MXPA00003668A - Antichafing strip for shaving equipment head and shaving equipment head comprising same - Google Patents

Abstract

The invention concerns an antichafing strip for a disposable shaving equipment obtained by extrusion of a polymer mixture comprising an insoluble polymer material and polyethylene oxide, having an initial dynamic friction coefficient (KD) of the order of or less than 0.2. The mixture to be extruded comprises exclusively, as polyethylene oxide, a product having a molecular weight average higher than 3.5 millions. Preferably, it is obtained by extrusion from a mixture comprising polystyrene and polyethylene oxide having a molecular weight average higher than 4 millions, in particular one single polyethylene with molecular weight average higher than 7 millions. The invention also concerns a shaving equipment head whereon said antichafing strip is fixed by ultrasonic bonding.

Description

ANTI-FRICTION BAND EXTRUDED FOR RASURING HEAD AND RASURING HEAD PRESENTING THAT BAND Field of the Invention The present invention concerns the domain of shaving by mechanical means with the aid of a disposable razor; refers more particularly to a shaving aid which is in the form of a band and is called a band, which is fixed on the head of a rake preferably in the vicinity of the shaving knife and which contains at least one component of helps shaving soluble in water. BACKGROUND OF THE INVENTION When shaving is started, the user sinks the head of the rake in hot water, which has the effect of making part of the shaving aid components accessible and lexivable and containing at least one shaving aid component. soluble in water . In document FR-A 2410541, the proposed shaving aid product is combined with a microporous microencapsulated water-soluble solid structure intended to retain the shaving aid component that can be chosen from a list of substances comprising a lubricant intended to reduce the effect between the shaver and the skin, an agent intended to reduce friction between the shaver and the skin, an agent capable of modifying the hair structure, a cleaning agent, a pharmaceutical agent, a cosmetic agent and a coagulating agent. As an example of a lubricant intended to reduce the effect of the shaving and skin interface, FR A-2410541 cites a microencapsulated silicone-based oil, and as an example of an agent intended to reduce friction between the shaver and the foot, The same document cites a polyethylene oxide having a molecular weight between 100,000 and 6,000,000, a non-ionic polyacrylamide and a natural polysaccharide derived from vegetable substances such as guar gum. In the document EP. B-0184440, it is envisaged to form the shaving aid, in the form of a strip, by extruding a mixture of soluble polymer material and insoluble in water. This document cites a list of water-soluble polymers comprising polyethylene oxide, polyvinylpyrrolidone, polyacrylamides, hydroxypropylcellulose, polyvinylimidazoline and hydroxyethyl polyacrylate. In a precise example of embodiment, the mixture intended to extrusion modeling the band is composed of 20% by weight of water-insoluble polystyrene and 80% by weight of a polyethylene oxide mixture comprising 60% polyethylene oxide " polyox csagulant "of molecular mass equal to 5,000,000 and 40% polyethylene oxide" poliox WSR N-750"of molecular mass equal to 3,000,000. No explanation is given in that document about the interest of that mixture of two types of polyethylene oxides, with the exception of obtaining an average molecular weight of approximately 3.5 million for the polyethylene oxide of the final mixture. In EP.B 0550 605 the mixture intended to extrusion form the shaving aid, in the form of a strip, contains in addition to the insoluble and water-soluble polymeric materials an agent of weak molecular weight that amplifies the release of the material water soluble polymer that constitutes the shaving aid component. Among all possible examples, this document cites polyethylene oxide as a helper component in lexiviable shaving by water and polyethylene glycol as a release amplifying agent. Characteristically, according to EP.B.0550 605 the mixture provided for extrusion forming the shaving aid in the form of a band comprises 20 to 60% by weight of insoluble polymeric material forming the band matrix, , 75% by weight of polymeric material soluble in water that will constitute the aid component in the restored lexiviable by water and from 5 to 20% by weight of the releasing amplifying agent. The same mixture of two types of polyethylene oxide already described in the above document EP.B.0184 440 namely 60% by weight of coagulating polyox and 40% by weight of polyox WSR is strictly found in all the examples cited in this document. N-750. In the examples cited, the release amplifying agent, is a polyethylene glycol whose molecular weight varies between 4500 and 20 thousand. The objective sought by the presence by the release amplifying agent is to allow maintaining a sufficient proportion of insoluble polymer to maintain an adequate mechanical strength in the extruded band both at the time it is initially produced and in the assembly, after leaching from a a significant amount of water-soluble material allowing a release of sufficient water-soluble shaving component to ensure efficient shaving aid for the total expected lifetime of the blade or the slats. In this document EP.B. 0550 605 no explanation is given as regards the reasons that allow certain determined agents of weak molecular weight to amplify the release of the shaving aid component, namely polyethylene glycol, methoxy polyethylene glycol, methyl cellulose and the polymethylene carboxy. It is noteworthy that the only 4 examples that are cited in that document, all refer to the aforementioned mixture of polyethylene oxide and the addition of polyethylene glycol, it can be remembered that the polyethylene oxide have the same formula no differentiating nothing but by the manufacturing process and by the average molecular weight, if you use the term polyethylene glycol to designate a compound whose molecular weight is generally less than 20 thousand. The term polyethylene oxide is used to designate a compound that has a molecular weight of 100 thousand, knowing that there is a wide variety of products proposed on the market that has as a general formula that of polyethylene oxide with average molecular weights of 100 thousand a 8000 000. Thus according to the applicant it can be thought that in the EPB document 650 605 polyethylene glycol is also used as a shaving aid component, complementing the low molecular weight polyethylene oxide (polyox WSRN-750) so as to obtain a sufficient release of shaving aid components during the lifetime of the shaving head pushable. Thus, the current evolution in this domain tends to privilege an important duration of soluble component of aid in shaving, especially polyethylene oxide, preferably with the addition of polyethylene glycol. Despite the fact of this important release, this component is present on the surface of the skin already shaved and is capable of forming a film when dried. To avoid this inconvenience, it is necessary that the user wash himself after shaving. In any case, depending on the quality of the available water, this drag is not always satisfactory and can subtract an annoying impression on the skin. If all or part of the soluble component remains on the skin, this may be a source of irritation especially for sensitive skin. To avoid these drawbacks, it has already been proposed in document E.P.B. 0321 679, a solution that is in principle different because it avoids the use of a soluble polymer when proposing to put into action, as an antifriction agent, a xerophilic gel which, with the absorption of water as a dispersing agent, is transformed into a lyophilic gel presenting a high sliding capacity on the skin of the user and a coefficient of friction μ, less than 0.25, addition of a dispersing agent, for example water, the xerophile gel is transformed back into lipophilic gel by swelling its outer surface becomes slippery and It has a weak coefficient of friction. In the course of this phase, the colloidal substance that forms the shaving of lyophilic gel does not pass in solution which allows to avoid the formation on the skin of a film constituted of a shaving aid component extracted from the band as had been the case in the aforementioned documents. In any case, according to the teaching of this document E.P.B. 032679 it is necessary to report the coating that forms the xerophilic gel on a support band in order to constitute the anti-friction band itself that is to be placed on the shaving head. In fact, the pre-known materials for forming the xerophilous gel do not resist temperatures that allow to plan the manufacture of the anti-friction band by extrusion. SUMMARY OF THE INVENTION The objective that has been raised by the applicant of the present invention, is to propose another solution, not putting in place a xerophilic gel that allows to obtain an anti-friction band by extrusion taking advantage of the sliding ability on the skin of the user and without presenting the risk of forming a film of soluble component on the skin of that This objective is achieved perfectly by the anti-friction strip for jet shaving of the invention, which in a known manner is obtained by extrusion from a polymer mixture and an insoluble polymeric material and as a soluble polymeric material, polyethylene oxide. Characteristically according to the invention, said band is characterized by a dynamic frontage coefficient (KD) initial of the order of or less than 0.2 and by the fact that the mixture to be extruded presents exclusively, as polyethylene oxide, a product having an average molecular weight greater than 3.5 million. The Applicant has indeed found that the presence of the weakest molecular weight polyethylene oxide even in admixture with the higher molecular weight polyethylene oxide leads to an increase in dynamic coefficient of frontage. Furthermore, it is known that the higher the molecular weight of the polyethylene oxide, the more its solubility in water decreases. There is then a polyethylene oxide of molecular weight higher than 3.5 million, a relatively weak release compared to the figures given in documents E.P.B. 184 440 and E.P.B. 60605. The risk of skin irritation or slippery skin sensation then decreases particularly when that fact is eliminated. In addition, the applicant has found in other shaving comparative tests another important technical advantage in the fact of using, in the mixture, a single high molecular weight polyethylene oxide, that is to keep a slip capacity, for the anti-friction band, which remains substantially constant or evolves relatively little in a series of shaves, using the same band. Comparatively, an anti-friction band having the lowest molecular weight polyethylene oxide, after two or three shaves, has a marked decrease in its shaving capacity, which translates into a very unpleasant feeling for the user. Preferably, with respect to this technical advance, the anti-friction band is obtained by extruding a mixture of polystyrene and a polyethylene oxide with an average molecular weight of more than 4 million. Another problem that the applicant has sought to solve lies in the fixing of the anti-friction band on the shaving head. In the FR.A. 2410 541, the band is fixed on the shaving head preferably in a housing provided for this purpose. No indication is given as to the fixing mode. In document E.P.B.184 440, the band has a particular profile being locked in position by structure elements of the shaving head. This solution makes the manufacture of the head in the E.P.B document more complex. 0550 605, the anti-friction band is fixed by a paste or glue on a cross part of the shaving head. This solution needs to use a glue paste particularly fast if you want to obtain a high rate of production. The applicant has proposed to use for the friction of the anti-friction band on the shaving head, the well-known technique of ultrasonic welding. This technique consists in creating vibration conditions by the action of ultrasound, allowing to locally create an increase in temperature of the two plastic materials in contact so that a localized interpenetration of these two materials is obtained. Since the applicant has found that the use in the anti-friction band of polyethylene oxide with a molecular weight of more than 3.5 million makes it possible to obtain, by the ultrasound welding technique, a good quality welding. It is designated as being a good quality weld between a first plastic base material and a reported plastic material, the case in which the rupture by mechanical stress is carried out mainly at the level of the base material and not at the level of the weld itself. There is a certain tearing of the material beyond the interpenetration zone of the two materials. The best results have been obtained with an anti-friction band manufactured by extruding a mixture of polystyrene and polyethylene oxide with an average weight of more than 7 million, fixed by ultrasonic welding on a portion of the shaving head in polystyrene. Detailed Description of the Invention The present invention, will be better understood with the reading of the description that will be made of an example of embodiment of anti-friction band with a weak coefficient of dynamic frontness, manufactured by extruding a mixture of polystyrene and polyethylene oxide having an average molecular weight greater than 3.5 million, illustrated by the attached drawing in which the single figure is a schematic representation of the test device for the determination of the dynamic frontage coefficient. To determine the slippage of the anti-friction band of the invention, the applicant has taken into account the registered French standard NF T 54-112, which he has adapted. The object of this standard is the measurement of coefficients of static and dynamic frontage of sheets in plastic when they slip on themselves or on other substances, the first plastic sheet being constituted in the present case, by the anti-friction band of the invention , and the second so-called sliding track, is a material in which the characteristics are close to those of the skin, for example a polyurethane sheet, a polyurethane coating and polyester (product reference 4PE100 / B09T , commercialized by the company (CATRY), or an acid catalysis melamine sheet (marketed under the trademark Velleda) It is clear that the precise value of the coefficient of dynamic coefficient will be a function of the material used for the slip track. dynamic frontage (KD) is the ratio of the tensile force that must be exerted to cause the slippage of a and the other of the two surfaces in relation to the supporting force of these two surfaces against each other. To calculate this coefficient, the force necessary to start and then maintain the displacement is measured, one with respect to the other of the two materials in contact, keeping the contact pressure between these two materials constant during the test. The device 1, used to carry out this test, is constituted by a horizontal support 2 which is intended to support the sliding track 3, for example by a 30cm long polyurethane sheet. and of width 15cm. , and of a steel skate 4 that has a mass of 198g, a length of 6.35cm. and a width of 3.4cm., a sample 9 of the anti-friction band to be tested is placed under the skate 4 in contact with the sliding track 3, the skate 4, is pulled by a cable 5 attached to a dynamometer 6, a return pulley 7, allows to obtain a horizontal displacement of the skate 4. The support 2 constitutes the bottom of a tank 8 with a thermostat in which the water heated to 42 ° C is found, in sufficient quantity for this water form a film between the slide track 3 and the sample 9 of the anti-friction band to be tested. A rectilinear displacement of the skate is made, carrying the sample, on the runway at a speed of 150 plus minus 15mm per minute at a distance of 12cm. 10 trials are carried out with the same sample. The average force necessary to maintain the displacement of the skate 4 is measured. The dynamic frontage coefficient (KD) is the ratio of this force on the weight of the set constituted by the skate 4 and the sample 9. The value of the dynamic frontage coefficient KD, which is the problem, is the initial value obtained in the first test. In effect, this value evolves, when a series of tests separated by a drying period of the band is carried out. It has also been noted that it evolves less, when at the end of the 10 tests an average value can be obtained by proceeding to abundant rinsing of the band, it is also preferable to clean and even replace the skid between two tests or tests. By carrying out this method, the applicant has carried out comparative tests between the anti-friction bands made by extrusion from a mixture of polystyrene and polyethylene oxide of different molecular weights. All the tests carried out have shown that the presence in the mixture of low molecular weight polyethylene oxide, especially of the order of 300 thousand, alone or in the presence of polyethylene giicol leads to a phenomenon of harmful glue to the sliding.

On the other hand, according to the invention, dynamic initial dynamic coefficients of order or less than 0.2 were obtained using polyethylene oxides with an average molecular weight of more than 3.5 million, coefficients characteristic of a good sliding without glue phenomenon. In more subjective comparative tests but closer to the conditions of shaving, have been made by the applicant, two anti-friction bands are pasted to be compared on a support plate, the two bands being parallel and distant from each other from 2 to 3cm. The tests include two operations repeated several times in succession and then the assembly in several continuous days: the first operation consists of inserting the insert in the warm water (of the order of 40-42 ° C), thus simulating the passage of the shaver under water hot of the key; the second consists of simultaneously rubbing the two bands with the help of two fingers of the same hand, thus simulating a shaving sequence. In each test, different durations are carried out for each operation. In a first example, the first operation lasts 15 seconds, and the second one minute, the two operations being carried out successively twice in total, in the second example, the first operation lasts 5 sec. and the second 30 sec carrying out the two operations 4 times in total. The set consisting of the repetition of these two operations is performed for several days in a row, for example 6, 7 days simulating the lifetime of the disposable razor. The sensation of sliding perceived simultaneously at the level of the two fingers, allows to make a relative classification of the bands, one with respect to the other, in terms of sliding ability or slip and to appreciate the variation of sliding between the two bands. In particular, thanks to these tests that closely reproduce the actual conditions of a restored one, the applicant has been able to make clear that an anti-friction band obtained by extrusion of a polymer mixture comprising polystyrene and a polyethylene oxide of the type Alcox 300 has a sliding capacity that is always higher than that of a public domain band obtained in the same conditions, but with a mixture of polyethylene oxide and polyethylene glycol; it is also remarkable that this variation is accentuated in proportion to the simulated shaving sequences. In the case of the anti-friction band of the invention, there is a slight decrease in the sliding capacity relatively regular from one day to the other, while, in the case of the band of the public domain mentioned above, there is this same decrease, but on the third or fourth day a brutal fall of sliding ability. With respect to the fixing of the antifriction bands of the invention on the shaving heads, the applicant claims to use the technique of ultrasonic welding. In order to verify the quality of ultrasonic welding between polystyrene and polyethylene oxide, polystyrene inserts have been welded onto extruded plates from a mixture of 60% polyethylene oxide and 40% polystyrene. To verify the quality of the welding, the extruded insert based on polystyrene and polyethylene oxide, is fixed on a support where the polystyrene plate sits for which you want to pull until the break, if the break is made at the level of the welding itself, or the break is made at the level of the polystyrene and polystyrene oxide insert. It is considered that a good quality welding is obtained when the break is made mainly at the level of the insert and not the weld. The table that follows gives the results obtained with the Alcox products 160, 240 to 300 that have been mentioned previously, a complementary test has been carried out with the Alcox E 100, where the molecular deposit announced by the manufacturer is between 2, 5 and 3 million. As can be seen, in the latter case, the quality of the welding is less good as all the ruptures are made at the level of the weld itself and not the material. In addition, there is a very important variation in terms of the average force in kilograms that has been necessary to obtain this break with the band manufactured from Alcox E 100 in relation to those obtained with the Alcox E 160, E 240 and E 300, where the results are very close to each other. The best result with regard to the coefficient of dynamic frontage and in regard to ultrasonic welding, is formed by the anti-friction band made by extrusion of a mixture of 40% by weight of polystyrene and 60% by weight. weight of polyethylene oxide, having a molecular weight between 7 and 8 million, said band is welded by ultrasound on a shaving head in polystyrene.

The preferred anti-friction band of the invention that allows to obtain the best results, both in terms of the sliding capacity and the durability of this capacity and in terms of manufacturing quality, is a band obtained by extrusion from of a polymer mixture having in the order of 30% polystyrene and in the order of 70% of a polyethylene oxide where the average molecular weight is greater than 7 million. The extruded mass is more compact than with lower molecular weight polyethylene oxides, which allows a more precise and more regular band profile. In a preferred embodiment using Alcox 300 (average molecular weight between 7 and 8 million), the mixture comprised 66.5% Alcox 300, 32% polystyrene and 1.5% additives, especially colored pigments. The anti-friction band of the invention, it is clear that it can also contain, in addition to the aforementioned characteristic polymeric materials, shaving additives, especially those mentioned in FR.2, 410541: cleaning agent, pharmaceutical agents, cosmetics and coagulating agents.

Claims (7)

1. NOVELTY OF THE INVENTION Having described the invention as above, the content of the following is claimed as property: CLAIMS 1.- Anti-friction band for disposable razor obtained by extrusion from a polymer mixture comprising an insoluble polymer material and oxide polyethylene, characterized by an initial dynamic coefficient of coefficient (KD) of the order of or less than 0.2 and because the mixture to be extruded presents exclusively as polyethylene oxide a product with an average molecular weight of more than 3.5 million.
2. 2. Anti-friction band according to claim 1, characterized in that it is obtained by extrusion from a mixture comprising polystyrene and polystyrene oxide with an average molecular weight of more than 4 million.
3. 3. Anti-friction band according to claim 2, characterized in that it is obtained by extrusion of a mixture of polystyrene and a single polyethylene oxide with a molecular weight greater than 7 million.
4. 4. Anti-friction band according to claim 3, characterized in that it is obtained by a mixture in the order of 30% polystyrene and in the order of 70% of a single polyethylene oxide of a molecular weight greater than 7 million.
5. 5. Anti-friction band according to claim 4, characterized in that it is obtained with a mixture of 32% polystyrene, 66.5% of a polyethylene oxide of a molecular weight comprised between 7 and 8 million and 1.5% of additives especially coloring pigments.
6. 6. Shaving head characterized in that an antifriction band according to one of claims 1 to 5 is fixed by electronic welding.
7. 7. - Shaving head according to claim 6, characterized in that the portion on which it is Fixed anti-friction band is made of polystyrene.