Particulate metal oxide particles comprising a metal oxide core and a coating layer comprising an inorganic material, a silane coupling agent and/or a hydrophobizing agent

Abstract

A particulate metal oxide has a metal oxide core and a coating layer containing an inorganic material and (i) a quaternary silane coupling agent, and/or (ii) a silane coupling agent and a hydrophobizing agent. Preferred materials are titanium dioxide core particles, an amino organosilane coupling agent and a fatty acid hydrophobizing agent. The particulate metal oxide is suitable for use in forming a dispersion, and the particles and dispersion can be used in an end-use sunscreen composition which is transparent, exhibits effective UV absorption properties, reduced photoactivity, and/or improved skin feel.

Claims

1. Coated metal oxide particles comprising metal oxide core particles each having thereon a coating layer comprising silica, a fatty acid and/or a salt thereof and a silane coupling agent, wherein the metal oxide comprises titanium dioxide, the silane coupling agent comprises at least one hydrolyzable group and an amine group, the coated metal oxide particles have an E.sub.308/E.sub.524 ratio of greater than 20, and the coated metal oxide particles have a BET specific surface area in a range from 75 to 100 m.sup.2g.sup.1.

2. The coated metal oxide particles of claim 1, wherein the fatty acid has 10 to 24 carbon atoms.

3. The coated metal oxide particles of claim 1, wherein the coating layer comprises 0.5% to 35% by weight of the silica, and/or 0.5 to 20% by weight of silane coupling agent, and/or 0.5% to 20% by weight of fatty acid and/or salt thereof, all based on the weight of the metal oxide core particles.

4. The coated metal oxide particles of claim 1, comprising 82% to 84% by weight of the metal oxide, 6.5% to 7.5% by weight of the silica, 4% to 5.5% by weight of silane coupling agent, and 4.5% to 6% by weight of fatty acid and/or salt thereof, all based on the total dry weight of the particles.

5. The coated metal oxide particles of claim 1, having a median volume particle diameter in dispersion of 40 to 55 nm.

6. The coated metal oxide particles of claim 1, having a BET specific surface area in a range from 85 to 90 m.sup.2g.sup.1.

7. The coated metal oxide particles of claim 1, having a maximum extinction coefficient (E.sub.max) in the range from 50 to 68 l/g/cm.

8. A dispersion comprising the coated metal oxide particles of claim 1 in a liquid dispersing medium, wherein the liquid dispersing medium is a cosmetically acceptable material.

9. The dispersion of claim 8, which comprises at least 30% by weight of the coated metal oxide particles.

10. The dispersion of claim 8, which comprises a dispersing agent.

11. A method of making the coated metal oxide particles of claim 1, comprising: (i) forming metal oxide core particles, and (ii) applying a coating layer to the metal oxide core particles comprising silica, the silane coupling agent, and the fatty acid and/or salt thereof.

12. The method of claim 11, wherein the coating layer is applied sequentially in the order of (1) silica, (2) silane coupling agent, and (3) fatty acid and/or salt thereof.

13. A sunscreen composition comprising the coated metal oxide particles of claim 1.

14. A method of improving skin feel in a sunscreen composition comprising applying to the skin a composition comprising coated metal oxide particles of claim 1.

15. The method of claim 14, wherein the improved skin feel includes a higher degree of lubricity to the skin.

16. A composition comprising: (i) coated metal oxide particles comprising metal oxide core particles each having thereon a coating layer comprising silica, a fatty acid and/or a salt thereof and a silane coupling agent, wherein the metal oxide comprises at least one member selected from the group consisting of titanium dioxide, zinc oxide and iron oxide, the silane coupling agent comprises at least one hydrolyzable group and an amine group, and the coated metal oxide particles have a BET specific surface area in a range from 75 to 100 m.sup.2g.sup.1; and (ii) a liquid medium selected from the group consisting of a C12-C15 alkyl benzoate, a fatty acid glyceride and isohexadecane.

Description

EXAMPLES

Example 1

(1) 1 mole of titanium oxydichloride in acidic solution was reacted with 3 moles of NaOH in aqueous solution. After the initial reaction period, the temperature was increased to above 70 C., and stirring continued. The reaction mixture was neutralised by the addition of aqueous NaOH, and allowed to cool below 70 C. Upon cooling to room temperature, the pH of the mixture was readjusted to pH>9, and the temperature was increased to 50 C. A sodium silicate solution was added, equivalent to 10% by weight SiO.sub.2 on TiO.sub.2 weight, whilst keeping the pH above 9. The temperature was maintained at 50 C. during the addition. After re-neutralising to pH 6.5 and stirring for 30 minutes, the mixture was heated to 60 C. and the pH adjusted to pH 9.5. 3-aminopropyl triethoxysilane was added, equivalent to 7.5% on TiO.sub.2 weight. The mixture was stirred for 30 minutes, after which the temperature was increased to 75 C. Sodium stearate (equivalent to 7.5% by weight of sodium stearate on TiO.sub.2) dissolved in hot water was added.

(2) The slurry was equilibrated for 45 minutes and neutralised by adding 20% hydrochloric acid dropwise over 15 minutes, before the slurry was allowed to cool to less than 50 C. The slurry was filtered using a Buchner filter until the cake conductivity at 100 gdm.sup.3 in water was <150 S. The filter cake was oven-dried for 16 hours at 110 C. and ground into a fine powder by an IKA Werke dry powder mill operating at 3,250 rpm.

(3) A dispersion was produced by mixing 7 g of polyglyceryl-3 polyricinoleate with 53 g of C12-C15 alkylbenzoate, and then adding 40 g of titanium dioxide powder produced above into the mixture. The mixture was passed through a horizontal bead mill, operating at 1500 r.p.m. and containing zirconia beads as grinding media for 15 minutes.

(4) The titanium dioxide particles or dispersion thereof were subjected to the test procedures described herein, and exhibited the following properties;

(5) (a) Dispersion particle size;

(6) i) D (v,0.5)=48 nm,

(7) ii) 10% by volume of particles have a volume diameter less than 28 nm,

(8) iii) 16% by volume of particles have a volume diameter less than 31 nm,

(9) iv) 30% by volume of particles have a volume diameter less than 38 nm,

(10) v) 70% by volume of particles have a volume diameter less than 62 nm,

(11) vi) 84% by volume of particles have a volume diameter less than 83 nm, and

(12) vii) 90% by volume of particles have a volume diameter less than 305 nm.

(13) (b) Extinction coefficients;

(14) TABLE-US-00001 E.sub.524 E.sub.308 E.sub.360 E(max) (max) E.sub.308/E.sub.524 1.2 45.0 8.7 59.6 276 38.5
(c) BET specific surface area=86.4 m.sup.2g.sup.1.
(d) Photogreying index=3.38.

Example 2

(15) The titanium dioxide dispersion produced in Example 1 was used to prepare a sunscreen emulsion formulation having the following composition;

(16) TABLE-US-00002 Trade Name INCI Name % w/w Phase A Cithrol DPHS PEG-30 2.0 (ex Croda) Dipolyhydroxystearate Crodamol IPM Isopropyl Myristate 15.0 (ex Croda) Candelilla Wax Euphorbia Cerifera 1.0 (Candelilla) Wax TiO.sub.2 dispersion 19.0 produced in Example 1 Phase B Water Aqua 57.3 Pricerine 9091 Glycerin 4.0 (ex Croda) Magnesium Sulphate Magnesium Sulphate 0.7 Heptahydrate Heptahydrate Phase C Euxyl K350 Phenoxyethanol, 1.0 Methylparaben, Ethylparaben, Ethylhexylglycerin, Propylene Glycol
Procedure
1. Combine Phase B ingredients with stirring and heat to 75-80 C.
2. Separately, combine Phase A ingredients, except TiO.sub.2 dispersion, and heat to 75-80 C.
3. Add TiO.sub.2 dispersion to Phase A ingredients with stirring, and briefly re-heat to 75-80 C.
4. Add Phase B to Phase A ingredients slowly with intensive stirring.
5. Homogenise for one minute.
6. Once below 40 C. add Phase C and mix until homogeneous.
7. Stir/cool to room temperature.

(17) The emulsion had an SPF value of 14 and exhibited good skin feel. The immediate afterfeel was assessed as 19.3% oily and 50.2% waxy. The 20 minute afterfeel was assessed as 3.9% oily and 73.2% waxy

Example 3

(18) The titanium dioxide dispersion produced in Example 1 was used to prepare a sunscreen emulsion formulation having the following composition;

(19) TABLE-US-00003 Trade Name INCI Name % w/w Phase A Cithrol DPHS PEG-30 2.5 (ex Croda) Dipolyhydroxystearate Arlamol HD Isohexadecane 3.0 (ex Croda) Arlamol PS15E PPG-15 Stearyl Ether 1.0 (ex Croda) DC 200 Fluid 350 Dimethicone 2.0 cst Solaveil CZ-100 Zinc oxide 37.0 (ex Croda) TiO.sub.2 dispersion 3.0 produced in Example 1 Phase B Water Aqua 44.7 Pricerine 9091 Glycerin 5.0 (ex Croda) Magnesium Sulphate Magnesium Sulphate 0.8 Heptahydrate Heptahydrate Phase C Euxyl PE9010 Phenoxyethanol 1.0
Procedure
1. Combine Phase B ingredients with stirring and heat to 75-80 C.
2. Separately, combine Phase A ingredients, except TiO.sub.2 dispersion, and Solaveil CZ-100 and heat to 75-80 C.
3. Add TiO.sub.2 dispersion to Phase A ingredients, and briefly re-heat to 75-80 C.
4. Add Phase B to Phase A ingredients slowly with intensive stirring.
5. Homogenise for one minute.
6. Once below 40 C. add Phase C and mix until homogeneous.
7. Stir/cool to room temperature.

(20) The emulsion had an SPF value of 28.

Example 4

(21) The titanium dioxide dispersion produced in Example 1 was used to prepare a sunscreen emulsion formulation having the following composition;

(22) TABLE-US-00004 Trade Name INCI Name % w/w Phase A Crodamol Caprylic/Capric 3.0 GTCC (ex Croda) triglyceride Crodamol ISIS Isostearyl 3.0 (ex Croda) Isostearate Pripure 3759 Squalane 3.0 (ex Croda) Crodacol S95 Stearyl Alcohol 2.0 (ex Croda) Tinosorb S Bis-Ethylhexyloxyphenol 3.5 Methoxyphenyl Triazine Uvinul A Dethylamine 2.0 Hydroxybenzoyl Hexyl Benzoate TiO.sub.2 dispersion 16.0 produced in Example 1 Phase B Water Aqua 55.5 Pricerine 9091 Glycerin 3.0 (ex Croda) Veegum Ultra Magnesium Aluminum 0.8 Silicate Arlacel LC Sorbitan Stearate (and) 3.5 Sorbityl Laurate Keltrol SFT Xanthan Gum 0.2 Tinosorb M Methylene Bis- 3.5 Benzotriazolyl Tetramethylbutylphenol Phase C Euxyl K350 Phenoxyethanol, 1.0 Methylparaben, Ethylparaben, Ethylhexylglycerin, Propylene Glycol
Procedure
1. Premix the Keltrol SFT, Veegum Ultra and Pricerine 9091, add water with stirring.
2. Add the remaining Phase B ingredients with stirring and heat to 75-80 C.
3. Separately, combine Phase A ingredients, except TiO.sub.2 dispersion, and heat to 75-80 C.
4. Homogenise Phase B ingredients for 30 seconds and allow to swell for 20 minutes at 75-80 C.
5. Add TiO.sub.2 dispersion to Phase A ingredients with stirring, and briefly re-heat to 75-80 C.
4. Add Phase A to Phase B ingredients with stirring.
5. Homogenise for one minute.
6. Once below 40 C. add Phase C and mix until homogeneous.
7. Stir/cool to room temperature.

(23) The emulsion had an SPF value of 41.

(24) The above examples illustrate the improved properties of a particulate metal oxide, dispersion and sunscreen product according to the present invention.