TWO OR POLYFUNCTIONAL COMPOUNDS AS ADHESION PRIMERS FOR CONDUCTIVE POLYMERS

Abstract

The present invention relates to a process for producing an electrolytic capacitor, the process comprising process steps i) ii): i) providing a capacitor body (1) that comprises an electrode body (2) of an electrode material, a dielectric (3) which at least partially covers the surface of this electrode material, and a solid electrolyte (4) at least comprising an electrically conductive material which at least partially covers the dielectric surface; ii) applying at least one primer compound e) to the capacitor body (1), followed by an application of a solution or dispersion a) comprising a conjugated polymer b) and a solvent or dispersant d), followed by an at least partial removal of the solvent or dispersant d) for the formation of the polymeric outer layer (5) that is formed onto the capacitor body (1);
wherein the primer compound e) is a di- or polyfunctional monomeric compound comprising at least one amine group, which optionally may be protonated, and at least one carboxylic or sulfonic acid group, which optionally may be deprotonated. The invention also relates to electrolytic capacitors produced by this process and to the use of such electrolytic capacitors.

Claims

1. A process for producing an electrolytic capacitor, the process comprising process steps i) and ii): i) providing a capacitor body that comprises an electrode body of an electrode material, a dielectric which at least partially covers the surface of this electrode material, and a solid electrolyte at least comprising an electrically conductive material which at least partially covers the dielectric surface, ii) applying at least one primer compound e) to the capacitor body, followed by an application of a solution or dispersion a) comprising a conjugated polymer b) and a solvent or dispersant d), followed by an at least partial removal of the solvent or dispersant d) for the formation of the polymeric outer layer that is formed onto the capacitor body; wherein the primer compound e) is a di- or polyfunctional monomeric compound comprising at least one amine group, which optionally may be protonated, and at least one carboxylic or sulfonic acid group, which optionally may be deprotonated.

2. The process according to claim 1, wherein the primer compound e) does not comprise an amine group and a carboxylic acid group that are bound to the same carbon atom.

3. The process according to claim 1, wherein in the primer compound e) the at least one amine group and the at least one carboxylic or sulfonic acid group are both covalently bound to the compound.

4. The process according to claim 1, wherein the primer compound e) is an aminofunctional sulfonic acid.

5. The process according to claim 4, wherein the aminofunctional sulfonic acid is selected from the group consisting of 4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid (HEPES), 4-morpholinepropanesulfonic acid (MOPS), 4-morpholineethanesulfonic acid (MES), 3-(cyclohexylamino)-1-propanesulfonic acid (CAPS) and 3-[N-Tris(hydroxymethyl)methylamino]-2-hydroxypropanesulfonic acid (TAPSO).

6. The process according to claim 1, wherein the primer compound e) is a compound of the structural formula (I) ##STR00007## in which R may be identical or different and represents a hydrogen, a C.sub.1-C.sub.18 aliphatic or hetero aliphatic group, a C.sub.6-C.sub.18 aromatic or hetero aromatic group or a C.sub.7-C.sub.18 aralkyl or hetero aralkyl group; A represents —NH.sub.2, —NHR.sup.1 or —NR.sup.1.sub.2, in which in case of —NR.sup.1.sub.2 residue R.sup.1 may be identical or different, and wherein R.sup.1 represents a C.sub.1-C.sub.18 aliphatic or hetero aliphatic group, a C.sub.6-C.sub.18 aromatic or hetero aromatic group or a C.sub.7-C.sub.18 aralkyl or hetero aralkyl group, and wherein group A may optionally be protonated; B represents —COOH or —SO.sub.3H, in which group B may optionally be deprotonated; n represents an integer in the range from 0 to 20.

7. The process according to claim 6, wherein the primer compound e) is selected from the group consisting of β-alanine, γ-aminobutyric acid, 6-aminohexanoic acid and β-aminoethanesulfonic acid (taurine).

8. The process according to claim 1, wherein the primer compound e) is a compound of the structural formula (II) ##STR00008## in which R may be identical or different and represents a hydrogen, a C.sub.1-C.sub.18 aliphatic or hetero aliphatic group, a C.sub.6-C.sub.18 aromatic or hetero aromatic group or a C.sub.7-C.sub.18 aralkyl or hetero aralkyl group; A may be identical or different and represent —NH.sub.2, —NHR.sup.1 or —NR.sup.1.sub.2, in which in case of —NR.sup.1.sub.2 residue R.sup.1 may be identical or different, and wherein R.sup.1 represents a C.sub.1-C.sub.18 aliphatic or hetero aliphatic group, a C.sub.6-C.sub.18 aromatic or hetero aromatic group or a C.sub.7-C.sub.18 aralkyl or hetero aralkyl group, and wherein groups A may optionally be protonated; B may be identical or different and represent —COOH or —SO.sub.3H, in which groups B may optionally be deprotonated; n represents an integer in the range from 0 to 20.

9. The process according to claim 8, wherein the primer compound e) is diaminoheptanedioic acid.

10. The process according to claim 1, wherein the primer compound is an α-amino acid selected from the group consisting of proline, tyrosine, threonine, serine, glutamic acid and aspartic acid.

11. The process according to claim 1, wherein in process step ii) the primer compound e) is applied to the capacitor body from a solution or dispersion comprising at least 0.5 wt.-%, based on the total weight the solution, of the primer compound e).

12. The process according to claim 1, wherein in process step ii) the primer compound e) is applied to the capacitor body from a solution or dispersion comprising whose pH is less than 11.

13. The process according to claim 11, wherein the solvent or dispersant of the solution or dispersion from which the primer compound e) is applied comprises at least water or at least one organic solvent or dispersant.

14. The process according to claim 1, wherein the primer compound e) is soluble in solution or dispersion a).

15. The process according to claim 1, wherein the conjugated polymer b) is a cationic polymer and wherein solution or dispersion a) comprises a polymeric anion serving as a counter-ion for conjugated polymer.

16. The process according to claim 14, wherein the polymeric anion is an anion of a polymeric carboxylic or sulfonic acid.

17. The process according to claim 1, wherein in process step ii) the primer compound e) and the solution or dispersion a) are applied sequentially and repeatedly.

18. The process according to claim 1, wherein the solution or dispersion a) comprises, as the conjugated polymer, an electrically conductive polymer selected from the group consisting of an optionally substituted polythiophene, an optionally polyaniline and an optionally substituted polypyrrole.

19. Electrolytic capacitor produced by a process according to claim 1.

20. Use of the electrolytic capacitors according to claim 19 in electronic circuits.

Description

[0160] FIG. 1 describes a schematic diagram of the construction of a solid electrolytic capacitor using the example of a tantalum capacitor comprising [0161] 1 capacitor body [0162] 5 polymeric outer layer [0163] 6 graphite/silver layer [0164] 7 wire contact to electrode body 2 [0165] 8 outer contacts [0166] 9 encapsulation [0167] 10 detail

[0168] FIG. 2 describes the enlarged detail 10 from FIG. 1 of the schematic layer structure of the tantalum capacitor comprising [0169] 10 detail [0170] 2 porous electrode body (anode) [0171] 3 dielectric [0172] 4 solid electrolyte (cathode) [0173] 5 polymeric outer layer [0174] 6 graphite/silver layer

[0175] When, instead of a porous sintered body, porous films, for example aluminum foils, are used as the electrode body, a similar construction to that described above arises in principle. In order to achieve higher capacitances, a plurality of films are preferably contact-connected and encapsulated together in parallel in one housing.

EXAMPLES

Example 1

Preparation of the Tantalum Anode:

[0176] Tantalum powder with a specific capacitance of 18000 μFV/g was pressed to pellets with incorporation of a Tantalum wire and sintered in order to form an electrode body with the dimensions of 1.5 mm×2.9 mm×4.0 mm. 5 of these porous electrode bodies were anodized to 100 V in a phosphoric acid electrolyte to form a dielectric.

Example 2

Polymer Dispersion for the Preparation of the Solid Electrolyte:

[0177] A 2 L glass reactor with stirrer and thermometer was initially charged with 868 g of deionized water, 330 g of an aqueous polystyrenesulfonic acid solution with a mean molecular weight (weight average M.sub.w) of 70000 g/mol and a solids content of 3.8% by weight. The reaction temperature was kept between 20° C. and 25° C. With stirring 5.1 g 3,4-ethylenedioxythiophene were added. The solution was stirred for 30 minutes. Subsequently, 0.03 g of iron(III) sulphate and 9.5 g of sodium persulfate were added and the solution was stirred for a further 24 hours. After the reaction had ended, 100 ml of a strongly acidic cation exchanger (Lewatit 5100, Lanxess AG) and 250 ml of a weakly basic anion exchanger (Lewatit MP62, Lanxess AG) were added to remove inorganic salts, and the solution was stirred for a further 2 h. The ion exchangers were filtered off.

[0178] The PEDOT/PSS dispersion was homogenized ten times at a pressure of 700 bar with a high-pressure homogenizer. Subsequently, the dispersion was concentrated to a solids content of 2.5% and then homogenized five times at a pressure of 1500 bar with a high-pressure homogenizer.

[0179] Subsequently, the dispersion was diluted to a solids content of 1.04% and 96 g of the diluted dispersion were admixed with 4 g of dimethyl sulfoxide (DMSO) and stirred intensively.

Example 3

Preparation of Primer Solutions:

[0180] In a beaker with a stirrer, 5 g of a primer compound e) mentioned in table 1 and 95 g of deionized water were mixed vigorously for one hour.

Example 4

Polymer Dispersion for the Preparation of the Outer Layer:

[0181] A 5 L glass reactor with stirrer and thermometer was initially charged with 1736 g of deionized water, 660 g of an aqueous polystyrenesulfonic acid solution with a mean molecular weight (weight average M.sub.w) of 70000 g/mol and a solids content of 3.8% by weight. The reaction temperature was kept between 20° C. and 25° C. With stirring 10.2 g 3,4-ethylenedioxythiophene were added. The solution was stirred for 30 minutes. Subsequently, 0.06 g of iron(III) sulphate and 19 g of sodium persulfate were added and the solution was stirred for a further 24 hours (h). After the reaction had ended, 200 ml of a strongly acidic cation exchanger (Lewatit 5100, Lanxess AG) and 500 ml of a weakly basic anion exchanger (Lewatit MP62, Lanxess AG) were added to remove inorganic salts, and the solution was stirred for a further 2 hours. The ion exchangers were filtered off. Subsequently, the dispersion was concentrated to a solids content of 1.5%.

[0182] In a beaker with a stirrer, 160 g of this concentrated dispersion, 28 g of deionized water, 6 g of a sulfopolyester (Eastek 1100, solids content 30%, mean molecular weight 10000-15000 g/mol, Eastman) 8 g of dimethyl sulfoxide, 1 g of 3-glycidoxypropyltrimethoxysilane (Silquest A-187, OSi Specialities) and 0.4 g of wetting agent (Dynol 604, Air Products) were mixed vigorously for one hour.

Example 5

[0183] Preparation of a Capacitor with the Primer Compound:

[0184] The oxidized electrode bodies from Example 1 were impregnated in the dispersion from Example 2 for 1 minute. This was followed by drying at 120° C. for 10 minutes. This sequence of impregnation and drying was carried out nine further times. Subsequently, an impregnation into the solution from Example 3 for 1 minute was carried out, followed by drying at 120° C. for 10 minutes. After this, an impregnation into the dispersion from Example 4 for 1 minute was carried out, followed by drying at 120° C. for 10 minutes.

[0185] Subsequently, an impregnation into the solution from Example 3 for 1 min was carried out, followed by drying at 120° C. for 10 min. After this, an impregnation into the dispersion from Example 4 for 1 min was carried out, followed by drying at 120° C. for 10 min. Subsequently, an impregnation into the solution from Example 3 for 1 minute was carried out, followed by drying at 120° C. for 10 minutes. After this, an impregnation into the dispersion from Example 4 for 1 minute was carried out, followed by drying at 120° C. for 10 minutes.

[0186] The completeness of the coating of the capacitor body with the polymeric outer layer was determined visually using a light microscope (“complete”: complete coverage of the capacitor body with the polymeric outer layer; “incomplete”: incomplete coverage of the capacitor body with the polymeric outer layer)

TABLE-US-00001 TABLE 1 primer compound e) coverage none incomplete 4-aminobutyric acid complete proline complete 2,6-diaminoheptanedioic acid complete 6-aminohexanoic acid complete taurine complete 3-(3,4-dihydroxyphenyl)-alanine complete (DOPA) 4-(2-hydroxyethyl)piperazine-1-ethanesulfonic complete acid (HEPES) 4-morpholinepropanesulfonic acid complete (MOPS) 4-morpholineethanesulfonic acid (MES) complete 3-(cyclohexylamino)-l-propansulfonic acid complete (CAPS) 3-[N-Tris(hydroxymethyl)methylamino]-2- complete hydroxypropanesulfonic acid (TAPSO) β-alanine complete tyrosine complete threonine complete serine complete glutamic acid complete aspartic acid complete