DE4334390A1 - Process for the preparation of a processable, conductive, colloidal polymer - Google Patents

Abstract

The invention relates to a process for the preparation of a dispersion of a processable, conductive, colloidal polymer in an aqueous reaction medium. A polymer emulsion diluted with aqueous medium is used as steric stabiliser for aromatic heterocyclic monomers during the preparation of the colloidal polymer. The colloidal polymer prepared is further dispersed in a solvent which is miscible with the steric stabiliser. The dispersion can be coated onto a nonconductive substrate in order to metallise the substrate, and it can also be used as an antistatic coating for plastics and fibres.

Description

The present invention relates to a method for producing a ver workable, electrically conductive, colloidal polymers and in particular a process for the production of the colloidal polymer by oxida polymerizing an aromatic heterocyclic monomer in an aqueous reaction medium with a polymer emulsion as one steric stabilizer.

The production of printed circuit boards or printed circuit boards or plati NEN does not require the provision of a conductive surface on one conductive substrate, such as a plastic substrate. Conventional Methods include sensitizing and activating an etched Plastic substrates to a thin layer of a precious metal, such as et wa palladium, to be provided on its surface, whereupon the activate te substrate in a copper plating tank, which contains copper sulfate and Contains formaldehyde is given to the plastic substrate to metal lize, that is, to coat it on its surface with a copper film hen. The palladium acts as a catalyst to accelerate the oxi dations-reduction reaction of copper sulfate and formaldehyde.

The above conventional methods are complicated and require one Series of chemical reagents in the process. The cost of the Edelme tall connection are also very high. Since it continues as a reduction formaldehyde is a carcinogenic material, is its Use in electroless plating in many countries eventually the United States. Furthermore, during the Sensitization and activation treatments formed strongly acidic Wastewater during the electroless copper plating process formaldehyde-containing, strongly basic wastewater formed in serious pollution problems result.

Conjugated conductive polymers are due to growing interest on their use in antistatic coatings, conductive paint ben, with electromagnetic shielding, electrode coating gene and the like have been widely investigated. You are just  so in coated through holes of printed circuit boards and in the Me tallization of non-conductive substrates have been used. For example describes PCT Patent Application No. PCT / EP89 / 00204 (September 8, 1989) a method for coating a non-conductive substrate with a conductive polymer. This procedure includes the following three Stages: (1) Oxidation step: immersing the substrates in a permangan solution containing at an operating temperature between 80 ° and 90 ° C to form a layer of manganese dioxide on the wall of be layered through holes; (2) Activation level: immersion of the oxidized substrate in a monomer of the conductive polymer alcohol solution to form a layer of the manganese dioxide layer To apply monomers; and (3) fixing step: polymerizing the mono mer by immersing the activated substrate in an acidic solution, to metallize the substrate. Coat it with conductive polymer The substrate is then electrochemically coated with copper. The ar operations of this procedure are also very complicated.

Polypyrrole, when in its doped form, is relatively stable to air and is one of the most important conjugated conductive polymers. On due to the rigid conjugated bonds that polypyrrole has, cannot be dissolved in solvents, nor can it be melted the. Therefore, when polypyrrole is used, it is necessary to use a disper sion of a colloidal Poylpyrrols to make it processable to improve.

In general, a ge is used to produce a colloidal dispersion suitable steric stabilizer added to the Kol contained therein stabilize loide and prevent them from coagulating, which egg ne would precipitate the colloids.

It is known that in the manufacture of a colloidal dispersion of Polypyrrole two types of steric stabilizers are currently used. The first type consists of water-soluble steric stabilizers, such as such as poly (vinyl alcohol-co-vinyl acetate) (J. Colloid Int. Sci., 1987, 118,  410), polyvinylpyrrolidone (J. Chem. Soc., Chem. Commun., 1987, 288), Polyethylene oxide (J. Chem. Soc., Chem. Commun., 1988, 1189), Methylcel lulose (J. Chem. Soc., Chem. Commun., 1986, 1293), polyvinylpyridine and its copolymers [U.S. Patent 4959 162 (1990)]. The other type exists from steric stabilizers, which dissolve in organic solvents are. So far, only one type of such stabilizers has been known, näm polyvinyl acetate (PVAc) [U.S. Patent No. 5021 193 (1991)]. They use The dispersion media are esters, such as methyl formate and methyl lacetate.

The aqueous dispersion of colloidal polypyrrole has at Be layering on a substrate has the disadvantage of poor drying. To prolonged exposure to air, it absorbs moisture and swells, which reduces its bond strength to the substrate. Next nor is the aqueous dispersion of colloidal polypyrrole ge is suitable for use in an aqueous environment, for example, if a substrate with a conductive polypyrrole layer. which by Coating and subsequent drying of the aqueous dispersion was kept, following the electrochemical coating with Kup fer undergoes, the conductive polypyrrole layer peels off, whereby a failure of the copper plating results, or the colloidal part Chen fall off, destroying homogeneity and continuity of the coated copper film results due to water corrosion. Furthermore, it may happen that copper is not possible on the sub strat electrochemically to coat due to the rapid decrease the conductivity of the conductive polymer, which is caused by an excessive rapid reduction speed is caused. Continues to take the conductivity of the colloids decreases with time.

Another disadvantage of using a water-soluble polymer as a steric stabilizer for the dispersion of polypyrrole consists in that the dispersion (except for one with stabilizer, Polyvi nyl alcohol) does not become a film when coated on a substrate, for example a plastic substrate for a printed circuit board, who cast  that can. Although the aqueous dispersion using Polyvi can be poured into a film as a stabilizer mechanical strength is not sufficient, so that the practical Application is not possible.

Colloidal polypyrrole dispersions using organic solvents Solvents as a steric stabilizer can not egg too cast in a film and the conductivity of the colloids is too low, to perform the subsequent electrochemical copper plating to be able to. The use of an ester as a dispersion medium, as in the U.S. Patent No. 5,021,193, eventually causes one Air pollution because the ester is volatile.

An object of the invention is therefore to provide an improved ver driving to produce a processable, conductive, colloidal bottom lymeren or a dispersion of a processable, conductive, colloid len polymers, the improved process being easy to perform is supposed to be, does not cause pollution and is able to colloidal polymer with high conductivity and a dispersion with drawn film-forming properties when coating on a To yield substrate.

This object is achieved by a method according to An claim 1 and claim 13 solved. Advantageous embodiments are specified in the subclaims.

The inventive method for producing a dispersion of a Processible, conductive, colloidal polymers include the steps:

• (a) providing a polymer emulsion as a steric stabilizer;
• (b) Diluting the polymer emulsion with an aqueous dispersion medium;  
• (c) oxidatively polymerizing an aromatic heterocyclic Mo nomeren, which consists of the pyrrole, N-substituted pyrrole, beta-sub substituted pyrrole, thiophene, analine, furan and mixtures thereof standing group is selected, in an aqueous medium, which a Oxidizing agent for the aromatic heterocyclic monomer and includes dilute polymer emulsion;
• (d) separating the processable, conductive, colloidal polymer from the aqueous medium; and
• (e) dispersing the obtained, processable, conductive, colloidal Polymers in a solvent, which with the polymer in the poly meremulsion is miscible.

The present invention will be described with reference to the following detailed description and examples as well as the attached drawing explained in more detail, which show:

Fig. 1 is a scanning electron microscope (SEM) of the -Photographie kolloi Dalen film of Example 1;

Fig. 2 is a SEM photograph of the copper layer from application examples Game 1.

In the process according to the invention, the polymerization of the aromati rule heterocyclic monomers in an aqueous reaction medium carried out. This is the main feature of the Ver driving. Suitable aromatic heterocyclic monomers include pyr rol and other pyrroles, such as N-substituted pyrroles and beta-substi acted pyrroles, thiophene, aniline and furan. The substituent groups can alkyl, aryl, aralkyl, alkaryl, hydroxy, alkoxy, chlorine, bromine and include nitro groups. Among these, pyrrole is considered aromatic hey terocyclic monomer is particularly preferred.  

The aqueous reaction medium comprises oxidizing agents and a ver thin polymer emulsion. The diluted emulsion is diluted a polymer emulsion with an aqueous medium. That at Polymerization process used oxidizing agents must oxidati capable of polymerizing the aromatic heterocyclic monomer his. Examples of the oxidizing agents include iron (III) -, copper (II) - and Cesium (IV) salts from persulfate, halide, nitrate, dichromate, permang anate, manganate and periodate. The preferred oxidant is egg sen (IIl) chloride.

The molar ratio of oxidant to aromatic heterocycli The monomers in the aqueous reaction medium can be from 2: 1 to 5: 1 vary. The molar ratio of oxidizing agent is preferably to monomer 2.33: 1. The reaction temperature is 0 ° C to 100 ° C, and is preferably around room temperature.

The poly suitable for use in the process according to the invention Meremulsions as a steric stabilizer are emulsions from Polyviny lacetate (PVAc) and polyacrylate (s). An emulsion of PVAc is for that lying method preferred. The polyacrylates include poly (methyl methacrylate-co-butyl acrylate), poly (methyl methacrylate-co-butyl acrylate acrylic acid) and poly (methyl methacrylate-co-butyl acrylate-co-vinyl acetate).

The main function of the polymer emulsion is to control the aromatic heterocyclic monomers and oxidizing agents inside or on the surface of the polymer particles contained in the emulsion are to be absorbed, so that the polymerization of the monomers in situ can be done to precipitate due to coagulation tion when the colloidal particles generated are redispered in solvents be greed to prevent.

The aqueous medium for diluting the polymer emulsion can be deionized water or an acidic aqueous solution. The polymer emulsion should usually be 20 to 100 times their volume  become thin. For example, if you have a polymer emulsion of PVAc 1-5 ml of the PVAc emulsion (solid content 50%) with deionized water to 100 ml for use in the present invention diluted.

After the oxidative polymerization is complete, the right resulting conductive polymer particles are separated. According to the Invention can the colloidal particles from the aqueous reaction medium separated by filtration, then washed with water, to remove excess oxidizing agents and steric stabilizers distant. The separated colloidal particles can be in any Solvents that are miscible with PVAc are redispersed, to get a dispersion. Suitable examples include methanol, Benzene, toluene, chloroform, dimethylformamide (DMF), acetone, butanone, Esters and the like.

It should be noted that the order of addition of the monomer and the oxidizing agent to the dilute polymer dispersion, the Sta the resulting colloidal polymer dispersion can. According to the method according to the invention, it is preferred add the monomer to the diluted polymer emulsion first the monomer is absorbed by the polymer particles in the emulsion and then add the oxidizing agent so as to form colloidal particles that are not absorbed by the steric stabilizer be prevented.

The dispersion of the Conductive colloidal polymers can be applied directly to a non-conductive Substrate or be on the walls of through holes of a circuit board be coated to make them conductive and electrochemically coatable close. The colloidal dispersion can also be used with an antistatic agent layering, electromagnetic shielding and the like be used.  

The following examples illustrate the invention. The conductivities in the The following examples were made using the four-point feeler method measured.

example 1

1 ml of polyvinyl acetate (hereinafter referred to as "PVAc") emulsion with a solids content of 50% was diluted with deionized water to a total volume of 100 ml. 5.47 g of ferric chloride was added to the diluted emulsion with stirring. After the iron (III) chloride was completely dissolved, 1 ml of pyrrole was added and allowed to react at room temperature for 24 hours. A predi version of colloidal polypyrrole was obtained. The predispersion was filtered and washed with deionized water until the filtrate was colorless. The resulting colloids, which had a PVAc content of 19% by measurement using elemental analysis, were then redispersed in methanol to obtain a dispersion with a solids content in the range from about 2% to 3%. The dispersion was dried and the colloid obtained was ground to a fine powder. The conductivity of a compressed pellet from the powder was measured to be 2.8 × 10 ^-2 S / cm.

Example 2

The same procedures as described in Example 1 were used, with the exception that 2 ml of PVAc emulsion were used. The conductivity of a compressed pellet from the powder was measured to be 5.5 × 10 ^-3 S / cm.

Example 3

The same procedures as described in Example 1 were used, with the exception that 3 ml of PVAc emulsion were used. The conductivity of a compressed pellet from the powder was measured to be 1.4 × 10 ^-3 S / cm.

Example 4

The same procedures as described in Example 1 were used, with the exception that 5 ml of PVAc emulsion were used. The dispersion was cast into a film, but only a small area film was obtained. The conductivity of the resulting film was measured to be 9.1 × 10 ^-3 S / cm.

Example 5

The same procedures as described in Example 1 were used, with the exception that 1 ml of PVAc emulsion was diluted with 1 M toluenesulfonic acid to a total volume of 100 ml. The conductivity of a compressed pellet from the powder was measured to be 2.5 × 10 ^-3 S / cm.

Example 6

The same procedures as described in Example 1 were used, with the exception that 1 ml of PVAc emulsion was diluted with 0.1 M hydrochloric acid to a total volume of 100 ml. The conductivity of a compressed pellet from the powder was measured to be 3.0 × 10 ^-6 S / cm.

Example 7

The same procedures as described in Example 1 were used, with the exception that 7.52 g of ammonium persulfate were added as the oxidizing agent. The conductivity of a compressed pellet from the powder was measured to be 4.3 × 10 ^-5 S / cm.

Example 8

2 ml of PVAc were diluted to a total volume of 50 ml with deionized water. 1 ml of pyrrole was added to the diluted emulsion with stirring. After swelling for 30 to 60 minutes, 50 ml of an aqueous solution containing 5.47 g of ferric chloride was added and allowed to react at room temperature for 24 hours. A predispersion of the colloidal polypyrrole was obtained. The predispersion was filtered and washed with deionized water until the filtrate was colorless. The resulting colloids were redispersed in methanol. A dispersion of the colloid was obtained. The dispersion was dried and then ground to a fine powder. The conductivity of a compressed pellet from the powder was measured to be 2.4 × 10 ^-2 S / cm.

Example 9

The same procedures as described in Example 8 were used, with the exception that 4 ml of PVAc emulsion were used. The dispersion was cast into a film to obtain a large area film. The conductivity of the resulting film was measured to be 9.5 × 10 ^-4 S / cm.

Example 10

2 ml poly (methyl methacrylate-co-butyl acrylate) (monomer molar ratio = 1: 1, solids content = 14%) emulsion with deionized water diluted to a total volume of 150 ml. Then 5.47 g of egg Sen (III) chloride added with stirring. After the ferric chloride was completely dissolved, 1 ml of pyrrole was added and at room temperature allowed to react for 12 hours. It became a predisper sion of colloidal polypyrrole obtained. The predispersion was filtered and washed with deionized water until the filtrate was colorless. The resulting colloids were redispersed in butanol. there has been a  Preserved dispersion of the colloid. The dispersion was dried and added grind to a fine powder. The conductivity of a compressed pel lets from the powder were measured at 0.5 S / cm.

Example 11

15 ml poly (methyl methacrylate-co-butyl acrylate) emulsion, which the in Example 10 had the composition described, were with entioni diluted water to a total volume of 90 ml. Then were 10 ml of a solution containing 5.47 g of ferric chloride with stirring admitted. Then 1 ml of pyrrole was added and at room temperature Reacted for 13 hours. It became a predispersion of the colloid len polypyrroles obtained. The predispersion was filtered and with entioni washed water until the filtrate was colorless. The resulting Colloids were redispersed in butanol to form a dispersion of the colloid to obtain. The dispersion was cast into a film, a film was obtained with a large area. The conductivity of the resulting Film was measured at 0.1 S / cm.

Example 12

The same procedures as described in Example 11 were followed with the exception that 10 ml of poly (methyl methacrylate-co-bu tylacrylate-co-acrylic acid) copolymer (monomer molar ratio of MMA: BA: AA = 2: 3: 1, solids content = 15%) were used. The Dis persion was cast into a film, being a film with a large area was obtained. The conductivity of the resulting film became 0.2 S / cm measured.

Example 13

The same procedures as described in Example 10 were followed with the exception that 6 ml of poly (methyl methacrylate-co-bu  tylacrylate-co-vinyl acetate) copolymer (monomer molar ratio of MMA: BA: VAc = 1: 1: 1, solids content = 15%) were used and that the reaction time was 15 hours. The dispersion was dried and grind to a fine powder. The conductivity of a kompri Milled pellets from the powder were measured at 0.09 S / cm.

Comparative Example 1

In this example, the procedure for making the pyrrole-PVAc colloid as described in US Patent 5021,193 (1991) was repeated. 1 g of PVAc was dissolved in methyl formate to obtain a solution. Then 5.47 g of ferric chloride was added to the solution with stirring. After the ferric chloride was completely dissolved, 1 ml of pyrrole was added and allowed to react at room temperature for 16 to 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 then ground to a fine powder. The conductivity of a compressed pellet from the powder was measured to be 2.5 × 10 ^-6 S / cm.

A second experiment was carried out in a similar manner, with the exception that 1 g of PVAc was dissolved in methyl acetate. The conductivity of the resulting compressed pellet was measured at 1.1 × 10 ^-6 S / cm.

It shows that the conductivities are the same as in Comparative Example 1 polypyrrole colloids are obviously lower than those that prepared in Examples 2, 3 and 4.

Comparative Example 2

The same procedures were used as described in Example 1, with the exception that no PVAc emulsion as steric  Stabilizer was used. The conductivity of the resulting com primed pellets were measured to be 0.4 S / cm. It turns out that whether probably isolating the polypyrrole colloids prepared according to Example 1 It contains PVAc, the conductivity of which is obviously not lower than those produced according to Comparative Example 2.

Application example 1

The dispersion prepared in Example 1 was coated on a substrate (glass fiber / epoxy) for a printed circuit board and allowed to dry. A composite film was formed from the colloidal polypyrrole. The coated substrate was used as a cathode in a copper electrocoating cell; A copper plate was used as the anode in this cell. The electrocoating solution contained 220 g / l copper sulfate, 60 g / l sulfuric acid and 0.1 g / l hydrochloric acid. The current density used was in the range: 1 to 5 A / dm². After the electrocoating was completed, a uniform layer of copper was deposited on the composite film of colloidal polypyrrole. The copper-coated substrate could also be immersed in a solution containing antioxidants to prevent loss of metallic luster due to oxidation. Figs. 1 and 2 are SEM photographs of the colloidal film before and after the copper electroplating.

Example of use 2

The same procedures as described in Application Example 1 were used, with the exception that the dispersions prepared in Examples 10, 11, 12 and 13 were coated onto the substrate for a printed circuit board. The SEM photographs of the colloidal films and the deposited copper layers are similar to FIGS. 1 and 2.

Example of use 3

The dispersion prepared in Example 12 was applied to the through holes coated on a circuit board and left to dry. It became a too composite film of colloidal polypyrrole on the wall of the holes educated. The plate was then placed in an electroplating cell as Ka method used; a copper plate was used as the anode in the cell det. The electrocoating solution contained 220 g / l copper sulfate, 60 g / l Sulfuric acid and 0.1 g / l hydrochloric acid. The electricity applied density was in the range: 1 to 5 A / dm². After the electro coating was complete, there was an even layer of copper on the walls of the holes, which makes it possible to cover the two sides of the To connect copper layers with each other. The record could continue in a solution containing antioxidants can be immersed in a Loss of the metallic luster of the copper layer due to oxides tion to prevent.

Example of use 4

The dispersion prepared in Example 9 was applied to a polyethylene tereph thalat (PET) substrate coated and allowed to dry. The bin Formation of the coated film on the substrate was found to be very good the. The coated substrate was rubbed with a cloth and immediately checked for the generation of a static electrical charge by the substrate was held over shredded paper. It wasn't a dress hung the paper chips in the direction of the coated substrate be careful, indicating that no static electrical charge was generated. However, it was found that the uncoated substrate the shredded paper tightened after being rubbed with a cloth is. Comparing the above two substrates shows that that with the colloidal dispersion coated substrate good anti-electrostatic Possesses properties. Thus, the dispersion of the colloidal poly pyrrols as packaging material for electrical parts or as antistati cal coating for plastics and fibers can be used.

Claims (27)

1. A process for producing a processable, conductive, colloidal polymer in an aqueous medium, characterized by the steps:

• (a) providing a polymer emulsion as a steric stabilizer;
• (b) diluting the polymer emulsion with an aqueous dispersion medium;
• (c) oxidatively polymerizing an aromatic heterocyclic monomer selected from the group consisting of pyrrole, N-substituted pyrrole, β-substituted pyrrole, thiophene, aniline, furan and mixtures thereof, in an aqueous medium containing an oxidizing agent for the aromatic heterocyclic monomer and the dilute polymer emulsion; and
• (d) separating the processable, conductive, colloidal polymer from the aqueous medium.

2. The method according to claim 1, characterized in that the poly meremulsion is an emulsion of polyvinyl acetate. 3. The method according to claim 1, characterized in that the poly meremulsion is an emulsion of acrylates. 4. The method according to claim 3, characterized in that the Acrylate is poly (methyl methacrylate-co-butyl acrylate). 5. The method according to claim 3, characterized in that the Acrylate is poly (methyl methacrylate-co-butyl acrylate-co-acrylic acid). 6. The method according to claim 3, characterized in that the Acrylate is poly (methyl methacrylate-co-butyl acrylate-co-vinyl acetate).   7. The method according to at least one of claims 1-6, characterized ge indicates that the aqueous dispersion medium is water. 8. The method according to at least one of claims 1-6, characterized ge indicates that the aqueous dispersion medium is an acidic aqueous Solution is. 9. The method according to at least one of claims 1-8, characterized ge indicates that the oxidizing agent from the iron (III) -, Kup fer (II) and cesium (IV) salts from persulfate, halide, silver nitrate or Nitrate, dichromate, permanganate, manganate and periodate existing Group is selected. 10. The method according to claim 9, characterized in that the oxi dation agent is iron (III) chloride. 11. The method according to at least one of claims 1-10, characterized ge indicates that the aromatic heterocyclic monomer is pyrrole. 12. The method according to at least one of claims 1-11, characterized ge indicates that the separation is carried out by filtration. 13. A process for producing a dispersion of a processable, conductive, colloidal polymer in an aqueous medium, characterized by the steps:

• (a) providing a polymer emulsion as a steric stabilizer;
• (b) diluting the polymer emulsion with an aqueous dispersion medium;
• (c) oxidatively polymerizing an aromatic heterocyclic monomer selected from the group consisting of pyrrole, N-substituted pyrrole, β-substituted pyrrole, thiophene, aniline, furan and mixtures thereof, in an aqueous medium containing an oxidizing agent for the aromatic heterocyclic monomer and the dilute polymer emulsion;
• (d) separating the processable, conductive, colloidal polymer from the aqueous medium; and
• (e) dispersing the obtained, processable, conductive, colloidal polymer in a solvent which is miscible with the polymer in the polymer emulsion.

14. The method according to claim 13, characterized in that the bottom lymeremulsion is an emulsion of polyvinyl acetate. 15. The method according to claim 13, characterized in that the bottom lymeremulsion is an emulsion of acrylates. 16. The method according to claim 15, characterized in that the Acrylate is poly (methyl methacrylate-co-butyl acrylate). 17. The method according to claim 15, characterized in that the Acrylate is poly (methyl methacrylate-co-butyl acrylate-co-acrylic acid). 18. The method according to claim 15, characterized in that the Acrylate is poly (methyl methacrylate-co-butyl acrylate-c-vinyl acetate). 19. The method according to at least one of claims 13-18, characterized characterized in that the aqueous emulsion medium is water. 20. The method according to at least one of claims 13-18, characterized characterized in that the aqueous dispersion medium is an acidic aqueous solution. 21. The method according to at least one of claims 13-20, characterized  characterized in that the oxidizing agent from the iron (III) -, Kup fer (II) and cesium (IV) salts from persulfate, halide, nitrate, dichro mat, permanganate, manganate and periodate group selected becomes. 22. The method according to claim 21, characterized in that the Oxidizing agent is ferric chloride. 23. The method according to at least one of claims 13-22, characterized characterized in that the aromatic heterocyclic monomer pyrrole is. 24. The method according to at least one of claims 13-23, characterized characterized in that the separation is carried out by filtration. 25. The method according to at least one of claims 13-24, characterized characterized in that the solvent used in step (e) from the from methanol, benzene, toluene, chloroform, dimethylformamide (DMF), Ace ton, butanone and ester group. 26. The method according to claim 25, characterized in that the in Solvent used in step (e) is methanol. 27. The method according to claim 25, characterized in that the in Stage (e) solvent used is butanone.