FIELD OF THE INVENTION

The present invention is concerned with hair removal from the human body and relates to improved depilatory wa strips and their application to hair removal by epilation.

BACKGROUND TO THE INVENTION

The removal of body hair by epilation and depilation, particularly for cosmetic purposes, can be performed using several techniques.

One of the most commonly used epilation techniques, aimed at removing the entire hair strand, including parts below the skin surface in the follicles, involves the application of hot or cold depilatory wa formulations to an area of skin from which hair is to be removed, and the rapid pulling off of a strip of wax with hairs entrained in the set wax. In contrast to warm (or hot) wax epilation, where the wax is applied in liquid / pasty consistency directly onto the skin with a spatula or the like, and a textile strip is subsequently applied onto the wax and subsequently pulled-off to effect hair removal, cold wax formulations are pre- applied in a pasty state onto a backing strip of paper, textile (non-woven) or multi- film composition, and either covered with an easily removable protective film, or with a second backing strip so as to provide a two-in-one strip configuration. The wax formulation stays malleable and tacky during storage, and in most cases must be softened prior to use by gentle heating, eg by the user gently rubbing the strip and friction -heating it.

in use, the user removes the cover film protecting the wax layer from the strip, or separates the two backing films which sandwich the cold wax layer, presses the strip wax side down firmly onto the skin area to be epilated (and if need be rubs down the strip to increase penetration embedding of hair stems in the wax layer), and then one end of the backing strip is grasped and pulled sharply away from the area to be epilated, thus removing hair entrained in the wax from the skin.

It will be appreciated that the interface between backing strip and wax is devised to provide sufficient adhesion between wax and the surface of the strip onto which the wax is applied, so that the wax is substantially retained on the backing material in the process of pulling off the backing strip from the skin surface. Considerable research has gone into this requirement, and an example of a prior art document directed to cold wax depilatory strips and whic illustrates this is WO 96/21419 A1 of Reckitt & Coleman Products Ltd., the contents of which is incorporated herein by wa of cross-reference. There are numerous different formats of cold wax strips on the Australian (and international) market, exemplified by Veet (brand) wax strips, Nad's (brand) wax strips, ail of which are characterised by exhibiting backing strips devised to minimise wax remaining on the user's skin upon the strip being pulled from the user's skin.

In contrast to epilation, depilation is aimed at removing only the part of the hair above the skin surface. A typical depilation technique is shaving. Another technique used, though to lesser extent in western countries, involves the use of mitts and pads having an abrasive coating or sheet. In use, the pads / mitts are rubbed with vigour and a certain degree of pressure over the skin area in order to mechanically break down hair shafts without destroying or removing hair follicles. The hair stem above the skin is buffed away, during which process the skin surface is exfoliated too, the degree of exfoliation being in part a function of the coarseness of the abrasive / polishing surface.

In the context of this specification, the terms epilation and depilation are used interchangeably, noting that body hair removal using application of wax onto skin and pulling the wax off the skin is commonly referred to as wax depilation.

One problem that arises with cold wax depilation is that the user's skin ought to be cleaned (eg using soap or skin cleansing preparations) in order to remove excessive skin oils before application of the waxed backing strip, to achieve optimal epilation results. Further, in particular when hair removal is carried out at an early stage of hair (re-)growth, after a previous epilation operation, when hair stem length is short and hair growth is fine, cold wax hair removal tends to be less efficient. Without wanting to be tied down to the correct scientific explanation, this may be consequence of the fineness and smoothness of regrowing hair. Furthermore, it is not uncommon to encounte in-grown hairs during hair regrowth after epilation treatments which pose a problem in that wax will not remove these. The present invention is aimed at providing in particular cold wax depilation strips with improved functionality.

SUMMARY OF THE INVENTION

In accordance with a preferred first aspect of the invention there is provided a depilatory strip comprising an adhesive depilation paste, in particular a cold depilation wax formulation, and first and second backing sheets, preferably eac incorporating a non-woven fabric, wherein the backing sheets are removably joined to one another in facing relationship and sandwiched between them a layer of the depilation paste which adheres to both backing sheets in such manner that peeling the backing sheets awa from one another maintains a layer of said depilation paste on a first face of each of the backing sheets, characterised in that at least one of the backing sheets has on its other face a coarse surface structure adapted to effect exfoliation of human skin.

During a typical manufacturing process of such depilatory strip, the wax is applied to the first face of one of the backing sheets only and then the second backing sheet is rolled over and sealed onto the first backing sheet. An alternative manufacturing process would see a thin layer of depilation paste applied onto the first face of both backing sheets which are subsequently brought into face abutting relationship and pressed together. In either case, on separating the strips, the depilation paste / wax will remain present on both sheets.

In accordance with a second aspect, the present invention provides a depilatory strip comprising an adhesive depilation paste, in particular a cold depilation wax formulation deposited on one face of a backing sheet, preferably incorporating a non-woven textile (fabric), characterised by the backing sheet having on its other face a coarse surface structure adapted to effect exfoliation of human skin. A protective film that is easily removable from the depilation paste, such as a silicon coated paper, would then be applied onto the depilation paste to seal the strip off for packaging and storage purposes.

Adhesive depilation paste formulations, including cold depilation waxes, are known in the art and will not be described in detail herein.

Preferably, in the strip according to the first aspect, both backing sheets will have a coarse surface structure on the face opposite the one onto which the adhesive depilation paste is applied, whereby the coarse surface structure on the sheets may be the same or different as regards coarseness values and/or topography.

The term 'coarse surface structure adapted to effect exfoliation of human skin' is used in the present specification to denote the presence of a surface topography on at least one of the faces of the backing sheet, provided by fine abrasive particles or strands on the exposed sheet face, that are conducive in effecting gentle skin exfoliation when the backing sheet is rubbed back and forth or in a circular motion (or in one direction) on human skin.

Preferably, the coarse surface structure has roughness values in the ranges of R _a = 15 to 38, R _c « 22 to 98, R _z = 77 to 210, The surface uniformity (Rc/R _z ) is preferably within the range of 40 to 50%.

The R _a value is the mean deviation of profile calculated by integrating the areas between the mean line (a line bisecting the roughness curve such that the areas above and below the line are equal) and the surface profile, and dividing by the evaluation length. The R ₀ value is the average profile height, calculated by summing the height of each peak from the preceding valley, and dividing by the number of peaks along the evaluation length. The R _z value is the maximum height of profile calculated by summing the height of the maximum profile peak and the maximum valley depth in an evaluation length, with reference to the mean line.

The static coefficient of friction of the coarse surface structure is preferably in the range of 0.380 to 0.425, and the kinetic coefficient of friction of the coarse surface structure in the range of 0.305 to 0.340, tested by the method described in AST D1 894-14 and using leather as the substrate material. There are different ways in which the coarse surface structure may be implemented. The structure may be formed by a separate coating or film applied onto a carrier sheet (substrate) or may be formed by the exposed face of a heterogeneous non -woven textile substrate itself in which abrasive strands or particles stand proud of a planar mean surface plane.

The surface of sanding paper may provide an illustration of one implementation of such coarse surface structure. Sandpaper contains numerous 'sharp edges' (particles) that abrasively cut away into a substrate surface (in the case of exfoliation: top human skin layer). The particles are glued onto or otherwise embedded into backing materia! such as Kraft paper, textile backings or composite plastic film laminates, with a bonding agent in random or specific pattern(s). Different grades of sandpaper represent the difference in quality of the abrasives, the backing material and the bonding agents. The grit size, or number of abrasive particles per surface area unit, in addition to the particle size and particle size distribution, are quality indicators affecting exfoliation outcomes. The density of the grit is important too, noting that a more open-coated exfoliating sheet surface has larger gaps between the particles, allowing for exfoliated skin particies to gather so that they do not interfere with exfoliation.

in one embodiment, the backing sheet of the strip may exhibit the same type of abrasive media as used in conventional (industrial) sanding paper, which use primarily aluminum oxide, garnet, silicon carbide, ceramic or similar inorganic / mineral abrasive particles.

However, in the present invention it is preferred to use abrasive media that is less prone to roughen (or damage) the skin dermis when too much pressure is applied in the exfoliation / rubbing process.

Furthermore, given that the coarse surface structure is not intended to effect depiiation per se but rather gentle skin exfoliation, the backing sheet is preferably manufactured to comprise a non-woven core layer onto which are adhesively deposited / coated or otherwise embedded particles, filaments and/or fibers of a material selected from cellulose, polymers (preferably bio-degradable), botanicals and combinations thereof. The term 'botanicals' is used herein to denote plants and plant materials that are used in the manufacture of exfoliating particies and fibers, such as ground coffee, corn mea!, jojoba beads, Aloe Vera fibers, ground coconut husks, etc.

it will be understood by the skilled person that the abrasive filaments / fibers need to adhere to the backing sheet (substrate) or be embedded therein in such manner that they will remain substantially attached to the sheet for the intended one-time use which cold wax strips are usually devised for.

It will be equally apparent to the skilled person that the backing sheet may be of multi-layer composite nature, such as described in the above mentioned patent publication WO 1996/021419 A1 , and in particular comprise on the adhesive depiiation paste carrying face a carrier film whose properties are optimized to provide the desired adhesiveness to ensure the wax remains attached to the backing sheet when it is peeled off the skin during the depiiation process.

The present invention thus provides a single product which allows the user to exfoliate the skin using the waxing strip itself, by gently rubbing it with its coarse surface structure against the skin. Furthermore, the rubbing process will generate heat and soften the wax formulation of the strip, so that once any protective film is removed from the adhesive depiiation paste (eg the cold wax layer) or the two backing sheets of the strip are peeled from one another, the wax-carrying face of the backing sheet(s) can be applied onto the skin area for subsequent epilation. The exfoliation process will remove not only dead skin particles but also other impurities and skin oils and release ingrown hairs, and thus assist in preparing the skin for the cold wax application for the subsequent epilation process.

in another aspect of the present invention there is provided a method for beautification of human skin by first using a depilatory waxing strip in accordance with the first or second aspect of the invention to effect exfoliation of a desired area of a user's skin by rubbing, wherein the depiiation paste is warmed by said rubbing action, then either removing the protective film of the strip of the first aspect or peeling-off the two backing sheets of the stri of the second aspect from one another, and then applying the backing sheet, depiiation paste side down, unto the skin area, pressing the backing sheet down firmly and subsequently quickly stripping the backing sheet from the user's skin area to effect epilation.

Further preferred features of the invention will become apparent from the following illustrative description of a preferred embodiment of the present invention, provided with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is an perspective view of a depilatory cold wax strip in a first embodiment of the invention, comprising two backing sheets, in which one sheet is shown partially peeled-off;

Figure 2 is a schematic cross-section across the depilatory cold wax strip of figure 1 ; Figure 2A is an enlarged view of part of the depilatory cold wax strip showing the detail of the coarse surface structure;

Figure 3 is an exploded view of a depilatory cold wax strip in a second embodiment of the invention, comprising two identical backing sheets; and

Figure 4 is an exploded view of a depilatory cold wax strip in a third embodiment of the invention, comprising different types of backing sheets.

DESCRIPTION OF PREFERRED EMBODIMENT

Figure 1 and 2 schematically illustrate a cold wax depilation strip 10 comprising two backing sheets 15, 20 onto each of which is applied on respective inner faces 161 and 211 a relatively thin layer 17, 22 of a cold wax depilation formula, and which are joined in wax facing relationship to one another by the tacky and pasty wax as is known in the art. This construction provides two useable depilation strips once the backing sheets 15, 20 are peeled-off each other.

The backing sheets 15, 20 are composite substrates, which may be of multi layer make-up, wherein the inner faces 16Ϊ and 21 i are provided by a non- woven fabric or textile formulated to provide complementary adhesive properties to those of the coid wax depilation formula used for the strip 10 to ensure the wax layer 17, 22 remains attached to the respective backing sheets 15, 20 in the course of an epilation procedure, as is known. The non-woven or textile backing sheets may be coated with other substances, for example PE.

Relevantly, and in contrast to known cold wax depilatory strips, the exterior face or surface of the backing sheets 15, 20 is not smooth, and in accordance with the invention, exterior face layers 16e and 21 e of backing sheets 15, 20 comprise and define coarse surface structures 18, 23 suitable for skin exfoliation purposes.

It will be noted from the detailed enlargement of figure 2 that the layer make-up of the backing sheets 15 and 20 need not be the same for the upper sheet 20 and the lower sheet 15, although this would be preferred. Furthermore, it can be seen that the upper backing sheet 20 can be comprised of two distinct layers which provide the inner and exterior faces 21 i and 21 e of the non-woven textile backing sheet 20, respectively, although a single layer where the surface texture at the inner face 21 i and at the outer (or exterior) face 21 e are different can be used. The lower backing sheet 15 in figure 2 is shown to be comprised of three distinct iayers, wherein a core component 19 may be a non-woven fabric onto which are permanently joined an inner non-woven, wax carrying layer or coating 16i on one face and an exterior non-woven textile layer 16e of a composition different than the core and inner sheet components.

i either case, the exterior faces (Iayers) 16e and 21 e in the embodiment illustrated in figure 2 provide coarse surface structures 18 and 23 that are different to one another as regards coarseness. In other words, the topography of the exterior faces is different; so as to provide the strip 10 with two distinct exfoliation grits, but which if desired could be the same.

The embodiment of a waxing strip 10' shown in exploded view in figure 3 comprises identical multi-layer backing sheets 15' and 20 ⁵ comprised of an exfoliating external sheet 21 e and 16e respectively bonded to an internal film 21 i and 16i of polyethylene which carries wax layer 22 and 17. The exfoliating external sheet 21 e and 16e has roughness values in the ranges of R _a = 15 to 38, R _c = 22 to 98, R _z = 77 to 210, with a surface uniformity (R _c /Rz) of 40 to 50%. The static coefficient of friction of the coarse surface structure is in the range of 0.380 to 0.425, and the kinetic coefficient of friction of the coarse surface structure in the range of 0.305 to 0.340, tested by th method described in ASTM D1894-14 and using leather as the substrate material.

The embodiment of another waxing strip 10" in accordance with the present invention is shown in figure 4 and comprised of a standard or conventional waxing strip 15" (comprised of an external, smooth PE film bonded to an interior non-woven depilatory backing sheet as per standard products available on the market) and another backing sheet 20" of same construction as present in the embodiment of figure 2 and sheet 20' of figure 3.

A depilatory strip 10 as described above with reference to figures 1 and 3 has been manufactured by the applicant, using a depilatory cold wax composition formulated using viscoelastic materials based on rosin (colophony) and rosin derivatives, pliable film-forming agents based on bees wa and paraffin, and optional ingredients in small amounts selected from emollients, moisturisers, botanical extracts, skin soothing agents, skin smoothing agents, perfumes, colorants, preservatives, colour stabilisers, mica pigments and antioxidants. The backing sheets 15 and 20 were selected to be identical in make-up and structure (and thus exhibiting the same coarseness at both exterior surface structures 18 and 23). These backing sheets ar composite non -woven laminates comprising a mix of polyester, polypropylene and cellulose fibres at a basis weight of 45 g/m2 in a PE matrix at basis weight of 20 g/m2 (for a total grammage of 65 g/m2), with an average thickness of 230 μητ, a tensile strength in lamination direction of 1400 N/m and in traverse direction of 940 N/m, and fracture elongation values at 8% and 16% in lamination and travers direction, respectively, amongst other technical characteristics.