Preparation And Modification Of Hydroxy Acrylic Resin Dispersion And Application Of Two-component Polyurethane Coatings

This paper is divided into three parts.The first part was a study on the acrylic resin and dispersion modified by organosilicon condensation.The second part was a research on the acrylic resin and dispersion modified by polycarbonate diol.The third part was about the waterborne two-component polyurethane coatings modified by silicon for PP plastic coatings.(1)An active organosilicon condensate was synthesized by hydrolysis and condensation of Vinyltriethoxysilane(VTEOS)with tetraethyl orthosilicate(TEOS).A series of acrylic resin and dispersions modified by silicon condensation for two-component polyurethane coating with isocyanate curing agent were synthesized by solution polymerization with acrylate monomers and silicon condensation.The structure of silicon condensation was studied by Fourier transform infrared(FTIR).Results showed that there was absorption peak at 1085 cm-1,which is the antisymmetric stretching vibration peak of Si-O-Si,meaning that the formation of silicon condensation;In the process of resin polymerization,increasing the amount of silicon condensate,the particle size of dispersion increased,and the particle size distribution became wider;Thermal storage experiment showed that when the content of silicone condensation was lower than 6%,with increase of the condensation content,the stability of dispersion decreased slightly,while the content was increased to 8%,the stability of dispersion decreased significantly;Meanwhile,influence of silicone condensation content on the properties of coating was studied.The results showed that:introduction of silicon condensate improved the surface properties,solvent resistance,adhesion and hardness of the coating,but the wear resistance of the coating was decreased;the heat resistance of the coating was remarkably improved by introduction of Si-O-Si into the molecular structure of the resin;thermogravimetric analysis indicated when the silicon condensate dosage was 6%,the final residual amount of the coating was increased from 10%to 21%.Acrylic dispersions and two-component polyurethane coatings with outstanding performance could be prepared by addition of silicon condensate with the content of 6%.(2)Carboxyl was introduced in polycarbonate diol(PCDL)modified by isophorone diisocyanate(IPDI),dimethylol propionic acid(DMPA).By measuring the value of-NCO in the solution,when(PCDL):n(IPDI)was 0.5 and(DMPA):n(PCDL)was slightly larger than 2,the reaction finished.A series of modified acrylic resin and dispersions for two-component waterborne polyurethane were synthesized by copolymerization with acrylate monomers and modifiied or unmodified PCDL.Effect of PCDL addition manner on resin synthesis and influences of PCDL dosage on the particle size,zeta potential and stability of acrylic dispersions were studied.Meanwhile,modified PCDL dosage on the mechanical properties,heat resistance and water resistance impact of coating were investigated.Results indicated that:when PCDL was introduced by mixing with acrylic monomers,the acrylic resin exhibited better performance;as the amount of modified PCDL increased,the particle size of the dispersion firstly increased and then decreased,and the particle size increased with the amount of unmodified PCDL increased;the zeta potential test showed that when modified PCDL dosage was 0?10%,the zeta potential of the dispersion decreased with the increase of PCDL,and it was increasing when the PCDL dosage went on increasing,while the potential was increasing with increase of the unmodified PCDL;thermnal storage experiment results showed that the stability of the dispersions with modified PCDL was better than that of the dispersions with unmodified PCDL;surface properties,solvent resistance,wear resistance of the coating with the addition of PCDL were improved:when PCDL dosage was 10%,the highest number of solvent resistant wipes was 311,water contact angle reached 90.2°,and coating loss was as low as 16.21 mg;thermogravimetric analysis and electrochemical tests showed that addition of PCDL improved the water resistance and heat resistance of the coating because of carbonyl group with strong polarity and carbonate bond with strong cohesion in molecular structure.(3)A two-component polyurethane topcoat was prepared by the acrylic dispersions modified by silicone condensate,which was compatible with commercially available CPP oil-based primers for PP plastic coatings.The spraying of oil-based primer promoted the adhesion of top coat on PP plastic and improved the scratch resistance of the coating;The thickness of the base film had an influence on the adhesion of the composite coating,when film thickness was controlled at 20-25?m,adhesion of the coating was the best;Using Bayhydur XP 2487/1 curing agent,waterproof and adhesive properties of coating were optimal.When-NCO/-OH ratio was 1.3,the coating crosslink density was suitable,which was beneficial to improve the water resistance of the coating.The adhesion of the topcoat on the primer was improved with the addition of adhesion promoter,which obviously improved the adhesion of the coating.When the baking temperature of the coating was increased to 90?,the effect of adhesion promoter was brought into full play so as to improve the adhesion and water resistance of the coating.