US2398193A

US2398193A - Lubricant

Info

Publication number: US2398193A
Application number: US512365A
Authority: US
Inventors: Thomas E Sharp
Original assignee: Standard Oil Co
Current assignee: Standard Oil Co
Priority date: 1943-11-30
Filing date: 1943-11-30
Publication date: 1946-04-09
Anticipated expiration: 1963-04-09

Description

Patented Apr. 9, 1946 LUBRICANT Thomas E. Sharp, Chicago, 111., amino: to

Standard Oil Company, Chicago, Ill., a corporation of Indiana Drawing. Application November 30, 1843,

Serial No. 512,385

14 Claims.

This invention relates to improved protective coatings and lubricants. More particularly it relates to compounded lubricants which have, in addition to valuable lubricating properties, the property of preventing corrosion of metal surfaces.

Metallic equipment,'especially iron and steel equipment, exposed to the atmosphere for conslderable periods or time without operation ire= quently develops considerable corrosion, sulll= cient in many cases to impede subsequent operation of the equipment and to reduce its operat ins life.

The above observations apply with particular force to internal combustion engines and other equipment exposed to severely corrosive atmos pheres, such a are encountered, fo example, on shipboard, in coastal areas, and in many indus= trial areas. Engines in military equipment, for example, in automobiles, tanks, trucks, airplanes, tractors, are often subjected to storage in a. corrosive environment for extended periods, for example. as deck cargo in transoceanic shipping. Furthermore, the operation of internal combustion engines, especially spark ignition engines. results in the production of gases which corrode various metal engine parts with which they come in contact. Particularly corrosive gases are generated in the operation of internal combustion engines with fuels containing ethyl fluid.

Heretofore it has been proposed to protect metal surfaces from corrosion by the use of readily removable protective coatings known as slushing compounds. Slushing compounds are petroleum rust preventives and are usually classifled as oils and greases, from the standpoints of appearance, handling and service properties.

Lubricating oils which can also be used as rust preventlves, especially for internal combustion engines, in addition to meeting the usual pecifications concerning viscosity, volatility, ash content. residual carbon deposits, and pour point, must have the following additional properties:

1. Ability to protect metal surfaces from high humidity and moisture condensation;

2. Ability to neutralize acidic corrosive materlals;

3. Ability to be readily applied to and removed from metal surfaces, e. g. relatively inaccessible parts of an engine assembly.

It is an object of this invention to provide compodtions which aflord protection against corrosion to metal surfaces coated thereby. Another object of this invention is to provide corrosion preventive lubricants for metallic equipment stored or operated in a corrosive environment. Still another object of this invention is to provide lubricants which will prevent the occurrence of corrosion in internal combustion engines. A iurther object or this invention is to provide rust preventive lubricants particularly adapted for the lubrication of ordnance. Yet another object or this invention is to provide a method of preventing corrosion on metal surfaces by the application thereto of novel protective coatings or lubricants.

it will be apparent that practical specifications lewd on the properties desired in rust preventive lubricants can hardly be absolute in nature, but relative standards, represented by certain tests have been oil'ered and have received rather wide acceptance. These tests will be described briefly. Unless otherwise indicated all tests are carried out upon polished, cold-rolled, sandblasted S. A. E. 1020 steel panels.

In the humidity test, the small steel panel are suspended in a. highly humid atmosphere, generally about 100% humidity, at a. fixed temperature in a special cabinet and the time of initial corrosion of the panels is noted. The humidity cabinet is provided with heating units and thermal regulators for automatic temperature control. A water level of two inches or more i maintained in the bottom of the cabinet to assure high humidity at all times. The steel panels are coated by dipping into the rust preventive material and are suspended by glass hooks from a glass rod running across the top of the humidity cabinet. Generally from 1 to 1.5 complete changes of air per hour are provided in the cabinet. The minimum acceptable period of protection offered by the rust preventive material in the humidity cabinet test is determined in accordance with the severity of the contemplated service conditions under which the rust preventive material will be applied.

A number of hydrobromic acid tests have been designed to measure the ability of rust preventive lubricants to neutralize acidic corrosive materials. particularly the acidic products of combustion of internal combustion engines. In a well recognized hydrobromic acid test, duplicate steel panels, such as are used in humidity cabinet tests, are swirled for a short time (usually either so or 60 seconds) in an emulsion prepared by vigorous agitation of a mixture of one part of aqueous hydrobromic acid and nine parts of the rust preventive lubricant. Very dilute aqueous hydrobromic acid is used. generally either 0.1 or 55 0.2%. The duplicate panels are then stored in a wood block support in the laboratory atmosphere for four hours and then subjectedto a 24 hour test period in a humidity cabinet, as generally described above. After exposure in the humidity cabinet the duplicate panels are examined for evidence of corrosion or pitting.

I have found that compositions comprising an ester of an anhydroalkitol and a lubricant possess the combination or properties desired in corrosion preventive lubricants. I have further found that soaps of preferentially oil-soluble petroleum sulronic acids constitute a useful addition when added in small proportions to corrosion preventive lubricants containing an ester of an anhydroalkitoi.

By an anhydroalkitol I mean to designate a product of intramolecular dehydration of an alkitol. By an alkitol, I intend to denote a polyhydric alcohol having at least four carbon atoms and at least four hydroxyl groups. Alkitols can be produced by the hydrogenation oi polyhydroxy aldehydes or ketones which occur in nature as sugars or saccharides. Depending on the spatial configuration of the polyhydric alcohol, it can be either optically active or optically inactive, due either to the presence or a meso form of the molecule or to racemic mixtures oi optically active molecules. Exemplary alkitols are the erythritols; pentitols: arabitol, adonital, xylitol, prepared for example by the hydrogenation of pentoses; hexane pentols, e. g. rhamnitol; hexitols: sorbitol, mannitol, dulcitol, iditol, talitol; heptane hexols, e. g. rhamnohexitol: heptitois: mannoheptitol, glucoheptitol, galaheptitol; ctitols: gluco-octitol, manno-octitol; nonitols, e. g. glucononitols, and the like.

The alkitols readily undergo intramolecular dehydration to produce anhydroalkitols, which are polyhydric cyclic ethers. When one molecule of water is lost from an alkitol by intramolecular dehydration, a polyhydric monocyclic ether which I designate as a monoanhydroalkitol or alkitan is produced. When two molecules of water are lost from an alkitcl by intramolecular dehydration, a hydroxy bicyclic ether which I designate as a dianhydroalkitol or alkide is produced.

Intramolecular dehydration or etheritlcation generally results in the production oi 4- to 7 membered cyclic ether, or oxido, rings. The 3- membered cyclic ether ring is sometimes called the oxidopropan ring. The 4-membered ring is usually called the furan ring. The 5-membered ring is usually called the pyran ring. In general, there are manifold possibilities for intramolecular dehydration of alkitols, especially of the higher alkitols, such as hexitols, heptitols and the like. In the higher alkitols it is conceivable that there is some possibility of forming even tricyclic ethers.

It will be appreciated that whenever the terms "alkitan" and alkide" are used, or whenever specific alkitans and alkides are designated, that these terms do not necessarily mean a single chemical compound but may refer to a mixture of several anhydroalkitol derivatives falling therein.

In order to demonstrate the meaning of the nomenclature given above, it will be applied to the alkitol known as sorbitol, which is generally produced by the hydrogenation of glucose. Sorbitol has the following structure:

Upon intramolecular dehydration with the loss of one molecule of water, sorbitol can form a variety oi cyclic monoethers, but generally the main product is an ether containing a furan ring: thus,

nocncnon In acsoncmon and no-cn-cnon somcn n-cmon In addition 4-, 6- and 7-membered oxido rings may be produced to some extent:

once noon cnon s, n-cnion o noon-anon no a non H: H: o

HOCHCH CH:

H! H non Another dianhydrosorbitol may have the following structure:

o\ W/ \CHI C lHOCH-CHOH 1 have found that esters oi anhydroalkitois can be compounded in small proportions with lubricants to produce corrosion preventive lubricants. Esters suitable for the purposes of my invention can be obtained by esterltying anhydroalkitols by conventional esteriflcation procedures. The acid components of the esters may be derived from a variety oi acids, such as the aliphatic carboxylic acids, e. g. fatty acids, or aliphatic carboxylic acids containing a branched-chain structure and/or an odd number of carbon atoms; cyclic carboxylic acids, e. g. cycloaliphatic carboxylic acids or naphthenic acids; aromatic carboxylic acids, alkylaromatic carboxylic acids. aralkyl carboxylic acids, rosin acids; sultonic acids, such as alh'l or aryl suli'onic acids, and the like.

I prefer to use esters ct anhydroalkitols and fatty acids for the purposes oi my invention.

Particularly suitable esters are derived from the unsaturated fatty acids, particularly olelc acid.

Either part or all of the free hydroxyl groups available for esteriiication in the anhydroalkltol can be esterifled to produce products for the purposes of my invention. However, I have found that superior products are obtained when part only of the free hydroxyl groups in anhydroaliritols are esterifled, and preservative and corrosion preventive lubricants containing partial esters, particularly mono-esters of anhydroaikitols constitute a preferred product of my invention.

Also useful for the purposes of my invention are the products obtained by reacting partial esters of anhydroalkitols with alkylene oxides, such as ethylene oxide or propylene oxide to produce polyoxyalkylene derivatives.

It will be appreciated that although a wide variety and large number of esters of anhydroalkitols are available for use in corrosion preventive lubricants and protective coatings, they are not all precisely equivalent. The choice of a particular ester for compounding in accordance with the principles of my invention, will depend on the nature of the base stocks, 1. e. whether it is an oil, grease, wax, etc., the solubility of the particular ester in the selected base stock, the severity of service conditions which is contemplated, the eosts involved, etc.

The esters which are useful for the purpose of my invention can be compounded with a wide variety of hydrocarbon lubricating oils, which may also contain additions oi animal, vegetable or marine oils. The esters can also be compounded with lubricating greases, by which I means solid or gel-like dispersions of soaps in hydrocarbon lubricating oils, or with waxes, e. g. paraflin wax. petrolatum, or ester-type waxes.

In general, esters of anhydroalkitols can be compounded with base stocks in proportions in the range of about 0.5% to about by weight. preferably about 1 to about 10% by weight, based on the total composition. It is generally preferable that the particular ester chosen for use he soluble in the base stock in the proportions which it is desired to use. In the event that the particular ester which it is desired to use is not sumciently soluble in the base stock, the use of conventional solubillzation or dispersion techniques may become necessary.

The following examples will serve to illustrate my invention:

Example 1 Sorbitan mono-oleate can be prepared, for example, by intrarnolecular dehydration and esterification of a three-fold molecular excess of technical sorbitol syrup with oleic acid from white oleine by treatment under a blanket of inert gas such as CO2. at about 500" F. A rust preventive lubricating oil particularly adapted for the protection of aviation engines was prepared by dissolving 3.'I5% by weight of sorbitan mono-oleate in a lubricating oil having a. viscosity index of about 95 and a viscosity of 120 seconds Saybolt Universal at 210 F. The rust preventive oil passed the humidity cabinet test described above, affording ample protection to sandblasted steel strips for 150 hours in a cabinet operating at 120 1". at 100% humidity. The rust preventive oil was likewise subjected to the hydrobromic acid test employing 0.2 hydrobromic acid in emulsion and swirling time of 60 seconds and found to afford sumclent protection.

trample Z A rust preventive lubricant adapted for the protection and lubrication of internal combustion engines was prepared by compounding 5% by weight of sorbitan mono-oieate with 82% by weight of a lubricating oil having a viscosity of 4'? seconds Baybolt Universal at 210 F. and 38% by weight of a lubricating oil having a viscosity of 94 seconds Saybolt Universal at 210 F. The compounded oil thus prepared passed a humidity cabinet test of 50 hours duration at 100 F. and 95-100% humidity. the air in the cabinetbeing circulated at the rate of 1-1.5 complete changes per hour. It likewise passed the hydrobromlc acid test employing 0.1% aqueous hydrobromic acid in the emulsion and a swirling period of 60 seconds.

When tested in a spark ignition engine for six hours at about 2600 R. P. M. at a crankcase oil temperature of 250 I". it was found that there was less than 200 mg. loss per whole bearing. whereas a loss of 500 mg. is commonly tolerated in this type of product.

I have found that soaps of preferentially oilsoluble petroleum sulfonic acids constitute desirable addants to rust preventive lubricants and protective coatings containing esters of anhydro-alkitols.

Petroleum sulfonates are soaps of sulfonic acids obtained by the treatment of petroleum oils with strong sulfuric acid, usually fuming sulfuric acid. The preferentially oil-soluble sulfonic acids remain dissolved in the acid-treated oil; they are commonly known as mahogany acids. Although a wide variety of mahogany soaps can be used for the purposes of this invention, I have found that they exhibit some variation in eflicacy in my corrosion preventive lubricating compositions, depending on their method of preparation.

I have found that superior mahogany acids and soaps therefrom, for the purpose of this invention, can be produced by treating distillates of from about 50 seconds to about 1000 seconds or higher, and preferably from about 200 to about 400 seconds Saybolt Universal viscosity at F. with from about 6 to about 9. pounds, and preferably from about 7 to about 8 pounds of concentrated sulfuric acid, preferably fuming sulfuric acid, per gallon of oil.

The method of obtaining these desirable soaps of preferentially oil-soluble sulfonic acids derived from petroleum oils is illustrated by the following example, which describes the preparation of a sodium soap.

A petroleum oil distillate having a Saybolt Universal viscosity at 100 F. of from about 200 seconds to about 850 seconds is treated with from about '7 to about 8 pounds of fuming sulfuric acid per gallon of oil in one-half pound increments or "dumps." After the acid sludge from each one-half pound acid dump is settled and withdrawn, the next one-half pound of fuming sulfuric acid is added to the oil. The temperature of the oil before the fuming acid is added thereto is maintained below about 60 F. but due to the heat of reaction upon the addition of the sulfuric acid, the temperature of the oil may rise to from about 90 F. to about 100 F. After the required total amount of fuming sulfuric acid has been added to the oil and the oil freed of acid sludge. the acid treated oil containing oil-soluble sulfonic acids dissolved therein, is neutralized with a solution of sodium hydroxide. The aqueous alkali solution is then separated from the oil solution containing dissolved therein sodium soaps of sulfonic acids and the latter then separated from the oil by extraction with alcohol of about 60% strength. The alcohol layer containing dissolved sodium sulfonates is then separated from the oil and subsequently distilled to recover the alcohol and remove water. The crude sulfonic soap obtained in this manner contains from about 30% to about 60% sodium sulfonate, from about 30% to about 60% oil, from about 1% to about water, and up to 10% of inorganic salts which may be removed by the procedure hereinafter described.

The above procedure may be modified after the acid sludge is removed from the acid-treated oil. The 011 containing dissolved sulfonie acids is extracted with about 60% alcohol to remove the sulfonic acid; which may then be neutraliud with sodium hydroxide and subsequently freed of the alcohol by distillation.

The crude soaps of these preferentially oilsoluble sulionlc acids obtained by the procedure described above may be freed of inorganic salts by purification. This purification is preferably accomplished by dilution of the crude soap with from about A to about 10 parts, preferably 1 to 2 parts of 50% or higher strength alcohol, preferably alcohol of 60 to 70% strength, and allowing the salts to settle while maintaining the mixture within the temperature range of 130 to 175 Pt, preferably 155 to 165 1". when the salts have settled the supernatant alcohol-soap layer is separated and the alcohol is recovered by conventlonal distillation procedure. By this method of purification the salt content of the crude suli'onic soap can be readily reduced to 5% or less, e. g., to about 8.5%.

Although I have described a specific method for the preparation of petroleum sulfonic acids suitable for the purposes of my invention, it should be understood that my invention i not restricted thereto, but that suitable organic suifonates having similar properties can be used, however made.

Suitable soaps of preferentially oil-soluble petroleum sulfonic acids for the purposes of my invention include those of metals in groups I, II, III, IV, VI and VIII of the periodic table. Thus. for example, I can employ the sodium, potassium, lithium, calcium, barium. tin, lead, aluminum. chromium, colbalt and nickel soaps of preferentially oil-soluble petroleum sulfonic acids. I can also employ the ammonium, alkylammonium and alkylolamine soaps of preferentially oil-soluble petroleum sulfonlc acids. It is not intended to imply that the wide variety of-sulfonates mentioned above are exactly equivalent for the purpose of my corrosion preventive lubricatin compositions. Because of their relative cheapness and high eflicacy I prefer to use the sodium soaps. especially the sodium soaps of the preferred mahogany acids whose preparation has been described above! The exact proportion of petroleum sulfonate to be used in my corrosion preventive lubricatin compositions will vary with the particular sillfonate chosen for use and upon the severity of the service conditions which are anticipated. In general, I have found that a useful range of commercial petroleum sulfonate is about 5% to about 40%, the actual sulfonate soap content being in the range of about 2% to 16% based on the total composition, the remainder of the commercial aulfonate being associated oil and a small proortion of mineral salts.

The following example is adduced to illustrate the use of a soap of preferentially oil-soluble petroleum sulfonic acid together with an ester of an anhydroalkitol to produce a preservative lubricant in accordance with my invention. All percentages are by weight.

Example 3 U. S.patents:

m? Patentoo Patent am 1,903,011-- F.H.MacLaren... H.-. Iuneiii, 1034 1,003.01 Junal9,l03i 2.0mm?"-....do.- I Feb. 11.1mm 2,051,104-- nmmmmnmarssmmne... Oct. l3, was

,055. F.H.Maoliaren.... Aug.10,1037

The compounded all passed a humidity cabinet test of 200 hours at F. and 100% humidity. fresh saturated air beingdirected through the humidity cabinet at a rate between 1 and 1.5 complete chang s per hour.

As an indication that the rust preventive oil was not itself corrosive, it was found that it did not discolor a bright copper strip to a greater extent than exposure to dry heat in an oven at 212 1''. for three hours.

The compounded oil was applied to a 0.50 caliber M2 basic aircraft machine gun, the gun retained in a cold room at 70 1". for three hours and then 26 rounds fired at full automatic fire. No stoppages occurred during firing and an examination of the gun revealed that satisfactory lubrication was being obtained.

My novel rust preventive compositions may, in addition, contain polymeric thickener-s, viscosity index improvers, oiliness agents, pour point depressants, antioxidants and other well known types of addition agents. Although the use of my rust preventive compositions for the protection of the interiors of internal combustion engines during storage has been emphasized, it is to be understood that they are applicable generally for the protection of metal surfaces, as in gun barrels and breeches, metal containers for pretroleum products or other corrosive materials, idle machinery. finished machine parts and accessories, stand-by or emergency equipment, and the like. The novel antirust agents of my invention may be compounded with a wide variety of normally liquid. semi-solid or solid lubricating or other media.

I claim:

1. A rust preventive lubricant comprising a major proportion of a lubricating oil an ester of and minor corrosion inhibiting proportions of an anhydroalkltol and a carboxyiic acid and an aliphatic soap of a preferentiall oil-soluble petroleum sulfonic acid.

2. A composition comprising a minor corrosion inhibiting proportions of a partial ester of an anhydroalkitol and a fatty acid and a soap of a preferentially oil-soluble etroleum sulfonic acid, and a major proportion of a lubricating oil.

3. A composition comprising a minor corrosion inhibiting proportions of a partial ester of an alkitan and a fatty acid and a soap of a preferentially oil-soluble sulionic acid, and a major proportion of a lubricating oil.

4. The method of inhibiting the corrosion of a metal exposed to a corrosive environment which comprises coating said metal with a sloshing compound comprising minor corrosion inhibiting proportions of an ester of a hexitan and an unsaturated fatty acid and a soap of a preferentially 8. A rust preventive lubricating composition comprising about 5% of sorbitan mono-oleate, about 5% of a soap of a preferentially oil-soluble petroleum sulfonic acid, and a hydrocarbon lubricating oil.

9. A rust preventive lubricating composition comprising about 5% of sorbitan mono-oleate,

about 5% of a soap of a preferential y oil-soluble petroleum sulfonic acid produced y treating a petroleum distillate having a viscosity in the range of about 50 to about 1000 seconds Saybolt oil-soluble petroleum sulfonic acid produced by treating a petroleum distillate having a viscosity in the range of about 50 to about 1000 seconds Saybolt Universal at 100 F. with from 6 to about 9 pounds of strong sulfuric acid per gallon of dis tillates and a major proportion of a hydrocarbon lubricating oil.

5. A rust preventive lubricating composition comprising a major proportion of a hydrocarbon lubricant and minor corrosion inhibiting proportions of an ester of an aliphatic carboxylic acid and an anhydroalkitol and a soap of a preferentially oil-soluble petroleum sulfonic acid produced by treating a petroleum distillate having a viscosity in the range of about 50 to about 1000 seconds Saybolt Universal at 100 F. with from about 6 to about 9 pounds of strong sulfuric acid per gallon of distillate.

6. A rust preventive lubricating composition comprising a major proportion of a lubricating oil and minor corrosion inhibiting proportions of a partial ester of a fatty acid and a hexitan, and a soup of preferentially oil-soluble petroleum sulfonic acid.

'7. A rust preventive lubricating composition comprising a major proportion of a lubricatingoil and minor corrosion inhibiting proportions of a mono-ester of a hexitan and oleic acid and a soap of: preferentially oil-soluble petroleum sulfonic ac Certificate Patent No. 2,398,193.

Universal at F. with from about 6 to about 9 pounds of strong sulfuric acid per gallon of distillate, and a hydrocarbon lubricating oil.

10. A rust preventive lubricant comprising a major proportion of a lubricating oil, a minor corrosion inhibiting proportion of a partial ester of an anhydroalkitol and an aliphatic carboxylic acid, and a soap of a preferentially oil-soluble petroleum sulfonic acid.

11. A rust preventive lubricant comprising a major proportion of a lubricating oil, between about 0.5 and about 15% of a partial ester of an anhydroalkitol and an aliphatic carboxylic acid, and between about 5% and about 40% of a soap of a preferentially oil-soluble petroleum sulfonic acid.

12. A composition comprising a minor, corrosion inhibiting proportion of an ester of an anhydroalkitol and a fatty acid, a soap of a preferentially oil-soluble petroleum sulfonic acid, and a lubricating oil.

13. A composition comprising between about 0.5% and about 15% of an ester of an anhydroalkitol and a fatty acid, between about 5% and about 40% of a soap of a preferentially oil-soluble petroleum sulfonic acid, and a lubricating oil.

14. A composition comprising a minor, corrosion inhibiting proportion of an ester of an anhydroalkitol and an'unsaturated fatty acid, a soap of a preferentially oil-soluble petroleum sulfonic acid, and a lubricating oil.

THOMAS E. SHARP.

of Correction April 9, i946.

THOMAS E. SEAR? certifi d that error appears in the printed It is hereby a correction as follows: Page 74, secon numbered patent requiring 71 inclusive, claim 1, proportions of an anhydroalhitol and it instead and minor eo roston mhtbclmg n carlnyltc Md and a; with the Patent Oflice.

Signed and sealed this 4th day of June,

[ant] lmf th correction therein that the same may conform )3 an tar Of and strike out the zarbox; 'c acid and an aliphatic" and insert onions of an ester f at the said Letters Patent specification of the above d column, lines 68 to minor corrosion inhibiting a'nh droalk'iiol and should be read the record of the case in mm 4 Fird Accident Pm.-

preferentially oil-soluble etroleum sulfonic acid, and a major proportion of a lubricating oil.

THOMAS E. SHARP.

of Correction April 9, i946.

Signed and sealed this 4th day of June,