A process for preparing a thermoplastic poly(imidesulfone) is disclosed. This resulting material has thermoplastic properties which are generally associated with polysulfones but not polyimides, and solvent resistance which is generally associated with polyimides but not polysulfones. This system is processable in the 250 to 350 C range for molding, adhesive and laminating applications. This unique thermoplastic poly(imidesulfone) is obtained by incorporating an aromatic sulfone moiety into the backbone of an aromatic linear polyimide by dissolving a quantity of a 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) in a solution of 3,3'-diaminodiphenylsulfone and bis(2-methoxyethyl)ether, precipitating the reactant product in water, filtering and drying the recovered poly(amide-acid sulfone) and converting it to the poly(imidesulfone) by heating

St.clair, T. L.

Yamaki, D. A.

English

NASA Technical Reports Server

United States Patent 4,398,021 
St. Clair et al. 1451 Aug. 9, 1983 
[54] SOLVENT RESISTANT, THERMOPLASTIC 
AROMATIC POLY(IMIDESULF0NE) AND 
PROCESS FOR PREPARING SAME 
[75] Inventors: Terry L. St. Clair, Poquosod, Va.; 
David A. Yamaki, Deptford, N.J. 
[73] Assignee: The United States of America as 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
[21] Appl. No.: 407,240 
[22] Filed: Aug. 11, 1982 
[5 11 Int. (21.3 .............................................. C08C 73/10 
1521 U.S. C1. .................................... 528/222; 264/137; 
264/258; 264/331.12; 264/331.46; 528/226 
[58] Field of Search ........................ 528/226, 222, 353 
[561 References Cited 
U.S. PATENT DOCUMENTS 
3,440,202 4/1969 Boldebuck et al. ................. 528/226 
3,506,583 4/1970 Boram et ai. ....................... 528/226 
3,700,649 10/1972 Boram et al. ....................... 528/226 
3,793,281 2/1974 Acle, Jr. .............................. 528/226 
4,094,862 6/1978 Bell ...................................... 528/226 
Primary Examiner-Lester L. Lee 
Attorney, Agent, or Firm-Howard J. Osborn; John R. 
Manning; Wallace J. Nelson 
P71 ABSTRACT 
A process for preparing a thermoplastic poly(imidesu1- 
fone) is disclosed. This resulting material has thermo- 
plastic properties which are generally associated with 
polysulfones but not polyimides, and solvent resistance 
which is generally associated with polyimides but not 
polysulfones. This system is processable in the 
250"-350" C. range for molding, adhesive and laminat- 
ing applications. This unique thermoplastic poly(imide- 
sulfone) is obtained by incorporating an aromatic sul- 
fone moiety into the backbone of an aromatic linear 
polyimide, by dissolving a quantity of a 3,3',4,4'-benzo- 
phenonetetracarboxylic dianhydride (BTDA) in a solu- 
tion of 3,3'-diaminodiphenylsulfone and bis(2-methox- 
yethyl)ether, precipitating the reactant product in wa- 
ter, filtering and drying the recovered poly(amide-acid 
sulfone) and converting it to the poly(imidesu1fone) by 
heating. 
5 Claims, No Drawings 
https://ntrs.nasa.gov/search.jsp?R=19830025770 2020-03-22T01:04:32+00:00Z
4,398,021 
1 2 
Aromatic polyimides, conversely, are a class of poly- 
mers which are generally considered not to be readily 
processable via thermoplastic techniques, but exhibit 
exceptional resistance to solvents. 
Both the aromatic polysulfones and aromatic polyi- 
mides have good thermal stabilities with the use temper- 
atures thereof being generally governed by the soften- 
ing temperature of each system. 
There is thus a definite need in the art for a solvent 
resistant polysulfone and a thermoplastic polyimide 
which can be used as a molding compound, as an adhe- 
sive, and as a resin for the fabrication of fiber reinforced 
composites. 
Accordingly, an object of the present invention is to 
provide a solvent resistant aromatic polysulfone. 
Another object of this invention is to produce a ther- 
moplastic aromatic polyimide. 
Another object of this invention is to make a thermo- 
plastic, solvent resistant polymer which can be utilized 
as a molding resin. I 
Another object of this invention is the production of 
a thermoplastic, solvent resistant polymer which can be 
utilized as an adhesive. 
Another object of this invention is to provide a ther- 
moplastic, solvent resistant polymer which can be uti- 
lized as a matrix resin for fiber reinforced composites. 
Another object of the present invention is a process 
for thermoplastically forming moldings, adhesive bonds 
and fiber reinforced composites from solvent resistant 
aromatic polysulfones. 
An additional object of the present invention is a 
process for combining two high temperature polymer 
systems to retain the advantageous properties of each 
while minimizing or eliminating the disadvantages 
thereof. 
where n is an integer and represents up to several hun- 
In the above structure, it is concluded that the 3,3'- 
diphenylsulfone segment of the polymer chain causes 
the polymer to be thermoplastic. This conclusion is 
based on the experimetal results obtained by use of the 
40 following segments, when substituted for the diphenyl- 
sulfone in the basic structure, resulted in polyimides that 
were not thermoplastic: 
35 dred repeat units. 
50 
60 
65 
3 
4,398,021 
4 
&!A, and 
-continued TABLE I-continued 
Adhesive Properties of Poly(imidesulfone) 
Test Temperature & Exposure 
5 177" C initial 3200 
232" C. initidl 2600 
25" C. after IO00 hr @ 232' C. 3500 
177" C after IO00 hr @ 232" C 3200 
232" C. after IO00 hr @ 232" C 2900 
Lap Shear Strength', psi 
w W' 
,o *Tmniurn Adherends 
Also, unfilled moldings prepared from the poly(imide- 
thermoplastic nature to the base polyrner, but lacked the properties that are reasonable for a linear thermoplastic. 
thermoplastic completeness obtained .by the 3,3'-diphe- 15 This data is listed in TABLE 11. 
nylsulfone: 
TABLE I1 
Properties of Unfilled Poly(imidesu1fone) Moldings 
Property 
Tensile strength, ksi 9.2 
Strain to failure, in/in 0015 
Modulus, ksi 
Poisson's ratio 0.37 
Glass Transition Temperature, "C 239 
The groupings did impart degree of sulfone) of the present invention were clear and had 
o S % o  and 20 700 
GI,, Joules/meter* 1400 
0 
Graphite fiber reinforced moldings (composites) were 
prepared using unidirectional high tensile strength fi- 
bers in the resin. Physical data on these samples are 
presented in TABLE 111. 
TABLE 111 
Unidirectional Graphite Fiber Reinforced Composites 
of Poly(imidesulfone) 
l Q T ~ l Q P 5  
Both exemplary polymers prepared with these moieties 
had only limited flow in the 250"-350" C. range when 3o 
compared to the 3,3'-diphenylsulfone containing poly- 
imide of the present invention. 
The improvement in solvent resistance for the poly(i- 
midesulfone) of the present invention was proven by 
comparing it to the polysulfone of the following struc- 35 
ture: Test Temp 
Thickness, cm 
Interlaminar Shear Strength, psi 
RT 11,500 
121" c. 7,000 
177" C. 6,900 
Softening Temperature, "C 205 
Resin Content, % 33 
{ o & ~ o ~ s o ~ ~  C H ~  40 Density, g/cc 1.5 
0.25 
CH3 
SPECIFIC EXAMPLES where n is an integer and represents several hundred 
repeat units. 45 Example I 
This polymer was found to swell, and subsequently Preparation of the poly(amide-acid sulfone) of 
3,3'-diaminodiphenylsulfone cresol, chloroform, cyclohexanone, methylenechloride, 1,1,2,2-tetrachloroethane, and aircraft hydraulic fluid 
which contains tricresylphosphate. By contrast, when 50 25.8 g (0.08 moles) of 3,3',4,4'-benzophenonetetracar- 
thin films of the poly(imidesu1fone) of the present inven- boxylic dianhydride (BTDA) was added to a solution of 
tion were placed in these solvents, they were not af- 19.9 g (0.08 moles) of 3,3'-diaminodiphenylsulfone (3,3'- 
fected. After removal from the solvents, films prepared DDS) in 258.6 g (1.9 moles) of bis(2-methoxyethy1)e- 
by the present invention had the same softening temper- ther. This mixture was allowed to rapidly stir until all of 
ature as before exposure. Even slight solvation of the 55 the BTDA had dissolved. Slower stirring was contin- 
polymer would be expected to cause a considerable ued for an additional two hours in order to allow molec- 
lowering of the softening temperature. ular weight to build. At this stage, the polymer in solu- 
Adhesive lap shear samples prepared with the poly(i- tion is a poly(amide-acid)sulfone. 
midesulfone) of the present invention has exceptionally 
high strengths when tested at ambient temperature, 177" 6o Example I1 
C. and 232" c. both before and after aging for Precipitation and isolation of the Poly(amide-acid 
hours at 232" C. in a flowing air oven (See TABLE I Sulfone) 
below). 
The viscous polymer solution from Example I was 
TABLE I 65 poured into a mechanical blender containing water. The 
Adhesive Properties of Poly(imidesulfone) contact with water caused the poly(amide-acid sulfone) 
Lap Shear Strength*, psi to precipitate and the blender blades chopped this mate- 
4200 rial to fluffy consistency. The solid polymer was iso- 
when a prepared therefrom was placed in 3,3'4,4'-benzophenonetetracarboxylic dianhydride and 
Test Temperature & Exposure 
25" C initial 
4,398,021 
5 
lated by suction filtration and was allowed to dry over- 
night. 
Example I11 
Conversion of the Poly(amide-acid)Sulfone to the 
Poly(imidesu1fone) 
The dried polymer from Example I1 was poured into 
a container which was placed in a forced air oven and 
subsequently heated to 100" C. The polymer was held at 
this temperature for one hour to drive off residual water 
and solvent. The temperature was then increased to 
200" C. to effect conversion of the amide-acid portions 
of the polymer to the imide. 
Example IV 
Preparation of Unfilled Molding of the 
Poly(imidesu1fone) 
The polymer from Example 111 was placed in an open 
mold in a hydraulic press equipped with heated platens. 
The open mold containing the polymer was heated to 
220" C. and held at that temperature for 15 minutes. A 
plunger was next placed in the cavity of the mold and 
pressure was applied on the polymer. The pressure was 
increased over a five minute period to 300 pounds per 
square inch. The temperature of the mold containing 
the polymer was next increased to 280" C. at a rate of 5" 
C. per minute. Pressure was maintained on the polymer 
at this temperature for 30 minutes. The mold was al- 
lowed to cool to approximately loo" C. befare pressure 
was released. The mold was opened and the molded 
part was removed. 
Example V 
Preparation of Adhesive Bonds with 
Poly(imidesu1fone) 
Duplicate one inch wide strips of 0.050 inch thick 
titanium alloy were grit blasted with 120 mesh alumi- 
num oxide and subsequently coated with the poly(a- 
mide-acid sulfone) from Example I. Several layers were 
built up with thermal treatments between layers. The 
thermal treatment included 15 minutes at loo" C. and 15 
minutes at 200" C .  to remove solvent and convert the 
amide-acid to the imide, respectively. These strips were 
next overlapped so that the adhesive layers met. A thin 
(0.004 inch) piece of woven glass cloth was inserted 
between the strips to control the bond-line thickness. 
Pressure was applied (200 pounds per square inch) and 
the sample was heated at 5" C. per minute to 300" C .  
The system was cooled and the bonded specimen was 
removed. 
Example VI 
Preparation of Fiber Reinforced Moldings 
The polymer solution from Example I was used to 
coat graphite fiber at a 40 percent by weight dried resin 
to 60 percent by weight fiber mix. The 40/60 ratio of 
resin to fiber mix is precalculated to yield the 40 percent 
6 
diameter of 7 X 10-6 M and a product of the Celanese 
Corporation. After the solvent had evaporated (expo- 
, sure to 35"-40" C. for 12 hours), the coated fiber was cut 
into pieces 3 inches by 6 inches. These pieces were 
5 placed in an oven and heated for 30 minutes at loo" C. 
and subsequently 30 minutes at 220" C. This thermal 
treatment was done to remove solvent and convert 
amide-acid to imide. Twelve individual dried and imi- 
dized pieces were stacked in a mold cavity and a top 
lo inserted. The closed mold was placed in a hydraulic 
press equipped with platens for heating. Pressure was 
applied (400 psi) and the temperature was raised to 280" 
C. and held under these conditions for one hour. The 
system was cooled to approximately 100" C. and the 
l5 mold was opened and the graphite fiber reinforced 
molding was removed. 
It is thus seen that the foregoing specific Examples 
are illustrative of a novel poly(imidesulfone) system 
2o having improved thermoplastic and solvent resistant 
property characteristics and the process for preparing 
same, and useful as molding resins, adhesives and in the 
preparation of fiber reinforced composites. 
The specific Examples described herein are to merely 
25 illustrate the invention and are not to be deemed as 
exhaustive. Thus, various modifications and variations 
of the present invention will be apparent to those skilled 
in the art without departing from the spirit and scope of 
the appended claims. 
What is claimed as new and desired to be secured bv 30 
35 
40 
45 
50 
55 
by weight resin content after removal of the solvent by 6o 
evaporation. In the specific Examples described herein, 
the graphite fiber employed was Celion 3000, having a 
Letters Patent of the United States is: 
sulfone) comprising: 
1. A process for preparing thermoplastic poly(imide- 
incorporating an aromatic sulfone moiety into the 
backbone of an aromatic linear polyimide by dis- 
solving a quantity of a 3,3'4,4'-benzophenonetet- 
racarboxylic dianhydride (BTDA) in a solution of 
3,3'-diaminodiphenylsulfone and bis(2-methoxye- 
thyl)ether, precipitating the reactant product in 
water, filtering and drying the recovered poly(a- 
mide-acid sulfone) and converting it to the poly(i- 
midesulfone) by heating. 
2. The process of claim 1 wherein the imide conver- 
sion step involves heating for approximately one hour at 
100" C. to drive off residual water and solvent and 
thereafter increasing to and maintaining a temperature 
of approximately 200" C. for at least fifteen minutes to 
effect imidization. 
3. The process of claim 1 wherein the BTDA-3,3'- 
diarninodiphenylsulfone and bis(2-methoxyethy1)ether 
solution is stirred for at least two hours prior to precipi- 
tating the reactant product in water. 
4. The process of claim 3 wherein the precipitation 
step is performed in a mechanical blender and the 
blender used to chop the precipitate into a fluffy consis- 
tency solid polymer. 
5. The process of claim 4 wherein the fluffy consis- 
tency solid polymer is isolated by suction filtration, and 
dried overnight at room temperature prior to the heat 
conversion treatment. * * * * *  
65 


Solvent resistant thermoplastic aromatic poly(imidesulfone) and process for preparing same

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