Acid anhydride complex and process for producing same, and composition containing same

An acid dianhydride complex which is characterized in anti-hydrolysis, good stability, and high solubility in an organic solvent, is prepared by a reaction of a basic organic compound having a donor number of at least 20 and being free from an active hydrogen atom in the molecule and a carboxylic dianhydride compound.

BACKGROUND OF THE INVENTION 
(1) Field of the Industrial Utilization 
The present invention relates to an acid anhydride complex and a process 
for producing same, and to the composition etc. containing same. 
The complex of the present invention can be utilized for the stabilization 
of acid anhydride compounds during storage, for the improvement of 
solubility of the acid anhydride compounds to organic solvents, for the 
viscosity control of polyamic acids, for the technology which is 
applicable to the manufacturing processes of an electronic device with the 
composition, varnishes, films, fibers, each of which is containing the 
acid anhydride complex, and the acid anhydride complex itself. 
(2) Description of the Prior Art 
An acid anhydride has superior characteristics as a cross-linking agent, a 
monomer for synthesis of polymers. But, an acid anhydride has strong 
reactivity in general, and cautious consideration is required for its 
storage and the condition of its usage. Especially, it is a big problem in 
the industry that an acid anhydride reacts with moisture in the air and 
loses its reactivity. For example, an acid anhydride has superior 
characteristics as a hardner of an epoxy resin, but its utilization is 
restricted by easiness of causing hydrolysis. 
In case of synthesis of polyamic acids etc., hydrolysis of the acid 
anhydride causes lowering of reactivity as a monomer, and causes a problem 
to prevent the polymer from getting higher degree of polymerization. 
Hitherto, according to such unstability, the usage of an acid anhydride 
have been restricted in spite of its superior characteristics. Therefore, 
at the time of using an acid anhydride, a special treatment such as 
storage in dry condition, reactivation by heating just before the using, 
dehydration of a solvent, are required to prepare for the unstability of 
the acid anhydride. 
In case of synthesis of a polyamic acid etc., the degree of polymerization 
changes greatly depending on the equivalent ratio of the acid anhydride 
monomer and a reactant monomer such as an amine. That is, the molecular 
weight increases to infinity theoretically at the exact equivalent ratio 
and decreases sharply with deviating the ratio from the equivalence. 
Accordingly, the molecular weight of the polymer can be controlled easily 
by controlling the equivalent ratio. A solution of an oligomer having 
small molecular weight is easy in handling because of its low viscosity 
even with a high concentration. But, a film having small molecular weight 
has a problem in mechanical strength. 
On the other hand, a solution of a polymer having large molecular weight 
produces generally a strong film, but the solution has a problem that 
slight increment of the concentration of the solution causes sharp 
increment of viscosity and make it impossible to work with the solution. 
The solubility of the acid anhydride mentioned above is very poor, for 
instance, an acid anhydride is soluble very slightly even in 
N-methylpyrrolidon which is recognized as having the most preferable 
solubility, and the small solubility is deemed as a big problem in use of 
acid anhydrides, but there have not been any suitable means to solve the 
problem. 
At the present, a polymer solution having large molecular weight and having 
easiness in handling even with high concentration and also of superiority 
in heat resistance, mechanical strength, and resistance to chemicals after 
it is hardened, is needed widely. A method to use an oligoamic acid 
obtained by making the molecular weight of polyamic acid small, and a 
method to use an imide oligomer and an isoimide oligomer both of which 
have good solubility responds to the need mentioned above. The methods 
mentioned above made it possible to use a high concentration-low viscosity 
solution. The usage of the solution is aimed to make it easy to coat in 
spin coating etc. by using an oligomer solution, and to obtain a superior 
coating film by causing a reaction at the reactive end groups of the 
oligomer by heat treatment to get finally a large molecular weight 
polymer. As for the reactive end groups, a partially esterified acid 
anhydride, an ethynyl group, a vinyl group, and a biphenylene group etc. 
have been investigated. For instance, an electronic device manufactured 
with an oligomer having vinyl group or acetylene group as an end group of 
the molecule was disclosed in the Japanese Patent Application Laid-Open 
No. 60-120723 (1985). 
A complex crystal having a molar ratio of 1:1 of pyromellitic acid (PMDA) 
and N,N-dimethylacetamide(DMAC) is described in the Journal of Polymer 
Science (Part II, vol. 1, pp. 3135-3150). But there are not any 
description on the properties of the complex and whether it may be 
convertible to polyimide. 
SUMMARY OF THE INVENTION 
(1) Objects of the Invention 
An acid anhydride has such problems as it is unstable in storage condition, 
and as difficulty to control the molecular weight of the polyamic acid 
because of strong reactivity with organic compounds such as amines, and 
hardly soluble to organic solvents. The acid anhydride complex and 
polyamic acid complex which are obtained by the present invention resolves 
such problems of acid anhydride mentioned above, and it is possible to use 
properly depending on the objects and the condition of the usage. 
The one of the objects of the present invention is to provide a new acid 
anhydride complex and a method of producing same. 
The another object of the present invention is to provide a composition, a 
varnish, a film, a coating etc., each of which contains the acid complex. 
The another object is to provide a composition, a varnish, a film, a 
coating etc., each of which contains the polyamic acid complex, in which a 
part of the acid anhydride complex reacted with diamine. 
The another object of the present invention is to provide a method to 
produce a polyimide layer, which is necessary for production of an 
electronic device, with the acid anhydride complex and the polyamic acid 
complex described above. 
(2) Methods Solving the Problems 
The objects mentioned above are achieved by acid anhydride derivatives 
having a carbonyl carbon with a controlled electrophilic reactivity. The 
feature of the present invention is a complex comprising a base substance 
B having a donor number of at least 20 and an acid anhydride Ar, and the 
complex is presented by the general formula, 
EQU Ar.aB(where 2.gtoreq.a&gt;1) 
The base substance is free from an active hydrogen atom in the molecule in 
order to not open the acid anhydride. 
A carboxylic acid dianydride used in the present invention is an carboxylic 
acid dianhydride such as pyromellitic dianhydride (PMDA), benzophenone 
tetracarboxylic dianhydride (BTDA),3,3',4,4'-biphenyl tetracarboxylic 
dianhydride (s-BPDA), 3,3',4,4'-biphenylsulfone tetracarboxylic 
dianhydride (DSDA), 2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane 
tetracarboxylic dianhydride (6FDA), methylpyromellitic dianhydride, 
dimethylpyromellitic dianhydride, trifluoromethylpyromellitic dianhydride, 
bis (trifluoromethyl) pyromellitic dianhydride, 3,3',4,4'-oxydiphenylene 
tetracarboxylic dianhydride etc. The acid dianhydrides mentioned above are 
used separately or together depending on the necessity. 
In the present invention, an expression "donor number" is defined by a 
definition described on page 21-29 of the book entitled "Youeki Han-nou no 
Bunshikan Sougosayou" (Published in 1986 by Gakkai Shuppan Center, 
Translated by Ohtaki Hitoshi et al.) translated from a book of 
"Donor-Acceptor Approach to Molecular Interaction" (V. Gutmann, 1978). 
That is, a donor number is defined as the value of Molar enthalpy of a 
reaction between 10-.sup.3 M SbCl.sub.5 in dichloroethane which is 
selected as a standard acceptor and a donor (D). 
Especially, in the case of using a basic organic substance having a donor 
number of at least 25, the production of a complex is easier in the 
reaction mentioned above. A basic organic substance, that is an electron 
donor used in the reaction is such substances having a donor number of at 
least 20 as tetrahydrofuran(THF), trimethylphosphate(TMP), 
tributylphosphate(TBP) etc. Especially effective substances having a donor 
number of at least 25 are such as dimethylformamide(DMF), 
N-methylpyrrolidon(NMP), N-dimethylacetamide(DMA), 
dimethylsulfoxide(DMSO), N-diethylformamide(DEF), N-diethylacetamide(DEA), 
N-methylacetamide, pyridine(PY), hexamethylphosphate triamide(HMPA), 
tetramethylurea, triethylamine(TEA), etc. In addition, 
.gamma.-propiolactam and .epsilon.-caprolactam etc. are used. The electron 
donors are used separately or together. 
The reactivity of an acid anhydride is generally controlled by a method of 
hydrolysis to a carboxylic acid or a method of esterification with an 
alcohol. But, in case of using the methods, the acid anhydride is 
stabilized too much to require generally heating up to nearly 200.degree. 
C. for the reactivation. Therefore, the methods have been used in 
extremely limited area. 
An acid anhydride complex obtained by the present invention is able to 
recover its activity as an acid anhydride easily with heating. Moreover, 
the complex is extremely stable at moderate temperature which is, it 
depends on the kinds of complex, generally under 150.degree. C., in some 
cases under 80.degree. C. 
As a result that a complex accepted electrons from an electron donor the 
degree of .delta.+ of the carbonyl carbon in the acid anhydride is 
decreased. The reactivity of the complex for an electrophilic reaction 
such as hydrolysis and acylation etc. is controlled by the degree of 
.delta.+. 
The case of using a complex is different from the case wherein the 
reactivity is lowered by hydrolysis or esterification, and an aimed 
reaction is easily caused by heating. Therefore, a method of stabilization 
by the present invention does not harm any of the reactivity of an acid 
anhydride. Accordingly, a method to produce a complex disclosed in the 
specification is extremely superior as a stabilizing method of an acid 
anhydride. Additionally, as a result of investigation on the stability of 
a complex, it is revealed that such a basic substance having a donor 
number of at least 25 and N-methylpyrrolidon, dimethylsulfoxide, 
triethylamine, and pyridine etc. gives specially good stability to the 
complex. 
Tetracarboxylic dianhydride has generally very poor solubility to organic 
solvents in a condition not forming a complex, and only slightly soluble 
to an organic solvent such as N-methylpyrrolidon etc. Therefore, a solvent 
using in a reaction is strictly limited. On the other hand, the solubility 
of an acid anhydride complex related to the present invention is improved 
significantly, and the complex is soluble easily to tetrahydrofuran which 
is practically not used hitherto for acid anhydrides. Thus, an acid 
anhydride complex obtained by the present invention is very effective to 
the improvement of solubility. An acid anhydride complex related to the 
present invention is an electron donor-accepter complex with electron 
donor as a complex former, which combines to one of the carbon atoms of 
the carbonyl group of the acid anhydride by a cordinate bond. 
##STR1## 
If there are too many molecules of electron donor around one acid 
anhydride molecule, for example, the case that an acid anhydride is 
dissolved in a solvent of electron donor, electron donor molecules 
surround one molecule of the acid anhydride and cause solvation which 
prevent the formation of a cordinate bond. In the case described above, 
the formation of the acid anhydride complex is not completed and, even if 
the solution is heated, the equivalent ratio of an acid anhydride and an 
electron donor in a complex is nearly 1:1 at most and the yield is less 
than 30%. To make the equivalent ratio larger than 1:1, it is necessary to 
make an acid anhydride contact with an electron donor in the gaseous 
state. For instance, a contact of an acid anhydride with a vapourized 
electron donor causes a sufficient reaction without making solvation. In 
other case, the reaction occures by adding dropwise of a small amount of 
an electron donor to an acid anhydride powder with agitation under heating 
condition. And, another case is a dropwise addition of an electron donor 
under a heating condition to a liquid in which an acid anhydride is 
dispersed in a solvent which dissolve the complex but not the acid 
anhydride. 
In any cases, a complex having an equivalent ratio of 1:2 of an acid 
anhydride and an electron donor is the most stable against hydrolysis and 
is superior in solubility to an organic solvent. Depending on the reaction 
condition, a complex having an equivalent ratio slightly less than 1:2 is 
obtainable. It is clear that even a complex having a combination ratio 
slightly less than 1:2 has better stability and solubility than a complex 
having a combination ratio of 1:1. 
It is possible to make a complex with an oligomer by a reaction of a 
complex obtained by the present invention and an diamine compound. 
##STR2## 
An acid dianhydride complex obtained by the present invention is related to 
Ar.2B and a mixture of Ar.2B and Ar.B. By selecting the reaction 
condition, the mixing ratio of Ar.2B and Ar.B can be changed, and a 
condition which enable Ar and B react sufficiently increases Ar.2B. It is 
preferable to make a Ar.aB having at least 1.5 of a for best use of 
anti-hydrolysis property and solubility of a complex related to the 
present invention. The Ar.aB having at least 1.5 of a is obtainable by a 
one step reaction or by a suitable mixing of Ar.2B and Ar.B which are made 
separately. According to the superior characteristics of the complex, 
various applications are possible. Polyimide, an important substance in 
industry, is generally obtained by coating as polyamic acid and subsequent 
heating and hardening. In the sythesis of a polyamic acid, a precursor of 
polyimide, a complex related to the present invention is applicable to 
produce a varnish which has easiness in handling even with high 
concentration and the same superior mechanical characteristics, heat 
resistance, and resistance to chemicals after hardening as the case of 
using high molecular weight polyamic acid. That is, a varnish containing 
an acid anhydride complex having a monomer or an oligomer structure in the 
molecule and an equivalent amine compound polymerizes to be a high 
molecular weight substance by heating which causes a reaction between an 
acid anhydride complex and an amine compound. 
The viscosity of the varnish in the case is far low comparing with that of 
a conventional polyamic acid varnish of the same concentration, because 
the viscosity of a high polymer solution is proportional to the three 
powers of molecular weight. Therefore, a densely concentrated solution can 
be practically usable by applying a varnish containing the complex 
mentioned above. Moreover, the varnish after hardening becomes a high 
molecular weight substance which has the same superior mechanical 
characteristics, heat resistance, and resistance to chemicals as the case 
of using a conventional polyamic acid varnish. And of course, it is 
possible to adjust easily the viscosity of a varnish by changing the 
content of the complex in the acid anhydride. 
It is well known that a polyimide having a rod-like structure has a low 
thermal expansion coefficient. Therefore, by using a monomer which will 
produce a polyimide having a rod-like structure, it is possible to obtain 
a polyimide type resin precursor which has a superior property to produce 
an insulating film having flat and small thermal stress. It is easily 
assumed that, if a polyimide obtained finally has a rigid rod-like 
structure, it has a low thermal expansion coefficient. And, as the low 
thermal expansion property comes from the structure of skeleton of the 
main chain, it is obvious that an improvement of the property is possible 
by introducing a substitute selecting from the group of alkyl, fluorinated 
alkyl, alkoxyl, fluorinated alkoxyl, aryl, halogen etc., to the monomer. 
By copolymerization with other diamine compounds and acid dianhydrides, 
other improvements are possible such as producing a more flexible 
polyimide by copolymerization with a polymer having soft structure like as 
3,3',4,4'-benzophenone etc. within the range of not losing a property of 
low thermal expansion, as improving of adhesiveness by copolymerization 
with a substance such as 1,3 bis [3,4-dicarboxy(1,2,2)bicyclo] 
tetramethyldicyloxane dianhydride etc. And it is also possible to control 
ability of wet etching, which is important in a manufacturing process of 
large scale integrated circuit (LSI), by copolymerization with 
pyromellitic acid dianhydride and 3,3',4,4'-biphenyltetracarboxylic 
dianhydride. 
An acid anhydride complex related to the present invention is a compound in 
which an electrophilic reactivity of an acid dianhydride is controlled by 
formation of a complex with a basic organic compound which is an electron 
donor having a donor number of at least 20 and being free from an active 
hydrogen and a carboxylic dianhydride compound, and has a characteristics 
to recover the reactivity fast by heating. By utilizing the 
characteristics mentioned above, it is possible to obtain an acid 
anhydride complex which is stable against hydrolysis reaction and a 
varnish which produces an polyimide having a property to be a high 
molecular weight substance by heating and to reveal a superior 
characteristics although it has low viscosity and densely concentrated low 
molecular weight substance in a varnish state. 
The acid anhydride complex related to the present invention also can be 
used as a curing agent of an epoxy resin etc. by utilizing a property to 
be reactive by heating. 
A study on the thermal decomposition temperature of the complex obtained by 
the present invention reveals the results shown in Table 1. The data in 
Table 1 shows that it is possible to obtain an acid anhydride complex 
having a property to be active at a desired temperature by suitable 
selection of an electron donor in the present invention. 
On the other hand, the thermal decomposition temperature of s-BPA, which is 
obtained by hydrolysis of s-BPDA, is 173.degree. C. and its endothermic 
peak is 257.degree. C. 
Besides, the melting point of acid anhydrides are as followings; s-BPDA: 
294.degree. C., BTDA: 230.degree. C., PMDA: 228.degree. C., 6FDA: 
241.degree. C., DSDA:280.degree. C., 
TABLE 1 
______________________________________ 
Acid Complex Endothermic 
anhydride former peak (.degree.C.) 
______________________________________ 
s-BPDA NMP 104 
" DMSO 126 
" PY 203 
" TEA 239 
BTDA NMP 102 
" DMSO 222 
" PY 190 
" TEA 254 
PMDA NMP 155 
" DMSO 231 
" TEA 155 
6FDA NMP 208 
" DMSO 210 
" PY 221 
" TEA 257 
OPDA DMSO 210 
______________________________________ 
OPDA: 218.degree. C. 
And, the boiling point of electron donors are as followings; 
NMP: 203.degree. C., DMSO: 185.degree. C., PY: 115.degree. C., TEA: 
89.degree. C.

DETAILED DESCRIPTION OF THE EMBODIMENTS 
EXAMPLE 1 
An acid anhydride complex having an equivalent ratio 1:2 of s-BPDA:PY was 
obtained by a reaction with s-BPDA and saturated PY vapour in 40 hours at 
100.degree. C. The nuclear magnetic resonance spectrum of s-BPDA is shown 
in FIG. 1. And the nuclear magnetic resonance spectrum of the obtained 
complex is shown in FIG. 2. The solvent used at the measurement was 
DMF-d.sub.7. After heating of the acid anhydride complex in DMSO 2 hours 
at 120.degree. C., the yield of the acid anhydride complex was 50%. And 
after heating of the acid anhydride complex in PY 1 hour at 100.degree. 
C., the yield of the acid anhydride complex was 60%. 
EXAMPLE 2 
An acid anhydride complex having an equivalent ratio 1:2 of s-BPDA:NMP was 
obtained nearly quantitatively by a reaction with s-BPDA and saturated NMP 
vapour in 40 hours at 200.degree. C. The nuclear magnetic resonance 
spectrum of the obtained complex is shown in FIG. 3. 
EXAMPLE 3 
An acid anhydride complex having an equivalent ratio 1:2 of s-BPDA:TEA was 
obtained by a reaction with s-BPDA and saturated TEA vapour in 40 hours at 
80.degree. C. 
EXAMPLE 4 
An acid anhydride complex having an equivalent ratio 1:2 of PMDA: PY was 
obtained by a reaction with PMDA and saturated PY vapour in 40 hours at 
100.degree. C. 
EXAMPLE 5 
An acid anhydride complex having an equivalent ratio 1:2 of PMDA: TEA was 
obtained nearly quantitatively by a reaction with PMDA and saturated TEA 
vapour in 40 hours at 80.degree. C. The nuclear magnetic resonance 
spectrum of the obtained PMDA complex is shown in FIG. 5. 
EXAMPLE 6 
An acid anhydride complex having an equivalent ratio 1:2 of PMDA: NMP was 
obtained nearly quantitatively by a reaction with PMDA and saturated NMP 
vapour in 40 hours at 200.degree. C. 
EXAMPLE 7 
An acid anhydride complex having an equivalent ratio 1:2 of BTDA: PY was 
obtained nearly quantitatively by a reaction with BTDA and saturated PY 
vapour in 40 hours at 100.degree. C. After heating the acid anhydride 
complex in DMSO 2 hours at 120.degree. C., the yield of the acid anhydride 
complex was 75%. 
EXAMPLE 8 
An acid anhydride complex having a combination ratio 1:2 of 6FDA: PY was 
obtained nearly quantitatively by a reaction with 6FDA and saturated PY 
vapour in 40 hours at 100.degree. C. The nuclear magnetic resonance 
spectrum of the obtained 6FDA complex is shown in FIG. 7. 
EXAMPLE 9 
An acid anhydride complex having an equivalent ratio 1:2 of 6FDA: TEA was 
obtained nearly quantitatively by a reaction with 6FDA and saturated TEA 
vapour in 40 hours at 80.degree. C. 
EXAMPLE 10 
A reaction was occured by adding of NMP dropwise in 3 hours to 60 g. of 
s-BPDA powder with stirring under a condition heated at 80.degree. C. 
-120.degree. C. in inactive atmosphere, and a brown powder was obtained. 
The nuclear magnetic resonance spectrum of s-BPDA and the reaction product 
were measured. The formation of an acid anhydride complex was confirmed by 
observation of a peak shifting to lower magnetic field. 
EXAMPLE 11 
A reaction was occured by adding of DSMO dropwise in 3 hours to 60 g. of 
s-BPDA powder with stirring under a condition heated at 80.degree. C. 
-120.degree. C. in inactive atmosphere, and a brown powder was obtained. 
The nuclear magnetic resonance spectrum of the reaction product was 
measured. The formation of an acid anhydride complex was confirmed by 
observation of a peak shifting to lower magnetic field. 
EXAMPLE 12 
A reaction was occured by adding of THF and .gamma.-propiolactam dropwise 
in 3 hours to 60 g. of s-BPDA powder with stirring under a condition 
heated at 80.degree. C.-120.degree. C. in inactive atmosphere, and a brown 
powder was obtained. The nuclear magnetic resonance spectrum of the 
reaction product was measured. The formation of an acid anhydride complex 
was confirmed by observation of a peak shifting to lower magnetic field. 
With other experiments which used lactams having different ring size from 
5 to 10 under the same condition, the formation of acid anhydride 
complexes were confirmed by the observation of nuclear magnetic resonance 
spectrums. And in the case using N-methylacetamide, which is a same 
secondary amide as a lactam, the formation of a complex was also 
confirmed. 
EXAMPLE 13 
A mixture of 240 g. of THF and 6 g. of s-BPDA was heated 1-3 hours with PY 
in inactive atmosphere, and a yellow transparent solution was obtained. By 
adding the yellow solution to 20 times volume of n-hexane, a pale yellow 
substance was precipitated. The precipitate was separated from the liquid 
by filtration and was dried 12 hours at 60.degree. C. in vacuum. A 7.2 g. 
of powder was obtained. The formation of a complex was confirmed by 
observation of a same peak shifting to lower magnetic field as shown in 
FIG. 2 in the nuclear magnetic resonance spectrum of the powder. 
EXAMPLE 14 
A mixture of 240 g. of caprolactam, 6 g. of s-BPDA, and 
.gamma.-propiolactam was heated 1-3 hours in inactive atmosphere, and a 
yellow transparent solution of a complex was obtained. The formation of a 
complex was confirmed by observation of a same peak shifting to lower 
magnetic field as shown in FIG. 2 in the nuclear magnetic resonance 
spectrum of the solution. 
EXAMPLE 15 
The formation of a complex in the reaction product obtained by a same 
experiment as Example 10 except using BTDA instead of s-BPDA was confirmed 
by observation of a peak shifting to lower magnetic field in the nuclear 
magnetic resonance spectrum of the reaction product and BTDA. 
EXAMPLE 16 
The formation of a complex in the reaction product obtained by a same 
experiment as Example 10 except using PMDA instead of s-BPDA was confirmed 
by observation of a peak shifting to lower magnetic field in the nuclear 
magnetic resonance spectrum of the reaction product and PMDA. 
Comparative Example 1 
A mixture of 240 g. of NMP, 60 g. of s-BPDA, and .epsilon.-caprolactam was 
heated 36 hours at 180.degree. C.-200.degree. C. in inactive atmosphere, 
and a brown solution was obtained. The nuclear magnetic resonance spectrum 
of the solution is shown in FIG. 8. The formation of any complex is not 
observed, but a quantitative formation of bisimide compound was confirmed. 
The time depending change of the yield of the product was measured by a 
chromatographic method, and the results are shown in FIG. 9(a) to FIG. 
9(c). The reaction was very slow and the formation of bisimide carboxylic 
acid was scarsely observed in the reaction of 1-3 hours. 
EXAMPLE 17 
A mixture of s-BPDA and a complex comprising s-BPDA and DMSO was dissolved 
in DMSO contianing water. The changing of the composition was observed by 
measurement of nuclear magnetic resonance spectrum. The results are shown 
in FIG. 10 and FIG. 11. It was revealed that s-BPDA was hydrolized as the 
peaks of s-BPDA which were observed at the dissolution had been 
disappeared after 18 hours. On the other hand, the peaks of S-BPDA complex 
were observed even after 18 hours without any change. The result of the 
experiment mentioned above revealed that the formation of a complex 
achieved lowering of the hydrolizing property and significant stabilizing 
of s-BPDA. 
EXAMPLE 18 
A reaction was occured by adding slowly an equivalent p-PDA to a solution 
of s-BPDA complex which was obtained in Example 1 with stirring and 
ice-cooling. The viscosity of the varnish after the reaction of 3 hours 
with stirring was 8 poises at 30 wt. % of solid content. 
EXAMPLE 19 
A same experiment as Example 9 except using an equivalent DDE instead of 
p-PDA was held. The viscosity of the varnish obtained by the experiment 
was 15 poises at 30 wt. % of solid content. 
EXAMPLE 20 
A reaction was occured by adding slowly an equivalent p-PDA to a solution 
of a complex obtained in Example 4 in NMP with stirring. The viscosity of 
the varnish after the reaction of further 3 hours with stirring was 42 
poises at 30 wt. % of solid content. 
Comparative Example 2 
A solution was prepared by dissolving 22 g. of p-PDA in 240 g. of NMP with 
stirring. A reaction was occured by adding an equivalent (60 g.) s-BPDA to 
the solution slowly with stirring by a stirrer connected to a motor and 
ice-cooling in inactive atmosphere. The viscosity of the reactant was 
increased as the addition of the solution was going on, and finally, at 
the time when total solution had added, it became impossible to stir the 
reactant because of increased viscosity. 
Comparative Example 3 
A same reaction as Comparative example 2 except using an equivalent (41 g.) 
of DDE instead of p-PDA was held. It became impossible to stir the 
reactant on the half way of the reaction. 
EXAMPLE 21 
A varnish which was obtained in Example 17 and applied on the surface of a 
glass substrate with an applicator was dried one hour at 100.degree. C., 
and was hardened by heating up to 400.degree. C. at the rate of 
200.degree. C./hour and kept 10 minutes at 400.degree. C. A film obtained 
was cut out into a test piece of 5 mm.times.50 mm, and its mechanical 
strength was measured. The break strength of the film was 36 kg./mm.sup.2 
and the break elongation was 25%. And the durable temperature defined as 
the temperature at which 3% loss in its weight occurs in 100 minutes was 
520.degree. C. 
EXAMPLE 22 
A varnish synthesized in Example 19 was hardened at 350.degree. C. as the 
final hardening temperature and was measured the mechanical strength of 
the film. The break strength was 28 kg./mm.sup.2 and the break elongation 
was 52%. The durable temperature defined same as Example 21 was 
491.degree. C. 
EXAMPLE 23 
A film was prepared from a varnish synthesized in Example 20 by the same 
process as Example 12 and was measured the mechanical strength. The break 
strength was 41 kg./mm.sup.2 and break elongation was 22%. The durable 
temperature defined same as Example 20 was 517.degree. C. 
Comparative Example 4 
A reaction was occurred by adding 2/3 of an equivalent (54.4 g.) s-BPDA 
slowly to a solution of 30 g. of p-PDA in 200 g. of NMP. The reaction was 
carried on further 5 hours after s-BPDA was added, and a dense green 
solution was obtained. By adding 27.2 g. of phthalic anhydride to the 
solution so as to make the ratio of amine and acid anhydride an equivalent 
and carrying on the reaction further 5 hours, a yellow transparent 
oligomer varnish having viscosity of 25 poises was obtained. The varnish 
was hardened by the same process as Example 20. In the hardening process, 
a large number of cracks were generated on the surface of the hardened 
body and any of film was not obtained. The measurement of mechanical 
strength was impossible. 
Comparative Example 5 
A reaction was occurred by adding 2/3 of an equivalent (31.3 g.) PMDA 
slowly to a solution of 50 g. of DDE in 200 g. of NMP. The reaction was 
carried on further 5 hours after PMDA was added, and a dense green 
solution was obtained. By adding 21.6 g. of phthalic anhydride to the 
solution so as to make the ratio of amine and acid anhydride an equivalent 
and carrying on the reaction further 5 hours, a yellow transparent 
oligomer varnish having viscosity of 19 poises was obtained. The varnish 
was hardened by the same process as Example 20. In the hardening process, 
a large number of cracks were generated on the surface of the hardened 
body same as comparative example 6 and any of film was not obtained. The 
measurement of mechanical strength was impossible. 
Comparative Example 6 
A half-esterified solution was synthesized by a reaction of 60 g. of s-BPDA 
and 2 times of an equivalent ethyl alcohol in 200 g. of NMP in 2 hours at 
100.degree. C. The solution was cooled down to room temperature and was 
added with an equivalent of p-PDA to s-BPDA. By dissolving the additives 
with stirring, a varnish having a half-ester as a functional group to 
cause polymerization in hardening process was obtained. The viscosity of 
the varnish was 1.8 poises. In the same hardening process as Comparative 
example 5, a large number of cracks were generated on the surface of the 
hardened body and any of film was not obtained. The measurement of 
mechanical strength was impossible. 
Comparative Example 7 
A varnish solution having a concentration of 40 wt. % and viscosity of 42 
poises was obtained by dissolving a resin having ethynyl groups at the 
terminal of the molecular chain in NMP. The varnish was hardened by the 
same process as Example 21. An obtained film was too fragile to be 
measured the mechanical strength. 
EXAMPLE 24 
The result of the measurement of flatness of a film produced from the 
varnish synthesized in Example 17 by applying it on the surface of an 
aluminum pattern of which structure is shown in FIG. 12 and hardened there 
was 0.80. The flatness is defined by the following equation and the value 
is more preferable as it close to 1. 
##EQU1## 
The symbols in the equation (3) are defined in FIG. 13. The evaluation 
pattern to be used for the measurement of the flatness of a polyimide film 
is shown in FIG. 12. Using the pattern, the flatness of a film produced on 
the surface of the pattern was measured according to the definition shown 
in FIG. 13. 
EXAMPLE 25 
The result of the measurement of flatness of a film produced from the 
varnish synthesized in Example 18 by applying it on the surface of an 
aluminum pattern of which structure is shown in FIG. 12 and hardened there 
was 0.83. 
Comparative Example 8 
A polyamic acid varnish having a concentration of 15 wt. % which was 
synthesized from p-PDA and s-BPDA by a conventional process was applied 
and hardened by the same process as Example 25, and the flatness of the 
film was measured. The result was 0.44. 
EXAMPLE 26 
A transparent brown solution of a complex was obtained by adding 6 g. of 
BTDA to 240 g. of THF and heating 1-3 hours with DMSO in inactive 
atmosphere. The formation of a complex was confirmed by observation of the 
nuclear magnetic resonance spectrum of the solution which was measured 
after the same treatment as Example 13. 
EXAMPLE 27 
A transparent brown solution of a complex was obtained by adding 6 g. of 
BTDA and .gamma.-propiolactam to 240 g. of THF and heating 1-3 hours in 
inactive atmosphere. In the nuclear magnetic resonance spectrum measured 
after the same treatment as Example 13, a peak shifting to lower magnetic 
field was observed and the formation of a complex was confirmed. And in 
the same experiment except using different ring size of lactam from 5 to 
10, the formation of a complex was confirmed by the nuclear magnetic 
resonance spectrum. And in the case of using N-methylacetamide, the 
formation of a complex was also confirmed. 
EXAMPLE 28 
A transparent yellow solution was obtained by adding 6 g. of BTDA to 240 g. 
of THF and heating 1-3 hours with PY in inactive atmosphere. A yellow 
precipitate was obtained by adding the solution to 20 times volume of 
n-hexane. After the same treatment as Example 13, the nuclear magnetic 
resonance spectrum was measured. In the spectrum, a peak shifting to lower 
magnetic field was observed and the formation of a complex was confirmed. 
EXAMPLE 29 
A transparent yellow solution of a complex was obtained by adding of 6 g. 
of BTDA and .gamma.-propiolactam to 240 g. of caprolactone and heating 1-3 
hours in inactive atmosphere. After the same treatment as Example 13, the 
nuclear magnetic resonance spectrum was measured. A peak shifting to lower 
magnetic field was observed and the formation of a complex was confirmed. 
Comparative Example 9 
A brown solution was obtained by adding 6 g. of BTDA and 
.epsilon.-caprolactam to 240 g. of NMP and heating 36 hours at 180.degree. 
C.-200.degree. C. in inactive atmosphere. According to the nuclear 
magnetic resonance spectrum of the solution, the formation of a complex 
was not observed, but quantitative yield of bisimide compound was 
confirmed. By measuring the time depending change of the yield of the 
product by a liquid chromatographic method, it was revealed that the 
reaction went on very slowly and the formation of bisimide carboxylic acid 
was scarcely observed in the reaction of 1-3 hours. 
EXAMPLE 30 
A mixture of BTDA and a complex comprising BTDA and DMSO was dissolved into 
DMSO containing water, and the change of the solution was measured with a 
nuclear magnetic resonance spectrum. The result revealed that the peaks of 
BTDA which was observed at the moment of dissolving disappeared after 18 
hours and hydrolysis of BTDA had occurred. On the other hand, the peaks of 
the complex including BTDA was observed even after 18 hours without any 
change, and it was confirmed that the formation of a complex achieved 
lowering of hydrolyzing property and significant stabilizing of BTDA. 
EXAMPLE 31 
A transparent brown solution of a complex was obtained by adding 60 g. of 
DSDA to 240 g. of THF and heating 3 hours with NMP in inactive atmosphere. 
According to the nuclear magnetic resonance spectrum which was measured 
after the solution was treated by the same process as Example 13, a peak 
shifting to lower magnetic field was observed and the formation of a 
complex was confirmed. 
EXAMPLE 32 
A transparent brown solution of a complex was obtained by adding 6 g. of 
DSDA to 240 g. of THF and heating 3 hours with DMSO in inactive 
atmosphere. According to the nuclear magnetic resonance spectrum which was 
measured after the solution was treated by the same process as Example 13, 
a peak shifting to lower magnetic field was observed and the formation of 
a complex was confirmed. 
EXAMPLE 33 
After adding 60 g. of DSDA and .gamma.-propiolactam to 240 g. of THF, the 
solution was heated 3 hours in inactive atmosphere. After the solution was 
treated by the same process as Example 13, a nuclear magnetic resonance 
spectrum was measured. A peak shifting to lower magnetic field was 
observed in the spectrum and the formation of a complex was confirmed. And 
in the same experiment except changing the ring size of lactams to 5-10, 
the formation of a complex was confirmed with the nuclear magnetic 
resonance spectrum. And in the case of using N-methylacetamide which is a 
same secondary amine as lactam, the formation of a complex was also 
confirmed. 
EXAMPLE 34 
A transparent yellow solution was obtained by adding 6 g. of DSDA to 240 g. 
of THF and heating 3 hours with PY in inactive atmosphere. A pale yellow 
precipitate was obtained by adding the solution into 20 times of volume of 
n-hexane. After the precipitate was treated with the same process as 
Example 4, a nuclear magnetic resonance spectrum was measured. A peak 
shifting to lower magnetic field was observed and the formation of a 
complex was confirmed. 
EXAMPLE 35 
A transparent yellow solution was obtained by adding 60 g. of DSDA and 
.gamma.-propiolactam to 240 g. of caprolactone and heating 3 hours with 
.gamma.-propiolactam in inactive atmosphere. After the precipitate was 
treated with the same process as Example 4, the nuclear magnetic resonance 
spectrum was measured. A peak shifting to lower magnetic field was 
observed and the formation of a complex was confirmed. 
Comparative Example 10 
A brown solution was obtained by adding 60 g. of DSDA and 
.epsilon.-caprolactam to 240 g. of NMP and heating 36 hours at 180.degree. 
C.-200.degree. C. in inactive atmosphere. According to the nuclear 
magnetic resonance spectrum of the solution, the formation of a complex 
was not observed, but the quantitative formation of bisimide carboxylic 
acid was confirmed. The reaction went on slowly and the formation of 
bisimide carboxylic acid was scarcely observed in the reaction of 1-3 
hours. 
EXAMPLE 36 
A mixture of DSDA and a complex of DSDA was dissolved into DMSO containing 
water and change of the solution was measured with the nuclear magnetic 
resonance spectrum. The peak of DSDA which was observed at the moment of 
dissolution disappeared after 18 hours and hydrolysis of DSDA was 
confirmed. On the other hand, the peak of a complex of DSDA was observed 
even after 18 hours without any change. The result revealed that the 
formation of a complex achieved lowering of hydrolyzing property and 
significant stabilizing of DSDA. 
EXAMPLE 37 
A transparent brown solution of a complex was obtained by adding 60 g. of 
6FDA to 240 g. of NMP and heating 3 hours at 80.degree. C.-120.degree. C. 
in inactive atmosphere. In the nuclear magnetic resonance spectrum of 6FDA 
and of the solution, a peak shifting to lower magnetic field was observed 
and the formation of a complex was confirmed. 
EXAMPLE 38 
A transparent brown solution of a complex was obtained by adding 6 g. of 
6FDA to 240 g. of THF and heating 3 hours with DMSO in inactive 
atmosphere. After the solution was treated by the same process as Example 
4, the nuclear magnetic resonance spectrum was measured. A peak shifting 
to lower magnetic field was observed and the formation of a complex was 
confirmed. 
EXAMPLE 39 
A transparent brown solution of a complex was obtained by adding 60 g. of 
6FDA and .gamma.-propiolactam to 240 g. of THF and heating 3 hours in 
inactive atmosphere. And after the solution was treated with the same 
process as Example 4, the nuclear magnetic resonance spectrum was 
measured. The formation of a complex was confirmed by the observation of a 
peak shifting to lower magnetic field in the spectrum. And, in the same 
experiment except changing the ring size of lactam to 5-10, the formation 
of a complex was confirmed with the nuclear magnetic resonance spectrum. 
And also, in an experiment using N-methylacetamide which is same secondary 
amide as lactam, the formation of a complex was confirmed. 
EXAMPLE 40 
A transparent yellow solution was obtained by adding 6 g. of 6FDA to 240 g. 
of THF and heating 3 hours in inactive atmosphere. According to the 
nuclear magnetic resonance spectrum measured after the solution was 
treated by the same process as Example 4, a peak shifting to lower 
magnetic field was observed and the formation of a complex was confirmed. 
EXAMPLE 41 
A transparent yellow solution of a complex was obtained by adding 60 g. of 
6FDA and .gamma.-propiolactam to 240 g. of caprolactone and heating 3 
hours in inactive atmosphere. According to the nuclear magnetic resonance 
spectrum measured after the solution was treated by the same process as 
Example 4, the same peak shifting to lower magnetic field as seen in FIG. 
2 and 3 was observed and the formation of a complex was confirmed. 
Comparative Example 11 
A brown solution was obtained by adding 60 g. of 6FDA and 
.epsilon.-caprolactam to 240 g. of NMP and heating 36 hours at 180.degree. 
C.-200.degree. C. in inactive atmosphere. According to the nuclear 
magnetic resonance spectrum of the solution, the formation of any complex 
was not observed. But, the quantitative formation of bisimide compound was 
confirmed. The time depending change of the yield of the product was 
measured with a liquid chromatographic method, and it was revealed that 
the reaction went on very slowly and the formation of bisimide carboxylic 
acid was scarcely observed in reaction of 1-3 hours. 
EXAMPLE 42 
A mixture of 6FDA and a complex comprising 6FDA and DMSO was dissolved into 
DMSO containing water and a change of the solution was measured with a 
nuclear magnetic resonance spectrum. The peaks of 6FDA, which was observed 
at the time of the dissolution, was disappeared after 18 hours and 
hydrolysis of 6FDA was confirmed. On the other hand, the peak of the 
complex was observed without any change. With this observation, it was 
confirmed that the formation of a complex achieved lowering of hydrolizing 
property and significant stabilizing of 6FDA.