Tooth pastes

[0004] The present invention relates to bleaching and hygienizing compositions having improved chemical and chemical-physical stability which is maintained during the time even after prolonged storage (shelf stability), even over 6 months.

[0005] More specifically the invention relates to compositions to be used for preparing tooth pastes of complex compositions.

[0006] The bleaching and hygienizing properties of organic peroxiacids, in particular of aliphatic peroxyphthalimidic acids, such as typically the epsilon-phthalimido peroxyhexanoic acid, known as PAP, are known, see for examples EP 325,289 and EP 325,288. The reactivity of the aliphatic peroxyphthalimidic acids makes their use interesting in various applications, but it is also a technical problem from the point of view of the preparation of formulations having high stability during the time. Indeed said organic peroxyacids react very quickly wherefore it is not possible to prepare complex formulations, such as those of the tooth pastes, stable during the time.

[0007] The shelf-stability of the tooth paste formulation is therefore an essential feature for the same.

[0008] In tooth pastes one could think to use organic peroxyacids and specifically the phthalimido-peroxyalkanoic acids introduced in many component compositions as chemical agents having bleaching and hygienizing action to improve these properties with respect to the conventional compositions, which are based on the physical-mechanical action of the abrasive compounds contained in the tooth pastes. However it must be noted that organic peroxides must be able to operate under particularly mild conditions and at the same time to maintain their activity during the time even after prolonged storage, without changing the system organoleptic characteristics, as defined below.

[0009] As regards tooth pastes it is known the efficacy of the proxyacetic acid for the preparation of formulations having an improved bleaching effect, see for example EP 545,594.

[0010] The efficacy of phthalimido-alkanoic and/or cationic peroxyacids for the preparation of tooth systems having a bleaching activity is also known, see for example patent application WO 96/05802. In the case of the phthalimido-peroxyalkanoic acids, which have a remarkable chemical reactivity and bleaching and hygienizing activity, besides favourable toxicological properties, it is difficult to obtain monocomponent formulations for tooth pastes having polyfunctional characteristics. In said patent application, in order to prepare tooth pastes, a bicomponent system formed of two complementary but separated formulations, which are mixed together at the time of the use, is employed. This solution allows to maintain all the properties of the phthalimido-alkanoic peroxyacids but from the practical point of view it represents a limitation since it requires more complex equipments typical of bicomponent systems.

[0011] The solution which allows to obtain a monocomponent formulation comprising the phthalimido-alkanoic proxyacids has been described in EP 895,777. In this patent adducts between said peroxyacids and cyclodextrins are used, which allow to improve the stability of the peroxycarboxylic acids without reducing the activity and efficacy thereof.

[0012] Tests carried out by the Applicant have shown that with the formulations exemplified for tooth pastes in EP 895,777 tooth pastes having a greater stability in the time are obtained, however it is required that tooth pastes of industrial and commercial interest show a greater stability as regards organoleptic properties, also in the long term. More specifically the stability required to tooth pastes of industrial and commercial interest represents not only the substantial maintenance of the active oxygen titre, the sole characteristic of stability reported in EP 895,777, but also the maintenance of the organoleptic properties such as: colour, taste, homogeneity (uniformity) of the paste for a long time, combined with easiness to flow from the consumer tube and maintenance of this feature for a long period, and of the chemical-physical properties such as: pH, density and viscosity.

[0013] The need was felt to have available commercially usable tooth paste compositions having improved stability as above defined.

[0014] It has been surprisingly and unexpectedly found by the Applicant that it is possible to further improve said stability by the formulations described hereinafter:

[0015] An object of the present invention are tooth pastes comprising:

[0016] a) imido-alkanpercarboxylic acids of general formula:

[0017] wherein A is a group of formula

[0018] n is an integer 0, 1 or 2,

[0019] R¹is hydrogen, chlorine, bromine, C₁-C₂₀alkyl,

[0020] C₂-C₂₀alkenyl, aryl or alkylaryl,

[0021] R²is hydrogen, chlorine, bromine or a group of formula —SO₃M, —CO₂M, —CO₃M, —OSO₃M,

[0022] M is hydrogen, an alkaline metal or ammonium ion or the equivalent of an alkaline-earth metal ion and x is C₁-C₁₉alkylene or arylene;

[0023] Y is a C₃-C₁₉, alkylene, under the form of adducts with cyclodextrins, preferably beta-cyclodextrins,

[0024] b) aliphatic carboxylic acids having a solubility in water at room temperature higher than or equal to 5% by weight and containing one or more carboxylic functions.

[0025] Aliphatic oxyacids containing one or more —OH functions are the preferred components b). In particular, as an example, lactic acid, citric acid, tartaric acid, etc., can be mentioned. Also various kinds of isomers can be used where possible. For example as for tartaric acid the (L), (D), meso or racemic form can be used.

[0026] The component b) amount ranges from 0.05 to 5% by weight, preferably 0.1-1% by weight, of the tooth paste.

[0027] Preferably component b) is used encapsulated, f.i. as it is common in the pharmaceutical field.

[0028] In component a) the molar ratio between the peroxyacids of the invention and cyclodextrins, PAP-cyclodextrins adduct, is in the range 1:1-1:2.

[0029] Among immidoalkanpercarboxylic acids of component a) the phthalimido-peroxycarboxylic acids are preferred, more preferably the epsilon-phthalimido-peroxyhexanoic acid.

[0030] Among cyclodextrins we can mention alpha, beta, gamma or delta cyclodextrins, modified alpha, beta, gamma or delta cyclodextrins with acyl, alkyl, hydroxyalkyl groups, generally having from 1 to 10 carbon atoms, preferably from 2 to 6; the mixtures of said cyclodextrins and the mixtures of said cyclodextrins with dextrins or linear oligosaccharides; beta-cyclodextrins are preferably used.

[0031] A process for preparing the adducts of peroxyacid and in particular of the epsilon-phthalimido peroxyhexanoic acid with cyclodextrins, in particular beta-cyclodextrins, is described in EP 895,777, herein incorporated by reference.

[0032] Tooth pastes contain as well known, among others, the conventional components indicated below, which must however show the characteristic to be chemically compatible with component a). This compatibility (COMPATIBILITY TEST) is experimentally determined by measurements of the adduct thermal stability in the presence of the single conventional component. By thermal stability it is meant the maintenance from the component a) of its titre in active oxygen, i.e. a maximum reduction of said titre of 10% after one week of exposure at the temperature of 450° C. As typical conventional components: wetting agents, preservatives, thickeners, dyes, aromas, sweeteners, abrasives and detergents can be mentioned.

[0033] It has been found by the Applicant that the above test is satisfied with the typical conventional components of the tooth paste.

[0034] Among wetting agents there can be water, glycerine, sorbitol; among preservatives: parabens, imidazolidinylurea; among thickeners: cellulose esters, alginates, silica, carrageen; among dyes those of common food use; among aromas especially the derivatives of mint, carnation, anise, orange, bergamot, eucalyptus, etc.; among sweeteners saccharin and its derivatives, xylitol and mannitol; among abrasives: silica, alumina, dihydrate calcium phosphate; among detergents sodium lauryl sulphate, etc.

[0035] Preferred tooth pastes according to the invention are the following: (% by weight):

[0036] Aromas can be used as such, preferably they are used comilled. With comilled it is meant a mixture between aroma and an inert specific support, for example silica, carboxymethylcellulose and other cellulose derivatives, obtainable for example by a comilling process.

[0037] Some examples are hereinafter reported for illustrative purposes but they are not limitative of the present invention.

[0038] 10 kg of tooth paste have been prepared with a turbo emulsifier under vacuum by using the following composition (in % by weight):

[0039] The compatibility of each component has been evaluated by using the compatibility test indicated in the description. This test was satisfied by each component.

[0040] An uniform (homogeneous) product having the following characteristics was obtained:

[0041] organoleptic properties: a homogeneous translucid gel appearance having a green-blue colour and a pleasant, fresh and persistent taste, consistency of isotropic fluid; pH=5.7 (in dispersion at 10% in water at 25° C.), density 1.334 Kg/l at 20° C., viscosity 304,000 centipoise at 20° C. measured by Brookfield viscometer. The tooth paste obtained was put into a conventional tube for tooth paste and showed an easiness to flow for 8 months, by opening and closing the tube three times a day. The tooth paste maintained the homogeneity for 8 months. The test was stopped at 8 months.

[0042] The organoleptic characteristics have been evaluated as follows:

[0043] Appearance: visually;

[0044] Colour: visually;

[0045] Taste: during the use;

[0046] Consistency: visually.

[0047] The results are reported in Table 1.

[0048] 10 kg of tooth paste have been prepared with a turbo emulsifier under vacuum by using the following composition (in % by weight):

[0049] The used comilled aroma was a mixture between aroma and silica (as support).

[0050] An uniform product having the following characteristics was obtained:

[0051] organoleptic properties: a homogeneous translucid gel appearance having a green-blue colour and a pleasant, fresh and persistent taste, consistence of isotropic fluid; pH=5.6 (in dispersion at 10% in water at 250° C.), density 1.330 Kg/l at 20° C., viscosity 306,000 centipoise at 20° C. measured by Brookfield viscometer.

[0052] The results are reported in Table 1.

[0053] 10 kg of tooth paste have been prepared with a turbo emulsifier under vacuum by using the following composition (in % by weight):

[0054] The used comilled aroma was a mixture between aroma and carboxymethylcellulose (as support).

[0055] An uniform product having the following characteristics was obtained:

[0056] organoleptic properties: a homogeneous translucid gel appearance having a green-blue colour and a pleasant, fresh and persistent taste, consistency of isotropic fluid; pH=5.9 (in dispersion at 10% in water at 250° C.), density 1.332 Kg/l at 20° C., viscosity 308,000 centipoise at 20° C. measured by Brookfield viscometer.

[0057] The results are reported in Table 1.

[0058] 10 kg of tooth paste have been prepared with a turbo emulsifier under vacuum by using the following composition (in % by weight):

[0059] An uniform product having the following characteristics was obtained:

[0060] organoleptic properties: a homogeneous translucid gel appearance having a green-blue colour and a pleasant, fresh and persistent taste, consistency of isotropic fluid; pH=6.9 (in dispersion at 10% in water at 25° C.), density 1.330 Kg/l at 20° C., viscosity 300,000 centipoise at 20° C. measured by Brookfield viscosimeter.

[0061] The results are reported in Table 1.

[0062] A quick ageing test has been carried out under controlled conditions by putting the samples of the tooth pastes obtained in the Examples from 1 to 4 in a stove at a constant temperature of 40° C. for 180 days.

[0063] The data noticed at the end of the ageing test concerning the organoleptic and chemical-physical properties of the samples are reported in Table 1.

[0064] The data show that the invention pastes remain stable from the organoleptic point of view also after quick ageing of 180 days and therefore they are suitable to marketing. The pastes not according to the invention lose their organoleptic characteristics due to ageing and therefore they have no industrial interest.

[0065] Example 3 has been repeated, but using as aroma a combination of free aroma and comilled aroma in the following amounts: 0.5% by weight and 2.7% by weight respectively.

[0066] Both the obtained product and its stability characterization (see Example 5) are similar to those of Example 3.

[0067] 10 kg of tooth paste have been prepared with a turbo emulsifier under vacuum by using the following composition (in % by weight):

[0068] An uniform product having the following characteristics was obtained:

[0069] organoleptic properties: appearance of a paste with green-blue coloured microgranules having a pleasant, fresh and persistent taste, consistency of isotropic fluid; pH=5.8 (in dispersion at 10% in water at 25° C.), density 1.336 Kg/l at 200° C., viscosity 308,000 centipoise at 20° C. measured by Brookfield viscometer.

[0070] The organoleptic characteristics have been evaluated as before, the results are similar to Ex. 1.

[0071] The easiness to flow has been evaluated as in Ex. 1 but for 1 year. The tooth paste passed this test and homogeneity was maintained.