Molecular weight control in olefin polymerization

Details Molecular weight control in olefin polymerization Molecular weight control in olefin polymerization

1999-05-21

2001-06-26

Wu, David W. (Department: 1713)

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

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S161000, C526S169100, C526S171000, C502S155000

Reexamination Certificate

active

06252022

ABSTRACT:

FIELD OF THE INVENTION
In olefin polymerizations in which iron or cobalt complexes of 2,6-pyridinecarboxaldehyde diimines or 2,6-diacylpyridine diimines are used as polymerization catalysts, hydrogen may be used as a chain transfer agent to reduce polyolefin molecular weight.
TECHNICAL BACKGROUND
Polymerization of olefins using early transition metal containing catalysts such as vanadium and zirconium is a well known and commercially important technology. In many instances it is desirable to lower the molecular weight of the polyolefin that would normally be produced. For example lower molecular weight polymers are usually considered easier to melt process, since they have lower melt viscosities. While polymerization process conditions can sometimes be altered to change the molecular weight of the resulting olefin, often a chain transfer agent such as hydrogen is deliberately added to the process to lower the polyolefin molecular weight.
The polymerization of olefins, especially ethylene and propylene, using iron or cobalt complexes of 2,6-pyridinecarboxaldehyde diimines or 2,6-diacylpyridine diimines containing catalysts, see for instance U.S. patent applications Ser. No. 08/991,372, filed Dec. 16, 1997 (now U.S. Pat. No. 5,955,555), and Ser. No. 09/006,031, filed Jan. 12, 1998 (now U.S. Pat. No. 6,150,482). However, methods for lowering the molecular weight of polyolefins produced in such processes are not known (except that decreasing the steric bulk of the ligand often results in lower molecular weight polymer).
SUMMARY OF THE INVENTION
This invention concerns a process for the polymerization of a polymerizable olefin using as a polymerization catalyst an iron or cobalt complex of a 2,6-pyridinecarboxaldehyde diimine or a 2,6-diacylpyridine diimine, wherein the improvement comprises, using as a chain transfer agent an effective amount of hydrogen.
This invention also concerns a process for the polymerization of one or more polymerizable olefins, comprising, contacting under polymerizing conditions:
(a) one or more polymerizable olefins;
(b) hydrogen in an amount effective as a chain transfer agent; and
(c) an active polymerization catalyst which contains an iron or cobalt complex of a 2,6-pyridinecarboxaldehyde diimine or a 2,6-diacylpyridine diimine.
DETAILS OF THE INVENTION
In the polymerization processes and catalyst compositions described herein certain groups may be present. By hydrocarbyl is meant a univalent radical containing only carbon and hydrogen. By saturated hydrocarbyl is meant a univalent radical which contains only carbon and hydrogen, and contains no carbon-carbon double bonds, triple bonds and aromatic groups. By substituted hydrocarbyl herein is meant a hydrocarbyl group which contains one or more (types of) substitutents that does not interfere with the operation of the polymerization catalyst system. Suitable substituents in some polymerizations may include some or all of halo, ester, keto (oxo), amino, imino, carboxyl, phosphite, phosphonite, phosphine, phosphinite, thioether, amide, nitrile, and ether. Preferred substituents are halo, ester, amino, imino, carboxyl, phosphite, phosphonite, phosphine, phosphinite, thioether, and amide. Which substitutents are useful in which polymerizations may in some cases be determined by reference to U.S. patent application Ser. No. 08/991,372, filed Dec. 16, 1997 (now U.S. Pat. No. 5,955,555), and Ser. No. 09/006,031, filed Jan. 12, 1998 (now U.S. Pat. No. 6,150,482), which are hereby included by reference. If not otherwise stated, hydrocarbyl, substituted hydrocarbyl and all other groups containing carbon atoms, such as alkyl, preferably contain 1 to 20 carbon atoms.
Noncoordinating ions are mentioned and useful herein. Such anions are well known to the artisan, see for instance W. Beck., et al., Chem. Rev., vol. 88, p. 1405-1421 (1988), and S. H. Strauss, Chem. Rev., vol. 93, p. 927-942 (1993), both of which are hereby included by reference. Relative coordinating abilities of such noncoordinating anions are described in these references, Beck at p. 1411, and Strauss at p. 932, Table III. Useful noncoordinating anions include SbF
6
−
, BAF, PF
6
−
, or BF
4
−
, wherein BAF is tetrakis[3,5-bis(trifluoromethyl)phenyl]borate.
A neutral Lewis acid or a cationic Lewis or Bronsted acid whose counterion is a weakly coordinating anion may also present as part of the catalyst system. By a “neutral Lewis acid” is meant a compound which is a Lewis acid capable of abstracting X from (I) to form a weakly coordinating anion.
In (I), M is Co or Fe, each X is independently an anion and each X is such that the total negative charges on X equal the oxidation state of M (for R
1
through R
7
see below). The neutral Lewis acid is originally uncharged (i.e., not ionic). Suitable neutral Lewis acids include SbF
5
, Ar
3
B (wherein Ar is aryl), and BF
3
. By a cationic Lewis acid is meant a cation with a positive charge such as Ag
+
, H
+
, and Na
+
.
A preferred neutral Lewis acid, which can alkylate the metal, is a selected alkyl aluminum compound, such as R
9
3
Al, R
9
2
AlCl, R
9
AlCl
2
, and “R
9
AlO” (alkylaluminoxanes), wherein R
9
is alkyl containing 1 to 25 carbon atoms, preferably 1 to 4 carbon atoms. Suitable alkyl aluminum compounds include methylaluminoxane (which is an oligomer with the general formula [MeAlOn]
n
) , (C
2
H
5
)
2
AlCl, C
2
H
5
AlCl
2
, and [(CH
3
)
2
CHCH
2
]
3
Al. Metal hydrides such as NaBH
4
may be used to bond hydride groups to the metal M.
By an iron or cobalt complex of a 2,6-pyridinecarboxaldehyde diimine or a 2,6-diacylpyridine diimine is meant a Fe or Co complex of a ligand of the formula:
wherein:
R
1
, R
2
and R
3
are each independently hydrogen, hydrocarbyl, substituted hydrocarbyl, or an inert functional group;
R
4
and R
5
are each independently hydrogen, hydrocarbyl, an inert functional group or substituted hydrocarbyl; and
For compounds such as (I) and (II) and similar compounds, preferred formulas are found in U.S. patent applications Ser. No. 08/991,372, filed Dec. 16, 1997 (now U.S. Pat. No. 5,955,555), and Ser. No. 09/006,031, filed Jan. 12, 1998 (now U.S. Pat. No. 6,150,482), both of which are hereby included by reference, and preferred groupings and compounds in these applications are also preferred herein. However the compound numbers and group (i.e., R
x
) numbers in these Applications may vary from those herein, but they are readily convertible. These applications also describe synthesis of the various ligands and iron and cobalt complexes.
In one type of preferred compound such as (I) or (II) R
1
, R
2
and R
3
are hydrogen, and/or R
4
and R
5
are each independently hydrogen or alkyl, especially hydrogen or methyl, and/or R
6
is
and/or R
7
is
wherein:
R
8
and R
13
are each independently hydrocarbyl, substituted hydrocarbyl or an inert functional group;
R
9
, R
10
, R
11
, R
14
, R
15
and R
16
are each independently hydrogen, hydrocarbyl, substituted hydrocarbyl or an inert functional group;
R
12
and R
17
are each independently hydrogen, hydrocarbyl, substituted hydrocarbyl or an inert functional group;
and provided that any two of R
8
, R
9
, R
10
, R
11
, R
12
, R
13
, R
14
, R
15
, R
16
and R
17
that are vicinal to one another, taken together may form a ring.
There are many different ways of preparing the active polymerization catalysts of iron and cobalt which are used herein, many of which are described in U.S. patent applications Ser. No. 08/991,372, filed Dec. 16, 1997 (now U.S. Pat. No. 5,955,555), and 09/006,031, filed Jan. 12, 1998 (now U.S. Pat. No. 6,150,482), and those so described are applicable herein. “Pure” compounds which themselves may be active polymerization catalysts may be used, or the active polymerization catalyst may be prepared in situ by a variety of methods. Other methods for preparing active polymerization catalyst will be found in this patent application and in the Examples herein.
Which active polymerization catalysts will polymerize which olefins (not all cataly

Affiliated with

Also associated with

Rating

Molecular weight control in olefin polymerization does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Molecular weight control in olefin polymerization, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Molecular weight control in olefin polymerization will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2502233