GB1581868A - Deposit control additives - Google Patents

Description

(54) DEPOSIT CONTROL ADDITIVES (71) We, CHEVRON RESEARCH COMPANY, a corporation duly organized under the laws of the State of Delaware, United States of America, of 575 Market Street, San Francisco, California, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to hydrocarbon fuels for use in internal combustion engines and is concerned with compounds suitable for use as deposit control additives in such fuels.

In recent years, numerous fuel detergents or "deposit control" additives have been developed. These materials when added to hydrocarbon fuels employed in internal combustion engines effectively reduce deposit formation which ordinarily occurs in carburetor ports, throttle bodies, venturies, intake ports and intake valves. The reduction of these deposit levels has resulted in increased engine efficiency and a reduction in the level of hydrocarbon and carbon monoxide -emissions.

Thus, the introduction of fuel compositions containing deposit control additives has resulted in many cases in the reduction of harmful atmospheric pollutants and, since greater engine efficiencies are maintained, fuel savings.

A complicating factor has, however, recently arisen. With the advent of automobile engines that require the use of non-leaded gasolines (to prevent disablement of catalytic converters used to reduce emissions), a serious problem has arisen in providing 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 requirement increase, herein called "ORI", which is caused by deposits formed in the combustion chamber while the engine is operating on commercial gasoline.

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 equilibrium. This is apparently caused by an amount of deposits in the combustion chamber. Equilibrium is typically reached after 5000 to 15,000 miles of automobile operation.

Octane requirement increases at equilibrium with commercial gasolines, in particular engines will vary 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 1975 or 1976 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 exists in some degree with engines operated on leaded fuels. U.S.- Patents 3,144,311 and 3,146,203 disclose lead-containing fuel compositions having reduced ORI properties.

It is believed, however, by many experts that the ORI problem, while present with leaded gasolines, is much more serious with unleaded fuel because of the different nature of the deposits formed with the respective fuels, the size of increase, and because of the lesser availability of high-octane non-leaded fuels. This problem is compounded by the fact that the most common means of enhancing the octane of unleaded gasoline, increasing its aromatic content, also appears to increase the eventual octane requirement of the engine.

The problem is compounded by the recently discovered fact that some of the presently used nitrogen-containing deposit control additives and the mineral oil or polymer carriers commonly used with such additives appear to contribute significantly to the ORI of engines operated on unleaded fuel.

It is, therefore, highly desirable to provide deposit control additives which effectively control deposits in intake systems (carburetor, valves, etc.) of engines operated with fuels containing them, but do not contribute to the combustion chamber deposits which cause increased octane requirements.

In accordance with the present invention deposit control additives are provided which maintain cleanliness of engine intake systems and do not themselves contribute to combustion chamber deposits. The deposit control additives are poly(oxyalkylene) carbamates soluble in a hydrocarbon fuel boiling in the gasoline range. The carbamates comprise at least one hydroxy- or hydrocarbyloxy-terminated poly(oxyalkylene) chain, preferably of from 21 to 30 oxyalkylene units containing 2 to 5 carbon atoms, preferably 3 carbon atoms, per unit bonded through an oxycarbonyl group to a nitrogen atom of ethylenediamine. The hydrocarbyloxy group will contain from 1 to 30, preferably 2 to 20, carbon atoms.

The preferred compounds may be represented by the general formula: R - NH - CH2 - CH2 - NH2 in which R is a group of the formula

in which g, g' and g" are integers 1 to 2; h' and h" are 0 or 1; i, i' and i" are integers 1 to 3; the sum ofg and his 2; Mis methyl or ethyl; j,j' andj" are integers and the sum ofj + j' + j" is an integer 21 to 30, preferably 22 to 28; Z is H or hydrocarbyl of 1 to 30 carbons. Sufficient of the oxyalkylene units in R are other than ethyleneoxy to render the compound soluble in hydrocarbon fuel boiling in the gasoline range.

The additives are usually prepared by the reaction of a suitable polyether alcohol with phosgene to form a chloroformate followed by reaction of the chloroformate with ethylenediamine to form the active carbamate.

The polyethers or poly(oxyalkylene) materials which are utilized in preparing the polyether carbamates are- condensation polymers of the lower aliphatic oxides such as ethylene oxide, propylene oxide, the butylene oxides and the pentylene oxides. The preferred materials are the propylene oxide polymers or poly(propylene glycol). These materials may be terminated or capped on one end by a suitable hydrocarbyl group. For example, particularly preferred materials are capped with a butyl or oleyl group. Also suitable are mixtures of materials which are capped with different alkyl groups, e.g. with C16, C18 and C20 alkyls.

Aryloxy termination is also suitable. Thus, phenols and substituted phenols such as 4-t-butyl phenol, 4-tetrapropenyl phenol, or 2-n-propyl phenol, may be used. While materials with two terminal hydroxyl groups can be employed, the use of a material containing but one is preferred since chloroformylation will produce a preferred monochloroformate which can then be reacted with a suitable amine to produce the preferred carbamyl material. However, even though some dicarbamate will be formed with the dihydroxy materials, the presence of small amounts of these materials are, though not preferred, not detrimental to the performance of the materials.

The materials may be prepared from mixture of oxide monomers, i.e. when the reactivities of the oxides are relatively equal, random polymers can be prepared. In certain cases, with ethylene oxide, in combination with other oxides, the ethylene oxide reaction rate is much greater, and random polymers cannot be easily prepared. In those cases, block copolymers are prepared.

Particular types of polymer that can be prepared and have been commercially prepared are represented by materials which are prepared by polymerizing propylene oxide to form a first material and then polymerizing ethylene oxide on one or both ends of the poly(oxypropylene). Materials of this type are marketed by Wyandotte Chemicals as "Pluronics". The word "Pluronic" is a Trade Mark. Block copolymers of propyleneoxy and butyleneoxy groups are also suitable.

The additives of this invention may be most conveniently prepared, as has been previously noted, by reaction of phosgene with the poly(oxyalkylene) compound followed by reaction of the product with ethylenediamine.

The reaction of the poly(oxyalkylene) material is carried out on an.essentially equimolar basis utilizing only a slight excess of phosgene, although an excess of phosgene is not detrimental. The reaction may be carried out at temperatures from - 10 to 100"C, preferably in the range of 0 to 30"C. The reaction will usually be complete within 1/4 to 5 hours. Times of reaction will usually be in the range of from 1/2 to 3 hours.

A solvent may be used in the chloroformylation reaction. Suitable solvents include benzene and toluene. It is preferred that the phosgene be dissolved in a suitable solvent before reaction with the poly(oxyalkylene) material.

The reaction of the chloroformate with the ethylenediamine may be carried out neat or in solution. The molar ratio of amine to chloroformate will usually be in the range of 0.5 to 5.

Temperatures of from -10" to 200"C may be utilized. The desired product may be obtained by water wash and stripping, usually by the aid of vacuum, of any residual solvent.

The mol ratio of the polyether chloroformates to amine will generally be in the range from 0.2 to 20 mols of amine per mol of chloroformate, and more usually 0.5 to 5 mols of amine per mol of chloroformate. The mol ratio will depend upon the particular chloroformate and the desired ratio of polyether to amine. If suppression of polysubstitution of the ethylenediamine is desired, large mol excesses of the amine will be used.

The reaction or reactions may be conducted with or without the presence of a reaction solvent. A reaction solvent is generally employed whenever necessary to reduce the viscosity of the reaction product. These solvents should be stable and inert to the reactants and reaction product. Preferred solvents include aliphatic or aromatic hydrocarbons. Depending on the temperature of the reaction, the particular chloroformate used, the mol ratios as well as the reactant concentrations, the time may vary from 1/4 to 24 hours, more usually from about 2 to 3 hours. Times greatly in excess of 3 hours do not particularly enhance the yield and may lead to undesirable degradation, especially at higher temperatures. It is therefore preferred to limit the reaction time to less than 3 hours.

After the reaction has been carried out for a sufficient length of time, the reaction mixture may be subjected to extraction with a hydrocarbon or hydrocarbon-alcohol medium to free the product from any low-molecular-weight amine salts which have formed and any unreacted ethylenediamine. The product may then be isolated by evaporation of the solvent.

Small amounts of halogen may be present as the hydrohalide salt of the polyether carbamates.

Depending on the particular application of the composition of this invention, the reaction may be carried out in the medium in which it will ultimately find use, e.g. polyether carriers and be formed at concentrations which provide a concentrate of the detergent composition.

Thus, the final mixture may be in a form to be used directly for blending in fuels.

The polyether carbamates will generally be employed in a hydrocarbon distillate fuel. The proper concentration of additive necessary in order to achieve the desired detergency and dispersancy varies depending upon the type of fuel employed, the presence of other detergents, dispersants and other additives, etc. Generally, however, from 30 to 2000 weight parts per million, preferably from 100 to 700 ppm of polyethercarbamate per part of base fuel is needed to achieve the best results. When other detergents are present, a lesser amount of polyether carbamate may be used. For performance as a carburetor detergent only, lower concentrations, for example 30 to 70 parts per million may be preferred.

The detergent-dispersant additive may be formulated as a concentrate, using an inert stable oleophilic organic solvent boiling in the range from 1500 to 4000F. Preferably, an aliphatic or an aromatic hydrocarbon solvent is used, such as benzene, toluene, xylene or higher boiling aromatics or aromatic thinners. Aliphatic alcohols of about 3 to 8 carbon atoms, such as isopropanol, isobutylcarbinol or n-butanol, in combination with hydrocarbon solvents are also suitable for use with the detergent-dispersant additive. In the concentrate, the amount of the additive will be ordinarily at least 10 percent by weight and generally not exceed 70 percent by weight and preferably from 20 to 60 weight percent.

In gasoline fuels, other fuel additives may also be included such as antiknock agents, e.g., methylcyclopentadienyl manganese tricarbonyl, tetramethyl or tetraethyl lead, or other dispersants or detergents such as various substituted succinimides or amines. Also included may be lead scavengers such as aryl halides, e.g., dischlorobenzene or alkyl halides, e.g., ethylene dibromide. Additionally, antioxidants, metal deactivators and emulsifiers may be present.

A particularly useful additive is a fuel-soluble carrier oil. Exemplary carrier oils include nonvolatile poly(oxyalkylene)s; other synthetic lubricants or lubricating mineral oil. Particularly preferred carrier oils are poly(oxyalkylene) mono and polyols, such as the Pluronics marketed by BASF Wyandotte Corp., and the UCON LB-series fluids marketed by Union Carbide Corp. The word "Ucon" is a Trade Mark. These materials have been found to exhibit a synergistic deposit-control effect in combination with the polyether amines. When used, these oils are believed to act as a carrier for the detergent and assist in removing and retarding deposits. They are employed in amounts from about 0.05 to 0.5 percent by volume, based on the final gasoline composition.

The following Examples are presented to illustrate specific embodiments of the practice of this invention and should not be interpreted as limitations upon the scope of the invention.

Example 1 - Preparation of Poly(oxypropylene) Chloroformate Phosgene (298 g, 3.0 mols) was condensed into toluene (2.5 liters) at OOC. Poly(oxypropylene) (5.0 kg, 2.78 mols) with a molecular weight of about 1800 was added to the phosgene solution in a rapid stream, with stirring. The mixture was stirred an additional 30 minutes after completion of the addition, and excess phosgene was removed by purging with nitrogen while the temperature rose to ambient (about 2 hours). The product showed a strong chloroformate absorption at 1790 cm Example 2 - Reaction of Poly(oxypropylene) Chloroformate with Ethylenediamine The chloroformate solution from Example 1 was divided in half, diluted with toluene (6 liters), and each half was added to ethylenediamine (527 g, 8.6 mol) in toluene (1 liter) at 0 C, with vigorous stirring. Immediate precipitation of ethylenediamine hydrochloride occurred. The reaction temperature was kept below 25"C and stirring was continued for one hour after addition. n-Butanol (5 liters) was added, and the mixture was extracted with hot water (approximately 15 liters). The two batches were combined and solvent was removed on a 5-gallon rotary evaporator. The product (5050 g) contained 1.12% nitrogen and 0.46% basic nitrogen by ASTM D-2896. Infrared analysis revealed a typical carbamate absorption at 1725 em The polyether carbamates were blended in gasoline and their deposit reducing capacity tested in an ASTM/CFR Single-Cylinder Engine Test.

In carrying out the tests, a Waukesha CFR single-cylinder engine is used. The run is carried out for 15 hours, at the end of which time the intake valve is removed, washed with hexane and weighed. The previously determined weight of the clean valve is substracted from the weight of the valve. The differences between the two weights is the weight of the deposit with a lesser amount of deposit measured connoting a superior additive. The operating conditions of the test are as follows: water jacket temperature 100 C (212 F); manifold vacuum of 12 in Hg, intake mixture temperature of 50.2"C (125"F); air-fuel ratio of 12; ignition spark timing of 40 BTC; engine speed is 1800 rpm; the crankcase oil is a commercial 30W oil. The amount of carbonaceous deposit in milligrams on the intake valves is measured and reported in the following Table I.

The base fuel tested in the above extended detergency test is a regular octane unleaded gasoline containing no fuel detergent. The base fuel is admixed with varying amounts of detergent additives.

TABLE I INTAKE VALVE DEPOSIT TESTS' Additive Carrier Average Washed Description Deposit, mg ppm 11A Engine 12A Engine Base Fuel - 25922 1023 PPG-18004 EDA Carbamates 333 12 6 PPG-18004 167 PPG-18004 EDA Carbamates 200 33 18 PPG-14504 300 1Single evaluations unless noted 2Average of 8 runs 3Average of 4 runs 4The designation PPG-x refers to a monobutyl capped poly(oxypropylene) glycol of about x molecular weight.

prepared as in Example 2.

The tendency of the additives to contribute to ORI was evaluated in a laboratory engine test. The test engine is a CLR single-cylinder, balanced, high-speed, four-cycle engine designed primarily for oil test and research work. It is manufactured by the Laboratory Equipment Corporation ofMooresville, Indiana. The major engine dimensions are: Bore 3.80 In.

Stroke 3.75 In.

Displacement 42.5 Cu. In.

Compression Ratio 8:1 The carburetor, intake manifold, and distributor have been slightly modified to facilitate our test procedure. These modifications have made the engine's ORI characteristics comparable to modern day automobiles.

The test procedure involves engine operation for 80 hours (24 hours a day) on a prescribed load and speed schedule representative of typical vehicle driving conditions. The cycle for engine operation during the test is as follows: TABLE II Deposit Accumulation Cycle CLR Single Cylinder Time in Manifold Engine Mode, Vacuum, Speed, Mode Sec. In. Hq rpm 1. Idle 140 16 900 2. Heavy Cruise, Low Speed 70 7. 2000 3. Light Cruise, Low Speed 140 f3 2000 4. Deceleration 140 ' 18 1800 .5. Heavy Cruise, Low Speed 70 7 2000 6. . Light Cruise, Low Speed 140 .13 2000 7. Idle 210 16 900 8. Heavy Cruise, Low Speed 70 7 2000 9. Light.Cruise,.Low Speed 70 13 2000 10. -Heavy Cruise, High Speed 70 9 2500 11. Light Cruise, High Speed 140 is 2500 12. Deceleration 140 18 1800 All of the test runs were made with the same base gasoline, which was representative of commercial unleaded fuel. The results are set forth in Table III.

TABLE III Laboratory ORI Test Results Combustion Additive, Carrier Concentration, Chamber Description ppm Deposits, q -- -- 3.4 Commercially available nitrogen-containing DC additive 467 -- 7.1 Mineral carrier oil 1600 PPG-1800 EDA Carbamate* 286 1.3 2.5 PPG-1450* 214 PPG-1800 EDA Carbamate* 286 1.6 2.4 PPG-1450* 214 *See Table I Simple arithmetic averages of the results indicate: base fuel gives an ORI of 3.1 and combustion chamber deposits weighing 1.3 g, the commercial additives averaged 6.3 units ORI and had combustion chamber deposits weighing 2.1 g, and the polyether carbamates gave an ORI of 2.5 and combustion chamber deposits averaging 1.5 g. Generally, these results indicate that the polyether carbamates, which have been demonstrated to be excellent inlet system deposit control additives, do not contribute significantly to increasing octane requirements (over base fuel) of the engines in which they are employed.

The test for evaluating the ability of fuel additives to control carburetor deposits employs a 1973 model year, 240 CID, 6-cylinder Ford engine. The word "Ford" is a Trade Mark. The internal bore of the carburetor throttle body is equipped with a thin, removable aluminum sleeve. The difference between sleeve weights determined before and after an engine run represents the change in amount of surface deposit occurring during that run.

For additive evaluation, two test phases are run as set forth in Table IV.

TABLE IV Carburetor Deposit Test Procedure 1. Dirty-Up Phase (Starting with Clean Sleeve Objective: Establish deposits on carburetor sleeve.

Duration: 15 hours.

Operating Cycle: 7 minutes moderate load and speed, 4 minutes idle.

Engine Setup: Crankcase blowby gases routed to carburetor air inlet.

Fuel: Deposit-forming fuel containing heavy FCC component.

Evaluation: Sleeve weights are determined at the beginning and end of the dirty-up phase, and sleeve deposits are rated visually on a scale of0 to 10 (10 = clean).

TABLE IV (continued) Carburetor Deposit Test Procedure 2. Cleanup Phase (Begins with Sleeve Deposits Formed Pursing Dirty- Up Phase Objective: Measure additive performance in cleaning up deposits.

Duration: 4 hours.

Operating Cycle: Same as dirty-up phase.

Engine Setup: Crankcase blowby cases diverted from carburetor inlet - EGR shutoff.

Fuel: Commercial-type gasoline containing additive under test.

Evaluation: The sleeve is reweigh d and rerated visually. Differences between initial and final values represent additive -- .~ effectiveness.

Table V presents average values for the performance of PPG-amine carbamate additives.

Also, presented are values for a commercial deposit control additive having recognized performance in the field. Deposit level changes with a commercial-type unleaded gasoline without additive are also shown.

TABLE V Carburetor Test Results Average Additive Performance Deposit Concen- Weight Visual Deposit tration, Reduc Ratings Runs ppm tion, % Initial Final A -PPG-1800 EDA Carbamatel 4 200 88 493 8.13 3.23 Commercial Additive 8 150 91 5.3 o 8.4 3.1 -None 2 - 63 4.6 e 6.0 1.4 1Visual Deposit rating (10 = clean) ; see Table I 2Similar to product of Example 4 3Data for 3 runs only These data show that the polyether carbamates are as effective carburetor deposit control additives as the recognized commercial additive.

The previously mentioned U.S. Patent 3,359,303 discloses compounds similar in structure to the current compounds. However, by their nature they are limited to amines containing at least two alkylene groups, e.g., the derivative of diethylenetriamine. It has been found that the ethylenediamine derivative of this invention shows unexpectedly superior watertolerance properties, an important consideration for use in fuels.

The following table shows the comparative water-tolerance properties for the ethylenediamine and diethylenetriamine compounds. Also, the water-tolerance properties of the 1,2-propylenediamine and di-(1,2-propylene) triamine derivatives are shown. The polyether in each case was butyl-capped polyoxypropylene material having a molecular weight of about 1483 and containing 25 oxypropylene units. The water-tolerance test is a modified Enjay Waring Blender Haze Test wherein 300 ml of fuel and 3 ml of water are mixed at 13,000 rpm for 30 seconds. The samples of both the water and fuel phases are rated from 1 to 5. For the water phase, 1 indicates free water after 30 minutes: 5 is total emulsion at 20 hours. For the fuel phase, 1 is bright and clear; 5 is extreme haze (no light passing through bottle). A rating of 3 is considered a marginal pass. The tests were run with and without a commercial demulsifier. The demulsifier was used at 5 ppm concentration. Table VI shows the results without demulsifier.

TABLE VI Water Tolerance of Polyether Carbamate Fuel Phase Water Amine Phase 3 hrs 20 hrs Ethylenediamine 3 2 1 Ethylenediamine * 1 3 1 Diethylenetriamine 3 4 1 Diethylenetriamine* 1 4 1 1,2-Propylenediamine 1 2 1 1,2-Propylenediamine* 1 3 1 di-(l,2-propylenetriamine). 1 2 1 di-(1 2-propylenetriamine)* 1 3 1 * Contains 5 ppm of commercial demulsifier This shows that the ethylenediamine derivative is surprisingly superior to the diethylenetriamine derivative. Note that the propylenediamine and dipropylenetriamines were equivalent. Note also that the diethylenetriamine derivative fails to pass even with a demulsifier present.

WHAT WE CLAIM IS: 1. Compounds suitable for use as deposit control additives in internal combustion engines, which compounds are poly(oxyalkylene) carbamates having at least one hydroxy- or C1 - C30 hydrocarbyloxy-terminated poly(oxyalkylene) chain having oxyalkylene units containing 2 to 5 carbon atoms per unit bonded through an oxycarbonyl group to a nitrogen atom of ethylenediamine.

2. The compounds claimed in Claim 1, wherein the poly(oxyalkylene) chain contains from 21 to 30 oxyalkylene units.

3. The compounds claimed in Claim 1 or 2, wherein the oxyalkylene units contain 3 carbon atoms per unit.

4. The compounds claimed in Claim 1, 2 or 3, wherein the group terminating the poly(oxyalkylene) chain is a hydrocarbyloxy group containing from 2 to 20 carbon atoms.

5. The compounds claimed in Claim 4, wherein the hydrocarbyloxy group is butoxy.

6. The compounds claimed in Claim 4, wherein the hydrocarbyloxy group is oleyloxy.

7. The poly(oxyalkylene) carbamate as prepared in Example 2.

8. A hydrocarbon fuel composition comprising a hydrocarbon distillate fuel and a compound as claimed in any one of Claims 1 to 7.

9. A hydrocarbon fuel additive concentrate comprising from 10 to 70 weight percent of a compound as claimed in any one of Claims 1 to 7 and an inert stable oleophilic organic solvent boiling in the range from 150 to 400"F.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. mixed at 13,000 rpm for 30 seconds. The samples of both the water and fuel phases are rated from 1 to 5. For the water phase, 1 indicates free water after 30 minutes: 5 is total emulsion at 20 hours. For the fuel phase, 1 is bright and clear; 5 is extreme haze (no light passing through bottle). A rating of 3 is considered a marginal pass. The tests were run with and without a commercial demulsifier. The demulsifier was used at 5 ppm concentration. Table VI shows the results without demulsifier. TABLE VI Water Tolerance of Polyether Carbamate Fuel Phase Water Amine Phase 3 hrs 20 hrs Ethylenediamine 3 2 1 Ethylenediamine * 1 3 1 Diethylenetriamine 3 4 1 Diethylenetriamine* 1 4 1 1,2-Propylenediamine 1 2 1 1,2-Propylenediamine* 1 3 1 di-(l,2-propylenetriamine). 1 2 1 di-(1 2-propylenetriamine)* 1 3 1 * Contains 5 ppm of commercial demulsifier This shows that the ethylenediamine derivative is surprisingly superior to the diethylenetriamine derivative. Note that the propylenediamine and dipropylenetriamines were equivalent. Note also that the diethylenetriamine derivative fails to pass even with a demulsifier present. WHAT WE CLAIM IS:

1. Compounds suitable for use as deposit control additives in internal combustion engines, which compounds are poly(oxyalkylene) carbamates having at least one hydroxy- or C1 - C30 hydrocarbyloxy-terminated poly(oxyalkylene) chain having oxyalkylene units containing 2 to 5 carbon atoms per unit bonded through an oxycarbonyl group to a nitrogen atom of ethylenediamine.

2. The compounds claimed in Claim 1, wherein the poly(oxyalkylene) chain contains from 21 to 30 oxyalkylene units.

3. The compounds claimed in Claim 1 or 2, wherein the oxyalkylene units contain 3 carbon atoms per unit.

4. The compounds claimed in Claim 1, 2 or 3, wherein the group terminating the poly(oxyalkylene) chain is a hydrocarbyloxy group containing from 2 to 20 carbon atoms.

5. The compounds claimed in Claim 4, wherein the hydrocarbyloxy group is butoxy.

6. The compounds claimed in Claim 4, wherein the hydrocarbyloxy group is oleyloxy.

7. The poly(oxyalkylene) carbamate as prepared in Example 2.

8. A hydrocarbon fuel composition comprising a hydrocarbon distillate fuel and a compound as claimed in any one of Claims 1 to 7.

9. A hydrocarbon fuel additive concentrate comprising from 10 to 70 weight percent of a compound as claimed in any one of Claims 1 to 7 and an inert stable oleophilic organic solvent boiling in the range from 150 to 400"F.