Case Study: High-Shear Emulsifier Application in Ointment Production
In the pharmaceutical and daily chemical industries, the quality of ointments is primarily determined by emulsion uniformity, particle size distribution, phase stability, and compliance with regulatory standards. Ointments, as semi-solid formulations, often involve oil-water two-phase systems that require precise emulsification to ensure consistent texture, skin adaptability, and long-term storage stability. Traditional emulsification methods frequently encounter technical challenges such as uneven phase mixing, excessive particle size, poor batch consistency, and failure to meet strict stability test requirements. This case study focuses on how a customized high-shear emulsifier optimized the ointment production process, resolved core technical bottlenecks, and enhanced product quality compliance and production efficiency.
1. Background and Production Challenges
The production facility specializes in semi-solid formulations, with ointments (including oil-in-water and water-in-oil types) as its core products. Prior to upgrading equipment, the facility relied on conventional agitator-type emulsifiers and colloid mills for ointment production. Long-term operational practice revealed several prominent issues that restricted product quality and production scalability.
Firstly, particle size control failed to meet consistency standards. Conventional equipment lacked sufficient shearing force to break down oil droplets and solid particles into uniform micro-sized dispersions, resulting in an average particle size of 20-30 μm. Some batches exhibited visible granularity, leading to poor spreadability on the skin and inconsistent drug release (for pharmaceutical ointments). Secondly, phase stability was inadequate. Insufficient fusion between oil and water phases caused the ointments to undergo stratification, oil separation, or crystallization precipitation after storage, failing to pass the accelerated stability test (conducted at 40℃±2℃, relative humidity 75%±5%) and long-term stability test (conducted at 25℃±2℃, relative humidity 60%±10%) as required by regulatory guidelines.
Thirdly, batch consistency was difficult to guarantee. Manual operation of traditional equipment led to variations in emulsification time, temperature, and mixing intensity across batches, resulting in fluctuations in key quality indicators such as viscosity (ranging from 15,000 to 30,000 mPas) and pH value. This increased the risk of non-compliance during quality inspections. Additionally, the production process was time-consuming and energy-intensive. The traditional process required multiple rounds of emulsification and grinding, with each batch taking approximately 3.5 hours to complete. Frequent wear of colloid mill components and complex cleaning procedures also raised maintenance costs and extended downtime.
To address these issues, the facility sought a technical solution that could achieve precise particle size control, enhance phase stability, improve batch consistency, and comply with pharmaceutical production standards. After conducting small-batch process verification and equipment performance evaluation, a customized high-shear emulsifier with sterile design and precision control functions was selected for the production line.
2. Equipment Selection and Technical Adaptation
Considering the characteristics of ointment production—including oil-water two-phase compatibility, sensitivity of active ingredients to temperature, requirement for particle size ≤5 μm, and compliance with GMP standards—the selected high-shear emulsifier was customized to match the formulation and process needs. The core design features of the equipment are as follows:
The emulsifier adopts a triple-stage rotor-stator structure, with a maximum rotational speed of 15,000 rpm and a linear speed of 48 m/s. This structure generates intense shearing, cavitation, and turbulent forces in the 0.05-0.3 mm adjustable gap between the rotor and stator, effectively breaking down oil droplets and solid particles into uniform dispersions. The particle size distribution Span value is controlled below 0.95, ensuring consistent emulsion quality. The equipment is equipped with a precision frequency conversion system, enabling stepless speed adjustment from 1,000 to 15,000 rpm to adapt to different ointment formulations (such as high-oil-content and high-viscosity types).
In terms of material and sterile design, all parts in contact with the product are made of 316L stainless steel, undergoing electrolytic polishing to achieve a surface roughness Ra ≤ 0.4 μm. This design prevents material adhesion and residue, reduces cross-contamination risks, and facilitates cleaning-in-place (CIP) operations. A jacketed temperature control system with precision ±1℃ regulates the processing temperature between 20-50℃, avoiding thermal denaturation of active ingredients and ensuring the stability of the ointment matrix. The equipment also integrates a sterile vacuum system with a vacuum degree of up to -0.098 MPa, which removes air bubbles generated during emulsification and prevents oxidative degradation of sensitive components.
To enhance operational safety and compliance, the emulsifier is equipped with a touchscreen automatic control system that records key process parameters (temperature, speed, emulsification time, vacuum degree) in real time, supporting data traceability. The modular structure allows quick replacement of wearing parts (such as rotor-stator sets) and compatibility with different formulation volumes, from laboratory-scale pilot tests to mass production. Additionally, the equipment meets EHEDG guidelines and 3A certification, complying with global pharmaceutical production regulatory requirements.
3. Implementation Process and Process Optimization
Before formal mass production, the technical team conducted multi-batch pilot tests to optimize the emulsifier parameters for different ointment formulations. The tests focused on adjusting rotational speed, emulsification time, temperature, and phase addition sequence to determine the optimal parameter combination for each product type, with a focus on particle size control and phase stability.
In the pilot test phase, the team found that the optimal parameters for oil-in-water ointments were: rotational speed 10,000 rpm, emulsification time 20 minutes, temperature 35℃, and water phase added to the oil phase in a gradient manner. For water-in-oil ointments, the optimal parameters were: rotational speed 12,000 rpm, emulsification time 25 minutes, temperature 40℃, and oil phase added to the water phase under vacuum conditions. Under these parameters, the average particle size of the ointments was controlled at 1.5-3 μm, the Span value was ≤0.85, and no phase separation occurred after preliminary stability testing. Based on these results, the production line was adjusted to integrate the emulsifier into the existing process flow.
The optimized production process is as follows: First, oil-phase ingredients (such as凡士林 and lanolin) are melted and heated to the preset temperature in a dedicated tank, while water-phase ingredients (including active pharmaceutical ingredients and stabilizers) are dissolved and heated to the same temperature to avoid temperature differences causing phase separation. The two phases are then pumped into the high-shear emulsifier in the optimized addition sequence, with the vacuum system activated simultaneously. The emulsifier operates under preset parameters, and the material is circulated through the rotor-stator area 3-5 times to ensure complete dispersion. After emulsification, the ointment is cooled to room temperature under gentle stirring and then transferred to the next stage for filling and packaging.
Compared with the traditional process, the optimized process integrates emulsification and dispersion functions, eliminating the need for secondary grinding. The automatic parameter control and real-time monitoring reduce manual intervention, ensuring consistent operation across batches. The team also adjusted the feeding speed to match the emulsifier's processing capacity, avoiding material accumulation and ensuring continuous and stable production.
4. Application Results and Performance Improvements
After the high-shear emulsifier was put into formal operation, the production line achieved significant improvements in product quality compliance, production efficiency, and operational costs. The specific results are reflected in the following aspects:
In terms of product quality, particle size control was significantly improved. The average particle size of all ointment formulations was stabilized at 1.5-3 μm, and the Span value was controlled within 0.85, eliminating granularity and improving skin spreadability. Stability performance was fully compliant with regulatory requirements—after 6 months of accelerated testing (40℃±2℃, RH 75%±5%) and 12 months of long-term testing (25℃±2℃, RH 60%±10%), no phase separation, oil precipitation, or crystallization occurred. The content of active ingredients remained within the allowable variation range (±5%), and pH value and viscosity fluctuations were controlled within ±0.3 and ±1,000 mPas, respectively. Batch consistency was greatly enhanced, with the pass rate of quality inspections increasing from 88% to 99.5%.
In terms of production efficiency, the processing cycle per batch was shortened from 3.5 hours to 50 minutes, a reduction of 76.2%. The emulsifier's high throughput capacity enabled the facility to increase daily production from 5 tons to 18 tons, effectively meeting the increased market demand during peak periods. The automatic control system and data traceability function reduced the time required for batch record sorting by 60%, and the simplified process reduced labor intensity, with each operator capable of monitoring two production lines simultaneously.
In terms of operational costs, energy consumption per ton of product decreased by 38% compared with the traditional process, thanks to the high-efficiency emulsification and frequency conversion speed regulation function. Maintenance costs were reduced by 45%—the wear-resistant rotor-stator structure extended the service life of core components by 2-3 times, and the easy-to-clean design shortened cleaning time by 50% and reduced detergent consumption. Additionally, the equipment's compliance with pharmaceutical regulatory standards reduced the risk of non-compliance penalties and product recalls, lowering potential economic losses.
Furthermore, the stable product quality improved user feedback—complaints related to skin irritation caused by uneven particles decreased by 90%, and the product's market reputation was significantly enhanced. The emulsifier's compatibility with multiple formulations also provided flexibility for new product development, reducing the pilot test cycle for new ointment products by 40%.
5. Summary and Experience
The application of the customized high-shear emulsifier in ointment production successfully resolved the technical bottlenecks of traditional processes, achieving a balance between product quality compliance, production efficiency, and regulatory adaptation. The key to this success lies in the precise matching between the equipment's technical characteristics and the unique requirements of ointment formulations—its high shearing force, precision temperature control, vacuum deaeration, and data traceability functions effectively addressed the problems of uneven particle size, poor phase stability, and inconsistent batches.
For enterprises engaged in pharmaceutical and daily chemical semi-solid formulations, selecting emulsification equipment that meets regulatory standards and matches formulation characteristics is a crucial step in process optimization. Sufficient pilot tests to determine optimal parameters and integrating equipment functions into the existing production flow can maximize the equipment's performance. The modular and intelligent design of the emulsifier also provides scalability for future production adjustments, enabling quick adaptation to changes in formulation specifications and regulatory requirements.
In the context of increasingly strict global pharmaceutical regulatory requirements and rising consumer demand for product quality, the application of high-efficiency, stable, and compliant emulsification equipment has become an important way to enhance core competitiveness. This case provides practical reference for the process optimization of ointments and similar semi-solid formulations, demonstrating the significant value of advanced processing equipment in promoting industrial upgrading and quality improvement in the pharmaceutical and daily chemical industries.
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