CA1055515A

CA1055515A - Water soluble triglyceride compositions and method for their preparation

Info

Publication number: CA1055515A
Application number: CA217,566A
Authority: CA
Inventors: Fred O. Barrett; Robert J. Sturwold
Original assignee: EMERY INDUSTRIES
Current assignee: EMERY INDUSTRIES
Priority date: 1974-01-31
Filing date: 1975-01-08
Publication date: 1979-05-29
Also published as: SE7501047L; AU496748B2; IT1033119B; JPS50108460A; AU7770675A; ES434298A1; ZA75569B; CH612991A5

Abstract

ABSTRACT OF THE DISCLOSURE

Water soluble mixed ester lubricants derived from triglycerides are obtained by transesterifying a triglyceride selected from animal oils or fats, or drying.
Semi-drying or non-drying vegetable oils with a low molecular weight polyoxyethylene glycol having a molecular weight of 200-1000, preferably from 400-800 in the presence of short-chain mono- or dicarboxylic acids having from 2 to 12 carbon atoms. The mixed ester compositions are readily water soluble and are excellent lubricants for metal working operations. Water solubility is achieved with the mixed ester products even though they have higher triglyceride contents than previously known ester lubricants.

Description

This invention relates to water soluble mixed esters.
The reaction of triglycerides and polyoxyethylene glycols to obtain mixed esters is known. For example, British Patent No. 847,517 published September 7, 1960 in the name of E. Mahler and M. Gattefosse shows the reaction of two mols triglyceride with one mol polyoxyethylene glycol at an elevated temperature in the presence of a catalyst to obtain partial interesterification while avoiding complete deesterification of the triglyceride. The resultino mixed ester compositions, consisting of mono-, di- and triglycerides with mono- and diesters of polyoxyethylene glycol, are miscible with hydrocarbons and emulsifiable with water. The ready emulsifiability of these materials is the result of a substantial portion of the mixture being mono- and diesters of polyoxyethylene glycols which are known nonionic surface active agents. United States - Patent No. 3,202,607 issued August 24, 1965 to J. E. Koch, Jr. shows the formation of polyoxyethylene adducts of castor oil containing from 10%
to 80% by weight combined ethylene oxide and the conhination of the resulting adducts with propylene glycol or dipropylene glycol to provide functional fluids for use as aqueous dispersions in the working of alloys and steels.
l~hile emulsions and dispersions of luhricant esters are accep-table in many applications there are some common problems associated with their use for lubrication. Their biggest drawback is the tendency to separate upon standing. Even the best lubricant ester emulsions are not stable indefinitely and upon prolonged standing, such as, for example, during storage, the emulsions separate and thus require re-emulsification which is costly and time-consuming. Additionally, it is often difficult to obtain uniform lubrication with lubricant emulsion systems particular-ly in high-speed operations. For these and other reasons the trend has been toward the use of lubricants which are water soluble, as opposed to those which are only emulsifiable or dispersible in water (see United States Patent No. 3,676,345 issued July 11, 1972 to V. P. Kuceski). Clear lubricant solutions are especially desirable since they have the added 10555~5 advantage that the operators can constantly visllally monitor the lubri-cant and determine the amount of contaminants, such as, for example, dirt and scale, picked up during the operation.
United States Patent No. 3,634,245 issued January 11, 1972 to I. D. Meisters discloses ester lubricants which are soluble in 100F.
water but which have distinct cloud points below 180F. and a two-step process for their preparation. To obtain the "water soluble" products of that invention, castor oil is first transesterified with 0.75 to 2.0 mol equivalents polyoxyethylene glycol having a molecular weight of at least 1000 until the reaction product is soluble, i.e., when 5 grams of the product are completely soluble in 100 mls of water at 100F. The product is then further modified in a separate and distinct step by reacting with a mono- or dicarboxylic acid. The second reaction is continued until the acid number of the composition falls below 6. This product is then diluted with water to obtaiD aqueous solutions contianing 5 to 50% by weight of the ester product.
While the ester compositions of United States Patent No.
3,634,245 are useful lubricants, they are not completely soluble in water at room temperature and they have distinct cloud points below 180F.
Other disadvantages are that the process requires two distinct reaction steps and is apparently limited to use with castor oil if useful products are to be obtained. Additionally, in order to obtain useful ester com-positions polymeric alkylene oxide glycols having molecular weights of at least 1000 are necessarily employed.
It would be extremely useful and advantageous if water soluble triglycerides could be obtained employing a one-step process and if the resulting products were readily soluble in cold water to give clear aqueous solutions. It would be still more useful if a wide variety of triglycerides and low molecular weight polyoxyethylene glycols could be .
used to obtain useful ~ubricants.

A ~ -2-Mixed ester products are provided herein which are obtained by a single-step transesterification reaction of triglycerides selected from the group consisting of animal oils, animal fats, drying vegetable oils, semi drying vegetable oils and non drying vegetable oils, low molecular A~ -2a-. . ~

weight (less than 1000) polyoxyethylene glycols and ' short-chain mono- or dibasic acids containing from 2 to 12 carbon atoms which are readily soluble in cold water in all proportions to provide clear lubricant solutions.
Aqueous solutions of these esters have superior lubricating properties. Additionally, the lubricants of aspects of the present inventlon have negative heats of solution so that while they are completely soluble in water at lower temperatures they come out of solution as the temperature is raised. This feature is highly desirable in certain metal working operations, such as, for example, hot rolling, since the ester lubricant will deposit from solution onto the surface of the metal to provide more effective lubrication.
Over and above the desirability of having water soluble ester lubricants with improved properties and negative heats of solution, the utility of aspects of this invention is enhanced by the ability to obtain these mixed ester products by a one-step reaction employing polyoxyethylene glycols having molecular weights less than 1000. Ester products having the above-mentioned desirable properties are not possible when high molecular weight polyoxyethylene glycols are substituted in the one-step reaction procedure of aspects of this invention.
The ester products of aspects of the present invention are obtained by the single-step reaction of a triglyceride selected from the group consisting of animal oils, animal fats, drying vegetable oils, semi drying vegetable oils and non-drying vep,et:able oils, a polyoxyethylene glycol having an average molecular weight less than 1000 desirab~y from 200 to 1000 and ~ . . . . .. _. .

preferably from 400-800, and a mono- or dicarboxylic acid containing from 2 to i2 carbon atoms. Especially useful in one variant of the present invention are triglycerides derived from predominantly ethylenically unsaturated C18 fatty acids, polyoxyethylene glycols having average molecular weights between 400 and 800 and in another variant, aliphatic acids containing 2 to 12 carbon atoms or cycloaliphatlc and aromatic acids containing from 7 to 12 carbon atoms. The ester compositions according to broad aspects of this invention will contain from 5 to 35% by weight triglyceride, 4 to 20 wt. %
carboxylic acid and 60 to 85 wt. % polyoxyethylene glycol, but preferably by a variant thereof, 10-30% triglyceride, 65-75~ polyoxyethylene, and 5-15% fatty acid. The ester products will generally have acid values of 10 or below.
0.1 to 25% by weight of the ester is preferably dissolved in water to provide the useful aqueous lubricant solutions.
r ~' -3a-1055S~5 The mixed ester compositions of aspectS of this invention are the reaction products of a triglyceride, a polyoxyethylene glycol of molecular weight less than lQ00 and a short-chain monobasic or dibasic acid. The transesterification reaction is completed in a single step to obtain the mixed esters which are soluble in cold water in all propor-tions to provide clear aqueous lubricant solutions which do not separate on standing. The lubricant esters of aspects of the present invention have excellent lubricating properties.
To obtain the ester compositions of aspects of this invention, any of the commonly known triglycerides can be employed and yield water soluble mixed ester products. Natural and synthetic fatty acid trigly-cerides including the drying, semi-drying and non-drying vegetable oils, animal oils and fats are useful and are within the scope of those which may be used to provide esters of aspects of the present invention. Tri-glycerides of the above types include olive oil, palm oil, almond oil, ground nut oil, apricot kernel oil, linseed oil, castor oil, soybean oil, oiticica oil, tung oil, crambe oil, coconut oil, peanut oil, rapeseed oil, neatsfoot oil, cottonseed oil, tallow, lard, whale oil and the like.
The oils may be used as such or may be hydrogenated or modified prior to use. They may be used individually or a mixture of two or more trigly-cerides employed. For example, if a highly conjugated triglyceride such as, for example, tung oil or oiticica oil, is used it may be advantageous to include a second oil of an unconjugated nature. Especially useful tri-glycerides for the preparation of the ester compositions of aspects of this invention are those derived from predominantly ethylenically unsatu-rated C18 fatty acids such as, for example, oleic acid, linoleic acid, linolenic acid and mixtures thereof. Oleic-linoleic acid oils and lino-lenic acid oils, and more particularly linseed oil and soybean oil, are especially useful triglycerides for use in providing esters of aspects of the present invention.
The polyoxyethylene glycols useful for the purpose of providing esters of aspects of this invention have average molecular weights less than 100 but preferably above 200. It is possible to employ polyoxy-ethylene glycols containing higher and lower molecular weight materials so long as the resulting mixtures fall within the approximate foregoing ranges. A broad molecular weight distribution of the polyoxyethylene glycols is generally not detrimental to the lubricant properties; how-ever, appreciable amounts of glycols having molecular weights greater than 1000 should not be present if optimum results are to be obtained.
Best results are obtained with polyoxyethylene glycols having average molecular weights between 400 and 800.
To achieve the improved water soluble mixed ester compositions of aspects of this invention one or more carboxylic acids are included when the triglyceride and low molecular weight polyoxyethylene glycol are reacted. Useful acids can generally be defined as low molecular weight short-chain mono- and dicarboxylic acids and, more specifically, contain from 2 to 12 carbon atoms. Acids suitable for use in the process include aliphatic, cycloaliphatic and aromatic acids which contain one or two carboxyl groups. Tri- and tetracarboxylic acids may also be employed if desired as may other polyfunctional compounds such as, for example, trimellitic anhydride. Useful cycloaliphatic and aromatic acids contain from 7 to 12 carbon atoms and include acids such as, for example, benzoic acid, phenylacetic acid, toluic acid, phthalic acids, p-tert butyl benzoic acid, cyclohexanecarboxylic acid, cyclohexanedicarboxylic acid and the like. Aliphatic acids can either be branched or straight-chain and can contain from 2 to 12 carbon atoms. Useful aliphatic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, suberic acid, dodecanedioic acid, acetic acid, buty-ric acid, valeric acid, caproic acid, caprylic acid, capric acid, lauric acid and the like. Especially useful acids for the purpose of provid~ng esters of aspects of this invention are aliphatic, preferably saturated and straight-chain, mono- and dicarboxylic acids containing from 6 to 10 carbon atoms.
Numerous water soluble mi~ed ester products can be obtained depending on the ratio of reactants employed. For best results, however, both from the standpoint of water solubility and lubricant properties, the triglyceride will constitute 5 to 35% by weight of the total reac-tant charge with the carboxylic acid and polyoxyethylene glycol compris-ing 1 to 20~ by weight and 60 to 85% by weight, respectively. Extremely effective lubricant esters which are readily soluble in cold water are obtained with 10 to 30% by weight triglyceride, 5 to 15% by weight car-boxylic acid and 65 to 75% by weight polyoxyethylene glycol. These ester products are particularly useful if derived from linseed or soybean oil, a C6 10 straight-chain saturated mono- or dicarboxylic acid and polyoxyethylene glycol having a molecular weight from 400 to 800.
Numerous advantages are realized when the above-described reactants are combined in the prescribed amounts as a unit charge and reacted in a single step. Most importantly, ester products having good lubricant properties and substantially complete solubility in cold water in substantially all proportions are obtained. Additional advantage is ; realized, however, from the fact that the so-produced esters have nega-tive heats of solution.
I~ile the above two features by themselves are useful and truly unexpected, there are still other important aspects of this invention including the ability to use low molecular weight polyoxyethylene glycols, the ability to achieve water solubility with reduced polyoxyethylene glycol contents and the ability to achieve water solubility regardless of the particular triglyceride used, which are also useful and highly desirable features. Previously, only high molecular weight polyoxyethy-lene glycols could be used if water solubility was to be achieved but it is now possible with this invention to use low molecular weight polyoxy-ethylene glycols and achieve the same result. Somewhat related to the ability to employ low molecular weight polyoxyethylene glycols is the fact that with this invention it is also possible to obtain water solubi-lity using reduced levels of polyoxyethylene glycol. Through the use of low molecular weight short-chain carboxylic acids it is possible to ~055515 reduce the polyoxyethylene glycol content by as much as 20% and still obtain water solub]e products. By so doing, the triglyceride content in the product is also increased, in some cases by as much as 10% and thus the resulting ester composition has much improved lubrication properties.
Still another surprisin~ and useful aspect of this invention is the fact that contrary to previously known processes which yielded water soluble esters with only a few of the more compatible triglycerides, such as, for exa~ple, castor oil, it is now possible to render a wide variety of ~commonly available triglycerides completely soluble in cold water.
While the present invention is primarily directed in its main aspect to water soluble mixed ester products, it is also possible, by utilizing reactant ratios outside the previously specified range, to obtain ester compositions which are not completely water soluble but which are, nevertheless, extremely useful for their lubricant properties.
These esters are typically readily emulsifiable with water without the use of external emulsifying aids and the resulting emulsions find general application in the treatment of fibers to reduce static charge buildup and improve the lubricity of the fiber and they are also highly efficient lubricants for metal working. These emulsions have the added advantage of improved stability, i.e. resistance to phase separation over lubricant emulsions formed with external emulsifiers. The improved emulsion properties apparently result from the presence of the mono- or dicarboxy-lic acid since similar ester compositions prepared in the same manner froma triglyceride and polyoxyethylene glycol but without the short-chain carboxylic acid do not possess these same characteristics.
The reaction of the triglyceride, polyoxyethylene glycol and mono- or dicarboxylic acid to obtain the useful mixed ester products is conducted in a single step in accordance with known transesterification procedures. The reaction mixture is typically maintained at an elevated temperature until an acid value less than 10, more preferably less than 6, is attained. The temperature of reaction may range from 100C. to 300C. but more usually will fall between 175C. and 275C. Water formed during the reaction is removed to facilitate esterification. While the use of reduced pressure is not necessary in carrying out the reaction it is often advantageous, especially in the latter stages of the reaction if low acid va]ues are desired, in order to drive the reaction to com-pletion. Catalysts are not essential to the successful completion of the transesterification; however, they are usually desirable in order to speed the rate of reaction. The amount and type of catalyst can be widely varied. Known catalysts such as, for example, tetrabutyl titanate, zinc acetate, sodium carbonate, sodium acid sulfate, p-toluence sulfonic acid, methane sulfonic acid, sulfuric acid, phosphoric acid and the like may be employed. The amount of catalyst will generally range between 0.01 to 1.0% by weight of the total reactant charge. Most often the catalyst charge will be from 0.03 to 0.5% by weight based on the total reactants.
The reaction may be conducted in an inert diluent which is unaffected under the reaction conditions employed. Hydrocarbon diluents, such as, for example, xylene, are useful in this process. Preferred diluents should be capable of forming azeotropes with water to facilitate removal of water formed durin~ the reaction. If diluents are not employed, which is the most commonly practiced method of conducting the reaction, the mixed ester reaction product can be directly utilized, i.e., as obtained from the reactor, without any additional treatment.
The mixed ester products of aspects of this invention consist primarily of monoglycerides, diglycerides, unreacted triglycerides, mono-esters of polyoxyethylene glycol, diesters of polyoxyethylene glycol and the like. Polymeric materials may also be present in small amounts parti-cularly if the low molecular weight short-chain carboxylic acid is a di-functional acid. The various constituents and the amount of each of these constituents present in the result~ng product is governed by the reactants and reaction conditions. While the makeup may vary considerably depending on the reaction temper2ture and pressure, amount and type of catalyst, ratio of reactants and the like, tllis compositional variation is not detrimental to the lubricant properties as long as the reaction is con-ducted in accordance with the foregoing description and within the speci-fied range of reactant ratios.
The mixed esters of aspects of the present invention vary in physical form from low viscosity liquids to semi-solid masses. While most of the mixed ester compositions are fluid oils~ highly viscous and even semi-solid products result if triglycerides, such as, for example, tallow, derived predominantly from saturated fatty acids are used. The clear liquid ester products which flow readily at room temperature are readily soluble in cold water in all proportions and give clear aqueous lubricant solutions which do not separate upon standing. With the more viscous oils or the semi-solid products it may be necessary first to heat or melt the ester product prior to addition of the water in order to obtain clear aqueous solutions. These products are, however, readily soluble upon melting and do not separate from solution evén upon cooling.
The mixed ester products of aspects of thi8 invention generally have r flash and fire points greater than 500F. with 210F. viscosities from lO to 20 centistokes and 100F. viscosities from 60 to 120 centistokes, more preferably the 210F. and 100F. viscosities of these products are between 12 and 16 centistokes and 70 and 90 centistokes, respectively.
The ester compositions of aspects of this invention are excel-lent lubricants for both ferrous and non-ferrous metals and are useful for a wide variety of other lubricating applications. They may be used as such or, as they are more commonly employed, in aqueous solutions.
Aqueous solutions are particularly useful in forging, rolling, diecasting and metalworking operations, particularly where the working of hot metals is involved, since these solutions are capable of providing a thin uni-form lubricant film on the surface of hot metals and since they also provide a high degree of cooling. These lubricants may also be used ln machining operations such as, for example, drilling, grinding, polishing, etc. to increase the tool life and improve the finish on the machined article. The fact that the aqueous lubricant solutions are clear and do not separate is also advantageous. The esters of aspects of the present invention and solutions thereof may be applied to the metal and/or metal-working elements or the metal by spraying, immersing or by similar means.
To improve the efficiency of the operation and reduce the cost, the lubricants may be collected, refiltered, if necessary, and reused.
For certain applications it is advantageous that these esters have negative heats of solution since the lubricant esters separate from solution at higher temperatures and are thus deposited on the surface of the hot metals or where friction occurs. As a result of this "plating out" maximum lubricating efficiency is provided at the points where it is needed most. This feature is also useful in certain rolling operations where heated rolls are employed since in this way a continuous lubricant film will be present on the surface of the roll and friction can be minimized thereby permitting more rapid rolling while retaining good -surface quality. Numerous other advantages for lubricants having nega-tive heats of solution are evident to those skilled in the art.
The esters of aspects of this invention may be formulated with other additives, stabilizers, corrosion inhibitors, and the like,and they may be blended witll one or more other petroleum or synthetic lubri-cants if desired. When employed in aqueous systems the concentration ofthe ester composition will normally range from 0.1 to 25~ by weight even though these esters mix with cold water in all proportions. Aqueous solutions of the present mixed ester products typically have cloud points above 95C.
In addition to being useful as lubricants for metals, the esters of aspects of this invention also find utility in other areas. Aqueous lubricant solutions of these esters are useful as finishing agents for polymeric fibers such as, for example, polyolefins, polyesters, polyamides and polyacrylonitriles. Such finishing agents are required during the processing of the fibers into yarns and fabrics to increase the surface lubricity of the fibers, thereby reducing the fiber-fiber friction and friction between the fibers and guides, draw pins, etc. of the process - 1055SlS

equipment. These lubricants can be applied to the fibers by spraying, immersing or the like. By lubricating the fibers it is possible to de-crease filament breakage, reduce static charge buildup in the fibers and facilitate the various process step. The ester of aspects of the present invention are especially suited for use in polyester and poly-amide fiber-forming operations. The esters may also be used for hydraulic fluids, paint formulations, cosmetic formulations, oil well drilling muds and osst other uses where synthetic ester lubricants are commonly employed.
The following examples illustrate the invention more fully.
All parts and percentages in the invention are on a weight basis unless otherwise indicated.

To a glass reactor equipped with a stirrer, thermometer, H-trap connected to a water cooled condenser and nitrogen inlet were cha ged 840 grams (2.86 equivalents) soybean oil, 2380 grams (11.9 equivalents) polyethylene glycol (PEG) having an average molecular weight of 400 and 280 grams (2.98 equivalents) azelaic acid (known by the Trade Mark of EMEROX 1144). The weight ratio of oil:PEG 400:acid was 24:68:8. This mlxture was heated with agitation while pulling a vacuum to dry the sys-tem. Tetrabutyltitanate catalyst (0.03 weight percent based on the total reactant charge) was then charged to the reactor and the reaction mixture heated to 250C. under a nitrogen atmosphere for 11 hou~s while periodi-cally taking samples to determine the acid value (AV). After 11 hours reaction the product (AV 0.19) was completely soluble in cold water to give sparkling clear solutions. Heating was terminated at this point.
The mixed ester product had a hydroxyl value of 141.2 and viscosities at 100F. and 210F. (ASTM D 445-65) of 78.8 centistokes and 12.9 centi-stokes, respectively.
To demonstrate the versatility of the resulting ester and the ability of the product to function as a lubricant, an aqueous solution of the ester was applied as a finish to a polyester yarn. Such finishes are commonly used to improve lubrication at the fiber-metal interface thereby re-ducing the static charge accumulation on the fiber during processing. The mixed ester was applied at 0.5% o.w.f. on 150 denier polyester which was sol-vent stripped to re ve any previous finish. Finishes were applied from aqueous solutions using an Atlab Finish Applicator. Before testing, the treated yarns were conditioned for 24 hours at 70F and 65% relative himidity.
Frictional properties of the yarn were then measured with a Rothschild F-Meter holding the tension constant at 100 grams using a yarn speed of 100 meters per minute and a yarn/metal contact angle of 180..Static properties were determined by insulating one of the pulleys and connecting it to a voltmeter and measuring the static 'ibuildup" on the pulley in 8 seconds.
The ester composition described above was compared to sorbitan monolaurate, a commercially available product commonly employed for textile finishing, and shown to have a lower coefficient of friction and a significantly lower voltage buildup (300 volts for the mixed ester as compared to 550 for the sorbitan ester) indicating improved fiber lubricity when the mixed ester product is used as a finishing agent.
EXAMPLE II
Employing a procedure similar to that described in Example I the following materials were charged to a reactor:
GRAMS CHARGED WEIGHT RATIO
Cochin Coconut Oil 120 24 Polyethylene Glycol 400 340 68 Azelaic Acid 40 8 About one-half of the tetrabutyltitanate catalyst was added at the beginning of the heating and the remainder charged after a portion of the water had been removed. Heating (250C) was terminated when the acid value of the re-action product reached 5.3. The resulting mixed ester product containing 68% bound polyoxyethylene glycol, had a viscosity of 70.6 centistokes at 100F, and was immediately soluble in cold tap water with essentially no agitation.
The effectiveness of the mixed ester product of this Example as a metal-working lubricant was determined using a Falex machine. This machine provides a convenient and reliable method for determining the film strength or load-carrying properties of lubricants under extreme pressures. The Fa-lex wear test (ASTM D 2670-67) is conducted with a 60 gram sample of the es-ter product or, if aqueous solutions of the mixed ester lubricants are being evaluated, a 600 gram sample of the aqueous solution is used. The cup con-taining the lubricant is positioned so that the steel pin and blocks are com-pletely immersed in the sample. The machine is started and an initial load of 300 pounds applied for 5 minutes. The load is then increased to 1000 pounds and maintained for 30 minutes. The difference between the readings taken at the beginning and the end of the 30 minute periods indicates the amount of wear. The mixed ester product of Example II showed only 47 units wear. This is a marked improvement over mineral oil of comparable viscosity which fails before the 1000 pound load level is reached and dioctyl sebacate which fails at the 300 pound load level after only 30 seconds operation. A
5~ aqueous solution of the mixed ester evaluated on the Falex machine also registered only 71 units wear. These results demonstrate the superior lub-ricating properties of the mixed ester products of the present invention.
EXAMPLE III
A reaction was conducted employing identical amounts and types of reactants as described in Example I. Zinc acetate (0.1 percent by weight based on the soybean oil) was used to catalyze the reaction. After about 5-1/2 hours of heating at 250C the acid value dropped to 0.9. The resulting lubricant ester product had a hydroxyl value of 85.6, flash and fire point (ASTM D 92-66) of 550F and 590F, respectively, and a 210F viscosity of 12.6 centistokes. The product was readily soluble in cold water producing a clear solution effective as a lubricant for both metal and fiber uses.
When the above Example was repeated using polyoxyethylene glycol having an average molecular weight of 800 a similar product was obtained.
EXAMPLES IV - VII
To demonstrate the versatility of this invention and the ability to obtain water soluble ester lubricants with triglycerides other than soybean oil and coconut oil, a series of r~ns were conducted in which PEG 400 andazelaic acid were reacted with linseed oil, palm oil, tallow and castor oil.
In each of these runs the triglyceride constituted 24% of the charge with polyoxyethylene glycol (68%) and azelaic acid (8%) making up the remainder.
The reactisns were all conducted similarly, following the procedure of Example I. Physical properties and Falex test results for the resulting ester prod-ucts are set forth below. Cloud points for the esters were obtained by determining the temperature at which printed matter was no longer legible through 100 mls of a 5% aqueous solution of the ester in a 250 ml glass bea-ker. At room temperature and below all of these products provide sparkling clear solutions, however, as these solutions are heated they become cloudy.
N NO. IV V VI VII
Triglyceride Linseed Palm Oil Tallow Castor Oil Oil Acid Value 0.3 0.7 0.2 1.2 100F Viscosity (cS)74.8 81.5 82.0 110 210F Viscosity (cS)12.5 12.8 12.7 15.6 Flash Point (F) 555 515 505 530 Fire Point (F) 590 565 560 575 Cloud Point (F) 97 102 100 100 Units of ~Year on the Falex Machine:
100~ Ester 25 34 37 22 5% Ester in Water 96 100 107 73 The ability to obtain clear solutions with palm oil and tallow is truly sur-prising in view of the fact that these saturated triglycerides are generally very difficult even to emulsify.
EXAMPLES VIII - XII
A series of water soluble soybean oils were prepared in accordance with the already described procedures. The polyoxyethylene glycol used had an average molecular weight of about 400 but the modifying acids were varied to include aliphatic and aromatic mono- and dicarboxylic acids. The weight ratio of soybean oil:PEG 400: acid was 24:68:8. The following table lists the various acids used and the properties of the resulting esters.

EXAMPLE NO. ACID COMPONENT ACID VALUE CLOUD POINT (F) VIII pelargonic 1.4 102 IX p-tert-butylbenzoic 0.5 91 X dodecanedioc 1.5 118 XI isophthalic 0.5 90 XII terephthalic 2.0 88 All these esters provided sparkling clear solutions in concentrations of 5 to 25% using room temperature tap water. These esters had good lubricating abil-ity both as the neat oils and in aqueous solution.
EXAMPLE XIII
A preparation was made using soybean oil, azelaic acid and polyoxy-ethylene glycol having an average molecular weight of 2000. The procedure, weight ratios of reactants and catalyst were the same as in Example II. The reaction was continued until an acid value less than 10 was achieved. m e resulting ester product did not form a clear solution with room temperature water but was readily emulsifiable to provide a moderately stable emulsion.
EXAMPLE XIV
Soybean oil was modified following the procedure of Example I ex-cept that the reactant charge was varied. In this preparation the weight ratio of soybean oil:PEG 400:azelaic acid was 28:78:1. m e ester product was read-ily soluble in water at room temperature and had good lubricating properties.
EXAMPLES XV - XVII
Palm oil, castor oil and coconut oil were charged as follows with PEG 400 and azelaic acid:
EXAMPLE WEIGHT PERCENT OF TOTAL CHARGE

Palm Castor Coco PEG Azelaic Oil Oil Oil 400 Acid These materials were reacted in the usual manner to obtain mixed ester products having acid values of 0.1, 2.6, and 2.8 respectively. The ester products demonstrated good lubricant properties when evaluated with the Falex machine and they formed clear aqueous solutions at room temperature.
EXAMPLE XVIII
The versatility of the present process and the ability to obtain useful ester products using low molecular weight short-chain carboxylic acids, even though the reactant ratios are outside the defined ranges, is evident from the following preparation where soybean oil, PEG 400 and azelaic acid were reacted at a weight ratio of 90:6:4. Tetrabutyltitanate was used to catalyze the reaction which was carried out at 200C. The ester obtained (AV 5.4) did not form a clear solution with water but was readily emulsifi-able in water without the use of external emulsifying aids. The ester had viscosities at 100F and 210F of 44cS and 9.2cS, respectively, with a 550F
flash point and 625F fire point. A 5% aqueous emulsion of the ester showed essentially no wear at the end of the standard testing period in the Falex machine while the neat oil gave only 49 units wear.

Claims

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

1. A water soluble mixed ester product obtained by the single-step transesterification of:
(a) a triglyceride selected from the group consisting of animal oils, animal fats, drying vegetable oils, semi-drying vegetable oils and non-drying vegetable oils;
(b) a polyoxyethylene glycol of average molecular weight from 200 to 1000; and (c) a carboxylic acid containing one or two carboxyl groups and from 2 to 12 carbon atoms; said reactants (a), (b) and (c) respectively comprising 5 to 35%, 60 to 85% and 1 to 20%, by weight, of the total charge.

2. The water soluble mixed ester product of claim 1 wherein (a) is derived predominantly from C18 fatty acids containing ethylenic unsaturation and (c) is an aliphatic acid.

3. The water soluble mixed ester product of claim 2 having an acid value less than 10 with flash and fire points greater than 500°F., at 210°F viscosity from 10 to 20 centistokes and a 100°F. viscosity from 60 to 120 centistokes.

4. The water soluble mixed ester product of claim 1 wherein (b) is a polyoxyethylene glycol having an average molecular weight from 400 to 800.

5. The water soluble mixed ester product of claim 4 wherein (a) is an oleic- linoleic acid oil or linoleic acid oil, (b) is a polyoxyethylene glycol having an average molecular weight from 400 to 800 and (c) is a saturated, straight-chain aliphatic mono- or dicarboxylic acid containing 6 to 10 carbon atoms.

6. The water soluble mixed ester product of claim 5 where (a) is linseed oil or soybean oil.

7. The water soluble mixed ester product of claim 5 wherein the reactant charge is comprised 10 to 30% (d), 65 to 75% (b) and 5 to 15% (c).

8. An aqueous solution of the mixed ester product of claims 1, 4 or 6 said solution being clear at room temperature but having a distinct cloud point above 95°F.