KR20050110911A - Process for the preparation of high glutinous conductive polyaniline blend and conductive coating solution comprising the blend - Google Patents

Abstract

The present invention relates to a method for preparing a conductive polyaniline blend and a conductive polyaniline coating solution comprising the mixed solution and an aqueous binder. According to the present invention, 1) a polyaniline is immersed in ammonia water and then filtered. Doping; 2) dissolving the primary dedoped polyaniline in a solution of N-methylpyrrolidone (NMP) saturated with ammonia gas, followed by secondary dedoping by removing solids, drying and washing; 3) dissolving the secondary dedoped polyaniline in a phenolic solvent; And 4) preparing a conductive polyaniline mixture by a method comprising mixing and doping a polyaniline solution dissolved in a phenolic solvent with an NMP containing a dopant, wherein the polyaniline mixture is a coating solution when used as a raw material of the conductive coating solution. It has excellent conductivity and adhesiveness, which can be usefully used in various industrial fields such as anti-corrosion, anti-static and electromagnetic shielding.

Description

A method for preparing a conductive polyaniline mixed liquid having excellent adhesiveness and a conductive coating solution containing the mixed liquid {PROCESS FOR THE PREPARATION OF HIGH GLUTINOUS CONDUCTIVE POLYANILINE BLEND AND CONDUCTIVE COATING SOLUTION COMPRISING THE BLEND}

The present invention relates to a method for preparing a conductive polyaniline blend and a conductive polyaniline coating solution comprising a dimixture.

Electroconductive polymers (e.g., polypyrrole, polythiophene or polyaniline, etc.) having a π-conjugated structure are dopants that do not exhibit conductivity by themselves, as shown in Scheme 1 below. When doping (doping) is a transition phenomenon having electrical conductivity while maintaining the general physical and mechanical properties of the polymer.

Therefore, in recent years, the field of organic semiconductors using such polymers has been attracting attention, and infinite applications have been proposed for various industries in the field of antistatic, electromagnetic shielding, corrosion prevention, and other semiconductor fields.

Accordingly, research on polyaniline, polypyrrole, polythiophene, etc., which is capable of mass synthesis, excellent conductivity and processability, and is stable to air, heat, and the like, is being actively conducted. As a doping material, large organic acids having high solubility in organic solvents are used. In order to improve the processability and conductivity by producing a blend or composite together with a general-purpose polymer having excellent physical properties, many studies are being conducted. However, most of the doping process has a lot of constraints on the industrial application, such as the stability of the conductive polymer or the prepared conductive polymer is insoluble in the general organic solvent.

On the other hand, polyaniline, which is one of the conductive polymers, is polymerized relatively simply by chemical oxidation and has stable properties in air in a state of high conductivity. In particular, many studies have been conducted on the structure, synthesis and application of polyaniline because they show different chemical structures in the redox, doped and dedoped states, and since these structural changes are reversible, they exhibit stable and diverse electrochemical properties. Is going on. However, like other conductive polymers, polyaniline has a π-conjugated structure, and since the benzene ring is bonded in a planar structure, the molecular chain is inflexible and strong attractive force between molecules acts, resulting in a lack of structural flexibility. It is insoluble in organic solvents due to the influence of negative ions, etc., and exhibits insoluble properties that do not melt even when heated. In spite of such many advantages, polyaniline has little industrial use due to its poor workability and difficulty in film formation, and researches are currently being actively conducted to solve this problem.

Specifically, Korean Patent No. 212199 discloses a method for preparing a composite resin using polyaniline and polypyrrole, but the present invention is limited to ABS (acrylonitril-butadiene-styrene) latex emulsion, and thus has a limited scope of application. -200017 proposed a method for preparing soluble polyaniline using iron sulfate as a catalyst, but reported only solubility for NMP (N-methyl pyrrolidone) and DMP (N, N-dimethyl formamide). There is a problem of poor availability.

In addition, Korean Patent No. 205912 introduced a method of adding a dopant when dissolving the synthesized polyaniline in an organic solvent in order to prepare a soluble polyaniline, but the film has a disadvantage that the transparency and surface hardness are reduced. In addition, U.S. Patent Nos. 5,100,977, 5,560,870, 5,776,659, etc., introduce a π-conjugation by introducing a substituent into the polyaniline backbone by copolymerizing N-alkyl aniline and aniline or sulfonating polyaniline to increase the solubility of polyaniline. Although a method of increasing the flexibility of the molecular chain by reducing the system has been proposed, the solubility, conductivity, and other physical properties of the prepared polyaniline are insufficient, and thus industrial use is difficult.

Therefore, the inventors of the present invention focuses on the fact that polyaniline has excellent conductivity and stability but poor adhesion to various substrates, and it is not easy to remove a large amount of oxidizing agent and proton acid contained in the solution when it is introduced as it is, so that it is not suitable as a coating agent. Thus, the present invention has been achieved as a result of intensive studies focusing on the invention for producing polyaniline having excellent high-purity processability.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for preparing a conductive polyaniline mixed liquid having excellent conductivity and stability and high industrial utilization, and a conductive coating solution containing the mixed liquid.

In accordance with the above object, the present invention comprises the steps of: 1) immersing polyaniline in ammonia water, followed by filtration to first dedoping; 2) dissolving the primary dedoped polyaniline in an N-methylpyrrolidone (NMP) solution saturated with ammonia gas, followed by secondary dedoping by removing solids, drying and washing; 3) dissolving the secondary dedoped polyaniline in a phenolic solvent; And 4) mixing a polyaniline solution dissolved in a phenolic solvent with NMP including a dopant to dope the polyaniline, thereby providing a method for producing a conductive polyaniline blend.

The present invention also provides a conductive polyaniline coating solution in which an aqueous binder is added to the polyaniline mixed solution obtained by the above method.

Hereinafter, the present invention will be described in detail.

The method for preparing the polyaniline mixed solution of the present invention is characterized in that the polyaniline synthesized by the precipitation polymerization method is purified by two-step dedoping without directly doping to obtain pure polyaniline and then doping treatment.

Specifically, the manufacturing method of the present invention

1) immersing the synthesized polyaniline in ammonia water, followed by filtration to first dedoping;

2) dissolving the primary dedoped polyaniline in an NMP solution saturated with ammonia gas, followed by secondary dedoping by removing solids, drying and washing;

3) dissolving the secondary dedoped polyaniline in a phenolic solvent; And

4) mixing and doping the polyaniline solution dissolved in a phenolic solvent with NMP containing a dopant.

Excess oxidant and oligomer are used to synthesize polyaniline by precipitation polymerization. Therefore, in order to obtain high purity polyaniline, it is important to remove excess oxidizing agent and excess acid after polyaniline synthesis. To this end, the present invention introduces a second dedoping process in the preparation of the polyaniline solution.

In step 1 of the present invention, ammonia water (NH ₄ OH) is added to the polyaniline powder synthesized by the precipitation polymerization method, followed by reaction with methanol and distilled water to remove excess oxidant and excess acid. At this time, the ammonia water is added in a composition of 0.1 to 1 N, preferably 0.1 to 0.2 N, 100 to 1000 ml, preferably 200 to 400 ml per 10 g of the synthesized polyaniline powder, the reaction is 5 to 25 ℃ For example, it may be performed at 5 to 15 ° C. for 0.5 to 6 hours, preferably 1 to 3 hours. In the first dedoping process, the agglomerated powder is dispersed in the basic aqueous solution so that only the surface of the sample powder is dedoped, so it is difficult to completely remove the oxidant and acid present therein.

Therefore, in the present invention, the first de-doped polyaniline is dissolved in NMP saturated with ammonia gas, and then the solids are removed, dried and washed with secondary de-doping (step 2). In this step, a small amount of polyaniline powder firstly dedoped to NMP saturated with ammonia gas is added to dissolve the polyaniline and react with the base to remove precipitates by reacting the oxidizing agent and acids remaining after the first dedoping with a base. As a dedoping process, this step allows the production of pure polyaniline free of impurities. At this time, the amount of polyaniline powder added to NMP saturated with ammonia gas is 0.1 to 30% by weight, preferably 1 to 5% by weight, and the second dedoping reaction is 0 to 30 ° C, preferably 5 to 10 ° C. In 1 to 5 hours, preferably 1 to 3 hours.

The high-purity polyaniline solution prepared through the above steps of the present invention is first dissolved in a phenolic solvent and mixed with NMP containing a dopant to dope the polyaniline in order to prepare a highly conductive polyaniline blend. .

Since polyaniline has a stable conductivity in an acidic state, it is generally doped with an acidic dopant. However, environmentally friendly commercial coatings (or binders) are mostly neutral or weakly basic aqueous binder solutions, so when the doped polyaniline is prepared as a coating mixture, the stability of the conductive polyaniline mixture is due to the pH difference between the polyaniline and the aqueous binder. This breaking problem occurs. Thus, the present invention is characterized by using a weakly basic NMP containing a dopant. In addition, since the NMP has a disadvantage of lowering the conductivity of the polyaniline, in the present invention, after dissolving the high-purity polyaniline obtained as described above in a phenolic solvent, the NMP solvent containing a dopant is mixed in an appropriate ratio. .

Specifically, the high-purity polyaniline prepared in step 2 is redissolved in a phenolic solvent (step 3), and mixed with NMP containing a dopant to obtain a conductive polyaniline solution according to the present invention (step 4). The phenolic solvent of step 3 is m -cresol, o, p -cresol, phenol, trifluoro- m -cresol, ethylphenol, allylphenol, methoxyphenol, trifluoroacetic acid, dichloroacetic acid, hexafluoropropanol , Trifluoroethanol, trichloroethanol, hexafluoro-2-phenyl-2-propanol, octafluoropentanol or chloroform and the like can be used, with m -cresol being preferred. The polyaniline concentration in the phenol solvent is 0.1 to 10% by weight, preferably 1 to 5% by weight.

In addition, the dopants used in step 4 include 10-cambosulfonic acid (CSA), benzenesulfonic acid (BSA), p-toluenesulfonic acid (p-TSA), dodecylbenzenesulfonic acid (DBSA), polystyrenesulfonic acid (PSSA), 2- Dopants having excellent solubility, such as sulfonic acid (-SO ₃ H), carboxylic acid (-COOH), or phosphoric acid, such as naphthalene sulfonic acid (2-NSA) and dinonylnaphthalene sulfonic acid (DNNSA), can be used. %, Preferably it is used by melt | dissolving in the density | concentration of 0.01-10 weight%.

The mixing molar ratio of the dopant and polyaniline is used to be 0.5: 1 to 1: 1, preferably 0.5: 1. In the doping process of the present invention, it is important to use the ratio of the polyaniline complex solvent within a range in which phase separation does not occur. When m -cresol is used as the polyaniline solvent, the amount of m -cresol is 20% by weight or less compared to NMP. desirable.

The conductive polyaniline mixture prepared according to the present invention has excellent conductivity and maintains stability of the conductive polyaniline even when mixed with an aqueous binder. Therefore, the conductive polyaniline mixed solution of the present invention may be mixed with the aqueous binder at various concentrations to prepare a conductive coating solution having excellent conductivity and adhesion. In particular, the mixing of the conductive polyaniline mixed solution and the aqueous binder is performed immediately after the mixing process of the NMP containing the polyaniline solution and the dopant dissolved in the phenolic solvent of step 4, thereby preventing the aggregation of polyaniline chains by the NMP. desirable.

As the aqueous binder, an acrylate-based and copolymer thereof including epoxy-based, poly (ethylene-co-acrylate) (PEA), polyurethane-based, polyvinyl alcohol-based, or vinyl-based and copolymers thereof may be used. Can be. The aqueous binder may be used diluted with distilled water, wherein the concentration of the diluted aqueous binder is in the range of 1 to 20%, preferably 5 to 10%. The mixing ratio of the conductive polyaniline and the aqueous binder is in the range of 0.01: 1 to 1: 1 weight ratio, preferably 0.05: 1 to 0.5: 1 weight ratio, based on solids.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are only for illustrating the present invention, and the scope of the present invention is not limited thereto.

Example 1 Preparation of Conductive Polyaniline Blend

Step 1) Synthesis of Polyaniline

20 ml of purified aniline (aniline, Aldrich) was dissolved in 300 ml of 1 M HCl, placed in a 1 L dual jacket reactor and maintained at 0 ° C. 22 g of an oxidizing agent (NH ₄ ) ₂ S ₂ O ₈ (Aldrich) was dissolved in 200 ml of 1 M HCl, and slowly added to the aniline in the reactor for 2 hours, and then reacted with stirring for 3 hours. After the reaction, the precipitated powder was collected, filtered and washed with distilled water until pH 6-7. This was washed with methanol until the filtrate was clean, and then washed with ethyl ether to remove the remaining water and methanol to synthesize polyaniline.

Step 2) First Dedoping

The polyaniline solution synthesized as in step 1 was placed in a vacuum oven at room temperature and dried for 48 hours. The dried powder was placed in 1.5 L of 0.1 N aqueous ammonia (NH ₄ OH) and reacted for 16 hours with vigorous stirring. The reaction solution was washed sequentially with 0.1 N aqueous ammonia and distilled water under reduced pressure filtration, and then dried in a Buchner funnel for 30 minutes. The dry powder was added again to 550 ml of 0.1 N ammonia water and the same procedure was repeated three more times. Finally, the dried powder was dispersed in 1 L of methanol, stirred vigorously for 15 minutes, washed with filtrate with excess methanol until it became clear, and then dried in a vacuum oven for 72 hours to give a purple vision. A conductive polyaniline powder was obtained.

Step 3) Secondary Dedoping

The polyaniline powder prepared in step 2 was dissolved in 1% by weight to 5% by weight in an NMP (N-methylpyrrolidione) solution saturated with ammonia gas, and then centrifuged at 5 ° C. at 10000 rpm for 30 minutes. After centrifugation, the supernatant was collected, placed in a vacuum oven at 90 ° C., dried to remove 90% of the solvent, and washed several times with distilled water to obtain high-purity polyaniline from which oxidants and acids remaining therein were removed.

Step 4) Preparation of Optimal Mixed Solvent for Polyaniline Doping

To prepare a conductive polyaniline mixture solution that is soluble in an aqueous emulsion and has excellent conductivity and adhesion, polyaniline is added to a mixture of water, NMP, and m -cresol of various compositions so that 0.5% by weight of the total solution is added. After standing in the phase separation and precipitation formation was observed to confirm the stability of the conductive polyaniline.

As a result, as shown in Figure 1, it was confirmed that the conductive polyaniline is stable when m -cresol compared to 20% by weight or less compared to NMP.

Based on these results, a conductive polyaniline mixture was prepared under the composite solvent system according to the present invention. Specifically, the high-purity polyaniline prepared in step 3 was dissolved in m -cresol and centrifuged to prepare a 5% by weight polyaniline standard solution (the concentration of the standard solution was completely dried by putting a part of the solution in a vacuum oven. Weighed to determine). 20 g of polyaniline standard solution (5% by weight) was mixed with 1.2625 g (0.5 times of polyaniline mole) of dopant camphorsulfonic acid (CSA, Aldrich, USA) in a solution of 2: 8 weight ratio in a solution of 80 mg of NMP. The mixture was stirred vigorously for an hour to prepare a conductive polyaniline mixed solution (1% by weight).

Example 2: Preparation of Conductive Polyaniline Coating Solution

33.54 wt% poly (ethylene-co-acrylate) emulsion (PEA), a transparent adhesive coating, was diluted to 10 wt% with distilled water. The conductive polyaniline coating solution was prepared by adding 1% by weight of the conductive polyaniline mixture prepared in Example 1 to 2 g of the PEA emulsion diluent in an amount of 1 to 100% by weight based on the PEA solid content and mixing at room temperature for 1 to 3 hours.

Comparative Example 1

According to the method of Example 2, except that 5 g of the high-purity polyaniline prepared in step 3 of Example 1 was dissolved in 500 g of NMP solution containing CSA without directly dissolving in m -cresol. Coating solution was prepared.

Conductivity measurement

The conductive polyaniline coating solution prepared in Example 2 and the coating solution of Comparative Example 1 were applied to a glass plate of 1.5 × 1.5 cm to a thickness of 5 to 10 μm and first dried in a 60 ° C. oven for 3 hours, and then 90 to 100 ° C. Final drying in a vacuum oven of 6 to 12 hours to obtain a conductive thin film. At this time, the glass substrate used in the coating was washed with H ₂ O ₂ / H ₂ SO ₄ solution of 80/20 ratio to remove the organics and then washed with distilled water, and then put it in acetone and ultrasonic washing (ultrasonication) for 20 minutes Corning glass products were used.

Based on the polyaniline content, the thin films were subjected to a four-terminal method to measure sheet resistivity, and an alpha step was performed to measure thickness, and then the respective conductivity (S / cm) was calculated based on the results. It was.

As a result, as shown in Figure 2, the coating solution of Comparative Example 1, the conductivity gradually increased from 15 to 20% by weight to about 10 ^-6 S / cm on average, at 10 ^-5 S / cm at 35% by weight The overall conductivity was very low. In contrast, in the case of the conductive polyaniline coating solution prepared in Example 2, the conductive polyaniline coating solution exhibited conductivity of about 10 ⁻⁴ S / cm from 15 wt%, and exhibited excellent conductivity of 10 ⁻³ S / cm at 25 wt% or more. .

Absorbance measurement

In order to confirm the reason why the conductive polyaniline coating solution of the present invention prepared in Example 2 had excellent conductivity compared to the coating solution of Comparative Example 1, the polyaniline coating solution of Example 2 and the coating solution of Comparative Example 1 were respectively The solvent m-cresol: NMP was diluted to be 0.005% by weight or less using a composite solvent (Example 2) and NMP (Comparative Example 1) with 2: 8, and was analyzed qualitatively through an ultraviolet-visible spectrum.

As a result, as shown in FIG. 3, the absorbance of the conductive polyaniline coating solution prepared in Example 2 was long tail, whereas the absorbance of the coating solution of Comparative Example 1 showed a polaron peak at a wavelength of 850 to 900 nm. It was confirmed that the form continued to rise while having. This means that m-cresol contained in the conductive polyaniline coating solution prepared in Example 2 made polyaniline into an unbroken chain to induce efficient overlap with each other.

Optical microscope observation

The polyaniline coating solution prepared in Example 2 (50% by weight of polyaniline) was prepared as a conductive thin film according to the method proposed for measuring conductivity, and optical microscope observation was performed.

As a result, as shown in Figure 4, the coating solution of Example 2 formed a homogeneous thin film did not occur phase separation, it can be seen that this is consistent with the results of the triangular diagram shown in FIG.

As described above, the high-purity conductive polyaniline mixture prepared according to the present invention and the conductive coating solution using the same have stable and excellent conductivity as well as excellent adhesiveness, and thus, various industries such as corrosion prevention, antistatic and electromagnetic shielding. It can be usefully used in the field.

1 is a triangular diagram analyzing the stability of polyaniline in various complex solvent systems,

Figure 2 shows the results of analyzing the conductivity (S / cm) according to the polyaniline content of the conductive thin film prepared in the coating solution of Example 2 and Comparative Example 1,

3 is an ultraviolet-visible spectrum analysis result of the coating solution of Example 2 and Comparative Example 1,

Figure 4 is a photograph of the conductive thin film made of a coating solution prepared in Example 2 observed with an optical microscope.

Claims (12)

1) immersing the polyaniline in ammonia water, followed by filtration to first dedoping; 2) dissolving the primary dedoped polyaniline in an NMP solution saturated with ammonia gas, followed by secondary dedoping by removing solids, drying and washing; 3) dissolving the secondary dedoped polyaniline in a phenolic solvent; And 4) mixing a polyaniline solution dissolved in a phenolic solvent with NMP containing a dopant to dope the conductive polyaniline blend. The method of claim 1, In step 2), polyaniline is added to the NMP solution saturated with ammonia gas in an amount of 0.1 to 30% by weight. The method of claim 1, Process for producing a polyaniline dissolved in a phenolic solvent in step 3) is 0.1 to 10% by weight. The method of claim 3, wherein Phenolic solvents include m -cresol, o, p -cresol, phenol, trifluoro- m -cresol, ethylphenol, allylphenol, methoxyphenol, trifluoroacetic acid, dichloroacetic acid, hexafluoropropanol, trifluoro A process according to claim 1, wherein the method is selected from the group consisting of ethanol, trichloroethanol, hexafluoro-2-phenyl-2-propanol, octafluoropentanol and chloroform. The method of claim 1, When the polyaniline solution dissolved in the phenolic solvent in step 4) and the NMP containing a dopant, the phenolic solvent is in the range of 20% by weight or less compared to NMP. The method of claim 1, Method 4 characterized in that the mixing molar ratio of dopant and polyaniline in step 4) is from 0.5: 1 to 1: 1. The method of claim 1, A dopant is an organic compound having an acid group selected from sulfone groups (-SO ₃ H), carboxyl groups (-COOH) and phosphoric acid groups. The method of claim 7, wherein The sulfonic group-containing organic compounds include 10-cambosulfonic acid (CSA), benzenesulfonic acid (BSA), p-toluenesulfonic acid (p-TSA), dodecylbenzenesulfonic acid (DBSA), polystyrenesulfonic acid (PSSA), 2-naphthalenesulfonic acid ( 2-NSA) and dinorylnaphthalenesulfonic acid (DNNSA). A conductive polyaniline coating solution comprising a conductive polyaniline mixture obtained according to any one of claims 1 to 8 and an aqueous binder. The method of claim 9, The aqueous binder is an epoxy-based, acrylate-based or copolymer thereof, polyurethane-based, polyvinyl alcohol-based, or vinyl-based or a copolymer solution thereof. The method of claim 9, A coating solution, characterized in that the mixing ratio of the conductive polyaniline and the aqueous binder is 0.01: 1 to 1: 1 by weight based on the solid content. A method for producing a conductive polyaniline coating solution comprising mixing a polyaniline solution dissolved in a phenolic solvent and an NMP solution comprising a dopant according to the method of claim 1 and immediately mixing with an aqueous binder.