Patent Application
20120272988
The present invention relates to a depilatory method and kit.
Depilatory compositions are cosmetic hair removal formulations. They comprise keratin reducing agents, which attack the disulphide bonds in hair to weaken it, such that subsequent gentle scraping and/or wiping completes severance of the hair from the skin and effects hair removal. Commercially, the most common keratin reducing agents are thioglycolates, which are typically formulated at high pH. An unwanted side effect of chemical depilation is that the depilatory composition comes into contact with and must have a relatively long residence time on skin to achieve effective hair removal and this long residence time combined with the alkaline conditions needed for effective hair removal may give rise to skin irritation.
The above problem has been recognized in the art. Reference is made to U.S. Pat. No. 4,401,663 and U.S. Pat. No. 4,424,205 the disclosures of which are similar to one another. These documents teach to use certain compounds as topical analgesics and an example given of a situation in which it is suggested to use such materials is to reduce depilatory irritation. The carrier formulas disclosed to be suitable for formulation with the analgesics include lotions and creams.
Reference is also made to US 2004/0219118, which discloses treatment with a “lipophilic” material before application of a thioglycolate-based reactive depilatory composition. Lipophilic materials exemplified in this patent application are oils, such as mineral oil. As shown hereinbelow, the present applicants have tested a range of lipophilic materials to determine their ability to prevent thioglycolate penetration and, thereby, their ability to reduce or prevent skin irritation Applicants have surprisingly found that oils, such as mineral oil, have no or a low ability to prevent thioglycolate penetration to the skin. There thus exists a need to develop a pre-treatment composition which better reduces skin irritation.
According to a first aspect of the invention, a method of removing hair from skin is provided, comprising the steps of:
According to a second aspect of the invention, a depilatory kit is provided, comprising:
The protective composition used in the method and comprised within the kit according to the invention comprises from 1% to 60%, preferably from 2% to 24% and, more preferably, 3% to 15% wax by weight of the protective composition. As demonstrated by the Franz Cell data below, the presence of some wax in the protective composition surprisingly reduces penetration by thioglycolic acid in comparison with oils. Without wishing to be bound by theory, applicants believe that this may be because the wax militates against the tendency otherwise exhibited by oils to ball up on skin and therefore disrupt the barrier. The wax also ensures that a thin barrier of the protective composition can be evenly distributed across the skin, even at a low dosage per unit area. The wax may form a substantive barrier across the skin (enhanced by an amorphous mix of the oil & wax) that is chemically resistant to ingress from the thioglycolate (or other reducing) actives, therefore physically reducing the ability for the harsh chemistry to come into contact with the skin. This reduction in contact means that the stratum corneum may be maintained in a better state than if no barrier were present with correspondingly reduced signs of irritation, such as erythema, tingling and stinging. At wax levels above 60% by weight, the protective composition may become difficult to handle and apply and may also be brittle, crack and fall off the skin.
Applicants have also established that the use of the present protective composition still permits hair weakening and destruction by the keratin reducing agent, so that reduced skin irritation can be achieved while still removing hair.
A reduction of thioglycolic acid penetration of 45% or more according to the Franz Cell method may be shown to correlate to a significant and user-noticeable reduction in irritation.
As used herein, the term “wax” includes, but is not limited to, any hydrophobic material that is:
The wax may comprise natural wax, synthetic wax, silicone wax, or mixtures thereof.
Non-limiting examples of suitable natural waxes include Abies Alba Leaf Wax, Acacia Dealbata Leaf Wax, Acacia Farnesiana Flower Wax, Beeswax, Ceresin, Cetyl Esters, Cistus Labdaniferus Flower Wax, Aurantium Amara (Bitter Orange) Flower Wax, Aurantium Dulcis (Orange) Peel Wax, Copernicia Cerifera (Carnauba) Wax, Eclipta Prostrata Wax, Euphorbia Cerifera (Candelilla) Wax, Helichrysum Angustifolium Wax, Jasminum Officina le (Jasmine) Flower Wax, Jasminum Sambac (Jasmine) Flower Wax, Jojoba Esters, Jojoba Wax, Lanolin Wax, Lavandula Angustifolia (Lavender) Flower Wax, Lawsonia Inermis Wax, Mink Wax, Montan Acid Wax, Montan Wax, Myrica Cerifera (Bayberry) Fruit Wax, Ocimum Tenuiflorum Wax, Olive Wax, Oryza Sativa (Rice) Bran Wax, Ouricury Wax, Palm Kernel Wax, Persea Gratissima (Avocado) Wax, Pistacia Lentiscus Leaf Wax, Polianthes Tuberosa Flower Wax, Pyrus Malus (Apple) Peel Wax, Ribes Nigrum (Black Currant) Wax, Rosa Centifolia Flower Wax, Salvia Sclarea (Clary) Wax, Shellac Wax, Simmondsia Chinensis (Jojoba) Butter, Soft Olive Wax, Spent Grain Wax, Stipa Tenacissima Wax, Sunflower Seed Wax, Vegetable Wax, Vitis Vinifera (Grape) Leaf Wax and mixtures thereof.
Non-limiting examples of suitable synthetic waxes include Hydrogenated Japan Wax, Hydrogenated Jojoba Oil, Hydrogenated Jojoba Wax, Hydrogenated Microcrystalline Wax, Hydrogenated Rice Bran Wax, Hydrolyzed Beeswax, Microcrystalline Wax, Oxidized Beeswax, Oxidized Microcrystalline Wax, Ozokerite, Paraffin, PEG-6 Beeswax, PEG-8 Beeswax, PEG-12 Beeswax, PEG-20 Beeswax, PEG-12 Carnauba, Potassium Oxidized Microcrystalline Wax, Sulfurized Jojoba Oil, Synthetic Beeswax, Synthetic Candelilla Wax, Synthetic Carnauba, Synthetic Japan Wax, Synthetic Jojoba Oil, Synthetic Wax and mixtures thereof.
Non-limiting examples of suitable silicone waxes include DC2503 Cosmetic Wax, DC580 wax, DC AMS-C30 Cosmetic Wax, C30-45 Alkyl, Methicone, DC Silkywax 10, Hexamethyldisiloxane, DC ST-Wax 30, C30-45 Alkyldimethylsilyl Polypropylsilsesquioxane, DC SW-8005 resin wax, C26-28 Alkyl Dimethicone, C26-28 Alkyl Methicone, Polyphenylsilsesquioxane and mixtures thereof.
Advantageously, the wax comprises beeswax, carnauba wax, candelilla wax, jojoba wax, paraffin wax, microcrystalline wax, ozokerite, arachidyl behenate, or mixtures thereof.
The protective composition used in the method and comprised within the kit according to the invention comprises ethanol. While the presence of wax in the protective composition may significantly improve its barrier properties, it has been observed that, depending upon factors such as the type of wax used and the amount of wax used, the protective composition may be too viscous to spread effectively, reducing efficiency in use. The presence of the defined amount of ethanol may thin the composition, facilitation improved spreadability and ease of application, while retaining acceptable barrier properties.
The protective composition comprises from 1% to 25%, preferably from 5% to 21% and more preferably from 9% to 21% by weight of the protective composition of ethanol.
The protective composition used in the method and comprised within the kit according to the invention may comprise one or more oils. As used herein, the term “oil” includes, but is not limited to any non-aqueous substance that is practically insoluble in water according to the United States' Pharmacopeia (USP) definition in 31/NF 26 Vol. 2 General Notices, Page Xvii. (which, according to that definition, means that more than 10,000 parts of water are needed to dissolve 1 part solute) and is liquid at 20° C.
The protective composition used in the method and comprised within the kit according to the invention may comprise from 40-98%, preferably from 76% to 98% and, more preferably, from 85% to 97% oil by weight of the protective composition.
The oil may be selected from natural oil, synthetic oil, silicone oil and mixtures thereof.
Non-limiting examples of suitable natural oils include Acetylated Castor Oil, Acetylated Hydrogenated Castor Oil, Actinidia Chinensis (Kiwi), Seed Oil, Adansonia Digitata Oil, Aleurites Moluccana Seed Oil, Anacardium Occidentale (Cashew) Seed Oil, Arachis Hypogaea (Peanut) Oil, Arctium Lappa Seed Oil, Argania Spinosa Kernel Oil, Argemone Mexicana Oil, Avena Sativa (Oat) Kernel Oil, Bertholletia Excelsa Seed Oil, Borago Officinalis Seed Oil, Brassica Campestris (Rapeseed) Seed Oil, Calophyllum Tacamahaca Seed Oil, Camellia Japonica Seed Oil, Camellia Kissi Seed Oil, Camellia Oleifera Seed Oil, Canola Oil, Caprylic/Capric/Lauric Triglyceride, Caprylic/Capric/Linoleic Triglyceride, Caprylic/Capric/Myristic/Stearic Triglyceride, Caprylic/Capric/Stearic Triglyceride, Caprylic/Capric Triglyceride, Carthamus Tinctorius (Hybrid Safflower) Seed Oil, Carthamus Tinctorius (Safflower) Seed Oil, Carum Carvi (Caraway) Seed Oil, Carya Illinoensis (Pecan) Seed Oil, Castor Oil Benzoate, Chenopodium Quinoa Seed Oil, Cibotium Barometz Oil, Citrullus Vulgaris (Watermelon) Seed Oil, Cocos Nucifera (Coconut) Oil, Cod Liver Oil, Coffea Arabica (Coffee) Seed Oil, Coix Lacryma-Jobi (Job's Tears) Seed Oil, Corylus Americana (Hazel) Seed Oil, Corylus Avellana (Hazel) Seed Oil, Cucumis Sativus (Cucumber) Oil, Cucurbita Pepo (Pumpkin) Seed Oil, Daucus Carota Sativa (Carrot) Seed Oil, Elaeis Guineensis (Palm) Kernel Oil, Elaeis Guineensis (Palm) Oil, Gossypium (Cotton) Seed Oil, Helianthus Annuus (Hybrid Sunflower) Oil, Helianthus Annuus (Sunflower) Seed Oil, Hippophae Rhamnoides Oil, Human Placental Lipids, Hydrogenated Canola Oil, Hydrogenated Castor Oil, Hydrogenated Castor Oil Laurate, Hydrogenated Castor Oil Triisostearate, Hydrogenated Coconut Oil, Hydrogenated Cottonseed Oil, Hydrogenated C12-18 Triglycerides, Hydrogenated Fish Oil, Hydrogenated Lard, Hydrogenated Menhaden Oil, Hydrogenated Mink Oil, Hydrogenated Olive Oil, Hydrogenated Orange Roughy Oil, Hydrogenated Palm Kernel Oil, Hydrogenated Palm Oil, Hydrogenated Peanut Oil, Hydrogenated Rapeseed Oil, Hydrogenated Shark Liver Oil, Hydrogenated Soybean Oil, Hydrogenated Sunflower Seed Oil, Hydrogenated Tallow, Hydrogenated Vegetable Oil, Isatis Tinctoria Seed Oil, Juglans Regia (Walnut) Seed Oil, Lauric/Palmitic/Oleic Triglyceride, Umnanthes Alba (Meadowfoam) Seed Oil, Unum Usitatissimum (Linseed) Seed Oil, Lupinus Albus Seed Oil, Macadamia Integrifolia Seed Oil, Macadamia Ternifolia Seed Oil, Maleated Soybean Oil, Mangifera Indica (Mango) Seed Oil, Marmot Oil, Melaleuca Alternifolia (Tea Tree) Leaf Oil, Melia Azadirachta Seed Oil, Melissa Officina lis (Balm Mint) Seed Oil, Menhaden Oil, Mink Oil, Moring a pterygosperma Seed Oil, Mortierella Oil, Neatsfoot Oil, Nelumbium Speciosum Flower Oil, Nigella Sativa Seed Oil, Oenothera Biennis (Evening Primrose) Oil, Olea Europaea (Olive) Fruit Oil, Olea Europaea (Olive) Husk Oil, Orange Roughy Oil, Orbignya Cohune Seed Oil, Orbignya Oleifera Seed Oil, Oryza Sativa (Rice) Bran Oil, Oryza Sativa (Rice) Germ Oil, Ostrich Oil, Oxidized Corn Oil, Oxidized Hazel Seed Oil, Papaver Orientale (Poppy) Seed Oil, Passiflora Edulis Seed Oil, Persea Gratissima (Avocado) Oil, Pistacia Vera Seed Oil, Placental Lipids, Prunus Amygdalus Amara (Bitter Almond) Kernel Oil, Prunus Amygdalus Dulcis (Sweet Almond) Oil, Prunus Armeniaca (Apricot) Kernel Oil, Prunus Avium (Sweet Cherry) Seed Oil, Prunus Cerasus (Bitter Cherry) Seed Oil, Prunus Persica (Peach) Kernel Oil, Pyrus Malus (Apple) Oil, Ribes Nigrum (Black Currant) Seed Oil, Ricinus Communis (Castor) Seed Oil, Rosa Canina Fruit Oil, Rosa Moschata Seed Oil, Salmon Oil, Salvia Hispanica Seed Oil, Santalum Album (Sandalwood) Seed Oil, Sesamum Indicum (Sesame) Seed Oil, Shark Liver Oil, Solanum Lycopersicum (Tomato) Seed Oil, Soybean Lipid, Sphingolipids, Taraktogenos Kurzii Seed Oil, Telphairia Pedata Oil, Vegetable Oil, Vitis Vinifera (Grape) Seed Oil, Zea Mays (Corn) Germ Oil, Zea Mays (Corn) Oil and mixtures thereof.
Non-limiting examples of suitable synthetic oils include mineral oil, isopropyl pamitate, isopropyl stearate, isohexadecane, isododecane, polyglyceryl triisostearate and mixtures thereof. Non-limiting examples of suitable silicone oils include dimethicones (including partial esters of dimethicones and fatty acids derived from natural/synthetic oils), cyclomethicones, polydimethlysiloxanes (e.g. DC200 from Dow Corning), phenyl trimethicones, trimethyl pentaphenyl trisiloxane, dimethicone copolyols and mixtures thereof.
The protective composition used in the method and comprised within the kit according to the invention may comprise one or more triglycerides, the or each triglyceride having the following formula:
wherein R, R′ and R″ may be the same as or different from one or both of the others, wherein each of R, R′ and R″ is a fatty acid and wherein the or each triglyceride is solid at 25° C.
Advantageously, the or each triglyceride has an onset temperature of less than 65° C. as measured by Differential Scanning calorimetry. At and above an onset temperature of 65° C., the composition may become increasingly difficult to apply and may, in addition, crack and fall off in use.
Suitable oils from which triglycerides may be formed from include, but are not limited to, the oils listed herein. Suitable fatty acids for formation of triglycerides include, but are not limited to, Myristoleic acid, Palmitoleic acid, Sapienic acid, Oleic acid, Linoleic acid, α-Linolenic acid, Arachidonic acid, Eicosapentaenoic acid, Docosahexaenoic acid, Lauric acid (C12), Myristic acid (C14), Palmitic acid (C16), Stearic acid (C18), Arachidic acid (C20) and mixtures thereof.
Specific sources of triglycerides suitable for inclusion in the protective composition include include Butter, Shea Butter, Butyrospermum Parkii, Lipex Shea, Theobroma Cacao (Cocoa) Seed Butter, Cocoa Butter, Hydrogenated Shea Butter, Hydrogenated Cocoa Butter, Irvingia Gabonensis Kernel Butter, Tallow, Lard, Mangifera Indica (Mango) Seed Butter, Kokum Butter and mixtures thereof. The triglyceride(s) may fall under the definition of “wax” or “oil” as used herein and, in such a case, should be included as a wax or oil for the purposes of determining the proportions of wax or oil.
The protective composition used in the method and comprised within the kit according to the invention may comprise skin active agents such as, but not limited to oil soluble vitamins, such as vitamin E derivatives, including vitamin E acetate and tocopherol nicotinate; oil-soluble vitamin A derivatives, such as retinyl palmitate; lanolin; ceramides; sterols and sterol esters; salicylic acid; camphor; eucalyptol; essential oils and mixtures thereof. These materials may fall under the definition of “wax” or “oil” as used herein and, in such a case, should be included as a wax or oil for the purposes of determining the proportions of wax or oil.
The protective composition used in the method and comprised within the kit according to the invention may include further ingredients such as, but not limited to metal oxides, organic and inorganic dyes, lakes, micas, flavourings, perfumes and mixtures thereof.
Any depilatory composition comprising a suitable keratin reducing agent may be used in the present method and included in the present kit. Non-limiting examples of suitable keratin reducing agents include: sulphide salts such as Li2S, Na2S, K2S, MgS, CaS, SrS or BaS, hydrogen sulphide salts such as NaSH or KSH; thioglycol; thioglycerol; thioglycolamide; thioglycolhydrazide; thioglycolic acid; thioglycolate salts (such as potassium thioglycolate, calcium thioglycolate, ammonium thioglycolate, diammonium dithioglycolate, glyceryl monothioglycolate, or monoethanolamine thioglycolate); thiosalicylic acid; thiomalic acid; ammonium thiolactate; monoethanolamine thiolactate; dithioerythritol; 2-mercaptopropionic acid; 1,3-dithiopropanol; glutathione; dithiothreitol; cysteine; homocysteine; N-acetyl-L-cysteine and cysteamine. Advantageously, the keratin reducing agent is comprised within the depilatory composition in an amount from 0.3% to 20%, preferably from 0.8% to 15%, more preferably from 1% to 10% by weight of the depilatory composition.
Advantageously, the depilatory composition may comprise at least one thioglycolate salt or thioglycollic acid acting as a hair removal agent when the depilatory composition is applied to unwanted hair. Preferably, the depilatory composition comprises sodium, potassium, magnesium, calcium, beryllium, strontium, zinc, monoethanolamine, ammonium, tetralkylammonium, imidazolium, pyridinium, phosphonium or glyceryl thioglycolate salts, or mixtures thereof, which may include dianion forms of thioglycolate. More preferably, the depilatory composition comprises at least one of sodium, potassium, magnesium or calcium thioglycolate, or mixtures thereof. Even more preferably the depilatory composition comprises potassium or calcium thioglycolate, or mixtures thereof.
The pH of the depilatory composition may advantageously be in the range of from 6 to 13.8, preferably from greater than 7 to 13, more preferably from 9 to 12.9, even more preferably from 10 to 12.8, even more preferably still from 12 to 12.75 and yet more preferably from 12.3 to 12.6 to improve the efficacy of the active ingredient. The depilatory composition may, in a preferred embodiment, comprise at least one base to control the pH. Preferably, the depilatory composition comprises potassium hydroxide; sodium hydroxide; lithium hydroxide; calcium hydroxide; barium hydroxide; caesium hydroxide; sodium hydroxide; ammonium hydroxide; strontium hydroxide; rubidium hydroxide; magnesium hydroxide; zinc hydroxide; sodium carbonate; pyridine; ammonia; alkanolamides (including monoethanolamine, diethanolamine, triethanolamine), phosphates (including tetrasodium phosphate), arginine or mixtures thereof. More preferably, the depilatory composition comprises at least one buffering base, even more preferably the depilatory composition comprises calcium hydroxide, magnesium hydroxide; barium hydroxide; strontium hydroxide; zinc hydroxide; arginine or mixtures thereof. Still more preferably the depilatory composition comprises calcium hydroxide; magnesium hydroxide, zinc hydroxide, sodium hydroxide, potassium hydroxide or mixtures thereof. Even more preferably still, the depilatory composition comprises calcium hydroxide, sodium hydroxide or mixtures thereof.
In an advantageous embodiment, the base is present at a concentration of from 0.1% to 10.0%, more preferably from 0.5% to 8.0% and even more preferably from 1.0% to 5.0%, by weight of the depilatory composition.
The concentration of water in the depilatory composition is preferably at least 40%, more preferably from 50% to 98%, even more preferably from 60% to 95% and even more preferably still from 70% to 90%, by weight of the depilatory composition.
The depilatory composition may optionally comprise a thickening agent. A representative but not exhaustive list can be found in “The Encyclopaedia of Polymers and Thickeners for Cosmetics” compiled and edited by Robert Y. Lochhead, PhD and William R. Fron, Department of Polymer Science, University of Southern Mississippi. Exemplary classes of thickening agents include gums, carbomers, polymers and copolymers of acrylic acid, associated thickeners, layered silicates/clays and natural polymers (including polysaccharides). One or more thickening agents may be included in the aqueous depilatory composition. The thickening agent may be present at a level of from about 0.01% to about 20%, preferably from about 0.1% to about 10% by weight of the depilatory composition.
The depilatory composition may also include other skin care ingredients such as conditioning agents selected from the group consisting of humectants, moisturizers, or skin conditioners (including mineral oil; almond oil; chamomile oil; jojoba oil; avocado oil; shea butter, niacinamide and glycerine); skin rejuvenation compositions (for example targeted for fine lines, wrinkles and uneven skin tone, including retinoids), cosmetic compositions; anti-inflammatory agents (including corticosteroids); anti-oxidants (including flavonoids) radical scavengers; sunscreen agents; skin cooling or warming agents and the like. The depilatory composition may comprise one or more skin care ingredients present in an amount of from about 0.001% to about 10%, more preferably from about 0.01% to about 7%, and even more preferably from about 0.025% to about 5%, by weight of the depilatory composition.
An accelerant may be employed in the depilatory composition. This optional component accelerates the rate of depilatory action of the depilatory agent. Suitable accelerants include, but are not limited to, urea; thiourea; dimethyl isosorbide; arginine salts; ethoxydiglycol; propylene glycol and methylpropyldiol. The accelerant may be present in a concentration range of from 0.5% to 10%, more preferably from 2% to 8% and even more preferably from 2% to 5% by weight of the depilatory composition.
The depilatory composition may further comprise components known, conventionally used, or otherwise effective for use in cosmetic compositions, such as dyes; pigments (including ultra marines and talc); anionic, cationic, non-ionic and/or amphoteric or zwitterionic surfactants, polymers (including hydrophobically modified polymers); dispersing agents; solvents; lubricants; fragrances; preservatives; chelants, proteins and derivatives thereof, plant materials (e.g. aloe, chamomile and henna extracts); silicones (volatile or non-volatile, modified or non-modified); film-forming agents; film forming promoters and mixtures thereof.
The depilatory composition may be formulated in any common delivery form, such as a cream or lotion. Alternatively, it may be delivered on a substrate, such as a thin film of depilatory composition coated onto the substrate. The substrate may be configured in any suitable form, such as a strip, mask or patch.
In addition to the protective composition and the depilatory composition, the kit according to the second aspect of the invention may comprise one or more of:
Prior to applying the method or using the kit according to the present invention, a user should advantageously remove all make-up from the skin, to ensure good adherence and effective application of both the protective composition and the depilatory composition.
The method according to the first aspect of the invention comprises the step of applying the above-defined protective composition to an area of skin on which unwanted hair is growing. The area of skin may be located on any part of the human body.
Advantageously, the protective composition is not just applied to the area to be depilated, but also to an immediately juxtaposing area thereabout (that is, the protective composition is applied to an area of skin which is greater than just the area which is to be depilated).
Advantageously, the user will apply from 0.3-2 mg of protective composition per square centimetre of skin, preferably from 0.4-1 mg/cm2, more preferably from 0.4 to 0.7 mg/cm2.
Following application, the protective composition is advantageously massaged into the skin. Preferably, massaging is effected for at least 10 seconds, and, more preferably, massaging is effected as a circular motion. Without wishing to be bound by theory, it is believed that the protective composition may trap hair within it thereby shielding it from the to-be-applied depilatory composition; massaging may help to release the hairs from the skin and ensure improved access thereto by the depilatory composition.
The method according to the first aspect of the invention comprises the subsequent step of applying the above-defined depilatory composition to an area of skin on which unwanted hair is growing and to which protective composition has already been applied. Advantageously, the user will apply a layer of depilatory composition which is from 0.1 mm to 5 mm, preferably from 0.3 to 3 mm, more preferably from 0.5 to 2 mm in thickness.
Subsequently, according to the method of the first aspect of the invention, the depilatory composition is advantageously left in place for at least 1 minute, preferably from 1 to 10 minutes, more preferably from 3 to 10 minutes, depending on the thickness of the hair and the hair removal efficacy of the depilatory composition (which, in turn, is dependent upon the concentration of keratin reducing agent in the depilatory composition).
Subsequently, according to the method of the first aspect of the invention, the protective composition and the depilatory composition are advantageously removed. This may be achieved using one or more of a cotton wool ball, pad or wand, a tissue, a cloth, or a tool, such as a spatula or a scraper. Advantageously, the skin from which hair has been removed is then rinsed with water.
In an advantageous subsequent step, a post-treatment skin care composition may be applied to the area of skin from which hair has been removed. Such a post-treatment skin care composition may comprise ingredients to promote skin conditioning; moisturizers, skin rejuvenation compositions (targeted for fine lines, wrinkles and uneven skin tone, for example), cosmetic compositions (e.g., foundation, rouge), sunscreens and the like. The post-treatment skin care composition may be leave-on or a rinse-off composition.
This method is the American Oil Chemists' Society Method Cj 1-94, as reapproved in 2009 and it determines the “onset temperature” (that is the temperature of onset of melting) of oils and fats by differential scanning calorimetry (DSC).
1. Aluminum capsules.
2. DSC instrument, capable of holding temperature at −60° C. and achieving a temperature of 80° C.
1. Indium, powder—60 mesh, 99.999%, such as Aldrich Chemical Co., Milwaukee, Wis. 53233, or equivalent.
2. n-Decane, 99+%, such as Aldrich Chemical Co., Milwaukee, Wis. 53233, or equivalent.
3. Methyl stearate, 99%, such as Aldrich Chemical Co., Milwaukee, Wis. 53233, or equivalent.
1. Standardization of equipment—Proceed with the normal standardization using both indium and n-decane as reference standards. Follow instrument manual for adjustment to lock onto these two reference points and flatten the baseline slope as much as possible when empty pans are analyzed. Analyze the secondary standard (methyl stearate). Weigh 5 mg of the standard into the same kind of pan which will be used for the test portion (if hermetically sealed, it may be reused at a later date). Use the method sequence in Procedure, 2-7 to obtain the melting point onset (because of the high purity, only a 2 min hold is necessary for the standard after crystallization). Be certain that the heating rate during the definitive heating pattern is at 5° C./min. The melting point onset should be within ±2.00° C. of 36.5° C. If not, recheck calibration.
Note—be certain to use identical capsules for the test portion as those used for reference standards and the instrument blank reference.
2. Melt each test portion completely and weigh 7±0.200 mg of each test portion into the same kind of capsule used for the blank and reference samples (aluminum) and seal to minimize oxidation and other changes.
3. Place capsules in DSC at room temperature.
4. Heat rapidly to 80° C. and hold for 10 min.
5. Cool to −60° C. at 10° C./min and hold for 30 min.
6. Heat to 80° C. at 5° C./min.
7. Use the baseline obtained for an empty capsule analysis from the final melt segment of the program to define the position of the baseline under the sample peaks. Overlay the final melting curve of the test portion over the curve for the empty capsule with a flexible ruler or other curve guide to define the baseline of the test portion back to where it intersects the initial deviation of the melting curve from its baseline. The baseline beneath the test portion should be a continuation of the baseline where there are no sample components present. If a shift has occurred in the heat capacity of the test portion after the melt, it will be evident relative to the baseline of the empty capsule. Have the instrument calculate the sigmoid baseline if it can, or connect the end of the peak point with the last point in which the test portion was in conjunction with the baseline of the empty capsule.
Determine the onset temperature in ° C., which, if not computer generated, is an extrapolation to baseline of the steepest slope of the principal peak.
This method is applicable for using Franz cell apparatus for the in-vitro assessment of penetration of thioglycolic acid (TGA) and its salts through a skin mimic after the application of a depilatory composition following pre-treatment with a protective composition.
Penetrated TGA is quantified using Reverse Phase High Performance (or Pressure) Liquid Chromatography (RP-HPLC) with external standard quantitation at 240 nm.
Reference is made to
1. Prepare the Vitro-Skin (IMS Vitro-Skin®, Catalogue number: P&G1013, made by IMS Inc., Portland, Me., USA) samples by cutting 8×6.2 cm segments and placing them textured side up on the racks into a hydration chamber (manufactured & sold by IMS) containing a 14.7% glycerol solution. The hydration chamber should be sealed and the vitro-skin left to hydrate at room temperature and a humidity of 80.4%±3.5% for 24 hours.
2. Prepare the receptor solution for the Franz-cell by mixing 1.90 ml formic acid (98% wt+ Fluka, by Sigma Aldrich, or equivalent), 30 ml acetonitrile (RP-HPLC grade) and 968.1 ml water (RP-HPLC grade). Set up the static Franz cell (Permegear or equivalent, 15 mm diameter unjacketed cell with a 12 ml receptor volume) by clamping it in place over suitable stirrer plates (not shown) and add a small stirrer bar (6) to each cell, fill the receptor cell (2) to the brim with the required amount of receptor solution.
3. Once hydrated, remove a sheet of vitro-skin from the hydration chamber and lay textured side up on a clean flat surface then dose 100 μl (˜2 mg/cm2) of protective composition (not shown) onto the vitro-skin and spread evenly over the surface by rubbing for 30 seconds with a gloved finger.
4. Using a scalpel blade cut the vitro-skin segment (3) into two equal sections, each large enough to completely cover the top of the cell. Place the relevant size o-ring (5) (22 mm, for the specified Franz-cell) onto each section of the vitro skin and dose to 150 mg/cm2 of depilatory composition (4) (“Veet Normal Skin Hair Removal Cream” or an equivalent (an equivalent being a composition comprising 3.7% wt thioglycolic acid)) into the centre then, using a glass rod, evenly spread the cream around the inside of the o-ring (5). Using tweezers pick up the vitro-skin segment and place the vitro-skin segment, depilatory and o-ring centrally over the receptor cell (2), place donor cell (1) over the top and clamp in place. Turn on stirrer plate and start 10 minute countdown timer. After 10 minutes; turn off stirrer and remove the clamp, donor cell (1) and vitro-skin segment and place the receptor solution in a suitable container for analysis.
5. A reference sample should also be run without protective composition treatment on the vitro-skin. Remove a sheet of vitro-skin from the hydration chamber and lay textured side up on a clean flat surface. Repeat step 4 of the protocol to produce the reference sample.
For RP-HPLC analysis, prepare a 50 mM Formic acid (98%+ Fluka) solution and mix 970 ml of this solution with 30 ml acetonitrile (HPLC grade) to act as a mobile phase during the analysis.
A reference standard solution should be made with a concentration of Calcium Thioglycolate Trihydrate of 0.94 mg/ml.
Install a Waters Atlantis T3 3 μm 4.6×50 mm column into the HPLC (although any silica-based C18 reversed phase RP-HPLC column may be used), and ensure all solvent lines for the RP-HPLC are primed and free of leaks. Allow the mobile phase to circulate through the system for 25 minutes at 0.7 mL/Min in order to equilibrate the column. Detection of the thioglycolic acid is via UV spectroscopy.
The RP-HPLC conditions are as follows:
Calculate the concentration of Thioglycolic Acid in the sample
Calculate the concentration of thioglycolic acid in the sample using the following formula:
concentration (mg/ml)=A/B×C×E/f
C=Thioglycolic Acid final STD concentration in mg/ml (0.94 mg/ml)
E=Molecular weight of Thioglycolic acid (92.12 g/mol)
F=Molecular weight of Calcium thioglycolate (184.23 g/mol)
The efficacy of the barrier provided by the protective composition (resistance to TGA penetration) can be calculated as a percentage decrease in TGA in the receptor solution:
For example, if TGA in solution without protective composition=75 μg/ml and TGA in solution with barrier=15 μg/ml
A reduction of TGA penetration of 45% or more is believed to correlate to a significant and user-noticeable reduction in irritation.
A TA AR1000 Rheometer was used to measure the steady state viscosity at a shear rate of 10 s-1, a temperature of 25° C., a plate separation of 1000 μm using a plate having the following geometry: 40 mm stainless steel serrated plate with a stainless steel serrated bottom plate. Steady state viscosity was measured at a shear rate of 10 s-1, Three consecutive measurements were made within a 5% tolerance to achieve the defined viscosity.
Inventive Examples 1 and 2 and Comparative Examples 1 and 2 were made by heating all elements of the composition to the melting temperature of the wax and then mixing until a homogenous mixture was obtained. Comparative Examples 6 and 7 were made by simply mixing the elements together. The compositions were tested using the Franz Cell method defined above.
1Sucrose polycottonseedate oil, a mixture of esters of Cottonseed Acid (q.v.) and Sucrose (q.v.).
As demonstrated by the Franz Cell data, oils, on their own (see Comparative Examples 3 and 4), or mixed with small amounts of triglycerides (see Comparative Examples 5 and 6), such as rhea or cocoa butter, provide little to no barrier to thioglycolic acid. The addition of a small amount of wax surprisingly increases the barrier to penetration by a significant amount (see Inventive Examples 1 and 2 and Comparative Examples 1 and 2). The presence of ethanol (Inventive Examples 1 and 2) does not significantly affect the barrier properties, but does create a thinned and more spreadable composition to be prepared, as demonstrated by the viscosity data.
The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm”.
Every document cited herein, including any cross referenced or related patent or application, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.
While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.
This application claims the benefit of U.S. Provisional Application No. 61/479,875, filed 28 Apr. 2011.
| Number | Date | Country | |
|---|---|---|---|
| 61479875 | Apr 2011 | US |
