Structure Design,synthesis And Property Research On Water-based Polyesters Containing Sodium Sulfonate Groups

Polyester is a kind of resin with a large number of ester bonds which obtained by direct esterification or transesterification of polybasic acid and polyols.Synthetic polyester has special functional groups on its matrix through molecular design.Reactive cross-linking materials were synthesized by step-by-step polymerization,which were mainly used in coating binders,adhesives,coating agents,chemical fibers and polishing agents.However,with the environmental problems becoming more and more prominent and the environmental protection policies being improved,the coatings industry began to develop polyester hydration technology to reduce volatile organic gas emissions(VOC).The water-solubility of polyester is generally achieved by introducing ionic groups,carboxyl groups and amino groups into the polyester molecule without changing the composition of the polyester matrix,so as to make the polyester matrix hydrophilic.Therefore,waterborne polyester is water-soluble while retaining the inherent mechanical properties,processability,electrical properties and chemical corrosion resistance of polyester matrix.Thus,VOC reduction,cost reduction and combustibility elimination can be achieved.In this paper,a new waterborne polyester with self-emulsifying properties was prepared by introducing hydrophilic second monomer and optimizing the synthesis process.In this article,Environmental friendly waterborne polyesters(WPEs)were obtained by copolymerization of diethylene glycol(DEG),isophthalic acid(IPA)and 5-sulfoisophthalic acid monosodium salt(5-SSIPA).The effects of the 5-SSIPA content on the properties of the resultant copolymers,including dispersity,crystallinity,dynamic thermo-mechanical properties,thermal stability and surface properties,were investigated.The 5-SSIPA contents in the intended polymers were determined by the peak areas of proton nuclear magnetic resonance(1H-NMR)spectra.Transmission electron microscopy(TEM),electrophoretic light scattering(ELS)and dynamic light scattering(DLS)were used to characterize the dispersion and stability performance of waterborne polyester solutions.The crystallinity of the WPEs was determined by using differential scanning calorimetry(DSC)and X-ray diffraction(XRD).The results show that as the 5-SSIPA content increased,the glass-transition temperature(Tg)of the WPEs increased significantly according to dynamic mechanical analysis(DMA),the thermal stability of the WPEs was deteriorated according to thermogravimetric analysis(TGA),the mechanical properties of waterborne polyester were characterized by tensile test.The results showed that the tensile strength of waterborne polyester increased with the increase of 5-SSIPA,but its elongation at break decreased.surface roughness did not change according to atomic force microscopy(AFM),and their solid surface tension was increased from 28.47 to 32.90 m J/m~2 based on static contact angle measurements.Water contact angle(WCA)measurements proved that WPE dispersions could be used for enhancing the hydrophilicity of the PET surface.Furthermore,the self-emulsifying waterborne polyester was used as the main film-forming material to prepare the super hydrophilic anti-fog coating on the surface of PET by multi-layer coating method.Firstly,the surface of PET was corona treated,and then coated with the water-borne polyester(WPE)and amino resin(crosslinking agent)as the underlying coating.After partial crosslinking,Tween containing a large number of ether bonds and hydroxyl groups was coated as the upper coating.Finally,the reaction cured completely.The surface modified PET film retains excellent transparency and super hydrophilic surface properties.The hydroxyl and carboxyl groups between the super-hydrophilic coatings and the substrates of the new super-hydrophilic film can form a unified whole with the help of crosslinking agent.The lower polyester layer provides the necessary mechanical properties,water resistance and adhesion through chemical crosslinking and polyester compatibility,and the upper layer provides the superhydrophilic properties of the surface.By changing the ratio of polyester to crosslinking agent and testing the adhesion(ASTM D3359),it was determined that the coating had the best adhesion when the mass ratio of polyester to crosslinking agent was greater than 4:1.Change the curing time of the first layer,only hydrophilic monomers are coated on the second layer.After curing,the results of wet wear resistance test(ASTM D4828)and water contact angle test show that when the solidification time of the bottom layer is 10minutes,the cross-linking between the upper layer and the bottom layer is the most complete.Finally,the water contact angle of these coatings and the coatings after wet friction experiments were tested by changing the ratio of hydrophilic monomer to crosslinking agent.The results showed that the hydrophilicity and wet resistance of the anti-fog coatings were the best when the mass ratio of Tween to crosslinking agent was 1.5:1.