TITANIUM DIOXIDE PARTICLES

Abstract

Titanium dioxide particles have high UVB absorption properties, an effective UVA efficacy and transparency. The titanium dioxide can be produced by calcining precursor titanium dioxide particles. The titanium dioxide particles can be used to form dispersions. The titanium dioxide particles and dispersions thereof can be used to produce sunscreen products which are suitable for use in a wide range of personal care applications.

Claims

1. Titanium dioxide particles comprising a volume based median particle diameter D(v,0.5) of greater than 175 nm and an (E.sub.308E.sub.360)/E.sub.524 value of greater than 300 l/g/cm.

2. The titanium dioxide according to claim 1 comprising: (i) a number based median particle diameter D(n,0.5) of greater than 100 nm, and/or (ii) a Z-average particle size of greater than 80 nm, and/or (iii) an intensity mean particle size of greater than 90 nm.

3. The titanium dioxide according to claim 1 comprising a mean aspect ratio of 1.05 to 1.55:1.

4. Titanium dioxide particles comprising: (i) a mean crystal size of 30.0 to 51.0 nm, and/or (ii) a mean aspect ratio of 1.05 to 1.55:1.

5. The titanium dioxide according to claim 4 comprising a mean width of 22.0 to

46. 0 nm.

6. The titanium dioxide according to claim 1 comprising: (i) a mean crystal size of 30.0 to 51.0 nm, and/or (ii) a mean width of 22.0 to 46.0 nm.

7. The titanium dioxide according to claim 1 comprising an (E.sub.308E.sub.360)/E.sub.524 value of greater than or equal to 320 l/g/cm.

8. The titanium dioxide according to claim 1 comprising a mean crystal size of 37.0 to 47.0 nm.

9. The titanium dioxide according to claim 1 comprising a BET specific surface area of 15 to 43 m.sup.2g.sup.1.

10. The titanium dioxide according to claim 1 comprising: (i) a mercury porosimetry total pore area at 59,950.54 psia of 22 to 55 m.sup.2g.sup.1, and/or (ii) a mercury porosimetry average pore diameter of 65 to 150 nm.

11. The titanium dioxide according to claim 1 comprising an E.sub.308E.sub.360 value of greater than 1800 (l/g/cm).sup.2 and less than 3500 (l/g/cm).sup.2.

12. Titanium dioxide particlescomprising: (i) an (E.sub.308E.sub.360)/E.sub.524 value of greater than or equal to 320 l/g/cm, and optionally (ii) an E.sub.524 of less than or equal to 7.5 l/g/cm, and/or an E.sub.308E.sub.360 value of greater than 2100 (l/g/cm).sup.2.

13. The titanium dioxide according to claim 1 comprising an (E.sub.308E.sub.360)/E.sub.524 value of 320 to less than 650 l/g/cm.

14. The titanium dioxide according to claim 1 comprising at least one selected from the group consisting of: (i) an E.sub.524 of 5.2 to 7.5 l/g/cm, (ii) an E.sub.360 of 32 to 50 l/g/cm, (iii) an E.sub.308 of greater than 45 l/g/cm, and (iv) an E.sub.308E.sub.360 value of greater than 1800 to 3300 (l/g/cm).sup.2.

15. The titanium dioxide according to claim 14 comprising at least two selected from the group consisting of (i), (ii), (iii) and (iv).

16. The titanium dioxide according to claim 15 comprising all of (i), (ii), (iii) and (iv).

17. A dispersion comprising a dispersing medium and titanium dioxide particles as defined in claim 1.

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

19. A method of producing titanium dioxide particles which comprises: (i) forming precursor titanium dioxide particles having a mean aspect ratio of 3.0 to 7.0:1, (ii) calcining the precursor particles to produce calcined titanium dioxide particles having a mean crystal size of 30.0 to 51.0 nm and/or a mean aspect ratio of 1.05 to 1.55:1, and optionally (iii) applying an inorganic and/or organic coating to the calcined titanium dioxide particles.

20. The method according to claim 19 wherein (i) the mean aspect ratio of the calcined particles is 1.15 to 1.45:1, and/or (ii) the mean crystal size of the calcined particles is 37.0 to 47.0 nm.

21. The method according to claim 19, wherein the calcined titanium dioxide particles comprise: (i) an E.sub.524 of less than or equal to 7.5 l/g/cm, and/or (ii) an E.sub.308E.sub.360 value of greater than 1800 (l/g/cm).sup.2.

22. The method according to claim 19, wherein the calcined titanium dioxide particles comprise at least one selected from the group consisting of: (i) an E.sub.524 of 4.7 to 7.5 l/g/cm, (ii) an E.sub.360 of 32 to 50 l/g/cm, (iii) an E.sub.308 of greater than 45 l/g/cm, and (iv) an E.sub.308E.sub.360 value of greater than 1800 to 3300 (l/g/cm).sup.2.

23. The method according to claim 19, wherein on calcining: (i) the mean width of the titanium dioxide particles is increased by 60 to 200%, and/or (ii) the BET specific surface area is reduced by 35 to 95%, and/or (iii) the mean crystal size is increased by 200 to 400%.

24.-28. (canceled)

Description

EXAMPLES

Example 1

[0144] 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, the resulting filter cake of precursor titanium dioxide particles was further dried using a rotary dryer operating at 6 r.p.m, to 20% by weight of water. Using a screw conveyor, this material was fed into a rotating calciner operating at 710 C. with a residence time of 20 minutes. The processed titanium dioxide was ground into a fine powder using an IKA Werke dry powder mill operating at 3,250 r.p.m. 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 24 hours at 110 C. and ground into a fine powder by an IKA Werke dry powder mill operating at 3,250 r.p.m.

[0145] A dispersion was produced by mixing 5.5 g of polyhydroxystearic acid with 39.5 g of C12-C15 alkylbenzoate, and then adding 55 g of dried calcined titanium dioxide powder produced above, into the mixture. The mixture was passed through a horizontal bead mill, operating at 4,500 r.p.m. and containing zirconia beads as grinding media, for 60 minutes.

[0146] The precursor titanium dioxide particles, calcined titanium dioxide particles, coated titanium dioxide particles and dispersion thereof, were subjected to the test procedures herein described, and exhibited the following properties;

[0147] 1) Precursor Titanium Dioxide Particles:

[0148] BET specific surface area=101 m.sup.2g.sup.1

[0149] Mercury porosimetry average pore diameter=77.6 nm

[0150] Mercury porosimetry total pore area at 59,950.54 psia=72.6 m.sup.2g.sup.1

[0151] Mean crystal size=10 nm

[0152] Mean length=75 nm

[0153] Mean width=15 nm

[0154] Mean aspect ratio=5.0:1

[0155] 2) Calcined Titanium Dioxide Particles:

[0156] BET specific surface area=31.9 m.sup.2g.sup.1

[0157] Mercury porosimetry average pore diameter=119 nm

[0158] Mercury porosimetry total pore area at 59,950.54 psia=36.7 m.sup.2g.sup.1

[0159] Mean crystal size=42.4 nm

[0160] Mean length=44 nm

[0161] Mean width=34 nm

[0162] Mean aspect ratio=1.3:1

[0163] 3) Change in Titanium Dioxide Particle Properties on Calcining:

[0164] Reduction in BET specific surface area=68.4%

[0165] Increase in mercury porosimetry average pore diameter=53.4%

[0166] Reduction in mercury porosimetry total pore area at 59,950.54 psia=49.4%

[0167] Increase in mean crystal size=324%

[0168] Increase in mean width=126.7%

[0169] 4) Coated Titanium Dioxide Particles:

[0170] BET specific surface area=28.6 m.sup.2g.sup.1.

[0171] Mercury porosimetry average pore diameter=107.9 nm

[0172] Mercury porosimetry total pore area at 59,950.54 psia=37.9 m.sup.2g.sup.1

[0173] 5) Titanium Dioxide Dispersion:

[0174] (a) Particle size by sedimentation;

[0175] i) D (v,0.5)=271 nm,

[0176] ii) D (n,0.5)=200 nm,

[0177] (b) Particle size by light scattering

[0178] i) Z-average =148 nm

[0179] ii) Intensity mean =158 nm

[0180] (c) Extinction coefficients;

TABLE-US-00001 E.sub.524 E.sub.308 E.sub.360 E (max) (max) E.sub.308/E.sub.524 E.sub.360/E.sub.524 6.5 65.8 43.1 67.4 317 10.1 6.6 E.sub.360/E.sub.308 E.sub.524 + E.sub.360 E.sub.524 E.sub.360 E.sub.308 E.sub.360 (E.sub.308 E.sub.360)/E.sub.524 0.66 49.6 280.2 2836 436.3

Example 2

[0181] An aqueous dispersion was produced by mixing 6.2 g polyglyceryl-2 caprate, 2.6 g sucrose stearate, 2 g jojoba oil, 0.6 g squalane, 1 g caprylyl caprylate, 37.4 g of demineralised water, and then adding 50 g of titanium dioxide powder produced in Example 1. The mixture was passed through a horizontal bead mill, operating at 4,500 r.p.m. and containing zirconia beads as grinding media, for 60 minutes. The titanium dioxide dispersion was subjected to the test procedures herein described, and exhibited the following properties;

[0182] Extinction Coefficients;

TABLE-US-00002 E.sub.524 E.sub.308 E.sub.360 E (max) (max) E.sub.308/E.sub.524 E.sub.360/E.sub.524 7.3 65.7 45.4 68.0 319 9.0 6.2 E.sub.360/E.sub.308 E.sub.524 + E.sub.360 E.sub.524 E.sub.360 E.sub.308 E.sub.360 (E.sub.308 E.sub.360)/E.sub.524 0.69 52.7 331.4 2983 408.6

Example 3

[0183] The titanium dioxide dispersion produced in Examples 1 was used to prepare a sunscreen emulsion formulation having the following composition;

TABLE-US-00003 Trade Name INCI % w/w Phase A Arlacel 165 (ex Glyceryl stearate (and) 6.0 Croda) PEG-100 stearate Span 60 (ex Croda) Sorbitan stearate 0.5 Tween 60 (ex Polysorbate 60 2.7 Croda) Stearyl alcohol Stearyl alcohol 1.0 Light mineral oil Mineral oil 7.8 Crodamol OP (ex Ethylhexyl palmitate 2.5 Croda) DC 200 350 cps Dimethicone 2.0 Unimer U-15 (ex VP/Eicosene copolymer 1.0 Induchem) TiO.sub.2 dispersion (55% 18.2 solids) produced in Example 1) Phase B Water Aqua 53.2 Keltrol RD Xanthan gum 0.1 Propylene gylcol Propylene glycol 4.0 Phase C Euxyl K 350 Phenoxyethanol (and) 1.0 methylparaben (and) ethylparaben (and) ethylhexylglycerin (and) propylene glycol

[0184] Procedure [0185] 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. [0186] 2. The oil Phase B ingredients were combined and heated to 75-80 C. [0187] 3. The oil phase was added to the water phase with stirring. [0188] 4. The mixture was homogenised for 1 minute. [0189] 5. The resulting emulsion was cooled to room temperature with stirring, with the Phase C preservative being added below 40 C.

[0190] The sunscreen formulation was subjected to the test procedures herein described, and exhibited the following properties;

[0191] i) SPF=34

[0192] ii) UVA/UVB ratio=0.684

[0193] iii) UVAPF=13

[0194] iv) Critical Wavelength=379 nm

[0195] v) L=13.5

[0196] vi) L/SPF ratio=0.40

Example 4

[0197] 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, the resulting filter cake of precursor titanium dioxide particles was further dried using a fluid bed (at approximately 150 degrees for 2 hours), to 5% by weight of water. Using a screw conveyor, this material was fed into a rotating calciner operating at 710 C. The processed titanium dioxide was ground into a fine powder using an IKA Werke dry powder mill operating at 3,250 r.p.m. 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 24 hours at 110 C. and ground into a fine powder by an IKA Werke dry powder mill operating at 3,250 r.p.m.

[0198] 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 4,500 r.p.m. and containing zirconia beads as grinding media, for 60 minutes.

[0199] The titanium dioxide dispersion was subjected to the test procedures herein described, and exhibited the following properties;

[0200] (a) Particle size by sedimentation;

[0201] iii) D (v,0.5)=196 nm,

[0202] iv) D (n,0.5)=137 nm,

[0203] (b) Particle size by light scattering

[0204] i) Z-average=182 nm

[0205] ii) Intensity mean=203 nm

[0206] (c) Extinction coefficients;

TABLE-US-00004 E.sub.524 E.sub.308 E.sub.360 E (max) (max) E.sub.308/E.sub.524 E.sub.360/E.sub.524 6.0 57.1 36.8 59.7 317 9.5 6.1 E.sub.360/E.sub.308 E.sub.524 + E.sub.360 E.sub.524 E.sub.360 E.sub.308 E.sub.360 (E.sub.308 E.sub.360)/E.sub.524 0.64 42.8 220.8 2101 350.2

[0207] The above examples illustrate the improved properties of titanium dioxide particles, method of producing thereof, titanium dioxide dispersion, and/or sunscreen product, according to the present invention.