The Synthesis And Properties Of Waterborne Coatings Polymer Dispersant

In this study, several kinds of acrylate polymer dispersants were synthesized by radical aqueous solution polymerization. Effect of initiator, chain transferer, temperature and time on products showed that different molecular weight and molecular weight distribution were obtained by means of changing all these factors. At 68℃, products with appropriate molecular weight were achieved when chain transferer which is low molecular alcohol and 2% percent initiator were used. Because of pollution and odour of mercaptoacetic, isopropyl alcohol was chose to initiate the reaction of chain transfer. About at 85℃, middle or low molecular weight acrylic acid/methyl acrylate copolymer was obtained when 4～12 percent initiator and water-low molecular alcohol co-boil system were used, even the solution of monomers and the aqueous solution of initiator were added at the same time.A series of pigment slurries with titanium were prepared though a high-speed mixer. Influences of dispersants on it were studied by rotational viscosity. The microscopic dispersation phase of pigment slurries were observed through a phase differential microscope. And the dispersation state was characterized by degree of dispersation.Polyacrylic acid was neutralized with NaOH, ethanolamine, 2-aminobutanol and diethanolamine respectively. Effects of different anti-ions on dispersivity indicated that the best dispersivity was gained when diethanolamine was used.Polyacrylic acid was neutralized by NaOH, effects of degree of neutralization on dispersivity were investigated which demonstrated that the deeper the degree of carboxyl neutralization, the better the dispersivity. The optimum dispersivity was achieved when pH values was about 9.Effects of monomer ratio and molecular weight of acrylic acid/methyl acrylate copolymers on pigment slurry were studied. Results showed that the dispersivity of pigment slurries improved with the increasing of the monomer ratio(acrylic acid/methyl-acrylate). The optimum dispersivity was achieved at the ratio of 5/1. Continual increasing of the ratio resulted in a stable dispersivity. The viscosity, microscopic dispersation phase, degree of dispersation and settling time were all excellent when the molecular weight of copolyner was 6200.Difference of dispersivity of homopolymer and copolymer was compared. Dispersivity of them were similar in middle or low solid content of pigment(≤50%), but the latter got better result than the former with the contincal incressing of solid content.Applied performances of dispersants were examined by confecting coatings, the results showed that the performance of synthetical dispersant has arrived at the same level of the foreign congeneric products.