Preparation of silica sol
AssigneeNalco Chemical Company
InventorsRobert D. Jones, Curran M. Simpson
Life of this patent
Estimating the term…
Abstract
A method for producing a silica sol containing less than 200 ppm sodium having an average particle size of 2-110 nm, and a particle size distribution with a coefficient dispersion of 0.16-0.4. The silica sols are produced using a lower alkanolamine containing heal to which aliquots of silicic acid are added. The aliquots are added to maintain a substantially constant concentration of colloidal silica in the product. Subsequent to production, the sol may be concentrated by ultrafiltration. Preparation of low sodium silica sol utilizing a constant silica technique by heating the initial heel to 94.degree..+-.4.degree. C. and adding additional silica maintaining constant total silica. The stabilization is effected with an alkanolamine.
Claims7
A low sodium aqueous silica sol containing no more than 150 ppm of an alkali metal, and having a silica concentration of 5-55 weight % SiO.sub.2 ;
- said colloidal silica having a particle size greater than 2 nm;
- produced by a method comprising the steps of:
- A. providing a 0.1%-5% aqueous solution of a lower alkanol amine;
- B. heating the aqueous solution of the lower alkanol amine to at least 80.degree. C., but less than reflux temperatures;
- C. adding to the heated aqueous solution of the lower alkanol amine a 2 to 10% by weight aqueous solution of silicic acid in a volume ratio of from 2:1 to 15:1, the mole ratio of SiO.sub.2 to lower alkanol amine being in the range of 1:1 to 150:1;
- and
- D. concentrating the dilute aqueous sol by either distillation or ultrafiltration so as to recover an aqueous colloidal silica sol which contains 5-55% by weight SiO.sub.2 having pH of 8-10.5 and containing less than 150 ppm alkali metal.
A low sodium aqueous silica sol containing no more than 130 ppm of an alkali metal, and having a silica concentration of 5-55 weight % SiO.sub.2 ;
- said colloidal silica having a particle size greater than 2 nm;
- produced by a method comprising the steps of:
- A. providing a 0.1%-5% aqueous solution of a lower alkanol amine;
- B. heating the aqueous solution of the lower alkanol amine to at least 80.degree. C., but less than reflux temperatures;
- C. adding to the heated aqueous solution of the lower alkanol amine a 2 to 10% by weight aqueous solution of silicic acid in a volume ratio of from 2:1 to 15:1, the mole ratio of SiO.sub.2 to lower alkanol amine being in the range of 1:1 to 150:1;
- and
- D. concentrating the dilute aqueous sol by either distillation or ultrafiltration so as to recover an aqueous colloidal slica sol which contains 5-55% by weight SiO.sub.2 having pH of 8-10.5 and containing less than 130/ppm alkali metal.
Dependencies are inferred from the claim text.