Preparation and property analysis of polyacrylate dispersant for calcium carbonate

Two types of dispersants for calcium carbonate were synthesized by condensation polymerization. One was the acrylic homopolymer (Dispersant-A), and the other was copolymer of acrylic acid with unsaturated esters (Dispersant-B). For the former, the optimal synthesizing parameters were determined: ammonium persulfate of 4.0% as the initiator; isopropanol/water of 1.25 as the chain-transfer, and sodium hydroxide as the neutralization agent. For the latter, the proper weight ratio of unsaturated ester/acrylic acid was found to be 1:4. Comparison was made between the dispersants and the popular products such as Acumer9400 synthesized in US, SP40M produced in Taipei, and SN5040 from Japan. Dispersion experiments for 3000-mesh calcium carbonate showed that Dispersant-B had the highest dispersing capability of the four dispersants. The dispersing capability of Dispersant-A was close to that of Acumer9400, but higher than that of SP40M at the dosage range of 1.2–2.0‰. Dispersant-B and SN5040 were the suitable dispersants for the dispersion of nanometer calcium carbonate. The grinding experiment of 325-mesh calcium carbonate revealed a logarithmic relation between the weight percentage of fine particles and the cumulative specific energy input. Moreover, a power-low function was well established between the median size and the cumulative specific energy input.