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Preparation of amorphous, precipitated silica and siliceous filler-reinforced microporous polymeric separator

  • US 4,681,750 A
  • Filed: 04/18/1986
  • Issued: 07/21/1987
  • Est. Priority Date: 07/29/1985
  • Status: Expired due to Term
First Claim
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1. In a siliceous filler-reinforced microporous polymeric battery separator, the improvement wherein the siliceous filler comprises amorphous, precipitated silica prepared by the sequential steps of:

  • (a) establishing an agitated aqueous solution of alkali metal silicate having (1) an initial alkali metal oxide concentration of from about 2.1 to 2.6 grams per liter and a temperature of from about 179°

    F. to 186°

    F., or (2) an initial alkali metal oxide concentration of from about 5.6 to 7.2 grams per liter and a temperature of between about 190°

    F. and about 198°

    F.,(b) adding slowly to the said aqueous solution further alkali metal silicate in amounts of (1) from about 14.5 to about 19 times, or (2) from about 2 to about 5 times, basis the aforesaid respective initial alkali metal oxide concentration, the amount of alkali metal silicate initially present in the aqueous solution while simultaneously adding acidifying agent to the said aqueous solution in amounts sufficient to maintain the alkali metal oxide concentration in the aqueous solution at substantially its initial level, thereby to form an aqueous slurry of precipitated silica,(c) adding additional acidifying agent to the slurry of step (b) until the pH thereof is from about 8 to about 9,(d) ageing the slurry of step (c) at (1) between about 176°

    F. and 186°

    F., or (2) between about 188°

    F. and 198°

    F., basis the aforesaid respective initial temperatures of the initial aqueous alkali metal silicate solution, for from about 15 to 90 minutes, and thereafter(e) adding additional acidifying agent to the slurry of step (d) in amounts such that the final solid silica product has an essentially neutral pH.

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