Note: Descriptions are shown in the official language in which they were submitted.
~030883
--1--
HIGH MODULUS RUBBER COMPOSITION
-
Background of the Invention
It is sometimes desirable to increase the modulus
of rubber compounds. For instance, it is generally
desirable to increase the modulus of rubber compounds
which are utilized in tire tread base compositions and
in tire wire coat compounds. A higher degree of
stiffness in such rubber compositions is conventionally
attained by incorporating larger amounts of fillers,
such as carbon black~ into the rubber compounds and/or
by increasing the state of cure of such compounds.
Unfortunately, both of these techniques lead to
undesirable results. For instance, the incorporation
of additional carbon black into rubber compounds
typically leads to high levels of hysteresis.
Accordingly, the utilization of such compounds in tires
results in excessive heat build-up and poor cut growth
characteristics. The utilization of high amounts of
sulfur to attain a high state of cure typically leads
to poor aging resistance. Furthermore, it is highly
impractical to reach high levels of stiffness by
increased state of cure alone. For these reasons, it
is not possible to attain the desired degree of
stiffness in tire tread base compounds by simply adding
higher levels of fillers or curatives.
Summary of the Invention
The subject invention reveals a technique for
preparing a high modulus rubber composition. The high
modulus rubber compositions made by this technique are
well suited for applications where a high degree of
stiffness is desired. However, rubber compositions
made by this technique do not have an increased degree
of hysteresis.
~ . .
~, ~
2~308~9
The subject invention specifically discloses a
process for preparing a high modulus rubber composition
which comprises: (1) polymerizing at least one
diisocyanate with at leas~ one member selected from the
group consisting of diols and diamines in a polymer
cement of a rubbery elastomer under conditions which
result in the formation of a rubber cement having
polyurea or polyurethane dispersed therein; and (2)
recovering the high modulus rubber composition from the
rubber cement. The high modulus rubber compositions
prepared by this technique are highly dispersed blends
of a polyurethane or polyurea in a rubbery elastomer.
Polyureas are formed by the polymerization of a
diisocyanate with a diamine. Polyurethanes are
produced by the polymerization of a diisocyanate with a
diol. Since the polymerization reactions of this
invention are conducted in the polymer cement of an
elastomer, a highly dispersed blend of the polyurea or
polyurethane is produced. The highly dispersed blend
of the polyurea or polyurethane in the rubber can be
recovered in dry form as a high modulus rubber
composition.
The high modulus rubber compositions of this
invention can also be prepared by reacting a
diisocyanate with a diol or diamine in the matrix of a
dry rubber. Such polymerizations are typically
conducted in an extruder or mixer wherein the dry
rubber is subjected to shearing forces. Such a process
can be carried out by (1) mixing the diisocyanate in a
first portion of the rubber, (2) mixing the diol or
diamine in a second portion of the rubber, and (3)
mixing the rubber containing the diisocyanate with the
rubber containing the diol or diamine. The process can
also be carried out by sequentially adding the two
2030~89
monomer components to the same rubber. For example,
the diol or diamine can be mixed into the rubber
followed by the subsequent addition of the
diisocyanate. It is, of course, possible to reverse
this order of monomer addition. When the diisocyanate
comes into contact with either the diol or the diamine,
a polymerization resulting in the formation of a
polyurea or polyurethane occurs. Because the process
is carried out within the matrix of the dry rubber, a
highly dispersed blend of the polyurea or polyurethane
with the dry rubber results.
The subject patent application further reveals a
process for preparing a high modulus rubber composition
which comprises polymerizing at least one diisocyanate
with at least one member selected from the group
consisting of diols and diamines within the matrix of
at least one dry rubber to produce said high modulus
rubber composi.ion.
Detailed Description of the Invention
Virtually any type of elastomer can be utilized in
preparing the high modulus rubber compositions of this
invention. The rubbers which are utilized in
accordance with this invention typically contain repeat
units which are derived from diene monomers, such as
conjugated diene monomers and/or nonconjugated diene
monomers. Such conjugated and nonconjugated diene
monomers typically contain from 4 to about 12 carbon
atoms and preferably contain from 4 to about 8 carbon
atoms. Some representative examples of suitable diene
monomers include 1,3-butadiene, isoprene,
2,3-dimethyl-1,3-butadiene, 2-methyl-1,3-pentadiene,
3,4-dimethyl-1,3-hexadiene, 4,5-diethyl-1,3-octadiene,
phenyl-1,3-butadiene and the like. The polydiene
2030889
rubber can also contain repeat units which are derived
from various vinyl aromatic monomers, such as styrene,
l-vinylnaphthalene, 2-vinylnaphthalene,
~-methylstyrene, 4-phenylstyrene, 3-methylstyrene, and
the like. Some representative examples of polydiene
rubbers that can be modified by utilizing the high
modulus rubber compositions of this invention include
polybutadiene, styrene-butadiene rubber (SBR),
synthetic polyisoprene, natural rubber,
isoprene-butadiene rubber, isoprene-butadiene-styrene
rubber, nitrile rubber, carboxylated nitrile rubber,
and EPDM rubber. The technique of this invention is
particularly well suited for utilization in modifying
natural rubber, synthetic polyisoprene, and
cis-1,4-polybutadiene.
The elastomers utilized in the high modulus rubber
compositions of this invention can be made by solution
polymerization, emulsion polymerization or bulk
polymerization. It is, of course9 also possible to use
natural rubber in preparing the rubber compositions of
this invention. In cases where a dry rubber is used to
produce the high modulus rubber composition, the manner
by which the dry rubber was synthesized is not of great
importance. However, in the embodiment of this
invention wherein a rubber cement is used in the
preparation of the high modulus rubber composition, it
is preferred for the rubber to be made by solution
polymerization. In this scenario, it is not necessary
to recover the rubber from the organic solvent in which
it is dissolved. In other words, the rubber cement can
be used in the process of this invention without first
recovering the rubber in dry form. By doing so the
unnecessary steps of removing the rubber from the
organic solvent and redissolving it are eliminated. It
2030889
is also possible to dissolve natural rubber or a rubber
prepared by emulsion polymerization or bulk
polymerization in an organic solvent so as to prepare a
rubber cement which can be utilized in accordance with
this invention.
It is generally preferred for the high modulus
rubber compositions of this invention to be prepared by
synthesizing a polyurea or polyurethane in the polymer
cement of the rubbery elastomer. The polyurea or
polyurethane is prepared by polymerizing at least one
diisocyanate with at least one diol or at least one
diamine. Such polymerizations result in the formation
of a highly dispersed blend of the polyurea or
polyurethane within the rubber cement. The organic
solvent in the rubber cement serves as the solvent for
the monomers being polymerized as well as the solvent
for the rubber. Essentially homogeneous solutions of
the polyurethane or polyurea and the rubbery elastomer
in the organic solvent result from such
polymerizations.
Because the rubber cement containing the polyurea
or polyurethane is essentially homogeneous in nature,
highly dispersed blends of the polyurea or polyurethane
in the rubbery elastomer can be recovered in dry form
from the organic solvent. In other words, highly
dispersed dry blends of the polyurethane or polyurea in
the rubber can be prepared utilizing the technique of
this invention. The organic solvent can be removed
utilizing conventional techniques, such as coagulation
or evaporation, to recover such highly dispersed
blends.
The polymer cement can be prepared by polymerizing
one or more diene monomers in a suitable inert organic
solvent. The organic solvent utilized will normally be
~ '
" ~;
2030889
a saturated aliphatic hydrocarbon or an aromatic
hydrocarbon. Some representative examples of suitable
aromatic solvents include benzene, toluene, xylene,
ethylbenzene, diethylbenzene, isobutylbenzene, and the
like. Some representative examples of suitable
aliphatic solvents include n-hexane, cyclohexane,
methylcyclohexane, isohexane, n-heptane, n-octane,
isooctane, n-decane, 2,2-dimethylbutane, petroleum
ether, kerosene, petroleum spirits, petroleum naphtha,
and the like. However, it will normally be desirable
to select a solvent which is inert with respect to the
catalyst system which will be employed to initiate the
polymerization reaction.
The rubber cement can be prepared by polymerizing
one or more diene monomers in the organic solvent. As
has been explained, the diene monomer utilized can be a
conJugated or nonconjugated diene monomer.
Vinyl-substituted aromatic monomers can also be
copolymerized with one or more diene monomers into
suitable rubbery elastomers, such as styrene-butadiene
rubber (SBR).
High cis-1,4-polybutadiene can be prepared by
polymerizing 1,3-butadiene monomer in an organic
solvent in a continuous or batch polymerization
process. A three-component nickel catalyst system
which includes an inorgano aluminum compound, a soluble
nickel containing compound, and a fluorine containing
compound can be utilized to catalyze the
polymerization.
The organoaluminum compound that can be utilized
has the structural formula:
2030~89
Al-R2
R3
in which Rl is selected from the group consisting of
alkyl groups (including cycloalkyl), aryl groups,
alkaryl groups, arylalkyl groups, alkoxy groups,
hydrogen and fluorine; R2 and R3 being selected from
the group consisting of alkyl groups (including
cycloalkyl), aryl groups, alkaryl groups, and arylalkyl
groups. Some representative examples of organoaluminum
compounds that can be utilized are diethyl aluminum
hydride, di-n-propyl aluminum hydride, di-n-butyl
aluminum hydride, diisobutyl aluminum hydride, diphenyl
aluminum hydride, di-p-tolyl aluminum hydride, dibenzyl
aluminum hydride, phenyl ethyl alumin~m hydride,
phenyl-n-propyl aluminum hydride, p-tolyl ethyl
aluminum hydride, p-tolyl n-propyl aluminum hydride,
p-tolyl isopropyl aluminum hydride, benzyl ethyl
aluminum hydride, benzyl n-propyl aluminum hydride, and
benzyl isopropyl aluminum hydride, diethylaluminum
ethoxide, diisobutylaluminum ethoxide, dipropylaluminum
methoxide, trimethyl aluminum, triethyl aluminum,
tri-n-propyl aluminum, triisopropyl aluminum,
tri-n-butyl aluminum, ~riisobutyl aluminum, tripentyl
aluminum, trihexyl aluminum, tricyclohexyl aluminum,
trioctyl aluminum, triphenyl aluminum, tri-p-tolyl
aluminum, tribenzyl aluminum, ethyl diphenyl aluminum,
ethyl di-p-tolyl aluminum, ethyl dibenzyl aluminum,
diethyl phenyl aluminum, diethyl p-tolyl aluminum,
di~thyl benzyl aluminum and other triorganoaluminum
compounds. The preferred organoaluminum compounds
include triethyl aluminum (TEAL), tri-n-propyl
aluminum, triisobutyl aluminum (TIBAL), trihexyl
2030~89
--8--
aluminum, diisobutyl aluminum hydride (DIBA-H), and
diethyl aluminum fluoride.
The component of the catalyst which contains nickel
can be any soluble organonickel compound. These
S soluble nickel compounds are normally compounds of
nickel with a mono-dentate or bi-dentate organic ligand
containing up to 20 carbon atoms. A ligand is an ion
or molecule bound to and considered bonded to a metal
atom or ion. Mono-dentate means having one position
through which covalent or coordinate bonds with the
metal may be formed. Bi-dentate means having two
positions through which covalent or coordinate bonds
with the metal may be formed. The term "soluble"
refers to solubility in butadiene monomer and inert
solvents.
Generally, any nickel salt or nickel containing
organic acid containing from about 1 to 20 carbon atoms
may be employed as the soluble nickel containing
compound. Some representative examples of soluble
nickel containing compounds include nickel benzoate,
nickel acetate, nickel naphthanate, nickel octanoate,
nickel neodecanoate, bis(-furyl dioxime) nickel,
nickel palmitate, nickel stearate, nickel
acetylacetonate, nickel salicaldehyde,
bisScyclopentadiene) nickel, bis(salicylaldehyde)
ethylene diimine nickel, cyclopentadienyl-nickel
nitrosyl, bis(n'-allyl nickel),
bis(~rcycloocta-1,5-diene), bis(n--allyl nickel
trifluoroacetate), and nickel tetracarbonyl. The
preferred component containing nickel is a nickel salt
of a carboxylic acid or an organic complex compound of
nickel. Nickel naphthanate, nickel octanoate, and
nickel neodecanoate are highly preferred soluble nickel
containing compounds. Nickel 2-ethylhexanoate, which
~030889
is commonly referred to as nickel octanoate ~NiOct) is
the soluble nickel containing compound which is most
commonly used due to economic factors.
The fluorine containing compound utilized in the
catalyst system is generally hydrogen fluoride or boron
trifluoride. If hydrogen fluoride is utilized, it can
be in the gaseous or liquid state. It, of course,
should be anhydrous and as pure as possible. The
hydrogen fluoride can be dissolved in an inert solvent,
and thus, can be handled and charged into the reaction
zone as a liquid solution. Optionally, butadiene
monomer can be utilized as the solvent. Inert solvents
include alkyl-, alkaryl-, arylalkyl-, and
aryl-hydrocarbons. For example, benzene and toluene
are convenient solvents.
The boron trifluoride component of the catalyst can
be gaseous boron trifluoride. It should also be
anhydrous and as pure as possible.
The hydrogen fluoride and/or boron trifluoride can
also be utilized as complexes in the catalyst system as
the fluorine containing compound. Hydrogen fluoride
complexes and boron trifluoride complexes can readily
be made with compounds which contain an atom or radical
which is capable of lending electrons to or sharing
electrons with hydrogen fluoride or boron trifluoride.
Compounds capable of such associating are ethers,
alcohols, ketones, esters, nitriles and water.
The ketone subclass can be defined by the formula
O
R'-C-R
wherein R' and R are selected from the group consisting
of alkyl radicals, cycloalkyl radicals, aryl radicals,
` 203088g
-10-
alkaryl radicals, and arylalkyl radicals containing
from 1 to about 30 carbon atoms; and wherein R' and R
can be the same or different. These ketones represent
a class of compounds which have a carbon atom attached
by a double bond to oxygen. Some representative
examples of ketones that are useful in the preparation
of the ketone-hydrogen fluoride complexes or boron
trifluoride complexes of this invention include
dimethyl ketone, methylethyl ketone, dibutyl ketone,
methyl isobutyl ketone, ethyl octyl ketone,
2,4-pentanedione, butyl cycloheptanone, acetophenone,
amylphenyl ketone, butylphenyl ketone, benzophenone,
phenyltolyl ketone, quinone and the like. The
preferred ketones that can be used to form the
ketone-hydrogen fluoride compounds and the ketone-boron
trifluoride compounds of this invention are the dialkyl
ketones of which acetone is most preferred.
The nitrile subclass can be represented by the
formula RCN where R represents alkyl groups, cycloalkyl
groups ? aryl groups, alkaryl groups or aryLalkyl groups
that contain up to about 30 carbon atoms. The nitriles
contain a carbon atom attached to a nitrogen atom by a
triple bond. Representative but not exhaustive of the
nitrile subclass are acetonitrile, butyronitrile,
acrylonitrile, benzonitrile, tolunitrile,
phenylacetonitrile, and the like. The preferred
hydrogen fluoride-nitrile complex or boron trifluoride
nitrile complex is the hydrogen fluoride benzonitrile
complex or the boron trifluoride benzonitrile complex.
The alcohol subclass can be defined by the formula
ROH where R represents alkyl radicals, cycloalkyl
radicals, aryl radicals, alkaryl radicals, or arylalkyl
radicals containing from about 1 to about ~0 carbon
atoms. These alcohols represent a class of compounds
2030889
-11-
which have a carbon atom attached by a single bond to
oxygen which is in turn attached to a hydrogen by a
single bond. Representative but not exhaustive of the
alcohols useful in the preparation of hydrogen fluoride
complexes and boron trifluoride complexes are methanol,
ethanol, n-propanol, isopropanol, phenol, benzyl
alcohol, cyclohexanol, butanol, hexanol and pentanol.
The preferred hydrogen fluoride-alcohol complex or
boron trifluoride alcohol complex is hydrogen fluoride
phenolate complex or boron trifluoride phenolate
complex.
The ether subclass can be defined by the formula
R'OR where R and R' represent alkyl radicals,
cycloalkyl radicals, aryl radicals, alkaryl radicals,
and arylalkyl radicals containing from about 1 to about
30 carbon atoms; wherein R and R' may be the same or
dissimilar. The R may also be joined through a common
carbon bond to form a cyclic ether with the ether
oxygen being an integral part of the cyclic structure
such as tetrahydrofuran, furan or dioxane. These
ethers represent a class of compounds which have two
carbon atoms attached by single bonds to an oxygen
atom. Representative but not exhaustive of the ethers
useful in the preparation of the hydrogen fluoride
complexes or boron trifluoride complexes of this
invention are dimethyl ether, diethyl ether, dibutyl
ether, diamyl ether, diisopropyl ethers,
tetrahydrofuran, anisole, diphenyl ether, ethyl methyl
ether, dibenzyl ether and the like. The preferred
hydrogen fluoride-ether complexes or boron
trifluoride-ether complexes are hydrogen fluoride
diethyl etherate, hydrogen fluoride dibutyl etherate,
boron trifluoride diethyl etherate, boron trifluoride
dibutyl etherate complexes.
2030889
The ester subclass can be defined by the formula
R'-C-O-R
s
wherein R and R' are selected from the group consisting
of alkyl radicals, cycloalkyl radicals, aryl radicals,
alkaryl radicals and arylalkyl radicals containing from
1 to about 20 carbon atoms. The esters contain a
carbon atom attached by a double bond to an oxygen atom
as indicated. Representative but not exhaustive of
such esters are ethyl benzoate, amyl benzoate, phenyl
acetate, phenyl benzoate and other esters conforming to
the formula above. The preferred hydrogen
fluoride-ester complex is hydrogen fluoride ethyl
benzoate complex. The preferred boron
trifluoride-ester complex is boron trifluoride ethyl
benzoate complex.
Such complexes are usually prepared by simply
bubbling gaseous boron trifluoride or hydrogen fluoride
into appropriate amounts of the complexing agent, for
instance, a ketone, an ether, an ester, an alcohol, or
a nitrile. This should be done in the absence of
moisture, and measures should be taken to keep the
temperature from rising above about 100F (37.7C). In
most cases, boron trifluoride and hydrogen fluoride
complexes are prepared with the temperature being
maintained at room temperature. Another possible
method would be to dissolve the hydrogen fluoride or
30 the complexing agent in a suitable solvent followed by
adding the other component. Still another method of
mixing would be to dissolve the complexing agent in a
solvent and simply bubble gaseous hydrogen fluoride or
boron trifluoride through the system until all of the
203~889
-13-
complexing agent is reacted with the hydrogen fluoride
or boron trifluoride. The concentrations can be
determined by weight gain or chemical titration.
The three component catalyst system utilized can be
preformed. If the catalyst system is preformed, it
will maintain a high level of activity over a long
period of time. The utilization of such a preformed
catalyst system also results in the formation of a
uniform polymeric product. Such preformed catalyst
systems are prepared in the presence of one or more
preforming agents selected from the group consisting of
monoolefins, nonconjugated diolefins, conjugated
diolefins, cyclic nonconjugated multiolefins,
acetylenic hydrocarbons, triolefins, vinyl ethers and
aromatic nitriles.
Some representative examples of olefins that can be
used as the preforming agent in the preparation of
stabilized catalysts are trans-2-butene, mixed cis- and
trans-2-pentene, and cis-2-pentene. Some nonconjugated
diolefins that can be used as preforming agents are
cis-1,4-hexadiene, 1,5-heptadiene, 1,7-octadiene, and
the like. Representative examples of cyclic
nonconjugated multiolefins that can be used include
1,5-cyclooctadiene, 1,5,9-cyclododecatriene, and
4-vinyl cyclohexene-l. Some representative examples of
acetylenic hydrocarbons which can be used as the
preforming agent are methyl acetylene, ethyl acetylene,
2-butyne, l-pentyne, 2-pentyne, l-octyne, and phenyl
acetylene. Triolefins that can be used as the
preforming agent include 1,3,5-hexatriene,
1,3,5-heptatriene, 1,3,6-octatriene,
5-methyl-1,3,6-heptatriene and the like. Some
representative examples of substituted conjugated
diolefins that can be used include 1,4-diphenyl
.
2030889
-14
butadiene, myrcene (7-methyl-3-methylene-1,6-
octadiene), and the like. Ethyl vinyl ether and
isobutyl vinyl ether are representative examples of
alkyl vinyl ethers that can be used as the preforming
agent. A representative example of an aromatic nitrile
that can be used is benzonitrile. Some representative
examples of conjugated diolefins that can be used
include 1,3-butadiene, isoprene, and 1,3-pentadiene.
The preferred preforming agent is 1,3-butadiene.
A method of preparing the preformed catalyst so
that it will be highly active and relatively chemically
stable is to add the organoaluminum compound and the
preforming agent to the solvent medium before they come
into contact with the nickel compound. The nickel
compound is then added to the solution and then the
fluoride compound is added to the solution. As an
alternative, the preforming agent and the nickel
compound may be mixed, followed by the addition of the
organoaluminum compound and then the fluoride compound.
Other orders of addition may be used but they generally
produce less satisfactory results.
The amount of preforming agent used to preform the
catalyst may be within the range of about 0.001 to 3
percent of the total amount of monomer to be
polymerized. Expressed as a mole ratio of preforming
agent to nickel compound, the amount of preforming
agent present during the preforming step can be within
the range of about 1 to 3000 times the concentration of
nickel. The preferred mole ratio of preforming agent
to nickel is about 3:1 to 500:1.
These preformed catalysts have catalytic activity
immediately after being prepared. However, it has been
observed that a short aging period, for example 15 to
30 minutes, at a moderate temperature, for example
2030889
50C, increases the activity of the preformed catalyst
greatly.
In order to properly stabilize the catalyst, the
preforming agent must be present before the
organoaluminum compound has an opportunity to react
with either the nickel compound or the fluoride
compound. If the catalyst system is preformed without
the presence of a~ least a small amount of preforming
agent, the chemical effect of the organoaluminum upon
the nickel compound or the fluoride compound is such
that the catalytic activity of the catalyst is greatly
lessened and shortly thereafter rendered inactive. In
the presence of at least a small amount of preforming
agent, the catalytic or shelf life of the catalyst is
greatly improved over the system without any preforming
agent present.
The three component nickel catalyst system can also
be premixed. Such premixed catalyst systems are
prepared in the presence of one or more polymeric
catalyst stabilizers. The polymeric catalyst
stabilizer can be in the form of a monomer, a liquid
polymer, a polymer cement, or a polymer solution.
Polymeric catalyst stabilizers are generally
homopolymers of conjugated dienes or copolymers of
conjugated dienes with styrenes and methyl substituted
styrenes. The diene monomers used in the preparation
of polymeric catalyst stabilizers normally contain from
4 to about 12 carbon atoms. Some representative
examples of conjugated diene monomers that can be
utilized in making such polymeric catalyst stabilizers
include isoprene, 1,3-butadiene, piperylene,
1,3-hexadiene, 1,3-heptadiene, 1,3-octadiene,
2,4-hexadiene, 2,4-heptadiene, 2,4-octadiene and
1,3-nonadiene. Also included are
2Q3088g
-16-
2,3-dimethylbutadiene, 2,3-dimethyl-1,3-hexadiene,
2,3-dimethyl-1,3-heptadiene, 2,3-dimethyl-1,3-octadiene
and 2,3-dimethyl-1,3-nonadiene and mixtures thereof.
Some representative examples of polymeric catalyst
stabilizers include polyisoprene, polybutadiene,
polypiperylene, copolymers of butadiene and styrene,
copolymers of butadiene and ~-methylstyrene, copolymers
of isoprene and styrene, copolymers of isoprene and
~-methylstyrene, copolymers of piperylene and styrene,
copolymers of piperylene and ~-methylstyrene,
copolymers of 2,3-dimethyl-1,3-butadiene and styrene,
copolymers of 2,3-dimethyl butadiene and
~-methylstyrene, copolymers of butadiene and
vinyltoluene, copolymers of 2,3-dimethyl-1,3-butadiene
and vinyltoluene, copolymers of butadiene and
B-methylstyrene, and copolymers of piperylene and
3-methylstyrene.
In order to properly stabilize the catalyst system
by this premixing technique, the polymeric catalyst
stabilizer must be present before the organoaluminum
compound has an opportunity to react with either the
nickel compound or the fluorine containing compound.
If the catalyst system is premixed without the presence
of at least a small amount of polymeric catalyst
stabilizer, the chemical effect of the organoaluminum
compound upon the nickel compound or the fluoride
compound is such that the catalytic activity of the
catalyst system is greatly lessened and shortly
thereafter rendered inactive. In the presence of at
least a small amount of polymeric catalyst stabilizer,
the catalytic or shelf life of the catalyst system is
greatly improved over the same system without any
polymeric catalyst stabilizer present.
--` 2Q30889
One method of preparing this premixed catalyst
system so that it will be highly active and relatively
chemically stable is to add the organoaluminum compound
to the polymer cement solution and mix thoroughly
before the organoaluminum compound comes into contact
with the nickel containing compound. The nickel
compound is then added to the polymer cement solution.
Alternatively, the nickel compound can be mixed with
the polymer cement first, followed by the addition of
the organoaluminum compound. Then the fluorine
containing compound is added to the polymer cement
solution. This is not intended to preclude other
orders or methods of catalyst addition, but it is
emphasized that the polymer stabilizer must be present
before the organoaluminum compound has a chance to
react with either the nickel containing compound or the
fluorine containing compound.
The amount of polymeric catalyst stabilizer used to
premix the catalyst system can be within the range of
about 0.01 to 3 weight percent of the total amount
monomer to be polymerized. Expressed as a weight ratio
of polymeric catalyst stabilizer to nickel, the amount
of polymeric catalyst stabilizer present during the
premixing step can be within the range of about 2 to
2000 times the concentration of nickel. The preferred
weight ratio of polymeric catalyst stabilizer to nickel
is from about 4:1 to about 300:1. Even though such
premixed catalyst systems show catalytic activity
immediately after being prepared, it has been observed
that a short aging period, for example 15 to 30
minutes, at moderate temperatures, for example 50C,
increases the activity of the preformed catalyst
system.
.
-- 2030~9
-18-
A "modified in situ" technique can also be used in
making the three component nickel catalyst system. In
fact, the utilization of catalysts made by such
"modified in situ" techniques results in more uniform
control of the polymerization and the polymeric
product. In such a "modified in situ" technique, the
organoaluminum compound is added to neat 1,3-butadiene
monomer with the nickel containing compound being added
later. The butadiene monomer containing the
organoaluminum compound and the nickel containing
compound is then charged into the reaction zone being
used for the polymerization with the fluorine
containing compound being charged into the reaction
zone separately. Normally, the organoaluminum compound
and the nickel containing compound are charged into the
reaction zone soon after being mixed into the butadiene
monomer. In most cases, the organoaluminum compound
and the nickel containing compound are charged into the
reaction zone within 60 seconds after being mixed in
the butadiene monomer. It will generally be desirable
to utilize organoaluminum compounds and nickel
containing compounds which have been dissolved in a
suitable solvent.
The three component nickel catalyst systems
utilized in the practice of the present invention have
activity over a wide range of catalyst concentrations
and catalyst component ratios. The three catalyst
components interact to form the active catalyst system.
As a result, the optimum concentration for any one
component is very dependent upon the concentrations of
each of the other two catalyst components.
Furthermore, while polymerization will occur over a
wide range of catalyst concentrations and ratios, the
most desirable properties for the polymer being
2030889
-19-
synthesized are obtained over a relatively narrow
range. Polymerizations can be carried out utilizing a
mole ratio of the organoaluminum compound to the nickel
containing compound within the range of from about
0.3:1 to about 300:1; with the mole ratio of the
fluorine containing compound to the organonickel
containing compound ranging from about 0.5:1 to about
200:1 and with the mole ratio of the fluorine
containing compound to the organoaluminum compound
ranging from about 0.4:1 to about 10:1. The preferred
mole ratios of the organoaluminum compound to the
nickel containing compound ranges from about 2:1 to
about 80:1, the preferred mole ratio of the fluorine
containing compound to the nickel containing compound
ranges from about 3:1 to about 100:1, and the preferred
mole ratio of the fluorine containing compound to the
organoaluminum compound ranges from about 0.7:1 to
about 7:1. The concentration of the catalyst system
utilized in the reaction zone depends upon factors such
as purity, the reaction rate desired, the
polymerization temperature utilized, the reactor
design, and other factors.
The three component nickel catalyst system can be
continuously charged into the reaction zone utilized in
carrying out continuous solution polymerization at a
rate sufficient to maintain the desired catalyst
concentration. The three catalyst components can be
charged into the reaction zone "in situ", or as has
been previously described, as a preformed or premixed
catalyst system. In order to facilitate charging the
catalyst components into the reaction zone "in situ"
they can be dissolved in a small amount of an inert
organic solvent or butadiene monomer. Preformed and
premixed catalyst systems will, of course, already be
- , .
~ , . ,; ~
.. .. .. .
:, , : : .. -
203~889
-20-
dissolved in a solvent. The polymerization medium
being utilized will normally contain about 5 weight
percent to about 35 weight percent monomers and polymer
with about 65 weight percent to 95 weight percent of
the polymerization medium being solvent.
One or more molecular weight regulators can also be
included in the polymerization medium. The molecular
weight regulators which can be used include those which
are known to be useful in solution polymerizations of
1,3-butadiene monomer which utilize nickel catalyst
systems, such as those disclosed in U.S. Patent
4,383,097 and South African Patents 83/2555, 83/2557
and 83/2558, which are incorporated herein by
reference. These molecular weight regulators are
selected from the group consisting of ~-olefins,
cis-2-butene, trans-2-butene, allene, 1,4-pentadiene,
1,5-hexadiene, 1,6-heptadiene,
1,2,4-trivinylcyclohexene, 1-trans-4-hexadiene, and
4-vinyl-1-cyclohexene. The a-olefins that can be
utilized generally contain from 2 to about 10 carbon
atoms. Some representative examples of ~-olefins that
can be utilized for this purpose include ethylene,
propylene, l-butene, l-pentene, and l-hexene. l-butene
is a preferred molecular weight regulator. This is
because it has a boiling point of -6.3C which is very
close to the boiling point of 1,3-butadiene (-4.5C)
and because it is effective as a molecular weight
regulator at low concentrations and is not a poison to
the polymerization catalyst even if its concentration
increases markedly.
The amount of molecular weight regulator that needs
to be employed varies with the type of molecular weight
regulator being utilized, with the catalyst system,
with the polymerization temperature, and with the
2030889
-21-
desired molecular weight of the polymer being
synthesized. For instance, if a high molecular weight
polymer is desired, then a relatively small amount of
molecular weight regulator is required. On the other
hand, in order to reduce molecular weights
substantially, relatively larger amounts of the
molecular weight regulator will be utilized.
Generally, greater amounts of the molecular weight
regulator are required when the catalyst system being
utilized contains hydrogen fluoride or is an aged
catalyst which contains boron trifluoride. Extremely
effective molecular weight regulators, for example
allene, can be used in lower concentrations and will
nevertheless suppress molecular weights to the same
degree as do more typical molecular weight regulators
at higher concentrations. More specifically, allene
will suppress the molecular weight of the polymer being
synthesized in the solution polymerization when
utilized at concentrations as low as 0.005 phm (parts
per hundred parts of monomer). Generally, the
molecular weight regulator will be utilized at a
concentration ranging between abou~ 0.005 phm and 20
phm. It will normally be preferred for the molecular
weight regulator to be utilized at a concentration of
0.1 phm to 15 phm with the most preferred concentration
being between 1 phm and 10 phm.
In continuous polymerizations, the molecular weight
regulator is continuously charged into the reaction
zone at a rate sufficient to maintain the desired
concentration of the molecular weight regulator in the
reaction zone. Even though the molecular weight
regulator is not consumed in the polymerization
reaction, a certain amount of molecular weight
regulator will need to be continuously added to
---" 203088~
-22-
compensate for losses. The total quantity of the
1,3-butadiene monomer, the catalyst system, the
solvent, and the molecular weight regulator (if
desired) charged into the reaction zone per unit time
is essentially the same as the quantity of high
cis-1,4-polybutadiene cement withdrawn from the
reaction zone within that unit of time.
High cis-1,4-polybutadiene can also be prepared
under solution polymerization conditions utilizing rare
1~ earth catalyst systems, such as lathanide systems,
which are normally considered to be "pseudo-living".
Such rare earth catalyst systems are comprised of three
components. These components include (1) an
organoaluminum compound, (2) an organometallic compound
which contains a metal from Group III-B of the Periodic
System, and (3) at least one compound which contains at
least one labile halide ion. The organoaluminum
compound which can be utilized in conjunction with such
rare earth catalyst systems are the same as those
described for utilization in conjunction with the three
component nickel catalyst system previously described.
In the organometallic compound which contains a
metal from Group III-B of the Periodic System the metal
ion forms the central core of atom to which ligand-type
groups or atoms are joined. These compounds are
sometimes known as coordination-type compounds. These
compounds may be symbolically represented as ML3
wherein M represents the above-described metal ions of
Group III-B and L is an organic ligand containing from
1 to 20 carbon atoms selected from a group consisting
of (1) o-hydroxyaldehydes, (2) o-hydroxyphenones, (3)
aminophenols, (4) hydroxy esters, (5) hydroxy
quinolines, (6) ~-diketones, (7) monocarboxylic acids,
(8) ortho dihydric phenols, (9) alkylene glycols, (10)
2030889
-23-
dicarboxylic acids, tll) alkylated derivatives of
dicarboxylic acids and (12) phenolic ethers.
The Group III-B metals which are useful in the
organometallic compound include scandium, yttrium, the
lanthanides, and the actinides. The lanthanides
include lanthanum, cerium, praseodymium, neodymium,
promethium, samarium, europium, gadolinium, terbium,
dysprosium, holmium, erbium, thulium, ytterbium and
lutetium. The actinides include actinium, thorium,
protactinium, uranium, neptunium, plutonium, americium,
curium, berkelium, californium, einsteinium, fermium,
mendelerium, and lawrencillm. The preferred actinides
are thorium and uranium which have atomic numbers of 90
and 92, respectively. The preferred Group III-B metals
are cerium, praseodymium, neodymium and gadolinium
which have atomic numbers of 58, 59, 60, and 64
respectively. The most preferred lanthanide metal is
neodymium.
In the organometallic compound utilized the organic
portion includes organic type ligands or groups which
contain from 1 to 20 carbon atoms. These ligands can
be of the monovalent and bidentate or divalent and
bidentate form. Representative of such organic ligands
or groups are (1) o-hydroxyaldehydes such as
salicylaldehyde, 2-hydroxyl-1-naphthaldehyde,
2-hydroxy-3-naphthaldehyde and the like; (2)
o-hydroxyphenones such as 2'-hydroxyacetophenone,
2'-o-hydroxybutyrophenone, 2'-hydroxypropiophenone and
the like; (3) aminophenols such as o-aminophenol,
N-methyl o-aminophenol, N-ethyl o-aminophenol and the
like; (4) hydroxy esters such as ethyl salicylate,
propyl salicylate, butyl salicylate and the like; (5
phenolic compounds such as 2-hydroxyquinoline,
8-hydroxyquinoline and the like; (6) ~-diketones such
` 2030889
-24-
as acetylacetone, benzoylacetone, propionylacetone,
isobutyrylacetone, valerylacetone, ethylacetylacetone
and the like; (7) monocarboxylic acids such as acetic
acid, propionic acid, valeric acid, hexanoic acid,
2-ethylhexanoic acid, neodecanoic acid, lauric acid,
stearic acid and the like; (8) ortho dihydric phenols
such as pyrocatechol; (9) alkylene glycols such as
ethylene glycol, propylene glycol, trimethylene glycol,
tetramethylene glycol and the like; (10) dicarboxylic
acids such as oxalic acid, malonic acid, maleic acid,
succinic acid, o-phthalic acid and the like; (11)
alkylated derivatives of the above-described
dicarboxylic acids; (12) phenolic ethers such as
o-hydroxyanisole, o-hydroxyethyl phenol ether and the
like.
Representative organometallic compounds of the
Group III-B metals, correspondiDg to the formula ML3,
which may be useful in this invention include cerium
acetylacetonate, cerium naphthenate, cerium
neodecanoate, cerium octanoate, tris-salicylaldehyde
cerium, cerium tris-(8-hydroxyquinolate), gadolinium
naphthenate, gadolinium neodecanoate, gadolinium
octanoate, lanthanum naphthenate, lanthanum octanoate,
neodymium naphthenate, neodymium neodecanoate,
neodymium octanoate, praseodymium naphthenate,
prasodymium octanoate, yttrium acetylacetonate, yttrium
octanoate, dysprosium octanoate, tris(~'-allyl) uranium
chloride, tris(~-allyl) uranium bromide,
tris(~r-allyl) uranium iodide, uranium tetramethoxide,
uranium tetraethoxide, uranium tetrabutoxide, uranium
octanoate, thorium ethoxide, tris(~-allyl) thorium
chloride, thorium naphthenate, uranium isovalerate, and
other Group III-B metals complexed with ligands
containing from 1 to 20 carbon atoms.
20~0889
The third catalyst component utilized in such rare
earth catalyst systems is a compound which contains a
halide ion. Some representative examples of halide
ions which can be utilized include bromide ions,
chloride ions, fluoride ions, and iodide ions. A
combination of t~o or more of these ions can also be
utilized. These halide ions can be introduced as (1)
hydrogen halides; (2) alkyl, aryl, alkaryl, aralkyl and
cycloalkyl metal halides wherein the metal is selected
from the Groups II, III-A and IV-A of the Periodic
Table; (3) halides of metals of Groups III, IV, V, VI-B
and VIII of the Periodic Table and (4~ organometallic
halides corresponding to the general formula MI(3 y)Xy
wherein M is a metal selected from the group consisting
of metals of Group III-B of the Periodic Table having
atomic numbers of 21, 39 and 57 through 71 inclusive; L
is an organic ligand containing from 1 to 20 carbon
atoms and selected from the group consisting of (a)
o-hydroxyaldehydes, (b) o-hydroxyphenones, (c)
hydroxyquinolines, (d) ~-diketones, (e) monocarboxylic
acids, (f) ortho dihydric phenols, (g) alkylene
glycols, (h) dicarboxylic acids, (i) alkylated
derivatives of dicarboxylic acids and (j) phenolic
ethers; X is a halide ion and y is an integer ranging
from 1 to 2 and representing the number of halide ions
attached to the metal M. The organic ligand L may be
of the monovalent and bidentate or divalent and
bidentate form.
Representative examples of such compounds
containing a labile halide ion include (1) inorganic
halide acids, such as hydrogen bromide, hydrogen
chloride and hydrogen iodide; (2) organometallic
halides, such as ethylmagnesium bromide, butylmagnesium
bromide, phenylmagnesium bromide, methylmagnesium
-- 203088~
-26-
chloride, butylmagnesium chloride, ethylmagnesium
iodide, phenylmagnesium iodide, diethylaluminum
bromide, diisobutylaluminum bromide, methylaluminum
sesquibromide, diethylaluminum chloride, ethylaluminum
S dichloride, ethylaluminum sesquichloride,
diisobutylaluminum chloride, isobutylaluminum
dichloride, dihexylaluminum chloride,
cyclohexylaluminum dichloride, phenylaluminum
dichloride, didodecylaluminum chloride, diethylaluminum
fluoride, dibutylaluminum fluoride, diethylaluminum
iodide, dibutylaluminum iodide, phenylaluminum
diiodide, trimethyltin bromide, triethyltin chloride,
dibutyltin dichloride, butyltin trichloride,
diphenyltin dichloride, tributyltin iodide and the
like; (3) inorganic halides, such as aluminum bromide,
aluminum chloride, aluminum iodide, antimony
pentachloride, antimony trichloride, boron tribromide,
boron trichloride, ferric chloride, gallium
trichloride, molybdenum pentachloride, phosphorus
tribromide, phosphorus pentachloride, stannic chloride,
titanium tetrachloride, titanium tetraiodide, tungsten
hexachloride and the like; and (4) organometallic
(Group III-B) halides, such as
t-butylsalicylaldehydrocerium (III) chloride,
salicylaldehydrocerium (III) chloride,
5-cyclohexylsalicylaldehydrocerium (III) chloride,
2-acetylphenolatocerium (III) chloride, oxalatocerium
(III) chloride, oxalatocerium (III) bromide and the
like. The preferred compounds which contain a labile
halide ion are inorganic halide acids and
organometallic halides.
The rare earth metal catalyst system can be
prepared using an "in situ" technique or it can be
"preformed." By "in situ" is meant that the catalyst
'
-" 203088~
-27-
components are added separately to the monomer to be
polymerized. By "preformed" is meant the manner in
which the catalyst components are mixed together prior
to exposure of any of the components to the monomer to
be polymerized. It is also known that when employing
the type of catalyst system described in this
invention, the presence of monomer is not essential to
the formation of an active catalyst species, thus,
facilitating the use of "preformed" catalysts. Also,
it is known that freshly "preformed" catalysts are
frequently more active than catalysts which have been
allowed to age before use. Greatly improved
"preformed" catalysts can be prepared by carrying out
the "preforming" in the presence of small amounts of
conjugated diolefins. Preforming in the presence of
monomers results in homogeneous (soluble) catalyst
systems, whereas those prepared by mixing in the
absence of monomers are frequently heterogeneous
(insoluble). Such a "preforming" technique is
described in detail in United States Patent 3,794,604
which is incorporated herein by reference.
The proportions of the components of the
poLymerization catalyst compositions of this invention
can be varied widely. When the halide ion of the
halogen containing compound is bromide, chloride or
iodide ion, the atomic ratio of the halide ion to the
Group III-B metal can vary from about 0.1/1 to about
6/1. A more preferred ratio is from about 0.5/1 to
about 3.5/1 and the most preferred ratio is about 2/1.
However, when the halide ion of the halogen-containing
compound is fluoride ion, the ratio of the fluoride ion
to the Group III-B metal ion ranges from about 20/1 to
about 80/1 with the most preferred ratio being about
30/1 to about 60/1. The molar ratio of the
,
.
'
2030889
-28-
trialkylaluminum or alkylaluminum hydride to Group
III-B metal can range from about 4/1 to about 200/1
with the most preferred range being from about 8/1 to
about 100/1. The molar ratio of diolefin to Group
III-B metal can range from about 0.2/1 to 3000/1 with
the most preferred range being from about 5/1 to about
500/1.
The amount of rare earth catalyst charged to the
reduction system can be varied over a wide range; the
sole requirement being that a catalytic amount of the
catalyst composition, sufficient to cause
polymerization of the 1,3-butadiene monomer, be present
in the reaction system. Low concentrations of catalyst
ar~ desirable in order to minimize ash problems. It
has been found that polymerizations will occur when the
catalyst level of the Group III-B metal varies between
0.05 and 1.0 millimole of Group III-B metal per 100
grams of monomer. A preferred ratio is between 0.1 and
0.3 millimole of Group III-B metal per 100 grams of
monomer.
The concentration of the total catalyst system
employed, of course, depends upon factors such as
purity of the system, polymerization rate desired,
temperature and other factors. Therefore, specific
concentrations cannot be set forth except to say that
catalytic amounts are used.
Temperatures at which such polymerization reactions
employing rare earth catalyst systems are carried out
can be varied over a wide range. Usually the
temperature can be varied from extremely low
tempera~ures such as -60C up to high temperatures such
as 150C or higher. Thus, temperature is not a
critical factor in the polymerization of 1,3-butadiene
monomer with rare earth catalyst systems. It is
,
. .
~ ' ~
- 203088~
-29-
generally preferred, however, to conduct the
polymerization reaction at a temperature in the range
of from about 10C to about 90C. The pressure at
which the polymerization is carried out can also be
varied over a wide range. The reaction can be
conducted at atmospheric pressure or, if desired, it
can be carried out at sub-atmospheric or
super-atmospheric pressure. Generally, a satisfactory
polymerization is obtained when the reaction is carried
out at about autogenous pressure, developed by the
reactants under the operating conditions used.
Vinyl halides can be utilized in conjunction with
rare earth catalyst systems as molecular weight
regulators as described in U.S. Patent 4,663,405 to
Throckmorton which is incorporated herein by reference.
The vinyl halides that can be utilized as molecular
weight regulators include vinyl fluoride, vinyl
chloride, vinyl bromide and vinyl iodide. Vinyl
bromide, vinyl chloride and vinyl iodide are preferred.
Generally, vinyl chloride and vinyl bromide are most
preferred. The amount of vinyl halide utilized will
vary with the molecular weight which is desired for the
polymer being synthesized. Naturally, the use of
greater quantities of the vinyl halide results in the
production of a polymer having lower molecular weights.
As a general rule, from about 0.05 to 10 phm (parts per
hundred parts of monomer) of a vinyl halide will be
utilized. In most cases from 0.1 phm to 2.5 phm of a
vinyl halide will be present during the polymerization.
Persons skilled in the art will be able to easily
ascertain ~he amount of vinyl halide in order to
produce a polymer having a specifically desired
molecular weight.
- .
2030~89
-30-
Metals from Groups I and II of the Periodic System
can also be u~ilized as catalysts for polymerizing
1,3-butadiene monomer into 1,4-polybutadiene. The
utilization of initiator systems of this type results
in the formation of "living" polymers. The metals
which are most commonly utilized in initiator systems
of this type include barium, lithium, magnesium,
sodium, and potassium. Lithium and magnesium are the
metals that are most commonly utilized in such
initiator systems. The metal initiator systems which
are most commonly utilized in polymerizing butadiene
monomer into polybutadiene are in the form of
organometallic compounds. For instance, lithium is
commonly utilized to catalyze such polymerizations in
the form of an organoaluminum compound. Such
organoaluminum compounds generally having the
structural formula: Li-R, wherein R represents an
alkyl group containing from l to 20 carbon atoms. More
commonly, ~he alkyl group in such alkyl lithium
compounds will contain from 2 to 8 carbon atoms. For
instance, butyl lithium is very commonly utilized as
the initiator for such polymerizations.
It is possible to prepare polybutadiene cements
utilizing catalyst systems other than those described
herein. It is also contemplated that such
polybutadiene cements can be utilized in preparing the
blends of this invention.
Rubber cements of other elastomers, such as
polyisoprene, styrene-butadiene rubber (SBR) and
styrene-isoprene-butadiene rubber (SIBR), can also be
synthesized utilizing known solution polymerization
techniques. Such rubber cements can, of course, also
be utilized in preparing the highly dispersed blends of
this invention.
~030889
-31-
The polyurea or polyurethane is synthesized by
simply adding a diisocyanate and a diamine or diol to
the rubber cement. An approximate stoichiometric
amount of diisocyanate and diamine or diol will
typically be added. The amount of monomers added will
depend upon the desired level of incorporation of the
polyurethane or polyurea in the highly dispersed blend
being prepared. Typically an amount of monomers
sufficient to prepare a blend containing from about 2
phr to about 50 phr (part per hundred parts of rubber)
of the polyurea or polyurethane will be added. It is
typically preferred for the highly dispersed blend to
contain from about 5 phr to about 40 phr of polyurea or
polyurethane. The most preferred amount of polyurea or
polyurethane in the blend will depend upon the ultimate
application of the high modulus rubber composition. As
a general rule, amounts within the range of about lO
phr to about 30 phr are most preferred.
The solution of the monomers in the rubber cement
will normally contain from about 5 weight percent to
about 35 weight percent monomers and polymers, based
upon the total weight of the polymerization medium
(monomers, rubber, and solvent). The polymerization
medium will preferably contain from about 10 percent to
about 30 percent monomers and polymers. It will
generally be more preferred for the polymerization
medium to contain from about 15 weight percent to about
25 weight percent monomers and polymers. In commercial
operations, the polymerization medium will typically
contain about 20 weight percent monomers and polymers.
Virtually any type of diisocyanate monomer can be
utilized. These diisocyanate monomers will typically
have the structural formula:
-` 2030889
-32-
O=C=N A-N=C=O
wherein A represents an alkylene, cycloalkylene,
arylene or cycloarylene moiety. Some representative
examples of diisocyanate monomers which can be employed
include 1,6-hexamethylene diisocyanate, 4,4'-methylene
diphenyl diisocyanate, toluene diisocyanate,
naphthalene diisocyanate, and isophorone diisocyanate.
Isophorone diisocyanate is also known as
~-isocyanato-l-(isocyanatomethyl)-1,3,3-trimethyl-
cyclohexane and has the structural formula:
CH3 CH2-N=C=O
~ ~
~ CH3
O=C=N CH3
Polyureas can be prepared by reac~ing virtually any
type of diamine monomer with the diisocyanate monomer.
Some representative examples of diamine monomers which
can be utilized include ethylene diamine, phenylene
diamine, 1,6-hexanediamine, naphthalyne diamines,
1,4-butylene diamine, piperazine, hydrazine and the
like. By the same token, polyurethanes can be prepared
by reacting virtually any diol with the diisocyanate
monomer. Some representative examples of diol monomers
which can be employed include ethylene glycol, butylene
glycol, neopentyl glycol, cyclohexane dimethanol and
1,6-hexanediol. Small amounts of polyiisocyanates,
polyamines, or polyols can be copolymerized into the
polymer to cause cross-linking. In some cases, it is
desirable to utilize an aromatic diamine because of the
" . ~ ~ ~
,
2030889
generally fast reaction rate which is attained. Fast
reaction rates are particularly desirable in cases
where the polyurea or polyurethane is being synthesized
within the matrix of a dry rubber.
The diisocyanate monomer can be blended into the
matrix of a dry rubber containing a diamine monomer or
a diol monomer to prepare the high modulus rubber
composition. In such a procedure it is normally
preferred to mix the diisocyanate monomer into the
rubber and then subsequently to blend the diamine or
the diol into the rubber which already contains the
diisocyanate monomer. It is also possible to reverse
this order with the diamine monomer or diol monomer
being mixed into the rubber with the diisocyanate
monomer being added subsequently. It is typically not
desirable for the diisocyanate monomer to be added to
the dry rubber at the same time that the diol monomer
or diamine monomer is being added.
In another preferred embodiment of this invention,
the polyiisocyanate is dispersed into a first portion
of dry rubber. The diol monomer or diamine monomer is
blended into a second portion of the rubber. The two
components can then be blended so as to mix the rubber
containing the diisocyanate with the rubber containing
the diol or diamine monomer. This procedure also
results in the production of a highly dispersed blend
of polyurethane or polyurea within the matrix of the
dry rubber.
The polyurea or polyurethane can be synthesized in
the rubber matrix or polymer cement solution over a
wide temperature range. As a mafter of convenience,
such solution polymerizations are typically conducted
at room temperature (about 20C to about 30C). In
cases where the polyurea or polyurethane is prepared
2030889
-34-
within the matrix of a dry rubber, the temperature at
which the polymerization is conducted is typically
within the range of about 60C to about 200C. It is
preferred for such polymerizations to be conducted at a
temperature within the range of about 100C to about
160C with it being most preferred for the
polymerization ~o be done at a temperature within the
range of about 120C to about 140C.
In cases where the polyurea or polyurethane is
being synthesized within the matrix of a dry rubber,
the polymerization is carried out while the rubber and
monomers are being subjected to mechanical shearing
forces. Typically the polymerization will be carried
out in an extruder or a mixer which is capable of
providing sufficiently high shearing forces so as to
homogeneously disperse the monomers throughout the dry
rubber. Banbury mixers and Brabender mixers are very
suitable for utilization in this procedure.
This invention is illustrated by the following
working examples which are presented merely for the
purpose of illustration and are not to be regarded as
limiting the scope of the invention or the manner in
which it can be practiced. Unless specifically
indicated otherwise, parts and percentages are given by
weight.
Example 1
In this experiment a highly dispersed blend of
polyurea in polybutadiene was prepared by solution
polymerization. In the procedure utilized, 30 grams of
a 10% solution of polybutadiene in hexane was well
mixed under nitrogen at a temperature of about 40C
with 0.39 grams of 1,6-hexane diamine. Subsequently
0.75 grams of isophorone diisocyanate was added drop
~ 2030889
wise to the polybutadiene/1,6-hexane diamine solution
with the solution being stirred rapidly. This resulted
in the solution turning opaque rapidly as the polyurea
was formed. However, the resultant solution showed no
separation after standing overnight.
The mixture was poured onto a non-stick tray and
the hexane solvent was allowed to evaporate. Residual
hexane solvent was removed in a vacuum oven. The dried
rubber was milled to press out air and tensile bars
were cut out of the sheet for tensile testing on an
instron machine. The polyurea ~odified polybutadiene
rubber showed greatly improved tensile properties ov~r
those of unmodified polybutadiene.
Example 2
220 grams of polycisisoprene solution (about 19%
solid in hexane), 220 grams of hexane and 6 grams of
hexane diamine were mixed together. When hexane
diamine was dissolved, 12 grams of isophorone
diisocyanate was added dropwise to the solution with
fast stirring. The resultant elastomer was then dried
in the vacuum oven set at 55C. The elastomer was
pressed out at 200 to 230F and tensile properties were
tested. The data in Table I shows that the 30/70
polyurea/polyisoprene blends have higher tensile values
at both 50% and 100% elongation, as well as break
elongation. In some cases, the tensile properties were
two to three times higher. Both average and best
values of the break elongation were also much higher
than the unmodified polyisoprene control. This is
probably due to the strong hydrogen bonding effect of
the polyurea components.
2030889
-36-
0i~ ,~
h
U~ ~
oo
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aJ
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p:
JJ b~
cn g 5~
Q) ~ ~
~ ~ td
0 ~ ~ ~ U~ 0
~ ~o ¢
¢
~ .
$
0~ ~ U~ 00 00 rl
~ o ~ ~ u~
~ ~ C~ ~
U~ ~ ~0
~0
E~
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OO ~ 0
GqS~ CO
rl ~ O r~
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-
:
:
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203Q889
The polyisoprene control had an average break
elongation of 291% and the polyurea/polyisoprene blend
had an average break elongation of 515%. The highest
break elongation measured for the polyisoprene samples
tested was 515%. The polyurea/polyisoprene blend which
had the highest break elongation was measured at 700%.
Example 3
In this experiment highly dispersed blends of
polyurea in polyisoprene made by the procedures
specified in Example 1 were cured with the mechanical
properties of the cured blends being measured on an
instron. In the procedure utilized the
polyurea/polyisoprene blend was compounded with 45 phr
of carbon black, 9 phr of an oil, 2 phr of
N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylene diamine, 1
phr of a wax, 3 phr of stearic acid, 3 phr of zinc
oxide, 0.8 phr of N-oxydiethylene
benzodithiazole-2-sulfenamide, 0.4 phr of guanidine and
1.6 phr of insoluble sulfur. The rubber composition
was then cured at 300F (149C) for 25 minutes. The
50% modulus, 100% modulus, tensile strength and
elongation of the cured rubber samples made are
reported in Table II.
.
2030~89
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2030889
- .. ..
-39-
:'
Example 4
In this experiment a highly dispersed blend of
polyurea was prepared in the matrix of dry
polyisoprene. In the procedure used, 175 grams of
polyisoprene was mixed for 3 minutes with 25 grams of ;
1,6-hexane diamine in a Brabender mixer which was
,
operated at 120C. Subsequently, 50 grams of
isophorone diisocyanate was added drop-wise to the
blending mixture for 5 minutes.~ The blending
temperature was main~tained within~thé ran~ge of about
160C to about i700C~
The~resultant~gum rubber was~pressed out to about
~- 0~.125 inch (3.2~mm) sheet and~tens~ile bars~were cut
therefrom for testing. Control~samples~had a breaking
s~trength of 43 psi (2.96 X~ 10 pascals)~and a breaking ~-`
elongation of 166%. The po~lyurea modified "
polybutadiene blends had a breaking tensile strength of
114 psi (7.86 X 105 pascalsj~and~a brèaking elongation
of 357%. This example cl~early shows that the
advantages of this invention can also be realized by
preparing the polyurea;within the matrix;of a dry
rubber.~
j Example 5
-~ 25 Highly dispersed blends of polyurea~in polyLsoprene
~were made by reactor blending utilizing the general -
procedure described in Example 3. In this experiment -
blends containing 10 phr, 20 phr, and 30;phr of the
polyurea in polyisoprene were prepared. The green `~
rubber blends made were then cured utilizing the
procedure described in Example 2. The tensile
properties of the cured rubber blends are reported in
Table III.
,. . ,. , , , , ~ .
,,, , . ., .: ~ . . ., - , -
., ~ , - ,
203~889
-40-
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2030889
-41-
_ample 6
In this experiment an aromatic polyurea was
utilized to modify polyisoprene. The aromatic polyurea
was incorporated into dry polyisoprene by reacting
S modified liquid diphenylmethane 4,4'-diisocyanate with
1,6-hexane diamine using the general procedure
described in Example 3. The aromatic polyurea produced
seemed to be more effective in improving the tensile
modulus of the final polyurea/rubber blend. At
equivalent levels of modification, the aromatic
polyurea is almost twice as effective as that of the
aliphatic polyurea. This may be attributed to the more
rigid aromatic structure. The physical properties of
the cured blends prepared are reported in Table IY.
'
2~30~8~
-42-
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2030889
-43-
While certain representative embodiments and
details have been shown for the purpose of illustrating
the subject invention, it will be apparent to those
skilled in this art that various changes and
modifications can be made therein without departing
from the scope of the subject invention.
