Method for olefin polymerization with recycling of co-catalyst

Details Method for olefin polymerization with recycling of co-catalyst Method for olefin polymerization with recycling of co-catalyst

2000-01-31

2002-01-22

Wu, David W. (Department: 1713)

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

Synthetic resins

Removing and recycling removed material from an ongoing...

C526S067000, C526S069000, C526S129000, C526S160000

Reexamination Certificate

active

06340728

ABSTRACT:

CROSS REFERENCE TO RELATED APPLICATION
This application is based on application Nos. 99-3027 and 99-62906 filed in the Korean Industrial Property Office on Jan. 30, 1999 and Dec. 27, 1999, respectively, the content of which are incorporated here into by reference.
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to an olefin polymerization process with the recycling of co-catalyst, particularly to a method of recycling co-catalyst for the activation of single-site pre-catalyst in the olefin polymerization. This invention, therefore, provides an olefin polymerization process that can reuse expensive co-catalyst for subsequent olefin polymerization so that the total amount of co-catalyst required can be significantly reduced.
(b) Description of the Related Art
In 1976, Professor Kaminsky of Germany reported that olefin polymerization could be accomplished by using zirconocendichloride compound as a catalyst with a methylaluminoxane (MAO) co-catalyst which was obtained through a partial hydrolysis of trimethylaluminum (A. Anderson, J. G. Corde. J. Herwing, W. Kaminsky, A. Merck, R. Mottweiler, J. Pein, H. Sinn, and H. J. Vollmer, Angew. Chem, Int. Ed. Engl. 15, 630 (1976)). MAO is conventionally called an aluminoxane because it is prepared by mixing trimethylaluminum with other alkyl aluminum. This single-site catalyst shows unique polymerization characteristics that can not be embodied by the conventional Ziegler-Natta catalysts. That is, molecular weight distribution of the produced polymer is narrow, co-polymerization is easy, and the co-monomer distribution is uniform. Furthermore, changes in catalyst ligands lead to variations in the molecular weight and degree of co-polymerization. Additionally, the stereoselectivity in the polymers can be changed according to the molecular symmetry of the catalysts. Therefore, a lot of attention has been drawn to the single-site catalysts due to these advantageous characteristics.
Compared to the Ziegler-Natta catalysts that have several independent active sites, the single-site catalysts have only one type of active site and are composed of various transition metals with suitable ligands. As described in detail below, transition metal metallocene compounds with one or two cyclopentadienyl ligands are the most representative examples, but non-metallocene type transition metal compounds with diimine ligands have also been studied recently (L. K. Johnson, C. K. Killian, M. Brookhart,
J. Am. Chem. Soc.,
117, 6414 (1995); L. K. Johnson, S. Mecking, M. Brookhart,
J. Am. Chem. Soc.,
118, 267 (1996); J. D. Scollard, D. H. McConville, N. C. Payne, J. J.
Vittal, Macromol.,
29, 5241 (1996); B. L. Small, M, Brookhart, A. M. A. Bennett,
J. Am. Chem. Soc.,
120, 4049 (1998); C. Wang, S. Friedrich, T. R. Younkin, R. T. Li, R. H. Grubbs. D. A. Bensleben, M. W. Day,
Organometallics,
17, 3149 (1998)).
The metallocene type compounds of the above single-site pre-catalyst are described by the following General Formulae 1 or 2.
(C
5
R
3
m
)
p
B
s
(C
5
R
3
m
)MQ
3−p
  [General Formula 1]
In the above General Formulae 1 and 2, M is a transition metal of Group 4, 5 (IVA, VA in the previous IUPAC form), or lanthanide series; (C
5
R
3
m
) and (C
5
R
3
n
) are a cyclopentadienyl, a substituted cyclopentadienyl ligand, or a substituted cyclopentadienyl ligand in which two adjacent carbon atoms of a C
5
are joined together to form one or more C
4
-C
16
rings by a hydrocarbyl radical, in which each R
3
, which can be the same as or different from other R
3
, is a hydrogen radical, or an alkyl, cycloalkyl, aryl, alkenyl, alkylaryl, arylalkyl, or arylalkenyl radical having from 1 to 20 carbon atoms, or a metalloid of Group 14 (IVB in the previous IUPAC form) substituted by hydrocarbyl radicals;
B is an alkylene carbon chain, alkenylene carbon chain having from 1 to 4 carbon atoms, arylene carbon chain, dialkyl germanium, dialkyl silicon, alkyl phosphine, or alkyl amine radical substituting on and bridging two cyclopentadienyl ligands, or a cyclopentadienyl ligand and JR
4
z-y
ligands by a covalent bond;
R
4
is a hydrogen radical, or an alkyl, aryl, alkenyl, alkylaryl, or arylalkyl radical having from 1 to 20 carbon atoms;
J is an element of Group 15 (VB in the previous IUPAC form) or Group 16 (VIB in the previous IUPAC form);
each Q, which can be the same as or different from other Q, is a halogen radical, an alkyl, alkenyl, aryl, alkylaryl, or arylalkyl radical having from 1 to 20 carbon atoms, or an alkylidene radical having from 1 to 20 carbon atoms;
L is a Lewis base;
s is 0 or 1 and p is 0, 1 or 2 provided that when p is 0, then s is 0, when s is 1, then
m is 4, and when s is 0, then m is 5;
z is a valence number of J provided that when J is an element of Group 15 (VB in the previous IUPAC form), then z is 3, and when J is an element of Group 16 (VIB in the previous IUPAC form), then z is 2;
x is 0 or 1 provided that when x is 0, then n is 5, y is 1, and w is greater than 0, and when x is 1, then n is 4, y is 2, and w is 0);
However, the single-site pre-catalyst itself described above does not have polymerizing activity. To activate this pre-catalyst, excess aluminoxane co-catalyst is required. In the polymerization process utilizing the single-site catalysts and co-catalysts, it takes hundreds to tens of thousands of moles of aluminum co-catalyst per each mole of single-site compounds in order to achieve commercially desired level of catalyst activity.
Excess aluminoxane remains in the polymer and deteriorates the physical properties of the resins. Furthermore, it obstructs the commercial applications of the catalyst system due to the increased price of the catalyst resulting from the high aluminoxane cost.
The polyolefin process can also be divided into solution, bulk, high pressure, slurry, and gas phase processes. Substituting conventional Ziegler-Natta catalysts with single-site catalysts has been applied to existing processes due to economic reasons. The greatest difficulty in the application of the single-site catalyst to the existing processes is the complete loss of the aluminoxane, which is not only costly but also used in large excess in each polymerization process.
Once a single-site catalyst and a co-catalyst are introduced in a polymerization reactor, the single-site catalyst and excess co-catalyst are discharged out of the polymerization reactor along with polymers and solutions (or monomers in a bulk process) at the end of a polymerization process resulting in a loss of catalyst activity. In other cases, in order to prevent problems in the post treatment process, various catalyst poisons are added to deactivate catalysts. Therefore, the single-site catalyst and co-catalyst are completely lost in each polymerization reaction. As described above, there are difficulties in commercializing single-site catalysts under existing technologies due to the high catalyst cost. Furthermore, the physical properties of resins deteriorate due to excessive quantities of aluminum residue in resins. Therefore, it would be preferable to develop single-site catalyst preparing technologies that not only decrease the amount of aluminoxane consumption, but also maintain effective activities in order for such single-site catalyst technologies to be commercialized at a lower cost.
The role of aluminoxane is to activate single-site pre-catalyst so that a cationic active species is formed, and to stabilize the corresponding cation as a counter anion. Furthermore, aluminoxane is also known to play a role as a scavenger, removing impurities during the polymerization. Therefore, the aluminoxane consumption can be greatly reduced if the excess aluminoxane is recycled except for that which is required to activate single-site pre-catalyst and to stabilize the active cationic species as a counter anion.
The inventors of this invention have also developed a related technology in which polymerization solution containing co-catalyst is recycled after separation of the produced polymer from the polymerization solu

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