MXPA98009099A - Adulteral polianiline solutions - Google Patents

Abstract

Polymethylan based adulterated polymers are formed with fibers, films and coatings with a solvent of N-ethylpyrrolidone. Said solvent system is particularly useful for the formation of a solid electrolyte on a capacit element.

Description

ADULTERATED POLIANYLINE SOLUTIONS FIELD PE INVENTION The invention relates to adulterated polyaniline solutions, solvent systems used therein and conductive articles formed therefrom. BACKGROUND OF THE INVENTION The acid adulterated polyaniline is finding an increasing level of interest as a solid electrolyte for capacitors and other electronic devices. The adulterants are selected from a relatively small group of acids that increase the solubility in organic solvents with a low dielectric constant, v. gr. , a dielectric constant of less than about 17. Acid-adulterated polyaniline polymers are generally considered to have no practical solubility in solvents with a dielectric constant greater than about 17. See U.A.A. Patent. No. 5,567,356. The most preferred polyaniline adulterant is dinonyl naphthalene sulfonic acid (DNSA). A commercially available solution contains polyaniline adulterated with DNSA in a mixture of solvents comprising xylene, monobutyl ether of ethylene glycol. Unfortunately, this solvent system is characterized by toxicity, objectionable odor and solvency for inorganic salts that is sufficiently low to prevent the use of the solvent to co-deposit said salts with the polymer.

It would be useful to have a solvent system that exhibits a low vapor pressure and low toxicity. It could be even more beneficial to have a solvent system that also has a relatively high boiling point with a dielectric constant. The boiling point could facilitate the use and handling of the solvent in a commercial equipment. A higher dielectric constant could increase the conductivity to a point that was similar to systems using polar solvent salt systems and could be useful for some types of capacitors when an electrically conductive waste remained after evaporation of the solvent. Improved systems for forming polymeric films and coatings based on polyaniline could be particularly useful in the manufacture of capacitors. In such articles, one or more polymer coatings based on electrically conductive polyaniline could be used as a solid electrolyte between the dielectric oxide layer and the electrodes. It could be useful to have a polymer dissolution system based on polyaniline that would not give problems and limitations to the previous xylene solvent systems. It is an object of the invention to provide a process for depositing a polyaniline film coating of a solution using a solvent characterized by a pressure with less toxicity and lower vapor content, superior solvency for inorganic salts, of higher boiling, and higher dielectric constant than the previously used xylene-based solvent systems. In accordance with these and other objects of the invention it will be apparent from the description hereof that a process, coating and article coated according to the invention are based on the use of a solvent system using N-ethyl -pyrrolidone as the solvent for acid-adulterated polyaniline-based polymers. This solvent is characterized by lower toxicity, lower vapor pressure, higher solvency for inorganic salts, higher boiling point and higher dielectric constant than solvent systems based on xylene. DETAILED DESCRIPTION The polymer based on acid adulterated polyaniline is dissolved in the solvent N-ethyl-pyrrolidone and used to form conductive articles. Such articles include fibers, films, coatings (particularly coatings to dissipate static electricity), coated articles, batteries, electrolyte sensors and capacitor elements. A coated article of particular interest is a capacitor element that uses an acid-adulterated polyaniline-based polymer as a solid or liquid electrolyte. The anode body of said capacitor is preferably formed of a valve metal such as aluminum or tantalum, the tantalum being generally more preferred between the two.

The polyaniline-based polymers applicable for the present invention are generally described in the U.S. Patent. No. 5,069,820, the description of which is incorporated herein by reference. The '820 patent describes electrically conductive polyaniline-based polymers having the following general formula: where n is an integer from 0 to 5; m is an integer from 0 to 5 as long as the sum of n and m equals 5; R2 and R4 are the same or different and are hydrogen or alkyl of 1-10 carbon atoms; R3 is the same or different and is selected from alkyl, alkenyl, alkoxy, cycloalkoxy, cycloalkenyl, alkanoyl, alkylthio; alkylamino, aryloxy, alkylthioalkyl, alkylaryl, arylalkyl, amino, dialkylamino, aryl, aryloxyalkyl, alkylsulfinylalkyl, alkylsulfonyl, arylsulfonyl, carboxylic acid, halogen, cyano, suifonic acid, nitro, alkylsilane or alkyl substituted with one or more of suifonic acid, carboxylic acid , halo, nitro, cyano, or portions of epoxy; or any of two R3 groups taken together can form an alkylene or alkylene chain that complete an aromatic or acyclic ring of 3, 4, 5, 6, or 7 members which may include one or more divalent atoms of nitrogen, sulfur, sufinyl, ester, carbonyl, sulfonyl or oxygen; R3 is an aliphatic portion having repeating units of the formula: - (OCH2CH2) q- or - (OCH2CH (CH3)) qO- where q is a positive integer. The acid adulterants used for the polyaniline-based polymers are generally selected from sulfonic acid anions (e.g., dionyl naphthalene suphonic acid (DNSA), toluene sulfonic acid, dodecylbenzin suifonic acid, camphor suifonic acid, allylsulfonic acid, 1-acid) propanesulfonic, 1-butanesulfonic acid, 1-hexanesulfonic acid, 1-heptanesulfonic acid, benzenesulfonic acid, styrenesulfonic acid, naphthalenesulfonic acid, including homologs and analogs thereof), and carboxylic acids (e.g., acetic acid and oxalic acid) . Preferred organic sulfonic acid adulterants include toluene sulfonic acid, deodecylbenzin suifonic acid and camphor suifonic acid. The main solvent useful in the present invention is N-ethylpyrrolidone. This solvent is characterized by a high dielectric constant (approximately 28), high solution conductivity, the ability to wet substrates that are somehow difficult to wet and a freezing point of approximately -70 ° C. The high dielectric constant suggests that the solvent might be able to dissolve salts to co-deposit with the polyaniline-based polymer. The solvent of the invention allows polymer solutions based on polyaniline to be formed at a variety of concentrations of 0.01-35% by weight with stirring and heating at 80 ° -85 ° C at higher concentrations. The most commercially useful concentrations for the uniform impregnation and coating of porous substrates is a solution having from about 10 wt% to about 20 wt% polymer based on polyaniline. Said concentrations in solution are compared with those commercially available with solvent systems based on xylene. The polyaniline polymer solution of the present invention is particularly suitable in the manufacture of capacitor elements that utilize an acid-adulterated polyaniline polymer, electrically conductive as an electrolyte. These capacitor elements are made of metallic valve powders that are anodized to form a dielectric layer on the surface of the anode body, are coated with an electrically conductive polymer to form an electrolyte layer, re-formed, coated / rendered to form until the desired thickness of the electrolyte is achieved and terminated. Liquid electrolytes are generally preferred for high voltage capacitor elements. The valve metals from which the capacitor elements are formed are preferably made of materials that form an insulating film when the body is positively charged. When the body is negatively charged, the movie will lead. Suitable materials include Group IV and V metals (particularly niobium, tantalum, zirconium and titanium) and aluminum. When in powder, the appropriate powder sizes are within the range of 0.05 to 50 microns. These powders are pressed with or without a binder to form a vertex anode body having a density of about 30-70% theoretical density. The green body is then compressed at a temperature within the range of about 1200 ° C to about 1800 ° C. Preferably aluminum is used in the form of a sheet or engraved sheet that is rolled or stacked. The anode is then "anodized" to suspend the constricted body in an electrolyte solution at a formation voltage of 3-4 times the base voltage of the element. For example, a normal part estimated at 10 volts could be formed at 30-40 volts, usually 35 volts. Suitable electrolyte solutions include phosphoric acid or ammonium nitrate in water with or without thickening agents, solvents, co-solvents, surfactants, or other conventional additives. Once anodized, the anode is coated with one or more layers of an electrically conductive, acid-adulterated polyanilin-based polymer by immersing the capacitor element in a solution that coats the polymer in the solvent. The element then coated with heating to expel the solvent. Suitable heating temperatures are within the range of about 35 ° C to about 120 ° C. The polymer coated capacitor element is then "reformed" by immersing the element in an acid reforming solution. After heating, there may be monomer materials from residual byproducts that are undesirable in the final capacitor element. Said materials are easily removed by washing with water, solvents and / or surfactants. Preferred washing agents include methane or acetone. The thickness of the electrolyte layer can be increased by repeating the above process steps until an adequate thickness is achieved. In general, the polymeric coating can be constructed with 1-20 repetitions of the impregnation, heating and washing steps. The reformed capacitor element is then terminated to make a spare part. The finish could normally encompass - an external coating of the solid electrolyte polymer nc adulterated, the printing of the element with an electrode pattern sealing the unit in a non-conductive material, v. gr. , epoxy, and form a set of multiple elements (if desired). EXAMPLES Example 1 A 25% solution containing 10 grams of polyanilin α adulterated with DNSA is prepared by dissolving polyanimine in a solution of N. E. P. ™ (International Specialty Chemicals Corp.) at 80 ° C, a commercially available product of N-ethyl-2-pyrrolidone. The solution has a dielectric constant of 28.1. Resistance measurements were made at 1 kHz with a Y.S. I. (cell constant = 1.0) and are reported in Table 1. Table 1 TEMPERATURE (° C) RESISTIVITY (OHM-CM) -35 8350 20 2070 80 1000 The conductivity of this solution is similar to that of a solution in polar solvent salts.

Claims (21)

1. REIVINATION DICATIONS 1. A process for forming a polymeric film by means of the steps comprising: applying to an article a solution comprising an adulterated polyaniline polymer with acid dissolved in a solvent comprising N-ethylpyrrolidone; and allowing said solvents to evaporate.
2. 2. A process according to claim 1, wherein the article is a capacitor element.
3. 3. A process according to claim 2, wherein the capacitor element is formed of a valve metal.
4. 4. A process according to claim 3, wherein the valve metal is tantalum.
5. 5. A process according to claim 1, wherein the article is a metal surface.
6. 6. A process according to claim 1, wherein the acid adulterated polyaniline polymer is a polyaniline polymer adulterated with suifonic acid.
7. 7. A process according to claim 6, wherein the acid adulterated polyaniline polymer is a polyaniline polymer adulterated with dinonylnaphthalenesulfonic acid.
8. 8. A process according to claim 1, further comprising: washing the polymer coating with acetone or methanol.
9. 9. A process for capacitor elements that include the steps of: a. anodizing a metal powder anode body of the valve to form a dielectric surface layer; and b. coating the anode with electrically conductive solid electrolyte by applying to said electrical surface layer a solution comprising a polyaniline polymer adulterated with acid dissolved in a solvent containing N-ethylpyrrolidone.
10. 10. A process according to claim 9, wherein the anode body is made of tantalum.
11. 11. A process according to claim 9, wherein the acid-adulterated polyaniline polymer is a polymer of polyaniline polymer adulterated with suifonic acid.
12. 12. A process according to claim 11, wherein the acid adulterated polyaniline polymer is a polyaniline polymer adulterated with dinonyl naphthalene suphonic acid.
13. 13. A process according to claim 9 further comprising: washing the polymer coating with ethanol or acetone.
14. 14. A process according to claim 9, wherein the capacitor element uses the liquid electrolyte.
15. 15. A liquid solution containing: N-ethylpyrrolidone and a polyaniline based polymer adulterated with acid.
16. 16. A liquid solution according to claim 15, wherein the acid adulterated polyaniline polymer is a polyaniline polymer adulterated with suifonic acid.
17. 17. A liquid solution according to claim 16, wherein the acid adulterated polyaniline polymer is a polyaniline polymer adulterated with dinonylnaphthalenesulfonic acid.
18. 18. A liquid solution according to claim 15. which contains 0.01-35% by weight of the polymer.
19. 19. A liquid solution according to claim 18. wherein the polymer is polyaniline adulterated with dinonylnaphthalenesulfonic acid.
20. 20. A liquid solution according to claim 18. which contains from 10-20% by weight of the polymer. twenty-one . A liquid solution according to claim 20 wherein the polymer of a polyaniline adulterated with dinon i l naphthalene suphonic acid.