Note: Descriptions are shown in the official language in which they were submitted.
SOLUTION POLYMERIZATION
This invention relates to compositions of (1) barium, cal-
cium andior strontium alcoho]ates, (2) organoaluminum compounds
and (3) organomagnesium compounds and their use as catalysts for
the solution polymerization of ethylenically unsaturated monomers
like butadiene, butadiene,/styrene and isoprene and for the poly-
merization of heterocyclic monomers like oxiranes, thiiranes,
siloxanes, thiatanes and lactams.
Background of the Invention
The use of dialkylmagnesium or alkylmagnesium iodide in
combination with barium ethoxide particularly additionally with
l,l-diphenylethylene as initiators of polymerization of butadiene
to give polybutadiene having a trans-1,4 content as high as 78%
and a vinyl content oE 6% has been disclosed by the Physico-
Chemical Research Institute, Polymer Science U.S.S.R., 18 (9),
2325 (1976). This paper, also, shows that a catalyst system of
magnesium and barium tert-butoxide gave a polybutadiene with only
45% trans-1,4 content (200 hours polymerization time and conver-
sion of only 10%).
U. S. Patent No. 3,846,385 (U. S. Patent No. 3,903,019 is a
Division of the same) shows the preparation of random butadiene-
styrene copolymers haviog a high trans-1,4 content and a vinyl
content of 9%. The trans-1,4 content increased as the-mol ratio
of Ba(t-BuO)2/(Bu)2Mg decreased with little variation in
either the vinyl content or heterogeneity index. A copolymer
exhibited a well defined crystalline melting temperature at
32.6C by differential thermal analysis (DTA). The Molecular
Weight Distribution (MWD) of these copolymers was characterized
by having heterogeneity indices (MW/Mn) raslging from 1.4 to
2.2. Polybutadienes made with these catalysts exhibited a
trans-1,4 content as high as 78~. No polymerization or copoly-
merization occurred when only one of the catalyst components was
used alone.
\B ~
Polymerization of butfldiene with some cyc1ization in hexane
or toluene at 100C using Bu2Mg-BuMgI is reported in "Chem.
Abstracts," 1963, 4045e.
Polymerization of butadiene using Ba(OEt)2 with Et2Mg,
4 9 3 g2I or (C6H13)2Mg is reported in "Chem.
Abstracts," Vol. 84, 1976, 151067n.
Dialkylmagnesium compounds and their complexes with organo--
aluminum or with organolithium compounds are said to be cocata-
lysts with Ziegler based catalyst systems (transition metal com-
pounds) for the polymerization of dienes and olefins. This hasbeen described by Texas Alkyls (Product Data Sheet MAGALA-6E) and
Lithium Corporation of America (Product and Technical Bulletin on
"Polymerization Using Magnesium Alkyl Catalysts,l- 1978).
British Patent No. 1,531,085 discloses in the working
examples the preparation of polybutadienes and butadiene-styrene
copolymers having inherent viscosities of 0.8 to 5, trans-1,4
contents of 34 to 90% and vinyl contents of 2 to 38~. A two
component catalyst is used. As shown by the working examples the
first component can comprise a BalAl(C2H5)412,
Ba[Al(C2H5)3OR]2 where R is a nonyl phenate radical, LiAl-
(C2H5)4. NaAl(C2H5)4~ KAl(C2H5)4'
( 2H5)3OCH(CH3)2, LiOAl(C2H5)2 compound andso forth. The second component is a polar compound or the like
such as tetrahydrofuran, methanol, water, tetramethylethylene
diamine, acetone, barium nonyl phenate, lithium isopropylate, Na-
tert-amylate, acetonitrile and so forth. The molar ratio between
the polar compound and the organic compound of metal of Group
IIIA such as Al is from 0.01 to 100.
U. S. Patent No. 4,079,176 discloses a process for polymer-
izing dienes and for copolymerizing dienes and vinyl aromaticcompounds with a catalyst composition comprising (A) an organo-
lithium and (B) a compound having the formula
Ma(MbRlR2R3R4) or MalMc(Rl)
where Ma is Ba, CA, Sr or Mg; Mb is B or Al; MC is Zn or
Cd; Rl, R2 and R3 are alkyl or aralkyl radicals; R4 is an
alkyl, aralkyl radical or oR5 where R5 is an alkyl or aralkyl
radical. The working examples show the polymerization of BD and
copolymerization of BD with STY to provide polymers exhibiting
intrinsic viscosities of 0.81 to 1.6, trans-1,4 contents of 76 to
85% and vinyl contents of 2 to 6~.
U. S. Patent No. 4,080,492 discloses a method for polymeriz-
ing BD or copolymerizing BD and vinyl aromatic compounds using a
catalytic composition of (a) an organolithium compound and ~b) a
cocatalyst system which comprises a Ba or Sr compound and an
organometallic compound from Groups IIB or IIIA like zinc or
aluminum. Examples of the Ba or Sr compounds are their hydrides,
organic acid salt, alcoholates, thiolates, phenates, alcohol and
phenol acid salts, betadiketonates and so forth. Table VIIA
shows the use of barium tertiobutanolate. Examples of the Group
IIB and IIIA materials are diethylzinc, diethyl cadmium, triethyl
aluminum and so forth. The working examples for the preparation
of polymers of BD and copolymers of BD and STY show ~ of .34 to
20 2.15, trans-1,4 of 61 to 90% and vinyl contents of 2.4 to 9%.
U. S. Patent No. 4,092,268 is similar to U. S. Patent No.
4,080,492 but it includes isoprene and shows in Examples 11 and
12 the polymerization of isoprene and the copolymerization of
isoprene and styrene.
British Patent No. 1,516,861 has a somewhat similar dis-
closure to that of U. S. 4,080,492 and both are based on the same
French patent application. The U. S. case apparently deleted
reference to the polymerization of isoprene.
British Patent No. 1,525,381 (patent of addition to Br.
30 1,516,861, above) discloses a process for polymerizing butadiene
and copolymerizing butadiene and styrene using a catalyst compo-
sition of (a~ an organolithium, (b) a compound of barium, stron-
tium or calcium, (c) an organometallic compound of a metal of
Group IIB or IIIA and (d) an amino or ether alcoholate of an
alkali metal. An example of (a) is n-butyl lithium; of (b) is
l:~Lfi~
-- 4 --
Ca, Ba or Sr alcoholate or phenate particularly barium nonyl
phenate; of (c) is
2 5)2 n, (C2H5)3 Al or (i-butyl)3 Al;
and of (d) is C2H5(0CH2CH2)2 OLi,
2 5)2NCH2CH20Li or CH2(0CH2CH2)20Na.
The working examples for the polybutadienes and butadiene-styrene
copolymers made show inherent viscosities of 0.9 to 2.4,
trans-1,4 contents of ôO to 90X and vinyl contents of 2 to 4X.
For Example 2 it is stated that the green strength test on the
black loaded uncured copolymers showed a similar resistance to
elongation to that of natural rubber.
A class of crystalli~ing elastomers based on butadiene
containing sufficient amounts of the trans-1,4 structure to
crystallize has been disclosed in U. S. Patent No. 3,992,S61
lS (divisional U. S. patents of the same Nos. 4,020,115; 4,033,900
and 4,048,427 have the same disclosure in the specification).
The catalyst for the preparation of these polymers comprises an
alkyl lithium compound such as n-butyl lithium and a barium
t-alkoxide salt such as a barium salt of t-butanol and water.
The polymerization temperature, the nature of the solvent and the
mole ratio of the catalyst components and its concentration were
found to control the polybutadiene microstructure and molecular
weight. It is stated that the crystalline melting temperature of
the high trans polybutadienes can be depressed near or below room
temperature by the copolymerization of styrene, still permitting
the rubber to undergo strain induced crystallization. The
butadiene polymers and butadiene-styrene copolymers exhibited
green strength and tack strength. A high trans polybutadiene
exhibited a broad bimodal molecular weight distribution. This
patent discloses in the working examples for the invention
polybutadiene and butadiene-styrene copolymers exhibiting
intrinsic viscosities of 1.43 to 7.39, trans-1,4 contents of 63
to 80.4% and vinyl contents of 6 to 9%.
.
l~t~ t..`~
Copending United States Patent Application Serial No. 077~42S filed September
20, 1979, now United States Patent No. 4,260,712 ~Patent No. 4,260,519 is a div-
ision), discloses an improved barium t-alkoxide salt for use with a hydrocarbon
lithium compound for the preparation of polybutadiene and butadiene-styrene co-
polymers. It shows in the working examples for polybutadiene and butadiene-
styrene copolymers intrinsic viscosities of from ~.74 to 7.68, trans-1,4 contents
of 73 to 82% and vinyl contents of 6 to 13%.
"Gummi-Asbest-Kunststoffe," pages 832 to 842, 1962 reviews several catalyst
systems for polymerizing unsaturated monomers and discusses the properties of
several polymers. On page 835, Table 4, it discloses the use of a catalyst sys-
tem of R2Mg and RMgHal to polymerize butadiene to make a polybutadiene having
45-49 trans-1,4 units.
Objects
An object of the present invention is to provide a new composition useful as
a catalyst for the solution polymerization of ethylenically unsaturated monomers
and heterocyclic monomers.
Another object of the present invention is to provide a method for solution
polymerization of ethylenically unsaturated monomers and heterocyclic monomers
using an anionic catalyst complex or composition.
These and other objects and advantages of the present invention will become
more apparent from the following detailed description, examples and accompanying
drawings in which
Figure 1 is a graph showing copolymer composition variation with percent
conversion using different catalyst systems;
Figure 2 is a graph showing the polybutadiene microstructure versus the
mole ratio of Ba[(t-RO)2 x(OH)x~ to (Bu)2Mg at Mg/Al = 5.4/1 (Example l);
Figure 3 is a graph showing the gel permeation chromatograms of polystyrene
and polystyrene-polybutadiene diblock copolymer prepared with the Mg-Al-Ba
composition catalyst;
, ~
- 5a -
Figure 4 is a graph showing the effect of chain extension on the mo1ecular
weight distribution of high trans styrene-butadiene copolymer rubber (15%
styrene);
~ D
~.~t;~ t~
Figure 5 is a graph showing the effect of chain extension of high trans
styrene-butadiene (copolymer) rubber on variation of viscosity with shear-rate;
Figure 6 shows x-ray diffraction patterns for a high trans styrene-
butadiene rubbery copolymer ~about 15% sty; 85% Trans) of this invention;
Figure 7 (which appears on the same sheet as Figure 5) is a graph
showing the "green-strength," stress-strain, of uncured but compounded (45 phr
of carbon black) of various rubbers and
Figure 8 is a graph showing the effect of contact time on tack strength
of high trans styrene-butadiene (copolymer) rubber (15% styrene) of this inven-
tion and natural rubber (SMR-5), both uncured but compounded with 45 phr carbon
black and 13 phr oil.
Summary of the Invention
This invention provides a composition of matter useful as an anionic
polymerization catalyst comprising (1) an alcoholate selected from the group
consisting of barium alcoholate, calcium alcoholate and strontium alcoholate
and mixtures thereof, (2) an organoaluminum compound and (3) an organomagnesium
compound, where the mol ratio computed as metal of barium, calcium and/or
strontium to magnesium is from about 1:10 to 1:2 and where the mol ratio com-
puted as metal of magnesium to aluminum is from about 105:1 to 1.5:1.
In a second aspect, this invention provides the method which comprises
polymerizing under inert conditions in a hydrocarbon solvent at a temperature
of from about 0 to 150C. a monomer selected from the group consisting of a
polymerizable heterocyclic monomer and a polymerizable ethylenically unsaturated
monomer having an activated double bond with a catalyst in a minor effective
amount sufficient to polymerize said monomer to obtain a polymer, said catalyst
comprising (1) an alcoholate selected from the group consisting of barium
alcoholate, calcium alcoholate and strontium alcoholate and mixtures thereof,
-- 6 --
(2) (m organoaluminum compound and (3) an organomagnesium compound, where the
mol ratio compu~ed as metal of barium, calcium and/or strontium to magnesium
is from about 1:10 to 1:2 and where the mol ratio computed as metal of magnesium
to aluminum is from about 105:1 to 1.5:1.
In a third aspect, this invention provides for a rubbery copolymer
of butadiene-1,3 and up to about 30% by weight total of said copolymer of
copolymerized styrene, said copolymer exhibiting:
a. a glass transition temperature of from about -50 to --100C as
determined by differential thermal analysis,
b. a crystalline melting point ~peak values) in the unstretched state
of from about -10 to +40C as determined by differential thermal
analysis,
c. a trans-1,4 content of from about 81 to 90% and a vinyl content
of up to about 4% for the butadiene units,
d. a heterogeneity index of from about 2.5 to 5,
e. a number average molecular weight of from about 50,000 to 500,000~
f. crystallinity when stretched in the uncompounded and uncured state
as shown by x-ray diffraction data and
g. quick-grab, green strength and building tack.
Finally, in a fourth aspect, this invention provides for a homopoly-
butadiene having a trans content of from abcut 64 to 90%, a vinyl content of
from about 2 to 7%, an intrinsic viscosity of from about 0.~0 to 4.29 in
deciliters per gram in toluene at 25C and a peak crystalline melting temperaure
of from about -16 to 70C.
According to the present invention a composition of a barium alcoholate
or alkoxide salt, an organoaluminum compound and an organomagnesium compound
has been found useful as an anionic polymerization catalyst for the solution
- 6a -
polymerization of butadiene as well as butadiene and styrene to make polymers
having a high trans content. In place of barium alkoxide, calcium alkoxide or
strontium alkoxide can be used. The catalyst may be used for the polymerization
of other ethylenically unsaturated monomers as well as heterocyclic monomers
like oxiranes, thiiranes, siloxanes, thiatanes and lactams.
The homopolymer of butadiene and copolymer of butadiene with styrene
of this invention have a high content of trans-1,4 linkages (~5-90%) and a low
vinyl content ~2-3%) which provide sufficient amounts of trans-1,4 polybutadiene
placements to permit crystallization. The copolymers of butadiene with styrene
of this invention exhibit a glass transition temperature of from about -50 to
-100C as determined by differential thermal analysis, and a heterogeneity
index of from about 2.5 to 5. The catalyst for these polymerizations comprises
an organomagnesium-organoaluminum complex, (1) [(a)alkyl2Mg:(b)alkyl3A1], where
the mole ratio of (a) to (b) is from about 105/1 to 1.5/1, in combination with,
(2) a barium, calcium and/or strontium (barium being preferred) salt of alcohols,
or alcohols and water, the alcohol is preferably a tert-
_ 6b -
lt~
-- 7 --
alcohol, the mole ratio of barium metal to magnesium metal being
from about 1/10 to 1/2.
It has been found that the trans-1,4 content of the polybut-
adïene segments generally is controlled by the following fac-
tors: (1) the mole ratio of barium to magnesium (Ba2 /Mg2 ~present in the Mg alkyl-Al alkyl-Ba salt catalyst composieion,
(2) the mol ratio of Mg to Al, (3) the nature of the polymeriza-
tion solvent used, (4~ the polymerization temperature, and (5)
the catalyst concentration. By the use of appropriate polymeri-
zation variables, the trans-1,4 content is sufficiently high (ca
81 to 90%) to provide a crystalline polybutadiene and for certain
copolymer compositions (with styrene contents up to about 30%) a
strain-crystallizing SBR and Mn about 50,000 to 500,000S linear
and branched.
Copolymerization of butadiene and styrene with barium
t-alkoxide salts and a complex of an organomagnesium with an
organoaluminum (Mg-Al), for example, 5.4 (n-C4H9)2Mg -
(C2H5)3Al (MAGALA-6E, Texas Alkyls, Inc.) exhibit 8 a higher
initial rate of incorporation of styrene than a n-C4HgLi
catalyzed copolymerization as shown by Figure 1.
Proton NMR analysis of these high trans SBR's (15% styrene)
shows a distribution of the styrene throughout the polymer from
isolated units to styrene sequences longer than tetrads. The
amount of block polystyrene placements in the copolymer chain
appears to rapidly increase as the extent of conversion increases
from 90~ to lOOX. However, it has not been possible to isolate
any polystyrene from the products of oxidative degradation with
tert-butylhydroperoxide and osmium tetroxide lfollowing the
technique of I.M. Kolthoff, T. S. Lee and C. W. Carr, J. Polymer
Sci., 1, 429 (1946)] of a high trans SBR polymerized to 92%
conversion and containing 23 weight percent (wt.~) total styrene.
One of the main factors which controls the butadiene
microstructure at constant Mg/A1 ratio is the mole ratio of
Ba2 /Mg2+. This is shown by Figure 2 for a Mg/Al ratio of
5.4/1. rne trans-1,4 content of polybutadiene, prepared in
cyclohexane at 50C, increases and the vinyl content decreases as
*Trade Mark
-- 8 --
Ba jMg2 decreases. Polybutadienes with trans-1,4 contents
as high as 90Z with vinyl contents of 2~ have been prepsred with
this system at mole ratios of 8a /Mg of 1/5. The optimum
Ba /Mg ratio is approximately 1/5.
In particular, complexes of Mg-Al with compounds of barium
tert-alkoxide or barium (tert-alkoxide-hydroxide) are highly
effective for the preparation of high trans-1,4 polybutadiene (up
to about 90X trans). The barium salts useful in the polymeriza-
tion are prepared in liquid monomethylamine or liquid ammonia by
reacting barium metal with a tert-alcohol or mixture of t-alco-
hols, or mixture of tert-alcohol(s) and water (0.01-0~1 equiva-
lents of the available barium is reacted with water). Certain
barium salts, such as barium (tert-decoxide-tert-butoxide-hydrox-
ide), molar ratio of tert-decanol/tert-butanol/H20 (30/59/11),
have the advantage that they are soluble to greater ~han 20 wt.%
in toluene and the solutions are stable indefinitely. Thus, they
provide a soluble barium compound of invariant solution compo-
sition during storage.
Complexes of barium tert-butoxide (which is only sparingly
soluble (0.1 wt.%) in toluene at room temperature) with Mg-Al
alkyls are, however, also effective catalysts for the preparation
of 90% trans-1,4 polybutadienes.
The polymerization activity and the amount of trans-1,4
content are very much dependent on the Mg/Al ratio in these
Ba-Mg-A1 catalysts. It has been found that Mg-Al complexes
containing (n-C4Hg)2Mg to (C2H5)3Al in mole ratios of
about 5.4 and 7.6 (MAGALA-6E and MAGALA-7.5E, Texas Alkyls,
Inc.), respectively, are effective for preparing 90X trans-1,4
polybutadiene at constant Ba/Mg = 0.20. In addition, Mg-A1-Ba
complexes containing Mg and Al in ratios of 27 and 105 are capa-
ble of polymerizing butadiene to polymers having trans-1,4 con-
tents of about 81-83Z. However, a complex of (n-C4Hg)2Mg .
2(C2H5)3Al with Ba salts did not polymerize butadiene.
It is possible to prepare polybutadienes with trans-1,4
contents greater than 85Z with Ba-Mg-Al catalysts consisting of a
romplex of barium salts with (sec-C4Hg)Mg (n-C4Hg) and
_ 9 _
(C2H5)3Al, prepared in situ, in mole ratios of Mg/Al rang-
ing from about 2 to 7.6.
Alternatively, soluble catalyst compositions can be prepared
by~mixing clear colorless solutions of, e.g., MAGALA-6E in hep-
tane with barium (tert-alkoxide-hydroxide) in toluene. Optional-
ly, the catalyst can be preformed by heating the solution for 15
minutes at 60C. A yellow colored solution forms upon heating,
indicating complex formation (Ba /Mg - 1/5). A small
amount of lightly colored precipitate is also formed. Active
catalyst components for trans-1,4 addition are present in the
solution phase. The insoluble phase in toluene represents only a
small fraction of the total metallic compounds.
In addition to the effect of catalyst composition, the
nature of the polymerization solvent and temperature influence
the microstructure of the butadiene based polymers. Polybuta-
dienes prepared in paraffinic and cycloparaffinic hydrocarbon
solvents have slightly higher trans-1,4 contents and higher
lecular weights than polymers prepared in toluene. The stereo-
regularity of butadiene based polymers prepared in cyclohexane
with a Mg-Al-Ba catalyst is dependent on polymerization tempera-
ture. The decrease in trans-1,4 content with increasing polymer-
ization temperature occurred with a corresponding increase in
both vinyl and cis-1,4 contents.
The concentration of catalyst affects both the trans-1,4
content and molecular weight of polybutadiene prepared in cyclo-
hexane at 50C. The trans-1,4 content increases non-linearly
with a decrease in the molar ratio of the initial b~tadiene to
(n-C4H9~2Mg concentration, at a constant Ba/Mg ratio. The
trans-1,4 content appears to reach a limiting value of about 90X
for polybutadienes prepared with relatively large amounts of
catalyst.
Molecular weight increases with an increase in the molar
ratio of butadiene to (n-C4Hg)2Mg as well as with an
increase in the extent of conversion. In addition, the viscosity
of a solution of non-terminated polybutadienyl anion increases
with the addition of more monomer. The above results demonstrate
- lo
that a certain fraction of the poly~er chain ends retain their
capacity to add monomer.
The crystalline melting temperatures (45C, 70C) of these
poiybutadienes can be decreased to near or below room temperature
(about 25C) by adjustments of the trans-1,4 content and the
incorporation of a comonomer (styrene). The resultant copolymers
are then amorphous at room temperature but will undergo strain-
induced crystallization. The rubbers are characteri~ed by both
green strength and tack strength equal to or higher than natural
rubber. As such, these synthetic rubbers can be expected to be
of value in those applications where natural rubber is used. One
of these applications is as a tire rubber, especially in radial
ply tire construction. In addition, the ability to control the
molecular structure of these rubbers makes them useful materials
in tire tread compounds.
For styrene-butadiene copolymers, prepared with Mg-Al-Ba
catalysts at Ba/Mg of 0.20 to 0.25, the molecular weight appears
to be controlled by both the level of Mg and Ba used in the
polymerization. The moleculflr weight of higll trans polybutadiene
and polystyrene as well as STY-BD copolymers increases with an
increase in initial molar concentrations of monomer(s)/Mg at
constant Ba/Mg.
Discussion of Details and Preferred Embodiments
The barium (preferred), calcium or strontium alcoholate or
alkoxide salt or mixture of such salt is made by reacting an
alcohol, prefersbly a tertiary alcohol or mixture of tertiary
alcohols, optionally additionally including water, with Ba, Ca
and/or Sr. It is better to conduct the reaction in liquid NH3
or amine solvent at a temperature of from about -100C up to the
boiling point of the solvent or above the boiling point under
pressure. After the reaction, the NH3 or amine can be removed
from the salt by distillation, vacuum evaporation and solvent
extraction. Preferably, the salt is dried in a vacuum at reduced
pressure for a period of time sufficient to reduce the nitrogen
content of the salt to not greater than about 0.1, preferably not
greater than about 0.01~, by wei~ht. Metllods of making the barium alkoxide salts,
such as barium t-alkoxide salts, which also will be applicable to the correspond-
ing Ca and Sr salts, are shown in United States Patent No. 3,992,561 and copend-ing ~nited States Application Serial No. 077,428~ filed September 20, 1979,
Aggarwal et al, now United States Patent No. 4,260,712 ~Patent No. 4,260,519 is
a division).
Examples of alcohols to use to make the Ba, Ca and/or Sr salts or alcoholates
are methanol, ethanol, propanol, isopropanol, n-butanol, cyclopentanol, cyclo-
heptanol, cyclohexanol, s-butanol, t-butanol, pentanol, hexanol, octanol, and
decanol and so forth and mixtures of the same. Examples of such alcoholates are
calcium diethoxide, di(t-butoxy) strontium, di(isopropoxy) barium, di~cyclohexy-loxy) barium and so forth. If a non-tertiary alcohol or carbinol is used, it is
preferred that the mixture contain at least 50 mol % of a tertiary carbinol.
The preferred carbinol to use is a tertiary carbinol, having the general
formula
HO-C-R where the
Rs are selected from the group consisting of alkyl or cycloalkyl radicals of
from 1 to 6 carbon atoms which may be the same or different such as a methyl,
ethyl, propyl, butyl, isopropyl, amyl, cyclohexyl and the like radicals. Examples
of these tertiary carbinols are t-butanol, 3-methyl-3-pentanol, 2-methyl-2-
butanol, 2-methyl-2-pentanol, 3-methyl-3-hexanol, 3,7-dimethyl-3-octanol, 2-
methyl-2-heptanol, 3-methyl-3-heptanol, 2,4-dimethyl-2-pentanol, 2,4,4,-trimethyl-
2-pentanol, 2-methyl-2-octanol, tricyclohexyl carbinol, dicyclohexyl propyl
carbinol, cyclohexyl dimethyl carbinol, t-decanol ~4-n-propyl-heptanol-4),
3-ethyl-3-pentanol, 3-ethyl-3-hexanol, 3-ethyl-3-heptanol, 3-ethyl-3-octanol,
5-ethyl-5-nonanol, 5-ethyl-5-decanol, 6-ethyl-6-undecanol, 5-butyl-5-nonanol,
4-isop~opyl-4-heptanol, 2-methyl-4-n-propyl-4-heptanol, 4-n-propyl-4-nonanol, 5-n-propyl-5-nonanol, 2,2-dimethyl-4-n-propyl-4-heptanol, 4-n-propyl-4-
B
- 12 -
decanol, 5-n-propyl-5-decanol, 2,6-dimethyl-4-isobutyl-4-heptan-
ol, 3,3,6-trimethyl-4-n-propyl-4-heptanol, 6-n-propyl-6-undecan-
ol, 5-n-butyl-5-decanol, 6-n-butyl-6-undecanol, 6-n-pentyl-6-un-
decanol, 2,8-dimethyl-5-isopentyl-5-nonanol, and 2,8-dimethyl-5-
isobutyl-5-nonanol and the like and mixtures of the same.
There, also, may be used a tertiary carbinol having the
general formula
H0-C-R'' where R' is an alkyl radical of from I to 4 carbon
\R'
atoms which may be the same or different and where R" is a
hydrocarbon radical having a molecular weight of from about 250
to 5,000. These materials may be obtained by polymerizing in
solvent media butadiene and/or isoprene with or without a minor
amount of styrene and/or alpha methyl styrene using a monolithium
hydrocarbon catalyst such as butyllithium to obtain a liquid
lithium terminated polymer or oligomer. The preparation of such
liquid diene containing polymers is known. See U. S. Patent No.
3,078,254. Appreciable amounts of catalyst are used to obtain
liquid polymers, See U. S. Patent No. 3,301,840. The resulting
polymer solution is then treated with an epoxide such as isobu-
tylene oxide
o~C,H3
(H2C-C-CH3, I,1-dimethyl-1, 2-epoxyethane or
1,2-epoxy-2-methyl propane)
to obtain a product which may be shown as:
CIH3
polymer-cH2-7-oLi .
CH3
In place of isobutylene oxide there can be used 1,1-diethyl-1,2-
epoxyethsne, l,l-dipropyl-1,2-epoxyethane, I,l-diisopro W 1-1,2-
epoxyethane, l,l-dibutyl-1,2-epoxyethane, 1,1-diisobutyl-1,2-
epoxyethane and the like epoxide and mixture thereof. See U. S.
Patent No. 3,538,043. These epoxide treated lithium terminated
f.`~
- 13 -
polymers can then be hydroly~ed with water to form the tertiary
carbinol or alcohol:
CH3
polymer-CH2-C-OLi + H20 ~ LiOH and
CH3
,H3
polymer-CH2-C-OH. See V. S. Patent No. 3,055,952.
CH3
The hydrolyzed polymer or liquid tertiary carbinol is then
removed from the organic solvent and is ready for reaction with
barium to form a barium tertiary alkoxide salt.
Mixtures of the above tertiary carbinols can be used.
Water, if used in preparing the Ba, Ca or Sr alcoholates or
salts, is employed in the alcohol or alcohol mixture as follows:
from about 0 to 20, preferably from about 0 to 12, mol~ of
water to from about 100 to 80, preferably from about 100 to
88, molX of the alcohol or alcohol mixture.
The resulting preferred alcoholate or alkoxide salt, or
lS mixture of said salts, preferably containing not over about 0.1~,
and even more preferably not over about 0.01% by weight of
nitrogen, have the following general formulae:
/R ~R'
Ml(O-C-R)a(OH)b]2 and/or Ml(0-C\R' )a(H)bl2
where the mol ratio of a to b is from about 100:0 to 80:20,
preferably from about 100:0 to 88:12, and where R, R' and R " are
the same as defined above and where M is barium, calcium and/or
strontium, preferably barium, or mixture of said metal salts or
alcoholates.
The organoaluminum compounds used in the practice of the
present invention are alkyl and cycloalkylaluminum compounds.
These compounds can be prepared by reacting aluminum metal with
an olefin in the presence of hydrogen. Another method, for
example, comprises the reaction:
- 2Al+3(cH3)2Hg~ 3Hg+2(CH3)3Al.
l~t~t~ 3
- 14 -
Other methods can be used~ See "Aluminum Alkyls," Texas Alkyls,
Copyright lg76 by Stauffer Chemical Company, Westport, Connec-
ticut, 71 pages including the bibliography shown therein and
"Encyclopedia of Polymer Science and Technology," Vol. 1, 1964,
Interscience Publishers a division of Jolln Wiley & Sons, Inc.,
New York, Pages 807 to 822. These organoaluminum compounds have
ehe general formula R3IIAl where RIII is an alkyl radical
or cycloalkyl radical, which may be the same or different~ of
from 1 to 20, preferably of from 1 to 10, carbon atoms. Mixtures
of these organoaluminum compounds can be used. Examples of such
compounds are trimethyl aluminum, triethyl aluminum, tri-n-propyl
aluminum, triisopropyl aluminum, pentyl diethyl aluminum,
2-methylpentyl-diethyl aluminum, tri-n-butyl aluminum,
triisobutyl aluminum, dicyclohexylethyl aluminum, tri-n-pentyl
aluminum, tri-n-hexyl aluminum, tri-n-octyl aluminum, tri
(2-ethylhexyl) aluminum, tricyclopentyl aluminum, tricyclohexyl
aluminum, tri (2,2,4-trimethylpentyl) aluminum, tri-n-dodecyl
aluminum, and tri (2-methylpentyl) aluminum and the like.
The organomagnesium compounds used in the practice of the
present invention are alkyl and cycloalkyl magnesium compounds.
These compounds can be prepared by the action of R2Hg on
magnesium, the reaction being facilitated by the presence of
ether. They, also, may be prepared by allowing olefins to react
under pressure at about 100C with magnesium metal in the
presence of hydrogen. Please see "Organometallic Compounds,"
Coates et al, Vol. 1, 1967, 3rd Ed., Methuen & Co. Ltd., London.
These organomagnesium compounds have the general formula
RI2VMg where RIV is an alkyl radical or cycloalkyl radical,
which may be the same or different, of from 1 to 20, preferably
of from 1 to 10, carbon atoms. Mixtures of these organomagnesium
compounds can be used. Examples of such compounds are dimethyl
magnesium, diethyl magnesium, dipropyl magnesium, di-n-butyl
magnesium, di-sec-butyl magnesium, di-n-amyl magnesium, methyl-
ethyl magnesium, n-butyl ethyl magnesium (BEM), n-propylethyl
magnesium, di-n-hexyl magnesium, dicyclohexyl magnesium,
- 15 -
cyclohe~ylethyl magnesium, didecyl magnesium, di-ter-butyl
magnesium and didodecyl magnesium and the like.
Organo Mg-Al complexes can be used instead of mixtures of Mg
and Al compounds. One method of preparation is to add the
organoaluminum compound to a reactor containing the reaction
products of organic halides with magnesium in hydrocarbon
solvent. After filtraticn of the reaction mixture, there is
obtained a solution of the complex containing little soluble
halides. Please see Malpass et al, "Journal of Organometallic
Chemistry," 93 (1975), Pages 1 to 8. These complexes will have
the general formula Rm Aln.Rp Mgq where the mol
ratio of Al to MB is as set forth herein, where m, n, p and q are
numbers sufficient to satisfy the required valences of the radi-
cals and atoms and where RIII and RI are alkyl or cycloalkyl
radicals, which may be same or different, as described above.
In the catalyst composition the mol ratio computed as metal
of magnesium to aluminum is from about 105:1 to 1.5:1, and the
mol ratio computed as metal of barium, calcium and/or strontium
to magnesium is from about 1:10 to 1:2.
Just prior to polymerization, the barium salt, the organo-
aluminum compound and the organomagnesium compound (or the
organoaluminum magnesium complex) each in hydrocarbon solution
are mixed together. The time required to form a catalyst complex
or composition ranges from a few minutes to an hour or longer
depending on the reaction temperature. This should be accomp-
lished under an inert atmosphere, and the ingredients may be
heated to speed reaction at temperatures of from about 25 to
100C, preferably from about 40 to 60C. After the catalyst
composition has formed, the polymerization solvent and monomer(s)
may be charged to the catalyst, or the preformed catalyst dis-
solved in its solvent may be injected into a reactor containing
the monomers dissolved in the hydrocarbon polymerization solvent.
The monomers to be polymerized can be ethylenically unsatur-
ated monomers or heterocyclic monomers. The ethylenically unsat-
urated polymerizable monomers to be polymerized with the cata-
lysts of the present invention are those having an activated
4`3~
- 16 -
unsaturated double bond, for example, those monomers where
adjacent to the double bond there is a group more electrophilic
than hydrogen and which is not easily removed by a strong base.
Examples of such monomers are nitriles like acrylonitrile and
methacrylonitrile; acrylates and alkacrylates like methyl
~acrylate, ethyl acrylate, butyl acrylate, ethyl hexyl acrylate,
octyl acrylate, methyl methacrylate, ethyl methacrylate, butyl
methacrylate, methyl ethacrylate, ethyl ethacrylate, butyl
ethacrylate and octyl ethacrylate; the dienes such as butadiene-
1,3 and isoprene; and the vinyl benzenes like styrene, alphamethyl styrene, p-tertiary butyl styrene, divinyl benzene, methyl
vinyl toluene and para vinyl toluene and the like and mixtures of
the same. Examples of polymerizable heterocyclic monomers are
oxiranes like ethylene oxide, propylene oxide, 1,2-butylene
oxide, styrene oxide, isobutylene oxide, allyl glycidyl ether,
phenyl glycidyl ether, crotyl glycidyl ether, isoprene monoxide,
butadiene monoxide, vinyl cyclohexane monoxide and the like and
mixtures thereof. Other heterocyclic monomers which may be
polymerized are siloxanes such as octamethyl tetrasiloxane,
thiiranes like propylene sulfide, thiatanes like thiacyclobutane
and lactams like epsilon-caprolactam. Depending on the monomer
employed, the resulting polymers can be rubbery, resinous, or
thermoplastic. For example, a homopolybutadiene prepared accord-
ing to the present invention having 90~ trans content is thermo-
plastic or resinous, while a copolymer of butadiene and styrenecontaining about 15-20X styrene and 90% trans i9 still rubbery.
Preferred monomers for use in the practice of the present
invention are mixtures of butadiene-1,3 and up to about 30~ by
weight total of the mixtures of styrene to make rubbery co-
polymers exhibiting a high trans-1,4 content and a low vinyl
content. Moreover, by altering the butadiene-styrene copolymer
composition or microstructure a rubber can be prepared which has
behavior closely simulating that of natural rubber in building
tack and green strength. Thus, it is within the scope of this
invention to prepare polymers which can serve as replacements in
- 17 -
those applications where natural rubber is employed such as in
tires.
The obtained number-average molecular weight in the absence
of-chain transfer i9 controlled by the molecular weight calculat-
ed from the ratio of grams of monomer polymerized to moles ofcatalyst charged. Conversions of monomer to polymer up to about
100% may be obtained.
Temperstures during solution polymerization can vary from
about 0 to 150C. Preferably, polymerization temperatures are
from about 30 to 100C. Time for polymerization will be
dependent on the temperature, amount of catalyst, type of
polymers desired and so forth. Only minor amounts of the cata-
lyst composition are necessary to effect polymerization. How-
ever, the amount of catalyst employed may vary with the type of
polymer desired. For example, in general, when making polymers
having a high average molecular weight using a given amount of
monomer, only a small amount of the catalyst complex is necessary
whereas when making a low average molecular weight polymer, larg-
er amounts of the catalyst complex are employed. Moreover, since
the polymer is a living polymer, it will continue to grow as long
as monomer is fed to the polymerization system. Thus, the molec-
ular weight can be as high as a million or even more. ~n the
other hand, very high molecular weight polymers require lengthy
polymerization times for a given amount of the catalyst complex,
and at lower catalyst complex concentrations the polymerization
rate will drop. A usef~l range of catalyst complex to obtain
readily processable polymers in practicable times is from about
0.00001 to 0.10, preferably from about 0.00033 to 0.005, mol of
the catalyst complex or composition computed as magnesium per 100
grams total of monomer(s).
Since the polymer in solution in the polymerization media is
a living polymer or since the polymerization is a non-terminating
polymerixation (unless positively terminated by failure to add
monomer or by adding a terminating agent such as methanol), block
polymers can be prepared by sequential addition of monomers or
functional groups can be added. Also, since the living polymer
- 18 -
contains a terminal metal ion, it as shown above can be treated
with an epoxide like ethylene oxide and then with water to
provide a polymer with a terminal hydroxyl group for reaction
with a polyisocyanate to jump the polymer through formation of
polyurethane linkages.
The polymerization is conducted in a liquid hydrocarbon
solvent. While bulk polymerization may be used, such presents
heat transfer problems which should be avoided. In solvent
polymerizations it is preferred to operate on a basis of not over
about 15 to 20% polymer solids concentration in the solvent to
enable ready heat transfer and processing. Solvents for the
monomers and polymers should not have a very labile carbon-hydro-
gen bond and should not act at least substantially as chain
terminating agents. They preferably should be liquid at room
temperature (about 25C). Examples of such solvents are benzene
(less desirable), toluene, the xylenes, the trimethyl benzenes,
hemimellitene, pseudocumene, mesitylene, prehnitene, isodurene,
o, m, and p cymenes, ethylbenzene, n-propylbenzene, cumene,
1,2,4- or 1,3,5-triethylbenzene, n-butyl benzene and other lower
alkyl substituted benzenes, hexane, heptane, octane, nonane,
cyclohexane, cycloheptane, cyclooctane and the like and mixtures
of the same. The saturated aliphatic and cycloaliphatic solvents
and mixtures thereof are preferred. Some solvents may give lower
trans contents but on the other hand may give higher molecular
weights.
Polymerization, of course, should be conducted in a closed
reactor, preferably a pressure reactor, fitted with a stirrer,
heating and cooling means, with means to flush with or pump in an
inert gas such as nitrogen, neon, argon and so forth in order to
polymerize under inert or non-reactive conditions, with means to
charge monomer, solvent and catalyst, venting means and with
means to recover the resulting polymer and so forth.
The rate of polymerization can be increased by the addition
of small (catalytic) amounts of ethers, amines or water. For
example, the sddition of anisole to the Mg-Al-Ba catalyst system
increased the rate of copolymerization of butadiene with styrene
_ 19 _
in cyclohexane at 50C without affecting the percent trans-1,4
content and the rate of incorporation of styrene. Anisole
appears to be more effective for increasing the rate of polymeri-
zation than triethylamine but less effective than tetrahydrofuran
(THF). However, a polybutadiene prepared in the presence of THF
had a microstructure of 75% trans and 6% vinyl.
A small amount (catalytic) of free water, oxygen or ammonia,
also, seems to be beneficial in the preparation of polymers with
the Ba-Al-Mg initiator system. The addition of a small amount of
either of these materials increases the polymerization rate and
the molecular weight of polymers prepared with this novel initi-
ator system. When the free water is added in small amounts, the
trans-1,4 content of the polybutadiene or butadiene-1,3/styrene
copolymer is not affected if the mole ratio of the Ba salt to the
organomagnesium compound is kept at Ba/Mg = 0.20.
The rate of polymerization can also be increased by
increasing the initial molar concentrations of monomers like
butadiene and the Mg-Al-Ba catalyst composition.
Since the polymers produced by the method of the present
invention contain active sites or are living polymers, they can
be chain extended or branched at any practical time prior to
termination or short stopping the polymerization reaction. This
may be obtained by adding to the polymerization reaction media
chain extenders such as dibromomethane, 1,2-dibromoethane,
silicon tetrachloride and hexachlorosilane. Other chain
extenders that may be used include divinyl and trivinyl aromatic
compounds like divinyl benzene (1,2; 1,3 or 1,4), 1,3 divinyl
naphthalene, 1,2,4-trivinyl benzene, and so forth; diisocyanates
and polyisocyanates like l,6-diisocyanate hexane (may be
carcinogenic), diphenylmethane diisocyanate and 90 forth
(isocyanates like tolylene diisocyanate and tetramethylene
diisocyanate may be unsatisfactory); diepoxides like cyclohexane
diepoxide, l,4-pentane diepoxide and so forth; diketones like
2,4-hexane-di-one, 2,5-hexane-di-one and so forth and dialdehydes
like 1,4-butanedial, 1,5-pentanedial and so forth (see ~. S.
Patent No. 3,985,830). The chain extender should be soluble in
- 2Q -
the polymerization media such as the solvent. Moreover, the
chain extender should not kill the carbanions, or if it does,
there should be sufficient carbanions present so that the chain
extens;on proceeds in a satisfactory manner before the chain
extension reaction ceases.
After polymerization the catalyst may be terminated by
adding water, alcohol or other agent to the polymeric solution.
After the polymer has been recovered and dried, a suitable anti-
oxidant such as 2,6-di-tert-butyl-p-cresol or other antioxidant
may be added to the same. Rowever, the antioxidant may be added
to the polymeric solution before it is stripped of solvent.
The polymers produced by the method of the present invention
can be compounded and cured in the same manner as other plastic
and rubbery polymers. For example, they can be mixed with sulfur
lS or sulfur furnishing materials, peroxides, carbon black, SiO2,
TiO2, Sb203, red iron oxide, other rubber fillers and
pigmen~s, tetramethyl or ethyl thiuram disulfide, benzothiazyl
disulfide and rubber extending or processing mineral or petroleum
oils and the like. Stabilizers, antioxidants, UV light absorbers
and other antidegradants can be added to these polymers. They
can also be blended with~other polymers like natural rubber,
butyl rubber, butadiene-styrene~acrylonitrile terpolymers,
polychloroprenej S~R, polyurethane elastomers and so forth.
The polymers produced by the method of the present invention
can be used in making protective coatings for fabrics; body and
engine mounts for automobiles; gaskets; sidewalls, treads and
carcasses for tires; belts; hose; shoe soles; and electric wire
and cable insulation; and as plasticizers and polymeric fillers
for other plastics and rubbers. With large amounts of sulfur
hard rubber products can be made.
: ~
The following examples will serve to illustrate the present
invention with more particularity to those skilled in the art.
Parts are parts by weight unless otherwise stated.
The polymerizations described in the examples were carried
out in an argon atmosphere in capped glass bottles fitted with
neoprene rubber gasket inner liners. Solvents were purified by
~ ~ .
~ .
' '
- 21 -
passing the liquid through columns of 5A molecular sieves. Buta-
diene (99 mol %) was purchased from Phillips Petroleum Company.
Purification was accomplished by passing the BD through columns
of-13X molecular sieves. Isoprene was purchased from Phillips
Petroleum (99.5 mol Z pure) and was further purified by distil-
lation from sodium ribbon. Styrene was purchased from Gulf Oil
Chemical and El Paso Products, Texas, and vacuum distilled from a
small quantity of (n-butyl) (sec-bueyl) magnesium. Propylene
oxide was used a~ received from Oxirane Corporation (contained
75 parts of water per million).
In charging the polymerizations, the order of addition of
materials was solvent first, then Mg-Al alkyls, next the barium
salt, and finally the monomer(s). The copolymer composition and
percent polybutadiene microstructure were obtained from infrared
analysis, unless otherwise noted, and from C NMR (Nuclear
Magnetic Resonance) for certain polymers. The microstructure
values determined from IR and 1 C NMR were essentially identi-
cal. The trans-1,4 and vinyl content were determined using the
967 cm 1 and 905 cm 1 infrared absorption bands, respective-
ly. Intrinsic viscosities were determined in toluene at 25C.Gel permeation chromatograms (GPC) were obtained using a Waters
Gel Permeation Chromatograph. Solutions at 1 wt.~ were injected
onto columns at a flow rate of 1 ml/minute. The instrument oven
and the differential refractometer were at 50C. The column set
configuration used, as designated by Waters Associates, was 1 x
106~ + 1 x 105~ + 1 x 104R + 1 x 103R.
All thermal transitions were obtained by Differen~inl Therm-
al Analysis (DTA) using a heating rate of 20C/minute. Crystal-
line melting temperatures were determined from the position of
30 the endothermic peak(s) present in the curve, obtained after
cooling the sample from 125C to -150C at approximately
20C/minute.
X-ray diffraction patterns were obtained from films cured
with 1% dicumyl peroxide in the absence of fillers. All the
35 experiments were carried out at room temperature using CuK~
radiation and a nickel filter.
- 22 -
Example 1
(a) Barium Salt
To 82.2 milliequivalents (meq) of barium metal (5.65 g) was
~ added 325 ml of monomethylamine which had been flash dis-
tilled from Na-dispersion. The reactor was cooled to -78C
with rapid stirring and fl deep blue colored solution,
characteristic of the amine solution of the metal, was
obtained. To this solution a mixture of t-decanol (21
milliequivalents), t-butanol (40 milliequivalents) and water
(7.3 milliequivalents) in benzene (3.75 mols total t-alco-
hols in benzene) was slowly added and the reaction mixture
was stirred for 3 hours and then allowed to stand for 2 days
at -15C, which resulted in the quantitative conversion of
the alcohols and water to barium salts. After flash distil-
lation of the amine, the resulting white solid (11.28 g) was
dried at 100C under vacuum. Toluene (475 g) was added to
the salts and the reactor was heated to 70C for 2 hours;
The total alkalinity of a hydrolyzed aliquot of the clear
colorle~s solution, removed from the excess barium metal,
measured 0.148 meq of hydroxide per gram or 2.4 wt.~ barium
salts, demonstrating total dissolution of the Ralt. The
empirical composition of this product can be represented as:
Ba[(t-c4H9o)l 17(t-cloH2lo)o.6l(oH)o~22]
(b) Barium-~-Al Catalyst Complex Composition
Solutions of (1) [5.4 (n-C4Hg)2Mg (C2H5)3Al]
complex (MAGALA-6E) and (2) barium salts, prepared according
to Example 1 (a) above, were charged to the polymerization
solvent under an inert atmosphere. Prior to addition of
nomer(s), the catalyst mixture was permitted to react
initially at 60C for 15 minutes. The mole ratio of barium
to magnesium was based on the moles of total alkalinity of
the soluble barium salts (one-half the milliequivalents of
titratable base) to the moles of magnesium in MAGALA-6E.
.~
~ti~i~t'O
23 -
MAGALA-6E was obtained from Texas Alkyls (25 w~.% in
heptane) and diluted with cyclohexane to a concentration of
0.28 meq of magnesium (0.075 meq aluminum) per gram of
solution. The magnesium and aluminum contents were deter-
mined by atomic absorption spectroscopy, and the molar ratio
of Mg/Al was found to be 5.4/1 for a complex designated by
Texas Alkyls, Inc., as MAGALA-6E
(5.4 1(n-C4Hg)2Mg] [C2H5)3All).
Example 2
This example demonstrates the usefulness of the catalyst,
described in Example 1, for the preparation of crystalline
butadiene based polymers. Table I, below, shows that poly-
butadienes o~ this invention have a high degree of stereoregu-
larity with crystalline melting temperatures of 43C and 70C.
The high trans-1,4 configuration (89%) results in a thermoplastic
polymer which is hard and highly crystalline at room temperature.
Isoprene can be polymerized with a Mg-Al-Ba catalyst compo-
sition, as described in Table I. A polyisoprene was obtained
with an isomer content of 49% trans, 39% cis and 12% 3,4.
- 24 -
Table I
Molecular Structure of Polydiene and Styrene-Butadiene Copolymer
Prepared in Cyclohexane at 50C
with Mg-Al-Ba Catalyst Composition
(Mg/Al = 5.4/1, Ba/Mg = 1/5, mol ratios of metal)
g. Total
Monomers %
RunMonomer(s) per mMConversionl~t.% Styrene
No.(grams) (BU)2M8 (hours)Charged Found
10 1 Butadiene 38.7 100(91) -- --
(27.1)
2Butadiene/Styrene45.5 86 (118) 22 17
(24.4/7.0)
3 Isoprene 34.1 98 (77) -- --
(23.9)
Peak
tol Crystalline
Run % Diene Structure [nl25 Melting Temp.
No. Trans-1,4 Vinyl dl/g (C)
1 89 2 2.11 43, 70
20 2 88a 2a 1.60 19
3 49a (12)a~b 0.92 None observed.
a - percent microstructure determined by 13C NMR
b - value in parenthesis represents 3,4 content
The rate of polymerization is faster for butadiene polymers
than for butadiene-styrene copolymers. For example, complete
conversion of butadiene to polymer is readily obtained in 24
hours at 65C. With butadiene-styrene copolymers, it is diffi-
cult to obtain a conversion in exceqs of 907~ in 24 hours at
65C. Further, the remaining 10% monomer in the SBR system is
primarily styrene, and it requires in excess of 72 hours at 65C
to obtain complete conversion. Viscosities (n) are intrinsic
viscosities in deciliters per gram in toluene at 2SC.
V
- 25 -
A polystyrene-polybutadiene diblock copolymer (41~ styrene)
was prepared with the Mg-Al-Ba catalyst composition (described in
Example 1) by the addition of butadiene to a non-terminated solu-
tion of polystyryl carbanions. Styrene was polymerized to 96%conversion, see Table II, below, and the resulting polystyryl
carbanion was used in Run 5. All polymerizations were conducted
in cyclohexane at 50C.
Table II
Preparation of Polystyrene-Polybutadiene Diblock Copolymer
and Hydroxyl Terminated Polybutadiene with Mg-Al-Ba Catalyst
g. Total
Monomers % Mn tol
Run Monomers(s) per mM Conversion Wt.% x (d) ~nl25(d)
15 No. (grams) (Bu)2Mg (hours) Composition 10-3 dl~g
4 Styrenea 15.996a (48)% styrene 20C 0.20
(10.5) = 100
5 Polystyryl 1. 96 (48)
(10.5)
20Butadiene 39.1 2. 98 (119) ~ styrene 114C 0.93
(14.8) = 41
6Butadiene 23.5 88 (115)
(24.2)
Ethylene % hydroxyl 51b 1.31
Oxide = 0.031
(0~09)
a - polystyrene precursor used in the preparation of polystyrene-
polybutadiene diblock copolymer (Run 5).
b - Mn measured by membrane osmometry.
c - Mn estimated by GPC.
d - final polymer.
o
- 26 -
Figure 3 shows two MWD (Molecular Weight Distribution)
curves of ehis diblock copolymer (Run 5) and its polystyrene
precursor (Run 4). A comparison of the peak positions in the MWD
curves and the shapes of the curves demonstrates the successful
preparation of a diblock copolymer. Homopolymers of styrene or
butadiene could not be extracted from the reaction products using
acetone/cyclohexane (75/25) snd n-pentane as solvents for poly-
styrene and polybutadiene, respectively, and as nunsolvents for
the diblock copolymer.
A hydroxyl terminated polybutadiene (Run 6) was prepared by
the addition of ethylene oxide at the end of a butadiene polymer-
ization initiated with Mg-Al-Ba catalyst (see Table II). The
terminal alkoxide units were then hydrolyzed to form the carbi-
nol. The hydroxyl functionality of this polymer was 0.91 based
on hydroxyl equivalent molecular weight and number-average molec-
ular weight.
These results demonstrate that polybutadiene or polystyrene
chain ends retain their capacity to add monomer and can be deriv-
atized to result in useful materials. Thus, block copolymers,
functionally terminated polymers and polymers with different
molecular architecture and molecular weight distribution can be
prepared.
t~7~.`V
- 27 -
Example 4
Polymerizations of butadiene were carried out according to
Run 1, Example 2 using various Ba and Ca compounds suhstituted
for barium (t-decoxide-t-butoxide-hydroxide), designated as the
control. The results are given in Table IIII below. Ba salts of
t-butanol and mixtures of t-butanol and water, both prepared
according to Example 1, were equally effective as the control for
the preparation of about 90% trans-1,4 polybutadiene. Barium
ethoxide complexed with Mg-Al alkyls polymerized butadiene to a
high molecular weight polymer having a diene structure of 76%
trans-1,4 and 7~ vinyl. Complexes of Mg-Al alkyls with
Ca[(t-C4HgO)l 8(0H)o 2] are catalysts for the quantita-
tive polymerization of butadiene (see Runs 10-13, Table III).
However, the maximum in trans-1,4 content of 77% occurred for a
Ca2 /Mg2 ratio of 0.51 in comparison to a trans-1,4 of up to
90~ for a Ba2~/Mg2 ratio of 0.20. This example demonstrates
the usefulness of certain Ba and Ca alkoxide salts in preparing
high trans-1,4 crystallizing polybutadiene.
- 28 -
Table Ill
Effect of Composition oE Various Ba and Ca Compounds
on the Molecular Structure of Polybutadienea
Composition of Mole Ratio Conversion
Run No. Group IIA SaltM 2+IM 2+ (h rs)
1 Ba[(t-cloH2lo)o~6l 0.20 100 (91)
(t-C4H90)l,l7(0H)o~22l
(CONTROL)
7 Bsl(t~c4HgO)l~8(oH)o~2l0.20 90 (43)
8 ( 4 9 )2 0.20 96 (71)
( 2 5 )2 0.18 82 (168)
Cal(t-C4H9O)1,8(OH)0,2]0.11 99 (47)
11 " 0.25 98 (71)
lS 12 " 0.51 97 (24)
13 " 0.90 100 (72)
13-1 Bal(t-cloH2lo)l~8(oH)o~2] 0.20 100 (70)
% Crystalline tol
Diene StructureMelting [ nl 25
20 Run No. Trans Vinyl Temp., C dllg
1 89 2 43, 70 2.11
7 90 3 29, 59 1.38
8 88 2 41, 68 2.92
9 76 7 9 1.68
64 8 -30 Soft
Polymer
11 70 7 -11 Soft
Polymer
12 77 6 11, 27 0.90
13 72 6 -2 1.36
13-1 86 3 38,58 Rubber
a - polymerization solvent: cyclohexane - polymerization
temperature: 50C. Me2+:Ba2~ or Ca2+
`l,`V
- 29 -
Example 5
The effect of the mole ratio of Mg/Al in organometallic
complexes of magnesium and aluminum on percent polybutadiene
microstructure is shown in Table IV, below. The Mg Al-Ba
catalysts were prepared according to Example 1 at constant Ba/Mg
mole ratio of about 1/5. A control polymeriæation of butadiene
with (sec-C4H9)Mg(n-C4H9) in combination Witll a barium
salt prepared according to Example 1 resulted in a trans-1,4
content of 67%, in the absence of Et3Al. A trans-1,4 content
of only 81~ was obtained in polymers made with a Ba-MgAl complex
at Mg/Al = 105/1 (MAGALA-DNHM, Texas Alkyls, Inc.) catalyst (~un
20). No polymerization of butadiene occurred with a barium salt
in combination with MAGALA-0.5E (Mg/Al = 1/2) (Runs 14, 15 and 16
below). The highest degree of stereoregularity was obtained with
complexes of barium salts with MAGALA-6E or MAGALA-7.5E (Runs 17
and 18). The trans-1,4 contents in these polybutadienes were 89%
with 2% or 3% vinyl unsaturation.
- 30 -
Table IV
__
Effect of Mg/Al Mole Ratio in Mg-Al Complexes
on Microstructure of Polybutadiene
% Diene
5 RunOrganometallic Mole Ratios Structure
No.Complex of Mg and Al Mg/Al Ba/Mg Al/Ba Trans Vinyl
al(n-Bu)2Mg 2(Et)3A1 0.54 0.19 9.70No Poly-
merization
15al(n-Bu)2Mg~2(Et~3A1 0.54 0.29 6.40No Poly-
merization
16al(n-Bu)2Mg~2(Et)3A1 0.54 0.61 3.00No Poly-
merization
b5.4(n-Bu)2Mg~l(Et)3Al* 5,4* 0.19 0.97 89 2
18b7.6(n-Bu) Mg~l(Et)3Al# 7.6# 0.16 0.82 89 3
1519b27(n-hexyl)2Mg~l(Et)3A127.0 0.22 0.17 83c4C
20b105(n-hexyl)2Mg.l(Et)3Ald105.0 0.22 0.04 81 4
2lb(sec-Bu)Mg(n-Bu) No Al 0.12 0 67 10
a - polymerizations were carried out in n-hexane at 65C.
b - polymerizations were carried out in cyclohexane at 50C.
c - estimated values from infrared spectrum of polymer film.
d - MAGALA DNHM, Texas Alkyls, Inc. - di-n-hexyl magnesium
containing 1-2 mole % Et3Al relative to the Mg compound.
* MAGALA-6E; 5.4 ratio as analyzed.
# MAGALA-7.5E; 7.6 ratio as analyzed.
- 31 -
Example 6
The effect of the mole ratio of barium (t-decoxide-t-butox-
ide-hydroxide), prepared according to Example 1, to dibutylmag-
ne-sium in MAGALA-6E on polybutadiene microstructure and molecular
weight is summarized in Table V, below. The polymerization
charge was the same as given in Run 1 of Example 2. Figure 2
shows that the amount of trans-1,4 structure is increased to a
maximum of about 90% as the mole ratio of Ba /Mg is
decreased from 1.0 to about 0.2. Concurrently, the vinyl content
decreased from 7% to 2~. No polymeriza~ion of butadiene was
observed in cyclohexane at 50C after 3 days with MAGALA-6E alone
or with a mole ratio of Ba2 /Mg2 = 0.05.
Polybutadienes prepared with mole ratios of Ba2 /Mg2
equal to 0.2 are characterized by trans-1,4 contents of about
90~, crystalline melt temperatures of 43C and 70C, intrinsic
viscosities of about 2.0 in toluene at 25C, and absence of gel.
Table V
Effect of Mole Ratio of Barium Salts to
(Bu)2Mg in Mg-Al-Ba Catalyst on
Molecular Structure of Polybutadiene
~ % Diene Crystalline tol
Run Mole Ratios Conversion Structure Melting [nl25
2+ 2+ 3+ 2+
No. Ba /Mg Al /Ba (hours) Trans ~ Temp., C dl/g
22 0 0No spparent - - - -
pzn. of
butadiene
with
MAGALA-6E,
alone
23 0.05 3.91No apparent - - ~ -
pzn.
(72 hours)
24 0.11 1.6763 (72) 87 2 36, 60 2.35
1 0.20 0.85100 (91) 89 2 43, 70 2.11
0.30 0.6296 (72) 79 3 -9, 33 2.26
2026 0.52 0.3599 (74) 73 4 -16, 24 1.82
27 1.00 0.1894 (44) 64 7 -15 0.82
Polymerization Conditions: 1. Polymerizations were carried out
in cyclohexane at 50C.
2. Molar concentrations of butadiene
25and (Bu)2Mg were approximately:
[Butadiene]O = 2.4;
~(Bu)2Mglo = 2.8 x 10 3
l ~t;~o
- 33 -
Example 7
The catalyst complex of MAGALA-6E and barium (t-decoxide-t-
butoxide-hydroxide), Example 1, was used to prepare polybutadi-
enes according to Example 2, in n-hexane and toluene, as well as
cyclohexane. The structural analysis, as shown in Table VI,
below, shows that a high trans-1,4 polybutadiene was formed in
these solvents. A slightly lower trans-1,4 content and intrinsic
viscosity were obtained for the polymer prepared in toluene.
Table VI
Effect of Solvent on the Molecular Structure of
Butadiene Based Polymers Prepared with Ba[(t-RO?2_x~OH)x]
5.4 (n-Bu)2Mg 1 (Et)3Al (MAGALA-6E)
Catalyst Composition of Example 1.
Polymerization Temp. = 50C
% Diene tol Crystalline
Run Polymerization% Structure [~]25 Melting
No.SolventStyrene Trans Vinyl dl/g Temp., C
28 n-hexane8 88 2 2.02 23, 34
1Cyclohexane0 89 2 2.11 43, 70
2029 Toluene0 85 3 1.84 24, 36
It, also, is possible to prepare polybutadienes in cyclo-
hexane at 50C with trans-1,4 contents of 88% (3% vinyl) with
Mg-Al-Ba catalysts obtained by combining barium (t-al~oxide-hy-
droxide) with (sec-C4Hg)Mg-(n-C4H9) and (C2H5)3AI,
instead of the commercial MAGALA, in mole ratios of M~/AI of 2 to
3 and Ba/Mg of 0.20. An increase in Mg/Al mole ratio (at con-
stant Ba/Mg) from 3 to 6 to 15 to 25 results in a decrease in
trans-1,4 content from 88% to 86% to 83X to 80X.
~ ~ti~3'1't`0
- 34 -
ex~
Table VII, below, compares the temperature dependence for
SBR's prepared with the Mg-Al-Ba catalyst composition of Example
1 in cyclohexane. Trans-1,4 content increased from 83% to 90% as
polymerization temperature decreased from 75C to 30C. The
increase in trans-1,4 content with decreasing polymerization
temperature occurred with corresponding decreases in both vinyl
and cis-1,4 contents. It is to be noted that high trans-1,4
SBR's can be prepared over a fairly wide range of polymerization
temperatures with this catalyst system.
Table VII
Effect of Polymerization Temperature on
Molecular Structure of High Trans SBR
Polymerization ~ % Diene tol
Run Wt. ~ Temperature Conversion Structure [nl25
No. Styrene - (C) (hours)Trans Vinyl dl/g
30 6.5 30 55 (172) 90.0 1.6 0.88
31 17.0 50 86 (118) 88.0 2.1 1.60
32 22.0 65 95 (119~ 85.6 3.1 1.54
20 33 23.2 75 92 (23) 82.9 3.7 1.49
Mole Ratio: Ba/Mg = 0.20
Q
- 35 -
Example 9
The concentration of the Mg-Al-Ba catalyst composition of
Example 1 with constant Ba /Mg2 ratio (0.20) has a marked
effect on the trans-1,4 content of polybutadiene, as shown in
Table VIII, below. The trans-1,4 content approaches a limiting
value of about 90% as the molar ratio of butadiene to dibutyl-
magnesium decreases from 1549 to 795. The intrinsic viscosity
increases with an increase in this ratio suggesting that the
polymer m~lecular weight is controlled by the ratio of grams of
butadiene polymerized to moles of catalyst charged.
Table VIII
-
Effect of Catalyst Concentration on Molecular Structure
of Polybutadiene Prepared with Mg-Al-Ba Catalyst
Initiator Initial
15Charged Bd Molar Ratio % ~ Diene tol
Run (mM) Charged IBdlo/ Conv. Structure [~25
No. Ba Salt (BU)2Mg (grams) [(8U)2Mg]o (hrs.) Trans Vinyl dl/g
__
7 0.36 1.76 28.5299 90 90 3 1.38
(M = 8,100)a (43)
20 1 0.14 0.63 27.1_ 795 100 89 2 2.11
(M =21,500)a (91)
34 0.07 0.29 24.3_ 1549 100 80 3 4.29
(M =4l~9oo)a (96)
Solvent: cyclohexane. Temperature: 50C. Mole Rat;o: Ba/Mg=0.20.
a: Mn calculated from grams of BD charged to gram-equivalents of
Mg charged (carbon-Mg).
`t~``Q
- 3C -
Example lO
Figure 4 shows that the MWD of high trans SBR (15% styrene)
can be broadened (changed or controlled) by chain extension with
divinylbenzene (DVB). DVB was added at 87~ conversion, and the
linking reaction of chain ends with DVB (mole ratio of DVB/Mg =
1.0) was carried out in cyclohexane at 82C for 6 hours.
The shape of the MWD of the linear precursor SBR (Run 35) is
fairly narrow with a small fraction of low molecular weight tail-
ing. Heterogeneity indices (M /M ) of 2.0 to 3.0 (estimated
by GPC) are representative values of these linear SBR's. A com-
parison of the shapes of the MWD curves in Figure 4 shows a
buildup in the amount of high molecular weight polymer and an
increase in molecular weight as a result of linking of chain ends
with DVB.
High trans SBR's chain extended with DVB can be oil extend-
ed. They have less cold flow (Table IX below) and improved mill
processibility behavior relative to linear high trans SBR's.
Figure 5 compares the rheological behavior of a linear high trans
SBR of this invention and a corresponding SBR chain extended with
DVB. Measurements of complex viscosity (n~-) of these raw poly-
mers at various shear rates were obtained with a Rheometric
Mechanical Spectrometer at 90C with an eccentric rotating disc
(ERD). It can be seen that the chain extended SBR shows higher
viscosity at low shear rates and lower viscosity at high shear
rates than the linear control polymer. This information corre-
lates well with the lower cold flow of high trans SBR chain
extended with DVB.
~ ~.ti~i'~`~.`O
- 37 -
Table IX
Effect of Chain Extension of
High Trans SBR on Cold Flow
Wt.% tol Cold Flow
Styrene in ~ n] 25 MW/Mn Oil Content ML-4 at 50Cc
Run No. Composition dl/g (by GPC) (phr) (100C) (m&/min.)
35a 15 1.583.7 0 48 20.0
368 20 1.58 - 0 - 11.9
37b 15 1.953.2 14 40 3.4
38b 22 2.20Bimodal 0 - 0
39b 21 2.20Bimodal 37.5 41.5 1.0
a - linear SBR, unextended.
b - SBR's chain extended with divinylbenzene (DVB) after 80-90%
conver~ion.
c - Phillips Chem. Co. Method WATB 5.01.20 of December 1, 1961.
~6~'`f3
- 38 --
Example 11
An SBR, prepared by the process of tl~e present invention and
containing 14.8% styrene with 84.5% trans-1,4 placements in the
po-lybutadiene portion, was cured in the absence of fillers with
1~ dicumyl peroxide. The crystalline melt temperature of the
peroxide cross-linked SBR was 18C, obtained on a Perkin-Elmer
DSC-II instrument. The cured rubber film was mounted in the
unstretched state on an x-ray unit. The sample was subjected to
x-ray analys;s using CuK~ radiation and a nickel filter at room
temperature. As shown in Figure 6, this SBR gum vulcaniæate in
the unstretched state exhibited a diffuse halo characteristic of
a non-crystalline material. At 200% strain, a diffraction
pattern of oriented crystalline polymer (equatorial arcs) was
observed. Several off-axial reflections appeared in the X-ray
scan in addition to the equatorial fiber arc as the sample was
elongated to 700%. This result demonstrates the ability of this
rubber to undergo strain-induced crystallization. Building tack
and green strength are properties often characteristic of a
crystalli~able elastomer such as natural rubber. It will be
demonstrated in the following examples that this set of proper-
ties is also chsracteristic of the SBR's of this invention.
With respect to Figure 6 the following information is given:
Sample
% HoursDistance of Polymer Sample
25 PhotographElongationExposureto X-ray Film, Approx.
A 0 4 30 mm.
B 200 ~4- 30 mm.
C 700 6 50 mm.
D 700 17 50 mm.
- 39 -
E~ample 12
Green strength is a quality that is possessed by natural
rubber and is essentially absent in emulsion SBR. In fact, very
few synthetic rubbers have green strength comparable to natural
rubber. Green strength is a measure of the cohesiveness in
stretched, uncured rubber. The presence of green strength in a
rubber prevents the occurrence of thinning down and breakinB
during fabrication of an uncured tire. It ig ~enerally accepted
that the green strength of natural rubber arises from strain-in-
duced crystallization.
Green strength has been measured for an uncompounded high
trans SBR prepared with the Mg-Al-Ba catalyst of this invention.
The SBR contained 20% styrene with 88~ trans-1,4 polybutadiene
placements and exhibited a crystalline melting temperature of
22C, as measured by DTA. Green strength data was obtained from
stress-strain measurements on unvulcanized polymers with an
Instron tester at room temperature. The crosshead speed was 50.8
cm/minute. Sample specimens were prepared by press molding ten-
sile sheets at 121C for 5 minutes with a ram force of 11360 kg.
The data in Table X, below, demonstrate that the green strength
(0.95 MPa) of the uncompounded and uncured experimental high
trans SBR of this invention was equivalent to natural rubber
(MV-5) (peptized No. 3 ribbed smoked sheets; uncured and uncom-
pounded).
The stress-strain curves of uncured, compounded (45 phr HAF
carbon black) high trans SBR (15X styrene) with 85X trans content
of this invention are compared with natural rubber ~SMR-5) and an
emulsion SBR in Figure 7. The green tensile strengths of NR and
high trans SBR are nearly equivalent (1.4 MPa). The stress-
strain cu N es of NR and the experimental high trans SBR of this
invention have positive slopes above 150% elongation relative to
a negative slope in the stress-strain cu N e of emulsion SBR
(SBR-1500~. The presence of a positive slope can be taken as
evidence for strain-induced crystallization.
- 40 -
Table X
Comparison of Green Tensile Strength of
Unfilled, Uncured High Tranc SBR ~ith Natural Rubber
Run No.
36
Natural
RubberHigh Trans SBR
(MV-5)(20% Styrene)
Mooney Viscosity
ML-4 (100C) 72 30
Tensile Strength
PSI ` 139 138
MPa 0.96 0.95
Elongation at break, X 633 1395
- 41 -
Example 13
Tack strength is defined as the force required to separate
two uncured polymer surfaces after they have been brought into
contact. The limiting tack strength of a rubber is necessarily
its green strength, or the force required for its cohesive fail-
ure. Although high green strength is necessary, it is, by it-
self, insufficient to insure good tack. High tack strength is an
especially desirable property in the fabrication of articles, es-
pecially those having a complex geometry, prior to vulcani~ation.
10Tack strength was measured using the Monsanto Tel-Tak*
machine. The test specimens were raw and compounded polymers
pressed between Mylar film at 100C. Two 0.64 cm x 5.08 cm die- ,
- cut sample strips were placed at right angles to each other and
retained in special sample clamps. A fixed load, 0.221 MPa, was
then applied for 30 seconds. The samples were pulled apart at a
constant separation rate of 2.54 cm/minute. The test was run at
room temperature. The true tack values reported in Table XI, be-
low, represent the difference between the apparent tack (rubber
versus rubber) and the value obtained for rubber versus stainless
steel. The results in Table XI for several uncompounded and un-
cured rubbers show that the apparent tack strength of high trans
SBR (0.28 MPa) of this invention is higher than natural rubber.
The presence of carbon black (45 phr HAF) in formulations of
high trans SBR (15% styrene, 85% trans) of this invention and NR
(SMR-5) resulted in an increase in tack strength, as shown by
comparing data in Tables XI and XII, below. The compounded tack
strength of high trans SBR of this invention is equivalent to NR
within experimental error. The tack strength of a blend of equal
amounts of high trans SBR of this invention and NR was slightly
higher than the respective unblended polymers.
It is important in construction of tires that tack strength
is developed quickly when two strips of rubber are brought into
contact. Figure 8 shows that high tack strength is obtained for
low contact times (6 seconds) for both high trans SBR of this
3S invention and NR. Both rubbers have what is often referred to as
"quick-grab".
*Trade Mark
f~
`t.`~
- 42 -
Table XI
Monsanto Tel-Tak*of Uncompounded, Uncured Rubbers
Crystalline Tack Strength
Melting Apparent True
Run No. Polymer Description Temp., C PSI MPa PSI MPa
39bHigh Trans SBR
of this invention
(21% styrene,
87% trans) 24 41 0.28 35 0.24
10 40Natural Rubber
(MV-5) 28 34 0.23 32 0.22
41Trans-polypentenamer 9 38 0.26 35 0.24
42High Trans SBR
of this invention
15 (23~ styrene,
83% trans) -1 34 0.23 23 0.16
43Cis-1,4 Polybutadiene
(99% cis) -6 27 0.19 15 0.10
44SBR-1500 (Emulsion)CNone
Observed 22 0.15 4 0.03
a - 30 seconds contact time, 32 oz. load.
b - 37.5 phr Philrich 5*oil added to polymer.
c - BD-STY rubber, about 23.5% bound styrene, cold polymerized.
*Trade Mark
~ .
- 43 -
Table XII
Monsanto Tel-Tak of Compounded, Uncured Rubbers
Apparent
Contact Time Tack Strength
5 Run No.Polymer Description (minutes) PSI MPa
High Trans SBR 0.5 52 0.36
(15% styrene, 85% trans) 3.0 69 0.48
6.0 69 0.48
46 Natural Rubber 0.5 65 0.45
(SMR-5) 3.0 64 0.44
6.0 67 0.46
47 Blend of 50/50 0.5 71 0.49
High Trans SBR/NR 3.0 69 0.48
(SMR-5) 6.0 73 0.50
Formulation for the Above Compounded but Uncured Rubber,
Parts by Weight
IngredientHigh Trans SBR NR Blend
Polymer 100 10050/50, NR/High Trans SBR
HAF Carbon Black 45 45 45
20 Oil 5 Naphthenic 0 7 Naphthenic
ZnOlStearic Acid 5/3 5/3 5/3
Antioxidant 2 2 2
Tackifier 775 3 3 3
Sulfur 1.0 1.0 1.0
25 Total Accelerator 1.8 1.8 1.8
,<~
- 44 -
Example 14
A high trans SBR of this invention was prepared according to
Run No. 2 in Example 2. The resulting copolymer contained 20%
styrene with 86% trans-1,4 content in the polybutadiene portion.
The intrinsic viscosity in toluene at 30C was 1.82 dltg. The
copolymer showed a crystalline melt temperature of 20C in the
DTA thermogram.
A description of the compound recipe and cure conditions for
the above SBR along with a commercial butadiene-styrene copolymer
(SBR-1500) and natural rubber (SMR-5) is given in Table XIII, be-
low. Satisfactory rates of cure in the SBR's were obtained with
a sulfur cure accelerated with 2-(morpholino) thiobenzothiazole
(NOBS Special) and tetramethylthiuram monosulfide (TMTM). A com-
parison of the physical properties for these rubbers is given in
Table XIV, below.
It should be noted that high trans SBR has higher tear
strength than SBR-1500. This can be related to strain-induced
crystallization in the high trans SBR. It is clear that the
vulcanizate properties of high trans SBR approach those of
natural rubber.
- 45 -
Table XIII
Formulations (PHR)
Natural Rubber High Trans SBR
SBR-1500(SMR-5)(20% Styrene)
Run No.: 48 49 50
Ingredients
Rubber 100 100 100
Antioxidant 2246a 2 2 4e
Zinc Oxide 5 5 5
10 Stearic Acid 3 3 3
Atlantic Wax 3 3
Tackifier 775b 3 3 3
HAF Carbon Blsck 45 45 42
PHILRICH 5*0il
15 (Phillips Pet.) 5 5 14f
NOBSC 1.6 0.5 1.&
TMTMd 0.2 - 0.2
CRYSTEX*Sulfurg
(Stauffer Chem.) 1.3 2.5 1.3
20 Cured, min./C 45/142 35/142 21/142
a - 2,2'-methylenebis (4-methyl-6-tert-butylphenol)
b - octylphenol formaltehyde (non-heat reactive)
c - 2-(morpholino) thiobenzothiazole (American Cyanamid)
d - tetramethylthiuram monosulfide
e - 2phr, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylene diamine and
2phr, N,N'-Bis(1,4-dimethylpentyl)-p-phenylene diamine
f - Naphthenic Oil (Circosol 42 ~ Sun Oil Co.)
g - CRYSTEX*contains 80% sulfur in mineral oil
.
*Trade Mark
- ~ti -
Table XIV
Comparis;on of Properties of High Tran~ SBR of This Invention
with S~R-1500 (Emulsion Polymèr) and Natural Rubber
Run No.
548 49 50
SBR-1500 Natural Rubber High Trans SBR
_ _ ___~ _
Modulus at 100%, MPa 1.51 1.50 1.38
Modulus at 300~, MPa 6.47 7.34 3.68
Tensile Strength~ MPa 21.94 25.23 20.13
10Elongation, X 700 ti50 770
Hardness, Shore A 66 59 63
Tear Strength,
Crescent, kN/m 83 123 112
Goodrich Heat Buildup
(100C), ~T C 32 28 28
Perm. Set, Z
(100C) 10.2 18.6 6.4
DeMattia No. of
Flexes x 10-3 100 100 100
Crack Growth, ~ 100 41 75
- 47 -
Example 15
To n-butylethyl magnesium (Texas Alkyls, Inc., BEM, a
mixture of n~butylethyl magnesium and triethyl aluminum, mole
ratio of Mg to Al of 50:1, in heptane) was added cyclohexane and
additional triethyl aluminum to give a mole ratio of Mg/Al = 4.8
to 1. To tlle Mg-AI composi~ion was added
Ba[(t-cloH2lo)o~96(t-c4~l9o)o~96( )0.08
in toluene to provide a mole ratio of Ba/Mg = 0.26. The result-
ing Ba-Al-Mg catalyst complex was then used to polymerize propyl-
ene oxide (P0) at 80C to obtain a tacky solid. The polymeriza- .
tion conditions used were as follows:
Grams P0 %
P0 Solvents, grams Per mM Conv.
Grams Cyclohexane Heptane TolueneMg (Hrs.~ -
1540.2 8.8 3.8 19.1 10.9 40(64)
, .. .... ... . .
, . . .
l~ti~t~O
- 47a -
SUPPLEMENTARY DISCLOSURE
The method of this invention, also, can provide homopolybutadienes having
trans contents of ~rom about 64 to 90%, vinyl contents of from about 2 to 7%
intrinsic viscosities of from about 0.90 to 4.29 in deciliters per gram in
toluene at 25C, and peak crystalline melting temperatures of from about -16
to 70C, preferably rubbery polymers having a trans content of from about 75
to 80% and vinyl content of from about 2 to 4%.
EXAMPLE 16
Two batches of polybutadiene were prepared, the batches blended and then
vacuum dried. The polymerization recipe, reaction contains and charging pro-
cedure are shown below:
Polymerization Recipe
Grams Mole
Butadiene -1,3 2,000
n-Hexane 8,000
[?-6 tn-c4H9)2Mg (C2H5)3Al] 5.9 Bu2Mg 0.0424 Bu2Mg
MAGALA-7.6E 0.6 Et3A1 0.0056 Et3Al
Ba[(t-C4HgO)1 g(OH)o l] 3.2 0.0115
Mole Ratios
Ba/Mg = 0.27
Mg/Al = 7.6
a: Commercially available (Texas Alkyls) as a 10 wt.% solution in
n-Heptane.
b: Prepared in liquid NH3 by reacting Ba with a mixture of t-butanol
and H20
Reaction Conditions
Temperature - 65C
Time - 24 hours
% Conversion - 100%
B
- ~7~ -
Charging Procedure
1. Phillips Petroleum Company 99% pure n-hexane was charged to the reactor.
Prior to charging, the hexane was dried by passing through 5 R molecular
sieves.
2. Phillips Petroleum Company Rubber Grade ~99%) butadiene -1,3 was charged
to the reactor. Prior to charging, the butadiene -1,3 was passed as a
liquid through Linde 13 X molecular sieves.
3. A solution of the complex (MAGALA-7.6E) of dibutylmagnesium-triethyl-
aluminum in n-heptane was charged to the reactor followed by a solution
of the barium salt in toluene.
4. The batch was heated to 65C.
5. Polymerization was carried out for 24 hours and then the batch was
cooled to 25C.
6. Just prior to discharging the batch, 1 part per hundred (phr) AØ 2246
(2,2'-methylene bis(4-methyl-6-tert-butyl phenol) and 1 phr lauric acid
were mixed with the batch
A description of the blended polybutadienes is given in Table XV, below.
For comparison purposes, the corresponding data for a commercially available
high cis polybutadieneis included. The experimental polybutadiene rubber
or elastomer has a much higher trans/cis ratio, lower cold flow and a different
crystalline melt endotherm. Polymer molecular weight, as measured by GPC, is
essentially the same.
iB
- 47c ~ V
TABLE XV
Characterization Data of
Experimental Poly BD RUBBER and High Cis BD Rubber
Commercial Experimental
Cis Poly BDa Trans PolyBD
Diene Structure ~%~
Trans 4 77
Cis 92 20
Vinyl 4 3
Brookfield Viscosity ~cps at 23C)b 143 117
Intrinsic Viscosity, tol. at 30C (dl/g)2.46 2.11
Mooney Viscosity ~ML-4 at 100C) 47 55
Cold Flow at 50 (mg/min.)C 3.2 0.5
By GPC:
Mn 149,000 152,000
Mw 401,000 409,000
_ _ 2.69 2.70
~/Mn
By DTA:
Tg, C -100 -92
Tm~ C - 25 26
a -Butadiene solution polymerized using Ziegler/Natta type catalyst system.
b -5% wt.!wt. in toluene ~#3 spindle, 100 rpm)
c -Phillips Chem. Co. Method WATB 5.01.20 of December 1, 1961.
The data in Table XVI and Table XVII below, show the formulations and
tread vulcanizate properties of the commercially available high cis poly BD and
the experimental trans poly BD in blends with emulsion SBR-1714. The experi-
B
- 47d -
mental rubbcr was cured with one additional part of stearic acid. Laboratory
evaluation sho~ed the experimental rubber to be generally equivalent except
for high Pico abrasion index ~175 versus 149) and slightly lower dry skid
resistance ~120 versus 125). Based on the data presented herein, it is seen
that the cxperimental rubber may be useful as a substitute for the commcrcially
available high cis poly BD in passenger tire tread compounds. The superior
abrasion resistance, although not expected on the basis of the relative Tg
values, suggests an advantage in treadwear over the commercially available high
cis poly BD containing blends.
TABLE XVI
Compound Recipes ~phr)
Run A Run B
SBR-1714a 60 60
Commercially available high
CisPoly BD, above 40 --
Experimental Trans poly BD, above -- 40
PHILRICH 5*oil, aromatic, ~total) b
tPhillips Petroleum Co.) 44 44
HAF-HS Carbon Black 75 75
Santoflex 13C~ 1.4 1.4
Santoflex 77d* 1.4 1.4
Atlantic Wax 3.0 --
Zinc Oxide 3.0 3.0
Stearic Acid 2.0 3.0
Santocure NSe* 1.1 1.1
TMTM 0.11 0.11
Sulfur 1.98 1.95
*Trade Mark
'~
` v
- ~7~ -
a - Free radical cold emulsion polymerized butadiene -1,3/styrene copolymer
target bound styrene of 23.5%, nominal Mooney viscosity ML 1+4(212F) of
52, contains target 50 phr highly aromatic oil.
b -Total oil in recipe including that in SBR-1714~
c -N-~1,3-Dimethylbutyl)-N'-phenyl-p-phenylene-diamine ~Monsanto, Rubber
Chemicals Div.).
d -N,N'-Bis~1,4-dimethyl-pentyl)-p-phenylenediamine ~Monsanto, Rubber
Chemicals Div.).
e -N-t-butyl-2-benzothiazolesulfenamide (Monsanto, Rubber Chemicals Div.).
f-Tetramethylthiuram monosulfide.
TABLE XVII
Vulcanizate Properties
Run A Run B
Compound Mooney, ML-4~100C) 58 57
T95, minutes/142C 35 28
Modulus at 300%, MPa (PSI) 9.3(1355) 8.6 (1250)
Tensile Strength, MPa (PSI) 18.4(2670) 17.8 (2580)
Elongation at Break ~%) 520 510
Shore A 66 67
Coodrich HBU, 100C ~TC) 33 31
Permanent Set ~%) 14 13
Pico Abrasion Index 149 175
Skid Resistance (dry) 125 120
Goodyear Rebound (%) 49 47
Goodyear Rebound Decay (tan~) 0.22 0.23
Cure Time/Temp. 35 min/287F28min/287F
~B
- 47f ~ iti~
Even though the above experimental trans polybutadiene, prepared with
the Mg-Al-Ba catalyst system, has a significantly higher trans/cis ratio than
tha commercially available high cis poly BD, the vinyl contents ~3-4%) are very
similar. The mole ratio of catalyst components, monomer/catalyst ratio and
polymerization temperature can be used to control the trans polybutadiene
microstructure and polymer molecular weight. A trans-1,4 configuration of 77%
results in a material which is rubbery at room temperature. Although the raw
experimental trans BD polymer crystallizes as does the commercially available
high cis poly BD, the tendency to crystallize can be largely suppressed by
cross-linking.
Relative to the preparation of a 90% trans-1,4 polybutadiene, with the
barium salt in combination with (Bu)2Mg and Et3Al, the experimental trans
poly BD is prepared with the same catalyst system but using a higher Ba/Mg
mole ratio. A small increase in Ba content results in a decrease in the amount
of trans-1,4 structure from 90% to about 75-80%.
IB
