Deposit control additives for hydrocarbon fuels and lubricants for use in internal combustion engines

Abstract

 Additives for use in internal combustion engines are provided which particularly in unleaded fuels maintain cleanliness of the intake system without contributing to combustion chamber deposits. The additives are hydrocarbyl-terminated poly(oxyalkylene) polyamine ethanes comprising a hydrocarbyl-terminated poly(oxyalkylene) chain formed from 1 to 30 2-5 carbon oxyalkylene units bonded to an ethane or branched ethane chain containing from 2 to 8 carbon atoms in turn bonded to a nitrogen atom of a polyamine having from 2 to 12 amine nitrogens and from 2 to 40 carbon atoms with a carbon:nitrogen ratio between 1:1 and 10:1. The terminal hydrocarbyl group contains from 1 to 30 carbon atoms and the additive has a molecular weight in the range from 300 to 2500. The additive may be formulated as a concentrate in an inert oleophilic organic solvent or may be formulated as a lubricant composition for use in an internal combustion engine by incorporation in a lubricating oil.

Description

[0001] This invention relates to deposit control additives for hydrocarbon fuels and lubricants to be used in internal combustion engines, especially internal combustion engines designed to run on unleaded gasoline.

[0002] Numerous deposit-forming substances are inherent in hydrocarbon fuels. These substances when used in internal combustion engines tend to form deposits on and around constricted areas of the engine contacted by the fuel. Typical areas commonly and sometimes seriously burdened by the formation of deposits include carburetor ports, the throttle body and venturies, and engine intake valves.

[0003] Deposits adversely affect the operation of the engine. For example, deposits on the carburetor throttle body and venturies increase the fuel to air ratio of the gas mixture to the combustion chamber thereby increasing the amount of unburned hydrocarbon and carbon monoxide discharged from the chamber. The high fuel-air ratio also reduces the gas mileage obtainable from the engine.

[0004] Deposits on the engine intake valves when they get sufficiently heavy, on the other hand, restrict the gas mixture flow into the combustion chamber. This restriction starves the engine of air and fuel and results in a loss of power. Deposits on the valves also increase the probability of valve failure due to burning and improper valve seating. In addition, these deposits may break off and enter the combustion chamber possibly resulting in mechanical damage to the piston, piston rings, or engine head.

[0005] The formation of these deposits can be inhibited as well as removed by incorporating an active detergent into the fuel. These detergents function to cleanse these deposit-prone areas of the harmful deposits, thereby enhancing engine performance and longevity. There are numerous detergent-type gasoline additives currently available which, to varying degrees, perform these functions.

[0006] A complicating factor has, however, recently arisen. With the advent of automobile engines that require the use of unleaded gasolines (to prevent disablement of catalytic converters used therewith to reduce emissions), it has been found difficult to provide gasoline of high enough octane to prevent knocking and the concomitant damage which it causes. The chief problem lies in the area of the degree of octane require- . ment increase, herein called "ORI", which is caused by deposits formed in the commercial gasoline.

[0007] The basis of the ORI problem is as follows: each engine, when new, requires a certain minimum octane fuel in order to operate satisfactorily without pinking and/or knocking. As the engine is operated on any gasoline, this minimum octane increases and, in most cases, if the engine is operated on the same fuel for a prolonged period, will reach an equilibrium. This is-apparently caused by an amount of deposits in the combustion chamber. Equilibrium is typically reached after 5000 to 15,000 miles (8047 to 24140 km) of automobile operation.

[0008] The octane requirement increase in particular engines used with commercial gasolines will vary at equilibrium from 5 or 6 octane units to as high as 12 or 15 units, depending upon the gasoline compositions, engine design and type of operation. The seriousness of the problem is thus apparent. A typical automobile with a research octane requirement of 85, when new, may after a few months of operation require 97 research octane gasoline for proper operation, and little unleaded gasoline of that octane is available. The ORI problem also exists in some degree with engines operated on leaded fuels.

[0009] The ORI problem is compounded by the fact that the most common method for increasing the octane rating of unleaded gasoline is to increase its aromatic content. This, however, eventually increases even more the necessary octane requirement. Moreover, some of the nitrogen- containing compounds presently used as deposit-control additives and their mineral oil or polymer carriers may also significantly contribute to ORI in engines using unleaded fuels.

[0010] It is, therefore, particularly desirable to provide deposit control additives which effectively control the deposits in intake systems of engines, without themselves eventually contributing to the problem.

[0011] According to the present invention there are provided deposit control additives which, when incorporated in hydrocarbon fuels, are effective in maintaining the cleanliness of engine intake systems. The additives are hydrocarbyl-terminated polyoxyalkylene poly- amine ethanes soluble in hydrocarbon fuel boiling in the gasoline range. The hydrocarbyl-terminated polyoxyalkylene chain contains oxyalkylene units of from 2 to 5 carbon atoms. The polyoxyalkylene chain, which preferably contains from 1 to 30 oxyalkylene units, is bonded through a terminal carbon to an ethane or branched ethane chain or connecting group which is in turn bonded to the nitrogen atom of a polyamine having from 2 to 12 amine nitrogens and from 2 to 40 carbon atoms with a carbon-nitrogen ratio in the range from 1:1 to 10:1. The ethane moiety contains from 2 to 8 carbon atoms. The hydrocarbyl-terminating group contains from 1 to 30 carbon atoms and is bonded to the polyoxyalkylene units through an ether oxygen atom. The additives normally have a molecular weight in the range from 300 to 2500, preferably from 800 to 1500.

[0012] The polyoxyalkylene polyamine ethane additives of the invention can be incorporated in a liquid hydrocarbon fuel generally in an amount of from 30 to 10,000 ppm by weight of said additive. Advantageously the additive will be incorporated in the hydrocarbon fuel in the form of an additive concentrate comprising the additive and an inert stable oleophilic organic solvent. The additive may also be incorporated in a lubricating oil composition for use as a lubricant in an internal combustion engine.

[0013] The additive consists of three parts or moieties. The first is the polyamine moiety, and the second the poly(oxyalkylene) moiety comprising at least one hydrocarbyl-terminated polyoxyalkylene polymer, bonded through the third moiety, an ethane connecting group or linkage, connected in turn to the nitrogen atom of the polyamine.

[0014] As fuel additives, the polyoxyalkylene moiety, the polyamine moiety, and the ethane moiety are selected to provide solubility in the fuel composition and deposit control activity without contributing to octane requirement increase (ORI). As lubricating oil additives, the moieties may be selected to provide solubility in lubricating oil compositions and dispersant activity. The additives may be termed hydrocarbyl poly(oxyalkylene) polyamine ethanes or for convenience, "polyether polyamine ethanes". The additives may be prepared from the reaction of a suitable halogenating agent containing the desired ethane moiety, such as ethylene chlorohydrin, with the appropriate substituted epoxide, polymerizing to the polyoxyalkylene chain. This is in turn reacted with the appropriate hydrocarbyl cap which is followed by reaction of the capped polyether chloride with the appropriate polyamine to form the required additive.

Poly(oxyalkylene) Component

[0015] The polyoxyalkylene moiety is ordinarily prepared by the reaction of an appropriate chlorohydrin containing the desired ethane connecting group. In the preferred embodiment ethylene chlorohydrin is used, which is reacted under polymerization conditions with the lower alkylene oxides or oxiranes such as propylene oxide or butylene oxide. In the polymerization reaction, a single type of alkylene oxide may be employed. Copolymers, however, are equally satisfactory and random copolymers are readily prepared by contacting the ethylene chlorohydrin compound with a mixture of alkylene oxides. Blocked copolymers of oxyalkylene units also provide satisfactory polyoxyalkylene polymers for the practice of the present invention. Blocked copolymers are prepared by reacting the chlorohydrin with first one alkylene oxide and then the other in any order, or repetitively, under polymerization conditions.

[0016] The resulting polyoxyalkylene ethylene chloride is then reacted with the suitable hydrocarbyl cap to complete the precursor of the polyoxyalkylene moiety. The hydrocarbyl cap (R-) contains from 1 to 30 carbon atoms, preferably from 2 to 20 carbon atoms. The hydrocarbyl group may be any straight chain or branched aliphatic, olefinic or alkyl aryl hydrocarbon chain. The hydrocarbyl cap is added to the polyoxyalkylene precursor by the addition of the desired compound group to the polyoxyalkylene ethylene chloride in a catalyzed reaction utilizing an acid ion exchange resin reaction.

[0017] The hydrocarbyl polyoxyalkylene ethane moiety consists of one or more, preferably 1 or 2, more preferably one hydrocarbyl-terminated poly(oxyalkylene) polymer, composed of oxyalkylene units containing 2 to 5, preferably 3 or 4, carbon atoms. The poly(oxyalkylene) polymer contains at least one oxyalkylene unit, generally 1 to 30 units, preferably 5 to 30 units and most preferably 10 to 25 oxyalkylene units.

[0018] The terminal carbon atom at the hydroxyl end of the polyoxyalkylene chain is bound to the ethane or branched ethane connecting group which is in turn bound to the nitrogen atom of the polyamine.

[0019] In general, the poly(oxyalkylene) compounds are mixtures of compounds that differ in polymer chain length. However, their properties closely approximate those of a polymer represented by the average composition and molecular weight.

[0020] The ethane connecting group ordinarily consists of a 2-carbon chain ethylene group or an ethylene group with branched units extending from the carbons of the ethylene. The branches of the connecting group consists of low molecular weight alkyl groups of up to 2 carbon atoms. Additionally, in the present invention when the ethylene connecting groups contain branched alkyl groups, the branched groups will not generally contain the same number of carbon atoms as those extending from the oxyalkylene units of the polyoxyalkylene moiety.

[0021] The utilization of compounds containing the ethane or branched ethane connecting groups enhances the composition's use as a deposit control additive, ORI inhibitor, or dispersant agent by providing the molecule with less steric hindrance and greater polarity at the amine moiety end of the molecule. This allows the molecule to "bind" better to metal engine surfaces and/or in the system and combustion chamber deposits thereby enhancing its detergency effect.

Polyamine Component

[0022] The polyamine moiety of the polyether polyamine is derived from a polyamine having from 2 to 12 amine nitrogen atoms and from 2 to 40 carbon atoms. The polyamine preferably has a carbon to nitrogen ratio of from 1:1 to 10:1. The polyamine will contain at least 1 primary or secondary amine nitrogen atom. The polyamine may be substituted with a substituent group selected from (A) hydrogen; (B) hydrocarbyl groups of from 1 to 10 carbon atoms; (C) acyl groups of from 2 to 10 carbon atoms; and (D) monoketo, monohydroxy, monocyano, lower alkyl and lower alkoxy derivatives of (B) or (C). "Lower", as used in lower alkyl and lower alkoxy, means a group containing from 1 to 6 carbon atoms. "Hydrocarbyl" denotes an organic radical composed of carbon and hydrogen which may be aliphatic, alicyclic, aromatic or combinations thereof, e.g. aralkyl. Preferably, the hydrocarbyl group will be free of aliphatic unsaturation, i.e. ethylenic and acetylenic, particularly acetylenic unsaturation. The substituted polyamines used in the present invention are generally, but not necessarily, N-substituted polyamines. The acyl groups falling within the definition of the aforementioned (C) substituents are, for example, propionyl or acetyl. The more preferred substituents are hydrogen, C₁ to C₆ alkyls, and ^C₁-C₆ hydroxyalkyls.

[0023] The more preferred polyamines finding use in the present invention are polyalkylene polyamines, including alkylene diamine and including substituted polyamines, e.g. alkyl and hydroxyalkyl substituted polyalkylene polymines. Preferably the alkylene groups contain from 2 to 6 carbon atoms, there being preferably 2 or 3 carbon atoms betwen the nitrogen atoms. Such groups are exemplified by ethyleneamines and include ethylene diamine, diethylene triamine, di(trimethylene) triamine, dipropylenetriamine and triethylenetetramine. Such amines encompass isomers which are the branched-chain polyamines and the previously mentioned substituted polyamines, including hydroxy and hydrocarbyl-substituted polyamines. Among the polyalkylene polyamines, those containing 2 to 12 amine nitrogen atoms and 2 to 24 carbon atoms are especially preferred and the C₂ or C₃ alkylene polyamines are most preferred, in particular, the lower polyalkylene polyamines, e.g. ethylene diamine or tetraethylenepentamine.

[0024] In many instances a single compound will not be used as reactant in the preparation of the additives of this invention, in particular the polyamine component. That is, mixtures will be used in which one or two compounds will predominate with the average composition indicated. For example, tetraethylene pentamine prepared by the polymerization of aziridine or the reaction of dichloroethylene and ammonia will have both lower and higher amine numbers, e.g. triethylene tetramine, substituted piperazines and pentaethylene hexamine, but the composition will be mainly tetraethylene pentamine and the empirical formula of the total amine composition will closely approximate that of tetraethylene pentamine.

[0025] The final compositions comprising the additives of the present invention are prepared by the reaction on the hydrocarbyl capped polyoxyalkylene-ethane moiety containing a reactable chlorine or other halogen with the appropriately selected amine or polyamine. The basic substitution reaction yields the attachment of the polyamine to the polyoxyalkylene and the elimination of the hydrogen halide.

[0026] The class of preferred polyether polyamine ethanes may be defined by the following general formula:

wherein R = C₁ to C₃₀ aliphatic, olefinic or alkylaryl hydrocarbon;

R' = hydrogen, CH₃ or ^C₂^H₅;

R'' and R ''' = hydrogen, (-CH₂CH₂NH)_x wherein

x = 0 to 5, or C1 to C₁₀ ;

_R² and R3 = _H, or low molecular alkyl groups up to 5 carbons, and where R' = R² and/or R³; and

x = 1 to 30 oxyalkylene units.

[0027] The polyether ethylene amines can be used as additives in hydrocarbon distillate fuel and, in particular, unleaded gasoline. The concentration of the additive necessary in order to achieve the desired deposit control effect or carburetor detergency is dependent upon a variety of factors, including for instance the type of fuel used and the presence of other detergents or dispersants or other additives. Generally, however, the range of concentration of the additive in the base fuel is 30 to 10,000 weight parts per million, preferably from 30 to 2,000 weight parts per million, and most preferably from 100 to 700 parts per million of polyether polyamine ethane per part of base fuel. If other detergents are present, a lesser amount of polyether polyamine ethane may be used.

[0028] The oils which find use in producing lubricating oil compositions containing the additives of this invention are generally oils of lubricating viscosity derived from petroleum or synthetic sources. Oils of lubricating viscosity normally have viscosities in the range from 35 to 50,000 Saybolt Universal Seconds (SUS) at 100°F (37.8°C) and more usually from 50 to 10,000 SUS at 100°F (37.8°C). Examples of such base oils are naphthenic bases, paraffin base and mixed base mineral oils, synthetic oils, for example, alkylene polymers, such as the polymers of propylene or butylene, and mixtures thereof.

[0029] Usually included in the oils in addition to the additives of the invention are one or more of such additives as dispersants/detergents, rust inhibitors, antioxidants, oiliness agents, foam inhibitors, viscosity index improvers and pour point depressants. Usually, these other additives will be present in amounts of from 0.5 to 15 weight percent of the total composition. Generally, each of the additives will be present in the range from 0.01 to 5 weight percent of the total composition.

[0030] It is also contemplated that the polyether polyamine ethanes may be used as concentrates, and could be used as additive to fuels or lubricating oils subsequent to their preparation. In concentrates, the weight percent of these additives will usually range from 0.3 to 50, preferably 10 to 50, weight percent. The concentrate would ordinarily comprise an inert stable oleophilic organic solvent generally boiling in the range from 150 to 400°F (65.6 to 204.4°C) and the concentrate would preferably contain from 10 to 50 weight percent of the polyether polyamine ethane compound.

[0031] The following Example illustrates the preparation of an additive in accordance with the invention.

Example

Preparation of 1-butyl-capped polyoxyalkylene-2-N'-ethylene diamine ethane

[0032] To an ice-cold solution of 2 mls (3 mmoles) ethylene chlorohydrin in 30 m1s of CH₂C1₂ was added 0.5 ml (3.8 mmoles) of boron trifluoride:diethylether (undis- tilled) in one portion under a nitrogen atmosphere. The cooling bath was removed and butylene oxide added dropwise. The temperature rose rapidly to approximately 40°C. An additional 30 mls (348 mmoles) of butylene oxide was added at such a rate as to maintain an even refluxing, i.e. approximately 2 drops per second. After the addition was complete, the reaction product was allowed to cool to room temperature over a four-hour period and was diluted with additional CH₂Cl₂. The solution was extracted with cold water, then with a saturated solution of sodium bicarbonate and then with additional water. The product was stripped without drying and afforded 23.4 grams of a translucent oil after pumping with high vacuum. The product was redried in diethylether over anhydrous magnesium sulphate and was stripped to afford 22.6 grams of polyoxyalkylene ethane chloride.

[0033] To a solution of 1.73 grams (2.2 mmoles) of the polyoxyalkylene ethane chloride and 1.07 grams (5.4 meq) Amberlyst cation ion exchange resin (H⁺form) in 5 ml of hexane cooled in dry ice and under a nitrogen atmosphere, was transferred 2.0 ml (2.21 mmoles) of isobutylene. The reaction mixture was warmed to room temperature with stirring.

[0034] After 88 hours, the reaction product was diluted with hexane, filtered and stripped to afford 1.7 grams of a clean oil. The crude product was taken up in diethylether and washed three times with water, dried over magnesium sulphate and stripped to afford 1.4 grams of a clean oil.

[0035] To an ice-cold solution of 15 ml (224 mmoles) of ethylene diamine was added 1.0 gram of the above product dropwise. The mixture was placed under a nitrogen atmosphere and brought to 80°C. After 23 hours the reaction was cooled, the aliquot removed, diluted with diethylether and washed with distilled water several times, using methanol to keep emulsions down. After neutrality was reached, as indicated by pH paper, using water washings, the ether layer was washed three more times with water, dried over anhydrous potassium carbonate and stripped to afford 0.9 gram of a yellow oil which was the desired product. The basic nitrogen of the resulting product was 2.35%.

Claims

1. A deposit control additive for use in an internal combustion engine which is a hydrocarbyl-terminated polyoxyalkylene polyamine ethane having a molecular weight in the range from 300 to 2500, wherein the hydrocarbyl group contains from 1 to 30 carbon atoms, the polyoxyalkylene moiety comprises from 1 to 30 oxyalkylene units each having from 2 to 5 carbon atoms, the ethane moiety contains from 2 to 8 carbon atoms and the polyamine moiety comprises from 2 to 12 amine nitrogen atoms and from 2 to 40 carbon atoms with a carbon:nitrogen ratio in the range from 1:1 to 10:1.

2. An additive as claimed in Claim 1, wherein the oxyalkylene units are selected from oxyalkylene units having 3 or 4 carbon atoms.

- 3. An additive as claimed in Claim 1 or 2, wherein said hydrocarbyl-terminated polyoxyalkylene polyamine ethane has a molecular weight in the range from 800 to 1500.

4. An additive as claimed in Claim 1, 2 or 3, wherein said hydrocarbyl group contains from 2 to 20 carbon atoms.

5. An additive as claimed in Claim 1, 2, 3 or 4, wherein said ethane moiety contains from 2 to 4 carbon atoms.

6. An additive as claimed in any preceding claim, wherein said ethane moiety contains branched units which do not contain the same number of carbons as the branches of the oxyalkylene units of the polyoxyalkylene moiety.

7. An additive as claimed in any preceding claim, wherein said polyamine moiety is derived from a lower polyalkylene polyamine and contains at least one primary or secondary amine nitrogen atom.

8. An additive as claimed in Claim 7, wherein said lower polyalkylene polyamine is ethylene diamine or diethylene triamine.

9. A hydrocarbon fuel composition for use in an internal combustion engine, comprising a hydrocarbon boiling in the gasoline range and a deposit control additive as claimed in any one of Claims 1 to 8.

10. A fuel composition as claimed in Claim 9, wherein the additive is present in an amount of from 30 to 10,000 ppm by weight.

11. A fuel composition as claimed in Claim 9 or 10, wherein said hydrocarbon is an unleaded gasoline.

12. An additive concentrate comprising an inert stable oleophilic organic solvent and an additive as claimed in any one of Claims 1 to 8.

13. A concentrate as claimed in Claim 12, wherein the organic solvent boils in the range from 150 to 400°F (65.6 to 204.4°C) and contains from 10 to 50 weight percent of the additive.

14. A lubricating oil composition for use in an internal combustion engine, comprising an oil of lubricating viscosity and a deposit control additive as claimed in any one of Claims 1 to 8.