Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2000-12-04
2002-03-12
Teskin, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S128000, C526S133000, C526S160000, C526S346000, C502S118000, C502S152000
Reexamination Certificate
active
06355745
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a process for polymerizing monovinylidene aromatic monomers, such as styrene, to produce polymers having a high degree of syndiotacticity, using a catalyst composition comprising a Group 4 metal complex.
In U.S. Pat. No. 4,680,353, there is disclosed a process for the preparation of syndiotactic polymers of monovinylidene aromatic monomers, using a catalyst system comprising a titanium catalyst and an alumoxane cocatalyst. However, this process uses relatively high amounts of cocatalyst which increases the cost of production.
WO93/03067 discloses a process for the preparation of syndiotactic polymers using a catalyst comprising a borane metal complex. However, this process generally yields lower catalyst activity and higher residual metal in the polymer.
Therefore, there remains a need for an activating cocatalyst composition which yields high catalyst activity and requires less aluminoxane, thus producing a polymer having lower levels of residual aluminum.
SUMMARY OF THE INVENTION
One aspect of the present invention is an activating cocatalyst composition used in the production of syndiotactic polymers from monovinylidene aromatic monomers wherein the composition comprises an aluminoxane and an electrophilic borane compound.
Another aspect of the present invention is a process for preparing syndiotactic polymers from monovinylidene aromatic monomers comprising contacting at least one polymerizable monovinylidene aromatic monomer under polymerization conditions with a catalyst composition comprising:
a) a Group 4 metal complex; and
b) an activating cocatalyst composition comprising an aluminoxane and an electrophilic borane compound.
This activating cocatalyst composition and process allows for the reduction in the amount of aluminoxane needed for high catalyst activity, thus decreasing the amount of residual aluminum in the polymer and lowering catalyst cost. The resulting syndiotactic polymers may be used in the preparation of articles such as a moldings, films, sheets and foamed objects.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is a method of producing a syndiotactic monovinylidene aromatic polymer. As used herein, the term “syndiotactic” refers to polymers having a stereoregular structure of greater than 50 percent syndiotactic of a racemic triad as determined by
13
C nuclear magnetic resonance spectroscopy. Such polymers may be usefully employed in the preparation of articles and objects (for example, via compression molding, injection molding or other suitable technique) having an extremely high resistance to deformation due to the effects of temperature.
In the practice of the present invention, suitable monovinylidene aromatic monomers useful in preparing the syndiotactic monovinylidene aromatic polymers include those represented by the formula:
wherein each R* is independently hydrogen; an aliphatic, cycloaliphatic or aromatic hydrocarbon group having from 1 to 10, more suitably from 1 to 6, most suitably from 1 to 4, carbon atoms; or a halogen atom. Examples of such monomers include, styrene, chlorostyrene, n-butylstyrene, vinyltoluene, and &agr;-methylstyrene, with styrene being especially suitable. Copolymers of styrene and the above monovinylidene aromatic monomers other than styrene can also be prepared.
The catalyst composition used in the process of the present invention comprises a Group 4 metal complex and an activating cocatalyst composition. All reference to the Periodic Table of the Elements herein shall refer to the Periodic Table of the Elements, published and copyrighted by CRC Press, Inc., 1989. Also, any reference to a Group or Series shall be to the Group or Series as reflected in this Periodic Table of the Elements, utilizing the IUPAC system for numbering groups.
The Group 4 metal complex preferably corresponds to the formula:
Cp
m
MX
n
X′
p
wherein:
Cp is a single &eegr;
5
-cyclopentadienyl or &eegr;
5
-substituted cyclopentadienyl group, the substituted cyclopentadienyl group being optionally also bonded to M through a substituent X;
M is a metal of Group 4 or the Lanthanide Series of the Periodic Table;
X each occurrence is an inert anionic ligand of up to 20 nonhydrogen atoms and optionally X and Cp are joined together;
X′ is an inert, neutral donor ligand;
m and p are independently 0 or 1;
n is an integer greater than or equal to 1; and
the sum of m and n is equal to the oxidation state of the metal.
Illustrative but nonlimiting examples of X include hydrocarbyl, silyl, halo, NR
2
, PR
2
, OR, SR, and BR
2
, wherein R is C
1-20
hydrocarbyl.
Illustrative but nonlimiting examples of X′ include ROR, RSR, NR
3
, PR
3
, and C
2-20
olefins or diolefins, wherein R is as previously defined. Such donor ligands are able to form shared electron bonds but not a formal covalent bond with the metal.
Preferred monocyclopentadienyl and substituted monocyclopentadienyl groups for use according to the present invention are more specifically depicted by the formula:
wherein:
M is titanium;
X independently each occurrence is hydrogen, halide, R, or OR;
R is C
1-10
hydrocarbyl group;
X′ is a C
4-40
conjugated diene;
n is 1, 2 or 3;
p is 1 when n is 1, and p is 0 when n is 2 or 3;
R′ is in each occurrence independently selected from the group consisting of hydrogen, halogen, R, NR
2
, PR
2
; OR; SR or BR
2
, or one or two pairs of adjacent R′ hydrocarbyl groups are joined together forming a fused ring system.
Preferably, the cyclic moiety comprises a cyclopentadienyl- indenyl-, fluorenyl-, tetrahydrofluorenyl-, or octahydrofluorenyl-group or a C
1-6
hydrocarbyl substituted derivative thereof, n is three, p is zero, X is C
1-4
alkyl or alkoxide. Most highly preferred metal complexes comprise pentamethylcyclopentadienyltitanium trimethyl, pentamethylcyclopentadienyltitanium tribenzyl, pentamethylcyclopenta-dienyltitanium trimethoxide, octahydrofluorenyltitanium tribenzyl, octahydrofluorenyltitanium trimethyl or octahydrofluorenyltitanium trimethoxide.
In a preferred embodiment, the metal complex is a metal trialkoxide which is combined with a trialkylaluminum or trialkylboron compound such as triethyl aluminum, tri-n-propyl aluminum, tri-isopropyl aluminum, tri-n-butyl aluminum, triisobutyl aluminum, and mixtures thereof, either prior to or simultaneously with the activating cocatalyst composition to form the active catalyst composition. It is believed, without wishing to be bound by such belief that the trialkylaluminum compound or trialkylboron compound causes the in situ transfer of the alkyl group to the Group 4 metal complex prior to activation thereof.
The Group 4 metal complexes are rendered catalytically active by combination with an activating cocatalyst. The cocatalyst composition of the present invention comprises an aluminoxane and an electrophilic borane compound.
Suitable aluminoxanes for use herein include polymeric or oligomeric aluminoxanes, especially methylalumoxane(MAO), isobutylaluminoxane, triisobutyl aluminum modified methylalumoxane, isopropyl alumoxane or diisobutylalumoxane. A preferred aluminoxane is methylalumoxane.
Electrophilic boranes suitable for use herein include tri(hydrocarbyl)boron compounds and halogenated derivatives thereof, having from 1 to 10 carbons in each hydrocarbyl or halogenated hydrocarbyl group, especially tris(fluoroaryl)boranes, tris(trifiuoromethyl substituted aryl)boranes, and tris(pentafluorophenyl)borane. Preferably, the borane is tris(pentafluorophenyl)borane. Activating cocatalysts and activating techniques have been previously taught with respect to different metal complexes in the following references: EP-A-277,003, U.S. Pat. Nos. 5,153,157, 5,064,802, EP-A-468,651, EP-A-520,732, and WO93/23412, the teachings of which are hereby incorporated by reference.
The aluminoxane and electrophilic borane compound are preferably premixed prior to their addition to the Group 4 metal catalyst. Typical mole ratios of aluminoxanelborane are from 1:1 to 150:1, preferably from 2:1 to 100:1, more pref
Borodychuk Karen K.
Newman Thomas H.
Teskin Fred
The Dow Chemical Company
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