Лако-красочные материалы — производство

The client requires an effective antiperspirant product which is to be dispensed as an aerosol spray using a propane-butane blend as the propellent gas. Figure 9.4 illustrates the basic components of an aerosol.

The formulation that the applications chemist uses (Figure 9.5) is a powder in volatile silicone-fluid (cyclomethicone) suspension. This type of formulation requires the use of a special valve and actuator system, which allows the powder active (activated aluminium chlorhydrate) to be dispensed without clogging. The antiperspirant active chosen gives good sweat reduction, and has a suitable particle-size distribution which can be effectively dispensed through the valve and actuator. The cyclomethicone carrier fluid is sufficiently volatile to evaporate from the skin surface and is soluble in the propellant blend, giving a suspension system that is easily dispensed from the can. A high molecular weight silicone gum (diluted in cyclomethicone) is also included to help prevent the formation of an aerosol ‘cloud’, which can cause choking or sneezing if inhaled. It also provides a soft,

Figure 9.4 The basic components of an aerosol

Preparation

Thoroughly disperse the bentonite and activated aluminium chlorhydrate in the isopropyl myristate and DC 344 fluid, using a high-shear mixer. Add the DC 1401 and the fragrance, mixing well. Fill into internally lacquered aluminium aerosols, as shown above.

Figure 9.5 Dry aerosol antiperspirant formulation (a cyclomethicone, ex Dow Corning Int., Brussels, Belgium; b cyclomethicone and dimethiconol, ex Dow Corning)

moisturized skin feel, which is important for the image of such a prestige product.

What sort of problems can an aerosol antiperspirant cause the perfumer and the applications chemist? Empirical testing in a range of antiperspirant bases has identified a number of unstable perfumery ingredients, such as phenolic materials, unsaturated terpene alcohols and their esters (such as linalool, linalyl acetate), unsaturated or reactive aldehydes (such as Lilial® and Ligustral®) some essential oils (such as bergamot, lavender and rosemary), citrus oils, and spices, (such as nutmeg and black pepper), that can undergo chemical reactions in the presence of the acidic antiperspirant active. Such materials should be avoided. Being an aerosol product does in itself create a challenge; traces of metal ions can cause the active or perfume to discolour to pink or brown, which would not be very attractive under the arm or on clothes!

Solubility of the fragrance in the volatile silicone and the propane — butane, although not visible to the consumer, might cause a change in note of the perfume as it is dispensed. The potential for the product to cause can corrosion must also be evaluated. This can be tested by storage testing of the finished product in production specification cans. It is rare for modern anhydrous systems to present major corrosion problems, although all formulations should be checked, especially if they contain significant levels of water.

In any type of product, and especially aerosols, the balance between how the different components of the fragrance are perceived, the so — called odour balance, is altered compared with the neat fragrance oil. Very generally, in an aerosol system, the increased surface area afforded by the droplets of the aerosol spray, combined with the highly volatile propellant, tend to give a greater bias towards the more volatile components of the fragrance compound. This causes the initial fragrance perception to be biased towards the top-notes. Such a change in odour balance is especially marked in a product such as the anhydrous antiperspirant, with its high level of propellent. This is why all aerosol fragrances should be evaluated with a formulation and valve system as close as possible to the one used in the finished product. It is also a factor that the perfumer needs to consider when creating the ‘Eve’ fragrance modifications for this product.

In conclusion, this product is probably the most aggressive and potentially complex product of the five to perfume. It is highly likely that the fine fragrance formulation will need to be significantly modified to be stable in this medium, whilst still giving the overall impression (in use) that it has essentially the same smell.