NASA CASE NO.

PRINT FIG. _N/A

/ _.j / z.,/'p C .

LAR 15205-1

The invention disclosed in this document resulted from research in aeronautical

and space activities performed under programs of the National Aeronautics and Space

Administration. The invention is owned by NASA and is, therefore, available for

licensing in accordance with the patent licensing regulations applicable to U.S.

Government-owned inventions (37 CFR 404.1 _ seq.).

To encourage commercial utilization of NASA-owned inventions, it is NASA

policy to grant licenses to commercial concerns. Although NASA encourages

nonexclusive licensing to promote competition and achieve the widest possible

utilization, NASA will provide the necessary incentive to the licensee to achieve early

practical application of the invention.

Address inquiries and all applications for license(s) for this invention to the

Technology Applications Team, NASA Langley Research Center, Code 200, Hampton,

Virginia 23681-0001.

Serial No.: 08/359,752

Filed: 12/16/94 LaRC

(NASA-Case-LAR-15205-1) TOUGH,

SOLUBLE, AROMATIC, THERMOPLASTIC

COPOLYIMIOES Patent Application

(NASA. Langley Research Center)

27 p

N95-22882

Unclas

G3/27 0042563
AWARDS ABSTRACT 

TOUGH, SOLUBLE, AROMATIC, THERMOPLASTIC COPOLYIMIDES 

NASA Case Number: LAR 15205-1 

Aromatic, thermoplastic polyimides are a class of polymers used in a variety of 

high performancelhigh temperature applications. The thermoplastic polyimides 

are usually soluble in either high boiling polar protic phenolic solvents, or 

halogenated solvents, many of which are highly toxic and are not used in large 

scale industrial processes without solvent recovery systems. As a result, the 

majority of polyimide thermoplastics are solution processed in the polyamic acid 

state using milder solvents and subsequently cyclodehydrated to form the final 

polyimide article. However, there is a disadvantage to this process in that the 

polyamic acid is unstable, susceptible to hydrolysis and generates water during 

imidization. 

By the present invention, wholly aromatic, thermoplastic polyimide copolymers 

were prepared based on 4,4'-oxydiphthalic anhydride, 3,4,3',4'- 

biphenyltetracarboxylic dianhydride and 3,4'-oxydianiline. These copolyimides 

were found to be tough thermoplastics which are soluble in common amide 

solvents such as N,N1-dimethyl acetamide (DMAc), N-methylpyrrolidinone 

(NMP), and dimethyl formamide (DMF) which allows these copolyimides to be 

applied as the fully imidized copolymer in addition to the amic acid solution. 

Because of the versatility of these copolyimides, they can be used to prepare a 

wide range of articles such as: solvent cast films, extrudable objects, fiberreinforced composites, neat resin moldings, coatings, hot-melt adhesive films, 

hot-melt adhesive cloths, hot-melt adhesive tapes, fibers, filled resin moldings 

and matrix composites comprising plastic, metal, graphite and ceramic powders. 

The novelty of this invention resides in the structure of the copolyimide, which 

had not been prepared previously. The nonobviousness is found in the 

unexpected combination of properties which includes solubility in common amide 

solvents, toughness and the ability for these copolyimides to be used in a broad 

range of applications. 

Inventor: Robert G. Bryant 

P.O. Box 2272 

Poquoson, VA 23662 

SS: 

Employer: NASA LaRC 

Initial Evaluator: Terry L. St. Clair 

Serial No.: 081359,752 

Filing Date: 1211 6/94 
LAR 15205-1 -1- PATENT APPLICATION

TOUGH, SOLUBLE, AROMATIC, THERMOPLASTIC COPOLYIMIDES

Origin of the Invention

5 The invention described herein was made by an employee of the

United States Government, and may be manufactured and used by or for the

Government without payment of any royalties thereon or therefor.

10

Background of the Invention

1, Field of the Invention

15

The present invention relates to copolyimides. In particular, it relates

to soluble copolyimides prepared from 4,4'-oxydiphthalic anhydride, 3,4,3',4'-

biphenyltetracarboxylic dianhydride and 3,4'-oxydianiline.

2. Description of the Related Art

20

25

Aromatic, thermoplastic polyimides are a class of polymers used in a

variety of high performance/high temperature applications. Such applications

include adhesives, matrix resins for composites, and high strength films and

coatings. These thermoplastic polyimides are usually soluble in either high

boiling polar protic phenolic solvents, such as m-cresol and chlorophenol or

halogenated solvents such as tetrachloroethylene and multihalogenated

aromatics, many of which are highly toxic and are not used in large scale

industrial processes without solvent recovery systems. Thus, the majority of

polyimide thermoplastics are solution processed in the polyamic acid state

using milder solvents and subsequently cyclodehydrated to form the final

polyimide article. However, there is a disadvantage to using the polyamic
5

10

15

20

25

30

LAR 15205-1 -2- PATENT APPLICATION

acid intermediates in that they are unstable, susceptible to hydrolysis, and

generate water during imidization.

Attempts to increase the solubility of polyimides generally involve the

modification of the polymer backbone through monomer selection. These

modifications include the incorporation of flexible aliphatic units, polar and

nonpolar pendent substituents, heteroatoms or groups, and polyimide

copolymers which contain either mixtures of the above monomers with

common aromatic diamines and dianhydrides, or block segments of soluble

oligomers. Although most of these polyimides meet and even exceed some

of the criteria required to find wide spread use as high performance materials,

cost limits their acceptance.

By the present invention, wholly aromatic, thermoplastic polyimide

copolymers were prepared based on 4,4'-oxydiphthalic anhydride, 3,4,3',4'-

biphenyltetracarboxylic dianhydride and 3,4'-oxydianiline. These

copolyimides were found to be tough thermoplastics which are soluble in

common amide solvents such as N,N,-dimethyl acetamide (DMAc), Nmethylpyrrolidinone (NMP), and dimethyl formamide (DMF) and thus can be

applied as the fully imidized copolymer in addition to the amic acid solution.

Meterko et al. (U.S. 5,171,828) had prepared copolyimides from 4,4'-

oxydiphthalic anhydride, 3,4,3',4'-biphenyltetracarboxylic dianhydride and

4,4'-oxydianiline or para-phenylenediamine. The difference between the

present invention and that of Meterko et al. lies in the use of 3,4'-oxydianiline

as compared to 4,4'-oxydianiline. Meterko et al. prepared polyimide films by

pouring the polyamic acid into the desired form. The polyamic acid was then

cured either by heating or through chemical imidization. Meterko et al. found

that their copolyimides had unexpectedly high comparative tracking indexes

which made the copolyimides useful as insulators for various electronic

applications. It is important to note that Meterko et al. applied their

copolyimide as a polyamic acid prior to imidizing and not as an imidized

solution.
5

10

15

2O

LAR 15205-1 -3- PATENT APPLICATION

St. Clair et al. (U.S. 5,147,966) prepared polyimide molding powders,

coatings, adhesives and matrix resins from 3,4'-oxydianiline and 4,4'-

oxydiphthalic anhydride. They found that by preparing polyimides and

polyamic acids from these monomers, along with suitable endcaps,

adhesives, composite matrix resins, neat resin moldings, and films or

coatings had identical or superior properties to commercially available

polyimides. Unfortunately, as with Meterko et al., these polyimide

homopolymers were applied as the amic acid solution.

Tamai et al. (U.S. 5,268,446) prepared readily melt-processable

polyimides by reacting 3,3',4,4'-biphenyltetracarboxylic dianhydride with 3,4'-

oxydianiline. They found that these polyimides had excellent processability

and chemical resistance in addition to essential heat resistance. These

polymers may be used in various fields such as electric and electronic

appliances, space and aeronautical equipment and transportation machinery.

They note in example 1 that the polyimide was insoluble in halogenated

hydrocarbon solvents such as methylene chloride and chloroform. In

addition, they prepared films from the amic acid solution instead of from the

imide powder.

An object of the present invention is to prepare a tough, soluble,

aromatic, thermoplastic copolyimide.

Another object of the invention is to prepare a diverse group of articles

from the copolyimide.

25

_ummary of the Invention

The foregoing and additional objects of the invention were achieved by

preparing a tough, soluble, aromatic, thermoplastic copolyimide by reacting

4,4'-oxydiphthalic anhydride with 3,4,3',4'-biphenyltetracarboxylic dianhydride

and 3,4'-oxydianiline.
5

10

15

20

25

LAR 15205-1 -4- PATENT APPLICATION

The tough, soluble, aromatic, thermoplastic copolyimide may be used

to prepare the following articles: a solvent cast film, an extrudable object, a

fiber-reinforced composite, a neat resin molding, a coating, a hot-melt

adhesive film, a hot-melt adhesive cloth, a hot-melt adhesive tape, a fiber, a

filled resin molding and a matrix composite. The matrix composite further

comprises a powder. As a preferred embodiment, this powder is selected

from the group consisting of: plastic, metal, graphite and ceramic.

The copolyimide of the present invention may be terminated with either

a monofunctional anhydride or a monofunctional amine endcapper. The

endcapper is added to the copolyimide at an amount ranging from about 2

mole percent to about 10 mole percent. An example of this endcapper is

phthalic anhydride. These endcapped copolyimides may be used to prepare

the articles listed above.

The 4,4'-oxydiphthalic anhydride and the 3,4,3',4'-

biphenyltetracarboxylic dianhydride are added to the 3,4'-oxydianiline at a

ratio of 4,4'-oxydiphthalic anhydride to 3,4,3',4'-biphenyltetracarboxylic

dianhydride ranging from about 25 mole percent to about 75 mole percent

(25:75) to about 75 mole percent to about 25 mole percent (75:25). These

copolyimides may be endcapped with either a monofunctional anhydride or a

monofunctional amine at an amount ranging from about 2 mole percent to

about 10 mole percent. The preferred endcapper is phthalic anhydride. The

articles prepared from these copolyimides are the same as those listed

above.

In particular, the 4,4'-oxydiphthalic anhydride and the 3,4,3',4'-

biphenyltetracarboxylic dianhydride are added to the 3,4'-oxydianiline at a

ratio of 50 mole percent 4,4'-oxydiphthalic anhydride to 50 mole percent

3,4,3',4'-biphenyltetracarboxylic dianhydride. An endcapper such as a

monofunctional anhydride or a monofunctionat amine may also be added to

the copolyimide at an amount ranging from about 2 mole percent to about 10
LAR 15205-1 -5- PATENT APPLICATION

mole percent. Preferably, the endcapper is phthalic anhydride. These

copolyimides may be used to prepare the articles which are listed above.

5

10

Descri.Dtion of the Preferred Embodiments

By the present invention, a copolyimide was prepared by reacting 4,4'-

oxydiphthalic anhydride (ODPA) with 3,4,3',4'-biphenyltetracarboxylic

dianhydride (BPDA) and 3,4'-oxydianiline (3,4'-ODA). This copolyimide has

the following repeat unit:

15

20

25

and has been found to be a tough thermoplastic material. In addition, the

copolyimide may be redissolved in common amide solvents such as DMAc,

NMP and DMF after the imide powder has been formed, provided that the

polyimide is not exposed to temperatures above its glass transition

temperature (Tg). (Typically, once a polyamic acid has been converted to the

imide, it cannot be redissolved in common amide solvents.) This unique

property, allows these copolyimides to be used for a large number of

applications. For example films, which were cast from the copolyimide after it

had been dissolved in solvent and dried above the Tg were found to exhibit

high modulus, good chemical resistance and be self bonding. The self

bonding property and insolubility above the Tg allows layered films and

coatings to be prepared. These copolyimides can also be extruded which

provides them with the capability to form a wide range of objects. Because of

their unique combination of properties, fiber-reinforced composites can also

be prepared from these copolyimides. Coatings prepared from these

copolyimides were successfully used to coat Kapton®, glass, aluminum,
5

10

15

20

25

30

LAR 15205-1 -6- PATENT APPLICATION

copper, ceramic and titanium substrates. It was found that these

copolyimides are capable of bonding to themselves as well as many other

materials and thus, they are useful as hot-melt adhesive films, hot-melt

adhesive cloths and hot-melt adhesive tapes. As yet another application,

these copolyimides find utility as neat resin moldings and filled resin

moldings, and can be processed at temperatures slightly below the Tg of the

copolyimide which can be readily machined and polished. Matrix composites,

which can also be processed at temperatures slightly below the Tg of the

copolyimide, have been successfully prepared from these copolyimides.

These composites were prepared by combining the copolyimide with

whiskers and/or a powder. Any powder known to those skilled in the art may

be used. Examples of these powders include but are not limited to: graphite,

ceramic, metal, plastic, copper, iron, diamond dust, polyimide powder, boron,

aluminum, and chopped carbon fibers. More specifically, ceramic powders

such as silicon nitride, quartz, zirconia, mixed oxides and aluminum oxide

may be used. Plastic powders which may be used include any powder which

may withstand the high processing temperature. As a preferred embodiment,

the powder may be a plastic, metal, graphite or ceramic powder.

The degree of solubility of these copolyimides can be controlled by the

processing conditions used to prepare the copolyimide. Several factors were

found to affect the solubility of the copolyimide. One of these factors was the

mole ratio of ODPA to BPDA. in addition, the percentage of solids and the

solvent used to synthesize the copolyimide was also found to have an effect

on the solubility. For example, it was observed that when the ratio of ODPA

to BPDA was 75 mole percent to 25 mole percent (75/25), and the

copolyimide was prepared at 30% solids in NMP, a turbid gel formed when

the solution was cooled to room temperature. However, for the same mole

ratio, when a 15% solids solution was prepared, the copolyimide remained

soluble in NMP when the solution was cooled to room temperature. For a

50/50 mole ratio of ODPA to BPDA copolyimide prepared in NMP, it was
5

10

15

20

25

LAR 15205-1 -7- PATENT APPLICATION

found that the copolyimide remained soluble and if allowed to remain

undisturbed for 6 to 48 hours (depending on the percent solids) formed a

thermally and mechanically reversible gel when the copolyimide was

prepared using up to 60% solids. When DMAc was substituted as the

solvent, the copolyimide was soluble at 15% solids but precipitated out at

30% solids. As with the 75/25 ODPA/BPDA ratio, copolyimides synthesized

at a molar ratio of 25/75 ODPA/BPDA were found to remain soluble in NMP at

30% solids during imidization but when cooled to room temperature formed

either a turbid gel or an elastomeric homogeneous gel. At 15% solids in

NMP, the copolyimides remained soluble. It was also observed that all of the

copolyimides remained soluble in m-cresol. In addition to controlling the mole

ratio and percent solids, it was found that controlling the molecular weight of

the copolyimide affected the sol-gel behavior.

In order to control the molecular weight of these copolyimides, the

stoichiometry may be offset and the copolyimide may be terminated with an

endcapper such as a monofunctional anhydride or a monofunctional amine.

A preferred endcapper is phthalic anhydride. The endcapper may be added

to the copolyimide at an amount ranging from about 2 mole percent to about

10 mole percent depending on the desired properties of the copolyimide. The

addition of the endcapper may allow for better processing in some instances.

As a preferred embodiment of the invention, it was found that good

results were obtained when the ODPA and the BPDA were added to the 3,4'-

ODA at a ratio of ODPA to BPDA ranging from about 25 mole percent to

about 75 mole percent (25:75) to about 75 mole percent to about 25 mole

percent (75:25). More preferably, the best results were obtained when the

ratio of ODPA to BPDA was 50 mole percent to 50 mole percent (50:50). The

addition of an endcapper such as a monofunctional amine or a

monofunctional anhydride allowed for molecular weight control which

provides versatility in the final end-use of the copolyimides.
5

LAR 15205-1 -8- PATENT APPLICATION

The following examples illustrate the preparation and use of the

copolyimides. These examples are merely illustrative and intended to enable

those skilled in the art to practice the invention in all of the embodiments

flowing therefrom, and do not in any way limit the scope of the invention as

defined by the claims.

EXAMPLES

10

15

20

In a 500 mL resin kettle equipped with a nitrogen inlet, overhead

stirring assembly, Dean-Stark trap, and condenser were placed ODPA

(commercially available from Imitec, Inc.) (17.0257 g, 0.0549 mol), BPDA

(commercially available from Ube Industries, Inc.) (5.4137 g, 0.0184 mol),

3,4'-ODA (commercially available from Mitsui Toatsu Chemical Co.)

(15.0231g, 0.07502 mol), phthalic anhydride (0.4533g, 0.00306 mol) and

NMP (216 g). The solution was stirred overnight at room temperature.

Toluene (50 g) was added to the solution and the mixture was heated to

165°C for 7 hours during which time water was removed by azeotropic

distillation. The reaction was cooled to room temperature. The solution was

forced through a 51_mfilter. The copolyimide was precipitated using water

and chopped in a blender. The resulting polymer powder (bright yellow in

color) was collected by filtration, extracted with methanol for 48 hours and

dried in vacuo at 200°C for 9 hours.

25

30

In a 100 mL resin kettle equipped with a nitrogen inlet, overhead

stirring assembly, Dean-Stark trap, and condenser were placed ODPA

(15.9407 g, 0.0514 mol), BPDA (5.0395 g, 0.0171 mol), 3,4'-ODA (14.1435 g,

0.0706 mol), phthalic anhydride (0.6277 g, 0.0042 m01) and NMP (81.5 g).

The solution was stirred overnight at room temperature. Toluene (20 g) was

added to the solution and the mixture was heated to 165°C for 7 hours during
5

LAR 15205-1 -9- PATENT APPLICATION

which time water was removed by azeotropic distillation. The reaction was

cooled to room temperature forming a turbid gel. The copolyimide was

precipitated in water and chopped with a blender. The resulting polymer

powder (bright yellow in color) was collected by filtration, extracted with

methanol for 48 hours and dried in vacuo at 200°C for 9 hours.

10

15

20

25

3O

In a 500 mL resin kettle equipped with a nitrogen inlet, overhead

stirring assembly, Dean-Stark trap, and condenser were placed ODPA

(16.0239 g, 0.05165 mol), BPDA (15.1975 g, 0.05165 mol), 3,4'-ODA

(20.6862 g, 0.1033 mol) and NMP (120 g). The solution was stirred overnight

at room temperature forming a heavy gel. Toluene (25 g) was added to the

solution and the mixture was heated to 165°C for 7 hours, during which time

water was removed by azeotropic distillation. The reaction was cooled to

room temperature. The solution was forced through a 5_m filter. The

remaining copolyimide powder was precipitated using water and chopped in a

blender. The resulting polymer powder (bright yellow in color) was collected

by filtration, extracted with methanol for 48 hours and dried in va,cuo at 200°C

for 12 hours.

In a 1 L resin kettle equipped with a nitrogen inlet, overhead stirring

assembly, Dean-Stark trap and condenser were placed ODPA (35.8835 g,

0.1156 mol), BPDA (34.0329 g, 0.1156 mol), 3,4'-ODA (46.7922 g, 0.2367

mol), phthalic anhydride (0.6922 g, 0.00467 mol) and NMP (274 g). The

solution was stirred overnight at room temperature. Toluene (50 g) was

added to the solution and the mixture was heated to 165°C for 7 hours,

during which time water was removed by azeotropic distillation. The reaction

was cooled to room temperature. The solution was forced through a 51_m

filter. The copolyimide was precipitated using water and chopped in a
LAR 15205-1 -10- PATENT APPLICATION

blender. The resulting polymer powder (bright yellow in color) was collected

by filtration, extracted with methanol for 48 hours and dried in vacuo at 180°C

for 9 hours.

5

10

15

In a 1 L resin kettle equipped with a nitrogen inlet, overhead stirring

assembly, Dean-Stark trap and condenser were placed ODPA (213.13 g,

0.6870 mol), BPDA (202.14 g, 0.6870 mol), 3,4'-ODA (280.76 g, 1.4020 mol),

phthalic anhydride (8.3072 g, 0.0561 mol) and NMP (1640 g). The solution

was stirred overnight at room temperature. Toluene (300 g) was added to the

solution and the mixture was heated to 165°C for 7 hours, during which time

water was removed by azeotropic distillation. The reaction was cooled to

room temperature. The solution was forced through a 51_m filter. The

copolyimide was precipitated using water and chopped in a blender. The

resulting copolyimide powder (bright yellow in color) was collected by

filtration, extracted with methanol for 48 hours and dried in vacuo at 180°C for

9 hours.

20

25

3O

Exa,rnDle 6

In a 1 L resin kettle equipped with a nitrogen inlet, overhead stirring

assembly, Dean-Stark trap, and condenser were placed ODPA (39.2347 g,

0.1265 mol), BPDA (37.2112 g, 0.1265 mol), 3,4'-ODA (51.6841 g, 0.2581

mol), phthalic anhydride (1.5292 g, 0.0132 mol) and DMAc (740 g). The

solution was stirred overnight at room temperature. Toluene (100 g) was

added to the solution and the mixture was heated to 165°C for 7 hours during

which time water was removed by azeotropic distillation. The reaction was

cooled to room temperature. The solution was forced through a 51_m filter.

The copolyimide was precipitated using water and chopped in a blender. The

resulting polymer powder (bright yellow in color) was collected by filtration,
LAR 15205-1 -11- PATENT APPLICATION

extracted with methanol for 48 hours and dried in vacuo at 200°C for

12 hours.

5

10

15

20

25

In a 1 L resin kettle equipped with a nitrogen inlet, overhead stirring

assembly, Dean-Stark trap, and condenser were placed ODPA (3.6850 g,

0.01246 mol), BPDA (3.6656 g, 0.01246 mol), 3,4'-ODA (5.0922 g, 0.02543

mol), phthalic anhydride (0.1506 g, 0.00102 mol) and m-cresol (38 g). The

solution was stirred overnight at room temperature forming a slurry. The

mixture was heated to 195°C for 6 hours. The reaction was cooled to room

temperature. The solution was forced through a 51_m filter. The copolyimide

was precipitated using methanol and chopped in a blender. The resulting

copolyimide powder (bright yellow in color) was collected by filtration,

extracted with methanol for 48 hours and dried in vacuo at 180°C for 9 hours.

In a 1 L resin kettle equipped with a nitrogen inlet, overhead stirring

assembly, Dean-Stark trap, and condenser were placed ODPA (38.8358 g,

0.1251 mol), BPDA (36.8329g, 0.1251 mol), 3,4'-ODA (15.6861 g,

0.2581 mol), phthalic anhydride (2.2939 g, 0.0155 mol) and NMP (303 g).

The solution was stirred overnight at room temperature. Toluene (23 g) was

added to the solution and the mixture was heated to 165°C for 7 hours during

which time water was removed by azeotropic distillation. The reaction was

cooled to room temperature. The solution was forced through a 51_m filter.

The copolyimide was precipitated using water and chopped in a blender. The

resulting polymer powder (bright yellow in color) was collected by filtration,

extracted with methanol for 48 hours and dried in vacuo at 200°C for 9 hours.

3O
5

10

LAR 15205-1 -12- PATENT APPLICATION

In a 1 L resin kettle equipped with a nitrogen inlet, overhead stirring

assembly, Dean-Stark trap, and condenser were placed ODPA (40.3856 g,

0.1301 mol), BPDA (38.3028 g, 0.1301 mol), 3,4'-ODA (55.4641 g,

0.2769 mol), phthalic anhydride (4.9232 g, 0.03324 mol) and NMP (325 g).

The solution was stirred overnight at room temperature. Toluene (35 g) was

added to the solution and the mixture was heated to 165°C for 7 hours during

which time water was removed by azeotropic distillation. The reaction was

cooled to room temperature. The solution was forced through a 51_mfilter.

The copolyimide was precipitated using water and chopped in a blender. The

resulting polymer powder (bright yellow in color) was collected by filtration,

extracted with methanol for 48 hours and dried in vacuo at 180°C for 9 hours.

15

20

25

In a 1 L resin kettle equipped with a nitrogen inlet, overhead stirring

assembly, Dean-Stark trap, and condenser were placed ODPA (41.1663 g,

0.1327 mol), BPDA (39.0432 g, 0.1327 mol), 3,4'-ODA (55.9411 g,

0.2793 mol), phthalic anhydride (4.1379 g, 0.02794 mol) and NMP (327 g).

The solution was stirred overnight at room temperature. Toluene (30 g) was

added to the solution and the mixture was heated to 165°C for 7 hours,

during which time water was removed by azeotropic distillation. The reaction

was cooled to room temperature. The solution was forced through a 51_m

filter. The copolyimide was precipitated using water and chopped in a

blender. The resulting polymer powder (bright yellow in color) was collected

by filtration, extracted with methanol for 48 hours and dried in vacuo at 180°C

for 9 hours.

30

Exam.Die 11

In a 500 mL resin kettle equipped with a nitrogen inlet, overhead

stirring assembly, Dean-Stark trap, and condenser were placed ODPA
5

10

LAR 15205-1 -13- PATENT APPLICATION

(5.9869 g, 0.0193 mol), BPDA (17.0345 g, 0.0579 mol), 3,4'-ODA (15.7326 g,

0.07877 mol), phthalic anhydride (0.4667 g, 0.00315 mol) and NMP (225 g).

The solution was stirred overnight at room temperature. Toluene (50 g) was

added to the solution and the mixture was heated to 165°C for 7 hours,

during which time water was removed by azeotropic distillation. The reaction

was cooled to room temperature. The solution was forced through a 5_m

filter. The copolyimide was precipitated using water and chopped in a

blender. The resulting polymer powder (bright yellow in color) was collected

by filtration, extracted with methanol for 48 hours and dried in vaCuo at 200°C

for 9 hours.

15

20

In a 100 mL resin kettle equipped with a nitrogen inlet, overhead

stirring assembly, Dean-Stark trap, and condenser were placed ODPA

(5.5076 g, 0.01775 mol), BPDA (15.6707 g, 0.05326 mol), 3,4'-ODA

(14.5104 g, 0.07246 mol), phthalic anhydride (0.4293 g, 0.0029 mol) and

NMP (84 g). The solution was stirred overnight at room temperature.

Toluene (15 g) was added to the solution and the mixture was heated to

165°C for 7 hours during which time water was removed by azeotropic

distillation. The reaction was cooled to room temperature forming a solid gel.

The gel was placed in water and chopped with a blender. The resulting

polymer powder (bright yellow in color) was collected by filtration, extracted

with methanol for 48 hours and dried In vacuo at 200°C for 9 hours.

25

3O

Copolyimide films were prepared from polyamic acid solutions using

the following procedure. The polyamic acid solutions were doctored onto

plate glass and placed in a dust free chamber until they were tack free. The

dry polyamic acid films were cured at 100,200 and 300°C for 1 hour each in

air. The thin films were cut into 0.20 inch strips and the tensile properties
LAR 15205-1 -14- PATENT APPLICATION

were determined at several temperatures. These properties are given in

Table 1.

Table 1

ODPA/BPDA

ratio

100/0 (control)

75/25

50/50

25/75

0/100 (control)

Test

Temperature

(oc)

23

23

150

177

23

150

177

23

15O

177

23

150

177

Tensile Strength

Ks±

18.2±1

17.6+1.1

10.6+0.6

8.8+0.5

17.4±0.4

10.1±0.7

9.1±0.7

18.9±0.4

10.0±1.0

8.0±0.6

17.1±2

12.3±1

11.2±1

Tensile Modulus

Ks±

468+2

443±26

306+14

261±27

451±14

363±19

332±14

469+7

297+4

250+20

589±25

371±13

354±33

% Elongation

6.8+1

17.1±11

21.6±14

22.2±25

9.5+1

9.0+6

5.8±4

7.0+1.5

9.3±4

18.9+15

4.7+0.8

3.6±0.5

3.4±0.6

5

10

A Copolyimide film was prepared directly from the reaction mixture

containing BPDA/ODPA (50/50), 3,4'-ODA copolyimide at a 2% offset ratio

according to the following procedure. The copolyimide solution was doctored

onto plate glass and placed in a dust free chamber until it was tack free. The

dry copolyimide film was heated at 100,200 and 300°C for 1 hour each in air.

The thin film was cut into 0.20 inch strips and the tensile properties were

determined at several temperatures. The results are given in Table 2.
LAR 15205-1 -15-

Table 2

PATENT APPLICATION

Casting

Solvent

NMP

Test

Temperature

(oc)

23

150

177

Tensile

Strength

(Ksi)

20.6+2

12.6+0.8

11.1+1

Tensile

Modulus

(Ksi)

588+80

369+31

382±57

% Elongation

7.2+2

24+15

33+20

Color

Dark

Orange

5

10

15

The following procedure was followed to prepare copolyimide films

from the copolyimide powder. Copolyimide powders prepared at 2% offset

were dissolved in a NMP/toluene or mixed xylenes (9/1 weight) solution over

a 12 hour period at 23°C to form 10-15% by weight solid solutions. These

copolyimide solutions were doctored onto plate glass and placed in a dust

free chamber until they were tack free. The copolyimide films were heated

under several conditions: 100 and 200°C; 100 and 225°C; 100,200, 300°C;

or 100, 225 and 350°C for 1 hour each in air. The films were removed from

the glass plates by soaking in water. The thin films were cut into 0.20 to 0.75

inch strips and used for adhesive bonding, solvent resistance and the

determination of tensile properties. The unoriented thin film properties for the

films cured at 100,200 and 300°C for 1 hour each in air are listed in Table 3.

Table 3

ODPA/BPDA

ratio

5O/5O

25/75

Test

Temperatu re

(oc)

23

150

177

23

15O

177

Tensile

Strength

(Ksi)

20.6+2

12.6+0.8

11.1+1

18.2+2

11.2+1

9.9+0.7

Tensile

Modulus

(Ksi)

588+80

382+57

369+31

491+64

361+38

294+ 14

% Elongation

7.2+2

24+15

33+20

25+13

24+22

82+40

20
5

10

LAR 15205-1 -16- PATENT APPLICATION

Neat resin moldings were prepared from the copolyimide powder using

the following procedure. The copolyimide powder (2% offset) was placed in a

stainless steel mold which had been pretreated with a release agent. Various

molding conditions (summarized in Table 4) were used to form consolidated

moldings. The glass transition temperature (Tg) was determined from the

molding flash using Differential Scanning Calorimetry (DSC) at a heating rate

of 20°C per minute. The results are given in Table 4. Neat resin properties of

the molded specimens were also tested. These properties are summarized in

Table 5.

Table 4

ODPA/BPDA Temperature Pressure Time Tg (°C)

Ratio (°C) (PSI) (Minutes) l'tRun 2°_Run

25/75 300 200 30 236 243

25/75 350 200 30 240 245

50/50 225 3000 30 227 251

50/50 250 2000 30 240 251

50/50 300 200 30 248 251

50/50 350 150 30 245 253

75/25 35O 20O 3O 258 259

Table 5

15

ODPA/BPDA

ratio

50/50

50/50

50150

Molding

Conditions

250°C

1/2 hour

2000 psi

300°C

1/2 hour

200 psi

350°C

Test

Temp. (°C)

23

23

177

Tensile

Modulus

(GPa)

1/2 hour 23

150 psi 177

"From compact tension specimens.

bFrom data compact tension and microdumbell.

4.23

3.16

4.45

3.26

Tensile

Strength

(MPa)

111.2

42.8

111.2

53.1

3.5

4.4

4.3

G,¢b

(KJ/re')

4.6

4.2
5

10

15

LAR 15205-1 -17- PATENT APPLICATION

Physical and thermal properties were determined for copolyimide (PI)

solutions and thin films which were prepared having a 3% offset ratio and

endcapped with phthalic anhydride. The inherent viscosities (q_o,)were

obtained in copolyimide/NMP solutions (0.5 g/dL) at 25°C as well as for the

polyamic acids (PAA). Differential scanning calorimetry (DSC) was

performed on copolyimide films (dried at 100,200 and 300°C for 1 hour in air)

at a heating rate of 20°C/min with the glass transition temperature (Tg) taken

at the inflection point in the heat flow vs. temperature curve and the melting

temperature (Tm) taken at the minimum of the endothermic depression.

Thermogravimetric analysis (TGA) was performed on the polyimide films at a

heating rate of 2.5°C/min under flowing air and nitrogen. Polymer densities

were obtained at 23°C using thin films (cured at 100,200 and 300°C for 1

hour in air) and a density gradient column consisting of aqueous zinc

chloride. These results are given in Table 6.

Table 6

ODPA/.BPDA

ralio

TI,.,,(dL/g)

PAA PI

50/50

DSC

Tg(°C) mm(°C)

100/0 (control) 0.23 Ins. 232 291

75/25 0.44 0.37" 239 --- 474 480

248 --- 484 484

25/75

0.40 0.33

0.44 0.45 a 253 ---

5% Weight Loss

Air (°C) N_(°C)

491 491

0/100 (control)

50/50

(4,4'-ODA)

510 508

0.54 Ins. 260 387 490 493

0.60 Ins. 240 315 491 492

Density(g/ml)

1.389±1e "3

1.376±4e "4

1.376±7e "4

1.378±2e"

1.406±6e"

>1.45

20

"2% offset polyimide polymerized in a

Ins. - insoluble

15% solids NMP solution.

25

Melt viscosities were run on copolyimides having an offset in

stoichiometry ranging from 1% to 5% and had been endcapped with phthalic

anhydride. The ratio of ODPA to BPDA was 50/50. Table 7 summarizes the

results.
LAR 15205-1 -18-

Table 7

PATENT APPLICATION

% Offset Extrusion Temperature (°C) Melt Viscosity (Poise)

2

3

4

29O

304

338

285

303

337

281

303

340

285

3O3

340

285

3O3

337

>6,000,000

3,951,000

610,000

4,028,000

603,000

351 _000

1,318,000

311,000

931000

351,000

127,000

30,000

269,000

92,000

91000

5

10

Adhesion testing was conducted using a 50/50 BPDA/ODPA

copolyimide having a 2% offset in stoichiometry. Lap shear joints were

constructed using titanium (Ti, 6AI-4V) coupons as the substrates. One

bonding film was solvent cast and dried at 200°C for 1 hour in air to provide a

thin film with approximately a 5% volatile content. Another bonding film was

solvent cast and dried at 100,200 and 300°C for 1 hour each in air to provide

a film which had less than 0.1% volatiles. Scrim cloth samples were coated

several times and dried at 100 and 225°C for 1 hour each in air between

coats with a final soak at 300°C for 30 minutes. The bonding conditions and

results from this testing are given in Table 8.
LAR 15205-1 -19-

Table 8

PATENT APPLICATION

Adhesive

ThinFilm

~5%volatiles

ThinFilm

<0.1%volatiles

ScrimCloth

0.3%volatiles

BondingConditions

50psi

300°C

30minutes

50psi

350°C

30minutes

Test

Temperature

(°C)

23

150

177

23

150

177

Bondline(mils)

2.1

1.2

1.5

3.9

2.8

3.9

15psi/350°C/30min

25psi/350°C/30min

50psi/350°C/30min

23

23

23

11.5

12.0

13.5

ShearStrength

(psi)

5600

5000

3900

4365

3760

3360

4O3O

4405

5230

5

10

Matrix composites were prepared using a 50/50 blend of BPDA/ODPA

at a 2% offset and endcapping with phthalic anhydride. Iron, diamond dust,

Upilex R® plastic powder, quartz, graphite and graphite/copper combinations

were the powders used to prepare the composites. In this example, the

copolyimide serves as a binder for the particles. Table 9 summarizes the

fabrication conditions for these composites. Three point bend geometry

testing was performed on the graphite and graphite/copper composites at

23°C. The results of this testing are given in Table 10. Parts prepared from

these composites could be cut and machined to form various ports or molded

directly to form different objects for various unique applications.
LAR 15205-1

Material

(totalweight%)

Iron(98)

Diamond Dust (95)

Upilex R® (95)

Quartz (95)

Quartz (95)

Quartz (95)

Quartz (90)

Graphite (86.5)

Graphite/Copper

(85/5)

Graphite/Copper

(85/5)

Graphite/Copper

(76/19)

-20-

Polyimide

(total weight %)

2

10

13.5

Table 9

PATENT APPLICATION

Molding Conditions

min / Ksi / °C

30 / 40 / 250-350

30 / 2O / 35O

30 / 10 / 350

3O/ 5 / 35O

30 / 10 / 350

3O / 20 / 35O

30 / 10 / 350

30 / 10 / 25O

Density

(g/cm 3)

6.98

2.75

1.41

1.72

1.71

1.77

1.83

1.89

10 30 / 1.5 / 350 1.85

10 30 / 5 / 350 2.00

5 30 / 5 / 350 2.09

Table 10

Material Composition

(% by weight)

Graphite/PI (86.5/13.5)

Graphite/Copper/PI

(85/5/1 O)

Graphite/Copper/PI

(85/5/10)

Graphite/Copper/PI

(76/19/5)

PI - copolyimide

Molding

Conditions

min/Ksi/°C

Flexural

Modulus

(Msi)

2.36

Flexural

Strength

(psi)

6130

% Strain

30 / 10 / 300 0.3

30 / 1.5 / 350 3.00 7610 0.3

30 / 5 / 350 2.40 5400 0.3

30 / 5 / 350 2.50 5400 0.3

10

The following procedure was followed to dip coat a copper wire. A

10% solution of the copolyimide in NMP was prepared. A 10 gauge copper

wire was dipped into the solution and dried at 300°C for 1 hour in air. This

process was repeated several times to build up a multi-layer protective

coating. The coated copper wire could be bent without causing the coating to

peel away from the wire.
5

LAR 15205-1 -21- PATENT APPLICATION

The following procedure was used to prepare a molding of a filled

copolyimide. The 50/50 BPDA/ODPA 2% offset polyimide powder was mixed

with a blend of 15% by weight of graphite powder and 10% by weight of

Teflon® powder. The mixture was blended using a shaker and subsequently

compression molded at 300°C for 30 minutes at 200 psi to afford a solid

uniform block. The block was machined and cut to various shapes.

10

15

20

25

3O

Substrates were coated using the following procedure. A solution

consisting of 10% by weight of the 50/50 BPDA/ODPA 2% offset polyimide

was doctored onto clean Kapton® and aluminum foil. The coated substrates

were placed into a dust free chamber until they were tack-free. The tack-free,

coated substrates were then treated at 100,200 and 300°C for one hour

each in air. The substrates were then folded in half with the copolyimide to

the inside and placed in a hot press for consolidation. The press was set at

300°C and 100 psi and the exposure time was 15 minutes. This yielded a

self-bonded material which could not be torn apart without destroying the

substrates.

The following procedure was used to mold particles which had been

coated with the copolyimide to substrates. Graphite powder which had been

coated with a 10% by weight 50/50 BPDA/ODPA 2% offset copolyimide was

placed in a stainless steel mold. A piece of aluminum foil which had been

coated with 50/50 BPDA/ODPA 2% offset copolyimide was placed on top of

the graphite powder with the coating facing the graphite powder to form a

composite preform. The composite preform was molded at 300°C and 5000

psi for 30 minutes to form a consolidated graphite part having a foil backing.

The aluminum foil could not be removed without being destroyed.
5

10

15

2O

25

LAR 15205-1 -22- PATENT APPLICATION

The following example is for the preparation of a composite from the

copolyimide. A 30% by weight solids in NMP solution of BPDA/ODPA 50/50

copolyimide having a 3% offset ratio was used to solution coat continuous

IM-7 carbon fibers (commercially available from Hercules) creating a 3 inch

wide unidirectional tape. This tape was then cut into 3x3 inch and 3x6 inch

sections (plies) and stacked to form panels which were 12 and 24 plies thick.

The panels were consolidated at 300°C and 200 psi for 1 hour to yield a

consolidated continuous carbon fiber composite.

Exam.Die 26

The following procedure was used to form thermally and mechanically

reversible gels from the copolyimides. Several liquid solutions consisting of

10%, 30% and 60% by weight solids in NMP were prepared from 50/50

BPDA/ODPA copolyimides having a 2% offset. The liquid solutions were

made through direct synthesis of the copolyimide and by redissolving the

required amount of the copolyimide in the solvent. The liquid solutions were

allowed to stand for 24 hours at room temperature whereby a thick gel

formed. The gelled solutions were then heated until the liquid solution

reformed. In addition to heating the gelled solutions, the 10% and 30% by

weight gelled solutions were mechanically agitated to reform the liquid

solution. The reformed liquid solutions were allowed to stand at room

temperature which caused the gel to reform. As a result, the sol-gel process

was shown to be both thermally and mechanically reversible. This is

demonstrated by the DSC data shown in Table 11.
LAR 15205-1 -23-

Table 11

PATENT APPLICATION

Weight % Solids of Gel 1st Run Tm (°C) 2nd Run Tm (°C)

30 119 None Detected

60 178 None Detected

5

10

Solvent resistance testing was performed on a copolyimide prepared

from BPDA/ODPA (50/50) 2% offset polyimide film which had been dried at

300°C. The thin films were weighed and twisted around a steel paper clip

which was subsequently placed into a jar containing a specific solvent for 10

days. After removing the films from the jar, they were blotted dry, visually

examined, weighed and creased. The results from this test along with the

respective solvents which were used are recorded in Table 12.

15

20

25

Table 12

Solvent Test Temp Weight Loss Appearence

Water 23°C <0.1% NCC, Creasible

Jet Fuel 23°C <0.1% NCC, Creasible

Toluene 23°C <0.1% NCC, Creasible

MEK 23°C <0.1% NCC, Creasible

Methylene Chloride 23°C <0.1% NCC, Wrinkled,

Creasible

Hydraulic Fluid (TSP Based) 23°C <0.1% NCC, Creasible

NMP 23°C 7.5% NCC, Some

Fracture

THF 23°C <0.1% NCC., Creasible

Ethylene Glycol 23°C <0.1% NCC, Creasible

NCC = No Color Change

30

The following procedure was followed to prepare a sprayable dielectric

coating. A formulated solution of BPDA/ODPA 50/50 2% offset copolyimide

(10% solids in NMP) was applied to different substrates using an airbrush.
5

LAR 15205-1 -24- PATENT APPLICATION

Examples of these substrates include: glass, ceramic, aluminum, Kapton®,

copper, Yttrium stabilized zirconia (YSZ), and Lead Zirconate Titanate (PZT).

The coating was initially dried in air at 44°C and subsequently at 300°C. The

typical coating thickness range was from 0.00025 inches to 0.0005 inches.

The coating was found to serve as a good dielectric adhesive which readily

accepted the deposition of gold, copper and aluminum circuitry, showing that

the ultra-thin coating of the copolyimide forms an excellent finish for allowing

the attachment of dissimilar electronic materials to various substrates.

10

15

20

25

Exam ole 29

Thin film multilayer flexible circuits were prepared using the

BPDA/ODPA 50/50 2% offset copolyimide (10% solids by weight in NMP)

solution as a film substrate and as a spray, to fabricate multilayer thin films.

The process involved metallizing a piece of the copolyimide film by means of

evaporation or sputtering and transferring a circuit pattern to the metallized

film by means of a standard photolithography process.

The copolyimide was solvent cast onto a releasable surface such as

glass to afford a film thickness ranging from 0.0003 inches to 0.0005 inches.

The copolyimide film was initially dried at 44°C and dried at a final

temperature of 300°C for 30 minutes. The film was then metallized and

patterned using a standard photolithography process. After the circuit was

formed, multiple coats of the copolyimide solution (1 part of BPDA/ODPA

50/50 2% offset to 8 parts of NMP solvent by weight) were sprayed to isolate

the newly formed circuit. The sprayed coating was dried in a similar manner

and metallized with 300 Angstroms of chrome and 2,000 Angstroms of gold.

A circuit was patterned onto the newly coated film using the same

photolithography process. This process was repeated multiple times in order

to form a multilayer thin film flexible circuit.

30
5

10

LAR 15205-1 -25- PATENT APPLICATION

The following process was used to bond films and foils together.

BPDA/ODPA 50/50 2% offset copolyimide (10% solids in NMP) solution was

sprayed onto various polyimide films and aluminum/copper foils in order to

bond them together. After the film or foil was sprayed with the copolyimide, it

was dried at 100 and 250°C for one hour each in air. The film and foil were

stacked and hot pressed at a temperature of 300°C using 100 psi for

15 minutes to secure the bond. The bonded film could be flexed without

delamination showing that it could be used in the formation of ultra-thin

multilayer polyimide metal-film laminates.
LAR 15205-1 PATENT APPLICATION

TOUGH, SOLUBLE, AROMATIC, THERMOPLASTIC COPOLYIMIDES

i 5

10

Abstract of the Disclosure

Tough, soluble, aromatic, thermoplastic copolyimides were prepared

by reacting 4,4'-oxydiphthalic anhydride, 3,4,3',4'-biphenyltetracarboxylic

dianhydride and 3,4'-oxydianiline. These copolyimides were found to be

soluble in common amide solvents such as N,N'-dimethyl acetamide, Nmethylpyrrolidinone, and dimethylformamide allowing them to be applied as

the fully imidized copolymer and to be used to prepare a wide range of

articles.