Study On Polymeric Dispersants For Water-based Super-fine Pigment Dispersions

Copolymer of methyl methacrylate and maleic anhydride (MM) was prepared by free radical solution polymerization methods. The structure of copolymer was characterized by techniques of Fourier-Transform Infrared spectroscopy and 1H Nuclear Magnetic Resonance spectroscopy and Gel Permeation Chromatography. The application was studied by techniques of spectrophotometry and particle sizer and zeta meter and Scanning Electron Microscope (SEM).The experimental results showed that the water soluble polymeric dispersant was a partly hydrolyzed MM and the Mol ratio of methyl methacrylate and maleic anhydride in the copolymer was 3:1. Mn was 45,103, and the polydispersity was 1.65.The polymer MMH was a good dispersant for super-fine organic pigment in water. It was found that the best dispersity was achieved when the maleic anhydride was 25 percent in the dispersant and the monomer ratio of maleic anhydride to methyl methacrylate was 1:1.5. The stability increased and then decreased as the dosage of the MMH increased. The dispersity of polymeric dispersant MMH and the traditional dispersants were compared in this paper. It was indicated that the polymeric dispersant had better dispersity than the traditional ones. The SEM of dispersions indicated that the polymeric dispersant made the pigment microparticles smaller and well-distributed. In the dispersion spacial steric hindrance played the effective role besides static repulsion. The polymeric dispersant contained two parts in its molecular structure. One part was solvatable chain, the maleic anhydride, which stretched in the water and formed an adsorption layer with adequate thickness on the pigment surface. Another part was anchoring group, poly(the methyl methacrylate), which could betightly absorbed on the surface of pigment, and this effectively prevented the reconglomeration of pigment particles.