Olefin polymerization catalyst and process for preparing...

Details Olefin polymerization catalyst and process for preparing... Olefin polymerization catalyst and process for preparing...

2001-06-12

2003-03-25

Wu, David W. (Department: 1713)

Catalyst, solid sorbent, or support therefor: product or process

Catalyst or precursor therefor

Plural component system comprising a - group i to iv metal...

C502S126000, C502S104000, C502S114000, C502S110000, C526S124800, C526S125300, C526S142000

Reexamination Certificate

active

06537942

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to novel olefin polymerization catalysts and processes for preparing polypropylenes and propylene block copolymers using the novel catalysts. The present invention also relates to processes for preparing propylene block copolymers using specific olefin polymerization catalysts.
The polypropylene according to the present invention has a high isotacticity. The propylene block copolymer according to the present invention contains a polypropylene component having a high isotacticity and a rubber component having a high intrinsic viscosity [&eegr;].
BACKGROUND OF THE INVENTION
There have been known homopolypropylene generally having excellent rigidity and heat resistance, and propylene block copolymers comprising both polypropylene component and a rubber component and having excellent rigidity and heat resistance as well as excellent impact resistance.
Propylene polymers have also a low specific gravity and can be easily recycled, and therefore, they have been paid much attention with respect to environmental protection and are now desired to be more extensively utilized.
Such propylene polymers are prepared using so-called a Ziegler-Natta catalyst comprising a compound containing a transition metal of Group IV to VI of the periodic table and an organometallic compound containing a metal of Group I to III, and they are widely used.
However, the propylene polymers obtained by the prior art techniques have not always sufficient rigidity and heat resistance in some uses, so that they have limited uses for some purposes.
It is known that the rigidity and the heat resistance of propylene polymers can be further improved by increasing the isotacticity of homopolypropylene or a polypropylene component in a propylene block copolymer, in other words, these properties can be improved by the use of a catalyst capable of providing a high isotacticity for the propylene polymers in the preparation thereof.
However, a polymer of an olefin such as propylene obtained by the use of such a catalyst capable of providing a high isotacticity tends to have a molecular weight higher than that those obtained by using conventional catalysts. Accordingly, it has generally been necessary to add hydrogen as a chain transfer agent in a large amount to the polymerization system in order to regulate a molecular weight and a melt flow rate (MFR) of the resulting polymer. Such a large amount of hydrogen present in the polymerization system, especially when the propylene is per se used as the polymerization solvent, increases the pressure of polymerization system, so that a polymerization reactor may need reinforcing its pressure resistance.
Propylene block copolymers can be prepared by a multi-step polymerization (so-called block copolymerization) process which generally comprises initially polymerizing propylene to form a polypropylene component and then copolymerizing ethylene and an &agr;-olefin to form a rubber component. If this polymerization process is carried out continuously (or in one batch) using the above-mentioned catalyst capable of providing a high isotacticity, a large amount of hydrogen gives rise to a problem. That is, the hydrogen added in the initial step to prepare the polypropylene component remains unreacted in a large amount and then, in the subsequent step, prevents the rubber component from attaining a high molecular weight (instrinsic viscosity [7].
Accordingly, it has been desired that a catalyst system used for the preparation of a polypropylene and a propylene block copolymer be developed, which makes it possible not only to readily regulate the molecular weight and the melt flow rate (MFR) of the resulting polymers using a small amount of hydrogen, but also provide a high isotacticity for the resulting polypropylene and the propylene component of the resulting propylene block copolymer.
Further, it has also been desired that a process for preparing a propylene block copolymer by which the molecular weight and the melt flow rate (MFR) of the resulting copolymer can be easily regulated even with a small amount of hydrogen, isotacticity of a polypropylene component in the resulting copolymer can be heightened, and a molecular weight of a rubber component in the resulting copolymer can also be increased.
OBJECT OF THE INVENTION
The present invention has been made in the light of the foregoing prior art technique, and it is an object of the invention to provide olefin polymerization catalysts by the use of which the molecular weight and the melt flow rate (MFR) of the resulting polypropylene can be easily regulated even with a small amount of hydrogen and highly isotactic polypropylene can be prepared, and to provide processes for preparing polypropylene using said olefin polymerization catalysts.
It is another object of the invention to provide processes for preparing a propylene block copolymer by which the molecular weight and the melt flow rate (MFR) of the resulting copolymer can be easily regulated even with a small amount of hydrogen, isotacticity of the polypropylene component in the resulting copolymer can be heightened, and the molecular weight of the rubber composition in the resulting copolymer can also be increased.
SUMMARY OF THE INVENTION
The olefin polymerization catalyst (1) according to the invention is a novel catalyst and formed from:
[I-1] a contact product obtained by contacting:
(A) a solid titanium catalyst component comprising magnesium, titanium, halogen and an electron donor,
(B) an organometallic compound catalyst component, and
(C) an organosilicon compound represented by the following formula (c-i)
R
a
n
Si (OR
b
)
4−n
  (c-i)
 wherein n is 1, 2 or 3; when n is 1, R
a
is a secondary or tertiary hydrocarbon group; when n is 2 or 3, at least one of R
a
is a secondary or tertiary hydrocarbon group, and plural R
a
may be the same or different; R
b
is a hydrocarbon group of 1 to 4 carbon atoms; and when 4-n is 2 or 3, plural OR
b
may be the same or different;
[II-1] (D) a compound having at least two ether linkages spaced by plural atoms; and optionally,
[III] an organometallic compound catalyst component.
The contact product [I-1] in the catalyst (1) may be replaced by a prepolymerized catalyst component [Ia-1] which is obtained by prepolymerizing an olefin of 2 or more carbon atoms in the presence of the catalyst components for forming the contact product [I-1] in such a way that the amount of the prepolymer formed is 0.01 to 2,000 g based on 1 g of the solid titanium catalyst component (A).
The olefin polymerization catalyst (2) according to the invention is formed from:
[I-2] a contact product obtained by contacting:
(A) a solid titanium catalyst component,
(B) an organometallic compound catalyst component, and
(D) compound having at least two ether linkages spaced by plural atoms;
[II-2] (C) an organosilicon compound represented by the above formula (c-i); and optionally,
[III] an organometallic compound catalyst component.
The contact product [I-2] in the catalyst (2) may be replaced by a prepolymerized catalyst component [Ia-2] which is obtained by prepolymerizing an olefin of 2 or more carbon atoms in the presence of the catalyst components for forming the contact product [I-2] in such a way that the amount of the prepolymer formed is 0.01 to 2,000 g based on 1 g of the solid titanium catalyst component (A).
The process for preparing a polypropylene according to the invention comprises polymerizing propylene in the presence of the above-mentioned olefin polymerization catalyst (1) or (2).
The polypropylene prepared by the process of the invention preferably has the following properties:
(i) a boiling heptane-insoluble component is contained in said polypropylene in an amount of not less than 80% by weight,
a pentad isotacticity [M
g
] of the boiling heptane-insoluble component determined by the following formula (1) using a
13
C-

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