Abstract:
Deposits on intake valves in gasoline internal combustion engines are reduced by an additive for fuel compositions comprising a mixture of (1) a polyalkylene succinimide, (2) a polyalkylene and (3) a mineral oil. The invention also comprises a fuel composition made up of a major amount of liquid hydrocarbon fuel such as gasoline or diesel and a minor amount of the aforesaid mixture. In still another aspect the invention comprises a method for removing and/or preventing engine deposits which adversely affect the performance of gasoline powered engines by running the engine with a fuel containing an effective amount of the previously described mixture.

Description:
RELATED APPLICATIONS 
     This application is a continuation-in-part of copending application Ser. No. 292,139, filed on Dec. 30, 1988 now abandoned. 
    
    
     NATURE OF THE INVENTION 
     This invention relates to additives for controlling or preventing engine deposits and to fuel compositions containing these additives. 
     BACKGROUND OF THE INVENTION 
     Hydrocarbyl succinimides, such as those derived from poly-alkylene polyamines, are known materials which have been widely used as fuel detergents. For example, U.S. Pat. No. 4,240,803, which is incorporated herein by reference, describes the use of alkenyl succinimides in gasoline to reduce engine deposits. U.S. Pat. No. 4,482,357, which is also incorporated by reference, discloses additive mixtures for diesel fuels which include a hydrocarbyl succinimide or succinamide and the reduction of coke deposition by the use of these additive mixtures. 
     An object of this invention is to provide an additive for fuel compositions which will contribute to and promote both valve and carburetor cleanliness. 
     SUMMARY OF THE INVENTION 
     Briefly stated this invention comprises in one aspect an additive for fuel compositions comprising a mixture of (1) a polyalkylene succinimide, (2) a liquid polyalkylene and (3) a mineral oil. In another aspect this invention comprises a fuel composition made up of a major amount of gasoline or diesel fuel and a minor amount of the aforesaid mixture. In still another aspect this invention comprises a method for removing and/or preventing engine deposits which can adversely affect the performance of gasoline- or diesel-powered engines by running the engine with a fuel containing an effective amount of the previously described mixture. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The polyalkylenesuccinimide utilized to make the additive composition of this invention is prepared by reacting a polyalkylenesuccinic acid or anhydride, wherein the polyalkylene is derived from a C 2 , C 3 , or C 4  olefin, or mixtures thereof, with a polyalkylene polyamine of the formula 
     
         NH.sub.2 --(RNH).sub.n --R--NH.sub.2 
    
     in which R is an alkylene radical having from 1 to 5 carbon atoms and &#34;n&#34; is from 0 to 10. 
     The polyalkylenesuccinic anhydride can be made in accordance with a prior art process involving the thermal condensation of a polyalkylene or polyalkylene mixture with maleic anhydride. This is conveniently carried out at from about 150° C. to about 250° C., preferably about 175° C. to 225° C. 
     Particularly preferred is the succinic acid or anhydride derived from a polyalkylene such as isobutylene. Suitable polyamines include methylene diamine, ethylene diamine, diethylene triamine, dipropylene triamine, triethylene tetramine, tetraethylene pentamine, pentamethylene hexamine, hexaethylene heptamine, undecaethylene dodecamine, and the like. 
     One series of reactions, showing one possible product, is as follows: ##STR1## 
     In the formula above, R&#39; is polyalkylene containing 12 to 500 carbons, R is alkylene containing 1 to 5 carbon atoms and n is from 0 to 10. 
     The reaction mixture may contain from 1 mole of the anhydride per mole of the amine, or it may have an amount of anhydride equivalent to the total NH functions in the amine, i.e., up to 14 moles of anhydride per mole of amine. 
     Although a mono-succinimide reaction product is shown above, it is to be understood that bis-succinimide reaction products and mixtures of mono-succinimdes and bis-succinimides have utility in the practice of the present invention. As those skilled in the art would recognize, such a bis-succinimide reaction product would have the following structure: ##STR2## wherein, once again, R&#39; is polyalkylene containing 12 to 500 carbons, R is alkylene containing 1 to 5 carbon atoms, and n is from 0 to 10. 
     The polyalkylene component of the additive composition preferably is a liquid polyalkylene where the average number of carbon atoms per molecule is between 12 and 500. Preferably the polyalkylene is a polymer of ethylene or propylene or butylene and even more preferably is polyisobutylene wherein the average number of carbon atoms per molecule is between 12 and 500. 
     The mineral oil can be characterized as one having a viscosity from 100 to 800 SUS at 100° F., and a minimum viscosity index of 90, more typically 91. 
     The three-component additive composition is formulated by mixing the components in the following broad and preferred proportions: 
     
         ______________________________________           Parts by Weight           Range  Preferred Range______________________________________Polyalkylene succinimide             20 to 30 22 to 28Polyalkylene      35 to 55 40 to 50Mineral oil (100 SUS)             24 to 36 27 to 33orMineral oil (700 SUS)             32 to 42 35 to 39______________________________________ 
    
     In general, the invention contemplates the use of the additive in a fuel composition in a concentration of from 80 lbs. to 400 lbs. per 1,000 barrels of fuel, and most preferably, from 120 lbs. to 250 lbs. per 1,000 barrels, the base gasoline containing less than 0.1 weight percent sulfur. Since sulfur and olefins are believed to contribute to gum formation, their reduction is advantageous in obtaining good cleanliness performance. The gasoline can also contain conventional additives such as antioxidants, metal deactivators, lead alkyls, lead scavengers, and corrosion inhibitors. 
    
    
     Having described the invention broadly, the following specific examples will illustrate it. It should be understood that the Examples are illustrative only and are not intended to limit the invention. 
     EXAMPLE 1 
     Premium unleaded gasoline containing various quantities of a polyisobutylene succinimide, polyalkylene, and a mineral oil mixed in the ratios shown below were evaluated in a single cylinder CLR engine using a 10 W-30 mineral oil lubricant. After 40 hours of operation at 1100 rpm and 10 to 12 inches manifold vacuum, the intake valve was removed, its combustion chamber side cleaned and the gross weight determined. Deposits were then removed mechanically and the valve&#39;s tare weight was measured in order to calculate the net weight of the deposits. 
     The table below presents the results for several runs with premium unleaded gasoline containing various additive package components alone and in specific combinations. As indicated, use of polyisobutylenesuccinimide alone at 50 pounds per 1000 barrels (Run B) increased ITV deposits 171% compared to Run A in which no additives were present in the fuel. The use of 60 pounds of mineral oil per 1000 barrels (Run D) also increased ITV deposits, but only slightly. Polyalkylene alone at 100 pounds per thousand barrels (Run C) did reduce intake valve deposits to 37% of Run A. However, significant further reductions in deposits were obtained when packages of the type described herein were used (Runs E and F). 
     
                                           TABLE I__________________________________________________________________________CLR Intake Valve Cleanliness Test ResultsConcentration,Pounds Per 1000 Barrels Of Fuel            100 SUS                 700 SUS       Poly-            Mineral                 Mineral                      Intake Valve DepositsPkg.   PIB-Succinimide       alkylene            Oil  Oil  Weight, Mgs.                             Percent of Base__________________________________________________________________________A  --       --   --   --   .sup. 298.sup.1                             --B  50       --   --   --   511    171C  --       100  --   --   109     37D  --       --   60   --   351    117E  50        90  60   --    54     18F  56       133  --   111   10     3__________________________________________________________________________ .sup.1 Average of 8 runs 
    
     Premium unleaded gasoline, for example, Phillips J alone and containing additive packages C and E were evaluated in the standard CRC carburetor cleanliness test. After 20 hours of operation with the standard cycle, the tared carburetor sleeve was removed and weighed to determine the weight of deposits thereon. Table II below presents the results of several runs. Use of a polyalkylene package in C provided no carburetor keep-clean performance. The package E embodying this invention provided significant improvements in carburetor cleanliness. 
     
                                           TABLE II__________________________________________________________________________Carburetor Cleanliness Test ResultsConcentration,Pounds Per 1000 Barrels Of Fuel            LightPIB-        Poly Mineral                 Carburetor Sleeve DepositPkg.   SUCCINIMIDE       Alkylene            Oil  Weight, Mgs.                        Percent of Base__________________________________________________________________________A  --       --   --   24     --C  --       100  --   23     96E  50        90  60    2      8__________________________________________________________________________ 
    
     Although the present invention has been described with preferred embodiments, it is to be understood that modifications and variations may be utilized without departing from the spirit and scope of this invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the amended claims.