Silicone Modified Acrylic Soap-free Waterborne Coatings Research

The properties of acrylate emulsion can be modified by organosilicon. However, the introduction of organosilicon into the emulsion system induces some difficulties in application, for example: the hydrolysis facility of reactive organosilicon with double bond bothers the emulsion polymerization; the use of hindering organosilicon in the emulsion polymerization causes the long solidification time of the coatings. These two problems can be resolved by soap-free emulsion polymerization, which has not been reported by others.The suitable reaction conditions were determined by studying the influences of monomer ratios, reaction temperature, the amount of initiator, reaction time and the way of monomer addition on the soap-free emulsion polymerization and the properties of the latex. It was found that with the continuous drop-wised monomer addition the soap-free emulsion polymerization can be effectively conducted by using methyl methacrylate(MMA) and butyl acrylate(BA)(monomer ratio: 1/1) as the main monomers, methyl acrylic acid(MAA) as the functional monomer, DNS-86 as the surface active monomer, K2S2Og as the initiator and by adopting the reaction temperature as 80 + 1 The mechanism of soap-free emulsion polymerization was also discussed in this article.There are two methods that can be used for the modification of acrylate soap-free emulsion by organosilicon. One is the addition of epoxysilicone as the crosslinker and the other is the addition of hindering organosilicon that can be copolymerized directly in the soap-free emulsion polymerization. The introduction of functional monomer MMA as a comonomer into the soap-free emulsion polymerization makes the modification by the reaction between carboxyl group of MMA and epoxy group of epoxysilicone. The epoxysilicone improves the Ca2+ stability of the emulsion and the hardness , gloss, water-repellency of the film. The Ca2+ stability of the emulsion and the gloss of the film decrease while the hardness and the water-repellency of the film increase with the increment of epoxysilicone. The influences of it on the particle size and the viscosity of the latex were also studied and the mechanism of polymerization was also proposed in this article. On theother hand, the soap-free emulsion polymerization can be carried out by the copolymerization of hindering organosilicon and acrylates, which produced a good soap-free emulsion. The latex thus obtained has a suitable solidification time (about 1 hour), which means that it is good for the outdoor-application. The two organosilicon adopted in our experiments both greatly enhanced the general properties of the acrylate emulsion.