Field of the Invention The present invention relates to oral care compositions. More particularly the invention relates to oral care compositions which comprise fatty acyl isethionate.

Background of the Invention Foam is a desirable characteristic of oral care compositions such as dentifrices, since it enables the dentifrice to spread throughout the oral cavity during brushing and contact tooth surfaces thoroughly. Compositions with good foaming ability are also preferred by consumers since the foaming provides the perception that the composition is cleaning effectively.

Good foaming ability is generally achieved in oral care compositions by the use of an anionic surface active agent. Sodium lauryl sulphate (SLS) is the most commonly used anionic surfactant, and a typical dentifrice contains up to 2 or 3% of SLS (by weight based on total weight) for its foaming and surfactant action.

Anionic surface active agents such as SLS have been associated in some cases with mild adverse effects such as unpleasant flavour reactions when drinking or eating citrus shortly after tooth brushing. Accordingly, for consumers susceptible to these effects it would be desirable to reduce the content of anionic surface active agents such as SLS.

It is an object of the present invention to provide oral care compositions in which SLS may be reduced (compared to conventional levels) or omitted without compromising foamability or product rheology. Summary of the Invention

The present invention provides an oral care composition comprising:

(a) a liquid continuous phase comprising water or polyhydric alcohol or a mixture thereof;

(b) from 3 to 75wt% (by weight based on the total weight of the oral care composition) of particulate abrasive cleaning agent;

(c) from 0.5 to 5wt% (by weight based on the total weight of the oral care composition) of fatty acyl isethionate product; (d) from 0.1 to 2wt% (by weight based on the total weight of the oral care composition) of amphoteric surfactant, and (e) from 0 to 1 .5wt% (by weight based on the total weight of the oral care composition) of alkyl sulfate anionic surfactant; in which the fatty acyl isethionate product is defined as a mixture comprising: (i) from 40 to 80wt% (by weight based on the total weight of the fatty acyl isethionate product) of one or more fatty acyl isethionate salts having the general formula (I):

R C(0)OR ² S0 ₃ M (I) in which R is selected from monovalent, linear or branched, saturated or unsaturated hydrocarbon radicals having 5 to 31 carbon atoms, R ² is selected from divalent, linear or branched, saturated hydrocarbon radicals having 2 to 6 carbon atoms, and M is a solubilising cation (such as lithium, sodium, potassium, ammonium or substituted ammonium), and

(ii) from 15 to 50wt% (by weight based on the total weight of the fatty acyl isethionate product) of one or more fatty acids of formula R C(0)OX, wherein R is as defined above and X is hydrogen or a solubilising cation M as defined above.

Detailed Description of the Invention Liquid continuous phase

The composition of the invention has a liquid continuous phase comprising water or polyhydric alcohol or a mixture thereof.

Preferred product forms for compositions of the invention are those which are suitable for brushing and/or rinsing the surfaces of the oral cavity.

In such preferred product forms, the amount of water and/or polyhydric alcohol will generally be at least 10wt%, preferably at least 30wt%, more preferably at least 50wt% (by total weight water and/or polyhydric alcohol based on the total weight of the composition).

An example of a preferred type of product form in the context of the present invention is a dentifrice. The term "dentifrice" generally denotes formulations which are used to clean the surfaces of the oral cavity. The dentifrice is an oral composition that is not intentionally swallowed for purposes of systemic

administration of therapeutic agents, but is applied to the oral cavity, used to treat the oral cavity and then expectorated. Typically the dentifrice is used in conjunction with a cleaning implement such as a toothbrush, usually by applying it to the bristles of the toothbrush and then brushing the accessible surfaces of the oral cavity. Preferably the dentifrice is in the form of a paste or a gel (or a combination thereof).

A dentifrice composition according to the invention will usually contain a liquid continuous phase in an amount of from 40 to 99wt% (by total weight liquid continuous phase based on the total weight of the dentifrice). Such a liquid continuous phase will typically comprise a mixture of water and polyhydric alcohol in various relative amounts, with the amount of water generally ranging from 10 to 45wt% (by total weight water based on the total weight of the dentifrice) and the amount of polyhydric alcohol generally ranging from 30 to 70wt% (by total weight polyhydric based on the total weight of the dentifrice). Typical polyhydric alcohols include humectants such as glycerol, sorbitol, polyethylene glycol, polypropylene glycol, propylene glycol, xylitol (and other edible polyhydric alcohols),

hydrogenated partially hydrolyzed polysaccharides and mixtures thereof.

Particulate abrasive cleaning agent

The composition of the invention comprises a particulate abrasive cleaning agent in an amount of from 3 to 75wt% (by total weight particulate abrasive cleaning agent based on the total weight of the oral care composition). Suitable particulate abrasive cleaning agents include silica xerogels, hydrogels and aerogels and precipitated particulate silicas; calcium carbonate, dicalcium phosphate, tricalcium phosphate, calcined alumina, sodium and potassium metaphosphate, sodium and potassium pyrophosphates, sodium trimetaphosphate, sodium hexametaphosphate, particulate hydroxyapatite and mixtures thereof. Fatty acyl isethionate product

The fatty acyl isethionate product as defined above may typically be prepared by the reaction of at least one fatty acid of formula R C(0)OH (in which R has the definition described above) with at least one hydroxyalkylsulfonic acid salt of the formula HOR ² S03M (in which R ² and M have the definitions described above).

Suitable fatty acids for use in the preparation of the fatty acyl isethionate product include those in which R is a linear or branched, saturated or unsaturated hydrocarbon radical having 5 to 21 carbon atoms. Such fatty acids may be naturally occurring or synthetic or a mixture thereof. Naturally occurring fatty acids are usually mixtures of acids having a hydrocarbon chain of varying length. For example, "coconut fatty acid" as used herein is a mixture containing a range of carboxylic acids in which the R carbon chain length ranges from about 7 to 17 carbon atoms, with some unsaturation which may be removed by hydrogenation. Thus, hydrogenated coconut fatty acid is a mixture containing a range of carboxylic acids in which the R carbon chain length ranges from about 7 to 17 carbon atoms, mostly lauric and myristic acids, together with some capric and caprylic acids, and contains very little, if any, unsaturation.

Preferred fatty acids are those in which R is a linear or branched, saturated or unsaturated hydrocarbon radical having 7 to 17 carbon atoms. Specific examples of preferred fatty acids include coconut fatty acid (R having 7 to 17 carbon atoms), hydrogenated coconut fatty acid (R having 7 to 17 carbon atoms), lauric acid (R having 1 1 carbon atoms), palmitic acid (R having 15 carbon atoms), palm kernel fatty acid (R having 7 to 17 carbon atoms), oleic acid (unsaturated R having 17 carbon atoms), stearic acid (saturated R having 17 carbon atoms), tallow fatty acid (partially unsaturated R mainly having 15 and 17 carbon atoms), and hydrogenated tallow fatty acid. Mixtures of any of the above described fatty acids may also be used.

Suitable hydroxyalkylsulfonic acid salts for use in the preparation of the fatty acyl isethionate product include those in which R ² has the general formula (II):

-CH(R ³ )-CH(R ⁴ )- (II) in which R ³ and R ⁴ are each independently selected from H,

-CH ₃ and -CH2CH3.

Specific examples of preferred hydroxyalkylsulfonic acid salts include

hydroxyethylsulfonic acid salts such as sodium hydroxyethylsulfonate. Other specific examples of preferred hydroxyalkylsulfonic acid salts include alkyl- substituted hydroxyethylsulfonic acid salts such as the sodium salts of methyl and/or ethyl-substituted hydroxyethylsulfonic acid salts, for example sodium 1 - methyl 2-hydroxy ethane 1 -sulfonate, sodium 2-methyl, 2-hydroxy ethane 1 - sulfonate, sodium 1 -ethyl 2-hydroxy ethane 1 -sulfonate and sodium 2-ethyl, 2- hydroxy ethane 1 -sulfonate.

Mixtures of any of the above described hydroxyalkylsulfonic acid salts may also be used. In a typical process used to prepare the fatty acyl isethionate product (termed the "direct esterification route"), the fatty acid and hydroxyalkylsulfonic acid salt are mixed and heated in the presence of a metal catalyst. Generally, an excess of fatty acid is used in order to shift the reaction equilibrium to fatty acyl isethionate synthesis. Thus, the molar ratio of fatty acid to hydroxyalkylsulfonic acid salt may range from 1 .3:1 to 1 .1 :1 . The resulting fatty acyl isethionate product is usually termed "directly esterified fatty isethionate" (or DEFI) and may be characterized as a mixture of 40 to 80wt% fatty acyl isethionate (formed from the reaction), 15 to 50wt% free fatty acids, in addition to unreacted hydroxyalkylsulfonic acid salt (generally at levels less than 5 wt%) and traces of other impurities (generally at levels less than 2 wt%).

A preferred class of fatty acyl isethionate product for use in the present invention, and obtainable by a direct esterification process such as that described above, comprises:

(i) from 65 to 80wt% (by weight based on the total weight of the fatty acyl isethionate product) of one or more fatty acyl isethionate salts of general formula R C(0)OR ² S0 ₃ M, in which R is a linear or branched, saturated or unsaturated hydrocarbon radical having 7 to 17 carbon atoms, R ² is -CH ₂ CH ₂ - or -CH(CH3)- CH ₂ - , and M is a solubilising cation such as sodium; and

(ii) from 15 to 30wt% (by weight based on the total weight of the fatty acyl isethionate product) of one or more fatty acids of formula R C(0)OX, wherein R is as defined above and X is hydrogen or a solubilising cation such as sodium.

Most preferably the one or more fatty acyl isethionate salts (i) are selected from sodium cocoyl isethionate, sodium cocoyl methyl isethionate, sodium cocoyl ethyl isethionate and mixtures thereof. Most preferably the one or more fatty acids (ii) may be defined as a mixture (for example of coconut fatty acid and stearic acid and/or their corresponding sodium salts), in which the content of long chain material (typically C16 to ds) is at least 25wt% by weight based on the total weight of the fatty acids (b). The total amount of fatty acyl isethionate product in compositions of the invention preferably ranges from 1 to 4wt%, more preferably from 1 .1 to 3.5wt% (by total weight fatty acyl isethionate product based on the total weight of the composition). Amphoteric surfactant

Compositions according to the invention comprise from 0.1 to 2wt% (by weight based on the total weight of the oral care composition) of amphoteric surfactant. Examples of suitable amphoteric surfactants include alkyl amine oxides, alkyl betaines, alkyl amidopropyl betaines, alkyl sulphobetaines (sultaines), alkyl glycinates, alkyl carboxyglycinates, alkyl amphopropionates,

alkylamphoglycinates, alkyl amidopropyl hydroxysultaines, acyl taurates and acyl glutamates. The alkyl and acyl groups generally contain from 8 to 22 carbon atoms, may be straight or branched chain, and may be saturated or unsaturated.

A preferred class of amphoteric surfactants for use in the invention are alkyl amidopropyl betaines of general formula: R ⁵ -CO-NH-(CH ₂ )3-N ⁺ (CH3)2-CH ₂ COO- in which R ⁵ is a straight or branched chain alkyl group having 10 to 18, preferably 12 to 14 carbon atoms. Mixtures of any of the foregoing amphoteric surfactants may also be suitable.

The total amount of amphoteric surfactant in compositions of the invention preferably ranges from 0.3 to 1 .5%, more preferably from 0.4 to 1 .2% by weight based on the total weight of the composition. Alkyl sulfate anionic Surfactant

The oral care composition of the invention comprises from 0 to 1 .5% alkyl sulfate anionic surfactant (by total weight alkyl sulfate anionic surfactant based on the total weight of the composition).

By "alkyl sulfate anionic surfactant" is generally meant one or more Ce-ie alkyl sulfates and/or Ce-ie alkyl ether sulfates, such as those materials having the general formula:

R ⁶ 0(CH ₂ CH ₂ 0) _n S0 ₃ M in which R ⁶ is an alkyl or alkenyl group having from 8 to 18 (preferably 12 to 18) carbon atoms; n is a number having an average value between 0 and 3 and M is a solubilising cation such as sodium, potassium, ammonium or substituted ammonium. Specific examples include sodium lauryl sulfate (SLS), sodium dodecyl sulfate (SDS), sodium lauryl ether sulfate (SLES) having an average degree of ethoxylation of from 0.5 to 3 (preferably 1 to 3) and mixtures thereof. The total amount of alkyl sulfate anionic surfactant in compositions of the invention preferably ranges from 0 to 0.5%, more preferably from 0 to 0.25% by weight based on the total weight of the composition.

Especially preferred compositions according to the invention comprise:

(a) a liquid continuous phase as defined above;

(b) from 3 to 75wt% (by weight based on the total weight of the oral care composition) of a particulate abrasive cleaning agent as defined above; (c) from 1 .1 to 3.5wt% (by weight based on the total weight of the oral care composition) of a fatty acyl isethionate product as defined above, the product comprising: from 65 to 80wt% (by weight based on the total weight of the fatty acyl isethionate product) of one or more fatty acyl isethionate salts (i) selected from sodium cocoyl isethionate, sodium cocoyl methyl isethionate, sodium cocoyl ethyl isethionate and mixtures thereof; from 15 to 30wt% (by weight based on the total weight of the fatty acyl isethionate product) of one or more fatty acids (ii) which are defined as a mixture (for example of coconut fatty acid and stearic acid and/or their corresponding sodium salts), in which the content of long chain material (typically Ci6 to C-is) is at least 25wt% by weight based on the total weight of the fatty acids (ii);

(d) from 0.4 to 1 .2wt% (by weight based on the total weight of the oral care composition) of an amphoteric surfactant which is cocamidopropyl betaine, and

(e) from 0 to 0.25wt% (by weight based on the total weight of the oral care composition) of an alkyl sulfate anionic surfactant which is sodium lauryl sulphate.

A composition according to the invention will generally contain further ingredients to enhance performance and/or consumer acceptability.

For example, a composition according to the invention which is formulated as a dentifrice will usually contain one or more thickening agents. Suitable thickening agents include carboxyvinyl polymers (such as polyacrylic acids cross-linked with polyallyl sucrose or polyallyl pentaerythritol), hydroxyethyl cellulose, hydroxypropyl cellulose, water soluble salts of cellulose ethers (such as sodium carboxymethyl cellulose and sodium carboxymethyl hydroxyethyl cellulose), natural gums (such as carrageenan, gum karaya, guar gum, xanthan gum, gum arabic, and gum tragacanth), finely divided silicas, hectorites, colloidal magnesium aluminium silicates and mixtures thereof.

The one or more thickening agents will generally be present in sufficient quantities to ensure that the dentifrice is extrudable, retains its shape when squeezed from a tube onto a toothbrush, and will not fall between the bristles of the brush during normal consumer usage. The total amount of such one or more thickening agents in compositions of the invention generally ranges from 0.1 to 15wt% (by total weight thickening agent based on the total weight of the composition). The individual levels of such one or more thickening agents depends on the material chosen. Polymeric thickening agents (such as the carboxyvinyl polymers and natural gums described above) will generally be present in individual amounts ranging from about 0.1 to about 1 % by weight based on the total weight of the composition. Inorganic thickening agents (such as the finely divided silicas described above) will generally be present in individual amounts ranging from about 2 to about 10%, preferably about 3 to about 8%, weight based on the total weight of the composition.

Compositions of the present invention (such as in particular dentifrices) may also contain further optional ingredients customary in the art such as fluoride ion sources, anticalculus agents, buffers, flavouring agents, sweetening agents, colouring agents, opacifying agents, preservatives, antisensitivity agents and antimicrobial agents.

The invention is further illustrated with reference to the following, non-limiting Examples. EXAMPLES

The following formulations illustrate dentifrice compositions according to the invention:

Directly esterified fatty isethionate (DEFI): a mixture of about 70wt% (by weight based on total mixture weight) of sodium cocoyi isethionate with about 20wt% (by weight based on total mixture weight) of free palmitic and stearic fatty acids

Branched DEFI with sodium lauroyl methyl isethionate

The above formulations were evaluated for foam height, foam quality and rheology. All gave good, creamy foam, with the required rheology profile for a dentifrice.