US2440530A - Stabilized organic compositions - Google Patents

Description

. oxidation of the lubricant.

retested Apr. 27, 1948 STABILIZED ORGANIC COMPOSITIONS m... J. Yates, Martinez, cum, asslgnor a Shell Development Company, San Francisco, cum. a corporation of Delaware No Drawing- Aliplication November 4, 1944,

Serial N0. 562,039

'lClalms. (Cl-252-51-5) This invention relates to compounded lubricating oil and to organic compositions possessing unusual oxidation stability and other desirable qualities due to the presence of the herein-described additives. I

- Organic compositions undergo oxidation upon exposure to air. This process is accentuated by increased temperature such as occurs in engines and other operating machinery. When such organic compositions are used as machinery lubricants, their stability is still further drastically reduced due to their contact with metal surfaces which give up metal into the lubricant. Such dissolved metals or metal salts act as oxidation catalysts in the lubricant and their action seems to be particularly drastic when both iron and copper are present. In addition, water also causes corrosion of metal parts and accentuates Such water, even though not originally present in the oil, may come from a variety of sources such as condensa- Further, application of the presentaddition agents is not limited to their use in hydrocarbon or mineral oil (petroleum) compositions but they may be employed similarly in lubricants composed in whole-or in part of animal or vegetable ingredients such as natural waxes, sperm oil,

whale oil, palm oil. Jojoba oil, olive oil, Perilla oil, linseed oil, tung oil, soyabean oil, .iiaxseed oil,

tallow, lard, stearine pitch, etc.. as well as socalled synthetic lubricants such as polymerized olefins, alcohols", esters, etc.

Likewise, employment of the present additives is not limited to their use in lubricating composition from the atmosphere due to changes in temtions but they are broadly applicable to the stabilization of any organic compositions which are likely to come in contact with metal whether at elevated temperatures or not. They may be used lem two additives-that is, an anticorrosive agentand an antioxidants-rather than try to make one additive perform both functions. A primary reason for this is that different amounts of the two types of ingredients are usually required.

to high temperatures in the presence of iron, copper and water. The occurrence of rusting also contributes to the degradation of the oil and the rust may circulate through the oil system,interfere with clearances and clog delicate engine parts such as the governor mechanism. In addition, specifications for turbine lubricants require that the mineral oil base be highly refined and this. although it improves the lubricant in other respects, unfortunately tends to remove natural oxidation inhibitors from the oil. Further, since the prevention or minimization of emulsions is also an essential requirement in turbine operations, the use of many otherwise beneficial additives is precluded because of their tendency to contribute to emulsion formation.

Turbine oils can be produced, for example. from well refined lubricating oils of the proper viscosity range which may be about 75 to 750 Say. Univ. sec. at 100 F. V

Similar problems of oxidation stability of lubricants used in contact with metal surfaces arise in connection with damping or hydraulic oils, tranformer or electrical insulating oils. reirlgerator oils, etc.

Also, since the anticorrosive agent generally functions by forming a film on the metal surface,- if it were also employed as an antioxidant this film formation would withdraw it from the solution, thus diminishing the oxidation protection 1 of the organic composition.

The corrosion or rust inhibitor used'inthe; present combination is a relatively high molecu-v lar weight dibasic acid. By dibasic acid is meant anacid having two acidic or ionizablehydrogen ions. The two acidic radicals should be separated by no more than about four carbon atoms and preferably by no more than two or three. Such acids are, for instance, high molecular weight saturated or unsaturated polycarboxylic acids stable under ordinary lubricating conditions, such as alkylated aliphatic polycarboxylic acids like alkylated succinic, glutaric, adipic, etc., acids. The oxygen in the acid radicals may also be re placed in whole or in part by sulfur to give the corresponding thio equivalents as thiolic (COSH), thionic -CBOH), or thionothiolic (-CSSH) acids.

The may also be monocarboxylic acids whose second acidic hydrogen atom is supplied or activated by a radical such as hydroxyl. nitro, nltroso, cyano, hydrosulflde, or aromatic sulionyl which is not more than about two or three carbon atoms monocarboxylic acids themselves should contain a minimum of 12 to 16 carboh atoms in addition to the added radical. Thus, taking stearic acid as an example, its dibasic corrosion-inhibiting derivatives would be alpha or, beta hydroxystearic acid, alpha or beta nitrostearic acid, alpha or beta nitrosostearic acid, alpha or beta cyanostearic acid, alpha or beta mercaptostearic acid, alpha or beta phenylsulfonylstearic acid, etc,

One. or both of the acidic groups may be attached to an aromatic nucleus, as in alkylated salicylic acid (e. g. .di-isopropylsalicylic acid), alpha (orthocarboxyl aryloxy) carboxylic acids. e. g.

ocncoon uHu nooo

etc.

One may also use dibaslc acids wherein the two 'acidic groups are joined through an oxygen, sulfide, disulfide or nitrogen linkage, as

RCH(CHa)-COOH (a-c-coon on are also effective dibaslc corrosion inhibitors.

These corrosion inhibitors may also contain ether, amino. sulfide, disulflde, etc., radicals elsewhere in the molecule. Those dibasic acids having at least one carboxylic radical are preferred. Mixtures of-the various dibasic acids. as well as the pure compounds, may be used.

The saturated acids are preferred because of their greater stability toward oxidation which results in longer active life. Also, thesecorrosion inhibitors consisting only of carbon, hydrogen and oxygen are preferred. The most useful and practical dibasic acids for the present purposes are alkylated succlnic acids having a minimum of about 16 carbon atoms and preferably those having 20 or more carbon atoms. Suitable acids may be produced by taking oleflns boiling above about 800 C., such as may be obtained by cracking paraflin wax or by dehydration of long chain fatty alcohols, etc., and condensing then with maleic acid anhydride to produce an alkylene succinic anhydride, hydrolyzing to produce the corresponding free acid which may then be hydrogenated if desired. Such acids have been described in U. S. Patent No. 2,133,734.

The second additive in the present combination is an oil-soluble organic compound in which have the basic formula wherein X represents no more than two carbon,

nitrogen, oxygen, phosphorus, aluminum, boron, arsenic, antimony or sulfur atoms. Th9 WP! pounds in which X is a carbon or sulfur atom or a disulilde group are preferred.

The amine groups may be primary, secondary or tertiary. Thus, the amino nitrogen atoms, as well as the phenyl nucleii may carry such low molecular weight alkyl radicals as methyl, ethyl, normal and isopropyl, n-, iso-, secondary-, and tertiary-butyl, amyl, hexyl, heptyl, octyi and higher homolcgs and isomers. When the valences of X are not all taken by the two phenyl groups, the additional bonds may be occupied by like alkyl radicals, by hydrogen atoms, additional phenyl or aryl radicals, etc. Also, the phenyl radicals may, if desired, carry more than one amino group. Thus, when X is a carbon atom, illustrative examples are tetramethyl diamino diphenyl methane, tetraethyl diamino diphenyl methane, tetramethyl triamino diphenyl methane, tetramethyl diamino triphenyl methane, tetraethyl diamino triphenyl methane, and the like. The alkyl, aryl, aralkyl, alkaryl, alicyclic or heterocyclic radical afllxed to X, to the amino groups or to the phenyl nucleii may also have such substituents as halogen or sulfur, and like radicals and substituents may also occur on the phenyl nucleus.

.The described antioxidants in which X is monoor di-sulfide may be illustrated by NW C. in the presence of water, oxygen and an iron copper catalyst, the time required to build up a neutralization number of 2.0 mg. KOH/gm. oil being determined. The essential features of the test are as follows:

The oxidation cell is a glass tube mm. x 600 mm. fitted with a mushroom water condenser and an oxygen delivery tube with fritted glass outlet. The catalyst consists of lengths of No. 14 A. w. g. open-hearth iron wire and electro lytic copper wire, each three meters long and wound into coils about 0.625 in. in diameter. The cell containing 300 ml. 011 sample and the iron-copper catalyst is assembled with the condenser and oxygen' inlet tube and placed in a thermostatically controlled bath capable of maintaining a temperature of i0.5 C. in the sample. Oxygen is admitted at a rate of 3:0.5 liter per hour and at the end of 30 minutes, 60 ml. of distilled water-is added to the cell. The test is then-continued until acids areformed to the extent that the neutralization number of the oil reaches a value of 2.0.

In this test a turbine oil, refined from California petroleum, had an oxidation life of approximately hours by itself, Another sample of the same 011, to which had been added 0.01% w. of saturated alkyl succinlc acid of approximately 370 molecular weight showed the same oxidation stability as the straight oil. A third sample of this turbine oil, to which had been added 0.2% w. of tetramethyl diamino diphenyl methane had an oxidation life of 2500 hours. A fourth sample, however, which contained both 0.01% of the alkyl succinic acid-and 0.2% of the tetramethyl diamino diphenyl methane exhibited an oxidation stability of around 6000 hours.

It will be noted that the corrosion inhibitor,

alkyl succinic acid, are not by itself appreciably ailect the oxidation stability of the oil (although it inhibited rusting oi the contingent metal suriace) but, when the tetramethyl diamino diphenyl methane was present in addition, the oxidation life of the oil was more than double the expected additive effect which might be calculated from the result with each additive alone.

when the two are used together an adequate amount of both generally does not exceed a total oi 0.25 to 1%. The corrosion-inhibiting dibaslc acid should be present-in a minimum of about 0.002595, the polyamino polyphenyl compound in a minimum oi about 0.01%. Usually a combined weight of 0.01 to 0.2% is satisfactory. although the combination oi additives is not without eiiect even at much lower concentrations in a turbine or electrical insulating oil.

In some instances it may also be advantageous to incorporate an additional antioxidant in about the same proportions as the polyamino polyphenyl compound. The function of this supplemental antioxidant or third additive is to reinforce the primary antioxidant. different types of antioxidants seem to exhibit a maximum effectiveness in the presence of particular metal surfaces or metallic oxidation catalysts and a minimum effectiveness with other metals. Hence when several diiierent metals are in contact with the lubricant, it is well to have antioxidants which are particularly effective toward two or more types of metals. 1

Two classes oi supplemental antioxidants have been iound especially advantageous in association with the present dibasic acid corrosion inhibitors and the polyamino polyph'enyl antioxidants. The first class consists of the N-aryl naphthylamines, typified by phenyl alpha naphthylamine, phenyl beta naphthylamine and dinaphthylamines.

The second class consists of polyalkyl arylhydr'oxy compounds. That is, they may have only one hydroxyl group (alkyl phenols) or more than one hydroxyl group (alkyl cresol, alkyl resorcinol, etc.). Preferably short alkyl groups-having up to about eight or ten carbon atoms-are attached to the aromatic nucleus at the two, four and/or six positions; advantageously at least one of the alkyl radicals is a tertiary alkyl. Particular examples are ditertiary-butyl para-cresol, 2,4-dimethyl-B-tertiary octylph'enol, pentamethylor pentaethyl-phenol and tritertiar-y-butyl phenol.

Sulfur-containing antioxidants may also be present. These should .have a minimum of about carbon atoms. Such antioxidant sulfur may This is desirable because 6 Many suliur compounds naturally occurring in petroleum oils are useiul antioxidants, pro video they have the proper reactivity. This may be determined by heating such compounds with finely divided metallic copper at 300' O. for 10 hours. These compounds in which about 20% to 60% oi the total suliur content reacts with the also good antioxidants..

Among the suliurized olefins found to beespeciaily useiul are, for example: suliurized paramn wax (as produced by chlorination oi paramn wax. having a molecular weight between about 225 and 425. dehydrochlorination oi the chlorinated product to produce wax oleiins, and suliurization oi the latter): suliurized olefin or diolefin polymers boiling above about 400 C. such as obtained as lay-products in the refining of cracked distillates with clay or other refining agents, or in the polymerization oi normally gaseous olefins to produce gasoline or the like (e. g. suliurized methyl pentadiene polymer); suliurized esters of unsaturated fatty acids with monohydric alcohols, as methyl, ethyl, propyl, etc. oleate, or linoleate; suliurized sperm oil; suliurized jojoba oil; etc.

Also particularly efiective are the oil-soluble reaction products of polychlor parafi'in wax with sodium polysulfide which are compounds of the ype (Basin) J is 1'1 wherein n=2 or more.

A compounded lubricating oil may also contain other additives likeadditional corrosion inhibitors, such as sulfonic or iatty acids and their I bases include various nitrogen bases as primary,

be in the form of mercaptans, as in decyl mercaptans, dodecyl mercaptans, cetyl mercaptans, oleyl mercaptans, stearyl mercaptans; butyl or other higher alkyl thiophenes: thionaphthols, alkyl thionaphthols, etc.: or of polysulfides sulfide, etc.) 'or of sulfur compounds formed by attaching sulfur to an oleflnic double bond (as a by reacting sulfur with olefinsat temperatures of about C. to 300 C.) which compounds are believed to contain the structure (sulfur in epithio llnkage) secondary, tertiary and quaternary amines.

Examples oi detergent forming acids are the various fatty acids oi, say, 10 to 30 carbon atoms. wool fat acids, paraflln wax acids (produced by oxidation of parafiin wax), chlorinated fatty acids. aromatic carboxylic acids includingfaryl fatty acids, aryl hydroxy iatty 'acids, parafiln wax benzoic acids, various alkyl salicylic acids,

,phthalic acid mono esters, aromatic keto acids.

aromatic ether acids; diphenols as diialkyl phenol) sulfides and disulfides, methylene bisalkyl-phenols; sulfonic acids such as may be produced by treatment of alkyl aromatic hydrocarbone or high boiling petroleum oils with sulfuric acid; sulfuric acid mono esters; phosphoric acid mono and di-esters, including the corresponding thiophosphoric acids, phosphonic and arsonic acids, etc.

Non-metallic detergents include compoundssuch as the phosphatides (e. g. lecithin) certain iatty oils as rapeseed oils, voltollzed iatty or mineral oils.

Other detergents are the alkaline earth phosphate di-esters, including the thiophosphate diesters; the alkaline earth diphenolates, speciiicale ly the calcium and barium salts oij'diphenol as HCHC), CHiCHO, etc.) with alkylated aryl hydroxy products (such as alkyl phenol, alkyl naphthol, etc). They may be typified by the calcium salt oi the reaction product of iormalde- I hyde and iso-octyl phenol wherein n is a small integer such as 2, 3 or 4 or the product is a mixture of such polymers.

Detergents are employed in proportions of about A to about 5% weight.

The invention claimed is:

1. A refined mineral oil which is normally subject to oxidative decomposition in the presence of a metal surface and containing a total of about 0.01% to 0.5% by weight oi tetramethyldiamino diphenylmethane and a saturated alkyl succinic acid of at least 16 carbon atoms, the tetramethyldiamino diphenylmethane being present in a minimum amount oi about 0.01% and the balance, not less than 0.0025% beings, saturated alkyl succinic acid, the total amount not exceeding 0.5% by weight. w

2. A mineral oil composition comprising a major proportion of a refined mineral oil which is normally subject to oxidative decomposition in the presence of a metal surface, a minimum amount of about 0.0025% of a saturated alkvl succinic acid of at least 16 carbon atoms and a I amount of the two additives not exceeding about 1.0% by weight.

3. A mineral oil composition comprising a major proportion of a mineral oil which is normally subject to oxidative decomposition in the presence of a metal surface, a minimum amount of about 0.0025% of an alkylated succinic acid of at least 16 carbon atoms and a minimum amount oi about 0.01% of an N-alkylated diamino diphenylmethane, the total amount oi the two additivesnot exceeding about 1.0% by weight.

4. An organic composition comprising a major proportion of a mineral oil which is normally subject to oxidative decomposition in the presence oi a metal surface, a minimum amount of about 0.0025% of an alkylated succinic acid 01 at least 16 carbon atoms, and a minimum amount oi ence oi a metal suriacaa minimum amount-oi about 0.0025% 01 a-saturated alkyl succinic-acid oi at least 16 carbon atoms, and a minimum amount oi about 0.01% oi tetramethyldiamino diphenylmethane, the total amount oi the two additives not exceeding .about 1.0% byweight and a minor amount of about 1.0% alkylarylhydroxy compound.

6. An organic composition comprising a major proportion of a mineral oil which is normally subjected to oxidative decomposition in the presence oi a metal suriace, a minimum amount of about 0.0025% of a saturated alkylsuccinic acid of at least 16 carbon atoms, and a minimum amount of about 0.01% of tetramethyldiamino oi a polydiphenylmethane. the total amount oi the two additives not exceeding about 1.0% by' weight and a minor amount ,of about 1.0% of a phenyl alpha naphthylamine.

7. An organic composition comprising a major proportion of a mineral oil which is normally subjected to oxidative decomposition in the presence of a metal surface, a minimum amount of about 0.0025% 01' a saturated alkyl succinic acid oi at least 16 carbon atoms and a minimum amount oi about 0.01% oi tetramethyldiaminodiphenylmethane, the total amount oi the two additives not exceeding about 1.0% by weight and a minor amount oi about 1.0% of a ditertiary-butyl-paracresol.

' WALLACE J. YATES.

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

Brandes .1..... June 4, 1940 about 0.01% oi tetrame'thyldiamino diphenyl- ,methang the total amount oi the two'additives not exceeding about "by weight and a minor ,amount oi about 1.0% oi an N-aryl naphthyl- "amine,

p 5. An organic composition comprising a major proportion oi a mineral oil which is normally. subjected to oxidative decomposition in the pres- Certificate of Correction Patent No. 2,440,530. April 27, 1948.

WALLACE J. YATES It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 3, lines 70 to 72 inclusive, for the formula and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 8th day of March, A. D. 1949.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.