ELEKTROLYTISCHE BZW. ELEKTROLYSEZELLEN MIT SEPARATOR BZW. TRENNWAND

1451892 Coated electrode D E F E N C E SECRETARY OF STATE FOR 19 Sept 1973 [25 Sept 1972] 44137/72 Heading B2E [Also in Division H1] A separator positioned between a positive electrode and a negative in an electrolytic cell comprises a moulding of particulate polymer material comprising particles having a nucleus of thermoplastic polymer material surrounded by a cross-linked polymer layer and an outer polar graft-copolymer layer. Preferably at least 30% of the particles have a diameter less than 100. The thermoplastics material forming the nucleus of the particles may also form the base polymer of the outer graft-copolymer layer and when cross-linked a cross-linked polymer layer. Preferably the thermoplastics material is selected from polyethylene, polypropylene, polytetrafluoroethylene, partially fluorinated polyolefins, partially chlorinated polyolefins or nylons. The comonomer of the outer graft-copolymer layer is preferably selected from acrylic acid, methacrylic acid, acrylamides or methacrylamides. The moulding form the separator may be produced by depositing the moulding on the surface of one of the electrodes by sintering the particulate polymer material into a coherent coating around the electrode using heat and/or pressure. Alternatively the particulate polymer material may be moulded into a case, envelope, sheet or film which is used to wrap around or encase one of the electrodes. The particulate polymer may be prepared by graftpolymerisation of a particulate thermoplastic polymer in a solution of a reactive monomer. In a typical example the particulate polymer is prepared by graft-polymerisation of polyethylene powder in an aqueous solution of acrylic acid. The grafted powder is then placed in a metal template on both sides of a silver electrode, the assembly placed between two sheets of photographic glazing plate and pressed in an electrically heated, hydraulic press. The electrolytic cell may be a battery, fuel cell, cell used for the production of metals and compounds by electrochemical separation methods.