Metal oxide dispersions

• US 20020054999A1
• Filed: 11/20/2001
• Published: 05/09/2002
• Est. Priority Date: 05/25/1999
• Status: Active Grant

• Current Assignee: Croda International PLC
• Original Assignee: ACMP LLC
• Inventors: Kessell, Lorna Margaret
• Granted Patent: US 6,683,130 B2
• Time in Patent Office: Days
• US Class Current: 428/447
• CPC Class Codes: A61K 2800/413 Nanosized, i.e. having sizes below 100 nm
• CPC Class Codes: A61K 8/11 Encapsulated compositions
• CPC Class Codes: A61K 8/19 containing inorganic ingredients
• CPC Class Codes: A61K 8/27 Zinc; Compounds thereof
• CPC Class Codes: A61K 8/29 Titanium; Compounds thereof
• CPC Class Codes: A61K 8/90 Block copolymers A61K8/89 takes precedence
• CPC Class Codes: A61Q 17/04 Topical preparations for affording protection against sunlight or other radiation; Topical sun tanning preparations
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C01P 2002/84 by UV- or VIS- data
• CPC Class Codes: C01P 2004/03 obtained by SEM
• CPC Class Codes: C01P 2004/10 extending in one dimension, e.g. needle-like
• CPC Class Codes: C01P 2004/32 Spheres
• CPC Class Codes: C01P 2004/64 Nanometer sized, i.e. from 1-100 nanometer
• CPC Class Codes: C01P 2004/84 one phase coated with the other
• CPC Class Codes: C01P 2006/60 Optical properties, e.g. expressed in CIELAB-values
• CPC Class Codes: C01P 2006/90 Other properties not specified above
• CPC Class Codes: C09C 1/043 Zinc oxide
• CPC Class Codes: C09C 1/24 Oxides of iron
• CPC Class Codes: C09C 1/3684 Treatment with organo-silicon compounds
• CPC Class Codes: C09C 3/12 Treatment with organosilicon compounds C09C3/006 takes precedence
• CPC Class Codes: Y10T 428/31663 : As siloxane, silicone or silane

Abstract

A dispersion comprises at least 30 per cent by weight of particles of a metal oxide having an average primary particle size of less than 200 nm dispersed in a siloxane fluid dispersing medium and a dispersing agent wherein said metal oxide particles are hydrophoobic, and the dispersing agent is polylkylene oxide/polyalkylsiloxane block copolymer comprising at least 30 per cent by weight of the copolymer of polyalkylsiloxane. The dispersion is particularly suitable for use as an ingredient in sunscreening cosmetics.

Claims

1. A dispersion comprising at least 30 per cent by weight of particles of a metal oxide having an average primary particle size of less than 200 nm dispersed in a sitoxane fluid dispersing medium and a dispersing agent wherein said metal oxide particles are hydrophobic, and said dispersing agent is a polyalkylene oxide/polyalkylsiloxane block copolymer comprising at least 30 per cent by weight of the copolymer of polyalkylsiloxane.

2. A dispersion according to claim 1 wherein the polyalkylene oxide/polyalkylsiloxane block copolymer has the formula (1)

3. A dispersion according to claim 1 wherein the metal oxide is an oxide of titanium, zinc or iron.

4. A dispersion according to any one of the preceding claims wherein the particles of metal oxide are titanium dioxide having an acicular shape with an average largest dimension less than 150 nm, and a ratio of largest dimension to shortest dimension in the range 10:

1 to 2;

1.

5. A dispersion according to any one of claims 1 to 3 wherein the particles of metal oxide are zinc oxide with an average primary particle size in the range 30 to 100 nm.

6. A dispersion according to any one of the preceding claims wherein the particles of metal oxide carry an inorganic coating.

7. A dispersion according to any one of the preceding claims wherein the particles of metal oxide have been treated with a water-repellent material selected from fatty acids, salts of fatty acids, fatty alcohols, silicones and reactive silicones to render them hydrophobic.

8. A dispersion according to claim 7 wherein the amount of water-repellent material present is up to 20 per cent by weight calculated with respect to the weight of uncoated or inorganically-coated metal oxide particles.

9. A dispersion according to any one of the preceding claims wherein the particles of metal oxide are present in an amount of at least 40 per cent by weight with respect to total weight of dispersion.

10. A dispersion according to any one of the preceding claims wherein the siloxane fluid dispersing medium is a cyclic oligomeric dialkylsiloxane, a linear dimethyl-siloxane oligomer or polymer or phenyltris(trimethylsiloxy)silane.

11. A dispersion according to any one of the preceding claims wherein the polyalkylene oxide/polyalkylsiloxane block copolymer contains greater than 40 per cent by weight of polyalkylsiloxane.

12. A dispersion according to any one of the preceding claims wherein the moieties represented by (Y¹)_p and (Y²)_r in formula (1) are oxyethylene/oxypropylene copolymeric moieties.

13. A dispersion according to any one of the preceding claims wherein the moieties represented by X¹ and X² are both (CH₂)₃.

14. A dispersion according to any one of the preceding claims wherein the amount of dispersing agent present is in the range 15 to 40 per cent by weight based on weight of particles of metal oxide.

16. A method according to claim 15 wherein the polyalkylene oxide/polyalkylsiloxane block copolymer has the formula (1)

18. A process according to claim 17 in which the emulsion contains from 0.5 to 30 per cent by weight of the particles of metal oxide, from 10 to 60 per cent by weight of oil phase, from 40 to 90 per cent by weight of aqueous phase and from 0.5 to 10 per cent by weight of emulsifier.

15. A method of preparing dispersions of metal oxides comprising milling with a particulate grinding medium particles of metal oxide in a siloxane fluid dispersing medium and in the presence of a dispersing agent which is a polyalkylene oxide/polyalkylsiloxane block copolymer comprising at least 30 per cent by weight of the copolymer of polyalkylsiloxane, the particles of metal oxide being hydrophobic and being present in an amount such that the proportion of particles of metal oxide in the dispersion is at least 30 per cent by weight and the milling being continued until the primary particles of metal oxide produced have an average particle size less than 200 nm.

17. A process for preparing an emulsion comprising the steps of

(a) preparing a dispersion of particles of metal oxide consisting essentially of at least 30 per cent by weight of hydrophobic particles of metal oxide having a primary particle size of less than 200 nm, a siloxane fluid dispersing medium and a dispersing agent which is a polyalkylene oxide/polyalkylsiloxane block copolymer comprising at least 30 per cent by weight of the copolymer of polyalkylsiloxane,

(b) subsequently mixing said dispersion with at least one cosmetically acceptable hydrophobic material to form an oil phase and,

(c) subsequently mixing said oil phase with an aqueous phase in the presence of at least one emulsifier in order to produce an emulsion.