Aluminum alkyl complexes as cocatalysts

Details Aluminum alkyl complexes as cocatalysts Aluminum alkyl complexes as cocatalysts

1998-11-25

2003-07-22

Nazario-Gonzalez, Porfirio (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Aluminum containing

C556S176000, C502S103000, C502S117000, C526S160000, C526S943000

Reexamination Certificate

active

06596890

ABSTRACT:

The present invention relates to organometallic aluminium compounds of the general formula (I)
where
X
1
is NH, NH
2
*, NH—A*, N—A, N(A)
2
*, O, OA*, O-Aryl*, S, SA*, P, P(A)
2
* or a single bond,
X
2
is NH, N—A, O, S, PA or X
1
coordinated to Al(R
1
)
3
, or a single bond,
R
1
is H; Hal if n=0; A which may be covalently bound to Al; Si(A)
3
if X
1
=O,
R
2
is A which may be covalently bound to Al;
CH
2
—CH═CH, CH
2
—C≡C when Z
1
=H;
R
3
and R
4
are, independently of one another, a bond or R
2
or Si(A)
3
or Si(A)
2
,
Z
1
is a bond or H bound to R
2
,
Z
2
is a bond or H bound to R
2
or R
3
, where
A is branched or unbranched C
1-
C
7
-alkyl, C
1-
C
7
-alkylidene or C
1-
C
7
-alkenylidene,
Aryl is phenyl, naphthyl,
Hal is F, Cl,
and, independently of one another,
n is 0, 1,
m is 0, 1,
p is 0, 1,
q is 1, 2 and
l is 0, 1,
where coordinative bonds can exist between X
1
, X
2
and Al, and R
1
, R
2
, R
3
, R
4
, X
1
, X
2
, Z
1
and Z
2
can each, independently of one another, take on any of the above meanings at different positions in the molecule and X
1
can only take on the meanings denoted by “*” if l=0 and R
1
, R
2
, R
3
or R
4
are not present, which can serve as cocatalysts in olefinic polymerization reactions. In particular, these compounds having improved properties can be used for preparing new Ziegler-Natta catalysts or new coordination catalyst systems which have high activities even at low temperatures and a pressure of about 10 bar.
Customary coordination catalyst systems are extraordinarly diverse catalysts which are used in chemical reactions of and with olefinically unsaturated compounds. These include, in particular, processes for preparing olefin polymers by coordination polymerization and the metathesis of alkenes or alkynes. Processes of substantial industrial importance are the preparation of various polyethylenes for different applications, e.g. high density polyethylene (HDPE) or polyethylene having a particularly low density (linear low density polyethylene, LLDPE) and of polymers and copolymers of ethylene, propylene or other 1-alkenes and alkynes. Catalysed metathesis makes it possible to prepare relatively highly unsaturated hydrocarbon compounds in a targeted manner from unsymmetrical alkenes or alkynes and to obtain long-chain unsaturated hydrocarbons from unsaturated cyclic hydrocarbon compounds. The long-chain unsaturated hydrocarbons are employed, for example, in the preparation of elastomers. In addition, coordination catalysts are employed in further reactions, for instance in alkene hydrogenation or in organometallic syntheses.
On the basis of present-day scientific knowledge of the mechanism of action of coordination catalysts, it is assumed that in each case a transition metal compound forms the catalytically active centre to which the olefinically unsaturated compound is coordinated in a first step. Olefin polymerization proceeds via coordination of the monomers and a subsequent insertion reaction into a transition metal-carbon or transition metal-hydrogen bond. The presence of organometallic compounds in the coordination catalyst systems or during the catalyzed reaction is necessary to activate the catalyst or maintain its activity by reduction and possibly alkylation or formation of a complex system (cation/anion). These compounds are therefore also known as cocatalysts. The compound containing the catalytically active transition metal atom is known as the primary catalyst or precatalyst.
In recent years, coordinative polymerization using complex initiator systems has achieved great industrial importance, particularly for the polymerization of ethylene at low pressures. In the USA alone, over 8×10
9
metric tons of PE were produced in 1995 (S. W. Bigger; Eur. Polym. J. Vol. 32, No. 4, pp 487, 1996).
The industrially most important catalysts in this field are the Ziegler-Natta catalysts. These are systems consisting of a combination of compounds of metals of transition groups IV-VII of the Periodic Table of the Elements with, for example, alkyl compounds, aryl compounds or hydrides of the elements of main groups I-III. Typical Ziegler catalysts are formed, for example, in the reaction of TiCl
4
with Et
3
Al or of TiCl
3
with AlEt
2
Cl. These systems are heterogeneous catalysts; they are obtained as a fine suspension in an organic solvent (e.g. heptane).
The most important aluminium alkyls which are preferably used are AlEt
3
, Al-i-Bu
3
, AlEt
2
Cl, AlEtCl
2
, and AlEt
2
OR, all very sensitive to oxygen and moisture in the atmosphere and therefore difficult to handle. In place of the titanium chlorides, compounds of vanadium and chromium are of particular interest, in specific applications also molybdenum, cobalt, rhodium and nickel. In place of the aluminium alkyls, numerous other organometallic compounds of, in particular, sodium, lithium and cadmium have been described as effective in combination with titanium compounds (H. J. Sinn et al., Polymerisation und Insertionsaktivität von Aluminiumtrialkylen und Ziegler-Natta Katalysatoren, Angew. Chem. 72 (1960) 522).
An example of an industrially important solution polymerization process for preparing HDPE is the Dow process.
Here, a mixture of TiCl
x
and AlR
3
in hydrocarbons (C
8
-C
9
) is prepared at a pressure p>10 bar and a reaction temperature T>180° C. The activity in the continuous process (140° C., 30 bar; TiCl
4
:AlR
3
=1:5) is 6323 g of PE/h. (Dow, U.S. Pat. No. 3,491,073, 1970).
In a process patented by Du Pont, Ti/V halides are combined with AlR
3
in cyclohexane at pressures of 200 bar and a temperature of 180-270° C. The activity is 20-50 kg of PE/g of metal×hour and the viscometrically determined molar mass is M
&eegr;
=1.8×10
5
g/mol. (Du Pont, U.S. Pat. No. 2,862,917, 1958; J. P. Forsman, Hydrocarbon Processing, 51(11), 130 (1972).
An example of an industrially important suspension polymerization process for preparing HDPE is the Mitsubishi process. Here, HDPE is produced using a titanium catalyst in n-hexane at 5-10 bar and 30-90° C. in a stirred reactor. (A. Kageyama, Hydrocarbon Processing 51(7), 115(1972)). Another example is the Montedison process, which is carried out using titanium catalysts in petroleum spirit at 1-15 bar and 50-100° C. in a stirred reactor. The activity is 200 kg of PE/g of Ti. (A. Heath, Chemical Engineering (April 3) 66(1972).
A further important supplier of HDPE is Hoechst. A heterogeneous catalyst (titanium/support) is used together with aluminium trialkyls in hexane at 8-10 bar and 80-90° C. in a stirred reactor for producing polyethylene. (Kreuter, Chemical Engineering (August 5) 62 (1972)).
After, in the initial phase, this heterogeneity had been held primarily responsible for the catalytic activity (“catalytic surface”), soluble (homogeneous) systems which had approximately the same effectiveness were subsequently found.
Thus, a homogeneous Ziegler catalyst is formed, for example, by combining bis(cyclopentadienyl)titanium dichloride (cp
2
TiCl
2
) or vanadyl chloride (VOCl
3
) with diethylaluminium chloride (Et
2
AlCl) or aluminoxane ([—OAl(CH
3
)—]
n
). A further important homogeneous catalyst system is: cp
2
ZrMe
2
/aluminoxane (homogeneous).
TiCl
4
on MgCl
2
catalyst systems were discovered in 1970 and are referred to as second generation catalyst systems. An example of this heterogeneous system is: MgCl
2
/AlR
3
/TiCl
4
. The catalyst activity is 200 kg of PE/g of Ti×h. (A. D. Jenkins, A. Ledwith; Reactivity, Mechanism and Structure in Polymer Chemistry).
All these known catalyst systems have the disadvantages that they can be used only at elevated temperature and a pressure above 10 bar and, despite this, a satisfactory catalyst activity is not achieved in all cases.
The practical use of these catalysts and related types in the wide range of process variants which have been developed can give products which sometimes have very different properties. In the case of olefin polymers which are of generally known importance as m

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