Note: Descriptions are shown in the official language in which they were submitted.
2~
This inven-tion relates -to the solution polymerization
of cyclic polychlorophosphazenes represented by the general for-
mula (NPCl2)n in which n is 15 o~ less, usually 3 or 4~ to pro-
duce essentially linear polydichlorophosphazenes in which the
degree of polymerization is selectively controlled within the
range of 20 to 50,000.
The bulk polymerization of low molecular weight cyclic
polydichlorophosphazenes is described i.n United States Patent
3,370,020 issued February 20, 1968 and elsewhere in the lite-
rature. .
.It is also known that the thermal polymerization of
hexachlorocyclophosphazene and octachlorocyclophosphazene can
be effected in the presence of various catalysts as reported in
"phosphorus-Nitrogen Compounds" published 1973 by Interscience
Publishers, New ~ork.
Previous attempts to polymerize cyclic dichlorophos- :
phazenes in solution have resulted in excessive gelation and
the production of unusable products.
It has now been found that instead of controlling the
temperature and other reaction conditions in order to obtain
polymer of a desired molecular weight, it is now possible to ob-
tain products with a desired molecular weight by choice of a
suitable solvent as the reaction medium.
It has also been found that the presence of a small
amount of sulfur either as elemental sulfur or as a sulfur com- `
pound in the solution in the polvmerization mixtures appears to
overcom~ a tendency of the solvents to react with cyclochloro- ~ :
phosphazenes at high tempera-tures Eorming an intractable gel.
It has further been found that the choice o~ solvent
or mixture of solvents significantly affects the molecular weight
of the resulting polymer and that as a consequence polymer of a
desired molecular weight is produced by selecting an appropriate :
.:'
B ~ ~:
~ ~ ~ 5f~
solvent and suitable reaction conditions.
A princip~l object of the present invention is there-
fore to provide a new and improved process for the solution poly-
merization of cyclic dichlorophosphazenes which yields essen~
tially linear polydichlorophosphazene polymers.
Another object of the invention is to provide a solu~
tion polymerization process which can be con~ucted at atmosphe-
ric pressure and at comparatively moderate temperatures and under
a relatively inert and easilY controlled atmosphere.
A further object of the invention is to polymerize cy- ;
clic dich~orophosphazene oligomers to produce linear polydichlo-
rophosphazene polymers exhibiting a unique, very narrow range or
molecular weights, heretofore unobtainable in previously prac
ticed bulk polymerizations.
In accordance with the invention, these and other ob-
jects are achieved by polymerizing solutions comprising cyclic
dichlorophosphazene oligomers dissolved in a liquid solventCha-
Ying a dielectric constant o~ at least two~ in the presence of
about 1 to up to 20 millimoles of elemental sulfur-or sulfur
donating compound per mol of cyclic dichlorophosphazene oligomer.
The solvent is selected so as to be solvent for both the oli-
gomers and the sulfur or sulfur donating compound~and the poly~
merization is conducted'for up to 300 hours at a temperature
between about 140C and 225C in a reactor which may be either
glass lined stainless steel vessels or unlined stainless steel
vessels, or galss vessels. Preferably, the oligomers are dissol-
ved in between about 10% and up to 80% by weight of selected
solvent.
As solvent medium in which the thermal polymerization
of low molecular weight cyclic polydichloroPhosphazenes is con- ~
ducted, use can be made of aromatic hydrocarbon or cyclo-alipha- ~ .
tic hydrocarbon solvent.
-- 3 --
' 'B ,
. . : : '
~5~2~ ~
Suitable hydrocarbon solvents include decalin, tetra-
lin, naphthalene, cyclohexane, toluene, dimethylbenzene, dihy-
droanthracene, tetramethylbenzene, cumene, cymen, mono-, di-,
tri-, tetra- substituted aromatic compounds where the substi-
tuents are straight cahin or branched chain hydrocarbons with
up ~o 10 carbon atoms.
As other solvents, use can also be made of liquids ha- -
ving a dielectric constant of at least two, and which are sol-
vents for both the cyclic dichlorophosphazene starting materials
and for the sulfur or sulfur-donating compound presentas catalysts.
A further solvents suitable for such polymerizations,
use can be made of aromatic compounds carrying polar groups such
as methoxy, N, N-disubstituted amino, halogens particularly mono-,
di-, tri- or tetra-halogen substituents on the aromatic nucleus,
and mixtures of said solvents or other hydrocarbon solvents of
a similar nature.
Still other solvents which have been used-include aro-
matic compounds including those which are monocyclic or polycyclic
and which are either unsubstituted or substituted, especially
~ with polar substituents such as halogen, N,N ' -diakylamino, alkoxy,
and other polar groups. Aromatic solvents with up to four polar
substituents on the aromatic ring have been employed. These
polar substituents can be on the ring or on a side-chain. For
example, the aromatic ring can have either electron withdrawing
groups or electron supplying groups. Examples of such solvents
are 2-chloro toluene; 2,3-dichlorotoluene; 2,3-dichloroethyl- ~ ~
benzene; and 2,3,4-trichloroethylbenzene. ~ ;
In accordance with the invention, use must also be made
of small but significant amounts of elemental sulfur or sulfur
donating compounds such as tri- or tetra-sulfides o~ organic
compounds or tri- or tetra-sulfides o~ inorganic compounds in
inorganic sulfides and organic sulfides. Sulfur donor compounds
-- 4 ~
,~
f~ 3
which are suitable are compounds which release sulfur at the --
temperatures at which the solution polymerization is conducted.
Such compounds are commonly used in the vulcanization of rubbers
include tetramethylthiuram tetrasulfides, and other tetraalkyl
thiuram tetrasulfides; the reaction products of alkylene chlo-
rides and sodium polysulfides, amine disulfides such as 4,4'-
dithio dimorpholine and other compounds which release sulfur
when heated to about 200C.
Briefly the present invention includes polymerization
of cyclic dichlorophos~hazenes in aromatic or cycloaliphatic
hydrocarbon solvents by proceeding as follows.
All of the constituents, i.e. solvent, cyclic dichlo-
rophosphazene oligomers and sulfur or sulfur donating compounds
were charged into the reaction vessel. The sulfur was added as
a solution in the hydrocarbon solvent, for ease in handling.
For solvents with boiling points below 150C pressu-
rized systems were utilized with pressure from 0-1000 psig and
~a preferred range of 0'-200 psig.
For solvents with boiling points between 150C and
250C reactions were carried out at atmospheric pressure. Dry
Argon gas was passed over the reaction mixture. Care was taken
at all points to prevent oXyqen or moisture from being introduced
: : , . . . .
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into reaction mi~ture. Apparatus wa~ preheated ln 140C oven
for 24 hour~ be~ore use~ ,
Stirring was by means o~ magneti~ bars. Polymeri~a~
tions were conducted ~or rrom 40-300 hours preferably at 200-
~20C bath temperature. The polymerizatlon reaction mlxture wasusually solid at completion of reaction. Unreacted cyclics and
hydrocarbon solvent were s~ripped by repeated washing with dry
~exane in inert, dry atmosphere. RecoYered polymer was dissol-
~ed in benzene yieldln~ a mostly soluble polymer, eXhibiting
dilute ~olution ~iscosi~ies between from about 0.09 to,1.2
- (DSV 1~ equivaient to inherent vlscosity stated in decal1ter~
ram~.
Volatile material ~wept ~rom the reaction mixture ino-
luded H~S and HCl.
The same polymerizat,ion reaction carried out under the
; l ame reaction conditions to converslons Or 60% or more except
hat lt was conducted ln the absence o~ sul~ur or sulrur dona-
ting compound~ produced products which were usually ~eiled and
in~oluble ln benzene. The exact nature Or the effect o~ the
Z0 ~ul~ur on ~he pol~merization is not rully understood.
The inventlon will be further described in the follow-
ing ~x~mple~ given by way o~ illu~tration and not intended to
llmit the inventlon. The data in Table I was obtained by pro-
ceeding as ~ollowa: .
'''-; ''"''" ~ ' ''' "' ~''
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-6-
:~15'~'Æ:~ I
: E~ample
The lndicated number mllllmole~ Or elemental sulfur
dissolved in te~ralin or other solvent was added to a solution
Or cycllc dlchlorophosphazene trimer in the indlcated solvent
. in a glass or stainless steel reaction vessel. An ~rgon rlow
of 1 to ~ ml/minute was maintained across the ~ur~ace of the
~olution. Temperature wa~ maintained ~or the indicated tl~e~
. ~ and yields o~ 25-60% C0AVer~lOn tO polymer uere ob~ain~d.
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Xt ~an be seen rrom Table I that the phosphonitrlle
trimer can be polymerized usin~ decalin as the solvent producln~
hlgh molecular weigh~ polymers,~while various solvents 3uch as
tetralin, naphthalene, decalin/tetralin mixture7 prehnltene
. pro~uced polymerq o~ somewha~ di~erent molecular wei~hts.
' ... ~ .
. :'
. '~:~ ' .
. . . .
~or solven~s wlth boillng points below 190C~ ~uch
. ~ as toluene it was necessary ~o use a pressurlzed sy~tem. An
: . Argon blanket was maintained over the polymerization solution
10 : at 10-~00 psig. Every 2-6 hours the system was ~lushed by low- ~:
. ering the pressure and repre~suring with rresh Argon. Other .
i conditiona were a~ indicated in Table ~. ~ .
". ' ...... , :. . , . ' ' : . .
''.' '..... . . . . ' . , . '.
. . TABL~' II
. ~ ,
. . Milllmoles o~
.X (NPC12)n Sul~ur per Temp. Time % Conv-
Sol~ent in Solventmol (NPC12) C Hrs ersion
--3 _ _
., . ' `' . ~ ., '. :~,
Toluene 49 2. 5 205 93 76
Toluene ~ 60 3 . 205 46 33
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.
Example 1 was repeated employing the solvents ~hown
ln Table III, resultlng in 90-96% converslon Or phosphonitrilic
chlorlde oligomer~ to hlgh molecular weight polymer. The .
. resultin~ product arter recovery was derivatlzed as described .
. in United States Patent 3,970~533 issued July 20, 1976 using
C2 and C5 ~luorinated alcohols and with o-allyl phenol for cura-
. tive sites~ Table III gives the rlnal derivatl~ed phosphonitrl-
lic chloride polymer with tri~luoro ethanol and octafluoro- . .,.
~entanol with comple~e molecular weight determinations. The .
~ho~phonitrilio chloride polymer obtained rrom the examples dis- .
. ~u3sed in Table I can be derlvatized to useful f1uoroallcoxlde f
~ ~ ff ~la9tor rs, In the ~am- manner.
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