Drug – bio-affecting and body treating compositions – Dentifrices
Reexamination Certificate
2000-05-16
2001-11-06
Rose, Shep K. (Department: 1614)
Drug, bio-affecting and body treating compositions
Dentifrices
C106S162800, C106S731000, C106S805000, C162S027000, C162S076000, C162S187000, C426S658000, C426S573000, C514S781000
Reexamination Certificate
active
06312669
ABSTRACT:
This application is an application under 35 U.S.C. Section 371 of International Application Number PCT/FR98/01888, filed on Sep. 03, 1998.
The present invention relates to the use of essentially amorphous cellulose nanofibrils in buccodental formulations, and to the formulations thus obtained.
More specifically, the present invention relates to a novel thickener for buccodental formulations, which has in particular better thermal and ionic stability than the conventional thickeners, without any adverse impact on the other advantages required.
Usually, buccodental formulations contain wetting agents such as glycerol, polyethylene glycol or sorbitol, inorganic abrasive agents such as amorphous silica, hydrated or unhydrated dicalcic phosphates, calcium carbonate, washing surfactants, active agents such as antibacterial agents, for instance chlorhexidine, fluorine derivatives, enzymes and sweeteners such as sodium saccharinate, as well as many other components which contribute more particularly towards giving the said formulations a specific appearance, a particular taste and/or specific properties.
Among all of these compounds, some are in a water-soluble form while others, on the other hand, are in a solid powder form. To formulate them as a homogeneous mixture, it is thus necessary also to incorporate into the formulation at least one auxiliary agent acting more particularly as a binder for these various compounds. In parallel with this function, this agent generally contributes towards giving the buccodental formulation adequate rheological behaviour for the application envisaged, and is directed in particular towards thickening it. As representative examples of these conventional thickeners for buccodental formulations, mention may be made of thickening silicas, alginates, polysaccharides such as natural gums, for instance carrageenans, xanthan and guar and most particularly cellulose derivatives such as carboxymethylcellulose and hydroxyethylcellulose.
In point of fact, the thickeners of cellulose derivative type currently available are not entirely satisfactory.
It is necessary to use large amounts of them, about 1% approximately, in order to obtain a suitable viscosity. Moreover, formulations containing them are subject to considerable variations in viscosity when faced with high temperatures, or comprise a high ionic charge.
Lastly, the formulations based on these cellulose derivatives are not entirely satisfactory in aesthetic terms. Thus, compositions such as toothpaste, thickened with these cellulose derivatives, do not behave well on the toothbrush.
The object of the present invention is, precisely, to propose a novel thickener which is free of the abovementioned drawbacks but which has, on the other hand, advantageous rheological behaviour.
The Applicant has thus demonstrated that cellulose nanofibrils, that are essentially amorphous and advantageously obtained from primary walls, advantageously satisfy these two imperatives. Unexpectedly, cellulose fibres of this type show good compatibility with regard to the other components present in buccodental compositions.
In general, native cellulose is always in a fibrillar form. Its fibrils are well-known materials which have, in particular, already been proposed for modifying the texture of media into which they are introduced. In the case of fluid media, they modify their viscosities or even their rheological profiles.
Cellulose fibrils can be of diverse origin, for example of plant, bacterial, animal, fungal or amoebic origin.
Cellulose fibrils are usually strongly self-associated in the walls or the fibres. Secondary walls, which are mainly found in wood, are distinct from primary walls, a typical example of which is parenchyma. Examples of parenchyma consist of sugarbeet pulp, citrus fruits (lemons, oranges and grapefruit) and most fruit and vegetables.
In the secondary walls, these fibrils are organized in the form of highly oriented sheets thus forming an indissociable fibre. They are conventionally in the form of aggregates from a few tens of nanonetres to a few micrometres. These aggregates consist of elementary microfibrils which cannot be disentangled, during their homogenization, without resulting in breaking them.
In the context of the present invention, the cellulose fibrils considered are cellulose nanofibrils, CNF, preferably obtained from cells with primary walls.
In contrast with the cellulose microfibrils from secondary walls discussed above, they have a diameter of not more than a few nanometres and have the appearance of filaments. Advantageously, it is possible to disentangle these cellulose nanofibrils from primary walls during homogenization steps.
The main subject of the present invention is thus a buccodental formulation, characterized in that it comprises at least one thickener comprising cellulose nanofibrils, the said cellulose nanofibrils being essentially amorphous and having a degree of crystallinity of less than or equal to 50 %.
In the preferred variant of the invention, the cellulose nanofibrils are obtained from cells preferably consisting of at least about 80% primary walls. Preferably, the amount of primary walls is at least 85% by weight.
The nanofibrils will, in this case, have at least 80% of cells with primary walls.
They preferably have a section of between about 2 and about 10 nm. More preferably, this is between about 2 and about 4 nm.
In the context of the invention, the nanofibrils considered are so-called essentially amorphous nanofibrils, in contrast with so-called crystalline fibrils.
The term essentially amorphous is understood to define nanofibrils whose degree of crystallinity is less than or equal to 50%. According to a specific variant of the present invention, this degree of crystallinity is between 15% and 10% and more preferably less than 50%.
These essentially amorphous cellulose nanofibrils are particularly advantageous with regard to crystalline microfibrils, in the sense that they are dispersible in aqueous media, they give very specific rheological properties of rheofluidifying type and they are stable, either thermally or in media containing high ionic charges. In this regard, the essentially amorphous nanofibrils according to the invention advantageously give excellent viscosity to the formulations incorporating them and do so for a low concentration, of about 0.15% by weight, as against 1% for standard cellulose derivatives.
This good efficacy shown, at low dose, by the cellulose nanofibrils is in fact a consequence of their excellent rheological behaviour in terms of viscosity and rheofluidifying power.
The cellulose nanofibrils used according to the invention moreover show an ability to reinforce the flavours present in the buccodental formulations into which they are introduced. The sensory perception of the flavour by the user is accentuated.
According to a preferred mode of the invention, the cellulose nanofibrils forming part of the formulations claimed are laden at the surface with carboxylic acids and with acidic polysaccharides, alone or as a mixture.
The term carboxylic acids is understood to refer to simple carboxylic acids, as well as salts thereof. These acids are preferably chosen from uronic acids and are more particularly galacturonic acid and/or glucuronic acid.
As acidic polysaccharides, mention may be made of pectins including, more particularly, polygalacturonic acids. These acidic polysaccharides can be present as a mixture with hemicelluloses.
In fact, these surface-laden nanofibrils do not result from a simple mixing between the said nanofibrils and the acids and polysaccharides. Rather, it is a close combination between these two types of compounds derived directly From the process used to prepare the nanofibrils. The reason for this is that this preparation process can be such that the acids and polysaccharides are not totally separated from the fibres but remain at the surface of these fibres, thus giving them very specific properties. It is important to emphasize that these same properties will not be reproduced if the process su
Cantiani Robert
Willemin Claudie
Rhodia Chimie
Rose Shep K.
Seugnet Jean-Louis
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