Sifting of HPMC (Hydroxypropyl Methylcellulose) powder is an important process in pharmaceutical, food, and chemical industries to ensure particle size uniformity, remove contaminants, and improve the product's flowability. HPMC is widely used as a binder, film former, thickening agent, and stabilizer in various formulations, especially in tablet production and controlled-release systems.
Background
Particle Size Control: HPMC comes in different grades based on molecular weight and particle size, so sifting is essential to ensure consistency in the final product. The uniform particle size ensures homogeneity, enhances flow properties and aids in uniform mixing, which is crucial for tablet manufacturing.
Removal of Lumps/Agglomerates: HPMC may form lumps or agglomerates during storage due to its hygroscopic nature. Sifting helps break down these lumps to improve the powder's consistency and uniformity.
Elimination of Foreign Particles: Sifting helps remove any foreign particles or impurities that may have been introduced during handling or storage, ensuring product purity and quality.
Flowability: HPMC tends to absorb moisture, which can reduce its flowability. Sifting can help improve the powder’s flow characteristics, which is important for downstream processes like compression or capsule filling.
Complications
Problems Faced in Sifting HPMC Powder:
Poor Flowability: HPMC is inherently hygroscopic, meaning it can absorb moisture from the environment, making the powder sticky and difficult to sift. This can lead to blockages or clumping during sifting, particularly if the ambient humidity is high.
Static Charge Build-up: HPMC particles may develop static electricity during sifting, leading to the powder sticking to equipment or sieves. This can slow down the process and reduce yield.
Clogging of the Sieve: HPMC tends to form lumps due to moisture absorption, which can clog the sieve mesh, leading to frequent stoppages for cleaning and reducing efficiency.
Sieving Equipment Wear and Tear: HPMC can have varying viscosities and fineparticle sizes, which may cause abrasive wear on sifting equipment over time, leading to increased maintenance costs.
Particle Size Segregation: If HPMC grades are not uniform, particle size segregation may occur during sifting, leading to inconsistency in the final product.
Operator Safety and Dust Formation: Fine powders like HPMC can create dust clouds, leading to operator exposure and potential respiratory issues. Proper dust control measures are necessary to avoid health risks and ensure a safe working environment.
To mitigate these challenges, manufacturers often use specialized equipment like vibratory sifters, air jet sieves, or ultrasonic sifting machines and control environmental conditions to minimize moisture and static charge.
Current Framework
One of the clients approached Gansons with a specific challenge related to the sifting process of HPMC (Hydroxypropyl Methylcellulose), a fine material that posed significant difficulties in handling. The client struggled with efficiently sifting the HPMC, particularly due to the presence of black particles that were difficult to remove. Additionally, the generation of dust during the process was another major concern for the client, as it could potentially affect the work environment and product quality.
Understanding the client's needs, Gansons carefully evaluated the problem and suggested a solution. They recommended using the Hanningfield Kwik Sift KS-20, a highly efficient sifting machine designed to handle fine materials like HPMC. This machine offers faster sifting and helps mitigate the dust generation issue, addressing both clients’ concerns effectively.
We conducted a trial on the Hanningfield Kwik Sifter KS-20 using 100 kg of HPMC provided by the client. The material was exceptionally fine, with a particle size below 150 microns, making it difficult to sift efficiently. Due to these challenges, Hanningfield carried out multiple trials using screens of varying sizes to identify the most suitable option for the process.
The client’s key concern was the time required for sifting, so Hanningfield specifically focused on optimizing this aspect. A diffusion-bonded screen was used during the trials, demonstrating excellent results. It not only reduced the sifting time but also improved overall efficiency.
Experiment procedure
All the batches of material weighed and kept in poly bags.
The machine was turned on and the parameter was set.
The material was fed manually through the hopper with control feeding.
Materials were collected in drums and the sifter basket was checked for retention of black particles.
Table 1: Trial summary and observations for Sifting.
Findings
The trial showed that foreign particles present in the HPMC were effectively captured in the retention chamber, ensuring the purity of the sifted material. The output of the sifting process was highly satisfactory, delivering a refined product in significantly less time, and addressing both quality and time-related concerns raised by the client.
Conclusion
The trials conducted using the Hanningfield Kwik Sifter KS-20 proved to be highly successful in addressing the client’s concerns about sifting fine HPMC, which contained particles smaller than 150 microns. The process challenges were primarily related to the fineness of the material, the presence of foreign particles, and the time required for effective sifting.
By experimenting with different screen sizes, Hanningfield was able to identify an optimal solution—a diffusion-bonded screen—which significantly reduced the time required for the process without compromising quality. The retention of unwanted foreign particles in the retention chamber further ensured the purity of the sifted HPMC, contributing to a cleaner and higher-quality output.
The results of this trial demonstrate that the Hanningfield Kwik Sifter KS-20 is an ideal solution for handling fine, sensitive materials like HPMC, especially when time and material purity are critical factors. The trial's success highlights the machine’s ability to improve operational efficiency and product quality, providing a clear path forward for clients facing similar challenges
