Method for producing polyisobutylenes

#The present invention relates to a process for the preparation of polyisobutenes by cationic polymerization of isobutene or isobutene-containing hydrocarbon streams in the liquid phase in the presence of boron trifluoride as a catalyst, the catalytic activity of the boron trifluoride being eliminated at a desired time by means of a solid deactivator.

#High molecular weight polyisobutenes having molecular weights of up to several 100 000 Dalton have long been known, and their preparation is described, for example, in H. Guterbock: Polyisobutylen und Mischpolymerisate, pages 77 to 104, Springer Verlag, Berlin 1959. The highly reactive polyisobutenes, which as a rule have average molecular weights of from 500 to 5 000 Dalton and a high content of terminal double bonds, i.e. vinylidene groups, of, preferably, substantially more than 60 mol %, can be distinguished from these conventional polyisobutenes.

#Such highly reactive polyisobutenes are used as intermediates for the preparation of additives for lubricants and fuels, as described, for example, in DE-A 27 02 604. For the preparation of these additives, polyisobutene/maleic anhydride adducts, in particular polyisobutenyl/succinic anhydrides, are first produced by reacting the terminal double bonds of the polyisobutene with maleic anhydride and are then reacted with specific amines to give the final additive. The amount of terminal vinylidene groups in the molecule is one of the most important quality criteria for this type of polyisobutene, since it is mainly the terminal vinylidene groups which react in the adduct formation with maleic anhydride, whereas, depending on their position in the macromolecule, the double bonds present further toward the interior of the macromolecule lead to substantially lower conversion, if any at all, without the addition of halogens.

#The average molecular weights (Mn) of the polymers prepared according to the examples were determined by means of gel permeation chromatography, polyisobutenes having defined known average molecular weights being used for calibration. The number average molecular weight Mn was calculated from the resulting chromatograms according to the equation 1 M n = Σ ⁢ ⁢ Σ ⁢ C i ⁢ C i M i

#where Ci is the concentration in each case of an individual polymer species i in the polymer mixture obtained and Mi is the molecular weight of this individual polymer species i. The weight average molecular weight Mw was obtained from the resulting chromatograms with the aid of the formula 2 M W = Σ ⁢ C 1 ⁢ M 1 ⁢ Σ ⁢ C i

#The dispersity D was calculated from the ratio of weight average molecular weight (Mw) to the number average molecular weight (Mn) according to the equation 3 D = M W M n .