Razor head comprising an anti-friction element joined to a base which is secured by means of welding

Description of the invention

The present invention relates to a method of attaching a friction reducing element to a shaver head.

There are numerous shavers that include a friction reducing element or strip, also called a lubricating strip or shaving aid strip, which comprises a polymer or polymer mixture, one component having lubricating or cosmetic properties and being water soluble. Thus, with each pass of the shaver, a layer of the cosmetic product or lubricant is applied to the skin of the user to make shaving easier and / or more enjoyable.

Such shavers are described, for example, in FR 2 410 541, EP 550 605 and EP 184 440.

There are several groups of lubricating strips, classified, for example, according to their shape and composition. Thus, the lubricating strips may have a simple structure, i.e. a flat shape, attached to the shaving head, or also a special complex shape that cooperates with the shape of the head to provide a press fit or pinch fit. There are also numerous compositions of these lubricating strips, which may be made of a mixture of polymeric materials or which may contain various layers of superimposed polymers, which serve in particular for wear control, as described, for example, in GILLETTE EP 772 311 and WARNERLAMBERT EP 773 855. In general, in the case of flat lubricating strips, the fixation is provided by gluing.

There are three large families of adhesives in the market today:

- so-called "cyan" adhesives, which require a slow gluing process (and therefore shaver production) due to the initial non-stickiness and which also have other disadvantages, assuming that the cyan glue penetrates the lubricating strip, where it can interact with the ingredients and is not resistant on the water;

- hot-melt adhesives which show tackiness immediately but make connections between the lubricating strip and the shaving head via a flexible layer, the thickness of which is difficult to reproduce and which can be easily pulled out;

- thermally activated adhesives, which imposes a slow gluing process (and therefore the production of the razor).

In addition, the adhesive bonding processes use adhesive components that are in the form of a more or less viscous fluid. The use of such products causes problems in high-speed manufacturing processes such as the industrial production of shavers.

It is therefore desirable, in order to alleviate these drawbacks, to find a method for attaching the lubricating strip to the shaving head which does not entail modifying the properties of the lubricating strip, which is easy and quick to use industrially, and which provides a very resistant connection between the shaving head and the lubricating strip.

The applicant company has already considered the use of a lubricating strip made of a mixture of an insoluble polymer and a soluble polymer attached to the shaving head by ultrasonic welding as described in patent application FR 2 769 535. However, this method of attachment has proved to be quite difficult to implement and its quality is it is often unsatisfactory.

In the course of further in-depth research, the applicant company found that it is possible to simultaneously obtain good performance of the lubricating strip and good speed and ease of attaching the lubricating strip to the shaving head by using a special fastener that does not require the use of glue.

A method for attaching a friction reducing element to a shaver head wherein a friction reducing element containing water-soluble agents is attached to a pad containing at least one insoluble polymer, according to the invention, is characterized in that the friction reducing element is secured to the pad by simultaneous extrusion. co-molding or double injection of the layer of constituent polymers, then the layer obtained in this way is welded, preferably ultrasonically, side of the pad to the head of the shaver, next to the blades.

A backing is used comprising at least one polymer adapted to be fixed by welding, especially selected from the group consisting of polyethers, styrene resins such as polystyrene, ABS, polyolefin resins such as polypropylene and polyethylene, acrylic resins such as PMMA, and vinyl resins, such as plasticized or unplasticized polyvinyl chloride or mixtures thereof.

There is used a friction reducing element intended to come into contact with the skin during shaving, containing a mixture of insoluble polymers, especially selected from the group consisting of polyethers, styrene resins such as polystyrene, ABS, polyolefin resins such as polypropylene and polyethylene, resins. acrylic such as PMMA and vinyl resins such as plasticized or unplasticized polyvinyl chloride or mixtures thereof and soluble polymers, especially selected from the group consisting of polyoxyethylenes, polyacrylamides, polysaccharides or mixtures thereof.

A shim with a thickness of 0.05 to 0.6 mm, preferably 0.05 to 0.4 mm, and most preferably about 0.3 mm is used.

A layer containing water-soluble polymers with a thickness of 0.1 to 1.5 mm, preferably 0.3 to 1 mm, is used.

The friction reducing element is a layer of a mixture containing from 20 to 60% of an insoluble thermoplastic polymer, preferably polystyrene, from 20 to 80% of polyoxyethylene with a molecular weight of between 100,000 and 6,000,000, which is extruded simultaneously with the layer of polystyrene constituting the backing.

A friction reducing element is used, also containing from 1 to 20% of polyoxyethylene with a molecular weight of less than 30,000.

The friction reducing strip is attached to the shaving head via the washer by ultrasonic welding. This process does not require the introduction of any additional products and can be easily introduced into a high speed production line without reducing the speed of the production lines and without modifying the chemical composition of the top layer which is to come into contact with the skin.

The subject matter of the invention is illustrated in the drawing, in which Fig. 1a shows a top view of the lubricating strip connected to the base, in a first embodiment of the invention, Fig. 1b shows a sectional view along the line AA 'in Fig. 1a, Fig. 2a shows a top view of the lubricating strip connected to the base, in a second embodiment of the invention, Fig. 2b is a side sectional view along line BB 'of Fig. 2a, Fig. 3 shows the apparatus used in Example 2 to evaluate the quality of welding.

The pad 3 is joined to the layer intended to be in contact with the skin during shaving by gluing, molding, simultaneous extrusion, co-molding or double injection, preferably by simultaneous extrusion.

The simultaneous extrusion process is carried out at a temperature of the stamping die used in the thermoplastic technique, preferably from 120 to 300 ° C, more preferably from 150 to 220 ° C.

When the friction reducing element 1 is non-linear, it is especially advisable to use a double shot or co-molding process.

Of course, layers of intermediate polymers may be sandwiched between the pad 3 and the top band that is intended to contact the skin during shaving. Such intermediate layers may be soluble or insoluble and may contain adjuvants selected from the group consisting in particular of dyes, pigments, emollients, perfumes, vitamins, cosmetic products.

If there is incompatibility between the materials forming on the one hand the backing and the top strip intended to be in contact with the skin during shaving, on the other hand, a third polymer mixture may be incorporated and serve as a transition between the two layers for bonding them.

The thickness of the shim is from 0.05 to 0.6 mm, preferably from 0.05 to 0.4 mm, and most preferably about 0.3 mm. The thickness of the layer containing the water-soluble polymer or polymers is 0.1 to 1.5 mm, preferably 0.3 to 1 mm. The topsheet intended to be in contact with the skin during shaving may be completely flat or may have a semicircular cross section to achieve a gentle skin contact.

The thickness of the skin contact layer is such that it has a sufficient amount of water-soluble polymers necessary for the strip to function effectively as long as the razor blades are operational.

In a particularly preferred embodiment of the razor head 5 according to the invention, the friction reducing element 1 is a layer of a mixture comprising 20 to 60% insoluble thermoplastic polymer, preferably polystyrene, 20 to 80% polyoxyethylene with a molecular weight of between 100,000 and 6,000,000, which is simultaneously extruded. with the polystyrene layer constituting the shim 3, and the shim 3 is ultrasonically welded onto the shaver head. The friction reducing element 1 may also contain from 1 to 20% of polyoxyethylene with a molecular weight of less than 30,000.

PL 197 852 B1

Figure 1a shows a top view of a strip, i.e. a friction reducing member 1, according to the invention, which comprises a pad 3 with a skin-engaging top layer that has a semicircular cross-section (Figure 1b).

In another embodiment of a razor head according to the invention, shown in Fig. 2, the razor head 5 comprises a guard to which a strip is welded, i.e. a friction reducing member 1, which is not linear but has a side projection at its two ends such that the blades are welded onto the strip. 6 are placed in front of the strip, i.e. the friction reducing element 1 in the space between the two side projections.

As in the previous embodiment, the friction reducing strip includes a pad and a skin contact layer that has a semicircular cross section (Fig. 2b).

The invention will be described in more detail with examples which are presented by way of illustration only.

Example 1

A friction reducing strip is made connected to the base as shown in Fig. 1 by simultaneously extruding polystyrene (S) and composition (C), which is a mixture comprising per 100 g: 30 g of polystyrene and about 70 g of high molecular weight polyoxyethylene. of 5,000,000, marketed under the name PEG 115M.

(S) and (C) are fed into two separate single screw type extruders having an extrusion head allowing the layering of material at a temperature of 180 to 200 ° C. The capacities of the extruders are set such that the height of the upper strip will be 0.5 mm and the height of the shim, i.e. the layer (S) - 0.3 mm. The width of the strip is 3.5 mm. The extruder die allows to obtain the upper layer (C) in a slightly bulging shape, so as to ensure gentle contact with the skin during use. The strip made is then cut into 35 mm long pieces.

The pad of each strip is then ultrasonically welded by a 36 kHz machine manufactured by TELSONIC onto the shaving head of a disposable polystyrene razor adjacent to the cutting blade.

Example 2

Comparative tests were performed to verify the durability of ultrasonic welding.

Done:

- on the one hand, 20 friction reducing strips (A) by extrusion from a mixture containing 30 g of polystyrene and 70 g of high molecular weight polyoxyethylene 5,000,000, sold under the name PEG 115M. These strips have the following dimensions: width: 3.5 mm, length: 35 mm, height: 0.8 mm; and

- on the other side, 20 friction reducing strips (B) connected to a washer prepared according to example 1.

Each strip was ultrasonically welded onto the shaving head of a disposable shaver made of polystyrene as in Example 1.

With the apparatus shown in Fig. 2, the durability of the ultrasonic welding was measured as follows.

The razor head 5 is held at its two ends by a clamping system 7. A 25 mm long adhesive tape 8 was attached perpendicular to the length of the ultrasonically welded strip on the razor head, a tensile force was applied to the adhesive tape by means of a crocodile clip 8 connected to a dynamometer in such a way as to detach the strap. The applied breaking force of this strip was measured and the results obtained are summarized in Table 1 below.

Table 1

<td>Belt (A)</td><td> 1</td><td> 2</td><td> 3</td><td> 4</td><td> 5</td><td> 6</td><td> 7</td><td> 8</td><td> 9</td><td> 10</td><td> 11</td><td> 12</td><td> 13</td><td> 14</td><td> 15</td><td> 16</td><td> 17</td><td> 18</td><td> 18</td><td> 20</td>

<td>Applied force (N)</td><td> 2</td><td> 5</td><td> 1</td><td> 1</td><td> 2</td><td> 1</td><td> 4</td><td> 1</td><td> 2</td><td> 1</td><td> 2</td><td> 2</td><td> 2</td><td> 1</td><td> 3</td><td> 5</td><td> 1</td><td> 4</td><td> 2</td><td> 5</td>

<td>Belt (B)</td><td> 1</td><td> 2</td><td> 3</td><td> 4</td><td> 5</td><td> 6</td><td> 7</td><td> 8</td><td> 9</td><td> 10</td><td> 11</td><td> 12</td><td> 13</td><td> 14</td><td> 15</td><td> 16</td><td> 17</td><td> 18</td><td> 18</td><td> 20</td>

<td>Applied force (N)</td><td> 20</td><td> 20</td><td> 19</td><td> 20</td><td> 19</td><td> 20</td><td> 20</td><td> 20</td><td> 20</td><td> 20</td><td> 20</td><td> 20</td><td> 19</td><td> 20</td><td> 20</td><td> 20</td><td> 19</td><td> 20</td><td> 20</td><td> 20</td>

The comparative tests show that welding of the simultaneously extruded strips withstands breaking much better than the strips known from the state of the art (A), the force needed to

The breaking point was significantly greater for the strips (B). In addition, this high force detached the topsheet intended to come into contact with the skin during shaving from the pad, but did not detach the pad which remained attached to the razor head.

Moreover, the welding quality of the strips (B) is much more even than that of the strips (A), the spread of the test results is much smaller for strips (B) than for strips (A).