Synthesis and characterization of cationic acrylic resin used in cathodic electrodeposition coatings

Abstract

The radical copolymerization was used to synthesize cationic acrylic resin, which the methyl methacrylate (MMA) was used as the main hard monomer and styrene (St) was added to replace the function of MMA to reduce the cost of raw materials. Butyl acrylate (BA) was used as the main soft monomer to reduce the glass transition temperature of the polymer. Hydroxypropyl methacrylate (HPMA) was used to provide cross-linked hydroxyl groups for resin, and hydroxyl groups also had a certain hydrophilic properties. Dimethylaminoethyl methacrylate (DMAEMA) was used to provide tertiary amine group for the resin, which was acidified by organic acid to form ammonium salt. The cathodic electrodeposition (CED) coatings were prepared by mixing the resultant resin and blocked isocyanate. The conditions of synthesizing the cationic acrylic resin were optimized. The optimum synthetic conditions were the following. The mass ratio of (MMA + St) to BA was 3:2. The amount of DMAEMA was 12–15% in total monomer. The amount of HPMA was 20% in total monomer. The amount of the initiator was 2%. The neutralization degree was 80%. The reaction temperature was 90 °C. Both the conductivity of electrophoretic coating and its film were good when the cationic acrylic resin was synthesized under the optimum conditions. Besides, the characterization of Fourier transform infrared spectrometer (FTIR) and differential scanning calorimetry (DSC) confirmed that the cationic acrylic resin had been synthesized successfully.