Patent ID: 8778140

Claim:
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, and the first flocculating agent being amphoteric and has a net charge; c) adding a microparticle to the dispersion in an amount insufficient cause significant flocculation of the filler particles before, simultaneous to, and/or after adding the first flocculating agent, and prior to adding a second flocculating agent; d) adding the second flocculating agent to the dispersion in an amount sufficient to initiate flocculation of the filler particles in the presence of the first flocculating agent wherein the second flocculating agent has opposite charge to the net charge of the first amphoteric flocculating agent; e) shearing the flocculated dispersion to provide a dispersion of filler flocs having the desired particle size; and f) flocculating the filler particles prior to adding them to a paper stock and wherein no paper stock is present during the flocculation; wherein the filler is anionically dispersed and a low molecular weight, cationic coagulant is added to the dispersion to at least partially neutralize its anionic charge prior to the addition of the first flocculating agent or microparticle.