Process for the production of precipitated silica

US5484581A · kind A · utility

Assignee

• Degussa AG · DE

Inventors

• Heinz Esch · Wesseling, DE
• Robert Kuhlmann · Lechenich, DE
• Mattias Neumueller · Hasselroth, DE
• Karin Otto · Bonn, DE
• Ralf Rausch · Alzenau, DE

Key dates

• Filing date: Aug 4, 1994
• Grant date: Jan 16, 1996
• Expiry date: Aug 4, 2014

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C01P2006/22
• WIPO field: Pharmaceuticals
• WIPO sector: Chemistry

Abstract

Precipitated silica which has a BET surface area of 10-130 m.sup.2 /g, a CTAB surface area of 10-70 m.sup.2 /g , an average particle diameter of 5-20 .mu.m, a Cu abrasion value in a 10% glycerol dispersion of 4-50 mg and thickening behavior in a CMC solution (20% dispersion) of 300-3500 mPa.multidot.s, is produced by simultaneously adding alkali silicate (weight modulus SiO.sub.2 :alkali oxide=2.5-3.9:1) and a mineral acid to an initial amount of water which has been adjusted to a pH value of 7.0 to 9.9 or 10.0 to 10.7 by the addition of water glass, holding the pH value constant between 7.0 and 9.9 or 10.0 to 10.7 during addition, wherein the initial precipitation temperature is 50.degree.-90.degree. C. and an increase in viscosity occurs after at most 25% of the duration of precipitation, adjusting the pH value to .ltoreq.6, preferably 3.5, once a silica content of greater than 120 g/l or greater than 150 g/l, preferably .gtoreq.160 g/l to 240 g/l, has been reached, separating the solid by filtration, washing, drying and grinding it. The precipitated silica may be used as an abrasive and/or thickening component in toothpastes.