FUEL ADDITIVES

Abstract: An additive for gasoline petroleum fuel comprises an oil soluble polyolefin polyamine containing at least one olefinic polymer chain as a first component and a polymer of a C2 to C6 monoolefin, said polymer having a number average molecular weight of up to 500, as a second component. In use of fuel containing the additive in a spark ignition internal combustion engine, detergency is provided and engine deposits, e.g. in the combustion chamber, and valve sticking are reduced.

Description: FUEL ADDITIVES This invention relates to additive compositions and their use in gasoline petroleum fuel. EP-A-0 062 940 (corresponding to US-A-4 357 148) describes a method for operating a spark ignition internal combustion engine which comprises introducing with the combustion intake charge to said engine an octane requirement increase inhibiting amount of (a) an oil soluble aliphatic polyamine, containing at least one olefinic polymer chain, and having a molecular weight in the range from about 600 to about 10,000 and attached to nitrogen and/or carbon atoms of the alkylene radicals connecting the amino nitrogen atoms, and at a concentration of 0.2-1.5 ppm basic nitrogen content based upon the fuel component of said intake charge; and (b) a polymeric component which is (i) a polymer of a C2 to Cβ monoolefin, (ii) a copolymer of a C2 to C~ monoolefin, (Hi) the corresponding hydrogenated polymer or copolymer, or (iv) mixtures of at least two of (i), (ii) and (iii), said polymeric component having a number average molecular weight in the range from about 500 to 1500, and at a concentration of 250-1200 ppmw based upon the fuel component of said intake charge. In a specific example therein, the polymeric component is polyisobutylene of number average molecular weight by osmometry of about 730. US-A-4 832 702 describes the use of polybutyl or polyisobutylamines as fuel additives, particularly as valve-cleaning additives or additives for keeping valves clean, and states that since, in fuel additives, about 50% of their weight can be replaced by polyisobutene (PIB) without loss of efficiency, the addition of PIB is particularly advantageous. Such PIB, it is stated, may have a molecular weight MN of from 300 to 2000, preferably from 500 to 1500. It has now however been found in accordance with this invention that combinations of aliphatic polyamines and copolymers of C2 to Cβ monoolefins can give rise to unexpected advantages when used as additives in gasoline petroleum fuels. Thus, the invention provides in a first aspect the use of an additive in a gasoline petroleum fuel for reducing valve sticking in use of the fuel in a spark ignition internal combustion engine, the additive comprising an oil soluble polyolefin polyamine containing at least one olefinic polymer chain as a first component and a polymer of a C2 to β monoolefin, said polymer having a number average molecular weight of up to 2000, for example up to 1500, as a second component. The above use may additionally be as a detergent or for reducing deposition in the engine or both. It has also been found that unexpected advantages are obtained when said polymer has a number average molecular weight below 500. A combination of technical advantages may be obtained such as improvements in detergency and reduction in combustion chamber deposition, in addition to reduction in valve sticking. Detergency includes the effect of additives in the fuel for washing away deposits and dirt such as may be present in the intake system, e.g. carburettor, due to the fouling thereof. Deposition includes deposition on one or more of the intake system, carburettor, valves, injectors and manifolds as well as in the combustion chamber. Experimental evidence in support of said technical advantages is provided in specific examples in this specification. Moreover, the invention provides a reduced tendency to form washable gum as specified by Japanese Gum Specification No ASTM 0381-87 IP131/89 in comparison with polyolefin polyamine/mineral oil formulations known In the art and used commercially. Thus, in a second aspect, the invention provides a composition comprising a mixture of a major proportion of a gasoline petroleum fuel and a minor amount of an additive as defined in the first aspect of the invention wherein said polymer has a number average molecular weight of up to or less than 500. In a third aspect, the invention provides a liquid concentrate for use in a gasoline petroleum fuel comprising an additive as defined in the first aspect of the invention in solution in a solvent therefor. In a fourth aspect, the invention provides a method of operating a spark ignition which includes introducing to the engine, as a fuel therefor, a composition of the second aspect of the invention. The features of the invention will now be discussed in greater detail POLYOLEFIN POLYAMINE COMPONENT (FIRST) As stated above, examples of such materials are known in the art. Preferably, the polyamine component contains at least one olefinic polymer chain attached to nitrogen atoms or to carbon atoms of the alkylene radicals connecting the amine nitrogen atoms or to both. For example, the polyamine may have the structural formula: where R 1 is hydrogen or polyolefin provided that at least one R 1 is polyolefin; R 2 is alkylene having from 1 to 8 carbon atoms; R 3 is hydrogen or alkyl having from 1 to 6 carbon atoms; and x is from 0 to 5. Each of R 1 , R 2 and R 3 can be independently straight or branched chain. R 1 may, for example, be polyethylene, polypropylene, polybutylene, polyisobutylene, polyethylene/polypropylene, or polyethylene/poly-alpha-methyl styrene. Polyisobutylene is particularly preferred. The polyamine component may be made by reacting an olefinic polymer such as exemplified above with a polyamine. Such polyamines may have, for example, from 2 to 12 nitrogen atoms and from 2 to 40 carbon atoms. They may be derived, for example, from polyalkylene polyamines including alkylene diamines and substituted polyalkylene polyamines. Preferably, the alkylene has 2 to 6 carbon atoms, more preferably 2 to 3 carbon atoms, between nitrogen atoms. Specific examples of such polyamines are primary and secondary low molecular weight aliphatic polyamines such as ethylene diamine, diethylene triamine, triethylene tetramine, propylene diamine, butylene diamine, trimethyl trimethyiene diamine, tetramethylene diamine, diaminopentane or pentamethylene diamine, hexamethylene diamine, heptamethylene diamine, diaminooctane, decamethyleπe diamine, and higher homologues up to 18 carbon atoms. Ethylene diamine is preferred. The number average molecular weight of the polyolefin of the polyamine component is as measured by gas phase chromatography (GPC). Said molecular weight may, for example, be in the range from 600 to 10,000, such as from 900 to 10,000. A preferred range is from 800 to 1800, more preferably from above 1000 to 1800. The polyolefin polyamine component, such as polyisobutenyl amines, and their use as fuel additives are known and are described in, for example, US-A- 3275554 and DE-A-2125039. Methods described in the art for their preparation include halogenating a polyolefin and reacting the resulting halide with a polyamine, and hydroformylating a polybutene or polyisobutene and subjecting the resulting oxo product to a Mannich reaction or amination under hydrogenating conditions, as described in US-A-4 832702. POLYMER COMPONENT (SECOND) The polymer is based on a major amount of a C2 to Cβ olefin, for example a homo or copolymer of ethylene, propylene, butylene (1- or 2-), pentylene or isobutylene. Polyisobutylene is especially preferred. When the polymer is a copolymer, it may be a copolymer of two or more of the specified monomers, or a copolymer of one or more of the specified monomers with a copolymerisable unsaturated monomer. When it is a copolymer, it may be a block or a random copolymer. The number average molecular weight of the polymer is as measured by GPC. Preferably, said molecular weight is in the range of 300 to 500, most preferably in the range of 350 to 450. The polymer may, for example, have a kinematic viscosity at 100°C in the range of 1 to 20 cSt, preferably 4 to 16 cSt, more preferably 8 to 12 cSt. The polymer may be made, for example, by catalysed polymerisation using cationic catalyst systems described in the art such as AICI3/H2O; AICI3/HCI; Et AICI2/HCI; BF3; or Ziegler-Natta type catalysts. PROPORTIONS In the additive included in this invention, the ratio of the first component to the second component may be in the weightrweight ratio within the range of 10:1 to 1 :10, preferably within the range of 2:1 to 1 :6. The proportion of additive in the fuel may be the range of, for example, 20 to 5000 (e.g. 2000), preferably 50 to 2000 (e.g. 500) ppm (weight of additive based on the weight of the gasoline petroleum fuel). When the invention is a concentrate, the solvent therefor may be, for example, a hydrocarbon or an oxygen-containing hydrocarbon. Examples of hydrocarbons are alkanes or aromatic hydrocarbons such as benzene and xylene. Examples of oxygen-containing hydrocarbons are a butanol, a pentanol. and a hexanol. The concentration of the additive in the concentrate may be varied within wide limits according to needs and restrictions. In general, it may be in the range of 5 to 90% by weight, for example 10 to 70% by weight. OTHER ADDITIVE COMPONENTS In the practice of this invention, the additive may be used in combination with other additives, for example additives providing particular properties such as plasticiser esters for example, adipates and mixtures thereof, scavengers, anti- oxidants, ignition improvers, and metal deactivators. Such other additives may, for example, be present in the fuel in the range of 50 to 500 ppm (weight/weight). FUEL The fuels employed are compositions comprising hydrocarbons such as straight chain paraffins, branched chain paraffins, olefins, aromatic hydrocarbons, and naphthenic hydrocarbons. Examples are those with initial boiling points of about 70°F (21 β C) and final boiling points of about 450 β F (232 β C) (ASTM D-86). The fuel components can be derived by any of the conventional refining and blending processes. Synthetic fuels are also included. The additive of the present invention can be added to the fuel as a mixture or separately in any order using conventional fuel additive injection methods. Preferably, the additive is added as a concentrate according to the third aspect of the invention. EXAMPLES The invention will now be particularly described in the following examples in which additive formulations identified as A1 , A2, and C, as defined below, were tested in a General Motors engine of 1.6L displacement valve sticking for inlet valve detergency and combustion chamber deposition. FORMULATIONS Formulations containing a ratio of 1 :1.5 of an aminated polyisobutylene to another component (weighfcweight) were made up and were each added to a sample of the same test gasoline petroleum fuel (identified as REDBOP 8 90811/89). The formulations were as follows where the amounts given in ppm are the amounts of a particular component in admixture in the test fuel (weight per weight of fuel), and where the number average molecular weight are as measured by GPC. A1 - A polyisobutylene polyamine prepared by aminating a polyisobutylene whose number average molecular weight is about 1300 with ethylene diamine dissolved, in a proprietary aromatic solvent based on a mixture of substituted xylenes at 75% by wt ai (258 ppm; 193.5 ppm of polyamine) in admixture with a polyisobutylene whose number average molecular weight is about 450 (384 ppm) and whose kinematic viscosity at 40°C is 110 cSt and at 100°C is 13 cSt. A2 - An aminated polyisobutylene as used in formulation A1 (236 ppm; 177 ppm of polyamine) in admixture with a polyisobutylene as used in formulation A (354 ppm). C - An aminated polyisobutylene as used in formulation A (300 ppm; 225 ppm of polyamine) in admixture with a mineral carrier oil known in the art as a carrier for aminated polyisobutylene (STANCO 600) (450 ppm), said oil having a kinematic viscosity at 40 β C of 113 cSt and at 100 β C of 12 cSt. Formulations A1 and A2 are formulations of this invention, formulation A2 being used at a lower treat rate than formulation A1. Formulation C is not a formulation of this invention and is for comparison purposes, being of similar type to formulations such as those described in the art as being effective as detergents in fuels (for example as described in US-A-3 438 757) and which have been used commercially. Also, in formulation C, the viscosity of the oil is similar to that of the polyisobutylene used in formulations A1 and A2. TESTS The following tests were carried out using one or more samples of fuel in which each of additive formulations A1 , A2 and C had been dissolved. The tests were carried out on the above-described engine which was run on the test fuel under conditions simulating the driving patterns of the police or sales personnel, i.e. mixed loads, urban, highway and country road driving, the daily mileage being from 350 to 500 and there being a cool down phase of about one hour between the engine being switched off and restarted at low ambient temperature. At the end of each run, the following tests were carried out: 1. Valve Sticking Effect The cylinder head was removed and the engine inverted. The ease, or otherwise, with which the valves fell from the cylinder head under their own weight was used as a measure of the valve sticking effect. 2. Inlet Valve Detergency The inlet valves of the engine were weighed and compared with their weights before the run. The average weight of deposition on the inlet valves per valve was calculated therefrom. 3. Combustion Chamber Deposition The cylinder head and valves were removed and each combustion chamber photographed to record the extent of combustion chamber deposition. RESULTS OF TESTS 1. Valve Sticking Effect The results were: Formulation A2: none of the inlet valves of the engine was observed to have stuck after the test. Thus, the inlet valves fell quickly under their own weight with no resistance to their movement. Formulation C: the results were similar to those obtained with Formulation A2 but the inlet valves did not fall quite so readily. 2. Inlet Valve Detergency The average weight of deposit per valve (in mg) is given in the Table below: Fo mulation Average Deposit Weight A1 152 A2 162 C 172 It can be seen that the detergent effect of the formulations of the invention (A1 and A2) is better than that of the known formulation (C). Comparing figures for A1 and A2 shows that the detergent effect is enhanced when a greater concentration of the aminated polyisobutylene is present as in formulation A1. Moreover, although C provides a higher concentration of aminated polyisobutylene, which is a known detergent, in the fuel, the table above shows that its detergent effect is less than that provided by either A1 or A2 thereby illustrating the beneficial effect on detergency of using polyisobutylene in combination with the aminated polyisobutylene as in each of A1 and A2. 3. Combustion Chamber Deposition It was observed that formulations A1 and A2 (i.e. formulations falling within this invention) give rise to limited combustion chamber deposition. The results of the above tests show that additive formulations of this invention can produce a reduction in valve sticking effect, and an enhancement in inlet valve detergency compared with additive formulations of a known general type, and can reduce combustion chamber deposition.

Claims: CLAIMS: 1. The use of an additive in a gasoline petroleum fuel for reducing valve sticking in use of the fuel in a spark ignition internal combustion engine, the additive comprising an oil soluble polyolefin polyamine containing at least one olefinic polymer chain as a first component and a polymer of a C2 to C monoolefin, said polymer having a number average molecular weight of up to 2000, as a second component. 2. The use of claim 1 additionally as a detergent or for reducing deposition in the engine or both. 3. The use of claim 1 or claim 2 wherein said polymer has a number average molecular weight of up to 500. 4. A composition comprising a mixture of a major proportion of a gasoline petroleum fuel and a minor amount of an additive as defined in claim 1 wherein said polymer has a number average molecular weight of up to 500. 5. A liquid concentrate for use in a gasoline petroleum fuel comprising an additive as defined in claim 1 wherein said polymer has a number average molecular weight of up to 500 in solution in a solvent therefor. 6. A method of operating a spark ignition internal combustion engine which includes introducing to the engine, as the fuel therefor, a composition of claim 4. 7. The use, composition, concentrate or method of any of the preceding claims wherein the number average molecular weight of said polymer is in the range of 300 to less than 500. 8. The use, composition, concentrate or method of claim 7 wherein the range is 350 to 450. 9. The use, composition, concentrate or method of any of the preceding claims wherein the weight:weight ratio of the first component to the second component is in the range of 10:1 to 1 :10. 10. The use, composition, concentrate or method of claim 9 wherein the range is 2:1 to 1 :6. 11. The use, composition, concentrate or method of any of any of the preceding claims wherein the proportion by weight of the additive in the fuel is in the range of 50 to 2000 ppm. 12. The concentrate of claim 5 and any of claims 6 to 11 when appendant to claim 5 wherein the solvent is a hydrocarbon or an oxygen-containing hydrocarbon. 13. The concentrate of claim 12 wherein the additive is present in a proportion by weight in the range of 10 to 70%. 14. The use, composition, concentrate or method of any of the preceding claims wherein said polymer is polyisobutylene. 15. The use, composition, concentrate or method of any of the preceding claims wherein the polyamine component contains at least one olefinic polymer chain attached to nitrogen atoms or carbon atoms of the alkylene radicals connecting the amine nitrogen atoms or both. 16. The use, composition, concentrate or method of claim 15 wherein the polyamine component has the structural formula: RlN-R 2 -(NR 2 ) x -NR 3 where R 1 is hydrogen or polyolefin provided that at least one R 1 is polyolefin; R 2 is alkylene having from 1 to 8 carbon atoms; R 3 is hydrogen or alkyl having from 1 to 6 carbon atoms; and x is from 0 to 5, R 1 , R 2 and R 3 being each independently straight or branched chain where appropriate. 17. The use, composition, concentrate or method of claim 16 wherein the polyamine is polyisobutylene aminated with ethylene diamine.

Inventors: BLOCK DIRK, BLOCK, DIRK
Applicants: EXXON CHEMICAL PATENTS INC, EXXON CHEMICAL PATENTS INC.
Application year: 1992
Main classification: C10L1
IPC codes: C10L1, C10L10