This invention relates to galvanic battery cells and more particularly to sealants applied to such cells in their manufacture to prevent the escape of electrolyte from the cells.
The problem of electrolyte leakage from battery cells is well known. In attempts to overcome this problem, various mechanical solutions have been proposed such as seal rings and gaskets (e.g. U.S. Pat. No. 3,068,312, issued to Daley et al shows a seal ring and U.S. Pat. No. 3,068,313, also issued to Daley et al shows a seal gasket).
Typically, such seal rings have been coated with a dielectric material. As those skilled in the art are aware, the coating should be soft enough to deform so as to fill the imperfections or gaps between the cell container and the sealing ring or gasket, thereby shutting off all significant leakage of electrolyte.
Prior to the present invention, a common battery sealant consisted of a mixture of three parts (by volume) of naphtha solvent and one part (by volume) of Pioneer asphalt paint. Such a sealant has been commercially marketed by the Pioneer Division of the Witco Chemical Company of Perth Amboy, New Jersey. The Pioneer asphalt paint has been marketed under the name Pioneer 609 paint and is in accordance with Federal Specification MIL-C-450B Type II; TT-C-494 Type II.
The naphtha in the sealant provided by Pioneer meets the specifications of Federal Specification TT-N-95B Type I.
Although the Pioneer 609/naphtha solution has functioned adequately in battery cells to prevent the leakage of electrolyte, its application has involved problems because of the flammability of the solution.
It is therefore an object of this invention to provide a battery cell sealant which prevents electrolyte leakage but which is less flammable than sealants containing naphtha.
It is a further object of this invention to provide a battery sealant of low flammability which has unexpectedly improved sealing characteristics.