JPH07157549A - Production of processible conductive colloidal polymer - Google Patents

Abstract

PURPOSE: To provide a processible conductive colloidal polymer which is excellent in covering properties, film-forming properties, etc., and is useful for a conductive coating compsn., etc., by polymerizing a specific heterocyclic monomer in an aq. medium contg. an oxidant therefor and a diluted polymer emulsion prepd. in advance and then separating the resultant polymer.

CONSTITUTION: A polymer emulsion (e.g. a polyvinyl acetate emulsion) is prepd. as a stereostabilizer, which is diluted with an aq. dispersion medium to give a diluted polymer emulsion. In an aq. medium contg. an oxidant (e.g. ferric chloride) and the diluted polymer emulsion, an arom. heterocyclic monomer selected from among (N-substd. or β-substd.) pyrrole, thiophene, aniline, furan, and mixtures thereof is oxidatively polymerized and then the resultant polymer is separated from the aq. medium, thus giving the objective polymer.

COPYRIGHT: (C)1995,JPO

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to a process for preparing processable conductive colloidal polymers, and more particularly to the oxidative polymerization of aromatic heterocyclic monomers in an aqueous reaction medium using a polymer emulsion as a steric stabilizer. To a method for producing a colloidal polymer.

[0002]

BACKGROUND OF THE INVENTION The manufacture of printed circuit boards requires the provision of a conductive surface on a non-conductive support, such as a plastic support. The usual method is to sensitize and activate the etched plastic support to create a thin layer of noble metal such as palladium on its surface, and then to activate the support to copper sulfate and formaldehyde containing copper. It is placed in a plating bath to metallize the plastic support (ie coat its surface with a film of copper). This palladium acts as a catalyst for promoting the redox reaction of copper sulfate and formaldehyde.

The conventional methods described above are complicated and require many chemical reagents in their operation. The cost of precious metal compounds is also very high. Further, since formaldehyde used as a reducing agent is a carcinogen, its use in electroless plating is prohibited in many countries including the United States. In addition, formaldehyde, including strongly acidic wastewater formed during photosensitization and activation operations and strong basic wastewater formed during copper electroless plating operations, can cause serious pollution problems.

Composite conductive polymers have been extensively studied because of their growing interest in their use in antistatic coatings, conductive coatings, electromagnetic shielding, electrode coatings and the like.
These polymers have also been utilized in the plated through-holes of printed circuit supports and also for metallization of non-conductive supports. For example, PCT patent application NO.PCT / EP89 / 0020
4 (September 8, 1989) discloses a method of coating a conductive polymer on a non-conductive support. This method consists of the following three steps: (1) Oxidation step: 80 ° C-90
The support is immersed in a solution containing permanganate at an operating temperature of ° C to form a manganese dioxide layer on the walls of the plated through holes; (2) activation step: alcohol containing a monomer of a conductive polymer. Immersing the oxidized support in solution, coating the monomer layer on the manganese dioxide layer; and (3) immobilization step: polymerizing the monomer by soaking the activated support in an acidic solution, Metallize the support. The conductive polymer coated support is then plated with copper. The operation of this method is also quite complicated.

Polypyrrole is relatively stable to air in the form of a concentrated solution and is one of the most important composite conducting polymers. Due to its rigid conjugated bond, polypyrrole cannot be dissolved or melted in a solvent. Therefore, when using polypyrrole,
It is necessary to prepare a dispersion of colloidal polypyrrole to enhance its processability.

Suitable steric stabilizers are commonly added for the preparation of colloidal dispersions to stabilize the colloids contained therein and prevent them from coagulating and causing colloidal precipitation. It is known that two types of steric stabilizers are currently used in the preparation of polypyrrole colloidal dispersions. The first type is water-soluble steric stabilizers,
For example, poly (vinyl alcohol-co-vinyl acetate) (J. Colloid Int. Sci., 1987, 118, 410), poly (vinyl pyrrolidone) (J. Chem. Soc., Chem. Com.
mun., 1987, 228), poly (ethylene oxide) (J.
Chem. Soc., Chem.Commun., 1988, 1189), methylcellulose (J. Chem. Soc., Chem. Communi., 198)
6, 1293), poly (vinyl pyridine) and copolymers thereof [US Pat. No. 4,959,162 (1990)] and the like. Another class is steric stabilizers that are soluble in organic solvents. To date only one such steric stabilizer has been disclosed, which is poly (vinyl acetate) (PVAc).
[US Patent No. 5,021,193 (1991)]. The dispersion medium used is an ester such as methyl formate or methyl acetate

[0007].

Aqueous dispersions of colloidal polypyrrole have the disadvantage that they do not dry easily when coated on a support. After prolonged exposure to air, it absorbs moisture and swells, reducing its binding strength to the support. Furthermore, an aqueous dispersion of colloidal polypyrrole is also not suitable for use in an aqueous environment, for example, a support having a conductive polypyrrole layer obtained by coating the support with an aqueous dispersion and then drying, Subsequent electroplating with copper results in the conductive polypyrrole layer peeling off, causing damage to the copper plating or colloidal particles falling off, resulting in uniformity and continuity of the plated copper film due to water corrosion. Will be destroyed as. In addition, it may not be possible to plate copper on the support due to the rapid drop in conductivity of the conducting polymer caused by the extremely fast reduction rate. Furthermore, the conductivity of colloids will decrease over time.

Another drawback of using water-soluble polymers as steric stabilizers for the dispersion of polypyrrole is that the dispersions (other than those using the steric stabilizer poly (vinyl alcohol)) are supports, For example, when coated on a plastic support of a printed circuit board, it cannot be cast into a film. Colloidal dispersions using poly (vinyl alcohol) as a stabilizer can be cast into films, but they also lack practical utility because their mechanical strength is undesired.

A polypyrrole colloidal dispersion using an organic solvent as a steric stabilizer cannot be cast on a film, and the electric conductivity of the colloid is too low to achieve the subsequent electroplating of copper. Further, the above-mentioned US Patent No. 5,021,193
The use of an ester as described in 1 above as the dispersion medium will cause air pollution due to the volatility of the ester.

Accordingly, it is an object of the present invention to provide an improved process for preparing processable conductive colloidal polymer dispersions. The improved method is simple to operate, does not cause environmental pollution, and makes it possible to produce colloidal polymers with good film-forming dispersibility and high conductivity when coating the support.

[0011]

In order to achieve the above object, a process for producing a processable conductive colloidal polymer dispersion is (a) preparing a polymer emulsion as a steric stabilizer; (b) Diluting the polymer emulsion with an aqueous medium;
(C) an aromatic heterocyclic monomer selected from the group consisting of pyrrole, N-substituted pyrrole, beta-substituted pyrrole, thiophene, aniline, furan and mixtures thereof, with an oxidant and a diluting polymer for the aromatic heterocyclic monomer. Polymerizes oxidatively in an aqueous medium containing an emulsion;
(D) separating the processable conductive colloidal polymer from the aqueous reaction medium; and (e) dispersing the resulting processable conductive colloidal polymer in an emulsion in a solvent miscible with the polymer. The process consists of

According to the method of the present invention, the polymerization of aromatic heterocyclic monomers is carried out in an aqueous reaction medium. This is the main feature of the method of the present invention. Suitable aromatic heterocyclic monomers include pyrrole and other pyrroles such as N
There are -substituted pyrroles and beta-substituted pyrroles, thiophenes, anilines, and furans. The substituents may be alkyl, aryl, aralkyl, alkaryl, hydroxy, alkoxy, chloro, bromo and nitro groups. Of these, pyrrole is particularly suitable as the aromatic heterocyclic monomer.

The aqueous reaction medium comprises a polymer emulsion diluted with oxidant. Diluted emulsions are made by diluting a polymer emulsion with an aqueous medium. The oxidant used in the polymerization process must be capable of oxidatively polymerizing aromatic heterocyclic monomers. Examples of oxidants are persulfuric acid, halogens, nitric acid, nicronic acid, permanganic acid, manganic acid, salts of periodic oxygen with iron, copper, and cesium (IV). The preferred oxidant is ferric chloride.

The molar ratio of oxidant to aromatic heterocyclic monomer in the aqueous reaction medium is from 2: 1 to 5: 1. Suitably, the molar ratio of oxidant to monomer is 2.33: 1. The reaction temperature is from 0 ° C to 100 ° C, and more preferably about room temperature.

Polymer emulsions suitable for use as steric stabilizers in the present method include poly (vinyl acetate) (PVA
c) and poly (acrylate) emulsions. PV
An emulsion of Ac is suitable for this method. Examples of the polyacrylate include poly (methyl methacrylate-co (c
o: same as below) -butyl acrylate), poly (methyl methacrylate-co-butyl acrylate-co-acrylic acid) and poly (methyl methacrylate-co-butyl acrylate-co-vinyl acetate).

The main role of the polymer emulsion is to carry out in situ polymerization of the monomers in order to prevent precipitation by coagulation when the colloidal particles produced are redispersed in a solvent.
As it can be carried out in step u), the aromatic heterocyclic monomer and the oxidant are absorbed inside or on the surface of the polymer particles contained in the emulsion.

The aqueous medium for the dilution of the polymer emulsion can be deionized water or an acidic aqueous solution. Generally, the polymer emulsion should be diluted to 20-100 times its volume. For example, referring to a polymer emulsion of PVAc, typically 1-5 ml of PVAc emulsion (solid content, 50%) is diluted to 100 ml with deionized water for use in the present invention.

After completion of the oxidative polymerization, the resulting conductive polymer particles can be separated. According to the present invention, the colloidal particles can be separated from the aqueous reaction medium by filtration and then washed with water to remove excess oxidant and steric stabilizer. The separated colloidal particles are PV
The dispersion can be obtained by redispersing it in a solvent miscible with Ac. Suitable examples include methanol, benzene, toluene, chloroform, DMF, acetone, butanone, esters and the like.

It should be noted that the order in which the monomer and oxidant are added to the diluted polymer dispersion can affect the stability of the resulting colloidal polymer redispersion. According to the method of the present invention, the monomer is first added to the diluted polymer emulsion in order to absorb the monomer into the polymer particles in the emulsion,
It is then desirable to add an oxidant to prevent the formation of colloidal particles that are not absorbed by the steric stabilizer.

The dispersion of conductive colloidal polymer prepared by the method of the present invention is coated directly on a non-conductive support or on the through-hole wall of a printed circuit board to render them conductive and to render them suitable for plating. There is. The colloidal dispersion can also be used for antistatic coatings, electromagnetic shielding and the like.

[0021]

The following specific examples are intended to illustrate the invention in full, without limiting the scope of the invention, as many modifications and variations will be apparent to those skilled in the art. Because it will be. The conductivity of all of the following examples is 4
It was measured using the point probe method.

(Example 1) 1 m having a solid content of 50%
l poly (vinyl acetate) (hereinafter “PVAc”)
(Referred to as)) was diluted with deionized water to a total volume of 100 ml. 5.47 g ferric chloride was added to the above diluted emulsion with stirring. After ferric chloride was completely dissolved, 1 ml of pyrrole was added, and the mixture was reacted at room temperature for 24 hours. A pre-emulsion of colloidal polypyrrole was obtained. The pre-emulsion was filtered and washed with deionized water until the filtrate became colorless. The resulting colloid (which was found to contain 19% PVAc therein as determined by the use of elemental analysis) was redispersed in methanol to give a dispersion with a solids content in the range of about 2% to 3%. . This dispersion was dried, and the obtained colloid was crushed to obtain fine powder. The conductivity of compressed pellets obtained from this powder was measured to be 2.8 x 10 ^-2 S / cm.

Example 2 The same method as described in Example 1 was used, except that 2 ml of PVAc emulsion was used. The conductivity of compressed pellets from powder is 5.5 × 10 ^-3 S / c
It was measured as m. (Example 3) except that 3 ml of PVAc emulsion was used.
The same method described in Example 1 was used. The conductivity of the compressed pellets from the powder was measured as 1.4 × 10 ⁻³ S / cm.

Example 4 The same method as described in Example 1 was used, except that 5 ml of PVAc emulsion was used. The dispersion was cast into a film, but only a small area film was obtained. The conductivity of the obtained film is 9.1 × 10.
^-3 S / cm was measured.

Example 5 1 ml of PVAc emulsion was added to 1
100m total volume by diluting with toluene sulfonic acid
The same method as described in Example 1 was used except that it was 1.
The conductivity of compressed pellets from powder is 2.5 × 10 ^-3 S
/ Cm was measured.

Example 6 The same method as described in Example 1 was used, except that 1 ml of PVAc emulsion was diluted with 0.1 mol hydrochloric acid to bring the total volume to 100 ml. The conductivity of the compressed pellets from the powder was measured as 3.0 × 10 ⁻⁶ S / cm.

Example 7 The same procedure as described in Example 1 was used except 7.52 g of ammonium persulfate was added as an oxidant. The conductivity of compressed powder pellets was measured to be 4.3 × 10 ⁻⁵ S / cm.

Example 8 2 ml of PVAc was diluted with deionized water to a total volume of 50 ml. While stirring the diluted emulsion, 1 ml of pyrrole was added. Thirty
After swelling for -60 minutes, 50 ml of an aqueous solution containing 5.47 g of ferric chloride was added and allowed to react for 24 hours at room temperature. A pre-dispersion of colloidal polypyrrole was obtained. The predispersion was filtered and washed with deionized water until the filtrate was colorless. The obtained colloid was redispersed in methanol. A colloidal dispersion was obtained. The dispersion was dried and then ground to a fine powder. The conductivity of the compressed pellets of this powder was measured to be 2.4 × 10 ^-2 S / cm.

Example 9 The same method as described in Example 8 was used, except that 4 ml of PVAc emulsion was used. The dispersion liquid was cast into a film, and a wide-area film was obtained. The conductivity of the obtained film is 9.5 × 10 ⁻⁴ S /
It was measured in cm.

Example 10 An emulsion of 2 ml of poly (methyl methacrylate-co-butyl acrylate) (monomer molar ratio = 1: 1, solid content = 14%) was diluted with deionized water, and the whole was diluted. The product was 150 ml. Then 5.4
7 g ferric chloride was added with stirring. 1 ml of pyrrole was added after ferric chloride was completely dissolved, and the mixture was reacted at room temperature for 12 hours. A pre-dispersion of colloidal polypyrrole was obtained. The predispersion was filtered and washed with deionized water until the filtrate was colorless. The obtained colloid was redispersed in butanol. A dispersion of the colloid was obtained. This dispersion was dried and pulverized into a fine powder. The conductivity of compressed pellets from this powder was measured to be 0.5 S / cm.

Example 11 15 ml of an emulsion of poly (methylmethacrylate-co-butylacrylate) having the same composition described in Example 10 was diluted with deionized water to a total volume of 90 ml. Then 10 ml of a solution containing 5.47 g of ferric chloride was added with stirring. Next, 1 ml of pyrrole was added and reacted at room temperature for 13 hours. A pre-dispersion of colloidal polypyrrole was obtained.
The predispersion was filtered and washed with deionized water until the filtrate was colorless. The obtained colloid was redispersed in butanol to obtain a colloidal dispersion. A film having a wide area was obtained by casting this dispersion liquid as a film. The conductivity of the resulting film was measured to be 0.1 S / cm.

Example 12 10 ml poly (methyl methacrylate-co-butyl acrylate-co-acrylic acid) copolymer (MMA: BA: AA monomer molar ratio = 2: 3: 1, solid content = 15%) The same method described in Example 11 was used, except that This dispersion was cast to obtain a wide area film as a film. The conductivity of the resulting film was measured to be 0.2 S / cm.

Example 13 6 ml of poly (methyl methacrylate-co-butyl acrylate-co-vinyl acetate) copolymer (MMA: BA: VAc monomer molar ratio = 1: 1: 1, solid content = 15%) ) Was used and the same method described in Example 10 was used except that the reaction time was 15 hours. This dispersion was dried and pulverized into a fine powder. The conductivity of compressed powder pellets is 0.09 S /
It was measured in cm.

Comparative Example 1 The method for preparing the pyrrole-PVAc colloid disclosed in US Pat. No. 5,021,193 (1991) was repeated in this comparative example. A solution is prepared by dissolving 1 g of PVAc in methyl formate. 5.47 g ferric chloride was added to the solution with stirring. After ferric chloride is completely dissolved,
1 ml of pyrrole was added and reacted at room temperature for 16-18 hours. After separation and redispersion, it was found that the resulting dispersion could not be cast into a film. The dispersion was dried and ground into a fine powder. The conductivity of the compressed pellets of the powder was measured to be 2.5 × 10 ⁻⁶ S / cm.

A second run was carried out in the same manner except that 1 g of PVAc was dissolved in methyl acetate. The conductivity of the obtained compressed pellets was measured to be 1.1 × 10 ⁻⁶ S / cm. It can be seen that the conductivity of the polypyrrole colloid prepared in Comparative Example 1 is clearly lower than that prepared in Examples 2, 3 and 4.

Comparative Example 2 The same method as described in Example 1 was used except that the PVAc emulsion of the steric stabilizer was not added. The conductivity of the obtained compressed pellets is 0.4 S / cm
Was measured. It can be seen that the polypyrrole colloids prepared in Example 1 contained insulating PVAc therein, but their conductivity was not significantly lower than that prepared in Example 2.

Application Example 1 The dispersion prepared in Example 1 was coated on a support (fiberglass / epoxy) for a printed circuit board and dried. A composite film was formed from colloidal polypyrrole. The coated support was placed in a copper electroplating bath as the cathode; the copper plate served as the anode in the bath. The electroplating solution contained 220 g / liter copper sulfate, 60 g / liter sulfuric acid and 0.1 g / liter hydrochloric acid. The current density used was 1-5
It was in the range of A / dm ² . After electroplating is completed,
A uniform copper layer was deposited on the colloidal polypyrrole composite film. In addition, the copper-plated substrate could be dipped into a solution containing an antioxidant to prevent loss of metallic luster due to oxidation. 1 and 2 are SEM photographs of each colloidal film before and after copper plating.

Application Example 2 The same method as described in Application Example 1 was used, except that the dispersion prepared in Examples 10, 11, 12 and 13 was coated on the support of the printed circuit board. SEM photographs of the colloidal film and the deposited copper layer resemble FIGS. 1 and 2. (Application 3) The dispersion prepared in Example 12 was coated on the through holes of the printed circuit board and dried. A composite film of colloidal polypyrrole was formed on the hole wall.
The plate was then placed in the electroplating bath as the cathode;
The copper plate was used as the anode in the bath. The electroplating solution contained 220 g / liter copper sulfate, 60 g / liter sulfuric acid and 0.1 g / liter hydrochloric acid. The current density used was in the range of 1-5 A / dm ² . After electroplating was completed, a uniform layer of copper was deposited on the walls of the holes connecting the two sides of the copper layer. Furthermore, the board could be dipped in a solution containing an antioxidant to prevent loss of metallic luster of the copper layer due to oxidation.

Application Example 4 The dispersion prepared from Example 9 was coated on a poly (ethylene terephthalate) (PET) support and dried. It has been found that the bond of the coating film to the support is very good. The coated support was rubbed with a cloth and immediately placed on a piece of paper to examine the generation of electrostatic charge. No piece of paper was observed to be attracted towards the coated support, indicating that no electrostatic charge had developed. However, it has been found that the uncoated substrate attracts a piece of paper after rubbing with a cloth. Comparing the above two supports, it was found that the support coated with the colloidal dispersion had excellent antistatic properties. Therefore, the colloidal polypyrrole dispersion can be used as a packaging material for electrical parts and as an antistatic coating for plastics and fibers.

[0040]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, a colloidal polymer having a dispersibility and a high electric conductivity, which does not cause environmental pollution and has excellent film-forming property on a support, can be obtained by a simple operation. Can be made.

[Brief description of drawings]

FIG. 1 is a scanning electron microscope (SEM) photograph of the particle structure of a colloidal film of Application Example 1.

FIG. 2 is an SEM photograph of a grain structure of a copper layer of Application Example 1.

Claims (27)

[Claims] 1. A method for producing a conductive colloidal polymer processable in an aqueous medium, wherein (a) a polymer emulsion is prepared as a steric stabilizer, and (b) the polymer emulsion is diluted with an aqueous dispersion medium. c) an aromatic heterocyclic monomer selected from the group consisting of pyrrole, N-substituted pyrrole, beta-substituted pyrrole, thiophene, aniline, furan and mixtures thereof, an oxidant and a diluted polymer emulsion for the aromatic heterocyclic monomer. A process for producing a processable conductive colloidal polymer in an aqueous medium, which comprises the step of oxidatively polymerizing in an aqueous medium containing (d) and separating the processable conductive colloidal polymer from the aqueous medium. . 2. The method of claim 1, wherein the polymer emulsion is a poly (vinyl acetate) emulsion. 3. The method of claim 1 wherein the polymer emulsion is an acrylate emulsion. 4. The method according to claim 3, wherein the acrylate is poly (methyl methacrylate-co-butyl acrylate). 5. The method according to claim 3, wherein the acrylate is poly (methyl methacrylate-co-butyl acrylate-co-acrylic acid). 6. The method according to claim 3, wherein the acrylate is poly (methyl methacrylate-co-butyl acrylate-co-vinyl acetate). 7. The method according to claim 1, wherein the aqueous dispersion medium is water. 8. The method according to claim 1, wherein the aqueous dispersion medium is an acidic aqueous solution. 9. The oxidant is selected from the group consisting of iron, copper, persulfates, halogens, silver nitrate, nicronates, permanganates, manganates, periodates and cesium (IV). The method described. 10. The method of claim 9 wherein the oxidant is ferric chloride. 11. The method of claim 1, wherein the aromatic heterocyclic monomer is pyrrole. 12. The separation according to claim 1, wherein the separation is carried out by filtration.
The method described. 13. A method for producing a processable conductive colloidal polymer dispersion in an aqueous medium, comprising: (a) preparing a polymer emulsion as a steric stabilizer, and (b) diluting the polymer emulsion with an aqueous dispersion medium. , (C) an aromatic heterocyclic monomer selected from the group consisting of pyrrole, N-substituted pyrrole, beta-substituted pyrrole, thiophene, aniline, furan and mixtures thereof, an oxidant and a diluted polymer milk for the aromatic heterocyclic monomer. Oxidatively polymerizing in an aqueous medium containing a suspension, (d) separating the processable conductive colloidal polymer from the aqueous medium, and (e) obtaining the processable conductive colloidal polymer as a polymer emulsion. In particular, it comprises a step of dispersing in a solvent miscible with the polymer. A method for producing a processable conductive colloidal polymer dispersion in an aqueous medium. 14. The method of claim 13, wherein the polymer emulsion is a poly (vinyl acetate) emulsion. 15. The method of claim 13 wherein the polymer emulsion is an acrylate emulsion. 16. The method of claim 15, wherein the acrylate is poly (methylmethacrylate-co-butylacrylate). 17. The method of claim 15, wherein the acrylate is poly (methyl methacrylate-co-butyl acrylate-co-acrylic acid). 18. The method according to claim 15, wherein the acrylate is poly (methyl methacrylate-co-butyl acrylate-co-vinyl acetate). 19. The method of claim 13 wherein the aqueous dispersion medium is water. 20. The method of claim 13, wherein the aqueous dispersion medium is an acidic aqueous solution. 21. The oxidant is selected from the group consisting of persulfuric acid, halogen, nitric acid, nitric acid, permanganic acid, manganic acid, and salts of periodic acid with iron, copper and cesium (IV). the method of. 22. The method of claim 21, wherein the oxidant is ferric chloride. 23. The method of claim 13, wherein the aromatic heterocyclic monomer is pyrrole. 24. The method according to claim 1, wherein the separation is performed by filtration.
3. The method described in 3. 25. The method according to claim 13, wherein the solvent used in step (e) is selected from the group consisting of methanol, benzene, toluene, chloroform, DMF, acetone, butanone and ester. 26. The method according to claim 25, wherein the solvent used in step (e) is methanol. 27. The method according to claim 25, wherein the solvent used in step (e) is butanone.