Method for producing halogen-free reactive polyisobutene

Details Method for producing halogen-free reactive polyisobutene Method for producing halogen-free reactive polyisobutene

1999-08-06

2002-08-27

Teskin, Fred (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S095000, C526S101000, C526S103000, C526S106000, C526S107000, C526S130000, C526S172000, C526S348700

Reexamination Certificate

active

06441110

ABSTRACT:

The present invention relates to a process for preparing halogen-free, reactive polyisobutene;having a terminal double bond content of more than 50 mol % and an average molecular weight A M
n
of 280-10000 dalton by the cationic polymerization in the liquid phase of isobutene or hydrocarbon mixtures containing the isobutene.
The polymerization of isobutene yields an inseparable mixture of polyisobutenes, in which the position of the double bond varies between the individual polyisobutenes. Polyisobutenes of formula
wherein n is the degree of polymerization which in turn is derived from the average molecular weight M
n
of the polyisobutene prepared, contain terminal C—C double bonds of the vinylidene type which are herein also referred to as &agr;-olefinic double bonds owing to their position in the polyisobutene molecule. Accordingly, the double bonds in polyisobutenes of formula II
are referred to as &bgr;-olefinic. If the polymerization of isobutene is carried out without taking special measures, a random mixture is formed which comprises polyisobutenes having &agr;-olefinic, i.e. terminal, double bonds, &bgr;-olefinic double bonds and double bonds located further toward the interior of the polyisobutene molecule. The terminal double bond content and the &bgr;-olefinic double bond content of a polyisobutene product prepared by a particular process are both reported in mol %.
Polyisobutenes having molecular weights of up to 100000 dalton are known. These olefins are usually prepared by Lewis acid-catalyzed isobutene polymerization employing aluminum chloride, alkylaluminum chloride or boron trifluoride as Lewis acids, as described, for example, in H. Guterbock, Polyisobutylene und Mischpolymerizate, p. 77-104, Springer Verlag, Berlin, 1959. However, the resulting polymers have a relatively low vinylidene type terminal C—C double bond content of less than 10 mol %.
In contrast, reactive polyisobutene (PIB) having molecular weights of usually 500-5000 dalton has a high terminal vinylidene group content of, preferably, more than 50 mol %. These reactive polyisobutenes are used as intermediates in the preparation of lubricant and motor fuel additives as described, for example, in DE-A 27 02 604 (see U.S. Pat. No. 4,152,499). These additives are prepared by initially reacting polyisobutene with maleic anhydride. The preferred reactive sites for this reaction are the terminal double bonds of the vinylidene type, whereas double bonds located further toward the interior of the macromolecule react to a lesser extent if at all, depending on their position in the molecule. The polyisobutene/maleic anhydride adducts formed are then reacted with certain amines to give the corresponding additives. It is therefore absolutely necessary for polyisobutenes used as starting materials for the abovementioned additives to have a high terminal double bond content. The same applies to the preparation of the polyisobuteneamines of EP-A 244 616 (see U.S. Pat. No. 4,832,702) which are also used as motor fuel additives and which are prepared by hydroformylation of the reactive polyisobutene and subsequent reductive amination of the resulting polyisobutene aldehyde. For this process, preference is likewise given to using polyisobutene having a high terminal double bond content, but &bgr;-olefinic polyisobutenes also give the desired product when the hydroformylation is carried out using cobalt catalysts, owing to their double bond isomerization activity.
The preparation of reactive polyisobutene by homogeneously catalyzed polymerization of isobutene is already known. According to DE-A 27 02 604, for example, a polyisobutene product having a terminal double bond content of up to 88% is obtained by reacting isobutene in the presence of boron trifluoride. EP-A 145 235 (see U.S. Pat. No. 4,605,808) teaches the polymerization of isobutene in the presence of a complex of boron trifluoride and a primary alcohol at from −100° C. to +50° C. to give products with similarly high vinylidene double bond contents. According to U.S. Pat. No. 5,286,823, highly reactive polyisobutene can also be prepared using complexes of boron trifluoride and secondary alcohols as catalysts.
The disadvantages of this homogeneously catalyzed process are that the Lewis acid catalysts used are corrosive and that there is a risk that, apart from the desired reactive polyisobutene, halogenated polymeric byproducts are formed which are virtually inseparable from PIB and adversely affect the product and processing characteristics of the PIB. In these processes, the homogeneous catalyst is usually separated by quenching with a nucleophile to destroy the catalyst and subsequently removing the PIB from the quenching mixture by extraction. These additional workup steps are a further disadvantage of the homogeneously catalyzed PIB preparation process.
WO 94/28036 discloses, inter alia, the preparation of polyisobutene using heterogeneous Lewis acid-like catalysts.
Catalysts used are salts of elements of transition groups III, IV, V and VI of the Periodic Table of the Elements, which salts are insoluble in the reaction medium, preferably halides, sulfates, perchlorates, trifluoromethanesulfonates, nitrates and fluorosulfonates thereof. In the examples of this application, only the halides of these elements are used as catalysts for isobutene polymerization. No information is given about the properties of the polyisobutene obtained in these examples in terms of their molecular weight or their terminal double bond content. The polymerization is terminated by adding methanolic ammonia solution to the reaction medium to destroy or at least substantially inactivate the catalysts in question.
The preparation of PIB using heterogeneous catalysts is also known. U.S. Pat. No. 4,288,649 describes a process for preparing polyisobutene having an average molecular weight of >1250 dalton by polymerizing C
4
hydrocarbon mixtures comprising isobutene over halided alumina catalysts. These catalysts are prepared by treating the alumina with a haliding agent, preferably with a chloriding agent, in particular with carbon tetrachloride, at an elevated temperature. The disadvantage of this process is that some of the chlorine is transferred from the catalyst to the polymer which forms. For example, the polymerization of a mixture of n-butane, isobutane and isobutene over a chlorided alumina catalyst prepared in this manner gives, after a reaction time of 2 hours, a polyisobutene product having a chlorine content of 46 ppm.
U.S. Pat. No. 5,326,920 discloses a process for polymerizing isobutene by employing as heterogeneous catalyst an oxidic support material, preferably silica, which has been activated with a metal chloride attached thereto, preferably with an aluminum chloride. Particular preference is given therein to an SiO
2
—AlCl
2
catalyst in which AlCl
2
groups are anchored on the SiO
2
support via oxygen linkages. The disadvantages of this process are that the polyisobutene products obtained have an extremely broad molecular weight distribution D of from 8 to 14, a low terminal double bond content and a chlorine content in the ppm range. Furthermore, this process requires the presence of promoters such as water, alcohols, alkyl halides or hydrogen chloride to achieve a catalyst activity which is sufficient for industrial operation. Similar catalyst systems for the polymerization of isobutene are described in WO 95/26815, WO 95/26816, WO 95/26814 and WO 96/26818.
JP-A 139 429/1981 utilizes heterogeneous zirconium dioxide and molybdenum oxide catalysts to prepare isobutene oligomers having a molecular weight of less than 300 dalton. These catalysts can be mixed with aluminum fluoride to increase their activity. According to this publication, the reaction of an isobutene-comprising C
4
cut (composition: 46% of isobutene, 28% of 1-butene, 8% of 2-butenes, 12% of n-butane, 5% of isobutane, 1% of 1,3-butadiene) over an MoO
3
/ZrO
2
catalyst having a molybdenum content, calculated as MoO
3
, of 13% by weight at 120° C. yields an isobutene oligome

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