Laporte Industries Limited

Hubert Harold Chambers

Brian John Tear

Inorganic oxides pigments, coated with alumina are treated with water soluble hydroxy acids or salts for example sodium citrate, and with water soluble di- or polyhydric alcohols, for example pentaerythritol, or with a water soluble reaction product of excess di- or polybasic organic hydroxy acids with di- or polyhydric alcohol. Titanium dioxide pigment so treated may be used in both emulsion paint and in organic based paint systems.

Method of treating inorganic oxide pigments

A high solids metal oxides coated titanium dioxide aqueous slurry requires a negative charge and a high pH for use in aqueous paint media. A hot ageing of the coated titanium dioxide can alter the isoelectric point of the slurry and make practicable the avoidance of mixtures of metal oxide coating agents which give rise to processing difficulties and the use of mixtures of metal oxides which would not without the hot ageing step give suitable charge and pH characteristics. An example of a suitable mixture of metal oxide coating agents is a 1:1 molar Al.sub.2 O.sub.3 : TiO.sub.2 mixture. An example of hot ageing conditions is the use of a temperature of 98.degree. C - 100.degree. C for 1 hour while avoiding loss of water and under alkaline conditions.

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Waltham, United Kingdom

Hubert Harold Chambers