PRODUCTION OF LUBRICATING OIL DISPERSANT

Abstract: A lubricating oil composition having improved dispersancy and viton seal compatibility. The dispersant is prepared by coupling partly acylated (preferably glycolated) succinimides with an aldehyde and a phenol. A preferred dispersant is a Mannich base phenol coupled glycamide bis-alkenyl succinimide.

Description: The present invention relates to a method for producing dispersants for a lubricating oil-composition. Internal combustion engines operate under a wide range of temperatures including low temperature stop-and-go service as well as high temperature conditions produced by continuous high speed driving. Stop-and-go driving, particularly during cold, damp weather conditions, leads to the formation of a sludge in the crankcase and in the oil passages of a gasoline or a diesel engine. This sludge seriously limits the ability of the crankcase oil to effectively lubricate the engine. In addition, the sludge with its entrapped water tends to contribute to rust formation in the engine. These problems tend to be aggravated by the manufacturer's lubrication service recommendations which specify extended oil drain intervals. It is known to employ nitrogen containing dispersants and/or detergents in the formulation of crankcase lubricating oil compositions. Many of the known dispersant/detergent compounds are based on the reaction of an alkenylsuccinic acid or anhydride with an amine or polyamine to produce an alkylsuccinimide or an alkenylsuccinamic acid as determined by selected conditions of reaction. It is also known to chlorinate alkenylsuccinic acid or anhydride prior to the reaction with an amine or polyamine in order to produce a reaction product in which a portion of the amine or polymaine is attached directly to the alkenyl radical of the alkenylsuccinic acid or anhydride. The thrust of many of these processes is to produce a product having a relatively high level of nitrogen in order to provide improved dispersancy in a crankcase lubricating oil composition. Four cylinder internal combustion engines must operate at relatively higher engine speeds or RPM's than 6- and 8-cylinder engines in order to produce the required torque output and it has become increasingly difficult to provide a satisfactory dispersant lubricating oil composition for such four cylinder engines. Another problem facing the lubricant manufacturer is that of seal deterioration in the engine. All internal combustion engines use elastomer seals, such as Viton seals, in their assembly. "Viton" is a commercial designation for a synthetic rubber derived from vinylidene fluoride and hexafluoropropylene. Over time, these seals are susceptible to serious deterioration caused by the lubricating oil composition. A lubricating oil composition that degrades the elastomer seals in an engine is unacceptable to engine manufacturers and has limited value. US-A-3 172 892 and 4 048 080 disclose alkenylsuccinimides formed from the reaction of an alkenylsuccinic anhydride and an alkylene polyamine and their use as dispersants in a lubricating oil composition. US-A-2 568 876 discloses reaction products prepared by reacting a monocarboxylic acid with a polyalkylene polyamine followed by a reaction of the intermediate product with an alkenyl succinic anhydride. US-A-3 216 936 discloses a process for preparing an aliphatic amine lubricant additive which involves reacting an alkylene amine, a polymer substituted succinic acid and an aliphatic monocarboxylic acid. US-A-3 131 150 discloses lubricating oil compositions containing dispersant-detergent mono- and di-alkyl-succinimides or bis(alkenylsucinimides). NL-A-7 509 289 discloses the reaction product of an alkenylsuccinic anhydride and an aminoalcohol, namely a tris(hydroxymethyl)-aminomethane. US-A-4 579 674 discloses a hydrocarbyl-substituted succinimide dispersant having a secondary hydroxy-substituted diamine or polyamine segment and a lubricating oil composition containing same. US-A-4 338 205 discloses alkenyl succinimide and borated alkenyl succinimide dispersants for a lubricating oil with impaired diesel dispersancy in which the dispersant is treated with an oil-soluble strong acid. EP-A-0 119 675 discloses lubricating oil additives obtained by acylating alkenyl succinimides with hydroxycarboxylic acid acylating agents. FR-A-1 559 643 discloses lubricating oil additives obtained by Mannich condensation of a polyalkylene polyamine with phenol and formaldehyde, followed by conversion of the product into an imide by reaction with an alkenyl succinic anhydride. The present invention provides a novel method for producing an additive which improves the dispersancy and viton seal compatibility of a lubricating oil. The present invention therefore provides a method for preparing a dispersant for a lubricating oil composition said dispersant being adapted to constitute a minor proportion of said composition, which method comprises: a) reacting a polyamine having the formula given below with an alkyenyl succinic acid anhydride to form a bis-alkenyl succinimide; b) acylating said bis-alkenyl succinimide to form a partially acylated bis-alkenyl succinimide; c) adding an excess of an aldehyde to said partially acylated bis-alkenyl succinimide to form a Mannich base of the acylated bis-ackenyl succinimide; d) adding a phenol to said Mannich base, thereby forming a Mannich phenol coupled acylamide bis-alkenyl succinimide; and e) recovering said Mannich phenol coupled acylamide bis-alkenyl succinimide. The polyamine compositions employed in practice of the process of this invention are primary amines or secondary amines having the formula: In this formula 'a' is 1 to 8 preferably 1 or 3 to 6, and most preferably about 5; and n is 0 or 1. In the above compound, R' is hydrogen or a hydrocarbyl group selected from alkyl, aralkyl, cycloalkyl, aryl, alkaryl, alkenyl, and alkynyl including such radicals when inertly substituted. When R' is alkyl, it may typically be methyl, ethyl, n-propyl, iso-propyl, n-butyl, i-butyl, sec-butyl, amyl, octyl, decyloroctadecyl. When R' is aralkyl, it may typically be benzyl or beta-phenylethyl. When R' is cycloalkyl, it may typically be cyclohexyl, cycloheptyl, cyclooctyl, 2-methylcyclo-heptyl, 3-butylcyclohexyl or 3-methylcyclohexyl. When R' is aryl, it may typically be phenyl or naphthyl. When R' is alkaryl, it may typically be tolyl or xylyl. When R' is alkenyl, it may typically be vinyl, allyl or 1-butenyl. When R' is alkynyl, it may typically be ethynyl, propynyl or butynyl. R' may be inertly substituted i.e. it may bear a non-reactive subsitutent such as alkyl, aryl, cycloalkyl, ether, halogen or nitro. Typically inertly substituted R' groups may include 3-chloropropyl, 2-ethoxyethyl, carboethoxymethyl, 4-methyl, cyclohexyl, p-chlorophenyl, p-chlorobenzyl or 3-chloro-5-methylphenyl. The preferred R' groups may be hydrogen or lower alkyl, i.e. C₁-C₁₀ alkyl, groups including eg methyl, ethyl, n-propyl, i-propyl, butyls, amyls, hexyls, octyls or decyls. R' may preferably be hydrogen. R" is a hydrocarbylene group selected from the same group as R' subject to the fact that R" is divalent and contains one less hydrogen. Preferably R' is hydrogen and R" is -CH₂CH₂. Typical amines which may be employed may include those listed below in Table I. propylenediamine (PDA) diethylenetriamine (DETA) triethylenetetriamine (TETA) tetraethylenepentamine (TEPA) pentaethylenehexamine (PEHA) The preferred amine may be tetraethylenepentamine. The aldehyde which may be employed may include those preferably characterized by the formula R²CHO. In the above compound, R² may be hydrogen or a hydrocarbon group selected from alkyl, aralkyl, cycloalkyl, aryl, alkaryl, alkenyl, and alkynyl including such radicals when inertly substituted. When R² is alkyl, it may typically be methyl, ethyl, n-propyl, iso-propyl, n-butyl, i-butyl, sec-butyl, amyl, octyl, decyl or octadecyl. When R² is aralkyl, it may typically be benzyl or beta-phenylethyl. When R² is cycloalkyl, it may typically be cyclohexyl, cycloheptyl, cyclooctyl 2-methylcyclo-heptyl, 3-butylcyclohexyl or 3-methylcyclohexyl. When R² is aryl, it may typically be phenyl or naphthyl. When R² is alkaryl, it may typically be tolyl or xylyl. When R² is alkenyl, it may typically be vinyl, allyl or 1-butenyl. When R² is alkynyl, it may typically be ethynyl, propynyl or butynyl. R² may inertly substituted i.e. it may bear a non-reactive substituted such as alkyl, aryl, cycloalkyl, ether, halogen or nitro. Typically inertly substituted R groups may include 3-chloropropyl, 2-ethoxyethyl, carboethyoxymethyl, 4-methyl cyclohexyl, p-chlorophenyl, p-chlorbenzyl or 3-chloro-5-methylphenyl. The preferred R² groups may be lower alkyl, i.e. C₁-C₁₀ alkyl, groups including eg methyl, ethyl, n-propyl, i-propyl, butyls, amyls, hexyls, octyls or decyls. R² may preferably be hydrogen. Typical aldehydes which may be employed may include those listed below in Table II. formaldehyde, ethanal, propanal, butanal. The preferred aldehyde may be formaldehyde employed as its polymer-paraformaldehyde. The phenols which may be employed in practice of the process of this invention may preferably be characterized by the formula HR³OH. It is a feature of these phenols that they contain an active hydrogen which will be the site for substitution. Poly-phenols (eg compounds containing more than one hydroxy group in the molecule whether on the same ring or not) may be employed. The rings on which the hydroxy groups are sited may bear inert substitents. However, at least two positions, e.g., ortho- and para-, to a phenol hydroxy group, must be occupied by an active hydrogen as this is the point of reaction with the iminium salt, R³ may be an arylene group typified by -C₆H₄-, -C₆H₃(CH₃)-, or -C₆H₃(C₂H₅)-. Typical phenols which may be employed may include those listed below in Table III. Phenol, Bisphenol A, Resorcinol, Mono-nonyl phenol, Beta-naphthol. The preferred phenols may be phenol or mono-nonyl phenol. In practice of the process of this invention, the reagents are step wise reacted with a succinic acid anhydride bearing a polyolefin substituent containing residual unsaturation in a "one pot reaction". The succinic acid anhydride may be characterized by the following formula In the above formula, R may be a residue (containing residual unsaturation) from a polyolefin which was reacted with maleic acid anhydride to form the alkenyl succinic acid anhydride. R may have a molecular weight M n ranging from 500 to 2000, preferably 1000 to 1300, and more preferably about 1300. The Mannich phenol coupled acylamide bis-alkenyl succinimide is prepared in one embodiment by the following sequence of steps in a single flask preparation as shown below in Scheme I. The first step of the reaction sequence involves reacting a polyethyleneamine with an alkenyl succinic acid anhydride (ASAA), respectively, in a 1:2 molar ratio to form the bis-alkenyl succinimide (A) intermediate. To this intermediate (A) is added enough glycolic acid to acylate all of the free basic amines except for one or one equivalent amine to form the partially glycolated bis-alkenyl succinimide (B). To this succinimide (B) is added an excess of paraformaldehyde to form the Mannich base of the glycolated bis-alkenyl succinimide (C). Immediately after the addition of formaldehyde (3 min) is added one half of an equivalent of phenol relative to the polyethylenediamine, or any other phenolic compound capable of reacting therewith to give the derived product of Mannich phenol coupled glycamide bis-alkenyl succinimide (D). The product so obtained may be a 50-80, say 50 wt.% solution of the desired additive in inert diluent; and preferably it is used in this form. The preferred acylating agents which are carboxylic acids may be glycolic acid; oxalic acid; lactic acid; 2-hydroxymethyl propionic acid, or 2,2-bis(hydroxymethyl) propionic acid. The most preferred is glycolic acid. Acylation may be effected preferably by addition of the acylating agent (e.g., glycolic acid or oxalic acid) to the reaction product of the polyethyleneamine and the succinic acid anhydride. Acylation is preferably effected by adding the acylating agent (typically oxalic acid or glycolic acid) in an amount of 0.5 to 3.0 equivalents per mole of active amine employed. For example, when tetraethylenepentamine (TEPA) is employed, there are 1.7 equivalents of glycolic acid added. Similarly, when triethylenetetramine (TETA) is used, about 0.7 equivalent of glycolic acid is added; and when pentaethylenehexamine (PEHA) is employed, about 2.7 equivalents of glycolic acid are added to the reaction. During acylation, the carboxyl group of the acylating agent bonds to a nitrogen atom to form an amide. Acylation is carried out at 100°C - 180°C, say 160°C for 2 - 24 hours, say 8 hours preferably in the presence of an excess of inert diluent-solvent. The partially acylated product may in one of its embodiments be represented by the formula wherein R is polyisobutylene. The invention will now be described by way of illustration only in the following Examples. In order to illustrate the effectiveness of the present compounds, i.e., coupled glycolated succinimides, as dispersants with viton seal compatibility, there are several tests to which the present succinimides have been subjected. These tests include the Bench VC and VD Tests, the Bench Sequence VD Test, the Caterpillar I-G2 Engine Test, and the Daimler - Benz Viton Compatibility Test. These tests are described below in more detail as well as the results of the various tests are provided below in Tables IV, V, VI, and VII. EXAMPLE 1 THE BENCH VC TEST (BVCT) This test is conducted by heating the test oil mixed with a synthetic hydrocarbon blowby and a diluting oil at a fixed temperature for a fixed time period. After heating, the turbidity of the resulting mixture is measured. A low percentage turbidity (0 to 10) is indicative of good dispersancy while a high value (20 to 100) is indicative of an oil's increasingly poor dispersancy. The results obtained with the known and present dispersants are set forth in Table IV below at 6 and 4 percent by weight concentration respectivley, in an SAE 10W-40 fully formulated motor oil. EXAMPLE II THE BENCH VD TEST (BVDT) In the Bench VD Test, (BVDT), oil samples are artificially degraded by bubbling air for six hours through a mixture of test oil and synthetic blowby at 143°C (290°F). Every hour, synthetic blowby is added and at the 5th and 6th hour of the test, samples are removed and diluted with SNO-7/20 diluent oil and their turbidity measured. Low turbidity in the BVDT indicates good lubricant dispersancy as related to the Sequence VD Test. The Sequence VD engine correlation work predicts that SF (i.e. satisfactory) quality lubricants should read 60 or less in the BVDT (turbidity units); oils 70 or greater would be predicted to do significantly poorer in the Sequence VD Test. Reference standard: The reference oil standard used in this test has had an average Sequence VD deposit rating of 6.81 = Average varnish, 9.56 = Average sludge. In the BVDT the 6 hour turbidity should be 55+/-12. The reference oil is included in each BVDT run. The resultant BVDT runs are provided below in Table IV. EXAMPLE III SEQUENCE VD TEST Various dispersants including known dispersants and the present dispersants were tested by the Sequence VD gasoline engine test in fully formulated oil motor at about 5.7 wt.% and gave the results shown below in Table V. The Sequence VD test evaluates the performance of engine oils in terms of the protection provided against sludge and varnish deposits as well as valve train wear. The test was carried out with a Ford 2.3 litre 4 cylinder gasoline engine using cyclic low and mid range engine operating temperatures and a high rate of blowby. EXAMPLE IV THE CATERPILLAR 1-G2 TEST The diesel engine performance of Example II, as measured by the Caterpillar 1-G2 testing in SAE 30 fully formulated oil formulation using 0.055 wt.% nitrogen from the dispersant gave the results shown in Table VI. EXAMPLE V THE DAIMLER - BENZ VITON COMPATIBILITY TEST An important property of a lubricating oil additive and a blended lubricating oil composition containing additives is the compatibility of the oil composition with the rubber seals employed in the engine. Nitrogen-containing succinimide dispersants employed in crankcase lubricating oil compositions have the effect of seriously degrading the rubber seals in internal combustion engines. In particular, such dispersants are known to attack Viton AK-6 rubber seals which are commonly employed in internal combustion engines. This deterioration exhibits itself by sharply degrading the flexibility of the seals and in increasing their hardness. This is such a critical problem that the Daimler-Benz Corporation requires that all crankcase lubricating oils must pass a Viton Seal Compatibility Test before the oil compositon will be rated acceptable for engine crankcase service. The AK-6 Bend Test is described below and is designed to test the Viton seal compatibility for a crankcase lubricating oil composition containing a nitrogen-containing dispersant. The AK-6 Bend Test is conducted by soaking a sample of Viton AK-6 rubber at an elevated temperature in the oil being tested then determining the bending properties and hardness of the Viton rubber sample against a suitable sample. Specifically, a 38 by 9.5 mm slab of a Viton AK-6 rubber cut with the grain of the rubber is placed in a 30 ml wide-mouth bottle with 20 ml of the test oil. The bottle is sealed and the test sample placed in an oven at 149°C for 96 hours. The bottle is removed from the oven and the rubber specimen taken from the initial bottle and placed into a second bottle with a new charge of test oil. After 30 minutes in the new oil charge, the rubber specimen is removed from the second bottle and submitted to a Bend Test. This is done by bending the rubber specimen 180°. The degree of cracking is observed and reported as follows: no cracking (NC) surface cracking (SC) or cracking (C). If cracking is observed, the test is terminated on that particular sample. If no cracking has been observed, the rubber speciment is returned to the bottle containing the second oil charge and this bottle is returned to the oven maintained 149°C., the bottle is removed from the oven and the rubber specimens withdrawn and placed into another bottle containing a fresh oil charge for 30 minutes, following which the bend test is repeated. If the rubber specimen continues to pass the bend test, the test is continued for 2 more heat-soak cycles of 96 hours and 72 hours respectively, each heat-soak cycle being followed by the bend test for total test time of 336 hours from the time the specimens were initially put into the oven. Following the above procedure, each rubber specimen is removed from its bottle, washed in naphtha to remove all oil traces and then air dried. The rubber specimens are then submitted to a hardness test according to the procedure described in ASTM D2240 following which a final bend test is made on all specimens. The results of the Daimler-Benz test runs are provided below in Table VII.

Claims: A method for preparing a dispersant for a lubricating oil composition which method comprises: a) reacting a polyamine having the formula wherein a is 1 to 8, n is 0 or 1, R' is hydrogen or a hydrocarbyl group selected from unsubstituted or inertly substituted alkyl, aralkyl, cycloalkyl, aryl, alkaryl, alkenyl and alkynyl, and R" is a hydrocarbylene group selected from unsubstituted or inertly substituted alkylene, aralkylene, cycloalkylene, arylene, alkarylene, alkenylene and alkynylene, with an alkenyl succinic acid anhydride to form a bis-alkenyl succinimide; b) acylating said bis-alkenyl succinimide to form a partially acylated bis-alkenyl succinimide; c) adding an excess of an aldehyde to said partially acylated bis-alkenyl succinimide to form a Mannich base of the acylated bis-alkenyl succinimide; d) adding a phenol to said Mannich base, thereby forming a Mannich phenol coupled acylamide bis-alkenyl succinimides, at least two positions on the phenol being occupied by active hydrogen. e) recovering said Mannich phenol coupled acylamide bis-alkenyl succinimide. A method according to Claim 1 characterised in that said amine is selected from propylene-diamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine and pentaethylenehexamine. A method according to Claim 1 or 2 characterised in that the acylating agent is selected from glycolic acid, oxalic acid, lactic acid, 2-hydroxymethyl propionic acid and 2,2-bis(hydroxymethyl) propionic acid. A method according to Claim 3 characterised in that the acylating agent is glycolic acid and the amine is polyethylene amine. A dispersant according to any one of claims 1 to 4 characterised in that from 0.5 to 3.0 equivalents of glycolic acid are added per mole of polyamine. A method according to any one of the preceding claims wherein the aldehyde is selected from formaldehyde, paraformaldehyde, ethanal, propanal and butanal. A method according to any one of the preceding claims characterised in that said phenol is selected from phenol, bisphenol A, resorcinol, mono-nonyl phenol, and beta-naphthol. A method according to any one of the preceding claims characterised in that the reaction product of step (a) has the formula: where R is polyisobutylene and x is 1 to 6. A dispersant for a lubricating oil composition of the formula: where R is a polyisobutylene and x is 1 to 6. A lubricating oil composition comprising a major proportion of a lubricating oil and a minor proportion of a dispersant prepared by a method according to any one of the preceding claims.

Inventors: NALESNIK, THEODORE EUGENE
Applicants: TEXACO DEVELOPMENT CORPORATION
Application year: 1986
Main classification: C10M159
IPC codes: C10M133, C10M159