(470a) Defining a Scale-up Strategy for an Oil in Water Cosmetic Emulsion
A major driver in the cosmetic market is the rate at which new and innovative products are designed and engineered to fulfill consumerâs needs. As a result, the time required to introduce a product in the market is a paramount objective during product design. Despite different tools have been developed for in-silico product conception and design, and novel technologies enable high throughput prototyping and manufacturing, a major limiting factor remains in the scale-up process. During development of structured products in the cosmetics industry (e. g. emulsions), scale-up to industrial production is a time-consuming, resources-intensive, and complex process, reason why it frequently involves trial and error techniques.
Several variables need to be considered to ensure the product desired properties and its long-term stability. Variables such as mixing times, stirring rates, emulsification temperature, heating or cooling rates, equipment geometry, and ingredients addition procedures play a major impact in the final characteristics of the emulsified products. In the scale-up process all these variables require to be tuned and adjusted, through trial and error methods. This makes this process highly inefficient.
In this direction, different systematic scale-up techniques have been developed for emulsions production. Specifically, for water in oil, the use of process invariants such as some dimensionless numbers of the form NDÎ±, have been incorporated as key parameters during change of scale. While these techniques mainly focus in maintaining a defined drop size distribution, it has been verified that this doesnât guarantee to maintain all the emulsion characteristics. Additionally, most emulsified cosmetic products are oil in water emulsions, and there is lack of scale-up data in the open literature for this type of products.
Thus, the aim of this work is to study the influence of some process variables (emulsification temperature, stirring rates, cooling rate, and addition time) in the characteristics of an oil in water emulsion (drop size distribution, stability and rheological behavior). These were studied at different processing scales in order to define suitable scale-up strategies.
Experiments were carried out using a rotor stator mixer with tip speed between 0.5 m/s and 2 m/s, an anchor mixer in rates among 0.01 m/s and 0.5 m/s, addition times between 2 min and 9 min and emulsification temperatures between 70°C and 90°C. Additionally, the cooling rate was varied using cooling fluid temperatures between 6°C and 24°C. Based upon the obtained results at the different levels, a scale-up methodology is proposed for the production of oil in water emulsion products, taking into account resources and the time-to-market minimization.