Novel Dispersant-Vi Improvers and Lubricating Oil Containing Same

This invention relates to the art of lubrication and more specifically to novel polymers endowed with the properties of dispersing sludge formed in lubricating oil during use and of improving the viscosity-index or temperature behavior of such oils.

There are many patents or processes for modifying polymeric lube oil additives and some of these relate to the grafting of monomers to polymers that are still being processed. Accordingly, this background disclosure is restricted to those which are believed most relevant.

In considering this invention, the applicants are aware of U.S. Pat. No. 3,785,980 which shows a lubricating oil additive which is the reaction product of a primary or secondary amine and a hydroperoxized atatic ethylene/propylene copolymer. This additive has a thickening power in the range of 50-150 SUS and has an infrared spectrum containing distinguishing absorbance peaks at specific frequencies.

Coassigned U.S. Pat. No. 4,123,661 is pertinent for its disclosure of dispersant viscosity index improvers consisting of the free radical catalyzed reaction product of di(lower)alkylamino-(lower)alkylamine with a hydroperoxidized ethylene/propylene copolymer or terpolymer.

U.S. Pat. No. 3,789,980 discloses an additive consisting of the reaction product of a primary or secondary amine, and a hydroperoxized ethylene/propylene copolymer. U.S. Pat. No. 3,687,849 describes lubricant additives consisting of graft polymers prepared from various polymerizable unsaturated monomers and an oxidized degraded interpolymer of ethylene and propylene. U.S. Pat. No. 3,879,304 reports a terpolymer having thereon a graft of a polymethacrylate. U.S. Pat. No. 3,076,791 discloses lubricating oil additives produced by the free radical reaction of an ethylene/propylene copolymer with an amine.

Oxidation of hydrocarbon polymers is disclosed in U.S. Pat. Nos. 2,811,514; 3,110,708, and 3,232,917. Hydroperoxidation of ethylene/propylene copolymers followed by subsequent reduction of the hydroperoxide sites to hydroxyl groups is disclosed in U.S. Pat. Nos. 3,388,067; 3,404,091 and 3,404,092. Reaction of hydrocarbon or oxygenated hydrocarbon polymers with nitrogen-containing compounds is disclosed in U.S. Pat. Nos. 3,293,326; 3,350,381 and 3,481,908.

As will be seen hereinafter none of these patents disclose, hint, or suggest applicants' novel, unique and unobvious process and composition.

The present invention, in its composition aspect, resides in a lubricating formulation comprising in major portion a lubricating oil and a lesser amount of an effective dispersing and viscosity improving additive obtained by oxidizing until the formation of a significant carbonyl IR band, in a suitable solvent, from 5 to 20 parts thereof of an ethylene/propylene copolymer or terpolymer the termonomer being thereof an unsaturated hydrocarbon and said polymer having a molecular weight of 5000 to 500,000 the oxidation optionally being carried out in the presence of a free radical initiator catalyst, by passing air through the reaction medium; and reacting the resulting polymer oxidate with a dispersant derived from polyisobutenyl monocarboxylic acids or dicarboxylic acid anhydrides reacted with polyamines, including polyethyleneamines and polypropyleneamines; derivatives of chlorinated polybutylenes and polyamine or derivatives of formaldelyde-polyamine adducts of polyisobutyl phenols.

In its product aspect, the present invention is a lube oil additive consisting of the oxidation product of an ethylene-propylene copolymer or terpolymer wherein the termonomer is an unsaturated hydrocarbon and the polymer has a molecular weight in the range of 5000 to 500,000 condensed with from 0.5 to 10 weight percent of a dispersant derived from polyisobutenyl monocarboxylic acids or dicarboxylic acid anhydrides reacted with polyamines including polyethyleneamines or polypropyleneamines; derivatives of chlorinated polybutylenes; or polyamines and derivatives of formaldehyde-polyamine adducts of polyisobutyl phenols.

The process of the invention comprises oxidizing in an inert atmosphere using air or oxygen at 140.degree. to 160.degree. C. with agitation a 5000 to 500,000 molecular weight ethylene/propylene copolymer or a terpolymer the termonomer thereof being an unsaturated hydrocarbon, in an inert solvent or in a mineral oil, until the formation of a substantial concentration of carbonyl bonds is observed and then reacting the thus formed polymer oxidate by heating with a dispersant derived from polyisobutenyl monocarboxylic acids or dicarboxylic anhydrides and amines; derivatives of chlorinated polybutylenes and polyamines; or derivatives of formaldehyde-polyamine adducts of polyisobutyl phenols.

The ethylene-propylene polymer reactant (EP) used herein is generally atactic and contains about 45-65 mole percent of ethylene and 55 to 35 mole percent of propylene and 0 to 5 percent of an unsaturated hydrocarbon such as a diene, cycloalkene or bicycloalkene. The copolymer or terpolymer preferentially will have a molecular weight of 5,000 to 500,000.

Examples of suitable nitrogeneous dispersants derived from polyalkenyl monocarboxylic acids and dicarboxylic anhydrides reacted with amines include polyisobutenyl succinimides, and products derived from chlorinated polybutanes and amines or formaldehyde-polyamine adducts of polybutenyl phenols.

A preferred class of dispersants is disclosed in coassigned U.S. Pat. No. 4,048,080 which is incorporated by reference in the present disclosure. These dispersants have the formula: ##STR1## where x ranges from 1 to 6 and R is an alkenyl radical having from about 64 to about 300 aliphatic carbon atoms in the chain. The preferred dispersant is one where R is polyisobutenyl having a molecular weight of about 1250 and x is 4.

The oxidation is carried out in a suitable inert solvent such as benzene, chlorobenzene, toluene or preferably in the lubricating oil whose properties are to be improved.

Any of the well-known organic peroxides, azo and diazo free radical initiators optionally may be used in the oxidation such as dicumylperoxide, t-butyl peroxide, azobisisobutyronitrile, benzoyl peroxide and t-butyl perbenzoate. The free radical initiator is employed in a proportion ranging from about 0.1 to 2.0 weight percent based on the weight of the hydrocarbon polymer.

The oxygen source may be oxygen, air, or other oxygen-containing gas supplied as an external source of oxygen to the oxidation reaction chamber. Preferably, a 50--50 mixture of air and nitrogen is used. The gas may be introduced in the chamber at any flow rate. Usually, the gas is provided at a rate sufficient to exchange all of the oxygen in the oxidation reaction chamber every few seconds. Means are provided for maintaining the chamber at an elevated temperature in the range of about 50.degree.-200.degree. C., usually about 70.degree.-180.degree. C. Means are also provided for agitating the mixture of ethylene/propylene copolymer, initiator, and solvent in order to provide optimum mixing of the components.

When infrared measurements indicate that an adequate carbonyl absorbtion band at 5.78 microns is formed, the nitrogenous dispersant and the oxidized polymer then are reacted by heating in the same solvent which was used for the oxidation. By "adequate absorption band" is meant a ratio of infrared CO/CH.sub.3 absorption bands (near 5.78 and 7.35 microns) of about 0.8 to 2.2. The oxidate/dispersant mixture is reacted at a temperature of 130.degree. to 140.degree. C. for about one hour followed by heating for about two hours at about 160.degree. C. Where the solvent used is other than an oil, the oil whose properties are to be improved is added at the end of the oxidation. The inert solvent then is distilled out at atmospheric pressure and the residual oil solution is heated to around 160.degree. C. for about 3 hours.

In the present reaction, the actual ratio of nitrogenous dispersant to polymer oxidate is not critical but molar ratios ranging from 0.5:1 to 3:1 of dispersant to polymer oxidate group are preferred.

The invention is further illustrated in nonlimiting fashion by the following examples:

A solution of EP copolymer (10% by weight) in benzene containing azobisisobutyronitrile (0.4% by weight) was heated to 70.degree.-75.degree. C. and with rapid stirring a stream of air (167 ml./min. per 1000 gm. solution) was passed through the mixture for 18 to 24 hours. At the end of that period, a solvent neutral oil having a specific gravity of 0.85, and a viscosity in SUS units at 100.degree. F. to 100 in the amount of about 3.3 g. per gram of polymer was added. The benzene was stripped off at atmospheric pressure and the residual oil solution heated to 160.degree. C. for 3 hours. The degree of polymer oxidation was thereupon measured by infrared spectroscopy.

The dispersant used as the reactant was the alkenylsuccinimide derived from tetraethylene pentamine and polyisobutenyl succinic anhydride having an average molecular weight of about 1400.

The dispersant was added in amounts sufficient to react with the polymer oxidate and the resulting blend was heated under a nitrogen atmosphere to 130.degree. C. for 2 hours, then 160.degree. C. for one hour. The final product may be filtered as necessary. Dispersancy tests on the products are shown in Tables I and II.

A solution of 30 grams ethylene-propylene copolymer (EP) in 170 grams of a solvent neutral oil having a sp.gr of 0.85, a viscosity 100% SUS of 123-133 was air oxidized for varied time periods at temperatures of 140.degree. to 160.degree. C. to form various products listed in Table III. After the formation of an adequate carbonyl band due to oxidation, as measured by the ratio of infrared absorption bands near 5.78 and 7.35 microns, the oxidation was ceased and the oxidates reacted with varying amounts of the above dispersant (1.2% N) for 2 hours at 130.degree. C. followed by one hour at 160.degree. C. to yield the products described in Table IV. The products of Table IV were then tested for dispersancy in typical motor oil formulations using the Bench VC (BVCT) Test.

A 600 gram quantity of an ethylene-propyleneethylidenenorbornene terpolymer, having a molecular weight of 76,000 was dissolved in 1998 grams of a Pale Oil. (sp.gr. 0.86, API gravity 32, vis SUS at 100.degree. F. of 145) and oxidized at 180.degree. C. with a 1/1 mixture of air and nitrogen for 3.5 hours at 1000 ml gas/minute. The mixture was then held at 160.degree. C. under nitrogen for one hour; cooled to 130.degree. C. and subsequently reacted with 861 grams (1.2% N) of the above dispersant for two hours at 130.degree. C. and one hour at 160.degree. C. The product was vacuum filtered through paper and contained (Calculated): 17.3% polymer and 0.299% nitrogenous dispersant.

The products of the invention were evaluated for effectiveness by various tests. Of these, the Bench VC Test (BVCT) is conducted by heating the test oil mixed with a synthetic hydrocarbon blowby and a diluent oil at a fixed temperature for a fixed time period. After heating, the turbidity of the resultant mixture is measured. A low percentage turbidity (0-10) is indicative of good dispersancy while high results (200-100) are indicative of increasingly poor dispersancy of the oil blends tested.

The Sequence VC Test (Seq. VC) is detailed in the ASTM Special Technical Publication under heating 310-F. The subject test is used to evaluate crankcase motor oils with respect to sludge and varnish deposits as well as their ability to keep the positive crankcase ventilation (PVC) valve clean and functioning properly. Ratings of 0 to 10 are given, a 10 representing absolutely clean and a 0 rating representing heavy sludge and varnish deposits.

The Test results appear in Tables I to IV following.

Table I illustrates an evaluation of representative samples of such reaction products of oxidized EP copolymers for Example I, made by oxidation in benzene, and dispersant using the Bench VC Test. This laboratory test correlates well with motor oil performance in the Seq. VC engine test.

In Table I, the first two products (A, B) are derived from a high molecular weight EP copolymer (mol. wt. of 80-100,000 containing ca. 35% propylene). As shown in the Table, the low BVCT values for blended oils containing the polymer-dispersants were excellent, illustrating the remarkable effectiveness of these materials compared to the standard dispersant when measured at equivalent dispersant nitrogen levels. Examples C and D show similar products derived from oxidized EP polymers of much lower molecular weight (ca. 40,000, 44% mole propylene). A blend of standard dispersant, not reacted with polymer, is included at the bottom of the table for comparison. About three times more of the standard dispersant was required for the same BVCT rating as with products A-D.

That the improved dispersancy which arises by reacting the oxidized polymer with the succinimide is the result of a chemical combination there between and not simply a blending effect, is proven by the data in Table II. Here, the dispersant and oxidized polymer either were mixed at 70.degree. C., heated at 130.degree. C. or at 160.degree. C. As can be seen, the best dispersancy (lower numbers) was given by product H formed at the highest temperature, a condition at which more complete chemical condensation of the amine function of the succinimide and the oxidized portions of the polymer will occur. The worst performance was that the product E which contained no dispersant.

Table III shows the results of Seq. VC engine tests on formulations containing oxidized EP polymer dispersant reaction products from Example I (Product I and from the method of Example III, Product J). In the first test, using Product I as the sole dispersant-VI improver, in a 10W-40 multigrade type formulation, a passing result meeting SE specification was obtained. In a second engine test, using a lesser amount of dispersant derived from a more highly oxidized polymer (Product J) in a single grade (30W) formulation, the sludge and overall varnish ratings were passing but the piston skirt varnish was marginally below that required for an SE motor oil. The result, however, did indicate the effectiveness of this type of dispersant.

Table IV illustrates laboratory dispersancy evaluation of blends (1) of reaction products of oxidized EP copolymer, made by oxidation in a lube oil base stock, and dispersant from Example II.

Table IV below shows the results of an evaluation of dispersant VI improvers from Example II by the Bench VC Test. Product K was made by oxidation at 140.degree. C. for 8 hours (infrared CO/CH.sub.3 ratio=1.08.sup.(a)) and reaction with 22 g of the same alkenylsuccinimide dispersant. Calc'd for product: 13.7% polymer content, 0.115%. N. Product L was made by oxidation at 140.degree. C. for 14 hours (infrared CO/CH.sub.3 ratio=0.9) and reaction with 34 g of the same dispersant. Calc'd for product: 12.7% polymer content and 0.18% N. Product M was made by oxidation at 150.degree. C. for 2 hours (infrared CO/CH.sub.3 ratio=2.08) and reaction with 60 g of the dispersant. Calc'd for product: 11.51% polymer content and 0.279% N.

Table V below shows the results of an evaluation of the dispersant VI improver from Example III with blends of the above in a premium type motor oil formulation containing no other VI improvers. The base oil stock for blending was a solvent neutral oil which had an API gravity of 31.5-33.5; a viscosity of SUS 123-122 and a pour point of 0.degree. F.

Thus while the invention has been illustrated mainly by reference to the performance of the reaction product of EP copolymer oxidates with a dispersant consisting of an alkenylsuccinimide derived from tetraethylene pentamine and polyisobutenyl succinic anhydride, equivalent results are obtained when the dispersant consists of products derived from chlorinated polybutanes and amines or formaldehyde polyamine adducts of polybutenyl phenols.