from - dticreaction of nitrosyl chloride with pentafluorophenyl lithium. 6 b. polymerization. 7 c....
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USANL ltr 8 Mar 1967
I1' IT1'"1'.,
t* *
CONTRACT NO. DA 19-129-AMC-152(N)(OI9116)
WITH
U. S. ARMY NATICK LABORATORIES
ï’ Report Period: 26 February 1966 - 26 May 1966
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SYNTHESIS AND POLYMERIZATION OF FLUORINATED SULFUR MODIFIED
NITROSO RUBBER
I
By
Eugene C. Stump, Calvin D. Padgett and Charles R. Wetzel
26 June 1966
Peninsular ChemResearch, Inc. Post Office Box 14318
Gainesville, Florida 32601
D C J-p'"'1-
SEP 61966 !
Ü
617 ' - -'S - >A-i9- 129-AMC- 1 í
WITH
U. S. ARMY NATICK LABORATORIES
Report Period: 26 February 1966 - 26 May 1966
6J SYNTHESIS AND POLYMERIZATION OF "“S. FLUORINATED SULFUR MODIFIED ¿
X NITROSO RUBBER . /
26
© 1: i~'
Peninsular ChemResearch, Inc. Post Office Box 14318
Gainesville, Florida 32601
FOREWORD
This report was prepared by Peninsular ChemResearch, Inc.
under Contract No. DA 19-129-AMC-152(N)(OI9116) for the U. S. Army
Natick Laboratories with Mr. C. B. Griffis as Project Officer. This is
the eleventh Quarterly Report under this contract and covers the period
26 February 1966 through 26 May 1966.
Personnel engaged in this research are Eugene C. Stump, Project
Supervisor (140 hours), Calvin D. Padgett, Research Chemist (517-1/4
hours), and Charles R. Wetzel, Research Chemist (518-3/4 hours).
Analytical work was oerformed under the suoervision of Van A. May.
Drs. Paul Tarrant and George Butler are acting consultants.
It is estimated that 90% of the work is completed and that 85%
of the estimated costs have been incurred to date. To the contractor's
best knowledge the funds remaining unexpended are sufficient to complete
the work called for in the contract.
ABSTRACT
^Additional quantities (245 g. ) oí ONtCF^CO^CH^ have been
prepared and polymerized with CF^’NO and CF^CF^ . A total of 526 g. of
nitroso ester terpolymer (NET) in charged compositions of 2-10 mole %
has been submitted for compounding and curing studies.J Investigation of
the synthesis of other termonomers includes CH O
II ^.^- (CH3)2NC(CJF-2t3TJ0, and C H CF=CF .
Vrhe high boiling material formed in the pyrolysis of
ONO OC (C Pp ^C O; C has been identified as ^H^C^CtCF V^NCKCF^^CC^CH^'.
A new copolymer was prepared from CF^NO and CF£=C=CHr but
was found to decompose at room temperature.
• ii-
(i)MtSIK
Ik,
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TABLE OF CONTENTS
I INTRODUCTION. !
II DISCUSSION. 2
A. Monomer Synthesis. 2
B. Polymerization. 4
III EXPERIMENTAL. 5
A. Monomer Synthesis. 5
!• Methyl •y-Nitrosoperfluorobutyrate ... 5
2. Tetrafluoroallene. 5
3. Reaction of Methyl Nitrite with Tetrafluoroethylene. 5
4. Reaction of N-Nitrosodimethylamine with Perfluoroglutaric Anhydride. ... 6
5. Reaction of Methyl Lithium and Butyl Lithium with Tetrafluoroethylene. ... 6
6. Reaction of Nitrosyl Chloride with Pentafluorophenyl Lithium. 6
B. Polymerization. 7
C. Cross-Linking. 7
1. CF3NO/CF2 = CFCF=CF2 Copolymer . . 7
D. Synthesis of Intermediates. 7
1. Perfluoroglutaric Anhydride. 7
-iii-
2. Methyl Nitrite 11
I
I I I
Í
I I
I
I
TABLE OF CONTENTS (Continued)
IV MONOMER PROCUREMENT.
V SAMPLES SUBMITTED ....
TABLES
Table 1 Preparation of Nitroso Ester Terpolymers
Table 2 Copolymers.
Table 3 Terpolymers ......
8
9
10
!
I. INTRODUCTION
The research described in this report is part of a continuing
program „pommred by the U. S. Army Natick Laboratories and concerned
with the development of so-called "nitroso rubber, " a 1:1 copolymer of
trifluoromtrosomethane and tetrafluoroethylene. A list of references
describing prior research was given in the Quarterly Report No. 1, dated
21 October 1963.
The original objective of this contract was to enhance the desirable
properties, in particular the low-temperature flexibility, of nitroso rubber
by the incorporation of sulfur atoms in a modified polymer structure.
Secondary objectives included the synthesis of desirable monomers, includ¬
ing monomers not containing sulfur, and their polymerization in the nitroso
rubber system. This research has been described in previous reports.
During the course of the contract the objectives were modified and
increased in scope. Recent work, and work described in this report, has
been directed toward the preparation of nitroso terpolymers containing a
reactive site for cross-linking.
II. DISCUSSION
A. Monomer Synthesis
In order to prepare larger quantities oí CF3NO/CF2=CF2/ON(CF2) CO CH
(N. E. T. ) terpolymer for testing, it was necessary to synthesize additional ^
samples of the nitroso ester. A total of 245 g. of fractionated monomer was
prepared in an average conversion of 21%. Passage of pure nitric oxide
through the pyrolysis chamber at 5 mm. pressure produced no increase in
conversion as desired. As previously reported, 1 pyrolysis of the nitrite
ester gives a higher boiling material in addition to the nitroso ester. On the
basis of its infrared spectrum this material was believed to be a diester,
which could presumably result from coupling of the CH^CfCF^- radical.
Recent NMR and elemental analysis have identified this compound, however,
as CH302C^CF2^3]2N0ÍC:F2^3C02CH3 • The NMR spectrum is described
below. Tetramethyl silane and trifluoroacetic acid were used as reference.
Designation
H
F A
B, C
D
E
F
Chemical Shift
6. 22 tau
+10. 2 ppm
+ 17. 2
+41.2
+43. 5
+47. 8
Pattern and Splitting Rel. Area
Sharp singlet
Broad 2.6
Non-equiv. 4.7 quartet, broad
Broad, overlapping peaks 9.o
Broad 5, j
Broad 2. 5
Assignment
"OCH3
-cf2o
-cf2n
-CF2C02 -cf2-
—CF -
A similar compound, (C^^NOC^, has been reported2 and Wc
prepared by pyrolysis of C^NO. The NMR spectrum of this compound
(1) Quarterly Report No. 10, this contract.
(2) R. E. Banks, et al., J. Chem. Soc., 7203(1965).
-2-
exhibited the same chemical shift and non-equivalence of the fluorine atoms
in the CF^N groups as the triester. In addition, the infrared spectra of the
two compounds exhibited a peak, attributed to C-N stretch, at 10.25 microns,
In an attempt to prepare an alkoxy-substituted nitroso compound,
methyl nitrite and tetrafluoroethylene were combined and irradiated with an
ultraviolet lamp. Th * only nitroso compound isolated from the reaction mix¬
ture was identified as ONCF^CF^NO^. This reaction will be repeated using
sunlight.
N-Nitrosqdimethylamine was combined with perfluoroglutaric anhydride
in an attempt to prepare a nitrite amide and subsequently a nitroso amide as
shown. The experiment was terminated by an explosion and will be repeated
O O
II II (CH3)2NNO + 0=C(CF2)3C=0-> (CH3)2NC(CF2)3CONO
(CH3)2NC(CF2)3NO
using other conditions.
Tetrafluoroethylene has been reacted with butyl lithium to give
C^HgCF=CF2. Difficulty was encountered in separating the olefin from the
hexane solvent. Purification by bromination, followed by distillation and
debromination, will be examined.
The reaction of nitrosyl chloride with pentafluorophenyl lithium has
been reexamined using tetrahydrofuran as a solvent. As before, no C, F_NO o 5
was obtained. In order to determine the stability of C.F NO in the presence O D
of lithium reagent, perfluoronitrosobenzene was dissolved in THF and butyl
lithium added at -78°. An immediate reaction occurred, giving an unidenti¬
fied light brown solid. Due to this apparent instability in the presence of
lithium reagent, this approach will be discontinuea.
(3) Quarterly Report No. 4, this contract.
-3-
B. Polymerization
As indicated in Table 1, several explosions occurred during the bulk
polymerization of CF^O/CF^CF^/0N(CF¿)3C02CH3. Since these runs
were larger than those previously carried out, without incident, it is felt
that these explosions are due to the inability of the system to conduct heat
from the vessel rapidly enough to prevent an uncontrolled, exothermic poly¬
merization. This problem could probably be resolved by carrying out the
polymerization in suspension in the 2-1. , stirred autoclave, but due to the
possibility of hydrolysis of the ester group by this method, it was felt
desirable to use the bulk method. Batches of about 200 g. or less can be
polymerized without difficulty.
During this period a new polymer was prepared from CF3NO and
CF =C=CH . This copolymer is surprisingly unstable and decomposes at
room temperature with the evolution of an unidentified fluorine-containing
gas. A terpolymer containing CF2=C=CH2 was also found to have very low
thermal stability as it decomposed at 7 0°.
An attempt to copolymerize CF3NO and CF3^FCF2 with activated
charcoal was unsuccessful.
-4-
7
III. EXPERIMENTAL
A. Monomer Synthesis
I • Methyl y-Nitrosoperfluorobutyrate
The reaction of methyl nitrite with perfluoroglutaric anhydride was
carried out ten times as previously described. 4 A total of 432 g. of methyl
nitrite and 1579 g. of perfluoroglutaric acid gave ONOOCÍCF^CO^CK^ in
an average conversion of 90%. Decarboxylation to the nitroso ester was
accomplished by both ultraviolet irradiation and pyrolysis as before. ^ A
total of 245 g. of pure ON(CF2)3CO¿CH3 was prepared in an average con¬
version of 21%. -
2. Tetrafluoroallene
Tetrafluoroallene was prepared as previously reported. 5 A total
of 275 g. of CF2BrCH2CF¿Br was obtained by the addition of CF Br to
CH^CF^. Dehydrobromination in two steps, with the second step being
carried out according to the method described by Jacobs and Bauer, ^ gave
24 g. of CF2 = C=CF2. Conversion was 24% based on CF BrCH CF Br. ¿ Z 2
3- Reaction of Methyl Nitrite with Tetrafluoroethylene
Tetrafluoroethylene (25 g., 0. 25 moles) and methyl nitrite (13. 7 g.,
0. 225 moles) were charged to a 12 1. flask equipped with a quartz immer¬
sion well. After u.v. irradiation for 48 hours with a No. 8A36 Hanovia
lamp, trap to trap distillation gave mostly unreacted tetrafluoroethylene. A
higher boiling blue product was also partially purified. Further purification
of this product on VPC gave a pure sample. The compound was identified
as ONCF2CF¿N02 by NMR and infrared analysis.
(4) Quarterly Report No. 8, this contract.
(5) Quarterly Report No. 10, this contract.
(6) T. L. Jacobs and R. S. Bauer, J. Am. Chem. Soc. , 81, 608 (1959).
-5-
4. Reaction of N-Nitrosodimethylamine with Perfluoroglutaric Anhydride
Perfluoroglutaric anhydride (22.2 g., 0. 1 mole) and N-nitrosodimethyl-
amine (7. 4 g. , 0. 1 mole) were charged to a Fischer-Porter tube cooled to
-183. After melting had occurred the reactants were mixed thoroughly by
shaking. Soon after this the tube explooed.
7 5. Reaction of Methyl Lithium and Butyl Lithium with Tetrafluoroethylene
Dry ether (500 ml. ) and butyl lithium (195 ml. , 0. 30 mole) in hexane
solution were placed in a 1-1. flask fitted with an air driven stirrer and inlet
with a helium sweep. The flask was cooled by a Dry-Ice/acetone bath. Tetra¬
fluoroethylene (36 g. 0. 36 moles) was condensed into the flask by means of
a cold finger condenser at -96°. After stirring for two hours, the flask was
allowed to warm slowly to room temperature. After washing with dilute HC1
and drying over anhydrous CaSO^, the mixture was fractionated and the 65°-
75° cut was collected. An IR spectrum and VPC indicated that the product
(b. p. 70°) was obtained but its separation from hexane (b. p. 69°) could not
be effected on a large scale.
A similar preparation of CH^CF^F^ was attempted using 5% CH^Li
in ether ( 1. 3 moles) and tetrafluoroethylene, (100 g., 1. 50 moles) with
reaction time of 4 hours at -78°. Work up yielded no material boiling at
18°. Most of the CH^Li appeared to be unreacted.
6. Reaction of I\itrosyl Chloride with Pentafluorophenyl Lithium
3 A reaction run in an earlier report between nitrosyl chloride and
pentafluorophenyl lithium was repeated using tetrahydrofuran as a solvent.
The reaction again failed to give perfluoronitrosobenzene.
In order to determine the stability of perfluoronitrosobenzene in the
presence of excess lithium reagent the following experiment was run.
Perfluoronitrosobenzene (2. 0 g., 0. 01 moles) was dissolved in 30 ml.
(7) S! Dixon) J, Org. Chem. , 21/ 400 (1956).
-6-
of tetrahydrofuran and cooled to -78°. Butyl lithium in hexane (6. 5 ml. ,
0. 01 mole) was added slowly. Immediate discoloration took place. After
2 hours the black solution was warmed to room temperature, washed with
dilute HC1, dried and evaporated to a tarry material. Washing with metha¬
nol gave a light brown material with typical fluoroaromatic absorption in
the infrared, as well as an absorption at 5. 92 microns.
In light of the above experiment, inverse addition of the reactants at
-96° was tried; however, work up gave no nitrosobenzene.
B. Polymerization
Polymers prepared during this report period are described in Tables
Procedures for preparing and working up the polymers are the same as
previously reported.
C. Cross-Linking
1 • CF3NO/CF:, = CFCF=CF2 Copoly mer
A small amount (5. 0 g. ) of the copolymer CF NO/CF =CFCF=CF -»2 2
was thoroughly mixed with hexanitrosobenzene, C6(NO)6, (0. 5 g. ). The
mixture was placed in a press and heated at 60° for 1 hour with no apparent
reaction.
The following materials were placed in a 250-ml. flask and refluxed
overnight: ICF^F^ (9.2 g. ), CF3NO/CF2=CFCF=CF2 (5. 0 g. ), FC-43
(50 ml. ), and benzoyl peroxide (1.2 g.). After the reflux was completed
the gum could not be recovered. The product was a liquid, apparently from
the decomposition of the polymer.
D- Synthesis of Intermediates
1. Perfluoroglutaric Anhydride
(a) Perfluoroglutaric anhydride (822 g. ) was prepared as previously 4
reported from perfluoroglutaric acid in 89% conversion.
-7-
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(b) Perfluorogiutaric anhydride (502 g. ) was prepared directly from g
perfluoroglutaryl chloride by the following method. Per fluor oglutaryl
chloride (1000 g. , 3.6 moles) was charged to a 2-1. flask fitted with Dry-Ice/
acetone condensers atop a reflux condenser and protected from moisture by
an anhydrous CaSO^ trap. Water(65 g., 3. 6 moles) was added slowly by
means of a dropping funnel to the mecahnically stirred acid chloride. After
the addition was complete, the mixture was refluxed for 10 hours. X-<ower
boiling liquid products were distilled from the mixture leaving 150 g. of
residue which was hydrolyzed to perfluorogiutaric acid. Careful fractiona¬
tion of the liquid products gave 502 g. of material b. p. 71-74° (perfluoro¬
giutaric anhydride) and 110 g. of higher boiling material whose IR spectrum
indicated it to be perfluoroglutaryl chloride. Conversion to the anhydride was
63%.
2. Methyl Nitrite
4 Methyl nitrite was prepared as previously reported. Two prepara¬
tions gave 290 g.
(8) E. Dorfman and W. E. Emerson, "Perfluoroalkylenetriazine Elastomeric Polymers, " Technical Documentary Report No. ML-TDR- 64-249 Part II under Contract AF 33(61 5)-1636, August 1965, p. 29.
1
-11-
IV. MONOMER PROCUREMENT
During this report period the following sample was received from outside sources:
40 8- University of Florida
V. SAMPLES SUBMITTED
During this report period the following samples were submitted to
the U. S. Army Natick Laboratories for evaluation:
Designation
QC-35.2. 1
QC-35. 2. 2
QC-59.2.2
QC-59.4
QC-59. 5
QC - 59.6
QC-60. 4
QC-60. 5
CWP-6
Charged Composition
CF3NO( 19)/CF2=CF2( 14)/CF2=CFCH=CH2(5)
(soluble portion)
CF3NO(19)/CF2=CF2(14)/CF? = CFCH=CH2(5)
(insoluble portion)
CF3N0/CF2=CF2/CH302(CF2)3N0 (10 mole %)
CF3N0/CF2CF2/CH302(CF2)3N0 (8 mole %)
H tl
Il H (2 mole %)
CF3NO/CF2 = CF2 (suspension)
(bulk)
cf3no(2)/cf2=cf2(i)/cf2=c=cf2(1)
Amount
23 g.
20 g.
34 g.
165 g.
245 g.
82 g.
99 g.
80 g.
19.5 g.
-13-