WO2018122121A1 - Metal oxide oil dispersion sunscreen formulations - Google Patents

Abstract

A sunscreen formulation comprises an oil carrier, a particulate metal oxide sunscreen active agent and a polymeric rheology modifier that maintains the particulate sunscreen active agent in a stable dispersion in the formulation. In one aspect the polymeric rheology modifier is obtainable by co-polymerizing a monomer mixture comprising at least one alkyl (meth)acrylate and at least one of the following monomers: a bicyclic (meth)acrylate ester different from the alkyl (meth)acrylate, and an aromatic vinyl monomer. In one embodiment the polymeric rheology modifier is crosslinked.

Description

METAL OXIDE OIL DISPERSION SUNSCREEN FORMULATIONS

Field of the Disclosure

This application relates to personal care sunscreen oil dispersion formulations comprising an oil-based carrier, rheology modifiers and particulate sunscreen active agents, and to methods of stabilizing such oil dispersions using rheology modifiers.

Background

Va ous types of sunscreen product formulations are available commercially to protect a user's skin from UVA and UVB rays that are present in solar radiation. Sunscreen formulations are typically categorized as either aqueous or non-aqueous compositions. Aqueous sunscreen compositions are typically creams formed as emulsions containing the active UV absorbing compounds and additional ingredients such as waterproofing agents, fragrances, emollients and other skin care ingredients. Non-aqueous sunscreen formulations include solvent-based compositions that can be formed as gels for topical application or sprayed-on, for example from an alcohol based solution of the ingredients. Also known are clear liquid oil sunscreen formulations containing oils and organic sunscreen active agents. Sunscreen products may be in a solid form, a liquid form, a paste form, or a gelled stick form.

Sunscreen active agents include both organic agents and inorganic agents. Inorganic sunscreen active agents include metal oxides such as titanium dioxide (Ti0₂), zinc oxide (ZnO), aluminum oxide (Al₂0₃), and iron oxide (FeO). Such metal oxides exist as particles that are insoluble in aqueous systems, alcohol systems, emulsions, and oil-based systems. Inorganic sunscreen active agents in the current art are typically used in aqueous based sunscreen formulations containing typically about 5% - 20% Ti0₂ (and/or ZnO), along with other cosmetically acceptable additives such as emollients.

Inorganic sunscreen active agents of proper particle sizes can block both UVA and UVB radiation, while organic sunscreen active agents generally only block either UVA or UVB radiation. In addition, inorganic sunscreen active agents are chemically stable, while organic sunscreens may undergo chemical degradation when exposed to the sun. Inorganic sunscreen active agents may be less preferred than organic sunscreen active agents in certain formulations because they can take longer to rub in, they may look "ashy" when dried, and they tend to have poor water resistance in aqueous or emulsion-based carrier systems. Water resistance is a key performance indicator for a sunscreen formulation for consumers who engage in outdoor water activities, or outdoor activities that may cause significant perspiration. Prior efforts to provide stable dispersions of metal oxide powders in an oil vehicle have focused on incorporating an organic component with the metal oxide powder, such as by encapsulation, surface treatment, or covering a lipophilic base powder with metal oxide powder particles.

EP 2455061 discloses an oily dispersion containing only two components, namely, an oil dispersion medium and a surface-treated inorganic microparticle oxide powder treated with 1 - 30% by weight of the content of branched fatty acid containing isostearic acid as a primary constituent component, or a metal salt containing isostearic acid as a primary constituent component. Also disclosed is a cosmetic material having a high SPF value and using the oily dispersion. Eospoly Sun Cream (XP-002659382) discloses a sun screen light day protection cream comprising spherical composites of titanium dioxide encapsulated into a polymer structure, and wherein the cream is an emulsion.

JP 2014 091735 A discloses an oil-in-water type emulsion comprising a crosslinked (meth) acrylic acid ester resin powder; acrylic acid/ sodium acryloyldimethyltaurine copolymer; a liquid oil agent; a hydrophobically treated powder; and water. The hydrophobic powder can be any extender pigment or coloring pigment used in ordinary cosmetics, which includes metal oxides and others. The hydrophobic treatment can be, for example, adsorption of fats and oils on the surface of the powder.

JP 2014 080377 A discloses an oil-in-water type emulsion stated to have excellent temporal stability and comprising a particulate zinc oxide subjected to surface coating treatment with trialkoxyalkyl silane and or alkyl titanate; a non-silicone based surfactant; an oil solution; a polyoxyethylene hardened castor oil; an acrylamide based thickener; and water.

EP 1576947 discloses an oily skin preparation comprising a complex powder (the surface of lipophilic base powder is covered with zinc oxide) and an oil component, wherein the complex powder is dispersed in the oil component, and wherein the zeta-potential of the lipophilic base powder is a negative value at the pH of skin. The lipophilic base powder can be selected from silicone resin, silicone rubber, silicone resin-covering-silicone rubber, polyamide, polymethyl methacrylate and ethyl carbamate. The reference notes at [0048] that because of its hydrophilic property, zinc oxide powder by itself is hardly dispersed in oily base and aggregation occurs. It appears there is a need for a ready to use metal oxide oil dispersion (OD) sunscreen formulation that is storage stable and has good water resistance.

There is further a need for a ready to use metal oxide oil dispersion sunscreen formulation that is storage stable and has good water resistance, and that allows for dispersion of the metal oxide particles without incorporation of the metal oxide particles with an organic component, such as by encapsulation, surface-coating, coating of the metal oxide on a lipophilic base powder, or other pre-treatment of the particles.

Summary We have discovered that, unexpectedly, effective sunscreen formulations can be prepared comprising metal oxide particulate sunscreen active agents, one or more oils, and one or more selected polymeric rheology modifiers, to provide a thickened metal oxide oil dispersion sunscreen formulation in which the metal oxide particulates are dispersed in the formulation. The thickened sunscreen formulations are dispersions having long-term storage stability, whereby the metal oxide particulates remain in the dispersed state in the formulations when stored over a long term. In a first aspect the disclosure provides a thickened sunscreen formulation comprising an oil-based carrier comprising at least one oil, at least one particulate metal oxide sunscreen active agent, and at least one polymeric rheology modifier.

The formulation is not in the form of a water-in-oil or oil-in-water emulsion. In one embodiment, the metal oxide particles do not include an organic component.

The polymeric rheology modifier is obtainable by co-polymerizing a monomer mixture comprising at least one alkyl (meth)acrylate and at least one of the following monomers: a bicyclic (meth)acrylate ester different from the alkyl (meth)acrylate, and an aromatic vinyl monomer. In one embodiment, the polymeric rheology modifier comprises 5 to 50 wt% bicyclic (meth)acrylate ester, 25 to 70 wt% alkyl (meth)acrylate, and 10 to 40 wt% aromatic vinyl monomer. In another embodiment, the polymeric rheology modifier comprises 20 to 70 wt% bicyclic (meth)acrylate ester, and 30 to 80 wt% alkyl (meth)acrylate. In an embodiment, the bicyclic (meth)acrylate ester is isobornyl methacrylate, the alkyl (meth)acrylate is isobutyl methacrylate, and the aromatic vinyl monomer is styrene.

In one embodiment the alkyl (meth)acrylate is a lower alkyl (meth)acrylate and/or a fatty alkyl (meth)acrylate and the polymeric rheology modifier is obtainable by co-polymerizing at least two of the following monomers: a bicyclic (meth)acrylate ester,

· a lower alkyl (meth)acrylate,

a fatty alkyl (meth)acrylate, and

an aromatic vinyl monomer. In one embodiment the polymeric rheology modifier is obtainable by co-polymerizing at least a bicyclic (meth)acrylate ester.

In one embodiment, the polymeric rheology modifier comprises 10 to 30 wt% bicyclic (meth)acrylate ester, 10 to 25 wt% lower alkyl (meth)acrylate, 30 to 40 wt% fatty-alkyl (meth)acrylate, and 15 to 30 wt% aromatic vinyl monomer. In an embodiment, the bicyclic (meth)acrylate ester is isobornyl methacrylate, the lower alkyl (meth)acrylate is isobutyl methacrylate, the fatty alkyl (meth) acrylate is lauryl methacrylate and the aromatic vinyl monomer is styrene.

In one embodiment, the polymeric rheology modifier is a cross-linked polymer. Advantageously, the cross-linked polymeric rheology modifier provides both thickening of the formulation and suspension of the dispersed metal oxide particulates.

In one embodiment the polymeric rheology modifier is a cross-linked polymer that further comprises a cross-linking monomer in the amount of between about 20 ppm to about 2000 ppm, preferably about 200 ppm to about 1500 ppm, more preferably between 300 ppm and 1000 ppm, more preferably about 350 ppm to about 650 ppm. Preferably, the cross-linking monomer is a di-functional or multifunctional (meth) acrylate monomer, such as 1 ,6-hexanediol di(meth)acrylate or trimethylolpropane triacrylate.

In a second aspect the disclosure provides a method of making a thickened sunscreen formulation, the method comp sing combining an oil-based carrier comphsing at least one oil with at least one particulate metal oxide sunscreen active agent and at least one cross-linked polymeric rheology modifier, wherein the at least one particulate metal oxide sunscreen active agent is dispersed in the formulation.

In a third aspect the disclosure provides a method of protecting a user from the deleterious effects of UVA and/or UVB radiation, the method comphsing applying to the skin of a user a thickened sunscreen formulation comphsing an oil-based carrier comphsing at least one oil, at least one particulate metal oxide sunscreen active agent, and at least one cross-linked polymeric rheology modifier, wherein the at least one particulate metal oxide sunscreen active agent is dispersed in the formulation.

In a fourth aspect the disclosure provides a thickened formulation comphsing an oil-based carrier comphsing at least one oil, at least one particulate metal oxide sunscreen active agent, and at least one cross-linked polymeric rheology modifier, wherein the at least one particulate metal oxide sunscreen active agent is dispersed in the formulation, for use in reducing the deleterious effects of UVA and/or UVB radiation on the skin of a user. Detailed Description

In this disclosure all weight percentages are stated as based on the total weight of the formulation unless stated otherwise.

In this disclosure the term "oil carrier" and "oil-based carrier" means that the vehicle of the formulation comprises an oil or combination of oils and that the formulation is not in the form of a water-in-oil or oil-in-water emulsion.

In this disclosure the term "viscosity" means Brookfield viscosity measured by Brookfield viscometers at 10 rpm at 22°C, unless stated otherwise. Viscosity was measured using a Brookfield DV-II+ Viscometer or a Brookfield DV-I Prime Viscometer as indicated in the examples below.

In this disclosure the terms "rheology modifier" and "thickener" are used interchangeably to mean a material that when added at 3% w/w to an oil carrier increases the value of the viscosity of the composition as defined above by at least five times, preferably 10 times, more preferably at least 20 times, and more preferably at least 50 times as measured using a Brookfield viscometer at 10 rpm at 22°C.

As used herein, shear-thinning refers to non-Newtonian fluids which have decreased viscosity when subjected to shear strain. For the purposes of the current disclosure, formulations have strong shear thinning property if the viscosity ratio of the formulation at 10 rpm and 100 rpm is greater than 2 as measured by a Brookfield viscometer. For a stable formulation in our examples, the viscosity ratio is greater than 2, and typically greater than 2.5.

In this disclosure, the term "substantially free of" in the context of a formulation means that the formulation contains less than 10 wt %, or less than 5 wt%, or less than 4 wt%, or less than 3 wt%, or less than 2 wt% or less than 1 wt%, of the indicated ingredient on basis of the total weight of the formulation. The term "substantially free of in the context of a polymer or copolymer means that the polymer contains less than10 wt %, or less than 5 wt%, or less than 4 wt%, or less than 3 wt%, or less than 2 wt% or less than 1 wt%, of the indicated ingredient on basis of the total weight of the polymer.

In this disclosure the term "(meth)acrylate" refers to acrylate and methacrylate.

In the context of the disclosure the term "(co)polymer" indicates polymer or copolymer. The terms "polymer" and the term "copolymer" are used herein interchangeably.

In one aspect a sunscreen formulation of the disclosure comprises 1 - 20%, preferably 2 - 20%, and more preferably 3 - 20% of one or more metal oxide particulate sunscreen active agents; wherein the formulation is a stable dispersion.

In one aspect a sunscreen formulation of the disclosure has a viscosity of at least 100 mPas, preferably at least 300 mPas, more preferably at least 1000 mPas, still more preferably at least 4000 mPas. A sunscreen formulation of the disclosure can be in the form of liquid or a gel.

In one aspect the sunscreen formulations of the disclosure are substantially free of water.

In one aspect the sunscreen formulations of the disclosure are substantially free of organic solvents. In one embodiment, the sunscreen formulations are substantially free of organic solvents that are C C₃ alcohols. In one aspect the sunscreen formulations of the disclosure are substantially free of emulsifiers.

In one aspect the sunscreen formulations of the disclosure are substantially free of glycols.

In one aspect the sunscreen formulations of the disclosure are substantially free of dispersants other than the recited polymeric rheology modifiers.

In one aspect the sunscreen formulations of the disclosure are substantially free of emollients. In one aspect the sunscreen formulations of the disclosure are substantially free of ingredients that are not dermatologically acceptable, such as chemicals intended for use in agricultural applications, industrial uses, or other uses that are not related to personal care products.

Non-limiting examples of the metal oxide sunscreen active agents are titanium dioxide (Ti0₂), zinc oxide (ZnO), aluminum oxide (Al₂0₃), iron oxide (Fe₂0), and zirconium dioxide (Zr0₂). Preferably the metal oxides are Ti0₂ or ZnO. The most preferred metal oxide is Ti0₂. In one aspect the metal oxide sunscreen active agents do not include an organic component.

The Polymeric Rheology Modifiers

The polymeric rheology modifiers selected for the formulations of the disclosure will be polymers that are dermatologically acceptable for use in personal care formulations.

For the polymeric rheology modifiers of the disclosure to be suitable for modifying the rheology of oil-based sunscreen formulations, the polymer is preferably soluble in the oil carrier of the formulation. In the context of the present disclosure, a polymer is soluble in an oil if at least 3 wt% of polymer can be dissolved in the oil. Solubility can be determined by adding 3 wt% of a polymer to the oil and observing the clarity of the oil with the naked eye. The oil with dissolved polymer will be clear or have a slight translucent color or turbidity in it due to light scattering, but will not contain detectable polymer particles or a separate polymer-rich phase.

The polyme c rheology modifier is obtainable by co-polymerizing a monomer mixture comp sing at least one alkyl (meth)acrylate and at least one of the following monomers: a bicyclic (meth)acrylate ester different from the alkyl (meth)acrylate, and an aromatic vinyl monomer.

In one embodiment, the polymehc rheology modifier is a cross-linked polymer comphsing at least one alkyl (meth)acrylate monomer and at least one cyclic monomer, wherein the cyclic monomer is selected from the group consisting of a bicyclic (meth)acrylate ester, an aromatic vinyl monomer, and combinations thereof.

In one aspect, the cross-linked polymehc rheology modifier is obtainable by co-polymerizing at least two of the following ethylenically unsaturated monomers:

a bicyclic (meth)acrylate ester,

an alkyl (meth)acrylate, and

an aromatic vinyl monomer.

In one aspect, the polymehc rheology modifier is a cross-linked copolymer comphsing two or more monomers selected from a bicyclic (meth)acrylate ester, a lower alkyl (meth)acrylate, a fatty alkyl (meth)acrylate, and an aromatic vinyl monomer, as long as the monomers comphsing the copolymer include a bicyclic (meth)acrylate ester and/or an aromatic vinyl monomer.

For purposes of this disclosure, the term "lower alkyl (meth)acrylate" means Ci-C₆ alkyl (meth)acrylate.

For purposes of this disclosure, the term "fatty alkyl (meth)acrylate" means C₈-C₂₄ alkyl (meth)acrylate.

For purposes of this disclosure, the term "total alkyl (meth)acrylate" means the total of the weight percentages of any lower alkyl (meth)acrylates and fatty alkyl (meth)acrylates present in the copolymer.

In one aspect, the polymehc rheology modifier is a cross-linked copolymer comphsing at least one cyclic monomer and at least one alkyl (meth)acrylate monomer, wherein

• said at least one cyclic monomer is selected from the group consisting of a bicyclic (meth)acrylate ester, an aromatic vinyl monomer, and combinations thereof; and

• said at least one alkyl (meth)acrylate monomer is selected from the group consisting of a lower alkyl (meth)acrylate, a fatty alkyl (meth)acrylate, and combinations thereof. In one aspect, the polymeric rheology modifier comp ses 5 to 50 wt% bicyclic (meth)acrylate ester, 25 to 70 wt% total alkyl (meth)acrylate, and 10 to 40 wt% aromatic vinyl monomer. In another embodiment, the rheology modifier comphses 20 to 70 wt% bicyclic (meth)acrylate ester, and 30 to 80 wt% total alkyl (meth)acrylate. In an embodiment, the bicyclic (meth)acrylate ester is isobornyl methacrylate (IBOMA), the lower alkyl (meth)acrylate is isobutyl methacrylate (IBMA), and the aromatic vinyl monomer is styrene.

In another aspect, the rheology modifier is a cross-linked copolymer comprising a lower alkyl (meth)acrylate and/or a fatty alkyl (meth)acrylate and the rheology modifier is obtainable by co- polymerizing at least two of the following monomers:

· a bicyclic (meth)acry late ester,

a lower alkyl (meth)acrylate,

a fatty alkyl (meth)acrylate, and

an aromatic vinyl monomer,

as long as the monomers comprising the copolymer include a bicyclic (meth)acrylate ester and/or an aromatic vinyl monomer.

In one aspect, the polymeric rheology modifier comphses 10 to 30 wt% bicyclic (meth)acrylate ester, 10 to 25 wt% lower alkyl (meth)acrylate, 30 to 40 wt% fatty-alkyl (meth)acrylate, and 15 to 30 wt% aromatic vinyl monomer. In an embodiment, the bicyclic (meth)acrylate ester is isobornyl methacrylate, the lower alkyl (meth)acrylate is isobutyl methacrylate, the fatty alkyl (meth)acrylate is lauryl methacrylate and the aromatic vinyl monomer is styrene.

In one embodiment, the cross-linked polymeric rheology modifier comphses isobornyl methacrylate and isobutyl methacrylate,

In one embodiment, the cross-linked polymeric rheology modifier comphses styrene and isobutyl methacrylate.

In one embodiment, the cross-linked polymeric rheology modifier comphses styrene, isobutyl methacrylate and lauryl methacrylate,

In one embodiment, the cross-linked polymeric rheology modifier comphses isobornyl methacrylate, styrene, and isobutyl methacrylate, In one embodiment, the cross-linked polymeric rheology modifier comphses isobornyl methacrylate, isobutyl methacrylate and lauryl methacrylate,

In one embodiment, the cross-linked polymeric rheology modifier comphses isobornyl methacrylate, isobutyl methacrylate and ethylhexyl methacrylate, In one embodiment, the cross-linked polymeric rheology modifier comprises isobornyl methacrylate, styrene, isobutyl methacrylate and lauryl methacrylate.

Throughout this document, the weight percentages of the monomer that constitute the copolymer are based on the total weight of the monomers used, whereby the total weight of the monomers adds up to 100 wt%.

The bicyclic (meth)acrylate ester of the disclosure contains a (meth)acryloyl radical bonded to a six-membered carbon atom b dged ring and said group of monomers include products like decahydronaphthyl (meth)acrylates, and adamantyl (meth)acrylates, but preferred are products according to formula (I)

wherein

R is H or -CH₃,

A is -CH₂-, -CH(CH₃)- or -C(CH₃)₂-, and

one or more M is covalently bonded to any carbon of the bicyclic rings, preferably to a carbon atom of the six-membered ring, and is selected from the group consisting of hydrogen, halogen, methyl and methylamino group or a plurality thereof. Non-limiting examples of the bicyclic (meth)acrylate esters include isobornyl (meth)acrylate, bornyl (meth)acrylate, fenchyl (meth)acrylate, isofenchyl (meth)acrylate, norbornyl (meth)acrylate, cis, (endo) 3-methylamino- 2-bornyl (meth)acrylate, 1 ,4,5,6,7,7-hexachlorobicyclo [2.2.1 ]-hept-5-ene-2-ol (meth)acrylate (HCBOMA) and 1 ,4,5,6,7,7-hexachlorobicyclo [2.2.1 ]-hept-5-ene-2 methanol (meth)acrylate (HCBMA), and mixtures of such bicyclic (meth)acrylates. Preferably the bicyclic (meth)acrylate ester of the disclosure is a b dged bicyclic (meth)acrylate ester. For purposes of this disclosure, a bhdged bicyclic monomer means a monomer with two rings that share three or more atoms, separating the two bridgehead atoms by a bridge containing at least one atom. A suitable bicyclic (meth)acrylate ester is isobornyl methacrylate. The bicyclic (meth)acrylate esters are known per se and may be prepared in known fashion or may be obtained from commercial sources. The bicyclic (meth)acrylate is preferably chosen from monomers which, when polymerized, form a homopolymer that is soluble in the oil carrier of the sunscreen formulation. Alkyl (meth)acrylates of the disclosure include lower alkyl (meth)acrylates, fatty-alkyl (meth)acrylates and mixtures thereof. In an embodiment, the alkyl (meth)acrylates are linear or branched. In one embodiment the alkyl (meth)acrylates are substituted. Lower alkyl (meth)acrylates of the disclosure are C-_\-C₆ alkyl (meth)acrylates. More particularly, lower alkyl (meth)acrylates of the disclosure are compounds wherein a (meth)acryloyl radical is bonded to a lower alkyl group, herein defined as a Ci-C₆ alkyl group, which can be linear or branched, substituted or unsubstituted, saturated or unsaturated. Lower alkyl (meth)acrylates of the disclosure include compounds such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate and hexyl (meth) acrylate. A preferred lower alkyl (meth)acrylate is isobutyl (meth)acrylate. The lower alkyl (meth )acry late is preferably chosen from monomers which, when polymerized, form a homopolymer that is soluble in one or more of the oils of the formulations of the disclosure, and combinations thereof. When the homopolymer that is formed from the lower alkyl methacrylate is not soluble in the oils of the present formulations, the amount of this monomer in the polymeric rheology modifier is preferably limited to less than about 60%, more preferably less than 50% and more preferably less than about 40% by weight of the polymer.

Fatty-alkyl (meth)acrylates of the disclosure are C₈-C₂₄ alkyl (meth)acrylates. More particularly, the fatty-alkyl (meth)acrylates of the disclosure are compounds wherein a (meth)acryloyl radical is bonded to a fatty alkyl group, herein defined as a C₈-C₂4 alkyl group, which can be linear or branched, substituted or unsubstituted, and saturated or unsaturated. Examples of a fatty alkyl (meth)acrylate include 2-ethylhexyl (meth )acry late, decyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, methacrylate ester 13.0 (CAS#: 90551-76-1 ), tetradecyl (meth)acrylate, hexadecyl (meth)acrylate, methacrylate ester 17.4 (CAS#: 90551 -84-1 ), and stearyl (meth)acrylate. Preferred fatty-alkyl (meth)acrylates are chosen from monomers which, when polymerized, form a homopolymer which is soluble in the one or more of the oils of the formulations of the disclosure, and combinations thereof. In another embodiment 2-ethylhexyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth )acry late, methacrylate ester 13.0 (CAS#: 90551-76-1 ), methacrylate ester 17.4 (CAS#: 90551 -84-1 ), and/or stearyl (meth)acrylate is used. Suitably lauryl methacrylate or 2-ethylhexyl (meth)acrylate is used. The aromatic vinyl monomers of the disclosure contain a vinyl group bonded to an aromatic group. Examples include styrene, substituted styrene, vinyl naphthalene, and mixtures thereof. Preferred substituted styrenes include ortho-, meta- and/or para- alkyl, alkyloxy or halogen substituted styrenes, such as methyl styrene, 4-tert-butyl styrene, tert-butyloxy styrene, 2- chlorostyrene and 4-chlorostyrene. The preferred aromatic vinyl monomer is styrene. The use of styrene can increase the Tg of the polymer and reduce the cost. When the homopolymer that is formed from the aromatic vinyl monomer is not soluble in one or more of the oils of the formulations of the disclosure, and combinations thereof, the amount of this monomer in the polymeric rheology modifier is preferably limited to less than about 60%, more preferably less than 50% and more preferably less than about 40% by weight. Other ethylenically unsaturated monomers different from the monomers above can also be included in the polymeric rheology modifier. These include but are not limited to monomers such as (meth)acrylic acid, maleic acid, 2-acrylamido-2-methylpropane, dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, N-[3-(dimethylamino) propyl] methacrylamide, N-[3- (dimethylamino) propyl] acrylamide, (3-acrylamidopropyl)-trimethyl-ammonium chloride, methacrylamido propyl trimethyl ammonium chloride, (meth)acrylamide, N-alkyl (meth)acrylamides, N-vinyl pyrrolidone, vinyl formamide, vinyl acetamide, and N-vinyl caprolactams. When one of these other monomers contains a hydroxyl, acid, basic nitrogen, or heterocylic functionality it is preferred that the polymer rheology modifier contain less than 2.5%, more preferably, less than 1 .5% and most preferably less than 1 % by weight of these monomers.

In another aspect, the polymeric rheology modifier of the disclosure is largely free of the polymerized residues of polar monomers. Polar monomers are defined as monomers that contain hydroxyl, carboxylic acid, nitrogen, or heterocyclic functionality.

In another aspect, the polymeric rheology modifiers are cross-linked polymers and further comprise suitable cross-linking monomers. Cross-linking monomers (or cross-linkers) contain two or more ethylenically unsaturated functionalities. These include, but are not limited to divinyl benzene, 1 ,6-hexanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, trimethylol propane tri(meth)acrylate, trimethylolpropane triacrylatel, trimethylol propane diallyl ether, trimethylol propane triallyl ether, pentaerythritol triallyl ether, pentaerythritol tetraallyl ether, and pentaerythritol tri(meth)acrylate. The amount of cross-linker optionally present in the polymeric rheology modifier, based on the total weight of all monomers in the polymer, is from about 20 mg/kg to about 2000 mg/kg, preferably about 200 mg/kg to about 1500 mg/kg, more preferably about 300 mg/kg to about 1000 mg/kg, more preferably about 350 mg/kg to about 650 mg/kg. In some preferred embodiments, the amount of cross- linker in the polymeric rheology modifier is 200 mg/kg, or 220 mg/kg, or 240 mg/kg, or 260 mg/kg, or 280 mg/kg, or 300 mg/kg, or 320 mg/kg, or 340 mg/kg, or 360 mg/kg, or 380 mg/kg, 400 mg/kg, or 420 mg/kg, or 440 mg/kg, or 460 mg/kg, or 480 mg/kg, 500 mg/kg, or 520 mg/kg, or 540 mg/kg, or 560 mg/kg, or 580 mg/kg, 600 mg/kg, or 620 mg/kg, or 640 mg/kg, or 660 mg/kg, or 680 mg/kg, or 700 mg/kg, or 720 mg/kg, or 740 mg/kg, or 760 mg/kg, or 780 mg/kg, 800 mg/kg, or 820 mg/kg, or 840 mg/kg, or 860 mg/kg, or 880 mg/kg, 900 mg/kg, or 920 mg/kg, or 940 mg/kg, or 960 mg/kg, or 980 mg/kg, or 1000 mg/kg, or 1020 mg/kg, or 1040 mg/kg, or 1060 mg/kg, or 1080 mg/kg, or 1 100 mg/kg, or 1120 mg/kg, or 1 140 mg/kg, or 1 160 mg/kg, or 1 180 mg/kg, or 1200 mg/kg, or 1220 mg/kg, or 1240 mg/kg, or 1260 mg/kg, or 1280 mg/kg, or 1300 mg/kg, or 1320 mg/kg, or 1340 mg/kg, or 1360 mg/kg, or 1380 mg/kg, or 1400 mg/kg, or 1420 mg/kg, or 1440 mg/kg, or 1460 mg/kg, or 1480 mg/kg, or 1500 mg/kg, or 1520 mg/kg, or 1540 mg/kg, or 1560 mg/kg, or 1580 mg/kg, or 1600 mg/kg, or 1620 mg/kg, or 1640 mg/kg, or 1660 mg/kg, or 1680 mg/kg, or 1700 mg/kg, or 1720 mg/kg, or 1740 mg/kg, or 1760 mg/kg, or 1780 mg/kg, or 1800 mg/kg, or 1820 mg/kg, or 1840 mg/kg, or 1860 mg/kg, or 1880 mg/kg, or 1900 mg/kg, or 1920 mg/kg, or 1940 mg/kg, or 1960 mg/kg, or 1980 mg/kg, or 2000 mg/kg.

The amount of cross-linker will be selected to optimize the ability of the polymer to both thicken the oil and suspend the metal oxide particles. If the level of cross-linker is either too low or too high the particles will not remain in a stable dispersion. The amount of cross-linker that will optimize system performance may vary depending on the selection of monomers, the relative proportions of the monomers in the polymer, the oil used as a carrier in the formulation, the size and type of particles to be suspended, and other ingredients to be included in the formulation.

Where the polymeric rheology modifiers are crosslinked, it will be understood that the wt% values of the monomers as stated herein are approximate so as to allow for the presence of the monomeric crosslinker.

Preferably, the glass transition temperatures (Tg) of the polymeric rheology modifier is high enough that the polymer can be isolated and handled as a solid at room temperature (approximately 22 °C). Preferably the Tg of the polymeric rheology modifier is greater than about 45 °C, more preferably greater than about 60 °C and more preferably greater than about 75 °C. Tg can be measured using standard procedures such as differential scanning calorimetry. For the Tg values described herein, the Tg of the polymer was determined by placing a vial containing the polymer powder to be measured into a hot water bath (e.g., 75 °C) for 10 minutes. If the powder remained free flowing after 10 minutes in the hot water bath, the Tg of the powder was determined to be at least the temperature of the water bath. The temperature of the water bath was increased incrementally until the polymer was no longer free flowing to determine the Tg where appropriate. In other instances, a Tg was determined to be "greater than" the last water bath temperature in cases were an upper end transition temperature was not determined. The polymeric rheology modifiers of the present disclosure typically have a Tg > 75 °C.

The weight averaged molecular weight (Mw) of the copolymer of the invention, when measured in accordance withthe method described below in Example 9, is preferably at least 20,000,000 Dalton (D), suitably at least 50,000,000 (D); 100,000,000 (D); 150,000,000; and/or at least 200,000,000 D.

The polymeric rheology modifier of the disclosure may be synthesized by conventional methods for vinyl addition polymerization known to those skilled in the art, such as, but not limited to, solution polymerization, precipitation polymerization, and dispersion polymerizations, including suspension polymerization and emulsion polymerization. The preferred process is emulsion polymerization. In an embodiment in which the polymeric rheology modifiers of the disclosure are formed by emulsion polymerization, one or more monomers are dispersed in an aqueous phase and polymerization is initiated using a water soluble initiator. The monomers are typically water insoluble or very poorly soluble in water, and a surfactant or soap is used to stabilize the monomer droplets in the aqueous phase. Polymerization occurs in the swollen micelles and latex particles. Other ingredients that might be present in an emulsion polymerization include chain transfer agents such as mercaptans (e.g. dodecyl mercaptan) to control molecular weight, small amounts of water soluble organic solvents such as but not limited to acetone, 2-butanone, methanol, ethanol, and isopropanol, to adjust the polarity of the aqueous phase, and electrolytes to control pH. Suitable initiators include alkali metal or ammonium salts of persulfate such as ammonium persulfate, water-soluble azo compounds such as 2,2'-azobis(2- aminopropane)dihydrochloride, and redox systems such as Fe(ll) and cumene hydroperoxide, and tert-butyl hydroperoxide-Fe(ll)-sodium ascorbate. Suitable surfactants include anionic surfactants such as fatty acid soaps (e.g. sodium or potassium stearate), sulfates and sulfonates (e.g. sodium dodecyl benzene sulfonate or calcium dodecylbenzene sulfonate), sulfosuccinates (e.g. dioctyl sodium sulfosuccinate); non-ionic surfactants such as octylphenol ethoxylates and linear and branched alcohol ethoxylates, and alkylamine alkoxylates; cationic surfactants such as cetyl trimethyl ammonium chloride; and amphoteric surfactants. Anionic surfactants and combinations of anionic surfactants and non-ionic surfactants are most commonly used. Polymeric stabilizers such as polyvinyl alcohol-co-vinyl acetate) can also be used as surfactants. The solid polymer product free of the aqueous medium can be obtained by a number of processes including destabilization/coagulation of the final emulsion followed by filtration, solvent precipitation of the polymer from latex, or spray drying of the latex.

If the powder particle size is too large (e.g., more than mesh size 60 or 250 microns), the powder particles require a long time to dissolve in the oil carrier of the sunscreen formulation. In some cases, if the sample is left un-agitated, the swollen polymer particles could stick together, preventing further dissolution. Hence, the particle size of the powder is preferably smaller than 60 mesh size, more preferably smaller than 100 mesh size (or -150 microns). The polymeric rheology modifiers of the present disclosure are preferably a free flowing powder obtained by a spray drying process or by any suitable drying processes known in the art. However, a liquid latex of polymeric rheology modifier can also be used if the application can tolerate the presence of some water. As used herein, mesh size refers to standard United States (US) mesh size. The mesh size number indicates the number of openings located along 1 linear inch of mesh.

In one aspect, the polymeric rheology modifiers used in the sunscreen formulations of the present disclosure comprise at least 5 wt% of bicyclic (meth)acrylate ester, in another aspect at least 10 wt%, in another aspect at least 20 wt%, in another aspect at least 40 wt%, in still another aspect at least 60 wt%, and in still another aspect at least 70 wt%. In one embodiment the preferred range of bicyclic (meth)acrylate ester present in the rheology modifier is 5 to 50 wt%. In another embodiment, the preferred range of bicyclic (meth)acrylate ester present in the rheology is 10 to 30 wt%. In another embodiment, the preferred range of bicyclic (meth)acrylate ester present in the rheology is 20 to 70 wt%, or 25 to 60 wt%, or 30 to 55 wt%. In some preferred embodiments, the amount of bicyclic (meth)acrylate ester in the polymeric rheology modifier is 5 wt%, or 10 wt%, or 15 wt% or 20 wt%, or 25 wt%, or 30 wt%, or 35 wt% or 40 wt%, or 45 wt%, or 50 wt%, or 55 wt% or 60 wt%, or 65 wt%, or 70 wt%, or 75 wt%.

In another aspect, the polymeric rheology modifiers used in the sunscreen formulations of the present disclosure comprise at least 25 wt% of total alkyl (meth)acrylates, in another embodiment at least 35 wt%, in another embodiment at least 50 wt%, in another embodiment at least 65 wt%, and in another embodiment at least 80 wt%. In one embodiment the preferred range of total alkyl (meth)acrylate present in the rheology modifier is 25 to 70 wt%. In another embodiment, the preferred range of total alkyl (meth)acrylate present in the rheology is 30 to 80 wt%, or 40 to 75 wt%, or 45 to 70 wt%. In some preferred embodiments, the amount of total alkyl (meth)acrylate in the polymeric rheology modifier is 25 wt%, or 30 wt%, or 35 wt% or 40 wt%, or 45 wt%, or 50 wt%, or 55 wt% or 60 wt%, or 65 wt%, or 70 wt%, or 75 wt% or 80 wt%, or 85 wt%, or 90 wt%.

In another aspect, polymeric rheology modifiers used in the sunscreen formulations of the present disclosure comprise at least 10 wt% of lower alkyl (meth)acrylates, in another embodiment at least 15 wt%, in another embodiment at least 20 wt%, in another embodiment at least 25 wt%, or at least 30 wt%, or at least 40 wt%, or at least 50 wt %, or at least 60 wt %, or at least 65 wt%, or at least 70 wt %, or at least 75 wt%, or at least 80 wt%, or at least 85 wt%, or at least 90 wt%. In one embodiment the preferred range of lower alkyl (meth)acrylate present in the rheology modifier is 50 to 90 wt%. In another aspect, the polymeric rheology modifiers used in the sunscreen formulations of the present disclosure comprise at least 10 wt% of fatty alkyl (meth)acrylates, or at least 20 wt%, or at least 30 wt%, or at least 35 wt%, or at least 40 wt%. In an embodiment the preferred range of fatty alkyl (meth)acrylate present in the rheology modifier is 20 to 40 wt%. In another aspect, the polymeric rheology modifiers used in the sunscreen formulations of the present disclosure comprise less than about 40 wt% of aromatic vinyl monomers, in another embodiment less than about 35 wt%, less than about 30 wt%, less than about 25 wt%, in another embodiment less than about 20 wt%, and in another embodiment less than about 15 wt%. In another embodiment, the preferred range of aromatic vinyl monomer present in the rheology modifier is 10 to 40 wt%, or 15 to 30 wt%.

In an aspect, the polymeric rheology modifier used in the sunscreen formulations of the present disclosure is polymerized from a reaction mixture comprising:

· about 5 to about 50 wt% of the bicyclic (meth)acrylate ester

• about 25 to 85 wt% of the lower alkyl (meth)acrylate, and

• 10 to 40 wt% of the aromatic vinyl monomer.

In another aspect, the polymeric rheology modifier used in the sunscreen formulations of the present disclosure is polymerized from a reaction mixture comprising:

• 20 to 70 wt%, preferably 25 to 60 wt%, and more preferably 30 to 55 wt% bicyclic (meth)acrylate ester, and

• 30 to 80 wt%, preferably 40 to 75 wt%, and more preferably 45 to 70 wt% total alkyl (meth)acrylate.

In another aspect, the polymeric rheology modifier used in the sunscreen formulations of the present disclosure is polymerized from a reaction mixture comprising:

• 10 to 30 wt% bicyclic (meth)acrylate ester,

• 10 to 25 wt% lower alkyl (meth)acrylate,

• 30 to 40 wt% fatty-alkyl (meth)acrylates, and

• 15 to 30 wt% aromatic vinyl monomer.

In another aspect, the polymeric rheology modifier used in the sunscreen formulations of the present disclosure is obtainable by copolyme zing a lower alkyl (meth)acrylate monomer with at least one additional monomer selected from:

a bridged bicyclic (meth)acrylate ester monomer,

an aromatic vinyl monomer, and

a fatty-alkyl (meth)acrylate monomer,

as long as the monomers comprising the copolymer include a bridged bicyclic (meth)acrylate ester and/or an aromatic vinyl monomer, and wherein each of said monomers can be substituted or unsubstituted. Throughout this document, the weight percentages of the monomer that constitute the copolymer are based on the total weight of the monomers used, whereby the total weight of the monomers adds up to 100 wt%, except for the presence of cross-linker. In the copolymer rheology modifiers of the disclosure, the monomers may be arranged in any fashion, such as in blocks or randomly. Preferably, the copolymer is a randomly arranged copolymer.

The rheology modifiers used in the sunscreen formulations of the present disclosure are preferably a free flowing powder obtained by a spray drying process or by any suitable drying processes known in the art. However, a liquid form can also be used.

Oils

The oils are selected from one or more oils that are dermatologically acceptable and suitable for use in a sunscreen formulation, and are preferably in the liquid state at the temperature of application. Non-limiting examples of oils suitable for use in the sunscreen formulations of the disclosure include triglycerides, esters, silicone oils with aromatic groups, organic sunscreen active ingredients, and aromatic compounds. Preferred triglycerides are plant de ved oils including soybean oil, sunflower oil, safflower oil, canola oil, rapeseed oil, corn oil, macadamia oil, and tea oil. Non-limiting examples of triglycerides are caprylic capryl triglyceride, glycerol tri- 2-ethylhexyl, and oils of various plants. More preferred triglycerides are caprylic capryl triglyceride and oils from various plants. More preferred oils from various plants are soy bean oil, rapeseed oil, canola oil, corn oil, and linseed oil. Preferred esters are fatty acid esters, lactates, maleates, adipates, citrates, succinates, and benzoate esters. The fatty acid esters suitable for use in the formulations of the present disclosure refer to any dermatologically acceptable ester of an oil de ved from vegetables or animals, including but not limited to hydrogenated and non-hydrogenated, epoxidized and non- epoxidized, soy methyl esters, rapeseed methyl esters, canola methyl esters, safflower methyl esters, ricinoleic acid methyl esters, castor methyl esters, isopropyl myristate, isopropyl palmitate, methyl oleate, and C₈-C₁₀ methyl esters. The fatty acid esters of the disclosure are preferably plant dehved. The preferred lactates are 2-ethylhexyl lactate, butyl lactate and propyl lactate. The preferred maleate is diethyl maleate. The preferred adipate is dimethyl adipate. The preferred citrates are acetyl tributyl citrate, butyryltri-n-hexyl citrate, and tributyl citrate. The preferred succinate is diethyl succinate. The preferred benzoates are methyl benzoate, ethyl benzoate, and C12/15 benzoate. The term "oil" can also include certain organic sunscreen active agents. For purposes of the present application, a "sunscreen active agent" or "sunscreen active" shall include all of those materials, singly or in combination, that are regarded as acceptable for use as active sunscreen ingredients based on their ability to absorb UV radiation. Such compounds are generally desc bed as being UV-A, UV-B, or UV-A/UV-B active agents. Approval by a regulatory agency is generally required for inclusion of active agents in formulations intended for human use. Those active agents which have been or are currently approved for sunscreen use in the United States include organic and inorganic substances including, without limitation, para aminobenzoic acid, avobenzone, cinoxate, dioxybenzone, homosalate, menthyl anthranilate, octyl salicylate, oxybenzone, padimate O, phenylbenzimidazole sulfonic acid, sulisobenzone, trolamine salicylate, diethanolamine methoxycinnamate, digalloy trioleate, ethyl dihydroxypropyl PABA, glyceryl aminobenzoate, lawsone with dihydroxyacetone, red petrolatum. Examples of additional sunscreen actives that have not yet been approved in the US but are allowed in formulations sold outside of the US include ethylhexyl triazone, dioctyl butamido triazone, benzylidene malonate polysiloxane, terephthalylidene dicamphor sulfonic acid, disodium phenyl dibenzimidazole tetrasulfonate, diethylamino hydroxybenzoyl hexyl benzoate, bis diethylamino hydroxybenzoyl benzoate, bis benzoxazoylphenyl ethylhexylimino triazine, drometrizole trisiloxane, methylene bis-benzotriazolyl tetramethylbutylphenol, and bis- ethylhexyloxyphenol methoxyphenyltriazine, 4-methylbenzylidenecamphor, and isopentyl 4- methoxycinnamate. The preferred organic sunscreen active ingredients are octyl salicylate, ethylhexyl methoxycinnamate, homosalate, octocrylene, and menthyl anthranilate (meradimate). However, as the list of approved sunscreens is currently expanding, those of ordinary skill in the art will recognize that the invention is not limited to sunscreen active agents currently approved for human use but is readily applicable to those that may be allowed in the future.

Preferred organic sunscreen active ingredients are octyl salicylate, ethylhexyl methoxycinnamate, homosalate, octocrylene, and menthyl anthranilate (meradimate). Due to regulations in various countries, the amount of total organic sunscreen active ingredients in a formulation cannot be greater than 32%. Because of this limitation, if organic sunscreen active ingredients are used in the sunscreen formulations of the disclosure, at least one other oil of the disclosure is also used in the formulation.

Preferred silicone oils with aromatic groups include phenyl trimethicone (Dow Corning 556 oil). Mixtures of oils also can be used. Other dermatologically acceptable oils will be known to those skilled in the dermatological arts.

In one aspect, the sunscreen formulation comprises, based on total formulation weight, 40 - 99.5 wt% oil, preferably 60 - 80 wt% oil. In some preferred embodiments, the amount of oil in the thickened oil composition is 40 wt%, or 45 wt%, or 50 wt% or 55 wt%, or 60 wt%, or 65 wt%, or 70 wt% or 75 wt%, or 80 wt%, or 85 wt%, or 90 wt% or 95 wt%, or 99.5 wt%.

In one aspect, the sunscreen formulation comprises, based on total formulation weight, 0.5 - 15% rheology modifier, or 1 - 10%, or 2 - 8% rheology modifier, or 3-5 % rheology modifier. In some preferred embodiments, the amount of rheology modifier in the sunscreen formulation is 0.5 wt%, or 1 wt%, or 2 wt% or 3 wt%, or 4 wt%, or 5 wt%, or 6 wt% or 7 wt%, or 8 wt%, or 9 wt%, or 10 wt% or 1 1 wt%, or 12 wt%, or 13 wt%, or 14 wt% or 15 wt%.

In one aspect, the sunscreen formulation comprises, based on total formulation weight, metal oxide particulate sunscreen active agents at a concentration of between 2 to 50 wt%, preferably 3 - 40 wt%, and more preferably 4 - 35 wt%.

Throughout this document, the weight percentages of the formulation are based on the total formulation weight, whereby the total weight of the formulation adds up to 100 wt%. Other ingredients

The sunscreen formulations of the disclosure can optionally contain additional cosmetically acceptable ingredients, as long as those ingredients are either soluble in the formulation or are in the form of particulates that exist in stable dispersions in the formulations.

Other dermatologically acceptable rheology modifiers that are soluble in oil can be used in the sunscreen formulations of the present disclosure, and can be polymeric or non-polymeric. Non- limiting examples include the thickeners disclosed in "Diverse Technologies for Polymeric Oil Thickeners" posted on March 14, 2014 by George Deckner at http://knowledge.ulprospector.com/388/pcc-diverse-technologies-polymeric-oil-thickeners, the contents of which are incorporated herein by reference in their entirety. Preferably they are selected from the following group of rheology modifiers: Asensa CL 300 (ethylene/vinyl acetate copolymer) and SC 401 (ethylene/acrylic acid copolymer) (both from Honeywell); Syncrowax ORM (Sorbitol/Sebacic Acid Copolymer Behanate) (Croda); Hostacerin DP (Dextrin Palmitate) (Clariant); Rheopearl ISK2/ISL2 (Stearoyl Inulin) (Chiba Flour Milling Ltd); Versagels (thickened oil gels) (Calumet Penreco); Intelimer IPA 13-6 and Intelimer IPA 13-1 (poly C10-30 alkyl acrylates)(Air Products and Chemicals);; Kraton G1702 Polymer (styrene and ethylene/propylene diblock copolymer); and hydrogenated castor oil. Atlox Rheostrux 200 and Atlox Rheostrux 100 , and Oleocraft LP-20 (Polyamide-8 from Croda).

The compositions of the present invention may contain a wide range of additional, optional components which are referred to herein as "cosmetic components", but which can also include components generally known as pharmaceutically active agents. The CTFA Cosmetic Ingredient Handbook, Seventh Edition, 1997 and the Eighth Edition, 2000, which is incorporated by reference herein in its entirety, describes a wide variety of cosmetic and pharmaceutical ingredients commonly used in skin care compositions, which are suitable for use in the compositions of the present invention. Examples of these functional classes disclosed in this reference include: abrasives, antioxidants, vitamins, biological additives, chemical additives, colorants, cosmetic astringents, cosmetic biocides, drug astringents, external analgesics, film formers, fragrance components, sunscreen agents, ultraviolet light absorbers, and SPF boosters.

Fragrances are aromatic substances which can impart an aesthetically pleasing aroma to the sunscreen composition. Typical fragrances include aromatic materials extracted from botanical sources (i.e., rose petals, gardenia blossoms, jasmine flowers, etc.) which can be used alone or in any combination to create essential oils. Alternatively, alcoholic extracts may be prepared for compounding fragrances. However, due to the relatively high costs of obtaining fragrances from natural substances, the modern trend is to use synthetically prepared fragrances, particularly in high-volume products. One or more fragrances can optionally be included in the sunscreen composition in an amount ranging from about 0.001 to about 5 weight percent, preferably about 0.01 to about 0.5 percent by weight.

Essential oils can be included in the sunscreen formulations. The preferred essential oils are sandalwood oil, cedarwood oil, chamomile oil, vanilla oil, tea tree oil, eucalyptus oil, peppermint oil, bergamot oil, lavender oil, rosemary oil, rose oil, cinnamon oil, frankincense oil, lemongrass oil, geranium oil, orange oil, vetiver oil, lemon oil, jasmine oil, cedar oil, and grapefruit oil. Pine oil and d-limonene also can be used.

Advantageously, such essential oils also can be thickened by the cross-linked polymeric rheology modifiers of the disclosure. Additional preservatives may also be used if desired and include well known preservative compositions such as benzyl alcohol, phenyl ethyl alcohol and benzoic acid, diazolydinyl, urea, chlorphenesin, iodopropynyl and butyl carbamate, among others.

The compositions of the invention may further include insect repelling components. The most widely used insect repelling active agent for personal care products is N,N-Diethyl-m-toluamide, frequently called "DEET" and available in the form of a concentrate containing at least about 95 percent DEET. Other synthetic chemical repellents include ethyl butylacetylaminoproprionate (also known as IR 3535), dimethyl phthalate, ethyl hexanediol, indalone, di-n- propylisocinchoronate, bicycloheptene, dicarboximide and tetrahydrofuraldehyde. Certain plant- derived materials also have insect repellent activity, including citronella oil and other sources of citronella (including lemon grass oil), limonene, rosemary oil and eucalyptus oil. Choice of an insect repellent for incorporation into the sunscreen emulsion will frequently be influenced by the odor of the repellent. The amount of repellent agent used will depend upon the choice of agent; DEET is useful at high concentrations, such as up to about 15 percent or more, while some of the plant-derived substances are typically used in much lower amounts, such as 0.1 percent or less. The method of making the sunscreen formulations of this application comprises the steps of mixing the polymeric rheology modifier in the oil carrier with adequate agitation and for a sufficient period of time (usually < 30 minutes) to dissolve the rheology modifier in the carrier, and then mixing in the metal oxide particulates of desired size (< 10 microns) with adequate agitation and for a sufficient period of time to obtain a dispersion. Additional ingredients can be added to the formulation either before the rheology modifier is added to the oil carrier, or after the rheology modifier has been added but before the metal oxide particulates are added, or after the metal oxide particulates are added. In most cases, the formulations can be prepared at room temperatures using an overhead stirrer. In few cases, if the rheology modifier takes a long time (> 2 hours) to dissolve, heating may be used to facilitate dissolution of the rheology modifier into the oils. If homogenization is used, add the rheology after homogenization or limit the homogenization duration to less than 3 minutes if the rheology modifier is in the formulation.

Typical application of the compositions of the invention described herein to skin of a human will provide enhanced protection against deleterious effects of ultraviolet radiation (UVR). Thus, the subject invention further provides a method for protecting human skin against the deleterious effects of solar radiation, more particularly UVR, which method comprises topically applying thereto an effective amount of the compositions as described herein. An esthetically beneficial result of exposure of skin to UVR (i.e., light radiation wavelengths of from 280 nm to 400 nm) is the promotion of tanning of the human epidermis. Another benefit of sun exposure comes from production of vitamin D within the skin. UVR is typically divided into UV-A (light wavelengths from 320 to 400 nm) and UV-B (wavelengths ranging from 280 to 320 nm) regions. Overexposure to UV-B irradiation is generally understood to lead to skin burns and erythema. In addition, overexposure to UV-A radiation may cause a loss of elasticity of the skin and the appearance of wrinkles, promoting premature skin aging. Such irradiation promotes triggering of the erythemal reaction or amplifies this reaction in certain individuals and may even be the source of phototoxic or photoallergic reactions. It is increasingly believed that overexposure to UV-A may also lead to melanoma. Thus, the application of the compositions of the invention to the skin of an individual will provide enhanced UVR photoprotection (UV-A and/or UV-B) of the skin of the individual.

Rheology Modification The rheology modifiers of the disclosure have the ability to thicken personal care oils suitable for use as oil carriers in sunscreen formulations. For the purposes of this disclosure, thickening a composition means to increase the viscosity of the oil carriers by at least five times, or at least 10 times, preferably at least 20 times, and more preferably at least 50 times in the presence of 3 %w/w or less of the rheology modifier compared to the same fluid in the absence of the rheology modifier. Viscosity is measured by Brookfield viscometers at 10 rpm at 22 °C, using either a Brookfield DV-II+ Viscometer or a Brookfield DV-I Prime Viscometer as indicated in the examples below. Typically, the viscosity of an oil is low and pure oils are generally Newtonian fluids. For example, fatty acid ester is less than 10 mPas and soy oil is ~ 50 mPas and they are Newtonian.

The thickened sunscreen formulations of the disclosure can be gel-like (very high viscosity) but preferably the viscosity of the formulations is less than -10000 mPas, preferably less than 5000 mPas.

In an aspect, the viscosity of the thickened sunscreen formulations of the disclosure is at least 150 mPas, preferably at least 300 mPas, more preferably at least 600 mPas, and still more preferably at least 1000 mPas.

In one aspect, the thickened sunscreen formulations of the disclosure display shear thinning property and the formulation viscosity does not increase by more than 50%, preferably not more than 30%, more preferably not more than 20%, and still more preferably not more than 10%, after storage tests.

As used herein, shear-thinning refers to non-Newtonian fluids which have decreased viscosity when subjected to shear strain. For the purposes of the current disclosure, formulations have strong shear thinning property if the viscosity ratio of the formulation at 10 rpm and 100 rpm is greater than 2 as measured by a Brookfield viscometer. For a stable formulation in our examples, the viscosity ratio is greater than 2, and typically great than 2.5.

Examples

Exemplary polymeric rheology modifiers were made using different combinations of monomers. Isobornyl methacrylate (IBOMA), isobutyl methacrylate (IBMA), 2-ethylhexylmethacrylate (2- EHMA) and isodecyl methacrylate (IsoCIO MA) were obtained from Sigma-Aldrich. Lauryl methacrylate (LMA) was methacrylic ester 13.0 obtained from Evonik (VISIOMER^® terra CI S- MA). All monomers are available from Evonik as well, including isobutyl methacrylate (VISIOMEFT i-BMA), isobornyl methacrylate (VISIOMEFT Terra IBOMA) 2-EHMA (VISIOMER^® EHMA), and isodecyl methacrylate (VISIOMER^® IDMA).

Example 1. Synthesis of Cross-Linked Isobornyl methacrylate - Isobutyl methacrylate polymeric rheology modifier Exemplary polymeric rheology modifier (Synthesis Example 1 ) was prepared according to the following basic procedure.

Table 1. Materials for Synthesis of Example 1 Polymeric Rheology Modifier

Polymerization Procedure

A 2 L, 4-neck round bottom flask was equipped with an overhead mechanical stirrer; a Y-tube equipped with a nitrogen purge outlet-topped condenser and a thermometer; and two septa. To the flask were charged deionized water and Aerosol OT-75 PG. Using a thermostat controlled water bath, the reaction temperature was brought to about 48 °C. A 12 minute sub-surface nitrogen purge was then initiated via a needle inserted through one of the septa while maintaining a 200 rpm agitation rate. While maintaining the nitrogen purge, the monomer mixture and acetone were charged to the reaction vessel. The sub-surface nitrogen purge was continued after the monomer/acetone addition. In a separate container, a reductant solution consisting of sodium ascorbate and iron (II) sulfate heptahydrate dissolved in deionized water was prepared. The iron (II) sulfate heptahydrate was added after the ascorbate had dissolved and just before use of the reductant solution.

The reaction was purged for an additional 12 minutes after the monomer/acetone addition, and then the resulting dark blue ascorbate solution was added via syringe to the reaction vessel in one shot while maintaining the sub-surface nitrogen purge.

About 10 minutes after the addition of the reductant, 0.85 ml_ of a t-butyl hydroperoxide solution in water (0.0348 g/mL) was added to the reaction via syringe in one shot while maintaining the sub-surface nitrogen purge.

Within about 7 minutes, the onset of an exotherm was noted, and the sub-surface nitrogen purging was stopped in favor of above-surface nitrogen purging. As the reaction progressed, a bluish tint was noted in the emulsion, and it became increasingly more translucent, and a slight increase in viscosity was noted. The reaction temperature reached a maximum of about 56 °C (initial temp: 48 °C) before it began to subside after about 40 min. The reaction temperature was maintained thereafter at 48-50 °C using the water bath. After a total of 5 h reaction time, the reaction was cooled and poured through cheesecloth into a container. The product was a milky liquid with a solid content of ~ 29.0% (measured gravimetrically).

Solid polymer was isolated by adding the undiluted emulsion polymer to an excess of 0.5 N ammonium acetate in deionized water. The resulting precipitate was collected by vacuum filtration and washed extensively with water, and the solid was dried to a constant weight in a forced air oven at 60 °C. Alternatively, solid polymer can be obtained by pan-drying or spray drying the liquid product at elevated temperatures with various techniques known to the skilled in the art. The solid obtained after drying can be further ground into a fine powder with various techniques known to the skilled in the art. The powder was passed through a 100 mesh screen in this example. Example 2. Synthesis of Additional Polyme c Rheology Modifiers

Additional polymehc rheology modifiers were prepared following the basic procedure used to prepare Synthesis Example 1 . The compositions of these polymers and those of Synthesis Example 1 are summarized in the Table 2 below. The amount of t-BHP initiator is expressed in pphm, which is parts per hundred monomer.

Table 2. Exemplary Polymehc Rheology Modifiers.

2.30 35 65 A 500 0.0073

2.31 50 50 A 1000 0.0091

2.32 50 50 A 2000 0.0091

2.33 50 50 B 218 0.0091

2.34 50 50 B 436 0.0091

2.35 50 50 C 218 0.0091

2.36 50 50 C 436 0.0091

2.37 75 25 A 500 0.0091

2.38 10 90 A 250 0.0091

2.39 10 90 A 500 0.0091

2.40 10 90 A 757 0.0091

2.41 4.98 13.02 82 A 250 0.0091

2.42 4.98 13.02 82 A 400 0.0091

2.43 4.98 13.02 82 A 500 0.0091

2.44 4.98 13.02 82 A 600 0.0091

2.45 4.98 13.02 82 A 750 0.0091

2.46 9.41 24.59 66 A 250 0.0091

2.47 9.41 24.59 66 A 500 0.0091

2.48 9.41 24.59 66 A 500 0.0091

2.49 9.41 24.59 66 A 650 0.0123

2.50 9.41 24.59 66 A 350 0.0123

2.51 9.41 24.59 66 A 1000 0.0123

2.52 9.41 24.59 66 A 350 0.0123

2.53 9.41 24.59 66 A 650 0.0155

2.54 9.41 24.59 66 A 650 0.0155

2.55 9.41 24.59 66 A 1000 0.0187

2.56 9.41 24.59 66 A 350 0.0187

2.57 50 25 25 A 500 0.0091

2.58 30 50 20 A 500 0.0091

2.60 65 35 A 504 0.0091

2.61 65 35 A 507 0.0091

2.62 35 65 0 0.0091

2.63^** 35 65 A 500 0.0091

2.64 80 20 0 0.0091

2.66 50 50 A 501 0.0091

2.67 9.41 24.59 66 A 500 0.0091

2.68 9.41 24.59 66 B 730.8 0.0155

2.69 55 35 10 0 0.0091

2.70 40 50 10 0 0.0091

2.71 25 22 18 35 0 0.0091

2.73 50 50 0 0.0091 2.75 10 90 0 0.0091

2.76 4.98 13.02 82 0 0.0091

2.77 9.41 24.59 66 0 0.0091

2.79 65 35 0 0.0091

2.80 65 35 0 0.0091

^*Percentage of monomer as a mass percent of the total amount of monomer

^**Sample was spray dried using a Mobile Minor Spray Dryer from GEA with a rotary atomizer AF-05-A, made by Costruzioni Meccaniche Turbine with inlet temperature 145°C and outlet temperature 78°C. IBOMA = isobornyl methacrylate; IBMA = isobutyl methacrylate; LMA = lauryl methacrylate; SMA = stearyl methacrylate; 2-EH MA = 2-ethylhexyl methacrylate; IsoCI O MA = isodecyl methacrylate;

Crosslinker "A" is 1 ,6-hexanediol diacrylate (1 ,6-HDDA); Crosslinker "B" is trimethylolpropane triacrylate (TMPTA); Crosslinker C is pentaerythritol allyl ether (PEAE); t-BHP = t-butyl hydroperoxide. The oven dried powders were ground and passed through a 60 or 100 mesh screen before use

in the following experiments. Powder can also be used without passing the 60-100 mesh screen

but it would take longer time to dissolve.

Example 3. Polyme c Rheology Modifier Thickening Performance in Fatty Acid Esters The viscosity of exemplary polymeric rheology modifiers of Table 2 in soy methyl ester (SME)

was measured. SME is a clear low viscosity liquid with a viscosity of about 3 - 8 mPas at room

temperature. Increased viscosity is indicative of thickening ability of the rheology modifier being

analysed. The SME used was from Cargill (trade name Methyl soyate), Enviro Saver (trade

name soy methyl ester), or Chempoint (trade name SoyGold 1000). The source of SME did not

cause significant difference in results.

To prepare the samples, the polyme c rheology modifiers were dispersed slowly into SME

under adequate agitation and were dissolved fully with agitation before the viscosity

measurement. Viscosity of the thickened oil samples above was measured with a Brookfield

DV-I Prime viscometer on a sample within a glass jar having a 2 inch inner diameter using a

standard Brookfield viscometer process well known to those skilled in the art. Except where

noted otherwise in Table 3, viscosities for the samples in this Example 3 were measured at

about 22 °C with a #3 spindle. Table 3. Thickened SME Oil with Exemplary Polymeric Rheology Modifiers

^*Viscosity measured 1 day after preparation at 27.5^°C

"Viscosity measured with a #4 spindle. The results in this Table 3 show that the rheology modifiers shown in Example 3 are able to thicken SME and that the thickened oil compositions display shear thinning property (e.g. viscosity is lower at higher shear rate). High shear thinning property is an advantageous property and is believed to be associated with the ability of the polymeric rheology modifier to suspend solids. Example 4. Additional Thickening Properties in Oils Example 4A - Viscosity measurements

Samples were prepared in accordance with the method of Example 3. The viscosities of a thickened oil composition containing soy methyl ester and soy oil (PMC Biogenix) in this Example were measured with a Brookfield DV-II+ viscometer with spindle setting #64 at 22 °C.

Table 4. Thickened Oils (SME and Soybean Oil) with Exemplary Polymeric Rheology Modifiers of Table 2

Table 4 shows that the rheology modifiers of the present disclosure can thicken mixtures of SME and soybean oil. Example 4B. Thickening of various oils with thickeners of the present invention

The thickening ability of various thickeners of the present disclosure in various oils was studied. The studied samples contained 5% thickener and 95% oils. Each sample was prepared by adding 5% thickener to 95% oil and immediately mixed vigorously for about 15 - 30 minutes. Samples 4.8 - 4.22 and 4.32 of Table 4B_were prepared at room temperature. Samples 4.23 - 4.31 of Table 4B were prepared at ~70°C for 15 - 30 minutes. Samples were placed at room temperature overnight and were shaken by hand before observation to generate air bubbles. Appearance of each sample at room temperature and thickening of each were observed and recorded in Table 4B. The thickening was determined qualitatively and it could be easily compared to the original organic liquid by eye estimate. The thickening was observed by looking at how long the bubbles remained suspended in the liquid after shaking. Generally, the bubbles rise to the surface quickly (less than ~ 10 seconds) in pure oils after shaking because the viscosity of the oils are low (typically < 100 mPas). If thickening occurs, the bubbles in a thickened oil tend to remain suspended in the liquid for at least more than a few minutes, and in some cases at least 15 minutes longer than the bubbles in the pure oil. All samples in Table 4B were able to trap bubbles for more than 15 minutes longer than in the respective pure oils except where indicated.

Table 4B. Composition of example 4 - thickening of 95% oils with 5% thickener

viscous

Silicone oil with

4.22 2.63 Dow Corning® 550 Fluid Clear aromatic group

4.23 2.63 Soybean oil Triglyceride Clear liq

Estol 3609 (glycerol tri-2-

4.24 2.63 Triglyceride Clear liq ethylhexanoate ester oil)

Prisorine 2041 glycerol

4.25 2.63 Triglyceride Translucent liquid triisostearate

4.26 2.63 Corn oil Triglyceride Clear

4.27 2.63 Soybean oil Triglyceride Clear

4.28 2.63 Rapeseed oil Triglyceride Clear

4.29 2.63 Canola oil Triglyceride Clear

4.30 2.63 Linseed oil Triglyceride Clear

4.31 2.63 Macadamia oil Triglyceride Clear

Caprylic capryl triglyceride

4.32 2.63 Triglyceride Clear

(Myritol 318)

Butyloctyl Salicylate (Hallbrite Aromatic

4.33 2.63 Clear

BHB) compound

4.34 2.25 Methyl benzoate Ester Clear

4.35 2.58 Methyl benzoate Ester Clear

Clear, Trapped

4.36 2.64 Methyl benzoate Ester bubbles for ~ 15 mins

4.37 2.55 Methyl benzoate Ester Clear

4.38 2.57 Methyl benzoate Ester Clear

4.39 2.63 Methyl benzoate Ester Clear

4.40 2.63 Acetyl tributyl citrate Ester Clear

4.41 2.63 Butyryltri-n-hexyl citrate Ester Clear

4.42 2.63 Tributyl citrate Ester Clear

4.43 2.63 methyl cocoate Ester Clear

4.44 2.63 2-ethylhexyl lactate Ester Clear

4.45 2.25 Butyl lactate Ester Clear

Clear. Trapped

4.46 2.64 Butyl lactate Ester bubbles for < 15 mins

4.47 2.43 Butyl lactate Ester Clear

4.48 2.12 Butyl lactate Ester Clear

4.49 2.20 Butyl lactate Ester Clear

4.50 2.12 Butyl lactate Ester Clear

4.51 2.55 Butyl lactate Ester Clear

4.52 2.56 Butyl lactate Ester Clear

4.53 2.24 Butyl lactate Ester Hazy. No thickening

4.54 2.58 Butyl lactate Ester Clear

4.55 2.63 Propyl lactate Ester Clear

4.56 2.63 Dimethyl adipate Ester Clear

4.57 2.63 Diethyl maleate Ester Clear

4.58 2.63 Methyl oleate Ester Clear

4.59 2.63 Diethyl succinate Ester Clear

4.60 2.63 Methyl ester of C810 acid Ester Clear

^*UV cocktail: Avobenzone 9.37 wt%, Homosalate 40.62 wt%, Octisalate 15.63

Octocrylene 15.63 wt%, Oxybenzone 18.75 wt% It can be seen from the results shown in Table 4B that the thickeners of the present disclosure can thicken various oils useful in personal care formulations and in sunscreen formulations in particular. Comparative samples containing no cross-linker (2.64) and samples containing a very high level of cross-linker (2.24) showed limited bubble suspension ability. Example 5. TiO? oil dispersion formulations Preparation of Formulations

Dispersion formulations were prepared using soy methyl ester as the oil component, exemplary rheology modifier 2.9, and Ti0₂ as the dispersed particulate. The rheology modifier Ex. 2.9 was dissolved in the SME at room temperature first before adding Ti0₂.

For formulations A-F and J, the Ti0₂ was Tiona® Ti0₂ 569 from Cristal Global, the soy methyl ester was Methyl Soyate from Cargill, and the viscosity was measured with a Brookfield DV-II+ Viscometer. Formulation C is a control sample. For exemplary formulation G the Ti0₂ was UV Titan M-170 from Presperse, the soy methyl ester was from Enviro Saver, and viscosity was measured with a Brookfield DV-I Prime. All viscosity measurements were taken at room temperature. The results are presented in Table 5A.

Table 5A

Evaluation of aesthetic properties Two dispersion formulations were prepared by the method of Example 5A. A drop of each formulation (~ 0.05 g) was deposited on the skin (back of the hand) of a user, and rubbed in gently. The skin feel was evaluated subjectively. Whiteness persistency was also evaluated subjectively with naked eyes. The water repellency was evaluated by rinsing the hand with the rubbed-in sample in tap water for three minutes. If the water droplets beaded up on the part of the skin with sample applied after the water rinsing period, the water repellency was rated "excellent". The results are presented in Table 5B.

Table 5B

*Time it took for the whiteness appearance to disappear after applying on skin.

Whiteness persistency is considered a desirable performance attribute in some market segments.

Example 6. Water Resistance Study Water resistance was evaluated by measuring SPF performance after initial application of the formulaton to a test sample and after immersion of the test samples in water, and comparing the results.

Sample Preparation and Initial SPF Measurements

All SPF measurements were made in vitro using a UV-1000S Ultraviolet Transmittance Analyzer, available from Labsphere, and VITRO-SKIN® synthetic skin substitute, available from IMS Inc. To begin, the VITRO-SKIN® synthetic skin substitute was hydrated for 16 hours in a controlled humidity chamber per the protocol suggested by the manufacturer. For each sample, a 6.2cm x 8.0cm section of VITRO-SKIN® was cut. The VITRO-SKIN® was placed rough side up on a foam block used to simulate the flexibility of human skin and a product dose of 2μΙ_/οηι² (approximately 100 μΙ_) of the sunscreen formulation was applied using a micropipettor evenly across the VITRO-SKIN® surface. The sunscreen formulation was gently rubbed in with a gloved finger for 20 to 30 seconds, mimicking the application of sunscreen to a body. Once the sunscreen was spread, the sample was transferred to a 6cm x 6cm glassless slide mount and allowed to dry for 15 minutes. SPF measurements were made using the UV-1000S Ultraviolet Transmittance Analyzer. The SPF values given herein are the average of five measurements taken at different locations on each sample.

Water Immersion Test and Post-Immersion SPF

The following test was used to determine the percent of an SPF rating for the sunscreen composition that was lost following immersion in water for 80 minutes. When the terms "post-immersion SPF" and "initial SPF" are used herein, the post-immersion SPF refers to the SPF of the sunscreen composition after being subjected to the following water immersion test, and the "initial SPF" refers to the SPF of the sunscreen composition prior to immersion in water for 80 minutes, as described herein. All SPF values and values for percent SPF rating decrease following water immersion given herein are based on in vitro testing.

To begin, each sunscreen sample in Table 6 was applied to a hydrated VITRO-SKIN® synthetic skin substrate and the initial SPF of the composition was measured as described above. The sunscreen composition-treated VITRO-SKIN® samples were then transferred to a water bath at the same time at 40°C with agitation at 200 rpm for 80 minutes. The samples were removed from the water bath after 80 minutes, patted dry, and the post-immersion SPF of the samples was tested using the Labsphere UV-1000S Ultraviolet Transmittance Analyzer. The post-immersion SPF values given herein are the average of five measurements taken at different locations on each sample.

A sunscreen formulation of the present invention was prepared. The soy methyl ester was from Enviro saver. Ti0₂ was UV Titan M-170 from Presperse. The formulation was compared to a commercial product J&J Pure and Free™ Baby Sunscreen Lotion (SPF 60) which states on the label that it has "Water resistance (80 minutes)". The viscosity was measured by a Brookfield RVDV-I Prime Viscometer with RV -C(93) helipath @ 10rpm.

The results are shown in Table 6.

Table 6

The rheology modifier was dissolved in the soy methyl ester. Then Ti02 was added and the sample was mixed using a regular mixer until homogeneous.

It can be concluded from the results shown in the Table that the exemplary oil dispersion formulations have better water resistance and supe or SPF retention as compared to the commercial product J&J Pure and Free Baby.

Example 7. Formulations of Polymeric Rheology Modifiers and Talc Model Powder

The ability of fatty acid ester formulations containing polymeric rheology modifiers of the disclosure to suspend powder was analyzed using talc model powder. Talc model powder (Talc-Luzena c 10 mo, particle size < 10 microns) was formulated in soy methyl ester (SME) as set forth below. Viscosity and shear thinning values were measured according to the procedures set forth above.

Formulation samples (each 100 g in a 4 oz bottle) were prepared by mixing the thickener in the SME until dissolved into a clear liquid, followed by adding the talc. Overhead mixer was used to mix the sample for about 30 minutes at room temperature. The formulation samples were maintained at 50°C for 14 days in an oven. Some samples were maintained under this condition for 60 days. The polymeric rheology modifier is considered an effective thickener (or suspension aid) if the sunscreen formulations containing 4 wt% polymeric rheology modifier are stable (no separation after 2 weeks storage at 50^° to 54°C). Top clear means the top portion of the composition containing no solid particle as visually observed and as measured in relation to the total composition height.

Table 7A. Thickened Oil Compositions Stabilizing Talc Powder

7.3 80.5 17 2.1 1 (650) 2.5 No separation

7.4 80.5 17 2.12 (350) 2.5 No separation

7.5 79.5 17 2.13 (650) 3.5 No separation

7.6 80 17 2.21 (465.3) 3 No separation

No separation after 14 days at 50C. 5% top clear and no sediment after 60

7.7 80.5 17 2.10 (500) 2.5 days at 50C.

No separation after

7.8 80.5 17 2.27 (500) 2.5 60 days at 50C.

7.9 82 15 2.6 (200) 3 No separation

7.10 80 17 2.47 (500) 3 No separation

7.1 1 80 17 2.43 (500) 3 No separation

7.12 80 17 2.27 (500) 3 No separation

7.13 80 17 2.18 (465.3) 3 1 .8% top clear

7.14 80 17 2.17 (756) 3 No separation

7.15 79.5 17 2.20 (1046.8) 3.5 2% top clear

7.16 79.5 17 2.22 (1500) 3.5% 3.6% top clear

7.17 79.5 17 2.23 (2000) 3.5% 72.7% top clear

7.18 79.5 17 2.62 (0) 3.5% 69.8% top clear

7.19 79.5 15 2.24 (3000) 3.5% 72.7% top clear

7.21 80 17 2.21 3 1 .8% top clear

7.22 83 15 2.73 (0) 2 70% top clear

7.23 82 15 2.73 (0) 3 23.3% top clear

7.24 81 15 2.73 (0) 4 15% top clear

7.25 83 15 2.25 (204) 2 5.6% top clear

7.26 82 15 2.25 (204) 3 5.7% top clear

7.27 81 15 2.25 (204) 4 5.4% top clear

7.28 83 15 1 (500) 2 5.4% top clear

7.29 82 15 1 (500) 3 No separation

7.30 81 15 1 (500) 4 No separation

7.31 83 15 2.31 (1000) 2 44.7% top clear

7.32 82 15 2.31 (1000) 3 5% top clear

7.33 81 15 2.31 (1000) 4 No separation

7.34 82 15 2.32 (2000) 3 44% top clear

7.35 81 15 2.32 (2000) 4 No separation

It is possible to adjust both the amount of cross-linker in the polymer and the amount of polymer in the formulation to achieve optimum thickening for a particular application and optimum suspension of particulates. The data shows that if the cross-linker level in the polymer is too low (samples 7.18, 7.22-7.24) or too high (samples 7.17, 7.19, and 7.34), the suspension of talc particles will not be stable over time. In some cases it is possible to improve suspension stability by increasing the amount of polymer in the formulation (compare samples 7.28 and 7.29, samples 7.31 -7.33, and samples 7.34 and 7.35).

Table 7B. Viscosities of Table 7A Formulations

The result in this example shows that polymeric rheology modifiers of the disclosure have the ability to thicken SME and suspend talc particles (and by extension suspend other solid particles of similar size). The viscosity remained relatively stable after the storage test.

Example 8. Thickened oil composition and suspension of Ti0₂ in thickened oil compositions where organic sunscreen active ingredients are used as part of the oil

In this example, the oily components were mixed together first to obtain an oil phase. Ti02 was added to the oily phase, followed by thickener 2.63. After adding the thickener 2.63, the sample was shaken immediately by hands for about 1 minute. The sample was placed in a shaker for about 2 hours. The viscosity data was obtained next day. The viscosity data (for two of the samples) and storage stability result are shown in Table 8. Table 8. Viscosity and stability of a thickened oil with sunscreen Als and suspensions of Ti02 in the thickened oils with sunscreen Als

Example 9. Molecular weight of polymeric rheology modifiers of the disclosure

Molecular weight was determined by Hydrodynamic Chromatography with multiangle light scattering detection (MALS). This method is similar to a standard GPC/MALS, except a smaller pore size column is used compared to standard GPC/MALS, which results in all the separation taking place in the interstitial volume of the GPC column.

Samples were prepared by dissolving about 10 mg of sample in about 10 ml of butylated hydroxytoluene (BHT) stabilized tetrahyrofuran (THF). Some samples were further diluted 10- fold with THF as necessary. Column: PL-Gel 100A 5um 30cm x 7.8mm

Column Temp: 40°C

Solvent: tetrahydrofuran with 0.1 % BHT preservative

Injection: 50 μΙ or 25 μΙ

Detection: Wyatt Dawn Heleos 18 angle MALS 633 nm and Wyatt Optilab T-Rex

Refractive index detector

Table 9. Molecular weight values of polyme c rheology modifiers of the invention

The foregoing examples are presented by way of illustration and not by way of limitation. Those skilled in the art will understand other examples and embodiments are encompassed within the present invention. The spirit and scope of the present invention are to be limited only by the terms of any claims presented hereunder.

Claims

What is claimed is:

A sunscreen formulation comprising,

an oil-based carrier comprising at least one oil,

at least one particulate metal oxide sunscreen active agent, and at least one polymeric rheology modifier, wherein the polyme c rheology modifier is obtainable by co-polymerizing a monomer mixture comprising at least one alkyl (meth)acrylate and at least one of the following monomers: a bicyclic (meth)acrylate ester different from the alkyl (meth)acrylate, and

an aromatic vinyl monomer.

The sunscreen formulation of claim 1 wherein said polymeric rheology modifier is crosslinked.

The sunscreen formulation of claim 1 or claim 2 wherein said at least one alkyl (meth)acrylate monomer is selected from the group consisting of a C C₆ alkyl (meth)acrylate, a C₈-C₂4 alkyl (meth)acrylate, and combinations thereof.

The sunscreen formulation of any of claims 1 -3 wherein the polymehc rheology modifier comprises:

5 to 50 wt% of bicyclic (meth)acrylate ester,

25 to 70 wt%, of C C₆ alkyl (meth)acrylate, and

10 to 40 wt% of aromatic vinyl monomer.

The sunscreen formulation of claim any of claims 1 -4 wherein the polymehc rheology modifier comprises:

10 to 30 wt% of bicyclic (meth)acrylate ester,

10 to 25 wt%, of d-Cealkyl (meth)acrylate,

30 to 40 wt% of C₈-C₂₄alkyl (meth)acrylates, and

15 to 30 wt% of aromatic vinyl monomer.

The sunscreen formulation of any of claims 1 -5 wherein said metal oxide sunscreen active agent does not include an organic component.

7. The formulation of any of claims 1-6 wherein the weight percent of the polyme c rheology modifier based on the total formulation weight is about 0.5% to 15%, or 1 % to 10%, or 2% to 8%, or 3% to 5%.

The sunscreen formulation of any of claims 1-7 wherein said formulation is substantially free of at least one ingredient selected from the group consisting of water, emulsifiers, glycols, emollients, added dispersant, and organic solvents.

The sunscreen formulation of any one of claims 1-8 wherein said polyme c rheology modifier is crosslinked and is obtained by using a cross-linking monomer in the amount, based on the total weight of all monomers in the polymer, of between 20 mg/kg to 2000 mg/kg, or 100 mg/kg to 1500 mg/kg, or 200 mg/kg to 1000 mg/kg, or 300 mg/kg to 750 mg/kg.

The sunscreen formulation of claim 9 wherein the cross-linking monomer is selected from one or more of 1 ,6-hexanediol di(meth)acrylate, trimethylolpropane triacrylate and pentaerythritol allyl ether.

The sunscreen formulation of any one of the preceding claims wherein the amount of particulate metal oxide sunscreen active agent concentration on total formulation weight is about 1 % to 20%, preferably 2% to 15%, more preferably 3% to 10%, and still more preferably 4% - 8%.

The sunscreen formulation of any of claims 1-1 1 wherein said oil is selected from any one or more of triglycerides, esters, silicone oils, organic sunscreen active ingredients, and aromatic compounds, and is preferably selected from one or more of the group consisting of plant oils, fatty acid esters, lactates, adipates, maleates, succinates, benzoates, phenyl trimethicone, octocrylene, homosalate, octyl salicylate, menthyl anthranilate, ethylhexyl methoxycinnamate, and butyloctyl salicylate.

A method of making a sunscreen formulation, the method comprising combining an oil-based carrier comprising at least one oil with at least one particulate metal oxide sunscreen active agent and at least one polymehc rheology modifier, wherein the polymehc rheology modifier is obtainable by co-polymerizing a monomer mixture comprising at least one alkyl (meth)acrylate and at least one of the following monomers:

- a bicyclic (meth)acrylate ester different from the alkyl (meth)acrylate, and

- an aromatic vinyl monomer.

A method of protecting a user from the deleterious effects of UVA and/or UVB radiation, the method comprising applying to the skin of a user a sunscreen formulation comprising an oil-based carrier comprising at least one oil, at least one particulate metal oxide sunscreen active agent, and at least one polymeric rheology modifier, wherein the the polymeric rheology modifier is obtainable by co- polymerizing a monomer mixture comprising at least one alkyl (meth)acrylate and at least one of the following monomers:

- a bicyclic (meth)acrylate ester different from the alkyl (meth)acrylate, and

- an aromatic vinyl monomer..

A sunscreen formulation comprising an oil-based carrier comprising at least one oil, at least one particulate metal oxide sunscreen active agent, and at least one polymeric rheology modifier, wherein the polymeric rheology modifier is obtainable by co-polymerizing a monomer mixture comprising at least one alkyl (meth)acrylate and at least one of the following monomers:

- a bicyclic (meth)acrylate ester different from the alkyl (meth)acrylate, and

- an aromatic vinyl monomer, for use in reducing the deleterious effects of UVA and/or UVB radiation on the skin of a user.