Process for producing conjugated diolefinic polymers

A process for producing a conjugated diolefinic polymer by polymerizing at least one conjugated diolefin or copolymerizing at least one conjugated diolefin with at least one vinyl aromatic hydrocarbon in a hydrocarbon solvent in the presence of an alfin catalyst and at least one molecular weight regulator selected from the group consisting of (A) unsaturated halohydrocarbons represented by the general formula, RCX .dbd. CYZ, wherein R represents hydrogen, an alkyl group having 1 to 7 carbon atoms, a vinyl group, a phenyl group, a substituted phenyl group, or a halogen atom and X, Y and Z represent independently a hydrogen or halogen atom, at least one of said R, X, Y and Z being a halogen atom, (B) halogenated aromatic hydrocarbons, (C) ethers, polyethers, and acetals and (D) tertiary amines and, if necessary, a dihydro aromatic hydrocarbon, characterized in that said polymerization or copolymerization is effected in the presence of 0.03 to 0.9 mole of water and/or an alcohol per mole of organosodium contained in said alfin catalyst. According to this invention, there is obtained a polymer or copolymer excellent in green strength and processability of the unvulcanized compound and in physical properties of the vulcanizate.

This invention relates to a process for producing conjugated diolefinic 
polymers. More particularly, it relates to a process for producing 
conjugated diolefinic homopolymers or copolymers excellent in green 
strength (tensile strength of the unvulcanized rubber) and processability 
of the unvulcanized compound and also in physical properties of the 
vulcanizate, which is characterized by adding water and/or an alcohol to 
the reaction system in polymerizing conjugated diolefins or copolymerizing 
conjugated diolefins with vinyl aromatic hydrocarbons with an alfin 
catalyst in the presence of (A) an unsaturated halohydrocarbon, (B) a 
halogenated aromatic compound, (C) an ether, a polyether or an acetal or 
(D) a tertiary amine, as the molecular weight regulator. 
It has been well known that a polymer obtained by contacting a conjugated 
diolefin or a mixture of a conjugated diolefin and a vinyl aromatic 
hydrocarbon with an alfin catalyst (hereinafter such a polymer is referred 
to as alfin rubber) is a synthetic rubber excellent in abrasion 
resistance, felxural strength, and tensile strength when vulcanized and 
particularly excellent in green strength, as not seen in other synthetic 
rubbers. Difficulties encountered in processing the alfin rubber, owing to 
its extremely high molecular weight, are being eliminated by the discovery 
of various molecular weight regulators. 
The molecular weight regulators are divided into two broad classes, one 
being hydrocarbon type and the other being compounds containing halogen, 
oxygen or nitrogen atoms. Effective molecular weight regulators of the 
hydrocarbon type are dihydro aromatic hydrocarbons (Japanese Patent 
Publication No. 15,034/62) and 1,4-dienes (U.S. Pat. No. 3,518,238). 
Regulators containing halogen, oxygen, or nitrogen atoms include 
unsaturated halohydrocarbons (U.S. Pat. No. 3,953,409), aromatic 
halogenated compounds (Belgian Pat. No. 706,516), ethers and acetals (U.S. 
Pat. No. 2,841,574), polyethers (Japanese Patent Publication No. 
36,517/70) and tertiary amines (U.S. Pat. No. 2,841,574). 
Of the above molecular weight regulators, those of the hydrocarbon type 
have an advantage of producing a polymer of a high trans-1,4 content 
characteristic of the alfin rubber without causing any change in 
microstructure of the polymer, and the resulting alfin rubber is 
characterized by a high green strength. The alfin rubber thus obtained, 
however, shows disadvantages in processing such as, for example, an 
extremely high rolling temperature. On the other hand, the alfin rubber 
formed by using regulators containing halogen, oxygen or nitrogen atoms in 
characterized in that it has excellent processability and can be processed 
by substantially the same procedures as used in processing customary 
generalpurpose rubbers. However, the use of said regulator results in a 
change in microstructure of the alfin rubber obtained, that is to say, the 
trans-1,4 content is reduced and the vinyl content is increased. Further, 
the green strength of the polymer obtained is low, whereby the feature as 
alfin rubber is weakened. 
The present inventors have made various studies to overcome the 
disadvantages exhibited by the latter class of molecular weight regulators 
and, as a result, have found that when water and/or an alcohol is present 
in the above reaction system, the excessive decrease in molecular weight 
(or Mooney viscosity) is prevented to impart an adequate molecular weight 
to the resulting polymer, and the trans-1,4 content of the polymer is 
increased, whereby a polymer excellent in all of the green strength, 
processability, and physical properties of the vulcanizate is obtained. 
An object of this invention is to provide a process for producing an alfin 
rubber which is excellent in green strength, processability and the 
physical properties of vulcanizate. 
Other objects and advantages of this invention will become apparent from 
the following description. 
According to this invention, there is provided a process for producing a 
conjugated diolefinic polymer by polymerizing at least one conjugated 
diolefin or copolymerizing at least one conjugated diolefin with at least 
one vinyl aromatic hydrocarbon in a hydrocarbon solvent in the presence of 
an alfin catalyst and at least one molecular weight regulator selected 
from the group consisting of (A) unsaturated halohydrocarbons represented 
by the general formula, RCX .dbd. CYZ, wherein R represents hydrogen, an 
alkyl group having 1 to 7 carbon atoms, a vinyl group, a phenyl groups, a 
substituted phenyl group, or a halogen atom and X, Y and Z represent 
independently a hydrogen or halogen atom, at least one of said R, X, Y and 
Z being a halogen atom, (B) halogenated aromatic hydrocarbons, (C) ethers, 
polyethers, and acetals, and (D) tertiary amines and, if necessary, a 
dihydro aromatic hydrocarbon, characterized in that said polymerization or 
copolymerization is effected in the presence of 0.03 to 0.9 mole of water 
and/or an alcohol per mole of organosodium in said alfin catalyst. 
The molecular weight regulators (A) to (D) used in this invention include 
the following examples: 
(A) Examples of the unsaturated halohydrocarbons represented by the general 
formula RCX .dbd. CYZ are, for instance, vinyl chloride, vinyl bromide, 
vinyl iodide, vinyl fluoride, vinylidene chloride, vinylidene fluoride, 
isopropenyl chloride, trichloroethylene, 2-chloro-1-butene, 
.alpha.-chlorostyrene, chloroprene and the like, vinyl chloride and 
vinylidene chloride being particularly preferred. 
(B) Examples of the halogenated aromatic hydrocarbons are, for instance, 
chlorobenzene, bromobenzene, o-dichlorobenzene, m-dichlorobenzene, 
p-dichlorobenzene, o-chlorotoluene, .alpha.-chloronaphthalene and the 
like. 
(C) Examples of the ethers, polyethers, and acetals are, for instance, 
diethyl ether, diisopropyl ether, ethyl butyl ether, methyl benzyl ether, 
ethylene glycol diethyl ether, diethylene glycol dimethyl ether, 
1,1-dimethoxyethane, and benzaldehyde dimethyl acetal. 
(D) Examples of the tertiary amines are, for instance, diethylmethylamine, 
triethylamine, trimethylamine, triisopropylamine, dimethylpropylamine, 
dimethylaniline, and the like. 
The amount of the molecular weight regulator to be used may be such as is 
sufficient to produce a polymer having a desired Mooney viscosity and may 
be varied depending on the type of regulator. The amount of the regulator 
used per 100 g of the monomer is usually 0.01 to 1,000 mM (millimoles) in 
the case of (A), 0.05 to 2,000 mM in the case of (B), 0.01 to 10,000 mM in 
the case of (C), and 0.02 to 10,000 mM in the case of (D). These 
regulators may be used alone or in admixture or in admixture with 
regulators of the hydrocarbon type. As the regulators of the hydrocarbon 
type, dihydro aromatic hydrocarbons are particularly preferred because the 
resultant polymer has excellent physical properties. The dihydro aromatic 
hydrocarbons include, for example, 1,4-dihydrobenzene, 1,2-dihydrobenzene, 
1,4-dihydronaphthalene, 1,2-dihydronaphthalene, dihydrotoluene, 
dihydroxylene, dihydroanthracene, and the like. 
Particularly preferable is a combination of an unsaturated halohydrocarbon 
(A) represented by the general formula RCX .dbd. CYZ, and a halogenated 
aromatic hydrocarbon (B), with a dihydro aromatic hydrocarbon. With the 
above combination no gel is formed and a polymer having a Mooney viscosity 
of about 30 to 70 is readily obtained in a yield as high as 90% or more. 
Moreover, as compared with conventional alfin rubbers, the polymer thus 
obtained is characterized by lower content of both ultrahigh molecular 
weight fraction and low molecular weight fraction, better processability, 
and better and well-balanced physical properties of vulcanizate, such as, 
for example, modulus of elasticity, tensile strength, and elongation. A 
further advantage of the above procedure is that the molecular weight 
regulating effect is constant throughout the initial, intermediate, and 
final stages of polymerization, so that the alfin rubber can be produced 
in a continuous manner. 
According to this invention, in addition to the above-mentioned advantages, 
the use of water or an alcohol together with the molecular weight 
regulators enables a further improvement of the green strength and 
processability of the polymer as well as the physical properties of the 
vulcanizate. 
The water and/or alcohol is added to the reaction system in such an amount 
that the effect can be obtained without causing hindrance of the 
polymerization, and it ranges from 0.03 to 0.9 mole, preferably from 0.05 
to 0.6 mole, per mole of organosodium in the catalyst. If the amount is 
below 0.03 mole, the advantage of this invention cannot be sufficiently 
obtained, while if it exceeds 0.9 mole, polymerization is hindered. 
The alcohol to be added to the reaction system is one represented by the 
general formula, R--OH, wherein R is a saturated or unsaturated aliphatic 
or alicyclic hydrocarbon radical having 1 to 20 carbon atoms. Examples of 
the alcohol are, for instance, methanol, ethanol, isopropanol, n-butanol, 
n-dodecyl alcohol, cyclohexyl alcohol, cyclooctyl alcohol, and the like. 
Of these, methanol, ethanol, isopropanol, and n-butanol are preferred, and 
particularly preferable are isopropanol and n-butanol. 
Since water and/or alcohol is added to the reaction system in this 
invention, it is not necessary to use an anhydrous solvent, and it has an 
economical and an operational effect. Addition of the alcohol can also 
easily be carried out, because the alcohol used in this invention is 
easily soluble in the reaction medium. 
Although the way of adding water and/or an alcohol to the reaction system 
is not critical, it is desirable to add water and/or an alcohol to the 
solvent prior to contacting the catalyst with a monomer or monomers. 
Alternatively, a suitable amount of the hydrocarbon solvent containing a 
large quantity of water and/or an alcohol may be added to the 
polymerization system, or a solvent containing a suitable amount of water 
and/or an alcohol may also be used. 
A typical alfin catalyst used in this invention is a ternary mixture or a 
complex comprising allyl sodium, sodium isopropoxide and sodium chloride, 
formed by reacting in a hydrocarbon solvent with stirring, n-amyl chloride 
with a sodium dispersion and further reacting the resultant n-amyl sodium 
successively with isopropyl alcohol and propylene. 
As known well (e.g. Leo Reich: "Polymerization by Organometallic 
Compounds", pp. 402-430, 1966, Interscience Publishers), the allyl sodium 
may be replaced by benzyl sodium, xylyl sodium, pentenyl sodium, cymyl 
sodium, mesityl sodium, and the like. It is also possible to replace 
isopropoxide by 2-butoxide, 3-pentoxide, cyclopentoxide, cyclobutoxide, 
tert-butoxide, and the like. Further, other alkali metal salts such as 
potassium salts and lithium salts may be used in place of the sodium 
salts. Other alkyl halides such as n-butyl chloride may be used in place 
of n-amyl chloride. The conditions for the preparation of an alfin 
catalyst and the catalyst compositions may, of course, be freely varied 
according to the known techniques. 
The monomers which can be polymerized according to this invention are 
conjugated dienes such as 1,3-butadiene, isoprene, piperylene, 
2,3-dimethyl-1,3-butadiene, and the like. Two or more of these conjugated 
dienes may also be copolymerized. It is also possible to copolymerize 
these conjugated dienes with vinyl aromatic hydrocarbons such as styrene, 
divinylbenzene, .alpha.-methylstyrene, .beta.-methylstyrene, 
3-vinyltoluene, 1-vinylnaphthalene, 2-vinylnaphthalene, p-methoxystyrene, 
p-bromostyrene, and the like. 
Polymerization according to this invention may be carried out in a 
batchwise or continuous manner according to knwon techniques by contacting 
the monomer or monomers with an alfin catalyst in a hydrocarbon solvent in 
the presence of a molecular weight regulator and other additives. The 
polymerization temperature may be varied in a wide range of from about 
-50.degree. to 150.degree. C, preferably from about -20 .degree.to 
80.degree. C. Any reaction pressure sufficient to keep the reactant 
mixture in the liquid phase may be used. It is generally in the range of 1 
to 5 atmospheres. It is desirable to carry out the polymerization under an 
atmosphere of an inactive gas such as argon, helium, or nitrogen. 
The catalyst is used in an amount of about 0.1 to about 100 millimoles in 
terms of organosodium per 100 g of the monomer. The weight ratio of 
hydrocarbon solvent to monomer is roughly 1 : 1 to 100 : 1. 
As the hydrocarbon solvent, there may be used aliphatic hydrocarbons, 
alicyclic hydrocarbons, aromatic hydrocarbons, and partially hydrogenated 
aromatic hydrocarbons. Preferable solvents are n-pentane, isopentane, 
n-hexane, n-heptane, n-octane, and isooctane among the aliphatic 
hydrocarbons; cyclohexane and cyclooctane among the alicyclic 
hydrocarbons; benzene, toluene, and xylene among the aromatic 
hydrocarbons; and tetrahydronaphlthalene among the partially hydrogenated 
aromatic hydrocarbons. 
When the polymerization has proceeded to a desired stage, the reaction is 
terminated by adding an excess of water, an alcohol, or other catalyst 
inactivating agents to the reaction mixture. The solvent is then removed 
in a customary manner to obtain the objective polymer or copolymer. Before 
the removal of the solvent, it is desirable to add an antioxidant such as 
phenyl-.beta.-naphthylamine to the reaction mixture. 
The invention is illustrated below in further detail with reference to 
Examples, which are merely by way of illustration and not by way of 
limitation. The alfin catalyst used in the Examples and Comparative 
Examples was prepared in the following manner: 
Into a four-necked flask provided with a stirrer, a reflux condenser, a 
thermometer and an external cooling bath was charged 300 parts of dry 
n-hexane. To the flask was added 23 parts (1.0 gram atom) of finely 
divided sodium (2 .mu. in particle size), and the contents of the flask 
were cooled to -10.degree. C. Thereafter, 53.3 parts (0.5 mole) of dry 
amyl chloride was added gradually with gentle stirring, while maintaining 
the reaction system at -10.degree. C. After the completion of the 
addition, stirring was further continued for about one hour. Then 15 g 
(0.25 mole) of dry isopropyl alcohol was gradually added with stirring, 
and the stirring was continued for an additional 45 minutes. After an 
excess of dry propylene had been introduced into the reaction system, the 
reaction temperature was maintained at -10.degree. C until the propylene 
began to reflux. Then, the temperature was gradually elevated until it 
finally reached 25.degree. C. After the reaction system had been kept at 
this temperature for about 2 hours while being stirred, the excess 
propylene was removed from the system. To the resulting reaction mixture 
was added dry n-hexane to make a total volume of 800 ml. All the above 
procedures were carried out under a nitrogen atmosphere. 
In the Examples and Comparative Examples, the intrinsic viscosity of the 
polymer was measured in toluene at 30.degree. C by means of a Ubbelohde's 
viscometer. The microstructure of polybutadienes was determined by the 
infrared absorption spectrum method proposed by D. Morero Chim. e Ind., 
41, 758 (1959)!. The styrene content is a styrene-butadiene copolymer was 
determined from the absorbancy at 699 cm.sup.-1 in infrared absorption 
spectrum according to the base line method. 
The Mooney viscosity of the polymer was measured in accordance with the 
testing method specified in Japanese Industrial Standard (JIS) K 6300under 
the following conditions: dies with square grooves; speed of rotor, 2 rpm; 
type of rotor, L (large size); warm-up time, 1 minute; running time of 
rotor, 4 minutes; temperature of test, 100.degree. C. Accordingly, the 
viscosity value was given under the designation of ML .sub.1+4 
(100.degree. C). 
The water content in the polymerization system was determined by means of 
Karl Fischer's apparatus for measuring water content. 
COMATIVE EXAMPLE 1 
Into a 5-liter autoclave, after the air therein has been thoroughly 
replaced by high-purity nitrogen, were introduced 2,250 g of dry 
cyclohexane, 41 millimoles of 1,4-dihydronaphthalene, and 25 g of styrene 
through an inlet at the top of the autoclave. The autoclave was closed and 
the stirring was started. Immediately thereafter, 225 g of liquid 
butadiene was introduced under pressure into the autoclave through a 
rubber packing at the bottom. After the temperature had been adjusted to 
40.degree. C, 51 ml of an alfin catalyst (containing 0.3 millimole of 
allyl sodium in 1 ml) was introduced under pressure into the autoclave 
through the rubber packing at the bottom and the reaction was allowed to 
proceed for 3 hours with stirring. On analysis, the reaction mixture was 
found to contain 0.024 mole of water per mole of allyl sodium in the 
catalyst, although no water had been intentionally added. After the 
completion of the reaction, the contents of the autoclave were withdrawn 
from the bottom into another vessel. After the addition of an antioxidant, 
the solvent was removed by steam distillation to obtain a solid polymer in 
the form of white bread crumbs. 
The above solid polymer was washed with water and dried at 40.degree. C 
under reduced pressure for 2 days. The yield of the polymer thus obtained 
was 99 %, and the polymer had the following microstructure: 65% of 
trans-1,4 configuration; 32% of vinyl configuration; and 3% of cis-1,4 
configuration. It contained 10% of combined styrene and had an intrinsic 
viscosity .eta.! of 2.62 dl/g and ML.sub.1+4 (100.degree. C) of 50. These 
data are shown in Run No. 1 in Table 1. 
The same procedure as above was repeated, except that the water content in 
the reaction system was varied by using, as a part of the solvent, 
cyclohexane saturated with water to obtain the results shown in Run No. 2 
in Table 1. 
Table 1 
__________________________________________________________________________ 
Intrinsic 
Water* Combined 
viscosity 
Run 
content 
Yield 
Microstructure (%) 
styrene 
.eta.! 
No. 
(mole) 
(%) Trans 
Vinyl 
Cis (%) (dl/g) 
ML.sub.1+4 (100.degree. C) 
__________________________________________________________________________ 
1 0.024 
99 65 32 3 10 2.62 50 
2 0.221 
96 66 31 3 10 2.66 53 
__________________________________________________________________________ 
Note: *Water content is the amount of water contained in the reaction 
mixture, in moles per mole of allyl sodium in the catalyst (the same 
applies hereinafter).