AU727150B2

AU727150B2 - Titanium dioxide particles

Info

Publication number: AU727150B2
Application number: AU18834/97A
Authority: AU
Inventors: Thierry Chopin; Dominique Dupuis; Claudie Willemin
Original assignee: Rhodia Chimie SAS
Current assignee: Rhodia Chimie SAS
Priority date: 1996-02-15
Filing date: 1997-02-12
Publication date: 2000-12-07
Anticipated expiration: 2017-02-12
Also published as: FR2744914B1; FR2744914A1; AU1883497A; ES2146083T3; JPH11506155A; CA2253223A1; WO1997030130A1; ATE192475T1; RU2162443C2; BR9707499A; DE69701859T2; CA2253223C; DE69701859D1; CN1211272A; IL125779A; IL125779A0; EP0880564A1; EP0880564B1; JP3091496B2; CN1083472C

Abstract

Anatase titanium dioxide particles no larger than 100 nm and coated with a layer of a metal oxide, hydroxide or oxohydroxide, said particles having a BET specific surface area of at least 70 m<2>/g and a density of around 2.2. A method for preparing said particles, and the use thereof as an anti-UV agent, in particular for preparing formulations for cosmetics, varnishes, paints and plastics, are also disclosed.

Description

-1- TITANIUM DIOXIDE PARTICLES The present invention relates to novel anatase titanium dioxide particles exhibiting anti-UV properties which can be used in particular in cosmetic formulations.

It is known to use titanium dioxide as anti-UV agent in numerous applications, in particular in cosmetics, paint, plastics, and the like.

In these applications, the titanium dioxide is generally provided in the form of particles with a size of less than 100 nm as a dispersion in an aqueous or organic phase.

The problem resulting from the use of these dispersions of titanium dioxide particles arises from the fact that the latter are often unstable. To control their stability, it is known to add dispersing agents to them, generally organic polymers.

However, the addition of these dispersing agents is not a solution which is without its disadvantages. This is because, when the titanium dioxide dispersion is mixed with other products in order to prepare a cosmetic, paint or plastic formulation, this agent can exhibit behaviour incompatible with the application (stability, agglomeration, toxicity, and the like) or be incompatible with the other components of the formula.

It is an object of the invention to overcome or ameliorate at least one of the problems associated with the prior art.

In preferred embodiments, the present invention is thus generally directed to provide dispersions of titanium dioxide particles which are stable and which do not contain dispersing agent.

In a first aspect the invention thus relates to anatase titanium dioxide particles with a size of at most 100 nm, the said particles being at least partially covered with a -2layer of at least one metal oxide, hydroxide or hydroxide oxide and exhibiting a BET specific surface of at least 70 m 2 /g and a relative density of the order of 2.2.

In a second aspect, the invention also relates to the process for the preparation of these particles in which at least one metal oxide, hydroxide or hydroxide oxide is precipitated at the surface of anatase titanium dioxide particles with a size of at most 100 nm exhibiting a BET specific surface of at least 200 m 2 /g and a relative density of the order of Finally, and in a third aspect the invention also relates to the use of these particles as anti-UV agent in cosmetic, paint or varnish formulations and in plastics; and more particularly to an anti-UV cosmetic composition comprising particles according to the invention in an amount such that the content of titanium dioxide in the said composition is at least 1% and preferably at most 25% by weight.

The dispersions formed from particles according to the j, 3 invention in addition exhibit the advantage of being stable over a wide pH range without addition of dispersing agent.

They can also exhibited high solids contents, while remaining stable and exhibiting a low viscosity, in particular of less than 1000 mPa-s.

Moreover, it is observed that these dispersions retain the same dispersion index even when they have been mixed with the components of a formulation, for example a cosmetic formulation.

Other characteristics, details and advantages of the invention will become more clearly apparent on reading the description and examples which will follow.

The invention first of all relates to anatase titanium dioxide particles with a size of at most 100 nm, the said particles being at least partially covered with a layer of at least one metal oxide, hydroxide or hydroxide oxide and exhibiting a BET specific surface of at least 70 m 2 /g and a relative density of the order of 2.2.

The particles according to the invention are based on titanium dioxide with a largely anatase crystalline structure. "Largely" means that the level of anatase in the titanium dioxide particles of the coating is greater than 50% by mass. Preferably, the particles of the coating exhibit a level of anatase of greater than 80%. The degree of crystallization and the nature of the crystalline phase are measured by X-ray 1t 4 diffraction.

The mean diameter of these particles is at most 100 nm, preferably at least 25 nm, more preferably still between 50 and 70 nm. This diameter is measured by transmission electron microscopy (TEM) The particles according to the invention exhibit a BET specific surface of at least 70 m 2 /g, preferably of at least 100 m 2 /g.

BET specific surface is understood to mean the specific surface determined by nitrogen adsorption in accordance with the ASTM standard D 3663-78 drawn up from the Brunauer-Emmett-Teller method described in the periodical "The Journal of the American [lacuna] Society", 60, 309 (1938). In order to measure the specific surface of the particles according to the invention, when they are provided in the form of a dispersion, it is essential to follow the measuring protocol, which'consists in removing the liquid phase from the dispersion and then in drying the particles under vacuum at a temperature of 150 0 C for at least 4 hours.

The particles according to the invention also exhibit a relative density of the order of 2.2. "Of the order" is understood to mean that the relative density is 2.2 0.2. Such a relative density value is low with respect to the conventional relative density of anatase titanium dioxide, which is 3.8. This relative density is measured by picnometry.

LU

~a isJ The particles according to the invention are at least partially covered with an inorganic layer based on at least one metal oxide, hydroxide or hydroxide oxide. These metal oxides, hydroxides or hydroxide oxides can be chosen in particular from SiO 2 ZrO 2 or aluminium, zinc, titanium or tin oxides, hydroxides or hydroxide oxides, in the simple or mixed form. Mixed is understood to mean a metal compound based on at least two of the abovementioned elements (silicoaluminates, and the like).

In general, the ratio by weight of the metal oxide(s), hydroxide(s) or hydroxide oxide(s) to the titanium dioxide is at most 60% by weight. This ratio depends on the application for which the particles are intended. Preferably, when the particles are used in a cosmetic application, this ratio is at most 25%, more preferably still at most This amount of metal oxide, hydroxide or hydroxide oxide is measured on the dispersed particles by X-ray fluorescence.

According to the preferred form of the invention, the particles are at least partially covered with a layer of silica and/or of an aluminium oxide, hydroxide or hydroxide oxide, in the simple or mixed form.

According to a preferred alternative form, the particles are covered with a layer of silica and of aluminium hydroxide or hydroxide oxide in contents by weight of 30% of SiO 2 and 15% of A1 2 0, with respect to the titanium dioxide.

According to an even more preferred alternative form, the particles are covered with a layer of silica and of aluminium hydroxide or hydroxide oxide in contents by weight of 15% of SiO 2 and 5% of A1 2 0 3 with respect to the titanium dioxide are particularly advantageous.

According to the preferred form of the invention, the particles are provided in the form of a dispersion.

This dispersion generally exhibits a conductivity of at most 3 msiemens.

This dispersion can exhibit a proportion of suspended solid (solids content) of between 10 and by weight, preferably of at least 35%, more preferably still of at least The dispersion of particles according to the invention exhibiting a solids content of at least have the advantage of being only very slightly viscous; thus, their viscosity is generally at most 1000 mPa-s.

This dispersion generally exhibits a dispersion index of the particles in the liquid phase of at most The dispersion index is determined by the formula: REPLACEMENT SHEET (RULE 26) 084-016 1= 2050 in which: 084 is the diameter of the particles for which 84% of the particles have a diameter of less than 084, 0,,16 is the diameter of the particles for which 16% of the particles have a diameter of less than 016, 0 is the mean diameter of the particles.

The diameters of use in the determination of the dispersion index are measured by centrifugal sedimentation of the particles of the dispersion, monitored by X-rays, using a Brookhaven type XDC device.

Such an index reflects the good dispersibility of the particles. In the case of aqueous dispersions, this index is obtained over a wide pH range which can vary from 5.5 to 10. The dispersions are stable and they retain this index value over time, despite the absence of dispersing agent.

The particles according to the invention can also be agglomerated and be provided in the form of a powder. The size of the agglomerates can be between 1 and 40 Am, measured by TEM.

REPLACEMENT SHEET (RULE 26) Following an organic treatment, this powder can exhibit good redispersibility in water or in organic medium. This organic treatment can be carried out, for example, by atomization in the presence of a fatty acid, such as stearic acid, or of a metal salt of a fatty acid or alternatively by grafting a trialkoxysilane, and the like.

The invention also relates to the process for the preparation of these particles, which consists in precipitating at least one metal oxide, hydroxide or hydroxide oxide at the surface of anatase titanium dioxide particles with a size of at most 120 nm exhibiting a BET specific surface of at least 200 m 2 /g and a relative density of the order of This precipitation can be carried out by: introducing, into a dispersion of particles of titanium dioxide exhibiting the characteristics defined hereinabove, precursors of the metal oxides, hydroxides or hydroxide oxides, generally in the form of aqueous salt solutions, then, modifying the pH in order to obtain the precipitation of these oxides, hydroxides or hydroxide oxides on the titanium dioxide particles.

This precipitation is generally carried out at a temperature of at least 50 0

C.

In the case of the precipitation of silica and of an aluminium hydroxide or hydroxide oxide, the REPLACEMENT SHEET (RULE 26) 4.

9 precipitation can be carried out at acidic or basic pH.

The pH is controlled by the addition of an acid, such as sulphuric acid, or by the simultaneous and/or alternating introduction of an alkaline compound of silicon and of an acidic compound of aluminium. In this case, the pH is preferably between 8 and The silica can be precipitated from a silicon salt, such as an alkaline silicate.

The aluminium hydroxide or hydroxide oxide can be precipitated from an aluminium salt, such as aluminium sulphate, sodium aluminate, basic aluminium chloride or aluminium diacetate hydroxide.

It is possible, after the precipitation, to recover and wash the particles obtained following the treatment, before redispersing them. This stage can be carried out by centrifuging and washing or, preferably, by washing by ultrafiltration. The pH of the aqueous wash liquor is advantageously of the order of 5.5. The particles are then redispersed in another liquid medium, so as to obtain a dispersion of titanium dioxide particles. This liquid medium can be acidic or basic; it is preferably a basic solution exhibiting a pH of the order of 8-9.

To obtain a powder of particles according to the invention, the dispersion resulting from the process is dried, generally at a temperature of less than 110 0

C.

The starting anatase titanium dioxide particles must exhibit a size of at most 100 nm, a BET specific surface of at least 200 m 2 /g and a relative density of the order of The starting particles are based on titanium dioxide with a mainly anatase crystalline structure, as defined above.

The mean diameter of these particles is at most 100 nm, preferably at least 25 nm, more preferably still between 50 and 70 nm. This diameter is measured by transmission electron microscopy (TEM) The starting particles exhibit a BET specific surface of at least 200 m 2 preferably of at least 250 m 2 /g.

This BET specific surface is measured in the same way as defined above.

The starting particles also exhibit a relative density of the order of 2.5. "Of the order" is understood to mean that the relative density is 0.2. This relative density is given by the following formula: relative density 1 (l/p)+Vi in which: p is the relative density of the anatase, i.e.

3.8, Vi is the volume contributed by the intraparticle pores; it is measured by the BJH method. Volume measured by the BJH method is understood to mean the volume measured from the Barrett-Joyner-Helenda method described in the article in the work Techniques de l'Ing6nieur [Techniques of the Engineer] and entitled "Texture des solides poreux ou divis6s" [Texture of porous or divided solids], p.3645-1 to 3645-13.

In order to measure the volume contributed by the intraparticle pores of the particles according to the invention, when they are provided in the form of a dispersion, it is essential to follow the measuring protocol which consists in removing the liquid phase from the dispersion and then in drying the particles under vacuum at a temperature of 150 0 C for at least 4 hours.

Such particles can be obtained by hydrolysis Sof at least one titanium compound A in the presence of at least one compound B chosen from: the acids which exhibit: either a carboxyl group and at least two hydroxyl and/or amine groups, or at least two carboxyl groups and at least one hydroxyl and/or amine group, (ii) the organic phosphoric acids of following formulae: HO O R2 O OH \II I II P (C)n-P I HO R1 OH HO O OH O OH l I II I P C- P I HO R3 OH 0 OH HO O CH P OH

II

P-CH

2

(CH

2 )Jp- N HO CH 2

CH

2 P- OH I II O P-OH O OH

I

OH

in which n and m are integers of between 1 and 6 and p is an integer of between 0 and 5, R1, R2 and R3, which are identical or different, representing a hydroxyl, amino, aralkyl, aryl or alkyl group or hydrogen, (iii) the compounds capable of releasing sulphate ions in acidic medium, (iv) the salts of the acids described above, and in the presence of anatase titanium dioxide seeds exhibiting a size of at most 8 nm and in a ratio by weight, expressed as TiO 2 present in the seeds/titanium present before introduction of the seeds in the hydrolysis medium, expressed as TiO 2 of between 0.01% and 3%.

The starting solution, intended to be hydrolysed, is preferably completely aqueous; it is optionally possible to add another solvent, for example an alcohol, provided that the titanium compound A and the compound B used are then substantially soluble in this mixture.

As regards the titanium compound A, use is generally made of a compound chosen from titanium halides, oxyhalides or alkoxides, sulphates and more particularly synthetic sulphates.

Synthetic sulphates are understood to mean titanyl sulphate solutions prepared by ion exchange from very pure titanium chloride solutions or by reaction of sulphuric acid with a titanium alkoxide.

The preparation is preferably carried out with titanium compounds of the titanium halide or oxyhalide type. The titanium halides or oxyhalides which are more particularly used in the present invention are titanium fluorides, chlorides, bromides and iodides (respectively oxyfluorides, oxychlorides, oxybromides and oxyiodides).

According to a particularly preferred form, the titanium compound is titanium oxychloride TiOC1 2 The amount of titanium compound A present in the solution to be hydrolysed is not critical.

The initial solution additionally contains at 14 least one compound B as defined above. Mention may be made, as non-limiting examples of compounds B coming within the scope of the present invention, of in particular: hydroxypolycarboxylic acids and more particularly hydroxydi- or hydroxytricarboxylic acids, such as citric acid, maleic acid and tartaric acid, (polyhydroxy)monocarboxylic acids, such as, for example, glucoheptonic acid and gluconic acid, poly(hydroxycarboxylic) acids, such as, for example, tartaric acid, dicarboxylic monoacids and their corresponding amides, such as, for example, aspartic acid, asparagine and glutamic acid, hydroxylated or non-hydroxylated monocarboxylic amino acids, such as, for example, lysine, serine and threonine, aminotri(methylenephosphonate), ethylenediaminotetra(methylenephosphonate), triethylenetetraaminohexa(methylenephosphonate), tetraethylenepentaaminohepta(methylenephosphonate) or pentaethylenehexaaminoocta(methylenephosphonate), methylenediphosphonate, 1,1'-ethylenediphosphonate, 1,2-ethylenediphosphonate, 1,1'-propylenediphosphonate, 1,3-propylenediphosphonate, 1,6-hexamethylenediphosphonate, 2,4-dihydroxypentamethylene- 2,4-diphosphonate, 2,5-dihydroxyhexamethylene-2,5-diphosphonate, 2,3-dihydroxybutylene-2,3-diphosphonate, l-hydroxybenzyl-l,1'-diphosphonate, 1-aminoethylene- 1-1'-diphosphonate, hydroxymethylenediphosphonate, 1-hydroxyethylene-1,1'-diphosphonate, 1-hydroxypropylene-l-l'-diphosphonate, 1-hydroxybutylene- 1-l'-diphosphonate or 1-hydroxyhexamethylene- 1,1'-diphosphonate.

As already indicated, it is also possible to use, as compound B, all the salts of the abovementioned acids. In particular, these salts are either alkali metal salts, more particularly sodium salts, or ammonium salts.

These compounds can also be chosen from sulphuric acid and ammonium or potassium sulphates, and the like.

The compounds B as defined above are preferably hydrocarbon-comprising compounds of aliphatic type. In this case, the length of the main hydrocarbon-comprising chain preferably does not exceed carbon atoms and more preferably 10 carbon atoms.

The preferred compound B is citric acid.

The amount of compound.B is not critical. The molar concentration of the compound B with respect to that of the titanium compound A is generally between 0.2 and 10% and preferably between 1 and Finally, the starting solution comprises titanium dioxide seeds used in a specific way.

Thus, the titanium dioxide seeds used in the present invention must first of all exhibit a size of less than 8 nm, measured by X-ray diffraction. Use is preferably made of titanium dioxide seeds exhibiting a size of between 3 and 5 nm.

Subsequently, the ratio by weight of the titanium dioxide present in the seeds to the titanium present in the hydrolysis medium before introduction of the seeds, that is to say contributed by the titanium compound A, and expressed as TiO 2 is between 0.01 and This ratio can preferably be between 0.05 and The bringing together of these two conditions with respect to the seeds (size and ratio by weight), in combination with the process as described above, makes it possible to precisely control the final size of the titanium dioxide particles, a level of seeds being associated with a particle size. It is thus possible to obtain particles for which the size varies between and 100 nm.

Use is made of titanium dioxide seeds in the anatase form, so as to induce precipitation of the titanium dioxide in the anatase form. Generally, due to their small size, these seeds instead exist in the form of poorly crystallized anatase. The seeds are generally provided in the form of an aqueous suspension composed of titanium dioxide. They can generally be obtained in a known way by a process of neutralization of a titanium salt by a base.

The following stage consists in hydrolysing this starting solution by any means known to a person 17 skilled in the art and generally by heating. In the latter case, the hydrolysis can preferably be carried out at a temperature greater than or equal to 70 0 C. It is also possible to operate, firstly, at a temperature below the boiling temperature of the medium and, then, to maintain the hydrolysis medium level at the boiling temperature.

Once hydrolysis has been carried out, the titanium dioxide particles obtained are recovered by separation of the precipitated solid from the mother liquors before being redispersed in a liquid medium so as to obtain a titanium dioxide dispersion. This liquid medium can be acidic or basic. It is preferably a basic solution, for example an aqueous sodium hydroxide solution. It is from this dispersion that the stage of precipitation of the metal oxides, hydroxides or hydroxide oxides will be carried out.

According to a specific alternative form, after the recovery of the particles obtained following the hydrolysis and before they are redispersed, the particles are neutralized and subjected to at least one washing operation. The particles can be recovered, for example by centrifuging the solution resulting from the hydrolysis; they are subsequently neutralized with a base, for example a sodium hydroxide or aqueous ammonia solution, they are then washed by redispersing them in an aqueous solution, and finally the particles are separated from the aqueous washing phase. After optionally one or more other washing operations of the same type, the particles are redispersed in an acidic or basic solution.

These particles generally exhibit a high degree of purity, compatible with an application in cosmetics.

Finally, the invention relates to the use of the particles described above as anti-UV agent. They can be used in particular as anti-UV agent in cosmetic, varnish or paint formulations and in plastics.

Introduced into cosmetic formulations, these titanium dioxide dispersions or powders make it possible to obtain an SPF (Sun Protection Factor) number of at least Moreover, the formulations obtained are photostable, that is to say that they do not exhibit blueing after exposure to UV according to the test defined in the examples.

They are particularly stable on storage and it may be observed that the titanium dioxide particles retains their dispersion index in the formulation.

The invention relates to anti-UVWcosmetic compositions comprising particles as described above in an amount such that the titanium dioxide content in the said compositions is at least preferably at most by weight and more preferably still between 2 and by weight.

It is possible to introduce into the cosmetic 19 compositions particles exhibiting different particle sizes.

The compositions forming the subject-matter of the invention can be formulated as a large number of types of products, such as anti-sun products of gel, lotion, oil or cream type and more generally make-up products, self-tanning agents, care products, hairs, total blocks for the lips and many other compositions of the same type.

The term cosmetic composition or formulation is understood to mean all cosmetic products or preparations, such as those described in Appendix I ("Illustrative list by category of cosmetic products") of European Directive No. 76/768/EEC of 27 July 1976, known as the cosmetic directive.

The cosmetic compositions forming the subject-matter of the invention can involve a vehicle, or a mixture of several vehicles, which act as diluent, dispersant or support for the other constituents of the composition and make possible their distribution when the composition is spread over the skin or hair.

The vehicles other than water can be liquid or solid emollients, solvents, humectants, thickeners or powders. The following types of vehicles can be used, for example, alone or as a mixture: emollients, such as stearyl alcohol, glyceryl monoricinoleate, oleyl alcohol, cetyl alcohol, isopropyl isostearate, stearic acid, isobutyl palmitate, isocetyl stearate, isopropyl laurate, hexyl laurate, decyl oleate, octadecan-2-ol, isocetyl alcohol, eicosanyl alcohol, behenyl alcohol, cetyl palmitate, silicone oils, such as dimethylpolysiloxne, di-n-butyl sebacate, isopropyl myristate, isopropyl palmitate, isopropyl stearate, butyl stearate, polyethylene glycol, lanolin, cacao butter, cottonseed oil, olive oil, palm oil, rapeseed oil, soybean oil, sunflower oil, avocado oil, almond oil, sesame oil, coconut oil, groundnut oil, castor oil, mineral oil, butyl myristate, isostearic acid, palmitic acid, isopropyl linoleate, lauryl lactate, decyl oleate or pyristyl myristate; propellants, such as: propane, butane, isobutane, dimethyl ether, carbon dioxide or nitrogen dioxide; solvents, such as: ethanol, methylene chloride, isopropanol, acetone, ethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether, dimethyl sulphoxide, dimethylformamide or tetrahydrofuran; powders, such as chalk, talc, kaolin, starch, gums, colloidal silica, poly(sodium acrylate), tetraalkyl- and/or trialkylarylammonium smectites, chemically modified magnesium aluminosilicate, organically modified montmorillonite, hydrated aluminium silicate, pyrogenic silica, polycarboxyvinyl, sodium carboxymethylcellulose or ethylene glycol monostearate.

The compositions according to the invention generally comprise from 10 to 99% by weight of at least one vehicle as described above.

The compositions according to the invention are preferably provided in the form of emulsions, in which an oily component is present with an emulsifier, so as to form an oil-in-water or water-in-oil emulsion, depending on the value of the hydrophile/lipophile balance (HLB).

Thus, the compositions according to the invention can comprise one or more oily components or components having the properties of an oil.

It can relate to vegetable or mineral oils, such as those provided in the above list of emollients.

It is also possible used volatile or non-volatile silicone oils, such as polydimethylsiloxanes.

These oily components can represent up to preferably from 10 to 80%, of the volume of the composition.

The compositions according to the invention can also comprise one or more emulsifiers. Depending on the nature of these emulsifiers, the compositions will be provided in the form of an oil-in-water or water-inoil emulsion.

For the preparation of an emulsion of waterin-oil type, the emulsifier or emulsifiers chosen must exhibit a mean HLB of between 1 and 6. For the preparation of an emulsion of oil-in-water type, the emulsifier or emulsifiers chosen must exhibit a mean HLB greater than 6. The amount of these emulsifier in the compositions according to the invention can vary between 1 and 50% by weight, preferably between 2 and These cosmetic compositions can also comprise surface-active agents which serve to disperse, emulsify, dissolve or stabilize various compounds used for their emollient or humectant properties. These surface-active agents are used in these compositions at concentrations varying from 0.05 to 50% by weight of the preparation. Anionic, non-ionic, cationic, zwitterionic or amphoteric surfactants or mixtures of these surfactants are thus found, such as: anionic surfactants: Salkyl ester sulphonates of formula

R-CH(SO

3 M)-COOR', where R represents a C 8

-C

20 preferably Ci-C 16 alkyl radical, R' a C 1

-C

6 preferably CI-C 3 alkyl radical and M an alkali metal cation (sodium, potassium or lithium), substituted or unsubstituted ammonium (methyl-, dimethyl-, trimethyl- or tetramethylammonium, dimethylpiperidinium, and the like) or derivative of an alkanolamine (monoethanolamine, diethanolamine, triethanolamine and the like). Mention may very particularly be made of methyl ester sulphonates in which the R radical is

C

14

-C

16 Salkyl sulphates of formula ROSO 3 M, where R represents a Co-C, 2 preferably C,-C 20 and very particularly C 12

-C

8 alkyl or hydroxyalkyl radical, M representing a hydrogen atom or a cation with the same definition as above, and their ethoxylenated (EO) and/or propoxylenated (PO) derivatives exhibiting, on average, from 0.5 to 6, preferably from 0.5 to 3, EO and/or PO units; Salkylamide sulphates of formula

RCONHR'OSO

3 M, where R represents a C 2

-C

22 preferably

C

6 -C20, alkyl radical and R' a C 2

-C

3 alkyl radical, M representing a hydrogen atom or a cation with the same definition as above, and their ethoxylenated (EO) and/or propoxylenated (PO) derivatives exhibiting, on average, from 0.5 to 60 EO and/or PO units; salts of saturated or unsaturated C 8

-C

2 4 preferably C, 4

-C

20 fatty acids, C 9

-C

20 alkylbenzenesulphonates, primary or secondary C 8

-C

22 alkyl sulphonates, alkyl glycerol sulphonates, the sulphonated polycarboxylic acids described in GB-A- 1,082,179, paraffin sulphonates, N-acyl-Nalkyltaurates, alkyl phosphates, alkyl isethionates, alkyl succinamates, alkyl sulphosuccinates, monoesters or diesters of sulphosuccinates, N-acylsarcosinates, sulphates of alkyl glycosides or polyethoxycarboxylates, the cation being an alkali metal (sodium, potassium or lithium), a substituted or unsubstituted ammonium residue (methyl-, dimethyl-, trimethyl- or tetramethylammonium, dimethylpiperidinium, and the like) or derivative of an alkanolamine (monoethanolamine, diethanolamine, triethanolamine, and the like); non-ionic surface-active agents: polyoxyalkylenated (polyethoxyethylenated, polyoxypropylenated or polyoxybutylenated) alkylphenols, the alkyl substituent of which is C 6

-C

12 containing from 5 to 25 oxyalkylene units; mention may be made, by way of example, of Triton X-45, Triton X-114, Triton X-100 or Triton X-102 sold by Rohm Haas Cy.; Sglucosamides or glucamides; *glycerolamides derived from N-alkylamines (US-A-5,223,179 and FR-A-1,585,966); polyoxyalkylenated C8-C22 aliphatic alcohols containing from 1 to 25 oxyalkylene (oxyethylene or oxypropylene) units; mention may be made, by way of example, of Tergitol 15-S-9 or Tergitol 24-L-6 NMW, sold by Union Carbide Corp., Neodol 45-9, Neodol 23-65, Neodol 45-7 or Neodol 45-4, sold by Shell Chemical Cy., or Kyro EOB, sold by The Procter Gamble Cy.; *the products resulting from the condensation of ethylene oxide with a hydrophobic compound resulting from the condensation of propylene oxide with propylene glycol, such as the Pluronic sold by BASF; amine oxides, such as (C10-C18 alkyl)dimethylamine oxides or (C 8

-C

22 alkoxy)ethyldihydroxyethylamine oxides; the alkyl polyglycosides described in US-A- 4,565,647 and their polyoxyalkylenated [lacuna]; Samides of C 8

-C

20 fatty acids; *ethoxylated fatty acids; *ethoxylated amides, amines or amidoamines; amphoteric and zwitterionic surface-active agents: Salkyltrimethylsulphobetaines, condensation products of fatty acids and of protein hydrolysates, alkyl amphopropionates or -dipropionates, alkyl sultaines, or amphoteric derivatives of alkylpolyamines, such as Amphionic XL', sold by Rh6ne- Poulenc, or Ampholac 7T/X and Ampholac 7C/X', sold by Berol Nobel, are used to decrease the irritation caused by other surface-active agents, mainly anionic surfaceactive agents.

Use may also be made of an emulsifier chosen from those on the following list: Chemical name of the Trade name HLB emulsifier Sorbitan trioleate Arlacel 85 1.8 Sorbitan tristearate Span 65 2.1 Glycerol monooleate Aldo MD 2.7 Glycerol monostearate Glycerol monolaurate Sorbitan sesquioleate Sorbitan rnonooleate Sorbitan monostearate Polyoxyethylene stearyl ether Polyoxyethylene sorbitol derivative of beeswax Polyglyceryl -3 diisostearate PEG 200 dilaurate Sorbitan monopalmitate PEG 200 monostearate Sorbitan monolaurate PEG 400 dioleate Polyoxyethylene (5) monostearate Polyoxyethylene (4) sorbitan monostearate 26 Atmul 84S Aldo MC Arlacel 8.' Arlacel 8( Arlacel 61 Brij 72 2.8 3.3 3.7 4.3 4.7 4.9 G-1702 Plurol Diisostearic Emerest 2622 Arlacel 40 Tegester PEG 200 MS Arlacel 200 Tegester PEG 400-DO Ethofat 60-16 Tween 61 6 6.3 6.7 8.6 8.8 9.6 Polyoxyethylene (4) lauryl ether Polyoxyethylene (5) sorbitan monooleate PEG 300 monooleate Polyoxyethylene (20) sorbitan tristearate Polyoxyethylene (20) sorbitan trioleate Polyoxyethylene monostearate PEG 400 monooleate PEG 400 monostearate Polyoxyethylene 10 monooleate Polyoxyethylene 10 stearyl ether Polyoxyethylene 10 cetyl ether Polyoxyethylene (4) sorbitan monolaurate PEG 600 monooleate PEG 1000 dilaurate 27 Brij 30 Tween 81 Neutronyx 834 Tween 65 Tween 85 Myrj 45 Emerest 2646 Tegester PEG 400 Ethofat 0/20 Brij 76 Brij 56 Tween 21 Ernerest 2660 Kessco 9.7 10. 0 10.4 10.5 11.0 11.1 11.7 11.9 12 .2 12.4 12 .9 13 .3 13 .7 13 .9 Polyoxyethylene sorbitol derivative of lanolin G-1441 14 .0 Polyoxyethylene (12) lauryl ether PEG 1500 dioleate Polyoxyethylene (14) laurate Polyoxyethylene (20) sorbitan monostearate Polyoxyethyleie (20) sorbitan monooleate Ethosperse LA-12 Pegosperse 1500 Arosurf HFL-714 Tween Tween 80 14 .4 14. 6 14 .8 14 .9 15.0 Polyoxyethylene stearyl ether (20) Brij 78 15.3 Polyoxyethylene sorbitan monopalmitate Polyoxyethylene cetyl ether Polyoxyethylene oxypropyl ene (20) (20) (25) Tween 40 Brij 58 Monostearate G-2162 15.6 15.7 16.0 Polyoxyethylene (20) sorbitol monolaurate Tween 20 16.7 Polyoxyethylene (23) Brij 35 16.9 lauryl ether Polyoxyethylene (50) Myrj 53 17.9 monostearate PEG 4000 monostearate Pegoperse 4000 MS 18.7 The compositions according to the invention can comprise water in a content which can range up to by volume, preferably between 5 and The compositions according to the invention can additionally comprise a high molecular weight silicone surface-active agent which can be an emulsifier used instead of those mentioned hereinabove.

This agent can be a high molecular weight dimethylpolysiloxane with polyoxyethylene and/or polyoxypropylene chains having a molecular weight of between 10,000 and 50,000 and with the structure:

CH

3 CH

CH

3 CH 3 I I I

I

CH3 Si Si [Si -Ol Si CH3 I I I I

CH

3 R' R"

CH

3 in which: the R' and R" groups are chosen from H, Cz-C, 8 alkyl and [CH 2 CH20]a([CH 2

CH(CH

3 )O]bH; one of the R' and R" groups can be lauryl, the other having a molecular weight of between 1000 and 5000, a is between 9 and 115, preferably between and 114, b is between 0 and 50, preferably between 0 and 49, x is between 133 and 673, preferably between 388 and 402, y is between 25 and 0.25, preferably between 15 and 0.75.

The dimethylpolysiloxane can be used in the form of a dispersion in a volatile siloxane, this dispersion comprising from 1 to 20% by volume of dimethylpolysiloxane.

The dimethylpolysiloxanes can be chosen from cyclomethicone and dimethicone coplyols, such as DC 3225C from Dow Corning, or lauryl methicone copolyol, such as DC Q2-5200 from Dow Corning.

It can also relate to Mirasil DMCO from Rh6ne-Poulenc or the cetyl dimethicone copylol Abil from Th. Goldschmidt AG.

The composition according to the invention can comprise up to 25% by weight of such a surfaceactive agent.

The compositions according to the invention can also comprise an organic sunscreen, such as, for example: CTFA Name Trade name Sold by 3-Benzophenone Uvinul M-40 BASF 4 -Benzophenone 8- Benzophenone Glyceryl PABA Octocrylene Octyl dimethyl

PABA

Octyl methoxycinnarnate Octyl salicylate

PABA

2- Phenylbenz suiphonic acid 3- (4-Methylbenzylidene) camphor 4-I sopropyldi benzoylmethane Butylmethoxydi benzoylmethane Etocrylene 31 Uvinul MS-40 Specra-Sorb UV-24 Nipa GMPA tjvinul N-539 SG Escalol 507 Parsol MCX Uvinul 0-18 No. 102 Eusolex 232 Eusolex 6300 Eusolex 8020 Parsol 1789 Uvinul N-35 BAS F American Cyanami d Nipa Labs BAS F

ISP

Givaudan/Roux

BASE

Merck Merck EM Ind.

EM Ind.

Givaudan/Roux BAS F It is also possible to use, as sunscreen, any compound authorized in European Directive No. 76/768/EEC and its appendices.

The composition according to the invention can also comprise inorganic sunscreens, such as: zinc oxide in the form of particles with a mean size of between 1 and 300 nm, iron oxide in the form of particles with a mean size of between 1 and 300 nm and silica in the form of particles with a mean size of between 1 and 100 nm.

The compositions can also comprise additives, such as: preservatives, for example parahydroxybenzoate ester; antioxidants, such as butylhydroxytoluene; humectants, such as glycerol, sorbitol, dibutyl phthalate, gelatin or PEGs, for example PEGs 200-600; buffer solutions, such as mixtures of lactic acid and of sodium hydroxide or of triethanolamine; waxes, such as beeswax or paraffin wax; plant extracts; preservatives, such as the methyl, ethyl, propyl and butyl esters of p-hydroxybenzoic acid, sodium benzoate, Germaben (trade name) or any chemical agent which prevents bacterial proliferation or moulds and which is conventionally used of the cosmetic compositions, are generally introduced into these compositions at a level of 0.01 to 3% by weight. The ~~C1 amount of these products is generally adjusted in order to prevent any proliferation of bacteria, moulds or yeasts in the cosmetic compositions. As an alternative to these chemical agents, it is sometimes possible to use agents which modify the activity of the water and which greatly increase the osmotic pressure, such as carbohydrates or salts; The cosmetic compositions forming the subject-matter of the invention can also comprise fixative resins. These fixative resins are generally present at concentrations of between 0.01 and preferably between 0.5 and The constituent fixative resins of the cosmetic compositions forming the subject-matter of the invention are preferably chosen from the following resins: acrylate/acrylamide copolymer, poly(vinyl methyl ether)/maleic anhydride copolymer, vinyl acetate/crotonic acid copolymer, octylacrylamide/acrylate/butylaminoethyl methacrylate copolymer, polyvinylpyrrolidone (PVP), copolymers of polyvinylpyrrolidone and of methyl methacrylate, copolymer of polyvinylpyrrolidone and of vinyl acetate poly(vinyl alcohol), copolymer of poly(vinyl alcohol) and of crotonic acid, copolymer of poly(vinyl alcohol) and of maleic anhydride, hydroxypropyl cellulose, hydroypropyl guar, sodium polystyrenesulphonate, polyvinylpyrrolidone/ethyl methacrylate/methacrylic acid terpolymer, monomethyl ether of poly(methyl vinyl ether maleic acid), poly(ethylene glycol terephthale)/poly(ethylene glycol) copolymers, poly(ethylene glycol terephthalate)/poly(ethylene glycol)/poly(sodium sulphoisophthalate) copolymers, and their mixtures. The fixative resins can also comprise grafted functionalized polyorganosiloxane units, as described in Patent WO 95/06079.

The fixative resins will preferably be of the following type: polyvinylpyrrolidone (PVP), copolymers of polyvinylpyrrolidone and of methyl methacrylate, copolymer of polyvinylpyrrolidone and of vinyl acetate poly(ethylene glycol terephthale)/poly(ethylene glycol) copolymers, poly(ethylene glycol terephthalate)/poly(ethylene glycol)/poly(sodium sulphoisophthalate) copolymers, and their mixtures.

These fixative resins are preferably dispersed or dissolved in the chosen vehicle.

The cosmetic compositions forming the subject-matter of the invention can also comprise polymeric derivatives exercising a protective function.

These polymeric derivatives can be present in amounts of the order of 0.01 to 10%, preferably approximately 0.1 to 5% and very particularly of the order of 0.2 to 3% by weight, agents such as cellulose derivatives, such as cellulose hydroxyethers, methylcellulose, ethylcellulose, hydroxypropyl methylcellulose or hydroxybutyl methylcellulose poly(vinyl ester)s grafted onto polyalkylene backbones, such as poly(vinyl acetate)s grafted onto polyoxyethylene backbones (EP-A-219,048) poly(vinyl alcohol)s *polyester copolymers based on ethylene terephthalate and/or propylene terephthalate and polyoxyethylene terephthalate units, with an ethylene terephthalate and/or propylene terephthalate (number of units)/polyoxyethylene terephthalate (number of units) molar ratio of the order of 1/10 to 10/1, preferably of the order of 1/1 to 9/1, the polyoxyethylene terephthalates exhibiting polyoxyethylene units having a molecular weight of the order of 300 to 5000, preferably of the order of 600 to 5000 (US-A-3,959,230, US-A-3,893,929, US-A-4,116,896, US-A-4,702,857 and US- A-4,770,666); sulphonated polyester oligomers obtained by sulphonation of an oligomer derived from from ethoxylated allyl alcohol, dimethyl terephthalate and 1,2-propylenediol exhibiting from 1 to 4 sulphonated groups (US-A-4,968,451) polyester copolymers based on propylene terephthalate and polyoxyethylene terephthalate units and terminated by ethyl or methyl units (US-A- 4,711,730) or polyester oligomers terminated by alkyl polyethoxy groups (US-A-4,702,857) or anionic sulphopolyethoxy (US-A-4,721,580) or anionic 36 sulphoaroyl (US-A-4,877,896) groups Spolyester polyurethanes obtained by reaction of a polyesters with a number molecular mass of 300-4000, obtained from adipic acid and/or from terepthalic acid and/or from sulphoisophthalic acid and from a diol with a mass of less than 300, with a prepolymer containing terminal isocyanate groups obtained from a polyoxyethylene glycol with a molecular mass of 600-4000 and from a diisocyanate ((FR-A-2,334,698) ethoxylated monoamines or polyamines or polymers of ethoxylated amines (US-A-4,597,898 and EP-A-11,984) sulphonated polyester oligomers obtained by condensation of isophthalic acid, of dimethyl sulphosuccinate and of diethylene glycol (FR-A-2,236,926).

The performances of the cosmetic compositions forming the subject-matter of the invention can also be improved by the use of plasticizers. The plasticizer can constitute between 0.1 and 20% of the formulation, preferably from 1 to 15%. Mention may be made, -among particularly useful plasticizers, of adipates, phthalates, isophthalates, azelates, stearates, silicone copolyols, glycols, castor oil or their mixtures.

It is also advantageously possible to add, to these compositions, metal-sequestering agents, more particularly those sequestering calcium, such as 37 citrate ions, or emollients, such as silicones or oils or fatty substances used in this connection in the cosmetics industry (mineral oils, fatty acid esters, triglycerides, silicones, and the like).

It is also possible to add water-soluble or water-dispersible polymers, such as collagen or certain non-allergizing derivatives of animal or plant proteins (wheat protein hydrolisates, for example), natural hydrocolloids (guar gum, locust bean gum, tara gum, and the like) or hydrocolloids resulting from fermentation processes, such as xanthan gum, and derivatives of these polycarbohydrates, such as modified celluloses (for example, hydroxyethylcellulose or carboxymethylcellulose), or guar or locust bean derivatives, such as their cationic derivatives or nonionic derivatives (for example, hydroxypropylguar) or anionic derivatives (carboxymethylguar and carboxymethylhydroxypropylguar).

Inorganic powders or particles, such as calcium carbonate, inorganic oxides in the powder form or in the colloidal form (particles with a size of less than or of the order of a micrometre, sometimes of a few tens of nanometres), such as silica, aluminium salts generally used as antiperspirants, kaolin, talc, clays and their derivatives, and the like, can be added in combination to these compounds.

One or more fragrances, colouring agents, among which may be mentioned the products described in Appendix IV ("List of colouring agents allowed for use in cosmetic products") of European Directive No.

76/768/EEC of 27 July 1976, known as the cosmetic directive, and/or opacifying agents, such as pigments, can generally be added to these ingredients to increase the attractiveness during use of the composition by the consumer.

Finally, the composition can also contain viscosifying or gelling polymers, such as crosslinked polyacrylates (Carbopol, sold by Goodrich), cellulose derivatives, such as hydroxypropylcellulose or carboxymethylcellulose, guars and their derivatives, locust bean, tara or cassia gum, xanthan gum, alginates, carrageenans, or chitin derivatives, such as chitosan, used alone or in combination, or the same compounds, generally in the form of water-soluble polymers modified by hydrophobic groups bonded covalently to the polymer skeleton, as described in Patent WO 92/16187, and/or water, in order to bring the total of the constituents of the formulation to 100%.

The cosmetic compositions forming the subject-matter of the invention can also comprise polymeric dispersing agents in an amount of the order of 0.1 to 7% by weight, in order to control the calcium and magnesium hardness, agents such as: Swater-soluble salts of polycarboxylic acids with a molecular mass of the order of 2000 to 100,000, obtained by polymerization or copolymerization of ethylenically unsaturated carboxylic acids, such as acrylic acid, maleic acid or anhydride, fumaric acid, itaconic acid, aconitic acid, mesaconic acid, citraconic acid or methylenemalonic acid, and very particularly polyacrylates with a molecular mass of the order of 2000 to 10,000 (US-A-3,308,067) or copolymers of arylic acid and of maleic anhydride with a molecular mass of the order of 5000 to 75,000 (EP-A-66,915) Spoly(ethylene glycol)s with a molecular mass of the order of 1000 to 50,000.

The following examples illustrate the invention without, however, limiting the scope thereof.

EXAMPLES

Example 1 Preparation of a dispersion of particles according to the invention with a silicabased treatment Preparation of the starting particles The following are successively added to 1300 g of a 1.73 mol/kg titanium oxychloride solution: 121 g of 36% hydrochloric acid, 15.14 g of citric acid, 1562 g of purified water, 10.30 g /TiO 2 of anatase seeds exhibiting a size of between 5 and 6 nm.

The mixture is brought to boiling point is is maintained there for 3 h.

The solution is subsequently filtered and the particles obtained are washed with water until the chlorides have been completely removed. They are subsequently redispersed at pH 9 (controlled by the addition of sodium hydroxide) with a solids content of by weight.

The size of the particles, measured by TEM, is 60 nm. X-ray diffraction analysis shows that the particles are based on titanium dioxide solely in the anatase form.

The relative density is 2.52 (Vi 0.14 cc/g).

The specific surface, measured by the BET method on the particles of the dispersion dried at a degassing temperature of 150 0 C, is 300 m 2 /g.

Treatment of the particles with silica 750 g of the above dispersion are introduced with stirring into 750 g of deionized water.

The mixture obtained is transferred into a reactor and the temperature is raised to 90 0 C. The pH is adjusted to 9 by the addition of sodium hydroxide.

A sodium silicate solution (solution containing 335 g/l of SiO 2 containing the equivalent of 30 g of SiO 2 and an 80 g/l sulphuric acid solution are introduced therein continuously and simultaneously.

The flow rate of the alkali metal silicate solution is set at 2 ml/min and the pH is regulated at 9 by the addition of sulphuric acid.

After introducing the reactants, the temperature is maintained at 90 0 C for 2 h.

After cooling, the dispersion is centrifuged.

The cake obtained is washed three times with water and then redispersed at pH 8.5 with a solids content of by weight.

Properties of the particles obtained The size of the particles, measured by TEM, is 60 nm.

The specific surface, measured by the BET method on the particles of the dispersion which have been dried under vacuum at a temperature of 150 0 C for 4 hours, is 140 m 2 /g.

The level of SiO 2 measured by X-ray fluorescence, is 19% by weight with respect to the titanium dioxide.

The relative density is 2.2.

The viscosity is 750 mPa's.

The dispersion index is 0.45. This dispersion is particularly stable: after one month, the measurement of the dispersion index remains at 0.45.

Example 2 Preparation of a dispersion of particles according to the invention with a treatment based on silica and on aluminium hydroxide The starting particles are the same as in Example 1.

Treatment of the particles with silica and with aluminium oxide, hydroxide or hydroxide oxide 750 g of the starting dispersion are introduced into a reactor with a stirrer. 750 g of purified water are then added and the temperature is raised to 90 0 C. The pH of the dispersion is adjusted to 9 by the addition of sodium hydroxide.

First of all, a sodium silicate solution (solution containing 335 g/l of SiO 2 containing the equivalent of 22.5 g of SiO 2 and an 80 g/l sulphuric acid solution, in an amount such that the pH is maintained at 9, are introduced continuously and simultaneously. The flow rate of the sodium silicate solution is set at 2 ml/min. A maturing time of 1 h at 0 C is subsequently observed.

Subsequently, an aqueous sodium aluminate solution (solution containing 240 g/l as A1 2 0 3 containing the equivalent of 7.5 g of A1 2 0 3 is introduced continuously at pH 9 and at 90 0 C. The flow rate of the aluminate solution is 2 mi/min and the pH is regulated at 9 by simultaneous introduction of a 6N aqueous sulphuric acid solution.

When the reactants have been introduced, a maturing time of 2 h at 90 0 C is observed and then the dispersion is cooled.

The dispersion obtained is centrifuged. The cake obtained is washed three times with water and is then redispersed.

The pH of the dispersion is adjusted to by addition of H 2

SO

4 and it exhibits a solids content of by weight.

43 Properties of the particles obtained The size of the particles, measured by TEM, is 60 nm.

The specific surface, measured by the BET method on the particles of the dispersion which have been dried under vacuum at a temperature of 150 0 C under vacuum, is 135 m 2 /g.

The level of SiO 2 measured by X-ray fluorescence, is 14.9% by weight and that of A1 2 0 3 is The viscosity is 750 mPa's.

The relative density is 2.15.

Example 3 Stability of the dispersion of Example 2 as a function of the pH The pH of the dispersion of Example 2 is varied by addition of sulphuric acid or sodium hydroxide. The dispersion indices associated with each pH are combined in the following table.

pH dispersion index 0.43 0.35 (Ex. 2) 0.45 8 0.31 0.31 It is observed that, for a pH varying from to 10, the dispersion index remains below 0.45.

Example 4 Anti-UV cosmetic preparation An anti-UV cosmetic composition according to the invention is prepared from the titanium dioxide dispersion of Example 3, the following formulation being followed:

CTFA

cyclomethicone and diphenyl dimethicone caprylic capric triglyceride octyl palmitate mineral oil PVP/eicosene copolymer vitamin E acetate glyceryl stearate propyleme glycol stearate glyceryl isostearate Ingredients Mirasil

C-DPDM

Miglyol 812 N Crodamol OP Marcol 82 Antaron V220 Hydrolactol by weight 4 4 4 3 0.3 propyleme glycol isostearate olleth ceteth potassium cecyl phosphate polysorbate 20 preservative allantoin xanthan gum dispersion, Example 2 Amphisol K Tween 20 Germaben II Rhodicare D 2 1 0.2 0.2 0.2 15.6 as TiO2) q.s. q.s. 100 lactic acid deionized water Measurement of photostability of the composition The cosmetic composition to be tested is introduced via a quartz cell into a Heraeus Sun-Test device and subjected to energy E of 500 W/m 2 at a temperature T of 30 0 C for 1 h.

The photostability is monitored by visual observation of the colouring of the formulation.

Visually, no blueing is observed.

Measurement of the in vitro SPF (Sun Protection Factor) number This number was measured using an SPF290 optometry device according to the method described in "Cosmetics Toiletries", Vol. 107, No. 10, p.119.

The SPF number is 20 2 for an application of 2 mg/cm 2 46 Measurement of the dispersion index of the titanium particles in the formulation The dispersion index is 0.45, that is to say identical to that of the dispersion of titanium dioxide particles before formulation.

ViT~2L

Claims

1. Anatase titanium dioxide particles with a size of at most 100 nm, wherein these particles are at least partially covered with a layer of at least one metal oxide, hydroxide or hydroxide oxide and wherein these particles exhibit a BET specific surface of at least 70 m 2 /g and a relative density of the order of 2.2.

2. Particles according to claim 1, wherein the ratio by weight of the metal oxide(s), hydroxide(s) or hydroxide oxide(s) to the titanium dioxide is at most 60% by weight.

3. Particles according to claim 1 or 2, wherein they are at least partially covered with 0S a layer of silica or of an aluminium hydroxide or hydroxide oxide in the simple or mixed 10 form. ooS

4. Particles according to claim 2, wherein they are covered with a layer of silica and S•of aluminium hydroxide or hydroxide oxide in contents by weight of 15% of Si0 2 and '0 5% of A1 2 0 3 with respect to the titanium dioxide.

Particles according to any one of the preceding claims, wherein they are provided S.1: 15 in the form of a dispersion.

6. Particles according to claim 5, wherein their dispersion index of the particles in the liquid phase is at most

7. Particles according to claim 5 or 6, wherein the liquid phase of the dispersion is o...aqueous. 20

8. Particles according to claim 7, wherein the dispersion exhibits a conductivity of at most 3 msiemens. /21088-00DO 2 088-00.DOC -48-

9. Particles according to any one of claims 5 to 7, wherein the solids content of the dispersion is at least 35% by weight and in that the viscosity of the said dispersion is at most 1000 mPa-s.

Particles according to any one of claims 1 to 4, wherein they are agglomerated and are provided in the form of a powder.

11. Process for the preparation of particles according to any one of claims 1 to wherein at least one metal oxide, hydroxide or hydroxide oxide is precipitated at the surface of anatase titanium dioxide particles with a size of at most 100 nm exhibiting a BET specific surface of at least 200 m 2 /g and a relative density of the order of 10

12. Preparation process according to claim 11, wherein at least one metal oxide, 0 hydroxide or hydroxide oxide is precipitated at the surface of titanium dioxide particles obtained by hydrolysis of at least one titanium compound A in the presence of at least one compound B chosen from: the acids which exhibit: 15 either a carboxyl group and at least two *0 C

21088-0.DOC -49- hydroxyl and/or amine groups, or at least two carboxyl groups and at least one hydroxyl and/or amine group, (ii) the organic phosphoric acids of following formulae: O R2 O HO OH P -P HO" R1 OH O OH O HO OHH HO II 1 II 'OH P -C p HO R3 OH O OH II/ HO O CH 2 -P-OH P-CH 2 -[N-(CH 2 )mp-N HO CIH CH 2 -P-OH O=P-OH O OH *OH in which n and m are integers of between 1 and 6 and p is an integer of between 0 and 5, R1, R2 and R3, which are identical or different, representing a hydroxyl, amino, aralkyl, aryl or alkyl group or hydrogen, (iii) the compounds capable of releasing sulphate ions in acidic medium, (iv) the salts of the acids described above, and in the presence of anatase titanium dioxide seeds exhibiting a size of at most nm and in a ratio by weight, expressed as TiO 2 present in the seeds/titanium present before introduction of the seeds in the hydrolysis medium, expressed as TiO 2 of between 0.01% and 3%.

13. Process according to claim 12, wherein the titanium compound A is titanium oxychloride.

14. Process according to claim 12 or 13, wherein the compound B is citric acid. Use of particles according to any one of claims 1 to 9 as anti-UV agent. 16. Use according to claim 15 in cosmetic, varnish or paint formulations and in plastics. 17. Anti-UV cosmetic composition, wherein it comprises titanium dioxide particles according to any one of claims 1 to 10, in an amount such that the content of titanium dioxide in the said composition is at least 1% and preferably at most 25% by weight. 18. Anatase titanium dioxide particles substantially as herein described with'reference to any of the examples but excluding comparatives. 19. A process for the preparation of anatase titanium dioxide particles substantially as herein described with reference to any of the examples but excluding comparatives. An anti-UV cosmetic composition substantially as herein described with reference to any of the examples but excluding comparatives. DATED this 13th Day of September, 2000 •RHODIA CHIMIE RHDI Attorney: CHARLES W. TANSEY Registered Patent Attorney of 20 The Institute of Patent and Trade Mark Attorneys of Australia of BALDWIN SHELSTON WATERS