Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y5/00—Nanobiotechnology or nanomedicine, e.g. protein engineering or drug delivery
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K8/00—Cosmetics or similar toiletry preparations
  • A61K8/18—Cosmetics or similar toiletry preparations characterised by the composition
  • A61K8/19—Cosmetics or similar toiletry preparations characterised by the composition containing inorganic ingredients
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K8/00—Cosmetics or similar toiletry preparations
  • A61K8/18—Cosmetics or similar toiletry preparations characterised by the composition
  • A61K8/19—Cosmetics or similar toiletry preparations characterised by the composition containing inorganic ingredients
  • A61K8/27—Zinc; Compounds thereof
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K8/00—Cosmetics or similar toiletry preparations
  • A61K8/18—Cosmetics or similar toiletry preparations characterised by the composition
  • A61K8/19—Cosmetics or similar toiletry preparations characterised by the composition containing inorganic ingredients
  • A61K8/28—Zirconium; Compounds thereof
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P43/00—Drugs for specific purposes, not provided for in groups A61P1/00-A61P41/00
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61Q—SPECIFIC USE OF COSMETICS OR SIMILAR TOILETRY PREPARATIONS
  • A61Q17/00—Barrier preparations; Preparations brought into direct contact with the skin for affording protection against external influences, e.g. sunlight, X-rays or other harmful rays, corrosive materials, bacteria or insect stings
  • A61Q17/04—Topical preparations for affording protection against sunlight or other radiation; Topical sun tanning preparations
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K2800/00—Properties of cosmetic compositions or active ingredients thereof or formulation aids used therein and process related aspects
  • A61K2800/20—Chemical, physico-chemical or functional or structural properties of the composition as a whole
  • A61K2800/26—Optical properties
  • A61K2800/262—Transparent; Translucent
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K2800/00—Properties of cosmetic compositions or active ingredients thereof or formulation aids used therein and process related aspects
  • A61K2800/40—Chemical, physico-chemical or functional or structural properties of particular ingredients
  • A61K2800/41—Particular ingredients further characterized by their size
  • A61K2800/413—Nanosized, i.e. having sizes below 100 nm

Definitions

• This invention relates to a substantially visibly clear and transparent topical sunscreen composition having a dermatologically acceptable level of SPF and broad spectrum UVA/UVB protection for shielding the skin from ultraviolet radiation relying on physical UV screening agents alone.
• the composition comprises a sufficient weight percentage of nano-sized particles of a physical UV screening agent to provide the desired level of SPF without any chemical UV screening agents being added.
• UV radiation with wavelengths between 290 nm and 400 nm damages the human epidermis, both in the short term, leading to sunburn, and, in the long term, leading to premature aging of the skin and skin cancer.
• UVB radiation having wavelengths between 290 and 320 nm is well known to cause burns and erythema and should be screened out. UVA contributes to the damage caused by UVB and in addition may cause other harmful effects such as polymorphic light eruption and photosensitivities to certain chemicals.
• Sunscreen compositions are broadly classified into “chemical” (organic) or “physical” (inorganic) sunscreens depending on the nature of the active ingredient which acts to screen out UVA and UVB radiation.
• Chemical sunscreens typically contain conjugated molecular structures that absorb UVB and/or UVA wavelengths and then retransmit the energy at longer safer wavelengths.
• range of wavelengths against which chemical sunscreens protect is narrower than for the physical sunscreens and only partial protection is achieved against UVA, even in what are labelled "broad spectrum products”.
• Physical sunscreens typically consist of a dispersion of particles of inert inorganic compounds which preferentially absorb UV radiation and which may also scatter UV and visible radiation depending on the size of the particles, the wavelength of the UV radiation, and the difference in refractive index of the dispersed particles and the dispersion medium.
• certain metal oxides including zinc oxide and titanium oxide, are effective physical UV screening agents.
• Zinc oxide in particular is known to have * a high absorptance to UV radiation over virtually the entire spectrum of UVB and UVA radiation whereas titanium dioxide provides UV protection over a more limited spectrum.
• the inclusion of zinc oxide as a physical UV absorber in sunscreens is known.
• Physical sunscreens are preferred over chemical sunscreens in that chemical sunscreens are known to be photosensitive and may be degraded or altered by UV radiation. Moreover, the long-term effects of chemical sunscreens on skin and general health of the user are unknown. Physical sunscreens are preferable, particularly those containing zinc oxide, as such physical sunscreens are known to be UV stable and exhibit no known adverse effects associated with long-term contact with the skin.
• SPF Sun Protection Factor
• SPF Sun Protection Factor
• the efficacy of sunscreens is usually characterised by an SPF (Sun Protection Factor) which is a measure of the increase in exposure time to UV radiation required to induce erythema.
• SPF is typically expressed as a number followed by a "+”. For example, an SPF of 15+ indicates that the SPF is at least 15. Dermatologically acceptable levels of SPF vary from country to country.
• sunscreen formulations have an SPF of 15+ or 30+.
• SPF tests are conducted "in- vivo" or "in- vitro”. In Australia, in- vivo SPF tests are carried out according to Australian Standard AS/NZS 2604: 1998.
• UVA UV emission of the solar simulator used in the SPF test
• UVA radiation above about 350 nm when compared with the spectrum of natural sunlight. This may be important because there is mounting evidence that exposure to UVA may be a significant risk factor for premature aging of the skin and certain forms of skin cancer.
• various short-term and long-term adverse effects may be relatively more sensitive to UVA than is sunburn erythema.
• UVA/UVB ratio which is equal to the ratio of the UVA to UVB radiation absorbed by the sunscreen.
• a further parameter used to evaluate the effectiveness of sunscreens over the entire UV spectrum is the critical wavelength parameter, defined as the wavelength above which 90% of the total UV radiation is absorbed.
• results of any of the above-mentioned tests are dependent on the particular thickness of the layer of the sunscreen composition or formulation being tested. Most SPF tests require that 2 mg/cm 2 of the sunscreen composition or formulation corresponding to a layer thickness of about 20 microns, be applied to the subject. If a thinner layer of sunscreen is used, the degree of UV blockage is lowered.
• the transparency decreases with increasing concentration of the physical sunscreen particles because of increased scattering of light by the particles, which causes a whitening effect in the layer of sunscreen.
• the whitening effect limits the maximum concentration of physical UV screening agents, such as zinc oxide or titanium oxide, to values which are unable to provide adequate UVA/UVB protection.
• acceptable values of SPF can only be achieved by adding chemical UV screening agents to the sunscreen.
• US Patent No. 5,573,753 discloses a method of preparing sunscreens containing zinc oxide particles of 5 nm to 150 nm, which is claimed to be substantially transparent to visible light while screening UV radiation.
• US Patent No. 5,531,985 describes a sunscreen which includes a dispersion of zinc oxide particle 10 nm to 100 microns in size.
• any sunscreen composition would be able to claim to be transparent. However, such a sunscreen would not have a dermatologically acceptable level of SPF.
• An object of the present invention is to provide a substantially visibly transparent topical sunscreen composition which for the first time is able to provide the requisite level of SPF without the need to include photodegrading and potentially biosensitive chemical UV screening agents.
• transparent is to be understood as meaning the "property of transmitting rays of light through its substance so that bodies situated beyond or behind can be distinctly seen” (as distinguished from translucent and opposed to opaque) and the term “clear” is to be understood to mean “free from whiteness or cloudiness”.
• Clarity refers to the degree to which a formulation is clear.
• UV screening agents throughout this specification in no way imply or suggest that 100% blockage of UV radiation occurs. These terms are merely used to describe the role of the agent or composition in reducing the extent to which UV radiation is able to access the skin of the user.
• a substantially visibly clear and transparent topical sunscreen composition for shielding the skin from ultraviolet radiation, said composition comprising: a sufficient weight percentage of nano-sized particles of a physical UV screening agent to provide a dermatologically acceptable level of SPF and broad spectrum protection from UVA and UVB radiation in a dermatologically acceptable carrier whereby said composition contains no chemical UV screening agents.
• composition is intended to cover a dispersion, an emulsion (either a cream or a lotion), a stick, a gel, a spray, a clear lotion, or a wipe or any other composition suitable for use in protecting skin against sun damage.
• the dispersion or emulsion may be a water-in-oil emulsion, or an oil-in water emulsion, or a multiple phase emulsion.
• stratum has been chosen to cover the situation of various countries setting a minimum SPF that a given sunscreen must comply with in order to be able to be sold to consumers in a given country. For example, based on current regulations, many South East Asian countries only require that sunscreen products have an SPF of 8+. In Australia, the majority of sunscreens sold have a minimum SPF of 15+.
• a sunscreen formulator would be readily able to determine the weight percentage of the physical UV screening agent required to achieve the requisite level of SPF.
• the sunscreen composition would rely on zinc oxide alone as the physical UV screening agent and the majority of the testing included in the following description relates to the use of zinc oxide alone.
• titanium dioxide, cerium oxide or other physical UV screening agents or mixtures thereof it is within the scope of the present invention for titanium dioxide, cerium oxide or other physical UV screening agents or mixtures thereof to be included along with zinc oxide in the role of the physical UV screening agent to achieve the desired level of SPF.
• Zinc oxide is preferred due to its superior performance as a UV screening agent over a broader range of UV radiation. It is to be clearly understood that the sunscreen composition of the present invention would still achieve the promise of claim 1 with up to 10% of titanium dioxide, or other physical UV screening agents or mixtures thereof, used in addition with zinc oxide as the physical UV screening agent.
• said substantially visibly clear and transparent sunscreen composition has a specular extinction coefficient of less than 2 (wt%mm) "1 measured at a wavelength of 550 run. More preferably still, said substantially transparent dispersion has a specular extinction coefficient of less than 1 (wt%mm) "1 measured at a wavelength of 550 nm.
• the value of the specular extinction coefficient provides a unique measure of the degree of "clearness” or "lack of whiteness” achieved using the present invention. This measure is independent of the thickness of the layer of the composition being tested or applied. It is envisaged that an amount of one or more chemical UV screening agents may be added to the sunscreen composition of the present invention as an alternative to the physical UV screening agent. However, it is to be understood that the dermatologically acceptable SPF is achievable without the need for any chemical UV screening agents to be added and the addition of chemical UV screening agents is generally not preferred.
• the nano-sized zinc oxide particles have a mean particle size of less than 30 nm and have a narrow particle size distribution.
• the narrow particle size distribution is characterised in that, based- on a number-weighted size distribution measured by photo-correlation spectroscopy, the number-weighted size distribution has a standard deviation of less than 20 nm. More preferably, the number-weighted size distribution measured by photo-correlation spectroscopy has a standard deviation of less than 10 nm. More preferably still, the number-weighted size distribution measured by photo-correlation spectroscopy has a standard deviation of less than 5 nm.
• said particles have a photoactivity which is reduced by treatment with a surfactant.
• said surfactant is a steric surfactant.
• the steric surfactant could be chosen from the list of stearic acid, recinolieic acid, poly 12-hydroxy stearic acid, metal hydroxy stearic acid, oleic, palmitic, lauric, plearagonic and myristic acids and esters of those acids (or connotations thereof), as well as poly electrolytes, such as sodium polyphosphate.
• said particles may be coated with a layer of one or more of a metal hydroxide, a metal oxide or a hydrous metal oxide.
• a metal hydroxide a metal oxide or a hydrous metal oxide.
• metal oxide a metal oxide or a hydrous metal oxide.
• a wide range of metals are considered suitable but the preferred metals are silicon, aluminium, zirconium.
• a zinc oxide powder for use in a substantially visibly clear and transparent topical sunscreen composition for shielding the skin from ultraviolet radiation, said powder comprising: a mean particle size of less than 30 nm and a narrow particle size distribution.
• the narrow particle size distribution is characterised by a number-weighted size distribution measured by photo-correlation spectroscopy with a standard deviation of less than 20 nm. More preferably, the narrow particle size distribution is characterised by a number-weighted size distribution measured by photo-correlation spectroscopy with a standard deviation of less than 10 nm. More preferably, the narrow particle size distribution is characterised by a number-weighted size distribution measured by photo- correlation spectroscopy with a standard deviation of less than 5 nm.
• the particles have a photoactivity which is reduced by treatment with a surfactant.
• the surfactant is a steric surfactant.
• the particles are coated with a metal hydroxide, a metal oxide and/or a hydrous metal oxide.
• a metal hydroxide a metal oxide and/or a hydrous metal oxide.
• metals are considered suitable but the preferred metals are silicon, aluminium, zirconium.
• Figure 1 illustrates graphically the particle size distribution of a ZnO powder suitable for use in a topical sunscreen composition according to at least one embodiment of the present invention as measured by Photon Correlation Spectroscopy;
• Figure 2 illustrates a Transmission Electron Micrograph of particles of a ZnO powder suitable for use in a topical sunscreen composition according to at least one embodiment of the present invention
• Figure 3 illustrates graphically the UV-Vis specular transmittance spectra of 0.1 wt% slurry of the ZnO powder of Example 1 in deionised water;
• Figure 4 illustrates graphically the effect of the size of the ZnO particles on the UV-Vis specular transmittance spectra
• Figure 5 illustrates graphically the UV-Vis specular transmittance spectra of 0.01 wt% ZnO for the samples of Example 2 dispersed in deionised water
• Figure 6 illustrates graphically the decay rate of the indicators for samples A, B and C of Example 3 under UV exposure
• Figure 7 illustrates graphically the UV-Vis specular transmittance spectra of ZnO of Example 4 dispersed into Isostearyl Benzoate from aqueous solution
• Figure 8 illustrates graphically the UV-Vis specular transmittance spectra of ZnO of Example 5 dispersed into canola oil from aqueous solution
• Figure 9 illustrates graphically the UV-Vis specular transmittance spectra of ZnO of Example 6 dispersed into hexane from aqueous solution, (a) as dispersed, (b) after drying and redispersion;
• Figure 10 illustrates graphically the effect of mean particle size of a preferred embodiment of the ZnO powder according to Example 7 of the present invention on UV- Vis total transmittance measurements;
• Figure 11 illustrates graphically the effect of mean particle size of a preferred embodiment of the ZnO powder according to Example 7 on % total transmittance at 550 nm;
• Figure 12 illustrates graphically the effect of mean particle size of a preferred embodiment of the ZnO powder according to Example 7 on % total transmittance at 330 nm;
• Figure 13 illustrates graphically the effect of mean particle size of a preferred embodiment of the ZnO powder according to Example 7 on the Whiteness index for 20 micron thick films;
• Figure 14 illustrates graphically the effect of particle size and of a preferred embodiment of the ZnO powder according to Example 7 on in- vitro SPF (Transpore tape method);
• Figure 15 illustrates graphically the absorptance spectrum for a sample consisting of 30% of a preferred embodiment of the ZnO powder according to Example 7 dispersed in Isostearyl Benzoate;
• Figure 16 illustrates graphically the effect of mean particle size on the specular transmittance at 550 nm for various values of in- vitro SPF
• Figure 17 illustrates graphically an observed linear correlation between the in- vitro SPF and in-vivo SPF values
• Figure 18 illustrates graphically the data of Figure 23 redrawn using the correlation of Figure 24 showing the effect of mean particle size on the specular transmittance at 550 nm for various values of in-vivo SPF;
• Figure 19 illustrates graphically the extinction coefficient as a function of the particle size for a specular transmittance of 550 nm using the data of Figure 11 ;
• Figure 20 illustrates graphically the UV-Vis specular transmittance spectra of 16 wt% ZnO in chemical-free sunscreen formulations
• Figure 21 illustrates graphically the specular extinction coefficient of 16 wt% ZnO in chemical-free sunscreen formulations
• Figure 22 illustrates graphically the CIE L* coordinate of 16 wt% ZnO in chemical-free sunscreen formulations for 20 micron thick films
• Figure 23 illustrates images of 8 micron thick films of 16 wt% ZnO for various chemical-free sunscreen formulations
• Figure 24 illustrates graphically In-vitro SPF levels calculated from total transmittance data of sunscreen formulations using a quartz cell having an optical-path- length of 8 micron;
• Figure 25 illustrates graphically the relationship between in-vitro SPF measured using 8 micron cell and in-vivo SPF values, for 25 nm sized ZnO nanoparticle suspension in Finsolv-TN having different concentrations;
• Figure 26 illustrates graphically In-vivo SPF levels for the sunscreen formulations of Figures 20 and 21;
• Figure 27 illustrates graphically the extinction coefficient for a specular transmittance at 550 nm for the 25 nm ZnO for the sunscreen formulations of Examples 7, 8 and 9;
• Figure 28 illustrates graphically the UV-Vis total transmittance spectra of
• Figure 29 illustrates graphically a comparison of the whiteness index of a sunscreen composition of the present invention with the whiteness index of various other commercially available products as a function of the weight percentage of zinc oxide particles included in that composition for 20 micron thick films.
• the present invention derives from the ability of the applicant to be able to manufacture nano-sized zinc oxide particles with a far greater control on particle size, size distribution and agglomeration than previously achievable. Having manufactured such particles, the applicant realised that when formulated into a sunscreen, the particles exhibited unexpectedly high transmittance in the visible spectrum and far less whiteness than any other commercially available zinc oxide particles used in such sunscreens.
• the weight percentage of zinc oxide required to provide a particular level of SPF is dependent on the other ingredients included in a given formulation.
• typically 5 to 12 wt.% may be required to achieve an SPF of 15+, and at least 12 wt% to achieve an SPF of 30+.
• the sunscreen formulation of the preferred embodiments of the present invention does not need to rely on the inclusion of one or more chemical UV screening agents, the amount of zinc oxide particles required to be included in a given formulation to achieve the required dermatologically acceptable level of SPF may be reduced by chemical UV screening agents added to such a formulation. Again, it is considered that it would be a matter of routine experimentation for a sunscreen formulator to determine the specific amounts of zinc oxide required to be added to achieve the required level of SPF when chemical UV screening agents are included.
• the zinc oxide particles of the preferred embodiments have a mean particle size of less than 30 nm.
• the size distribution of such particles is preferably very narrow.
• the preferred manufacturing techniques allow for the size distribution to be controlled in such a way that based on a number-weighted size distribution measured by photo-correlation spectroscopy, the number-weighted size distribution has a standard deviation of less than 20 nm. More preferably, the number- weighted size distribution has a standard deviation of less than 10 nm and, more preferably still, less than 5 nm.
• the manufacturing process developed by the applicant has resulted in the production of zinc oxide particles that have a relatively non-reactive surface compared with other conventional manufacturing methods.
• the surface may be treated after manufacture to further assist in minimising agglomeration.
• stearic acid coatings may be used to improve dispersibility.
• the particles may be coated with one or more layers consisting of hydroxides, oxides or hydrous oxides of silicon, aluminium, zirconium or other suitable metal or a mixture thereof.
• Zinc oxide particles used in accordance with the present invention may be manufactured using the mechano-chemical process described in the applicant's US Patent No. 6,203,768, the contents of which are incorporated herein by reference.
• Mechano- chemical processing involves a mechanically activated chemical reaction between a precursor metal compound and a suitable reactant during mechanical milling or during subsequent heat treatment of the milled powder.
• a nano- composite structure is formed which consists of nano-sized grains of the nanophase substance within a matrix of a non-reactant diluent.
• the volume fraction of the diluent must be above a critical value to ensure substantially complete separation of the particles of the desired phase. Proper removal of the diluent yields substantially unagglomerated nanometre sized particles of the desired phase.
• mechano-chemical processing can be used to economically manufacture zinc oxide nano powders in accordance with the present invention, the powders having not only a smaller mean size but, equally importantly, a narrow size distribution, and enhanced stability.
• the powders are dispersed into a sunscreen formulation, the result is both enhanced visible transmittance and enhanced UV absorptance.
• the milling process be designed so that it is as uniform as possible, both temporally and spatially, while still providing sufficient collision energy to mechanically activate the reactants.
• batch milling is employed so that each particle experiences the same milling time. With the batch milling of dry constituents, there is a tendency for the powder to not circulate efficiently through the mill but rather remain near the container walls in a zone of reduced collision energy, resulting in non-uniform, inefficient milling.
• An attrition mill has been found to be a suitable mill for mechanical activation which can be scaled up for commercial production.
• a conventional attrition mill consists of a stationary cylindrical container filled with grinding balls that are stirred by impeller arms extending from a central drive shaft.
• the impellers do not extend to the wall of the container; instead a gap equal to 3 to 4 ball diameters separates the ends of the impellers from the wall of the vessel to minimise wear of the container walls.
• Mechano-chemical processing to produce nano-sized zinc oxide particles is best accomplished through the milling of a precursor zinc compound such as zinc chloride and a reactant such as sodium carbonate as described in Example 2. It is, however, to be clearly understood that other suitable reactants may be employed that would still fall within the scope of the present invention.
• a nano-composite grain structure is formed. If the milling temperature is sufficiently high (T>140°C), the ZnCl 2 may react with Na 2 CO 3 during milling, forming nano grains of ZnO within a matrix of NaCl, with CO 2 gas being given off during the reaction. Alternatively, the milled nano- composite may be heat-treated after milling.
• the zinc chloride reacts with sodium carbonate during milling to form nano-composite particles of zinc carbonate within the sodium chloride phase.
• the ZnCO 3 is converted to ZnO by heat treating the milled powder at temperatures above 250 C.
• An excess non-reactant diluent phase such as NaCl may be added to promote separation of the nano-composite particles during their formation.
• the presence of a sufficient volume fraction of a non-reactant diluent enables separation of the zinc oxide particles and thus a minimum of agglomeration or sintering together of particles occurring during heat treatment.
• the volume fraction of the diluent phase should be at least 80% to ensure fully separated particles.
• the non-reactant diluent phase is removed by, for example, dissolution in a solvent and filtering.
• Particles heat-treated at 350 C exhibited a significantly increased dispersibility which may be attribute to the higher heat treatment temperature stabilising the particle surfaces.
• Suitable surfactants include stearic acid, recinolieic acid, poly 12-hydroxy stearic acid, metal hydroxy stearic acid, oleic acid, palmitic acid, lauric acid, plearagonic acid and myristic acid or esters of these acids either alone or in combination.
• the topical sunscreen composition of the present invention may be formulated by including one or more of the following components in addition to a suitable quantity of zinc oxide particles:
• one or more film-formers are optionally present.
• one or more water-proofing materials are provided.
• one or more antimicrobial preservatives are provided.
• acid or alkali added to adjust the pH of the aqueous phase to above about 7.0.
• one or more fragrance materials are provided.
• one or more organic sunscreen actives are provided.
• one or more solvents for the organic sunscreens are optionally one or more solvents for the organic sunscreens.
• one or more materials to photostabilise the organic sunscreens are optionally one or more materials to photostabilise the organic sunscreens.
• one or more materials to prevent or reverse the effects of premature aging of the skin by the sun are optionally used.
• suitable emulsifiers include, but are not limited to, the following: Ethoxylated sorbitan esters (available commercially under the trade name Tween); Polyethoxylated esters of hydrogenated castor oil (available commercially under the trade name Arlacel 989); Sorbitan sesquioleates (available commercially under the trade name Arlacel 83); PEG 30 Dipolyhydroxystearate (available commercially under the trade name Arlacel P135); Glycerol sorbitan oleostearate (available commercially under the trade name Arlacel 481); Polyoxyethylene Glycerol sorbitan isostearate (available commercially under the trade name Arlacel 582); PPG PEG Glycerol sorbitan hydroxyisostearate (available commercially under the trade name Arlacel 780); Glycerol sorbitan fatty acid ester (available commercially under the trade name Arlacel 986); Abil WE09; Abil
• Suitable emulsifiers for oil-in-water emulsions usually have HLBs (hydrophile/lipophile balances) greater than about 7. They are often used in combination with one or more low HLB emulsifiers. Many examples of such emulsifiers are listed in McCutcheon's "Emulsifiers and Detergents”.
• Waxes that may be used include, but are not restricted to, one or more of the following: Ozokerite, paraffin wax, beeswax, carnauba wax, ceresin, candelilla wax, castor wax, long chain fatty alcohols such as cetyl alcohol, stearyl alcohol, behenyl alcohols, and synthetic spermaceti wax.
• Electrolytes that may be used include, but are not restricted to, one or more of the following: salts of monovalent metals such as sodium chloride, salts of divalent metals such as magnesium sulfate.
• Dihydric or polyhydric alcohols that may be used include, but are not restricted, to one or more of the following: propylene glycol, sorbitol, and glycerol.
• Moisturisers and skin conditioners that may be used include, but are not restricted to, one or more of the following: urea, glycolic acid and its salts, lactic acid and its salts, aloe vera, sorbitol, glycerol, butylene glycol, hexylene glycol and other polyhydric alcohols, polyethylene glycol, sugar and its derivatives, starch and its derivatives, hyaluronic acid and its salts, urea, guanidine, and mixtures thereof.
• Water-soluble polymers that may be used include, but are not restricted to, one or more of the following: xanthan gum, cellulose derivatives, polymers of acrylic acid and derivatives, carbomers, PVP, alginates, guar gum.
• Other thickeners and stabilisers for the water phase may include, but are not restricted to, one or more of the following: magnesium aluminium silicate, sodium aluminium silicate, colloidal silica, fumed silica, sodium stearate, acrylates/steareth 20 methacrylate copolymer (Aculyn 22), acrylates copolymer emulsion (Aculyn 33 A), PEG150/decyl alcohol/SMDI copolymer (Aculyn44), PEG150/stearyl alcohol/SMDI copolymer (Aculyn46).
• said thickeners for the oil phase include polyethylene, hydrophobic silica, metal stearates such as zinc stearate, and any of one or more of the a
• Film formers and waterproofing agents include, but are not restricted to, one or more of the following: Acrylates/t-octylpropenamide copolymer (Dermacryl 79); alkylated polyvinylpyrrolidones (Antaron V216 and Antaron V220); tricontanyl polyvinylpyrrolidone (AntaronWP660).
• Emollients that may be used include, but are not restricted to, one or more of the following: hydrocarbon oils, such as paraffin oil or mineral oils; vegetable oils such as sunflower oil, apricot oil, jojoba oil and its derivatives, shea butter; silicone oil and its derivatives; fatty acid esters, such as isopropyl palmitate, isopropyl myristate, isopropyl neopentanoate, cetearyl octanoate, C12-15 alkyl benzoate, cetyl palmitate, octyl palmitate and mixtures thereof, silicone oils and derivatives of silicone oils.
• hydrocarbon oils such as paraffin oil or mineral oils
• vegetable oils such as sunflower oil, apricot oil, jojoba oil and its derivatives, shea butter
• silicone oil and its derivatives such as isopropyl palmitate, isopropyl myristate, isopropyl neopentanoate, cetearyl octanoate
• Sunscreen compounds that may be used include, but are not restricted to, one or more of the following: 2-ethylhexyl-p-methoxycinnamate, isoamyl-p-methoxycinnamate, 2- ethoxyethyl p-methoxycinnamate, 2-ethylhexyl N,N-dimethyl- ⁇ -aminobenzoate, 4- aminobenzoic acid, 2-phenyl-benzimidazole-5-sulfonic acid and its potassium sodium and triethanolamine salts, homosalate, oxybenzone, 2-ethylhexyl salicylate, 3-(4'- methylbenzylidene)d-l -camphor, Benzophenone-2, Benzophenone-4, Benzophenone-5, Dioxybenzone, menthyl anthranilate, octocrylene, octyl triazone, triethanolamine salicylate, titanium dioxide, PEG25 PABA,
• the sunscreen of the present invention may be included as one component of a zinc cream or of cosmetic products such as foundation, lipstick or tanning lotion.
• a zinc cream or of cosmetic products such as foundation, lipstick or tanning lotion.
• the raw materials used were anhydrous ZnCl 2 powder (Fluka, >98.0%, -10 mesh), Na 2 CO 3 powder (Sigma, 99.8%, -100 mesh), and NaCl powder (Cleeze, 99.5%, -10 mesh). 5 kg of the starting powder mixture of ZnCl , Na 2 CO 3 and NaCl in a molar ratio of 1 : 1 :3.4 corresponding to the reaction
• the milled and heat-treated powder was slurried into filtered deionised water to dissolve and remove the NaCl by-product/diluent phase. Using a settling and filtration technique, the salt content in the nanopowder-containing slurry was reduced to less than 10 ppm.
• PCS Photon Correlation Spectroscopy
• Figure 3 shows UV-Vis Spectroscopy results for a diluted slurry of the ZnO in deionised water having 0.01 wt% of ZnO and 0.0008 wt% of Dispex-A40 dispersant.
• the measurements show that the suspension has a high transmittance in the visible light range, over 80% at 500 nm and strong absorption in the UV light range, indicative of fully dispersed 30 nm particles.
• the UV-Vis Spectroscopy for the ZnO slurry was compared to slurries containing larger particle sizes.
• Figure 4 shows a comparison of the results for the ZnO described above with slurries containing ZnO of 50 nm, 90 nm, and 250 nm mean particle size, respectively. All slurries were prepared in an identical manner using Dispex A40. The measurements show that the visible transmittance increases significantly with decreasing particle size, while the UV transmittance decreases with decreasing particle size.
• Example 2 A sample milled in the same manner as in Example 1 was heat treated at 250°C for 1 hour in air and cooled to room temperature. Examination of the heat-treated powders by X-ray diffraction showed that the phases present in the powder consisted of ZnO and NaCl.
• UV-Vis Spectroscopy measurement of a diluted slurry of the sample in deionised water having 0.01 wt% of ZnO and 0.0008 wt% of Dispex- A40 was carried out and compared o with a sample heat treated at 350 C following milling in accordance with Example 1.
• the aqueous suspension of the powder heat treated at 350 C had a high transmittance in the visible light range as well as high absorption in the UV light range.
• the suspension of the powder heat-treated at 250 C resulted in poor transmittance in the visible light range and low absorption in the UV light range ( Figure 5).
• Particles heat-treated at 350 C exhibited a significantly increased dispersibility associated with the effect of the higher heat treatment temperature stabilising the particle surfaces.
• Example A An aqueous slurry of mechano-chemically produced ZnO (sample A) was prepared using the method described in Example 1.
• Sample A had a BET surface area of 44.1 m 2 /g which corresponds to the spherical particle size of 24 nm.
• the ZnO particles were coated with stearic acid to form powder dispersed in Isostearyl Benzoate (C17 alkyl Benzoate), as described in Example 4.
• the suspension was diluted into 0.01 wt% in Isostearyl Benzoate, and ultrasonicated for 30 minutes.
• sample B Commercially available dry ZnO powders synthesised by vapour condensation method (sample B) and wet chemical precipitation method (sample C) respectively were dispersed in water by ultrasonication, and coated with stearic acid to form powder dispersed in Isostearyl Benzoate, as described in Example 4.
• Samples B and C had BET surface areas of 13.1 and 13.8 m 2 /g respectively, which corresponds to spherical particle sizes of 82 and 77 nm respectively.
• the suspension was diluted into 0.01 wt% in Isostearyl Benzoate and ultrasonicated for 30 minutes.
• UV-Vis spectra of the mixtures were measured at a wavelength range of 400 to 700 nm, before and during UV exposure at 5-minute intervals. Isostearyl Benzoate was used as a reference sample. The change in transmittance at 520 nm, which is the peak position of the absorption band of DPPH, as a function of UV exposure time was calculated and defined as Decay Rate. DPPH is attacked by the photocatalytic activities of ZnO, resulting in the disappearance of its purple colour originated from the absorption band. Therefore, the decay rate is a measure of photocatalytic activities of ZnO.
• a slurry of 30 nm ZnO in water of total mass 1.63 kg (11.2 wt% ZnO) was prepared.
• the ZnO was manufactured according to Example 1. Separately, 27 grams of stearic acid (corresponding to 15% of the mass of ZnO) was mixed with 180 grams of Isostearyl Benzoate until the stearic acid dissolved.
• Both phases were then loaded into a Hobart planetary mixer and mixed for 2 hours. During mixing, the ZnO was transferred from the water phase into the Isostearyl Benzoate phase, forming a thick paste. The water was then removed.
• the liquids were mixed together in a Hobart planetary mixer for 1 hour during which time the zinc oxide was transferred from the water to the hexane phase.
• the water was removed and 4.9 grams of Solsperse 3000 dispersant and 100 grams of hexane were added, and the zinc oxide was fully dispersed using a high shear mixer.
• the hexane was removed by evaporation at 60 C for 3 hours, resulting in a dry, free-flowing powder.
• the dry ZnO powder was then dispersed in hexane to form a 0.01 wt% solution using an ultrasonic bath.
• UV-Vis spectroscopy measurements carried out on the sample prior to drying and the sample after drying and redispersion in a 10 mm path-length sample holder are shown in Figure 9.
• the visible specular transmittance curve for the dried and redispersed sample is nearly identical with the undried sample, indicating that it was possible to fully redisperse the dried powder.
• Example 7 Properties of Sunscreen Formulations
• UV-Vis measurements were carried out on samples prepared by dispersing ZnO particles manufactured using the method of Example 1 into Isostearyl Benzoate using the method of Example 4.
• Isostearyl Benzoate is a common base used for sunscreen formulations.
• the concentration of ZnO was varied from 2 wt% to 30 wt%.
• samples containing 50 nm, 90 nm and 250 nm mean particle size dispersed in Isostearyl Benzoate were also tested.
• Figure 10 shows UV-Vis curves for samples with mean particle sizes of 25, 50 and 90 nm. It is seen that the total transmittance in the visible light region from 400 to 700 nm increases with decreasing particle size, while in the UV region (200-400 nm) the transmittance decreases (absorptance increases) with decreasing particle size.
• Figure 11 shows the variation of visible transmittance at 550 nm with particle size.
• Figure 12 shows the variation of UV transmittance at 330 nm with particle size.
• Figure 13 shows the effect of the mean particle size on the CIE Whiteness Index.
• Figure 14 shows the effect of particle size and concentration on the in-vitro SPF. It is seen that for a given concentration of ZnO, the highest SPF is achieved with the smallest particle size. On the basis of Figures 10 to 14 it is concluded that significant enhancement of sunscreen performance is achieved by decreasing the mean particle size of ZnO to below 30 nm.
• Figure 15 shows measurements of absorptance as a function of wavelength in the UV region for a sample containing 30 wt% ZnO dispersed in Isostearyl Benzoate. The UV measurements were made using the Transpore tape method. Sunscreen performance values for this sample are shown in Table 1.
• Table 1 Sunscreen performance values for 30 wt% ZnO in Isostearyl Benzoate
• Figure 16 shows the effect of particle size on transparency as a function of in-vitro SPF (Transpore tape method). This figure was produced using the data of Figures 11 and 14.
• Figure 11 shows the relation between size, wt% and transmittance.
• Figure 14 shows the relation between size, wt% and in-vitro SPF. Therefore, from Figures 11 and 14, the relation between size, transmittance and in-vitro SPF can be deduced via the wt% of ZnO.
• Figure 16 shows the importance of small particle size for transparent sunscreen having a high SPF value; smaller particles contributing to higher transparency at a fixed SPF. Of particular importance is the increase in Transmittance % as the particle size is reduced from 50 nm to 25 nm. Since there is a linear correlation between in-vitro SPF (Transpore Tape method) and in-vivo SPF as shown in Figure 17, Figure 16 can be re-drawn as Transmittance % as a function of in-vivo SPF ( Figure 18).
• Figure 19 can be deduced from Figure 11 where Transmittance % was plotted against particle size and concentration.
• specular extinction coefficient is, by its definition, normalised with concentration and film thickness. As such, it is a direct measure of scattering power of particles having different particle sizes. This means that in order to obtain high transparency at a high SPF value, it is essential to use small particles having a low specular extinction coefficient.
• Example 8 Effect of ZnO particle size on the properties of Water-in-oil emulsion of Chemical Free sunscreen
• UV-Vis measurements were carried out on samples prepared by using the following formulation. This formulation contains no organic/chemical UV screening agent.
• the mean particle sizes of the zinc oxide powders for use in the above formulation were 25 nm (using the manufacturing method described in Example 1), 50 nm, 90 nm and 250 nm.
• the first step in the preparation of this formulation was to prepare a water phase by dissolving magnesium sulphate and propylene glycol in water. Keltrol was then dispersed in the water phase by adding it slowly while stirring at 80 to 85°C.
• An oil phase was prepared by heating Zinc Oxide in Finsolv-TN along with Arlacel P135, Monomuls 90-018 and Performalene 400 to 90 to 95°C for 5 minutes. The mixture was stirred until melted. The water phase was then added to the oil phase. The mixture was stirred using a high shear mixer and then cooled down to 40 to 45°C. Germall Plus was then mixed in.
• Figure 20 shows the specular transmittance of sunscreens using a 20 micron quartz cell.
• Figure 21 shows the specular extinction coefficient at 550 nm calculated from Figure 20.
• Figure 22 shows CIE L* coordinate calculated from diffuse reflectance measurements. CIE L* coordinate is a measure of brightness of samples, and thus an indication of whitening effect. From Figures 20, 21 and 22, it is evident that the smaller the mean particle size of the zinc oxide particles the better the clarity achieved. There was a surprising improvement in the transparency for a mean particle size of 25 nm than would have been extrapolated from the data for 50 nm particles or greater mean particle diameter.
• Figure 23 illustrates the superior transparency of the 25 nm zinc oxide formulation using images of the sunscreen formulations in an 8-micron optical-path-length quartz cell.
• the mean particle size for each formulation was printed on each of two columns using the same font/font-size.
• the quartz cell was placed on top of the letters that correspond to the particle size in the sunscreen formulation. It is clearly evident that the sample containing zinc oxide particles with a mean particle size of 25 nm had the highest transparency of the formulations so tested.
• in-vitro SPF measurements were carried out for each of the four formulations having a mean particle size of 25 nm, 50 nm, 90 nm and 250 nm.
• Figure 24 shows the in-vitro SPF as a function of particle size. The SPF value was higher for smaller particles. Since the in-vitro SPF measured using 8 micron cell has a linear relation with in-vivo SPF values for ZnO suspension in Finsolv-TN ( Figure 25), Figure 20 can be re-plotted as in Figure 26.
• Example 9 Water-in-oil emulsion of Chemical Free_sunscreen having a SPF value greater than 30, and excellent clarity on the skin UV-Vis measurements were carried out on samples prepared by using the following formulation. This formulation contains no organic/chemical UV screening agent. Ingredients: %w/w
• a water phase was made by dissolving magnesium sulphate and propylene glycol in water.
• Keltrol was dispersed in water phase by adding it slowly while stirring at 80-85°C.
• An oil phase was then prepared by heating Zinc Oxide in Finsolv-TN along with Isopropyl Palmitate, beeswax, Dehymuls and Monomuls to 80-85°C for 5 minutes. The mixture was stirred until melted.
• the water phase was then added to the oil phase and the mixture was stirred using a high shear mixer, and then cooled down to 40-45°C. Germall Plus was then mixed in.
• Example 10 Water-in-oil emulsion of sunscreen including organic UV absorbers, having a SPF value of 30+, and excellent clarity on the skin UV-Vis measurements were carried out on samples prepared by using the following formulation containing no organic/chemical UV screening agents:
• a water phase was prepared by dissolving magnesium sulphate in water. Keltrol was dispersed in the water phase by adding it slowly while stirring at 80-85°C.
• An oil phase was prepared by heating zinc oxide in C12-15 alkyl benzoates along with Isopropyl palmitate, PCL Liquid and zinc stearate to 80 to 85°C for 5 minutes. Beeswax, Dehymuls and Monomuls were then added and the mixture was stirred until melted. Cab-O-Sil, Parsol MCX, Parsol 5000, BHT, propylene glycol were then added and stirred for 2 to 3 minutes. The water phase was then added to the oil phase.
• Example 11 Extinction Coefficient for specular transmittance of 550 nm for various formulations.
• Figure 27 illustrates the extinction coefficient at a specular transmittance of 550 nm for zinc oxide particles with a mean particle size of 25 nm dispersed in Finsolv-TN as per Example 7, as well as the formulations of Examples 7, 8 and 9. From Figure 27 it is readily apparent that the values of the specular extinction coefficient for either complex formulations such as those of Examples 7, 8, and 9, as well as a simple formulation using Finsolv-TN alone, are less than 2.0 (wt%.mm) "1 with the simple formulations being less than 1.0 (wt%.mm) "1 .
• Example 12 Comparison with other commercially available products
• Figure 28 compares the UV-Vis total transmittance spectra of two samples, designated Sample 1 and Sample 2 for 10 micron thick films.
• the data presented for Sample 1 was calculated from the data disclosed in an Affidavit filed under 37 C.F.R. 1,132 by Mark Mitchnick during re-examination of US Patent No. 5,587,148 for a dispersion of 122 nm ZnO in mineral oil (40 wt%, 28 micron thick film) using Beer's law.
• Sample 2 was a dispersion of 25 nm sized ZnO particles in accordance with the present invention in Finsolv-TN oil (40 wt%, 28 micron film thick).
• the UV-Vis data for Sample 2 was calculated from the spectrum of Sample 2, using Beer's law.
• Figure 28 demonstrates that Sample 2 has a significantly increased transparency in the visible light range compared with Sample 1. Also, the UV screening efficiency significantly increased for Sample 2 over Sample 1, which corresponds to approximately a factor of two increase in SPF value.
• the total transmittance is a sum of the diffuse and specular transmittance values.
• Specular transmittance is directly related to transparency. For example, "clarity" of plastic sheets is defined as specular transmittance according to ASTM D 1746-97. Diffuse transmittance is caused by light scattering by particles and thus a measure of cloudiness or whitening effect. If the whitening effect is large, diffuse transmittance is large as well, and hence total transmittance may increase in spite of low transparency. It can be misleading to use total transmittance for the evaluation of transparency. Therefore, transparency should be evaluated using specular transmittance measurements, as explained below.
• Figure 29 shows a comparison of the whiteness index of various commercially available formulations with that of the present invention when the mean particle size of the zinc oxide particles is 25 nm.
• the whiteness index is shown as a function of the concentration of such zinc oxide powders within the composition and a linear relationship between whiteness index and weight percent of zinc oxide was observed for the formulation made in accordance with the present invention. More importantly, Figure 29 clearly indicates that the sunscreen compositions of the present invention provide significantly reduced whiteness over the full range of weight percentages of zinc oxide particles likely to be included in such a sunscreen when compared with other commercially available sunscreens.
• the sunscreen composition of the present invention and the zinc oxide particles included therein have many advantages over the prior art including, but not limited to, the following: (i) the ability for the first time to make available to the market a sunscreen that can deliver a dermatologically acceptable level of SPF in a substantially visibly clear, transparent sunscreen without needing to include chemical UV sunscreen agents; (ii) the ability due to (i) to protect the user from the potentially unfavourable effects of chemical UV screening agents; (iii) a more photostable sunscreen due to the ability to avoid the inclusion of chemical UV screening agents; (iv) improved cosmetic acceptability due to far superior whiteness and specular extinction coefficients compared with prior art sunscreens without a reduction in

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