Лако-красочные материалы — производство

Whereas it used to be thought that the skin was an impermeable barrier to the outside world, it is now known that a large number of chemicals are absorbed to some degree, including those used in fragrances (Hotchkiss, 1994). The actual amount that penetrates the skin depends on how much is applied to which area of the body, the area that it is spread over, whether the skin is covered or not and whether the product is rinsed from the skin before absorption can take place. The nature of the product being used can also affect the level of absorption, as it has been shown that the alcohol used as a carrier in fine fragrances and aftershaves enhances the penetration of some fragrance ingredients. Not that penetration per se is harmful, as many angina sufferers will testify. The absorbtion of glyceryl trinitrate through the skin used to be used as a rapid way of relieving the pain of this complaint.

For some fragrance ingredients, penetration through the stratum corneum into the epidermis can elicit an immune response leading to allergic contact dermatitis or skin sensitization. Initially, exposure to a skin sensitizer has no effect, but repeated exposure can induce an allergy, which can then occur on contact with the material at levels below that needed to have an irritant effect. This allergy usually appears 1-2 days after contact and often becomes more severe over the next 2-3 days. The reaction does not diminish as an irritant reaction does, but may last several days or even weeks after exposure. In severe cases the sufferer not only needs to avoid the cause of the allergy, but also any products that contain a significant percentage of it.

For those materials that RIFM has shown to be sensitizers, IFRA has either applied a restriction or banned their use (Table 10.1). In some

cases, IFRA has ruled that only material of a set purity or botanical source can be used in fragrances. For example, IFRA recommends that crude gums of American and Asian styrax should not be used as fragrance ingredients. Only extracts or distillates (resinoids, absolutes and oils), prepared from exudations of Liquidamber styracifua L var macrophylla or Liquidamber orientalis Mills, can be used and should not exceed a level of 0.6% in a consumer product. For acetylated vetiver oils, IFRA has recommended that they only be used as fragrance ingredients if they are produced by a method which gives products free from allergens. Such acetylated vetiver oils can be prepared using acetic anhydride:

—without a catalyst and at a temperature not exceeding 120 °С;

—with ortho-phosphoric acid at room temperature;

—with sodium acetate in toluene at reflux temperature.

The first two products can be used in their crude form after the usual washing procedures, but may be further purified. In the last case, distillation is necessary to give a suitable product.

Table 10.1 gives a list of the materials that are banned or restricted by the guidelines. It is interesting to note that the sensitization caused by some fragrance ingredients can be suppressed. Neither lemongrass oil nor litsea cubeba oil are sensitizers although both contain over 70% of citral (5), which can cause sensitization at levels below 0.5% (Opdyke, 1976). Both of these oils also contain up to 20% of citrus terpenes, such as d-limonene (6) and a-pinene (7), which have been shown to prevent citral inducing a sensitization reaction (Opdyke, 1979), an effect which the industry refers to as ‘quenching’. IFRA now recommends that citral be used only in conjunction with 25% of d — limonene or a-pinene. Other sensitizers that can be ‘quenched’ include cinnamic aldehyde (8) with an equal weight of d-limonene or eugenol (9) and phenylacetaldehyde (10) with equal weights of 2-phenyl — ethanol (11) or dipropylene glycol (12).