An innovative Silicone resin gum technology for long-lasting performances

Transcription

1 An innovative Silicone resin gum technology for long-lasting performances Authors: Morgane Le Meur 1, Anne-Marie Vincent 1, Marc Eeman 1, Céline Bougaran 1 and Isabelle Van Reeth 2 1 Dow Corning Europe S.A., Seneffe, Belgium 2 Dow Corning (China) Holding Co., Ltd., Shangai, China There is a growing consumer demand for a high long-lasting performance from foundations, blemish balm creams, lipsticks and mascaras. Personal Care formulators have capitalized on various solutions that allow resistance to parameters such as moisture, sebum, sweat, friction of clothes... These solutions include several silicone technologies providing filmforming and non-transfer properties. Based on their chemistry, silicones can be tailored to form a variety of films ranging from brittle to continuous, hard to flexible, transient to substantive with designed skin affinity. 1. Objective The objective of this study was to demonstrate the long-lasting performances of an innovative film-forming silicone technology named Silicone Resin Gum (Si RG). This unique technology was compared to three other silicone technologies: Silicone Acrylate, Silicone MQ Resin and Silicone Gum. Several test methods were used to demonstrate the long-lasting benefits of the materials, either neat or formulated into different color cosmetic applications. 2. Materials and methods 2.1 Materials Silicone materials Silicone Resin Gum (Si RG): Trimethylsiloxysilicate / Dimethiconol Crosspolymer, 4% active in isododecane. Silicone Acrylate (Si Acrylate): Acrylates / Polytrimethylsiloxymethacrylate Copolymer, 4% active in isododecane. Silicone MQ Resin (Si Resin): Trimethylsiloxysilicate, 1% active. Silicone Gum (Si Gum): Dimethiconol, 1% active.

2 2.1.2 Color cosmetic formulations Liquid foundations as Water-in-Oil emulsion, formulated at various contents of the silicone material in order to be at 5% active in the formulation. No silicone film-forming technology was added in the control formulation. Mascaras, formulated at various contents of the silicone material in order to be at 4% active in the formulation. No silicone film-forming technology was added in the control formulation. 2.2 Methods Water and sebum resistances are tested in vitro using a contact angle goniometer (CAM, KSV Instruments Ltd., Finland). The silicone material is diluted at wt% in isododecane and coated on glass slides at 5 µm. 3 µl sessile droplets of test fluids, ultrapure water or artificial sebum, are formed at the film surface and contact angles are measured over a 2 min period. Values are recorded directly after formation of the drop (T) and 2 min after (T2min). The experiment is performed in 4 replicates Film flexibility is also assessed following an in vitro test method. The silicone material is diluted at wt% in isododecane and manually coated on.33 mm thick red elastic rubber band (Four D Rubber Co. Ltd., United Kingdom) using a 5 µm gap cube applicator system (Sheen Instrument, CA, United States). Flexibility performance is evaluated by observing the development of film fractures whilst the rubber band is elongated up to % of its initial length Friction resistance is determined in vitro using a rubbing device (Washability tester, Braive Instruments, Belgium) and based on X-Ray Fluorescence analysis (Lab X, Oxford Instruments, UK) (Figure 1). The silicone material is diluted at wt% in isododecane, coated on a collagen film at 5 µm and dried at 32 C for 24 h. The film is then rubbed-off on a felt band 5-times at controlled speed, force and distance. The friction resistance is quantified by the amount of silicon atom present on the collagen surface. The experiment is performed in triplicate. Figure 1: Rubbing device (left) and XRF device (right)

3 2.2.4 The color durability of foundation is measured in vitro using a rubbing device (Washability tester, Braive Instruments, Belgium) and a portable spectrocolorimeter (Spectro-guide 45/ Gloss, BYK-Gardner GmbH, Germany) (Figure 2). Foundations are coated on Vitro-Skin (IMS Inc., ME, USA) at 25 µm and dried at 32 C for 24 h. The film of foundation is then rubbed-off on a felt 5-times and the color loss is quantified. The experiment is performed in duplicate. Figure 2: Rubbing device (left) and portable spectro-colorimeter (right) The color resistance of mascara is evaluated in vitro using an internallydeveloped test method..4g of mascaras are coated on Vitro-Skin (IMS Inc., ME, USA) on a test zone of 2.5 cm² using a spatula. Films are dried in an oven (Memmert GmbH, Germany) at 32 C for 12 h. 5 droplets ( µl each) of ultrapure water are spread onto the mascara coating using a small plastic spatula. A piece of soft Velcro (Velcro Industries, B.V., Netherland Antilles), which has been previously fixed to a weight of 14 g, is put in contact with the mascara surface for 15 s. The amount of mascara transferred to the Velcro is evaluated by measuring the L* value with a portable colorimeter from BYK-Gardner (Spectroguide 45/ Gloss, BYK-Gardner GmbH, Germany) on the Velcro (Figure 2 right). The experiment is performed in triplicate. 3 Results and discussion 3.1 Water and sebum contact angles Silicone polymers are known to form coatings of low surface energy. As expected, the four silicone technologies under investigation showed high water repellency properties with contact angle values above 1 at T (Figure 3). The four silicone technologies exhibited also high sebum repellency properties as shown by high contact angle values above 5 at T (Figure 4). The Si RG and Si Gum even reached values above 67 at T suggesting improved sebum resistance (Figure 4).

4 Sebum CA ( ) 33,9 53, 49,1 53, 67,7 62,4 74, 69,6 Water CA ( ) 13,3 99, 1,4 95,9 15,2 11,3 1,8 115,6 14 T : dark colors - T 2min : light colors Figure 3: Water contact angles ( ± standard deviation) T : dark colors - T 2min : light colors Figure 4: Sebum contact angles ( ± standard deviation)

5 3.2 Film flexibility The Si RG technology showed an excellent flexibility with no cracks appearing after % elongation of the film (Figure 5). This is an improvement compared to the Si Acrylate which demonstrated fine cracks and to the Si MQ Resin which showed poor film flexibility. Note that the Si Gum showed as well a high flexibility performance. Before elongation After % elongation Silicone Acrylate rylate Silicone MQ Resin Silicone Resin Gum Silicone Gum Figure 5: Pictures of the film surfaces before and after elongation 3.3 Friction resistance Higher amounts of residual silicon at the film surface after friction cycles translate into higher level of friction resistance. The neat Si RG demonstrated similar level of in vitro friction resistance than existing Si MQ Resin but less good than Si Acrylate (Figure 6). Note that the Si Gum film had no friction resistance.

6 Residual Si at the membrane surface 1 1 (% versus initial amount) Silicone Acrylate Silicone MQ Resin Silicone Resin Gum Silicone Gum Number of cycles on felt band Figure 6: Residual amounts of silicon (% ± standard deviation) as a function of the number of friction cycles. Higher values indicate higher friction resistance performance. 3.4 Color durability of foundation The lower the color loss, the higher is the color resistance. The foundation containing Si RG showed a higher color durability than the formulation chassis and the Si Gum based formulation (Figure 7). The Si RG based foundation had a similar level of color durability to the Si MQ Resin one but less efficient than the Si Acrylate one. Those results are in accordance with the friction resistance assessment performed on the neat films (Paragraph 3.3).

7 Color loss (ΔE) Formulation chassis Silicone Acrylate Silicone MQ Resin Silicone Resin Gum Silicone Gum Number of cycles on felt band Figure 7: Color loss of various foundations (± standard deviation) as a function of the number of friction cycles. Lower values indicate higher color resistance. 3.5 Color resistance of mascara The L* value corresponds to the level of darkness from (black) to 1 (white). The results are expressed as a difference from a blank Velcro. The lower the difference, the lower the mascara transfer. The mascara containing Si RG showed an increased transfer resistance after exposure to water compared to the Si MQ Resin based mascara (Figure 8). This last one demonstrated a poor level of mascara resistance which was similar to the formulation chassis.

8 L* difference 1,28 1,88 6,82 Formulation Chassis Silicone MQ Resin Silicone Resin Gum Figure 8: Color resistance of various mascaras expressed as the L* difference (± standard deviation) from blank Velcro. Lower values indicate lower color transfer after exposure to water. 4 Conclusion The Si RG technology demonstrated various long-lasting properties thanks to its ability to form a film on skin. Higher sebum contact angles were obtained for the neat Si RG suggesting a better sebum resistance than for both the Si Acrylate and Si MQ Resin. In addition, higher film flexibility was observed for the Si RG than for both the Si Acrylate and Si MQ Resin. With regard to the color resistance, the Si RG outperformed the Si MQ Resin in a mascara formulation after exposure to water but underperformed the Si Acrylate in a foundation formulation. The Si RG technology hence combines the high flexibility of Si Gum (poor long-lasting film former) with the long-lasting performances of film-forming agents like Si MQ Resin, hence giving the formulator an additional tool to meet consumer need for long-lasting cosmetics with comfort to wear. The Silicone Resin Gum technology provides long wear performance while keeping an aesthetically pleasing film at the skin surface. Additional cosmetic formulations were developed to characterize other benefits such as powder compaction, sensory profile and compatibilities with active ingredients, opening a wider horizon for multifunctional formulations.