FIELD OF THE INVENTION

This invention relates generally to personal care compositions comprising voided latex particles and infrared actives.

BACKGROUND

Personal care compositions contain a variety of additives that provide a wide array of benefits to users, such as protecting skin from solar radiation. Most sun protection is focused on ultraviolet (“UV”) radiation, which can damage the skin. UV radiation can be classified as UVA (long wave; i.e., wavelengths of 320-400 nm) and UVB (short wave; i.e., wavelengths of 290 to 320 nm). Infrared (“IR”) radiation is also known as being associated with oxidative damage and IR has been additionally linked to adverse heat effects on skin. For example, over-exposure to IR radiation can be related to skin-aging and affect the appearance of skin.

Personal care compositions comprising light scatterers and UV absorbing agents have been disclosed. For example, WO 2017/027286 discloses compositions comprising voided latex particles and pigment grade inorganic metal oxide particles, wherein the latex particles have a particle size of from 400 nm to 1500 nm. Although the prior art discloses such particles for use in boosting the UV absorption of a composition in combination with a UV absorbing agent or UV light scatterer, the prior art does not disclose a voided latex particle with a particle size that is effective for IR protection with an IR active.

Consequently, there is a need to develop new personal care compositions for use in skin lightening applications, including compositions that improve upon the state of the art with respect to the effectiveness of such compositions over time. STATEMENT OF INVENTION

One aspect of the invention provides a personal care composition comprising (A) voided latex particles comprising (i) at least one core polymer comprising polymerized structural units of (a) 20 to 60 weight % of monoethylenically unsaturated monomers containing at least one carboxylic acid group, based on the total weight of the core polymer, and (b) 40 to 80 weight % of non-ionic ethylenically unsaturated monomers, based on the total weight of the core polymer, and (ii) at least one shell polymer comprising polymerized structural units of (a) 55 to 85 weight % of non-ionic ethylenically unsaturated monomers, based on the total weight of the shell polymer(s), and (b) 15 to 45 weight % of

polyethylenically unsaturated monomers, based on the total weight of the shell polymer(s), and (B) at least one infrared active, wherein the infrared active is present in an amount of from 0.5 to 10 weight %, based on the total weight of the composition, and wherein the voided latex particles contain a void and have an average particle size of from 800 nm to 2,000 nm.

Another aspect of the invention provides a personal care composition comprising (A) voided latex particles comprising (i) 2 to 10 weight % of at least one core polymer comprising polymerized structural units (a) 20 to 60 weight % of monoethylenically unsaturated monomers containing at least one carboxylic acid group, based on the total weight of the core polymer, and (b) 40 to 80 weight % of non-ionic ethylenically unsaturated monomers, based on the total weight of the core polymer, (ii) 24 to 32 weight % of a first intermediate shell polymer comprising polymerized structural units of (a) 90 to 99.5 weight % of non-ionic ethylenically unsaturated monomers, based on the total weight of the shell polymer(s), and (b) 0.5 to 10 weight % of monoethylenically unsaturated monomers containing at least one carboxylic acid group, based on the total weight of the first intermediate shell polymer, (iii) 23 to 31 weight % of a second intermediate shell polymer comprising polymerized structural units of (a) 90 to 99 weight % of non-ionic ethylenically unsaturated monomers, and (b) 1 to 10 weight % of polyethylenically unsaturated monomers, based on the total weight of the second intermediate shell polymer, and (iv) 35 to 43 weight % of an outermost shell polymer comprising polymerized structural units of (a) 40 to 50 weight % of non-ionic ethylenically unsaturated monomers, (b) 45 to 55 weight % of polyethylenically unsaturated monomers, and (c) 1 to 10 weight % of monoethylenically unsaturated monomers containing at least one non-carboxylic acid group, based on the total weight of the outermost shell polymer, and (B) an infrared active having a particle size of from 275 nm to 2,000 nm, wherein the infrared active is present in an amount of from 0.5 to 10 weight %, based on the total weight of the composition, and wherein the voided latex particles contain a void and have an average particle size of from 800 nm to 2,000 nm.

DETAILED DESCRIPTION

The inventors have now surprisingly found that voided latex particles comprising a core polymer and a shell polymer, and having an average particle size of from 800 nm to 2,000 nm are capable of enhancing the efficacy of certain inorganic metal oxides when applied to the skin. Advantageously, when the voided latex particles are present in a skin care composition containing an infrared (“IR”) active, the voided latex particle boosts the IR scattering and absorption of the IR active. Moreover, in some embodiments as described herein, the voided latex particles act synergistic ally in boosting the efficacy of the IR actives. That is, the voided latex particles and IR actives, in combination, are more effective than would be expected from their individual performance. Accordingly, the present invention provides in one aspect a personal care composition comprising voided latex particles comprising a core polymer and a shell polymer, and at least one IR active.

In the present invention,“personal care” is intended to refer to cosmetic and skin care compositions for leave on application to the skin including, for example, lotions, creams, gels, gel creams, serums, toners, wipes, masks, liquid foundations, make-ups, tinted moisturizer, oils, face/body sprays, and topical medicines, as well as rinse off application to the skin including, for example, body/face/hand washes, soaps, and cleansers.“Personal care” relates to compositions to be topically administered (i.e., not ingested). Preferably, the personal care composition is cosmetically acceptable. “Cosmetically acceptable” refers to ingredients typically used in personal care compositions, and is intended to underscore that materials that are toxic when present in the amounts typically found in personal care compositions are not contemplated as part of the present invention. The compositions of the invention may be manufactured by processes well known in the art, for example, by means of conventional mixing, dissolving, granulating, emulsifying, encapsulating, entrapping or lyophilizing processes.

As used herein, the term“polymer” refers to a polymeric compound prepared by polymerizing monomers, whether of the same or a different type. The generic term “polymer” includes the terms“homopolymer,”“copolymer,” and“terpolymer.” As used herein, the term“polymerized structural units” of a given monomer refers to the remnant of the monomer after polymerization. As used herein, the term“(meth)acrylic” refers to either acrylic or methacrylic.

As used herein, the terms“glass transition temperature” or“T _g ” refers to the temperature at or above which a glassy polymer will undergo segmental motion of the polymer chain. Glass transition temperatures of a polymer can be estimated by the Fox equation ( Bulletin of the American Physical Society, 1 (3) Page 123 (1956)) as follows:

l/Tg = Wl/Tg(l) + H¾/7g(2)

For a copolymer, wi and wi refer to the weight fraction of the two comonomers, and 7g(i) and T _g(2) refer to the glass transition temperatures of the two corresponding homopolymers made from the monomers. For polymers containing three or more monomers, additional terms are added ( w _n /T _glni) . The T _(g) of a polymer can also be calculated by using appropriate values for the glass transition temperatures of homopolymers, which may be found, for example, in“Polymer Handbook,” edited by J. Brandrup and E.H. Immergut, Interscience Publishers. The T _g of a polymer can also be measured by various techniques, including, for example, differential scanning calorimetry (“DSC”). The values of T _g reported herein are measured by DSC.

The inventive personal care compositions contain voided latex particles. Voided latex particles useful in the invention comprise a multistaged particle containing at least one core polymer and at least one shell polymer. The ratio of the core weight to the total polymer weight is from 1:4 (25% core) to 1:100 (1% core), and preferably from 1:8 (12% core) to 1:50 (2% core).

The at least one core polymer includes polymerized structural units of

monoethylenically unsaturated monomers containing at least one carboxylic acid group, and non-ionic ethylenically unsaturated monomers. The core polymer may be obtained, for example, by the emulsion homopolymerization of the monoethylenically unsaturated monomer containing at least one carboxylic acid group or by copolymerization of two or more of the monoethylenically unsaturated monomers containing at least one carboxylic acid group. In certain embodiments, the monoethylenically unsaturated monomer containing at least one carboxylic acid group is copolymerized with one or more non-ionic (that is, having no ionizable group) ethylenically unsaturated monomers. While not wishing to be bound by theory, it is believed that the presence of the ionizable acid group makes the core swellable by the action of a swelling agent, such as an aqueous or gaseous medium containing a base to partially neutralize the acid core polymer and cause swelling by hydration.

Suitable monoethylenically unsaturated monomers containing at least one carboxylic acid group of the core polymer include, for example, (meth)acrylic acid,

(meth)acryloxypropionic acid, itaconic acid, aconitic acid, maleic acid, fumaric acid, crotonic acid, citraconic acid, maleic anhydride, monomethyl maleate, monomethyl fumarate, and monomethyl itaconate, and other derivatives such as corresponding anhydride, amides, and esters. In certain preferred embodiments, the monoethylenically unsaturated monomers containing at least one carboxylic acid group are selected from acrylic acid and methacrylic acid. In certain embodiments, the core comprises polymerized structural units of monoethylenically unsaturated monomers containing at least one carboxylic acid group in an amount of from 20 to 60 weight %, preferably from 30 to 50 weight %, and more preferably from 35 to 45 weight %, based on the total weight of the core polymer. In certain preferred embodiments, the monoethylenically unsaturated monomers containing at least one carboxylic acid group are methacrylic acid monomers, and are present in an amount of from 35 to 45 weight %, based on the total weight of the core polymer.

Suitable non-ionic ethylenically unsaturated monomers of the core polymer include, for example, styrene, vinyltoluene, ethylene, vinyl acetate, vinyl chloride, vinylidene chloride, acrylonitrile, (meth)acrylamide, (Ci-C22)alkyl and (C3-C2o)alkenyl esters of (meth)acrylic acid, such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl

(meth) acrylate, 2-ethylhexyl (meth) acrylate, benzyl (meth)acrylate, lauryl (meth)acrylate, oleyl (meth)acrylate, palmityl (meth)acrylate and stearyl (meth)acrylate. In certain preferred embodiments, the non-ionic ethylenically unsaturated monomers are selected from methyl methacrylate and butyl methacrylate. In certain embodiments, the core comprises polymerized units of non-ionic ethylenically unsaturated monomers in an amount of from 40 to 80 weight %, preferably from 50 to 70 weight %, and more preferably from 55 to 65 weight %, based on the total weight of the core polymer. In certain preferred embodiments, the non-ionic unsaturated monomers are methyl methacylate monomers, and are present in an amount of from 55 to 65 weight %, based on the total weight of the core polymer. The voided latex particles suitable for use in the present invention also include at least one shell polymer. The at least one shell polymer(s) comprise polymerized structural units of non-ionic ethylenically unsaturated monomers and polyethylenically unsaturated monomers. In certain embodiments, at least one shell polymer optionally comprises polymerized structural units of at least one of monoethylenically unsaturated monomers containing at least one carboxylic acid group and monoethylenically unsaturated monomers containing at least one“non-carboxylic” acid group. In certain embodiments, the shell portion of the voided latex particles are polymerized in a single stage, preferably in two stages, and more preferably in at least three stages. As used herein, the term“outermost shell” refers to the composition of the final distinct polymerization stage used to prepare the voided latex particles. In certain embodiments wherein the outermost shell is provided by a multistage polymerization process, the outermost shell comprises at least 25 weight %, preferably at least 35 weight %, and more preferably at least 45 weight % of the total shell portion of the voided latex particle.

Suitable non-ionic ethylenically unsaturated monomers for the shell polymer(s) include, for example, vinyl acetate, acrylonitrile, methacrylonitrile, nitrogen containing ring compound unsaturated monomers, vinylaromatic monomers, ethylenic monomers and selected (meth)acrylic acid derivatives. Suitable (meth)acrylic acid derivatives include, for example, (Ci-C22)alkyl (me th) acrylate, substituted (meth)acrylate, and substituted

(meth) acrylamide monomers. In certain preferred embodiments, the (meth)acrylic acid derivatives are selected from methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, dimethylaminoethyl methacrylate, dimethylaminopropyl methacrylamide, and mixtures thereof. Suitable vinylaromatic monomers include, for example, styrene, oc-methylstyrene, vinyltoluene, alkyl-substititued styrene (such as t-butylstyrene and ethylvinylbenzene), and halogenated styrenes (such as chlorostyrene and 3,5-bis (trifuoromethyl) styrene). In certain preferred embodiments, the vinylaromatic monomers are selected from styrene, ethylvinylbenzene, t-butylstrene, and mixtures thereof. In certain embodiments, the shell polymer(s) comprise polymerized units of non-ionic ethylenically unsaturated monomers in an amount of from 55 to 85 weight %, preferably from 60 to 80 weight %, and more preferably from 65 to 75 weight %, based on the total weight of the shell polymer(s).

Suitable polyethylenically unsaturated monomers for the shell polymer(s) include, for example, di(meth)acrylates, tri(meth)acrylates, tetra(meth)acrylates, polyallylic monomers, polyvinylic monomers, and (meth)acrylic monomers having mixed ethylenic functionality. Suitable polyvinylic monomers include, for example, diethyleneglycol divinyl ether, divinylbenzene, divinyl ketone, divinylpyridine, divinyl sulfide, divinyl sulfone, divinyltoluene, divinylxylene, glycerol trivinyl ether, trivinylbenZene, 1,2,4- trivinylcyclohexane, N,N’-ethylenebisacrylamide, partially fluorinated a, co-dienes (such as CF2=CFCF2CF2CH2CH=CH2), trifluoroalkadienes, trifluorodivinylbenzenes, and fluorinated divinyl ethers of fluorinated l,2-ethanediol. In certain preferred embodiments, the polyvinylic monomer comprises divinylbenzene. Suitable (meth)acrylic monomers having mixed ethylenic functionality include, for example, the acrylate ester of neopentyl glycol monodicyclopentenyl ether, allyl acryloxypropionate, allyl acrylate, allyl methacrylate, crotyl acrylate, crotyl methacrylate, 3-cyclohexenylmethyleneoxyethyl acrylate, 3-cyclohexenylmethyleneoxyethyl methacrylate, dicyclopentadienyloxyethyl acrylate, dicyclopentadienyloxyethyl methacrylate, dicyclopentenyl acrylate,

dicyclopentenyl methacrylate, dicyclopentenyloxyethyl acrylate, dicycol pentenyloxyethyl methacrylate, methacrylate ester of neopentyl glycol monodicyclopentenyl ether, methallyl acrylate, trimethylolpropane diallyl ether mono-acrylate, trimethylolpropane diallyl ether mono-methacrylate, and N-allyl acrylamide. In certain preferred embodiments, the (meth)acrylic monomers having mixed ethylenic functionality comprise allyl methacrylate. In certain embodiments, the shell polymer(s) comprise polymerized units of

polyethylenically unsaturated monomers in an amount of from 15 to 45 weight %, preferably from 20 to 35 weight %, and more preferably from 22 to 30 weight %, based on the total weight of the shell polymer(s). In certain embodiments, the outermost shell comprises polymerized units of polyethylenically unsaturated monomers in an amount of from 10 to 100 weight %, preferably from 15 to 70 weight %, and more preferably from 20 to 60 weight %, based on the weight of the outermost shell polymer.

Suitable monoethylenically unsaturated monomers containing at least one carboxylic acid group for the shell polymer(s) include, for example, (meth)acrylic acid,

(meth)acryloxypropionic acid, itaconic acid, aconitic acid, maleic acid, fumaric acid, crotonic acid, citraconic acid, maleic anhydride monomethyl maleate, monomethyl fumarate, and monomethyl itaconate, and other derivatives such as corresponding anhydride, amides, and esters. In certain preferred embodiments, the monoethylenically unsaturated monomers containing at least one carboxylic acid group are selected from acrylic acid and methacrylic acid. In certain embodiments, the shell polymer(s) comprises polymerized units of monoethylenically unsaturated monomers containing at least one carboxylic acid group in an amount of from 0.1 to 10 weight %, preferably from 0.3 to 7.5 weight %, and more preferably from 0.5 to 5 weight %, based on the total weight of the shell polymer(s).

Suitable monoethylenically unsaturated monomers containing at least one“non- carboxylic” acid group for the shell polymer(s) include, for example, allylsulfonic acid, allylphosphonic acid, allyloxybenzenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid (the acryonym“AMPS” for this monomer is a trademark of LubriZol Corporation, Wickliffe, Ohio, USA), 2-hydroxy- 3 -(2-propenyloxy)propanesulfonic acid, 2-methyl-2- propene-l -sulfonic acid, 2-methacrylamido-2-methyl-l-propanesulfonic acid, 3- methacrylamido-2-hydroxy-l-propanesulfonic acid, 3-sulfopropyl acrylate, 3-sulfopropyl methacrylate, isopropenylphosphonic acid, vinylphosphonic acid, phosphoethyl methacrylate, styrenesulfonic acid, vinylsulfonic, acid and the alkali metal and ammonium salts thereof. In certain preferred embodiments, the monoethylenically unsaturated monomers containing at least one“non-carboxylic” acid group are selected from 2- acrylamido-2-methylpropanesulfonic acid, styrenesulfonic acid, and sodium styrene sulfonate. In certain embodiments, the shell polymer(s) comprise polymerized units of monoethylenically unsaturated monomers containing at least one“non-carboxylic” acid group in an amount of from 0.1 to 10 weight %, preferably from 0.5 to 7.5 weight %, and more preferably from 1 to 5 weight %, based on the total weight of the shell polymer(s).

The shell polymer(s) of the latex particles suitable for use in the present invention have T _g values which are high enough to support to support the void within the latex particle. In certain embodiments, the T _g values of at least one shell are greater than 50°C , preferably greater than 60°C, and more preferably greater than 70°C.

In certain embodiments, the voided latex particles of the present invention contain a core polymer, a first intermediate shell polymer, a second intermediate shell polymer, and an outermost shell polymer. In certain embodiments, the core polymer is present in an amount of from 2 to 10 weight %, preferably from 4 to 8 weight %, and more preferably from 5 to 7 weight %, based on the total weight of the voided latex particle. In certain embodiments, the first intermediate shell polymer is present in an amount of from 24 to 32 weight %, preferably from 26 to 30 weight %, and more preferably from 27 to 29 weight %, based on the total weight of the voided latex particle. In certain embodiments, the second intermediate shell polymer is present in an amount of from 23 to 31 weight %, preferably from 25 to 29 weight %, and more preferably from 26 to 28 weight %, based on the total weight of the voided latex particle. In certain embodiments, the outermost shell polymer is present in an amount of from 35 to 43 weight %, preferably from 37 to 41 weight %, and more preferably from 38 to 40 weight %, based on the total weight of the voided latex particle.

The first intermediate shell polymer of the voided latex particle contains polymerized structural units of non-ionic ethylenically unsaturated monomers and monoethylenically unsaturated monomers containing at least one carboxylic acid group. In certain embodiments, the first intermediate shell polymer contains non-ionic ethylenically unsaturated monomers containing at least one carboxylic acid group in an amount of from 90 to 99.5 weight %, preferably from 93 to 99 weight %, and more preferably from 95 to 98 weight %, based on the first intermediate shell polymer. In certain embodiments, the first intermediate shell polymer contains monoethylenically unsaturated monomers containing at least one carboxylic acid group in an amount of from 0.5 to 10 weight %, preferably from 1 to 7 weight %, and more preferably from 2 to 5 weight %, based on the total weight of the first intermediate shell polymer. In certain preferred embodiments, the non-ionic ethylenically unsaturated monomers of the first intermediate shell are selected from butyl methacrylate, methyl methacrylate, and combinations thereof, and the monoethylenically unsaturated monomers containing at least one carboxylic acid group of the first intermediate shell are methacrylic acid monomers.

The second intermediate shell polymer of the voided latex particle contains polymerized structural units of non-ionic ethylenically unsaturated monomers and polyethylenically unsaturated monomers. In certain embodiments, the second intermediate shell polymer contains non-ionic ethylenically unsaturated monomers in an amount of from 90 to 99 weight %, preferably from 92 to 98 weight %, and more preferably from 94 to 96 weight %, based on the total weight of the second intermediate shell polymer. In certain embodiments, the second intermediate shell contains polyethylenically unsaturated monomers in an amount of from 1 to 10 weight %, preferably from 2 to 8 weight %, and more preferably from 4 to 6 weight %, based on the total weight of the second intermediate shell polymer. In certain preferred embodiments, the non-ionic ethylenically unsaturated monomers are styrene monomers, and the polyethylenically unsaturated monomers are divinylbenzene monomers.

The outermost shell polymer of the voided latex particle contains polymerized structural units of non-ionic ethylenically unsaturated monomers, polyethylenically unsaturated monomers, and monoethylenically unsaturated monomers containing at least one non-carboxylic acid group. In certain embodiments, the outermost shell polymer contains non-ionic ethylenically unsaturated monomers in an amount of from 40 to 50 weight %, preferably from 43 to 49 weight %, and more preferably from 45 to 48 weight %, based on the total weight of the outermost shell polymer. In certain embodiments, the outermost shell polymer contains polyethylenically unsaturated monomers in an amount of from 45 to 55 weight %, preferably from 48 to 53 weight %, and more preferably from 50 to 52 weight %, based on the total weight of the outermost shell polymer. In certain embodiments, the outermost shell polymer contains monoethylenically unsaturated monomers containing at least one non-carboxylic acid group in an amount of from 0.5 to 10 weight %, preferably from 1 to 6 weight %, and more preferably from 2 to 4 weight %, based on the total weight of the outermost shell polymer. In certain preferred embodiments, the non-ionic ethylenically unsaturated monomers are styrene monomers, the

polyethylenically unsaturated monomers are divinylbenzene monomers, and the

monoethylenically unsaturated monomers containing at least one non-carboxylic acid group are sodium styrene sulfonate monomers.

In certain preferred embodiments, the voided latex particles of the present invention contain 5 to 7 weight % of a core polymer, 27 to 29 weight % of a first intermediate shell polymer, 26 to 28 weight % of a second intermediate shell polymer, and 38 to 40 weight % of an outermost shell polymer, based on the total weight of the voided latex particle, wherein the core polymer contains polymerized structural units of 35 to 45 weight % methacrylic acid monomers, and 55 to 65 weight % methyl methacrylate monomers, based on the total weight of the core polymer, and wherein the first intermediate shell polymer contains polymerized structural units of 6 to 10 weight % of butyl methacrylate monomers, 86 to 91 weight % of methyl methacrylate monomers, and 2 to 5 weight % of methacrylic acid monomers, based on the total weight of the first intermediate shell polymer, and wherein the second intermediate shell polymer contains polymerized structural units of 94 to 96 weight % of styrene monomers, and 4 to 6 weight % of divinylbenzene monomers, based on the total weight of the second intermediate shell polymer, and wherein the outermost shell polymer contains polymerized structural units of 45 to 48 weight % of styrene monomers, 50 to 52 weight % of divinylbenzene monomers, and 2 to 4 weight % of sodium styrene sulfonate monomers, based on the total weight of the outermost shell polymer.

In certain embodiments, the core polymer and shell polymer are made in a single polymerization step. In certain other embodiments, the core polymer and shell polymer are made in a sequence of polymerization steps. Suitable polymerization techniques for preparing the voided latex particles contained in the inventive personal care compositions include, for example, sequential emulsion polymerization. In certain embodiments, the monomers used in the emulsion polymerization of the shell polymer of the voided latex particles comprise one or more non-ionic ethylenically unsaturated monomer. Aqueous emulsion polymerization processes typically are conducted in an aqueous reaction mixture, which contains at least one monomer and various synthesis adjuvants, such as the free radical sources, buffers, and reductants in an aqueous reaction medium. In certain embodiments, a chain transfer agent may be used to limit molecular weight. The aqueous reaction medium is the continuous fluid phase of the aqueous reaction mixture and contains more than 50 weight % water and optionally one or more water miscible solvents, based on the weight of the aqueous reaction medium. Suitable water miscible solvents include, for example, methanol, ethanol, propanol, acetone, ethylene glycol ethyl ethers, propylene glycol propyl ethers, and diacetone alcohol.

In certain embodiments, the void of the latex particles is prepared by swelling the core with a swelling agent containing one or more volatile components. The swelling agent permeates the shell to swell the core. The volatile components of the swelling agent can then be removed by drying the latex particles, causing a void to be formed within the latex particles. In certain embodiments, the swelling agent is an aqueous base. Suitable aqueous bases useful for swelling the core include, for example, ammonia, ammonium hydroxide, alkali metal hydroxides, such as sodium hydroxide, or a volatile amine such as

trimethylamine or triethylamine. In certain embodiments, the voided latex particles are added to the composition with the swelling agent present in the core. When the latex particles are added to the composition with the swelling agent present in the core, the volatile components of the swelling agent will be removed upon drying of the composition. In certain other embodiments, the voided latex particles are added to the composition after removing the volatile components of the swelling agent.

In certain embodiments, the voided latex particles contain a void with a void fraction of from 1% to 70%, preferably from 5% to 50%, more preferably from 10% to 40%, and even more preferably from 25% to 35%. The void fractions are determined by comparing the volume occupied by the latex particles after they have been compacted from a dilute dispersion in a centrifuge to the volume of non- voided particles of the same composition.

In certain embodiments, the voided latex particles have an average particle size of from 800 nm to 2,000 nm, preferably from 1,400 nm to 1,900 nm, and more preferably from 1,550 nm to 1,850 nm, as measured by a Brookhaven BI-90.

A person of ordinary skill in the art can readily determine the effective amount of the voided latex particles that should be used in a particular composition in order to provide the benefits described herein (e.g., improved light scattering to compositions containing inorganic metal oxide particles, and providing a long lasting whitening effect when applied to skin), via a combination of general knowledge of the applicable field as well as routine experimentation where needed. By way of non-limiting example, the amount of voided latex particles in the composition of the invention may be in the range of from 0.5 to 20 solids weight %, preferably from 1 to 7 solids weight %, more preferably from 1 to 2 solids weight %, based on the total weight of the composition.

The personal care compositions of the present invention also contain IR actives. Suitable IR actives include, for example, IR scatterers and IR absorbers. Suitable IR scatterers include, for example, titanium dioxide (TiC ) particles having an average particle size of from 275 nm to 2,000 nm, preferably from 300 nm to 1,750 nm, and more preferably from 500 nm to 1,500 nm. Suitable TiCT particles include, for example, those commercially available under the trade names MP-100 and MPY-100M from Tyca Corporation. Suitable IR absorbers include, for example, SnCh having an average particle size of from 1 nm to 300 nm, preferably from 10 nm to 150 nm, and more preferably from 30 to 110 nm.

The compositions of the invention may also include a dermatologically acceptable carrier. Such material is typically characterized as a carrier or a diluent that does not cause significant irritation to the skin and does not negate the activity and properties of active agent(s) in the composition. Examples of dermatologically acceptable carriers that are useful in the invention include, without limitation, water, such as deionized or distilled water, emulsions, such as oil-in-water or water-in-oil emulsions, alcohols, such as ethanol, isopropanol or the like, glycols, such as propylene glycol, glycerin or the like, creams, aqueous solutions, oils, ointments, pastes, gels, lotions, milks, foams, suspensions, powders, or mixtures thereof. In some embodiments, the composition contains from about 99.99 to about 50 percent by weight of the dermatologically acceptable carrier, based on the total weight of the composition. The personal care composition of the invention may also include, for instance, a thickener, additional emollients, an emulsifier, a humectant, a surfactant, a suspending agent, a film forming agent, a lower monoalcoholic polyol, a high boiling point solvent, a propellant, a mineral oil, silicon feel modifiers, or mixtures thereof. The amount of optional ingredients effective for achieving the desired property provided by such ingredients can be readily determined by one skilled in the art.

Other additives may be included in the compositions of the invention such as, but not limited to, abrasives, absorbents, aesthetic components such as fragrances, pigments, colorings/colorants, essential oils, skin sensates, astringents (e.g., clove oil, menthol, camphor, eucalyptus oil, eugenol, menthyl lactate, witch hazel distillate), preservatives, anti-caking agents, a foam building agent, antifoaming agents, antimicrobial agents (e.g., iodopropyl butylcarbamate), antioxidants, binders, biological additives, buffering agents, bulking agents, chelating agents, chemical additives, colorants, cosmetic astringents, cosmetic biocides, denaturants, drug astringents, external analgesics, film formers or materials, e.g., polymers, for aiding the film-forming properties and substantivity of the composition (e.g., copolymer of eicosene and vinyl pyrrolidone), opacifying agents, pH adjusters, propellants, reducing agents, sequestrants, skin bleaching and lightening agents (e.g., hydroquinone, kojic acid, ascorbic acid, magnesium ascorbyl phosphate, ascorbyl glucosamine), skin-conditioning agents (e.g., humectants, including miscellaneous and occlusive), skin soothing and/or healing agents (e.g., panthenol and derivatives (e.g., ethyl panthenol), aloe vera, pantothenic acid and its derivatives, allantoin, bisabolol, and dipotassium glycyrrhizinate), skin treating agents, and vitamins (e.g., Vitamin C) and derivatives thereof. The amount of option ingredients effective for achieving the desired property provided by such ingredients can be readily determined by one skilled in the art.

As noted above, personal care compositions of the present invention are highly effective as IR protective agents. The voided latex particles act synergistically in boosting the efficacy of the IR actives. That is, the voided latex particles and IR actives, in combination, are more effective than would be expected from their individual performance. Thus, in one aspect the present invention provides that the personal care compositions may be used in a method for protecting the skin from infrared radiation. In practicing the methods of the invention, the personal care compositions are generally administered topically by applying or spreading the compositions onto the skin. A person of ordinary skill in the art can readily determine the frequency with which the compositions should be applied. The frequency may depend, for example, on the level of skin lightening that an individual is likely to desire. By way of non-limiting example, administration on a frequency of at least once per day may be desirable.

Some embodiments of the invention will now be described in detail in the following

Examples.

EXAMPLES

Example 1

Preparation of Exemplary Voided Latex Particles

Exemplary voided latex particles in accordance with the present invention contain the components recited in Table 1. Table 1. Exemplary Voided Latex Particles (“Polymer A”)

V1MA = methyl methacrylate

BMA = butyl methacrylate MAA = methacrylic acid

Sty = styrene

DVB = divinylbenzene

SSS = sodium styrene sulfonate

To a 3-liter, 4-neck round bottom flask equipped with overhead stirrer, thermocouple, heating mantle, adapter inlet, Claisen head fitted with a water condenser and nitrogen inlet, and an inlet adapter, was added 950.0 grams (g) deionized water which was heated to 84°C under nitrogen. 0.30 g acetic acid, 1.70 g sodium persulfate in 15.5 g of deionized water was added to the heated water followed by the addition of an aqueous dispersion of 31% poly(MMA/MAA//60/40) acrylic seed (core) polymer (67.45g), having an average particle diameter of approximately 133 nm. A monomer emulsion containing 64.4 g deionized water, 1.9 g aqueous solution of 23% SDBS, 82.4 g MMA, 8.0 g BMA and 2.8 g MAA was metered in to the heated mixture over 90 minutes at 82°C, followed by a deionized water rinse. Next, a solution of 0.98 g sodium persulfate in 32.8 g deionized water was added over 90 minutes and the reaction temperature was raised to 90°C concurrent with the addition of a second monomer emulsion containing 34.8 g deionized water, 0.51 g aqueous solution of 23% SDBS, 86.8 g Sty, 4.65 g DVB and 0.50 g linseed oil fatty acid over 30 minutes. At the completion of addition of the second monomer emulsion, 7.2 g aqueous 28% ammonium hydroxide was added, and held for 10 min. A third monomer emulsion containing 107.0 g deionized water, 5.58 g aqueous solution of 23%SDBS, 61.0 g Sty and 67.4 g DVB, 3.57 g SSS, and 0.64 g linseed oil was added to the reaction mixture at 91 °C over 60 minutes, followed by a deionized water rinse. The reactor contents were held at 9l°C for 30 minutes, then 5.8 g of aqueous solution containing 0.01 g of FeS04.7H20 and 0.01 g of versene was added followed by the concurrent addition over 60 minutes of 5.10 g of t-butylhydrogen peroxide (70%) in 26.3 g of deionized water and 2.6 g isoascorbic acid in 29.0 g deionized water, to the reactor maintained at 91 °C. The latex was cooled to room temperature and then filtered. Example 2

Characterization of Exemplary Voided Latex Particles

Voided latex particles as prepared in Example 1 were evaluated for particle size and percent void fraction, as shown in Table 2.

Table 2. Characterization of Voided Latex Particles

The particle size was measured using a Brookhaven BI-90. The percent void fraction of the latex particles was measured by making a 10% by weight dispersion of each sample with propylene glycol, which was then mixed and poured into a weight-per-gallon cup which was capped and weighed. A 10 % water blank was also measured, and the difference in the weight was used to calculate the density of the sample, from which the percent void fraction was determined.

Example 3

Preparation of Exemplary and Comparative IR Scattering Formulations

Exemplary formulations containing IR scatterers according to the present invention and comparative formulations contain the components recited in Table 3.

Table 3. Exemplary IR Scattering Formulations

*Compartive

Available from Lubrizol

² Available from Tyca Corporation (MPY-100) ³ Available from Protameen

4Available from RITA

⁵ Available from Tyca Corporation (MPY-100M)

⁶ Available from Ashland.

7Available from The Dow Chemical Company

The IR scattering formulations were prepared by adding Ultrez 10 and l,3-butanediol to water and mixing until the Ultrez 10 was completely dissolved. The remaining components of Phase I were then added to the mixture. Phase II components were mixed separately and heated to 70°C to ensure that all components were melted. Phases I and II were then combined while mixing and cooled to about 50°C, at which point Phase III components were added to the mixture. The mixture was allowed to cool to about 30°C, and the pH was adjusted to a pH of about 5.5-6.0 by adding triethanolamine dropwise.

Example 4

Preparation of Exemplary and Comparative IR Absorber Formulations

Exemplary formulations containing IR absorbers according to the present invention and comparative formulations contain the components recited in Table 4.

Table 4. Exemplary IR Absorbing Formulations

Comparative

Available from Lubrizol

2Available from Protameen

3Available from RITA

4Available from Ashland

5Available from Nyacol ⁶ Available from The Dow Chemical Company

The IR absorber formulations were prepared by adding Ultrez 10 and l,3-butanediol to water and mixing until the Ultrez 10 was completely dissolved. The remaining components of Phase I were then added to the mixture. Phase II components were mixed separately and heated to 70°C to ensure that all components were melted. Phases I and II were then combined while mixing and cooled to about 50°C, at which point Phase III components were added to the mixture. The mixture was allowed to cool to about 30°C, and the pH was adjusted to a pH of about 5.5-6.0 by adding triethanolamine dropwise.

Example 5

IR Reflectance Study of Exemplary and Comparative IR Scattering Formulations

The IR reflectance/scattering effect of exemplary formulations including 2.5 weight % T1O2 and 2.5 weight % Polymer A voided latex particles (formulations El and E2), were compared against comparative formulations containing 5 weight % T1O2 (formulations Cl and C2) and 5 weight % Polymer A (formulation C3), all as prepared in Example 3. The IR reflectance was measured in a reflection geometry by a MicroNIR™ spectrometer (Viavi Solutions Inc.). Each spectrum was acquired for 1 second over the spectral range of 950- 1650 nm. For each sample, the reflectance was measured on a total of 10 spots from 2 separate drawdowns. The results of the reflectance measurements are shown in Table 5 as percent reflectance. Table 5. Reflectance of Exemplary and Comparative IR Scattering Formulations

The results show the boosting effect of the compositions of the invention on the IR scattering performance of TiCE. In addition, examples El and E2 demonstrate a synergistic effect between the voided latex particles when used with TiCh.

Example 6

IR Absorber Study of Exemplary and Comparative IR Absorber Formulations

The IR absorption effect of exemplary formulations including 2.5 weight % SnCh and 2.5 weight % Polymer A voided latex particles (formulation E3) was compared against comparative formulations containing 5 weight % SnCh (formulation C4), 2.5 weight %

SnCh (formulation C5), 5 weight % Polymer A voided latex particles (formulation C6), and 2.5 weight % Polymer A voided latex particles (formulation Cl), all as prepared in Example 4. The IR absorbance and transmittance was measured in the transmission mode and reflection mode in a PerkinElmer UV-vis spectrometer equipped with an integrating sphere. The IR absorption of the formulations was determined by subtracting the % reflectance and % transmittance from the 100% total light intensity. The results of the absorption measurements are shown in Table 6 as percent transmittance· Table 6. Transmittance of Exemplary and Comparative IR Absorber Formulations

The results show the boosting effect of the compositions of the invention on the IR absorbance of SnCK In addition, example E3 demonstrate a synergistic effect between the voided latex particles when used with SnCK