초록 ▼

Precipitated amorphous silica useful for manufacturing microporous battery separators is prepared by establishing an aqueous solution of alkali metal silicate having an alkali metal oxide concentration of (a) from 2.1-2.6 grams per liter and a temperature of from about 179°F. to 186°F., or (b) from

Precipitated amorphous silica useful for manufacturing microporous battery separators is prepared by establishing an aqueous solution of alkali metal silicate having an alkali metal oxide concentration of (a) from 2.1-2.6 grams per liter and a temperature of from about 179°F. to 186°F., or (b) from 5.6 to 7.2 grams per liter and a temperature of from 190°to 198°F.; adding from (a) 14.5 to 19 times or (b) 2 to 5 times respectively the amount of alkali metal silicate initially present in the initial aqueous solution simultaneously with acidifying agent, e.g., sulfuric acid, to the initial aqueous solution while maintaining the initial alkali metal oxide concentration therein substantially constant; reducing the pH of the resulting slurry to from 8 to 9; ageing the slurry at precipitation temperatures for from 15 to 90 minutes; reducing the pH of the aged slurry to from 3.8 to 4.7 and then recovering, e.g., separating, the silica from its entraining slurry, washing the recovered silica, and drying the washed precipitated silica. Optionally, the recovered and dried silica is milled after drying to produce a product having a median agglomerate particle size of from 6 to 15 micrometers.

대표청구항 ▼

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 met

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.