US2940929A - High-temperature lubricants - Google Patents

Description

atent fice 2,940,929 Patented June 14-, 1 960 mon-rnr/nnmrunn LUBRICANTS Hyman Diamond, Berkeley, Calif., assignor to Shell Gil Company, a corporation of Delaware No Drawing. Filed June 26, 1958, Ser. No. 744,653 6 Claims. (Cl. 25233.6)

This invention relates to lubricating compositions. More particularly, it relates to lubricating compositions especially designed for use at elevated temperatures and under oxidizing conditions.

Aircraft and gas-turbine engine lubricants require special properties, such as high-temperature stability, and oxidation stability which are not possessed to a sufiicient degree by conventional lubricants. They must possess a high viscosity index in order to provide adequate lubrication over a wide range of temperatures. They must be thermally stable and must be either stable to oxidation or amenable to stabilization against oxidation in order that they may retain their usual properties atfer operation for extended periods at high temperatures. While it is preferred that they have low pour points, this is not essential, since the mechanisms containing them may be heated in such a way as to maintain high-pour-point materials in a fluid condition during down time or cold operating periods.

Many fluids have been proposed for operation under such conditions but for the most part each of them inherently possesses one or more shortcomings making their use undesirable in that respect. For example, the silicone fluids are extremely stable at high temperatures but are notorious for their poor lubricating properties. Ester lubricants on the other hand are excellent where low operating temperatures are concerned due to their low pour points and high viscosity indices, but for the most part do not have satisfactory thermal stability at temperatures in the order of 400 F. and above.

Mineral lubricating oils which exhibit satisfactory lowtemperature viscosities have generally been found to have flash points that are dangerously low and high-temperature viscosities that are below those required. In other words, when the mineral oil is thin enough at low temperatures, it is too volatile at high temperatures, where it is also too thin to possess satisfactory lubricity. It has een found that generally speaking additive agents do not enhance these essential properties to a satisfactory extent.

One of the most important properties that any lubricant must possess in addition to those normally associated with lubricants, such as a suitable viscosity and suflicient lubricity, is that of a combination of high thermal stability and oxidation stability. The latter property constitutes a basic and essential attribute which can be satisfied in one of two ways and preferably a combination of both. This constitutes an inherent stability against degradation due to oxidation or the ability of the compound to respond to stabilization against oxidation by the presence of additive materials. Under ordinary temperature conditions, such as those existing in ordinary lubrication up to about 400 F., the stabilization of organic materials is not regarded as being especially difficult since many compounds are known and available which will stabilize such materials under these relatively low-temperature conditions. However, as temperatures are raised, such as in the operation of aircraft and gas-turbine engines, there is a drastic change in the course of oxidation and the ability of known compounds to prevent the oxidation of organic materials. Up to the present time where operation of organic fluids over for about 400 F., was concerned, it has been necessary in most instances to depend upon the inherent oxidation stability of the fluid per se since virtually no additive materials were known which would stabilize a substance at these elevated temperatures. The rate of oxidation accelerates rapidly as the temperatures are raised and many compounds which normally perform a function of oxidation stabilization at lower temperatures reverse their roles at elevated temperatures and indeed become pro-oxidant substances.

Recent studies in the synthetic lubricant fields have indicated that certain restricted classes of polyphenyl others have excellent thermal stability and possess suflicient oxidation resistance as aninherent characteristic for use at extremely high operating temperatures. Unfortunately, however, even these stable materials are of limited utility especially when the temperatures exceed about 450 F. since they tend to decompose and must be either replenished or replaced within relatively short periods.

It is an object of the present invention to provide improved lubricant compositions especially useful for operation of engines, motors and moving metallic elements at high operating temperatures. it is a particular object of this invention to extend the operating life of certain polyphenyl ethers at operating temperatures exceeding about 450 F. in the presence of oxidizing conditions. Other objects will become apparent during the following detailed description of the invention.

Now, in accordance with the present invention, compositions are provided which are especially useful for lubricating purposes at elevated temperatures comprising a major proportion of polyphenyl ethers and minor proportions sufiicient to stabilize said ethers against oxidation at temperatures in excess of about 450 F., said additive material being basic and neutral indium salts of fatty acids, thiafatty acids, and of alkylated benzoic acids, all as more particularly defined hereinafter. Still in accordance with the present invention, especially useful results have been obtained even when catalytic amounts of copper are present by the synergistic combination of one of at least one of the above-named indium salts with additive proportions of a bromo-phenyl ether and of a bisalkylated phenol monosulfide.

As stated hereinbefore, the stabilization against oxidation of organic substances at temperatures in excess of about 450 F. is extremely dificult and may follow a different mechanism than that which occurs at lower operating temperatures.

The indium salts found to be effective for the present purpose include the neutral or basic salts of fatty acids, especially those having from 8 to '15 carbon atoms per molecule; indium salts of alkyl mercapto fatty acids, otherwise known as thiafatty acids; and indium salts of alkylated benzoic acids, the latter being indium salts of benzoic acid derivatives wherein the benzoic acid nucleus bears 1-4 alkyl radicals having 3-10 carbon atoms each. Table I which follows lists typical indium salts coming within the limits defined above. It will be noted that the fatty acids include not only the straight-chain fatty acids but also branched-chain fatty acids. Also, the thiafatty acids may be those in which the mercapto radical is attached to a secondary carbon atom or to a tertiary carbon atom. In efiect, this difierentiates between straight-chain thiafatty acids and branched-chain thiafatty acids. It is preferred that the mercapto radical contain an aliphatic hydrocarbon radical having from 4-12 carbon atoms each and that the hydrocarbon radical separating the carboxyl group be an aliphatic radical having from 1-4 carbon atoms each.

While the salts are highly effective for stabiliz: 7

.butyl or alphacumyl radicals without adverse effects.

TABLE I Indium salts t A. Salts of fatty acids:

' Straight-chain-- n-Octanoic acid n-Decanoic acid n-Tridecanoic acid n-Pentadecanoic acid Brar 1ched-chain--- 2-ethyl hexoic acid Z-ethyl decanoic acid 2-ethy1 tridecanoic acid 3-n butyl'hexanoic acid 3-tert-butyl hexanoic acid 2,4- din'iethylhexanoic acid 7 2-,4-dimethyl-3-ethyl hexanoic acid B. Salts of alkyl mercapto fatty acids:

3-thiatridecanoic acid 4-thiadodecanoic acid S-thiaheptadecanoic acid S-thiatetradecanoic acid 4-tbiatridecanoicacid S-thiapentadecanbic acid Q. Salts of alkylated benzoic acids:

' pt(n-Octy1)benzoic acid p-(2.-re'thylhexyl) benzoic acid m-(n-HexyDbenzoic acid m-( 3-methyloctyl) benzoic acid 2 ,3-dimethyl-4-(n-octyl)benzoic acid 2,4-di(n-heptyl) benzoic acid According to Table II it will be seen that the bromophenyl ethers'usefulgin conjunction with the other two types of additives include the monoand di-bromo-phenyl materials in which the bromine radicals may be ortho,

. meta or para with respect to the position of the ether linkage. Moreover, the ethers may be mixed ethers wherein the two bromo-phenyl radicals difier either with respect to the position of the bromine atom, with respect to, the number of bromine radicals attached to the phenyl radical or with respect to the presence or absence of tertbut-yl or alpha-'cumyl radicals. The bromo-phenyl ethers B dn rcmq eny k r.

B stn rcm phe lk he V Bis(o-bromophenyl)ether (p-Bromophenyl) (m-brornophenyl) ether (p-Bromophenyl) (o-bron1ophenyl)ethen ('m -Bromophenyl) (o-bromophenyl ether Bis(2,4-dibromophenyl)ether A 4 Bis (2,3 -dibromophenyl) ether 7 Bis (2,5 -dibromophenyl) ether TABLE In o Dip!zenol monosulfides V b Di(4-hydroxyphenyl)monosulfide Di(Z-hydroxy-5-phenylphenyl)monosulfide I Di Z-hydroxy-S -t-arnylphenyl monosulfide Di( 3,5 t-dimethyl-4-hydroxyphenyl) monosulfide Di( 3-methyl-4-hydroxy-5 -butylphenyl) monosulfide a Di(3-amyl-4-hydroxyphenyl)monosulfide Di 2-methyl-4-hydroxy-S -buty1phenyl) monosulfide' Di 2-methyl-4-hydroXy-5 -propylphenyl) monosulfide Di( 3-phenyl-4-hydroxyphenyl) monosulfide' Di 2-methyl-4-hydroxy-5-cyclohexylphenyl monosulfide Di(2-hydroxy-3-butyl-6-methylphenyl)rnonosulfide modified by the presence of 1-4 alkyl radicals (including phenyl ether alone or with the'indium salt alone does 3 varieties which are unsubstituted polyphenyl-ethers or uents causes the formation of polyphenyl ethers which 1 bility of the'unsubstituted ethers'as well. The presence 'resp'ec't' to'the two 'other types of 'polyphenyl ethers,

Di 2-hydroxy-3-butyl-5-methylphenyl) monosulfide Di(Z-hydroxy-3-t-butyl-5-methylphenyl)monosulfide Di(Z-hydroxy-Z -methyl-5-phenylphenyl)monosulfide Di(Z-hydroxy-3,5-di-sec-amylphenyl) monosulfide Di(2-hydroxy-3-butyl-5,6-dimethylphenyl)monosulfide Di(2 hydroxy 3-cyclohexyl-5-ethylphenyl)monosulfide The preferred category of the diphenol monosulfides includes those in which the phenol radical is modified by the presence of tertiary alkyl groups, preferably tertiary butyl groups. The monosulfide phenol radical may be cycloalkyl radicals) having from 1 to 8 carbon atoms each. The preferred species which has been found to be highly effective in the compositions of thisinvention is di(2- hydroxy-S-terti'ary butyl-S- methylphenyDmonosulfide. a

The data which followshow that the monosulfidemust be combined with the other two additives described above in order to provide a polyphenyl ether composition which is stable against oxidation at elevated temperatures, The combination of the monosulfide with either the bromonot provide satisfactory stabilization especially intthe pres-t ence of copper catalysts for the oxidation reaction;

The polyphenyl ethers subject to stabilization against oxidation by means of either the indium salts or the come bination of additives described above are confined to the those which are substituted with either tertiary butyl radicals or with alpha-cumyl radicals or both. While the stabilizers are most effective when used with the sub stituted ethers, they enhance the initially excellent staof other substituents; such' as methyl radicals'and the like, is undesirable and is not contemplated as falling within the scope of the present invention. 'This'is due to the fact that the presence of these undesired substitare not subject to adequate oxidation stabilization when the elevated temperature is contemplated or involved.

The unsubstituted polyphenyl ethers have been found to be outstandingly stable but may be' improved in their operating life at temperatures above 400 F. by the presence of the subject classes of additives as described herein. However the'major use of the present inventionis with namely, those containing tertiary butyl substituents, alphacumyl substituents or both; i Miirtures of the unsubstituted p'olyphenyl ethers with the tertiary butyl oralpha cumyl substituted ethers is contemplated.

It is 'futhermore contemplated to utilize polyphenyl ethers containing ortho, meta or para linkages and preferably a mixture of these linkages so as to promote relatively low pour points in the materials. The meta linkage has been found to be that which produces polyphenyl ethers having the lowest pour points. Consequently, in accordance with the present invention, compositions are provided which are especially useful for lubricating purposes and have good lubricating oil pour points comprising certain restricted classes of polyphenyl ethers, at least two of said ethers being present in the composition and at least one-third of the linkages between phenyl radicals being in meta positions relative to each other. More particularly, and in order to maintain the maximum thermal stability, the polyphenyl ethers with which this invention is concerned are restricted to the unsubstituted polyphenyl ethers and those containing tertiarybutyl and/or alpha-cumyl substitutents as well as ethers in which up two-thirds of the oxygen linkages are replaced with isopropylidene linkages. 4 Still in accordance with this invention it is preferred that the mixture of polyphenyl ethers have an average of 3-8 pheny radicals per molecule and preferably between 4 and 6 phenyl radicals per molecule.

A preferred form of the present invention comprises a mixture of the subject classes of polyphenyl ethers wherein at least one member of the mixture contains both meta linkages between phenyl groups and ortho or para linkages within the same molecule. This is an especially effective way of reducing the pour point of the mixture in addition to mixing two non-identical polyphenyl ethers. The efiect is magnified when the proportion of meta linkages is at least two-thirds of those present and preferably between about 75 and 90% of the linkages, the remaining being either ortho or para linkages, preferably para. When the polyphenyl ether comprises one in which there is an oxygen linkage between two groups of polyphenyl linkages, it is sufiicient that at least 50% of the linkages other than the one specified oxygen linkage are in the meta position relative to said ether linkage. As stated hereinbefore, these additional linkages between phenyl radicals may be either oxygen or isopropylidene. Table IV, which follows, lists typical polyphenyl ethers which may comprise principal or minor components in the mixtures under consideration.

TABLE IV Polyphenyl ethers Bis (meta-phenoxyphenyl) ether Bis para-pheno'xyphenyl ether Bis (ortho-phenoxyp'henyl) ether Meta-bis(meta-phenoxyphenoxy)benzene Meta-bis (para-phenoxyphenoxy)benzene Para-bis (meta-phenoxyphenoxy)benzene Meta(meta phenoxyphenoxy)(meta-tert-butylphenoxyphenoxy) benzene Meta(meta-alpha-cumylphenoxyphenoxy) (meta-phenoxyphenoxy) benzene Meta (meta-tert-butylphenoxyphenoxy) (para tert butylphenoxyphenoxy)benzene It is preferred that from the above types of polyphenyl ethers at least 50% of the mixture be a species either containing nothing but meta linkages or wherein at least about 60% of the mixture comprising the lubricating composition be a species of polyphenyl ether wherein at least about two-thirds of the linkages between phenyl radicals are in the meta position relative to each other. Furthermore, it is preferred that at least about 25% (e.g. 25-75% by weight) of the composition be unsubstituted polyphenyl ethers containing nothing but oxygen linkages between phenyl radicals and bearing no substituents on the carbocyclic rings other than hydrogen.

It is within the contemplation of the present invention to provide compositions wherein no unsubstituted polyphenyl ethers are present, the compositions being composed of single species or mixtures of tertiary butyl substituted polyphenyl ethers, alpha-cumyl substituted polyphenyl ethers or polyphenyl ethers wherein a substantial portion of the oxygen linkages are replaced with isopropylidene linkages. Still more explicitly, mixtures of the latter types may comprise two or more tertiary butyl substituted polyphenyl ethers,two or more alpha-curnyl substituted ethers or two or more polyphenyl ethers containing isopropylidene linkages substituted for a portion of the oxygen linkages. It is also possible to provide mixtures comprising one or more tertiary butyl substituted polyphenyl ethers with one or more of the other two types of derivative classes.

Mixtures of polyphenyl ethers comprising the preferred base fluid to be used in the present invention include those wherein at least about one-third and preferably 35- 60% of the inter-phenyl linkages are in meta relationship to each other and wherein between about 40 and 100% by weight thereof are oxygen linkages, the remaining linkages being either oxygen or isopropylidene. The reaction mixtures are normally liquid at room temperatures although some of the higher average molecular wei ht mixtures may be low-melting solids. For many purposes, this is not a disadvantage since such materials are especially useful for use where high temperatures are involved. Since the individual components of the lubricant mixtures when unmodified by the isomeric materials as described herewith have pour points substantially above room temperature, it will be seen that the present mixtures have a definite advantage when the intended purpose is that of an operating fluid for engines, motors or radiation-emitting equipment.

In summary, preferred mixtures comprise an ether having the configuration seem together with an ether having the configuration wherein A is a radical of the group consisting of oxygen and isopropylidene and B is a radical of the group consisting of tert-butyl, alpha cumyl and hydrogen, the mol ratio of the first ether to the second ether being between about 1:2 to 9:1.

When utilizing mixtures of unsubstituted polyphenyl ethers with the tertiary butyl or alpha-cumyl substituted polyphenyl ethers, it is preferred that the composition contain from 10 to of unsubstituted ethers containing 2-6 phenyl radicals per molecule together with 90-10% by weight based on the total composition of the substituted polyphenyl ethers as defined above. The principal function of the unsubstituted polyphenyl ethers is to enhance the outstanding high-temperature stability which this class of compounds has been found to exhibit. The substituted polyphenyl ethers as outlined above impart low melting points and in mixture with the unsubstituted polyphenyl ethers causes the melting point of the entire composition to be substantially lower than that of the unsubstituted polyphenyl ethers themselves.

The proportion of additives present in the composition will depend in part upon the temperature and other conditions which the composition will be expected to encounter. Normally, the proportion of additive will be in the order of 0.25-2.5% by weight based on the total composition. This is true when the indium salt is used alone and, in the case of a triple, combination of additives, the proportion of eachadditive will bewithin the above recited range. Proportions of the additives above about 3%. have been found to be somewhat less effective than when the additive is present in the order of 0.5-1.5

efollowing dataillustrate the use of the present invention,-. the test given having been performed with bis[para (para-tertiary-butyl-phenoxy)phenyl]ether. It is to be emphasized, however, that this is merely a typical ether of: the group considered and that similar results are obtained when other polyphenyl ethers falling Within the-scope of the present invention are employed either alone or in conjunction with the material tested. As

,typicalindium salts, indium 2-ethylhexoate, indium 3- th'iatridecanoate and indium para-'octylbenzoate were employed. These were tested in the base stock at temperatures of 500, 525 and 550 F., the test conditions being essentially those to be found in the Domte oxidation test equipment as follows: Temperature asabove; oxidizing medium; pure oxygen at 760 mm. pressure, recirculated at. 25 'cc./minute through a S-gram sample of material under test.

Table -V shows that the indium salts substantially increase the life-of the material especially under conditions where no adverse catalyst, such as copper or iron, is present:

TABLE V 500 F., Dornte oxygen-absorption test- Antioxidant Effectiveness Ratio No Catalyst 0.5 mol (per 500 g.),

Absorption Time, hr.

No Catalyst Additive 1% Indium 3-thiatridecanoate Table VI shows that the eflect of stabilizers becomes more pronounced at 525 F. and this appears to be optimum of the range oftmperatiiies tested. Itwill be noted that, the threeclasses of indium salts are roughly equivalent in their stabilizing ability when no catalyst is present; The stabilizers have little efiiect upon the life of the material when' a copper catalyst is present at this temperature, but a substantial eiTect is noted when the catalyst present is iron. However, at 550 F. (see Table VIII) a beneficial eflect is obtained from the use of the indium salts either 'when no catalyst is present or when either copper or iron catalyst is involved.

Table VII demonstrates the synergistic effect obtained by. the combination of the three additives specified, namely, the indium salt, the phenol sulfide, and the bromoethen, According to Table VII, it will be'seen that even in th'epresence of a copper catalyst the 'combinatio'n'o'f the three additives provides outstanding oxidation stabilityfi Ihe :data-also "show that it is necessary for all three additives to be present, any single :one or combi nation o'f 'two oftheadditives being insufficient for this power-"1i:- r f x? TABLES/II.

Synergistic" composition, 525 Dor ritefco ppjer cotalyzfd V V oxygen-absorption ll M" V v I 7 0.5 mol O Antioxidant Additives 7 (per 500 g.), Efieetiveness Absorption Ratio A Time, hr. V

None 5. 9 5.9 1. 0 3. 4 0. 6 5. 7 1. 0 7. 8 1.3 12. 1 1. 7. 1% Sulfide+0.5% Bromo-ether 3.1 0. 5 1% Salt-l-l% Sulfide+0.5% Br'oznoether-- 22. 3 3. 8

1 Indium 2-ethylhexanoate.

' 1 Bis (2-hydroxy-3-tert-butyl-5-methylphenyl) sulfide. 1

Bis(p-bromophenyl)ether. V

i TA VIII/t 550 F. Dor'ri'febxygen absorption test 0.5 1161 0, (per 500 g.), Antioxidant Adsorption Time, hr. Efiectiveness Ratio Additives No Cu Fe No Cu 7 Fe Catalyst Catalyst None 4. 5 2. 4 4.1 0.5% Indium Z-ethylhexanoate- 5. 9 1. 3. 0.5% Indium caprylate.; 7. 5 l. 7 1% indium S-thiatrir V V deeanoate 10.5 3.4 7.8 2.3 1.4. 1.9

- Iclaim as my invention: q a

1.".As a new'lubricating composition ama'jor. proportion of-bis[p-(petertrbutylphenoxyphenyl)]ether and 025- 2.5% by weight each of'bis (p-bromophenyl) ethenbis (2:hydroxy-3,etert-butyl-5-methylphenyl). sulfide and indiumcaprylate. r 7 1 r 2. As a new lubricatingcomposition a major proportion ofpolyphenylethers having 3-8 phenyl radicals per molecule, at least one-third of the linkages between phen: yl radicals being in meta positions relative toeachother, theonly.substituentsdirectly attached to phenyl ring carbon 'atoms' being of the group consisting of hydrogen, tertiary butyl radicals, and alpha-cumyl radicals, and 0.25- 2.5% by weight each "of bromoh-substituted polyphenyl ether, bis(alkylated hydroxyphenyl) sulfide, the alkyl radicals of which has l-6 carbon atoms each and an indium salt of an aliphatic monoca rboxylic acid.

3. As a new lubricating composition a major proportion of polyphenyl ethers having 3-8 phenyl radicals 'per' molecule, the only substitue'nts directly attached tophenyl ring carbon atoms being of the group consisting of hydrogen, tertiary butyl radicals, and alpha-cumyl-radi cals, said ethers containing 0.25%2.5%' by weight of the indium salt of an alkylated benzoic acid,'the benzoic acid nucleus of which bears 1.-.4 'alkyl radicals having 3-10 carbon atoms each. 7 a V 4. As a new lubricating composition a major proper tion of polyphenyl ethers having'at least 3 phenyl radicals per molecule, the only substituentsdirectly attached to phen'yl ring carbon atoms. being of theQgroup consisting of hydrogen, tertiarybutyl radicals and alpha-cumyl radicals,.s'aid .etherscontaining 0.25%.2.5% by weight of the indium salt of a thiafatty acid wherein R is an aliphatic hydrocarbon radical having 4-12 carbon atoms and R is an aliphatic hydrocarbon radical havin'g'1-4 carbon atoms] 1 '5. 'As a new lubricating composition a major proportion of polyphenyl e'thershavingB-S phenyl radicals per molecule, at least one-third of the linkagesbetween phenyl radicals being in rheta positionsrelative to'each 76 other, the only substituents directlyattached to phenyl ring carbon atoms being of the group consisting of hydrogen, tertiary butyl radicals, and alpha-cumyl radicals, said ethers containing 0.25-2.5% by weight of indium salts of fatty acids having 8-15 carbon atoms per molecule.

6. As a new lubricating composition a major proportion of polyphenyl ethers having at least 3 phenyl radicals per molecule, the only substituents directly attached to phenyl ring carbon atoms being of the group consisting of hydrogen, tertiary butyl radicals, and alpha-cumyl radicals, said ethers containing 0.25-2.5% by weight of at least one indium salt of an acid of the group consisting of fatty acids having 8-15 carbon atoms per molecule, alkylated benzoic acids, the benzoic acid nucleus of which bears 1-4 alkyl radicals having 3-10 carbon atoms each, acids having the general structure n -s-m-coon wherein R is an aliphatic hydrocarbon radical having 4-12 carbon atoms and R is an aliphatic hydrocarbon radical having 1-4 carbon atoms, and mixtures thereof.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Annalen der Chemie, 350 (1906), pp. 84 and 101 pertinent.

Claims (2)

1. 2. AS A NEW LUBRICATING COMPOSITION A MAJOR PROPORTION OF A POLYPHENYL ETHERS HAVING 3-8 PHENYL RADICALS PER MOLECULE, AT LEAST ONE-THIRD OF THE LINKAGES BETWEEN PHENYL RADICALS BEING IN META POSITIONS RELATIVE TO EACH OTHER, THE ONLY SUBSTITUENTS DIRECTLY ATTACHED TO PHENYL RING CARBON ATOMS BEING OF THE GROUP CONSISTING OF HYDROGEN, TERTIARY BUTYL RADICALS, AND ALPHA-CUMYL RADICALS, AND 0.25-2.5% BY WEIGHT EACH OF BROMO-SUBSTITUTED POLYPHENYL ETHER, BIS(ALKYLATED HYDROXYPHENYL) SULFIDE, THE ALKYL RADICALS OF WHICH HAS 1-6 CARBON ATOMS EACH AND AN INDIUM SALT OF AN ALIPHATIC MONOCARBOXYLIC ACID.
2. 6. AS A NEW LUBRICATING COMPOSITION A MAJOR PROPORTION OF POLYPHENYL ETHERS HAVING AT LEAST 3 PHENYL RADICALS PER MOLEUCLE, THE ONLY SUBSTITUENTS DIRECTLY ATTACHED TO PHENYL RING CARBON ATOMS BEING OF THE GROUP CONSISTING OF HYDROGEN, TERTIARY BUTYL RADICALS, AND ALPHA-CUMYL RADICALS, SAID ETHERS CONTAINING 0.25-2.5% BY WEIGHT OF AT LEAST ONE INDIUM SALT OF AN ACID OF THE GROUP CONSISTING OF FATTY ACIDS HAVING 8-15 CARBON ATOMS PER MOLECULE, ALKYLATED BENZOIC ACIDS, THE BENZOIC ACID NUCLEUS OF WHICH BEARS 1-4 ALKYL RADICALS HAVING 3-10 CARBON ATOMS EACH, ACIDS HAVING THE GENERAL STRUCTURE