Лако-красочные материалы — производство

An alcoholic fragrance provides almost complete freedom of choice; there is the possibility of acetal formation due to the interaction of the aldehyde and ketone functional groups, with the alcohol used as the carrier, but this often has a softening effect on the fragrance and is not perceived as a disadvantage. No other serious chemical constraints are placed on the choice of ingredients, i. e. most of the ingredients are stable in the aqueous alcoholic product. As discussed later, stability plays a major role in the choice of ingredients for an antiperspirant product.

The safety constraint has been defined in the brief and can be checked by computer analysis or by the safety officer at any time.

One of the ways in which ingredients can be classified is by their perceived odour properties. The most important facet, as far as the perfumer is concerned, is the odour description. Each perfume com­pany tends to have its own system of classifying odour, but in general there are invariably a set of odour families that tend to be subdivided into odour descriptors. Other important properties are odour intensity (and how sensitive the intensity is to dilution) and longevity of the ingredient on a relevant substrate; in this instance, the skin. During the development phase the relative longevity of initial perfume trials is compared on smelling blotters (thin, absorbent paper strips); only towards the end does the perfumer fine tune with trials on the skin. This is for practical reasons such as keeping the immediate environ­ment as odour free as possible, and that space on the perfumer’s arms is limited!

A search is made for ingredients that have the desired odour characteristics. For the Business Scents Ltd brief, market research indicates that exotic, tropical, fruity and watery floral muguet notes are desirable. This is the acceptable odour (hedonic) constraint in the degrees of freedom analogy. An initial trawl through the various databases indicates several-dozen contenders. Many of the tropical, fruity notes will have an ester or sulfurous functional grouping, whilst several aldehyde groups exhibit the desired watery muguet character, e. g. Lilial®, Lyral®, cyclamen aldehyde, Bourgeonal® and hydroxy — citronellal. Interestingly, a perfumer can often distinguish the typical odour of certain functional groups. Salicylates tend to have a woody character, which is modified by the length of the attached aliphatic chain or ring structure. Nitriles often smell somewhat metallic. Phenyl acetates usually exhibit aspects of honey, and so on.

The perfumer usually consults colleagues in the Natural Products Analysis department to establish new ideas for natural tropical, fruity notes (see Chapter 12). They provide some headspace analyses that should add interesting, novel top-notes to the fragrance creation… in this case a headspace analysis based on a selection of tropical fruits purchased from a market stall in Jakarta, Indonesia. Having checked with Quest’s Buying Department as to the commercial availability of the chemicals reported in the headspace analysis, it was found that several of those available had already been incorporated into a perfume called Tropical Cocktail. This has been used as a building block at approximately 2% in the final fragrance mix. Details of the headspace analysis of muguet and broom were also provided and the decision made to use a small quantity of broom absolute in the ‘Project Eve’ fragrance, to add a natural, fresh florality which would fit well with the watery muguet theme.

So, having collected a set of watery, floral ingredients and some exotic, fruity ingredient ideas, the perfumer starts to place the ingre­dients together in groups. The watery ingredients could be blended with other light, floral and woody ones. Similarly, an accord of exotic fruity materials may be combined with other suitable odorous ingredients, such as musk and citrus notes, for example bergamot and grapefruit. These two accords are mixed in various ratios until a satisfactory blend is achieved. Other ingredients can be added one by one to this composition to modify the effect. For example, touches of camomile oil add an interesting twist to the fruity top-notes, whilst a small quantity of Amberlyn® provides subtle amber end-notes. The process is iterative in that a trial formula is made, assessed on a smelling blotter, the formula adjusted, reassessed, and so on. At all times the overall evaporation profile of the fragrance is considered, together with any cost and skin safety constraints set by the customer. The ingredients used have a range of volatilities and intensities, and need to be blended carefully together so that no single ingredient dominates the effect of the others. The overall effect, as the perfume evaporates on warm skin, should be a gradual change from the volatile top-notes of the fragrance through the middle-note theme to the eventual end-notes retained on the skin. The ‘shape’ of the perfume should be maintained at all times; so, for example, as soon as a volatile note such as a fruity ester has evaporated there is a less volatile fruity note available to maintain the fruity theme in the middle period of the dry-down. Similarly, at the end of the fragrance life-cycle on the skin, still less volatile fruity notes (e. g. lactones) should be available. In the same way, the green muguet floral notes should keep their shape throughout the evaporation period. For an alcoholic fragrance, the top-notes approximately represent the first 15 minutes of the evaporation; the middle-notes account for the next 3-4 hours and constitute the heart of the fragrance, whilst the end-notes represent the final 5-8 hours and give tenacity and depth to the theme.