Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2003-02-19
2004-03-23
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...
C526S212000, C526S237000, C526S348700, C528S485000
Reexamination Certificate
active
06710140
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a process for the preparation of polyisobutylenes by cationic polymerization of isobutylene or isobutylene-containing hydrocarbon streams in the liquid phase in the presence of boron trifluoride acting as catalyst, the catalytic activity of the boron trifluoride being extinguished by means of a solid deactivator following a given timelapse.
DESCRIPTION OF THE BACKGROUND
High-molecular polyisobutylenes having molecular weights of up to several 100,000 dalton have been known for a number of years, and the preparation thereof is described for example in H. Gueterbock: “Polyisobutylen and Mischpolymerisate”, pp 77 to 104, Springer Verlag, Berlin 1959. These conventional polyisobutylenes differ from the so-called highly reactive polyisobutylenes, which usually have average molecular weights of from 500 to 50000 dalton and a high content of terminal double bonds, so-called vinylidene groups, of preferably distinctly more than 60 mol %.
Such highly reactive polyisobutylenes are used as intermediate products for the synthesis of additives for lubricants and automotive fuels, as described, for example, in DE-A 2,702,604. For the preparation of these additives there are first of all produced, by reaction of the terminal double bonds of polyisobutylene with maleic anhydride, polyisobutylene/maleic anhydride adducts, particularly polyisobutenylsuccinic anhydrides, which are then caused to react with certain amines to form the finished additive. The content of terminal vinylidene groups in the molecule is a most important quality criterion for this polyisobutylene type, since the formation of the adduct with maleic anhydride mainly involves reaction of the terminal vinylidene groups, whereas the double bonds located further inside the macromolecules react either not at all or to a distinctly lesser extent, depending on their position in the macromolecule, when no halogens are added.
Theories on the realization of the terminal vinylidene groups and the isomerization of the terminal double bonds in isobutylene macromolecules to internal double bonds are described in the article by Puskas et al. in J. Polymer Sci.: Symposium No. 56, 191 (1976) or in EP-A 628,575. The protonations, deprotonations and molecular rearrangements which take place during this operation are balanced reactions in which the formation of more highly alkyl-substituted cations is thermodynamically assisted. The said reactions are usually assisted by traces of acid, particularly by the acid catalyst used for the polymerization itself, which is usually a Lewis acid.
Another quality criterion for polyisobutylenes used for the said purpose is their average molecular weight (M
N
).
In addition, the molecular-weight distribution (dispersity, D) of the polyisobutylene macromolecules is a quality criterion for the purpose in mind, since the broader it is, ie, the greater the degree of scatter of the molecular weights of the polyisobutylene macromolecules, the less suitable the products frequently are for resolving the present problem.
The person skilled in the art already knows a number of processes for the preparation of reactive polyisobutylenes from isobutylene having average molecular weights and dispersities which satisfy the said requirements and in which boron trifluoride is used as catalyst.
Boron trifluoride is used in this case predominantly in the form of donor complexes, particularly with water, alcohols, phenols, carboxylic acids, carboxylic anhydrides, hydrogen fluoride, ethers or mixtures of these compounds. Boron trifluoride is an extremely effective catalyst even at low temperatures, alone or in the form of said complexes (cf eg DE-A 2,702,604, EP-A 145,235 or EP-A 322,241).
Thus if it is desired to stop the boron trifluoride-catalyzed conversion of isobutylene once a defined degree of conversion and/or a defined selectivity toward the polymeric products has been achieved, the boron trifluoride must usually be rapidly and completely deactivated. Such deactivation usually consists in decomposing the boron trifluoride with liquid substances or substances which are soluble in the reaction medium or converting it to other donor complexes such that it has virtually no more influence on the reaction process.
Suitable prior art substances for such complexing deactivation of boron trifluoride with organochemical deactivators in liquid phase are for example alcohols and acetonitrile (cf eg DE-A 4,306,384, EP-A 145,235).
A common feature of the known methods of deactivating boron trifluoride is that they necessitate the removal or purification of large amounts of liquids laden with boron trifluoride, its degradation products and/or organic compounds. When use is made of alcohols for such deactivation, reaction with the boron trifluoride may cause the formation of corrosive hydrogen fluoride, which necessitates the use of high-quality, expensive materials for construction of the apparatus used.
In view of this state of affairs, solutions to the present problem have already been developed using solid deactivators for boron trifluoride.
U.S. Pat. No. 4,384,162 proposes the abstraction of the boron trifluoride from the reaction solution by means of solid polyvinyl alcohol. The process suffers from the drawback, however, that it does not satisfy the requirements for polymerization of isobutylene, because boron trifluoride, despite adsorption thereof onto the polyvinyl alcohol, retains part of its activity, as a result of which undesirable oligomers may be formed as an after-effect.
U.S. Pat. No. 4,433,197 discloses the use of silica gel for the same purpose. However, here again, the deactivation achieved is insufficient. U.S. Pat. No. 4,213,001 even teaches the use of boron trifluoride/silica gel as catalyst for the oligomerization of 1-olefins, which indicates that boron trifluoride is still catalytically active after said adsorption.
The prior German Application having the file number 1,003,5298.7 already proposes, for this purpose, the use of a deactivator containing boron trifluoride-binding primary, secondary, tertiary and/or quaternary nitrogen atoms, which is insoluble in the reaction mixture. However, these deactivators are not always readily available.
SUMMARY OF THE INVENTION
It is thus an object of the present invention to provide a process for the synthesis of highly reactive polyisobutylene from isobutylene in the presence of boron trifluoride acting as catalyst, involving the use of a readily available and cheap solid deactivator for boron trifluoride which abstracts boron trifluoride from the reaction process more effectively than known deactivators of this kind.
This object is achieved by means of a process for the preparation of polyisobutylenes by cationic polymerization of isobutylene or isobutylene-containing hydrocarbon streams in the liquid phase in the presence of boron trifluoride acting as catalyst, the catalytic activity of the boron trifluoride being partly or completely extinguished by means of a solid deactivator following a given timelapse, which is characterized in that the solid deactivator used is an inorganic, anhydrous or hydrous oxygen compound of aluminum which is insoluble in the reaction mixture.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
By terminal vinylidene groups or terminal double bonds we mean the double bonds depicted below, whose position in the polyisobutylene macromolecule is defined by the general formula I 4 3 1 R
in which R stands for the remaining portion of the polyisobutylene macromolecule. The type and quantity of the double bonds present can be determined with the aid of
3
C NMR spectroscopy, the two carbon atoms marked in formula I with &agr; and &bgr; of the terminal double bond being identifiable in the
13
C NMR spectrum by their signals derived from the chemical shift values of 114.4 and 143.6 respectively relatively relative to tetramethylsilane. The amount of terminal double bonds in relation to other types of double bonds is determined by calculating the ratio of the peak areas of the individu
Borchers Dirk
Rath Hans Peter
Verrelst Wim
Wettling Thomas
BASF - Aktiengesellschaft
Teskin Fred
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