Note: Descriptions are shown in the official language in which they were submitted.
11~963~
METAL SALT CATALYZED POLYMERIZATION
OF (NPC12) OLIGOMERS
This invention relates to improvements in the production of substantial-
ly linear (NPC12) polymer from cyclic trimeric (NPC12)3 or other low molecular
weight dichlorophosphazene oligomers.
In one known practice of the process, e.g., as described in United
States Patent 3,370,020 issued February 20, 1968, the polymerization proceeds
smoothly during the initial stages until a substantial conversion has occurred,
after which a benzene-insoluble gel forms which is not amenable to derivatiza-
tion for the production of such useful products as are described in that United
States Patent and in United States Patent 3,515,688 issued June 2, 1970,
and in an article published in the Scientific American in March, 1974 and
elsewhere in the literature on polyphosphazenes.
The published prior art describes efforts which have been made to
prevent the formation of the benzene-insoluble gel and to increase the
percentage conversion of cyclic trimer to soluble linear polymer. Control of
the molecular weight of the linear polymer has also been the subject of a
number of investigations since the properties of the ultimate derivatives
often depend on this.
The present invention provides an improved process for polymerizing
cyclic oligomer or oligomers having the structure (NPC12)n, wherein n -
is from 3 to 9, which comprisés polymerizing the oligomer or oligomers
at a temperature of from 20Q-300C. under an inert atmosphere or in a
vacuum in the presence of from about 0.002 to about 0.50 weight percent of a
hydrated inorganic metal halide salt, wherein the resultant linear polymer
is represented by the structure (NPC~2)X, wherein x is between 20 and 50,000.
Preferably the oligomers are the trimer and tetramer.
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The data shown in Table I below was obtained by conducting
the polymerization of (NPC12)3 as follows:
The indicated weight of CrC13 or other salt was added to 25
grams of purified hexachlorocyclotriphosphazene (NPC12)3 which had been
purified by recrystallization from hexane and the mixture was charged into
a glass polymerization tube which was then evacuated, heated to melt the
charge, cooled, subjected to vacuum again, cooled and then sealed, thereafter
the sealed tube was heated to 250 C. and maintained at that temperature
for the number of hours indicated in Table I. After completion of the
run, the tube was opened unreacted cyclic oligomers were removed, and the
dilute solution viscosity of the substantially linear (or polymeric) product,
the % gel and the % conversion were determined. The results are shown in
Table I.
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TABLE I
Wt. % of Hrs. @
Additive 250 C% Conv. DSV % Gel
t
1. 0 tcontrol) 10 11.7 2.73 0
2. 0 ~control) 20 21.2 3.50 16.5
3. 0 (control) 30 30.9 3.70 0
4. 0.005% CrC13-6H20 30 28.7 1.71 2.99
5. 0.01% CrC13'6H20 10 15.1 0.98 0
6. 0.01% CrC13-6H20 20 28.8 1.25 o
0 7. 0.01% CrC13-6H20 30 38.7 1.40 0
8. 0.2% CrC13-6H20 30 65.6 0.34
9. 0.1% CrCl3 30 46.8 1.45 1.17
10. 0.2% CrC13 10 18.6 1.07 0
11. 0.2% CrC13 20 42.5 1.12 1.91 ~;
12. 0.2~ CrC13 30 54.3 1.28 0.47 5
13. 0.5% CrC13 30 46.0 0.83 0
14. 0.18Za CoC12-6H20 22.1 49.0 0.48 4.8*
a - Level equal to 0.2% CrC13-6H20 based on water.
* Gel due to additive ppt.
While not wishing to be bound by any speciflc explanation as
to the difference between the effect of the hydrated compounds and the
effect of the anhydrous compound, it appears that the hydrates may be
functionlng as sources of water and hence catalyzing the polymerization
as described in United States Patent 3,937,790 issued February 10, 1976.
If this is correc~, the hydrated metal salts may be seen to offer a much
more readily controlled means of introducing small amounts of water to the
polymerization reaction.
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636
From the data in Table I it will be readily apparent that in the
absence of any modifier the % conversion is usually lower than when it i8 .
present, and it will also be seen`that the hydrated salts are more effective
in increaslng the X conversion`than the nonhydrated (anhydrous) salts. As
will also be noted, polymers produced in the presence of such difiers
exhibit a lower dilute solution'viscosity (DSV) than polymers produced in
the absence of'such modlfierR. This provides significant advantages in the
processing and use of such polymers. Small amounts of gel ( < 3%) do not
have any adverse effects on'subsequent derivatizations. Large amounts of
gel'such as the'16.5~ obtained'in the'control'run would preclude successful
derlvatlzation. '
Other'metal hallde salts which may be used in place of chromium
chloride include hallde salts of'the following metals: Ni, Co, Cu, Mn, Fe,
and Mg; particularly preferred salts being~hydrates of'metal chlorides or
other halides.
The'amounts of such inorganic metal ha}ide salts which may be
employed'as modifiers in the~polymerization process may vary somewhat. Thus,
from about 0.002 to about 0.50 weight percent of such modifiers based on
the welght of cyclic oligomer may in general be employed, with the preferred
range being from 0.005 to 0.20 weight percent.
~ Th~e purity of the startlDg cycllc material (NPC12)3 will influence
the effectiveness of'the metal halides. In the past, when attempts have
been made to thermally polymerize exceptlonally pure trimer (NPC12)3 some
batches'are found not to polymerize to any noticeable extent even after pro~
longed~heatinB at 250C. Thu~s thè terms"slow" or "ordinarily non-polymerizing"
as used`hereln refer`to cyclic oligomers having a substantially higher degree
of purity than those ordinarily or conventionally employed in the polymeriza- ¦
tion'process.
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Table II~illustrates the catalytic effect produced by the addition
of small amounts of CrC13~6H2O to such material.
TABLE II
EFFECT OF CrC13^6H20 ON POLYMERIZATION
OF "ORD~NARILY NON-POLYMERIZ~NG" TIMER
Wt. % Hrs. @
CrCl 6H 250C % Conv. Product Description
1. 0 26 4.2 An oil-like substance
2. 0 24 4.8 An oil-like substance
3. 0 168 7.7 An oil-like substance
4. 0 168 7.6 An oil-like substance
5. 0.005 31 45.7 An elastomer, DSV -
1.12, 0.09% Gel
6. 0.01 24 32.8 An elastomer, DSV =
1.17, 0% Gel
7. 0.01 24 35.1 An elastomer, DSV =
0.94, 0.75% Gel
Tables III(a) and III(b) illustrate the effect of various other
metal halide salts on the polymerization of cyclic trimer. The desired
influence on viscosity or molecular weight is clear. However, it will be
noted from the data in the Tables that in several instances the rate of
polymerization (as measured by percent conversion) of polymer prepared
with modifier appears reduced as compared to the rate of polymerizatlon of
polymers prepared without ~odifier, This is very likely due to the fact
that the starting trimer employed in these evaluations are of lesser
purity and, therefore, polymerizes faster than the trimer employed in the
preceding examples.
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TABLE III(a~
HrsO @ Inh.
Additive Wt. % 250 C % Conv. Visc.~ Gel
None 0 14.9 35.3 2.87 *
NiC12-6H20 0-00914.9 21.5 1.090.46
gC12 6H2 000714.9 26.4 1.091.42
12 2 0.02514.9 25.3 1.11 *
MnCl '4H 0 0.01114.9 29.6 1.180.60
CuC12 C.2 14.9 18.4 1.59 *
3 2 0.2 22.0 49.4 0.48 o o
* Had gel, filtered slowly but could not determine % gel.
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TABLE III(b)
Hrs @ Inh.
Addltlve Wt. ~ 250 C % Conv. Visc.% Gel
None 0 23.0 48.0 1.320.46
CrCl '6H 0 0.01623.0 35.0 0.790.53
CrF3-3~H20 0.0524 23.0 33.0 0,53 0.84
CoBr 6H 0 0.0372 23.0 34.0 0.78 0.35
CoI 2H 0 0.0532 23.0 53.0 0.62 0.37
FeCl 4H 0 0.0272 23.0 39.0 0.72 0.21
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The use of anhydrous metal salts to catalyze the reaction between ~;
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NH4Cl and PC15 whereby tNPC12)3 and other low molecular weight poly(dichloro- Lphosphazenes) are products, as described in Canadian Patent 614,267 issued
February 7, 1961 should not be confused with the present invention in which
the product of such processes is the starting material of the process of the
present lnvention, the product of which ls a substantially linear (NPC12)
product ln which a desired x ls achieved by monitoring the amount of metal 4
salt added to the (NPC12) cyclic oligomer which is to be polymerized.
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