Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2000-09-12
2002-03-26
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, C526S132000, C526S161000, C526S164000, C526S165000, C526S907000, C526S346000
Reexamination Certificate
active
06362293
ABSTRACT:
The present invention relates to a process for polymerizing vinylidene aromatic monomers, such as styrene, to produce polymers having a high degree of syndiotactidty, 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 polymers of vinylidene aromatic monomers having a stereoregular structure of high syndiotacticity, by the use of a catalyst system comprising a titanium catalyst and an alumoxane cocatalyst. The catalyst system is used as a dilute mixture in an organic solvent.
In U.S. Pat. No. 5,066,741 there are disclosed certain cationic metal compounds formed by reacting a Group 4 metal complex with ammonium or phosphonium salts of Bronsted acids containing a non-coordinating compatible anion or with cationic oxidizers containing a noncoordinating compatible anion. The complexes are usefully employed as catalysts in the polymerization of polymers of vinylidene aromatic monomers having a stereoregular structure of high syndiotacticity.
In U.S. Pat. No. 5,374,696, certain Group 4 metal complexes wherein the metal is in the +3 oxidation state and their use as addition polymerization catalysts are disclosed.
According to the present invention there is now provided a novel process for preparing polymers of vinylidene aromatic monomers having a high degree of syndiotacticity. The process comprises contacting at least one polymerizable vinylidene aromatic monomer under polymerization conditions with a concentrated catalyst premix composition comprising:
a) a Group 4 metal complex corresponding to the formula:
CpmMXnX′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 is in each occurrence 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; and
b) an activating cocatalst,
wherein the concentrated catalyst premix composition contains no additional solvent.
Compared to polymerization processes utilizing a similar catalyst composition which is diluted with an inert solvent, the present process achieves a significantly improved conversion of monomer and greater efficiency in use, thereby permitting a reduction in the quantity of metal complex employed and eliminating the solvent removal or recycle. Lower metal residuals give the additionally advantage of improved color and thermal stability in the polymer produced.
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 vinylidene 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 vinylidene aromatic monomers useful in preparing the syndiotactic vinylidene 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 vinylidene aromatic monomers other than styrene can also be prepared.
The concentrated catalyst premix composition used in the process of the present invention comprises a Group 4 metal complex and an activating cocatalyst. 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.
With respect to the metal complexes, 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 trialkyialuminum 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 to form the active catalyst premix 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 metal complexes are rendered catalytically active by combination with an activating cocatalyst. Suitable activating cocatalysts for use herein include polymeric or oligomeric alumoxanes, especially methylalumoxane(MAO), triisobutyl aluminum modified methylalumoxane, isopropyl alumoxane or diisobutylalumoxane; strong Lewis acids, such as C
1-30
hydrocarbyl substituted Group 13 compounds, especially tri(hydrocarbyl)aluminum- or tri(hydrocarbyl)boron- compounds and halogenated derivatives thereof, having from 1 to 10 carbons in each hydrocarbyl or halogenated hydrocarbyl group, especially tris(pentafluorophenyl)borane; and nonpolymeric, inert, compatible, noncoordinating, ion forming compounds (including the use of such compounds under oxidizing conditions). The foregoing 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.
Suitable nonpolymeric, inert, compatible, noncoordinating, ion forming compounds useful as cocatalysts in one embodiment of the present invention comprise a cation which
Borodychuk Karen K.
Newman Thomas H.
Teskin Fred
The Dow Chemical Company
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