Synthesis of high vinyl rubber

Metal salts of saturated aliphatic alcohols can be used as modifiers in lithium initiated solution polymerizations of diene monomers into rubbery polymers. Sodium t-amylate is a preferred modifiers because of its exceptional solubility in non-polar aliphatic hydrocarbon solvents that are employed as the medium for such solution polymerizations. However, using sodium t-amylate as the polymerization modifier in commercial operations where recycle is required can lead to certain problems. These problems arise due to the fact that sodium t-amylate reacts with water to form t-amyl alcohol during steam stripping in the polymer finishing step. Since t-amyl alcohol forms an azeotrope with hexane, it co-distills with hexane and thus contaminates the feed stream. The present invention solves the problem of recycle stream contamination. This invention is based upon the discovery of highly effective modifiers that do not co-distill with hexane or-form-compounds during steam stripping which co-distill with hexane. The modifiers of this invention are metal salts of cyclic alcohols. Since the boiling points of these metal salts of cyclic alcohols are very high, they do not co-distill with hexane and contaminate recycle streams. Additionally, metal salts of cyclic alcohols are considered to be environmentally safe. The, subject invention more specifically discloses an initiator system which is comprised of (a) a lithium initiator, (b) a metal salt of a cyclic alcohol, and (c) a polar modifier.

BACKGROUND OF THE INVENTION 
It is highly desirable for tires to exhibit good traction characteristics 
on both dry and wet surfaces. However, it has traditionally been very 
difficult to improve the traction characteristics of a tire without 
compromising its rolling resistance and tread wear. Low rolling resistance 
is important because good fuel economy is virtually always an important 
consideration. Good tread wear is also an important consideration because 
it is generally the most important factor which determines the life of the 
tire. 
The traction, tread wear, and rolling resistance of a tire is dependent to 
a large extent on the dynamic viscoelastic properties of the elastomers 
utilized in making the tire tread. In order to reduce the rolling 
resistance of a tire, rubbers having a high rebound have traditionally 
been utilized in making the tire's tread. On the other hand, in order to 
increase the wet skid resistance of a tire, rubbers which undergo a large 
energy loss have generally been utilized in the tire's tread. In order to 
balance these two viscoelastically inconsistent properties, mixtures of 
various types of synthetic and natural rubber are normally utilized in 
tire treads. For instance various mixtures of styrene-butadiene rubber and 
polybutadiene rubber are commonly used as a rubber material for automobile 
tire treads. However, such blends are not totally satisfactory for all 
purposes. 
The inclusion of styrene-butadiene rubber (SBR) in tire tread formulations 
can significantly improve the traction characteristics of tires made 
therewith. However, styrene is a relatively expensive monomer and the 
inclusion of SBR is tire tread formulations leads to increased costs. 
Carbon black is generally included in rubber compositions which are 
employed in making tires and most other rubber articles. It is desirable 
to attain the best possible dispersion of the carbon black throughout the 
rubber to attain optimized properties. It is also highly desirable to 
improve the interaction between the carbon black and the rubber. By 
improving the affinity of the rubber compound to the carbon black, 
physical properties can be improved. Silica can also be included in tire 
tread formulations to improve rolling resistance. 
U.S. Pat. No. 4,843,120 discloses that tires having improved performance 
characteristics can be prepared by utilizing rubbery polymers having 
multiple glass transition temperatures as the tread rubber. These rubbery 
polymers having multiple glass transition temperatures exhibit a first 
glass transition temperature which is within the range of about 
-110.degree. C. to -20.degree. C. and exhibit a second glass transition 
temperature which is within the range of about -50.degree. C. to 0.degree. 
C. According to U.S. Pat. No. 4,843,120, these polymers are made by 
polymerizing at least one conjugated diolefin monomer in a first reaction 
zone at a temperature and under conditions sufficient to produce a first 
polymeric segment having a glass transition temperature which is between 
-110.degree. C. and -20.degree. C. and subsequently continuing said 
polymerization in a second reaction zone at a temperature and under 
conditions sufficient to produce a second polymeric segment having a glass 
transition temperature which is between -20.degree. C. and 20.degree. C. 
Such polymerizations are normally catalyzed with an organolithium catalyst 
and are normally carried out in an inert organic solvent. 
U.S. Pat. No. 5,137,998 discloses a process for preparing a rubbery 
terpolymer of styrene, isoprene, and butadiene having multiple glass 
transition temperatures and having an excellent combination of properties 
for use in making tire treads which comprises: terpolymerizing styrene, 
isoprene and 1,3-butadiene in an organic solvent at a temperature of no 
more than about 40.degree. C. in the presence of (a) at least one member 
selected from the group consisting of tripiperidino phosphine oxide and 
alkali metal alkoxides and (b) an organolithium compound. 
U.S. Pat. No. 5,047,483 discloses a pneumatic tire having an outer 
circumferential tread where said tread is a sulfur cured rubber 
composition comprised of, based on 100 parts by weight rubber (phr), (A) 
about 10 to about 90 parts by weight of a styrene, isoprene, butadiene 
terpolymer rubber (SIBR), and (B) about 70 to about 30 weight percent of 
at least one of cis 1,4-polyisoprene rubber and cis 1,4-polybutadiene 
rubber wherein said SIBR rubber is comprised of (1) about 10 to about 35 
weight percent bound styrene, (2) about 30 to about 50 weight percent 
bound isoprene and (3) about 30 to about 40 weight percent bound butadiene 
and is characterized by having a single glass transition temperature (Tg) 
which is in the range of about -10.degree. C. to about -40.degree. C. and, 
further the said bound butadiene structure contains about 30 to about 40 
percent 1,2-vinyl units, the said bound isoprene structure contains about 
10 to about 30 percent 3,4-units, and the sum of the percent 1,2-vinyl 
units of the bound butadiene and the percent 3,4-units of the bound 
isoprene is in the range of about 40 to about 70 percent. 
U.S. Pat. No. 5,272,220 discloses a styrene-isoprene-butadiene rubber which 
is particularly valuable for use in making truck tire treads which exhibit 
improved rolling resistance and tread wear characteristics , said rubber 
being comprised of repeat units which are derived from about 5 weight 
percent to about 20 weight percent styrene, from about 7 weight percent to 
about 35 weight percent isoprene, and from about 55 weight percent to 
about 88 weight percent 1,3-butadiene, wherein the repeat units derived 
from styrene, isoprene and 1,3-butadiene are in essentially random order, 
wherein from about 25% to about 40% of the repeat units derived from the 
1,3-butadiene are of the cis-microstructure, wherein from about 40% to 
about 60% of the repeat units derived from the 1,3-butadiene are of the 
trans-microstructure, wherein from about 5% to about 25% of the repeat 
units derived from the 1,3-butadiene are of the vinyl-microstructure, 
wherein from about 75% to about 90% of the repeat units derived from the 
isoprene are of the 1,4-microstructure, wherein from about 10% to about 
25% of the repeat units derived from the isoprene are of the 
3,4-microstructure, wherein the rubber has a glass transition temperature 
which is within the range of about -90.degree. C. to about -70.degree. C., 
wherein the rubber has a number average molecular weight which is within 
the range of about 150,000 to about 400,000, wherein the rubber has a 
weight average molecular weight of about 300,000 to about 800,000, and 
wherein the rubber has an inhomogeneity which is within the range of about 
0.5 to about 1.5. 
U.S. Pat. No. 5,239,009 reveals a process for preparing a rubbery polymer 
which comprises: (a) polymerizing a conjugated diene monomer with a 
lithium initiator in the substantial absence of polar modifiers at a 
temperature which is within the range of about 5.degree. C. to about 
100.degree. C. to produce a living polydiene segment having a number 
average molecular weight which is within the range of about 25,000 to 
about 350,000; and (b) utilizing the living polydiene segment to initiate 
the terpolymerization of 1,3-butadiene, isoprene, and styrene, wherein the 
terpolymerization is conducted in the presence of at least one polar 
modifier at a temperature which is within the range of about 5.degree. C. 
to about 70.degree. C. to produce a final segment which is comprised of 
repeat units which are derived from 1,3-butadiene, isoprene, and styrene, 
wherein the final segment has a number average molecular weight which is 
within the range of about 25,000 to about 350,000. The rubbery polymer 
made by this process is reported to be useful for improving the wet skid 
resistance and traction characteristics of tires without sacrificing tread 
wear or rolling resistance. 
U.S. Pat. No. 5,061,765 discloses isoprene-butadiene copolymers having high 
vinyl contents which can reportedly be employed in building tires which 
have improved traction, rolling resistance, and abrasion resistance. These 
high vinyl isoprene-butadiene rubbers are synthesized by copolymerizing 
1,3-butadiene monomer and isoprene monomer in an organic solvent at a 
temperature which is within the range of about -10.degree. C. to about 
100.degree. C. in the presence of a catalyst system which is comprised of 
(a) an organoiron compound, (b) an organoaluminum compound, (c) a 
chelating aromatic amine, and (d) a protonic compound; wherein the molar 
ratio of the chelating amine to the organoiron compound is within the 
range of about 0.1:1 to about 1:1, wherein the molar ratio of the 
organoaluminum compound to the organoiron compound is within the range of 
about 5:1 to about 200:1, and herein the molar ratio of the protonic 
compound to the organoaluminum compound is within the range of about 
0.001:1 to about 0.2:1. 
U.S. Pat. No. 5,405,927 discloses an isoprene-butadiene rubber which is 
particularly valuable for use in making truck tire treads, said rubber 
being comprised of repeat units which are derived from about 20 weight 
percent to about 50 weight percent isoprene and from about 50 weight 
percent to about 80 weight percent 1,3-butadiene, wherein the repeat units 
derived from isoprene and 1,3-butadiene are in essentially random order, 
wherein from about 3% to about 10% of the repeat units in said rubber are 
1,2-polybutadiene units, wherein from about 50% to about 70% of the repeat 
units in said rubber are 1,4-polybutadiene units, wherein from about 1% to 
about 4% of the repeat units in said rubber are 3,4-polyisoprene units, 
wherein from about 25% to about 40% of the repeat units in the polymer are 
1,4-polyisoprene units, wherein the rubber has a glass transition 
temperature which is within the range of about -90.degree. C. to about 
-75.degree. C., and wherein the rubber has a Mooney viscosity which is 
within the range of about 55 to about 140. 
U.S. Pat. No. 5,654,384 discloses a process for preparing high vinyl 
polybutadiene rubber which comprises polymerizing 1,3-butadiene monomer 
with a lithium initiator at a temperature which is within the range of 
about 5.degree. C. to about 100.degree. C. in the presence of a sodium 
alkoxide and a polar modifier, wherein the molar ratio of the sodium 
alkoxide to the polar modifier is within the range of about 0.1:1 to about 
10:1; and wherein the molar ratio of the sodium alkoxide to the lithium 
initiator is within the range of about 0.05:1 to about 10:1. By utilizing 
a combination of sodium alkoxide and a conventional polar modifier, such 
as an amine or an ether, the rate of polymerization initiated with 
organolithium compounds can be greatly increased with the glass transition 
temperature of the polymer produced also being substantially increased. 
The rubbers synthesized using such catalyst systems also exhibit excellent 
traction properties when compounded into tire tread formulations. This is 
attributable to the unique macrostructure (random branching) of the 
rubbers made with such catalyst systems. 
U.S. Pat. No. 5,620,939, U.S. Pat. No. 5,627,237, and U.S. Pat. No. 
5,677,402 also disclose the use of sodium salts of saturated aliphatic 
alcohols as modifiers for lithium initiated solution polymerizations. 
Sodium t-amylate is a preferred sodium alkoxide by virtue of its 
exceptional solubility in non-polar aliphatic hydrocarbon solvents, such 
as hexane, which are employed as the medium for such solution 
polymerizations. However, using sodium t-amylate as the polymerization 
modifier in commercial operations where recycle is required can lead to 
certain problems. These problems arise due to the fact that sodium 
t-amylate reacts with water to form t-amyl alcohol during steam stripping 
in the polymer finishing step. Since t-amyl alcohol forms an azeotrope 
with hexane, it co-distills with hexane and thus contaminates the feed 
stream. 
SUMMARY OF THE INVENTION 
The present invention solves the problem of recycle stream contamination. 
This invention is based upon the discovery of highly effective modifiers 
that do not co-distill with hexane or form compounds during steam 
stripping which co-distill with hexane. The modifiers of this invention 
are metal salts of cyclic alcohols. These modifiers that provide similar 
modification efficiencies to sodium t-amylate. Since the boiling points of 
these metal salts of cyclic alcohols are very high, they do not co-distill 
with hexane and contaminate recycle streams. Additionally, metal salts of 
cyclic alcohols are considered to be environmentally safe. In fact, sodium 
mentholate is used as a food additive. 
The subject invention further discloses a process for preparing a rubbery 
polymer having a high vinyl content which comprises: polymerizing at least 
one diene monomer with a lithium initiator at a temperature which is 
within the range of about 5.degree. C. to about 100.degree. C. in the 
presence of a metal salt of a cyclic alcohol and a polar modifier, wherein 
the molar ratio of the metal salt of the cyclic alcohol to the polar 
modifier is within the range of about 0.1:1 to about 10:1; and wherein the 
molar ratio of the metal salt of the cyclic alcohol to the lithium 
initiator is within the range of about 0.05:1 to about 10:1. 
The subject invention further discloses a process for preparing high vinyl 
polybutadiene rubber which comprises: polymerizing 1,3-butadiene monomer 
with a lithium initiator at a temperature which is within the range of 
about 5.degree. C. to about 100.degree. C. in the presence of a metal salt 
of a cyclic alcohol and a polar modifier, wherein the molar ratio of the 
metal salt of the cyclic alcohol to the polar modifier is within the range 
of about 0.1:1 to about 10:1; and wherein the molar ratio of the metal 
salt of the cyclic alcohol to the lithium initiator is within the range of 
about 0.05:1 to about 10:1. 
The subject invention also reveals an initiator system which is comprised 
of (a) a lithium initiator, (b) a metal salt of a cyclic alcohol, and (c) 
a polar modifier; wherein the molar ratio of the metal salt of the cyclic 
alcohol to the polar modifier is within the range of about 0.1:1 to about 
10:1; and wherein the molar ratio of the metal salt of the cyclic alcohol 
to the lithium initiator is within the range of about 0.01:1 to about 
20:1. 
DETAILED DESCRIPTION OF THE INVENTION 
The polymerizations of this invention are normally carried out as solution 
polymerizations in an inert organic medium utilizing a lithium catalyst. 
However, metal salts of cyclic alcohols can also be employed in accordance 
with this invention as modifiers for bulk polymerizations or vapor phase 
polymerizations. The vinyl content of the rubbery polymer made is 
controlled by the amount of modifier present during the polymerization. 
The rubbery polymers synthesized using the modifiers of this invention can 
be made by the homopolymerization of a conjugated diolefin monomer or by 
the copolymerization of a conjugated diolefin monomer with a vinyl 
aromatic monomer. It is, of course, also possible to make rubbery polymers 
by polymerizing a mixture of conjugated diolefin monomers with one or more 
ethylenically unsaturated monomers, such as vinyl aromatic monomers. The 
conjugated diolefin monomers which can be utilized in the synthesis of 
rubbery polymers in accordance with this invention generally contain from 
4 to 12 carbon atoms. Those containing from 4 to 8 carbon atoms are 
generally preferred for commercial purposes. For similar reasons, 
1,3-butadiene and isoprene are the most commonly utilized conjugated 
diolefin monomers. Some additional conjugated diolefin monomers that can 
be utilized include 2,3-dimethyl-1,3-butadiene, piperylene, 
3-butyl-1,3-octadiene, 2-phenyl-1,3-butadiene, and the like, alone or in 
admixture. 
Some representative examples of ethylenically unsaturated monomers that can 
potentially be copolymerized into rubbery polymers using the modifiers of 
this invention include alkyl acrylates, such as methyl acrylate, ethyl 
acrylate, butyl acrylate, methyl methacrylate and the like; vinylidene 
monomers having one or more terminal CH2.dbd.CH-- groups; vinyl aromatics 
such as styrene, .alpha.-methylstyrene, bromostyrene, chlorostyrene, 
fluorostyrene and the like; .alpha.-olefins such as ethylene, propylene, 
1-butene and the like; vinyl halides, such as vinylbromide, chloroethane 
(vinylchloride), vinylfluoride, vinyliodide, 1,2-dibromoethene, 
1,1-dichloroethene (vinylidene chloride), 1,2-dichloroethene and the like; 
vinyl esters, such as vinyl acetate; .alpha.,.beta.-olefinically 
unsaturated nitriles, such as acrylonitrile and methacrylonitrile; 
.alpha.,.beta.-olefinically unsaturated amides, such as acrylamide, 
N-methyl acrylamide, N,N-dimethylacrylamide, methacrylamide and the like. 
Rubbery polymers which are copolymers of one or more diene monomers with 
one or more other ethylenically unsaturated monomers will normally contain 
from about 50 weight percent to about 99 weight percent conjugated 
diolefin monomers and from about 1 weight percent to about 50 weight 
percent of the other ethylenically unsaturated monomers in addition to the 
conjugated diolefin monomers. For example, copolymers of conjugated 
diolefin monomers with vinylaromatic monomers, such as styrene-butadiene 
rubbers which contain from 50 to 95 weight percent conjugated diolefin 
monomers and from 5 to 50 weight percent vinylaromatic monomers, are 
useful in many applications. 
Vinyl aromatic monomers are probably the most important group of 
ethylenically unsaturated monomers which are commonly incorporated into 
polydienes. Such vinyl aromatic monomers are, of course, selected so as to 
be copolymerizable with the conjugated diolefin monomers being utilized. 
Generally, any vinyl aromatic monomer which is known to polymerize with 
organolithium initiators can be used. Such vinyl aromatic monomers 
typically contain from 8 to 20 carbon atoms. Usually, the vinyl aromatic 
monomer will contain from 8 to 14 carbon atoms. The most widely used vinyl 
aromatic monomer is styrene. Some examples of vinyl aromatic monomers that 
can be utilized include styrene, 1-vinylnaphthalene, 2-vinylnaphthalene, 
.alpha.-methylstyrene, 4-phenylstyrene, 3-methylstyrene and the like. 
Some representative examples of rubbery polymers which can be 
asymmetrically tin-coupled in accordance with this invention include 
polybutadiene, polyisoprene, styrene-butadiene rubber (SBR), 
.alpha.-methylstyrene-butadiene rubber, .alpha.-methylstyrene-isoprene 
rubber, styrene-isoprene-butadiene rubber (SIBR), styrene-isoprene rubber 
(SIR), isoprene-butadiene rubber (IBR), 
.alpha.-methylstyrene-isoprene-butadiene rubber and 
.alpha.-methylstyrene-styrene-isoprene-butadiene rubber. 
In solution polymerizations the inert organic medium which is utilized as 
the solvent will typically be a hydrocarbon which is liquid at ambient 
temperatures which can be one or more aromatic, paraffinic or 
cycloparaffinic compounds. These solvents will normally contain from 4 to 
10 carbon atoms per molecule and will be liquids under the conditions of 
the polymerization. It is, of course, important for the solvent selected 
to be inert. The term "inert" as used herein means that the solvent does 
not interfere with the polymerization reaction or react with the polymers 
made thereby. Some representative examples of suitable organic solvents 
include pentane, isooctane, cyclohexane, normal hexane, benzene, toluene, 
xylene, ethylbenzene and the like, alone or in admixture. Saturated 
aliphatic solvents, such as cyclohexane and normal hexane, are most 
preferred. 
The lithium catalysts which can be used are typically organolithium 
compounds. The organolithium compounds which are preferred can be 
represented by the formula: R--Li, wherein R represents a hydrocarbyl 
radical containing from 1 to about 20 carbon atoms. Generally, such 
monofunctional organolithium compounds will contain from 1 to about 10 
carbon atoms. Some representative examples of organolithium compounds 
which can be employed include methyllithium, ethyllithium, 
isopropyllithium, n-butyllithium, sec-butyllithium, n-octyllithium, 
tert-octyllithium, n-decyllithium, phenyllithium, 1-napthyllithium, 
4-butylphenyllithium, p-tolyllithium, 1-naphthyllithium, 
4-butylphenyllithium, p-tolyllithium, 4-phenylbutyllithium, 
cyclohexyllithium, 4-butylcyclohexyllithium, and 4-cyclohexylbutyllithium. 
Organo monolithium compounds, such as alkyllithium compounds and 
aryllithium compounds, are usually employed. Some representative examples 
of preferred organo monolithium compounds that can be utilized include 
ethylaluminum, isopropylaluminum, n-butyllithium, secondary-butyllithium, 
normal-hexyllithium, tertiary-octyllithium, phenyllithium, 
2-napthyllithium, 4-butylphenyllithium, 4-phenylbutyllithium, 
cyclohexyllithium, and the like. Normal-butyllithium and 
secondary-butyllithium are highly preferred lithium initiators. 
The amount of lithium catalyst utilized will vary from one organolithium 
compound to another and with the molecular weight that is desired for the 
rubber being synthesized. As a general rule in all anionic 
polymerizations, the molecular weight (Mooney viscosity) of the polymer 
produced is inversely proportional to the amount of catalyst utilized. As 
a general rule, from about 0.01 phm (parts per hundred parts by weight of 
monomer) to 1 phm of the lithium catalyst will be employed. In most cases, 
from 0.01 phm to 0.1 phm of the lithium catalyst will be employed with it 
being preferred to utilize 0.025 phm to 0.07 phm of the lithium catalyst. 
Normally, from about 5 weight percent to about 35 weight percent of the 
monomer will be charged into the polymerization medium (based upon the 
total weight of the polymerization medium including the organic solvent 
and monomer). In most cases, it will be preferred for the polymerization 
medium to contain from about 10 weight percent to about 30 weight percent 
monomer. It is typically more preferred for the polymerization medium to 
contain from about 20 weight percent to about 25 weight percent monomer. 
The polymerization temperature will normally be within the range of about 
5.degree. C. to about 100.degree. C. For practical reasons and to attain 
the desired microstructure the polymerization temperature will preferably 
be within the range of about 40.degree. C. to about 90.degree. C. 
Polymerization temperatures within the range of about 60.degree. C. to 
about 90.degree. C. are most preferred. The microstructure of the rubbery 
polymer is somewhat dependent upon the polymerization temperature. 
The polymerization is allowed to continue until essentially all of the 
monomer has been exhausted. In other words, the polymerization is allowed 
to run to completion. Since a lithium catalyst is employed to polymerize 
the monomer, a living polymer is produced. The living polymer synthesized 
will have a number average molecular weight which is within the range of 
about 25,000 to about 700,000. The rubber synthesized will more typically 
have a number average molecular weight which is within the range of about 
150,000 to about 400,000. 
To increase the level of vinyl content the polymerization is carried out in 
the presence of at least one polar modifier. Ethers and tertiary amines 
which act as Lewis bases are representative examples of polar modifiers 
that can be utilized. Some specific examples of typical polar modifiers 
include diethyl ether, di-n-propyl ether, diisopropyl ether, di-n-butyl 
ether, tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, ethylene 
glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol 
diethyl ether, triethylene glycol dimethyl ether, trimethylamine, 
triethylamine, N,N,N',N'-tetramethylethylenediamine, N-methyl morpholine, 
N-ethyl morpholine, N-phenyl morpholine and the like. 
The modifier can also be a 1,2,3-trialkoxybenzene or a 
1,2,4-trialkoxybenzene. Some representative examples of 
1,2,3-trialkoxybenzenes that can be used include 1,2,3-trimethoxybenzene, 
1,2,3-triethoxybenzene, 1,2,3-tributoxybenzene, 1,2,3-trihexoxybenzene, 
4,5,6-trimethyl-1,2,3-trimethoxybenzene, 
4,5,6-tri-n-pentyl-1,2,3-triethoxybenzene, 
5-methyl-1,2,3-trimethoxybenzene, and 5-propyl-1,2,3-trimethoxybenzene. 
Some representative examples of 1,2,4-trialkoxybenzenes that can be used 
include 1,2,4-trimethoxybenzene, 1,2,4-triethoxybenzene, 
1,2,4-tributoxybenzene, 1,2,4-tripentoxybenzene, 
3,5,6-trimethyl-1,2,4-trimethoxybenzene, 5-propyl-1,2,4-trimethoxybenzene, 
and 3,5-dimethyl-1,2,4-trimethoxybenzene. Dipiperidinoethane, 
dipyrrolidinoethane, tetramethylethylene diamine, diethylene glycol, 
dimethyl ether and tetrahydrofuran are representative of highly preferred 
modifiers. U.S. Pat. No. 4,022,959 describes the use of ethers and 
tertiary amines as polar modifiers in greater detail. 
The utilization of 1,2,3-trialkoxybenzenes and 1,2,4-trialkoxybenzenes as 
modifiers is described in greater detail in U.S. Pat. No. 4,696,986. The 
teachings of U.S. Pat. No. 4,022,959 and U.S. Pat. No. 4,696,986 are 
incorporated herein by reference in their entirety. The microstructure of 
the repeat units which are derived from butadiene monomer is a function of 
the polymerization temperature and the amount of polar modifier present. 
For example, it is known that higher temperatures result in lower vinyl 
contents (lower levels of 1,2-microstructure). Accordingly, the 
polymerization temperature, quantity of modifier and specific modifier 
selected will be determined with the ultimate desired microstructure of 
the polybutadiene rubber being synthesized being kept in mind. 
It has been unexpectedly found that a combination of a metal salt of a 
cyclic alcohol and a polar modifier act synergistically to increase the 
vinyl content of rubbery polymer synthesized in their presence. The 
utilization of this synergistic modifier system can also be employed 
advantageously in the synthesis of a wide variety of rubbery polymers, 
such as high vinyl polybutadiene rubber, styrene-butadiene rubber (SBR), 
styrene-isoprene-butadiene rubber (SIBR), and isoprene-butadiene rubber. 
The metal salt of the cyclic alcohol will typically be a Group Ia metal 
salt. Lithium, sodium, potassium, rubidium, and cesium salts are 
representative examples of such salts with lithium, sodium, and potassium 
salts being preferred. Sodium salts are typicaly the most preferred. The 
cyclic alcohol can be mono-cyclic, bi-cyclic or tri-cyclic and can be 
aliphatic or aromatic. They can be substituted with 1 to 5 hydrocarbon 
moieties and can also optionally contain hetero-atoms. For instance, the 
metal salt of the cyclic alcohol can be a metal salt of a di-alkylated 
cyclohexanol, such as 2-isopropyl-5-methylcyclohexanol or 
2-t-butyl-5-methylcyclohexanol. These salts are preferred because they are 
soluble in hexane. Metal salts of disubstituted cyclohexanol are highly 
preferred because they are soluble in hexane and provide similar 
modification efficiencies to sodium t-amylate. Sodium mentholate is the 
most highly preferred metal salt of a cyclic alcohol that can be empolyed 
in the practice of this invention. Metal salts of thymol can also be 
utilized. The metal salt of the cyclic alcohol can be prepared by reacting 
the cyclic alcohol directly with the metal or another metal source, such 
as sodium hydride, in an aliphatic or aromatic solvent. 
The molar ratio of the metal salt of the cyclic alcohol to the polar 
modifier will normally be within the range of about 0.1:1 to about 10:1 
and the molar ratio of the metal salt of the cyclic alcohol to the lithium 
initiator will normally be within the range of about 0.01:1 to about 20:1. 
It is generally preferred for the molar ratio of the metal salt of the 
cyclic alcohol to the polar modifier to be within the range of about 0.2:1 
to about 5:1 and for the molar ratio of the metal salt of the cyclic 
alcohol to the lithium initiator to be within the range of about 0.05:1 to 
about 10:1. It is generally more preferred for the molar ratio of the 
metal salt of the cyclic alcohol to the polar modifier to be within the 
range of about 0.5:1 to about 1:1 and for the molar ratio of the metal 
salt of the cyclic alcohol to the lithium initiator to be within the range 
of about 0.2:1 to about 3:1. 
After the polymerization has been completed, the living rubbery polymer can 
optionally be coupled with a suitable coupling agent, such as a tin 
tetrahalide or a silicon tetrahalide. The rubbery polymer is then 
recovered from the organic solvent. The polybutadiene rubber can be 
recovered from the organic solvent and residue by any means, such as 
decantation, filtration, centrification and the like. It is often 
desirable to precipitate the rubbery polymer from the organic solvent by 
the addition of lower alcohols containing from about 1 to about 4 carbon 
atoms to the polymer solution. Suitable lower alcohols for precipitation 
of the rubbery polymer from the polymer cement include methanol, ethanol, 
isopropyl alcohol, normal-propyl alcohol and t-butyl alcohol. The 
utilization of lower alcohols to precipitate the rubber from the polymer 
cement also "kills" the living polymer by inactivating lithium end groups. 
After the rubbery polymer is recovered from the solution, steam stripping 
can be employed to reduce the level of volatile organic compounds in the 
polymer. The inert solvent and residual monomer can then be recycled for 
subsequent polymerization. 
There are valuable benefits associated with utilizing polybutadiene rubber 
made with the modifiers of this invention in tire tread compounds. For 
instance, tire tread compounds can be made by blending polybutadiene 
rubbers having at least three different vinyl contents. It is normally not 
necessary to include additional rubbers, such as styrene-butadiene rubber, 
in such blends. A highly preferred blend of this type contains: (1) 
super-high vinyl polybutadiene rubber which has a vinyl content which is 
within the range of 80 percent to 100 percent and a glass transition 
temperature which is within the range of about -15.degree. C. to about 
0.degree. C., (2) high vinyl polybutadiene rubber which has a vinyl 
content which is within the range of 60 percent to 79 percent and a glass 
transition temperature which is within the range of about -45.degree. C. 
to about -40.degree. C., (3) medium vinyl polybutadiene rubber which has a 
vinyl content which is within the range of 35 percent to 59 percent and a 
glass transition temperature which is within the range of about 
-75.degree. C. to about -45.degree. C., and (4) low vinyl polybutadiene 
rubber which has a vinyl content which is within the range of 8 percent to 
34 percent and a glass transition temperature which is within the range of 
about -95.degree. C. to about -75.degree. C. It is important for such 
blends to contain at least three of the four members of the group 
consisting of super-high vinyl polybutadiene rubber, high vinyl 
polybutadiene rubber, medium vinyl polybutadiene rubber, and low vinyl 
polybutadiene rubber. 
In such blends it is also critical for at least one of the polybutadiene 
rubbers in the blend to have a vinyl content which is within 35 percentage 
points of the vinyl content of at least one other polybutadiene rubber in 
the blend to provide compatibility. It is preferred for at least one of 
the polybutadiene rubbers in the blend to have a vinyl content which is 
within 30 percentage points of the vinyl content of at least one other 
polybutadiene rubber in the blend. It is more preferred for at least one 
of the polybutadiene rubbers in the blend to have a vinyl content which is 
within 25 percentage points of the vinyl content of at least one other 
polybutadiene rubber in the blend. For instance, it would be highly 
preferred for the blend to contain a super-high vinyl polybutadiene rubber 
having a vinyl content of 90 percent and a high vinyl polybutadiene rubber 
having a vinyl content of 65 percent (the vinyl content of the high vinyl 
polybutadiene rubber differs from the vinyl content of the super-high 
vinyl polybutadiene by only 25 percentage points). 
It is also important for the three different polybutadiene rubbers employed 
in the blend to have vinyl contents which differ from the other two 
polybutadiene rubbers employed in the blend by at least 5 percentage 
points. In other words, the vinyl contents of the different polybutadiene 
rubbers utilized in the blend must differ by at least 5 percentage points. 
For example, if a super-high vinyl polybutadiene rubber having a vinyl 
content of 80 percent and a high vinyl polybutadiene rubber are employed 
in the blend, the vinyl content of the high vinyl polybutadiene must be 
less than 75 percent. It is preferred for the three different 
polybutadiene rubbers employed in the blend to have vinyl contents which 
differ from the other two polybutadiene rubbers employed in the blend by 
at least 10 percentage points. Thus, it would be highly preferred to 
utilize a super-high vinyl polybutadiene rubber having a vinyl content of 
85 percent and a high vinyl polybutadiene rubber having a vinyl content of 
70 percent in the blend (there is a 15 percentage point difference between 
the vinyl contents of the two polybutadiene rubbers. Stated in still 
another way, the vinyl content of the first polybutadiene rubber can not 
have a vinyl content which is within 5 percentage points of the vinyl 
content of the second polybutadiene rubber or the third polybutadiene 
rubber, and the vinyl content of the second polybutadiene rubber can not 
have a vinyl content which is within 5 percentage points of the vinyl 
content of the third polybutadiene rubber. 
It is also important for the blend as a whole to have a total vinyl content 
of at least 40 percent and preferably 45 percent. The total vinyl content 
of the blend as a whole is the sum of the products of the number of parts 
of each of the polybutadiene rubbers included in the blend and the vinyl 
contents of those polybutadiene rubbers, with that sum being divided by 
the total number of parts of polybutadiene rubber included in the blend. 
For example, if the blend included 40 parts of a low vinyl polybutadiene 
rubber having a vinyl content of 20 percent, 40 parts of a medium vinyl 
polybutadiene rubber having a vinyl content of 40 percent, and 20 parts of 
a super-high vinyl polybutadiene rubber having a vinyl content of 80 
percent, the blend as a whole would have a total vinyl content of 40 
percent. In another example, if the blend included 20 parts of a low vinyl 
polybutadiene rubber having a vinyl content of 30 percent, 40 parts of a 
high vinyl polybutadiene rubber having a vinyl content of 60 percent, and 
40 parts of a super-high vinyl polybutadiene rubber having a vinyl content 
of 90 percent, the blend as a whole would have a total vinyl content of 66 
percent. 
Such polybutadiene rubber blends will contain at least 10 phr (parts per 
100 parts by weight of rubber) of the first polybutadiene rubber, at least 
10 phr of the second polybutadiene rubber, and at least 10 phr of the 
third polybutadiene rubber. The blend will preferably contain at least 20 
phr of the first polybutadiene rubber, at least 20 phr of the second 
polybutadiene rubber, and at least 20 phr of the third polybutadiene 
rubber. The blend will more preferably contain at least 25 phr of the 
first polybutadiene rubber, at least 25 phr of the second polybutadiene 
rubber, and at least 25 phr of the third polybutadiene rubber. 
Such polybutadiene rubber blends can be compounded utilizing conventional 
ingredients and standard techniques. For instance, the polybutadiene 
rubber blends will typically be mixed with carbon black and/or silica, 
sulfur, fillers, accelerators, oils, waxes, scorch inhibiting agents, and 
processing aids. In most cases, the polybutadiene rubber blends will be 
compounded with sulfur and/or a sulfur containing compound, at least one 
filler, at least one accelerator, at least one antidegradant, at least one 
processing oil, zinc oxide, optionally a tackifier resin, optionally a 
reinforcing resin, optionally one or more fatty acids, optionally a 
peptizer and optionally one or more scorch inhibiting agents. Such blends 
will normally contain from about 0.5 to 5 phr (parts per hundred parts of 
rubber by weight) of sulfur and/or a sulfur containing compound with 1 phr 
to 2.5 phr being preferred. It may be desirable to utilize insoluble 
sulfur in cases where bloom is a problem. 
Normally from 10 to 150 phr of at least one filler will be utilized in the 
blend with 30 to 80 phr being preferred. In most cases at least some 
carbon black will be utilized in the filler. The filler can, of course, be 
comprised totally of carbon black. Silica can be included in the filler to 
improve tear resistance and heat build up. Clays and/or talc can be 
included in the filler to reduce cost. The blend will also normally 
include from 0.1 to 2.5 phr of at least one accelerator with 0.2 to 1.5 
phr being preferred. Antidegradants, such as antioxidants and 
antiozonants, will generally be included in the tread compound blend in 
amounts ranging from 0.25 to 10 phr with amounts in the range of 1 to 5 
phr being preferred. Processing oils will generally be included in the 
blend in amounts ranging from 2 to 100 phr with amounts ranging from 5 to 
50 phr being preferred. The polybutadiene blends of this invention will 
also normally contain from 0.5 to 10 phr of zinc oxide with 1 to 5 phr 
being preferred. These blends can optionally contain from 0 to 10 phr of 
tackifier resins, 0 to 10 phr of reinforcing resins, 1 to 10 phr of fatty 
acids, 0 to 2.5 phr of peptizers, and 0 to 1 phr of scorch inhibiting 
agents. 
To fully realize the total advantages of such polybutadiene rubber blends, 
silica will normally be included in the tread rubber formulation. The 
processing of the polybutadiene rubber blend is normally conducted in the 
presence of a sulfur containing organosilicon compound to realize maximum 
benefits. Examples of suitable sulfur containing organosilicon compounds 
are of the formula: 
EQU Z--Alk--S.sub.n --Alk--Z (I) 
in which Z is selected from the group consisting of 
##STR1## 
where R.sup.1 is an alkyl group of 1 to 4 carbon atoms, cyclohexyl or 
phenyl; wherein R.sup.2 is alkoxy of 1 to 8 carbon atoms, or cycloalkoxy 
of 5 to 8 carbon atoms; and wherein Alk is a divalent hydrocarbon of 1 to 
18 carbon atoms and n is an integer of 2 to 8. 
Specific examples of sulfur containing organosilicon compounds which may be 
used in accordance with the present invention include: 
3,3'-bis(trimethoxysilylpropyl) disulfide, 3,3'-bis(triethoxysilylpropyl) 
tetrasulfide, 3,3'-bis(triethoxysilylpropyl) octasulfide, 
3,3'-bis(trimethoxysilylpropyl) tetrasulfide, 
2,2'-bis(triethoxysilylethyl) tetrasulfide, 
3,3'-bis(trimethoxysilylpropyl) trisulfide, 3,3'-bis(triethoxysilylpropyl) 
trisulfide, 3,3'-bis(tributoxysilylpropyl) disulfide, 
3,3'-bis(trimethoxysilylpropyl) hexasulfide, 
3,3'-bis(trimethoxysilylpropyl) octasulfide, 
3,3'-bis(trioctoxysilylpropyl) tetrasulfide, 
3,3'-bis(trihexoxysilylpropyl) disulfide, 
3,3'-bis(tri-2"-ethylhexoxysilylpropyl) trisulfide, 
3,3'-bis(triisooctoxysilylpropyl) tetrasulfide, 
3,3'-bis(tri-t-butoxysilylpropyl) disulfide, 2,2'-bis(methoxy diethoxy 
silyl ethyl) tetrasulfide, 2,2'-bis(tripropoxysilylethyl) pentasulfide, 
3,3'-bis(tricyclonexoxysilylpropyl) tetrasulfide, 
3,3'-bis(tricyclopentoxysilylpropyl) trisulfide, 
2,2'-bis(tri-2"-methylcyclohexoxysilylethyl) tetrasulfide, 
bis(trimethoxysilylmethyl) tetrasulfide, 3-methoxy ethoxy propoxysilyl 
3'-diethoxybutoxy-silylpropyltetrasulfide, 2,2'-bis(dimethyl 
methoxysilylethyl) disulfide, 2,2'-bis(dimethyl sec.butoxysilylethyl) 
trisulfide, 3,3'-bis(methyl butylethoxysilylpropyl) tetrasulfide, 
3,3'-bis(di t-butylmethoxysilylpropyl) tetrasulfide, 2,2'-bis(phenyl 
methyl methoxysilylethyl) trisulfide, 3,3'-bis(diphenyl 
isopropoxysilylpropyl) tetrasulfide, 3,3'-bis(diphenyl 
cyclohexoxysilylpropyl) disulfide, 3,3'-bis(dimethyl 
ethylmercaptosilylpropyl) tetrasulfide, 2,2'-bis (methyl 
dimethoxysilylethyl) trisulfide, 2,2'-bis(methyl ethoxypropoxysilylethyl) 
tetrasulfide, 3,3'-bis(diethyl methoxysilylpropyl) tetrasulfide, 
3,3'-bis(ethyl di-sec. butoxysilylpropyl) disulfide, 3,3'-bis(propyl 
diethoxysilylpropyl) disulfide, 3,3'-bis(butyl dimethoxysilylpropyl) 
trisulfide, 3,3'-bis(phenyl dimethoxysilylpropyl) tetrasulfide, 3-phenyl 
ethoxybutoxysilyl 3'-trimethoxysilylpropyl tetrasulfide, 
4,4'-bis(trimethoxysilylbutyl) tetrasulfide, 6,6'-bis(triethoxysilylhexyl) 
tetrasulfide, 12,12'-bis(triisopropoxysilyl dodecyl) disulfide, 
18,18'-bis(trimethoxysilyloctadecyl) tetrasulfide, 
18,18'-bis(tripropoxysilyloctadecenyl) tetrasulfide, 
4,4'-bis(trimethoxysilyl-buten-2-yl) tetrasulfide, 
4,4'-bis(trimethoxysilylcyclohexylene) tetrasulfide, 
5,5'-bis(dimethoxymethylsilylpentyl) trisulfide, 
3,3'-bis(trimethoxysilyl-2-methylpropyl) tetrasulfide, 
3,3'-bis(dimethoxyphenylsilyl-2-methylpropyl) disulfide. 
The preferred sulfur containing organosilicon compounds are the 
3,3'-bis(trimethoxy or triethoxy silylpropyl) sulfides. The most preferred 
compound is 3,3'-bis(triethoxysilylpropyl) tetrasulfide. Therefore as to 
formula I, preferably Z is 
##STR2## 
where R.sup.2 is an alkoxy of 2 to 4 carbon atoms, with 2 carbon atoms 
being particularly preferred; Alk is a divalent hydrocarbon of 2 to 4 
carbon atoms with 3 carbon atoms being particularly preferred; and n is an 
integer of from 3 to 5 with 4 being particularly preferred. 
The amount of the sulfur containing organosilicon compound of formula I in 
a rubber composition will vary depending on the level of silica that is 
used. Generally speaking, the amount of the compound of formula I will 
range from about 0.01 to about 1.0 parts by weight per part by weight of 
the silica. Preferably, the amount will range from about 0.02 to about 0.4 
parts by weight per part by weight of the silica. More preferably the 
amount of the compound of formula I will range from about 0.05 to about 
0.25 parts by weight per part by weight of the silica. 
In addition to the sulfur containing organosilicon, the rubber composition 
should contain a sufficient amount of silica, and carbon black, if used, 
to contribute a reasonably high modulus and high resistance to tear. The 
silica filler may be added in amounts ranging from about 10 phr to about 
250 phr. Preferably, the silica is present in an amount ranging from about 
15 phr to about 80 phr. If carbon black is also present, the amount of 
carbon black, if used, may vary. Generally speaking, the amount of carbon 
black will vary from about 5 phr to about 80 phr. Preferably, the amount 
of carbon black will range from about 10 phr to about 40 phr. It is to be 
appreciated that the silica coupler may be used in conjunction with a 
carbon black, namely pre-mixed with a carbon black prior to addition to 
the rubber composition, and such carbon black is to be included in the 
aforesaid amount of carbon black for the rubber composition formulation. 
In any case, the total quantity of silica and carbon black will be at 
least about 30 phr. The combined weight of the silica and carbon black, as 
hereinbefore referenced, may be as low as about 30 phr, but is preferably 
from about 45 to about 130 phr. 
The commonly employed siliceous pigments used in rubber compounding 
applications can be used as the silica. For instance the silica can 
include pyrogenic and precipitated siliceous pigments (silica), although 
precipitate silicas are preferred. The siliceous pigments preferably 
employed in this invention are precipitated silicas such as, for example, 
those obtained by the acidification of a soluble silicate, e.g., sodium 
silicate. 
Such silicas might be characterized, for example, by having a BET surface 
area, as measured using nitrogen gas, preferably in the range of about 40 
to about 600, and more usually in a range of about 50 to about 300 square 
meters per gram. The BET method of measuring surface area is described in 
the Journal of the American Chemical Society, Volume 60, page 304 (1930). 
The silica may also be typically characterized by having a dibutylphthalate 
(DBP) absorption value in a range of about 100 to about 400, and more 
usually about 150 to about 300. The silica might be expected to have an 
average ultimate particle size, for example, in the range of 0.01 to 0.05 
micron as determined by the electron microscope, although the silica 
particles may be even smaller, or possibly larger, in size. 
Various commercially available silicas may be considered for use in this 
invention such as, only for example herein, and without limitation, 
silicas commercially available from PPG Industries under the Hi-Sil 
trademark with designations 210, 243, etc; silicas available from 
Rhone-Poulenc, with, for example, designations of Z1165MP and Z165GR and 
silicas available from Degussa AG with, for example, designations VN2 and 
VN3. 
Tire tread formulations which include silica and an organosilicon compound 
will typically be mixed utilizing a thermomechanical mixing technique. The 
mixing of the tire tread rubber formulation can be accomplished by methods 
known to those having skill in the rubber mixing art. For example the 
ingredients are typically mixed in at least two stages, namely at least 
one non-productive stage followed by a productive mix stage. The final 
curatives including sulfur vulcanizing agents are typically mixed in the 
final stage which is conventionally called the "productive" mix stage in 
which the mixing typically occurs at a temperature, or ultimate 
temperature, lower than the mix temperature(s) than the preceding 
non-productive mix stage(s). The rubber, silica and sulfur containing 
organosilicon, and carbon black if used, are mixed in one or more 
non-productive mix stages. The terms "non-productive" and "productive" mix 
stages are well known to those having skill in the rubber mixing art. The 
sulfur vulcanizable rubber composition containing the sulfur containing 
organosilicon compound, vulcanizable rubber and generally at least part of 
the silica should be subjected to a thermomechanical mixing step. The 
thermomechanical mixing step generally comprises a mechanical working in a 
mixer or extruder for a period of time suitable in order to produce a 
rubber temperature between 140.degree. C. and 190.degree. C. The 
appropriate duration of the thermomechanical working varies as a function 
of the operating conditions and the volume and nature of the components. 
For example, the thermomechanical working may be for a duration of time 
which is within the range of about 2 minutes to about 20 minutes. It will 
normally be preferred for the rubber to reach a temperature which is 
within the range of about 145.degree. C. to about 180.degree. C. and to be 
maintained at said temperature for a period of time which is within the 
range of about 4 minutes to about 12 minutes. It will normally be more 
preferred for the rubber to reach a temperature which is within the range 
of about 155.degree. C. to about 170.degree. C. and to be maintained at 
said temperature for a period of time which is within the range of about 5 
minutes to about 10 minutes. 
Tire tread compounds made using such polybutadiene rubber blends can be 
used in tire treads in conjunction with ordinary tire manufacturing 
techniques. Tires are built utilizing standard procedures with the 
polybutadiene rubber blend simply being substituted for the rubber 
compounds typically used as the tread rubber. After the tire has been 
built with the polybutadiene rubber containing blend, it can be vulcanized 
using a normal tire cure cycle. Tires made in accordance with this 
invention can be cured over a wide temperature range. However, it is 
generally preferred for the tires to be cured at a temperature ranging 
from about 132.degree. C. (270.degree. F.) to about 166.degree. C. 
(330.degree. F.). It is more typical for the tires of this invention to be 
cured at a temperature ranging from about 143.degree. C. (290.degree. F.) 
to about 154.degree. C. (310.degree. F.). It is generally preferred for 
the cure cycle used to vulcanize the tires to have a duration of about 10 
to about 20 minutes with a cure cycle of about 12 to about 18 minutes 
being most preferred. 
By utilizing such polybutadiene rubber blends in tire tread compounds, 
traction characteristics can be improved without compromising tread wear 
or rolling resistance. Since such polybutadiene rubber blends do not 
contain styrene the cost of raw materials can also be reduced. This is 
because styrene and other vinyl aromatic monomers are expensive relative 
to the cost of 1,3-butadiene.

This invention is illustrated by the following examples which are 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, all parts and percentages are given by 
weight. 
EXAMPLE 1 
In this experiment, 2300 g of a silica/alumina/molecular sieve dried premix 
containing 11.0 weight percent 1,3-butadiene was charged into a one-gallon 
(3.8 liters) reactor. After the impurity of 1.5 ppm was determined, 7.42 
ml of 1M solution of N,N,N',N'-tetramethylethylene diamine (TMEDA) in 
hexanes, 0.21 ml of 1.12M solution of sodium mentholate (SMT) in hexanes 
and 1.1 ml of a 1.03M solution of n-butyllithium (n-BuLi) in hexanes (0.9 
ml for initiation and 0.2 ml for scavenging the premix) were added to the 
reactor. The molar ratio of SMT to TMEDA and to n-BuLi was 0.25:8:1. 
The polymerization was carried out at 65.degree. C. for 10 minutes. The GC 
analysis of the residual monomer contained in the polymerization mixture 
indicated that the polymerization was complete at this time. Then one ml 
of 1M ethanol solution in hexanes was added to shortstop the 
polymerization and polymer was removed from the reactor and stabilized 
with 1 phm of antioxidant. After evaporating hexanes, the resulting 
polymer was dried in a vacuum oven at 50.degree. C. 
The polybutadiene produced was determined to have a glass transition 
temperature (Tg) at -25.degree. C. It was then determined to have a 
microstructure which contained 85 percent 1,2-polybutadiene units and 15 
percent 1,4-polybutadiene units. The Mooney ML-4 viscosity at 100.degree. 
C. was 83 for this polybutadiene. 
EXAMPLES 2-8 
The procedure described in Example 1 was utilized in these examples except 
that the SMT/TMEDA/n-BuLi ratio was varied. The Tgs and ML-4s of the 
resulting polybutadienes are listed in Table I. 
TABLE I 
______________________________________ 
Example SMT/TMEDS/n-BuLi Ratio 
Tg (.degree. C.) 
ML-4 
______________________________________ 
1 0.25:8:1 -25.4 83 
2 0.25:5:1 -26.9 81 
3 0.25:3:1 -28.9 87 
4 0.25:1:1 -35.6 88 
5 0.25:0.5:1 -49.2 88 
6 0.15:3:1 -26.9 
7 0.5:3:1 -26.5 81 
8 1:3:1 -26.1 
______________________________________ 
EXAMPLE 9 
The procedure described in Example 1 was utilized in this example except 
that isoprene was used as the monomer and the SMT/TMEDA/BuLi ratio was 
changed to 0.5:3:1. It took about 20 minutes to complete the 
polymerization. The polymer was determined to have a Tg at -2.degree. C. 
and a ML-4 of 60 at 100.degree. C. 
EXAMPLES 10-13 
The procedure described in Example 1 was utilized in these examples except 
for the fact that a mixture of styrene and 1,3-butadiene in hexane was 
employed as the monomer solution and that the SMT/TMEDA/n-BuLi ratio was 
varied as shown in Table II. The polymerization temperature was also 
changed to 90.degree. C. The glass transition temperatures of the 
resulting styrene-butadiene rubber (SBR) and the time required to complete 
the polymerization are also shown in Table II. The styrene sequence 
distributions in all of the SBR produced was random. 
TABLE II 
______________________________________ 
Example 
S:Bd SMT/TMEDA/n-BuLi 
Tg (.degree. C.) 
Time 
______________________________________ 
10 40:60 0.25:2:1 -19 5 min. 
11 45:55 0.25:2:1 -8 4 min. 
12 50:50 0.25:2:1 +5 2 min. 
13 60:40 0.25:2:1 -14 3 min. 
______________________________________ 
EXAMPLES 14-18 
The procedure described in Example 1 was utilized in these examples except 
that a mixture of styrene and 1,3-butadiene in hexanes was used as the 
monomer solution and the SMT alone was used as the modifier. The 
polymerization temperature was also changed to 90.degree. C. The glass 
transition temperatures of the resulting SBR and the time required to 
complete the polymerizations are listed in Table III. The sequence 
distributions of all of the SBR samples made was again random. 
TABLE III 
______________________________________ 
Example S:Bd SMT/n-BuLi Tg (.degree. C.) 
Time 
______________________________________ 
14 10:90 0.2:1 -72 15 min. 
15 15:85 0.2:1 -63 25 min. 
16 20:80 0.2:1 -65 15 min. 
17 25:75 0.2:1 -54 20 min. 
18 20:80 0.15:1 -80 40 min. 
______________________________________ 
Variations in the present invention are possible in light of the 
description of it provided herein. It is, therefore, to be understood that 
changes can be made in the particular embodiments described which will be 
within the full intended scope of the invention as defined by the 
following appended claims.