Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2002-04-04
2003-11-04
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...
C526S064000, C526S209000, C526S212000, C526S348700
Reexamination Certificate
active
06642329
ABSTRACT:
The present invention relates to a process for the continuous preparation of polyisobutene having a number average molecular weight of from 500 to 50,000 and containing at least 50 mol % of terminal double bonds by one-stage or multistage, continuous polymerization of isobutene in the liquid phase in the presence of a catalyst comprising boron trifluoride and at least one oxygen-containing compound at below +40° C.
Polyisobutenes are usually prepared by cationic polymerization of isobutene in the liquid phase or in the gas phase in the presence of polymerization catalysts, such as aluminum trichloride or alkylaluminum chlorides. Polyisobutenes thus prepared, have, as a rule, only a low content (less than 10 mol %) of terminal double bonds and a comparatively broad molecular weight distribution, characterized by a dispersity above 2. The dispersity is understood as meaning the quotient of number average molecular weight {overscore (M)}
W
and the number average molecular weight {overscore (M)}
N
.
For a number of applications, polyisobutenes having number average molecular weights {overscore (M)}
N
of from 500 to 50,000 Dalton and a high content, i.e. at least 50 mol %, of terminal double bonds are of interest. Such polyisobutenes are referred to as highly reactive polyisobutenes. They are prepared, as a rule, by polymerization of isobutene or isobutene-containing hydrocarbons with BF
3
-complexes as catalysts. They are used as intermediates for the preparation of additives for lubricants and gels. The molecular structural principle of these additives is based on the linkage of polar structures with the nonpolar, oleophilic polyisobutenyl radical. The linkage of the polar structure with the nonpolar, oleophilic radical is effected by functionalization of the terminal double bond in the polyisobutene, a reactive functionality first being introduced into the polyisobutene, for example by hydroformulation, by epoxidation, by reaction with phenols or by reaction with maleic anhydride, and then being modified in a subsequent reaction, for example by reaction with ammonia, amines, amino alcohols, hemiaminals or polyalkylene oxides, if required under reducing conditions.
Fuel and lubricant additives based on polyisobutene are disclosed, for example, in DE-A 2702604, EP-A 244616, EP-A 277345, EP-A 476485, EP-A 539821, EP-A 568873, WO-92/12221, WO-92/14806, WO-94/24231, DE-A 3611230 and DE-A 19645430. Since, in the abovementioned functionalization reactions, preferably the terminal double bonds (vinylidene double bonds) and, only to a minor extent, the double bonds located further toward the interior of the polymer chain undergo reaction, the content of terminal double bonds in the polyisobutene is an important quality criterion. Regarding the formation of terminal double bonds in the cationic polymerization of isobutene, reference may be made to the equation proposed by Puskas et al., J. Polym. Sci., Symp. 56, (1996) 191 (cf. also WO-96/40808 page 3).
A further, important quality criterion for reactive polyisobutenes is the width of their molecular weight distribution, characterized by the dispersity{overscore (M)}
W
/{overscore (M)}
N
. Dispersities {overscore (M)}
W
/{overscore (M)}
N
below 1.8 are desirable.
DE-A 2702604 discloses a process for the preparation of reactive polyisobutenes, in which isobutene is polymerized in the presence of boron trifluoride at from −50° C. to +30° C. Here, polyisobutenes having up to 88 mol % of terminal double bonds are obtained. Polyisobutenes having a dispersity of <1.8 are not obtained by this process.
EP-A 145235 describes the preparation of reactive polyisobutenes containing at least 70 mol % of terminal double bonds. This object is achieved by polymerizing isobutene in the presence of a preformed complex of boron trifluoride and a primary alcohol at from −100° C. to +50° C. with a contact time of more than 8 minutes. It is true that polyisobutenes having a comparatively narrow molecular weight distribution are also obtained by this process. The object of obtaining a narrow molecular weight distribution in combination with a high content of terminal double bonds is achieved here at the expense of a low isobutene conversion, so that the polyisobutenes thus obtained are particularly expensive to prepare.
U.S. Pat. No. 5,286,823 describes a process for the polymerization of isobutene to give highly reactive polyisobutene in the presence of a catalyst comprising boron trifluoride and at least one secondary alcohol of 3 to 20 carbon atoms. In the examples, polyisobutenes have a number average molecular weight {overscore (M)}
N
of from 800 to 2200 Dalton, containing at least 80 mol % of terminal double bonds and having dispersities of from 1.3 to 2.0 are obtained. Polyisobutenes having a specific average molecular weight in combination with simultaneously low dispersity and a high content of terminal double bonds cannot be selectively prepared by this process.
WO-96/40808 discloses a two-stage process for the preparation of highly reactive polyisobutene having number-average molecular weights of 500 to 20,000 Dalton and containing more than 80 mol % of terminal double bonds.
It is an object of the present invention to provide an economical process, which is simple to realize, for the preparation of highly reactive polyisobutene, which process makes it possible to achieve a relative optimum with regard to the content of terminal double bonds for a given composition of the reaction mixture.
We have found, surprisingly, that this object is achieved by a continuous process for the polymerization of isobutene in the liquid phase in the presence of boron trifluoride complex catalysts, if the liquid reaction phase has a viscosity of from 6 to 20 mm
2
/s (kinematic viscosity, determined according to DIN 51562, part 1-4) under reaction conditions, i.e. at reaction temperature or at the temperature of the reaction phase under reaction conditions.
The present invention accordingly relates to a process for the continuous preparation of polyisobutene having a number-average molecular weight {overscore (M)}
N
of from 500 to 50,000 and containing at least 50 mol % of terminal double bonds by one-stage or multistage, continuous polymerization of isobutene in the liquid phase in the presence of a catalyst comprising boron trifluoride and at least one oxygen-containing compound at below +40° C., wherein the liquid reaction phase has a viscosity of from 6 to 20 mm
2
/s (determined according to DIN 51562, part 1-4), at least in the first polymerization stage.
Below, liquid reaction phase is understood as meaning the liquid mixture comprising isobutene, polyisobutene, if required solvent and polymerization catalysts, which mixture is present in the polymerization reactor under polymerization conditions. Unless stated otherwise, concentration data are based on the total weight of the liquid reaction phase.
The stated viscosity values correspond to the kinematic viscosity of the liquid reaction phase (liquid reaction mixture) under reaction conditions. Preferably, the novel process is carried out at a viscosity of the liquid reaction phase in the range from 6 to 16, in particular from 7 to 12 mm
2
/s. It is presumed that, if the viscosity values are too low, the poor solubility of the BF
3
catalyst complexes in the reaction medium leads to the formation of a second liquid phase, whereas, if the viscosity values are too high, effective heat removal from the liquid reaction phase is no longer guaranteed. The two effects impair the polymer quality, in particular with regard to the content of terminal double bonds. Preferably, the novel process is carried out at virtually constant kinematic viscosity of the liquid reaction phase.
The viscosity of the liquid reaction phase depends on the reaction temperature, the concentration of polyisobutene in the liquid reaction mixture, the molecular weight of the polyisobutene and the chosen solvent. Thus, the viscosity of the liquid reaction phase increases with decreasing reaction temperature. W
BASF - Aktiengesellschaft
Keil & Weinkauf
Teskin Fred
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