Nielsen Anne Flachs, Poul Bertelsen, Kristensen Henning Gjelstrup, Kristensen Jakob, Hovgaard Lars
The Danish University of Pharmaceutical Sciences, Copenhagen, Denmark.
Pharm Dev Technol. 2006;11(2):243-53. doi: 10.1080/10837450600561455.
Effervescent atomizers belong to the group of internal mixing atomizers. The effervescent approach might be a potential alternative to traditional atomization techniques, e.g., for applications where low atomization air consumption is advantageous In this paper, performance of one proposed design of the effervescent atomizer is investigated and compared to that of a standard pneumatic atomizer. The purpose of the comparison is to evaluate the actual potential of the specific effervescent atomizer in pharmaceutical relevant aqueous coating applications. Aqueous solutions of Hypromellose 5 as well as Povidone K-90F were characterized in terms of rheological properties and surface tension. Solutions were atomized by means of a standard Schlick pneumatic atomizer as well as a customized inside-out type effervescent atomizer. Spray droplet size distributions were recorded by a Spraytec instrument. Increased shear viscosity in the range 24-836 mPa.s had a modest effect on spray mean diameters for pneumatic sprays of the Newtonian solutions of Hypromellose 5. In contrast, mean droplet diameters increased by a factor of 3-5 in pneumatic sprays of Povidone K-90F solutions 11-175 mPa.s in viscosity, where non-Newtonian behavior was observed. Further, sprays of all solutions of Povidone K-90F have considerably larger mean droplet size. The effervescent atomizer atomized low viscosity solutions of Povidone K-90F more efficiently than Hypromellose 5 solutions of corresponding shear viscosity. However, atomization of high viscosity Povidone K-90F results in a coarser spray than that of the corresponding Hypromellose 5 solution. Viscosity, visco-elasticity, and surface tension of solutions all seem to affect atomization efficiency. The pneumatic atomizer was not sensitive to changes in airflow above 8.4 kg/h and liquid flow only had a considerable effect at suboptimal air flows. In its current design the effervescent atomizer improved efficiency throughout the investigated range of air flow of 0.18-0.84 kg/h and consistently produced smaller drops at liquid flow of 10 g/min compared to 35 g/min. In spite of the very low level of air consumption, the effervescent atomizer can produce fine sprays. Within its working range, the standard pneumatic atomizer, however, is capable of producing sprays of even smaller mean droplet size. All together this suggests the described effervescent atomizer as an alternative for applications where advantages of reduced atomization air flow outweigh the disadvantages of a less fine spray, e.g., in coating of attrition-prone substrate.
泡腾雾化器属于内部混合雾化器组。泡腾方法可能是传统雾化技术的一种潜在替代方法，例如，对于低雾化空气消耗有利的应用。在本文中，研究了一种提出的泡腾雾化器设计的性能，并将其与标准气动雾化器的性能进行了比较。比较的目的是评估特定泡腾雾化器在药物相关水性包衣应用中的实际潜力。对羟丙甲纤维素5以及聚维酮K - 90F的水溶液进行了流变学性质和表面张力的表征。溶液通过标准的施利克气动雾化器以及定制的由内向外型泡腾雾化器进行雾化。喷雾液滴尺寸分布由Spraytec仪器记录。在24 - 836 mPa·s范围内增加的剪切粘度对羟丙甲纤维素5牛顿溶液的气动喷雾的喷雾平均直径有适度影响。相比之下，在粘度为11 - 175 mPa·s的聚维酮K - 90F溶液的气动喷雾中，平均液滴直径增加了3 - 5倍，其中观察到非牛顿行为。此外，聚维酮K - 90F所有溶液的喷雾具有相当大的平均液滴尺寸。泡腾雾化器比具有相应剪切粘度的羟丙甲纤维素5溶液更有效地雾化低粘度的聚维酮K - 90F溶液。然而，高粘度聚维酮K - 90F的雾化产生的喷雾比相应的羟丙甲纤维素5溶液更粗糙。溶液的粘度、粘弹性和表面张力似乎都影响雾化效率。气动雾化器对高于8.4 kg/h的气流变化不敏感，并且仅在次优气流下液体流量才有相当大的影响。在其当前设计中，泡腾雾化器在0.18 - 0.84 kg/h的研究气流范围内提高了效率，并且与35 g/min相比，在10 g/min的液体流量下始终产生更小的液滴。尽管空气消耗水平非常低，但泡腾雾化器仍能产生细喷雾。然而，在其工作范围内，标准气动雾化器能够产生平均液滴尺寸甚至更小的喷雾。总体而言，这表明所描述的泡腾雾化器可作为一种替代方案，用于雾化空气流量减少的优点超过喷雾不太细的缺点的应用，例如在易磨损基材的包衣中。
