Sulfonated aniline-type copolymer and process for production thereof

Sulfonated aniline-type copolymer and a process for their preparation are disclosed. These products comprise a water soluble and alcohol soluble copolymer of a compound (A) selected from the group of aniline, N-alkylaniline and phenylenediamine, and aminobenzene sulfonic acid (B); said sulfonated product being a following compound of a general formulae I to V stated in the specification, or a mixture thereof. Also, process for the sulfonated aniline-type copolymer comprises the steps: PA0 copolymerizing a compound (A) selected from the group of aniline, N-alkyl aniline and phenylene diamine, and aminobenzene sulfonic acid (B) to obtain a copolymer; and PA0 sulfonating the thus obtained copolymer with a sulfonating agent.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a sulfonated aniline-type copolymer and a process 
for the production thereof. More particularly, this invention provides an 
electric conductive polymer which is soluble in water or an alcoholic 
solvent. 
The obtained polymer solution may be applied to various kinds of antistatic 
treatment using a simple method such as a coating, spray or dipping 
method. 
2. Description of the Related Art 
A proton-doped polyaniline is well known as an electric conductive polymer, 
however, the proton-doped aniline has a drawback in the molding step or 
the processing step owing to the insolubility of almost all solvents. 
Under these circumstances, a water soluble sulfonated polyaniline that 
reveals electric conductivity without the addition of a dopant, as well as 
a process for the production thereof have been proposed. 
Examples of the process for the production of the sulfonated polyaniline 
are as follows: a process for the production of a sulfonated polyaniline 
by electrochemically polymerizing an aniline and an m-aminobenzene 
sulfonic acid (Nihon Kagakukaishi, 1985, 1124; Japanese Unexamined Patent 
Publication No. 2-166165); a process for the production of a sulfonated 
polyaniline by chemically polymerizing an aniline and o- or m-aminobenzene 
sulfonic acid (Japanese Unexamined Patent Publication No. 1-301714 
corresponding to U.S. Pat. No. 4,956,441); a method of sulfonating an 
emeraldine-type polymer (polyaniline) obtained by polymerizing chemically 
or electrochemically using a conc. sulfuric acid (Japanese Unexamined 
Patent Publication No. 58-210902 corresponding to EP-96319A); a method of 
sulfonating using anhydrous sulfuric acid and a triethyl phosphate complex 
(Japanese Unexamined Patent Publication No. 61-197633) and a method of 
sulfonating using a fuming sulfuric acid (J. Am. Chem. Soc., 1991, 113, 
2665-2671; J. Am. Chem. Soc., 1990, 112, 2800, WO91-06887) and the like. 
The first mentioned process (Nihon Kagaku kaishi, 1985, 1124; Japanese 
Unexamined Patent Publication No. 2-166165) had drawbacks in that the 
isolating process for the product was complicated because of the formation 
of the product on the electrode, and because a large number of products 
were difficult to synthesize. 
The present inventors attempted to follow the second-mentioned process 
(Japanese Unexamined Patent Publication No. 1-301714). Namely, the present 
inventors carried out the process for the polymerization of aniline and 
m-aminobenzene sulfonic acid using an ammonium peroxodisulfate, as is 
described in said publication. It was then found that only about one 
sulfonic acid group per five repeating units was introduced in the 
obtained product. 
Furthermore, the present inventors carried out the process for sulfonating 
a polyaniline using a fuming sulfuric acid as was described in Japanese 
Unexamined Patent Publication No. 61-197633 mentioned above. It was also 
found that only about one sulfonic acid group per five repeating units was 
introduced in the obtained product as described in the publication, page 
7, because the reaction proceeded in the dispersion state owing to 
insufficient solubility of the polyaniline with regard to the sulfonating 
solvent, and there was a problem in that the obtained sulfonated 
polyanilines, including a small amount of the sulfuric acid group therein, 
were found to be deficient with regard to electric conductivity and 
solubility. 
Next, when sulfonating a polyaniline with a fuming sulfuric acid, about one 
sulfonic acid is introduced into two repeating units (J. Am. Chem. Soc., 
1991, 113, PP2665-2671; J. Am. Chem. Soc., 1990, 112, 2800). 
However, when fully sulfonating polyaniline by means of the above process, 
it is necessary to add an aniline to an amount of the fuming sulfuric 
acid, because of insufficient solubility of a polyaniline with regard to 
the fuming sulfuric acid. 
Furthermore, when the amount of fuming sulfuric acid is insufficient, a 
part of the polyaniline solidifies and is not sulfonated thereon. 
Therefore, it is necessary to determine a method of introducing much more 
sulfonic acid groups into the aromatic ring in order to reveal the 
electric conductivity and improve solubility without the addition of a 
dopant to a polymer. 
Also, when considering the molding properties, such as a film forming 
property using a coating and in particular when considering the 
probability of coating the polymer on both a hydrophic and a hydrophobic 
substrate material, the obtained polymer should preferably enjoy good 
solubility with regard to water and alcohol and the like. 
However, the prior sulfonated polyaniline has good solubility with regard 
to water, but has low solubility with regard to alcoholic solvents. 
SUMMARY OF THE INVENTION 
In view of the problems of the prior art described above, an object of the 
present invention is to provide a sulfonated aniline-type copolymer and a 
process for the production thereof, with said copolymer revealing high 
electric conductivity and enjoying high solubility against water or 
alcoholic solvents and also enjoying good coating properties. 
Another object of the present invention is to provide a new sulfonated 
polyaniline in which the ratio of a sulfonic acid group introduced into an 
aromatic ring as an electroconductive polyaniline is high and provide a 
new process for the production thereof. 
The present inventors have conducted research with a view to attain the 
foregoing objects, and as a result have found the following. 
Namely, copolymerizing an aniline compound and an aminobenzene sulfonic 
acid compound in order to obtain a copolymer in which a sulfonic acid 
group has been previously introduced is very effective for increasing 
solubility with regard to the solvent, followed by effecting the process 
of sulfonation. 
Therefore, the present invention relates to a sulfonated aniline-type 
copolymer that comprises a water soluble and alcohol soluble copolymer of 
a compound (A) selected from the group of aniline, N-alkylaniline and 
phenylenediamine, and aminobenzene sulfonic acid (B); said sulfonated 
product being a following compound of a general formulae I to V, or a 
mixture thereof: 
##STR1## 
wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are independently selected 
from the group consisting of hydrogen, methoxy, C.sub.1 -C.sub.2 alkyl and 
hydroxyl and SO.sub.3 H, wherein at least one of the R.sub.1, R.sub.2, 
R.sub.3 and R.sub.4 is SO.sub.3 H; 
R' is hydrogen or C.sub.1 -C.sub.4 alkyl, and preferably methyl; 
x is an arbitrary number from 0 to 1. 
The molecular weight of the present copolymer ranges from 300 to 500,000 
daltons. 
The present invention further relates to a process for the above-mentioned 
sulfonated aniline-type copolymer product that comprises the following 
steps: 
copolymerizing a compound (A) selected from the group of aniline, N-alkyl 
aniline and phenylene diamine, and aminobenzene sulfonic acid (B) so as to 
obtain a copolymer; and 
sulfonating the thus obtained copolymer with a sulfonating agent. 
The term "water soluble" means that a non-solubilized product would not be 
produced when 1% by weight of a sulfonated aniline-type copolymer is 
dissolved in 0.1N of an ammonia aqueous solution. 
The term "alcohol soluble" means that a non-solubilized product would not 
be produced when 1% by weight of a sulfonated aniline-type copolymer is 
dissolved in 0.1N of an ammonia-methanol solution.

DETAILED DESCRIPTION OF THE INVENTION 
In this invention, the component (A) is at least one of the compounds 
selected from the group of aniline, N-alkylaniline and phenylenediamines 
as mentioned above. 
N-alkylaniline herein can be N-methylaniline, N-ethylaniline, 
N-n-propylaniline, N-iso-propylaniline, N-butylaniline and the like. 
Phenylenediamines herein can be phenylenediamine, N-phenylphenylenediamine, 
N,N'-diphenylphenylenediamine, N-aminophenyl-N'-phenylphenylenediamine, 
hydroxydiphenylamine and the like. 
Note that the monomer (A) component consisting of aniline, N-alkylaniline 
and phenylenediamine may be employed in a single form, or in a mixed form. 
The use of N-alkylaniline may improve solubility with regard to an 
alcohol-type solvent and may improve the coating properties with regard to 
a hydrophobic substrate. 
Also, the use of phenylenediamine may improve solubility against water due 
to the increase in the introduction ratio of the sulfonic acid. 
The desired ratio of N-alkylaniline to aniline and (or) phenylenediamine is 
0 to 30:100. If the ratio of N-alkylaniline is too high, solubility 
against water could be lowered, and electroconductivity could deteriorate. 
Aniline and phenylenediamine can be employed in a single form respectively, 
or can be employed as a mixture in which both compounds are mixed in an 
optional ratio. 
Generally, when employing only one component of aniline as a component (A) 
effecting copolymerization of aniline and aminobenzenesulfonic acids, 
there is a tendency for the introduction ratio of the sulfonic acid group 
to decrease. 
On the other hand, the use of phenylenediamines such as phenylenediamine, 
N-phenylphenylenediamine and the like may lead to a high sulfonic acid 
introduction ratio in proportion to the added amount. 
It is possible to employ any one of o-, m-, or p-amino-benzenesulfonic acid 
and anilinedisulfonic acid as the (B) component of aminobenzenesulfonic 
acids. 
Note that a copolymer of aniline and o-aminobenzene sulfonic acid or 
m-aminobenzene sulfonic acid is described in the following publications of 
J. Am. Chem. Soc., 1991, 113, 2667 and Japanese Unexamined Patent 
Publication No. 1-301714. 
However, the present inventors have discerned that aniline and 
p-aminobenzenesulfonic acid can copolymerize effectively. 
Note that this chemical structure is different from that of the prior known 
straight polymer (having the repeating units of bonding at para-position). 
The preferred ratio of the component (A) monomer consisting of aniline, 
N-alkylaniline and phenylenediamine to the component (B) consisting of 
aminobenzenesulfonic acids to be polymerized is 100 parts by weight of the 
component (A) monomer (total amount):10-500 parts by weight of the 
component (B) monomer. 
Note that the monomer (B) component consisting of o-, m-, and 
p-aminobenzenesulfonic acid can be employed in a single form, or in a 
mixed form in an optional ratio thereof. 
The present copolymer can be obtained by means of oxidation polymerization 
with an oxidizing agent in the acidic solvent. 
The preferred solvents are water, methanol, ethanol, isopropanol, 
acetonitrile, methylethylketone, dimethylformamide, dimethylacetoamide and 
the like. The preferred oxidizing agent is ammonium peroxodisulfate, 
hydrogen peroxide, and the like. 
The ratio to be employed of the oxidizing agent to the monomer is 0.1-10 
mol:one mol. The preferred ratio of the oxidizing agent to the monomer is 
0.5-5 mol:one mol. 
The preferred acids to be employed are, for example, sulfuric acid, 
hydrochloric acid and p-toluenesulfuric acid or the like and a mixture 
thereof. 
The concentration of the acid is 0.1-5 mol/l, preferable 0.2-3 mol/l. The 
reaction temperature is preferably not more than 70.degree. C., and more 
preferably a temperature ranging from -20.degree. C. to 50.degree. C. 
Here, the copolymer of aniline and(or) N alkylaniline and 
aminobenzenesulfuric acids is insufficient in electroconductivity and 
solubility due to a low introduction rate (10-25%) of a sulfonic acid 
group with regard to the aromatic ring. 
However, the copolymer of phenylenediamine and aminobenzenesulfuric acids 
enjoys both electroconductivity and solubility due to a high introduction 
rate (25-40%) of a sulfonic acid group with regard to the aromatic ring. 
In this invention, the obtained copolymer is further sulfonated in the 
solvent or without a solvent. 
The copolymer of phenylenediamine and aminobenzenesulfonic acid, and also 
the copolymer of aniline and(or) N-alkylaniline and aminobenzene sulfonic 
acid enjoys high solubility with regard to the sulfonating agent and 
solvent, compared with polyaniline, because the monomer component 
originally contains sulfonic acid on a part of an aromatic ring, which 
leads to high operability and a high introduction ratio of a sulfonic acid 
group. 
The preferable sulfonating agent may include conc. sulfuric acid, fuming 
sulfuric acid, fuming sulfuric acid complex and the like. 
When sulfonation is carried out using a conc. sulfuric acid or a fuming 
sulfuric acid as the sulfonating agent, said sulfonation is preferably 
carried out without a solvent. 
When sulfonation is carried out using a sulfur trioxide or a sulfur 
trioxide complex as the sulfonating agent, said sulfonation is preferably 
carried out in a solvent. 
Suitable solvents are dimethylformamide, dimethylacetoamide, 
dimethylsulfoxide, N-methylpyrrolidone, pyridine and the like. 
Sulfuric acid or fuming sulfuric acid may be employed in an amount of 1 to 
100 g, preferably 5 to 50 g per one gram of copolymer. 
The solvent may be employed in an amount of 10 to 300 g, preferably 20 to 
200 g per one gram of copolymer. 
The reaction temperature is preferably not more than 200.degree. C., and 
more preferably from 0.degree. to 100.degree. C. 
The introduction ratio of a sulfonic acid group into an aromatic ring 
increases to a level of 40 to 80% in the obtained sulfonation product, 
which in this invention is suitable. 
The molecular weight of the thus obtained sulfonated polyaniline ranges 
from 300 to 500,000 daltons. 
Also, the thus obtained sulfonated polyaniline may be dissolved in water or 
alcohol such as methyl alcohol, ethyl alcohol and isopropyl alcohol. 
Note that the above-mentioned water contains therein a base such as 
ammonia, alkylamine and the like, or else contains the cation of the above 
base such as ammonium acetate, ammonium oxalate and the like. 
The invention will be understood more readily with reference to the 
following examples; however these examples are intended to illustrate the 
invention and do not limit the scope of the invention. 
EXAMPLE 
Synthesis of the Copolymer 
Examples 1-14 (Refer to Tables 1 and 2) 
An aminobenzene sulfonic acid and at least one compound selected from the 
group consisting of aniline, N-alkylaniline and phenylenediamine was 
dissolved in hydrochloric acid, sulfuric acid or p-toluenesulfonic acid, 
and the solution of ammonium peroxodisulfate in sulfuric acid or 
p-toluenesulfonic acid was then added in a dropwise manner. 
After the addition of the solution was completed, the reaction mixture was 
further stirred for a period of time, the reaction product was filtrated, 
washed with methanol and acetone, and dried to yield the desired copolymer 
in the form of a powder. 
More detailed conditions for the copolymerization reaction were listed in 
Table 1 and Table 2. 
TABLE 1 
__________________________________________________________________________ 
Monomer Oxidizing reagent 
Example 
Component 
Component Oxidizing 
No. 1 2 AS Solvent 
reagent 
Solvent 
__________________________________________________________________________ 
1 Aniline 
-- m-AS 1N--HCl 
(NH.sub.4).sub.2 S.sub.2 O.sub.8 
1N--HCl 
15 mmol 15 mmol 
45 ml 30 mmol 
30 ml 
2 Aniline 
-- p-AS 1N--HCl 
(NH.sub.4).sub.2 S.sub.2 O.sub.8 
1N--HCl 
15 mmol 30 mmol 
68 ml 45 mmol 
45 ml 
3 Aniline 
N-Me m-AS 1N--HCl 
(NH.sub.4).sub.2 S.sub.2 O.sub.8 
1N--HCl 
13.5 mmol 
Aniline 
15 mmol 
45 ml 30 mmol 
30 ml 
1.5 mmol 
4 Aniline 
N-Pr m-AS 1N--HCl 
(NH.sub.4).sub.2 S.sub.2 O.sub.8 
1N--HCl 
13.5 mmol 
Aniline 
15 mmol 
45 ml 30 mmol 
30 ml 
1.5 mmol 
5 N-Ph PDA 
-- p-AS 1N--HCl 
(NH.sub.4).sub.2 S.sub.2 O.sub.8 
1N--HCl 
15 mmol 30 mmol 
68 ml 45 mmol 
45 ml 
6 N-Ph.sub.2 PDA 
-- m-AS IN-- HCl 
(NH.sub.4).sub.2 S.sub.2 O.sub.8 
IN--HCl 
10 mmol 25 mmol 
48 ml 30 mmol 
30 ml 
7 N-Ph PDA 
-- m-AS IN--PTS 
(NH.sub.4).sub.2 S.sub.2 O.sub.8 
IN--PTS 
10 mmol 40 mmol 
48 ml 30 mmol 
30 ml 
8 N-Ph PDA 
-- m-AS 2N--H.sub.2 SO.sub.4 
(NH.sub.4).sub.2 S.sub.2 O.sub.8 
2N--H.sub.2 SO.sub.2 
20 mmol 40 mmol 
146 ml 
60 mmol 
60 ml 
9 N-Ph PDA 
-- m-AS 2N--H.sub.2 SO.sub.4 
(NH.sub.4).sub.2 S.sub.2 O.sub.8 
2N--H.sub.2 SO.sub.4 
20 mmol 40 mmol 
146 ml 
30 mmol 
30 ml 
10 N-Ph.sub.2 PDA 
-- O-AS 2N--H.sub.2 SO.sub.4 
(NH.sub.4).sub.2 S.sub.2 O.sub.8 
2N--H.sub.2 SO.sub.4 
20 mmol 40 mmol 
80 ml 90 mmol 
120 ml 
11 N-Ph.sub.2 PDA 
-- O-AS 2N--H.sub.2 SO.sub.4 
(NH.sub.4).sub.2 S.sub.2 O.sub.8 
2N--H.sub.2 SO.sub.4 
20 mmol 40 mmol 
80 ml 60 mmol 
80 ml 
12 N-Ph.sub.2 PDA 
-- O-AS 2N--H.sub.2 SO.sub.4 
(NH.sub.4).sub.2 S.sub.2 O.sub.8 
2N--H.sub.2 SO.sub.4 
20 mmol 20 mmol 
60 ml 40 mmol 
55 ml 
13 Aniline 
-- Anilinedi- 
2N--H.sub.2 SO.sub.4 
(NH.sub.4).sub.2 S.sub.2 O.sub.8 
2N--H.sub.2 SO.sub.4 
10 mmol sulfonic 
71.5 ml 
30 mmol 
30 ml 
Acid 
20 mmol 
14 Hydroxy- 
-- O-AS 2N--H.sub.2 SO.sub.4 
(NH.sub.4).sub.2 S.sub.2 O.sub.8 
2N--H.sub.2 SO.sub.4 
diphenyl- 25 mmol 
70 ml 50 mmol 
50 ml 
Amine 
25 mmol 
__________________________________________________________________________ 
[Note 
As: Aminobenzene sulfonic acids 
NMe aniline: Nmethyl aniline 
NPr aniline: Npropyl aniline 
NPh PDA: Nphenylphenylenediamine 
NPh.sub.2 PDA: N,Ndiphenylphenylenediamine 
PTS: ptoluenesulfonic acid 
TABLE 2 
______________________________________ 
Introduction 
Surface ratio of 
Example 
Reaction condition resistance 
sulfonic 
No. Temp. Hrs. Yield [.OMEGA./.quadrature.] 
acid group 
______________________________________ 
1 20.degree. C. 
6 hr 2.1 g 1.4 .times. 10.sup.10 
21% 
2 40.degree. C. 
6 hr 1.8 g 4.8 .times. 10.sup.10 
19% 
3 25.degree. C. 
6 hr 2.3 g 1.5 .times. 10.sup.10 
20% 
4 30.degree. C. 
12 hr 2.0 g 2.0 .times. 10.sup.10 
21% 
5 10.degree. C. 
12 hr 5.7 g 2.6 .times. 10.sup.9 
35% 
6 40.degree. C. 
12 hr 2.8 g 1.0 .times. 10.sup.10 
30% 
7 25.degree. C. 
12 hr 2.1 g 1.2 .times. 10.sup.10 
24% 
8 25.degree. C. 
12 hr 3.8 g 3.4 .times. 10.sup.10 
27% 
9 25.degree. C. 
12 hr 3.3 g 2.7 .times. 10.sup.10 
28% 
10 25.degree. C. 
12 hr 4.8 g 5.0 .times. 10.sup.10 
32% 
11 25.degree. C. 
12 hr 3.8 g 7.6 .times. 10.sup.9 
34% 
12 25.degree. C. 
12 hr 2.8 g 6.5 .times. 10.sup.9 
30% 
13 25.degree. C. 
12 hr 0.5 g 6.8 .times. 10.sup.9 
40% 
14 25.degree. C. 
12 hr 1.2 g 2.5 .times. 10.sup.10 
25% 
______________________________________ 
Sulfonation 
Examples 15-17, 20 (Refer to Tables 3 and 4) 
2.0 g of the copolymer prepared using the procedure described in the 
Examples 1 to 6 is added to 90 g of the fuming sulfuric acid, and stirred 
for 6 hours at a certain temperature to yield the reaction mixture. 
The thus obtained reaction mixture was added dropwise to ethyl alcohol to 
yield the precipitates. The obtained precipitates were filtered off, 
washed with methanol and acetone, and the washed product were dried to 
yield sulfonated polyaniline. 
FIG. 1 is a graph illustrating the FT-IR spectra (KBr method) of the 
present copolymer obtained in Example 2, and FIG. 2 is a graph 
illustrating the FT-IR spectra (KBr method) of the present copolymer 
obtained in Example 8. 
Two peaks band appearing at 1000 to 1100 cm.sup.-1 in FIGS. 1 and 2 are 
based on the absorption of the sulfonic acid group. The intensity of this 
band shown in FIG. 2 is stronger than that in FIG. 1, which demonstrates 
that the introduction ratio of the sulfonic acid group in Example 8 is 
higher than that in Example 2. 
Example 18 (Refer to Tables 3 and 4) 
30 g of sulfur trioxide was added to 200 g of dimethylformamide and stirred 
for one hour, followed by the addition of 2.0 g of the copolymer prepared 
by the procedure described in Example 4, and stirred at a temperature of 
20.degree. C. for 6 hours to yield the reaction mixture. The thus obtained 
reaction mixture was added to ethyl alcohol to yield the precipitates. The 
thus obtained precipitates were filtered off, washed with methanol and 
acetone, and dried to yield the sulfonated polyaniline. 
Example 19 (Refer to Tables 3 and 4) 
2.0 g of the copolymer prepared by the procedure described in Example 5 was 
added to 200 g of sulfuric acid and stirred for 6 hours at a temperature 
of 70.degree. C. to yield a reaction mixture. The thus obtained reaction 
mixture was added to ethyl alcohol to yield the precipitates. The obtained 
precipitates were filtered off, washed with methanol and acetone, and 
dried to yield a sulfonated polyaniline. 
Examples 21 to 28 (Refer to Tables 3 and 4) 
0.5 g of the copolymer prepared by the procedure described in Examples 7-14 
was added to 50 g of sulfuric acid and stirred for 1-2 hours at a 
temperature of 100.degree. C. to yield a reaction mixture. The thus 
obtained reaction mixture was added to ethyl alcohol to yield the 
precipitates. The obtained precipitates were filtered off, washed with 
methanol and acetone, and dried to yield a sulfonated polyaniline. 
Comparative Example 1 
A sulfonated polyaniline was prepared in accordance with the description of 
J. Am. Chem. Soc., 1991, 113, P2666. 
2.0 g of polyaniline was added to 200 g of fuming sulfuric acid. The 
mixture was stirred into a solution at room temperature and when 
polyaniline was added, a part of the polymer solidified; thereafter, more 
than 24 hours was needed for the solution to clear. Methyl alcohol was 
added to the obtained solution. Next, acetone was added to yield the 
complete precipitates. The obtained precipitates were filtered off, and 
washed with methanol and acetone, and then dried in a dynamic vacuum for 5 
hours to yield 1.9 g of sulfonated polyaniline. The sulfonated ratio for 
the sulfonated polyaniline was 42%. 
One gram of the product was dissolved in 100 g of 0.1N aqueous ammonia 
solution, however, some insoluble matter (30% per whole product) was found 
after filtration of the solution. 
The filtrate was coated on a glass substrate to form a thin film. The 
surface resistance of this film was measured and the formula 
7.6.times.10.sup.10 .OMEGA./.quadrature. was obtained. 
Also, the above sulfonated polyaniline was dissolved in 0.1N ammonia 
containing a methanol solution, but insoluble matter was also found. 
Comparative Example 2 
A sulfonated polyaniline was prepared in accordance with the description of 
Japanese Unexamined Patent Publication No. 61-197633 (pages 6 to 7). 
2.0 g of ethyl phosphate was dissolved in 16 g of 1.2-dichloroethane to 
yield the solution. 1.8 g of anhydrous sulfuric acid was added to the 
solution to prepare the sulfonating reagent solution. 
1.0 g (11 mmol) of the polyaniline was finely ground into powder form. This 
powder was added to 1,2-dichloroethane to prepare a dispersion. 
The above-mentioned sulfonating reagent solution was added dropwise to the 
dispersion while being kept cool with ice. 
After completion of the said addition, the mixture matured for one hour 
while being ice-cooled to yield a product. 
The product was filtered off, washed with 1,2-dichloroethane and methanol, 
dried for 8 hrs at 50.degree. C. to yield 1.2 g of sulfonated polyaniline. 
The introduction ratio of the sulfonic acid group was 17%. 
Scarcely one gram of the sulfonated polyanilion was dissolved in 100 g of 
0.1N aqueous ammonia solution. 
Comparative Example 3 
A copolymer of aniline and m-aminobenzenesulfonic acid was synthesized in 
accordance with the described Example (page 3) in the Japanese Unexamined 
Patent Publication No. 1-301714. 
1.6 g (17 mmol) of aniline and 5.7 g (33 mmol) of m-aminobenzenesulfonic 
acid were dissolved in 80 ml of 2N were dissolved in 80 ml of 2N sulfuric 
acid to prepare a solution. 
75 ml of a sulfuric acid solution containing 17 g (75 mmol) of ammonium 
peroxodisulfate was added dropwise to the solution for 0.5 hrs at a 
temperature of 20.degree. C. 
After completion of the said addition, the mixture matured for one hour at 
a temperature of 20.degree. C. to yield a product. 
The product was filtered off, washed with methanol and acetone, and dried 
for 8 hrs at a temperature of 50.degree. C. to yield 2.5 g of a copolymer. 
The introduction ratio of the sulfonic acid group was 22%. 
One gram of the thus obtained product was dissolved in 100 g of 0.1N 
aqueous ammonia solution, however, insoluble matter (70% per the whole 
product) was found after said filtration of the solution. 
The filtrate was coated on a glass substrate to form a thin film. The 
surface resistance of this film was measured and the formula 
3.4.times.10.sup.10 .OMEGA./.quadrature. was obtained. 
Also, the above sulfonated polyaniline was dissolved in 0.1N ammonia 
containing methanol solution, however, insoluble matter was also found. 
TABLE 3 
______________________________________ 
Reaction 
Sulfonation condition 
Example Sulfonating Temper- 
No. Polymer reagent Solvent 
ature Hour 
______________________________________ 
15 Example 1 Fuming -- 5.degree. C. 
6 hr 
2.0 g sulfuric acid 
90 g 
16 Example 2 Fuming -- 5.degree. C. 
6 hr 
2.0 g sulfuric acid 
90 g 
17 Example 3 Fuming -- 20.degree. C. 
6 hr 
2.0 g sulfuric acid 
90 g 
18 Example 4 Sulfur DMF 20.degree. C. 
6 hr 
2.0 g trioxide 200 g 
30 g 
19 Example 5 Fuming -- 70.degree. C. 
6 hr 
2.0 g sulfuric acid 
200 g 
20 Example 6 Fuming -- 10.degree. C. 
6 hr 
2.0 g sulfuric acid 
90 g 
21 Example 7 Conc. H.sub.2 SO.sub.4 
-- 100.degree. C. 
2 hr 
0.5 g 50 g 
22 Example 8 Conc. H.sub.2 SO.sub.4 
-- 100.degree. C. 
2 hr 
0.5 g 50 g 
23 Example 90 
Conc. H.sub.2 SO.sub.4 
-- 100.degree. C. 
2 hr 
.5 g 50 g 
24 Example 10 
Conc. H.sub.2 SO.sub.4 
-- 100.degree. C. 
2 hr 
0.5 g 50 g 
25 Example 11 
Conc. H.sub.2 SO.sub.4 
-- 100.degree. C. 
2 hr 
0.5 g 50 g 
26 Example 12 
Conc. H.sub.2 SO.sub.4 
-- 100.degree. C. 
2 hr 
0.5 g 50 g 
27 Example 13 
Conc. H.sub.2 SO.sub.4 
-- 100.degree. C. 
2 hr 
0.5 g 50 g 
28 Example 14 
Conc. H.sub.2 SO.sub.4 
-- 100.degree. C. 
2 hr 
0.5 g 50 g 
______________________________________ 
DMF: Dimethylformamide 
TABLE 4 
______________________________________ 
Introduction 
Insoluble matter 
Ex- Surface ratio of Aqueous 
Alcohol 
ample resistance 
sulfonic solvent- 
solvent- 
No. Yield [.OMEGA./.quadrature.] 
acid group 
type type 
______________________________________ 
15 2.4 g 1.8 .times. 10.sup.9 
48% Non Non 
16 2.2 g 5.0 .times. 10.sup.9 
43% Non Non 
17 2.5 g 1.5 .times. 10.sup.9 
47% Non Non 
18 1.7 g 2.0 .times. 10.sup.9 
45% Non Non 
19 1.9 g 8.7 .times. 10.sup.8 
54% Non Non 
20 2.3 g 4.2 .times. 10.sup.8 
56% Non Non 
21 0.42 g 6.4 .times. 10.sup.8 
47% Non Non 
22 0.40 g 9.6 .times. 10.sup.8 
42% Non Non 
23 0.40 g 6.8 .times. 10.sup.8 
48% Non Non 
24 0.32 g 8.6 .times. 10.sup.7 
51% Non Non 
25 0.40 g 7.0 .times. 10.sup.7 
47% Non Non 
26 0.34 g 7.0 .times. 10.sup.7 
44% Non Non 
27 0.26 g 8.0 .times. 10.sup.7 
55% Non Non 
28 0.27 g 1.8 .times. 10.sup.9 
40% Non Non 
______________________________________ 
[Note] 
Surface resistance after film formation: 
Ong gram of the obtained product was dissolved in 100 g of 0.1N aqueous 
ammonium solution and filtered off. The filtrate was coated on a glass 
substrate to form a thin film having a thickness of 200 to 500 .ANG., and 
the surface resistance of this film was measured. 
Method for measurement of the introduction ratio of sulfonic acid group: 
The sample was decomposed in a combustion flask, the sulfur-containing 
ratio was then measured by means of an ion-chromatography method. The 
introduction ratio of the sulfonic acid group was calculated from the data 
of the sulfur-containing ratio. 
Evaluation Method of Solubility 
Sulfonated polyaniline was dissolved in one % by weight of the following 
solvents (1) and (2); the appearance of the insoluble matter was then 
observed. 
(1) Aqueous solvent-type: Dissolved in 0.1N aqueous ammonium solution. 
(2) Alcoholic solvent-type: Dissolved in 0.1N ammonia-methanol solution. 
According to the present invention, the introduction ratio of sulfonic acid 
in the polymer is increased, and electroconductivity is improved without 
the addition of a dopant and further, solubility w/r to water and alcohol 
is enhanced. 
Therefore, when forming a thin film on the substrate by means of a coating, 
spray method, dipping and the like, using a solvent containing the present 
polymer, it is possible to obtain a uniform and high electroconductive 
thin film that does not have any pin holes.