Coating Granulation by Rapid Expansion of Supercritical Fluid Solutions in a Fluidized Bed

采用超临界CO_2溶液快速膨胀法，在流化床中将二氧化硅微粒包覆在玻璃微珠表面，制备了一种新型的包覆造粒方法。超临界CO_2溶液快速膨胀沉积石蜡时，二氧化硅微粒进入核颗粒周围的层中。最初，单个细颗粒由于粘附力而附着到芯颗粒上，然后由于粘合剂的沉积而通过固体桥接而结合。实现了稳定的包衣造粒，而没有过度团聚。在低气体速度下，粘合剂材料沉积在粘附到芯颗粒的细颗粒的涂层上。这导致通过使细颗粒分层而实现均匀的包衣造粒。在高气速下，核心颗粒上形成了小团聚体和细颗粒，并在多孔颗粒表面包覆了一层薄膜，利用超临界CO_2溶液在流化床中的快速膨胀控制释放。通过红色素释放速率的测定和扫描电镜观察，考察了该涂料的性能。结果表明，通过控制操作条件可以控制释放速率。所有颗粒在包衣过程中均呈单分散状态，无团聚现象。实验中对药物的释放速率和涂层表面进行了分析。

The coating granulation by the rapid expansion of supercritical CO_2 solutions of binder (paraffin) was performed to coat the surface of core particles (glass beads) with fine silica particles in a fluidized bed. The deposition of paraffin by rapid expansion of supercritical CO_2 solutions incorporated fine silica particles into the layers around core particles. Initially individual fine particles are attached to the core particles due to the adhesion force and then are bounded by solid bridging due to the deposition of binder. A stable coating granulation was achieved without the excess agglomeration. At low gas velocity the binder material was deposited on the coating layer of fine particles adhered to the core particle. This leads to the uniform coating granulation by layering fine particles. On the other hand, at high gas velocity small agglomerates and fine particles are found to be layered on the core particles.In addition, porous particles were coated with film masking for releasing control by the rapid expansion of supercritical CO_2 solution in a fluidized bed. The coating characteristics was examined by the measurements of releasing rate of red pigment and SEM observation. It was found that the releasing rate can be controlled by controlling the operation condition. All the particles in mono-dispersion in the coating process with out agglomeration in granules. The releasing rate and the coating surface analysis was analyzed in the experiment.