| Latex prepared by soap-free emulsion polymerization of styrene (ST)/butyl acrylate (BA)/acrylic acid (AA), styrene (ST)/butyl acrylate (BA)/allyloxy alcohol polyoxyethylene ether sulfate (SR-10) and styrene (ST)/butyl acrylate (BA)/allyloxy alcohol ethoxylates (ER-10) were explored. Effects of process parameters on the stability of polymerization were discussed. Latex particle size and morphology, surface energy as well as the properties of latex film of soap-free styrene-acrylate latex prepared by different reactive surfactants were studied.Influence of the dosage of acrylic monomers and initiator, neutralization degree on the latex stability, monomer conversion, particle size and distribution as well as mechanism of nucleation were investigated in ternary polymerization of ST/BA/AA system. The results show that stable soap-free acrylic emulsion are obtained when the amount of acrylic in the total monomers mass is 10%, pH=5.6. In addition, the monomer conversation rate is increased with the increase of acrylic monomer and initiator dosage while the neutralization degree is a constant value. The major nucleation mode is homogeneous nucleation. The monodisperse coefficient of latex particles is less than 1.03.The effects of anion and the nonionic surfactants on styrene-acrylate emulsion were studied comparatively. Our results suggest that anionic surfactants (SR-10) have high emulsification and good copolymerization with styrene and acrylate. Furthermore, stable soap-free emulsion prepared by SR-10 can be obtained by different process. Latex particle size decreased with increasing the amount of SR-10. Water resistance of latex film was determined by the dosage of SR-10 as well as reaction activity between SR-10 and co-monomer. The best water resistance of latex film, the highest conversion rate and the lowest coagulation rate is obtained when the amount of SR-10 in monomer is 2%. However, nonionic surfactants (ER-10) have poor emulsification in styrene-acrylate emulsion. Because the reactive surfactants concentration in the water is far more than its critical micelle concentration (200mg/L) at the beginning of polymerization. With the polymerization time increasing, ER-10 undergo copolymerization with ST/BA, while homopolymerization itself occurred at the same time, which generating water-soluble homopolymers or copolymers. As a result, conglomeration of latex particle is easily occurred in the polymerization, getting a stable soap-free styrene acrylic emulsion is difficult. |
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