Moulding composition for producing bipolar plates
View Patent ↗Compositions comprising (a) an epoxy resin, (b) a hardener for the epoxy resin, (c) a product of the reaction of a microgel containing carboxylic acid groups and a nitrogen-containing base, and (d) an electrically conducting filler combination comprising, based on the total amount of filler, at least 75% by weight of graphite, are particularly suitable for producing biopolar plates.
1. A solvent-free composition consisting essentially of:
(a) an epoxy resin,
(b) a hardener for the epoxy resin,
(c) a product of the reaction of a microgel containing carboxylic acid groups and a nitrogen-containing base, selected from the group consisting of an amine, a polyamine and an imidazole, and
(d) an electrically conducting filler combination comprising, based on the total amount of filler, at least 75% by weight of graphite.
2. The composition according to claim 1 , wherein component (a) is a solid ether-based epoxy resin.
3. The composition according to claim 1 , wherein component (a) is an epoxy phenol novolak or an epoxy cresol novolak.
4. The composition according to claim 1 , wherein the microgel in component (c) is a copolymer of at least one unsaturated carboxylic acid and at least one polyfunctional crosslinker.
5. The composition according to claim 4 , wherein the unsaturated carboxylic acid is acrylic acid or methacrylic acid.
6. The composition according to claim 4 , wherein the polyfunctional crosslinker is a polyfunctional acrylate or methacrylate of an aliphatic, cycloaliphatic or aromatic polyol, an addition product of acrylic acid or methacrylic acid and a polyglycidyl compound, an addition product of acrylic acid or methacrylic acid and glycidyl acrylate or methacrylate, an alkenyl acrylate or alkenyl methacrylate, a dialkenylcyclohexane, or a dialkenylbenzene.
7. The composition according to claim 4 , wherein the polyfunctional crosslinker is selected from the group consisting of ethylene glycol diacrylate, ethylene glycol dimethacrylate, propylene glycol diacrylate, propylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,4-butanediol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, polypropylene glycol diacrylate, polypropylene glycol dimethacrylate, 1,1,1-trimethylolpropane triacrylate, 1,1,1-trimethylolpropanetrimethacrylate, bisphenol A diglycidyl ether diacrylate, bisphenol A diglycidyl ether dimethacrylate, allyl acrylate, allyl methacrylate, divinylcyclohexane, and divinylbenzene.
8. The composition according to claim 1 , wherein the nitrogen-containing base is 2-phenylimidazole, 2-isopropylimidazole, 2-dodecylimidazole, 2-heptadecylimidazole, 2-ethyl imidazole, or 2-ethyl-4-methylimidazole.
9. The composition according to claim 1 , wherein the filler combination (d) comprises graphite powder with an average particle diameter of from 0.1 to 500 μm.
10. The composition according to claim 9 , wherein the filler combination (d) comprises graphite powder with an average particle diameter of from 1 to 300 μm.
11. The composition according to claim 10 , wherein the filler combination (d) comprises graphite powder with an average particle diameter of from 10 to 250 μm.
12. The composition according to claim 11 , wherein the filler combination (d) comprises graphite powder with an average particle diameter of from 50 to 100 μm.
13. The composition according to claim 1 , wherein the filler combination (d) comprises graphite powder in the form of synthetic graphite.
14. The composition according to claim 1 , wherein component (b) is provided at from 20 to 75 parts by weight, based on 100 parts by weight of component (a).
15. The composition according to claim 1 , wherein component (c) is provided at from 0.1 to 25 parts by weight, based on 100 parts by weight of component (a).
16. The composition according to claim 1 , wherein component (d) is provided at from 50 to 90% by weight, based on the entire composition of components (a)+(b)+(c)+(d).
17. The composition according to claim 16 , wherein component (d) is provided at from 70 to 85% by weight, based on the entire composition of components (a)+(b)+(c)+(d).
18. The composition according to claim 1 , further comprising an organosilane.
19. The composition according to claim 18 , wherein the organosilane is provided at from 0.05 to 1 parts by weight, based on the entire composition.
20. The composition according to claim 19 , wherein the organosilane is provided at from 0.1 to 0.5 parts by weight, based on the entire composition.
21. An electrically conductive material produced by hardening a composition according to claim 1 .
22. A process for the production of bipolar plates comprising applying the technique of injection molding, transfer molding or compression molding to form a bipolar plate from the composition of claim 1 .