US 3006849 A
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United This invention relates to water-base lubricant and coolant compositions, and is particularly concerned with prow'ding a transparent non-flammable metal working composition. In its general aspect, the invention provides a composition having general utility in cooling and in lubricating surfaces which are in frictional contact. In a special aspect, the invention provides a transparent waterbase cutting fluid for metal working operations.
Lubricants employed in metal working operations such as turning, cutting, drilling, grinding and the like are primarily of two types-the mineral oils and the so-called soluble-oils. These latter are o-il-in-Water emulsions prepared from hydrocarbon oils, water. and an emulsifying agent. Mineral oils, particularly when containing compounds of sulfur or chlorine are of special value in heavy duty applications where the metal working operations are at low speed, and where the avoidance of rusting is desired. Mineral oils, however, are highly flammable and, at higher cutting speeds when cooling ability is a primary requirement, a lubricant of higher specific heat such as a water-based soluble-oil is preferred. Unfortunately, water has its well known propensity to cause rusting of ferrous metal surfaces, and much effort and expense has been devoted to developing rust inhibitors which are suitably effective but Which will not degrade the oil-Water emulsion. These efforts have not been entirely successful. Also, currently available soluble-oils are frequently subject to creaming, or breaking of the emulsion, which results in a flammable oil layer and an aqueous layer entirely lacking in lubricity. In addition, soluble-oils generally are relatively poor extreme pressure lubricants, and also are milky and opaque, thus preventing the machinist from observing the workpiece and machine.
It is therefore a primary object of my invention to provide a lubricant and coolant composition which combines the lubricity and antirust characteristics of mineral oils with the high speed properties of soluble-oils, yet which is non-flammable and is almost perfectly transparent.
In accordance with the invention, the new lubricating and metal working formulation comprises a major amount of water and additive amounts of (a) an alkanolamine, (b) an aliphatic polycarboxylic acid having from about 12 to about 60 carbon atoms inclusive per molecule, an alkyl ester of phosphoric acid, and, preferably, (d) an alkali metal nitrite, in relative proportions to afford a formulation having a pH between about 6 and about 13. The composition of the invention may also contain a glycol ether and, if desired, may contain certain other additives such as antifoamants, etc.
The alkanolamines, in accordance herewith, are the amino alcohols which contain both an amino group and a hydroxyl group attached to different carbon atoms. The alkanolamines may be represented by the following structural formula: N(Q,,H ,OH)bH In this formula a desirably rep-resents any number from 1 to about 10, but is preferably from 2 to 4 inclusive. The letter b may be 1, 2, or 3. It appears that the most desirable alkanolamines are the ethanolamines, viz., monoethanolamine (41:2, 5:1), diethanolamine (a:2, 12:2) and triethanolamine (11:2, b:3). Of the three ethanolamines, triethanolamine is the most satisfactory from the standpoint of having the lowest foaming tendency. It is commercially available in technical purity, in admixture with other ethanolamines. Other alkanolamines which may be employed in place of, or in combination with, the ethanolamines include diethylethanolamine, dipropanolamine, methyldiethanolamine, etc.
It has been found that polymerized carboxylic acids such as dilinoleic and trilinoleic acids have particular value as the polycanboxylic acid component of the additive combination. Although alkanolamines form soaps readily with a wide variety of organic acids, the nature, size, and polyfunctionality of the acidic component appear to be quite critical for the purposes of the invention. Thus, alkanolamine soaps of monocarboxylic acids such as oleic or stearic are well known rust inhibitors for mineral oils, but in water base cutting fluids they are markedly less effective as antirusts; one formulation made from oleic acid was only one-third as effective as a comparable formulation according to the invention. Since mineral oils may be present during the metal working operation, the polycarboxylic acid must possess a balance of solubility between oil and water phases in order to emulsify the oil. Additives formed with acids of less than about 12 carbon atoms tend to remain exclusively in the cutting fluid and do not adequately remove mineral oils from the workpiece and permit the phosphate ester (extreme pressure additive) to reach the cutting area. Additives formed with acids containing more than about 60 carbon atoms appear to lose effectiveness in the water phase. Although both dicarboxylic and tricarboxylic acids give excellent performance in protection against rusting, it appears that the tr-icarboxylic acids approach the optimum in this respect. The use of mixtures of polycarboxylic acids such as may be derived by polymerization of unsaturated mono-acids, rather than pure acids, reduces cost and appears to be advantageous in terms of function as well.
A useful, commercially available dimeric carboxyl-ic acid is available from Emery Industries Inc. under the trade name Emery 955-Dimer Acid. Since the commercial product is produced by dimerization of linoleic acid, it is usually referred to as dilinoleic acid. The commercial acid typically contains about of dilinoleic acid, about 12% of trilinoleic acid and about 3% of monomeric acid. The dimeric acid has the following structural formula:
Typical specifications for the commercial product are as follows:
Iodine value 80-95 Acid value -192 Saponification value -195 Unsaponi-fiable 2.0% max. Color, Gardner 12 max. Neutralization equivalent 290-610 Refractive index at 25 C 1.4919 Specific gravity at 15.5 C./l5.5 C 0.95 Flash point, F 530 Fire point, F 600 Viscosity at 25 C. (Gardner-Holdt) Z4 Viscosity at 25 C., centistokes 10,000 Viscosity at 100 C., centis-tokes 100 The most satisfactory acid for use in forming the new inhibitors, measured in terms of anti-n1st effectiveness, is a mixture of polymerized fatty acids predominating in trilinoleic acid. Such mixtures may be exemplified by Emery 3055 Acids, containing about 85% trimer and about 15% higher polymers. A particularly satisfactory acid is commercially available from the Harchem Division of Wallace and Tiernan Company under the tradename of D-50 Acids; it contains about l15% monomer, 30-35% dimer, and 4050% trimer and higher polymers. A similar product is marketed by Rohm & Haas Company under the trade name VR-l Acids. Such acids may be produced as by-product still-residues in the manufacture of sebacic acid by the distillation of castor oil in the presence of caustic. A method of obtaining such by-product still-residues in the preparation of sebacic acid is described in US. 2,470,849, issued to W. E. Hanson May 24, 1949. The mixture of high molecular weight unsaturated fatty acids comprises monomers, dimers, trimers and higher polymers in the ratio of from about 45% to about 55% of a monomers and dimers fraction having a molecular weight in excess of 600. The fatty acid polymers result in part from a thermal polymerization of fatty acid type constituents of the castor oil, and in part from other reactions, such as the inter-molecular esterification, of such acid to form high molecular weight products. The acid mixture, which is mainly a mixture of polymeric long chain polybasic carboxylic acids, is further characterized by the following specifications:
Acid No.150 to 164 Saponification No.175 to 186 Free fatty acids--75 to 82% Iodine value44 to 55 The trimeric acid which is a major constituent of the above described acids and which is believed to be responsible for the superior properties thereof has the fol- (Tn'mer acid) Although the above are examples of commercially available mixed polycarboxylic acids, other polycarboxylic acids derived by polymerization of unsaturated acids and corresponding oil soluble polycarboxylic acid type materials, e.g. lecithin, also may be used.
For example, various naturally occurring or synthetic acids may be linked together to provide useful polycarboxylic acids by means well known to organic chemists, e. g. polymerization of unsaturated acids or condensation of alpha-halogenated acids, to produce polymeric forms of readily available carboxylic acids such as lauric, stearic, oleic, linoleic, oxo acids (e.g. isooctyl acids), synthol acids and the like. The point of linkage desirably is such that several carboxylic groups are orientable in a common plane at one end of the molecule in film formation on a metal surface. u-Distearic acid is an illustration.
The third component of the composition is a phosphate ester having the formula (RO),,(HO) PO where c 1, 2, or 3, and the R groups are the same or different alkyl radicals. Dialkyl esters (C=2) are especially suitable. The total number of carbon atoms in all of the R groups should preferably be less than about 40 so as to retain good aqueous phase solubility; this is of special importance when the phosphate ester is to be used in comparatively high concentrations, e.g. above about 1%. For optimum solubility, it is preferred that each R group have from 1 to about 20 carbon atoms per group (i.e., that it be prepared from an alcohol having from 1 to about 20 carbon atoms per group) and also that the ester be either dialkyl (C=2) or mono-alkyl (C=l).
As illustrative examples of suitable alkyl R groups, there are methyl, ethyl, propyl, isobutyl, isoamyl, n-hexyl, cyclohexyl, noctyl, oxo-decyl, dodecyl (lauryl), hexadecyl, and the like. Among the phosphate esters which are at present commercially available, there may be mentioned triethyl, tri'butyl, trioctyl, tri(2-ethyl hexyl), dilauryl, di-n-butyl, etc., which are obtainable in technically pure forms. Di-lauryl phosphate is marketed by the Du Pont Company as Ortholeum 162. It is within the scope and spirit of the present invention to employ alkyl polyphosphate esters such as tetraethyl pyrophosphate or hexaethyl tetraphosphate which, upon hydrolysis, form phosphate esters having the formula previously given.
The composition of the invention may also contain an alkali metal nitrite such as sodium or potassium nitrite. These nitrites appear to serve a dual purpose; not only do they passivate ferrous metal surfaces but they appear to stabilize the composition as well. For example, a composition lacking in alkali metal nitrite may evolve a gas of undetermined composition and, in one observed instance, reduce the A-lmen test rating at :1 dilution from an initial value of 30 pounds (the maximum limit of the machine) to 8 pounds after permitting the composition to stand for several hours.
Glycol ethers such as ethylene glycol monoethyl or diethyl ether are also advantageously incorporated in the present fluid where temperatures below about 5060 F. are to be encountered. They serve as solvents for mineral oils and reduce the tendency of the alkanolaminepolycarboxylic acid soap to separate out of solution. Other suitable water soluble glycol ethers include ethylene glycol monobutyl ether (known by the trade name Butyl Cellosolve, and manufactured by Carbide and Carbon Chemicals Co.), diethylene glycol monoalkyl ethers known as Carbitols (Carbide and Carbon Chemical Co.), Methyl Carbitol, Methyl Cellosolve, Butyl Carbitol, etc.
Antifoam additives such as Dow Corning antifoam, a silicone type material, may be incorporated for the purpose of reducing the tendency of the composition to froth or foam in use. In general, however, when the alkanolamine comprises triethanolamine foam formation is not a significant problem.
A preferred method of preparing the present compositions is to form a mixture of the alkanolamine with the polycarboxylic acid and the phosphate ester, and then introduce the alkali metal nitrite and any other additives. For best corrosion inhibition and least dermatological properties the pH of the resultant mixture, after dilution, should be within the range of from about 6 to about 13, preferably from about 7 to about 11. In an illustrative preparation, from one-tenth to ten parts by weight of a polycarboxylic acid such as Harchem D-SO Acids, and one part of a phosphate ester such as dilauryl phosphate are placed in an open vessel at room temperature, and at least the stoichiometric amount (based on carboxyl and unesterified phosphoric acid groups) of triethanolamine is added. The mixture heats up spontaneously, and on cooling to room temperature a clear brown liquid is formed. From about 20 to about 500% of water is introduced as an inert diluent and then from about 1% to about 30% each (based on total reactants) of sodium nitrite and Butyl Cellosolve are added. A
typical concentrate thus prepared may have, on a waterfour.
It is ordinarily convenient to make up the concentrate at a total additive concentration of from about to 100%, with the balance being water. In this form, the concentrate may be stored, shipped, and diluted conveniently.
When using the above concentrate as a dope for water-base cutting fluids, it may be diluted with from about 10 to 200 or more parts of water per part of concentrate. Ordinary tap Water, if not too hard, is adequate for this purpose although distilled water, deionized water, or steam condensate gives a cutting fluid which is almost completely haze-free. The dilution is desirably controlled so that the resultant cutting fluid contains from about .001 to about 10% by weight of total additives. The optimum level will depend of course on the service requirement of the fluid, the nature of the metal surfaces being machined, etc. If the composition is to be used as a lubricant for such purposes as air compressors or pneumatic tools, the same or even slightly higher concentrations are advisable.
To illustrate several specific non-limiting embodiments of the invention, various compositions were prepared and tested by one or more of the following procedures. The first test procedure, the steel billet rust test, is in the nature of a quantitative screening test for water base fluids, and furnishes an indication of the tendency of the fluid to cause rusting of both exposed and protected surfaces. A top quality concentrate will show no rust in dilutions of 100:1 or more. This test is described in detail in a subsequent paragraph. One composition was made up in a large batch and employed in actual cutting operations in the shop. Several compositions were tested for lubricity in the Falex extreme pressure tester, described, for example, in Erdol U. Kohle, volume 11, page 202, March 1958.
STEEL BILLET RUST TEST This test is a measure of a rust preventive action of a cutting fluid in the presence and in the absence of air. The test is conducted using cylinders of type 1018 steel about 1" in diameter and about 1 /2 long. For the single specimen portion of the test, a flat surface of a billet is cleaned with 180-grit emery paper. With the flat surface uppermost, one half cc. of the cutting fluid, at the desired dilution, is placed on the flat surface and permitted to evaporate to dryness overnight. At the end of this period, the surface is examined; no rust on the exposed sanded surface is rated zero, up to 25% rust is rated one, from 25 to 50% rust is rated two, from 50 to 75% is rated three, and from 75 to 100% rust is rated In the matched specimen test, flat surfaces on each of two 1018 steel billets are cleaned with 180-grit paper, and with one billet having its cleaned surface uppermost, one-half cc. of cutting fluid is placed on the cleaned surface, and the corresponding cleaned surface of the second billet is placed atop the first. After standing overnight, the surfaces are rated as in the single specimen test.
In the following examples, all compositions are expressed on a weight percent basis unless otherwise indicated.
Example I In this example, the following concentrate was made up and tested.
16 wt. percent triethanolamine 6 wt. percent Harchem D-50 Acids 8 wt. percent dilauryl phosphate 4 wt. percent sodium nitrite 5 wt. percent Butyl Cellosolve 61 wt. percent water In the steel billet rust test, it exhibited the following outstanding propertim.
Single specimen The dilauryl phosphate is a commercial product sold by the Du Pont Company under the trademark Ortholeum 162.
Example 11 Another additive composition according to the invention was prepared and had the following composition and properties.
20 wt. percent triethanolamine 5 wt. percent Harchem D50 Acids 12 wt. percent dilauryl phosphate 4 wt. percent sodium nitrite 59 wt. percent water STEEL BILLET RUST TEST Single specimen Matched specimen Example III STEEL BILLET RUST TEST Single specimen Matched specimen DIP- Example IV In this example, to demonstrate the outstanding properties of the composition as a cutting fluid, a concentrate was prepared, diluted 30:1 with tap water, and the resultant cutting fluid was used in machining stainless steel. The concentrate had the following composition:
25 wt. percent triethanolamine 19 wt. percent Emery 3055 Acids 6 wt. percent dilauryl phosphate 0.05 wt. percent Dow Corning silicone antifoam 50 wt. percent water A 4" diameter cylinder of stainless steel was employed in constructing a high pressure autoclave. The cylinder was chucked in a lathe and a /3" pilot hole was drilled using the above cutting fluid as lubricant; the chips were at least 0.015, yet the piece remained at a temperature below F. The pilot hole was then drilled out to 2% diameter, feeding the drill by hand with a severe force feed. The chips were at least 0.020" thick, and
came off with no discoloration. The workpiece was cool to the touch, as were the chips. There was no rusting on either the guide or the ways of the lathe.
The original mixture of gallons water plus 1 /2 pints of concentrate was diluted with an additional 3 gallons of water. Using this concentration, an 0.015" cut was taken on the inside using a boring bar. The chips came off cool with no discoloration, and the workpiece remained cool. Because of the high dilution, some slight rusting of the chip container occurred overnight although the lathe was unalfected. The estimated dilution in this instance was 65:1.
By comparison, when 30:1 dilutions of typical solubleoils are used in the above operations, the piece and cutting tools become so hot that the tool rapidly loses its temper and there is actual steaming at the work area. Similarly, mineral cutting oils used at the same conditions result in a hot workpiece and a smoking oil.
Example V In this example, a cutting fluid was prepared and used in drilling and boring a steel bar. The fluid was composed of 5 gallons of water and one-and-one-half pints (30:1 dilution) of:
25 wt. percent triethanolamine 19 wt. percent Emery 3055 Acids 6 wt. percent dilauryl phosphate 0.05 wt. percent Dow Corning silicone antifoam 50 wt. percent water A type 4140 steel bar was turned with a A tool, taking an 0.015 cut. The piece ran extremely cool, and there was no discoloration of the chips. The chips were cool to the touch, and neither the chips nor the ways were rusted after several days use.
Example VI Another illustrative composition was prepared and had the following composition and properties:
8 wt. percent monoethanolamine 6 wt. percent Harchem D-SO Acids 8 wt. percent dilauryl phosphate 4 wt. percent sodium nitrite 5 wt. percent Butyl Cellosolve 69 Wt. percent water STEEL BILLET RUST TEST Example VII Another illustrative composition was prepared and had the following composition and properties:
16 wt. percent diethanolamine 6 wt. percent Harchem D50 Acids 8 wt. percent dilauryl phosphate 4 Wt. percent sodium nitrite 5 wt. percent Butyl Cellosolve 61 Wt. percent water STEEL BILLET RUST TEST Single Specimen 0 0 Matched Specimen 0 2 FALEX EXTREME PRESSURE TEST Pin Sheared lbs Example VIII Another illustrative composition was prepared and had the following composition and properties:
16 wt. percent triethanolamine 6 wt. percent Harchem D-50 Acids 8 wt. percent Di-n-butyl phosphate 4 wt. percent sodium nitrite 5 wt. percent Butyl Cellosolve 61 Wt. percent water STEEL BILLET RUST TEST From the foregoing presentation it is clear that water base formulations according to the present invention are extremely useful lubricants and coolants. The fluids are almost completely transparent and non-flammable and possess exceptional extreme pressure lubricity characteristics. They also are outstanding antirusts.
1. A substantially transparent aqueous base lubricant and coolant composition comprising a major amount of water and from about 0.001% to about 10% of an additive mixture comprising (a) about 570% of an alkanolamine, (b) about 3-90% of an aliphatic polycarboxylic acid having from about 12 to about 60 carbon atoms per molecule, and (c) about 540% of an alkyl ester of phosphoric acid, said additive mixture imparting lubricity and anti-rust properties to said composition, and said composition having a pH between about 6 and about 13.
2. The lubricant and coolant composition of claim 1 wherein said alkanolamine is an ethanolamine.
3. The lubricant and coolant composition of claim 1 wherein said aliphatic polycarboxylic acid is a polymerized linoleic acid.
4. The lubricant and coolant composition of claim 1 wherein said alkyl ester of phosphoric acid has from about 4 to about 20 carbon atoms in each alkanol group.
5. The lubricant and coolant composition of claim 1 wherein (0.) about 220% of an alkali metal nitrite is also present.
6. The lubricant and coolant composition of claim 1 wherein (e) about 220% of a water soluble glycol ether is also present.
7. The lubricant and coolant composition of claim 2 wherein the ethanolamine is triethanolamine.
8. The lubricant and coolant composition of claim 4 wherein said alkyl ester is a dialkyl ester.
9. The lubricant and coolant composition of claim 5 wherein the alkali metal nitrite is sodium nitrite.
10. The lubricant and coolant composition of claim 6 wherein the glycol ether is a butyl ether of ethylene glycol.
11. The lubricant and coolant composition of claim 8 wherein the dialkyl ester is dila-uryl phosphate.
12. The lubricant and coolant composition of claim 8 wherein the dialkyl ester is di-n-butyl phosphate.
13. An additive concentrate suitable for dilution with water to form a transparent aqueous base lubricant and coolant composition having a pH between about 6 and about 13 and having lubricity and anti-rust properties, which concentrate consists essentially of water and more than 10% by weight of an additive mixture comprising (a) about 570% of an alkanolamine, (b) about 390% of an aliphatic polycarboxylic acid having from about 12 to about 60 carbon atoms per molecule, and about -40% of an alkyl ester of phosphoric acid.
14. The additive concentrate of claim 13 wherein (d) about 2-20% of an alkali metal nitrite is also present.
15. A method of lubricating and cooling metal working operations which comprises lubricating and cooling such operations with a lubricant comprising a major amount of Water and from about 0.001% to about of an additive mixture comprising (a) about 5-70% of an alkanolamine, (b) about 390% of an aliphatic polycarboxylic acid having from about 12 to about carbon atoms per molecule, and (0) about 5-40% of an alkyl ester of phosphoric acid, said additive mixture imparting lubricity and anti-rust properties to said composition, and said composition having a pH between about 6 and about 13.
16. The method of claim 15 wherein (d) an alkali metal nitrite is also present.
References Cited in the file of this patent UNITED STATES PATENTS 2,291,066 Waugh July 28, 1942 2,406,671 Diamond Aug. 27, 1946 2,452,321 Kluge et a1. Oct. 26, 1948 2,474,325 Rodgers June 28, 1949 2,825,693 Beaubien et a1. Mar. 4, 1958 2,830,021 Smith et a1. Apr. 8, 1958 OTHER REFERENCES Cellosolve and Carbitol Solvents, pub. by Carbide and Carbon Chem. Corp., January 1947, pp. 3-6.