Polyimides from oxydiphthalic anhydride and 2,4-diaminotoluene

Soluble polyimides are formed from oxydiphthalic anhydride and 2,4-diaminotoluene. Optionally, up to 30 mole % of an alternate diamine and up to 50 mole % of an alternate dianhydride can be used with the oxydiphthalic anhydride and 2,4-diaminotoluene.

BACKGROUND OF THE INVENTION 
Aromatic polyimides are known for their excellent thermal stability, 
chemical and solvent resistance, and light stability. They are used as 
industrial films, coatings, adhesives, and moldings. Economic fiber 
development from polyimide polymer has been hindered because of the 
insolubility of the imidized polymer in conventional solution-spinning 
solvents; fiber formation from melts has been hindered because the melt 
temperatures are very close to or higher than the polymer decomposition 
temperature. 
Processing in the prior art has dealt with this problem by forming 
materials from the polyimide precursor, poly(amic acid). A typical method 
of manufacture consists of reaction of a dianhydride and a diamine to form 
a poly(amic acid). The latter is normally soluble and processable. After 
forming into a fiber or film, the poly(amic acid) is heat treated to 
imidize the carboxylic groups. This forms the completed insoluble 
polyimide. 
SUMMARY OF THE INVENTION 
The present invention provides an aromatic polyimide polymer consisting 
essentially of the following repeat units: 
##STR1## 
where X is 
##STR2## 
with from 0 to 50 mole % 
##STR3## 
and Y is 
##STR4## 
with from 0 to 30 mole % 
##STR5## 
which is soluble in organic solvents, and is capable of being formed into 
oriented structures. 
The polyimide is formed from the reaction of oxydiphthalic anhydride and 
2,4-diaminotoluene. Optionally, up to 30 mole % of the 2,4-diaminotoluene 
can be replaced by another diamine, such as 3,4'-oxydianiline or 
m-phenylenediamine; up to 50 mole % of the oxydiphthalic anhydride can be 
replaced by another aromatic dianhydride, such as pyromellitic 
dianhydride. The polyimide can be made into shaped articles such as film 
and fiber. 
DETAILED DESCRIPTION OF THE INVENTION 
This invention provides an aromatic polyimide with certain desired 
properties, namely solubility in amide solvents. It is prepared from 
oxydiphthalic anhydride (ODPA), and a particular diamine, namely 
2,4-diaminotoluene (TDA). It has been found that the reaction of these two 
monomers forms an aromatic polyimide which is soluble in organic solvents 
such as N-methyl-2-pyrrolidone (NMP). 
This invention provides a polyimide which can be made and processed in a 
very simple manner. The polyimide can be synthesized in an organic 
solvent; and, after reaction byproducts and excess solvent are distilled 
off and the polymerization is complete, the polymer solution can be formed 
directly into films or fibrous materials. 
Also, it has been found that amide-soluble polyimides result even where up 
to 50 mole % of the ODPA is replaced by pyromellitic dianhydride, or other 
suitable dianhydride and/or up to 30 mole % of the TDA is replaced by 
m-phenylenediamine, 3,4'-oxydianiline, or other suitable diamines. 
The polyimide of this invention is made under a dry inert atmosphere. The 
diamine is supplied to a suitable reaction vessel equipped with a stirrer. 
The desired organic solvent is then added and the mixture stirred until a 
solution is formed. The dianhydride is then added, along with additional 
solvent, and the solution stirred for from 1 to 12 hours. 
Water is a byproduct of the reaction and is removed by the addition of 
o-dichlorobenzene (ODCB), which forms an azeotrope with the water and can 
be removed by distillation. The solution is then heated for about 4 to 12 
hours until the imidization is complete. Solutions containing from 15 to 
35% solids have been prepared. Distillation may also remove some of the 
solvent from the solution. 
The aromatic polyimide of this invention exhibits an inherent viscosity 
greater than 0.5 and can be spun into fibers using conventional methods. 
It is also useful in films, pulps, etc. 
TEST METHODS 
Thermomechanical Analysis (TMA) was run on a T-A Instruments Model 2940 
with a Model 2200 controller. The samples were run under nitrogen with a 
0.050N load at a ramp rate of 5.degree. C. per minute. 
Inherent Viscosity. The inherent viscosity of a polymer which is soluble in 
a suitable solvent is conventionally used as a measure of the degree of 
polymerization of the polymer and is defined as 
##EQU1## 
measured by determining the flow times of a solution of the polymer at a 
concentration C in the solvent at a temperature of 30.degree. C., where t 
is the flow time of the solution and t.sub.o is the flow time of the 
solvent alone. With the polymers of the invention, the inherent viscosity 
values were determined using a solution in N-methylpyrrolidone (NMP) as 
the solvent, in which the polymer sample was dissolved at a concentration 
of about 0.5 g of the polymer per 100 ml of the solvent. The inherent 
viscosity should be sufficient to form films and for fibers of the 
polymer. Values in excess of about 0.5 are useful for this purpose.