TITANIUM DIOXIDE PARTICLES

Abstract

Titanium dioxide particles have high UVB absorption properties, an effective UVA efficacy and improved 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 140 nm and an E.sub.524 of less than or equal to 5.0 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 50 nm, and/or (ii) a Z-average particle size of greater than 60 nm and less than 180 nm, and/or (iii) an intensity mean particle size of greater than 70 nm and less than 175 nm.

3. The titanium dioxide according to claim 1 comprising a mean aspect ratio of 1.4 to 2.9:1.

4. Titanium dioxide particles comprising: (i) a mean crystal size of 15.0 to 30.0 nm, and (ii) a mean aspect ratio of 1.4 to 2.9:1.

5. The titanium dioxide according to claim 4 comprising a mean width of 15.0 to 37.0 nm.

6. The titanium dioxide according to claim 1 comprising: (i) a mean crystal size of 15.0 to 30.0 nm, and/or (ii) a mean width of 17.0 to 33.0 nm.

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

8. The titanium dioxide according to claim 1 comprising a mean crystal size of 18.0 to 28.0 nm.

9. The titanium dioxide according to claim 1 comprising a BET specific surface area of 25 to 55 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 35 to 70 m.sup.2g.sup.1, and/or (ii) a mercury porosimetry average pore diameter of 55 to 130 nm.

11. The titanium dioxide according to claim 1 comprising an E.sub.308E.sub.360 value of greater than 1350 (l/g/cm).sup.2 and less than 2100 (l/g/cm).sup.2.

12. Titanium dioxide particles comprising: (i) an (E.sub.308E.sub.360)/E.sub.524 value of greater than or equal to 350 l/g/cm, (ii) an E.sub.524 of 2.0 to 5.5 l/g/cm, and (iii) optionally an E.sub.308E.sub.360 value of greater than 1350 (l/g/cm).sup.2 and less 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 greater than or equal to 350 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 2.5 to 5.0 l/g/cm, (ii) an E.sub.360 of greater than 15 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 1450 to 2000 (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 15.0 to 30.0 nm and/or a mean aspect ratio of 1.4 to 2.9:1, 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 1.6 to 2.6:1, and/or (ii) the mean crystal size of the calcined particles is 18.0 to 28.0 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 5.5 l/g/cm, and/or (ii) an E.sub.308E.sub.360 value of greater than 1350 (l/g/cm).sup.2 and less than 2100 (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 1.5 to 5.5 l/g/cm, (ii) an E.sub.360 of 20 to 45 l/g/cm, (iii) an E.sub.308 of 50 to 75 l/g/cm, and (iv) an E.sub.308E.sub.360 value of 1450 to 2000 (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 15 to 200%, and/or (ii) the BET specific surface area is reduced by 25 to 80%, and/or (iii) the mean crystal size is increased by 40 to 250%.

24.-28. (canceled)

Description

EXAMPLES

Example 1

[0139] 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 610 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 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 6.5% 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.

[0140] 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.

[0141] 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;

[0142] 1) Precursor titanium dioxide particles:

[0143] BET specific surface area=101 m.sup.2g.sup.1

[0144] Mercury porosimetry average pore diameter=77.6 nm

[0145] Mercury porosimetry total pore area at 59,950.54 psia=72.6 m.sup.2g.sup.1

[0146] Mean crystal size=10 nm

[0147] Mean length=75 nm

[0148] Mean width=15 nm

[0149] Mean aspect ratio=5.0:1

[0150] 2) Calcined titanium dioxide particles:

[0151] BET specific surface area=44.5 m.sup.2g.sup.1

[0152] Mercury porosimetry average pore diameter=106 nm

[0153] Mercury porosimetry total pore area at 59,950.54 psia=50.4 m.sup.2g.sup.1

[0154] Mean crystal size=23.8 nm

[0155] Mean length=51 nm

[0156] Mean width=24 nm

[0157] Mean aspect ratio=2.1:1

[0158] 3) Change in titanium dioxide particle properties on calcining:

[0159] Reduction in BET specific surface area=56%

[0160] Increase in mercury porosimetry average pore diameter=36.6%

[0161] Reduction in mercury porosimetry total pore area at 59,950.54 psia=31.1%

[0162] Increase in mean crystal size=138%

[0163] Increase in mean width=60%

[0164] 4) Coated titanium dioxide particles:

[0165] BET specific surface area=38.2 m.sup.2g.sup.1

[0166] Mercury porosimetry average pore diameter=79.7 nm

[0167] Mercury porosimetry total pore area at 59,950.54 psia=50.8 m.sup.2g.sup.1

[0168] 5) Titanium dioxide dispersion:

[0169] (a) Particle size by sedimentation;

[0170] i) D (v,0.5)=187 nm,

[0171] ii) 10% by volume of particles have volume diameter less than 156 nm,

[0172] iii) 16% by volume of particles have volume diameter less than 162 nm,

[0173] iv) 84% by volume of particles have volume diameter less than 239 nm, and

[0174] v) 90% by volume of particles have volume diameter less than 277 nm.

[0175] vi) D (n,0.5)=171 nm,

[0176] vii) 10% by number of particles have volume diameter less than 139 nm,

[0177] viii) 16% by number of particles have volume diameter less than 145 nm,

[0178] ix) 84% by number of particles have volume diameter less than 207 nm, and

[0179] x) 90% by number of particles have volume diameter less than 220 nm.

[0180] (b) Particle size by light scattering:

[0181] i) Z-average=123 nm

[0182] ii) Intensity mean=130 nm

[0183] (c) Extinction coefficients;

[00001]$\frac{E_{524}}{3.8}$$\frac{E_{308}}{59.4}$$\frac{E_{360}}{28.8}$$\frac{E\left(\max \right)}{62.2}$$\frac{\left(\mathrm{Max}\right)}{308}$$\frac{E_{308}/E_{524}}{15.5}$$\frac{E_{360}/E_{524}}{7.5}$$\frac{E_{360}/E_{308}}{0.48}$$\frac{E_{524}+E_{360}}{32.6}$$\frac{E_{524}{E}_{360}}{110.3}$$\frac{E_{308}{E}_{360}}{1710.7}$$\frac{\left(E_{308}{E}_{360}\right)/E_{524}}{450.2}$

Example 2

[0184] Titanium dioxide particles were produced according to the procedure of Example 1, except that no alumina/stearate coating was applied. A dispersion was produced according to the procedure of Example 1, except that 4 g of polyhydroxystearic acid, 56 g of C12-C15 alkylbenzoate, and 40 g of dried calcined titanium dioxide powder produced above were used.

[0185] The titanium dioxide dispersion was subjected to the test procedures herein described, and exhibited the following properties;

[0186] Extinction coefficients;

[00002]$\frac{E_{524}}{3.1}$$\frac{E_{308}}{58.8}$$\frac{E_{360}}{23.3}$$\frac{E\left(\max \right)}{58.9}$$\frac{\left(\mathrm{Max}\right)}{307}$$\frac{E_{308}/E_{524}}{19.0}$$\frac{E_{360}/E_{524}}{7.5}$$\frac{E_{360}/E_{308}}{0.40}$$\frac{E_{524}+E_{360}}{26.4}$$\frac{E_{524}{E}_{360}}{72.2}$$\frac{E_{308}{E}_{360}}{1370}$$\frac{\left(E_{308}{E}_{360}\right)/E_{524}}{438.2}$

Example 3

[0187] 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.

[0188] The titanium dioxide dispersion was subjected to the test procedures herein described, and exhibited the following properties;

[0189] Extinction coefficients;

[00003]$\frac{E_{524}}{3.3}$$\frac{E_{308}}{70.8}$$\frac{E_{360}}{25.5}$$\frac{E\left(\max \right)}{71.5}$$\frac{\left(\mathrm{Max}\right)}{318}$$\frac{E_{308}/E_{524}}{21.5}$$\frac{E_{360}/E_{524}}{7.7}$$\frac{E_{360}/E_{308}}{0.36}$$\frac{E_{524}+E_{360}}{28.8}$$\frac{E_{524}{E}_{360}}{84.2}$$\frac{E_{308}{E}_{360}}{1805.4}$$\frac{\left(E_{308}{E}_{360}\right)/E_{524}}{547.1}$

Example 4

[0190] Titanium dioxide particles were produced according to the procedure of Example 1, except that filter cake which contained between 25-45% by weight of water was calcined for 5 minutes at 650 C. in a rotary calciner. After the alumina/stearate coating described in Example 1 was applied, the resultant slurry was filtered using a filter press until the wash-water conductivity was <150 S. The filter cake was dried and ground into a fine powder. A titanium dioxide dispersion was produced according to the procedure of Example 1.

[0191] The titanium dioxide dispersion was subjected to the test procedures herein described, and exhibited the following properties;

[0192] Extinction coefficients;

[00004]$\frac{E_{524}}{3.2}$$\frac{E_{308}}{63.6}$$\frac{E_{360}}{25.0}$$\frac{E\left(\max \right)}{64.4}$$\frac{\left(\mathrm{Max}\right)}{280}$$\frac{E_{308}/E_{524}}{19.8}$$\frac{E_{360}/E_{524}}{7.8}$$\frac{E_{360}/E_{308}}{0.40}$$\frac{E_{524}+E_{360}}{28.2}$$\frac{E_{524}{E}_{360}}{80.0}$$\frac{E_{308}{E}_{360}}{1590}$$\frac{\left(E_{308}{E}_{360}\right)/E_{524}}{496.9}$

Example 5

[0193] The titanium dioxide dispersion produced in Example 1 was used to prepare a sunscreen emulsion formulation having the following composition;

TABLE-US-00001 Trade Name INCI % w/w Phase A Arlacel 165 (ex Glyceryl stearate (and) PEG-100 6.0 Croda) 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 1.0 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 (40% 25.0 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

[0194] Procedure [0195] 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. [0196] 2. The oil Phase B ingredients were combined and heated to 75-80 C. [0197] 3. The oil phase was added to the water phase with stirring. [0198] 4. The mixture was homogenised for 1 minute. [0199] 5. The resulting emulsion was cooled to room temperature with stirring, with the Phase C preservative being added below 40 C.

[0200] The sunscreen formulation was subjected to the test procedures herein described, and exhibited the following properties;

[0201] i) SPF=44

[0202] ii) UVA/UVB ratio=0.578

[0203] iii) UVAPF=9

[0204] iv) Critical Wavelength=375 nm

[0205] v) L=9.26

[0206] vi) L/SPF ratio=0.21

Example 6

[0207] 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 C. for 2 hours), to 5% by weight of water. Using a screw conveyor, this material was fed into a rotating calciner operating at 630 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. The pH of the resulting slurry was adjusted to pH>9, and the temperature was increased to 50 C. A sodium silicate solution was added, equivalent to 5% 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 slurry was heated to 60 C. and the pH adjusted to pH 9.5. 3-aminopropyl triethoxysilane was added, equivalent to 3.75% on TiO.sub.2 weight. The slurry was stirred for 30 minutes, after which the temperature was increased to 75 C. Sodium stearate (equivalent to 3.75% by weight of sodium stearate on TiO.sub.2) dissolved in hot water was then 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.

[0208] A dispersion was produced by mixing 5 g of polyglyceryl-3 polyricinoleate with 55 g of caprylic/capric triglyceride, 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 4500 r.p.m. and containing zirconia beads as grinding media for 30 minutes.

[0209] The titanium dioxide dispersion was subjected to the test procedures herein described, and exhibited the following properties;

[0210] Extinction coefficients;

[00005]$\frac{E_{524}}{3.6}$$\frac{E_{308}}{58.5}$$\frac{E_{360}}{27.9}$$\frac{E\left(\max \right)}{58.5}$$\frac{\left(\mathrm{Max}\right)}{307.0}$$\frac{E_{308}/E_{524}}{16.3}$$\frac{E_{360}/E_{524}}{7.8}$$\frac{E_{360}/E_{308}}{0.48}$$\frac{E_{524}+E_{360}}{31.5}$$\frac{E_{524}{E}_{360}}{100.4}$$\frac{E_{308}{E}_{360}}{1632}$$\frac{\left(E_{308}{E}_{360}\right)/E_{524}}{453.4}$

[0211] A second dispersion was produced by mixing 5 g of polyglyceryl-3 polyricinoleate with 55 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 4500 r.p.m. and containing zirconia beads as grinding media for 30 minutes.

[0212] The titanium dioxide dispersion was subjected to the test procedures herein described, and exhibited the following properties;

[0213] (a) Particle size by sedimentation:

[0214] i) D (v,0.5)=163 nm

[0215] ii) D (n,0.5)=108 nm

[0216] (b) Particle size by light scattering:

[0217] i) Z-average=142 nm

[0218] ii) Intensity mean=153 nm

[0219] 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.