Water-dispersible lubricating blend for metal working processes

Abstract

The invention relates to an aqueous mixture of esters and acids from the reaction of at least one polyhydric alcohol and at least one monoacid and at least one diacid coupled with a surfactant and an effective amount of base to solubilize the mixture.

Description

TECHNICAL FIELD

[0001] The invention relates to water-soluble or water-dispersible physical blends of a mixture of polymeric esters, polymeric partially esterified acids, salts derived thereof, and polyethylene glycol fatty esters. These blends can be used effectively in processing metal parts made of a variety of metals such as steel and aluminum.

BACKGROUND OF THE INVENTION

[0002] The machining industry employs lubricants which are often described generically as metal working fluids to reduce friction and wear generated during metal processes. If a metal working fluid is used by diluting it further with tap water, the fluid is called a coolant or a soluble oil. Coolants by definition contain no petroleum-derived oils, but rather water-soluble or water-dispersible components and are formulated using water as a base carrier for all other components. By contrast, soluble oils consist of both oil-soluble and water-soluble components with a petroleum oil being used as the base carrier for all other components.

[0003] Coolants are generally preferred due to the fact that they contain no petroleum oil which is not readily biodegradable, and therefore, undesirable in subsequent waste water treatment processing. Coolants may contain water-soluble additives which can be ethoxylated surfactants, polyol esters of carboxylic acids, salts of fatty acids, or salts of chlorinated fatty acids. The salts can be sodium, potassium, or amine salts. The amine salts can be made by neutralizing fatty acids with alkanolamines such as monoethanolamine and triethanolamine.

[0004] Presently, soluble oils used in processing steel and aluminum often contain chlorinated additives which are synthesized by substituting hydrogen atom in the hydrocarbon chains of paraffin waxes with chlorine atoms. Soluble oils containing chlorine function extremely well in processing steel and aluminum. Chlorine-containing soluble oils are the metal working fluids of choice for most severe applications involving both steel and aluminum. The drawback for this type of metal working fluid again is waste water treatment involving the separation of water-insoluble petroleum oil and the disposal of chorine-containing additives.

[0005] At the present, commercial water-soluble additives tend to create a foaming problem when a coolant is circulated during use. If the fatty acid is a chlorine-containing additive such as chlorinated stearic acid commonly used for processing steel and aluminum, its amine salt can cause severe foaming and corrosion. Additionally, there is a concurrent concerted effort in the machining industry to avoid all chlorine and amine-containing additives due to the costly procedures required to separate and treat chlorine-containing waste which can generate hydrochloric acid if incinerated. Amines are also undesirable due to the possibility of formation of carcinogenic nitrosamine in used coolant. In addition to the amine salts, sodium and potassium salts of fatty acids can be utilized as an alternative way to solubilize fatty acids which otherwise are insoluble in water. However, the solutions or dilutions of these salts tend to foam severely, and their foams in many cases are very stable, breaking at a very slow rate.

[0006] Moreover, another deficiency in the prior art is that the best coolant thus far in the market cannot match the performance of chlorine-containing soluble oil in processing aluminum parts. Again, soluble oils are less desirable than coolants due to more difficulty in treating petroleum oil and other insoluble additives. Therefore, it is highly desirable to develop a coolant totally free of petroleum oil which can perform equally well to soluble oil counterpart in aluminum applications.

[0007] The water-dispersible lubricating additive combination described in this invention satisfies all the foregoing mentioned deficiencies of the prior art. It can consist of either amine, sodium, or potassium salts of polymeric esters or partially esterified polymeric carboxylic acids. And its sodium or potassium salts are very low-foaming in nature due to the high molecular weights of the polymeric esters and acids. The coolant can be made amine-free by employing sodium or potassium hydroxide in forming the corresponding salts. It can be used to formulate chlorine-free coolant as it contains no chlorine. It can be used to formulate a very effective coolant in processing aluminum with a comparable performance to a chlorine-containing soluble oil which so far is the best in the market for such an application. The coolant of the present invention is highly desirable due to the non-toxic nature of all its components.

SUMMARY OF THE INVENTION

[0008] In accordance with the present invention, there is provided a water-dispersible lubricating additive combination which removes essentially all of the foregoing mentioned deficiencies of the prior art. The invention covers physical blends of a mixture of polymeric esters, polymeric partially esterified acids, salts derived therefrom, and a polyethylene glycol fatty ester.

[0009] It is an object of this invention to formulate a low foaming coolant which contains either amine, sodium, or potassium salts of polymeric esters or partially esterified polymeric carboxylic acids.

[0010] It is another object of this invention to formulate a low foaming coolant which is amine-free by employing sodium or potassium hydroxide in forming the corresponding salts.

[0011] It is yet another object of this invention to formulate a chlorine-free coolant.

[0012] It is still yet another object of this invention to formulate a coolant which is non-toxic.

[0013] It is,a further object of this invention to formulate a coolant which is low-foaming in nature due to the high molecular weights of the polymeric esters and acids.

[0014] These and other objects of this invention will be evident when viewed in light of the detailed description and the pending claims.

DETAILED DESCRIPTION OF THE INVENTION

[0015] Two major components are believed to be responsible for the performance of the novel lubricating additive blend: (1) the polymeric esters and partially esterified acids; and (2) a polyol ester of a fatty acid.

[0016] The first major performance component which is described herein as “complex” or “polymeric” esters and partially esterified acids mean a mixture of esters and acids from the reaction of two or more of monohydric aliphatic alcohols, monobasic aliphatic acids, aliphatic glycols or polyglycols, polyhydric aliphatic alcohols, dibasic aliphatic acids, or polybasic aliphatic acids, where at least one polyhydric alcohol and at least one polybasic acid are used. The preferred monobasic acid is isostearic acid or oleic acid. The preferred polybasic acids are sebacic acid, adipic acid, azelaic acid and dimethylpropionic acid. The preferred polyhydric alcohols are pentaerythritol, dipentaerythritol, neopentyl glycol, trimethylolpropane. The polyols can have internal ether linkages. These alcohols and carboxylic acids used in preparing polymeric esters have either straight or branched chains, and hydrocarbon chain lengths ranging from 4 to 25 carbon atoms.

[0017] This kind of polymeric esters and acids have a final form of a clear viscous fluid with an acid number of 4 to 65 mg KOH per gram of sample. As the polymeric component inherently contains some partially esterified acids, it can be converted into the corresponding salts by neutralizing the acids with a strong base such as sodium hydroxide or alkanolamines in order to achieve a water-soluble or water-dispersible form, applicable to a coolant formulation.

[0018] Thus far, there is no commercial product equivalent to the salts of polymeric esters and acids. The present commercial unneutralized mixture of polymeric esters and acids are Syn-Esters GY-series offered by Gateway Additive Division of Lubrizol Corporation. The polymeric esters and acids described herein were also described in U.S. Pat. Nos. 3,016,353, 4,130,494, 5,798,322 which describe the synthetic methods, compositions of the polymeric esters or end uses and lubricating formulation containing such a polymeric esters and acids. However, none of these patents cover the use of such an additive composition in a water-dispersible or water-reducible lubricant application or coolant.

[0019] The second major component is an ester of a polyethylene glycol and a fatty acid. This component, besides providing additional lubricity, provides a coupling or solubilizing effect to the salts of polymeric acids and esters helping the latter to disperse more easily in water. This polyol ester can be substituted successfully with the following similar chemical class of surfactants or couplers such as polyoxyethylene alkyl esters, nonionic surfactants, ethoxylated alcohol, polyethyleneglycols, poly(ethyleneoxy)ethanol, alcohol ethoxylates, ethoxylated carboxylic acid esters, ethoxylated phosphate esters, polyethylene glycol fatty ester, ethoxylated fatty acids, amine ethoxylate, or hydroxy alkanolamine ethoxylated, alkyl amide ethoxylate.

[0020] All these above-mentioned chemicals might have been described more than once using different terminology. For ethoxylated alcohols, their derived carboxylic esters and phosphate esters are also covered in this invention. All these coupling surfactants or esters share the common characteristic of either containing ethylene oxide or ether linkages,—(CH2CH2O)—.

[0021] A physical blend of the following composition can be made simply by mixing all components together without any heating or special treatment:

EXAMPLE #1

[0022] The synthesis of the polymeric acids and esters may be effected as follows. Into a 1000-ml four-necked round bottom flask, equipped with a nitrogen sparger, a Celsius thermometer, a reflux condenser, and a mechanical mixer, 615.55 grams or 2.1244 moles oleic acid; 186.25 grams or 0.9223 mole sebacic acid; 136.00 grams or 1.0000 mole pentaerythritol; and 1 gram methane sulfonic acid catalyst were charged. Subsequently, gradual heating was applied along with gentle nitrogen sparging. The batch was refluxed at 120-135° C. for about one hour to dissolve most of pentaerythritol. After one hour, the reflux condenser was removed to allow the cooking temperature gradually rose to the final temperature of 150° C. The batch was maintained at 150° C. with a gentle nitrogen sweep until an acid number of 13-65 mg KOH/g, preferably 14-40 mg KOH/g or a predetermined value was obtained.

EXAMPLE #2

[0023] A water-dispersible lubricating blend or coolant was made by blending the polymeric acids esters cited in Example #1 with a polyethylene glycol oleate (PEG 400) (M.W. 400), and with the other ingredients, and having the following composition on a weight percentage basis.

Components                       Weight %
Polymeric esters and acids (Ex. #1) 45.85%
Polyethylene glycol (PEG 400) oleate 27.51%
20% caustic solution             6.99%
Propylene glycol                 6.30%
Tap water                        5.90%
TOTAL                            100.00%

EXAMPLE #3

[0024] A foaming test was performed using the blend of Example #2.

[0025] 100 mls of a 2% aqueous dilution of Example #2 was placed in 100 ml graduated cylinder which was also equipped with a glass stopper. The whole cylinder was shaken violently for about ten times. The initial foam height was measured in term of milliliters of foam generated. The rate of foam breaking was also observed.

Sample	Initial Foam Height	Foam Breaking
2% Example #2 in water	3 ml	very fast
2% sodium salt of chlorinated stearic acid (32% Cl)	>50 ml	very slow

EXAMPLE #4

[0026]

A FALEX EP Test (ASTM D 2670-67) was performed with the following results.
Sample	Falex EP Max. Load	Torque
2% Example #2 in water	4,000 lbs	51 lb-in.
2% sodium salt of chlorinated stearic acid (32% Cl)	4,000 lbs	64 lb-in.

[0027] A maximum load of 4,000 pounds out of a possible 4,500 pounds is indicative of very good performance for a coolant. The blend of Example #1 which is formulated in Example #2 of this invention performed equally well to a sodium salt of a chlorinated stearic acid, which is a commercial additive standard for a high performance coolant.

EXAMPLE #5

[0028] A tapping torque test was performed with aluminum parts, using a MegaTap II -G8 unit manufactured by MicroTap USA Inc.

Sample	Average Torque
2% Example #2 in water	94	N-cm
2% commercial soluble oil (15% Cl)	94	N-cm
2% sodium salt of chlorinated stearic acid (32% Cl)	100	N-cm
100% tap water (no additive)	>120	N-cm

[0029] A good lubricant should generate the least friction or the least torque during such an operation as tapping. This test illustrates that the blend of Example #1 as formulated in Example #2 of this invention is essentially equivalent to the chlorinated soluble oil which is the best candidate in processing aluminum. It also illustrates that Example #2 is far better than a typical commercial coolant represented here by the solution of sodium salt of chlorinated stearic acid.

EXAMPLE #6

[0030] A tapping torque test was performed with steel parts, using a MegaTap II-G8 unit manufactured by MicroTap USA Inc.

Sample                           Average Torque
2% Example #2 in water           181 N-cm
2% commercial soluble oil (15% Cl) 183 N-cm

[0031] A difference of two percent or higher in the average tapping torque is statistically significant based on field correlation. In this example, the two lubricating solutions are considered equal in performance on steel.

EXAMPLE #7

[0032] A corrosion test was performed using polished metal strips of steel, copper, or aluminum which were submersed in a 2% testing solution of Example #2 inside a closed glass jar. The whole set-up was then placed in 70° C. oven for 24 hours. And any staining observed on the metallic surface was noted.

Sample                 Staining
2% Example #2 in water no stain on copper strip
                       no rust on steel strip
                       slight stain on aluminum strip (same as pure
                       water)

[0033] Example #2 of this invention is non-corrosive to a variety of metallic surfaces.

EXAMPLE #8-#14

[0034] A series of polymeric acids and esters were prepared in accordance with the following molar quantities evidenced in the table. Into a 1000-ml four-necked round bottom flask, equipped with a nitrogen sparger, a Celsius thermometer, a reflux condenser, and a mechanical mixer, a diacid, a monoacid and pentaerythritol were charged with a catalytic amount of methane sulfonic acid catalyst. Subsequently, a gradual heating was applied along with gentle nitrogen sparging. The batch was refluxed at 120-135° C. for about one hour to dissolve most of pentaerythritol. After one hour of refluxing, the reflux condenser was removed to allow the cooking temperature gradually rose to the final temperature of 150° C. The batch was maintained at 150° C. with a gentle nitrogen sweep until an acid number of 13-65, preferably 14-40 mg KOH/g was obtained.

Moles	Ex. #8	Ex. #9	Ex. #10	Ex. #11	Ex. #12	Ex. #13	Ex. #14
sebacic acid	1.00	0.91	0.92	0.92	0.92	0.93
azelaic acid							0.92
isostearic acid						2.19
oleic acid	2.01	2.15	2.12	2.12	2.12	—	2.12
pentaerythritol	1.00	1.00	1.00	1.00	1.00	1.00	1.00
SSU/100° F. of	gelled	115,494	15,793	3,700	651	18,294	30,250
polymeric acids/esters
mg KOH/g of		13.1	26.0	47.2	65.2	21.6	23.9
polymeric acids/esters
Clarity of Coolant	N/A	hazy	clear	clear	clear	clear	clear
(Example #2)
Tapping torque	N/A		94	96	105	93.5	94
(N-cm)(1)
Tapping efficiency(2)	N/A		100	98	87.5	100.5	100.0
Falex EP Load (lbs)(3)	N/A		4,000	4,000	3,250	4,000	4,000
(1)run at 2% dilution with tap water, against 2% commercial soluble oil (15% Cl)
(2)<100% tapping efficiency is undesirable
(3)Falex EP tests were stopped after 4,000 lbs load was achieved

[0035] Therefore, what has been shown is that by reacting: (1) at least one polyhydric alcohol; (2) at least one polybasic acid; and (3) at least one monobasic acid, then combining the mentioned polymeric acid esters with a polyester of a fatty acid, a water-soluble coolant can be formulated with properties superior or equal to those oil-based formulations present used. In a preferred embodiment, the polyesters or polymeric acid esters composition will have a viscosity of about 100,000 to about 600 SSU at 100° F. and an acid number of about 13-65 mg KOH/g.

[0036] Therefore, what has been shown is that the molar ratio of the charge for polymeric acid ester synthesis should fall within the following range: diacid/monoacid/polyhydric alcohol of 0.6-1.4/1.6-2.4/1.0, more preferably, 0.8-1.2/1.8-2.2/1.0, most preferably, 0.9/2.1/1.0.

Component	General Formula	Preferred Mole Ratio
mono acids	R1—CO2H	0.91
	wherein R1 is selected from the group consisting of
	C5-20 alkyl, C5-20 alkenyl, C6-26 aryl, C6-30 alkaryl and
	C6-30 aralkyl, including branched and straight chain
	moieties
diacids	HO2C—R2—CO2H	2.12
	wherein R2 is selected from the group consisting of
	C2-36 alkyl, C3-36 alkenyl, C6-42 aryl, C6-42 alkaryl and
	C6-42 aralkyl, including branched and straight chain
	moieties
polyhydric alcohols	1	1.00
	and
	2
	wherein
	each R3 is selected independently from the group
	consisting of H, (R4)nOH, C1-12 alkyl, C2-14 alkenyl,
	C6-36 aryl, C6-36 alkaryl and C6-36 aralkyl, including
	branched and straight chain moieties;
	R4 is selected from the group consisting of C1-8
	alkyl, C2-8 alkenyl, including branched and straight
	chain moieties;
	R5 and R6 are independently selected from the
	group consisting of R4;
	x is an integral value from 2-4 inclusive;
	y is an integral value from 0 to 1 inclusive;
	z is an integral value from 0 to 1 inclusive; and
	n is an integral value from 0 to 1 inclusive.
alkylene glycol fatty acid ester	3
	wherein
	R7 is selected from the group consisting of C2-36
	alkyl, C3-36 alkenyl, C6-42 aryl, C6-42 alkaryl and C6-42
	aralkyl, including branched and straight chain
	moieties;
	R8 is selected from the group consisting of C1-6 alkyl
	and C2-8 alkylene;
	a is an integral value from 1 to 40.

[0037] It is of course recognized that both branched and unbranched moieties are included in the Markush formulations presented above. It is additionally defined that when the term “alkaryl” is used, that a moiety that combines both alkyl and aryl groups is meant, and that the aryl properties predominate, and that when the term “aralkyl” is used, that a moiety that combines both aryl and alkyl groups is meant, and that the alkyl properties predominate.

[0038] In a preferred embodiment, the physical properties of the polymeric acid esters should be:

Property                   Value
Acidity or mg KOH/g sample 15-40
Optimal acidity            24
Viscosity, SSU/100° F.     4,000-30,000
Optimal Viscosity          15,000

[0039] While not being held to any one theory of operation or methodology, it is believed that at least some mono acids are necessary to practice the invention to tie up some base and minimize crosslinking as well as control the molecular weight of the polymeric acid esters, which could crosslink and gel if the molecular weight is too high. The amount of base added can vary within experimental ranges determined by the amount required to make the composition water-soluble. The polyesters formed are believed to be highly branched and “star-like” moieties. Before neutralization, they are water insoluble, but after addition of a sufficient quantity of base, they become water-soluble.

[0040] This invention has been described in detail with reference to specific embodiments thereof, including the respective best modes for carrying out each embodiment. It shall be understood that these illustrations are by way of example and not by way of limitation.

Claims

1. A water-soluble or water-dispersible composition which comprises a combination of a reaction product of a monoacid, a diacid and a polyhydric alcohol inclusive of their derived salts with a polyalkylene glycol ester and further wherein (a) said monoacid and salts thereof is of formula (I) R1—CO2H wherein R1 is selected from the group consisting of C5-20 alkyl, C5-20 alkenyl, C6-26 aryl, C6-30 alkaryl and C6-30 aralkyl; (b) said diacid and salts thereof is of formula (II) HO2C—R2—CO2H wherein R2 is selected from the group consisting of C2-36 alkyl, C3-36 alkenyl, C6-42 aryl, C64-2 alkaryl and C64-2aralkyl; (c) said polyhydric alcohol is selected from the group of formulas (III) and (IV) R34−x—C—((R4)nOH)x and R34−x—(R5)y—O—(R6)z—((R4)nOH)x wherein each R3 is selected independently from the group consisting of H, (R4)nOH, C1-12 alkyl, C2-14 alkenyl, C6-36 aryl, C6-36 alkaryl, C6-36 aralkyl and salts thereof; R4 is selected from the group consisting of C1-8 alkyl and C2-8 alkenyl; R5, R6 are independently selected from the group consisting of R4; x is an integral value from 2-4 inclusive; y is an integral value from 0 to 1 inclusive; z is an integral value from 0 to 1 inclusive; and n is an integral value from 0 to 1 inclusive; and (d) said alkylene glycol ester is of formula (V) 4wherein R7 is selected from the group consisting of C2-36 alkyl, C3-36 alkenyl, C6-42 aryl, C6-42 alkaryl and C6-42aralkyl; R8 is selected from the group consisting of C1-6 alkyl and C2-8 alkylene; and a is an integral value from 1 to 40.

2. The composition of claim 1 wherein (a) a molar ratio of said diacid/monoacid/polyhydric alcohol is between a range of ratios of about 0.6-1.4/1.6-2.4/1.0.

3. The composition of claim 2 wherein (a) said molar ratio is between a range of ratios of about 0.8-1.2/1.8-2.2/1.0.

4. The composition of claim 3 wherein (a) said molar ratio is about 0.9/2.1/1.0.

5. The composition of claim 3 wherein (a) said composition has a viscosity of about 100,000 to about 600 SSU at 100° F.

6. The composition of claim 5 wherein (a) said composition has an acid number of about 13-65 mg KOH/g.

7. The composition of claim 1 wherein (a) said monoacid is selected from the group consisting of oleic acid and isostearic acid; (b) said diacid is selected from the group consisting of sebacic acid, azelaic acid, adipic acid and dimethylpropionic acid; (c) said polyhydric alcohol is selected from the group consisting of pentaerythritol, dipentaerythritol, neopentyl glycol and trimethylol propane; and (d) said polyalkylene glycol ester is polyethyleneglycol oleate having a molecular weight of about 400.

8. The composition of claim 7 wherein (a) said monoacid is oleic acid; (b) said diacid is sebacic acid; and (c) said polyhydric alcohol is pentaerythritol.

9. The composition of claim 7 wherein (a) said monoacid is oleic acid; (b) said diacid is azelaic acid; and (c) said polyhydric alcohol is pentaerythritol.

10. The composition of claim 7 wherein (a) said monoacid is isostearic acid; (b) said diacid is sebacic acid; and (c) said polyhydric alcohol is pentaerythritol.

11. The composition of claim 7 wherein (a) said monoacid is oleic acid; (b) said diacid is adipic acid; and (c) said polyhydric alcohol is pentaerythritol.

12. A process which comprises the steps of: (a) blending a monoacid, a diacid and a polyhydric alcohol with heating until an acid number of between about 13-65 is obtained for the blended moiety; and (b) adding a polyalkylene glycol ester and a sufficient amount of base to solubilize said ester in an aqueous solution.

13. The process of claim 12 wherein (a) said monoacid and salts thereof is of formula (I) R1—CO2H wherein R1 is selected from the group consisting of C5-20 alkyl, C5-20 alkenyl, C6-26 aryl, C6-30 alkaryl and C6-30 aralkyl; (b) said diacid and salts thereof is of formula (II) HO2C—R2—CO2H wherein R2 is selected from the group consisting of C2-36 alkyl, C3-36 alkenyl, C6-42 aryl, C6-42 alkaryl and C6-42 aralkyl; (c) said polyhydric alcohol is selected from the group of formulas (III) and (IV) R34−x—C—((R4)nOH)x and R34−x—(R5)y—O—(R6)z—((R4)nOH)x wherein each R3 is selected independently from the group consisting of H, (R4)nOH, C1-12 alkyl, C2-14 alkenyl, C6-36 aryl, C6-36 alkaryl, C6-36aralkyl and salts thereof; R4 is selected from the group consisting of C1-8 alkyl and C2-8 alkenyl; R5, R6 are independently selected from the group consisting of R4; x is an integral value from 2-4 inclusive; y is an integral value from 0 to 1 inclusive; z is an integral value from 0 to 1 inclusive; and n is an integral value from 0 to 1 inclusive; and (d) said alkylene glycol ester is of formula (V) 5wherein R7 is selected from the group consisting of C2-36 alkyl, C3-36 alkenyl, C6-42 aryl, C6-42 alkaryl and C6-42 aralkyl; R8 is selected from the group consisting of C1-6 alkyl and C2-8 alkylene; and a is an integral value from 1 to 40.

14. The process of claim 13 wherein (a) a molar ratio of said diacid/monoacid/polyhydric alcohol is between a range of ratios of about 0.6-1.4/1.6-2.4/1.0.

15. The process of claim 14 wherein (a) said molar ratio is between a range of ratios of about 0.8-1.2/1.8-2.2/1.0.

16. The process of claim 15 wherein (a) said molar ratio is about 0.9/2.1/1.0.

17. The process of claim 14 wherein (a) said composition has a viscosity of about 100,000 to about 600 SSU at 100° F.

18. The process of claim 17 wherein (a) said composition has an acid number of about 13-65 mg KOH/g.

19. The composition of claim 13 wherein (a) said monoacid is selected from the group consisting of oleic acid and isostearic acid; (b) said diacid is selected from the group consisting of sebacic acid, azelaic acid, adipic acid and dimethylpropionic acid; (c) said polyhydric alcohol is selected from the group consisting of pentaerythitol, dipentaerythritol, neopentyl glycol and trimethylol propane; and (d) said polyalkylene glycol ester is polyethyleneglycol oleate having a molecular weight of about 400.

20. A process for using a metal working fluid which comprises: (a) forming a water-soluble polymeric ester and acid blend comprising (i) a monoacid; (ii) a diacid; (iii) a polyhydric alcohol; and (b) combining said blend with (i) an ester of a polyalkylene glycol and a fatty acid; and (ii) an effective amount of a base to solubilize the blend and said ester in water to form an aqueous lubricant; and (c) using said lubricant as a lubricating additive blend.

21. The process of claim 20 wherein (a) said monoacid is of formula (I) R1—CO2H wherein R1 is selected from the group consisting of C5-20 alkyl, C5-20 alkenyl, C6-26 aryl, C6-30 alkaryl and C6-30 aralkyl; (b) said diacid is of formula (II) HO2C—R2—CO2H wherein R2 is selected from the group consisting of C2-36 alkyl, C3-36 alkenyl, C6-42 aryl, C6-42 alkaryl and C6-42aralkyl; (c) said polyhydric alcohol is selected from the group of formulas (III) and (IV) R34−x—C—((R4)nOH)x and R34−x—(R5)y—O—(R6)z—((R4)nOH)x wherein each R3 is selected independently from the group consisting of H, (R4)nOH, C1-12alkyl, C2-14 alkenyl, C6-36 aryl, C6-36 alkaryl, C6-36 aralkyl and salts thereof; R4 is selected from the group consisting of C1-8 alkyl and C2-8 alkenyl; R5, R6 are independently selected from the group consisting of R4; x is an integral value from 2-4 inclusive; y is an integral value from 0 to 1 inclusive; z is an integral value from 0 to 1 inclusive; and n is an integral value from 0 to 1 inclusive; and (d) said alkylene glycol ester is of formula (V) 6wherein R7 is selected from the group consisting of C2-36 alkyl, C3-36 alkenyl, C6-42 aryl, C6-42 alkaryl and C6-42 aralkyl; R8 is selected from the group consisting of C1-6 alkyl and C2-8 alkylene; and a is an integral value from 1 to 40.

22. The process of claim 21 wherein (a) a molar ratio of said diacid/monoacid/polyhydric alcohol is between a range of ratios of about 0.6-1.4/1.6-2.4/1.0.

23. The process of claim 22 wherein (a) said molar ratio is between a range of ratios of about 0.8-1.2/1.8-2.2/1.0.

24. The process of claim 23 wherein (a) said molar ratio is about 0.9/2.1/1.0.

25. The process of claim 21 wherein (a) said composition has a viscosity of about 100,000 to about 600 SSU at 100° F.

26. The process of claim 25 wherein (a) said composition has an acid number of about 13-65 mg KOH/g.

27. The composition of claim 21 wherein (a) said monoacid is selected from the group consisting of oleic acid and isostearic acid; (b) said diacid is selected from the group consisting of sebacic acid, azelaic acid, adipic acid and dimethylpropionic acid; (c) said polyhydric alcohol is selected from the group consisting of pentaerythitol, dipentaerythritol, neopentyl glycol and trimethylol propane; and (d) said polyalkylene glycol ester is polyethyleneglycol oleate having a molecular weight of about 400.

28. A composition which comprises: (a) a mixture of esters and acids from the reaction of at least one polyhydric alcohol with at least one monoacid and at least one diacid; and (b) a polyol ester.

29. The composition of claim 28 wherein (a) said polyol ester is an ester of a polyalkylene glycol and a fatty acid.

30. The composition of claim 29 wherein (a) said monoacid and salts thereof is of formula (I) R1—CO2H wherein R1 is selected from the group consisting of C5-20 alkyl, C5-20 alkenyl, C6-26 aryl, C6-30 alkaryl and C6-30 aralkyl; (b) said diacid and salts thereof is of formula (II) HO2C—R2—CO2H wherein R2 is selected from the group consisting of C2-36 alkyl, C3-36 alkenyl, C6-42 aryl, C6-42 alkaryl and C64-2 aralkyl; (c) said polyhydric alcohol is selected from the group of formulas (III) and (IV) R34−x—C—((R4)nOH)x and R34−x—(R5)y—O—(R6)z—((R4)nOH)x wherein each R3 is selected independently from the group consisting of H, (R4)nOH, C1-12 alkyl, C2-14 alkenyl, C6-36 aryl, C6-36 alkaryl, C6-36 aralkyl and salts thereof; R4 is selected from the group consisting of C1-8 alkyl and C2-8 alkenyl; R5, R6 are independently selected from the group consisting of R4; x is an integral value from 2-4 inclusive; y is an integral value from 0 to 1 inclusive; z is an integral value from 0 to 1 inclusive; and n is an integral value from 0 to 1 inclusive; and (d) said alkylene glycol ester is of formula (V) 7wherein R7 is selected from the group consisting of C2-36 alkyl, C3-36 alkenyl, C6-42 aryl, C6-42 alkaryl and C6-42aralkyl; R8 is selected from the group consisting of C1-6 alkyl and C2-8 alkylene; and a is an integral value from 1 to 40.

31. The composition of claim 30 wherein (a) a molar ratio of said diacid/monoacid/polyhydric alcohol is between a range of ratios of about 0.6-1.4/1.6-2.4/1.0.

32. The composition of claim 31 wherein (a) said molar ratio is between a range of ratios of about 0.8-1.2/1.8-2.2/1.0.

33. The composition of claim 32 wherein (a) said molar ratio is about 0.9/2.1/1.0.

34. The composition of claim 32 wherein (a) said composition has a viscosity of about 100,000 to about 600 SSU at 100° F.

35. The composition of claim 34 wherein (a) said composition has an acid number of about 13-65 mg KOH/g.

36. The composition of claim 32 wherein (a) said monoacid is selected from the group consisting of oleic acid and isostearic acid; (b) said diacid is selected from the group consisting of sebacic acid, azelaic acid, adipic acid and dimethylpropionic acid; (c) said polyhydric alcohol is selected from the group consisting of pentaerythitol, dipentaerythritol, neopentyl glycol and trimethylol propane; and (d) said polyalkylene glycol ester is polyethyleneglycol oleate having a molecular weight of about 400.

37. A composition which comprises: (a) a mixture of esters and acids from the reaction of at least one polyhydric alcohol and at least one monoacid and at least one diacid inclusive of their derived salts; and (b) a surfactant selected from the group consisting of polyol esters, polyoxylethylene alkyl esters, nonionic surfactants, ethoxylated alcohols, ethoxylated carboxylic acid esters, ethoxylated phosphate esters, polyethyleneglycols, poly(ethyleneoxy) ethanol, alcohol ethoxylates, polyalkylene glycol fatty esters, ethoxylated fatty acids, amine ethoxylates, hydroxy alkanolamine ethoxylated moieties and alkyl amide ethoxylates.

38. The composition of claim 37 wherein (a) the derived salts are sodium and potassium salts.

39. The composition of claim 37 wherein (a) the derived salts are amine salts.

40. A method comprising the step of (a) using the composition of claim 37 as a metal-working fluid.