Note: Descriptions are shown in the official language in which they were submitted.
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BUTYL-TYPE RUBBER WITH HIGH VISCOSITY
FIELD OF THE INVENTION
The present invention relates to an elastomer having repeating units derived
from at least one isomonoolefin monomer, at least one diisoalkenylbenzene
monomer, .
and optionally further copolyrnerizable monomers, said polymer having a Mooney
viscosity (ML 1+8@125 °C according to ASTM D1646) of more than 80 units
as well
as a curable composition comprising said elastomer and a shaped article
manufactured
from said curable composition.
BACKGROUND
In many of its applications, isoolefin copolymers, in particular butyl rubber
is
used in the form of cured compounds.
Rubbery copolymers of isoolefins of 4 to 7 carbon atoms, such as isobutylene,
and aliphatic dienes of 4 to 14 carbon atoms, such as isoprene or butadiene,
are known
by the generic name of "butyl rubbers"(IIR).
Butyl rubber is manufactured by copolymerizing isobutylene and isoprene in
methyl chloride diluent using aluminum chloride as a catalyst. This cationic
polymerization is carried out in a continuous reactor at temperatures below -
90 °C. A
solution process is also known, with a CS-C7 hydrocarbon as solvent and an
aluminum
alkylhalide catalyst.
The isoprene incorporated in IIR (ca. 0.5-2.5 mol %) provides double bonds,
which allow the rubber to be vulcanized with sulfur and other vulcanizing
agents.
Butyl rubber and its vulcanizates are characterized by impermeability to air,
high
damping of low frequency vibrations, and good resistance to aging, heat,
acids, bases,
ozone and other chemicals. These characteristics lead to the use of butyl
rubber in tire
inner tubes, tire curing bladders and bags, vibration insulators, roof and
reservoir
membranes, pharmaceutical bottle stoppers and other applications.
The polymer is similar in structure to polyisobutylene and has a similar glass
transition temperature, Tg, of -72 °C. A large number of methyl groups
positioned
along the maeromolecular chains interfere mechanically with each other and
reduce the
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speed with which the molecules respond to deformation. This explains the low
rebound
resilience and typical damping properties of this product. On the other hand,
the
relatively low mobility of the molecule segments gives butyl rubber its well-
known
impermeability to oxygen, nitrogen, carbon monoxide, water and other
substances,
which do not swell the vulcanizate.
As is well known to those skilled in the art, the viscosity of elastomers is
usually measured using the Mooney viscosity test. During this test, a flat,
serrated disc
rotates in a mass of rubber contained in a grooved cavity under pressure. The
torque
required to rotate the disc at 2 rpm at a fixed temperature is defined as the
Mooney
viscosity.
Normal butyl elastomers are gel-free - that is, they are entirely soluble in
hydrocarbon solvents (hexane, mineral spirits, benzene, toluene). The usual
range of
molecular weights of butyl rubber is 250,000 -750,000 g/mol. As with other
rubbers,
the Mooney viscosity of the polymer has a strong influence on the processing
behavior,
low viscosity grades being easier to process. However, if the compound needs
fairly
good dimensional stability or shape retention, the grades with higher
viscosity are
preferred.
The usual range of Mooney viscosity values for butyl rubber is 30-50 units (ML
1+8@125 °C), depending on the grade. Bayer manufactures also a special
erosslinked
grade of butyl rubber under the trademark of XL-10000TM. These are isobutylene
isoprene-divinylbenzene terpolymers with Mooney viscosity typically in the
range of
60-75 units (ML 1+8@125 °C). These products are often used in
sealants/adhesives
and in electrolytic condenser caps.
For some specific applications, high-viscosity rubber is needed. For example,
this is the case with soft printing rollers. The function of the rollers used
in printing
presses is not just to exert pressure. In fact, the rollers used in inking
units in
letterpresses and offset printing equipment must actually be particularly
soft. However,
the production of suitable rubber blends for this particular application
presents a major
challenge for engineers. A simple addition of large amounts of plasticizers
often does
not solve the problem. Low-viscosity rubbers, in particular, turn into a
sticky mass
upon the addition of large quantities of plasticizers, making them even more
difficult to
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process. In the vulcanized state the compounds can undergo profound
dimensional
changes because plasticizers can be washed out by the oil- containing printing
inks or
dissolved in detergents. The result is poorer print quality, combined with
higher
printing costs due to frequent adjustments that have to be made to the inking
system.
Butyl rubber is also known to be useful in printing blankets for the dry
offset
cup, tube and lid printing markets. This industry prints on rigid containers
including
cups, tubes and pails. Properly formulated butyl rubber compounds offer
optimum
resistance to most W and IR printing inks, as well as provide excellent
solvent
resistance.
The free radical initiated polymerization of diisopropenylbenzes (DIPB's) is
known. However, this free radical initiated polymerizations produced
crosslinked gels.
The use of an anionic technique made it possible to produce essentially
linear,
soluble polymer in which only one unsaturation site of each DIPB molecule was
consumed. At low conversions, the aromatic ring of each pendant group carried
an
unreacted isopropenyl group ("Makromol. Chem.", 183. (2787 (1982), US. Pat.
4,499,248). Branching and crosslinking could occur at higher conversions (> 50
%).
The cationic polymerization of DIPB's was found to produce polymers
containing predominantly a polyindane structure ("J. Polym. Sci.", 28, 629
(1958). The
molecular weight increased in a stepwise manner with time and the overall
process was
kinetically more akin to a polycondensation than to a conventional vinyl
polymerization. The continuation of the vinyl addition beyond the dimer stage
led to
crosslinked products.
D'Onofrio ("J. Appl. Polym. Sci." 8, 521 (1964) demonstrated that linear, high
molecular weight, soluble polyindane was produced from diisopropenylbenzenes
at
polymerization temperature above 70 °C using a complex Lewis acid type
initiating
system (LiBu-TiCl4-HCl). It was pointed out that with the use of BF3, TiCl4,
SnCl4,
etc., a narrow polymerization range (70-100 °C) was necessary in order
that soluble
polymer was obtain. At temperatures below 70 °C crosslinked products
resulted. At
temperatures higher than 100 °C, the activity of the catalyst
decreased.
Sonnabend (US Pat, 3,004,953) claimed a direct cationic copolymerization of
diisopropenylbenzenes with phenol. The process was complicated by the
simultaneous
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occurrence of propagation and alkylation reactions, with products exhibiting
branching
and ultimately gelation.
H. Colvin et al. described a direct cationic copolymerization of m
diisopropenylbenzene and m-dimethoxybenzene (in "New Monomers and Polymers",
B. Culbertson and C. Pittman (Eds.), Plenum Press, New York 1984, 415-428).
The
dimethoxybenzene could be incorporated into the polymer backbone or as a
pendant
group. The most important variable in controlling the ratio of mono- to
dialkylated
dimethioxybenzene was the catalyst. The MW of the polymer was below 50,000
g/mol
and the properties were poor.
Copolymers of p- or m- diisopropenylbenzene with styrene exhibited unusually
high melting points and increased chemical and heat resistance (GB 850, 363).
These
copolymers containing at least 5 % of the difunctional monomer could be useful
as
moulding resins, adhesives, priniting inks and as additives for lubricating
oils to raise
the viscosity index of the oil. The preferred catalyst was a cationic
catalyst.
US Pat. 3,067,182 taught that uniform copolymers of isopropenylbenzene
chloride with isobutylene could be made under cationic copolyrnerization
conditions at
temperatures below - 100 °C. Such copolymers could be readily
crosslinked with
amines or phenols or by adding a Friedel-Crafts catalyst to obtain cure by
self
alkylation.
Multi-arm star polyisobutylenes were prepared by the "arm-first" method
("Macromol. Symp.", 95, (1995) 39-56). This synthesis was accomplished by
adding
various linking agents ("core builders") such as p- and m- divinylbenzene and
p- and
m- diisopropenylbenzene (DIPB) to living PIB+ charges and thus obtaining a
crosslinked aromatic core holding together a corona of well-defined arms. The
products were characterized in terms of overall arm/core composition,
molecular
weight and molecular weight distribution.
Star-shaped polymer, useful as viscosity modifier for lubricating oil,
comprised
poly(diisopropenylbenzene) as core with at least three polyisobutylene arms
(EP
1099717 A). Polymerization occurred in the presence of titanium tetrachloride
and
pyridine (living polymerization).
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Ca-pending applications CA-2,386,628 and CA-2,368,646 provide a compound
comprising at least one elastomeric polymer comprising repeating units derived
from at
least one C4 to C~ isomonoolefin monomer, at least one C4 to C14 multiolefin
monomer
or (3-pinene, at least one multiolefin cross-linking agent and at least one
chain transfer
agent, said polymer containing less than 15 wt.°!° of solid
matter insoluble within 60
min in cyclohexane boiling under reflux, at least one filler and a peroxide
curing
system. The multiolefin cross-linking agent is a multiolefinic hydrocarbon
compound.
Examples of these are norbornadiene, 2-isopropenylnorbornene, 2-vinyl-
norbornene,
1;3,5-hexatriene, 2-phenyl-1,3-butadiene, divinylbenzene,
diisopropenylbenzene,
divinyltoluene, divinylxylene or C1 to C2o alkyl-substituted derivatives of
the above
compounds.
A co-pending application filed with the Canadian Intellectual Property Office
on Aug. O5, 2003 under the attorney docket POS 1142 CA provides a method of
improving reversion resistance of a peroxide curable polymer comprising at
least one
polymer having repeating units derived from at least one isomonoolefin monomer
and
at least one aromatic divinyl monomer by polymerizing the monomers in the
presence
of at least one m- or p-diisoalkenylbenzene compound.
However, none of the prior art is actually disclosing an elastomer having
repeating units derived from at least one isomonoolefin monomer, at least one
diisoalkenylbenzene monomer, and optionally further copolymerizable monomers,
said
elastomer having a Mooney viscosity (ML 1+g@125 °C according to ASTM
D1646) of
more than 80 units.
SUMMARY
The present invention relates to an elastomer having repeating units derived
from at least one isomonoolefin monomer, at least one diisoalkenylbenzene
monomer,
and optionally further copolymerizable monomers, said elastomer having a
Mooney
viscosity (ML 1+8@125 °C according to ASTM D1646) of more than 80 units
and to a
process of obtaining said elastomer via a direct cationic reaction of at least
one
isomonoolefin monomer, at least one diisoalkenylbenzene monomer, and
optionally
further co-monomers.
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At the same time, a predominant portion (> 50 %) of said elastomer is soluble
in
a hydrocarbon solvent, such as cyclohexane under reflux for 60 min. This
modified
butyl-type rubber has fully saturated main polymer chains and is curable with
sulfur
curing agents. It is useful in applications where other types of very high
Mooney
viscosity rubber are being used which do not display advantages typical for
butyl
polymer or polyisobutylene, such as e.g., NBR elastomers.
DETAILLED DESCRIPTION OF THE INVENTION
The present invention preferably relates to butyl-like polymers. The
terms "butyl rubber", "butyl polymer" and "butyl rubber polymer" are used
throughout
this specification interchangeably. While the prior art in using butyl rubber
refers to
polymers prepared by reacting a monomer mixture comprising a C4 to C~
isomonoolefin monomer and a C4 to Cr4 multiolefin monomer or ~i-pinene, this
invention relates to elastomeric polymers comprising repeating units derived
from at
least one isomonoolefin monomer, at least one diisoalkenylbenzene monomer, and
optionally further copolyrnerizable monomers, said elastomer having a Mooney
viscosity (ML 1+8@125 °C according to ASTM D1646) of more than 80
units.
Preferred are elastomeric polymers comprising repeating units derived from at
least one
isomonoolefin monomer and at least one diisoalkenylbenzene monomer, which due
to
the lack of further comonomers, such as multiolefin monomer/conjugated
aliphatic
dime or (3-pinene, have no double-bonds in the polymer chains.
The present invention is not restricted to any particular isomonoolefin
monomer, however C4 to C~ isomonoolefin monomers are preferred. Preferred C4
to C~
monoolefins are isobutylene, 2-methyl-1-butene, 3-methyl-1-butene, 2-methyl-2-
butene, 4-methyl-1-pentene and mixtures thereof. The most preferred
isomonoolefin
monomer is isobutylene.
The present invention is not restricted to any particular diisoalkenylbenzene
provided that the diisoalkenylbenzene is copolymerisable with the isoolefin
monomers) present. Examples of suitable diisoalkenylbenzenes are the meta- or
para-
isomers of diisopropenylbenzene and dimethallylbenzene.
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The monomer mixture preferably comprises no multiolefin monomers, such as
isoprene, butadiene, 2-methylbutadiene, 2,4-dimethylbutadiene, piperyline, 3-
methyl-
1,3-pentadiene, 2,4-hexadiene, 2-neopentylbutadiene, 2-methyl-1,5-hexadiene,
2,5-
dimethyl-2,4-hexadiene, 2-methyl-1,4-pentadiene, 2-methyl-1,6-heptadiene,
cyclopenta-diene, methylcyclopentadiene, cyclohexadiene, 1-vinyl-
cyclohexadiene.
Preferably, the monomer mixture to be polymerized comprises in the range of
from 65 % to 99.99 % by weight of at least one isomonoolefin monomer and in
the
range of from 0.01 % to 35 % by weight of at least one diisoalkenylbenzene
monomer
or a mixture thereof. More preferably, the monomer mixture comprises in the
range of
from 85 % to 99.95 % by weight of a C4 to C~ isomonoolefin monomer, in the
range of
from 0.05 % to 15 % by weight of at least one diisoalkenylbenzene compound or
a
mixture thereof. In case there are further copolymerizable comonomers, it will
be
apparent to the skilled in the art that the ranges given above will change and
result in a
total of all monomers of 100 % by weight.
The monomer mixture may contain minor amounts of one or more additional
polymerizable co-monomers. For example, the monomer mixture may contain a
small
amount of a styrenic monomer. Preferred styrenic monomers are p-methylstyrene,
styrene, a-methyl-styrene, p-chlorostyrene, p-methoxystyrene, indene
(including indene
derivatives) and mixtures thereof. If present, it is preferred to use the
styrenic
monomer in an amount of up to 5.0% by weight of the monomer mixture. The
values
of the isomonoolefin monomers) will have to be adjusted accordingly to result
again in
a total of 100 % by weight.
The use of even other monomers in the monomer mixture is possible provided,
of course, that they are copolyrnerizable with the other monomers in the
monomer
mixture.
The inventive polymer has a Mooney viscosity ML (1+8 @125 °C) of
greater
than 80, preferably greater than 90, more preferably greater than 95 units.
The elastomer of the present invention is prepared by a cationic process for
polymerising the monomer mixture. This type of polymerisation is well known to
the
skilled in the art and usually comprises contacting the reaction mixture
described above
with a catalyst system. Preferably, the polymerization is conducted at a
temperature
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conventional in the production of butyl polymers - e.g., in the range of from -
100°C to
+50°C. The polymer may be produced by polymerization in solution or by
a slurry
polymerization method. Polymerization is preferably conducted in suspension
(the
slurry method) - see, for example, Ullmann's Encyclopedia of Industrial
Chemistry
(Fifth, Completely Revised Edition, Volume A23; Editors Elvers et al., 290-
292).
As an example, in one embodiment the polymerization is conducted in the
presence of an inert aliphatic hydrocarbon diluent (such as n-hexane) and a
catalyst
mixture comprising a major amount (in the range of from 80 to 99 mole percent)
of a
dialkylaluminum halide (for example diethylaluminum chloride), a minor amount
(in
the range of from 1 to 20 mole percent) of a monoalkylaluminum dihalide (for
example
isobutylaluminum dichloride), and a minor amount (in the range of from 0.01 to
10
ppm) of at least one of a member selected from the group comprising water,
aluminoxane (for example methylaluminoxane) and mixtures thereof. Of course,
other
catalyst systems conventionally used to produce butyl polymers can be used to
produce
a butyl polymer which is useful herein - see, for example, "Cationic
Polymerization of
Olefins: A Critical Inventory" by Joseph P. Kennedy (John Wiley & Sons; Inc. D
1975,
10-12).
Polymerization may be performed both continuously and discontinuously. In
the case of a continuous operation, the process is preferably performed with
the
following three feed streams:
I) solvent/diluent + isomonoolefin(s) (preferably isobutene)
II) diisoalkenylbenzene monomer(s), and optionally, other copolymerizable
monomers e.g., p-methylstyrene
III) catalyst
In the case of discontinuous operation, the process may, for example, be
performed as follows: The reactor, pre-cooled to the reaction temperature, is
charged
with solvent or diluent and the reactants. The initiator is then pumped in the
form of a
dilute solution in such a manner that the heat of polymerization may be
dissipated
without problem. The course of the reaction may be monitored by means of the
evo
lution of heat.
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The inventive polymer may be compounded. The compound comprises the
inventive polymer and at least one active or inactive filler. The filler is
preferably:
- highly dispersed silicas, prepared e.g., by the precipitation of silicate
solutions or the flame hydrolysis of silicon halides, with specific surface
areas of in the range of from 5 to 1000 rn2/g, and with primary particle sizes
in the range of from 10 to 400 nm; the silicas can optionally also be present
as mixed oxides with other metal oxides such as those of Al, Mg, Ca, Ba,
Zn, Zr and Ti;
synthetic silicates, such as aluminum silicate and alkaline earth metal
silicate like magnesium silicate or calcium silicate, with BET specific
surface areas in the range of from 20 to 400 m2/g and primary particle
diameters in the range of from 10 to 400 nm;
natural silicates, such as kaolin and other naturally occurring silica;
- glass fibres and glass fibre products (matting, extrudates) or glass
microspheres;
- metal oxides, such as zinc oxide, calcium oxide, magnesium oxide and
aluminum oxide;
- metal carbonates, such as magnesium carbonate, calcium carbonate and
zinc carbonate;
- metal hydroxides, e.g. aluminum hydroxide and magnesium hydroxide;
- carbon blacks; the carbon blacks to be used here are prepared by the lamp
black, furnace black or gas black process and have preferably BET (DIN 66
131) specific surface areas in the range of from 20 to 200 m2/g, e.g. SAF,
ISAF, HAF, FEF or GPF carbon blacks;
- rubber gels, especially those based on polybutadiene, butadiene/styrene
copolymers, butadiene/acrylonitrile copolymers and polychloroprene;
or mixtures thereof.
Examples of preferred mineral fillers include silica, silicates, clay such as
bentonite, gypsum, alumina, titanium dioxide, talc, mixtures of these, and the
like.
These mineral particles have hydroxyl groups on their surface, rendering them
hydrophilic and oleophobic. This exacerbates the difficulty of achieving good
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interaction between the filler particles and the tetrapolymer. For many
purposes, the
preferred mineral is silica, especially silica made by carbon dioxide
precipitation of
sodium silicate. Dried amorphous silica particles suitable for use in
accordance with
the invention may have a mean agglomerate particle size in the range of fibm 1
to 100
microns, preferably between 10 and 50 microns and most preferably between 10
and 25
microns. It is preferred that less than 10 percent by volume of the
agglomerate particles
are below 5 microns or over 50 microns in size. A suitable amorphous dried
silica
moreover usually has a BET surface area, measured in accordance with DIN
(Deutsche
Industrie Norm) 66I3I, of in the range of from 50 and 450 square meters per
gram and
a DBP absorption, as measured in accordance with DIN 53601, of in the range of
from
150 and 400 grams per 100 grams of silica, and a drying loss, as measured
according to
DIN ISO 787/11, of in the range of from 0 to 10 percent by weight. Suitable
silica
fillers are available under the trademarks HiSil~ 210, HiSiIU 233 and HiSil~
243 from
PPG Industries Inc. Also suitable are Vulkasil~ S and Vulkasil~ N, from Bayer
AG.
It might be advantageous to use a combination of carbon black and mineral
filler in the inventive compound. In this combination the ratio of mineral
fillers to
carbon black is usually in the range of from 0.05 to 20, preferably 0.1 to 10.
For the
rubber composition of the present invention it is usually advantageous to
contain
carbon black in an amount of in the range of from 20 to 200 parts by weight,
preferably
30 to 150 parts by weight, more preferably 40 to 100 parts by weight.
The compound further comprises at least one curing system, such as a sulfur
curing system.
The invention is not limited to a special sulfur curing system. For further
reference, see, chapter 2, "The Compounding and Vulcanization of Rubber", of
"Rubber Technology", 3'd edition, published by Chapman & Hall, 1995, the
disclosure
of which is incorporated by reference with regards to jurisdictions allowing
for this
procedure. The preferred amount of sulfur is from 0.3 to 2.0 parts by weight
per
hundred parts of rubber. An activator, for example zinc oxide, may also be
used, in an
amount of from 5 parts to 2 parts by weight. Other ingredients, for instance
stearic
acid, antioxidants, or accelerators may also be added to the elastomer prior
to curing.
Sulphur curing is then effected in known manner.
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Even if it is not preferred, the compound may further comprise other natural
or
synthetic rubbers such as BR (polybutadiene), ABR (butadienelacrylic acid-Cl-
C4-
alkylester-copolymers), CR (polychloroprene), IR (polyisoprene), SBR
(styrene/butadiene-copolymers) with styrene contents in the range of 1 to 60
wt%, NBR
(butadienelacrylonitrile-copolymers with acrylonitrile contents of 5 to 60
wt%, HNBR
(partially or totally hydrogenated NBR-rubber), EPDM (ethylene/propylene/diene-
copolymers), FKM (fluoropolymers or fluororubbers), and mixtures of the given
polymers.
The compound described herein above can contain further auxiliary products for
rubbers, such as reaction accelerators, vulcanizing accelerators, vulcanizing
acceleration auxiliaries, antioxidants, foaming agents, anti-aging agents,
heat
stabilizers, light stabilizers, ozone stabilizers, processing aids,
plasticizers, tackifiers,
blowing agents, dyestuffs, pigments, waxes, extenders, organic acids,
inhibitors, metal
oxides, and activators such as triethanolamine, polyethylene glycol,
hexanetriol, etc.,
which are known to the robber industry. The rubber aids are used in
conventional
amounts, which depend inter alia on the intended use. Conventional amounts are
e.g.
fibm 0.1 to 50 wt.%, based on rubber. Preferably the composition fiu-thermore
comprises in the range of 0.1 to 20 phr of an organic fatty acid, preferably
an
unsaturated fatty acid having one, two or more carbon double bonds in the
molecule
which more preferably includes 10% by weight or more of a conjugated diene
acid
having at least one conjugated carbon-carbon double bond in its molecule.
Preferably
those fatty acids have in the range of from 8 to 22 carbon atoms, more
preferably 12-
18. Examples include stearic acid, palrnic acid and oleic acid and their
calcium-, zinc-,
magnesium-, potassium- and ammonium salts.
The ingredients of the final compound are mixed together; suitably at an
elevated temperature that may range from 25 °C to 200 °C.
Normally the mixing time
does not exceed one hour and a period of time from 2 to 30 minutes is usually
adequate.
The mixing is suitably carned out in an internal mixer such as a Banbury
mixer, or a
Haake or Brabender miniature internal mixer. A two roll mill mixer also
provides a
good dispersion of the additives within the elastomer. An extruder also
provides good
mixing, and permits shorter mixing times. It is possible to carry out the
mixing in two
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or more stages, and the mixing can be done in different mixing. devices, for
example the
first stage in an internal mixer and the second one in an extruder. However;
it is
important that no unwanted pre-crosslinking (= scorch) occurs during the
mixing stage.
For compounding and vulcanization see also: Encyclopedia of Polymer Science
and
Engineering, Vol. 4, p. 66 et seq. (Compounding) and Vol. 17, p. 666 et seq.
(Vulcanization).
The polymer prepared according to the inventive method and a compound
comprising said polymer is useful for the manufacture of shaped rubber parts,
such as
printing rollers, containers, tubes and bags for non-medical applications,
parts of
electronic equipment, in particular insulating parts, parts of containers
containing
electrolytes, rings, dampening devices, seals and sealants or shaped rubber
parts either
solid, foamed, or fluid-filled useful to isolating vibrations and dampening
vibrations
generated by mechanical devices.
The invention is further illustrated by the following examples.
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POS 11 S3 CA
Examules
CA 02448337 2003-11-03
Methyl chloride (Dow Chemical) serving as a diluent for polymerization and
isobutylene monomer (Matheson, 99 %) were transferred into a reactor by
condensing a
vapor phase. Aluminum chloride (99.99 %) was from Aldrich and used as
received.
S Commercial divinylbenzene (ca. 64 %) was from Dow Chemical. It was purified
using a
disposable inhibitor-removing column from Aldrich.
The mixing of a compound with carbon black (IRB #7) and peroxide (DI-CUP
40C, Struktol Canada Ltd.) was done using a miniature internal mixer
(Brabender MIM)
from C. W. Brabender equipped with a drive unit (Plasticorder~ Type PL-V 1 S 1
).
The Mooney viscosity test was carried out according to ASTM standard D-1646
on a Monsanto MV 2000 Mooney Viscometer ML (1+8 ~a 12S deg.C).
The Moving Die Rheometer (MDR) test was performed according to ASTM
standard D-5289 on a Monsanto MDR 2000 (E). The upper die oscillated through a
small
arc of 1 degree.
1 S The solubility of a polymer was determined after the sample refluxed in
cylohexane over 60-minute period.
Curing was done using an Electric Press equipped with an Allan-Bradley
Programmable Controller.
Stress-strain tests were carried out using the Instron Testmaster Automation
System, Model 4464.
Ezamoles 1-3 (comparative)
Three different samples of commercial crasslinked IB-IP-DVB terpolymer (XL-
10000T"~ obtained from Bayer Inc. were tested for Mooney viscosity and
solubility
2S (Table 1).
Table 1. N~ooney viscosity and solubility values for three commercial samples
of
XL-10000.
Example Mooney viscositySolubility(wt.
fo)
M 1'+8' 12SC
1 60.2 26.9
2 69.9 25.1
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Example Mooney viscosity Solubility(wt. %)
ML 1'+8' 125°C
3 79.8 20.5
These three different terpolymers with Mooney viscosity values between 60-80
units had a content of a soluble fraction in a hydrocarbon solvent below 30
wt.%.
Higher values of Mooney viscosity seem to be accompanied by lower values of a
polymer fraction soluble in a hydrocarbon solvent.
Ezample 4 ~comnarative~
To a 250 mL Erlenmeyer flask, 0.45 g of AlCl3 was added, followed by 100 mL
of methyl chloride at - 30 °C. The resulting solution was stirred for
30 min at - 30 °C
and then cooled down to - 95 °C, thus forming the catalyst solution.
To a 2000 mL glass reactor equipped with an overhead stirrer, 900 mL of
methyl chloride at - 95 °C was added, followed by 120.0 mL of
isobutylene at - 95 °C
and 4.8 mL of DVB (ca. 64 %) at room temperature. The reaction mixture was
brought
to - 95 °C and 10 rnL of the catalyst solution was added to start the
reaction.
1 S The polymerization was carried out in MBRAUN~ dry box under the
atmosphere of dry nitrogen. The reaction was terminated after 10 minutes by
adding
into the reaction mixture 10 mL of ethanol containing some sodium hydroxide.
The obtained product was steam coagulated and dried to a constant weight in
the vacuum oven at. 70 °C. The yield of the reaction was 96.1 %. The
solubility of the
rubber in cyclohexane was 32.9 %.
It was found that a crosslinking process took place during the Mooney
viscosity
test for this rubber. The final value obtained form this test was 41.7 units
(on a
scorched polymer) while the lowest value of MV recorded before the onset of
crosslinking was 32.0 units.
Example 5
The reaction described in Example 4 was repeated except that divinylbenzene in
the monomer feed was replaced with 3.84 mL of m-diisopropenylbenzene. This
way,
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POS 1153 CA
CA 02448337 2003-11-03
the molar amounts of neat I?VB (Example 4) and m-diisopropenylbenzene (Example
5)
were equal.
The yield of the reaction was 97.6 %. The solubility of the rubber in
cyclohexane was 82.4 %. The Mooney viscosity of this product was 60.8 units.
No
scorch was observed during the Mooney viscosity test.
Comparison of results from the Examples 4 and 5 is given in Table 2.
Table 2. Comparison of Mooney viscosity and solubility values of two
isobutylene-
containing copolymers described in Examples 4 and Example 5.
Example Copolymer Yield Mooney ViscositySolubilityComment
(wt. ML(1'+8'@125 (wt.
%) %)
C
4 IB-divinylbenzene96.1 41.7/(32.0) 32.9 MV
scorch
5 IB-(m- 97.6 60.8 82.4 no MV
diisopropenyl- scorch
benzene
These results indicated that under the above-given reaction conditions the
copolymer isobutylene-(m-diisopropenylbenzene) had a much higher Mooney
viscosity
and solubility than the analogous copolymer composed of isobutylene and
divinylbenzene.
Example 6
To a 250 mL Erlenmeyer flask, 0.63 g Of AlCl3 Was added, followed by 140 mL
of methyl chloride at - 30 °C. The resulting solution was stirred for
30 min at - 30 °C
and then cooled down to - 95 °C, thus forming the catalyst solution.
To a 2000 mL glass reactor equipped with an overhead stirrer, 900 mL of
methyl chloride at - 95 °C was added, followed by 120.0 mL of
isobutylene at - 95 °C
and 15.0 mL of m-diisopropenylbenzene at room temperature. The reaction
mixture
was brought to - 95 °C and 20 mL of the catalyst solution was added to
start the
reaction.
POS 1153 CA
CA 02448337 2003-11-03
The polymerization was carned out in MBRAUN~ dry box under the
atmosphere of dry nitrogen. The reaction was terminated after 30 minutes by
adding
into the reaction mixture 10 mL of ethanol containing some sodium hydroxide.
The obtained product was steam coagulated and dried to a constant weight in
the vacuum oven at 70 °C. The yield of the reaction was 95.3 %. The
solubility of the
rubber in cyclohexane was 54.6 %. The Mooney viscosity of this elastomer was
102.7
units.
'This demonstrated that this butyl-type rubber had a very high Mooney
viscosity
despite the fact that a predominant portion of it was soluble in a hydrocarbon
solvent.
This behavior is different from that known for commercial XL-10000TM
terpolymers.
Example 7
The polymer described in Example 6 (Polymer 6) was compounded using the
following recipe:
Polymer: 100 phr
Carbon black N334TM (available from Cabot Canada): 50 phr
Stearic acid (EmersolTM 132 NF) (available from H. M. Royal): 1.0 phr
Zinc oxide (Kadox~ 920) (from St. Lawrence Chem. Co. Ltd.): 3.0 phr
Sulfur NBS (available from National Bureau of Standards): 1.75 phr
Methyl Tuads (TMTD) (available from R. T. Vanderbilt): 1.0 phr
The mixing was done in a Brabender internal mixer (capacity ca. 75 cc). The
starting temperature was 60 °C and the mixing speed 50 rpm. The
following steps were
carried out:
0 min: polymer added, followed by carbon black and stearic acid
3 min: sweep (during mixing of carbon black with the polymer and other
powdery materials it is unavoidable that small pieces of carbon black
and other powders fall off the rolls of a mill or from a mixing chamber
of an internal mixer. 'There is usually a metal tray under a mixer - and
with a small brush these fallen pieces are carefully sweeped and then
16
. POS 1153 CA
CA 02448337 2003-11-03
added again on the mill or into the mixing chamber - this step assures
that all intended ingredients are added to the compound without any
losses.)
3.5 min: Zn0 added, followed by sulfur and TMTD
7 min: mix removed
The compound was passed six times through a mill (6"x 12") with a tight nip
gap.
The obtained compound was tested using the Moving Die Rheometer (MDR).
Also, after curing at 160 °C it was tested for stress-strain
properties. The results are
given in Table 3.
Table 3. MDR and some stress-strain characteristics for a sulfur-cured
compound
based on Polymer 6.
MDR Stress-strain
MH ~ ~ UltimateUltimate
Stress@300%
(dNm) t' S0 Tensile Elongation
MH -t' 10 (MPa)
- Mr_,
dNm {min (MPa) (%)
24.59 14.29 9.06 4.95 730 3.53
These results demonstrated that copolymers IB-(m-Di-IPB) could be vulcanized
with sulfur curing systems.
17
