Synthesis is basis for preparation of polyurethanes that are compatible with liquid oxygen. The two step process preparation from fluorocarbon diacid fluorides is explained in text

Warner, D. A.

English

NASA Technical Reports Server

August 1971
	 Brief 71-10300 
NASA TECH BRIEF 
Marshall Space Flight Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D. f. 20546. 
Synthesis of a New Class of Highly Fluorinated Aliphatic Diisocyanates 
A laboratory process has been developed for the 
synthesis of a new class of highly fluorinated aliphatic 
diisocyanates to be used as a basis for the prep-
aration of polyurethanes that would be compatible 
with liquid oxygen. Polyurethanes are normally 
produced from the aromatic toluene diisocyanate, 
with and without fluorocarbon or other halocarbon 
moieties, by reaction with various polyols. Although 
there are a number of commercially available aro-
matic diisocyanates containing large proportions of 
fluorine to render them resistant to oxidation, 
polyurethanes produced from these compounds 
generally have poor mechanical properties (flexibility, 
elasticity, tensile strength) at very low temperatures. 
The polyurethanes prepared by reacting the newly 
developed fluorinated aliphatic diisocyanates with 
fluorinated polyols, however, are expected to have 
outstanding resistance to attack by strong oxidizing 
agents (e.g., liquid oxygen) and improved mechanical 
properties at temperatures in the cryogenic region. 
Members of the fluorinated aliphatic polyurethanes 
should be curable by conventional methods because 
the reactive, aliphatic urethane linkage is retained in 
the "backbone" 'of the polymer molecule. 
The preparation of the fluorinated aliphatic diiso-
cyanates from fluorocarbon diacid fluorides Consists 
of a two-step process, indicated by the following 
equations in which R denotes a fluorinated aliphatic 
radical: 
	
o 0	 0 0 
	
1111
	
it
II 
FC—R—CF + 2NaN 3 —. N 3C—R—C + 2NaF	 (1) 09 
N 3 —R—CN 3
 OCN—R-NCO + 2N 2	 (2) 
In the first step, carried out at room temperature, 
a solution of 0.1 mol of a fluorocarbon diacid 
fluoride in 37 cc of CF2CI-CFCl 2
 is added dropwise,
over a period of two hours, to a suspension of 0.24 
mol (0.04 mol in excess of the stoichiometric 
amount) of activated sodium azide (NaN 3 ) (see 
Reference) in 75 cc of dry acetonitrile. After being 
stirred for an additional two hours, the reaction 
mixture is washed free of salts, using a 5% aqueous 
NaHCO 3
 solution, and is then dried over anhydrous 
MgSO4. 
In the second step, the solution resulting from 
completion of the first step is slowly stirred into 
a distillation flask containing 100 cc of near-boiling 
toluene. The lower-boiling solvents are distilled 
off, the azide is allowed to decompose exothermally, 
and nitrogen is evolved. When the exothermic reac-
tion subsides, the mixture is distilled free of aceton-
itrile and CF2CI-CFCl2 and then refluxed for two 
hours in order to ensure complete conversion of the 
9 
acyl azide (N 3
—) groups to isocyanate (OCN—) 
groups. The distillate is recombined with the residue 
in the reflux flask and then fractionated to give the 
diisocyanate products, in approximately 30 to 60% 
yield, based on the starting fluorocarbon diacid fluor-
ide. A 58% yield of a specific diisocyanate fraction 
obtained by this method is represented by the fol-
lowing formula: 
F3	 CF3	 CF3
OCN —CF(OCF,C F) 10(CF,)4(CF,0CF) 1
 NCO 
where m+n=2. 
The identity of each of the diisocyanate fractions 
was established by infrared analysis, nuclear magnetic 
resonance, molecular weight, and elemental analysis. 
Reference: 
Smith, P.A.S.; Organic Reactions. John Wiley 
& Sons, New York, 1946 (p. 382)
oii1iiitictI ,, eflez,j 
Now
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately ownedrights.
https://ntrs.nasa.gov/search.jsp?R=19710000299 2020-03-17T02:21:46+00:00Z
Notes: 
1. The novelty of this method lies particularly in 
the choice of acetonitrile as a solvent in step 1. 
Its polar nature promotes the indicated ionic 
reaction; its aprotic property minimizes side reac-
tions; and its volatility facilitates subsequent re-
moval by distillation. 
2. Because of inefficiencies inherent in the small-scale 
experimentation, the yields obtained were not 
optimum. Considerably larger yields of the diiso-
cyanates would be attainable in controlled large-
scale production. 
3. Requests for further information may be directed 
to:
Technology Utilization Officer 
Code A&TS-TU 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: B71-10300
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to: 
Patent Counsel 
Mail Code A&TS- PAT 
George C. Marshall Space Flight Center 
Marshall Space Flight Center, Alabama 35812 
Source: D. A. Warner of

Peninsular Chemresearch, Inc.

under contract to

Marshall Space Flight Center

(MFS-20883)
.. 
Brief 71-10300
	 Category 04


Synthesis of a new class of highly fluorinated aliphatic diisocyanates

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