METHOD FOR THE POLYMERIZATION OF COMPOUNDS HAVING A SYSTEM OF CONJUGATED DOUBLE BONDS

PROCEDE DE POLYMERISATION DE COMPOSES AYANT UN SYSTEME DE LIENS DOUBLES CONJUGUES

English Abstract

ABSTRACT OF THE DISCLOSURE :
The present invention is directed to a method for poly-
merizating a compound containing at least one non-aromatic
system of conjugated carbon-carbon double bonds, which rom-
prises contacting the monomer with, as sole catalyst, a com-
pound produced by the reaction in an ethereal solvent of
equimolar quantities of sodium and an ethylenic compound having
the formula :
<IMG>
wherein each of R1, R2, R3 and R4, which can be the same or
different, is a hydrogen atom or an alkyl, aryl, aralkyl or
alkaryl radical, with the proviso that at least one of R1, R2,
R3 and R4 is selected from aryl, aralkyl and alkaryl radicals.

Claims

The embodiments of the invention in which an
exclusive property or privilege is claimed are defined as
follows:-
1. A method for polymerizing a compound con-
taining at least one non-aromatic system of conjugated carbon-
carbon double bonds, which comprises contacting the monomer with,
as sole catalyst, a compound produced by the reaction in an
ethereal solvent of equimolar quantities of sodium and an
ethylenic compound having the formula:
<IMG>
wherein each of R1, R2, R3 and R4, which can be the same or dif-
ferent, is a hydrogen atom or an alkyl, aryl, aralkyl or alkaryl
radical, with the proviso that at least one of R1, R2, R3 and
R4 is selected from aryl, aralkyl and alkaryl radicals.
2. A method according to claim 1, wherein at
least two of R1, R2, R3 and R4 are selected from aryl, aralkyl
and alkaryl radicals.
3. A method according to claim 1 or 2, wherein
the ethylenic compound is stilbene, tetraphenylethylene,
1,1-diphenylethylene or 1,1,2-triphenylethylene.
4, A method according to claim 1, wherein the
interaction between the sodium and the ethylenic compound takes
place at a temperature in the range from -78°C to +70°C.

5. A method according to claim 4, wherein the
temperature of the interaction is in the range from 0°C to +30°C.
6. A method according to claim 1, 2 or 4,
wherein the interaction between the sodium and the ethylenic
compound takes place in the presence of a solvent selected from
tetrahydrofuran (THF), methyltetrahydrofuran, dioxane, diethyl
ether, dimethyl ether, dibutyl ether, diethylene glycol-diethyl
ether, diethylene glycol-dimethyl ether, or admixtures of any two
or more thereof.
7. A method according to claim 1, wherein the
polymerization is carried out at a temperature in the range from
-50°C to +100°C.
8. A method according to claim 1, wherein the
polymerization is carried out under a pressure of at least
atmospheric pressure.
9. A method according to claim 1, 7 or 8,
wherein the polymerization is carried out in the presence of a
solvent selected from polar compounds or mixtures of aliphatic,
cycloaliphatic or aromatic compounds with polar compounds.
10. A method according to claim 1, wherein the
monomer to be polymerized is butadiene, isoprene, piperylene,
a C4 - C5 fraction of compounds containing at least one system of
conjugated carbon-carbon double bonds or a mixture of two or more
thereof.

Description

This lnvention re~late~ to a rne~hod for poly-
merizing a compound containing at least one non-aromatic system
of conjuc3ated carbon-carbon double bonds, which comprises con-
tacting the mo~omer with, as sole catalyst, a compound produced
by the xeaction in an ethereal solvent of equinolar quantities
of sodium and an ethylenic compound having the formula
Rl ~ / R4
C = C
R / \ R3
wherein each of Rl, R2, R3 and R4, which can be the same or dif~
ferent, is a hydrogen atom or an alkyl, aryl, aralkyl or alkaryl
radical, with the proviso that at least one of Rl, R2, R3 and
R i5 selected from aryl, aralkyl and alkaryl radicals or an
alkyl radical.
It is known from US Patent Speciication 3.177.190
to use a catalyst system composed by organic derivatlves of lith-
ium (lithium-isoprenyl) or by adducts o such derivatives with
cycloaliphatic or aromatic molecules (such as Li-isobutyl, and
the dilithiumstilbene-dimethylbutadiene adduat) to pxepare
polymers having reactive termlnal yroups.
It is likewise known (Die Makromolekulare Chemie,
92 (1966), pages 180-197) that is is possible to employ composi-
tions of the kind referred to hereinabove in the polymerization
of a few monovinyl monomers, such as acrylonitrile, styrene,
methylmetacrylate, in which electron-attractlng groups are con-
tained.
We have now found, and this is the subject
matter of this invention, that it is possible to polymerize
-- 2 -- ...
L~ ~

compounds which contain at least one system o conjugatea double
bonds in the presence of a catalys-t system composed by the prod-
uct of interaction of an alkali metal with organic substrates
as defined hereinabove. This fact is actually surprising, since
it is contrary to the expectations to which the above scientific
papers would lead and more particularly it is against the first
paper cited above ln which the a~kali metal is employed in the
form o~ an alkyl or alkenyl derivative.
A particularly advantageous embodiment of the
present invention is a methvd as outlined above in which the
alkali metal is sodlum, which is not too expensive and readily
available as compared with the other alkali metals, and the
organic compound is selected from among stilbene, tetraphenyl-
ethylene, l,l-diphenylethylene, 1,1,2-triphenylethylene and so
forth.
It is obvious, anyhow, that the extension to
the other alkali metals is obviously feasible and that anyone
skilled in the art will meet with no dlficulty in selecting the
catalyst couple which is the most suitable ~7ithout ~hereby de~
parting from the scope of the present invention.
The interaction reaction between Na and the
organic compound takes place between -78C and ~70C~ prefer-
ably at a ternperature from 0C to ~30C in polar solvents and
preferably in THFj methyl-THF, dioxane, diethyl ether, dimethyl
ether, dibutyl ether, diethylene glycol-diethyl ether, diethylene
glycol-dimethyl ether or admixtures of any two or more thereof.
The product of this reaction can be used as such
in the polymerization mixture, possibly together with other sol-
vents, in order to obtain particular effects on the molecular
B

weight and/or on-~el~crostructure.
Such a polymeriæation is preerably carxled ou~
at a temperature comprised be~ween -50C and -~lOO~C, under a
pressure which can be varied from atmospherical pres5ure to the
pressure which is proper o the monomer-solvent system.
i
More particularly, the polymerization solvent
can be selected from among the polar compounds and the mixtures
of allphatic; or cycloaliphatic., or aromatic compounds with
such polar compounds.
The monomers which can be polymerized according
to the method of this invention are those which contain at least
one system of conjugated double honds, such as butadiene,
p~-el~e
piperylene, C - C
4 5 fraction and, lastly, mixtures
of monomers . - ~
.. . .. ., _ ~ _ . . ..
.. _ .. ..... .. . _ . .. ..
.___ . .
B

of the diolefinconjugated type.
As cornpared with khe conventiorlal polymerization
methods and more par-ticularly with Na naphthalene, the
method according to the present invention permits -to achieve
a few undeniable advantages such as:
a) an improved stability of khe catalyst in time (the
Na-stilbene system is stable for a few days at room
temperature) and at temperatures up to 60C - 70C.
b) Higher polymer yields with the same quantity of
alkali metal contained in the initiator, the other
pol~nerization parameters belng equal (a mol
percent of catalyst relative to the monomer,
variable from 0.1% to 5% is generally sufficient)~
c) Shorter polymerization times for obtaining a
complete converslon (from 10 minutes to one hour,
the other parameters being equ~
d) A wider versatility of the catalyst system in regula-
ting the molecular weight (according to the type of
solvent which is used,) there are obtained oligomer~
with a mol~ wt. Erorn 500 to 2,000 iE one worlc~ in
toluene or polyme~rs having a high rnolecular weight,
~OC
(~ tx ~ 0.5) if one works in THF - Intermed:iate
viscosity values are obtained by operating with
mixtures of the two solvents.
e) Possibility of controlling the microstructure of
the pol~ner obtained and moré particularly the
possibility of obtaining high contents of 1,2- in the
case of -the polybutadiene, and high 3,4- in the
case of polyisoprenes. The vinyl-addition contents
can be varied, however, according to the nature of
the solvent and consistently with the in-tended
practical uses.
.,

EXAMPLE 1
A) q~e pol~merization catalyst is prepared by reacting
10 mill:imols of stilbene with a stuichiometrical quantit,y Oe
Na and sand in 70 mls of THF and by keeping the reac-tion
mixture stirred at 25C for 5 hours. The mixture is then
filtered and titrated. The yield relative to the reacted Na
is 95%.
B) 2 mls of the anhydrous solution in THF (0.2 millimol
of catalyst) prepared as specified in A) are placed in a bottle
stoppered with a crown-cap, which bottles has been de-aerated
and nitrogen-purged a-t a tempera-ture of 25C. There are added
18 mls of anhydrous toIuene, the bottle is stoppered and there
are introduced by injection 2.8 grams of butadiene (50 milli-
mols).
After 30 minutes, the polymerization mixture is
treated with a 1/1 solution of water and methanol in a
separatory funnel, the supernatant layer is recovered and
evaporated to dryness.
rrhere are obtained 2.8 grams (yield = 100%) of a
polymer having a liquid consistency (mol.wt. 800) the micro-
structure oE which is as follows:
1, 2- : 84.7% , 1,~- : 15.3% , l,~-cis : 0%
EXAMPLE 2
.
In a bottle equipped with a crown-cap stopper,which
has been de-aerated and purged by nitrogen, there are placed
2 mls of a solution of catalyst in THF (O.2 millimol of
catalyst) prepared as in Example 1 (A~.
rrhere are added 2 mls of THF and 16 mls toluene, the
bottle is sealed and there are introduced by injection 2.8
grams of butadiene (50 millimols). After 30 minutes the
polymerization mixture is trea-ted with a 1/1 solution of
methanol and water in a separatory funnel, the toluene layer

10~
is recovered and evaporated to dryness.
There are obtained 2.8 grarns (yield = 100%) of a
pol~ner having a r~2 73Oolcene = 0.26 and the following
microstructure :
1~2-: 85% i 1~4-: 15% ~ 1,4-CiS: 0%.
EXAMPLE 3
A pol~nerization reac-tor, which has been previously
deaerated and scavenged with nitrogen is charged, a-t -40C~
with . ~ -~~
t

0.2 millimol (calcu~ated relative to Na) of' a solut,lon composed
by the product of interactlon obtalnecl by reaction for 4 hour.g
at -40C of Na and s-tilbene in THF. THF is added until reachiny
a total volume of 20 mls and there are added 2.8 grams of
butadiene (50 millimols).
After 2 hours the polymerization mixture is
treated with CH30H and a polymer is obtained having a ~ ]toluene
= l.l and a microstructure as follows :
1,2- : 87% ; 1,4-cis : 0~ ; 1,4-trans = 13~ .
The yield of solid polymer is 80~.
EXAMPLE 4
.
A de-aerated, nitrogen-scavenged polymerization
bottle having a crown~cap stopper is charged at a temperature of
25~C with 0.2 millimol of the product of interaction of Na and
stilbene, prepared as in Example 1 (A).
There are added 18 mls toluene and 5 mls iso-
prene (50 millimols). The bottle is sealed and stirred. After
2 hours, coagulation of the polymer with methanol is carried out.
There are obtained 2.9 grams of a polymer
~yield = 85%) havlng a / ~ 7t 1 ~ 0.12 and the ~ollowing micro-
structure :
3,4- : 85% ; 1,2~ : 15%.
EXAMPLE 5
A de-aerated. nitrogen-scavenged polymerization
bottle having a crown-cap stopper is charged at a temperature of 25% with
30 milligrams (0.2 millim~l relative to Na) of the interaction product of
Na and stiIbene (1 : l) in dioxane. There are added 10 mls of diethylenegly-
col~methyl ether and, by injection, 2.8 grams of butadiene.
At,er 15 muns. the polym~r is coagulated with methanol.
mere ar,e obtained 2.8 grams of polymer tyield = 100%) having a
= 0.5 and the following microstructure :
1,2- : ~5~ ; 1,4-trans : 15~ .
E~ F 6
A) The Na-tetraphenylet,hylene adduct is prepared by reac-ting
D-
- 6 -

n~J
10 millimols oE tetraphenylethylene with stoichiornetrica]
quan-tities of Na sand ln 80 mls oE aTIhydrous THF and ,stirring
at 25C for 4 hours. The solution is filtered and then ti~
trated~ The yield relative to the reacted Na is 94%. ~ote:
the reaction can be carried out also at -78C with yields
which are comparable to the above, the reaction time being
the same.
B) One millimol of catalyst solution prepared as in A)
is placed in a bot-tle having a crown-cap stopper with a total
volume of 20 mls of THF. The bottle is sealed and 2.8 grams
of butadie~e (50 millimols) are introduced therein by injection.
Aftér two hours the polymerization mixture is coagulated with
methanol. There are obtained 2.8 grams of polybutadiene
30C
(yield = 100%) haviny a /~ tolu~n~ = 0 9 and -the follow-
ing microstructure:
1,2- = 90% , 1,4-trans : 10% ' 1,4-cis : 0%.
EXAMPLE 7
. .
By adopting a high-vacuum technique the Na-stilb~ne
catalyst is prepared in a reactor by reacting in situ 18
mil:Ligrams o~ Na (0.'75 rnill:irrlol) and 64 milligrams of stilbene
(0.35 millimol) in 60 mls of THF during one hour at a tempera~
ture of 25C. There are introduced 2.4 grams of butadiene
(45 millimols) and polymerization is caused to occur during 30
minutes. The mixture is cooled to -78C and there are added
2.2 grams of styrene (21 millimols). The solution is allowed
to stand at room temperature for 10 hours. The mixture is
coagulated from methanol and 4.3 grams of polymer are obtained
(yield 100% of raw polymer). Extraction is carried out for
24 hours with acetone. A polymer is obtained which contains
30% of styrene, expressed in millimols.
- 7 -