|Title of Invention||
"POLYMERIZATION PROCESS USING ZINC HALIDE INITIATORS"
|Abstract||A cationic polymerization process for isoolefins using a zinc halide initiator. The zinc halide initiator is added to a solution of the isoolefin in a suitable solvent, preferably a halocarbon solvent. Polymerization reactions are normally conducted at temperatures high enough to allow the zinc halide initiator to dissolve in the solution. An alkyl halide activator may optionally be used and is preferably added to the solution prior to the zinc halide initiator. A multiolefin may optionally be present in the solution. The process is particularly useful in the formation of isoolefin homopolymers and co-polymers of isoolefins and multiolefins, such as butyl rubber.|
|Full Text||POLYMERIZATION PROCESS USING ZINC HALIDE INITIATORS
Field of the Invention
The invention relates to the cationic polymerization of isoolefins and
optionally multiolefins using zinc halide initiators. More particularly, the invention
relates to the cationic polymerization of isobutene and isoprene to form butyl rubber
polymers using zinc halide initiators and optionally alkyl halide co-initiators.
Poly(isobutylene-co-isoprene), or MR, is a synthetic elastomer commonly
known as butyl rubber which has been prepared since the 1940's through the
random cationic copolymerization of isobutylene with small amounts of isoprene
2 mole %) . As a result of its molecular structure, IIR possesses superior air
impermeability, a high loss modulus, oxidative stability and extended fatigue
Butyl rubber is a copolymer of an isoolefin and one or more, preferably
conjugated, multiolefins as comonomers. Commercial butyl comprises a major
portion of isoolefin and a minor amount, not more than 2.5 mol %, of a conjugated
Butyl rubber or butyl polymer is generally prepared in a slurry process using
a suitable polymerization solvent, such as methyl chloride, and a Friedel-Crafts
catalyst, such as AICI3, as the polymerization initiator. The methyl chloride offers
the advantage that Aids, a relatively inexpensive Friedel-Crafts catalyst, is soluble
in it, as are the isobutylene and isoprene comonomers. Additionally, the butyl
rubber polymer is insoluble in the methyl chloride and precipitates out of solution as
fine particles. The polymerization is generally carried out at temperatures of about -
90° C to -100° C. See U.S. Patent No. 2,356,128 and Ullmanns Encyclopedia of
Industrial Chemistry, volume A 23, 1993, pages 288-295. The low polymerization
temperatures are used to achieve molecular weights which are sufficiently high for
Other compounds that have been found to be active as catalysts for
polymerizing isoolefins include organometallic compounds in combination with a
cation-generating agent, for example CsMesTiMes/B^eFsh (WO-00/04061-A1),
Cp2AIMe/B(C6F5)3 (US-5,703,182), and combinations of zirconocenes and related
complexes with either B(C6F5)3 or CPh3[B(C6F5)4] (WO-95/29940-A1 , DE-A1-198 36
663), Song, X.; Thornton-Pett, M.; Bochmann, M. Organometallics 1998, 17, 1004,
Carr, A. G.; Dawson, D. M.; Bochmann, M. Macromol. Rapid Commun. 1998,
Nuyken, in collaboration with M. Bohnenpoll (Chem. Eur. J. 2004, 10, 6323),
published a system based on [Mn(NCMe)6]2+ salts of non-coordinating borate
anions which was active at room temperature:
This system operated at +30°C in IB/CH2CI2 but showed no activity 0°C.
Polymerizations were generally slow (55 - 110 h for IB homopolymerizations), and
there was some doubt about the mechanism. IB homopolymers and copolymers
had Mn = 8,000 - 10,000. Conversion was rapidly depressed at higher IP feed.
Zinc compounds have not commonly been used as catalysts for isoalkene
polymerizations. Indeed, ZnCI2 in the presence or absence of alkyl halide activators
(such as MeaCCI or MeCOCI) and used either in neat isobutene or in
isobutene/methyl chloride mixtures, proves to be inactive, and no polymer is
obtained. Recently however, Bochmann and coworkers filed a patent on the use of
Zn(C6P5)2 / Bu'CI system for IB homo- and IB/IP copolymerizations (Canadian
patent application 2,441,079, filed September 16, 2003). Zinc had never been used
as an initiator for cationic polymerizations before. This patent teaches that this
system possessed particularly good copolymerization characteristics and allowed
the formation of IB/IP copolymers in neat IB solutions (no solvent). The polymers
had up to 15 mol-% IP, with little gel content. However, monitoring the reaction of
Zn(C6F5)2 with tert-butyl chloride fBuCI) always found substantial amounts of C6F5H
together with insoluble precipitates. In addition, the Zn(CeF5)2 is expensive to use in
a commercial scale process and lower cost alternatives are therefore being sought.
The need therefore remains for improved polymerization processes using
Summary of the Invention
According to the present invention, there is provided a process for the
cationic polymerization of an isoolefin monomer using a zinc-based initiator, the
process comprising: providing a solution of the isoolefin monomer in a halocarbon
solvent; adding a zinc-based initiator comprising an alkyl or aryl zinc halide to the
solution; and, reacting the solution containing the zinc-based initiator to form a
polymer comprising the isoolefin.
Polymerization reactions may be conducted at temperatures high enough to
allow the zinc halide initiator to dissolve in the solution. An alkyl halide activator may
optionally be used and is preferably added to the solution prior to the zinc halide
initiator. Multiolefins may optionally be present with the isoolefin in the solvent and
may participate in the reaction to form co-polymers with the isoolefin. The isoolefin
may comprise isobutene, the multiolefin may comprise isoprene and the polymer
may comprise butyl rubber.
The zinc halide initiators used in the process of the present invention
advantageously exhibit high solubility in the solvent and are low in cost.
Further features of the invention and preferred embodiments thereof will now
be more thoroughly described.
The present invention relates to isoolefin homopolymers and co-polymers of
isoolefins, multiolefins and optionally other co-polymerizable monomers. In a
preferred embodiment, the co-polymer is a butyl rubber polymer. The terms "butyl
polymer", "butyl rubber" and "butyl rubber polymer" are used interchangeably
throughout this specification and are intended to mean a polymer prepared by
reacting a major portion of an isoolefin monomer with a minor portion of a multiolefin
The process is not limited to a specific isoolefin. However, isoolefins within
the range of from 4 to 16 carbon atoms, in particular 4-8 carbon atoms, such as
isobutene, 2-methyl-1-butene, 3-methyl-1-butene, 2-methyl-2-butene, 4-methyl-1-
pentene and mixtures thereof are preferred. Most preferred is isobutene.
When multiolefins are present in the reaction mixture, the process is not
limited to a specific multiolefin. Every multiolefin copolymerizable with the isoolefins
known by the skilled in the art can be used. Multiolefins with in the range of from 4-
14 carbon atoms are preferred. A preferred C4 to Cu multiolefin comprises a C4 to
Cio conjugated diolefin. Some specific non-limiting examples of suitable multiolefins
include isoprene, butadiene, 2-methylbutadiene, 2,4-dimethylbutadiene, piperyline,
3-methyl-1,3-pentadiene, 2,4-hexadiene, 2-neopentylbutadiene, 2-methly-1,5-
hexadiene, 2,5-dimethly-2,4-hexadiene, 2-methyl-1,4-pentadiene, 2-methyl-1,6-
heptadiene, cyclopenta-diene, methylcyclopentadiene, cyclohexadiene, 1-vinylcyclohexadiene
and mixtures thereof. Isoprene is particularly preferably used.
The polymer may be derived from a mixture comprising only the isoolefin
monomer. The polymer may also be derived from a mixture from about 70 to 99.5
parts by weight of the C4 to CQ isoolefin monomer and from about 30 to about 0.5
parts by weight of the C4 to Ci4 multiolefin monomer. More preferably, the polymer
is derived from a mixture comprising from about 80 to about 99.5 parts by weight of
the C4 to Ca isoolefin monomer and from about 20 to about 0.5 parts by weight of
the C4 to Ci4 multiolefin monomer. A most preferred polymer according to the
present invention is derived from a mixture comprising from about 97 to about 99.5
parts by weight of isobutylene and from about 3 to about 0.5 parts by weight of
Those of skill in the art will recognize that it is possible to include an optional
third monomer to produce a butyl terpolymer. For example, it is possible to include
a styrenic monomer in the monomer mixture, preferably in an amount up to about
15 percent by weight of the monomer mixture. The preferred styrenic monomer
may be selected from the group comprising p-methylstyrene, styrene, amethylstyrene,
p-chlorostyrene, p-methoxystyrene, cyclopentadiene,
methylcyclopentadieneindene, indene derivatives and mixtures thereof. The most
preferred styrenic monomer may be selected from the group comprising styrene, pmethylstyrene
and mixtures thereof. Other suitable copolymerizable termonomers
will be apparent to those of skill in the art.
Suitable polymerization processes for producing isoolefin-containing
polymers, particularly butyl rubber polymers, are known to persons skilled in the art
and are further described in US 2,356,128. Generally, the processes involve
providing the monomer mixture dissolved in a suitable solvent. The solvents are
generally organic fluids. Organic fluids suitable for use in commercial butyl rubber
polymerization include inert Ci to C4 halogenated hydrocarbons and mixtures
thereof, Cs to Ca aliphatic hydrocarbons, Cs to Cs cyclic hydrocarbons, mixtures of
one or more of the halogenated hydrocarbons and one or more of the aliphatic
hydrocarbons, and mixtures of one or more of the halogenated hydrocarbons and
one or more of the cyclic hydrocarbons. Examples of preferred inert organic fluids or
solvents include pentane, hexane, heptane and mixtures thereof with one another
or with halogenated hydrocarbons such as methyl chloride and/or dichloromethane .
Most preferably the organic fluid is a halogenated hydrocarbon selected from the
group consisting of methyl chloride, dichloromethane and mixtures thereof.
A zinc based initiator according to the present invention comprises a divalent
zinc halide Lewis acid that is preferably soluble in either neat IB or in mixtures of IB
and a suitable organic solvent. Although zinc chloride (ZnCI2) is a simple zinc halide
that would be suitable for use as an initiator, it is not soluble in either neat IB or
IB/solvent mixtures. The preferred zinc halides therefore comprise soluble organic
zinc halides, more preferably alkyl or aryl zinc halides, yet more preferably shortchain
alkyl zinc halides. Since the zinc is divalent, there is only one alkyl or aryl
group present in addition to the halide group. The zinc halide preferably does not
comprise an alkoxide. The preferred halogen is chlorine, although bromine may
also be used. Examples of preferred zinc halides include compounds of the
R is methyl, ethyl, propyl or butyl; and,
X isCI, Br, or I.
It might be advantageous to further add an activator or co-initiator to the
monomer mixture. The invention is not limited to any special co-initiator/activator as
long as the co-initiator compound does not adversely affect the polymerisation
reaction. Preferred are activators of the general formula HX, RX, R3CX or RCOX
with each R independently being a Ci to C5o hydrocarbon radical which may be
linear, branched or cyclic and may contain one or more non-carbon atoms in the
carbon-chain, such as methyl, ethyl, n-propyl, n-butyl, s-butyl, t-butyl, pentyl, hexyl,
octyl, nonyl, decyl, dodecyl, cumyl, 3-methylpentyl, 2,4,4-trimethylpentyl and 3,5,5-
trimethylhexyl and each X being a halogen, preferably chlorine, bromine or iodine.
Preferred co-initiators are Me3CCI, 'BuCI, cumyl chloride, TMP-2-chloride, MeCOCI,
and Me3CBr. Most preferred are teuCI and cumyl chloride.
The preferred ratio of zinc compound to co-initiator(s) is in the range of from
1:0.1 to 1:10 by mol, and the most preferred ratio is in the range of from 1:1 to
Ethyl zinc chloride (EtZnCI) is a particularly preferred zinc-based initiator that
exhibits good solubility in mixtures of IB with the halocarbon solvent
dichloromethane (CH2CI2), but limited solubility in neat IB. EtZnCI is a Cl-bridged
tetramer. The solid is soluble in organic solvents at room temperature. The system
EtZnCI / Bu'CI shows good activity for IB polymerization and IB/IP
copolymerizations. Because even in this system the in-situ generated ZnCI2 is
insoluble in IB/CHzCfe mixtures at -78°C, the system shows best activities at
temperatures > -35°C. However, the system EtZnCI / cumyl chloride has improved
low temperature solubility and exhibits good polymerization activity at temperatures
of -78°C down to -90 °C or lower. The monomers are therefore preferably
polymerized at temperatures in the range of from -100°C to 40°C, more preferably
in the range of from -90°C to 35°C, yet more preferably in the range of from -80°C
to 35°C, even more preferably in the range of from -70°C to 35°C, still more
preferably in the range of from -60°C to 35°C, yet even more preferably in the
range of from -50°C to 35°C, yet still more preferably in the range of from -35°C to
20 35°C and at pressures in the range from 0.1 to 4 bar.
The use of a continuous reactor as opposed to a batch reactor may have a
positive effect on the process. Preferably, the process is conducted in at least one
continues reactor having a volume of between 0.1 m3 and 100 m3, more preferable
between 1 m3 and 10 m3.
If polymerization is performed continuously, the process is preferably
performed with at least the following feed streams:
I) solvent/diluent (preferably dichloromethane) + isoolefin (preferably
isobutene) + multiolefin (if present, preferably a diene, such as
II) zinc halide compound (preferably ethyl zinc chloride)
The alkyl halide activator (if present) can be either pre-dissolved in the
solvent or added to the solvent in conjunction with or following addition of the
monomers. The alkyl halide activator is preferrably provided prior to addition of the
zinc halide initiator.
The zinc halide initiator system may be used to produce either IB
homopolymers of co-polymers of IB and a diene monomer. When the diene
monomer is isoprene, the co-polymer of IB and IP is butyl rubber. The IB
homopolymer has a molecular weight (Mn) in the range of from 25,000 to 500,000
and the IB/IP co-polymer has a molecular weight in the range of from 15,000 to
Polymers comprising residual double bonds resulting from the inventive
process may be the starting material for a halogenation process in order to produce
halo-butyl polymers. Bromination or chlorination can be performed according to the
procedures described in Rubber Technology, 3rd Ed., Edited by Maurice Morton,
Kluwer Academic Publishers, pp. 297 - 300 and references cited within this reference.
The copolymers presented in this invention are ideally suitable for the
production of moldings of all kinds, in particular tire components and industrial
rubber articles, such as bungs, damping elements, profiles, films, coatings. The
polymers are used to this end in pure form or as a mixture with other rubbers, such
as NR, BR, HNBR, NBR, SBR, EPDM or fluororubbers. The preparation of these
compounds is known to those skilled in the art. In most cases carbon black is
added as filler and a sulfur based curing system is used. Peroxide based curing
systems may also be used, particularly when the polymer contains at least 4 mol%
of repeating units derived from at least one multiolefin monomer. For compounding
and vulcanization, reference is made to Encyclopedia of Polymer Science and
Engineering, Vol. 4, S. 66 et seq. (Compounding) and Vol. 17, S. 666 et seq.
(Vulcanization). The vulcanization of the compounds is usually effected at
temperatures in the range of 100 to 200°C, preferred 130 to 180°C (optionally under
pressure in the range of 10 to 200 bar).
The following Examples are provided to illustrate the present invention.
Example 1: EtZnCI system for IB homopolvmerizations
IB (9 ml) was condensed into a graduated vessel at -78 °C. Pre-chilled
dichloromethane was injected to complete a 22 ml total reaction volume. A 'BuCI
stock solution in dichloromethane (100 ^mol/ ml_ CH2CI2) was prepared at -78 °C.
An aliquot with the appropriate amount of 'BuCI was added to the reactor, followed
by the addition of solid EtZnCI. At this temperature the white solid did not change.
However, when the mixture was allowed to warm to -35°C (checked with internal
thermocouple) the solid dissolved completely. EtZnCI was used in an excess, and
'BuCI was used to control the polymerization rate as the limiting reagent. Reactions
were quenched in methanol, dried at 60 °C until constant weight. Results are
reported in Tables 1-4.
The system was sealed and was warmed to the set temperature indicated in
the tables. For reactions at 20°C the internal pressure has been calculated to be 2
bar. The solution became very cloudy after one minute (the time required for the
mixture to reach the critical temperature of -35 °C where reaction starts). Cooling
again to -78°C gave only traces of polymer (run 637). This shows that the zinc
species involved in the polymerization are insoluble at -78 °C. However, if the
system is sealed in order to avoid IB evaporation, very high conversions are
reached at room temperature (run 639). Polymers thus prepared showed Mn values
of 25 - 47 x 103. High concentrations of 'BuCI (Run 654-655) were used to give
nearly quantitative conversions after a 30 minute reaction. A decrease of
temperature increases the molecular weights of the polymers. A molecular weight of(Table Removed)
1) A process for the cationic polymerization of an isoolefin monomer using a zincbased
initiator, the process comprising:
a) providing a solution of the isoolefin monomer in a halocarbon solvent;
b) adding a zinc-based initiator comprising an alkyl or aryl divalent zinc halide to the
c) reacting the solution containing the zinc-based initiator to form a polymer
comprising the isoolefin.
2) The process according to claim 1, wherein the isoolefin is isobutene.
3) The process according to claim 1, wherein the halocarbon solvent is
4) The process according to claim 1, wherein the ratio of isoolefin to halocarbon solvent
is in the range of from 1:1 to 1:3 by volume.
5) The process according to claim 1, wherein the process further comprises adding an
alkyl halide activator to the solution prior to addition of the zinc-based initiator.
6) The process according to claim 5, wherein the alkyl halide activator is tert-butyl
chloride ('BuCI) or cumyl chloride.
7) The process according to claim 5, wherein the alkyl halide activator is present in a
molar amount less than or equal to the molar amount of the zinc-based initiator.
8) The process according to claim 1, wherein the zinc-based initiator is added to the
solution as a solid.
9) The process according to claim 1, wherein the zinc-based initiator is added at a
temperature of from -90 °C to -35 °C.
10)The process according to claim 1, wherein the reaction is conducted at a
temperature of from -90 °C to 35 °C.
11 )The process according to claim 1, wherein the polymer is an isoolefin homopolymer.
12)The process according to claim 1, wherein the solution further comprises a
multiolefin monomer in an amount of from 1 to 15 mol % of total monomers in the
13)The process according to claim 12, wherein the polymer is a co-polymer of the
isoolefin and the multiolefin monomers.
14)The process according to claim 12, wherein the isoolefin monomer is isobutene, the
multiolefin monomer is isoprene and the polymer is butyl rubber.
15)A polymer prepared by the process according to claim 1.
16)The polymer of claim 15, wherein the isoolefin is isobutene and wherein the polymer
is a homopolymer of isobutene.
17)The polymer according to claim 16, wherein the polymer has a molecular weight
(Mn) of from 25,000 to 500,000.
18)A polymer prepared by the process according to claim 12.
19)The polymer of claim 18, wherein the isoolefin monomer is isobutene, the multiolefin
monomer is isoprene and the polymer is butyl rubber.
20)The polymer according to claim 19, wherein the polymer has a molecular weight
|Indian Patent Application Number||440/DEL/2007|
|PG Journal Number||09/2013|
|Date of Filing||28-Feb-2007|
|Name of Patentee||LANXESS INC.|
|Applicant Address||CITY OF SARNIA,IN THE PROVINCE OF ONTARIO,CANADA N7T 7M2|
|PCT International Classification Number||C08F210/00|
|PCT International Application Number||N/A|
|PCT International Filing date|