1. Field of the Invention
The present invention relates to reaction products of polyisobutenes having an average degree of polymerization P of from 10 to 100 and a content E of from 60 to 90% of double bonds which can be reacted with maleic anhydride, where E=100% would correspond to the theoretical value for the case where each molecule of the polyisobutene has such a reactive double bond, with oxides of nitrogen or mixtures of oxides of nitrogen and oxygen.
The present invention furthermore relates to the use of these reaction products as fuel and lubricant additives and to gasoline engine fuels and lubricants containing these reaction products.
2. Discussion of the Background
The carburetor and intake system of gasoline engines, as well as injection systems for metering fuel into gasoline and diesel engines, are contaminated with impurities which are caused by dust particles from the air, uncombusted hydrocarbon residues from the combustion space and the crankcase vent gases passed into the carburetor.
The residues shift the air/fuel ratio in the idling state and in the lower part-load range so that the mixture becomes richer and the combustion more incomplete and in turn the proportions of uncombusted or partially combusted hydrocarbons in the exhaust gas increase and the gasoline consumption rises.
It is known that these disadvantages can be avoided by using fuel additives for keeping valves and carburetor or injection systems clean (M. Rossenbeck in Katalysatoren, Tenside, Mineraloladditive, Editors J. Falbe and U. Hasserodt, page 223 et seq., G. Thieme Verlag, Stuttgart, 1978).
Depending on the mode of action, but also on the preferred place of action of such detergent additives, a distinction is now made between two generations of such assistants.
The first generation of additives could prevent only the formation of deposits in the intake system but could not remove existing deposits, whereas the additives of the second generation can accomplish both (keep-clean and clean-up effect) and can do so because of their excellent heat stability, in particular in zones at relatively high temperatures, ie. in the intake valves.
In general terms, the molecular structural principle of fuel detergents can be expressed as the linking of polar structures with generally relatively high molecular weight, nonpolar or lipophilic radicals.
Typical members of the second generation of additives are often products based on polyisobutenes in the nonpolar moiety. Among these in turn, additives of the polyisobutylamine type are particularly noteworthy.
U.S. Pat. No. 3,576,742 (1), filed in 1968 and granted in 1971, describes reaction products of branched long-chain aliphatic olefins, for example polypropylene, polyisobutylene or copolymers of ethylene and isobutylene, and oxides of nitrogen as detergents for lubricants. These olefins are prepared from lower olefins of 2 to 6 carbon atoms by conventional polymerization methods. In the resulting nitro-containing reaction products, the presence of further functional groups, such as hydroxyl, nitroso, nitrate, nitrite or carbonyl, and the relative proportions thereof are unknown. The structure and composition of these olefins are thus undefined.
DE-C 27 02 604 (2) published in 1978 describes a preparation process for polyisobutenes having an average degree of polymerization of from 10 to 100, by means of which highly reactive polyisobutenes, ie. those having predominantly terminal double bonds, were obtained for the first time. On the other hand, the polyisobutenes prepared by conventional polymerization methods, as in (1), have only a low content of terminal double bonds.
The nitro-containing reaction products disclosed in (1) and based on conventional polyisobutene do have a certain action as lubricant additives, but this action is still unsatisfactory. Furthermore, it is said that the compositions can also be used as additives for fuels for gasoline engines.