US3676346A - Lubricating oil compositions containing improved sludge inhibiting additives - Google Patents

Abstract

Mineral lubricating oil compositions are prepared containing sludge dispersing amounts of conventional ashless dispersants and, optionally, their sulfurized derivatives, and also containing sludge inhibiting or oxidation inhibiting amounts of sulfurized oil-soluble pour point depressant type organic compounds. The ashless dispersants used are the polyalkylene polyamine condensation products of alkenyl succinic acids or anhydrides or of alkenyl substituted lower fatty acids wherein the alkenyl radical is of C40 to C250 length used either alone or along with their sulfurized derivatives. The pour point depressants are those heretofore conventionally used but in their sulfurized form, such as sulfurized wave alkylated naphthalene, sulfurized polymeric long chain alkyl esters of acrylic or methacrylic acids.

Description

United States Patent LUBRICATING OIL COMPOSITIONS CONTAINING IMPROVED SLUDGE INHIBITING ADDITIVES Sliih-En Hu, Westfield, NJ.

Esso Research and Engineering Company Feb. 19, 1970 Int. Cl. ..Cl0m l/38 Field of Search ..2S2/47.5, 51.5, 45, 48.6, 406

References Cited UN lTED STATES PATENTS 11/1966 Le Suer ..2S2/5l.5 A

3/1968 Le Suer et a1... 6/1968 Ol-lalloran..... 7/1969 Le Suer et a1. 3/1970 Smith Rogers et al. Jones et al ..252/45 1 July 11, 1972 FOREIGN PATENTS OR APPLlCATIONS 952,151 3/1964 Great Britain OTHER PUBLICATIONS Kalichevsky et al. Petroleum Refining with Chemicals" (1956) pages 525- 534 Primary Examiner-Daniel E. Wyman Assistant Examiner-W. Cannon Attorney-Pearlman and Stahl and Ernest V. Haines ABSIRACT Mineral lubricating oil compositions are prepared containing sludge dispersing amounts of conventional ashless dispersants and, optionally, their sulfurized derivatives, and also contain ing sludge inhibiting or oxidation inhibiting amounts-of sulfurized oil-soluble pour point depressant type organic com pounds. The ashless dispersants used are the polyalkylene polyamine condensation products of alkenyl succinic acids or anhydrides or of alkenyl substituted lower fatty acids wherein the alkenyl radical is of C to C length used either alone or along with their sulfurized derivatives. The pour point depressants are those heretofore conventionally used but in their sulfurized form, such as sulfurized wave alkylated naphthalene, sulfurized polymeric long chain alkyl esters of acrylic or methacrylic acids.

7Claims, No Drawings LUBRICATING OIL COMPOSITIONS CONTAINING IMPROVED SLUDGE INHIBITING ADDITIVES The present invention relates to the use in mineral lubricating oil compositions of a combination of oil-soluble sulfurized pour point depressant-type compounds with the so-called ashless dispersants which are likewise oil-soluble and which have been used in lubricating oil compositions for several years. In addition, the additive admixtures may contain sulfurized ashless dispersants of the same or different ashless dispersants used.

Numerous addition agents have heretofore been prepared for use in mineral lubricating oils including the so-ca1led heavy duty oils which are employed in railroad diesel engines and gas engines. Prior researchers have been successful in finding various types of oil-soluble organic compounds which exhibit speciali zed and specific properties of a beneficial nature when they are incorporated into mineral lubricating oils. For many years now, organic compounds have been added in minor amounts to lubricating oils for the purpose of lowering their pour point, of improving their viscosity index, of affording increased resistance to oxidation, of imparting antiwear properties, of inhibiting sludge formation and of dispersing sludge when it is formed during use of the oils. The use of such additives at the present time enjoys widespread commercial acceptance. Good oxidation stability and good dispersing along with good detergency have become essential requirements for engine lubricating oils. This is particularly so in connection with lubricating oils used in so-called heavy duty engines such as gas engines and railroad diesel engines. Additionally the additives employed must necessarily be accepted from the standpoint of lack of wear or attack on the specialized types of bearings employed in internal combustion engines at the present time. Copper-lead containing bearings are usually susceptible to wear and corrosion and suitable compounded oils must exhibit low corrosion and low bearing wear with respect to such specialized bearings in order to be acceptable commercially.

In the past, it has been proposed to add sulfurized polyisobutylene to lubricating oils. See, for example, Cohen U.S. Pat. No. 2,312,750. Also, it has been proposed in the past to employ sulfurized ashless dispersants in lubricating oils, see British Pat. No. 1,101,040 and U.S. Pat. No. 3,390,086.

By incorporating elemental sulfur into oil-soluble pourpoint-depressant-type organic compounds, many of which have been conventionally used heretofore as pour point depressants, it is possible to impart, in addition to the pour point properties, (which are not materially sacrified) anti-oxidant properties as well, so that even in the case of lubricating oil compositions being subjected to extremely high temperatures during use the combined or dual properties are utilized. It has now been discovered that the tendency of formation of sludge and other deposits in lubricating oils is lessened or minimized by using, in combination in such lubricating oils, at least two additives, namely an ashless dispersant which tends to disperse sludge and to prevent its deposition in the engine and a sulfurized pour point depressant or a sulfurized compound closely akin to such depressants which has anti-oxidant properties and which imparts an initial and added resistance to sludge formation through oxidation inhibition. Such a combination of additives leads to an enhanced elimination of the tendency to form sludge by chemical reduction of the sludge precursors in addition to the usual dispersion of the sludge that is formed. It has been discovered, however, there is a synergistic enhancement of the desired properties in lubricating oils when these two types of materials are used together in a mineral lubricating oil composition.

Although it is not necessary that the pour point depressant types of compounds in and of. themselves possess pour point depressant properties when added to lubricating oils, the present invention finds its greatest utility when conventional pour point depressant compounds are subjected to a reaction with elemental sulfur, for it has been discovered that the pour point depressant properties of such compounds which have been conventionally employed in the past are not destroyed but in addition by the introduction of the elemental sulfur into a chemical bond with such compounds additional properties are imparted to these pour point depressants, namely antioxidant and sludge precursor destroying properties which tend to minimize and decrease the normal tendency of such oils to degradative oxidation and hence sludge formation. Other compounds may be employed, i.e. compounds other than those which in their unsulfurized form do, in fact, depress the pour point of such mineral lubricating oils. These compounds are referred to as pour point depressant type compounds because their chemical comfiguration is analogous to the chemical configuration of the compounds which do possess pour point depressant properties and they are homologues or analogues thereof which are oil-soluble. Both types of compounds, i.e. pour depressants and the closely related compounds not possessing pour point depressant properties, are intended to be included in the expression pour point depressant type compound or the expression pour point depressant type organic compound as used herein and in the claims.

The types or classes of compounds that may be treated with elemental sulfur or its chemical equivalent, i.e. sodium polysulfide, for example, are all oil-soluble and have generally number average molecular weights of between about 900 and about 20,000, preferably between about 1200 and about 10,000. They may be broadly defined in the following classes:

1. long chain C,,C alkylated-benzene, -phenols, naphthalene, -naphthols, i.e. paraffin-wax-alkylated naphthalene, wax alkylated phenol;

2. long chain (C -C alkylated C C alkyl substituted benzene, naphthalene, phenol, or naphthol compounds, i.e. paraffin-wax-alkylated cresols, wax-alkylated toluene, wax-alkylated alpha or beta methyl naphthalene, wax alkylated 1- methyl beta naphthol, etc.;

3. polymers of C C alkyl esters of monoolefinically unsaturated monocarboxylic acids, e.g. acrylic, methacrylic, or vinyl acetic acid esters of butyl, amyl, hexyl, decyl, lauryl, cetyl or stearyl alcohols; polylauryl acrylate, polymers of mixed C, C, (Lorol) alcohols esterified with acrylic acid or methacrylic acids;

4. polymers of C -C dialkyl or dialkenyl esters of alphabeta unsaturated dibasic carboxylic acids or anhydrides thereof, e.g. maleic or fumaric acid esterified with octyl alcohol or C oxo alcohols, di-Lorol fumarates, didodecyl maleate;

5. polymeric C -C acylated polystyrene, e.g. bchenyl polystyrene; acetyl wax alkylated polystyrene;

6. polyacryl amides, i.e. N-vinyl pyrrolidone or N-vinyl pyrrolidone copolymerized with C C fatty acids, polymeric N- octadecyl methacrylamide, N-octadecenyl polyethylacrylamides;

7. copolymers of vinyl esters of C C fatty acids, or C C alpha monoolefins, with monomers of (4) i.e. di C -C dialkyl esters of alpha beta unsaturated dicarboxylic acids or anhydrides; copolymers of di-Lorol (C |s) fumarate with vinyl acetate, copolymers of di C alkyl fumarate with isobutylene.

All of the above-mentioned classes of compounds are old compositions, most of which have heretofore been used in automotive and marine engines as additives in crankcase lubricants. Their sulfurized derivatives are the novel additives in such crankcase lubricants as described, supra. Various U.S. patents described the methods of preparation and the lubricating oil additive usage of these unsulfurized compounds, for example, group (1) and (2) compounds have been used for many years as pour point depressants as exemplified by the disclosures ofU.S. Pat. Nos. 1,815,022; 2,015,748; 2,087,682; 2,174,246 and 2,191,498; group (3) compounds by U.S. Pat. Nos. 2,100,993; 2,125,885 and 2,628,225; group (4) compounds by U.S. Pat. No. 2,618,602; group (5) compounds by U.S. Pat. Nos. 2,703,817 and 3,248,186; group (6) compounds by U.S. Pat. No. 2,387,501 and group (7) compounds by U.S. Patents Nos. 2,666,746; 2,721,877; 2,721,878;

2,694,685; 2,825,717 and Reissue 26,134, which disclosures are incorporated herein by reference. No real need is seen for duplicating the description of the usage of the unsulfurized pour point depressants in lubricating oils, herein, nor for duplicating, herein, their methods of production, since they are well known; they have become commercialized and widely marketed additives for their pour point depressant efiects and have now been so used for many years. The starting materials, i.e. the materials to be sulfurized in accordance with the present invention are old and widely available on the commercial market.

The pour point depressant type organic compounds are subjected to reaction with elemental sulfur in order to chemically combine the sulfur into the compound. The elemental sulfur or its chemical equivalent, for example, sodium polysulfide, is added in the required amounts and the reacting mixture is maintained at a temperature between about 100 and 260 C., preferably between about 120 and 250 C. for a period of time ranging between about 30 minutes and 40 hours, preferably for between about 4 and about 12 hours. The relative amount of elemental sulfur employed per mole of pour point dispersant type organic compounds used may vary considerably but is generally between about 2 and about 0.5 mole of sulfur, preferably between about 1 and about 0.5 mole of sulfur per mole of organic compound to be sulfurized. The final product will contain sulfur to the extent of between about 1.0 and about 10.0 wt. percent, preferably between about 1.5 and about 7.5 wt. percent sulfur. The sulfurization reaction is preferably carried out in the liquid phase. A particularly convenient liquid reaction medium has been found to be a mineral lubricating oil for the reason that the sulfurized product upon completion of the sulfurization reaction is present in the lubricating oil to the extent of some 50-80 wt. percent and so the entire reaction mixture once it has been purged of hydrogen sulfide by sweeping with nitrogen or other inert gas is suitable for use as an oil concentrate. A typical oil base that has been used as a carrier for the reaction is a solvent extracted neutral lubricating oil of 150 SUS at 100 F. To some extent this oil also is sulfurized but its small amount of sulfurization is not beneficial, per se. The ashless dispersant with or without the addition of sulfurized ashless dispersant may be added to this concentrate. When a lubricating oil concentrate of the sulfurized pour point type organic compound is finally produced or is compounded, the oil-soluble ashless dispersant as well as the sulfurized ashless dispersant, if used, may be added as such or it may be added in the form of a similar solvent neutral 150 SUS base lubricating oil concentrate of from 50-80 wt. percent active ingredient concentration. The amount of the sulfurized pour depressant type organic compound, the amount of the oil-soluble ashless dispersant and the amount of the sulfurized ashless dispersant finally employed in a lubricating oil composition may vary considerably. Suffice it to say that these concentrations are sufficiently large to impart sludge inhibiting, dispersing and/or antioxidant properties to the lubricating oil. The amount involved so far as the upper limit is concerned, is relatively immaterial so long as the minimum effective amount is employed. For practical purposes, all three types of additives are each employed (when employed) in an amount ranging from 0.05 to 10.0 wt. percent based on the total oil composition, preferably between about 0.1 and about 5.0 wt. percent on the same basis.

The oil-soluble ashless dispersants employed are those conventionally employed in lubricating oil compositions. In general, they are formed by a condensation of at least one polyalkylene polyamine with at least one of the following: alkenyl succinic acid, alkenyl succinic anhydride, alkenyl substituted lower fatty acid, wherein the alkenyl group contains from about 40 to about 250 carbon atoms per alkenyl radical. Also, the sulfurized derivatives of such oil-soluble ashless dispersant may be used as before stated and as heretofore referred to as being disclosed in British Pat. No. 1,101,040 and U.S. Pat. No. 3,390,086. These patents not only disclose the production of the sulfurized ashless dispersants of the type herein contemplated for use but also disclose several methods of preparing the unsulfurized ashless dispersants of the polyalkylene polyamine-alkenyl succinic anhydride or alkenyl fatty acid condensation type. The disclosure of U.S. Pat. No. 3,390,086 is incorporated herein by reference not only as to the sulfurized dispersants but also to lend support and basis for the preparation and use of the unsulfurized ashless dispersants therein disclosed. The Anderson patents and the LeSuer U.S. Pat. Nos. 3,185,646; 3,185,647; 3,200,107 and 3,216,936 are also incorporated herein by reference. They show the preparation and use of these unsulfurized ashless dispersants. The number average molecular weight of the ashless dispersants will generally be between about 700 and about 5,000, preferably between about 800 and about 2,000 and preferably the alkenyl radical constitutes a polyisobutylene or a polypropylene having the requisite 40-250 carbon atoms per radical. An example of a suitable alkenyl lower fatty acid which is condensed with a polyalkylene polyamine is polyisobutenyl propionic acid. This is formed by halogenating the polyisobutylene and condensing it with acrylic acid or an analog, such as alpha methylacrylic acid, crotonic or isocrotonic acid. The polyisobutenyl succinic anhydride or polyisobutenyl succinic acid is obtained conventionally by condensing the polyisobutylene or chloropolyisobutylene with maleic or fumaric acids or maleic anhydride.

The polyalkylene polyamines which are reacted with the carboxylic acids or their anhydrides encompass a considerable number of compounds and are fully described under the heading Ethylene Amines in Encyclopedia of Chemical Technology, Kirk & Othmer, Volume 5, pages 898-905 (1950). Any number of specific polyethylene polyamines are available in commerce and marketed. A preferred polyamine which is widely used in preparing the ashless dispersant type condensation products is tetraethylenepentamine. One method of preparing the condensation products of, for example, polyisobutenyl succinic anhydride and tetraethylene-pentamine is disclosed in U.S. Pat. No. 3,172,892 and this material is the material which has been used as the ashless dispersant additives in the hereinafter described specific examples.

The lubricating oils employed as the base oils are preferably mineral lubricating oils which may be derived from naphthenic, parafiinic, aromatic, or mixed crude oils. Generally they will have a viscosity at 210 F. of between about 45 and about SUS (Saybolt Universal Seconds) and at F. a viscosity of between about and about 1,100 SUS. The viscosity indices of these oils will generally range between about 0 and about 100. in the case of oils employed in high speed, heavy duty diesel engines, oils of high viscosity indices are often preferred, i.e. of the order of 100 or higher. Usually most diesel engines employ lubricating oils having viscosities of between about 75 and about 80 SUS at 210 F. and at 100 F. of between about 800 and about 1,250 SUS, with viscosity indices ranging between about 55 and about 80.

Amounts similar to the amounts specified for the novel additives are likewise employed for the conventional additives which are also used in such lubricating oils. These additives are corrosion inhibitors, (sorbitan mono-oleate), antioxidants, (N-phenyl alpha naphthylamine) pour point depressants, (unsulfurized wax alkylated naphthalene), viscosity index improvers (unsulfurized polyisobutylene or polymethyl methacrylates), antiwear agents (the zinc salt of di (C ,-C 5 alkyl) dithiophosphate), detergents (the alka-line earth metal salts of alkyl substituted phenol thioethers or sulfides), and dispersants (alkaline earth metal salts of petroleum sulfonic acids or of alkaryl sulfonic acids and the like.

The following examples are illustrative of the character and nature of the invention but it is not intended that the invention be limited thereto.

EXAMPLE 1 About 400 grams of paraffin wax alkylated naphthalene, which is conventionally employed as a pour point depressant for lubricating oils, was reacted with about 8 grams of sulfur at a temperature of 180 C. (356 F.) for 7 hours. After filtration of the product, the filtrate analyzed about 1.42 wt. percent of sulfur.

The resultant material and the starting material were both subjected to a series of comparative sludge inhibition tests in which the base oil composition involved the use of a sludgecontaining used oil which was freed of solid sludge by centrifuging for one hour at 1,800 rpm. Ten grams of the supematant oil freed of solid sludge particles, but containing oil-soluble sludge precursors, was employed as the base oil in this test. The oil, without any further additives, upon heating to the temperature applied in the test, would tend to form additional oil-insoluble deposits of sludge. In a tared stainless steel centrifuge tube, 10 grams of the supernatant used oil containing 1.0 wt. percent of the additive to be tested with or without 0.4 wt. percent of an ashless dispersant was heated to 150". C. (300 F.) for 2 hours in a constant temperature oil bath. Following the heating, the tube was cooled and then centrifuged for one hour at 1,800 rpm. The supernatant oil was decanted again from the tube and any residual sludge deposits were washed carefully with 99 percent n-pentane to remove all remaining oil associated therewith. The weight of the solid sludge formed during the test was determined. Blank or other comparative runs were also carried out in which either no additive was employed or an additive, to be compared, was employed. A substantial decrease in the amount of sludge deposited, as compared with the amount deposited in the case of the blank run, indicates the extent, if any, that the additives had a sludge inhibition effect, through the actual measurement, in milligrams, of the weight of the sludge formed. The following comparative data were obtained:

Note: Run F additive was prepared by reacting the unsulfurized solvent 150 neutral oil (400 grams) with elemental sulfur (16 grams) at 180 C. for 10 hours and stripping the reacted mixture with nitrogen at 120 C. for 1 hour. The product analyzed 1.42 wt. percent of sulfur. The blank used oil showed 10.5 mg. of sludge per 10 grams of oil.

It is apparent from these data that the use of sulfurized wax alkylated naphthalene in combination with the ashless dispersant which is identified as being formed by condensing polyisobutenyl succinic anhydride with tetraethylenepentamine as disclosed in US. Pat. No. 3,172,892 (a conventionally marketed and commercially available ashless dispersant) resulted in the production of less sludge under the conditions of testing than did the use of any other combination of sulfurized or unsulfurized materials with or without the presence of the ashless dispersant.

EXAMPLE 2 150 grams of the copolymer of di-Lorol fumarate and vinyl acetate as a 50 percent concentrate in solvent neutral 150 mineral lubricating oil having molecular weights of about 10,000 (this can vary between 8000 and 12,000) was reacted with 7.5 grants of elemental sulfur at a temperature of 180 C. for about 6 k hours. The unreacted sulfur was removed from the reacted mixture by filtration. The filtrated product had a combined sulfur content of about 1.75 wt. percent.

The sludge inhibition test described in Example 1 was carried out using the same used oil containing sludge precursors as was employed to secure the data in Table l. The used oil containing 1 percent of the sulfurized product of Example 2 showed a sludge formation of 7.1 mg. per 10 grams of used oil while the used oil containing no sulfurized product showed the formation of 10.5 mgs. of sludge per 10 grams of used oil.

EXAMPLE 3 grams, as a 60 percent concentrate in lubricating oil, of a polymer of the ester formed by esterifying a mixture of methacrylic acid with a mixed C, C,,, alcohol fraction and having the molecular weight of about 10,000 was sulfurized with 7.5 grams of elemental sulfur at a temperature of C. for about 6.5 hours. The unreacted sulfur was removed by filtration and the filtrate had a combined sulfur content of 1.73 wt. percent.

The same sludge inhibition test on used oil, as described in Example 1, was undertaken on a comparative basis with and without the presence of a conventional ashless dispersant. The comparative data are as follows:

dispersant as shown in Table l, i.e. the condensation product of polyisobutenyl succinic anhydride with tetraethylenepentamine and was used as a 70 percent concentrate in mineral lubricating oil in securing the data in Table 1.

EXAMPLE 4 56 grams as a 50 percent oil concentrate of C C acylated (behenyl) polystyrene having a molecular weight of about 5,000 was sulfurized with about 6 grams of elemental sulfur at a temperature of 200 C. for about 5 hours. The sulfurized material was extracted with about 200 cc. normal heptane, filtered and stripped under nitrogen overnight. The recovered product had a combined sulfur content of about 1.2 wt. percent.

The same inhibition-oxidation test involving used oil containing sludge precursors as was carried out and described in Example 1 was employed in the following comparative runs:

TABLE 111 Sludge, Milligrams Per 10 Grams Used Run No. Oil

P 1% product of Example 4 14.3

Note: the same ashless dispersant as described in Tables 1 and 11 was employed in securing the data appearing in Table III.

It is apparent from the study of the comparative data appearing in Tables II and III that the combination of using an ashless dispersant together with a sulfurized polymeric material having a sufficiently high molecular weight to impart oil solubility and having a structural configuration so as to give, in unsulfurized form, a pour point depressant effect gives unexpected oxidation-inhibition when used in mineral lubricating oils which normally have a tendency to form sludge.

What is desired to be secured by Letters Patent is:

What is claimed is:

l. A lubricating oil composition comprising a major proportion of a mineral lubricating oil,

a minor sludge inhibiting amount of a sulfurized polymeric C, to C alkyl ester of acrylic or methacrylic acid, said ester having lubricating oil pour point depressant properties, said sulfurized ester containing about 1 to wt. percent of sulfur,

and a minor sludge dispersing amount of at least one oilsoluble ashless sludge dispersant selected from the group consisting of condensation products of polyalkylene polyamines with alkenyl succinic acid, alkenyl succinic anhydride, and alkenyl propionic acid, wherein the alkenyl radical has from about 40 to 250 carbon atoms.

2. A lubricating oil composition as defined by claim 1 wherein said sulfurized ester and said ashless dispersant are each present in a concentration between about 0.05 and about 10 wt. percent of the total composition.

3. A lubricating oil composition as defined by claim 1 which also contains a minor sludge inhibiting amount of at least one sulfurized ashless dispersant wherein said ashless dispersant is as set forth in claim 1.

4. A lubricating oil composition as defined by claim 1 wherein said sulfurized polymeric ester is a sulfurized polymeric mixed C, C alkyl methacrylate.

5. A lubricating oil composition as defined by claim 1 wherein said polyalkylene polyamine is tetraethylene pentamine.

6. A lubricating oil composition as defined by claim 1 wherein said alkenyl radical is polyisobutenyl.

7. A lubricating oil composition as defined by claim 1 wherein said ashless dispersant is the condensation product of tetraethylene pentamine and polyisobutenyl succinic anhydride.

Claims (6)

1. 2. A lubricating oil composition as defined by claim 1 wherein said sulfurized ester and said ashless dispersant are each present in a concentration between about 0.05 and about 10 wt. percent of the total composition.
2. 3. A lubricating oil composition as defined by claim 1 which also contains a minor sludge inhibiting amount of at least one sulfurized ashless dispersant wherein said ashless dispersant is as set forth in claim 1.
3. 4. A lubricating oil composition as defined by claim 1 wherein said sulfurized polymeric ester is a sulfurized polymeric mixed C12-C18 alkyl methacrylate.
4. 5. A lubricating oil composition as defined by claim 1 wherein said polyalkylene polyamine is tetraethylene pentamine.
5. 6. A lubricating oil composition as defined by claim 1 wherein said alkenyl radical is polyisobutenyl.
6. 7. A lubricating oil composition as defined by claim 1 wherein said ashless dispersant is the condensation product of tetraethylene pentamine and polyisobutenyl succinic anhydride.