Surface modification to improve powder bulk behavior under humid conditions

Synthesis of Hydrophobic Nanosized Silicon Dioxide with a Spherical Particle Shape and Its Application in Fire-Extinguishing Powder Compositions Based on Struvite

Textural and morphological features of hydrophobic silicon dioxide, obtained by the hydrolysis of tetraethoxysilane in an ammonia medium followed by modification of a spherical SiO₂ particles surface with a hydrophobic polymethylhydrosiloxane, were studied in this work. The size of silicon dioxide particles was controlled during preparation based on the Stöber process by variation of the amount of water (mol) in relation to other components. The ratio of components, synthesis time and amount of the hydrophobizing agent were determined to obtain superhydrophobic monodisperse silicon dioxide with a spherical particle size of 50-400 nm and a contact angle of more than 150°. In the case of the struvite example, it was demonstrated that the application of spherical- shaped hydrophobic silicon dioxide particles in powder compounds significantly improves the flowability of crystalline hydrates. The functional additive based on the developed silicon dioxide particles makes it possible to implement the use of crystalline hydrates in fire-extinguishing powders, preventing agglomeration and caking processes. The high fire-extinguishing efficiency of the powder composition based on struvite and the developed functional additive has been proven by using thermal analysis methods (TGA/DSC).

Improving the Effectiveness of the Conical Screen Mill as a Dry-Coating Process at Lab and Manufacturing Scale

The conical screen mill (comill) is investigated as a dry-coating process for flowability and bulk density enhancement of pharmaceutical powders. In this study, the effectiveness of the comill is improved by using modified screens with reduced open area. In comparison to the screens provided by the comill manufacturer, the modified screens increase mean residence time of the process and improve the extent of flowability and bulk density enhancement. The effectiveness of the comill as a dry-coating process is demonstrated using Avicel PH 105, a fine grade of microcrystalline cellulose, as a model cohesive powder. The process is evaluated thoroughly using a lab scale comill and scalability is demonstrated using a manufacturing scale model. The use of the modified screens is also compared against the so-called "multi-pass" approach in which material is passed through the comill, collected, and passed through once or several times. While the "multi-pass" approach is offered as a simple method to increase mean residence time and to improve process effectiveness, the use of the modified screens is shown to be the superior approach. Due to the ubiquitous use of the comill and the improvement in effectiveness attained in this study, dry-coating is shown to be a practical and readily implemented process for the pharmaceutical industry.

A Continuous Conical-Mill Operation for Dry Coating of Pharmaceutical Powders: The Role of Processing Time

Over the last decade, the conical mill has emerged as a potential piece of equipment to use for continuous dry coating pharmaceutical powders. In this work, silicon dioxide was used as a guest particle on two excipients, fast flow lactose (FFL) and grade PH200 microcrystalline cellulose (MCC), for dry coating by a conical mill with a modified screen that permitted batch and continuous mode operation. Samples were pre-processed in a V-blender. SEM images, particle size distribution, and EDS mapping were used to characterise the treated powders. Pre-processed samples showed some discrete coating of the host particle. After batch processing, the samples were covered with a complete coating. When processed at high impeller speed, coating of FFL was a mix of A200P and FFL fines generated by attrition. Continuous mode processed samples, which had a lower processing time, were coated discretely and showed a better coating than the pre-processed samples. Increasing guest/host mass ratio with FFL host particle had a positive impact on the quality of the coating. These results help to build the case that the processing time of the conical mill is a key parameter to the success of the conical mill as dry coating equipment in the pharmaceutical industry.

Enhancing flowability of fine cohesive active pharmaceutical ingredients

OBJECTIVE

The effectiveness of pharmaceutical excipients and hydrophobic nano-silica as flow aid/regulator was studied and two active pharmaceutical ingredients, i.e. paracetamol and ibuprofen were used to gauge the effectiveness. Avicel PH-101 and Avicel PH-102 were chosen as pharmaceutical excipients and Aerosil R972 Pharma was used as hydrophobic nano-silica, the API's and the excipients were micro-sized.

SIGNIFICANCE

Fine powders lead to many operational difficulties in the pharmaceutical industry which need to be alleviated. The reliability and repeatability of the Powder Flow Tester need to be established.

METHODS

Flow function, wall friction, and bulk density tests to gauge the said effect were conducted on Brookfield Powder Flow Tester. The samples for testing were prepared by blending (rigorous mixing) to ascertain the capability of inexpensive mixing in comparison to expensive blenders and machines.

RESULTS

The study undertook shows that blending (rigorous mixing) was sufficient in improving the flow of active pharmaceutical ingredient powders. Blending with excipients Avicel PH-101 and Avicel PH-102 improved the flow substantially but the maximum improvement was seen in the nano blended samples.

CONCLUSIONS

The study conducted underlined the efficacy of the blending process by showing significant improvement in flow properties. The Powder Flow Tester confirmed the anticipated results of the powder blends indicative of its reliability. Moreover, repeatable results were obtained which established the repeatability of the instrument.