Preparation Of Zero-Voc Acrylic Emulsion And Its Wood Coatings Properties

Zero-VOC coatings are in which the content of VOCs is low or even tends to zero. Residual monomers, coalescent and pH regulator are major sources of VOC in water-based wood coatings. Optimized polymerization must be used to eliminate the residual monomers; Zero-VOC functional latex can be prepared with the method of core-shell polymerization, adding functional monomers or blending latex can settle the conflict between minimum film forming temperature and mechanical properties. Research of zero-VOC acrylic emulsion preparation and its wood coating properties has both theory and practical application values.Main results:1) Latex has a small particle size of below200.00nm, a large molecular of above8.00x105, a high conversion rate of above99.00wt%and a low gel fraction of below0.50wt%when the latex is prepared with the method of semi-continuous pre-emulsification polymerizations, with the temperature of between80.00℃and85.00℃, with the stirring speed of300rpm, with the concentration of initiator of APS of0.60wt%to total monomers, and with the concentration of complex emulsifier of6.00wt%to total monomers.2) The polymers in the core have different designed Tg temperature (45.00℃) with those in the shell(65.00℃). Results showed that the emulsion with core-shell structure has a low film forming temperature of5.00℃, a high pencil hardness of3H, an excellent adhesion of level0and a elongation of above500.00%when the weigh ratio of core and shell latex is40:60. Cross-linking monomer can make properties of latex improved in a certain extent. However, when the amount of HPA exceeds2.00wt%to the total monomers, or the amount of GMA exceeds2.00wt%to the total monomers, or the amount of HEMA exceeds10.00wt%to the total monomers, the emulsion will become unstable and precipitation occurs.3) Latexes of P (MMA/BA/AA) with a higher Tg (about40.00℃) and P (2-EHA/BMA/AA) with a lower Tg (about-40.00℃) were mixed physically to obtain the best properties. The results showed that blending latex has a low film forming temperature of5.00℃, a good gloss, a high pencil hardness of3H, an excellent adhesion of level0, a strong impact resistance above50.00kg-cm and a wonderful flexibility of1.00mm when the weigh ratio of P(MMA/BA) latex and P(2-EHA/BMA) latex is30:70. Latex prepared meets the application requirements of water-based coatings.4) The study of amplified polymerization using self-designed polymerization installations showed that properties of latex have good reproducibility, and the latex can be easily industrialized.5) Film formed by perpared latex using a small amount of additives has good gloss. Costs of production can be saved with good properties maintained if titanium dioxide is partially substituted by calcium sulfate whisker.