US2628942A - Lubricating oils containing metal derivatives of cyclic imides - Google Patents

Description

Patented Feb. 17, 1953 I LUBRIGATING OILS CONTAINING METAL DERIVATIVES or c clic nnncs John R. Morris, Fishkill, and James R; Roach, Beacon, N. Y., assignors to The Texas Company. New York, N. Y., a corporation of Delaware No Drawing Application'June 27, 195-1,

. serial No. 233,942

6.Glaims- (o1. aria -49.7) r

I case lubricants in internal combustion engines tend to oxidize at the high temperatures to which they are subjected in this type of service with the formation of gums and sludges, which clog the oil feed lines and form varnish-like deposits on the surfaces of rings, pistons, cylinders and other engine parts. Such deposits decrease the efficiency of operation of the engine and.- eventually lead-to piston sticking and scoring of the cylinder walls. Y

It is common practice to add to crankcase oils small amounts of so-called detergents, which hovel-he p oper y of r ng h s formation of sludges and varnishes, Various types of metal organic compounds are known to be effective for this Purpos particularly thos compounds where nt metal is linked to an organic group through an oxygen atom. For example, Davis ct al. in U. S. Patent No 2,335,261 disclose that polyvalent metal salts of high molecular weight fatty acids such as wax acids and alkyla d aromatic acids such as alkylatecl benzoic and phthalic acids are eff ive for this purpose Th metal phenates, particularly the polyvalent metal h na es. a isclosed for example by Gardiner glutaric acids, having aliphatic substituent groups et al in Uv S. Patents No. 2,228,661 and No, 7

However, c mpou s of th above type have the disadvantage hat th y are uns able in the pres nc of Water. so that th y hydro yze with the formation or water soluble metal compounds r sludg as Well as. iactiona le corrosive maerials. The detergen mpounds thus become d s royed or removed from the lubricating com p sition when th l r becomes contamina ed with water, such as may occur n hand ng a d in storage.

In c rdance with ourinvention lubricating oils having superior detereen y and stability, suitable for use as crankcase oils in automotive. diesel and airpla e en ines, are pr duced by adding to mineral lubricating oils small amounts of compounds of the class consisting of oilsoluble metal cyclic imilles derived irom aliphatic liicarboxylic acids. Su table compounds 01 this type are metal derivati es oi stable cyclic'imides,

of suflicient size to impart oil solubility to the molecule. We have found that compounds of this class wherein. a metal is linked directly to a nitrogen atom positioned between two acyl groups possess excellent detergency and anti -sludging properties in mineral lubricating oils, and are furthermore. characterized by a remarkable stability and resistance to hydrolysis as compared with the corresponding compounds containing the metal motion linka e which have been employed heretofore in'lubricatlng oil to promote engine cleanliness. They are particularly Valli able for use in producing lubricating oils to meet the severe requirements of airplane engine oils.

The preferred comp unds employed as lubrieating oil additives ac ording to our vention may be repr sented by the general-formula Rice-00 moo, s- M Ba- O(.) H I 11 wherein M is a metal, a is an integer equal to the valency of, the metal, R is a methylene group, n

is 1 or 0, and R1, R2 and R are members of: the group consisting of hydrogen and aliphatic hy= drocarbon groups, at leastone of them being an alkenyl or alkyl group containing from about .15

to about 30 carbon atoms. and most suita y from about 18 to 25 carbon atoms. M of the formula may be any alkali metal, alkaline earth metal or other metal ca ble of forming compounds of this type, as for ex mple sodium, potassium, lithium calcium, barium, strontium. magnesium, -a1-uininum; tin, zinc cobalt, nickel, titanium r man anese. It is preferably a polyvalent metal. The bivalent metals, particularly zinc and mag: nesium, are especially uitable,

As suitable examples of the above class of comipounds may be mentioned mag esium docosenyl succinimide, calcium qocosenyl glutarimicle, zinc a methyl-p-pentadeceny1 succinimide, co baltous nondecenyl glutarimide, calcium penta: cosenyl succinimide, titanous a-propyl-fl-eicosenyl succinimide, a'ndSO forth.

.lhe above described imide derivative may e employed varying amounts depending upon the'characteristics oi the lubricating oil and the c nditions under which his to be employed.

Even in very small amounts, as about 0.01 per cent by weight, they impart substantial improvement in the detergency characteristics of mineral lubricating oils. Ordinarily they are employed in crankcase oils in amounts within the range of from about 0.5 to about 5 per cent by Weight, and preferably with the range of from about 0.5 to about 3 per cent by weight of the composition.

The metal imides of this invention are formed by treating aliphatic substituted succinimides and glutarimides with metal compounds under conditions such that the hydrogen atom of the imido group is replaced by metal. The aliphatic substituted succinimides and glutarimides may conveniently be obtained by reacting the anhydrides of maleic, glutaconic, citraconic, homomesaconic, or itaconic acids, or homologues thereof, with unsaturated aliphatic hydrocarbons, and then converting the aliphatic-substituted anhydrides obtained to the corresponding imides by treating with ammonia. V Alkenyl substituted anhydrides, which are obtained when olefinic anhydrides are reacted with olefin polymers, may be hydrogenated if desired either before or after conversion to the imides to obtain the corresponding alkyl substituted compounds.

In forming the polyvalent metal salts the imide may be treated. directly with a suitable compound of the polyvalent metal or the imide may be first treated with an alkali metal compound and the alkali metal imide derivative then converted to the polyvalent metal derivative by double decomposition with a suitable polyvalent metal compound.

The following examples illustrate the preparation of these metal imide derivatives by each of the above methods.

EXAMPLE 1 The magnesium derivative of an alkenyl succinimide was prepared by the following procedure: An alkenyl succinic anhydride was first from 100 C. to 240 C. and the heating then con- 'tinued for hour longer without the introduction of ammonia. The product was taken up in ether and washed free of excess ammonia, the ether stripped out and the product dried by adding toluene and again stripping to remove the f toluene and water. 405 grams of the alkenyl succinimide thus obtained were dissolved in toluene and a solution of magnesium methylate obtained by dissolving 12.4 grams of magnesium metal in dry methanol added. The mixture was heated under reflux for 18 hours and the solvent stripped oil. 417 grams of product were obtained analyzing 3.10% magnesium and 3.44% of nitrogen, as compared with the theoretical values 3.00% and 3.48%, respectively, for magnesium alkenyl (C21) succinimide.

EXAMPLE 2 The zinc derivative of an alkenyl succinimide was prepared as follows. An alkenyl succinimide was prepared as described in Example 1, employing in the alkylation of the maleic anhydride a propylene polymer having a molecular weight corresponding to 21 carbon atoms per molecule. 324 grams of the alkenyl succinimide thus obtained were added to a solution of sodium methylate obtained by dissolving 19.2 grams of sodium metal in methanol, and the reaction mixture refluxed for two hours. 52 grams of zinc chloride dissolved in methanol were then added and the mass stirred for four hours, the alcohol stripped out and the residue taken up in ether and Washed with water until the wash water was free of chlorine. The ether was then stripped out and the product dried by adding toluene and again stripping. 338 grams of product were obtained which analyzed 9.82% of ash as compared with the theoretical value of 9.63% of zinc oxide for zinc alkenyl (C21) succinimide.

The compounds obtained as described in the above examples were oil-soluble and water-stable and possessed outstanding properties with regard to detergency and an-ti-sludging properties in lubricating oils. Table I below shows test data obtained on the magnesium alkenyl succinimide obtained as described in Example 1.

l A different base oil giving only 304 mg; of deposit was used in this test.

The water stability test of the above table is carried out in the following manner: 200 grams of oil containing additive and 200 grams of distilled water are stirred together for 15 minutes at room temperature by means of a Mixmaster running at 700 R. P. M. The emulsion is then centrifuged and an ash determination made on the clarified oil. The per cent of additive removed is calculated from the difference between the ash content of this washed sample and that of the original oil.

The carbon black dispersion test of the foregoing table is a bench test designed to show the detergency characteristics of an oil. The test is carried out in the following manner: A ml. portion of a suspension prepared by thoroughly mixing 1 gram of carbon black into a solution consisting of grams of the test oil and 150 grams of kerosine is placed in a centrifuge tube and centrifuged at 2000-2100 R. P. M. for 5 minutes. About 35 m1. of the centrifuged suspension is immediately poured from the top of the centrifuge tube and a 5 ml. portion of this taken and diluted to 60 ml. with kerosine in a tall bottle or Nessler tube. The sample thus prepared is compared visually with a series of graduated standards containing various amounts of carbon black suspended in a similarly diluted oil of the same character as the test oil. The dispersion value of the test oil is expressed in terms of arbitrary numbers assigned to these standards on the basis of the relative amounts of suspended carbon which they contain. This test measures specifically the ability of an oil to hold in suspension or dispersion carbon black, which may be considered comparable to blow-by carbon in an internal combustion engine, and it ga e-m also provides Ia generally good. indication of the oil-ringsludging characterof an oil inservice.

The high temperature depositsv test- .of the table is also a bench test wheren an aluminum cylinder one inch in diameter and three inches long is repeatedly dipped-into a beaker containing a sample of the test .oil maintained at 525 F. for a period of 20 hours. The depositremaining on the test specimen .after washing with pentane and drying is determined.

As shown in Table I, the magnesium alkenyl succinimide was highly effective in dispersing carbon black and in reducing varnish-formation in a mineral lubricating oil at high temperatures.

1 It was markedly superior in these tests indicating the ability of an oil to maintain engine cleanliness in comparison with magnesium alkyl phenolate, which is considered to be one of the most efiective compounds employed for this purpose at the present time. In addition the compound of our invention has a satisfactory degree of water-stability, equal to over three times that of the phenolate. The improved water-stability of this compound is in agreement with tests performed on another typical compound of this class wherein barium alkenyl succinimide was heated for an hour in sulfuric acid without substantial change.

The detergency characteristics of compounds prepared as described in Examples 1 and 2 were further determined by means of the C. F. R.

I high speed engine test, which is a test for determining the ability of an oil to reduce engine deposits under severe operating conditions. This test is carried out with a standard C. F. R. single cylinder internal combustion engine operating under the following conditions:

Compression ratio 6.5:1. Speed, R. P. M. 1300. Air/fuel ratio 13:1.

7 Jacket temperature 285 F.

Oil in temperature 185 F.

Oil out temperature 200 F.

Fuel 100 octane (minimum) aviation type containing 4 cc. TEL/gal.

Duration of run 50 hours.

At the termination of each run, electrical measurements are taken of the piston skirt deposit with respect to the extent or percentage of surface area of the piston skirt which is covered by the lacquer deposit as well as the average thickness of the deposit. The carbonaceous deposits in the piston ring grooves are also carefully scraped oil and weighed. Extensive laboratory testing has shown that a crank case lubricating oil which will markedly reduce the tough black lacquer deposit on the piston skirt and the carbonaceous deposits occurring in the ring belt area, can be expected to reduce deposits at all points where high temperatures are encountered. The tests listed are therefore an accurate indication of the engine cleanliness of the oil compositions under test.

The following table gives the results obtained in the above test on an oil containing small amounts of our compounds as compared with the base oil alone, which was a highly refined residual lubricating oil from a parafiin base crude employed as an airplane engine lubricating oil. The magnesium alkenyl succinimide of the table is that prepared as described in Example 1. The zinc alkenyl succinimide was prepared as described in Example 2 except that a propylene Table 11' c. F. R. HIGH srn'a'n ENGINE rrns'rs Piston Skirt Deposit Additive l Percent Thickness Covered 'In. 10-

None (Base oil) 2. 0 1% Mg alkcnyl succinimide 0.5% Zn alkenyl succinimidc -0. 0 '0. 0

The data given in Table II show the outstanding properties of our compounds in reducing engine deposits in an actual engine test. In this test an oil was produced by the use of small amounts of typical compounds of our invention which gave zero engine deposits after 50 hours of severe operating conditions corresponding to those encountered in airplane engine lubrication, as compared with heavy varnish deposits covering per cent of the piston skirt obtained with the uninhibited base oil under the same conditions.

Lubricating compositions containing the additives of our invention may also contain other additives such as are ordinarily employed in lubricants, such as oxidation inhibitors, pour point depressors, viscosity index improvers, corrosion inhibitors, and so forth, as well as other detergents such as metal phenates, sulfonates and other metal salts- Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations ficient to improve the detergency thereof of a compound of the general formula H R1C-CO Rim N- M B3 CO wherein M is a polyvalent metal, a: is an integer equal to the valency of the metal, R. is a methylene group, n is 1 or 0, and R1, R2 and Re are members of the group consisting of hydrogen and aliphatic hydrocarbon groups, at least one of them being an aliphatic hydrocarbon group containing from about 15 to about 30 carbon atoms.

2. The lubricant according to claim 1 wherein the metal is a divalent metal.

3. A lubricant consisting essentially of a refined minerallubricating oil and about 0.1 to about 5 per cent by weight of the magnesium salt of a succinimide substituted on one of its methylene groups by an aliphatic hydrocarbon group containing from about 15 to 30 carbon atoms.

4. A lubricant consisting essentially of a refined mineral lubricating oil and about 0.1 to about 5 per cent by weight of the zinc salt of a succinimide substituted on one of its methylene groups by an aliphatic hydrocarbon group containing from about 15 to 30 carbon atoms.

5. A lubricant consisting essentially of a refined mineral lubricating oil containing about 0.5 to 3.0 per cent by weight of magnesium alkenyl (C1540) succinimide and about 0.5 to 2.0 per cent by weight of zinc alkenyl (Cm-30) succinimide.

6. A lubricant consisting essentially of a refined mineral lubricating oil containing from about 0.1 to about 5 per cent by weight of a mixture consisting of a magnesium salt of a succinimide substituted on one of its methylene groups by an aliphatic hydrocarbon group containing from about 15 to about 30 carbon atoms and a zinc salt of a succinimide substituted on one 10 of its methylene groups by an aliphatic hydrocarbon group containing from about 15 to about 30 carbon atoms.

JOHN R. MORRIS. JAMES R. ROACH.

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

UNITED STATES PATENTS Number Name Date 2,363,516 Farrington Nov. 28, 1944 2,417,833 Lincoln Mar. 25, 1947 2,458,425 Rocchini Jan. 4, 1949 2,490,744 Trlgg Dec. 6, 1949

Claims (1)

1. A LUBRICATING CONSISTING ESSENTIALLY OF A REFINED MINERAL LUBRICATING OIL AND A SMALL AMOUNT SUFFICIENT TO IMPROVE THE DETERGENCY THEREOF OF A COMPOUND OF THE GENERAL FORMULA