US2491772A - Extreme pressure lubricants - Google Patents

Description

Patente Dec, 20, 1949 M'ED STATES PATENT QFFICE Standard Oil Develo ration of Delaware pment Company, a corpo- No Drawing. Application December 29, 1945, Serial No. 638.433

7 Claims. (Cl. 252-475) The present invention relates to lubricants gen erally, and, more particularly, to lubricants providing a lubricatin film capable of withstanding high loads or pressures without rupture of the lubricant film.

It has been established that straight mineral lubricating oils do not provide lubricating films of sufficiently high film strength to adequately lubricate moving metal parts which contact each other under high pressures such as are encountered in certain types of bearings, engines, gears, etc., and for the purpose of improving as much as possible upon the load-carrying characteristics of ordinary mineral lubricating 011, many E. P. additives, oiliness agents, etc., are known to the art and have been extensively used with considerable success. Among the many E. P, additives heretofore recommended, those hydrocarbon derivatives containin both active halogen and active sulfur have proved themselves to be very effective in increasing the load-bearing characteristics of mineral lubricating oil. Even though these sulfur-halogen compounds are exceedingly successful as E. P. additives many of them have one characteristic which detracts from their acceptability. This characteristic is that these sulfur-halogen compounds tend to be somewhat unstable during storage, especially at temperatures above 100 F., liberating a hydro-halogen acid which is corrosive to metal containers.

Such sulfur-halogen compounds are frequently too corrosive for use with certain types of bearings. Attempts have been made to overcome this excessive corrosiveness of sulfur-halogen compounds by the use of inhibitors but without much success. While the use of inhibitors is somewhat successful in delaying the appearance of evidence of the corrosiveness of sulfur-halogen E. P. additives, they are often objectionable for the reason that they react with the additive or its decomposition products to give insoluble precipitates. Such reaction both detracts from the quality of the E. P. additive and destroys the inhibitor.

An object of the present invention is the production of a novel, less corrosive type of sulfurhalogen compound. Another object is an improvement in E. P. lubricants. These and other objects will be apparent to those skilled in the art upon reading the following description.

The present invention is based upon the discovery that the reaction product of a chlorinated hydrocarbon containing active chlorine and an alkali metal salt of alkyl or aryl dithiocarbamic acid, which may also be designated as alkyl or aryl-substituted alkali metal dithioaminoformate, is an oil-soluble compound having the property in oil solution of increasing the load-bearing characteristics of a mineral lubricating oil, and is stable during storage and relatively non-corrosive to metals. This reaction is illustrated by the following equation:

XCSSMet+RHalx+XCSSRHalx-1+MetHal wherein X is a radical selected from the group consisting of (1) dialkyl amines or amines having two like or different alkyl, cycloalkyl, aryl, etc, radicals, such as diamyl amine, (2) monoalkylaryl amines such as xylidine, and (3) piperidine; R. is a hydrocarbon residue derived from a petroleum mineral oil distillate such as paraffin wax, kerosene and aromatic petroleum fractions having from 8 to carbon atoms to the molecule; Met is an alkali metal such as sodium, patassium, lithium, etc.; Hal is one of the halogens such as chlorine, bromine or iodine, of which chlorine is preferred and m is a positive number of sufiicient magnitude that the weight per cent of halogen in the compound RHalx will range between 5 and preferably 30-40%. The value of a: will therefore normally range between 2 and 5. The reaction may be carried out in the presence of a ketone solvent such as methyl ethyl ketone or acetone, although any other organic solvent, except alcohol, which is capable of dissolving the carbamate, may be used, and at the reflux temperature of the particular solvent employed. After the reaction is complete, which generally requires from 1-3 hours, the reaction mixture is filtered to remove inorganic salts, after which the solvent is recovered by distillation and the product is refiltered to remove any residual inorganic salts that may be present.

The halogenated hydrocarbon represented by R"Halx which may be a halogenated paraffin wax, kerosene or aromatic petroleum fraction is made by halogenating the hydrocarbon selected until on a weight percentage basis the halogen content of the halogenated hydrocarbon ranges from about 5% to as much as 50%. One example of a suitable halogenated hydrocarbon is one made by chlorinatlng kerosene to a chlorine content of about 40%, by passing chlorine through kerosene at atmospheric pressure and a temperature of about -200 F. for 3 hours. The time required to suiliciently chlorinate a petroleum mineral oil distillate under these conditions of temperature and pressure will range from about 30 minutes to 5 hours. Within the range specified, the chlorine content of the chlorinated hydrocarbon may be varied to accommodate any previously determined sulfur-chlorine requirements in the final product.

The alkali metal salt of the hydrocarbon substituted dithiocarbamic acid is made by reacting a primary or secondary amine, carbon disulfide and alkali metal hydroxide according to the following equation:

In this formula the radicals R and R possess the same designations as were ascribed to R and R in the preceding formula illustrating the reaction between the carbamate salt and the halogenated hydrocarbon. Where the hydrocarbon substitutent in the dithiocarbamic acid is of the piperidine type, the above formula is slightly changed since R. and R form a part of a closed ring. In this case, the formula may be repre-' sented more generically as XCSSNa which, upon condensation with the halogenated hydrocarbon, becomes XCSSEster, wherein X is an amine group, a nitrogen atom being attached to two carbon atoms which may form parts of separate hydrocarbon radicals or may be a part of a single cyclic hydrocarbon structure. The reaction is carried out by suspending stoichiometricamounts of amine and caustic in a solvent such as methyl ethyl ketone, which suspension isthen cooled in an ice bath or other equivalent cooling means, and carbon disulfide is then added slowly with agitation. Since the reaction is exothermic, the carbon disulfide must be added cautiously so as to maintain the reactants at a low temperature and prevent undue volatilization of the carbon disulfide. In view of the fact that carbon disuh fide is a highly volatile liquid, some excess, up to about over that theoretically required, may be used Without any harmful efiects, for the purpose of compensating for any carbon disulfide lost through volatilization.

The substituted dithiocarbamlc halogenated esters, containing from about 2 to 10% of sulfur and to of chlorine, resulting from the re-. action between the alkali metal salt of the sub stituted dithiocarbamic acid and the chlorinated hydrocarbon can then be blended in amounts ranging from 2 to 30% by weight, based on the total composition, preferably about 10%, in a mineral lubricating oil to yield an extreme pressure lubricant. In compounding such an extreme pressure lubricant, any of the numerous types of low pour point lubricating oils may be used; it is preferred, however, to use a Pennsylvania type oil having a viscosity in the range of from about to about 150 seconds S. U. V. at 210 F. and a cold test below 0 F. The following examples will serve to illustrate specific embodiments of the invention:

EXAMPLE 1 20 parts by weight sodium hydroxide 42.6 parts by weight piperidine 43.2 parts by weight carbon disulfide 407 parts by weight chlorinated kerosene con taining 39.8% of chlorine dium piperidyl dithioiormate in the solvent. The chlorinated kerosene and 250 cc. additional methyl ethyl ketone were placed in a separate reactor equipped with a reflux condenser; the heavy yellow suspension was then added to the chlorinated kerosene in methyl ethyl ketone and the whole refluxed for 2 hours. The reaction mixture was then cooled and filtered to remove sodium chloride and the filtrate distilled under a reduced pressure of 37 mm. to remove the methyl ethyl ketone. The residue from the distillation was again filtered to take out any last traces of sodium chloride. 435 parts by weight of a product containing 4.9% sulfur and 31.2% chlorine were obtained. A 10% blend of this product in a mineral lubricating oil of 45 seconds vis. at 210 F. carried a full shock load of 15 weights in the Almen test as compared with 3 weights carried by the straight mineral oil. The reaction product in this example may be appropriately described as a piperidyl dithioformic chloro-alkyl ester where the ester-forming group is chlorinated kerosene. As previously indicated, this group may be a halogenated paraffin wax or a halogenated aromatic petroleum fraction instead of kerosene if desired.

EXAMPLE 2 20 parts by weight sodium hydroxide e25 parts by weight carbon disulfide 7 8.7 parts by weight diamyl amine 407 parts by weight chlorinated kerosene con taining 39.8% of chlorine The carbon disulfide was reacted with the caustic and amine in the same manner as described in Example 1, resulting in a clear yellow solution which was then refluxed with the chlorinated kerosene for 2 hours and the product isolated. 485 parts by weight of a product containing 5.3% of sulfur and 28.6% chlorine was obtained. A 10% blend of this product in mineral lubricating oil carried a full shock load of 15 weights in the Almen test. The composition thus formed may be considered to be a diamyl dithiocarbamio chloro-alky'l ester where the ester-forming group is chlorinated kerosene. Instead of chlorinated kerosene, as previously indicated, halogenated paraffin wax or halogenated aromatic petroleum fractions may be used. More specifically, a. chlorinated pentadecyl hydrocarbon may be used in lieu of or as a part of the chlorinated kerosene in which case the reaction product would comprise or consist of diamyl dithiocarbamic pentadecyl ester.

EXAMPLE 3 20 parts by weight sodium hydroxide 43.5 parts by weight carbon disulfide 62.1 parts mixed xylidines 405 parts of chlorinated kerosene containing 39.8% of chlorine The caustic, xylidines and carbon disulfide were reacted in the presence of methyl ethyl ketone as described in Example 1, yielding a heavy yellow suspension which was refluxed with the chlorinated kerosene in methyl ethyl ketone. After removal of the solvent and inorganic salts, 449 parts of a product containing 3.4% sulfur and 30.4% chlorine was obtained. A blend of 10% of this product in mineral lubricating oil (45 vis. at 210 F.) carried a full shock load of 15 weights in the Almen test. As in Examples 1 and 2 above, other halogenated hydrocarbons may obviously be substituted for chlorinated kerosene.

To illustrate the improved corrosion characteristics of the compounds of the present invention,

8 10% blends of these products in a highly refined mineral lubricating oil (15 seconds vis. at 210 F.) were made up and tested according to the following procedure. 200 cc. of the blend and 2 cc. of Water were vigorously agitated for 3 minutes. A Timken cup and an Almen pin were then placed in the lubricant and the lubricant stored in an oven at 120 F. for 48 hours at which time the extent of corrosion was noted. The results of these tests are shown in the following table.

Table I Extent of Corrosion Lubricating Oil+l% Commercial Extreme Marked.

Pressure Additive. Lubricating Oi.+l0% oi the product made in Very Slight. Example 1.

Llibl'iCafllng2 Oil+l0% oi the product made in Slight Stain.

xampe Lubricating Oil+l0% of the product made in Do.

Example 3.

Commercial extreme pressure additive containing sulfur and chlorine, but no nitrogen.

What is claimed is:

1. An extreme pressure lubricant comprising a highly refined mineral lubricating oil and 2 to 30% by weight, based on the total composition of piperidyl dithioformic chloralkyl ester, where the ester-forming group is a chlorinated kerosene containing 5 to 50% by weight of chlorine.

2. An extreme pressure lubricant comprising a highly refined mineral lubricating oil and by weight, based on the total composition of piperidyl dithioformic chloralkyl ester, where the ester-forming group is a chlorinated kerosene containing 5 to 50% by weight of chlorine.

3. An extreme pressure lubricant comprising a highly refined mineral lubricating oil and 2 to 30% by weight, based on the total composition of diamyl dithiocarbamic chloralkyl ester where the chloralkyl ester-forming group is chlorinated kerosene containing 5 to 50% by weight of chlorine.

4. An extreme pressure lubricant comprising a highly refined mineral lubricating oil and 10% by weight, based on the total composition of diamyl dithiocarbamic chloralkyl ester where the chloralkyl ester-forming group is chlorinated kerosene containing 5 to by weight of chicrme.

5. An extreme pressure lubricant comprising a highly refined mineral lubricating oil and 2 to 30% by weight, based on the total composition of xylyl dithiocarbamic chloralkyl ester, where the ester-forming group is chlorinated kerosene containing 5 to 50% by weight'of chlorine.

6. An extreme pressure lubricant comprising a highly refined mineral lubricating oil and 10% by weight, based on the total composition of xylyl dithiocarbamic chloralkyl ester, where the esterforming group is chlorinated kerosene containing 5 to 50% by weightof chlorine.

7. An extreme pressure lubricant composition comprising a major proportion of highly refined mineral lubricating oil and 2 to 30% by weight, based on the total composition, of the reaction product of an alkali metal salt of a hydrocarbon substituted dithiocarbamic acid with a chlorinated hydrocarbon, said reaction product having the formula XCSSEster where X is a radical selected from the group consisting of dialkyl amines, monoalkylaryl amines, and the piperidine radical, the ester- Iorming group being a chlorinated petroleum hydrocarbon radical of 8 to 30 carbon atoms containing at least 5% and not more than 50% by