METHOD OF MAKING THE POWDER MATERIAL IMPREGNATED AGAINST THE HUMIDITY,DETERMINATED FOR PRODUCTION OF ELECTRODES BY THE DIFFUSING GAS

摘要

1392341 Wetproofed carbon powder ZLEHIT PRI BAN 16 March 1972 [29 March 1971] 12445/72 Heading C1A [Also in Divisions D1 and H1] A method for producing powdered wetproofed materials, suitable for the production of gas diffusion electrodes, comprises mixing a "micropore-free" electroconductive powder, directly or as an aqueous suspension, with a wetproofing agent in the form of an aqueous dispersion or a solution in an organic solvent. "Micropore-free" means particles which are not thoroughly transpierced by the micropores. The mixing process proceeds at normal or elevated temperature, and after homogenization has been achieved the disperse medium is discarded and the solid phase (wetproofed material) dried. When using an aqueous dispersion of the wetproofing agent the dispersion stabilizers are removed, e.g. by heating at 250-350‹ C. for 30 to 90 min. or by washing and subsequently heating at 100-140‹ C., and the material is ground anew. The electroconductive powder is preferably carbon black and may comprise 3-5% by weight of the suspension. The wetproofing agent is a substance having a contact angle greater than 90 degrees and may comprise one or more hydrophobic polymers, e.g. polytetrafluoroethylene, polyethylene (high pressure), polyisobutylene, polypropylene, natural rubber or synthetic (butadiene-styrene) rubber. The polymer may be present in an amount of 10-60% by weight of the dispersion or solution. When using solu ions of the wetproofing agents the electroconductive powder may be introduced at the boiling temperature of the solvent. The powdered wetproofed materials may be made into gas diffusion electrodes using various catalysts, e.g. activated carbon.