Synthesis And Application Of Polyester Resin For A New Low-temperature-cured Powder Coatings

In recent years,low-temperature-curing powder coatings has become a major object researched by many enterprises and research institutes.The powder coatings is playing a significant role not only in saving energy but also reducing energy-consumption.Moreover,it will expand the application in different fields,and expedite the replacement of the traditional coatings by new ones.Here,we start from the introduction of the polyester resin used in the coatings.By introducing new type of monomer,we upgrade the formulation and processing of production to improve the flexibility of the main chain of polyester resin along with the activities of end group.And by adding cure accelerator which has a special effects in reducing the curing temperature of the powder coating and shortening the time of solidification from 10 minutes under 200 ℃ down to 20 minutes under 130℃.Meanwhile,each performance of the polyester resin is tested in power coatings,including its appearance and weather resistance capability.Contrasted by experiments,the polyester resin which is for triglycidyl isocyanurate(TGIC)cure,the acid value of 40-45 mgKOH/g will show better low-temperature-curing tendency.By synthesizing the main raw materials,includes phthalic acid,isophalic acid,1,4-cyclohexanedicarboxylic acid,adipic acid,fumaric acid,neopentyl glycol,2-butyl-2-ethyl-1,3-propanediol,1,6-hexanediol,trimethylolpropane together with monobutyltin oxide,antioxidant and cure accelerator,We can get a kind of colorless particles that has acid value of 42.4 mgKOH/g,melt viscosity of 3160 mPa.s,softening of point 111 ℃.By the proportion of 92:8,mixed the polyester resin with TGIC,coupled with matching pigment,filler and additives,we can get a satisfactory powder coating by mixing,meltting extrusion,grinding,sieving,spraying and baking for 20 minutes under temperature of 130℃.Then the polyester resin was characterized by the methods of GPC,DSC,NIR and FT-IR.The results show that the number average molecular weight of polyester resin is 5519,the heavy molecular weight is 8425,and the molecular weight distribution width is 1.53,moderate molecular weight distribution width.The glass transition temperature of polyester resin is 58.8 ℃ measured by differential scanning calorimeter,which is suitable for stable storage.By the artificial accelerated aging test on the prepared powder coatings,it reaches the excellent standard in respects of losing gloss,chalking and fading.