GB1578049A - Succinimide derivatives of a copolymer of ehtylene and propylene - Google Patents

Description

(54) SUCCINIMIDE DERIVATIVES OF A COPOLYMER OF ETHYLENE AND PROPYLENE (71) We, TEXACO DEVELOPMENT CORPORATION, a Corporation organized and existing under the laws of the State of Delaware, United States of America, of 135 East 42nd Street, New York, New York 10017, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to novel compounds or adducts, and methods of preparing the same, useful as additives for lubricating oils, particularly petroleum based automotive lubricating oils, to impart shear stability, improved viscosity index (VI) and dispersancy in lubricating oil compositions containing the same.

Various compositions and adducts are known and have been employed to improve the viscosity index and dispersancy in lubricating oil compositions containing the same, see particularly U.S. Patents 3,179,716, 3,316,177, 3,329,658, 3,413,104, 3,449,250, 3,471,458, 3,496,249 and 3,513,095.

Ethylene-propylene copolymers have been employed in lubricating oil compositions as ashless shear stable VI improvers, These copolymers, however, do not act to any substantial degree as dispersants in lubricating oil compositions containing the same.

It has been discovered that the N-(3-dimethylaminopropyl) succinimides of an ethylene-propylene copolymer said copolymer having a molecular weight of at least 5000 are useful as shear stable VI improvers and dispersants in lubricating oils, particularly petroleum based automotive lubricating oils. This succinimide is obtained by reacting the ethylene-propylene copolymer, in a solvent with maleic anhydride in the presence of a free radical initiator, such as a peroxide, e.g. benzoyl peroxide, or dicumyl peroxide. The resulting alkyl succinic anhydride, derived by the addition of RH across the double bond of the maleic anhydride, wherein R is an ethylene-propylene copolymer radical, after addition of a diluent oil and removal of excess maleic anhydride and solvent is converted into the corresponding N-(3-dimethylaminopropyl) succinimide by reaction with 3 dimethylamino-l-propylamine. Upon completion of the reaction, the excess amine is removed by distillation to yield the resulting succinimide as product.

More particularly, and in accordance with one embodiment of the practice of this invention directed to a method of preparing the succinimide derivatives of the ethylene-propylene copolymer, a solution containing l(00/ by weight of an ethylene-propylene copolymer, particularly a narrow molecular weight distribution amorphous ethylene-propylene copolymer of the type employed as a lubricating oil additive, in a suitable solvent, such as an aromatic solvent, e.g. benzene, or chlorobenzene, or in a saturated, aliphatic or cycloaliphatic hydrocarbon solvent, such as cyclohexane, is prepared. The resulting solution is heated e.g. to a temperature of 80--1300C. in the presence of added excess maleic anhydride and a small amount of a free radical initiator, such as benzoyl peroxide or dicumyl peroxide. The resulting reaction product is the corresponding alkyl succinic anhydride derived by the addition of RH across the double bond of the maleic anhydride, wherein R is an ethylene-propylene copolymeric radical. There is added to the resulting reaction mixture a relatively high boiling, substantially inert, diluent oil and the excess maleic anhydride and solvent is removed by vacuum distillation. The remaining polymer succinic anhydride, i.e. the succinic anhydride grafted onto the ethylene-propylene copolymer, is converted to the corresponding N-(3-dimethylaminopropyl) succinimide by heating in the presence of an excess of the corresponding polyamine, viz. 3-dimethylamino-l-propylamine. Upon completion of the reaction the excess amine is removed by distillation and the resulting reaction product filtered.

In the practices of this invention, it is preferred to employ shear stable ethylene-propylene copolymer of the type suitable for incorporation into a lubricating oil as a VI improver. When shear stable ethylene-propylene copolymer is employed in the above-described reaction for the preparation of the succinimide derivative thereof the resulting reaction product of this invention is also shear stable.

In the preparation of the succinimide derivatives of a copolymer of ethylene and propylene in accordance with this invention, it has been noted that to obtain optimum dispersant characteristics when incorporated in a lubricating oil, the amount of the free radical initiator, e.g. benzoyl peroxide or dicumylperoxide, employed is desirably controlled such that the final polymer succinimide product of this invention contains in the range 0.150.4% by weight nitrogen to achieve optimum results when the resulting succinimide product is employed as a lubricating oil additive. By way of illustration, there are set forth in accompanying Table I test results with respect to the polymer succinimides prepared in accordance with this invention and having varying nitrogen content. The test results based on the Bench Sludge Test II (BSII) and the Resin Inhibition Test (RIT) indicate the minimum nitrogen content for optimum dispersancy in lubricating oil compositions: TABLE I V (wt.)N Vn (wt.) Polymer in Polymer in Blend BSII RIT 0.09 1.5 2.2 30 0.11 ,, 1.5 27.5 0.15 " 1.7 29 0.19 ,, 0.9 16 0.29 ,, 0.8 13 0.19 1.0 1.0 50 0.29 ,, 1.5 47 0.37 ,, 1.4 - RIT and BSII are minimized at 0.19--0.290/, in the polymer.

Engine testing of the polymer succinimides of this invention with respect to the dispersancy of the polymer succinimides in lubricating oil compositions has also indicated promising results. Engine testing of multigrade petroleum based automotive lubricating oils containing ethylenepropylene copolymer dimethylaminopropylsuccinimide (E-P-DMAPS) as the sole VI improver therein and dispersant gave excellent results. The motor oil compositions or blends in accordance with this invention tested, in addition to containing the polymer succinimides, also contained a pour depressant additive, an overbased calcium sulfonate detergent, a zinc dialkyldithiophosphate oxidation-corrosion inhibitor and an antifoam additive, with the balance of the blend or composition comprising solvent neutral oil.

The effectiveness of the reaction product of the invention was determined by formulating a motor oil composition and testing it in the MS-VB Engine Test. The MS-VB Engine Test was conducted in accordance with the detailed procedures found in ASTM Special Technical Bulletin No. 315D, "Engine Test Sequences for Evaluating Automatic Lubricants for API Service MS," published by the American Society for Testing Materials, 1916 Race Street, Philadelphia, Pa. 19103. The MS VB Engine Test is a low temperature, low speed cycling test designed to determine the oil's ability to prevent sludge drop-out and varnish formation in automobile gasoline engines equipped with closed positive crankcase ventilation. The test is cyclic in nature alternating between operating and "soak" periods. At test termination engine inspection according to standard procedures is conducted in the completely disassembled engine and the results of various lubricants compared accordingly.

The results of these tests are set forth in accompanying Table II.

TABLE II /" N in Polymer 0.2 0.3 /,, Polymer in Blend 1.4 0.9 Vis. Grade 10W90 10W--30 Sludge 48.5 47.7 Varnish 39.8 36.7 Piston Skirt Varnish 7.8 7.4 In the practices of this invention for the preparation of the polymer succinimide, various solvents have been disclosed as being useful in the initial reaction wherein the ethylene-propylene is reacted with maleic anhydride. In connection with this initial reaction it has been mentioned that it is desirable, if not necessary, to employ a large excess of maleic anhydride. An excess of the polyamine, 3-dimethylaminopropylamine, is also desirable, if not necessary, in the second stage reaction wherein the polymer succinic anhydride is converted to the corresponding polymer succinimide. Excess maleic anhydride and 3-dimethylaminopropylamine is necessary particularly when a saturated cycloaliphatic hydrocarbon, such as cyclohexane, is employed as the solvent due to significant side reactions between the cyclohexane solvent, maleic anhydride and the polyamine.

It has been determined, however, that the excess of both maleic anhydride and the polyamine, 3-dimethylaminopropylamine, can be significantly reduced when an inert solvent, such as an aromatic solvent, such as an aromatic hydrocarbon, e.g.

benzene, or chlorobenzene, is employed as solvent instead of a saturated cycloaliphatic hydrocarbon solvent, such as cyclohexane. Indeed, by employing an inert solvent, such as chlorobenzene or benzene, the amount of 3-dimethylaminopropylamine employed in the reaction for the preparation of the polymer succinimide can be substantially reduced, such as to an amount about l0V greater than the stoichiometric amount required for complete reaction with the intermediate succinic anhydride. This reduction in the amount of excess amine required results in the elimination of the amine stripping step with consequent lower processing and manufacture costs for the produced additive, the polymer succinimide. Also, the final product, the polymer succinimide, contains a lower amount of non-polymer nitrogen-containing or nitrogenous impurities. When the polymer succinimide is prepared employing cyclohexane as the solvent there is present in the resulting product appreciable or substantial quantities of reaction products derived from side reactions involving the solvent cyclohexane, maleic anhydride and dimethylaminopropylamine. The resulting side reaction products, when present in the final product, tend to cause excessive corrosion in the lubricating oil blends containing the product polymer succinimide as an additive, based on engine tests, such as the CLR L-38 bearing corrosion test.

Illustrative of the advantages of the practices of this invention there is set forth in accompanying Table III results of tests showing the reduction in amounts of maleic anhydride and 3-dimethylaminopropylamine employed in the presently preferred practices of this invention when an inert solvent, such as an inert aromatic solvent, e.g. benzene or chlorobenzene, is employed as compared with a reactive solvent, such as cyclohexane.

TABLE III Process Solvents Step Cyclohexane Chlorobenzene Maleic anhydride 8 g/100 g polymer 2.7 g/100 g polymer charge Dicumylperoxide 0.3 g/100 g polymer 0.43 g/100 g polymer charge 3-Dimethylamino- 8 g/100 g polymer 1.2 g/100 g polymer propylamine charge Final amine Excess amine stripped No stripping required stripping at 215"C/20 mm Hg after reaction with amine The following is an example of the practices of this invention.

Example 400 grams of ethylenepropylene copolymer (molecular weight range useful as a lube oil improver) solution containing 31 wit.% copolymer in hexane solution obtained from Copolymer Rubber and Chemical Corp. and 550 grams of chlorobenzene were combined. 330 grams of solvent were removed by distillation from the resulting solution. There resulted a solution containing 20 wt.% ethylenepropylene copolymer in chlorobenzene. Upon cooling to about 1300C., 3.35 grams of maleic anhydride and 0.53 gram dicumylperoxide were added to the solution.

The resulting mixture was heated and maintained at 1300C. for 6 hours. Infrared examination of a sample of the polymer separated by precipitation in boiling acetone indicated that the resulting polymer contained a proportion of anhydride groups such that, upon conversion to the corresponding succinimide, the neat polymer would contain 0.30V0 nitrogen. 1116 grams-of a high boiling point inert, neutral diluent hydrocarbon oil were added to the resulting solution and the chlorobenzene solvent and excess unreacted maleic anhydride were removed by stripping to a temperature of 180"C. at an absolute pressure of 0.08 mm Hg.

Thereupon 0.605 gram of 3-dimethyl-aminopropylamine was added with stirring to 500 grams of the resulting oil solution at a temperature of 125"C. The resulting stirred reaction admixture was maintained at 1250C. for 2 hours. The resulting produced polymer succinimide product analyzed .033% nitrogen, the same as the theoretical nitrogen content based on the amount of amine added. The polymer succinimide product was subjected to comparative automotive engine oil evaluation tests with a polymer succinimide prepared employing cyclohexane as the solvent instead of an inert aromatic solvent, such as benzene. The results of these tests are set forth in accompanying Table IV. The test data presented therein indicate that both products are equivalent with regard to oil solution properties, shear stability and dispersancy.

TABLE IV Chlorobenzene Cyclohexane Test Data' Solvent Product Solvent Product Orig. Vis., 100OF., SUS 426 397 210eF., SUS 69.0 68.6 Fuel Injector Shear Stability Test* Initial Vis., 210OF., SUS 65.2 63.3 Axis., 210OF., SUS (after 20 passes) 3.8 5.3 ( Thickening Power Loss, 210OF2 14 20 Pour Pt., "F. -45 -45 CCS "F., c.p. 1580 1600 Bench Sludge I 0.4 0.4 II 0.4 0.9 'Tested at 1.5 wt.% (neat polymer basis) in above-described diluent oil.

2The 210OF. viscosity of the base oil (diluent oil) was assumed to be 42.3 SUS for this calculation.

*This test is disclosed in Paper 57A of the SAE Transactions for June 1958, and in U.S. Patent No. 3522180.

The polymer succinimide was also prepared employing benzene as the inert aromatic solvent, using also dicumylperoxide as the radical initiator for the addition of the ethylene-propylene copolymer to the maleic anhydride. The reaction was carried out at a temperature of 130--132"C. under autogeneous pressure and the reactant ratios were similar to those set forth hereinabove with respect to the Example wherein chlorobenzene was employed as the solvent. It was observed that the resulting produced polymer succinimide exhibited oil solution properties, shear stability and dispersancy at least equivalent to the polymer succinimide prepared with the use of chlorobenzene as the aromatic solvent.

Desirably, the ethylene-propylene copolymer employed in the preparation of the polymer succinimides derived therefrom in accordance with the practices of this invention is suitable per se as an additive to petroleum based lubricating oils, such as VI improvers therefor. Suitable such ethylene-propylene copolymers are known and have a molecular weight greater than 5000, such as a molecular weight in the range 5,00050,000 and higher.

As indicated hereinabove, however, ethylene-propylene copolymers are preferred with a molecular make-up such that the ethylene-propylene copolymers contain in the range 1090 mol% ethylene and 90-10 mol% propylene, preferably in the range 3070 mol% and 7030 molt/, propylene.

An amorphous ethylene-propylene copolymer which serves as a viscosity index improvement additive in lubricating oils and which is particularly useful in accordance with the practices of this invention may be prepared as described in U.S. Patent 3,522,180. Therein it is disclosed that the copolymer is prepared in a hydrogen-moderated reaction at moderate temperatures and pressures in the presence of a solvent soluble Ziegler-Natta catalyst. Gaseous mixtures of propylene and ethylene together with hydrogen are introduced into a reactor containing a solvent which does not deactivate the catalyst, such as carbon tetrachloride, hexane, n-heptane, benzene or cyclohexane. Reaction temperatures in the range -40"F. to 250OF. and a pressure in the range 0300 psig may be satisfactorily employed. The two component Ziegler-Natta catalyst employed comprises as the first component a hydrocarbyl vanadate, a hydrocarboxy vanadyl halide or a vanadyltrihalide and as the second component an alkyl aluminum halide. Preferred catalyst systems include tri-n-butyl orthovanadate as the first component and ethyl aluminum dichloride, diethylaluminum chloride or ethyl aluminum sesquichloride as the second component.

The above-described Ziegler-Natta catalyst promoted hydrogen moderated polymerization reaction is used to produce ethylene-propylene copolymers having an amorphous structure, by infrared analysis, a propylene content of 20 to 70 mol percent, a number average molecular weight between 10,000 and 100,000 and a narrow molecular weight distribution, measured by gel permeation chromotography (GPC), of less than 5. Not only do these copolymers increase the viscosity index of lubricating when added thereto but they exhibit a substantially high resistance to the high shearing forces experienced in lubricating service, which shearing forces often mechanically degrade a long chain polymer.

As indicated hereinabove, the reaction between the ethylene-propylene copolymer, in the presence of a solvent and in the presence of maleic anhydride and a free radical initiator is preferably carried out at a temperature in the range 80--130"C. Higher or lower temperatures, however, may be employed, if desired.

Moreover, free radical initiators other than benzoyl peroxide and dicumylperoxide are also usefully employed. Similarly, the reaction of the polyamine with the resulting produced succinic anhydride may also be carried out at a suitable elevated temperature, such as 80--130"F., as desired. These reactions are carried out to completion. The high boiling point, substantially inert or neutral diluent oil employed in the reaction particularly to aid in stripping the aromatic solvent, such as chlorobenzene, and any excess maleic anhydride or any remaining polyamine from the reaction mixture, is advantageously a petroleum based oil of lubricating oil quality so that the desired product, the polymer succinimide, contained therein in the resulting reaction product can be readily incorporated as an additive in lubricating oils.

As indicated and demonstrated inert solvents, preferably inert aromatic solvents, are preferred in the preparation of the polymer succinimides.

Cyclohexanes and other cycloaliphatic solvents, e.g. cyclopentane and methylcyclohexane are too reactive. The relatively inert solvents are preferred, such as the halogenated hydrocarbons, e.g. halogenated aromatic hydrocarbons, such as chlorobenzene.

It is indicated hereinabove that the polymer succinimide in accordance with this invention is incorporated in minor amounts as an additive in petroleum based automotive lubricating oils, such as an amount in the range 0.05-10% by weight.

Amounts of the polymer succinimide in the range 0.52.5% by weight up to 34 /" by weight in lubricating oil compositions would be conventionally employed to impart shear stability, improved VI and dispersancy to the resulting oil compositions. Desirably, the polymer succinimide incorporated in lubricating oils as an additive therein would have a % by weight nitrogen content in the range from 0.02-0.05 to 0.1-1.0, preferably in the range 0.2-0.3.

To facilitate the introduction of the copolymer derivative as an additive into a final lubricating oil blend, the copolymer derivative as an additive may be prepared as a concentrate with a solvent, such as a light lubricating oil having a viscosity of between 75 and 300 SUS at 100OF., to form an additive concentrate containing in the range from 5 to 30%, preferably 1015% by weight of the copolymer derivative additive.

Claims (25)

WHAT WE CLAIM IS:

1. An N - (3 - dimethylaminopropyl) - substituted succinimide derivative of an ethylene-propylene copolymer said copolymer having a molecular weight of at least 5000.

2. A derivative as claimed in Claim 1 which contains from 0.02 to 1.0 /" by weight of nitrogen.

3. A derivative as claimed in Claim I or 2 which contains from 0.15 to 0.4 /" by weight of nitrogen.

4. A derivative as claimed in any preceding claim which contains from 0.2 to 0.3% by weight of nitrogen.

5. A derivative as claimed in any preceding claim, wherein the ethylenepropylene copolymer has a molecular weight of from 5000 to 50,000.

6. A derivative as claimed in any preceding claim, wherein the ethylenepropylene copolymer comprises 10 to 90 mol percent of ethylene and 90 to 10 mol percent of propylene.

7. A derivative as claimed in Claim 6, wherein the ethylene-propylene copolymer comprises 30 to 70 mol percent of ethylene and 70 to 30 mole percent of propylene.

8. A derivative as claimed in any of Claims 1 to 4, wherein the ethylenepropylene copolymer has an amorphous structure, a propylene content of 20 to 70 mol percent, a number average molecular weight between 10,000 and 100,000, and á molecular weight distribution, measured by gel permeation chromatography, of less than 5.

9. A method of preparing a succinic derivative according to any of the preceding claims which comprises reacting the ethylene-propylene copolymer with maleic anhydride in the presence of a free radical initiator and a solvent for the reaction mixture to produce a resulting alkyl succinic anhydride derivative of the ethylene-propylene copolymer, adding an inert liquid diluent, removing any unreacted maleic anhydride and said solvent and reacting the alkyl succinic anhydride derivative therein with dimethylaminopropylamine.

10. A method as claimed in Claim 9, wherein the solvent is an aromatic solvent.

11. A method as claimed in Claim 10, wherein the aromatic solvent is benzene, or chlorobenzene.

12. A method as claimed in any of Claims 9 to 11, wherein the copolymer and maleic anhydride are reacted at a temperature from 80 to 1300C.

13. A method as claimed in any of Claims 9 to 12, wherein the free radical initiator is benzoyl peroxide or dicumylperoxide.

14. A method as claimed in any of Claims 9 to 13, wherein the diluent is a high boiling point petroleum based oil.

15. A succinic derivative when prepared by a method as claimed in any of Claims 9 to 14.

16. A lubricating oil composition which comprises a lubricating oil and a minor amount of the succinimide derivative as claimed in any of Claims 1 to 18 and 15.

17. A lubricating oil composition as claimed in Claim 16, wherein said lubricating oil is a petroleum based lubricating oil.

18. A composition as claimed in Claim 16 or 17, wherein the minor amount is 0.05 to 10% by weight.

19. A composition as claimed in Claim 18, wherein the minor amount is 0.5 to 2.50% by weight.

20. An oil additive concentrate-which comprises a hydrocarbon solvent and 5 to 30% by weight, based on the solvent, of the succinimide derivative as claimed in any of Claims 1 to 8 and 15.

21. A concentrate as claimed in Claim 20, wherein the hydrocarbon solvent is of lubricating oil quality.

22. A concentrate as claimed in Claim 20 or 21, wherein the succinimide derivative is present in an amount from 10 to 15 /" by weight.

23. A succinimide derivative as claimed in Claim 1 and substantially as hereinbefore described with reference to the Example.

24. A method as claimed in Claim 9 and substantially as hereinbefore described.

25. A lubricating oil composition as claimed in Claim 16 and substantially as hereinbefore described.