Coating of urea granules by in situ polymerization in fluidized bed reactors

Abstract The main objective of the present work is to produce and characterize urea granules coated with polymers prepared with aqueous solutions of acrylic acid and glycerol. Both coating and drying of urea granules were performed in a fluidized bed reactor. Fourier transform infrared spectroscopy analyses indicated the presence of poly(acrylic acid) and acrylic acid / glycerol copolymers on the granule coating and the formation of chemical bonds between urea and the polymer coating. Scanning electron microscopy images showed that the original and coated urea granules presented different characteristics, reinforcing the idea that coating occurs in the fluidized bed. Finally, rates of urea release showed that the coated granules presented slightly slower rates of urea dissolution in water due to the presence of the coating layer. Therefore, it is shown that it is possible to produce coated urea granules through in-situ polymerization onto the granule surface using a fluidized bed.

摘要 本研究的核心目标为制备并表征以丙烯酸与甘油水溶液聚合得到的聚合物作为包覆材料的尿素颗粒。尿素颗粒的包覆与干燥工序均在流化床反应器中完成。傅里叶变换红外光谱（Fourier transform infrared spectroscopy）分析表明，尿素颗粒包覆层中存在聚丙烯酸以及丙烯酸/甘油共聚物，且尿素与聚合物包覆层之间形成了化学键。扫描电子显微镜（scanning electron microscopy）图像显示，原始尿素颗粒与包覆后尿素颗粒的形貌特征存在显著差异，进一步佐证了流化床内包覆过程的发生。最终的尿素释放速率测试结果表明，由于包覆层的存在，包覆后尿素颗粒在水中的溶解速率略有减缓。综上，本研究证实，可通过流化床内尿素颗粒表面的原位聚合反应，成功制备聚合物包覆尿素颗粒。