Preparation of Al(OH)3/Acrylic Copolymer Latex by Emulsion Polymerization

The Al(OH)₃/acrylic copolymer latexes were synthesized through the emulsion polymerization of acrylic monomers, butyl acrylate and 2-ethylhexyl acrylate in the presence of surface-functionalized Al(OH)₃ filler particles. The polymerization was stabilized by polyoxyethylene (50) nonyl phenyl ether (NP-1050, nonionic surfactant) and ammonium (POE) alkyl aryl ether sulfate (EU-S133D, anionic surfactant) to produce stable composite latexes. The improved compatibility of Al(OH)₃ surface with acrylic monomers was achieved by the modification with 3-(trimethoxysilyl) propyl methacrylate (γ-MPS). Transmission electron microscopy showed that nano-sized Al(OH)₃ particles were slightly agglomerated in the copolymer latex. When pristine Al(OH)₃ was used as a filler or γ-MPS-modified Al(OH)₃ particles were added above 30 wt% with respect to monomers, unstable latexes were obtained, which were partially precipitated out on standing for prolonged time. The flame retardation effect was not apparent with the incorporation of Al(OH)₃ in the latexes by 30 wt% as shown by LOI test.