Process for the production of record material

A process for the production of record material carrying a colour developer composition incorporating a hydrated silica/hydrated alumina composite in which hydrated silica predominates, in which process the composite is precipitated from an aqueous medium containing a solution of a metal silicate and an aluminum salt, and a coating composition incorporating the precipitated composite is formulated and then applied to a substrate which is subsequently dried to produce said record material, the process comprising the steps of:

• (a) gradually adding a metal silicate solution to a solution of an aluminum slat which is initially at a pH below 4 until the pH of the resulting mixture is approximately 4, thereby to induce some precipitation and to form a sol;
• (b) gradually adding alkali to said sol to raise the pH to approximately 7,thereby to induce further precipitation and gel the sol or further gel the sol, said gelled sol being a hydrated silica/hydrated alumina composite;
• (c) separating the gel from the aqueous medium and washing the resulting product to remove dissolved salts;
• and
• (d) drying the washed product to an extent effective to collapse the structure of the gel and convert the gel structure form a hydrogen to a xerogel, and reducing it in particle size before formulation into the coating composition,
• with the proviso that if hydrated zirconia is also present in the precipitated composite, the zirconia content is less than about 10% on a dry basis, based on the total dry weight of alumina, silica and zirconia in the composite.