Preparation, Mechanism And Application Of Zinc Ion Self-crosslinkable Styrene Acrylate Latex At Ambient Temperature

The metal ion self-cross-linkable latex is cured by the cross-linking reaction betweenmetal ions and pendant acid, with the advantages of convenient construction, stabilizedstorage, one-component packaging, environmentally friendly. Meanwhile, it can be used toprepare a high performance water-based wood primer due to the faster drying rate, which canimprove the sandability and the speed of the hardness establishment of the film.The zinc ion self-cross-linkable poly-acrylate latexes were synthesized by seededsemi-continuous emulsion polymerization with zinc oxide (ZnO) as cross-linker. Theexperimental results showed that the film owned a good basic hardness when the Tg ofpolymer was40°C. Zn2+-PAs could be prepared with appropriate viscosity and particle size,and stabilized storage when the amount of the seed monomer was7%, the DowFax2A-1asemulsifier was2%; the KPS as initiator was0.5%, and with the post-adding redox initiator.The influences of ZnO and methacrylic acid (MAA) mass content and adding method onthe degree of cross-linking, and the properties of self-cross-linkable latex were discussed. Theexperimental results showed that in a certain range, the average particle size decreases withthe increasing content of MAA, while the latex stability was improved obviously. Theoptimum mass content of MAA is12%of the total monomers. The optimum amount of ZnOadded was25%(mole fraction) of MAA, and the optimum temperature to introduce ZnO was60°C.Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimeter (DSC),transmission electron microscopy (TEM) and thermal gravimetric analysis (TGA) were usedto determine the structure and properties of PAs. TEM analyses showed that the latex particleswere coarse spherical particles with surface enriching comprising abundant carboxyl groups,and zinc ions were dissociated as zinc ammine complex in the aqueous phase. FT-IR analysesconfirmed that the chelate cross-linking occured between zinc ions and carboxylic acid duringthe film-forming process. The DSC results indicated that the glass transition temperature (Tg)of PAs increased as a function of the formation of the coordinate structure, and the resultedfilm exhibited excellent initial hardness and sandability. TGA analyses demonstrated that theintroduction of ZnO evidently enhances the thermal stability of self-cross-linkable PAs.Finally, a high performance water-based wood primer based on the resulted PAs wasdeveloped, with the advantages of high solid content, high degree of transparency, and fastdrying rate. In the formula design process, two contradictions, namely the contradictionbetween the high solid content and high transparency, the high Tg and low film formation temperature had been solved. Ultimately, the primer had a higher solid content and good filmtransparency when the amount of emulsion was75%and talc was10%. EB and DPnB ascoalescent were added to ensure a good film forming at low temperature and recoating, whosecontents were18%and20%of solid content of emulsion respectively. The TEGO Foamex810and TEGO Airex902W as defoamers were added to eliminate bubbles obviously at the stageof grinding and paint mixing respectively. Association polyurethane thickener RM-8W andRM-2020were used together with an appropriate amount of alkali swelling type thickenerASE-60, which could prevent the sinking of filler and improve the storage stabilityeffectively.