant used will vary from 0 to about 2 percent and preferably will be from about 0.001 to about 1.0 percent by weight based on the total weight of the fluid composition. Typical antioxidants include phenolic compounds, such as 2,2-di- (4-hydroxyphenyl) propane, phenothiazine, phenothiazine carboxylic acid esters, N-alkyl or N- arylphenothiazines, such as N-ethyl phenothiazine, N- phenyl phenothiazine, etc.; polymerized trimethyldihydroquinoline; amines, such as phenyl-alpha naphthylamine, phenyl-beta-naphthylamine, dioctyl diphenylamine, N,N-di-fl-naphthyl-p-phenylene diamine, p-isopropoxy diphenylamine, N,N-dibutyl-pphenylene diamine, diphenyl-p-phenylene diamine, N,N'bis( 1 ,4-dimethylpentyl)-p-phenylene diamine, N,N'-diisopropyl-p-phenylene diamine, p-hydroxydiphenylamine, etc.; hindered phenols such as dibutyl cresol, 2,6-dimethyl-p-cre sol, butylated 2,2-di-(4- hydroxyphenyl) propane, n-butylated arninophenol, butylated hydroxyanisoles, such as 2,6-dibutyl-phydroxyanisole; anthraquinone, dihydroxyanthraquinone, hydroquinone, 2,5-di-tertiarybutylhydroquinone, Z-tertiary butylhydroquinone, quinoline, p-hydroxydiphenylamine, phenyl benzoate, 2,6-dimethyl pcresol, p-hydroxyanisole, nordihydroquaiaretic acid, pyrocatechol, styrenated phenol, polyalkyl polyphenols, sodium nitrite, etc. Mixtures of the abovementioned antioxidants can be employed, if desired. it should be emphasized that with a variety of the fluids of this invention, which are suitable for a wide range of industrial application, a separate antioxidant is not required.

The above-noted inhibitors and additives are merely exemplary and are not intended as an exclusive listing of the many well-known materials which can be added to hydraulic fluid compositions to obtain various desired properties. Numerous additives useful in hydraulic fluids are disclosed in Introduction to Hydraulic Fluids by Roger B. Hatton, Reinhold Publishing Corp., I962).

Formulation of the novel fluid of this invention is accomplished by blending the components to a homogeneous stage in a mixing vessel. The preferable blending temperature is from about 50-l25F. It is preferable to warm the solution during preparation to facilitate dissolution. The blending of the compounds is conveniently conducted at atmospheric pressure in the absence of moisture.

In general, any suitable method can be used in preparing the liquid compositions of this invention. The components can be added together or one at a time, in any desired sequence.

The following examples which illustrate various embodiments of this invention are to be considered not limitative.

EXAMPLE 1 A hydraulic fluid composition having the following composition was prepared:

Percent by Weight [CH (OCH CH ),O] -B 75.00 Triethylene glycol monomethyl ether 9.30 Tetraethylene glycol monoethyl ether 14.48 Monoethanolamine [.00 Benzotriazole 0.20 Sodium Nitrite 0.02 100.00

Properties:

Reflux boiling point 535F. pH 7.6 Viscosity at 40F. 1595 cs. Appearance after two weeks with added water Volume water added Appearance 3.5 clear 5 clear 7 clear 10 clear l3 clear EXAMPLE 2 A hydraulic fluid composition having the following composition was prepared:

Percent by Weight [CH3(OCHgC 2)30]3-B 75.00 Triethylene glycol monoethyl ether 8.60 Tetraethylene glycol monoethyl ether 14.48 Monoethanolarnine i .70

Benzotriazole 0.20 Sodium Nitrite 0.02 100.00

Properties:

Reflux boiling point 3 3"F.

Viscosity at --40F. 2100 cs.

Appearance after two weeks with added water Volume water added Appearance 3.5 clear 5 clear 7 clear 10 clear 1.3 clear EXAMPLE 3 A hydraulic fluid having the following composition was prepared:

Percent by Weight [CH (OCH,CH,) O] -B 79.0 lsoctanol 20.0 Monoethanolamine l .0

Properties:

Reflux boiling point (dry) 463F. Reflux boiling point (wet) (3.5 ml. water +100 ml. fluid) 310F. Viscosity at -40F. 816 cs.

EXAMPLE 4 A hydraulic fluid having the following composition was prepared:

Percent by Weight [CH;,(OCH CH,) O] -B 79.0 Hexylene glycol 20.0 Monoethanolamine l .0 100.0

Properties:

Reflux boiling point (dry) 489F. Reflux boiling point (wet) (3.5 ml. water 100 ml. fluid) 343F. Viscosity'at 40F. 982 cs.

EXAMPLE 5 A hydraulic fluid having the following composition was prepared:

Percent by Weight [CH (OCH,C H,) O],-B 89.0 Diethylene glycol 10.0 Monoethanolamine l .0

Properties:

Reflux boiling point (dry) 522F. Reflux boiling point (wet) (3.5 ml. water 100 ml. fluid) 392F. Viscosity at -40F. 3050 cs.

EXAMPLE 6 A hydraulic fluid was prepared having the following composition:

Percent by Weight Tetraethylene glycol monoethyl ether 15.00 Triethylene glycol monoethyl ether 39.00 l 4 4 )al: 20-00 Monoethanolamine 1.00 100.00

Properties:

Reflux boiling point (dry) 436F.

Reflux boiling point (wet) (3.5 ml. water+ ml. fluid) 304F. v

Viscosity at -40F. 607.1 cs.

EXAM PLE 7 A hydraulic fluid was prepared having the following composition:

Percent by Weight Borate Ester [CH,(OCH,CH,),O],-B 30.0 Tetraethylene glycol monomethyl ether 22.0 Triethylene glycol monoethyl ether 42.0 [CH,O(C,H.O)]=Cl-l, 5.0 Monoethanolamine 1.0 100.0

Properties:

' Reflux boiling point (dry) 467F.

Reflux boiling point (wet) (3.5 ml. water +100 ml. fluid) 321F. Viscosity at -40F. 660 cs.

EXAMPLE 8 A hydraulic fluid composition having the following composition was prepared:

precipitate A comparison of the hydraulic fluids of this invention wherein monoethanolamine is used as an alkaline buffering agent with hydraulic fluids using diethanolamine is made by observing the results of Examples 1, 2 and 8. ln Examples 1 and 2 when monoethanolamine was used, no precipitate formed after the addition of 7, l0

and 13 percent by volume, however, when diethanolamine was used a precipitate was formed. This clearly points out the advantage of the hydraulic fluids of this invention which will be able to operate under normal use conditions wherein the possibility of water accumulation in the hydraulic system through faulty components, improper system maintenance etc., does exist.

What is claimed is:

l. A hydraulic fluid composition consisting essentially of (A) from about 20 to about 96 percent by weight, based on the total weight of the hydraulic fluid composition, of at least one base fluid or lubricant selected from the group consisting of (a) a borate ester of the formula:

wherein R, is alkyl of from one to four carbon atoms, R, is alkylene of from two to four carbon atoms and y is an integer of from two to four; (b) a borate ester of the formula:

wherein R, is alkyl of from one to four carbon atoms, Rg is a heteric oxyalkylene chain of the formula:

[ 2 2)r C z a);]

wherein the sum of r and s is not more than and wherein the weight percent of the oxyethylene units is not less than 20 based on the total weight of all the oxyalkylene units; and (d) a borate ester of the formula:

wherein T,, T and T are each an independently selected alkyl group having from one to four carbon atoms; R R R R R and R are independently selected from the group consisting of hydrogen and methyl, n and m are positive integers independently selected in each chain and whose sum in each chain is from two to 20, and with the proviso that in no more than two of chains is the sum of n and m the same and (B) from about 0.1 to about 8 percent by weight, based on the total weight of the hydraulic fluid composition, of monoethanolamine.

2. The hydraulic fluid composition of claim 1 wherein from about 0.5 to about 5 percent of weight of said monoethanolamineis used.

3. The hydraulic fluid composition of claim 1 .wherein from about 1 to about 3 percent of weight of said monoethanolamine is used.

4. The hydraulic fluid composition of claim 1 additionally containing from O to about 79.9 percent by weight, based on the total weight of the fluid composition, of at least one diluent selected from the group consisting of: glycol ethers having the formula:

wherein R is alkyl of from one to four carbon atoms, R is selected from the group consisting of hydrogen and alkyl of from one to four carbon atoms, R" is alkylene of from two to four carbon atoms and y is an integer of from 2 to 4; (bb) glycols and polyglycols having a molecular weight of from about 60 to about 450 and (cc) aliphatic saturated monohydric alcohols having from six to 13 carbon atoms is incorporated therein.

5. The hydraulic fluid composition of claim 4 wherein there is incorporated from 0 to about 40 percent by weight, based on the total weight of the hydraulic fluid composition, of at least one bis( glycol ether) formal having the formula:

wherein R, is alkyl of one to six carbon atoms, R, is alkylene of two to four carbon atoms and x is an integer of 1 to 5.

6. The hydraulic fluid composition of claim 1 wherein said borate ester is of type (a).

7. The hydraulic fluid composition of claim 4 wherein said borate ester is of type (a) and said diluent is of type (aa).

8. The hydraulic fluid composition of claim 7 wherein from about 1 to about 3 percent by weight of said monoethanolamine is used.

9. In the operation of a fluid pressure operating device which uses hydraulic pressure transmission fluid, the improvement comprising using as said hydraulic pressure transmission fluid, a composition consisting essentially of (A) a borate ester base fluid or lubricant selected from the group consisting of (a) a borate ester of the formula:

wherein R, is alkyl of from one to four carbon atoms, R, is alkylene of from two to four carbon atoms and y is an integer of from 2 to 4; (b) a borate ester of the formula:

wherein R, is alkyl of from one to four carbon atoms, R and R are independently selected from the group consisting of hydrogen and methyl, m and n are positive integers whose sum is from two to 20, and with the proviso that one of R and R is methyl and one of R and R is hydrogen; (c) a borate ester of the formula:

wherein the sum of r and s is not more than 20 and wherein the weight percent of the oxyethylene units is not less than 20 based on the total weight of all the oxyalkylene units; and (d) a borate ester of the formula:

wherein T,, T and T are each an independently selected alkyl group having from one to four carbon atoms; R.,, R R R R and R are independently selected from the group consisting of hydrogen and methyl, n and m are positive integers independently selected in each chain and whose sum in each chain is from two to 20, and with the proviso that in no more than two of the chains is the sum of n and m the same; 10. The method of claim 9 wherein from about 0.5 to and (B) from about 0.1 to about 8 percent by weight, about percent by weight of said monoethanolamine is based on the total weight of the hydraulic fluid comused. 1 position, of monoethanolamine. =11 t mg UNITED STATES PATENT OFFICE CERTIFICATE @F QOECTEON Patent No. 17 13 7 Dated January 16, 1973 Inventor(s) Arthur W. Sawyer and David A. Gsejka It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected ,as shown below:

7301. 2, line 27, "gas" should read "has". w

Col. 5, line 50, "CHCHs)sQ 7-s]3" should read --CHCH3)3Q73-B--.

C01. 5, line 56, "(OCI-ICH CHCI-Is2 4 Q73-B" should read --(OCI-IC H3CHCH3)2 4 Q73-B-- C01. 5, line 11, "54 4" should read "54.4 m. line 12, "54 4" should read "54. l". 001. l, line 52, "wherein" should read -whe'rein--.

Col. 5, line 3, "EH3(ocH2cH2)3(ocH2cHcHe)e 0 7e-B should read "EH3 (OCH2CH2 e- 2 H e 5Q73 -B-- Col. 8, line 33, ."0 about 15" should read --0 to about l5--. 7 Col. 15, claim 3 for weight" should read "by weight--. Col. 15, claim 4, line 59 "glycol" should read e-(aa) glyool--.

Signed and sealed this 3rd day of July 1973.

(SEAL) Atte'st: v V

EDWARD M.FLETCHER,JR, I Rene Tegt e er Attesti g Officer Y Acting Commissioner of Patents 5g3? UNITED STATES PATENT OFFICE CERTIFICATE OF CORECTKON Patent No. 3,7 Dated January 16, 1975 Inventor(s) Arthur W. Sawyer and David A. Csejka It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

F2301. 2, line 27, "gas" should read "has". '1 C01. 3, line 30, "CHCHQSQJB-B" should read -CHCH Q7 -B--.

Col. 5, line 56; "(OCHCH CHCHs2 Q73-B" should read ---(OCHCH CHGH )2.. Q7 -B-- 7 Col. 3, line 11, "54 l" should read "54.4". line l2, "54 4" should read "54. Col. 4, line 52, "wherein" should read -.-wherein--.

col. 5, line 5, 5H ,(oCHzCHa)s(OCI-I2CHCHa)5 973-13 should read --EI-I3(OCH CH2)s-(OCH2CHCH3) Q7 -B--- a I 001. 8,-lihe 53,. "o about 15" should read --o to about 15--. C01- 13, claim 5 "of weight" sh uld read -by'weight-m :Col. 15, claim 4, line 59 "glycol" should read --(aa) glyool--.

Signed and sealed this 3rd day of July 1973 (SEAL) Attest:

EDWARD M. FLETCHER,JR. Rene Tegtmeyer Attesting Officer Acting Commissioner of Patents

Claims

2. The hydraulic fluid composition of claim 1 wherein from about 0.5 to about 5 percent of weight of said monoethanolamine is used.
3. The hydraulic fluid composition of claim 1 wherein from about 1 to about 3 percent of weight of said monoethanolamine is used.
4. The hydraulic fluid composition of claim 1 additionally containing from 0 to about 79.9 percent by weight, based on the total weight of the fluid composition, of at least one diluent selected from the group consisting of: glycol ethers having the formula: R(O-R'''')yOR'' , wherein R is alkyl of from one to four carbon atoms, R'' is selected from the group consisting of hydrogen and alkyl of from one to four carbon atoms, R'''' is alkylene of from two to four carbon atoms and y is an integer of from 2 to 4; (bb) glycols and polyglycols having a molecular weight of from about 60 to about 450 and (cc) aliphatic saturated monohydric alcohols having from six to 13 carbon atoms is incorporated therein.
5. The hydraulic fluid composition of claim 4 wherein there is incorporated from 0 to about 40 percent by weight, based on the total weight of the hydraulic fluid composition, of at least one bis(glycol ether) formal having the formula: (RbO(RaO)x)2CH2 , wherein Rb is alkyl of one to six carbon atoms, Ra is alkylene of two to four carbon atoms and x is an integer of 1 to 5.
6. The hydraulic fluid composition of claim 1 wherein said borate ester is of type (a).
7. The hydraulic fluid composition of claim 4 wherein said borate ester is of type (a) and said diluent is of type (aa).
8. The hydraulic fluid composition of claim 7 wherein from about 1 to about 3 percent by weight of said monoethanolamine is used.
9. In the operation of a fluid pressure operating device which uses hydraulic pressure transmission fluid, the improvement comprising using as said hydraulic pressure transmission fluid, a composition consisting essentially of (A) a borate ester base fluid or lubricant selected from the group consisting of (a) a borate ester of the formula: (R1(O-Ra)y-O)3-B, wherein R1 is alkyl of from one to four carbon atoms, Ra is alkylene of from two to four carbon atoms and y is an integer of from 2 to 4; (b) a borate ester of the formula: (R1-(OCH2CHR2)m-(OCH2CHR3)nO)3-B, wherein R1 is alkyl of from one to four carbon atoms, R2 and R3 are independently selected from the group consisting of hydrogen and methyl, m and n are positive integers whose sum is from two to 20, and with the proviso that one of R2 and R3 is methyl and one of R2 and R3 is hydrogen; (c) a borate ester of the formula: (R1(Rg) O)3-B , wherein R1 is alkyl of from one to four carbon atoms, Rg is a heteric oxyalkylene chain of the formula: (- (OCH2CH2)r , (OCH2CHCH3)s -) , wherein the sum of r and s is not more than 20 and wherein the weight percent of the oxyethylene units is not less than 20 based on the total weight of all the oxyalkylene units; and (d) a borate ester of the formula: wherein T1, T2 and T3 are each an independently selected alkyl group having from one to four carbon atoms; R4, R5, R6, R7, R8 and R9 are independently selected from the group consisting of hydrogen and methyl, n and m are positive integers independently selected in each chain and whose sum in each chain is from two to 20, and with the proviso that in no more than two of the chains is the sum of n and m the same; and (B) from about 0.1 to about 8 percent by weight, based on the total weight of the hydraulic fluid composition, of monoethanolamine.
10. The method of claim 9 wherein from about 0.5 to about 5 percent by weight of said monoethanolamine is used.