Patent GB-1110221-A (GB)
Title: Improvements in or relating to separators for storage batteries
Inventor: SILVESTRI NATHAN JOHN
IPC: H01M50/463
Filed: 1965-04-09
Abstract: Compositions for making cellular ribs for battery separators comprise a first thermoplastic resin having a specific viscosity of at least 0.5 and a second thermoplastic resin having a plasticizer tolerance of at least 6 and a specific viscosity of 0.3 to 0.4.  Examples of the first thermoplastic resins are polymers and copolymers of vinyl chloride, e.g. vinyl chloride-acetate copolymer, and the second thermoplastic resin may be polyvinyl chloride, polyvinyl acetate, polyvinyl butyrate, vinyl choride-acetate copolymers. Examples of plasticizers are given. Blowing agents may be incorporated as well as fillers, pigments, stabilizers, blowing agent catalysts, examples of which are given.  In Example 1 the composition comprises 95 parts polyvinyl chloride (specific viscosity 0.500), 5 parts polyvinyl chloride (specific viscosity 0.37), 2.5 parts azodicarbonamide, 35 parts clay, 3 parts sodium silicate sulphate, 1.5 parts zinc octonoate, 100 parts dioctyl phthalate.ALSO:A separator for separating plates of a liquid-containing storage battery comprises a panel having affixed to at least one side thereof a plurality of resilient cellular ribs in which the ribs are formed from a composition including a first thermoplastic resin having a specific viscosity of at least 0.5 and a second thermoplastic resin having a plasticizer tolerance of at least 6 and a specific viscosity of 0.3 to 0.4; and a plasticizer.  The separator is formed by applying in strips to the panel a composition including the resins, and a blowing agent, and heating the strips to a temperature such that the composition is fluxed and the blowing agent decomposes to impart a cellular structure to the composition.  The panel may be any dimensionally-stable material which will not conduct electrically but will permit passage of electrolyte and is inert in the cell environment, such as a lead-acid cell, e.g. a cellulosic material impregnated with a thermosetting resin such as phenol-aldehyde resin, say phenol-formaldehyde, and cured. Examples of the first thermoplastic resins are polymers and copolymers of vinyl chloride e.g. copolymer of vinyl chloride and vinyl acetate.  Examples of the second thermoplastic resins are polyvinyl chloride, polyvinyl acetate, polyvinyl butyrate and copolymers of vinyl chloride and vinyl acetate.  The compositions include a plasticizer e.g. primary plasticizers such as dioctyl phthalate, diisooctyl phthalate, dodecyl phthalate, di(n-octyl, n-decyl) phthalate, acetyl tributyl citrate, dioctyl sebacate, dihexyl adipate, 2-ethylhexyl diphenyl phosphate, and tricresyl phosphate; secondary plasticizers such as petroleum residue p  products to supplement or replace part of the primary plasticizer. Blowing agents mentioned are azodicarbonomide, dinitrosopenta-methylene tetramine, diazoaminobenzene, p,p\sv-oxylis benzen sulfonyl hydrazide, sodium carbonate, ammonium carbonate and ammonium bicarbonate, the nitrogen-cooling compounds being preferred. Other additives which may be included in the resin compositions are fillers such as anhydrous calcium sulphate, talc, wood, flour, clay, diatomaceous earth and asbestos; stabilizers such as sodium silicate, sulphate, tetrasodium pyrosphasphate, tribasic lead silicate sulphate, calcium stearate, organo-tin complexes, epoxy resins and epoxidized oils; pigments such as carbon black, titanium dioxide and aluminium powder; dispersing agents such as zinc resinate, lecithin, glycol stearate, propylene glycol laurate and glycerol monooleate; blowing agent catalysts such as metal soaps, e.g. lead stearate, zinc stearate, zinc octonoate, and dibasic lead phosphate.  The resin composition may be extruded in a plurality of spaced strips, preferably parallel, on to say cellulosic web or paper impregnated with a phenol-formaldehyde resin, and partially cured by passing over a heated drum.  The assembly is then passed into a circulating air jet oven with an air temperature sufficient to flux the polymer rib composition and complete the arc of the phenol-formaldehyde resin e.g. 185 to 205 DEG C.