The following patents describe different methods to overcome the problems of perfume instability and volatility, and to improve its lifespan on application
Fragrances are often compounds having two or more conjugated double bonds, and are sensitive to various chemicals and to oxidation. Consequently, unwanted interactions with ingredients in formulations may lead to an alteration of the fragrance note. In addition, fragrances or perfumes are mostly highly volatile, so perfume is lost in storage and after application.
The following patents provide different methods aimed at achieving these desirable outcomes.
1. Process for preparing liquid personal cleansing compositions which provide enhanced perfume deposition
US Patent 5,891,833
Application No 08/667,138
Granted 6 April 1999
Assignee Procter & Gamble
Described is a process for preparing liquid personal cleansing compositions that provide enhanced perfume deposition on the skin with increased fragrance longevity after application. The compositions in the patent include shower gels, hand soaps and shampoos, and comprise, in their most basic form, anionic and amphoteric surfactants; a volatile perfume; and water.
To enhance perfume deposition and longevity it is first mixed with a cationic polymer and, of the many mentioned, polyquaternium-10 is preferred by the applicants. The polymer must be fully hydrated and the method described in the patent involves adding 2g of polymer to 98g water at room temperature.
The solution is stirred overnight until the polymer is fully hydrated and the solution becomes clear. To 15g of this solution is added 0.50g of the volatile perfume to form a premix.
The personal cleansing composition is preferably a shower gel composed of about 10-15% sodium laureth sulfate and 3-5% cocamidopropyl betaine with sufficient sodium chloride to adjust the viscosity to between 5,000cps and 10,000cps.
Other optional ingredients are present to adjust its pH and to improve the aesthetics and sensorial properties of the composition; to this is added the perfume premix and the balance of the composition is water. There are many variations of this composition mentioned in the patent and this should only be accepted as an illustration.
The applicants claim that it is believed that the cationic material and the anionic surfactant form coacervates or ion-pairs and that the perfume becomes physically entrapped within the coacervate. The coacervate is believed to deposit onto the skin during the wash/rinse process, and the slow release of perfume from the coacervate provides a fragrance longevity benefit.
2. Cosmetic compositions including a crosspolymer obtained from copolymerisation of at least two different polyols and at least one dicarboxylic acid and at least one fragrance
US Patent 9,708,566
Application No 14/109,905
Granted 18 July 2017
The objective of the applicants was to improve the life of the fragrance after topical application of a composition to the skin. It was found that blending a fragrance with an effective amount of a crosspolymer obtained from the copolymerisation of at least two different polyols and at least one dicarboxylic acid provided powerful fixatives for all kinds of fragrances.
The long lasting effect is applied to both the top and base notes of a perfume, thus maintaining the complex profile required.
The preferred polyols are glycerol and trimethylpentanediol and their mixtures, and the preferred dicarboxylic acid is adipic acid. The preferred crosspolymer is a copolymerisation product of trimethylpentanediol, glycerol and adipic acid, and this is commercially available as Lexorez 200 from Inolex (INCI: Trimethylpentanediol/adipic acid/glycerin crosspolymer).
This type of polymer is also used for sunscreen, tanning and exfoliating compositions, and for skin lightening and insect repellents.
The fragrance can be any typically used in cosmetic products and present at a level of up to 12% of the final composition with the level of fixative approximately 25-50% that of the perfume.
3. Cosmetic composition comprising a bitter compound, a fragrance, an extract of Stevia and a salt
US Patent 9,750,673
Application No 13/601,446
Granted 5 September 2017
Many cosmetic compositions that are applied to the face may come into contact with the lips and have a bitter teste. Described is the use of an extract of Stevia in combination with sodium chloride for masking the bitterness of cosmetic or dermatological compositions without changing the nature of the fragrance or the colour of the composition.
Bitterness is a characteristic felt at the back of the tongue and palate, and the bitterness of an ingredient can be evaluated by placing 0.2g of an aqueous solution containing 0.1% and 5% by weight thereof on the area around the lips or on the lips of the members of a panel.
An aqueous solution of an ingredient is considered to be bitter if the average bitterness evaluated by the panel is at least equal to that of 0.2g of an aqueous solution of quinine at 8mmol/l.
Plants of the Stevia genus grow naturally in Paraguay, and are also cultivated in South America and Asia. In order to extract the sweetening agent, leaves of the plant are dried and reduced to powder, before undergoing aqueous extraction and then purification.
This powder is then used in conjunction with sodium chloride to mask the bitterness imparted to cosmetic compositions by organic components such as UV absorbers and perfumes.
Sufficient sweetener to mask the bitterness of the organic ingredient without destabilising the composition is generally from 0.4-0.5% of the Stevia extract with 0.2-0.4% sodium chloride by weight in the final composition and tests show that bitterness was masked for a minimum period of 15 minutes.
4. Fixing of perfume on wet skin
US Patent 9,107,841
Application No 13/606,570
Granted 18 August 2015
Imparts a scent-sensory impression both during use under the shower and after it, which has a long lasting effect that can be readily perceived by the consumer.
It is substantially emulsifier-free and comprises microcrystalline wax with one or more lipophilic perfume ingredients and one or more lipophobic perfume ingredients with a weight ratio of lipophilic to lipophobic of from about 0.5:1 to about 4:1. It was found that formulating outside of this range produces a different perfume impression where it is either not recognisable while showering or can no longer be perceived after showering.
Many possible fragrance components are listed and the total perfume level in the final composition is about 1%.
The composition also contains at least two polyacrylic polymers; acrylates/C10-30 alkyl acrylate crosspolymers and carbomers are much preferred. At least one polymer has emulsifying properties and at least one improves the sensory and stability properties of the final composition. These are present up to a combined maximum level of 2% by weight.
The final composition also contains 3-14% fatty alcohols, at least 5% hydrocarbon oils and at least 15% microcrystalline wax, and the total of microcrystalline wax plus hydrocarbon oils is between 20-40% by weight.
The fatty alcohols are a mixture of myristyl alcohol, stearyl alcohol and cetearyl alcohol.
The final composition also contains at least 4% glycerin and 45% water.
Other ingredients may be incorporated that improve the aesthetics and shelf life of the preparation, but surfactants are to be avoided.