Use as a rheology agent in a filled plastic paste of a dryground calcium carbonate with a copolymer of (meth)acrylic acid with an alkoxy or hydroxy polyalkyleneglycol group

A method for reducing the viscosity of a paste consisting of a thermoplastic or thermosetting resin and calcium carbonate, wherein said carbonate is dry-ground in the presence of a copolymer grinding aid agent comprising:

• a) at least one anionic monomer chosen from acrylic acid, methacrylic acid and their blends,
• b) and of at least one non-ionic monomer, of formula (I):
• where:
• m, n, p and q are integers such that:
• m, n, p≦150, q≧1, and 5≦(m+n+p)q≦150,
• R1 represents hydrogen or the methyl or ethyl radical,
• R2 represents hydrogen or the methyl or ethyl radical,
• R represents a radical containing an unsaturated polymerisable function chosen from the group of vinylics, the group of acrylic, methacrylic, and maleic esters, the group of unsaturated urethanes selected from the group consisting of acrylurethane, methacrylurethane, α-α′ dimethyl-isopropenyl-benzylurethane, and allylurethane, the group of allylic or vinylic ethers, whether or not substituted, the group of ethylenically unsaturated amides or imides, and the group consisting of acrylamide and methacrylamide, and
• R′ represents hydrogen or a hydrocarbonated radical with 1 to 40 carbon atoms,
• or a blend of several monomers of formula (I),
• c) and optionally at least one other monomer chosen from (meth)acrylic anhydride and (meth)acrylamide, the esters chosen from the acrylates and methacrylates with 1 to 20 carbon atoms in their ester radical, and the hydroxylated methacrylates selected from the hydroxyethyl and hydroxypropyl methacrylates, the aromatic vinylic monomers chosen from styrene, α-methylstyrene, and styrene sulfonate, and acrylamido-2-methyl-2-propane-sulfonic acid, the organophosphate monomers chosen from the acrylate and methacrylate phosphates of ethylene glycol, and the acrylate and methacrylate phosphates of oxyethylene and/or oxypropylene glycol, and their blends.