Metal Oxide Dispersion

Abstract

A dispersion contains particles of metal oxide having a median volume particle diameter in the range from 24 to 42 nm which are dispersed in a medium which includes a mixture of at least one polar material having an interfacial tension of less than 30 mNm−1 and at least one non-polar material having an interfacial tension of greater than 30 mNm−1. The dispersion can be fused in a sunscreen product that exhibits effective UV protection, transparency, and improved skin feel.

Description

EXAMPLES

Example 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. An alkaline solution of sodium aluminate was then added, equivalent to 10.5% by weight Al₂O₃ on TiO₂ weight. The temperature was maintained below 70° C. during the addition. The temperature was increased to above 70° C., and sodium stearate equivalent to 13.5% by weight sodium stearate on weight of TiO₂ was added. The dispersion was neutralised by adding hydrochloric acid solution. The resultant slurry was filtered, washed with demineralised water, dried in an oven, and then micropulverised to produce particulate titanium dioxide.

A dispersion was produced by mixing 6 g of polyhydroxystearic acid with 47 g of triethylhexyl triglyceride and 47 g of isohexadecane, and then adding 100 g of titanium dioxide produced above into the solution. The mixture was passed through a horizontal bead mill, operating at approximately 2100 r.p.m. and containing zirconia beads as grinding media for 15 minutes.

The dispersion was subjected to the test procedures described herein, and the titanium dioxide exhibited the following properties:

i) Mean crystal size=7 nm,

ii) Median volume particle diameter=33 nm,

• • 16% by volume of particles have a volume diameter of 8 nm below the median volume particle diameter,
  • 30% by volume of particles have a volume diameter of 4.5 nm below the median volume particle diameter,
  • 70% by volume of particles have a volume diameter of 6 nm above the median volume particle diameter,
  • 84% by volume of particles have a volume diameter of 15 nm above the median volume particle diameter,

iii) Extinction Coefficients;

	E524	E450	E308	E360	E (max)	λ (max)
	0.8	1.5	45.1	7.1	61.4	277

Example 2

The titanium dioxide dispersion produced in Example 1 was used to prepare a sunscreen product having the following composition.

% w/w
Phase A:
ARLACEL P135 (ex Uniqema)        2.0
ESTOL 1512 (ex Uniqema)          16.7
Candelilla Wax (ex Eggar&Co Chemicals Ltd) 1.0
Titanium Dioxide dispersion produced above 15.0
Phase B:
PRICERINE 9091 (ex Uniqema)      4.0
Magnesium Sulfate                0.7
Demineralised Water              60.1
Phase C:
Germaben II                      0.5

The ingredients of oil phase A were mixed and heated to 75-80° C. The ingredients of aqueous phase B were mixed and heated to 75-80° C., and slowly added to phase A with intensive mixing, followed by stirring with a Silverson mixer for 2 minutes. The mixture was cooled to 45° C. with intensive stirring, and the preservative phase C added. The mixture was further cooled to room temperature with stirring.

The sunscreen product was subjected to the test procedures described herein and exhibited the following properties:

i)	Greasy Skin Feel	30% immediate (43% for conventional sunscreen)
		38% after 20 minutes (47% for conventional
		sunscreen)
ii)	Whiteness ΔL	1.1
	Whiteness Index	39%
iii)	SPF	25

The above examples illustrate the improved properties of a dispersion and sunscreen product according to the present invention.

Claims

1. A dispersion comprising particles of metal oxide having a median volume particle diameter in the range from 24 to 42 nm, dispersed in a medium which comprises a mixture of at least one polar material having an interfacial tension of less than 30 mNm−1 and at least one non-polar material having an interfacial tension greater than 30 mNm−1.

2. A dispersion according to claim 1 wherein the metal oxide particles have a mean crystal size in the range from 4 to 10 nm.

3. A dispersion according to claim 1 where at least 40% by weight of metal oxide particles have a crystal size within the range 5 to 9 nm.

4. A dispersion according to claim 1 wherein less than 16% by volume of metal oxide particles have a volume diameter of less than 9 nm below the median volume particle diameter.

5. A dispersion according to claim 1 wherein less than 30% by volume of metal oxide particles have a volume diameter of less than 5 nm below the median volume particle diameter.

6. A dispersion according to claim 1 wherein more than 84% by volume of metal oxide particles have a volume diameter of less than 17 nm above the median volume particle diameter.

7. A dispersion according to claim 1 wherein more than 70% by volume of metal oxide particles have a volume diameter of less than 6 nm above the median volume particle diameter.

8. A dispersion according to claim 1 wherein the metal oxide particles have an extinction coefficient at 524 nm in the range from 0.4 to 1.2 l/g/cm.

9. A dispersion according to claim 1 wherein the metal oxide particles have an extinction coefficient at 360 nm in the range from 5 to 11 l/g/cm.

10. A dispersion according to claim 1 wherein the metal oxide particles have an extinction coefficient at 308 nm in the range from 40 to 52 l/g/cm.

11. A dispersion according to claim 1 wherein the metal oxide particles have (i) a median volume particle diameter in the range from 29 to 37 nm, and/or (ii) less than 10% by volume of particles having a volume diameter of less than 11 nm below the median volume particle diameter, and/or (iii) less than 16% by volume of particles having a volume diameter of 8 nm below the median volume particle diameter, and/or (iv) less than 30% by volume of particles having a volume diameter of less than 5 nm below the median volume particle diameter, and/or (v) more than 90% by volume of particles having a volume diameter of less than 27 nm above the median volume particle diameter, and/or (vi) more than 84% by volume of particles having a volume diameter of less than 17 nm above the median volume particle diameter, and/or (vii) more than 70% by volume of particles having a volume diameter of less than 6 nm above the median volume particle diameter.

12. A dispersion according to claim 1 wherein the particles of metal oxide have an extinction coefficient at 524 nm in the range from 0.5 to 1.1 l/g/cm, an extinction coefficient at 450 nm in the range from 1.0 to 2.0 l/g/cm, an extinction coefficient at 360 nm in the range from 6 to 10 l/g/cm, an extinction coefficient at 308 nm in the range from 44 to 48 l/g/cm, a maximum extinction coefficient in the range from 60 to 64 l/g/cm, and a λ(max) in the range from 274 to 282 nm.

13. A dispersion according to claim 1 wherein the polar material has an interfacial tension in the range from 10 to 25 mNm−1.

14. A dispersion according to claim 1 wherein the non-polar material has an interfacial tension in the range form 35 to 45 mNm−1.

15. A dispersion according to claim 1 wherein the difference in the interfacial tension of the polar material and the non-polar material is in the range from 13 to 20 mNm−1.

16. A dispersion according to claim 1 wherein the ratio of polar to non-polar material is in the range from 30 to 70:30 to 70% by weight.

17. A dispersion according to claim 1 wherein the polar material is selected from the group consisting of are triethylhexyl triglyceride, C12-15 alkyl benzoate, caprylic/capric triglyceride, isononyl isononanoate, isostearyl neopentanoate, and octyldodecyl neopentanoate.

18. A dispersion according to claim 1 wherein the non-polar material is selected from the group consisting of isohexadecane, hydrogenated polyisobutene, and squalane.

19. A dispersion comprising particles of metal oxide having a median volume particle diameter in the range from 24 to 42 nm, dispersed in a medium which comprises a mixture of (i) at least one polar material selected from the group consisting of, C12-15 alkyl benzoate, caprylic/capric triglyceride, cetearyl isononanoate, ethylhexyl isostearate, ethylhexyl palmitate, isononyl isononanoate, isopropyl isostearate, isopropyl myristate, isostearyl isostearate, isostearyl neopentanoate, octyldodecanol, pentaerythrityl tetraisostearate, PPG-15 stearyl ether, triethylhexyl triglyceride, dicaprylyl carbonate, ethylhexyl stearate, helianthus annus (sunflower) seed oil, isopropyl palmitate, and octyldodecyl neopentanoate, and (ii) at least one non-polar material selected from the group consisting of, C13-14 isoparaffin, isohexadecane, paraffinum liquidum (mineral oil), squalane, squalene, hydrogenated polyisobutene, and polydecene.

20. A sunscreen product formed from a dispersion comprising particles of metal oxide having a median volume particle diameter in the range from 24 to 42 nm, dispersed in a medium which comprises a mixture of at least one polar material having an interfacial tension of less than 30 mNm−1 and at least one non-polar material having an interfacial tension of greater than 30 mNm−1.

21. A sunscreen product comprising particles of metal oxide having a median volume particle diameter in the range from 24 to 42 nm, and (i) at least one polar material selected from the group consisting of are triethylhexyl triglyceride, C12-15 alkyl benzoate, caprylic/capric triglyceride, isononyl isononanoate, isostearyl neopentanoate, and octyldodecyl neopentanoate, and (ii) at least one non-polar material selected from the group consisting of isohexadecane, hydrogenated polyisobutene, and squalane.

22. The use of a dispersion comprising particles of metal oxide having a median volume particle diameter in the range from 24 to 42 nm, dispersed in a medium which comprises a mixture of at least one polar material having an interfacial tension of less than 30 mNm−1 and at least one non-polar material having an interfacial tension of greater than 30 mNm−1, to produce a sunscreen having improved skin feel.

23. The use of a dispersion comprising particles of metal oxide having a median volume particle diameter in the range from 24 to 42 nm, dispersed in a medium which comprises a mixture of at least one polar material having an interfacial tension of less than 30 mNm−1 and at least one non-polar material having an interfacial tension of greater than 30 mNm−1, in the manufacture of a transparent sunscreen having improved skin feel.