Synthesis And Application Of Polyesteracrylate For Ultra Violet Curable Powder Coatings

Firstly, a carboxyl-terminated polyester was synthesized using 1,4-cyclohexanedimethanol with excessive adipic acid by melting method. Then a UV curable polyesteracrylate was synthesized by reaction of carboxyl-terminated polyester with Glycidyl Methacrylate (GMA) by solution method. The influences of the types and content of catalyst and inhibitor, the reaction temperature on the conversion and the degree of crosslinking of UV cured film were studied. The structure of the UV curable polyesteracrylate was characterized by FT-IR Spectrometer. The FT-IR results showed that the carbon-carbon double bond existed in the UV curable polyesteracrylate. The experimental results showed that the conversion increased with the increase of the content of the catalyst. When the content of the catalyst reached 3 wt%, the conversion increased gently. The conversion also increased with the increase of the reaction temperature. But the increase of the reaction temperature may also result in the pre-polymerization of the carbon-carbon double bond of the UV curable polyesteracrylate, which may lead to the decrease of the degree of the crosslinking of the UV cured films. The suitable reaction conditions are tetrabutylammonium bromide 3 wt%, 4-Hydroxy-2,2,6,6-tetramethylpiperidinyloxy (ZJ-701) 0.1 wt% , reaction temperature 100℃and reaction time 3 h. Thirdly, a UV curable polyesteracrylate was synthesized by melting method. The influences of the types of the dicarboxylic acids and OH/COOH mole ratio on the melting point, milling and storage stability of the UV curable polyesteracrylate were studied. The melting point was characterized by Differential Scanning Calorimeter (DSC). The DSC result showed that the melting point of the UV curable polyesteracrylate was about 100°C, which meet the requirement of UV curable powder coatings; Long carbon chain in the structure of the UV curable polyesteracrylate may decrease the melting point of the resin; The increase of the OH/COOH mole ratio may improve the storage stability of the UV curable polyesteracrylate. The suitable reaction conditions are OH/COOH mole ratio 0.92-0.94, tetrabutylammonium bromide 3 wt%, reaction temperature 120°C and reaction time 1 h. In order to synthesize low melting point UV curable polyesteracrylate with good storage stability, the sebacic acid was introduced into the structure and the OH/COOH mole ratio was increased to improve the storage stability. The suitable formulation are the OH/COOH mole ratio 0.96, the mole content of the sebacic acid 10%, while the melting point of the UV curable polyesteracrylate was about 90°C. Finally the formulation and the process of the UV curable powder coatings were studied. The experimental results showed that the suitable formulation are the content of the photoinitiator(TPO) 3 wt%, leveling agent(GLP505) 1 wt%, benzoin 0.5 wt%, hydroquinone 0.5 wt%. The suitable temperature for the melting and flowing was 110℃, and then cured under the ultraviolet (80W/cm) for 20s.