on of a polymer means that particles of the polymer are suspended in the aqueous medium.The term aqueous for the purposes of the present invention means containing at least 60% by volume of water, preferably at least 80% by volume of water, and optionally containing water-miscible organic solvents such as alcohols e.g. methanol,ethanol, 2-propanol, butanol, iso-amyl alcohol, octanol, cetyl alcohol