Group IV elements-bridged metallocene catalyst for preparing...

Details Group IV elements-bridged metallocene catalyst for preparing... Group IV elements-bridged metallocene catalyst for preparing...

1997-06-23

2001-10-02

Teskin, Fred (Department: 1713)

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

Organic compounds

Heavy metal containing

C556S028000, C556S031000, C556S052000, C556S053000, C526S943000

Reexamination Certificate

active

06297392

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a novel Group IV elements-bridged metallocene complex, and more particularly, to a Group IV element-bridged metallocene complex which has two catalytic sites and is capable of preparing olefin polymers having a bimodal molecular weight distribution. The Group IV elements include Group IVA elements and Group IVB metals.
2. Description of the Prior Art
Polyolefins, which include high density polyethylene (HDPE), are some of the most versatile thermoplastic resins and they have been used in a wide range of applications.
Most of the physical and mechanical properties of polyolefins, such as the high strength and high impact, stress, and puncture resistances, together with high toughness, are attributed, at least in part, to their relatively high molecular weight. However, as the molecular weight of the resin increases, the processability of the resin usually decreases.
In recent years, it has been found that polyolefins having a multimodal (typically bimodal) molecular weight distribution (MWD) can, not only retain the advantageous properties associated with high molecular weight, but also exhibit improved processability.
A bimodal MWD polymer (which can be also simply referred to as “bimodal polymer”) is defined as a polymer having two distinct molecular weight distribution curves as observed from the gel permeation chromatography (GPC). In other words, a bimodal polymer can be considered as a mixture containing a first polymer with a relatively higher molecular weight and a second polymer with a relatively lower molecular weight that are blended together.
Various approaches have been disclosed for producing bimodal polyolefins. The simplest approach is to physically blend together two polymers having different molecular weights. However, this simplistic approach suffers from the problem that only with polymers that can be completely molten, homogenization can be obtained. If one of the polymers is not completely molten, then the polymer blend will be inhomogeneous. This can cause a myriad of problems.
U.S. Pat. Nos. 5,284,613 and 5,338,589 disclose a two stage polymerization process for preparing a bimodal polyolefin. In the first stage, olefin monomers are contacted with a catalyst under polymerization conditions to produce a relatively high molecular weight (HMW) polymer powder, wherein the polymer is deposited on the catalyst particles. In the second stage, the HMW polymer powder containing the catalyst is further polymerized with additional olefin monomers to produce a relatively low molecular weight (LMW) polymer much of which is deposited on and within the HMW polymer/catalyst particles from the first. The disadvantages of such a two stage process are that two reactors are needed, resulting in undesirably high capital investment.
U.S. Pat. No. 5,369,194 discloses a process for preparing bimodal polyolefins in a single reactor. The catalyst system so used includes two different transition metal catalysts supported on the same solid support material. Therefore, high and low molecular weight polymers can be formed on the same catalyst particle. The shortcoming is that procedures for preparing the solid support material which is supported with two different catalysts is complicated and difficult. Moreover, the preferable activities for the two different catalysts may be at different conditions. Therefore, when one catalyst is activated, the other catalyst may be inactivated.
SUMMARY OF THE INVENTION
The primary object of the present invention is to solve the above-mentioned problems by providing a novel metallocene complex which can be used for preparing bimodal olefin polymers using a single reactor. The metallocene complex disclosed in the present invention is bridged by a Group IV element. This creates two catalytic sites in a single metallocene complex catalyst. Thus, the olefin monomer can be polymerized into a bimodal olefin polymer using a single catalyst in a single reactor, and the catalytic activity of the catalyst is comparable to commercially available catalysts.
To achieve the above-mentioned object, a novel metallocene complex is developed in the present invention which is represented by the following formula (I):
wherein
R and R
1
are different and are independently selected from the group consisting of &eegr;
5
-cyclopentadienyl group, substituted &eegr;
5
-cyclopentadienyl group, indenyl group, and fluorenyl group,
wherein the substituent of the substituted &eegr;
5
-cyclopentadienyl group is selected from the group consisting of C
1-12
alkyl group, C
1-12
aryl group, and silyl group;
R
2
is selected from the group consisting of —N(CH
3
)
2
, —N(C
2
H
5
)
2
, halogen, alkoxy, —(C═O)NH
2
, C
1-12
hydrocarbyl groups;
M is a Group IVA element; and
M
1
is a Group IVB metal.
DETAILED DESCRIPTION OF THE INVENTION
The present invention discloses a novel metallocene complex which is bridged by a Group IV element, and is represented by the following formula (I):
wherein
R and R
1
are different and are independently selected from the group consisting of &eegr;
5
-cyclopentadienyl group, substituted &eegr;
5
-cyclopentadienyl groups, indenyl group, and fluorenyl group;
R
2
is selected from the group consisting of —N(CH
3
)
2
, —N(C
2
H
5
)
2
, halogen, alkoxy, —(C═O)NH
2
, and C
1-12
hydrocarbyl group;
M is a Group IVA element, such as carbon, silicon, germanium, and tin; and
M
1
is a Group IVB metal, such as titanium, zirconium, and hafnium.
The substituent of the substituted &eegr;
5
-cyclopentadienyl group can be C
1-12
alkyl group, C
1-12
aryl group, and silyl group. Examples of the substituted &eegr;
5
-cyclopentadienyl include &eegr;
5
-methylcyclopentadienyl group and &eegr;
5
-tetramethylcyclopentadienyl group.
According to a preferred embodiment, the metallocene complex of the present invention is prepared by first reacting MCl
4
with RX to obtain MR
3
Cl, wherein
M is a Group IVA element as defined earlier,
R is a &eegr;
5
-cyclopentadienyl group, a substituted &eegr;
5
-cyclopentadienyl group, an indenyl group, or a fluorenyl group, and
X is an alkaline metal.
Subsequently, the MR
3
Cl so obtained is reacted with R
1
Y to obtain R
1
MR
3
, wherein
R
1
, which is different from R, is a &eegr;
5
-cyclopentadienyl group, a substituted &eegr;
5
-cyclopentadienyl group, an indenyl group, or a fluorenyl group, and
Y, which can be the same as or different from X, is an alkaline metal.
Finally, the R
1
MR
3
so obtained is reacted with M
1
(R
2
)
4
to obtain the metallocene complex represented by formula (I):
wherein
M is a Group IVB element
M
1
is a Group IVB metal, and
R
2
is —N(CH
3
)
2
, —N(C
2
H
5
)
2
, halogen, alkoxy, —(C═O)NH
2
, or a C
1-12
hydrocarbyl group.
Taking as an example to facilitate better understanding, when R is Cp (cyclopentadienyl), R
1
is methylcyclopentadienyl, R
2
is NMe
2
[N(CH
3
)
2
], M is Sn, and M
1
is Zr, the above-mentioned process for preparing the metallocene complex of formula (I) can be summerized by the following three reactions:
In the present invention, the Group IV elements-bridged metallocene complex can be combined with an activating cocatalyst to form a catalyst composition, which can be used for preparing olefin polymers. The group IV elements include Group IVA elements and Group IVB mentals.
The activating cocatalyst can be methyl aluminoxane (MAO), a trialkyl aluminum, a dialkyl aluminum, a salt of an inert and non-coordinating anion, or a mixture thereof.
The trialkyl aluminum can be selected from the group consisting of trimethyl aluminum, triethyl aluminum, tripropyl aluminum, trisopropyl aluminum, tributyl aluminum, and triisobutyl aluminum (TIBA).
The inert and non-coordinating anion can be a borate. Borates that are suitable for use in the present invention include N,N-dimethyl anilinium tetrakis(pentafluorophenyl)borate, triphenyl carbenium tetrakis(pentafluorophenyl)borate, trimethyl ammonium tetrakis(pentafluorophenyl)borate, ferrocenium tetrakis(pentafluorophenyl)borate, dime

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