Bis- and tris-imides derived from tris (m-aminophenyl) phosphine oxides by reaction with maleic anhydride or its derivatives, and addition polymers of such imides, including a variant in which a mono-imide is condensed with a dianhydride and the product is treated with a further quantity of maleic anhydride. Such monomers or their oligomes may be used to impregnate fibers and fabrics which when cured, are flame resistant. Also an improved method of producing tris (m-aminophenyl) phosphine oxides from the nitro analogues by reduction with hydrazine hydrate using palladized charcoal or Raney nickel as the catalyst is described

Fohlen, G. M.

Parker, J. A.

Varma, I. K.

English

NASA Technical Reports Server

[54] PIWIBSiPHBRUS-CONTAINING IMIDE 
ESIBNS 
1751 Inventors: Indra K. Varma, New Delhi, India; 
George M. Fohlen, Millbrae; John A. 
Parker, Los Altos, both of Calif. 
1731 Assignee: The United States of America as 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
[21] Appl. No.: 288,267 
[22] Filed: Jnl. 30, 1981 
Related U.S. Application Data 
[63] Continuation-in-part of Ser. No. 175,452, Aug. 5, 1980, 
Pat. No. 4,276,344. 
[51] Hnt. Q.3 ................... CQ7D 26)7/26; C07D 209/34 
[52] U.S. a. ..................................... 548/413; 548/415 
[58] Field of Search ....................... 260/326 E, 326.26; 
548/413, 415 
[561 References Cited 
U.S. PATENT DOCUMENTS 
4,166,168 8/1979 D’Alelio .................... 260/326.26 X 
4,168,360 9/1979 DAlelio .................... 260/326.26 X 
4,168,366 9/1979 DAlelio .................... 260/326.26 X 
4,168,367 9/1979 D’Alelio .................... 260/326.26 X 
4,276,344 6/1981 Frosch ............................ 428/902 X 
4,316,843 2/1982 Waitkus et al. ............. 260/326 E X 
4,316,844 2/1982 Waitkus et al. ............. 260/326 E X 
4,316,845 2/1982 DAlelio et al. ............ 260/326 E X . 4,321,198 3/1982 DAlelio et al. ............ 260/326 E X 
Primary Examiner-Joseph Paul Brust 
Attorney, Agent, or Firm-Darrell G. Brekke; John R. 
Manning 
[571 ABSTRACT 
Bis- and tris-imides derived from tris(m-aminophenyl) 
phosphine oxides by reaction with maleic anhydride or 
its derivatives, and addition polymers of such imides, 
including a variant in which a mono-imide is condensed 
with a dianhydride and the product is treated with a 
further quantity of maleic anhydride. Such monomers 
or their oligomers may be used to impregnate fibers and 
fabrics which when cured, are flame resistant. Also an 
improved method of produciqg tris(m-aminophenyl) 
phosphine oxides from the nitro analogues by reduction 
with hydrazine hydrate using palladized charcoal or 
Raney nickel as the catalyst. 
8 Claims, No Drawings 
https://ntrs.nasa.gov/search.jsp?R=19830023583 2020-03-22T01:22:00+00:00Z
4395,557 
1 2 
PHOSPHORUS-CONTAINING IMIDE RESINS 
n e 
ORIGIN OF THE INVENTION 
The invention described herein was made in the per- 
formance of work under a NASA contract and is sub- 
ject to the provisions of Section 305 of the National 
Aeronautics and Space Act of 1958, Public Law 85-568 
(72 Stat. 435; 42 U.S.C. 2457). 
DESCRIPTION 
This application is a continuation-in-part of our co- 
pending application Ser. No. 175,452, filed Aug. 5, 
1980, now U.S. Pat. No. 4,276,344 issued June 30, 1981. 
TECHNICAL FIELD 
This invention relates to addition polyimide resins 
and to fiber or fabric-reinforced composites made from 
them. 
BACKGROUNDART 
Strong light-weight composites can be made by em- 
bedding various types of fibers or fabrics in a resin 
matrix. The polymer used for such a matrix is generally 
an epoxy resin, although several other resins such as 
phenolic, novolac, poly(ether-sulfone), poly(pheny1- 
sulfone), and bismaleimide resins have also been used 
for certain applications. As fibers or fabrics, carbon and 
graphite products have been quite useful in the compos- 
ite structures. 
The search for flame resistant materials to form lami- 
nates that can be used with greater safety in places such 
as aircraft cabins, has led to the selection of high tem- 
perature resins such as bismaleimides which have high 
anaerobic char yield (Scientific & Technological Aero- 
space Reprints, 1976, 14-16, Abstract N76-25354), and 
to the inclusion of phosphorus-containing compounds 
either in a mixture with or as an integral part of the resin 
used as matrix. Searle, in U.S. Pat. No. 2,444,536, dis- 
closes a widely used method for the preparation of 
maleimide polymers. As to the use of phosphorus-con- 
taining compounds, Kourtides et al. (Proceedings of the 
Adhesive for Industry Conference, El Segundo, CA, 
June 24-25, 1980) have shown substantial improvement 
in various properties of certain epoxy resins by prepar- 
ing them with a bis(3-aminopheny1)methylphosphine 
oxide or its bisphenol analog, instead of the conven- 
10 1 2 
0 0 
20 3 
25 The monomers(bisimides) 3 can be used to impregnate 
fibers and cloth and, upon polymerization, confer fire 
resistant qualities on the fiber or fabric. 
It is an object of the present invention to provide 
30 improvements upon such monomers, polymers and 
impregnated fibers and fabrics. 
DISCLOSURE OF THE INVENTION 
35 We have found that the trisamino precursor typified 
by the following: 
40 
45 
0 
4 
50 can be used in place of the bisamino precursor. This 
results in curing at a lower temperature, e.g., 180” C., 
with good fire resistance. A further advantage is the 
greater ease of preparing the trisamino precursors. 
tional diamine or phenol monomers or curing agents of 55 
the art. In summary, however, it can be stated that 
We have also found an improved method of reducing 
the nitro precursors of these trisamino compounds, 
while the introduction of phosphorus into organic poly- wherein the nitro groups are reduced using hydrazine 
merS has generally in reduced hydrate as the reducing agent and palladium/charcoal 
increased adhesion, and better solubility in polar sol- 60 or Raney nickel as a catalyst. 
vents, none of the resins used in the composite art are 
non-flammable. DETAILED DESCRIPTION OF THE 
In copending application Ser. No. 175,452, filed Aug. 
5, 1980, entitled “Phosphorus-Containing Bisimide Res- 65 
ins” now U.S. Pat. No. 4,276,344 issued June 30, 1981, 
bisimides are prepared from phosphine oxides by a reac- 
tion typified by the following: 
INVENTION 
Using the triamine 4 and the anhydride 2 as models, 
and in a variant using also a coupling agent (a dianhY- 
dride), the following monomers result. 
4,395,557 
3 
2 5 
(3) 
8 9 
10 
In the equations above, R1 and R2 may be H, lower 
alkyl (e.g., methyl, ethyl, etc.), chlorine, or such other 
atoms or groups as are compatible with the respective 
reactions and with polymerization of the monomers. 
4,395,557 
6 
X is a linking entity which may be a valence bond, a are dissolved in solvents such as dimeEhyl foormamide 
bivalent atom (e.g., >Q or >S or a bivalent group, and glass fibers or carbon fibers or synthetic organic 
[e.g.,-C,Hz,-(n= 1, 2, 3, etc.)], >G=8, >=S, fibers in the form of filaments or fabric are impregnated 
>6(CF3)2, >SO2 or any other bivalent group which is with the solution. The solvent is then removed by evap- 
compatible with reaction (4) and with polymerization of 5 oration in an air oven at 125"-135" C. and layers of the 
the monomers. R3 is -NN2 or the imide group. impregnated fiber materials are formed by means of 
pressure and high temperature into the desired molded 
laminate. The laminate is then cured at, for example, 
180"-2(Eo0 c. 
The imide resins according to the present invention 
have noteworthy advantages over the imide resins of 
the aforesaid copending application. The curing of 
these resins can be done at relatively low temperatures 
while retaining the outstanding flame resistant proper- 
15 ties of the laminates. Furthermore, the tris(amino- 
pheny1)phosphine oxide is more easily obtained than the 
bis(aminophenyl)methylphosphine oxide. 
The following examples serve to illustrate the present 
invention. 
0 
10 
II 
0 
Further, the benzene rings may be Substituted by 
functional and/or non-functional groups provided they 
do not interfere with the reactions involved in forming 
the monomers and provided they do not interfere with 
polymerization and with thermal stability of the poly- 20 
mers. Examples of substituents are alkyl, e.g., C1 to C5 EXAMPLE 1 
straight and branched chain alkyl; chlorine; aryl, e.g., Tris(m-aminopheny1)phosphine oxide, 24.25 g, was 
Phenyl and tolyl. Condensed ring Phosphine oxides may placed in a flask with 110 ml dimethyl formamide 
be used. (DMF). Maleic anhydride was added (7.35 g) in two 
PolYmerization is accomplished thermally Or by 25 portions over a period of ten minutes. The solution was 
means of a catalyst Such as cobalt Or other metal naPh- stirred at 50" C. for one hour. Benzophenone tetracar- 
thenates together with peroxides. Partial polymeriza- boxy]ic dianhydride (BTDA) (12.15 g) was then intra- 
tion may be carried Out with the monomer; fibers or duced and stirring was continued overnight. The solu- 
fabric may then be impregnated with the resulting tion was then heated at 145" C.+2" G. for one hour and 
oligomer Or hwer Polymer; and the impreganted mate- 30 then refluxed for 30 minutes. The polymerization prod- 
rial may then be cured at a higher temperature. The uct obtained in this manner can further be processed as 
trisimides polymerize by opening of the olefinic double fo~~ows: 
bonds. With the bisimides nucleophilic addition of the The graphite fabric (8 harness satin-weave designated 
free amino group to the double bond may also Occur. as style 133 fabric) is coated with this resin solution. The 
The linking groups illustrated in 10 above resulq in 35 impregnated fabric is then dried in a circulating air oven 
Polymers having diminished Cross linking denSltY, at 125"- 135" G. for 20 minutes. Several pre-impregnated 
hence in impregnated fabrics having greater toughness. graphite fabric pieces are placed one upon the other 
The phosphine oxide component of the imides of this (4-9 plies) into a platen press and the laminate is hard- 
invention can be made from triPhenYlPhosPhine oxide ened under a pressure of 125 psi and a temperature of 
by nitration, followed by reduction of the nitro group to 40 180" C. for 150 minutes. Post-curing of the hardened 
the amino group by, for example, Stannous chloride laminate was done at 220" C. for 16 hours. Physical 
dihydrate and CO~centrated hydrochloric acid, Or by properties of such laminates were tested by an Instron 
hydrazine hydrate and palladized charcoal. Tensile Tester. A laminate hawing 21-22% resin was 
Imides can be prepared by reacting stoichiometric 
quantities of the reactants in a polar solvent (e.g., di- 
methyl formamide, dimethylacetamide, N-methyl pyr- 55 
rolidone, etc.) and cyclodehydrating the intermediate found to have a short beam shear strength of 3300 psi 
amic acid by sodium acetate and acetic anhydride. AI- and a flexural strength of 96,040 psi. The laminate did 
ternatively refluxing the reactants in glacial acetic acid not burn in pure oxygen. The glass transition tempera- 
or dimethyl formamide can also be used to prepare ture of a 4-ply laminate was found to be 385" 6. No 
imides. The resulting imides can be cured in the temper- 60 delamination was observed by boiling these laminates in 
ature range of 180"-30" C. water for 20 hours. 
The resins produced according to the process just Alternatively, the imide moaomer can be isolated 
described are suitable for many applications in which from the DMF solution by precipitating it with water 
good adhesion and excellent resistance to heat, fire, and washing with boiling methanol and acetone. Curing 
solvents and chemicals are required. In the aerospace 65 of this resin was done thermally at 180" C., 225" C., and 
industry, the new resins may be used as adhesives and as 232" C. and an anaerobic char yield of cured resin was 
matrix material for fiber-reinforced lightweight com- found to be 68-7076. Elemental analysis gave following 
posites. To produce such composites, the imide resins results: C=65.16%, W=3.54%,, N=7.12%, P=4.40%. 
4,3 95,5 57 
7 8 
The values calculated for formula C61H38P2011N6 are 
EXAMPLE 2 
Tris(m-aminopheny1)phosphine oxide 4.27 g, was 
dissolved in 25 ml DMF and 2.69 g of maleic anhydride 
added. The solution was stirred at 50" C. for one hour. 
BTDA (2.09 g) was then introduced and solution stirred 
overnight. The solution was heated at 145" C.f2" C. 
for 45 minutes and refluxed for 10 minutes. 
A graphite cloth laminate was cured in a manner 
similar to that described in Example 1. This material 
had a glass transition temperature of 314" C. as obtained 
by DMA. 
Trisimide monomer could be isolated by precipitation 
from the DMF solution with water. An anaerobic char 
yield of 62-69% was obtained. Elemental analysis 
showed the following results: C=64.40%, H=3.6%, 
N=6.92%, P=5.41%. The values calculated for for- 
mula C6gH38P2015N6 are C=66.13%, H=3.03%, 
N= 6.71, P=4.95%. 
C=67.03, H=3.47%, N=7.69, P=5.67%. 
EXAMPLE 3 
Tris(aminopheny1phosphine oxide) 1.615 g and di- 
chloromaleic anhydride 2.49 g were dissolved sepa- 
rately in glacial acetic acid and mixed. This solution was 
then refluxed gently for 29 hours. The trisimide was 
isolated by precipitation in water. The yellow precipi- 
tate was dissolved in and recrystallized from chloro- 
form and petroleum ether. The anaerobic char yield of 
the polymer formed from this monomer by curing at 
305" C. for 30 minutes was found to be 65%. 
EXAMPLE 4 
Tris(aminopheny1)phosphine oxide 1.61 g and citra- 
conic anhydride 1.12 g were separately dissolved in 
glacial acetic acid. The two solutions were mixed and 
gently refluxed for 24 hours. The imide was isolated by 
precipitation in water. The precipitates were dissolved 
in acetone and solution was concentrated. The imide 
was recovered by addition of petroleum ether. Elemen- 
tal analysis gave following results: C=65.33%, 
H=4.45%, N=7.31% and P=5.42%. Calculated val- 
ues for the formula C28H22P05N3 C=65.75%, 
H=4.30%, N=8.21% and P=6.06%. Anaerobic char 
yield of resin cured at 232" C. for 2 hours was 62.5%. 
EXAMPLE 5 
Tris(aminopheny1)phosphine oxide 1.61 g was dis- 
solved in 10 ml DMF and 1.62 g of maleic anhydride 
added. The solution was stirred overnight and then 
heated at 135"-145" C. for 50 minutes and refluxed for 
another 10 minutes. The trismaleimide was isolated by 
precipitation in water and recrystallized from acetone 
and petroleum ether. The anaerobic char yield of the 
imide resin formed by curing at 232" C. for 2 hours was 
found to be 64.5%. 
EXAMPLE 6 
Alternatively, the trismaleimide was prepared by 
dissolving 1.62 g of maleic anhydride and 1.61 g of the 
triamine 4 separately in 25 ml of glacial acetic acid. The 
solutions were then mixed and refluxed for 12-15 hours. 
Imide monomer was isolated by precipitation in water 
and filtration. The residue was washed several times 
with sodium bicarbonate solution until free from acid. 
After drying, the purification was done with chloro- 
form and petroleum ether. 
Trismaleimide was also prepared by dissolving 1.61 g 
of triamine 4 in 10 ml dimethylformamide and adding 
1.62 g of maleic anhydride. The solution was stirred at 
room temperature for 1 hour and then 0.5 g of fused 
sodium acetate was added followed by 3.5 ml of acetic 
anhydride. The solution was stirred at 60" C. for 2 
hours. Trismaleimide was isolated as mentioned above. 
EXAMPLE 7 
Triscitraconimide was also prepared by carrying out 
cyclodehydration with fused sodium acetate and acetic 
anhydride as in Example 6. Alternatively the condensa- 
tion reaction of triamine and citraconic anhydride was 
15 done in glacial acetic acid by reacting 1.61 g of amine 
with 1.85 g of citraconic anhydride and refluxing the 
solution for 12-15 hours. Triscitraconimide was isolated 
by precipitation in water and filtration. Further process 
was similar to Example 6. 
As stated above, we have also discovered an im- 
proved method of reducing tris(nitropheny1)phosphine 
oxides to the triamino compounds. This improved 
method employs hydrazine hydrate as the reducing 
agent and a palladium/charcoal or Raney nickel cata- 
25 lyst. These systems have been used heretofore to reduce 
nitro groups in mono- and dinitroaromatic compounds; 
see Furst, Chem. Rev. 65, 51 (1965) and Fieser and 
Fieser, "Reagents for Organic Syntheses", p. 440 
(1967), John Wiley. However, as far as we know, such 
30 systems have not been employed to reduce nitrophenyl- 
phosphine oxides. The system may be used to reduce 
nitro groups in dinitro compounds such as 1 above or 
trinitro compounds such as 4 above. The following 
EXAMPLE 8 
41.3 g of the trinitro oxide 11 (0.1 mol) (m.p. 
244"-245" C.) and 420 ml of 95% ethanol were placed in 
40 a 1 1 three-necked flask equipped with a reflux con- 
denser, thermometer and dropping funnel. 1.70 g of 
10% palladium on carbon (ROC/RIC) was added and 
the mixture warmed to 35O-40" C. Stirring was done 
with a magnetic stirrer. About 38 ml of hydrazine hy- 
45 drate (0.75 mole) (Baker Chem. Co., 99%) was added 
from the dropping funnel over a 40 minute period. The 
reaction is exothermic and addition of hydrazine has to 
be done dropwise. 0.3 g more of Pd/C was then added 
and mixture refluxed for 1 h. The hot solution was then 
50 filtered with gentle suction through a thin layer of Cel- 
ite. The flask was rinsed with hot ethanol and the cata- 
lyst and Celite were washed with it. The combined 
filtrates on cooling gave white crystals of triamine 
which were collected by filtration and suction dried. 
55 The precipitates after washing with water were dried in 
a vacuum oven at 80" C., yield=28-29 g (88-89%, m.p. 
258"-263" C.). The filtrate was concentrated under re- 
duced pressure and when the volume was reduced to 
6o about 30 ml it was added to water. A second crop of 
white precipitate of amine was obtained (1-1.5 g). 
For easier control the hydrazine hydrate can be di- 
luted with alcohol before addition. The Pd/C can be 
reused. 
Elemental analysis of the amine gave following re- 
sults: C=66.7%, H=5.67%, N= 12.95%, P=9.98% 
Calculated values for C18H18N3PO: C=66.81%, 
H=5.61, N=13.0%, and P=9.6% 
lo 
20 
35 examples will illustrate this aspect of our invention. 
65 
9 
4,395,557 
1 
n EXAMPLE 9 
Bis-(m-aminopheny1)methyl phosphine oxide was 
also prepared in a similar way by reduction of the dini- 
tro compound. The alcoholic filtrate was concentrated 5 
under reduced pressure to a small volume and then 
amine was precipitated by adding an equal volume of 
toluene: petroleum ether. (yield= 80%, m.p. 145"-149" 
C.). 
In the mass spectra of these amines M-1 ion was the 10 2. Imides of claim 1 wherein R3 is the amino group. 
3- Imides of claim 1 wherein R3 is an imide group. 
4. Imides of claim 1 wherein R1 and R2 are each hy- 
5. Monomers having the structure 
base peak. Eight most intense peaks, i.e., fragment ion 
values are listed in order to decreasing relative abun- 
dances (base peak is given first). Tris(m-aminopheny1)- 
phosphine oxide: 322, 323, 93, 65, 229, 182, 230. 
drogen. 
wherein R1 and R2 are selected from the class consisting 
of hydrogen chloro, and lower alkyls, R3 is -NH2 or 
the imide group 
25 
0 
30 
+R2 
II 
Bis(m-aminopheny1)methylphosphine oxide: 245, 0 
246, 65, 92, 93,231, 214, 63. The infra-red spectra of the 
amines showed characteristic absorption due to amino 
and P=O groups. 
The trinitro compound 1 1  of Example 8 and the dini- 
tro compound of Example 9 were, respectively, the 
m-nitro compounds. 
and wherein x is a linking entity selected from the class 
35 consisting of a valence bond, -0-, -S-, -CnH2,-- 
wherein n is 1, 2 or 3, 
CF3 
-c-, -c-, -c- 
0 S CF3 
We claim: I 
40 It II I I. Imides having the structure 
0 0 
II 'I R I  and --SO2--. R I  6. Monomers of claim 5 wherein R3 is an amino 
of claim 5 wherein R3 is an imide group. 
8. Monomers of claim 5 wherein R1 and R2 are each 
0 hydrogen and .X is 0 
-C-. 
0 
50 
R2 
II 
wherein R1 and R2 are selected from the class consisting 
of chloro, lower alkyls and hydrogen and R3 is the 
amino group or an imide group * * * * *  
55 
65 


Phosphorus-containing imide resins

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