WO1995018201A1

WO1995018201A1 - Biodegradable two-cycle oil composition

Info

Publication number: WO1995018201A1
Application number: PCT/US1994/014481
Authority: WO
Inventors: George Mortimer Tiffany, Iii; Beth Ann Morgan; George Conrad L'heureux; Lewis H. Gaines
Original assignee: Exxon Chemical Patents Inc.
Priority date: 1993-12-30
Filing date: 1994-12-16
Publication date: 1995-07-06
Also published as: AU1437395A

Abstract

A biodegradable two-cycle oil composition having improved detergency and biodegradability containing a dispersant and wherein the base oil comprises at least one biodegradable ester of a carboxylic acid.

Description

BIODEGRADABLE TWO-CYCLE OIL COMPOSITION

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to biodegradable two-cycle oil compositions comprising a biodegradable base oil, an amide/imidozoline-containing dispersant.

2. Description of Related Art

Two-cycle engines are lubricated by mixing the lubricant with the fuel for the engine. The mixture of fuel and lubricant passes through the crankcase of a two-cycle engine, where it lubricates the moving parts in the lower portion of the engine and then flows through intake ports into the combustion chamber. There it lubricates the cylinder zone of the engine and is burned. The combustion products are vented from the combustion chambers through exhaust ports. As a consequence, a satisfactory lubricant for a two-cycle engine must not only provide adequate lubrication for moving engine parts but also must be able to pass into the combustion chamber leaving no objectionable deposits in the intake ports; must bum cleanly to avoid fouling the combustion chamber and spark plug with undesirable deposits; control varnish and sludge formation which leads to ring sticking and in turn to failure of the sealing function of piston rings; must not result in plugging of the exhaust ports and most importantly biodegrade to natural materials upon contact with the environment.

Various methods and compositions have been suggested for obtaining dispersant or biodegradable benefits for lubricating oils.

For example, U.S. Patent No. 5,221,491 discloses controlling gel formation in two-cycle oil with an additive comprising a reaction product of a monocarboxylic acid, a polyalkylene polyamine, and a high molecular weight acylating agent. The application further disclosed additive compositions also containing a polyolefin and a pour point depressant type flow improver. EP Application No. 0,552.554 Al discloses lubricating oil compositions which have a major proportion of a biodegradable base fluid that is a blend of (a) at least one ester of isotridecyl alcohol and a mono-, di or polycarboxylic acid and (b) at least one hydrocarbon oil which has no more than 10% on a weight basis of aromatic hydrocarbons, the rest being aliphatic. The portion of (a) in the blend is disclosed to be in the range from 25 to 55% on a weight basis.

EP Application 0,259,809 A2 discloses a lubricating oil composition comprising 9 to 60% by weight of mineral oil and 3 to 40% by weight of polyester. The mineral oil is disclosed to have a viscosity at 100°C of 2 to 50 centistokes, a pour point of -5 to -30°C and a viscosity index of not less than 80.

However, the composition of the invention provides a level of cleanliness in water cooled two-cycle engines that is surprisingly better and more environmentally friendly than that hereto obtained using commercially available composition.

SUMMARY OF THE INVENTION

In its broadest form, this invention concerns a biodegradable two-cycle oil composition particularly suited for water-cooled outboard engines which comprises a biodegradable base oil that degrades to natural products when in contact with the environment and an amide/imidazoiine-containing dispersant. More specifically, this invention relates to a two-cycle oil composition comprising (a) a biodegradable base oil comprising from 60 to 100 vol. % of at least one ester of carboxylic acid, and from 0 to 40 vol. % of a hydrocarbon oil; and (b) at least one amide/imidazoiine-containing dispersant prepared by reacting a monocarboxylic acid acylating agent with a polyamine, and optionally a high molecular weight acylating agent.

DETAILED DESCRIPTION OF THE INVENTION

Biodegradable Base Oil

Suitable biodegradable esters of carboxylic acids that comprise the biodegradable base oil are derived from carboxylic acids such as phthalic acid, succinic acid, alkyl succinic acids, aikenyl succinic acid, maleic acid, azelaic acid, suberic acid, sebacic acid, fumaric acid, adipic acid, linoieic acid dimer, malonic acid, aikyl malonic acid, and alkenyi malonic acid. Suitable alcohols which can be used to prepare the carboxylic acid esters of the invention are C to C^g alcohols, preferably Cg to Cj3 alcohols, and most preferably C13 alcohols. These alcohols may be either straight chain or branched chain alcohols. Among the alcohols operable in preparing the esters are butanoi, isooctanol, isononanol, isodecanol, tridecanol, dodecanol, dϋsotridecanol and 2-ethylhexyl alcohol. Suitable synthetic esters of the invention are dioctyl adipate. triisodecyl adipate, isotridecyl adipate, diisotridecyl adipate, di(2- ethylhexyl)sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, dϋsodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, the 2- ethylhexyl diester of linoleic acid dimer, the complex ester formed by reacting one mole of sebacic acid with two moles of tetraethylene glycol and two moles of 2- ethylhexanoic acid and the like.

Hydrocarbon oils as described herein can be obtained from natural or synthetic sources. Suitable natural oils include mineral oils such as liquid petroleum oils and solvent-treated or acid-treated mineral lubricating oils of the paraffinic, naphthenic or mixed paraffinic-naphthenic types and include oil based on hydrocracked wax distillates. Oils of lubricating viscosity derived from coal or shale and vegetable oils (e.g. palm, rapeseed, etc.), are also useful herein as hydrocarbon base oils.

Hydrocarbon oils include synthetic lubricating oils such as polymerized and interpoiymerized olefins (e.g., PAO), alkylated diphenyl ethers and alkylated diphenyl sulfides and the derivatives, analogs and homologs thereof, and the like.

Oils made by polymerizing olefins of less than 5 carbon atoms and mixtures thereof are typical synthetic polymer oils. Methods of preparing such polymer oils are well known to those skilled in the art as is shown by U.S. Patent Nos. 2,278,445; 2,301,052; 2,318,719; 2,329,714; 2,345,574; and 2,422,443.

Al ylene oxide polymers (i.e., homopolymers, interpolymers, and derivatives thereof where the terminal hydroxyl groups have been modified by esterification, etherification, etc.) constitute a class of known synthetic lubricating oils for the purpose of this invention. They are exemplified by the oils prepared through polymerization of ethylene oxide or propyiene oxide, the aikyl and aryl ethers of these polyoxyalkylene polymers (e.g., methyl polypropylene glycol ether having an average molecular weight of 1000, diphenyl ether of polyethylene glycol having a molecular weight of 500-1000, diethyl ether of polypropylene glycol having a molecular weight of 1000- 1500, etc.) or mono- and poiycarboxylic esters thereof, for example, the acetic acid esters mixed C3 to Cg fatty acid esters, or the C 13 Oxo acid diester of tetraethylene glycol.

Synthetic oils include polyol esters prepared by the reaction of polyols (including aliphatic dihydroxy compounds such as ethylene glycol, propylene glycol and hexylene glycol; trihydroxy compounds such as trimethyl propanol) with monocarboxylic acids including aliphatic monocarboxylic acids of from 1 to 18 carbon atoms and aromatic acids such as benzoic and toluic. Particularly preferred are polyol esters of C5 to C _jg monocarboxylic acids and polyol ethers thereof such as neopentyl glycol, trimethylol propane, pentaerythritol, dipeπtaerythritol, tripentaerythritol, and the like.

Unrefined, refined and rerefined oils, either natural or synthetic (as well as mixtures of two or more of any of these) of the type disclosed hereinabove can be used in the compositions of the present invention. Unrefined oils are those obtained directly from a natural or synthetic source without further purification treatment. For example, a shale oil obtained directly from retorting operations, a petroleum oil obtained directly from primary distillation or an ester oil obtained directly from an esterification process and used without further treatment would be an unrefined oil. Refined oils are similar to unrefined oils except they have been further treated in one or more purification steps to improve one or more properties. Many such purification techniques are known to those of skill in the art such as solvent extraction, secondary distillation, acid or base extraction, filtration, percolation, etc. Rerefined oils are obtained by processes similar to those used to obtain refined oils which have been already used. Such rerefined oils are also known as reclaimed or reprocessed oils and often are additionally processed by techniques directed to removal of spent additives and oil breakdown products.

Particularly preferred hydrocarbon oils are oils having a viscosity index above 120. These special oils additionally possess superior qualities of volatility and pour point. These oils are paraffinic base oils and include, inter alia, oils based on hydrocracked wax distillates. It is preferred that these paraffinic base oils have up to 99.5% by weight aliphatic hydrocarbons, preferably up to 97% by weight, and not more than 10% by weight aromatic hydrocarbons preferably less than 3% by weight wherein the total amount of aliphatics and aromatics is 100%. Most preferred are EXXSYN base stocks commercially available from Exxon. The base oil should be present in the oil composition in an amount ranging from 40 to 95 vol. % based on the volume of the blend, preferably from 85 to 95 vol.

Dispersant

The Amide/Irnidazoline-Containing Dispersant

The amide imidazoiine-containing dispersant of the invention comprises a reaction product of a monocarboxylic acid acylating agent, an polyamine and optionally a high molecular weight acylating agent. Such dispersants can also comprise imide moieties formed when the high molecular weight acylating agent is an appropriate diacid or anhydride thereof.

Throughout this specification and claims, any reference to carboxylic acids as acylating agent is intended to include the acid-producing derivatives such as anhydrides, esters, acyl halides, and mixtures thereof unless otherwise specifically stated.

Polvamines

The polyamines useful as a reactant may be generally characterized by the formula:

H₂N (-R NH)_n H

I Rl

wherein R is a C₂ or C3 alkylene radical or mixtures thereof; R* is H or an aikyl radical of from about 1 to about 16 carbon atoms and n is an integer of one or greater.

Preferably, n is an integer less than about 6, and the alkylene group R is ethylene or propylene. Non-limiting examples of the polyamine reactants are ethylenediamine; diethylenetriamine; triethylene-tetramine; tetra-ethylenepentamine; di-(methylethyl-ene)triamine; hexa-propyleneheptamine; tri-(ethyl-ethylene)tetramine; dipropylenetriamine; penta-( 1 -methylpropylene)-hexamine; hexa-( 1 , 1 -dimethyl- ethyiene)-heptamine; tri-(l,2,2-trimethylethylene)tetramine; triamine; tetra-(l,3- dimethylpropylene )-pentamine: penta-( 1 ,2-dimethyl- 1 -isopropylethylene)hexamine; penta-(l-methyl-2-benzyiethyiene)hexamine; tetra-( l-methyl-3-benzylpropylene) pentamine; tri-( l -methyl- l -phenyl-3- propyipropylene)tetramine; and tetra-( 1 -ethyl-2- benzylethyleneipentamine. The ethylene amines are especially useful. They are discussed in some detail under the heading "Ethylene Amines" in "Encyclopedia of Chemical Technology" Kirk and Othmer, Vol. 5, pages 898-905. Interscience Publishers. New York (1950). Such compounds are prepared most conveniently by the reaction of alkylene dihalide, e.g., ethylene dichloride, with ammonia or primary amines. This reaction results in the production of somewhat complex mixtures of alkylene amines including cyclic condensation products such as piperazine and N-alkyl substituted piperazines. These mixtures find use in the compositions of this invention.

Monocarboxylic Acid Acylating Agent

The monocarboxylic acid acylating agent utilized in the preparation of the two-cycle oil composition of the present invention may preferably be any monocarboxylic acid having at least two carbon atoms and generally less than 40 carbon atoms, or aromatic monocarboxylic acids or acid-producing compounds. Generally, the number of carbon atoms in the monocarboxylic acid will range from 8 to 40, preferably from 10 to 30.

Aromatic, heterocyciic monocarboxylic acids, as well as the aliphatic monocarboxylic acids, can be used. Monocarboxylic acids containing substituent groups, are also useful herein so long as they do not contribute to engine rusting or gel formation in finished oils. However, the preferred monocarboxylic acids reactants are the aliphatic monocarboxylic acids, i.e., the branched-chain saturated or branched or straight chain unsaturated monocarboxylic acids, and the acid halides and acid anhydrides thereof. Mixtures of branched and straight chain acids can be used so long as the straight chain acid content is limited so gel or sediment will not form in finished oil. Normally, the straight chain content is limited to less than 10% of the mixture. Particularly preferred are the aliphatic monocarboxylic acid reactants having a relatively long carbon chain length, such as a carbon chain length of between about 10 carbon atoms and about 30 carbon atoms. Non-limiting examples of the monocarboxylic acid reactant; acetic acid; acetic anhydride; acetyl fluoride; acetyl chloride; propionic acid: propiolic acid; propionic acid anhydride; propionyl bromide; butyric acid anhydride; isobutyric acid; crotonic acid chloride; crotonic acid anhydride; isocrotonic acid; β-ethylacryiic acid; valeric acid; acryiic acid anhydride; allyacetic acid; hexanoic acid; hexanoyi chloride; caproic acid anhydride; sorbic acid; nitrosobutyric acid; aminovaieric acid; aminohexanoic acid; heptanoic acid; heptanoic acid anhydride: 2-ethylhexanoic acid; decanoic acid: dodecanoic acid; undecylenic acid; oleic acid: heptadecanoic acid; stearic acid; isostearic acid; linoleic acid; linolenic acid; phenylstearic acid; xylylstearic acid; α-dodecyltetradecanoic acid; behenolic acid; cerotic acid; hexahydrobenzoyl bromide; furoic acid; thiophene carboxylic acid; picolinic acid; nicotinic acid; benzoic acid; benzoic acid anhydride; benzoyliodide; benzoyl chloride: toluic acid; xylic acid; toiuic acid anhydride: cinnamic acid; cinnamic acid anhydride; aminocinnamic acid; salicylic acid; hydroxytc iuic acid; naphthoyl chloride; and naphthoic acid.

Isostearic acid, a commercially available mixture of methyl branched C_j carboxylic acid containing minor amounts of other acids impurities, is the preferred monocarboxylic acid acylating agent. It is also preferred that the commercial isostearic acid have a lactone content of less than 1.0 wt. % and that the straight chain content (GC area percent analysis) be less than 10% and preferably less than 8% of the acid. In addition, the non-Ci acid content, comprised primarily of C 12, C 14 and Cι<5 acids is preferably less than 7 %. A preferred isostearic acid is PRISORINE\3502 available from Unichema International of 4650 South.Racine Avenue, Chicago, Illinois 60609.

High Molecular Weight Acylating Agent

The high molecular weight acylating agent, if employed, may comprise at least one aliphatic or aromatic mono or dicarboxyiic acid. High molecular weight as used herein defines the substituted acylating agent comprising number average molecular weights (Mn) which range from 700 to 4000 and preferably from 900 to 2500. The polymer molecular weight distribution (Mw/Mn), wherein Mw is the weight average molecular weight, is generally less than 4.5:1, preferably less than 3 : 1 and more preferably 1.5: 1 to 3: 1.

The acylating agent may contain polar substituents provided that the polar substituents are not present in portions sufficiently large to significantly alter the hydrocarbon character of the acylating agent exclusive of the carboxyl groups, or cause excessive rusting when the finished additive is used in two-cycle oil. Typical suitable polar substituents include halo, (such as chloro and bromo), oxo, oxy, formyl, sulfenyl, sulfinyi, thio, nitro, etc. Such polar substituents. if present, preferably do not exceed 10 % by weight of the total weight of the hydrocarbon portion of the acylating agent.

Carboxylic acyiating agents used to prepare the high molecular weight acylating agents are well known in the art and have been described in detail, (see, for example, U.S. Patent Nos. 3,087,936; 3,163,603; 3,172,892; 3,219,666; 3,272,746; 3,306,907; 3,346,354; and 4,234,435). These patents disclose suitable mono- and polycarboxylic acid acylating agents which can be used as starting materials in the present invention.

As disclosed in the foregoing patents, there are several well known processes for preparing the high molecular weight acids used in this invention. Generally, the process involves the reaction of (1) an ethylenically unsaturated carboxylic acid, acid halide, or anhydride with (2) an ethylenically unsaturated hydrocarbon containing at least about 40 aliphatic carbon atoms. The ethylenically unsaturated hydrocarbon reactant can, of course, contain polar substituents, other oil-solubilizing pendant groups, and be unsaturated within the general limitations explained hereinabove. It is these hydrocarbon reactants which frequently, but not always, provide most of the aliphatic carbon atoms present in the acyl moieties of the final products.

When preparing the high molecular weight carboxylic acid acylating agent, the carboxylic acid reactant usually corresponds to the formula

Ro-(-COOH)_n,

where R_Q can be aikyl but more frequently is characterized by the presence of at least one ethylenically unsaturated carbon-to-carbon covalent bond and n is an integer from 1 to 6 and preferably 1 or 2. The acidic reactant can also be the corresponding carboxylic acid halide, anhydride, ester, or other equivalent acylating agent and mixtures of one or more of these. Ordinarily, the total number of carbon atoms in the acidic reactant will not exceed 10 and generally will not exceed 4. Preferably the acidic reactant will have at least one ethylenic linkage in an alpha-beta position with respect to at least one carboxyl function. Exemplary acidic reactants are acrylic acid, methacrylic acid, maleic acid, maleic anhydride, succinic and succinic anhydride, fumaπc acid, itaconic acid, itaconic anhydride, citraconic acid, citraconic anhydride, mesaconic acid, glutaconic acid, aconitic acid, crotonic acid, methyicrotonic acid, sorbic acid, 3-hexenoic acid, 10-decenoic acid, and the like. As is apparent from the foregoing discussion, the high molecular weight carboxylic acid acylating agents may contain cyclic and/or aromatic groups. However, the acids are essentially aliphatic in nature and in most instances, the preferred high molecular weight acid acylating agents are aliphatically substituted succinic acids or anhydrides.

The aliphatic hydrocarbon-substituted succinic acid and anhydrides are especially preferred as acylating agents used as starting materials in the present invention. These succinic acid acylating agents are readily prepared by reacting maleic anhydride with a high molecular weight olefin or a chlorinated hydrocarbon such as a chlorinated poiyolefin. The reaction involves heating the two reactants at a temperature of about 100°-300°C, preferably, 100°-200°C. The product from such a reaction is a substituted succinic anhydride where the substituent is derived from the olefin or chlorinated hydrocarbon as described in the patents cited above on page 9. The product may be hydrogenated to remove all or a portion of any ethylenically unsaturated covalent linkages by standard hydrogenation procedures, if desired. The substituted succinic anhydrides may be hydrolyzed by treatment with water or steam to the corresponding acid and either the anhydride or the acid may be converted to the corresponding acid halide or ester by reacting with phosphorus halide, phenols, or alcohols.

The ethylenically unsaturated hydrocarbon reactant and the chlorinated hydrocarbon reactant used in the preparation of the high molecular weight acylating agents are principally the high molecular weight, substantially saturated petroleum fractions and substantially saturated olefin polymers. The polymers that are derived from mono-olefins having from 2 to about 30 carbon atoms are preferred. The especially useful polymers are the polymers of 1 -mono-olefins such as ethylene, propene, 1-butene, isobutene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 2-methyl-l- heptene, 3 -cyclohexyl- 1-butene, and 2-methyl-5-propyl- 1-hexene. Polymers of medial olefins, i.e., olefins in which the olefinic linkage is not at the terminal position, are also useful. These are exemplified by 2-butene, 3-pentene, and 4-octene.

The interpolymers of 1 -mono-olefins such as illustrated above with each other and with other interpolymerizable olefinic substances such as aromatic olefins, cyclic olefins, and polyolefins, are also useful sources of the ethylenically unsaturated reactant. Such interpolymers include for example, those prepared by polymerizing isobutene with styrene, isobutene with butadiene, propene with isoprene, propene with isobutene, ethylene with piperylene, isobutene with p-methyl-styrene, 1-hexene with 1,3-hexadiene. 1-octene with 1-hexene, 1 -heptene with 1-pentene, 3-methyl-l- butene with 1-octene, 3,3-dimethyl-l-pentene with 1-hexene. isobutene with styrene and piperylene. etc.

For reasons of hydrocarbon solubility, and stability the interpolymers contemplated for use in preparing the high molecular weight acylating agents of this invention should be substantially aliphatic and substantially saturated, that is, they should contain at least about 80% and preferably about 95%, on a weight basis, of units derived from aliphatic mono-olefins. Preferably, they will contain no more than about 5% olefinic linkages based on the total number of the carbon-to-carbon covalent linkages present.

The chlorinated hydrocarbons and ethylenically unsaturated hydrocarbons used in the preparation of the acylating agents can have molecular weight (Mn) of up to about 4000 or even higher. The preferred reactants are the above-described polyolefins and chlorinated polyolefins containing an average of at least 40 carbon atoms, preferably at least 60.

The high molecular weight acylating agent may also be prepared by halogenating a high molecular weight hydrocarbon such as the above-described olefin polymers to produce a polyhalogenated product, converting the polyhalogenated product to a polynitrile, and then hydrolyzing the poiynitrile. They may be prepared by oxidation of a high molecular weight poiydric alcohol with potassium permanganate, nitric acid, or a similar oxidizing agent. Another method for preparing such polycarboxylic acids involves the reaction of an olefin or a polar-substituted hydrocarbon with an unsaturated polycarboxylic acid such as 2-pentene- 1,3,5- tricarboxyiic acid prepared by dehydration of citric acid.

High molecular weight monocarboxylic acid acylating agent may be obtained by oxidizing a monoalcohol with potassium permanganate or by reacting a halogenated high molecular weight olefin polymer with a ketene. Another convenient method for preparing monocarboxylic acid involves the reaction of metallic sodium with an acetoacetic ester or a malonic ester of an alkanol to form a sodium derivative of the ester and the subsequent reaction of the sodium derivative with a halogenated high molecular weight hydrocarbon such as brominated wax or brominated polyisobutene. High molecular weight monocarboxylic and polycarboxyiip acid acylating agents can also be obtained by reacting chlorinated mono- and polycarboxylic acids, anhydrides, acyl halides, and the like with ethylenically unsaturated hydrocarbons or ethylenically unsaturated substituted hydrocarbons such as the polyolefins and substituted polyolefins described hereinbefore in the manner described in U.S. Patent No. 3,340,281.

The high molecular weight monocarboxylic and polycarboxylic acid anhydrides are obtained by dehydrating the corresponding acids. Dehydration is readily accomplished by heating the acid to a temperature above about 70°C, preferably in the presence of a dehydration agent, e.g., acetic anhydride. Cyclic anhydrides are usually obtained from polycarboxylic acids having acid radicals separated by no more than three carbon atoms such as substituted succinic or glutaric acid, whereas linear anhydrides are obtained from polycarboxylic acids having the acid radicals separated by four or more carbon atoms.

The acid halides of the monocarboxylic and polycarboxylic acids can be prepared by the reaction of the acids or their anhydrides with a halogenating agent such as phosphorus tribromide, phosphorus pentachloride, or thionyl chloride.

Although it is preferred that the high molecular weight acylating agent is an aliphatic mono- or polycarboxylic acid, and more preferably a dicarboxylic acid, the substituted carboxylic acylating agent also may be prepared from aromatic mono- or polycarboxylic acid or acid-producing compound. The aromatic acids are principally mono- and dicarboxy-substituted benzene, naphthalene, anthracene, phenanthrene or like aromatic hydrocarbons. The substituted aikyl groups may contain up to about 300 carbon atoms. The aromatic acid may also contain other substituents such as hydroxy, lower alkoxy, etc. Specific examples of aromatic mono- and polycarboxylic acids and acid-producing compounds useful in preparing the high molecular weight acylating agent include benzoic acid, m-toluic acid, salicyclic acid, phthalic acid, isophthalic acid, terephthalic acid, 4-propoxy-benzoic acid, 4-methyl-benzene-l,3- dicarboxyiic acid, naphthalene- 1 ,4-dicarboxyiic acid, anthracene dicarboxylic acid, 3- dodecyl-benzene-l,4-dicarboxylic acid, 2,5-dibutylbenzene-l,4-dicarboxylic acid, etc. The anhydrides of the dicarboxylic acids also are useful as the substituted carboxylic acylating agent.

It is essential to the present invention, however, that when a high molecular weight carboxylic acylating agent is used to prepare the dispersant the combined acylating agents be selected to provide a total number of carbon atoms in the acylating agents which is sufficient to render the dispersant hydrocarbon-soluble. Generally, the sum of the carbon atoms in the two acylating agents will be at least about 40 carbon atoms and more generally will be at least about 175 carbon atoms. Accordingly, if the high molecular weight acylating agent contains a large number of carbon atoms, the monocarboxylic acid acylating agent does not need to contain a large number of carbon atoms.

Acylation of the polyalkylenepolyamine in the manner disclosed herein results in a variety of acylated polyalkylenepolyamine-containing molecular entities. As a result, the polyalkylenepolyamine molecules may not be completely acylated with the monocarboxylic acid acylating agent or both high molecular weight acylating agent and monocarboxylic acid acylating agent nor are all polyalkylene polyamine molecules acylated to the same extent. A distribution of acylated products is obtained in which the number of amine groups acylated on different amine-containing molecules ranges from zero in the extreme (no acylation) to acylation of all 1° and 2° amines (complete acylation).

Ideally, for the ashless dispersant of this invention, the distribution of acylated products is maintained as narrow as possible. Preferably, all the amine groups should not be acylated (insufficient polarity for function as a dispersant). The other extreme i.e. low acylated molecules relative to the total amine content, will result in too high polarity for satisfactory oil solubility and dispersancy and would also provide a matrix for gel formation in the finished oil.

Generally, the equivalents or molar ratio of acylating agent(s) to amine will be such that, on average, the dispersant molecules will have between 1 and 2 amine groups unreacted to provide polarity. The exact number depends on the ratio of the acylating agent to alkylenepoiyamine and the ratio of the monocarboxylic acid to the optional acylating agent when the optional acylating agent is used and the specific composition of the polyalkylenepolyamine. A molar ratio of acylating agent(s) for instance, to tetraethylene pentamine can range from 1 :1 to 5:1 with a ratio of 2:1 to 4.5:1 being preferred.

The ratio of the monocarboxylic acid acylating agent to high molecular weight acylating agent (when used) should be at least 2:1, preferably from 3: 1, most preferably from 5: 1 to 59: 1 and most desirably 5: 1 to 12:1 and wherein the ratio of tertiary amine to total amine in the final product is at least about 0.7:1, preferably at least 0.85:1 due to ring closure of amide/amine functionality to imidazoline.

The equivalent weight of the polyalkylene-polyamine for purposes of acylation is based on the number of primary and secondary amine groups per molecule, and the equivalent weight of these acylating agents is based on the number of carboxy groups per molecule. To illustrate, ethylene diamine has 2 equivalents per mole, and therefore, has an average equivalent weight of 1/2 its molecular weight and tetraethylene pentamine has 5 equivalents per mole and therefore, has an average equivalent weight of 1/5 of its molecular weight. The monocarboxylic acids have one carboxy group, and therefore the equivalent weight of the monocarboxylic acids is its molecular weight. The succinic and aromatic dicarboxylic acid acylating agents, on the other hand, have two carboxy groups per molecule, and therefore, the equivalent weight of each is one-half its molecular weight. Frequently, the equivalent weight of the polyalkylenepolyamine is determined by its nitrogen content, and the equivalent weight of acylating agents is determined by their acidity or potential acidity as measured by the neutralization or saponification equivalents.

However, many commercially available polyalkyleneamines have some tertiary nitrogen containing groups which will not acyiate. For example, commercial tetraethylene pentamine contains about 10% aikyl substituted piperazine rings and probably has some tertiary amine groups formed by other branching reactions during the amine synthesis. Thus, the equivalent weight for purposes of acylation calculated from total nitrogen content will be higher that is actually the case.

Equivalent weights of polyalkyleneamines can also be calculated from total amine values measured by titration with hydrochloric acid or preferably perchloric acid. However, the same limitations described above are in effect in that tertiary amine groups will titrate but not acyiate.

The amide/imide/imidazoline dispersant of this invention is a complex molecule comprising oil soluble non-polar hydrocarbon containing moiety or moieties and polar unreacted amine containing moieties. For example, as discussed above for tetraethylene pentamine, the number of acylated amine groups varies in different molecules from 1 to as high as 5. The lower acylated portion of the molecules can form a matrix for gel in finished oils. This can be further exacerbated if too large a portion of the acylating groups are (1) of low molecular weight (2) are straight-chain and (3) contain undesirable pendant groups such as hydroxyi from lactone impurities in the monocarboxylic acid. Therefore, the tendency to gel formation can be reduced by increasing the average molecular weight of the combined acylating groups and increasing the ratio of acyiating groups to available amine groups. However, either of the above can be detrimental if excessive. Increasing use of high molecular weight acylation agent beyond a reasonable amount would reduce the effectiveness of the dispersant in two-cycle oil. Also, increased use of both high and low molecular weight acylating agents again beyond a reasonable amount would also have a detrimental effect by disrupting the hydropholic/hydrophylic balance of the dispersant. A corollary to the above is that the preferred ranges for the ratio of high molecular weight acylating agent to low and both acylating agents to amine must be controlled to provide a dispersant which is balanced in detergency and gel avoidance.

The broad range of acylating groups to amine stated above (molar or equivalent) should leave an average of from 0% to 50 wt. % of the amine groups of the polyamine unreacted. It is preferred, however, to have from 20 to 40% of the amine groups that are titratable with hydrochloric acid before acylation still left unreacted after acylation. The most desirable amount left unreacted should be from about 30 to about 40%. As use herein, percent unreacted amine is determine by the American Oil Chemists Society (A.O.C.S.) Method Tf lb-64 incorporated herein by reference. The solvents are modified slightly to facilitate seeing the end points, i.e., 80% isopropyl alcohol/water is used for tetraethylene-pentamine and 90/10 by volume isopropylalcohol/toluene for the dispersants. The error band for this method is about +3%. Such a product would not only give acceptable gel control even with low ratios of high molecular weight acylating agent to the mono-acid but should also still have sufficient polarity (unacylated amine groups) to provide acceptable dispersant capability regardless of whether the amine is a primary, secondary or tertiary amine.

The precise composition of the amide imide imidazoline dispersant additive of this invention is not known. The polar portion of the product, however, should be comprised substantially of tertiary amines in heterocyclic rings wherein the ratio of tertiary amine to total amine is about 0.7:1 (as measured by the AOCS method Tf lb- 64) and more desirably, at least 0.85:1. The effectiveness of the additive in providing dispersancy is dependant in part on the ratio of the monocarboxylic acid acylating agent to the high molecular weight acylating agent and in part on the ratios of acyiating agent to amine. It is also dependent on the reaction conditions under which it is formed. The temperature and pressure of the final stage of the reaction used to prepare the amide/imidazoline or amine/'imide/imidazoline dispersants of this invention is critical to maximizing tertiary amine formation, and generally, reaction temperatures ranging from 120°C up to the decomposition temperature of any of the reactants or the product and pressures of from 0.1 to 760 mm of Hg absolute can be utilized. Preferably, however, the temperature will be above about 150°C and more generally from about 150 to about 240°C. The pressures used range generally from about 130 to 760 mm of Hg absolute. The higher the temperature the less need there is to reduce the pressure to eliminate water and form tertiary amines as heterocycles.

The preparation of the amide imidazoline or amide imide imidazoline dispersant of the invention is conducted by reaction of optionally a high molecular weight acylating agent, the alkylene polyamine and the carboxylic acylating agent or agents preferably by adding the acids or their equivalents to the amine in a "reverse addition" mode i.e. acylating agent to amine.

The reaction is preferably conducted by the addition of the acid(s) or equivalent to the amine in the "reverse addition" mode, however, the initial addition of the amine to a portion of the carboxylic acid acyiating agent or a mixture- of the acylating agent(s) followed by the subsequent addition of the remaining acid(s) or the separate addition of the acid(s) in any order is also acceptable.

As indicated above, the optimum raw material addition sequence is to initially add all of the polyalkylenepolyamine. The order of addition of the carboxylic acylating agent and the high molecular weight acylating agent probably has no significant effect on the final product and they may be added simultaneously. However, the "reverse addition" of acid to amine may be impractical due to mixing limitations in a batch reactor. A modification of the preferred mode comprises initially charging some acid(s) to the reactor. Generally, an amount ranging up to 50% by volume of the acid(s) is charged to cover the impellers of the reactor. Preferably, the amount charged should be just sufficient to cover the impellers. Then the amine is charged followed by the remaining acid(s). The reactor temperature at the initial charge of acids can range from 80°C to 150°C and preferably from 110°C to 130°C.

The reaction time is dependent upon the size of the charge and the reaction temperature. Generally, after the charging of all the acid to the reactor the reactor temperature is increased to from 140°C to 160°C and allowed to soak at reflux generally from about 2 to 4 hours. It is important that some water be present in the system (produced by acylation) during reflux to maximize the acylation reaction. If water is stripped as produced, the amine amide groups tend to form heterocycles too soon and this reduces the number of amine groups available for acylation by the acid. Low acid conversion results in an unsatisfactory product. Allowing water to remain directs the reaction towards maximizing acylation of the available amine/amide groups of the polyamine.

After reflux, the temperature is then increased to from about 170°C to 190°C for a period of time, generally from 3 to 10 hours during which most of the water formed during the acylation reaction is removed and a residual total acid number of below 10 is obtained. A small amount of water remains however, which limits cyclization of amide/amine groups. In the final stage, the reactor temperature is again increased, to further remove water including water eliminated by cyclization, to from about 195°C to about 240°C with inert gas purge. Alternatively, vacuum stripping may be used at about 150° to about 195°C for the time required at a reduced pressure of from about 130 to about 250 mm Hg (absolute) with a inert gas bleed. Either method is directed to achieving a tertiary amine to total amine ratio of about at least 0.7:1 or preferably 0.85:1 to 0.95:1. It is desirous to have a free water level below about 0.2 wt. %, preferably below 0.05 wt. % in the final product.

Stripping is conducted as disclosed at a temperature and pressure to cause cyclization of remaining ethyleneamine groups with adjacent amide groups. The effect of this conversion to heterocycles containing tertiary amine groups may be measured by following the increase in the tertiary amine or the reduction in primary and secondary amines. With cyclization, the total titratable amine does not change, since only one of the nitrogen atoms in the heterocyclic rings is titratable with HC1. The ring structures or tertiary amine-containing groups are still polar and provide the hydrophilic moieties of the dispersant molecule.

The additive should be present in the oil composition at a level of from 5 to 60 vol. % and preferably at a level of from 5 to 15 vol. % based on the weight of the composition.

It was discovered that a more stable product, one which also avoids gel formation is achieved by maximizing the conversion of the amine nitrogen to tertiary amines. The reaction process disclosed above is directed to ultimately decreasing the primary and secondary amine content and increasing the tertiary amine content of the reaction product to the ranges specified above.

The components of the present invention can be incorporated into a lubricating oil in any convenient way. Thus, the compounds or mixtures thereof, can be added directly to the oil by dissolving the same in the desired oil at the desired level or concentrations. Alternatively, the components can be blended with a suitable oil soluble solvent such as mineral spirits and/or base oil to form a concentrate and then the concentrate may be blended with lubricating oil to obtain the final formulation.

The two-cycle oil composition of the invention can contain other additives for improving the performance of the oil in two-cycle engines. Such other additives can comprise, for example, antiwear agents and lubricating additives (including general load bearing additives), particularly phosphorous-containing antiwear agents, polyolefins (e.g., polybutene and polyisobutylene), bright stock, sulfurized olefins, molybdenum compounds, and the like; antioxidants, such as sulfurized phenols; pour point depressants such as polyacrylates, polymethacrylates and comb polymers such as Cg to Cig aikyl esters of C4 to Cg mono- or dicarboxylic acids and copolymers thereof with other carboxylic acid esters such as vinyl acetates (e.g., fumarate-vinyl acetates), and other dispersants as, for example, ashless dispersants such as those prepared by reacting a hydrocarbyl substituted carboxylic acid acylating agent with an alkylene polyamine.

Claims

CLAIMS :

1. (a) A two-cycle oil composition comprising (a) a biodegradable base oil comprising from 60 to 100 vol. % of at least one ester of carboxylic acid and 0 to 40 vol. % of a hydrocarbon oil; and (b) at least one arnide/iniidazoiine-containing dispersant prepared by reacting a monocarboxylic acid acylating agent with a polyalkylene polyamine and optionally a high molecular weight acylating agent.

2. The composition of claim 1 wherein the biodegradable oil comprises 40 to 95 vol. % of the composition and the dispersant comprises 5 to 60 vol. % of the composition.

3. The composition of claim 2 wherein the base oil comprises a tridecyl adipate optionally in combination with at least one other hydrocarbon oil.

4. The composition of claim 1 wherein the dispersant comprises the reaction product of a monocarboxylic acid and a polyamine.

5. The composition of claim 1 wherein the dispersant compπses the reaction product of a monocarboxylic acid, a polyamine and a high molecular weight acylating agent.

6. The composition of claim 1 wherein the polyamine has the formula:

H₂N (-R NH)_n H

I

K-

wherein R is a C₂ to C3 alkylene radical or mixtures thereof; R* is H or an aikyl radical of from about 1 to about 16 carbon atoms and n is an integer of one or greater.

7. The composition of claim 6 wherein the polyamine is tetraethylene pentamine.

8. The composition of claim 1 wherein the dispersant is a reaction product of isostearic acid and tetraethylenepentamine.

9. The composition of claim 1 wherein the dispersant comprises the reaction product of isostearic acid, tetraethylenepentamine. and polyisobutylene succinic acid.

10. The composition of claim 1 wherein the ratio of the monocarboxylic acid to high molecular weight acylating agent is at least 2:1.