The invention relates to a process for producing aqueous silica-based sols
which comprises providing a cationic ion exchange resin having at least
part of its ion exchange capacity in hydrogen form; bringing said ion
exchange resin in contact with an aqueous alkali metal silicate to form
an aqueous slurry; adjusting the pH of the aqueous slurry and separating
the ion exchange resin from the aqueous slurry, as well as the
silica-based sols obtained by the process.The invention also relates to
silica-based sols obtained by the process, as well as a process for
producing paper which comprises providing an aqueous suspension
comprising cellulosic fibres; adding to the suspension one or more
drainage and retention aids comprising a silica-based sol according to
the invention; and dewatering the obtained suspension to provide a sheet
or web of paper.