US3114711A

US3114711A - Lubricant composition

Info

Publication number: US3114711A
Application number: US99730A
Authority: US
Inventors: Frank A Stuart; Goldschmidt Alfred
Original assignee: California Research LLC
Current assignee: California Research LLC
Priority date: 1961-03-31
Filing date: 1961-03-31
Publication date: 1963-12-17
Anticipated expiration: 1980-12-17

Description

United States Patent 3,114,711 LUERICANT C(PMPUSHION Frank A. Stuart, Urinda, and Aifred Gcidschmidt, El

Cerrito, Calif., assignnrs to California Research Corporation, San Francisco, Calif., a corporation of Delaware No Drawing. Fi led Mar. 31, 1961, Ser. No. 9,730 6 Claims. (til. 252-323) This invention is directed to a novel lubricant composition. More particularly the invention is concerned with a superior new lubricant composition containing an ashless polymeric detergent for use in internal combustion engines.

Lubricant compositions containing detergents are employed to prevent the deposit of solid materials on engine surfaces which come into contact with the lubricant composition. Such deposits of solid materials tend to interfere with proper circulation of the lubricant composition and also act as abrasives which cause excessive Wear of engine parts.

Unfortunately a major proportion of modern engine deposits is attributable to the additives commonly present in lubricant compositions. This is particularly the case with metal-containing additives, such as the metal salt detergents. Such metal-containing additives may form an ash when the lubricant is consumed in the engines and this ash will deposit out on engine surfaces coming in contact with the lubricant composition.

It has now been found that a superior new ashless detergent lubricant composition is provided in the cornposition comprising a major portion of an oil of lubricating viscosity and a minor portion sufiicient to enhance the detergent characteristics of the composition of an oil-soluble copolymer which comprises (A) at least one alkyl ester of an unsaturated monocarbcxylic acid of 3 to carbon atoms having from 4 to 30 carbon atoms in each alkyl group and (B) at least one ester of an unsaturated monocarboxylic acid of 3 to 5 carbon atoms and glycidol, the epoxy ring of the glycidyl portion of the polymer being reacted with a linear polyamide amine containing from about 5 to about 30 amido groups, the molar ratio of the glycidyl portion to linear polyamide chain being approximately 1:1, said copolymer containing from about 5 to about 40 monomer units of (A) "ice superior polymers for lubricant compositions and are ob tainable in commercial quantities.

The reaction products of glycidyl esters of unsaturated monocarboxylic acids of 3 to 5 carbon atoms and linear polyamide chains which are employed as the (B) monomers of the copolymers according to the present invention are produced by the reaction of the epoxy group of the glycidyl ester with the terminal amino group of the linear polyamide. This results in a monomeric material which may be conveniently illustrated by the following structural formula:

in which R and R are hydrogen or alkyl groups containing a total of not more than 3 carbon atoms and (A) is a linear polyamide chain containing from 4 to 29 recurring amide units.

The linear polyamide chains are derived by reaction of amines and acids, such as alkylene diamines and dibasic aliphatic and aromatic acids according to known procedures. For present purposes, two main types are preferred as indicated by the following general structural formula:

in which R is an alkylene group of 4 to 8 carbon atoms or an arylene group, such as o-phenylene, m-phenylene or p-xylylene, R is an alkylene group of 3 to 6 carbon atoms or an arylene group, R is an alkyl group of from 1 to 18, and preferably 4 to 12 carbon atoms, R is an al-kyl group containing 5 carbon atoms, and R is hydrogen or an alkyl group of from 1 to 4 carbon atoms. in the above formula the letter x is the integer indicating the recurring amide units sufiicient to make up the total as set out in the foregoing description.

Linear polyamides illustrative of the two general types mentioned above are those obtained by the reaction of hexamethylcne diamine and adipic acid. Such linear polyamides are illustrated by the following formula:

0 o H II for each monomer unit of (B) and having a total molecular weight of at least about 2,000.

The lubricant composition of this invention as described above is unusually eifective in the prevention of engine deposits. There is no metal component in the detergent copolymer of the composition and therefore it is substantially free of ash forming tendencies. This is a particular advantage over conventional detergent lubricant compositions which contain organic metal salts to prevent deposits.

The alkyl esters of the (A) monomers in the copolymers of the present invention are preferably alkyl esters of alpha, beta-unsaturated monocarboxylic acids of from 3 to 5 carbon atoms having alkyl groups of at least 4 carbon atoms and more preferably of from 8 to 30 carbon atoms. Representative acids of this type are the acrylic, methacrylic, crotonic, tiglic, angelic, hydrosorbic acids, and the like. Representative alkyl groups are butyl, hexyl, heptyl, octyl, decyl, dodecyl, tridecyl, octadecyl, eicoxyl, etc. Even more desirable are the alkyl esters of acrylic and methacrylic acids and mixtures thereof containing from 8 to 24 carbon atoms in the alkyl groups. They are found to provide highly Additional linear polyamides are those obtained by reacting alkyl amine, such as Z-ethylhexylamine with caprolactam. Such polyamides are illustrated by the formula:

In the above formula 2; indicates the number of recurring amide groups as already mentioned.

In preparing the polymers of the invention it is only necessary that conditions be chosen which insure polymerization and the formation of polymers having suitable oil solubility and polarity. The oil-solubilizing (A) monomers vary somewhat in their solubilizing characteristics. Thus in some cases it is entirely satisfactory to employ oil-solubilizing (A) ester monomers and glycidylpolyamide (B) monomers in ratios as low as 1:1 in order to obtain monomers which are soluble in oil. In other cases it is advantageous to raise the ratio of (A) to (B) to a much higher value, for example about :1 in order to obtain a polymer product having optimum oil solubility and polarity characteristics. As a general rule, however, polymers having excellent dispersant character- 3 istics, together with the required oil solubility (which should be at least 0.5 and is preferably as greater as 10% by Weight of the lubricant composition) can be prepared by employing oil-solubilizing (A) allryl ester monomers and polar acting glycidylpolyamide (B) monomers in ratios of from about 5:1 to about 40: 1.

The polymeric dispersants of this invention can be prepared by any one of several methods as known in the art. Briefly, there are three general methods with respect to the mode of attachments oi the polyamide chains to the polymeric backbone. As one method the glycidylpolyamide group may be incorporated in the polymer molecule by reacting a preformed polymer of alkyl ester and unsaturated monocarboxylic acid which would thus contain free carboxyl groups as reactive centers. This copolymer would then be reacted with glycidol following which the epoxy group of the glycidyl radical would be reacted with the terminal amino group of the polyamide chains. In the second method of attachment the glycidyl ester group is introduced as the monomer, prepared by (a) reacting glycidol with the unsaturated monocarboxylic acid of 3 to 5 carbon atoms to give the corresponding glycidyl ester which is then polymerized to give a glycldyl ester containing copolymer in which the epoxy groups of the glycidyl radical are suitable for reaction with the amino group terminated polyamide chain or (B) reacting the aforementioned glycidyl ester monomer with the amino terminated polyamide chain prior to polymerization with the oilsclubilizing (A) monomer and any optional (C) polar monomers of types other than the polyamide-glycidyl ester monomers. In a third method of attaching the polyamide chains the glycidol and the amino terminated polyamide chain may be reacted first to give a glycidol-amide reaction product which may be then attached by reaction with the carboxylic acid reacting centers as described in t e first mentioned method.

In each of the above-mentioned methods it is desirable to employ an excess of the amine terminated polyamide chains in order to avoid cross-linking and insure linear oil-soluble polymers. Excess amine terminated polyamide is readily removed by extraction, precipitation or any other conventional separation process. Such excesses are usually at least three to live-fold and range as high as to times the theoretical amount required to react one mole of the amino-terminated amide with one mole of the epoxy group of the glycidyl ester compound.

When the polymeric additive of this invention, or a suitable polymeric intermediate, is prepared by the reaction of monomeric components, such copolymers can be prepared by conventional bulk, solution or emulsion methods in the presence of additional polymerization initiators. Preferably, however, the copolymerization is effected in an inert organic solvent such as benzene, toluene, xylene or petroleum naphtha in the presence of a free radical-liberating type of initiator such as peroxy compound, for example, benzoyl peroxide, acetyl peroxide, tert. butyl hydroperoxide, di-tert. butyl peroxide, dibenzoyl peroxide, or di-tert. amyl peroxide, or an azo initiator such as 1,1'-azodicyclohexane, carbonitrile or alpha,alpha-azodiisobutyronitrile. The catalyst, or polymerization initiator, can be employed in an amount of from about 0.01 to 10%, with a preferred range being from 0.01 to 2%. If desired, the catalyst can be added in increments as the reaction proceeds. Likewise, additional portions of the solvent can also be added from time to time in order to maintain the solution in a homogeneous condition. The temperature of copolymerization varies from about 100 to 300 F. with the optimum temperature for any given preparation depending on the nature of the solvent, the concentration of monomers present in the solvent, the catalyst and the duration of the reaction. Much the same conditions are employed when the copolymerization is effected in bulk rather than in the presence of an inert solvent.

The additives of this invention have apparent molecu- 3. lar weights as determined by standard light scattering methods and viscosity measurements of at least 2,000 and preferably at least 50,000. For practical purposes molecular Weights of from 100,000 to 1,000,000 are most suitable from the standpoint of viscosity and other physical characteristics of the polymeric additives.

The following examples are illustrative of typical methods for preparing the glycidyl ester-amino polyamide polymeric type additives and intermediates according to the invention. 7

EXAMPLE I This example illustrates the preparation of an amino group terminated caprolactarn polyamide.

In a reaction vessel 113 g. of caprolactam is reacted with 42.7 g. of Z-ethylhexylamine. The reaction mixture is heated to 400 F. over a period of three hours and then maintained at 400 through 450 F. for fourteen hours. The reaction product is stripped of unreacted materials by distillation at 5 mm. of mercury pressure and a maximum temperature of about 420 F.

The reaction product was titrated and determined to have an equivalent weight of 760. This corresponds to an average of 5.5 caprolactam units per molecule in the polyamide chain.

EXAMPLE II In this example the above steps were repeated with g. of caprolactam and 20 g. of ethylhexylamine.

The reaction product has an equivalent weight of 1410. This corresponds to an average of 11.3 caprolactam units in the polyamide chain.

EXAMILE III This example illustrates the preparation of an intermediate copolymer in which the monomers are mixed dodecyl and octadecyl methacrylates and glycidyl methacrylate.

In a reaction vessel 750 g. of mixed alkyl methacrylates having 60% by Weight dodecyl and 40% by Weight octadecyl alkyl groups, 14.2 g. of glycidyl methacrylate and 510 g. of benzene are heated to reflux in an atmosphere of nitrogen. The refluxing materials are polymerized over a period of seven hours by the addition of a 2% solution of bis-azoisobutyronitrile in benzene as catalyst which is added at a rate of 3.8 ml. every fifteen minutes.

The polymeric reaction product is precipitated by the addition of a four-fold volume of acetone. A determination of the oxirane oxygen in the glycidyl portion indicates the presence of 1.85% by weight of glycidyl methacrylate in the copolymer. This indicates that the alkyl methacrylate and glycidyl methacrylate are present in a 25 :1 mole ratio.

EXAMPLE IV In this example the preparation of a copolymer of alkyl methacrylate and polyamide-glycidyl methacrylate is illustrated.

The mixture of g. of the alkyl methacrylate and glycidyl methacrylate copolymer of Example 111 in 300 ml. xylene and 60 g. of the caprolactam polyamide of Example 1 in 120 ml. of dimethylformamide is refluxed in a reaction Vessel equipped With refluxing apparatus. The refluxing of the mixture is carried out over a period of six hours. The reaction mixture is then precipitated three times by the addition of methanol.

The polymeric product obtained in this example upon analysis is 0.83% nitrogen which corresponds to 6.8% by Weight of caprolactam polyamide in the copolymer. This shows a ratio of alkyl methacrylate to polyamide of about 30:1.

EXAMPLE V This example illustrates variations in the type of alkyl methacrylate and polyamide-glycidyl methacrylate reaction products.

In a reaction vessel 75 g. of the 20:1 ratio copolymer of mixed dodecyl and octadecyl methacrylate and glycidyl methacrylate of the above-described type, 25 g. of caprolactam polyamide of Example 11, 100 ml. of dibutyl ether and 60 ml. of dimethylformamide are mixed. The mixture is refluxed for 26 hours. Following this the reaction mixture is precipitated three times with methanol.

The polymeric product upon analysis shows 0.65% nitrogen which is equivalent to 5.5% polyarnide. This corresponds to an actual molar ratio of alkyl methacrylate to polyamide-glycidyl methacrylate of 80: 1.

In general, excellent determent and antiwear properties can be imparted to lubricating oils by dissolving therein a quantity of from about 0.1 to by weight of the polymers of the type described above, although a preferred range is from about 1 to 5% by weight. On the other hand, since the polymers of this invention are unusually compatible with mineral and other lubricating oils in substantially all proportions, as much as 75% of the present polymeric additives can be dissolved in a suitable lubricating oil for the purpose of preparing a concentrate capable of dilution with lubricating oils and the like to prepare the final lubricant composition. Such concentrates, which may also contain other additives in desired amounts, and which normally contain at least 10% of the polymer, comprise a convenient method for handling the polymer and may be used as a compounding agent for lubricants in general.

The polymeric additives of this invention can be used with good efiect in the case of any one of a wide variety of oils of lubricating viscosity, or of blends of such oils. Thus, the base oil can be a refined Pennsylvania or other paraffin base oil, a refined naphthenic base oil, or a synthetic hydrocarbon or nonhydrocarbon oil of lubricating viscosity. As synthetic oils there can be mentioned alkylated waxes and similar alkylated hydrocarbons of relatively high molecular weight, hydrogenated polymers of hydrocarbons, and the condensation products of chlorinated alkyl hydrocarbons with aryl compounds. Other suitable oils are those which are obtained by polymerization of lower molecular weight alkylene oxides such as propylene and/or ethylene oxide. Still other synthetic oils are obtained by etherification and/or esterification of the hydroxy groups in alkylene oxide polymers such as, for example, the acetate of the 2-ethylhexanol-initiated polymer of propylene oxide. Other important classes of synthetic oils include the various esters as, for example, di-(2-ethylhexyl)sebacate, tricresyl phosphate and silicate esters. If desired, the oil can be a mixture of mineral and synthetic oils.

While satisfactory lubricant compositions can be obtained by adding to the base oil employed only one or more of the polymeric additives of the type described above, it also falls within the purview of this invention to provide lubricant compositions which contain not only such polymers, but also other additives such as pour point depressants, oiliness and extreme pressure agents, antioxidants, corrosion inhibiting agents, blooming agents, thickening agents, and/or compounds for enhancing the temperature-viscosity characteristics of the oil. The present invention also contemplates the addition to the lubricant composition (particularly when the amount of copolymer employed is relatively small) of auxiliary detergents and/ or anti-wear agents.

Illustrative lubricant compositions of the above type containing the copolymeric additives of the invention in combination with other agents may include, for example, from about 0.1 to 10% by weight of alkaline earth metal higher alkylphenate detergent and wear reducing agents such as calcium alkylphenates having an average of approximately 14 carbon atoms in the alkyl group as well as organic thiophosphate corrosion and high temperature oxidation inhibitors such as the reaction product of pinene and P 8 and the bivalent metal dithiophosphate and zinc tetradecylphenyl dithiophosphate in amounts of from about 0.1 to 10% by weight of the composition. Temperature-viscosity improving agents which may be employed in the compositions, usually in amounts of from about 1 to 10% by weight, include by way of example the homopolymers of alkyl methacrylates such as the dodecyl methacrylate polymers known to the trade as Acryloid 710 and Acryloid 7 63, products of Rohm & Haas Company, and high molecular weight butene polymers such as laratone ENJ 15P, a product of the Enjay Company.

The polymeric additives of the invention as described above are evaluated as detergents in lubricating oils in a number of tests. The results of the tests along with a description of the polymeric additives are set out in the following table.

In the tests as described below the base oil is a solvent refined wax free SAE 30 grade mineral lubricating oil. The polymeric additive is employed in the oil in an amount of 1.0% by weight of polymer based on total composition. The base oil contains 12 niM/kg. of the conventional Zinc dialkyl dithiophosphate having mixed butyl and hexyl alkyl groups as a corrosion in high temperature oxidation inhibitor.

In the determination of the piston varnish ratings of the oils, a given lubricating oil composition is tested as the crankcase lubricant in a 6-cylinder Chevrolet engine using a low grade gasoline especially prone to cause engine deposits, the conditions being those defined in the standard FL-2 test procedure as described in the June 21, 1948, report of the Coordinating Research Council. This procedure requires the maintenance of a jacket temperature of F. and a crankcase oil temperature of F. at 2500 rpm. and 45 brake horsepower of 40 hours, and therefore closely simulates the relatively cold engine conditions which are normally experienced in city driving. At the end of each test, the engine is dismantled and the amount of engine deposits on the piston determined and expressed as the piston varnish rating. This value is obtained by visually rating (on a scale of 0 to 10, with 10 representing the absence of any deposit) the amount of deposit on each piston skirt and averaging the individual ratings so obtained for the various pistons. Under the conditions of this test, a piston varnish rating of 3.5 is indicative of detergent performance, though preferably this rating should be 4 or above. In the case of the base oil alone without the addition of any additives, it is found that the piston varnish rating is approximately 3.0. On the other hand, as indicated by the data presented in the table below, when the base oil is compounded with the indicated amounts of a copolymer, greatly superior results are obtained.

Table I Example Piston No. Polymeric Dispersant Varnish Rating VI None 3.0 VII. Copolymer of Mixed Dodecyl Methacrylate and 3. 2

Oetadecyl methacrylate and Glycidyl Methacrylate in 4:6:1 ratio. VIII Alkyl Methacrylate and Polyamide-Glycidyl 4. 7

Methacrylate Copolymer of Example IV. IX -1 Alkyl Methacrylate and Polyamide-Glyeidyl 5. 4

Methacrylate Copolymer of Example V.

prises (A) at least one aikyl ester of an unsaturated monocarboxyiic acid of from 3 to 5 carbon atoms having from 4 to 30 carbon atoms in each alltyl group and (B) at least one ester of an unsaturated monocarboxylic acid of 3 to 5 carbon atoms and glycidol, the epoxy ring of the glycidyl portion of the polymer being reacted with a primary alkyl amine initiated caprolactam polyamide chain, said primary aikyi amine having from 1 to 12 carbon atoms in the alkyl group and said poiyamide chain containing from about 5 to about 3 recurring amide units, said oil-soluble copoiyrner having from about to about 40 monomer units of (A) for each monomer unit of (B) and a total molecular Weight of at least about 2000.

2. A lubricant composition comprising a major portion of mineral lu'oricatin oil, a minor oxidation and corrosion inhibiting proportion of Zinc dialkyldithiophosphate and from about 0.1 to by weight of an oil-soluble copolymer of (A) at least one alkyi methacrylate having 4 to carbon atoms in each alkyl group and (B) glycidyl methacrylate, the epoxy ring of said giycidyl portion of the polymer being reacted with Z-ethylhexylamine initiated caprolactam linear polyamide having from 5 to 30 recurring poiyamide units, said copolymer containing from about 5 to about monomer units of (A) for each monomer unit of (B) and having a molecular Weight of at 25 least 2000.

3. A iubricant composition comprising a major portion of mineral lubricating oil, a minor oxidation and corrosion inhibiting proportion of zinc dialkyldithiophosphate and from about 0.1 to 10% by Weight of an oil-soluble copolymer of (A) a mixture of dodecyl methacrylate and octadecyl methacrylate and (B) glycidyl methacrylate, the epoxy ring of said giycidyl portion of the poiymer being reacted With Z-ethyihexylarnine initiated caproiactam linear 5 to about 40 monomer units of (A) for each monomer unit of (B) and having a molecular weight of at least 2000.

4. A lubricant composition comprisin a major portion of mineral lubricating oil, a minor oxidation and corrosion inhibiting proportion of zinc dialkyldithiophosphate and from about 0.1 to 10% by Weight of an oil-soluble copolymer of (A) a mixture of dodecyl methacrylate and octadecyl methacrylate and (B) glycidyl methacrylate, the epoxy ring of said glycidyl portion of the polymer being reacted with 2-ethylhexylamine initiated caprolactam linear poiyamide having an average of about 5.5 recurring caproiactam units, said copolymer containing from about 5 to about 40 monomer units of (A) for each monomer unit of (B) and having a molecular Weight of at least 2000.

5. The lubricant composition of claim 3 in which the zinc dialkyldithiophosphate is zinc butyl hexyl dithiophosphate.

6. The lubricant composition of claim 4 in which the zinc dialkyldithiophosphate is zinc butyl hexyl dithiophosphate.

References Qited in the file of this patent UNITED STATES PATENTS Great Britain Nov. 9, 1960 OTHER REFERENCES BisWell et al.: A New Class of Polymeric Dispersants for Hydrocarbon Systems, ACS th National Meeting, Kansas City, Mo, March 23 to April 1, 1954. Pub. by

polyarnide having an average of about 11.3 recurring 35 E. I. du Pont de Nemours and Co., pages 3-4 pertinent.

caprolactarn units, said copolymer containing from about

Claims

1. A LUBRICANT COMPOSITION COMPRISING A MAJOR PORTION OF AN OIL OF LUBRICATING VISCOSITY AND A MINOR PORTION SUFFICIENT TO ENHA CE THE DETERGENT CHARACTERISTICS OF THE COMPOSITION, OF AN OIL-SOLUBLE COPOLYMER, WHICH COMPRISES (A) AT LEAST ONE ALKYL ESTER OF AN UNSATURATED MONOCARBOXYLIC ACID OF FROM 3 TO 5 CARBON ATOMS HAVING FROM 4 TO 30 CARBON ATOMS IN EACH ALKYL GROUP AND (B) AT LEAT ONE ESTER OF AN UNSATURATED MONOCARBOXYLIC ACID OF 3 TO 5 CARBON ATOMS AND GLYCIDOL, THE EPOXY RING OF THE GLYCIDYL PORTION OF THE POLYMER BEING REACTED WITH A PRIMARY ALKYL AMINE INITIATED CAPROLACTAM POLYAMIDE CHAIN, SAID PRIMARY ALKYL AMINE HAVING FROM 1 TO 12 CARBON ATOMS IN THE ALKYL GROUP AND SAID POLYAMIDE CHAIN CONTAINING FROM ABOUT 5 TO ABOUT 30 RECURRING AMIDE UNITS, SAID OIL-SOLUBLE COPOLYMER HAVING FROM ABOUT 5 TO ABOUT 40 MONOMER UNITS OF (A) FOR EACH MONOMER UNIT OF (B) AND A TOTAL MOLECULAR WEIGHT OF AT LELAST ABOUT 2000.

2. A LUBRICANT COMPOSITION COMPRISING A MAJOR PORTION OF MINERAL LUBRICATING OIL, A MINOR OXIDATION AND CORROSION INHIBITING PROPORTION OF ZINC DIALKYLDITHIOPHOSPHATE AND FROM ABOUT 0.1 TO 10% BY WEIGHT OF AN OIL-SOLUBLE COPOLYMER OF (A) AT LEAST ONE ALKYL METHACRYLATE HAVING 4 TO 30 CARBON ATOMS IN EACH ALKYL GROUP AND (B) GLYCIDYL METHACRYLATE, THE EPOXY RING OF SAID GLYCIDYL PORTION OF THE POLYMER BEING REACTED WITH 2-ETHYLHEXYLAMINE INITIATED CAPROLLACTAM LINEAR POLYAMIDE HAVING FROM 5 TO 30 REU CURRING POLYAMIDE UNITS, SAID COPOLYMER CONTAINING FROM ABOUT 5 TO ABOUT 40 MONOMER UNITS OF (A) FOR EACH MONOMER UNIT OF (B) AND HAVING A MOLECULAR WEIGHT OF AT LEAST 2000.