A Natural Emollient Composition Field of the invention

The invention relates to emollient emulsion compositions, and uses thereof in the topical treatment of human skin.

Back2round of the invention

There are a large number of emollients available in the marketplace that are designed to increase the skin's appearance and/or hydration content. These products typically include large numbers of complex ingredients to ensure that the product delivers one or more of the following functions, hydration, water loss reduction, improve appearance, pleasant sensory experience and ensure product through life stability. Some ingredients utilised to formulate the emulsion are skin sensitising agents that can have short and long term negative impact to the skin. Examples include Sodium Lauryl Sulfate (or other emulsifiers), stabilisers and perfumes.

There are often ingredients added to address a specific skin defect such as blemishes, wrinkles, blotches, laxity and pigmentation or to address the general effects of aging. In addition the inclusion of these ingredients facilitates particular claims on pack, e.g., 'anti-wrinkle', 'skin brightening cream' and 'visibly younger skin in just seven days'.

Examples of functional ingredients are:

Retinol (form of vitamin A): Reduces fine lines and pores

Epidermal Growth Factor (low-molecular- weight polypeptide): stimulates cell renewal and collagen protection to reduce fine lines, wrinkles and sagging

- Alpha Hydrox Acids: chemical peels that aid the dissolution of the intracellular glue that holds the dead cells together

Peptides: acts of a signal to the skin that it needs to produce more collagen. More collagen counters the skin aging process. In many cases the benefits of these large ingredient based creams are limited to cosmetic and have no impact on the health of the skin. In fact a significant number can damage the skin, can aggravate and in some cases cause skin sensitisation and conditions such as eczema. US2014/0328774 describes an oil-in-water emulsion skincare composition comprising 2-15% silicone particles, 3-25% oil, 0.1-5% emulsifier and 30-90% water.. US2005/0053634 describes talc-containing cosmetic cleansing emulsions that contain surfactant for the purpose of cleaning the skin, and having no skin hydration function. WO2014184228 describes cosmetic compositions comprising a natural organic oil and about 2% by weight of porous crosslinked polymethylmethacrylate beads having a particle size (Dso) of 6-15μ.

Summary of the invention

This Applicant has discovered that an effective emollient composition that has a non-greasy skin- feel and can effectively hydrate the skin can be provided using as few as three ingredients and in the absence of convention skin sensitizing emulsifiers and stabilising agent. The three ingredients are liquid paraffin or a natural oil (for example a vegetable oil or a mineral oil) provided in about one part, water provided in about two parts, and a minor amount of an acrylate gelling agent. The Applicant has discovered that the acrylate gelling agent, when mixed with the water, forms a polymeric matrix or lattice that helps emulsify the oil phase when added into the gel, promotes formation of small oil droplets, and stabilises the formed oil-in-water emulsion.

Broadly, the invention provides an emollient emulsion composition comprising (or consisting essentially of) about one third oil, about two thirds water, a minor amount of a water soluble acrylate gelling agent, and optionally a suitable preservative.

An emollient emulsion composition according to the invention provides a stable, oil in water, emulsion that provides a non-greasy sensory feeling when applied to the skin and that can be prepared without conventional emulsifiers or stabilising agents. The composition can be prepared with as few as three ingredients using uncomplicated processing methods. The invention also provides a method of making an emollient emulsion composition comprising mixing about one part water with a minor amount of an acrylate-based gelling agent to solubilise the gelling agent and form a gel, and adding oil to the gel with application of shear forces to form the emollient emulsion composition.

In this specification, the term "emollient emulsion composition" means a cream comprising an oil- in-water emulsion that is suitable for application to the skin of a human and is capable of hydrating and moisturising the skin, preventing or inhibiting dry skin, or increasing the elasticity of the skin. In this specification, the term "about one third" as applied to the oil means 30-40% of the composition (v/v).

In this specification, the term "about two thirds" as applied to the water means 60-70% of the composition (v/v).

In this specification, the term "minor amount" as applied to the water soluble acrylate gelling agent means about less than 3%, typically about 0.2 to 2% of the composition (v/v).

In this specification, the term "water soluble acrylate gelling agent" means a gelling agent comprising optionally cross-linked, optionally modified, acrylate or polyacrylate groups that is soluble in water in amounts of up to 3% (w/v). In one embodiment, the gelling agent is provided as a powder having a D50 particle size of less than 1μ. . Preferably, the gelling agent is an alkyl acrylate crosspolymer. Ideally, the gelling agent is a C10-C30 alkyl acrylate crosspolymer. Examples of alkyl acrylate crosspolymers include EDT2020, Ultraz20, Ultraz21 and Pemulen TRl. Examples of additional water soluble acrylate gelling agents include ARONVIS, JUNLON, RHEOGIC. In one embodiment, the term excludes gelling agents in bead form.

In this specification, the term "oil" means an oil of vegetable or non-vegetable origin. Examples are provided below. In one embodiment, the oil comprises or consists essentially of liquid paraffin. The term "suitable preservative" means a preservative commonly used in emolient or moisturiser composition. Examples will be known to the person skilled in the art and include sodium benzoate and benzalkonium chloride. Other examples are provided below. In one embodiment, the composition comprises less than 0.2% preservative (w/v). In one embodiment, the composition comprises less than 0.2%, 0.15% or 0.1% preservative (w/v).

In a preferred embodiment, the composition does not include an emulsifier.

Preferably, the composition comprises or consists essentially of:

- 0.2 to 2% (w/v) of a water soluble acrylate gelling agent;

- 30 to 40% (v/v) of the oil;

- 69.8 to 58% (v/v) water;

optionally, a preservative at less than 0.1%; and

optionally a fragrance/perfume less than 0.1%

Preferably, the composition comprises or consists essentially of:

0.2 to 2% (w/v) of a water soluble acrylate gelling agent;

- 31-35% (v/v) of the oil;

- 68.8 to 63% (v/v) water;

- optionally, a preservative at less than 0.1%; and

optionally a fragrance/perfume.

Preferably, the composition comprises or consists essentially of:

0.5 to 1.5% (w/v) of a water soluble acrylate gelling agent;

- 32-34% (v/v) of the oil;

- 78.8 to 63% (v/v) water;

optionally, a preservative at less than 0.1%; and

optionally a fragrance/perfume Preferably, the composition comprises or consists essentially of:

0.5 to 0.99% (w/v) of a water soluble acrylate gelling agent; - 32-34% (v/v) of the oil;

- 78.8 to 63% (v/v) water;

optionally, a preservative at less than 0.1%; and

optionally a fragrance/prfume

Preferably the oil is a mineral oil. Preferably the composition comprises 30-36% oil (v/v). Preferably, the composition comprises 31-35% oil (v/v). Preferably, the composition comprises 32-34% oil (v/v). Preferably, the composition comprises about 33% oil (v/v). Preferably, the oil has a viscosity of 50-500 centipoise (as determined using the method described below).

Preferably the composition comprises 0.5 to 1.5% water soluble acrylate gelling agent (w/v). Preferably the composition comprises 0.5 to 1.0% water soluble acrylate gelling agent (w/v). Preferably the composition comprises 0.5 to 0.75% water soluble acrylate gelling agent (w/v). In one embodiment, the water soluble acrylate gelling agent is a crosslinked acrylate copolymer. In one embodiment, the acrylate copolymer is a polyacrylic acid copolymer. In one embodiment, the crosslinked acrylate copolymer is hydrophobically modified. In one embodiment, the crosslinked acrylate copolymer is selected from ETD2020 (an example of cross linked polyacrylic acid copolymer), Ultrez20 or Ultra21 (examples of a hydrophobically modified cross linked acrylate copolymer). In one embodiment, the soluble acrylate gelling agent comprises a hydrophobic comonomer. Examples include PEMULEN TR1 and TR2.

Preferably, the composition comprises no more than 6 ingredients. Preferably, the composition comprises no more than 5 ingredients. Preferably, the composition comprises no more than 4 ingredients.

Preferably, the composition consists essentially of water, oil, water soluble acrylate-based gelling agent, and preservative, and optionally one or more of a colouring agent and a fragrance. In one embodiment, the composition is free of silicone particles. In one embodiment, the composition is free of surfactant. In one embodiment, the composition is free of talc.

The invention also provides a non-therapeutic method of treating the skin of a human to hydrate or moisturise the skin, the method comprising a step of administering an emollient emulsion composition of the invention topically to the skin.

The invention also provides a non-therapeutic method of treating the skin of a human to reduce the appearance of wrinkles, the method comprising a step of administering an emollient emulsion composition of the invention topically to the skin.

The invention also provides a non-therapeutic method of treating the skin of a human to increase the elasticity of the skin, the method comprising a step of administering an emollient emulsion composition of the invention topically to the skin.

The invention also provides a use of an emollient emulsion composition of the invention as an emollient for human skin.

The invention also provides a use of an emollient emulsion composition of the invention as a skin care product.

The invention also provides a method of making an emollient emulsion composition comprising mixing about one part water with a minor amount of an acrylate-based gelling agent to solubilise the gelling agent and form a gel, and adding oil to the gel with application of shear forces to form the emollient emulsion composition.

Brief Description of the Ffeures

Fig. 1 Bar chart showing the rating of the six samples Fig. 2 Bar chart showing values recorded for the parameters of firmness, consistency, cohesiveness and index of viscosity for the six samples analysed. Fig. 3 Interaction plot of the variable factors: OC X PC; OC X PT; PC X PT

Fig. 4 Bar chart showing percentage weight loss upon drying; Sample size: 3.0 g; Temperature: 105 °C; Duration: 48 hours

Figs 5-10 show the TGA profiles of the semi-solid preparations evaluated; each sample was tested in triplicate. The Y-l axis shows the percentage weight loss with increasing temperature, while the Y-2 axis expresses the derivative (with respect to time) data. It can be seen that the trends of weight loss with increasing temperature are reasonably reproducible for each product.

Figs 11-16 show the continuous flow plots produced for each of the semi-solids tested. The X-axis displays Shear rate (s ¹ ), the Y-l axis Shear Stress (Pa) and the Y-2 axis Apparent Viscosity (Pa.s).The plots show considerable differences in the rheological profiles of the BHP product and the newly developed products compared with the commercial products tested.

Detailed description of the invention

The present invention is a skin cream composition composed primarily of water and oil blended together to create a stable oil in water emollient that delivers a non-greasy sensory experience when applied to the skin. The only additional required ingredient is a small percentage, typically less than 2%, of a hydrogel.

By delivering oils and water to the skin the emollient locks the water onto the skin. The oils are similar to oils found in the skin, and reduce water loss (moisture barrier) while simultaneously increasing the smoothness of the skin. The water hydrates the skin, increases skin' s elasticity and prevents dry skin. Hydrated skin helps to keep skin younger as well as allowing skin to be brighter and more radiant. The emollient contains either a single oil or a blend of oils to deliver unique sensory experiences. By having the oils, polymer and water in the correct ratio within the emollient it creates a stable emulsion while avoiding the need to add skin sensitising agents. The invention provides a stable structure created with a small number of ingredients combined in the right proportion, and excludes the need to add complex mixtures of stabilising agents.

The present invention relates to an emollient that provides improved skin moisturisation with a better sensory feel as a result of it being a different architecture to other available emollients. Generally the invention is directed to skin care formulations comprising a polymer formed lattice wherein there is dispersed oil droplets in an oil in water formulation. When applied to the skin the lattice network locks oil onto the skin. In an embodiment of the invention the polymers may be made from a variety of materials and can include but are not limited to organic materials and inorganic materials. Examples of such materials include ETD2020 @ 0.6% w/v, Ultrez20 @ 0.6% w/v, Ultrez 21, PEMULEN polymeric emulsifiers such as TR1 or TR2, and the like. An emollient is an oleaginous or oily substance which helps to smooth and soften the skin and may also reduce its roughness, cracking or irritation. The oils used include organic and inorganic oils. These include but are not limited to mineral oils having a viscocity in the range of 50-500 centripoise (cps), lanolin oil, triglycerides and free fatty acids, cholesterol, phospholipids, ceramides, squalene, and phytosterol, colloidal oatmeal, bees wax, suitable preservative, cocoa butterhyaluronic acid coconut oil, cocoa butter, olive oil, almond oil, macadamia nut oil, aloe extracts such as aloe vera lipoquinone, synthetic jojoba oils, natural Sonora jojoba oils, safflower oil, corn oil, liquid lanolin, avocado oil, sweet almond oil, aloe vera extract, liquid paraffin, cottonseed oil, grapeseed oil, sweet almond oil and peanut oil and the like. As the list of available oils is currently expanding those of ordinary skill will recognize that the invention is not limited to oils currently approved for human use but is readily applicable to those that may be allowed in the future.

The compositions of the present invention may contain a wide range of additional optional components which can also include components generally known as botanical agents. The CTFA Cosmetic Ingredient Handbook, Seventh Edition 1997 and the Ninth Edition 2002 particularly at page XV, which is incorporated by reference herein in its entirety, describes a wide variety of cosmetic and botanical agents and active ingredients commonly used in skin care compositions which are suitable for use in the compositions of the present invention. Examples of these functional classes disclosed in this reference include: absorbents, abrasives, anti-caking agents, anti-foaming agents, anti-oxidants, binders, biological additives, buffering agents, bulking agents, chelating agents, chemical additives, colourants, cosmetic astringents, cosmetic biocides, denaturants, drug astringents, external analgesics, film formers, fragrance components, humectants, opacifying agents, pH adjusters, plasticizers, reducing agents, skin bleaching agents, skin conditioning agents (emollient, such as silicones, humectants, miscellaneous and occlusive), skin protectants, solvents, foam boosters, hydrotropes, solubilizing and emulsifying agents, suspending agents (nonsurfactant), sunscreen agents, ultraviolet light absorbers, SPF boosters, waterproofing agents and viscosity increasing agents (aqueous and non-aqueous).

As used herein the terms 'sunless tanning agent' or 'self-tanning compositions' refer to compositions which, when applied to human skin impart thereto an appearance similar to that achieved by exposing the skin to natural or artificial sunlight.

A humectant is a moisturizing agent that promotes retention of water due to its hygroscopic properties. Suitable humectants include glycerin and polymeric glycols. Fragrances are aromatic substances which can impart an aesthetically pleasing aroma to the emollient. Typical fragrances include aromatic materials extracted from botanical sources (rose petals, gardenia blossoms, jasmine flowers etc) which can be used alone or in combination to create essential oils. Alternatively, alcoholic extracts may be prepared for compounding fragrances. However due to the relatively high costs of obtaining fragrances from natural substances the modern trend is to use synthetically prepared fragrances, particularly in high volume products.

Anti-inflammatory agents such as glycyrrhetinic acid, N-palmitoylthanolamine may also be added.

Additional preservatives may also be used if desired and include well known preservative compositions such as benzyl alcohol, benzalkonium chloride, phenyl ethyl alcohol, benzoic acid, urea, diazolydinyl, chlorphenesin, iodopropynyl butyl carbamate and ethylhexyl glycerin among others.

The composition if the invention can further comprise skin protectant active agents, including allantoin, aluminium hydroxide gel, calamine, cod liver oil, colloidal oatmeal, dimethicone, glycerin, hard fat, kaolin, petrolatum, sodium bicarbonate, white petrolatum, zinc acetate, zinc carbonate.

The compositions of the invention may further include insect repelling components i.e. N,N- Diethyl-m-toluamide, frequently called 'DEET and available in the form of a concentrate containing at least about 95% DEET.

Experimental A - Manufacture of Emolient Composition

Example 1

ETD2020 @ 0.6% w/v is dissolved in deionised water._Once fully dissolved, the solution was neutralized to pH 7 with NaOH 18% w/v. 0.005% Bezalkonium chloride is added as a preservative. Then the cream is made by adding 33% (volume per weight of finished composition) paraffin oil to the gel using mortar and pestle. A fine cream was obtained.

Example 2

ETD2020 @ 0.6% w/v is dissolved in deionised water._Once fully dissolved, the solution was neutralized to pH 7 with NaOH 18% w/v. 0.005% Bezalkonium chloride is added as a preservative. Then the cream is made by adding 33% (volume per weight of finished composition) soybean oil to the gel using mortar and pestle. A fine cream was obtained.

Example 3

ETD2020 @ 0.6% w/v is dissolved in deionised water._Once fully dissolved, the solution was neutralized to pH 7 with NaOH 18% w/v. 0.005% Bezalkonium chloride is added as a preservative. Then the cream is made by adding 33% (volume per weight of finished composition) paraffin oil to the gel using mortar and pestle. A fine cream was obtained.

Example 4

Ultrez20 @ 0.6% w/v is dissolved in deionised water._Once fully dissolved, the solution was neutralized to pH 7 with NaOH 18% w/v. 0.005% Bezalkonium chloride is added as a preservative. Then the cream is made by adding 33% (volume per weight of finished composition) paraffin oil to the gel using mortar and pestle. A fine cream was obtained.

Example 5

TR1 @ 1.2% w/v is dissolved in deionised water ._Once fully dissolved, the solution was neutralized to pH 7 with NaOH 18% w/v. 0.005% Bezalkonium chloride is added as a preservative. Then the cream is made by adding 33% (volume per weight of finished composition) paraffin oil to the gel using mortar and pestle. A fine cream was obtained.

Example 6

Example 5 is repeated with the exception that 31 % paraffin oil was employed. A fine cream was obtained.

Example 7

Example 5 is repeated with the exception that 35% paraffin oil was employed. A fine cream was obtained. Experimental B - Characterisation and Testing of Emolient Composition

Materials and Methods

Materials

The VO and Sodium Hydroxide were obtained from Sigma- Aldrich (Ireland); Acrylate polymers were a generous gift from Surfachem Group Limited (Leeds, UK). These materials were used for the formulation of the semi-solid preparations.

Sample preparation

All samples were prepared from an Acrylate polymer gel by steady the addition of a liquid oil phase in a ceramic mortar and pestle using shear. In the case of the BHP formulation, the gel used was a commercially available Aloe vera gel product, and the oil phases were commercially available Evening Primrose and Vitamin E oils. In the case of #1 and #2, the gel consisted of Acrylate polymer dissolved in the required volume of deionised water using a magnetic stirrer bar to create agitation. The solution was subsequently neutralised to pH 7.0 using 18% w/v NaOH to yield the gel product. The oil phase utilised in these preparations was VO, and was included in concentrations ranging from 20-33% v/w. Commercially available semi-solid preparations for the treatment of skin conditions such as AD were purchased from community pharmacies. These included Aqueous Cream BP (AC), Elave® Intensive Cream and E45® Cream and all were used as received.

Questionnaire

A questionnaire to identify the clinical characteristics of topical semi-solid preparations desired by volunteers was created and submitted to the Clinical Research Ethics Committee (CREC) for approval. The questionnaire required volunteers to rank six samples based on their smoothness, hydration ability and rate of absorption upon application and five minutes after application. A copy of the questionnaire can be found in Appendix 3 of this document.

Texture Profile Analysis (TP A )

TPA of each formulation was carried out using a Stable Micro Systems TA.XTplus texture analyser with the A/BE back extrusion rig and a 45 mm compression disc. Samples were loaded into the standard size back extrusion container, taking care to avoid the introduction of air bubbles, and were evaluated at ambient temperature. The probe was compressed once into each sample to a depth of 25 mm at a rate of 2 mm s ^"1 . The profiles generated were analysed using a modified version of the pre-installed macro for analysis of moisturising cream samples. The firmness of the sample is given by the maximum positive peak value, the consistency by the area of the positive curve, the cohesiveness by the maximum negative peak and the index of viscosity by the area of the negative peak.

Factorial Design

A 2 ³ factorial design was designed using Minitab 16 software and in conjunction with texture profile analysis it was used to evaluate the effect of formulation changes on the four measurable variables in the final product; firmness, consistency, cohesiveness and index of viscosity. The three variables used were oil concentration, polymer concentration and polymer type, each at two levels. The significance of these effects was assessed by means of a two way analysis of variance (ANOVA), where P<0.05 represented significance.

Loss on Drying (LOD)

The water and volatile content of the samples was determined by LOD; approximately 3.0 g of preparation was loaded into formed aluminium containers. Samples were maintained at 105 °C for 24 hours, and then until constant mass at 48 hours.

Thermo gravimetric Analysis (TGA ) TGA was conducted using a TA instruments Q500 machine with an auto-sampler attachment. Samples were examined using a heat ramp with a heating rate of 10 °C min ^"1 from 20-200 °C in a platinum pan and aluminium container. Each sample was analysed in triplicate, with sample sizes ranging from 25-35 mg.

Rheometry

Rheological assessment of the samples was performed using a Haake RotoViscol rheometer with a cup and bob geometry (Z41Ti model). Samples of 17.5g were gently loaded into the cup with a minimum of stirring using a plastic spatula and the bob was compressed into the sample at a rate of 3.0 rnnxs ^"1 in order to minimise sample shear. The sample was allowed to rest for 3 minutes for temperature equilibration, then a further 10 minutes to allow sample recovery. Rotational ramps from 0-100 s ^"1 over 5 minutes and then from 100-0 s ^"1 over 5 minutes were completed. Data was analysed using RheoWin software.

Results

Clinical Evaluation

The data obtained from the clinical questionnaire is presented in Figure 1. Each product was graded with regard to its smoothness, ability to hydrate the skin and its rate of absorption upon application. It is evident that the volunteers expressed preference for the BHP product. The newly developed products (#1 , #2) were ranked in second and third place, while the commercial products were rated in fourth, fifth and sixth places.

Texture Profile Analysis (TP A)

The firmness, consistency, cohesiveness and index of viscosity of the six samples tested can be seen in Figure 2. It is apparent that the BHP product and the newly developed products produce lower readings than any of the commercial products for each of the parameters measured by this technique.

Factorial Design

The raw data obtained from Texture Profile analysis was analysed using Minitab 16 software, and Table I shows a summary of the statistical analysis of the effects of increasing the concentrations of Oil (OC) and Polymer (PC) and changing the Polymer Type (PT) on Formulation Firmness, Consistency, Cohesiveness and Index of Viscosity. It is evident that each individual factor has a significant effect; however there are no significant additive, or interactive, effects between the factors.

Table 1

Note. Statistical design was a 2 ³ factorial. Results were analysed using a two-way ANOVA, where P<0.05 represented significance.

Figure 3 shows an interaction plot of the data presented above for the cohesiveness parameter. It is clear that there is no interaction between any of the variable factors, as indicated by the parallel lines on each of the plots.

Loss on Drying (LOD) The results obtained from the LOD analysis are presented in Figure 4 below. It is evident from this chart that the water and volatile organic content of each of the samples is variable, with the BHP product containing the greatest quantity of water and volatiles of the products tested.

Thermo gravimetric Analysis (TGA )

Figures 5-10 show the TGA profiles of the semi-solid preparations evaluated; each sample was tested in triplicate. The Y-l axis shows the percentage weight loss with increasing temperature, while the Y-2 axis expresses the derivative (with respect to time) data. It can be seen that the trends of weight loss with increasing temperature are reasonably reproducible for each product.

Rheometry

The continuous flow plots produced for each of the semi-solids tested can be seen in Figures 11- 16. The X-axis displays Shear rate (s ¹ ), the Y-l axis Shear Stress (Pa) and the Y-2 axis Apparent Viscosity (Pa.s).The plots show considerable differences in the rheological profiles of the BHP product and the newly developed products compared with the commercial products tested. The invention is not limited to the embodiment hereinbefore described which may be varied in construction and detail without departing from the spirit of the invention.