Note: Descriptions are shown in the official language in which they were submitted.
'C! 94/15989 ~ ~ ~ PCT/US93/12695
DESCRIPTION
DIARYL CARF3INOL METATHESIS CATALYSTS
Technical Field
The present invention relates to an improved process
and catalyst system for the ring-opening metathesis polymer
ization of cyclic olefins, such as dicyclopentadiene (DCPD) .
More specifically, this invention relates to an improved
organo transition metal catalyst for metathesis
polymerization.
Background Art
Cyclic olefins are subjected to ring-opening metathesis
polymerization to produce thermoplastic and thermoset
polymers having physical properties which make them suitable
for structural and elsactronic applications, such as molded
plastic items and electrical laminates. Such polymer-
izations are commonly carried out in reaction injection
molding (RIM) processes, in which a metathesis catalyst and
a monomer are charged to a heated mold, and polymerization
of the monomer and forming of the polymer into the desired
shape are carried out simultaneously in the mold.
In such RIM processes, it is important that the
polymerization reaction occur rapidly and with as complete
incorporation of the charged monomers as possible. For
example, the presence of unreacted monomers in molded
polydicyclopentadiene has been found to result in a molded
part with an unpleasant odor, and less than optimum physical
properties. Finding a RIM process that reacts in as short
a cycle time as possible and at mold temperatures at or near
room temperature is economically desirable. It is also
advantageous to be able to use a less than pure monomer
stream and thus avoid extensive purification of the monomer
prior to polymerization.
Numerous patents and literature references relate to
such polymerization in the presence of a variety of olefin
metathesis catalysts. Among the pore effective ring-opening
polymerization catalysts are homogenous catalyst systems
based on tungsten or molybdenum halides, often employed with
an organotin or organoaluminum co-catalyst. Examples of
1
21~2~31
WO 94115989 PCT/US93/12695
such catalyst systems are disclosed by Sjardijn et al. , U. S.
Patent Nos. 4,810,762 and 5,093,441, wherein phenolic
tungsten halides are used with organotin hydrides. Similar
catalyst systems are disclosed by Sjardijn et al. in U.S.
4,729,976, which have been found to be highly active in a
relatively impure DCPD feed stream. While many such
metathesis catalysts containing aryloxy ligands are known,
these catalysts generally require the presence of a co-
catalyst to achieve good reactivities.
Catalysts which exhibit high reactivity, especially in
the absence of co-catalysts, are desirable to reduce
polymerization cycle time and to lower the costs associated
with the co-catalyst.
Disclosure of the Invention
The present invention provides an improved cyclic
olefin metathesis catalyst system for the ring-opening
polymerization of cyclic olefins, such as dicyclopentadiene.
More particularly the invention provides a catalyst system
comprising the reaction product of a transition metal halide
and a diaryl carbinol, and an optional co-catalyst. The
transition metal halide is preferably a tungsten, or
molybdenum halide or oxyhalide, most preferably a tungsten
halide such as tungsten hexachloride. The diaryl carbinol
may be optionally substituted with C1_lz alkyl, Ci_lz alkoxy, Cl_
,z alkylamino, C~zo aryl, halide, or C1_6 haloalkyl (such as
trifluoromethyl), or any combinations thereof. The
preferred diaryl carbinol is 9-hydroxyfluorene and
substituted derivatives thereof. The catalyst of this
invention can be used with a co-catalyst such as organo tin
hydrides, borohydrides, or organo aluminum compounds.
The present invention also provides a process for the
metathesis polymerization of cyclic olefins, specifically
norbornenes such as dicyclopentadiene. The monomer is mixed
with the above-described catalyst system, and the reaction
mixture is injected into a mold under conditions sufficient
for polymerization of the monomer and formation of a molded
article.
2
~C~ 94115989 ~ PCTIUS93112695
Hest Mode for Carrying Out the Invention
The Catalyst
The polymerization catalyst desc~'.i.bed herein is highly
reactive in the ring-opening metathesis polymerization of
cyclic olefins. Ring-opening metathesis catalysts
facilitate the breaking of the monomer ring at double bonds
to form linear and crosslinked unsaturated polymers.
The catalyst of the present invention comprises a
transition metal halide complex prepared using an optionally
substituted diaryl carbinol. The transition metal compounds
useful as starting materials to make the catalysts of the
instant invention are: generally in the form of a salt,
including such salts as halides and oxyhalides. Because of
the high activity of the resultant catalyst, the transition
metal is preferably a~ metal of Group VB and VIB such as
tungsten, molybdenum or tantalum.
Examples of such transition metal halides include
tungsten hexachloride, tungsten oxytetrachloride, tungsten
oxytetrabromide, molybdenum oxytetrachloride, molybdenum
trioxyhexachloride, molybdenum pentachloride, molybdenum
oxytetrafluoride, molybdenum oxytrichloride, and tantalum
pentachloride.
The transition metal metathesis catalysts of this
invention are the reaction products of: the above transition
metal salts with optionally substituted diaryl carbinols.
The diaryl carbinol can be represented by the general
formula:
OH
Gg -~ Gg
'' RR
where G is independently C1_12 alkyl, C1_~2 alkoxy, C~_~z
alkylamino, C~ZO aryl., halide, or C1_6 haloalkyl (e.g.
trifluoromethyl); g is independently 0 to 4; R is
3
CA 02152931 2004-10-14
-4-
independently hydrogen or G or the Rs are combined as a single bond or as a
bridging group X, where X is O (e.g. 9-hydroxyxanthene), -CHz , -CHzCHz (e.g.
dibenzosuberol), S, SO, SOZ or NRI; and R' is H or C~_6 alkyl.
Examples of suitable substituted diaryl carbinols include diphenyl carbinol
(benzhydrol), 9-hydroxyfluorene, 2-methylbenzhydrol, 4-methylbenzhydrol, 4-
chlorobenzhydrol, 4,4'-dichlorobenzhydrol, 4,4'-difluorobenzhydrol, 2,3,4,5,6-
pentafluorobenzhydrol, decafluorobenzhydrol, 4,4'- dimethoxybenzhydrol, 4,4'-
bis(dimethylamino)benzhydrol, dibenzosuberol, 9-hydroxyxanthene, 2-chloro-9-
hydroxyfluorene, 1,2,3,4,5,6,7,8-octafluoro-9-hydroxyfluorene, 2,7-dimethyl-9-
hydroxyfluorene, 4,4'-bis(trifluoromethyl)benzhydrol, 4-phenylbenzhydrol, and
1-,
2-, 3-, and 4-nonyl-9-hydroxyfluorene.
Preferred diaryl carbinols are the optionally substituted 9-hydroxyfluorenes,
and 9-hydroxyfluorene is particularly preferred.
The diaryl carbinol will generally be present in the catalyst preparation in
an
amount of from 0.5 to 4 moles per mole of the transition metal halide,
preferably
from 1 to 2 moles.
The reaction product of transition metal halide and diaryl carbinol can be
prepared by contacting, under an oxygen-free inert atmosphere, the diaryl
carbinol
compound and the transition metal compound each in an inert organic liquid
with
mild heat (25°C to 125°C, preferably 30°C to 75°C)
and removal of generated
hydrogen halide. Suitable inert organic liquids for the reaction include
cyclopentane,
cyclohexane, benzene, toluene, xylene, chlorobenzene and dichlorobenzene. The
inert organic liquid is then preferably distilled off under vacuum. The
reaction
product is preferably stored neat at room temperature or dissolved in an inert
organic
solvent such as toluene.
The Co-Catalvst
The catalyst of the present invention may be used in combination with one or
more co-catalysts for accelerating
/IJ 94/15989 215 ~ 9 3 l PCT/US93112695
the onset of the ring opening polycycloolefin
polymerization. An example of a suitable co-catalyst is a
borohydride co-cataly;st, including those compounds which can
be represented by the formula [Y+] [BH~,Zo]-, in which Y+
a represents an organic or organometallic cationic counterion,
Z is a substituent group such as alkyl, cyano, halide, and
the like, m > 0 and m + n = 4. Particularly preferred are
borohydrides represented by the formula [R23P]2[M+]BH4-, in
which each Rz is independently selected from C~_ZO, preferably
CZ_lz, hydrocarbyl, preferably aryl. Examples of such
borohydrides include transition metal-based borohydrides
such as bis(triphenylphosphine) copper (I) borohydride and
ammonium borohydride~; such as bis(triphenylphosphoranyli-
dene) ammonium borohydride.
1!> Effectiveness of the borohydride depends to some extent
on its solubility :in the monomer to be polymerized.
Borohydrides with poc>r solubility such as sodium triethyl
borohydride, sodium borohydride and tetrabutyl ammonium
borohydride are generally not active co-catalysts in non-
polar cyclic olefins :such as DCPD. Preferred co-catalysts,
because of their activity in DCPD and similar monomers, are
those represented by i~he above borohydride formula in which
m - 4, n - 0 and 5!+ includes aromatic groups such as
triarylphosphine and tetraaryldiphosphine, such as 1,2-
2.°i bis(diphenylphosphine)ethane, moieties.
Suitable co-cata.lysts can also include, for example,
an organo aluminum compound, including trialkyl aluminum,
alkylaluminum dihali.des, dialkyl aluminum halides or
alkyl(alkyloxy) aluminum halides. Suitable co-catalysts can
also include an organo tin hydride compound, including
compounds which can be represented by the formula Sn(R3)3H,
in which each R3 is selected independently from hydrogen,
substituted or unsubst~~t~ated aryl, or C~_2o alkyl. Specific
examples of such co-catalysts include ethyl aluminum
3°.> chloride, diethyl aluminum chloride, trioctyl aluminum,
tributyltin hydride, tripentyltin hydride, diphenyltin
dihydride, trioctyltin hydride, methyldicyclohexyltin
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2~.a2~~1
WO 94/15989 PCT/US93112695
hydride, cyclopentyldimethyltin hydride, triphenyltin
hydride, phenyldimethyltin hydride and allyltin trihydride.
Tributyltin hydride, trioctyltin hydride, and triphenyltin
hydride are preferred catalysts. Substituents on the R3
groups in the above formula can include, for example, Cl_2o
alkoxy and halides.
Catalyst System
As used herein, the catalyst system composition
comprises the transition metal halide catalyst and
optionally a co-catalyst, a moderator or a boron halide
promoter. The co-catalyst can be present in the catalyst
system composition in an amount effective to enhance the
activity of the transition metal halide catalyst, which will
vary depending upon the specific components present and the
reaction conditions. In general, the co-catalyst can be
present in a molar amount of from 15:1 to 0.5:1, preferably
from 8:1 to 1:1, based on moles of transition metal
catalyst.
The catalyst system may optionally include a moderator
to delay the initiation of polymerization if the selected
catalyst and co-catalyst cause instant polymerization upon
contact. Ethers, esters, ketones, nitriles and polar cyclic
olefins are among suitable moderators for catalyst systems
comprising tungsten catalyst and alkyl aluminum co-catalyst.
Ethyl benzoate, butyl ether bis(2-methoxyethyl) ether and
polar cyclic olefins are preferred moderators. Moderators
are generally not necessary for catalyst systems having a
tin hydride or borohydride co-catalyst.
The catalyst system may also optionally include a boron
halide promoter, including boron trihalides, boron trihalide
complexes and tetrahaloborates. The boron promoter can be,
for example, such boron halides as boron tribromide, boron
trifluoride, boron trifluoride diethyl ether complex, boron
trifluoride dibutyl ether complex, boron trifluoride
ethylamine, tetrafluoroboric acid diethyl ether, methyl
boron difluoride, phenyl boron dichloride, triphenylmethyl
fluoroborate, ammonium tetrafluoroborate, bis(2-ethyl-1-
6
'O 94/15989 ~ PCT/US93/12695
hexyl)ammonium tetr;afluoroborate, boron trichloride
dimethylsulfide, boron trifluoride alcohol complexes, and
the like. The boron compound wil:L be present in the
polymerization reaction mixture in an amount effective to
promote polymerization of the cyclic olefin monomer,
generally from 0.01 to to moles, preferably from 0.05 to 2
moles, per mole of transition metal. The optimum level will
vary depending upon the catalyst and the co-catalyst, and
amounts of boron ha7Lide above the optimum may inhibit
polymerization. The presently-preferred boron halides,
because of their high activity and stability, are boron
trifluoride and its ei~hyl ether and butyl ether complexes.
Polymerization
The polymerization process of the invention involves
contacting one or more cyclic olefin monomers with the
catalyst system composition. Preferred cyclic olefin
monomers and comonomers include polycycloolef ins containing
a norbornene (bicyclo-[2.2.1]heptene) group which can be
represented by the structural formulas:
_R~ \' R.
~~R,and ~ > R.
in which each R° is ;elected independently from hydrogen,
C,_ZO alkyl, C1_ZO alkenyl., C3_a cycloalkyl, C3_8 cycloalkenyl and
C~ZO aryl and, with R4 groups linked together through carbon
atoms, saturated and unsaturated cyclic hydrocarbon groups.
Included in such monomers and comonomers are dicyclopenta-
2°_> diene, norbornene, norbornadiene, 5-(2-propenyl)norbornene,
cyclohexenylnorbornene, and the like; and adducts of vinyl-
cyclohydrocarbons, e.g. 4-vinylcyclohexene and cyclopenta-
diene or 3,5-divinyl~cyclopentene and cyclopentadiene and
others as described in Kelsey, United States Patent Numbers
5,095,082 and 5,143,992. Commercial cyclic olefins are
available at various levels of purity, ranging from 92 to
7
99.9, the upper parity ranges v~lr.c, the result of
distillation and further treatment for removal of
contaminants and olefins which would be co-polymerized under
polymerization conditions. As a general rule, transition
metal catalysts employing an alkyl aluminum compound as co-
catalyst require a high-purity monomer for acceptable
polymerization activity, while the use of a tin hydride or
borohydride co-catalyst permits the use of lower purity,
technical-grade (83-95~%j dicyclopentadiene monomer. An
lC; advantage of the invention catalyst is that it is very
active in relatively impure (90-95%) dicyclopentadiene.
The ring-opening polymerization of the invention is
conducted by contacting the cycloolefin monomer and the
catalyst system under polymerization conditions. It is, on
1F some occasions, useful to provide an inert diluent in order
to solubilize the catalyst system components. Any co-
catalyst is generally combined with the transition metal
catalyst in the react:ion mixture as <i solution with the
monomer to be polymerized. The boron halide promoter, if
20 used, is generally combined with the transition metal and/or
co-catalyst solution. The catalyst system components will
typically have the necE~ssary solubility in the cycloolefin
to be polymerized and .in the preferred embodiment no added
diluent is employed and the catalyst system components and
2~ the cycloolefinic monomer are contacted directly. Suitable
polymerization conditions for such contacting include a
polymerization temperature of from 20°C to 250°C with
polymerization temper<~tures from 30°C to 150°C being
preferred. The polymerization pressure is that pressure
3C~ required to maintain the polymerization mixture in a non-
gaseous state. Such pressures will vary with the reaction
temperature but pressures up to about 5.2 kg/cm2, (5
atmospheres) are satisfactory and frequently ambient
pressure is suitable .and is preferred.
The inventive polymerization process is preferably
carried out by reaction injection molding (RIM), in which
a solution of the catalyst system, preferably in the
monomer
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'Vt) 94/15989 ~ ~ ~ ~~ PCT/US93/12695
liquid to be polymerized, is injected into a mold
simultaneously with 'the monomer, in liquid form, to be
polymerized. The catalyst is generally employed in a molar
ratio of RIM monomer t~o transition metal (mole:mole) of from
°. 200:1 to 12,000:1, preferably 500:1 to 8000:1, most
preferably 1000:1 to :5000:1.
In an illustrative polymerization, the monomer and
catalyst system are mixed at a relatively low temperature
at which rapid pohymerization does not occur. The
1G relatively low reaction rate permits efficient mixing or
other processing of the polymerization mixture including the
incorporation of fillers, reinforcements, antioxidants,
stabilizers, pigments, elastomers or other materials
provided to influence the properties of the polymerization
1_°°~ product. A particularly contemplated embodiment of the
process is in a reaction injection molding (RIM) process.
Because of the relati~rely low initial rate of reaction, the
monomer and catalyst system are mixed, typically by
provi ~ng each component of the catalyst system with a
2C~ portion of the cycloolefinic monomer, and the mixture is
then transferred (injected) to a suitable mold including
those molds for the production of large castings of complex
shape. Notwithstanding the low initial reaction rate, the
mixing and transfer must be accomplished rather quickly, for
2.~ in a typical RIM process, the mixing/transfer time is on the
order of a few seconds. Moreover, shortly after mixing of
the monomer and catalyst system, a significant reaction
exotherm occurs wl~iich substantially increases the
temperature of the polymerizing mixture. While such an
3C~ exotherm is at least in part beneficial in that the time for
polymerization in the mold is reduced, it also requires that
processing of the po v~~merization mixture be rapidly
completed.
In an alternative RIM polymerization technique, a
3~ stream of the transii:ion metal catalyst component in the
monomer to be polymerized and a monomer stream containing
any co-catalyst employed are combined in the mixing head of
9
i
CA 02152931 2003-10-23
-10-
a RIM machine just prior to injection of the combined
stream into a mold. The boron halide promoter, if used, is
injected into the mixing head with the transition metal
stream, with the co-catalyst stream, or in a separate
monomer solution stream.
The initial mold temperature will generally be within
the range of 20 to 200°C, preferably 30 to 7.50°C. The mold
pressure is generally within the range of 0.7 kg/cm2 (10
psi) to 3.5 kg/cm2 (50 psi). After injection of the
catalyst and monomer into the mold, there is an interval of
time, called the "induction time," before onset of a rapid
exotherm from the exothermic polymerization reaction. In a
commercial RIM process, this induction time should be
sufficiently long to permit filling of the mold, typically
2 minutes, preferably less than thirty seconds. Once the
polymerization reaction is initiated, polymerization should
occur quite rapidly, usually within 10 seconds to 1 minute,
and is accompanied by a rapid rise in temperature.
Various optional components can be present in the
reaction mixture during polymerization, including solvents,
fillers, anti-oxidants, flame retardants, blowing agents,
stabilizers, foaming agents, pigments, plasticizers,
reinforcing agents and impact modifers. Particularly
preferred, is the addition of from 1 to l0 weight percent,
based on the weight of the monomer, of an elastomer for
impact modification of the polymer: These components are
most conveniently added to the reaction as constituents of
one or more of the reaction mixture streams, as liquids or
as solutions in the monomer.
After the polymerization reaction is complete, the
molded object may be subjected to an optional post-cure
treatment at a temperature in the range of 100 to 300°C for
1 to 24, preferably 1 to 2 hours. Such a post-cure
treatment can enhance certain polymer properties, including
glass transition temperature.
The polymerized products of this invention are soluble
linear thermoplastic polymers or hard, insoluble,
'NIJ 94115989 PCT/US93112695
crosslinked thermoset polymers having utility such as parts
for cars, agriculture, housings for instruments or machines,
in electronics, and marine applications.
The invention i:~ further described by the following
..°i example which should not be regarded as limiting.
EXAMPLE I
In a nitrogen glove box, a reaction flask was charged
with 0.813g (2.05 mmol) of resublimed grade tungsten
hexachloride and 20 mL of toluene that had been dried four
lp times over molecular sieves and degassed. A dried serum
bottle was charged with 37.35g (2.05 mmol) of a 1% solution
of 9-hydroxyfluorene in toluene. The 9-hydroxyfluorene
solution had been dried three times over molecular sieves.
A second serum bottle: was charged with 10 mL dry toluene.
1..°i The reaction flask and serum bottle were transferred to the
hood. The reaction flask was connected to an argon source
and heated to about 70°C. The 9-hydroxyfluorene solution
was added via syringe: over about 25 minutes and rinsed in
with the 10 mL toluene. The solution was then heated and
20 stirred at about 70°C for about 26 hours under a flow of
argon to remove the HC1 byproduct (about 3 millimoles based
on the weight increase of the polyvinylpyridine trap
connected to the reaction flask), and the toluene was then
removed by distillation to give a dark solid residue.
2 °.i EXAMPLE I I
The catalyst as described in Example I above was used
in a laboratory polymerization of dicyclopentadiene (DCPD)
(about 94% pure). The polymerizations of 16g DCPD were
carried out in a 90°C oil bath. The following table shows
3~J the polymerization results with or without tributyltin
hydride co-catalyst. Polymerization of dicyclopentadiene
results in good polymerization without co-catalyst, but in
the presence of tri-n-butyltin hydride co-catalyst a
somewhat faster onset: is achieved.
11
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WO 94/15989 PCT/US93/12695
Polymerization
of 16g
Dicyclopentadiene
with
Catalyst
of Example
I
Onset Onset Maximum Maximum
Catalyst Co-CatalystTime Temp. Time Temp.
(mmol) Co-Catalyst(mmol) (min.)(C) (min.) (C)
0.059 Tributyltin0.236 3.00 64.4 4.70 197.0
hydride
0.122 None 0.000 4.50 90.4 5.10 210.0
0.059 None 0.000 NE' NE
' NE = no exotherm
While various modifications and changes will be
apparent to one having ordinary skill in the art, such
changes are included in the spirit and scope of this
invention as defined by the appended claims.
12
