Addition of monomer in production of liquid polymers

Incremental addition of a monomer to be polymerized or copolymerized in a reaction medium comprising an alkyl aromatic, an organic lithium compound, and a transmetallation compound is effected to obtain liquid polymers and/or copolymers of narrow molecular weight range distribution suitable for conversion to lubricating oil as by hydrogenation. A conjugated diene, e.g., butadiene, alone, or together with a vinyl aromatic, e.g., styrene, is added incrementally to permit substantially complete reaction of at least the incrementally added monomer(s) and transmetallation to occur from living polymer to the alkyl aromatic in the reaction mass before addition of a succeeding increment.

BRIEF SUMMARY OF THE INVENTION 
Oligomerization and/or cooligomerization are effected under conditions 
permitting polymerization to proceed at a rate much faster than 
transmetallation rate, e.g., addition of a plurality of small monomer, 
e.g., diene and/or vinyl aromatic, increments, seriatim, with use of high 
organolithium compound/conjugated diene ratios, thus obtained, and 
relatively low temperatures with time between addition of increments to 
permit substantially complete conversion of the added monomer and complete 
transmetallation from a living polymer to alkyl aromatic present in the 
reaction mass. The products are useful in production of lubricants, e.g., 
lubricating oils, as by their hydrogenation. 
DETAILED DESCRIPTION 
This invention relates to the production of a liquid polymer. In one of its 
aspects the invention relates to the production of a liquid polydiene, 
e.g., polybutadiene. In another of its aspects it relates to production of 
a liquid copolymer of a conjugated diene and a vinyl aromatic. In a more 
specific aspect the invention relates to the production of liquid 
polybutadiene, oligomer, or a liquid cooligomer of, say, butadiene and 
styrene. 
In one of its concepts the invention provides a process for the production 
of a liquid polydiene which comprises bringing into presence of an 
initiator for an oligomerization reaction, e.g., an organolithium 
compound, and a solvent, e.g., an alkyl-substituted aromatic hydrocarbon, 
successive increments of a conjugated diene, injecting the increments in a 
short time with good mixing or stirring and allowing time between addition 
of increments sufficient to permit substantially the complete conversion 
of the diene and complete transmetallation from the living oligomers 
formed to the alkyl aromatic. In another of its concepts, in a preferred 
sequence, the reactants are added to the reaction vessel in the following 
sequence: solvent, transmetallation compound(s), the first increment of 
conjugated diene, and finally the organolithium compound. In a further 
concept, next preferred, the sequence is: solvent, transmetallation 
compound(s), organolithium compound, and finally the first increment of 
the conjugated diene. In another of its concepts the invention provides, 
as described herein, a process for the production of liquid cooligomers as 
from a conjugated diene, e.g., butadiene and a vinyl aromatic, e.g., 
styrene, by adding separately or together increments of at least one, but 
preferably of both monomers, also as herein described. 
In U.S. Pat. No. 3,356,754 issued Dec. 5, 1967, Clinton F. Wofford, there 
is disclosed the preparation of liquid polymers by the polymerization of 
conjugated dienes alone or in admixture with another conjugated diene or 
vinyl-substituted aromatic hydrocarbon in the presence of a catalyst 
formed on mixing an organolithium compound and an organic compound of an 
alkali metal selected from the group consisting of potassium, rubidium, 
and cesium together with at least 30 wt.% of a diluent employed being an 
alkyl-substituted aromatic hydrocarbon. The disclosure of the patent is 
incorporated herein by reference. 
The present invention deals with polymerization of a conjugated diene and a 
conjugated diene with a vinyl aromatic by means of an initiator in the 
presence of a solvent that is involved in the chain transfer. 
Suitable solvents are those disclosed in the patent. Included are the 
solvents: 
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toluene 1,4-di-n-propylbenzene 
xylenes 1,4-dimethyl-3-isopropylbenzene 
1,2,3-trimethylbenzene 
1-ethyl-2,5-di-n-propylbenzene 
1,2,4-trimethylbenzene 
tert-butylbenzene 
1,3,5-trimethylbenzene 
n-butylbenzene 
1,2,4,5-tetramethylbenzene 
1,3-di-n-butylbenzene 
1-methyl-2-ethylbenzene 
n-amylbenzene 
2,4-diethylbenzene 
1-(n-amyl)-2-isopropylbenzene 
ethylbenzene 1,2-dimethyl-4-(n-hexyl)benzene 
isopropylbenzene 
n-octylbenzene 
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The initiator for the oligomerization or cooligomerization reaction is an 
organolithium compound or a composition made by mixing (1) an 
organolithium compound and (2) transmetallation compounds comprising an 
organic compound of sodium, potassium, rubidium, or cesium and/or an 
aliphatic tertiary amine. 
Examples of organolithium compounds are given in the patent and included 
are: 
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methyllithium 1,4-dilithiobutane 
isopropyllithium 
1,10-dilithiodecane 
n-butyllithium 1,20-dilithioeicosane 
sec-butyllithium 
1,4-dilithiocyclohexane 
tert-octyllithium 
1,4-dilithio-2-butene 
n-decyllithium 1,8-dilithio-3-decene 
phenyllithium 1,4-dilithiobenzene 
naphthyllithium 1,2-dilithio-1,2-diphenylethane 
4-butylphenyllithium 
1,2-dilithio-1,8-diphenyloctane 
p-tolyllithium 1,3,5-trilithiopentane 
4-phenylbutyllithium 
1,5,15-trilithioeicosane 
cyclohexyllithium 
1,3,5-trilithiocyclohexane 
4-butylcyclohexyllithium 
1,3,5,8-tetralithiodecane 
4-cyclohexylbutyllithium 
1,5,10,20-tetralithioeicosane 
dilithiomethane 1,2,4,6-tetralithiocyclohexane 
4,4'-dilithiobiphenyl 
and the like. 
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Examples of organic compounds of the alkali metals noted are also listed in 
the patent and included are all of those given in the patent in column 3, 
lines 13 to column 4, line 67. These compounds are not here repeated. 
These compounds do not form any part of the essence of the present 
invention but to the extent involved have been herein incorporated by 
reference. 
Examples of tertiary amines are trimethylamine, triisopropylamine, and 
ditertiary amines such as N,N,N',N',-tetramethylethylenediamine (TMEDA) 
and 1-dimethylamino-2-ethoxyethane. 
Conjugated dienes that can be used in the oligomerization reaction contain 
from 4 to 10 carbon atoms and include 1,3-butadiene, isoprene, 
1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, 2-methyl-1,3-pentadiene, 
2,3-dimethyl-1,3-pentadiene, and 2-phenyl-1,3-butadiene. 
Vinyl-substituted aromatics which can be used in the cooligomerization of 
the invention include styrene, and alpha-methylstyrene. 
The liquid oligomers made according to the instant invention have molecular 
weights that lie substantially in the range that is suitable for 
conversion to lubricating oil, i.e., they contain from about 24 to about 
44 carbon atoms and have a normal boiling point in the approximate range 
of from about 380.degree. to 550.degree. C. 
The cooligomers of the invention, similarly, can be produced to have 
molecular weights in the range rendering them suitable for producing 
lubricating oils. These, usually, will contain 23 to 43 carbon atoms and 
will boil in the approximate range of from about 390.degree. to about 
550.degree. C. 
Reaction Conditions 
The polymerizations of this invention can be carried out at any temperature 
within the range of about -20.degree. to 120.degree. C.; but preferably 
the temperature will be in the range of from about 50.degree. to about 
90.degree. C. 
It is desirable for the reactants to be substantially in the liquid phase. 
Accordingly the reaction can be carried out at autogenous pressure. 
Neither the reaction rate nor the product of reaction appear to be changed 
significantly by raising the pressure above the vapor pressure of the 
monomeric conjugated diene at reaction temperature. 
The process of this invention is carried out by the incremental addition of 
monomeric conjugated diene and/or vinyl aromatic to a reaction zone that 
contains solvent and initiator. 
One skilled in the art in possession of this disclosure having studied the 
same, will be able to determine by routine test of the products obtained, 
the parameters or conditions of the reaction and of the amount or amounts 
of the increments to be added for optimum results, as well as whatever may 
be their order of addition when several monomers are used. To the extent 
that any monomer is added increment-wise and a time allowed for the extent 
of transmetallation desired to occur the basic concept of the invention is 
practiced. Thus, so long as a monomer addition is carefully controlled in 
increment size, time of addition, and the time at which it is added and 
during which it is added, there will result in inventive extent of control 
of the reaction, as desired. 
Presently, as indicated in the data herein, the increment-wise addition is 
preferred now to be practiced as therein given. 
The solvent as stated above is an alkyl-substituted aromatic hydrocarbon. 
It can be used undiluted or it can contain up to 50 weight percent of 
aliphatic and naphthenic hydrocarbons that are inert to the polymerization 
reaction. Examples of these diluents are isomeric butanes and pentanes, 
n-hexane, cyclohexane, methylcyclopentane, isooctane, and the like. 
Polymerization can be started by combining reactants (but only a fraction 
of the conjugated diene) in any sequence. It is preferred, however, to add 
reactants to the reaction vessel in the following sequence: solvent, 
transmetallation compound(s), the first increment of conjugated diene (see 
below), finally the organolithium compound. Next preferred is the sequence 
solvent, transmetallation compounds, organolithium compound, finally the 
first increment of conjugated diene. 
Because approximately one mole of the alkyl-substituted aromatic 
hydrocarbon solvent is incorporated chemically into each mole of liquid 
polymer produced, the quantity of said aromatic solvent to be taken cannot 
be less than the product of the number of moles of organolithium compound 
times the number of increments of monomer to be added; preferably a 
substantially larger quantity of the aromatic solvent will be used. 
The quantity of organolithium compound to be used to make a run is not less 
than one gram equivalent per 1000 moles of conjugated diene, preferably 
one gram equivalent of organolithium compound per 400 moles of conjugated 
diene to be reacted is taken. As stated, the diene is added incrementally 
to the oligomerization zone. The quantity to be reacted is added in at 
least ten approximately equal portions; it can be divided into as many as 
200 portions or even more. 
Polymerization initiator is prepared by combination of organolithium 
compound with a transmetallation compound such as an organic compound of 
sodium, potassium, rubidium, or cesium and/or an aliphatic tertiary amine. 
Per equivalent of organolithium compound the moles of the two 
transmetallation compounds, respectively, to be taken can range from 
0.01-3 and 0.01-6. The preferable concentration of the two 
transmetallation compounds, respectively, per equivalent of organolithium 
compound is 0.05-1 and 0.05-2. 
With process conditions as herein defined the polymerizations of this 
invention are effected under conditions that permit the conjugated diene 
polymerization rate to proceed at a rate that is much faster than the 
transmetallation rate. This is favored by the use of high organolithium 
compound; conjugated diene ratios, i.e., the addition of small diene 
increments, and by the use of relatively low temperatures. Thus it is 
desirable to inject the diene increments in a very short time and to mix 
(stir) the mixture well. The time between the addition of increments 
should be long enough to permit essentially complete conversion of the 
monomeric diene, and any vinyl aromatic present, and complete 
transmetallation from the living oligomers to the alkyl aromatic. 
Generally this will be about 3 to 20 minutes, or longer. 
The desired polymeric product of this invention can be recognized by a plot 
of its molecular weight distribution which will be symmetrical and narrow. 
Temperatures that are too high will produce polymers whose average 
molecular weight is too low; temperatures which are too low will produce 
oligomers or polymers whose average molecular weight is too high; the 
presence of an insufficient concentration of organolithium will produce a 
molecular weight distribution of increasing width.

EXAMPLE I 
The following examples illustrate this invention. Table I summarizes the 
oligomerization recipes and reaction conditions for four runs. Runs 1 and 
2 were made in a 300 mL autoclave, run 3 was made in a one-liter autoclave 
and run 4 was made in a one-gallon (3.8 liters) autoclave. Each run was 
made by adding to the dry, oxygen-free autoclave the toluene solvent, the 
transmetallation compound(s) dissolved in hexane, and incremental charge 
of butadiene, and finally the n-butyllithium dissolved in hexane. The run 
continued with the batch-wise addition of butadiene. In runs 1 and 2 it 
was added to the autoclave from stainless steel bombs pressurized with 
nitrogen gas. In runs 3 and 4 it was added with a positive displacement 
pump that was run intermittently during the polymerization. At the 
conclusion of each run the reactor was cooled in an ice bath, the contents 
were mixed with about one fourth to one half their volume of 2 N acetic 
acid to deactivate the initiator, washed with water, dried over a 
desiccant, and hydrogenated catalytically over palladium on carbon 
catalyst. Solvent was removed by distillation and the hydrogenated 
butadiene oligomer was distilled (under reduced pressure when necessary) 
through a Vigreux column to obtain the distillation analysis given in 
Table I. Run 1 is not considered to be a part of this invention; only five 
increments of butadiene were added. 
TABLE I 
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Comparison 
Invention 
Invention 
Invention 
Run 1 2 3 4 
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Reactants 
Hexane, mL 51 12 15 18 
Toluene, mL 90 120 300 1295 
Butadiene (total), g 55.8 72.7 160.6 
730.6 
n-Butyllithium, mmoles 25.2 11.6 10.5 34.0 
K tert-amyl oxide, mmoles 0 0 0 8.5 
TMEDA, mmoles 25.2 11.6 21.0 34.0 
Polymerization Conditions 
Temperature, .degree.C. 120 113 93 60 
No. of increments 5 14 45 80 
Time between increments, min. 
20 12.4 5.1 3.5 
Distillation Analysis of Hydrogenated Oligomer, Wt. % 
Lights (C.sub.11 -C.sub.22) 
18.7 18.2 8.3 10.3 
Lube Oil (C.sub.23 -C.sub.43) 
69.9 72.7 89.7 83.1 
Heavies (&gt;C.sub.43) 11.5 9.1 2.0 6.6 
Properties of Lube Oil Fraction 
Boiling range, .degree.C. 370-529 
392-535 
380-530 
380-545 
Phenyl groups/molecule (NMR) 
-- -- -- 0.57 
Methyl groups/butadiene conv. (NMR) 
-- -- -- 0.79 
Viscosity at 100.degree. F., SUS 
375 153.7 
184 269 
Viscosity at 210.degree. F., SUS 
53.9 43.1 45.3 51.8 
Viscosity index 81 93 96 99 
Pour Point, .degree.C. -25 -30 -40 -34 
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EXAMPLE II 
Preparation of liquid polymer by cooligomerization of butadiene and styrene 
is illustrated in this example. Through a port in a dry, nitrogen-purged 
1-liter autoclave 240 mL of toluene, 5.27 mL of a 2.54 molar solution of 
TMEDA in toluene and 13.7 mL of a 0.244 molar solution of potassium 
tert-amyl oxide in toluene were placed. The autoclave was evacuated three 
times, with the vacuum being released each time with dry nitrogen to 
insure removal of all oxygen. A 2.89 mL increment of a 50:50 (weight) 
mixture of butadiene-styrene was added, then 8.65 mL of 1.55 molar 
n-butyllithium in hexane. Forty-five additional increments of 
butadiene-styrene of the same size were added by pump that operated for 15 
seconds, then was off for 3 minutes. Temperature of the reaction mixture 
during the addition ranged from 57.degree.-71.degree. C. At the conclusion 
of the oligomerization reaction the autoclave was cooled to about 
25.degree. C. and catalyst was deactivated by the addition of 50 mL of 2 N 
aqueous acetic acid. The product was washed with water and dried over 
anhydrous MgSO.sub.4. Toluene solvent was removed on a rotary evaporator 
and the oligomer, diluted with 50 mL of hexane, was placed in an autoclave 
together with 0.5 g of 5% Pt on carbon hydrogenation catalyst. It was 
hydrogenated for about 3 hours at 160.degree. C., with stirring, under 
425-475 psig hydrogen pressure. Hydrogenated oil was rinsed from the 
autoclave with hexane which was then removed on a rotary evaporator. The 
oil was distilled through a Vigreux column at reduced pressure and the 
fraction boiling between 383.degree.-525.degree. C. (corrected) was 
tested. This fraction comprised 91.5 wt.% of the liquid polymer. It had 
the following properties: 
Viscosity at 40.degree. C., SUS: 120.3 
Viscosity at 100.degree. C., SUS: 40.8 
Viscosity index: 75 
Pour point, .degree.C.: -45 
Accordingly, it is an object of the present invention to provide an 
oligomer or cooligomer-containing product having a relatively narrow 
molecular weight distribution which is symmetrical and narrow. In another 
object of the invention to control an oligomerization or cooligomerization 
reaction to form a polymeric product having a high yield in the 
lubricating oil molecular weight range. 
Other aspects, concepts, objects, and the several advantages of the 
invention are apparent from a study of this disclosure and the appended 
claims. 
According to the present invention, polymerization of a conjugated diene or 
such a diene and a vinyl aromatic is effected in a reaction medium to 
which at least the conjugated diene is added in a number of increments 
which are relatively small; the increments are added in a short time under 
good mixing conditions and the time between addition of the increments is 
sufficiently long to permit substantially the complete conversion of at 
least the diene and essentially or substantially the complete 
transmetallation from living polymer to the alkyl aromatic which is 
present. 
In a now preferred form of the invention, the quantity of diene or monomer 
ultimately to have been added is divided into at least 10 portions, 
preferably approximately equal portions, each portion forming an increment 
to be added according to the invention. More preferably, according to the 
invention, the diene or monomers to be reacted are divided into as many as 
200 portions or even more to permit, ultimately, the obtaining of the 
desired product, herein described. The addition time for each increment 
can be varied. Initial increments may be added over a shorter time than 
later-added increments. Depending upon reaction conditions and the 
condition of the reaction mass, the time allowed or to be allowed for the 
transmetallation can also be varied. One skilled in the polymerization 
art, having studied this disclosure can determine the optimum conditions, 
increment sizes and their rates and times of addition by performing 
simple, routine tests. 
In U.S. Pat. No. 3,751,501 issued Aug. 7, 1973, it is described, in column 
5 in lines 15 et seq, that the conjugated diene monomer is to be added in 
a gradual and controlled manner. The present invention is to be 
distinguished sharply from such addition. The gradual and controlled 
manner addition described in column 5 in the paragraph beginning in line 
16 of the patent is also herein noted and is to be distinguished from the 
manner of addition, increment-wise, of the present invention. The present 
invention critically provides the time for transmetallation to occur. This 
cannot be the case with continuous or even continual addition unless 
prescribed as in the present disclosure. 
Reasonable variation and modification are possible within the scope of the 
foregoing disclosure and the appended claims to the invention the essence 
of which is that in the polymerization of at least one monomer, say, a 
conjugated diene and/or a vinyl aromatic, the monomer is added 
increment-wise, each increment being relatively small and the time between 
addition of each monomer added increment-wise being sufficient to allow 
for substantially complete conversion of the added monomer and 
substantially complete transmetallation from living polymer formed to the 
alkyl aromatic which is present.