Particulate titanium dioxide

Abstract

A particulate titanium dioxide has a median volume particle diameter of greater than 70 nm. The titanium dioxide can be produced by calcining precursor particles. The titanium dioxide has enhanced UVA efficacy. The particulate titanium dioxide can be used to form dispersions. The particulate titanium dioxide or dispersions can be used to produce sunscreen products having a UV protection which is at least one third of the label SPF value.

Claims

1. A particulate titanium dioxide having: i) an E524 of less than 9 l/g/cm, an E360 of 25 to 50 l/g/cm, and an E360/E308 ratio of 0.5 to 1.0; ii) a median volume particle diameter of 85 to 175 nm, as measured by a particle sizer in centrifugation mode using X-ray detection; iii) a BET specific surface area in a range from 22 to 40 m.sup.2g.sup.1; and iv) a mean aspect ratio of 1.2 to 2.0:1.

2. The titanium dioxide according to claim 1 wherein the median volume particle diameter is 100 to 160 nm.

3. The titanium dioxide according to claim 1 having a mean length of 30 to 75 nm and a mean aspect ratio of 1.3 to 1.8:1.

4. A dispersion comprising a dispersing medium and particulate titanium dioxide as defined in claim 1.

5. The dispersion according to claim 4 comprising at least 30% by weight of the titanium dioxide particles.

6. The dispersion according to claim 4, wherein the dispersing medium is an organic liquid.

7. A sunscreen product comprising the titanium dioxide particles as defined in claim 1.

8. The sunscreen product of claim 7, wherein the sunscreen product has an SPF/UVA PF ratio in a range from 1 to 5.

9. The sunscreen product of claim 7, wherein the defined titanium dioxide particles are essentially the only ultraviolet light attenuator present.

10. A sunscreen product comprising the dispersion of claim 4.

11. The sunscreen product of claim 10, wherein the sunscreen product has an SPF/UVA PF ratio in a range from 1 to 5.

12. The sunscreen product of claim 10, wherein the defined titanium dioxide particles are essentially the only ultraviolet light attenuator present.

13. A particulate titanium dioxide having: i) an E524 of less than 9 l/g/cm, an E360 of 25 to 50 l/g/cm, and an E360/E308 ratio of 0.5 to 1.0; ii) a median volume particle diameter of 115 to 150 nm, as measured by a particle sizer in centrifugation mode using X-ray detection; iii) a BET specific surface area in a range from 22 to 40 m.sup.2g.sup.1; and iv) a mean aspect ratio of 1.2 to 2.0:1.

14. A particulate titanium dioxide having: i) an E524 of less than 9 l/g/cm, an E360 of 25 to 50 l/g/cm, and an E360/E308 ratio of 0.5 to 1.0; ii) a median volume particle diameter of 125 to 140 nm, as measured by a particle sizer in centrifugation mode using X-ray detection; iii) a BET specific surface area in a range from 22 to 40 m.sup.2g.sup.1; and iv) a mean aspect ratio of 1.2 to 2.0:1.

15. The titanium dioxide according to claim 2 having a mean length of 30 to 75 nm and a mean aspect ratio of 1.3 to 1.8:1.

16. The titanium dioxide according to claim 13 having a mean length of 30 to 75 nm and a mean aspect ratio of 1.3 to 1.8:1.

17. The titanium dioxide according to claim 14 having a mean length of 30 to 75 nm and mean aspect ratio of 1.3 to 1.8:1.

18. The titanium dioxide according to claim 1 having a mean aspect ratio of 1.4 to 1.6:1.

19. The titanium dioxide according to claim 2 having a mean aspect ratio of 1.4 to 1.6:1.

20. The titanium dioxide according to claim 13 having a mean aspect ratio of 1.4 to 1.6:1.

21. The titanium dioxide according to claim 14 having a mean aspect ratio of 1.4 to 1.6:1.

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. After filtering, approximately 400 g of the resulting filter cake which contained 60% by weight of water was calcined using a Carbolite ESF chamber furnace at 650 C. for 2 hours and ground into a fine powder using an IKA Werke dry powder mill operating at 3,250 rpm. The powder was re-slurried in demineralised water. To the resulting slurry, an alkaline solution of sodium aluminate was added, equivalent to 3.5% by weight Al.sub.2O.sub.3 on TiO.sub.2 weight, whilst keeping the pH below 11. The temperature was maintained below 60 C. during the addition. The temperature of the slurry was then increased to 75 C., and 4.6% by weight of sodium stearate on TiO.sub.2 dissolved in hot water was added. 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.

(2) A dispersion was produced by mixing 5 g of polyhydroxystearic acid with 45 g of C12-C15 alkylbenzoate, and then adding 50 g of dried calcined 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.

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

(4) (a) Particle size;

(5) i) D (v,0.5)=133 nm,

(6) ii) 10% by volume of particles have volume diameter less than 113 nm,

(7) iii) 16% by volume of particles have volume diameter less than 117 nm,

(8) iv) 30% by volume of particles have volume diameter less than 124 nm,

(9) v) 70% by volume of particles have volume diameter less than 146 nm,

(10) vi) 84% by volume of particles have volume diameter less than 170 nm, and

(11) vii) 90% by volume of particles have volume diameter less than 194 nm.

(12) (b) Extinction coefficients;

(13) TABLE-US-00001 E.sub.360/ E.sub.524 E.sub.308 E.sub.360 E (max) (max) E.sub.308/E.sub.524 E.sub.524 E.sub.360/E.sub.308 6.0 48.9 37.2 51.5 326 8.2 6.2 0.76
(c) BET specific surface area=28.5 m.sup.2g.sup.1.
(d) Photogreying index=0.3.

Example 2

(14) A dispersion according to the procedure of Example 1 was produced, except that 4.5 g of polyhydroxystearic acid, 50.5 g of C12-C15 alkylbenzoate, and 45 g of dried calcined titanium dioxide powder were used.

(15) The titanium dioxide dispersion was subjected to the test procedures described herein, and exhibited the following properties;

(16) (a) Extinction coefficients;

(17) TABLE-US-00002 E.sub.308/ E.sub.524 E.sub.308 E.sub.360 E (max) (max) E.sub.524 E.sub.360/E.sub.524 E.sub.360/E.sub.308 6.6 47.6 38.4 50.6 326 7.2 5.8 0.81

Example 3

(18) Titanium dioxide particles were produced according to the procedure of Example 1, except that no alumina/stearate coating was applied.

(19) A dispersion was produced according to the procedure of Example 1, except that 1.68 g of polyhydroxystearic acid, 1.68 g of isostearic acid, 51.64 g of C12-C15 alkylbenzoate, and 45 g of dried calcined titanium dioxide powder produced above were used.

(20) The titanium dioxide dispersion was subjected to the test procedures described herein, and exhibited the following properties;

(21) (a) Extinction coefficients;

(22) TABLE-US-00003 E.sub.308/ E.sub.524 E.sub.308 E.sub.360 E (max) (max) E.sub.524 E.sub.360/E.sub.524 E.sub.360/E.sub.308 6.3 47.1 38.2 50.6 328 7.4 6.1 0.82

Example 4

(23) A dispersion was produced by mixing 110 g of polyhydroxystearic acid and 790 g of C12-C15 alkylbenzoate, and then adding 1100 g of dried calcined titanium dioxide powder produced in Example 1 to the mixture, using a Greaves ST-C-DC mixer. The mixture was then milled using a Netzsch Labstar horizontal bead mill, with a power input of 0.55 kWh/kg, operating at 2600 rpm and containing zirconia beads as grinding media.

(24) The titanium dioxide dispersion was subjected to the test procedures described herein, and exhibited the following properties;

(25) (a) Extinction coefficients;

(26) TABLE-US-00004 E.sub.308/ E.sub.524 E.sub.308 E.sub.360 E (max) (max) E.sub.524 E.sub.360/E.sub.524 E.sub.360/E.sub.308 5.2 47.6 34.4 49.1 321 9.1 6.6 0.72

Example 5

(27) An aqueous dispersion was produced by mixing 7 g of oleth-10 (Brij O10, ex Croda), 5 g of isodeceth-6 (Synperonic 10/6, ex Croda), 0.9 g of phenoxyethanol, 0.5 g simethicone (Silfar S184), 36.6 g of demineralised water, and then adding 50 g of dried calcined titanium dioxide powder produced in Example 1. The mixture was passed through a horizontal bead mill, operating at 1500 r.p.m. and containing zirconia beads as grinding media for 65 minutes.

Example 6

(28) The titanium dioxide dispersion produced in Example 2 was used to prepare sunscreen emulsion formulations F1 and F2 having the following composition;

(29) TABLE-US-00005 F1 F2 Trade Name INCI Name % w/w % w/w Phase A. Arlacel 165 FI (ex Glyceryl Stearate (and) 6 6 Croda) PEG-100 Stearate Span 60 (ex Croda) Sorbitan Stearate 0.5 0.5 Tween 60 (ex Croda) Polysorbate 60 2.7 2.7 Stearyl Alcohol Stearyl Alcohol 1 1 Light Mineral Oil Mineral Oil 8 4 Crodamol OP (ex Ethylhexyl Palmitate 2.5 2.5 Croda) DC 200 350 cps Dimethicone 2 2 Unimer U-15 (ex VP/Eicosene Copolymer 1 1 Induchem) TiO.sub.2 dispersion 22 33 Phase B. Water Aqua 49.2 42.2 Keltrol RD Xanthan Gum 0.1 0.1 Propylene Glycol Propylene Glycol 4 4 Phase C. Germaben II Propylene Glycol, 1 1 Diazolidinyl Urea, Methylparaben, Propylparaben

(30) Procedure 1. Keltrol RD was dispersed into water, and the remaining water Phase A ingredients added to the mixture, which was heated to 65-80 C. 2. The oil Phase B ingredients were combined and heated to 75-80 C. 3. The oil phase was added to the water phase with stirring. 4. The mixture was homogenised for 2 minutes. 5. The resulting emulsion was cooled to room temperature with stirring, with the Phase C preservative being added below 40 C.

(31) The formulations were subjected to the test procedures described herein, and exhibited the following properties;

(32) TABLE-US-00006 F1 F2 i) SPF 23.8 40.6 ii) Label SPF* 20 30 iii) UVA PF.sub.0 8.3 10.3 iv) UVA PF 8.0 (9.9 Jcm.sup.2).sup.+ 10.0 (12.4 Jcm.sup.2).sup.+ v) SPF/UVA PF.sub.0 2.9 4.0 vi) SPF/UVA PF 3.0 4.1 vii) Label SPF/UVA PF 2.5 3.0 viii) L 14.2 22.6 *According to EU recommendations for labelling of sunscreens, 22 Sep. 2006 .sup.+UV dose applied.

Example 7

(33) Titanium dioxide particles were produced according to the procedure of Example 1, except that approximately 400 kg of filter cake which contained 60% by weight of water was calcined for 8 hours at 650 C. in a static kiln. After alumina/stearate coating as described in Example 1, the resultant slurry was filtered using a filter press until the wash-water conductivity was <150 S. The filter cake was spray dried and ground into a fine powder.

(34) A dispersion was produced by mixing 12.5 kg of polyhydroxystearic acid with 89.7 kg of C12-C15 alkylbenzoate, and then adding 124.9 kg of dried calcined titanium dioxide powder produced above into the mixture. The mixture was passed through a horizontal bead mill containing zirconia beads as grinding media.

(35) The titanium dioxide dispersion was subjected to the test procedures described herein, and exhibited the following properties;

(36) (a) Particle size;

(37) i) D (v,0.5)=143 nm,

(38) ii) 10% by volume of particles have volume diameter less than 80 nm,

(39) iii) 16% by volume of particles have volume diameter less than 102 nm,

(40) iv) 30% by volume of particles have volume diameter less than 122 nm,

(41) v) 70% by volume of particles have volume diameter less than 168 nm,

(42) vi) 84% by volume of particles have volume diameter less than 197 nm, and

(43) vii) 90% by volume of particles have volume diameter less than 220 nm.

(44) (b) Extinction coefficients;

(45) TABLE-US-00007 E.sub.308/ E.sub.524 E.sub.308 E.sub.360 E (max) (max) E.sub.524 E.sub.360/E.sub.524 E.sub.360/E.sub.308 8.6 43.0 35.9 43.5 323 5.0 4.2 0.83

Example 8

(46) A dispersion according to the procedure of Example 7 was produced, except that 14.0 kg of polyhydroxystearic acid, 100.7 kg of C12-C15 caprylic/capric triglyceride, and 140.3 kg of dried calcined titanium dioxide powder were used.

(47) The titanium dioxide dispersion was subjected to the test procedures described herein, and exhibited the following properties;

(48) (a) Extinction coefficients;

(49) TABLE-US-00008 E.sub.308/ E.sub.524 E.sub.308 E.sub.360 E (max) (max) E.sub.524 E.sub.360/E.sub.524 E.sub.360/E.sub.308 8.8 44.6 38.6 46.6 330 5.1 4.3 0.87

Example 9

(50) (a) The titanium dioxide dispersion produced in Example 7 was used to prepare a sunscreen emulsion formulation having the following composition;

(51) TABLE-US-00009 Trade Name INCI Name % w/w Phase A. Cithrol (ex Croda) PEG-30 2.5 DPHS Dipolyhydroxystearate Crodamol AB (ex Croda) C12-15 Alkyl benzoate 13 Arlamol HD (ex Croda) Isohexadecane 3 Arlamol PS15E (ex Croda) PPG-15 Stearyl Ether 1 Xiameter PMX-245 Cyclopentasiloxane 2 TiO.sub.2 dispersion 12 Phase B. Water Aqua 60.2 Magnesium Sulphate Magnesium Sulphate 0.8 Heptahydrate Heptahydrate Pricerine 9091 (ex Croda) Glycerin 4.5 Phase C. Germaben II Propylene Glycol, 1 Diazolidinyl Urea, Methylparaben, Propylparaben
Procedure
1. The oil Phase A ingredients, except for the TiO.sub.2 dispersion, were combined and heated to 85 C.
2. The water Phase B ingredients were combined and heated to 85 C.
3. The TiO.sub.2 dispersion was added to the oil phase with stirring whilst maintaining the temperature.
4. The water phase was added to the oil phase slowly, with intensive stirring.
5. The mixture was homogenised for one minute.
6. The resulting emulsion was cooled to room temperature with stirring, with the Phase C preservative being added below 40 C.
(b) The titanium dioxide dispersion produced in Example 8 was used to prepare a sunscreen emulsion formulation having the following composition;

(52) TABLE-US-00010 Trade Name INCI Name % w/w Phase A. Arlacel 1690 (ex Croda) Sorbitan Isostearate (and) 3.5 Polyglyceryl-3 Polyricinoleate) Prisorine 3515 (ex Croda) Isostearyl Alcohol 2 Organic Jojoba Oil Simmondsia Chinensis Oil 5 Organic Coconut Oil Cocos Nucifera Oil 5 Pripure 3759 (ex Croda) Squalane 2 Candelilla Wax Euphorbia Cerifera 0.5 (Candelilla) Wax Dermosoft PEA eco Phenethyl Alcohol 0.8 TiO.sub.2 dispersion 24 Phase B. Water Aqua 52.1 Sodium Chloride Sodium Chloride 4 Keltrol RD Xanthan Gum 0.7 Pricerine 9091 (ex Croda) Glycerin 0.1 Phase C. Dermofeel Toco 70 Non-GMO Tocopherol 0.3
Procedure
1. The oil Phase A ingredients, except for the TiO.sub.2 dispersion, were combined and heated to 85 C.
2. The water Phase B ingredients were combined and heated to 85 C.
3. The TiO.sub.2 dispersion was added to the oil phase with stirring whilst maintaining the temperature.
4. The water phase was added to the oil phase with fast stirring.
5. The mixture was homogenised for one minute.
6. The resulting emulsion was cooled to room temperature with stirring, with the Phase C preservative being added below 40 C.

(53) The formulations were subjected to the test procedures described herein, and exhibited the following properties;

(54) TABLE-US-00011 (a) (b) i) SPF 19 38 ii) Label SPF* 15 30 iii) UVA PF.sub.0 6 13 iv) UVA PF 6 (10.4 Jcm.sup.2).sup.+ 13 (16.5 Jcm.sup.2).sup.+ v) SPF/UVA PF.sub.0 3.2 2.9 vi) SPF/UVA PF 3.2 2.9 vii) Label SPF/UVA PF 2.5 2.3 *According to EU recommendations for labelling of sunscreens, 22 Sep. 2006 .sup.+UV dose applied.

(55) The above examples illustrate the improved properties of a particulate titanium dioxide, dispersion, and/or sunscreen product according to the present invention.