Patent Grant
11007151
Much of the population has experienced a skin condition such as a rash, pressure ulcer, or a wound such as a cut or first degree burn, that has required topical application of a cream or ointment to assist in the healing process. Often, these conditions are more prevalent in infants, the elderly, and infirm. For instance, infants, the elderly, and infirm can be susceptible to developing incontinent dermatitis, which occurs when the skin is exposed to prolonged wetness, increased skin pH caused due to contact with urine and feces, and the resulting breakdown of the stratum corneum, or the outermost layer of the skin. Meanwhile, pressure ulcers, also known as decubitus ulcers or bedsores, are also a concern. Pressure ulcers are localized injuries to the skin and/or underlying tissue that usually occur over a bony prominence as a result of pressure, or pressure in combination with shear and/or friction. The most common sites are the sacrum, coccyx, heels or the hips, but other sites such as the elbows, knees, ankles or the back of the cranium can be affected. Pressure ulcers occur due to pressure applied to soft tissue resulting in completely or partially obstructed blood flow to the soft tissue. Factors that can contribute to the formation of ulcers include protein-calorie malnutrition, microclimate (skin wetness caused by sweating or incontinence), diseases that reduce blood flow to the skin, such as arteriosclerosis, or diseases that reduce the sensation in the skin, such as paralysis or neuropathy.
The aforementioned conditions, and other skin conditions, can be prevented or treated, for instance, by the application of zinc oxide to the affected area of the skin. Zinc oxide can help speed up the wound healing process and can also limit the skin's exposure to excessive moisture. As such, one approach for treating these skin conditions is to block moisture from reaching the skin, such as by the application of oil-based protectants or barrier creams, including various over-the-counter creams or ointments containing zinc oxide, to the affected area. However, if the skin is not thoroughly dry, some of these oil-based protectants and creams can actually seal the moisture inside the skin rather than outside the skin. Further, such protectants and creams are very viscous and can be greasy, resulting in difficulty in removing the protectants and creams from one's hands after application onto the affected area of the skin. In addition, rubbing these products into the skin can cause additional discomfort or pain, and in the event that a caretaker or healthcare provider must apply the product to a patient, this could lead to embarrassment for both the patient and caretaker depending on the location of application.
As such, a need exists for a composition that can provide a sufficient moisture barrier without the risk of sealing moisture inside the skin and that can be more easily applied without causing discomfort. One approach is to use a treatment composition in conjunction with a propellant to create an aerosol spray composition. However, the high viscosity of the resulting aerosol spray composition means that it is often difficult to formulate the composition into a medium that can be sprayed due to issues with clogging of the valves and nozzle in the dispenser. Further, many propellants have too high of a vapor pressure, which could result in an erratic spray or stream of product that is not evenly controlled, meaning that applying a smooth, even coating of the aerosol spray composition to the area of the skin requiring treatment cannot be achieved.
Still another problem associated with the aforementioned sprayable compositions is that the particulate ingredients of the sprayable compositions, such as zinc oxide, often settles to the bottom of the container in which the sprayable composition is stored, resulting in settling of the composition and caking of the product in the container. In addition, many sprayable compositions have a low viscosity to allow for spraying, but this results in compositions that are not viscous enough when applied to the skin's surface, resulting in a runny product that does not evenly coat or effectively contact the skin.
As such, a need exists for a sprayable zinc oxide composition containing zinc oxide particles that remain substantially homogeneously distributed and that can be evenly sprayed onto the skin as a fine mist.
In accordance with one embodiment of the present invention, a sprayable zinc oxide composition is disclosed. The composition includes a fluoro-olefin propellant and zinc oxide particles.
In accordance with another embodiment of the present invention, a method of forming a sprayable zinc oxide composition is disclosed. The method includes forming a base zinc oxide composition, wherein the base zinc oxide composition includes zinc oxide particles and a carrier fluid; introducing the base zinc oxide composition into a spray container; and injecting a hydrofluoro-olefin propellant into the container.
In accordance with yet another embodiment of the present invention, a method of applying a zinc oxide composition to a surface is disclosed. The method includes spraying the composition onto the surface to leave a coating thereon, wherein the composition includes a fluoro-olefin propellant and zinc oxide particles.
Other features and aspects of the present invention are set forth in greater detail below.
A full and enabling disclosure of the present invention, including the best mode thereof to one skilled in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figure, in which:
Repeat use of reference characters in the present specification and drawing is intended to represent the same or analogous features or elements of the present invention.
It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only, and is not intended as limiting the broader aspects of the present invention.
Generally speaking, the present invention is directed to a sprayable composition that can be used in the treatment of a skin condition. The composition includes a propellant particularly useful for forming a sprayable composition that includes zinc oxide particles. The propellant can, for instance, be a hydrofluoro-olefin propellant. The present inventors have found that by selectively controlling certain aspects of the propellant, such as the specific gravity, vapor pressure, and/or molecular weight, a composition having a substantially homogeneous distribution of zinc oxide particles can be achieved. Further, the sprayable composition can be stable such that less than about 3 wt. %, such as less than about 2 wt. %, such as less than about 1 wt. % of the zinc oxide particles in the composition settle when stored in a container at 21° C. for 3 days. This results in a composition that can be evenly sprayed on a surface as a substantially uniform coating of zinc oxide particles.
The ratio of the specific gravity of the propellant to specific gravity of the composition can range from about 0.7 to about 1.6, such as from about 0.8 to about 1.5, such as from about 0.9 to about 1.4. Such a specific gravity ratio results in the propellant having a specific gravity similar to the overall composition, which means that the propellant can be substantially homogeneously distributed throughout the composition. Because the propellant is distributed throughout the composition in this manner, settling of the zinc oxide particles and other particulates contained in the sprayable zinc oxide composition can be prevented. Further, the propellant can have a specific gravity ranging from about 1.03 to about 1.3, such as from about 1.05 to about 1.25, such as from about 1.07 to about 1.2 as determined at 21° C. and based on water having a density of 1.0 at 21° C. Meanwhile, the sprayable zinc oxide composition can have a specific gravity of from about 0.8 to about 1.3, such as from about 0.85 to about 1.25, such as from about 0.9 to about 1.2, as determined at 21° C.
In addition, the propellant can provide a high enough vapor pressure to the composition such that it can be atomized and sprayed in aerosol form, yet the vapor pressure is not so high that the resulting spray creates excessive misting or discomfort when sprayed onto the skin or requires a specially designed aerosol container. For instance, the vapor pressure at room temperature (21° C.) can be less than about 60 psi. In some embodiments, for example, the vapor pressure can range from about 30 psi to about 60 psi, such as from about 35 psi to about 55 psi, such as from about 40 psi to about 50 psi. Without intending to be limited by theory, it is believed that the fluoro-olefin propellants of the present invention, which have a lower vapor pressure at room temperature compared to other propellants, can be used in larger amounts in the sprayable zinc oxide composition, which results in a smoother, more easily controlled, spray and also ensures complete evacuation of the container in which the sprayable zinc oxide composition is stored. Further, because the propellant's low vapor pressure, it is not necessary to use a high pressure aerosol container as is required when utilizing other propellants.
In addition, the molecular weight of the propellant can be greater than 100 grams per mole, such as from about 100 grams per mole to about 400 grams per mole, such as from about 105 grams per mole to about 300 grams per mole, such as from about 110 grams per mole to about 200 grams per mole. By using a propellant having a molecular weight in this range, settling of the zinc oxide particles can be further prevented.
The amount of the fluoro-olefin propellant contained in the sprayable zinc oxide composition of the present invention can range from about 5 wt. % to about 95 wt. % based on the total weight of the composition. Meanwhile, the amount of the zinc oxide particles contained in the sprayable zinc oxide composition of the present invention can range from about 0.5 wt. % to about 30 wt. % based on the total weight of the composition.
I. Sprayable Zinc Oxide Composition
a. Propellant
The sprayable zinc oxide composition of the present invention includes a hydrofluoro-olefin propellant. The propellant can provide the energy needed to aid in the delivery of the zinc oxide particles to a surface of the skin affected with skin conditions such as rashes, ulcers, cuts, or wounds. In other words, the hydrofluoro-olefin propellant can provide the propulsive forced needed to spray the zinc oxide particles onto the skin. As such, the propellant has enough dispersive energy to overcome the surface tension of the liquid components of the sprayable zinc oxide composition.
In one embodiment, the propellant of the present invention includes at least one fluoro-olefin. In one particular embodiment, the propellant includes a hydrofluoro-olefin containing from 3 to 4 carbon atoms, such as three carbon atoms. The hydrofluoro-olefin propellant of the present invention can be referred to as an “HFO” when it contains at least one hydrogen, at least one fluorine and no chlorine. HFOs are derivatives of alkenes. In some embodiments, the HFO propellant of the present invention can contain two carbon-carbon double bonds.
In one particular embodiment, the sprayable zinc oxide composition of the present invention includes a propellant represented by Formula I below:
where each R is independently a hydrogen or a halogen such as fluorine (F), bromine (Br), iodine (I), or chlorine (Cl), and preferably fluorine (F),
R′ is (CR2)nY,
Y is CRF2, and
n is 0 or 1.
Further, in one particular embodiment, Y is CF3, n is 0, and at least one of the remaining Rs is F. In another particular embodiment, Y is CF3, at least one R on the unsaturated terminal carbon is H, and at least one of the remaining Rs is F. In still other embodiments, the fluoro-olefin propellant of the present invention can include one or more tetrafluoropropenes, and such a propellant can be referred to herein as a HFO-1234 propellant. Examples of tetrafluoropropenes contemplated by the present invention are HFO-1234yf (specific gravity of 1.092 at 21° C.) and HFO-1234ze (specific gravity of 1.17 at 21° C.), in the cis- and/or trans-forms. It should be understood that HFO-1234ze refers to 1,1,1,3-tetrafluoropropene, independent of whether it is the cis- or trans-form, and the terms “cisHFO-1234ze” and “transHFO-1234ze” are used herein to describe the cis- and trans-forms of 1,1,1,3-tetrafluoropropene, respectively.
In some embodiments, the HFO-1234ze can include a combination of transHFO-1234ze and cisHFO-1234ze, such as from about 90% to about 99% trans-isomer on the basis of total HFO-1234ze, with the cis-isomer comprising from about 1% to about 10% of the same basis. As such, in some embodiments, the propellant of the present invention can include a combination of cisHFO-1234ze and transHFO-1234ze, preferably in a cis- to trans-weight ratio of from about 1:99 to about 10:99, such as from about 1:99 to about 5:95, such as from about 1:99 to about 3:97.
Although the properties of cisHFO-1234ze and transHFO-1234ze differ in at least some respects, it is contemplated that each of these compounds is adaptable for use, either alone or together with other compounds including its stereoisomer, as a propellant in the sprayable zinc oxide composition of the present invention. For example, while transHFO-1234ze has a relatively low boiling point (−19° C.), it is nevertheless contemplated that cisHFO-1234ze, with a boiling point of 9° C., can also be used as a propellant in the sprayable zinc oxide composition of the present invention. Further, it is to be understood that the terms HFO-1234ze and 1,1,1,3-tetrafluoropropene refer to both stereo isomers, and the use of these terms covers both the cis- and trans-forms.
The amount of the fluoro-olefin propellant contained in the sprayable zinc oxide composition of the present invention can range from about 5 wt. % to about 95 wt. %, such as from 10 wt. % to about 80 wt. %, such as from about 15 wt. % to about 60 wt. % based on the total weight of the composition.
b. Zinc Oxide Particles
Additional components that can be present in the sprayable zinc oxide composition will now be discussed in more detail. First, the sprayable zinc oxide composition of the present invention further includes zinc oxide particles, which repel moisture and create a barrier between the skin and environment to protect the skin from excessive moisture. The zinc oxide particles can have an average particle size of from about 20 nanometers to about 200 nanometers, such as from about 25 nanometers to about 150 nanometers, such as from about 30 nanometers to about 100 nanometers.
The zinc oxide particles can be hydrophobic, for example, by application of a hydrophobic coating on the surface of the zinc oxide particles, as described in more detail below. The particles can also carry an inorganic coating, separately or in combination with the hydrophobic coating, as described in more detail below. The zinc oxide particles may be coated with alumina, silica, an organic material, silicones, or combinations thereof. Other suitable surface treatments may include: phosphate esters (including lecithins), perfluoroalkyl alcohol phosphates, fluorosilanes, isopropyl titanium triisostearate, stearic or other fatty acids, silanes, dimethicone and related silicone polymers, or combinations thereof.
For example, zinc oxide particles may be coated with oxides of other elements such as oxides of aluminum, zirconium or silicon, or mixtures thereof such as alumina and silica. Alternatively, the zinc oxide particles may be treated with boron nitride or other known inorganic coatings, singly or in combinations before incorporation into the voids of the particulate. The inorganic coating may be applied using techniques known in the art. A typical process can include forming an aqueous dispersion of zinc oxide particles in the presence of a soluble salt of the inorganic element whose oxide will form the coating. This dispersion is usually acidic or basic, depending upon the nature of the salt chosen, and precipitation of the inorganic oxide is achieved by adjusting the pH of the dispersion by the addition of acid or alkali, as appropriate. The inorganic coating, if present, can be applied as a first layer to the surface of the zinc oxide particles.
In another embodiment, the zinc oxide particles can include an organic coating that provides hydrophobicity. The organic coating can be applied to the inorganic coating, if present, or directly to the zinc oxide. The hydrophobic coating agent may be, for example, a silicone, a silane, a metal soap, a titanate, an organic wax, or combinations thereof. The hydrophobic coating can alternatively include a fatty acid, for example, a fatty acid containing 10 to 20 carbon atoms, such as lauric acid, stearic acid, isostearic acid, and salts of these fatty acids. The fatty acid may be isopropyl titanium trisostearate. With respect to the silicone, the hydrophobic coating may be a methicone, a dimethicone, their copolymers or mixtures thereof. The silicone may also be an organosilicon compound, for example dimethylpolysiloxanes having a backbone of repeating -Me2SiO— units (“Me” is methyl, CH3), methyl hydrogen polysiloxanes having a backbone of repeating -MeHSiO— units and alkoxysilanes of formula RnOSiH(4-n) where “R” is alkyl and “n” is the integer 1, 2 or 3. With respect to the silane, the hydrophobic coating agent may be an alkoxysilanes, for example an alkyltriethoxy or an alkyltrimethoxy silanes available from OSI Specialties or PCR. The alkoxysilane may be a triethoxycaprylylsilane or a perfluoroalkylethyl triethoxysilane having a C3 to C12 alkyl group that is straight or branched. Zinc oxide particles with a triethoxycaprylylsilane coating are commercially available under the name ZANO™ 10 Plus from Umicore Zinc Chemicals.
The amount of zinc oxide particles contained in the sprayable zinc oxide composition of the present invention can range from about 0.5 wt. % to about 30 wt. %, such as from 1 wt. % to about 25 wt. %, such as from about 2 wt. % to about 20 wt. % based on the total weight of the sprayable zinc oxide composition.
c. Carrier Fluid
The propellant and zinc oxide particles can each be substantially homogeneously distributed in a carrier fluid as part of a solution or as components in a colloidal suspension or dispersion. For instance, the propellant, zinc oxide particles, and carrier fluid can form a water-in-oil emulsion or an oil-in-water emulsion. It is also to be understood, however, that the carrier fluid can be oil or water.
Suitable oils that can be used in the carrier fluid include mineral oils, plant-based oils, silicone oils, or a combination thereof. Examples of commercially available mineral oils, which are liquid petroleum derivatives that may be used in accordance with the present invention can include Witco Corporation's CARNATION™ mineral oil or Penreco Corporation's DRAKEOL™ mineral oil. Suitable plant-based oils, which are non-petroleum biomass derived oils, that can be used include vegetable or fruit oils, such as almond oil, peanut oil, wheat germ oil, linseed oil, jojoba oil, apricot pit oil, walnut oil, palm nut oil, pistachio nut oil, sesame seed oil, rapeseed oil, cade oil, corn oil, peach pit oil, poppy seed oil, pine oil, castor oil, soybean oil, avocado oil, safflower oil, coconut oil, hazelnut oil, olive oil, grape seed oil, sunflower oil, apricot kernel oil, geranium oil, rice bran oil and mixtures thereof. Silicone oils that can be used include disiloxane, cyclomethicone, dimethicone and derivatives thereof, and polydimethylsiloxane fluids. Cyclomethicone is a volatile compound and evaporates when applied to the skin's surface, such that the resulting coating is drier to the touch. Other similar volatile compounds that can be used include isododecane.
Water can also be used as a carrier fluid either alone or in conjunction with any of the oils described above as part of a water-in-oil emulsion or an oil-in-water emulsion. It is of course not intended that the carrier fluid be limited to the materials described above.
When both an oil and water are utilized, the oil can be present in the composition in an amount ranging from about 1 wt. % to about 35 wt. %, such as from about 3 wt. % to about 30 wt. %, such as from about 5 wt. % to about 25 wt. % based on the total weight of the composition. Meanwhile, the water can be present in an amount less than about 50 wt. %, such as an amount ranging from about 1 wt. % to about 50 wt. %, such as from about 5 wt. % to about 45 wt. %, such as from about 10 wt. % to about 40 wt. % based on the total weight of the composition. Further, in some embodiments, it should be understood that the water is present in an amount less than 30 wt. % based on the total weight of the composition.
Regardless of the particular carrier fluid or combination of carrier fluids utilized, the total amount of the carrier fluid or fluids present in the composition can range from about 10 wt. % to about 70 wt. %, such as from about 15 wt. % to about 65 wt. %, such as from about 20 wt. % to about 60 wt. % based on the total weight of the composition.
d. Emulsifiers
The sprayable zinc oxide composition can also include one or more emulsifiers as part of an emulsifier system to help create a stable, substantially homogeneous, uniform dispersion of the propellant and the zinc oxide particles by preventing the separation of the sprayable zinc oxide composition into constituent phases. The emulsifier system may include one or more nonionic, anionic, and/or amphoteric emulsifiers, including mixtures containing different species or mixtures of different surfactants within the same species.
Nonionic surfactants, which typically have a hydrophobic base (e.g., long chain alkyl group or an alkylated aryl group) and a hydrophilic chain (e.g., chain containing ethoxy and/or propoxy moieties), can be particularly suitable. Some suitable nonionic surfactants that may be used include, but are not limited to, ethoxylated alkylphenols, ethoxylated and propoxylated fatty alcohols, polyethylene glycol ethers of methyl glucose, polyethylene glycol ethers of sorbitol, ethylene oxide-propylene oxide block copolymers, ethoxylated esters of fatty (C8-C18) acids, condensation products of ethylene oxide with long chain amines or amides, condensation products of ethylene oxide with alcohols, fatty acid esters, monoglycerides, or diglycerides of long chain alcohols, and mixtures thereof. Particularly suitable nonionic emulsifiers may include ethylene oxide condensates of fatty alcohols (e.g., sold under the trade name Lubrol), polyoxyethylene ethers of fatty acids (particularly C12-C20 fatty acids), polyoxyethylene sorbitan fatty acid esters (e.g., sold under the trade name TWEEN®), and sorbitan fatty acid esters (e.g., sold under the trade name SPAN™ or ARLACEL®), etc. The fatty components used to form such emulsifiers may be saturated or unsaturated, substituted or unsubstituted, and may contain from 6 to 22 carbon atoms, in some embodiments from 8 to 18 carbon atoms, and in some embodiments, from 12 to 14 carbon atoms.
Although any emulsifier may generally be employed, the present inventors have discovered that a certain combination of hydrophilic and lipophilic nonionic emulsifiers is particularly effective in stabilizing the emulsion. As is known in the art, the relative hydrophilicity or lipophilicity of an emulsifier can be characterized by the hydrophilic/lipophilic balance (“HLB”) scale, which measures the balance between the hydrophilic and lipophilic solution tendencies of a compound. The HLB scale ranges from 0.5 to approximately 20, with the lower numbers representing highly lipophilic tendencies and the higher numbers representing highly hydrophilic tendencies. Desirably, the emulsion of the present invention can include at least one “hydrophilic” emulsifier that has an HLB value of from about 10 to about 20, in some embodiments from about 12 to about 19, and in some embodiments, from about 14 to about 18. Likewise, the emulsion can also include at least one “lipophilic” emulsifier that has an HLB value of from about 0.5 to about 10, in some embodiments from about 1 to about 9, and in some embodiments, from about 2 to about 8. If desired, two or more surfactants may be employed that have HLB values either below or above the desired value, but together have an average HLB value within the desired range. Regardless, the present inventors have discovered that the weight ratio of lipophilic emulsifiers to hydrophilic emulsifiers in the sprayable zinc oxide composition is typically within a range of from about 5 to about 30, in some embodiments from about 7.5 to about 25, and in some embodiments, from about 10 to about 20. Further, the present inventors have discovered that the overall HLB value of the sprayable zinc oxide composition is generally lipophilic and ranges from about 3 to about 10, such as from about 4 to about 9, such as from about 5 to about 8.
One particularly useful group of “lipophilic” emulsifiers are sorbitan fatty acid esters (e.g., monoesters, diester, triesters, etc.) prepared by the dehydration of sorbitol to give 1,4-sorbitan, which is then reacted with one or more equivalents of a fatty acid. The fatty-acid substituted moiety can be further reacted with ethylene oxide to give a second group of surfactants. The fatty-acid-substituted sorbitan surfactants are made by reacting 1,4-sorbitan with a fatty acid such as lauric acid, palmitic acid, stearic acid, oleic acid, or a similar long chain fatty acid to give the 1,4-sorbitan mono-ester, 1,g-sorbitan sesquiester or 1,4-sorbitan triester. The common names for these surfactants include, for example, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monoestearate, sorbitan monooleate, sorbitan sesquioleate, and sorbitan trioleate. Such surfactants are commercially available under the name SPAN™ or ARLACEL™, usually with a letter or number designation which distinguishes between the various mono-, di- and triester substituted sorbitans. SPAN™ and ARLACEL™ surfactants are lipophilic and are generally soluble or dispersible in oil, but not generally soluble in water. One particularly suitable surfactant is sorbitan oleate, which is commercially available as SPAN™ 80. Generally these surfactants will have HLB value in the range of 1.8 to 8.6.
Other useful lipophilic emulsifiers that can be used can include, for example, silicone water-in-oil emulsifiers. By silicone it is meant a molecule that includes at least one siloxane (—Si—O—) repeating unit and further includes a hydrophobic moiety and a hydrophilic moiety. The HLB value of the silicone water-in-oil emulsifier is relatively low. For example, in some embodiments, the silicone emulsifier can have an HLB value in the range of 2 to 9.
Examples of suitable silicone water-in-oil emulsifiers can include non-crosslinked dimethicone copolyols such as alkoxy dimethicone copolyols, silicones having pendant hydrophilic moieties such as linear silicones having pendant polyether groups, branched polyether and alkyl modified silicones, branched polyglycerin and alkyl modified silicones, and combinations thereof. Examples of commercially available non-crosslinked dimethicone copolyols include the following from Dow Corning of Midland, Mich.: cyclopentasiloxane and PEG/PPG-18/18 dimethicone available as DC 5225C, and cyclopentasiloxane and PEG-12 dimethicone crosspolymer available as DC9011. Certain non-crosslinked dimethicone copolyols are cetyl dimethicone copolyols such as cetyl PEG/PPG-10/1 dimethicone sold under the name ABIL™ EM-90, branched polyether and alkyl modified silicones such as lauryl PEG-9 polydimethylsiloxyethyl dimethicone sold under the name KF-6038, and branched polyglycerin and alkyl modified silicones such as lauryl polyglyceryl-3 polydimethylsiloxyethyl dimethicone sold under the name KF-6105. Other non-crosslinked dimethicone copolyols include, for example, bis-PEG/PPG-14/dimethicone copolyol sold under the name ABIL™ EM-97 and the polyglyceryl-4 isostearate/cetyl dimethicone copolyol/hexyl laurate mixture sold under the name ABIL™ WE 09. ABIL™ EM-90, ABIL™ EM-97, and ABIL™ WE 09 are available from Evonik Goldschmidt GmbH of Essen, Germany. KF-6038 are KF-6105 are available from Shin-Etsu Silicones of Akron, Ohio. One particularly suitable emulsifier for use in the present invention is ABIL™ WE 09, which has an HLB value of about 5. Another particularly suitable emulsifier is ABIL™ EM 90, which also has an HLB value of about 5.
Still another suitable nonionic lipophilic emulsifier that can be included in the sprayable zinc oxide composition of the present invention is octyldodecanol/octyldechyl xyloside/PEG-30, which is commercially available from Seppic S.A. under the name EASYNOV™.
Meanwhile, sorbitan fatty acid esters (e.g., monoesters, diester, triesters, etc.) that have been modified with polyoxyethylene are likewise a particularly useful group of “hydrophilic” emulsifiers. These materials are typically prepared through the addition of ethylene oxide to a 1,4-sorbitan ester. The addition of polyoxyethylene converts the lipophilic sorbitan ester surfactant to a hydrophilic surfactant that is generally soluble or dispersible in water. Such materials are commercially available under the designation TWEEN™ (e.g., TWEEN™ 80, polysorbate 80, or polyethylene (20) sorbitan monooleate). TWEEN™ surfactants generally have a HLB value in the range of 9.6 to 16.7. For instance TWEEN™ 80 has an HLB value of 15. Still other suitable hydrophilic emulsifiers can include sucrose fatty acid esters, such as saccharose monopalmitate (HLB of 15) and saccharose monostearate (HLB of 11), or PEG-32 glyceryl laurate (HLB of 14), as well as polyethylene glycol (PEG) n-alkanol esters of the BRIJ™ family such as BRIJ™ 35, 56, 58, 76, 78, and 99, which have an HLB in the range 0112.4 to 16.9. BRIJ™ 56 is polyoxyethylene[10] cetyl ether, for example, has an HLB value of 12.9.
Regardless of the particular emulsifiers utilized, the emulsifiers can be present in the sprayable zinc oxide composition in an amount ranging from about 0.1 wt. % to about 20 wt. %, such as from about 0.5 wt. % to about 15 wt. %, such as from about 1 wt. % to about 10 wt. % based on the total weight of the sprayable zinc oxide composition. Further, the present inventors have discovered that the weight ratio of lipophilic emulsifiers to hydrophilic emulsifiers in the sprayable zinc oxide composition is typically within a range of from about 5 to about 30, in some embodiments from about 7.5 to about 25, and in some embodiments, from about 10 to about 20.
e. Viscosity Modifier
In addition, the composition can include one or more viscosity modifiers which can also help to prevent the separation of the various components of the composition. For instance, in some embodiments, such as when the carrier fluid includes more than one component, one or more viscosity modifiers can be added to the oil phase or the water phase of an emulsion to adjust the viscosity such that separate components in the composition are more miscible. Further, the viscosity of the overall composition can be adjusted so that it is not so high that the composition cannot be sprayed onto a surface, but it is not so low that the composition is too runny such that it does not evenly coat the surface. As such, the composition can have a viscosity greater than about 1000 centipoise, such as from about 1000 centipoise to about 8000 centipoise, such as from about 1500 centipoise to about 6000 centipoise, such as from about 2000 centipoise to about 4000 centipoise.
When a water-in-oil emulsion or an oil-in-water emulsion is utilized in the sprayable zinc oxide composition, the one or more viscosity modifiers can be added to the water phase of the water-in-oil emulsion or the oil-in-water emulsion to enhance the miscibility between the water phase and the oil phase, which promotes the substantially homogeneous distribution of the components of the sprayable zinc oxide composition. It is also to be understood, however, that the viscosity modifier can be added to an already-formed oil-in-water or water-in-oil emulsion to adjust the viscosity as needed.
Suitable viscosity modifiers include carboxylic acid polymers which are crosslinked compounds containing one or more monomers derived from acrylic acid, substituted acrylic acids, and salts and derivatives of these acrylic acids and substituted acrylic acids. They can be crosslinked homopolymers of an acrylic acid or of a derivative thereof, such as acrylamidopropylsulfonic acid. They can be also crosslinked copolymers having (i) a first monomer selected from the group consisting of (meth)acrylic acid, derivatives thereof, short chain (i.e., C1-C4) acrylate ester monomers, and mixtures thereof, and (ii) a second monomer which is a long chain (i.e., C8-C40) substituted polyethylene glycol acrylate ester monomer.
Examples of commercially available carboxylic acid polymers include CARBOPOL™ 1342, PEMULEN™ TR-1, and PEMULEN™ TR-2 available from Lubrizol Corp.; Sepigel 305, SIMULGEL™ EG, SIMULGEL™ NS, and SIMULGEL™ 600, available from Seppic S.A.; VISCOLAM™ AT100P and VISCOLAM™ AT64/P, available from Lamberti S.p.A. One commercially available viscosity modifier is available from Seppic S.A. as SIMULGEL™ NS. SIMULGEL™ NS includes a hydroxylethyl acrylate/sodium acryloyldimethyl taurate copolymer, squalane, and polysorbate 60, which can be added to an oil phase of a water-in-oil or oil-in-water emulsion.
Other suitable viscosity modifiers that can be used include cornstarch (topical starch), talc, rice starch, oat starch, tapioca starch, potato starch, legume starches, soy starch, turnip starch, microcrystalline cellulose, kaolin, aluminum starch octenyl succinate, and mixtures thereof. Water soluble aluminum starch octenyl succinates are commercially available from National Starch & Chemical Co. as DRY FLO™ Pure, DRY FLO™ XT, DRY FLO™ PC, and/or DRY FLO™ AF (aluminum free grade) and are water soluble such that they can be included in a water phase of a water-in-oil emulsion or an oil-in-water emulsion.
Regardless of the particular viscosity modifiers utilized, the viscosity modifier can be present in the sprayable zinc oxide composition in an amount ranging from about 0.05 wt. % to about 15 wt. %, such as from about 0.1 wt. % to about 10 wt. %, such as from about 0.5 wt. % to about 5 wt. % based on the total weight of the sprayable zinc oxide composition.
f. Additional Moisture Brier/Repellant Materials
The sprayable zinc oxide composition can also include other moisture barrier or repellant materials in addition to the zinc oxide particles discussed above. For example, the sprayable zinc oxide composition can include paraffin, microcrystalline wax, petrolatum, beeswax, or a combination thereof. Such moisture repellant materials can be present in the sprayable zinc oxide composition in an amount ranging from about 0.1 wt. % to about 6 wt. %, such as from about 0.25 wt. % to about 4 wt. %, such as from about 0.5 wt. % to about 2 wt. % based on the total weight of the composition.
g. Conditioning Agents
The sprayable zinc oxide composition can further include one or more conditioning agents to help condition the skin. For example, the composition can include thymol iodide, sodium chloride, magnesium dichloride, magnesium sulfate, lanolin, lanolin oil, lanolin wax, lanolin alcohols, lanolin fatty acids, isopropyl lanolate, ethoxylated lanolin, ethoxylated lanolin alcohols, ethoxylated cholesterol, propoxylated lanolin alcohols, acetylated lanolin alcohols, lanolin alcohols linoleate, lanolin alcohols ricinoleate, acetate of lanolin alcohols, ricinoleate, acetate of ethoxylated alcohols-esters, hydrogenolysis of lanolin, ethoxylated hydrogenated lanolin, ethoxylated sorbitol lanolin, or a combination thereof. Thymol iodide and magnesium sulfate may be particularly useful. One or more conditioning agents can be present in the sprayable zinc oxide composition in an amount ranging from about 0.05 wt. % to about 10 wt. %, such as from about 0.1 wt. % to about 7.5 wt. %, such as from about 0.5 wt. % to about 5 wt. % based on the total weight of the composition.
h. Additional Components
Other optional components in the sprayable zinc oxide composition can include skin care-additives such as emollients, as well as fragrances and preservatives. For instance, an emollient such as caprylic/capric triglyceride can be included in the sprayable zinc oxide composition. Other suitable emollients include stearoxy trimethyl silane, cetyl lactate, and alkyl lactate, such as C12-C15 alkyl lactate. When emollients are used, the sprayable zinc oxide composition can feel smooth to the touch when applied to the skin. One or more emollients can be present in the sprayable zinc oxide composition in an amount ranging from about 0.1 wt. % to about 25 wt. %, such as from about 0.5 wt. % to about 20 wt. %, such as from about 1 wt. % to about 15 wt. % based on the total weight of the composition.
Further, a fragrance can be present in the sprayable zinc oxide composition in an amount ranging from about 0.005 wt. % to about 2 wt. %, such as from about 0.01 wt. % to about 1.5 wt. %, such as from about 0.02 wt. % to about 1 wt. % based on the total weight of the composition.
Meanwhile, preservatives can be present in the composition in an amount ranging from about 0.01 wt. % to about 6 wt. %, such as from about 0.02 wt. % to about 4 wt. %, such as from about 0.05 wt. % to about 1 wt. % based on the total weight of the composition. Suitable preservatives include paraben-based preservatives such as methylparaben and propylparaben.
Further, the present inventors have found that a freezing point depressant can be included in the composition to limit the amount of crystallization of any solid components, which can then reduce or limit clogging of the composition when sprayed. If desired, one or more freezing point depressants may be employed, such as glycols (e.g., ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, hexylene glycol, polyethylene glycols, ethoxydiglycol, dipropyleneglycol, etc.); glycol ethers (e.g., methyl glycol ether, ethyl glycol ether, isopropyl glycol ether, etc.); and so forth. Such freezing point depressants can be present in the composition in an amount ranging from about 0.1 wt. % to about 15 wt. %, such as from about 0.5 wt. % to about 10 wt. %, such as from about 1 wt. % to about 5 wt. % based on the total weight of the composition.
II. Formation of the Sprayable Zinc Oxide Composition
Generally, the sprayable zinc oxide composition of the present invention can be made by forming a base zinc oxide composition from a carrier fluid and zinc oxide particles, introducing the base zinc oxide composition into a spray container, and injecting a propellant, such as a hydrofluoro-olefin propellant, into the container. When the base zinc oxide composition is in the form of a water-in-oil emulsion or an oil-in-water emulsion, for example, the base zinc oxide composition can be made by first separately forming an oil phase and a water phase.
The manner in which the water-in-oil emulsion or the oil-in-water emulsion is formed may vary as is known to those skilled in the art. In one embodiment, for example, the oil can be initially blended with any optional emulsifiers, emollients, conditioning agents, etc. to form the oil phase. In such embodiments, the oil phase can contain oils in an amount of from about 30 wt. % to about 80 wt. %, such as from about 35 wt. % to about 70 wt. %, such as from about 40 wt. % to about 60 wt. % based on the total weight of the oil phase. Further, the oil phase can include emulsifiers in an amount ranging from about 5 wt. % to about 35 wt. %, such as from about 10 wt. % to about 30 wt. %, such as from about 15 wt. % to about 25 wt. % based on the total weight of the oil phase. The addition of the emulsifiers can result in an oil phase having an HLB value between about 6 and about 7. In addition, the oil phase can include emollients in an amount ranging from about 10 wt. % to about 45 wt. %, such as from about 15 wt. % to about 40 wt. %, such as from about 20 wt. % to about 35 wt. % based on the total weight of the oil phase. Moreover, the oil phase can include conditioning agents in an amount ranging from about 0.5 wt. % to about 10 wt. %, such as from about 1 wt. % to about 7.5 wt. %, such as from about 1.5 wt. % to about 5 wt. % based on the total weight of the oil phase.
Meanwhile, the water phase can be formed by blending water and other components, such as conditioning agents, viscosity modifiers, etc. In such embodiments, the water phase can include water in an amount ranging from about 50 wt. % to about 99 wt. %, such as from about 55 wt. % to about 98 wt. %, such as from about 60 wt. % to about 97 wt. %. The water phase can also include conditioning agents in an amount ranging from about 0.5 wt. % to about 15 wt. %, such as from about 1 wt. % to about 10 wt. %, such as from about 1.5 wt. % to about 7.5 wt. % based on the total weight of the water phase. Additionally, the water phase can include viscosity modifiers in an amount ranging from about 0.25 wt. % to about 10 wt. %, such as from about 0.5 wt. % to about 7.5 wt. %, such as from about 1 wt. % to about 5 wt. % based on the total weight of the water phase.
After the oil phase and water phase are separately formed, the water phase can be added to the oil phase to form a water-in-oil emulsion. The combination of the phases may be facilitated through agitation (e.g., stirring) and control of the temperatures of each mixture. Next, the zinc oxide particles can be added to the water-in-oil emulsion. The zinc oxide particles can be present in the water-in-oil emulsion in an amount ranging from about 0.25 wt. % to about 35 wt. %, such as from about 0.5 wt. % to about 30 wt. %, such as from about 1 wt. % to about 25 wt. %, such as from about 5 wt. % to about 15 wt. % based on the total weight of the base zinc oxide composition. Then, if desired, other components such as fragrances, preservatives, freezing point depressants, and additional viscosity modifiers can be added to the emulsion. Fragrances can be added in an amount ranging from about 0.01 wt % to about 5 wt. %, such as from about 0.05 wt. % to about 2.5 wt. %, such as from about 0.1 wt. % to about 1 wt. % based on the total weight of the base zinc oxide composition. Likewise, preservatives can be added in an amount ranging from about 0.01 wt. % to about 5 wt. %, such as from about 0.05 wt. % to about 2.5 wt. %, such as from about 0.1 wt. % to about 1 wt. % based on the total weight of the base zinc oxide composition. In addition, freezing point depressants can be added in an amount ranging from about 0.5 wt. % to about 15 wt. %, such as from about 1 wt. % to about 10 wt. %, such as from about 2 wt. % to about 8 wt. % based on the total weight of the base zinc oxide composition. Further, viscosity modifiers can be added in an amount ranging from about 0.1 wt. % to about 15 wt. %, such as from about 0.5 wt. % to about 10 wt. %, such as from about 1 wt. % to about 8 wt. % based on the total weight of the base zinc oxide composition. As such, it is to be understood that in some embodiments, a first viscosity modifier can be added during formation of the water phase, while a second viscosity modifier can be added after forming the emulsion by combining the water and oil phases to form the base zinc oxide composition.
Regardless of which phase is being formed, the temperature can range from about 15° C. to about 40° C., such as from about 18° C. to about 35° C., such as from about 20° C. to about 30° C. After the separate phases are mixed as described above, the resulting base zinc oxide composition can then be filled into a spray container, such as an aerosol spray container. The container can then be sealed, after which the propellant can be introduced into the container, such as via a valve. The container can be filled with the propellant at a pressure ranging from about 130 psi to about 230 psi, such as from about 140 psi to about 220 psi, such as from about 150 psi to about 210 psi.
III. Spray Delivery System
Various aerosol spray containers can be used in conjunction with the sprayable zinc oxide composition to form a system for spraying the composition onto a surface such as skin. One embodiment of a spray delivery system contemplated by the present invention is described with reference to
The spray head 102 is provided with a valve 105 that is retained by the flange 104. The valve 105 is kept closed in its normal condition by the energizing force of a spring 106, but it opens when the spray head 102 is pressed. The spray head 102 further has a spray nozzle 107 which communicates with the valve 105 through a conduit pipe 108. Meanwhile, a dip tube 109 is connected to the valve 105 and extends to the bottom of the spray container 101. By pressing the spray head 102 downwardly against the spring 106, the valve 105 opens to form a fluid passage from the lower end port of the dip tube 109 to the spray nozzle 107 through the valve 105 and conduit pipe 108.
The sprayable zinc oxide composition 110 as discussed above can be charged into the spray container 101. Then, by pressing the spray head 102, the sprayable zinc oxide composition is discharged in the form of a fine mist from the spray nozzle 107 through the aforementioned fluid passage by the pressure associated with the propellant that is substantially homogeneously dispersed in the sprayable zinc oxide composition 110.
Another embodiment of a spray delivery system is described with reference to
The spray system is discussed in more detail below in reference to
Turning now to
The dimensions of the various components can be selected to further minimize the risk of clogging. For instance, the stem 302 can have a diameter of from about 3 millimeters to about 5.5 millimeters, such as from about 3.5 millimeters to about 5 millimeters, such as from about 4 millimeters to about 4.5 millimeters. Meanwhile, the stem orifice 303 can have a diameter of from about 0.5 millimeters to about 0.75 millimeters, such as from about 0.55 millimeters to about 0.7 millimeters, such as from about 0.6 millimeters to about 0.65 millimeters. Additionally, the tailpiece orifice 310 can have a diameter of from about 0.75 millimeters to about 2 millimeters, such as from about 1 millimeter to about 1.75 millimeters, such as from about 1.25 millimeters to about 1.5 millimeters. Further, the vapor tap 306 can have a diameter of from about 0.1 millimeters to about 0.5 millimeters, such as from about 0.15 millimeters to about 0.45 millimeters, such as from about 0.2 millimeters to about 0.4 millimeters. By selectively controlling the aforementioned dimensions, the propellant of the sprayable zinc oxide composition can remain substantially homogeneously distributed throughout the base zinc oxide composition to reduce settling of the zinc oxide particles, and the sprayable zinc oxide composition can leave the exit orifice 204 as a fine mist with less fly away and can be more evenly distributed than when, for instance, a mechanical actuator is utilized.
IV. Application of the Sprayable Zinc Oxide Composition
As a result of the combination of the type of spray delivery system utilized and the characteristics of the sprayable composition, a substantially uniform coating of the composition can be applied to a surface. For instance, the composition of the present invention can be applied to a surface of the skin for the treatment of various skin conditions or irritations such as diaper rash; dry skin; ulcers; superficial cuts, scrapes, wounds, and first degree burns; etc. Areas of skin that can be treated include the buttocks, particularly in the case of diaper rash/incontinent dermatitis, as well as the arms, elbows, hands, abdomen, back, sacrum, coccyx, hips, knees, feet, ankles, heels, etc. As the composition reaches the skin's surface, the propellant can evaporate, leaving a substantially uniform coating of the base zinc oxide composition on the skin. Further, the zinc oxide particles can be distributed throughout the coating in a substantially uniform manner. After the composition has been sprayed onto the skin in the form of a substantially uniform coating, the amount of zinc oxide present in the composition on the skin can range from about 0.25 wt. % to about 35 wt. %, such as from about 0.5 wt. % to about 30 wt. %, such as from about 1 wt. % to about 25 wt. %, such as from about 5 wt. % to about 15 wt. % based on the total weight of the resultant coating (e.g., the sprayable zinc oxide composition excluding the evaporated components such as the propellant).
The present invention may be better understood by reference to the following examples.
A sprayable zinc oxide composition was formed from a base zinc oxide composition including a preservative phase, an oil phase, a water phase to which a propellant was added. First, to make the preservative phase of the base zinc oxide composition, a freezing point depressant was added to a beaker and agitated with a propeller. Next, preservatives were added to the beaker and mixing was initiated using a stirrer equipped with an anchor-type sidewipe agitator. Agitation was continued for at least 15 minutes until the solution was completely dissolved. The preservative phase was then set aside.
Next, to make the oil phase of the base zinc oxide composition, emollients were added to a separate beaker and agitated with a propeller to initiate mixing while maintaining a temperature between 20° C. and 23° C., after which the polyglyceryl-4 isostearate/cetyl dimethicone copolyol/hexyl laurate emulsifier was added, followed by the cetyl PEG/PPG-10/1 dimethicone emulsifier, the sorbitan oleate emulsifier, the polysorbate 80 emulsifier, and the octyldodecanol/octyldechyl xyloside/PEG-30 emulsifier. Mixing via agitation was continued, while maintaining a temperature between 20° C. and 25° C. Next, the silicone oil was added to the beaker, while maintaining a temperature between 20° C. and 23° C. A homogenizer was then used for agitation, using cooling water to maintain a temperature between 20° C. and 25° C., after which a conditioning agent was added. Agitation was continued for at least 15 minutes until the solution was completely dissolved, maintaining a temperature between 20° C. and 28° C. The resulting oil phase of the base zinc oxide composition had an HLB value between 6 and 7.
Next, the water phase of the base zinc oxide composition was prepared in a separate beaker. Water was added to the beaker while maintaining a temperature between 20° C. and 28° C. Mixing was initiated using a stirrer equipped with a stainless steel three propeller blade. A water-soluble conditioning agent was added to the beaker and mixing was continued for at least 15 minutes until all solids were dissolved. Then, the viscosity modifier containing hydroxyethyl acrylate/sodium acryloyldimethyl taurate copolymer, squalane, and polysorbate 60 was added to the beaker, and mixing was continued for at least 15 minutes.
To prepare the base zinc oxide composition emulsion, the oil phase beaker was maintained at a temperature between 20° C. and 25° C. The water phase was then slowly transferred to the oil phase beaker under homogenizer agitation, where the transfer time was at least 20 minutes. The homogenizer speed was increased as needed, while maintaining a temperature between 20° C. and 25° C. The resulting water-in-oil emulsion was then covered and mixed for at least 30 minutes. The preservative phase was then added to the beaker while continuing mixing for at least 15 minutes and maintaining a temperature of from 20° C. to 25° C. After ensuring that all powders were off the surface and increasing the mixing speed as needed, zinc oxide particles were added under homogenizer agitation and mixed for at least 5 minutes, increasing the speed as needed and maintaining a temperature of from 20° C. to 25° C. Then the viscosity modifier aluminum starch octenylsuccinate was added under homogenizer agitation and mixed for at least 5 minutes, increasing the speed as needed and maintaining a temperature of from 20° C. to 25° C. Thereafter, fragrance was added to the beaker under homogenizer agitation, and the emulsion was mixed for at least 15 minutes. The resulting base zinc oxide composition had an HLB value of 7.42.
After the base zinc oxide composition was formed, it was filled into an aerosol spray container, after which the container's valve was sealed or crimped to the top of the container. Then, HFO-1234ze propellant was pressure filled via the valve into the container at a pressure of about 200 pounds. The resulting sprayable zinc oxide composition was a substantially homogeneous blend of the propellant and the base zinc oxide composition, which contained 22 wt. % of the propellant and 78 wt. % of the base zinc oxide composition. The sprayable composition had a specific gravity of about 1.045. The weight percentages of the components used in the sprayable zinc oxide composition are summarized below in Table 1. Once sprayed on a surface (e.g., skin) as a substantially uniform coating, the composition contained 10.4 wt. % of zinc oxide particles due to evaporation of the propellant.
These and other modifications and variations of the present invention may be practiced by those of ordinary skill in the art, without departing from the spirit and scope of the present invention. In addition, it should be understood that aspects of the various embodiments may be interchanged both in whole or in part. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and is not intended to limit the invention so further described in such appended claims.
The present application claims priority to U.S. Provisional Application Ser. No. 61/939,826, filed on Feb. 14, 2014, which is incorporated herein in its entirety by reference thereto.
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