Preparation And Properties Of High Solid Content Aqueous Acrylic Polyol Dispersions

Two-component waterborne polyurethane(2K-WPU)has been a hotspot in the world coating industry due to its eco-friendly performance and excellent coating properties.The2K-WPU is composed of waterborne polyol and water-dispersible polyisocyanate.As one of waterborne polyols,the aqueous acrylic polyol dispersion has become more and more important for 2K-WPU due to its small particle size,uniform distribution of hydroxyl groups,controllable relative molecular weight and distribution and high gloss of coating films.However,the existing aqueous acrylic polyol dispersions have some disadvantages including low solid content,high viscosity,high VOC content and insufficient crosslink density,resulting in poor coating film resistance and workability,which seriously restrict its application and promotion.In this paper,a self-made hydrophilic vinyl monomer contained ethoxy and sulfonic group was synthesized to prepare high solid content and low vicosity aqueous acrylic polyol dispersion by radical solution polymerization.The effect on the solid content and vicosity of dispersions,the dosages and catergories of sulfosalt monomers were studied.Furthermore,vinylsilane monomers are used to modify sulfonated aqueous acrylic polyol dispersion to improve the properties of 2K-WPU film properties.The vinyl sulfonated monomers were used to prepare high solid aqueous acrylic polyol dispersion.The effect of dosages and catergories of sulfosalt monomers on the properties of dispersions and coating films was studied.The polymerization process was optimized.It was found that dispersion prepared with self-made vinyl sulfonated monomers(SAP)had high solid content,low vicosity and good storage stability because the SAP contained strong hydrophilic anionic sulfonic groups and high-molecular-weight non-ionic ethoxy group segment.The sulfonic group could significantly increase the solid content while the ethoxy groups improve the storage stability,freeze-thaw stability and cationic stability.The solid content and storaged stability of dispersion increased with the increase of the SAP and the vicosity of dispersion decreased with the increase of the SAP.The results indicated that adding 2.5%SAP,the prepared dispersion has solid content up to 45%and viscosity at 205mPa·s.The dispersions exhibit good properties with excellent storage stability over six months.The GPC analysis shows that the molecular weight of the resin is M_n=6037,M_w=13800,and the molecular weight distribution index is 2.28.The water absoption of cured film is 11.68%and the pencil hardness is greater than F which meets the requirements for use.The vinyl siloxane monomer was used to modify the sulfonic aqueous acrylic polyol dispersions.The effect of the types and dosages of the vinyl siloxane monomer on the properties of dispersions and 2K-WPU films was investgated.It was found that the silicone monomer effectively improved the coating film hardness and chemical resistance,while the the storaged stability of dispersion decreased with the increase of the silane.The vinyl siloxane monomer with a large steric hindrance has excellent polymerization stability and storage stability.The vinyl siloxane monomer KH1706 performed best.When the KH1706dosage is 3%,the obtained aqueous dispersion meets the requirements of use and the best comprehensive performance of the 2K-WPU film with solid content of 45%and viscosity of357 mPa·s.The GPC analysis showed that the resin had a molecular weight of M_n=7032,M_w=13349,polydispersity(PDI)1.89.The water absorption of the coating film is 5.52%and pencil hardness is 2H,which are better than the foreign advanced products.