CA1047478A - Ester lubricants suitable for use in aqueous systems - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Ester lubricants derived from high molecular weight dimer acids, polyoxyalkylene glycols and monofunctional alcohols are provided.
These ester compositions are useful as lubricants and are readily emulsifiable with water. Aqueous emulsions of these esters have superior lubricating and rust inhibiting properties.

Description

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:. ¦This invention relates to ester compositions useful as lubricants, ¦ and to the aqueous lubricant compositions provIded includin~ such ester ¦ compositions.
e use of organic esters, primarily alipllatic esters, as :-synthetic lubricants is well docwnented in the literature. ~lese compounds l are useful in the neat form in a variety of lubrication applications. They ¦ are especially important for their use in engines because of their abili~y to perform acceptably over a wide temperature range. Complex synthetic ester lubricants obtained from the reaction of glycols and dibasic acids ¦ with monobasic acids and alcohols are also widely used. These complex I esters are generally characterized by their excellent thermal stability, ¦ oxidation-corrosion resistance and low temperature properties.

; ¦ Recently the use of aqueous lubricant systems has become increasingly important. In the metalworking industry, for example, because I of the high cooling requirements of many of the high-speed operations ¦ employed for the processing of metals straight mineral oil or vegetable and ¦ animal oil lubricants are no longer completely satisfactory because they I do not have sufficient cooling capacity. This is particularly true in hot ; I rolling operations. The trend has therefore been to the use of aqueous l lubricant systems to overcome the cooling problem as ~ell as reduce i ; ¦ sludging, discoloration and other related problems. Typically, aqueous emulsions containing fromØ1 to 25% of an emulsifiable oil are employed for this purpose.
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The conventional simple and complex synthetic ester lubricants have heretofore not been adaptable for use in aqueous systems for metalworking even though they are in themselves highly efficient lubricants.
~hey are incompatible with water and these oils do not form acceptable en~lsions or dispersions without the use of highly efficient emulsifying aids.

; It would be highly advantageous to have modified synthetic ester lubricants available which are readily emulsifiable with water and useful for working both ferrous and non-fe.rous metals. It would be particularly userul if uniform aqueous emulsiors _ould be formed with these modi~ied ; ester lubricants without the use c external emulsifying aids by moderate agitation of the lubricant and water and if stable, i.e. did not undergo rapid phase separation, emulsions resulted. It would be even more desira~le if the resulting aqueous lubricant systems had superior rust i~libiting and , ¦¦ I icatin~ properties.

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U4'7~8 It has now been discover~d that es-ter compositions derived from high molecular weigh-t dimer acids, monofunctional alcohols and po]yoxyalkylene glycols are excellen-t lubricants, D
both in the neat form and when emu:Lsified with wa-ter. These esters form stable emulsions with water which are useful for working both ferrous and non-ferrous metals. In addition to the superior lubricating properties obtained with aqueous emulsions formed with -the esters of aspects of -the present invention, superior rust inhibiting properties are also obtained.
The esters of aspects of this invention are reaction products comprising 0.05 to 0.5 equivalent polyoxyalkylene glycol and 0.5 -to 0.95 equivalent monofunctional alcohol per equivalent dimer acid. By a variant thereof, the dimer acid contains 32 -to 52 carbon atoms and is ob-tained by the polymeriza-tion of a monocarboxylic acid containing from 16 to 26 carbon atoms. Excellen-t resui-ts are obtained when the esters contain i, 0.1 to 0.4 and 0.6 to 0.9 equivalent monofunctional alcohol - reacted with an equivalent dibasic acid. Additional hydroxylic : 20 or carboxylic reactan-ts not exceeding 0.4 equivalent can be included. The esters -typically have hydroxyl values and acid values less -than 25 and preferably these values are less than 10. The polyoxyalkylene glycols used have molecular weights from 200 to 1000. The high molecular weight dibasic acids con-tain from 32 to 52 carbon atoms with dimer acids containing predominantly C36 dibasic acids being preferred. Useful monofunctional alcohols will contain from 1 -to 20 carbon atoms and preferably from 6 to 16 carbon atoms. In preparing the aqueous emulsions the concentration of the es-ter in water will range from 0.1 to 25% by weight.

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By another varian-t, the .~cid value is less than 10, the hydroxyl va~ue is :Less than 10 and w~lich con-tains ~rom ,, 5 to 30 weight percellt polyoxyalky:Lene glycol.
By still ano-thcr varian-t, -the polyoxyal]cylene glycol -' is a polyethylene glycol havirlg a molecular weight from 300 '; to 800.
By yet another varian-t, 0.1 -to 0.4 equivalent polyethylene glycol and 0.6 to 0.9 equivalen-t monofunctional alcohol containing from 6 -to 16 carbon atoms are reacted per equivalent , 10 dimer acid and the ester contains S to 30 weight percent ` polyethylene glycol.
, By a still fur-ther variant, the dimer acid con-tains ., .
~, 75% or more C36 dimer acid, the polyethylene glycol has a molecular weight of 400 and the acid value of -the ester is less than 10; especially where the monofunctional alcohol is 2-ethylhexanol.
,~ The improved synthetic ester lubricants of aspects of this invention sui-table for use in aqueous systems to impart ~ superior lubricating and rust inhibiting properties are complex ,~ 20 ester condensation products obtained by the reaction of a ~-- polyoxyalkylene glycol, a high molecular weight dibasic acid " and a monofunct,ional alcohol. One or more additional other compounds capable of being incorporated into the ester may be included in small amounts.
~ By ano-ther aspect of this invention, an aqueous ', lubricant composition is provided, which,is suitable for metal-working and having improved rust protection properties containing 0.1 to 25 percent by weight of an ester comprising the condensation product of 0.05 to 0.5 equiva1,ent polyoxyalkylene glycol having a molecular weight from 200 to 1000 and having A~ ~

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~47478 repeatin~ alk~lene uni-ts con-ta lirlg rro~n ~ to 4 carbon a-tGins, 0.5 to 0.95 e~llivalerl~t ~)no~lirlrt;or~al .-ilco!lo~l ,f ~he ~ormula I~OI-I where ~ is a hydrocarbon radical con-taining ~rom 1 to 20 carbon ato~ns and 1.0 equivalent of a dibasic acid containing from 30 to 60 carbon atoms, such ester having an acid value less than 25, a hydroxyl value less -than 25 and containing 2 to 40 percent by weight polyoxyalkylene glycol.
The es-ter composition used in -this lubricant cornposi-tion may be ai~y o~ the varian-ts described above.

The poLyox~alkylene glycols employed have molecular weights from 200 to 1000 with recurring alkylene groups containing 2 to 4 carbon atoms. Polyoxyalkylene glycols satisfying the above requirements include ' polyethylcne glycol, polypropylene glycoL,poly~utylene glycol, poly(ethy-lenepropylene) glycol and the like. Especially useful for the ester lubricants of an aspect of this invention are polyethylene glycols having molecular weights from 300 to 800. The polyethylene glycols are available from commercial suppliers under the Trade Marks "Carbowax" and "Polyox"
: or they may be synthesized in the conventional manner. Molecular weights indicated for the polyoxyalkylene glycols are average molecular weights and it is understood that the compositions are mixtures of glycols ranging above and below the specified average molecular weight value. Polyoxy-alkylene glycols having molecular weights less than 200 or greater than 1000 should not, however, be present in significant amounts.
The high molecular weight dibasic acids condensed with the polyoxyalkylene glycol will contain from 30 to 60 carbon atoms. Especial-ly useful dibasic acids are the so-called dimer acids containing from 32 to 52 carbon atoms. The dibasic acids may be obtained by processes known to tile art but, as with the dimer acids, they are usually obtained from the polymerization of monocarboxylic acids containing from 16 to 26 car-bon atoms. These unsaturated monomer acids may contain one or more sites 3 ~ ~ -3a-'' . ',~
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Or ava:i1a~Le Ull'i.llUl~ W~t~ t~ mo:lecuJe. I)imer acids conLaining prudominantly C3( dibilsic acids and ~)btained from the dimerization of , .
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oleic acid, linoleic acid, eleostearic acid and similar singly or doubly unsaturated C16 monobasic acids are particularly useful for the prepara-tion of the present lubricants. To obtain the dimer acids 2 moles of the unsaturated monocarboxylic acid are reacted, generally in the presence of a catalytic material such as, for example, an alkaline, acid or neutral earth.
To remove ethylen c unsaturation the dimer acids may be hydro-genated. Mixtures of dimer acids derived from different sources may be employed and also trimer and ~-_ramer acids may be present with the dimer ~, acid. Trimer and tetramer acids are by-product acids obtained in the dimerization process and they do not adversely affect the properties of the resulting ester compositions so long as 50% by weight of the mixture .
are dimer acids. In some i3~tances the presence of these trimer and tetramer acids may even be advantageous, such as, for example, when a higher viscosity for the ester is desirable. Excellent results are obtained when the high molecular weight dibasic acid contains 75% or more C36 dimer acid. Commercially available compositions sold under the Trade Mark "Empol", which are mixtures of polymerized fatty acids having -C36 dimer acid as the major constituent, may be advantageously employed to form the esters of aspec~s of this invention.
The monofunctional alcohols condensed with the polyoxyalkylene glycols and high molecular weight dibasic acid contain from 1 to 20 car-bon atoms. These alcohols have the general formula ROH where R is a - hydrocarbon radical containing from 1 to 20 carbon atoms which can be either straight-chain or branched, and if branched may contain one or more alkyl groups containing from 1 to 4 carbon atoms, and which may be saturated or contain unsaturation. The use of mixed alcohols of the above types is not detrimental to the compositions of aspects of this invention and in some instances is even advantageous. Especially useful alcohols for the compositions of aspects of this invention contain from 6 to 16 carbon atoms. Illustrative of the alcohols suitable for use in the process to provide compositions of aspects of the invention to obtain iQ~7~'7~3 improved ester products are: isopropanol, butanol, t-butanol, isoamyl alcohol, n-hexanol, 2-ethylhexanol, n-octanol, isooctanol, isodecanol, capryl alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, tridecyl alcohol, which is mainly tetramethyl-l-nonanol, and hexadecyl alcohol which is a complex mixture of primary alcohols charac-terized as 2,2-dialkyl-1-e_s~ols where the alkyl groups are typically methyl-branched C6 and C8 radicals. Branched alcohols containing from 6 to 16 carbon atoms and which are saturated or essentially so are an especially preferred embodimen. to prepare the compositions of aspects of the invention.
The alcohols may be obtained from any of the conventional pro-cesses. For example, long chain linear alcohols may be obtained from ,~ natural sources or producea synthetically from ethylene using Ziegler-type reactions. Tridecyl and hexadecyl alcohols, as well as other ` branched chain alcohols, are obtainable from the oxo reaction, that is, by the reaction of carbon monoxide and hydrogen with a suitable olefin.
j In addition to the reactants described above, namely, the high ,~ molecular weight dibasic acids, polyoxyalkylene glycols and monofunction-al alcohols which are essential to obtain the improved esters of aspects of this invention useful as aqueous lubricants, small amounts of other reactants may also be included without detracting from the lubricating properties. In some instances, such additional modification may even impart enhanced physical properties and characteristics to the esters, such as, for example, increased, viscosity, lubricity, oxidation and heat stability or the like. For example, small amounts of monobasic acids may be included in the preparation of the esters. Similarly, short-chain glycols and short-chain dibasic acids can be present. Such materials include, for example, glycols such as, for example, ethylene glycol, 1,3-propanediol, 1,5-pentanediol, 1,6-hexanediol, l,9-nonanediol, 1,10-decanediol, neopentyl glycol (2,2-dimethyl-1,3-propanediol), adipic acid, sebacic acid, succinic acid, oxalic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid and the like. Aromatic and cycloaliphatic ~47478 diols and dicarboxylic acids may also be used. Tri- and polyfunctional materiaIs including triols, tricarboxylic acids, polyols and polycarboxy-; lic acids can also be used. Hydroxylic and carboxylic compounds of this .,' - ' .
type include glycerol,sorbitol, pentaerythritol, monohydroxypivalate, ~ trimethylolpropane, the previously mentioned trimer and tetramer acids, .: j trimesic acid, trimellitic acid and the like. Still other materials having mixed functionality, such as, for example, alkanolamines, can be ~ employed.
- These compounds can ~ included in the ester preparation in small amounts to modify the physical properties of the esters. This aspect of the invention finds particular application where the resulting ; ester, in addition to being used as a lubricant in an aqueous emulsion, may also be used as the ne_t oil, thus eliminating the need for the user to keep several different lubricant ester compositions on hand for these different applications.
The reaction of the dibasic acid, polyoxyalkylene glycol, -~ monofunctional alcohol and any other hydroxylic or carboxylic compounds which may be present is carried out using conventional esterification procedures, that is, by heating the reaction mixture with or without a catalyst at a temperature from 100 to 300 C. while removing the water of reaction. These condensation reactions are most generally conducted over the temperature range 175 to 250C. It is not necessary that a catalyst be employed for the reaction; however, conventional acid catalyts, such as, for example, sulfuric acid, alkyl and aryl sulfonic acid, such as, for example, p-toluene sulfonic acid, or the like can be used to advantage. The reaction may be carried out in a diluent which is inert to the reaction conditions employed and which preferably will form an azeotrope with water to facilitate its removal. The reaction is con-tinued until the esterlfication is complete or essentially so. This may readily be determined by following the decrease in acid value or hydroxyl value or by measuring the amount of water evolved.

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The dibasic acid, polyoxyalkylene glycol and monofunctional alco- L
hol may be added to the reactor as a unit charge and the reaction conducted ~ -until the acid value indicates complete or near complete reaction of the r carboxyl groups or until a predetermined amount of water is recovered. When ~-` following this procedure the reactant charge should roughly correspond to ~; the ratio of the reactants desired in the ester product. The reaction sys-; tem should be essentially balanced but a slight excess of one or more of the reactants can be present. An alternative procedure, is to react the r dibasic acid and the polyoxyalkylene glycol and when this reaction is com-plete, or essentially so, to charge the monofunctional alcohol and to com-plete the reaction. Still another process for preparing the esters would i be to react the dibasic acid and monofunctional alcohol and when this r esterification is complete to add the polyoxyalkylene glycol and complete the reaction. In this latter instance an excess of the monofunctional al-cohol may be initially reacted; in fact, the dibasic acid may be completely ' reacted with monofunctional alcohol so that no free carboxyl groups remain.
The polyoxyalkylene glycol may be added and a transesterification reaction undertaken to displace the appropriate amount of monofunctional alcohol.
The higher boiling polyoxyalkylene glycols readily displace the monofunc-tional alcohols using suitable transesterification conditions and the re-sulting products are comparable in all respects to those obtained using conventional unit charge or step-wise esterification procedures. l`he com-mon esterification and transesterification catalysts can be used.
An alternative but less desirable procedure for the preparation of ester lubricants of aspects of this invention would be to react the di-mer and monofunctional alcohol in the presence of ethylene oxide; in other words, the polyoxyalkylene glycol would be prepared in situ. Suitable cat-alysts and/or diluents could be added. For maximum control of the reaction and of the products obtained it is preferred that the polyoxyalkylene gly-- 30 col be prepared prior to reaction with the monofunctional alcohol and high molecular weight dibasic acid.
It is evident that considerable variation is possible in the ~0~7~';'~3 preparation of the esters of aspects of this invention; however, to obtain acceptable emulsifiability and lubrication it is necessary to maintain a balance between the high molecular weight dibasic acid and polyoxyalkylene glycol. The esters should contain at least 2% by weight reacted polyoxy-alkylene in order to obtain acceptable emulsification with water; however, the amount of polyoxyalkylene glycol reacted should not exceed 40% by weight since above this level the lubrication properties and the rust prop-erties begin to decrease. For best results the esters should contain 5 to 30 weight percent reacted polyoxyalkylene glycol.
- 10 The esters of aspects of this invention have acid values and hy-droxyl values less than 25 and preferably the acid values and hydroxyl values are less than 10. It is evident, therefore, that while the ester r compositions need not be balanced with regard to stoichiometry, best re-sults are observed when a balanced or essentially balanced ester is obtained.
The reactant charge can be varied, of course, depending on the particular process used to prepare the ester as discussed above. In general, however, the polyoxyalkylene glycol will range from 0.05 to 0.5 equivalent per equivalent of high molecular weight dibasic acid and, more preferably, will range from 0.1 to 0.4. The monofunctional alcohol will range from 0.5 to 0.95 equivalent per equivalent dibasic acid; however, best results are obtained with 0.6 to 0.9 equivalen~ monofunctional alcohol per equiv-alent dibasic acid. If other hydroxylic reactants are included in the ester preparation the amount of polyoxyalkylene glycol and/or monofunc-tional alcohol will be reduced accordingly. If a second carboxylic com-pound is included in the reaction the amount of dibasic acid will be re-duced accordingly. In general the amount of additional reactants, either hydroxyllc or carboxylic, will not exceed 0.4 equivalent and preferably will be less than 0.25 equivalent.
The ester lubricants of aspects of the instant invention find particular utility in metalworking operations where a high degree of cooling by the lubricant is required. The esters are preferably used as aqueous emulsions where the concentration of the ester in water ranges from 0.1 to 74t7~

25 percent by weight and, more preferably, from 1 to ]0~ by weight. The resulting aqueous lubricant formulations may be added to the metalworking ~ ~
; elements, such as, for example, the working rolls, or may be applied to the - -.
metal itself by spraying or immersion of the metal sheet in a suitable bath. These esters applied in the form of aqueous emulsions form a uni-form continuous lubricant film between the working rolls and the metal to .
~- provide efficient lubrication. In addition they have a high degree of cooling capacity. The lubricant emulsions are useful for the working of both ferrous and nonferrous metals. They may be formulated with other ad-ditives such as, for example stabilizers, corrosion inhibitors and the like.
The lubricant emulsions may be conveniently recycled for reuse with the result that considerablé economic advantage can be realized. Makeup water may be required to bring the ester to the original concentration. It may also be desirable upon recycling to strain or filter the residue in order to remove metal scale or other particles picked up during the processing ~
operation. This is particularly true where the aqueous lubricant emulsions ~ -are applied by the use of spray nozzles. -The esters of aspects of the present invention are readily emul- L~J
sifiable with water in the proportions indicated above and do not require the use of additional external emulsifying ~ids to obtain a stable emul-sion. The emulsions are readily formed using simple agitation and, once formed, the emulsions do not undergo rapid phase separation but remain emulsified for long periods. In certain instances where extremely stable emulsions are desired, it may be advantageous to add a small amount of one or more other external emulsifying aids commonly employed for this purpose;
however, this is not necessary to get a good emulsion .
In addition to use in the emulsified state, the esters of aspects of the present invention can also be used in the neat form, that is, the straight oil can be utilized as a lubricant. The modification of these esters with polyoxyalkylene glycol does not significantly impair the lubri- ---cating effectiveness of the esters. When used in the neat form the oil may be blended with o*her synthetic ester lubricants, mineral oils or the like g ~47~'~8 and combined with additives to achieve the desired formulation.
The following examples directed to the preparation of the esters ; described above and their utilization as lubricants illustrate the inven-tion more fully. All parts and percentages in the examples are given on a weight basis unless otherwise indicated.
EXAMPLE I
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To a glass reactor equipped with a stirrer, thermometer and water ~
trap fitted to a condenser were charged 212.8 gms hexadecyl alcohol (a com- ~ r mercially available complex mixture of primary alcohols characterized as

2,2-dialkyl-1-ethanols where the alkyl groups are typically methyl-branched), I
35.2 gms polyoxyethylene glycol having an average molecular weight of 400 and 252 gms dimer acid (a commercially available polymerized acid sold un- ~!e der the Trade Mark Empol 1018 and consisting of 83% C36 dibasic acid and 17% C54 tribasic acid). A slight excess of the hexadecyl alcohol was em-ployed based on the calculated equivalents charge ratio of 0.8:0.2:1.0 (hexadecyl alcohol:polyoxyethylene glycol:dimer). The reaction mixture was heated at 220C under a nitrogen atmosphere for 12 hours until the acid value had decreased to 3.8 and 15.7 mls were taken off. Acid values are ~h~ `
determined in accordance with A.O.C.S. Test Method Te la-64-T. The mixture was then heated to 250C. under vacuum for 1 hour to strip off the excess hexadecyl alcohol. 42.5 Grams hexadecyl alcohol were re ved. The result-ing lubricant ester had an acid value of 3.1 and hydroxyl value of 5.6.
A portion (20 mls) of the ester was poured into 100 mls of cold tap water while stirring with a glass rod. The ester immediately emulsi-fied. This emulsion was stable and showed no signs of phase separation af-ter standing 24 hours at room temperature. Even after 72 hours the emulsion ~ `
was not completely broken and was readily reformed with minimal agitation.
A 1% aqueous emulsion was prepared and used to determine the rust resistance of the aqueous lubricants. The test is conducted by placing a filter paper into a Petri dish and lightly sprinkling cast iron filings over the paper. The aqueous emulsion is then poured over the filings to wet the paper and cover about one-half the filings. The dish is covered, , ~

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allowed to stand undisturbed and the amount of discoloration (rust forma-tion) observed at 15 minute intervals. If after 2 hours there is no dis-; coloration or only a trace of discoloring the aqueous emulsion is consid- -, ered to have good resistance to rust formation. The rust resistance of the ~- 1% aqueous emulsion prepared with the above ester was rated good even un-, . . ~ .
der these severe test conditions.
To demonstrate the effectiveness of esters of aspects of this in-vention as lubricants, both as aqueous emulsions and in the neat form, they were evaluated using a Falex machine. This machine provides a convenient and reliable means of determining the film strength or load-carrying capac-ity of lubricants as extreme pressures are applied. Falex testing is recog-nized throughout the industry as a means of measuring the relative effective-ness of various lubricants. The Falex wear test (ASTM D 2670-67) utilized 60 gm sample of the ester lubricant or 5% aqueous emulsion thereof. The loading device is attached and the cup containing the sample positioned so that the steel pin and blocks are completely immersed in the test sample. ~`
The load is then increased to 350 pounds and run for 5 minutes. After this ~ time the load is further increased to 1000 pounds and maintained for 30 :-. ~
~ minutes. The difference between the readings taken at the beginning and end - 20 of the 30 minutes indicates the amount of wear. Each unit represents 0.0000556 inches of wear. The lower the wear number the better the mate-rial is considered as a lubricant. When dealing with 5% aqueous emulsions, wear values less than 25 are considered good and numbers less than 15 are rated excellent. A 5% aqueous emulsion of the above ester gave only 9 units of wear which is excellent.
To further demonstrate the ability of these aqueous emulsions to function as lubricants under extreme pressures, additional testing was con-ducted with the Falex machine. After satisfactory completion of the test-ing at 1000 pounds for 30 minutes the load is increased by 250 pounds and run for one minute at the increased load. If the metal pin does not fail this procedure is continued until failure. Upon failure, the last load reading prior to the failure is reported. The aqueous lubricant prepared " lU474'~'8 with the ester of an aspect of the prese~t invention satisfactorily with-stood a loading of 2750 pounds before failure.
EXAMPLE II r Employing equipment and chemicals similar to that described in Example I, except that isooctyl alcohol was substituted for hexadecyl alco-hol a lubricant ester was prepared. 351 Grams dimer acid and 49 gms poly-oxyethylene glycol were first reacted with stirring between 200C and 210C for 2 1/2 hours until the acid value was 136 and 3.5 mls water was collected. The reaction mixture was then cooled and 159.7 gms isooctyl alcohol charged. The reactor and its contents were then heated at 220C L
for 7 1/2 hours. After this time the acid value of the reaction mixture was 5.2. A vacuum was applied to the system for 1 hour to remove unreacted h isooctyl alcohol. The resulting ester product, which based on the amount of unreacted isooctyl alcohol recovered, contained 0.2 equivalent of PEG
400 and 0.8 equivalent Isooctyl alcohol reacted per equivalent of dimer acid, had an acid value of 5.2 and a hydroxyl value of 9.2. The ester had a flashpoint of 595F and firepoint of 640F as determined using ASTM test procedure D 92-66. ~iscosities (ASTM D 445-65) at 100F and 210F were ~-181 and 21.4 centistokes, respectively. The ester formed stable emulsions very readily without the aid of exte m al emulsifying aids. A 1% aqueous emulsion of the ester tested in accordance with the rust test previously described showed good resistance to rust formation. The Falex test on a 5% emulsion showed 25 and reached 2250 pounds before failure. Significant ~ -improvement of the performance properties of these aqueous emulsions is possible by the addition of suitable additives such as, for example, EP
agents, antifoam agents, bacteriostats, etc. and the emulsions give good response to the addition of these materials.
EXAMPLE III
To demonstrate the versatility of another aspect of this invention, a lubricant ester was prepared by reacting 1 equivalent dimer acid, 0.2 equivalent polyoxyethylene glycol, 0.3 equivalent neopentyl glycol and 0.5 equivalent 2-ethylhexanol. The reactants were added as a unit charge, ' .: ~()474'~ ~
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heated initially at 180C and then at 220C until the near theoretical amount of water was evolved. A vacuum was pulled on the system for one-half hour at 220C to remove the slight excess of 2-ethylhexanol which was present .; and unreacted. The reaction mixture was cooled and flltered after the ad-dition of a diatomacious earth filtering aid. The ester product had an acid value of 5.5, a flashpoint of 615F and firepoint of 655F. ~he vis- L~'S~
cosities of the ester at 100F and 210F were 376 and 37.4, respectively. ~b The ester emulsified readily and a 5% emulsion showed only 8 units wear in F
the F~lex 'est. This is even more surprising considering that the undilu-ted ester gave 116 units wear in the same test.
EXAMPLE IV
Following the procedure described in Example II, except that the monobasic alcohol was butanol, an ester was prepared utilizing 1 equivalent , .
dimer acid, 0.2 equivalent PEG 400 and 0.8 equivalent butanol. The final ester product had an acid value of 6.2, a hydroxyl value of 5.3, with flash- t;'~
and firepoints of 580F and 640F, respectively. Stable emulsions were ob-tained with the ester and a 1% aqueous emulsion was rated good in the rust ~'-test. Falex wear with a 5% aqueous emulsion gave only 20 units wear.
EXAMPLE V
Using a similar procedure and the reactants described in Example IV, except that the polyoxyethylene glycol had an average molecular weight of 600, a useful lubricant ester composition was similarly obtained. Sta-ble emulsions were readily prepared with the ester and these emulsions gave good results when evaluated in the rust test and Falex wear test.
EXAMPLES VI and VII
Employing a preparative technique similar to that described in Example II, esters having the following equivalents ratios were prepared:
EXA~IPLES
VI VII ;
Dimer Acid 1.0 eq. 1.0 eq.
PEG 400 0.1 eq. 0.4 eq.
2-Ethylhexanol 0.9 eq. 0.6 eq.

7~ 8 Ester VI was reacted to an acid value of 2.3 while the lubricant ester VII
had an acid value of 4.3. Both esters were readily emulsifiable with water with moderate agitation and the emulsions were homogeneous and did not un-dergo rapid phase separation. One percent aqueous emulsions of both of these esters had good ratings in the rust test. A 5% aqueous emulsion of r the ester of Example VI showed 25 units of wear in the Falex test while the emulsion prepared with the ester of Example VII gave 22 units of wear.
lhe superior and unexpected results obtained with the synthetic esters of an aspect of the present invention are evident from the following ~ 10 demonstration wherein an ester was similarly prepared except that the PEG L
i 400 was not included in the reaction. 'l`he ester was the reaction product of 1 equivalent dimer acid with 1 equivalent 2-ethylhexanol and had an ~' acid value of 2.5 and a hydroxyl value of 0.7. This ester was not emul-sifiable with either hot or cold water even with vigorous agitation. To obtain an emulsion with this ester required the use of 20 wt. % of an ex-ternal emulsifying aid (Igepal 630-the Trade Mark of a commercially avail-able ethoxylated nonyl phenol) and even then the emulsion was not stable. r An emulsion containing 5% of this ester gave 140 units of wear in the Falex ~-test. Also these emulsions had poor rust prevention properties. ~,.
EXAMPLES VIII - X
- Esters having an equivalent ratio of 1.0:0.2:0.8 (dimer acid:PEG
400:monobasic alcohol) were prepared. Various commercially available mixed straight-chain alcohols manufactured by the oxo process were used in these examples. For ester VIII a mixture of Clo and C12 alcohols was used while for preparation IX mixed C12 and C14 alcohols were employed. A mixture of linear alcohols containing 16 to 20 carbon atoms was used in Example X. r The table below sets forth the acid value and hydroxyl value obtained for the resulting esters and the results obtained in the Falex wear test and rust test with emulsions prepared with these esters:
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VIII IX X
Acid Value 2.2 2.2 2.3 Hydroxyl Value 8.5 6.2 7.6 .` ' ~, Rust Test Results Good Good Good ; Units Wear in Falex Test 20 11 10 .; ~. ,.
The emulsions obtained with the above esters were all homogeneous and had good stability. I i EXA~LE XI
An ester comprising the reaction product of 1 equivalent C36 di-basic acid, 0.2 equivalent polyoxyethylene glycol having an average molecu- I~vlar weight of 400 and 0.8 equivalent tridecyl alcohol, consisting mainly of tetramethyl-l-nonanols, was prepared using a procedure similar to that de-scribed in Example II. The resulting lubricant ester was readily emulsifi-able in water in all proportions and the emulsions so prepared had excellent stability and showed good rust resistance when placed in contact with cast iron filings. A 5~ aqueous emulsion of the ester gave only 11 units wear after 30 minutes testing at 1000 pounds and withstood 3250 pounds pressure before failure.
EXAMPLE XII
To demonstrate further the advantage of aspects of the present in-vention when compared to other esters an ester was prepared by reacting 1 equivalent of the dimer acid with 2 equivalents polyoxyethylene glycol (400 average molecular weight) at 200C to 220C until the acid value reached S.05. There were insoluble materials present when it was attempted to emul-sify this ester with cold water. The ester could be emulsified in hot water but after only one-half hour the emulsion was essentially, completely separated. An emulsion containing S~ by weight of the ester gave 139 units of wear in the Falex test.
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Claims (13)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An ester composition useful as a lubricant and having improved emulsifiability with water and rust protection properties comprising the condensation product of 0.05 to 0.5 equivalent polyoxyalkylene glycol having a molecular weight from 200 to 1000 and having recurring alkylene units containing from 2 to 4 carbon atoms, 0.5 to 0.95 equivalent monofunctional aliphatic alcohol of the formula ROH where R is an aliphatic hydrocarbon radical containing from 1 to 20 carbon atoms and 1.0 equivalent of dimer acid containing from 30 to 60 carbon atoms, said ester having an acid value less than 25, a hydroxyl value less than 25 and containing 2 to 40 percent by weight polyoxyalkylene glycol.

2. The ester composition of claim 1 wherein said dimer acid contains 32 to 52 carbon atoms and is obtained by the polymerization of a monocarboxylic acid containing from 16 to 26 carbon atoms.

3. The ester composition of claims 1 or 2 wherein the acid value is less than 10, the hydroxyl value is less than 10 and which contains from 5 to 30 weight percent polyoxyalkylene glycol.

4. The ester composition of claims 1 or 2 wherein the polyoxyalkylene glycol is a polyethylene glycol having a molecular weight from 300 to 800.

5. The ester composition of claims 1 or 2 wherein the polyoxyalkylene glycol is a polyethylene glycol having a molecular weight from 300 to 800, and further wherein 0.1 to 0.4 equivalent polyethylene glycol and 0,6 to 0.9 equivalent monofunctional alcohol containing from 6 to 16 carbon atoms are reacted per equivalent dimer acid and the ester contains 5 to 30 weight percent polyethylene glycol.

6. The ester composition of claims 1 or 2 wherein the polyoxyalkylene glycol is a polyethylene glycol having a molecular weight from 300 to 800, and further wherein 0.1 to 0.4 equivalent polyethylene glycol and 0.6 to 0.9 equivalent monofunctional alcohol containing from 6 to 16 carbon atoms are reacted per equivalent dimer acid and the ester contains 5 to 30 weight percent polyethylene glycol, and still further wherein the dimer acid contains 75% or more C36 dimer acid, the polyethylene glycol has a molecular weight of 400 and the acid value of the ester is less than 10.

7. The ester composition of claims 1 or 2 wherein the polyoxyalkylene glycol is a polyethylene glycol having a molecular weight from 300 to 800, and further wherein 0.1 to 0.4 equivalent polyethylene glycol and 0.6 to 0.9 equivalent monofunctional alcohol containing from 6 to 16 carbon atoms are reacted per equivalent dimer acid and the ester contains 5 to 30 weight percent polyethylene glycol, and still further wherein the dimer acid contains 75% or more C36 dimer acid, the polyethylene glycol has a molecular weight of 400 and the acid value of the ester is less than 10, wherein the monofunctional alcohol is 2-ethylhexanol.

8. An aqueous lubricant composition suitable for metal-working and having improved rust protection properties containing 0.1 to 25 percent by weight of an ester comprising the condensation product of 0.05 to 0.5 equivalent polyoxyalkylene glycol having a molecular weight from 200 to 1000 and having repeating alkylene units containing from 2 to 4 carbon atoms, 0.5 to 0.95 equivalent monofunctional aliphatic alcohol of the formula ROH where R is an aliphatic hydrocarbon radical containing from 1 -to 20 carbon atoms and 1.0 equivalent of dimer acid containing from 30 to 60 carbon atoms, said ester having an acid value less than 25, a hydroxyl value less than 25 and containing 2 to 40 percent by weight polyoxyalkylene glycol.

9. The aqueous lubricant composition of claim 8 wherein said dimer acid contains 37 to 52 carbon atoms and is obtained by the polymerization of a monocarboxylic acid containing From 16 to 26 carbon atoms.

10. The aqueous lubricant composition of claim 9 wherein the polyoxyalkylene glycol is a polyethylene glycol having a molecular weight from 300 to 800, the monofunctional alcohol contains from 6 to 16 carbon atoms and the dibasic acid is a dimer acid containing 32 to 52 carbon atoms.

11. The aqueous lubricant composition of claim 10 wherein 0.1 to 0.4 equivalent polyethylene glycol and 0.6 to 0.9 equivalent monofunctional alcohol are reacted per equivalent dimer acid, the ester contains from 5 to 30 weight percent polyethylene glycol and has an acid value less than 10 and a hydroxyl value less than 10.

12. The aqueous lubricant composition of claim 11 containing from 1 to 10 weight percent of an ester derived from a dibasic acid containing 75% or more C36 dimer acid, a poly-ethylene glycol having a molecular weight of 400 and 2-ethylhexanol.

13. The aqueous lubricant composition of claim 12 wherein the monofunctional alcohol is 2-ethylhexanol.