US3523895A - Metal working lubricant - Google Patents

Description

United States Patent U.S. Cl. 252-17 18 Claims ABSTRACT 0F THE DISCLOSURE An emulsion lubricant for the cold-rolling of metals containing, on a water-free basis, from about 20% to about 50% by weight of the neat composition of a solid aliphatic monocarboxylic acid having from about to about 30 carbon atoms provides excellent rolling characteristics. The emulsion lubricants containing the solid acids are particularly useful in the cold rolling of steel.

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of U.S. application Ser. No. 781,648, filed Sept. 9, 1968, which in turn is a streamlined continuation of U.S. application Ser. No. 553,319, filed on May 27, 1966, both now aban- .doned.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to emulsion-type lubricants and in particular oil-water emulsion lubricants used in the rolling of metals.

Description of the prior art The most modern rolling procedures presently used to produce extremely thin gauge metal or strip products have increased the burden on the roll lubricants. The overriding necessity of obtaining increasingly higher gauge reduction per roll pass and at even faster rates than used in the past has increased the standard loadcarrying and cooling requirements of roll oils even more so. Present commercial lubricants cannot perform adequately in the cold-rolling of steel, for example, wherein gauge reduction of over 80% are sought in a single mill throughput at a strip rate of above 1500 feet per minute. The rolling pressures are considerably greater there fore requiring lubricants to form tougher load-carrying films than hitherto known. The high degree of heat generating from the fast rolling rates must be dissipated quickly and thus the lubricant must be an equally eifeotive coolant. The roll oil must also be able to remove metal fines from the metal being rolled, otherwise they would mar the finished surface. Also the metal fines should be easily removed from the oil. If permitted to remain in the oil, they can cause metal surface defects in later rolling operations. Moreover, the known roll oils tend to remain on surface of the metals during the annealing stage, leaving severe stains thereon.

U.S. Pat. No. 3,071,544 describes rolling oil emulsions containing a number of components, including a small amount of an organic acid. The acid is either liquid or oil soluble or is reacted with other components in the formulation to provide oil soluble soaps, such as the soaps of alkanolamines, U.S. Pat. No. 3,311,557 describes emulsions for the hot rolling of nonferrous metals which contain a fatty acid, a polyol and ethanolamine. The ethanolamine reacts with the acid in sulfi- 3,523,895 Patented Aug. 11, 1970 ice cient proportion to provide a ratio of base number to acid number of from 0.15 to 0.4. Specific examples of this patent show the use of oil-soluble, liquid fatty acids.

SUMMARY OF THE INVENTION In accordance with the invention, it has now been discovered that faster rates of metal rolling may be accomplished with improved reduction of metal gauge by the use of oil-in-water emulsion lubricants wherein the neat oil composition, on a water-free basis, contains from about 20% by Weight to about 50% by weight of a solid aliphatic monocarboxylic acid having from about 10 to about 30 carbon atoms, the remainder being oil and emulsifiers therefor.

DESCRIPTION OF SPECIFIC EMBODIMENTS The lubricant emulsions used in the cold rolling of metal in accordance with this invention broadly consists of about 0.75% to 10% by weight of an oil-solid acid composition in water. The mixed oil-acid neat composition contains from about 20% to about 50%, preferably from about 20% to 40%, by weight of the solid acid. The oil-soluble phase, being about to about 50% by weight of the oil-acid composition, includes a lubricating oil, such as a mineral oil, emulsifiers and emulsion stabilizers. The oil may constitute from about 20% to about 60% by weight of the neat composition.

When the oil-acid composition is mixed with the water, the oil-soluble components become emulsified in the water and the solid acid remains as solid particles adhered to the emulsified oil droplets. Hence the typical final lubricant emulsion of this invention consists of water, emulsified oil droplets, and the solid acid closely attached to the droplets.

With regard to the oil-soluble phase, the components include from about 1% to about 15% by weight of the oil phase of an alkanolamine having from about 2 to about 4 carbon atoms per alkanol group and from about 1% to about 15 by weight of the oil phase of an emulsifier preferably having a hydrophilic-lipophilic balance of at least 10. In addition to these two components, the oil phase may also contain from about 0.05% to about 2% by weight of an aromatic sulfonate and from about 2% to about 15% by weight of an alkyl or aromatic phosphate ester.

In the most preferred form, the oil-acid composition contains the components in the following percentages: (1) from about 30% to about 50% by weight of a lubricating oil; (2) from about 20% to about 40% by Weight of the solid aliphatic saturated mono-carboxylic acid having from about 14 to about 26 carbon atoms; (3) from about 3% to about 12% by weight of an alkanolamine having from 2 to about 4 carbon atoms; (4) from about 5% to about 10% by weight of an alkyl or aromatic phosphate ester; (5) about 3% to about 12% by weight of, an emulsifier having a hydrophilic-lipophilic balance of at least 10; and (6) from about 0.1% to about 1.5% by weight of an aromatic sulfonate.

It has been found that by using the components of the lubricant composition as a 0.75 to 10% emulsion there is provided a surprisingly effective lubricant-coolant which overcomes the arduous requirements encountered in the high speed cold-rolling of metals, such as steel. Mill speeds of greater than 1500 feet per minute, and even higher than 2000 feet per minute, with final gauge sizes of as low as 0.0075 inches have been attained with the use of the lubricants of this invention.

One of the reasons for the effectiveness of these lubricants is believed to be the uniform distribution of such a large quantity of the solid monocarboxylic acid in the emulsion. Thus one aspect of this invention is directed to roll oil lubricants consisting of about a 0.75% to 10% by weight oil-in-water emulsion, wherein, as pre 3 viously described, the neat phase, on a water-free basis, contains from about to about of said solid acid.

The mixing equipment needed for combining the components of this invention are of a conventional nature, known in the art. Preferably the oil, the water, the acid and the other components, with the exception of component (6), are mixed together initially at a temperature of from 50 C. to about 100 C., and preferably 80 to 90 C., for a sufiicient period to obtain a uniform composition. From about 30 minutes to about 7 hours, preferably 1 hour, of mechanical mixing is ordinarily sufi'icient to obtain the desired emulsion mixture. It may be found necessary to subject the mixture to a particle size reduction step in order to obtain uniformity. Such a step may be carried out by means of suitable equipment for this purpose, such as a colloid mill, homogenizer and the like. The preferred mixing procedure is performed by first using a mechanical mixer and then the homogenizer, maintaining the temperature higher than preferably from about to about C. The mixture is cooled rapidly to a temperature below 50 C., and the aromatic sulfonate is mixed in. The mixture is thereafter submitted to a final homogenizing treatment.

Often mixing equipment is not readily available at the mill and, moreover, too much time may be spent at the mill in forming the emulsion lubricant. For the purpose of convenience and the saving of time and expense, a concentrated emulsion may be initially prepared by the supplier prior to shipment to the mill. For the best emulsion concentrate, that is, the compositions which will require the least mixing time in the mill equipment, compositions containing from about 20% to about 60% by weight of the above components (1) to (6) and from about 80% to about 40% by weight of water are preferred. These concentrates are simply diluted in further amounts of water to produce the 0.75% to 10% emulsion for use.

The components of the water free, or neat composition discused hereinafter, are of critical importance, especially at the concentrations at which each component is used. The finished formulations provide the unexpected results hitherto unavailable with conventional lubricants.

The oils used in this invention include both naphthenic and parafiinic mineral oils having a Saybolt viscosity in the range of 110 through 300 S.U.S. at F. and synthetic lubricants, such as synthetic ester lubricants, polyolefin fluids, alkylene oxide-derived fluids and the like. The oil is present in amounts ranging from about 20% to 60% by Weight of the neat composition, and preferably from about 30% to about 50%.

From about 20% to about 50% by weight of neat composition is an aliphatic, saturated monocarboxylic acid having from about 10 to about 30, and preferably from about 14 to 28, carbon atoms. This range includes myristic, palmitic, stearic, arachidic, and behenic acids which are all normally solid, and insoluble in mineral oils and water. Preferably, stearic acid is employed. At elevated mixing temperatures and at mill operating temperatures these acids may become liquefied. However, at reservoir temperatures, it is believed that although the emulsions are stable, a heterogeneous system may result. It is therefore within the scope of this invention to use acids which may be in a solid and undissolved state, such as a large particle or suspensoid, at any point during the use or storage of the emulsion lubricant.

The alkanolamine is used as an emulsifying agent in the lubricant, in amounts ranging from about 1% to 15% and preferably 3% to 12% by weight of neat composition. Primary, secondary, and tertiary alkanolamines may be used. Triethanolamine, isopropanolamine, tri-isopropanolamine, and isobutanolamine are examples of suitable compounds for use in this invention.

The fourth component is an alkyl or aromatic phosphate ester which includes, typically, tributyl phosphate, trioctyl phosphate, triphenyl phosphate, phenyl dicresyl phosphate, tricresyl phosphate, tri-(p-tertiaryamyl)phenyl phosphate and the like wherein the alkyl groups, including those on the aryl groups, contain up to 20 carbon atoms. Most preferred of these is tricresyl phosphate. The concentration of this component is in the range of 2% to 15 by weight of neat composition and preferably from about 5% to about 10%.

The concentration of the emulsifiers or emulsion stabilizers, preferably having a hydrophilic-lipophilic balance of at least 10 or higher, may range from about 1% to about 15 and preferably from about 3% to about 12% by weight. Included in this category of emulsifiers are cationic, anionic and monionic emulsifiers, such as amines having from 4 to 36 carbon atoms and the C C alkyl phenols, and fatty or rosin alcohols, fatty acids, esters and partial esters of fatty acids and polyols and fatty acid amides, each having from 4, and preferably from 8, to 36 carbon atoms. A preferred group of emulsifiers are the alkoxylated derivatives of the above-lised organic compounds obtained by reacting them with an alkylene oxide having from about 2 to 4 carbon atoms, such as etheylene oxide (also termed ETO). A preferred group of emulsifiers is the N-acyl-substituted dialkanolamides, the acyl group having 8 to 30 carbon atoms, such as lauroyl diethanolamide. Other emulsifiers include gum Arabic, often used in the preparation of wax emulsions.

The aromatic sulfonate acts as a control agent of the particle size and viscosity of the emulsion. It is present in relatively minor proportion, ranging from 0.05% to 2.0%, and preferably 0.1% to about 1.5%, by weight of the emulsion concentrate. The aromatic sulfonates include oil soluble metal salts of petroleum sulfonic acids and synthetic alkaryl sulfonic acids, particularly those having a molecular weight of from about 300 to 800. The preferred alkyl substituents on the aromatic ring contain from about 8 to 24 carbon atoms. The aromatic sulfonate used in the lubricants of this invention is an oil-soluble beta-naphthalene sulfonic acid-aldehyde condensate, and particularly useful is the formaldehyde condensate. Preparations for producing such condensates are generally known in the art. They may also be used in the form of an alkali metal salt.

In connection with the use of the lubricants of this invention, emulsion compositions containing additionally a liquid fatty acid, having from about 12 to about 22 carbon atoms, preferably oleic acid or linoleic acid, in combination with an aliphatic fatty acid amide having from about 10 to about 18 carbon atoms, preferably lauroyl amide, possess further improved anti-corrosion properties in the cold-rolling of steel. Oleic acid offers additional oilness characteristics which aid in the film-forming properties of the lubricant, but is does not provide any anticorrosion protection by itself. It is known that amides do provide some anti-corrosion properties alone. However, in the presence of oleic acid, the fatty acid amide acts in an improved manner evidencing unusual cooperation, as between co-agents. The combination of oleic acid and lauroyl amide protects the surface of the metal strip against rust in a very effective maner. The oleic acid is used in minor quantities ranging from 1% to about 5% by weight of concentrate. The amide is used in amounts ranging from about 4% to about 8% by weight of concentrate.

As indicated heretofore, the compositions of this invention are particularly useful in the cold-rolling of steel, as well as in other metal-working operations. The lubricants herein described permit the high speed gauge reduction of the metal in metal rolling operations. They also provide an unusual improvement in removing metal fines caused in the rolling. It is well known that in rolling of metal, when the metal billet is fed into rollers, small particles of metal may break off. These particles usually remain in the lubricant. When normal lubricants are used, the smaller particles, or fines, do not always settle out when the lubricant is passed into the reservoir or holding tank at the conclusion of the rolling operation. Hence.

when the lubricant is used again, these fines may be carried onto the metal surface in the succeeding rolling operation and cause surface blemishes. While it is true that the used lubricant is skimmed in the holding tank, it has been found that skimming does not always remove all of the metal fines, and the finished metal strip may be marred. The performance of the emulsion lubricants of this invention is unique in that the presence of the solid acid may act to reject the metal fines from the emulsion and float them to the surface where they are removed in the skimming step.

It is theorized that at the point of maximum pressure in the rolling operation, or the rolling point, a small portion of solid acid separates from the emulsion and is formed into flakes. It is at this point that the metal fines are also formed. It is believed that these metal fines are then mechanically or chemically taken off in the solid acid. The used oil, passing from the rollers into the skimming tank, contains both the emulsified oil and the adhered solid acid particles, free oil, and the solid acid flakes having the metal fines entrapped thereon. In the skimming tank, the free acid flakes containing the metal fines float to the surface Where they are mechanically removed, e.g. skimmed off, leaving the resulting emulsified composition almost completely free of metal fines. The larger metal particles which could not be entrapped by the acid flakes present little problem, since they usually do not remain dispersed in the emulsion but settle to the bottom of the holding tank by gravity. Hence, in the succeeding rolling operations, there are essentially no metal particles, including the fines, present in the oil which can mar the surface of the rolled metal, thereby producing metal strip shaving almost mirror-like appearance.

The following examples show how the lubricants of this invention are prepared and utilized:

Example I.In this example the neat composition contains about 30% by weight of solid acid.

An emulsifiable composition was prepared for providing about a 30% concentrate in water using the following substances:

Parts by weight 30% cone. Neat Mineral oil Trieresyl phosph The mineral oil is a naphthenic oil having a viscosity of 100 S.U.S. at 100 P.

All the components, except for the sulfonate-formaldehyde condensate, were combined under agitation with sufficient water to provide the 30% emulsion. The mixing was performed for about 1 hour, at about 80 to 90 C. The mixture was then passed through a Manton-Gaulin homogenizer for an additional hour. The resulting emulsion was cooled and the condensate was added over a halfhour period, with agitation, at a temperature below 50 C. The cooled mixture was again passed through the homogenizer, while maintaining the temperature below 50 C., for 1 hour.

The properties of the resulting emulsion concentrate are as follows:

Specific gravity 0.999 Viscosity, S.U.S. 100 F. 150 saponification number 34 Neutralization number 21 pH 8.8

This 30% emulsion concentrate is diluted with further amounts of water to produce a 3-10% emulsion at the rolling mill just prior to use. The saponification and neutralization numbers and the pH remain constant.

The 5% emulsion was used in producing steel strip in a production scale S-stand tandem cold strip rolling mill. The original gauge of the steel sheet is about 0.13 inch. The rolling of the metal was performed at a rolling speed of between 1800 2200 f.p.m. The final gauge was about 0.0345 inch, or a reduction of about 73.5%.

Another rolling operation was performed at a roll speed of about 2000 f.p.m. The original gauge of the steel was about 0.0787 inch; the final gauge of the strip was about 0.00787 inch. This indicates a reduction of about It is clear that even higher speeds than 2000 f.p.m. may be employed without incurring the penalty of an undue loss in gauge reduction. Each of the rolled metals was checked for surface stains after the annealing step. The surface in each case was free of stains.

Example IL-In this example, the neat composition contains about 26.7% by weight of solid acid.

Using the same procedure as in Example I, a 30% emulsion concentrate was prepared from a mixture of about 70 parts of water and about 30 parts of the following:

Parts by weight 30% cone. Neat Mineral oil. 12. 0 40. 0 Stearic acid-.. 8.0 26. 7 Trlethanolarnine... 3. 0 10. 0 Tricresyl phosphate 2. 0 6. 7 Lauroyl diethanolamide 2. 0 6. 7 Naphthalene sulfonate-formaldehyde condensate 0. 3 1. 0

To this mixture was also added 3 parts of a 2:1 mixture of lauroylamide:oleic acid. The mineral oil used was the same as in Example 1. The specific gravity of the 30% emulsion is 0.999 the saponification number is 35, the neutralization number is 21, and the pH is about 8.7.

The 30% and 10% emulsions were subjected to a modified four-ball extreme pressure test. A set of these steel balls are held stationary in a ball cup; the lubricant is added to cover the balls. A fourth ball is held in a chuck which is rotated by a vertical spindle. This ball is forced against the three stationary balls and is rotated at a speed of about 200 r.p.m. The force is increased in crementally by hydraulic loading until failure, or welding, occurs. The higher the load or pressure at failure, the better the load carrying ability of the lubricant. The 30% emulsion permitted a loading of about 114 p.s.i.; for the 10% emulsion, the load was about p.s.i.

Example 3.In this example, the neat composition contains about 48% by weight of solid acid.

Using the same procedure as in Example 1 to prepare the emulsions, a 30% emulsion concentrate was prepared by mixing about 70 parts of water and about 30 parts of the following components:

7 The mineral oil is the same as that of Example 1, a naphthenic oil having a viscosity of 100 S.U.S. at 100 F.

After the emulsion concentrate was made, the properties were as follows:

Viscosity, S.U.S. 100 F. 150 pH 8.0-8.2

This lubricant was tested in the four-ball extreme pressure test described previously. The lubricant permitted a load of about 150 p.s.i.

The results of the tests and the plant operations involving the compositions of this invention show that these lubricants are of an exceptional nature. The ultrathin gauges for steel, so important in metal-liner, steel foil, and other applications, are readily produced at speeds never previously attained by use of known lubricants. The metal surfaces during rolling and annealing are clear of corrosion or staining. From such results, it is believed that the presence of each component described in the amounts specified is of critical importance. Any deviation from such formulations may lead to poor rolling results.

The illustrations and examples have been used herein to better describe our invention; our invention is therefore not to be considered in any way limited, except as appears in the appended claims.

We claim:

1. An emulsifiable lubricating composition consisting essentially of (1) from about 20% to about 50% by weight of a solid aliphatic saturated monocarboxylic acid containing from about to about 30 carbon atoms;

(2) from about 1% to about by weight of an alkanolamine having from about 2 to 4 carbon atoms in the alkanol group;

(3) from about 1% to about 15% by weight of an emulsifier selected from the group consisting of amines, fatty acids, fatty acid amides, alkyl phenols, aliphatic alcohols, esters of fatty acids and polyols and alkylene ovide derivatives of these, said alkylene containing from 2 to 4 carbon atoms, fatty acid alkanolamides, said emulsifiers having from 4 to 36 carbon atoms, and gum arabic;

(4) from about 0.05% to about 2% by Weight of an aromatic sulfonate;

(5) from about 2% to about 15% by weight of a phosphate ester selected from the group consisting of alkyl and aryl phosphate esters containing from about 1 to about carbon atoms;

(6) the remainder being a lubricating oil; wherein the said solid acid remains as a solid component in the composition.

2. The composition of claim 1 wherein the solid acid contains from about 14 to about 28 carbon atoms.

3. An emulsion lubricant concentrate composition comprising from about 20% to about 60% by weight of the composition of claim 1 and from about 80% to about 40% by weight of water, wherein the said solid acid remains as a solid component in the said emulsion composition.

4. An emulsion lubricant composition comprising from about 0.75% to about 10% by weight of a composition of claim 1 and from about 99.25% to about 90% by weight of water, wherein the said solid acid remains as a solid component in the said emulsion composition.

5. The composition of claim 1 wherein the said solid acid is stearic acid.

6. The composition of claim 1 wherein the said alkanolamine is triethanolamine.

7. The composition of claim '1 wherein the said emulsifier is lauroyl diethanolamide.

8. The composition of claim 1 wherein the aromatic sulfonate is a naphthalene sulfonate-formaldehyde condensate.

9. The composition of claim 8 wherein the said condensate is in the form of an alkali metal salt thereof.

8 10. The composition of claim 1 wherein the phosphate ester is tricresylphosphate.

11. An emulsifiable lubricating composition according to claim 1, consisting essentially of:

(1) from about 30% to about 50% by weight of a lubricating oil; (2) from about 20% to about 40% by weight of a solid aliphatic saturated monocarboxylic acid containing from about 14 to 28 carbon atoms;

(3) from about 3% to about 12% by weight of an alkanolamine having from 2 to about 4 carbon atoms per alkanol group;

(4) from about 5% to about 10% by weight of a phosphate ester selected from the group consisting of alkyl and aryl phosphate esters containing up to about 20 carbon atoms;

(5) from about 3% to about 12% by weight of an organic alkylene oxide derivative having a hydrophilic-lipophilic balance of at least 10 wherein the alkylene oxide contains from 2 to 4 carbon atoms, said derivative being obtained from the said alkylene oxide and a member selected from the group consisting of C -C alkyl phenols, C C alcohols, fatty acids, esters of fatty acids, and polyols, and fatty acid amides and alkanolarnides, said fatty acid containing from 8 to about 30 carbon atoms; and

(6) from about 0.1% to about 1.5% by weight of an aromatic sulfonate; wherein the said solid acid of (2) remains as a solid component upon the emulsification of the remaining composition in water.

12. An oil-in-water emulsion lubricant, as defined in claim 4 for cold-rolling metals, wherein from about 20% to about 50% of the neat phase, on a water free basis, is a solid aliphatic monocarboxylic acid, from about 1% to about 15% of the oil phase, on a water-free basis, is an alkanolamine having from 2 to about 4 carbon atoms per alkanol group, and from about 1% to about 15% of the oil phase on a water-free basis consists of an N- acyl dialkanolamide wherein the acid group of said amide contains from about 8 to about 30 carbon atoms, and the alkanol groups attached to the nitrogen atom are derived from an alkylene oxide having 2 to 4 carbon atoms in the alkylene group.

13. The emulsion lubricant of claim 12 wherein the acid is stearic acid.

14. The emulsion lubricant of claim 12 wherein the N-acyl alkanolamide is lauroyl diethanolamide.

15. The emulsion lubricant of claim 12 wherein from about 0.1% to about 1.5% by weight of the oil phase on a water-free basis is a naphthalene sulfonate-formaldehyde condensate.

16. An emulsifiable lubricant composition having improved anti-corrosion properties consisting essentially of the composition of claim 11 and added therein in admixture from 1% to about 5% by weight of a liquid fatty acid having from about 12 to about 22 carbon atoms and from about 4% to about 8% by weight of an aliphatic fatty acid amide having from about 10 to 18 carbon atoms.

17. The composition of claim 16 wherein the admixture consists essentially of oleic acid and lauroyl amide.

18. A method of removing metal fines from a roll oil emulsion lubricant comprising the steps of (1) subjecting a metal to a rolling operation using as the lubricant therefor a composition consisting of an oil-in-water emulsion and a solid, aliphatic monocarboxylic acid having from about 10 to about 30 carbon atoms adhering to the oil droplets of said emulsion, said solid acid having a concentration, on a water-free basis, of from about 20% to about 50% by weight of the total acid and oil-soluble phases; (2) causing fine metal particles normally formed during metal rolling operations and a portion of said solid acid to become combined, wherein the combined acid-metal particles, after the rolling operation, are permitted to float to the surface of the lubricant; and (3) mechanically removing the said acid-metal particles PATRICK P. GARVIN, Primary Examiner therefrom.

References Cited I. VAUGHN, Assistant Examiner UNITED STATES PATENTS US. Cl. X.R.

3,071,544 1/1963 Rue 252-333 7242; 208-180; 210-60, s3; 2s2-33.4, 49.5

3,311,557 3/1967 Schiermeier et a1. 252-495