US3723314A - Lubricant for metalworking - Google Patents

Abstract

AN EMULSION LUBRICANT FOR USE IN COLD-ROLLING OF METALS CONTAINING, ON A WATER-FREE BASIS, FROM ABOUT 20% TO ABOUT 50% OF AN ORGANIC ACID, IS IMPROVED WITH RESPECT TO ITS HARD WATER STABILITY BY HAVING IN THE LUBRICANT AN AMOUNT OF A MIXTURE OF MONO- AND DIOLEYL PHOSPHATES.

Description

United States Patent 3,723,314 LUBRICANT FOR METALWORKING Robert H. Davis, Pitman, N.J., assignor to Mobil Oil Corporation N0 Drawing. Filed Mar. 24, 1971, Ser. No. 127,764 Int. Cl. C10m 1/06, 1/46 US. Cl. 252-334 9 Claims ABSTRACT OF THE DISCLOSURE An emulsion lubricant for use in cold-rolling of metals containing, on a water-free basis, from about 20% to about 50% of an organic acid, is improved with respect to its hard water stability by having in the lubricant an amount of a mixture of monoand dioleyl phosphates.

CROSS-REFERENCE TO 'RELATED APPLICATIONS The subject matter of this application is related to that of an application filed of even date herewith in the name of Michael C. Churn, entitled Lubricant Useful in Metalworking. The mentioned related application concerns an improvement in metal working lubricants similar to those of this invention, the improvement comprising the use of an aromatic oil. The application is Ser. No. 127,763, filed Mar. 24, 1971.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to emulsifiable lubricants useful in the cold-rolling of metals. More particularly, the invention is concerned with such lubricants which have improved hard water stability properties.

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 therefore 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 effective 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 the surface of the metals during the annealing stage, leaving severe stains thereon.

Although a lubricant might overcome all the abovementioned problems under ideal conditions, it may still be subject to other deficiencies due to conditions en countered in everyday practice. One of these is the formation of insoluble salts in hard Water. The additive of this invention permits the use of hard water by inice creasing the stability of the lubricant emulsion therein. This eliminates the costly step of reducing the hardness level of such water in those areas wherein soft water is not available naturally.

US. 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. US. 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 suflicient 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.

U.S. Pat. 3,432,434 teaches a metal rolling lubricant containing an alkylaromatic hydrocarbon which might contain an alkali or alkaline earth metal phosphate or an amine phosphate.

U.S. Pat. 3,523,895 discloses a lubricant composition closely paralleling the composition of this disclosure. However, there is no disclosure or suggestion of the improvement attainable from the use of the specific phosphate of this invention.

SUMMARY OF THE INVENTION This invention provides an emulsifiable lubricant comprising an oil from the group which includes paraflinic and naphthenic mineral oils, synthetic ester lubricants, polyolefin fluids and polyoxyalkylene oxide fluids, a solid aliphatic monocarboxylic acid and an amount suflicient to improve the hard water stability thereof of a mixture of monooleyl and dioleyl phosphates.

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 an oil, such as a mineral oil, i.e. parafiinic or naphthenic oils, 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 a monoor dioleyl 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 by weight of a mixture of monoand dioleyl 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 inch have been attained with the use of the lubricants of this invention.

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 sufficient 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 60 C., preferably from about 80 to about 90 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 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 various individual components of the water-free or neat composition are discussed hereinafter. The formulations set forth overcome the disadvantages of some prior art compositions, i.e. they improve the brightness and cleanliness of cold roll steels, both in the operation and following annealing. They also improve the hard water stability of such formulations.

The oils used in this invention include both naphthenic and paraflinic mineral oils having a Saybolt viscosity in the range of from about 40 to about 500 S.U.S., preferably cfrom about 60 to about 300 S.U.S. at 100 F. and synthetic lubricants, such as synthetic ester lubricants, polyolefin fluids, alkylene oxide-derived fluids and the like having the same broad and preferred viscosity ranges. 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 ad 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 phosphate used in the practice of this invention is a mixture of monoand dioleyl phosphates, wherein the concentration of each component is within well defined limits. The concentration of mono-oleyl phosphate will range between about 30 and about 45% of the phosphate mixture, and the concentration of dioleyl phosphate [C O P(O) OH] will constitute the remainder, i.e., from about 70 to about 55% of the mixture. The phosphates may be prepared in known ways. For example, the monoand dioleyl phosphates can be made separately by reacting oleyl alcohol and POCl in the usual ratio, followed by forming the acid. The individually made components can then be combined to form the mixture of the invention. In addition, the mixed monoand dioleyl phosphates can be made in one step by reacting oleyl alcohol with P 0 usually in the ratio of 3 moles of alcohol to 1 mole of P 0 It will be understood by those skilled in this art that of oleyl alcohol, as commercially obtainable, is not pure C So, the preferred oleyl alcohol, even one prime commercial grade, is not made up wholly of C18 but is about 60% of unsaturated C with lesser amounts of C C C and C alcohols, which may only be partially unsaturated. Some stearyl alcohol may also be present.

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 nonionic emulsifiers, such as amines having from 4 to 36 carbon atoms and the C.;C alkyl phenols, and fatty or resin 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-listed organic compounds obtained by reacting them with an alkylene oxide having from about 2 to 4 carbon atoms, such as ethylene 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 to about 18 carbon atoms, preferably lauroyl amide, possess further improved anti-corrosion properties in the cold-rolling of steel. Oleic acid offers additional oiliness characteristics which aid in the filmforming properties of the lubricant, but it does not provide any anti-corrosion 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 coagents. The combination of oleic acid and lauroyl amide protects the surface of the metal strip against rust in a very effective manner. 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 metalworking 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.

The following examples show how the hereindisclosed lubricants are improved with respect to hard water stability by using the mixed phosphate esters of the invention.

Naphthenic oil havin%a viscosity of 100 S.U.S. at 100 F.

Solvent refined para nic oil having 8. 71500811237 of 100 S.U.S. at 100 F.

Hydrogenated tallow fatty acids having the COmDOSI'tIOD (wt. percent): 13% C14; 23-33% C10; and 6577% C15.

All the components, except for the sulfonate-formaldehyde condensate, were combined under agitation with sutficient water to provide the 30% emulsion. The mixing was performed for about 1 hour, at about to 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 half-hour period, with agitation, at a temperature below 50 C. The cooled mixture was again passed through the homogenizer, while maintaining the temperature be low 50 C., for 1 hour.

The above emulsion was stored for one month at ambient temperatures. At the end of that time, solids separation on dilution was measured by centrifuging. A sample diluted to 3% in ASTM hard water (345 p.p.m.) and centrifuged 10 minutes gave 15 ml. of solids.

EXAMPLE 2 A formulation like that of Example 1 was prepared, with the following exceptions:

(a) 1.0 part of lauroyl diethanolamide instead of 2.0

parts;

(b) 2.0 parts of a mixture of about 40% of monooleyl phosphate and about 60% of dioleyl phosphate in place of the tricresyl phosphate; and

(c) 69.85 parts of water instead of 68.85 parts.

After storing for one month at ambient temperatures, this emulsion gave the following results regarding stability in water. A sample diluted to 3% in the ASTM hard water of Example 1, when centrifuged for 10 minutes gave 6 ml. of solids.

It can be seen. from the results shown in Examples 1 and 2 that the addition of the oleyl phosphate esters of this invention gives a significant reduction in the solids obtained in hard water. Thus, at a 3% concentration in hard water, the mixed phosphate of this invention affords a reduction of 9 ml. of solids (from 15 ml. to 6 ml.). It should be noted also that the specific phosphates of this invention significantly reduce the amount of solids obtainable in distilled water. In this connection, 5% of the Example 1 composition in distilled water gave 7 ml. of solids after 3 minutes of centrifuging, Whereas a 3% dilution of the Example 2 formulation in distilled water gave only 3 ml. of solids after 10 minutes of centrifuging.

I claim:

1. An emulsifiable lubricating composition suitable for the cold-rolling of metals and having increased hard water stability, said composition made by mixing from about 20% to about 60% by weight of a lubricating oil selected from the group consisting of naphthenic and parafiinic mineral oils, synthetic ester lubricants, polyolefin fluids, and polyoxyalkylene fluids, from about 20% to about 50% by weight of a saturated solid aliphatic monocarboxylic acid having from 10 to about 30 carbon atoms, from about 1% to about 15% by weight of an alkanolamine having from 2 to about 4 carbon atoms per alkanol group, from about 1% to about 15% by weight of an emulsifier having a hydrophylic-lipophilic balance of at least 10, from about 0.05% to about 2.0% by weight of an aromatic sulfonate having a molecular weight between about 300 and 800 and from about 2% to about 15 by weight of a phosphate, the improvement whereby said phosphate is a mixture of from about 30 to about 45% of monooleyl phosphate and from about 70 to about 55% of dioleyl phosphate.

2. The composition of claim 1 wherein the mixture of phosphates is present to the extent of from about 5 to about 10% by weight.

3. The composition of claim 1 comprising from about 20% to about 40% by weight of acid having from about 10 to about 20 carbon atoms, from about 3% to about 12% by weight of alkanolamine, from about 3% to about 12% by weight of the emulsifier, and from about 0.1% to about 1.5% by weight of aromatic sulfonate.

4. An emulsion lubricant composition comprising from about 0.75% to about 10% by weight of a composition of claim 3 and from about 99.25% to about 90% by weight of water.

5. The composition of claim 3 wherein the acid is hydrogenated tallow fatty acid.

6. The composition of claim 3 wherein the alkanolamine is triethanolamine.

7. The composition of claim 3 wherein the emulsifier is lauroyl diethanolamide.

8. The composition of claim 3 wherein the aromatic sulfonate is a naphthalene sulfonate-formaldchyde condensate.

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

References Cited UNITED STATES PATENTS 3,523,895 8/1970 Ishibashi et al. 25249.5 X 3,496,104 2/1970 Shimada et a1. 25249.5 X 2,291,066 7/1942 Waugh 252-495 X PATRICK P. GARVIN, Primary Examiner W. H. CANNON, Assistant Examiner US. Cl. X.R.