USRE23229E - Compounded lubricating oil - Google Patents

Description

Reissued May 9, 1950 Van'Ess; Berkeley, Calif.,

assignors to Shel-I Development Company; San Francisco, Calif., a

corporation of Delaware Nonrawin Original No. 2,416,652, dated N vember 5, 1946, Sfidl' NO. 591,404, May'l, 1945: Application forreis'sue J anu'ary 21, 1950,"Serial- Matter enclosed in heavy brackets appears in the originalpatent-but"formsno partof this reissuespecification;matter printed -in-italics indicates the additionsmadelay reissue This invention-relates to addition agents "which contribute valuable-properties to lubricating oil. It also relates to im-proved 'lubricating compositions containing-the herein -described additivesl 1 It is known that-a substantially non corrosive, undoped; lubricating oil generally becomes progressively corrosive under ordinary conditions of engine usewThis tendency is increased or accelerated,--for instance; by an elevation oftem perature, by traces'of dissolved GOPDEIybY deg radation products formed in theoil, and byother factors. It is a common-practicetoadd a detergent to a lubricating oil in-order to assist in the removal ofsoot or sludge which is formed in the engine operation and thus to help keepthe bearing surfaces clear. However, normally such detergents simultaneously contribute to or increase the corrosiveness of the lubricating oil. Similarly, additives employed for other purposes may also prove corrosive. Thisresult is 'particu larly unfortunate, if uncorrected whenit occurs in enginescontainingrmodern alloy bearings,- such as those of copper-lead,cadmium-silver, cadmium-nickel, etc since; such bearings, despite their other beneficial properties, are especially susceptible to'such corrosion.

The kinds ofbo'rrdsi'ciri, like the causes, are complex in nature" and varied in origin; For '1 example, acids found'or formed in' an oil orfue'l may attack copper-Headbearings to preferen tially'rernove" the lead? or'aqu'e'ous acidsolutions' may preferentiallyremove-the coii'perl Again,

1e 'effectfat high temperatures on modern'bea 1115's;- ofsulfurdrived froni certfih of its cornpoundsor even found free in the "oilor 'fuel;"-'

b e've'ry seriousz Thus; the "presence-of sulfur may induce pitting of 'bearingsurfacesi such as exhaust valve'stemfguidesj etc -whichare'formed of certain"alloys, -e.' g.-:copper zinc'." Also; in" hot countries-a crankcasetemperature of 250 TE 300 Fjmay occur, with the corresponding bearingtemperatures-goin'g upto=-325 F. or 350 1 Under these conditions sulfur can produce hard; brittle, black deposits orr-copper lead-or silver bearings. Such deposits may adhere and reduce the bearingclearanceor they may break up and 1 gougeout the bearing, in either event resulting in hearing failure.

The problem of engine deposits is particularly f acute in aviation-and similar engines, in which the high temperatures developed in the cylinders tend to act upon lubricating oils to cause thedeposition of resinous and varnish-like products on the pistons and elsewhere and to--produce lacquer-like coatingsand carbonaceous materials, I which in time tend to causering and'valve stick ing and interfere with engine operation. --High piston temperatures formed especially in avia 7 tion engines promote the formation of deposits which, in turn, aggravate thesituation by reducing' the heat transfe'n I Furthermore fuel residues from incomplete combustion of fuel con tribute to the deposition of lacquer-like and carbonaceous materials inth'e engine. High exhaust gas temperatures foster corrosion by-pitting,- etc.

Solution of'the problem is additionally complicated byrig'id government specifications for avia tion lubricating oil which restrict theincorpora} tion of any additives, such asmetallic salts,'-which would leave a nonvolatile ash uponco'mbustion.

At the most, the total jashcontent" should not exceed about 0.25%"(det'ermined as-sulfat'e) and preferably should be below 0.2%;

corrosion resistance-stability in -presence of-cop per-or crankcasecatalyst, oxidation stability, and

the like. Another purpose is to produce a superior heavy duty lubricant particularly suitable for use in aircraft and other internal combustion engines operating at relatively high cylinder temperatures. Other objects will be apparent from the following description.

It has now been found that such lubricating problems may be overcome to a notable extent by the incorporation in a lubricating oil of two additives. The first of these additives is an oilmiscible metal salt of the condensation product of a low molecular weight aldehyde with a hydrocarbon-substituted phenol. The second additive is an aromatic amine antioxidant (as will be more fully described hereafter).

The first additive is more fully described by the following. It is initially a condensation product of a phenol with an aldehyde. The phenol must have an available ortho position, i. e. an unsubstituted position ortho to the hydroxyl radical, and also such substituent groups, preferably in the 4 or 2,4 positions, as will promote oil solubility. For example, alkyl, cycloalkyl or aryl groups, such as butyl, amyl, hexyl, heptyl, octyl, nonyl, decyl, lauryl, stearyl, oleyl, cyclohexyl, methylcyclohexyl, ethylcyclohexyl, dimethylcyclohexyl, propylcyclohexyl, trimethylcyclohexyl, dicyclohexyl, methylated dicyclohexyl, benzyl, ethylphenyl, etc., are effective. The aromatic nucleus as well as attached hydrocarbon radicals may also contain chlorine. The aromatic nucleus may be monoor di-cyclic, resulting in such nuclei as naphthalene, tetraline, diphenyl, etc.

A lower molecular aldehyde, preferably formaldehyde or acetaldehyde, is condensed with the phenol at the ortho position by ways known to the art, for example by heating with acid or basic catalyst, whereby a resinous condensation product is obtained. Depending upon starting materials and condensation conditions, the products vary in appearance from viscous liquids to more or less brittle solids which may or may not be crystallized. A number of such resinous condensation products are commercially available, and since their methods of manufacture are generally known, further details regarding such manufacture will not be recounted here.

The phenolic resin is in turn converted to the metallic salt, for example, by treating with lime to produce'the calcium salt. In general, the alkaline earth metals are preferred to form the salt, although other polyvalent metals such as Cu, Zn, Al, Pb, Fe, Ni, Co, Mn, Cr and Sn may be employed.

The resultant metal phenates may be diflicultly soluble in oil. However, they may be incorporated in oil by the procedure described by Cornell in U. S. Patent 2,042,880. A simpler method which is effective for many of these salts is to dissolve them in a suitable solvent such as benzene, and then, while adding oil, gradually remove the benzene by distillation, for example, by passing an inert gas (nitrogen, natural gas, etc.) through the mixture at an elevated temperature. This generally results in a stable concentrate of the detergent salt in the lubricating oil which may then be diluted with further oil to give the desired salt concentration when needed. On the other hand, the salt may often be incorporated in a lubricating oil, without preparing an intermediate concentrate, by simply adding the desired concentration of the salt to the oil at an elevated temperature with agitation.

The amounts of the phenol-aldehyde resin salt which may be added to aviation and similar high temperature lubricating oils ordinarily must not exceed about 0.25% ash, because ash in these lubricating oils eventually accumulates in the combustion chamber of the aviation engine by leaking past the piston and piston rings, or else leaking into the super-charger (with which most aviation engines are now equipped) whence it returns with the air to the combustion chamber. About 90% of the oil lost in aviation engines is normally by way of the super-charger.

It has been stated that phenol-aldehyde resin salts ct as anti-oxidants in lubricating oils. However, we found that under the high temperature conditions in aviation engines and in the amounts of ash contents of about 0.25% or less,

such is not the case. Only when added in much larger amounts, i. e. of ash contents of 0.3% or higher, do these salts show anti-oxidant properties in aviation lubricants under aviation lubricating conditions.

As a result of their lack of anti-oxidant properties, aviation lubricating oils containing these salts in the permissible amounts are not only oxidation unstable, but may also be corrosive, and to overcome these detrimental efiects, we add a second addition agent to lubricating oil as described below.

The second additive is an oil-soluble, relatively stable, aromatic amine anti-oxidant, free from corrosive sulfur, preferably having at least two aromatic rings, which may be condensed in one radical attached to the nitrogen atom. Especially valuable are those amines which contain at least one aromatic nucleus having two or more condensed or polycyclic aromatic rings. Thus, preferred anti-oxidants are, for example, the naphthylamines: primary, secondary or tertiary alkyl, aryl or aralkyl amines in which the alkyl, aryl or aralkyl radicals are attached to an aromatic nucleus or preferably to the nitrogen atom or both, such as phenyl-alpha or beta-naphthylamine, tetraline naphthylamine, alpha alpha, alpha beta, or beta beta dinaphthylamines, various phenanthryl, anthryl or picyl naphthylamines, xenyl naphthylamines, benzyl phenyl naphthylamines, diphenyl naphthylamines, phenyl xenyl naphthylamines, dixenyl naphthylamines; also various phenanthryl, anthryl or picyl phenyl amines, etc. The N-aryl substituted naphthylamines are in general more useful for our purpose.

If desired, however, other aryl amine anti-oxidants may be used, such as diamino diaryl alkanes, e. g., diamino diphenyl methane, tetra- 1 methyl diamino diphenyl methane, tetra methyl diamino triphenyl methane, tetra ethyl diamino triphenyl methane, diamino diphenyl ethane, diamino ditolyl ethane, etc., alkylated diaryl amines, e. g., p-ethyl diphenylamine, m-ethyl diphenylamine, p-isopropyl diphenylamine, monoand poly amyl, hexyl, heptyl, octyl, nonyl, decyl, hexadecyl, cyclohexyl, methyl cyclohexyl and other alkyl substituted diphenylamines, etc.

The aryl amine anti-oxidants may, in some cases, contain one or more substituents, such as hydroxyl, chloro, alkoxy, hydroxyalkyl, amino, n-alkylated amino, n-alkylated amino alkylene, etc., radicals. As illustrative of these substituted aryl amine anti-oxidants, the following may be mentioned: p-methoxy p'-isopropyl diphenyl amine, and Lil-diamino naphthalene.

Effective amounts of the aryl amino anti-oxidants in an aviation lubricating oil are in the order of 0.1% to 0.5% by weight. although quantities 5 of between 0.2% and 0.4% are usually sumcient. Amounts of the metallic phenate between about 0.04% and 0.2% sulfate ash are generally used, although in some cases up to about 0.25% may be employed. It willgbeseen. that. the: small amounts of additives. sufficient to. accomplish the present.

purpose. are. much lessthan: would be required to alter theviscosity of. thelubricating composition. Ithas-been found that: the-combination of the aldehyde-phenolcondensatemetal salt. and. an.

To appreciate these advantages, it. may be well to consider a. few of the difficultieswhich confront the producer of improved. aviation lubricants. It is well known that ring sticking is one of the most frequent causes of damage to aviation engineswhich are. lubricated by straight mineral lubricating oils. While ring sticking can bBIOVB1- come to a certain extent by the use of taperedpiston rings, this advantage is gained atthe expense of a new difficulty, namely, ring feather- 3 ing. Ring sticking in aviation engines. is a hightemperature detergenc'y problem, while ring feathering is a wear problem.

Many detergents have been proposed to overcome ring sticking. However, with few exceptions they fail to function at the high temperatures of aviation engine operation, their beneficial action being. restricted inmost instances to lower temperatures such as occur in Diesel engines and automotive engines. It has been discovered, however, that the aldehyde-phenol condensate salts of this invention exertv an unexpected detergency at high temperatures, but not at low temperatures. At the same time, these salts somewhat reduce engine wear and also cause a very pronounced softening of hard. carbon normally formed.

Now asaresult of the presence. of ametal-containing detergent, corrosiveness of the. oil increases. It has been. said. that anti-oxidants overcome. corrosifvenessv induced by detergents. However, this does not always appear to be true. For example, the aldehyde-phenol. condensate salts are known to exhibit anti-oxidant action at low temperature and therefore might be expected to inhibit ccrrosiveness.

0.2% (sulfate ash) of the additive. Certain other anti-oxidants do to some extent inhibit this corrosiveness, but have thedisadvantage of causing at least a partial loss of the carbon softening properties. Moreover, these inhibitors, like the ordinary phenolic inhibitors, such as the 2,6-ditertiary-butyl-4-methyl-phenol, fail-to have any However, this was found not to be the case whenemploying,

ill

tion in itself is believed to be unusual. As a rule, two wear reducing agents do not cooperate unless they meet certain conditions indicated below, and on the contrary merely compete for the surface, the more, stron ly adsorbed compound displacing the other. Therefore, in so far as wear reduction is concerned, only the stronger agent is active.vv Qnly where sO-calledWchemical polishing agents and wedging compounds are combined, asshown by Beeck and Givensin their articles on The mechanism of boundary lubrication, Proceedings of. the Royal Society of London, Serial A, No..9.68, voll'l'l, pp. 90 to 118, December, 1940, and in the. Proceedings. of. the special summer conferenceon friction and surface finish of Massachusetts Institute of Technology, Cambridge, Mass, June's, 6 and. '7, 1940, p. 112, has it been known that two. or more reducing agents cooperate. However, neither of the two additives of this. invention is. a chemical polishing agent or a wedging compound.

Due to-this strong wear-reducing effect combined with the detergency, the present oil will ameliorate high. temperature: difficulties whether due to ring sticking or ring feathering, so that it maybeemployed: advantageously with either the straight or tapered type of piston ring.

In: military aircraft engine service in which piston ring belt lubrication is a primary problem, thislubricating oil composition, by its reduc tion of ring stickingand wear, offers a unique and heretofore.- unobtainable solution to this problem. Various other advantages of the present lubricant may be seen from consideration of the data hereinafter recorded.

The preparation of a typical aldehyde-phenol. condensate salt is illustrated by reference to the use of calcium salts of methylene bis p-iso-octylphenol. This compound was prepared by condensing phenol and diisobutylene to yield an (principally para) iso-octylphenol. This was then condensed with formaldehyde to yield the resinous condensation product containing about five molecules of iso-octylphenol per molecule of resin, but which for convenience is called methylene bis-p-iso-octylphenol. The condensate was converted to. calcium salt by reaction with lime as follows: About equal weights of resin and CaO were ground together to a fine powder. Water was added and the mixture heated on a steam bath in an open vessel. A vigorous reaction took place involving hydration of 09.0 and formation of the phenate. salt. The salt was taken up in warm benzene and filtered from excess Ca(OH) 2. The bulk of the benzene was removed by distillation at atmospheric pressure; the remainder of the solvent was stripped under reduced pressure.

The resulting. residue, a glassy amorphous solid,

was then ground to a yellow-green powder. The sulfate ash values of different batches varied from about 20% to 22%.

The doped and undoped oils were tested? by a test known as the Thrust bearing corrosion test (described in the National Petroleum News, September' 17', 1941, pp. R-294296), which is carried out as follows: A hardened steel disc is made to rotate for 20 hours under constant pressure against three fiat. copper-lead bearings. The bearing assembly rests in. a steel cup filled with the oil to be tested, and the temperature of the oil is maintained at a predetermined figure by thermostatic control. The. bearings are weighed before and: after the test, the difference in weight representing the loss sustained during the test.

I i V Tenn: 7

Tests in thrust bearing corrosion machine [Fixed conditions: Cu-Pb bearings, 20 hours duration, 125 p. s. l. Thrust, 2400 R. P. M. A refined, undoped, commercial aviation lubricating oil, 115-125 S. U. at 210 F. was employed, except where noted] q Bearing weight loss in mgJcm. at- Additive Edt h 1 None 1 I 0. 3 Y O. 1 i). 3 26. 8

2 Calcium salt of methylene bis p-iso-octylphenoL. 2,11% '5: 3 3: 8:; g 7 -e 3 Calcium salt of methylene bis-p-isc-octylphenol. 0.05% S. A. 58

+calcium petroleum sulfonate 0.1% S.

4 Calcium salt of methylene bis p-iso-octylphenol 0.1% S 24 7 +phenyl alpha HaDhthylLrninP 0.1% w

5 Calcium salt of methylene bis p-iso-octylphenol. 0.05% S. 58 5 +phenyl alpha naphthylamine 0.1% wt 17 6 44. 6 41 9 +calcium petroleum sulfonate 0.1% S. A.- 0.1 0.5 7 2 21.6 63 6 6 Calcium salt of methylene bis p-iso-octylphenoL. 0.05% S. A.

+phenyl alpha naphthyhmine 05% wi- 29, 2 +ca1eium petroleum sulionate 0.1% S. A-

7 Calcium salt of methylene his p iso-octylphenol 0.25% S. A

+phenyl alpha naphthylamine 0.25% wt 4 7 +calcium petroleum sull'onate 8 Calcium salt of methylene bis p-iso-0ctylphenol.. 0 S A +phenyl alpha naphthylamine 0 24 3. 2 2 0 +calcium petroleum sulfonatc 2. 6 2 9 Calcium salt of methylene bis p-iso-ootylphenol.. 0.2% S. A.--" 0. 3 8 2 13. 0 l9. 4 2.4 15. 5 2 10 Calcium salt of methylene bis p-1sc-octylpheno1. 0.3% S. A. 0.11 0. 2 2 11 Calcium salt of methylene bis p-iso-octylphenoL. 0.2% S. A 0.0 1. 1

+calcium petroleum sultcnate 0 1 0 2 I 0.1% S. A..-" 0.2 24.8 2 12 Calcium salt of methylene bis p-1so-octylphenol- 0.2% S. A..

+calcium petroleum sulfonatc--- A- 0. 0 0. 0 0 2 17. 9 +phenyl-alpha naphthylamine 0.2% wt 5 13 Calcium salt of methylene his p-iso-octylphenol 0.2% S. A..- 1. 65

+Calcium petroleum sulfouate 0 12 4.16 +phenyl-alpha naphthylamima" 1 1 Based on sulfate ash. I 2 In tests 9-13, a refined, undoped, industrial lubricating oil, S. A. E. grade, was employed as the base oil.

Effectiveness of alubricant containing the presas oil-soluble salts of various bases with deterent combination of lubricating oil additives in acgent forming acids. Such bases includes metal as tual engine tests as well as comparison with some well as organic bases. Metallic bases include other blends may be seen from the following those of the alkali metals and other metals, such data: Mg, Ca, Sr, Ba, Zn, Cd, Al, Sn, Cr, Ni, 00, etc. BEARING Coasosxvsmzss AND USED On. PROPERTIES rg bases include various nitrogen bases as primary, secondary, tertiary and quaternary Lauson l-cylinder liquid-cooled engine a,mines s eed R. P. M 1,700 Examples of detergent forming acids are the BMEP p. s. i 55 various fatty acids, of say, 10 to 30 carbon atoms, Load H. P. (1 kw. 1.6 Wool fat acids, parafiin wax acids (produced by Jacket temp. C 100 oxidation of paraflin, wax), chlorinated fatty Oil sump temp C 140 acids, rosin acids, aromatic carboxylic acids in- Fuel Aviation base stock eluding aromatic fatty acids, aromatic hydroxy Test length hours 40 fatty acids, paraflin wax benzoic acids, various [A refined, undoped, commercial aviation lubricating oil, 115-125 S. U. at 210 F. was employed] Concentra- Cu-Pb I Oil con- Sap. N o. Neut. No. Isopent. Chlor. Additive $3 1 3. g fiff g sumptlon, MgKOH, MgKOlI, ins, 11.5.,

' cc. g. per cent per cent sulfate ash nag/cm, g

None 1. 3 21.1 v o. s 0. or o. 01 Calcium salt of methylene bis pisooctylphenol g: &2 5:: g: 3: Calcium salt of methylene bis p-is0octylphenol 0.10

+phenyl alpha naphthylamine l 0. 2 1- 9 2. 6 4. 5 0. 7 0. 06 0.05 +sod1'um petroleum sulfonate 0. 02 Calcium salt of methylene bis p-isooctylphenoL 0. 225

+phenyl alpha naphthylamine 1 0. 2 1. 2 3. 9. 9 2. 4 1. 6 0, 05 +ca1cium petroleum sulfonate 0. 075

1 Per cent by weight.

Other additives may also be present, such as alkyl salicylic acids, phthalic acid monoesters, blooming agents, pour-point depressants or visaromatic keto acids, aromatic ether acids; dicosity improvers, anti-oxidants, extreme pressure phenols as di(alkylphenol) sulfides and disulfides, agents, anti-foaming agents, etc. methylene bis alkylphenols; sulfcnic acids such In order to provide detergency for the lubrias may be produced by treatment of alkyl aryl eating oil when employed at low temperatures, hydrocarbons or high boiling petroleum oils with other oil-soluble detergents maybe included, such sulfuric acid: sulfuric acid mono-esters; phosphoric, arsenic and antimonic acid monoand di-esters, including monoand diesters of the corresponding thio phosphoric. thio arsenic and thio antimonic acids; pliosphonic and arsonic acids, etc.

Additional detergents are the alkaline earth phosphate di-esters, including the thiophosphate di-esters; the alkaline earth diphenolates, specifically the calcium and barium salts of diphenol mono and polysulfides.

Non-metallic detergents include compounds such as the phosphatides (e. g. lecithin), certain fatty oils as rapeseed oils, voltolized fatty or mineral oils, etc.

An excellent metallic detergent for the present purpose is the calcium salt of oil soluble petroleum sulfonic acids. This may be present advantageously in the amount of about 0.025% to 0.2% sulfate ash.

Anti-oxidants comprise several types, for example alkyl phenols such as 2,4,6-trimethylphenol, pentamethylphenol, 2A-dimethyl-S-tertiarybutylphenol, ZA-dimethyl-6-octy1phenol, 2,6-ditertiary-butyl-4-methy1phenol, 2,4,6-tritertiarybutylphenol, etc.

Corrosion inhibitors or anti-rusting compounds may also be present, such as dicarboxylic acids of 16 and more carbon atoms; alkali metal and alkaline earth salts of sulfonic acids and fatty acids;

organic compounds containing an acidic radical in close proximity to a nitrile, nitro or nitroso group (e. g. alpha cyano stearic acid).

This application is a continuation-in-part of our copending application, Serial No. 502,706,

filed September 15, 1943, now U. S. Patent No.

2,375,222, issued May 8, 1945.

We claim as our invention:

1. A low ash content lubricating oil for high temperature internal combustion engines containing an oil miscible metal salt of the condensation product of an aldehyde and an aromatic hydroxy compound in amount sufiicient to give high temperature detergent action, but not exceeding about 0.25%, based on sulfate ash, and an oxidation-inhibiting quantity of an oil-soluble, relatively stable aromatic amine anti-oxidant.

2. An aviation lubricating oil containing from about 0.04% to 0.25% (based on sulfate ash) of an oil miscible metal salt of the condensation product of a low molecular weight aldehyde and an aromatic hydroxy compound and from about 0.1% to 0.5% by weight of an oil-soluble, arcmatic amine anti-oxidant, substantially free from sulfur and metallic radicals and containing condensed aromatic rings.

3. The composition of claim 2 wherein the metal is calcium.

4. The composition of claim 2 wherein the aldehyde is formaldehyde.

5. The composition of claim 2 wherein the aldehyde is acetaldehyde.

6. The composition of claim 2 wherein the aromatic hydroxy compound is an oil-soluble alkyl phenol.

7. The composition of claim 2 wherein the aromatic hydoxy compound is an alkyl naphthol.

8. The composition of claim 2 wherein the aromatic hydroxy compound is an octyl phenol.

9. The composition of claim 2 wherein the antioxidant is a naphthylamine.

10. The composition of claim 2 wherein the anti-oxidant is N-aryl substituted naphthylamine.

11. The composition of claim 2 which additionally contains a detergent quantity of calcium salt of oil-soluble petroleum sulfonic acid.

12. The composition of claim 2, wherein anti-oxidant i phenyl alpha naphthylamine.

13. The composition of claim 2, wherein anti-oxidant is dinaphthylamine.

14. The composition of claim 2, wherein anti-oxidant is di-beta naphthylamine.

15. The composition of claim 2, wherein anti-oxidant is 1,8-diamino naphthalene.

JOHN R. GRIFFIN, JR. PAUL R. VAN ESS.

the

the

the

the

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,121,748 Suit June 21, 1938 2,167,273 Cool; -1 July 25, 1939 2,308,502 Farrington et a1. Jan. 19, 1943 2,375,222 Griflin et a1. May 8, 1945