Solving the challenges of high-viscosity biopharma mixing with effective design choices
Manufacturers of topical ointments, gels and lotions for BioPharma and personal care products face several critical product quality challenges in their mixing processes. The better you understand the nature of these challenges, the better you will be able to design processing equipment to optimize your quality and productivity.
Recognizing Challenges in BioPharma Products
Topically-applied products are among the highest viscosity manufactured products; viscosities can range from water-like to more than 1,000,000 cps. Mixing systems for these products must have sufficient power to move thick, heavy batch ingredients for consistent blending. Robust, heavy-duty design and construction of the drive system, mixing components and vessel are a must, to produce this mixing power and ensure long service life, especially in high-volume processing conditions.
In addition to powerful mixing action to move the batch throughout the vessel or mixing system, high-viscosity BioPharma and personal care products require heavy-duty, counter-rotating agitation to adequately blend batch ingredients. As viscosities approach and exceed 10,000 cps, the mixing action of a conventional high-shear mixer becomes confined to a localized agitation near the high-shear mixer. This can mean little or no mixing action occurs throughout the rest of the vessel.
All pharmaceutical ointments, gels or lotions require precise distribution of their active ingredients throughout the batch. This ensures every single product package contains the exact same percentage of the active ingredients. Achieving this consistent ingredient dispersion also requires trouble-free introduction of individual ingredients and elimination of air bubbles during batch mixing and processing, both of which are best accomplished under vacuum in the vessel.
Why Conventional High-Viscosity Mixing Systems Don’t Address Challenges
BioPharma and personal care product manufacturers may initially consider several types of mixing systems for processing high-viscosity topical products:
- Single vessel with multiple mixing heads: Manufacturers may use a single vessel with dual-mixing heads to handle their high-viscosity products. A vessel with both slower-moving scrape surface agitation and a separate high-shear mixing head operating at the bottom of the vessel can provide the two kinds of mixing action required.
For high-viscosity products, however, this design is inefficient. Due to the limited amount of mixing bars on this style of agitation, the mixing action is reduced, which can increase mixing time and potentially leave pockets of unmixed ingredients at the bottom of the vessel.
- Multiple vessels: Processors may also use two separate mixing tanks to handle high-viscosity products. In this configuration, a manufacturer would use one tank with a propeller or high-shear mixer alongside a separate mixing vessel with a double-motion, scraped surface agitator, mixing their high-viscosity product in a two-stage process. In this case, the propeller or high-shear mixer would be used to pre-mix certain ingredients into solution before final processing in the second, slower-speed mixing vessel. These steps require additional processing time as well as additional transfer lines and pumps to move product from one vessel to the other. For FDA regulated products, use of multiple vessels and product transfer steps may also require additional regulatory approval to keep the product's manufacturing process in compliance.
- Recirculating bottom-shear mixing systems: Some manufacturers use recirculating bottom-shear mixing systems in their high-viscosity processing operation. These mixers are high-performance systems that constantly recirculate the product through a high-speed mixing apparatus and are capable of mixing products to fine sub-micron consistencies. Although this system may perform better than single vessel with dual-mixing heads or multiple-stage vessel configurations, it is far more expensive due to the additional built-in components. Recirculating bottom-shear mixing systems also utilize additional product transfer lines, potentially complicating clean-in-place (CIP) requirements.
A More Efficient, Cost-Effective System for High Viscosity BioPharma Mixing Applications
The disadvantages of each of these mixing options—the inefficiency of conventional dual-mixing vessels and multiple mixing vessels, and the high cost of bottom-shear recirculating systems—are a challenge to process engineers seeking the most efficient and cost-effective mixing solution for their high-viscosity BioPharma or personal care products.
The Lee Industries Tri-Mix™ Turbo-Shear™ mixing system integrates robust scrape surface agitation with a unique, proprietary high-shear mixing unit to blend miscible and non-miscible ingredients commonly used in BioPharma and personal care products. It is built to handle viscosities as high as 2,000,000 cps and particle sizes as small as two microns. Through its unique design, the Tri-Mix™ system overcomes the drawbacks of conventional dual-head mixing systems and multiple vessel processing. It is also significantly less expensive than more complex bottom-shear recirculating mixing systems. The Tri-Mix™ system is available in many customized configurations to meet a wide variety of product and process requirements for high-viscosity BioPharma and personal care products.
Designing a processing system to handle high-viscosity BioPharma products can be a demanding process, and there are many factors to consider. To learn more about how Lee Indusries can help you meet these challenges, download the Guide to BioPharma Process Engineering Services: Vessel and Tank Design for Demanding BioPharma Processing Applications.