US2371763A - Lubricant and process for preparing the same - Google Patents

Description

, fled method of preparing the desired compounded PatentedMar. 20, 1945 Arthur Lazar, Concord, Paul Moritz Buedrich,

Berkeley, and Raymond Le Roy Frazier, Concord, Calif., assignors to Associated Oil Company, a corporation of California, Tide ,Water Associated Oil Company, a corporation of Delaware No Drawing.s Application January 5, 1937, 3

erial No. 119,158 13 Claims. (01. 252+) This invention relates to improvements in lubricants and has for a principal object the provision of a compounded hydrocarbon lubrieating oil of highly improved oiliness characteristics. I

Another object of the invention is to provide a lubricating oil having pronounced non-sludgin characteristics.

Another object of the invention is to provide a lubricating oil of sumciently high stability to m prevent the formation of gummy and resinous oxidation and polymerization products. Another object is to provide a novel and simpli lubricating oil.

Further objects will become apparent as the invention hereinafter becomes more fully disclosed.

Lubricating oils for use in engines, particularly internal combustion engines, must have certain properties which tend to assure long continued operation of the engineby providing complete lubrication of the parts thereof, especially the cylinders,- pistons and piston rings which are subject to severe heat conditions.

TLG above is particularly true of lubricating oils manufactured specifially for use in internal combustion engines of the Diesel t e in which higher compression pressures and higher airfuel ratios are essential operating factors.

To maintain such high compression for efliciency reasons the piston rings must fuction perfectly without sticking under the concomitant heat conditions to which the piston and piston rings are subject.

Also the above facts are true when applied to any type of internal combustion engine other than the'Diesel type, even though in the ordinary spark ignition type of engine operating under relatively lower compression pressures than 0 the Diesel type, the operating temperature range of the pistons and piston rings of said spark ignition type may be higher than that of similar parts of the Diesel type.

This is particularly true of the high speed Diesel type of engine equipped with aluminum pistons on account of the better heat conductivity of aluminum when compared to iron. However the object of the invention is to design a compounded lubricating oil which will show the desired stability towards oxidation and polymerization over a wide range of heat and pressure conditions in order to fit into the service of any kind'of internal combustion engine, as partially illustrated by,

(1) Engines operating on spark ignition of compressed gaseous fuels (gas engines) (2)-Engines operating on spark ignition of vaporized liquid fuels (gasoline engines) (3) Engines operating with compression ignition of atomized heavy liquid fuels (Diesel engines).

In all these services it is essential that the lubricant has good aflinity for metal surfaces,

which is maintained at the conditions prevailing on those surraces under a wide range of temperatures and pressures;

In order to more fully comprehend the scope of the invention, it should be understood that mineral oils suitable for lubricating oils consist of a mixture of different series of hydrocarbons.

Depending on the origin of the crude oil, such mixture may include the saturated, the unsaturated, and the aromatic series of hydrocarbons, which are thus above defined for the purposes of the invention and any boning range of Iimsned lubricating oil may include one or more of the above series.

Heretofore in refining lubricating crude oil, it has been considered advisable to so treat the oil that most of the unsaturates and aromatic hydrocarbons will be removed and leave only a body of substantially saturated hydrocarbons for use as a lubricating oil. However such saturated oils are not only deficient in him strength or oiliness, and adherence to metal surfaces, but upon exposure to air at high temperature and high pressures, oxidation occurs in the cylinders of an engine, whereby acidic compounds are formed which is considered the initial step in their deterioration as lubricating oils.

Such oxidation products are of a resinous, oil insoluble, type which gather around the piston rings inthe ring grooves and cause piston ring sticking and thus the ultimate seizure and scor ing of the piston in the cylinder.

Inasmuch as oxidation in general is largely.

a function of temperature, there is a certain temperature range within which saturated hydrocarbons might function well as lubricating oil in internal combustion engines without deteriorabe treated as herein set forth. The processin of the basic' oil may be by well known methods, such as by selective solvents like liquid sulphur dioxide, phenol, dichlorethylether, furfural, nitrobenzene and the like, or by sulphuric acid, or by both, to'any desired degree of refinement.

In the removal of the undesirable constituents of the oil by the above mentioned methods it may be desirableto retain inthe oil certain compounds of acidic nature, as originally present in raw lubricating oil distillates. Reference is specifically made to the so-called naphthenic acids, which by proper application of the treating methods may be left in the refined lubricating. oil. This will be further illustrated in the following description of the process herein disclosed.

There are two methods by which the invention may be practiced. In the first method a raw, lubricating oil distillate containing organic acids normally present in such oil, such as naphthenic acids, is treated in a usual manner preferably with a selective solvent of the type liquid sulphur dioxide, phenol, dichlorethylether, furfural, ni-

trobenzene, or the like to yield a raffinate comprising substantially those hydrocarbons which have the desired characteristics of a lubricating oil. To such treated oil is added suflicient metal oxide or hydroxide; preferably calcium oxide or hydroxide, to form ametal soap in, the oil; such soap comprising about between 0.01% and 1.0% by weight of the oil. The oxides or hydroxides are preferably selected from the group of the soap may be accomplished by adding instead of calcium oxide or hydroxide, the free calcium metal or even a suitable calcium salt, such as calcium acetate, in which the acetic acid radical can be easily displaced by that of the less volatile higher molecular weight organic acids.

Alternatively, where the organic acid content of the lubricating oil is insufilcient to provide a alkaline earth and earth metals, namely, calcium,

strontium, barium, magnesium, zinc, aluminum, chromium. Most preferred of those enumerated is calcium oxide or hydroxide, not only by reason of economygibut also particularly because the calcium soaps are most effective for the purpose of imparting resistance to oxidation and non-sludging characteristics to the oil, but the invention is not limited thereto.

Alternatively the conversion of the free organic acid to a metal soap, more specifically a calcium desired percentage of incorporated soap as above described, suflicient organic acids may be added to the oil prior to saponification to obtain the required soap content, or a desired pre-formed metal soap may be added to an oil lacking in organic, acidity in the desired proportions.

Again, in the event that the treated lubricating oil is lacking in contained organic acids, such acids may be added in the form of fatty acids together with equivalent portions of metal base to form the metal soaps.

In general, the higher molecular weight fatty acids are to be preferred where their calcium soaps areito be used and the type fatty acid to be used may include saturated or unsaturated, hydroxy, or. polybasic fatty acids, or mixtures of the same. Carboxylic acids derived from cyclic nuclei in general are not particularly suitable for our purposes, primarily on account of their very low solubility but also on account of the relative instability of their metal soaps.

However, aryl-substituted fatty acids of the type CnH2n2(Ar) COOH, resemble in their solubility and stability the ordinary fatty acids and therefore may be used in form of their alkaline earth metal soaps.

As examples of different organic acids, which I have been tried, the following tabulation may be presented, showing the solubility characteristics, the stability of the compounded oil and the sludge inhibiting characteristics of each particular soap. The sludging test was carried out by heating a 100 gram sample of the oil, containing 1% by weight of the particular soap, to 330 F., for 24 hours in presence of a metallic catalyst, which contains all the metallic elements present in the oil circulation system of an internal combustion engine (iron, copper, lead) which are also known as accelerators for oxidation.

The color of the original oil before heating and the addition of the soap, was between 10 and 20 TABLE No. 1

. Characteristics of compounded oil after heat test Solubiliity oi seeps Metal soap added to mineral lubricating oil g Thm tures Appearance 54," cell Lovibond None Slight carbonaceous deposit 550 Calcium soup: of saturated acids Melissic acid, 030E500: Slight Slight ppte. of soap 4o Montsnic acid, CflHleOi ..do ..do 45 Cerotic acid, CzaHnO: 5o Lignoceric acid, CuHuOz- Beliemic acid, CaHHOL- Aracbidic acid, 0 11400. 110 Stearic acid, 0 911" 1.... 130 Palmitic acid, CldH32OI-- 180 Myristic acid, 0141111102.. 240 Laurie acid, 0 2151401 300 Capric acid, CmHillOI- 400 Butyric acid, C4Hs0:-- Opaque Acetic acid, CzH Opaque Calcium snaps of unsaturated acids Erucic acid, Cannon-.- Moderate lear 110 Oleic acid, CnHuOa High Slight ppte of soap. Elaidic acid, CisHu I. -....d0 Trace oi soap 60 Linoleic acid, CnHuO: ..do Heavy ppte. of soap Teliairlc acid, curb-o- Y do do Llnolenic acid, fin 200 Chancteristim of com unded oil after h Solubility olsoeps m Metal soap added to mineral lubricating oil Thm color a tum A pearance cell Lovibond Calcium soaps of saturated hydroau acids r Mono-hydroxy stea'riq acid, lBHll02(0H)- Moderate... Clear u. 12o Di-hydroxy stearic acid, CuHuOdOH): do ...do 130 Tri-hydroxy stearic acid, CnHnOflOHh. Trace of soap.. 7 Tctra-hydroxy stearic acid, CuHuOKQHM. do. o 2m Hexmhydroxy stearic acid, C1sHw0:(0H)| Very slight Slight ppte. of soap., 260

' Calcium snaps of unsaturated hydrozy acids Ricinoleic acid, C1aHsa 2( High Gummy ppte 200 Calcium soup: of chlorinated acids i Chlorinated stearic scid...-.' Moderate Clear Chlorinated oleic acid "r Hig "do 150 Calcium soups of cyclic acids Benzoic acid, CaHsCOOH Salicylic acid, C6H4(0H)COOH- Cinnamic acid, aH| H= H 0H..... 550 Hydrocinnamic acid, CflHlCHzCHflCOOH 550 Phthalic acid, CoH|(CO0H)2 c 550 Naphthoic acid, CmHvCOOH 550 Abietic acid, CnHznCO0H Naphthenic acid (extracted irom petroleum) 55 Slight ppte. of soap -1'50 1 Cle 130 Strontium 'naphtheuate. 30 Barium stearato l 150 Barium oleate 110 Barium ricinoleate. 220 Barium abietate Barium naphthenate. Aluminum stearate Clear Aluminum oleate. Slight ppte. of soap. 350 Aluminum abietate Heavy ppte. of A110 400 Aluminum naphthenate Clear 150 Zinc steerato .dc. Zinc oleate. do 200 Zinc abietate g l .d0 250 Zinc naphthenate.. Slight ppte. of ZnO 400 Chromium oleate Heavyppte. oi ch03. 220 Chromium naphthenate -.d0 ..do 250 I Up to 0.1% by weight, 9 Up to 0.5% by weight. 3 More than 0.5% by. weight.

in a Lovibond cell. A darkening of the colorv is therefore indicated by through color substany y 5 treated or untreated, have a higher solvency tially above 20.

In this mode of operation the formation of the soaps involves the formation of molecular equivalents of water by reaction. This water has to be removed from the system because it interieres with the homogeneity of the soap-oil-mixture. To this end, during the formation or addi-* is found that the solubility of most of the soaps in the oil requiring stabilization is definitely limited and is in the lower brackets of: the above percentages. Such solubility varies inversely with the carbon-hydrogenratio f the oil, or with the degree of saturation of the oil. In consequence, the solubility of the alkaline earth metal soaps may be sufficient to retain the soapin a certain oil without precipitation up to a relatively high percentage while, on the other hand, certain, other desired hydrocarbon oilswill precipitate out a portion of the stabilizing soaps desired to be retained.

As an instance of this, lubricating oils derived from asphalt or naphthene base crudes, whether treated lubricating oil distillate has a higher solvency power for these soaps than one which had been treated with either selective solventsor sulphuric acid.

The second method of treatment herein comprehends the incorporation and retention of alkaline earth metal soaps in a lubricating oil regardless of the origin or degree of refinementof the oil.

An increase in the solubility of alkaline earth metal soap and permanency of its solution in an oil maybe accomplished by subjecting the mixture during formation of the soap or after the addition thereof to a temperature of at least about 400 F., for a period of time sufiicient to drive off all water formed by the saponification. However,

with this heat treatment of certain oils, undesirable darkening will occur, and thereforeit is preferred to use an agent which has a dispersing and homogenizing effect on the soap at lower temperature to make the same completely and permanently soluble in the oil and furtherto effect (A) Agents which are of a boiling range lower than that of the oil andwhich are removed from the oil after having exercised their dispersing function.

(B) Agents which are of a boiling range not necessarily lower than that of the oil which will remain in the oil to serve as homogenizers for 'the compounded oil.

.such compounds foundsultable, are compiled in Table No. 2 (Dispersing agents).

TABLE N0. 2 v

Group ADispe1'sing ag nts Dispersing Material used action upon soap Amy} L 1 Poor. Octyl alcohol- Fair. Lauryl alcohoL Good. Benzyl elmhnl Do. Ethylene glycol. Diethylene glycoL. Phen (from! Hexahydrophenol. Good. Amyl ether Poor. Methyl ether oi: ethylene glycol... Good. Methyl ether diethylene glycol--. Fair. Methyl phenyl ether Benzyl ether Do. Butyric acid Poor. Laurie acid.. Good. Nephthenic acid Do. Am lnnafnfn POOL Cellosolve acetate Do. Dimethyl phthalatego. 0. Fair. Good. Poor. 7

D0. Fair. Citral Good. Benzaldehyd Do. Aniline. Poor. Pyridine Do. Dichlorethyl ether--. Do. 'letrachlorethane Do. Chlc m Good. Chlornaphthalene Do. Petroleum naphtha Poor. Coal tar dis Do. Methyl ngphfhnlnnl F in Tetrahydr -f D0.

. Of these listed the methyl ether of monoethylene glycol is particularly useful in the process.

This solvent has a boiling pointof 285 F., and

,metal soap, such as calcium oleate for instance,

which has been made from hydrated lime 'and oleic acid, and the water formed therefrom is tenaciously retained, is mixed with the described performed while under agitation with an inert gas, such as carbon dioxide, nitrogen or the like, which prevents darkening of the oil, and the mixture may thereafter be heated to a temperature corresponding to the boilingi point of the solvent, in the presence of the inert gas, or '8. temperature sufiieient to drive off all the solvent and all the water but insuflicient to distil the oil. I

Experiments confirm the fact that the desired dispersing agents of the type class A should exercise the double function of dehydrating the soap while being soluble in the oil and by the mechanics of these functions it may readily be seen that .an anhydrousv soap is easily dispersed throughout the anhydrous oil to stay in permanent solution therein;

In order to render the solution of soap in oil permanent, it is preferred to subject the mixture to a prolonged heat treatment after the solvent (and water) has been driven off. Ordinarily there is a tendency for some of the soap to form a precipitate-if suddenly chilled, or reduced in temperature immediately after removal of the water anda temperature of about 150 F., andabove is maintainedon the mixture for a period of about '24 hours, a clear solution will result whichwill remain clear indefinitely.

In this respect, it is preferable to so. mix the soap and solvent with a small portion of the hydrocarbon oil and to make a soap stock concentrate and then at a later period, when convenient, to distribute the same in larger amounts of oil to bring the percentage of soap in the final product within the stated limits. This will be better appreciated when it isknown that the ether, water of reaction is abstracted from the soap by the ether and thereby permits the complete solution of the soap in the oil. 7

The mixing of soap and oil is preferably be illustrative.

solubility of calcium oleate a California motor oil of S. A. E. 30 grade at room temperature is between0.1%. and 0.5% 'byweight, whereas by following our specified procedure of dispersing and homogenizing as described under class A, it is possible to maintain up to at least 10% of calcium oleate in solution, and hence more concentrated solutions may be reduced by dilution to the desired percentage.

Agents 'of class B, which may be called homogenizing agents, include such types of compounds as the esters or ethers, or ester-ethers of high molecular weight fatty acids such as oleic or stearic acid; of which methylether of ethylene glycol oleate, diglycol laurate, diglycol oleate, may

Also the esters of mono or polyhydric alcohols, partially or fully esterified, such as derivatives of amyl alcohol, glycol or glycerol, of which butyloleate and amyl stearate are illustrativ'e. By this method it is possible to incorporate even higher percentages of alkaline earth soap into any type of lubricating oil. As an example, it is possible to make a solution of up to 30% by weight of calcium oleate in an S. A. E. 30 grade motor oil, which will stay permanently clear and fluid and which can be blended in with more mineral oil to give a permanent clear solution of any desired concentration between 0 and 30%. Examples of various homogenizing agents 15 used are illustrated in Group Bot Table No. 2A.

- affinity of the lubricating oil.

assures TABLE No. 2A

Group B-Homoqeni2ino agents Homogen- Material used izing action upon soap Butyl stearate Fair. Am lstearaie. Good. D ycol steal-ate Poor.

Et yl oleatc Good.

Butyl oieate Do. Diglycoi oleate. Fair. Phenyl oleate Good. lein Do. Methyl Celiosolve oleate Do. But 1 Cellosclve stearate Fair.

Met yl ester of monochlor stearlc acid. Methyl ester of monochlor oleic Do. Chlordiphenyl i Do.

Furtheragents of class B include halogenated aromatic compounds such as chlorine substitution products of aromatic hydrocarbons and more specifically chlorinated diphenyl. Also certain aliphatic halogen compounds may, be used advantageously as stabilizing agents for the compounded oils, such as halogen substitution products of high molecular weight fatty acids, or their esters. As an example may be given the methylester of monochlorstearic acid.

It is interesting to know that the use of homogenizing agents as above described has an added beneficial effect upon the film strength and metal This is particularly striking with the halogen containing inradients. v

As a special case of great interest we wish to emphasize the following, in which a metal soap, more specifically a calcium soap of a halogenated high molecular fatty acid is used as an oxidation inhibitor. We have found that metal" soaps of a great number of halogen substituted fatty acids are not only readily soluble in mineral oils, but also impart very pronounced oxidation inhibiting characteristics to those oils.

lowing table shows a comparison between a straight mineral oil and a compounded product made from the same oil by addition of a metal soap, using either dispersing agents or homog,

enizers, or by addition of metal soaps of chlorinated' fatty acids.

Teens: No. 3

Comparison of straight mineral oil with oil compounds for stabilization Viscosity s. U. Gray. Flash Fire Californialubrlcsting oils slam.-. 223 no 460 so? no 58' Same, containing 1% by we lit 1 Ca oieate incorporated, us

methyicellosoive as dispersing agents V. 22.2 410 460 612 231 58 Same, containing 1% by weight oi Ca cleats-0.5% oi amylstoarateasbomogenizing t. 22.1 410 465 618132 59 Same containing 1% b we ght V of (5s soap of men orstearic acid 22.2 415 410 612 2&0 as

In the above disclosure a numbervof preferred methods have been indicated for the manufacture of a compounded lubricant containing from relatively minute to large quantities of desired soaps. It should, however, be understood that this invention is not limited to the above examples, and it is possible to also manufacture compounded lubricants by a combination of these steps, and particularly within certain ranges of solubility, by the manufacture of a soap dissolved in a dispersing or homogenizing agent and the utilization of this mixture in compounding the oil. Thescope of the invention is more clearly It appears that the presence of the halogen in the fatty acid radical takes care of thedesirable solubility characteristics as well as the film strength characteristics of the added ingredient, while the fatty acid radical still has preserved its oxidation inhibiting quality.

Metal soaps of the following halogen substituted fatty acids have been found effective.

In compounding'mineral lubricating oils in the various manners described, the general physical characteristics such as gravity, flash, and fire points, and viscosity, are not materially changed so'that the desired stability features in these lubricating oils can be obtained without necessitating any changes in S. A. E. rating. The fol- We claim:

1. The process of preparing a lubricating oil having increased non-oxidizing and non-sludging characteristics under operating conditions in an internal combustion engine, which comprises: preventing oxidation of hydrocarbonsin. a body of petroleumlubricating oil and its normally con tained organic acids by adding to said body sufflcient oxide or hydroxide of a metal from the group calcium, strontium, barium, magnesium, zinc, aluminum, chromium to form a soap theredefined by the following claims.

in comprising about between 0.01% and 1.0% by weight of the oil, agitating the mixture with a common solvent for the oil and soap to efiectpermanent dispersion of the soap in the oil, and

heating the mixture-to a temperature sufficient to distil oil? the solvent with the water of reaction, but insuflicient to distil the oil.

2. In a process for preventing oxidation of pe; troleum hydrocarbon oil exposed to operating conditions of an internal combustion engine in which soap derived from the reaction of a high molecular weight organic acid with a metal base of the group calcium, strontium, barium, mag-i nesium, zinc, aluminum, chromium is dissolved throughout a body of said oil in the proportion of from about 0.01% to 30.0% by weight of the oil under conditions where water is present, the steps which comprise: increasing the solubility of said soap in said oil by adding to the mixture a com mon solvent for said oil and said soap and distilling oil? the water and solvent; said solvent being of an organic nature other than hydrocarbons and having a boiling range lower than the oil but higher than that of water.

3. In a'process for preventing oxidation of petroleum hydrocarbon oil exposed to operating conditions of an internal combustion engine in which soap derived from the reaction of a high molecular weight organic acid with a metal base of the group calcium, strontium, barium, magnesium, zinc, aluminum, chromium is dissolved throughout a body ofsaid oil in the proportion of ,from about 0.01% to 30.0% by weight of the oil under conditions where water is present, the steps which comprise: increasing the solubility of said soap in said oil by adding to the mixture a common solvent for said oil and said soap and distilling ofi the water and solvent; then maintainthe mixture a common solvent for the oil and the soap, and distilling ofl the water of reaction and the solvent.

ingthe mixture under a temperature of about 150 F. for a period of about 24 hours.

4. A lubricating oil for internal combustion en-v venting the sticking of the piston rings of internal combustion engines at high temperatures and pressures.

5. The process of preparing a stable lubricating oil which comprises: dispersing throughout a body of liquid hydrocarbon lubricating oil from 0.01%

s to 30% of a soap derived from the reaction of a high molecular weight organic acid with a metal base of the group calcium, strontium, barium. magnesium, zinc, aluminum, chromium, while in the continued presenceof a agent other than hydrocarbons sufiicient to maintain such dispersion and suflicient to maintain the mixture liquid at normal room temperature when the dispersing agent is removed, then removing the dispersing agent by distillation.

6. The process of preparing lubricating oils which comprises: treating a hydrocarbon lubricating distillate and its normally contained organic acids with a selective solvent and removing the solvent, adding to the oil still containing acids sufiicient oxide or hydroxide of a metal from the group calcium, strontium, barium, magnesium, zinc, aluminum, chromium, to neutralize said acids and form a soap therein comprising between 0.01% and 1.0% by weight of the oil, adding to not less than ten carbon atoms to the moleculev '1. The process of increasing the stability'of lubricating oil so as to lessen or avoid piston ring sticking, which comprises dispersing from .0i%

to 30% by weight'of an oxidation inhibiting soap inthe oil by action of a common solvent for the soap and oil, and then heating the mixture to distill off the solvent and any water that might be present, le'aving the soap permanently dispersed in anhydrous'oil.

8.- The process of claim 7 followed by maintaining the oil for about 24 hours at a temperature above about 150 F.

9. The process of claim '7 in which the soapv is the reaction product of an organic acid having with a metal base of the group calcium, stron- .tium, barium, magnesium, zinc, aluminum, chromium.

10. Ardehydrated soap concentrate comprising -mineral lubricating oil containing oil-soluble-calcium soap of chlorinated fatty acids having at least ten carbon atoms to the molecule and containing chlorine representative of a preponderance of dichloro acids, the composition being substantially free from calcium chloride.

11. A lubricating oil, which is normally freely liquid comprising mineral lubricating oil and at least about one per cent of calcium chloro fatty I acid soap containing chlorine corresponding generally with the dichloro soap, the soap being almost completely anhydrous and freely soluble in the oil without imparting substantial viscosity increase or grease-like characteristics to the original lubricating oil.

12. A lubricating oil according to claim 1l wherein the mineral oil is a naphthenic base oil.

13. A normally liquid Diesel engine lubricatin oil comprising a viscous mineral lubricating oil containing a small percentage of a freely oilsoluble calcium soap of an organic acid having at least about ten carbon atoms per molecule with a film-strength-increasing agent consisting of'chlorine, the soap being present in amount sufficient to overcome substantially deposit of gummy and varnish-like materials in Diesel engine: without producing appreciable viscosity inc'reasr in the original oil and without imparting grease like characteristics.

ARTHUR LAZAR. PAUL MORITZ RUEDRICH. RAYMOND LE ROY FRAZIER.