Title:
Multifunctional gasoline additive compositions
United States Patent 3909214


Abstract:
Disclosed herein are gasoline-soluble, gasoline additive compositions useful to clean carburetors and to control intake valve deposits in spark ignition engines. The compositions consist essentially of, in combination, (i) aliphatic C4 to C10 monoamine salts of branched chain primary C8 to C16 alkyl acid esters of orthophosphoric acid, and (ii) liquid polypropylene having a molecular weight between about 600 to 1200.



Inventors:
POLSS PERRY
Application Number:
05/383252
Publication Date:
09/30/1975
Filing Date:
07/27/1973
Assignee:
E. I. Du Pont de Nemours and Company (Wilmington, DE)
Primary Class:
Other Classes:
585/4, 585/10, 585/13, 585/14
International Classes:
C10L1/14; C10L1/16; C10L1/26; (IPC1-7): C10L1/26
Field of Search:
44/58,72,DIG.4
View Patent Images:



Primary Examiner:
Wyman, Daniel E.
Assistant Examiner:
Smith, Mrs. Harris Y.
Attorney, Agent or Firm:
Costello, James A.
Claims:
The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows

1. A gasoline-soluble, gasoline-additive composition consisting essentially of

2. A composition according to claim 1 wherein the neutral salt is the amine salt of a mixture of esters comprising from about 40 to 60 mole percent of mono-C8 to C13 Oxo-alkyl dihydrogen phosphate and 60 to 40 mole percent of di- C8 to C13 Oxo-alkyl monohydrogen phosphate.

3. A composition according to claim 2 wherein the amine salt is the isobutylamine salt.

4. A composition according to claim 2 wherein the amine salt is the 2-ethylhexylamine salt.

5. A composition according to claim 3 wherein the mixture of esters comprises mono-Oxo-tridecyldihydrogen phosphate and di-Oxo-tridecyl monohydrogen phosphate.

6. A composition according to claim 4 wherein the mixture of esters comprises mono-Oxo-tridecyldihydrogen phosphate and di-Oxo-tridecyl monohydrogen phosphate.

7. A composition according to claim 1 wherein the polypropylene has a molecular weight of about 800 to 900.

8. A composition according to claim 6 wherein the polypropylene has a molecular weight of about 800 to 900.

9. A solution concentrate of the composition of claim 1 in a hydrocarbon solvent wherein there is from about 10 to 50% by weight of solvent and from about 50 to 90% by weight of the composition of claim 1.

10. A gasoline composition containing from about 0.02 to 0.10% by weight of the composition of claim 1, having up to about 0.25%, by weight of the composition, of top cylinder oil.

Description:
BACKGROUND OF THE INVENTION

One of the operational difficulties of internal combustion engines in motor vehicles is caused by the formation of deposits on the tulips of the intake valves. These deposits can build up sufficiently to cause improper valve closing with attendant rough idling, loss of power and in severe cases, valve burning. It is generally believed that the two primary sources of these deposits are fuels and lubricating oils. Automotive gasolines frequently contain small amounts of relatively unstable, high molecular weight compounds. A certain amount of lubricating oil also passes between the valve stem and valve guide. Upon exposure to air and the relatively high temperatures of the intake valve tulips, these components from the fuel, and the lubricating oil as well as certain additives in the lubricating oil undergo a series of reactions which probably involve oxidation and thermal decomposition, leading to the formation of solids or semi-solid residues which are called deposits.

Another of the operational difficulties is that caused by the accumulation of deposits in the carburetor, particularly on the throttle plate and on the surrounding wall. Harmful deposits are derived from contaminants in fuel and air, particularly from fumes vented from the crankcase as well as from materials introduced via the exhaust gas recirculation system normally present. The accumulation of the deposits in the carburetor results in rough idling and frequent stalling of the engine.

A need exists for a fuel additive which is effective in overcoming the described operational difficulties of internal combustion engines, which is effective at low usage levels and which is multifunctional in activity, that is, is capable of overcoming several of the difficulties. The compositions of this invention fulfill the need.

SUMMARY OF THE INVENTION

This invention concerns a gasoline-soluble, gasoline-additive composition consisting essentially of

I. a gasoline-soluble neutral salt of a C4 to C10 aliphatic monoamine wherein each radical attached to the amine nitrogen is attached through a saturated carbon atom and a C8 to C16 branched chain primary alkyl acid ester of orthophosphoric acid, and

Ii. from about 1 to 50 parts by weight per part of said salt of liquid polypropylene having a number average molecular weight in the range of about 600 to 1200.

Included within the scope of this invention are solution concentrates of the additives in a suitable carrier solvent such as a liquid hydrocarbon. Such concentrates contain from about 10 to 50% by weight solvent and from about 50 to 90% by weight of the additive compositions described herein.

Also included are gasoline compositions containing from about 0.02 to 0.10% by weight of the compositions described herein.

The hydrocarbon fuel in which the additive of the invention is used is gasoline or a mixture of hydrocarbons boiling in the gasoline boiling range. For convenience, such fuels are referred to herein as gasoline. The base fuel (gasoline) can consist of straight chain or branched chain paraffins, cycloparaffins, olefins, and aromatic compounds or any mixture of such hydrocarbons, obtainable from straight run naphtha, polymer gasoline, natural gasoline, thermally or catalytically cracked hydrocarbon stocks and catalytically reformed stocks. The gasoline may contain varying amounts of conventional fuel additives such as antiknock compounds including tetramethyllead, tetraethyllead, mixed alkyl lead, scavenging agents, dyes, antoxidants, anti-icing agents, rust inhibitors, detergents, anti-preignition agents and the like.

The term "aliphatic monoamine" means a compound which contains only one amino nitrogen to which is attached one to three aliphatic radicals and is sufficiently basic to form neutral salts with the defined alkyl acid phosphates. The amines can be primary, secondary or tertiary amines and the aliphatic radical attached to the nitrogen may be alicyclic or acyclic. The aliphatic radical can be saturated or unsaturated, provided that the carbon atom attached to the nitrogen atom is a saturated carbon. The amines are generally unsubstituted hydrocarbon amines.

DETAILS OF THE INVENTION

The amine salts are prepared by reacting primary alkyl acid phosphates wherein the primary alkyl groups have 8 to 16 carbon atoms in branched chain configuration with aliphatic monoamines containing 4 to 10 carbon atoms and wherein each aliphatic radical attached to the amine nitrogen is attached through a saturated carbon atom.

Branched chain primary alkyl acid phosphates are those phosphate esters in which only one or two of the three acidic hydrogen atoms of orthophosphoric acid have been replaced with branched chain primary alkyl groups, i.e. they are monoalkyl dihydrogen phosphates and dialkyl hydrogen phosphates. Such alkyl acid phosphates can be obtained according to known methods which involve reacting an alcohol with phosphorus pentoxide (P2 O5). Usually about 2 to 4 moles of alcohol per mole of P2 O5 are used. Preferably about 3 moles of alcohol per mole of P2 O5 are used. When 3 moles of alcohol per mole of P2 O5 are used, the reaction mixture is theoretically an equimolar mixture of monoalkyl dihydrogen phosphate and dialkyl hydrogen phosphate, but the range may vary from about 40 to 60 mole percent of monoester to about 60 to 40 mole percent of dialkyl ester. These mixtures of mono- and dialkyl esters are preferred but other mixtures as well as the monoesters or diesters alone, can also be used.

For the preparation of the branched chain primary alkyl acid phosphates, the alcohol used will be a branched chain primary alcohol of 8 to 16 carbon atoms, preferably 8 to 13 carbon atoms or a mixture of two or more of such alcohols. The preferred branched chain primary alcohols are those prepared by the well-known Oxo process and therefore the alkyl groups of the preferred alkyl acid phosphates will have branched chain primary alkyl groups derived from Oxo-process alcohols.

Normally, a molecule of amine is used for each molecule of monoalkyl dihydrogen phosphate and for each molecule of dialkyl hydrogen phosphate. The resulting salts are substantially neutral, i.e. they exert a pH of between 6 and 7 in water.

Examples of suitable primary amines are n-butylamine, isobutylamine, isoamylamine, n-hexylamine, cyclohexylamine, octylamine, 2-ethylhexylamine, 1,1,3,3-tetramethylbutylamine, and commercial t-nonylamine which consists mainly of C9 amine with small amounts of C8 and C10 amines. Examples of secondary amines are di-n-butylamine, di-sec-butylamine, di-isobutylamine and di-amylamine. Examples of suitable tertiary amines include N,N-dimethylcyclohexylamine and N,N-diethylcyclohexylamine.

Preferably, the amine will be an alkyl primary monoamine of 4 to 8 carbon atoms and most preferably 8 carbon atoms. If an amine is a secondary amine or a tertiary amine, it is preferable that it contain a total of at least 8 carbon atoms. The most preferred amines are 2-ethylhexylamine and isobutylamine.

A preferred class of amine salts comprises substantially neutral salts wherein the alkyl acid phosphates component is a mixture of about 40 to 60 mole percent of mono C8 to C13 Oxo-alkyl dihydrogen phosphate and 60 to 40 mole percent of di- C8 to C13 Oxo-alkyl monohydrogen phosphate. Particularly preferred because of their low cost and exceptional detergency effect are the isobutylamine salt and the 2-ethylhexylamine salt of the above mixture of mono-Oxo-tridecyldihydrogen phosphate and di-Oxo-tridecyl monohydrogen phosphate. The useful amine salts and the methods of preparation as set out above are more fully described in U.S. Pat. No. 3,228,758 which is incorporated herein by reference.

The polypropylene component of the novel composition consists essentially of a homopolymer of propylene having a molecular weight of about 600 to 1200. The polypropylene can be prepared by any of the art-known polymerization processes, e.g. "Linear and Stereoregular Addition Polymers" Gaylord and Mark, Interscience Publishers, New York, N.Y., 1959.

The molecular weights referred to herein are number average molecular weights as determined by vapor pressure osmometry (ASTM D2503). In the 600 to 1200 molecular weight range, the polypropylenes are liquids at normal temperatures, have 100°F. SUS viscosity of from about 2500 to about 70,000, and are highly soluble in hydrocarbons. SUS viscosity is determined according to ASTM D445-446. The preferred polypropylene has a molecular weight in the range of 800 to 900.

Normally, the proportion of polypropylene to amine phosphate salt is such that there is present from about 1 to 50 parts of polypropylene for each part of amine phosphate salt, preferably about 2 to 30 parts, most preferably about 4 to 15 parts. The two components can be added separately to the gasoline or they can be added in combination or as a concentrate of the combination in a suitable carrier.

The concentrate will contain from about 10 to 50 percent by weight of the solvent, and preferably from about 15 to 30 percent by weight of the solvent. Suitable carrier solvents include such hydrocarbons as hexane, isooctane, kerosene, benzene, toluene, xylene and the like. Commercially available mixed xylenes are the preferred solvent. Representative concentrates contain from about 1 to 45 percent by weight of amine phosphate, from about 25 to 88 percent by weight of polypropylene and from about 10 to 50 percent by weight of hydrocarbon solvent. Most preferably, the solvents will contain from about 2 to 28 percent by weight of amine phosphate, from about 47 to 82 percent by weight of polypropylene and from about 15 to 30 percent by weight of solvent, and most preferably will contain from about 3 to 17 percent by weight of amine salt, from about 56 to 80 percent by weight of polypropylene and from about 15 to 30 percent by weight of solvent.

The most preferred additive concentrate of the invention contains: 3 to 17 percent by weight of the 2-ethylhexylamine salt of a mixture of mono-Oxo-tridecyl dihydrogen phosphate and di-Oxo-tridecyl hydrogen phosphate; 56 to 80 percent by weight of polypropylene having a molecular weight of about 850; and 15 to 30 percent by weight of a hydrocarbon solvent consisting essentially of mixed xylenes. When added to gasoline in amounts of 50 to 250 lbs./1000 barrels, which corresponds to 0.02 to 0.10 percent by weight, this composition will provide from 0.0008 to 0.017 percent of the amine salt and from 0.011 to 0.08 percent of the polypropylene. The preferred 75 to 125 lbs./1000 barrels dosage provides from about 0.0012 to 0.0085 percent of the amine salt and from about 0.017 to 0.04 percent of the polypropylene.

The designed mode of operation of newly designed automotive engines involving such conditions as higher intake air temperatures, leaner fuel/air ratio, and retarded spark timing, together with auxiliary devices to control exhaust emissions of undesirable components, have caused the intake valves, particularly the tulip portions of the intake valves to operate at considerably higher temperatures than those of the older automotive engines, such temperature increase being about 130° to 140°F. on the average. It is believed that these higher intake valve temperatures prevent the additives suggested in the art for controlling intake valve deposits from being effective in the "hotter" engines. It is unexpected that the combination of amine phosphate salt and polypropylene of the invention is highly effective in controlling deposit accumulation on intake valves of hotter engines.

It is generally believed that deposits are formed on the intake valves by pyrolysis and oxidation of fuel components, fuel additives, lubricants and lubricant additives. Based on that belief it would have been expected that polypropylene having a polymer chain consisting of --CH2 (CH3)CH-- units would be quite susceptible to oxidation and deposition because of the presence of readily oxidizable carbon atoms containing reactive tertiary hydrogen. Unexpectedly, the composition of this invention does not contribute to deposition but, rather, contributes to controlling such deposition.

It has also been discovered, unexpectedly, that combining a polypropylene with an amine phosphate salt of the invention provides carburetor cleanup efficiency considerably in excess of that expected from the cleanup performance of either the amine phosphate or the polypropylene alone.

As has been discussed, fuel additives other than those taught herein can be employed for various purposes in a gasoline composition that also contains the novel additives. One such additive is a nonvolatile lubricating mineral oil, e.g. solvent extracted bright stock having a viscosity at 100°F. of 500 to 1500 SUS. These oils, often referred to as top cylinder oils, are used in amounts of 0.04 to 0.25% by weight of the fuel composition, preferably about 0.16% by weight.

The following Examples illustrate this invention. Employed in each Example was the composition of the invention made according to the following preparative procedure.

PREPARATION

142 grams (1 mole) of P2 O5 was gradually stirred into 600 grams (3 moles) of Oxo-tridecyl alcohol. During the addition of the P2 O5, the temperature was allowed to rise to 65°C. and held thereabouts by external cooling. After the addition of the P2 O5 was completed, the reaction mass was stirred at about 65°C. for 12 hours, when it was shown by potentiometric titration to consist essentially of an approximately 1:1 molar mixture of mono-Oxo-tridecyl dihydrogen phosphate and di-Oxo-tridecyl monohydrogen phosphate.

To the reaction mass, was added, dropwise, 258 grams (2 moles) of 2-ethylhexylamine, with the temperature kept below 65°C., to produce the mixed 2-ethylhexylammonium mono- and di-Oxo-tridecyl phosphates as a viscous amber oil. The mixed phosphates were then combined with polypropylene in the amount and of the M.W. as shown in the Tables.

EXAMPLE 1

This Example illustrates the ability of the additive combination of the invention to clean up a dirty engine as demonstrated by the carburetor detergency test described below.

Chevrolet 6 cylinder, 230 cu. in. engines having Carter No. 3511-S carburetors and ice towers with heaters were used. One engine was used to produce, in the shortest time, sufficient throttle body deposit for the clean-up phase of the test. Since the deposit accumulation phase of the test is carried out over a period of about 10 hours and the clean-up phase of the test requires about 50 hours, by utilizing one engine for deposit accumulation and several engines for the clean-up portion of the test, the testing may be accomplished in the shortest time. In the deposit accumulation engine the ring gap of the top piston ring was increased by 1/8 to 0.138 inch and the ring was installed in place of the second compression ring, leaving the top ring groove empty thus increasing the blowby. The total blowby was directed to the carburetor air cleaner from the dome cover. The air cleaner element was eliminated. The exhaust line was modified to supply engine exhaust to the carburetor air cleaner.

The engine was operated under the following conditions: the distributor vacuum advance was eliminated to maintain spark advance of 4° before top center; engine speed at 700 ± 10 rpm; water outlet temperature 175 ± 2.5°F.; air/fuel mixture at maximum vacuum; carburetor air cooled by passage through an ice tower and then reheated to 90°-95°F.; and engine exhaust supplied to carburetor air inlet as described below.

The fuel used was MS-08, an industry standard fuel used for Sequence MS oil testing. The engine was started with the exhaust feed valve to engine inlet air closed. The speed was adjusted to 700 rpm at maximum vacuum. The exhaust feed value was opened and the engine speed maintained at 700 rpm. The exhaust feed valve setting is critical. The setting was such as to feed the maximum amount of exhaust that the engine would accept and still operate smoothly without stalling. The engine was operated for about 10 hours or until it could no longer be kept running under these conditions. The carburetor was removed and rated using a visual rating chart. A rating of 100 is clean. If a rating cleaner than 30 is obtained, additional deposit accumulation was required.

For the clean-up phase of the test, the "dirty" carburetor was installed in another engine and the operating conditions described above were used except that normal piston rings were used and the blowby and exhaust were not fed into the air inlet. Before the test new spark plugs were installed, SAE 30 low detergent oil placed in the crankcase and the air cleaner housing and exhaust system were cleaned.

The clean-up procedure was followed for 50 hours in five 10-hr. segments, the ratings being made at appropriate intervals to determine the amount and speed of clean-up. The percent clean-up was determined according to the following formula ##EQU1## wherein RD is the carburetor rating after deposit accumulation and RO is the carburetor rating after clean-up.

The results with base fuel (MS-08) alone and base fuel containing additive components individually and in combination are summarized below in Table 1. The amine phosphate employed was the 2-ethylhexylamine salt of mixed mono-Oxo-tridecyldihydrogen phosphate and di-Oxo-tridecylmonohydrogen phosphate. The results show that the additive combination of the invention is effective in cleaning deposits from dirty carburetors. The cleanup effect of the combination is greater than that which would be expected on the individual performance of polypropylene or amine phosphate salt.

TABLE 1 ______________________________________ Carburetor Detergency Polypropylene Amine 850 M.W. Phosphate Run No. Wt.% Wt.% Clean-up ______________________________________ 1 None None 16 2 None 0.003 21 3 None 0.006 21 4 0.038 None 21 5 0.038 0.003 27 6 0.038 0.006 32 7 0.06 0.003 29 ______________________________________

EXAMPLE 2

This Example demonstrates the unexpected efficiency of the composition of the invention in controlling intake valve deposit accumulation.

Valve Deposit Test

In the first test the engine used was a 1968, 250 cu. in. 6 cylinder Chevrolet engine equipped with "Power-Glide" transmission and inertia flywheel. The engine was on a test stand equipped with a dynamometer to absorb the power output. The heads were completely reconditioned, deposits removed from piston tops and carburetor overhauled. One of the intake valves had a thermocouple lead attached to the tulip for recording temperature. New PCV valve, spark plugs, points and gasoline filter were installed. The oil filter was changed and 10W-30 oil put in. The fuel used was previously described MS-08. The fuel contained tetraethyllead (2.9 g. Pb/gal.) as well as 0.5 theory ethylene dibromide and 1.0 theory ethylene dichloride.

The test was performed by operating the engine for 100 one-hour cycles. Each cycle consisted of the following conditions:

Time Interval Engine Speed, Dyno Speed (min.) rpm rpm Throttle ______________________________________ 0-5 -- 1300 ± 50 Idle-WOT* 5-8 600 -- Idle 8-12 -- 1700 ± 50 Idle-WOT* 12-15 600 -- Idle 15-18 -- 2050 ± 75 Idle-WOT* 18-21 600 -- Idle 21-26 -- 1300 ± 50 Idle-WOT* 26-29 600 -- Idle 29-34 -- 2800 ± 75 Idle-WOT* 34-60 600 -- Idle ______________________________________ *5 sec. idle, 5 sec. wide open throttle

The engine coolant fluid inlet and outlet temperatures, the engine oil temperature and pressure, the transmission oil temperature and the engine and dynamometer speeds were recorded. The oil and spark plugs were changed at 50 hours.

At the end of the 100 cycles, the preweighed intake valves were removed, cleaned by scraping off all but tulip deposits and weighed again. The valve tulip temperature measured by the thermocouple during the test ranged from about 310° to 490°F. with the average temperature 392°F. The results are summarized in Table 2.

TABLE 2 ______________________________________ Amine Valve Phosphate Deposit Polymer Salt Wt. g. (M.W.) Wt.% Wt.% (Av.) ______________________________________ None -- None 1.38 Polypropy- lene (850) 0.031 0.003 0.30 ______________________________________

In the second test, designed to have the intake valves operate at higher temperatures than in the first test, the following procedure and conditions were used.

Buick Intake Valve Deposit (IVD) Test

Buick Electras (1971) with 435 CID, low compression engines (8.5:1) equipped with 4-barrel carburetors and automatic transmissions were used. Air conditioning, standard equipment in these automobiles, was used. Completely reconditioned heads with weighed intake valves were installed before tests. One of the intake valves had a thermocouple lead attached to the tulip for recording temperature. Deposits from piston heads were removed and the intake manifold was solvent-cleaned. New spark plugs, points, PCV valve, air filter and oil filter were installed. Carburetor adjustments and timing were carried out according to the manufacturer's specifications.

Mileage accumulation was carried out on a Programmed Chassis Dynamometer (PCD) according to the following schedule.

______________________________________ Time in Mode Mode (sec.) Conditions, mph ______________________________________ 1 60 Idle 2 20 Accelerate to 70 3 30 Alternate acceleration/ deceleration between 60 and 70 at 5 sec. intervals 4 25 Decelerate to 40 5 15 Accelerate to 70 6 100 Repeat Modes 3, 4, 5 and 3 7 25 Decelerate to idle 8 -- Repeat above for 110 hours ______________________________________

At the conclusion of the test, deposits on the intake valves were weighed and expressed as g./valve. The intake valve tulip deposits were also rated using the standard CRC merit rating scale wherein a clean valve has a rating of 10. Deposits on the valve stem were also rated with a clean stem having a rating of 10. Stem rating is carried out by comparison with a standard photographic scale.

The valve tulip temperature measured by the thermocouple during the test ranged from about 480° to 590°F. and averaged 527°F. The results of the tests using the above-described MS-08 fuel and the additive of the Preparation are summarized in Table 3.

As the data indicate, excellent control of deposits is shown by the weights of deposits, tulip and stem ratings. Incorporatioin was made of 0.08 wt. % of top cylinder oil in the fuel composition containing polypropylene and 2-ethylhexylamine salt of the mixed mono- and di-Oxo-tridecyl phosphate (Run 7) to provide outstanding control of intake valve deposits. The top cylinder oil used was solvent extracted bright stock 29.5° API Gravity, viscosity at 100°F., 763 SUS, viscosity at 210°F., 78 SUS.

TABLE 3 __________________________________________________________________________ Amine IVD Polymer (M.W.) Phosphate g./Valve % Tulip Rating Stem Rating Run No. 0.038 Wt. % (Wt. %) (Av.) Reduction ΔRating ΔRating __________________________________________________________________________ 4 None None 2.32 -- 7.1 -- 5.1 -- 5 Polypropylene 0.003 0.85 63 7.6 +0.5 9.5 +4.4 (850) 6 Polypropylene 0.004 1.20 48 7.1 0 8.9 +3.8 (850) 7 Polypropylene 0.003 0.25 89 9.0 +1.9 9.8 +4.7 (850) __________________________________________________________________________