AU2015100879B4 - Depilatory Strip with Exfoliating Backing II - Google Patents

Abstract

The present invention is concerned with hair removal from the human body and relates to improved depilatory wax strips and their application to hair removal by epilation. A depilatory strip is disclosed comprising an adhesive depilation paste, in particular a cold depilation wax formulation, deposited on one face of a backing sheet, in particular incorporating a non-woven fabric, characterised by the backing sheet having on its other face a coarse surface structure adapted to effect exfoliation of human skin. Figure 2

Description

1 DEPILATORY STRIP WITH EXFOLIATING BACKING FIELD OF THE INVENTION The present invention is concerned with hair removal from the human body 5 and relates to improved depilatory wax 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. 10 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 wax 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, 15 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 20 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 25 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 30 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 2 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 which illustrates this is WO 96/21419 Al of Reckitt & Coleman Products Ltd., the contents of 5 which is incorporated herein by way 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, all 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. 10 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 15 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 20 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 25 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 30 of regrowing hair. Furthermore, it is not uncommon to encounter in-grown hairs during hair regrowth after epilation treatments which pose a problem in that wax will not remove these.

3 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 5 provided a depilatory strip comprising an adhesive depilation paste, in particular a cold depilation wax formulation, and first and second backing sheets, preferably each incorporating a non-woven fabric, wherein the backing sheets are removably joined to one another in facing relationship by a layer of the depilation paste sandwiched between them and which adheres to both backing sheets in 10 such manner that peeling the backing sheets away 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 with a roughness value sufficient to effect exfoliation of human skin, the roughness values being in a range of Ra = 15 to 38 pm, R, = 22 15 to 98 pm, Rz = 77 to 210 pm. The surface uniformity (R/Rz) is preferably within the range of 40 to 50%. 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 20 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. The Ra 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 25 areas above and below the line are equal) and the surface profile, and dividing by the evaluation length. Ra is the most commonly used one-dimensional roughness parameter, despite modern devices being able to provide a more detailed 2D and 3D characterisation of a 'rough' surface. Additional parameters give an informed user additional information that help characterise the roughness of a specimen 30 surface. 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 (one-dimensional value). The Rz value is the maximum height of profile calculated by summing the height of the maximum 4 profile peak and the maximum valley depth in an evaluation length, with reference to the mean line. 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 5 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. 10 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 which comprises a non-woven textile (fabric), characterised by the backing sheet having on its other face a coarse surface structure with a surface roughness value 15 sufficient to effect exfoliation of human skin, the roughness values being in a rangw of Ra = 15 to 38 pm, Rc = 22 to 98 pm, Rz = 77 to 210 pm. The surface uniformity (Rc/Rz) is preferably within the range of 40 to 50%. 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 20 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 25 adhesive depilation paste is applied, whereby the coarse surface structure on the sheets may be the same or different as regards roughness values and/or topography. For the second aspect embodiment, while the backing sheet could have zones (surface areas) with different roughness values, it is preferred to provide a more or less uniform roughness across the entire coarse surface. 30 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 ASTM D1894-14 and using leather as the substrate material.

5 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 an exposed face of a heterogeneous non-woven textile substrate itself in which abrasive strands or 5 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, although such is not a preferred embodiment; see below. Sandpaper contains numerous 'sharp edges' (particles) that abrasively cut away into a substrate surface (in the case of exfoliation: top 10 human skin layer). The particles are glued onto or otherwise embedded into backing material 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 15 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 particles to gather so that they do not interfere with exfoliation. 20 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 25 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 depilation per se but rather gentle skin exfoliation, the backing sheet is preferably manufactured to comprise a non-woven core layer onto which are 30 adhesively deposited, coated or 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 particles and 6 fibers, such as ground coffee, corn meal, jojoba beads, Aloe Vera fibers, ground coconut husks, etc. As noted, it is preferred that the backing sheet comprises a non-woven textile with one surface (or face) exhibiting surface roughness values conducive 5 to skin exfoliation. In one preferred form, such non-woven will comprise a polymer matrix material film, such as PE, at basis weight of between 15 to 25, but preferably 20 to 22 g/m 2 , in which a mix of polyester, polypropylene and/or cellulose fibres at a basis weight of between 35 to 55, but preferably 45 g/m 2 will be embedded, for a 10 total grammage of between 50 to 80, but preferably 65 g/m 2 , with an average thickness of between 200 and 250, but preferably 230 pm, a tensile strength in lamination direction of between 1200 and 1600, but preferably 1400 N/m and in traverse direction of between 920 and 960, but preferably 940 N/m, and fracture elongation values at around 8% and around 16% in lamination and traverse 15 direction, respectively, amongst other technical characteristics. The thickness of the backing sheet can be selected to have other values, as long as its flexibility in particular during removal of the strip from the skin, is ensured. It will be understood by the skilled person that the abrasive filaments / fibers need to adhere to the backing sheet (substrate) or be embedded in its 20 matrix 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 Al, and in particular comprise on the 25 adhesive depilation 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 depilation process. The present invention thus provides a single product which allows the user 30 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 depilation paste (eg the cold wax 7 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 5 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 10 area of a user's skin by rubbing, wherein the depilation 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 strip of the second aspect from one another, and then applying the backing sheet, depilation paste side down, unto the skin area, pressing the backing sheet down firmly and 15 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. 20 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 25 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 30 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.

8 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 16i and 21i a relatively thin layer 17, 22 of a cold wax depilation 5 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 10 multi layer make-up, wherein the inner faces 16i and 21i are provided by a non woven fabric or textile formulated to provide complementary adhesive properties to those of the cold 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 15 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 21e of backing sheets 15, 20 comprise and define coarse surface structures 18, 23 suitable for skin exfoliation 20 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 25 layers which provide the inner and exterior faces 21i and 21e of the non-woven textile backing sheet 20, respectively, although a single layer where the surface texture at the inner face 21i and at the outer (or exterior) face 21e are different can be used. The lower backing sheet 15 in figure 2 is shown to be comprised of three distinct layers, wherein a core component 19 may be a non-woven fabric 30 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.

9 In either case, the exterior faces (layers) 16e and 21e 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 5 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' comprised of an exfoliating external sheet 21 e and 16e respectively bonded to an internal film 21i and 16i of polyethylene which carries wax layer 22 and 17. The exfoliating 10 external sheet 21e and 16e has roughness values in the ranges of Ra = 15 to 38 pm, Re = 22 to 98 pm, Rz = 77 to 210 pm, with a surface uniformity (Rc/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 the method described in ASTIM 15 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 20 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 25 derivatives, pliable film-forming agents based on bees wax 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 30 and structure (and thus exhibiting the same coarseness at both exterior surface structures 18 and 23). These backing sheets are composite non-woven laminates comprising a mix of polyester, polypropylene and cellulose fibres at a basis weight of 45 g/m2 10 in a PE matrix at basis weight of 20-22 g/m2 (for a total grammage of 65-67 g/m2), with an average thickness of 230 pm, 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 traverse direction, 5 respectively, amongst other technical characteristics.

Claims (5)

1. A depilatory strip comprising an adhesive depilation paste, in particular a cold depilation wax formulation, deposited on one face of a first backing sheet which comprises a non-woven substrate, characterised by the backing sheet having on its other face a coarse surface structure with surface roughness values selected to effect exfoliation of human skin, the roughness values being within a range of R, = 15 to 38 pm, Rc = 22 to 98 pm and R, = 77 to 210 pm.

2. The depilatory strip of claim 1, further comprising a second backing sheet incorporating a non-woven fabric, wherein the backing sheets are removably joined to one another in facing relationship by sandwiching between them a layer of the depilation paste which adheres to both backing sheets in such manner that peeling the backing sheets away from one another maintains a layer of said depilation paste on a first face of each of the backing sheets, characterised in that the second backing sheets has on its other face a coarse surface structure adapted to effect exfoliation of human skin..

3. The depilatory strip of claim 2, wherein the coarse surface structure on both of the backing sheets is the same or different as regards roughness values and/or topography.

4. The depilatory strip of any one of the preceding claims, wherein the backing sheet(s) comprises a non-woven composite with a matrix onto or into which are adhesively deposited, coated or embedded particles, filaments and/or fibers of a material selected from cellulose, polymers botanicals and combinations thereof.

5. The depilatory strip of any one of the preceding claims, wherein 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 frictions of the coarse surface structure is in a range of 0.305 to 0.340, tested by the method described in ASTM D1 894-14 and using leather as the substrate material.