Preparation of amorphous, precipitated silica and siliceous filler-reinforced microporous polymeric separator
Patent 4681750 Issued on July 21, 1987. Estimated Expiration Date: 
April 18, 2006. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
April 18, 2006. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 2302832 2940830 3351495 3696061 Battery separator Novel precipitated siliceous products and methods for their use and production Flexible, microporous rubber base articles Process of manufacturing a microporous sheet material Microporous film, particularly battery separator, and method of making Patent #: 4335193 InventorsAssigneeApplicationNo. 06/853506 filed on 04/18/1986US Classes:423/339, By precipitating106/287.34, Silicon dioxide containing429/252, Silicon containing429/254, Rubber or thermoplastic resin521/64Removing a liquid to form a cellular productExaminersPrimary: Skapars, AnthonyAttorney, Agent or FirmInternational ClassesC01B 33/193 (20060101)C01B 33/00 (20060101) H01M 2/16 (20060101) AbstractPrecipitated 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.Other References
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