Silica-Embedded Polyurea Microspheres with Rough Surface for Matte Leather Finishing

Abstract

A type of polyurea microspheres with rough surfaces and different sizes (1-12 μm), which was used for waterborne polyurethane matte leather coating, were prepared by precipitation polymerization in H 2 O/acetonitrile system, using isophorone diisocyanate as polymerized monomer, 2,4-diaminobenzenesulfonic acid sodium salt as hydrophilic monomer and nano-SiO 2 as surface roughener. The effect of the loading of isophorone diisocyanate and 2,4-diaminobenzenesulfonic acid sodium salt, the volume ratio of H 2 O/acetonitrile and the addition stage of nano-SiO 2 on the particle size and surface roughness were investigated so as to achieve the excellent matte effect of the coating. The results indicated that the adding of hydrophilic monomer can reduce the particle size of microspheres and improve its re-dispersibility in water, while the increase of the proportion of acetonitrile in the mixed solvent and the loading of polymerized monomer can enlarge the size of the polyurea microspheres. As surface roughener, with the increase of nano-SiO 2 loading, the surface roughness and the particle size of microspheres increase. When nano-SiO 2 is added at the stage of the reaction system getting turbid, the maximum surface roughness of polyurea microspheres can be achieved. Polyurea microspheres with particle size (1-2 μm) and high surface roughness have better matting effect, and the gloss of the prepared waterborne polyurethane coating can be adjusted to less than 1.6° (60°-incident Angle).