Uv-protective compositions

Abstract

Disclosed are UV-protective compositions comprising swelled polymer matrix macroparticles comprising a thermoplastic polymer swelled with at least one swelling agent, and a plurality of nanoparticles of an inorganic UV-protective agent comprising at least one solid inorganic crystal and a dispersant associated with the crystal, wherein the inorganic nanoparticles are dispersed and embedded in the swelled polymer matrix macroparticles. Method of preparation and uses of such compositions are also provided.

1 . A UV-protective composition comprising:
 swelled polymer matrix flakes comprising a thermoplastic polymer swelled with an oil; and   a plurality of nanoparticles including inorganic nanoparticles of at least one inorganic UV-protective agent, each of said inorganic nanoparticles comprising at least one solid inorganic crystal and a dispersant associated with said crystal, wherein said inorganic nanoparticles are dispersed and embedded in said swelled polymer matrix flakes;   wherein each flake of said swelled polymer matrix flakes has a flake length (Lf), a flake width (Wf), and a flake thickness (Tf), said swelled polymer matrix flakes having a dimensionless flake aspect ratio (Rf) defined by:
     Rf= ( Lf·Wf )/( Tf ) 2    
   wherein, with respect to a representative group of said swelled polymer matrix flakes, an average Rf is at least 5;   wherein said inorganic UV-protective agent has a Mohs Hardness Number within a range of 3.5 to 8;   and wherein said plurality of inorganic nanoparticles within said representative group has an average particle size (D N 50) of at most 100 nm.   
     
     
         2 . The UV-protective composition according to  claim 1 , wherein at least one of said flake length (Lf) and said flake width (Wf) is at most 50 μm, at most 25 μm, at most 10 μm, or at most 5 μm. 
     
     
         3 . The UV-protective composition according to any one of  claim 1  or  claim 2 , wherein said flake thickness (Tf) is at most 1000 nm, at most 900 nm, at most 750 nm, at most 650 nm, at most 600 nm, at most 550 nm, at most 500 nm, at most 450 nm, at most 400 nm, at most 350 nm, at most 300 nm, or at most 250 nm. 
     
     
         4 . The UV-protective composition according to any one of  claim 1  to  claim 3 , wherein said flake aspect ratio (Rf) is within a range of 5 to 2000, 10 to 1000, 12 to 500, 12 to 200, or 15 to 100. 
     
     
         5 . The UV-protective composition according to any one of  claim 1  to  claim 4 , wherein said representative group is disposed in an instrumental field of view containing at least 10 of said swelled polymer matrix flakes, and optionally hundreds of said inorganic nanoparticles. 
     
     
         6 . The UV-protective composition according to any one of  claim 1  to  claim 5 , said inorganic nanoparticles having at least one of:
 (i) a unimodal particle size distribution; and 
 (ii) an at least bimodal distribution having a first peak representing a first population of particles having a first average size and at least a second peak representing at least a second population of particles having at least a second average size exceeding said first average size, wherein an area under said first peak exceeds a cumulative area under said at least second peak. 
 
     
     
         7 . The UV-protective composition according to any one of  claim 1  to  claim 6 , said nanoparticles having a particle size distribution (PSD) on a particle number basis, a standard deviation of said PSD being at most 60 nm, at most 50 nm, at most 40 nm, at most 35 nm, at most 30 nm, at most 25 nm, or at most 20 nm, and/or said PSD being at most 80%, at most 60%, at most 50%, at most 40%, at most 30%, at most 25%, or at most 20%. 
     
     
         8 . The UV-protective composition according to any one of  claim 1  to  claim 7 , wherein a concentration of said oil, with respect to said thermoplastic polymer, in the swelled polymer matrix flakes, is:
 (a) within a first range of 10 to 50%, 10 to 35%, 10 to 30%, 12 to 25%, or 15 to 25%, on a weight per weight (w/w) basis, and/or 
 (b) within a second range of 6 to 65%, 12 to 45%, 12 to 40%, 16 to 32%, or 20 to 30%, on a volume per volume (v/v) basis. 
 
     
     
         9 . The UV-protective composition according to any one of  claim 1  to  claim 8 , wherein said solid inorganic crystal comprises a crystal of a doped or undoped metal oxide. 
     
     
         10 . The UV-protective composition according to  claim 9 , wherein said metal oxide is selected from the group consisting of BaTiO 3 , Bi 2 O 3 , BiVO 4 , TiO 2 , ZnO, ZnTiO 4 , and Bi 4 Ti 3 O 12 . 
     
     
         11 . The UV-protective composition according to any one of  claim 9  or  claim 10 , wherein said metal oxide is doped with a metal cation selected from the group consisting of copper, iron, manganese and lanthanum. 
     
     
         12 . The UV-protective composition according to any one of  claim 1  to  claim 11 , wherein, with respect to said representative group of said swelled polymer matrix flakes, said D N 50 is at most 90 nm, at most 80 nm, at most 70 nm, or at most 60 nm. 
     
     
         13 . The UV-protective composition according to  claim 1  or  claim 12 , wherein at least 60%, at least 75%, or at least 90% of said plurality of nanoparticles have a cumulative particle size (D N 60, D N 75, and D N 90, accordingly) of at most 100 nm, at most 90 nm, at most 80 nm, at most 70 nm, or at most 60 nm. 
     
     
         14 . The UV-protective composition according to any one of  claim 1  to  claim 13 , wherein a concentration of said inorganic nanoparticles, with respect to said thermoplastic polymer, is:
 (a) within a range of 0.1 to 60%, 1 to 40%, 2 to 30%, or 4 to 25%, on a weight per weight basis, and/or 
 (b) within a range of 0.01 to 20%, 0.1 to 15%, or 1 to 10%, on a volume per volume basis. 
 
     
     
         15 . The UV-protective composition according to any one of  claim 1  to  claim 14 , wherein a concentration of said inorganic nanoparticles, with respect to the UV-protective composition, is:
 (a) within a range of 0.01 to 40% 0.1 to 30%, 1 to 20%, or 1 to 20%, on a weight per weight basis, and/or 
 (b) within a range of 0.01 to 20%, 0.01 to 15%, 0.1 to 10%, or 0.5 to 5%, on a volume per volume basis. 
 
     
     
         16 . The UV-protective composition according to any one of  claim 1  to  claim 15 , wherein said thermoplastic polymer comprises at least one ethylene polymer, ethylene-acrylic acid (EAA) polymer, ethylene-methacrylic acid (EMMA) polymer, ethyl vinyl acetate (EVA) polymer, substituted or modified versions thereof and ionomers thereof, the thermoplastic polymer or combination thereof preferably having at least one of a softening point and a melting point not exceeding 200° C., said softening point or melting point optionally being of at least 60° C. 
     
     
         17 . The UV-protective composition according to  claim 1 , wherein said dispersant has a hydrophilic-lipophilic balance (HLB) value of at most 9, at most 6, at most 4, or at most 3. 
     
     
         18 . The UV-protective composition according to any one of  claim 1  to  claim 17 , the composition containing a total concentration of at most 5%, at most 4%, at most 3%, at most 2%, at most 1%, at most 0.5%, at most 0.1%, at most 0.05% of organic ultraviolet-absorbing agents on a weight per weight basis, or being substantially devoid of said organic ultraviolet-absorbing agents. 
     
     
         19 . The UV-protective composition according to any one of  claim 1  to  claim 18 , the composition containing a total concentration of at most 5%, at most 4%, at most 3%, at most 2%, at most 1%, at most 0.5%, at most 0.1%, at most 0.05% of additional inorganic ultraviolet-absorbing agents on a weight per weight basis, or being substantially devoid of said additional inorganic ultraviolet-absorbing agents. 
     
     
         20 . The UV-protective composition according to any one of  claim 1  to  claim 19 , formulated as: (a) a skin-care composition for application to human or non-human animal skin; (b) a hair-care composition for application to human or non-human animal hair; or (c) a coating composition for application to an inanimate surface. 
     
     
         21 . The UV-protective composition according to any one of  claim 1  to  claim 20 , for use in protecting a subject or an inanimate subject against a harmful effect of ultraviolet radiation. 
     
     
         22 . A method of preparing a UV-protective composition, the composition being according to any one of  claim 1  to  claim 21 , the method comprising:
 (a) combining said thermoplastic polymer with a first oil, said first oil be same as or different from said oil; 
 (b) mixing said combination of thermoplastic polymer and first oil of step (a) to obtain a homogeneous paste of polymer matrix wherein the thermoplastic polymer is swelled with said first oil; 
 (c) adding said plurality of inorganic nanoparticles of inorganic UV-protective agent to said homogeneous paste of step (b), the inorganic nanoparticles being dispersed with the dispersant in a second oil, said second oil being same as or different from said first oil; and 
 (d) milling a mixture of inorganic nanoparticles and polymer matrix obtained in step (c), so as to size reduce the polymer matrix into swelled polymer matrix flakes, while dispersing and embedding the plurality of nanoparticles of inorganic UV-protective agent in said swelled polymer matrix flakes. 
 
     
     
         23 . The method according to  claim 22 , wherein said mixing of step (b) is performed while heating said combination to a swelling temperature of from 0° C. to 20° C., from 0° C. to 30° C., or from about 0° C. to 40° C. above a melting temperature or softening temperature of said thermoplastic polymer. 
     
     
         24 . The method according to any one of  claim 22  or  claim 23 , wherein the homogenous paste obtained in step (b) is cooled to a temperature below the lowest of a melting temperature or softening temperature of said thermoplastic polymer and a melting temperature or softening temperature of said homogeneous paste, said cooling being performed prior to step (c) or prior to step (d). 
     
     
         25 . The method according to any one of  claim 22  to  claim 24 , wherein the milling of step (d) is performed while maintaining the mixture at a temperature below the lowest of a melting temperature or softening temperature of said thermoplastic polymer and a melting temperature or softening temperature of the homogeneous paste of step (b). 
     
     
         26 . The method according to any one of  claim 22  to  claim 25 , wherein subsequent to step (d) any of the first oil and the second oil is optionally partially replaced by a third oil, the combination of first oil, second oil and optional third oil, constituting the oil of the swelled polymer matrix flakes of the UV-protective composition. 
     
     
         27 . The method according to any one of  claim 22  to  claim 26 , further comprising adding to said swelled polymer matrix flakes at least one of a carrier, an additive and an excipient, each independently suitable to form a topical UV-protective composition.