US2795553A - Lubricant compositions - Google Patents

Description

LUEREQANT COMPOSITIONS Warren Lowe, Berkeley, Calif., assignor to California Research Corporation, San Francisco, Calif., a corporation of Delaware No Drawing. Application June 29, 1954, Serial No. 440,280

3 Claims. (Cl. 252-491 This invention relates to novel lubricant compositions. More particularly, the invention is concerned with novel lubricating oil compositions having improved oxidation and corrosion inhibiting properties.

Lubricating oils generally have a tendency to deteriorate due to oxidation and form decomposition products which are corrosive to metals. Since lubricating oils in use today almost invariably come into contact with metal surfaces, the problem of overcoming oxidation and corrosion is considered to be one of major importance. Operating conditions encountered in modern internal combustion engines in which these oils are commonly employed involve increased temperatures, higher speeds and reduced clearances which tend to promote decomposition and the formation of corrosive products. Furthermore, these engines generally employ alloy metal bearings which, besides their possible catalytic eifect on the decomposition of the hydrocarbon type mineral lubricating oils, are easily corroded and this, in turn, has seriously accentuated the oxidation and corrosion problems in mineral lubricating oils.

Inhibitors have been added to lubricating oils to improve their resistance to decomposition and avoid corrosivity. Mineral lubricating oils for internal combustion engines, due to the severity of their service, have also been compounded with additional agents such as Wear inhibitors, sludge inhibitors and detergents to loosen and suspend products of decomposition and counteract their effect. Unfortunately, many of these agents may adversely affect the eificiency of the oxidation and corrosion inhibitors and it is a problem to find inhibitors Which will function in combination wth them. Furthermore, some of the most eifectve oxidationand corrosion inhibitors contain active sulfur and are, therefore, ex-

tremely corrosive to silver and similar metals which are subject to attack by active sulfur. These types of metals, although once not so Widely used in contact with lubricating oils and therefore considered to constitute only a minor problem, are being increasingly employed today. Particularly in certain important classes of internal combustion engines as, for example, marine and railroad diesel engines, silver metal-containing bearings are more and more common and the problem of providing proper lubrication for them is one' of major importance.

It is, therefore, a general object of this invention to provide lubricating oil compositions having improved antioxidant and anticorrosion properties.

A more particular object of the invention is to provide lubricating oil compositions Which are noncorrosive to silver and similar metals.

Another more particular object is the provision of mineral lubricating oil compositions in which the tendency to corrode alloy bearings of internal combustion engines has been inhibited. V

A further and somewhat related object is 'to' provide compounded mineral lubricating oil compositions-having improved anticorrosion properties without adversely afice - 2 fecting the stabilizing, deterging and lubricating qualities of the hydrocarbon oil composition.

Another and still more particular object of the invention is the provision of mineral lubricating oil compositions which are noncorrosive to silver metal-containing bearings of the type employed in railroad diesel engines.

Additional objects of the invention will become apparent from the description and claims which follow.

In the accomplishment of the above objects, it has been found that compositions comprising an oil of lubricating viscosity and a complex of titanic acid with a member of the group consisting of glycols and polyhydroxy benzenes have greatly enhanced anticorrosion properties. It has also been found that, in particular, compositions comprising a compounded mineral lubricating oil for internal combustion engines which is normally corrosive to alloy bearings and such a complex are substantially noncorrosive.

The normal tendency of oils to become oxidized and corrosive is definitely inhibited in the improved compositions of the invention. Metal surfaces in general are not corroded by contact with these compositions and internal combustion engine alloy bearings, in particular, are remarkably benefited. Bearings of silver and similar metals which, as stated above, are increasingly important due to their presently expanded use in marine and railroad diesel engines, are not corroded by these compositions whereas conventional oxidation inhibited 'oils have severely pitted and corroded such bearings. The ad-' vantages of these improvements are obtained in the compositions of this invention without loss of stability or detergency in the composition.

The titanic acid complexes of the compositions according to this invention are prepared by the reaction of a mixture of a reactive titanic acid derivative, such as the titanium tetrahalides or titanium tetra-alkyl esters. and glycol or polyhydroxy benzene. The mixtures are ordinarily heated to accelerate the reaction. Although the nature of the reaction is not definitely known, it is believedthat two of the hydroxyl groups of a single glycol or polyhydroxy benzene react with the titanic acid derivative to form What is commonly termed a metal chelate compound. These compounds are characterized by a claw type of structure in which one or more rings of similar or unlike structure due to the use of mixed glycols or polyhydroxy benzenes are formed including the titamum.

The glycols which are reacted with the titanic acid derivative are preferably alphaand beta-alkanediols containing from 2 to 18 carbon atoms. Such glycols include, for example, ethylene glycol, 1,2- and 1,3-propanediol, 1,3-pentanediol, 2,3-butanediol, 1,2-hexanediol, 2-methyl- 1,3-pentanediol, 1,2- and 1,3-octylene glycols including 2-ethylhexane-l,3-diol, 1,2-dodecanediol, 2,4- diethyloctane-l,3-diol, and 2,4,6-triethyl-decane-l,3-diol. The glycols containing from 6 to 10 carbon atoms are more preferred since they impart an optimum degree of oil solubility to the titanate. Alphaand beta-octylene glycols such as 2-ethylheXane-1,3-diol have been found to be the most satisfactory for present purposes since they give unusually effective oxidation and corrosion inhibitors.

The polyhydroxy benzenes are preferably vicinal dihydric phenols such as catechol, 3,4-dihydroxy toluene, tert.-butylcatechol, cetylcatechol, and the like. They may contain additional hydroxyl groups, as for example, 1,2,4- trihydroxy benzene. Alkyl catechols containing from 2 to 18 carbon atoms in the alkyl group are at present most preferred since the titanates prepared from them possess the most satisfactory oil-solubility characteristics.

Suitable reactive titanic acid derivatives, as illustrate invention. eating oils of naphthenic, parafiinic, and mixed naphsuitable.

be prepared by heating a mixture of the complex of titanic acid with glycol or polyhydroxy benzene and an organic amine such as trimethyl amine, triethanol amine,lauryl amine, phenyl-alpha-naphthylamine, amino phenol, pyridine, etc. The esters may be prepared by reacting the titanium tetrahalide at the beginning with aliphatic alcohols and glycols such as ethyl alcohol, butyl alcohol, 2-ethylhexanediol-l,3, pentaerythritol, cetyl alcohol, etc.

The complex of titanic acid with glycol or polyhydroxy benzene is present in the compositions of the invention in an amount at least sufficient to inhibit corrosion .orv oxidation. Small amounts, usually from about 0.01 to about 5.0 percent by weight based on the oil, are effective. Proportions ranging from about 0.05 to about 1.0 percent are preferred in most lubricating oil compositions. Concentrates containing larger proportions, up to '50 percent, either in solution or suspension, are particularly suitable in compounding operations.

Any of the well-known types of oils of lubricating viscosity are suitable base oils for the compositions of the They include hydrocarbon or mineral lubritheme and paratfinic types. They may be refined by any of the conventional methods such as solvent refining and acid refining. Synthetic hydrocarbon oils of the a-lkylene polymer type or those derived from coal and shale may also be employed. Alkylene oxide polymers and their derivatives such as the propylene oxide polymers and' their ethyl esters and acetyl derivatives in which the terminal hydroxyl groups have been modified are also Synthetic oils of the dicarboxylic acid ester type including dibutyl adipate, di-Z-ethylhexyl seba'cate, di-n-hexyl fumaric polymer, dilauryl azelatc, and the like may be used. Alkyl benzene types of synthetic oils such as tetradecyl benzene, etc. are also included. Liquid esters of acids of phosphorus including tricresyl phosphate, diethyl esters of decane phosphonic acid, and the like may also be employed. Also suitable are the polysiloxane oils of the type of polyalkyl, polyaryl, polyalkoxy and polyaryloxy siloxanes such as polymethyl siloxane, polymethylphenyl siloxane and polymethoxyphenoxy siloxane and silicate ester oils such as tetraalkyl and tetraaryl silicates of the tetra-2-ethylhexyl silicate and tetrap-tert.-butylphenyl silicate types.

In a preferred embodiment of the invention, as mentioned above, the complexes of titanic acid with glycol or polyhydroxy benzene are employed in combination with compounded mineral lubricating oils of the internal combustion engine type which are normally corrosive to alloy bearings. In such an embodiment, as in the case of the other, straight oils of lubricating viscosity, a major proportion of the lubricating oil normally corrosive to metals and/or subject to oxidation and a small amount, suflicient :0 inhibit said corrosion and/or oxidation, of a titanic acid complex provides a remarkably improved composi- Lion. These compounded oils customarily contain deergents such as the oil-soluble petroleum sulfonates and itabilizers such as the metal alkyl phenates. Other tgCIltS such'as oiliness agents, viscosity index improvers, :our point depressants, blooming agents, peptizing agents, to. may also be present. 1

In further illustration of the invention, the following :xamples are submitted showing" the preparation of the itanic acid complexes and evaluation of their effectivea'reasss W EXAMPLE 1 Into a reaction flask equipped with a mechanical stirrer and vented through a calcium chloride drying tube are placed 148 grams of anhydrous butyl alcohol and 850 milliliters of toluene. The flask is immersed in an ice bath. When the temperature of the contents reaches 10 C., 1.90 grams of titanium tetrachloride are added dropwise at a rate so the temperature is maintained between 10 C. and 15 C. Stirring is continued for 2 hours While nitrogen gas is bubbled through the reaction mixture to remove hydrogen chloride. When the reaction is complete, which is indicated by hydrogen chloride no longer being evolved, the toluene solvent is removed by vacuum distillation at 1 mm. Hg pressure leaving the dibutyl dichlorotitanate reaction product.

The dibutyl dichlorotitanate obtained above is added to 292 gramsof 2-ethylhexanediol-1,3 in a reaction flask. 180 grams of pyridine are added to take up the hydrogen chloride formed and the mixture is warmed slightly to accelerate the reaction. When the reaction is complete, the solid pyridine hydrochloride is separated from the liquid portion of the reaction mixture. The pyridine hydrochloride is washed with several portions of anhydrous toluene which are collected and added to the liquid reaction mixture. The combined liquid portions are then vacuum distilled at a pressure of 1 mm. Hg to remove the toluene and excess 2-ethylhexanediol-1,3 leaving the dibutyl ester of di(2-ethylhexanediol-l,3) titanate as a clear, light yellow, highly viscous, tacky product which is insoluble in water, soluble in ethyl alcohol and very soluble in hydrocarbon solvent.

EXAMPLE 2 Approximately 500 grams of dibutyl ester of di(2- ethylhexanediol-l,3) titanate of the type illustrated in the above example are combined with about 50 grams of water. The mixture is agitated with a mechanical stirring arrangement. The butyl alcohol produced by hydrolysis is removed from the mixture by vacuum distillation at 1 mm. Hg pressure and amounts to approximately 150 grams which corresponds closely to theoretical. The di(2-ethylhexanediol-1,3) titanate is separated from the aqueous mixture obtained above by decanting the supernatent water. It is a light yellow, tacky, semisolid closely similar to the dibutyl ester of di(2-ethylhexanediol-1,3)' titanate of the preceding illustration,

The efiectiveness of the lubricating oil compositions of the invention is demonstrated by the copper-lead strip corrosiontest. In thistest a polished copper-lead strip is weighed and immersed in 300 cubic centimeters of test oil in a 400-milli1iter lipless Berzelius beaker. The test oil is maintained at 340 F..under a pressure of one atmosphere of oxygen, and stirred with a mechanical stirrer at 1,000

'R. P. M. After two hours a synthetic naphthenate catalyst is added, unless otherwise specified, to provide the following catalytic metals:

Percent by weight Iron 0.008 Lead 0.004, Copper 0.002 Manganese 0.0005 Chromium 0.004

The test is continued. 20 hours. The copper-lead strip is then removed, rubbed vigorously with a soft cloth and mineral oil and a compounded mineral lubricatingoil corrosive to alloy bearings. .vent 'refined-SAE 40 mineral lubricating oil base having a of the internal combustion engine type which is normally The compounded oil isa solviscosity index of 60 and containing 10 mM/kg. of neutral calcium petroleum sulfonate and 20 mM/kg. of calcium alkyl phenate, sulfurized. The results of the test are shown in the following table. The concentrations of titanic acid complex employed are given in either millimoles of titanium per kilogram of oil or percent by weight of the composition.

Table I COPPER-LEAD STRIP CORROSION TEST Copper- Lea Additive Base Oil Strip Weight Loss e None Mineral lub. oil 105, 4.0% di(2-ethylhexanediol-1,3) titanate Same .r 79.0 None Oompounded oi1 302. 0 0.6% dibutyl ester of di(2-ethylhexanedi- Same 8. 2

01-1, titanate. 0.3% dibutyl ester of di(2-ethylhexane-' 56.4

d1ol-1,3).titanate. 0.5% di(2-ethylhexanediol-1,3) titanate 41. 0 1.0% dl(2-ethy1l1exanediol-l,3) titanate l4. 7 0.6% monobutyl tri(2-ethylhexanediol- 14.0

1,3) titanate.

As shown by the above test data, straight mineral lubricating oil alone gives a copper-lead strip weight loss due to corrosion of over 105 milligrams in the 20-hour period. By way of distinction, compositions in accordance with this invention containing the same straight mineral lubricating oil base and a titanate corrosion inhibitor give as little as 79 milligrams weight loss. In the case of the conventional compounded mineral lubricating oils of the internal combustion engine type which are normally corrosive to copper-lead bearings, the improvement is even more remarkable. The compounded oil alone gives copperlead strip weight losses ranging as high as 300 milligrams whereas the lubricating oil compositions of the invention containing the same compounded base oil plus a glycol fomplex of titanic acid result in very little or no corrosion oss.

The lubricating oil compositions illustrative of the invention are also evaluated for their efiectiveness as inhibitors in gasoline type internal combustion engines. This test is termed the L-4 Strip Corrosion Test because of its correlation with the L-4 Chevrolet Engine Test referred to in the C. R. C. Handbook, 1946 edition, Coordinating Research Council, New York, New York. In the test the same apparatus and conditions as described in the above copper-lead strip corrosion test are employed with two essential modifications. The temperature is maintained at 295 F. to simulate lower temperatures encountered in gasoline engines and a synthetic naphthenate catalyst of the following type is used containing lead in further duplication of gasoline engine operation:

Percent by weight Copper 0.0095 Iron 0.0056 Manganese 0.0005 Lead -i 0.11 Tin 0.0049

The reference oil is a compounded oil consisting of a solvent refined 140 neutral mineral lubricating oil base containing 3.75% by weight based on the composition of a polymethacrylate glycol ester ashless detergent.

The nature of the improved lubricating oil compositions of the invention and their effectiveness should be readily apparent from the many illustrations given above. Oxidation and corrosivity in the compositions are definitely inhibited to a very substantial degree. Particularly corrodible metals such as engine alloy bearings of copper, lead, and the like, as well as bearings of silver, are not adversely afiected. This is indeed remarkable since the problem of devising lubricant compositions uniformly noncorrosive to both types of bearing metals has long confronted workers in the art. The advantagesof these improvements are obtained without loss of other desirable properties of the lubricant compositions.

As mentioned above, the titanium compounds of the compositions according to this invention are preferably formed from titanic acid, etc. and an alphaor beta-diol or vicinal dihydroxy benzene. Although the present invention is in no way limited to any theory concerning the structure of the compounds, it is believed that they may be illustrated by the following formulae:

Diglycol titanates OH 1\O/ Di-pyrocatechol tltana'tes wherein R is hydrogen or a group of hydrocarbon structures as previously described.

Although the above types of compounds are distinctly preferred in the compositions of the invention, other compounds of similar structure having substituents on the hydrocarbon groups which do not adversely affect the reaction may likewise be employed. Such substituents include: hydroxyl groups, as when a polyhydroxy alcohol or benzene such as glycerol, pentaerythritol, sorbitol or trihydroxy benzene is used; ester groups, as when glycerol monooleate or sorbitan monooleate is used; and halogens, others, amides, etc., as will be apparent to those skilled in the art from the above description of the invention.

Although the compositions of the invention have been primarily described as crankcase lubricants for internal combustion engines, they are also useful as turbine oils, hydraulic fluids, instrument oils, constituent oils in grease manufacture, ice-machine oils, and the like.

I claim:

1. A lubricant composition comprising an oil of lubricating viscosity and a member of the group consisting of titanates of .alphaand beta-glycols" of 6 'to-10'carb'on atoms in an amount sufficient to inhibit corrosion.

'2. 'A' lubricant composition comprising anoil of lubricating viscosity and 0.01 to 5.0 percent by weight based on the oil of a titanate of 2-ethylheXane-L3-sdio1.

' 3.. A lubricant composition comprising a mineral lubricating oil for internal combustion engines which is normally corrosive to alloy bearings anda member of the group consisting of titanate of alphaand beta-glycols of 6 to 10 carbon atoms in an amount sufficient to inhibit corrosion.

4. A lubricant composition comprising a mineral lubricating oil for internal combustion engineswhich is normazlly corrosive to alloy bearings and a titanate of an alpha-alkanediol containing from 6 to 10 carbon atoms in an amount sufficient to inhibit corrosion.

5. A lubricant composition comprising a mineral lubrieating oil for internal combustion engines which is normally corrosive to alloy bearings and a titanate of a betaalkanediol containing from 6 to 10 carbon atoms in an amount suflicient to inhibit corrosion.

6. A lubricant composition comprising a mineral lubrieating oil for internal combustion engines which is normally corrosive to alloy bearings and from about 0.01 to about 5.0 percent by weight based on the oil of a titanate of 2-ethylhexane-1,3-diol. r

7. A lubricant composition comprising a mineral lubricating oil for internal,combustionfengines'which is normally corrosive to alloy bearings and from about'0.01 to to about 5.0 percent by weight based on the oil of dibutyl ester of di(2-ethylheXanedio1-l,3) titanate.

8. A lubricant composition comprising a mineral lubricating oil for internal combustion engines which is normally corrosive to alloy bearings and from about 0.01 to about 5.0 percent by weight based on the oil of K1i(2-ethy1 hexane:diol-1,3) titanate.

References Cited in the file of this patent UNITED STATES PATENTS Swiss Mar. 22, 1949

Claims (1)

1. A LUBRICANT COMPOSITION COMPRISING AN OIL OF LUBRICATING VISCOSITY AND A MEMBER OF THE GROUP CONSISTING OF TITANATES OF ALPHA- AND BETA-GLYCOLS OF 6 TO 10 CARBON ATOMS IN AN AMOUNT SUFFICIENT TO INHIBIT CORROSION.