EP3643198A1 - Applicator brush for viscous products - Google Patents

Abstract

An application method of a viscous product and applicator brush thereof is disclosed, the latter comprising a support stem wherefrom a plurality of bristles consisting of radially protruding monofilaments project, wherein
said monofilaments are arranged with a density ranging between 10 and 50 per coil,
the lateral surface of said monofilaments is provided with flocking fibres extending substantially radially with respect to the longitudinal axis of said monofilaments,
said flocking fibres are of a length between 0.4 mm and 2 mm and a cross-section between 0.9 and 22 Dtex, and wherein
said flocking fibres are arranged with a flocking density per coil (DFs) between about 1 and about 3 and a bristle flocking density (DFf) between 0.060 mg and 0.200 mg where $$\mathit{DFs}=\frac{\mathit{PF}-\mathit{PN}}{\mathit{NS}}\times 1000$$

$$\mathit{DFf}=\frac{\mathit{PF}-\mathit{PN}}{\mathit{NM}}\times 1000$$

wherein PN = weight of the unflocked brush in mg, PF = weight of the flocked brush in mg, NS = Number of coils and NM = Number of monofilaments.

Description

FIELD OF THE INVENTION
• The present invention relates to an applicator brush, in particular to a brush provided with a bristled stem suitable for applying viscous products, such as mascara.
BACKGROUND ART
• It is well known that, in the cosmetic field, various types of applicators exist which are used to draw fluid or pasty cosmetic agents, for example mascara, from the respective packages, and then applying them onto the user's skin, eyelashes or hair.
• Applicator operation provides to meet opposite requirements, especially when the product to be applied is viscous, since on the one hand the applicator must retain the product to draw it from the package and, on the other, it must easily lay and release the product onto the surfaces desired by the user.
• Over time a number of shapes and technologies have hence been suggested for manufacturing these applicators, finding each time compromises to meet the various requirements.
• In that respect, a fist significant distinction between the various types of applicators, is defined between conventional brushes - obtained by fastening bristles onto a support stem (for example consisting of twisted metal wires) - and shaped applicators - provided with wider surfaces, made more receptive with the use of surface treatments, among which flocking processes. Examples of applicators obtained with a flocking process are illustrated in US4404977 , EP1358818 , EP1971239 and US8245716 .
• A combination of the two solutions has also been suggested, in particular providing a flocking on the surfaces of some parts making up a conventional bristled brush. For example, WO2006106128 provides a flocking on the stem and EP2717739 is provided with flocking on some portions of the support.
• However, these existing configurations did not prove fully satisfactory. As a matter of fact, the brush is provided with bristles in conventional ways and, in addition, it is provided with flocking on some surfaces only. Beyond pleasant appearance or texture, the presence of flocking fibres also increases the ability to retain the cosmetic product which is characteristic of the bristled brush: this increase thus becomes excessive and the applicator tends to "pack" or "clogged", that is it accumulates an excessive volume of conglomerate cosmetic product, which is then uneasily distributed onto the surface to be processed, also with other side effects (for example, the mascara no longer tends to adhere to the user's lashes and the brush also loses its lash combing properties).
• Solutions have also been conceived wherein flocking on the bristles of brush is also provided, see for example EP 1 836 924 , EP 1 175 847 and FR 2 663 826 . None of these documents provides useful information on the arrangement that flocking should take.
• However, on a practical level, these solutions have never met with success on the market due to the above highlighted problems and because no advantage could be gained therefrom with respect to a higher flocking cost.
PROBLEM AND SOLUTION
• The object of the present invention is therefore to achieve a further improvement of prior art brushes, in particular bristled brushes, using an optimised arrangement to be able to exploit also the features typical of flocking fibres.
• In particular, it is intended to supply an arrangement which is effective for retaining the viscous material, but which at the same time delivers satisfactorily the material on a user's lashes, without creating a brush clogging (packing).
• Such object is achieved with a brush and a method as briefly described in the attached main claims. The dependent claims describe preferred features of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
• Further features and advantages of the invention will become in any case more evident from the following detailed description of a preferred embodiment, given purely as a non-limiting example and illustrated with the help of the attached drawings, wherein:
• fig. 1A is a diagram view showing a stem with the relative monofilaments forming the active part of a brush;
• fig. 1B is a photograph of three exemplifying brushes according to the invention, taken in a side elevation view, with three different flocking densities;
• figs. 2A and 2B are photographs with 31.4X enlargement, of a peripheral portion and of a central portion of a brush, respectively, with monofilaments having low-density flocking according to the invention;
• figs. 3A and 3B are photographs with 31.4X enlargement of a peripheral portion and of a central portion of a pipe brush, respectively, with monofilaments having medium-density flocking according to the invention; and
• figs. 4A and 4B are photographs with 31.4X enlargement of a peripheral portion and of a central portion of a brush, respectively, with monofilaments having high-density flocking according to the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
• In the following the invention will be illustrated in connection with a brush for cosmetic use, in particular for mascara. However, it is not ruled out that it may find effective application also in other sectors (for example in the medical sector) where the product to be applied or removed has physical features similar to those of mascara.
• An applicator brush 1 consists, in a manner known per se, of a support stem T on which a plurality of bristles S is fastened according to a preset pattern (fig. 1A). The surface of bristles S, as well as the envelope profile of the relative ends, makes up the active portion of the applicator brush, which performs the cosmetic product drawing and application function. In the context of this description, by the term bristles the individual monofilaments or groups of close monofilaments are indifferently intended, regardless of the material they consist of or of the construction technique with which they are arranged on the stem. As a matter of fact, the bristles can be formed of synthetic filaments cut to measure and then fastened on a stem in the form of a twisted metal wire, or they are obtained by injection moulding of plastic material directly onto the stem, or by other techniques.
• Typically, stem T consists of a twisted metal wire, between the coils of which monofilaments S are constrained, which thus form a spiral with a certain density of monofilaments, expressed in terms of monofilament number per coil. Monofilaments are preferably made of synthetic materials, such as nylon or polyester, but they could be also of natural fibres (such as cotton).
• The brush can be built also in a different manner, for example with bristles in the shape of monofilaments obtained by extrusion or by injection moulding or other methods, obtained integrally with the stem or engaged therewith with a suitable process. In these cases, the monofilaments will not necessarily be arranged in a spiral shape along the longitudinal development of the supporting stem, but it is nevertheless possible to identify a certain "bristle density" by expressing it in terms of the number of monofilaments per length unit of the stem.
• Stem T is meant to be fastened to a gripping component (not shown in fig. 1A), which is part of a package of a cosmetic product
• The package is typically conceived as a container of a cosmetic product, which has a mouth which the brush can be removed from and introduced into. The gripping portion to which the stem is fastened is normally shaped so as to act also as cap of the package.
• The mouth has a hole for the applicator brush to go through, preferably provided with rigid or flexible mouth means, which act as chafing system on the monofilaments of the brush, to remove the amount of cosmetic product which has adhered in excess to the bristles.
• According to the invention, at least the peripheral surface of the bristles is coated with a flocking process. In other words, once completed the brush with the relative bristles, it undergoes a treatment by which the surface of the monofilaments forming the bristles is coated with a thin adhesive film, onto which the ends of flocking fibres are then caused to adhere.
• Flocking fibres can be of all types of synthetic and/or natural fibres, but are preferably made of nylon, cotton or polyester.
• The individual flocking fibres are selected with length between 0.4 mm and 2.0 mm and a cross section (of any shape, but preferably circular) which determines a title of 0.9 to 22 dtex, that is according to the known conversion formula (wherein ρ represents material density) $$Ø=\sqrt{\frac{4\ast {10}^{-6}\ast \mathit{detx}}{\mathit{\pi \rho }}}$$

  

  a diameter of about 10-49 micron depending on the material they are made of.
• Flocking fibres are furthermore preferably arranged with a radial attitude with respect to the longitudinal axis of the individual bristles/monofilaments. In order to obtain such arrangement, the ends of the flocking fibres are caused to adhere to an adhesive film previously laid onto the bristles by a spraying or immersion process and removal of the excess adhesive. In order to obtain the desired radial orientation, fibre orientation methods can be used during the flocking process, for example by electrostatically charging the fibres and using orientation electric fields.
• According to an advantageous feature of the invention, it has been detected that the operating effectiveness of the applicator brush is achieved with specific balanced density ranges of the bristle monofilaments and laying density of the flocking fibres, outside of which ranges the applicator brush does not produce the desired behaviour with the viscous cosmetic products.
• In particular, with monofilament diameters of 3mils (0.0762 mm) to 11 mils (0.280 mm), bristle density must remain preferably within the range between 10 and 50 monofilaments per coil.
• At the same time, flocking density per coil (DFs) is chosen in the range between about 1 and about 3 while the flocking density on bristles (DFf) is between 0.060 mg and 0.200 mg, where such densities are defined as $$\mathit{DFs}=\frac{\mathit{PF}-\mathit{PN}}{\mathit{NS}}\times 1000$$

  

  $$\mathit{DFf}=\frac{\mathit{PF}-\mathit{PN}}{\mathit{NM}}\times 1000$$

  

  wherein PN = Weight of unflocked brush in mg, PF = Weight of flocked brush in mg, NS = Number of coils and NM = Number of monofilaments.
• In fig. 1B three examples of brushes according to the invention are illustrated, with flocking density at the lower limits, medium and at the upper limits.
• In the enlargements of figs. 2A-4B the arrangement of the flocking fibres can be noticed in detail in the three flocking density levels.
• The Applicant, after extensive experimentation, was able to identify the above-detailed ranges as the most suitable ones to obtain a brush with optimal operation and suitable to meet its opposite requirements. As a matter of fact, the relatively low bristle density prevents the presence of the flocking fibres from leading the cosmetic product to obstruct or "pack" the active part of the applicator brush but, at the same time, produces an excellent combing effect on the user's lashes; while the presence of the short flocking fibres on the bristles/monofilaments allows to optimally collect the viscous product from the package, which products then easily deposit on the part to be treated.
• In particular, it was detected that this brush is excellent in the application of products having the typical density of mascara for cosmetic use.
• It must be noted that such arrangement is particularly effective in the presence of a package mouth with a run-through diameter 30% bigger and 85% smaller than the outer diameter defined by the surface envelope of the ends of the radial bristles. As a matter of fact, with this sizing the excess cosmetic product which tends to remain adhering to the applicator brush according to the invention is suitably removed: the applicator brush hence preserves the correct amount of cosmetic product, partly detached from the flocking fibres, which is very effectively deposited on the user's lashes.
• As can be inferred from what has been described above, the specific construction proposed by the invention, with fibre flocking at least on the individual bristles arranged with a specific density, offers excellent results for the application of cosmetic products, in particular of mascara.
• It must be considered that in any case flocking may be provided also on other brush parts, for example on the stem, where, however, it will contribute only to the aesthetic appeal of the brush and not to the functional efficiency thereof.
• However, it is understood that the invention must not be considered limited to the particular embodiments described in detail, but that different variants are possible, all within the reach of a person skilled in the field, without departing from the scope of protection of the invention, which is exclusively defined by the following claims.

Claims (4)

1. Applicator brush of a viscous product, comprising a support stem wherefrom a plurality of bristles consisting of radially protruding monofilaments project, characterised in that
   said monofilaments are arranged with a density between 10 and 50 per coil,
   the lateral surface of said monofilaments is provided with flocking fibres extending substantially radially with respect to the longitudinal axis of said monofilaments,
   said flocking fibres are of a length between 0.4 mm and 2 mm and of a cross-section between 0.9 and 22 Dtex, and in that
   said flocking fibres are arranged with a flocking density per coil (DFs) between about 1 and about 3 and a bristle flocking density (DFf) between 0.060 mg and 0.200 mg where $$\mathit{DFs}=\frac{\mathit{PF}-\mathit{PN}}{\mathit{NS}}\times 1000$$

   

   $$\mathit{DFf}=\frac{\mathit{PF}-\mathit{PN}}{\mathit{NM}}\times 1000$$

   

   wherein PN = weight of unflocked brush in mg, PF = weight of flocked brush in mg, NS = Number of coils and NM = Number of monofilaments.
2. Applicator brush as in 1, wherein said flocking fibres are of Nylon or Polyester.
3. Applicator brush as in 1 or 2, wherein said monofilaments have a diameter in the range between about 3 mils and about 11 mils.
4. Application method of a viscous cosmetic product to a user's eyelashes, comprising the steps of

   providing an applicator brush provided with a radial-bristle portion,

   inserting said radial-bristle portion into a package containing a viscous cosmetic product and provided with mouth means having a diameter greater by 30% and smaller by 85% than the outer diameter defined by said radial bristles, and

   removing said radial-bristle portion from said package through said mouth means before bringing said applicator brush in contact with the eyelashes,

   characterised in that said applicator brush is as in any one of the preceding claims.

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