Preparation of polymers of vinylaromatic compounds under...

Details Preparation of polymers of vinylaromatic compounds under... Preparation of polymers of vinylaromatic compounds under...

1997-09-04

2001-08-28

Zitomer, Fred (Department: 1713)

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

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S133000, C526S134000, C526S159000, C526S160000, C526S169000, C526S170000, C526S183000, C526S346000

Reexamination Certificate

active

06281304

ABSTRACT:

The present invention relates to a process for preparing polymers of vinylaromatic compounds at from 0 to 150° C. in the presence of metal-locene complexes as catalysts.
The present invention further relates to the use of the polymers obtainable in this way for producing moldings.
Owing to their property profile, polymers of vinylaromatic compounds, in particular polystyrenes, are used in many fields, for example as packaging materials or as insulating coatings for plastics, specifically in electrical applications.
EP-A 312 976 discloses the polymerization of vinylaromatic compounds, specifically of styrene or substituted styrenes, in the presence of metallocene complexes as catalysts in an aromatic solvent. This leads to the solvent having to be removed at high temperatures in the work-up of the polymers.
It is an object of the present invention to provide novel processes for preparing polymers of vinylaromatic compounds which are less complicated in process terms and, in particular, make the energy-intensive removal of the solvent superfluous.
We have found that this object is achieved by a process for preparing polymers of vinylaromatic compounds at from 0 to 150° C. in the presence of metallocene complexes as catalysts, wherein the polymerization is carried out at a pressure of from 5 to 300 bar in the presence of aliphatic C
1
-C
4
-hydrocarbons using a coordination complex selected from the group consisting of strong, uncharged Lewis acids, ionic compounds having Lewis acid cations and ionic compounds having Brönsted acid cations as cocatalyst.
Furthermore, the present invention provides for the use of the polymers obtainable in this way for producing moldings.
Suitable vinylaromatic compounds are, in particular, compounds of the formula I
where the substituents have the following meanings:
R
1
is hydrogen or C
1
-C
4
-alkyl,
R
2
to R
6
are, independently of one another, hydrogen, C
1
-C
12
-alkyl, C
6
-C
18
-aryl, halogen or two adjacent radicals together form a cyclic group having from 4 to 15 carbon atoms.
Preference is given to using vinylaromatic compounds of the formula I in which
R
1
is hydrogen and R
2
to R
6
are hydrogen, C
1
-C
4
-alkyl, chlorine or phenyl or two adjacent radicals together form a cyclic group having from 4 to 12 carbon atoms so that the compounds of the formula I are, for example, naphthalene derivatives or anthracene derivatives.
Examples of such preferred compounds are:
styrene, p-methylstyrene, p-chlorostyrene, 2,4-dimethylstyrene, 4-vinylbiphenyl, 2-vinylnaphthalene or 9-vinylanthracene.
It is also possible to use mixtures of different vinylaromatic compounds, but preference is given to using only one vinylaromatic compound.
Particularly preferred vinylaromatic compounds are styrene and p-methylstyrene.
The preparation of vinylaromatic compounds of the formula I is known per se and is described, for example, in Beilstein 5, 367, 474, 485.
In the process of the present invention, metallocene complexes used are preferably those of the formula II
where the substituents and indices have the following meanings:
R
7
to R
11
are hydrogen, C
1
-C
10
-alkyl, 5- to 7-membered cycloalkyl which in turn may bear C
1
-C
6
-alkyl groups as substituents, C
6
-C
15
-aryl or aralkyl or two adjacent radicals may also together form a cyclic group having from 4 to 15 carbon atoms, or Si(R
12
)
3
,
where R
12
is C
1
-C
10
-alkyl, C
6
-C
15
-aryl or C
3
-C
10
-cycloalkyl,
M is a metal of transition groups III to VI of the Periodic Table of the Elements or a lanthanide metal,
Z
1
to Z
5
are hydrogen, halogen, C
1
-C
10
-alkyl, C
6
-C
15
-aryl, C
1
-C
10
-alkoxy or C
1
-C
15
-aryloxy and
z
1
to z
5
are 0, 1, 2, 3, 4 or 5, where the sum z
1
+z
2
+z
3
+z
4
+z
5
corresponds to the valence of M minus 1.
Particularly preferred metallocene complexes of the formula II are those in which
M is a metal of transition group IV of the Periodic Table of the Elements, in particular titanium, and
Z
1
to Z
5
are C
1
-C
10
-alkyl, C
1
-C
10
-alkoxy or halogen.
Examples of such preferred metallocene complexes are:
pentamethylcyclopentadienyltitanium trichloride, pentamethylcyclopentadienyltrimethyltitanium and pentamethylcyclopentadienyltitanium trimethoxide.
It is also possible to use metallocene complexes as described in EP-A 584 646.
Mixtures of various metallocene complexes can also be used.
Such complexes can be synthesized by methods known per se, with preference being given to reacting the corresponding substituted, cyclic hydrocarbon anions with halides of titanium, zirconium, hafnium, vanadium, niobium or tantalum.
Examples of appropriate preparative methods are described, inter alia, in Journal of Organometallic Chemistry, 369 (1989), 359-370.
In the process of the present invention, the polymerization is carried out at a pressure of from 5 to 300 bar, preferably from 6 to 100 bar, in particular from 7 to 50 bar, in the presence of aliphatic C
1
-C
4
-hydrocarbons. Preference is given to linear or branched aliphatic C
3
-C
4
-hydrocarbons, in particular propane and isobutane. Mixtures of various aliphatic C
1
-C
4
-hydrocarbons can likewise be used.
As cocatalyst, use is made of a coordination complex selected from the group consisting of strong, uncharged Lewis acids, ionic compounds having Lewis acid cations and ionic compounds having Brönsted acid cations.
As strong, uncharged Lewis acids, preference is given to compounds of the formula III
M
1
X
1
X
2
X
3
  (III)
where
M
1
is an element of main group III of the Periodic Table, in particular B, Al or Ga, preferably B,
X
1
, X
2
and X
3
are hydrogen, C
1
-C
10
-alkyl, C
6
-C
15
-aryl, alkylaryl, arylalkyl, haloalkyl or haloaryl each having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical, or fluorine, chlorine, bromine or iodine, in particular haloaryls, preferably pentafluorophenyl.
Particular preference is given to compounds of the formula III in which X
1
, X
2
and X
3
are identical, preferably tris(pentafluorophenyl)borane. These compounds and methods for preparing them are known per se and described, for example, in WO 93/3067.
Suitable ionic compounds having Lewis acid cations are compounds of the formula IV
[(A
a+
)Q
1
Q
2
. . . Q
z
]
d+
  (IV)
where
A is an element of main groups I to VI or transition groups I to VIII of the Periodic Table,
Q
1
to Q
z
are radicals bearing a single negative charge, for example C
1
-C
28
-alkyl, C
6
-C
15
-aryl, alkylaryl, arylalkyl, haloalkyl, haloaryl each having from 6 to 20 carbon atoms in the aryl radical and from 1 to 28 carbon atoms in the alkyl radical, C
1
-C
10
-cycloalkyl which may bear C
1
-C
10
-alkyl groups as substituents, halogen, C
1
-C
28
-alkoxy, C
6
-C
15
-aryloxy, silyl or mercaptyl groups,
a is an integer from 1 to 6,
z is an integer from 0 to 5,
d corresponds to the difference a-z, but d is greater than or equal to 1.
Particularly suitable cations are carbonium cations, oxonium cations and sulfonium cations and also cationic transition metal complexes. Particular mention may be made of the triphenylmethyl cation, the silver cation and the 1,1′-dimethylferrocenyl cation.
They preferably have non-coordinating counter-ions, in particular boron compounds as are also mentioned in WO 91/09882, preferably tetrakis(pentafluorophenyl)borate.
Ionic compounds having Brönsted acids as cations and preferably likewise non-coordinating counter-ions are mentioned in WO 93/3067; the preferred cation is N,N-dimethylanilinium.
The metallocene complexes can be used in unsupported form, but they are preferably used in supported form.
Suitable support materials are, for example, silica gels, preferably those of the formula SiO
2
·bAl
2
O
3
, where b is from 0 to 2, preferably from 0 to 0.5; these are thus essentially aluminosilicates or silicon dioxide. The supports preferably have a particle diameter range from 1 to 200 &mgr;m, in particular from 30 to 80 &mgr;m. Such products are commercially available, e.g. as silica gel 332 from Grace.
F

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