Int J Cosmet Sci. 2014 Apr;36(2):148-58. doi: 10.1111/ics.12108.
Water-in-oil emulsions in lipsticks could have the potential to improve moisturizing properties and deliver hydrophilic molecules to the lips. The aim of this work was to investigate the effect of a continuous process (scraped surface heat exchanger (SSHE) and pin stirrer (PS)) on the physical and material properties of an emulsion-based lipstick by altering the processing conditions of both the SSHE and PS.
Emulsion formation was achieved using a SSHE and PS. Emulsions were analysed using nuclear magnetic resonance restricted diffusion (droplet size), texture analysis and rheology (mechanical properties).
Results showed that a higher impeller rotational velocity (IRV) (1500 r.p.m.) and a lower exit temperature (52°C) produce the smallest droplets (~ 4 μm), due to greater disruptive forces and a higher viscosity of the continuous phase. The addition of a PS reduces the droplet size (14-6 μm) if the SSHE has a low IRV (500 r.p.m.), due to greater droplet disruption as the emulsion passes through the PS unit. Results also show that if the jacket temperature of a SSHE is 65°C, so that crystallization occurs in both process and post-production, droplets can be integrated into the network resulting in a stiffer wax network (G' - 0.12, in comparison to 0.02 MPa). This is due to small crystals creating a shell around water droplets which can form connections with the continuous network forming a structured network. The addition of a pin stirrer can disrupt a formed network reducing the stiffness of the emulsion (0.3-0.05 MPa).
This work suggests the potential use of a continuous process in producing an emulsion-based lipstick, particularly when wax crystals are produced in the process. Future work should consider the moisturizing or lubricating properties of wax continuous emulsions and the release of hydrophilic compounds from the aqueous phase.
口红中的油包水乳液有可能改善保湿性能，并将亲水分子递送到嘴唇上。本工作的目的是通过改变刮面式换热器（SSHE）和搅拌棒（PS）的加工条件，研究连续工艺（SSHE 和 PS）对基于乳液的口红的物理和材料性能的影响。
使用 SSHE 和 PS 形成乳液。使用核磁共振受限扩散（液滴尺寸）、质地分析和流变学（力学性能）分析乳液。
结果表明，较高的叶轮转速（IRV）（1500 r.p.m.）和较低的出口温度（52°C）产生最小的液滴（~4μm），这是由于连续相的破坏力更大和粘度更高。如果 SSHE 的 IRV 较低（500 r.p.m.），则添加 PS 会减小液滴尺寸（14-6μm），因为乳液通过 PS 单元时液滴的破坏更大。结果还表明，如果 SSHE 的夹套温度为 65°C，导致在加工和生产后都发生结晶，则液滴可以整合到网络中，从而形成更硬的蜡网络（G' - 0.12，与 0.02 MPa 相比）。这是因为小晶体在水滴周围形成壳，可以与连续网络形成连接，形成结构化网络。添加搅拌棒可以破坏形成的网络，降低乳液的刚度（0.3-0.05 MPa）。
本工作表明，连续工艺在生产基于乳液的口红方面具有潜在用途，特别是在过程中产生蜡晶体时。未来的工作应考虑蜡连续乳液的保湿或润滑性能以及亲水分子从水相的释放。
