US2371851A - Lubricating oil compositions and methods of making the same - Google Patents

Description

pH value between 5.5 and 7.5.

Patented Mar. 2o,'194s LUBRIOATING 01L GOLIPOSITIONS AND DIETHODS MAKING THE SAME Y Herschei'G. Smith, Wallingford, and Troy L.

Pennsyl No Drawing.

Lsnsdowne, Pm, asslgnors to Gulf Oil Corporation, Pittsburgh, Pa., a corporation of Application November 25, 1941, Serial No. 420,438

8 Claims. (01. 252-51) This invention relates improvements in lubrieating oil compositions and methods of-making the same. More particularly this invention is concerned with lubricating oil compositions of acharacter adaptedto protect ferrous and other metal surfaces to which they are applied, from rust and other types of corrosion, in addition to aiiording lubrication of such surfaces.

Simple mineral oil films afford limited protection to metal surfaces from rust and other types of corrosion, but do not afford any great protection under severe conditions use. Many socalled anti-rust lubricating oils have been proposed, consisting of mineral-oils with added constituents intended to protect metallic surfaces from corrosion, tarnish or rust.

Most of them are 0! rather limited applicability,

in that while they may ail'ord satisfactory protection to one class of metals, they may be ineiiective, or even deleterious, with another class. This shortcoming is serious for example in the case of electric motors, where surfaces of both steel and sensitivity to moisture and air and other substances to which they are exposed. It is also found that some compounded oils which are effective as regards preventing rust, are deficient in lubricating properties.

Among the objects of the present invention is lishing and, maintaining the composition on the surfaces thereof, remain bright indefinitely, and

copper-alloy bearings (which present a diflicult problem in protection from corrosion) are maintained in'their highly-finished condition even 7 under unfavorable conditions of use. Copper, aluminum, zinc, tin and their alloys are all eiiectively guarded against corrosion and are well household lubricants, machine oils, gun oils, turbine oils, slushing. oils, and the like are prepared,

by selecting a suitable lubricating oil or base and dissolving the required amount of the inhibitor described in the oil.

The invention finds special utility in the case of relatively light (low viscosity) oils, for lubrithe provision of an anti-corrosive lubricating oil composition, of excellent lubricating properties,

adapted to protect steel from rusting while being of itself free from tendencies to corrode copper and other metallic surfaces, and being in itself relatively inert and unaffected by air and molsture.

These and other objects of the invention are achieved by the provision of a lubricating oil composition including, as a rust inhibitor, the

substantially neutral product obtained by reactfatty amines containing from 8 to is carbon atoms; reaction being conducted under conditions such that the reaction product This composition proves to be very ,eflectiveas an anti-corrosion lubricant, ior metal suriaces in general. It forms a tightly adherent oily film on.

the metal, protecting the surface from moisture and air, In addition, the composition itself is tree from any tendency toattack the metal, by reaction. therewith or otherwise. Polished or highly-finished steel surfaces protected by estabormixturehasa -i ng isoamyl octyl acid phosphate with primary cating light mechanism such as electric fans, guns, etc. For example, the invention is especially well suited for improving highly refined lubricating oils, of Saybolt Universal viscosity about to 150 at R, oils of 100' viscosity beingespecially suitable.

Usually 0.5 per cent or less of the inhibitor is sufllcient to impart to lubricating oils adequate rust-inhibiting properties for articles exposed to moisture and air, but as much as 25 per cent by Y weight on the oil is sometimes incorporated to aflord prolonged and complete protection fromrust under extremely severeconditions. Such cellent lubricating and other characteristics in addition to ailording practically complete rust protection under extraordinary conditions.

' The reaction products employed in the present invention are relatively stable compositions un-- der ordinary conditions. At'room temperatures some of them are heavy viscous liquids, others soit solids which melt to oily liquids at slightly elevated temperatures. All are relatively non-j volatile, and are insoluble in water and more or less water repellant. They are very resistant to hydrolysis. The reaction products arehowever soluble in 0. both mineral oils and fatty oils. The solubility varies somewhat with the particular oil, but is quite high in general. 1

. In preparing our rust inhibitors, the isoamyl octyl acid phosphate is caused to react with the primary fatty amine in approximately equal mo-' ,lecular ratios, and the reaction is controlled'so as to produce substantially neutral reaction mixpared by known methods and any of the commercial acid esters may be employed. This acid ester is a di-ester oi ortho-phosphoric acid and has the following formula:

' n n n o n n mc--te-d-o-ko-d-d-cmi H: H 1 H H 1H0 This compound is also known as 3-methyl-butyl,

Z-ethyl-hexyl ortho-phosphate.

The primary fatty amine employed to react with the acid phosphate ester may be represented by the following generic formula:

HrN-CH:( CH!) a-CH:

' wherein n is an even number between 8 and 16.

. I". after mixing the two components. To the This generic class includes the following membars: 7 Mono-capryl amine, canon cumin Mono-lauryl amine, CH; (CH1) roCHa'NH:

Mono-myristyl amine, CH3(CHz)1sCHaNI-I2 Mono-palmityl amine, CHaiCHz) uCHsNHa Mono-stearyl amine, CH:(CH:)10CH:NH2

We sometimes prepare the rust inhibitors by reaction of the ester with some particular one of these amines, but more usually mixtures of amines of this group are employed, as they afford a somewhat better product than if only one amine is used. One commercially available mixture which we ordinarily employ is so-called coco amine, made in known ways by conversion of coconut oil fatty acids into the corresponding amines. Coco amine contains a molar amount of mono-lauryl amine (the C1: amine) with minor amountsof its adjacent homologs. The average molecular weight of coco amine ranges between 200 and 210. A value within this range is considered as the molar weight in reacting with the ester.

The following example illustrates one good way of preparing a rust inhibitor within the purview of the present invention.

Example I.'I'o a suitable vessel equipped with heating and cooling coils and means for mechanical agitation are added 200 pounds of coco amine, and 281 pounds of isoamyl octyl acid phosphate, commercial grade, are slowly added, slowly so 'as to keep the temperature of the reaction mixture below 180 F. whereby to avoid splitting out water from the mixture. After the addition of isoamyl octyl acid phosphate, the mixture has a tained in Example I is soluble in mineral oils,

as are the amines from which it is prepared. Accordingly, we sometimes prepare concentrated solutions of the rust inhibitor in mineral oil by forming them in situ in the oil. In such processes, the fatty amine is first dissolved in the mineral oil, and then the acid phosphate ester added, the mixture being stirred and maintained at desired temperatures until the reaction is complate and the mixture has a pH value within the specified. range. In preparing the oil concentrate, sometimes additional amine is added in the later stages to adiust the pH value as desired. Preparation ofsu'ch a concentrated rust inhibitor is illustrated in the following example:

above mixture 175 pounds of isoamyl octyl acid phosphate were added over a period of two hours. The mixture was agitated with air during the addition and the temperature rose to 185 F. The pH of the mixture at this stage was 3.4. To increase the pH of the mixture, 5 pounds of coco amine were added, which increased the pH from 3.4 to 4.0. Another 4 pounds of coco amine were added to bring the pH into a higher range, and

the pH after this addition was 6.0. Finally 5 pounds more of the coco amine were added to the mixture, which gave a final pH of 6.7. The above mixture, after the final pH adjustment, was added to the mineral oil.

The reaction products prepared as described above may be dissolved in various types of min eral oils and improved anti-rust and non-corrosive oil compositions obtained capable of inhibiting or retarding the rusting of ferrous metals as described.

Example III.-In preparing an oil especially suitable for lubricating household appliances or instruments, the rust inhibitor of the class described is dissolved in a refined paraflinic oil hav- Base oil Improved oil Gravity, API lsoosity, SUV, 100 F Color, Baybolt These oils were then tested for non-rusting properties by the following test: Thirty-six cc. of the oil to be tested and 4 cc. of water are placed in, a l" x 8" Pyrex test tube, and a polished copper or steel strip is immersed in the oil-water mixture; 2000 cc. of humidified air per. hour are bubbled through the mixture, so as to provide mixing of the oil and water. The apparatus is set in a water bath maintained at 122 F. C.) and the original water level in the tube is main tained by additions of fresh water every 24 hours. The test is continued for 12 days, regardless of whether or not the strip shows signs of corrosion. The base oil began to show rust on a steel strip after 6 hours in the test whereas after 12 days the improved oil showed no evidence of rust. 0rdinarily an uninhibited oil will tarnish a copper strip within approximately twelve hours, and will attack a steel strip. Generally the addition of as little as 0.05 per cent by weight of a rust inhibitor such as alkylamine isoamyl octyl phosphate, will maintain both the copper and thelsteel strips free from tarnish and rust for periods up to twelve days, the maximum duration of the test. The test may be carried out with copper, steel, or other metallic strips, such as zinc and tin.

In certain special cases the prevailing conditions are so extreme as to require that a lubricant be extremely highly protective toward metal surfaces. In this case a higher percentage of rust inhibitor is incorporated in the oil.

Example IV.-In preparing one such lubricant,

Example II.-One hundred pounds r 1mm 1" as per cent of the rust inhibitor-was incorporated.

asraeei The oil base selected and the improved lubricant made from it have the following properties:

Base oil Improved oil Gravity, API E. 28. 4 Viscosity, SUV, 100 F 110 109 Color, N PA l. 25 l. 25

This oil is capable of preventlngrusting and corrosion of metals under extreme conditions,

even in the presence of salt or sea water. In.

testing it an aqueous solution of salt is substituted for the water employed in the test given above. the procedure otherwise being the same. Both the base oil and the improved oil were tested.

The improved oil showed no evidence or corroding either copper or steel after 12 days in either of the above tests, whereas the base oil allowed the steel strip to rust in approximately 8 hours in the fresh water test and in about 3 hours in the salt water test. The copper strips were more slowly attacked, but overnight were coated with a greenish deposit.

The specific embodiments described above are merely illustrative of the practice of this invention and other embodiments thereof may be used as desired; for instance, these rust inhibitors are compatible with various other compounding ingredients and they may be added to blended oil bases or compounded lubricants to obtain other types of improved lubricants. Improved oil compositions can be prepared from base oil containthe opum results for a given not of the agent in oil are secured when the pH value is mainted wi the stated range of 5.5 to 7.5 for the compounding agent. There is usuall a slight drop in pH value in the dilute finished oil solution as compared with the values for the compoding agents or mixtures thereof. The "i ..;;.1 ed oil (which usually contains only a small should test between 5.0 and 6.0; advantageously around 5.7.

Any substantial departure from the stated re either on the alkaline or acid side gives less desirable results. For example, with an unduly low pH value (acid-side) there is some rustins of steel surfaces by our steel'strlp corrosion test, while compositions with an excessivel high value (alkaline side) may produce greenish cor rosion effects by the oxidation tests with copper surfaces and'the like, although not afiecting steel to any appreciable extent. The exact adjustment is attained'in preparing the compound (e. g. cocoamine salt of isoamyl octyl phosphate) by reacting the desired molecular proportions of the two agentsinthe manner described, and after the neutralization or compounding reaction has progressed practically to completion, by testing the ing varying amounts of fatty oils admixed with mineral oil, such blends being especially useful as household lubricants. By the present invention, any of the previously known household or other lubricants containing relatively light lubricatng oils can be improved by adding small amounts of our rust inhibitors as described.

The invention is equally applicable to heavy mineral oils, petrolatum oils. greases, and jellies;

in fact to any petroleum lubricant ,or coating oil,

in which corrosion-preventive properties are desired. In the claims the term lubricant includes mineral oils, jellies and the like even when used for purposes other than strict lubrication; e. g. slushing oils and gun greases.

One important application of the present invention is to the prevention of rusting in aviation engines after these have been used, either upon aging inintermittent actual service or in storage of engines or planes awaiting completion of assembly, shipment, and other delays after engine break-in. Such rusting is aggravated by the presence in 'the crankcase and crankcase-0110i reaction product, and making any minor adjustments that are necessary for exact control by adding the required small additional proportion of the amines (if on the acid side of our desired range) or the isoamyl octyl phosphate (if on the alkaline side) In measuring the pH of the agents of the present invention and oils containing them, which are both substantiallywater-insoluble, the samby electrometric or colorimetric procedures; the.

sion thereof in the presence of moisture and air,

comprising a. petroleum lubricant containing in solution in a proportion sumcient to prevent rust ind, a substantially neutral addition product of 3-methyl-butyl, 2j-ethylhexyl acid phosphate and a primary fatty amine containing from 8 to 18 moisture, Sulfur, oxidation products from petroleum, tetraethyl lead, decomposition products, etc. Attempts have been made to remedy this conditionby washing out all motor oil from the cranh= case of 'an engine if it is to be stored for any appreciable time, or adding compounds containing .large amounts of oiliness agents and the like.

The present invention presents a more economical remedy for these conditions, for corrosion iseifectively retarded under such conditions when from 0.5 to 1.0 per cent by weight of our compounds is added to a used motor oil. Adding-the highly potent rust preventive compound during the latter part of the break-in period for the new engine, with operation for sufficient time after addition to assure .full mixing and coating of parts, will prevent rusting.

Extensive tests in which the pH values of the agent of the present invention as employed in tinished oils were varied confirm our discovery that carbon atoms, said product having a pH between 5.5 and 7.5 and cone the said acid phosphate and amine chemically combined together in molar ratios between 1:1 and 1:l.l.

2. The compositio oi' claim 1 wherein said amineiscocoamine.

s. The composition of claim 1 wherein said p troleum lubricant contains from 0.01 to 25 per cent of said substantially neutral addition product dissolved therein.

4. A composition effective as a lubricant for metal'surfaces and capable of preventing corrosion thereof in the presence of moisture and air, comprising a. mineral oil containing in solution I from 0.01 to 25 per cent of'a substantially neutral addition product or 3-methyl-butyl, 2-ethyl-hexy1 acid phosphate and a primary fatty amine containlng from 8 to 18 carbon atoms, said product having a pH.between 5.5 and 7.5 and containing the said acid phosphate and amine chemically combined together in molar ratios between 1:1

and 1; 1.1.

ropoition of the dilute compounding agent) 5, A lubricating oil for metal surfaces capable of preventing corrosion thereof in the presence of moisture and air comprising a mineral 011 containing between 0.01 and 0.5 per cent of a substantially neutral addition product of 3-methylbutyl, z-ethyl-hexyi acid phosphate and a primary fatty amine containing from 8 to 18 carbon atoms, said product having a pH between 5.5 and 7 .5 and containing thesaid acid phosphate and amine chemically combined together in molar ratios between 1:1 and 1: 1.1.

6. A method of preparing an oily composition, useful as a rust preventive lubricant, which comprises admixing with a mineral oil at least one primary fatty amine containing 8 to 18 carbon ,atoms, dissolving in said mixture an equimolecular quantity of 3-methyl-butyl, Z-ethyl-hexyl acid phosphate and maintaining the oil solution of reactants at a temperature between 80 and 185 F. until the reaction is substantially complete and then adjusting the pH of the reaction mixture to within the range 5.5 to 7.5 by the further addition of approximately 0.1 mole of said amine.

7. The method of claim 6 wherein said primary fatty amine is cocoamine.

8. A method of preparing lubricant compositions, capable of preventing corrosion oi steel and, other metal surfaces in the presence of moisture and air, which comprises dissolving in mineral oil at least one primary fatty amine containing 8 to 18 carbon atoms, gradually adding an equimolecular quantity of 3-methyl-butyl, 2-ethylhexyl acid phosphate to the oil solution of said amine, at such a rate as to control the vigorous exothermi: reaction and maintaining the reac-' tion mixture below 185 F., agitating the oil solution of said. reactants at such temperatures until the reaction is substantially complete, and then adjusting the pH of the reaction product to within the range 5.5.to 7.5 by the further addition of approximately 0.1 mole of said amine.

nnnscnm. 6. SMITH. \TRQY n CAN'I'RELL.