Patent ID: 7615587

Claim:
A process for grinding an aqueous suspension of a mineral filler comprising: 1) preparing a mixture comprising an aqueous suspension of mineral filler, a grinding aid agent and a grinding substance; 2) grinding the mixture; and 3) concentrating the ground aqueous suspension of a mineral filler and a grinding aid agent after grinding; wherein a per cent dry weight of the mineral filler and grinding aid agent is less than 71% in the aqueous suspension before concentrating; and said grinding aid agent is introduced into the aqueous suspension at the rate of 0.3% to 1% by dry weight with respect to the dry weight of mineral material, the grinding aid agent comprises homopolymers and/or copolymers of acrylic acid and/or methacrylic acid with one or more acrylic, vinyl or allyl monomers neutralised so that the molar percentage of neutralisation of the active acid sites of the polymer by means of a neutralisation agent containing a calcium ion is between 15% and 40% with a molar percentage of neutralisation of the active acid sites by means of one or more monofunctional neutralisation agents of between 7% and 70%, a molar percentage of neutralisation of the active acid sites of the polymer by means of a neutralisation agent containing magnesium, barium, zinc or aluminum ion, or a difunctional amine, or mixtures thereof, of between 0% and 30%, and a molar percentage of non-neutralised active acid sites of between 15% and 78%, and a weight average molecular weight of the homopolymers and/or copolymers of acrylic acid and/or methacrylic acid with one or more acrylic, vinyl or allyl monomers is between 5000 and 25,000.