Unilever Patent Holdings B.v.

Joseph Crosfield & Sons, Ltd.

James P Quinn

Derek Aldcroft

John R Newton

Peter W Stanier

Donald Barby

Anthony Leonard Lovell

Peter W Stainier

An amorphous silica, especially precipitated silica, suitable for use in toothpastes, has a high abrasivity represented by a perspex abrasion value in the range from about 23 to about 35.

Amorphous silica

A precipitated silica, suitable for use in toothpastes, has a high absorbency, i.e. 110 to 180 cm.sup.3 100 g, and good abrasivity with a plastics abrasion value of 12 to 20. The silica provides abrasion even at a relatively low particle size.

Precipitated silicas

Silicas

A multistage precipitation and flocculation production process is disclosed in which primary silica particles are prepared and flocculated useing an alkali metal salt solution and further silica precipitated in the presence of the salt, the pH of the mixture reduced and the silica isolated, purified carefully dried and optionally milled.

Process for the preparation of precipitated silicas having morphology

This invention discloses a new form of wet precipitated silica which is characterised in terms of energy required to breakdown particles and a defined thickening effect. A multistage precipitation and flocculation production process is also disclosed in which primary silica particles are prepared and flocculated using an alkali metal salt solution and further silica precipitated in the presence of the salt, the pH of the mixture reduced and the silica isolated, purified carefully dried and optionally milled.

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Birkenhead, United Kingdom

James P Quinn