Method for producing carrier-borne catalysts

Details Method for producing carrier-borne catalysts Method for producing carrier-borne catalysts

2000-11-08

2002-09-03

Wu, David W. (Department: 1713)

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

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C502S103000, C502S109000, C502S152000, C526S160000, C526S943000, C526S165000

Reexamination Certificate

active

06444766

ABSTRACT:

The present invention relates to a process for preparing a supported catalyst. It also relates to supported metallocene catalysts obtainable by this process, to a novel copolymer as support material for metallocene catalysts, and to a process for polymerizing olefins in the presence of a catalyst of the invention.
Supported transition metal catalysts have long been known and are employed, for example, for polymerizing olefins. The activity and productivity of these catalysts is critically dependent on their preparation process. The support materials for such transition metal catalysts are usually crosslinked polymers or inorganic substances such as silica gel, for example. Examples of such supported catalysts are described, for example, in WO 94/28034, in EP-A1-295 312, and in WO 98/01481.
The fixing of metallocenes to the surface of inorganic materials, and the subsequent polymerization, may, however, be accompanied by a number of deleterious effects. It is difficult, for instance, to distribute the catalyst component homogeneously over the surface of the porous support material. In the course of polymerization, there is generally fragmentation of the catalyst and of the support material. Owing to the nonhomogeneous distribution of the catalyst components over the surface of the support, in turn, this fragmentation produces nonhomogeneous catalyst particles, which can adversely affect the polymerization product.
It is therefore an object of the present invention to find a process for preparing a supported catalyst without the disadvantages of the prior art and allowing homogeneous distribution of the catalyst components on the support material.
We have found that this object is achieved by a process for preparing a supported catalyst, comprising the steps of
(1) preparing a copolymer comprising at least monomer units I and II
 where
A is a direct chemical bond or a group
X is a substitutable leaving group,
R
1
is identical or different at each occurrence and is hydrogen, substituted or unsubstituted aryl or branched or unbranched alkyl or alkenyl, and
n is an integer from 1 to 8;
(2) reacting in polymer-analogous manner the copolymer obtained in (1) with a cyclopentadienyl compound III or a fulvene compound IIIa
 to give a corresponding copolymer in which at least some of the leaving groups X have been replaced by radicals III′ or III′a
 where independently of one another
R
2
, R
3
, R
4
and R
5
are hydrogen, C
1
-C
10
-alkyl, or substituted or unsubstituted phenyl, or one of them is —QR
6
R
7
X
2
in which
Q is carbon, CR
6
R
7
C, germanium or silicon,
R
6
and R
7
independently of one another are hydrogen, methyl, ethyl or phenyl, and
X
2
is halogen, methyl, methoxy or ethoxy; and
R
8
radicals are identical or different C
1
- to C
4
-alkyl radicals or substituted or unsubstituted phenyl, and
(3) reacting the modified copolymer obtained in (2) with a compound IV or IVa
CpM(X
3
)
3
  IV
M(X
3
)
4
  IVa
 where
Cp is a substituted or unsubstituted cyclopentadienyl radical,
M is Ti, Zr or Hf, and
X
3
is halogen, hydrogen, C
1
-C
10
-alkyl, C
1
-C
10
-alkoxy or amido, it being possible for different substituents X
3
to have different meanings.
We have also found a supported metallocene catalyst obtainable by this process, a copolymer obtainable by steps 1 and 2 of the process of the invention, as a support material for metallocene catalysts, and a process for polymerizing olefins in the presence of the catalyst of the invention.
In step 1 of the process of the invention a copolymer is first prepared which is used as a starting material for the catalyst support. This copolymer comprises at least the monomer units I and II. Of these, monomer unit II serves as the framework of the support material. The monomer unit I, on the other hand, has the function of introducing a substitutable leaving group into the copolymer, which can subsequently be modified by polymer-analogous reaction with a cyclopentadienyl compound or a fulvene compound. In addition to the comonomers I and II, it is possible for any other olefinic comonomers to be employed in the copolymerization of step (1) provided they do not interfere disruptively with the reactions of steps (2) and (3). Examples that may be mentioned are acrylates or methacrylates, or acrylonitriles or methacrylonitriles. These additional comonomers may, for example, modify the polarity of the copolymeric supports in a desired manner.
A in the formula I can be a direct chemical bond but is preferably p-benzylene or p-phenylene.
Suitable examples of the substitutable leaving group X are the nucleophilically substitutable leaving groups such as the halogens—i.e. fluorine, chlorine, bromine or iodine—or other nucleophilically substitutable leaving groups familiar to the person skilled in the art, such as tosylate, trifluoroacetate, acetate or azide, for example. A monomer unit I preferred in the case of nucleophilically substitutable leaving groups X being used is p-(chloromethyl)styrene.
The substituted leaving group X can also be an organometallic functional group such as Li or MgX
4
, where X
4
is halogen, i.e., fluorine, chlorine, bromine or iodine. In general, the copolymers containing organometallic functional groups are prepared not by addition polymerization of the corresponding monomers I and II but instead by addition polymerization of comonomers II and suitable comonomers I′ which can be converted into the corresponding monomer units I by means of polymer-analogous reactions. Examples of suitable monomers I′ are p-halostyrenes, of which p-bromostyrene is particularly preferred.
Of the radicals R
1
in the formula II preferably at least one is a substituted or unsubstituted phenyl, pyrenyl, naphthyl or alkenyl. Preferred monomers II are styrene, butadiene or isoprene.
To prepare the copolymer by step I of the process it is possible to employ two or more different comonomers I or I′ and two or more different comonomers II. Good results are also obtained, however, when only one compound I or I′ is copolymerized with one compound II. The proportions of the comonomers I or I′ and II can be varied within a wide range. It is common to employ a larger proportion of the comonomer II.
The amount of the comonomer I as a proportion of the overall copolymer is advantageously from 3 to 30% by weight, based on the overall mass of the copolymer, with particular preference from 5 to 20% by weight and, in particular, from 7 to 15% by weight.
In step 2 of the process of the invention the copolymer obtained in step 1 is reacted in polymer-analogous manner with a cyclopentadienyl compound III or with a fulvene compound IIIa.
The cyclopentadienyl compound III can be either unsubstituted cyclopentadiene or mono- to tetrasubstituted cyclopentadienes. Particularly suitable substituents R
2
to R
5
are C
1
-C
10
-alkyls, in other words methyl, ethyl and the various isomers of propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl and decyl. Other suitable radicals R
2
to R
5
are substituted or unsubstituted phenyls, especially unsubstituted phenyls. In addition, one of R
2
to R
5
can also be —QR
6
R
7
X
2
, where Q is especially silicon, R
6
and R
7
are especially methyl, and X
2
is halogen, methyl, methoxy or ethoxy. Particular preference is given to a group —QR
6
R
7
X
2
of the formula —Si(CH
3
)
2
X
2
. Such a group can be used to construct a bridged metallocene structure on the copolymer framework. The preferred cyclopentadienyl compound III for use in step 2 of the process, however, is unsubstituted cyclopentadiene.
Suitable fulvene compounds IIIa include not only fulvene compounds unsubstituted on the 5-membered ring but also fulvene compounds substituted from 1 to 4 times on the 5-membered ring, the radicals which come into consideration being the same as those for the cyclopentadienyl compounds III. Preferred fulvenes IIIa are unsubstituted on the 5-membered ring. The fulvenes IIIa are substituted twice by radicals R
8
on the methylene carbon, suitable sub

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