Controllable filler prefloculation using a dual polymer system

A method of preparing a stable dispersion of flocculated filler particles having a specific particle size distribution for use in papermaking processes comprising:

• a) providing an aqueous dispersion of filler particles;
• b) adding a first flocculating agent to the dispersion in an amount sufficient to mix uniformly in the dispersion without causing significant flocculation of the filler particles, the first flocculating agent being a flocculant;
• c) adding a second flocculating agent to the dispersion after adding the first flocculating agent, in an amount sufficient to initiate flocculation of the filler particles in the presence of the first flocculating agent, the second flocculating agent being of opposite charge to the first flocculating agent;
• and
• d) optionally, shearing the flocculated dispersion to provide a dispersion of filler flocs having the desired particle size.